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	description	This application claims the benefit, under 35 U.S.C. §119(e), of U.S. Provisional Application No. 61/973,979, filed on Apr. 2, 2014, and which is hereby incorporated by reference in its entirety. The present disclosure relates to photo-masks for lithography. In standard integrated circuit (IC) fabrication, lithography is typically used to transfer a desired pattern formed on a photo-mask to a silicon wafer, in which the photo-mask contains an enlarged view of the pattern (e.g., a magnification of the pattern by about 4 times). One example of a photo-mask format typically used in IC fabrication is known as the “6025” format (i.e., the mask is 6″×6″×0.25″ in size). In a desire to continue reducing the minimum feature size, fabrication processes relying on a type of lithography known as extreme ultraviolet (EUV) lithography are being developed. Furthermore, demands for increased throughput may lead to requiring even larger mask sizes. With smaller feature sizes and larger masks, it is increasingly important to control mask qualities such as roughness, flatness and defect size/number, in order to minimize errors when transferring a pattern to a wafer. Additionally, in certain high throughput fabrication processes, photo-masks may be subjected to high accelerations (e.g., in excess of 10-20 times gravitational acceleration) during scanning. The forces resulting from the high accelerations can cause deformations in the photo-masks, leading to further degradation in the image transferred to a wafer. This disclosure relates to photo-masks that include a substrate layer that is composed of a high specific stiffness material. Photo-masks having high specific stiffness can be resistant to deformation under high acceleration, and can therefore prevent or minimize distortion of a mask pattern to be imaged. Various aspects of the disclosure are summarized as follows. In general, in a first aspect, the subject matter of the present disclosure may be embodied in a photo-mask for use in extreme ultraviolet (EUV) lithography, in which the photo-mask includes a cordierite ceramic substrate layer. Implementations of the photo-mask may include one or more of the following features and/or features of other aspects. For example, in some implementations, the cordierite ceramic has a Young's modulus between about 120 GPa to about 157 GPa. In some implementations, the cordierite ceramic has a coefficient of thermal expansion between −50 parts per billion/° C. and +50 parts per billion/° C. In some implementations, the cordierite ceramic has a coefficient of thermal expansion between −20 parts per billion/° C. and +20 parts per billion/° C. In some implementations, the photo-mask of claim 1, wherein the cordierite ceramic has a bulk density between about 2500 kg/m3 and about 2700 kg/m3. In some implementations, the photo-mask of claim 1, wherein the cordierite ceramic has a thermal conductivity between about 3.0 W/(m·K) and about 5.0 W/(m·K). In some implementations, the substrate layer has a thickness of about 0.25 inches or less, and the photo-mask has a surface area for a first side of the photo-mask of about 81 square inches or less. In some implementations, the photo-mask further includes a reflector layer on a front surface of the substrate layer, a capping layer on the reflector layer, an absorber layer on the capping layer, an anti-reflection coating on the absorber layer, and a backside coating on a back surface of the substrate layer, in which the back surface is opposite the front surface. In general, in another aspect, the subject matter of the present disclosure may be embodied in methods of fabricating a photo-mask for EUV lithography, in which the method includes obtaining a cordierite ceramic substrate layer, applying full-aperture polishing or sub-aperture polishing to the cordierite ceramic substrate layer, depositing a reflector layer on a frontside surface of the substrate layer, wherein the reflector layer comprises a plurality of alternating first and second thin films configured to form a Bragg reflector, depositing a Ru capping layer on the reflector layer, depositing a TaN absorbing layer on the capping layer, and patterning the absorbing layer to form a desired pattern. Implementations of the methods may include one or more of the following features and/or features of other aspects. For example, in some implementations, the method includes applying both sub-aperture polishing and full-aperture polishing to the substrate layer, in which sub-aperture polishing is applied subsequent to applying the full-aperture polishing. In general, in another aspect, the subject matter of the present disclosure may be embodied in an illumination system that includes an EUV light source, an illumination optical system, a projection optical system, and a photo-mask having a cordierite ceramic material, in which the illumination optical system is configured to receive EUV light from the light source and redirect the EUV light onto the photo-mask, and in which the projection optical system is configured to receive EUV light reflected from the photo-mask and image the reflected EUV light onto an object located at an image plane of the projection optical system. Implementations of the illumination system may include one or more of the following features and/or features of other aspects. For example, in some implementations, the cordierite ceramic has a Young's modulus between about 120 GPa to about 157 GPa. In some implementations, the cordierite ceramic has a coefficient of thermal expansion between −50 parts per billion/° C. and +50 parts per billion/° C. In some implementations, the cordierite ceramic has a coefficient of thermal expansion between −20 parts per billion/° C. and +20 parts per billion/° C. In some implementations, the cordierite ceramic has a bulk density between about 2500 kg/m3 and about 2700 kg/m3. In some implementations, the cordierite ceramic has a thermal conductivity between about 3.0 W/(m·K) and about 5.0 W/(m·K). In some implementations, the substrate layer has a thickness of about 0.25 inches or less, and the photo-mask has a surface area for a first side of the photo-mask of about 81 square inches or less. In general, in another aspect, the subject matter of the present disclosure may be embodied in an a photo-mask for use in extreme ultraviolet (EUV) lithography, in which the photo-mask includes a substrate layer comprising a Young's modulus between about 120 GPa to about 157 GPa and a coefficient of thermal expansion between −50 parts per billion/° C. and +50 parts per billion/° C., e.g., between −20 parts per billion/° C. and +20 parts per billion/° C. In general, in another aspect, the subject matter of the present disclosure may be embodied in a device that includes an EUV lithography photo-mask, the photo-mask including an oxide ceramic MgaLibFecAldSieOf substrate layer, in which a, b, c, d, e, and f are in the range of 1.8 to 1.9, 0.1 to 0.3, 0 to 0.2, 3.9 to 4.1, 6.0 to 7.0, and 19 to 23, respectively, and in which the substrate layer has a Young's modulus between about 120 GPa to about 157 GPa and a coefficient of thermal expansion between −50 parts per billion/° C. and +50 parts per billion/° C. In general, in another aspect, the subject matter of the present disclosure may be embodied in a device that includes an EUV lithography photo-mask, the photo-mask including a substrate layer, in which the substrate layer includes cordierite as a primary component, and one or more selected from the group consisting of La, Ce, Sm, Gd, Dy, Er, Yb and Y in an oxide equivalent amount of 1 to 8 mass %, in which a mass ratio between the primary components has the following ratios: 3.85≦SiO2/MgO≦4.60, and 2.50≦Al2O3/MgO≦2.70, and in which the substrate layer has a Young's modulus between about 120 GPa to about 157 GPa and a coefficient of thermal expansion between −50 parts per billion/° C. and +50 parts per billion/° C. Certain implementations may have particular advantages. For example, a photo-mask having a substrate layer composed of a high-specific stiffness material may be resistant to deformation under high acceleration, and can therefore prevent or minimize distortion of a mask pattern to be imaged. In some instances, a high specific stiffness material for the substrate layer allows fabrication of a photo-mask that has less total mass for a particular overall mask stiffness and/or higher accelerations can be accommodated with such a high specific stiffness mask for a given amount of mask distortion. In some cases, the use of cordierite as the substrate layer material provides an increase in thermal conductivity of the mask, so that more heat can be removed from the mask during use. The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features and advantages will be apparent from the description, the drawings, and the claims. FIG. 1 is a schematic illustrating an example of a reflective photo-mask 100 for use in EUV lithography applications. The photo-mask is constructed of several layers including a substrate layer 102, a reflector layer 104 that contains alternating thin films of Molybdenum and Silicon (e.g., 40 or more Mo/Si thin-film layer pairs), a capping layer 106, an absorber layer 108, and an anti-reflection coating (ARC) layer 110. The mask 100 may also include a backside coating 112 (e.g., composed of chrome nitride (CrN)) that allows for electrostatic chucking. Since nearly all matter absorbs EUV, the substrate layer 102 should be formed of a material having a relatively low coefficient of thermal expansion (CTE) to prevent the mask 100 from warping or otherwise distorting the pattern formed on the mask. The alternating thin films of the reflector layer 104 form a Bragg reflector that is configured to maximize reflection at the wavelength of the incident radiation (e.g., at about 13.5 nm for current EUV and/or 6.7 nm being contemplated for future tools). The capping layer 106 is formed from a material such as ruthenium (Ru) to prevent oxidation of the underlying reflector layer 104. The absorber layer 108 may be composed of, for example, tantalum boron nitride (TaBN), and covered with an anti-reflective oxide as the ARC coating layer 110. The absorber layer 108 is constructed to have the desired pattern that will be transferred from the mask 100 to the wafer. For instance, the example shown in FIG. 1 includes an absorber layer 108 arranged as a series of parallel lines. In order to inhibit deformation that the mask may experience as a result of high accelerations during scanning operations, the substrate layer material includes a low CTE material that has a relatively high specific stiffness. Specific stiffness can be expressed as the elastic modulus per mass density of a material, such that a material with high specific stiffness has either high Young Modulus or low density, or both high Young Modulus and low density. With a higher specific stiffness, the substrate layer 102, and therefore the mask as a whole, is resistant to deformation under high acceleration, and can prevent distortion of the mask pattern to be imaged. Alternatively, the higher specific stiffness allows the mask as a whole to undergo higher accelerations and speeds, while maintaining the same level of distortion that a mask having a substrate layer composed of lower Specific Stiffness would experience at lower accelerations and speeds. By translating the masks at higher speeds without an increase in distortion, the throughput (e.g., number of silicon wafers processed per unit time) can be increased. A class of materials that provides high specific stiffness is the cordierite class of ceramics. Cordierite ceramics typically includes a mixture of magnesium oxide (e.g., MgO), aluminum oxide (e.g., Al2O3) and silicon dioxide (SiO2). For instance, a type of cordierite ceramic fabricated by various chemical manufacturers has a relative ratio of primary components as follows: 2MgO-2Al2O3-5SiO2. This material is also called “Cordierite” or α-cordierite. Table 1 below provides a representative example of the key properties of different cordierite materials (CO211, CO711, CO712, and CO720) fabricated by the manufacturer Kyocera and provides a comparison to Zerodur® available from Schott®: TABLE 1PropertyUnitsCO211CO711CO712CO720Zerodur ®Bulkkg/m3 ·2.672.682.72.552.53Density103Water%00000Absorp-tionVickersGPa7.27.77.77.76.2HardnessFlexuralMPa15023625222580StrengthYoung'sGPa14014314414490ModulusPoisson's0.310.310.310.31—0.24RatioCTEppb/° C.0 ± 1000 ± 500 ± 200 ± 200 ± 20(@22° C.)ThermalW/(m · K)4.04.04.04.31.5Conduc-tivityVolumeΩ · cm>1014>1014>1014>1014—Resis-tivity As can be seen from TABLE 1, the cordierite materials have a Young's modulus that substantially exceeds the Young's modulus of Zerodur® (i.e., about a 55% increase) and a density that is only slightly higher than the density of Zerodur®. Moreover, the cordierite materials have a CTE that is comparable to the CTE of Zerodur®, indicating that cordierite is a suitable candidate as a mask substrate layer for use in EUV lithography applications, since it will not substantially expand when absorbing the EUV rays. In addition, cordierite's thermal conductivity is almost three times higher than that of Zerodur®, allowing the material to remove heat to a greater extent during use. While the high Young's Modulus of cordierite is useful for minimizing distortion of the mask during high speed scanning, the increased stiffness may alternatively allow a reduction in the photo-mask size. That is, to obtain a substrate layer having a particular overall stiffness, less mass may be required using cordierite than using materials having lower Young's Modulus, such as Zerodur®, ultra low expansion (ULE) glass-ceramics, and ClearCeram®. Accordingly, using cordierite as the substrate layer material allows the size (e.g., thickness) of the substrate layer to be reduced while maintaining the same overall mask stiffness obtained with substrates having lower Young's Modulus. For instance, the thickness of the substrate composed of cordierite could be reduced by 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, or 55% relative to substrates composed of materials having a lower Young's Modulus, while retaining the same overall stiffness. Different cordierite ceramics may have different values from those listed in TABLE 1. For instance, the range of bulk density for a cordierite ceramic may be between about 2500 kg/m3 and about 2700 kg/m3, including about 2500 kg/m3, about 2600 kg/m3, or about 2650 kg/m3. The range of Vickers hardness for a cordierite ceramic may be between about 7 GPa to about 8.5 GPa, including about 7 GPa, about 7.5 GPa, about 8.0 GPa, about 8.1 GPa, or about 8.5 GPa. The range of flexural strength for a cordierite ceramic may be between about 100 MPa to about 300 MPa, including about 116 MPa, about 185 MPa, about 210 MPa, about 230 MPa, about 250 MPa, about 290 MPa, or about 300 MPa. The Young's modulus for a cordierite ceramic may be between about 120 GPa to about 157 GPa, including about 120 GPa, about 125 GPa, about 130 GPa, about 135 GPa, about 145 GPa, about 150 GPa, about 155 GPa, or about 157 GPa. The CTE for a cordierite ceramic material may be within 0±100 ppb/° C., including within 0±5 ppb/° C., within 0±10 ppb/° C., within 0±20 ppb/° C., within ±0 30 ppb/° C., within 0±40 ppb/° C., within 0±50 ppb/° C., within 0±60 ppb/° C., within 0±70 ppb/° C., within 0±80 ppb/° C., or within 0±90 ppb/° C. The thermal conductivity of a cordierite ceramic may be between about 3.0 W/(m·K) and about 5.0 W/(m·K), including about 3.5 W/(m·K), about 3.6 W/(m·K), about 3.7 W/(m·K), about 3.8 W/(m·K), about 3.9 W/(m·K), about 4.1 W/(m·K), about 4.2 W/(m·K), about 4.4 W/(m·K), about 4.5 W/(m·K), about 4.6 W/(m·K), about 4.7 W/(m·K), about 4.8 W/(m·K), about 4.9 W/(m·K), or about 5.0 W/(m·K). The volume resistivity of a cordierite ceramic may be between about 1010 Ω·m and about 1015 Ω·m. Unlike mask materials such as ULE and others used in traditional photolithography, cordierite is not transparent, and therefore not an immediately apparent substrate material. However, since EUV masks can be constructed so that the pattern to be image on the wafer is formed based on a combination of absorption and reflection of EUV light from the mask, not transmission through the mask, cordierite can be used as an acceptable substrate material despite its opacity. As explained above, it is important to control mask qualities such as roughness, flatness and defect size/number in EUV lithography, in order to minimize errors when transferring a pattern to a wafer. TABLE 2 below provides an example of stringent guidelines for mask flatness, roughness and defect density generally followed by industry. Examples of guidelines can be found in Semiconductor Equipment and Materials International (SEMI) P37-0613 entitled “Specification for Extreme Ultraviolet substrates and blanks” and SEMI P40-1109 entitled “Specification for mounting requirements for Extreme Ultraviolet lithography mask.” TABLE 2PropertyRequirementsFrontside (FS) Flatness (PV)≦30nmBackside (BS) Flatness (PV)≦30nmFS Roughness (λ ≦ 10 μm) rms≦0.1nmFS Local slope (400 nm ≦ λ ≦ 100 mm)<1mradBS Roughness (50 nm ≦ λ ≦ 10 μm)≦0.50nmDefect Density @ 50 nm (SiO2 Eq.)≦0.008 However, synthetic cordierite ceramic materials are, in general, polycrystalline and the corresponding local anisotropy poses a significant challenge when trying to achieve the strict requirements for roughness and flatness necessary for using EUV masks in large throughput industrial applications. For instance, the removal rate of a chemical mechanical polishing process or other polishing process may vary between the different plane orientations of the polycrystalline material limiting the minimum roughness that can be achieved. To obtain super-low roughness including less than 0.3 nm roughness (e.g., 0.2 nm or less rms roughness, or 0.1 nm or less rms roughness), the cordierite substrate layer is polished using full-aperture polishing and/or sub-aperture polishing. Full-aperture polishing processes (sometimes referred to as “continuous polishers”) typically refer to polishing processes where the polishing pad of a polishing machine is bigger than the surface of the substrate being polished, resulting in an effective polishing area substantially equivalent to the area of the substrate. Full-aperture polishing methods often require multiple, long, iterative cycles involving polishing, metrology and process changes (e.g., adjusting type and particle size distribution of abrasives, adjusting type of polishing pads, adjusting polishing speed, and/or adjusting polishing pressure) to achieve the desired surface figure. For instance, to achieve very low roughness, a very fine grain cerium oxide and/or colloidal silica abrasive could be used while adjusting pH of the polish (e.g., between 2-12, such as between 4 to 6), polishing pad pressure (e.g., less than 2 pounds per square inch (PSI), such as between 1 to 1.5 PSI), and/or polishing pad velocity (e.g., a polishing pad wheel speed of about 50 RPM). Sub-aperture polishing processes typically refer to polishing processes where the polishing zone (sometimes referred to as “spot”) is substantially smaller than the surface of the substrate being polished. Examples of sub-aperture polishing processes include computer controlled polishing (CCP), computer controlled optical surfacing (CCOS), ion beam finishing (IBF) and magneto-rheological finishing (MRF). This polishing process is capable of obtaining roughness values below at or below about 0.430 nm rms (e.g., at or below about 0.421 nm rms, at or below about 0.415 nm rms, at or below about 0.400 nm rms, at or below about 0.350 nm rms, at or below about 0.300 nm rms, at or below about 0.250 nm rms, at or below about 0.200 nm rms, at or below about 0.150 nm rms, at or below about 0.100 nm rms, and at or below about 0.050 nm rms). Full-aperture and/or sub-aperture processing also can be used to achieve the desired level of flatness (e.g., less than or equal to 30 nm PV for front side (FS) and back side (BS)) The level of flatness of the cordierite material that can be obtained using either full or sub-aperture polishing is, e.g., at or below about 100 nm, at or below about 50 nm, at or below about 30 nm, at or below about 25 nm, at or below about 20 nm, at or below about 15 nm, at or below about 10 nm, at or below about 5 nm, at or below about 2 nm, and at or below 1 nm. An example of a manufacturing process 200 for an EUV mask having cordierite material as a substrate layer is shown in FIG. 2 and includes: obtaining (202) raw cordierite material; grinding (204) the cordierite material to the approximate dimensions of the photo-mask; applying full-aperture polishing (206) to the cordierite; optionally applying sub-aperture finishing (208) (e.g., using techniques such as CCP, CCOS, IBF or MRF); depositing a reflector layer (210) on a frontside surface of the substrate layer (e.g., using ion-beam sputtering of alternating thin-films of Si and Mo); depositing a capping layer on the reflector layer (212) (e.g., using ion-beam sputtering of Ru); depositing and patterning an absorber layer (214) (e.g., using ion-beam sputtering of TaN). The absorber layer may be patterned using e-beam writing, chemical etching or lift-off techniques. In some cases, an ARC film is formed on the surface of the absorber layer, and a CrN film is formed on a backside surface of the substrate layer (216). Those films also may be deposited using ion-beam sputtering. Surface metrology may be performed on the cordierite substrate layer between any of the foregoing steps and intermittently during each step to evaluate the surface quality (e.g., flatness, roughness, and defects) of the mask. For additional details on full and sub-aperture polishing see, e.g., EP 2089186, incorporated herein by reference in its entirety. In some implementations, the substrate layer may be fabricated to have a pre-defined shape, such as slightly concave or slightly convex. By forming the substrate layer with a pre-defined shape, it may compensate for deformation and distortions in the substrate layer caused by stress from thin-film coatings, gravity and/or mounting the substrate layer (e.g. mounting the substrate layer using electrostatic chucking) That is, any bowing or bending caused by film stress, gravity and/or mounting may be balanced out by the pre-defined concave or convex shape of the substrate layer so that, during use, the photo-mask is substantially flat. The size of the mask formed using the substrate may vary as well. For example, in some implementations, the front side of the mask may have an area that is about 81 square inches or less, about 64 square inches or less, about 49 square inches or less, about 36 square inches or less, or about 25 square inches or less. The substrate layer may have a thickness of about 0.25 inches or less, such as about 0.20 inches or less, about 0.15 inches or less, or 0.10 inches or less. In some implementations, the chuck on which the photo-mask is secured also may be substantially composed of a cordierite material. An advantage of forming the chuck from the same material as the substrate layer is that the chuck and photo-mask will have closely matching CTEs, thus minimizing the occurrence of forces that cause the photo-mask to deform (i.e., forces that would otherwise occur due to differential expansion between the photo-mask and the chuck under absorption of EUV). In some implementations, a cordierite-based sintered body which includes cordierite as a primary component, and one or more selected from the group consisting of La, Ce, Sm, Gd, Dy, Er, Yb and Y in an oxide equivalent amount of 1 to 8 mass %, in which a mass ratio between the primary components has the following ratios: 3.85≦SiO2/MgO≦4.60, and 2.50≦Al2O3/MgO≦2.70, can be used for the EUV mask, e.g., as the mask substrate material. Such materials can have thermal expansions of within ±0.02 ppm/K and a Young's modulus of between about 120 GPa to about 157 GPa, EUV masks formed from a cordierite-based sintered body which includes cordierite as a primary component, and one or more selected from the group consisting of La, Ce, Sm, Gd, Dy, Er, Yb and Y in an oxide equivalent amount of 1 to 8 mass %, can be fabricated and polished using the same procedures as set forth herein with respect to cordierite. In some implementations, material other than cordierite that has high specific stiffness, low CTE material, and the same or similar crystal structure as cordierite also can be used for an EUV mask, e.g., as the mask substrate material. For instance, oxide ceramic materials composed of regularly mixed solid solution crystals of the elements lithium, magnesium, aluminum, iron, silicon, and oxygen can be used as the mask substrate material. The solid solution can be substantially represented by the chemical formula MgaLibFecAldSieOf (where a, b, c, d, e, and f range from 1.8 to 1.9, 0.1 to 0.3, 0 to 0.2, 3.9 to 4.1, 6.0 to 7.0, and 19 to 23, respectively). An example of this material is called NEXCERA® (e.g., NEXCERA N113G) available from Nippon Steel Inc. The MgaLibFecAldSieOf oxide ceramics can have thermal expansions of within ±0.02 ppm/K, a Young's modulus of at least about 120 GPa, and a specific rigidity of at least about 50 GPa/g/cm3. EUV masks formed from the MgaLibFecAldSieOf oxide ceramic can be fabricated and polished using the same procedures as set forth herein with respect to cordierite. Lithography Tool Applications Lithography tools are especially useful in lithography applications used in fabricating large scale integrated circuits such as computer chips and the like. Lithography is the key technology driver for the semiconductor manufacturing industry. The function of a lithography tool is to direct spatially patterned radiation onto a photoresist-coated wafer. The process involves determining which location of the wafer is to receive the radiation (alignment) and applying the radiation to the photoresist at that location (exposure). During exposure, a radiation source illuminates a patterned photo-mask, which scatters the radiation to produce the spatially patterned radiation. In the case of reduction lithography, a reduction lens collects the scattered radiation and forms a reduced image of the mask pattern. The radiation initiates photo-chemical processes in the resist that convert the radiation pattern into a latent image within the resist. To properly position the wafer, the wafer includes alignment marks on the wafer that can be measured by dedicated sensors. The measured positions of the alignment marks define the location of the wafer within the tool. This information, along with a specification of the desired patterning of the wafer surface, guides the alignment of the wafer relative to the spatially patterned radiation. Based on such information, a translatable stage supporting the photoresist-coated wafer moves the wafer such that the radiation will expose the correct location of the wafer. In certain lithography tools, e.g., lithography scanners, the mask is also positioned on a translatable stage that is moved in concert with the wafer during exposure. In general, the lithography tool, also referred to as an exposure system, typically includes an illumination system and a wafer positioning system. The illumination system includes a radiation source for providing radiation such as extreme ultraviolet, ultraviolet, visible, x-ray, electron, or ion radiation, and a photo-mask for imparting the pattern to the radiation, thereby generating the spatially patterned radiation. The imaged radiation exposes resist coated onto the wafer. The illumination system also includes a mask stage for supporting the mask and a positioning system for adjusting the position of the mask stage relative to the radiation directed through the mask. The wafer positioning system includes a wafer stage for supporting the wafer and a positioning system for adjusting the position of the wafer stage relative to the imaged radiation. Fabrication of integrated circuits can include multiple exposing steps. FIG. 3 is a schematic that illustrates, in a meridional section, an example of a projection exposure system 1 for microlithography. An illumination system 2 of the projection exposure system 1, apart from a radiation source 3, has an illumination optical system 4 to expose a reflective mask 5 in an object plane 6. The reflective mask 5 carries a pattern to be projected with the projection exposure system 1 to produce microstructured or nanostructured semiconductor components. A projection optical system 7 is used to image the pattern from the mask 5 in an image field 8 in an image plane 9. The pattern on the mask is imaged on a light-sensitive layer of a wafer, which is arranged in the region of the image field 8 in the image plane 9 and is not shown in the drawing. The mask 5 may include an EUV mask, such as the EUV mask including a cordierite substrate layer, as described herein. The mask, which is held by a mask holder, not shown, and the wafer, which is held by a wafer holder, not shown, are synchronously scanned in the y-direction during operation of the projection exposure system 1. Depending on the imaging scale of the projection optical system 7, a scanning of the mask in the opposite direction relative to the wafer can also take place. The radiation source 3 is an EUV radiation source with an emitted useful radiation in the range between 5 nm and 30 nm. This may be a plasma source, for example a DPP source (Discharged Produced Plasma) or an LDP source (Laser Assisted Discharge Plasma). Other EUV radiation sources, for example those which are based on a synchrotron or on a free electron laser (FEL), are possible. EUV radiation 10, which is emitted from the radiation source 3, is bundled by a collector 11. A corresponding collector is known, for example, from EP 1 225 481 A. After the collector 11, the EUV radiation 10 propagates through an intermediate focus plane 12, before it impinges on a field facet mirror 13. The field facet mirror 13 is arranged in a plane of the illumination optical system 4, which is optically conjugated with the object plane 6. After the field facet mirror 13, the EUV radiation 10 is reflected by a pupil facet mirror 14. The pupil facet mirror 14 is arranged in a plane of the illumination optical system 4, which is a pupil plane of the projection optical system 7 or is optically conjugated to a pupil plane of the projection optical system 7. With the aid of the pupil facet mirror 14 and an imaging optical module in the form of a transmission optical system 15 with mirrors 16, 17 and 18 designated in the order of the beam path for the EUV radiation 10, the field facets of the field facet mirror 13 are imaged overlapping one another in the object field where mask 5 is located. The last mirror 18 of the transmission optical system 15 is a grazing incidence mirror. The illumination light 10 is guided from the radiation source 3 to the mask 5 by way of a plurality of illumination channels. Associated with each of these illumination channels is a field facet of the field facet mirror 13 and a pupil facet of the pupil facet mirror 14 arranged downstream thereof. The individual mirrors of the field facet mirror 13 and of the pupil facet mirror 14 may be tilted by actuator, so a change of the association of the pupil facets with the field facets and, accordingly, a changed configuration of the illumination channels can be achieved. Different illumination settings result, which differ with respect to the distribution of the illumination angles of the illumination light 10 over the mask 5. A number of embodiments have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Other embodiments are within the scope of the following claims.
	abstract	A support grid for a nuclear fuel assembly, the nuclear fuel assembly including a generally cylindrical fuel rod with a diameter, wherein the support grid includes a frame assembly having a plurality of generally circular cells and a plurality of helical frame members. The helical frame members are disposed in the cells and are structured to contact the cell as well as a fuel rod. The helical fuel rod contact portion may have a variable pitch.
051805448	summary	BACKGROUND OF THE INVENTION The present invention relates to a control blade for use in a nuclear reactor which is adapted to be inserted into and extracted from a nuclear reactor core for the purpose of controlling the power of the nuclear reactor. More particularly, the invention is concerned with a long-life flux-trap type control blade suitable for use in a boiling water reactor (BWR). In general, a control blade for use in a boiling water reactor has a central tie rod and a plurality of wings formed by U-shaped sheath plates attached to the tie rod, each wing containing a multiplicity of neutron absorber rods. Each neutron absorber rod is composed of a clad tube made of a steel such as stainless steel and grain of boron carbide (B.sub.4 C) charged in the clad tube. In order to prevent the grain of boron carbides from moving freely within the clad tube, partition balls are placed at a predetermined interval within the clad tube. The boron carbides in the form of grain charged in the neutron absorber rod progressively decreases its neutron absorption power (capacity) due to absorption of neutrons, and generates He gas as a result of reaction between boron-10 (.sup.10 B) and neutrons resulting in a rise of the pressure within the clad tube. The lifetime of the control blade determined by the neutron absorption power is referred to as "nuclear lifetime", while the lifetime determined by the internal gas pressure of the clad tube is referred to as "mechanical lifetime". The control blade, which is adapted to be inserted into and extracted from the nuclear reactor core, is not uniformly exposed to neutrons. For instance, the rate of neutron exposure rate is high at the side edges and upper end of each wing. This means that these portions of the control blade absorb greater amounts of neutron than other portions of the control blade and, therefore, the nuclear lifetime is reached earlier in these portions than in other portions of the control blade. In consequence, the control blade has to be disposed of as a radioactive waste, even though sufficient lifetime is left in other portions thereof. In order to obviate this problem, the present inventors have developed an improved control blade in which long-life neutron absorbers are disposed in the vicinity of side edges of wings where the degree of neutron exposure is high, as disclosed in Japanese Patent Laid-Open No. 74697/1978. This improved control blade, however, is still unsatisfactory from the view point of prolongation of lifetime of control blades, because it exhibits a lifetime which is only twice as long as that of ordinary control blades containing B.sub.4 C. In order to cope with the demand for prolongation of lifetime of control blades, the present inventors have developed a long-life control blade capable of operating much longer than the above-mentioned improved control blade. This long-life control blade has, as disclosed in Japanese Patent Laid-Open No. 55887/1983, solid neutron absorption plates made of a long-life neutron absorber and disposed in each wing thereof. The neutron absorption plate has apertures or recesses whose sizes and distribution are so determined that the amount of material removed by the presence of such apertures or recesses is comparatively small in the portion where the axial distribution of the shut down margin is small and is comparatively large in the portion where the axial distribution of the shut down margin is large. This long-life control blade, however, suffers from the following disadvantage, due to the use of hafnium (Hf) sheet as the neutron absorber. Namely, hafnium is expensive and has a large specific gravity (13.3 g/cm.sup.3) so that the cost and the weight of the control blade are increased undesirably. The increased weight of the control blade in turn requires a design of a control rod drive mechanism which can safely operate such heavy control blades because conventional control rod drive mechanism cannot withstand such heavy weight of the control blades. The inventors, however, have confirmed that there still is a margin for the removal of material in the hafnium sheet which is used as long-life neutron absorber for the purpose of reducing the weight of the hafnium sheet, and that ordinary control blade drives are still usable provided that the weight of the control blade is reduced by the removal of the material. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a long-life control blade for use in a nuclear reactor such as BWR in which the weight of the long-life neutron absorber and, hence, the overall weight of the control blade are effectively reduced so as to enable conventional control rod drive mechanism to safely drive such a long-life control blade, thereby overcoming the above-described problems of the prior art. Another object of the present invention is to provide a long-life control blade having almost the same size, shape and total weight as those of ordinary B.sub.4 C control blades and, hence, usable in existing boiling water reactors. Still another object of the present invention is to provide a long-life control blade for nuclear reactors, suitable for use in operation of the reactor at a high burn-up and in long-term operation of the reactor. A further object of the present invention is to provide a long-life control blade for nuclear reactors, which is improved in such a way as to effectively avoid damaging due to electrochemical corrosion. A still further object of the present invention is to provide a hybrid-type long-life control blade for nuclear reactors, which is improved in such a way as to avoid damaging due to electrochemical corrosion and to increase mechanical strength so as to exhibit greater resistance to deformation by any external force. A still further object of the present invention is to provide a long-life control blade for nuclear reactors, which is improved such as to exhibit a greater resistance to buckling while reducing the weight of sheaths, thus reducing the total weight of the control blade. According to the present invention, these and other objects can be achieved in one aspect by providing a control blade for nuclear reactors comprising: an upper structure; a lower structure; a central tie rod having radial projections and interconnecting the upper and lower structures together; and wings composed of sheath plates each having a substantially U-shaped cross-section and secured to the end of each projection of the central tie rod, and long-life neutron absorber charged in each of the sheath plate; wherein the neutron absorber in each sheath is divided into a plurality of neutron absorber elements (sections) along the axis of the central tie rod, each neutron absorber element (section) being composed of neutron absorber plates spaced from and opposing each other such that a water gap for guiding the flow of a moderator is defined between these neutron absorber plates. In this control blade, the reactivity worth is increased by virtue of the water gap for guiding the flow of a moderator (coolant) between the opposing neutron absorber plates. The provision of the water gap also enables the thickness of the neutron absorber plates to be reduced in accordance with the amount of the neutron exposure. For these reasons, the control blade can have almost the same size, shape and weight as those of ordinary B.sub.4 C type control blades, even though a heavy long-life neutron absorber such as hafnium sheets is used. Therefore, the control blade can be used in existing nuclear reactors without requiring modification of the control rod drive mechanism, and can operate for a period which is much longer than those offered by known control blades. In another aspect, the present invention provides, in order to avoid any electrochemical corrosion due to contact between different metals, a control blade for nuclear reactors comprising: an upper structure; a lower structure; a central tie rod having radial projections and interconnecting the upper and lower structures together; and wings composed of sheath plates each having a substantially U-shaped cross-section and secured to the end of each projection of the central tie rod, and long-life neutron absorber charged in each of the sheath plate; wherein the neutron absorber in each wing is composed of a plurality of neutron absorber plates such as of hafnium which are spaced from each other in the thicknesswise direction of the wing by means of supporting spacers, such that a water gap for guiding the flow of a moderator is defined between opposing neutron absorber plates, and wherein a water passage is formed between the external surface of each neutron absorber plate and the adjacent inner surface of the sheath. In still another aspect, the present invention provides, in order to prevent buckling through enhancement of strength to lateral bending force, a control blade for nuclear reactors comprising: an upper structure; a lower structure; a central tie rod having radial projections and interconnecting the upper and lower structures together; and wings composed of sheath plates each having a substantially U-shaped cross-section and secured to the end of each projection of the central tie rod, and long-life neutron absorber charged in each of the sheath plate; wherein the neutron absorber in each wing is divided into a plurality of neutron absorber elements along the axis of the tie rod, each the element being composed of a plurality of neutron absorber plates spaced from and opposing each other; and wherein a plurality of spacers are disposed between the opposing neutron absorber plates such that a linear flow passage for a moderator is defined so as to extend in the axial direction of the tie rod, the spacers being arranged at a substantially constant interval along the axis of the tie rod but the interval is slightly reduced in the regions between adjacent neutron absorber plates. These and other objects, features and advantages of the present invention will become clear from the following description of the preferred embodiments when the same is read in conjunction with the accompanying drawings.
	claims	1. A process for the treatment of mercury containing waste in a single reaction vessel comprising the steps: (a) stabilizing said waste by combining the waste with sulfur polymer cement under an inert atmosphere at a temperature of about 20xc2x0 C. to about 80xc2x0 C. to form a resulting mixture; (b) encapsulating the resulting mixture by: (i) heating the mixture to a temperature of between 120xc2x0 C.-150xc2x0 C. to form a molten product, and (ii) casting said molten product as a monolithic final waste form. 2. A process as described in claim 1 wherein additional sulfur polymer cement is added in step (b). claim 1 3. A process as described in claim 2 wherein the additional sulfur polymer cement is added in an amount to form a waste loading of about 5 to about 90 wt % waste in the final waste form. claim 2 4. A process as described in claim 2 wherein mercury containing waste is essentially mercury and the additional sulfur polymer cement is added in an amount to form a waste loading of about 25 wt % to about 80 wt % waste in the final waste form. claim 2 5. A process as described in claim 4 wherein the additional sulfur polymer cement is added in an amount to form a waste loading of about 50 wt % to about 70 wt % in the final waste form. claim 4 6. A process as described in claim 2 wherein mercury containing waste is essentially mercury contaminated bulk material or debris and the additional sulfur polymer cement is added in an amount to form a waste loading of about 10 wt % to about 50 wt % waste in the final waste form. claim 2 7. A process as described in claim 6 wherein the additional sulfur polymer cement is added in an amount to form a waste loading of about 30 wt % to about 35 wt % in the final waste form. claim 6 8. A process as described in claim 1 wherein said mercury containing waste contains radionuclides. claim 1 9. A process as described in claim 1 wherein the inert atmosphere is argon or nitrogen. claim 1 10. A process as described in claim 1 wherein the sulfur polymer cement and mercury containing waste in step (a) are combined in a weight ratio of about 0.2-3.0. claim 1 11. A process as described in claim 10 wherein the sulfur polymer cement and mercury containing waste in step (a) are combined in a weight ratio of about 1.0. claim 10 12. A process as described in claim 1 wherein the sulfur polymer cement is reduced to a particle size less than about 3000 microns before being added in step (a). claim 1 13. A process as described in claim 1 further comprising adding a stabilizing additive where the stabilizing additive is added to the mercury containing waste and the sulfur polymer cement in step (a). claim 1 14. A process as described in claim 10 wherein the stabilizing additive is selected from the group consisting of sodium sulfide, triisobutyl phosphine sulfide, calcium hydroxide, sodium hydroxide, calcium oxide, magnesium oxide, and a combination thereof. claim 10 15. A process as described in claim 13 wherein the stabilizing additive is selected from the group consisting of sodium sulfide, triisobutyl phosphine sulfide and a combination thereof. claim 13 16. A process as described in claim 15 wherein the sodium sulfide is added in an amount from about 2.0 wt % to about 3.0 wt % of the final waste form. claim 15 17. A process as described in claim 13 wherein the stabilizing additive has been reduced to a particle size of less than about 3000 microns. claim 13 18. A process as described in claim 13 wherein the stabilizing additive is added in an amount of from about 0.5 wt % to about 20 wt % of the final waste form. claim 13 19. A process as described in claim 18 wherein the stabilizing additive is added in an amount from about 1.0 wt % to about 12 wt % of the final waste form. claim 18 20. A process as described in claim 19 wherein the stabilizing additive is added in an amount from about 2.0 wt % to about 5.0 wt % of the final waste form. claim 19
	abstract	A neutron beam regulator has a magnetic coil configured around a neutron beam between the neutron beam source and a target. The magnetic coil may be used to contain the neutron beam and reduce the scattering of neutron. Neutrons have a magnetic moment and can be affected by exposure to magnetics fields. The magnetic coil may be used to modulate the neutron beam shape, intensity, velocity, direction and polarization. A magnetic coil may extend substantially the entire distance between a neutron beam source and a target. A magnetic coil may be a discrete magnetic coil having a separate power input and output from other magnetic coils and a plurality of discrete magnetic coils may be configured around the neutron beam. A magnetic coil may be a spiral magnetic coil and may be continuous, or extends substantially from the neutron beam source to the target.
	description	This application claims the benefit of U.S. Provisional Application No. 61/625,764 filed Apr. 18, 2012 and titled “UPPER INTERNALS”. U.S. Provisional Application No. 61/625,764 filed Apr. 18, 2012 titled “UPPER INTERNALS” is hereby incorporated by reference in its entirety into the specification of this application. This application claims the benefit of U.S. Provisional Application No. 61/625,261 filed Apr. 17, 2012 and titled “LOWER HANGER PLATE”. U.S. Provisional Application No. 61/625,261 filed Apr. 17, 2012 titled “LOWER HANGER PLATE” is hereby incorporated by reference in its entirety into the specification of this application. The following relates to the nuclear reactor arts and related arts. There is increasing interest in compact reactor designs. Benefits include: reduced likelihood and severity of abnormal events such as loss of a coolant accident (LOCA) event (both due to a reduction in vessel penetrations and the use of a smaller containment structure commensurate with the size of the compact reactor); a smaller and more readily secured nuclear reactor island (see Noel, “Nuclear Power Facility”, U.S. Pub. No. 2010/0207261 A1 published Aug. 16, 2012 which is incorporated herein by reference in its entirety); increased ability to employ nuclear power to supply smaller power grids, e.g. using a 300 MWe or smaller compact reactor, sometimes referred to as a small modular reactor (SMR); scalability as one or more SMR units can be deployed depending upon the requisite power level; and so forth. Some compact reactor designs are disclosed, for example, in Thome et al., “Integral Helical-Coil Pressurized Water Nuclear Reactor”, U.S. Pub. No. 2010/0316181 A1 published Dec. 16, 2010 which is incorporated by reference in its entirety; Malloy et al., “Compact Nuclear Reactor”, U.S. Pub. No. 2012/0076254 A1 published Mar. 29, 2012 which is incorporated by reference in its entirety. These compact reactors are of the pressurized water reactor (PWR) type in which a nuclear reactor core is immersed in primary coolant water at or near the bottom of a pressure vessel, and the primary coolant is suitably light water maintained in a subcooled liquid phase in a cylindrical pressure vessel that is mounted generally upright (that is, with its cylinder axis oriented vertically). A hollow cylindrical central riser is disposed concentrically inside the pressure vessel and (together with the core basket or shroud) defines a primary coolant circuit in which coolant flows upward through the reactor core and central riser, discharges from the top of the central riser, and reverses direction to flow downward back to below the reactor core through a downcomer annulus defined between the pressure vessel and the central riser. The nuclear core is built up from multiple fuel assemblies each comprising a bundle of fuel rods containing fissile material (typically 235U). The compact reactors disclosed in Thome et al. and Malloy et al. are integral PWR designs in which the steam generator(s) is disposed inside the pressure vessel, namely in the downcomer annulus in these designs. Integral PWR designs eliminate the external primary coolant loop carrying radioactive primary coolant. The designs disclosed in Thome et al. and Malloy et al. employ internal reactor coolant pumps (RCPs), but use of external RCPs (e.g. with a dry stator and wet rotor/impeller assembly, or with a dry stator and dry rotor coupled with a rotor via a suitable mechanical vessel penetration) is also contemplated (as is a natural circulation variant that does not employ RCPs). The designs disclosed in Thome et al. and Malloy et al. further employ internal pressurizers in which a steam bubble at the top of the pressure vessel is buffered from the remainder of the pressure vessel by a baffle plate or the like, and heaters, spargers, or so forth enable adjustment of the temperature (and hence pressure) of the steam bubble. The internal pressurizer avoids large diameter piping that would otherwise connect with an external pressurizer. In a typical PWR design, upper internals located above the reactor core include control rod assemblies with neutron-absorbing control rods that are inserted into/raised out of the reactor core by control rod drive mechanisms (CRDMs). These upper internals include control rod assemblies (CRAs) comprising neutron-absorbing control rods yoked together by a spider. Conventionally, the CRDMs employ motors mounted on tubular pressure boundary extensions extending above the pressure vessel, which are connected with the CRAs via suitable connecting rods. In this design, the complex motor stator can be outside the pressure boundary and magnetically coupled with the motor rotor disposed inside the tubular pressure boundary extension. The upper internals also include guide frames constructed as plates held together by tie rods, with passages sized to cam against and guide the translating CRA's. For compact reactor designs, it is contemplated to replace the external CRDM motors with wholly internal CRDM motors. See Stambaugh et al., “Control Rod Drive Mechanism for Nuclear Reactor”, U.S. Pub. No. 2010/0316177 A1 published Dec. 16, 2010 which is incorporated herein by reference in its entirety; and DeSantis, “Control Rod Drive Mechanism for Nuclear Reactor”, U.S. Pub. No. 2011/0222640 A1 published Sep. 15, 2011 which is incorporated herein by reference in its entirety. Advantageously, only electrical vessel penetrations are needed to power the internal CRDM motors. In some embodiments, the scram latch is hydraulically driven, so that the internal CRDM also requires hydraulic vessel penetrations, but these are of small diameter and carry primary coolant water as the hydraulic working fluid. The use of internal CRDM motors shortens the connecting rods, which reduces the overall weight, which in turn reduces the gravitational impetus for scram. To counteract this effect, some designs employ a yoke that is weighted as compared with a conventional spider, and/or may employ a weighted connecting rod. See Shargots et al., “Terminal Elements for Coupling Connecting Rods and Control Rod Assemblies for a Nuclear Reactor”, U.S. Pub. No. 2012/0051482 A1 published Mar. 1, 2012 which is incorporated herein by reference in its entirety. Another design improvement is to replace the conventional guide frames which employ spaced apart guide plates held together by tie rods with a continuous columnar guide frame that provides continuous guidance to the translating CRA's. See Shargots et al, “Support Structure for a Control Rod Assembly of a Nuclear Reactor”, U.S. Pub. No. 2012/0099691 A1 published Apr. 26, 2012 which is incorporated herein by reference in its entirety. The use of internal CRDMs and/or continuous guide frames and/or internal RCPs introduces substantial volume, weight, and complexity to the upper internals. These internals are “upper” internals in that they are located above the reactor core, and they must be removed prior to reactor refueling in order to provide access to the reactor core. In principle, some components (especially the internal RCPs) can be located below the reactor core, but this would introduce vessel penetrations below the reactor core which is undesirable since a LOCA at such low vessel penetrations can drain the primary coolant to a level below the top of the reactor core, thus exposing the fuel rods. Another option is to employ external RCPs, but this still leaves the complex internal CRDMs and guide frames. Disclosed herein are improvements that provide various benefits that will become apparent to the skilled artisan upon reading the following. In one disclosed aspect, an apparatus comprises: a pressure vessel comprising an upper vessel section and a lower vessel section; a nuclear reactor core comprising fissile material contained in a containing structure and disposed in the lower vessel section; and upper internals disposed in the lower vessel section above the nuclear reactor core. The upper internals include at least guide frames and internal control rod drive mechanisms (CRDMs) with CRDM motors mounted on a suspended support assembly including a plurality of hanger plates connected by tie rods. The plurality of hanger plates includes a lowermost hanger plate having alignment features configured to align the upper internals with the containing structure that contains the nuclear reactor core. In another disclosed aspect, a method is performed in conjunction with a nuclear reactor including a pressure vessel with upper and lower vessel sections, a nuclear reactor core comprising fissile material contained in a containing structure and disposed the lower vessel section, and upper internals disposed in the lower vessel section that include at least guide frames and internal control rod drive mechanisms (CRDMs) with CRDM motors mounted on a suspended support assembly including a plurality of hanger plates connected by tie rods. The method comprises inserting the upper internals into the lower vessel section and, during the inserting, aligning the upper internals with the nuclear reactor core by engaging alignment features of a lowermost hanger plate of the suspended support assembly with the containing structure that contains the nuclear reactor core. In another disclosed aspect, an apparatus comprises: a pressure vessel comprising an upper vessel section and a lower vessel section; a nuclear reactor core comprising fissile material contained in a containing structure and disposed the lower vessel section; and upper internals disposed in the lower vessel section, the upper internals including at least guide frames and internal control rod drive mechanisms (CRDMs) with CRDM motors mounted on a suspended support assembly including a plurality of hanger plates connected by tie rods, the plurality of hanger plates including a lowermost hanger plate engaging bottoms of the guide frames. With reference to FIG. 1, a small modular reactor (SMR) 1 of the of the integral pressurized water reactor (PWR) variety is shown in partial cutaway to reveal selected internal components. The illustrative PWR 1 includes a nuclear reactor core 2 disposed in a pressure vessel comprising a lower vessel portion 3 and an upper vessel portion 4. The lower and upper vessel portions 3, 4 are connected by a mid-flange 5. Specifically, a lower flange 5L at the open top of the lower vessel portion 3 connects with the bottom of the mid-flange 5, and an upper flange 5U at the open bottom of the upper vessel portion 4 connects with a top of the mid-flange 5. The reactor core 2 is disposed inside and at or near the bottom of the lower vessel portion 3, and comprises a fissile material (e.g., 235U) immersed in primary coolant water. A cylindrical central riser 6 is disposed coaxially inside the cylindrical pressure vessel and a downcomer annulus 7 is defined between the central riser 6 and the pressure vessel. The illustrative PWR 1 includes internal control rod drive mechanisms (internal CRDMs) 8 with internal motors 8m immersed in primary coolant that control insertion of control rods to control reactivity. Guide frames 9 guide the translating control rod assembly (e.g., each including a set of control rods comprising neutron absorbing material yoked together by a spider and connected via a connecting rod with the CRDM). The illustrative PWR 1 employs one or more internal steam generators 10 located inside the pressure vessel and secured to the upper vessel portion 4, but embodiments with the steam generators located outside the pressure vessel (i.e., a PWR with external steam generators) are also contemplated. The illustrative steam generator 10 is of the once-through straight-tube type with internal economizer, and is fed by a feedwater inlet 11 and deliver steam to a steam outlet 12. See Malloy et al., U.S. Pub. No. 2012/0076254 A1 published Mar. 29, 2012 which is incorporated by reference in its entirety. The illustrative PWR 1 includes an integral pressurizer 14 at the top of the upper vessel section 4 which defines an integral pressurizer volume 15; however an external pressurizer connected with the pressure vessel via suitable piping is also contemplated. The primary coolant in the illustrative PWR 1 is circulated by reactor coolant pumps (RCPs) comprising in the illustrative example external RCP motors 16 driving an impeller located in a RCP plenum 17 disposed inside the pressure vessel. With reference to FIGS. 2 and 3, a variant PWR design 1′ is shown, which differs from the PWR 1 of FIG. 1 by having a differently shaped upper vessel section 4′ and internal RCPs 16′ in place of the external pumps 16, 17 of the PWR 1. FIG. 2 shows the pressure vessel with the upper vessel section 4′ lifted off, as is done during refueling. The mid-flange 5 remains disposed on the lower flange 5L of the lower vessel 3. FIG. 3 shows an exploded view of the lower vessel section 3 and principle components contained therein, including: the nuclear reactor core 2 comprising fuel assemblies 2′ contained in a core former 20 disposed in a core basket 22. With continuing reference to FIGS. 1 and 3 and with further reference to FIGS. 4 and 5, above the reactor core assembly 2, 20, 22 are the upper internals which include a suspended support assembly 24 comprising an upper hanger plate 30, a mid-hanger plate 32, and a lower hanger plate 34 suspended by tie rods 36 from the mid-flange 5. More particularly, in the illustrative embodiment the upper ends of the tie rods 36 are secured to a riser transition section 38 that is in turn secured with the mid-flange 5. The central riser 6 disposed in the upper vessel section 4, 4′ (shown only in FIG. 1) is connected with the core basket 22 in the lower vessel section 3 by the riser cone (not shown) and riser transition section 38 to form a continuous hollow cylindrical flow separator between the columnar hot leg of the primary coolant path flowing upward and the cold leg that flows through the downcomer annulus surrounding the hot leg. The suspended support assembly 24 comprising hanger plates 30, 32, 34 interconnected by tie rods 36 provides the structural support for the CRDMs 8 and the guide frames 9 (note the CRDMs 8 and guide frames 9 are omitted in FIG. 3). The CRDMs 8 are disposed between the upper hanger plate 30 and the mid-hanger plate 32, and are either (1) top-supported in a hanging fashion from the upper hanger plate or (2) bottom-supported on the mid-hanger plate 32 (as in the illustrative embodiments described herein). Lateral support for the CRDMs 8 is provided by both plates 30, 32. (Note that in the illustrative embodiment, the CRDMs 8 actually pass through openings of the upper hanger plate 30 so that the tops of the CRDMs 8 actually extend above the upper hanger plate 30, as best seen in FIG. 1). The guide frames 9 are disposed between the mid-hanger plate 32 and the lower hanger plate 34, and are likewise either (1) top-supported in a hanging fashion from the mid-hanger plate 32 (as in the illustrative embodiments described herein) or (2) bottom-supported on the lower hanger plate. Lateral support for the guide frames 9 is provided by both plates 32, 34. One of the hanger plates, namely the mid-hanger plate 32 in the illustrative embodiments, also includes or supports a distribution plate that includes mineral insulated cabling (MI cables) for delivering electrical power to the CRDM motors 8M and, in some embodiments, hydraulic lines for delivering hydraulic power to scram latches of the CRDMs 8. In the embodiment of FIGS. 2 and 3 (and as seen in FIG. 3), the internal RCPs 16′ are also integrated into the upper internals assembly 24, for example on an annular pump plate providing both separation between the suction (above) and discharge (below) sides of the RCPs 16′ and also mounting supports for the RCPs 16′. The disclosed upper internals have numerous advantages. The suspension frame 24 hanging from the mid-flange 5 is a self-contained structure that can be lifted out of the lower vessel section 3 as a unit during refueling. Therefore, the complex assembly of CRDMs 8, guide frames 9, and ancillary MI cabling (and optional hydraulic lines) does not need to be disassembled during reactor refueling. Moreover, by lifting the assembly 5, 24, 8, 9 out of the lower vessel 3 as a unit (e.g. using a crane) and moving it to a suitable work stand, maintenance can be performed on the components 5, 24, 8, 9 simultaneously with the refueling, thus enhancing efficiency and speed of the refueling. The tensile forces in the tie rods 36 naturally tend to laterally align the hanger plates 30, 32, 34 and thus the mounted CRDMs 8 and guide frames 9. The upper internals are thus a removable internal structure that is removed as a unit for reactor refueling. The upper internals basket (i.e., the suspension frame 24) is advantageously flexible to allow for movement during fit-up when lowering the upper internals into position within the reactor. Toward this end, the horizontal plates 30, 32, 34 are positioned at varying elevations and are connected to each other, and the remainder of the upper internals, via the tie rods 36. The design of the illustrative upper internals basket 24 is such that the control rod guide frames 9 are hung from the mid-hanger plate 32 (although in an alternative embodiment the guide frames are bottom-supported by the lower hanger plate). In the top-supported hanging arrangement, the guide frames 9 are laterally supported at the bottom by the lower hanger plate 34. The upper internals are aligned with the core former 20 and/or core basket 22 to ensure proper fit-up of the fuel to guide frame interface. This alignment is achieved by keying features of the lower hanger plate 34. With reference to FIGS. 6 and 7, alternative perspective views are shown of the hanger plates 30, 32, 34 connected by tie rods 36 and with the guide frames 9 installed, but omitting the CRDMs 8 so as to reveal the top surface of the mid-hanger plate 32. In the illustrative embodiment, a distribution plate 40 is disposed on top of the mid-hanger plate 32, as best seen in FIG. 6. The distribution plate 40 is a load-transferring element that transfers (but does not itself support) the weight of the bottom-supported CRDMs 8 to the mid-hanger plate 32. This is merely an illustrative example, and the distribution plate can alternatively be integral with the mid-hanger plate (e.g., comprising MI cables embedded in the mid-hanger plate) or located on or in the upper hanger plate. (Placement of the distribution plate in the lower hanger plate is also contemplated, but in that case MI cables would need to run from the distribution plate along the outsides of the guide frames to the CRDMs. As yet another option, the distribution plate can be omitted entirely in favor of discrete MI cables run individually to the CRDMs 8). With reference to FIG. 8, which shows a corner of the upper hanger plate 30 as an illustrative example, the tie rods 36 are coupled to each plate by tie rod couplings 42, which optionally incorporate a turnbuckle (i.e. length adjusting) arrangement as described elsewhere herein. Note that the ends of the tie rods connect with a hanger plate, with no hanger plate connecting at a middle of a tie rod. Thus, the upper tie rods 36 extend between the upper and mid-hanger plates 30, 32 with their upper ends terminating at tie rod couplings 42 at the upper hanger plate 30 and their lower ends terminating at tie rod couplings 42 at the mid-hanger plate 32; and similarly, the lower tie rods 36 extend between the mid-hanger plate 32 and the lower hanger plate 34 with their upper ends terminating at tie rod couplings 42 at the mid-hanger plate 32 and their lower ends terminating at tie rod couplings 42 at the lower hanger plate 34. With reference to FIGS. 9 and 10, the lower hanger plate 34 in the illustrative embodiment provides only lateral support for the guide frames 9 which are top-supported in hanging fashion from the mid-hanger plate 32. Consequentially, the lower hanger plate 34 is suitably a single plate with openings 50 that mate with the bottom ends of the guide frames (see FIG. 10). To simplify the alignment, in some embodiments guide frame bottom cards 52 (see FIG. 9) are inserted into the openings 50 and are connected with the bottom ends of the guide frames 9 by fasteners, welding, or another technique. (Alternatively, the ends of the guide frames may directly engage the openings 50 of the lower hanger plate 34). In addition to providing lateral support for each control rod guide frame 9, locking each in laterally with a honeycomb-type structure (see FIG. 10), the lower hanger plate 34 also includes alignment features 54 (see FIG. 10) that align the upper internals with the core former 20 or with the core basket 22. The illustrative alignment features are peripheral notches 54 that engage protrusions (not shown) on the core former 20; however, other alignment features can be employed (e.g., the lower hanger plate can include protrusions that mate with notches of the core former). Also seen in FIG. 10 are peripheral openings 56 in the lower hanger plate 34 into which the tie rod couples 42 of the lower hanger plate fit. The lower hanger plate 34 is suitably machined out of plate material or forging material. For example, in one contemplated embodiment the lower hanger plate 34 is machined from 304L steel plate stock. With continuing reference to FIGS. 6 and 7 and with further reference to FIG. 11, the mid-hanger plate 32 provides top support for the guide frames 9 and bottom support for the CRDMs 8. The mid-hanger plate 32 acts as a load distributing plate taking the combined weight of the CRDMs 8 and the guide frames 9 and transferring that weight out to the tie rods 36 on the periphery of the upper internals basket 24. In the illustrative embodiment, the power distribution plate 40 is also bottom supported. Like the lower hanger plate 34, the mid-hanger plate 32 includes openings 60. The purpose of the openings 60 is to enable the connecting rod, translating screw, or other coupling mechanism to connect each CRDM 8 with the control rod assembly driven by the CRDM. To facilitate hanging the guide frames 9 off the bottom of the mid-hanger plate 32, an egg crate-type structure made of orthogonally intersecting elements 61 is provided for increased strength and reduced deflection due to large loads. With reference to FIGS. 12 and 13, the mid-hanger plate 32 can be manufactured in various ways. In one approach (FIG. 12), a forging machining process is employed to machine the mid-hanger plate 32 out of a 304L steel forged plate 62. The machining forms the openings 60 and the intersecting elements 61. In another approach (FIG. 13), a machined plate 64 and the intersecting elements 61 are manufactured as separate components, and the intersecting elements 61 are interlocked using mating slits formed into the intersecting elements 61 and welded to each other and to the machined plate 64 to form the mid-hanger plate 32. As previously noted, the illustrative bottom-supported distribution plate 40 can alternatively be integrally formed into the mid-hanger plate. With reference to FIG. 14, in an alternative embodiment the guide frames 9 are bottom supported by an alternative lower hanger plate 34′, and are laterally aligned at top by an alternative mid-hanger plate 32′. In this case the alternative lower hanger plate 34′ may have the same form and construction as the main embodiment mid-hanger plate 32 of FIGS. 11-13 (but with suitable alignment features to align with the core former and/or core basket, not shown in FIG. 14), and the alternative mid-hanger plate 32′ can have the same form and construction as the main embodiment lower hanger plate 34 of FIG. 10 (but without said alignment features). If the CRDMs remain bottom supported, then the alternative mid-hanger plate 32′ should be made sufficiently thick (or otherwise sufficiently strong) to support the weight of the CRDMs. As another variant, the alternative mid-hanger plate 32′ can be made too thin to directly support the CRDMs, and an additional thicker upper plate added to support the weight of the CRDMs. In this case the thicker plate would be the one connected with the tie rods to support the CRDMs. In the illustrative embodiments, the guide frames 9 are continuous columnar guide frames 9 that provide continuous guidance to the translating control rod assemblies. See Shargots et al, “Support Structure for a Control Rod Assembly of a Nuclear Reactor”, U.S. Pub. No. 2012/0099691 A1 published Apr. 26, 2012 which is incorporated herein by reference in its entirety. However, the described suspended frame 24 operates equally well to support more conventional guide frames comprising discrete plates held together by tie rods. Indeed, the main illustrative approach in which the guide frames are top-supported in hanging fashion from the mid-hanger plate 32 is particularly well-suited to supporting conventional guide frames, as the hanging arrangement tends to self-align the guide frame plates. With reference to FIG. 15, an illustrative embodiment of the upper hanger plate 30 is shown. Like the other hanger plates 32, 34, the upper hanger plate 30 includes openings 70, in this case serving as passages through which the upper ends of the CRDMs 8 pass. The inner periphery of each opening 70 serves as a cam to laterally support and align the upper end of the CRDM 8. The upper hanger plate 30 can also suitably be made by machining from either plate material or forging material, e.g. a 304L steel plate stock or forging. With reference to FIGS. 16-18, the tie bar (alternatively “tie rod”) couplings 42 are further described. FIG. 16 shows the suspended frame 24 including the upper, mid-, and lower hanger plates 30, 32, 34 held together by tie rods 36. For clarity, the tie bars are denoted in FIG. 16 as upper tie bars 361 and lower tie bars 362, and the various levels of tie bar couples are denoted as upper tie bar couples 421, middle tie bar couples 422, and lower tie bar couples 423. At the upper end, short tie rods (i.e. tie rod bosses) 36B have upper ends welded to the riser transition 38 and have lower ends threaded into the tops of upper tie bar couplings 421. The upper tie bars 361 have their upper ends threaded into the bottoms of upper tie bar couplings 421 and have their lower ends threaded into the tops of middle tie bar couplings 422. The lower tie bars 362 have their upper ends threaded into the bottoms of middle tie bar couplings 422 and have their lower ends threaded into the tops of lower tie bar couplings 423. FIGS. 17 and 18 show perspective and sectional perspective views, respectively, of the middle tie bar coupling 422. As best seen in FIG. 18, the tie rod coupling 422 has a turnbuckle (i.e. length adjusting) configuration including outer sleeves 81, 82 having threaded inner diameters that engage (1) the threaded outsides of the ends of the respective mating tie rods 361, 362, and (2) the threaded outsides of a plate thread feature 84. Thus, by rotating the outer sleeve 81 the position of tie rod 361 respective to the mid-hanger plate 32 can be adjusted; and similarly, by rotating the outer sleeve 82 the position of tie rod 362 respective to the mid-hanger plate 32 can be adjusted. (Note that the plate thread feature 84 can be a single element passing through the mid-hanger plate 32, or alternatively can be upper and lower elements extending above and below the mid-hanger plate 32, respectively). The tie bar coupling 421 is the same as tie bar coupling 422 except that the upper outer sleeve 81 suitably engages the tie rod boss 36B; while, the tie bar coupling 42 is the same as tie bar coupling 422 but omits the lower half (i.e. lower outer sleeve 82 and the corresponding portion of the plate thread feature 84), since there is no tie rod “below” for the tie bar coupling 423 to engage. Said another way, the tie rod coupling portions 81, 82 can be threaded on their inner diameter with threads matching that of the outer diameter of the tie rods 36 and on the threading feature 84 of any of the plates 30, 32, 34 or riser transition 38. This allows the coupling 42 to be threaded onto the tie rod 36 and onto the threading feature 84 of any other component. The advantages to a coupling such as this is that a very accurate elevation can be held with each of the above mentioned components 30, 32, 34, 38 within the upper internals, and that each of the above components can hold a very accurate parallelism with one another. Essentially, the couplings allow for very fine adjustments during the final assembly process. They also allow for a quick and easy assembly process. Another advantage to the couplings 42 is that they allow for the upper internals to be separated at the coupling joints fairly easily for field servicing or decommissioning of the nuclear power plant. In an alternative tie rod coupling approach, it is contemplated for the tie rods to be directly welded to any of the plates or riser transition, in which case the tie rod couplings 42 would be suitably omitted. However, this approach makes it difficult to keep the tie rod perpendicular to the plates making assembly of the upper internals more difficult. It also makes breaking the upper internals down in the field more difficult. With reference to FIG. 19, the riser transition 38 is shown in perspective view. The riser transition assembly 38 performs several functions. The riser transition 38 provides load transfer from the tie rods 36 of the upper internals basket 24 to the mid-flange 5 of the reactor pressure vessel. Toward this end, the riser transition 38 includes gussets 90 by which the riser transition 38 is welded to the mid-flange 5. (See also FIGS. 4 and 5 showing the riser transition 38 with gussets 90 welded to the mid-flange 5). One or more of these gussets 90 may include a shop lifting lug 91 or other fastening point to facilitate transport, for example when the upper internals are lifted out during refueling. The load transfer from the tie rods 36 to the mid-flange 5 is mostly vertical loading due to the overall weight of the upper internals. However, there is also some radial differential of thermal expansion between the riser transition gussets 90 and the mid-flange 5, and the riser transition 38 has to also absorb these thermal loads. As already mentioned, the riser cone and riser transition 38 also acts (in conjunction with the central riser 6 and core basket 22) as the flow divider between the hot leg and cold leg of the primary coolant loop. Still further, the riser transition 38 also houses or includes an annular hydraulic collection header 92 for supplying hydraulic power via vertical hydraulic lines 94 to the CRDMs (in the case of embodiments employing hydraulically driven scram mechanisms). The riser transition 38 also has an annular interface feature 96 for fit-up with the riser cone or other connection with the central riser 6, and feature cuts 98 to allow the passing of the CRDM electrical MI cable. With brief returning reference to FIGS. 4 and 5, the gussets 90 are suitably welded to the mid-flange 5 at one end and welded to the main body portion of the riser transition assembly 38 at the other end. The riser transition 38 is suitably made of 304L steel, in some embodiments, e.g. by machining from a ring forging. With reference to FIG. 20, an illustrative gusset 90 is shown, having a first end 100 that is welded to the mid-flange 5 and a second end 102 that is welded to the riser transition 38 as already described. The gusset 90 includes horizontal cantilevered portion 104, and a tensile-strained portion 106 that angles generally downward, but optionally with an angle A indicated in FIG. 20. The horizontal cantilevered portion 104 has a thickness dcant that is relatively greater than a thickness dG of the tensile-strained portion 106. The thicker cantilevered portion 104 handles the vertical loading component, while the tensile-strained portion 106 allows the gusset 90 to deflect in the lateral direction to absorb lateral loading due to thermal expansion. The angle A of the tensile-strained portion 106 provides for riser cone lead-in. The end 102 of the gusset 90 that is welded to the riser transition 38 includes an upper ledge 108 that serves as a riser cone interface. In the illustrative embodiments, the CRDMs 8 are bottom supported from the mid-hanger plate 32, and the tops of the CRDMs 8 are supported by the upper hanger plate 30, which serves as the lateral support for each CRDM, locking each in laterally with a honeycomb type structure (see FIG. 15). Even with this support structure, however, the CRDM 8 should be protected during an Operating Basis Earthquake (OBE) or other event that may cause mechanical agitation. To achieve this, it is desired to support the upper end of the CRDM to prevent excessive lateral motion and consequently excessive loads during an OBE. It is disclosed to employ a restraining device which still allows for ease of maintenance during an outage. Using spring blocks integrated into the CRDM 8 satisfies both of these requirements, as well as providing compliance that accommodates any differential thermal expansion. Integrating compliance features into support straps of the CRDM 8 allows the CRDM's to be removed while still maintaining lateral support. As the CRDM is lowered into its mounting location the compliant features come into contact with the upper hanger plate 30. The compliance allows them to maintain contact with the upper hanger plate yet allow for misalignment between the CRDM standoff mounting point and the upper hanger plate. Their engagement into the upper hanger plate 30 allows them to be of sufficient height vertically from the mounting base of the CRDMs to minimize the loads experienced at the base in an OBE event. Having no feature that extends below the upper hanger plate allows the CRDM to be removed from the top for service. With reference to FIGS. 21 and 22, an upper end of a CRDM 8 includes a hydraulic line 110 delivering hydraulic power to a scram mechanism. Straps 112, 114 secure the hydraulic line 110 to the CRDM 8. The strap 114 is modified to include compliance features 116. As seen in FIG. 22, the compliance features 116 comprise angled spring blocks that wedges into the opening 70 of the upper hanger plate 30 when the CRDM 8 is fully inserted. It will be appreciated that such compliance features 116 can be incorporated into straps retaining other elements, such as electrical cables (e.g. MI cables). The illustrative compliance features 116 can be constructed as angled leaf springs cut into the (modified) strap 114. Alternatively, such leaf springs can be additional elements welded onto angled ends of the strap 114. By including such springs on straps 114 on opposite sides of the CRDM 8, four contact points are provided to secure the CRDM against lateral motion in any direction. The wedged support provided by the straps 114 also leave substantial room for coolant flow through the opening 70 in the upper hanger plate 30. The disclosed embodiments are merely illustrative examples, and numerous variants are contemplated. For example, the suspended frame of the upper internals can include more than three plates, e.g. the power distribution plate could be a separate fourth plate. In another variant, the mid-hanger plate 32 could be separated into two separate hanger plates—an upper mid-hanger plate bottom-supporting the CRDMs, and a lower mid-hanger plate from which the guide frames are suspended. In such a case, the two mid-hanger plates would need to be aligned by suitable alignment features to ensure relative alignment between the CRDMs and the guide frames. The use of at least three hanger plates is advantageous because it provides both top and bottom lateral support for both the CRDMs and the guide frames. However, it is contemplated to employ only two hanger plates if, for example, the bottom support of the CRDMs is sufficient to prevent lateral movement of the CRDMs. In the illustrative embodiments, the suspended support assembly 24 is suspended from the mid-flange 5 via the riser transition 38. However, other anchor arrangements are contemplated. For example, the suspended support assembly could be suspended directly from the mid-flange, with the riser transition being an insert secured to the gussets. The mid-flange 5 could also be omitted. One way to implement such a variant is to include a ledge in the lower vessel on which a support ring sits, and the suspended support assembly is then suspended from the support ring. With the mid-flange 5 omitted, the upper and lower flanges 5U, 5L of the upper and lower vessel sections can suitably connect directly (i.e., without an intervening mid-flange). Instead of lifting the upper internals out by the mid-flange 5, the upper internals would be lifted out by the support ring. In the embodiment of FIGS. 2 and 3, the internal RCPs 16′ are incorporated into the upper internals and are lifted out with the upper internals. Other configurations are also contemplated—for example, internal RCPs could be mounted in the upper vessel and removed with the upper vessel. The preferred embodiments have been illustrated and described. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the invention be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.
	description	The present application is based on and claims priority to Japanese Patent Application No. 2008-132479 and 2008-212787 filed on May 20, 2008, and Aug. 21, 2008, the contents of which are incorporated in their entirety herein by reference. This application is also related to U.S. application Ser. No. 12/469,176, entitled “SEMICONDUCTOR EXPOSURE DEVICE USING EXTREME ULTRA VIOLET RADIATION,” filed simultaneously on May 20, 2009 with the present application. The present invention relates to a mirror for reflecting extreme ultra violet, to a method for manufacturing a mirror for extreme ultra violet, and to a far ultraviolet light source device which incorporates a mirror for extreme ultra violet. For example, a semiconductor chip may be created by projecting a mask upon which a circuit pattern is drawn, in reduced form, upon a wafer to which a resist has been applied, and by repeatedly performing processing such as etching and thin layer formation and so on. Along with the progressive reduction of the scale of semiconductor processing, the use of radiation of progressively shorter and shorter wavelengths is required. Thus, research is being performed into a semiconductor exposure technique which uses radiation of extremely short wavelength, such as 13.5 nm, and a reducing optical system. This type of technique is termed EUV-L (Extreme Ultra Violet Lithography: exposure using extreme ultra violet). Hereinafter, extreme ultraviolet will be abbreviated as “EUV”. Three types of EUV light sources are known: an LPP (Laser Produced Plasma: plasma produced by a laser) type light source; a DPP (Discharge Produced Plasma: plasma produced by a discharge) type light source; and an SR (Synchrotron Radiation) type light source. An LPP type light source is a light source which generates a plasma by irradiating laser radiation upon a target material, and which employs EUV radiation emitted from this plasma. A DPP type light source is a light source which employs a plasma generated by an electrical discharge. And a SR type light source is a light source which employs radiation emitted from tracks in a synchrotron. Among these three types of light source, there are better possibilities for obtaining EUV radiation of high output with an LPP type light source as compared to the other methods, since such a light source can provide increased plasma density, and since moreover the solid angle over which the radiation is collected can be made large. Since EUV radiation has a very short wavelength and can easily be absorbed by matter, accordingly the EUV-L technique uses a reflection type optical system. Such a reflection type optical system may be built by employing multi layers in which, for example, molybdenum (Mo) and silicon (Si) are used. Since the reflectivity of such an Mo/Si composite layer is high in the vicinity of 13.5 nm, accordingly EUV radiation of 13.5 nm wavelength is used in the EUV-L process. However, since the reflectivity of such a composite layer is around 70%, therefore the output gradually decreases as the number of reflections increases. Since the EUV radiation is reflected ten times or more within the exposure device, accordingly it is necessary for the EUV light source device to supply EUV radiation to the exposure device at rather high output. Thus, it is expected that the use of LPP type light sources as EUV light source devices will become more common (refer to Patent Reference #1). Moreover, the EUV light source device is required to supply EUV radiation of rather high purity to the exposure device. If radiation other than EUV radiation is mixed into the radiation which is supplied from the EUV light source device to the exposure device, then there is a possibility that the exposure contrast will be decreased, or that the accuracy of the patterning will be reduced. Thus, in the EUV-L process, in order to eliminate undesirable spectral components in the emitted radiation, a second prior art technique has been proposed (refer to Patent Reference #2) in which a spectrum purity filter (hereinafter termed a “SPF”) is employed. Although it is not explicitly so described in this second reference, the explanation herein will presume that this second prior art technique is applied to a LPP type light source device. In this case, liquid droplets of tin (Sn), for example, are supplied as targets within a vacuum chamber from a target supply device, these liquid droplets of tin are converted into plasma by being irradiated with radiation from a carbon dioxide gas laser, the radiation which is emitted from this plasma is collected by a collector mirror and is incident upon a reflective type planar diffraction lattice, and is converted into a spectrum by this planar diffraction lattice. Accordingly, in this second prior art technique, only the diffracted radiation in the EUV region centered around 13.5 nm is conducted to the exposure device. Now, the exposure resist which is used in the exposure device is photosensitive to radiation emitted from the plasma in the wavelength region from 130 nm (DUV: Deep Ultraviolet) to 400 nm (UV: Ultraviolet). Accordingly, if a substantial amount of radiation in the range of 130 nm˜400 nm is incident into the exposure device, this will cause deterioration of the exposure contrast. Moreover, if infrared radiation (IR: Infrared) is present in the radiation from the plasma, then this IR will be absorbed by optical components within the exposure device and by the mask and the wafer and so on and will cause thermal expansion, so that there is a possibility that the accuracy of the patterning will be decreased. In particular, in the case of an EUV light source device which uses a carbon dioxide gas pulse laser which emits infrared radiation of wavelength 10.6 μm (hereinafter termed a “CO2 laser”) as a light source for exciting a target consisting of tin, since some of the high output of CO2 laser radiation is scattered and reflected by the target, accordingly it is necessary to eliminate this scattered CO2 laser radiation with an SPF. For example, if the intensity of the EUV radiation centered around the wavelength of 13.5 nm is taken as unity, then it is necessary to keep down the intensity of the CO2 laser radiation included therein to 0.01 or less. Thus, in a second prior art technique, a reflective type planar diffraction lattice is provided which separates the EUV radiation from radiation of other wavelengths, and only the EUV radiation is supplied to the exposure device. The radiation of other wavelengths outside the EUV region is absorbed by a dumper which is provided in the neighborhood of the emission aperture, and is converted into thermal energy. Now, if a solid target such as a tin droplet is used, not all of the droplet target is excited into plasma by the CO2 laser; debris of diameter a few μm or greater is created. In other words, a portion of the target is not converted into plasma, but is expelled as waste. Thus, as shown in FIG. 1 of the second prior art technique detailed above, a thin filter is provided between the exposure device and the vacuum chamber, and thereby this debris is prevented from getting into the exposure device. By making this thin filter from a material such as zirconium (Zr) or silicon or the like whose transmittivity for EUV radiation is comparatively high, it is possible to endow the thin filter with the function of serving as an SPF. On the other hand, as shown in a third prior art document (refer to Patent Reference #3), in the case of an SPF which uses a reflective type diffraction lattice, it is necessary to provide blazed grooves in order to enhance the efficiency of diffraction of EUV radiation. However, since it is necessary to form extremely minute grooves whose heights are several tens of nanometers at a pitch of a few μm in order to eliminate aberration of the resulting diffracted EUV radiation, accordingly curved grooves are required whose pitch changes (refer to Non-Patent Reference #1). Thus, as described in a fourth prior art document (refer to Patent Reference #4), it is proposed to create a reflective type SPF by processing an Mo/Si composite layer which has been coated onto the front surface of a mirror into the shapes of blazed grooves. Patent Reference #1: Japanese Laid-Open Patent Publication 2006-80255. Patent Reference #2: U.S. Pat. No. 6,809,327. Patent Reference #3: U.S. Pat. No. 6,469,827. Patent Reference #4: U.S. Pat. No. 7,050,237. Non-Patent Reference: “EUV spectral purity filter: optical and mechanical design, grating fabrication, and testing”, H. Kierey et al., “Advances in Mirror Technology for X-Ray, EUV-Lithography, Laser and Other Applications”, edited by Ali M. Khounsary, Udo Dinnger, and Kazuya Ohta, Proceedings of SPIE, Vol. 5193. The following problems are present with the prior art techniques described above. The first such problem is that there are issues with the efficiency and the reliability of a thin layer type SPF. Since the transmittivity of the above thin layer type SPF which separates the exposure device from the EUV light source is as low as around 40%, the output efficiency for EUV radiation is decreased. Moreover, a thin layer type SPF can easily be damaged due to debris flying off and striking it. Furthermore, when a thin layer type SPF absorbs radiation of wavelengths other than that of EUV radiation so that its temperature becomes elevated, it may melt due to heat, which is undesirable. Thus, there are problems with a thin layer type SPF with regard to transmittivity to EUV radiation, and with regard to reliability and convenience of use. The second problem is that, with the fourth prior art technique described above in which the composite layer is subjected to blazing processing, it is necessary to superimpose a total of 2000 or more of the Mo/Si multi layers. In order reliably to separate the radiation into diffracted EUV radiation and regularly reflected radiation of other wavelengths, the blaze angle must be set to be large, and it becomes necessary to provide 2000 or more multi layers in order to increase the blaze angle in this manner. The third problem is that, both with a thin layer type SPF and with an SPF which uses a reflective type diffraction lattice, the diffraction efficiency and the transmittivity for EUV radiation is low, and around 30% of the output of the EUV light source is consumed uselessly in the SPF. The present invention has been conceived in view of the problems described above, and an objective thereof is to provide a mirror for extreme ultra violet, a manufacturing method for a mirror for extreme ultra violet, and a far ultraviolet light source device, which are capable of selecting only EUV radiation, without using any separate spectrum purity filter. Another objective of the present invention is to provide a mirror for extreme ultra violet, a manufacturing method for a mirror for extreme ultra violet, and a far ultraviolet light source device, which, by laminating together a plurality of regions in which the numbers and shapes of the multi layers are different, are capable of taking advantage of various different beneficial diffraction effects. Yet further objectives of the present invention will become clear from the subsequent description of certain embodiments thereof. In order to solve the problems described above, a mirror for extreme ultra violet according to a first aspect of the present invention comprises: a substrate portion; a foundation portion formed from a first composite layer which is provided on one side of the substrate portion; and a reflecting portion made by forming grooves of predetermined shapes in a second composite layer which is integrally provided on the other side of the foundation portion from the substrate portion. In a preferred embodiment, the reflecting portion may be formed so as to have a focal point, and so that extreme ultra violet reflected by the reflecting portion is gathered together at the focal point. In a preferred embodiment, a radiation shield member having an aperture portion for passing the extreme ultra violet may be provided in the neighborhood of the focal point. In a preferred embodiment, each of the first composite layer and the second composite layer may be formed integrally from a plurality of pair layers, with the thickness dimension of the plurality of pair layers which constitutes each of the first composite layer and the second composite layer being set according to the angle at which extreme ultra violet is incident thereupon. The grooves of predetermined shape may be made as blazed grooves. Or, the grooves of predetermined shape may be made as triangular roof-like grooves. Or, the grooves of predetermined shape may be made as undulating wave-like grooves. In a preferred embodiment, the grooves of predetermined shape may be provided as concentric circles or parallel lines. In a preferred embodiment, the total number of pair layers which constitute the combination of the first composite layer and the second composite layer is in the range from 100 to 1000. And, in order to solve the problems described above, in a method for manufacturing a mirror for extreme ultra violet according to a second aspect of the present invention, while rotating a substrate portion upon one surface of which is formed a composite layer consisting of a predetermined number of pair layers, portions of the composite layer are removed by irradiating a beam for processing upon the composite layer via a mask, so as to leave grooves of predetermined shapes. The beam for processing may be irradiated towards the composite layer while rotating the beam for processing around a predetermined rotational axis as a center. The predetermined rotational axis may correspond to a point at which plasma is generated. The reflecting portion may have a focal point; and the predetermined rotational axis may be set to correspond to the position of the focal point. And, in order to solve the problems described above, a source device for extreme ultra violet according to a third aspect of the present invention, which generates extreme ultra violet by irradiating laser radiation upon a target material and converting it to plasma, comprises: a first chamber to which a first exhaust pump is provided; a second chamber, connected to the first chamber, and to which a second exhaust pump is provided; a target material supply means which supplies the target material to within the first chamber; a laser light source which, by irradiating laser radiation upon the target material, converts the target material into plasma so that it emits extreme ultra violet; a mirror for extreme ultra violet which collects the extreme ultra violet emitted from the plasma by reflecting it towards a focal point which is provided within the second chamber; a radiation shield means which is provided in the neighborhood of the focal point, having an aperture portion which allows the passage of the extreme ultra violet, while attenuating electromagnetic waves of wavelength other than that of the extreme ultra violet with portions other than the aperture portion; and an interception valve which either communicates or intercepts an outlet portion at which the extreme ultra violet collected at the focal point is outputted; and the mirror for extreme ultra violet comprises: a substrate portion which is formed to be curved in at least one direction; a foundation portion formed from a first composite layer which is provided on one side of the substrate portion; and a reflecting portion made by forming grooves of predetermined shapes in a second composite layer which is integrally provided on the other side of the foundation portion from the substrate portion. The grooves of predetermined shapes may be blazed grooves, triangular roof-shaped grooves, or undulating wave-like grooves. Approximately at the position where the laser radiation reflected by the reflecting portion is focused, there may be provided an absorption means which absorbs this reflected laser radiation. There may also be included a plurality of magnetic field generation means, so that charged particles emitted from the plasma are captured by a magnetic field generated from the magnetic field generation means. In the following, various embodiments of the present invention will be described in detail with reference to the drawings. As explained subsequently, in these embodiments, a EUV collector mirror is shown as an example of a mirror which reflects EUV radiation. Moreover, in these embodiments, a reflective type diffraction lattice is provided internally to the EUV collector mirror, so that the collector mirror is endowed with both the function of focusing and also the function of serving as a SPF. Furthermore, in these embodiments, by providing grooves of predetermined shapes in the multi layers upon the collector mirror, it is possible to utilize three types of diffraction operation: Bragg reflection by the multi layers of the foundation portion and by the multi layers of the portion in which the grooves of predetermined shape are provided; diffraction due to the repeated pattern of the multi layers which emerges at the front surfaces of the grooves of predetermined shape; and diffraction due to the grooves of predetermined shape themselves. In these embodiments, as examples of these grooves of predetermined shapes, grooves shaped as blazed grooves, triangular roof-like grooves, and wave-like grooves will be explained. Embodiment 1 A first embodiment will now be explained on the basis of FIGS. 1 through 4. FIG. 1 is an explanatory figure showing a magnified view of an EUV collector mirror according to this first embodiment; FIG. 2 is an explanatory figure showing an EUV light source device which incorporates this EUV collector mirror 130; FIG. 3 is an explanatory sectional view showing a magnified view of blazed grooves of this EUV collector mirror 130; and FIG. 4 is a characteristic figure for the setting of Mo/Si pair layer thickness according to the angle of incidence of EUV radiation. First the structure of the EUV light source device 1 will be explained with reference to FIG. 2, and then the structure of the EUV collector mirror 130 will be explained with reference to FIG. 1 etc. The EUV light source device 1 shown in FIG. 2 comprises, for example, a vacuum chamber 100, a driver laser light source 110, a target supply device 120, the EUV collector mirror 130, coils for magnetic field generation 140 and 141, an SPF shield 150 having an aperture portion 151, dividing wall apertures 160 and 161, vacuum exhaust pumps 170 and 171, and a gate valve 180, each of which will be described hereinafter. The vacuum chamber 100 is made by connected together a first chamber 101 whose volume is relatively large, and a second chamber 102 whose volume is relatively small. The first chamber 101 is a main chamber in which generation of plasma and so on is performed. And the second chamber 102 is a connection chamber, and is for supplying the EUV radiation emitted from the plasma to the exposure device. The first vacuum exhaust pump 170 is connected to the first chamber 101 as a “first exhaust pump”, and the second vacuum exhaust pump 171 is connected to the second chamber 102 as a “second exhaust pump”. Due to this, each of these chambers 101 and 102 is maintained in a vacuum state. It would be acceptable to constitute each of these vacuum exhaust pumps 170 and 171 as a separate pump, or alternatively to constitute them as one single combined pump. The target supply device 120 supplies targets 200 as droplets of solid or liquid by, for example, applying heat to a material such as tin (Sn) or the like and melting it. It should be understood that while, in this explanation of the first embodiment, tin is suggested as an example of a target material, this is not limitative of the present invention; it would also be acceptable to utilize some other material, such as, for example, lithium (Li) or the like. Or, it would also be acceptable to provide a structure in which targets are supplied in any one of the gaseous, liquid, or solid state, using a material such as argon (Ar), xenon (Xe), krypton (Kr), water, alcohol, or the like. Furthermore, it would also be acceptable to supply targets consisting of liquid or frozen droplets of stannane (SnH4), tin tetrachloride (SnCl4), or the like. The driver laser light source 110 outputs laser pulses for exciting the targets 200 which are supplied from the target supply device 120. This driver laser light source 110 may, for example, consist of a CO2 (carbon dioxide gas) pulse laser light source. The driver laser light source 110 may, for example, emit laser radiation with the specification of: wavelength 10.6 μm, output 20 kW, pulse repetition frequency 100 khZ, and pulse width 20 nsec. It should be understood that, while a CO2 pulse laser is suggested here as an example of a laser light source, this should not be considered as being limitative of the present invention. The laser radiation for excitement which is outputted from the driver laser light source 110 is incident into the first chamber 101 via the focusing lens 111 and the incidence window 112. This laser radiation which is incident into the first chamber 101 irradiates a target 200 which is supplied from the target supply device 120, via an incidence aperture 132 which is provided to the EUV collector mirror 130. When the laser radiation irradiates the target, a target plasma 201 is generated. In the following, for convenience, this will simply be termed the “plasma 201”. This plasma 201 emits EUV radiation 202 centered around the wavelength of 13.5 nm. This EUV radiation 202 which has been emitted from the plasma 201 is incident upon the EUV collector mirror 130, and is reflected thereby. The reflected radiation 203 is focused at an intermediate focal point (IF: Intermediate Focus) which is a focal point. The details of the EUV collector mirror 103 will be described hereinafter with further reference to the figures. And this EUV radiation which has thus been focused at the focal point IF is conducted to the exposure device via the gate valve 180, which is in its opened state. A pair of coils 140 and 141 for magnetic field generation are provided above and below the optical path which the EUV radiation 202 and 203 pursues from the plasma 201 via the EUV collector mirror 130 towards the focal point IF. The axes of these two coils 140 and 141 coincide. Each of the coils 140 and 141, for example, may consist of an electromagnet which has a superconducting coil. When electrical currents flow in the same direction in both of the coils 140 and 141, a magnetic field is generated. This magnetic field has high magnetic flux density in the neighborhoods of the coils 140 and 141, and has a lower magnetic flux density at points intermediate between the coils 140 and 141. When the laser radiation is irradiated upon the target, debris is created. Debris which carries electric charge (ions such as plasma and so on) is captured by the magnetic field generated by the coils 140 and 141, and moves downward in FIG. 1 while executing helical motion due to Lorentz force. This debris which has moved downwards is sucked out by the first vacuum exhaust pump 170 and is exhausted to the exterior of the first chamber 101. The position at which the magnetic field generation device (in this embodiment, the coils 140 and 141) is installed should be a position at which the ionized debris can be discharged by the magnetic flux generated by the device, while avoiding the various optical components of the system. Accordingly, the configuration shown in the figure should not be considered as being limitative of the present invention. While the laser radiation which irradiates the target is exciting the target, it is scattered by being reflected by the target and by being reflected by the plasma 201. And the laser radiation which is thus reflected by the target and so on is incident upon the EUV collector mirror 130 and is reflected and diffracted thereby. However, this reflected and diffracted laser radiation has a wavelength which is different from that of EUV radiation, and is focused at a position which is different from that of the focal point IF. Accordingly, the reflected and diffracted laser radiation is intercepted by the SPF shield 150. In other words, since the aperture portion 151 of the SPF shield 150 (refer to FIG. 1) is provided so as to correspond to the focal point IF, accordingly the reflected and diffracted laser radiation 301 which is directed towards a position which is different from that of the focal point IF does not pass through the aperture portion 151, but is intercepted by the wall portion of the SPF shield 150. The aperture portion 151 may, for example, be formed to have an inner diameter of a few millimeters. Just as with the laser radiation (which is IR), the radiation other than EUV (such as DUV, UV, and VIS) which is generated from the plasma 201 is also focused at some position other than the focal point IF, and accordingly it is intercepted by the SPF shield 150 which is installed so as to correspond to the focal point IF. In this manner, the SPF shield 150 only passes the EUV radiation through its aperture portion 151, while intercepting radiation of other wavelengths which is proceeding towards the exposure device. Thus, the SPF shield 150 absorbs the DUV, UV, VIS, and IR and converts them to heat. Accordingly, the SPF shield 150 is provided with a water cooling system for heat radiation. Moreover, the substrate portion 135 of the EUV collector mirror 130 (refer to FIG. 3) is made from some material such as silicon or nickel (Ni) alloy whose thermal conductivity is good, and it may also be cooled with a water cooling jacket or the like. For convenience, explanation of the power supply device and the wiring which supply electrical current to the coils 140 and 141, and of the mechanisms for cooling the SPF shield 150 and the EUV collector mirror 130 and so on, will herein be omitted, and moreover these elements are not shown in the figures. However, without undue experimentation, a person of ordinary skill in the art will be able to design a suitable such power supply construction and a suitable such cooling construction based upon the disclosure in this specification, and will also be able actually to manufacture them. Two further dividing walls 160 and 161 with apertures are disposed before and after the focal point IF. In other words, when the direction of progression of the EUV radiation 203 which has been reflected by the EUV collector mirror 130 is taken as a reference, the first dividing wall 160 with its aperture is provided before the focal point IF, while the second dividing wall 161 with its aperture is provided after the focal point IF. The diameters of the apertures in these dividing walls 160 and 161 may, for example, be from a few millimeters to around ten millimeters. The first dividing wall 160 is provided in the neighborhood of the position where the first chamber 101 is connected to the second chamber 102, while the second dividing wall 161 is provided in the neighborhood of the position where the second chamber 102 is connected to the exposure device. The SPF shield 150 is provided so as to correspond to the focal point IF, at an intermediate position between the dividing walls 160 and 161. To put it in another manner, the focal point IF is provided so as to be positioned within the second chamber 102, i.e. outside the first chamber 101, and the dividing walls 160 and 161 are disposed so as to partition before and after the focal point IF. A high vacuum state is maintained within the first chamber 101 by the first vacuum exhaust pump 170, and a vacuum state is maintained within the second chamber 102 by the second vacuum exhaust pump 171. The pressure within the first chamber 101 is set to be lower than the pressure within the second chamber 102. Moreover, the ions (i.e. the electrified debris particles) within the first chamber 101 are captured by the magnetic field which is generated by the coils 140 and 141. Accordingly, it is possible to prevent any of the debris which is created within the first chamber 101 from getting into the second chamber 102. Moreover, even if some debris or the like should get into the second chamber 102, nevertheless, due to the operation of the second vacuum exhaust pump 171, it is possible to extract this debris or the like to the exterior of the second chamber 102. Because of this structure, it is possible effectively to prevent any debris or the like from getting into the exposure device. As described above, in this embodiment, the magnetic field which is created by the coils 140 and 141 is utilized as a protection means for protecting the various optical elements from debris which flies off from the plasma 201. These various optical elements include the EUV collector mirror 130, the incidence window 112, incidence windows for optical sensors of various types (not particularly shown) which are provided for observing phenomena within the vacuum chamber 100, and so on. Since the ions in the debris which is emitted from the plasma 201 are electrically charged, they are captured by the magnetic field and are discharged by the first vacuum exhaust pump 170. However, neutral debris which is not electrically charged is not constrained by the magnetic field. Accordingly, if no particular countermeasures were to be instituted, this neutral debris gradually contaminates the various optical elements within the vacuum chamber 100 and damages them. Moreover, if and when such neutral debris within the first chamber 101 gets into the exposure device via the second chamber 102, it may also even contaminate the various optical elements within the exposure device. By contrast, in this embodiment, the construction is such that the vacuum chamber 100 is subdivided into the first chamber 101 whose volume is relatively greater and the second chamber 102 whose volume is relatively smaller, and moreover the pressure within the first chamber 101 is set to be lower than the pressure within the second chamber 102. Furthermore, the first dividing wall 160 is provided so as to separate between the first chamber 101 and the second chamber 102, so that, in addition to limiting spatial migration from the first chamber 101 and the second chamber 102, the probability of neutral debris getting into the second chamber 102 from the first chamber 101 is reduced. Even if neutral debris should get into the second chamber 102, this debris will be discharged to the exterior by the second vacuum exhaust pump 171. Accordingly, in this embodiment, it is possible to prevent debris within the EUV light source device 1 from getting into the exposure device, before it even happens. Although it is possible to prevent the exposure device from being contaminated by debris, neutral debris gradually diffuses and piles up within the vacuum chamber 100. Accordingly, depending upon the time period which elapses, there is a possibility that the front surface 131 of the EUV collector mirror 130 may gradually become contaminated by debris. In this case, maintenance work should be performed. In such maintenance work, for example, the operation of the EUV light source device 1 is stopped, the gate valve 180 is closed so as perfectly to intercept communication between the exposure device and the vacuum chamber 100, and the EUV collector mirror 130 is cleaned with an etchant gas. For example, hydrogen gas, a halogen gas, a hydrogenated halogen gas, argon gas, or a mixture thereof may be used as the etchant gas. The EUV collector mirror 130 could also be heated by a heat application device not shown in the figures, in order to promote the cleaning thereof. Moreover, it might also be arranged to excite the etchant gas with RF (Radio Frequency) radiation or with microwaves, in order to promote the cleaning. When the cleaning has been completed, the supply of the etchant gas to the vacuum chamber 100 is stopped, and, after a sufficient level of vacuum has been established by the vacuum exhaust pumps 170 and 171, the gate valve 180 is opened, and the operation of the EUV light source device 1 is resumed. Next, the EUV collector mirror 130 will be explained with reference to FIGS. 2 and 3. In FIG. 1, for convenience, the incidence aperture 132 for allowing the passage of laser radiation is omitted. The front surface 131 of the EUV collector mirror 130 is made so as to possess at least one overall curvature. For example, this front surface 131 of the EUV collector mirror 130 may be made as a concave surface which is an ellipsoid of revolution, as a paraboloid, as a spherical surface, or as a concave surface having a plurality of curvatures. A composite layer which selectively reflects radiation at a predetermined wavelength is formed upon the front surface 131. In this embodiment, this predetermined wavelength is 13.5 nm. This composite layer is made by laminating together a large number of pair layers made from molybdenum and silicon (Mo/Si). Moreover, as shown in FIG. 3, a large number of blazed grooves 133 are formed upon this composite layer which covers the front surface 131. As shown in FIG. 1 and in magnified view in FIG. 3, the blazed grooves 133 of this embodiment are formed so that their abrupt step portions face towards the center of the mirror (the axis AX). To express this in the opposite manner, each of the blazed grooves 133 is formed so that its sloping portion inclines relatively gently from the center of the mirror (the axis AX) towards the outer edge of the mirror. It should be understood that the shapes of the blazed grooves 133 are not limited to those shown in FIG. 1. As will be shown in embodiments which are described subsequently, it is possible for the blazed grooves 133 to be formed in various shapes. As already described, the EUV radiation in the radiation which is generated by the plasma 201 is incident upon the EUV collector mirror 130 which has the blazed grooves 133 and is reflected and diffracted, and is focused at the focal point IF which is set to be within the second chamber 102. Among this EUV radiation which is incident upon the EUV collector mirror 130, around 60% to 70% is collected together at the focal point IF and is supplied to the exposure device as the EUV radiation 203. The laser radiation which is scattered or reflected by the target is incident upon the EUV collector mirror 130 and is reflected or diffracted. Both the reflected laser radiation 301A and the diffracted laser radiation 301B (the primary diffracted radiation) are directed towards positions which are different from the focal point IF. Due to this, the reflected laser radiation 301A and the diffracted laser radiation 301B are intercepted by the wall portion of the SPF shield 150, and are prevented from entering the exposure device. In a similar manner, DUV, UV, and VIS radiation are also intercepted by the wall portion of the SPF shield 150, and thus are not supplied into the exposure device. By contrast, the EUV radiation passes through the aperture portion 151 of the SPF shield 150 and is conducted to the exposure device. This is because all of the optical conditions are set in advance so that the EUV radiation is focused at the focal point IF, and the aperture portion 151 of the SPF shield 150 is provided so as to correspond to the focal point IF. FIG. 3 is a sectional view showing a portion of the EUV collector mirror in magnified form. In FIG. 3, the axial line AX1 is an axis which is perpendicular to the substrate portion 135 of the EUV collector mirror 130, while the other axial line AX2 is an axis which is perpendicular to the sloping surface of one of the blazed grooves 133. The substrate portion 135 of the EUV collector mirror 130 is made from a material such as silicon or nickel alloy or the like whose thermal conductivity is good, and is formed so as to have a concave surface (such as an ellipsoid of revolution) which has the focal point IF. A predetermined number of multi layers (Mo/Si pair layers) are coated upon the front surface of the substrate portion 135 (which is its upper surface in FIG. 3, and corresponds to “a surface” in the Claims). In this embodiment, the number of Mo/Si pair layers which are coated upon the substrate portion 135 is in the range from 100 to 1000. And desirably, in this embodiment, around 300 of these Mo/Si pair layers should be laid over one another upon the front surface 131. Each of these Mo/Si pair layers is a pair layer which consists of one molybdenum layer and one silicon layer, and the composite layer is made by laminating together a large number of such Mo/Si pair layers. The blazed grooves 133 are processed (to a depth H) into around 250 of the 300 pair layers of the composite layer upon the mirror front surface (whose total thickness is H0), while the approximately 50 layers at the bottom, which constitute a composite sub-layer) are left just as they are. The approximately 50 pair layers (the composite sub-layer of thickness AH) at the bottom of the composite layer correspond to the “first composite layer” of the Claims. A foundation portion 134 is formed from this composite sub-layer of thickness AH. In order to cause the EUV radiation to be reflected by this foundation portion 134 by Bragg reflection, this foundation portion 134 should consist of from around 40 to around 60 of the Mo/Si pair layers. The composite sub-layer (of thickness H) consisting of around 250 pair layers which is positioned over the foundation portion 134, and in which the blazed grooves 133 are formed, corresponds to the “second composite layer” of the Claims, while the blazed grooves 133 correspond to the “reflecting portion” of the Claims. It should be understood that the various numerical values given above for numbers of pair layers (sub-layer thicknesses) of 300, 250, and 50, are only cited by way of example for convenience of explanation; the present invention should not be considered as being limited to these numerical values. Finally, the number of the pair layers may be any value within the range from 100 to 1000, provided that the foundation portion 134 is able to manifest the function of reflecting the EUV radiation by Bragg reflection, while the blazed grooves 133 are able to manifest both the function of diffracting the EUV radiation due to the pattern of the multi layers, and also the function of diffracting the EUV radiation due to the pattern of the blazed grooves themselves. If the number of the pair layers is less than 100, then it is not possible to obtain the required blaze angle θB, so that sometimes it may be the case that it is not possible sufficiently to separate the EUV radiation from the radiation of other wavelengths. By contrast, if the number of the pair layers is greater than 1000, then a great deal of labor must be utilized during fabrication of the mirror, and moreover the internal stress is increased, so that there is a possibility that the composite layer may become detached. Thus, in this embodiment, as one example of a value between 100 and 1000, the value of 300 is selected for the number of pair layers, and the above described reflective type diffraction lattice made from this number of pair layers is provided integrally upon the EUV collector mirror 130. The more multi layers are provided as stacked over one another, the greater is it possible to make the blaze angle θB, so that it is possible to separate the EUV reflected radiation 203 and the radiation 301A and 301B of other wavelengths, in a simple and easy manner. In this embodiment, it is possible to set the number of Mo/Si pair layers which are laminated together to any value in the range from 100 to 1000, and it is possible to reduce the stress set up in the composite layer, and thus to prevent detachment of the composite layer. Moreover, with regard to the efficiency of reflection of EUV radiation, since it is possible to keep the performance around 60% to 70% which is similar to that of the prior art, accordingly it is possible to enhance the efficiency of supply of EUV radiation to the exposure device. If a structure is employed which incorporates both a conventional EUV collector mirror which is not equipped with any SPF function and also a separate reflective type diffraction lattice, then there is a loss of around 30% of the EUV radiation at the EUV collector mirror, and moreover there is also a further loss of around 30% of the EUV radiation at the separate reflective type diffraction lattice. In other words, in the case of this structure, it is only finally possible to supply around 50% of the EUV radiation to the exposure device, because the EUV radiation is reflected twice before being incident into the exposure device. By contrast, since the EUV collector mirror 130 of this first embodiment of the present invention is endowed with the function of acting as a SPF, accordingly it is possible to conduct the EUV radiation to the exposure device while only reflecting it once. In other words, the loss of the EUV radiation is limited to around 30%. Moreover, in this embodiment, the radiation other than EUV radiation, which is not required and is undesirable, is prevented from being incident into the exposure device by the SPF shield 150 which is provided to correspond to the focal point IF, and accordingly it is possible to supply only EUV radiation of high purity to the exposure device. It should be understood that it would also be acceptable, after the frontmost surface of the mirror has been processed in order to produce the blazed grooves 133, to coat it with ruthenium (Ru) or the like so that the exposed portion of the Mo/Si layer which has been processed does not become oxidized; and this results in a structure with which decrease of the diffraction efficiency for the EUV radiation is prevented. Moreover, as will be explained hereinafter with reference to FIG. 4, it is desirable for the thicknesses of the Mo/Si pair layers to be set according to the angle of incidence of the EUV radiation. A concrete example will now be described. On the assumption that the thicknesses of the Mo/Si pair layers are 6.9 nm, then the thickness H of 300 of these layers will be 2.070 μm. If the blazed grooves 133 are formed at a pitch P of 400 μm in a composite layer which consists of 250 of the pair layers, then the blaze angle θB is 4.3 mrad. Accordingly, 2θB is equal to 8.6 mrad. And, if for example it is supposed that the radius of curvature of the EUV collector mirror 130 is 181.8 mm and the conic constant is −0.67, then the distance from the elliptically shaped front surface 131 of the EUV collector mirror 130 (i.e. the mirror surface) to the focal point IF is about 1 m. If the angle of incidence of the EUV radiation 202 which is incident from the plasma 201 upon the EUV collector mirror 130 is termed α, then the EUV radiation 203 is reflected at almost the angle α towards the focal point IF, and passes through the aperture portion 151 of the SPF shield 150. By contrast, the DUV, UV, VIS, and IR radiation components such as the laser radiation are regularly reflected at an angle α+2θβ. Accordingly, at the position of the focal point which is approximately 1 m ahead, the EUV reflected radiation 203 and the regularly reflected radiation 301A such as laser radiation and so on, are separated by a gap of about 8.6 mm. Furthermore, IR radiation such as the laser radiation is diffracted at an angle of α+θd by the blazed grooves 133. Since, in this embodiment, the wavelength of the laser radiation is 10.6 μm, accordingly the angle θd in FIG. 3 is 27.6 mrad. Although for the sake of convenience this feature is not shown in the figure, the DUV, UV, and VIS are diffracted by the gratings which are formed by the periodic stripe patterns of the alternating molybdenum and silicon layers appearing upon the sloping surfaces of the blazed grooves 133 (in this embodiment, these stripe patterns have pitch of 1.54 μm), and follow paths at angles which are different from that of the EUV radiation 203. Accordingly, by arranging the aperture portion 151 which has a diameter of 4 to 6 mm at the position of the focal point IF at which the EUV radiation 203 is gathered together, it is possible to select only the EUV radiation 203, and to conduct it to the exposure device. As described above, a reflective type diffraction lattice is integrally provided upon the front surface of the EUV collector mirror 130 by processing the multiple Mo/Si layers of which it is composed into blazed grooves. As shown in FIG. 2, when the radiation 202 from the plasma 201 is incident at the angle α upon this EUV collector mirror 130, the EUV radiation therein is reflected at almost the angle α. The reflection efficiency is 60% to 70%. The radiation in the DUV and UV regions is reflected by the diffraction lattice which is formed by the periodic stripes of molybdenum and silicon appearing upon the processed sloping surfaces of the blazed groove shapes of the composite layer consisting of multiple Mo/Si pair layers, and is diffracted at an angle which is different from that of the EUV radiation 203. The radiation in the VIS and IR regions, and in particular the laser radiation (of wavelength 10.6 μm) from the driver laser light source 110, is diffracted by the blazed grooves 133 at the angle α+θd (or α−θd), which is different from the angle of the EUV radiation 203. Moreover, due to the blazed grooves 133 (which have blaze angle θB), except for the EUV radiation 203, the DUV, UV, VIS, and IR are regularly reflected at the angle of α+2θB by the surfaces which are at the angle θB. Accordingly it is possible to extract only the EUV radiation 203, which is reflected or diffracted at almost the angle α, and to supply it to the exposure device. In other words, this EUV collector mirror 103 also is endowed with the function of a SPF. FIG. 4 shows a characteristic for setting the thickness of the Mo/Si pair layers according to the angle of incidence (α) of the EUV collector mirror 130. As shown in FIG. 4, as the angle of incidence increases from 0° to 50°, the thickness of the pair layers increases from around 6 nm to around 10 nm. When the angle of incidence α is 12°, the thickness of the pair layers is 6.9 nm. From the general vicinity where the angle of incidence exceeds 50°, the rate of increase of the thickness of the pair layers becomes great. When the angle of incidence is around 70°, the thickness of the pair layers becomes around 20 nm. Naturally, the characteristic shown in FIG. 4 is only given by way of example; the present invention is not to be considered as being limited to the characteristic shown in FIG. 4. Since the EUV collector mirror 130 of this embodiment includes the foundation portion 134 and the blazed grooves 133, both of which are made from a composite of multiple Mo/Si pair layers, accordingly it is capable of providing diffraction operation of the following three types. The first diffraction operation is Bragg reflection. The Mo/Si composite layer which constitutes the foundation portion 134 positioned at the bottom surface of the EUV collector mirror 130 and the composite layer upon which the blazed grooves 133 are formed operate as a reflecting mirror in a similar manner to an EUV collector mirror in the prior art, and perform Bragg reflection of EUV radiation of wavelengths centered around 13.5 nm. As shown in FIG. 4, the thicknesses of the pair layers in the composite layer which is the foundation portion 134 and in the composite layer upon which the blazed grooves 133 are formed are changed according to the angle of incidence α, for example over the range from 6.9 nm to 20 nm. The second diffraction operation is diffraction by the periodic striped pattern of molybdenum and silicon which appears at the front surfaces (i.e. the sloping surfaces) of the blazed grooves 133. The pitch of this striped pattern varies according to the thicknesses of the pair layers, and changes within the range of several hundreds of nanometers to a few micrometers. The EUV, DUV, UV, and VIS are diffracted by this second diffraction operation. The third diffraction operation is diffraction by the blazed grooves 133 themselves. These blazed grooves 133 are formed at a comparatively large pitch, for example from several hundreds of micrometers to a few millimeters. The VIS and the IR are diffracted by this third diffraction operation. Here, by setting the thickness of the Mo/Si pair layers according to the angle of incidence α (refer to FIG. 4), it is possible to diffract the EUV radiation by the second diffraction operation at an angle which is almost the same as that at which it is diffracted by the first diffraction operation. In other words, the angle at which the EUV radiation is reflected by the foundation portion 134, and the angle of diffraction by the periodic striped pattern which appears on the sloping surfaces of the blazed grooves 133, are made to be almost the same, so that it is possible to supply the EUV radiation to the focal point IF in an efficient manner. With this embodiment which has the structure described above, since the blazed grooves 133 are formed by processing the sub-layer of the EUV collector mirror 130 which is made by superimposing a predetermined number of Mo/Si pair layers, accordingly not only is the EUV collector mirror 130 endowed with its basic function of reflecting the EUV radiation, but also with the function of acting as an SPF which separates the EUV radiation from the radiation of other wavelengths. Furthermore, in this embodiment, since the SPF shield 150 is provided at the focal point IF at which the EUV radiation is focused, accordingly it is possible to supply only the EUV radiation to the exposure device. Due to this, in this embodiment, it is possible to supply a greater proportion of the EUV radiation to the exposure device, as compared to the case in which a separate reflective type diffraction lattice is used, and moreover it is possible to reduce the number of components in the EUV light source device 1, thus keeping its manufacturing cost low. Since, in this embodiment, no thin layer type SPF is required, accordingly there is no danger that debris or heat will cause damage to such a thin layer type SPF or failure thereof, and accordingly the convenience of use and the reliability are enhanced. In this embodiment, the blazed grooves 133 are formed by laminating a number of Mo/Si pair layers in the range of 100 to 1000 upon the substrate portion 135. Accordingly, as compared with a prior art technique in which 2000 or more Mo/Si pair layers were superimposed, the stress in the composite layer is reduced, so that there is no fear that the composite layer may become detached due to such stress, and accordingly the reliability and the convenience of use are enhanced. Moreover, since the number of layers is reduced, accordingly the manufacturing cost of this EUV collector mirror 130 can also be reduced. Since, in this embodiment, the EUV collector mirror 130 is endowed with the function of a SPF, accordingly it is possible to provide the exposure device with EUV radiation of high purity which has been subjected to only a single reflection. Therefore it is possible to provide the exposure device with EUV radiation at a higher efficiency than in the case of the prior art, in which the EUV radiation was reflected a plurality of times. Embodiment 2 A second embodiment of the present invention will now be explained on the basis of FIGS. 5 through 7. The second and third embodiments of the present invention which are described below correspond to variants of the first embodiment described above. Accordingly, the explanation thereof will focus upon the aspects in which these embodiments differ from the first embodiment. The aspects of difference between this second embodiment and the first embodiment are that the blazed grooves are angled in the opposite direction, and that, along with this difference, a dumper 105 is additionally provided. FIG. 5 is an explanatory figure showing the EUV light source device 1A according to this second embodiment. A dumper 105 which is provided at a certain position upon the optical axis AX (refer to FIG. 6) absorbs the regularly reflected radiation 301A which has been deflected by the blazed grooves 133 and converts it to thermal energy. It may also be arranged for this dumper 105 to serve as a dumper for absorbing the laser radiation which is incident into the vacuum chamber 100. It is desirable for the dumper 105 to be cooled by some cooling mechanism such as a water cooling jacket or the like. It should be understood that the SPF shield 150A also serves as a dividing wall aperture. FIG. 6 is an explanatory figure showing the EUV collector mirror 130A and so on in magnified view. As shown in this FIG. 6, the dumper 105 is positioned between the point at which the plasma 201 is generated and the SPF shield 150A, and is provided at a position upon the optical axis at which the reflected radiation 301A is collected together. As shown in magnified view in FIG. 6, the blazed grooves 133 in this second embodiment are different from the blazed grooves of the first embodiment shown in FIG. 1, in that they are formed so that their abrupt step portions face away from the center of the mirror (the axis AX) towards the outer edge of the mirror. To express this in the opposite manner, each of the blazed grooves 133 is formed so that its sloping portion inclines relatively gently from the outside of the mirror towards the center of the mirror (the axis AX). FIG. 7 is an explanatory figure showing a portion of this EUV collector mirror 130A in magnified view. In this embodiment, a total of 850 of the Mo/Si pair layers are laid over one another upon the substrate portion 135. If the thickness of one of these pair layers is taken as being 6.9 nm, then the dimension H0 is 5.865 μm. And, in this embodiment, the blazed grooves 133 are formed at a pitch of 400 μm through the upper 800 layers (so that, in this case, their thickness is 5.520 μm). As a result, the angle θB becomes 13.8 mrad, so that 2θB is 27.6 mrad. If the mirror surface (131) of the EUV collector mirror 130A is, for example, an elliptical surface whose radius of curvature is 181.8 mm and whose cone constant is −0.67, then the focal point IF is at a distance of about 1 m from this mirror surface. If the angle of incidence of the radiation 202 which is incident upon this EUV collector mirror 130A is termed α, then the DUV, UV, VIS, and IR radiation 301A such as the laser radiation etc. is regularly reflected at the angle α−2θB towards the focal point at which the EUV radiation 203 is reflected at the angle α. Accordingly, at the position of the focal point IF which is about 1 m from the EUV collector mirror 130A, the EUV radiation 203 and the regularly reflected radiation 301A are separated by a gap of around 27.6 mm. However, in this embodiment, since the regularly reflected radiation 301A is absorbed by the dumper 105 which is provided upon the optical axis AX, accordingly, actually, the EUV radiation and the regularly reflected radiation such as the laser radiation and so on do not even appear together at the position of the focal point IF. The numerical value of 27.6 mm described above is only a hypothetical value which has been calculated provisionally on the assumption that the dumper 105 is not to be provided. In other words, even if the dumper 105 were not to be present, still it would be possible sufficiently to separate the EUV reflected radiation 203 and the other regularly reflected radiation 301A in the vicinity of the focal point IF, and it would still be possible to extract only the EUV radiation by the operation of the SPF shield 150A. The IR radiation such as the CO2 laser radiation and so on is diffracted at an angle of α−θD by the blazed grooves (which have pitch of 400 μm). In this embodiment Ed is 27.6 mrad, because the wavelength of the CO2 laser is set to be 10.6 μm. Although for convenience this feature is not shown in the figures, the DUV, UV, and VIS radiation are diffracted by the gratings which are formed by the periodic stripes of silicon and molybdenum appearing on the front surfaces of the blazed grooves 133 (which in this embodiment are at a pitch of 0.5 μm), and proceed onward at angles which are different from that of the EUV radiation 203. Accordingly, by disposing the SPF shield 150A which has the aperture portion of diameter 4 to 6 mm at the position of the focal point IF, it is possible to select only the EUV radiation 203 and to supply it to the exposure device. Thus, with this second embodiment having the above structure, it is possible to obtain similar beneficial effects to those obtained in the case of the first embodiment. Embodiment 3 A third embodiment of the present invention will now be explained on the basis of FIGS. 8 and 9. In this third embodiment, the blazed grooves are formed in a somewhat different manner. FIG. 8 is a figure showing the EUV collector mirror 130 as seen from the front. The blazed grooves 133 may be formed as concentric circles, as shown in FIG. 8(a), or may be formed as parallel straight lines, as shown in FIG. 8(b). If the blazed grooves 133 are formed as parallel straight lines as shown in FIG. 8(b), then it would also be possible, as shown in FIG. 9, to form the blazed grooves to extend in the same direction across the entire surface of the EUV collector mirror 130. Thus, with this third embodiment having the above structure, it is possible to obtain similar beneficial effects to those obtained in the case of the first embodiment. Embodiment 4 In the following, several examples of manufacturing methods for an EUV collector mirror 130 of the novel type described above which is endowed with the function of operating as an SPF will be explained. A fourth embodiment of the present invention, which relates to its aspect of providing a method for manufacturing such a mirror for extreme ultra violet, will now be explained on the basis of FIG. 10. As shown in FIG. 10(a), a mirror member 137 which is made by coating a predetermined number of multi layers upon a substrate portion 135 is loaded upon a rotational stage 400 and is rotated. And a cutting process for forming blazed grooves is performed by irradiating an ion beam 430 upon these multi layers, using an ion milling device 410 and a mask 420. And, as shown in FIG. 10(b), a pattern 421 shaped as a right angled triangle, and through which the ion beam 430 passes, is formed in the mask 420. Accordingly, the width P1 or P2 of the blazed grooves can be adjusted by changing the relative positional relationship between the pattern 421 and the ion beam 430. As shown on the left side of FIG. 10(b), when the area of overlap between the triangular shaped pattern 421 and the ion beam 430 is small, it is possible to form narrow blazed grooves 133 of width P1 as shown at the lower portion of this figure. On the other hand, as shown on the right side of FIG. 10(b), when the ion beam 430 is overlapped over the entire surface of the triangular shaped pattern 421, it is possible to form broad blazed grooves of width P2. Each time the formation of one blazed groove has been completed, the ion milling device 410 and the mask 420 are shifted in the radial direction (the horizontal direction in FIG. 10) by just the desired pitch for the grooves, and then the ion beam is again irradiated and a new blazed groove is formed. If blazed grooves like those shown in FIG. 3 are to be formed, then, as shown in FIG. 10(c), a mask 420 is used in which the orientation of the triangular shaped pattern 420 is changed. Thus, with this embodiment of the present invention having the structure described above, it is possible to manufacture the EUV collector mirrors 130 described above according to both the first and the second embodiments, in a simple and easy manner. Embodiment 5 A fifth embodiment will now be explained on the basis of FIG. 11. In this fifth embodiment, as well as the mirror stage 400 and the mirror being rotated, the ion milling device 410 and the mask 420 are swung around a rotational axis 412 which is positioned to correspond to where the intermediate focal point IF at which the EUV radiation is to be gathered together is to be formed. The ion milling device 410 and the mask 420 are fitted to a long tubular support device 411 so as to be shiftable along its axial direction. This support device 411 is rotatable in the left and right directions in FIG. 11 about the rotational axis 412 (which passes through the focal point IF) as a center. The rotational axis 412 (i.e. the focal point IF) is set to a distance which is separated from the center of the mirror surface of the mirror member 137 (i.e. from where the center of the mirror surface will be when it is completed) by just the distance desired for the focal point IF. Then the blazed grooves are formed while swinging the ion milling device 410 and the mask 420 axially in the sideways direction in the figure. Since the rotational axis 412 (i.e. the focal point IF) is set to the same position with respect to the EUV collector mirror 130 as the position at which the final focal point IF will be located, accordingly the ion beam is irradiated from the ion milling device 410 in the opposite orientation to the radiation beam 203 in FIG. 1. Due to this, it is possible to keep the angle at which the ion beam is incident upon the composite layer constant, and thus it is possible to process the blazed grooves in a constant shape. This means that it is possible to prevent shadow areas occurring upon the EUV collector mirror 130, in which the EUV radiation which is emitted from the plasma 201 is hindered by the edges of the blazed grooves and cannot be properly incident. Embodiment 6 A sixth embodiment will now be explained on the basis of FIG. 12. In this sixth embodiment, as shown in FIG. 12(a), the position of the rotational axis 412 (201) is set to the point at which the plasma 201 originates. Moreover, as shown in FIG. 12(b), a mask 420A is used whose length corresponds to the radius of the EUV collector mirror 130, and a pattern 421 consisting of a plurality of right angled triangles is provided upon this long mask 420A corresponding to each of the blazed grooves which are to be formed. Accordingly, it is possible to form the blazed grooves by simply irradiating the ion beam while swinging the ion milling device 410 in the diametrical direction and while rotating the mirror 130, without any necessity for shifting the mask 420A. With this fifth embodiment of the present invention having the structure described above, it is again possible to prevent the occurrence of so called shadow portions such as described above, and it is thus possible to provide an EUV collector mirror 130 which collects and separates out the EUV radiation with good efficiency. Embodiment 7 A seventh embodiment of the present invention will now be explained on the basis of FIGS. 13 through 15. The EUV collector mirror 130B of this seventh embodiment instead of blazed grooves, triangular roof-like grooves 133B are provided. And, in this EUV collector mirror 130B of this seventh embodiment, these triangular roof-like grooves 133B are, again, formed integrally in a composite layer which covers the front surface of the substrate portion 135. In a similar manner to the procedure for the first embodiment, for example, 300 pair layers of Mo/Si are layered together into a composite layer on the substrate portion 135, and then the triangular roof-like grooves or triangular roof shapes are formed in the uppermost 250 of these 300 pair layers, from the front surface inwards. In FIG. 13, the axial lines AX1a and AX1b are perpendiculars to the substrate portion 135, while the other axial lines AX2a and AX2b are axes which are perpendicular to the sloping roof-shaped surfaces of the triangular roof-like grooves 133B. Each of these triangular roof-like grooves 133B has two sloping surfaces 133B1 and 133B2. The tilt angles θb2 of these two sloping surfaces 133B1 and 133B2 may be set to be the same. Here, for convenience of explanation, the sloping surfaces on the left side in FIG. 13 will be termed the first sloping surfaces 133B1, while the sloping surfaces on the right side in FIG. 13 will be termed the second sloping surfaces 133B2. The triangular roof-like grooves 133B, for example, may be formed at a pitch P10 of around 800 μm. In this case, the first sloping surfaces 133B1 and the second sloping surfaces are defined alternatingly at intervals of 400 μm (which =P10/2) in the direction parallel to the substrate portion 135. To put this in another manner, with the EUV collector mirror 130B of this embodiment, the orientations of the sloping surfaces 133B1 and 133B2 change to and fro in opposite senses at this pitch P10/2. According to the inclinations of the sloping surfaces 133B1 and 133B2, the radiation other than the EUV radiation (i.e. the driver laser radiation, and DUV, UV, VIS, and IR) is regularly reflected by these sloping surfaces, and in directed in directions which are different from that of the reflected EUV radiation 203. The EUV radiation is Bragg diffracted by the foundation portion 135 and by the 10 to 50 Mo/Si pair layers which are laid thereupon underneath the portion in which the triangular roof-like grooves 133B are formed. The efficiency of this diffraction is the same as that of a mirror upon which Mo/Si pair layers are provided. Furthermore, due to the triangular roof-like grating structure having a period of 800 μm which is defined, the VIS and IR radiation described above are diffracted in directions which are different from that of the EUV radiation. Moreover, due to the gratings which are defined by the periodic stripe patterns of the Mo/Si pair layers which are exposed upon the sloping surfaces 133B1 and 133B2, the radiation of comparatively short wavelengths other than the EUV radiation and the IR radiation (i.e. the DUV, UV, and VIS) is diffracted in directions which are different from that of the reflected EUV radiation 202. It would also be acceptable to arrange to set the value of the pitch P10 to some other value such as 400 μm or the like, instead of to 800 μm. For example, if the pitch P10 is set to 400 μm, then it is possible to obtain optical diffraction operation as a grating of pitch 400 μm, in a similar manner to the case with the first embodiment. By contrast, if the pitch P10 is set to 800 μm, then it is possible to obtain optical diffraction operation as a grating of pitch 800 μm. Furthermore, it is not necessary to keep the pitch constant; it would also be acceptable to change the pitch according to the position in which the triangular roof-like grooves 133B are formed. Moreover, it would also be possible to set the pitch of the sloping surfaces 133B1 and the pitch of the sloping surfaces 133B2 to be different: for example, the pitch of the sloping surfaces 133B1 might be set to 300 μm and the pitch of the sloping surfaces 133B2 might be set to 500 μm. FIG. 14 is a plan view of a mask 420B for forming the triangular roof-like grooves 133B according to this seventh embodiment. When forming these triangular roof-like grooves by employing the process according to the fourth embodiment described above, this mask 420B shown in FIG. 14 is used. The mask 420B has a triangular shaped aperture pattern 421B which corresponds to the triangular roof-like grooves 133B. FIG. 15 is a plan view showing another mask 420C for forming the triangle roof-like grooves 133B according to this embodiment. When forming these triangular roof-like grooves by employing the process according to the sixth embodiment described above, such a mask 420C is used which has a length which corresponds to the radius of the EUV collector mirror 130B, as shown in FIG. 15. Aperture patterns 421B shaped as triangles are provided in this mask 420C so as to correspond to each of the triangular roof-like grooves 133B. Thus, with this seventh embodiment having the above structure, it is possible to obtain similar beneficial effects to those obtained in the case of the first embodiment. Embodiment 8 An eighth embodiment will now be explained on the basis of FIGS. 16 through 18. The EUV collector mirror 130C of this eighth embodiment is formed with relatively smooth undulating wave-like grooves 133C. The wave-like shape of these grooves 133C may, for example, be, at least approximately, a sinusoidal shape. In this embodiment as well, for example, 300 Mo/Si pair layers are laminated upon the foundation 135 as a composite layer, and then the wave-like grooves 133C are formed in the uppermost 250 of these pair layers, from the front surface. In FIG. 16, the axial lines AX1L and AX1R are lines which are perpendicular to the substrate portion 135, while the other axial lines AX2L and AX2R are lines which are perpendicular to the arcuate surfaces at their steepest points. The reference symbol 133C1 denotes a summit of one of the wave-like shapes, while the reference symbol 133C2 denotes a valley thereof. With the EUV collector mirror 130C according to this embodiment, the inclination of the surface changes relatively smoothly in a sinusoidal fashion repeatedly at the pitch P10 (which may be, for example, 600 μm). According to the inclinations of the arcuate surfaces, the radiation other than the EUV radiation (i.e. the driver laser radiation, and the DUV, UV, VIS, and IR) is reflected in a direction which is different from that of the reflected EUV radiation 203. However at places when these inclination are nearly horizontal, as at the summit 133C1, the EUV radiation and the radiation other than the EUV radiation (i.e. the driver laser radiation, and the DUV, UV, VIS, and IR) are all regularly reflected in approximately the same direction. As described above, the EUV radiation is Bragg diffracted by the foundation portion 135 and by the 10 to 50 Mo/Si pair layers which lie underneath the portion in which the wave-like grooves 133C are formed. The efficiency of this diffraction is the same as that of a mirror upon which Mo/Si pair layers are provided. Furthermore, due to the wave-like grating structure having, for example, a period of 600 μm, the VIS and IR radiation are diffracted in directions which are different from that of the EUV radiation. Moreover, due to the grating which is defined by the periodic stripe pattern of the Mo/Si pair layers which are exposed upon the arcuate surfaces, the radiation of comparatively short wavelengths other than the EUV radiation and the IR radiation (i.e. the DUV, UV, and VIS) is diffracted in directions which are different from that of the reflected EUV radiation 202. FIG. 17 is a plan view showing a mask 420D for forming these wave-like grooves 133C of this eighth embodiment. When forming the wave-like grooves 133C according to this eighth embodiment with the process according to the fourth embodiment described above, this mask shown in FIG. 17 is used. This mask 420D has a wave-like pattern 421D which corresponds to the desired pattern for the wave-like grooves 133C. FIG. 18 is a plan view showing another mask 420E for forming the wave-like grooves 133C of this eighth embodiment. When forming the wave-like grooves 133C according to this eighth embodiment with the process according to the sixth embodiment described above, as shown in FIG. 18, a mask 420E is used which has a length corresponding to the radius of the EUV collector mirror 130C. Wave-like aperture patterns 421D are provided in this mask 420E to correspond to each of the wave-like grooves 133C. It should be noted that, when using an EUV collector mirror 130 in which grooves, having shapes as shown in the seventh and eighth embodiments, are arranged in concentric circles as shown in FIG. 8(a), it is desirable for a dumper 105 and a SPF shield 150A as shown in FIG. 6 to be used, in order to intercept radiation other than the EUV radiation. It should be understood that the present invention is not limited to the embodiments described above. On the basis of the disclosure herein, a person of ordinary skill in the art would be able to make various additions and/or changes and so on to the details of any particular embodiment, within the scope of the present invention. For example, in order to obtain the desired effect in which the mirror also acts as an SPF, it would also be acceptable to make the shape of the mirror on its substrate as planar; and it is not necessary to keep the pitch P of the grooves at a constant value; this pitch P could be varied. Moreover, this collector mirror for extreme ultra violet is not limited to being used with an LPP type light source; it would also be possible to use, for example, a DPP light source with a collector mirror of this type. Or, it would also be possible to install this mirror for extreme ultra violet within the exposure device, as a reflecting mirror which is also endowed with the function of acting as an SPF. In this case, such a reflecting mirror for extreme ultra violet according to the present invention may be structured as a planar mirror, a concave surface mirror, a parabolic mirror, an ellipsoid of revolution, or the like. Such a mirror for extreme ultra violet according to the present invention may, for example, be installed as a portion of the optical system within the exposure device, and may be used for directing the component consisting of extreme ultra violet of high purity in some predetermined direction. It should be understood that the present invention is not limited to application to a extreme ultra violet light source or to an exposure device (i.e. to EUV lithography); it could also be used for various other applications in which extreme ultra violet is to be reflected and/or focused.
052767248	abstract	Several ten thousands or several millions of juxtaposed hollow thin tubes, each having a diameter of, for example, 12 .mu.m and a length of 1 mm, are joined to each other to form a window having a predetermined open surface area. The window having a diameter of, for example, 30 mm, can withstand a differential pressure of several atm. A high-vacuum X-ray source and the window consisting of thin tubes having the aforementioned dimensions are connected through a differential evacuating device having a plurality of stages connected with a partitioning wall having an orifice of predetermined dimensions provided between the adjacent stages. The pressures at the two sides of the window are maintained to the atmospheric pressure and a pressure which is 1/10th of the atmospheric pressure, respectively. X-rays having a long wavelength of 10 .ANG. or above and emitted by a SOR device under a high vacuum can be illuminated on a sample provided in an environment at the atmospheric pressure at a high transmittance and over a wide area which cannot be achieved by a conventional Be window.
047160179	summary	FIELD OF THE INVENTION The present invention relates to nuclear reactor fuel assemblies, and more particularly to a method, apparatus and tool for providing a concentric, reduced inside diameter or otherwise restricting large diameters of structural tubes used in the fabrication of nuclear fuel assemblies. BACKGROUND OF THE INVENTION A typical nuclear reactor fuel assembly includes top and bottom support members having a multiplicity of fuel rods and control rod guide tubes supported therebetween. Each fuel rod and control rod guide tube is separately held against lateral displacement by grids, generally of an egg crate configuration, which are axially spaced along the fuel assembly length. Since the fuel rods and control guide tubes are usually made of Zircoloy and the grid assemblies used for supporting these components are usually made of Inconel, the incompatibility of the materials requires that the grids be held in position along the fuel assembly length by mechanical means, rather than brazing, welding or the like. In one well-known grid design short sleeves, which correspond to the number of control rod guide tubes in the fuel assembly, are brazed at appropriate points in grid assembly cells which are formed by interleaved grid straps. Each sleeve projects on the order of about two inches beyond the edge of a grid strap. During assembly of the fuel assembly, the grids are mounted in an axial predetermined position and after the control rod guide tubes are pulled through the grid sleeves, a bulging tool is moved into the control rod guide tube and stopped at a point just below a grid strap, but still inside the sleeve which extends through the grid cell. The tool is then expanded to cause projections on the tool to plastically deform the control rod guide tube and sleeve. The bulging tool is then moved to a point just above the grid, and the process of plastically deforming the material again repeated with the result being that the grid is mechanically locked and rigidly secured to the control rod guide tubes in the fuel assembly. Prior art bulge tools, such as that described in U.S. Pat. No. 4,182,152, comprise a cylindrical housing having axially extending tines formed by slots cut into the walls of the cylindrical housing. Projections are integrally formed in the outer surface of the tines near the end of the cylindrical housing. These projections are made to move radially outward under the influence of an internally operating ram to form bulges in a sleeve and guide tube while plastically deforming the material thereof. As the sleeve and guide tube material is deformed by the action of the ram riding on the complementary inner surfaces of the tines, the inner diameter of the tubes is held to a predetermined minimum by a coacting effect of other tines, located between the tines having projections, and the ram surfaces. In the above-described prior art fuel assemblies, the sleeve and guide tubes are deformed with dimple-like bulges circumfunctially spaced about 90.degree. apart to capture the guide tube with respect to the grid straps. The guide tubes are therefore subject to local stresses at the bulges. In addition, the prior art expansion tools require several operations to create all of the necessary bulges to securely capture the guide tube at the various axially spaced grid locations in the fuel assembly. SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a device for centering an insert within a relatively large diameter structural tube. It is a further object of the present invention to provide a device for centering and capturing an insert within a relatively large diameter structural tube in a nuclear fuel assembly. It is a further object of the present invention to provide an effective reduced diameter inside of a relatively large diameter structural tube in a nuclear fuel assembly. It is a still further object of the present invention to provide a method and apparatus for automatically feeding and locating inserts for producing a reduced, concentric inside diameter in large diameter structural tubes. In accordance with a preferred embodiment of the invention, these and other objects are accomplished by providing a nuclear fuel assembly having a skeletal structure comprising a bottom nozzle assembly, a top nozzle assembly, at least one control rod guide tube extending between said top and bottom nozzle assemblies and at least one grid assembly, disposed in said fuel assembly between said top and bottom nozzle assemblies, the guide tube extending through and being captured with respect to said grid assembly. An instrumentation structural tube is provided which extends at least partially between the top and the bottom nozzle assemblies and through the grid assembly. A restricted inside diameter insert is coaxially disposed within the instrumentation structural tube at a location where the structural tube passes through the grid assembly. The restricted inside diameter insert is operable to provide a central opening having an engineered inside diameter and is further operable to lock the structural tube into the fuel assembly at the grid assembly location. In accordance with another embodiment of the invention, there is provided an insert for providing a reduced inside diameter for a structural tube having a nominal inside diameter. The insert is provided with one or more lobes for centering the insert within the structural tube inside diameter, and forming lobes, which are operable to expand and locally deform the structural tube inside diameter. Projections are provided on the reduced inside diameter of the insert which are operable to cooperate with an expansion tool to accurately position the expansion tool with respect to the forming lobes. In accordance with a further aspect of the present invention, there is provided an expansion tool which comprises a hollow, generally cylindrical housing. A plurality of tines are formed on an end portion of the housing. The end portion includes a head portion which has a forming surface for contacting an insert which is to be expanded. The tool has a shoulder which registers with a projection on the insert to accurately position the forming surface within the insert. A movable expander pin having a tapered section is adapted to be inserted into the cylindrical housing. The expander pin cooperates with the tines to radially expand the tines whereby the forming surface contacts and plastically deforms the insert. Finally, in accordance with another aspect of the present invention there is provided a method of securing structural tubes in grid assemblies having grid straps in a nuclear reactor fuel assembly. The method comprises the steps of loading a plurality of inserts having first and second projections on inside diameters thereof onto an expansion tool. The expansion tool is then inserted into the structural tube and a first of the inserts is aligned with a first grid assembly whereby first and second forming lobes, which are associated with the first and second projections respectively, straddle the grid straps. An expander pin is then inserted into the expansion tool to plastically deform the first expansion lobe against the structural tube to thereby plastically deform and mechanically lock together the insert and structural tube on one side of the grid strap. The expander pin is then withdrawn a distance sufficient to relax the expansion tool and the expansion tool is withdrawn within the structural tube until a shoulder thereof registers with the second projection of the first insert. The expander pin is then reinserted into the expansion tool to plastically deform the second expansion lobe against the structural tube thereby mechanically locking the insert and structural tube together on the other side of the grid strap. The expansion pin is then withdrawn a distance sufficient to relax the expansion tool and the expansion tool is withdrawn until the shoulder thereof registers with the first shoulder of a second insert. The second insert is then aligned with the second grid assembly and the steps are repeated until all the inserts have been expanded at the appropriate grid locations.
	description	This application is entitled to the benefit of and incorporates by reference essential subject matter disclosed in International Application No. PCT/SE2004/001244 filed on Aug. 30, 2004 and Swedish Patent Application No. 0302308-2 filed on Aug. 28, 2003. The present invention refers generally to the operation and control of nuclear light water reactors. More precisely, the invention refers to the operation and control of nuclear light water reactors of boiling water type. Especially, the present invention refers to a method for operating a nuclear light water reactor during an operation cycle including a cardinal cycle and a number of successive control rod cycles. An operation cycle is the time period during which the reactor is operating with the same core, i.e. without replacement or relocation of the fuel. A nuclear light water reactor of boiling water type includes a plurality of elongated fuel units, which contain fissible material, and a number of control rods. The fuel units may be designed as elongated fuel assemblies including a number of fuel rods each having a tubular cladding enclosing a pile of fissible fuel. In a boiling water reactor there is large number of such fuel assemblies, in the order of 400 to 800, and approximately a fourth of control rods, i.e. in the order of 100 to 200. The fuel units are arranged in parallel to each other and grouped in a plurality of cells which each may include four fuel units. These cells form together the core of the reactor. Substantially each such cell in the core includes a control rod position. In each of these control rod positions, one of the control rods is completely or partly introduceble. The control rods contain neutron absorbing material, such as boron or hafnium, and are used in a boiling water reactor for controlling and interrupting the nuclear reaction in the fuel. When all control rods are introduced, the reactor is shut down, i.e. more neutrons than being released in the fission process will be absorbed and the nuclear reaction decays. The fuel units, comprised in the core during an operation cycle, are different with regard to the amount of fissible material. This difference depends in the first place on the fact that the fuel units have been in operation during different time periods. A first type of fuel units may be the new ones thus including a relatively large amount of fissible material. A second type of fuel units may have a certain degree of burn out obtained during one or more preceding operation cycles in a reactor. This second type of fuel units thus includes a relatively smaller amount of fissible material. The fuel units may also from the beginning be designed with different amount and distribution of the fissible material. During an operation cycle the different types of fuel units are arranged in such a way that they are distributed and mixed in the core. The fuel units containing new fuel are preferably located in the proximity of the centre of the core whereas the fuel units having the largest burn out degree, i.e. the smallest amount of fissible material, preferably are located in the proximity of the periphery of the core. This reduces the leakage of neutrons out from the core and is economically advantageous, but also result in a higher effect and greater thermal loads on the centrally located fuel. The control rods may be divided into various groups, for instance shut down rods, which merely are introduced in the core when the reactor is shut down, and controlling control rods used for controlling the effect of the reactor. Before the reactor is started and an operation cycle is initiated, substantially all control rods are introduced in the core. When the operation cycle begins, a majority of the control rods, for instance about 90%, are extracted from the core. During normal operation of the reactor approximately a tenth of the control rods are thus completely or partly introduced in the core. The primary purpose with the controlling control rods, which are introduced during operation of the reactor, is to absorb excess reactivity in the core. The excess reactivity is built into the core to be successively consumed during the operation cycle, the length of which may vary significantly from less than 12 months to more than 24 months. A long operation cycle also requires correspondingly greater excess reactivity. Such an excess reactivity is accomplished by a larger part of the fuel being new and thus containing a higher concentration of fissible material. A secondary function of the controlling control rods is to control the effect distribution in the core, partly in such a way that no thermal limits are locally exceeded and partly in such a way that the burn out of fissible material is distributed so that no locally high effects arises when the control rods at the end of the operation cycle have to be extracted when the excess reactivity decreases. It is then required that merely the distribution of the fissible material can control the effect distribution. In this controlling function the control rods co-act with the initial distribution of fissible material and burnable absorbers, see below, which is co-optimised with calculations before each new operation cycle. The control rods are not themselves sufficient for absorbing all excess reactivity, especially not during operation cycles longer than 12 months. As a supplement burnable absorbers, for instance Gd2O3, which is fixedly included in the new fuel, are therefore provided. Such a burnable absorber is dimensioned to be burnt-out during the first operation cycle. The burnable absorbers also supplement the control of the effect distribution of the core. The control rods may also be divided into different groups depending on with which cells they are intended to co-act. The control rods may then include first control rods, which co-act with cells with one or several of the first type of fuel units with relatively new fuel, and second control rods, which co-act with cells with the second type of fuel units with partly burn out fuel. The uneven concentration of fissible material in the core, which depends on the fact that the core includes fuel with different degree of burn out, creates problems when determining which control rods are to be introduced during various phases of the operation cycle. The fuel units, which are located most closely to an introduced control rod, will not be burnt-out to the same extent as the fuel units which are located at a distance from this control rod. The relatively small number of control rods in the core during operation thus leads successively to an increasing uneveness in the concentration of fissible material in the core. In addition, a relatively large effect increase is obtained in the fuel units located most closely to the actual control rod position immediately after the control rod has been extracted from the core. Such an effect increase can lead to so called PCI-defects (Pellet Cladding Interaction). PCI, i.e. mechanical interaction between the pellet and the cladding, which via stress corrosion from fission products leads to a crack on the cladding from inside, is a now well investigated defect mechanism which is described in the specialist literature. For a defect to arise several conditions have to be obtained simultaneously: 1. The burn out is to be sufficiently high so that there is a sufficient amount of fission products, so that the cladding is irradiation hardened and so that there is mechanical contact between the pellet and the cladding. With the actual rod design this occurs at a burn out or 15-20 MWd/kgU. Approximately this is valid for about 60% of the core in the beginning of the operation cycle and for about 80% of the core at the end of the operation cycle. 2. The effect increase has to be so quick that the cladding material does not have time to creep and to reduce the stress level. At the first start after a reloading this is valid for a large part of the core, but the reloading is normally performed with the conditioning rules that have shown to be very efficient. During an operation cycle there are then only preconditions for sufficiently large and quick effect increases beside a controlling control rod that are manipulated during the operation cycle. 3. The end effect has to be sufficiently high, partly for the same reasons as for point 1. 4. The high stress level has to be maintained during a sufficiently long time period in order to permit the stress corrosion to act. From tests the required time period is judged to be from a 10 minutes to several hours. Sufficient durability (holding time) is always present in connection with stationary operation, however not at transients. 5. To these conditions it should also be added that local defect notches from, for instance pellet fragments from the manufacturing or cracking during operation, appear to be necessary. Both operation experiences and ramp tests show a significant distribution which hardly may be explained in any other way. These conditions are well proved empirically and PCI is generally regarded as an eliminated defect cause through more careful operation rules with slow effect increase (conditioning), through decreased longitudinal heat load (more and thinner fuel rods) and through different variants of Zr-liners (inner layer of soft, low-alloyed Zr on the inner side of the cladding tube). No protection is however 100% safe and it is important to introduce new operation modes in such a way that the risks are not unnecessarily increased. In this context it is also important to note that the PCI-stresses are significantly higher at the extraction of the control rods than at the introduction. The difference may be a factor 10. The fuel units beside the control rods does not only obtain a lower average burn out but also a skewed burn out since the fuel rods most closely to the control rods are burnt-out very slowly whereas fissible plutonium is generated at a substantially normal degree in these fuel rods. When the control rod is extracted after a long time period of operation, a skewed distribution of fissible material has thus been formed with a corresponding skewed effect distribution as a result, which means that the thermal margin is deteriorated. These problems may according to the prior art be solved in various ways. According to one known method one may during an operation cycle change the control rod configuration at relatively short intervals according to a predetermined sequence. Such a method is suggested in U.S. Pat. No. 3,385,758. A disadvantage of this known solution is that after a certain time of the operation cycle it may be difficult to find new control rod configurations with suitable positions for the control rods. Several disadvantages with this known method are described in U.S. Pat. No. 4,285,769, for instance that the reactor effect has to be decreased at each change of the control rod configuration. The factor of capacity, i.e. the average effect production capability of the reactor is decreased. U.S. Pat. No. 4,285,769 instead suggests that the core is divided into two different types of cells. The first type contains fuel assemblies with relatively new fuel with high reactivity and the second type contains fuel assemblies with partly burnt-out fuel with low reactivity. According to the method defined in U.S. Pat. No. 4,285,769 no control rods are introduced in the cells of the first type but all control takes place in that the control rods are introduced into a part of the cells of the second type. In such a way at least a part of the previously necessary control rod movements may be avoided. These known methods for controlling the control rods during operation are insufficient when the operation cycles become longer. They have been excellent at the relatively short operation cycles which previously have been used, i.e. an operation cycle of up to 1 year or in a best case in certain applications up to 1.5 years. It is now more common with longer operation cycles, i.e. up to 2 years. At such operation cycles with correspondingly higher excess reactivity new strategies are required for controlling the control rods. Further examples of control rod strategies are described in the following documents. U.S. Pat. No. 4,368,171 describes a method for controlling a nuclear reactor by means of control rods in order to obtain a more uniform radial effect distribution. The control rods are divided into different groups at different radial distance from the centre of the core. U.S. Pat. No. 5,217,678 describes another method for controlling a nuclear reactor by means of control rods which are positionable in different control rod patterns. This known method concerns the control of the control rods during change from one control rod pattern to another control rod pattern. U.S. Pat. No. 5,307,387 describes a method for loading fuel assemblies in a core in a reactor. The method is characterised in that peripherally located fuel assemblies are positioned in a central part of the core after at least two operation cycles. U.S. Pat. No. 5,677,938 describes a further method for operating a nuclear reactor. The core is divided into a central area, an intermediate area and a peripheral area. The control rods are grouped in different groups which each is distributed over the whole core. The different control rod groups are introduced after each other at least partly in the core during a desired time interval. This time interval is equally long for all control rod groups. The object of the present invention is an improved method for operating and controlling a nuclear reactor. A further object is a method for operating and controlling a nuclear plant by means of relatively long operation cycles. A still further object is a method for operating and controlling a nuclear reactor in such a way that the above mentioned skewed distribution after a certain time of the operation cycle may be avoided. This object is achieved by the method defined in claim 1. According to the proposed method the two previously known ways of controlling the control rods are combined in such a way that initially some of the control rods are permitted to be introduced during a relatively large part, for instance 40-60% or 10-15 months, of the whole time of the operation cycle. This period is in the following called the cardinal sequence or the cardinal cycle. Thereafter a more active control and movement of the control rods is applied, i.e. one starts to change control rod configuration relatively frequently, for instance every second month. By the method according to the invention the total number of control rod movements may thus be kept at a relatively low level, which contributes to a reduced risk for fuel defects. Furthermore, a relatively small number of control rod movements is advantageous since the effect has to be reduced in connection with the change of control rod configuration and this leads to a decreased factor of capacity. A further advantage is the increased possibility to find new suitable control rod positions for each new control rod cycle. Further advantages with the method according to the invention is that it is possible to keep the problems, connected to the skewed distribution of the reactivity that arises at the fuel units adjoining introduced control rods, at a low level. According to a further development of the method according to the invention the successive control rod cycles, i.e. the control rod cycles after the cardinal cycle, include: operating the reactor during the first of the subsequent control rod cycles with a second control rod configuration with the first group of control rods extracted and a second group of control rods at least partly introduced, and operating the reactor during a second of the subsequent control rod cycles with a third control rod configuration with the second group of control rods extracted and a third group of control rods at least partly introduced. Furthermore, the subsequent control rod cycles may also include: operating the reactor during a third of the subsequent control rod cycles with a fourth control rod configuration with the third group of control rods extracted and a fourth group of control rods at least partly introduced, operating the reactor during a fourth of the subsequent control rod cycles with a fifth control rod configuration with the fourth group of control rods extracted and a fifth group of control rods at least partly introduced, etc. The reactivity loss from the burning out of merely the fissible material is typically 1-1.2 reactivity percent per MWd/kgU and would require a quick control rod extraction as a compensation. During the cardinal cycle the control rods are to be moved relatively moderately in order to obtain the advantages and, preferably, they are to be introduced. This requires that the control rod dependent addition of burnable absorbers is dimensioned and distributed in such a way that they are burnt-out at a somewhat higher speed than the fissible material. A desired netto effect is a slightly increasing reactivity at 0.1-0.3 reactivity percent per MWd/kgU which thus in a convenient manner may be compensated by a slow introduction of control rods during the cardinal cycle. According to a further development of the method according to the invention the fuel includes uranium-235 and uranium-238, wherein the amount of uranium-235 in relation to the amount of uranium-238 is defined as the degree of enrichment of the fuel and wherein at least the first fuel units, which adjoin the control rods in the first group, have a control rod dependent modification of the degree of enrichment. In such a way the fuel units may initially be designed with a compensating skewed distribution of the amount of fissible material. It is thus possible to compensate for the skewed distribution of the reactivity following the fact that a control rod has been introduced during a relatively long time in the proximity of a fuel unit. Advantageously, the control rod dependent degree of enrichment may be such that the fuel rods, which are located in the proximity of the control rods in the first group have a reduced degree of enrichment. Furthermore, the core may have an average of degree of enrichment calculated on all fuel units. Said reduced degree of enrichment may then be at least 0.1% U-235 or at least 0.5% U-235 in the immediate proximity of the control rod. According to a further development of the method according to the invention, the modified degree of enrichment is such that the degree of enrichment of the fuel units, which adjoin the control rods in the first group, increases with an increasing distance from in the proximity of a centre of the control rod from said reduced degree of enrichment of the fuel rods located most closely to the control rod to the average degree of enrichment. According to a further development of the method according to the invention, the fuel units, which adjoin the control rods in the first group, have said control rod dependent addition of burnable absorber that has a capability of absorbing thermal neutrons. Said burnable absorber is consumed during the operation of the reactor. In such a way one may compensate for the increasing reactivity arising when the control rod is extracted due to the fact that plutonium has been generated and uranium-235 has not been consumed during the time during which the control rod was completely or partly introduced. The burnable absorber in the fuel rod will reduce the nuclear reaction until the absorber has been consumed. Said addition of burnable absorber is such that the burnable absorber in each of the fuel units located immediately beside a control rod in the first group is distributed on some of the fuel rods. Advantageously, said addition of burnable absorber may be distributed on 2 to 6 of the fuel rods. Furthermore, the fuel rods on which the control rod dependent addition of burnable absorber is distributed are located immediately beside a control rod in the first group. According to a further development of the method according to the invention, the operation cycle is at least 15 months, preferably at least 18 months and more preferably at least 24 months. FIGS. 1 and 2 disclose a nuclear light water reactor 1 of a boiling water type. The reactor 1 includes a reactor vessel 2 enclosing a core 3. The core includes a plurality of elongated fuel units 4 and a plurality of control rods 5. The fuel units 4, see FIG. 3, are in the embodiment disclosed designed as elongated so called fuel assemblies which each includes a number of fuel rods 6. Each fuel rod 6 has a tubular cladding enclosing a pile of fissible material in the form of so called fuel pellets. In the embodiment disclosed each fuel unit 4 may in a manner known per se also include a central water channel 7 and four thin water channels 8 dividing the fuel units 4 into four smaller longitudinal units, which each forms a part space arranged to receive a respective bundle of fuel rods 6. In a boiling water reactor there is a large number of such fuel units 4, in the order of 400 to 800, and approximately a fourth of that order of control rods 5, i.e. in the order of 100 to 200. For the purpose of illustration, FIGS. 1 and 2 thus disclose a reduced number of fuel units 4 and control rods 5. The fuel units 4 are arranged in parallel to each other and grouped in a plurality of cells which each may include four fuel units 4. Substantially each such cell includes a control rod position in which a respective control rod 5 is completely or partly introduceable by means of a respective drive member 11. The control rods 5 contain neutron absorbing material, such as boron or hafnium, and are used in a boiling water reactor for controlling and interrupting the nuclear reaction in the fuel. The drive members 11, which are controlled by means of a schematically disclosed control unit 12, are arranged to position the respective control rod 5 in an extracted position, see the two outer control rods in FIG. 1, or in a completely or partly introduced position. The fuel in the fuel rods 6 in the fuel units 4 includes uranium-235 and uranium-238. The amount of uranium-235 in relation to the amount of uranium-238 is defined as the degree of enrichment of the fuel. The fuel units 4, which are included in the core 3 during an operation cycle, are different with regard to the amount of fissible material, i.e. have different degree of enrichment. This difference depends in the first place on the fact that the fuel units 4 have been in operation during differently long time periods. The first type of fuel units 4 may be new and thus include a relatively large amount of fissible material. These fuel units have been designated with A in FIG. 2 and are preferably positioned in the proximity of the centre of the core 3. The second type of fuel units 4 may have a certain degree of burn out obtained during one or more previous operation cycles in a reactor. This second type of fuel units 4 thus has a lower degree of enrichment and includes a relatively smaller amount of fissible material. These fuel units 4 have been designated with B and C in FIG. 2 and are preferably positioned in the proximity of the periphery of the core 3, wherein the fuel units B has a higher degree of enrichment than the fuel units C. The fuel units 4 may also from the beginning be designed with different amount and distribution of the fissible material. For instance, one or several of the fuel units 4 which adjoin an introduced control rod 4 may have an initially reduced degree of enrichment at least in the immediate proximity of the respective control rod 5. This control rod dependent modification of the degree of enrichment may be at least 0.5 percent below an average degree of enrichment calculated on all fuel units 4 in the core 3. The control rod dependent modification of the degree of enrichment of the fuel units 4, which adjoin an introduced control rod 5, is such that the degree of enrichment increases with increasing distance from in the proximity of the centre of the control rod from said reduced degree of enrichment of the fuel rods 6, which are located most closely to the control rod 5, to the average degree of enrichment. FIG. 4 discloses the distribution of the enrichment in a fuel unit 4 with 96 fuel rods 6 in a normal case. This normal distribution is symmetric and used for most of the fuel units 4 in the core 3. FIG. 5 discloses a control rod dependent modification of the enrichment, which modification may be applied on the distribution in FIG. 4. FIG. 6 discloses a resulting control rod dependent distribution of the enrichment. This control rod dependent modification thus leads to an asymmetric distribution of the enrichment, which may be used for the fuel units 4, which are located immediately beside a control rod 5 introduced during the cardinal cycle, i.e. at least a part of the fuel units 4 that has been designated by A in FIG. 2. As appears from FIGS. 5 and 6, the enrichment is lower in the fuel rods 6 located in the proximity of the control rod 5. FIG. 4 discloses a symmetric distribution of the enrichment. It is common in reactors where this normal distribution of the enrichment is asymmetric from the beginning due to the asymmetrically arranged water gaps around the fuel units 4. The invention may still be applied in such a case simply by superposing the further asymmetrical control rod dependent modification of the enrichment according to FIG. 5. It is previously known to let at least some of fuel units 4 in the core include a certain amount of a burnable absorber for absorbing a part of the excess reactivity of the core 3. The burnable absorber, which has a capability of absorbing thermal neutrons, may for instance consist of Gd2O3. According to this invention, the fuel units 4, which have been designated by A in FIG. 2 and adjoin an introduced control rod 5, include, in addition to the above mentioned amount of burnable absorber, a control rod dependent addition or a raised content of burnable absorber. This addition is preferably distributed on some of the fuel rods 6′, which are located in immediate proximity of this control rod 5. The control rods 6, which are included by the expression, “in immediate proximity of the control rod” can be seen in FIG. 5, i.e. it is the rods which according to the invention have a control rod dependent reduction of the enrichment. Advantageously, the control rod dependent addition of burnable absorber may be distributed on a relatively small number of fuel rods 6′ in the actual fuel units 4, for instance on 2, 3, 4, 5, 6 or 7 fuel rods 6′. FIG. 4 discloses a fuel unit 54 with 5 such fuel rods 6′. The reactor disclosed may according to the invention be operated in the following manner. Before the reactor 1 is started and an operation cycle is initiated, substantially all control rods 5 are introduced in the core 3. Thereafter the reactor 1 is started by means of an extraction of substantially all control rods 5 except for a first group of control rods 5 which are at least partly introduced in the core 3. This initial control rod cycle, which is called the cardinal cycle, continues during a relatively long time, for instance 10-15 months or approximately 40-60% of the total time of the operation cycle. The total operation cycle is relatively long and may be at least 15 months, at least 18 months, at least 21 months, at least 24 months, at least 27 months or more. An operation cycle of for instance 24 months permits with today's reactor technology an effect output of 15-20 GW d/t. During the cardinal cycle, substantially no or merely small control rod movements take place and then, preferably, introduction of control rods. After the cardinal cycle, the reactor 1 is operated during a number of subsequent control rod cycles with a respective control rod configuration during which different groups of control rods 5 are at least partly introduced. Each of the subsequent control rod cycles are substantially shorter than the cardinal cycle. During a first of the subsequent control rod cycles, the reactor 1 is operated with a second control rod configuration, wherein the first group of control rods 5 are extracted and a second group of control rods 5 are at least partly introduced. During a second of the subsequent control rod cycles, the reactor 1 is operated with a third control rod configuration, wherein the second group of control rods 5 are extracted and a third group of control rods 5 are at least partly introduced. During a third of the subsequent control rod cycles, the reactor 1 is operated with a fourth control rod configuration, wherein the third group of control rods 5 are extracted and a fourth group of control rods 5 are at least partly introduced. During a fourth of the subsequent control rod cycles, the reactor 1 is operated with a fifth control rod configuration, wherein the fourth group of control rods 5 is extracted and a fifth group of control rods 5 is at least partly introduced. It is to be noted that individual control rods 5 may be included in one or more of the above mentioned control rod groups. The first group of control rods 5 may include some of the centrally located control rods 5. These control rods 5, which thus are completely or partly introduced during the cardinal cycle, have in FIG. 2 been drawn with continuous lines whereas the remaining control rods 5 have been drawn with dashed lines. These control rods 5 are located in cells including fuel units 4 with new fuel. This has been exemplified in FIG. 2 in that each of the cells includes two fuel units A and two fuel units B. The four of these fuel units 4 designated by A may have the above mentioned control rod dependent addition of burnable absorber, which is distributed on the fuel rods 6′ located immediately beside the two control rods 5 drawn by continuous lines. Two of these fuel units 4 have been designated by Ak, i.e. these fuel units 4 constitute cardinal fuel units that may have the control rod dependent, reduced, skewed distribution of enrichment disclosed in FIG. 6. The invention is not limited to the embodiment disclosed but may be varied and modified within the scoop of the following claims.
	description	This invention pertains generally to nuclear reactor systems employing ex-core detectors and more specifically to such nuclear reactor systems employing in-containment, ex-core detector low noise amplifier systems. In a pressurized water reactor power generating system, heat is generated within the core of a pressure vessel by a fission chain reaction occurring in a plurality of fuel rods supported within the core. The fuel rods are maintained in spaced relationship within fuel assemblies with the space between the rods forming coolant channels through which borated water flows. The hydrogen within the coolant water moderates the neutrons emitted from enriched uranium within the fuel to increase the number of nuclear reactions and thus increase the efficiency of the process. Control rod guide thimbles are interspersed within the fuel assemblies in place of fuel rod locations and serve to guide control rods, which are operable to be inserted into or withdrawn from the core. When inserted, the control rods absorb neutrons and thus reduce the number of nuclear reactions and the amount of heat generated within the core. Coolant flows through the assemblies out of the reactor to the tube side of steam generators where heat is transferred to water in the shell side of the steam generator at a lower pressure, which results in the generation of steam used to drive a turbine. The coolant exiting the tube side of the steam generator is driven by a main coolant pump back to the reactor in a closed loop cycle to renew the process. The power level of a nuclear reactor is generally divided into three ranges: the source or start-up range, the intermediate range, and the power range. The power level of the reactor is continuously monitored to assure safe operation. Such monitoring is typically conducted by means of neutron detectors placed outside and inside the reactor core for measuring the neutron flux of the reactor. Since the neutron flux in the reactor at any point is proportional to the fission rate, the neutron flux is also proportional to the power level. Fission and ionization chambers have been used to measure flux in the source, intermediate and power range of a reactor. Typical fission and ionization chambers are capable of operating at all normal power levels. However, they are generally not sensitive enough to accurately detect low level neutron flux emitted in the source range. Thus, separate low level source range detectors are typically used to monitor neutron flux when the power level of the reactor is in a source range. The fission reactions within the core occur when free neutrons at the proper energy levels strike the atoms of the fissionable material contained within the fuel rods. The reactions result in the release of a large amount of heat energy which is extracted from the core in the reactor coolant and in the release of additional free neutrons which are available to produce more fission reactions. Some of these released neutrons escape the core or are absorbed by neutron absorbers, e.g., control rods, and therefore do not cause additional fission reactions. By controlling the amount of neutron absorber material present in the core, the rate of fission can be controlled. There are always random fission reactions occurring in the fissionable material, but when the core is shut down the released neutrons are absorbed at such a high rate that a sustained series of reactions do not occur. By reducing the neutron absorbent material until the number of neutrons in a given generation equals the number of neutrons in the previous generation, the process becomes a self-sustaining chain reaction and the reactor is said to be “critical.” When the reactor is critical, the neutron flux is six or so orders of magnitude higher than when the reactor is shut down. FIG. 1 illustrates the primary side of a nuclear electric power generating plant 10 in which a nuclear steam supply system 12 supplies steam for driving a turbine generator (not shown) to produce electric power. The nuclear steam supply system 12 has a pressurized water reactor 14 which includes a reactor core 16 housed within a pressure vessel 18. Fission reactions within the reactor core 16 generate heat, which is absorbed by a reactor coolant, like water, which is passed through the core. The heated coolant is circulated through hot leg piping 20 to a steam generator 22. Reactor coolant is returned to the reactor 14 from the steam generator 22 by a reactor coolant pump 24 through the cold leg coolant piping 26. Typically, a pressurized water reactor has at least two and often three or four steam generators 22 each supplied with heated coolant through a separate hot leg 20, forming with the cold leg 26 and the reactor coolant pump 24, a primary loop. Each primary loop supplies steam to the turbine generator. Two such loops are shown in FIG. 1. Coolant returned to the reactor 14 flows downward through an annular downcomer and then upward through the core 16. The reactivity of the core, and therefore the power output of the reactor 14 is controlled on a short-term basis by control rods, which may be selectively inserted into the core. Long-term reactivity is regulated through control of the concentration of a neutron moderator such as boron dissolved in the coolant. Regulation of the boron concentration effects reactivity uniformly throughout the core as the coolant circulates through the entire core. On the other hand, the control rods effect local reactivity and therefore, result in an asymmetry of the axial and radial power distribution within the core 16. Conditions within the core 16 are monitored by several different sensor systems. These include an ex-core detector system 28, which measures neutron flux escaping from the reactor vessel 18. The ex-core nuclear instrumentation system 28 continuously monitors the state of the reactor and provides system status to the control room. As previously mentioned, there are three types of ex-core detectors; the source, intermediate and power range detectors. The intermediate range pre-amplifier assembly is a critical assembly that interfaces between the intermediate range detector and the Nuclear Instrumentation System Signal Processing Assembly (NISPA). The purpose of this system is to measure neutron radiation leaking out of the core to determine power level for reactor overpower protection and post-accident monitoring. The intermediate range detector measures power levels from near shutdown conditions to 200 percent power. The detectors have an integrated mineral insulated cable which connects the detector to a junction box where the mineral insulated cable is transitioned to a quadax-copper cable. FIG. 2 shows a high level circuit diagram of the ex-core intermediate range nuclear instrumentation system. The intermediate range detector 30 is positioned just outside the reactor vessel 18 in line with the reactor core 16. The output of the detector 30 is fed to a junction box 32 through the mineral insulated cable 40. The mineral insulated cable 40 is transitioned to the quadax-copper cable 42 through the junction box 32. The quadax-copper cable is connected through the penetration in the reactor containment 34 to the nuclear instrumentation system intermediate range pre-amplifier auxiliary panel 36 that contains the intermediate range pre-amplifier 44. The intermediate range pre-amplifier 44 is located outside the containment and amplifies the detector output which is then fed to a nuclear instrument signal interface 38 and a fiber optic modem 48 inside the nuclear instrumentation signal processing center 46. Ex-core detectors for intermediate and power range are required to withstand a loss of coolant accident (LOCA) condition in which the connectors and cables are exposed to elevated temperatures of 200 degrees centigrade and gamma radiation up to 36 MRads. Current detector cable, field cable and connector designs have been shown to be very susceptible to these environmental conditions. One potential solution is to relocate at least two junction boxes outside of the flood zone. This relocation presents several issues such as increased cable losses, the need for additional junction boxes and additional equipment qualification programs and significant additional costs. Accordingly, a solution is needed that can withstand the harsh environment while maintaining or exceeding the functionality of the current system. It is an object of this invention to provide such a solution. These and other objectives are achieved in a nuclear reactor system including a nuclear reactor vessel housing a nuclear core in which fission reactions take place, by a nuclear instrumentation system for monitoring the fission reactions within the nuclear reactor vessel, with at least a portion of the nuclear instrumentation system situated within a radiation shielded containment. The nuclear instrumentation system comprises a nuclear detector responsive to the number of fission reactions within the nuclear core to provide an electrical output indicative thereof. A detector cable connects at one end to the electrical output signal of the nuclear detector, with the detector cable extending between the electrical signal output of the nuclear detector and a termination location within the containment. A vacuum micro-electronic device low noise amplifier is situated at the termination location within the containment and has a vacuum micro-electronic device input connected to the detector cable, for receiving the electrical output of the nuclear detector. The vacuum micro-electronic device is operable to amplify the electrical output of the nuclear detector to provide a nuclear detector amplified output signal. A field cable is connected at an input location of the field cable to an output of the vacuum micro-electronic device low noise amplifier, with the field cable extending from the input location through a penetration in the containment to a field cable output at a processing location outside the containment. A Nuclear Instrumentation System Signal Processing Assembly is located outside the containment at the processing location and is connected at the field cable output and is operable to receive the nuclear detector amplified output signal and from the nuclear detector amplified output signal determine the level of neutron radiation emitted within the core to determine a power level of the nuclear reactor system. In one embodiment, the nuclear detector is an intermediate range nuclear detector and desirably the detector cable is an integrated mineral insulated cable. Desirably, the vacuum micro-electronic device replaces an intermediate range pre-amplifier in a conventional ex-core nuclear instrumentation system. Preferably, the vacuum micro-electronic device also replaces a junction box between the intermediate range pre-amplifier and the nuclear detector in a conventional ex-core nuclear instrumentation system. Desirably, the vacuum micro-electronic device is located within the containment in relatively close proximity to the nuclear detector. In one embodiment, the nuclear reactor vessel is supported within a reactor cavity and the vacuum micro-electronic device is supported adjacent to either side of the wall of the reactor cavity. In one such embodiment, the field cable is a quadax-copper cable. In still another embodiment, a power cable powers both the nuclear detector and the vacuum micro-electronic device. In one preferred embodiment the vacuum micro-electronic device comprises a first stage that primes the electrical output of the nuclear detector to a drive amplifier, with a signal output of the drive amplifier coupled to a converter which is operable to convert the signal output of the drive input to a form compatible with transmission through an optical cable to which the drive amplifier signal is connected. Preferably, an output of the vacuum micro-electronic device is a means square voltage output compatible with monitoring the nuclear flux at the upper end of the intermediate range nuclear detector range. Preferably, the desired amplification output of the vacuum micro-electronic device is obtained from a predetermined power supply input to the vacuum micro-electronic device. As previously explained, ex-core detectors for the intermediate and power range are required to withstand a loss of coolant accident condition in which the connectors and cables are exposed to elevated temperatures of 200 degrees centigrade and gamma radiation up to 36 MRads. Current detector cable, field cable and connector designs have been shown to be very susceptible to these environmental conditions. One potential solution is to relocate at least two junction boxes outside of the flood zone. This relocation presents several issues such as increased cable losses, the need for additional junction boxes, additional equipment qualification programs and significant added costs. A solution is needed that can withstand the harsh environment while maintaining or exceeding the functionality of the current system. This invention provides such a solution. The preferred embodiment comprises a vacuum micro-electronic device low noise amplifier which would replace the intermediate range pre-amplifier in a conventional ex-core nuclear instrumentation system. Given that the current intermediate range pre-amplifier is constructed from discrete components, (i.e., gates, amplifiers, etc.) and not microcontrollers or field programmable gate arrays, the vacuum micro-electronic device is a suitable replacement for these components and is less susceptible to being damaged by radiation and high temperatures and can be positioned much closer to the reactor vessel, either within the reactor vessel cavity or adjacent to the cavity. The vacuum micro-electronic device low noise amplifier improves the signal to noise ratio and noise figure significantly by the physical location of the amplifier closer to the reactor, which is much closer to the output of the ex-core detector (input to the entire nuclear instrumentation system signal transmission chain). Traditional signal theory shows that losses in the front end of a transmission chain influences the signal to noise ratio and noise figure more significantly than losses in later stages. Noise figure is a measure of how the signal to noise ratio is degraded by a device/system. The total noise factor attributed to the noise contribution of each stage in a cascade follow the Friis equation: nf = nf 1 + nf 2 - 1 g 1 + nf 3 - 1 g 1 ⁢ g 2 + … + nf N - 1 g 1 ⁢ g 2 ⁢ g 3 ⁢ ⁢ … ⁢ ⁢ g N - 1 where nfN and gN is the linear noise figure and linear gain, respectively, of stage N. Noise figure is noise factor expressed in decibels (dB). The noise factor equation shows that stage one has the most influence in the overall noise factor/figure of a system. As a result, to reduce the total noise figure, the first stage device should have low noise and relatively high gain. That is why a low noise amplifier is the first active device in a communication system or a system, which processes very low level signals and requires high precision, such as the ex-core nuclear instrumentation system. The vacuum micro-electronic device low noise amplifier is to be located between the ex-core detector output and the penetration, as close to the reactor vessel as practical, preferably in the reactor vessel cavity or in an area adjacent the cavity. This location enables a length reduction of the comparatively more expensive detector cable and more importantly, a reduction of the signal losses associated with approximately 200 feet of cabling. This solution does increase the length of field cable (quadax-copper cable) but reduces the complexity and costs of the junction box, the mating connectors and the field cable. The same power cable is preferably used to provide high voltage to the ex-core detector and to power the pulse amplifier in the vacuum micro-electronic device low noise amplifier. The overall reliability of the system would be improved since the vacuum micro-electronic device is not susceptible to the high temperature or radiation dose effects to which the current system has demonstrated vulnerability. FIG. 3 is a block diagram that shows the vacuum micro-electronic device in the system as it would replace the current intermediate range pre-amplifier 44 shown in FIG. 2. The design of this embodiment utilizes the vacuum micro-electronic devices to amplify the ex-core detector signal. The conventional design uses operational amplifiers that would not be reliable in a high radiation and high temperature environment. There are multiple stages of amplification that are required due to the low signal level of the sensors in the intermediate range detector. The new design will have multiple stages as needed for the various outputs. The first stage, the charge amplifier 54, will output a signal to the second stage, drive amplifier 56. The signal output of the drive amplifier 56 will be sent to amplifier 62 through the band pass filter 58 and to an optical cable 60. Two other means square voltage outputs 66 and 68 are also provided at the outputs of—buffer amplifiers 62 and 64, respectively. The means square voltage output is a method of measuring the neutron flux at the upper end of the intermediate range detector range. FIG. 4 is a circuitry schematic showing the ex-core detector signal processing by the vacuum micro-electronic devices. Each of the amplifiers 54, 56, 62 and 64 are vacuum micro-electronic devices, such as the SSVD supplied by Innosys Inc., Emeryville, Calif. A description of a vacuum micro-electronic device can be found in U.S. Pat. No. 7,005,783. Amplification stages could be eliminated by adjusting the power supply 70 inputs to each of the vacuum micro-electronic devices in order to achieve the gain needed for the specific amplification stage. Accordingly, this invention dramatically improves the accuracy, noise figure and signal to noise ratio of the ex-core nuclear instrumentation system while reducing the complexity associated with the existing instrumentation cabling. Vacuum micro-electronic device technology is radiation hardened and has temperature tolerant characteristics which would allow the ex-core amplifier to be located inside the containment within the vicinity of the reactor vessel and the intermediate range detectors. While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular embodiments disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the appended claims and any and all equivalents thereof.
	claims	1. An illumination optical unit, comprising:a hollow waveguide configured to guide EUV light from an entry opening of the hollow waveguide to an exit opening of the hollow waveguide during use of the illumination optical unit; andan imaging mirror optical unit downstream of the hollow waveguide along a path of the EUV light through the illumination optical unit during use of the illumination optical unit,wherein:the imaging mirror optical unit comprises first and second mirrors, which are the only mirrors of the imaging optical unit;a minimum distance between optically used faces of the first and second mirrors is less than 300 mm;during use of the illumination optical unit:the EUV light impinges on the first mirror and then the second mirror without impinging on a reflective surface between the first and second mirrors; andthe EUV light impinges on the first mirror and then the second mirror without any vector of the EUV light reversing direction;for each of the first and second mirrors, the EUV light is incident on the mirror with a mean angle of incidence greater than 60°; andthe imaging mirror optical unit is configured to image the exit opening of the hollow waveguide into an illumination field to illuminate a mask located in the illumination field. 2. The illumination optical unit of claim 1, wherein the imaging mirror optical unit comprises a Wolter telescope. 3. The illumination optical unit of claim 1, wherein a mirror selected from the group consisting of the first mirror and the second mirror comprises an ellipsoid mirror. 4. The illumination optical unit of claim 1, wherein a mirror selected from the group consisting of the first mirror and the second mirror comprises a hyperboloid mirror. 5. The illumination optical unit of claim 1, wherein a minimum angle of incidence of the EUV light in the hollow waveguide is greater than 80°. 6. The illumination optical unit of claim 1, wherein an overall reflectivity of the illumination optical unit for the EUV light is greater than 40%. 7. The illumination optical unit of claim 1, wherein the first mirror comprises an ellipsoid mirror, and the second mirror comprises an ellipsoid mirror. 8. The illumination optical unit of claim 1, wherein the first mirror comprises a hyperboloid mirror, and the second mirror comprises a hyperboloid mirror. 9. A system, comprising:an EUV light source;an illumination optical unit, comprising:a hollow waveguide configured to guide EUV light from an entry opening of the hollow waveguide to an exit opening of the hollow waveguide during use of the system; andan imaging mirror optical unit downstream of the hollow waveguide along a path of the EUV light through the illumination optical unit during use of the system, the imaging mirror optical unit being configured to image the exit opening of the hollow waveguide into an illumination field;a projection optical unit configured to image the illumination field into an image field; anda detection device configured to detect EUV incident on the image field,wherein:the imaging mirror optical unit comprises first and second mirrors, which are the only mirrors of the imaging optical unit;a minimum distance between optically used faces of the first and second mirrors is less than 300 mm; andduring use of the illumination optical unit:the EUV light impinges on the first mirror and then the second mirror without impinging on a reflective surface between the first and second mirrors;the EUV light impinges on the first mirror and then the second mirror without any vector of the EUV light reversing; andfor each of the first and second mirrors, the EUV light is incident on the mirror with a mean angle of incidence greater than 60°. 10. The system of claim 9, wherein the imaging mirror optical unit comprises a Wolter telescope. 11. The system of claim 9, wherein a minimum angle of incidence of the EUV light in the hollow waveguide is greater than 80°. 12. The system of claim 9, wherein an overall reflectivity of the illumination optical unit for the EUV light is greater than 40%. 13. The system of claim 9, wherein the first mirror comprises an ellipsoid mirror, and the second mirror comprises an ellipsoid mirror. 14. The system of claim 9, wherein the first mirror comprises a hyperboloid mirror, and the second mirror comprises a hyperboloid mirror. 15. A method, comprising:using an illumination optical unit to illuminate a lithography mask in an illumination field with EUV light, the illumination optical unit comprising:a hollow waveguide configured to guide the EUV light from an entry opening of the hollow waveguide to an exit opening of the hollow waveguide; andan imaging mirror optical unit downstream of the hollow waveguide along a path of the EUV light through the illumination optical unit,wherein:the imaging mirror optical unit comprises first and second mirrors, which are the only mirrors of the imaging optical unit;a minimum distance between optically used faces of the first and second mirrors is less than 300 mm;during the method:the EUV light impinges on the first mirror and then the second mirror without impinging on a reflective surface between the first and second mirrors;the EUV light impinges on the first mirror and then the second mirror without any vector of the EUV light reversing; andfor each of the first and second mirrors, the EUV light is incident on the mirror with a mean angle of incidence greater than 60°; andthe imaging mirror optical unit images the exit opening of the hollow waveguide into an illumination field. 16. The method of claim 15, further comprising using a projection optical unit to project an image of the lithography mask into an image field. 17. The method of claim 16, further comprising detecting EUV light incident on the image field. 18. The method of claim 15, further comprising detecting EUV light incident on the image field. 19. The method of claim 15, wherein the first mirror comprises an ellipsoid mirror, and the second mirror comprises an ellipsoid mirror. 20. The method of claim 15, wherein the first mirror comprises a hyperboloid mirror, and the second mirror comprises a hyperboloid mirror.
	claims	1. A composition effective to at least partially disrupt and dissolve radioactive deposits formed on a surface of a structure in a nuclear water reactor when the composition is in contact with the surface of the structure during non-operational conditions, the composition consisting essentially of:an aqueous component at ambient temperature;from about 0.001 M to about 2 M based on the composition, of at least one elemental metal additive to the aqueous component, selected from the group consisting of zinc, beryllium, aluminum, magnesium, iron, lithium, and mixtures thereof, in particulate, powder or colloidal form;from about 0.025 weight percent to about 5.0 weight percent based on total weight of the composition, of an additive selected from the group consisting of a sequestering agent, a chelating agent, and mixtures thereof;optionally a dispersant;optionally an oxygen scavenger;optionally a pH adjustment agent; andoptionally a reducing agent;wherein the radioactive deposits comprise oxide-containing radionuclides deposited on the surface, and wherein the surface is a primary side structure surface in the nuclear water reactor. 2. The composition of claim 1, wherein the elemental metal component is zinc. 3. The composition of claim 1, wherein the elemental metal is in colloidal form. 4. The composition of claim 3, wherein the colloidal form contains particles selected from the group consisting of micron-sized particles, nano-sized particles and combinations thereof. 5. The composition of claim 1, further comprising a dispersant. 6. The composition of claim 1, wherein the aqueous component has a pH in a range from about 3.0 to about 13.
	description	This patent application is a U.S. National Stage of PCT application number PCT/US2018/026443 filed in the English language on Apr. 6, 2018, and entitled “COMPACT PROTON BEAM ENERGY MODULATOR,” which claims priority to and benefit of U.S. Provisional Patent Application No. 62/482,743 (filed Apr. 7, 2017), which is incorporated here by reference in its entirety. Proton beams are used in medical applications to apply radiation treatment to areas of a patient's body. For example, a proton beam may be applied to a cancerous tumor with more precision than standard radiation techniques. Using a proton beam for treatment may reduce or eliminate radiation damage to tissues surrounding the targeted tumors. This is due, at least in part, to a proton's ability to deliver a radiation dose to a very small and condensed area compared to other radiation delivery techniques. Treatment consists of directing high energy protons into a patient's body such that the protons deposit their radiation energy inside the tumor. Prior to treatment, the tumor and surrounding area must be imaged. Typically, photon-based imaging techniques like x-ray have been used. However, the photons used by these techniques differ from the protons used for delivery of treatment and interact with the tissue differently. Thus, using a photon-based imaging system to guide the proton-based treatment may introduce a margin of error. For certain applications, it may be beneficial to provide a proton beam modulator to meet one or more of the following goals: a minimum modulation range of 25 cm WET, a maximum period of full range modulation less than 300 ms, a constant scattering angle during modulation, a minimum energy step resolution of 2 mm WET, a maximum random error of less than 0.5 mm WET, the ability to stop the beam entirely once per cycle period, a modulator size that may fit within a 10 cm cube, the ability to accommodate a 0.5 cm beam diameter, balanced weight around an axis of rotation to minimize vibration during rotation, ability to operate in a vacuum, and the ability to let a proton beam pass through the modulator unobstructed. In embodiments, a proton beam modulator includes a first modulating portion comprising a first material portion and a second material portion through which a proton beam passes; and a second modulating portion comprising a third material portion and a fourth material portion through which the proton beam passes; wherein the first and second modulating portions are positioned opposite each other on a rotating wheel. One or more of the following features may be included: The rotating wheel may be positioned so that the proton beam passes through a center of rotation of the rotating wheel. The rotating wheel may be positioned so that an axis of rotation of the rotating wheel is perpendicular to the proton beam. The first modulating portion and the second modulating portion may be positioned to create an open channel through the modulator so that, when the channel is parallel to the proton beam, the proton beam can pass through the open channel without passing through the first and second modulating portion. The first modulating portion may have a wedge shape. The first material portion and the second material portion are arranged radially from a center of rotation of the wheel so that the second material portion is inside the first material portion. A thickness of the wedge shape may decrease along an angular coordinate of the wedge shape. A thickness of the first material portion may decreases along the angular coordinate of the wedge shape and a thickness of the second material portion may increase along the angular coordinate of the wedge shape. The combination of the first, second, third, and fourth material portions may modulate an energy level of the proton beam and a scattering of the proton beam. The combination of the first, second, third, and fourth material portions may modulate the energy level of the proton beam such that the energy level of the proton beam changes as the modulator rotates. The first and second modulating portions are each provided having a wedge shape. The first and second modulating portions are each provided having a wedge shape and produce an energy modulation in the range of about 12 cm WET to about 32 cm WET. The combination of the first, second, third, and fourth material portions may modulate the scattering of the proton beam so that the scattering remains substantially constant as the modulator rotates. A circular plate may be positioned so that the first modulating portion and the second modulating portion are sandwiched between the rotating wheel and the circular plate. The first and second modulating portions may be removable from the rotating wheel and the circular plate. The first and third material portions may comprise stainless-steel. The second and fourth material portions may comprise lead. The rotating wheel may have a diameter of 10 cm or less. In another embodiment, a proton beam imaging system includes: a proton beam generator to generate a proton beam; a proton beam modulator through which the proton beam passes positioned between the proton beam generator and an image target; and a proton beam detector positioned to detect the proton beam existing the image target; wherein the proton beam modulator comprises: a rotating wheel having an axis of rotation positioned so that the proton beam passes through the axis of rotation and the axis of rotation is perpendicular to the proton beam; a first modulating portion comprising a first material portion and a second material portion through which a proton beam passes; and a second modulating portion comprising a third material portion and a fourth material portion through with the proton beam passes; wherein the first and second wedges are positioned opposite each other on the rotating wheel. One or more of the following feature may be included: The first and third material portions may comprise stainless-steel, and the second and fourth material portions may comprise lead. The first and third material portions may comprise a wedge shape having a varying thickness to modulate an energy level of the proton beam as the proton beam modulator rotates, wherein the proton beam may be modulated to have a varying energy level as the proton beam modulator rotates. The second and fourth material portions may comprise a wedge shape having a varying thickness to modulate a degree of scattering of the proton beam as the proton beam modulator rotates, wherein the proton beam may be modulated to have a substantially constant degree of scattering as the proton beam modulator rotates. The proton beam imaging system may comprise a gantry portion, wherein the proton beam modulator is situated within the gantry portion. In embodiments, a proton beam modulator includes a plurality of wedge-shaped modulating portions, each of the plurality of wedge-shaped modulating portions comprising a first material portion and a second material portion configured such that in response to a proton beam incident thereon, at least portions of the proton beam are capable of passing therethrough and wherein the of the plurality of wedge-shaped modulating portions are disposed in spatial relation such that the plurality of wedge-shaped modulating portions define an axis of rotation positioned such that an axis along which a proton beam is aligned is perpendicular to the axis of rotation defined by the plurality of wedge-shaped modulating portions. In embodiments, the plurality of wedge-shaped modulating portions are provided as a pair of modulating portions positioned opposite each and define an axis of rotation positioned such that an axis along which a proton beam is aligned is perpendicular to the axis of rotation defined by the pair of wedge-shaped modulating portions. FIG. 1 is a block diagram of a proton beam imaging system 100. Proton beam imaging system 100 includes a beam generator 102 which generates a proton beam 104. Proton beam 104 may be a columnar beam with a fixed or variable energy level. Modulator 106 may comprise a quantity of material through which proton beam 104 passes. As it passes through, proton beam 104 may lose energy due to dissipation or blocking by modulator 106. Modulator 106 may also scatter the protons in beam 104. As a result, the incident beam 108 that passes through modulator 106 may have a lower energy level (due to dissipation) and a wider area (due to scattering) than proton beam 104. Incident beam 108 may then pass through target 110, which may also affect the energy level and scattering profile of beam 108. In embodiments, target 110 may be the item to be imaged by proton imaging system 100. If proton imaging system 100 is used in a medical imaging application, for example, target 110 may be a portion of a patient's body. A proton detector array 112 may detect proton beam 111 exiting target 110. Once detected, the signals produced by proton detector array 112 may be processed (e.g. by a general purpose or image processor) to produce an image of target 110. Proton beam generator 102 may be housed in a gantry (not shown). For example, if the proton beam imaging system is a medical imaging system, a gantry may be suspended in or around a patient bed or examination table. In embodiments, the proton beam modulator may also be situated in the gantry so that proton beam 104 exits the gantry having already been modulated. Referring to FIG. 2, materials through which a proton passes may be qualified with a water equivalent thickness (“WET”) that indicates how much energy the material will dissipate from the proton as the proton passes through the material. Graph 200 illustrates the WET concept. The horizontal axis represents depth (in cm) through which a proton travels through water. The vertical axis represents radiation given off by the proton. When the energy of a proton is almost depleted, the proton delivers a maximum dosage of radiation called a Bragg peak. Peaks (e.g. peaks 202-214) represent the Bragg peaks of protons having various levels of initial energy. A proton with greater initial energy will travel further through water than a proton with relatively less initial energy. For example, peak 202, which occurs at about 6 cm of water depth, results from a proton having 100 MeV of energy (as shown by reference number 202a). Peak 214, which occurs at about 37 cm of water depth, results from a proton having 250 MeV of energy (as shown by reference number 214a). The other peaks result from protons having energy levels between 100 MeV and 250 MeV, as indicated by their respective energy levels labeled 202a-214a. Referring to FIG. 3, materials may be qualified by their WET rating. In FIG. 3, a proton passing through X cm of water results in Bragg peak 300. Similarly, a proton passing through material 302 results in Bragg peak 304. Because Bragg peaks 300 and 304 are the same, material 302 may be said to have a WET value of X cm. FIG. 4 is a diagram that illustrates the effect of modulators having different WET values. In this example, modulator 402 may have the smallest WET value, modulator 404 may have an intermediate WET value, and modulator 406 may have the largest WET value of the three modulators shown. As a result, protons that pass through modulator 402 may exit modulator 402 with a higher energy level than protons that pass through modulator 404 because modulator 404 will dissipate more energy from the protons than modulator 402. Similarly, protons that pass through modulator 404 may exit modulator 404 with a higher energy level than protons that pass through modulator 406. Because the protons have different levels, their respective Bragg peaks will occur at different locations. The proton that passes through modulator 402 has the highest energy level, thus its Bragg peak 410 occurs at a location further than Bragg peak 412 and 414. The proton that passes through modulator 404 has an intermediate energy level, thus its Bragg peak 412 occurs at a location between Bragg peaks 410 and 414. And the proton that passes through modulator 406 has the lowest energy, thus its Bragg peak 414 occurs before Bragg peaks 410 and 412. The variation in proton energy levels and the resulting difference in Bragg peak location can be detected by detector 416 to produce an image of patient 408. One reason to modulate the proton beam is so that the proton beam imaging system can create a dosage rate function on the proton detector 416 for each pixel of the created image. The dosage rate function is the curve representing the dose measured by the detector pixels vs time. It is created by modulating the incident proton beam energy. The dose measured on the detector is maximum when the Bragg peak lands on the detector 410 and is produced by the modulator having a WET 402. As the modulator varies in WET 404 & 406 vs time, the dose on the detector varies in time. The material and tissue of patient 408 that the proton beam passes through may have different water equivalent path lengths (WEPL). For example, bone may have a different WEPL than organ tissue, which may have a different WEPL than muscle tissue, etc. These different tissues may dissipate different amounts of energy from the proton beam, which may result in different dosage rate functions at the pixels receiving protons passing through that portion of the patient. These dosage rate functions at each pixel may be compared to calibration data consisting of dosage rate functions for known WET values. Thus, to create an accurate image, it is desirable to use this comparison to calculate the WEPL (water equivalent path length) from each pixel and reconstruct an overall image based on WEPL vs x and y. This WEPL image may result in a more accurate calculation of the relative stopping power (RSP) of the proton beam for treatment than current conversion from computed tomography (CT) images. FIG. 5 is a diagram of proton beam scattering by a modulator 500. Along with energy dissipation described above, a proton beam may scatter, i.e. spread out, as it passes through material such as modulator 500. Beam 502 may be a columnar beam when it enters modulator 500. However, proton beam 504 exiting modulator 500 may be scattered by an angle θ. This may cause a lateral spread x. Referring to FIG. 6, a proton beam modulator 600 of the prior art includes a cylindrical body 602 through which proton beam 604 passes. Body 602 has a thickness that varies around the body's circumference. For example, body 602 is thicker at point 608 than it is at point 606. If beam 604 passes through body 602 at point 608, body 602 will dissipate more energy from beam 604 than if beam 604 passed through body 602 at point 606. The scattering effect at points 606 and 608 may also be different. Proton beam modulator 600 may rotate about an axis 610, which may be parallel to and offset from proton beam 604. As modulator 600 rotates, proton beam 604 will pass through portions of body 602 with varying thickness. Thus, as modulator 600 rotates, the energy of beam 604 will vary. FIG. 7 is a block diagram of another embodiment of a proton beam imaging system. A proton beam generator 700 produces proton beam 702, which passes through modulator 704, through a target (not shown), and is detected by proton detector 706. Proton beam modulator 704 may be a cylindrical modulator that rotates while beam 702 passes through it. In embodiments, the axis of rotation of modulator 704 may be perpendicular to beam 702 (i.e. in a direction into or out of the page) so that modulator 704 rotates in the direction of arrow 708. Also, modulator 704 may be positioned so that beam 702 passes through the center of rotation 710. Proton beam modulator 704 may include two material sections 712 and 714 positioned so that beam 702 passes through section 712 and 714 as it passes through modulator 704. Material sections 712 and 714 may have variable thicknesses so that, as modulator 704 rotates, the thickness of the material that beam 702 passes through varies. As a result, as modulator 704 rotates, the thicker areas of material sections 712 and 714 will dissipate more energy from the proton beam and perform more scattering of the proton beam, so the energy level and scattering of beam 702 exiting the modulator will vary. Referring to FIGS. 8 and 8A, a modulator assembly 800 is mounted, or otherwise coupled or secured to, a drive system 801. In this illustrative embodiment, modulator assembly 800 is provided having a wheel-shape. Other shapes may, of course be used including but not limited to any regular or irregular geometric shape. Drive system 801 is capable of controlling the “spin” (i.e. the rate at which a modulator rotates around an axis of rotation) of at least a modulator 803 within modulator assembly 800. Specifically, modulator 801 is coupled to a shaft (e.g. a motor shaft) or other mechanical structure (not visible in FIG. 8) and drive system 801 turns the modulator 801 at a controllable and accurate rate of speed. In embodiments, drive system 801 is provided as a motor and modulator 801 is coupled to a motor shaft (not visible in FIG. 8). As shown, modulator assembly 800 is disposed relative to a proton beam generator such that an axis of rotation 802 of modulator assembly 800 is perpendicular to an axis 805 along which a proton beam is aligned. During operation, motor 801 may rotate at least modulator 803. As a proton beam 805 passes through modulator assembly 800 (and in particular through modulators portions 804, 806), wedge-shaped modulators 804, 806 (FIG. 8A) intercept a proton beam 805. The configuration of the wedge-shaped modulators 804, 806 cause the energy level of proton beam 805 to vary after passing therethrough. Thus, the energy level of proton beam 805 may be varied during, for example, an imaging operation. The beam with varying energy levels may pass through a target (not shown in FIG. 8) and be detected by a proton beam detector (also not shown in FIG. 8). The detector may produce a signal representing the detected protons, which can be used by a processor to form an image of the target. In embodiments, drive system 801 may be provided as a servo motor, or any other type of motor capable of precisely controlling the angular position and speed of rotation of the modulator within modulator assembly 800. It should, of course, be appreciated that any type of motor capable of rotating the modulator may, of course, also be used. In one illustrative embodiment, drive system 801 may rotate modulator 800 at about 15 to about 20 rpms (i.e. one rotation every three to four seconds) or faster. In other embodiments, drive system 801 may rotate modulator 800 at about 180 rpm (i.e. a period of about 300 ms) or faster. This allows the modulator to sweep the energy level from the highest to the lowest energy level (or vice versa) in the time that it takes a person to take a breath. This may be beneficial if, for example, the proton beam imaging system is collecting an image of a patient's lung or other movable body area. If the full sweep of modulation occurs within a few seconds, or within a few hundred milliseconds, the imaging system may be able to capture an image before much body movement has occurred. Referring now to FIG. 8A modulator 803 includes a plurality of material sections (with two wedge-shaped material sections 804 and 806 shown in the illustrative embodiment of FIG. 8A) positioned about axis of rotation 802. In embodiments, material sections may be placed symmetrically about axis of rotation 802 so that modulator 803 is balanced during rotation, which may help reduce rotational vibration. As beam 805 passes through material sections (e.g. material sections 804 and 806 in the illustrative embodiment of FIG. 8A), the material sections may modulate and scatter beam 805 as described above. The material sections may be provided having a shape such that when they are appropriately positioned, a straight, open channel 808 exists through modulator 803. When modulator 803 is rotated so that channel 808 is parallel to beam 805, beam 805 may pass through channel 808 without passing through the material sections. In other words, when channel 808 is parallel to beam 805, beam 805 may pass through modulator 803 without being modulated. This may be useful if it is desired to use the same proton beam for imaging and radiation delivery. For example, modulator 803 can modulate the beam as it passes through material sections 804 and 806 for imaging. Then, for radiation dosage delivery, modulator 800 may rotate to a position that allows beam 805 to pass through channel 808 without being modulated. In this position, the unmodulated proton beam 805 may be used to deliver doses of radiation that are higher in energy than the modulated beam to target tissue. In some applications, lower proton beam energies are used for treatment than for imaging. For example, a beam with lower energy may deliver its Bragg peak (and its resulting energy) within the patient at the site of treatment, rather than passing through the patient to be detected by the proton detector. If a lower proton beam is needed for treatment, it may seem counterintuitive to use open channel 808 during treatment because open channel 808 does not dissipate energy from beam 805. However, in embodiments, the proton beam treatment system may include another modulator specifically for modulating beam 805 during treatment. In these systems, the open channel 808 of modulator 800 may be used during treatment so that a separate treatment modular can be used to control the energy of beam 805 to deliver the proton beam's radiation to the treatment site within the patient. In embodiments, material sections 804 and 806 may each have a curved wedge shape. The wedge shape may provide each material section with a thickness that varies along the length (e.g. along the shape) of each wedge. For example, material section 806 may have a thick end 810 and a thin end 812. Likewise, material section 804 may have a thick end 814 and a thin end 816. The thicker areas may provide more energy dissipation than the thin ends. Thus, a proton passing through thick portion 810 and thick portion 814 may exit modulator 803 with a lower energy level than a proton passing through thin portions 812 and 816. As modulator 803 spins, the thickness of the material through which proton beam 805 varies, and thus the energy level of proton beam 805 exiting modulator 800 will vary. Material section 804 may comprise a first material 818 and a second material 820 coupled together to form the shape of material section 804. Similarly, material section 806 may comprise a first material 822 and a second material 824 coupled together to form the shape of material section 806. In embodiments, material 818 and material 822 may be the same material. Likewise, material 820 and material 824 may be the same material. In other embodiments, the materials may vary. Materials 818 and 820 of material section 804 may be chosen so that, as modulator 803 rotates, modulator 803 will vary the energy level of proton beam 805 across a desired energy range and also maintain a relatively constant scattering angle of proton beam 805. For example, as proton beam 805 passes through thick portion 814 it will exit modulator 803 with less energy than when it passes through thin portion 816. However, the scattering of proton beam 805 will remain relatively constant whether it passes through thick portion 814 or thin portion 816. This effect can be achieved by the type of material and relative thicknesses chosen for material sections 818 and 820 (and material sections 822 and 824). Different materials have different WET characteristics, as shown in table 1. TABLE 1MaterialThickness (cm)WET (cm)Lead4.525Aluminum11.925Human Tissue (lung)85.425Water2525Titanium725Stainless-steel4.625Table 1 shows the relative thickness of a material needed to achieve a WET characteristic of 25 cm. For example, lead having a thickness of about 4.5 cm will deplete the energy of a proton beam passing through it to the same degree as a tank of water with a thickness of 25 cm. Stainless-steel having a thickness of about 4.6 cm will deplete the energy of a proton beam passing through it to the same degree as a tank of water with a thickness of 25 cm. Different materials may also have different scattering effects on proton beam 805. For example, a quantity of lead with a particular thickness may scatter beam 805 to a greater degree than a quantity of stainless-steel with the same thickness. In embodiments, material 818 may be stainless-steel and material 820 may be lead. Similarly, material 822 may be stainless-steel and material 824 may be lead. Because lead and stainless-steel have similar WET values, it may be convenient to use them together in modulator 800 to perform modulation. However, any material may be used to perform the modulation so long as the material thickness is chosen to achieve the desired energy dissipation. As shown in FIG. 8, the overall thickness of material section 804 (which comprises material 818 and material 820) tapers from relatively thick to relatively thin as angle θ increases. Similarly, the thickness of material 818 tapers from relatively thick to relatively thin as angle θ increases. Also, having an opposite taper, the thickness of material 820 tapers from thin to thick as angle θ increases. If material section 804 consisted of a single type of material with varying thickness, then the energy level and the scattering effect of beam 805 may both vary as beam 805 traverses the single material. However, to achieve an accurate image from a proton beam imaging system, it may be desirable to vary the energy level of beam 805 while maintaining a relatively constant scattering of beam 805. Providing two materials having different scattering effects may allow modulator 800 to achieve this goal. As noted above, lead and stainless-steel have similar WET characteristics for dissipating energy from proton beam 805. In contrast, lead and stainless-steel may have different scattering effects on beam 805. Lead, for example, may provide more scattering than stainless-steel for a given thickness of material. As such, material section 804 may comprise both lead and stainless-steel sections. For example, as beam 805 passes through thick portion 814, stainless-steel section 818 may provide a relatively large amount of energy dissipation and scattering. As beam 805 passes through thin portion 816, stainless-steel section 818 may provide a relatively small amount of energy dissipation and scattering. Lead section 820, which may provide more scattering per cm of thickness than stainless-steel, may be relatively thicker at end 816 to compensate for the lack of scattering at end 816. Thus, the combination of materials may provide reduced energy dissipation and relatively constant scattering as angle θ increases. As noted above, beam 805 may pass through both material sections 804 and 806. Thus, beam 805 may pass through stainless-steel section 818, lead section 820, lead section 824, and stainless-steel section 822 as it passes through modulator 800. The effects of these sections on beam 805 may be additive. For example, if at a given point where beam 805 is passing through the modulator, the thickness of stainless-steel section 818 is 1 cm and the thickness of stainless-steel section 822 is 1 cm, the energy dissipation and scattering effect provided by these two sections may be the same or similar to a single stainless-steel section with 2 cm thickness. The same additive characteristic may be true for lead sections 820 and 824. Thus, the sum of the thicknesses of material sections 818, 820, 822, and 824 may be chosen so that the sections, in combination, provide the desired modulation and scattering effects. Although modulator 800 is shown with stainless-steel sections positioned along the outside circumference and lead sections positioned closer to axis of rotation 802, any placement of the materials may be used to achieve the desired dissipation and scattering effects. For example, the lead sections could be placed along the outside circumference and the stainless-steel sections could be placed closer to axis of rotation 802. Also, although the stainless-steel and lead sections are shown in direct contact with one another, in other embodiments there may be an air gap between the lead and stainless-steel sections. Additionally, although stainless-steel and lead are used as example materials, other materials may also be used to achieve the desired dissipation and scattering effects. In each of these alternate embodiments, the thickness of each material section may be altered and/or chosen so that the desired dissipation and scattering effects are achieved. In embodiments, material sections 804 and 806 need not be wedge-shaped. Other shapes (such as a sine wave shape, a triangle shape, etc.) may provide other modulation profiles if desired. In other embodiments, the thickness of material sections 804 and 806 is shown in the thickness profile of FIG. 10, which will be discussed below. FIG. 9 is an exploded isometric view of a portion 900 of a modulator assembly 800 (FIG. 8). In an embodiment, modulator assembly 800 (FIG. 8) comprises an inner plate 902 (here shown as a wheel-shaped inner plate 902) and an opposite, outer plate 904 (here shown as a wheel-shaped outer plate 904). Wedge-shaped material sections 804 and 806 (which together form modulator 803) are secured between plates 902 and 904. It should be appreciated that inner and outer plates may be provided having any shape suitable to secure the modulator 803. In embodiments, wedge-shaped material sections 804 and 806 may be secured between plates 902 and 904 using any securing, mounting or fastening technique known to those of ordinary skill in the art. In the illustrative embodiment of FIG. 9, bolts 906 and 908 which pass through holes in plate 904 and material sections 804 and 806 are used. Bolts 906 and 908 may engage threaded holes in plate 902 and may be tightened to secure plates 902 and 904 and material sections 804 and 806 in desired positions. In embodiments, modulator 800 includes additional bolts or pins through material sections 804 and 806 so they do not pivot out of place. Bolts 906 and 908 may be made from the same type of stainless-steel as material sections 818 and 822 so that they do not create inconsistencies in beam dissipation when beam 805 passes through bolts 906 and 908. Plate 902 may also include a hole 910 at the axis of rotation that can be used to mount modulator 800 on a motor spindle or shaft. A modular design such as the one shown in exploded view 900 may allow a user to easily swap components. For example, material sections 804 and 806 may be swapped for sections having other types of materials and shapes. Also, modulator assembly 800 (or just a modulator portion of a modulator assembly such as assembly 800) may be de-coupled or otherwise removed from motor 801 and replaced with another modulator and/or modulator assembly which provides a different modulation profile if needed for a particular application. FIG. 10 is a graph 1000 of material thickness versus scattering angle. The horizontal axis represents material thickness in cm. The vertical axis represents proton beam scattering angle in degrees. Curve 1002 is a scattering profile for stainless-steel and curve 1004 is a scattering profile for lead. As shown (and as discussed above) lead provides more scattering at a given thickness than stainless-steel. For example, 2 cm of lead causes approximately 3 degrees of scattering while 2 cm of stainless-steel causes approximately 1.5 degrees of scattering (see points 1006 and 1008, respectively). FIG. 11 is a graph 1100 that illustrates a thickness profile for material sections 818 and 820 (and/or material sections 822 and 824). (See FIG. 8). The horizontal axis represents the angle α and the vertical axis represents radial thickness in cm. Curve 1102 represents the thickness of stainless-steel section 818. As angle α increases from 0 to 150, the thickness of section 818 increases linearly from about 0 cm to about 3.2 cm. Curve 1104 represents the thickness of lead section 820. As angle α increases from 0 to 150, the thickness of section 818 decreases from about 0.7 cm to about 0 cm. In embodiments, curve 1104 may approximate an exponential decay. FIG. 11 illustrates thicknesses for one embodiment of modulator 800. Other thicknesses and shapes may also be used. FIG. 12 is a graph 1200 that illustrates a scattering effect (curve 1202) for a modulator (e.g. modulator 800) with the material thickness profile shown in graph 1100. The horizontal axis represents the angle α and the vertical axis represents scattering angle of a proton beam passing through modulator 800 at angle α. As angle α increases, the proton beam scattering angle stays relatively constant at about 2.3 degrees. FIG. 13 is a graph 1300 that illustrates proton beam energy modulation for a modulator (e.g. modulator 800) with the material thickness profile shown in graph 1100. The horizontal axis represents the angle α and the vertical axis represents the WET characteristic of modulator 800 as seen by a proton beam entering modulator 800 at angle α. As angle α increases (i.e. as the thickness of the material through which the proton beam passes increases), the WET characteristic of modulator 800 increases approximately linearly from about 10 WET to about 30 WET. In other embodiments, the WET characteristic of modulator 800 may range from less than about 12 WET to more than about 32 WET FIG. 14 is a graph 1400 of measured test results that illustrate Bragg peaks of a proton beam passing through modulator 800 during operation. In this example, after exiting the modulator, the proton beam enters a tank of water (or, in this case, test equipment that simulates a tank of water). The horizontal axis represents the depth that the protons travel in the water tank. The vertical axis represents arbitrary units of energy released by the protons. As shown, as modulator 800 operates, Bragg peaks 1402 can be seen ranging between 0 cm and about 25 cm in the water tank. In other embodiments, Bragg peaks 1402 may range between about 12 cm WET to about 32 cm WET. Bragg peak 1404 corresponds to the unmodulated proton beam that passes through open channel 808 without passing through material section 804 or 806. (See FIG. 8). Thus, because they are unmodulated, the proton or protons that generate Bragg peak 1404 have a significantly higher energy level. Having described various embodiments, which serve to illustrate various concepts, structures and techniques, which are the subject of this patent, it will now become apparent to those of ordinary skill in the art that other embodiments incorporating these concepts, structures and techniques may be used. Accordingly, it is submitted that that scope of the patent should not be limited to the described embodiments but rather should be limited only by the spirit and scope of the following claims. All references cited in this document are incorporated here by reference in their entirety.
	abstract	Image contrast grids include a body having openings and an x-ray absorbing material in the openings. The openings can be formed by various micromachining techniques and the x-ray absorbing material can be formed in the openings by various coating and deposition techniques. The image contrast grids can have contoured surfaces for improved focusing capabilities. The image contrast grids can remove Compton scattered x-rays in two, non-normal dimensions. The openings can be formed with fine structures that are not visible in most imaging modes.
	summary
059088842	description	EXAMPLES Example 1 Eighty eight % by weight of tungsten powder having an F.s.s.s. particle size of 3 .mu.m and 12% by weight of unvulcanized fluoro rubber containing a suitable amount of peroxide as a vulcanizer are weighed, and the tungsten powder and the unvulcanized fluoro rubber with a vulcanizer were mixed in an open roll mill for 15 minutes. Then, a 1 mm-thick vulcanized rubber sheet (hereinafter referred to as sample 1) was produced by pressing the mixture. On the other hand, 95% by weight of tungsten powder having the same F.s.s.s. particle size as described above and 5% by weight of unvulcanized EPDM rubber (ethylene-propylene rubber, hereinafter referred to as EPDM) containing a suitable amount of sulfur as a vulcanizer are weighed, and the latter was dispersed in the former in the same manner as described above to thereby prepare another sample (hereinafter referred to as sample 2). The respective sections of these samples 1 and 2 were observed by using an SEM (scanning electron microscope, hereinafter referred to as SEM). As a result, it was confirmed that tungsten powder was dispersed in a matrix of the vulcanized rubber substantially evenly. The specific gravity of the shielding material in each of the samples 1 and 2 was about 9 as a whole. As an example of radiation shielding ability, radiation absorbing characteristic in an X ray of 6 MV was measured. As a result, the radiation absorbing characteristic of each sample was about 96% of that of a lead alloy plate having the same thickness and was twice as much as that of an available lead-containing sheet (specific gravity: about 4) having the same thickness. That is, it was confirmed that each sample had radiation shielding ability which was substantially equal to that of the lead alloy and superior to that of the lead-containing sheet. The tensile strength measured in each of the samples 1 and 2 was not smaller than 60 Kg/cm.sup.2. It was confirmed that each sample was prevented from being hung or deformed by its own weight in use. Further, the extensibility (G.L.=100 mm, hereinafter the same rule is applied) was not smaller than 200%, that is, each sample had elastic deformability. It was confirmed that these samples 1 and 2 could be cut easily compared with a lead plate having the same thickness, and these samples 1 and 2 had elastic deformability in which each sample could be made to come close to a fine curved surface. When bending was repeated, the lead plate having the same thickness was broken by fatigue in the case where bending at 90 degrees was repeated 50 times (one reciprocating bending was counted as one time), whereas there was no influence on the samples 1 and 2. When an iron ball having a weight of 5 kg was naturally dropped onto each of the samples 1 and 2 from a position 2 m-higher than the position of the sample, there was no breaking such as cracks, or the like, in each sample. When a tungsten plate having the same size was subjected to the same dropping test as described above, cracks occurred. The samples 1 and 2 were exposed to air while the temperature of the air was being changed variously. As a result, the extensibility and tensile strength of the sample 1 were kept at least for 56 days at 200.degree. C. The extensibility and tensile strength of the sample 2 were lowered only in 1 day at 200.degree. C. but were kept at least for 56 days at 100.degree. C. The samples were immersed in various kinds of chemicals at room temperature. As a result, the sample 1 was little swollen by chemicals except ketones such as methylethyl ketone, and the like, that is, it was confirmed that the sample 1 was not dissolved at all. The sample 2 was little dissolved in chemicals except gasoline and benzene. The samples 1 and 2 and the lead alloy were left under the environment of a temperature of 60.degree. C. and a humidity of 90% for 100 hours. As a result, the occurrence of corrosion was observed in the lead alloy, whereas there was no occurrence of corrosion in the samples 1 and 2. Example 2 Fifteen % by weight of tungsten powder having an F.s.s.s. particle size of 1 .mu.m and 85% by weight of tungsten powder having an F.s.s.s. particle size of 8 .mu.m were mixed in advance. Then, the mixture powder was weighed by 90% by weight and unvulcanized fluoro rubber containing a suitable amount of peroxide as a vulcanizer was weighed by 10% by weight, and they were further mixed in an open roll mill for 15 minutes. Then, a 1 mm-thick vulcanized rubber sheet (hereinafter referred to as sample 3) was produced by pressing. On the other hand, the aforementioned mixture powder was weighed by 96% by weight and unvulcanized EPDM rubber containing a suitable amount of sulfur as a vulcanizer was weighed by 4% by weight, and they were used in the same manner as described above to thereby prepare a further sample (hereinafter referred to as sample 4). The respective sections of these samples 3 and 4 were observed by using an SEM. As a result, it was confirmed that tungsten powder was dispersed in a matrix of the vulcanized rubber substantially evenly. The specific gravity of the shielding material in each of the samples 3 and 4 was about 10 as a whole, so that the radiation shielding ability of each of the samples 3 and 4 was improved by about 10% compared with the samples 1 and 2 produced in the same manner by using only powder having particles of the same particle size. Further, the tensile strength, extensibility, heat resistance, chemical resistance and other characteristic of the samples 3 and 4 were substantially the same as those of the samples 1 and 2. Example 3 Further, tungsten powder having an F.s.s.s. particle size of 1 .mu.m and tungsten powder having an F.s.s.s. particle size of 10 .mu.m were mixed with various mixture proportions in advance. This mixture powder and unvulcanized fluoro rubber containing a suitable amount of peroxide as a vulcanizer were weighed and mixed in an open roll mill for 15 minutes. Then, a 1 mm-thick vulcanized rubber sheet (hereinafter referred to as sample 5) was produced by pressing. Here, the mixture proportion of the mixture powder and fluoro rubber was determined so that the tensile strength and extensibility of the sample 5 thus produced were the same as those of the sample 1 (the tensile strength was not smaller than 60 Kg/mm.sup.2 and the extensibility was not lower than 200%). Here, the particle size distribution of tungsten powder remaining after removal of the rubber component in the sample 5 was measured, and the percentage by weight of powder having a particle size in a range of from 4 .mu.m to 100 .mu.m was represented by X and the percentage by weight of powder having a particle size smaller than 4 .mu.m was represented by Y. The value of X, the value of Y, the mixture proportion of the mixture powder and fluoro rubber and the specific gravity thereof were as shown in Table 1. TABLE 1 ______________________________________ mixture fluoro X Y powder rubber specific extensibility (wt. %) (wt. %) (wt. %) (wt. %) gravity (%) ______________________________________ 30 70 84.1 15.9 7.8 200 or more 55 45 88.2 11.8 9.2 200 or more 60 40 88.9 11.1 9.5 200 or more 65 35 89.3 10.7 9.7 200 or more 70 30 89.7 10.3 9.8 200 or more 75 25 90.0 10.0 10.0 200 or more 80 20 90.2 9.8 10.1 200 or more 85 15 90.0 10.0 10.0 200 or more 90 10 89.7 10.3 9.8 200 or more 95 5 89.0 11.0 9.5 200 or more 97 3 88.5 11.5 9.3 200 or more 100 0 87.9 12.1 9.1 200 or more ______________________________________ From the aforementioned result, in the samples having the same tensile strength and extensibility as those of the sample 1, the specific gravity was not smaller than 9.5 in each and every sample containing 60% by weight to 95% by weight both (X value in the above table) of powder having a particle size in a range of from 4 .mu.m to 100 .mu.m, and 5% by weight to 40% by weight (Y value in the above table) of powder having a particle size smaller than 4 .mu.m. As an example of the radiation shielding ability of these samples, radiation absorbing characteristic was measured in an X ray of 6 MV. As a result, it was confirmed that these samples exhibited absorptivity obtained by multiplying the absorptivity of a lead alloy having the same thickness by a factor of from 1 to 1.1 and had more excellent radiation shielding ability than that of the lead alloy. Example 4 Further, a suitable amount of carbon black was mixed with a mixture of 92% by weight of tungsten powder having an F.s.s.s. particle size of 3 .mu.m and 8% by weight of unvulcanized SBR rubber (general synthetic rubber of styrene and butadiene) containing a vulcanizer in order to give electrical conductivity to the mixture. These materials were mixed in an open roll mill for 5 minutes. Then, a 1 mm-thick vulcanized rubber sheet (hereinafter referred to as sample 6) was produced by pressing. The measured radiation shielding ability of the sample 6 was reduced by about 20% compared with that of the sample 1, but electromagnetic wave shielding ability was obtained newly by giving electrical conductivity to the sample 6. That is, it was confirmed that electromagnetic wave shielding ability could be added to the radiation shielding ability in the material according to the present invention. Incidentally, tantalum (specific gravity: 16.6), rhenium (specific gravity: 21.0), osmium (specific gravity: 22.5), compounds or alloys thereof, etc., (whose .gamma.-ray absorption coefficient (cm.sup.-1) is in the range of about 0.7 to 1.2 when the energy of .gamma.-rays is 1.5 MeV) other than tungsten, tungsten compounds and tungsten based alloys may be used singly or in combination as the material of high radiation absorptivity. The kind of the rubber material, the kind of the vulcanizer and the mixture proportion thereof can be selected suitably correspondingly to the kind of powder such as tungsten powder, or the like, required radiation shielding ability, specific gravity and physical properties, and so on. In addition, carbon powder, or the like, can be added to the material according to the present invention in order to perform coloring, changing of physical properties or characteristic, etc.
	claims	1. A composition, comprising:water;at least one chelator selected from the group consisting of ethylenediaminetetraacetic acid, (2-hydroxyethyl)ethylenediaminetriacetic acid, ethylene glycol-bis-(2-aminoethyl)-tetracetic acid, ammonium molybdophosphate, and nitrilotriacetic acid;at least one of hydrochloric acid or nitric acid;at least one surfactant comprising a fatty alcohol ether sulfate;at least one fluoride salt; andammonium nitrate. 2. The composition of claim 1, further comprising gelatin. 3. The composition of claim 1, further comprising corn starch. 4. The composition of claim 1, wherein the fatty alcohol ether sulfate comprises at least one of a sodium salt of the fatty alcohol ether sulfate or an ammonium salt of the fatty alcohol ether sulfate. 5. The composition of claim 1, wherein the at least one surfactant is present at from about 0.1% by weight to about 10% by weight. 6. The composition of claim 1, wherein:the at least one chelator comprises nitrilotriacetic acid; andthe at least one fluoride salt comprises at least one of sodium fluoride or potassium fluoride. 7. The composition of claim 6, further comprising gelatin. 8. The composition of claim 6, further comprising corn starch. 9. The composition of claim 1, wherein:the water comprises from about 40% by weight to about 50% by weight of the composition;the at least one chelator comprises from about 4% by weight to about 60% by weight of the composition;the at least one surfactant comprises from about 0.1% by weight to about 10% by weight of the composition;the at least one fluoride salt comprises from about 0.1% by weight to about 10% by weight of the composition; andthe ammonium nitrate comprises from about 0.05% by weight to about 5.0% by weight of the composition. 10. The composition of claim 1, wherein the composition comprises water, nitrilotriacetic acid, hydrochloric acid, ammonium molybdophosphate, the fatty alcohol ether sulfate, sodium fluoride, potassium fluoride, and ammonium nitrate. 11. The composition of claim 1, wherein the composition comprises water, nitrilotriacetic acid, citric acid, hydrochloric acid, ammonium molybdophosphate, the fatty alcohol ether sulfate, sodium fluoride, potassium fluoride, and ammonium nitrate. 12. The composition of claim 1, wherein the pH of the composition is between about -0.5 and about 5. 13. The composition of claim 1, wherein the composition is formulated to generate a foam. 14. The composition of claim 1, wherein a pH of the composition is less than about 6. 15. A composition, comprising:water;a fatty alcohol ether sulfate;nitrilotriacetic acid;hydrochloric acid;sodium fluoride;potassium fluoride;ammonium nitrate; andgelatin. 16. The composition of claim 15, further comprising corn starch, citric acid, and ammonium molybdophosphate. 17. The composition of claim 15, wherein the composition comprises from about 0.03% by weight to about 1% by weight of nitrilotriacetic acid. 18. The composition of claim 15, wherein the composition comprises from about 20% by weight to about 35% by weight of hydrochloric acid. 19. A composition consisting essentially of:water;a fatty alcohol ether sulfate;nitrilotriacetic acid;hydrochloric acid;sodium fluoride;corn starch;citric acid;ammonium nitrate;potassium fluoride;ammonium molybdophosphate; andgelatin. 20. A method of decontaminating a surface, comprising:exposing a surface to a composition, the surface having a radioactive contaminant material thereon and the composition comprising:water;at least one acid;at least one surfactant;at least one fluoride salt; andammonium nitrate; andremoving at least a portion of the composition from the surface to remove at least a portion of the radioactive contaminant material from the surface. 21. The method of claim 20, wherein removing at least a portion of the radioactive contaminant material from the surface further comprises removing biological contaminant materials or chemical contaminant materials from the surface. 22. The method of claim 20, further comprising applying ultrasonic energy to the composition. 23. The method of claim 20, further comprising injecting a gas into the composition to produce a foam before exposing the surface to the composition. 24. The method of claim 20, wherein exposing the surface to a composition comprises exposing the surface to a composition comprising water, a fatty alcohol ether sulfate, nitrilotriacetic acid, hydrochloric acid, sodium fluoride, potassium fluoride, and ammonium nitrate. 25. The method of claim 20, wherein exposing a surface to a composition comprises exposing the surface to a composition wherein:the water comprises from about 40% by weight to about 50% by weight of the composition;the at least one acid comprises from about 20% by weight to about 60% by weight of the composition;the at least one surfactant comprises from about 0.1% by weight to about 10% by weight of the composition;the at least one fluoride salt comprises from about 0.1% by weight to about 10% by weight of the composition; andthe ammonium nitrate comprises from about 0.05% by weight to about 5.0% by weight of the composition.
052572986	summary	BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to nuclear fuel pellets including UO.sub.2 and UO.sub.2 -Gd.sub.2 O.sub.3, and more particularly to nuclear fuel pellets having a satisfactory solid-solution state, greater grain diameters and a second phase precipitated in grain boundaries. This invention also relates to a method of manufacturing the above-described nuclear fuel pellets. 2. Description of the Prior Art As for nuclear fuel to be loaded into a light water reactor or a fast breeder reactor, intactness of fuel has been confirmed at a high burnup level ever experienced in a reactor. However, at present, extension of burnup to still higher levels has been planned. This plan inevitably involves the following disadvantages. Specifically, so-called bubble swelling occurs due to fission gas deposited in grain boundaries, i.e., an apparent volume of pellets increases due to bubbles produced in pellets because of gaseous fission products. Thus, PCI (pellet-cladding interaction), which is a mechanical interaction between pellets and a cladding, increases. Further, an inner pressure of a fuel rod increases because of fission gas release from fuel pellets. These phenomena may cause intactness of fuel to be deteriorated. To avoid these disadvantages, the following techniques have been attempted. Specifically, a fission gas release fraction (a ratio of the released to the produced of fission gas) is suppressed by increasing diameters of pellets grains. This is based on that a fission gas release from pellets is rate-controlled by diffusion of fission gas in pellet grains. However, when the diameters of pellet grains are increased, a creep rate of the pellets is decreased. This provides an adverse effect on PCI. To increase a creep rate of pellets there have been disclosed two technique (Japanese Patent Applications No. 1-193691 and No. 2-242195) in which a sintering agent consisting of aluminum oxide and silicon oxide is added to uranium dioxide powder so that a second soft phase can be precititated in the grain boundaries of the pellets. In these techniques, the total amounts of the sintering agents to be added are about 0.1 wt % through about 0.8 wt %, and about 0.05 wt % through about 0.4 wt %, respectively. In general, it has been known that sinterability of a mixed oxide of UO.sub.2 and Gd.sub.2 O.sub.3 is lower than that of pure UO.sub.2. Further, when sintering is performed under a given condition, a sintered density and grain diameters of the mixed oxide of UO.sub.2 and Gd.sub.2 O.sub.3 become smaller than those in the case of pure UO.sub.2. Further, when sintering is performed in a flowing dry hydrogen, a large number of micro-cracks occur in pellets. To avoid the above-described disadvantages, in the case of UO.sub.2 having Gd.sub.2 O.sub.3 added thereto, sintering is generally performed in a humid hydrogen atmosphere or in a mixed gas atmosphere of carbon dioxide and carbon monoxide. Further, the sintering is performed at a relatively high temperature (1700.degree. C. or higher). However, assume that sintering is performed in such atmospheres and a sintering agent, which consists of aluminum oxide and silicon oxide in the above-described conventional proportion, is added to the mixed oxide of UO.sub.2 and Gd.sub.2 O.sub.3. In this case, pores are generated in pellets, probably due to evaporation of silicon oxides, so that a density of pellets becomes decreased. As the pellet density becomes lower, a thermal conductivity of the pellets degrades. As a result, a fuel center temperature increases in service, so that both bubble swelling and a fission gas release rate are enhanced. This is disadvantageous to the performance of nuclear fuel pellets. Further, it has also been experimentally confirmed that grain diameters of pellets and a solid-solution state thereof can no longer be improved even when a sintering agent of 500 ppm or more is added. SUMMARY OF THE INVENTION Accordingly, one object of the present invention is to provide nuclear fuel pellets including fission substance, the fission substance being UO.sub.2 alone or UO.sub.2 having Gd.sub.2 O.sub.3 added thereto, the pellets comprising a satisfactory solid-solution state (homogeneous state), large grain diameters, and a second phase precipitated in grain boundaries, and still having a sufficiently high density. Another object of the present invention is to provide a method of manufacturing the above-described nuclear fuel pellets. Briefly, in accordance with one aspect of the present invention, there are provided nuclear fuel pellets including fission substance, the fission substance being UO.sub.2 alone or UO.sub.2 having Gd.sub.2 O.sub.3 added thereto. The nuclear fuel pellets comprises UO.sub.2 or (U, G) O.sub.2 grains and aluminosilicate deposition phases of glassy and/or crystalline state. An average diameter of the grains is in the range from about 20 .mu.m through about 60 .mu.m. The aluminosilicate deposition phases have a composition consisting of SiO.sub.2 of 40 wt % through 80 wt % and Al.sub.2 O.sub.3 of residual on average. The amount of the alumina plus silica is about 10 through 500 ppm with respect to the total weight of the nuclear fuel pellets. Further, the total volume of as-fabricated pores in the pellets is 5 vol % at a maxiumum. In accordance with another aspect of the present invention, there is provided a method of manufacturing the above-described nuclear fuel pellets. The method comprises the steps of compacting an oxide powder of UO.sub.2 or UO.sub.2 having Gd.sub.2 O.sub.3 added thereto, and sintering the oxide powder compacts. More specifically, the method comprises the steps of mixing a sintering agent (including the precursor thereof) consisting of SiO.sub.2 of about 40 wt % through about 80 wt % and Al.sub.2 O.sub.3 of the residual with the above-described oxide powder, the mixing proportion thereof being about 10 ppm through about 500 ppm with respect to the total amount of the oxide powder and the sintering agent; pressing the mixed oxide powder so as to obtain green pellets; and sintering the green pellets at a temperature in a range of about 1500.degree. C. through 1800.degree. C. so as to obtain sintered pellets.
	claims	1. A radiation-shielding assembly for accommodating a container having a radioactive material disposed therein, the assembly comprising:a body comprising a radiation shielding material, the body having a cavity and a first opening to the cavity defined therein; anda locator disposed in a radiation shielding portion of the cavity opposite the opening, the locator having an aperture defined therethrough spanning between first and second sides of the locator, a first aperture opening of the aperture being defined at the first side of the locator and a second aperture opening of the aperture being defined at the second side of the locator, wherein a size of the first aperture opening is greater than a size of the second aperture opening, wherein the first side of the locator is disposed between the second side of the locator and the first opening in the cavity of the body, and wherein the locator includes an interior wall that defines the aperture therethrough, the interior wall being stepped. 2. The assembly of claim 1, wherein a cross-sectional area of the first aperture opening is greater than a cross-sectional area of the second aperture opening, and wherein the locator is made of a material transparent to radiation. 3. The assembly of claim 1, wherein the body has a second opening to the cavity defined therein, the second opening being defined at a portion of the body remote from where the first opening is defined. 4. The assembly of claim 3, wherein the first opening in the body is of a first size, the second opening in the body is of a second size, and the first opening is larger than the second opening. 5. The assembly of claim 4, wherein the locator is disposed adjacent the portion of the body in which the second opening is defined, such that a hypodermic needle may be disposed through both the second opening in the body and the aperture in the locator. 6. Use of the radiation-shielding assembly of claim 1 in eluting a radioisotope from a radioisotope generator. 7. A radiation-shielding assembly for accommodating a container having a radioactive material disposed therein, the assembly comprising:a body comprising a radiation shielding material, the body having a cavity and a first opening to the cavity defined therein; anda locator including a rigid non-shielding material, the locator being disposed in a radiation shielding portion of the cavity opposite the opening and having an aperture defined therethrough spanning between first and second sides of the locator, a first aperture opening of the aperture being defined at the first side of the locator and a second aperture opening of the aperture being defined at the second side of the locator, wherein a size of the first aperture opening is greater than a size of the second aperture opening, and wherein the first side of the locator is disposed between the second side of the locator and the first opening in the body. 8. The assembly of claim 7, wherein a cross-sectional area of the first aperture opening is greater than a cross-sectional area of the second aperture opening, and wherein the locator is made of a material transparent to radiation. 9. The assembly of claim 7, wherein the locator comprises an interior wall that defines the aperture therethrough, the interior wall being stepped. 10. The assembly of claim 7, wherein the locator comprises an interior wall that defines the aperture therethrough, the interior wall being tapered. 11. The assembly of claim 7, wherein the body has a second opening to the cavity defined therein, the second opening being defined at a portion of the body remote from where the first opening is defined. 12. The assembly of claim 11, wherein the first opening in the body is of a first size, the second opening in the body is of a second size, and the first opening is larger than the second opening. 13. The assembly of claim 12, wherein the locator is disposed adjacent the portion of the body in which the second opening is defined, such that a hypodermic needle may be disposed through both the second opening in the body and the aperture in the locator. 14. Use of the radiation-shielding assembly of claim 7 in eluting a radioisotope from a radioisotope generator. 15. A radiation-shielding assembly for accommodating a container having a radioactive material disposed therein, the assembly comprising:a body comprising a radiation shielding material, the body having a cavity, a first opening to the cavity defined therein, and a second opening to the cavity defined therein, the second opening being defined at a portion of the body remote from where the first opening is defined, wherein the first opening in the body is of a first size and the second opening in the body is of a second size; anda locator disposed in a radiation shielding portion of the cavity opposite the first opening, the locator having an aperture defined therethrough spanning between first and second sides of the locator, a first aperture opening of the aperture being defined at the first side of the locator and a second aperture opening of the aperture being defined at the second side of the locator, wherein a size of the first aperture opening is greater than a size of the second aperture opening, wherein the first side of the locator is disposed between the second side of the locator and the first opening in the body, and wherein the size of the second opening in the body is smaller than the size of the second aperture opening. 16. The assembly of claim 15, wherein a cross-sectional area of the first aperture opening is greater than a cross-sectional area of the second aperture opening, and wherein the locator is made of a material transparent to radiation. 17. The assembly of claim 15, wherein the locator comprises an interior wall that defines the aperture therethrough, the interior wall being stepped. 18. The assembly of claim 15, wherein the locator comprises an interior wall that defines the aperture therethrough, the interior wall being tapered. 19. The assembly of claim 15, wherein the locator is disposed adjacent the portion of the body in which the second opening is defined, such that a hypodermic needle may be disposed through both the second opening in the body and the aperture in the locator. 20. Use of the radiation-shielding assembly of claim 15 in eluting a radioisotope from a radioisotope generator.
043158315	claims	1. A process for encasing a solid mass of radioactive waste of large dimensions comprising: (1) premixing an ambient temperature-thermosetting resin with a cross-linking agent, a plasticizer, and an inert filler; (2) suspending said solid radioactive waste mass in said premixed resin; and (3) cross-linking said resin, said inert filler serving to reduce shrinkage and prevent cracking during said cross-linking, wherein said radioactive mass is encased in said resin under water. (1) premixing an ambient temperature-thermosetting resin with a cross-linking agent, a plasticizer, and an inert filler; (2) introducing said premixed resin into a mold; (3) suspending said solid radioactive waste mass in said premixed resin within said mold; and (4) cross-linking said resin, said inert filler serving to reduce shrinkage and prevent cracking during said cross-linking, wherein said radioactive mass is encased in said resin under water. 2. A process for encasing a solid mass of radioactive waste of large dimensions comprising:
	description	Pursuant to 35 U.S.C. § 119(a), this application claims the benefit of earlier filing date and right of priority to Korean Application No. 10-2012-0089643, filed on Aug. 16, 2012, the contents of which is incorporated by reference herein in its entirety. 1. Field of the Invention The present invention relates to a safety injection system capable of injecting coolant to a reactor coolant system when a loss-of-coolant-accident (LOCA) occurs on an integral type reactor. 2. Background of the Invention An integral type reactor has a characteristic that large pipes connected with main components such as a core, steam generators, a pressurizer, and pumps are not required, because the main components are installed in a reactor vessel. Pipes configured to connect a chemical and volume control system, a safety injection system, a shutdown cooling system, a safety valve, etc. with the reactor vessel of the integral type reactor are small. As the main components are accommodated in the integral type reactor, a great amount of coolant for a reactor coolant system is provided at an inner space of the reactor coolant system. In the occurrence of a loss-of-coolant-accident (LOCA), this is a small break-loss-of-coolant-accidents (SBLOCA) due to a pipe rupture, etc., the integral type reactor shows progress states different from those of a separate type reactor. In case of the separate type reactor provided with large pipes, coolant is drastically lost when the large pipes are ruptured. Further, as the coolant is discharged, the reactor is drastically depressurized for a rapid pressure equilibrium state between the reactor and a reactor building (or containment). As a result, safety injection by a gravitational head of water is facilitated, and the coolant is rapidly refilled into the reactor by a safety injection system. Unlike such separate type reactor requiring a rapid injection, the integral type reactor has a characteristic that pressure and level thereof are gradually lowered when a loss-of-coolant-accident occurs, because large pipes are eliminated. As a result, a pressure equilibrium state between the reactor and a reactor building cannot be rapidly implemented, and there is a difficulty in performing safety injection by a gravitational head of water. In order to solve such problems, the integral type reactor has been configured to adopt a safety injection tank using pressurized gas (generally, nitrogen) to inject coolant, or configured to comprise a specified passive safety injection system using a high pressure small containment. The passive safety injection system is configured to restrict the amount of coolant to be discharged by rapidly making a pressure equilibrium state between the reactor and a safeguard vessel, using a high pressure small containment such as a safeguard vessel, rather than a reactor building. The passive safety injection system uses a gravitational head of water, or a gas pressure, etc. A safety injection tank, one of the passive safety injection system, especially, an integral type safety injection tank configured to inject coolant using pressurized gas and having coolant and gas stored in a single tank, is very sensitive to a pressure change inside a reactor coolant system in the occurrence of a LOCA. In the occurrence of a large-break-loss-of-coolant-accident (LBLOCA), the reactor is drastically depressurized, safety injection is performed within a short time as coolant is rapidly injected. On the other hand, in the occurrence of a small LOCA, the reactor is gradually depressurized to cause safety injection not to be performed when required. In the safety injection tank configured to pressurize coolant using gas, if a reference pressure is set to be lower than a reactor pressure predicted in a large-break-loss-of-coolant-accident, coolant may not be safely injected into the reactor when a small-break-loss-of-coolant-accident occurs, because the reactor is little depressurized. On the other hand, if the reference pressure is set to be higher than the reactor pressure predicted in a small-break-loss-of-coolant-accident, a safety injection operation may be early terminated when a large-break-loss-of-coolant-accident occurs, because the reactor is rapidly depressurized. Accordingly, may be considered a safety injection system capable of injecting a comparatively constant amount of coolant regardless of a scale of a pipe rupture. Therefore, an aspect of the detailed description is to provide a separate type safety injection tank having a differentiated structure from the conventional art. Another aspect of the detailed description is to provide a separate type safety injection tank capable of performing a safety injection operation for a long time in a loss-of-coolant-accident (LOCA), by a required design characteristic of an integral type reactor. Still another aspect of the detailed description is to provide a separate type safety injection tank capable of coping with pipe rupture accidents of various scales. To achieve these and other advantages and in accordance with the purpose of this specification, as embodied and broadly described herein, there is provided a separate type safety injection tank, comprising: a coolant injection unit connected to a reactor coolant system by a safety injection pipe such that coolant stored therein is injected into the reactor coolant system by a pressure difference when a loss-of-coolant-accident (LOCA) occurs; a gas injection unit connected to the coolant injection unit, and configured to pressurize the coolant injected into the reactor coolant system, by introducing gas stored therein to an upper part of the coolant injection unit when the loss-of-coolant-accident occurs; and a choking device disposed between the coolant injection unit and the gas injection unit, and configured to contract a flow cross-sectional area of the gas introduced to the coolant injection unit, and configured to maintain a flow velocity and a flow rate of the gas introduced to the coolant injection unit as a critical flow velocity and a critical flow rate when a pressure difference between the coolant injection unit and the gas injection unit is more than a critical value. According to an embodiment, the coolant injection unit may be provided with a coolant tank for storing the coolant therein, and the gas injection unit may be provided with a gas tank for storing the gas therein. The coolant tank and the gas tank may be connected to each other by a connection pipe, and the choking device may be installed at the connection pipe. According to another embodiment, the safety injection unit and the gas injection unit may be implemented as a single safety injection tank, and the safety injection tank may be provided with a partition wall for partitioning the coolant injection unit and the gas injection unit from each other. The orifice may be installed at the partition wall. According to another embodiment, the separate type safety injection tank may further comprise a throttle member installed at the safety injection pipe such that a flow rate of the coolant injected into the reactor coolant system is restricted, and configured to contract a flow cross-sectional area of the safety injection pipe. According to another embodiment, the separate type safety injection tank may further comprise a check valve installed at the safety injection pipe such that the coolant inside the reactor coolant system is prevented from back-flowing and leaking into the separate type safety injection tank. At least part of the choking device may protrude from an inner side wall of the pipe line formed by the connection pipe or the partition wall. To achieve these and other advantages and in accordance with the purpose of this specification, as embodied and broadly described herein, there is also provided an integral type reactor comprising: a core makeup tank configured to inject coolant into a reactor coolant system using a gravity force and pressure balance when an accident occurs on the reactor, by reaching a pressure equilibrium state with the reactor coolant system; and a separate type safety injection tank connected to the reactor coolant system, and configured to inject coolant stored therein into the reactor coolant system when a loss-of-coolant-accident (LOCA) occurs, wherein the separate type safety injection tank comprises: a coolant injection unit connected to a reactor coolant system by a safety injection pipe such that coolant stored therein is injected into the reactor coolant system by a pressure difference when the loss-of-coolant-accident occurs; a gas injection unit connected to the coolant injection unit, and configured to pressurize the coolant injected into the reactor coolant system, by introducing gas stored therein to an upper part of the coolant injection unit in the loss-of-coolant-accident; and a choking device disposed between the coolant injection unit and the gas injection unit, and configured to contract a flow cross-sectional area of the gas introduced to the coolant injection unit, and configured to maintain a flow velocity and a flow rate of the gas introduced to the coolant injection unit as a critical flow velocity and a critical flow rate when a pressure difference between the coolant injection unit and the gas injection unit is more than a critical value. According to an embodiment, the coolant injection unit may be provided with a coolant tank for storing the coolant therein, and the gas injection unit may be provided with a gas tank for storing the gas therein. The coolant tank and the gas tank may be connected to each other by a connection pipe, and the choking device may be installed at the connection pipe. According to another embodiment, the safety injection unit and the gas injection unit may be implemented as a single safety injection tank, and the safety injection tank may be provided with a partition wall for partitioning the coolant injection unit and the gas injection unit from each other. The choking device may be installed at the partition wall. According to another embodiment, the integral type reactor may further comprise a throttle member installed at the safety injection pipe such that a flow rate of the coolant injected into the reactor coolant system is restricted, and configured to contract a flow cross-sectional area of the safety injection pipe. According to another embodiment, the integral type reactor may further comprise a check valve installed at the safety injection pipe such that the coolant inside the reactor coolant system is prevented from back-flowing and leaking into the separate type safety injection tank. At least part of the choking device may protrude from an inner side wall of the pipe line formed by the connection pipe or the partition wall. According to another embodiment, the integral type reactor may further comprise an isolation valve installed at a pipe which connects a lower end of the core makeup tank with the reactor coolant system, and configured to be open by an actuation signal generated when a related accident occurs, such that the coolant is injected into the reactor coolant system from the core makeup tank when an accident occurs on the reactor. According to another embodiment, the integral type reactor may further comprise a pressure balancing pipe having one end connected to the reactor coolant system and another end connected to the core makeup tank, such that a pressure balance (back pressure) with the reactor coolant system is formed at the core makeup tank. According to another embodiment, the integral type reactor may further comprise a passive residual heat removal system configured to remove heat of the core by circulating a fluid stored therein to a steam generator inside the reactor coolant system, when an accident occurs on the reactor. According to another embodiment, the integral type reactor may further comprise an isolation valve installed at a pipe which connects the passive residual heat removal system with the reactor coolant system, and configured to be open by an actuation signal generated when a related accident occurs. The present application can be applied to a general reactor, not only an integral type reactor. Further scope of applicability of the present application will become more apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from the detailed description. Description will now be given in detail of the exemplary embodiments, with reference to the accompanying drawings. For the sake of brief description with reference to the drawings, the same or equivalent components will be provided with the same reference numbers, and description thereof will not be repeated. As used herein, the singular forms are intended to include the plural forms as well, unless the context clearly indicates otherwise. Hereinafter, a separate type safety injection tank according to the present invention will be explained in more detail with reference to the attached drawings. The suffixes attached to components of the separate type safety injection tank, such as ‘unit’ and ‘system’ were used for facilitation of the detailed description of the present invention. Therefore, the suffixes do not have different meanings from each other. The passive safety injection systems (core makeup tanks and safety injection tanks) and the passive residual heat removal systems according to the invention may be provided as plural. Unless indicated otherwise, the passive safety injection system and the passive residual heat removal system may not exclude the meaning of plural. FIG. 1 is a conceptual view showing an operation of a separate type safety injection tank 100 according to an embodiment of the present invention. A passive safety injection system indicates a system capable of injecting coolant into a reactor coolant system using a natural force such as gravity, a natural circulation and a pressure difference (pressurized gas), when a loss-of-coolant-accident (LOCA) occurs in a reactor coolant system. A device of the passive safety injection system, a safety injection tank is an apparatus for injecting coolant stored therein into a reactor coolant system, using a pressurized gas. Referring to FIG. 1, the separate type safety injection tank comprises a coolant injection unit 101, a gas injection unit 102 and an orifice 103. The coolant injection unit 101 is filled with coolant (e.g., a boric acid solution of low temperature), and a lower part thereof is connected to a safety injection pipe 107 communicated with a reactor coolant system. In the occurrence of a LOCA in a reactor coolant system due to a pipe rupture, etc., the reactor coolant system starts to be depressurized. Due to a pressure difference between the reactor coolant system and the coolant injection unit 101, the coolant stored in the coolant injection unit 101 is injected into the reactor coolant system through the safety injection pipe 107. The gas injection unit 102 is connected to the coolant injection unit 101, and is configured to pressurize coolant to be injected into the reactor coolant system, by introducing gas stored therein to an upper part of the coolant injection unit 101 in the occurrence of a LOCA. As the gas, nitrogen gas may be used. The orifice 103 is provided between the coolant injection unit 101 and the gas injection unit 102, and is configured to reduce a flow cross-sectional area of gas injecting to the coolant injection unit 101 from the gas injection unit 102. The coolant injection unit 101 and the gas injection unit 102 may be connected to each other by a connection part 104, and the orifice 103 may be installed in the connection part 104. As shown, the connection part 104 may be a connection pipe installed to be communicated with the coolant injection unit 101 and the gas injection unit 102. The orifice 103 may be installed on an inner side wall of a pipe line of the connection part 104, or may be formed to contract the pipe line by partially protruding from the inner side wall. A pressure difference between the gas injection unit 102 and the coolant injection unit 101 is less than a critical value, a flow rate of gas to be injected increases until the pressure difference reaches the critical value. A critical pressure occurs when a compressible fluid flows, which indicates a downstream pressure in a state where a flow velocity is the same as the speed of sound while the downstream pressure gradually decreases. A critical pressure difference indicates a pressure difference between the upstream side and the downstream side when the fluid reaches the critical pressure. The downstream pressure may be lowered to the critical pressure or a value less than, so that the pressure difference between the downstream side and the upstream side may be the critical pressure difference or more than. In this case, even if the downstream pressure is lowered, the flow velocity and the flow rate are maintained as a critical fluid velocity and a critical flow rate without an increment. Such flow in a state where the downstream pressure is lower than the critical pressure, i.e., in a state where the pressure difference is more than the critical pressure difference, is called ‘choked flow’ or ‘critical flow’. If a pressure difference between the gas injection unit 102 and the coolant injection unit 101 reaches a critical value, the orifice 103 makes gas passing therethrough have a critical flow velocity and a critical flow rate. If a pressure difference between the gas injection unit 102 and the coolant injection unit 101 reaches a critical value, the orifice 103 chokes the gas passing therethrough so that the gas can maintain a critical flow velocity and a critical flow rate. As the gas passing through the orifice 103 maintains a critical flow velocity and a critical flow rate by the orifice 103, the coolant inside the coolant injection unit 101 may be slowly and continuously injected into the reactor coolant system in spite of a drastic pressure change of the reactor coolant system. FIG. 1(a) illustrates a state shortly before a safety injection operation starts as pressure (P3) of the reactor coolant system decreases to a value less than a preset pressure (P1) of the gas injection unit 102 after a loss-of-coolant-accident (LOCA) occurring in the reactor coolant system due to a pipe rupture, etc. If the pressure (P3) of the reactor coolant system decreases to a value less than the preset pressure (P1) of the gas injection unit 102 due to a LOCA occurring at the reactor coolant system, valves such as check valves installed at the safety injection pipe 107 is open, and the coolant stored in the coolant injection unit 101 starts to be injected into the reactor coolant system through the safety injection pipe 107. Once the coolant starts to be injected into the reactor coolant system from the coolant injection unit 101, the level of the coolant injection unit 101 is lowered and pressure (P2) of the gas injection unit 102 is reduced. As a result, there also occurs a pressure difference (P1−P2) between the gas injection unit 102 and the coolant injection unit 101. By such pressure difference (P1−P2), the gas stored in the gas injection unit 102 is introduced into the coolant injection unit 101 via the orifice 103. FIG. 1(b) illustrates a state that a pressure difference (P1′−P2′) between the gas injection unit 102 and the coolant injection unit 101 is greater than that of FIG. 1(a), which results from that the reactor coolant system is more depressurized. In a case where the pressure difference (P1′−P2′) is less than a critical value, a flow rate of gas to be injected into the coolant injection unit 101 from the gas injection unit 102 increases as a differential pressure increases. If the pressure difference (P1′−P2′) reaches a critical pressure difference, gas passing through the orifice 103 has a critical flow velocity and a critical flow rate. FIG. 1(c) illustrates a state that a pressure difference (P1″−P2″) between the gas injection unit 102 and the coolant injection unit 101 is greater than a critical value. The orifice 103 makes the gas introduced to the coolant injection unit 101 from the gas injection unit 102 maintain a critical flow velocity and a critical flow rate. Accordingly, the orifice 103 prevents the pressure inside the coolant injection unit 101 from increasing. A flow rate of coolant injected into the reactor coolant system is determined by a pressure difference (P2″−P3″) between the coolant injection unit 101 and the reactor coolant system. Accordingly, the separate type safety injection tank 100 having the orifice 103 can maintain a small flow rate of coolant to be injected, than an integral type safety injection tank where gas and coolant are not separated and stored in a single tank. This can prevent coolant from being injected into the reactor coolant system within a short time, but allow coolant to be continuously injected into the reactor coolant system for a desired time duration. A flow rate of coolant, which is injected into the reactor coolant system from the separate type safety injection tank 100, is comparatively constant without being much influenced by a pressure change of the reactor coolant system, due to a characteristic of a critical flow velocity. Accordingly, the separate type safety injection tank 100 may be applicable to various sizes of LOCAs such as a small, a middle, and a relatively large pipe rupture, etc. It is the coolant injection unit 101 of the safety injection tank 100 that is directly influenced by a pressure change inside the reactor coolant system. Therefore, in early and middle stages of a LOCA, a flow rate of gas introduced into the coolant injection unit 101 is significantly smaller than that in an integral type safety injection tank. This may cause the coolant injection unit 101 to be significantly depressurized if the coolant of the coolant injection unit 101 is injected into the reactor coolant system, because the volume of gas in the coolant injection unit 101 is very small. Consequently, the separate type safety injection tank 100 can prevent coolant from being rapidly injected into the reactor coolant system, without being sensitive to a pressure change inside the reactor coolant system. The separate type safety injection tank 100 is configured to inject coolant into the reactor coolant system using a pressurized gas and to prolong the injection period using a choked flow, thereby injecting coolant for a long time in a passive manner using a natural force. Therefore, the separate type safety injection tank 100 can enhance the safety of an integral type reactor. FIG. 2 is an enlarged sectional view of part ‘A’ of FIG. 1. Referring to FIG. 2(a), the orifice 103 protrudes from an inner side wall of the connection part 104 partially or wholly, thereby contracting the pipe line of the connection part 104. The orifice 103 contracts a flow cross-sectional area of gas passing through the connection part 104, thereby restricting a movement of the gas. The gas has a large flow cross-sectional area before reaching the orifice 103. However, the flow cross-sectional area is contracted as the pipe line is contracted. As shown in FIG. 1, a critical flow is formed at the orifice 103 when a pressure difference between the coolant injection unit 101 and the gas injection unit 102 is more than a critical value. The critical flow-occurred part has a smallest flow cross-sectional area, thereby reaching a small critical flow rate. Referring to FIG. 2(b), a sectional surface of the orifice (or a venturi) 103 may have a circular shape formed along an inner circumferential surface of the connection part 104. However, the shape of the orifice 103 is not limited to this. The orifice 103 may be formed only on part of an inner side wall of the connection part 104 as shown in FIG. 2(c). A movement of gas inside the pipe line may be variable according to a shape of the orifice 103. However, the fact that a critical flow always occurs when a pressure difference between the coolant injection unit 101 and the gas injection unit 102 is more than a critical value, is not changeable. FIG. 3 is a conceptual view of separate type safety injection tanks 110, 120, 130, 140 and 150 according to various modification embodiments of the present invention. As shown, the separate type safety injection tanks 110, 120, 130, 140 and 150 may be in different shapes, and may have various levels of coolant stored in coolant injection units 111, 121, 131, 141 and 151a. According to a level of coolant, a safety injection type for the coolant to be injected into the reactor coolant system may be determined. In the separate type safety injection tanks 110, 120, 130 and 140 of FIGS. 3(a) to 3(d), the coolant injection units 111, 121, 131 and 141 are provided with tanks separated from tanks of gas injection units 112, 122, 132 and 142. More specifically, the coolant injection units 111, 121, 131 and 141 are provided with coolant tanks 111, 121, 131 and 141 for storing coolant therein, and the gas injection units 112, 122, 132 and 142 are provided with gas tanks 112, 122, 132 and 142 for storing gas therein. The coolant tanks 111, 121, 131 and 141, and the gas tanks 112, 122, 132 and 142 are connected to each other by connection pipes 114, 124, 134 and 144. Orifices 113, 123, 133 and 143 are installed at the connection pipes 114, 124, 134 and 144. On the other hand, in the separate type safety injection tank 150 of FIG. 3(e), the coolant injection unit 151a and a gas injection unit 151b are implemented as a single safety injection tank 151. The safety injection tank 151 is provided with a partition wall 152 for partitioning the coolant injection unit 151a and the gas injection unit 151b from each other. The orifice 153 is installed at the partition wall 152 so that gas introduced from the gas injection unit 151b can pass through the orifice 153. Once the orifice 153 is installed between the coolant injection unit 151a and the gas injection unit 151b as shown in FIG. 3(e), a critical flow of gas can be formed. Therefore, the separate type safety injection tank 150 is not necessarily required to have a connection pipe where the orifice 153 is installed between the coolant injection unit 151a and the gas injection unit 151b. FIGS. 3(a) and 3(b) illustrate separate type safety injection tanks 110 and 120 having the same shape as the separate type safety injection tank 100 of FIG. 1, but having different safety injection characteristics according to a level of coolant. Referring to FIG. 3(a), the coolant tank 111 of the separate type safety injection tank 110 is partially filled with gas. Therefore, in an early stage of a pipe rupture accident, the gas filled in the coolant tank 111 is expanded so that a large amount of coolant is injected into the reactor coolant system. Then, a critical flow occurs between the gas tank 112 and the coolant tank 111, so that the coolant is gradually injected into the reactor coolant system in middle and later stages of a LOCA. Referring to FIG. 3(b), the coolant tank 121 is filled with coolant, and the coolant is stored up to part of the gas tank 122 of the separate type safety injection tank 120. Therefore, in an early stage of a pipe rupture accident, the coolant is injected into the reactor coolant system by the amount stored in the gas tank 122. After the coolant stored in the gas tank 122 is completely injected into the reactor coolant system, gas stored in the gas tank 122 forms a critical flow by the orifice 123, and the residual coolant is gradually injected into the reactor coolant system in middle and later stages of a LOCA. Referring to FIG. 3(c), the separate type safety injection tank 130 has the gas tank 132 of a shape transformed from the gas tanks 112 and 122 of the separate type safety injection tanks 110 and 120 shown in FIGS. 3(a) and 3(b). The gas tank 132 may be designed to have a shape to overcome a spatial restriction and to reduce waste of an unnecessary space, by a required design characteristic of an integral type reactor. The separate type safety injection tank 130 of FIG. 3(c) has a similar level of coolant to the separate type safety injection tank 120 of FIG. 3(b), and thus has the same safety injection process as the separate type safety injection tank 120 of FIG. 3(b). Referring to FIG. 3(d), the separate type safety injection tank 140 has the coolant tank 141 of a shape transformed from the coolant tanks 111 and 121 of the separate type safety injection tanks 110 and 120 shown in FIGS. 3(a) and 3(b). Like the gas tank 142, the coolant tank 141 may be designed to have a shape to overcome a spatial restriction and to reduce waste of an unnecessary space, by a required design characteristic of an integral type reactor. However, the separate type safety injection tank 140 has a different level of coolant from the separate type safety injection tanks 110, 120 and 130 of FIGS. 3(a), 3(b) and 3(c), and thus has a different safety injection operation therefrom. Rather, the separate type safety injection tank 140 has a similar safety injection operation to the separate type safety injection tank 100 of FIG. 1. In the separate type safety injection tank 140 of FIG. 3(d), coolant is gradually injected into the reactor coolant system by a critical flow of gas when a pipe rupture accident occurs, because there is no expansion of gas, and there is no coolant stored in the gas tank 142. Referring to FIG. 3(e), the coolant injection unit 151a and the gas injection unit 151b of the separate type safety injection tank 150 are implemented as a single safety injection tank 151. However, the coolant injection unit 151a and the gas injection unit 151b are separated from each other by the partition wall 152. Since the coolant injection unit 151a is filled with gas before a pipe rupture accident occurs, a large amount of coolant is injected into the reactor coolant system due to expansion of the gas in an early stage of a pipe rupture accident, in the same manner as in FIG. 3(a). A safety injection operation in middle and later stages of a pipe rupture accident is also the same as the operation aforementioned in FIG. 3(a). FIGS. 3(a) to 3(e) illustrate various modification embodiments of the present invention, in which a safety injection operation to inject coolant into a reactor coolant system is variable according to a shape of a separate type safety injection tank and a level of coolant. However, the present invention is not limited to this, but may be implemented through a combination of various types and levels of coolant according to a required characteristic of a reactor. Hereinafter, an operation of an integral type reactor having the above separate type safety injection tank will be explained in more detail. FIG. 4 is a conceptual view showing an arrangement of systems of an integral type reactor 200 having the separate type safety injection tank 100, during a normal operation, according to an embodiment of the present invention. The integral type reactor 200 comprises a reactor coolant system 210, a passive residual heat removal system 220, a core makeup tank 230 and the separate type safety injection tank 100. A large amount of coolant for the reactor coolant system is stored in the reactor coolant system 210. During a normal operation, a feed water valve 213a and a steam valve 214a are open, and feed water is supplied through a feed water pipe 213b to thus be converted into steam of a high temperature and a high pressure in a steam generator 211. Then, the converted steam is supplied to a turbine through the steam pipe 214b. Under such processes, electrical power is generated. The separate type safety injection tank 100 may be operated in a condition of a relatively high pressure. In a case where the integral type reactor 200 comprises the separate type safety injection tank 100 together with the passive residual heat removal system 220 for continuously removing heat of the reactor core, and the pressure balance type (back pressure type) core makeup tank 230 for injecting coolant into the reactor coolant system using a gravity force and a pressure balance with the reactor coolant system, there is required no electrical power system such as an emergency diesel generator for pump driving. Further, errors occurring from an operator action for operation of safety system can be reduced. This can significantly enhance reliability and stability of the integral type reactor 200. FIGS. 5 to 8 illustrate, in time order, an operation of a related system when a LOCA occurs due to a pipe rupture, etc. FIG. 5 is a conceptual view showing an early stage of a LOCA occurring on the integral type reactor 200 of FIG. 4, due to a pipe rupture, etc. Referring to FIG. 5, coolant of the reactor coolant system 210 starts to be lost to a ruptured part 240 when a pipe connected to the reactor coolant system 210 ruptures. As a result, the reactor coolant system 210 has a lowered level and is depressurized. FIG. 6 is a conceptual view subsequent to FIG. 5, which shows operational states of the passive residual heat removal system 220 and the core makeup tank 230. The passive residual heat removal system 220 is a system to remove sensible heat of a reactor coolant system and residual heat of a core 212. The feed water valve 213a, the steam valve 214a and containment isolation valves 241 are in a closed state when a containment isolation signal is generated as a related actuation signal initiating from high containment pressure, etc. Once the feed water valve 213a and the steam valve 214a in an open state are closed, an isolation valve 223 and a check valve 224 of the passive residual heat removal system 220 are open. At the same time, a fluid stored in the passive residual heat removal system 220 circulates through the steam generator 211 and a heat exchanger 222, thereby transmitting heat of the core to an emergency cooling tank 221. The core makeup tank 230 is a sort of safety injection system for injecting coolant to the reactor coolant system 210 in the occurrence of a loss-of-coolant-accident or non-loss-of-coolant-accident. The core makeup tank 230 performs a gravity driven and pressure balance type safety injection due to a level difference from the reactor coolant system 210. The core makeup tank 230 should be installed to have a proper height difference from the reactor coolant system 210, because it uses a gravitational head of water when injecting coolant into the reactor coolant system 210. If the reactor coolant system 210 is depressurized and has a lowered level, an operation signal is generated to open the isolation valves 232 and the check valve 233, and coolant is injected into the reactor coolant system 210 from the core makeup tank 230. A pressure balancing pipe 231 has one end connected to the reactor coolant system 210, and another end connected to the core makeup tank 230. The pressure balancing pipe 231 is configured to form a pressure balance between the core makeup tank 230 and the reactor coolant system 210, so that coolant can be smoothly injected into the reactor coolant system 210 from the core makeup tank 230. The core makeup tank 230 is provided with the pressure balancing pipe 231, thereby injecting coolant to the reactor coolant system 210 by a gravitational head of water using a pressure equilibrium state with the reactor coolant system 210. The core makeup tank 230 is not sensitive to a pressure change of the reactor coolant system 210, and has a limitation in an installation height to thus have a small design gravitational head of water. Due to such characteristics, it is not appropriate to apply the core makeup tank 230 to a situation requiring a rapid safety injection operation due to drastic depressurization of the reactor coolant system (e.g., a large break LOCA occurring on a separate type reactor), so it is a facility for non-loss-of-coolant-accident in a separate type reactor. Further, since the core makeup tank 230 should be installed at a position higher than the ruptured part of the reactor, it is difficult to apply the core makeup tank 230 to a small space. Referring to FIG. 6, the level of the reactor coolant system 210 is gradually lowered and the reactor coolant system 210 is depressurized as time lapses. The core makeup tank 230 operates in a higher pressure condition than the separate type safety injection tank 100. Accordingly, the core makeup tank 230 has already started its operation before the reactor coolant system 210 is depressurized to a value lower than a preset pressure of the separate type safety injection tank 100. However, the separate type safety injection tank 100 has not yet started its operation, because the reactor coolant system 210 has not been depressurized to a value less than a preset pressure of the separate type safety injection tank 100. FIG. 7 is a conceptual view subsequent to FIG. 6, which shows operational states of the passive residual heat removal system 220, the core makeup tank 230 and the separate type safety injection tank 100. Referring to FIG. 7, as time lapses after a LOCA, the level of the reactor coolant system 210 is more lowered, and the reactor coolant system 210 is more depressurized than in the case of FIG. 6. In FIG. 7, the reactor coolant system 210 is depressurized to a value less than a preset pressure of the separate type safety injection tank 100. Like in FIG. 5, the passive residual heat removal system 220 and the core makeup tank 230 continuously operate, thereby removing heat of the reactor core and injecting coolant to the reactor coolant system 210, respectively. The separate type safety injection tank 100 starts to perform safety injection of coolant into the reactor coolant system 210, as the check valve 105 installed at the safety injection pipe 107 is open when the reactor coolant system 210 is depressurized to a value lower than a preset pressure (the pressure inside the gas injection unit 102). Before a pressure difference between the gas injection unit 102 and the coolant injection unit 101 reaches a critical value, a flow rate of gas to be injected into the coolant injection unit 101 from the gas injection unit 120 increases as a differential pressure increases. Accordingly, a flow rate of coolant injected into the reactor coolant system 210 from the separate type safety injection tank 100 also increases. As shown, the separate type safety injection tank 100 may further comprise a check valve 105 installed at the safety injection pipe 107. During a normal operation, the check valve 105 prevents coolant inside the reactor coolant system 210 from back-flowing and leaking into the separate type safety injection tank 100 in a closed state. When the reactor coolant system 210 is depressurized to a value less than the pressure inside the gas injection unit 102, the check valve 105 is open to enable safety injection of coolant from the separate type safety injection tank 100. As shown, the separate type safety injection tank 100 may further comprise a throttle member 106 installed at the safety injection pipe 107. The throttle member 106 may be implemented as an orifice. The throttle member 106 is configured to contract the pipe line of the safety injection pipe 107 so that a flow rate of coolant injected into the reactor coolant system 210 from the separate type safety injection tank 100 can be restricted. Since a flow rate of coolant is restricted, a phenomenon that coolant is injected to the reactor coolant system 210 from the separate type safety injection tank 100 within a short time, can be prevented. Since the separate type safety injection tank 100 serves to pressurize coolant using gas, it does not require a pressure balancing pipe for a pressure equilibrium state with the reactor coolant system 210 unlike a pressure balance type safety injection tank. This can reduce the probability to cause the occurrence of a LOCA. FIG. 8 is a conceptual view subsequent to FIG. 7, which shows that the core makeup tank 230 has completed a safety injection operation, while the separate type safety injection tank 100 continues to perform a safety injection operation as time lapses. Referring to FIG. 8, the passive residual heat removal system 220 continuously removes heat of the core subsequent to FIG. 7, while the core makeup tank 230 has completed the operation to inject the coolant stored therein to the reactor coolant system 210. On the other hand, as shown in FIG. 1, even if a pressure difference between the gas injection unit 102 and the coolant injection unit 101 increases to a value more than a critical pressure difference as the reactor coolant system 210 is more depressurized, a flow rate of gas injected into the coolant injection unit 101 from the gas injection unit 120 is restricted to a critical flow rate due to a critical flow of a compressive fluid passing through the orifice 103. A flow rate of coolant injected into the reactor coolant system 210 is determined by a pressure difference between the coolant injection unit 101 and the reactor coolant system 210. Therefore, the flow rate of coolant injected into the reactor coolant system 210 is also restricted, and an injection velocity is lowered to enable a continuous safety injection. As the pressure inside the reactor coolant system 210 is stabilized, gas injection by a critical flow and coolant injection by a differential pressure can be performed for a long time. Gas is continuously discharged from the gas injection unit 102, and a pressure difference between the gas injection unit 102 and the coolant injection unit 101 is reduced. Referring to FIGS. 4 to 8, the core makeup tank 230 is designed to have a high pressure so that coolant can be injected into the reactor coolant system within a comparatively shorter time. On the other hand, in the separate type safety injection tank 100, coolant can be gradually injected into the reactor coolant system for a desired time duration over a long period of time. In the separate type safety injection tank 100, since a flow rate of coolant is effectively utilizable to safety injection, the size of a required tank can be reduced. Further, since an initial pressure of the gas injection unit 102 can be increased, safety injection could be possible even in a case where an automatic depressurization system to depressurize the reactor coolant system 210 does not operate. The separate type safety injection tank according to the present invention can have the following advantages. Firstly, in the occurrence of a LOCA, coolant can be safely injected into the reactor coolant system for a desired time duration over a long period of time, using a critical flow velocity of gas. As a result, a flow rate of coolant can be effectively utilizable to safety injection, thereby significantly reducing the size of a tank to be installed. Secondly, a comparatively constant amount of coolant can be injected into the reactor coolant system using a critical flow velocity of gas, even when pipes of various sizes are ruptured. This can allow an initial pressure of the gas injection unit to be set to be higher than a predicted pressure inside the reactor coolant system in the occurrence of a pipe rupture accident. As a result, the separate type safety injection tank can cope with various size LOCAs. Thirdly, as additional systems for safety injection of coolant of an intermediate pressure and a low pressure are not required, equipment can be simplified and economic feasibility can be enhanced. Further, as a pressure balance pipe for forming a pressure balance is not required, the probability of the occurrence of a pipe rupture accident is lower than that in a pressure balance type safety injection tank. This can enhance the safety. The foregoing embodiments and advantages are merely exemplary and are not to be considered as limiting the present invention. The present teachings can be readily applied to other types of apparatuses. This description is intended to be illustrative, and not to limit the scope of the claims. Many alternatives, modifications, and variations will be apparent to those skilled in the art. The features, structures, methods, and other characteristics of the exemplary embodiments described herein may be combined in various ways to obtain additional and/or alternative exemplary embodiments. As the present features may be embodied in several forms without departing from the characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be considered broadly within its scope as defined in the appended claims, and therefore all changes and modifications that fall within the metes and bounds of the claims, or equivalents of such metes and bounds are therefore intended to be embraced by the appended claims.
	abstract	A nuclear fuel assembly spacer grid defining a lattice of cells for receiving fuel rods is provided. The spacer grid includes a peripheral band composed of at least one peripheral strip delimiting a portion of the peripheral contour of the spacer grid, and at least one spacer grid positioning spring elastically deformable and formed in the peripheral band.
062158511	abstract	In accordance with the present invention, there is provided a proton beam target for generating gamma rays which are generated therefrom in response to an impinging proton beam. The proton beam target is provided with a .sup.13 C gamma reaction layer for generating the gamma rays therefrom. The proton beam target is further provided with a stopping layer for mitigating transmission of the proton beam therethrough. The stopping layer is formed of a refractory metal which is hydrogen soluble for dissolving implanted hydrogen molecules therewithin as a result of the impingement of the proton beam and which is chemically reactive with the .sup.13 C gamma reaction layer for chemically bonding therewith.
044255063	description	DETAILED DESCRIPTION OF THE INVENTION FIG. 1 shows an x-ray therapy machine 10 incorporating a magnetic deflection system 13. The therapy machine 10 comprises a generally C-shaped rotatable gantry 14, rotatable about an axis of revolution 16 in the horizontal direction. The gantry 14 is supported from the floor 18 via a pedestal 20 having a trunnion 22 for rotatably supporting the gantry 14. The gantry 14 includes a pair of generally horizontally directed parallel arms 24 and 26. A linear electron accelerator 27 communicating with quadrupole 28 is housed within arm 26 and a magnetic deflection system 11 and target 29 are disposed at the outer end of the horizontal arm 26 for projecting a beam of x-rays between the outer end of the arm 26 and an x-ray absorbing element 30 carried at the outer end of the other horizontal arm 24. The patient 32 is supported from couch 34 in the lobe of the x-rays issuing from target 28 or theraputic treatment. Turning now to FIGS. 2 and 3, a pole cap 50 of the polepiece of the invention is shown. A step 52 divides pole cap 50 into regions 54 and 56, the pole cap 50 in region 56 having a greater thickness than region 54 by the height h of the step 52. Consequently, the magnet comprising pole cap 50 and 50' is characterized by a relatively narrow gap of width d in the region 56 and a relatively wide gap (d+2h width) in the region 54. Accordingly, the magnet comprises a constant uniform region 54 of relatively low magnetic field and another constant uniform region 56 of relatively high magnetic field. Excitation of the magnet is accomplished by supplying current to axially separated coil structure halves 58 and 58' each disposed about respective outer poles 60 and 60' to which the pole caps 50 and 50' are affixed. The magnetic return path is provided by yoke 62. Trim coils 64 and 64' provide a vernier to adjustment of the field ratio in the regions 54 and 56. A vacuum envelope 67 is placed between the poles of the magnet and communicates with microwave linear accelerator cavity 68 through quadrupole Q. As discussed below, another important design parameter is the angle of incidence of the trajectory with respect to the field at the entrance of the deflector. The control of the fringing field to maintain the desired position and orientation of the outer virtual field boundary 69 with respect to the entrance region is accomplished with field clamp 66 displaced from the pole caps by aluminum spacer 66'. In similar fashion, the location of the exit field boundary and orientation is controlled by suitable shape and position of the field clamp 66 in this region. An interior virtual field boundary 55 may be defined with respect to step 52 by appropriate curvature of the stepped surfaces 53 and 53'. This curvature compensates for the behavior of the magnetic field as saturation is approached and controls the fringing field in this region. Such shaping is well known in the art. Neither field boundary 69 nor 55 constitutes well defined locii and each is therefore termed "virtual" in accord with convention. A parameter is associated with each virtual field boundary to characterize the fringing field behavior in the transition region from one magnetic field region to another. Thus a parameter K.sub.1 is a single parameter description of the smooth transition of the field from the entrance drift space l.sub.1 to region 54 along a selected trajectory, as for example, central orbit P.sub.0 (and between region 54 and the exit drift space l.sub.2 in similar fashion). The fringing field parameter K.sub.2 describes similar behavior between magnetic field regions 54 and 56. It is conventional in the discussion of dipole magnetic optical elements for the z axis of the coordinate system to be chosen tangent to a reference trajectory with origin z=0 at the entrance plane and z=1 at the exit plane. (The entrance and exit planes are, in general, spaced apart from the magnetic field boundaries by drift spaces as indicated and should not be identified with any field boundary). The x axis is selected as the displacement axis in the plane of deflection of the bending plane. The y axis then lies in the transverse direction to the bending plane. The y axis direction is conventionally called "vertical" and the x axis, "horizontal". In the plane of deflection, a central orbital axis labeled P.sub.0 is described by a particle of reference momentum arrow P.sub.0. It is desired that displaced trajectories C.sub.x and C.sub.y having initial trajectories parallel to P.sub.0 (in the bending plane and transverse thereto, respectively), produces a like displacement at the exit of the deflector. A trajectory that enters this system at an angle .beta..sub.i to the field boundary exits at an angle .beta..sub.f. In the present discussed embodiment it is desired that .beta..sub.i =.beta..sub.f =.beta.. The trajectory is characterized by a radius of curvature .rho..sub.1 in the region 54 of the magnet due to magnetic field B.sub.1. In the region 56, the corresponding radius of curvature is .rho..sub.2 due to the magnetic field B.sub.2. The notation .rho..sub.0,1 (see FIG. 2) refers to the radius of curvature of the reference trajectory P.sub.0 in the low field region. The line determined by the respective centers for radii of curvature .rho..sub.0, 1 and .rho..sub.0, 2 intersects the virtual field boundary 55 determining the angle of incidence .beta..sub.2 to region 56 (incoming) and from symmetry the angle of incidence through field boundary 55 as the trajectory again enters region 4. For simplicity, the 0 subscript will be deleted. The deflection angle in the bending plane in the region 54 (incoming) is .alpha..sub.1 and again an angle .alpha..sub.1 in the outgoing trajectory portion of the same field region 54. In the high field region 56 the particle is deflected through a total angle 2.alpha..sub.2 for a total deflection angle .chi.=2(.alpha..sub.1 +.alpha..sub.2) through the deflection system. It is a necessary and sufficient condition for an achromatic deflection element that momentum dispersive trajectory d.sub.x (initial central trajectory direction, having a magnitude of P.sub.0 +.DELTA.P) is dispersed and brought to parallelism with the central trajectory P.sub.0 at the midpoint deflection angle .alpha..sub.1 +.alpha..sub.2, that is, at the symmetry plane. Further, the trajectory of particles initially displaced from, and parallel with trajectory P.sub.0 (in the bending plane) are focused to a cross-over with trajectory P.sub.0 at the symmetry plane. These trajectories are known in the art as "cosine-like" and designated C.sub.x, where the subscript refers to the bending plane. Trajectories of particles initially diverging from trajectory P.sub.0 (in the bending plane) at the entrance plane of the magnet are shown in FIG. 2. These trajectories are known in the art as "sine-like" and are labeled as S.sub.x in the bending plane. The condition of maximum dispersion and parallel-to-point focussing occurs at the symmetry plane and therefore defining slits 72 are located in this plane to limit the range of momentum, angular divergence accepted by the system. In common with similar systems, these slits 72, which are secondary sources of radiation, are remote from the target and shielded by the polepieces of the magnet. In the present invention, the gap is narrower in precisely this region, wherefore the greater mass of the polepieces 50 and 50' more effectively shield the environment from slit radiation. Trajectories C.sub.y and S.sub.y refer to cosine-like and sine-like trajectories in the vertical (y-z) plane. It is therefore required to obtain the relationship of the radii of curvature .rho..sub.1 and .rho..sub.2 and therefore, the magnetic fields B.sub.1 and B.sub.2 for the parameters of .alpha..sub.1 and .alpha..sub.2, P.sub.0, and the field extension parameters K.sub.1 and K.sub.2 of the virtual field boundaries subject to the condition of zero angular divergence in the bending plane of the momentum dispersive trajectory at the symmetry plane, e.g., (.differential.d.sub.x /.differential..sub.8)=0 for deflection angle .chi./2. From this condition, imposed at the symmetry plane, it can be shown that d.sub.x and its divergence, d.sub.x' ' will vanish at the exit of the magnet. In a simple analytical treatment of the problem, transfer matrices through the system are written for the incoming trajectory through region 54, proceeding to the incoming portion of region 56 to the symmetry plane, and then outgoing from region 56 to the boundary with region 54 and again outgoing through region 54. These matrices for the bending plane are written as the matrix product of the transfer matrices corresponding to propagation of the beam through the four regions 54.sub.o, 56.sub.o, 56.sub.i, 54.sub.i as shown in FIG. 4 ##EQU1## where c.sub.1, s.sub.1, c.sub.2, s.sub.2, are a short notation for respectively, cosine .alpha. and sine .alpha. in the respective low (1) and high (2) field regions and .beta. here stands for tam .beta.. The variables .rho..sub.1 and .rho..sub.2 refer to radii of curvature in the respective regions 1 and 2 corresponding to regions 54 and 56. The C.sub.i and S.sub.i parameters are conventionally expressed as displacements with respect to the reference trajectory. Equation 1 can be reduced to yield, in the bending plane ##EQU2## The matrix element R.sub.11 expresses a coefficient describing the relative spatial displacement of the C.sub.x trajectory. The R.sub.12 element describes the relative displacement of S.sub.x. In similar fashion, the element R.sub.21 element describes the relative angular divergence of C.sub.x and the element R.sub.22 the relative angular divergence of the S.sub.x trajectory. Matrix elements R.sub.13 and R.sub.23 describes the displacement in the bending plane of the momentum dispersive trajectory d.sub.x (which was initially congruent with the central trajectory at the object plane) and R.sub.23 describes its divergence. Several conditions are operative to simplify the optics: (a) the apparatus maps incoming parallel trajectories to outgoing parallel trajectories at the entrance and exit planes respectively, which follows from the matrix element R.sub.21 =0; (b) the deflection magnet having no dependence upon the sense of the trajectory from which it follows that R.sub.22 =R.sub.11 ; (as is also apparent from consideration of the symmetry of the system); (c) the determinant of the matrix is identically 1 by Liouville's theorem. It follows from conditions (b) and (c) that R.sub.11 ==-1. The bottom row of the matrix describes the momentum in either plane. These elements are identically 0,0 and 1 because there is not net gain or loss in beam energy (momentum magnitude) in traversing any static magnet system. For an achromatic system, the dispersion displacement term R.sub.13 and its divergence, R.sub.23 must be 0. As expressed above, the condition on R.sub.23 at the symmetry plane is developed analytically to yield a relationship among certain design parameters of the system. As a result thereof one obtains the expression ##EQU3## which can be solved to yield the condition ##EQU4## Following conventional procedure the corresponding vertical plane matrices for the same regions 54 (incoming), 56 (incoming), 56 (outgoing), and 54 (outgoing) may be written and reduced to obtain the matrix equation for transverse plane propagation through the system. EQU y(1)=R.sub.y y(0) where 1 is the z coordinate location of the exit plane for the entrance plane, z=0. A principal design constraint is the realization of a parallel to parallel focusing in this plane is to be contrasted with the deflection plane where the corresponding condition follows from the geometry of the magnet. Thus far the transfer matrices R.sub.x and R.sub.y describe the transfer functions which operate on the inward directed momentum vector P(z.sub.1) at the field boundary 69 to produce outgoing momentum vector P(z.sub.2) at the field boundary 69 after transit of the magnet. In the preferred embodiment, drift spaces l.sub.1 and l.sub.2 are included as entrance and exit drift spaces, respectively. Drift matrices of the form ##EQU5## operate on the R.sub.x,y matrices which both exhibit the form of equation 2, e.g., ##EQU6## and it is observed that the magnet transfer matrix has the form of an equivalent drift space. Thus, the transformation through the total system with drift spaces l.sub.1 and l.sub.2 will yield total transfer matrices for the bending and transverse planes given by ##EQU7## where the minus sign refers to the matrix R.sub.x.sbsb..tau. and the plus sign refers to R.sub.y.sbsb..tau.. the lengths L.sub.x and L.sub.y are the distances from the exit plane to the projected crossovers of the S.sub.x and S.sub.y trajectories. Turning now to FIG. 5, the general situation is shown wherein the waist in the bending or radial plane and the waist in the transverse plane are achieved at different positions on the z axis. Thus, in one plane the beam envelope is converging while diverging in another plane. Previously, a plurality of quadrupole elements would be arranged to bring these waists into coincidence at a common location z. In the present invention, the condition d.sub.x '=0 and C.sub.y =0 are satisfied at the symmetry plane with the result that d.sub.x =0 at the field exit boundary. Moreover, it follows from this that C.sub.x characterizes parallel to parallel transformation through the magnet in the bending plane. In the transverse plane parallel to parallel transformation is imposed on the design. Consequently, the matrix describing either transverse or bending plane exhibits the form as given above. The effect of the quadrupole singlet at the entrance of the system takes the form ##EQU8## where s.sub.q may be identified with the (variable) quadrupole focal length. The waist of the beam is attained from expressions of the form EQU .vertline.x(.sub.1).vertline..sup.2 =.vertline.C.sub.x X.sub.(o).vertline..sup.2 +.vertline.S.sub.x X'.sub.(o) .vertline..sup.2 EQU .vertline.y.sub.(1) .vertline..sup.2 =C.sub.y y.sub.(o) .vertline..sup.2 +.vertline.S.sub.y Y'.sub.(o) .vertline..sup.2 It is noted that S.sub.x and S.sub.y are unaffected by the quadrupole inasmuch as these trajectories exhibit zero amplitude, by definition, at z=0. The displacement of trajectories C.sub.y and C.sub.x are of opposite side. If the range l.sub.1 +l.sub.2 has been properly selected the focal length of the quadrupole can be adjusted to bring the radial waist and transverse waist into coincidence. The matrix equations EQU X.sub.(1) =R.sub.x.sbsb..tau. X.sub.(o) EQU y.sub.(1) =R.sub.y.sbsb..tau. y.sub.(o) which describe the total system including drift spaces in the vertical and bending planes are most conveniently solved by suitable magnetic optics programs, such as, for example, the code TRANSPORT, the use of which is described in SLAC Report 91 available from Reports Distribution Office, Stanford Linear Accelerator Center, P.O. Box 4349, Stanford, CA 94305. The TRANSPORT code is employed to search for a consistent set of parameters: subject to selected input parameters, .rho..sub.1, the radius of curvature of P.sub.0 in region 54, .rho..sub.1 /.rho..sub.2, the relative radius of curvature of P.sub.0 in region 54 to the radius of curvature in region 56, .beta..sub.1, the angular incidence of trajectory P.sub.0 on virtual field boundary, .alpha..sub.2, the angular rotation of the central trajectory P.sub.0 in the high field region which also determines .beta..sub.2 the angle of incidence of P.sub.0 on the interior virtual field boundary, .alpha..sub.1, the rotation of the reference trajectory in the low field region, subject to the selected input parameters as follows: K.sub.1, the parameter of the virtual field boundary between the low field region and the external field free regions, K.sub.2 /K.sub.1, the relative parameter describing the virtual interior field boundary between the high field and low field regions, For the preferred embodiment symmetry has been imposed, e.g., .chi.=2(.alpha..sub.1 +.alpha..sub.2). In one representative set of design parameters for 270.degree. electron deflection, the desired mean electron energy is variable between 6 Mev and 40.5 Mev. First order achromatic conditions are required over this range. The angle of incidence .beta. for entrance and exit portions of the trajectory is 45.degree. and the outer virtual field boundary 69 is located at z=10 cm relative to the entrance collimator (z=0) aperture. The central trajectory rotates through an angle .alpha..sub.1 of 41.5.degree. under the influence of a magnetic field B.sub.1 of 4.17 kilogauss and intercepts the interior virtual field boundary 55 at z=33.5 cm at an angle .beta..sub.2 =90.degree.-.alpha..sub.2 of 31/2.degree. to reach the symmetry plane at z=37.4 cm and continued rotation through the angle .alpha..sub.2 (93.5.degree.) under the influence of magnetic field B.sub.2 of 15.90 kilogauss. The trajectory is symmetric within the magnetic field boundaries and the target is located at beyond the outer virtual field boundary. At the entrance collimator the beam envelope is 2.5 mm in diameter exhibiting (semi cone angle) divergence properties in both planes of 2.4 mr. The geometry of the magnet assures a parallel to parallel with deflection plane transformation. The condition that d.sub.x '=0 at the symmetry plane provides momentum independence. The parallel to parallel condition in the transverse plane is therefore a constraint. The bend angles .alpha..sub.1 and .alpha..sub.2 and the ratio of field intensities are varied to obtain the desired design parameter set. It has been found that a first order achromatic deflection system for a deflection angle of 270.degree. can be achieved with a variety of field ratios (B.sub.1 /B.sub.2) as shown from equation 3. Further, absolute values of corresponding matrix elements for both the horizontal and vertical planes can be obtained which are very nearly the same, yielding an image beam spot which is symmetric. One of ordinary skill in the art will recognize that other deflection angles may be accommodated by deflection systems similarly constructed. Moreover the interior field boundary may take the form of a desired curve if desired. Accordingly, the foregoing description of the invention is to be regarded as exemplary only and not to be considered in a limiting sense; thus, the actual scope of this invention is indicated by reference to the appended claims.
	description	The container as illustrated in FIG. 1 has the general form of a rectangular box. The container 1 is defined by four vertically arranged walls 2 and a base wall 3. The walls are provided at the corner joins with strengthening elements 4 in the form of L-shaped strips. The vertical strengthening elements 4 have portions 6 which extend beyond the lid 8 of the container. Feet 10 are provided on each corner of the base and engage with the portion 6 for easy and stable stacking. The outer skin forming the walls 2, base 3 and separate lid 8 are made of stainless steel. A peripheral flange 12 is provided around the container. The lid 8 is dimensioned to be slidably received within the boundaries of the L-shaped elements 4. The lid 8 has a flange 16 which corresponds with the peripheral flange 12 of the container. Handles 14 on the lid aid in its removal and insertion. In the closed and retained position shown the lid 8 is retained by a series of quick release nuts and bolts 18 which engage corresponding openings in the flange 16 of the lid 8. The lid is provided with suitable seals to prevent any ingress of water. Next to the steel skin the container is provided with a substantial thickness of a thermal insulator 20 formed from calcium silicate. This layer is provided in a series of sections, see FIG. 2. The materials provision in solid sections ensures accurate positioning during assembly and use. A single base layer of insulator 22 and four wall sections 24 line the container itself. When the container is loaded, as described below, a two piece insulating top layer is applied. These two pieces 26, 28 are shaped to interconnect with one another. The rectangular box defined by the interior surfaces of the insulating layers receives an internal container 30A having four walls and a base and also made of boronated steel or stainless steel. This container 30A is also provided with a lid 31 as shown in FIG. 1. As seen in FIG. 3 the container consists of a series of interlocking vertical walls 30 made of boronated steel/stainless steel. The container 30A has two pairs of internal walls 30 at 90 degrees to one another defining nine chambers 32 within the pail load. In use within each of the eight peripheral chambers a fuel drum or pail 36 is received. The central chamber 32A is provided with a polyethylene neutron absorber 38. The absorber 38 is itself provided in a steel container (not shown) which corresponds with the shape of the chamber 32 into which it is to be fitted. A lid is provided on the top of the absorber to retain the absorber in place in the chamber 32A. Once the internal container 30A has received all eight fuel drums 36, and the container 1 is sealed by applying the lid 31, the insulating top layer 26, 28, and the external lid 8. The lid 8 is secured to the container 1 by the quick release nuts and bolts 18. The fuel containing drum 36, as illustrated in FIG. 6, consists of a stainless steel cylinder wall 40 with a base plate 42 and releasable lid 44. The lid 44 is provided with a standard internal lever clamp band 46 which enables the lid to be secured to the fuel drum 36. The provision of the internal lever clamp band 46 within the outline of the drum 36 is important to minimise the space taken up. In the closed state the drum 36 is water tight avoiding any water ingress. The fuel 55 in either powder of pellet form is contained within polyethylene bags. The polyethylene bags filled with fuel are placed in a larger polyethylene bag which is placed in the drum. Once the larger bag is full this is then closed. The drum is then sealed with the lid 44. The fuel may typically be enriched uranium destined to form fuel rods. In the second embodiment of the invention illustrated in FIG. 7 the container 100 is once again in the form of a rectangular box. The external container 100 is defined in a similar manner to the container of the first embodiment by vertically arranged side walls 102 and a base wall 103. Other equivalent elements are numbered with reference numerals corresponding to those used in the first embodiment increased by 100. Thus the strengthening elements, feet, peripheral flange, lid fixing and lid alignment are provided in a similar manner. The container 100 is also provided with substantial thickness of thermal insulator 120 provided by a base section, wall sections and a section optionally mounted on the lid in a similar manner to the first embodiment of the invention. The arrangement within the internal cavity defined by these insulating layers differs, however. The cavity is provided with a series of stainless steel sleeves 150 which are rigidly mounted on a bottom plate standing on the base layer insulation. The cylindrical sleeves are hollow and have an internal dimension configured to snugly correspond to the external dimensions of the fuel containers 152 shown inserted in the sleeves 150. Nine sleeves 150 are used in a three by three arrangement with a fuel container 152 being positioned in each in use. The fuel containers are generally of the type illustrated in FIGS. 6 and 6A above, but include external fasteners projecting beyond the plan of the fuel containers. As shown in FIGS. 7, 8 and 9 the sleeves 150 are surrounded by a neutron absorbing material 158. This material is introduced to the volume surrounding the sleeves during the manufacture of the portion of the assembly filling the internal cavity by pouring in a liquid resin which is then allowed to harden. A resin tight unit is preferred as defining this cavity. The resin is loaded with boron preferably to a level of 2% to provide the desired neutron absorbing capability. A boron loading up to 6.5 wt % and/or a lead loading up to 15 wt % may be provided. The material offers between 1xc3x971022 and 1xc3x971023 hydrogen atoms/cm3. To reduce the cost and weight of the neutron absorbing material, typically 1.68 g/cm3 lighter materials such as polystyrene can be incorporated in portions where the neutron absorbing volume of material would otherwise be excessive. Thus at locations 162 between sets of 4 sleeves and externally at the corner locations 164 and locations 166 between the pairs of sleeves the neutron material may be replaced with the lighter material. This does not affect the neutron absorbing capability of the container. The fuel containing drums 152 and the manner in which the fuel, as powder or pellets is provided within them is as described above for the first embodiment of the invention. The present invention allows approximately 20%-40% of the outer container volume to be occupied by fuel 55 and yet still meets the necessary standards. This compares favorably with prior art systems. An increased payload is thus provided successfully. The use of stainless steel and the modular nature of the assembly assists in refurbishment and any cleaning stages required such as decontamination.
	claims	1. A core catcher for a nuclear reactor plant that has a reactor vessel, the core catcher comprising:a main body configured to be placed beneath the reactor vessel and having a plurality of cooling fins extending radially on a bottom surface of the main body;a plurality of cooling channels formed between the cooling fins in the main body and extending radially;a distributor arranged in a central region of the bottom surface of the main body and connected to the plurality of cooling channels so that cooling water in the distributor is led inside of the cooling channels; anda side wall part channel formed at a peripheral region of the main body. 2. The core catcher according to claim 1, wherein the main body is divided into a plurality of regions from a center to a periphery thereof and a number of the cooling fins extending radially in an outer region is more than a number of cooling fins extending radially in an inner region so that the cooling fins constitute more cooling channels in the outer region than the inner region. 3. The core catcher according to claim 2, wherein a plurality of the cooling channels are connected to an intermediate header being formed at a border of the regions, the intermediate header is a mixing region where cooling water which passes through each cooling channel is intermingled and supplies the cooling water from the cooling channels formed in the inner region to the cooling channels formed in the outer region. 4. The core catcher according to claim 1, wherein a heat resistant material layer is formed on a top surface of the main body. 5. The core catcher according to claim 4, wherein the heat resistant material layer is formed with one of metal oxide and basalt concrete. 6. The core catcher according to claim 4, wherein a drain sump is formed on a top surface of the heat resistant material layer. 7. The core catcher according to claim 4, wherein a sacrifice concrete layer is formed in a top surface of the heat resistant material layer. 8. The core catcher according to claim 4, wherein the heat resistant material layer is formed so that layering thickness of an outer part in a radial direction of the main body is larger than that of an inner part. 9. The core catcher according to claim 4, wherein the heat resistant material layer includes a first heat resistant material layer and a second heat resistant material layer, the second heat resistant material layer having smaller thermal conductivity than the first heat resistant material layer and being located further outward in a radial direction of the main body than the first heat resistant material layer. 10. The core catcher according to claim 1, wherein at least a part of the coolant injection piping is embedded in a pedestal side wall defining a space in which the main body is located. 11. The core catcher according to claim 1, wherein the main body comprises a combination of a plurality of body sub pieces, a plurality of cooling fins formed radially on a bottom surface of each body sub piece and cooling channels formed radially between the cooling fins. 12. The core catcher according to claim 11, wherein a side facing to a pedestal side wall of the body sub piece located at a periphery extends along the pedestal side wall. 13. The core catcher according to claim 1, further comprising a recirculation piping being configured to return the cooling water emitted from the cooling channel over the main body to the cooling channel. 14. The core catcher according to claim 13, wherein the recirculation piping includes first recirculation piping and second recirculation piping, a location where the second recirculation piping returns the cooling water to the cooling channel is downstream from a location where the first recirculation piping returns the cooling water to the cooling channel. 15. The core catcher according to claim 13, further comprising a dam located between an entering opening of the recirculation piping and an outlet opening of the cooling channel. 16. The core catcher according to claim 15, wherein the dam inclines toward the outlet opening of the cooling channel. 17. The core catcher according to claim 1, wherein at least a part of an inner upside surface of the cooling channel inclines against a horizontal line along a direction in which the cooling water flows. 18. The core catcher according to claim 17, wherein an inclination of the inner upside surface to the horizontal line is larger at downstream of the direction through which the cooling water flows. 19. The core catcher according to claim 1, wherein a plurality of dimples are formed on an inner wall of the cooling channel. 20. The core catcher according to claim 1, further comprising:detection means for detecting an indication of dropping of a molten core; andcooling water supply means for supplying the cooling water to the cooling channel through the cooling water injecting piping if the detection means detects the indication. 21. The core catcher according to claim 20, wherein the cooling water supply means includes:a cistern located above an outlet of the cooling channel and being configured to store the cooling water;an injection valve inserted in the cooling water injecting piping; andan injection valve controller connected to the detection means and being configured to open the injection valve if the detection means detects the indication. 22. The core catcher according to claim 21, whereinthe detection means detects temperature of atmosphere of a lower part of the reactor vessel, andthe injection valve controller opens the injection valve if the temperature of atmosphere of the lower part of the reactor vessel exceeds a predetermined temperature. 23. The core catcher according to claim 21, whereinthe detection means detects temperature of a lower head of the reactor vessel, andthe injection valve controller opens the injection valve if the temperature of the lower head of the reactor vessel exceeds a predetermined temperature. 24. The core catcher according to claim 21, whereinthe detection means detects a water level inside the reactor vessel, andthe injection valve controller opens the injection valve if a certain period elapses while the water level inside the reactor vessel remains less than a specific water level. 25. The core catcher according to claim 20, wherein the cooling water supply means includes:a cistern configured to store the cooling water;a pump configured to send out the cooling water to the water supply chamber from the cistern; anda pump controller connected to the detection means and configured to start the pump if the detection means detects the indication. 26. The core catcher according to claim 1, wherein the cooling channel is formed so that height of a flow area at an outer position of a radial direction is smaller than an inner position. 27. A core catcher for catching core debris generated when a reactor core in a reactor vessel melts and penetrates the reactor vessel, the core catcher comprising:a cooling channel having a plurality of fins attached to a bottom thereof and defining a debris holding region and a plurality of cooling water flow paths, the debris holding region being surrounded by a bottom surface inclined with respect to a horizontal plane and a wall spreading vertically at a periphery of the bottom surface and being opened upward, the cooling water flow paths extending parallel to each other with a fixed horizontal width along the bottom surface of the debris holding region as a top surface of the cooling water flow rises; andheat resistant material attached to a surface of the cooling channel facing to the debris holding region,wherein the cooling water flow paths are formed between the fins. 28. The core catcher according to claim 27, wherein lengths of the cooling water flow paths are equal to each other.
	claims	1. A computed tomography apparatus comprising: a scanning unit which is rotatable, relative to an examination zone, around an axis of rotation which extends through the examination zone; a radiation source for generating a primary radiation fan beam which traverses the examination zone; a two-dimensional detector array which includes a plurality of detector elements defining a measuring surface, a first part of the measuring surface for detecting primary radiation from the primary fan beam and a second part of the measuring surface for detecting scattered radiation produced in the examination zone; a modulation unit for the temporally and spatially periodic modulation of the primary fan beam, said modulation unit disposed between the radiation source and the examination zone and, a determining unit for determining a momentum transfer spectrum from cross-correlations between the measured scattered radiation of the individual detector elements and a modulation signal used for the modulation of the primary fan beam. 2. A computed tomography apparatus as claimed in claim 1 , wherein the modulation unit is constructed such that the intensity of the modulated primary fan beam has an intensity that is temporally modulated and a phase position that is spatially modulated. claim 1 3. A computed tomography apparatus as claimed in claim 1 , wherein the modulation unit is cylindrically symmetrically arranged around a modulation axis which extends perpendicularly to the axis of rotation and the connecting line between the focal point of the radiation source and the center of the detector array, and comprises two diaphragm elements which are diametrically arranged relative to the modulation axis, are arranged helically around the modulation axis, and are rotatable about the modulation axis. claim 1 4. A computed tomography apparatus as claimed in claim 3 , wherein the diaphragm elements are rotatable at a constant angular speed around the modulation axis for the temporal and spatial modulation of the primary fan beam. claim 3 5. A computed tomography apparatus as claimed in claim 3 , wherein the diaphragm elements comprise diaphragm blades which are radiation attenuating and are mounted so as to be helical and 180xc2x0 offset on a shaft extending along the modulation axis. claim 3 6. A computed tomography apparatus as claimed in claim 3 , wherein the modulation unit comprises a radiation attenuating external wall and the diaphragm elements include two radiation transparent slits which extend helically and in an offset fashion in the external wall. claim 3 7. A computed tomography apparatus as claimed in claim 1 , wherein in order to subdivide the primary fan beam, the modulation unit is subdivided into a plurality of neighboring fan beam units and is arranged for the separate modulation of the fan beam units. claim 1 8. A computed tomography apparatus as claimed in claim 1 , wherein the modulation unit comprises means for sinusoidal temporal and spatial modulation of the primary fan beam. claim 1 9. A computed tomography apparatus comprising: a scanning unit which is rotatable, relative to an examination zone, around a scanner axis of rotation which extends through the examination zone; a radiation source for generating a radiation beam directed towards the examination zone; a detector disposed across the examination zone from the radiation source, said detector including a plurality of detector elements for detecting primary radiation and scattered radiation that passes through the examination zone; a modulation unit disposed between the radiation source and the examination zone for temporally and spatially modulating the radiation beam; and cross-correlation means for cross-correlating the spattered radiation with a modulation signal used for the modulation of the radiation beam whereby a location-dependent momentum transfer spectrum is reconstructed. 10. A computed tomography apparatus as claimed in claim 9 , wherein the modulation unit comprises temporal means for temporally modulating the intensity of the modulated radiation beam and spatial means for spatially modulating the phase position of the modulated radiation beam. claim 9 11. A computed tomography apparatus as claimed in claim 9 , wherein the modulation unit is cylindrically symmetrically arranged around a modulation axis which extends perpendicularly to the scanner axis of rotation and a line passing from the focal point of the radiation source and the center of the detector array, and comprises a plurality of diaphragm elements arranged helically around the modulation axis. claim 9 12. A computed tomography apparatus as claimed in claim 11 , wherein the diaphragm elements rotate at a constant angular speed around the modulation axis. claim 11 13. A computed tomography apparatus as claimed in claim 11 , wherein the diaphragm elements comprise diaphragm blades which are radiation attenuating and are mounted so as to be helical and 180xc2x0 offset from one another on a shaft extending along the modulation axis. claim 11 14. A computed tomography apparatus as claimed in claim 11 , wherein the modulation unit comprises a radiation attenuating external wall and the diaphragm elements include radiation transparent slits which extend helically and in an offset fashion from one another in the external wall. claim 11 15. A computed tomography apparatus as claimed in claim 9 , wherein the modulation unit comprises dividing means for dividing the radiation beam into a plurality of radiation beam units. claim 9 16. A computed tomography apparatus as claimed in claim 9 , wherein the modulation unit comprises sinusoidal means for sinusoidally modulating the radiation beam temporally and spatially. claim 9 17. A method of computed tomography comprising the steps of: projecting a fan-shaped beam of radiation from a radiation source towards an examination region; modulating the fan-shaped beam of radiation temporally and spatially 7 using a modulation unit disposed between the radiation source and the examination region; detecting primary radiation and scattered radiation using a radiation detector array after the primary and scattered radiation have passed through the examination region; and obtaining a momentum transfer spectrum of the scattered radiation. 18. A method of computed tomography according to claim 17 wherein the step of modulating the fan-shaped beam of radiation includes sinusoidally modulating the fan-shaped beam of radiation. claim 17
046684441	abstract	Substantially isotropic spherical fuel and absorber elements for high temperature reactors are produced by molding corresponding fuel particles and graphite molding compositions. There is used as graphite molding powder a mixture of graphitized granules of coke and a hardenable resin binder. There are first produced in steel dies at 80.degree. to 120.degree. C. half shells and a nucleus with a pressed density of 1.0 to 1.4 g/cm.sup.3 followed by molding in a further steel die to the final format.
	claims	1. A charged particle beam trajectory corrector for modifying trajectories of charged particle beams to correct aberrations, comprising:a correction electrode group including an axial electrode provided on a straight-line axis which obliquely crosses an emission axis of a charged particle beam from an illumination lens and off-axis electrodes provided with rotational symmetry so as to surround the axial electrode; and,a magnetic lens which generates an electric field between the axial electrode and the off-axis electrodes, whereinthe charged particle beam is caused to obliquely intersect the straight-line axis, a voltage is applied between the axial electrode and the off-axis electrodes to relax electric field distortion, and the aberration is corrected by an action of the magnetic lens. 2. The charged particle beam trajectory corrector according to claim 1, wherein an intersection point between the emission axis of the charged particle beam and the straight-line axis matches an image-formation point of the illumination lens. 3. The charged particle beam trajectory corrector according to claim 1, wherein the off-axis electrodes are configured as an off-axis electrode group which includes a plurality of off-axis electrodes, and voltage values proportional to a voltage input value to a predetermined off-axis electrode of the plurality of off-axis electrodes are inputted to the other off-axis electrodes of the plurality of off-axis electrodes. 4. The charged particle beam trajectory corrector according to claim 1, wherein the magnetic lens is compounded so as to be a rotational symmetry that is coaxial with the straight-line axis on which the axial electrode of the correction electrodes is provided. 5. The charged particle beam trajectory corrector according to claim 1, wherein input values of the correction electrodes are controlled with a linear function of input values to the magnetic lens. 6. The charged particle beam trajectory corrector according to claim 1, further comprising:a supporting body to which is fixed one end of the axial electrode and the off-axis electrodes, whereinthe axial electrode is configured as a short rod-like electrode or a substantially point-like electrode surrounded by a ground-connected shield electrode, and the supporting body has an annular opening which limits an incident range of the charged particle beam to a periphery of a portion fixed to an end of the rod-like electrode. 7. The charged particle beam trajectory corrector according to claim 1, wherein the off-axis electrodes are divided in a circumferential direction to form a plurality of portion electrodes, and voltages are independently applied to the each portion electrode. 8. The charged particle beam trajectory corrector according to claim 1, further comprising:a movable limiting aperture having differing opening dimensions in a radial direction and a rotation direction from a center of an axis of rotational symmetry of the off-axis electrodes. 9. The charged particle beam trajectory corrector according to claim 1, further comprising:an incident astigmatism corrector for correcting convergence towards a radial direction and a rotation direction from a center of an axis of rotational symmetry of an incident charged particle beam; andan exit astigmatism corrector which restores a shape of the charged particle beam emitted from the correction electrodes. 10. A charged particle beam apparatus which illuminates a specimen with a charged particle beam and acquires a specimen image, comprising:a charged particle source which generates the charged particle beam;an illumination lens for converging the charged particle beam;a charged particle beam trajectory corrector for modifying a trajectory of the charged particle beam to correct aberration;an illumination deflector for illuminating the specimen with a modified-trajectory charged particle beam; andan image generating and processing unit which detects a reflected electron signal from the specimen and displays an image on an image display apparatus, whereinthe charged particle beam trajectory corrector includes: a correction electrode group including an axial electrode provided on a straight-line axis which obliquely crosses an emission axis of the charged particle beam from the illumination lens, and off-axis electrodes provided with rotational symmetry so as to surround the axial electrode; and a magnetic lens which generates an electric field between the axial electrode and the off-axis electrodes, andthe charged particle beam is caused to obliquely intersect the straight-line axis, a voltage is applied between the axial electrode and the off-axis electrodes to relax electric field distortion, and the aberration is corrected by an action of the magnetic lens. 11. The charged particle beam apparatus according to claim 10, wherein the illumination deflector corrects an incident direction of the charged particle beam. 12. The charged particle beam apparatus according to claim 10, whereinthe illumination deflector further includes a function for scanning an upper structure of the correction electrodes, andthe image generating and processing unit detects a reflected electron signal from the upper structure of the correction electrodes, generates images of the upper structure of the correction electrodes, and displays the images on the image display apparatus. 13. The charged particle beam apparatus according to claim 10, further comprising:a control unit which controls input voltage values of the correction electrodes with a linear function of input to the illumination deflector. 14. The charged particle beam apparatus according to claim 10, further comprising:a control unit which controls the illumination deflector by measuring shape distortion of an emission beam with respect to a plurality of input values to the illumination deflector, approximating the distortion amounts as a polynomial function, and computing from the polynomial function an input value to the illumination deflector to minimize the distortion amount.
051184621	abstract	A manipulator for handling operations for non-destructive testing in the vicinity of the nozzle of a vessel in the primary loop of a nuclear power plant includes a carriage being movable in circumferential direction of the nozzle of the vessel. A sled is disposed on the carriage and displaceable in the axial direction of the nozzle. A shoulder joint is disposed on the sled. A scissors half has an upper arm with one end supported in the shoulder joint and another end, a lower arm with a free end, another joint connecting the other end of the upper arm to the lower arm, a holder, and a further joint connecting the holder to the free end of the lower arm. A tool or a probe is disposed on the holder. A method for handling a device, especially a probe, in the vicinity of the nozzle of a vessel, especially in the primary loop of a nuclear power plant, with a manipulator, includes controlling the holder and the other joint along a predetermined path with a control device acting upon at least one drive motor, and varying a pivoting angle of at least one of the arms with at least one drive motor. The position of the sled may also be varied with a drive motor operatively connected to the sled.
048204730	claims	1. A method of reducing radioactivity in a nuclear plant by preliminarily forming oxide films on the surfaces of metallic structural members to be in contact with high-temperature and high-pressure reactor water containing radioactive substances before said metallic structural members are exposed to said reactor water, comprising the steps of: subjecting said structural members to a first-step oxidation treatment of heating said structural members in water of a temperature of at least 200.degree. C., and further subjecting the thus treated structural members to a second-step oxidation treatment of heating said treated structural members in water, of a temperature of at least 200.degree. C., having a higher oxidizing capacity than that of said water in said first-step oxidation treatment, such that in the first-step oxidation treatment a relatively thick and porous oxide film, as compared to the oxide film formed in the second-step oxidation treatment, is formed, and in the second-step oxidation treatment a relatively denser and thinner oxide film than the oxide film obtained in said first-step oxidation treatment is formed, so that adherence of radioactive substances to said metallic structural members is suppresed as compared to adherence of radioactive substances to metallic structural members not having been subjected to both the firstand second-step oxidation treatments. controlling the oxidizing capacity of pure water to be lower than that of said reactor water, subjecting said structural members to a first-step oxidation treatment of heating by circulation of pure water of a temperature of at least 200.degree. C., the pure water being the pure water having the oxidizing capacity controlled to be lower than that of the reactor water, further controlling the controlled pure water to have a higher oxidizing capacity than that of said reactor water, and further subjecting the thus treated structural members to a second-step oxidation treatment of heating by circulation of the further controlled pure water, of a temperature of at least 200.degree. C., further controlled to have the higher oxidizing capacity than that of said reactor water, such that in the first-step oxidation treatment a relatively thick and porous oxide film, as compared to the oxide film formed in the second-step oxidation treatment, is formed, and in the second-step oxidation treatment a relatively denser and thinner oxide film than the oxide film obtained in said first-step oxidation treatment is formed. subjecting feed water heater tubes to a first-step oxidation treatment of heating by circulating pure water of a temperature, of at least 200.degree. C., having a lower oxidizing capacity than that of reactor water passed through the heater tubes during operation of the nuclear plant for nuclear heating, and further subjecting the thus treated heater tubes to a second-step oxidation treatment of heating by circulating pure water of a temperature, of at least 200.degree. having a higher oxidizing capacity than that of said reactor water, such that in the first-step oxidation treatment a relatively thick and porous oxide film, as compared to the oxide film formed in the second-step oxidation treatment, is formed, and in the second-step oxidation treatment a relatively denser and thinner oxide film than the oxide film obtained in said first-step oxidation treatment is formed, said first- and second-step oxidation treatments being conducted before start of the nuclear heating in the nuclear plant which generates electric power by rotating a generator with a turbine driven by steam generated in a reactor. preparing reactor water, to be used in the nuclear plant, the reactor water being substantially free from radioactive substances; effecting a first control of the dissolved oxygen concentration of said reactor water so as to be less in its oxidizing capacity than that of the reactor water used in the nuclear plant; subjecting said structural members to a first-step oxidation treatment of heating said structural members in contact with said reactor water controlled in said first control of the dissolved oxygen concentration at 200.degree. C. or higher for a predetermined period of time, thereby to provide thick and porous oxide films on the surfaces of the structural members; effecting a second control of the dissolved oxygen concentration of said reactor water so as to be higher in the oxidizing capacity than that of the reactor water used in the nuclear plant; further subjecting said structural members treated in said first-step oxidation treatment to a second-step oxidation treatment of heating said treated structural members in contact with said reactor water controlled in said second control of the dissolved oxygen concentration at 200.degree. C. or higher for a predetermined period of time, thereby to make said oxide films into thick and dense oxide films; and then operating the nuclear plant to produce electric power. 2. A method of reducing radioactivity in a nuclear plant as claimed in claim 1, wherein said firststep oxidation treatment is conducted with pure water of a temperature of at least 200.degree. C., having a dissolved oxygen concentration of lower than 200 ppb. 3. A method of reducing radioactivity in a nuclear plant as claimed in claim 3, wherein said pure water in said first-step oxidation treatment has a dissolved oxygen concentration of 40 to 100 ppb. 4. A method of reducing radioactivity in a nuclear plant as claimed in claim 1, wherein said water in said first-step oxidation treatment is pure water of a temperature of at least 200.degree. C., containing one or more members selected from the group consisting of hydrazine and salts of organic acids. 5. A method of reducing radioactivity in a nuclear plant as claimed in claim 1, wherein said second-step oxidation treatment is conducted with pure water of a temperature of at least 200.degree. C., having a dissolved oxygen concentration of higher than 200 ppb. 6. A method of reducing radioactivity in a nuclear plant as claimed in claim 5, wherein said pure water in said second-step oxidation treatment has a dissolved oxygen concentration of 300 to 1,000 ppb. 7. A method of reducing radioactivity in a nuclear plant as claimed in claim 4, wherein said second-step oxidation treatment is conducted with pure water of a temperature of at least 200.degree. C. containing one or more members selected from the group consisting of hydrogen peroxide, chromates, and permanganates. 8. A method of reducing radioactivity in a nuclear plant as claimed in claim 7, wherein said pure water is weakly alkaline with a pH of 8 to 10. 9. A method of reducing radioactivity in a nuclear plant as claimed in claim 1, wherein said metallic structural members are made of steel. 10. A method of reducing radioactivity in a nuclear plant as claimed in claim 9, wherein said structural members are subjected to said first-step oxidation treatment so as to form an iron oxide film, and are subjected to said second-step oxidation treatment so as to form an iron oxide film denser and thinner than the iron oxide film formed in the first-step oxidation treatment. 11. A method of reducing radioactivity in a nuclear plant as claimed in claim 13, wherein the steel structural members are made of steel selected from the group consisting of carbon steel and stainless steel. 12. A method of reducing radioactivity in a nuclear plant as claimed in claim 11, wherein said structural members are subjected to said first-step oxidation treatment so as to form an iron oxide film, and are subjected to said second-step oxidation treatment so as to form an iron oxide film denser and thinner than the iron oxide film formed in the first-step oxidation treatment. 13. A method of reducing radioactivity in a nuclear plant as claimed in claim 1, wherein said reactor water has an oxidizing capacity, wherein the environment of a temperature of at least 200.degree. C. to which the structural members are subjected during the first-step oxidation treatment is water having a lower oxidizing capacity than that of said reactor water, and wherein the environment of the second-step oxidation treatment is water having a higher oxidizing capacity than that of said reactor water. 14. A method of reducing radioactivity in a nuclear plant as claimed in claim 1, wherein the thickness of the oxide film formed in the first-step oxidation treatment is 0.5 to 3 .mu.m, and the thickness of the denser oxide film formed in the second-step oxidation treatment is 0.05 to 0.5 .mu.m. 15. A method of reducing radioactivity in a nuclear plant as claimed in claim 2, wherein said second-step oxidation treatment is conducted with pure water of a temperature of at least 200.degree. C., having a dissolved oxygen concentration of higher than 200 ppb. 16. A method of reducing radioactivity in a nuclear plant by forming oxide films on the surfaces of metallic structural members which constitute a nuclear power plant which generates electric power by rotating a generator with a turbine driven by steam generated in a reactor, the oxide films being formed by circulating pure water of a temperature of at least 200.degree. C. from a pressure vessel of the reactor through a recycling system and partially through a reactor water purification system to said pressure vessel before said structural members are exposed to reactor water containing radioactive substances, said reactor water having an oxidizing capacity, comprising the steps of: 17. A method of reducing radioactivity in a nuclear plant as claimed in claim 16, wherein said metallic structural members are made of steel. 18. A method of reducing radioactivity in a nuclear plant as claimed in claim 17, wherein the steel structural members are made of steel selected from the group consisting of carbon steel and stainless steel. 19. A method of reducing radioactivity in a nuclear plant comprising the steps of: 20. A method of reducing radioactivity in a nuclear plant as claimed in claim 19, wherein said feed water heater tubes are made of steel. 21. A method of reducing radioactivity in a nuclear plant as claimed in claim 20, wherein the steel feed water heater tubes are made of steel selected from the group consisting of carbon steel and stainless steel. 22. A method of reducing radioactivity in a nuclear plant by forming oxide films on the surfaces of structural members made of steel to be in contact with high-temperature and high-pressure reactor water, comprising the steps of: 23. A method of reducing radioactivity in a nuclear plant as claimed in claim 22, wherein, in the first and second control steps, the dissolved oxygen concentrations are controlled to be 50 to 100 ppb and 300 to 1,000 ppb, respectively. 24. A method of reducing radioactivity in a nuclear plant as claimed in claim 23, wherein said first- and second-step oxidation treatments each are conducted for 100 to 500 hours. 25. A method of reducing radioactivity in a nuclear plant as claimed in claim 22, wherein the steel structural members are made of steel selected from the group consisting of carbon steel and stainless steel.
	claims	1. An X-ray radiography system for differential phase contrast imaging of an object under investigation by phase stepping, comprising:an X-ray emitter for generating electron ray beams;an X-ray image detector with pixels arranged in a matrix; anda diffraction or phase grating,wherein the X-ray emitter comprises an X-ray tube,wherein the X-ray tube comprises a cathode and an anode, andwherein the X-ray tube further comprises focusing electronics,wherein the electron ray beams emitted from the cathode are influenced by the focusing electronics to produce a first set of linear-shaped electron fan beams and a second set of further refined linear-shaped electron fan beams,wherein the second set of the further refined linear-shaped electron fan beams are incident on the anode, andwherein a spacing between lines of the first set of the linear-shaped electron fan beams and the second set of the further refined linear-shaped electron fan beams is changed by actuation of the focusing electronics. 2. The X-ray radiography system as claimed in claim 1, wherein the diffraction or phase grating is arranged between the object and the X-ray image detector, and wherein an analyzer grating is associated with the diffraction or phase grating. 3. The X-ray radiography system as claimed in claim 1, further comprising a magnetic deflection device which varies points of incidence of the second set of the further refined linear-shaped electron fan beams on the anode. 4. The X-ray radiography system as claimed in claim 1, wherein the spacing between the lines of the first set of the linear-shaped electron fan beams and the second set of the further refined linear-shaped electron fan beams is dimensioned in such a way that it satisfies Lau condition, a constructive overlaying of an interference pattern at a site of an image plane. 5. The X-ray radiography system as claimed in claim 1, wherein the lines of the second set of the further refined linear-shaped electron fan beams are moved perpendicularly to a direction of the lines.
043572979	summary	This invention generally relates to nuclear reactors and, more particularly, to cooling systems for primary vessels. In general, the temperature of the walls of a primary vessel or tank is controlled by the thermal resistance of the insulation in combination with the heat removal systems which cool the supporting structure of the reactor and its surrounding cavity. The thermal insulation protects the walls of the primary tank against axial temperature gradients, transient temperatures, and high temperatures per se. Such insulation is necessary in order to protect the tank and its internal structures from thermal stresses which could endanger the integrity of the primary coolant boundary. The present invention has application in any nuclear reactor including but not limited to pressurized water, boiling water, gas cooled and liquid metal cooled reactors. The preferred embodiment is disclosed in connection with a liquid metal cooled nuclear reactor because such reactors operate at higher temperatures. Typically, these reactors operate within a temperature range of between 650.degree. F. and 950.degree. F. In addition, sodium has a very high coefficient of heat transfer so that during the operation of these reactors thermal transients rapidly propagate through the system and can cause severe thermal stresses. The general problem of insulating a primary tank in order to limit temperature level, gradients, and transients, occurs in both loop and pool type reactor designs. The temperature gradient problem, however, increases with the size of the reactor vessel. The axial gradient stress increases as the square root of the product of the wall radius and the thickness. Also, the transient radial gradient stress increases with the wall thickness. FIG. 1 illustrates a typical sodium cooled nuclear reactor. This reactor is a pool type reactor and includes a reactor core 4 which is supported within a primary tank 6. The primary tank is suspended from a steel support 7 which is mounted on top of the side wall of the concrete reactor cavity. The reactor further includes a plurality of pumps 8 which circulate the sodium coolant through the reactor during operation. One such pump is illustrated in FIG. 1. The pumps draw relatively cool sodium from a cold pool 9 located in the bottom of the primary tank and discharge it into the bottom of the reactor core 4. The sodium then flows upward through the core while being heated therein and is discharged into the hot pool 10. The sodium thereafter flows downward through a plurality of intermediate heat exchangers 11 and is discharged back into the cold pool. One such heat exchanger is illustrated in FIG. 1. Within the intermediate heat exchanger 11, FIG. 1 the heat from the core is transferred to a secondary sodium coolant which is circulated between the intermediate heat exchanger 11 and a plurality of steam generators (not shown). The hot and cold pools are separated by a horizontal structure 12 that forms the boundary between the two pools and includes a plurality of vertical wells 16 that thermally separate each pump 8 from the hot pool. Only one of the pump wells is shown in FIG. 1. The reactor operates at nominally atmospheric pressure and has a level of sodium 13 in the hot pool which is substantially below the reactor cover 12. The space above the hot pool is filled with an inert gas such as helium. In the past the principal technique for cooling the walls of primary tanks or vessels has been bypass cooling. In bypass cooling a portion of the flow of the relatively cold coolant is directed against the side walls of the primary tank. In the reactor of FIG. 1, the bypass coolant is obtained from the cold pool 9 and is directed against the inner side wall of the primary tank. In effect, a moving barrier of relatively cold sodium is interposed between the hot pool 10 and the primary tank wall 6. In one bypass flow design a portion of the discharge from the coolant circulating pump is first directed against the inside of the primary tank in an upward direction. The coolant is thereafter redirected downward by a baffle and flows back into the cold pool. In this design there is an upward flow of sodium from the cold pool, thermal contact between the cold sodium and the primary tank wall and a downward flow of sodium in the space between the hot pool and the upward flowing cold sodium. An alternative approach has been to direct the cold sodium from the discharge of the pump upward along the sidewall of the hot pool and then downward along the inner side wall of the primary tank. In this alternative design there is a wide, annular space between the side wall of the hot pool and the primary tank. Although bypass cooling is an accepted technique, there are several problem areas which cause concern. The principal problem with bypass cooling is that a large temperature difference is developed across the structural boundaries between the hot pool and the bypass cooling flow. This temperature difference is typically about 300.degree. F. during normal operation. This difference can cause severe thermal stresses to be developed during accident conditions. Another problem with bypass cooling is that the system cannot be designed to optionally function at constant temperature at every power level. Most reactors are operated with a fairly constant cooling outlet temperature so that the cooling requirement for the vessel wall is preferably constant and independent of power level. The rate of bypass coolant flow, however, is a function of the output of the circulating pump. The result is that the flow of bypass coolant varies with power level and the amount of heat transfer and resultant vessel wall temperatures likewise vary. A further problem with bypass cooling is that the bypass coolant itself is subject to temperature transients. The bypass flow is typically taken from the cold pool which is subject to temperature transients such as the stoppage of the flow of secondary sodium through the intermediate heat exchanger. This stoppage causes a sharp transient in the temperature of the cold pool because the primary sodium flowing through the intermediate heat exchanger is no longer cooled and hot sodium is dumped into the cold pool. Still another problem with bypass cooling is that it decreases the overall output of the reactor. Bypass cooling requires the diversion of a portion of the flow of coolant away from the reactor core. This diversion represents an efficiency loss because the net electrical output of the reactor is decreased. An additional technique for cooling the walls of nuclear reactors is disclosed in U.S. Pat. No. 4,055,465 issued on Oct. 25, 1977 to La Mercier. A principal object of the present invention is to reduce the amount of axial temperature stresses in the primary tank of a nuclear reactor. In FIG. 1, there is a vertical temperature gradient between the point of support 7 and the horizontal structure 12. This temperature gradient, which is in the axial direction, and the rate of change of this temperature gradient causes meridian bending stresses. Reduction of axial temperature stresses is a principal object of this invention because it has been observed in large breeder reactors that this is the controlling stress consideration. If adequate provisions are made to control axial temperature stresses, then both steady state and transient radial temperature gradients usually provide no difficulties. A further object of the present invention is to reduce the temperature of the primary tank at the point of support to approximately 100.degree. F. In the embodiment of FIG. 1, the point of support is the ledge 7. Such a low temperature is necessary at the point of support in order to reduce differential thermal expansions which occur at that point. Typically, in the design of a top supported primary tank the change of the temperature gradient near the point of support produces the most intense stresses in the primary tank. A further object of the present invention is to design a passive temperature insulating apparatus suitable for all power levels and for constant temperature operation. In addition, the apparatus must limit the stresses caused by thermal gradients to acceptable values for approximately 40 years. The apparatus must also resist chemical attack from sodium and must avoid the formation of particulate materials that could circulate through the reactor. An additional object of the present invention is to insure that the integrity of the primary tank of the reactor is maintained during emergency conditions and that the reactor reliably functions without requiring in-vessel maintenance for a period of approximately 40 years. The objects and advantages of the present invention are achieved by an apparatus for thermally insulating a primary tank in a nuclear reactor. The apparatus includes a plurality of vertically oriented, reflective metal plates located within the primary tank and around the outside of the reactor core for thermally insulating the side walls of the tank from the temperatures generated by the reactor. The reflective metal plates are radially spaced apart and each has an arcuate cross section.
060382775	abstract	A plant operation apparatus for satisfying a separation criteria includes an operation panel, an operation display screen control device for controlling a display on the operation panel and a touch operation and for selecting a train in a software selection function based on the operation signal from the operation panel, a selection device having momentary push buttons and for resetting other push buttons in a hardware train selection function when an operator pushes one of the push buttons to select a train, and for outputting a control signal to select the train corresponding to the button pushed by the operator. The plant operation apparatus realizes the train selection system having multiplicity, diversity, and independence for satisfying the separation criteria.
042723191	summary	BACKGROUND OF THE INVENTION Field of the Invention The present invention pertains generally to dense plasma heating and more particularly to plasma heating by way of a relativistic electron beam. Plasma heating has, for some time, been of great interest to the scientific community, since heated plasmas can be utilized for a wide variety of functions. A typical use of a hot plasma is the generation of energy in the form of a radiation, neutrons, and alpha particles. Such an energy source can be useful in basic high energy density plasma physics research, with practical application in scientific areas such as controlled thermonuclear fusion, materials studies, and radiography. DESCRIPTION OF THE BACKGROUND OF THE INVENTION Numerous techniques have been proposed in the prior art to produce dense, kilovolt plasmas. One of the more well-known techniques is the compression and heating of the core of a structured pellet by a laser or low voltage electron beam. It has also been suggested that light or heavy ion beams could be utilized to obtain similar compression and heating. Accordingly, the structured pellet and its driving source are directly coupled through classical interactions by heating the outer layer of the structured pellet. Depending upon the characteristics of both the structured pellet and driving source, the outer layer explodes or ablates, leading to compression and heating of the core. Due to the direct coupling of all of these driving sources, preheat of the core has been found to reduce the effectiveness of the compression, thereby, reducing both density and temperature of the pellet core. The use of a laser as a driving source in the above described confinement system has the added inherent disadvantages of low efficiency and associated high development cost in producing lasers with the required power output for a directly driven structured pellet. Also, diffraction limitations and window damage thresholds make it difficult to focus proposed large lasers to millimeter diameters. Low impedance electron and light ion beams also face expensive technological advancement in order to focus these beams to millimeter diameters, and to obtain power levels necessary to achieve the desired compression of the structured pellet. Such sources have the additional disadvantage of limitations in the manner of propagation of the beam to the pellet. Heavy ion sources also require significant technological advancement to produce the desired compression of the structured pellet. In fact, development of heavy ion sources using conventional accelerator concepts appears to be considerably more expensive than the cost associated with the development of lasers. Propagation of the beam to the pellet is also a limitation when employing this concept. Another manner of producing high density, kilovolt plasmas is the use of fast liners. Such devices can be driven by either magnetic forces or high explosives, both of which lead to compression and heating of an interior plasma. Although both of these fast liner techniques have produced energy in the form of radiation, neutrons, and alpha particles, just as the inertially confined laser and low impedance electron beam driven plasmas described above, each technique has its own inherent disadvantage. The primary disadvantage of the high explosive driven liner is that the high explosives have a maximum power density of approximately 10.sup.10 watts/cm.sup.3 and a maximum detonation velocity of 8.8.times.10.sup.5 cm/sec, which limits the liner implosion velocity that can be achieved. Although useful in obtaining scientific data, such a system, would, needless to say, be difficult to develop into a reuseable apparatus. As to magnetically driven liners, the liner forms part of the electrical discharge circuit in which current flowing through the liner creates a large B.sub..theta. field which causes the liner to compress. Since the liner forms part of the electrical circuit, the external circuit resistance and finite liner resistivity lead to ohmic losses which lower the efficiency of converting electrical energy into liner kinetic energy. Also, since the liner must make electrical contact with the circuit, damage to the electrode connection between the moving liner and the electrode limits operability. For liners which essentially remain thin solid shells during the implosion, ohmic heating and magnetic field diffusion limits implosion velocities to approximately 1 cm/.mu.sec. To obtain the desired radiation, neutron, and alpha particle energy at such low implosion velocities, the plasma within the liner must be preionized and complex methods of overcoming heat conduction losses must therefore be incorporated into the system. Although liner implosion velocities exceeding 1 cm/.mu.sec can be achieved, ohmic heating and magnetic field diffusion converts solid liners into plasmas during operation. As a result, the thickness of the liner is increased, which lowers the potential for power multiplication. Even with very thin foils, implosion velocities are limited by the risetime of the driving current and the diffusion of the driving magnetic field through the plasma liner. Lasers have also been used to directly heat a magnetically confined plasma. According to this concept, a laser is used to heat a large volume of plasma to a thermonuclear temperature which is confined by an elaborate magnetic field system. Although the laser provides uniform ionization and rapid heating of a low temperature plasma, the characteristic deposition length increases approximately as T.sup.3/2 for plasma electron temperatures, T>10 eV. This characteristic of the deposition of laser energy in the plasma coupled with the large volume of plasma to be heated, places a total energy requirement for the laser which substantially exceeds present technology. Even if such lasers could be developed, the inherent low efficiencies associated with lasers would result in a large capital investment in such a system. A similar system incorporates a light or heavy ion beam to deposit its energy in a magnetically confined plasma. Since such beams are nonrelativistic, they exhibit a very low coupling efficiency and lack versatility obtainable by the relativistic interaction. The concept of using an intense relativistic electron beam to heat a confined plasma has been investigated experimentally for a number of years. Prior art experiments have concentrated primarily on heating a large volume of plasma to a thermonuclear temperature with the electron beam, while maintaining the plasma with an external magnetic field. A typical configuration of a prior art experimental apparatus is shown in FIG. 1. A cathode 10 is positioned within a vacuum chamber 12 which is separated from the plasma chamber 14 by an anode foil 16. A series of dielectric spacers are separated by a series of metal plates 20 which function to prevent breakdown between the cathode 10 and the diode support structure 22. A solenoidal or mirror magnetic field configuration 24 is produced by an external source along the axial direction of the device. In operation, a relativistic electron beam 26 is formed by charging the cathode 10 with a fast risetime high voltage pulse, causing electrons to be emitted from the cathode 10 penetrating the anode foil 16 so as to enter the plasma chamber 14 as a relativistic electron beam 26. As the relativistic beam propagates through the plasma along the externally applied axial magnetic field 24, the plasma is heated by the following methods: (a) relaxation heating due to relativistic streaming instabilities (two-stream and upper-hybrid instabilities), and PA0 (b) anomalous resistive heating due to the presence of a plasma return current (ion-acoustic and ioncyclotron instabilities). Typically, devices such as klystrons, magnetrons, vacuum tubes, etc., which are based upon electron bunching have been considered very efficient devices with respect to energy utilization. Therefore, the process of heating a plasma by electron bunching, i.e., method (a) by generating the two-stream and upper-hybrid instabilities, was initially expected to be an efficient technique for producing a thermonuclear plasma. Although all early experiments observed anomalous (nonclassical) coupling of the beam energy to the plasma resulting from the presence of the streaming instabilities, the coupling efficiency was only on the order of 15% at plasma densities of .apprxeq. 10.sup.12 electrons/cm.sup.3 and dropped rapidly to less than a few percent as the plasma density approached 10.sup.14 electrons/cm.sup.3. These results were obtained with anode foils having thicknesses on the order of 25 to 50 .mu.m and conventional electron beams available during this period which typically had relatively low voltages, i.e., 1 MeV or less. This combination of relatively thick anode foils and low voltage beams, caused classical anode foil scattering which prevented the relativistic streaming instabilities from efficiently coupling the beam energy to the plasma. In other words, although unknown to the experimentalists and theoreticians during the period 1970-1975, the foil thickness and low voltages of the electron beam used in the experiments caused the electron beam to scatter in a manner which prevented substantial electron bunching in the beam. This, in turn, produced the observed rapidly decreasing energy absorption efficiencies as the plasma density approached 10.sup.14 electrons/cm.sup.3. As a result of these low observed efficiencies, scientific attention shifted toward investigation of the resistive heating mechanism which was known to have several scientifically interesting properties. One property of the resistive heating mechanism is its ability to place a substantial fraction of the beam energy into plasma ions. This differs from the streaming instabilities which primarily heat the plasma electrons. Since the ions must eventually be heated in magnetically contained plasmas, direct heating of the ions eliminates an energy conversion step. Furthermore, when energy is initially deposited into plasma electrons rather than the ions, heat conduction is enhanced due to the initially elevated electron temperature, so that achievable plasma confinement time is shortened. Consequently, increased magnetic field strengths are required to produce comparable confinement. Another property of the resistive heating mechanism is its ability to heat a large volume of plasma in a uniform manner, rather than depositing energy in a small localized region, as is characteristic of the optimized streaming instability mechanism. The ability to directly heat a large volume of plasma in a uniform manner by resistive heating thus avoids problems of heat redistribution within the plasma. Moreover, the potential for developing a plasma heating system which could also be used in conjunction with devices requiring preheated plasmas and which, additionally have high political priority such as tokamaks, renders the resistive heating mechanism even more attractive. For these reasons, experimental attention was directed from the onset of plasma heating experiments by relativistic electron beams towards producing resistive heating in plasmas. Consequently, experimental apparatus to optimize resistive heating effects, such as low voltage electron beams with high .nu./.gamma. outputs, were utilized in ongoing experiments of relativistic electron beam heated plasmas. Here, .gamma. is the beam relativistic factor which is nearly proportional to the beam particle voltage. The ratio .nu./.gamma. is basically a measure of the beam magnetic energy to beam particle kinetic energy. The increased use of high .nu./.gamma. beams is more graphically shown in FIGS. 2 and 3 which illustrate the decrease in maximum beam voltage and increase in maximum .nu./.gamma. for relativistic electron beam experiments between 1970 and 1975. Thus the prior art experiments have, from the beginning, concentrated on high .nu./.gamma., low voltage, beams for optimizing the resistive heating mechanism, virtually ignoring the effect of streaming instabilities. In so doing, prior art experiments, have clearly pointed out the limitations of resistive heating, i.e., that resistive heating does not scale to higher density plasmas, but, to the contrary, is absolutely limited by self-stabilization within the plasma. More particularly, the experiments have shown that above a certain electron temperature, depending on the density of the plasma, low frequency instabilities which are responsible for resistive heating, are stabilized. Consequently, only classical resistivity, which is inadequate to couple significant energy to the plasma from the relativistic electron beam, has any effect in resistively heating the plasma. In addition to this inherent stabilization limitation, the technique of resistive heating has several other disadvantages in producing kilovolt plasmas. First, even if the experiments had shown that resistive heating was effective at high plasma density, the required .nu./.gamma. for efficient coupling would be at least an order of magnitude higher than that achievable by present day technology. Second, since resistive heating is not effective at high plasma densities, the mechanism is only suitable for low plasma densities which require long confinement times, dictated by external magnetic field strengths achievable within strength of material limitations. Additionally, such plasmas are very large in volume and the total energy required to heat said plasma would again be at least an order of magnitude beyond the total beam energy achievable by present technology standards. As a result of these limitations, and the belief by prior art theoreticians and experimentalists that resistive heating dominated anomalous energy deposition in a plasma, the relativistic electron beam plasma heating program in the United States was virtually abolished in 1975 without any further investigation into the streaming instability heating mechanism. SUMMARY OF THE INVENTION The present invention overcomes the disadvantages and limitations of the prior art by providing a novel method and device for relativistic electron beam heating of a high density plasma. The present invention utilizes streaming instabilities to locally heat a small volume of plasma to kilovolt temperatures. This is accomplished by utilizing .nu./.gamma. .perspectiveto. 1 relativistic electron beams having high voltages in conjunction with thin foils to reduce foil scattering effects, so as to enhance the streaming instabilities. In this manner, energy from the relativistic electron beam is deposited in the plasma with very high coupling efficiency due to the anomalous effects of the streaming instabilities. OBJECTS OF THE INVENTION It is therefore an object of the present invention to provide an improved method and device for relativistic electron beam heating of a high density plasma. It is also an object of the present invention to provide an improved method and device for relativistic electron beam heating of a high density plasma which is efficient in operation. Another object of the present invention is to provide a method and device for relativistic electron beam heating of a high density plasma which is relatively inexpensive to implement and simple in operation. Another object of the present invention is to provide a method and device for relativistic electron beam heating of a high density plasma which utilizes devices which are available according to present day or near term technology. Another object of the present invention is to provide a method and device for relativistic electron beam heating of a high density plasma which is capable of producing energy in the form of radiation, neutrons and alpha particles. Another object of the present invention is to provide a method and device for relativistic electron beam heating of a high density plasma which requires relatively low capital investment. Another object of the present invention is to provide a method and device for relativistic electron beam heating of a high density plasma utilizing relativistic streaming instabilities. Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. The detailed description, indicating the preferred embodiment of the invention is given only by way of illustration since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from the detailed description. The abstract of the disclosure is for the purpose of providing a nonlegal brief statement to serve as a searching and scanning tool for scientists, engineers, and researchers and is not intended to limit the scope of the invention as disclosed herein, nor is it intended to be used in interpreting or in any way limiting the scope or fair meaning of the appended claims.
041586816	summary	BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to sintering nuclear fuel and more particularly refers to a new method and apparatus for sintering pellets of nuclear fuel oxides and mixtures of nuclear fuel oxides in a reducing furnace atmosphere. 2. Description of the Prior Art Nuclear fuel is understood here to mean uranium, plutonium and thorium, alone or in mixture. For the sake of simplification, however, only uranium dioxide will be mentioned in the following discussion. Nuclear fuel pellets are manufactured in a known manner by pressing powdered UO.sub.2+x in which oxygen is in stoichiometric excess of the dioxide and/or mixtures of UO.sub.2+x containing oxygen in stoichiometric excess and powdered PuO.sub.2 to form pressed blanks of various geometry. These pressed blanks or pellets are produced either without the addition of binder and lubricating agents in pressing tools automatically lubricated with lubricating oil of differing origin, or with the addition of binder and lubricating agents such as, for example, Zn stearate, Zn behenate, paraffins or similar materials. After pressing, the formed blanks or pellets are placed in highly heat-resistant transport containers, called transport boats. The laden boats are pushed through a resistance-heated push-through sintering furnace lined with highly refractory blocks, where the stoichiometric excess oxygen of the UO.sub.2+x is first reduced to stoichiometric UO.sub.2.00 in reducing gases such a hydrogen and/or rare gas/hydrogen or nitrogen/hydrogen mixtures; and the pressed blanks or pellets sintered at temperatures of about 1700.degree. C. to form dense, stable pellets. In the special case of manufacturing sintered UO.sub.2 /PuO.sub.2 bodies for light-water reactors and breeder reactors, a gas mixture which maximally contains only 8% hydrogen is used for the reduction of stoichiometric excess oxygen UO.sub.2+x for safety reasons (possible formation of explosive oxygen-H.sub.2 mixtures). As a result of this lower hydrogen concentration in the gas mixture, the reduction potential of the gas mixture (as expressed as partial free enthalpy of the oxygen and thus, in the system H.sub.2 /H.sub.2 O, proportional to the H.sub.2 /H.sub.2 O ratio) is greatly lowered as compared to pure hydrogen. This lower reduction potential leads to a considerable lengthening of the reduction time and, with the sintering furnace following directly, to an equivalent lengthening of the sintering time. The reaction water produced in the reaction lowers the reduction potential further, as the water concentration in the gas increases. For the gas mixture still to have a reducing effect, the H.sub.2 /H.sub.2 O partial pressure ratio should not become lower than 10:1. In order to compensate for this change of the reduction potential, which itself is again proportional to the amount of oxide reduced per unit time, dry fresh gas can be introduced into the furnace. For throughputs of, say, 12 kg UO.sub.2.2 /hour, a total of 35 m.sup.3 of gas mixture is flushed through the furnace per hour, so that the ratio H.sub.2 /H.sub.2 O does not drop below 10:1. In sintering the UO.sub.2 /PuO.sub.2 fuel pellets, an overall stoichiometric oxygen deficient oxide, caused by the reduction of the Pu(IV) to Pu(III), can be produced at the prevailing high temperatures. Depending on the intended application, whether in a light-water reactor or in a breeder reactor, either a stoichimetric or a stoichiometric deficient oxide is desired. To adjust the respective desired stoichiometry, it is necessary to adjust a respectively different reduction potential in the high-temperature portion of the furnace. This is adjusted by humidifying the fresh gas entering the furnace to previously calculated water concentrations. The requirements which are thus obtained for the process technique with respect to the reduction potential in the reduction and sintering portion of the push-through furnace are therefore contradictory. If the inexpensive nitrogen/hydrogen mixture is used for the reduction and the sintering, one finds excessive contamination of the nuclear fuel by nitrogen. This can be reduced by a heat treatment at T>1000.degree. C. in rare gases or rare gas/hydrogen mixtures. Of necessity this leads to using only the expensive rare gas/hydrogen mixture as the reduction and sintering gas, if only one gas mixture is used for both parts of the furnace. SUMMARY OF THE INVENTION An object of the present invention is to provide a method, in which during the reduction of the pressing blanks containing oxygen in stoichiometric excess, a strong reducing gas can be used, i.e., a gas as dry as possible is flushed through the furnace in large quantities. Another object of the invention is to provide a method of reducing pressing blanks or pellets with the use of a relatively inexpensive gas mixture, particularly in view of the necessarily large amount of gas. A further object of the invention is to provide a method for using a gas mixture in the high-temperature zone, which can be adjusted to a different reduction potential lower than that in the reduction zone dependent on the different applications. A still further object of the present invention is to provide a method for use of a rare gas/hydrogen mixture as the gas mixture for cooling the sintered body to T<1000.degree. C. With the foregoing and other objects in view, there is provided in accordance with the invention a method for sintering nuclear fuel oxides and mixtures of nuclear fuel oxides having oxygen in stoichiometric excess of the dioxides in a reducing furnace atmosphere, which includes passing the nuclear fuel pellets run through a heated reduction furnace with a reducing atmosphere to effect reduction of at least substantially all the excess oxygen, regulating the residence time of the nuclear fuel oxides in the reducing furnace to produce reduced nuclear fuel oxides of desired oxygen content, cooling the reduced nuclear fuel oxides, passing the cooled-down nuclear fuel oxides to an intermediate station, subsequently passing the cooled-down nuclear fuel oxides through a sintering furnace, and independently regulating the residence time of the nuclear fuels oxides passing through the sintering furnace to effect sintering of the nuclear fuel pellets. The nuclear fuel pellets are treated in the two separated furnaces at different temperatures and the gas atmospheres in the two furnaces are independent of each other and have different compositions. In another embodiment the nuclear fuel pellets are treated in the two separated furnaces at different temperatures and the gas atmospheres in the two furnaces are independent of each other and the amounts of gas fed to each furnace are different. The gas atmosphere in the reduction furnace has a humidity concentration different from the humidity concentration in the gas atmosphere in the sintering furnace. In a further embodiment a gas mixture of N.sub.2 and 4 to 8% H.sub.2 is introduced into the reduction furnace to supply the gas atmosphere therein, and further a gas mixture of rare gas and 4 to 8% H.sub.2 is introduced into the sintering furnace to supply the gas atmosphere therein. In one method reducing gas is introduced in the reduction furnace to provide a reducing atmosphere and is discharged from the reduction furnace, and further the discharged gas is cooled to condense condensible constituents entrained by the gas in the reduction furnace, and the condensed constituents separated from the gas. In accordance with the invention there is provided apparatus for sintering nuclear fuel pellets of nuclear fuel oxides and mixtures of nuclear fuel oxides having oxygen in stoichiometric excess of the dioxide includes an externally heated elongated reduction furnace, inlet means to the reduction furnace for the entrance of nuclear fuel pellets to be reduced, outlet means from the reduction furnace for the discharge of reduced pellets from the furnace, a gas inlet to the reduction furnace for the introduction of a reducing gas in the furnace to provide a reducing atmosphere around the pellets in the reduction furnace, a gas outlet from the reduction furnace for the discharge of gas therein, cooling means for cooling the reduced pellets, an intermediate station, a transport canal through which the cooled reduced pellets are transported to the intermediate station, a second transport canal for the transport of pellets in the intermediate station to the entrance of a sintering furnace, outlet means from the sintering furnace for the discharge of sintered pellets from the sintering furnace, a gas inlet to the sintering furnace, independent of the gas entering the reduction furnace, for the introduction of gas around the pellets in the sintering furnace, a gas outlet from the sintering furnace, independent of the gas discharge from the reduction furnace, for the discharge of gas therein, and cooling means for cooling the sintered pellets.
062367021	description	DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 2, a fuel assembly spacer grid according to an embodiment of the present invention is illustrated. As shown in FIG. 2, the spacer grid, which is denoted by the reference numeral 1, includes a plurality of longitudinally-extending, parallel, spaced vertical straps 2 and a plurality of laterally-extending, parallel, spaced vertical straps 3 perpendicularly interconnecting the longitudinally-extending straps 2, in order to support fuel elements of a nuclear fuel assembly. The spacer grid 1 also includes a plurality of swirl deflectors 20 respectively provided at the upper ends of the interconnections between the straps 2 and 3, a plurality of springs 30 provided at the straps 2 and 3, and a plurality of dimples 40 provided at the straps 2 and 3. As shown in FIG. 3 viewing the spacer grid 1 from above, the springs 30 and dimples 40 have conformal contact portions having the same radius of curvature as fuel elements 11 to be supported by the spacer grid 1. The swirl deflectors 20 have an air vane structure including vanes 23. As shown in FIGS. 2 and 3, the swirl deflectors 20 are configured to have the same vane rotation direction. If desired in terms of an improvement in cooling performance, however, the swirl deflectors 20 may be configured to have reverse vane rotation directions at adjacent cooling water passages, respectively, as shown in FIG. 4. A detailed structure of the swirl deflectors 20 is shown in FIG. 5. As shown in FIG. 5, each swirl deflector 20 has a pair of intersecting triangular base plates 21 extending upwardly from the interconnecting straps 2 and 3 at the interconnection thereof, respectively, and four vanes 23 extending upwardly from respective side surfaces of the base plates 21. In order to generate a swirling flow, the vanes 23 of each swirl deflector 20 are bent in the same direction from the associated base plates 21, respectively. The bent angle of each vane 23 should not excess 90.degree.. Each swirl deflector 20 may be fixed to the straps 2 and 3 by means of welding. In order to obtain a desired strength of the spacer grid 1, the vanes 23 may have a controlled size. Although each swirl deflector 20 has four vanes 23 in the illustrated case, it may have only two vanes attached to a selected one of the straps 2 and 3. Where it is desired to increase the vane area, each vane 23 may be enlarged in such a manner that it has a larger width at the upper portion thereof than that at the lower portion thereof. FIG. 6 shows the shape of the vanes 23 given before the vanes 23 are bent. As shown in FIG. 6, each base plate 21 protrudes upwardly from the upper end of the associated strap 2 or 3. Vanes 23 are disposed on opposite sides of the base plate 21, respectively. FIGS. 7 and 8 illustrate a detailed structure of the springs 30. Each spring 30 protrudes from the associated strap 2 or 3. That is, the spring 30 is attached at one end thereof to the associated strap 2 or 3 and has an elastic free end at the other end thereof. The spring 30 also has a contact portion 31 contacting a fuel element 11. The contact portion 31 is configured to come into surface contact with the circumferential surface of the fuel element 11. In order to adjust the spring force, the spring 30 also has an opening 34. Although the opening 34 has a rectangular shape in the illustrated case, it may have a variety of shapes for desired spring characteristics. The free end of the spring 30 is inclinedly bent, thereby forming a bent end portion 33 having a shape inclined with respect to the axis of the fuel element 11 in such a manner that it has a width increasing gradually as it extends upwardly. The bent end portion 33 of the spring 30 is subjected to a hydraulic drag force when the spring 30 is positioned in a flow of cooling water. Thus, the spring 30 serves as a hydraulic pressure spring. The hydraulic pressure spring 30 varies its spring force in accordance with a variation in the flow rate of cooling water. As the flow rate of cooling water increases, the hydraulic pressure spring 30 increases in spring force, so that it supports the fuel element more firmly. FIG. 9 illustrates a detailed structure of the dimples 40 which serve to support fuel elements 11 at positions opposite to the springs 30. Each dimple 40 protrudes from the associated strap 2 or 3. The dimple 40 has a contact portion 41 contacting a fuel element 11. The contact portion 41 has the same radius of curvature as the fuel element 11 so that the dimple 40 has an increased contact area. By virtue of such an increased contact area, it is possible to reduce abrasion of the fuel element. The dimple 40 also has an opening 42 so as to have an increased height and a reduced strength. FIG. 10 is a partially-broken perspective view showing the interior of the spacer grid 1 shown in FIG. 2 whereas FIG. 11 is a sectional view of FIG. 10. These drawings show the contact relationship between the springs 30 and the fuel element 11 supported by the springs 30, and a method for supporting the fuel element 11. As shown in FIGS. 10 and 11, one spring 30, which is formed on each strap, is positioned at the middle portion (when viewed in a vertical direction) of the strap. Two dimples 40 are positioned above and beneath the spring 30. Accordingly, each fuel element is supported at six points by the surrounding fuel straps. FIG. 12 is a perspective view illustrating one of the longitudinally-extending straps 2 included in the spacer grid 1 of FIG. 2. The longitudinally-extending strap 2 is provided at the upper end thereof with a plurality of uniformly-spaced coupling grooves 2a so that it is interconnected with the laterally-extending straps 3 in a cross fashion. FIG. 13 is a perspective view illustrating one of the laterally-extending straps 3 included in the spacer grid 1 of FIG. 2. The laterally-extending strap 3 is provided at the upper end thereof with a plurality of uniformly-spaced coupling grooves 3a so that it is interconnected with the longitudinally-extending straps 2 in a cross fashion. FIG. 14 is a plan view illustrating the longitudinally-extending strap 2 shown in FIG. 12. As shown in FIG. 14, the vanes 23 of neighboring swirl deflectors are bent in the same direction. The spring 30 and dimples 40, which are provided at each strap, are arranged on the swirl deflector along the same vertical axis. The spring 30 and dimples 40 protrude from the strap in opposite directions in order to support fuel elements disposed at opposite sides of the strap, respectively. FIG. 15 is a cross-sectional view taken along the line A--A of FIG. 14. As shown in FIG. 15, the vanes 23 of each swirl deflector are bent from the base plate 21 of the swirl deflector by a desired angle in order to increase an effect of mixing flows of cooling water while minimizing an interference thereof with the associated fuel element 11. FIG. 15 also shows that each hydraulic pressure spring 30 is bent at its free end by a desired angle with respect to the vertical axis of the associated strap, so that it generates a horizontal pressure when it comes into contact with a flow of cooling water, thereby increasing the spring force supporting the associated fuel element 11. As apparent from the above description, the swirl deflector 20 provided at the spacer grid 1 according to the present invention can produce a strong swirling flow of cooling water, as compared to conventional devices. This is because the swirl deflector 20 includes four vanes 23 formed into an air vane shape at each interconnection between the straps 2 and 3. Where the vanes 23 of the swirl deflector 20 have a streamline shape, it is possible to produce a more efficient swirling flow of cooling water while achieving a reduction in pressure loss. For the production of a strong swirling flow of cooling water, four vanes having the above mentioned structure are provided at both the longitudinally and laterally-extending straps 2 and 3 at each interconnection, respectively. On the other hand, two vanes are provided at a selected one of the straps 2 and 3 at each interconnection for a reduction in the pressure loss caused by the provision of the swirl deflector 20. Since the vanes 23 of each swirl deflector 20 are formed in such a fashion that they are bent from the opposite side surfaces of the associated base plate 21, they swirl a flow of cooling water flowing upwardly from beneath, thereby efficiently guiding the cooling water flow. Accordingly, a reduced pressure loss occurs, as compared to conventional devices. Since each spring 30 is attached at one end thereof to the associated strap 2 or 3 while being provided at the other end thereof with an inclinedly-bent elastic free end, it is subjected to hydraulic pressure when it is positioned in a flow of cooling water. Accordingly, the spring 30 generates not only a mechanical spring force, but also an additional spring force resulting from the hydraulic pressure applied thereto. Thus, it is possible to compensate for a reduction in the initial spring force of the spring. In conventional devices, a flow of cooling water, which is introduced in the spacer grid through a central portion of the spacer grid, strikes a swirling flow of cooling water passing through the spacer grid, thereby offsetting the swirling effect of the swirling flow. In accordance with the present invention, however, the swirl deflector 20 has four integral vanes arranged on quadrant regions defined by the longitudinally and laterally-extending straps. Accordingly, a flow of cooling water, which is introduced in the spacer grid through a central portion of the spacer grid, is forced to be swirled when it passes through the swirl deflector 20 disposed at the downstream of the spacer grid. Thus, the swirling motion of the cooling water flow can be maintained far the downstream of the spacer grid. In accordance with the present invention, the swirling vanes 23 of each swirl deflector 20 are attached to opposite side surfaces of the triangular base plate 21 in such a manner that they extend inclinedly. Accordingly, it is possible to provide a larger vane area at the same projected area, as compared to the vanes of conventional devices. By virtue of such an increased vane area, there is an advantage in terms of the generation of a swirling flow of cooling water. By virtue of the generation of a strong swirling flow of cooling water and a delayed disappearance of the swirling flow, a centrifugal force generated in the cooling water flow causes bubbles of a lower density produced from the cooling water flow on the surfaces of fuel elements 11 to be concentrated on the swirling center of the cooling water flow while causing the liquid portion of the cooling water flow, which has a higher density, to move toward the surfaces of the fuel elements 11. Accordingly, an improvement in the cooling performance of the spacer grid 1 is achieved. In accordance with such an improvement in cooling performance, the spacer grid 1 ultimately suppresses a boiling phenomenon occurring in fuel elements, thereby preventing a leakage of radioactive materials from the fuel elements. This contributes to the safety of the nuclear reactor. Since the vanes 23 of each swirl deflector are attached to the triangular base plate 21 in accordance with the present invention, they have an elongated and inclined base. Accordingly, these vanes 23 are more stable structurally and mechanically, as compared to conventional vanes attached to a base plate having a shape other than the triangular shape. Therefore, it is possible to prevent the vanes from being easily deformed or broken due to an external impact applied thereto during a placement of a fuel assembly in the reactor core or during a transportation of the spacer grid. As apparent from the above description, the present invention provides a fuel assembly spacer grid including springs each configured to generate not only a main spring force caused by a displacement of the spring occurring when the spring comes into contact with a fuel element placed in a reactor core, but also an additional spring force caused by hydraulic pressure applied to the spring. Each spring, which is in a fixed state at one end thereof, has a free bent portion at the other end. When a flow of cooling water flowing upwardly from beneath strikes the bent portion of the spring, it reflects inclinedly from the bent portion of the spring while applying hydraulic pressure to the spring. As a result, the spring applies the pressure to the fuel element supported thereby. That is, the hydraulic pressure of the cooling water flow applied to the spring serves as an additional spring force. Thus, it is possible to compensate for a reduction in the initial spring force of the spring resulting from a change in the property of the spring material. The hydraulic pressure on the spring in the cooling water flow varies in accordance with a variation in the flow rate of the cooling water flow in such a fashion that it increases at a higher flow rate while decreasing at a lower flow rate. Accordingly, there is an advantage in that the spring force adapted to support fuel elements can be adjusted by controlling the flow rate of the cooling water flow. The spring force resulting from the cooling water flow is always generated at a substantially constant level unless the shape of the spring is changed. In an environment where the initial spring force of the spring is gradually reduced due to a repeated irradiation of neutrons, as in the interior of a nuclear reactor, it is possible to sufficiently compensate for the reduced portion of the spring force. Accordingly, the utility of the spring according to the present invention increases, in particular, in the case in which a fuel assembly is placed in a reactor core for an extended period of time. In accordance with the present invention, the spring has a conformal contact portion contacting the circumferential surface of a fuel element, supported thereby, in a larger area. By virtue of such an increased contact area, the spring exhibits a high resistance to a fretting abrasion of the fuel element caused by vibrations and resulting in a damage of the fuel element. In order to solve problems resulting from an excessive increase in the spring force caused by the increased contact area, the spring also has an opening at the conformal contact portion. Accordingly, it is possible to maintain a desired height of the contact between the spring and fuel element without reducing the height of the spring itself. Therefore, the insertion and withdrawal of fuel elements can be achieved without requiring an excessive force. This reduces the possibility of a damage of fuel elements. That is, there is no possibility of a corrosion of fuel elements occurring at damaged areas. Accordingly, it is possible to prevent the life of fuel elements from being reduced. Although the preferred embodiments of the invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.
046541829	description	DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, apparatus for containing plasma in a high energy plasma device 20 includes a vacuum tight liner wall generally indicated by reference numeral 22 in FIG. 1. The liner wall 22, which is preferably made of stainless steel, is part of a primary confinement vessel. The liner wall may be disposed within and supported by a shell (not shown) formed of a relatively thick copper wall forming a secondary chamber. Such an arrangement is shown in commonly-assigned U.S. Pat. No. 4,302,284, the teachings of which are incorporated herein by reference. While the wall 22 is exemplarily shown as a torus, it will be appreciated that it can be formed in any desired shape. The device includes a frame 24 for supporting the liner and a magnet system 26 which could be made up of toroidal, poloidal, helical and other coils or windings which may be either of superconductive or normal material. The purposes of the magnet system are to produce and confine the plasma inside the liner wall. The liner wall is preferably made up of a number of sections 28 with each section 28 having a closed peripheral wall defining an interior 30 with open ends. Adjacent interiors of adjacent sections form a plasma path 32. The sections 28 preferably have a relatively thin wall and have sufficient loop resistance that the penetration times for the magnetic field provided by the magnet system, are acceptably short. Certain of the sections are provided with ports 34 and associated piping for passage of the constituents of the plasma and for applying a vacuum. As shown in FIG. 2, each section 28 includes an inside surface 36 and an outside surface 38 with its interior being generally circular in cross section. Theoretically, a properly designed magnet system would provide sufficiently homogeneous magnetic fields that the plasma is contained in the liner wall out of contact with the liner wall inner surface. However, available magnet systems do not provide such ideal fields and the plasma contacts the liner wall inner surface. When the plasma contacts the inner surface of a section 28, energetic particles from the plasma impinge on the wall resulting in localized heating and causing melting and loss of vacuum integrity. Additionally metal ions from the sections enter and contaminate the plasma. The introduction of the metal ions into the plasma causes increased radiation resulting in power loss in the plasma. In order to protect the liner wall from damage due to contact by the plasma, the apparatus of the present invention includes a plurality of armature rings 40 disposed at spaced locations inside the liner wall. Each ring 40 includes means for entering into rolling engagement with the inside surface 36 of one of the segments 28 and each ring includes current-carrying armature conductors extending at an angle to lines of force extending inside the section and provided by the helical coil portion of the magnetic system 26. More specifically, as shown in FIG. 2, the magnetic system includes a plurality of spaced conductors 42 helically wound about the outer surface of the liner wall 22. For purposes of illustration, four conductors 42 are shown which carry direct current with adjacent conductors carrying current in opposite directions. As suggested in FIG. 3, the conductors 42 provide magnetic lines of flux which extend inside each section, generally normal to the plasma path. Referring to FIG. 4, the armature ring 40 is made of electrically conductive material and includes a first annular end 44, a second annular end 46 and a plurality of spaced bars 48, extending in the direction of the plasma path and constituting the armature conductors, interconnecting the annular ends 44 and 46. Positioned between adjacent bars 48 are rollers 50 having oppositely extending lugs 52 received in cavities 54 formed by channel-shaped sections of the annular ends between the bars 48. A spring 55 is positioned inwardly of its corresponding lug to bias the rollers outwardly into engagement with the inside surface 36 of the section 28 in which the armature ring is positioned. Accordingly, the armature uses the section inside surface as a race on which to rotate. The rollers are preferably formed of an electrically insulative material such as a ceramic. In the event the inner surface 36 is not circular in cross section, a track which did provide a circular race for the armature, could be attached to the liner wall for supporting the armature ring. The apparatus of the present invention also includes means for supplying direct current to the bars 48 of the armature ring. As shown in FIG. 4, a first brush 56 is mounted on a first conductive standard 58 extending through a hole 60 in the liner wall inside an insulative bushing 62. The bushing 62 and standard 56 completely fill the hole 60 to prevent vacuum leaks. The brush 56 slidably engages the first annular end 44 of the armature ring 40. Similarly, a second brush 64 is mounted on a second conductive standard 66 extending through another hole 60 in the liner wall inside an insulative bushing 62. The second brush 64 slidably engages the second annular end 46 of the armature ring at a position generally aligned with the location of engagement of the first brush 56. The conductive standards 58 and 66 are connected to a source of direct current 68 as shown in FIG. 3. Due to the electrical resistance of the armature annular ends 44 and 46, more current flows through the bar 48A closest the areas of contact of the brushes with the corresponding annular ends, than through any other bar 48. The brushes 56 and 64 are angularly displaced relative to the helical conductor 42A so that flux lines resulting from current in conductor 42A intersect the bar 48A closest the brushes generally radially with respect to the center of the section 28. The interaction of the magnetic flux and the current through the bar 48A results in a force, the Lorenz force, which is in a direction perpendicular to both the current in bar 48A and the flux lines. Thus, as in a direct current motor, the armature ring rotates. Preferably another set of brushes is located diametrically across the section 28 to provide current to another bar located 180 degrees from bar 48A. The force resulting from the interaction of this current and magnetic flux provided by conductor 42C aids the first force and results in a more balanced application of forces to the armature ring. The presence of the brushes bearing on the sides of the armature ring limit it to poloidal rotation and prevent movement of the ring in the direction of the plasma path. While the magnet system 26 generates fields other than those shown in FIG. 3, the rings 40 are restrained from other than rotational movement in a plane extending transversely to the plasma path. The armature ring carries a protective coating in the form of a plurality of armor tiles 70 facing the plasma path. These tiles preferably abut one another and form a ring fully covering the armature ring with respect to the plasma path and extend laterally over the brushes and standards to form a first wall for contact by the plasma. These tiles are formed of a material having a higher melting temperature than the material from which the liner wall 22 is formed. The tiles are preferably formed of silicon carbide coated carbon, ceramic material or a nickel-chromium-iron alloy, with coated high density carbon being most preferable. The tiles 70, can be affixed to the ring by, for example, pins 71 having heads received in countersunk apertures in the tiles, with the shanks of the pins received in an interference fit in apertures 73 in the armature ring 40. In the case of the liner wall 22 in the shape of a torus, the number of rings 40 employed is preferably sufficient so that, on the inner side of the torus, the tiles of adjacent rings almost touch. Arcuate surface segments 72 of the torus are not covered by the tiles, as shown on FIG. 2. Although the tiles do not overlie the surface segments 72, under many operating conditions they substantially protect the segments from impingement by high energy charged particles, which leave the plasma and give up their energy to the first surface they strike. This is because these particles predominantly follow the direction of the composite magnetic field. Typically the radial component of the composite magnetic field is much smaller than the toroidal component. Thus the paths taken by most of the escaping charged particles intersect the liner wall at shallow angles. These angles are so shallow that most charged particles strike the tiles which are disposed above the level of the segments 72 and not the segments. Put another way, although the segments are visible in plan, they are in the shadow of the tiles in view of the direction of the plasma particles. Each armature ring 40 is sized to lie closely adjacent but spaced from the inside surface 36 of the respective section 28 when the section and the ring are at ambient temperature to enable the ring to rotate inside the section on the rollers 50. The armature ring, however, is made of a material having a coefficient of thermal expansion somewhat greater than that of the material forming the section 28. Accordingly, as heat from the plasma is transferred from the tiles 70 to the armature ring 40, the armature ring expands into full surface engagement with the liner wall causing the ring to stop rotating, and heat from the armature ring to transfer to the liner wall. With a pulsed plasma, this full surface engagement occurs shortly after the plasma is turned off, due to thermal inertia. This is analogous to the brake shoe expanding against the wheel drum in an automobile brake. The outside surface of the liner wall is actively cooled, for example, by running coolant pipes (not shown), around the liner wall. With the rings firmly against the liner wall, heat is efficiently transferred from the tiles to the coolant through the ring and the liner wall. As the armature ring cools, it shrinks and the springs 55 bias the rollers outwardly to center the ring inside its corresponding section 28. While the first and second annular ends 44, 46 of the ring have been described as being made entirely of conductive material, the portions of the ends disposed between the bars could be formed of an electrically insulating material 76 as shown in FIG. 4. The use of insulating components between bars 48 has the advantage of limiting current to the particular bar aligned with the brushes 56 and 64. However, heat transfer from the tiles may be reduced and the insulating material should have a thermal coefficient of expansion close to that of the conductive material of the annular ends 44 and 46. Operation of the apparatus of the present invention is as follows: Energization of the helical conductors 42 results in formation of a magnetic field extending inside the liner wall 22. When direct current is supplied to the bars 48 of the armature ring 40, the interaction of the current in the bars and the magnetic field results in a force which turns the ring 40 in the poloidal direction. The armored tiles carried by the armature ring act as plasma limiters (a first wall) and are heated. Heat transfer from the tiles to the armature ring causes expansion thereof resulting in a armature ring stopping rotation in full surface contact with the liner wall. This allows heat to be transferred from the tiles to a cooling means, disposed outside the liner wall, through the armature ring and the liner wall. It will be appreciated that the rings may be rotated over a broad range of frequencies and rotation of the rings tends to spread the plasma heat load over the entire surface of the liner wall to prevent damage to the liner wall resulting from a localized heat concentration. The plasma may be of pulsed operation with the plasma being turned off prior to expansion of the ring against the liner wall. In this case, the heat flow through the tiles, even with the plasma turned off, may be sufficient to result in expansion of the armature ring against the liner wall. After the heat has been transferred out through the coolant, the spring loaded rollers center the armature ring after it has contracted and place the ring in position for another plasma discharge. As a method, the present invention includes several steps: a. An armature ring 40 is rotatably mounted inside one of the sections 28 making up the liner wall 22. The ring 40 carries rollers 50 for engaging the inside surface of the section 28 and further includes armature conductors 48 extending at an angle to lines of force provided by a magnet system in the high energy plasma device 20. b. Armor tiles 70 are affixed to the ring 40 facing the plasma path 32 from the liner wall 22 for acting as plasma limiters. c. Direct current is caused to flow through the armature conductors 48 so that the interaction of the magnetic field and the current in the armature conductors results in rotation of the armature ring 40 to prevent damage to the section due to localized heat concentration. In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained. As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.
060268980	abstract	A tubing head is provided for accommodating a rotator. The rotator includes a drive gear and a swivel tubing hanger which engages an internal surface of the tubing head and comprises a driven gear for engaging the drive gear. The tubing head defines a gear housing for the drive gear so that the drive gear may releasably engage the driven gear. The internal surface, gear housing and drive and driven gears are configured such that when the drive gear is in the gear housing, the tubing hanger engages the internal surface and the drive and driven gears are engaged, the tubing hanger may be removed from the tubing head by pulling it through the upper end without first disengaging the drive and driven gears. An apparatus is also provided comprising the tubing head, the swivel tubing hanger and the drive gear.
053533208	summary	The present invention relates generally to nuclear reactors, and, more specifically, to a nozzle joining a reactor pressure vessel to a water pool. BACKGROUND OF THE INVENTION In one type of nuclear reactor being developed, i.e., simplified boiling water reactor (SBWR), various pools of water are provided in the containment building surrounding a reactor pressure vessel which provide various functions, including providing makeup water to the pressure vessel in the event of a postulated loss of coolant accident (LOCA). The pressure vessel contains a nuclear reactor core which is effective for boiling water therein to generate steam under pressure which is conventionally discharged from the pressure vessel to provide a source of power to a steam turbine-generator, for example, for producing electrical power. In the event of a break in one of the several pipes joined to the pressure vessel, water and steam will leak from the pressure vessel, which will drop the level of water therein available for cooling the reactor core unless suitable provisions are made to provide makeup water into the pressure vessel. For example, a conventional boiling water reactor power plant includes a wetwell or suppression pool of water in the containment building surrounding the pressure vessel. The suppression pool provides various functions during the operation of the power plant, including, for example, being joined in flow communication to the pressure vessel by a suitable conduit extending from the suppression pool to a corresponding inlet nozzle joined to the pressure vessel. In the event of a LOCA condition, a suitable valve is opened for allowing water to flow by gravity from the suppression pool into the pressure vessel to provide makeup water therein. In order to provide additional makeup water during a LOCA condition, the SBWR design further includes a gravity driven cooling system (GDCS) which has a corresponding GDCS pool of water elevated above the suppression pool which is similarly joined to a corresponding inlet nozzle on the pressure vessel for selectively providing makeup water thereto upon opening of a suitable valve in the supply pipe therebetween. In both the GDCS pool and the suppression pool, it is desirable to have makeup water provided to the pressure vessel solely by gravity flow to avoid reliance on power operated pumps which could be rendered inoperative in the event of a power failure. However, since water supply lines must necessarily be provided between the pressure vessel and both the GDCS pool and the suppression pool, a break in one of these lines would also cause a loss of coolant accident as well as possibly disable their use for providing makeup water to the pressure vessel. Accordingly, it is desired to join inlet nozzles on the pressure vessel to the suppression pool and the GDCS pool with supply lines having minimum resistance to the gravity flow of makeup water from these pools in a forward flow direction into the pressure vessel in the event of a LOCA condition, but, a competing consideration requires relatively high flow resistance in the event of a break of one of these supply lines for restricting back flow of water from the reactor through these inlet nozzles. SUMMARY OF THE INVENTION A nozzle for joining a pool of water to a nuclear reactor pressure vessel includes a tubular body having a proximal end joinable to the pressure vessel and a distal end joinable in flow communication with the pool. The body includes a flow passage therethrough having in serial flow communication a first port at the distal end, a throat spaced axially from the first port, a conical channel extending axially from the throat, and a second port at the proximal end which is joinable in flow communication with the pressure vessel. The inner diameter of the flow passage decreases from the first port to the throat and then increases along the conical channel to the second port. In this way, the conical channel acts as a diverging channel or diffuser in the forward flow direction from the first port to the second port for recovering pressure due to the flow restriction provided by the throat. In the backflow direction from the second port to the first port, the conical channel is a converging channel which with the abrupt increase in flow area from the throat to the first port, will, increase resistance to flow therethrough.
	claims	1. A method for investigating a transport flow in a specimen, comprising:scanning image production laser beam illumination line by line over the specimen within definable specimen regions;scanning manipulation laser beam illumination line-by-line over the specimen;illumination with the image production laser beam illumination preceding illumination with the manipulation laser beam illumination in such a way that pixels of the definable specimen regions are illuminated with the image production laser beam illumination before such pixels are illuminated by the manipulation laser beam illumination;producing an image of the specimen following illumination with the manipulation laser beam illumination; andcalculating the transport flow from multiple images of the specimen each image of the multiple images being rotated with respect to one another by a definable angle. 2. The method according to claim 1, wherein calculating the transport flows comprises rotating each image of the multiple images by an image rotator or by activation of a scanning apparatus. 3. The method according to claim 1, wherein calculating the transport flows comprises acquiring multiple images for rotations of 0°, 90°, 180°, and 270°, respectively. 4. The method according to claim 1, wherein calculating the transport flows comprises acquiring multiple images for rotations of 0°, 120°, and 240°, respectively. 5. The method according to claim 1, wherein calculating the transport flow within the specimen comprises calculating linear combinations of the intensity values of the multiple images. 6. The method according to claim 1, wherein calculating the transport flow within the specimen comprises applying correction methods. 7. A method for investigating a transport flow in a specimen, comprising:scanning image production laser beam illumination line by line over the specimen within definable specimen regions;scanning manipulation laser beam illumination line-by-line over the specimen;illumination with the image production laser beam illumination preceding illumination with the manipulation laser beam illumination in such a way that pixels of the definable specimen regions are illuminated with the image production laser beam illumination before such pixels are illuminated by the manipulation laser beam illumination; andproducing an image of the specimen following illumination with the manipulation laser beam illumination;wherein boundary lines or boundary surfaces are plotted in the image of the specimen; andwherein the transport flow through the boundary lines or the boundary surfaces is indicated quantitatively. 8. The method according to claim 1, wherein each line of the specimen is scanned twice, first by the image production laser beam illumination and then by the manipulation laser beam illumination. 9. The method according to claim 1, wherein each line of the specimen is scanned only once, the lines respectively being illuminated alternately for image production and for manipulation of the specimen. 10. The method according to claim 1, wherein illumination with the image production laser beam illumination precedes illumination with the manipulation laser beam illumination of the specimen by a fixed correlation in time. 11. The method according to claim 1, wherein a separate laser light beam is used to generate an image production laser light beam and a manipulation laser light beam. 12. The method according to claim 11, wherein the image production and the manipulation laser light beams exhibit a fixed angle difference with respect to one another. 13. The method according to claim 1, wherein the method is carried out by means of a confocal microscope. 14. The method according to claim 1, wherein a speed of the-scanning steps is adapted to a speed of the transport flow. 15. The method according to claim 1, wherein scanning the manipulation laser beam illumination over the specimen is confined to the definable specimen regions. 16. The method according to claim 1, wherein scanning the manipulation laser beam illumination along a line comprises illuminating the specimen continuously. 17. The method according to claim 1, wherein scanning the manipulation laser beam illumination along a line comprises illuminating the specimen is interrupted to occur in a checkerboard-like pattern. 18. The method according to claim 1, wherein the manipulation laser beam illumination is spectrally selective. 19. The method according to claim 1, further comprising detecting the light proceeding from the specimen as spectrally sensitive detection. 20. The method according to claim 1, wherein producing the image of the specimen comprises visualizing measured data via color codings, vector diagrams, or contour line graphs. 21. The method according to claim 1, wherein boundary lines or boundary surfaces are plotted in the image of the specimen.
	abstract	A solidification method of radioactive waste is provided, including kneading a binder and an inorganic adsorbent to obtain a kneaded object, the in organic adsorbent included radionuclides; extruding the kneaded object to obtain an extruded material object; cutting the extruded material object to obtain at least one extruded material block; and firing the at least one extruded material block to solidify the at least one extruded material block.
	summary
	claims	1. A sealed cable inlet through external and internal containment walls of a nuclear power plant, comprising:a connection pipe installed through the internal wall;a cable input disposed within a cavity of the connection pipe and rigidly fixed to a portion of the connection pipe;a pipe installed through the external wall and coaxially aligned with the connection pipe;a first bellows located on a first end portion of the pipe, wherein the first bellows is proximate to an internal surface of the external wall;a cable output disposed within the pipe, wherein a first portion of the cable outlet is at least partially received within the first bellows;wherein an area defining a gap is formed between an internal surface of the pipe and an external surface of the cable output;a second bellows located on a second end portion of the pipe, wherein the first and second end portions are spaced and opposed from one another, wherein the second bellows is proximate to an external surface of the external wall, wherein a second portion of the cable outlet is at least partially received within the second bellows;wherein the first and second bellows each includes a free end, wherein the free ends of the first and second bellows are tapered to form narrowed portions thereof;wherein the cable output is supported by internal surfaces of the narrowed portions of the tapered free ends of the first and second bellows; andwherein the first and second bellows each include corrugated portions formed thereon, wherein a twisted conical compression spring is installed in an area defining an internal cavity of at least one of the corrugated portions of the first and second bellows. 2. The invention according to claim 1, further comprising:two protective pipes disposed within a space between the external and internal walls, wherein the two protective pipes are coaxially aligned with one another, wherein the two protective pipes each includes a free end;wherein the cable input is at least partially disposed within at least one of the two protective pipes;wherein one of the two protective pipes is cantilever fitted on an internal surface of the internal wall and the other one of the two protective pipes is cantilever fitted concentrically with the second bellows on the internal surface of the external wall;a cylinder-shaped bellows located between the two protective pipes; andwherein the cylinder-shaped bellows interconnects free ends of the two protective pipes. 3. The invention according to claim 1, wherein the gap includes a width that is operable to accommodate a change of cable coaxial position in the pipe due to seismic events or thermal expansion. 4. The invention according to claim 1, wherein the tapered ends of the first and second bellows are located inside the pipe and oriented towards each other. 5. The invention according to claim 1, wherein the cable input is suspended on springs that are disposed within the pipe.
043751040	claims	1. In a nuclear facility including interconnectable pools having a substantially vertically disposed gateway, means for providing a barrier to liquid flow between said pools comprising: a substantially vertically disposed frame removably positionable in said gateway and having a liquid impermeable sheet sealed thereon; an inflatable sealing tube mounted in a channel providing in the sides of said frame corresponding to said gateway, said tube engaging said gateway when inflated to effect a seal between said gateway and said frame; said channel of said frame being deeper than the thickness of said sealing tube when uninflated; a support ledge extending across at least the bottom of said gateway and having a sealing surface extending perpendicular to the plane of said frame when said frame is positioned in said gateway; at least one hook plate mounted for pivotal movement about an edge provided on said frame and cooperating with a spring for normally biasing said hook plate into an engagable position with said support ledge; and means remotely actuatable from the side of said hook plate and cooperating with said hook plate to effect the release thereof from said engagable position with respect to said support ledge. 2. Means for providing a barrier as in claim 1 including a plurality of hook plates each individually biased into engagable position with a portion of said support ledge and individually cooperating with a respective remotely actuatable release means. 3. In a nuclear facility including interconnectable pools having a removable liquid permeable shield wall disposed therebetween and having a substantially vertically disposed gateway adjacent a side of the shield wall, means for providing a barrier to liquid flow between said pools comprising: a substantially vertically disposed frame removably positionable in said gateway and having a liquid impermeable pliant sheet sealed thereon facing and conformable to said shield wall; an inflatable sealing tube mounted in a channel provided in the sides of said frame corresponding to said gateway, said tube engaging said gateway when inflated to effect a seal between said gateway and said frame; said channel of said frame being deeper than the thickness of said sealing tube when uninflated; a support ledge extending across at least the bottom of said gateway and having a sealing surface extending perpendicular to the plane of said frame when said frame is positioned in said gateway; at least one hook plate mounted for pivotal movement about an edge provided on said frame and cooperating with a spring biasing said hook plate into an engagable position with said support ledge; and means remotely actuatable from the side of said frame opposite said hook plate and cooperating with said hook plate to effect the release thereof from said engagable position with respect to said support ledge.
	claims	1. A radiation therapy apparatus comprising:a housing;a radiation source carried by said housing and including a radiation output having a first diameter;at least one aperture assembly carried by said housing and comprisinga radiation aperture body having an outside diameter less than the first diameter and an exposed upper surface with a shaped opening therein to control a radiation dosing profile,an aperture holder, an aperture-receiving passageway therein receiving said radiation aperture body, and having a recessed end, anda cover received within the recessed end of said aperture holder and retaining said radiation aperture body within said aperture holder, said cover having an opening aligned with the exposed upper surface of said radiation aperture body so as to define an interface therebetween that is exposed to the radiation output; anda radiation filter carried by said housing. 2. The radiation therapy apparatus according to claim 1 wherein said at least one aperture assembly comprises a plurality of stacked aperture assemblies. 3. The radiation therapy apparatus according to claim 1 wherein said radiation aperture body comprises a frusto-conical first portion; and wherein the aperture receiving passageway has a corresponding shape to the frusto-conical first portion. 4. The radiation therapy apparatus according to claim 1 wherein said radiation aperture body comprises a frusto-conical second portion; and wherein the opening of said cover has a corresponding shape to the frusto-conical second portion. 5. The radiation therapy apparatus according to claim 1 wherein the recessed end of said aperture holder and said cover define a threaded joint therebetween. 6. The radiation therapy apparatus according to claim 1 wherein said radiation aperture body comprises at least one alignment edge extending outwards therefrom; and wherein the aperture-receiving passageway further includes at least one recess receiving the at least one alignment edge. 7. The radiation therapy apparatus according to claim 1 wherein said radiation aperture body comprises brass. 8. The radiation therapy apparatus according to claim 1 wherein said aperture holder and said cover each comprises stainless steel. 9. The radiation therapy apparatus according to claim 1 wherein said radiation source generates protons. 10. An aperture assembly for radiation therapy comprising:a radiation aperture body having a shaped opening therein to control a radiation dosing profile, said radiation aperture body comprising a frusto-conical first portion;an aperture holder, an aperture-receiving passageway therein receiving said radiation aperture body, and having a recessed end; anda cover received within the recessed end of said aperture holder and retaining said radiation aperture body within said aperture holder, said cover having an opening aligned with the shaped opening in said radiation aperture body and having a shape corresponding to the frusto-conical first portion. 11. The aperture assembly according to claim 10 wherein said aperture holder has a disk shape. 12. The aperture assembly according to claim 10 wherein said aperture holder has a rectangular shape. 13. The aperture assembly according to claim 10 wherein said radiation aperture body comprises a frusto-conical second portion; and wherein the aperture receiving passageway has a corresponding shape to the frusto-conical second portion. 14. The aperture assembly according to claim 10 wherein the recessed end of said aperture holder and said cover define a threaded joint therebetween. 15. The aperture assembly according to claim 10 wherein said radiation aperture body comprises at least one alignment edge extending outwards therefrom; and wherein the aperture-receiving passageway further includes at least one recess receiving the at least one alignment edge. 16. The aperture assembly according to claim 10 wherein said radiation aperture body comprises brass. 17. The aperture assembly according to claim 10 wherein said aperture holder and said cover each comprises stainless steel. 18. A method for operating a radiation therapy apparatus comprising:providing a radiation source to generate a radiation output having a first diameter;positioning at least one aperture assembly within the radiation output of the radiation source, the at least one aperture assembly comprisinga radiation aperture body having an outside diameter less than the first diameter and an exposed upper surface with a shaped opening therein to control a radiation dosing profile,an aperture holder, an aperture-receiving passageway therein receiving the radiation aperture body, and having a recessed end, anda cover received within the recessed end of the aperture holder and retaining the radiation aperture body within the aperture holder, the cover having an opening aligned with the exposed upper surface of the radiation aperture body so as to define an interface therebetween that is exposed to the radiation output; andpositioning a radiation filter adjacent the at least one aperture assembly. 19. The method according to claim 18 wherein the radiation aperture body comprises a frusto-conical first portion; and wherein the aperture receiving passageway has a corresponding shape to the frusto-conical first portion. 20. The method according to claim 18 wherein the radiation aperture body comprises a frusto-conical second portion; and wherein the opening of the cover has a corresponding shape to the frusto-conical second portion. 21. The method according to claim 18 wherein the recessed end of the aperture holder and the cover define a threaded joint therebetween. 22. The method according to claim 18 wherein the radiation aperture body comprises at least one alignment edge extending outwards therefrom; and wherein the aperture-receiving passageway further includes at least one recess receiving the at least one alignment edge. 23. The method according to claim 18 wherein the radiation aperture body comprises brass. 24. The method according to claim 18 wherein the aperture holder and the cover each comprises stainless steel.
	description	This patent application claims the benefit of priority from Korean Patent Application No. 10-2013-0005989 filed on Jan. 18, 2013, and Korean Patent Application No. 10-2013-0110624 filed on Sep. 13, 2013, the contents of which are incorporated herein by reference. 1. Field of the Invention The present disclosure relates to a nuclear fuel rod for fast reactors that includes a metallic fuel slug coated with a protective coating layer and a fabrication method thereof. 2. Description of the Related Art The present invention relates to a process for improving the performance of nuclear fuel for reactors, and more particularly, to a technique that stabilizes components of a metallic fuel slug and fission products or impurities through the stabilization of surfaces of the metallic fuel slug and metallic fuel powder by a surface treatment. Nuclear fuel in fast reactors is designed in various types, such as a plate type, a pellet type, and a rod type, and a fissionable material that undergoes a nuclear reaction is included in a nuclear fuel rod. The fissionable material is sealed by a container, which is not reactive due to its good compatibility with a coolant and has good heat transfer characteristics, i.e. a cladding tube. The nuclear fuel rods being maintained at a constant spacing are assembled in the form of a fuel assembly and the assembly is charged into a nuclear reactor. In this case, the cladding tube surrounding the fuel must prevent chemical interactions between the fissionable material and the coolant by blocking a direct contact therebetween and must prevent the leakage of fission products. In addition, in fast reactors using metallic nuclear fuel, it is highly advantageous in terms of the safety and economic efficiency of nuclear fuel to also inhibit interactions between the cladding tube and the fissionable material. In particular, in fast reactors using metallic fuel, a phenomenon occurs, in which a melting temperature of a metallic fuel slug decreases or the strength of a cladding tube decreases by the interpenetration between components (uranium (U), plutonium (Pu), thorium (Th), minor actinides (MA), zirconium (Zr), molybdenum (Mo), fission products, etc.) of the metallic fuel slug and components (iron (Fe), chromium (Cr), tungsten (W), Mo, vanadium (V), niobium (Nb), etc.) of the stainless steel cladding tube by diffusion. Thus, the maximum allowable burnup and the maximum allowable operating temperature of the metallic fuel for fast reactors may be limited [J. Nucl. Mater., 204 (1993) p. 244-251 and J. Nucl. Mater., 204 (1993) p. 141-147]. Also, a diffusion couple experiment performed at 923 K by T. Ogata et al. demonstrated the occurrence of a reaction due to the interdiffusion between a metallic fuel slug and a cladding tube, and reported that the thickness of an interaction layer increased proportional to the reaction time [J. Nucl. Mater., 250 (1997) p. 171-175]. In order to prevent the interdiffusion reaction, General Electric (GE) disclosed a technique for inhibiting the interaction between a metallic fuel slug and a cladding tube by inserting an about 50 μm thick liner or sleeve formed of a metal of Zr, titanium (Ti), Nb, and Mo between the metallic fuel slug and the cladding tube. Since the technique of GE essentially requires the introduction of an additional process, the production of the nuclear fuel rod may not only be complicated, but considerable additional costs may also be required. Also, in order to remove quartz tube mold waste generated during the preparation of a fuel slug for fast reactors and simultaneously, to inhibit a fuel-cladding chemical interaction (FCCI) between metallic fuel slug and cladding tube, D. C. Crawford et al. melt-casted an about 200 μm thick zirconium tube and reported the results of their experiments. However, cracks may occur in the zirconium tube. Metallic fuel for reactors has been considered important as a nuclear fuel of sodium-cooled fast reactors, an advanced nuclear fuel, due to high thermal conductivity and high nuclear proliferation resistance in conjunction with pyroprocessing. However, with respect to the metallic fuel, since metallic uranium as a fuel material and a fuel cladding material interdiffuse and react above 650° C., i.e., an operating temperature of the reactor, the thickness of a cladding tube decreases according to the operating time. As a result, the lifetime of the cladding tube may decrease due to the deterioration of the soundness thereof. In order to prevent the interaction phenomenon and improve the performance of the cladding material, research into using a material for preventing the interdiffusion and reaction between the fuel and the cladding tube has been conducted. In Patent Document 1 (Korean Patent Application Laid-Open Publication No. KR-2009-0018396), a nuclear fuel rod for fast reactors, in which an oxide coating layer is formed on the inside of a cladding tube, is suggested in order to inhibit the fuel-cladding material interaction. Specifically, a concept of attaching chromium oxide, vanadium oxide, and zirconium oxide to the inside of the cladding tube by using an acid dissolution and oxidation method, a high-temperature oxidation method, an electrolytic oxidation method, and a vapor deposition method is suggested. In Patent Document 2 (Korean Patent Application Laid-Open Publication No. KR-2010-0114392), a concept of depositing functional materials, such as titanium, nickel, chromium, vanadium, and zirconium, in multilayers is suggested in order to inhibit the fuel-cladding material interaction and improve the performance of the fuel cladding tube. In Patent Document 3 (Korean Patent Application Laid-Open Publication No. KR-2010-0081961), a method of uniformly plating an inner wall of a fuel cladding tube and a concept of forming a nitride layer on a surface of the plating layer through an additional process of a nitridation treatment are suggested. In Patent Document 4 (Japanese Patent Application Laid-Open Publication No. 2012-237574), a typical main body that may accommodate nuclear fuel and is formed of an iron-based material; and a cladding tube including an inner layer part composed of a carbon-based material that is formed on an inner circumferential surface of the main body and a reactor including the cladding tube are suggested in order to provide a cladding tube that may improve high-temperature characteristics and power generation efficiency, and a reactor including the cladding tube. However, the fuel cladding tube for fast reactors is a seamless tube having a diameter of 7 mm, a thickness of 0.6 mm, and a length of 3,000 mm. Thus, there may be limitations in attaching the functional material for preventing interdiffusion to the inside of the thin and long tube, and treatment costs may be high. Accordingly, the present inventors found that the interdiffusion between a metallic fuel slug and a cladding tube may be prevented by stabilizing components of the metallic fuel slug and fission products or impurities though the simple and uniform formation of an oxide layer, a nitride layer, or a carbide layer on the surface of the metallic fuel slug, thereby leading to completion of the present invention. One object of the present invention is to provide a metallic fuel slug coated with a protective coating layer. Another object of the present invention is to provide a nuclear fuel rod for fast reactors including the metallic fuel slug. Still another object of the present invention is to provide a method of fabricating the nuclear fuel rod for fast reactors. In order to achieve the object, the present invention provides a metallic fuel slug used in a nuclear fuel rod for fast reactors, the metallic fuel slug having a surface coated with a single protective coating layer selected from the group consisting of an oxide layer, a nitride layer, and a carbide layer, wherein the protective coating layer is formed by oxidation, nitridation, or caburization of the metallic fuel slug. The present invention also provides a nuclear fuel rod for fast reactors including: a metallic fuel slug having a surface coated with a single protective coating layer selected from the group consisting of an oxide layer, a nitride layer, and a carbide layer, wherein the protective coating layer is formed by oxidation, nitridation, or caburization of the metallic fuel slug; and a cladding tube sealing the metal fuel slug. Furthermore, the present invention provides a method of fabricating a nuclear fuel rod for fast reactors including: coating a surface of a metallic fuel slug with a single protective coating layer selected from the group consisting of an oxide layer, a nitride layer, and a carbide layer by oxidation, nitridation, or caburization of the metallic fuel slug (step 1); and sealing a cladding tube after introducing the metallic fuel slug coated with the protective coating layer in step 1 into the cladding tube (step 2). The present invention also provides a method of fabricating a nuclear fuel rod for fast reactors including: coating a surface of metallic fuel powder with a single protective coating layer selected from the group consisting of an oxide layer, a nitride layer, and a carbide layer by oxidation, nitridation, or caburization of the metallic fuel powder (step 1); preparing a metallic fuel slug by forming the metallic fuel powder coated with the protective coating layer in step 1 (step 2); and sealing a cladding tube after introducing the metallic fuel slug prepared in step 2 into the cladding tube (step 3). Features and advantages of the present invention will be more clearly understood by the following detailed description of the present preferred embodiments by reference to the accompanying drawings. It is first noted that terms or words used herein should be construed as meanings or concepts corresponding with the technical sprit of the present invention, based on the principle that the inventor can appropriately define the concepts of the terms to best describe his own invention. Also, it should be understood that detailed descriptions of well-known functions and structures related to the present invention will be omitted so as not to unnecessarily obscure the important point of the present invention. Hereinafter, the present invention will be described in detail. The present invention provides a metallic fuel slug used in a nuclear fuel rod for fast reactors, the metallic fuel slug having a surface coated with a single protective coating layer selected from the group consisting of an oxide layer, a nitride layer, and a carbide layer, wherein the protective coating layer is formed by oxidation, nitridation, or caburization of the metallic fuel slug. In the metallic fuel slug coated with a protective coating layer according to the present invention, since components of the metallic fuel slug, fission products, or impurities are stabilized, an interdiffusion phenomenon occurred between the metallic fuel slug and the cladding tube sealing the metallic fuel slug during the fabrication of the nuclear fuel rod for fast reactors may be reduced. Also, according to the present invention, since a rare earth element, which is included on the surface of a metallic fuel fabricated by pyroprocessing to degrade the performance of the metallic fuel, may be transformed into a non-active compound, such as oxide, nitride, and carbide, the performance of the metallic fuel may be improved. With respect to the metallic fuel slug according to the present invention, the metallic fuel slug may be fabricated by including uranium (U), plutonium (Pu), thorium (Th), minor actinides (MA, neptunium (Np), americium (Am), and curium (Cm)), rare earth elements (RE, lanthanum (La), cerium (Ce), neodymium (Nd), praseodymium (Pr), promethium (Pm), samarium (Sm), europium (Eu), and gadolinium (Gd)), zirconium (Zr), and molybdenum (Mo) alone or in a mixture thereof. However, any metallic fuel slug applicable to the nuclear fuel rod for fast reactors may be used. With respect to the metallic fuel slug according to the present invention, a thickness of the protective coating layer may be in a range of 0.5 μm to 100 μm. In the case that the thickness of the protective coating layer is less than 0.5 μm, the interdiffusion phenomenon may not be sufficiently inhibited. In the case in which the thickness of the protective coating layer is greater than 100 μm, since thermal conductivity may decrease due to the thick coating layer, heat discharged from the fuel may not be efficiently transferred. The present invention also provides a nuclear fuel rod for fast reactors including a metallic fuel slug having a surface coated with a single protective coating layer selected from the group consisting of an oxide layer, a nitride layer, and a carbide layer, wherein the protective coating layer is formed by oxidation, nitridation, or caburization of the metallic fuel slug; and a cladding tube sealing the metal fuel slug. With respect to the nuclear fuel rod for fast reactors according to the present invention, the metallic fuel slug may be fabricated by including U, Pu, Th, MA (Np, Am, and Cm), RE (La, Ce, Nd, Pr, Pm, Sm, Eu, and Gd), Zr, and Mo alone or in a mixture thereof. However, any metallic fuel slug applicable to the nuclear fuel rod for fast reactors may be used. With respect to the nuclear fuel rod for fast reactors according to the present invention, a thickness of the protective coating layer may be in a range of 0.5 μm to 100 μm. In the case that the thickness of the protective coating layer is less than 0.5 μm, the interdiffusion phenomenon may not be sufficiently inhibited. In the case in which the thickness of the protective coating layer is greater than 100 μm, since thermal conductivity may decrease due to the thick coating layer, heat discharged from the fuel may not be efficiently transferred. With respect to the nuclear fuel rod for fast reactors according to the present invention, the cladding tube may include iron (Fe), chromium (Cr), tungsten (W), Mo, vanadium (V), titanium (Ti), niobium (Nb), tantalum (Ta), silicon (Si), manganese (Mn), nickel (Ni), carbon (C), nitrogen (N), and boron (B) alone or in the form of an alloy by mixing thereof. However, the present invention is not limited thereto. Furthermore, the present invention provides a method of fabricating a nuclear fuel rod for fast reactors including: coating a surface of a metallic fuel slug with a single protective coating layer selected from the group consisting of an oxide layer, a nitride layer, and a carbide layer by oxidation, nitridation, or caburization of the metallic fuel slug (step 1); and sealing a cladding tube after introducing the metallic fuel slug coated with the protective coating layer in step 1 into the cladding tube (step 2). In the fabricating method according to the present invention, step 1 is a step of forming the protective coating layer on the surface of the metallic fuel slug. Specifically, an oxide, nitride, or carbide coating layer may be formed on the surface of the metallic fuel slug by oxidation, nitridation, or caburization of the metallic fuel slug. In the fabricating method according to the present invention, step 2 is a step of sealing the cladding tube after introducing the surface-treated metallic fuel slug into the cladding tube. Formation of Oxide Protective Coating Layer A method of heat treating in a gas atmosphere containing oxygen, a method of dipping in an oxidation solution, and a method of performing an electrolytic treatment may be used as a method of forming an oxide protective coating layer. First, the method of heat treating in a gas atmosphere containing oxygen may be performed by heat treating a metallic fuel slug at a temperature ranging from 100° C. to 1000° C. and a pressure ranging from 1 atm to 50 atm in an atmosphere of oxygen, air, or inert gas containing oxygen. In the case that the heat treatment temperature is less than 100° C., the oxide layer may not be efficiently formed. In the case in which the heat treatment temperature is greater than 1000° C., transformation of the metallic fuel slug may occur and thus, the performance of the metallic fuel slug as a fuel may be degraded. Also, a pressurization treatment may be performed for the efficient heat treatment. In the case that the pressure of the heat treatment is 50 atm or more, an additional sealing apparatus may be required, and thus, economic efficiency of the process may be reduced. Next, the method of dipping in an oxidation solution may be performed by dipping a metallic fuel slug in a hydrochloric, sulfuric, nitric, sodium hydroxide, or potassium hydroxide solution, and heat treating the metallic fuel slug at a temperature ranging from 30° C. to 90° C. for 30 minutes to 5 hours. Finally, the method of performing an electrolytic treatment may be performed by plasma electrolytic oxidation, micro-arc oxidation, micro-arc discharge oxidation, spark anodizing, anodic spark deposition, micro-arc anodizing, micro plasma anodizing, micro plasma oxidation, and electro plasma oxidation of a metallic fuel slug. Formation of Nitride Protective Coating Layer A method of heat treating in a gas atmosphere containing nitrogen and an ion nitriding method may be used as a method of forming a nitride protective coating layer. First, the method of heat treating in a gas atmosphere containing nitrogen may be performed by heat treating a metallic fuel slug at a temperature ranging from 100° C. to 1000° C. and a pressure ranging from 1 atm to 50 atm in an atmosphere of nitrogen, ammonia, or inert gas containing nitrogen. In the case that the heat treatment temperature is less than 100° C., the nitride layer may not be efficiently formed. In the case in which the heat treatment temperature is greater than 1000° C., transformation of the metallic fuel slug may occur and thus, the performance of the metallic fuel slug as a fuel may be degraded. Also, a pressurization treatment may be performed for the efficient heat treatment. In the case that the pressure of the heat treatment is 50 atm or more, an additional sealing apparatus may be required, and thus, economic efficiency of the process may be reduced. Next, the ion nitriding method may be performed by using a method of applying a negative potential to an object to be ion-nitrided in a gas atmosphere containing nitrogen. The ion nitriding method may be completed by heat treating the object under conditions of a temperature ranging from 100° C. to 1000° C., a pressure ranging from 1 atm to 50 atm, and a potential ranging from 1 V to 1,000 V in an inert atmosphere containing nitrogen. In the case that the heat treatment temperature is less than 100° C., the nitride layer may not be efficiently formed. In the case in which the heat treatment temperature is greater than 1000° C., transformation of the metallic fuel slug may occur and thus, the performance of the metallic fuel slug as a fuel may be degraded. Also, a pressurization treatment may be performed for the efficient heat treatment. In the case that the pressure of the heat treatment is 50 atm or more, an additional sealing apparatus may be required, and thus, economic efficiency of the process may be reduced. With respect to the applied potential, efficient ion nitridation may not be achieved at a potential of less than 1 V. Since an additional insulation treatment may be required at a potential of greater than 1,000 V, economic efficiency of the process may be reduced. Formation of Carbide Protective Coating Layer A method of heat treating in a gas atmosphere containing carbon may be used as a method of forming a carbide protective coating layer. The method of heat treating in a gas atmosphere containing carbon may be performed by heat treating a metallic fuel slug at a temperature ranging from 100° C. to 1000° C. and a pressure ranging from 1 atm to 50 atm in an atmosphere of carbon, methane, carbon dioxide, or carbon monoxide. In the case that the heat treatment temperature is less than 100° C., the carbide layer may not be efficiently formed. In the case in which the heat treatment temperature is greater than 1000° C., transformation of the metallic fuel slug may occur and thus, the performance of the metallic fuel slug as a fuel may be degraded. Also, a pressurization treatment may be performed for the efficient heat treatment. In the case that the pressure of the heat treatment is 50 atm or more, an additional sealing apparatus may be required, and thus, economic efficiency of the process may be reduced. Also, the present invention provides a method of fabricating a nuclear fuel rod for fast reactors including: coating a surface of metallic fuel powder with a single protective coating layer selected from the group consisting of an oxide layer, a nitride layer, and a carbide layer by oxidation, nitridation, or caburization of the metallic fuel powder (step 1); preparing a metallic fuel slug by forming the metallic fuel powder coated with the protective coating layer in step 1 (step 2); and sealing a cladding tube after introducing the metallic fuel slug prepared in step 2 into the cladding tube (step 3). Since the method of fabricating a nuclear fuel rod for fast reactors according to the present invention may form the protective coating layer on the surface of the metallic fuel powder, components of fuel, fission products, or impurities may be stabilized and various types of fuels may be fabricated. In particular, the coated metallic fuel powder may be formed in the form of a metallic fuel slug during the fabrication of the nuclear fuel rod for fast reactors and thus, the interdiffusion phenomenon between the metallic fuel slug and the cladding tube sealing the metallic fuel slug may be reduced. In the fabricating method according to the present invention, step 1 is a step of forming the protective coating layer on the surface of the metallic fuel powder. Specifically, an oxide, nitride, or carbide coating layer may be formed on the surface of the metallic fuel powder by oxidation, nitridation, or caburization of the metallic fuel powder. Preferred conditions that may form the protective layers are as described in the above specification. In the fabricating method according to the present invention, step 2 is a step of preparing the metallic fuel slug by forming the metallic fuel powder. Specifically, a method of stacking the powder in a nuclear fuel rod composed of a cylindrical cladding tube, a method of sintering the powder by heat treating in a heat treatment furnace, and a method of forming a cylindrical sintered body by introducing the metallic fuel powder into a metal or ceramic matrix and heat treating. In the fabricating method according to the present invention, step 3 is a step of sealing the cladding tube after introducing the metallic fuel slug into the cladding tube. As described above, the nuclear fuel rod for fast reactors that includes the surface treated metallic fuel slug and the cladding tube according to the present invention has an excellent effect of stabilizing components of the metallic fuel slug and fission products or impurities, because the interdiffusion between the metallic fuel slug and the cladding tube does not occur. Also, since the uniform coating on the surface of the metallic fuel slug may be facilitated and fabrication costs may be significantly reduced in comparison to a typical technique of using a functional material for preventing the interdiffusion at an inner surface of the cladding tube, it may be suitable for fabricating the nuclear fuel rod for fast reactors. Hereinafter, the present invention will be described in more detail according to examples. However, the following examples are provided for illustrative purposes only, and the scope of the present invention should not be limited thereto in any manner. An oxide layer was formed on a surface of a metallic fuel slug by heat treating the metallic fuel slug formed of U-10Zr, a nuclear fuel material, at a temperature of 600° C. and a pressure of 5 atm for 2 hours in an argon gas atmosphere containing 20% oxygen. Then, the heat-treated metallic fuel slug was put into a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast reactors. An oxide layer was formed on a surface of a metallic fuel slug by heat treating the metallic fuel slug formed of U-10Zr, a nuclear fuel material, at a temperature of 150° C. and a pressure of 1 atm for 1 hour in an air atmosphere. Then, the heat-treated metallic fuel slug was put into a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast reactors. An oxide layer was formed on a surface of a metallic fuel slug by heat treating the metallic fuel slug formed of U-10Zr, a nuclear fuel material, at a temperature of 300° C. and a pressure of 1 atm for 1 hour in an air atmosphere. Then, the heat-treated metallic fuel slug was put into a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast reactors. An oxide layer was formed on a surface of a metallic fuel slug by dipping the metallic fuel slug formed of U-10Zr, a nuclear fuel material, in a hydrochloric acid solution at 50° C. for 2 hours. Then, the metallic fuel slug was put into a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast reactors. An oxide layer was formed on a surface of a metallic fuel slug by dipping the metallic fuel slug formed of U-10Zr, a nuclear fuel material, in a sulfuric acid solution at 50° C. for 2 hours. Then, the metallic fuel slug was put into a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast reactors. An oxide layer was formed on a surface of a metallic fuel slug by dipping the metallic fuel slug formed of U-10Zr, a nuclear fuel material, in a nitric acid solution at 50° C. for 2 hours. Then, the metallic fuel slug was put into a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast reactors. An oxide layer was formed on a surface of a metallic fuel slug by dipping the metallic fuel slug formed of U-10Zr, a nuclear fuel material, in a sodium hydroxide solution at 50° C. for 2 hours. Then, the metallic fuel slug was put into a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast reactors. An oxide layer was formed on a surface of a metallic fuel slug by dipping the metallic fuel slug formed of U-10Zr, a nuclear fuel material, in a potassium hydroxide solution at 50° C. for 2 hours. Then, the metallic fuel slug was put into a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast reactors. An oxide layer was formed on a surface of a metallic fuel slug through plasma electrolytic oxidation by dipping the metallic fuel slug formed of U-10Zr, a nuclear fuel material, in a potassium hydroxide solution and a sodium hydroxide solution, and then applying a positive voltage of 200 V thereto. Then, the metallic fuel slug was put into a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast reactors. An oxide layer was formed on a surface of a metallic fuel slug by micro-arc oxidation of the metallic fuel slug formed of U-10Zr, a nuclear fuel material. Then, the metallic fuel slug was put into a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast reactors. An oxide layer was formed on a surface of a metallic fuel slug by micro-arc discharge oxidation of the metallic fuel slug formed of U-10Zr, a nuclear fuel material. Then, the metallic fuel slug was put into a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast reactors. An oxide layer was formed on a surface of a metallic fuel slug by spark anodizing of the metallic fuel slug formed of U-10Zr, a nuclear fuel material. Then, the metallic fuel slug was put into a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast reactors. An oxide layer was formed on a surface of a metallic fuel slug by anodic spark deposition of the metallic fuel slug formed of U-10Zr, a nuclear fuel material. Then, the metallic fuel slug was put into a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast reactors. Reactors Having Oxide Layer Formed on Surface An oxide layer was formed on a surface of a metallic fuel slug by micro-arc anodizing of the metallic fuel slug formed of U-10Zr, a nuclear fuel material. Then, the metallic fuel slug was put into a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast reactors. An oxide layer was formed on a surface of a metallic fuel slug by micro plasma anodizing of the metallic fuel slug formed of U-10Zr, a nuclear fuel material. Then, the metallic fuel slug was put into a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast reactors. An oxide layer was formed on a surface of a metallic fuel slug by micro plasma oxidation of the metallic fuel slug formed of U-10Zr, a nuclear fuel material. Then, the metallic fuel slug was put into a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast reactors. An oxide layer was formed on a surface of a metallic fuel slug by electro plasma oxidation of the metallic fuel slug formed of U-10Zr, a nuclear fuel material. Then, the metallic fuel slug was put into a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast reactors. A nitride layer was formed on a surface of a metallic fuel slug by heat treating the metallic fuel slug formed of U-10Zr, a nuclear fuel material, at a temperature of 800° C. and a pressure of 2 atm for 2 hours in a 100% pure ammonia gas atmosphere. Then, the heat-treated metallic fuel slug was put into a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast reactors. A nitride layer was formed on a surface of a metallic fuel slug by heat treating the metallic fuel slug formed of U-10Zr, a nuclear fuel material, at a temperature of 500° C. and a pressure of 2 atm for 2 hours in a 100% pure ammonia gas atmosphere. Then, the heat-treated metallic fuel slug was put into a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast reactors. A nitride layer was formed on a surface of a metallic fuel slug by heat treating the metallic fuel slug formed of U-10Zr, a nuclear fuel material, at a temperature of 300° C. and a pressure of 2 atm for 2 hours in a 100% pure ammonia gas atmosphere. Then, the heat-treated metallic fuel slug was put into a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast reactors. A nitride layer was formed on a surface of a metallic fuel slug by heat treating the metallic fuel slug formed of U-10Zr, a nuclear fuel material, at a temperature of 150° C. and a pressure of 2 atm for 2 hours in a 100% pure ammonia gas atmosphere. Then, the heat-treated metallic fuel slug was put into a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast reactors. An ion-nitrided layer was formed on a surface of a metallic fuel slug by introducing the metallic fuel slug formed of U-10Zr, a nuclear fuel material, into a mixed gas containing 80% nitrogen and 20% argon gas, and heat treating the metallic fuel slug at a temperature of 800° C. and a negative voltage of 200 V for 2 hours. Then, the metallic fuel slug was put into a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast reactors. An ion-nitrided layer was formed on a surface of a metallic fuel slug by introducing the metallic fuel slug formed of U-10Zr, a nuclear fuel material, into a mixed gas containing 80% nitrogen and 20% argon gas, and heat treating the metallic fuel slug at a temperature of 500° C. and a negative voltage of 200 V for 2 hours. Then, the metallic fuel slug was put into a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast reactors. An ion-nitrided layer was formed on a surface of a metallic fuel slug by introducing the metallic fuel slug formed of U-10Zr, a nuclear fuel material, into a mixed gas containing 80% nitrogen and 20% argon gas, and heat treating the metallic fuel slug at a temperature of 300° C. and a negative voltage of 200 V for 2 hours. Then, the metallic fuel slug was put into a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast reactors. An ion-nitrided layer was formed on a surface of a metallic fuel slug by introducing the metallic fuel slug formed of U-10Zr, a nuclear fuel material, into a mixed gas containing 80% nitrogen and 20% argon gas, and heat treating the metallic fuel slug at a temperature of 150° C. and a negative voltage of 200 V for 2 hours. Then, the metallic fuel slug was put into a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast reactors. A carbide layer was formed on a surface of a metallic fuel slug by introducing the metallic fuel slug formed of U-10Zr, a nuclear fuel material, into carbon powder and heat treating the metallic fuel slug at a temperature of 700° C. and a pressure of 1 atm for 2 hours. Then, the heat-treated metallic fuel slug was put into a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast reactors. A carbide layer was formed on a surface of a metallic fuel slug by introducing the metallic fuel slug formed of U-10Zr, a nuclear fuel material, into carbon powder and heat treating the metallic fuel slug at a temperature of 500° C. and a pressure of 1 atm for 2 hours. Then, the heat-treated metallic fuel slug was put into a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast reactors. A carbide layer was formed on a surface of a metallic fuel slug by introducing the metallic fuel slug formed of U-10Zr, a nuclear fuel material, into carbon powder and heat treating the metallic fuel slug at a temperature of 300° C. and a pressure of 1 atm for 2 hours. Then, the heat-treated metallic fuel slug was put into a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast reactors. A carbide layer was formed on a surface of a metallic fuel slug by introducing the metallic fuel slug formed of U-10Zr, a nuclear fuel material, into carbon powder and heat treating the metallic fuel slug at a temperature of 150° C. and a pressure of 1 atm for 2 hours. Then, the heat-treated metallic fuel slug was put into a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast reactors. A carbide layer was formed on a surface of a metallic fuel slug by heat treating the metallic fuel slug formed of U-10Zr, a nuclear fuel material, at a temperature of 700° C. and a pressure of 1 atm for 2 hours in a methane gas atmosphere. Then, the heat-treated metallic fuel slug was put into a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast reactors. A carbide layer was formed on a surface of a metallic fuel slug by heat treating the metallic fuel slug formed of U-10Zr, a nuclear fuel material, at a temperature of 500° C. and a pressure of 1 atm for 2 hours in a methane gas atmosphere. Then, the heat-treated metallic fuel slug was put into a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast reactors. A carbide layer was formed on a surface of a metallic fuel slug by heat treating the metallic fuel slug formed of U-10Zr, a nuclear fuel material, at a temperature of 300° C. and a pressure of 1 atm for 2 hours in a methane gas atmosphere. Then, the heat-treated metallic fuel slug was put into a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast reactors. A carbide layer was formed on a surface of a metallic fuel slug by heat treating the metallic fuel slug formed of U-10Zr, a nuclear fuel material, at a temperature of 150° C. and a pressure of 1 atm for 2 hours in a methane gas atmosphere. Then, the heat-treated metallic fuel slug was put into a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast reactors. A carbide layer was formed on a surface of a metallic fuel slug by heat treating the metallic fuel slug formed of U-10Zr, a nuclear fuel material, at a temperature of 700° C. and a pressure of 1 atm for 2 hours in a carbon dioxide gas atmosphere. Then, the heat-treated metallic fuel slug was put into a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast reactors. A carbide layer was formed on a surface of a metallic fuel slug by heat treating the metallic fuel slug formed of U-10Zr, a nuclear fuel material, at a temperature of 500° C. and a pressure of 1 atm for 2 hours in a carbon dioxide gas atmosphere. Then, the heat-treated metallic fuel slug was put into a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast reactors. A carbide layer was formed on a surface of a metallic fuel slug by heat treating the metallic fuel slug formed of U-10Zr, a nuclear fuel material, at a temperature of 300° C. and a pressure of 1 atm for 2 hours in a carbon dioxide gas atmosphere. Then, the heat-treated metallic fuel slug was put into a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast reactors. A carbide layer was formed on a surface of a metallic fuel slug by heat treating the metallic fuel slug formed of U-10Zr, a nuclear fuel material, at a temperature of 150° C. and a pressure of 1 atm for 2 hours in a carbon dioxide gas atmosphere. Then, the heat-treated metallic fuel slug was put into a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast reactors. A carbide layer was formed on a surface of a metallic fuel slug by heat treating the metallic fuel slug formed of U-10Zr, a nuclear fuel material, at a temperature of 700° C. and a pressure of 1 atm for 2 hours in a carbon monoxide gas atmosphere. Then, the heat-treated metallic fuel slug was put into a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast reactors. A carbide layer was formed on a surface of a metallic fuel slug by heat treating the metallic fuel slug formed of U-10Zr, a nuclear fuel material, at a temperature of 500° C. and a pressure of 1 atm for 2 hours in a carbon monoxide gas atmosphere. Then, the heat-treated metallic fuel slug was put into a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast reactors. A carbide layer was formed on a surface of a metallic fuel slug by heat treating the metallic fuel slug formed of U-10Zr, a nuclear fuel material, at a temperature of 300° C. and a pressure of 1 atm for 2 hours in a carbon monoxide gas atmosphere. Then, the heat-treated metallic fuel slug was put into a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast reactors. A carbide layer was formed on a surface of a metallic fuel slug by heat treating the metallic fuel slug formed of U-10Zr, a nuclear fuel material, at a temperature of 150° C. and a pressure of 1 atm for 2 hours in a carbon monoxide gas atmosphere. Then, the heat-treated metallic fuel slug was put into a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast reactors. A surface treatment was not performed on a metallic fuel slug formed of U-10Zr, a nuclear fuel material, and the metallic fuel slug was put into a HT9 (12Cr-1Mo) cladding tube to fabricate a nuclear fuel rod for fast reactors. The following experiments were performed for evaluating the interdiffusivity between the metallic fuel slug and the cladding tube in the nuclear fuel rods for fast reactors fabricated in examples. Specifically, the nuclear fuel rods for fast reactors fabricated in Examples 1, 2, 3, and 18, and Comparative Example 1 were cut to a length of 10 mm, and the 10 mm long nuclear fuel rods were then cut in half in a radial direction. Then, metallic fuel slug-cladding tube diffusion couple experiments were performed at 800° C. for 25 hours. After the diffusion couple experiments, bonded samples were cooled and cross sections of the bonded samples were observed using a scanning electron microscope. The results thereof are presented in FIGS. 2 to 6. FIG. 2 is a scanning electron microscope image of the cross section of the nuclear fuel rod for fast reactors according to Example 1 of the present invention after the diffusion couple experiment. FIG. 3 is a scanning electron microscope image of the cross section of the nuclear fuel rod for fast reactors according to Example 2 of the present invention after the diffusion couple experiment. FIG. 4 is a scanning electron microscope image of the cross section of the nuclear fuel rod for fast reactors according to Example 3 of the present invention after the diffusion couple experiment. FIG. 5 is a scanning electron microscope image of the cross section of the nuclear fuel rod for fast reactors according to Example 18 of the present invention after the diffusion couple experiment. FIG. 6 is a scanning electron microscope image of the cross section of the nuclear fuel rod for fast reactors according to Comparative Example 1 of the present invention after the diffusion couple experiment. As illustrated in FIGS. 2 to 6, with respect to Example 1 (FIG. 2), Example 2 (FIG. 3), Example 3 (FIG. 4), and Example 18 (FIG. 5), it was observed that the interactions between the metallic fuel slugs and the cladding tubes did not occur because dense oxide layers and nitride layer were formed on the surfaces of the metallic fuel slugs. In contrast, with respect to Comparative Example 1 (FIG. 6), it may be observed that the metallic fuel slug material and the cladding tube material were interdiffused and reacted during the diffusion couple experiment. Therefore, the nuclear fuel rod for fast reactors that includes the surface treated metallic fuel slug and the cladding tube according to the present invention had an excellent effect of stabilizing components of the metallic fuel slug and fission products or impurities, because the interdiffusion between the metallic fuel slug and the cladding tube did not occur. Also, since the uniform coating on the surface of the metallic fuel slug may be facilitated and fabrication costs may be significantly reduced in comparison to a typical technique of using a functional material for preventing the interdiffusion at an inner surface of the cladding tube, it may be suitable for fabricating the nuclear fuel rod for fast reactors. Furthermore, according to the present invention, since a rare earth element, which is included on the surface of a metallic fuel fabricated by pyroprocessing to degrade the performance of the metallic fuel, may be transformed into a non-active compound, such as oxide, nitride, and carbide, the improvement of the performance of the metallic fuel and the extension of the lifetime of the metallic fuel may be expected. Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.
	summary
062597604	abstract	A unitary, transportable, assembled nuclear steam supply system (NSSS) with a lifetime fuel supply utilizes a fast or epithermal spectrum reactor core immersed in a pool of light water together with a plurality of steam generators through which the coolant is circulated by up to 100% natural circulation at full power, augmented by reactor coolant pumps also immersed in the pool. Redundant steam generators and reactor coolant pumps, together with the fast or epithermal spectrum reactor core and pool configuration, make it possible to operate the NSSS for 10 to 15 or more years without maintenance on the internals or refueling, thereby rendering the system proliferation resistant.
054901855	summary	BACKGROUND OF THE INVENTION This invention relates generally to the field of nuclear power plants, and in particular, it concerns a system for the automatic movement of fuel assemblies within a nuclear power plant during the refueling of the nuclear reactor. Nuclear power plants which employ light water reactors require periodic outages for refueling of the reactor. New fuel assemblies are delivered to the plant and are temporarily stored in a fuel storage building, along with used fuel assemblies which may have been previously removed from the reactor. During a refueling outage, a portion of the fuel assemblies in the reactor are moved from the reactor to the fuel storage building. A second portion of the fuel assemblies are moved from one core support location in the reactor to another core support location in the reactor. A third portion of the fuel assemblies are moved from the reactor into fuel assembly storage locations in the fuel storage building. New fuel assemblies are moved from the fuel storage building into the reactor to replace those fuel assemblies which were removed. These movements are done in accordance with a detailed sequence plan so that each fuel assembly is placed in a specific location in accordance with an overall refueling plan prepared by the reactor core designer. Refueling activities are often on the critical path for returning the nuclear plant to power operation, therefore the speed of these operations is an important economic consideration for the power plant owner. Furthermore, the plant equipment and fuel assemblies are expensive and care must be taken not to cause damage due to improper handling of the fuel assemblies or fuel transfer equipment. The precision of these operations is also important since the safe and economical operation of the reactor core depends upon each fuel assembly being in its proper location. Current refueling systems rely to a great extent upon the skill and discipline of the refueling crew, since human beings operate the fuel transfer equipment. There have been some efforts to automate portions of the refueling operations, for example, U.S. Pat. No. 4,427,623, issued to N. C. Howard, et al, teaches an apparatus and method for the automatic movement of fuel assemblies between locations in the reactor containment building. However, this patent does not address the movement of fuel assemblies within the fuel storage building or between the fuel storage building and the reactor containment building. Furthermore, existing systems have limited flexibility for dealing with unforseen changes in the refueling plan or sequence plan, such as may be necessitated by the discovery of a leaking or damaged fuel assembly. These plans are generated prior to the plant outage, and any revision to the plans requires the fuel shuffling operations to be placed on hold. In general, nuclear power plant refueling operations today are primarily controlled by human beings, with all of the schedular, safety, and economic limitations inherently associated with manual operations. SUMMARY In light of the speed, accuracy and safety limitations of existing nuclear power plant refueling equipment, it is an object of this invention to describe a refueling system which provides for the automatic movement of fuel assemblies. It is a further object of this invention to describe a system which provides improved speed of refueling operations and precise control of the fuel assembly movements in order to achieve safe refueling of the reactor. It is a further object to describe a system which provides improved flexibility for dealing with unforseen changes in the reload plan or sequence plan. Accordingly, an automatic refueling system for a nuclear power plant is described which includes a fuel transfer system operable to move fuel assemblies between a reactor building and a fuel storage building; a refueling machine operable to move fuel assemblies among core support locations within the reactor, as well as between the reactor and the fuel transfer system; a spent fuel handling machine operable to move fuel assemblies among the fuel assembly storage locations, as well as between the fuel assembly storage locations and the fuel transfer system; a means for operator interface; a network comprising a plurality of nodes interconnected by a data link, the network having nodes connected to the fuel transfer system, the refueling machine, the spent fuel handling machine, and the means for operator interface; and a means for controlling the refueling system, the means for controlling being connected to a node of the network and being operable to automatically control the operation of the fuel transfer system, the refueling machine, and the spent fuel handling machine so that fuel assembly moves are accomplished automatically.
	summary
	claims	1. A composition consisting of:94.5-95.5 mol % Na;2.5-3.5 mol % Pb; andthe balance being Sn. 2. The composition of claim 1, wherein the composition is:95 mol % Na;3 mol % Pb; andthe balance being Sn. 3. The composition of claim 1 wherein the composition supports a continuous reaction with air at a temperature higher than that which pure sodium supports a continuous reaction with air. 4. The composition of claim 1 wherein the composition supports a continuous reaction with air at a temperature at least about 100% higher than that which pure sodium supports a continuous reaction with air.
	summary
	abstract	A method of disposing of radioactive waste comprising the steps of: providing a pressure-equalizing container; filling the pressure-equalizing container with radioactive waste; and burying the waste filled container in a subduction fault region of the earth's crust. For a preferred embodiment of the process, the waste filled containers are buried in the mud on the ocean floor in a subduction fault region. Preferably, the containers are placed on the ocean side of the fault, rather than the continental shelf side. The pressure-equalizing container is preferably fabricated from stainless steel, with a lead seal, although containers fabricated from ceramic materials may also be used. The waste-filled containers are transported by ship to the area above a subduction fault, and an unpressurized, remote-controlled “submarine crawler” takes a number of containers to the ocean floor and buries them there, individually, in the mud or sediments.
	claims	1. A transmission electron microscope for imaging a sample, the transmission electron microscope showing a diffraction plane in which a diffraction pattern of the sample is formed, the diffraction plane representing an image of the sample in the Fourier domain, the transmission electron microscope comprising a blocking member positioned in the diffraction plane or an image thereof, the blocking member blocking a part of the Fourier domain, the blocked part of the Fourier domain in at least one direction extending from a low spatial frequency to a high spatial frequency,the highest spatial frequency blocked by the blocking member is lower than or equal to the lowest spatial frequency where an image of said diffraction plane imaged without the blocking member shows a Contrast Transfer of approximately 0.5, the microscope lacking a phase plate. 2. The transmission electron microscope of claim 1, wherein the blocking member is connected to a supporting arm. 3. The transmission electron microscope of claim 1, wherein the blocking member is supported by a thin film, said film transparent to the impinging electrons. 4. The transmission electron microscope of claim 1 in which the blocking member resembles a rectangle. 5. The transmission electron microscope of claim 1, wherein the blocking member resembles a trapezoid with varying width, wherein the diffraction pattern shows a spot of undiffracted electrons, and the blocked spatial frequency interval is chosen by positioning the beam of undiffracted electrons near a part of the blocking member with an appropriate width. 6. The transmission electron microscope of claim 1, wherein the blocking member shows a discrete number of steps, each with a different width. 7. The transmission electron microscope of claim 1, wherein the blocking member resembles a half-circle. 8. The transmission electron microscope of claim 7 in which the half-circle shows a straight edge connected to a support arm, and the support arm extends in a direction either perpendicular or parallel to said straight edge. 9. The transmission electron microscope of claim 1 in which the blocking member is placed in a plane that is an image of the diffraction plane and where an anamorphotic image of the diffraction plane is formed. 10. The transmission electron microscope of claim 1 in which the blocking member is placed in a plane that is an image of the diffraction plane and the imaging of the diffraction plane onto said plane is at least in part realized by transfer optics that are part of corrector optics, the corrector optics for correcting the aberrations of the lens forming the diffraction pattern. 11. The transmission electron microscope of claim 1 in which at least part of the blocking member is electrically isolated from earth and electrically connected to a current measurement unit for measuring the current impinging on at least a part of the blocking member. 12. The transmission electron microscope of claim 11 where the current measurement is used to position beam of undiffracted electrons with respect to the blocking member. 13. The transmission electron microscope of claim 1 further comprises means for heating the blocking member. 14. The transmission electron microscope of claim 1 wherein the diffraction pattern shows a spot of undiffracted electrons and the blocking member shows an indent at the location where the beam of undiffracted electrons is closest to the blocking member, as a result of which contamination of the blocking member is reduced. 15. Method of using of a blocking member in a transmission electron microscope, the method comprising:providing a blocking member in the diffraction plane of the transmission electron microscope, the blocking member blocking a part of the diffraction plane,the blocked part blocks in at least one direction spatial frequencies from a low frequency to a high frequency, the high spatial frequency lower than or equal to the lowest spatial frequency where an image of said diffraction plane imaged without the blocking member shows a Contrast Transfer Function of approximately 50%, andpassing electrons not blocked by the blocking member without those electrons passing through a phase plate. 16. A transmission electron microscope for imaging a sample, comprising;an electron source producing a beam of electrons;condenser lenses forming a parallel beam of electrons, the parallel beam irradiating the sample;a positioning unit for holding the sample and manipulating the position of the sample;an objective lens for forming an image, said objective lens defining a diffraction plane;a blocking member positioned at or near the diffraction plane such that the highest spatial frequency blocked by the blocking member is lower than or equal to the lowest spatial frequency where an image of said diffraction plane imaged without the blocking member shows a Contrast Transfer of approximately 0.5, the microscope lacking a phase plate;anda sensor for receiving an image projected by the objective lens. 17. The transmission electron microscope of claim 16 in which the blocking member resembles a rectangular, trapezoidal, or half-circular shape. 18. The transmission electron microscope of claim 16 in which the blocking member is supported by a thin film, said film transparent to the impinging electrons. 19. The transmission electron microscope of claim 16 in which the blocking member is placed in a plane that is an image of the diffraction plane and where an anamorphotic image of the diffraction plane is formed. 20. The transmission electron microscope of claim 16 in which the blocking member is electrically isolated from earth and electrically connected to a current measurement unit for measuring the current impinging on at least a part of the blocking member. 21. A transmission electron microscope for imaging a sample, the transmission electron microscope showing a diffraction plane in which a diffraction pattern of the sample is formed, the diffraction plane representing an image of the sample in the Fourier domain, the transmission electron microscope comprising a blocking member positioned in the diffraction plane or an image thereof, the blocking member blocking a part of the Fourier domain, the blocked part of the Fourier domain in at least one direction extending from a low spatial frequency to a high spatial frequency,the CTF in a large frequency band equals 50% of the envelope function and for a large frequency band substantially more than 50% of the envelope function, the microscope lacking a phase plate.
	description	This application is a continuation of U.S. Ser. No. 14/448,258, filed on Jul. 31, 2014, which is a continuation of U.S. Ser. No. 13/964,938, filed on Aug. 12, 2013, now U.S. Pat. No. 9,048,000, which is a continuation of U.S. Ser. No. 13/024,027, filed on Feb. 9, 2011, now U.S. Pat. No. 8,525,138, which claims the benefit of, and priority to U.S. Provisional Patent Application No. 61/302,797, filed on Feb. 9, 2010, the entire disclosure of which is incorporated by reference herein, Ser. No. 13/024,027 is also a continuation-in-part of U.S. Ser. No. 12/166,918, filed on Jul. 2, 2008, now U.S. Pat. No. 7,989,786, which is a continuation-in-part of U.S. Ser. No. 11/695,348, filed on Apr. 2, 2007, now U.S. Pat. No. 7,786,455, which is a continuation-in-part of U.S. Ser. No. 11/395,523, filed on Mar. 31, 2006, now U.S. Pat. No. 7,435,982, the entire disclosures of each of which are hereby incorporated by reference herein. The invention relates to methods and apparatus for providing a laser-driven light source. High brightness light sources can be used in a variety of applications. For example, a high brightness light source can be used for inspection, testing or measuring properties associated with semiconductor wafers or materials used in the fabrication of wafers (e.g., reticles and photomasks). The electromagnetic energy produced by high brightness light sources can, alternatively, be used as a source of illumination in a lithography system used in the fabrication of wafers, a microscopy system, or a photoresist curing system. The parameters (e.g., wavelength, power level and brightness) of the light vary depending upon the application. The state of the art in, for example, wafer inspection systems involves the use of xenon or mercury arc lamps to produce light. The arc lamps include an anode and cathode that are used to excite xenon or mercury gas located in a chamber of the lamp. An electrical discharge is generated between the anode and cathode to provide power to the excited (e.g., ionized) gas to sustain the light emitted by the ionized gas during operation of the light source. During operation, the anode and cathode become very hot due to electrical discharge delivered to the ionized gas located between the anode and cathode. As a result, the anode and/or cathode are prone to wear and may emit particles that can contaminate the light source or result in failure of the light source. Also, these arc lamps do not provide sufficient brightness for some applications, especially in the ultraviolet spectrum. Further, the position of the arc can be unstable in these lamps. Accordingly, a need therefore exists for improved high brightness light sources. A need also exists for improved high brightness light sources that do not rely on an electrical discharge to maintain a plasma that generates a high brightness light. The properties of light produced by many light sources (e.g., arc lamps, microwave lamps) are affected when the light passes through a wall of, for example, a chamber that includes the location from which the light is emitted. Accordingly, a need therefore exists for an improved light source whose emitted light is not significantly affected when the light passes through a wall of a chamber that includes the location from which the light is emitted. The present invention features a light source for generating a high brightness light. The invention, in one aspect, features a light source having a chamber. The light source also includes an ignition source for ionizing a gas within the chamber. The light source also includes at least one laser for providing energy to the ionized gas within the chamber to produce a high brightness light. In some embodiments, the at least one laser is a plurality of lasers directed at a region from which the high brightness light originates. In some embodiments, the light source also includes at least one optical element for modifying a property of the laser energy provided to the ionized gas. The optical element can be, for example, a lens (e.g., an aplanatic lens, an achromatic lens, a single element lens, and a Fresnel lens) or mirror (e.g., a coated mirror, a dielectric coated mirror, a narrow band mirror, and an ultraviolet transparent infrared reflecting mirror). In some embodiments, the optical element is one or more fiber optic elements for directing the laser energy to the gas. The chamber can include an ultraviolet transparent region. The chamber or a window in the chamber can include a material selected from the group consisting of quartz, Suprasil® quartz (Heraeus Quartz America, LLC, Buford, Ga.), sapphire, MgF2, diamond, and CaF2. In some embodiments, the chamber is a sealed chamber. In some embodiments, the chamber is capable of being actively pumped. In some embodiments, the chamber includes a dielectric material (e.g., quartz). The chamber can be, for example, a glass bulb. In some embodiments, the chamber is an ultraviolet transparent dielectric chamber. The gas can be one or more of a noble gas, Xe, Ar, Ne, Kr, He, D2, H2, O2, F2, a metal halide, a halogen, Hg, Cd, Zn, Sn, Ga, Fe, Li, Na, an excimer forming gas, air, a vapor, a metal oxide, an aerosol, a flowing media, or a recycled media. The gas can be produced by a pulsed laser beam that impacts a target (e.g., a solid or liquid) in the chamber. The target can be a pool or film of metal. In some embodiments, the target is capable of moving. For example, the target may be a liquid that is directed to a region from which the high brightness light originates. In some embodiments, the at least one laser is multiple diode lasers coupled into a fiber optic element. In some embodiments, the at least one laser includes a pulse or continuous wave laser. In some embodiments, the at least one laser is an IR laser, a diode laser, a fiber laser, an ytterbium laser, a CO2 laser, a YAG laser, or a gas discharge laser. In some embodiments, the at least one laser emits at least one wavelength of electromagnetic energy that is strongly absorbed by the ionized medium. The ignition source can be or can include electrodes, an ultraviolet ignition source, a capacitive ignition source, an inductive ignition source, an RF ignition source, a microwave ignition source, a flash lamp, a pulsed laser, or a pulsed lamp. The ignition source can be a continuous wave (CW) or pulsed laser impinging on a solid or liquid target in the chamber. The ignition source can be external or internal to the chamber. The light source can include at least one optical element for modifying a property of electromagnetic radiation emitted by the ionized gas. The optical element can be, for example, one or more mirrors or lenses. In some embodiments, the optical element is configured to deliver the electromagnetic radiation emitted by the ionized gas to a tool (e.g., a wafer inspection tool, a microscope, a metrology tool, a lithography tool, or an endoscopic tool). The invention, in another aspect, relates to a method for producing light. The method involves ionizing with an ignition source a gas within a chamber. The method also involves providing laser energy to the ionized gas in the chamber to produce a high brightness light. In some embodiments, the method also involves directing the laser energy through at least one optical element for modifying a property of the laser energy provided to the ionized gas. In some embodiments, the method also involves actively pumping the chamber. The ionizable medium can be a moving target. In some embodiments, the method also involves directing the high brightness light through at least one optical element to modify a property of the light. In some embodiments, the method also involves delivering the high brightness light emitted by the ionized medium to a tool (e.g., a wafer inspection tool, a microscope, a metrology tool, a lithography tool, or an endoscopic tool). In another aspect, the invention features a light source. The lights source includes a chamber and an ignition source for ionizing an ionizable medium within the chamber. The light source also includes at least one laser for providing substantially continuous energy to the ionized medium within the chamber to produce a high brightness light. In some embodiments, the at least one laser is a continuous wave laser or a high pulse rate laser. In some embodiments, the at least one laser is a high pulse rate laser that provides pulses of energy to the ionized medium so the high brightness light is substantially continuous. In some embodiments, the magnitude of the high brightness light does not vary by more than about 90% during operation. In some embodiments, the at least one laser provides energy substantially continuously to minimize cooling of the ionized medium when energy is not provided to the ionized medium. In some embodiments, the light source can include at least one optical element (e.g., a lens or mirror) for modifying a property of the laser energy provided to the ionized medium. The optical element can be, for example, an aplanatic lens, an achromatic lens, a single element lens, a Fresnel lens, a coated mirror, a dielectric coated mirror, a narrow band mirror, or an ultraviolet transparent infrared reflecting mirror. In some embodiments, the optical element is one or more fiber optic elements for directing the laser energy to the ionizable medium. In some embodiments, the chamber includes an ultraviolet transparent region. In some embodiments, the chamber or a window in the chamber includes a quartz material, suprasil quartz material, sapphire material, MgF2 material, diamond material, or CaF2 material. In some embodiments, the chamber is a sealed chamber. The chamber can be capable of being actively pumped. In some embodiments, the chamber includes a dielectric material (e.g., quartz). In some embodiments, the chamber is a glass bulb. In some embodiments, the chamber is an ultraviolet transparent dielectric chamber. The ionizable medium can be a solid, liquid or gas. The ionizable medium can include one or more of a noble gas, Xe, Ar, Ne, Kr, He, D2, H2, O2, F2, a metal halide, a halogen, Hg, Cd, Zn, Sn, Ga, Fe, Li, Na, an excimer forming gas, air, a vapor, a metal oxide, an aerosol, a flowing media, a recycled media, or an evaporating target. In some embodiments, the ionizable medium is a target in the chamber and the ignition source is a pulsed laser that provides a pulsed laser beam that strikes the target. The target can be a pool or film of metal. In some embodiments, the target is capable of moving. In some embodiments, the at least one laser is multiple diode lasers coupled into a fiber optic element. The at least one laser can emit at least one wavelength of electromagnetic energy that is strongly absorbed by the ionized medium. The ignition source can be or can include electrodes, an ultraviolet ignition source, a capacitive ignition source, an inductive ignition source, an RF ignition source, a microwave ignition source, a flash lamp, a pulsed laser, or a pulsed lamp. The ignition source can be external or internal to the chamber. In some embodiments, the light source includes at least one optical element (e.g., a mirror or lens) for modifying a property of electromagnetic radiation emitted by the ionized medium. The optical element can be configured to deliver the electromagnetic radiation emitted by the ionized medium to a tool (e.g., a wafer inspection tool, a microscope, a metrology tool, a lithography tool, or an endoscopic tool). The invention, in another aspect relates to a method for producing light. The method involves ionizing with an ignition source an ionizable medium within a chamber. The method also involves providing substantially continuous laser energy to the ionized medium in the chamber to produce a high brightness light. In some embodiments, the method also involves directing the laser energy through at least one optical element for modifying a property of the laser energy provided to the ionizable medium. The method also can involve actively pumping the chamber. In some embodiments, the ionizable medium is a moving target. The ionizable medium can include a solid, liquid or gas. In some embodiments, the method also involves directing the high brightness light through at least one optical element to modify a property of the light. In some embodiments, the method also involves delivering the high brightness light emitted by the ionized medium to a tool. The invention, in another aspect, features a light source having a chamber. The light source includes a first ignition means for ionizing an ionizable medium within the chamber. The light source also includes a means for providing substantially continuous laser energy to the ionized medium within the chamber. The invention, in another aspect, features a light source having a chamber that includes a reflective surface. The light source also includes an ignition source for ionizing a gas within the chamber. The light source also includes a reflector that at least substantially reflects a first set of predefined wavelengths of electromagnetic energy directed toward the reflector and at least substantially allows a second set of predefined wavelengths of electromagnetic energy to pass through the reflector. The light source also includes at least one laser (e.g., a continuous-wave fiber laser) external to the chamber for providing electromagnetic energy to the ionized gas within the chamber to produce a plasma that generates a high brightness light. A continuous-wave laser emits radiation continuously or substantially continuously rather than in short bursts, as in a pulsed laser. In some embodiments, at least one laser directs a first set of wavelengths of electromagnetic energy through the reflector toward the reflective surface (e.g., inner surface) of the chamber and the reflective surface directs at least a portion of the first set of wavelengths of electromagnetic energy toward the plasma. In some embodiments, at least a portion of the high brightness light is directed toward the reflective surface of the chamber, is reflected toward the reflector, and is reflected by the reflector toward a tool. In some embodiments, at least one laser directs a first set of wavelengths of electromagnetic energy toward the reflector, the reflector reflects at least a portion of the first wavelengths of electromagnetic energy towards the reflective surface of the chamber, and the reflective surface directs a portion of the first set of wavelengths of electromagnetic energy toward the plasma. In some embodiments, at least a portion of the high brightness light is directed toward the reflective surface of the chamber, is reflected toward the reflector, and passes through the reflector toward an output of the light source. In some embodiments, the light source comprises a microscope, ultraviolet microscope, wafer inspection system, reticle inspection system or lithography system spaced relative to the output of the light source to receive the high brightness light. In some embodiments, a portion of the high brightness light is directed toward the reflective surface of the chamber, is reflected toward the reflector, and electromagnetic energy comprising the second set of predefined wavelengths of electromagnetic energy passes through the reflector. The chamber of the light source can include a window. In some embodiments, the chamber is a sealed chamber. In some embodiments, the reflective surface of the chamber comprises a curved shape, parabolic shape, elliptical shape, spherical shape or aspherical shape. In some embodiments, the chamber has a reflective inner surface. In some embodiments, a coating or film is located on the outside of the chamber to produce the reflective surface. In some embodiments, a coating or film is located on the inside of the chamber to produce the reflective surface. In some embodiments, the reflective surface is a structure or optical element that is distinct from the inner surface of the chamber. The light source can include an optical element disposed along a path the electromagnetic energy from the laser travels. In some embodiments, the optical element is adapted to provide electromagnetic energy from the laser to the plasma over a large solid angle. In some embodiments, the reflective surface of the chamber is adapted to provide electromagnetic energy from the laser to the plasma over a large solid angle. In some embodiments, the reflective surface of the chamber is adapted to collect the high brightness light generated by the plasma over a large solid angle. In some embodiments, one or more of the reflective surface, reflector and the window include (e.g., are coated or include) a material to filter predefined wavelengths (e g, infrared wavelengths of electromagnetic energy) of electromagnetic energy. The invention, in another aspect, features a light source that includes a chamber that has a reflective surface. The light source also includes an ignition source for ionizing a gas within the chamber. The light source also includes at least one laser external to the chamber for providing electromagnetic energy to the ionized gas within the chamber to produce a plasma that generates a high brightness light. The light source also includes a reflector positioned along a path that the electromagnetic energy travels from the at least one laser to the reflective surface of the chamber. In some embodiments, the reflector is adapted to at least substantially reflect a first set of predefined wavelengths of electromagnetic energy directed toward the reflector and at least substantially allow a second set of predefined wavelengths of electromagnetic energy to pass through the reflector. The invention, in another aspect, relates to a method for producing light. The method involves ionizing with an ignition source a gas within a chamber that has a reflective surface. The method also involves providing laser energy to the ionized gas in the chamber to produce a plasma that generates a high brightness light. In some embodiments, the method involves directing the laser energy comprising a first set of wavelengths of electromagnetic energy through a reflector toward the reflective surface of the chamber, the reflective surface reflecting at least a portion of the first set of wavelengths of electromagnetic energy toward the plasma. In some embodiments, the method involves directing at least a portion of the high brightness light toward the reflective surface of the chamber which is reflected toward the reflector and is reflected by the reflector toward a tool. In some embodiments, the method involves directing the laser energy comprising a first set of wavelengths of electromagnetic energy toward the reflector, the reflector reflects at least a portion of the first wavelengths of electromagnetic energy toward the reflective surface of the chamber, the reflective surface directs a portion of the first set of wavelengths of electromagnetic energy toward the plasma. In some embodiments, the method involves directing a portion of the high brightness light toward the reflective surface of the chamber which is reflected toward the reflector and, electromagnetic energy comprising the second set of predefined wavelengths of electromagnetic energy passes through the reflector. The method can involve directing the laser energy through an optical element that modifies a property of the laser energy to direct the laser energy toward the plasma over a large solid angle. In some embodiments, the method involves directing the laser energy through an optical element that modifies a property of the laser energy to direct the laser energy toward the plasma over a solid angle of approximately 0.012 steradians. In some embodiments, the method involves directing the laser energy through an optical element that modifies a property of the laser energy to direct the laser energy toward the plasma over a solid angle of approximately 0.048 steradians. In some embodiments, the method involves directing the laser energy through an optical element that modifies a property of the laser energy to direct the laser energy toward the plasma over a solid angle of greater than about 2π (about 6.28) steradians. In some embodiments, the reflective surface of the chamber is adapted to provide the laser energy to the plasma over a large solid angle. In some embodiments, the reflective surface of the chamber is adapted to collect the high brightness light generated by the plasma over a large solid angle. The invention, in another aspect, relates to a method for producing light. The method involves ionizing with an ignition source a gas within a chamber that has a reflective surface. The method also involves directing electromagnetic energy from a laser toward a reflector that at least substantially reflects a first set of wavelengths of electromagnetic energy toward the ionized gas in the chamber to produce a plasma that generates a high brightness light. In some embodiments, the electromagnetic energy from the laser first is reflected by the reflector toward the reflective surface of the chamber. In some embodiments, the electromagnetic energy directed toward the reflective surface of the chamber is reflected toward the plasma. In some embodiments, a portion of the high brightness light is directed toward the reflective surface of the chamber, reflected toward the reflector and passes through the reflector. In some embodiments, the electromagnetic energy from the laser first passes through the reflector and travels toward the reflective surface of the chamber. In some embodiments, the electromagnetic energy directed toward the reflective surface of the chamber is reflected toward the plasma. In some embodiments, a portion of the high brightness light is directed toward the reflective surface of the chamber, reflected toward the reflector and reflected by the reflector. The invention, in another aspect, features a light source that includes a chamber having a reflective surface. The light source also includes a means for ionizing a gas within the chamber. The light source also includes a means for at least substantially reflecting a first set of predefined wavelengths of electromagnetic energy directed toward the reflector and at least substantially allowing a second set of predefined wavelengths of electromagnetic energy to pass through the reflector. The light source also includes a means for providing electromagnetic energy to the ionized gas within the chamber to produce a plasma that generates a high brightness light. The invention, in another aspect, features a light source that includes a sealed chamber. The light source also includes an ignition source for ionizing a gas within the chamber. The light source also includes at least one laser external to the sealed chamber for providing electromagnetic energy to the ionized gas within the chamber to produce a plasma that generates a high brightness light. The light source also includes a curved reflective surface disposed external to the sealed chamber to receive at least a portion of the high brightness light emitted by the sealed chamber and reflect the high brightness light toward an output of the light source. In some embodiments, the light source includes an optical element disposed along a path the electromagnetic energy from the laser travels. In some embodiments, the sealed chamber includes a support element that locates the sealed chamber relative to the curved reflective surface. In some embodiments, the sealed chamber is a quartz bulb. In some embodiments, the light source includes a second curved reflective surface disposed internal or external to the sealed chamber to receive at least a portion of the laser electromagnetic energy and focus the electromagnetic energy on the plasma that generates the high brightness light. The invention, in another aspect, features a light source that includes a sealed chamber and an ignition source for ionizing a gas within the chamber. The light source also includes at least one laser external to the sealed chamber for providing electromagnetic energy. The light source also includes a curved reflective surface to receive and reflect at least a portion of the electromagnetic energy toward the ionized gas within the chamber to produce a plasma that generates a high brightness light, the curved reflective surface also receives at least a portion of the high brightness light emitted by the plasma and reflects the high brightness light toward an output of the light source. In some embodiments, the curved reflective surface focuses the electromagnetic energy on a region in the chamber where the plasma is located. In some embodiments, the curved reflective surface is located within the chamber. In some embodiments, the curved reflective surface is located external to the chamber. In some embodiments, the high brightness light is ultraviolet light, includes ultraviolet light or is substantially ultraviolet light. The invention, in another aspect, features a light source that includes a chamber. The light source also includes an energy source for providing energy to a gas within the chamber to produce a plasma that generates a light emitted through the walls of the chamber. The light source also includes a reflector that reflects the light emitted through the walls of the chamber. The reflector includes a reflective surface with a shape configured to compensate for the refractive index of the walls of the chamber. The shape can include a modified parabolic, elliptical, spherical, or aspherical shape. In some embodiments, the energy source is at least one laser external to the chamber. In some embodiments, the energy source is also an ignition source within the chamber. The energy source can be a microwave energy source, an AC arc source, a DC arc source, a laser, or an RF energy source. The energy source can be a pulse laser, a continuous-wave fiber laser, or a diode laser. In some embodiments, the chamber is a sealed chamber. The chamber can include a cylindrical tube. In some embodiments, the cylindrical tube is tapered. The chamber can include one or more seals at one or both ends of the cylindrical tube. The chamber can include sapphire, quartz, fused quartz, Suprasil quartz, fused silica, Suprasil fused silica, MgF2, diamond, single crystal quartz, or CaF2. The chamber can include a dielectric material. The chamber can include an ultraviolet transparent dielectric material. The chamber can protrude through an opening in the reflector. In some embodiments, the light source also includes an ignition source for ionizing the gas within the chamber. The ignition source can include electrodes, an ultraviolet ignition source, a capacitive ignition source, an inductive ignition source, a flash lamp, a pulsed laser, or a pulsed lamp. The ignition source can include electrodes located on opposite sides of the plasma. In some embodiments, the light source also includes a support element that locates the chamber relative to the reflector. The support element can include a fitting to allow at least one of pressure control or filling of the chamber. In some embodiments, the light source includes at least one optical element. The optical element can modify a property of the light emitted through the walls of the chamber and reflected by the reflector. The optical element can be a mirror or a lens. The optical element can be configured to deliver the light emitted through the walls of the chamber and reflected by the reflector to a tool (e.g. a wafer inspection tool, a microscope, an ultraviolet microscope, a reticle inspection system, a metrology tool, a lithography tool, or an endoscopic tool). The invention, in another aspect, features a method for producing light. The method involves emitting a light through the walls of a chamber. The method also involves using a reflective surface of a reflector to reflect the light, wherein the reflective surface has a shape configured to compensate for the refractive index of the walls of the chamber. In some embodiments, the method also involves flowing gas into the chamber. In some embodiments, the method also involves igniting the gas in the chamber to produce an ionized gas. In some embodiments, the method also involves directing energy to the ionized gas to produce a plasma that generates a light (e.g. a high brightness light). In some embodiments, the method also involves directing laser energy into the chamber from at least one laser external to the chamber. In some embodiments, the method also involves directing the laser energy through an optical element that modifies a property of the laser energy. In some embodiments, the method also involves directing the reflected light through an optical element to modify a property of the reflected light. In some embodiments, the method also involves directing the reflected light to a tool. In some embodiments, the method also involves controlling the pressure of the chamber. In some embodiments, the method also involves expressing the shape as a mathematical equation. In some embodiments, the method also involves selecting parameters of the equation to reduce error due to the refractive index of the walls of the chamber below a specified value. In some embodiments, the method also involves configuring the shape to compensate for the refractive index of the walls of the chamber. In some embodiments, the method also involves producing a collimated or focused beam of reflected light with the reflective surface. In some embodiments, the method also involves modifying a parabolic, elliptical, spherical, or aspherical shape to compensate for the refractive index of the walls of the chamber to produce a focused, reflected high brightness light. The invention, in another aspect, features a light source including a chamber. The light source also includes a laser source for providing electromagnetic energy to a gas within the chamber to produce a plasma that generates a light emitted through the walls of the chamber. The light source also includes a reflector that reflects the electromagnetic energy through the walls of the chamber and the light emitted through the walls of the chamber, the reflector includes a reflective surface with a shape configured to compensate for the refractive index of the walls of the chamber. The invention, in another aspect, features a light source having a chamber. The light source also includes means for providing energy to a gas within the chamber to produce a plasma that generates a light emitted through the walls of the chamber. The light source also includes means for reflecting the light emitted through the walls of the chamber, the reflecting means including a reflective surface with a shape configured to compensate for the refractive index of the walls of the chamber. The invention, in another aspect, features a light source having a chamber. The light source also includes an ignition source for ionizing a medium (e.g., a gas) within the chamber. The light source also includes a laser for providing energy to the ionized medium within the chamber to produce a light. The light source also includes a blocker suspended along a path the energy travels to block at least a portion of the energy. In some embodiments, the blocker deflects energy provided to the ionized medium that is not absorbed by the ionized medium away from an output of the light source. In some embodiments, the blocker is a mirror. In some embodiments, the blocker absorbs the energy provided to the ionized medium that is not absorbed by the ionized medium. The blocker can include graphite. In some embodiments, the blocker reflects energy provided to the ionized medium that is not absorbed by the ionized medium. In some embodiments, the reflected energy is reflected toward the ionized medium in the chamber. In some embodiments, the blocker is a coating on a portion of the chamber. In some embodiments, the light source includes a coolant channel disposed in the blocker. In some embodiments, the light source includes a coolant supply (e.g., for supplying coolant, for example, water) coupled to the coolant channel. In some embodiments, light source includes a gas source that blows a gas (e.g., nitrogen or air) on the blocker to cool the blocker. In some embodiments, the light source includes an arm connecting the blocker to a housing of the light source. In some embodiments, the energy provided by the laser enters the chamber on a first side of the chamber and the blocker is suspended on a second side of the chamber opposite the first side. The invention, in another aspect, relates to a method for producing light. The method involves ionizing with an ignition source a medium within a chamber. The method also involves providing laser energy to the ionized medium in the chamber to produce a light. The method also involves blocking energy provided to the ionized medium that is not absorbed by the ionized medium with a blocker suspended along a path the energy travels. In some embodiments, blocking the energy involves deflecting the energy away from an output of the light source. In some embodiments, the blocker includes a mirror. In some embodiments, blocking the energy includes absorbing the energy. In some embodiments, blocking the energy includes reflecting the energy. In some embodiments, reflecting the energy includes reflecting the energy towards the ionized medium in the chamber. In some embodiments, the method also involves cooling the blocker. In some embodiments, cooling the blocker includes flowing a coolant through a channel in or coupled to the blocker. In some embodiments, the method involves blowing a gas on the blocker to cooler the blocker. The invention, in another aspect, relates to a method for producing light. The method involves ionizing with an ignition source a gas within a chamber. The method also involves providing laser energy to the ionized gas in the chamber at a pressure of greater than 10 atmospheres to produce a high brightness light. In some embodiments, the gas within the chamber is at a pressure of greater than 30 atmospheres. In some embodiments, the gas within the chamber is at a pressure of greater than 50 atmospheres. In some embodiments, the high brightness light is emitted from a plasma having a volume of about 0.01 mm3. The invention, in another aspect, relates to a light source having a chamber with a gas disposed therein, and ignition source and at least one laser. The ignition source excites the gas. The excited gas has at least one strong absorption line at an infrared wavelength. The at least one laser provides energy to the excited gas at a wavelength near a strong absorption line of the excited gas within the chamber to produce a high brightness light. In some embodiments, the gas comprises a noble gas. The gas can comprise xenon. In some embodiments, the excited gas comprises atoms at a lowest excited state. The gas can be absorptive near the wavelength of the at least one laser. The strong absorption line of the excited gas can be about 980 nm or about 882 nm. In some embodiments, the excited gas is in a metastable state. The invention, in another aspect, relates to a method for producing light. An ignition source excites a gas within a chamber. A laser is tuned to a first wavelength to provide energy to the excited gas in the chamber to produce a high brightness light. The excited gas absorbs energy near the first wavelength. The laser is tuned to a second wavelength to provide energy to the excited gas in the chamber to maintain the high brightness light. The excited gas absorbs energy near the second wavelength. In some embodiments, the laser is tuned to the first and second wavelengths by adjusting the operating temperature of the laser. In some embodiments, the laser is a diode laser and the laser is tuned approximately 0.4 nm per degree Celsius of temperature adjustment. The operating temperature of the laser can be adjusted by varying a current of a thermoelectric cooling device. The gas within the chamber can have atoms with electrons in at least one excited atomic state. The gas within chamber can be a noble gas, and in some embodiments, the gas within the chamber is xenon. In some embodiments, the first wavelength is approximately 980 nm. The second wavelength can be approximately 975 nm. The second wavelength can be approximately 1 nm to approximately 10 nm displaced from the first wavelength. The invention, in another aspect, relates to a light source. The light source includes a chamber having one or more walls and a gas disposed within the chamber. The light source also includes at least one laser for providing a converging beam of energy focused on the gas within the chamber to produce a plasma that generates a light emitted through the walls of the chamber, such that a numerical aperture of the converging beam of energy is between about 0.1 to about 0.8. In some embodiments, the numerical aperture is about 0.4 to about 0.6. The numeral aperture can be about 0.5. The light source can also include an optical element within a path of the beam. The optical element can be capable of increasing the numerical aperture of the beam. In some embodiments, the optical element is a lens or a mirror. The lens can be an aspheric lens. In some embodiments, a spectral radiance of the plasma increases with an increase in numerical aperture of the beam. The invention, in another aspect, relates to a method of pre-aligning a bulb for a light source. The bulb, having two electrodes, is coupled to a mounting base. The bulb and mounting base structure are inserting into a camera assembly. The camera assembly includes at least one camera and a display screen. At least one image of the bulb from the at least one camera is displays on the display screen. A position of the bulb within the mounted base is adjusted such that a region of the bulb between the two electrodes aligns with a positioning grid on the display screen. In some embodiments, a lamp for a light source is pre-aligned using the method described herein. In some embodiments, the method also includes toggling between the at least two cameras to align the bulb. The camera assembly can include two cameras. Images from the two cameras can be displayed in different colors. In some embodiments, the two cameras are positioned to capture images of the bulb from two orthogonal directions. The position of the bulb can be adjusted vertically and horizontally. The position of the bulb can be adjusted by a manipulator. The manipulator can be positioned above the bulb and can be capable of moving the bulb vertically and horizontally. The method can also include securing the bulb to a base after the region of the bulb between the two electrodes aligns with the positioning grid on the display screen. In some embodiments, the positioning grid is pre-determined such that when the center area of the bulb between the two electrodes aligns with the positioning grid on the display screen, the region is aligned relative to a focal point of a laser when the bulb and mounting base are inserted into a light source. The invention, in another aspect, relates to a method for decreasing noise within a light source. The light source includes a laser. A sample of light emitted from the light source is collected. The sample of light is converted to an electrical signal. The electrical is compared to a reference signal to obtain an error signal. The error signal is processed to obtain a control signal. A magnitude of a laser of the light source is set based on the control signal to decrease noise within the light source. These steps can be repeated until a desired amount of noise is reached. In some embodiments, the sample of light emitted from the light source is collected from a beam splitter. The beam splitter can be a glass beam splitter or a bifurcated fiber bundle. In some embodiments, the error signal is the difference between the reference sample and the converted sample. The error signal can be processed by a control amplifier. The control amplifier is capable of outputting a control signal proportional to at least one of a time integral, a time derivative, or a magnitude of the error signal. The sample can be collected using a photodiode. In some embodiments, the sample is collected using a photodiode within a casing of the light source. In some embodiments, the sample is collected using a photodiode external to a casing of the light source. In some embodiments, two samples are collected. One sample can be collected using a first photodiode within a casing of the light source and another sample can be collected using a second photodiode external to the casing of the light source. The invention, in another aspect, relates to a light source. The light source includes a chamber having one or more walls and a gas disposed within the chamber. The light source also includes at least one laser for providing energy to the gas within the chamber to produce a plasma that generates a light emitted through the walls of the chamber. A dichroic mirror is positioned within a path of the at least one laser such that the laser energy is directed toward the plasma. The dichroic mirror selectively reflects at least one wavelength of light such that the light generated by the plasma is not substantially reflected toward the at least one laser. The invention, in another aspect, relates to a light source. The light source has a chamber with a gas disposed therein and an ignition source for exciting the gas. The light source also has at least one laser for providing energy to the excited gas within the chamber to produce a high brightness light having a first spectrum. An optical element is disposed within the path of the high brightness light to modify the first spectrum of the high brightness light to a second spectrum. The optical element can be a prism, a weak lens, a strong lens, or a dichroic filter. In some embodiments, the second spectrum has a greater proportion of intensity of light in the ultraviolet range than the first spectrum. In some embodiments, the first spectrum has a greater proportion of intensity of light in the visible range than the second spectrum. The invention, in another aspect, relates to a method for decreasing noise of a light source within a predetermined frequency band. The light source includes a laser diode. A current of the laser diode is modulated at a frequency greater than the predetermined frequency band causing the laser to rapidly switch between different sets of modes to decrease noise of the light source within the predetermined frequency band. The foregoing and other objects, aspects, features, and advantages of the invention will become more apparent from the following description and from the claims. FIG. 1 is a schematic block diagram of a light source 100 for generating light that embodies the invention. The light source 100 includes a chamber 128 that contains an ionizable medium (not shown). The light source 100 provides energy to a region 130 of the chamber 128 having the ionizable medium which creates a plasma 132. The plasma 132 generates and emits a high brightness light 136 that originates from the plasma 132. The light source 100 also includes at least one laser source 104 that generates a laser beam that is provided to the plasma 132 located in the chamber 128 to initiate and/or sustain the high brightness light 136. In some embodiments, it is desirable for at least one wavelength of electromagnetic energy generated by the laser source 104 to be strongly absorbed by the ionizable medium in order to maximize the efficiency of the transfer of energy from the laser source 104 to the ionizable medium. In some embodiments, it is desirable for the plasma 132 to be small in size in order to achieve a high brightness light source. Brightness is the power radiated by a source of light per unit surface area into a unit solid angle. The brightness of the light produced by a light source determines the ability of a system (e.g., a metrology tool) or an operator to see or measure things (e.g., features on the surface of a wafer) with adequate resolution. It is also desirable for the laser source 104 to drive and/or sustain the plasma with a high power laser beam. Generating a plasma 132 that is small in size and providing the plasma 132 with a high power laser beam leads simultaneously to a high brightness light 136. The light source 100 produces a high brightness light 136 because most of the power introduced by the laser source 104 is then radiated from a small volume, high temperature plasma 132. The plasma 132 temperature will rise due to heating by the laser beam until balanced by radiation and other processes. The high temperatures that are achieved in the laser sustained plasma 132 yield increased radiation at shorter wavelengths of electromagnetic energy, for example, ultraviolet energy. In one experiment, temperatures between about 10,000 K and about 20,000 K have been observed. The radiation of the plasma 132, in a general sense, is distributed over the electromagnetic spectrum according to Planck's radiation law. The wavelength of maximum radiation is inversely proportional to the temperature of a black body according to Wien's displacement law. While the laser sustained plasma is not a black body, it behaves similarly and as such, the highest brightness in the ultraviolet range at around 300 nm wavelength is expected for laser sustained plasmas having a temperature of between about 10,000 K and about 15,000 K. Most conventional arc lamps are, however, unable to operate at these temperatures. It is therefore desirable in some embodiments of the invention to maintain the temperature of the plasma 132 during operation of the light source 100 to ensure that a sufficiently bright light 136 is generated and that the light emitted is substantially continuous during operation. In this embodiment, the laser source 104 is a diode laser that outputs a laser beam via a fiberoptic element 108. The fiber optic element 108 provides the laser beam to a collimator 112 that aids in conditioning the output of the diode laser by aiding in making laser beam rays 116 substantially parallel to each other. The collimator 112 then directs the laser beam 116 to a beam expander 118. The beam expander 118 expands the size of the laser beam 116 to produce laser beam 122. The beam expander 118 also directs the laser beam 122 to an optical lens 120. The optical lens 120 is configured to focus the laser beam 122 to produce a smaller diameter laser beam 124 that is directed to the region 130 of the chamber 128 where the plasma 132 exists (or where it is desirable for the plasma 132 to be generated and sustained). In this embodiment, the light source 100 also includes an ignition source 140 depicted as two electrodes (e.g., an anode and cathode located in the chamber 128). The ignition source 140 generates an electrical discharge in the chamber 128 (e.g., the region 130 of the chamber 128) to ignite the ionizable medium. The laser then provides laser energy to the ionized medium to sustain or create the plasma 132 which generates the high brightness light 136. The light 136 generated by the light source 100 is then directed out of the chamber to, for example, a wafer inspection system (not shown). Alternative laser sources are contemplated according to illustrative embodiments of the invention. In some embodiments, neither the collimator 112, the beam expander 118, or the lens 120 may be required. In some embodiments, additional or alternative optical elements can be used. The laser source can be, for example, an infrared (IR) laser source, a diode laser source, a fiber laser source, an ytterbium laser source, a CO2 laser source, a YAG laser source, or a gas discharge laser source. In some embodiments, the laser source 104 is a pulse laser source (e.g., a high pulse rate laser source) or a continuous wave laser source. Fiber lasers use laser diodes to pump a special doped fiber which then lasers to produce the output (i.e., a laser beam). In some embodiments, multiple lasers (e.g., diode lasers) are coupled to one or more fiber optic elements (e.g., the fiber optic element 108). Diode lasers take light from one (or usually many) diodes and direct the light down a fiber to the output. In some embodiments, fiber laser sources and direct semiconductor laser sources are desirable for use as the laser source 104 because they are relatively low in cost, have a small form factor or package size, and are relatively high in efficiency. Efficient, cost effective, high power lasers (e.g., fiber lasers and direct diode lasers) are recently available in the NIR (near infrared) wavelength range from about 700 nm to about 2000 nm. Energy in this wavelength range is more easily transmitted through certain materials (e.g., glass, quartz and sapphire) that are more commonly used to manufacture bulbs, windows and chambers. It is therefore more practical now to produce light sources that operate using lasers in the 700 nm to 2000 nm range than has previously been possible. In some embodiments, the laser source 104 is a high pulse rate laser source that provides substantially continuous laser energy to the light source 100 sufficient to produce the high brightness light 136. In some embodiments, the emitted high brightness light 136 is substantially continuous where, for example, magnitude (e.g. brightness or power) of the high brightness light does not vary by more than about 90% during operation. In some embodiments, the ratio of the peak power of the laser energy delivered to the plasma to the average power of the laser energy delivered to the plasma is approximately 2-3. In some embodiments, the substantially continuous energy provided to the plasma 132 is sufficient to minimize cooling of the ionized medium to maintain a desirable brightness of the emitted light 136. In this embodiment, the light source 100 includes a plurality of optical elements (e.g., a beam expander 118, a lens 120, and fiber optic element 108) to modify properties (e.g., diameter and orientation) of the laser beam delivered to the chamber 132. Various properties of the laser beam can be modified with one or more optical elements (e.g., mirrors or lenses). For example, one or more optical elements can be used to modify the portions of, or the entire laser beam diameter, direction, divergence, convergence, numerical aperture and orientation. In some embodiments, optical elements modify the wavelength of the laser beam and/or filter out certain wavelengths of electromagnetic energy in the laser beam. Lenses that can be used in various embodiments of the invention include, aplanatic lenses, achromatic lenses, single element lenses, and fresnel lenses. Mirrors that can be used in various embodiments of the invention include, coated mirrors, dielectric coated mirrors, narrow band mirrors, and ultraviolet transparent infrared reflecting mirrors. By way of example, ultraviolet transparent infrared reflecting mirrors are used in some embodiments of the invention where it is desirable to filter out infrared energy from a laser beam while permitting ultraviolet energy to pass through the mirror to be delivered to a tool (e.g., a wafer inspection tool, a microscope, a lithography tool or an endoscopic tool). In this embodiment, the chamber 128 is a sealed chamber initially containing the ionizable medium (e.g., a solid, liquid or gas). In some embodiments, the chamber 128 is instead capable of being actively pumped where one or more gases are introduced into the chamber 128 through a gas inlet (not shown), and gas is capable of exiting the chamber 128 through a gas outlet (not shown). The chamber can be fabricated from or include one or more of, for example, a dielectric material, a quartz material, Suprasil quartz, sapphire, MgF2, diamond or CaF2. The type of material may be selected based on, for example, the type of ionizable medium used and/or the wavelengths of light 136 that are desired to be generated and output from the chamber 128. In some embodiments, a region of the chamber 128 is transparent to, for example, ultraviolet energy. Chambers 128 fabricated using quartz will generally allow wavelengths of electromagnetic energy of as long as about 2 microns to pass through walls of the chamber. Sapphire chamber walls generally allow electromagnetic energy of as long as about 4 microns to pass through the walls. In some embodiments, it is desirable for the chamber 128 to be a sealed chamber capable of sustaining high pressures and temperatures. For example, in one embodiment, the ionizable medium is mercury vapor. To contain the mercury vapor during operation, the chamber 128 is a sealed quartz bulb capable of sustaining pressures between about 10 to about 200 atmospheres and operating at about 900 degrees centigrade. The quartz bulb also allows for transmission of the ultraviolet light 136 generated by the plasma 132 of the light source 100 through the chamber 128 walls. Various ionizable media can be used in alternative embodiments of the invention. For example, the ionizable medium can be one or more of a noble gas, Xe, Ar, Ne, Kr, He, D2, H2, O2, F2, a metal halide, a halogen, Hg, Cd, Zn, Sn, Ga, Fe, Li, Na, an excimer forming gas, air, a vapor, a metal oxide, an aerosol, a flowing media, or a recycled media. In some embodiments, a solid or liquid target (not shown) in the chamber 128 is used to generate an ionizable gas in the chamber 128. The laser source 104 (or an alternative laser source) can be used to provide energy to the target to generate the ionizable gas. The target can be, for example, a pool or film of metal. In some embodiments, the target is a solid or liquid that moves in the chamber (e.g., in the form of droplets of a liquid that travel through the region 130 of the chamber 128). In some embodiments, a first ionizable gas is first introduced into the chamber 128 to ignite the plasma 132 and then a separate second ionizable gas is introduced to sustain the plasma 132. In this embodiment, the first ionizable gas is a gas that is more easily ignited using the ignition source 140 and the second ionizable gas is a gas that produces a particular wavelength of electromagnetic energy. In this embodiment, the ignition source 140 is a pair of electrodes located in the chamber 128. In some embodiments, the electrodes are located on the same side of the chamber 128. A single electrode can be used with, for example, an RF ignition source or a microwave ignition source. In some embodiments, the electrodes available in a conventional arc lamp bulb are the ignition source (e.g., a model USH-200DP quartz bulb manufactured by Ushio (with offices in Cypress, Calif.)). In some embodiments, the electrodes are smaller and/or spaced further apart than the electrodes used in a conventional arc lamp bulb because the electrodes are not required for sustaining the high brightness plasma in the chamber 128. Various types and configurations of ignition sources are also contemplated, however, that are within the scope of the present invention. In some embodiments, the ignition source 140 is external to the chamber 128 or partially internal and partially external to the chamber 128. Alternative types of ignition sources 140 that can be used in the light source 100 include ultraviolet ignition sources, capacitive discharge ignition sources, inductive ignition sources, RF ignition sources, a microwave ignition sources, flash lamps, pulsed lasers, and pulsed lamps. In one embodiment, no ignition source 140 is required and instead the laser source 104 is used to ignite the ionizable medium and to generate the plasma 132 and to sustain the plasma and the high brightness light 136 emitted by the plasma 132. In some embodiments, it is desirable to maintain the temperature of the chamber 128 and the contents of the chamber 128 during operation of the light source 100 to ensure that the pressure of gas or vapor within the chamber 128 is maintained at a desired level. In some embodiments, the ignition source 140 can be operated during operation of the light source 100, where the ignition source 140 provides energy to the plasma 132 in addition to the energy provided by the laser source 104. In this manner, the ignition source 140 is used to maintain (or maintain at an adequate level) the temperature of the chamber 128 and the contents of the chamber 128. In some embodiments, the light source 100 includes at least one optical element (e.g., at least one mirror or lens) for modifying a property of the electromagnetic energy (e.g., the high brightness light 136) emitted by the plasma 132 (e.g., an ionized gas), similarly as described elsewhere herein. FIG. 2 is a schematic block diagram of a portion of a light source 200 incorporating principles of the present invention. The light source 200 includes a chamber 128 containing an ionizable gas and has a window 204 that maintains a pressure within the chamber 128 while also allowing electromagnetic energy to enter the chamber 128 and exit the chamber 128. In this embodiment, the chamber 128 has an ignition source (not shown) that ignites the ionizable gas (e.g., mercury or xenon) to produce a plasma 132. A laser source 104 (not shown) provides a laser beam 216 that is directed through a lens 208 to produce laser beam 220. The lens 208 focuses the laser beam 220 on to a surface 224 of a thin film reflector 212 that reflects the laser beam 220 to produce laser beam 124. The reflector 212 directs the laser beam 124 on region 130 where the plasma 132 is located. The laser beam 124 provides energy to the plasma 132 to sustain and/or generate a high brightness light 136 that is emitted from the plasma 132 in the region 130 of the chamber 128. In this embodiment, the chamber 128 has a paraboloid shape and an inner surface 228 that is reflective. The paraboloid shape and the reflective surface cooperate to reflect a substantial amount of the high brightness light 136 toward and out of the window 204. In this embodiment, the reflector 212 is transparent to the emitted light 136 (e.g., at least one or more wavelengths of ultraviolet light). In this manner, the emitted light 136 is transmitted out of the chamber 128 and directed to, for example, a metrology tool (not shown). In one embodiment, the emitted light 136 is first directed towards or through additional optical elements before it is directed to a tool. By way of illustration, an experiment was conducted to generate ultraviolet light using a light source, according to an illustrative embodiment of the invention. A model L6724 quartz bulb manufactured by Hamamatsu (with offices in Bridgewater, N.J.) was used as the chamber of the light source (e.g., the chamber 128 of the light source 100 of FIG. 1) for experiments using xenon as the ionizable medium in the chamber. A model USH-200DP quartz bulb manufactured by Ushio (with offices in Cypress, Calif.) was used as the chamber of the light source for experiments using mercury as the ionizable medium in the chamber. FIG. 3 illustrates a plot 300 of the UV brightness of a high brightness light produced by a plasma located in the chamber as a function of the laser power (in watts) provided to the plasma. The laser source used in the experiment was a 1.09 micron, 100 watt CW laser. The Y-Axis 312 of the plot 300 is the UV brightness (between about 200 and about 400 nm) in watts/mm2 steradian (sr). The X-Axis 316 of the plot 300 is the laser beam power in watts provided to the plasma. Curve 304 is the UV brightness of the high brightness light produced by a plasma that was generated using xenon as the ionizable medium in the chamber. The plasma in the experiment using xenon was between about 1 mm and about 2 mm in length and about 0.1 mm in diameter. The length of the plasma was controlled by adjusting the angle of convergence of the laser beam. A larger angle (i.e., larger numerical aperture) leads to a shorter plasma because the converging beam reaches an intensity capable of sustaining the plasma when it is closer to the focal point. Curve 308 is the UV brightness of the high brightness light produced by a plasma that was generated using mercury as the ionizable medium in the chamber. The plasma in the experiment using mercury was about 1 mm in length and about 0.1 mm in diameter. By way of illustration, another experiment was conducted to generate ultraviolet using a light source according to an illustrative embodiment of the invention. A model USH-200DP quartz bulb manufactured by Ushio (with offices in Cypress, Calif.) was used as the chamber of the light source for experiments using mercury as the ionizable medium in the chamber (e.g., the chamber 128 of the light source 100 of FIG. 1). The laser source used in the experiment was a 1.09 micron, 100 watt ytterbium doped fiber laser from SPI Lasers PLC (with offices in Los Gatos, Calif.). FIG. 4 illustrates a plot 400 of the transmission of laser energy through a plasma located in the chamber generated from mercury versus the amount of power provided to the plasma in watts. The Y-Axis 412 of the plot 400 is the transmission coefficient in non-dimensional units. The X-Axis 416 of the plot 400 is the laser beam power in watts provided to the plasma. The curve in the plot 400 illustrates absorption lengths of 1 mm were achieved using the laser source. The transmission value of 0.34 observed at 100 watts corresponds to a 1/e absorption length of about 1 mm. FIG. 5 is a schematic block diagram of a portion of a light source 500 incorporating principles of the present invention. The light source 500 includes a chamber 528 that has a reflective surface 540. The reflective surface 540 can have, for example, a parabolic shape, elliptical shape, curved shape, spherical shape or aspherical shape. In this embodiment, the light source 500 has an ignition source (not shown) that ignites an ionizable gas (e.g., mercury or xenon) in a region 530 within the chamber 528 to produce a plasma 532. In some embodiments, the reflective surface 540 can be a reflective inner or outer surface. In some embodiments, a coating or film is located on the inside or outside of the chamber to produce the reflective surface 540. A laser source (not shown) provides a laser beam 516 that is directed toward a surface 524 of a reflector 512. The reflector 512 reflects the laser beam 520 toward the reflective surface 540 of the chamber 528. The reflective surface 540 reflects the laser beam 520 and directs the laser beam toward the plasma 532. The laser beam 516 provides energy to the plasma 532 to sustain and/or generate a high brightness light 536 that is emitted from the plasma 532 in the region 530 of the chamber 528. The high brightness light 536 emitted by the plasma 532 is directed toward the reflective surface 540 of the chamber 528. At least a portion of the high brightness light 536 is reflected by the reflective surface 540 of the chamber 528 and directed toward the reflector 512. The reflector 512 is substantially transparent to the high brightness light 536 (e.g., at least one or more wavelengths of ultraviolet light). In this manner, the high brightness light 536 passes through the reflector 512 and is directed to, for example, a metrology tool (not shown). In some embodiments, the high brightness light 536 is first directed towards or through a window or additional optical elements before it is directed to a tool. In some embodiments, the light source 500 includes a separate, sealed chamber (e.g., the sealed chamber 728 of FIG. 7) located in the concave region of the chamber 528. The sealed chamber contains the ionizable gas that is used to create the plasma 532. In alternative embodiments, the sealed chamber contains the chamber 528. In some embodiments, the sealed chamber also contains the reflector 512. FIG. 6 is a schematic block diagram of a portion of a light source 600 incorporating principles of the present invention. The light source 600 includes a chamber 628 that has a reflective surface 640. The reflective surface 640 can have, for example, a parabolic shape, elliptical shape, curved shape, spherical shape or aspherical shape. In this embodiment, the light source 600 has an ignition source (not shown) that ignites an ionizable gas (e.g., mercury or xenon) in a region 630 within the chamber 628 to produce a plasma 632. A laser source (not shown) provides a laser beam 616 that is directed toward a reflector 612. The reflector 612 is substantially transparent to the laser beam 616. The laser beam 616 passes through the reflector 612 and is directed toward the reflective surface 640 of the chamber 628. The reflective surface 640 reflects the laser beam 616 and directs it toward the plasma 632 in the region 630 of the chamber 628. The laser beam 616 provides energy to the plasma 632 to sustain and/or generate a high brightness light 636 that is emitted from the plasma 632 in the region 630 of the chamber 628. The high brightness light 636 emitted by the plasma 632 is directed toward the reflective surface 640 of the chamber 628. At least a portion of the high brightness light 636 is reflected by the reflective surface 640 of the chamber 628 and directed toward a surface 624 of the reflector 612. The reflector 612 reflects the high brightness light 636 (e.g., at least one or more wavelengths of ultraviolet light). In this manner, the high brightness light 636 (e.g., visible and/or ultraviolet light) is directed to, for example, a metrology tool (not shown). In some embodiments, the high brightness light 636 is first directed towards or through a window or additional optical elements before it is directed to a tool. In some embodiments, the high brightness light 636 includes ultraviolet light. Ultraviolet light is electromagnetic energy with a wavelength shorter than that of visible light, for instance between about 50 nm and 400 nm. In some embodiments, the light source 600 includes a separate, sealed chamber (e.g., the sealed chamber 728 of FIG. 7) located in the concave region of the chamber 628. The sealed chamber contains the ionizable gas that is used to create the plasma 632. In alternative embodiments, the sealed chamber contains the chamber 628. In some embodiments, the sealed chamber also contains the reflector 612. FIG. 7 is a schematic block diagram of a light source 700 for generating light that embodies the invention. The light source 700 includes a sealed chamber 728 (e.g., a sealed quartz bulb) that contains an ionizable medium (not shown). The light source 700 provides energy to a region 730 of the chamber 728 having the ionizable medium which creates a plasma 732. The plasma 732 generates and emits a high brightness light 736 that originates from the plasma 732. The light source 700 also includes at least one laser source 704 that generates a laser beam that is provided to the plasma 732 located in the chamber 728 to initiate and/or sustain the high brightness light 736. In this embodiment, the laser source 704 is a diode laser that outputs a laser beam via a fiberoptic element 708. The fiber optic element 708 provides the laser beam to a collimator 712 that aids in conditioning the output of the diode laser by aiding in making laser beam rays 716 substantially parallel to each other. The collimator 712 then directs the laser beam 716 to a beam expander 718. The beam expander 718 expands the size of the laser beam 716 to produce laser beam 722. The beam expander 718 also directs the laser beam 722 to an optical lens 720. The optical lens 720 is configured to focus the laser beam 722 to produce a smaller diameter laser beam 724. The laser beam 724 passes through an aperture or window 772 located in the base 724 of a curved reflective surface 740 and is directed toward the chamber 728. The chamber 728 is substantially transparent to the laser beam 724. The laser beam 724 passes through the chamber 728 and toward the region 730 of the chamber 728 where the plasma 732 exists (or where it is desirable for the plasma 732 to be generated by the laser 724 and sustained). In this embodiment, the ionizable medium is ignited by the laser beam 724. In alternative embodiments, the light source 700 includes an ignition source (e.g., a pair of electrodes or a source of ultraviolet energy) that, for example, generates an electrical discharge in the chamber 728 (e.g., the region 730 of the chamber 728) to ignite the ionizable medium. The laser source 704 then provides laser energy to the ionized medium to sustain the plasma 732 which generates the high brightness light 736. The chamber 728 is substantially transparent to the high brightness light 736 (or to predefined wavelengths of electromagnetic radiation in the high brightness light 736). The light 736 (e.g., visible and/or ultraviolet light) generated by the light source 700 is then directed out of the chamber 728 toward an inner surface 744 of the reflective surface 740. In this embodiment, the light source 700 includes a plurality of optical elements (e.g., a beam expander 718, a lens 720, and fiber optic element 708) to modify properties (e.g., diameter and orientation) of the laser beam delivered to the chamber 732. Various properties of the laser beam can be modified with one or more optical elements (e.g., mirrors or lenses). For example, one or more optical elements can be used to modify the portions of, or the entire laser beam diameter, direction, divergence, convergence, and orientation. In some embodiments, optical elements modify the wavelength of the laser beam and/or filter out certain wavelengths of electromagnetic energy in the laser beam. Lenses that can be used in various embodiments of the invention include, aplanatic lenses, achromatic lenses, single element lenses, and fresnel lenses. Mirrors that can be used in various embodiments of the invention include, coated mirrors, dielectric coated mirrors, narrow band mirrors, and ultraviolet transparent infrared reflecting mirrors. By way of example, ultraviolet transparent infrared reflecting mirrors are used in some embodiments of the invention where it is desirable to filter out infrared energy from a laser beam while permitting ultraviolet energy to pass through the mirror to be delivered to a tool (e.g., a wafer inspection tool, a microscope, a lithography tool or an endoscopic tool). FIGS. 8A and 8B are schematic block diagrams of a light source 800 for generating light that embodies the invention. The light source 800 includes a chamber 828 that contains an ionizable medium (not shown). The light source 800 provides energy to a region 830 of the chamber 828 having the ionizable medium which creates a plasma. The plasma generates and emits a high brightness light that originates from the plasma. The light source 800 also includes at least one laser source 804 that generates a laser beam that is provided to the plasma located in the chamber 828 to initiate and/or sustain the high brightness light. In some embodiments, it is desirable for the plasma to be small in size in order to achieve a high brightness light source. Brightness is the power radiated by a source of light per unit surface area into a unit solid angle. The brightness of the light produced by a light source determines the ability of a system (e.g., a metrology tool) or an operator to see or measure things (e.g., features on the surface of a wafer) with adequate resolution. It is also desirable for the laser source 804 to drive and/or sustain the plasma with a high power laser beam. Generating a plasma that is small in size and providing the plasma with a high power laser beam leads simultaneously to a high brightness light. The light source 800 produces a high brightness light because most of the power introduced by the laser source 804 is then radiated from a small volume, high temperature plasma. The plasma temperature will rise due to heating by the laser beam until balanced by radiation and other processes. The high temperatures that are achieved in the laser sustained plasma yield increased radiation at shorter wavelengths of electromagnetic energy, for example, ultraviolet energy. In one experiment, temperatures between about 10,000 K and about 20,000 K have been observed. The radiation of the plasma, in a general sense, is distributed over the electromagnetic spectrum according to Planck's radiation law. The wavelength of maximum radiation is inversely proportional to the temperature of a black body according to Wien's displacement law. While the laser sustained plasma is not a black body, it behaves similarly and as such, the highest brightness in the ultraviolet range at around 300 nm wavelength is expected for laser sustained plasmas having a temperature of between about 10,000 K and about 15,000 K. Conventional arc lamps are, however, unable to operate at these temperatures. It is desirable in some embodiments of the invention to deliver the laser energy to the plasma in the chamber 828 over a large solid angle in order to achieve a plasma that is small in size. Various methods and optical elements can be used to deliver the laser energy over a large solid angle. In this embodiment of the invention, parameters of a beam expander and optical lens are varied to modify the size of the solid angle over which the laser energy is delivered to the plasma in the chamber 828. Referring to FIG. 8A, the laser source 804 is a diode laser that outputs a laser beam via a fiberoptic element 808. The fiber optic element 808 provides the laser beam to a collimator 812 that aids in conditioning the output of the diode laser by aiding in making laser beam rays 816 substantially parallel to each other. The collimator 812 directs the laser beam 816 to an optical lens 820. The optical lens 820 is configured to focus the laser beam 816 to produce a smaller diameter laser beam 824 having a solid angle 878. The laser beam 824 is directed to the region 830 of the chamber 828 where the plasma 832 exists. In this embodiment, the light source 800 also includes an ignition source 840 depicted as two electrodes (e.g., an anode and cathode located in the chamber 828). The ignition source 840 generates an electrical discharge in the chamber 828 (e.g., the region 830 of the chamber 828) to ignite the ionizable medium. The laser then provides laser energy to the ionized medium to sustain or create the plasma 832 which generates the high brightness light 836. The light 836 generated by the light source 800 is then directed out of the chamber to, for example, a wafer inspection system (not shown). FIG. 8B illustrates an embodiment of the invention in which the laser energy is delivered to the plasma in the chamber 828 over a solid angle 874. This embodiment of the invention includes a beam expander 854. The beam expander 854 expands the size of the laser beam 816 to produce laser beam 858. The beam expander 854 directs the laser beam 858 to an optical lens 862. The combination of the beam expander 854 and the optical lens 862 produces a laser beam 866 that has a solid angle 874 that is larger than the solid angle 878 of the laser beam 824 of FIG. 8A. The larger solid angle 874 of FIG. 8B creates a smaller size plasma 884 than the size of the plasma in FIG. 8A. In this embodiment, the size of the plasma 884 in FIG. 8B along the X-axis and Y-axis is smaller than the size of the plasma 832 in FIG. 8A. In this manner, the light source 800 generates a brighter light 870 in FIG. 8B as compared with the light 836 in FIG. 8A. An experiment was conducted in which a beam expander and optical lens were selected to allow operation of the light source as shown in FIGS. 8A and 8B. A Hamamatsu L2273 xenon bulb (with offices in Bridgewater, N.J.) was used as the sealed chamber 828. The plasma was formed in the Hamamatsu L2273 xenon bulb using an SPI continuous-wave (CW) 100 W, 1090 nm fiber laser (sold by SPI Lasers PLC, with offices in Los Gatos, Calif.)). A continuous-wave laser emits radiation continuously or substantially continuously rather than in short bursts, as in a pulsed laser. The fiber laser 804 contains laser diodes which are used to pump a special doped fiber (within the fiber laser 804, but not shown). The special doped fiber then lasers to produce the output of the fiber laser 804. The output of the fiber laser 804 then travels through the fiberoptic element 808 to the collimeter 812. The collimeter 812 then outputs the laser beam 816. The initial laser beam diameter (along the Y-Axis), corresponding to beam 816 in FIG. 8A, was 5 mm. The laser beam 816 was a Gaussian beam with a 5 mm diameter measured to the 1/e2 intensity level. The lens used in the experiment, corresponding to lens 820, was 30 mm in diameter and had a focal length of 40 mm. This produced a solid angle of illumination of the plasma 832 of approximately 0.012 steradians. The length (along the X-Axis) of the plasma 832 produced in this arrangement was measured to be approximately 2 mm. The diameter of the plasma 832 (along the Y-Axis), was approximately 0.05 mm. The plasma 832 generated a high brightness ultraviolet light 836. Referring to FIG. 8B, a 2X beam expander was used as the beam expander 854. The beam expander 854 expanded beam 816 from 5 mm in diameter (along the Y-Axis) to 10 mm in diameter, corresponding to beam 858. Lens 862 in FIG. 8B was the same as lens 820 in FIG. 8A. The combination of the beam expander 854 and the optical lens 862 produced a laser beam 866 having a solid angle 874 of illumination of approximately 0.048 steradians. In this experiment, the length of the plasma (along the X-Axis) was measured to be approximately 1 mm and the diameter measured along the Y-Axis remained 0.05 mm. This reduction of plasma length by a factor of 2, due to a change in solid angle of a factor of 4, is expected if the intensity required to sustain the plasma at its boundary is a constant. A decrease in plasma length (along the X-Axis) by a factor of 2 (decrease from 2 mm in FIG. 8A to 1 mm in FIG. 8B) resulted in an approximate doubling of the brightness of the radiation emitted by the plasma for a specified laser beam input power because the power absorbed by the plasma is about the same, while the radiating area of the plasma was approximately halved (due to the decrease in length along the X-Axis). This experiment illustrated the ability to make the plasma smaller by increasing the solid angle of the illumination from the laser. In general, larger solid angles of illumination can be achieved by increasing the laser beam diameter and/or decreasing the focal length of the objective lens. If reflective optics are used for illumination of the plasma, them the solid angle of illumination can become much larger than the experiment described above. For example, in some embodiments, the solid angle of illumination can be greater than about 2π (about 6.28) steradians when the plasma is surrounded by a deep, curved reflecting surface (e.g., a paraboloid or ellipsoid). Based on the concept that a constant intensity of light is required to maintain the plasma at its surface, in one embodiment (using the same bulb and laser power described in the experiment above) we calculated that a solid angle of 5 steradians would produce a plasma with its length equal to its diameter, producing a roughly spherical plasma. FIG. 9 is a schematic diagram of a light source 900 for generating light. The light source 900 includes a sealed chamber 928 (e.g., a sealed quartz bulb, sealed sapphire tube) that contains an ionizable medium (not shown). The light source 900 also includes an energy source (not shown). The energy source provides energy to a region of the chamber 928 to produce a plasma 932. The plasma 932 generates and emits a light 936 that originates from the plasma 932. The light 936 generated by the light source 900 is directed through the walls 942 of the chamber 928 toward the reflective surface 944 of the reflector 940. The reflective surface 944 reflects the light generated by the light source 900. The walls 942 of the chamber 928 allow electromagnetic energy (e.g., light) to pass through the walls 942. The refractive index of the walls is a measure for how much the speed of the electromagnetic energy is reduced inside the walls 942. Properties (e.g., the direction of propagation) of the light ray 936 generated by the plasma 932 that is emitted through the walls 942 of the chamber 928 are modified due to the refractive index of the walls 942. If the walls 942 have a refractive index equal to that of the medium 975 internal to the chamber 928 (typically near 1.0), the light ray 936 passes through the walls 942 as light ray 936′. If, however, the walls have a refractive index greater than that of the internal medium 975, the light ray 936 passes through the walls as light ray 936″. The direction of the light represented by light ray 936 is altered as the light ray 936 enters the wall 942 having an index of refraction greater than the medium 975. The light ray 936 is refracted such that the light ray 936 bends toward the normal to the wall 942. The light source 900 has a medium 980 external to the chamber 928. In this embodiment, the medium 980 has an index of refraction equal to the index of refraction of the medium 975 internal to the chamber 928. As the light ray 936 passes out of the wall 942 into the medium 980 external to the chamber 928, the light ray 936 is refracted such that the light ray (as light ray 936″) bends away from the normal to the wall 942 when it exits the wall 942 The light ray 936″ has been shifted to follow a route parallel to the route the light ray 936′ would have followed had the refractive index of the wall 942 been equal to the refractive indices of the internal medium 975 and external medium 980. This refractive shift of direction and the resulting position of the light ray 936 (and 936′ and 936″) is described by Snell's Law of Refraction:n1 sin θ1=n2 sin θ2 EQN. 1where, according to Snell's Law, n1 is the index of refraction of the medium from which the light is coming, n2 is the index of refraction of the medium into which the light is passing, θ1 is the angle of incidence (relative to the normal) of the light approaching the boundary between the medium from which the light is coming and the medium into which the light is passing, and θ2 is the angle of incidence (relative to the normal) of the light departing from the boundary between the medium from which the light is coming and the medium into which the light is passing (Hecht, Eugene, Optics, M. A., Addison-Wesley, 1998, p. 99-100, QC355.2.H42). If the internal medium 975 does not have an index of refraction equal to that of the external medium 980, the light ray 936 refracts to follow a route according to Snell's Law. The route the light ray 936 follows will diverge from the route that light ray 936′ follows when the internal medium 975, wall 942, and external medium 980 do not have equal indices of refraction. If the refractive index of the walls 942 of the chamber 928 is equal to the internal medium 975 and external medium 980, the reflective surface 944 reflects light ray 936′ and produces a focused beam of light 956. If, however, the refractive index of the walls 942 is greater than the internal medium 975 and external medium 980, the reflective surface 944 reflects light ray 936″ and does not produce a focused beam (the light ray 936″ is dispersed producing light 960). Accordingly, it is therefore desirable to have a light source that includes a chamber and a reflective surface with a shape configured to compensate for the effect of the refractive index of the walls of the chamber. In alternative embodiments, the reflective surface 940 is configured to produce a collimated beam of light when the refractive index of the walls 942 of the chamber 928 is equal to that of the internal medium 975 and external medium 980. However, if the refractive index of the walls 942 of the chamber 928 is greater than that of the internal medium 975 and external medium 980, the reflective surface 940 would produce a non-collimated beam of light (the reflected light would be dispersed, similarly as described above). In other embodiments, aspects of the invention are used to compensate for the effect of the refractive index of the walls 942 of the chamber 928 for laser energy directed in to the chamber 928. Laser energy is directed toward the reflective surface 944 of the reflector 940. The reflective surface 944 reflects the laser energy through the walls 942 of the chamber 928 toward the plasma 932 in the chamber 928 (similarly as described herein with respect to, for example, FIGS. 5 and 6). If the walls 942 of the chamber 928 have a refractive index greater than that of the internal 975 and external 980 media, the direction of the laser energy is altered as the energy enters the walls 942. In these embodiments, if the reflective surface 944 of the reflector 942 has a shape configured to compensate for the effect of the refractive index of the walls of the chamber, the laser energy entering the chamber 928 will not diverge. Rather, the laser energy entering the chamber 928 will be properly directed to the location of the plasma 932 in the chamber 928, similarly as described herein. In this manner, principles of the invention can be applied to electromagnetic energy (e.g., laser energy) that is directed in to the chamber 928 and electromagnetic energy (e.g., light) produced by the plasma 932 that is directed out of the chamber 928. FIG. 10A is a schematic block diagram of a light source 1000a for generating light. The light source 1000a includes a sealed chamber 1028a (e.g., a sealed quartz tube or sealed sapphire tube) that contains an ionizable medium (not shown). The light source 1000a also includes an energy source 1015a. In various embodiments, the energy source 1015a is a microwave energy source, AC arc source, DC arc source, or RF energy source. The energy source 1015a provides energy 1022a to a region 1030a of the chamber 1028a having the ionizable medium. The energy 1022a creates a plasma 1032a. The plasma 1032a generates and emits a light 1036a that originates from the plasma 1032a. The light source 1000a also includes a reflector 1040a that has a reflective surface 1044a. The reflective surface 1044a of the reflector 1040a has a shape that is configured to compensate for the refractive index of the walls 1042a of the chamber 1028a. The walls 1042a of the chamber 1028a are substantially transparent to the light 1036a (or to predefined wavelengths of electromagnetic radiation in the light 1036a). The light 1036a (e.g., visible and/or ultraviolet light) generated by the light source 1000a is directed through the walls 1042a of the chamber 1028a toward the inner reflective surface 1044a of the reflector 1040a. If the refractive index of the walls 1042a is not equal to that of the media internal and external (not shown) to the chamber 1028a, the position and direction of the light ray 1036a is changed by passing through the walls 1042a of the chamber 1028a unless the reflective surface 1044a has a shape that compensates for the refractive index of the walls 1042a of the chamber 1028a. The light 1036a would disperse after reflecting off the surface 1044a of the reflector 1040a. However, because the shape of the reflective surface 1044a of the reflector 1040a is configured to compensate for the refractive index of the walls 1042a of the chamber 1028a, the light 1036a does not disperse after reflecting off the surface 1044a of the reflector 1040a. In this embodiment, the light 1036a reflects off the surface 1044a of the reflector 1040a to produce a collimated beam of light. FIG. 10B is a schematic block diagram of a light source 1000b for generating light. The light source 1000b includes a sealed chamber 1028b (e.g., a sealed quartz tube or sealed sapphire tube) that contains an ionizable medium (not shown). The light source 1000b also includes an energy source 1015b. The energy source 1015b is electrically connected to electrodes 1029 located in the chamber 1028b. The energy source 1015b provides energy to the electrodes 1029 to generate an electrical discharge in the chamber 1028b (e.g., the region 1030b of the chamber 1028b) to ignite the ionizable medium and produce and sustain a plasma 1032b. The plasma 1032b generates and emits a light 1036b that originates from the plasma 1032b. The light source 1000b also includes a reflector 1040b that has a reflective surface 1044b. The reflective surface 1044b of the reflector 1040b has a shape that is configured to compensate for the refractive index of the walls 1042b of the chamber 1028b. The walls 1042b of the chamber 1028b are substantially transparent to the light 1036b (or to predefined wavelengths of electromagnetic radiation in the light 1036b). The light 1036b (e.g., visible and/or ultraviolet light) generated by the light source 1000b is directed through the walls 1042b of the chamber 1028b toward the inner reflective surface 1044b of the reflector 1040b. If the refractive index of the walls 1042b is not equal to that of media internal and external (not shown) to the chamber 1028b, the direction and position of the light ray 1036b is changed by passing through the walls 1042b of the chamber 1028b unless the reflective surface 1044b has a shape that compensates for the refractive index of the walls 1042b of the chamber 1028b. The light 1036b would disperse after reflecting off the surface 1044b of the reflector 1040b. However, because the shape of the reflective surface 1044b of the reflector 1040b is configured to compensate for the refractive index of the walls 1042b of the chamber 1028b, the light 1036b does not disperse after reflecting off the surface 1044b of the reflector 1040b. In this embodiment, the light 1036b reflects off the surface 1044b of the reflector 1040b to produce a collimated beam of light. FIG. 11 is a schematic block diagram of a light source 1100 for generating light that embodies the invention. The light source 1100 includes a sealed chamber 1128 (e.g., a sealed, cylindrical sapphire bulb) that contains an ionizable medium (not shown). The light source 1100 provides energy to a region 1130 of the chamber 1128 having the ionizable medium which creates a plasma 1132. The plasma 1132 generates and emits a light 1136 (e.g., a high brightness light) that originates from the plasma 1132. The light source 1100 also includes at least one laser source 1104 that generates a laser beam that is provided to the plasma 1132 located in the chamber 1128 to initiate and/or sustain the high brightness light 1136. In this embodiment, the laser source 1104 is a diode laser that outputs a laser beam 1120. The optical lens 1120 is configured to focus the laser beam 1122 to produce a smaller diameter laser beam 1124. The laser beam 1124 passes through an aperture or window 1172 located in the base 1124 of a curved reflective surface 1140 and is directed toward the chamber 1128. The chamber 1128 is substantially transparent to the laser beam 1124. The laser beam 1124 passes through the chamber 1128 and toward the region 1130 of the chamber 1128 where the plasma 1132 exists (or where it is desirable for the plasma 1132 to be generated by the laser 1124 and sustained). In this embodiment, the ionizable medium is ignited by the laser beam 1124. In alternative embodiments, the light source 1100 includes an ignition source (e.g., a pair of electrodes or a source of ultraviolet energy) that, for example, generates an electrical discharge in the chamber 1128 (e.g., in the region 1130 of the chamber 1128) to ignite the ionizable medium. The laser source 1104 then provides laser energy to the ionized medium to sustain the plasma 1132 which generates the light 1136. The chamber 1128 is substantially transparent to the light 1136 (or to predefined wavelengths of electromagnetic radiation in the light 1136). The light 1136 (e.g., visible and/or ultraviolet light) generated by the light source 1100 is then directed out of the chamber 1128 toward an inner surface 1144 of the reflective surface 1140. The reflective surface 1144 of the reflector 1140 has a shape that compensates for the refractive index of the walls 1142 of the chamber 1128. If the refractive index of the walls 1142 is not equal to that of the media internal and external (not shown) to the chamber 1128, the speed of the light 1136 would be changed by passing through the walls 1142 of the chamber 1128 if the reflective surface 1144 does not have a shape that compensates for the refractive index of the walls 1142 of the chamber 1128 (similarly as described above with respect to FIG. 9). FIG. 12 is a cross-sectional view of a light source 1200 incorporating principles of the present invention. The light source 1200 includes a sealed cylindrical chamber 1228 that contains an ionizable medium. The light source 1200 also includes a reflector 1240. The chamber 1228 protrudes through an opening 1272 in the reflector 1240. The light source 1200 includes a support element 1274 (e.g. a bracket or attachment mechanism) attached to the reflector 1240. The support element 1274 is also attached to a back end 1280 of the chamber 1228 and locates the chamber 1228 relative to the reflector 1240. The light source 1200 includes electrodes 1229a and 1229b (collectively 1229) located in the chamber 1228 that ignite the ionizable medium to produce a plasma 1232. The electrodes 1229a and 1229b are spaced apart from each other along the Y-Axis with the plasma 1232 located between opposing ends of the electrodes 1229. The light source 1200 also includes an energy source that provides energy to the plasma 1232 to sustain and/or generate a light 1236 (e.g., a high brightness light) that is emitted from the plasma 1232. The light 1236 is emitted through the walls 1242 of the chamber 1228 and directed toward a reflective surface 1244 of a reflector 1240. The reflective surface 1244 reflects the light 1236. In some embodiments, the electrodes 1229 also are the energy source that provides energy to the plasma 1232 sustain and/or generate the light 1236. In some embodiments, the energy source is a laser external to the chamber 1228 which provides laser energy to sustain and/or generate the light 1236 generated by the plasma 1232, similarly as described herein with respect to other embodiments of the invention. For example, in one embodiment, the light source 1200 includes a laser source (e.g., the laser source 104 of FIG. 1) and associated laser delivery components and optical components that provides laser energy to the plasma 1232 to and/or generate the light 1236. If the refractive index of the walls 1242 of the chamber is equal to that of the media internal and external (not shown) to the chamber 1228, and the reflective surface 1244 of the reflector 1240 is a parabolic shape, the light 1236 reflected off the surface 1244 produces a collimated beam of light 1264. If the refractive index of the walls 1242 of the chamber is equal to that of the media internal and external to the chamber 1228, and the reflective surface 1244 of the reflector 1240 is an ellipsoidal shape, the light 1236 reflected off the surface 1244 produces a focused beam of light 1268. If the refractive index of the walls 1242 of the chamber 1228 is greater than that of the media internal and external to the chamber 1228, the direction and position of the light ray 1236 is changed by passing through the walls 1242 of the chamber 1228 unless the reflective surface 1244 of the reflector 1240 has a shape that compensates for the refractive index of the walls 1242 of the chamber 1228. The light ray 1236 would disperse after reflecting off the surface 1244 of the reflector 1240. However, because the shape of the reflective surface 1244 of the reflector 1240 is configured to compensate for the refractive index of the walls 1242 of the chamber 1228, the light 1236 does not disperse after reflecting off the surface 1244 of the reflector 1240. In this embodiment, the refractive index of the walls 1242 of the chamber 1228 is greater than that of the internal and external media and the reflective surface 1242 has a modified parabolic shape to compensate for the refractive index of the walls 1242. The modified parabolic shape allows for the reflected light 1236 to produce the collimated beam of light 1264. If a parabolic shape was used, the reflected light 1236 would not be collimated, rather the reflected light would be dispersed. A modified parabolic shape means that the shape is not a pure parabolic shape. Rather, the shape has been modified sufficiently to compensate for the aberrations that would otherwise be introduced into the reflected light 1236. In some embodiments, the shape of the reflective surface 1242 is produced to reduce the error (e.g., dispersing of the reflected light 1236) below a specified value. In some embodiments, the shape of the reflective surface 1242 is expressed as a mathematical equation. In some embodiments, by expressing the shape of the reflective surface 1242 as a mathematical equation, it is easier to reproduce the shape during manufacturing. In some embodiments, parameters of the mathematical equation are selected to reduce error due to the refractive index of the walls 1242 of the chamber 1228 below a specified value. The light source 1200 includes a seal assembly 1250 at the top of the chamber 1228. The light source 1200 also includes a fitting 1260 at the bottom end of the chamber 1228. The seal assembly 1250 seals the chamber 1228 containing the ionizable medium. In some embodiments, the seal assembly 1250 is brazed to the top end of the chamber 1228. The seal assembly 1250 can include a plurality of metals united at high temperatures. The seal assembly 1250 can be, for example, a valve stem seal assembly, a face seal assembly, an anchor seal assembly, or a shaft seal assembly. In some embodiments the seal assembly 1250 is mechanically fastened to the top end of the chamber 1228. In some embodiments, there are two seal assemblies 1250, located at the two ends of the chamber 1228. The fitting 1260 allows for filling the chamber with, for example, the ionizable medium or other fluids and gases (e.g., an inert gas to facilitate ignition). The fitting 1260 also allows for controlling the pressure in the chamber 1228. For example, a source of pressurized gas (not shown) and/or a relief valve (not shown) can be coupled to the fitting to allow for controlling pressure in the chamber 1228. The fitting 1260 can be a valve that allows the ionizable medium to flow into the chamber 1228 through a gas inlet (not shown). FIG. 13 is a graphical representation of a plot 1300 of the blur or dispersal produced by a reflective surface (e.g., the reflective surface 1244 of FIG. 12) for a reflective surface having various shapes that are expressed as a mathematical expression having the form of EQN. 2. The blur or dispersal is the radius by which light rays reflected off of the reflective surface miss the desired remote focus point for the reflected light (e.g., the reflected light 1268 of FIG. 12 in the situation where the shape of the reflective surface 144 is a modified elliptical shape). r ⁡ ( z ) = a 1 ⁢ z + a 2 ⁢ z 2 + a 3 ⁢ z 3 + … + a n ⁢ z n 1 + b 1 ⁢ z + b 2 ⁢ z 2 + … + b m ⁢ z m EQN . ⁢ 2 The X-axis 1304 of the plot 1300 is the position along the optical axis (in millimeter units) where a particular ray of light reflects from the reflective surface (e.g. the reflective surface 1244) of FIG. 12). The Y-Axis 1308 of the plot 1300 is the radius (i.e., blur or dispersal) in millimeter units. The cylindrical chamber has an outer diameter (along the X-axis) of 7.11 mm and an inner diameter of 4.06 mm. Curve 1312 shows the radius by which light rays reflected off of the location along the optical axis of the reflective surface miss the desired remote focus point for the reflected light, in which the reflective surface is expressed as a mathematical equation (EQN. 2) in which n=2 and m=0. Curve 1316 shows the radius by which light rays reflected off of the location along the optical axis of the reflective surface miss the desired remote focus point for the reflected light, in which the reflective surface is expressed as a mathematical equation (EQN. 2) in which n=3 and m=1. Curve 1320 shows the radius by which light rays reflected off of the location along the optical axis of the reflective surface miss the desired remote focus point for the reflected light, in which the reflective surface is expressed as a mathematical equation (EQN. 2) in which n=4 and m=4. Curve 1324 shows the radius by which light rays reflected off of the location along the optical axis of the reflective surface miss the desired remote focus point for the reflected light, in which the reflective surface is expressed as a mathematical equation (EQN. 2) in which n=5 and m=5. In this embodiment, a ray tracing program was used to select (e.g., optimize) the parameters of the mathematical equation so the shape of the reflective surface compensates for the refractive index of the walls of the chamber containing the ionizable medium. Referring to FIG. 13 and EQN 2, the parameters are the order and coefficients of the mathematical equation. In this embodiment, a ray tracing program was used to determine the paths of the light rays emitted through the walls of a chamber in which the walls had a refractive index greater than that of the media internal and external to the chamber, and reflected off a reflective surface with a shape described according to EQN. 2 with selected order and coefficients. In this embodiment, the ray tracing program graphs the radii by which light rays originating at points along the optical path of the reflective surface miss the desired remote focus point. In this embodiment, the order and coefficients of the rational polynomial (EQN. 2) are adjusted until the radii by which light rays miss the remote focus point are within a threshold level of error. In other embodiments, the order and/or coefficients are adjusted until the full width at half maximum (FWHM) of the light rays emitted by the plasma converge within a specified radius of the remote focus point. In one embodiment, the specified radius is 25 μm. In other embodiments, the ray tracing program graphs the radii by which light rays originating at points along the optical path of the reflective surface miss a target collimated area at a specified distance from the vertex of the reflective surface. The parameters of the mathematical equation expressing the shape of the reflective surface are adjusted until the radii by which light rays miss the target collimated area are within a threshold level of error. In other embodiments, the order and/or coefficients are adjusted until the full width at half maximum (FWHM) of the light rays emitted by the plasma is located within a specified radii of a target collimated area at a specified distance from the vertex of the reflective surface. In alternative embodiments of the invention, alternative forms of mathematical equations can be used to describe or express the shape of the reflective surface of the reflector (e.g., reflective surface 1244 of reflector 1240 of FIG. 12). The principles of the present invention are equally applicable to light sources that have different chamber shapes and/or reflective surface shapes. For example, in some embodiments, the reflective surface of the reflector has a shape that is a modified parabolic, elliptical, spherical or aspherical shape that is used to compensate for the refractive index of the walls of the chamber. FIG. 14 is a schematic block diagram of a portion of a light source 1400, according to an illustrative embodiment of the invention. The light source 1400 includes a sealed chamber 1428 that includes an ionizable medium. The light source 1400 also includes a first reflector 1440 that has a reflective surface 1444. The reflective surface 1444 can have, for example, a parabolic shape, elliptical shape, curved shape, spherical shape or aspherical shape. In this embodiment, the light source 1400 has an ignition source (not shown) that ignites an ionizable gas (e.g., mercury or xenon) in a region 1430 within the chamber 1428 to produce a plasma 1432. In some embodiments, the reflective surface 1444 can be a reflective inner or outer surface. In some embodiments, a coating or film is located on the inside or outside of the chamber to produce the reflective surface 1444. A laser source (not shown) provides a laser beam 1416 that is directed toward a surface 1424 of a second reflector 1412. The second reflector 1412 reflects the laser beam 1420 toward the reflective surface 1444 of the first reflector 1440. The reflective surface 1444 reflects the laser beam 1420 and directs the laser beam toward the plasma 1432. The refractive index of the walls 1442 of the chamber 1430 affects the laser beam 1416 as it passes through the walls 1442 in to the chamber 1430 similarly as light passing through the walls 1442 of the chamber 1430 is affected as described previously herein. If the shape of the reflective surface 1444 is not selected to compensate for the refractive index, the laser energy disperses or fails to focus after entering the chamber 1430 and is not focused on the plasma 1432. Accordingly, in this embodiment, the reflective surface 1444 of the reflector has a shape that is selected to compensate for the refractive index of the walls 1442 of the chamber 1430 (similarly as described previously herein with respect to, for example, FIGS. 12 and 13). The laser beam 1416 provides energy to the plasma 1432 to sustain and/or generate a high brightness light 1436 that is emitted from the plasma 1432 in the region 1430 of the chamber 1428. The high brightness light 1436 emitted by the plasma 1432 is directed toward the reflective surface 1444 of the first reflector 1440. At least a portion of the high brightness light 1436 is reflected by the reflective surface 1444 of the first reflector 1440 and directed toward the second reflector 1412. Because the reflective surface 1444 of the reflector has a shape that is selected to compensate for the refractive index of the walls 1442 of the chamber 1430, the light 1436 reflected by the reflective surface 1444 produces the desired collimated beam of light 1436 that is directed towards the second reflector 1412. The second reflector 1412 is substantially transparent to the high brightness light 1436 (e.g., at least one or more wavelengths of ultraviolet light). In this manner, the high brightness light 1436 passes through the second reflector 1412 and is directed to, for example, a metrology tool (not shown). In some embodiments, the light 1436 is directed to a tool used for photoresist exposure, conducting ellipsometry (e.g., UV or visible), thin film measurements. In some embodiments, the high brightness light 1436 is first directed towards or through a window or additional optical elements before it is directed to a tool. FIG. 15A is a cross-sectional view of a light source 1500 incorporating principles of the present invention. FIG. 15B is a sectional view (in the Y-Z plane) of the light source 1500 of FIG. 15A. The light source 1500 includes a housing 1510 that houses various elements of the light source 1500. The housing 1510 includes a sealed chamber 1522 and has an output 1580 which includes an optical element 1520 (e.g., a quartz disk-shaped element) through which light can exit the housing 1510. The light source 1500 includes a sealed chamber 1528 that contains an ionizable medium (not shown). The light source 1500 also includes a reflector 1540. The light source 1500 also includes a blocker 1550. The light source 1500 includes electrodes 1529a and 1529b (collectively 1529) located in part in the chamber 1528 that ignite the ionizable medium to produce a plasma (not shown). The electrodes 1529a and 1529b are spaced apart from each other (along the Y-Axis) with the plasma located between opposing ends of the electrodes 1529. In some embodiments, the electrodes 1529 also are the energy source that provides energy to the plasma to sustain and/or generate the light. In this embodiment, the energy source is a laser (not shown) external to the chamber 1528 which provides laser energy 1524 (e.g., infrared light) to sustain and/or generate the light 1530 (e.g., a high brightness light including ultraviolet and/or visible wavelengths) generated by the plasma, similarly as described herein with respect to other embodiments of the invention. The laser energy 1524 enters the chamber 1528 on a first side 1594 of the chamber 1528. In some embodiments, the light source 1500 also includes associated laser delivery components and optical components that provide laser energy to the plasma to sustain and/or generate the light 1530. In this embodiment, the light source 1500 includes an optical element 1560 to delivery the laser energy 1524 from the laser to the plasma to sustain and/or generate the light 1530 that is emitted from the plasma. The light 1530 is emitted through the walls of the chamber 1528. Some of the light 1530 emitted through the walls of the chamber 1528 propagates toward a reflective surface 1532 of the reflector 1540. The reflective surface 1532 reflects the light through the optical element 1520 in the housing 1510 to a focal point 1525 of the reflector 1540. Some of the light 1536 propagates toward the optical element 1560. The optical element 1560 absorbs the light 1536, and the light 1536 is not reflected through the optical element 1520. As a result, the light reflected to the focal point 1525 is the light 1530 emitted from the plasma that is reflected by the reflector 1540 along paths shown as the regions 1540 and 1541. Consequently, the light source 1500 includes dark region 1542 due to the light that is radiated toward the optical element 1560 and therefore not reflected to the focal point 1525 of the reflectors 1540. Some of the laser energy delivered to the plasma is not absorbed by the plasma. The laser energy that is not absorbed (laser energy 1556) continues to propagate along the positive X-Axis direction towards the end of the housing 1510. The blocker 1550 is suspended on a second side 1596 of the chamber 1528. The blocker 1550 is suspended along a path 1562 the laser energy 1556 travels. The blocker 1550 is coupled to an arm 1555 that suspends the blocker 1550 in the chamber 1522 of the light source 1500. The blocker 1550 blocks the laser energy 1556 to prevent it from propagating toward the end of the housing and through an output 1580 of the light source 1500. In this embodiment, the blocker 1550 is a mirror that deflects the laser energy 1556 that is not absorbed by the plasma away from the opening 1520 and towards the walls of the housing 1510 (illustrated as laser energy 1584). The blocker 1550 reflects the laser energy 1556 toward a wall 1588 of the housing 1510. The housing 1510 absorbs part of the reflected laser energy 1584 and reflects part of the laser energy 1584 toward the opposite wall 1592 of the housing 1510. A portion of the laser energy 1584 is absorbed each time it impacts a wall (e.g., wall 1588 or 1592) of the housing 1510. Repetitive impact of the laser energy 1584 with the walls of the housing 1510 causes the laser energy 1584 to be substantially (or entirely) absorbed by the walls of the housing 1510. The blocker 1550 prevents laser energy (e.g., infrared wavelengths of electromagnetic energy) from exiting the housing 1510 through the opening 1580 by deflecting the laser energy 1556 using the blocker 1550. As a result, only the light produced by the plasma (e.g., ultraviolet and/or visible wavelengths) exits the housing 1510 through the opening 1580. The blocker 1550 is suspended in the housing 1510 in a location where the blocker 1550 would not deflect light 1530 reflected by the reflector 1540 through the opening 1580 to the focal point 1525. The blocker 1550 does not deflect the light 1530 because the blocker 1550 is located in the dark region 1542. In addition, the arm 1555 coupled to the blocker 1550 also does not deflect the light 1530 because the arm is positioned in the housing 1510 in a location that is aligned with the electrode 1529a along the positive X-Axis direction relative to the electrode 1529a. In this manner, the blocker 1550 and arm 1555 are positioned to minimize their blocking of the light 1530. The dark region 1542 tapers as the region 1542 approaches the opening 1580. To prevent the blocker 1550 from deflecting light reflected by the reflector 1540, the laser energy blocker 1550 is positioned at a location along the X-Axis where the cross-sectional area (in the Y-Z plane) of the blocker 1550 is equal to or less than the cross sectional area (in the Y-Z plane) of the dark region 1542. As a result, the smaller the cross-sectional area (in the Y-Z plane) of the blocker 1550, the closer along the X-Axis the blocker 1550 can be placed to the opening 1580. In some embodiments, the laser energy blocker 1550 is made of any material that reflects the laser energy 1556. In some embodiments, the blocker 1550 is configured to reflect the laser energy 1556 back toward the ionized medium in the chamber 1528. In some embodiments, the blocker 1550 is a coating on a portion of the chamber 1528. In some embodiments, the blocker is a coating on the optical element 1520 at the opening 1580. In some embodiments, the laser energy blocker 1550 is made of a material that absorbs, rather than reflects, the laser energy 1556 (e.g., graphite). In some embodiments in which the blocker absorbs the laser energy 1556, the blocker 1550 heats up because it absorbs the laser energy 1556. In some embodiments, the blocker 1550 is cooled. The blocker 1550 can include one or more coolant channels in the blocker 1550. The light source can also include a coolant supply coupled to the coolant channel which provides coolant to the coolant channel to cool the blocker 1550. In some embodiments, the light source 1500 includes a gas source (e.g., a pressurized gas canister or gas blower) to blow gas (e.g., air, nitrogen, or any other gas) on the blocker 1550 to cool the blocker 1550. In some embodiments, the light source 1500 includes one or more tubes (e.g., copper tubes) that wind around the laser energy blocker 1550. The light source 1500 flows a coolant (e.g., water) through the tubes to cool the blocker 1550. By way of illustration, an experiment was conducted to generate ultraviolet light using a light source, according to an illustrative embodiment of the invention. A specially constructed quartz bulb with a volume of 1 cm3 was used as the chamber of the light source (e.g., the chamber 128 of the light source 100 of FIG. 1) for experiments using xenon as the ionizable medium in the chamber. The bulb was constructed so that the chamber formed within the quartz bulb was in communication with a pressure controlled source of xenon gas. FIG. 16 is a graphical representation of brightness as a function of the pressure in a chamber of a light source, using a light source according to the invention. FIG. 16 illustrates a plot 1600 of the brightness of a high brightness light produced by a plasma located in the chamber as a function of the pressure in the chamber. The laser source used in the experiment was a 1.09 micron, 200 watt CW laser and it was focused with a numerical aperture of 0.25. The resulting plasma shape was typically an ellipsoid of 0.17 mm diameter and 0.22 mm length. The Y-Axis 1612 of the plot 1600 is the brightness in watts/mm2 steradian (sr). The X-Axis 1616 of the plot 1600 is the fill pressure of Xenon in the chamber. Curve 1604 is the brightness of the high brightness light (between about 260 and about 400 nm) produced by a plasma that was generated. Curve 1608 is the brightness of the high brightness light (between about 260 and about 390 nm) produced by the plasma. For both curves (1604 and 1608), the brightness of the light increased with increasing fill temperatures. Curve 1604 shows a brightness of about 1 watts/mm2 sr at about 11 atmospheres which increased to about 8 watts/mm2 sr at about 51 atmospheres. Curve 1608 shows a brightness of about 1 watts/mm2 sr at about 11 atmospheres which increased to about 7.4 watts/mm2 sr at about 51 atmospheres. An advantage of operating the light source with increasing pressures is that a higher brightness light can be produced with higher chamber fill pressures. To start a laser-driven light source (“LDLS”), the absorption of the laser light by the gas within the chamber (e.g., chamber 128 of FIG. 1) is strong enough to provide sufficient energy to the gas to form a dense plasma. However, during operation, the same absorption that was used to start the LDLS can be too strong to maintain the brightness of the light because the light can be prematurely absorbed before the light is near the laser focus. These criteria often come into conflict and can create an imbalance in the absorption needed to start a LDLS and the absorption needed to maintain or operate the LDLS. When starting a LDLS, the plasma density is generally low and hence, other things being equal, the absorption is weak. This can cause most of the laser light to leave the plasma region without being absorbed. Such a situation can lead to an inability to sustain the plasma by the laser alone. One solution to this problem is to tune the laser to a wavelength near a strong absorption line of the excited working gas within the chamber (e.g., chamber 128 of FIG. 1). However, after ignition this same strong absorption can become a liability because the laser energy can be absorbed too easily before the laser power reaches the core of the plasma near the laser focus. This latter condition can lead to a low brightness light source radiating from a large volume. One solution to this problem is to tune the laser wavelength away from the strong absorption line until a condition is reached where the maximum radiance is achieved. The optimum operating state can be a balance between small plasma size and sufficiently high power absorption. This scenario leads to a light source and a method of operation where the laser is first tuned to a wavelength nearer the absorption line and then tuned to another wavelength further away from the strong absorption line for optimum operation. A light source can use an excited gas that has at least one strong absorption line at an infrared wavelength to produce a high brightness light. For example, referring to FIG. 1, the light source 100 includes a chamber 128 that has a gas disposed therein. The gas can comprise a noble gas, for example, xenon, argon, krypton, or neon. An ignition source 140 can be used to excite the gas within the chamber 128. The ignition source 140 can be, for example, two electrodes. The excited gas has electrons at an energy level that is higher than the energy of the gas at its ground state, or lowest energy level. The excited gas can be in a metastable state, for example, at an energy that is higher than the ground state energy of the gas but that lasts for an extended period of time (e.g., about 30 seconds to about one minute). The specific energy level of the excited state can depend on the type of gas that is within the chamber 128. The excited gas has at least one strong absorption line at an infrared wavelength, for example at about 980 nm, 895 nm, 882, nm, or 823 nm. The light source 100 also includes at least one laser 104 for providing energy to the excited gas at a wavelength near a strong absorption line of the excited gas within the chamber 128 to produce a high brightness light 136. The gas within the chamber 128 can be absorptive near the wavelength of the laser 104. Operation of the light source to balance the conflicting criteria for starting and maintaining the high brightness light can comprise tuning a laser (e.g., laser 104 of FIG. 1) to a first wavelength to produce a high brightness light and then tuning the laser to a second wavelength to maintain the high brightness light. The first wavelength can be at an energy level that is capable of forming and sustaining a dense plasma, thus creating a high brightness light, and the second wavelength can be at an energy level such that the laser energy is not substantially absorbed by the plasma prior to the laser reaching its focus point. For example, a gas within a chamber (e.g., chamber 128 of FIG. 1) can be excited with an ignition source. In some embodiments, a drive laser at a power below 1000 W can be used to ignite the plasma. In other embodiments, a drive laser at a power above or below 1000 W can be used to ignite the plasma. To ignite the plasma and/or the excited gas within the chamber, a LDLS can be operated near the critical point of the gas within the chamber. The critical point is the pressure above which a gas does not have separate liquid and gaseous phases. For example, the critical point of xenon is at a temperature of about 290 Kelvin and at a pressure of about 5.84 MPa (about 847 psi). In some embodiments, other gases are used, for example neon, argon or krypton can be used. In other embodiments, combinations of gases can be used, for example, a mixture of neon and xenon. After the gas within the chamber is ignited, a laser (e.g., laser 104 of FIG. 1) can be tuned to a first wavelength to provide energy to the excited gas in the chamber to produce a high brightness light. The excited gas within the chamber absorbs energy near the first wavelength. After the high brightness light is initiated, the laser can be tuned to a second wavelength to provide energy to the excited gas within the chamber to maintain the high brightness light. The second wavelength can either be less than or greater than the first wavelength. The excited gas within the chamber absorbs energy near the second wavelength. The gas within the chamber can be, for example, a noble gas and can have atoms with electrons in at least one excited atomic state. Noble gases such as xenon, argon, krypton or neon can be transparent in the visible and near infrared range of the spectrum, but this is not the case when the gas is at high temperature or in the presence of excited molecular states, such as excimers. Any condition of the gas which results in population of high energy electronic states, such as the lowest excited state (e.g., the excited state closest in energy to the ground state) in xenon, will also result in the appearance of strong absorption lines due to transitions between the relatively high energy state and any of the several higher level states which lie at a level of order 1 eV above it. FIG. 17 shows a simplified diagram of the relevant energy levels in xenon. Each of the horizontal bars represents an energy level which can be occupied by an electron in the xenon atom or molecule (dimer). When an electron moves between two levels, a photon can be emitted or absorbed, e.g. a 980 nm photon. The groups of close together horizontal bars on the “Molecular Levels,” or left, side of the diagram show that the close association of xenon atoms in the molecule leads to broadening of the energy levels of the atom into bands. Transitions between these bands then allow for a broadened range of absorption, which explains the enhanced absorption even at wavelengths some distance (e.g., several nanometers) away from the exact atomic transition of 980.0 nm. Still referring to FIG. 17, an example of such an absorption line is the one at about 980 nm and about 882 nm in xenon which is a transition from the metastable atomic 5p5(2P°3/2)6s level to the 5p5(2P°3/2)6p level. The molecules have a corresponding set of transitions yielding a broadened 980 nm or 882 nm line. Such lines are also observed in emission due to the reverse transition. Other examples of suitable absorption lines in xenon are, for example, 881.69 nm, 823.1 nm, and 895.2 nm. Table 1 shows emission and absorption measurements and average temperature of the cathode spot of a xenon arc in the stationary mode. As shown, xenon in the plasma form has multiple absorbance lines in the IR spectrum. As shown by the high percentage of energy that can be absorbed at multiple wavelengths, 881.69 nm, 823.1 nm, and 895.2 nm, as well as 980 nm, are good wavelengths that can be used within a LDLS to initiate a high brightness light. TABLE 1(as measured by Lothar Klein (April 1968/Vol. 7, No. 4/APPLIEDOPTICS 677)).Nλ0Absorptionλ (Å)(W cm−1 sr−1 μ−1)(%)T (°K.)XeI82325,9008910,020cont85001,6152310,750XeI8819(peak)4,390979,160(wing)4,9609010,500XeI98003,400899,820XeI99233,340909,840XeI1052889228.59,950XeI1174290642.59,400XeI12623640379,920cont13100213178,870XeI147335755510,060XeI15418317379,840 FIG. 18 shows simplified spectral diagrams of the relevant energy levels in neon, argon, krypton and xenon. Each horizontal bar represents an energy level which can be occupied by an electron in the neon, argon, krypton, or xenon atom or molecule (dimer). The transition between these energy levels in the noble gases, allow for a broadened range of absorption. Therefore, these noble gases can be used in a LDLS to start and maintain a high brightness light in accordance with the systems and methods described herein. Tuning the laser several nanometer, as can be needed to adjust the wavelength of the laser from a first wavelength to initiate a high brightness light to a second wavelength to sustain the high brightness light, can be accomplished by adjusting the operating temperature of the laser. FIG. 19 shows a graph of laser output wavelength versus temperature for xenon, which can be used as a tuning mechanism for a laser of a LDLS. The laser bandwidth is approximately 5 nm and the xenon absorption lines 1905 are shown, for example, at about 980 nm. For example, the wavelength of a typical diode laser operating near the 980 nm absorption line of xenon can be tuned approximately 0.4 nm per degree Celsius of temperature change. The specific temperature or range of temperatures depends on the particular laser. The effect is that thermal expansion of the laser material causes the length of the laser cavity to increase with temperature, thereby shifting the resonant wavelength of the cavity to a longer wavelength. The temperature of the laser can be set by a thermoelectric cooling device (e.g., a Peltier cooling device) and quickly tuned by varying the current to the thermoelectric cooler (“TEC”). Electronic fan speed control of a cooling fan is another option for laser temperature control. Also, electric heating of the laser can be used to control the temperature. Temperature of the laser can be monitored by a sensor and controlled by a feedback circuit driving the cooling and/or heating means. The second wavelength that the laser of the LDLS is tuned to can be approximately 1 nm to approximately 10 nm displaced from the first wavelength. In some embodiments, the second wavelength is less than the first wavelength and in some embodiments the second wavelength is greater than the first wavelength. For example, to start a LDLS, the laser can be tuned to a wavelength of about 980 nm using xenon gas within the chamber of the light source. After a high brightness light is initiated, the laser can be tuned to a wavelength of about 975 nm to maintain the high brightness light. In some embodiments, the second wavelength is about 985 nm. Several different methods can be used to start and maintain the light source. In some embodiments, a high voltage pulse is applied to the ignition electrodes in the lamp. A DC current of about 1 to about 5 Amps can initially flow through the resulting plasma from an ignition power supply. The current can decay exponentially with a time constant of about 2 milliseconds. During this time the resulting plasma is illuminated by a focused laser beam at a wavelength of, for example, about 980 nm where the laser temperature is about 35 (see, e.g., FIG. 19, which shows that when the laser temperature is at about 35° C. the laser will emit energy at a wavelength of about 980 nm). The laser plasma is then sustained after the DC current decays to zero. A plasma light sensor can be used to determine that the plasma is sustained by the laser and then the laser is cooled to a temperature about 25° C. and the resulting wavelength of about 975 nm, or a desired predetermined operating wavelength, which can be determined by active feedback on the properties of the laser driven light source, such as radiance (e.g., brightness) (see, e.g., FIG. 19, which shows that when the laser temperature is at about 25° C. the laser will emit energy at a wavelength of about 975 nm). This method can rely on direct electron heating by the laser, and therefore, can require sufficient electron density to couple the laser power. This method can be used for a LDLS that operates at about 60 W. In some embodiments, a different starting scheme can be used, which is suitable for low laser powers, for example, laser powers between about 10 W and about 50 W. For example, a laser wavelength can be deliberately tuned to rely on direct absorption of the laser power by the neutral gas, which is absorptive at or near the laser wavelength. However, since laser photon energy is low (approximately 1.26 eV for 980 nm), compared to atomic excited states (e.g., the lowest xenon excited state is about 8.31 eV), this method cannot not rely on absorption from the ground state. In addition, multi-photon effects can require high power and usually a pulsed laser. Since the starting scheme cannot rely on absorption from the ground state, the starting scheme can instead rely on absorption from an excited state. However, this requires that at least one excited state of the gas within a chamber of a LDLS be populated with electrons. Some excited states have long life times, for example, the lifetime of metastable xenon is approximately 40 seconds. Due to the long lifetime, the metastable states tend to be preferentially populated. When choosing absorption lines of a gas near the laser wavelength, it can be preferred to choose those with lower level on a metastable state. In addition, at high pressures (e.g., pressures greater than about 0.1 bar), pressure and molecular effects broaden the absorption lines. A certain level of DC arc current can be required to start the LDLS, but less DC arc current can be required for a laser at higher power and operating closer to an absorption line of the gas within the chamber of the light source. A peak DC current can be varied by changing the resistance of a current limiting resistor after a booster capacitor. Threshold current is the laser driving current above which the plasma can be started when well aligned. Laser output power is proportional to laser current. Higher laser driving current can also make the laser center wavelength closer to an atomic line, for example, closer to 980 nm. FIG. 20 is a graph 2000 of power 2100 versus pressure 2200 for argon 2300 and xenon 2400. See Keefer, “Laser-Sustained Plasmas,” Laser-Induced Plasmas and Applications, published by Marcel Dekker, edited by Radziemski et al., 1989, pp. 169-206, at page 191. The graph 2000 shows the minimum power (about 30 W, with minimum power occurring below 20 atm.) required to sustain plasmas in argon and xenon as well as the maximum pressure that can be obtained. In addition, at points 2500 and 2600, the prior art laser sustained plasma can not be operated at any higher pressure when the laser sustained plasma is operated according to the prior art. For instance, the highest pressure that can be achieved for xenon 2400 is about 21 atm and the highest pressure that can be achieved for argon 2300 is about 27 atm. At these pressures, the prior art laser sustain plasma requires about 50 W of power to sustain a xenon plasma and about 70 W of power to sustain an argon plasma. Operating at higher pressure is beneficial because plasmas for the purpose of light generation can be obtained with higher brightness while lower powers are required when operated according to the present invention. To obtain lower powers the LDLS can be operated at a wavelength of about 980 nm. When the LDLS is operated at 980 nm, a higher maximum pressure is observed than the maximum pressures shown in FIG. 20. In addition, a maximum pressure, similar to that shown in FIG. 20, has not been achieved when a LDLS is operated at 980 nm. Therefore, when the LDLS is operated at the 980 nm wavelength, the LDLS can be operated at substantially higher pressures than prior art laser sustained plasmas. For example, the LDLS can be operated at pressures greater than about 30 atm. When the LDLS is operated at these high pressures and at a wavelength of about 980 nm, the power needed to sustain the plasma drops dramatically. For example, when the LDLS is operated at a pressure greater than about 30 atm, the power need to sustain the plasma can be as low as about 10 W. FIG. 21 shows different sized laser beams 2105, 2110, 2115 focused on a small plasma 2120. Each laser beam 2105, 2110, 2115 has a different numerical aperture (“NA”), which is a measure of the half angle of a cone of light. The NA is defined to be the sine of the half angle of the cone of light. For example, laser beam 2105 has a smaller NA than laser beam 2110, which has a smaller NA than laser beam 2115. As shown in FIG. 21, a laser beam with a larger NA, for example, laser beam 2115, can have an intensity that converges more quickly on plasma 2120 (e.g., it can converge more quickly to the laser focal point) than a laser beam with a smaller NA, for example, laser beam 2105. In addition, laser beams with a larger NA can rapidly decrease in intensity as the laser beam leaves the focus point and thus will have less of an effect on the high brightness light than a laser beam with a smaller NA. For example, laser beam 2105′ corresponds to laser beam 2105, laser beam 2110′ corresponds to laser beam 2110, and laser beam 2115′ corresponds to laser beam 2115. As shown by FIG. 21, the intensity of laser beam 2115 decreases more rapidly (2115′) after the focus point than laser beam 2105 due to the larger NA of beam 2115, which also results in less interference of the laser beam with the high brightness light. Referring to FIG. 1, a light source 100 can utilize the NA property of a beam of light to produce a high brightness light. The light source 100 can include a chamber 128 having one or more walls. A gas can be disposed within the chamber 128. At least one laser 104 can provide a converging beam of energy focused on the gas within the chamber 128 to produce a plasma that generates a light emitted through the walls of the chamber 128. The NA of the converging beam of energy can be between about 0.1 or about 0.8, or between about 0.4 to about 0.6, or about 0.5. In some embodiments, the laser 104 is a diode laser. A diode laser can include optical elements and can emit a converging beam of energy without any other optical elements present in the optical system. In some embodiments, an optical element is positioned within a path of the laser beam, for example, referring to FIG. 1, an optical element can be positioned between the laser 104 and the region 130 where the laser beam energy is provided. The optical element can increase the NA of the beam of energy from the laser. The optical element can be, for example, a lens or a mirror. The lens can be, for example, an aspheric lens. In FIG. 1, the combination of beam expander 118 and lens 120 serves to increase the NA of the beam. For example, a NA of 0.5 can be achieved when the illuminated diameter of lens 120 is equal to its focal length multiplied by 1.15. These conditions correspond to a beam half angle of 30 degrees. A laser beam having a large numerical aperture can be beneficial because a laser beam with a large NA can converge to obtain a high intensity in a small focal zone while having an intensity which rapidly decreases outside the small focal zone. This high intensity can sustain the plasma. In some embodiments, it is beneficial to have the plasma be in a sphere. A laser beam with a large NA can help to maintain the plasma in a spherical shape because of the convergence and focus of the laser beam on the plasma. In addition, a laser beam with a large NA can increase the spectral radiance or brightness of the emitted light because a high intensity light is emitted from a small, spherical plasma. In some embodiments it is beneficial to have the plasma be in any other geometric shape, including but not limited to an oval. In some embodiments, an aspheric lens for laser focus is used to achieve high NA and small plasma spot size. FIG. 22 is a graph 2200 showing spectral radiance on the y-axis and NA on the x-axis. As shown on FIG. 22, spectral radiance of the plasma increases with an increase in numerical aperture of the beam. For example, for a laser tuned to approximately 975 nm, as NA increases up to 0.55, the spectral radiance also increases. For example, when the NA is about 0.4, the spectral radiance is about 15 mW/nm/mm2/sr. When the NA is increased to about 0.5, the spectral radiance increases to about 17 mW/nm/mm2/sr. Therefore, when the NA was increased by about 0.1, the spectral radiance increased by about 2 mW/nm/mm2/sr. A laser beam having an NA of about 0.5 can produce a higher brightness light than a laser beam having a smaller NA. FIG. 23A shows a bulb 2300 having a chamber 2305 that can be used in a LDLS. To assure reliable ignition of a LDLS, a high degree of alignment can be achieved between the focus of the laser and a point 2315 within the bulb 2300 which lies on a line between the tips of the electrodes 2310, 2311 used for ignition and is approximately equidistant from the tips of the electrodes 2310, 2311. This line is important because the initial arc used for ignition of the laser plasma follows close to this line. In addition to this requirement, there can also be a need for simple replacement of a bulb at the point of use of the LDLS without complex alignment procedures. In the case of prior art aligned bulbs, the purpose of pre-alignment is to provide alignment of the light source zone with an optical system. That goal can be met in the LDLS by alignment of the laser beam, not the bulb, which assures alignment of the light emitting zone during operation and which alignment remains fixed independent of the replacement of a bulb. Therefore the purpose achieved by pre-aligning the bulb in the LDLS is primarily that of LDLS ignition, not optical alignment of the light emitting zone. In some embodiments, the lamps or bulbs can be pre-aligned. In one embodiment, the electrodes are positioned within a tolerance of about 0.01 to about 0.8 mm, and more specifically that the electrodes are within a tolerance of about 0.1 to about 0.4 mm. In some embodiments, the center of the plasma should be within about 0.001 to 0.02 mm of the center of the gap between the electrodes. With these tight tolerances, it can be beneficial to have the lamps/bulbs pre-aligned so that the end user does not have to align the lamps/bulbs upon replacement. A bulb for a light source can be pre-aligned so that an operator of the light source does not have to align the bulb prior to use. The bulb 2300 having two electrode 2310, 2311 can be coupled to a mounting base 2320, as shown in FIG. 23B. The bulb 2300 can be coupled to the mounting base 2320 by a dog-point set screw, a nail, a screw, or a magnet. The bulb and mounting based structure can be inserted into a camera assembly, for example, camera assembly 2400 of FIG. 24. The camera assembly includes at least one camera, for example, cameras 2405, 2410 and a display screen (not shown). The camera assembly 2400 can include more than two cameras. In some embodiments, a master pin 2415 is placed in an alignment base 2420. The alignment base 2420 and master pin 2415 can be placed into the camera assembly 2400 for use as a bulb centering target. After the camera assembly 2400 is initially set up with the alignment base 2420 and master pin 2415, the bulb 2300 and mounting base 2320 of FIG. 23B can be inserted into the camera assembly 2400 in place of the alignment base 2420 and master pin 2415. The two cameras 2405, 2410 can be arranged to look at the bulb from two orthogonal directions to allow a high accuracy (25 to 50 microns) when the bulb is positioned correctly with respect to the mounting base. The mounting base can be made of metal or any other suitable material. FIG. 25 shows a display screen 2500 that can be displayed from at least one of the cameras (e.g., cameras 2405, 2410 of FIG. 24) when a bulb (e.g., bulb 2300 of FIG. 23B) is mounted in the camera assembly (e.g., camera assembly 2400 of FIG. 24). The display screen can show two electrodes 2505, 2510 that are within a bulb. The arrows 2515, 2520 can be used to help position the electrodes 2505, 2510 and thus the bulb in a mounting base. The center point 2525 can be positioned equidistant from the tips of the electrodes 2505, 2510 when the tip of the electrodes 2505, 2510 is aligned with the arrows 2515, 2520, respectively. The arrows 2515, 2520 and the center grid 2530 can comprise a positioning grid with which the electrodes are aligned. If the bulb assembly is not positioned correctly within the mounting base (and thus the electrodes do not align properly in the display screen 2500), the position of the bulb within the mounting base can be adjusted such that a region of the bulb between the two electrode (e.g., center point 2525) aligns with a positioning grid on the display screen 2500. The position of the bulb can be adjusted either vertically or horizontally within the mounting base to align the electrodes 2505, 2510 with the positioning grid. The position of the bulb can be adjusted by a manipulator that is positioned above the bulb when the bulb is in the camera assembly. The manipulator can be capable of moving the bulb vertically and horizontally. For example, the manipulator can be a robotized arm that can clamp to the bulb. The robotized arm can be moved, for example, by a computer program. In some embodiments, the method of pre-aligning the bulb includes toggling between the two cameras (e.g., cameras 2405, 2410 of FIG. 24) to align the bulb. The display screen 2500 and a predetermined grid can change based on what camera is being displayed. In some embodiments, the images from the cameras are displayed side-by-side on the display screen. In some embodiments, the images from the two cameras are displayed in different colors, for example, one camera can display an image in red while another camera can display an image in green. The positioning grid on the display screen can be pre-determined such that when the center area 2525 of the bulb between the two electrodes 2505, 2510 aligns with the positioning grid on the display screen, the region 2525 is aligned relative to a focal point of a laser when the bulb and mounting base are inserted into a light source. When the bulb has been aligned, the bulb can be secured to the mounting base. In some embodiments, cement is cured to fix the bulb position permanently in the base. In some embodiments any other type of securing or fastening agent/material can be used to secure the bulb position permanently in the base. This pre-aligned bulb can be used by inserting the pre-aligned bulb into a light source. The user does not have to align the bulb in any way. The user can simply insert the pre-aligned bulb into a LDLS without having to make any adjustments for alignment. The mounting base can guarantee the alignment of the bulb when the bulb is placed into the LDLS. In one embodiment the base has one or more alignment features to guarantee the alignment of the bulb when it is placed into the LDLS. In another embodiment, the base has one or more mating features, for example, apertures, grooves, channels, or protuberances, to guarantee the alignment of the bulb when it is placed into the LDLS. A feedback loop can be installed in the LDLS to decrease the amount of noise within the LDLS. Noise can occur due to gas convection within the bulb or outside the bulb. Noise can also occur due to mode changes within the laser, and especially within laser diodes or due to mechanical vibration generated within or outside the LDLS. One solution to decrease the amount of noise is to install a feedback loop. Another solution to decrease the amount of noise is to tilt the laser to 90 degrees from a horizontal plane of the plasma. Another solution is to precisely stabilize the temperature of the laser, for example by sensing the laser temperature and using a feedback control system to maintain a constant temperature. Such a temperature stabilization system can utilize a thermoelectric cooler controlled by the feedback system. In some embodiments, the amount of noise increases as the laser is tilted closer to horizontal. FIG. 26 shows a flow chart 2600 for a method of decreasing noise within a light source. A sample of light that is emitted from the light source can be collected (step 2610). The sample of light that is collected from the light source can be collected from a beam splitter. The beam splitter can be a glass beam splitter or a bifurcated fiber bundle. The sample of light can be collected using a photodiode. The photodiode can be within a casing of the light source or the photodiode can be external to the casing of the light source. In some embodiments, two samples of light are collected. One sample can be collected by a first photodiode within the casing of the light source and one sample can be collected by a second photodiode external to the casing of the light source. The sample of light can be converted to an electrical signal (step 2620). The electrical signal can be compared to a reference signal to obtain an error signal (step 2630). The error signal can be the difference between the reference signal and the electrical signal. The error signal can be processed to obtain a control signal (step 2640). In some embodiments, the error signal is processed by a control amplifier. The control amplifier can be capable of outputting a control signal proportional to at least one of a time integral, a time derivative, or a magnitude of the error signal. A magnitude of a laser of the light source can be set based on the control signal to decrease noise within the light source (step 2650). Steps 2610-2650 can be repeated until a desired amount of noise is reached. Once the desired amount of noise is reached, steps 2610-2650 can continue to be repeated to maintain the amount of noise within the system. Steps 2610-2650 can be carried out by analog or digital electronics in a manner whereby the steps are not discrete, but rather form a continuous process. FIG. 27 shows a schematic illustration of a functional block diagram 2700 of an embodiment of a feedback loop. The circuit can consist of one or more modules 2705, 2706. In one embodiment, the circuit consists of two modules, for example, a lamp controller module 2705 and a lamp house module 2706. In one embodiment, universal AC 2710 is put into an AC to DC converter 2715. In one embodiment the AC power input is about 200 W. The AC to DC converter 2715 converts AC power to DC power. In some embodiments, the DC power is provided to a Laser Drive 2720. The laser drive 2720 can then operate the laser 2725, for example an IPG diode laser. In some embodiments, the laser 2725 is operated at about 975 nm and in other embodiments the laser is 2725 operated at about 980 nm. The laser 2725 can be coupled to a fiber 2730, for example a fiber optic cable, which transmits the laser beam to a bulb 2735. In some embodiments the bulb 2735 is a quartz bulb that is greater than 180 nm. In some embodiments, output light from the LDLS is stabilized so that the noise over a bandwidth of greater than 1 KHz is substantially reduced and long term drift is prevented. In some embodiments, a sample of the output beam is obtained by a beam splitter, or other means, so that the sample of light is taken effectively from the same aperture and the same NA or solid angle as the output light is taken from. As an example, a glass beam splitter can be placed in the beam. A few percent of the output power can be deflected from the beam, but it retains all the angular and spatial character of the actual output beam. Then, this sample is converted to electrical current by a detector and compared to a preset or programmable reference level. A signal representing the difference between the reference and actual detector current, e.g., an error signal, can then be processed by a control amplifier having, for example, the capability to produce an output control signal proportional to any or all of the time integral, the time derivative, and the magnitude of the error signal. The output of this control amplifier then sets the magnitude of the current flowing in the laser diode. The variation in laser output produced in this way can cancel out any fluctuation or drift in the output beam power. In some embodiments, one or more modules are connected to a tool 2740. The tool 2740 can be any device that can utilize a LDLS, for example, a high pressure/performance liquid chromatography machine (“HPLC”). In some embodiments, the tool 2740 contains a photodiode 2745 that converts the light emitted from the LDLS into either current or voltage. In some embodiments, the photodiode 2745 sends a signal 2746 to a control board 2750 that contains a closed loop control. This signal 2746 can then be compared with a reference signal and the resulting error signal can be used to adjust the LDLS so that the light monitored by the photodiode 2745 remains at a constant value over time. In some embodiments, water is used to cool the lamp control module 2705. In some embodiments, purge gas and/or room air are used to cool the lamp house module 2706. In some embodiments, other coolants are used to cool the lamp control module 2705 or the lamp house module 2706. In some embodiments the laser module is cooled by a thermoelectric cooler. The lamp house module 2706 can also include an igniter module 2755 that can be used to excite a gas within a chamber of the light source. The lamp house module 2706 can include a photodiode 2760 and a photodiode conditioning circuit 2765. The photodiode 2760 can provide a current signal proportional to the intensity of the high brightness light. Photodiode conditioning circuit 2765 can provide a robust, buffered electrical signal suitable for transmitting the photodiode signal to remotely located electronic control circuits. The photodiode signal can be used to establish that the lamp is ignited and operating properly and it can be used in an internal feedback loop as described herein. FIG. 28 shows a control system block diagram 2800 that employs two feedback loops. For example, one feedback loop can use an external photodiode (see the bolded boxes of FIG. 28) and another feedback loop can use an internal photodiode (see the bolded, dashed boxes of FIG. 28). In some embodiments, the external diode feedback loop results in a 0.3% pk-pk noise level. In some embodiments, the external photodiode feedback loop is a closed loop control (“CLC”) system with feedback from a sample of the output beam, sampled with the same aperture and NA as the output beam. The control system block diagram 2800 employing two feedback loops includes three modules, a lamp controller module 2805, a lamp house module 2806, and a fixture module 2807. Within the lamp controller module 2805 an internal reference 2810 is provided to a comparison tool 2815. The comparison tool can be a summing junction. The lamp controller module 2805 also includes a power supply 2820 to the laser that can obtain a signal from an external feedback PI controller 2825, an internal feedback PI controller 2830 or a fixed set point 2835 depending on the circuit 2840. For example, as shown in FIG. 28, the power supply 2820 is receiving a signal from the internal feedback PI controller 2830. The power supply 2820 sends power to a bulb 2845 within the lamp house module 2806. Light 2850 is emitted from the bulb 2845. A portion of the light 2850 can be used for the internal feedback loop. The internal feedback loop within the lamp house module 2806 includes optics 2855, a detector 2860, and a pre-amplified calibration, noise and power feedback 2865. The internal feedback loop can be send a signal to the comparison tool 2815 to be compared to the internal reference 2810 to obtain an error signal. The light 2850 emitted from the bulb 2845 can be sent to optics 2870. The light 2875 emitted from the optics 2870 can be the high brightness light that is used in a variety of applications, for example, an HPLC device. A portion of the light 2870 can be used for the external feedback loop. The internal feedback loop within the fixture module 2807 includes optics 2880, a detector 2885, and a pre-amplified calibration, noise and power feedback 2890. The external feedback loop can send a signal to the comparison tool 2815 to be compared to the internal reference 2810 or the internal feedback loop signal to obtain an error signal. In some embodiments, the feedback system can correct the laser drive current to maintain a constant intensity of light as measured in a sample of the output beam sampled from the same spatial region of the emitting area and from the same solid angle used in the application. In some embodiments, a beam splitter is used to obtain such a sample and deliver the sample of light to a photodetector, which generates the feedback signal. FIG. 29 shows an optical system 2900 of a light source with a noise measurement system and feedback loop. The optical system includes a collimator and focusing lens 2905 that focuses a beam of light 2910 from a laser (not shown) on a chamber 2915 of a bulb 2920. The light 2910 is emitted from the plasma 2925 within the chamber 2915 toward an off axis parabolic mirror (“OAP”) 2930. The light continues though an iris 2935, for example a 10 mm iris, and an optical filter 2940 to a second OAP 2945. The light 2910 passes through an aperture 2950, for example a 200 μm aperture. A beam sampler 2955 can be used to deflect a portion of the light 2910 to a feedback detector photodiode 2960 to be used as a sample in the feedback loop. The remaining light 2910 continues to an output beam detector photodiode 2965. The optical system 2900 simulates an application of the light source and allows measurement of the noise level achieved in the light reaching the output beam detector photodiode 2965, which light and noise level are representative of the light entering a users optical system, such as an HPLC detector. The use of a feedback loop or closed loop control (“CLC”) can decrease the amount of noise within a light source. Table 2 shows noise measurement data with and without a CLC circuit. Averaged for many scans, the Pk-Pk/Mean in a 20 second period is 0.74% without using a CLC system, and 0.47% with a CLC system. Even for a 200 second period the noise is 0.93% without CLC, and 0.46% with a CLC. TABLE 2Pk-Pk/Mean noise for LDLS with or without CLCLDLS withoutPk-Pk/Mean (%)CLCLDLS with CLC200ms0.390.332s0.610.4420s0.740.47200s0.930.46 As shown in FIG. 29 the plasma 2925 is imaged by the second OAP 2945 reflector onto a 200 μm aperture at the front end of a lens tube. A quartz lens (1″ diameter, 25 mm focusing length, Edmund Optics, NT48-293) is mounted in the same lens tube and forming a 1:1 image of the aperture 2950 to a noise measurement photodiode 2965 (Thorlabs DET25K) through a beam sampler 2955 (fused silica, 0.5° Wedged, Thorlabs, BSF10-A1). The beam reflected by the beam sampler 2955 is focused to a second photodiode 2960 (Thorlabs DET25K) which is the detector for a closed-loop control system. There is no aperture in front of the photodiodes so the photodiodes were under-filled by the image of the 200 μm aperture. In some embodiments, the LDLS noise is caused by the laser mode hopping. The output spectrum of a semiconductor laser employed for a LDLS has a discrete set of frequencies i.e., modes. Small fluctuation of the current running through the laser diode or laser temperature can cause the laser diode to switch to the different set of modes. The instantaneous switching between modes is called mode hopping. The mode hopping can cause rapid changes in the laser output spectrum and output power. As the plasma emission intensity depends on these parameters, the mode hopping also causes changes of the LDLS radiance and therefore can compromise the LDLS stability. This effect is undesirable as high stability is required for LDLS used for absorption detectors in chromatography applications. To eliminate the negative impact of the mode hopping on the LDLS stability, the current of the semiconductor laser can be modulated at a frequency of a few tens of kHz. The amplitude of modulation is about 10-20% of the total laser current. The modulation of the current can cause intentional switching of the laser diode between different sets of modes. If this switching occurred slowly it can be observed and measured as noise by instruments having a certain bandwidth, or a predetermined frequency band. However, a rapid modulation of the laser current, at a frequency greater than the predetermined frequency band, and corresponding rapid mode hopping, can have effects which are averaged out when measured within the predetermined frequency band. As an example of an application requiring low noise, the measurement in the chromatography application is relatively slow and takes about 0.1-2.0 seconds and therefore the frequency band of interest when measuring noise in that case is primarily about 0.5 Hz to 10 Hz and secondarily about 0.1 Hz to 100 Hz to allow for digital sampling of the data. The frequency of the modulation imposed on the laser current can then be a frequency higher than about 100 Hz and preferably about 10 kHz to 100 kHz. Multiple oscillations of the laser current can occur during the period of the measurement. The contribution of different modes averaged during the period of the measurement leads to effective reduction of noise in chromatographic measurements. Some applications, for which the LDLS can be used, for example a spectrometer, have light detectors that are sensitive in a specific wavelength range. A LDLS can output a high brightness light that is about 20 times as bright in the most sensitive wavelength range of the detector as previous light sources. This dramatic increase in spectral radiance can saturate the detector of the application, which can result in the application not being able to take advantage of light outside the detector's most sensitive wavelength range, even though the LDLS can have its greatest practical advantage outside the detector's most sensitive range, e.g., in the deep ultraviolet range. In other words, the high radiance in a less useful part of the wavelength spectrum can result in an inability to use the high radiance in the useful part of the spectrum. One solution to this problem is to use a light source that has a chamber with a gas disposed therein, an ignition source of exciting the gas and at least one laser for providing energy to the excited gas within the chamber to produce a high brightness light. The high brightness light has a first spectrum. The light source also includes an optical element disposed within the path of the high brightness light to modify the first spectrum of the high brightness light to a second spectrum. The optical element can be, for example, a prism, a weak lens, a strong lens, or a dichroic filter. The second spectrum can have a relatively greater intensity of light in the ultraviolet range than the first spectrum. The first spectrum can have a relatively greater intensity of light in the visible range than the second spectrum. The optical element can increase the intensity of the light at certain wavelengths relative to the intensity of light at certain other wavelengths. FIG. 30 shows a schematic illustration of a weak lens method 3000 for modifying a spectrum of a high brightness light. High brightness light from a LDLS 3005 is sent via a delivery fiber 3010 to a filter 3015. A weak lens 3020, which can focus certain, pre-determined wavelengths because the refractive index of the lens material is dependent on wavelength modifies the spectrum of the high brightness light. The lens can be made of glass or fused quartz or other materials whose refractive index is wavelength dependent. The spectrum is modified because the chromatic aberration of the weak lens causes some wavelengths of the light to focus at the aperture of the application 3050, while other wavelengths fail to focus there and are lost from the system. The high brightness light with a modified spectrum then goes to two OAPs 3025, 3030 and then to a beam splitter 3035. The beam splitter 3035 can send a portion of the high brightness light with the modified spectrum to a feedback fiber 3040. This sample of the light can be sent to a photodiode and PID controller 3045. The PID controller 3045 can control the current to the LDLS 3005 to maintain a constant output of high brightness light. The remainder of the high brightness light can be sent to an application 3050, for example a spectrometer. The light sent to the application can have a modified spectrum from the original high brightness light emitted from the LDLS 3005 due to the light passing through the weak lens 3020. FIG. 31 shows a schematic illustration of a strong lens method 3100 for modifying a spectrum of a high brightness light. Similar to the weak lens method of FIG. 30, high brightness light from a LDLS 3005 is sent via a delivery fiber 3010 to a filter 3015. The high brightness light then goes to an OAP 3025. A strong lens 3027 exhibiting chromatic aberration, as for the weak lens above, is positioned between the OAP 3025 and a beam splitter 3035. The strong lens 3027 can focus certain, pre-determined wavelengths to modify the spectrum of the high brightness light. After the high brightness light is modified, the light can be sent to an application 3050, for example a spectrometer. The light sent to the application can have a modified spectrum from the original high brightness light emitted from the LDLS 3005 due to the light passing through the strong lens 3020. The beam splitter 3035 can send a portion of the high brightness light with the modified spectrum to a feedback fiber 3040. This sample of the light can be sent to a photodiode and PID controller 3045. The PID controller 3045 can control the current to the LDLS 3005 to adjust the current to maintain a constant output of high brightness light. FIG. 32 shows a schematic illustration of a filter method 3200 for modifying a spectrum of a high brightness light. High brightness light from a LDLS 3005 is sent via a delivery fiber 3010 to a filter 3015. The high brightness light then goes to two OAPs 3025, 3030. A reflective filter 3205 is positioned between OAP 3030 and application 3050. The reflective filter 3205 can filter certain, pre-determined wavelengths to modify the spectrum of the high brightness lights. The light sent to the application 3050 can have a modified spectrum from the original high brightness light emitted from the LDLS 3005 due to the light passing through the reflective filter 3205. For example, the reflective filter can use many layers of materials having differing refractive indexes and be designated so that shorter wavelengths are efficiently reflected whereas longer wavelengths are at least partially transmitted or absorbed by the filter. A transmissive filter can also be applied. FIG. 33 shows a schematic illustration of a prism method 3300 for modifying a spectrum of a high brightness light. High brightness light from a LDLS 3005 is sent via a delivery fiber 3010 to a filter 3015. The high brightness light then goes to two OAPs 3025, 3030. A prism 3305, for example a 20° quartz prism, is positioned between the output OAP 3030 and the application 3050. The prism disperses the light according to wavelength and produces an elongated focus spot that contains a short wavelength enhanced spectrum at one end and a long wavelength enhanced spectrum at the other end. The light sent to the application 3050 can have a modified spectrum from the original high brightness light emitted from the LDLS 3005 due to the light passing through the prison 3305. For example, if the position of the elongated focus spot is adjusted so that the aperture leading into the application 3050 receives light from one end of the elongated focus spot the spectrum of light in the application will be primarily short wavelength light and long wavelengths will be suppressed. In some embodiments, it is desirable to minimize the laser power in the light source output to reduce the amount of safety procedures that are required to operate the LDLS. FIG. 34 is a schematic illustration of a laser-driven light source 3400. To minimize the laser power in the light source output, the laser beam 3410 is positioned to contact a mirror 3430. The mirror 3430 re-directs the laser beam at a 90° angle to the plasma 3420. Light output from the laser-driven light source 3400 is emitted from the system horizontally. In some embodiments, an absorbing structure or coating is placed on the inside of the enclosure 3470 where the residual laser beams (e.g., laser beams that are unabsorbed by the plasma) will strike after transiting the bulb. In some embodiments the mirror 3430 selectively reflects the laser wavelength. The mirror 3430 can be used to deliver the laser beam 3410 to the plasma 3420 as well as reduce the back reflection of light from the plasma to the laser and/or the laser delivery fiber 3440. For example, the mirror can be a dichroic mirror positioned within the path of the laser such that the laser energy is directed toward the plasma. The dichroic mirror can selectively reflect at least one wavelength of light such that the light generated by the plasma is not substantially reflected toward the at least one laser. The dichroic mirror can comprise glass with multiple layers of dielectric optical coatings. The optical coating can reflect energy at one wavelength and transmit energy at a different wavelength. Therefore, the dichroic mirror can reflect the wavelength energy of the laser to the plasma 3420. The high brightness light that is produced by the plasma can have a different wavelength than the laser energy. The high brightness light can pass through the mirror 3430 instead of being reflected back to the laser. In some embodiments, the mirror 3430 helps keep the fiber end and/or the connector from being damaged. In other embodiments, the mirror is used to change the direction of the laser beam 3410. A LDLS has numerous applications. For example, a LDLS can be used to replace D2 lamps, xenon arc lamps, and mercury arc lamps. In addition, a LDLS can be used for HPLC, UV/VIS spectroscopy/spectrophotometry, and endoscopy. Furthermore, a LDLS can be used in a microscope illuminator for protein absorption at 280 nm and DNA at 260 nm. A LDLS can also be used for general illumination in a microscope and for fluorescence excitation in a fluorescence based instrument or microscope. A LDLS can also be used in a confocal microscope. A LDLS can also be used for circular dichroism (“CD”) spectroscopy. A LDLS can provide brighter light at shorter wavelengths with lower input power, as compared to high wattage xenon arc lamps currently used. In addition, a LDLS can be used in atomic absorption spectroscopy to provide a brighter light source than arc lamps currently used. In addition, a LDLS can be used spectrometers or spectrographs to provide lower noise than arc lamps currently used. In some embodiments, a LDLS can be used with an absorption cell. A system using a LDLS with an absorption cell has the advantage that a very small cell can be used while still maintaining a high rate of photon flux through the cell due to the very high radiance, high brightness, of the LDLS. Thus, smaller volumes of material are needed to carry out an analysis in the cell, and for a given time resolution, lower flow rates are required. FIG. 35 is a schematic illustration of an absorption cell 3500. An absorption cell has a vessel 3505 with transparent walls 3506. The vessel 3505 can hold a gas or a liquid. The absorptivity or absorption spectrum of the gas or liquid can be measured. The absorption cell 3500 can contain one or more optical windows, 3510. In some embodiments the optical windows 3510 can let in light from a light source 3520. In some embodiments the light source 3520 is a LDLS. One of the windows 3510 can be illuminated by light 3530 from the LDLS which is delivered to the window 3510 by an optical system (not shown). The optical system can include a combination of lenses, mirrors, gratings and other optical elements. The system can be a focusing mirror to focus the LDLS light into the absorption cell 3500 while avoiding the chromatic aberration which can occur if a lens is used. The light 3530 can be detected by a detector 3540. The absorption cell 3500 can be used as the sample cell 3680 in FIG. 36 In some embodiments, a LDLS can be used with a UV detector. FIG. 36 is a schematic illustration of a UV detector 3600. The UV detector 3600 contains a light source 3610. In some embodiments the light source 3610 is a LDLS. Light 3615 from the light source 3610 follows the path of the arrows in FIG. 36. For example, the light 3615 emitted from the light source 3610, contacts a first curved mirror 3620 and then a second curved mirror 3630. The light 3615 then contacts a diffraction grating 3640 and returns to the second curved mirror 3630. The light 3615 then contacts a first plane mirror 3650 and then a second plane mirror 3660. The light 3615 passes through a first lens 3670. In some embodiments, the first lens 3670 is a quartz lens. The light 3615 then enters a sample cell 3680 and passes through a second lens 3690. In some embodiments, the second lens 3690 is a quartz lens. The light 3615 then enters a photo cell 3695. In some embodiments, a LDLS can be used with a diode array detector. FIG. 37 is a schematic illustration of a diode array detector 3700, according to an illustrative embodiment of the invention. In some embodiments, the diode array detector contains a light source 3710. In some embodiments, the light source 3710 is a LDLS. In some embodiments the light 3715 from the light source 3710 passes through an achromatic lens system 3720 and then a shutter 3730. The light 3715 then enters a flow cell 3740 and then entrance aperture 3745. The light 3715 exits the entrance aperture 3745 and contacts a holographic grating 3750. The holographic grating 3750 directs the light 3770 into a photo diode array 3760. In some embodiments, a LDLS can be used with a fluorescence detector. FIG. 38 is a schematic illustration of a fluorescence detector 3800, according to an illustrative embodiment of the invention. In some embodiments the fluorescence detector contains a light source 3810. In one embodiment the light source 3810 is a LDLS. The light 3815 from the light source 3810, passes through a first lens 3820. In some embodiments, the first lens 3820 is a quartz lens. The light 3815 then passes through a first window 3840 and enters chamber 3830. Some of the light 3815 exits the chamber 3830 through a second window 3845. In some embodiments the first and second windows 3840, 3845 are made of quartz. Some of the light 3815 exits through a transparent wall of the chamber 3830 and contacts a second lens 3850. The lens 3850 focuses the light 3815. The light 3815 then enters photo cell 3860. Variations, modifications, and other implementations of what is described herein will occur to those of ordinary skill in the art without departing from the spirit and the scope of the invention as claimed. Accordingly, the invention is to be defined not by the preceding illustrative description but instead by the spirit and scope of the following claims.
	abstract	A method of manufacturing a collimator mandrel having variable attenuation characteristics is presented. The manufacturing process includes the placement of a layer of attenuating material on a core of base material. The layer of attenuating material is relatively thin and varies in thickness circumferentially around the core. The collimator mandrel may be manufactured by placing a cast about a core of non-attenuating material, filling a void between the cast and the core with an attenuating material, allowing the material to cure, and removing the cast from the assembly.
048636827	claims	1. A stainless steel alloy composition for service exposed to irradiation, having resistance to irradiation promoted stress corrosion cracking and reduced long term irradiation induced radioactivity, consisting of a low carbon content austenitic stainless steel alloy composition comprising about 18 to 20 percent weight of chromium, about 9 to 11 percent weight of nickel, about 1.5 to 2 percent weight of manganese, a maximum of about 0.04 percent weight of carbon, a minimum of about 14 times of the carbon percent weight contents of a combination of niobium and tantalum together with the niobium of the combination limited to about 0.25 percent weight of the alloy composition, and the balance of the composition comprising iron with only incidental impurities. 2. The stainless steel composition of claim 1, wherein the alloy composition contains carbon within the range of about 0.02 to about 0.04 percent weight. 3. The stainless steel composition of claim 1, wherein the alloy composition contains tantalum in amounts up to about 0.4 percent weight. 4. The stainless steel composition of claim 1, wherein the alloy composition contains a combination of niobium and tantalum together in amounts of at least about 0.28 percent weight. 5. A stainless steel alloy composition for service exposed to irradiation, having resistance to irradiation promoted stress corrosion cracking and reduced long term irradiation induced radioactivity, consisting of a low carbon content austenitic stainless steel alloy composition comprising about 18 to 20 percent weight of chromium, about 9 to 11 percent weight of nickel, about 1.5 to 2 percent weight manganese, a maximum of about 0.04 percent weight of carbon, a minimum of about 14 times of the carbon percent weight contents of a combination of niobium and tantalum together with the niobium of the combination limited to no more than about 0.25 percent weight of the alloy composition, a maximum of about 0.005 percent weight of phosphorus, a maximum of about 0.004 percent weight of sulfur, a maximum of about 0.03 percent weight of silicon, a maximum of about 0.03 percent weight of nitrogen, a maximum of about 0.03 percent weight of aluminum, a maximum of about 0.01 percent weight of calcium, a maximum of about 0.003 percent weight of boron, a maximum of about 0.05 percent weight of cobalt, and the balance of the alloy composition comprising iron with incidental impurities. 6. The stainless steel composition of claim 5, wherein the alloy composition contains carbon within the range of about 0.02 to about 0.04 percent weight. 7. The stainless steel composition of claim 5, wherein the alloy composition contains tantalum in amounts up to about 0.4 percent weight. 8. The stainless steel composition of claim 5, wherein the alloy composition contains a combination of niobium and tantalum together in amounts of at least about 0.28 percent weight. 9. The stainless steel composition of claim 5, wherein the alloy composition contains a combination of niobium and tantalum together in a maximum amount of about 0.65 percent weight, with the niobium in a maximum amount of about 0.25 percent weight. 10. A stainless steel alloy composition for service exposed to irradiation, having resistance to irradiation promoted stress corrosion cracking and reduced long term irradiation induced radioactivity, consisting of a low carbon content austenitic stainless steel alloy composition comprising about 18 to 20 percent weight of chromium, about 9 to 11 percent weight of nickel, about 1.5 to 2 percent weight of manganese, about 0.02 to about 0.04 percent weight of carbon, a minimum of about 14 times of the carbon percent weight contents of a combination of niobium and tantalum together and a maximum amount of about 0.65 percent weight of said combined niobium and tantalum with the niobium in a maximum amount of about 0.25 percent weight of the alloy composition, a maximum of about 0.005 percent weight of phosphorus, a maximum of 0.004 percent weight of sulfur, a maximum of about 0.03 percent weight of silicon, a maximum of about 0.03 percent weight of nitrogen, a maximum of about 0.03 percent weight of aluminum, a maximum of about 0.01 percent weight of calcium, a maximum of about 0.003 percent weight of boron, a maximum of about 0.05 percent weight of cobalt, and the balance of the alloy composition comprising iron with incidental impurities.
	abstract	An apparatus for generating extreme ultraviolet light by exciting a target material to turn the target material into plasma may include: a frame; a chamber in which the extreme ultraviolet light is generated; a target supply unit for supplying the target material into the chamber; a first connection member for connecting the frame and the chamber flexibly; a mechanism for fixing the target supply unit to the frame; and a second connection member for connecting the target supply unit to the chamber flexibly.
040640035	abstract	The intermediate heat transport system for a sodium-cooled fast breeder reactor includes a device for rapidly draining the sodium therefrom should a sodium-water reaction occur within the system. This device includes a rupturable member in a drain line in the system and means for cutting a large opening therein and for positively removing the sheared-out portion from the opening cut in the rupturable member. According to the preferred embodiment of the invention the rupturable member includes a solid head seated in the end of the drain line having a rim extending peripherally therearound, the rim being clamped against the end of the drain line by a clamp ring having an interior shearing edge, the bottom of the rupturable member being convex and extending into the drain line. Means are provided to draw the rupturable member away from the drain line against the shearing edge to clear the drain line for outflow of sodium therethrough.
046363505	description	DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The high temperature reactor described in FIG. 1 comprises a core with a bed 1 of spherical fuel elements 2. This reactor has a capacity of 1637 Mw.sub.th. The reactor is charged according to the principle of the single passage of the fuel elements. The bed 1, through which the cooling gas is flowing from top to bottom, is surrounded by a roof reflector 3 and a cylindrical side reflector (not shown), together with a bottom reflector. A cavity 4 is located between the roof reflector 3 and the surface of the bed 1. The radius of the reactor core is 4.15 m. The roof reflector 3 has a thickness of 2 m and the cavity 4 has a height of 1 m. The spherical fuel elements have diameters of 6 cm; they contain on the average 10.343 g thorium and 10.285 g uranium with an enrichment of 93%. The filling factor of the bed 1 is 0.61. The shutdown and control installation contains 108 core absorber rods 5, arranged in the roof reflector 3 and capable of direct insertion in the bed 1. The high temperature reactor further has 42 absorber rods that may be moved in the wall of the side reflector. The core absorber rods 5 may be retracted into an upper terminal position 6 in the roof reflector. FIG. 1 shows a section of the rod grid of the 108 core absorber rods 5. To shut down the high temperature reactor, all of the rods 5 are inserted to a predetermined depth into the bed 1. For the control of the load, however, only a part of the core absorber rods 5 is inserted. The rods 5 forming the partial amount 5' at this point are indicated by black circles. The rest of the core absorber rods 5 located in their upper terminal position 6 constitute the group 5". In order to obtain a uniform exposure of all of the core absorber rods 5 following an extended period of operation, the rods belonging to groups 5' and 5" are mutually interchanged. In the embodiment chosen, the partial number 5' is formed by 30 core absorber rods 5. They have an effectivity of 4.8% .DELTA. K/K when inserted to the surface of the bed 1 of fuel elements (the entirety of all of the core absorber elements 5 would yield an effectivity of approximately 7% .DELTA. K/K when inserted to the same depth). In contrast, the load cycle of 100%-35%-100% requires a reactivity of 3.9% .DELTA. K/K and the load cycle of 100%-35% a reactivity of 2.6 .DELTA. K/K. It is, therefore, sufficient for a load cycle to insert the 30 core absorber rods of the partial number 5' within the cavity 4. According to calculations, the reactivity of 2.6% K/K required for a 100-35% load cycle is provided by the 30 core absorber rods of the partial amount 5' when the rods are inserted to a depth of 15 cm in the cavity 4 (measured from the lower edge of the roof reflector 3). The use of all of the 108 core absorber rods 5 for this load cycle process would result in a depth of insertion of 0 cm. The thermal neutron flux (E<1.9 eV) is approximately equal in both of the modes of insertion and amounts in the area of the rod tips to approximately 0.19.times.10.sup.15 (1/cm.sup.2 sec.). A further comparison of the two modes of insertion shows that the control of loads by means of 30 core absorber rods 5 results in a thermal exposure per unit time of all of the rods that is approximately one-half of the exposure incurred in the mode of insertion using the bank of 108 rods. The comparison is even more favorable in relation to the exposure to fast neutrons. It is lower by an approximate factor of 3 per unit time for the method using 30 rods than with 108 rods. A further advantage of the method using only 30 core absorber rods for load control is obtained in the determination of step dimensions for the method using 30 core absorber rods 5. As the maximum reactivity rise with the 30 rod bank is lower than with the 108 rod bank, the minimum step size may be correspondingly larger. The second example as shown in FIG. 2 illustrates the rapid shutdown of a high temperature reactor with spherical fuel elements according to the invention. The reactor has a core radius of 4.87 m and a capacity of 2250 MW.sub.th. The ceramic installations are similar to those of the reactor described in the first example. The roof reflector has a thickness of 2 m and the cavity a height of 1 m. The shutdown and control apparatus includes 150 core absorber rods arranged in an ideal triangular grid in the roof reflector. Additionally, 48 reflector rods are available. These rods are moved in the wall of the side reflector and are in principle fully inserted in the case of a rapid shutdown. In calculating the shutdown reactivity, initially a disturbance reactivity due to water penetration of 2.2 .DELTA. K/K must be assumed. With consideration of the temperature equalization from a full load to zero load and of the cooling of the reactor core by approximately 300.degree. including an uncertainty allowance of 10% and a minimum subcriticality of 0.5% .DELTA. K/K, the maximum shutdown requirement is 6.0 .DELTA. K/K. The necessary rod effectivity amounts to 7.5% .DELTA. K/K wherein the loss of the two most effective rods and a 10% uncertainty deduction is included. Of this rod effectivity, 0.8% .DELTA. K/K is provided by the 48 reflector rods so that the core absorber rods are required to furnish additionally 6.7% .DELTA. K/K. If, as planned heretofore, all of the 150 core absorber rods are used for load control, the tips of these rods are located after an extended operation at a full load prior to a rapid shutdown at a depth of 60 cm in the cavity measured from the lower edge of the rod reflector. The shutdown insertion required is 175 cm. After the rapid shutdown, the tips of the rods are thus inserted to a depth of 135 cm in the fuel element bed. If one-half of the core absorber rods are used both for load control and rapid shutdown, the rods are inserted prior to the rapid shutdown to a depth of 100 cm in the cavity and thus are touching the surface of the bed. The shutdown insertion now requires amounts to 200 cm so that the rod tips are immersed after the rapid shutdown to a depth of 200 cm in the bed of fuel elements. If as proposed hereinabove the disturbance reactivity required in the case of water penetration is provided by means of a special shutdown procedure, the requirement for a "normal" rapid shutdown is only 3.5% .DELTA. K/K for which a rod effectivity of approximately 4.5% .DELTA. K/K is necessary. If all 150 core absorber rods are used in a rapid shutdown, a shutdown insertion of 125 cm is needed so that the rod tips are inserted to a depth of 85 cm in the bed of fuel elements. An insertion of 119 cm is determined when using 75 core absorber rods and the depth of immersion of these rods in the bed thus amounts to 119 cm. In the case of a rapid shutdown with one-half of the core absorber rods, it is necessary to insert the latter only 34 cm deeper in the bed when all of the core absorber rods are used.
	description	This application claims the benefit of U.S. Provisional Patent Application No. 61/195,639, filed Oct. 9, 2008, entitled “Four-dimensional Electron Microscope,” U.S. Provisional Patent Application No. 61/236,745, filed Aug. 25, 2009, entitled “4D Nanoscale Diffraction Observed by Convergent-Beam Ultrafast Electron Microscopy,” and U.S. Provisional Patent Application No. 61/240,946, filed Sep. 9, 2009, entitled “4D Attosecond Imaging with Free Electrons: Diffraction Methods and Potential Applications,” which are commonly assigned, the disclosures of which are hereby incorporated by reference in their entirety. The following two regular U.S. patent applications (including this one) are being filed concurrently, and the entire disclosure of the other application is hereby incorporated by reference into this application for all purposes: application Ser. No. 12/575,285, filed Oct. 7, 2009, entitled “4D Imaging in an Ultrafast Electron Microscope”; and application Ser. No. 12/575,312, filed Oct. 7, 2009, entitled “Characterization of Nanoscale Structures Using an Ultrafast Electron Microscope”. The U.S. Government has certain rights in this invention pursuant to Grant No. GM081520 awarded by the National Institutes of Health, Grant No. FA9550-07-1-0484 awarded by the Air Force (AFOSR) and Grant No(s). CME0549936 & DMR0504854 awarded by the National Science Foundation. Electrons, because of their wave-particle duality, can be accelerated to have picometer wavelength and focused to image in real space. With the impressive advances made in transmission electron microscopy (TEM), STEM, and aberration-corrected TEM, it is now possible to image with high resolution, reaching the sub-Angstrom scale. Together with the progress made in electron crystallography, tomography, and single-particle imaging, today the electron microscope has become a central tool in many fields, from materials science to biology. For many microscopes, the electrons are generated either thermally by heating the cathode or by field emission, and as such the electron beam is made of random electron bursts with no control over the temporal behavior. In these microscopes, time resolution of milliseconds or longer, being limited by the video rate of the detector, can be achieved, while maintaining the high spatial resolution. Despite the advances made in TEM techniques, there is a need in the art for improved methods and novel systems for ultrafast electron microscopy. According to embodiments of the present invention, methods and systems for 4D ultrafast electron microscopy (UEM) are provided—in situ imaging with ultrafast time resolution in TEM. Thus, 4D microscopy provides imaging for the three dimensions of space as well as the dimension of time. In some embodiments, single electron imaging is introduced as a component of the 4D UEM technique. Utilizing one electron packets, resolution issues related to repulsion between electrons (the so-called space-charge problem) are addressed, providing resolution unavailable using conventional techniques. Moreover, other embodiments of the present invention provide methods and systems for convergent beam UEM, focusing the electron beams onto the specimen to measure structural characteristics in three dimensions as a function of time. Additionally, embodiments provide not only 4D imaging of specimens, but characterization of electron energy, performing time resolved electron energy loss spectroscopy (EELS). The potential applications for 4D UEM are demonstrated using examples including gold and graphite, which exhibit very different structural and morphological changes with time. For gold, following thermally induced stress, the atomic structural expansion, the nonthermal lattice temperature, and the ultrafast transients of warping/bulging were determined. In contrast, in graphite, striking coherent transients of the structure were observed in the selected-area image dynamics, and also in diffraction, directly measuring the resonance period of Young's elastic modulus. Measurement of the Young's elastic modulus for the nano-scale dimension, the frequency is found to be as high as 30 gigahertz, hitherto unobserved, with the atomic motions being along the c-axis. Both materials undergo fully reversible dynamical changes, retracing the same evolution after each initiating impulsive stress. Thus, embodiments of the present invention provide methods and systems for performing imaging studies of dynamics using UEM. Other embodiments of the present invention extend four-dimensional (4D) electron imaging to the attosecond time domain. Specifically, embodiments of the present invention are used to generate attosecond electron pulses and in situ probing with electron diffraction. The free electron pulses have a de Broglie wavelength on the order of picometers and a high degree of monochromaticity (ΔE/E0≈10−4); attosecond optical pulses have typically a wavelength of 20 nm and ΔE/E0≈0.5, where E0 is the central energy and ΔE is the energy bandwidth. Diffraction, and tilting of the electron pulses/specimen, permit the direct investigation of electron density changes in molecules and condensed matter. This 4D imaging on the attosecond time scale is a pump-probe approach in free space and with free electrons. As described more fully throughout the present specification, some embodiments of the present invention utilize single electron packets in UEM, referred to as single electron imaging. Conventionally, it was believed that the greater number of electrons per pulse, the better the image produced by the microscope. In other words, as the signal is increased, imaging improves. However, the inventor has determined that by using single electron packets and repeating the imaging process a number of times, images can be achieved without repulsion between electrons. Unlike photons, electrons are charged and repel each other. Thus, as the number of electrons per pulse increases, the divergence of the trajectories increases and resolution decreases. Using single electron imaging techniques, atomic scale resolution of motion is provided once the space-charge problem is addressed. According to an embodiment of the present invention, a four-dimensional electron microscope for imaging a sample is provided. The four-dimensional electron microscope includes a stage assembly configured to support the sample, a first laser source capable of emitting a first optical pulse of less than 1 ps in duration, and a second laser source capable of emitting a second optical pulse of less than 1 ns in duration. The four-dimensional electron microscope also includes a cathode coupled to the first laser source and the second laser source. The cathode is capable of emitting a first electron pulse less than 1 ps in duration in response to the first optical pulse and a second electron pulse of less than 1 ns in response to the second optical pulse. The four-dimensional electron microscope further includes an electron lens assembly configured to focus the electron pulse onto the sample and a detector configured to capture one or more electrons passing through the sample. The detector is configured to provide a data signal associated with the one or more electrons passing through the sample. The four-dimensional electron microscope additionally includes a processor coupled to the detector. The processor is configured to process the data signal associated with the one or more electrons passing through the sample to output information associated with an image of the sample. Moreover, the four-dimensional electron microscope includes an output device coupled to the processor. The output device is configured to output the information associated with the image of the sample. According to another embodiment of the present invention, a convergent beam 4D electron microscope is provided. The convergent beam 4D electron microscope includes a laser system operable to provide a series of optical pulses, a first optical system operable to split the series of optical pulses into a first set of optical pulses and a second set of optical pulses and a first frequency conversion unit operable to frequency double the first set of optical pulses. The convergent beam 4D electron microscope also includes a second optical system operable to direct the frequency doubled first set of optical pulses to impinge on a sample and a second frequency conversion unit operable to frequency triple the second set of optical pulses. The convergent beam 4D electron microscope further includes a third optical system operable to direct the frequency tripled second set of optical pulses to impinge on a cathode, thereby generating a train of electron packets. Moreover, the convergent beam 4D electron microscope includes an accelerator operable to accelerate the train of electron packets, a first electron lens operable to de-magnify the train of electron packets, and a second electron lens operable to focus the train of electron packets onto the sample. According to a specific embodiment of the present invention, a system for generating attosecond electron pulses is provided. The system includes a first laser source operable to provide a laser pulse and a cathode optically coupled to the first laser source and operable to provide an electron pulse at a velocity v0 directed along an electron path. The system also includes a second laser source operable to provide a first optical wave at a first wavelength. The first optical wave propagates in a first direction offset from the electron path by a first angle. The system further includes a third laser source operable to provide a second optical wave at a second wavelength. The second optical wave propagates in a second direction offset from the electron path by a second angle and the interaction between the first optical wave and the second optical wave produce a standing wave copropagating with the electron pulse. According to another specific embodiment of the present invention, a method for generating a series of tilted attosecond pulses is provided. The method includes providing a femtosecond electron packet propagating along an electron path. The femtosecond electron packet has a packet duration and a direction of propagation. The method also includes providing an optical standing wave disposed along the electron path. The optical standing wave is characterized by a peak to peak wavelength measured in a direction tilted at a predetermined angle with respect to the direction of propagation. The method further includes generating the series of tilted attosecond pulses after interaction between the femtosecond electron packet and the optical standing wave. According to a particular embodiment of the present invention, a method of operating an electron energy loss spectroscopy (EELS) system is provided. The method includes providing a train of optical pulses using a pulsed laser source, directing the train of optical pulses along an optical path, frequency doubling a portion of the train of optical pulses to provide a frequency doubled train of optical pulses, and frequency tripling a portion of the frequency doubled train of optical pulses to provide a frequency tripled train of optical pulses. The method also includes optically delaying the frequency doubled train of optical pulses using a variable delay line, impinging the frequency doubled train of optical pulses on a sample, impinging the frequency tripled train of optical pulses on a photocathode, and generating a train of electron pulses along an electron path. The method further includes passing the train of electron pulses through the sample, passing the train of electron pulses through a magnetic lens, and detecting the train of electron pulses at a camera. According to an embodiment of the present invention, a method of imaging a sample is provided. The method includes providing a stage assembly configured to support the sample, generating a train of optical pulses from a laser source, and directing the train of optical pulses along an optical path to impinge on a cathode. The method also includes generating a train of electron pulses in response to the train of optical pulses impinging on the cathode. Each of the electron pulses consists of a single electron. The method further includes directing the train of electron pulses along an imaging path to impinge on the sample, detecting a plurality of the electron pulses after passing through the sample, processing the plurality of electron pulses to form an image of the sample, and outputting the image of the sample to an output device. According to another embodiment of the present invention, a method of capturing a series of time-framed images of a moving nanoscale object is provided. The method includes a) initiating motion of the nanoscale object using an optical clocking pulse, b) directing an optical trigger pulse to impinge on a cathode, and c) generating an electron pulse. The method also includes d) directing the electron pulse to impinge on the sample with a predetermined time delay between the optical clocking pulse and the electron pulse, e) detecting the electron pulse, f) processing the detected electron pulse to form an image, and g) increasing the predetermined time delay between the optical clocking pulse and the electron pulse. The method further includes repeating steps a) through g) to capture the series of time-framed images of the moving nanoscale object. According to a specific embodiment of the present invention, a method of characterizing a sample is provided. The method includes providing a laser wave characterized by an optical wavelength (λ0) and a direction of propagation and directing the laser wave along an optical path to impinge on a test surface of the sample. The test surface of the sample is tilted with respect to the direction of propagation of the laser by a first angle (α). The method also includes providing a train of electron pulses characterized by a propagation velocity (vel), a spacing between pulses ( λ 0 ⁢ ⁢ v el c ) ,and a direction of propagation tilted with respect to the direction of propagation of the laser by a second angle (β). The method further includes directing the train of electron pulses along an electron path to impinge on the test surface of the sample. The first angle, the second angle, and the propagation velocity are related by sin ⁡ ( α ) sin ⁡ ( α - β ) = c v el . According to another specific embodiment of the present invention, a method of imaging chemical bonding dynamics is provided. The method includes positioning a sample in a reduced atmosphere environment, providing a first train of laser pulses, and directing the first train of laser pulses along a first optical path to impinge on a sample. The method also includes providing a second train of laser pulses, directing the second train of laser pulses along a second optical path to impinge on a photocathode, and generating a train of electron pulses. One or more of the electron pulses consist of a single electron. The method further includes accelerating the train of electron pulses and transmitting a portion of the train of electron pulses through the sample. Numerous benefits are achieved by way of the present invention over conventional techniques. For example, the present systems provide temporal resolution over a wide range of time scales. Additionally, unlike spectroscopic methods, embodiments of the present invention can determine a structure in 3-D space. Such capabilities allow for the investigation of phase transformation in matter, determination of elastic and mechanical properties of materials on the nanoscale, and the time evolution of processes involved in materials and biological function. Depending upon the embodiment, one or more of these benefits may be achieved. These and other benefits will be described in more detail throughout the present specification and more particularly below. These and other objects and features of the present invention and the manner of obtaining them will become apparent to those skilled in the art, and the invention itself will be best understood by reference to the following detailed description read in conjunction with the accompanying drawings. Ultrafast imaging, using pulsed photoelectron packets, provides opportunities for studying, in real space, the elementary processes of structural and morphological changes. In electron diffraction, ultrashort time resolution is possible but the data is recorded in reciprocal space. With space-charge-limited nanosecond (sub-micron) image resolutions ultrashort processes are not possible to observe. In order to achieve the ultrafast resolution in microscopy, the concept of single-electron pulse imaging was realized as a key to the elimination of the Coulomb repulsion between electrons while maintaining the high temporal and spatial resolutions. As long as the number of electrons in each pulse is much below the space-charge limit, the packet can have a few or tens of electrons and the temporal resolution is still determined by the femtosecond (fs) optical pulse duration and the energy uncertainty, on the order of 100 fs, and the spatial resolution is atomic-scale. However, the goal of full-scale dynamic imaging can be attained only when in the microscope the problems of in situ high spatiotemporal resolution for selected image areas, together with heat dissipation, are overcome. FIG. 1 is a simplified diagram of a 4D electron microscope system according to an embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims herein. One of ordinary skill in the art would recognize many variations, modifications, and alternatives. As illustrated in FIG. 1, a femtosecond laser 110 or a nanosecond laser 105 is directed through a Pockels cell 112, which acts as a controllable shutter. A Glan polarizer 114 is used in some embodiments, to select the laser power propagating in optical path 115. A beam splitter (not shown) is used to provide several laser beams to various portions of the system. Although the system illustrated in FIG. 1 is described with respect to imaging applications, this is not generally required by the present invention. One of skill in the art will appreciate that embodiments of the present invention provide systems and methods for imaging, diffraction, crystallography, electron spectroscopy, and related fields. Particularly, the experimental results discussed below yield insight into the varied applications available using embodiments of the present invention. The femtosecond laser 110 is generally capable of generating a train of optical pulses with predetermined pulse width. One example of such a laser system is a diode-pumped mode-locked titanium sapphire (Ti:Sapphire) laser oscillator operating at 800 nm and generating 100 fs pulses at a repetition rate of 80 MHz and an average power of 1 Watt, resulting in a period between pulses of 12.5 ns. In an embodiment, the spectral bandwidth of the laser pulses is 2.35 nm FWHM. An example of one such laser is a Mai Tai One Box Femtosecond Ti:Sapphire Laser, available from Spectra-Physics Lasers, of Mountain View, Calif. In alternative embodiments, other laser sources generating optical pulses at different wavelengths, with different pulse widths, and at different repetition rates are utilized. One of ordinary skill in the art would recognize many variations, modifications, and alternatives. The nanosecond laser 105 is also generally capable of generating a train of optical pulses with a predetermined pulse width greater than that provided by the femtosecond laser. The use of these two laser systems enables system miniaturization since the size of the nanosecond laser is typically small in comparison to some other laser systems. By moving one or more mirrors, either laser beam is selected for use in the system. The ability to select either laser enables scanning over a broad time scale—from femtoseconds all the way to milliseconds. For short time scale measurement, the femtosecond laser is used and the delay stage (described below) is scanned at corresponding small time scales. For measurement of phenomena over longer time scales, the nanosecond laser is used and the delay stage is scanned at corresponding longer time scales. A first portion of the output of the femtosecond laser 110 is coupled to a second harmonic generation (SHG) device 116, for example a barium borate (BaB2O4) crystal, typically referred to as a BBO crystal and available from a variety of doubling crystal manufacturers. The SHG device frequency doubles the train of optical pulses to generate a train of 400 nm, 100 fs optical pulses at an 80 MHz repetition rate. SHG devices generally utilize a nonlinear crystal to frequency double the input pulse while preserving the pulse width. In some embodiments, the SHG is a frequency tripling device, thereby generating an optical pulse at UV wavelengths. Of course, the desired output wavelength for the optical pulse will depend on the particular application. The doubled optical pulse produced by the SHG device propagates along electron generating path 118. A cw diode laser 120 is combined with the frequency doubled optical pulse using beam splitter 122. The light produce by the cw diode laser, now collinear with the optical pulse produced by the SHG device, serves as an alignment marker beam and is used to track the position of the optical pulse train in the electron generating path. The collinear laser beams enter chamber 130 through entrance window 132. In the embodiment illustrated in FIG. 1, the entrance window is fabricated from materials with high transparency at 400 nm and sufficient thickness to provide mechanical rigidity. For example, BK-7 glass about 6 mm thick with anti-reflection coatings, e.g. MgF2 or sapphire are used in various embodiments. One of ordinary skill in the art would recognize many variations, modifications, and alternatives. An optical system, partly provided outside chamber 130 and partly provided inside chamber 130 is used to direct the frequency doubled optical pulse train along the electron-generating path 134 inside the chamber 130 so that the optical pulses impinge on cathode 140. As illustrated, the optical system includes mirror 144, which serves as a turning mirror inside chamber 130. In embodiments of the present invention, polished metal mirrors are utilized inside the chamber 130 since electron irradiation may damage mirror coatings used on some optical mirrors. In a specific embodiment, mirror 144 is fabricated from an aluminum substrate that is diamond turned to produce a mirror surface. In some embodiments, the aluminum mirror is not coated. In other embodiments, other metal mirrors, such as a mirror fabricated from platinum is used as mirror 144. In an embodiment, the area of interaction on the cathode was selected to be a flat 300 μm in diameter. Moreover, in the embodiment illustrated, the frequency doubled optical pulse was shaped to provide a beam with a beam waist of a predetermined diameter at the surface of the cathode. In a specific embodiment, the beam waist was about 50 μm. In alternative embodiments, the beam waist ranged from about 30 μm to about 200 μm. Of course, the particular dimensions will depend on the particular applications. The frequency doubled optical pulse train was steered inside the chamber using a computer controlled mirror in a specific embodiment. In a specific embodiment, the optical pulse train is directed toward a front-illuminated photocathode where the irradiation of the cathode by the laser results in the generation of electron pulses via the photoelectric effect. Irradiation of a cathode with light having an energy above the work function of the cathode leads to the ejection of photoelectrons. That is, a pulse of electromagnetic energy above the work function of the cathode ejects a pulse of electrons according to a preferred embodiment. Generally, the cathode is maintained at a temperature of 1000 K, well below the thermal emission threshold temperature of about 1500 K, but this is not required by the present invention. In alternative embodiments, the cathode is maintained at room temperature. In some embodiments, the cathode is adapted to provide an electron pulse of predetermined pulse width. The trajectory of the electrons after emission follows the lens design of the TEM, namely the condenser, the objective, and the projector lenses. Depending upon the embodiment, there may also be other configurations. In the embodiment illustrated, the cathode is a Mini-Vogel mount single crystal lanthanum hexaboride (LaB6) cathode shaped as a truncated cone with a flat of 300 μm at the apex and a cone angle of 90°, available from Applied Physics Technologies, Inc., of McMinnville, Oreg. As is often known, LaB6 cathodes are regularly used in transmission and scanning electron microscopes. The quantum efficiency of LaB6 cathodes is about 10−3 and these cathodes are capable of producing electron pulses with temporal pulse widths on the order of 10−13 seconds. In some embodiments, the brightness of electron pulses produced by the cathode is on the order of 109 A/cm2/rad2 and the energy spread of the electron pulses is on the order of 0.1 eV. In other embodiments, the pulse energy of the laser pulse is reduced to about 500 pJ per pulse, resulting in approximately one electron/pulse Generally, the image quality acquired using a TEM is proportional to the number of electrons passing through the sample. That is, as the number of electrons passing through the sample is increased, the image quality increases. Some pulsed lasers, such as some Q-switched lasers, reduce the pulse count to produce a smaller number of pulses characterized by higher peak power per pulse. Thus, some laser amplifiers operate at a 1 kHz repetition rate, producing pulses with energies ranging from about 1 μJ to about 2 mJ per pulse. However, when such high peak power lasers are used to generate electron pulses using the photoelectric effect, among other issues, both spatial and temporal broadening of the electron pulses adversely impact the pulse width of the electron pulse or packet produced. In some embodiments of the present invention, the laser is operated to produce low power pulses at higher repetition rates, for example, 80 MHz. In this mode of operation, benefits available using lower power per pulse are provided, as described below. Additionally, because of the high repetition rate, sufficient numbers of electrons are available to acquire high quality images. In some embodiments of the present invention, the laser power is maintained at a level of less than 500 pJ per pulse to prevent damage to the photocathode. As a benefit, the robustness of the photoemitter is enhanced. Additionally, laser pulses at these power levels prevent space-charge broadening of the electron pulse width during the flight time from the cathode to the sample, thus preserving the desired femtosecond temporal resolution. Additionally, the low electron count per pulse provided by some embodiments of the present invention reduces the effects of space charge repulsion in the electron pulse, thereby enhancing the focusing properties of the system. As one of skill in the art will appreciated, a low electron count per pulse, coupled with a high repetition rate of up to 80 MHz provided by the femtosecond laser, provides a total dose as high as one electron/Å2 as generally utilized in imaging applications. In alternative embodiments, other suitable cathodes capable of providing a ultrafast pulse of electrons in response to an ultrafast optical pulse of appropriate wavelength are utilized. In embodiments of the present invention, the cathode is selected to provide a work function correlated with the wavelength of the optical pulses provided by the SHG device. The wavelength of radiation is related to the energy of the photon by the familiar relation λ(μm)≈1.24÷v (eV), where λ is the wavelength in microns and v is the energy in eV. For example, a LaB6 cathode with a work function of 2.7 eV is matched to optical pulses with a wavelength of 400 nm (v=3.1 eV) in an embodiment of the present invention. As illustrated, the cathode is enclosed in a vacuum chamber 130, for example, a housing for a transmission electron microscope (TEM). In general, the vacuum in the chamber 130 is maintained at a level of less than 1×10−6 torr. In alternative embodiments, the vacuum level varies from about 1×10−6 torr to about 1×10−10 ton. The particular vacuum level will be a function of the varied applications. In embodiments of the present invention, the short duration of the photon pulse leads to ejection of photoelectrons before an appreciable amount of the deposited energy is transferred to the lattice of the cathode. In general, the characteristic time for thermalization of the deposited energy in metals is below a few picoseconds, thus no heating of the cathode takes place using embodiments of the present invention. Electrons produced by the cathode 140 are accelerated past the anode 142 and are collimated and focused by electron lens assembly 146 and directed along electron imaging path 148 toward the sample 150. The electron lens assembly generally contains a number of electromagnetic lenses, apertures, and other elements as will be appreciated by one of skill in the art. Electron lens assemblies suitable for embodiments of the present invention are often used in TEMs. The electron pulse propagating along electron imaging path 148 is controlled in embodiments of the present invention by a controller (not shown, but described in more detail with reference to certain Figures below) to provide an electron beam of predetermined dimensions, the electron beam comprising a train of ultrafast electron pulses. The relationship between the electron wavelength (λdeBroglie) and the accelerating voltage (U) in an electron microscope is given by the relationship λdeBroglie=h/(2m0eU)1/2, where h, m0, e are Planck's constant, the electron mass, and an elementary charge. As an example, the de Broglie wavelength of an electron pulse at 120 kV corresponds to 0.0335 Å, and can be varied depending on the particular application. The bandwidth or energy spread of an electron packet is a function of the photoelectric process and bandwidth of the optical pulse used to generate the electron packet or pulse. Electrons passing through the sample or specimen 150 are focused by electron lens assembly 152 onto a detector 154. Although FIG. 1 illustrates two electron lens assemblies 146 and 152, the present invention is not limited to this arrangement and can have other lens assemblies or lens assembly configurations. In alternative embodiments, additional electromagnets, apertures, other elements, and the like are utilized to focus the electron beam either prior to or after interaction with the sample, or both. Detection of electrons passing through the sample, including single-electron detection, is achieved in one particular embodiment through the use of an ultrahigh sensitivity (UHS) phosphor scintillator detector 154 especially suitable for low-dose applications in conjunction with a digital CCD camera. In a specific embodiment, the CCD camera was an UltraScan™ 1000 UHS camera, manufactured by Gatan, Inc., of Pleasanton, Calif. The UltraScan™ 1000 CCD camera is a 4 mega-pixel (2048×2048) camera with a pixel size of 14 μm×14 μm, 16-bit digitization, and a readout speed of 4 Mpixels/sec. In the embodiment illustrated, the digital CCD camera is mounted under the microscope in an on-axis, below the chamber position. In order to reduce the noise and picture artifacts, in some embodiments, the CCD camera chip is thermoelectrically cooled using a Peltier cooler to a temperature of about −25° C. The images from the CCD camera were obtained with DigitalMicrograph™ software embedded in the Tecnai™ user interface, also available from Gatan, Inc. Of course, there can be other variations to the CCD camera, cooler, and computer software, depending upon the embodiment. FIG. 2 is a simplified perspective diagram of a 4D electron microscope system according to an embodiment of the present invention. The system illustrated in FIG. 2 is also referred to as an ultrafast electron microscope (UEM2) and was built at the present assignee. The integration of two laser systems with a modified electron microscope is illustrated, together with a representative image showing a resolution of 3.4 Å obtained in UEM2 without the field-emission-gun (FEG) arrangement of a conventional TEM. In one embodiment of the system illustrated in FIG. 2, the femtosecond laser system (fs laser system) is used to generate the single-electron packets and the nanosecond laser system (ns laser system) was used both for single-shot and stroboscopic recordings. In the single-electron mode of operation, the coherence volume is well defined and appropriate for image formation in repetitive events. The dynamics are fully reversible, retracing the identical evolution after each initiating laser pulse; each image is constructed stroboscopically, in seconds, from typically 106 pulses and all time-frames are processed to make a movie. The time separation between pulses can be varied to allow complete heat dissipation in the specimen. Without limiting embodiments of the present invention, it is believed that the electrons in the single electron packets have a transverse coherence length that is comparable to the size of the object that is being imaged. Since the subsequent electrons have a coherence length on the order of the size of the object, the electrons “see” the whole object at once. To follow the area-specific changes in the hundreds of images collected for each time scan, we obtained selected-area-image dynamics (SAID) and selected-area-diffraction dynamics (SADD); for the former, in real space, from contrast change and for the latter, in Fourier space, from changes of the Bragg peak separations, amplitudes, and widths. It is the advantage of microscopy that allows us to perform this parallel-imaging dynamics with pixel resolution, when compared with diffraction. As shown below, it would not have been possible to observe the selected temporal changes if the total image were to be averaged over all pixels, in this case 4 millions. As illustrated in FIG. 2, a TEM is modified to provide a train of electron pulses used for imaging in addition to the thermionic emission source used for imaging of samples. Merely by way of example, an FEI Tecnai™ G2 12 TWIN, available from FEI Company in Hillsboro, Oreg., may be modified according to embodiments of the present invention. The Tecnai™ G2 12 TWIN is an all-in-one 120 kV (λdeBroglie=0.0335 Å) high-resolution TEM optimized for 2D and 3D imaging at both room and liquid-nitrogen temperatures. Embodiments of the present invention leverage capabilities provided by commercial TEMs such as automation software, detectors, data transfer technology, and tomography. In particular, in some embodiments of the present invention, a five-axis, motor-driven, precision goniometer is used with computer software to provide automated specimen tilt combined with automated acquisition of images as part of a computerized tomography (CT) imaging system. In these embodiments, a series of 2D images are captured at various specimen positions and combined using computer software to generate a reconstructed 3D image of the specimen. In some embodiments, the CT software is integrated with other TEM software and in other embodiments, the CT software is provided off-line. One of ordinary skill in the art would recognize many variations, modifications, and alternatives. In certain embodiments in which low-electron content electron pulses are used to image the sample, the radiation damage is limited to the transit of the electrons in the electron pulses through the sample. Typically, samples are on the order of 100 nm thick, although other thicknesses would work as long as certain electrons may traverse through the sample. Thus, the impact of radiation damage on these low-electron content electron pulse images is limited to the damage occurring during this transit time. Radiation induced structural damage occurring on longer time scales than the transit time will not impact the collected image, as these damage events will occur after the structural information is collected. Utilizing the apparatus described thus far, embodiments of the present invention provide systems and methods for imaging material and biological specimens both spatially and temporally with atomic-scale spatial resolution on the order of 1 nm and temporal resolution on the order of 100 fs. At these time scales, energy randomization is limited and the atoms are nearly frozen in place, thus methods according to the present invention open the door to time-resolved studies of structural dynamics at the atomic scale in both space and time. Details of the present computer system according to an embodiment of the present invention may be explained according to the description below. Referring to FIG. 2, a photograph of a UEM2 in accordance with embodiments of the present invention is illustrated, together with a high-resolution image of graphitized carbon. As illustrated, two laser systems (fs and ns) are utilized to provide a wide range of temporal scales used in 4D electron imaging. A 200-kV TEM is provided with at least two ports for optical access to the microscope housing. Using one or more mirrors (e.g., two mirrors), it is possible to switch between the laser systems to cover both the fs and ns experiments. The optical pulses are directed to the photocathode to generate electron packets, as well as to the specimen to initiate (clock) the change in images with a well-defined delay time Δt. The time axis is defined by variable delay between the electron generating and clocking pulses using the delay stage 170 illustrated in FIG. 1. Details of development of ultrafast electron microscopy with atomic-scale real-, energy-, and Fourier-space resolutions is now provided. The second generation UEM2 described in FIG. 2 provides images, diffraction patterns, and electron-energy spectra, and has application for nanostructured materials and organometallic crystals. The separation between atoms in direct images, and the Bragg spots/Debye-Scherrer rings in diffraction, are clearly resolved, and the electronic structure and elemental energies in the electron-energy-loss spectra (EELS) and energy-filtered-transmission-electron microscopy (EFTEM) are obtained. The development of 4D ultrafast electron microscopy and diffraction have made possible the study of structural dynamics with atomic-scale spatial resolution, so far in diffraction, and ultrashort time resolution. The scope of applications is wide-ranging with studies spanning diffraction of isolated structures in reactions (gas phase), nanostructures of surfaces and interfaces (crystallography), and imaging of biological cells and materials undergoing first-order phase transitions. Typically, for microscopy the electron was accelerated to 120 keV and for diffraction to 30 keV, respectively, and issues of group velocity mismatch, in situ clocking (time zero) of the change, and frame referencing were addressed. One powerful concept implemented is that of “tilted pulses,” which allow for the optimum resolution to be reached at the specimen. For ultrafast electron microscopy, the concept of “single-electron” imaging is fundamental to some embodiments. The electron packets, which have a well-defined picometer-scale de Broglie wave length, are generated in the microscope by femtosecond optical pulses (photoelectric effect) and synchronized with other optical pulses to initiate the change in a temperature jump or electronic excitation. Because the number of electrons in each packet is one or a few, the Coulomb repulsion (space charge) between electrons is reduced or eliminated and the temporal resolution can reach the ultimate, that of the optical pulse. The excess energy above the work function determines the electron energy spread and this, in principle, can be minimized by tuning the pulse energy. The spatial resolution is then only dependent on the total number of electrons because for each packet the electron “interferes with itself” and a coherent buildup of the image is achievable. The coherence volume, given by:Vc=λdeBroglie2(R/α)2ve(h/ΔE)establishes that the degeneracy factor is much less than one and that each Fermionic electron is independent, without the need of the statistics commonly used for Bosonic photons. The volume is determined by the values of longitudinal and transverse coherences; Vc is on the order of 106 nm3 for typical values of R (distance to the source), a (source dimension), ve (electron velocity), and ΔE (energy spread). Unlike the situation in transmission electron microscopy (TEM), coherence and image resolution in UEM are thus determined by properties of the optical field, the ability to focus electrons on the ultrashort time scale, and the operational current density. For both “single electron” and “single pulse” modes of UEM, these are important considerations for achieving the ultimate spatio-temporal resolutions for studies of materials and biological systems. Atomic-scale resolution in real-space imaging can be achieved utilizing the second generation ultrafast electron microscopy system (UEM2) of FIG. 2. With UEM2, which operates at 200 keV (λde Broglie=2.507 pm), energy-space (electron-energy-loss spectroscopy, EELS) and Fourier-space (diffraction) patterns of nanostructured materials are possible. The apparatus can operate in the scanning transmission electron microscope (STEM) mode, and is designed to explore the vast parameter space bridging the gap between the two ideal operating modes of single-electron and single-pulse imaging. With these features, UEM2 studies provide new limits of resolution, image mapping, and elemental analysis. Here, demonstrated are the potential by studying gold particles and islands, boron nitride crystallites, and organometallic phthalocyanine crystals. FIG. 2A displays the conceptual design of UEM2, which, as with the first generation (UEM1—described generally in FIG. 1), comprises a femtosecond laser system and an electron microscope modified for pulsed operation with femtosecond electron packets. A schematic representation of optical, electric, and magnetic components are shown. The optical pulse train generated from the laser, in this case having a variable pulse width of 200 fs to 10 ps and a variable repetition rate of 200 kHz to 25 MHz, is divided into two parts, after harmonic generation, and guided toward the entries of the design hybrid electron microscope. The frequency-tripled optical pulses are converted to the corresponding probe electron pulses at the photocathode in the hybrid FEG, whereas the other optical pump beam excites (T-jump or electronic excitation) in the specimen with a well-defined time delay with respect to the probe electron beam. The probe electron beam through the specimen can be recorded as an image (normal or filtered, EFTEM), a diffraction pattern, or an EEL spectrum. The STEM bright-field detector is retractable when it is not in use. The laser in an embodiment is a diode-pumped Yb-doped fiber oscillator/amplifier (Clark-MXR; in development), which produces ultrashort pulses of up to 10 μJ at 1030 nm with variable pulse width (200 fs-10 ps) and repetition rate (200 kHz-25 MHz). The output pulses pass through two successive nonlinear crystals to be frequency doubled (515 nm) and tripled (343 nm). The harmonics are separated from the residual infrared radiation (IR) beam by dichroic mirrors, and the frequency-tripled pulses are introduced to the photocathode of the microscope for generating the electron pulse train. The residual IR fundamental and frequency-doubled beams remain available to heat or excite samples and clock the time through a computer-controlled optical delay line for time-resolved applications. The electron microscope column is that of a designed hybrid 200-kV TEM (Tecnai 20, FEI) integrated with two ports for optical access, one leading to the photocathode and the other to the specimen. The field emission gun (FEG) in the electron-generation assembly adapts a lanthanum hexaboride (LaB6) filament as the cathode, terminating in a conical electron source truncated to leave a flat tip area with a diameter of 16 μm. The tip is located in a field environment controlled by suppressor and extractor electrodes. The gun can be operated as either a thermal emission or a photoemission source. The optical pulses are guided to the photocathode as well as to the specimen by a computer-controlled, fine-steering mirror in an externally-mounted and x-ray-shielded periscope assembly. Each laser beam can be focused to a spot size of <30 μm full width at half maximum (FWHM) at its respective target when the beam is expanded to utilize the available acceptance angle of the optical path. Various pulse-energy, pulse-length, and focusing regimes have been used in the measurements reported here. For UEM measurements, the cathode was heated to a level below that needed to produce detectible thermal emission, as detailed below, and images were obtained using both the TEM and the UEM2 mode of operation. For applications involving EELS and energy-filtered-transmission-electron microscopy (EFTEM), the Gatan Imaging Filter (GIF) Tridiem, of the so-called post-column type, was attached below the camera chamber. The GIF accepts electrons passing through an entrance aperture in the center of the projection chamber. The electron beam passes through a 90° sector magnet as shown in FIG. 2A, which bends the primary beam through a 10 cm bending radius and thereby separates the electrons according to their energy into an energy spectrum. An energy resolution of 0.87 eV was measured for the EELS zero-loss peak in thermal mode operation of the TEM. A retractable slit is located after the magnet followed by a series of lenses. The lenses restore the image or diffraction pattern at the entrance aperture and finally it can be recorded on a charge-coupled device (CCD) camera (UltraScan 1000 FT) at the end of the GIF with the Digital Micrograph software. The digital camera uses a 2,048×2,048 pixel CCD chip with 14 μm square pixels. Readout of the CCD is done as four independent quadrants via four separate digitizing signal chains. This 4-port readout camera combines single-electron sensitivity and 16-bit pixel depth with high-speed sensor readout (4 Mpix/s). Additionally, for scanning-transmission-electron microscopy (STEM), the UEM2 is equipped with a bright-field (BF) detector with a diameter of 7 mm and an annular dark-field (ADF) detector with an inner diameter of 7 mm and an outer diameter of 20 mm. Both detectors are located in the near-axis position underneath the projection chamber. The BF detector usually collects the same signal as the TEM BF image, i.e., the transmitted electrons, while the ADF detector collects an annulus at higher angle where only scattered electrons are detected. The STEM images are recorded with the Tecnai Imaging & Analysis (TIA) software. To observe the diffraction pattern, i.e., the back focal plane of the objective lens, we inserted a selected area aperture into the image plane of the objective lens, thus creating a virtual aperture in the plane of the specimen. The result is a selected area diffraction (SAD) pattern of the region of interest only. Adjustment of the intermediate and projector lens determines the camera length. Diffraction patterns are processed and analyzed for crystal structure determination. Several features of the UEM2 system are worthy of note. First, the high repetition rate amplified laser source allows us to illuminate the cathode with 343 nm pulses of energies above 500 nJ, compared with typical values of 3 nJ near 380 nm for UEM1. Thus, a level of average optical power for electron generation comparable to that of UEM1 operating at 80 MHz, but at much lower repetition rates, was able to be delivered. The pulse energy available in the visible and IR beams is also at least two orders of magnitude greater than for UEM1, allowing for exploration of a much greater range in the choice of sample excitation conditions. Second, the hybrid 200-kV FEG, incorporating an extractor/suppressor assembly providing an extractor potential of up to 4 kV, allows higher resolving power and greater flexibility and control of the conditions of electron generation. Third, with simple variation of optical pulse width, the temporal and spatial resolution can be controlled, depending on the requirements of each experiment. Fourth, with variation of spacing between optical pulses without loss of pulse energy, a wide range of samples can be explored allowing them to fully relax their energy after each excitation pulse and rewind the clock precisely; with enough electrons, below the space-charge limit, single-pulse recording is possible. Finally, by the integration of the EELS spectrometer, the system is empowered with energy resolution in addition to the ultrafast time resolution and atomic-scale space resolution. The following results demonstrate the capabilities of UEM2 in three areas: real-space imaging, diffraction, and electron energy resolution. Applications of the present invention are not limited to these particular examples. First discussed are the images recorded in the UEM mode, of gold particles and gold islands on carbon films. FIGS. 2Ba-f are UEM2 images obtained with ultrafast electron pulses. Shown are gold particles (a, d) and gold islands (c, f) on carbon films. UEM2 background images (b, e) obtained by blocking the photoelectron-extracting femtosecond laser pulses. For the UEM2 images of gold particles, we used the objective (contrast) aperture of 40 μm to eliminate diffracted beams, while no objective aperture was used for the gold-island images. FIGS. 2Aa and 2Ad show gold particles of uniform size dispersed on a carbon film. From the higher magnification image of FIG. 2Ad, corresponding to the area indicated by the black arrow in FIG. 2Aa, it is found that the gold particles have a size of 15 nm, and the minimum particle separation seen in the image is 3 nm. It should be noted that FIGS. 2Ab and 2Ae were recorded under identical conditions to FIGS. 2Aa and 2Ad, respectively, but without cathode irradiation by the femtosecond laser pulses. No images were observed, demonstrating that non-optically generated electrons from our warm cathode were negligible. Similar background images with the light pulses blocked were routinely recorded and checked for all cathode conditions used in this study. The waffle (cross line) spacing of the cross grating replica (gold islands) seen in FIG. 2Ac is known to be 463 nm. The gold islands are observed in FIG. 2Af, where the bright regions correspond to the amorphous carbon support film and the dark regions to the nanocrystalline gold islands. It is found that the islands may be interconnected or isolated, depending on the volume fraction of the nanocrystalline phases. To test the high-resolution capability of UEM utilizing phase contrast imaging, an organometallic compound, chlorinated copper phthalocyanine (hexadecachlorophthalocyanine, C32Cl16CuN8), was investigated. The major spacings of lattice fringes of copper of this molecule in projection along the c-axis are known to be 0.88, 1.30, and 1.46 nm, with atomic spacings of 1.57 and 1.76 nm. FIGS. 2Ca-b are high-resolution, phase-contrast UEM images. Shown are an image in FIG. 2Ca and digital diffractogram in FIG. 2Cb of an organometallic crystal of chlorinated copper phthalocyanine The diffractogram was obtained by the Fourier transform of the image in FIG. 2Ca. The high-resolution image was taken near the Scherzer focus for optimum contrast, which was calculated to be 90.36 nm for a spherical aberration coefficient Cs of the objective lens of 2.26 mm. The objective aperture was not used. FIG. 2Da exhibits the lattice fringes observed by UEM, where the black lines correspond to copper layers parallel to the c-axis. The Fourier transform of FIG. 2Da is shown in FIG. 2Db, discussed below, and the clear reciprocity (without satellite peaks in the F.T.) indicates the high degree of order in crystal structure. FIG. 2D shows high-resolution, phase-contrast UEM image and structure of chlorinated copper phthalocyanine The high-resolution image shown in FIG. 2Da is a magnified view of the outlined area in FIG. 2Ca. The representation of the crystal structure shown in FIG. 2Db is shown in projection along the c axis, and the assignment of the copper planes observed in FIG. 2Da is indicated by the gray lines. The spheres are the copper atoms. FIG. 2Da is an enlargement of the area outlined in FIG. 2Ca, clearly showing the lattice fringe spacing of 1.46 nm, corresponding to the copper planes highlighted in gray in FIG. 2Db, in which a unit cell is shown in projection along the c-axis. Regions without lattice fringes are considered to correspond to crystals with unfavorable orientation, or amorphous phases of phthalocyanine, or the carbon substrate. It is known that in high resolution images, the lattice fringes produced by the interference of two waves passing through the back focal plane, i.e., the transmitted and diffracted beams, are observed only in crystals where the lattice spacing is larger than the resolution of the TEM. In the profile inset of FIG. 2Da, it should be noted that the FWHM was measured to be approximately 7 Å, directly indicating that our UEM has the capability of sub-nanometer resolution. The digital diffractogram obtained by the Fourier transform of the observed high-resolution image of FIG. 2Ca is shown in FIG. 2Cb. In the digital diffractogram, the peaks represent the fundamental spatial frequency of the copper layers (0.69 nm−1), and higher harmonics thereof. A more powerful means of obtaining reciprocal-space information such as this is the direct recording of electron diffraction, also available in UEM. FIGS. 2Ea-f show measured and calculated electron diffraction patterns of gold islands and boron nitride (BN) on carbon films, along with the corresponding real-space images of each specimen, all recorded by UEM. Shown are images and measured and calculated electron diffraction patterns of gold islands (a,b,c) and boron nitride (BN) (d,e,f) on carbon films. The incident electron beam is parallel to the [001] direction of the BN. All diffraction patterns were obtained by using the selected-area diffraction (SAD) aperture, which selected an area 6 μm in diameter on the specimen. Representative diffraction spots were indexed as indicated by the arrowheads. In FIG. 2Eb, the electron diffraction patterns exhibit Debye-Scherrer rings formed by numerous diffraction spots from a large number of face-centered gold nanocrystals with random orientations. The rings can be indexed as indicated by the white arrowheads. The diffraction pattern of BN in FIG. 2Ee is indexed by the hexagonal structure projected along the [001] axis as shown in FIG. 2Ef. It can be seen that there are several BN crystals with different crystal orientations, besides that responsible for the main diffraction spots indicated by the white arrowheads. In order to explore the energy resolution of UEM, we investigated the BN specimen in detail by EELS and EFTEM. FIG. 2F shows energy-filtered UEM images and spectrum. FIG. 2F shows a zero-loss filtered image (FIG. 2Fa), boron K-edge mapping image (FIG. 2Fb), thickness mapping image (FIG. 2Fc), and corresponding electron-energy-loss (EEL) spectrum (FIG. 2Fd) of the boron nitride (BN) sample. The 5.0- and 1.0-mm entrance aperture were used for mapping images and EEL spectrum, respectively. The thickness at the point indicated by the asterisk in FIG. 2Fc is estimated to be 41 nm. ZL stands for zero-loss. The boron map was obtained by the so-called three-window method. In the boron map of FIG. 2Fb, image intensity is directly related to areal density of boron. In the thickness map of FIG. 2Fc, the brightness increases with increasing thickness: d (thickness)=λ(β)ln(It/I0), where λ is the mean free path for inelastic scattering under a given collection angle β, I0 is the zero-loss (ZL) peak intensity, and It is the total intensity. The thickness in the region indicated by the asterisk in FIG. 2Fc was estimated to be 41 nm. In the EEL spectrum of FIG. 2Fd, the boron K-edge, carbon K-edge, and nitrogen K-edge are observed at the energy of 188, 284, and 401 eV, respectively. In the boron K-edge spectrum, sharp π* and σ* peaks are visible. The carbon K-edge spectrum is considered to result from the amorphous carbon film due to the existence of small and broad peaks at the position π* and σ, being quite different from spectra of diamond and graphite. With the capabilities of the UEM2 system described herein, structural dynamics can be studied, as with UEM1, but with the new energy and spatial resolution are achieved here. Specimens will be excited in a T-jump or electronic excitation by the femtosecond laser pulses (FIG. 2A) scanned in time with respect to the electron packets which will probe the changes induced in material properties through diffraction, imaging, or electron energy loss in different regions, including that of Compton scattering. Also planned to be explored is the STEM feature in UEM, particularly the annular dark-field imaging, in which compositional changes are evident in the contrast (Z contrast). Such images are known to offer advantages over high-resolution TEM (relative insensitivity to focusing errors and ease of interpretation). Electron fluxes will be optimized either through changes of the impinging pulse fluence or by designing new photocathode materials. In this regard, with higher brightness the sub-angstrom limit should be able to be reached. The potential for applications in materials and biological research is rich. FIG. 3 is a simplified diagram of a computer system 310 that is used to oversee the system of FIGS. 1 and 2 according to an embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims herein. One of ordinary skill in the art would recognize many other modifications, alternatives, and variations. As shown, the computer system 310 includes display device 320, display screen 330, cabinet 340, keyboard 350, and mouse 370. Mouse 370 and keyboard 350 are representative “user input devices.” Mouse 370 includes buttons 380 for selection of buttons on a graphical user interface device. Other examples of user input devices are a touch screen, light pen, track ball, data glove, microphone, and so forth. The system is merely representative of but one type of system for embodying the present invention. It will be readily apparent to one of ordinary skill in the art that many system types and configurations are suitable for use in conjunction with the present invention. In a preferred embodiment, computer system 310 includes a Pentium™ class based computer, running Windows™ NT, XP, or Vista operating system by Microsoft Corporation. However, the system is easily adapted to other operating systems such as any open source system and architectures by those of ordinary skill in the art without departing from the scope of the present invention. As noted, mouse 370 can have one or more buttons such as buttons 380. Cabinet 340 houses familiar computer components such as disk drives, a processor, storage device, etc. Storage devices include, but are not limited to, disk drives, magnetic tape, solid-state memory, bubble memory, etc. Cabinet 340 can include additional hardware such as input/output (I/O) interface cards for connecting computer system 310 to external devices external storage, other computers or additional peripherals, which are further described below. FIG. 4 is a more detailed diagram of hardware elements in the computer system of FIG. 3 according to an embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims herein. One of ordinary skill in the art would recognize many other modifications, alternatives, and variations. As shown, basic subsystems are included in computer system 310. In specific embodiments, the subsystems are interconnected via a system bus 375. Additional subsystems such as a printer 374, keyboard 378, fixed disk 379, monitor 376, which is coupled to display adapter 382, and others are shown. Peripherals and input/output (I/O) devices, which couple to I/O controller 371, can be connected to the computer system by any number of means known in the art, such as serial port 377. For example, serial port 377 can be used to connect the computer system to a modem 381, which in turn connects to a wide area network such as the Internet, a mouse input device, or a scanner. The interconnection via system bus allows central processor 373 to communicate with each subsystem and to control the execution of instructions from system memory 372 or the fixed disk 379, as well as the exchange of information between subsystems. Other arrangements of subsystems and interconnections are readily achievable by those of ordinary skill in the art. System memory, and the fixed disk are examples of tangible media for storage of computer programs, other types of tangible media include floppy disks, removable hard disks, optical storage media such as CD-ROMS and bar codes, and semiconductor memories such as flash memory, read-only-memories (ROM), and battery backed memory. Although the above has been illustrated in terms of specific hardware features, it would be recognized that many variations, alternatives, and modifications can exist. For example, any of the hardware features can be further combined, or even separated. The features can also be implemented, in part, through software or a combination of hardware and software. The hardware and software can be further integrated or less integrated depending upon the application. Further details of the functionality, which may be carried out using a combination of hardware and/or software elements, of the present invention can be outlined below according to the figures. Embodiments of the present invention enable ultrafast imaging with applications in studies of structural and morphological changes in single-crystal gold and graphite films, which exhibit entirely different dynamics, as discussed below. For both, the changes were initiated by in situ femtosecond impulsive heating, while image frames and diffraction patterns were recorded in the microscope at well-defined times following the temperature-jump. The time axis in the microscope is independent of the response time of the detector, and it is established using a variable delay-line arrangement; a 1-μm change in optical path of the initiating (clocking) pulse corresponds to a time step of 3.3 fs. FIG. 5 illustrates both time-resolved images and diffraction. In this example, the images in FIGS. 5A and 5B were obtained stroboscopically at several time delays after heating with the fs pulse (fluence of 1.7 mJ/cm2). The specimen is a gold single crystal film mounted on a standard 3-mm 400-mesh grid. Shown are the bend contours (dark bands), {111} twins (sharp straight white lines) and holes in the sample (bright white circles). The insets in FIG. 5B are image-difference frames Im(tref; t) with respect to the image taken at −84 ps. The gold thickness was determined to be 8 nm by electron energy loss spectroscopy (EELS). FIG. 5C illustrates the time dependence of image cross-correlations of the full image from four independent scans taken with different time steps. A fit to biexponential rise of the 1 ps step scan is drawn, yielding time constants of 90 ps and 1 ns. FIG. 5D illustrates the time dependence of image cross-correlations at 1 ps time steps for the full image and for selected regions of interest SAI #1, #2, and #3, as shown in FIG. 5A. FIGS. 5E and 5F are diffraction patterns obtained using a single pulse of 6×106 electrons at high peak fluence (40 mJ/cm2) and selected-area aperture of 25 μm diameter. Two frames are given to indicate the change. Diffraction spots were indexed and representative indices are shown as discussed below. FIGS. 5A and 5B illustrate representative time-framed images of the gold nanocrystal using the fs excitation pulses at a repetition rate of 200 kHz and peak excitation fluence of ˜1.7 mJ/cm2. In FIG. 5A, taken at −84 ps, before the clocking pulse (t=0), typical characteristic features of the single crystal gold in the image are observed: twins and bend contours. Bend contours, which appear as broad fuzzy dark lines in the image, are diffraction contrast effects occurring in warped or buckled samples of constant thickness. In the dark regions, the zone axis (the crystal [100]) is well aligned with the incident electron beam and electrons are scattered efficiently, whereas in the lighter regions the alignment of the zone axis deviates more and the scattering efficiency is lower. Because bend contours generally move when deformation causes tilting of the local crystal lattice, they provide in images a sensitive visual indicator of the occurrence of such deformations. At positive times, following t=0, visual dynamical changes are observed in the bend contours with time steps from 0.5 ps to 50 ps. A series of such image frames with equal time steps provide a movie of the morphological dynamics. To more clearly display the temporal evolution, image-difference frames were constructed. Depicted as insets in the images of FIG. 5B, are those obtained when referencing to the −84 ps frame; for t=+66 ps and +151 ps. In the difference images, the regions of white or black directly indicate locations of surface morphology change (bend contour movement), while gray regions are areas where the contrast is unchanged from that of the reference frame. It is noted that the white and black features in the difference images are nm-scale dynamical change, indicating the size of the induced deformations. Care was taken to insure the absence of long-term specimen drifts as they can cause apparent contrast change. To quantify the changes in the image the following method of cross-correlation was used. The normalized cross correlation of an image at time t with respect to that at time t′ is expressed as: γ ⁡ ( t ) = ∑ x , y ⁢ C x , y ⁡ ( t ) ⁢ C x , y ⁡ ( t ′ ) ∑ x , y ⁢ C x , y ⁡ ( t ) 2 ⁢ ∑ x , y ⁢ C x , y ⁡ ( t ′ ) 2 where the contrast Cx,y(t)=[Ix,y(t)−Ī(t)]/Ī(t); Ix,y(t) and Ix,y(t′) are the intensities of pixels at the position of (x,y) at times t and t′, and Ī(t) and Ī(t′) are the means of Ix,y(t) and Ix,y(t′), respectively. This correlation coefficient γ(t) is a measure of the temporal change in “relief pattern” between the two images being compared, which can be used as a guide to image dynamics as a function of time. Two types of cross-correlation plots were made, those referenced to a fixed image frame before t=0 and others that show correlation between adjacent time points. (Another quantity that shows time dependence qualitatively similar to that of the image cross-correlation is the standard deviation of pixel intensity in difference images). FIGS. 5C and 5D show the cross-correlation values between the image at each measured time point and a reference image recorded before the arrival of the clocking pulse. The experiments were repeated, for different time-delay steps (500 fs, 1 ps, 5 ps, and 50 ps), and similar results were obtained, showing that morphology changes are completely reversible and reproducible over each 5 μs inter-pulse interval. The adjacent-time cross-correlations reveal the timescales for intrinsic changes in the images, which disappear for time steps below 5 ps, consistent with full-image rise in time. Over all pixels, the time scale for image change covers the full range of time delay, from ps to ns, indicating the collective averaging over sites of the specimen; as shown in FIG. 5C the overall response can be fit to two time constants of 90 ps and 1 ns. The power of selected area image dynamics (SAID) is illustrated when the dynamics of the bend contours are followed in different selected areas of the image, noted in the micrographs as SAI #1, 2, and 3. The corresponding image cross-correlations (FIG. 5D) have different shape and amplitude from each other and from the full image correlation. The large differences observed here and for other data sets, including onsets delayed in time and sign reversals, indicate the variation in local deformation dynamics. In FIGS. 5G-L, a time-resolved SAI at higher magnification is depicted. A broad and black “penguin-like” contour is observed as the dominant feature of this area. As shown in the frames, a colossal response to the fs heating is noted. The gray region inside the black contour appears and broadens with time. Also, a new black contour above the large central white hole begins to be evident at 1200 ps, and gains substantial intensity over the following 50 ps. All frames taken can be used to construct a movie of SAID. The observed SAID changes correspond to diffraction contrast (bright-field) effects in bend contours, as mentioned above. It is known that the shape of bend contours can be easily altered by sample tilting or heating inside the microscope. However, here in the ultrafast electron microscope (UEM) measurements, the changes in local tilt are transient in nature, reflecting the temporal changes of morphology and structure. Indeed, when the experiments were repeated in the TEM mode of operation, i.e., for the same heating laser pulse and same scanning time but with continuous electron probe beam, no image change was observed. This is further supported by the change in diffraction observed at high fluences and shown in FIGS. 5E and 5F for two frames, at negative time and at +50 ns; in the latter, additional Bragg spots are visible, a direct evidence of the transient structural change due to bulging at longer times. Whereas real-space imaging shows the time-dependent morphology, the selected area diffraction dynamics (SADD) patterns provide structural changes on the ultrashort timescale. Because the surface normal of the film is parallel to the [100] zone axis, the diffraction pattern of the sample was properly indexed by the face-centered-cubic (fcc) structure projected along the zone axis at zero tilt angle (see FIG. 5E). From the positions of the spots in FIG. 5F, which are reflections from the {113} and {133} planes, forbidden in the [100] zone-axis viewing, we measured the interplanar spacings to be 1.248 and 0.951 Å, respectively. With selected area diffraction, Bragg peak separations, amplitudes, and widths were obtained as a function of time. The results indicate different timescales from those of image dynamics. FIG. 6A illustrates structural dynamics and heat dissipation in gold and FIG. 6B illustrates coherent resonance of graphite. Referring to FIG. 6A, SADD for fs excitation at 1.7 mJ/cm2 peak fluence (519 nm) is illustrated. The Bragg separation for all peaks and the amplitude of the {042} peaks are shown in the main panel; the inset gives the 2.2 μs recovery (by cooling) of the structure obtained by stroboscopic ns excitation at 7 mJ/cm2. The peak amplitude has been normalized to the transmitted beam amplitude, and the time dependence of amplitude and separation is fit as an exponential rise, and a delay with rise, respectively. Referring to FIG. 6B, resonance oscillations are observed for the Bragg (1 22) peak in the diffraction pattern of graphite; the amplitudes are similar in magnitude to those in FIG. 6A. The sample was tilted at 21° angle to the microscope axis and the diffraction pattern was obtained by using the SAD aperture of 6 μm diameter on the specimen. The graphite thickness is 69 nm as determined by EELS; the oscillation period (τp) is measured to be 56.3 ps. For a thickness of 45 nm, the period is found to be τp=35.4 ps. FIGS. 6D-G illustrate, for selected areas, time dependence of intensity difference (dark-field) for graphite. The image change displays the oscillatory behavior with the same τp as that of diffraction. The dark-field (DF) images were obtained by selecting the Bragg (1 22) peak. In FIG. 6H, each line corresponds to the difference in image intensities, Im(t−30 ps; t), for selected areas of 1×100-pixel slices parallel to contrast fringes in the DF image. The average amplitude of {042} diffraction peaks drop significantly; the rise time is 12.9 ps, whereas the change in separations of all planes is delayed by 31 ps and rises in 60 ps. The delay in the onset of separation change with respect to amplitude change is similar to the timescale for the amplitude to reach its plateau value of 15% reduction in the case of the {042} amplitude shown. In order to determine the recovery time of the structure, we carried out stroboscopic (and also single-pulse) experiments over the timescale of microseconds. The recovery transient in the inset of FIG. 6A (at 7 mJ/cm2) gives a time constant of 2.2 μs; we made calculations of 2D lateral heat transport with thermal conductivity (λ=3.17 W/(cm K) at 300 K) and reproduced the observed timescale. For this fluence, the maximum lattice spacing change of 0.08% gives the temperature increase ΔT to be 60 K, knowing the thermal expansion coefficient of gold (α=14.2×10−6 K−1). The atomic-scale motions, which lead to structural and morphological changes, can now be elucidated. Because the specimen is nanoscale in thickness, the initial temperature induced is essentially uniform across the atomic layers and heat can only dissipate laterally. It is known that for metals the lattice temperature is acquired following the large increase in electron temperature. The results in FIG. 6A give the temperature rise to be 13 ps; from the known electron and lattice heat-capacity constants [C1=70 J/(m3 K2) and C2=2.5×106 J/(m3 K), respectively] and the electron-phonon coupling [g=2×1016 W/(m3 K)] we obtained the initial heating time to be ˜10 ps for electron temperature T1=2500 K, in good agreement with the observed rise. Reflectivity measurements do not provide structural information, but they give the temperature rise. For bulk material, the timescale for heating (˜1 ps) is shorter than that of the nano-scale specimen (˜10 ps), due to confinement in the latter, which limits the ballistic motion of electrons in the specimen, and this is evident in the UEM studies. Because the plane separation is 0.4078 nm, the change of the average peak separation (0.043%), at the fluence of 1.7 mJ/cm2, gives a lattice constant change of 0.17 pm. Up to 30 ps the lattice is hot but, because of macroscopic lattice constraint, the atomic stress cannot lead to changes in lateral separations, which are the only separations visible for the [100] zone-axis probing. However, the morphology warping change is correlated with atomic (lateral) displacements in the structure as it relieves the structural constraint. Indeed the time scale of the initial image change is similar to that of plane separations in diffraction (60-90 ps). This initial warping, which changes image contrast, is followed by longer time (ns) minimization of surface energy and bulging, as shown in FIG. 5D. Given the picometer-scale structural change (0.17 pm), the stress over the 8-nanometer specimen gives the total expansion to be 3.4 pm over the whole thickness. Considering the influence of lateral expansion, the maximum bulge reaches 1 to 10 nm depending on the lateral scale. Finally, the calculated Debye-Waller factor for structural changes gives a temperature of 420 K (ΔT=125 K), in excellent agreement with lattice temperature derived under similar conditions, noting that for the nanoscale material the temperature is higher than in the bulk. Graphite was another study in the application of the UEM methodology. In contrast to the dynamics of gold, in graphite, because of its unique 2D structure and physical properties, we observed coherent resonance modulations in the image and also in diffraction. The damped resonance of very high frequency, as shown below, has its origin in the nanoscale dimension of the specimen and its elasticity. The initial fs pulse induces an impulsive stress in the film and the ultrafast electron tracks the change of the transient structure, both in SAID and SADD. In FIG. 6B, the results obtained by measuring changes of the diffraction spot (1 22) are displayed and in FIGS. 6D-G those obtained by dark-field (DF) imaging with the same diffraction spot being selected by the objective aperture and the specimen tilted, as discussed below. For both the image and diffraction, a strong oscillatory behavior is evident, with a well defined period and decaying envelope. When the transients were fitted to a damped resonance function [(cos2πt/τp)exp(−t/τdecay)], we obtained τp=56.3±1 ps for the period. The decay of the envelope for this particular resonance is significantly longer, τdecay=280 ps. This coherent transient decay, when Fourier transformed, indicates that the length distribution of the film is only ±2 nm as discussed in relation to the equation below. The thickness of the film was determined (L=69 nm) using electron energy loss spectra (EELS). In order to test the validity of this resonance behavior we repeated the experiments for another thickness, L=45 nm. The period indeed scaled with L, giving τp=35.4 ps. These, hitherto unobserved, very high frequency resonances (30 gigahertz range) are unique to the nanoscale length of graphite. They also reflect the (harmonic) motions due to strain along the c-axis direction, because they were not observed when we repeated the experiment for the electron to be along the [001] zone axis. The fact that the period in the image is the same as that of the diffraction indicates the direct correlation between local atomic structure and macroscopic elastic behavior. Following a fs pulse of stress on a freely vibrating nanofilm, the observed oscillations, because of their well-defined periods, are related to the velocity (C) of acoustic waves between specimen boundaries, which in turn can be related to Young's modulus (Y) of the elastic stress-strain profile: 1 τ p = nC 2 ⁢ L = n 2 ⁢ L ⁢ ( Y ρ ) 1 / 2 ,where n is a positive integer, with n=1 being the fundamental resonance frequency (higher n are for overtones). Knowing the measured τp and L, we obtained C=2.5×105 cm/s. For graphite with the density ρ=2.26 g/cm3, Y=14.6 gigapascal for the c-axis strain in the natural specimen examined. Pyrolytic graphite has Y values that range from about 10 to 1000 gigapascal depending on the orientation, reaching the lowest value in bulk graphite and the highest one for graphene. The real-time measurements reported here can now be extended to different length scales, specimens of different density of dislocations, and orientations, exploring their influence at the nanoscale on C, Y, and other properties. We note that selected-area imaging was critical as different regions have temporally different amplitudes and phases across the image. Uniting the power of spatial resolution of EM with the ultrafast electron timing in UEM provides an enormous advantage when seeking to unravel the elementary dynamics of structural and morphological changes. With total dissipation of specimen heat between pulses, selected-area dynamics make it possible to study the changes in seconds of recording and for selected pixels of the image. In the applications given here, for both gold and graphite, the difference in timescales for the nonequilibrium temperature (reaching 1013 K/s), the structural (pm scale) and morphological (nm scale) changes, and the ultrafast coherent (resonance) behavior (tens of gigahertz frequency) of materials structure illustrate the potential for other applications, especially when incorporating the different and valuable variants of electron microscopy as we have in our UEM. Embodiments of the present invention extend ultrafast 4D diffraction and microscopy to the attosecond regime. As described herein, embodiments use attosecond electron diffraction to observe attosecond electron motion. Pulses are freely generated, compressed, and tilted. The approach can be implemented to extend previous techniques including, for example phase transformations, chemical reactions, nano-mechanical processes, and surface dynamics, and possibly to other studies of melting processes, coherent phonons, gold particles, and molecular alignment. As described herein, the generation of attosecond resolution pulses and in situ probing through imaging with free electrons. Attosecond diffraction uses near mono-energetic attosecond electron pulses for keV-range of energies in free space and thus space charge effects are considered. Additionally, spatiotemporal synchronization of the electron pulses to the pump pulses is made along the entire sample area and with attosecond precision. Diffraction orders are shown to be sensitive to the effect of electron displacement and conclusive of the four-dimensional dynamics. A component of reaching attosecond resolution with electron diffraction is the generation of attosecond electron pulses in “free space,” so that diffraction from freely chosen samples of interest can take place independent of the mechanisms of pulse generation. Electrons with energies of 30-300 keV are ideal for imaging and diffraction, because of their high scattering cross sections, convenient diffraction angles, and the appropriate de Broglie wavelength (0.02 to 0.07 Å) to resolve atomic-scale changes. Moreover, they have a high degree of monochromaticity. For example, electrons accelerated to E0=30-300 keV with pulse duration of 20 attoseconds (bandwidth of ΔE≈30 eV) have ΔE/E0≈10−3-10−4, making diffraction and imaging possible without a spread in angle and resolution. Optical attosecond pulses have typically ΔE/E0≈0.5 and because of this reach of ΔE to E0, their duration is Fourier-limited to ˜100 attoseconds. Free electron pulses of keV central energy can, in principle, have much shorter duration, down to sub-attoseconds, while still consisting of many wave cycles. Pulses with a large number of electrons suffer from the effect of space charge, which determines both the spatial and the temporal resolutions. This can be avoided by using packets of single, or only a few, electrons in a high repetition rate, as demonstrated in 4D microscopy imaging. FIG. 7A depicts the relation of single electron packets to the effective envelope due to statistics. Each single electron (blue) is a coherent packet consisting of many cycles of the de Broglie wave and has different timing due to the statistics of generation. On average, multiple single electron packets form an effective electron pulse (dotted envelope). It will be appreciated that there is high dispersion for electrons of nonrelativistic energy. The small but unavoidable bandwidth of an attosecond electron pulse causes the pulse to disperse during propagation in free space, even when no space charge forces are present. For example, a 20-attosecond pulse with ΔE/E0≈10−3 would stretch to picoseconds after just a few centimeters of propagation. Embodiments of the present invention provide methods and systems for the suppression of dispersion and the generation of free attosecond electron pulses based on the initial preparation of negatively-chirped electron packets. As described herein, femtosecond electron pulses are generated by photoemission and accelerated to keV energies in a static electric field. Preceding the experimental interaction region, optical fields are used to generate electron packets with a velocity distribution, such that the higher-energy parts are located behind the lower-energy ones. With a proper adjustment of this chirp, the pulse then self-compresses to extremely short durations while propagating towards the point of diffraction. To achieve attosecond pulses, the chirp must be imprinted to the electron pulse on a nanometer length scale. Optical waves provide such fields. However, non-relativistic electrons move significantly slower than the speed of light (e.g. ˜0.3 c for 30 keV). The direct interaction with an optical field will, therefore, cancel out over time and can not be used to accelerate and decelerate electrons for compression. In order to overcome this limitation, we make use of the ponderomotive force, which is proportional to the gradient of the optical intensity to accelerate electrons out of regions with high intensity. By optical wave synthesis, intensity profiles can be made that propagate with less than the speed of light and, therefore, allow for co-propagation with the electrons. FIG. 7B illustrates a schematic of attosecond pulse generation according to an embodiment of the present invention. A synthesized optical field of two counter-propagating waves of different wavelengths results in an effective intensity grating, similar to a standing wave, which moves with a speed slower than the speed of light. Electrons can, therefore, co-propagate with a matched speed and are accelerated or decelerated by the ponderomotive force according to their position within the wave. After the optical fields have faded away, this velocity distribution results in self-compression; the attosecond pulses are formed in free space. Depending on the optical pulse intensity, the electron pulse duration can be made as short as 15 attoseconds, and, in principle, shorter durations are achievable. If the longitudinal spatial width of the initial electron pulse is longer than the wavelength of the intensity grating, multiple attosecond pulses emerge that are located with well-defined spacing at the optical minima. This concept of compression can be rigorously described analytically as a “temporal lens effect.” The temporal version of the Kapitza-Dirac effect has an interesting analogy. Some of our initial work was based on an effective ponderomotive force in a collinear geometry. In order to extend the approach to more complex arrangements, here we generalize the approach and consider the full spatiotemporal (electric and magnetic) fields of two colliding laser waves with an arbitrary angle and polarization. The transversal and longitudinal fields of a Gaussian focus were applied. We simulated electron trajectories by applying the Lorentz force with a fourth-order Runge-Kutta algorithm using steps of 100 attoseconds. Space charge effects were taken into account by calculating the Coulomb interactions between all single electrons for each time step (N-body simulations). FIG. 7B illustrates temporal optical gratings for the generation of free attosecond electron pulses for use in diffraction. (a) A femtosecond electron packet (blue) is made to co-propagate with a moving optical intensity grating (red). (b) The ponderomotive force pushes electron towards the minima and thus creates a temporal lens. (c) The induced electron chirp leads to compression to attosecond duration at later time. (d) The electron pulse duration from 105 trajectories reaches into the domain of few attoseconds. FIG. 7C depicts the compression of single electron packets in the combined field of two counter-propagating laser pulses with durations of 300 fs at wavelengths of 1040 nm and 520 nm. The pulse is shown just before, at, and after the time of best compression; the center along Z is shifted for clarity. The plotted pulse shape is a statistical average over 105 packets of single electrons. The beam diameter of the initial electron packet was 10 μm and the beam diameters of the laser pulses were 60 μm; the resulting compression dynamics is depicted before, just at, and some time after the time of best compression to a duration of 15 attoseconds (see FIG. 7C(b)). These results show that an optical wave with a beam diameter of only several times larger than that of the electron packet is sufficient to result in almost homogeneous compression along the entire electron beam. The characteristic longitudinal spread after the point of best compression, as depicted in FIG. 7C is the result of an “M”-shaped energy spectrum of the electrons after interactions with the sinusoidal intensity grating. Coulomb forces prevent concentration of a large number of electrons in a limited volume, and a compromise between electron flux and laser repetition rate must be found to achieve sufficiently intense diffraction. The laser pulses for compression have energies on the order of 5 μJ and can, therefore, be generated at MHz repetition rates with the resulting flux of 106 electrons/s, which is sufficient for conclusive diffraction. Nevertheless, having more than one electron per attosecond pulse is beneficial for improving the total flux. In order to investigate the influence of space charge on the performance in our attosecond compression scheme, we considered electron packets of increasing electron density and evaluated the resulting pulse durations and effective electron density per attosecond pulse. Two findings are relevant with the results shown in FIG. 8. First, the duration of individual attosecond electron pulses increases relatively insignificantly with the number of electrons contained within. Even for 40 electrons in a single pulse, the duration increases only from 15 to 25 attoseconds (see FIG. 8(a)). The reasons for this are the highly oblate shape of the electron pulses, and the approximate linearity of space charge forces in the longitudinal direction, which are compensated for by somewhat longer interaction in the ponderomotive forces of the optical waves. Secondly, for a train of pulses, there is an effect on synchronization. When the initial femtosecond electron packet covers several optical cycles of the compression wave, a train of attosecond pulses results as shown in FIG. 7B. Perfect synchronization to the optical wave is provided, because all attosecond pulses are located at the same optical phase of the fundamental laser wave. This phase matching relation, which permits attosecond resolution, despite the presence of multiple pulses, is altered under space charge conditions. The attosecond pulses repel each other and a temporal spreading of the comb-like train results. For a train of near 10 attosecond pulses, FIG. 8(b) displays the difference in timing for an adjacent attosecond pulse in relation to the central one, which is always locked to the optical phase because the space charge forces cancel out. The total timing mismatch is the product of the plotted value with the number of attosecond pulses in the entire electron packet (near 10 for this example). In order to keep the total mismatch to the optical wave below 20 attoseconds, 10 electrons per attosecond electron pulse represent an optimum value. The total pulse train then consists of 200 electrons for that group of pulses; of course the total flux of electrons is determined by the repetition rate. Note that mismatch to the compression wave is absent with isolated attosecond electron pulses, which are generated when the initial uncompressed electron packet is shorter than a few femtoseconds, or with optical fields of longer wavelength. Numerous imaging experiments have been successful with single electron packets. In state-of-the-art electron crystallography experiments, typically 500 electrons per pulse were used at a repetition rate of kHz to produce the needed diffraction. This is equivalent to having 5 electrons per attosecond pulse at 100 kHz, which is a convenient repetition rate for optical wave synthesis, and provides enough time for letting the material under investigation to cool back to the initial state. Laser systems with MHz repetition rates will provide even higher fluxes. Applications of attosecond electron pulses for diffraction and microscopy use synchronization of events in the pump-probe arrangement with an accuracy that is equal or better than the individual pulse durations. In contrast to recompression concepts that are based on time-dependent microwave fields, the application of laser waves for attosecond electron pulse generation provides exact temporal synchronization when the pump pulses are derived by phase-locking from the same laser system. Many common optical techniques, such as nonlinear frequency conversion, continuum generation in solids, or high-harmonic generation, all provide a phase lock in the sense that the outcome has the same relative phase and timing in relation to the incoming optical wave for each single pulse of the laser. A second requirement for reaching into the temporal resolution of attoseconds is the realization of spatial delay matching along extended areas of the diffraction. The use of large samples, for example with up to millimeters in size in some electron diffraction experiments, provides enhanced diffraction efficiency and offers the possibility to use electron beams with large diameter, in order to maximize the coherence and flux. In this case, the time resolution is limited by differences in the arrival times of pump and probe pulses at different points within the involved beam diameters (group velocity mismatch). Electron pulses at keV energies travel with significantly less than the speed of light (e.g. vel=0.3 c for 30 keV electrons) and are, therefore, “overtaken” by the laser wave. Embodiments of the present invention provide two arrangements for matching the group velocity of electrons with the phase velocity of optical pulses. Both arrangements are suitable for applications in noncollinear, ultrafast electron microscopy and diffraction. FIG. 9(a) presents a concept for the transmission geometry of diffraction and microscopy in which two angles are introduced, one between the laser beam and the electron beam (β), and another one (α) for the tilt angle of the sample (black) to the phase fronts of the laser wave. Total synchrony is achieved if the relative delay between the optical wave and the attosecond electron pulses is made identical for all points along the entire sample surface. Each small volume of the sample is then subject to an individual pump-probe-type experiment with the same time delay. The above condition is found when we match the coincidence along the entire width of the specimen. The effective surface velocity vsurface of the laser and of the electron pulses must be identical. From FIG. 9A, this requirement is expressed by the following equation: sin ⁡ ( α ) sin ⁡ ( α - β ) = c v el . ( 1 ) It follows that an angle of β=10°, for example, results in an optimum angle for the sample tilt of α=14.8°, which are both easily achievable angles in a real experiment. The effective tilt of the sample with respect to the electron direction is then α−β=4.8°. Naturally, if this value is not coincident with a zone axis direction, a complete rocking curve should be obtained in order to optimize α and β with tilt requirements. Although different portions of the laser wavefront impinge on the surface of the sample at different times, this behavior is matched by the electron pulse, resulting in all portions of the surface of the sample being phase matched. As illustrated in FIG. 9(a), the laser beam, also referred to as a laser wave, is used to activate the sample, for example, to heat the sample, cause motion of the sample, or to effect the chemical bonds present in the sample. The timing of the laser wave and the electron pulses are synchronized using the delay stage discussed in relation to FIG. 1. The train of electron pulses can be generated using the configuration illustrated in FIG. 10(a). Another option for synchronization along extended surfaces is the use of tilted electron pulses, for that the electron density makes an angle with respect to the propagation direction. Tilted optical pulses have been used for reaching femtosecond resolution in reflection geometry, but here tilted electron pulses are introduced for effective spatiotemporal synchronization to the phase velocity of the excitation pulses along the entire sample surface. FIG. 9B depicts the concept. If an angle γ is chosen between the laser (red) and the attosecond electron pulses (blue), the electron pulses need to be tilted likewise. The sample is located parallel to the optical phase fronts and its entire surface is illuminated by the attosecond electron pulse at once and at the same time of incidence relative to the optical pulse wave. Because the incidence is delay-free for all points along the surface, velocity matching is provided for the whole probed area. The generation of tilted attosecond electron pulses is outlined in FIG. 10(a). The introduction of an angle between the intensity grating (red) and the electron beam (blue) leads to formation of electron pulses with a tilt. As described above, a femtosecond electron packet (blue) is first generated by conventional photoelectron generation and accelerated in a static electric field. By intersecting the counter-propagating intensity grating at an angle, tilted electron pulses result with attosecond duration. The ponderomotive force accelerates the electrons towards the planes of destructive interference in the intensity wave and they form attosecond pulses that are compressed along the optical beam axis; but the pulses propagate in the original direction. Only a slight adjustment of the electrons' central energy is required to achieve phase matching to the moving optical grating. Based on this concept, we simulated the tilting effect by using 31-keV electron pulses with an initial duration of ˜15 femtoseconds and a spatial beam diameter of ˜10 μm. FIG. 10(b) illustrates the simulation results for an initial packet of 15-femtosecond duration (left) and an intersection angle of 5°. The tilted attosecond pulses have duration of ˜20 attoseconds when measured perpendicular to the tilt (note the different scale of Z and X). The optical intensity wave is synthesized by two counter-propagating laser pulses of 100-fs duration and wavelengths of 1040 and 520 nm. The angle between the electron beam and the laser wave is 5°. The results of compression are shown in FIG. 10(b): The attosecond electron pulses are formed at the minima of the optical intensity wave and, therefore, are tilted by 5° with respect to the electron propagation direction. For other incidence angles of the laser, the electron pulses are tilted accordingly. Perpendicular to the attosecond pulses, the measured duration is ˜20 attoseconds, given as the full width at half maximum. Based on the methodology for generation and synchronization of attosecond electron pulses described above, the diffraction and manifestation of electron dynamics in the patterns are described. By way of two different examples, embodiments of the present invention are utilized to observe electronic motions in molecules and materials with attosecond electron packets. We consider first the physics of electron scattering and the change in scattering factors which characterize individual atoms and the electron density involved. Diffraction from molecular crystals or other crystalline structures provides two distinct advantages over that obtained for gas phase ensembles. First, the sample density is many orders of magnitudes higher (1021 molecules/cm3 as compared to 1010 to 1016/cm3 in gas jets); diffraction is, therefore, more intense. Second, the crystalline order results in Bragg scatterings and they are concentrated into well-defined “spots” for ordered crystals; the patterns become rods for surfaces and narrow rings for amorphous substances. The diffraction results in intensities which are proportional to the square of the diffraction amplitude. As discussed below, coherence in diffraction is used in observing the changes of interest. The diffraction from molecular crystals, or other crystalline materials of interest, is defined by the summation over the contributions of all scatterers in a unit cell. The intensity I of a Bragg spot with the Miller indices (hkl) is determined by the positions (xyz) of the scatterers j in the unit cell: I ⁡ ( hkl ) ∝  ∑ j ⁢ f j ⁢ exp ⁡ [ - 2 ⁢ π ⁢ ⁢ ⅈ ⁡ ( hkl ) · ( xyz ) j ]  2 , ( 2 ) where fj are the atomic scattering factors. Electron diffraction is the result of Coulomb interaction between the incoming electrons and the potential formed by nuclei and electrons. The factors fj account for the effective scattering amplitude of atoms and are derived from quantum calculations that take into account the specific electron density distribution around the nuclei, including core electrons. The scattering we are considering here is the elastic one. In order to estimate the influence of electron dynamics on contributions to time-resolved diffraction patterns, we consider typical densities of electrons in chemical bonds, and the possible change. Static electron density maps show that typical covalent bonds consist of about one electron/Å3 and that this density is delocalized over volumes with diameters in the order of 1 Å. For estimating an effective scattering factor of such electron density, we consider a Gaussian sphere with a diameter of 1 Å, consisting of one electron. The electric potential is derived by Gauss' law and results in a radial dependence that is represented in FIG. 11, dotted line. The total scattering amplitude of free charges diverges at small angles, because of the long-range behavior of the potential. Since in real crystals the potential is localized in unit cells, we use a Gaussian distribution of the same magnitude in order to restrict the range to about ±1.5 Å. For potential of spherical symmetry, an effective scattering factor can be calculated from the radial potential Φ(r) according to f el ⁡ ( s ) = 8 ⁢ π 2 ⁢ m e ⁢ e h 2 ⁢ ∫ 0 ∞ ⁢ r 2 ⁢ Φ ⁡ ( r ) ⁢ sin ⁡ ( 4 ⁢ π ⁢ ⁢ sr ) 4 ⁢ π ⁢ ⁢ sr ⁢ ⅆ r , ( 3 ) where s=sin(σ/2)/λel is the scattering parameter for a diffraction angle σ and λel is the de Broglie wavelength of the incident electrons. The result for our delocalized electron density is shown in FIG. 11(b); for comparison we plot also the tabulated scattering factor of neutral hydrogen. Both have comparable magnitude, which is expected because of their similar sizes. Here, we consider the iodine molecule as a model case and invoke the transition from a bonding to an anti-bonding orbital. The crystal structure of iodine consists of nearly perpendicular iodine pairs with a bond length of ˜2.7 Å. Two electrons contribute to the intramolecular σ bond; the intermolecular bond is weaker. FIG. 12 depicts the system under study and the two cases considered. The effect of antibonding excitation is made by comparing the Bragg intensities for the iodine structure, including the binding electrons, to a hypothetical iodine crystal consisting only of isolated atoms (see FIG. 12(a)). In Table 1, we give the results of the calculations following equation 2 with the values off tabulated for iodine atoms and from equation (3) for the electronic distribution changes. Despite the large difference in f of the iodine nuclei and the electron (about 50:1), the changes of Bragg spot intensity are significant, being on an order of 10-30%. TABLE 1Effects of Electron Motion on Selected Molecular Bragg SpotsMiller Indices (hkl)(a) ΔITransition(b) ΔIMovement(0.08 Å)100, 010, 001(forbidden)(forbidden)200, 400, 60000002−35%0020 (weak)+100% −17%40000040−18%+13%00400111+15% −2%331−20%+15% In column (a), the mMagnitude of Bragg spot intensity change ΔI of crystalline iodine as a result of bonding to antibonding transition is given. In column (b), the magnitude of Bragg spot intensity change as a result of field interaction with charge density, also in iodine. This large change is for two reasons. First, the bonding electrons are located in-between iodine atoms and contribute, therefore, strongly to the enhancement or suppression of all Bragg spots that project from the inter-atomic distances of the molecular units. Second, the large effect is result of the intrinsic “heterodyne detection” scheme of diffraction; the total intensity of a Bragg spot scales with the square of the coherent sum of individual contributions (see equation (2)). Although the total contribution to the intensity of a Bragg spot from bonding electrons is lower by a factor of several hundreds than the intensity contributions from the iodine atoms, the modulation is on the order of several percents as a result of the coherence of diffraction on a nanometer scale. Symmetry in the crystal is evident in the absence of change in certain Bragg orders. From measurements of the dynamics of multiple spots, it follows that electron density movies could be made. This is best achieved in an electron microscope in diffraction geometry; however conventional diffraction is also suitable to simultaneously monitor many Bragg spots and is advantageous for the study of ordered bulk materials. The example given is not far from an experimental observation made on a metal-to-insulator transition for which a σ-type excitation was induced with a femtosecond pulse. As a second model case we consider the reaction of bonded electron density to external electric fields, such as the ones from laser fields. Depending on the restoring force and the resonance, an electron density will oscillate with the driving field in phase or with a phase delay. This charge oscillation re-radiates and is responsible for the refractive index of a dielectric material. In order to estimate the magnitude of charge displacement, we must take into account the polarizability, α, and the electric field strength, Elaser. In the limit of only one moving charge, the displacement D is approximately given by D ≈ α e ⁢ E laser . The polarizability of molecular iodine along the bond is a α≈130 ∈0 Å3 (˜70 a.u.) in the static limit and a similar magnitude is expected for the crystal for optical frequencies away from the strong absorption bands; the anisotropy of polarizability indicates the role of the bonding electrons. With femtosecond laser pulses, a field of Elaser=109 V/m is possible for intensities below the damage threshold. With these parameters, one expects a charge displacement of D≈0.08 Å, or about 3% of the bond length. FIG. 12(b) is a schematic for the change in charge distribution by an electric field. We assume an active role of only the bonded electrons, and take the polarization of the laser field to be along the b axis of solid iodine. This axis is chosen because it has the least symmetry; a is perpendicular to the bonds. Table 1 gives the intensity changes of selected Bragg spots; the change is in the range of ±20% for some of the indices. The total energy delivered to the molecular system by the laser field is only on the order of 0.01 eV. Nevertheless the changes of charge displacements on sub-angstrom scales are evident. This marks a central advantage of electron diffraction over spectroscopic approaches, which require large energy changes in order to have projections on dynamics. In contrast, diffraction allows for the direct visualization of a variety of ultrafast electron dynamics with combined spatial and temporal resolutions, and independent of the resolution of internal energy levels. The “temporal lens” concept can be used for the focus and magnification of ultrashort electron packets in the time domain. The temporal lenses are created by appropriately synthesizing optical pulses that interact with electrons through the ponderomotive force. With such an arrangement, a temporal lens equation with a form identical to that of conventional light optics is derived. The analog of ray diagrams, but for electrons, are constructed to help the visualization of the process of compressing electron packets. It is shown that such temporal lenses not only compensate for electron pulse broadening due to velocity dispersion but also allow compression of the packets to durations much shorter than their initial widths. With these capabilities ultrafast electron diffraction and microscopy can be extended to new domains, but, as importantly, electron pulses are delivered directly on the target specimen. With electrons, progress has recently been made in imaging structural dynamics with ultrashort time resolution in both microscopy and diffraction. Earlier, nuclear motions in chemical reactions were shown to be resolvable on the femtosecond (fs) time scale using pulses of laser light, and the recent achievement of attosecond (as) light pulses has opened up this temporal regime for possible mapping of electron dynamics. Electron pulses of femtosecond and attosecond duration, if achievable, are powerful tools in imaging. The “electron recombination” techniques used to generate such attosecond electron pulses require the probing electron to be created from the parent ions (to date no attosecond electron pulses have been delivered on an arbitrary target) and for general applications it is essential that the electron pulse be delivered directly to the specimen. In ultrafast electron microscopy (UEM), the electron packet duration is determined by the initiating laser pulse, the dispersion of the electron packet due to an initial energy spread and electron-electron interactions. Since packets with a single electron can be used to image, and the initiating laser pulse can in principle be made very short (sub-10 fs), the limiting factor for the electron pulse duration is the initial energy spread. In photoelectron sources this spread is primarily due to the excess energy above the work function of the cathode, and is inherent to both traditional photocathode sources and optically-induced field emission sources. Energy-time uncertainty will also cause a measurable broadening of the electron energy spread, when the initiating laser pulse is decreased below ˜10 fs. For ultrafast imaging techniques to be advanced into the attosecond temporal regime, methods for dispersion compensation and new techniques to further compress electron pulses to the attosecond regime need to be developed. As described herein techniques for compressing free electron packets, from durations of hundreds of femtoseconds to tens of attoseconds, using spatially-dependent ponderomotive potentials are provided by embodiments of the present invention. Thus, a train of attosecond pulses can be created and used in ultrafast electron imaging. Because they are generated independent of the target they can be delivered to a specimen for studies of transient structures and electronic excitations on the attosecond time scale. The deflection of electrons (as in the Kapitza-Dirac effect) by the ponderomotive potential of intense lasers and the diffraction of electrons in standing waves of laser light have been observed, and so is the possibility (described through computer modeling) of spatial/temporal focusing with combined time-dependent electric and static magnetic fields. The “temporal lens” description analytically expresses how ponderomotive compression can be used to both compensate for the dispersion and magnify, in this case compress, the temporal duration of electron packets. We obtain simple lens equations which have analogies in optics and the results of “electron ray optics” of temporal lenses allows for analytical expressions and for the design of different schemes using geometrical optics. Here, we consider two types of temporal lenses, thin and thick. For the realization of the temporal thin lens, a laser beam with a Laguerre-Gaussian transverse mode, radial index ρ=0 and azimuthal index l=0 (or, in common nomenclature, a “donut” mode, is utilized. In the center of the donut mode, electrons will experience a spatially-varying ponderomotive potential (intensity) that is approximately parabolic. This potential corresponds to a linear spatial force which, for chirped electron pulses, can lead to compression from hundreds of fs to sub-10 fs. The second type, that of a thick lens, is based on the use of two counter-propagating laser beams in order to produce a spatially-dependent standing wave that co-propagates with the electrons. A train of ponderomotive potential wells are produced at the nodes of the standing wave, leading to compression but now with much “tighter focus” (thick lens). Because the electron co-propagates with the laser fields, velocity is matched. Analytical expressions are derived showing that this lens has the potential to reach foci with attosecond duration. Finally, we discuss methods for creating tunable standing waves for attosecond pulse compression, and techniques for measuring the temporal durations of the compressed pulses. Space-charge dispersed packets of electrons that have a linear spatial velocity chirp may also be compressed with the temporal lenses described here. All electron sources, both cw and pulsed, have an initial energy spread. For pulsed electron sources this is particularly relevant as electron packets created in a short time disperse as they propagate. The initial energy spread leads to an initial spread in velocities. These different velocities cause the initial packet to spread temporally, with the faster electrons traveling a further distance and the slower electrons traveling a shorter distance in a given amount of time. The dispersion leads to a correlation between position (along the propagation direction) and electron velocity as described in relation to FIG. 14. The linear spatial velocity “chirp” can be corrected for with a spatially-dependent linear impulsive force (or a parabolic potential). Thus, if a pulsed, spatially-dependent parabolic potential can be made to coincide appropriately with the dispersed electron packet, the slow trailing electrons can be sped up and the faster leading electrons can be slowed down. The trailing electrons, now traveling faster, can catch the leading electrons and the electron pulse will thus be compressed. FIG. 13 illustrates dispersion of an ultrashort electron packet. At t=to the packet is created from a photocathode and travels with a velocity v0. As it propagates along the x-axis it disperses, with the faster electrons traveling further, and the slower ones trailing for a given propagation time t. At t=0 a parabolic potential is pulsed on, giving an impulsive “kick” to the dispersed electron packet. After the potential is turned off, t>τ, the trailing electrons now have a greater velocity than the leading electrons. After a propagation time t=ti, the pulse is fully compressed. Consider a packet of electrons, propagating at a speed v0 along the x-axis, with a spread in positions of Δxo=v0Δto, at time t=to. At t=0, a potential of the form U(x)=½Kx2 interacts with the electron packet for a duration τ in the lab frame. The waist, or spatial extent of the potential (temporal lens) is chosen to be w, while the duration τ is chosen such that it is short compared to w/v0. When this condition is met the impulse approximation holds, and the change in velocity is Δv=−τ/m(dU(x)/dx)=−τKx/m, for \|x\|<w, where m is the electron mass. After the potential is turned off, t>τ, the electrons will pass through the same position, xf−x=(v0+Δv)tf, at the focal time tf=−x/Δv=m/(Kτ). To include an initial velocity spread around v0 (due to an initial ΔE), consider electrons that all emanate from a source located at a fixed position on the x-axis. An electron traveling exactly at v0 will take a time t0 to reach the center of the potential well at x=0. Electrons leaving the source with other velocities v0+vk will reach a location x=vkto at t=0. The image is formed at a location where electrons traveling with a velocity v0 and a velocity v0+vk intersect, this is, when v0ti=x+(v0+Δv+vk)ti. The image time ti is then ti=−x/(Δv+vk). FIG. 14 illustrates ray diagrams for spatial and temporal lenses. The top figure in FIG. 14 depicts three primary rays for an optical thin spatial lens. The object is located at yo, and the spatial lens has a focal length, f. A real image of the object is created at the image plane, position yi. The bottom figure in FIG. 14 is a ray diagram for a temporal thin lens. The diagram is drawn in a frame moving with the average speed v0 of the electron packet. The slopes of the different rays in the temporal diagram correspond to different initial velocities that are present in the electron packet. As shown in the diagram, a temporal image of the original electron packet is created at the image time ti. The initial packet (object) is created at a time to with Δto=Δxo/v0, where the spatial extend of the pulse is directly related to the temporal duration of the object. The lens is pulsed on at t=0 and the temporal focal length of the lens is tf. The lens represents the ponderomotive potential and in this case is on for the very short time τ. For the object time, to=x/vk, image time ti=−x/(Δv+vk) and the focal time tf=−x/Δv, the temporal lens equation holds, 1 t o + 1 t i ⁢ = 1 t f . ( 4 ) Ray tracing for optical lenses is often used to visualize how different ray paths form an image, and is also useful for visualizing how temporal lenses work as shown in FIG. 14. As derived in later sections, the magnification M is defined as the ratio of the electron pulse duration (Δti) at the image position to the electron pulse duration (Δto), and is directly proportional to the ratio of the object and image times (−ti/to) and distances (−xi/xo). In polar coordinates, a Laguerre-Gaussian (LG01) mode has a transverse intensity profile given by, I(r,φ)=I0exp(1)2r2exp(−2(r/w)2)/w2 where w is the waist of the focus and I0 the maximum intensity. This “donut” mode has an intensity maximum located at r=√{square root over (2)}w/2 with a value of I0=2EP(√{square root over (ln 2/π3)} where EP is the energy of the laser pulse and τ is the full-width-at-half-maximum of the pulse duration, assuming a Gaussian temporal profile given by exp(−4ln 2(t/τ)2). The ponderomotive energy UP(x) is proportional to intensity, U P ⁡ ( x ) = 1 2 [ ⅇ 2 ⁢ λ 2 ⁢ exp ⁡ ( 1 ) ⁢ I 0 2 ⁢ π 2 ⁢ m ⁢ ⁢ ɛ 0 ⁢ c 3 ⁢ w 2 ⁢ ln ⁢ ⁢ 2 π ] ⁢ x 2 ≡ 1 2 ⁢ Kx 2 , ( 5 ) where m is the electron mass, e is the electron charge and λ the central wavelength of the laser radiation and replacing r with x. Near the center of the donut mode focus (or x<<w) the intensity distribution is approximately parabolic, and hence the ponderomotive energy near the donut center is also parabolic. In analogy with a mechanical harmonic oscillator, the quantity in the square brackets of equation (5) can be referred to as the stiffness K; it has units of J/m2=N/m, and at 800 nm has the numerical value of, K≈3.1×10−36EP/(w4τ). For this parabolic approximation to be applicable, the spatial extent of the dispersed electron pulse, at t=0, Δx(0)=v0Δto+Δvoto must be much smaller than the laser waist, where the object velocity spread is Δvo=ΔE/√{square root over (2mE)}. The effect of this parabolic potential on an ensemble of electrons emitted from a source will now be analyzed. The velocity distribution of the ensemble is centered around vo, with an emission time distribution centered on −to, where all electrons are emitted from the same location xo=−v0to. Assuming a single donut-shaped laser pulse is applied at t=0, and centered at x=0, the electron ensemble is then influenced by the potential U(x)=½Kx2. The kth electron in the ensemble has an initial velocity v0+vk and emission time −to+tk. Using a Galilean transformation to a frame moving with velocity v0, the propagation coordinate x (lab frame) is replaced with the moving frame coordinate {tilde over (m)}=x−v0t. At t=0 the potential exists for the ultrashort laser pulse duration τ, giving the electron an impulse (or “kick”) dependent on its instantaneous position in the parabolic potential. In both frames, the position of the electron at t=0 is xk(0)={tilde over (x)}k(0≡−v0tk+vkto−vktk, where xk(t) and {tilde over (x)}k (t) are in the lab and moving frames, respectively. Using the impulse approximation the electron trajectory immediately after the potential is turned off becomes,{tilde over (x)}k(t)=vkt+{tilde over (x)}k(0(1−t/tf). (6)where tf=m/(Kτ) is the focal time. The electron trajectories, before and after t=0, can be plotted in both frames to give the equivalent of a ray diagram as illustrated in FIG. 15. Electrons emitted at the same time, i.e. tk=0, but with different velocities, will meet at the image position, {tilde over (x)}k=0 in the moving frame at the image time The image time is found by setting {tilde over (x)}k (ti)=0, from equation (6), with tk=0, {tilde over (x)}k(ti)=vkti+vkto(1−ti/tf)=0 which is equivalent to the lens equation, equation (4): to−1+ti−1=tf−1. An expression for the magnification can be obtained when electrons that are emitted at different times tk and different velocities vk are considered. If the magnification is defined as M=−ti/to then the temporal duration at the image time becomes,Δti=MΔt0, (7)where Δto and Δti are the duration of the electron packet at the object and image time, respectively. Durations achievable with a thin temporal lens follow from equation (7). An experimentally realistic temporal lens would use a 50 fs, 800 nm laser pulse with 350 μJ energy, focused to a waist of w=25 μm. These values result in a stiffness of K=5.5×10−8 N/m and a focal time of tf=0.3 ns; tf=m/(Kτ). If the lens is applied 10 cm from the source, electrons emitted at v0=c/10 (3 keV) would have an object time of to=x0/v0=0.1/(c/10)=3.0 ns. Using the temporal lens equation, equation (4), ti is obtained to be 0.33 ns. Hence, a magnification of M=−ti/to=0.1. Consequently, a thin temporal lens can compress an electron packet with an initial temporal duration of Δto≈100 fs, after it has dispersed, to an image duration of Δti≈10 fs. While the example presented here is for 3 keV electrons, the thin lens approximation holds for higher energy electrons as long as τ is chosen to be short compared to w/v0. Experimentally, the thin temporal lens can be utilized in ultrafast diffraction experiments which operate at kHz repetition rates with lasers that typically possess power that exceeds the value needed for the ponderomotive compression. Referring to FIG. 15, thin lens temporal ray diagrams for the lab and co-propagating frames are illustrated. The upper left panel is a ray diagram drawn in the lab frame showing how different initial velocities can be imaged to a single position/time. The gray lines are rays representing electrons with different velocities. The lower left panel is a ray diagram drawn in a frame moving with the average velocity v0 of the electron packet. The rays represent velocities of v0/67, v0/100 and 0. In the co-propagating frame, the relationship between Δto and Δti can be visualized as Δti=−Δtoti/to. One major difference between the lab frame and the moving frame is that in the latter the position of the object and image are moving. The lines representing the object and the image positions are drawn with slopes of −v0. The upper right panel depicts the experimental geometry for the implementation of a thin temporal lens. Note that the laser pulse and electron packet propagate perpendicular to each other, and that the interception point between the electrons and photons is at x=0 and t=0. The lower right panel shows how the parabolic (idealized) potential compares to the experimentally realizable donut potential. The colored dots indicate the position of electrons following the rays indicated in the left bottom diagram. Above, it was analytically shown that free electron packets can be compressed from hundreds to tens of femtoseconds using a temporal thin lens, which would correspond to a magnification of ˜0.1. Co-propagating standing wave can be created by using two different optical frequencies, constructed by having a higher frequency (ω1) optical pulse traveling in the same direction as the electron packet and a lower frequency (ω2) traveling in the opposite direction. When the optical frequencies ω1, ω2, and the electron velocity v0 are chosen according to v0=c(ω1−ω2)/(ω1+ω2), a standing wave is produced in the rest frame of the electron as illustrated in FIG. 16. If the electron has a velocity v0=c/3, and ω1=2ω2 then the co-propagating standing wave has a ponderomotive potential of the form, U P ⁡ ( x ) = 1 2 ⁢ ( ⅇ 2 ⁢ λ ~ 2 ⁢ E 0 2 8 ⁢ π 2 ⁢ m ⁢ ⁢ c 2 ) ⁢ cos 2 ( k ~ ⁢ x ) , ( 8 ) where E0 is the peak electric field, {tilde over (λ)} the Doppler shifted wavelength. The envelopes of the laser pulses are ignored in this derivation, but they can be engineered so that the standing wave contrast is optimized. The standing waves can be provided outside the microscope housing or inside the microscope housing. The presence of the standing wave copropagating with the electron pulse or packet inside the microscope housing can produce a series of attosecond electron pulses as illustrated in FIG. 7B and FIG. 16. Depending on the geometry with which the laser beams interact, the standing wave and the electron pulse can overlap adjacent to the sample, providing attosecond electron pulse generation at distances close to the sample. The attosecond electron pulses can be single electron pulses. To find an analytic solution in the thick lens geometry, each individual potential well in the standing wave is approximated by a parabolic potential that matches the curvature of the sinusoidal potential, UP(x)=½[e2 E02/(2mc2)]x2≡½Kx2. Using the exact solution to the harmonic oscillator the focal time is,tf=cot(ωPτ)/ωP+τ, (9)where ωp=√{square root over (Km)} and τ is the duration that the lens is on. For τ→0, tf→m/(K τ), which is identical to the thin lens definition. The image time, ti, has a form,ti=(1/ωP2+totf−tfτ+τ2)/(to−tf+τ), (10)and after the two assumptions, τ→0 and to>>1/(tfωP2) becomes equivalent to equation (4), the lens equation: to−1+ti−1=tf−1. The standard deviation of the compressed electron pulse at arbitrary time ta is, Δ ⁢ ⁢ t a = t f 2 ( λ ~ 2 + 4 ⁢ t a 2 ⁢ Δ ⁢ ⁢ v o 2 ) + t a 2 ⁢ λ ~ 2 - 2 ⁢ t f ⁢ t a ⁢ λ ~ 2 48 ⁢ ⁢ t f 2 ⁢ v 0 2 , ( 11 ) which is valid for an individual well. The time when the minimum pulse duration occurs is ta=tf{tilde over (λ)}2/({tilde over (λ)}2+4tf2Δvo2)≈tf and for experimentally realistic parameter is equal to tf. This implies that the thick lens does not image the initial temporal pulse; it temporally focuses the electrons that enter each individual well. Since there is no image in the thick lens regime, the minimum temporal duration is not determined by the magnification M as in the thin lens section, but is a given by, Δ ⁢ ⁢ t f = t f 2 ⁢ λ ~ 2 ⁢ Δ ⁢ ⁢ v o 2 12 ⁢ v o 2 ( λ ~ 2 + 4 ⁢ ⁢ t f 2 ⁢ Δ ⁢ ⁢ v o 2 ) ≅ t f ⁢ Δ ⁢ ⁢ v o v o ⁢ 2 ⁢ 3 ( 12 ) It should be noted that neither the temporal focal length nor the temporal duration are directly dependent on the Doppler shifted wavelength {tilde over (λ)}, as long as the condition to<v0Δto/Δvo is met. An example illustrates what temporal foci are obtainable. A source emits electrons with an energy distribution of 1 eV and a temporal distribution of 100 fs. Electrons traveling at v0=c/3 and having an energy E=31 keV gives a velocity distribution of Δvo=1670 m/s. If the distance between the source and the temporal lens is 10 cm, to=1.0 ns is less than voΔto/Δvo≈6.0 ns, satisfying the condition to<v0Δto/Δvo and equation (12) is then valid. If the two colors used for the laser beams are 520 nm and 1040 nm, the Doppler-shifted wavelength is {tilde over (λ)}=740 nm. For a laser intensity of 3×1012Wcm−2 (available with repetition rates up to megahertz), the oscillation frequency in the potential well is ωp≈2×1012 rad/s, which gives a focal time of tf≈1 ps. With these parameters, equation (12) gives a temporal duration at the focus of Δtf≈5 as. To support this ˜5 as electron pulse, time-energy uncertainty demands an energy spread of ˜50 eV. The ponderomotive compression imparts an energy spread to the electron pulse which can be estimated from ΔE˜mv0{tilde over (λ)}(2tf), giving ˜50 eV similar to the uncertainty limit. This ΔE is very small relative to the accelerating voltage in microscopy (200 keV) and only contributes to a decrease of the temporal coherence. In optical spectroscopy such pulses can still be used as attosecond probes despite the relatively large ΔE when the chirp is well characterized. Combining the anharmonicity broadening of 15 as, we conclude that ultimately temporal pulse durations in the attosecond regime can be reached. In the temporal thick lens case, the use of ω and 2ω to create a co-propagating standing wave requires v0=c/3. However, the velocity of the electrons, vo, can be tuned by changing the angle of the two laser pulses. A co-propagating standing wave can still be obtained by forcing the Doppler-shifted frequencies of both tilted laser pulses to be equal. A laser pulse that propagates at an angle θ with the respect to the electron propagation direction has a Doppler-shifted frequency {tilde over (ω)}=γΩ(1±(v/c)cos θ), where ω is the angular frequency in the lab frame, {right arrow over (v)}={circumflex over (x)} is the electron velocity, and γ=1/√{square root over (1−v2/c2)}. When the two laser pulses are directed as shown in FIG. 16, a co-propagating standing wave occurs for an electron with a velocity v0=c(k1−k2)/(k1 cos θ1+k2 cos θ2), where the laser pulse travelling with the electron packet has a wave vector of magnitude k1 and makes an angle of θ1 with the electron propagation axis; the second laser pulse traveling against has a wave vector magnitude of k2 and angle θ2, in the lab frame. An electron moving at v0 will see a standing wave with an angular frequency, ω ~ = 2 ⁢ ( cos ⁢ ⁢ θ 1 + cos ⁢ ⁢ θ 2 ) 2 ⁢ ⁢ cos ⁢ ⁢ θ 1 + cos ⁢ ⁢ θ 2 ⁢ γ ⁢ ⁢ ω ⁡ ( 1 - β ) , ( 13 ) where 2k=k1=2k2 for experimental convenience, ω=kc, and the wavelength is {tilde over (λ)}=2πc/{tilde over (ω)}=2π/{tilde over (k)}. The standing wave created with arbitrary angles θ1 and θ2 will be tilted with respect to the electron propagation direction, which will temporally smear the electron pulse. This tilting of the standing wave can be corrected for by constraining the angles θ1 and θ2 to be: θ2=arcsin(2 sin θ1). For θ1=15° (forcing θ2≈31°, electrons with velocity v0=0.36c (E≈33 keV) see a standing wave. A 1 eV electron energy distribution at the source gives a velocity distribution of Δv0≈1630 m/s, at 33 keV. Using the same laser intensity as in the thick lens case, and the new v0 and Δvo, the condition to<v0Δto/Δvo is still satisfied, allowing equation (13) to be resulting in a duration at the focus of Δtf≈4.6 as. Using the tunable thick lens makes the experimental realization more practical, allowing for easy optical access and electron energy tuning, while at the same time keeping Δtf approximately the same. For additional tunability, an optical parametric amplifier can be used so that the laser pulse frequencies are not restricted to ω and 2ω. The ability to create electron pulses with duration from ˜10 fs to ˜10 as raises a challenge regarding the measuring of their duration and shape. Two different schemes are presented here for measuring pulses compressed by thick and thin temporal lenses. For measuring the thin lens compressed electron packet, the focused packet could be intersected by a laser pulse with a Gaussian spatial focus as illustrated in FIG. 17. An optical delay line would control the time delay between the measuring laser pulse and the compressed electron packet. As the time delay, Δt, is varied, so is the average energy of the electrons, as shown in FIG. 17. If the delay time is zero, then the average electron energy will be unaffected, as there is no force. If the delay line is changed so that the Gaussian pulse arrives early (late), then the average energy will decrease (increase). The change in the average energy is dependent on the duration of the electron pulse, and the intensity of the probing laser pulse. If the electron pulse is longer than the duration of the measuring laser pulse, then the change in the average energy will be reduced. The steepness of the average energy as a function of delay time, Ē(Δt), is a direct measure of the electron pulse duration, and using fs-pulsed electron energy loss spectra this scheme can be realized. For the thick lens a similar method is described here. At the focal position and time of the compressed temporal electron packet, a second co-propagating potential is introduced. The positions of the individual wells in the second co-propagating standing wave can be moved by phase shifting one of the two laser beams that create the probing potential (FIG. 17). By varying the phase shift, the potential slope (and hence the force) that the electrons encounter at the focus is changed. If no phase shift is given to the probing standing wave, no average energy shift results. When a phase shift is introduced, the electrons will be accelerated (or decelerated) by the slope of an individual well in the standing wave, and as long as the phase stability between the electrons and the probing standing wave is appropriate, attosecond resolution can be achieved. As the electron pulse duration becomes less than the period of the standing wave, the average electron energy change increases. The electron temporal duration of the compressed electron packet can be determined directly by the steepness of the Ē(φ) curve. Diffraction with focused electron probes is among the most powerful tools for the study of time-averaged nanoscale structures in condensed matter. Embodiments of the present invention provide methods and systems for four-dimensional (4D) nanoscale diffraction, probing specific-site dynamics with ten orders of magnitude improvement in time resolution, in convergent-beam ultrafast electron microscopy (CB-UEM). For applications, we measured the change of diffraction intensities in laser-heated crystalline silicon as a function of time and fluence. The structural dynamics (change in 7.3±3.5 ps), the temperatures (up to 366 K), and the amplitudes of atomic vibrations (up to 0.084 angstroms) are determined for atoms strictly localized within the confined probe area of 50-300 nm; the thickness was varied from 2 to 100 nm. A broad range of applications for CB-UEM and its variants are possible, especially in the studies of single-particles and heterogeneous structures. In fields ranging from cell biology to materials science, structures can be imaged in real-space using electron microscopy. Atomic-scale resolution of structures is usually available from Fourier-space diffraction data, but this approach suffers from the averaging over the selected specimen area which is typically on the micrometer scale. Significant progress in techniques has enabled localization of diffraction to nanometer and even angstrom-sized areas by focusing a condensed electron beam onto the specimen. Parallel illumination with a single electron wavevector is reshaped to a convergent beam with a span of incident wavevectors. This method of convergent beam electron diffraction (CBED), or electron microdiffraction, and with energy filtering, has made possible determination of structures in 3 dimensions with highly precise localization to areas reaching below one unit cell. The applications have been wide-ranging, from revealing bonding charge distribution and local defects and strains in solids to detecting local atomic vibrations and correlations. Today, aberration-corrected, atomic-sized convergent electron beams enable analytical probing using electron-energy-loss spectroscopy (EELS) and scanning transmission electron microscopy (STEM). In order to resolve structural dynamics with appropriate spatiotemporal resolution, femtosecond (fs) and picosecond (ps) electron pulses are ideal probes because of their picometer wavelength and their large cross section, resulting from the effective Coulomb interaction with atomic nuclei and core/valence electrons of matter. Typically, ultrafast electron diffraction is achieved by initiating the physical or chemical change with a pulse of photons (pump) and observing the ensuing dynamics with electron pulses (probe) at later times. By recording sequentially delayed diffraction frames a “movie” can be produced to reveal the temporal evolution of the transient structures involved in the processes under study. FIG. 18 is a simplified schematic diagram of a CB-UEM set-up (top), and observed low-angle diffraction discs according to an embodiment of the present invention. Femtosecond electron pulses are focused on the specimen to form a nanometer-sized electron beam. Structural dynamics are determined by initiating a change with a laser pulse and then observing the consequences using electron packets delayed in time. Insets (right) show the CB-UEM patterns taken along the Si [011] zone axis at different magnifications. At the high camera length used, only the ZOLZ discs indexed in the figure are visible; the kinematically-forbidden 200 disc appears as a result of dynamic scattering. In the reciprocal space representation of the diffraction process (bottom) the Ewald sphere has an effective thickness of 2α, the convergence angle of the electron beam. The diamond structure of Si forbids any reflections from odd numbered Laue planes when the zone axis is [011]. Embodiments of the present invention provide CB-UEM methods and systems with applications in the study of nanoscale, site-selected structural dynamics initiated by ultrafast laser heating (1014 K/s). Because of the femtosecond pulsed-electron capability, the time resolution is ten orders of magnitude improved from that of conventional TEM, which is milliseconds; and because of beam convergence, high-angle Bragg scatterings are visible with their intensities being very sensitive to both the 3D structural changes and amplitudes of atomic vibrations. The CB-UEM configuration is shown in FIG. 18; our chosen specimen is a crystalline silicon slab, a prototype material for such investigations. From these experiments, it is found that the structural change within the locally probed site occurs with a time constant of 7.3±3.5 ps, which is on the time scale of the rise of lattice temperature known for bulk silicon. For these local sites, the temperatures measured at different laser fluences range from 299° K to 366° K, corresponding to vibrational amplitude changes from 0.077 Å to 0.084 Å, respectively. The reported results would be impossible to obtain with conventional, parallel beam diffraction. The electron microscope is integrated with a fs oscillator/amplifier laser system. The fundamental mode of the laser at 1036 nm was split into two beams: the first was frequency doubled to 518 nm and used to initiate the heating of the specimen, whereas the second, which was frequency tripled, was directed to the microscope for extracting electrons from the cathode. The time delay between pump and probe was adjusted by changing the relative optical path lengths of these two pulses. The pulses were sufficiently separated in time (5 μs) to allow for cooling of the specimen. The electron packets were accelerated to 200 keV (corresponding to a de Broglie wavevector of 39.9 Å−1), de-magnified, and finally focused (with a 6 mrad convergence angle) to an area of 50-300 nm diameter on the wedge-shaped specimen, as shown in FIG. 18. A wide range of thicknesses, starting from ˜2 nm was accessible simply by moving the electron beam laterally. The silicon specimen was prepared by mechanical polishing of a wafer along the (011) planes, followed by Ar ion-milling for final thinning/smoothing; the wedge angle was 2°. In the microscope, Kikuchi lines were observed and used as a guide to orient the specimen with the [011] zone axis either parallel or tilted relative to the incident electron beam direction. FIG. 18 display the typical high-magnification (high-value camera length) CB-UEM patterns of Si obtained when the specimen is unexcited and the zone axis is very close to [011]; the magnification (>10×) cab be seen by comparing the disc length scale in FIG. 18 and ring radius in FIG. 19. Unlike parallel-beam diffraction which yields spots, convergent-beam diffraction produces discs in reciprocal space (back focal plane of the objective lens) with their diameter given by the convergence angle (2α) of the electron pulses. These discs form the Zero Order Laue Zone (ZOLZ) of the pattern; they show white contrast with thin specimens and exhibit the interference patterns displayed in FIG. 18 when the thickness is increased. In the reciprocal space, the effective thickness of the Ewald sphere is 2α (bottom panel of FIG. 18), giving rise to multiple spheres that can intersect with Higher Order Laue Zones (HOLZ) reflections, the focus of this study (see FIG. 19) and the key to 3D structural information; the first and second zones, FOLZ and SOLZ, are examples of such zones or rings. The interference patterns in the disks are the result of dynamical scattering in silicon and are reproduced in our CB-UEM patterns (FIG. 18). The scattering vectors of HOLZ rings (R) are related to the inter-zone spacing in the reciprocal space (hz in Å−1) by the tilt angle from the zone axis (η) and by the magnitude of the incident electron's wavevector (k0). In the plane of the detector and for our tilt geometry, the HOLZ ring scattering vector is given by (equation (14)):R≅(k02 sin2(η)+2k0hz)1/2−k0 sin(η), (14)where, for our case of the [011] zone axis, hz=n/(a√{square root over (2)}) with n=1,2,3 . . . for the different Laue zones. Additionally, for this zone axis, k+1=n, where (hkl) are the Miller indices of the reciprocal space. When k+l=1, for FOLZ, k and l must have different parity, which is forbidden by the symmetry of the diamond Si structure. Therefore, the FOLZ along the [011] zone axis should be absent and the first visible ring should belong to SOLZ; in general, all odd numbered zones will be forbidden. Here, HOLZ indexing is defined according to the fcc unit cell and not to the primitive one [1]. FIG. 19 illustrates temporal frames obtained using CBUED. In FIG. 19(a) high angle SOLZ ring obtained for a tilt angle of 5.15° from the [011] zone axis are shown. Besides SOLZ, Kikuchi lines and periodic bands (due to atomic correlations) are visible. The ZOLZ discs are blocked (top left) to enhance the dynamic range in the area of interest; the disc of the direct beam (the center one in FIG. 18 discs) is indicated by a circle. The intensity scale is logarithmic. In FIG. 19(b,c,d) time frames of the SOLZ ring are shown by color mapping for visualization of dynamics. The intensity of the ring changes within picoseconds, but the surrounding background remains at the same level. FIG. 19(a) presents the HOLZ ring taken with the CB-UEM. In order to reduce the strong on-zone-axis dynamic scattering (and to bring the high scattering angles into the range of the recording camera), the slab was tilted 5.15° away from the [011] zone axis, along the [02 2] direction. The scattering vector of the Bragg points of the ring, from the direct beam position, was measured to be 2.2 Å−1, close to the value of 2.22 Å−1 obtained by using equation (14) for n=2, which identifies the spots shown as part of the SOLZ. From this value, the know lattice separation of 5.4 Å was obtained for silicon. In addition to the SOLZ ring, Kikuchi lines and some oscillatory bands are also visible in the CB-UEM, as seen in FIG. 19(a). Kikuchi lines arise from elastic scatterings of the inelastically scattered electrons, whereas the oscillatory bands in the thermal diffuse scattering (TDS) background result from correlations between the atoms. We also observed deficit HOLZ lines and interference fringes in ZOLZ discs for a two-beam condition. The temporal behavior is displayed in FIG. 19, with three CB-UEM frames taken at time delays of t=−14.8 ps, +5.2 ps, and +38.2 ps, together with a static image; the zero of time is defined by the coincidence of the pump and probe pulses in space and time. The frame at negative time has higher ring intensity than that observed at +38.2 ps, whereas the +5.2 ps frame shows an intermediate intensity value. It is clear from the results that the intensity change is visible within the first 5 ps of the structural dynamics. For quantification, the intensities in each frame were normalized to the area of azimuthally integrated background. The normalization of the HOLZ ring intensities to the TDS background makes the atomic vibration estimations insensitive to the thickness changes of the probed area, which may result from slight beam jittering. FIG. 20 illustrates diffraction intensities at different times and fluences. Normalized, azimuthally-integrated intensity changes of the SOLZ ring are shown with time ranging from −20 ps to +100 ps, for two different laser powers. Whereas the 10 mW response does not show noticeable dynamics, the 107 mW transient has a clear intensity change with a characteristic time of 7.3±3.5 ps. The range of fluences studied was 1.7 to 21 mJ/cm2 (see FIG. 21). The red curve is a mono-exponential fit based on the Debye-Waller effect. The red dashed line through the 10 mW data is an average of the points after +20 ps. The dependence on fluence is given in FIG. 21. FIG. 20 depicts the transient behavior of the SOLZ ring intensity for two different laser power, 10 mW and 107 mW, corresponding to pulse fluence of 1.7 and 19 mJ/cm2, respectively; the heating laser beam diameter on the specimen is 60 μm. The intensities were normalized to the average value obtained at negative times. Whereas the intensity change is essentially absent in the 10 mW data, the results for the 107 mW set shows a transient behavior with a characteristic time of 7.3±3.5 ps, obtained from the mono-exponential fit shown in red in the figure. The temporal response of UEM-2 is on the fs time scale, as obtained by EELS, and it is much shorter than the 7 ps illustrated here. The local heating of the lattice is responsible for the SOLZ intensity change with time. A pump laser, in our case at 518 nm (2.4 eV), excites the valance electrons of Si to the conduction band; one-photon absorption occurs through the indirect bandgap at 1.1 eV, and multi-photon absorption excites electron-hole pairs through the direct gap. The excited carriers thermalize within 100 fs, via carrier-carrier scatterings, and then electron cooling takes place in ˜1 ps, by electron-phonon coupling. During this time lattice heating occurs through increased atomic vibration, reducing SOLZ intensity. The effective lattice temperature is ultimately established with a time constant of a few picoseconds depending on density of carriers or fluence However, in CB-UEM measurements the lattice-temperature rise could be slower than in bulk depending on the dimension of the specimen relative to the mean free path of electrons in the solid. The dynamical change can be quantified by considering a time-dependent Debye-Waller factor with an effective temperature describing the decrease in the Bragg spot intensity with time. If the root-mean-square (rms) displacement of the atoms, ux21/2, along one of the three principle axes is denoted by ux for simplicity, and the scattering vector by s, then the HOLZ ring intensity can be expressed as (equation (15)):IRingF(t)=I0(t−)exp [−4π2s2ux2(t)], (15)where IRingF(t) is the measured intensity for a given fluence, F, and the vibrational amplitude is now time dependent. Note that ux is ⅓ of the total, utotal. In the Einstein model of atomic vibrations, which has been used successfully for silicon, the atoms are treated as independent harmonic oscillators, with the three orthogonal components of the vibrations decoupled. As a result, a single frequency (ω) is sufficient to specify the energy eigenstates of the oscillators. The relationship of the vibrational amplitude to temperature can be established by simply considering the Boltzmann average over the populated eigenstates. Consequently, the probability distribution of atomic displacements is derived to be of Gaussian form, with a standard deviation corresponding to the rms (ux) of the vibration involved (equation (16)):ux=[(ℏ/2ωm)coth(ℏω/2kBTeff)]1/2 (16)where ℏ is Planck's constant, kB the Boltzmann constant, Teff in our case the effective temperature, and m the mass of the oscillator. In the high temperature limit, i.e. when ℏω/2kBT<<1, eq. 3 simplifies to mω2ux2=kBT, which is the classical limit for a harmonic oscillator; the zero-point energy, which contributes almost half of the mean vibration amplitude at room temperature, is included in equation (16). The value of ℏω is 25.3 meV. Despite its simplicity, the Einstein model in equation (16) was remarkably successful in predicting the HOLZ rings and TDS intensities by multi-slice simulations. FIG. 21 illustrates the amplitudes of atomic vibrations (rms) plotted against the observed intensity change at different fluences. The inset shows the mono-exponential temporal behavior, with the asymptotes highlighted (circles) for their values at different fluences. The fluence was varied from 1.7 to 21 mJ/cm2. This comparative study of the effect of the fluence was performed at a slightly different sample tilt (corresponding to s=2.7 Å−1), corresponding to a thickness of ˜80 nm. For each fluence, the temperature represents the effective value for the lattice structural change. The error bars given were obtained from the fits at the asymptotes shown in the inset, and they are determined by the noise level of temporal scans. In FIG. 21, we present the change in the asymptotic intensity with fluence (inset), and the derived vibrational amplitudes for the different temperatures. The amplitudes are directly obtained from equation (15), as s is experimentally measured. The relative temperature change (from t− to t+) is then derived from equation (16), taking the value of ux at room temperature (297° K.) to be 0.076 Å. The amplitude of atomic vibrations, and hence the temperature, increases as the fluence of the initiating pulse increases. Although the trend is expected for an increased ux with temperature, the absolute values, from 0.077 to 0.084 Å, correspond to a large 3.2% to 3.6% change in nearest neighbor separation; these values are still well below the 15% criterion for a melting phase transition. The linear thermal expansion coefficient has been accurately determined for silicon, and for a value of 2.6×10−6 K−1 at room temperature the vibrational amplitudes reported here are much higher than the equilibrium thermal values at the same temperature. This is because the effective temperature applies to a lattice arrested in a picosecond time window; at longer times, the vibrations equilibrate to a lower temperature. As such, measuring nanoscale local temperatures on the ultrashort time scale enhances the sensitivity of the probe thermometer by orders of magnitude. Moreover, the excitation per site is significantly enhanced. For a single-photon absorption at the fluence used, we estimate, for a 60 nm-thick specimen, the number of absorbed photons per Si atom (for the fs pulse employed) to be ˜0.01, as opposed to 10−9 photons per atom if the experiments were conducted in the time-averaged mode. The achievement of nanoscale diffraction with convergent-beam ultrafast electron microscopy opens the door to exploration of different structural, morphological, and electronic phenomena. The spatially focused and timed electron packets enable studies of single particles and structures of heterogeneous media. Extending the methodology reported here to other variants, such as EELS, STEM and nanotomography, promises possibilities for mapping individual unit cells and atoms on the ultrashort time scale of structural dynamics. With 4D electron microscopy, in situ imaging of the mechanical drumming of a nanoscale material is measured. The single crystal graphite film is found to exhibit global resonance motion that is fully reversible and follows the same evolution after each initiating stress pulse. At early times, the motion appears “chaotic” showing the different mechanical modes present over the micron scale. At longer time, the motion of the thin film collapses into a well defined fundamental frequency of 0.54 MHz, a behavior reminiscent of mode locking; the mechanical motion damps out after ˜200 us and the oscillation has a “cavity” quality factor of 150. The resonance time is determined by the stiffness of the material and for the 53-nm thick and 55-μm wide specimen used here we determined Young's modulus to be 0.8 TPa, for the in-plane stress-strain profile. Because of its real-time dimension, this 4D microscopy has applications in the study of these and other types of materials structures. Structural, morphological, and mechanical properties of materials have different length and time scales. The elementary structural dynamics, which involve atomic movements, are typically of picometer length scale and occur on the time scale of femto (fs) to picoseconds (ps). Collective phenomena of such atomic motions, which define morphological changes, are observed on somewhat longer time scale, spanning the ps to nanosecond (ns) time domain, and the length scale encompasses up to sub-micrometers. These microscopic structures are very different in behavior from those involved in the mechanical properties. On the nanoscale, when the membrane-like mechanical properties have high frequencies and complex spatial-mode structures, imaging becomes of great value in displaying the spatiotemporal behavior of the material under stress. Utilizing embodiments of the present invention, we have visualized nanoscale vibrations of mechanical drumming in a single-crystalline graphite film (53-nm thick). To study the transient structures, in both space and time, our method of choice has been 4D ultrafast electron microscopy (UEM). This microscope enables investigation of the atomic structural and morphological changes in graphite on the fs to ns time scale and for nm-scale resolution. Additionally, mechanical properties can be determined in real time, which are evident on the ns and microsecond (μs) time scale. The stress is introduced impulsively using a ns laser pulse while observing the motions in real space (in situ) in the microscope using the stroboscopic electron pulses. Remarkably, at times immediately following the initiating pulse the motion appears “chaotic” in the full image transients, showing the different mechanical modes present in graphite. However, after several μs the motion of the nanofilm collapses into a final global resonance of 0.54 MHz. From this resonance of mechanical drumming of the whole plate, we obtained the in-plane Young's modulus of 0.8 terapascal (Tpa). The reported coherent resonance represents the in-phase build up of a mechanical drumming, which is directly imaged without invasive probes. Graphite was chosen because of its unique material properties; it is made of stacked layers of 2D graphene sheets, in which the atoms of each sheet are covalently bonded in a honeycomb lattice, and the sheets separated by 0.335 nm are weakly held together by van der Waals forces. It displays anisotropic electromechanical properties of high strength, stiffness, and thermal/electric conductivity along the 2D basal planes. More recently, with the rise of graphene, a new type of nano-electromechanical system (NEMS) has been highlighted with a prototypical NEMS being a nanoscale resonator, a beam of material that vibrates in response to an applied external force. With the thicknesses reaching the one atomic layer, graphene remains in a high crystalline order, resulting in a NEMS with extraordinary thinness, large surface area, low mass density, and high Young's modulus. Briefly, the setup for ultrafast (and fast) electron imaging involves the integration of laser optical systems into a modified transmission electron microscope (TEM). Upon the initiation of a structural change by either heating of the specimen or through electronic excitation by the laser pulses, an electron pulse generated by the photoelectric effect is used to probe the specimen with a well-defined time delay. A microscopy image or a diffraction pattern is then taken. A series of time-framed snapshots of the image or the diffraction pattern recorded at a number of delay times provides a movie, which displays the temporal evolution of the structural (morphological) and mechanical motions, using either the fs or ns laser system. Because here the visualization is that of the mechanical modes with resonances on the MHz scale, the ns resolution was sufficient. The electrons are accelerated to 200 kV with a de Broglie wavelength of 2.5079 pm. Two laser pulses were used to generate the clocking, excitation pulse at 532 nm and another at 355 nm for the generation of the electron pulse for imaging. The time delay was controlled by changing the trigger time for electron pulses with respect to that of clocking pulses. The delay can be made arbitrarily long and the repetition rate varies from a single shot to 200 kHz, to allow complete heat dissipation in the specimen. The experiments were carried out with a natural single crystal of graphite flakes on a TEM grid. Graphite flakes were left on the surface, covering some of the grid squares completely. The observed dynamics are fully reversible, retracing the identical evolution after each initiating pulse; each image is constructed stroboscopically, in a half second, from typically 2500 pulses of electrons and completing all time-frames (movies) in twenty minutes. FIG. 22 illustrates images and the diffraction pattern of graphite. (A), an image shows features of fringes in contrast (scale bar: 5 μm). Sample thickness was measured to be 53 nm using electron energy loss spectroscopy (EELS). (B) Magnified view of the indicated square of panel A (scale bar: 1 μm). (C) Diffraction pattern obtained by using a selected area diffraction aperture (SAD), which covered an area of 6 μm in diameter on the specimen. The incident electron beam is parallel to the [001] zone axis. Bragg spots are indexed as indicated for some representative ones. Panels A and B of FIG. 22 show the UEM (bright field) images of graphite, and in panel C, a typical electron diffraction pattern is given. The Bragg spots are indexed according to the hexagonal structure of graphite along the [001] zone axis, with the lattice dimension of a=b=2.46 Å (c=6.71 Å). In FIG. 22A, and at higher magnification in FIG. 22B, contrast fringes are clear, typically consisting of linear fringes having ˜1 μm length and a few hundred-nm spacing. These contrast fringes are the result of physical bucking of the graphene layers by constraints or by nanoscale defects within the film. In the dark regions, the zone axis (the crystal [001]) is well aligned with the incident electron beam and electrons are scattered efficiently, whereas in the lighter regions the alignment of the zone axis deviates more and the scattering efficiency is lower. With these contrast patterns, changes in image provide a sensitive visual indicator of the occurrence of mechanical motions. The black spots are natural graphite particles. FIG. 23 illustrates representative image snapshots and difference frames. (A) Images recorded stroboscopically at different time delays, indicated at the top right corner of each image (t1, t2, t3, t4, and t5), after heating with the initiating pulse (fluence=7 mJ/cm2); t1=200 ns; t2=500 ns; t3=10 μs; t4=30 μs; t5=60 μs; and the negative time frame was taken at −1000 ns. Note the change in position of fringes with time, an effect that can be clearly seen in FIG. 23B. (B) Image difference frames with respect to the image taken at −1 μs, i.e., Im(−1 μs; t), which show the image change with time. The reversal in contrast clearly displays the oscillatory (resonance) behavior. In FIG. 23(A), we display several time-framed images of graphite taken at a repetition rate of 5 kHz and at delay times indicated with respect to the clocking (heating) pulse with the fluence of 7 mJ/cm2. At positive times, following t=0, visual changes are seen in the contrast fringes. With time, the contrast fringes change their location in the images, and with these and other micrographs of equal time steps we made a movie of the mechanical motions of graphite following the ns excitation impulse. To more clearly display the temporal evolution on the nanoscale, image-difference frames were constructed. In FIG. 23(B), depicted are the images obtained when referencing to the −1 μs frame, i.e., Im(−1 μs; t). In the difference images, the regions of white or black indicate locations of surface morphology change (contrast pattern movement), while gray regions are areas where the contrast is unchanged from that of the reference frame. Care was taken to insure the absence of long-term specimen drifts as they can cause apparent contrast change; note that in the difference images, the static features are not present. The image changes, reported in this study, are fully reproducible, retracing the identical evolution after each initiating laser pulse, as mentioned above. The reversal of contrast with time in FIG. 23(B) directly images the oscillatory behavior of the drumming The image change was quantified by using the method of cross-correlation. The normalized cross correlation of an image at time t with respect to that at time t′ is expressed as γ ⁢ ⁢ ( t ) = ∑ x , y ⁢ C x , y ⁡ ( t ) ⁢ C x , y ⁡ ( t ′ ) ∑ x , y ⁢ C x , y ⁡ ( t ) 2 ⁢ ∑ x , y ⁢ C x , y ⁡ ( t ′ ) 2 ( 17 ) where the contrast Cx,y(t) is given by [Ix,y(t)−Ī(t)]/Ī(t), and Ix,y(t) and Ix,y(t′) are the intensities of pixels at the position of (x,y) at times t and t′; t′; Ī(t) and Ī(t′) are the means of Ix,y(t) and Ix,y(t′), respectively. This correlation coefficient γ(t) is a measure of the temporal change in “relief pattern” between the two images being compared, which can be used as a guide to image dynamics as a function of time. Shown in FIG. 24 are cross-correlation values between the image at each measured time point and a reference image recorded before the arrival of the clocking pulse. FIG. 24 illustrates the time dependence of image cross correlation. The whole scan for 100 μs is made of 2000 images taken at 50-ns steps. Also depicted are the zoomed-in image cross-correlations of three representative time regimes (I, II, and III). In each zoomed-in panel, the selected-area image dynamics of five different regions are included. Note the evolution from the “chaotic” to the global resonance (drumming) behavior at long times. Over all pixels, the time scale for image change covers the full range of time delays, from tens of ns to hundreds of μs, indicating the collective averaging over the sites of the specimen. Upon impulsive heating at t=0, the image cross-correlation changes considerably with an appearance of a “chaotic” behavior, in the ˜5 μs range (regime I in FIG. 24). After 10 μs, e.g., regime II, the cross correlation change begins to exhibit periodicity (regime II), and at longer time, a well-defined resonance oscillation emerges (regime III). This is also evident in the selected-area image dynamics (SAID) in several regions (noted as 1 to 5) where the temporal behavior is of different shapes at early time but converges into a single resonance transient after several tens of μs. The shape of image cross correlation dynamics was robust at different fluences, from 2 to ˜10 mJ/cm2, but the amplitude varies. The overall decay of the transients is on a time scale shorter than the separation between pulses. In fact, we have verified the influence of repetition rate and could establish the full recovery at the time intervals indicated. Heat transfer must occur laterally. With an initial z-independent heat profile by absorption of the heating pulse in graphite, we estimated, using a 2D heat diffusion in a homogeneous medium, the time scale for an in-plane transfer, with thermal conductivity λ=5300 W/(m·K), density η=2260 kg/m3, and specific heat cv=707 J/(K·kg). For the radius at half height of the initial pulse heat distribution r0=30 μm, t1/2, the time for the axial temperature to drop to a half of its initial value, is deduced to be ˜720 ns, certainly much shorter than the 200-μs time interval between pulses. It follows that the decay of the oscillation [Q/(π·f0)], as derived below, is determined by the damping of mechanical motions. When the specimen absorbs intense laser light, the lattice energy, converted from carriers (electron energy) by electron-phonon coupling, in a few ps, builds up in the illuminated spot on the surface within the duration of the laser pulse. As a consequence, the irradiated volume will expand rapidly following phonon-phonon interaction on the time scale of tens of ps. The resulting thermal stress can induce mechanical vibration in the material, but a coherent oscillatory behavior, due to the thermoelastic stress, will only emerge in the image if the impulsive stress is on a time scale shorter than the period; probing of images should be over the entire time scale of the process, in this case 100 μs. On the ultrashort time scale we have observed the structural and morphological elastic changes. FIG. 25 illustrates resonance dynamics and FFT of graphite. (Left) Time dependences of image cross correlation of full image (A) and image intensity on the selected area of 4×6 pixels as indicated by the arrowhead (B) in FIG. 24. (Right) Fast Fourier transforms of image cross-correlation (C: 0-100 μs; D: 60-100 μs) and image intensity (E: 0-100 μs; F: 60-100 μs). Asterisks in the panels indicate overtones. Note the emergence of the resonance near 1 MHz in panel F. The resonance modes in graphite are highlighted in FIG. 25 by taking the fast Fourier transform (FFT) of image cross-correlation in the time regime of 0-100 μs. The FFT (FIG. 25C) shows several peaks of different frequencies, among which the strongest one around 2.13 MHz is attributed to the overtone of 1.08 MHz. The overtones, due to the truncated nature of cross-correlation close to the value of 1, are greatly reduced in the FFT of image intensity change (FIGS. 25E and 25F). In a few tens of μs, various local mechanical modes observed at early time damp out and one global mode around 1 MHz survives. The peak when fitted to a Lorentzian yields a resonant frequency of 1.08 MHz, and a “cavity” quality factor Q (=f0/Δf)=150±30. This dominant peak gives the fundamental vibration mode of the plate in graphite. For a period of vibration, the contrast pattern of image would recur twice to its initial feature giving the observed frequency to be twice that of structural vibration; the fundamental frequency is, thus, obtained to be 0.54 MHz. A square mechanical resonator clamped at four edges without tension has a fundamental resonance mode of f0 which is given by f 0 = A ⁢ ⁢ d L 2 ⁡ [ Y ( 1 - v 2 ) ⁢ ρ ] 1 / 2 + f ⁡ ( T ) ( 18 ) where f(T) due to tension T is zero in this case. Y is the Young's modulus; ρ is the mass density; v is the Poisson's ratio; L is the dimension of a grid square; d is the thickness of the graphite; and A is a constant, for this case equal to 1.655. We measured d to be 53 nm from EELS. Knowing ρ=2260 kg/m3 (300 K), v=0.16 for graphite, and L=55 μm, we obtained from the observed resonance frequency the Young's modulus to be 0.8 TPa, which is in good agreement with the in-plane value of 0.92 TPa, obtained using stress-strain measurements. This value is different by more than an order of magnitude from the c-axis value we measured using the microscope in the ultrafast mode of operation. Thus, using embodiments of the present invention, we have demonstrated a very sensitive 4D microscopy method for the study of nanoscale mechanical motions in space and time. With selected-area-imaging dynamics, the evolution of multimode oscillations to a coherent resonance (global) mode at long time provides the mapping of local regions in the image and on the nanoscale. The time scale of the resonance is directly related to materials anisotropic elasticity (Young's modulus), density, and tension, and as such the reported real-time observation in imaging can be extended to study mechanical properties of membranes (graphene in the present case) and other nanostructures with noninvasive probing. The emergent properties resolved here are of special interest to us as they represent a well-defined “self-organization” in complex macroscopic systems. The function of many nano and microscale systems is revealed when they are visualized in both space and time. Here, four-dimensional (4D) electron microscopy provided in accordance with an embodiment of the present invention is used to measure nanomechanical motions of cantilevers. From the observed oscillations of nanometer displacements as a function of time, for free-standing beams, we are able to measure the frequency of modes of motion, and determine Young's elastic modulus, the force and energy stored during the optomechanical expansions. The motion of the cantilever is triggered by molecular charge redistribution as the material, single-crystal organic semiconductor, switches from the equilibrium to the expanded structure. For these material structures, the expansion is colossal, typically reaching the micron scale, the modulus is 2 GPa, the force is 600 μN, and the energy is 200 pJ. These values translate to a large optomechanical efficiency (minimum of 1% and up to 10% or more), and a pressure of nearly 1,500 atm. We note that the observables here are real-material changes in time, in contrast to those based on changes of optical/contrast intensity or diffraction. As the physical dimensions of a structure approach the coherence length of carriers, phenomena not observed on the macroscopic scale (e.g., quantization of transport properties) become apparent. The discovery and understanding of these quantization effects requires continued advances in methods of fabrication of atomic-scale structures and, as importantly, in the determination of their structural dynamics in real-time when stimulated into a configuration of a nonequilibrium state. Of particular importance are techniques that are noninvasive and capable of nanoscale visualization in real-time. Examples of the rapid progress in the study of nanoscale structures are numerous in the field of micro and nanoelectromechanical systems (i.e., MEMS and NEMS, respectively). Recent advancements have resulted in structures having single-atom mass detection limits and binding specificities on the molecular level, and especially for biological systems. Beyond mass measurement and analyte detection, changes in the dynamics of these nanoscale structures have been shown to be sensitive to very weak external fields, including electron and nuclear spins, electron charge, and electron and ion magnetization. The response to external stimuli is manifested in deflections of the nanoscale, and a variety of techniques have been used to both actuate and detect the small-amplitude deflections. Optical interference is often used for measurement purposes, wherein the deflections of the structure cause a phase shift in the path-stabilized laser light thus providing detection sensitivities that are much less than the radius of a hydrogen atom. High spatiotemporal resolutions (atomic-scale) can be achieved in 4D ultrafast electron microscopy (UEM). Thus it is possible to image structures, morphologies, as well as nanomechanical motions (e.g., nanogating and nanodrumming) in real-time. Using embodiments of the present invention, we direct visualized nano and microscale cantilevers, and the (resonance) oscillations of their mechanical motions. The static images were constructed from a tomographic tilt series of images, whereas the in situ temporal evolution was determined using the stroboscopic configuration of UEM, which is comprised of an initiating (clocking) laser pulse and a precisely-timed packet of electrons for imaging. The pseudo-one-dimensional molecular material (copper 7,7,8,8-tetracyanoquinodimethane, [Cu(TCNQ)]), which forms single crystals of nanometer and micrometer length scale, is used as a prototype. The optomechanical motions are triggered by charge transfer from the TCNQ radical anion (TCNQ−) to copper (Cu+). More than a thousand frames were recorded to provide a movie of the 3D movements of cantilevers in time. As shown below, the expansions are colossal, reaching the micrometer scale, and the spatial modes are resolved on the nanoscale in the images (and angstrom-scale in diffraction) with resonances of megahertz frequencies for the fixed-free cantilevers. From these results, we obtained the Young's modulus, and force and energy stored in the cantilevers. Here, different crystals were studied and generally are of two types: (1) those “standing”, which are free at one end (cantilevers), and (2) those which are “sleeping” on the substrate bed; the latter will be the subject of another report. For cantilevers, the dimensions of the two crystals studied are 300 nm thick by 4.6 μm long and 2.0 μm thick by 10 μm long (see FIG. 26). As such, they define an Euler-Bernoulli beam, for which we expect the fundamental flexural modes to be prominent, besides the longitudinal one(s) which are parallel to the long axis of the crystal. Our interest in Cu(TCNQ) stems from its highly anisotropic electrical and optical properties, which arise from the nature of molecular stacking in the structure. As illustrated in FIG. 26, Cu(TCNQ) consists of an interpenetrating network of discrete columns of Cu− and TCNQ− running parallel to the crystallographic a-axis. The TCNQ molecules organize so that the π-systems of the benzoid rings are strongly overlapped, and the favorable interaction between stacked TCNQ molecules makes the spacing between the benzoid rings only 3.24 Å, significantly less than that expected from purely van der Waals-type interactions. It is this strong π-stacking that results in the pseudo-one-dimensional macroscale crystal structure and is responsible for the anisotropic properties of the material. With electric field or light, the material becomes mixed in valence with both Cu+(TCNQ−) and)Cu° (TCNQ° in the stacks, weakening the interactions and causing the expansion. At high fluences, the reversible structural changes become irreversible due to the reduction of copper from the +1 oxidation state to copper metal and subsequent formation of discrete islands of copper metal driven by Ostwald ripening. The methodology we used here for synthesis resulted in the production of single crystals of phase I. FIG. 26 illustrates atomic to macro-scale structure of phase I Cu(TCNQ). Shown in the upper panel is the crystal structure as viewed along the a-axis (i.e., π—stacking axis) and c-axis. The unit cell is essentially tetragonal (cf. ref. 19) with dimensions: a=3.8878 Å, b=c=11.266 Å, α=γ=90°, β=90.00(3)°; gray corresponds to carbon, blue corresponds to nitrogen, and yellow corresponds to copper. The hydrogen atoms on the six-membered rings are not shown for clarity. The lower panel displays a typical selected-area diffraction pattern from Cu(TCNQ) single crystals as viewed down the [011] zone axis along with a micrograph taken in our UEM. The rod-like crystal habit characteristic of phase I Cu(TCNQ) is clearly visible. FIG. 27 illustrates a tomographic tilt series of images. The frames show images (i.e., 2D-projections) of the Cu(TCNQ) single crystals acquired at different tilt angles of the specimen substrate. The highlighted region illustrates a large change in the position of the free-standing mircoscale crystal relative to another, which is lying flat on the substrate, as we change the tilt angle. The scale bar in the lower left corner measures two micrometers. The tilt angle at which each image was acquired is shown in the lower right corner of each frame in degrees. The tilt angle is defined as zero when the specimen substrate is normal to the direction of electron propagation in the UEM column. The tilt series images shown in FIG. 27 provide the 3D coordinates of the cantilevers. The dimensions and protrusion angles of these free-standing crystals were characterized by taking static frames at different rotational angles of the substrate. By placing the crystal projections into a laboratory frame orthogonal basis and measuring the length of the projections in the x-y (substrate) plane as the crystal is rotated by an angle α about the x-axis, the measured projections were obtained to be Θ of 37.8° and φ of 25.3°, where Θ is the angle the material beam makes with respect to substrate-surface normal and φ is the azimuthal angle with respect to the tilt axis, respectively. Note that the movie of the tilt series clearly shows the anchor point of the crystal to be the substrate. The dimensions and geometries of the crystals are determined from the tilt series images with 5% precision. To visualize real-time and space motions, the microscope was operated at 120 kV and the electron pulses were photoelectrically generated by laser light of 355 nm. The clocking optical pulses (671 nm laser), which are well-suited to induce the charge transfer in Cu(TCNQ), were held constant at 3 μJ giving a maximum fluence of 160 mJ/cm2. Because the relevant resonance frequencies are on the MHz scale, the ns pulse arrangement of the UEM was more than enough for resolving the temporal changes. The time delay between the initiating laser pulse and probe electron pulse was controlled with precision, and the repetition rate of 100 Hz ensured recovery of the structure between pulses. A typical static image and selected-area diffraction are displayed in FIG. 26. From the selected-area diffraction and macroscopic expansion we could establish the nature of correlation between unit cell and the crystal change. The 4D space-time evolution of cantilevers is shown in FIGS. 28 and 29. The referenced (to negative time, tref=−10 ns; i.e., before the arrival of the clocking pulse) difference images of the microscale (FIG. 28) and nanoscale (FIG. 29) free-standing single crystal clearly display modes of expansion on the MHz scale. Each image illustrates how the spatial location of the crystal has changed relative to the reference image as a function of the time delay, elucidating both the longitudinal and transverse displacements from the at-rest position. In order to accurately measure the positions in space we used a reference particle in the image. These reference particles, which are fixed to the surface of the substrate, do not appear in frame-reference images if drift is absent or corrected for. This is an important indication that the observed crystal dynamics do not arise from motion of the substrate due to thermal drift or photothermal effects. Moreover, there is no significant movement observed in images obtained before the arrival of the excitation pulse, indicating that, during the time of pulse separation, the motion has completely damped out and the crystal has returned to its original spatial configuration. The thermal, charging, and radiation effects of the electron pulses are negligible here and in our previous studies made at higher doses. This is evidenced in the lack of blurring of the images or diffraction patterns; no beam deflection due to sample charging was observed. Lastly, no signs of structural fatigue or plasticity were observed during the course of observation, showing the function of the cantilever to be robust for at least 107 pulse cycles. Shown in FIG. 30 is the displacement of the microscale single crystal as a function of time, in both the longitudinal and transverse directions, along with the fast Fourier transforms (FFT) of the observed spatial oscillations for the time range shown (i.e., 0 to 3.3 μs). The motions in both directions of measurement are characterized by a large initial displacement from the at-rest position. The scale of expansion is enormous. The maximum longitudinal expansion possible (after accounting for the protrusion angle) for the 10 μm crystal would be 720 nm or over 7% of the total length. For comparison, a piezoelectric material such as lead zirconate titanate has typical displacements of less than 1% from the relaxed position, but it is known that molecular materials can show enormous optically-induced elastic structural changes on the order of 10% or more. The large initial motion is transferred into flexural modes in the z and x-y directions, and these modes persist over the microsecond (or longer) scale. The overall relaxation of the crystal to its initial position is not complete until several milliseconds after excitation. From the FFTs of the measured displacements, we obtained the frequency of longitudinal oscillation to be 3.3 MHz, whereas the transverse oscillations are found at 2.5 and 3.3 MHz (FIG. 30). We note that the motion represents coupling of modes with dephasing, so it is not surprising that the FFT gives more than one frequency. In fact, from an analysis consisting of a decomposition of the motion via rotation of a principle axes coordinate system relative to the laboratory frame, we found that the plane of lateral oscillation of the crystal was tilted by 18° relative to the plane of the substrate. The nature of contact with the substrate influences not only the mode structure but also the damping of cantilevers. Because of the boundary conditions of a fixed-free beam, the vibration nodes are not evenly spaced and the overtones are not simple integer multiples of the fundamental flexural frequency (f1), but rather occur at 6.26, 17.5, and 34.4 for f2, f3, and f4, respectively. This is in stark contrast to the integer multiples of the fundamental frequency of a fixed-fixed beam. Taking 3 MHz to be the main fundamental flexural frequency of the microscale crystal, we can deduce Young's elastic modulus of the crystal. The expression for the frequencies of transverse (flexural) vibrations of a fixed-free beam is given by, f n = η ⁢ ⁢ π ⁢ ⁢ κ 8 ⁢ L 2 ⁢ c ≡ η ⁢ ⁢ πκ 8 ⁢ L 2 ⁢ Y ρ ( 19 ) where fn is the frequency of the nth mode in Hz, L is the beam length at rest, Y is Young's modulus, and ρ is the density. The radius of gyration of the beam cross section is κ and is given as t/√{square root over (12)}, where t is the thickness of the beam with rectangular cross section. The value of η for the beam is: 1.1942; 2.9882; 52; 72; . . . ; (2n−1)2, approaching whole numbers for higher η values. The overtones are not harmonics of the fundamental, and the numerical terms for f1 and f2, which result from the trigonometric solutions involved in the derivation, must be used without rounding. For the longitudinal modes of fixed-free beam, fn=(2n−1)c/4L. From the above equation, and knowing ρ=1.802 g·cm−3, we obtained Young's modulus to be 2 GPa, with the speed of sound, therefore, being 1,100 m·s−1; we estimate a 12% uncertainty in Y due to errors in t, L, and f This value of Young's modulus (N·m−2) is very similar to that measured for TTF-TCNQ single crystals using a mm-length vibrating reed under an alternating voltage. Both materials are pseudo-one-dimensional, and the value of the modulus is indicative of the elastic nature along the stacking axis in the direction of weak intercolumn interactions. Young's modulus slowly varies in value in the temperature range of 50 to 300 K but, when extrapolated to higher temperatures, decreases for both TTF-TCNQ and K(TCNQ). From the absorbed laser pulse energy (30 nJ), the amount of material (7.2×10−14 kg), and assuming the heat capacity to be similar to TTF-TCNQ (430 J·K−1·mol−1), the temperature rise in the microscale crystal is expected to be at most 260 K. Finally, we note that for the same modulus reported here, the frequency of longitudinal mode expansion [f=c/4L; n=1] should be nearly 25 MHz, which is not seen in the FFT with the reported resolution, thus suggesting that the observed frequencies in the longitudinal direction are those due to cantilever motion in the z direction; the longitudinal expansion of the crystal is about 1 to 2% of its length, which in this case will be 100 to 200 nm. The potential energy stored in the crystal and the force exerted by the crystal at the moment of full extension along the long axis just after time zero [cf. FIG. 30(A)] can be estimated from the amplitudes and using Hooke's law: V = 1 2 ⁢ ( YA L ) ⁢ Δ ⁢ ⁢ L 2 ( 20 ⁢ a ) F = ( YA L ) ⁢ Δ ⁢ ⁢ L ( 20 ⁢ b ) where V and F are the potential energy and force, respectively, and A is the cross-sectional area of the crystal. The bracketed term in equation (20) is the spring constant (assuming harmonic elasticity, and not the plasticity range), and by simple substitution of the values, we obtained 200 pJ and 600 μN for the potential energy and force, respectively, considering the maximum possible expansion of 720 nm; even when the amplitude is at its half value [see FIG. 30(A)], the force is very large (˜300 μN). For comparison, the average force produced by a single myosin molecule acting on an actin filament, which was anchored by two polystyrene beads, was measured to be a few piconewtons. In other words, because of molecular stacking, the force is huge. Also because of the microscale cross-section, the pressure of expansion translates to 0.1 GPa, only a few orders of magnitude less than pressures exerted by a diamond anvil. Based on the laser fluence, crystal dimensions, and absorptivity of Cu(TCNQ) at 671 nm (3.5×106 m−1), the maximum pulse energy absorbed by the crystal is 30 nJ. This means that, of the initial optical energy, a minimum of ˜1% is converted into mechanical motion of the crystal. But in fact, it could reach 10 or more percent as determined by the projection of the electric field of light on the crystal. In order to verify the trend in frequency shifts, the above studies were extended to another set of crystal beams, namely those of reduced dimensions. Because the resonant frequencies of a fixed-free beam are determined, in part, by the beam dimensions [cf. equation (19)], a Cu(TCNQ) crystal of different length than that shown in FIG. 30 should change the oscillation frequencies by the κ/L2 dependence. With a smaller cantilever beam we measured the oscillation frequencies for a crystal of 300 nm thickness and 4.6 μm length, using the same laser parameters as for the larger crystals, and found them to be at higher values (FIG. 31). This is confirmed by the FFTs of the displacement spanning the range 0 to 3.3 μs [FIGS. 31(C) and (D)]; a strong resonance near 9 MHz with another weaker resonance at 3.6 MHz in the longitudinal direction [FIG. 31(C)] is evident. Within a few microseconds, the only observed frequency in the FFT was near 9 MHz. This oscillation persists up to the time scans of 30 μs, at which point the amplitude was still roughly 40% of the leveling value near 2 μs. By taking this duration (30 μs) to be the decay time (τ) required for the amplitude to fall to 1/e of the original value, the quality factor (Q=πfτ) of the crystal free oscillator becomes near 1,000. However, on longer time scales, and with less step resolution, the crystal recovers to the initial state in a few milliseconds, and if the mechanical motion persists, Q would increase by an order of magnitude. It is clear from the resonance value of the flexural frequency at 9 MHz that as the beam reduces in size, the frequency increases, as expected from equation (19). However, if we use this frequency to predict Young's modulus we will obtain a value of 30 GPa, which is an order of magnitude larger than that for the larger microscale crystal. The discrepancy points to the real differences in modes structure as we reach nanometer-scale cantilevers. One must consider, among other things, the anchor-point(s) of the crystals, the frictional force with substrate and other crystals, and the curvature of the beam (see movie in supporting information). This curvature will cause the crystal to deviate from ideal Euler-Bernoulli beam dynamics, thus shifting resonance frequencies from their expected positions. Interestingly, by using the value of 30 GPa for Young's modulus, the minimum conversion efficiency increases by a factor of 15. These dependencies and the extent of displacement in different directions, together with the physics of modes coupling (dephasing and rephasing), will be the subject of our full account of this work. Thus, with 4D electron microscopy it is possible to visualize in real space and time the functional nanomechanical motions of cantilevers. From tomographic tilt series of images, the crystalline beam stands on the substrate as defined by the polar and azimuthal angles. The resonance oscillations of two beams, micro and nanocantilevers, were observed in situ giving Young's elastic modulus, the force, and the potential energy stored. The systems studied are unique 1D molecular structures, which provide anisotropic and colossal expansions. The cantilever motions are fundamentally of two types, longitudinal and transverse, and have resonance Q factors that make them persist for up to a millisecond. The function is robust, at least for 107 continuous pulse cycles (˜1011 oscillations for the recorded frames), with no damage or plasticity. With these imaging methods in real-time' and with other variants, it is now possible to test the various theoretical models involved in MEMS and NEMS. Electron energy loss spectroscopy (EELS) is a powerful tool in the study of valency, bonding and structure of solids. Using our 4D electron microscope, we have performed ultrafast EELS, taking the time resolution in the energy-time space into the femtosecond regime, a 10 order of magnitude increase, and for a table-top apparatus. It is shown that the energy-time-amplitude space of graphite is selective to changes, especially in the electron density of the π+σ plasmon of the collective oscillation of the four electrons of carbon. Embodiments of the present invention related to EELS enable the microscope to be used as an analytical tool. As electrons pass through the specimen, each type of material (e.g., gold, copper, or zinc) will have a different electron energy. Thus, it is possible to “tune” into a particular element and study the dynamic behavior of the material itself. In microscopy, EELS provides rich characteristics of energy bands describing modes of surface atoms, valence- and core-electron excitations, and interferences due to local structural bonding. The scope of applications thus spans surface and bulk elemental analysis, chemical characterization and electronic structure of solids. The static, time-integrated, EEL spectra do not provide direct dynamic information, and with video-rate scanning in the microscope could changes be recorded only with a time resolution of millisecond or longer. Dedicated time-resolved EELS apparatus, without imaging, have obtained millisecond resolution, being determined primarily by detector response and electron counts. However, for studies of dynamics of electronic structure, valency and bonding, the time resolution must increase by at least nine orders of magnitude. We have performed femtosecond resolved EELS (FEELS) using our ultrafast electron microscope (UEM), developed for 4D imaging of structures and morphology. Embodiments of the present invention are conceptually different from time-resolved EELS (termed TREELS) as the time resolution in FEELS is not limited by detector response and sweep rate. Moreover, both real-space images and energy spectra can be recorded in situ in UEM and with energy filtering the temporal resolution can be made optimum. We demonstrate the method in the study of graphite which displays changes on the femtosecond (fs) time scale with the delay steps being 250 fs. Near the photon energy of 2.4 eV (away from the zero energy loss peak), and similarly for the π+σ plasmon band, the change is observed, but it is not as significant for the π plasmon band. Thus it is possible to chart the change from zero to thousands of eV and in 3D plots of time, energy and amplitude; the decrease in EELS intensity at higher energies becomes the limiting factor. This table-top approach using electrons is discussed in relation to recent achievements using soft and hard (optical) X-rays in laboratory and large-scale facilities of synchrotrons and free electron lasers. According to embodiments of the present invention, the probing electrons and the initiating light pulses are generated by a fs laser, and the EEL spectra of the transmitted electrons are recorded in a stroboscopic mode by adjusting the time delay between the pump photons and the probe electron bunches. The concept of single-electron packet used before in imaging is utilized in this approach. When each ultrafast electron packet contains at most one electron, “the single-electron mode,” space-charge broadening of the zero-loss energy peak, which decreases the spectrometer's resolution, is absent. FIG. 32 is a schematic diagram of a microscope used in embodiments of the present invention. A train of 220 fs laser pulses at 1.2 eV was frequency doubled and tripled and then split into two beams. In other embodiments, a range of laser pulse widths could be used, for example from about 10 femtoseconds to about 10 microseconds. The frequency tripled light at 3.6 eV was directed to the microscope photocathode, and the photoelectron probe pulse was accelerated to 200 keV. The 2.4 eV pulses were steered to the specimen, and provided the excitation at a fluence of 5.3 mJ/cm2. In other embodiments, a fluence ranging from about 1 mJ/cm2 to about 20 mJ/cm2 could be utilized. By varying the delay time between the electron and optical pulses, the time dependence of the associated EEL spectrum was followed. The electrons pass through the sample and a set of magnetic lenses to illuminate the CCD camera, forming either a high resolution image of the specimen, a diffraction image, or they can be energy dispersed to provide the EEL spectra. The apparatus is equipped with a Gatan imaging filter (GIF) Tridiem, of the postcolumn type, which is attached below the transmission microscope camera chamber. The energy width of near 1 eV was measured for the EELS zero-loss peak and it is comparable to that obtained in thermal-mode operation of the TEM, but increases significantly in the space-charge limited regime. The experiments were performed at repetition rates of 100 kHz and 1 MHz, and no difference in the EEL spectra or the temporal behavior was observed, signifying a complete recovery of electronic structure changes between subsequent pulses. The reported temporal changes were missed when the scan resolution exceeded 250 fs, and the entire profile of the transient is complete in 2 ps. The electron beam passes through the graphite sample perpendicular to the sample surface while the laser light polarization was parallel to the graphene layers. Finally, the zero of time was determined to the precision of the reported steps, and was observed to track the voltage change in the FEG module of the microscope. The semi-metal graphite is a layered structure, which was prepared as free-standing film. The thickness of the graphite film was estimated from the EEL spectrum to be 106 nm (inelastic mean-free path of ˜150 nm), and the crystallinity of the specimen was verified by observing the diffraction pattern which was indexed as reported. FIG. 33 shows a static EEL spectrum of graphite taken in UEM. The distinct features are observed in the spectrum and indeed are typical of the electronic structure bands of graphite; the in-plane π plasmon is found near 7 eV, while at higher energy, the peak at 27 eV is observed with a shoulder at 15 eV. These latter peaks correspond to the π+σ oscillation of the bulk and surface plasmons, respectively. The results are in agreement with those of literature reports. The bands displayed in different colors (FIG. 33) are the simulations of the profiles with peak positions reproducing the theoretical values near 7, 15 and 27 eV. The 3D FEELS map of the time-energy evolution of the amplitude of the plasmon portion of the spectrum (up to 35 eV) is shown in FIG. 34, together with the EEL spectrum taken at negative time. The spectra were taken at 1 MHz repetition-rate, for a pump fluence of 5.3 mJ/cm2 at room temperature and for is =250 fs for each difference frame. The map reflects the difference for all energies and as a function of time, made by subtracting a reference EEL spectrum at negative time from subsequent ones. The relatively strong enhancement of the energy loss in the low energy (electron-hole carriers) region is visible and the change is near the energy of the laser excitation. This feature represents the energy loss enhancement due to the creation of carriers by the fs laser excitation in the ππ* band structure, as discussed below. At higher energy, the 7 eV π plasmon peak remains nearly unperturbed by the excitation, and no new features are observed at the corresponding energies. For the 27 eV π+σ bulk plasmon an increased spectral weight at positive time is visible as a peak in the time-resolved spectrum. In order to obtain details of the temporal evolution of the different spectroscopic energy bands, we divided the spectrum into three regions: the low energy region between 2 and 5 eV, the π plasmon region between 6 and 8 eV, and the π+σ plasmon region between 20 and 30 eV. The 3D data are integrated in energy within the specified regions of the spectrum, and the temporal evolution of the different loss features are obtained; see FIG. 35. For regions where changes occur, the time scales involved in the rise and subsequent decay are similar. In FEELS, the shortest decay is 700 fs taken with the steps of 250 fs. The duration of the optical pulse is ˜220 fs, but we generate the UV pulse for electron generation through a non-linear response, and it is possible that the pulses involved are asymmetric in shape and that multiphotons are part of the process; full analysis will be made later. We note that the observed ˜700 fs response indeed reflects the joint response from both the optical and electron pulses and it is an upper limit for the electronic change. It is remarkable that, in FIG. 35, the temporal evolution of the interlayer spacing of graphite obtained by ultrafast electron crystallography (UEC) at a similar fluence, i.e. 3.5 mJ/cm2, the timescale of the ultrafast compression corresponds well to the period in which the bulk plasmon is out of equilibrium; in this plot the zero of time is defined by the change of signal amplitude. In graphite, the characteristic time for the thermalization of photo-excited electrons is known to be near 500 fs at low fluences (a few μJ/cm2). When excited by an intense laser pulse, a strong electrostatic force between graphene layers is induced by the generated electron-hole (carrier) plasma. This causes the structure to be out of equilibrium for nearly 1 ps; a stressful structural rearrangement is imposed on the crystal, which, at very high fluences (above 70 mJ/cm2), has been proposed as a cause of the phase transformation into diamond. Because graphite is a quasi two-dimensional structure, distinct spectral features are visible in EELS. The most prominent and studied peaks are those at 7 eV and the much stronger one at 27 eV. From the solution of the in-plane and out-of-plane components of the dielectric tensor it was shown, for graphite, that the 7 eV band is a it plasmon, resulting from interband ππ* transitions in the energy range of 2-5 eV, whereas the 27 eV band is a π+σ plasmon dominated by ππ* transitions beyond 10 eV (FIG. 5). We note that in this case the plasmon frequencies are not directly given by the ππ* and σσ* transition energies as they constitute tensorial quantities. For example ϖ π + σ 2 = ϖ p 2 + 1 4 ⁢ ( Ω π 2 + 3 ⁢ Ω σ 2 ) ,where ωp=npe2/∈0m)1/2 is the free electron gas plasma frequency; Ωπ and Ωσ are the excitation energies for ππ* and σσ* transitions, respectively. For ωp, the electron density is np, n is the number of valence electrons per atom and p is the density of atoms, and ∈0 is the vacuum dielectric constant. It follows that the density of occupied and empty (π, σ, π, and σ) states is critical, and that the π Plasmon is from the collective excitation of the π electrons (one electron in the p-orbital, with screening corrections) whereas the π+σ plasmon is the result of all 4 valence electrons collectively excited over the coherent length scale of bulk graphite; there are also surface plasmons but at different energies. Recently it was demonstrated, both theoretically and experimentally, that the π and π+σ plasmons are sensitive to the inter-layer separation, but while the former shows some shift of peaks the latter is dramatically reduced in intensity, and, when reaching the grapheme limit, only a relatively small peak at ˜15 eV survives. This is particularly evident when the momentum transfer is perpendicular to the c-axis, the case at hand and for which the EEL spectrum is very similar to ours. With the above in mind, it is now possible to provide, in a preliminary picture, a connection between the selective fs atomic motions, which are responsible for the structural dynamics, and changes in the dielectric properties of Plasmon resonances, the electronic structure. The temporal behavior, and coherent oscillation (shear modes of ˜1 ps), of c-axis expansion display both contraction and expansion on the picometer length scale per unit cell. The contraction precedes the expansion, as shown in FIG. 35, with velocity that depends on the fluence, i.e., the density of carriers. With fs excitation, the electronic bands are populated anisotropically, and, because of energy and momentum conservation, the carriers transiently excite large-momentum phonons, so called strongly coupled phonons. They are formed on the fs time scale (electron-phonon coupling) but decay in ˜7 ps. The initial compression suggests that the process is a cooperative motion and is guided by the out-of-equilibrium structure change dictated by the potential of excited carriers; in this case ππ* excitation which weakens c-axis bonding. The initial atomic compression, when plotted with transient EELS data (FIG. 35), shows that it is nearly in synchrony with the initial change, suggesting that the spacing between layers (c-axis separation) is the rate determining step, and that in the first 1 ps, the compressed ‘hard graphite’ effect is what causes the increase in the amplitude of the π+σ plasmon peak. In other words, the decrease of the spectral weight due to the change of electronic structure upon increasing the interlayer separation (to form graphene) becomes an increase when the plates are compressed, because of the enhanced collectiveness of all four valence electrons of carbon. The change involves shear motions and it is not surprising that the π+σ peak (dominated by σσ* excitation) is very sensitive to such changes. The π peak is less influenced as only one electron is involved, as discussed above, and the amplitude change is relatively small. The faster recovery of EEL peaks in 700 fs is, accordingly, the consequence of expansion which ‘decouples’ the π and σ system. Lastly, the relatively large increase in EEL near the photon energy is due to carrier excitation (π*) which leads to a loss of electron energy at near 3 eV, possibly by electronic excitation involving the cy system (FIG. 36). The created carriers cause an increase in the Drude band as evidenced in the decrease in optical transmission. The demonstration of ultrafast EELS in electron microscopy opens the door to experiments that can follow the ultrafast dynamics of the electronic structure in materials. The fs resolution demonstrates the ability of UEM to probe transients on the relevant sub-picosecond time scale, while keeping the energy resolution of EELS. Moreover, the selectivity of change in the collective electron density (for graphite) suggests future experiments, including those with changes in polarization, shorter optical pulses, core excitation and oxidation sites. We believe that this table-top UEM-EELS should provide the methodology for studies which have traditionally been made using synchrotrons (and free electron lasers) especially in the UV and soft X-ray regions. Chemical bonding dynamics are important to the understanding of properties and behavior of materials and molecules. Utilizing embodiments of the present invention, we have demonstrated the potential of time-resolved, femtosecond electron energy loss spectroscopy (EELS) for mapping electronic structural changes in the course o nuclear motions. For graphite, it is found that changes of milli-electron volts in the energy range of up to 50 electron volts reveal the compression and expansion of layers on the subpicometer scale (for surface and bulk atoms). These nonequilibrium structural features are correlated with the direction of change from sp2 [two-dimensional (2D) grapheme] to spa (3D-diamond) electronic hybridization, and the results are compared with theoretical charge-density calculations. The reported femtosecond time resolution of four-dimensional (4D) electron microscopy represents an advance of 10 orders of magnitude over that of conventional EELS method. Bonding in molecules and materials is determined by the nature of electron density distribution between the atoms. The dynamics involve the evolution of electron density in space and the motion of nuclei that occur on the attosecond and femtosecond time scale, respectively. Such changes of the charge distribution with time are responsible for the outcome of chemical reactivity and for phenomena in the condensed phase, including those of phase transitions and nanoscale quantum effects. With convergent-beam electron diffraction, the static pattern of charge-density difference maps can be visualized, and using x-ray absorption and photoemission spectroscopy substantial progress has been made in the study of electronic-state dynamics in bulks and on surfaces. Electron energy loss spectroscopy (EELS) is a powerful method in the study of electronic structure on the atomic scale, using aberration-corrected microscopy, and in chemical analysis of selected sites; the comparison with synchrotron-based near-edge x-ray absorption spectroscopy is impressive. The time and energy resolutions of ultrafast electron microscopy (UEM) provide the means for the study of (combined) structural and bonding dynamics. Here, time-resolved EELS is demonstrated in the mapping of chemical bonding dynamics, which require nearly 10 orders of magnitude increase in resolution from the detector-limited millisecond response. By following the evolution of the energy spectra (up to 50 eV) with femtosecond (fs) resolution, it was possible to resolve in graphite the dynamical changes on a millielectronvolt (subpicometer motion) scale. In this way, we examined the influence of surface and bulk atoms motion and observed correlations with electronic structural changes: contraction, expansion, and recurrences. Because the EEL spectra of a specimen in this energy range contain information about plasmonic properties of bonding carriers, their observed changes reveal the collective dynamics of valence electrons. Graphite is an ideal test case for investigating the correlation between structural and electronic dynamics. Single-layered grapheme, the first two-dimensional (2D) solid to be isolated and the strongest material known, has the orbitals on carbon as sp2 hybrids, and in graphite the π-electron is perpendicular to the molecular plane. Strongly compressed graphite transforms into diamond, whose charge density pattern is a 3D network of covalent bonds with sp3 hybrid orbitals. Thus, any structural perturbation on the ultra-short time scale of the motion will lead to changes in the chemical bonding and should be observable in UEM. Moreover, surface atoms have unique binding, and they too should be distinguishable in their influence from bulk atom dynamics. The experiments were performed on a nm-thick single crystal of natural hexagonal graphite. The sample was cleaved repeatedly until a transparent film was obtained, and then deposited on a transmission electron microscopy (TEM) grid; the thickness was determined from EELS to be 108 nm. The fs-resolved EELS (or FEELS) data were recorded in our UEM, operating in the single-electron per pulse mode to eliminate Boersch's space charge effect. A train of 220 fs infrared laser pulses (λ=1038 nm) was split into two paths, one was frequency-doubled and used to excite the specimen with a fluence of 1.5 mJ/cm2, and the other was frequency-tripled into the UV and directed to the photoemissive cathode to generate the electron packets. These pulses were accelerated in the TEM column and dispersed after transmission through the sample in order to provide the energy loss spectrum of the material. The experimental, static EEL spectra of graphite in our UEM, with grapheme for comparison, are displayed in FIG. 37A; FIG. 37B shows the results of theoretical calculations. The spectral feature around 7 eV is the π Plasmon, the strong peak centered around 26.9 eV is the π+σ bulk plasmon, and the weaker peak on its low energy tail is due to the surface Plasmon. The agreement between the calculated EEL spectra and the experimental ones is satisfactory both for graphite and grapheme. Of relevance to our studies of dynamics is the simulation of the spectra for different c-axis separations, ranging from twice as large as naturally occurring (2c/a; a and c are lattice constraints) to 5 times as large. This thickness dependence is displayed in FIG. 37B. As displayed in FIG. 37, the surface and bulk Plasmon bands (between 13 and 35 eV) can be analyzed using two Voigt functions, thus defining the central position, intensity, and width. At different delay times, we monitored the changes and found that they occur in the intensity and position; the width and shape of the two spectral components are relatively unchanged. FIGS. 37C and 37D, show the temporal changes of the intensity for both the surface and bulk plasmons. As noted, the behavior of bulk dynamics is “out of phase” with that of the surface dynamics, corresponding to an increase in intensity for the former and a decrease for the latter. Each time point represents a 500-fs change. Within the first 1 ps, the bulk Plasmon gains spectral weight with the increase in intensity. With time, the intensity is found to return to its original (equilibrium) value. At longer times, a reverse in sign occurs, corresponding to a decrease and then an increase in intensity—an apparent recurrence or echo occurring with dispersion. The intensity change of the surface plasmon in FIGS. 37C and 37D, shows a π phase-shifted temporal evolution with respect to that of the bulk plasmon. The time dependence of the energy position of the different spectral bands is displayed in FIG. 38. The least-squares fit converges for a value of the surface plasmon energy at 14.3 eV and of the bulk plasmon at 26.9 eV. The temporal evolution of the surface plasmon gives no sign of energy dispersion, whereas the bulk plasmon is found to undergo first a blueshift and then a redshift at longer times (FIGS. 38A and 38B). The overall energy-time changes in the FEEL spectra are displayed in FIG. 39. To make the changes more apparent, the difference between the spectra after the arrival of the initiating laser pulse (time zero) and a reference spectrum taken at −20 ps before time zero is shown. The most pronounced changes are observed in the region near the energy of the laser itself (2.39 eV), representing the energy-loss enhancement due to the creation of carriers by the laser excitation, and in the region dominated by the surface and bulk plasmons (between 13 and 35 eV). Clearly evident in the 3D plot are the energy dependence as a function of time, the echoes, and the shift in phase. A wealth of information has been obtained on the spectroscopy and structural dynamics of graphite. Of particular relevance here are the results concerning contraction and expansion of layers probed by diffraction on the ultra-short time scale. Knowing the amplitude of contraction/expansion, which is 0.6 pm at the fluence of 1.5 mJ/cm2, and from the charge of plasmon energy with interlayer distance (FIG. 37), we obtained the results shown in FIG. 38C. The diffraction data, when now translated into energy change, reproduce the pattern in FIG. 38A, with the amplitude being within a factor of two. When the layers are fully separated, that is, reaching grapheme, the bulk plasmon, as expected, is completely suppressed. The dynamics of chemical bonding can now be pictured. The fs optical excitation of graphite generates carriers in the nonequilibrium state. They thermalize by electron-electron and electron-phonon interactions on a time scale found to be less than 1 ps, less than 500 fs, and −200 fs. From our FEELS, we obtained a rise of bulk plasmons in ˜180 fs (FIG. 39). The carriers generated induce a strong electrostatic force between grapheme layers, and ultrafast interlayer contraction occurs as a consequence. In FIG. 37D, the increase of the bulk plasmon spectral weight on the fs time scale reflects this structural dynamics of bond-length shortening because it originates from a denser and more 3D charge distribution. After the compression, a sequence of dilatations and successive expansions along the c axis follows, but, at longer times lattice thermalization dephases the coherent atomic motions; at a higher fluence, strong interlayer distance variations occur, and grapheme sheets can be detached as a result of these interlayer collisions. Thus, the observations reported here reflect the change in electronic structure: contraction toward diamond and expansion toward grapheme. The energy change with time correlates well with the EELS change calculated for different interlayer distances (FIG. 37). We have calculated the charge density distribution for the three relevant structures. The self-consistent density functional theory calculations were made using the linear muffin-tin orbital approximation, and the results are displayed in FIG. 40. To emphasize the nature of the changes observed in FEELS, and their connection to the dynamics of chemical bonding, we pictorially display the evolution of the charge distribution in a natural graphite crystal, a highly compressed one, and the extreme case of diamond. Once can see the transition from a 2D to a 3D electronic structure. The compressed and expanded graphite can pictorially be visualized to deduce the change in electron density as interlayer separations change. With image, energy, and time resolution in 4D UEM, it is possible to visualize dynamical changes of structure and electronic distribution. Such stroboscopic observations require time and energy resolutions of fs and meV, respectively, as evidenced in the case study (graphite) reported here, and for which the dynamics manifest compression/expansion of atomic planes and electronic sp2/sp3-type hybridization change. The application demonstrates the potential for examining the nature of charge density and chemical bonding in the course of physical/chemical or materials phase change. It would be of interest to extend the scale of energy from ˜1 eV, with 100 meV resolution, to the hundreds of eV for exploring other dynamical processes of bonding. The following articles are hereby incorporated by reference for all purposes: 4D imaging of transient structures and morphologies in ultrafast electron microscopy, Brett Barwick, et al., Science, Vol. 322, Nov. 21, 2008, p. 1227. Temporal lenses for attosecond and femtosecond electron pulses, Shawn A. Hibert, et al., PNAS, Vol. 106, No. 26, Jun. 30, 2009, p. 10558. Nanoscale mechanical drumming visualized by 4D electron microscopy, Oh-Hoon Kwon, et al., Nanoletters, Vol. 8, No. 11, Nov. 2008, p. 3557. Nanomechanical motions of cantilevers: direct imaging in real space and time with 4D electron microscopy, David J. Flannigan, et al., Nanoletters, Vol. 9, No. 2 (2009), p. 875. EELS femtosecond resolved in 4D ultrafast electron microscopy, Fabrizio Carbone, et al., Chemical Physics Letters, 468 (2009), p. 107. Dynamics of chemical bonding mapped by energy-resolved 4D electron microscopy, Fabrizio Carbone, et al., Science, Vol. 325, Jul. 10, 2009, p. 181. Atomic-scale imaging in real and energy space developed in ultrafast electron microscopy, Hyun Soon Park, et al., Nanoletters, Vol. 7, No. 9, Sep. 2007, p. 2545. It is also understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application and scope of the appended claims.
	description	This disclosure relates generally to diagnostic imaging and, more particularly, to an improved pre-patient collimator in computed tomography (CT). Typically, in computed tomography (CT) imaging systems, a rotatable gantry includes an x-ray tube, detector, data acquisition system (DAS), and other components that rotate about a patient that is positioned at the approximate rotational center of the gantry. X-rays emit from the x-ray tube, are attenuated by the patient, and are received at the detector. The detector typically includes a photodiode-scintillator array of pixelated elements that convert the attenuated x-rays into photons within the scintillator, and then to electrical signals within the photodiode. The electrical signals are digitized and then received within the DAS, processed, and the processed signals are transmitted via a slipring (from the rotational side to the stationary side) to a computer or data processor for image reconstruction, where an image is formed. The gantry typically includes a pre-patient collimator that defines or shapes the x-ray beam emitted from the x-ray tube. X-rays passing through the patient can cause x-ray scatter to occur, which can cause image artifacts. Thus, x-ray detectors typically include an anti-scatter grid (ASG) for collimating x-rays received at the detector. Imaging data may be obtained using x-rays that are generated at a single polychromatic energy. However, some systems may obtain multi-energy images that provide additional information for generating images. Dose management in CT has become increasingly important in recent years. Thus, in a typical CT scanner, a pre-patient collimator is used to limit x-ray exposure only to the region of interest (ROI) for imaging. To achieve this, collimator apertures made typically of tungsten are included that provided for a different beam width. In general, the pre-patient collimator is used to reduce overbeaming and to control it. Overbeaming is commonly referred to as an amount of the x-ray beam that is incident to the patient which lies outside the active detector area in the Z-axis. Because the focal spot in the Z-axis is not a point, there will typically be overbeaming due to the penumbra from the focal spot. The penumbra refers to the partial outer region that falls outside the umbra, and the umbra typically refers to a full inner region of the x-rays that pass through the patient from the source focal spot. The penumbra is fixed for x-ray apertures in Z. However, the ratio of overbeaming to the x-ray aperture will decrease with the size of the aperture. Consequently, the dose to the patient will increase when the total beam width decreases. Some manufacturers design the aperture(s) having moving edges or “Z-axis focal spot tracking” to track focal spot umbra and penumbra. In a design having moving edges, an algorithm tracks focal spot motion and controls position of the aperture through which the x-rays pass. This typically results in complex and expensive hardware to account for the geometric layout of the detector plane with respect to the focal spot, and the distances therebetween. Such a design can improve dose efficiency by maintaining a small aperture without affecting image quality. In such a design, when the focal spot moves in the Z-axis (such as due to mechanical or thermal drift), the aperture is adjusted and aligned to cover only the beam for the desired ROI. Such a design includes sophisticated control of the slit with high precision motors, typically including two or more motors. Thus, there is a need to improve tracking of the focal spot. Embodiments are directed toward a method of using and apparatus of an improved pre-patient collimator in computed tomography (CT). According to one aspect, a CT scanning system includes a rotatable gantry having an opening for receiving an object to be scanned, an x-ray tube, and a detector comprising an imaging area of pixels and a calibration area of pixels. The system further includes a pre-patient collimator positioned between the x-ray tube and the detector having first and second apertures that pass x-rays respectively to at least a portion of the imaging area of pixels, and to the calibration area of pixels, a motor configured to move the pre-patient collimator, and a computer programmed to determine a focal spot location using energy derived from x-rays that fall upon the calibration area of pixels, and issue commands to a motor to adjust a position of the pre-patient collimator based on the determination. According to another aspect, a method of CT imaging includes passing x-rays through an opening in a pre-patient collimator, through an object, and to at least a portion of a detector, the detector including imaging pixels and calibration pixels, determining a focal spot location using energy derived from x-rays that fall upon the calibration area of pixels, and adjusting a position of the pre-patient collimator based on the determination. Various other features and advantages will be made apparent from the following detailed description and the drawings. The operating environment of disclosed embodiments is described with respect to a sixteen-slice computed tomography (CT) system. Embodiments are described with respect to a “third generation” CT scanner, however it is contemplated that the disclosed embodiments are applicable to other imaging systems as well, and for CT systems having more or less than the illustrated sixteen-slice system. Referring to FIGS. 1 and 2, a computed tomography (CT) system 100 includes a gantry 102 having an opening 104. A patient table 106 is positioned on a support structure 108, and patient table 106 is axially controllable such that a patient (not shown) positioned on table 106 may be positioned within opening 104. A computer system 110 provides operator instructions and other control instructions to a control system 112. Computer system 110 also may include image reconstruction algorithms, or an image reconstructor may be provided as a separate processing unit. Control system 112 provides control commands for operating gantry 102, an x-ray tube 114, a gantry motor controller 116, as examples. Gantry 102 includes a cover or enclosure 118, which provides for aesthetic improvement, safety, etc. Gantry 102 includes a rotatable base 120, on which is mounted x-ray tube 114, a heat exchanger 122, a data acquisition system (DAS) 124, an inverter 126, a generator 128, and a detector assembly 130, as examples. System 100 is operated with commands entered by a user into computer 110. Gantry 102 may include gantry controls 132 located thereon, for convenient user operation of some of the commands for system 100. Detector assembly 130 includes a plurality of detector modules (not shown), which include an anti-scatter grid (ASG), scintillators, photodiodes, and the like, which detect x-rays and convert the x-rays to electrical signals, from which imaging data is generated. Gantry 102 includes a pre-patient collimator 134 that is positioned to define or shape an x-ray beam 136 emitted from x-ray tube 114. Although not shown, a shape filter may be positioned for instance between x-ray tube 114 and pre-patient collimator 134. In operation, rotatable base 120 is caused to rotate about the patient up to typically a few Hz in rotational speed, and table 106 is caused to move the patient axially within opening 104. When a desired imaging location of the patient is proximate an axial location where x-ray beam 136 will be caused to emit, x-ray tube 114 is energized and x-ray beam 136 is generated from a focal spot within x-ray tube 114. The detectors receive x-rays, some of which have passed through the patient, yielding analog electrical signals are digitized and passed to DAS 124, and then to computer 110 where the data is further processed to generate an image. The imaging data may be stored on computer system 100 and images may be viewed. An X-Y-Z triad 138, corresponding to a local reference frame for components that rotate on rotatable base 120, defines a local directional coordinate systems in a gantry circumferential direction X, a gantry radial direction Y, and gantry axial direction Z. Accordingly, and referring to triad 138, the patient passes parallel to the Z-axis, the x-rays pass along the Y axis, and the rotational components (such as detector assembly 130) rotate in a circumferential direction and in the X direction, and about an isocenter 140 (which is a centerpoint about which rotatable base rotates, and is an approximate position of the patient for imaging purposes). A focal spot 142 is illustrated within x-ray tube 114, which corresponds to a spot from which x-ray beam 136 emits. FIG. 3 illustrates an exemplary image chain 300, consistent with the operation described with respect to FIGS. 1 and 2. X-ray generation 302 occurs, using x-ray tube 114 and passing x-rays through pre-patient collimator 134, during which time table 106 passes 304 through opening 104 of gantry 102. In one example table 106 may have a patient thereon, and in another example a phantom may be used for calibration purposes. X-ray detection 306 occurs when x-rays having emitted from x-ray tube 114 pass to detector assembly 130. An anti-scatter grid (ASG) prevents x-ray scatter (emitting for example from the patient as secondary x-rays and in a direction that is oblique to x-ray beam 136), by generally passing x-rays that emit from x-ray tube 114. DAS 124 processes signals received from detector assembly 130. Image generation 308 occurs after the digitized signals are passed from a rotating side of gantry 102 (on rotatable base 120) to a stationary side, via for instance a slipring. Image generation 308 occurs in computer system 110, or in a separate processing module that is in communication with computer system 110. The data is pre-processed, and image views or projections are used to reconstruct images using known techniques such as a filtered backprojection (FBP). Image post-processing also occurs, after which the images may be displayed 310, or otherwise made available for display elsewhere (such as in a remote computing device). FIG. 4 illustrates an exemplary detector module 400 that is one of a plurality of modules for use in detector assembly 130. A diode-scintillator array 402 includes a pixelated scintillator 404 positioned on a pixelated photodiode array 406. The photodiode array 402 may be either a front-lit or a back-lit type of photodiode. The diode-scintillator array 402 is positioned on an A/D board 408 that includes electronics components for signal processing, wherein analog electrical signals from diode-scintillator array 402 are digitized and then passed to DAS 124. Diode-scintillator array 402 is positioned on a base substrate 410 that may include a ceramic or other solid base material. A heat sink 412 is in thermal contact with A/D board 408 for providing enhanced cooling to the electronics located on A/D board 408. Detector module 400 also includes an anti-scatter grid (ASG) 414 that, in one embodiment, includes a plurality of plates (a few exemplary plates are shown) that are approximately parallel with a Y-Z plane of detector assembly 130. ASG 414, in the illustrated example, includes mount holes 416 which may be used for mounting module 400 to detector assembly 130 and aligning it therewith. FIG. 4 illustrates a triad 418 that illustrates corresponding X-Y-Z coordinates, as illustrated also in FIG. 1. The CT system 100 of FIGS. 1 and 2 includes pre-patient collimator 134, rotatable gantry 102 having an opening 104 for receiving an object to be scanned, x-ray tube 114, and detector assembly 130. FIG. 5 illustrates a perspective view of aspects of pre-patient collimator 134, which includes a pre-patient collimator plate 500 having an opening or aperture 502 therein. Pre-patient collimator plate 500 extends in X-direction 504 and Z-direction 506, as illustrated therein, corresponding with triad 138. Pre-patient collimator 134 also includes a motor 508 that is coupled via control lines 510 to computer 110 and control system 112 of FIG. 1, to move pre-patient collimator plate 500 in Z-direction 506. Pre-patient collimator plate 500 includes a first aperture 512 and a second aperture 514. In the illustrated example, apertures 512 and 514 are contiguous with one another and, by one definition, constitute a single aperture. However, for the sake of clarity of discussion, apertures 512 and 514 are referred to as separate apertures, given that their separate sizes have relevance to the function of the disclosed method and device, although apertures 512 and 514 are contiguous with one another and are both part of opening or aperture 502. In one example, it is contemplated that apertures 512 and 514 may not be contiguous as a single aperture 502, but included as two separate apertures having a material therebetween. As will be further described, aperture 512 is used to pass x-rays used for imaging purposes, and aperture 512 is used to pass x-rays for calibration purposes and to better determine focal spot location 142 to improve image quality. As also will be further described, computer 110 is programmed to determine a focal spot location using energy derived from x-rays that fall upon a calibration area of pixels, and issue commands to a motor to adjust a position of the pre-patient collimator based on the determination. FIGS. 6 and 7 illustrate views 600, 700 of respective detector pixel arrays 602, 702 that are visible as seen from a perspective of a focal spot within x-ray tube 114. Each view 600, 700 includes imaging detector pixels over a respective length 604, 704. It is contemplated that lengths 604, 704 correspond with a plurality of widths of modules 400 which, in one example, include 57 modules 400, each having 16 pixels in width. Thus, the illustrated grid of pixels over lengths 604, 704 does not illustrate a number of pixels corresponding to the example of 16 pixels wide in 57 modules, but is shown having a much larger scale of pixel sizes to simply illustrate the fact that pixels extend over lengths 604, 704 such that illustrative pixels can be seen in the figures. Each view 600, 700 also includes a width 606, 706 which are different from one another. Views 600, 700, as mentioned, show detector pixel arrays 602, 702, which are actually the view of pixels in detector assembly 130 as seen in FIG. 2 and through per-patient collimator 134 therein. In one example, view 600 (FIG. 6) includes width 606, which is a width of an aperture, designated as aperture 502 in FIG. 5. As seen therein, aperture 502 is in pre-patient collimator plate 500, and is in the location of pre-patient collimator 134 as seen in FIG. 2, while the detector pixel array 602 is in detector assembly 130 as also seen in FIG. 2. Thus, width 606 of FIG. 6 illustrates a width of an aperture 608 that corresponds with, in one example, 16 pixels along a Z-direction 610. Pixel arrays 602, 702 are defined by a detector arc-length, such as along an arc length of detector assembly 130, and a plurality of pixels define an imaging Z-width such as width 606. In another example, similarly, view 700 (FIG. 7) includes width 706 which is a width of an aperture, designated as aperture 502 in FIG. 5. Thus, width 706 of FIG. 7 illustrates a width of an aperture 708 that corresponds with, in another example, 2 pixels along a Z-direction 710. Apertures 608, 708 correspond to imaging areas of pixels that are used to obtain imaging data for image reconstruction of an object. Apertures 608, 708 correspond with aperture 512 of FIG. 5 and, as mentioned, may have different widths to correspond with a different area of pixels that may be selected or available for imaging purposes. In one example (FIG. 7) two slices or pixel widths of data are available, and in another example (FIG. 6) 16 slices of data are available. Opening or aperture 502 includes a second aperture 514 that is used to determine a focal spot location using energy derived from x-rays that fall upon a calibration area of pixels. In the illustrated examples of FIGS. 5 and 6, second apertures 612, 712 are provided for calibration. Apertures 612, 712 include corresponding lengths 614, 714. Apertures 612, 712 also include corresponding widths 616, 716 which, in the illustrated examples, each include 8 pixel widths. Accordingly, pre-patient collimator 134 includes pre-patient collimator plate 500 that, in the example of FIG. 6, includes first aperture 608 having first length 604 and first width 606 such that x-rays pass therethrough to at least a portion of an imaging area 618 of pixel array 602. Pre-patient collimator plate 500 includes second aperture 612 having second length 614 and second width 610 such that x-rays pass therethrough to a calibration area 620 of pixel array 602. Thus, imaging area of pixels 618 and the calibration area of pixels 620 have different widths in a Z-direction of the CT scanning system. In the example of FIG. 7, pre-patient collimator 134 includes pre-patient collimator plate 500 that includes first aperture 708 having first length 704 and first width 706 such that x-rays pass therethrough to at least a portion of an imaging area 718 of pixel array 702. Pre-patient collimator plate 500 includes second aperture 712 having second length 714 and second width 710 such that x-rays pass therethrough to a calibration area 720 of pixel array 702. The calibration areas of pixels are used to track focal spot motion using pixels therein. For example, referring to FIG. 8, a calibration area of pixels 800 is shown that corresponds with calibration area of pixels 620 from FIG. 6. Calibration area of pixels 800 includes a first area of pixels 802 that are highlighted in FIG. 8 for illustration purposes, and a second area of pixels 804 at are on either side of first area of pixels 802. Second area of pixels 804 are for tracking focal spot motion such that the focal spot location of focal spot 142 is determined. The first area of pixels 802 is one or more rows of central pixels as defined along the Z-direction, and the second area of pixels 804 that in the illustrated embodiment is outermost rows of pixels on either side of the first area of pixels 802 as defined along the Z-direction. Thus, in this example, area 802 is used for providing reference signals and area or rows 804 of pixels are used to provide feedback related to Z-motion of focal spot 142 to control the focal spot position and always maintain in a stable position or use the data to correct any gain variation induced by imperfection of the detector channel-channel or module-module responses. Feedback for controlling the collimation aperture 502 is thereby provided by a few pixels 804 located at one extreme end of the collimator aperture 502 or slit. Pre-patient collimator plate 500 having aperture 502, comprised of two apertures 512, 514, is controlled by one motor. The aperture design is shown in FIG. 6 for a large aperture 608 and FIG. 7 for a small aperture 708. In these examples, the focal spot motion tracking aperture 800 is outside a field of view and is assigned a group of pixels 802 for reference channels and assigned a few pixels 804 for tracking the focal spot motion in Z-axis. The partial exposure of pixels 804 will lead to a linear signal as a function of the focal spot motion. By monitoring the partial exposure of pixels 804, the focal spot can be tracked and compensated for any drift by, for example, re-adjusting grid voltages within a cathode driving the focal spot position, as is understood within the art. The focal spot position in Z is found to a monotonic function of the ratio of the signal from pixels 804 over a signal from the reference signals of pixels 802. It is contemplated that different numbers of pixels may be used for both the reference signals (pixels 802) and Z-motion pixels (804). That is, referring to FIG. 8, reference pixels 802 include a width 806 that includes 6 pixels therein, in an example, along a Z-direction. However, more or less pixels may be used for the reference signal pixels, as it is contemplated that in general although focal spot motion may occur, its effect is observed as partial exposure of pixels 804, while pixels 802 remain fully exposed. Thus, x-rays impinging on pixels 802 are generally unaffected by focal spot motion. Pixels 804, on the other hand, experience partial x-ray exposure that indeed changes with focal spot motion. Therefore, the signal in pixels 804 generally changes with focal spot motion or drift, while the signal in pixels 802 generally remains constant—independent of focal spot motion. Likewise, pixels 802 are shown over a calibration length 808 that includes the illustrated number of pixels, but it is contemplated that the length 808 may also include more or less pixels than shown. Accordingly, based on the signal obtained and the ratio of signal from pixels, computer 110 is programmed to issue commands to motor 508 to adjust the position of the pre-patient collimator 500 in the Z-direction. Referring to FIG. 9, a collimator plate 900 that includes a plurality of apertures 902, each of which includes an imaging aperture 902 and a Z-motion calibration aperture 904. Each aperture 902 includes a different width in a Z-direction 906. Z-motion calibration apertures 904 may be the same width in the Z-direction, or may be different in the Z-direction. Calibration apertures 904 may have different widths, which effectively results in a different amount of pixels used for reference channels. However, in each instance, calibration apertures 904 include a row of channels at the two Z-ends of the aperture that correspond generally with pixels 804 of FIG. 8. In such fashion, a reference signal may be determined from the central pixels that correspond generally with pixels 802 of FIG. 8, while a variable signal that varies with Z-position of the focal spot is received in pixels 804. Accordingly, the pre-patient collimator 900 in one example includes the plurality of pre-patient apertures 902 that are not contiguous with one another. Each aperture may thereby correspond with the aperture 502 as described above, having apertures 512, 514 combined. In one example, all calibration areas 902 may be of different widths in the Z-direction, while in another example all calibration areas 902 may be approximately the same (as illustrated in FIGS. 6 and 7). Thus, the disclosure includes a method of CT imaging that includes passing x-rays through an opening in a pre-patient collimator, through an object, and to at least a portion of a detector, the detector including imaging pixels and calibration pixels, determining a focal spot location using energy derived from x-rays that fall upon the calibration area of pixels, and adjusting a position of the pre-patient collimator based on the determination. An implementation of system 100 in an example comprises a plurality of components such as one or more of electronic components, hardware components, and/or computer software components. An exemplary component of an implementation of the system 100 employs and/or comprises a set and/or series of computer instructions written in or implemented with any of a number of programming languages, as will be appreciated by those skilled in the art. An implementation of system 100 in an example employs one or more computer readable signal bearing media. A computer-readable signal-bearing medium in an example stores software, firmware and/or assembly language for performing one or more portions of one or more implementations. A computer-readable signal-bearing medium for an implementation of the system 100 in an example comprises one or more of a magnetic, electrical, optical, biological, and/or atomic data storage medium. For example, an implementation of the computer-readable signal-bearing medium comprises floppy disks, magnetic tapes, CD-ROMs, DVD-ROMs, hard disk drives, and/or electronic memory. In another example, an implementation of the computer-readable signal-bearing medium comprises a modulated carrier signal transmitted over a network comprising or coupled with an implementation of the system 100, for instance, an internal network, the Internet, a wireless network, and the like. According to one embodiment, a CT scanning system includes a rotatable gantry having an opening for receiving an object to be scanned, an x-ray tube, and a detector comprising an imaging area of pixels and a calibration area of pixels. The system further includes a pre-patient collimator positioned between the x-ray tube and the detector having first and second apertures that pass x-rays respectively to at least a portion of the imaging area of pixels, and to the calibration area of pixels, a motor configured to move the pre-patient collimator, and a computer programmed to determine a focal spot location using energy derived from x-rays that fall upon the calibration area of pixels, and issue commands to a motor to adjust a position of the pre-patient collimator based on the determination. According to another embodiment, a method of CT imaging includes passing x-rays through an opening in a pre-patient collimator, through an object, and to at least a portion of a detector, the detector including imaging pixels and calibration pixels, determining a focal spot location using energy derived from x-rays that fall upon the calibration area of pixels, and adjusting a position of the pre-patient collimator based on the determination. A technical contribution for the disclosed method and apparatus is that it provides for a computer-implemented apparatus and method of determining a focal spot location using energy derived from x-rays that fall upon the calibration area of pixels, and issuing commands to a motor to adjust a position of the pre-patient collimator based on the determination. When introducing elements of various embodiments of the disclosed materials, the articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Furthermore, any numerical examples in the following discussion are intended to be non-limiting, and thus additional numerical values, ranges, and percentages are within the scope of the disclosed embodiments. While the preceding discussion is generally provided in the context of medical imaging, it should be appreciated that the present techniques are not limited to such medical contexts. The provision of examples and explanations in such a medical context is to facilitate explanation by providing instances of implementations and applications. The disclosed approaches may also be utilized in other contexts, such as the non-destructive inspection of manufactured parts or goods (i.e., quality control or quality review applications), and/or the non-invasive inspection or imaging techniques. While the disclosed materials have been described in detail in connection with only a limited number of embodiments, it should be readily understood that the embodiments are not limited to such disclosed embodiments. Rather, that disclosed can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the disclosed materials. Additionally, while various embodiments have been described, it is to be understood that disclosed aspects may include only some of the described embodiments. Accordingly, that disclosed is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
	summary
	abstract	A hard disk drive memory which stores pattern data of a high-frequency to be applied for each combination of energy and intensity of the generated particle beam and a local memory, which reads a plurality of pattern data of a high-frequency for each patient together with a sequential order of changing energy and intensity from the hard disk drive memory and stores data in order to perform a scanning irradiation method in which a layered particle beam irradiation region in a depth direction of an affected part of the patient is formed sequentially by changing energy and intensity of the particle beam sequentially to irradiate an affected part of a patient which is an irradiation subject with the particle beam, and which reads out data faster than the hard disk drive memory are provided.
054870941	summary	BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a double-layer pellet which is to be placed in the high-temperature plasma generated in a fusion reactor or an experimental fusion apparatus, in order to refuel the reactor or the apparatus, to analyze particle transport, to improve plasma heating and to serve a similar purpose. The invention also relates to an apparatus and method for manufacturing the double-layer pellet. 2. Description of the Related Art Fossil fuel, which is the main energy source we use today, will be exhausted in the future. Energy-acquiring technology utilizing nuclear fusion is being developed in various regions over the world, such as EC, Japan, the U.S. and Russia. The progress in this development is accompanied by two things. The first is an increase in the size of the experimental apparatuses employed. The second is an increase in the size of the plasma generated therein. Of the fusion reactors hitherto known, a D-T type fusion reactor fueled with deuterium and tritium is most promising in view of its reaction efficiency. Generally known as a method of refueling the D-T type fusion reactor is gas puff method, in which deuterium gas and tritium gas are injected into plasma. The gas puff method is, however, disadvantageous in some respects. First, the fuel particles can hardly reach the core of the plasma, particularly when the plasma is large. Second, it is quite probable that the fuel particles are repelled back by the peripheral part of the plasma, known as "divertor layer," before they are injected into the plasma. To render the gas puff method more efficient, experiments have been conducted in which single-layer pellets made by solidifying tritium gas or a mixture of deuterium gas and tritium gas are injected into plasma. Such single-layer pellets are manufactured by an apparatus generally known in the art in such a manner that liquid helium is supplied to the cryo portion cooling metal pipes or a metal plate having holes to an extremely low temperature; hydrogen isotope gas is supplied into the metal pipes or the holes of the cooled metal plate, and then the gas is solided in the pipes or the holes, thus forming single-layer pellets. New technique of manufacturing single-layer pellets has recently been developed, as is disclosed in Jpn. Pat. Appln. KOKAI Publication No. 4-240102. This technique consists in forming a core of another hydrogen isotope within a single-layer pellet, thereby rendering the isotope-mixing ratio in the outer layer different from the isotope-mixing ratio in the core. The apparatus produces pellets in which solid tritium is present in the surface. When the pellets are placed in the plasma generated in a fusion reactor or the like, tritium is not only supplied into the central part of the plasma which is at high temperatures and high density and in which nuclear fusion may take place with high efficiency, but also supplied, undesirably, into the peripheral part of the plasma which is at relatively low temperatures. Tritium is a radioactive substance; it must be wasted as little as possible to minimize the load on the exhaust pump system, tritium-recollecting system and tritium-separating system of the fusion reactor. The tritium supplied to the divertor layer of the plasma is partly repelled from the plasma, and is not used at all in the nuclear fusion. Part of the tritium is adsorbed by the wall of the vacuum vessel of the reactor. The remaining part of the tritium is evacuated from the vacuum vessel by the vacuum pump system. This inevitably results in an increase in the load on the tritium-processing system. To solve these problems which are inherent in the use of single-layer pellets, there have been invented double-layer pellets. A double-layer pellet is made up of a core of solid tritium and an outer layer of solid deuterium, which completely covers the tritium core. An apparatus for manufacturing double-layer pellets is known, as is disclosed in Jpn. Pat. Appln. KOKAI Publication No. 4-335187. This apparatus has metal pipes in which gases solidify to form double-layer pellets. In this apparatus, each double-layer pellet is made in three steps. First, deuterium-gas is supplied into each metal pipe, forming a hollow cylinder or layer of solid deuterium on the cooled inner surface of the metal pipe. Then, tritium gas is supplied into the deuterium cylinder, forming an elongated tritium core. Finally, deuterium gas is applied into the pipe from both ends thereof, forming two deuterium layers which cover the ends of the elongated tritium core. As a result, a double-layer pellet is obtained which consists of a tritium core and a deuterium layer completely covering the core. To design an efficient fusion reactor it is necessary to know physical property of transport of particles and heat. This is because the size of the reactor greatly depends on the physical property of transport of particles and heat. Thus, the transport of particles and heat influences the cost of building a fusion reactor. This is very important from an industrial point of view. Despite the efforts made over years in the past, the transport of particles and heat in high-temperature plasma cannot be said to be well understood. An active particle transport diagnosis is known, which serves to analyze the transport of particles and heat. Known as two typical examples of active particle transport diagnosis are: laser blow-off method and impurity-pellet injection method. In the laser blow-off method, a substrate of glass or the like, having a silicon or aluminum or the other atom film bonded to it, is placed in a plasma-confining vacuum vessel, and a laser beam is irradiated on the silicon or aluminum film, thereby evaporating the silicon or aluminum and leading the resultant vapor into the plasma, and the behavior of particles is observed. In the impurity-pellet injection method, an apparatus is used to inject impurity pellets into the plasma present in a plasma-confining vacuum vessel. The apparatus has pipes or a metal plate having holes or pipes. Pellets made of a solid material such as lithium are set in the pipes or the holes of the metal plate and injected into the plasma, propelled by high-pressure gas or the like. The experimental fusion apparatus is equipped with no mechanism which can reliably determine the sizes of the outer layer and the core or the positional relation thereof. The active particle transport diagnosis, described above, cannot serve to analyze the physical aspects of transport of particles and heat in a fusion reactor. More specifically, the diagnosis cannot provide a reliable quantitative analysis of spatial changes in particle transport. This is because the absolute number of particles supplied is unknown, particularly in terms of space, and the particles are deposited in all locations from the peripheral part of the plasma into the central part of the plasma. There is another problem with a fusion reactor or an experimental fusion apparatus. The high-temperature plasma generated in the fusion reactor or apparatus contains tail ions produced by the ion cyclotron range of frequency (ICRF) heating method. If heated high-energy ions are present also in that region of the plasma in which energy loss is prominent, the heating efficiency inevitably decreases. To solve the problems mentioned above and to analyze the physical aspects of transport of particles and heat into a fusion reactor, there is a demand for double-layer pellets which have the similar structure as refueling pellets, each of which comprises a core and an outer layer whose sizes and positional relation can be reliably determined, and which can serve to inject particles, in no excess numbers, to a desired part of plasma. For example, double-layer pellets whose cores are tiny chips of, for example, lithium are particularly preferable. Double-layer pellets of this type cannot be manufactured by the conventional apparatus described above, however, due to the structure of the apparatus. To manufacture such double-layer pellets, chips used as cores may be made to float in air, and deuterium solidifies, forming outer layers on the chips. It is utmost difficult to manufacture the pellets by this method. SUMMARY OF THE INVENTION Accordingly it is an object of the present invention to provide a method and apparatus which can easily manufacture double-layer pellets whose cores and outer layers can be controlled in their size and their positional relationship, whose cores can be formed without fail, and which can therefore serve to supply fuel into a desired part of plasma in no excess amount. Another object of the invention is to provide a method and apparatus which can easily manufacture double-layer pellets whose cores are made of chips and whose cores and outer layers can be controlled in their sizes and their positional relationship, which serve to analyze transport of particles and heat in a fusion reactor and, hence, to inject particles to be observed, in no excess numbers, into a desired part of plasma. According to a first aspect of the present invention, there is provided a method of manufacturing a double-layer pellet, which comprises the steps of: supplying a first material for forming an outer layer, into a space provided in a pellet carrier body; cooling and solidifying the first material in the space, thereby forming a cylinder of the first material; forming a hole in a first end of the cylinder; supplying a second material for forming a core, into the hole formed in the first end of the cylinder; cooling and solidifying the second material in the hole, thereby forming a core; scraping a second end of the cylinder, which is opposite to the first end; and supplying an additional amount of the first material onto the first end of the cylinder, cooling and solidifying the additional amount of the first material, thereby forming a layer covering the core of the second material. According to a second aspect of the invention, there is provided an apparatus for manufacturing a double-layer pellet. The apparatus comprises: a pellet carrier body having a through hole and movable in one direction; cooling means for cooling at least a portion of the pellet carrier body, in which the through hole is formed; first material-supplying means reaching the pellet carrier body, for supplying a first material for forming an outer layer, into the through hole of the pellet carrier body, thereby cooling and solidifying the first material in the through hole and forming a cylinder of the first material; hole-forming means opposing the pellet carrier body and located downstream of the first material-supplying means, for forming a hole in a first end of the cylinder of the first material set in the through hole of the pellet carrier body; second material-supplying means opposing the pellet carrier body and located downstream of the first material-supplying means, for supplying a second material for forming a core, into the hole formed in the first end of the cylinder, thereby forming a core; pushing means opposing the pellet carrier body and located downstream of the chip-inserting means, for pushing the cylinder such that the second end portion of the cylinder projects from the through hole of the pellet carrier body; material-removing means opposing the pellet carrier body and located downstream of the second material-supplying means, for removing a second end portion of the cylinder; and a third material-supplying means opposing the pellet carrier body and located downstream of the material-removing means, for supplying an additional amount of the first material onto the first end of the cylinder, thereby forming a layer covering the core of the second material. According to a third aspect of this invention, there is provided a method of manufacturing a double-layer pellet, comprising: a first step of supplying a first material for forming an outer layer, into a space provided in a pellet carrier body; a second step of cooling and solidifying the first material in the space, thereby forming a cylinder of the first material; a third step of inserting a chip into a first end of the cylinder; a fourth step of scraping a second end of the cylinder, which is opposite to the first end; and a fifth step of supplying an additional amount of the first material onto the first end of the cylinder, cooling and solidifying the additional amount of the first material, thereby forming a layer covering the chip. According to a fourth aspect of the present invention, there is provided an apparatus for manufacturing a double-layer pellet. The apparatus comprises: a pellet carrier body having a through hole and movable; cooling means for cooling at least a portion of the pellet carrier body, in which the through hole is formed; first material-supplying means opposing the pellet carrier body, for supplying a first material for forming an outer layer, into the through hole of the pellet carrier body, thereby cooling and solidifying the first material in the through hole and forming a cylinder of the first material; chip-inserting means opposing the pellet carrier body and located downstream of the first material-supplying means, for inserting a chip into a first end of the cylinder formed in the through hole of the pellet carrier body; material-removing means opposing the pellet carrier body and located downstream of the chip-inserting means, for removing a second end portion of the cylinder; and second material-supplying means opposing the pellet carrier body and located downstream of the material-removing means, for supplying an additional amount of the first material onto the first end of the cylinder, thereby forming a layer covering the core of the second material. According to a fifth aspect of this invention, there is provided a double-layer pellet comprising: a core of a liquid or a solid material; and an outer layer made of a solid material and covering the entire core. In the apparatus according to the second aspect of the invention, the cooling means cools the pellet carrier body. Then, the pellet carrier body is moved until its hole comes to oppose the first material-supplying means. The first material-supplying means supplies a first material into the through hole of the carrier body. The first material is cooled and solidified, forming a cylinder in the through hole of the carrier body. Thereafter, the pellet carrier body is moved until its hole comes to oppose the hole-forming means. The hole-forming means forms a hole in a first end of the cylinder of the first material. Next, the carrier body is moved until its hole comes to oppose just the second material-supplying means. The second material-supplying means supplies a second material into the hole formed in the first end of the cylinder, thereby forming a core. The carrier body is then moved until its hole comes to oppose the the pushing means. The pushing means pushes the cylinder such that the second end portion of the cylinder projects from the through hole of the pellet carrier body for a prescribed distance. Next, the carrier body is moved until its hole comes to oppose the third material-supplying means. As the carrier body is so moved, the material-removing means removes a second end portion of the cylinder from the through hole of the pellet carrier body. Then, the third material-supplying means supplies an additional amount of the first material onto the first end of the cylinder, thereby forming a layer covering the core of the second material. In the apparatus according to the fourth aspect of the invention, the cooling means cools the pellet carrier body. Then, the pellet carrier body is moved until its hole comes to oppose the first material-supplying means. The first material-supplying means supplies a first material into the through hole of the carrier body. The first material is cooled and solidified, forming a cylinder in the through hole of the carrier body. Thereafter, the pellet carrier body is moved until its hole comes to oppose the chip-inserting means. The chip-inserting means inserts a chip into a first end of the cylinder of the first material. The carrier body is then moved until its hole comes to oppose the the pushing means. The pushing means pushes the cylinder such that the second end portion of the cylinder projects from the through hole of the pellet carrier body for a prescribed distance. Next, the carrier body is moved until its hole comes to oppose the second material-supplying means. As the carrier body is so moved, the material-removing means removes a second end portion of the cylinder from the through hole of the pellet carrier body. Then, the second material-supplying means supplies an additional amount of the first material onto the first end of the cylinder, thereby forming a layer covering the core of the second material. Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
042591562	description	Referring now to the drawing and first, particularly, to FIG. 1 thereof, there is shown a pressure vessel 1 of a boiling-water nuclear reactor provided with connecting pipes or unions 2 for core flood lines 2a, and unions 3 for feedwater manifold or distributor lines 3a, the unions 2 for the core flood lines 2a being disposed in a plane e1 axially normal to i.e. normal or perpendicular to the axis of the pressure vessel, and the unions 3 for the feedwater manifold or distribution lines 3a being disposed in a plane e2 also axially normal to the pressure vessel, a multiplicity of the unions 2 and 3 and lines 2a and 3a being distributed over the periphery of the pressure vessel 1. A core container 4, also referred to as moderator container, formed of a lower part 4.1 and a cover 4.2, is mounted in the interior of the pressure vessel 1. The core container 4 is suspended by straps or claws 4a located at the outer periphery thereof, only one of which is shown in FIG. 1, from corresponding brackets 5 located at the inner periphery of the pressure vessel 1, and are threadedly secured to the brackets 5 as shown diagrammatically at 5a. An upper guide grid or perforated support plate 6 for non-illustrated fuel elements and absorption rods rests on brackets 7 of the core container 4 and is fastened thereto by non-illustrated threaded fastening devices. In the modified embodiment of FIG. 4, the lower part 4.1 of the core container 4 is braced upon the spherical base 1a of the pressure vessel 1 and is welded thereto at 8. The pressure vessel 1 also is supported by a surrounding vertical frame 1b. Returning to FIG. 1, an axially normal parting line 9 between the core-container cover 4.2 and the lower part 4.1 of the core container 4 is clearly shown therein. The core container 4 is clamped together by means of axial tie rods 10 (shown at the left-hand side of FIG. 1), a multiplicity of the tie rods 10 being distributed over the periphery of the core container 4. The tension or tie rods 10 engage respective brackets 4.2a and 4.1a of the cover 4.2 and the lower part 4.1 of the core container 4. The tension or tie rods 10, respectively, have a shaft 10a and a sleeve 10b and, at the upper end of the respective tie rod 10, by means of a nut 10c (FIG. 3), the shaft 10a and the sleeve 10b are stayed or braced one to the other and, thereby, the cover 4.2 is also pressed against the lower part 4.1 of the core container 4. A hammerhead 10d extends through a slot formed in the lower bracket 4.1a and grips it from behind after the hammerhead 10d is turned about 90.degree.. For definition of the latched and unlatched position, at the location 4b, a guiding groove is provided in the sleeve 10b and a pin on the tie or tension rod shaft 10a. By means of a pair of guidance sleeves 11, 11', the tie rods 10 are guided, in the upper and middle regions thereof, to corresponding ring plates 12,12', which are firmly connected, on their part, to an array of steam separators DA, of which only one is illustrated, and to upper and lower grid support plates G and G' thereof. Risers DA1 of the steam separators DA are fitted into respective openings 4.2b formed in the cover 4.2 and are accordingly welded to the cover 4.2 at these locations. An additional tension or tie rod 13 (at least three thereof are likewise disposed over the periphery of the core container 4) is shown in FIG. 1 and extends through the ring plates 12, 12'. The lower end of the tie rod 13 engages the cover 4.2 of the core container 4 (bracket 4.2c). The tie rod 13 is provided at the upper end thereof with a support member 14 having an eye 15 in which a hook of a non-illustrated lifting device is engageable. Above the steam separators DA, a plurality of steam dryers DT are connected by means of a support plate 16a and a support ring 16b into a single unit and are mounted on brackets 17 at the inner periphery of the pressure vessel 1. A cylindrical apron or skirt 18a is connected to the support ring 16b and is provided at the inner periphery thereof with water outlet chests 18b fastened thereto, wherein outlet pipes 18c of the steam dryer DT terminate. The water level in the pressure vessel, is indicated by the horizontal line W. One of the multiplicity of guide rods 180 fastened to the inner peripheral surface of the pressure vessel, is shown in FIG. 1. The guide rods 180 serve for axial guidance of the structural unit B when it is introduced or removed from the pressure vessel 1, the structural unit B being described more fully hereinbelow. The core flood line 2a surrounds a first line or piping section 2a1 in the form of an otherwise non-represented thermosleeve pipe fastened in the union 2, and a second line or piping section 2a2 which is coupled at one end thereof to the first line section 2a1 through a spring-loaded thermally elastic pipe coupling 2b, and has a second end extending through the cover 4.2 of the core container 4 and connecting with a core spray ring line 181 which is, for its part, fixed to the inner peripheral surface of the core container-cover 4.2 by means of supporting or retaining dogs 182. The particular construction of this core floodline coupling 2b is not an objective of the invention of the instant application but is, indeed, the subject of co-pending Application Ser. No. 869,362 filed Jan. 13, 1977 of which the applicants of the instant application are coinventors. What is of importance with respect to the instant application, is that this coupling 2b is provided automatically without any additional auxiliary means when the structural unit B, formed of the core-container cover 4.2 and the steam separators DA is inserted therein and set into position; conversely, a loosening or release of this coupling 2b occurs also automatically without additional auxiliary equipment during removal of the structural unit B. The same basic principle is employed also for the coupling device 3b according to the invention, shown in the left-hand side of FIG. 1 as well as in FIG. 2, generally, and in detail in FIGS. 5 to 9, and indeed in a different form, because relatively little space is available in radial direction due to the disposition of the feedwater distributor or manifold line 3a. The first line section 3a1 is formed likewise of a thermosleeve pipe (FIG. 5), which extends sealingly through the union 3 and is fastened to the pressure vessel-housing wall.1.1 as is described in greater detail hereinbelow. The second line section 3a2 (only shown in part in FIGS. 1 and 2), which is constructed as a ring line, is sealingly couplable with the first line section 3a1 i.e. the upwardly directed mouthpiece 3a11. As mentioned hereinbefore, the steam separators DA and the core-container cover 4.2 together form a structural unit B. The second line section 3a2 is included in this structural unit. FIG. 2 shows the rigid or firm connection of the second line section 3a2 to the lower ring plate 12' through angle irons 121 welded at 120 and fixed by diagrammatically indicated non-unscrewable screws 122 to the ring plate 12'. The second line section 3a2 is consequently liftable together with the core container-cover 4.2 and the steam separators DA out of the pressure vessel 1, after the pressure vessel 1 has been opened for the purpose of inspection and/or maintenance, and is also reinsertable into the pressure vessel 1. In the structural unit B, there are also naturally, included the line sections 2a2 of the core floodline as well as the parts 13, 12, 12', G and G', in the embodiment of FIG. 1, further reference to which will be made in the description of the installation and removal of the structural unit B presented hereinafter. Reference is had initially to FIGS. 5 and 6 in the following, functionally like parts therein as well as in the remaining figures being identified by the same reference characters. The first line section 3a1 and the second line section 3a2 are in engagement with one another at the coupling location 3b thereof, by means of coaxial sealing surface members identified as a whole by reference numeral 19. In the illustrated embodiment, the sealing surface members 19 form a ball-cylinder seat with spherically shaped seating surfaces 19.2 at the union 3a21 of the second line section 3a2 and with cylindrical seating surfaces 19.1 at upwardly directed flanks 20a of an angle ring 20 also having undersided, inwardly directed flanks 20b. The manner of fastening the angle ring 20 is readily apparent in FIGS. 6 and 7. In this regard, the mouthpiece 3a11 of the first line section 3a has a support flange 3a12, and the angle ring 20 has retaining flanges 20c at the outer periphery thereof. Considering FIGS. 6 and 7 together with FIG. 8, it is readily apparent that the angle ring 20 is braced by the ring flange 20c thereof spring-elastically against the flange 3a12 of the mouthpiece 3a11. This is effected by means of hex-head threaded bolts 21 which are threadedly secured in the support flange 3a12, extend through a bore 20c 1 formed in the retaining flange 20c and, under prestressing of a cup or plate-spring packet 21b which is slipped over the shaft 21a and is seated between a contact washer 21d and a shell washer 21e with a mutually intervening gap 21c, pressing the angle ring 20 by the undersided flank 20b thereof. and, indeed, by spherical contact surface portions 20b1 (FIG. 9) thereof against corresponding contact surface portions 3a13 of the flange 3a12, due to force application upon the retaining flange 20c (contact surface portions 20c2). As is shown especially in FIGS. 5 and 7, the tube part of the upwardly extending mouthpiece 3a11 and, furthermore, the angle ring 20 and the union 3a21 of the second line section 3a2 are flattened in radial direction, considered with respect to the longitudinal axis of the pressure vessel 1, with the formation of a slot-like cross section, so that an especially compact, space-saving type of construction can be achieved. The flange 20c of the angle ring 20 is correspondingly constructed in the form of a pair of straps with a respective pair of threaded bolt pass-throughs or passageways 21 (FIG. 8). The threaded bolts 21, after adjusting for the gap 21c, are welded to the flange 3a12 (weldment 21f). The angle ring 20 constitutes a component part of the first line section 3a1. Due to the spherical contact surface portions 21d1 of the contact washer 21d and due to the gap 21c which is about 1 mm. wide, in practice, and furthermore due to the ball-cylinder seat 19.2, 20a as well as the spherical contact surface portions 20b1 which engage the opposing surface portions 2a 13 (note FIG. 9), slight tilting or tipping of the angle ring 20 with respect to the angle-ring axis a1 (FIG. 5) is afforded. This permits a tolerance equalization and elastic yielding of the angle ring 20 during introduction of the union 3a21 of the second line section 3a2. Furthermore, for varying axial, radial and tangential thermally effected movements of the first line section 3a1 and of the second line section 3a2, equalization or balance is thereby provided without having to come to compulsive forces. This is therefore significant, because the first line section 3a1 is connected to the pressure vessel 1, whereas the second line section 3a2 (note FIGS. 1 and 2) together with the steam separators DA and the core-container cover 4.2 form the structural unit B. As is shown especially in FIG. 9, the sealing surface portions 20b1, 3a12 and 19.1 of the first line section 3a1, as well as the sealing surface portions 19.2 of the second line section 3a2 or the union 3a21 thereof, are provided with applied weldments (armor) 22 formed of a wear-resistant alloy such as are known in Germany under the trade name Stellit or UTP 7000. The same material is used as armor for the contact surface portions 21d1 and 20c2 (note FIG. 8). The feedwater-union 3 and also the pressure vessel 1 per se (note FIG. 5) are provided at the inner peripheral surface thereof with a continuous plating 23. The first line section 3a1 initially extending radially as a thermosleeve pipe and then upwardly and flattened out within the interior of the pressure vessel, to the mouthpiece 3a11, is provided at the outer end 3a14 thereof with spherical, likewise armored sealing surface portions 3a15 with which it engages a beefed-up or reinforced plating region 23a, so that thermally induced radial mobility is provided. In the region of the outer deflection curve 3a16, pass-through or passageway bores 24 for feedwater are provided (note also FIG. 6). The first line section 3a1, during assembly, is inserted in direction of the arrow A into the bore of the union 3, the retaining straps 25, 25' on both sides thereof, being slid with retaining bolts 26, 26' into slots 27 (FIG. 7) formed in retaining brackets 28, 28' that are welded to the inner wall of the pressure vessel 1. Between the trap 25 shown at the right-hand side of FIG. 6 and the retaining bracket 28 associated therewith, a spacer bushing or sleeve 29 welded to the strap 25 is disposed and is provided with conical seating surfaces 29a centered at a correspondingly conically shaped recess 28a formed in the retaining strap 28 (for the purpose of forming a fixed or set point of the radial and tangential thermal expansion). In the left-hand side of FIG. 4, there is clearly shown a somewhat varied spacer bushing or sleeve 29' which is welded to the respective strap 25'. At the underside thereof, the bushing 29' is formed conically only in radial direction and, contrarily, planar in tangential direction and provided with armor or reinforcement 30. The first line section 3c is thus seated with the straps 25, 25' thereof upon the brackets 28, 28' with the intermediary of the bushings or sleeves 29, 29' and is braced firmly by means of the threaded bolts 26 and contrarily, spring-elastically by means of the threaded bolts 26' with respect to these brackets 28, 28', the head 26a of the respective bolts 26, 26' gripping behind the respective brackets 28, 28' and being welded with the upperside of the straps 25, 25', respectively, to the non-unscrewable bushings or sleeves 32 for the threaded bolts 26, 26' and the nuts 26b, 26b' thereof. In the spring-elastic bolt connection 26', a cup or plate spring 33 is inserted between the head 26a' of the bolt 26' and the bracket 28', a gap 340 ensuring thermally induced mobility between the bushing or sleeve 29' and the bracket 28' in tangential direction. The second line section 3a2 (note especially FIG. 6) forms, outgoing from the union 3a21, a pipe branching which merges in a V-shaped manner into the two ring line sections 35. The latter are formed with corresponding injection bores 24' for the feed-water. Conically running-in axial guide pins 36 are welded to the pipe branches 35 which, during insertion and coupling of the second line section 3a2, engage in respective guide bushings or sleeves 37 of the angle ring-retainer flange 20c. This engagement serves for centering during assembly; therefore, a given clearance or play S is provided, which does not prevent thermally induced motion of the line section 3a2 within the purported tolerance range. In the vicinity of the axial guide pins 36, the ends 36a of which run in conically, as is apparent for precentering, the flange 3a12 is provided with pass-through or passageway openings 38. Shown especially in FIGS. 5 and 9, is that, at the support flange 3a12 of the upwardly directed mouthpiece 3a11 of the first line section 3a1, a sheetmetal skirt or apron is welded, which shields the angle ring-sealing seat 19.1, 19.2 as well as 20b1, 3a13 from the pressure-vessel wall 1.1. The pressure-vessel wall 1.1 is thereby protected from possible small quantities of injected water. Removal of the structural unit B occurs as follows: After the steam dryers DT disposed above the structural unit B have been removed from the pressure vessel 1 (for this purpose, the pressure vessel 1 is opened beforehand and non-illustrated bracing means for the steam dryers DT have been loosened or released), and after loosening or releasing the nuts 10c and after releasing the hammerhead lock or latch 10d, the flange connection 4.2a, 4.1a can be opened and the steam separators DA together with the core-container cover 4.2 of the core floodline section 2a2 as well as of the second line section 3a1 of the feedwater distributor or manifold 3a (structural unit B) can be lifted upwardly, the tension or tie rods 13 with the support members 15 thereof serving to grip the lifting tool. The coupling 2b between the core floodline sections 2a1, 2a2, just as the coupling 3b between the first and the second line section 3a1, 3a2 are thereby released or loosened automatically, in contrast to which, during insertion or lowering of the structural unit B, again automatically attain sealing engagement. What is important for the coupling location 3b (just as for 2b), is that relative motion between the structural unit B and the first line section 3a1, which depends upon thermal expansion in axial direction and, to a slight extent, in radial and tangential directions, is permitted without impairing the sealing action. It is additionally important that the nominal location of the sealing engagement or contact in vicinity of the coupling 3b is attained through the weight per se of the structural unit B as well as through the axial bracing forces of the core container cover 4.2. The axial forces are transmitted by the core container 4 through support paws 4a thereof to brackets 5a welded to the inner peripheral surface of the pressure vessel 1 (several paws and brackets 4a, 5a are distributed over the periphery) and through the core container-bracing at 8, according to FIG. 4, to the bottom spherical wall or shell 1a of the pressure vessel. The vibration-proof coupling location movable by thermal inducement is employable advantageously not only with the illustrated embodiments. On the contrary, it is generally employable for such pressure vessels, for example, steam generators of pressurized water nuclear reactors, wherein the first line section extends sealingly through the pressure vessel-housing wall and is fastened thereto, and wherein a second line section disposed within the pressure vessel forms, together with installed equipment of the pressure vessel, a structural unit, the installed equipment, when the pressure vessel is closed, being held in position by loosenable or releasable bracing means against stops provided in the pressure vessel, and the coupling device of both line sections being held in engagement or contact position thereof through force-locking of the bracing means, so that, when loosening or releasing the bracing means and removing the installed equipment or when inserting the equipment and arresting the bracing means, automatic uncoupling or coupling of the coupling device is effected.
	claims	1. An isotope production system comprising:a cyclotron including a magnet yoke that surrounds an acceleration chamber, the cyclotron configured to direct a charged-particle beam from the acceleration chamber through the magnet yoke; anda target system located adjacent to the magnet yoke, the target system configured to hold a target material at a target location, the target location being outside of the magnet yoke such that the charged-particle beam is incident upon the target material outside of the magnet yoke, the target system including a radiation shield that encloses the target location and is configured to attenuate neutrons that are emitted from the target material; anda beam passage extending from the acceleration chamber through the magnet yoke and the radiation shield to the target location, the beam passage being at least partially formed by the magnet yoke and the radiation shield of the target system;wherein the magnet yoke has an exterior surface that forms a shield-acceptance cut-out, the beam passage extending through the magnet yoke from the acceleration chamber and into the shield-acceptance cut-out, wherein a portion of the radiation shield is shaped to fit within the shield-acceptance cut-out of the magnet yoke, the portion of the radiation shield extending out of the shield-acceptance cut-out toward the target location. 2. The isotope production system in accordance with claim 1 wherein the beam passage has a length measured from the target location to an interior surface of the magnet yoke that defines the acceleration chamber, the beam passage being linear along the length, wherein the length is between 0.5 and 1.5 meters. 3. The isotope production system in accordance with claim 1 wherein an exterior surface of the radiation shield directly abuts an exterior surface of the magnet yoke. 4. The isotope production system in accordance with claim 1 further comprising a common housing that contains the cyclotron and the target system, the housing including first and second moveable partitions that are configured to provide access to the acceleration chamber and the target system, respectively, when the first and second moveable partitions are in respective open positions, the second movable partition including a section of the radiation shield. 5. The isotope production system in accordance with claim 4 wherein the housing comprises polyethylene and lead. 6. The isotope production system in accordance with claim 1 wherein the radiation shield comprises a material composition configured to attenuate radiation emitting from the target material and the magnet yoke comprises a different material composition configured to attenuate radiation emitting from the acceleration chamber. 7. The isotope production system in accordance with claim 1 wherein the radiation shield has a shape that substantially conforms to a shape of the shield-acceptance cut-out. 8. The isotope production system in accordance with claim 1 wherein the radiation shield comprises a first shielding structure that encloses a target region having the target location, the first shielding structure comprising a first material composition that is configured to attenuate gamma rays that emit from the target material. 9. An isotope production system comprising:a cyclotron including a magnet yoke that surrounds an acceleration chamber, the cyclotron configured to direct a charged-particle beam from the acceleration chamber through the magnet yoke;a target system located adjacent to the magnet yoke, the target system configured to hold a target material at a target location, the target location being outside of the magnet yoke such that the charged-particle beam is incident upon the target material outside of the magnet yoke, the target system including a radiation shield that encloses the target location and is configured to attenuate neutrons that are emitted from the target material; anda beam passage extending from the acceleration chamber through the magnet yoke and the radiation shield to the target location, the beam passage being at least partially formed by the magnet yoke and the radiation shield of the target system;wherein the radiation shield comprises a first shielding structure that encloses a target region having the target location, the first shielding structure comprising a first material composition that is configured to attenuate gamma rays that emit from the target material; andwherein the radiation shield further comprises a second shielding structure that encloses the first shielding structure, the second shielding structure comprising a second material composition that is configured to attenuate neutrons emitting from the target material, the first and second material compositions being different. 10. The isotope production system in accordance with claim 1 wherein the magnet yoke has a geometric center located within the acceleration chamber, wherein an exterior boundary of the cyclotron has a dose rate of less than about 4 μSv/h at a distance of less than about 1 meter from the geometric center and an exterior boundary of the target system has a dose rate of less than about 4 μSv/h at a distance of less than about 1 meter from the target material, wherein the target material experiences a beam current of between about 20 μA and 30 μA and the cyclotron is configured to accelerate 1H− ions to an energy level of approximately 9.6 MeV or less. 11. An isotope production system comprising:a cyclotron supported by a platform, the cyclotron including a magnet yoke that surrounds an acceleration chamber, the cyclotron configured to direct a charged-particle beam from the acceleration chamber through the magnet yoke; anda target system located on the platform and adjacent to the magnet yoke, the target system including a radiation shield that has a target region configured to hold a target material at a target location, the target location being outside of the magnet yoke such that the charged-particle beam is incident upon the target material outside of the magnet yoke;a beam passage extending from the acceleration chamber to the target location, the beam passage being at least partially formed by the magnet yoke and the target system, the beam passage extending along a beam axis that intersects the platform; anda housing that encloses the cyclotron and the target system, the housing including first and second moveable partitions that are configured to provide access to the acceleration chamber and the target region, respectively, when the first and second moveable partitions are in open positions, the second movable partition including a section of the radiation shield. 12. The isotope production system in accordance with claim 11 wherein the radiation shield encloses the target location and is configured to attenuate gamma rays and neutrons that emit from the target material. 13. The isotope production system in accordance with claim 12 wherein the radiation shield has a target region including a space where the target location is held, the radiation shield including an exterior surface and a varying radial thickness that is measured from the target region to the exterior surface of the radiation shield, the radiation shield being supported by the platform, wherein the radiation shield includes first and second portions, the radial thickness of the first portion extending from the target region to the platform in a gravitational force direction, the radial thickness of the second portion extending from the target region away from the platform in a direction that is opposite the gravitational force direction, the radial thickness of the first portion being less than the radial thickness of the second portion. 14. The isotope production system in accordance with claim 12 wherein the radiation shield has an exterior surface that abuts an exterior surface of the magnet yoke. 15. The isotope production system in accordance with claim 11 wherein the beam passage is substantially linear from the acceleration chamber to the target location. 16. The isotope production system in accordance with claim 11 further comprising a turbomolecular pump that is fluidicly coupled to the acceleration chamber of the magnet yoke, the turbomolecular pump being oriented along a longitudinal axis that forms an angle with respect to a gravitational force direction, the angle being greater than 10 degrees. 17. The isotope production system in accordance with claim 1 wherein the radiation shield completely surrounds the target location except for the beam passage. 18. An isotope production system comprising:a cyclotron including a magnet yoke that surrounds an acceleration chamber, the cyclotron configured to direct a charged-particle beam from the acceleration chamber through the magnet yoke; anda target system located adjacent to the magnet yoke, the target system configured to hold a target material at a target location, the target location being outside of the magnet yoke such that the charged-particle beam is incident upon the target material outside of the magnet yoke, the target system including a radiation shield that encloses the target location and is configured to attenuate neutrons that are emitted from the target material; anda beam passage extending from the acceleration chamber through the magnet yoke and the radiation shield to the target location, the beam passage being at least partially formed by the magnet yoke and the radiation shield of the target system;wherein the radiation shield has a target region including a space where the target location is held, the radiation shield including an exterior surface and a varying radial thickness that is measured from the target region to the exterior surface of the radiation shield, wherein the radiation shield includes first and second portions, the radial thickness of the first portion extending from the target region to a platform in a gravitational force direction, the radial thickness of the second portion extending from the target region away from the platform in a direction that is opposite the gravitational force direction, the radial thickness of the first portion being less than the radial thickness of the second portion. 19. The isotope production system in accordance with claim 18 wherein the radiation shield includes first and second shielding structures, the first shielding structure surrounding the target location such that the first shielding structure encloses the target location, the second shielding structure surrounding the first shielding structure such that the second shielding structure encloses the first shielding structure, the second shielding structure including the exterior surface of the radiation shield. 20. The isotope production system in accordance with claim 1 wherein the radiation shield includes first and second shielding structures, the first shielding structure surrounding the target location such that the first shielding structure encloses the target location, the second shielding structure surrounding the first shielding structure such that the second shielding structure encloses the first shielding structure, the second shielding structure including the portion of the radiation shield that extends out of the shield-acceptance cut-out toward the target location. 21. The isotope production system in accordance with claim 20 wherein the first shielding structure consists essentially of lead and the second shielding structure comprises polyethylene. 22. The isotope production system in accordance with claim 20 wherein the first shielding structure is not located within the shield-acceptance cut-out. 23. The isotope production system in accordance with claim 11 wherein the radiation shield includes first and second shielding structures, the first shielding structure surrounding the target location such that the first shielding structure encloses the target location, the second shielding structure surrounding the first shielding structure such that the second shielding structure encloses the first shielding structure, wherein the beam axis extends through the target location and intersects each of the first and second shielding structures after the target location.
	abstract	An anti-scatter grid for radiology imaging having an anti-scatter layer with a plurality of metallized partitions that enable X-rays emitted from a source located above the grid to pass and absorbing X-rays not derived directly from this source. The grid has at least one plate of expanded polymer material fixed on one surface of anti-scatter layer. The grid may be positioned with a frame.
	summary
048428086	abstract	A pellet collating system includes a tray positioning station located adjacent a pellet collating line with a tray transfer robot located therebetween. The tray positioning station has mobile carts lodged thereat, some supporting pellet supply trays and others supporting pellet storage trays. Pellets on one supply tray and later placed on one storage tray are of the same enrichment. Pellet enrichments on some trays are different from on others. The collating line includes pellet input, work and output stations arranged in tandem. The robot is operable to transfer supply and storage trays one at a time to and from the positioning station and the respective input and output stations. An input sweep head is operable for sweeping pellets onto the work station from a supply tray on the input station. A gripping and measuring head is operable for measuring a desired length of pellets on the work station and then separating the measured desired length of pellets from the remaining pellets, if any. An output sweep head is operable for sweeping the measured lengths of pellets from the work station onto a storage tray at the output station. The output sweep head is also operable for sweeping the remaining pellets, if any, from the work station back onto the one supply tray disposed at the input station.
048470082	claims	1. A nuclear containment composition resulting from the solidification of a melt of (1) a lead phosphate glass consisting essentially of, in weight percent, 45-66% PbO, 34-55% P.sub.2 O.sub.5, (2) a radioactive metal oxide mixture incorporated in said glass, and (3) an effective corrosion-inhibiting concentration up to 9% Fe.sub.2 O.sub.3 incorporated in said glass, based on the total weight of said composition. 2. The composition of claim 1 in which the metal oxide mixture content by weight is up to 20% of the lead-phosphate glass. 3. An improved process for the containment of radioactivity comprising: (a) forming a melt, at a temperature in the range of 800.degree. C. to 1,500.degree. C., of a lead glass composition consisting essentially of 45-66% PbO, 34-55% P.sub.2 O.sub.5 or a compound readily decomposable to P.sub.2 O.sub.5 and an effective corrosion - inhibiting concentration of up to 9% Fe.sub.2 O.sub.3 ; and (b) incorporating up to 20%, based on the weight of the glass composition of a radioactive metal oxide mixture and then solidifying the melt.
	description	Field of the Invention The present invention relates to a laser welding apparatus for spacer grid of nuclear fuel assembly, and more particularly to a laser welding apparatus enhancing serviceability. Description of the Related Art A nuclear reactor is equipment that is made to control nuclear fission artificially to generate energy, or to be used for various purposes such as production of radioisotope or plutonium, or radiation field formation, etc. In general, light water reactor nuclear power plant uses enriched uranium in which ratio of uranium-235 is increased by 2 to 5%. For nuclear fuel to be used in nuclear reactors, fuel fabrication is processed in a way that cylindrical pellet hefting about 5 g is made of uranium. In order to manufacture a fuel rod, theses pellets come charging zircaloy cladding and spring and helium gas are put in and then an end plug is welded in a rod end. The fuel rods are charged in skeleton finally to form a fuel assembly and combusted by nuclear reaction in the nuclear reactor. Spacer grid in nuclear fuel assembly which forms skeleton with a fuel rod, instrument tube, and guide tube, is made by dozens of spacer grid straps. Each spacer grid strap has a plurality of incision parts such as a slot. Spacer girds are placed longitudinally and laterally at regular interval so that spacer grid straps cross each other respectively. Thus incision parts are interconnected to each other by fitting to each other so that spacer grid forms grid space. However these spacer grid straps are interconnected to each other by inserting into incision parts, spacer grid strap itself sways because of gaps in most incision parts. Thus the points of intersection where spacer grid straps cross each other cross parts, and parts in which connection is not solid such as outside, corner, etc. are welded in order to prevent spacer grids from swaying. Laser welding is mostly used for the welding method of spacer grid. For example, the present applicant's Korean Patent No. 10-0922162 registered on 9 Oct. 2009 suggests a laser welding device for spacer grid of nuclear fuel assembly for enhancing workability and productivity. The present inventor intends to improve further this conventional laser welding device for spacer gird of nuclear assembly. Korean Patent No. 10-0922162 (Registration Date: 9 Oct. 2009) The present invention is to improve the conventional laser welding device for spacer grid, and particularly to provide a laser welding apparatus which can enhance maintainability. The laser welding apparatus according to the present invention for accomplishing these objectives comprises a base frame in which a chamber installment hole is formed horizontally to the center in a way that the hole penetrates the chamber and a guide rail is installed along the chamber installment hole; a welding chamber unit assembled with the base frame in guidance by the guide rail and equipped with an operable door in front and a glass window at the top to be airtight; a laser welding unit mounted on the base frame for radiating laser through the glass window to weld spacer grid in the welding chamber; and a locking member for fixing the welding chamber on the base frame. Preferably the locking member according to the present invention comprises a locking block protruding from the bottom of the welding chamber unit; a locking arm arranged so as to be pivoted to the base frame to support the locking block; and a locking pin mounted on the base frame for restricting rotation of the locking arm. Preferably the locking member according to the present invention comprises a driving unit installed on the bottom surface of the chamber installment hole for driving the load back and forth; a bracket installed on the bottom surface of the chamber installment hole; and a locking lever assembled so as to be pivoted to the bracket and rotated by the load to support the welding chamber unit. More preferably, the locking lever further comprises a roller enabling to pivot to the end where the locking lever contacts the welding chamber. Preferably, the base frame according to the present invention further comprises a glass cover arranged to cover the glass window. And more preferably, the glass window is fixed on the flange in which a ventilation hole interconnected with the welding chamber unit is formed. And the flange is characterized by a ventilation valve arranged in it and controlled to be opened or closed by the glass cover. Preferably the welding chamber unit according to the present invention comprises a position detecting unit for detecting the standard position of a driving pad which rotates a welding rotation plate in which the spacer gird is settled, and outputting an electrical detection signal. The laser welding apparatus for spacer grid of nuclear fuel assembly according to the present invention arranges the base frame and the welding chamber mounted on the base frame for welding spacer grids so that the base frame and the welding chamber unit can be detached at the rear, and it can enhance work convenience at maintenance activities. Specific configuration or functional descriptions which set forth in exemplary embodiments according to the present invention are only for the purpose of describing exemplary embodiments, and the exemplary embodiments according to the concept of the present invention can be practiced in various forms. Thus the present invention is not limited to the described exemplary embodiments and all of appropriate variations, modifications and equivalents are considered to pertain to the scope of the present invention. Meanwhile, the terms used in the specification are for describing specific exemplary embodiments and they are not meant to limit the present invention. Singular expressions imply both singular and plural meaning unless they are distinctly different by context. Terms like “Comprise” or “have” and etc. in the specification intend to specify that the characteristic of practice, number, process, operation, component, part, or any combination thereof exist and they exclude neither existence of one or more of other characteristics, numbers, operations, parts, or any combination thereof nor additional potentiality. Specific exemplary embodiment of the present invention will be explained from the following detailed description when taken in conjunction with the accompanying drawings as follows. With reference to FIG. 1, a laser welding apparatus for spacer grid according to the present invention (hereinafter “a welding apparatus”) comprises a base frame 100, a welding chamber unit 200 detachably mounted on the base frame 100 in which welding spacer grid is performed, a laser welding unit 300 for welding spacer grid by radiating laser into the laser chamber unit 200, and a locking member 410 for fastening the detachable welding chamber unit 200 on the base frame 100. The base frame 100 on which main units are mounted has the laser welding unit 300 mounted on the top, and has a chamber installment hole formed horizontally through in the center in which the welding chamber unit 200 is installed. A guide rail 110 is arranged along the chamber installment hole so the welding chamber unit 200 can be installed or detached in guidance by the guide rail 110. An adjustment block 101 can be arranged in the lower part of the base frame 100 so that the position of the base frame 100 can be precisely adjusted from side to side or in its height by the adjustment block 101. A damper 120 is arranged in the end of the guide rail 110, the welding chamber unit 200 enters along the guide rail 110 and it is restricted to move forward by the damper 120. The welding chamber unit 200 is equipped with an operable door 210 in the front and a glass door window 220 at the top to be airtight in a closed structure. Specifically, the door 210 is arranged to be slidable up and down at the chamber 201, wherein the both ends of the door 210 can be slided up and down in guidance by the rail 211 arranged parallel to the chamber 201. A operable cylinder 212 is installed in the lower part of the door 210 in the chamber 201, and the end of a cylinder load 213 operated by the operable cylinder 212 is assembled with the door 210 by a hinge, and then the door 210 is opened or closed by the operable cylinder 212. The operable cylinder 212 can be automatically opened and closed by a control panel in sync with a loading device which charges automatically a spacer grid to be welded. Meanwhile, a glass cover 510 can be arranged adjacently to the glass window 220 on the top of the base frame 100, the upper part of the glass cover 510 is supported by a cover bracket 512, and the cover bracket 512 is movable horizontally by a driving means including the driving cylinder 511 installed in the base frame 110. Thus the glass cover 510 is arranged to cover the glass window 220. Preferably, a ventilation hole connecting to the welding chamber unit 200 is formed in the side wall inside the flange 221 to which the glass window 220 is fixed, and a ventilation hole is arranged in the upper part of the flange 221. Thus a ventilation valve operated by the glass cover 510 can be arranged. FIG. 6 and FIG. 7 are the enlarged longitudinal section showing respective opening and closing operation of the ventilation valve. With reference to FIG. 6, a ventilation hole 221a connecting to the inside of the welding chamber unit 200 is formed in the side wall inside the flange 221 to which the glass window 220 is fixed. A ventilation valve 222 is arranged at the flow path 221b which is interconnected with the ventilation hole 221a and the inside of the welding chamber unit 200. The ventilation valve 222 is supported by an elastic body 223, and arranged around the flow path. The first airtight member 01 and the second tight member 02 are inserted in the upper part and lower part of the ventilation valve 222 so the ventilation valve 222 can be airtight with the welding chamber unit 200. At this time, the first airtight member 01 comes apart from the inside wall of the welding chamber unit 200 according to the vertical position of the ventilation valve 222 and the ventilation hole 221a and a flow path 221b are interconnected with each other in structure. With reference to FIG. 7, if the glass cover 510 covers the glass window 220, the glass cover 510 comes to press the ventilation valve 222. Thus, as the first airtight member 01 comes apart from the welding chamber unit 200, the ventilation hole 221a and the flow path 221b are interconnected. In this way, vacuum operation is proceeded in the welding chamber unit 200 with the glass window 220 covered by the glass cover 510. Thus, the vacuum operation inside the welding chamber unit 200 can be done without pressure difference for the glass window 220, itself. Then, the vacuum operation is done inside the welding chamber unit 200, and oxygen and moisture etc. are removed inside the welding chamber unit 200, and then argon gas is injected to make the pressure higher than the atmospheric pressure, and then the glass cover 510 is moved to be opened and then laser welding operation is proceeded. FIG. 2 is a rear view of a welding chamber unit in a laser welding apparatus for spacer grid of nuclear fuel assembly. As illustrated in FIG. 2, a welding chamber unit 200 comprises a chamber frame 202. A chamber 201 is installed in the upper part of the chamber frame 202 in which a plurality of driving unit 203 connected by a driving pad 205 and belt are installed to operate tilting and rotation of a welding rotation plate arranged inside the chamber 201. Preferably, a position detection unit which can output electrical detection signal by detecting the standard position of a driving pad 205 can be arranged, the signal from the position detection unit is transmitted to a loading device which charges automatically a spacer grid in the welding chamber unit so that a spacer grid can be charged only at the right position by the welding rotation plate during the automatic loading process. Thus, it can prevent a malfunction that may occur in the automatic loading process of the spacer grid. This position detection unit can be provided by groove 205a and a light sensor 206 installed in the chamber 201 for detecting the position of the groove. There is no limit to a sensor for detecting the position; a variety of known sensors can be used for detecting position. In this way, a driving unit 203 for tilting and spinning a welding rotation unit is installed not in a base frame but a chamber frame 202. Thus, belt length can be shortened, which is advantageous in terms of backlash, and separation of the welding unit from the base frame for maintenance can be easy by excluding structural connection between the base frame and the welding chamber unit. In the lower part of the chamber frame 202, the guide block 204 corresponding to the guide rail 110 (See FIG. 3) is arranged and the groove 204a is formed in the guide block 204. Also, the chamber frame 202 can be moved horizontally along the chamber installment hole in guidance by the guide rail 110. Again with FIG. 1, the laser welding unit 300 comprises a vertical stage 310 which can be vertically driven by mounting an optical adapter with which welding is performed to a part to be welded using an optical cable connected to a laser generation unit, a horizontal table 320, 330 for enabling the vertical stage 310 to be driven horizontally on xy plane. The vertical stage 310 can be vertically moved up and down by a guidance meaning such as LM guide, and light source and an image sensor can be added to the vertical stage in order to monitor the welding status. In the present exemplary embodiment, the horizontal table 320, 330 comprises x-axis table 320, and y-axis table 330. In here the vertical stage 310 is settled on the upper part of the x-axis table 320, x-axis table 320 is settled on the upper part of the y-axis table 330. The x-axis table 320 can be moved in x-axis direction on the upper part of the y-axis table 330, and the y-axis table 320 can be moved in y-axis direction. A servo motor is arranged to drive the vertical stage 310 and the horizontal table 320, 330 respectively so that their positions can be precisely controlled. A locking member 410 is for fixing the welding chamber unit 200 to the base frame 100, and can be provided by a locking block 411, a locking arm 412, and a locking pin 413. The locking block 411 is arranged to be protruded in the lower part of the welding chamber unit 200. The locking arm 412 is arranged to meet the base frame 100 and support the locking block 411. The locking fin 413 restricts the rotation of the locking arm 412 by being assembled to the base frame 100. In the locking arm 412 a handle bar 412a is arranged to protrude in rotation axis direction so that rotation of the locking arm 412 can be operated by operating the handle bar 412a. In reference with FIG. 3, the welding chamber unit 200 is horizontally moved along the guide rail 110 of the base frame 100, and the welding chamber unit 200 is located forward to the damper 120 by moving along the guide rail 110. And then, the welding chamber unit 200 can be fixed by rotating the locking arm 412 to meet the locking block 411 and putting the locking pin 413 into the base frame 100. Meanwhile, the welding chamber unit 200 can be detached at the rear of the base from 100 in inverse order of assembly. FIG. 4 is a perspective view of a laser welding apparatus according to the present invention. In reference with FIG. 4, a locking member 420 according to another exemplary embodiment is installed in the floor surface of the chamber installment hole and the welding chamber unit can be fixed by air pressure or oil pressure. In reference with FIG. 5A, a locking member 420 according to another exemplary embodiment comprises a locking cylinder 421 for driving the cylinder load 422 back and forth, a bracket 423 installed on the floor surface of the chamber installment hole, and a locking lever 424 for supporting the welding chamber unit by being assembled to meet a bracket 423 and driven to rotated by the cylinder load 422. The locking cylinder 421 and the bracket 423 are installed in the upper part of the base plate 425, the base plate 425 can be fixed on the floor surface of the chamber installment hole by welding or installed by a locking member such as a bolt. The end of the cylinder load 422 is assembled to a hinge pin h1 so that it can be rotated with the locking lever 424, the middle of the locking lever 424 is assembled so that it can be rotated by the bracket 423 and the second hinge h2. Preferably, a roller 426 of free meeting can be arranged in the end of the locking lever 424 which is contacted to the welding chamber unit. As shown in FIG. 5B, if the signal of air pressure or oil pressure is applied to the locking cylinder 421, the locking lever 424 is rotated counter-clockwise by the cylinder load 422 and accordingly the roller 426 of the end of the locking lever 424 pressurizes the side wall of the rear end of the welding chamber unit 200 which is located on inside of the chamber installment hole, thereby fixing the welding chamber unit 200 securely. In the present exemplary embodiment, for rotary drive of the locking lever the cylinder driven by the signal of air pressure or air pressure was taken for example, however the present invention is not limited by this. Rotary drive can be operated by using a motorized actuator. Besides, the welding chamber unit 200 which is detachably mounted on the base frame 100 adopts not only a structural locking member 410 but a locking member 420 driven independently by oil pressure, air pressure or electrical signal. Thereby the welding chamber unit 200 can be fixed reliably. The present invention described above is not limited by the aforementioned embodiments and the accompanying drawings. It will be apparent to those who are skilled in the art that various substitution, variation and modification without departing from the scope of the spirit of the invention are possible.
048329010	summary	BACKGROUND OF THE INVENTION This invention relates to nuclear reactors and, more particularly, to a method for repairing bent mixing vanes found in the fuel assemblies of nuclear, pressurized-water reactors. As described in co-assigned U.S. Pat. No. 3,719,560 issued to MAYERS et al., located within a conventional nuclear, pressurized-water reactor is a plurality of parallel fuel rod supporting grids. These grids are made up of a plurality of thin bands or straps arranged in a lattice configuration to form individual fuel cells. Each fuel rod containing nuclear fuel pellets is inserted through a fuel cell within a grid. Each fuel rod is held in a fixed relationship within the fuel cell by a plurality of springs (see, e.g., co-assigned U.S. Pat. No. 3,379,618 issued to FRISCH), and punched, metal dimples arranged along the inner faces of each fuel cell. Each fuel rod is supported by being lightly pushed against the dimples via one or more of the springs. The grids also include metal fins or "mixing vanes" at the corners thereof, perpendicular to the grid straps, which may lightly abut, but do not mechanically support, the fuel rod. Mixing vanes are intended to disturb fluid flow, i.e., cause a swirling action to improve heat transfer and reduce the potential for hot spot temperatures at the fuel rods. During individual fuel rod removal and reassembly, e.g., at scheduled maintenance, the mixing vanes can be damaged, i.e., bent. A bent mixing vane interferes with normal fuel rod reinsertion, i.e., exerts bending moment on the fuel rod, thus causing the fuel rod to deflect and bow out of its intended path. Deflection causes the fuel rod to "hang-up" on the first grid below the grid with the bent mixing vane. If a fuel rod is hung up, it has been usual practice to remove the fuel rod and not to replace it. As a result, a void is left where fluid can leak through. The performance of the fuel assembly is degraded as a result of deleting one or a plurality of fuel rods which cannot be reinserted. In light of the above, a method for straightening bent mixing vanes is desired so that fuel rods can be reliably reinserted. SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a nuclear reactor fuel assembly mixing vane repair method which is capable of straightening bent mixing vanes efficiently and quickly, without having to dismantle the nuclear reactor and without having to introduce a man in the area of the bent mixing vane. It is another object of the present invention to provide a nuclear reactor fuel assembly mixing vane repair method which causes little interruption of nuclear reactor scheduled maintenance, is relatively simple in construction and steps, respectively, and does not significantly increase costs related to nuclear reactor operation or maintenance. To achieve the foregoing and other objects of the present invention, and in accordance with the purpose of the invention, there is provided herein a nuclear reactor fuel assembly mixing vane repair method preferably using a unique tool and a related tool handling device. The tool is made up of an elongated tube with a housing containing two sets of high-strength blades remotely movable between closed and opened positions. The tool is inserted into a fuel cell detected as having a grid with a bent mixing vane therein via the tool handling device to a location below the damaged grid with the blades in the closed position. The blades are then remotely opened via a cable and rod combination within the apparatus, and the tool is withdrawn. As the tool is withdrawn, a blade abuts the bent mixing vane and bends it back close to its original position. After straightening of the bent mixing vane, the blades are closed and the tool is fully extracted from the fuel cell. Once the tool is fully extracted, the fuel rod can again be reliably inserted into the repaired fuel cell. The method includes the steps of: introducing the apparatus with the blades closed below the damaged grid; opening the blades as the apparatus is withdrawn to abut and straighten the bent mixing vane; closing the blades; and fully extracting the apparatus from the fuel cell.
050911201	description	EXAMPLE 1 This example illustrates the two activation variants during the process according to the invention. A diameter 15 mm, length 10 cm uranium bar was oxidized in the presence of air at 600.degree. C. for 8 h. This gave a coarse U.sub.3 O.sub.8 powder crushed until a powder with an average grain size of approximately 27 .mu.m was obtained. This powder was subdivided into two parts. The first part (test 1) was activated by passing into a fluidized bed gas jet mill to give a powder with an average grain size of approximately 2 .mu.m. It was then reduced to UO.sub.2 by a mixture of H.sub.2 (20 l/min) and N.sub.2 (8 l/min) at 600.degree. C. for 5 h. The UO.sub.2 powder obtained was passivated at 50.degree. C. for 31/2 hours by an air-nitrogen mixture progressively enriched with air to 37% by volume. Its specific BET surface was then 1.74 m.sup.2 /g, its average grain size 2.1 .mu.m (laser grain size distribution carried out with the aid of the CILAS apparatus) and its apparent specific mass was 1.48 g/cm.sup.3. The uranium oxide powder obtained with the characteristics described hereinbefore was shaped by compacting and then fritted at 1740.degree. C. for 3 h under hydrogen. The density results of the fritted pellets are between 96.62 and 97.11% of the theoretical density of the uranium oxide and appear in table 1 (test 1). The second part (test 2) of the crushed U.sub.3 O.sub.8 powder was firstly reduced to the UO.sub.2 state and passivated under the same conditions as hereinbefore, followed by activation with the gas jet mill under the following conditions: Milling pressure, 6 bars relative at the end of the test, turbine rotation speed: 15,000 r.p.m. The uranium oxide powder obtained had a specific surface of 2.04 m.sup.2 /g, an average grain size of 0.8 .mu.m (CILAS laser granulometer) and an apparent specific mass of 2.03 g/cm.sup.3. The powder was shaped and fritted under the same conditions as in test 1. The density results of the fritted pellets are between 96.85 and 97.03% of the theoretical density and appear in table 1 (test 2). TABLE 1 ______________________________________ UO.sub.2 before Crude Fritted pellet compacting: Compacting pellet density Test specific surface pressure density % of theoretical No. m.sup.2 /g MPa t/cm.sup.2 g/cm.sup.3 density ______________________________________ 1 1.74 290 2.96 6.45 96.62 368 3.75 6.65 96.95 425 4.34 6.81 97.11 2 2.04 290 2.96 6.49 96.85 368 3.75 6.65 96.94 425 4.34 6.78 97.03 ______________________________________ It should be noted that in this example the compacting pressures are particularly low, but still correspond to crude and fritted densities well above the normal. EXAMPLE 2 This example compares pellets obtained without an activation treatment and those obtained with an activation treatment, the results being given in table 2. Firstly a metallic uranium bar was oxidized with air at a temperature between 450.degree. and 550.degree. C. for 8 h. This powder was crushed to 10 .mu.m in the manner described in example 1 and then divided into two parts (batches 1 and 2). The first part (batch 1) was reduced under 50% hydrogen: 50% nitrogen at 600.degree. C. for 41/2 hours and then screened to 250 .mu.m. Its specific surface was 1.05 m.sup.2 /g. Its average grain size was 7 .mu.m (Sedigraph sedimentation granulometer) and its apparent specific mass was 2.06 g/cm.sup.3. The thus obtained uranium oxide powder was subdivided into two further batches: Batch 3 was directly shaped without granulation and then fritted under hydrogen at 1700.degree. C. for 4 h. The densities of the fritted pellets were between 87.35 and 89.26% of theoretical density, despite the good crude densities (table 2, test 3). Batch 4 was granulated and then shaped and fritted under the same conditions as batch 3. Thus, optimum conditions existed for obtaining good densities of the fritted pellets. The fritted densities were between 89.26 and 89.58% of the theoretical density (table 2, test 4). They are better than the previous values, but are still inadequate. The second part (batch 2) of the coarsely milled U.sub.3 O.sub.8 powder was firstly reduced to the state UO.sub.2 by treatment under hydrogen identical to that carried out for batches 3 and 4. It was then activated by an oxidation-reduction treatment under the following conditions: ______________________________________ Oxidation: temperature 400.degree. C. atmosphere air (10 m.sup.3 /h) residence time 6 h Reduction: temperature 600.degree. C. atmosphere H.sub.2 (3 m.sup.3 /h) + N.sub.2 (3 m.sup.3 /h) residence time 6 h. ______________________________________ The powder obtained had an average grain size of 4.8 um (Sedigraph granulometer) a BET specific surface of 3.49 m.sup.2 /g and an apparent specific mass of 1.38 g/cm.sup.3. It was then directly shaped without prior granulation and then fritted in the manner described hereinbefore (H.sub.2, 1700.degree. C., 4 h). The fritted densities obtained were between 95.83 and 96.73% of the theoretical density (table 2, test 5). Table 2 also shows the strength of the crude pellets, which are generally shaped like cylinders of limited height. The test consists of inserting the pellet between two parallel planar jaws bearing on two diametrically opposite generatrixes of the pellet and measuring the force necessary for breaking, the value being given in table 2. TABLE 2 ______________________________________ Fritted UO.sub.2 be- pellet fore com- density, pacting: Crude % of Strength of specific Compacting pellet theoret- crude Test surface pressure density ical pellets No. m.sup.2 /g MPa (t/cm.sup.2) g/cm.sup.3 density daN ______________________________________ 3-1 1.05 200 (2.04) 5.60 87.35 3.4 3-2 1.05 242 (2.47) 5.80 88.17 4.3 3-3 1.05 303 (3.09) 5.80 88.92 7.0 3-4 1.05 345 (3.52) 6.10 89.26 10.0 4-1 1.05 187 (1.91) 5.60 89.26 3.4 4-2 1.05 229 (2.34) 5.80 89.47 4.6 4-3 1.05 290 (2.96) 6.00 89.34 6.5 4-4 1.05 332 (3.39) 6.20 89.58 7.5 5-1 3.49 479 (4.89) 5.50 95.87 58.3 5-2 3.49 526 (5.37) 5.80 96.30 92.6 5-3 3.49 588 (6.00) 6.00 96.49 115.8 5-4 3.49 684 (6.98) 6.20 96.73 124.2 ______________________________________ The powder of example 2, test 5, according to the invention, led to pellets with remarkable characteristics. The crude pellets are very strong, which is an advantage from the handling standpoint. Most of the fritted densities are above 96% and in all cases exceed the minimum required, whereas, without activation, it was not possible to obtain 90% of the theoretical density, even with a granulation operation.
049960210	claims	1. In a nuclear fuel assembly which includes an upper end fitting and a lower end fitting spaced therefrom and connected thereto by a plurality of elongated guide tubes of one alloy having an open upper end and a closed lower end with spaced fuel element retaining grids mounted on the guide tubes therebetween, the closed lower ends of said guide tubes including a threaded central passageway and the attachment of said guide tubes to said lower end fitting of another alloy being characterized by: an externally threaded bolt with a first end threadably received in said threaded central passageway of the lower end of said guide tube and a head at the other end on the side of the lower end fitting opposite said guide tube; an interruption in the external threads of said bolt which forms a groove which communicates the interior of the guide tube with the side of the lower end fitting opposite said guide tube and enhances its frictional engagement with said threaded central passageway, thereby to hold and attach said guide tube and lower end fitting firmly together, even through a series of temperature cycles. an externally threaded stainless steel bolt with a first end threadably received in said threaded central passageway of the lower end of said zircaloy guide tube and a head at its other end on the side of the stainless steel lower end fitting opposite said guide tube; an interruption in the external threads of said stainless steel bolt which forms a groove which communicates the interior of the zircaloy guide tube with the side of the stainless steel lower end fitting opposite said guide tube and enhances its frictional engagement with said threaded central passageway, thereby to hold and attach said zircaloy guide tube and stainless steel lower end fitting firmly together, even through a series of temperature cycles. 2. The attachment of said guide tubes to said lower end fittings of another alloy of claim 1 being characterized further in that said bolt is of substantially the same alloy as said lower end fitting. 3. The attachment of said guide tubes to said lower end fittings of another alloy of claim 1 being characterized further in that said bolt groove is a longitudinal cut made parallel to the bolt axis. 4. The attachment of said guide tubes to said lower end fittings of another alloy of claim 1 being characterized further in that said bolt includes an opening in its head. 5. The attachment of said guide tubes to said lower end fittings of another alloy of claim 1 which is characterized by said other alloy being stainless steel and said one alloy of said guide tubes being zircalloy. 6. The attachment of said guide tubes to said lower end fittings of another alloy of claim 5 further characterized by a zircalloy plug closing the lower end of said guide tubes and defining said threaded central passageway. 7. The attachment of said guide tubes to said lower end fittings of another alloy of claim 6 further characterized by a cup attached between the lower end fitting and the zircalloy guide tube by means of said bolt. 8. The attachment of said guide tubes to said lower end fittings of another alloy of claim 7 further characterized in that said cup is of stainless steel. 9. In a nuclear fuel assembly which includes an upper end fitting and a stainless steel lower end fitting spaced therefrom and connected thereto by a plurality of elongated guide tubes of a zircaloy alloy having an open upper end and a closed lower end with spaced fuel element retaining grids mounted on the guide tubes therebetween, the closed lower ends of said guide tubes including a threaded central passageway and the attachment of said guide tubes to said lower end fitting being characterized by:
040574687	description	DESCRIPTION OF THE PREFERRED EMBODIMENT The liquid metal cooled nuclear reactor core shown in FIG. 3 comprises a plurality of upstanding fuel element sub-assemblies 21 closely arranged side-by-side and secured at their lower ends to fuel support means 22. The support means 22 comprises a diagrid 23 and a plurality of fuel sub-assembly carriers 15 each of which is adapted to carry a group of fuel element sub-assemblies. The diagrid 23 also serves as a distributor for coolant flow to the fuel element sub-assemblies the coolant being delivered to the diagrid 23 by way of pipes 25. At the centre of each group of fuel element sub-assemblies 21 there is a control rod guide tube 24 and the entire assembly of fuel element sub-assemblies and control rod guide tubes is surrounded by a plurality of neutron shield rods 27. A fuel charge chute and fuel storage rotor are shown at 28 and 29. On assembly of the core the fuel element sub-assemblies 21 are free standing with small clearances between neighbouring assemblies. The fuel element sub-assemblies 21 are arranged in groups of sub-assemblies and the upstanding sub-assemblies of each group are disposed about a central member 14 (such as a control rod guide tube 24) of the group and are arranged to lean on the central member. The arrangement is shown in FIG. 2 and the sub-assemblies and central members, designated 13 and 14 in FIG. 2, plug into the carrier 15 associated with the core supporting diagrid. Contact between each sub-assembly and the central member is through a pad 16 attached to the sub-assembly. The inertia damper is shown attached to the top of a wrapper 17 of the sub-assembly and the upper sleeves 2 of the sub-assemblies, in combination, provide an upper shield for the reactor core. The inertia damper shown in detail in FIG. 1 comprises a cylindrical tubular spine 1 having upper and lower sleeves 2, 3. The lower sleeve 3 is welded to the spine 1 at 4 and is of hexagonal shape to provide an end plug for the hexagonal wrapper of a fast breeder reactor sub-assembly; the lower sleeve 3 has a flange 5 for abutting the end of the wrapper. The upper sleeve 2 is of massive steel to provide neutron shielding of hexagonal cross-section and has a cylindrical bore 6 there being a radial spacing 7 between the spine 1 and the upper sleeve 2. The upper and lower sleeves 2, 3 are resiliently coupled together by a bellows unit 8 and the lower end of the upper sleeve 2 has six spaced radial ducts 9 for enabling liquid metal coolant to flood the radial spacing 7. The spine 1 has a diverging tubular extension 10 attached to its upper end and the upper sleeve 2 has a complementary diverging bore 11. The sleeve 2, being captive, is retained on the spine by means of six radially extending retaining pegs 12. In operation, the reactor core is submerged in a pool of liquid metal coolant which is flowed upwardly through the sub-assembly wrappers in heat exchange with fuel pins therein. The radial spacings between the sleeves and the spines are flooded with liquid sodium so that when the upper sleeves vibrate the sodium in each radial spacing is forced from one side of the radial spacing to the other and its resistance to this motion provides a damping force. The damping force changes with the amplitude at a slow rate initially but finally at a very rapid rate so that, for average amplitudes, the damping rate is higher than that predicted for zero amplitude. Thus as a result of hardening of the damping rate with displacement of the upper sleeve relative to the spine, the final damping rate is so high that metal-to-metal contact between spine and upper sleeve is very unlikely. There is also a tendency for the upper sleeve to pump itself into concentricity with the spine even though concentricity may not be achieved in manufacture. The expected reduction in sub-assembly vibration amplitudes using such a device is in the region of 3 to 10 times. In inertia damping means for a fuel element sub-assembly wherein the upper sleeve has a bore of 90 mm nominal and parallel length 350 mm, a radial clearance between spine and upper sleeve of 1.20 mm is considered to be satisfactory.
	description	The invention relates generally to the use of information technology in industrial processes and more specifically to mass manufacturing processes. The problem addressed by the present invention is errors in mass manufacturing processes. Minimizing costs and improving product quality is a goal of any company developing products. To the manufacturer one of the most costly aspects in a product's life cycle is servicing product defects after the product has left manufacturing. Present methods use quality control tests on a manufactured item that are done by a single department such as a quality control department. Such tests are expensive to perform and it is also expensive and difficult to use the results. One present technology is Orthogonal Defect Classification (ODC) which addresses software defects found during development and by customers, but only software, not hardware and only defects found during development. Another known method is Orthogonal Problem Classification (OPC), which addresses software problems reported by customers, but does not address mass manufacturing industry, it only addresses software. Another technology, Warranty Management Solutions (WMS) facilitates handling by management of warranty related data but provides no feedback to modify production. Quality Control testing products before product release provide no feedback mechanism back to production and design facilities. In their report B. Freimut, C. Denger, and M Ketter, “An Industrial Case Study of Implementing and Validating Defect Classification for Process Improvement and Quality Management,” Proceedings of the 11th IEEE Software Metrics Symposium (METRICS 2005), Sep. 19-22, 2005, pages 19-29), provide a general description of a consulting-like engagement where they provide suggestions to a production organization based on an analysis of product defects. They do not provide any specifics of either their defect classifications or their analysis methods. In his report, Jack Silberman, “Robot Orthogonal Defect Classification Towards an In-Process Measurement System for Mobile Robot Development,” doctoral dissertation, Tech. Report CMU-RI-TR-99-05, Robotics Institute, Carnegie Mellon University, January, 1998, describes how the ODC methodology can be extended to determine and provide production process modification suggestion to an organization creating mobile robots, these robots including both hardware and software. He does not provide any description of how the ODC methodology can be used to support mass manufacturing of products that include both hardware and software. Therefore, there is a need for a solution that overcomes the deficiencies of the prior art. Briefly according to an embodiment of the invention, to solve the above-discussed problems a product service event classification (PSEC) method is used. The computer-implemented PSEC method of optimizing one or more of the production or testing processes in a mass manufacturing industry comprises steps of: collecting error data relating to a product at a plurality of points along its production and distribution chain; classifying the error data into categories of defects to provide classified error data; analyzing relationships among the classified error data; and suggesting modifications to one or more of the production or testing processes based on the analysis. The foregoing and other aspects, features, and advantages of the invention will become more apparent from the following description and from the claims. An embodiment of the invention is a method of optimizing the production and testing of products produced by a mass manufacturer, i.e. where many (virtually) identical copies of a given product are produced in exactly the same way. This is in contrast to cases where heroic, unique methods are used each time. The preferred embodiment will describe how the current invention is used to optimize the production and testing processes of a mass manufacturing plant 3010, whose products 1000 are sold by a product dealer 3020 and repaired by a product service provider 3030 (as will be described in detail with references to FIGS. 1-5). FIG. 1 is a component block diagram of an example of the product 1000 produced, sold and serviced in the preferred embodiment. As shown, the product 1000 includes a subsystem 1010, which includes apart 1020. Although only a single subsystem 1010 and a single part 1020 are shown, the current invention is also applicable to products 1000 that include two or more subsystems 1010 and subsystems 1010 that include two or more parts 1020. An example of such a product is a personal computer (product), a communication subsystem (the subsystem), and a chipset (port) according to a protocol such as the Ethernet. FIG. 2 is an illustrative flow diagram of the mass manufacturing industry's production, testing, and delivery processes 2000 according to an embodiment of the invention. As shown, the overall process 2000 begins at step 2010 where the design of the product 1000 is created. Next, in step 2020, the design is reviewed, and, if any errors (defects) are identified, control continues at step 2010, where the identified design error is corrected. Otherwise, in step 2030, an instance of the part 1020 is built, followed by step 2040 where the instance of the part 1020 is tested. If an error is identified, then step 2050 checks whether it is a part error. If so, control continues at step 2030 where the error is corrected. If the error is not a part error, then it must be design error and so control continues at step 2010 where the design is corrected to overcome the error. If no part error is found in step 2040, then control continues at step 2060 where an instance of the subsystem 1010 is built. Next, the instance of the subsystem 1010 is tested in step 2070. If an error is detected, then in step 2080 the error is checked to determine if it one with the subsystem. If so, control continues at step 2060 where the subsystem error is corrected. If the detected error is not one with the subsystem, then control continues at step 2050, which determines how the detected error, either a part or design error, is handled, as described above. If step 2070 does not detect any errors, then step 2090 is executed, where an instance of the product 1000 is built, following which the product 1000 instance is tested in step 2100. If an error is detected, then in step 2110 the error is checked to determine if it one with the product. If so, control continues at step 2090 where the product error is corrected. If the detected error is not one with the product, then control continues at step 2080, which determines how the detected error, either a subsystem, part or design error, is handled, as described above. If step 2100 does not detect any errors, then step 2120 is executed, where an instance of the mass manufactured product 1000 is created using the mass manufacturing process (e.g., including but not limited to an assembly line, and robotics), following which the mass manufactured product 1000 instance is tested in step 2130. If an error is detected, then in step 2140 the error is checked to determine if it one with the mass manufacturing process (e.g., the bolts that hold the wheels on are not being sufficiently tightened). If so, control continues at step 2120 where the mass manufacturing process error is corrected (e.g., wheel bolts are screwed on more tightly). If the detected error is not one with the mass manufacturing process, then control continues at step 2110, which determines how the detected error, either a product, subsystem, part or design error, is handled, as described above. If step 2130 does not detect any errors, then step 2120 is executed, where the instance of the mass manufactured product 1000 is transported to the Product Dealer 3020 (described in detail with reference to FIG. 3). Once delivered, mass manufactured product 1000 instance is tested in step 2160. If an error is detected, then in step 2170 the error is checked to determine if it one with the transportation process (e.g., the product's paint scratched by the vehicles that carry the product to the Product Dealer 3020). If the error is one with the transportation process, control continues at step 2150 where the transportation process error is corrected (e.g., the products are covered with a protective wrap before being shipped). If the detected error is not one with the transportation process, then control continues at step 2140, which determines how the detected error, either a mass manufacturing process, product, subsystem, part or design error is handled, as described above. Skilled artisans will appreciate that any of test processes other than Design Review 2020 (i.e., Part Test 2040, Subsystem Test 2070, Product Test 2100, Mass Manufacturing Test 2130 and Transportation Test 2160) could include stress testing (i.e., operating a given component [i.e., part, subsystem or product] up to or beyond one or more of its specified maximum limits) and environmental testing (i.e., testing a given component in one or more of is specified maximally adverse conditions). So, for example, the Part Test 2040 for tires could include running the inflated tires repeatedly of a series of bumps (for stress testing). Similarly for environmental testing, the Manufacturing Test 2130 could include driving each car (cars being the product) through 110 degree (Fahrenheit) heat. FIG. 3 depicts a network topology 3000 providing an execution environment implementing the functionality of a system for the current embodiment. The network topology 3000 includes: a Mass Manufacturing Plant 3010; a Product Dealer 3020; a Product Service Provider 3080; a Client D 3130, and a PSEC Server 3050. The Mass Manufacturing Plant 3010 comprises a location, including, but not limited to a building, or set of buildings, co-located or geographically distributed, wherein a Client A 3100 and an instance of mass manufactured product 1000 (MMP1 3060) is located. This location 3010 is where instances of the mass manufactured product 1000 are created. The Product Dealer 3020 comprises a location, including, but not limited to a building, or set of buildings, co-located or geographically distributed, wherein a Client B 3110 and an instance of mass manufactured product 1000 (MMP2 3070) is located. This location 3020 is where instances of the mass manufactured product 1000 are sold. The Product Service Provider 3030 depicts a location, including, but not limited to a building, or set of buildings, co-located or geographically distributed, wherein a Client C 3120 and an instance of mass manufactured product 1000, MMP3 3080 are located. This location 3030 is where instances of the mass manufactured product 1000 are repaired or serviced. Each of Clients A-D 3100-3130 and the PSEC Server 3050 are able to communicate with each other via a network 3090. The network 3090 comprises: the Internet, an internal intranet, or a public or private wireless or wired telecommunication network. Skilled artisans will appreciate that although only one each of the Mass Manufacturing Plant 3010, the Product Dealer 3020 and the Product Service Provider 3030 are depicted in FIG. 2, other embodiments are also applicable to cases where there are a greater number of one or more of these entities 3010-1030. Skilled artisans will also appreciate that other embodiments are also applicable to cases where the three entities 3010-3030 are co-located. Each of Clients A-D 3100-3130 enable an authorized user to interact with the PSEC Server 3050 (as will be discussed in further detail below) with reference to FIGS. 3-5. An example of a platform that supports the Clients A-D 3100-3130 includes any computing node that can act as web client (i.e., runs a web browser application and can communicate with the PSEC Server 3050 via the network 3090). Such software comprises Microsoft's Internet Explorer®. Still another example of a platform that supports the Clients A-D 3100-3130 includes, but is not limited to: an IBM ThinkPad running on a Windows based operating system such as Windows XP, or like operating system. Other contemplated operating systems include Linux, UNIX, and the like. Clients A-D 3100-3130 may also include network-connectable mobile (i.e., portable) devices such as some cellular telephones (i.e., devices which function as a cellular telephone and execute network applications, like web browsers). Although only four Clients A-D 3100-3130 are shown in FIG. 1, the current invention is also applicable to any number of client nodes greater than or equal to 1. Further, while the preferred embodiment includes a Web-based (i.e., HTTP) client 3100-3130, other forms of network communication are also applicable, such as a sockets-based client/server architecture, e.g., implementing secure sockets layer (SSL) or like network communications protocols. Skilled artisans will appreciate that the current invention is also applicable to cases where there is only a single client node, which resides on the same machine as the PSEC Server 3050, thereby eliminating the need for any network communication at all. FIG. 4 is a block diagram of the PSEC Server 3050. The PSEC Server 3050 is a computing node that acts as an HTTP server. The PSEC Server 3050 includes a CPU 4000, a network interface 4010, and a storage device 4020 such as a disk or data access storage device (DASD), and memory 4030, such as RAM. The network interface 4010 allows the PSEC Server 3050 to communicate with other network connected nodes via the network 3090. Such interfaces include, but are limited to: Ethernet, and wireless IP (Internet Protocol, e.g., LEAP, CDMA or WAP). In the present embodiment, the PSEC Server 3050 also includes PSEC Server logic 4040, which is embodied as computer executable code that is loaded into memory 4030 (for execution by CPU 4000) from a remote source (e.g., over the network 3090 via the network interface 4010), local permanent optic (CD-ROM), or from the storage device 4020 (e.g. disk or DASD). The PSEC Server logic 4040 stored in the memory 4030 includes an HTTP Server Handler 4050, which includes a PSEC Client Applet 4060 and a PSEC Client Interface Servlet 4070. The PSEC Server logic 4040 further includes a Defect Data Collection Handler 4080, a Defect Data Classification Handler 4090, an Analysis Handler 4100, a Suggested Actions Report Handler 4110, and a PSEC Server Database 4120. The HTTP Server Handler 4050 is an application that can respond to HTTP communications, comprising: the WebSphere™ product sold by IBM. The PSEC Client Applet 4060 and PSEC Client Interface Servlet 4070 together enable an authorized end-user to communicate with the Defect Data Collection Handler 4080, Defect Data Classification Handler 4090, Analysis Handler 4100, and Suggested Actions Report Handler 4110. When the end-user wants to interact with the PSEC Server 3050, the end-user first downloads the PSEC Client Applet 4060 to a web browser running on their client, Clients A-D 3100-3130. To download the PSEC Client Applet 4060, the end-user must provide sufficient credentials (e.g., user ID and password). After the PSEC Client Applet 4060 has been downloaded and enabled, the PSEC Client Applet 4060 communicates directly with the PSEC Client Interface Servlet 4070, which is executing in the HTTP Server Handler 4050. The HTTP Server Handler 4050, in turn, communicates locally with the other handlers 4090-4110 executing on the server 4050. Skilled artisans will recognize that this applet/servlet paring is well known in the art (e.g., see Jason Hunter with William Crawford, Java Servlet Programming (Sebastopol, Calif.: O'Reilly & Associates, Inc., 1988), pp. 277-337). Skilled artisans will also appreciate that the communication between the Clients A-D 3100-3130 and the handlers 4090-4110, in other embodiments can be implemented using other socket-based applications. The PSEC Server Database 4120 allows the PSEC Server 3050 to store, modify, and delete data related to misinformation, usage patterns, users, and online community servers. A detailed description of the information maintained by the PSEC Server Database 4120 is given below. The PSEC Server Database 4120 can be implemented using database tools such as the DB/2 product sold by IBM, and like database platforms. One with skill in the art will appreciate that in other embodiments, the PSEC Server Database 4120 can be a service that runs on another server and is accessed by the PSEC Server 3050 via the network 3090. The Defect Data Collection Handler 4080 enables the current invention to gather a set of defect data regarding the mass manufactured product 1000 and the processes of its production, testing and delivery 2000. This data includes but is not limited to: Defects founds during product 1000 development, such as design defects discovered during the design review 2020, Defects found in instances of the product 1000 after manufacturing 2110, but before delivery, such as cases where the mass manufacturing process 2120 has failed to tighten the bolts that hold the wheels on. Defects that occur as a result of the transportation process 2150, such as paint being chipped during shipping due insufficient secure restraints in the delivery vehicle, and Defects found at the Product Service Provider 3030, such as a case where an unreliable tire is identified by the fact that many instances of the product 1000 are brought in where one or more of the tires has burst during operation.Note that this data comes from in-process and post delivery. All such data is stored in the PSEC Server Database 4120. The Defect Data Classification Handler 4090 takes all of the stored defects and either types or adds types to each defect, storing results in the PSEC Server Database 4120. This set of attributes categories and associated values is called the PSEC scheme. It is it uses some of the categories and values of the ODC scheme, as well as adding new categories and new values. In the current invention there are two types of defect attributes: opener data, that which is known when the defect is first discovered, and closer data, which is only available after a given defect has been resolved. In the current invention, the opener data associated with each that is stored in the PSEC Server Database 4120 comprises: Unique ID, which can be used to distinguish one defect from all others. VIN (Vehicle Identification Number), which, in the preferred embodiment is the unique encoded alphanumeric string that every automobile has assigned to, this string not only including a unique ID (serial number) for the car, but also indication the car's make, model, and manufacturing plant (for details, see http://en.wikipedia.org/wiki/VIN). Ownership Duration indicates long the product was owned before the defect occurred. In one embodiment of the current invention these revealing conditions include, but are not limited to (note that they are listed in order of shortest to longest): Short—Year or less, Medium—1 to 5 years, Long—5 years to disposal. One skilled in the art will appreciate that the current invention also includes embodiments in which the Ownership Duration attribute has more or less than 3 values, and in which the values differ from those above (values applicable for the automotive industry). Such alternatives are needed for other mass manufacturing industries, such as the aeronautics industry, whose product: planes are owned and used for well over 5 years, on average. Thus the Long value would have to be greater than 5. Such values are also necessary because different industries have warranty periods of different length. Conditions Revealing Defect, indicates must be done to product for the defect to occur. In one embodiment of the current invention these revealing conditions include (but are not limited to): Single Function: execution of single feature, e.g., windshield wipers don't work correctly at any speed. Single Function with Option: execution of a single with some option, e.g. windshield wipers don't work at “slow.” Interaction, execution of multiple functions exposes the defect Sequencing: execution of multiple functions in a specific order. Workload/Stress: operating the entire product 1000 at extreme conditions. Recovery/Exception: testing product's reaction to crashes, e.g., airbags didn't deploy. Startup/Restart: e.g., restarting product 1000. Environmental: executing product in specific environmental condition. Stress: testing extremes at a part 1020 level Open Date indicates when the defect was reported. In-Process indicates whether or not the given defect occurred while the product was being developed. Product Impact indicates the most pronounced impact the defect had on the products. One embodiment of the current invention includes the following (note that they are listed in order or greatest to least importance): Fire Theft Product Inoperable/Damaged Safety Impairment Function Inoperable/Damaged Diminished Aesthetics (looks) Diminished Performance Non Product Impact indicates the most pronounced impact the given defect had on non-product entities. One embodiment of the current invention includes the following Note that values are listed from most to least important): Death—Death occurred due to defect Personal Injury—Personal Injury occurred due to defect Safety Impairment—Product Unsafe to operate Property Damage—Property Damaged occurred due to defect None In the current embodiment, the closer data associated with each that is stored in the PSEC Server Database 4120 comprises: Phase Found indicates where the defect should have been caught. One embodiment of the current invention includes the following. (Note that the values are listed from earlier to later in the overall mass manufacturing process 2000): Design Review 2020, Part test 2040, Subsystem test 2070, Product test 2100, Mass Manufacturing test 2130, and Transportation test 2160. Close Date indicates when the defect was finally corrected Repair Cost indicates how much it cost to fix the given defect. An example of values used by the preferred embodiment includes: Low—Less than $100, e.g., for simple part 1020 replacements and repairs, Medium—$100-$1,000, e.g., for subsystem 1010 replacements and repairs, High—$1,000-$100,000, e.g. for product 1000 replacement, repair and redesign, and Extreme—Greater than $100,000, e.g. for retooling and redesign of mass manufacturing or transportation processes. Part Hierarchy indicates an identification hierarchy for the defective element. One embodiment of the current invention uses the automobile part hierarchy from NHSTA TREAD: Body body:exterior body:exterior:decals body:exterior:exterior trim/moldings body:exterior:paint body:exterior:paint:paint-bumper body:exterior:paint:paint-door body:exterior:paint:paint-fender body:exterior:paint:paint-hood body:exterior:paint:paint-moldings/trim body:exterior:paint:paint-quarterpanel body:exterior:paint:paint-roof body:exterior:paint:paint-tailgate body:exterior:paint:paint-truck bed/box body:exterior:paint:paint-trunk/hatch body:glass body:glass:backglass body:glass:backglass:fixed backglass sealing body:glass:backglass:heated backglass elements body:glass:backglass:liftgate hinges and sealing body:glass:mirrors body:glass:mirrors:exterior mirrors body:glass:mirrors:interior mirrors body:glass:side glass body:glass:windshield body:glass:windshield:windshield sealing body:interior body:interior:carpet/floor mats body:interior:headlining body:interior:instrument panel/console/glove box body:interior:interior trim/panels body:locks/latches body:locks/latches:door body:locks/latches:door:door-front body:locks/latches:door:door-rear body:locks/latches:fuel door body:locks/latches:fuel door:remote release body:locks/latches:glove box/console/storage compartment body:locks/latches:hood body:locks/latches:hood:remote release body:locks/latches:ignition lock and cylinder body:locks/latches:power locks/rke body:locks/latches:tailgate body:locks/latches:tailgate:remote release body:locks/latches:trunk/hatch body:locks/latches:trunk/hatch:remote release body:restraints body:restraints:airbags body:restraints:airbags:airbag module/sensors body:restraints:airbags:clock spring body:restraints:airbags:driver airbag body:restraints:airbags:horn switch and assy body:restraints:airbags:passenger airbag body:restraints:airbags:side airbag/curtain body:restraints:seat belts body:restraints:seat belts:buckles body:restraints:seat belts:child seats body:restraints:seat belts:front belts body:restraints:seat belts:pretensioners body:restraints:seat belts:rear belts body:restraints:seat belts:retractors body:seating body:seating:covers/pads body:seating:headrests body:seating:seat frame body:seating:track/tilt body:seating:track/tilt:manual seat body:seating:track/tilt:power seat body:structure/sheetmetal body:structure/sheetmetal:bumpers body:structure/sheetmetal:cowl body:structure/sheetmetal:door body:structure/sheetmetal:door: door and sideglass sealing body:structure/sheetmetal:door:door-front body:structure/sheetmetal:door:door-rear body:structure/sheetmetal:fenders body:structure/sheetmetal:floorpan body:structure/sheetmetal:hood body:structure/sheetmetal:hood:liftcylinders body:structure/sheetmetal:quarterpanels body:structure/sheetmetal:roof body:structure/sheetmetal:roof:convertible body:structure/sheetmetal:roof:removable/hardtop body:structure/sheetmetal:roof:roof rack/bed accessories body:structure/sheetmetal:roof:sun/moonroof body:structure/sheetmetal:roof:t-top body:structure/sheetmetal:tailgate body:structure/sheetmetal:tailgate:tailgate sealing body:structure/sheetmetal:truck bed/box body:structure/sheetmetal:trunk/hatch body:structure/sheetmetal:trunk/hatch:liftcylinders body:structure/sheetmetal:trunk/hatch:trunk/hatch sealing body:structure/sheetmetal:unibody body:structure/sheetmetal:unibody:static metal sealing body:window mechanisms body:window mechanisms:manual mechanisms body:window mechanisms:power mechanisms chassis chassis:axle (solid) chassis:axle (solid):front axle chassis:axle (solid):rear axle chassis:differential chassis:driveshaft/halfshaft chassis:driveshaft/halfshaft:driveshaft (in-line) chassis:driveshaft/halfshaft:driveshaft (in-line):front driveshaft chassis:driveshaft/halfshaft:driveshaft (in-line):rear driveshaft chassis:driveshaft/halfshaft:halfshaft chassis:driveshaft/halfshaft:halfshaft:front halfshaft chassis:driveshaft/halfshaft:halfshaft:rear halfshaft chassis:frame chassis:parking brakes chassis:service brakes chassis:service brakes:abs/traction control chassis:service brakes:abs/traction control:abs module chassis:service brakes:abs/traction control:hydraulic control unit chassis:service brakes:abs/traction control:sensors/tone rings chassis:service brakes:air brake system chassis:service brakes:brake lines/hoses chassis:service brakes:brake pedal chassis:service brakes:caliper/wheel cylinder chassis:service brakes:hub/wheel bearings chassis:service brakes:master cylinder/booster/hydroboost chassis:service brakes:pads/shoes/linings chassis:service brakes:rotor/drum chassis:steering chassis:steering:steering column chassis:steering:steering gear/rack chassis:steering:steering lines/hoses chassis:steering:steering linkage chassis:steering:steering pump/reservoir chassis:steering:steering wheel chassis:suspension chassis:suspension:active suspension chassis:suspension:air suspension chassis:suspension:alignment chassis:suspension:alignment:front suspension chassis:suspension:alignment:rear suspension chassis:suspension:shock absorbers/struts chassis:suspension:shock absorbers/struts:front suspension chassis:suspension:shock absorbers/struts:rear suspension chassis:suspension:spindles/supports chassis:suspension:spindles/supports:front suspension chassis:suspension:spindles/supports:rear suspension chassis:suspension:springs chassis:suspension:springs:front suspension chassis:suspension:springs:rear suspension chassis:suspension:stabilizers chassis:suspension:stabilizers:front suspension chassis:suspension:stabilizers:rear suspension chassis:transfer case chassis:transfer case:bearings chassis:transfer case:case and housing chassis:transfer case:controls chassis:transfer case:gears chassis:transfer case:seals and gaskets chassis:transfer case:shafts chassis:wheel assy chassis:wheel assy:lugs and studs chassis:wheel assy:spare tire and stowage chassis:wheel assy:tire change/repair chassis:wheel assy:tire change/repair:jack chassis:wheel assy:tire change/repair:lug wrench chassis:wheel assy:tire change/repair:tire repair kit chassis:wheel assy:tire pressure monitoring system chassis:wheel assy:tires chassis:wheel assy:tires:tire bead chassis:wheel assy:tires:tire belts chassis:wheel assy:tires:tire sidewall chassis:wheel assy:tires:tire tread chassis:wheel assy:wheels/rims chassis:wheel assy:wheels/rims:tire valve stem and core chassis:wheel assy:wheels/rims:wheel balance weights chassis:wheel assy:wheels/rims:wheel covers/ornaments electrical electrical:accessories/entertainment electrical:accessories/entertainment:anti-theft electrical:accessories/entertainment:clock electrical:accessories/entertainment:compass/thermometer electrical:accessories/entertainment:mobile communication electrical:accessories/entertainment:navigation system electrical:accessories/entertainment:powerpoint/lighter electrical:accessories/entertainment:reverse sensing electrical:accessories/entertainment:sound system electrical:accessories/entertainment:sound system:antenna electrical:accessories/entertainment:sound system:cd player/changer electrical:accessories/entertainment:sound system:equalizer/amplifier electrical:accessories/entertainment:sound system:radio electrical:accessories/entertainment:sound system:sound system remote control electrical:accessories/entertainment:sound system:speakers electrical:accessories/entertainment:sound system:subwoofer electrical:accessories/entertainment:sound system:tape player electrical:accessories/entertainment:video system electrical:accessories/entertainment:voice control electrical:climate control electrical:climate control:a/c clutch electrical:climate control:a/c compressor electrical:climate control:blower motor electrical:climate control:cables/linkage/ducts electrical:climate control:controls/relays/switches electrical:climate control:heater core/cond/evap electrical:climate control:hoses electrical:climate control:refrigerant electrical:driving controls/multifunction switches electrical:driving controls/multifunction switches:electric tilt steering controls electrical:driving controls/multifunction switches:hazard light switch electrical:driving controls/multifunction switches:headlight dimmer switch/auto-lamp electrical:driving controls/multifunction switches:speed control switches electrical:driving controls/multifunction switches:turn signal switch electrical:driving controls/multifunction switches:wiper/washer controls electrical:instrument/display electrical:instrument/display:amp/voltage gauge electrical:instrument/display:boost gauge electrical:instrument/display:coolant temperature gauge electrical:instrument/display:coolant temperature gauge:coolant temperature sender/receiver electrical:instrument/display:fuel gauge electrical:instrument/display:fuel gauge:fuel gauge sender/receiver electrical:instrument/display:message center electrical:instrument/display:message center:fuel computer electrical:instrument/display:odometer/hour meter electrical:instrument/display:odometer/hour meter:tripminder electrical:instrument/display:oil pressure gauge electrical:instrument/display:oil pressure gauge:oil pressure sender/receiver electrical:instrument/display:oil temperature gauge electrical:instrument/display:oil temperature gauge:oil temperature sender/receiver electrical:instrument/display:speedometer electrical:instrument/display:speedometer:speedometer sender/receiver electrical:instrument/display:tachometer electrical:instrument/display:tachometer:engine speed sensor electrical:instrument/display:warning chimes/lights electrical:instrument/display:warning chimes/lights:4wd/range indicator/warning electrical:instrument/display:warning chimes/lights:abs/traction control warning electrical:instrument/display:warning chimes/lights:airbag warning electrical:instrument/display:warning chimes/lights:brake system warning electrical:instrument/display:warning chimes/lights:charge warning electrical:instrument/display:warning chimes/lights:check engine light/mil electrical:instrument/display:warning chimes/lights:coolant temperature warning electrical:instrument/display:warning chimes/lights:door ajar warning electrical:instrument/display:warning chimes/lights:lamp out indicator electrical:instrument/display:warning chimes/lights:low fuel warning electrical:instrument/display:warning chimes/lights:o/d indicator electrical:instrument/display:warning chimes/lights:oil pressure/level low warning electrical:instrument/display:warning chimes/lights:seat belt warning electrical:lamps/bulbs electrical:lamps/bulbs:back-up lamps electrical:lamps/bulbs:brakelamps/himount brakelamp electrical:lamps/bulbs:cargo/engine compartment lamps electrical:lamps/bulbs:cornering lamps electrical:lamps/bulbs:fog lamps electrical:lamps/bulbs:headlamps/daytime running lights electrical:lamps/bulbs:instrument illumination electrical:lamps/bulbs:interior lighting electrical:lamps/bulbs:license plate lamps electrical:lamps/bulbs:parking/marker lamps electrical:lamps/bulbs:puddle/mirror lamps electrical:lamps/bulbs:turn signal lamps electrical:start-charge electrical:start-charge:alternator/generator electrical:start-charge:battery electrical:start-charge:ignition switch electrical:start-charge:ignition switch:starting interlocks electrical:start-charge:ignition switch:warning chimes electrical:start-charge:starter electrical:start-charge:starter:starter relay electrical:start-charge:starter:starter solenoid electrical:start-charge:voltage regulator electrical:unique electric vehicle components electrical:unique electric vehicle components:ev charging electrical:unique electric vehicle components:ev propulsion electrical:unique electric vehicle components:ev storage/batteries electrical:wiper/washer electrical:wiper/washer:window washer electrical:wiper/washer:window washer:rear glass washer electrical:wiper/washer:window washer:washer pump and reservoir electrical:wiper/washer:window washer:windshield washer electrical:wiper/washer:window wipers electrical:wiper/washer:window wipers:headlight wipers electrical:wiper/washer:window wipers:rear glass wipers/motor electrical:wiper/washer:window wipers:windshield wipers/motor electrical:wiring electrical:wiring:circuit protection electrical:wiring:circuit protection:distribution box electrical:wiring:circuit protection:fuse box electrical:wiring:circuit protection:fuses/fusible links electrical:wiring:connectors electrical:wiring:entertainment/accessory wiring electrical:wiring:exterior lighting wiring/switches electrical:wiring:ground wires electrical:wiring:instrument panel wiring electrical:wiring:main body wiring electrical:wiring:start-charge wiring electrical:wiring:trailer tow wiring powertrain powertrain:aux/pto powertrain:engine powertrain engine:accel pedal/linkage/controls powertrain:engine:accessory drive powertrain:engine:accessory drive:belts powertrain:engine:accessory drive:pulley/tension powertrain:engine:air induction powertrain:engine:air induction:air cleaner assembly powertrain:engine:air induction:intake manifold powertrain:engine:air induction:supercharger powertrain:engine:air induction:throttle body powertrain:engine:air induction:turbocharger powertrain:engine:base engine powertrain:engine:base engine:block powertrain:engine:base engine:crankshaft/damper/bearings powertrain:engine:base engine:flywheel powertrain:engine:base engine:pistons and pins powertrain:engine:base engine:rods powertrain:engine:base engine:seals and gaskets (not oil pan or head gasket) powertrain:engine:cooling system powertrain:engine:cooling system:cooling fan and motor powertrain:engine:cooling system:cooling hoses/tubes powertrain:engine:cooling system:level/temp indicator powertrain:engine:cooling system:radiator powertrain:engine:cooling system:reservoir powertrain:engine:cooling system:thermostat powertrain:engine:cooling system:water pump powertrain:engine:cylinder head powertrain:engine:cylinder head:cylinder head gasket powertrain:engine:cylinder head:head body powertrain:engine:electronic engine control powertrain:engine:electronic engine control:diagnostics powertrain:engine:electronic engine control:engine control actuators powertrain:engine:electronic engine control:module powertrain:engine:electronic engine control:sensors powertrain:engine:emissions powertrain:engine:emissions:air pump powertrain:engine:emnissions:egr system powertrain:engine:eemissions:pcv system powertrain:engine:exhaust powertrain engine:exhaust:attachment powertrain:engine:exhaust:catalytic convertor powertrain:engine:exhaust:exhaust manifold powertrain:engine:exhaust:exhaust pipe powertrain:engine:exhaust:heat shields powertrain:engine:exhaust:muffler/resonator powertrain:engine:fuel system powertrain:engine:fuel system:attachment powertrain engine:fuel system:carburetor powertrain:engine:fuel system:evaporative system powertrain:engine:fuel system:filler neck/cap powertrain:engine:fuel system:fuel filter powertrain:engine:fuel system:fuel hoses/tubes powertrain:engine:fuel system:fuel pump powertrain:engine:fuel system:fuel rail powertrain:engine:fuel system:fuel tank powertrain:engine:fuel system:injector/seals powertrain:engine:fuel system:roll-over valve powertrain:engine:fuel system:tank selector powertrain:engine:ignition system powertrain:engine:ignition system:coil wire and plug wires powertrain:engine:ignition system:distributor powertrain:engine:ignition system:ignition coil powertrain:engine:ignition system:ignition module powertrain:engine:ignition system:spark/glow plugs powertrain:engine:miscellaneous controls powertrain:engine:miscellaneous tubes and hoses powertrain:engine:miscellaneous vacuum components powertrain:engine:mounts/dampers powertrain:engine:oil system powertrain:engine:oil system:level indicator/dipstick powertrain:engine:oil system:oil cap powertrain:engine:oil system:oil filter powertrain:engine:oil system:oil pan and crank sealing powertrain:engine:oil system:oil pump powertrain:engine:timing system powertrain:engine:timing system:camshaft powertrain:engine:timing system:tensioner/guides powertrain:engine:timing system:timing belt/chain powertrain:engine:timing system:timing gear/sprocket/aux. drive shaft powertrain:engine:valve train powertrain:engine:valve train:rocker arms and support powertrain:engine:valve train:seal—valve guide powertrain:engine:valve train:tappets and push rods powertrain:engine:valve train:valves powertrain:transmission powertrain:transmission:automatic powertrain:transmission:automatic:bands and servos powertrain:transmission:automatic:case and housing powertrain:transmission:automatic:clutch and sun gears powertrain:transmission:automatic:control valve assembly powertrain:transmission:automatic:cooler and tubes powertrain:transmission:automatic:differential and bearings powertrain:transmission:automatic:electronic trans controls powertrain:transmission:automatic:indicator/dipstick/filler tube powertrain:transmission:automatic:linkage/shift lever powertrain:transmission :automatic:output shaft powertrain:transmission:automatic:pan/gaskets/seals powertrain:transmission:automatic:parking pawl powertrain:transmission:automatic:planetary assembly powertrain:transmission:automatic:speedo drive powertrain:transmission:automatic:torque converter powertrain:transmission:automatic:trans fluid pump powertrain:transmission:automatic:vent area powertrain:transmission:clutch powertrain:transmission:clutch:clutch disc powertrain:transmission:clutch:clutch pedal and linkage powertrain:transmission:clutch:hub and bearing powertrain:transmission:clutch:pressure plate powertrain:transmission:manual powertrain:transmission:manual:bearings powertrain:transmission:manual:case and housing powertrain:transmission:manual:differential and bearings powertrain:transmission:manual:electronic trans controls powertrain:transmission:manual:gaskets and seals powertrain:transmission:manual:gears powertrain:transmission:manual:linkage/shift lever powertrain:transmission:manual:shafts powertrain:transmission:manual:speedo drive powertrain:transmission:manual:synchronizer assembly Publications publications:labels publications:owner's manual publications:scheduled maintenance guide Target, indicates the overall type of the defect. Mechanical Electrical Software/Firmware/Logic Scope of Fix Part Subsystem Product Manufacturing-related equipment Transportation-related equipment Corrective Action indicates what was done to overcome the defect. IN the preferred automobile-related embodiment of the current invention, these actions comprise: Replace, Replace an existing part with a new part Adjust/Lubricate, Make adjustment or lubrications to existing parts Reflash, Reprogram a part Appearance Fix, Correct problem with product's external finish (e.g., paint) Install-New, Install a new part that was not in the design Remove, Remove a part previously installed Reassemble, Re-Install the same part Install-Missing, Install a new part that was missing and included in the design Responsible Agent indicates the owner of the process that the caused problem. In the present automobile-related embodiment of the current invention this comprises: Tier 3, Parts Supplier Tier 2, Subsystem Supplier Tier 1, Product Developer OEM's Manufacturing Department OEM's Transportation Department Part # indicate the manufactures ID for the given defective effective part Charge Type indicates whether or not the charge for the repair of the given defect was covered by warranty or not. A skilled artisan will appreciate that in many cases it is possible for this attribute to be automatically computed by, e.g., by comparing the Ownership Duration to the Open Date. In addition to openers and closers, there are mapped attributes whose values for a given defect are computed from other attributes for the given defects. M-Symptoms-Reveal Conditions Part History indicates when defect was introduced. This is derived from the Part# and product VIN, which indicates the product's date and location of construction. These values comprise: Earlier, Part used in prior make/model/years New, First time part used in a make/model/year Engineering Change, Part used in make/model, noted engineering change Bad Fix, Previous fix did not address defect. Test Type indicates the type of test that should have caught the given defect. An example list from an embodiment follows: Part Testing, Smallest definable unit Subsystem Testing, Combination of Parts Product Testing, Combination of Subsystems (Vehicle) Safety Testing, Crash, Roll-Over, Skid, Fire, Airbags, Seat Belts, Look at Safety Features on Vehicle, Bumper Dents (Vehicle) Road Testing, Road test is like a final integration or system test of the vehicle (Vehicle) Manufacturing Testing, Manufacturing tests of the vehicle, done on each build The Test Type attribute can be determined from a given defect's conditions-revealing-defect and ownership-duration. An example of a set of mappings for the preferred embodiment is as follows: TABLE 1Test TypeRevealing ConditionsOwnership DurationPart TestingCoverageLongVariationLongStressLongSubsystem TestingInteractionLongSequenceLongProduct TestingStartup/RestartLongWorkload/StressLongSafety TestingRecovery/ExceptionLongRoad TestingEnvironmentalLongDriving ConditionsLongSensory InspectionLongManufacturing TestingHardware ConfigurationShortSoftware ConfigurationShortSensory InspectionShortCoverageShortVariationShort There are also derived attributes whose values for a given defect can only be computed when all of the defects and all other attributes have been computed # Units Affected, indicates the total number of product instances that have suffered from this same defect. It is derived by counting the number of defects that identical part # and corrective action value. Phase of Defect Injection indicates the process in which the given defect was created. This attribute can be determined from a given defect's scope of fix, corrective action and # of units. An example of a set of mappings for the preferred embodiment are as follows: TABLE 2Phasesof Defect InjectionScope of FixCorrective Action# of UnitsDesignPartRemoveAny number(Requires in-depthComponentRemoveAny numberanalysis to determinePartInstall-NewAny numberroot of defect -part,ComponentInstall-NewAny numbersubsystem or product)Part(s)Replace>1000ComponentReplace>1000PartAdjust/Lubricate>1000ComponentAdjust/Lubricate>1000Sub SystemReplaceAny numberSystem(s)ReplaceAny numberPart(s)ReflashAny numberComponentReflashAny numberSub SystemReflashAny numberSystem(s)ReflashAny numberManufacturing-BodySystemAdjustAny numberManufacturing-PaintPartAppearance Fix>1000SubsystemAppearance Fix>1000ProductAppearance Fix>1000Manufacturing-AssemblyPart(s)Replace1-1000ComponentReplace1-1000PartAdjust/LubricateAny numberComponentAdjust/Lubricate1-1000Sub SystemAdjust/LubricateAny numberSystemAdjust/LubricateAny numberPart(s)Install-MissingAny numberComponentInstall-MissingAny numberPart(s)ReassembleAny numberComponentReassembleAny numberPost Production Build &PartAppearance Fix1-1000Package/TransportationSubsystemAppearance Fix1-1000ProductAppearance Fix1-1000Post ProductionPartInstall-NewAny numberDealershipComponentInstall-NewAny numberOptionsA skilled artisan will appreciate that the current invention also covers the phase at which a given product's requirements are determined as a Phase of Defect Injection. Every defect is classified with each of the attributes above with all of the data stored in the PSEC Server Database 4120. Note that the PSEC Scheme includes data concerning not only software, but hardware and electronics as well (e.g., in the Parts Hierarchy). Further, note that the PSEC Scheme also includes data and analysis techniques targeting mass manufacturing production processes (e.g., Test Type:Manufacturing Test and Phase of Defect Injection: Manufacturing). As is described in detail with reference to FIG. 6, the Analysis Handler 4100 uses the classified defect data stored in the PSEC Server Database 4120 to provide data for and answers to questions related to the production and testing process of the mass manufacturer. As is described in detail with reference to FIG. 6, the Suggested Actions Reports handler 4110 compiles the charts and text results stored in the PSEC Server Database 4120 to generate a report containing suggested modification to one or more production or testing processes in the mass manufacturing industry's production, testing, and delivery processes. Such suggestions can include, but are not limited to the addition of a new test phase, or an indication of whether or not a given product is ready for public sale. In addition to textually described suggestions, the report can also include graphical charts justifying the given suggestions, often more than two or more such graphical charts per suggestion. A skilled artisan will appreciate that the current invention also includes a PSEC scheme that includes the service context in which a given defect was found as an attribute, with values including but not limited to:scheduled maintenance, nonscheduled maintenance, and product recall. A skilled artisan will further appreciate that the current invention also includes a PSEC scheme that includes the attributes that indicate the complexity level—e.g., indicated numerically—of other attributes. Examples include, but not limited to Condition Revealing Defect Complexity: 1 for Single Function 2 for Single Function with Option 3 for Interaction and Sequencing 4 for Workload/Stress, Recovery/Exception, Startup/Restart, Environmental, and Stress. FIG. 5 is a detailed flow diagram of the operation of the PSEC Server logic 4040. In step 5010, the HTTP Server Handler 4050 awaits an HTTP request. When such a request arrives, step 5020 checks whether it is a request for the Defect Data Collection Handler 4080. If so, this handler 4080 is invoked following which control continues at step 5010. If the request is not for the Defect Data Collection Handler 4080, then step 5040 checks whether it is a request for the Defect Data Classification Handler 4090. If so, this handler 4090 is invoked following which control continues at step 5010. If the request is not for the Defect Data Classification Handler 4090, then step 5050 checks whether it is a request for the Analysis Handler 4100. If so, this handler 4100 is invoked following which control continues at step 5010. If the request is not for the Analysis Handler 4100, then step 5040 checks whether it is a request for the Suggested Actions Report Handler 4110. If so, this handler 4110 is invoked following which control continues at step 5010. If the request is not for the Actions Report Handler 4110, then a miscellaneous handler, beyond the scope of the current invention, is called in step 5070, following which control continues at step 5010. Referring to FIG. 6, a flow diagram 5000 of the operation of the current embodiment is shown. In particular, a case involving an automobile manufacturer is given. First, in step 6010 all defect data for a particular make (e.g., Ford) and model (e.g., Corvette) of car is collected, this data being using the Defect Data Collection Handler 4080 from any of Clients A-D 3100-3130 via the PSEC Client Applet 4060. Skilled artisans will appreciate that any additions could be made manually (i.e. by a human typing information into a computer running the PSEC Client Applet 4060 via a web browser, or by an automatic data collection program, also which communicates with the PSEC server 3050 via the PSEC Client Applet 4060. Thus, the current embodiment allows a given mass manufacturing industry to automate its defect data collection. Skilled artisans will appreciate that this defect data includes in-process production data (e.g., data from the Mass Manufacturing Plant 3010), as well as post-sales, service data (e.g., from the Product Dealer 3020, or the Product Service Provider 3030). Next, in step 6020, the defect data is classified using the Defect Data Classification Handler 4090, again via accesses from Clients A-D 3100-3130. Skilled artisans will appreciate that although the classifications may be made by employees of the manufacturing organization (e.g., Ford), including but not limited to domain experts, a service organization could also provide one or more of the classifications. A skilled artisan will appreciate that if a given mass manufacturing organization obtained its parts 120 or subsystems 1010 from another given component supplier, and if that given component supplier used to current invention to analyze its defects, then the mass manufacturing organization could use the PSEC scheme-based classified defect data for its own defect analysis. Next, in step 6030, using the Analysis Handler 4100, relationships amongst the classified data are sought to answer questions relevant to the mass manufacturer (e.g., which production process(es) is(are) producing the defects that drive the majority of the warranty costs?). This research can also provide indications of salient problems. For example, suppose that a chart displaying the number of defects that escape from (i.e., are not caught by) each of the test processes 2020, 2040, 2070, 2100, 2130 and 2160 shows that vast majority come from the Part testing phase 2040. Then, if the goal of the given mass manufacturer is to save money, more attention and/or resources (e.g., time, and personnel) should be spent on Part testing 2040, so as to keep these defects from escaping to the later stages where they are more expensive to overcome. The Analysis Handler 4100 also includes rules that test the classified data to answer specific questions. Skilled artisans will appreciate that one or more of these rules can be provided when the current invention is first provided to a given organization (e.g., mass manufacturer). An example of such a rule would be one that reviews the Product Impact of the defects and then specifies the given product's reliability:e.g., “high” returned if none of the defects made the product inoperable, “average” if only a few did, and “low” if most defects did. Finally, in step 6040, the current invention compiles a charts and results into a report using the Suggested Actions Report Handler 4110. Skilled artisans will appreciate that Suggested Actions Report Handler 4110 could either of following methods: Automatic compilation of all charts and results generated by the Analysis Handler 4100 and stored in the PSEC Server Database 4120, or Allowing an end-user to select the charts and results they wish to include and then compiling only entities into the final report.A skilled artisan will appreciate that one or more members of a service organization could provide the chart and result selection described above instead of an employee of the mass manufacturer, A skilled artisan will also appreciate that the current invention could be executed multiple times by a given organization, e.g., periodically, say once a year, or to every new version of a given product. By doing this and comparing the results of each execution (e.g., comparing the reports produced in step 6040) the benefits realized by the given organization could include: Verifying that they are overcoming problem indicated in earlier reports, e.g., by checking the previous problems either vanish or are less severe in later reports.; Verifying that their product are becoming more stable, reliable, or safe, e.g., by comparing the respective levels of stability, reliability, and safety between reports; or Verifying that are maintaining a sufficient level of production and testing quality, e.g., by verifying that no new or higher severity problems are reported in later reports. A skilled artisan will further appreciate that PSEC analysis reports from different organizations could be compared so as to judge the strengths and weaknesses of the organizations. A skilled artisan will also appreciate that by using the both Charge Type attribute (i.e., whether or not the defect's repair was covered by warranty) and the Repair Cost attributes, the analysis provided by the Analysis Handler 4100 and reported by the Suggested Actions Report Handler could include consideration of each defect's warranty cost. Thus, a given organization interested in reducing their warranty-related costs could use the current invention to indicate relevant problems and to suggest corrective modifications to their production and testing processes. A skilled artisan will also appreciate that by comparing and analyzing the classified defects data, especially using the In-Process attribute, the current embodiment can be used to compare defects that escaped (i.e., were created and yet not caught) the product's development and production to those that occurred our in the field. A skilled artisan will finally appreciate that the current embodiment could be provided as a service by a service organization to the mass manufacturer. This service could include the service organization collecting the defects, classifying the defects, analyzing the classified defects and generating the report summarizing the analysis. This service could be offered on a continuing basis, e.g., the service organization could analyze and provide an analysis report to the mass manufacturer each year. The service could also include modifications and updates to the PSEC scheme used to analyze the given mass manufacturer. A skilled artisan will further appreciate that variations, modifications, and other implementations of what is described herein may occur to those of ordinary skill in the art without departing from the spirit and scope of the invention. Accordingly, the invention is defined by the following claims and not to be defined only by the preceding illustrative description.
	summary
	claims	1. A radiation monitor comprising:a radiation detector which detects a γ ray emitted from a measurement target nuclide and outputs an analog voltage pulse; anda radiation measuring instrument which receives the analog voltage pulse output from the radiation detector, and measures and outputs radiation in a measurement energy range,wherein the radiation measuring instrument includesa pulse amplifier which amplifies the input analog voltage pulse and removes superimposed high frequency noise,a high-energy count-rate-measuring instrument which discriminates the analog voltage pulse output from the pulse amplifier by a high-energy window and a low-energy window which are set so as not to be superimposed on each other in accordance with a voltage level, respectively, measures and outputs a high-energy count rate by performing a time constant process of the pulses entering the high-energy window so that a standard deviation becomes constant, and outputs an alert, when the high-energy count rate is increased beyond an acceptable set value,a low-energy count-rate-measuring instrument which measures and outputs a low-energy count rate by moving and averaging the pulse entering the low-energy window at a constant measurement time,an alert-diagnosis device which determines whether or not the low-energy count rate is in a set acceptable range, when an alert is output from the high-energy count-rate-measuring instrument, determines that the alert is caused by fluctuation, when the low-energy count rate is in the set acceptable range, determines that the alert is caused by any one of an increase in the γ ray which is a measurement target or enter of noise, when the low-energy count rate increases beyond the acceptable range, and outputs a result of the determination, anda display/user-operation device which displays each output and performs operations and settings of each unit. 2. The radiation monitor according to claim 1,wherein measurement time of the low-energy count-rate-measuring instrument is set to be 1 time to 3 times the time constant which is unequivocally determined from a background level and a standard deviation of the high-energy count rate of the high-energy count-rate-measuring instrument. 3. The radiation monitor according to claim 1,wherein, in a case where an alert is output from the high-energy count-rate-measuring instrument and it is determined that the alert is caused by any of an increase in the γ ray which is a measurement target or enter of noise, the alert-diagnosis device determines that the alert is caused by the noise, in a case where a ratio of a net increased amount from each background level is equal to or greater than a set value, regarding the low-energy count rate of the low-energy count-rate-measuring instrument and the high-energy count rate of the high-energy count-rate-measuring instrument. 4. The radiation monitor according to claim 1,wherein the high-energy count-rate-measuring instrument includesan up-down counter which receives a shaping pulse corresponding to the pulse entering the high-energy window through an up input,a negative feedback pulse generation circuit which generates a feedback pulse at a repetition frequency so as to respond the output of the up-down counter with a primary delay of the time constant and inputs the feedback pulse to a down input of the up-down counter, andan integration control circuit which performs weighing when the up-down counter performs the counting in accordance to the standard deviation of the count rate, anda count rate is operated so that the standard deviation becomes constant based on an addition/subtraction integrated value of the up-down counter. 5. A radiation monitor comprising:a radiation detector which detects a γ ray emitted from a measurement target nuclide and outputs an analog voltage pulse;a first radiation measuring instrument which receives the analog voltage pulse output from the radiation detector, measures radiation in a measurement energy range on a high energy side, outputs a result of the measurement, and outputs an alert, when the result of the measurement is increased beyond an acceptable set value;a second radiation measuring instrument which receives the analog voltage pulse output from the radiation detector, measures radiation in a measurement energy range on a low energy side, and outputs a result of the measurement; anda diagnosis apparatus which receives the output of the first radiation measuring instrument and the output of the second radiation measuring instrument, performs moving and averaging of a result of the measurement of the second radiation measuring instrument for a constant time, determines whether or not the moved average value is increased beyond a set acceptable range, determines that the alert is caused by fluctuation when the value is in the acceptable range, determines that the alert is caused by any of an increase in the γ ray which is a measurement target or enter of noise, when the value is increased beyond the acceptable range, and as a result of the determination, displays a trend of the result of the measurement of the first radiation measuring instrument and a trend of the moved average value,wherein measurement energy ranges of the first radiation measuring instrument and the second radiation measuring instrument are set not to be superimposed to each other. 6. The radiation monitor according to claim 5,wherein the measurement energy range of the second radiation measuring instrument is set so as to contain peak spectra of radioactive rare gas which is an emission management target and main Compton scattering spectra. 7. The radiation monitor according to claim 5,wherein a moving average time of the diagnosis apparatus is set to be 1 time to 3 times the time constant which is unequivocally determined from a background level and a standard deviation of the first radiation measuring instrument. 8. The radiation monitor according to claim 6, wherein a moving average time of the diagnosis apparatus is set to be 1 time to 3 times the time constant which is unequivocally determined from a background level and a standard deviation of the first radiation measuring instrument.
052934160	claims	1. A radiography apparatus for producing x-ray shadowgraphs comprising: an x-ray radiator having a focus from which an x-ray beam emanates; a detector array formed by a line of detector elements; and means for moving said x-ray radiator while said detector array remains stationary for transirradiating a measurement field, disposed between said x-ray radiator and said detector array, from different directions with said x-ray beam with said x-ray beam being incident on said detector array after passing through said measuring field from said different directions, said detector array generating electrical signals corresponding to the x-rays incident thereon; means for constructing an x-ray shadowgraph from said electrical signals; a computer tomography detector array curved around said focus of said x-ray radiator and forming, in combination with said x-ray radiator, a computer tomography measuring unit movable by said means for moving said x-ray radiator around a system axis, said detector array for producing x-ray shadowgraphs being disposed perpendicularly relative to said computer tomography detector array, said computer tomography detector array generating electrical signals corresponding to x-rays from said x-ray radiator incident thereon; and means for generating a computer tomogram from said electrical signals from said computer tomography detector array. 2. A radiography apparatus as claimed in claim 1 wherein said detector array for producing x-ray shadowgraphs is disposed above said computer tomography detector array. 3. A radiography apparatus as claimed in claim 1 wherein said detector array for producing x-ray shadowgraphs is disposed next to said computer tomography detector array.
055127592	claims	1. A condenser system for collecting synchrotron radiation from a synchrotron source that emits a fan of synchrotron emission light in the plane of the source and for illuminating the ringfield of a camera, comprising: collecting means, positioned about the periphery of a synchrotron source, for collecting a plurality of synchrotron light beams emitted from the fan of synchrotron emission light and for transforming the plurality of synchrotron light beams into a plurality of arc-shaped light beams, each one of the plurality of arc-shaped light beams having an arc-shaped cross-section; processing means, succeeding said collecting means, for rotating and directing the plurality of arc-shaped light beams toward the real entrance pupil of a camera and for positioning a plurality of substantially parallel arc-shaped light beams at the real entrance pupil of the camera; and imaging means, succeeding said processing means, for converging the substantially parallel arc-shaped light beams, for transmitting the plurality of the substantially parallel arc-shaped light beams through a resistive mask and into the virtual entrance pupil of the camera, and for illuminating the ringfield of the camera. said collecting means comprises at least two spherical mirrors, wherein one of the at least two spherical mirrors is concave and one of the at least two spherical mirrors is convex; said processing means comprises at least one correcting mirror, succeeding the at least two spherical mirrors, and a plurality of flat mirrors are positioned at a real entrance pupil of the camera and arranged in a symmetrical pattern within the real entrance pupil; and said imaging means comprises a spherical mirror that is concave. 2. The condenser system of claim 1, wherein: 3. The condenser system of claim 2, wherein the processing means rotates and directs the arc-shaped light beams toward the real entrance pupil of the camera in a symmetrical pattern to coincide with the symmetrical pattern of the plurality of flat mirrors. 4. The condenser system of claim 2, wherein the at least one correcting mirror is a flat mirror. 5. The condenser system of claim 2, wherein the symmetrical pattern of the light beams is arranged to produce uniform coherence properties for features on the resistive mask oriented at any angle. 6. The condenser system of claim 2, wherein the at least two spherical mirrors emit the plurality of arc-shaped light beams in a plane normal to the plane of the fan of synchrotron emission light and the correcting mirror receives the plurality of arc-shaped light beams from the at least two spherical mirrors and emits corresponding arc-shaped light beams in the plane of the fan of synchrotron emission light. 7. The condenser system of claim 2, wherein one of the at least two spherical mirrors is positioned below the plane of the fan of synchrotron emission light. 8. The condenser system of claim 2, wherein the plurality of flat mirrors emit the substantially parallel arc-shaped light beams. 9. The condenser system of claim 8, wherein the plurality of flat mirrors are individually tilted to emit the substantially parallel arc-shaped light beams. 10. The condenser system of claim 1, wherein said imaging means causes the arc-shaped light beams to be superimposed with respect to each other and formed a single arc-shaped composite beam that directly coincides with the ringfield of the camera. 11. The condenser system of claim 1, wherein the arc-shaped light beams received by the imaging means are substantially coplanar with respect to the plane of the fan of synchrotron emission light. 12. The condenser system of claim 1, wherein the imaging means is configured to image a ringfield with a width of W.gtoreq.100 .mu.m. 13. The condenser system of claim 1, wherein said collecting means collects synchrotron emission light over an arc of at least 100 mrad. 14. The condenser system of claim 1, wherein said collecting means collects synchrotron emission light over an arc of at least 200 mrad. 15. The condenser system of claim 1, wherein said collecting means, said processing means, and said imaging means comprise a plurality of multi-layer mirrors. 16. The condenser system of claim 1, wherein said collecting means collect synchrotron emission light in the wavelength range of .lambda.=50 to 700 .ANG.. 17. The condenser system of claim 1, wherein said collecting means collect synchrotron emission light at the wavelength of .lambda.=134 .ANG..
056152388	claims	1. A method for fabricating a primary target for the production of fission products comprising: a.) choosing a first substrate having a first substrate first surface, a first substrate second surface, a first substrate first end, a first substrate second end, a first substrate first raised shoulder at the first substrate first end, a first substrate second raised shoulder at the first substrate second end, and first substrate predetermined thickness; b.) positioning a welding rib onto the first substrate first surface, said welding rib having a welding rib first side surface, a welding rib second side surface, and a welding rib top surface, where said welding rib extends longitudinally from the first substrate first raised shoulder to the first substrate second raised shoulder; c.) sizing a foil of fissionable material, said foil having a foil first surface, a foil second surface, a foil first edged a foil second edge opposing the first edge, and a predetermined thickness; d.) preparing the first substrate first surface to receive the foil first surface so as to avoid diffusion bonding between the first substrate surface and the foil first surface to allow for later removal of the foil from the first substrate; e.) wrapping the foil around the first substrate such that the foil first surface is in contact with the first substrate first surface, the foil first edge abuts against the welding rib first side surface, and the foil second edge abuts against the welding rib second side surface; f.) choosing a second substrate having a second substrate first surface, a second substrate second surface, a second substrate first end, a second substrate second end, a slit extending longitudinally from the second substrate first end to the second substrate second end, wherein the slit has opposing edges, and a second substrate predetermined thickness; g.) preparing the second substrate first surface to receive the foil second surface so as to avoid diffusion bonding between the second substrate first surface and the foil second surface to allow for later removal of the foil from the second substrate; h.) assembling the foil-wrapped first substrate and the second substrate such that the foil second surface contacts the second substrate first surface and the opposing edges of the second substrate slit are aligned over the welding rib top surface, whereby the first substrate second surface and the second substrate second surface are exposed to ambient atmosphere; i.) mechanically compressing the second substrate to assure physical contact between all common surfaces of the first substrate, the foil, and the second substrate, to ensure good thermal conduction, whereby the opposing edges of the slit of the second substrate are moved into close proximity one to the other, and slit of the second substrate is aligned over the welding rib top surface; j.) attaching the two opposing edges of the slit of the second substrate to the welding rib; and k.) attaching the second substrate first end to the first substrate first raised shoulder and the second substrate second end to the second surface raised shoulder. choosing a first substrate having a first substrate first surface, a first substrate first end, a first substrate first raised shoulder of a predetermined height integral to said first substrate first end, a first substrate second end, a first substrate second raised shoulder of a predetermined height integral to said first substrate second end, a first substrate second surface, a first substrate peripheral edge, a first substrate predetermined thickness, a depressed surface between said first substrate first raised shoulder and said first substrate second raised shoulder, and a longitudinal welding rib, having a predetermined height, a first side surface and a second side surface, integrally attached to the first substrate first surface, the first substrate first raised shoulder and the first substrate second raised shoulder; preparing the first substrate first surface to receive a foil of fissionable material, said foil of fissionable material having a first foil surface, a second foil surface, a first side surface, a second side surface and a predetermined thickness; circumferentially contacting the foil first surface with the depressed surface of the first substrate first surface, so as to allow for later removal of the foil from the first substrate; abutting the first side surface and second side surface of said foil of fissionable material against the first side surface and second side surface of the longitudinal welding rib; choosing a second substrate having a second substrate first surface, a second substrate second surface, a second substrate peripheral edge, a second substrate first end, a second substrate second end, a slit extending longitudinally the entire length of the second substrate from the second substrate first end to the second substrate second end, wherein the slit has opposing edges, and a second substrate predetermined thickness; preparing the second substrate first surface to receive the foil second surface so as to allow for later removal of the foil from the second substrate; attaching the first substrate peripheral edge to the second substrate peripheral edge such that the first substrate second surface and the second substrate second surface are exposed to ambient atmosphere, wherein the foil is sandwiched between the first substrate and second substrate to prevent foil exposure to ambient atmosphere and the opposing edges of said slit overlay the longitudinal welding rib of the first substrate; compressing the exposed first substrate second surface and the second substrate second surface to assure physical contact between the foil and the first substrate first surface and between the foil and the second substrate first surface; sizing the first substrate raised shoulders so that the predetermined heights of the first substrate first raised shoulder and the first substrate second raised shoulder are of the same height relative to the first substrate first surface, thereby creating a depressed center section coextensive with the depressed surface of said first substrate; sizing the welding rib so that the predetermined height of the welding rib is commensurate with the predetermined thickness of the foil of fissionable material, wherein said foil abuts against the first and second side surfaces of said welding rib to retain the foil within the depressed center section; welding the opposing edges of the slit of said second substrate to the rib of said first substrate. a.) an inner cylinder having an interior surface, an exterior surface, a first end, a second end, a first raised shoulder at the first end, and a second raised shoulder at the second end; b.) a raised welding rib forming an integral part of said inner cylinder and extending longitudinally from the first raised shoulder to the second raised shoulder, said welding rib having a top surface, a first side surface, and a second side surface; c.) a foil of fissionable material having a first surface, a second surface, a first edge, and a second edge which opposes the first edge, wherein the length from the first edge to the second edge is less than the circumference of the inner cylinder exterior surface, and whereby said foil forms a layer on the inner cylinder exterior surface so that the foil first surface contacts the inner cylinder exterior surface, the foil first edge abuts against the welding rib first side surface, and the foil second edge abuts against the welding rib second side surface; d.) an outer cylinder having an interior surface, an exterior surface, a first end, a second end, and a slit extending longitudinally from the outer cylinder first end to the outer cylinder second end, the slit having a first edge and a second edge, whereby the outer cylinder forms a layer on the foil such that the outer cylinder interior surface contacts the foil second surface, the outer cylinder first end contacts the inner cylinder first raised shoulder, the outer cylinder second end contacts the inner cylinder second raised shoulder, and the slit first edge and the slit second edge are aligned over the welding rib top surface; e.) first means for attaching the outer cylinder slit edges to the welding rib top surface; f.) second means for attaching the outer cylinder first end to the inner cylinder first raised shoulder and the outer cylinder second end to the inner cylinder second raised shoulder, whereby said foil is contained between the inner and outer cylinders. 2. The invention as recited in claim 1 wherein the raised shoulders on said first substrate are sized to a height which accommodates the foil thickness. 3. The invention as recited in claim 1 wherein the first and second substrates are nonfissionable metal materials selected from the group consisting of stainless steel, nickel, nickel alloys, zirconium, zircaloy, aluminum, or zinc coated aluminum. 4. The invention as recited in claim 1 wherein the foil of fissionable material consists of low enriched uranium metal or plutonium metal. 5. The invention as recited in claim 1 wherein the first substrate predetermined thickness is selected from a range of between approximately 0.025 inches and 0.060 inches, and the second substrate predetermined thickness is selected from a range of between approximately 0.025 inches and 0.060 inches. 6. The invention as recited in claim 5 wherein the predetermined thickness of the foil of fissionable material exceeds 0.05 millimeters. 7. A method for fabricating a primary target for the production of fission products comprising: 8. The invention as recited in claim 1 wherein the steps of preparing the first substrate first surface and the second substrate first surface consist of chemically treating the first substrate first surface and the second substrate first surface to avoid chemical bonding of the foil to the first substrate first surface and the second substrate first surface. 9. A primary target for the production of fission products, comprising: 10. A primary target as recited in claim 9, wherein the inner cylinder first and second raised shoulders are raised to a height which accommodates the predetermined thickness of foil. 11. A primary target as recited in claim 9, wherein the foil has a thickness selected in the range of between 0.05 millimeters and 0.25 millimeters. 12. A primary target as recited in claim 9, wherein the foil consists of low enriched uranium metal or plutonium metal. 13. A primary target as recited in claim 9, wherein said inner cylinder and said outer cylinder have a thickness selected from the range of between approximately 0.025 inches and 0.060 inches. 14. A primary target as recited in claim 9, wherein said inner cylinder and said outer cylinder are nonfissionable metal materials selected from the group consisting of stainless steel, nickel, nickel alloys, zirconium, zircaloy, aluminum, or zinc coated aluminum. 15. A primary target as recited in claim 9, wherein said inner cylinder exterior surface and said outer cylinder interior surface are chemically prepared so as to avoid bonding between the cylinder surfaces and the foil to allow for later removal of the foil. 16. A primary target as recited in claim 15, wherein the chemical preparation consists of anodizing or nitriding. 17. A primary target as recited in claim 9, wherein said first means for attaching is a single unifying weld. 18. A primary target as recited in claim 9, wherein said second means for attaching is a weld. 19. The invention as recited in claim 8 wherein said chemically treating the first substrate first surface and the second substrate first surface to minimize chemical bonding of the foil comprise the process of anodizing or nitrating said first substrate first surface and second substrate first surface.
	summary
054220475	abstract	Provided is a method for making high-temperature high-performance fuel particles wherein fertile or fissile metal carbides are dispersed in spherical graphite skeletons. That is, a fissile metal salt, such as uranyl nitrate, is added to an aqua-mesophase in alkaline solution, to form a fuel solution. The fuel solution is added to an oil bath to form an emulsion of aqueous pitch-derrived spheres in oil. The emulsion is heated and stirred to drive water from the spheres to dry them into solid spheres which contain the above metal salts. The solid spheres are then heated to between 700-1100 C. to carbonize them and convert the metal salts to metal oxides and then the spheres are further heated to between 2000.degree.-3000.degree. C., to carburize the metal oxides to metal carbides and graphitize the carbon. The resulting fuel spheres are then preferably coated by deposition thereon, of a carbon or carbide coating to contain the future reaction products thereof. The invention includes the above spherical graphite nuclear fuel particles and the method for preparing same.
044407173	description	DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows a nuclear reactor vessel 10 and reactor vessel closure head 12 vertically disposed in a concrete reactor cavity 14. Reactor vessel 10 is connected to the other components of the nuclear steam supply system (not shown) by a reactor coolant inlet nozzle 16 and outlet nozzle 18. Prior to start-up of the reactor, the entire volume within reactor vessel 10 is filled with a fluid coolant such as water. During normal reactor operation, the liquid coolant enters reactor vessel 10 through inlet nozzle 16, follows flowpath 20 down the outside of core support barrel 22, up through core support assembly 24 through fuel assemblies 26, collectively core 29, to remove heat generated therein, through fuel alignment plate 28 and exits from reactor vessel 10 through outlet nozzle 18. A small portion of the flow through core 29 passes up through shroud 110 into the plenum beneath reactor vessel closure head 12. Reactor vessel 10 coolant inventory may be affected by changes in the state of the coolant or by changes in the quantity of inventory in the reactor coolant system. Reactor vessel 10 coolant inventory may be decreased by a loss of reactor coolant system fluid due to a break in the system. Reactor vessel 10 coolant inventory may also be decreased by contraction due to system cooling as caused by a break in a steam line. Reactor vessel 10 coolant inventory may also be decreased due to displacement of water by noncondensables or steam as the result of flashing. The coolant inventory above fuel alignment plate 28 is available for cooling core 29 should one of the above incidents cause a decrease in reactor vessel 10 coolant inventory. Heated junction thermocouple level measurement system 32 monitors the liquid level in reactor 10 above fuel alignment plate 28. This liquid level represents the portion of total volume above fuel alignment plate 28 that is occupied by liquid coolant. As shown in FIG. 2, heated junction thermocouple level measurement system 32 is mounted above fuel alignment plate 28. During normal operation of the pressurized water reactor, heated thermocouple junction level measurement system 32 is covered with and senses liquid coolant and the level is not particularly difficult to establish. During accidents which affect the level of coolant, the coolant in the reactor vessel 10 is not necessarily a subcooled liquid but rather may consist of a two-phase fluid. The two-phases are liquid and gas. When the coolant is water the liquid phase is water and the gaseous phase is steam. Steam bubbles rise to the top of the vessel due to buoyant forces thereby forming a steam region above a water level. Liquid level measurement in reactor vessel 10 is further complicated by the varying void fraction of the two-phase coolant. FIG. 2 shows heated thermocouple junction level measurement system 32 mounted between the upper guide structure support plate 30 and fuel alignment plate 28. Electrical leads from heated junction thermocouple level measurement system 32, collectively conductors 48, 50, 52, 54 and 56, exit through vessel head 12 by way of seal plug 34. In this position, heated junction thermocouple level measurement system 32 monitors the level of coolant above the core. An embodiment of the axial spacing of sensors 36 has sensors equally spaced over the range of level sensing of heated junction thermocouple level measurement system 32. The sensors need not be equally spaced over the level sensing range. FIG. 3 is a vertical section of a sensor 36. Pins 38, 40, 42, 44 and 46 connect to conductors 48, 50, 52, 54 and 56, respectively, in receptacle 58. Conductors 48, 50, 52, 54 and 56 further pass through seal plug 60 entering housing 62. Conductors 48 and 56 are copper leads to heater coil 64. A controllable power supply (not shown) is electrically connected to pins 38 and 46. Chromel conductor 54 and Alumel conductor 52 are joined within housing 62 to form unheated thermocouple junction 66. Alumel conductor 52 extends beyond unheated thermocouple junction 66 to within heater coil 64 and joins with Chromel conductor 50 forming heated thermocouple junction 68. Heated thermocouple junction 68 is located central to the 1 inch wound inconel heater 64. A thermally conductive and electrically insulating means such as ceramic insulating material 70 fills the housing through at least the length containing the thermocouple junctions. Unheated thermocouple junction 66 is located approximately 4.5 inches above heated thermocouple junction 68 so that there is substantially no effect by heat input from heater 64 on unheated thermocouple junction 66. Unheated thermocouple junction 66 and heated thermocouple junction 68 are wired in series. The net voltage generated by thermocouple junctions 66 and 68 is a function of the temperature difference between the two thermocouple junctions. Heated thermocouple junction 68 will generate a voltage representative of its temperature. Unheated thermocouple junction 66 will also generate a voltage representative of its temperature. When the fluid surrounding housing 62 is liquid, heated thermocouple junction 68 remains at approximately the same temperature as unheated thermocouple junction 66 as the heat transfer from heater 64 through the thermally conductive and electrically insulating means 70 and housing 62 to the surrounding fluid is very good. The net voltage across pins 40 and 44 is approximately zero. When the fluid surrounding housing 62 is gaseous, the heat transfer from heater 64 through thermally conductive and electrically insulating means 70 and housing 62 to the gaseous fluid is not as good and the temperature of heated thermocouple junction 68 will rise above the temperature of unheated junction 66 producing a net voltage across pins 40 and 44 representative of the temperature difference between junctions 66 and 68. Thus, there will be a substantial difference in heat transfer between housing 62 and the surrounding fluid depending upon whether the coolant is liquid or gaseous. The differential temperature measurement between unheated thermocouple junction 66 and heated thermocouple junction 68 is used to indicate coolant level. In addition to having available the net voltage generated by unheated thermocouple junction 66 and heated thermocouple junction 68, a voltage representative of the absolute temperature of both unheated junction 66 and heated junction 68 is available. The voltage representative of the temperature of unheated thermocouple junction 66 is available across pins 42 and 44. The voltage representative of the temperature of heated thermocouple junction 68 is available across pins 40 and 42. The temperature of unheated thermocouple junction 66 indicates the temperature of the coolant in the reactor head region regardless of whether the coolant is water or steam. When supplied to an appropriate calculator, this coolant temperature can be utilized in the calculation of subcooled margin. Subcooled margin provides an indication of the margin to saturation conditions in the reactor coolant system. The temperature of heated thermocouple junction 68 is used to control the power delivered to heater 64. The heater power controller 165 shown in FIG. 4 is designed to maintain a constant heater power sufficient to insure that a voltage signal is generated by heated thermocouple junction 68. To protect heater coil 64, heater power is reduced when the temperature of heated thermocouple junction 68 rises above a preselected value. There are two heater power controllers per channel. Each heater power controller controls the power delivered to four heater coils. During testing it was found that liquid impinging on housing 62 in the region of heater 64 caused spurious cooling. It was further found that the effects of temperature decrease due to cooling were more rapid than the effects of temperature increase caused by heater 64. Since housing 62 could be cooled by spurious water droplets more rapidly than it could be heated by heater 64, it was imperative that spurious water droplets be kept off housing 62 in the region of heater 64 to obtain an accurate water level. To overcome the effects of spurious water droplets, a 4 inch long stainless steel splash guard 72 was disposed to surround housing 62 in the region of heater 64. Splash guard 72 is joined to housing 62 by continuous weld or braze 74 at one end and continuous weld or braze 76 at the other end. Splash guard 72 is generally cylindrical with circumscribing recessed regions 80 and 84 near the top and bottom thereof. The portion of housing 62 disposed within splash guard 72 is in fluid communication with the coolant outside splash guard 72 through upper lateral inlet-outlet ports 78 in recessed region 80 and lower lateral inlet-outlet ports 82 in recessed region 84 as stainless steel plug 85 seals the upper end of splash guard 72 and stainless steel plug 83 seals the lower end of splash guard 72. Splash guard 72 acts as a stilling chamber to provide a nonturbulent interface between liquid and gaseous coolant surrounding housing 62 within the range of level sensed by sensor 36. Inlet-outlet ports 78 and 82 permit the coolant level within splash guard 72 to fluctuate with the coolant level outside splash guard 72. The fluid splashing outside splash guard 72 impinges on splash guard 72 thereby eliminating the spurious cooling effect experienced without splash guard 72. Should coolant splash or condense on housing 62 above splash guard 72 then run down housing 62 onto weld or braze 74, stainless steel plug 85 and splash guard 72, heated thermocouple junction 68 will not experience spurious temperature decreases. The lower surface of lower lateral inlet-outlet ports 82 are at the top of stainless steel plug 83 and allow virtually complete drainage of the volume within splash guard 72 when the liquid coolant level drops below inlet-outlet ports 82. Upper lateral inlet-outlet ports 78 and lower lateral inlet-outlet ports 82 are multiple small ports sized to permit the coolant level inside splash guard 72 to respond to rapid changes in the level of coolant outside splash guard 72 within an acceptably short period of time. The number and size of inlet-outlet ports 78 and 82 will vary depending upon the volume enclosed by splash guard 72, the rate at which the coolant level outside splash guard 72 is expected to change and the time period acceptable for the level to equalize inside and outside splash guard 72. Generally the number and size of upper lateral inlet-outlet ports 78 are the same as the number and size of lower lateral inlet-outlet ports 82. In one application having a four inch long, three-eighths inch outside diameter splash guard, lateral inlet-outlet ports 78 and 82 were two in number, diametrically opposed across the splash guard and one-eighth inch in diameter. It was found that for a rapid coolant level change outside the splash guard the level inside the splash guard equalized in a fraction of the time required for the thermocouples to respond. Since inlet-outlet ports 78 and 82 are sized for a rapid change in coolant level and since a rapid change in coolant level is a worse case than a slower change in coolant level, inlet-outlet ports 78 and 82 function adequately for slower changes in coolant level. It is not necessary to enclose unheated thermocouple junction 66 within splash guard 72 as unheated thermocouple junction 66 does not discriminate between liquid or gaseous fluid surrounding housing 62. When the fluid surrounding housing 62 is a two-phase fluid, the saturation temperature detected by unheated thermocouple junction 66 will be the same for both the liquid and gaseous phases. The unheated thermocouple junction thereby compensates for temperature changes in the coolant and no further temperature compensation is necessary in the heated junction thermocouple level measurement system 32. FIG. 4 shows a vertical section through separator tube 86. Separator tube 86 encloses eight fixedly mounted sensors 36 and functions as a stilling chamber to hydraulically separate the two-phase fluid into a liquid phase and a gaseous phase. It is this liquid level that is measured by the heated junction thermocouple level measurement system 32. The level of liquid measured is indicative of the liquid inventory above the core. Separator tube 86 is a tubular element with end 88 completely enclosed. End 88 prevents rising bubbles of steam from passing through the separator tube and disturbing the liquid-vapor interface thereby giving a flase indication of level. Lateral inlet-outlet ports 90 and 92 permit fluid communication between the volume enclosed by separator tube 86 and the volume within support tube 100. Upper lateral inlet-outlet ports 90 and lower lateral inlet-outlet ports 92 are multiple inlet-outlet ports sized to permit the coolant level inside separator tube 86 to respond to rapid changes in the level of coolant outside separator tube 86 within an acceptably short period of time. The number and size of inlet-outlet ports 90 and 92 will vary depending upon the volume enclosed by separator tube 86, the rate at which the coolant level outside separator tube 86 is expected to change and the time period acceptable for the level to equalize inside and outside separator tube 86. Upper lateral inlet-outlet ports 90 permit fluid communication between the volume enclosed by separator tube 86 and the volume within support tube 100 at or above the level of inlet-outlet ports 78 of uppermost sensor 36a. Lower lateral inlet-outlet ports 92 permit fluid communication between the volume enclosed by separator tube 86 and the volume within support tube 100 at or below the level of inlet-outlet ports 82 of lowermost sensor 36h. Due to a decrease in pressure in reactor vessel 12 or a change in water level, water may pass through inlet-outlet ports 90 and 92 or water that has flashed to steam may pass through inlet-outlet ports 90 and 92 to equalize the water level inside and outside separator tube 86. Heated junction thermocouple level measurement system 32 is mounted in the plenum above core 29 where coolant tends to move vertically and laterally toward outlet nozzle 18. In this location heated junction thermocouple level measurement system 32 is subjected to cross flow as the reactor coolant exits through nozzle 18. To prevent steam bubbles entrained in a two-phase fluid cross flow from entering lateral inlet-outlet ports 90 and 92 of separator tube 86, separator tube 86 is enclosed by and fixedly mounted in support tube 100. Support tube extension 101 supports but does not hydraulically seal against separator tube 86. Support tube 100 is a tubular element with end 108 completely enclosed. It is not necessary that end 108 be completely enclosed. Lateral inlet-outlet ports 102 are spaced throughout the length of support tube 100. Lateral inlet-outlet ports 102 are sufficient in size and number to permit the coolant level inside support tube 100 to respond to rapid changes in the level of coolant within reactor vessel 10 above the core within an acceptably short period of time. Lateral inlet-outlet ports 102 in the lower portion of support tube 100 are axially offset from lateral inlet-outlet ports 92 of separator tube 86 because at least the lower portion of heated junction thermocouple level measurement system 32 is subjected to crossflow. Lateral inlet-outlet ports 102 in the upper portion of support tube 100 may be axially offset from lateral inlet-outlet ports 90 of separator tube 86 depending upon the crossflow in this region in a particular application. In some applications, support tube 100 may be located in a generally cylindrical, otherwise unused, control element assembly shroud 110. Shroud 110 is a tubular element open on the bottom that has lateral inlet-outlet ports 112 at least near the top to permit liquid level fluctuations to equalize inside and outside shroud 110. Shroud 110 further prevents steam bubbles in the cross flow from disrupting the coolant level measured by heated junction thermocouple level measurement system 32 but is not necessary for heated junction thermocouple level measurement system 32 to function properly. One embodiment of the cross sectional spacing of sensors 36 within separator tube 86 and support tube 100 is shown in FIG. 5 taken through line 5--5 of FIG. 4. A uniform cross sectional spacing is used because it efficiently utilizes the space within separator tube 86; the cross sectional spacing of sensors 36 need not be uniform. FIG. 6 shows an alternate embodiment of heated junction thermocouple level measurement system 32 in which hydraulic plug 94 divides the length of separator tube 86 into two level sensing sections 96 and 98 at the level of internal physical structure 114. This embodiment may be used when the internal physical structure 114 of the reactor could restrict coolant flow resulting in two liquid levels. Level sensing section 96 is above hydraulic plug 94 and internal physical structure 114 while level sensing section 98 is below hydraulic plug 94 and internal physical structure 114. Each level sensing section 96 and 96 has lateral inlet-outlet ports 90 or 90' at the top of the respective level sensing section and lower inlet-outlet ports 92 or 92' at the bottom of the respective level sensing section. Each level sensing section 96 and 98 contains at least one sensor 36 so that two separate liquid levels may be monitored. This concept can be extended to sense more than two liquid levels when the physical structure surrounding support tube 100 would impede the coolant flow. When separator tube 86 is divided by hydraulic plug 94 to measure two liquid levels, it is necessary to similarly divide support tube 100 into two corresponding level measuring PG,17 sections. Support tube extension 101 in this embodiment hydraulically seals against separator tube 100. The two level sensing sections remain 96 and 98. Upper level sensing section 96 has lateral inlet-outlet ports 102 in support tube 100 at least near the top and bottom thereof. Lower level sensing section 98 also has lateral inlet-outlet ports 102 at least near the top and bottom thereof. The level may equalize inside and outside level sensing sections 96 and 98 of support tube 100 through inlet-outlet ports 102. Inlet-outlet ports 102 are axially offset from lateral inlet ports 90, 90', 92 or 92' at least where support tube 100 is subjected to cross flow. In those applications where support tube 100 is located in shroud 110, shroud extension 111 hydraulically divides shroud 110 into the same level sensing sections 96 and 98. Also during accident conditions, heated junction thermocouple level measurement system 32 can be used to detect the presence of noncondensable gas bubbles in the reactor vessel head, thereby providing information to the operator for use in controlling the reactor vent system. In addition to being used during normal operation and accident conditions, the heated junction thermocouple level measurement system 32 can be used by the operator to determine if a recovery operation has been successful. Heated junction thermocouple level measurement system 32 can also be used to determine when sufficient reactor coolant has been removed from the primary system to permit refueling operations. Heated junction thermocouple level measurement system 32 has in some applications been designed to be handled in the same manner as other top mounted incore instrumentation devices during refueling operations and can be retrofitted into operating reactors and reactors under construction.
	description	The present application is a continuation of U.S. patent application Ser. No. 14/271,101 filed May 6, 2014, which is a divisional of U.S. patent application Ser. No. 12/709,094 filed Feb. 19, 2010, which is a continuation-in-part of U.S. Non-provisional patent application Ser. No. 11/352,601, filed Feb. 13, 2006, which in turn claims the benefit of U.S. Provisional Patent Application 60/652,363, filed Feb. 11, 2005, the entireties of which are hereby incorporated by reference in its entirety. The present invention relates generally to the field of storing high level waste, and specifically to systems and methods for storing spent nuclear fuel in ventilated vertical modules that utilize passive convective cooling. In the operation of nuclear reactors, it is customary to remove fuel assemblies after their energy has been depleted down to a predetermined level. Upon removal, this spent nuclear fuel is still highly radioactive and produces considerable heat, requiring that great care be taken in its packaging, transporting, and storing. In order to protect the environment from radiation exposure, spent nuclear fuel is first placed in a transportable canister. An example of a typical canister used to transport, and eventually store, spent nuclear fuel is disclosed in U.S. Pat. No. 5,898,747 to Krishna Singh, issued Apr. 27, 1999. Such canisters are commonly referred to in the art as multi-purpose canisters (“MPCs”) and are hermetically sealable to effectuate the dry storage of spent nuclear fuel. Once the canister is loaded with the spent nuclear fuel, the loaded canister is transported and stored in large cylindrical containers called casks. A transfer cask is used to transport spent nuclear fuel from location to location while a storage cask is used to store spent nuclear fuel for a determined period of time. In a typical nuclear power plant, an open empty canister is first placed in an open transfer cask. The transfer cask and empty canister are then submerged in a pool of water. Spent nuclear fuel is loaded into the canister while the canister and transfer cask remain submerged in the pool of water. Once fully loaded with spent nuclear fuel, a lid is typically placed atop the canister while in the pool. The transfer cask and canister are then removed from the pool of water, the lid of the canister is welded thereon and a lid is installed on the transfer cask. The canister is then properly dewatered and back filled with inert gas. The canister is then hermetically sealed. The transfer cask (which is holding the loaded and hermetically sealed canister) is transported to a location where a storage cask is located. The canister is then transferred from the transfer cask to the storage cask for long term storage. During transfer from the transfer cask to the storage cask, it is imperative that the loaded canister is not exposed to the environment. One type of storage cask is a ventilated vertical overpack (“VVO”). A VVO is a massive structure made principally from steel and concrete and is used to store a canister loaded with spent nuclear fuel. Existing VVOs stand above ground and are typically cylindrical in Shape and extremely heavy, weighing over 150 tons and often having a height greater than 16 feet. VVOs typically have a flat bottom, a cylindrical body having a cavity to receive a canister of spent nuclear fuel, and a removable top lid. In using a VVO to store spent nuclear fuel, a canister loaded with spent nuclear fuel is placed in the cavity of the cylindrical body of the VVO. Because the spent nuclear fuel is still producing a considerable amount of heat when it is placed in the VVO for storage, it is necessary that this heat energy have the ability to escape from the VVO cavity. This heat energy is removed from the outside surface of the canister by passively ventilating the VVO cavity using natural convective forces. In passively ventilating the VVO cavity, cool air enters the VVO chamber through bottom ventilation ducts, flows upward past the loaded canister, and exits the VVO at an elevated temperature through top ventilation ducts. The bottom and top ventilation ducts of existing VVOs are located circumferentially near the bottom and top of the VVO's cylindrical body respectively, as illustrated in FIG. 1. While it is necessary that the VVO cavity be vented so that heat can escape from the canister, it is also imperative that the VVO provide adequate radiation shielding and that the spent nuclear fuel not be directly exposed to the external environment. The inlet duct located near the bottom, of the overpack is a particularly vulnerable source of radiation exposure to security and surveillance personnel who, in order to monitor the loaded overpacks, must place themselves in close vicinity of the ducts for short durations. Additionally, when a canister loaded with spent nuclear fuel is transferred from a transfer cask to a storage VVO, the transfer cask is stacked atop the storage VVO so that the canister can be lowered into the storage VVO's cavity. Most casks are very large structures and can weigh up to 250,000 lbs. and have a height of 16 ft. or more. Stacking a transfer cask atop a storage VVO/cask requires a lot of space, a large overhead crane, and possibly a restraint system for stabilization. Often, such space is not available inside a nuclear power plant. Finally, above ground storage VVOs stand at least 16 feet above ground, thus, presenting a sizable target of attack to a terrorist. FIG. 1 illustrates a traditional prior art VVO 1. The prior art VVO 1 comprises a flat bottom 7, a cylindrical body 2, and a lid 4. The lid 4 is secured to a cylindrical body 2 by a plurality of bolts 8. The bolts 8 serve to restrain separation of the lid 4 from the body 2 if the prior art VVO 1 were to tip over. The cylindrical body 2 has a plurality of top ventilation ducts 5 and a plurality of bottom ventilation ducts 6. The top ventilation ducts 5 are located at or near the top of the cylindrical body 2 while the bottom ventilation ducts 6 are located at or near the bottom of the cylindrical body 2. Both the bottom ventilation ducts 6 and the top ventilation ducts 5 are located around the circumference of the cylindrical body 2. The entirety of the prior art VVO 2 is positioned above grade and, therefore, suffers from a number of the drawbacks discussed above and remedied by the present invention. It is therefore an object of the present invention to provide a system and method for storing high level waste, such as spent nuclear fuel, that reduces the height of the stack assembly during canister transfer procedure. Another object of the present invention to provide a system and method for storing high level waste, such as spent nuclear fuel, that requires less vertical space. Yet another object of the present invention is to provide a system and method for storing high level waste, such as spent nuclear fuel, that utilizes the radiation shielding properties of the subgrade during storage while providing adequate passive ventilation of the high level waste. A further object of the present invention is to provide a system and method for storing high level waste, such as spent nuclear fuel, that provides the same or greater level of operational safeguards that are available inside a fully certified nuclear power plant structure. A still further object of the present invention is to provide a system and method for storing high level waste, such as spent nuclear fuel, that decreases the dangers presented by earthquakes and other catastrophic events and virtually eliminates the potential damage from a World Trade Center or Pentagon type of attack on the stored canister. It is also an object of the present invention to provide a system and method for storing high level waste, such as spent nuclear fuel, that allows an ergonomic transfer of the high level waste from a transfer cask to a storage VVO. Another object of the present invention is to provide a system and method for storing high level waste, such as spent nuclear fuel, below grade. Yet another object of the present invention is to provide a system and method of storing high level waste, such as spent nuclear fuel, that reduces the amount of radiation emitted to the environment. Still another Object of the present invention is to provide a system and method of storing a plurality of canisters containing high level waste in separate below grade cavities while facilitating adequate passive ventilated cooling of each canister. These and other objects are met by the present invention which in one aspect is a system for storing high level waste emitting a heat load, comprising: an air-intake shell forming a substantially vertical air-intake cavity; a plurality of storage shells, each storage shell terming a substantially vertical storage cavity; a hermetically sealed canister for holding high level waste positioned in each of the storage cavities so that a gap exists between the storage shell and the canister, the horizontal cross-section of each storage cavity accommodating no more than one canister; a removable lid positioned atop each of the storage shells so as to form a lid-to-shell interface, the lid containing an outlet vent forming a passageway between an ambient environment and the storage cavity; and a network of pipes forming a passageway between a bottom portion of the intake cavity and a bottom portion of each of the storage cavities. Preferably, the system of the present invention is used to store spent nuclear fuel in a below grade environment. In such an embodiment, the storage shells are positioned so that at least a major portion of their height is located below grade (i.e., below the surface level of the ground). The network of pipes are also located below grade while the lids positioned atop the storage shells are located above grade. A radiation absorbing material preferably surrounds the storage shells and covers the network of pipes. The radiation absorbing material can be concrete, an engineered fill, soil, and/or a combination thereof. It is further preferable that the storage shells, the air-intake shell, the network of pipes, and all connections therebetween be hermetically constructed so as to prohibit the ingress of below grade liquids. The air-intake shell, the storage shells and the network of pipes are preferably constructed of a metal or alloy. All connections can be achieved by welding or other suitable procedures that result in an integral hermetic structure. In this below grade embodiment of the system, the air-intake cavity forms an air passageway between the above grade air and the network of pipes. Similarly, the vents in the lids positioned atop the storage shells form passageways between the storage cavitiesand the above grade air. As a result of this design, when the hermetically sealed canisters (which are loaded with the hot high level waste) are loaded in the storage cavities, cool ambient air will enter the air-intake cavity, travel through the network of pipes, and enter the bottom portion of the storage cavities. Heat from the high level waste within the canisters will warm the cool air causing it to rise through the gap that exists between the storage shell and the canister. Upon continuing to rise, the heated air will then exit the storage cavities via the vents in the lids. The chimney effect of the heated air escaping the storage cavities siphons additional cool air into the air-intake cavity, through the network of pipes, and into the storage cavities. Thus, the below grade storage of multiple spent nuclear fuel canisters can be achieved while affording adequate ventilation for cooling. As in typical overpack systems, the canisters are preferably non-fixedly positioned within the storage cavities in a substantially vertical orientation. In other words, the canisters are positioned within the storage cavities free of anchors and are free-standing. As a result, the canisters can be easily inserted, removed and transferred from the storage cavities, as necessary. A lid can also be positioned atop the air-intake shell so as to form a lid-to-shell interface with the air-intake shell. This lid preferably contains an inlet vent that forms a passageway between the ambient environment and the air-intake cavity. As a result, cool air can be siphoned into the air-intake cavity while prohibiting the entrance of debris and/or rain water. The network of pipes preferably comprises one or more headers that couple the storage shells to the air-intake shell. The headers act as a manifold and assist in evenly distributing the incoming cool air to the storage cavities. A layer of insulating material can also be provided to circumferentially surround the storage shells. The insulation facilitates in prohibiting the incoming cool air from becoming: heated prior to entering the storage cavities. In other words, the insulation prohibits the heat emanated by the canisters from conducting into the radiation absorbing material surrounding the storage shells, thereby keeping the air-intake cavity and the network of pipes cool. Preferably, the system further comprises means for supporting the canisters in the storage cavities so that a first plenum exists between a bottom of the canister and a floor of the storage cavity. It is further preferable that a second plenum exists between a top of the canister and a bottom surface of the lid that encloses the storage cavity. In this embodiment, the network of pipes form passageways between the air-intake cavity and the first plenums while the outlet vents within the lids form passageways between the ambient environment and the second plenums. In one embodiment, the support means can comprise a plurality of circumferentially spaced support blocks. It is further preferable that the gaps that exist between the storage shells and the canisters be a small annular gap. In one embodiment, the storage shells can surround the air-intake shell so as to form an array of shells, arranged in side-by-side relation. The dimensions of the array can vary as desired. In another aspect, the invention can be a ventilated, system for storing high level waste having a heat load, the system comprising: an array of substantially vertically oriented shells arranged in a side-by-side relation, each shell forming a cavity a hermetically sealed canister for holding high level waste positioned in one or more of the cavities, the cavities having a horizontal cross-section that accommodates no more than one of the canisters; a removable lid positioned atop each of the shells so as to form a lid-to-shell interface, each lid containing a vent forming a passageway between an ambient environment and the storage cavity; a network of pipes forming air passageways between bottoms of all of the cavities; and wherein at least one of the cavities is empty so as to allow cool air to enter the network of pipes. In yet another aspect, the invention is a method of storing and passively ventilating high level waste comprising: providing a system comprising an array of substantially vertically oriented shells arranged in a side-by-side relation, each shell forming a cavity, and a network of pipes forming air passageways between bottom portions of all of the cavities; positioning the system in a below grade hole so that a major portion of the height of the shells is below grade; filling the below grade hole with a radiation absorbing material so as to surround the shells and cover the network of pipes, the cavities being accessible from above grade; lowering a hermetically sealed canister containing high level waste into the cavity of one or more of the shells so that a gap exists between the canister and the shell, the cavity having a horizontal cross-section that accommodates no more than one of the canisters; positioning a removable lid atop the shell containing the canister so as to form a lid-to-shell interface, the lid containing a vent forming a passageway between an above grade atmosphere and the cavity containing the canister; maintaining at least one of the cavities empty; and cool an entering the empty cavity the cool air being draw into the network of pipes and into the cavity containing the canister, the cool air being warmed by heat from the canister, the warm air rising in the gap and exiting the cavity through the vent of the lid. In a further aspect, the invention can be a ventilated system for storing high level waste emitting heat, the system comprising: an air-intake shell forming an air-intake cavity; a plurality of storage shells, each storage shell forming a storage cavity; a lid positioned atop each of the storage shells; an outlet vent forming a passageway between an ambient environment and a top portion of each of the storage cavities; and a network of pipes forming hermetically sealed passageways between a bottom portion of the air-intake cavity and at least two different openings at a bottom portion of each of the storage cavities such that blockage of a first one of the openings does not prohibit air from flowing from the air-intake cavity into the storage cavity via a second one of the openings. In another aspect, the invention can be a ventilated system for storing high level waste emitting heat, the system comprising: an air-intake shell forming an air-intake cavity; a plurality of storage shells, each storage shell forming a storage cavity; a lid positioned atop each of the storage shells; an outlet vent forming a passageway between an ambient environment and a top portion of each of the storage cavities; and a network of pipes forming hermetically sealed passageways between a bottom portion of the air-intake cavity and a bottom portion of each of the storage cavities, wherein the network of pipes is configured so that a line of sight does not exist between any of the storage cavities through the passageways. Referring first to FIG. 2, a manifold storage system 100 is illustrated according to an embodiment of the present invention. As illustrated in FIG. 2, the manifold storage system 100 is removed from the ground. However, as will be discussed in greater detail below, the manifold storage system 100 is specifically designed to achieve the dry storage of multiple hermetically sealed canisters containing spent nuclear fuel in a below grade environment. The manifold storage system 100 is a vertical, ventilated dry spent fuel storage system that is fully compatible with 100 ton and 125 ton transfer casks for spent fuel canister transfer operations. The manifold storage system 100 can be modified/designed to be compatible with any size or style transfer cask. The manifold storage system 100 is designed to accept multiple spent fuel canisters for storage at an Independent Spent Fuel Storage Installation (“ISFSI”) in lieu of above ground overpacks (such as prior art VVO 2 in FIG. 1). All canister types engineered for the dry storage of spent fuel in above-grade overpack models can be stored in the manifold storage system 100. Suitable canisters include multi-purpose canisters (“MPCs”) and thermally conductive casks that are hermetically sealed for the dry storage of high level wastes, such as spent nuclear fuel. Typically, such canisters comprise a honeycomb grid-work/basket, or other structure, built directly therein to accommodate a plurality of spent fuel rods in spaced relation. An example of an MPC that is particularly suitable for use in the present invention is disclosed in U.S. Pat. No. 5,898,747 to Krishna Singh, issued Apr. 27, 1999 the entirety of which is hereby incorporated by reference. In some embodiments, the invention may include the canister or MPC positioned within the manifold storage system 100. The manifold storage system 100 is a storage system that facilitates the passive cooling of storage canisters through natural convention/ventilation. The manifold storage system 100 is free of forced cooling equipment, such as blowers and closed-loop cooling systems. Instead, the manifold storage system 100 utilizes the natural phenomena of rising warmed air, i.e., the chimney effect, to effectuate the necessary circulation of air about the canisters. In essence, the manifold storage system 100 comprises a plurality of modified ventilated vertical modules that can achieve the necessary ventilation/cooling of multiple canisters containing spent nuclear in a below grade environment. The manifold storage system 100 comprises a vertically oriented air-intake shell 10A and a plurality of vertically oriented storage shells 10B. The storage shells 10B surround the air-intake shell 10A. In the exemplified embodiment, the air-intake shell 10A is structurally identical to the storage shells 10B. However, as will be discussed below, the air-intake shell 10A is intended to remain empty (i.e., free of a heat load and unobstructed) so that it can act as an inlet passageway for cool air into the manifold storage system 100. The storage shells 10B are adapted to receive hermetically sealed canisters containing spent nuclear fuel and to act as storage/cooling chamber for the canisters. However, in some embodiment of the invention, the air-intake shell 10A can be designed to be structurally different than the storage shells 10B so long as the internal cavity of the air-intake shell 10A allows the inlet of cool air for ventilating the storage shells 10B. Stated simply, the cavity of the air-intake shell 10A acts as a downcomer passageway for the inlet of cooling air into the piping network 50. For example, the air-intake shell 10A can have a cross-sectional shape, cross-sectional size, material of construction and/or height that can be different than that of the storage shells 10B. While the air-intake shell 10A is intended to remain empty during normal operation and use, if the heat load of the canisters being stored in the storage shells 10B is sufficiently low such that circulating air flow is not needed, the air-intake shell 10A can be used to store a canister of spent fuel. Both the air-intake shell 10A and the storage shells 10B are cylindrical in shape. However, in other embodiments the shells 10A, 10B can take on other shapes, such as rectangular, etc. The shells 10A, 10B have an open top end and a dosed bottom end The shells 10A, 10B are arranged in a side-by-side orientation forming a 3×3 array. The air-intake shell 10A is located in the center of the 3×3 array. It should be noted that while it is preferable that the air-intake shell 10A be centrally located, the invention is not so limited. The location of the air-intake shell 10A in the array can be varied as desired by simply leaving one or more of the storage shells 10B empty. Moreover, while the illustrated embodiment of the manifold storage system 100 comprises a 3×3 array of the shells 10A, 10B, and other array sizes and/or arrangements can be implemented in alternative embodiments of the invention. The shells 10A, 10B are preferably spaced apart in a side-by-side relation. The horizontal distance between the vertical center axis of the shells 10A, 10B is in the range of about 10 to 20 feet, and more preferably about 15 feet. However, the exact distance between shells will be determined on case by case basis and is not limiting of the present invention. The shells 10A, 10B are preferably constructed of a thick metal, such as steel, including low carbon steel. However, other materials can be used, including without limitation metals, alloys and plastics. Other examples include stainless steel, aluminum, aluminum-alloys, lead, and the like. The thickness of the shells 10A, 10B is preferably in the range of 0.5 to 4 inches, and most preferably about 1 inch. However, the exact thickness of the shells 10A, 10B will be determined on a case-by-case basis, considering such factors as the material of construction, the heat load of the spent fuel being stored, and the radiation level of the spent fuel being stored. The manifold storage system 100 further comprises a removable lid 12 positioned atop each of the shells 10A, 10B. The lids 12 are positioned atop the shells 10A, 10B, thereby enclosing the open top ends of the cavities formed by the shells 10A, 10B. The lids 12 provide the necessary radiation shielding so as to prevent radiation from escaping upward from the cavities formed by the storage shells 10B when the loaded canisters are positioned therein. The lids are secured to the shells 10A, 10B by bolts or other connection means. The lids 12 are capable of being removed from the shells 10A, 10B without compromising the integrity of and/or otherwise damaging either the lids 12 or the shells 10A, 10B. In other words, each lid 12 forms a non-unitary structure with its corresponding shell 10A, 10B. In certain embodiments, however, the lids 12 may be secured to the shells 10A, 10B via welding or other semi-permanent connection techniques that are implemented once the shells 10A, 10B are loaded with a canister loaded with HLW. Each of the lids 12 comprises one or more inlet ducts that form a passageway from the ambient air into the cavity formed by the shells 10A, 10B. The structural details of the lids 12 will be discussed in greater detail below with respect to FIGS. 6A and 6B. The interaction of the lids 12 with the shells 10A, 10B will described in greater detail below with respect to FIG. 7. In certain embodiments, however, the lids 12 may be solid structures that do not have passageways therein that allow heated air to escape the shells 10B or that allow cool air to enter the shell 10A. In such an embodiment, the top ends of the shells 10A, 10B may be modified to include ducts that form the necessary fluid passageways into the shells 10A, 10B. For example, cutouts or other holes may be provided on the sidewalls of the shells 10A, 10B themselves to which a tortuous duct is attached that allows air flow to and/or from the interior cavity of the shells 10A, 10B. Suitable structural configurations of storage shells wherein ducts are provided at the top end of the shells are disclosed in U.S. Pat. No. 7,590,213 to Krishna P. Singh, issued Sep. 15, 2009, the entirety of which is hereby incorporated by reference. Referring still to FIG. 2, the manifold storage system 100 further comprises a network 50 of pipes/ducts that fluidly connect all of the storage shells 10B to the air-intake shell 10A (and to each other). The network 50 comprises two headers 51, a plurality of straight pipes 52, and a plurality of curved expansion joints 53. The headers 51 are used as manifolds to fluidly connect all of the storage shells 10B to the air-intake shell 10A in order to more evenly distribute the flow of incoming cool air to the storage shells 10B as needed. The curved expansion joints 53 provide for thermal expansion: extraction of the network as needed The straight pipes complete the network 50 so that all shells 10A, 10B are hermetically and fluidly connected. The piping network 50 connects at or near the bottom of the shells 10A, 10B to form a network of fluid passageways between the internal cavities of all of the shells 10A, 10B. Of course, appropriately positioned openings are provided in the sidewalls of the shells 10A, 10B to which the piping network 50 is fluidly coupled. As a result, the piping network 50 provides passageways from the internal cavity of the air-intake shell 10A to all of the internal cavities of the storage shells 10B via the headers 51. As a result, cool air entering the air-intake shell 10A can be distributed to all of the storage shells 10B via the piping network 50. It is preferable that the incoming cool air be supplied to at or near the bottom of the internal cavities of the storage shells 10B (via the openings) to achieve cooling of the canisters positioned therein. The network of pipes 50 is configured so that the quantity of air drawn by each of the storage shells 10B adjusts to comply with Bernoulli's law. The air-flow through each storage shell 10B (which is effectuated by the canister heat load) is influenced by the air-flow drawn by any other of the storage shells 10B in the network. Additionally, every storage cavity 10B in the network is fed with air by at least two inlet passages such that blockage in any one flow artery will not cause a sharp temperature rise in the affected cells. Thought of another way, the network of pipes 50 is configured so that two different paths exist through the hermetically sealed fluid passageway formed by the network of pipes 50 from the downcomer air-intake cavity of the intake shell 10A to each of the storage cavities of the storage shells 10B. Preferably, neither of the two different paths pass through any of the other storage cavities of the storage shells 10B. However, the invention is not so limited and in some instances. In certain embodiments, the existence of two different paths through the passageways of the piping network 50 includes situations where two paths exist through the passageways of the piping network that overlap for a portion of the paths, but not the entirety of the two paths. It is further preferred that the final pipe in each of the two different paths not be the same pipe. In this embodiment, the two different paths from the air-intake shell 10A to each storage shell 10B through the passageways of the piping network 50 includes a first path that passes through a first pipe that terminates in a first opening into the a storage shell 10B and a second path that passes through a second pipe that terminates in a second opening into that same storage shell 10B, wherein the first and second pipes are not the same pipe. The configuration of the piping network 50 makes it resilient to change in environmental conditions, including upset conditions such as a pipe blockage. Moreover, due to the special configuration of the piping, network, if one storage shell 10B in the array was left empty, this empty storage shell 10B would become another air intake downcomer passageway (similar to the air intake shell 10A). In other words, the air in the empty storage shell 10B would flow downwards and begin feeding piping network with cool air. In fact, any storage shell 10B loaded with a low heat emitting canister can also become a downdraft cell. To determine which way the air will flow in any given canister loading situation, one will need to solve a set of non-linear (quadratic in flow) simultaneous equations (Bernoulli's equations for piping networks) with the aid of a computer program. A manual calculation in the manner of Torricelli's law is not possible. The advantages of the inter-connectivity of the piping network 50 becomes obvious when one considers the consequences of blocking a pipe leading to one storage shell 10B (a compulsory safety question in nuclear plant design work) because that storage shell 10B would not be deprived of the intake air as the neighboring storage shells 10B could provide relief to the distressed shell 10B through an alternate pathway. While one embodiment of a plumbing/layout for the piping network 50 is illustrated, the invention is not limited to any specific layout. Those skilled in the art will understand that an infinite number of design layouts can exist for the piping network 50. Furthermore, depending on the ventilation and air flow needs of any given manifold storage system, the piping network may or may not comprise headers and/or expansion joints. The exact layout and component needs of any piping network will be determined on case-by-case design basis. The internal surfaces of the piping network 50 and the shells 10A, 10B are preferably smooth so as to minimize pressure loss. Similarly, ensuring that all angled portions of the piping network are of a curved configuration will further minimize pressure loss. The size of the pipes/ducts used in the piping network 50 can be of any size. The exact size of the ducts will be determined on case-by-case basis considering such factors as the necessary rate of air flow needed to effectively cool the canisters. In one embodiment, a combination of steel pipes having a 24 inch and 36 inch outer diameter are used. The components 51, 52, 53 of the piping network 50 are seal joined to one another at all connection points. Moreover, the piping network 50 is seal joined to all of the shells 10A, 10B to form an integral/unitary structure that is hermetically sealed to the ingress of water and other fluids. In the case of weldable metals, this seal joining may comprise welding or the use of gaskets. In the case of welding, the piping network 50 and the shells 10A, 10B will form a unitary structure. Moreover, as shown in FIG. 7, each of the shells 10A, 10B further comprise an integrally connected floor 11. Thus, the only way water or other fluids can enter any of the internal cavities of the shells 10A, 10B or the piping network 50 is through the top open end of the internal cavities. An appropriate preservative, such as a coal tar epoxy or the like, is applied to the exposed surfaces of shells 10A, 10B and the piping network 50 to ensure sealing, to decrease decay of the materials, and to protect against fire. A suitable coal tar epoxy is produced by Carboline Company out of St. Louis, Mo. under the tradename Bitumastic 300M. Referring to FIG. 9, the piping network. 50 can also be designed so that a direct line of sight does not exist between any two internal cavities of the storage shells 10B. This eliminates shine between canisters loaded in the cavities of the storage shells 10B, which is possible due to the fact that the network of pipes 50 connect to side walls of the storage shells 10B. Of course, the concept could be expanded to situations where the network of pipes 50 is connected to the floor of the storage shells 10B. Furthermore, the elimination of the line-of-sight between any two internal cavities of the storage shells 10B can be effectuated through a number of piping configurations, including the creation of a tortuous path, a segmented path, an angled path, or combinations thereof. Referring now to FIGS. 2 and 3, it can be seen that a layer of insulating material 20 circumferentially surrounds each of the storage cavities 10B. Suitable forms of insulation include, without limitation, blankets of alumina-silica fire clay (Kaowool Blanket), oxides of alumina and silica (Kaowool S Blanket), alumina-silica-zirconia fiber (Cerablanket), and alumina-silica-chromia (Cerachrome Blanket). The insulation 20 prevents excessive transmission of heat from spent fuel canisters within the storage shells 10B to the surrounding structure material, such as the concrete monolith 60 (FIG. 7) the air-intake shell 10A and the piping network 50. Insulating the storage shells 10B serves to minimize the heat-up of the incoming cooling air before it enters the cavities of the storage shells 10B. This facilitates in maintaining adequate ventilation/cooling of the spent fuel canisters stored therein. The insulating process can be achieved in a variety of ways, none of which are limiting of the present invention. For example, in addition to adding a layer of the insulating material 20 to the exterior of the storage shells 10B, insulating material can also be added to surround the components of the piping network 50 and/or the air-intake shell 10A. Furthermore, in addition to or instead of an insulating material, it may be possible to provide the necessary insulation of the incoming cool air by providing gaps in the concrete monolith 60 (FIG. 7) at the appropriate places. These gaps may be filled with an inert gas or air if desired. Referring now to FIG. 4, the manifold storage system 100 is illustrated with the lids 12 removed from the shells 10A, 10B. As can be seen, each of the shells 10A, 10B comprise a container ring 13 at or near their top. The container rings 13 are thick steel ring-like structures. The container rings 13 circumferentially surround the periphery of the shells 10A, 10B and are secured thereto by welding or another connection technique. In addition to adding structural integrity to the shells 10A, 10B, the container rings 13 also interface with the shear rings 23 (FIGS. 6A, 6B) on the lids 12 to provide resistance to lateral forces. With reference to FIGS. 3 and 4, it can be seen that the network of pipes 50 connects to side walls of the storage shells 10B and the air-intake shell 10A. Additionally, the storage shells 10B and the air-intake shell 10A are arranged in a side-by-side relation so that the bottoms surfaces of the shells 10A, 10B are located in the same plane. Preferably, the entirety of the network of pipes 50 is located in or above this plane (i.e., the network of pipes 50 does not extend below this plane). Referring to FIGS. 6A and 6B, the lid 12 is illustrated in detail according to an embodiment of the present invention. In order to provide the requisite radiation shielding for the spent fuel canisters stored in the storage shells 10B, the lid 12 is constructed of a combination of low carbon steel and concrete. More specifically, in constructing one embodiment of the lid 12, a steel lining is provided and filled with concrete (or another radiation absorbing material). In other embodiments, the lid 12 can be constructed of a wide variety of materials, including without limitation metals, stainless steel, aluminum, aluminum-alloys, plastics, and the like. In some embodiments, the lid may be constructed of a single piece of material, such as concrete or steel for example. The lid 12 comprises a flange portion 21 and a plug portion 22. The plug portion 22 extends downward from the flange portion 21. The flange portion 21 surrounds the plug portion 22, extending therefrom in a radial direction. A plurality of outlet vents 28 are provided in the lid 12. Each outlet vent 28 forms a passageway from an opening 29 in the bottom surface 30 of the plug portion 22 to an opening 31 in the top surface 32 of the lid 12. A cap 33 is provided over opening 31 to prevent rain water or other debris from entering and/or blocking the outlet vents 28. The cap 33 is secured to the lid 12 via bolts or through any other suitable connection, including without limitation welding, clamping, a tight fit, screwing, etc. The cap 33 is designed to prohibit rain water and other debris flom entering into the opening 31 while affording heated air that enters the vents 28 via the opening 29 to escape therefrom. In one embodiment, this can be achieved by providing a plurality of small holes (not illustrated) in the wall 34 of the cap 33 just below the overhang of the roof 35 of the cap. In other embodiments, this can be achieved by non-hermetically connecting the roof 35 of the cap 33 to the wall 34 and/or constructing the cap 33 (or portions thereof) out of material that is permeable only to gases. The opening 31 is located in the center of the lid 12. In order to further protect against rain water or other debris entering opening 31, the top surface 32 of the lid 12 is sloped away from the opening 31 (i.e., downward and outward). The top surface 32 of the lid 12 (which acts as a roof) overhangs beyond the side wall 135 of the flange portion 21. The outlet vents 28 are curved so that a line of sight does not exist therethrough. This prohibits a line of sight from existing from the ambient environment to a canister that is loaded in the storage shell 10B, thereby eliminating radiation shine into the environment. In other embodiments, the outlet vents may be angled or sufficiently tilted so that such a line of sight does not exist. The lid 30 thriller comprises a shear ring 23 secured to the bottom surface 37 of the flange portion 31. The shear ring 23 may be welded, bolted, or otherwise secured to the bottom surface 37. The shear ring 23 is designed to extend downward from the bottom surface 37 and peripherally surround and engage the container ring 13 of the shells 10A, 10B, as shown in FIG. 7. While not illustrated, it is preferable that duct photon attenuators be inserted into all of vents 28 of the lids 12 for both the storage shells 10B and the air-intake shell 10A, irrespective of shape and/or size. A suitable duct photon attenuator is described in U.S. Pat. No. 6,519,307, Bongrazio, the teachings of which are incorporated herein by reference in its entirety. It should be noted that in some embodiments, the air-intake shell 10A may not have a lid 12. Referring now to FIG. 7, the cooperational relationship of the elements of the lid 12 and the elements of the shells 10A, 10B will now be described. In order to avoid redundancy, only the interaction of the lid 12 with a single storage shell 10B will be described in detail with the understanding that those skilled in the art will appreciate that the below discussion applies to all of the storage shells 10B and the air-intake shell 10A. When the lid 12 is placed atop the storage shell 10B of the manifold storage system 100 (e.g., during the storage of a canister loaded with spent fuel), the plug portion 22 of the lid 12 is lowered into the cavity 24 formed by the storage shell 10B until the flange portion 21 of the lid 12 contacts and rests atop the storage shell 10B thereby forming a lid-to-shell interface. More specifically, the bottom surface 37 (FIG. 6B) of the flange portion 21 of the lid 12 contacts and rests atop the top surfaces of the storage shell 10B so as to form the lid-to-shell interface. The lid 12 and the storage shell 10B form a non-unitary structure. At this point, the shear ring 23 of the lid 12 engages and peripherally surrounds the outside surface of the container ring 13. The interaction of the shear ring 23 and the container ring 13 provides enormous shear resistance against lateral forces from earthquakes, impactive missiles, or other projectiles. The lid 12 is secured in place via bolts (or other fastening means) that can either extend into holes in the concrete monolith 60 or into the storage shell 10B itself. While the lid 12 is secured the storage shell 10B and/or the concrete monolith 60, the lid 12 remains non-unitary and removable. While not illustrated, one or more gaskets can be provided at some position at the lid-to-shell interface so as to form a hermetically sealed interface, When the lid 12 is properly positioned atop the storage shell 10B as illustrated in FIG. 7, the vents 28 are in spatial cooperation with the cavity 24 formed by the storage shell 10B. In other words, each of the vents 28 form a passageway from the ambient atmosphere to the cavity 24 itself. The vents in the lid positioned atop the air-intake shell 10A provide a similar passageway. With respect to the air-intake shell 10A, the vents 28 act as a passageway that allows cool ambient air to siphoned into the cavity 24 of the air-intake shell 10A, through the piping network 50, and into the bottom portion of the cavities 24 of the storage shells 10B. When a canister containing spent fuel (or other HLW) having a heat load is positioned within the cavities 24 of one or more of the storage shells 10B, this incoming cool air is warmed by the canister, rises within the cavity 24, and exits the cavity 24 via the vents 28, in the lids 12 atop the storage shells 10B. It is this chimney effect that creates the siphoning effect in the air-intake shell 10A. Referring now to FIGS. 7 and 8, the shells 10A, 10B form vertically oriented cylindrical cavities 24 therein. While the cavities 24 are cylindrical in shape, the cavities 24 are not limited to any specific shape, but can be designed to receive and store almost any shape of canister without departing, from the spirit of the invention. The horizontal cross-sectional size and shape of the cavities 24 of the storage shells 10B are designed to generally correspond to the horizontal cross-sectional size and shape of the spent fuel canisters 80 (FIG. 8) that are to be stored therein. The horizontal cross-section of the cavities 24 of the storage shells 10B accommodate no more than one canister 80 of spent fuel. The horizontal cross-sections of the cavities 24 of the storage shells 10B are sized and shaped so that when spent fuel canisters 80 are positioned therein for storage, a small gap/clearance 25 exists between the outer side walls of the canisters 80 and the side walls of cavities 24. When the shells 10B and the canisters 80 are cylindrical in shape, the gaps 25 are annular gaps. In one embodiment, the diameter of the cavities 24 of the storage shells 10B is in the range of 5 to 7 feet, and more preferably approximately 6 feet. Designing the cavities 24 of the storage shells 10B so that a small gap 25 is formed between the side walls of the stored canisters 80 and the side walls of cavities 24 limit the degree the canisters 80 can move within the cavities 24 during a catastrophic event, thereby minimizing damage to the canisters 80 and the cavity walls and prohibiting the canisters 80 from tipping over within the cavities 24. These small gap 25 also facilitates flow of the heated air during spent nuclear fuel cooling. The exact size of the gap 25 can be controlled/designed to achieve the desired fluid flow dynamics and heat transfer capabilities for any given situation. In one embodiments, the gap 25 has a width of about 1 to 3 inches. Making the width of the gap 25 small also reduces radiation streaming. Support blocks 42 are provided on the floors 11 of the cavities 24 of the storage shells 10B so that the canisters 80 can be placed thereon. The support blocks 42 are circumferentially spaced from one another around the floor 11. When the canisters 80 are loaded into the cavities 24 of the storage shells 10B, the bottom surfaces 81 of canisters 80 rest on the support hocks 42, forming an inlet air plenum 27 between the bottom surfaces 81 of the canisters 80 and the floors 11 of the cavities 24. The support blocks 42 are made of low carbon steel and are preferably welded to the floors 11 of the cavities 26 of the storage shells 10B. Other suitable materials of construction include, without limitation, reinforced-concrete, stainless steel, and other metal alloys. The support blocks 42 also serve an energy/impact absorbing function. The support blocks 32 are preferably of a honeycomb grid style, such as those manufactured by Hexcel Corp., out of California, U.S. When the canisters 80 are positioned atop the support blocks 32 within the storage shells 10B, outlet air plenums 26 are formed between the top surfaces 82 of the canisters 80 and the bottom surfaces 30 of the lids 12. The outlet air plenums 36 are preferably a minimum of 3 inches in height, but can be any desired height. The exact height will be dictated by design considerations such as desired fluid flow dynamics, canister height, shell height, the depth of the cavities, the canister's heat load, etc. The cavity 24 of the air-intake shell 10A is deeper than the cavities 24 of the storage shells 10B and serves as a sump for ground water or rain water (if there is a leak and/or debris). The cavity 24 of the air-intake shell 24 is typically empty and, therefore, can be readily cleared of debris. Additionally, the piping network 50 is preferably sloped toward the air-intake shell 10A and away from the storage shells 10B so that any water seepage collects in the bottom of the cavity 24 of the air-intake shell 10A. If desired, a drain can be included at the bottom on the cavity 24 of air-intake shell 10B. In FIGS. 7 and 8, the illustrated embodiment of the manifold storage system 100 further comprises a concrete monolith 60 surrounding the shells 10A, 10B and piping network 50. The concrete monolith 60 provides the necessary radiation shielding for the spent fuel canisters 80 stored in the storage shells 10B. The concrete monolith 60 provides non-structural protection for shells 10A, 10B and the piping network 50. The entire height of the shells 10A, 10B are surrounded by the concrete monolith 60 with only the lids 12 protruding therefrom and resting atop its top surface. While the vents 28 that allow the warmed air to escape the storage shells 10B are illustrated as being located within the lids 12, the present invention is not so limited. For example, the vents 28 can be located in the concrete monolith 60 itself. In such an embodiment, the openings of the vents to the ambient air can be located in the top surface of the monolith 60 and a line of sight should not exist to the ambient. Similar to when the outlet vents are located in the lid, the outlet vents can take on a variety of shapes and/or configurations, such as S-shaped or L-shaped. In all embodiments of the present invention, it is preferred that the outlet openings of the vents 28 from the storage shells 10B be azimuthally and circumferentially separated from the intake openings of the vents 28 into the air-intake shell 10A to minimize interaction between inlet and outlet air streams. As discussed above, a layer of insulating material 20 is provided at the interface between storage shells 10B and the concrete monolith 60 (and optionally at the interface between the concrete monolith 60 and the piping network 50 and the air-intake shell 10A. The insulation 20 is provided to prevent excessive transmission of heat decay from the spent fuel canisters 80 to the concrete monolith 60, thus maintaining the bulk temperature of the concrete within FSAR limits. The insulation 20 also serves to minimize the heat-up of the incoming cooling air before it enters the cavities 24 of the storage shells 10B. As mentioned above, the manifold storage system 100 is particularly suited to effectuate the storage of spent nuclear fuel and other high level waste in a below grade environment. Referring to FIG. 8, the manifold storage system 100 is positioned so that the entire concrete monolith 60 (including the entire height of the storage shells 10B) is entirely below the grade level 73 at an ISFSI. The entire piping network 50 is also located deep underground. By positioning the manifold storage system 100 below grade level 73, the system 100 is unobtrusive in appearance and there is no danger of tipping over. The low profile of the underground manifold storage system 100 does not present a target for missile or other attacks. Additionally, the underground manifold storage system 100 does not have to contend with soil-structure interaction effects that magnify the free-field acceleration and potentially challenge the stability of an above ground free-standing overpack. While the entire height of the storage shells 10B is illustrated as being below grade level 73, in alternative embodiments a portion of the storage shells 10B can be allowed to protrude above the grade level 73. In such embodiments, at least a major portion of the height of the storage shells 10B are positioned below grade level 73. Any portion of the storage shells 10B that protrude above the grade level 73 must be surrounded by the necessary radiation shielding structure. In all embodiments, the Storage shells 10B are sufficiently below grade level so that when canisters 80 of spent fuel are positioned in the cavities 24 for storage, the entire height of the canisters are below the grade level 73. This takes full advantage of the shielding effect of the surrounding soil at the ISFSI. Thus, the soil provides a degree of radiation shielding for spent fuel stored that can not be achieved in aboveground overpacks. With reference to the manifold storage system 100, a method of constructing the underground manifold storage system of FIG. 7 at an ISFSI or other location, will be discussed. First, a hole is dug into the ground at a desired position at the ISFSI having a desired depth. Once the hole is dug and its bottom properly leveled, a base foundation is placed at the bottom of the hole. The base can be a reinforced concrete slab designed to satisfy the load combinations of recognized industry standards, such as ACI-349. However, in some instances, depending on the load to be supported and/or the ground characteristics, the use of a base may be unnecessary. Once the foundation/base is properly positioned in the hole, the integral structure of FIG. 2 (which consists of the storage shells 10B, the air-intake shell 10A, and the piping network 50) is lowered into the hole in a vertical orientation until it rests atop the base. The integral structure then contacts and rests atop the top surface of the base. If desired, the integral structure can be bolted or otherwise secured to the base at this point to prohibit future movement of the integral structure with respect to the base. Once the integral structure is resting atop the base in the vertical orientation, the hole is filled with concrete to form the concrete monolith 60 around the integral structure. The concrete monolith 60 also acts a moisture barrier to the below grade components. Alternatively, soil or an engineered fill can be used instead of concrete to fill the hole. Suitable engineered fills include, without limitation, gravel, crushed rock, concrete, sand, and the like. The desired engineered fill can be supplied to the hole by any means feasible, including manually, dumping, and the like. The concrete is supplied to the hole until it surrounds the integral structure and fills hole to a level where the concrete reaches a level that is approximately equal to the ground level 73. When the hole is filled, the concrete monolith 60 is formed. The shells 10A, 10B protrude slightly from the top surface of the concrete monolith 60 so that the cavities 24 of the shells 10A, 10B are accessible from above grade. Additionally, the lids 12 can be positioned atop the shells 10A, 10B as described above. Because the integral structure is hermetically sealed at all below grade junctures, below grade liquids can not enter into the cavities 24 of the shells 10A, 10B or the piping network 50. An embodiment of a method of using the underground manifold system 100 of FIGS. 7 and 8 to store a spent nuclear fuel canister 80 will now be discussed. Upon being removed from a spent fuel pool and treated for dry storage, the spent filet canisters 80 is hermetically sealed and positioned in a transfer cask. The transfer cask is then carried by a cask crawler to an empty storage shell 10B for storage. Any suitable means of transporting the transfer cask to a position above the storage shell 10B can be used. For example, any suitable type of load-handling device, such as without limitation, a gantry crane, overhead crane, or other crane device can be used. In preparing the desired shell 10B to receive the canister 80, the lid 12 is removed so that the cavity 24 of the storage shell 10B is open and accessible from above. The cask crawler positions the transfer cask atop the storage shell 10B. After the transfer cask is properly secured to the top of the storage shell 10B, a bottom plate of the transfer cask is removed. If necessary, a suitable mating device can be used to secure the connection of the transfer cask to storage shell 10B and to remove the bottom plate of the transfer cask to an unobtrusive position. Such mating devices are well known in the art and are often used in canister transfer procedures. The canister 80 is then lowered by the cask crawler from the transfer cask into the cavity 24 of the storage shell 10B until the bottom surface 81 of the canister 80 contacts and rests atop the support blocks 42 on the floor 11 of the cavity 24. The canister 80 is free-standing in the cavity 24, free of anchors or other securing means. When resting on the support blocks 42 within the cavity 24 of the storage shell 10B, the entire height of the canister 80 is below the grade level 73. Once the canister 80 is positioned and resting in the cavity 24, the lid 12 is positioned atop the storage shell 10B, substantially enclosing the cavity 24. The lid 12 is then secured to the concrete monolith 60 via bolts or other means. When the canister 80 is so positioned within the cavity 24 of the storage shell 10B, an inlet air plenum 27 exists between the floor 11 and the bottom surface 81 of the canister 80. An outlet air plenum 27 exists between the bottom surface 30 of the lid 12 and the top surface 82 of the canister 80. A small annular gap 25 also exists between the side walls of the canister 80 and the wall of the storage shell 10B. As a result of the chimney effect caused by the heat emanating from the canister 80, coot air from the ambient is siphoned into the cavity 24 of the air-intake shell 10A via the vents 28 in its lid 12. This cool air is then siphoned through the piping network 50 and into the inlet air plenum 27 at the bottom of the cavity 24 of the storage shells 10B. This cool air is then warmed by the heat emanating from the spent fuel canister 80, rises in the cavity 24 via the annular gap 25 around the canister 80, and into the outlet air plenum 26 above the canister 80. This warmed air continues to rise until it exits the cavity 24 as heated air via the vents 28 in the lid 12 positioned atop the storage shell 10B. While the invention has been described and illustrated in sufficient detail that those skilled in this art can readily make and use it, various alternatives, modifications, and improvements should become readily apparent without departing from the spirit and scope of the invention Specifically, in one embodiment, the shells 10A, 10B and/or the piping network 50 can be omitted. In this embodiment, the cavities of the shells and the passageways of the piping network can be formed directly into the concrete monolith if desired.
	abstract	A system, method and program product for monitoring the beam angle integrity of an ion beam generated by an ion implanter system are disclosed. The invention utilizes at least one template with each template having a template surface that impedes the motion of an ion. Each template is configured such that an ion impacts the surface of the template if the trajectory of the template deviates from the optimum trajectory by a pre-determined maximum variance angle. The change caused by the impact of the ions with the template and/or a target is then measured to determine the amount of variance in the ion beam. Adjustments can then be made to the ion beam generator to correct for a misaligned beam.
	summary
	summary
	summary
059268573	description	DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS According to FIG. 1, the armor with rollers is essentially formed by a jacket 1, a pair of gauntlets 2 extending up to the user's arm and articulated at the elbow around a pivot 3, and a pair of leg-pads articulated around a pivot 5 on shoes 6 equipped with roller skates 7. A helmet of conventional type 8 also forms an integral part of this armor. These different holding elements are made of a sufficiently rigid material and are provided with articulations and with closing elements 9 enabling the user to fit them in place and to fix them onto the associated parts of his trunk or his members. Each gauntlet 2 is equipped on the one hand at the level of the elbow joint with a pair of rollers 10, 10' mobile around a common fixed rotation axis 11 in such a way as to define an assembly that can be broadly speaking assimilated to conventional roller skates, and on the other hand, beyond the hand, with a fixed roller 12 of larger dimension. A gripping opening 13 is also provided enabling the user to have the use of his hands. According to FIG. 1, the leg-pads are provided at the level of the knee joint with a pair of rollers 14, 14' fitted around a common fixed rotation axis 15 in such a way as to constitute an assembly that is broadly speaking equivalent to the pairs of rollers 10, 10' with which the gauntlets are equipped at the level of the elbow joint. According to the example represented in the figures, the skates 7 fitted on the shoes 6 articulated on the leg-pads 4 comprise four rollers 22 grouped in pairs in conventional manner. The skates 7 are moreover equipped with a pair of complementary rollers 23 notably similar to the rollers 22 and situated at the front part of the shoes 6 at the level of the user's toes. The jacket 1 is for its part equipped respectively at the front part P and at the dorsal part D with an abdominal frame 16 and a dorsal frame 17 both fitted by means of flexible securing parts. According to FIG. 1, the abdominal frame 16 is equipped with three rollers mounted loose, i.e. two rollers 18, 18' respectively situated at the level of the shoulders and one roller 19 situated at the level of the pelvic region. Two rails of obstacles 20, 20' are also provided on the abdominal frame 16 enabling the user to slide on steps or on a balustrade. In a manner which is not represented, the dorsal frame 17 has a configuration to a great extent similar to that of the abdominal frame 16, but is equipped not with three but with four rollers mounted loose, i.e. two rollers situated at the level of the shoulders and also two rollers situated at the level of the lumbar region. Two buttock support rollers 21, 21' are also provided, represented schematically by a broken line and fitted affixed to the bottom part of the dorsal part of the jacket 1. According to FIG. 2a, after he has put on the armor with rollers according to the invention, the user can start off his run as if he was on roller skates, then kneel down and place one knee on the ground as in FIG. 2b, then his hands and both knees so as to reach the position represented in FIG. 2c before spreading himself out onto all fours (FIG. 2d) and then lying down in the fully supine position represented in FIG. 2e. He can then get up while still rolling by performing the same movements as to lie down but in the reverse order. When he wants to slow down from the supine position represented in FIG. 2e, the user can perform with his arms a movement derived from the snow-plough well known to skiers by opening his elbows out and pressing down on them while closing up his forearms in the direction of the arrows a (FIG. 2f) to bring his hands together according to the position represented in FIG. 2g. From the kneeling position represented in FIG. 2c, the user can also move onto his back by moving his arms to the rear according to FIG. 2h while keeping contact with the ground, and then rocking on his feet according to FIG. 2i to the seated position represented in FIG. 2j before rocking backwards to the supine position according to FIG. 2k. Here again, to get up the user has to perform the same movements but in the reverse order.
059075880	abstract	A device for collecting core melt from a reactor pressure vessel improves a flow of the core melt out of the reactor pressure vessel. A prechamber is disposed below the reactor pressure vessel and a spreading chamber for the core melt is disposed laterally next to the reactor pressure vessel. The spreading chamber is connected to the prechamber through a channel. A base unit forms a bottom region at least of the prechamber and is made of a material having high thermal conductivity.
	abstract	This invention relates to a process and apparatus for growing agricultural products with a reduced abundance of radioactive carbon-14 (14C) by employing centrifugal separation of atmospheric gases to selectively remove carbon dioxide (CO2) with 14C. Agricultural products with reduced 14C content can be grown in controlled environments with filtered atmospheric gases for the benefit of reducing harmful damage to human DNA that is unavoidable with our current food chain, due to the natural abundance of 14C in atmospheric gases. Bilateral and unilateral compression helikon vortex apparatus provide efficient and economical removal of CO2 with 14C from atmospheric gases with a single filtration pass, which is ideally suited for large scale agricultural production.
	description	Nuclear fission reactors include breed-and-burn fast reactors (also referred to as traveling wave reactors, or TWRs). TWR means a reactor that would be designed to operate indefinitely using natural uranium, depleted uranium, spent light water reactor fuel, or thorium as a reload fuel after start up, and in which waves that breed and then burn would travel relative to the fuel. Thus, in some aspects, the TWR is a once-through fast reactor that runs on subcritical reload fuel which is bred up to a useful state and burned in situ. In a TWR, a wave of breeding and fissioning (a “breed-burn wave”) is originated in a central core of the reactor and moves relative to the fuel. In cases where the fuel is stationary, the breed and burn wave expands outward from the ignition point. In some cases, the fuel may be moved so that the breed and burn wave stays stationary relative to the core (e.g., a standing wave) but moves relative to the fuel; a standing wave is to be considered a type of TWR. Movement of fuel assemblies is referred to as “fuel shuffling” and can accomplish the standing wave, adjustment to reactor characteristics (heat, flux, power, fuel burn up, etc.). The central core in which the fuel assemblies are shuffled is disposed in a reactor vessel. The fuel assemblies include fissile nuclear fuel assemblies and fertile nuclear fuel assemblies. Reactivity control assemblies may also be disposed in the central core for adjustment of reactor characteristics. Fission energy defined by the standing wave creates thermal energy which is transferred in series through one or more primary coolant loops and intermediate coolant loops to steam generators to produce electricity, and low temperature heat is rejected through a set of water-cooled vacuum condensers. The separation of coolant systems into both primary and intermediate coolant loops helps maintain the integrity of the core and the primary coolant loops. In the TWR, both the primary and intermediate coolant loops utilize liquid sodium as the coolant. A conduit housing is disclosed. In one aspect, a conduit housing includes a top face, a pair of side faces, and a front side. The top face includes a plurality of vertical conduit ports arranged in a plurality of rows. The pair of side faces are disposed opposite each other and adjacent to the top face. The front side is positioned between the pair of side faces and defining a plurality of stepped faces. The stepped faces include a plurality of downward faces, where each of the plurality of downward faces defining a downward face plane. The stepped faces also include a plurality of upward faces, where each of the plurality of upward faces defining an upward face plane. Each upward face includes a plurality of pitched conduit ports. The conduit housing also includes a rear side disposed opposite the front side and adjacent the top face. Optionally, the number of vertical conduit ports alternate between even and odd on adjacent rows. Also, optionally, the vertical conduit ports are evenly spaced and offset from adjacent rows. Optionally, the number of pitched conduit ports alternates between even and odd on adjacent upward faces. Optionally, the pitched conduit ports are evenly spaced and offset on adjacent upward faces. In rear side may also define a plurality of secondary stepped faces. The secondary stepped faces include a plurality of secondary downward faces, each of the plurality of secondary downward faces defining a downward face plane, and where each downward face plane is parallel to an adjacent downward face plane. The stepped faces include a plurality of secondary upward faces, each of the plurality of secondary upward faces defining an upward face plane, and where each upward face plane is parallel to an adjacent upward face plane. Also, each upward face includes a plurality of secondary pitched conduit ports. Optionally, a portion of a plurality of conduits are positioned within the housing and each of the plurality of conduits is connected to a vertical conduit port or a pitched conduit port. Optionally, the conduits are configured to exit the housing in a direction opposite the top face. Optionally, each downward face plane is parallel to an adjacent downward face plane and each upward face plane is parallel to an adjacent upward face plane. FIG. 1 illustrates, in a block diagram form, some of the basic components of a travelling wave reactor (TWR) 100. In general, the TWR 100 includes a reactor core 102 containing a plurality of fuel assemblies (not shown). The core 102 is disposed at the lowest position within a pool 104 holding a volume of liquid sodium coolant 106. The pool 104 is referred to as a hot pool and has a sodium temperature higher than that of a surrounding cold pool 108 (due to the energy generated by the fuel assemblies in the reactor core 102), which also contains liquid sodium coolant 106. The hot pool 104 is separated from the cold pool 108 by an inner vessel 110. An optional headspace 112 above the level of the sodium coolant 106 may be filled with an inert cover gas, such as argon. A containment vessel 114 surrounds the reactor core 102, hot pool 104, and cold pool 108, and is sealed with a reactor head 116. The reactor head 116 provides various access points into the interior of the containment vessel 114. The size of the reactor core 102 is selected based on a number of factors, including the characteristics of the fuel, desired power generation, available reactor 100 space, and so on. Various embodiments of a TWR may be used in low power (around 300 MWe-around 500 MWe), medium power (around 500 MWe-around 1000 MWe), and large power (around 1000 MWe and above) applications, as required or desired. The performance of the reactor 100 may be improved by providing one or more reflectors, not shown, around the core 102 to reflect neutrons back into the core 102. The sodium coolant 106 is circulated within the vessel 114 via a primary sodium coolant pump 118. The primary coolant pump 118 draws sodium coolant 106 from the cold pool 108 and injects it into the hot pool 104, proximate (e.g., below) the reactor core 102, where the coolant 106 is heated due to the reactions taking place within the reactor core 102. A portion of the heated coolant 106 enters an intermediate heat exchanger 120 from an upper portion of the hot pool 104, and exits the intermediate heat exchanger 120 at a location in the cold pool 108. This primary coolant loop 122 thus circulates sodium coolant 106 entirely within the reactor vessel 114. The intermediate heat exchanger 120 also includes liquid sodium coolant and acts as a barrier between the primary coolant loop 122 and a power generation system 123, so the integrity of the core 102 and primary coolant loop 122 can be ensured. The intermediate heat exchanger 120 transfers heat from the primary coolant loop 122 (fully contained within the vessel 114) to an intermediate coolant loop 124 (that is only partially located within the vessel 114). The intermediate heat exchanger 120 passes through an opening in the inner vessel 110, thus bridging the hot pool 104 and the cold pool 108 (so as to allow flow of sodium 106 in the primary coolant loop 122 therebetween). In an embodiment, four intermediate heat exchangers 120 are distributed within the vessel 114. The intermediate coolant loop 124 circulates sodium coolant 126 that passes through pipes into and out of the vessel 114, via the reactor head 116. An intermediate sodium pump 128 located outside of the reactor vessel 114 circulates the sodium coolant 126. Heat is transferred from the sodium coolant 106 of the primary coolant loop 122 to the sodium coolant 126 of the intermediate coolant loop 124 in the intermediate heat exchanger 120. The sodium coolant 126 of the intermediate coolant loop 124 passes through a plurality of tubes 130 within the intermediate heat exchanger 120. These tubes 130 keep separate the sodium coolant 106 of the primary coolant loop 122 from the sodium coolant 126 of the intermediate coolant loop 124, while transferring heat energy therebetween. A direct heat exchanger 132 extends into the hot pool 104 and provides additional cooling to the sodium coolant 106 within the primary coolant loop 122. The direct heat exchanger 132 is configured to allow sodium coolant 106 to enter and exit the heat exchanger 132 from the hot pool 104. The direct heat exchanger 132 has a similar construction to the intermediate heat exchanger 120, where tubes 134 keep separate the sodium coolant 106 of the primary coolant loop 122 from a sodium coolant 136 of a direct reactor coolant loop 138, while transferring heat energy therebetween. Other ancillary reactor components (both within and outside of the reactor vessel 114) include, but are not limited to, pumps, check valves, shutoff valves, flanges, drain tanks, etc., that are not depicted but would be apparent to a person of skill in the art. Additional penetrations through the reactor head 116 (e.g., a port for the primary coolant pump 118, inert cover gas and inspection ports, sodium processing ports, etc.) are not depicted. A control system 140 is utilized to control and monitor the various components of the reactor 100. Broadly speaking, this disclosure describes configurations that improve the performance of the reactor 100 described in FIG. 1. Specifically, embodiments, configurations, and arrangements of instrumentation conduit housings positioned on the reactor head 116 are shown and described in more detail below with reference to FIGS. 3A-4. FIG. 2 is a partial perspective view of a reactor core of a TWR reactor 150 and access and control mechanism related thereto. Two instrumentation conduit housings 200 are positioned on a rotating plug assembly 152 that is disposed within the reactor head (not shown). Conduits extend from the conduit housing 200, through the plug assembly 152, and into the hot pool 104 of the reactor 150. The conduits are not depicted, but pass through a collector duct 154 (are associated with each instrumentation conduit housing 200). The conduits terminate above the reactor core. Instrumentation capable of monitoring various reactor parameters, such as temperature and flow rate, are inserted into the conduits and positioned proximate the core 102. Such instrumentation may include sensors, wires, probes, combinations thereof, and so on, as required or desired for particular purposes. Generally, the instrumentation conduit housing 200 supports the conduits and also provides direct access to each conduit for instrumentation access. Each conduit is associated with a specific active fuel position in the reactor core. A fitting, not shown, may be used to secure the conduit to the surface of the housing 200. The fitting limits the movement of the conduits relative to the housing 200 and seals the inner space of the housing. Further, the portion of the conduits passing through the fitting may be sealed. The ports conduits may be staggered on multiple faces of the conduit housing 200, which decreases the required size of the housing 200. Each conduit has a minimum bend radius, which is about 1.5 meters in the embodiments shown in FIGS. 3A-4. Such a bend radius is required to allow instrumentations or other elements to be inserted into the conduits and fed therethrough down without binding, into the reactor core. Thus, the upward staggered faces enable access to the conduits while maximizing the bend of the conduit, especially as compared to ports that would be positioned on a planar, vertical side face, or on a downward staggered face. Ports located on a top surface of the housing 200 minimizes the height of the conduit housing 200. That is, without ports on the top surface, the conduit housing 200 would need to include additional stepped faces to provide ports for every conduit, thereby adding height to the conduit housing 200. As an example, in the embodiments shown, the conduit housing 200 would require six more stepped faces to accommodate all the conduits. Adding height to the conduit housing is generally undesirable because of seismic considerations and ease of access. Additionally, the alternating positioning of the ports further enhances access to the conduits and maximizes spatial utilization within the housing, which also decreases the size of the conduit housing 200. In the embodiments shown, there are 235 active fuel positions and two conduit housings 200, each having 121 conduit ports. Thus, there are seven more conduit ports than active fuel positions. In other embodiments, there is one conduit for each active fuel position in the reactor core. Other quantities of conduit ports and active fuel positions are possible. Further, the number of ports in subsequent rows alternates between two values (although more or less can be contemplated in different embodiments). However, the number may be the same between one or more adjacent rows in other embodiments. Regardless, the relative positioning of the conduit ports is such that each adjacent row is offset from the one or more adjacent rows. FIGS. 3A-3D show an example embodiment of an instrumentation conduit housing 200. In FIG. 3B, outer surfaces of the instrumentation conduit housing 200 are depicted transparent to show the conduits 201 therein. The conduit housing 200 includes a top face 202, a pair of side faces 204, a front face 206, and a rear face 208. In the embodiment shown, the top face 202 and the front face 206 define a plurality of 210, 212 conduit ports. Any number of vertical conduit ports 210, 212 may be utilized. The front face 206 includes a plurality of stepped faces 205 and 207, as well as a curved lower portion 209. The stepped faces include a plurality of upward faces 205 and a plurality of downward faces 207. Each upward face 205 is substantially planar and parallel to the other upward faces 205. Similarly, each downward face 207 is substantially planar and parallel to the other downward faces 207. Additionally, each upward face 205 is substantially normal to the adjacent downward faces 207. In other embodiments, the upward 205 and downward 207 faces may intersect at non-normal angles. The upward faces 205 include pitched conduit ports 212. The number of pitched conduit ports 212 may alternate on adjacent upward faces 205. That is, one upward face may have five pitched conduit ports while an adjacent upward face may have six pitched conduit ports, and so on. Additionally, the pitched conduit ports 212 in adjacent upward faces 205 are aligned in an offset fashion, such that the pitched conduit ports 212 are aligned in every other upward face 205. The number of ports on adjacent or subsequent upward faces may vary as appropriate. The top face 202 defines vertical conduit ports 210 that may be set back a distance D from the top-most upward face 205. This distance provides spacing for the conduits that are curving from the top-most upward face 205 downward toward the reactor head. The top face 202 defines a plurality of rows of vertical conduit ports 210. The rows of vertical conduit ports 210 may alternate between an even number of vertical conduit ports 210 and an odd number of vertical conduit ports 210. As shown, the rows alternate between having five and six vertical conduit ports 210 in each row. Additionally, each row of vertical conduit ports 210 is offset from adjacent rows. Thus, vertical conduit ports 210 in every other row are aligned and have the same number of vertical conduit ports 210. Having an offset alignment facilitates the efficient use of space within the conduit housing 200 as well as provides space for tools, such as wrenches, to be used to tighten nuts, swage locks, or other securing members to the conduit housing 200. The curved lower portion 209 of the front face 206 accommodates the bend radius of the conduits 201. Thus, any upward faces defining ports in the curved lower portion 209 would require the conduits to bend more than their design tolerances (as required to allow passage of an instrumentation inserted therein). The curved lower portion 209 minimizes the footprint of the housing 200 on the reactor head. In other embodiments with different bend radius specifications, the curved lower portion 209 may be smaller or larger. Conduits 201 are specifically shown through transparent surfaces on FIGS. 3B and 3D. For clarity, only some of the conduits 210 are depicted. Each terminates at a single one of ports 210 or ports 212, which may be scaled. In examples, each conduit 201 may be sealed against its associated surface. The conduits 201 exit the conduit housing 200 through openings 250 and pass into the interior of the reactor. In an example, after the conduits exit the conduit housing 200, they may be twisted to prevent a direct line of radiation into the housing. Alternatively or additionally, a plurality of steel balls may be positioned proximate the exit point of the conduits so as to refract the radiation. FIG. 4 is a perspective view of a second embodiment of a conduit housing 300. The second embodiment 300 has pitched conduit ports 312 on a front face 306 and on a rear face 308, with side faces 304 positioned therebetween. The front face 306 and the rear face 336 are similarly sized and configured, with the same number of upward faces 305, downward faces 307, and congruent curved portions 309. The pitched conduit ports 312 are arranged similarly on the upward faces 305 of the front face 306 and the rear face 336. The top face 302 includes rows of vertical conduit ports 310. It is to be understood that this disclosure is not limited to the particular structures, process steps, or materials disclosed herein, but is extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting. It must be noted that, as used in this specification, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. It will be clear that the systems and methods described herein are well adapted to attain the ends and advantages mentioned as well as those inherent therein. Those skilled in the art will recognize that the methods and systems within this specification may be implemented in many manners and as such is not to be limited by the foregoing exemplified embodiments and examples. In this regard, any number of the features of the different embodiments described herein may be combined into one single embodiment and alternate embodiments having fewer than or more than all of the features herein described are possible. While various embodiments have been described for purposes of this disclosure, various changes and modifications may be made which are well within the scope contemplated by the present disclosure. Numerous other changes may be made which will readily suggest themselves to those skilled in the art and which are encompassed in the spirit of the disclosure.
	abstract	A radiation monitor includes a high-energy count-rate-measurement functional unit, a low-energy count-rate-measurement functional unit, and an alert-diagnosis functional unit. The alert-diagnosis functional unit receives an alert from the high-energy count-rate-measurement functional unit, receives a low-energy count rate from the low-energy count-rate-measurement functional unit, determines whether or not the low-energy count rate is in a set acceptable range by performing synchronizing with alert transmission, determines that the alert is caused by fluctuation, when the low-energy count rate is in the acceptable range, determines that the alert is caused by any of an increase in the γ ray which is a measurement target or enter of noise, when the low-energy count rate is increased beyond the acceptable range, and outputs results of determination.
	summary
	summary
048760730	description	The process comprises reacting osmium metal, generally in powder form, with sodium hydroxide and sodium hypochlorite to form a complex of the formula Na.sub.2 [OsO.sub.4 (OH).sub.2 ], which is acidified and OsO.sub.4 is extracted by means of a suitable solvent, such as chloroform or carbon tetrachloride, converted by means of sodium hydroxide to a complex as defined above, reduced with formaldehyde to give Na.sub.2 [OsO.sub.2 (OH).sub.4 ] which is reacted with hydrochloric acid to give the desired complex, designated herein as Os(VI)-A, which is believed to consist mainly of Na.sub.2 [OsO.sub.2 Cl.sub.4 ], possibly in combination with lesser quantities of Na.sub.2 [OsO.sub.2 (OH).sub.2 Cl.sub.2 ]. The hydrophobic solvent serves to separate the osmium compound from salts and oxidants which may interfere in the next steps of the preparation. Formaldehyde is preferred as reduction agent as it makes it possible to reintroduce the osmium compounds fully in the aqueous phase. The process is characterized by a high overall yield of the complex calculated on the osmium metal starting material: the yield is better than 90 per cent. The process is a simple and speedy one and only about one hour is required for the initial dissolution of the osmium metal powder; the other stages which are simple reactions with solvent extraction steps, being rapid and convenient ones, the overall time required for the formation of the OS(VI)-A complex being about 15-20 minutes, starting with the dissolved osmium. The thus obtained complex is sorbed on a suitable carrier in a column. Good results have been obtained with a system designated as SG-336 which is Aliquot 336, a quaternary ammonium salt having the formula (R.sub.3 N.sup.+ CH.sub.3) Cl.sup.- where R =C.sub.8 - C.sub.10 (methyl tricaprylyl ammonium chloride) sorbed on silica gel. The recovery of the iridium is about 50 per cent when elution is effected with saline at a suitable pH, such as about pH 1, the breakthrough of osmium being very low (of the order of 0.05%), when no scavenger is used. It is advantageous to provide a further column with an Os-scavenger, such as 2,3-dihydroxy-benzoic acid, 3,4,5-trihydroxy benzoic acid or the like, and when this is used the Ir recovery is about 35% with a breakthrough as low as about 0.0025% of osmium. It has been found that the system Aliquot 336/silica gel is highly advantageous, and degradation of the carrier by the radioactive material is negligible. The thus produced generator is avantageously stored until use at a low temperature (about 0.degree.-4.degree. C) and under such storage conditions highly active generators did not deteriorate during about 14 days. Instead of the anion exchanger chosen, other anion exchangers can be used although the chosen one seemed to give especially advantageous results. An important feature is the use of an organic anion exchange agent supported by a suitable inorganic support. Various ratios of Aliquot 336 on silica gel were tried, and satisfactory results were obtained with from 10 to 35% w/w of Aliquot 336 on silica gel. Generally about 1 ml of silica gel is charged with about 8 mg Os calculated as metal or about 16 mg calculated as the complex; this contains a certain fraction of radioactive isotope (about 10.sup.-6), the overall quantity of radioactive Os being about 500800 mCi, although charges of up to about 1000 mCi per gram can be provided. The silica gel used is advantageously of small size, of the order of 30-40.mu. particles. In the charged column there exists a steady state between .sup.191 Os and .sup.191m Ir which has a half-life of 4.9 seconds. When to be used, the column is eluted with a pH 1 solution, generally acidified saline and a quantity of from 1 to about 1.5 ml of such solution is admixed with about 7 to 8 ml of buffered saline and injected into the patient at a final pH of about 3.5 intravenously. For radioangiography, the quantity eluted varies between 20 to 100 mCi according to the patient. As the recovery of Ir is of the order of 35%, and as the Os breakthrough is of the order of 2.times.10.sup.-3 %, only very low quantities of .sup.191 Os are administered, and the procedure can be repeated without an undue exposure of the patient to radiation and without establishing a hindering background radiation. The column charged with the Os complex is advantageously followed with a scavenging column of a substance known to be an effective complexing agent for osmium. The columns used were prepared by soaking the SG-336 material in an aqueous solution of a substance such as 2,3-dihydroxy-benzoic acid catechol or 3,4,5-trihydroxy benzoic acid. The use of such scavengers considerably improves the ratio of Ir/Os. Preliminary tests with laboratory animals have confirmed the utility and usefulness of the novel generator for use as source of radionuclides for radioangiography. Similar tests for the production of short-lived nuclides can be provided based on other radioactive elements. Thus, for example, the following can be used: ##EQU1## which gives X-rays of 55 and 65 KeV. The active compound is advantageously applied in the form of tungstic acid on a column supporting an anionic exchange agent. Biorad AG 1.times.8 can be used, the elution being with 0.15 n HCl +0.01% H.sub.2 O.sub.2. ##EQU2## which gives X-rays of 262 KeV. The active material is advantageously applied in the form of mercury nitrate Hg(NO.sub.3).sub.2, on zinc sulfide supported by a silica column. The elution is with sodium thiosulfate. The following Example is to be construed in a non-limitative manner. EXAMPLE a. To 10 ml of sodium hypochlorite solution (composed of 500 mg NaOH dissolved in 5% aqueous solution of NaOCl), 100 mg of radioactive Osmium powder (5 Ci) is added (about 100 mesh). b. The mixture is stirred (by magnetic stirrer, for example) at room temperature, for about 2 hours to get a clear red colored solution (stock solution). c. To 0.6 ml of the osmium stock solution (300 mCi) a few drops of 4N HCl are added, that bring the solution to an acidic pH. d. The Osmium compound is then extracted from the aqueous solution by adding 1 ml of chloroform (CHCl.sub.3). At this stage more than 90% of the osmium compound is moved from the aqueous to the organic phase. To the separated aqueous phase, another 1 ml of fresh chloroform is added to extract the rest of the osmium compound from the aqueous phase. The aqueous fractions are then discarded while the organic fractions are combined. e. The combined organic phase is washed with 2 ml of double distilled water. The aqueous phase is then discarded while the organic phase is kept for the next stage. f. To the organic phase (in which the osmium compound is dissolved) 1 ml of 4N NaOH is added and well mixed. At this stage, the aqueous fraction (at the top of the test tube) is clear, red-colored, while the organic phase (at the bottom of the test tube) is clear and not-colored. The aqueous fraction is then collected while the organic fraction is discarded. g. To the clear red-colored aqueous solution, 1 ml of 30% formaldehyde solution is added to get immediately a clear purplecolored solution. To this solution, 0.5 ml of concentrated hydrochloric acid is then added to get a clear caramel-colored solution (Os(VI)-A), the activity of which is 280 mCi. h. The Os(VI)-A is then loaded on SG-336(10%) 4.times.55 mm column and then washed with 10 ml of saline pH 1, removing impurities and also some iridium. The thus obtained column is ready for use. ______________________________________ ##STR1## No Scav. With Scav. ______________________________________ Ir recovery 50 35 (%) Os Breakthrough 8 .multidot. 10.sup.-2 2 .multidot. 10.sup.-3 (%) .epsilon. = Enrichment factor 630 17.500 Shelf-Life = 4 weeks ______________________________________ In another experiment the Os(VI)-A complex was applied to silica gel impregnated with 10% (weight by weight) of methyltridodecylammonium chloride (designated by us as SGMTDAC), the particle size of the silica being in the range of 30 to 60 microns. The results obtained were as follows: Ir recovery: without scavenger - 60%: with scavenger - 35%; Os breakthrough: without scavenger 10.sup.-2 %, with scavenger: 4.10.sup.-4 %, the enrichment factor being: without scavenger about 6000; with scavenger - about 88,000. The shelf life was also about 4 weeks. The extremely low breakthrough is of paramount importance. Instead of the above quaternary ammonium compound, others having at least two alkyl groups with at least 8 carbon atoms, and preferably 10 carbon atoms; or such compounds with at least one phenyl group and at least one alkyl of at least 8 carbons, can be used to obtain similar results. The quaternary ammonium ion exchange agent may thus have the formula (R.sub.3 N.sup.+ CH.sub.3)Cl.sup.- wherein the R groups are C.sub.8 -C.sub.12 alkyl, or at least one of the R groups is phenyl and the remaining groups are C.sub.8 -C.sub.10 alkyl.

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