Split (2)

train · 33.5k rows

patent_number stringlengths 0 9	section stringclasses 4 values	raw_text stringlengths 0 954k
	claims	1. Apparatus for characterizing a surface of a sample with a probe, the apparatus comprising:an actuator;a first member carried by the actuator and having a distal end which is extensible and retractable relative to the surface;a second member carried by the actuator and having a distal end which is extensible and retractable relative to the surface;a detector that produces a signal corresponding to the location of the probe relative to the surface;a first control device operatively connected to the detector and the first and second members which causes the distal ends of the first and second members to extend or retract substantially synchronously and in response to the signal of the detector, and that controls movement of the probe at a first rate relative to the surface in response to a first feedback signal; anda second control device operatively connected to the first control device and the actuator that causes the actuator to move the probe at a second rate relative to the surface in response to a second feedback signal. 2. The apparatus as defined in claim 1 further comprising an actuator movable both toward and away from a sample. 3. The apparatus as defined in claim 1 further comprising a mount assembly carried by the distal end of the first member, wherein the mount assembly comprises (i) a probe mount and (ii) a cantilever probe having a fixed end carried by the mount and including a stylus spaced from the fixed end and disposed toward the sample; and further comprising a counterbalance carried by the distal end of the second member. 4. The apparatus as defined in claim 1 wherein a momentum of the first member and mount assembly together is balanced by a momentum of the second member and counterbalance together. 5. The apparatus as defined in claim 1 wherein a mass of the first member and mount assembly together is substantially the same as a mass of the second member and counterbalance together. 6. The apparatus as defined in claim 1 wherein a mass of the first member and mount assembly together is not the same as a mass of the second member and counterbalance together. 7. The apparatus as defined in claim 1, wherein the first and second control devices are proportional, integral, derivative controllers. 8. The apparatus as defined in claim 1 wherein the second control device produces the second feedback signal if the signal of the detector is not reduced to zero by the first control device. 9. The apparatus as defined in claim 1 wherein the first member has a range of motion and wherein the first control device and the second control device maintain the first member in substantially a middle portion of the range of motion. 10. The apparatus as defined in claim 1, wherein the first control device produces the first feedback signal in response to the signal of the detector for movement of the probe relative to the sample surface within a range of about 1 micrometer, and wherein the first feedback signal causes the second control device to produce the second feedback signal for movement of the actuator relative to the sample surface within a range of about 15 micrometers. 11. Apparatus for characterizing a surface of a sample with a probe, the apparatus comprising:an actuator;a first member carried by the actuator and having a distal end which is extensible and retractable relative to the surface;a second member carried by the actuator and having a distal end which is extensible and retractable relative to the surface;a detector that produces a signal which corresponds to the location of the probe relative to the surface of the sample;a first control device operatively connected to the detector and the first and second members for causing the distal ends of the first and the second members to extend or retract in response to the detector signal, for moving the probe at a first rate relative to the surface, wherein the distal ends of the first and the second members substantially synchronously either both extend or both retract in response to the signal from the detector;and a second control device operatively connected to the detector and the actuator for causing the actuator to move the probe at a second rate relative to the surface. 12. The apparatus as defined in claim 11, wherein the first control device is a proportional, integral, derivative controller, wherein the second control device is a proportional, integral, derivative controller. 13. The apparatus as defined in claim 11, wherein the first control device provides relatively quicker response to the first and second members than the second control device provides to the actuator. 14. The apparatus as defined in claim 11, further including (i) a high-pass filter operatively connected to the detector and to the first control device for providing relatively higher frequency signals to the first control device and (ii) a low-pass filter operatively connected to the detector and to the second control device for providing relatively lower frequency signals to the second control device, wherein the first control device produces a first control signal in response to the higher frequency signals for causing the distal ends of the first and the second members either to extend or retract, and wherein the second control device produces a second control signal in response to the lower frequency signals for causing the actuator to move toward or away from the sample surface. 15. The apparatus as defined in claim 11, further including (i) a high-pass filter operatively connected to the detector and to the first control device for providing relatively higher frequency signals to the first control device, and (ii) a low-pass filter operatively connected to the detector and to the second control device for providing relatively lower frequency signals to the second control device, wherein the first control device produces a first control signal in response to the higher frequency signals for causing the distal ends of the first and the second members either to extend or retract, for moving the probe relative to the sample surface within a range of approximately 1 micron, wherein the second control device produces a second control signal in response to the lower frequency signals for causing the actuator to move toward or away from the sample surface, for moving the probe relative to the sample surface within a range of approximately 15 microns, and wherein the lower frequency signals and the higher frequency signals cooperate to drive the probe toward the sample surface. 16. A method of reducing parasitic oscillations in an apparatus having a probe which interacts with the surface of a sample and which is moved relative to the surface by a fast Z actuator and by a slow Z actuator, the method comprising:converting a signal related to the position of the probe into a first control signal fed to the fast Z actuator which moves the probe at a first rate;converting the first control signal into a second control signal which is fed to the slow Z actuator which moves the probe at a second rate; andbalancing the momentum of the fast Z actuator so that the net momentum of the fast Z actuator is essentially zero. 17. The method as defined in claim 16 wherein the second control signal is zero if the first control signal is reduced to zero by the probe moving at a first rate. 18. The method as defined in claim 16 wherein the momentum is balanced by moving a mass equal to the mass of the fast Z actuator at a velocity equal to the velocity of the fast Z actuator and in a direction opposite that of the fast Z actuator and synchronously therewith.
	abstract	Apparatus for X-ray analysis of a sample includes an X-ray source, which irradiates the sample, and an X-ray detector device, which receives X-rays from the sample responsive to the irradiation. The device includes an array of radiation-sensitive detectors, which generate electrical signals responsive to radiation photons incident thereon. Processing circuitry of the device includes a plurality of signal processing channels, each coupled to process the signals from a respective one of the detectors so as to generate an output dependent upon a rate of incidence of the photons on the respective detector and upon a distribution of the energy of the incident photons.
	claims	1. A method of attaching nanotube to probe holder, said method being characterized in that said method comprises: first process in which nanotubes ( 24 ) to be used as a probe needle are caused to adhere to an electrode in a protruding fashion; a second process in which said electrode to which nanotubes ( 24 ) are caused to adhere in a protruding fashion and a holder ( 2 a ) are caused to approach very close to each other, so that each of said naxiotubes ( 24 ) is contacted to said holder ( 2 a ) in such a manner that a base end portion ( 24 b ) of said nanotube ( 24 ) adheres to a surface of said holder with a tip end portion ( 24 a ) of said nanotube in a protruding fashion; and a third process in which an appropriate region of said base end portion of said nanotube adhering to said surface of said holder is irradiated by an electron beam so as to form a coating treatment so that said nanotube ( 24 ) is fastened to said holder ( 2 a ) by a resulting coating film ( 29 ) wherein at least said second and third processes are performed by direct observation in an electron microscope.
	description	The present invention will now be described with reference to the drawings wherein like reference numerals are used to refer to like elements throughout. The present invention provides for beam containment in a low energy, high current ion implantation system at low pressures without requiring the introduction of externally generated plasma by enhancing the beam plasma using a multi-cusp magnetic field in combination with RF or microwave energy to create an ECR condition in a mass analyzer. However, it will be appreciated that the invention may be advantageously employed in applications other than those illustrated and described herein. Referring now to the drawings, in FIG. 1A, a low energy ion implanter 10 is illustrated, having a terminal 12, a beamline assembly 14, and an end station 16. The terminal 12 includes an ion source 20 powered by a high voltage power supply 22. The ion source 20 produces an ion beam 24 which is provided to the beamline assembly 14. The ion beam 24 is conditioned by a mass analysis magnet 26. The mass analysis magnet 26 passes only ions of appropriate charge-to-mass ratio to a wafer 30. The conditioned ion beam 24 is then directed toward the target wafer 30 in the end station 16. Referring also to FIG. 1B, an ion implanter 100 is illustrated in greater detail in accordance with an exemplary aspect of the present invention, and has an ion source 112, a mass analysis magnet 114, a beamline assembly 115, and a target or end station 116. An expansible stainless steel bellows assembly 118, which permits movement of the end station 116 with respect to the beamline assembly 115, connects the end station 116 and the beamline assembly 115. Although FIG. 1B illustrates an ultra low energy (ULE) ion implanter, the present invention has applications in other types of implanters as well. The ion source 112 comprises a plasma chamber 120 and an ion extractor assembly 122. Energy is imparted to an ionizable dopant gas to generate ions within the plasma chamber 120. Generally, positive ions are generated, although the present invention is applicable to systems wherein negative ions are generated by the source 112. The positive ions are extracted through a slit in the plasma chamber 120 by the ion extractor assembly 122, which comprises a plurality of electrodes 127. Accordingly, the ion extractor assembly 122 functions to extract a beam 128 of positive ions from the plasma chamber 120 and to accelerate the extracted ions into the mass analysis magnet 114. The mass analysis magnet 114 functions to pass only ions of an appropriate charge-to-mass ratio to the beamline assembly 115, which comprises a resolver housing 123 and a beam neutralizer 124. The mass analysis magnet 114 includes a curved beam path 129 within a passageway 139 defined by an aluminum beam guide having side walls 130, evacuation of which is provided by a vacuum pump 131. The ion beam 128 that propagates along this path 129 is affected by the magnetic field generated by the mass analysis magnet 114, to reject ions of an inappropriate charge-to-mass ratio. The strength and orientation of this dipole magnetic field is controlled by control electronics 132 which adjust the electrical current through the field windings of the magnet 114 through a magnet connector 133. The dipole magnetic field causes the ion beam 128 to move along the curved beam path 129 from a first or entrance trajectory 134 near the ion source 112 to a second or exit trajectory 135 near the resolving housing 123. Portions 128xe2x80x2 and 128xe2x80x3 of the beam 128, comprised of ions having an inappropriate charge-to-mass ratio, are deflected away from the curved trajectory and into the walls of an aluminum beam guide 130. In this manner, the magnet 114 passes to the resolving housing 123 only those ions in the beam 128 which have the desired charge-to-mass ratio. The passageway 139 further comprises a magnetic device including one or more magnets 170 disposed laterally along the beam path 129. The magnets 170 are mounted above and below the beam path 129 to create a multi-cusped magnetic field (not shown in FIG. 1B) in the passageway 139. A high frequency electric field (not shown in FIG. 1B) is also provided in the passageway 139 via a microwave injection port 172 which couples a power source 174 with the passageway 139. The multi-cusped magnetic field and the high frequency electric field in the passageway 139 cooperatively interact to create an electron cyclotron resonance condition in at least one region (not shown in FIG. 1B) of the passageway in order to provide beam containment of the ion beam 128, as described in greater detail infra. The resolver housing 123 includes a terminal electrode 137, an electrostatic lens 138 for focusing the ion beam 128, and a dosimetry indicator such as a Faraday flag 142. The beam neutralizer 124 includes a plasma shower 145 for neutralizing the positive charge that would otherwise accumulate on the target wafer as a result of being implanted by the positively charged ion beam 128. The beam neutralizer and resolver housings are evacuated by a vacuum pump 143. Downstream of the beam neutralizer 124 is the end station 116, which includes a disk-shaped wafer support 144 upon which wafers to be treated are mounted. The wafer support 144 resides in a target plane which is generally perpendicularly oriented to the direction of the implant beam. The disc shaped wafer support 144 at the end station 116 is rotated by a motor 146. The ion beam thus strikes wafers mounted to the support as they move in a circular path. The end station 116 pivots about point 162, which is the intersection of the path 164 of the ion beam and the wafer W, so that the target plane is adjustable about this point. FIG. 2 illustrates an exemplary mass analyzer beam guide 200 for use in a low energy ion implantation system (e.g., low energy ion implanter 10 of FIG. 1B), having an arcuate longitudinal passageway 202 defined by inner and outer arcuate side walls 204 and 206, respectively, along an ion beam path 208. The beam guide 200 extends longitudinally along the path 208 from an entrance end 210 to an exit end 212 through an arc angle xcex8 which may be approximately 135 degrees, for example. Beam guide 200 further comprises a microwave injection port 214 which provides coupling of RF or microwave energy from a power source 216 with the passageway 202 via a cable 218. The beam guide further includes a mass analysis magnet comprising two arcuate magnet poles (not shown in FIG. 2) to provide a dipole magnetic field in the passageway 202 which allows ions of a selected charge-to-mass ratio to reach the exit end 212 along the path 208. FIGS. 3A and 3B illustrate an end elevation view and a sectional plan view, respectively, of the exemplary mass analyzer beam guide 200 of FIG. 2, having a plurality of magnets 220 associated therewith for generating a multi-cusped magnetic field in accordance with an aspect of the invention. Magnets 220 extend laterally between an inner radius R1 and an outer radius R2 in the passageway 202 in a longitudinally spaced relationship along the path 208, with an angular spacing xcex82, which may be, for example, 5.326 degrees. In one exemplary implementation of the invention, the inner radius R1 may be about 300 mm and the outer radius R2 may be about 500 mm. The passageway 202 is further defined by top and bottom walls 222 and 224, respectively. The dipole field may be generated externally to the beamguide 200 by an electromagnet (not shown). In another implementation of the invention the magnets 220 are embedded into one or both of the beamguide walls 222 and 224 in slots machined from the outside thereof, such that the magnets 220 remain outside of the vacuum chamber. In addition, it will be recognized that magnets 220 may be provided in one or both of the top and bottom walls 222, and 224, respectively, or on one or both of the side walls 204 and 206, respectively, or any combination thereof. FIGS. 4 and 5 respectively illustrate the mass analyzer beam guide 200 in longitudinal and lateral section along section lines 4xe2x80x944 and 5xe2x80x945 of FIG. 2. As seen in FIG. 5, magnets 220 are magnetized longitudinally along the propagation direction of the ion beam path 208, and are staggered such that adjacent magnets have like polarity poles facing each other. For clarity, the magnets 220 having south poles facing toward the entrance end 210 of the beam guide 200 are indicated as 220A and magnets 220 having south poles facing toward the exit end 212 of the guide 200 are indicated as 220B. In order to facilitate the mass analysis function, a dipole magnetic field is established in the passageway 206, for example, via an external electromagnet (not shown) having vertical field lines 230 as illustrated in FIG. 4. Referring also to FIG. 6, the exemplary bipolar magnets 220A and 220B create individual magnetic fields, illustrated for simplicity with exemplary field lines 232A and 232B which cooperate to form multi-cusped magnetic fields near and spaced from the top and bottom walls 222 and 224, respectively, in the passageway 206. The exemplary placement of magnets 220A and 220B illustrated in the various figures illustrates similarly oriented magnets 220 vertically aligned (e.g., magnet 220A directly above magnet 220A, magnet 220B directly above magnet 220B). However, it will be appreciated that orientations other than those specifically illustrated and described herein are possible and are contemplated as falling within the scope of the present invention. The orientation of magnets 220A and 220B illustrated in FIGS. 5 and 6, for example, advantageously provides additive magnetic field lines in the areas between adjacent magnets 220, although this is not required for the invention. Where RF or microwave energy is provided in the passageway 206 (e.g., via power source 216 and microwave injection port 214 of FIG. 2), the cooperative interaction between the magnetic and electric fields results in the creation of an electron cyclotron resonance (ECR) condition in regions 234 spaced a distance 236A and 236B from the magnets 220. The ECR condition in regions 234 advantageously provides enhancement of the beam plasma associated with an ion beam traveling through the passageway 206 along the path 208, whereby beam integrity is improved along the longitudinal length of the mass analyzer beam guide 200. The creation of an ECR condition in one or more regions 234 around an ion beam prevents beam xe2x80x9cblow-upxe2x80x9d by facilitating the transfer of energy to the plasma surrounding the beam, thereby enhancing the plasma. An electron cyclotron resonance condition occurs when an alternating electric field is applied to a charged particle in a static magnetic field, such that the frequency of the electric field matches the natural frequency of rotation of the charged particle around the static magnetic field lines. Where this resonance condition is attained (e.g., in regions 234), a single frequency electromagnetic wave can accelerate a charged particle very efficiently. It will be appreciated that the sizing, orientation, and spacing of the magnets 220 within the passageway 206 allow the location of the ECR regions 234 to be generated in accordance with desired ion beam containment goals. For example, the strength of the magnets 220 may be varied in order to change the distance 236A and/or 236B between the inner surfaces of the magnets 220 and the ECR regions 234. In this manner, the distances 236A and 236B may be adjusted according to the passageway size and/or the desired ion beam size. In addition, the spacing between adjacent magnets 220 may be changed in order to vary the spacing between adjacent ECR regions 234. Furthermore, the relative orientations of the magnetic pole faces of adjacent magnets may be varied in order to provide additive magnetic field lines between adjacent magnets 220. Many different magnet sizes, orientations, and spacings are possible and contemplated as falling within the scope of the present invention. In accordance with the present invention, the multi-cusped magnetic field employed to obtain the ECR condition may be successfully superimposed near the edges of the dipole field. The plasma produced at the resonance surface where the correct magnetic field strength value is obtained expands toward the center of the ion beam along the dipole field lines, in a direction opposite to the field gradient. The introduction of the electric field into the beam guide passageway 202 may further be aided by the use of a waveguide in the passageway as illustrated and described in greater detail infra. Referring now to FIGS. 7A and 7B, another aspect of the invention is illustrated in reference to mass analyzer beam guide 200, wherein a sectional side elevation view is provided. The beam guide 200 comprises top and bottom walls 222 and 224, respectively, an outer sidewall 206, and an inner side wall (not shown) defining a passageway 202 through which an ion beam (not shown) propagates along a path 208. A plurality of magnets 220A and 220B (collectively designated as 220) are provided in similar fashion to the magnets 220 of FIGS. 3A-6 which extend laterally between the inner side wall and the outer side wall 206, in a spaced relationship to each other such that the longitudinally opposite magnet poles of adjacent magnets 220 face one another. Oriented in this fashion, the magnets 220 provide a multi-cusped magnetic field in the passageway 202 near the top and bottom walls 222 and 224, which field is illustrated by exemplary field lines 232A and 232B. A mass analysis electromagnet (not shown) outside of the beamguide may provide a dipole magnetic field (not shown) adapted to provide the mass analysis functionality discussed supra. Unlike the mass analyzer implementations in the previous figures, the beam guide 200 of FIGS. 7A and 7B further comprises one or more waveguides 250. The waveguide comprises a suitable propagation medium such as quartz, that is metalized on all sides by a thin coating (e.g., aluminum). Since the skin depth at 2.54 GHz is less than one micrometer, a metalization layer coating thickness of a few microns is adequate. Laterally extending ports or slots 254 are provided in the inwardly facing metalization layers of the waveguides 250 between adjacent magnets 220 for coupling RF or microwave energy from the waveguide 250 into the passageway 202 of the beam guide 200 as described in greater detail infra. The waveguides 250 may be coupled to an RF or microwave power source (e.g., source 216 of FIG. 2) through any known method (e.g., windows, antennas, and the like), whereby standing wave resonance may be established in the waveguides 250 along the longitudinal length thereof. It will be appreciated that although two waveguides (e.g., upper and lower) 250 are illustrated in the figures, that other configurations, including a single waveguide 250, may be employed according to the invention. The RF or microwave energy provides electric fields in the passageway 202 illustrated by exemplary electric field lines 256A and 256B in FIG. 7B which cooperatively interact with the multi-cusped magnetic fields generated by the magnets 220 to provide ECR regions 234 spaced from the top and bottom walls 222 and 224. As discussed supra, the ECR condition promotes the enhancement of the beam plasma associated with an ion beam (not shown) propagating through the passageway 202 of the beam guide 200 along the path 208, whereby the integrity of the beam is maintained by the reduction or elimination of beam xe2x80x9cblow-upxe2x80x9d. The ports or slots 254 in the waveguide 250 extend laterally between the inner side wall (not shown in FIGS. 7A and 7B) and the outer side wall 206 having a width 260 and adjacent ports or slots 254 are longitudinally spaced by an angular pitch distance 262 which is the pitch spacing of the magnets 220. Referring also to FIGS. 8A and 8B, another exemplary waveguide 250 is illustrated in section, mounted between wall 222 and the multi-cusped field magnets 220. According to another aspect of the invention, the waveguide 250 comprises upper and lower metalized layers 280 and 282, respectively above and below a base layer 284 adapted to propagate RF or microwave energy for introduction into the passageway 202 of the beam guide 200. Laterally extending ports or slots 254 are provided in the lower support layer 282 exposing the base layer 284 to the interior of the passageway 202. In addition, O-rings 286 may be provided encircling the slots 254 in order to seal the magnets from the vacuum region. According to still another exemplary aspect of the invention, the base layer 284 may be made from quartz, the upper and lower metalized layers 280 and 282, respectively, may be made from aluminum, the O-rings 286 may be made from a suitable elastomer, and the beam guide cover 288 may be made from aluminum. Alternatively, however, other materials may be employed and are contemplated as falling within the scope of the present invention. Referring now to FIGS. 8C and 8D, side section views of the exemplary beamguide 200 and waveguide 250 are illustrated. In accordance with the invention, the top wall 222 may include a recess for supporting the waveguide 250, as well as a seating surface for compressing the o-ring 286 around the slot 254. The beamguide 200 may further include a top cover 290 allowing removable mounting of the waveguide 250 in the top wall 222. Referring also to FIG. 8D, the top wall 222 may also include a recess or pocket in which the magnets 220 are seated. The o-rings 286 around the slots 254 thus providing for isolation of the magnets from the vacuum of the inner passageway 202. Referring now to FIG. 9, the waveguide 250 is shown installed in a beam guide 200, where the waveguide 250 extends along the path 208 of the ion beam propagation. The pitch spacing of the magnets 220 is the same as that of the waveguide ports or slots 254, having an angular value of xcex82, for example 5.326 degrees, providing for 25 equally spaced magnets 220 along an angular beam guide length of xcex81, for example, approximately 135 degrees. In operation, RF or microwave energy (e.g., provided by power source 216 via cable 218 and microwave injection port 214) is propagated in the waveguide 250 located behind the multi-cusped magnetic field generating magnets 220. The energy is coupled to the beam plasma (not shown) via the periodically distributed ports or slots 254 for creation of the ECR condition (e.g., in regions 234 of FIGS. 7A and 7B) conducive to plasma enhancement employed for beam containment. As illustrated further in FIG. 10, the waveguide 250 furthers the generation of RF or microwave electric fields of sufficient magnitude orthogonal to the fixed magnetic fields at many locations (e.g., regions 234 of FIGS. 7A and 7B) along the beam propagation path 208. Toward that end, the length of the waveguide 250 may be set at a multiple of xc2xd wavelengths (e.g., nxcex/2, where n is an integer) corresponding to the RF or microwave power source frequency (e.g., 2.45 GHz), with the coupling ports or slots 254 located at xc2xd wavelength locations. The waveguide 250 may therefore constitute a resonant structure where standing waves can be produced therein with the ports or slots 254 located where the E field is minimum and the H field is maximum (e.g., xe2x80x9cHxe2x80x9d coupling). The length of the ports or slots 254 in the waveguide 250 may be maximized (e.g., slots 254 are nearly as long laterally as the width of the waveguide 250) and the width may be optimized for nominal impedance matching. For example, in the exemplary waveguide 250, the angular slot spacing (an hence the spacing of the magnets 220) is approximately 5.326 degrees, the inner radius R1 is approximately 370 mm, and the outer radius R2 is approximately 430 mm. The length of the ports or slots 254 in this example is approximately 50 mm, and the width is approximately 5 mm. In order to obtain consistent electric field patterns in the beam guide 200, it is desirable to excite a single dominant propagation mode. For example, the TE10 propagation mode for rectangular cross-section waveguides provides an electric field that is normal to the broadwall of the guide with a (1) peak in the center of the broadwall. The field magnitude is constant along the direction parallel to the narrow wall (e.g., xe2x80x9c0xe2x80x9d peaks). This TE10 has the lowest cut-off frequency. The cut-off frequencies for the TEx0 modes depend only on the broadwall dimension. Higher order modes TEn0 have progressively higher cut-off frequencies. According to one aspect of the invention, by choosing the size of the broadwall such that the cut-off frequency for the TE20 mode is slightly larger than the operating frequency (e.g., 2.45 GHZ), the widest possible waveguide 250 is selected which will only propagate the single TE10 mode. Once the waveguide dimensions are so chosen, the propagation wavelength is determined. An electric field develops across the ports or slots 254 outside the waveguide 250 in the interior of the beam guide passageway 202, which is oriented along the ion beam propagation direction (e.g., path 208). A magnetic field (e.g., multi-cusped field) is generated that is perpendicular to the electric field, with the proper magnitude for creating the ECR resonance condition in the regions 234 of the passageway 202. For example, a BF2+ion beam at an energy of 1.19 keV requires a magnetic field strength of 873 Gauss to follow the proper trajectory in a mass analyzer of a nominal 400 mm bending radius for creating the ECR condition. The ECR regions 234 may be located advantageously close enough to the slots 254 in the waveguide 250 to benefit from the high electric field intensity, yet sufficiently spaced from any surface (e.g., magnets 220, waveguide 250, etc.) to minimize plasma losses. For example, the ECR regions 234 of FIGS. 7A and 7B may be located a distance 236 away from the magnets 220, which may be in the range of about 4 to 6 mm, with a nominal distance of about 5 mm providing proper operation. Referring now to FIG. 11, a method 300 of providing ion beam containment in a low energy ion implantation system is illustrated. The method begins at step 302 wherein an ion beam is produced along a longitudinal path using an ion source. A mass analyzer is provided at step 304 having an inner passageway, a high frequency power source, a mass analysis magnet mounted in the inner passageway, and a magnetic device mounted in the inner passageway. The ion beam is received in the mass analyzer from the ion source at step 306, and ions of appropriate charge-to-mass ratio are directed at step 308 from the mass analyzer along the path toward a wafer or other target to be implanted with ions. At step 310, an electric field is generated in the passageway using a high frequency power source. A multi-cusped magnetic field is generated at step 312 using a magnetic device mounted in the passageway, which may create advantageously an ECR condition therein. Although the invention has been shown and described with respect to a certain applications and implementations, it will be appreciated that equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. In particular regard to the various functions performed by the above described components (assemblies, devices, circuits, systems, etc.), the terms (including a reference to a xe2x80x9cmeansxe2x80x9d) used to describe such components are intended to correspond, unless otherwise indicated, to any component which performs the specified function of the described component (i.e., that is functionally equivalent), even though not structurally equivalent to the disclosed structure, which performs the function in the herein illustrated exemplary implementations of the invention. In addition, while a particular feature of the invention may have been disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired and advantageous for any given or particular application. Furthermore, to the extent that the terms xe2x80x9cincludesxe2x80x9d, xe2x80x9cincludingxe2x80x9d, xe2x80x9chasxe2x80x9d, xe2x80x9chavingxe2x80x9d, and variants thereof are used in either the detailed description or the claims, these terms are intended to be inclusive in a manner similar to the term xe2x80x9ccomprisingxe2x80x9d.
	abstract	Disclosed are an in-vessel control rod drive mechanism and a nuclear reactor with the same. The in-vessel control rod drive mechanism includes a control rod drive mechanism for regulating and a control rod drive mechanism for shutdown provided at an upper or lower space of a reactor core to insert or withdraw a regulating rod and a shutdown rod into/from the reactor core based on an operation state of the nuclear reactor, wherein the control rod drive mechanism for regulating and the control rod drive mechanism for shutdown are alternately arranged in the vertical direction. Therefore, a space of containment can be minimized due to the installation of the in-vessel control rod drive mechanism, and thus a rod ejection accident can be prevented, and a loss-of-coolant accident can be reduced.
062890719	abstract	The present invention provides a positron source essentially consisting of a carbon member having .sup.18 F bound onto the surface thereof, a method of preparing the same, and an automated system for supplying the same. In the present invention, the positron source is prepared by irradiating a solution containing both H.sub.2.sup.18 O and a small amount of natural fluorine ions with a beam of charged particles to generate .sup.18 F, and then passing an electric current through the solution using a carbon member 40 as an anode to cause to bind the generated .sup.18 F onto the surface of the carbon member.
	claims	1. A particle energy modulating device for variably changing the energy of particles of a particle beam passing through the particle energy modulating device, which has at least one variable energy varying device, characterized by at least one control value correcting device for correcting a control value supplied to the particle energy modulating device; the control value correcting device is embodied and equipped so that the control values supplied to the particle energy modulating device are at least sometimes and/or at least partially corrected through the use of calibration data characterized in that in at least some regions, calibration data have been determined over an area in the form of a two-dimensional grid including a plurality of measurement points where actual damping action is measured for calculating values of the calibration data. 2. The particle energy modulating device according to claim 1, characterized in that the control value correcting device has at least one interpolation means. 3. The particle energy modulating device according to claim 1, characterized in that the control value correcting device, at least sometimes and/or in at least some areas, carries out a correction with regard to the change in the energy of the particles passing through the particle energy modulating device. 4. The particle energy modulating device according to claim 1, characterized in that the control value correcting device, at least sometimes and/or in at least some areas, carries out a correction with regard to the trajectory of the particles. 5. The particle energy modulating device according to claim 1, characterized in that the control value correcting device has at least one electronic computing device and/or at least one electronic memory device. 6. The particle energy modulating device according to claim 1, characterized in that the at least one variable energy varying device has at least one energy absorption device, which is at least partially and/or in at least some areas embodied as a sliding-wedge device, as a fast-moving water column device, and/or as a modulator wheel device. 7. A control value correcting device for correcting a control value supplied to a particle energy modulating device for variably changing the energy of the particles of a particle beam passing through the particle energy modulating device, characterized in that the control value correcting device is embodied and equipped so that control value supplied to the particle energy modulating device are at least sometimes and/or at least partially corrected through the use of calibration data, characterized in that in at least some regions, calibration data have been determined over an area in the form of a two-dimensional grid including a plurality of measurement points where actual damping action is measured for calculating values of the calibration data. 8. A method for determining correction values for a particle energy modulating device, wherein the method comprises:determining calibration data over a grid arrangement extending over an area, including:approaching a measurement point,measuring actual damping action of an energy damping unit and/or an energy modulator at the measurement point, andcalculating a valid calibration value for the current measurement point; anddetermining corrected control values, including:reading in a desired damping value for the energy damping device and/or the energy modulator,determining a setpoint position of at least one energy absorption device,correcting the determined setpoint position using the valid calibration value to result in a corrected setpoint position, andadjusting the at least one energy absorption device into the corrected setpoint position. 9. The method according to claim 8, characterized in that the calibration data are acquired before a use of the control value correcting device and/or before a use of the particle energy modulating device and/or are stored in an electronic memory device. 10. The particle energy modulating device according to claim 4, wherein the correction is carried out with regard to a travel direction of the particles and/or with regard to a transverse offset of the travel direction. 11. The method according to claim 8, characterized in that the step of determining corrected control values, at least sometimes and/or in at least some areas, includes carrying out a correction with regard to the change in the energy of the particles passing through the particle energy modulating device. 12. The method according to claim 8, characterized in that the step of determining corrected control values, at least sometimes and/or in at least some areas, includes carrying out a correction with regard to the trajectory of the particles.
044141777	summary	TECHNICAL FIELD This disclosure relates to an apparatus for monitoring the presence of coolant in liquid or mixed liquid and vapor, and superheated gaseous phases at one or more locations within an operating nuclear reactor core, such as pressurized water reactor or a boiling water reactor. BACKGROUND ART There exists a need for systems capable of detecting the proximate phase of coolant flow in a reactor core, and for instruments capable of detecting liquid level in the core. United States governmental regulations specify "thermal hydraulic" measurement capabilities in all operating power reactors. These needs and requirements are the result of the TMI accident. During such an "event" in a pressurized water reactor, there might be a period during which the reactor pressurizer will overfill with water while the primary pumps are operating. The reactor coolant may be in two-phase flow through the coolant loop and might have a significant void fraction. At the present time, the reactor operator has no instrumentation which would indicate a void fraction or liquid level exists in the core. If the pumps are shut off, the void fraction in the coolant will separate, exposing a portion of the core. Because of the unavailability of monitoring systems for either of these conditions, the operators of the reactor may be unaware of these conditions until serious damage results to the core itself. The present system is designed to provide continuous monitoring of coolant conditions at one or more locations within an operating reactor vessel. It can be used to determine the nominal coolant phase at a designated location. DISCLOSURE OF THE INVENTION The apparatus comprises a length of small diameter tubing having an open end positioned within the coolant at the location to be monitored. The tubing leads through the vessel or pipe walls to its exterior to deliver pressurized coolant from its open end. The exterior end of the length of tubing is closed. A temperature sensing device, such as a thermocouple, is mounted at the open end of the length of tubing. Leads from it extend through the tubing to the exterior of the vessel. A pressure sensing device, such as a pressure transducer, is operably connected to the interior of the tubing at a location exterior to the vessel. Since discernible temperature differences exist between liquid and superheated gaseous phases of coolant at reactor vessel pressures, and the saturated temperature is well defined for any given pressure, an indication of the coolant phase condition can be obtained by comparing the measured liquid temperature to the measured pressure. These two measured parameters are compared to pressure and temperature tables inserted in a programmable memory. The measured pressure is utilized to select a set of temperatures from the memory which are compared to the measured temperature. Because the liquid temperature doesn't change at T saturation, this device cannot recognize these changing phase conditions. To obtain a usable readout from this device the output must be divided into three categories: (1) T measured is below T saturation=output reading normal liquid, (2 ) T measured is above T saturation but below some preselected superheated steam temperature (say T saturation+5.degree. F.)=output reading interpreted as possible void fraction, and (3) T measured is above T saturation+5.degree. F.=output reading indicated the presence of superheated steam, therefore, liquid level is below sensing location. This can be accomplished by a properly programmed analyzer with readout capability or annunciators for indicating the condition of the coolant at the monitored location. By using a multiple number of lengths of tubing with open ends incrementally spaced at different elevations, one can then monitor coolant level.
046793771	abstract	An improved apparatus for applying an end plug to an end of a fuel rod tube includes a housing having spaced inlet and outlet ends adapted to receive the end plug and tube end, respectively, one of three alternative embodiments of a guide arrangement which defines an internal guide channel aligned in tandem with the inlet and outlet ends of the housing along a common axis, and cylindrical ram movable along the axis for engaging and moving the end plug from the inlet end through the guide channel to the outlet end where the plug is applied to the tube end. The guide arrangement, whether is takes the form of a deformable bushing, a series of radially-mounted inwardly-biased runners or a series of parallel-mounted inwardly-biased rolls, defines the guide channel with a cross-sectional size smaller than that of the end plug and when contacted by the moving plug yieldably expands such that the guide channel conforms to the external surface of the end plug and thereby establishes and maintains guiding contact therewith as the end plug is moved through the guide channel.
055442110	abstract	A fuel assembly has part length and full length fuel rods, and a pair of large-diameter water rods which occupy an area which can accommodate 7 fuel rods. Natural uranium regions are provided in the upper and lower end portions of the effective fuel zone of the fuel assembly. An intermediate region between these upper and lower natural uranium regions provides an enriched uranium region which has three axial sections: an upper section, a middle section and a lower section. The middle section has the highest average enrichment, the lower section has the medium average enrichment and the upper section has the smallest average enrichment. The difference in the average enrichment between the middle section and the lower section is smaller than that between the middle section and the upper section. The upper section has a lower concentration of burnable poison than other sections of the enriched uranium region. According to this arrangement, a greater burn-up degree of the fuel assembly can be achieved with minimal increment of the average enrichment, while preserving sufficiently large safety margin such as the thermal margin of the reactor and the reactor cold shut down margin.
	description	The present invention relates to a plasma diagnosis system using Thomson scattering, and more particularly, a plasma diagnosis system using multiple-reciprocating-pass Thompson scattering system can capable of rejecting background noise due to stray lights and measuring an pure Thomson scattering signal without noise by measuring a Thomson scattering signal and a background noise in plasma by using an optical system configured to rotate a plane of polarization of a multi-passing laser pulse by 90 degrees in every consecutive roundtrip. In tokamak-type nuclear fusion, typically, deuterium atoms and tritium atoms are heated up to so high temperature to generate a plasma state in which ionized atomic nuclei and electrons have free mobility, and the plasma is confined by using a strong toroidal magnetic field, so that the nuclei overcome Coulomb force and come close enough to cause fusion reaction at sufficiently high temperature. In order to stably operate and control this high-temperature, high-density plasma state, it is necessary to know the temperature and density of the plasma, and thus, accurate measurement thereof is required. As a result of this request, various types of plasma diagnosis apparatuses have been developed and used. As one of the plasma diagnosis apparatuses, there is a diagnosis apparatus using Thomson scattering, which is an essential diagnosis apparatus for measuring temperature and density of electrons. FIG. 1 is a configuration diagram schematically illustrating a diagnosis apparatus using Thompson scattering in the related art for diagnosing a state of plasma in a tokamak of a nuclear fusion reactor. Referring to FIG. 1, a diagnosis apparatus 1 using Thomson scattering in the related art for diagnosing a state of plasma in a tokamak 5 of a nuclear fusion reactor includes a laser which outputs a strong laser pulse linearly polarized in the direction perpendicular to the plane containing the propagation vector of the laser pulse and the optic axis of the collection optics 130, which will be referred as the vertical direction, an optical system 110 which focuses the vertically polarized laser pulses beam in the vertical polarization state into a prescribed position of the plasma in the TOKAMAK, a laser beam dump 120 which is mounted outside the tokamak and absorbs and removes the used laser pulses, and a collection optics 130 which collects the light scattered by the plasma in the focused region of the laser pulses. More specifically, in order to measure the temperature and density of electrons in a plasma, the above-described diagnosis apparatus 1 using Thomson scattering focuses a high energy laser pulse with a single wavelength (1064 nm, for example) from the outside of the tokamak 5 into the plasma-filled tokamak by using the laser 100 and the optical system 110. The positively charged ions or nuclei in a fusion reactor, and electrons constituting the plasma are accelerated by the oscillating electric field of the focused high intensity, linearly polarized laser pulse. At the driving laser frequency, accelerated charges, mainly electrons, radiate lights, for which a light beam with the same frequency as the incident laser beam is emitted and is subjected to Thompson scattering. As a consequence, the Thomson scattering has the largest cross section along the direction perpendicular to the oscillating electrons or the direction of incident polarization and there is no radiation along the direction parallel to the polarization. Therefore, the maximum collection efficiency can be expected along the optic axis of the collection optics, if the plane of polarization of the incident laser pulse is orthogonal to the plane containing the laser pulse propagation vector and the optic axis of the collection optics, which will be referred to as the vertical polarization. On the contrary, in the case where the polarization of the incident laser pulse is horizontal, or 90 degrees to the vertical polarization, Thomson scattering to the collection optics is negligible. Since high temperature plasmas are moving fast, the scattered lights do a Doppler shift in wavelength due to the Doppler effect. Therefore, the diagnosis apparatus using Thomson scattering can acquire the temperature of electrons in plasma by measuring the wavelength shift due to the Doppler effect and can also acquire the density of electrons according to the intensity of light to be measured. That is, if signals of the Thomson scattered light in plasma are accurately measured, the temperature and density of the plasma can be accurately acquired. However, there exist the light beams that are reflected by incomplete optical parts to be incident on the tokamak and the light beams that are scattered multiple times by wall surfaces of the tokamak and the like, and these light beams are called stray light. As the background noise caused by the stray light is included in the Thomson scattering signal measured by the diagnosis apparatus using Thomson scattering in the related art, there is a problem in that the accuracy of the measured Thompson scattering signal is lowered. In order to solve the problems described above, the present invention is to provide a plasma diagnosis system using a multiple-reciprocating-pass Thompson scattering system which can reject background noise due to stray lights by rotating the plane of polarization of the laser pulse by 90 degrees at every roundtrip in the multiple-reciprocating-pass. According to an aspect of the present invention, there is provided a plasma diagnosis system using Thomson scattering, including: a laser which outputs a laser pulse having predetermined polarization and wavelength; an optical system configured to run the laser pulse along the given path multiple times, rotates a plane of polarization of the laser pulse by 90 degrees in each roundtrip, and focuses the laser pulse to a predetermined location in the plasma in order to provide alternately vertical and horizontal polarizations of the laser pulse to a focal point in plasma; a collection optics which is configured with a lens or a combination of lenses, collects lights scattered from a focal point in plasma, whereas the collected light by the vertical polarization of the laser pulse is referred to as ‘first collected scattering’ and the collected light by the horizontal polarization of the laser pulse is referred to as ‘second collected scattering’; a polychromator which filters and outputs spectral characteristics of the first and second collected scatterings; and a computer which measures spectral characteristics of the first and second collected scatterings and outputs a background noise and a Thomson scattering signal with the background noise, wherein the noise is generated by scattering in plasma due to stray lights and is obtained from the second collected scattering and the Thomson scattering signal with the noise is obtained from the first collected scattering. Preferably, in plasma diagnosis system using Thomson scattering according to the above aspect, the optical system may include: a polarizing beam splitter (PBS) which is inserted in the optical path and reflects or transmits an incident laser pulse according to a polarization state of the incident laser pulse; a first reflecting mirror (M1) which reflects the laser pulse exited from the PBS back into the incident optical path; a Faraday rotator which rotates a plane of polarization of the output laser pulse from the PBS by 45 degrees; a focusing lens which focuses the output laser pulse from the Faraday rotator to the predetermined position in plasma; and a second reflecting mirror (M2) which reflects the laser pulse exited from the focal point in plasma to the focusing lens, and wherein the vertical polarization of the laser pulse and the horizontal polarization of the laser pulse are alternately focused into the focal point in plasma. Preferably, the plasma diagnosis system using Thomson scattering according to the above aspect, may further include an optical isolator between the laser and the optical system, and wherein the optical isolator prevents any back reflected lights from feeding back into the laser. Preferably, the plasma diagnosis system using Thomson scattering according to the above aspect, may further include a trigger module which is configured with a photo detector and outputs a trigger signal when the photo detector detects a part of the laser pulse on a predetermined position, wherein a signal processing of the polychromator is synchronized by using the trigger signal. Preferably, the plasma diagnosis system using Thomson scattering according to the above aspect, further comprises a computer which measures a pure Thomson scattering signal without the background noise by subtracting the background noise from the Thomson scattering signal contaminated with the background noise. Preferably, the plasma diagnosis system using Thomson scattering according to the above aspect may be applied to a tokamak-type nuclear fusion reactor, wherein the optical system focuses a laser pulse into a predetermined region of the confined plasma in the tokamak, the collection optics collects the scattered lights and sends the collected lights to a polychromator by using a transmission link, typically an optical fiber. A computer interfaced high-speed multi-channel data analyzer is used for subtracting the background noise from the Thomson scattering signal contaminated with the noise and analyzing the output signals from the different channels of the polychromator to provide correct information on the temperature and density of electrons at the focused region of hot plasma. The computer measures and supplies the pure Thomson scattering signal without noise in the tokamak. The multiple-reciprocating-pass plasma diagnosis system according to the present invention alternately supplies a vertical polarization of a laser pulse and a horizontal polarization of a laser pulse to a tokamak using the optical system to be focused in plasma through multiple reciprocating paths, so that it is possible to measure and supply the pure Thomson scattering signal from which the background noise is removed. In a plasma diagnosis system using Thomson scattering according to the present invention, a vertical polarization of a laser pulse and a horizontal polarization of a laser pulse are alternately supplied in plasma of a tokamak in a nuclear fusion reactor through multiple reciprocating paths, and scattering signals in plasma of the tokamak are collected and measured, so that it is possible to accurately measure a pure Thomson scattering signal from which a background noise is removed. Hereinafter, a structure and operation of a plasma diagnosis system using Thompson scattering according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. FIG. 2 is a block diagram schematically illustrating a plasma diagnosis system using multiple-reciprocating-path Thompson scattering according to a preferred embodiment of the present invention. Referring to FIG. 2, a plasma diagnosis system 2 according to the present invention is installed outside a tokamak 5 of a nuclear fusion reactor and includes a laser 200, an optical system 220 which sequentially and alternately supplies a vertical polarization of the laser pulse and a horizontal polarization of the laser pulse to plasma of the tokamak, a collection optics 230 which collects lights scattered in plasma of the tokamak, a trigger module 240, a polychromator 245 and a computer 250. The laser 200 outputs a laser pulse in a horizontal polarization with a single wavelength of 1064 nm and a strong electric field intensity. The first half wave plate (HWP) 214 is disposed on the optical path of the laser pulse output from the laser and rotated a plane of a polarization of the incident laser pulse by 90 degrees to select and maintain the polarization state of the propagating laser pulse. The optical system 220 is configured to run the laser pulse to passes along a closed optical path, focus and collimate the laser pulse in plasma when enters and exits a plasma vessel, respectively, place a predetermined focal point in plasma, and rotate a plane of polarization by 90 degrees at each complete pass to provide and focus alternately horizontal and vertical polarizations of the laser pulse to the predetermined focal point in plasma. The optical system 220 is located between the laser and the tokamak 5 to supply and focus alternately a vertical polarization of the laser pulse and a horizontal polarization of the laser pulse to plasma in the tokamak when the laser pulse is supplied from the laser. The optical system is configuring to alternately focus the vertical and horizontal polarizations of the laser pulse on the focal point in plasma. The optical system 220 includes a polarizing beam splitter (PBS) 221, a Faraday rotator (FR) 222, a second half wave plate (HWP) 224, and a focusing lens 226, a second reflecting mirror 227, and a first reflecting mirror 229. The second reflecting mirror 227 includes a lens, a convex lens or a combination of lenses 227 may be installed inside or outside the tokamak. The second reflecting mirror 227 is configured to reflect the laser pulse exited from the focal point in plasma to the focusing lens. The first reflecting mirror 229 includes a lens, a convex lens or a combination of lenses and is inserted in the optical path and reflects the laser pulse exited from the PBS back into the optical path. The polarizing beam splitter (PBS) 221 is inserted in the optical path and reflects or transmits an incident laser pulse according to a polarization state of the incident laser pulse. The PBS transmits the horizontal polarization of the laser pulse and reflects the vertical polarization of the laser pulse. Therefore, the laser pulse having two polarization components may be split to two paths by passing through the PBS. The focusing lens 226 focuses the laser pulse output from the Faraday rotator on the predetermined focal point in plasma. When the laser pulse is focused into the focal point in plasma of the tokamak by the focusing lens, the first Thomson scattering is strongly generated in the direction of the collection optic. As a result, the first-1 collection signal, in which the noise and the Thomson scattering signal are mixed, is collected by the collection optics 230 and is transmitted to a polychromator using optical fibers, by which the collection signal is measured for each wavelength band. The Faraday rotator 222 rotates a plane of polarization of the laser pulse passing through the PBS by 45 degrees. The Faraday rotator 222, the second half wave plate 224, and the focusing lens 226 are sequentially disposed on the optical path of the laser pulse passing through the PBS 220. The second half wave plate 224 rotates a plane of polarization of the incident laser pulse by 90 degrees, so that the horizontal polarization of the laser pulse is convert to the vertical polarization by the Faraday rotator 222 and the second half wave plate 224. The first half wave plate 214 may be omitted in the case where the laser pulse output from the laser is a perfectly horizontal polarization. In some cases, in principle, the second half wave plate 224 may be omitted according to the position of a Thomson scattering collection unit. The collection optics 230 is comprising of a lens or a combination of lenses and collects the lights scattered from the focal points in plasma and supplies the collected lights to the polychromator 245. The collected light is referred to as “first collected scattering” if the plane of polarization of the laser pulse is orthogonal (referred to as “vertical polarization of the laser pulse”) to the plane containing optic axis of the collection optics and the propagation vector of the laser pulse. In addition, the collected light is referred to as “second collected scattering” if the plane of polarization of the laser pulse is parallel (referred to as “horizontal polarization of the laser pulse”) to the plane containing optic axis of the collection optics and the propagation vector of the laser pulse. Thomson scattered lights are contaminated with the noise due to stray lights in the first collected scattering while the noise due to stray lights are dominant in the second collected scattering. The trigger module 240 generates the trigger signals and outputs the trigger signals to the collection optics and/or the computer when the horizontal polarization of the laser pulse and the vertical polarization of the laser pulse are supplied from the optical system. The trigger module may detect an extra laser beam signal transmitted through a folding mirror disposed at a trigger point set between the laser and the optical system or at an arbitrary position of the optical system to use the extra laser beam signal as a trigger signal. The collection optics is driven according to the trigger signal output from the trigger module to collect light scattered in the tokamak and supply the scattered light. The polychromator 245 may be consisted of typically 5 channels of broad band pass filters which can be used for analyzing spectral characteristics of the lights, which are the first and second collected scatterings. Each channel of the polychromator filters the collected lights provided from the collection optics according to spectral characteristics and outputs the filtered lights. Therefore, the polychromator output the filtered lights according to spectral characteristics of the collected lights to the data acquisition system 250 through the 5 channels. The data acquisition system 250 may be included amplifiers and a computer which measures and analyses spectral characteristics of the first and second collected scatterings by using the filtered signal provided from the polychromator and measures a pure Thomson scattering signal by using the spectral characteristics. The computer of the data acquisition system 250 measures and supplies a pure Thomson scattering signal without the background noise by using the first and second collected scatterings. The computer may measure temperature and density of electrons in plasma by analyzing the spectral characteristics obtained in the polychromator. More specifically, the computer controls to generate the Thomson scattering on the plasma in the tokamak by the vertical polarization of the laser pulse and measures the Thomson scattering signal which is contaminated with the noise. In addition, the computer controls not to generate the Thomson scattering on the plasma in the tokamak by the horizontal polarization of the laser pulse and measures a noise which is scattered from plasma due to stray lights. Therefore, the computer can accurately measure the pure Thomson scattering signal without the noise due to stray lights by removing the noise from the Thompson scattering signal with the noise. Hereinafter, the operation of the plasma diagnosis system using multiple-reciprocating-path Thompson scattering having the above-described configuration according to the preferred embodiment of the present invention will be described in detail with reference to FIG. 3. In plasma diagnosis system according to the preferred embodiment of the present invention, when the laser pulse is output from the laser, the laser pulse is reciprocated four times through the optical system, so that Thompson scatterings are generated in plasma. Hereinafter, FIG. 3 is a diagram illustrating a polarization state of the laser pulse in each stage in plasma diagnosis system using multiple-reciprocating-path Thompson scattering according to the preferred embodiment of the present invention. Referring to FIG. 3, when a horizontal polarization of a laser pulse is output and supplied from the laser, in the first forward stage, the laser pulse passes through the PBS 221, passes through the FR 222 to be rotated the plane of the polarization of the laser pulse by 45 degrees, and is rotated by 45 degrees again by the second HWP 224, so that the polarization of the laser pulse is converted to the vertical polarization. When the vertical polarization of the laser pulse is focused on the focal point in plasma of the tokamak, the first Thomson scattering is strongly generated in the direction of the collection optics 230. As a result, the collection optics collects a light scattered from the focal point in plasma and sends the collected light to the polychromator as the first-1 collection signal due to the first Thompson scattering. The first-1 collection signal due to the first Thompson scattering is configured with the Thomson scattering signal with the noise which the Thomson scattering signal is contaminated with the background noise due to stray lights. Next, the laser pulse focused on the focal point of the plasma propagates after the first Thompson scattering and is reflected by the second reflecting mirror 227, and then the first backward stage proceeds. In the first backward stage, as the laser pulse is refocused into the focal point of plasma of the tokamak, the second Thomson scattering is generated. The collection optics collects a light scattered from the focal point in plasma and sends the collected light to the polychromator as the first-2 collection signal due to the second Thompson scattering. The first-2 collection signal due to the second Thompson scattering is configured with the Thomson scattering signal with the noise. Next, in the first backward stage, the vertical polarization of the laser pulse passing through the tokamak passes through the second HWP 224 and is rotated by 45 degrees in the backward direction, and returns to the original state and a plane of the polarization of the laser pulse is rotated by 45 degrees by the FR 222 again, so that the polarization of the laser pulse is converted to the vertical polarization. The vertical polarization of the laser pulse is reflected by the PBS 221 and propagates to the first reflecting mirror 229. The vertical polarization of the laser pulse reflected by the first reflecting mirror is incident on the PBS 221 again and then reflected. Next, in the second forward stage, the vertical polarization of the laser pulse incident on the PBS from the first reflecting mirror is reflected by the PBS and then passes through the FR 222 so that the plane of the polarization of the laser pulse is rotated by 45 degrees. The polarization of the laser pulse is converted to the horizontal polarization by the second HWP 224. As the horizontal polarization of the laser pulse is focused on the focal point of the plasma, Thomson scattering is not generated in the direction of the collection optics 230, and a background scattering due to stray lights is generated. Therefore, the collection optics collects a light scattered from the focal point in plasma by the background scattering and sends the collected light to the polychromator as the second-1 collection signal due to the background scattering. The second-1 collection signal is configured with only the background noise which is a light scattered from the focal point of the plasma due to the stray lights. Next, the laser pulse focused on the focal point of the plasma propagates and is reflected by the second reflecting mirror 227, and the second backward stage proceeds. In the second backward stage, the horizontal polarization of the laser pulse is focused again on the focal point of the plasma and then propagates to the focusing lens with no Thomson scattering in the direction of the collection optics 230. The background scattering due to stray lights is generated in the focal point of the plasma. At this time, the collection optics collects a light scattered from the focal point in plasma and sends the collected light to the polychromator as the second-2 collection signal due to the background scattering. The polychromator and the computer measure the second-2 collection signal configured with only the noise. The computer receives the first-1 and first-2 collection signals which are configured with the Thomson scattering signal contaminated with the noise and receives the second-1 and second-2 collection signals which are configured with only the noise. Therefore, it is possible to accurately measure the pure Thomson scattering signal without the noise by subtracting the background noise from the Thomson scattering signal contaminated with the background noise. As described above, the plasma diagnosis system using the multiple-reciprocating-path Thomson scattering according to the present invention can accurately measure the Thomson scattering signal. On the other hand, the plasma diagnosis system according to the present invention can be applied to a tokamak-type nuclear fusion reactor. In this case, the optical system focuses the laser pulse into the tokamak, the collection optics collects the scattered optical signals in the tokamak, and the computer measures the pure Thomson scattering signal without the noise in the tokamak. While the present invention has been particularly illustrated and described with reference to exemplary embodiments thereof, it should be understood by the skilled in the art that the invention is not limited to the disclosed embodiments, but various modifications and applications not illustrated in the above description can be made without departing from the spirit of the invention. In addition, differences relating to the modifications and applications should be construed as being included within the scope of the invention as set forth in the appended claims. The plasma diagnosis system according to the present invention can be used variously in apparatuses requiring measurement of the temperature and density of plasma, and in particular, can be used to diagnose the state of plasma inside a tokamak-type nuclear fusion reactor.
	description	This application is a division of U.S. patent application Ser. No. 12/909,252, filed Oct. 21, 2010, now U.S. Pat. No. 9,378,853, the entire disclosure of which is incorporated by reference herein. The following relates to the nuclear power reactor arts, nuclear reaction control apparatus arts, control rod assembly arts, and related arts. In nuclear power plants, a nuclear reactor core comprises a fissile material having size and composition selected to support a desired nuclear fission chain reaction. To moderate the reaction, a neutron absorbing medium may be provided, such as light water (H2O) in the case of light water reactors, or heavy water (D2O) in the case of heavy water reactors. The reaction may be controlled or stopped by inserting “control rods” comprising a neutron-absorbing material into aligned passages within the reactor core. When inserted, the control rods absorb neutrons so as to slow or stop the chain reaction. The control rods are operated by control rod drive mechanisms (CRDMs). In so-called “gray” control rods, the insertion of the control rods is continuously adjustable so as to provide continuously adjustable reaction rate control. In so-called “shutdown” control rods, the insertion is either fully in or fully out. During normal operation the shutdown rods are fully retracted from the reactor core; during a SCRAM, the shutdown rods are rapidly fully inserted so as to rapidly stop the chain reaction. Control rods can also be designed to perform both gray rod and shutdown rod functions. Typically, a number of control rods are connected with a single CRDM by an assembly including a connecting rod coupled with the CRDM and terminating in a “spider” or other coupling element that supports the plural control rods. In such an assembly, the CRDM moves the plural control rods, along with the spider and the connecting rod, together as a unit. When the control rods are partially or wholly withdrawn from the reactor core, they are supported by a control rod guide frame so as to ensure that the control rods remain in precise alignment with the aligned passages within the reactor core. In one typical guide frame configuration, a plurality of spaced apart guide plates are secured together by a frame. In operation, the control rods are guided by openings in the guide plates. Such a guide frame design has advantages including low weight and material cost, and limited impedance of primary coolant flow due to the largely open design. The use of guide plates to define the control rod guiding surfaces also provides a convenient planar form for the precision metalwork. In one aspect of the disclosure, an apparatus comprises a control rod guide frame comprising a stack of two or more columnar elements defining a central passage having a constant cross-section as a function of position along the central passage. In another aspect of the disclosure, an apparatus comprises: a control rod guide frame comprising a stack of two or more columnar elements defining a central passage having a constant cross-section as a function of position along the central passage; a control rod assembly comprising at least one control rod parallel aligned with the central passage of the control rod guide frame; wherein the at least one control rod is movable into and out of the central passage of the control rod guide frame; and wherein any portion of the at least one control rod disposed in the central passage is guided by the central passage over the entire length of the portion of the at least one control rod that is disposed in the central passage In another aspect of the disclosure, an apparatus as set forth in the immediately preceding paragraph is disclosed, further comprising: a control rod drive mechanism (CRDM) operatively connected with the control rod assembly to control movement of the at least one control rod into and out of the central passage of the control rod guide frame; a nuclear reactor core; and a reactor pressure vessel containing at least the nuclear reactor core, the control rod guide frame, and the at least one control rod; wherein as the at least one control rod moves out of the central passage of the control rod guide frame it moves into the nuclear reactor core and as the at least one control rod moves into the central passage of the control rod guide frame it moves out of the nuclear reactor core. In another aspect of the disclosure, an apparatus comprises: a control rod assembly comprising a plurality of control rods; and a control rod guide frame defining a central passage into which the at least one control rod can be withdrawn, the central passage providing continuous guidance along the entire length of the portion of each control rod of the plurality of control rods that is withdrawn into the central passage. In another aspect of the disclosure, an apparatus comprises a control rod guide frame comprising a self-supporting stack of two or more columnar elements defining a central passage. In another aspect of the disclosure, an apparatus comprises a control rod guide frame comprising a self-supporting stack of two or more columnar elements defining a central passage, wherein the control rod guide frame does not include an exoskeleton supporting the self-supporting stack of two or more columnar elements. In another aspect of the disclosure, an apparatus as set forth in either one of the two immediately preceding paragraphs is disclosed, wherein the columnar elements include mating features that mate at abutments between adjacent columnar elements of the stack. In another aspect of the disclosure, an apparatus as set forth in either one of the two immediately preceding paragraphs is disclosed, further comprising a control rod drive mechanism (CRDM) operatively connected with a control rod assembly, and a nuclear reactor core, wherein the CRDM moves at least one control rod into and out of the nuclear reactor core under guidance of the control rod guide frame. In another aspect of the disclosure, a method comprises forming at least one columnar element defining a central passage, and constructing a control rod guide frame including the at least one columnar element. In another aspect of the disclosure, a method comprises forming a plurality of columnar elements each defining a central passage, and constructing a control rod guide frame by stacking the columnar elements end-to-end. In another aspect of the disclosure, a method as set forth in either one of the two immediately preceding paragraphs is disclosed, wherein the forming comprises extruding at least one columnar element defining a central passage. In another aspect of the disclosure, a method as set forth in either one of the two immediately preceding paragraphs is disclosed, wherein the forming comprises casting at least one columnar element defining a central passage. In another aspect of the disclosure, a method as set forth in either one of the two immediately preceding paragraphs is disclosed, wherein the forming comprises forming at least one columnar element defining a central passage using electrical discharge machining (EDM). An open control rod guide frame comprising spaced apart guide plates secured together by an exterior frame has advantages including low weight and material cost, limited primary coolant flow impedance, and manufacturing convenience. However, numerous disadvantages of this guide frame configuration are recognized herein. The spacing apart of the guide plates can potentially allow bowing of the control rods upon insertion if there is sufficient drag. Such bowing can cause the control rod assembly (that is, the plural control rods secured together to a connecting rod by a single spider or other coupling element) to get stuck within the guide frame and not allow it to be inserted into the nuclear core. Such a failure in the case of gray rods is at least a substantial inconvenience, and could require opening the reactor vessel for repair if the gray rods are essential to maintain acceptable reactivity control. In the case of hybrid and/or shutdown rods, bowing-induced rod insertion failure could hinder or even prevent successful SCRAM of a malfunctioning reactor, thus raising serious safety issues. An issue related to the potential rod bowing is shutdown speed and robustness. The rate at which the hybrid or control rods are inserted during a SCRAM impacts the shutdown speed. Potential rod bowing in the spaces between guide plates imposes an upper limit on the force (and hence speed) with which the control rods can be driven toward the reactor core, since too much force could cause control rod bending. The limited driving force can also adversely impact reliability. There is the potential for blockage or impediment to rod insertion into the reactor core. Sources of blockage or impediment include, for example, sediment or other contamination within the reactor vessel, or a burr or other defect in the guiding surfaces of the guide plate and/or the aligned passages within the reactor core, or so forth, possibly aggravated by thermal expansion during an elevated reactivity incident. Any such blockage or impediment is less likely to be overcome by a reduced driving force during rod SCRAM, thus raising the likelihood of a SCRAM failure. Another issue with using spaced apart guide plates is that the spider or other connecting element is not always aligned with any particular guide plate. When the spider is between spaced apart guide plates it is susceptible to movement due to any horizontal forces, for example due to horizontal primary coolant flow components, or movement of the reactor vessel itself (for example, during an earthquake, or at any time in the case of a maritime reactor). Any horizontal movement of the spider increases likelihood of misalignment and consequent failure of the control rods attached to the spider. Yet another issue with using spaced apart guide frames is the potential for flow induced vibrations acting on the control rods. For example, if the guide plates are treated as vibrational “null” points, the spaced apart guide plates may support natural vibration modes having wavelengths (or “half-wavelengths”) that are multiples of the spacing between the guide plates. Such vibrations can adversely impact stability of the reactivity control and can contribute to material fatigue and ultimately to failure of the control rods. It is recognized herein that these difficulties are alleviated by a guide frame providing continuous support. In such a case, rod bowing is suppressed or prevented entirely. This allows the use of greater force in driving the control rods into the core during a SCRAM, thus improving reactivity shutdown speed and reliability. The spider or other connecting element is also supported by the guide frame at every point in its travel between the fully withdrawn and fully inserted control rod positions. Vibrations are also suppressed or eliminated entirely by the continuous support. With reference to FIG. 1, a relevant portion of an illustrative nuclear reactor pressure vessel 10 includes a core former 12 located proximate to a bottom of the pressure vessel 10. The core former 12 includes or contains a reactive core (not shown) containing or including radioactive material such as, by way of illustrative example, enriched uranium oxide (that is, UO2 processed to have an elevated 235U/238U ratio). A control rod drive mechanism (CRDM) unit 14 is diagrammatically illustrated. The illustrative CRDM 14 is an internal CRDM that is disposed within the pressure vessel 10; alternatively, an external CRDM may be employed. FIG. 1 shows the single illustrated CRDM unit 14 as an illustrative example; however, more generally there are typically multiple CRDM units each coupled with a different plurality of control rods (although these additional CRDM units are not shown in FIG. 1, the pressure vessel 10 is drawn showing the space for such additional CRDM units). Below the CRDM unit 14 is a control rod guide frame 16, which in the perspective view of FIG. 1 blocks from view the connecting rod (not shown in FIG. 1). Extending below the guide frame 16 is a plurality of control rods 18. FIG. 1 shows the control rods 18 in their fully inserted position in which the control rods 18 are maximally inserted into the core former 12. In the fully inserted position, the spider or other connecting element is located at a lower location 20 within the control rod guide frame 16 (hence also not visible in FIG. 1). In the illustrative embodiment of FIG. 1, the CRDM unit 14 and the control rod guide frame 16 are spaced apart by a standoff 22 comprising a hollow tube having opposite ends coupled with the CRDM unit 14 and the guide frame 16, respectively, and through which the connecting rod (not shown in FIG. 1) passes. The lower end of the control rod guide frame 16 connects with a support plate 24, which may be an upper portion of the core former 12, or may be a separate plate mounted above the upper end of the core former 12. FIG. 1 shows only a lower portion of the illustrative pressure vessel 10. In an operating nuclear reactor, an open upper end 26 of the illustration is connected with one or more upper pressure vessel portions that together with the illustrated lower portion of the pressure vessel 10 form an enclosed pressure volume containing the reactor core (indicated by the illustrated core former 12), the control rods 18, the guide frame 16, and the internal CRDM unit 14. In an alternative embodiment, the CRDM unit is external, located above the reactor pressure vessel. In such embodiments, the external CRDM is connected with the control rods by a control rod/CRDM coupling assembly in which the connecting rod extends through a portal in the upper portion of the pressure vessel. With reference to FIG. 2, the control assembly including the CRDM unit 14, the control rod guide frame 16, the intervening standoff 22, and the control rods 18 is illustrated isolated from the reactor pressure vessel. Again, the control rod/spider assembly is hidden by the control rod guide frame 16 and the standoff 22 in the view of FIG. 2. With reference to FIG. 3, the control rod guide frame 16 is shown in perspective view and in isolation from the remaining components (such as the CRDM, control rods, and so forth). The control rod guide frame 16 is a continuous guide frame rather than being constructed of spaced apart guide plates. The guide frames disclosed herein, in general, comprise one or more columnar elements. The illustrative control rod guide frame 16 includes an illustrative seven columnar elements 30, which are identical and are stacked to form the illustrative control rod guide frame 16. However, the number of columnar elements can be one, two, three, four, five, six, the illustrative seven, eight, nine, ten, or more. Moreover, while the illustrative seven columnar elements 30 are all identical to each other, this is not required. For example, different columnar elements may have different heights, or the different columnar elements may variously include or omit fluid flow passages (optional features discussed further elsewhere herein), or so forth. Each pair of adjacent columnar elements 30 is connected at an abutment 31. (This is not pertinent in the limiting case in which the number of columnar elements equals one, since in that case there are no adjacent columnar elements). Since there are seven illustrative columnar elements 30, there are 7−1=6 abutments 31. More generally, if there are N stacked columnar elements then there are N−1 abutments. The illustrative control rod guide frame 16 comprises a self-supporting stack of the (illustrative seven) columnar elements 30. There is no exoskeleton supporting the stack of columnar elements 30. (This is indicated diagrammatically in FIG. 3 by showing an exoskeleton Ex in phantom so as to indicate that the exoskeleton is omitted, that is, is not included in the control rod guide frame 16.) In other embodiments, however, it is contemplated to include an exoskeleton to provide some support for the stack of columnar elements. Each columnar element 30 has a column height h, so that the illustrative control rod guide frame 16 in which the seven columnar elements 30 are identical has a column height H=7h. More generally, the height is the sum of the heights of the constituent columnar elements. In the limiting case of a guide frame comprising one columnar element, H=h. An upper end of the illustrative control rod guide frame 16 includes an upper plate 32 that may connect with the CRDM unit 14 via the standoff 22 (see FIG. 2), while a lower end of the illustrative control rod guide frame 16 includes a lower plate 34 that connects with the support plate 24 (see FIG. 1) which is an upper part of, or proximate to, the fuel core former 12. Although not shown, it is contemplated to include mounting blocks or other intermediate components to facilitate the connection of the guide frame 16 with the CRDM unit 14 and/or with the support plate 24. The foregoing height values neglect any height contribution of the upper and/or lower plates 32, 34 or of any mounting blocks or intermediate components. With reference to FIG. 4, a perspective sectional view of the illustrative control rod guide frame 16 is shown, with the section revealing a connecting rod 40 and a coupling element 42 disposed inside the illustrative control rod guide frame 16. In FIG. 4, the upper end of the connecting rod 40 is shown extending above the guide frame 16, in isolation. As will be understood by comparing FIG. 4 with FIGS. 1 and 2, the upper end of the connecting rod 40 extends into and couples with the CRDM 14. FIG. 4 shows the configuration with the connecting rod/coupling element assembly 40, 42 in their most “downward” position, corresponding to the control rods (not shown in FIG. 4) fully extended into the reactor core (as shown in FIGS. 1 and 2). In some embodiments, a spider serves as the coupling element for attaching a plurality of control rods to a single connecting rod. A spider typically comprises metal tubes or arms (typically made of stainless steel) extending generally radially outward from a central attachment point at which the spider attaches with the connecting rod, and optionally further includes additional supporting cross-members provided between the radially extending tubes. The spider is thus a lightweight, “spidery” structure having large lateral openings between the tubes or arms to reduce the actual surface area oriented broadside to the SCRAM direction. In illustrative FIG. 4, however, the coupling element 42 is a coupling element that has substantial elongation along the SCRAM direction S, and is bulky rather than having a lightweight “spidery” configuration as in a conventional spider. With reference to FIGS. 5 and 6, a perspective view and a side-sectional perspective view, respectively, of the coupling element 42 is shown. The coupling element 42 includes a substantially hollow casing 50 having upper and lower ends that are sealed off by upper and lower casing cover plates 52, 54. Four upper casing cover plates 52 are illustrated in FIG. 5 and two of the upper casing cover plates 52 are shown in the side-sectional perspective view of FIG. 6. The tilt of the perspective view of FIG. 5 occludes the lower cover plates from view, but two of the lower cover plates 54 are visible “on-edge” in the side-sectional view of FIG. 6. The illustrative coupling element 42 includes four lower casing cover plates 54 arranged analogously to the four upper casing cover plates 52 illustrated in FIG. 5. The coupling element 42 is cylindrical with a cylinder axis parallel with the SCRAM direction S and a uniform cross-section transverse to the cylinder axis. That cross-section is complex, and defines a central passage 56 for coupling with the lower end of the connecting rod 40. To increase the weight (or average density) of the coupling element 42, the casing 50 defines four cavities spaced radially at 90° intervals around the central passage 50. These cavities are filled with a filler 58 (only two filled cavities are visible in the sectional view of FIG. 6) of a dense material. The cross-section of the hollow casing 40 also defines numerous small passages 60 (that is, small compared with the central passage 56), only some of which are labeled in FIGS. 5 and 6. These small passages 60 pass completely through the casing 50, and provide mounting points for attachment of the upper ends of the control rods 18. The optional filler 58 increases the mass (or average density) of the coupling element 42 in order to increase SCRAM force and speed. The filler 58 comprises a heavy material, where the term “heavy material” denotes a material that has a higher density than the stainless steel (or other material) that forms the hollow casing 50. For example, the filler 58 may comprise tungsten, depleted uranium, molybdenum, or tantalum, by way of some illustrative examples. Alternatively, the cavities can be omitted and the entire coupling element 42 can be made of stainless steel, by way of example. Such a configuration still provides a substantial weight increase over a conventional lightweight, “spidery” spider due to the extension of the coupling element 42 along the SCRAM direction S and due to its more “filled” configuration. The illustrative “heavy” coupling element 42 is described in further detail in U.S. patent application Ser. No. 12/862,124 filed Aug. 24, 2010 and titled “Terminal elements for coupling connecting rods and control rods in control rod assemblies for a nuclear reactor”, which is incorporated herein by reference in its entirety. The illustrative “heavy” coupling element 42 has advantages such as providing greater SCRAM force and consequently faster shutdown (in the case of shutdown or hybrid control rods). However, more generally the control rod guide frames 16 disclosed herein are suitably used with conventional spiders, or with coupling elements such as the illustrative coupling element 42, or with no connecting element at all (for example, a configuration in which a single control rod is directly coupled with the lower end of a connecting rod). With returning reference to FIGS. 3 and 4 and with further reference to FIGS. 7-9, the illustrative control rod guide frame 16 is further described. FIG. 7 illustrates a side view of one columnar element 30. FIGS. 8 and 9 show respectively Section A-A and Section B-B indicated in FIG. 7. As best seen in the sectional views of FIGS. 8 and 9, the columnar element 30 defines a central passage 70 through the columnar element 30. The central passage 70 has a constant cross-section as a function of position along the central passage 70 (for example, having substantially the same cross-section at the position of Section A-A and at the position of Section B-B, as shown in respective FIGS. 8 and 9). Said another way, the columnar element 30 (or, equivalently, guide frame 16 comprising the stack of columnar elements 30) defines a central axis 72 (labeled in each of FIGS. 2, 4, 7, 8, and 9, where in FIGS. 8 and 9 the sectional views are down the central axis 72) and the central passage 70 lies along the central axis 72 and has a constant cross-section in the plane transverse to the central axis at positions along the central axis. The connecting rod 40 and the control rods 18 are assembled to be parallel with the central axis 72 defined by the control rod guide frame 16. (Or, viewed in the alternative, the control rod guide frame 16 is assembled such that its central axis 72 is in parallel with the connecting rod 40 and the control rods 18). In the illustrative example (see FIG. 4), the connecting rod 40 and coupling element 42 are centered on the central axis 72. Such centering provides advantageous a balance-enhancing symmetry to the moving assembly; however, it is also contemplated for the connecting rod and/or the spider or other coupling element to be positioned “off-center” respective to the central axis 72. It will also be noted that the SCRAM direction S is along (or parallel with) the central axis 72. The central passage 70 is sized and shaped to receive the illustrative coupling element 42 (or to receive the spider, in embodiments employing a spider as the coupling element) with a relatively small tolerance between the outer surface of the coupling element 42 (defined by the casing 50 in the illustrative example) and the surfaces of the central passage 70. The central passage 70 also includes control rod guidance channels 74 (labeled in FIG. 8) which are parallel with the central axis 72 and extend completely through the columnar element 30. Each control rod guidance channel 74 is sized and positioned to receive a corresponding control rod of the plurality of control rods 18. Because the central passage 70 (including the guidance channels 74) has a constant cross-section as a function of position along the central passage, any portion of a control rod that is disposed in the central passage 72 (and more particularly in the control rod guidance channel 74 aligned with that control rod) is guided by the central passage 70 (and more particularly is guided by the surfaces of the aligned control rod guidance channel 74) over the entire length of the portion of the control rod that is disposed in the central passage. Said another way, the control rod guidance channel 74 provides continuous guidance for the entire portion of the control rod that is withdrawn into the control rod guide frame 16. Phraseology such as “guidance” or “guiding surfaces” denote surfaces or structures (e.g., the guidance channels 74) that guide the control rods insofar as they keep the control rod straight in its intended orientation within a specified tolerance. Typically, the guidance channels 74 have a slightly larger diameter as compared with the control rods, with the difference defining the allowed tolerance of movement of the guided control rod. If the control rod attempts to deviate beyond this tolerance, for example due to mechanical vibrational force or incipient bowing of the control rod, the control rod cams against the guiding surfaces of the guidance channels 74 to prevent vibrational movement or bowing of the control rod beyond the allowable tolerance. By making the guidance channel 74 slightly larger than the control rod diameter, the control rod is allowed to move down or up (that is, inserted into or withdrawn from the core) without frictional resistance from the guidance channel 74. However, it is also contemplated for the guidance channel 74 to be sized to precisely match the diameter of the control rod, so that the motion tolerance is minimized at the cost of some frictional resistance to control rod insertion or withdrawal. The foregoing sizing of the guidance channels 74 is also suitably chosen taking into account any differential thermal expansion of the control rods compared with the stainless steel or other material comprising the columnar element 30. It will be noted that the illustrative guidance channels 74 do not form complete closed cylindrical passages, but rather are partially “connected” with the main volume of the central passage 70. The central passage 70, including the guidance channels 74, thus has a simply connected cross-section without any “detached” passage cross-section portions. This allows the assembly including the coupling element 42 and the coupled bundle of control rods 18 to move unimpeded through the length of the central passage 70. Each guidance channel 74 surrounds the circular cross-section of its guided control rod over a sufficient perimeter so as to prevent movement of the control rod beyond allowable tolerance in any direction. Moreover, while the illustrative guidance channels 74 are shaped to guide control rods having circular cross-sections, it is also contemplated for the control rods to have square, hexagonal, octagonal, or other cross-sections, in which case the corresponding control rod guidance channels have correspondingly shaped cross-sections that again are typically slightly enlarged compared with the control rod in correspondence with the allowable motion tolerance for the guided control rod. With continuing reference to FIGS. 7-9 and with further reference to FIG. 10, in embodiments (such as the illustrative embodiment) in which two or more columnar elements 30 are stacked to define the guide frame 16, the central passage 70 of each columnar element 30 is sized and shaped the same and is aligned in the stacking so as to define a “stacked columnar passage” having a constant cross-section as a function of position along the “stacked central passage”. Said another way, guide frame 16 comprising the stack of columnar elements 30 defines the central axis 72, and the common central passage 70 of the stack lies along the central axis 72 and has a constant cross-section in the plane transverse to the central axis 72. The alignment of the columnar elements 30 includes aligning the control rod guidance channels 74 over the entire stack. This is diagrammatically shown in FIG. 10, which illustrates a stack of three columnar elements 30. Shown in phantom are two illustrative control rod guidance channels 74, with the coupling element 42 shown in phantom at a position in the middle columnar element 30 of the stack. Two illustrative control rods 18 extend downward from the coupling element 42, and are partway withdrawn into the stack of columnar elements 30. In this position, portions of the two illustrative control rods 18 are disposed in the aligned control rod guidance channels 74 of the lowest columnar element 30 and part of the middle columnar element 30 of the stack. Thus, these portions of the two illustrative control rods 18 are provided with continuous guidance along the entire length of the portions disposed in the stack. With reference to FIGS. 3 and 7, the stack of columnar elements 30 comprising the control rod guide frame 16 is optionally a self-supporting stack in which the exoskeleton Ex is omitted. Toward this end, at each abutment between adjacent columnar elements 30, one columnar element includes an abutting end with a first set of mating features and the other columnar element includes an abutting end with a second set of mating features. The first and second sets of mating features are sized and shaped to mate together in the abutment. FIG. 7 illustrates an example, in which the columnar element 30 has a first (upper) abutting end 80 having a first set of mating features which in the illustrative example comprise protruding stubs 82, and also has a second (lower) abutting end 84 having a second set of mating features which in the illustrative example comprise recessed holes 86 (shown in phantom in FIG. 7). When one columnar element 30 is stacked on top of another, the recessed holes 86 in the abutting end 84 of the higher columnar element receive and mate with the protruding stubs 82 of the abutting upper end 80 of the lower columnar element. Such mating features assist in ensuring proper alignment, so that the central passages 70 of the stacked columnar elements form a continuous well-aligned passage through the entire guide frame 16. Depending on the nature of the mating features (e.g., the lengths of the stubs 82 and depths of the holes 86 in the illustrative example), the mating features may also provide some structural support contributing to the self-support of the stack. In some embodiments, the stack of two or more columnar elements has a constant outer perimeter as a function of position along the central passage 70. This is the case for the illustrative stack of columnar elements 30. Such a configuration provides advantages such as enhanced interchangeability of the constituent columnar elements, and simplified design of the usage of space within the reactor pressure vessel. However, it is also contemplated for the stack of two or more columnar elements to have an outer perimeter that varies as a function of position along the central passage 70. An advantage of the continuous guidance is that control rod bowing is suppressed or eliminated, which allows for higher SCRAM driving force and faster reactor shutdown times. However, these advantages can be reduced if hydraulic pressure builds up in the central passage 70 during a SCRAM so as to resist insertion of the control rods. Such a pressure buildup may be enhanced if the “bulky” coupling element 42 is used, since it does not provide substantial openings for flow of the primary coolant fluid past the coupling element 42. One way to alleviate hydraulic pressure buildup in the central passage 70 during a SCRAM is to employ a spider or other coupling element having substantial openings for flow of the primary coolant fluid past the spider or other coupling element. However, this approach reduces the weight of the coupling element, which may be disadvantageous. With reference to FIGS. 7 and 8, an additional or alternative way to alleviate hydraulic pressure buildup in the central passage 70 during a SCRAM is to include fluid flow passages in one or more of the columnar elements to provide fluid communication between the central passage 70 and the exterior of the columnar element. In the illustrative example, each columnar element 30 includes flow passages comprising an upper set of slots 90 and a lower set of slots 92. The slots 90, 92 are formed into the body of the columnar element 30, and are not coextensive with the height h of the columnar element 30 (and hence are not part of the central passage 70 which passes through the columnar element 30). In this regard, notice that illustrative Section A-A shown in FIG. 8 passes through the slots 90, and so the slots 90 are visible in Section A-A. In contrast, illustrative Section B-B shown in FIG. 9 passes between the slots 90 and the slots 92, and so no slots are visible in Section B-B. In the illustrative embodiment the control rod guide frame 16 comprises a stack of seven identical columnar elements 30, each of which include the slots 90, 92. More generally, however, it is contemplated to include fluid flow passages in only some of the columnar elements. The slot-shaped fluid flow passages 90, 92 are illustrative examples, and other shapes and dimensions of fluid flow passages are also contemplated, such as holes (square, circular, or otherwise-shaped), spiraling slots, or so forth. With reference to FIG. 11, the disclosed control rod guide frame comprising a stack of one or more columnar elements defining a central passage of constant cross-section can be employed in a spaced-apart combination to obtain the substantial benefit of continuous guidance while reducing the total amount of material. FIG. 11 shows a control rod guidance structure comprising an upper continuous control rod guide frame 161 and a lower continuous control rod guide frame 162 which are spaced apart by a spacer 96. The two continuous control rod guide frames 161, 162 are similar to the continuous control rod guide frame 16, except that they include fewer columnar elements 30 and have variant terminations. More particularly, the upper continuous control rod guide frame 161 includes three columnar elements 30 and hence includes two abutments 31; while the lower continuous control rod guide frame 162 includes four columnar elements 30 and hence includes three abutments 31. The upper continuous control rod guide frame 161 also omits the lower plate 34 in favor of a lower connection with the spacer 96, and similarly the lower continuous control rod guide frame 162 omits the upper plate 32 in favor of an upper connection with the spacer 96. A potential advantage of a configuration such as that of FIG. 11 is that the spacer 96 can be made with large gaps to alleviate hydraulic pressure buildup in the central passage 70 during a SCRAM, so that it serves a similar purpose to the slots 90, 92. A potential disadvantage of the spacer 96 is that it presents a discontinuity in the control rod guidance. Thus, tradeoffs can be made between the “openness” of the control rod guidance structure (which is promoted by including more spacers of larger height) and the guidance continuity (which is promoted by fewer spacers of lower height, or no spacers at all as per the guide frame 16). It will be noted that in the control rod guidance structure of FIG. 11, each of the constituent guide frames 161, 162 provide continuous guidance along their respective lengths (or heights). This continuous guidance tends to bias the control rods into the “straight” configuration, which may suppress control rod bowing even in the unguided spacer 96. The columnar elements 30 are suitably made of stainless steel, although other materials are also contemplated. Manufacturing of the columnar elements 30 can employ various techniques, such as casting, extrusion, or electrical discharge machining (EDM). After initial formation by casting, extrusion, or EDM, the castings are optionally machined to meet specified tolerances. The recessed holes 86 are suitably made by drilling, while the protruding stubs 82 are suitably separately manufactured components that are welded or otherwise secured in holes drilled in the columnar element 30. A suitable number of one or more columnar elements 30 are then stacked on top of each other, assisted by mating of the optional mating features 82, 86, to reach the specified overall height of the guide frame. Alternatively, as shown in FIG. 11, two or more such continuous guide frames can be assembled in a spaced apart fashion to reach the specified overall height. An advantage of the disclosed self-supporting stacked continuous guide frames is the optional elimination of an external frame (that is, exoskeleton), with anchoring of the guide frame provided by the upper and lower plates 32, 34 which serve as attachment locations for both the guide frame and optional mounting blocks (not shown) that facilitate the guide frame mounting. Another advantage of the disclosed stacked continuous guide frames is reduced manufacturing labor and reduced welding of small components. The illustrative guide frame 16 can be constructed using only tack welds at the abutments 31 between adjacent columnar elements 30. Some welding may also be applied at the interface of the stack and the upper and lower plates 32, 34, and at any mounting blocks used in the guide frame mounting. The optional fluid flow passages 90, 92 are suitably cut into the sides of the columnar elements 30 to reduce the likelihood of hydraulic pressure buildup in the central passage 70. It is also noted that such fluid flow passages 90, 92 may have the advantage of reducing the impact of the guide frame 16 on cross-flow of the primary coolant fluid. As already mentioned, the columnar element 30 may be suitably formed by casting, extrusion, or EDM. In the latter technique (Electrical Discharge Machining or EDM), the columnar element 30 is cut out of a solid block of material (e.g., a solid block of stainless steel) to represent the geometry. Optionally, a rougher casting is first formed and the EDM is then used to refine the rough casting toward the final shape of the columnar element 30. Some suitable EDM manufacturing techniques include wire-cut EDM. The constant cross-section central passage 70 and optional constant outer perimeter of the columnar element 30 is naturally conducive to formation by extrusion, which is another suitable approach for forming the columnar element 30. The use of extrusion to form the columnar element 30 is advantageous due to low cost, and because extrusion does not constrain the maximum height h of the columnar element 30. (By way of contrasting example, casting constrains the maximum height h to the maximum feasible casting mold size). This makes extrusion particularly well-suited for forming a columnar element of large height h, such as is typically needed in the case of a guide frame comprising a single columnar element. Using a single columnar element reduces the amount of labor and welding involved with manufacturing the guide frame, and eliminates the need to align a plurality of stacked columnar elements. While a continuous constant cross section is preferred, in one alternative embodiment the cross section geometry tapers slightly along a vertical axis of at least on columnar element such that a degree of hydraulic resistance may be utilized to enable additional control of the component velocity during SCRAM. In another alternative embodiment the cross section geometry may vary slightly between and amongst multiple columnar elements. 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 a continuation of U.S. patent application Ser. No. 14/289,545 filed May 28, 2014 which claims the benefit of U.S. Provisional Patent Application No. 61/828,017 filed May 28, 2013. U.S. patent application Ser. No. 14/289,545 is further a continuation-in-part of International Patent Application No. PCT/US13/42070 filed May 21, 2013, which claims of benefit of U.S. Provisional Patent Application No. 61/649,593 filed May 21, 2012. The entireties of the foregoing application are incorporated herein by reference. The present invention relates nuclear reactors, and more particularly to a passive cooling system for use in the event of a loss-of-coolant accident and a reactor shutdown. The containment for a nuclear reactor is defined as the enclosure that provides environmental isolation to the nuclear steam supply system (NSSS) of the plant in which nuclear fission is harnessed to produce pressurized steam. A commercial nuclear reactor is required to be enclosed in a pressure retaining structure which can withstand the temperature and pressure resulting from the most severe accident that can be postulated for the facility. The most severe energy release accidents that can be postulated for a reactor and its containment can generally be of two types. One thermal event of potential risk to the integrity of the containment is the scenario wherein all heat rejection paths from the plant's nuclear steam supply system (NSSS) are lost, forcing the reactor into a “scram.” A station black-out is such an event. The decay heat generated in the reactor must be removed to protect it from an uncontrolled pressure rise. Loss-of-Cooling Accident (LOCA) is another type of thermal event condition in which a breach in the pressure containment boundary of reactor coolant system (RCS) leads to a rapid release of flashing water into the containment space. The reactor coolant (primary coolant), suddenly depressurized, would violently flash resulting in a rapid rise of pressure and temperature in the containment space. The in-containment space is rendered into a mixture of air and steam. LOCA events are usually postulated to occur due to a failure in an RCS system pipe containing the primary coolant water. The immediate consequence of a LOCA is rapid depressurization of the RCS and spillage of large quantities of the primary coolant water until the pressure inside the RCS and in the containment reach equilibrium. Nuclear plants are designed to scram immediately in the wake of the RCS depressurization which suppresses the reactor's criticality and stops the chain reaction. However, the large enthalpy of the primary coolant water spilling from the RCS into the containment and the ongoing generation of decay heat in the core are sources of energy that would cause a spike in the containment pressure which, if sufficiently high, may threaten its pressure retention capacity. More recently, the containment structure has also been called upon by the regulators to withstand the impact from a crashing aircraft. Containment structures have typically been built as massive reinforced concrete domes to withstand the internal pressure from LOCA. Although its thick concrete wall could be capable of withstanding an aircraft impact, it is also unfortunately a good insulator of heat, requiring pumped heat rejection systems (employ heat exchangers and pumps) to reject its unwanted heat to the external environment (to minimize the pressure rise or to remove decay heat). Such heat rejection systems, however, rely on a robust power source (off-site or local diesel generator, for example) to power the pumps. The station black out at Fukushima in the wake of the tsunami is a sobering reminder of the folly of relying on pumps. The above weaknesses in the state-of-the-art call for an improved nuclear reactor containment system. What is needed is an efficient energy expulsion system to bring the internal pressure in the containment in the wake of a LOCA to normal condition in as short a time as possible. To ensure that such a system would render its intended function without fail, it is further desirable that it be gravity operated (i.e., the system does not rely on an available power source to drive any pumps or motors). A passive nuclear reactor cooling system for use in the event of a loss-of-coolant accident (LOCA) and complete reactor shutdown is provided that overcomes the foregoing drawbacks. The cooling system is configured to create a completely passive means to reject the reactor's decay heat without any reliance on and drawbacks of pumps and motors requiring an available electric power supply. In one embodiment, the cooling system relies entirely on gravity and varying fluid densities to extract and induce flow of cooling water through the system which includes a heat exchanger. The cooling system is engineered to passively extract decay heat from the reactor in the event of a LOCA station black out or another postulated accident scenario wherein the normal heat rejection path for the nuclear fuel core is lost such as via a ruptured pipe in the primary coolant piping or other event. In one configuration, the passive cooling system utilizes the reserve cooling water in the reactor well as a vehicle to extract and reject decay heat from the reactor via a heat exchanger attached to the reactor containment vessel walls. The cooling water flows via gravity in a closed flow loop between the reactor well and the heat exchanger to reject heat through the containment vessel walls to an external heat sink. In one embodiment, the heat sink may be an annular reservoir filled with cooling water that surrounds the containment vessel. In further embodiments, as further described herein, an in-containment auxiliary reservoir (e.g. storage tank) of cooling water may be provided which is fluidly coupled to the reactor well to provide a supplemental source or reserve of cooling water. The cooling system closed flow loop may circulate cooling water between both the reactor well and auxiliary reservoir heat exchanger and the heat exchanger. In one embodiment, a passive reactor cooling system usable after a loss-of-coolant accident includes a containment vessel in thermal communication with a heat sink, a reactor well disposed in the containment vessel, a reactor vessel disposed at least partially in the reactor well, the reactor vessel containing a nuclear fuel core which heats primary coolant in the reactor vessel, a water storage tank disposed in the containment vessel and in fluid communication with the reactor well, the tank containing an inventory of cooling water, and a heat exchanger disposed in the containment vessel, the heat exchanger in fluid communication with the reactor well via a closed flow loop. Following a loss of primary coolant, the tank is configured and operable to flood the reactor well with cooling water which is converted into steam by heat from the fuel core and flows through the closed flow loop to the heat exchanger. In one embodiment, the steam condenses in the heat exchanger forming condensate, and the condensate flows via gravity back to the reactor well. The heat exchanger comprises an array of heat dissipater ducts integrally attached to the containment vessel in one embodiment. In another embodiment, a passive reactor cooling system usable after a loss-of-coolant accident includes a containment vessel in thermal communication with a heat sink, a reactor well disposed in the containment vessel, a reactor vessel disposed at least partially in the reactor well, the reactor vessel containing a nuclear fuel core and primary coolant heated by the fuel core, a water storage tank disposed in the containment vessel and in fluid communication with the reactor well, the tank containing an inventory of cooling water, and a heat exchanger disposed in the containment vessel, the heat exchanger in fluid communication with the reactor well via an atmospheric pressure closed flow loop. Following a loss of primary coolant, the tank is configured and operable to flood the reactor well with cooling water. The cooling water in the flooded reactor well is heated by the fuel core and converted into steam, the steam flows through the closed flow loop to the heat exchanger and condenses forming condensate, and the condensate flows back to the reactor well. The heat exchanger comprises an array of heat dissipater ducts integrally attached to the containment vessel in one embodiment. A method for passively cooling a nuclear reactor after a loss-of-coolant accident is provided. The method includes: locating a reactor vessel containing a nuclear fuel core and primary coolant in a reactor well disposed inside a containment vessel; at least partially filling a water storage tank fluidly coupled to the reactor well with cooling water; releasing cooling water from the water storage tank into the reactor well; heating the cooling water with the fuel core; converting the cooling water at least partially into steam; accumulating the steam in the reactor well; flowing the steam through a heat exchanger; condensing the steam forming condensate in the heat exchanger; and returning the condensate to the reactor well, wherein the coolant steam and condensate circulates through a closed flow loop between the heat exchanger and reactor well. In one embodiment, the steam is produced within an insulating liner assembly disposed on an outside surface of the reactor vessel, the liner assembly being fluidly coupled to the reactor well via flow-hole nozzles disposed at the bottom and top portions of the reactor vessel. The liner assembly may comprise a plurality of spaced apart liners. The condensing step may further include the heat exchanger rejecting heat from the steam to an annular reservoir holding water that surrounds the containment vessel. The heat exchanger may comprises an array of heat dissipater ducts integrally attached to the containment vessel adjacent the annular reservoir. According to other aspects of the disclosure, the present invention further provides nuclear reactor containment system that overcomes the deficiencies of the foregoing arrangements for rejecting heat released into the environment within the containment by a thermal event. The containment system generally includes an inner containment vessel which may be formed of steel or another ductile material and an outer containment enclosure structure (CES) thereby forming a double walled containment system. In one embodiment, a water-filled annulus may be provided between the containment vessel and the containment enclosure structure providing an annular cooling reservoir. The containment vessel may include a plurality of longitudinal heat transfer fins which extend (substantially) radial outwards from the vessel in the manner of “fin”. The containment vessel thus serves not only as the primary structural containment for the reactor, but is configured and operable to function as a heat exchanger with the annular water reservoir acting as the heat sink. Accordingly, as further described herein, the containment vessel advantageously provides a passive (i.e. non-pumped) heat rejection system when needed during a thermal energy release accident such as a LOCA or reactor scram to dissipate heat and cool the reactor. In one embodiment according to the present disclosure, a nuclear reactor containment system includes a containment vessel configured for housing a nuclear reactor, a containment enclosure structure (CES) surrounding the containment vessel, and an annular reservoir formed between the containment vessel and containment enclosure structure (CES) for extracting heat energy from the containment space. In the event of a thermal energy release incident inside the containment vessel, heat generated by the containment vessel is transferred to the annular reservoir which operates to cool the containment vessel. In one embodiment, the annular reservoir contains water for cooling the containment vessel. A portion of the containment vessel may include substantially radial heat transfer fins disposed in the annular reservoir and extending between the containment vessel and containment enclosure structure (CES) to improve the dissipation of heat to the water-filled annular reservoir. When a thermal energy release incident occurs inside the containment vessel, a portion of the water in the annulus is evaporated and vented to atmosphere through the containment enclosure structure (CES) annular reservoir in the form of water vapor. Embodiments of the system may further include an auxiliary air cooling system including a plurality of vertical inlet air conduits spaced circumferentially around the containment vessel in the annular reservoir. The air conduits are in fluid communication with the annular reservoir and outside ambient air external to the containment enclosure structure (CES). When a thermal energy release incident occurs inside the containment vessel and water in the annular reservoir is substantially depleted by evaporation, the air cooling system becomes operable by providing a ventilation path from the reservoir space to the external ambient. The ventilation system can thus be viewed as a secondary system that can continue to cool the containment ad infinitum. According to another embodiment, a nuclear reactor containment system includes a containment vessel configured for housing a nuclear reactor, a containment enclosure structure (CES) surrounding the containment vessel, a water filled annulus formed between the containment vessel and containment enclosure structure (CES) for cooling the containment vessel, and a plurality of substantially radial fins protruding outwards from the containment vessel and located in the annulus. In the event of a thermal energy release incident inside the containment vessel, heat generated by the containment vessel is transferred to the water filled reservoir in the annulus through direct contact with the external surface of the containment vessel and its fins substantially radial thus cooling the containment vessel. In one embodiment, when a thermal energy release incident occurs inside the containment vessel and water in the annulus is substantially depleted by evaporation, the air cooling system is operable to draw outside ambient air into the annulus through the air conduits to cool the heat generated in the containment (which decreases exponentially with time) by natural convection. The existence of water in the annular region completely surrounding the containment vessel will maintain a consistent temperature distribution in the containment vessel to prevent warping of the containment vessel during the thermal energy release incident or accident. In another embodiment, a nuclear reactor containment system includes a containment vessel including a cylindrical shell configured for housing a nuclear reactor, a containment enclosure structure (CES) surrounding the containment vessel, an annular reservoir containing water formed between the shell of the containment vessel and containment enclosure structure (CES) for cooling the containment vessel, a plurality of external (substantially) radial fins protruding outwards from the containment vessel into the annulus, and an air cooling system including a plurality of vertical inlet air conduits spaced circumferentially around the containment vessel in the annular reservoir. The air conduits are in fluid communication with the annular reservoir and outside ambient air external to the containment enclosure structure (CES). In the event of a thermal energy release incident inside the containment vessel, heat generated by the containment vessel is transferred to the annular reservoir via the (substantially) radial containment wall along with its internal and external fins which operates to cool the containment vessel. Advantages and aspects of a nuclear reactor containment system according to the present disclosure include the following: Containment structures and systems configured so that a severe energy release event as described above can be contained passively (e.g. without relying on active components such as pumps, valves, heat exchangers and motors); Containment structures and systems that continue to work autonomously for an unlimited duration (e.g. no time limit for human intervention); Containment structures fortified with internal and external ribs (fins) configured to withstand a projectile impact such as a crashing aircraft without losing its primary function (i.e. pressure & radionuclide (if any) retention and heat rejection); and Containment vessel equipped with provisions that allow for the ready removal (or installation) of major equipment through the containment structure. All drawings are schematic and not necessarily to scale. References herein to a single drawing figure (e.g. FIG. 22) which has associated sub-parts (e.g. FIGS. 22A and 22B) shall be construed as a reference to the figure and sub-parts unless otherwise indicated. The features and benefits of the invention are illustrated and described herein by reference to illustrative embodiments. This description of illustrative embodiments is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description. Accordingly, the disclosure expressly should not be limited to such illustrative embodiments illustrating some possible non-limiting combination of features that may exist alone or in other combinations of features. In the description of embodiments disclosed herein, any reference to direction or orientation is merely intended for convenience of description and is not intended in any way to limit the scope of the present invention. Relative terms such as “lower,” “upper,” “horizontal,” “vertical,”, “above,” “below,” “up,” “down,” “top” and “bottom” as well as derivative thereof (e.g., “horizontally,” “downwardly,” “upwardly,” etc.) should be construed to refer to the nominal orientation as then described or as shown in the drawing under discussion. These relative terms are for convenience of description only and do not require that the apparatus be constructed or operated in a rigorously specific orientation denoted by the term. Terms such as “attached,” “affixed,” “connected,” “coupled,” “interconnected,” and similar refer to a relationship wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both movable or rigid attachments or relationships, unless expressly described otherwise. Referring to FIGS. 1-15, a nuclear reactor containment system 100 according to the present disclosure is shown. The system 100 generally includes an inner containment structure such as containment vessel 200 and an outer containment enclosure structure (CES) 300 collectively defining a containment vessel-enclosure assembly 200-300. The containment vessel 200 and containment enclosure structure (CES) 300 are vertically elongated and oriented, and define a vertical axis VA. In one embodiment, the containment vessel-enclosure assembly 200-300 is configured to be buried in the subgrade at least partially below grade (see also FIGS. 6-8). The containment vessel-enclosure assembly 200-300 may be supported by a concrete foundation 301 comprised of a bottom slab 302 and vertically extending sidewalls 303 rising from the slab forming a top base mat 304. The sidewalls 303 may circumferentially enclose containment vessel 200 as shown wherein a lower portion of the containment vessel may be positioned inside the sidewalls. In some embodiments, the sidewalls 303 may be poured after placement of the containment vessel 200 on the bottom slab 302 (which may be poured and set first) thereby completely embedding the lower portion of the containment vessel 200 within the foundation. The foundation walls 303 may terminate below grade in some embodiments as shown to provide additional protection for the containment vessel-enclosure assembly 200-300 from projectile impacts (e.g. crashing plane, etc.). The foundation 301 may have any suitable configuration in top plan view, including without limitation polygonal (e.g. rectangular, hexagon, circular, etc.). In one embodiment, the weight of the containment vessel 200 may be primarily supported by the bottom slab 302 on which the containment vessel rests and the containment enclosure structure (CES) 300 may be supported by the base mat 304 formed atop the sidewalls 303 of the foundation 301. Other suitable vessel and containment enclosure structure (CES) support arrangements may be used. With continuing reference to FIGS. 1-15, the containment structure vessel 200 may be an elongated vessel including a hollow cylindrical shell 204 with circular transverse cross-section defining an outer diameter D1, a top head 206, and a bottom head 208. In one embodiment, the containment vessel 200 (i.e. shell and heads) may be made from a suitably strong and ductile metallic plate and bar stock that is readily weldable (e.g. low carbon steel). In one embodiment, a low carbon steel shell 204 may have a thickness of at least 1 inch. Other suitable metallic materials including various alloys may be used. The top head 206 may be attached to the shell 204 via a flanged joint 210 comprised of a first annular flange 212 disposed on the lower end or bottom of the top head and a second mating annular flange 214 disposed on the upper end or top of the shell. The flanged joint 210 may be a bolted joint, which optionally may further be seal welded after assembly with a circumferentially extending annular seal weld being made between the adjoining flanges 212 and 214. The top head 206 of containment vessel 200 may be an ASME (American Society of Mechanical Engineers) dome-shaped flanged and dished head to add structural strength (i.e. internal pressure retention and external impact resistance); however, other possible configurations including a flat top head might be used. The bottom head 208 may similarly be a dome-shaped dished head or alternatively flat in other possible embodiments. In one containment vessel construction, the bottom head 208 may be directly welded to the lower portion or end of the shell 204 via an integral straight flange (SF) portion of the head matching the diameter of shell. In one embodiment, the bottom of the containment vessel 200 may include a ribbed support stand 208a or similar structure attached to the bottom head 208 to help stabilize and provide level support for the containment vessel on the slab 302 of the foundation 301, as further described herein. In some embodiments, the top portion 216 of the containment vessel shell 204 may be a diametrically enlarged segment of the shell that forms a housing to support and accommodate a polar crane (not shown) for moving equipment, fuel, etc. inside the containment vessel. This will provide crane access to the very inside periphery of the containment vessel and enable placement of equipment very close to the periphery of the containment vessel 200 making the containment vessel structure compact. In one configuration, therefore, the above grade portion of the containment vessel 200 may resemble a mushroom-shaped structure. In one possible embodiment, the enlarged top portion 216 of containment vessel 200 may have an outer diameter D2 that is larger than the outer diameter D1 of the rest of the adjoining lower portion 218 of the containment vessel shell 204. In one non-limiting example, the top portion 216 may have a diameter D2 that is approximately 10 feet larger than the diameter D1 of the lower portion 218 of the shell 204. The top portion 216 of shell 204 may have a suitable height H2 selected to accommodate the polar crane with allowance for working clearances which may be less than 50% of the total height H1 of the containment vessel 200. In one non-limiting example, approximately the top ten feet of the containment vessel 200 (H2) may be formed by the enlarged diameter top portion 216 in comparison to a total height H1 of 200 feet of the containment vessel. The top portion 216 of containment vessel 200 may terminate at the upper end with flange 214 at the flanged connection to the top head 206 of the containment vessel. In one embodiment, the diametrically enlarged top portion 216 of containment vessel 200 has a diameter D2 which is smaller than the inside diameter D3 of the containment enclosure structure (CES) 300 to provide a (substantially) radial gap or secondary annulus 330 (see, e.g. FIG. 4). This provides a cushion of space or buffer region between the containment enclosure structure (CES) 300 and containment vessel top portion 216 in the advent of a projectile impact on the containment enclosure structure (CES). Furthermore, the annulus 330 further significantly creates a flow path between primary annulus 313 (between the shells of the containment enclosure structure (CES) 300 and containment vessel 200) and the head space 318 between the containment enclosure structure (CES) dome 316 and top head 206 of the containment vessel 200 for steam and/or air to be vented from the containment enclosure structure (CES) as further described herein. Accordingly, the secondary annulus 330 is in fluid communication with the primary annulus 313 and the head space 318 which in turn is in fluid communication with vent 317 which penetrates the dome 316. In one embodiment, the secondary annulus 330 has a smaller (substantially) radial width than the primary annulus 313. Referring to FIGS. 1-4, the containment enclosure structure (CES) 300 may be double-walled structure in some embodiments having sidewalls 320 formed by two (substantially) radially spaced and interconnected concentric shells 310 (inner) and 311 (outer) with plain or reinforced concrete 312 installed in the annular space between them. The concentric shells 310, 311 may be made of any suitably strong material, such as for example without limitation ductile metallic plates that are readily weldable (e.g. low carbon steel). Other suitable metallic materials including various alloys may be used. In one embodiment, without limitation, the double-walled containment enclosure structure (CES) 300 may have a concrete 312 thickness of 6 feet or more which ensures adequate ability to withstand high energy projectile impacts such as that from an airliner. The containment enclosure structure (CES) 300 circumscribes the containment vessel shell 204 and is spaced (substantially) radially apart from shell 204, thereby creating primary annulus 313. Annulus 313 may be a water-filled in one embodiment to create a heat sink for receiving and dissipating heat from the containment vessel 200 in the case of a thermal energy release incident inside the containment vessel. This water-filled annular reservoir preferably extends circumferentially for a full 360 degrees in one embodiment around the perimeter of upper portions of the containment vessel shell 204 lying above the concrete foundation 301. FIG. 4 shows a cross-section of the water-filled annulus 313 without the external (substantially) radial fins 221 in this figure for clarity. In one embodiment, the annulus 313 is filled with water from the base mat 304 at the bottom end 314 to approximately the top end 315 of the concentric shells 310, 311 of the containment enclosure structure (CES) 300 to form an annular cooling water reservoir between the containment vessel shell 204 and inner shell 310 of the containment enclosure structure (CES). This annular reservoir may be coated or lined in some embodiments with a suitable corrosion resistant material such as aluminum, stainless steel, or a suitable preservative for corrosion protection. In one representative example, without limitation, the annulus 313 may be about 10 feet wide and about 100 feet high. In one embodiment, the containment enclosure structure (CES) 300 includes a steel dome 316 that is suitably thick and reinforced to harden it against crashing aircraft and other incident projectiles. The dome 316 may be removably fastened to the shells 310, 311 by a robust flanged joint 318. In one embodiment, the containment enclosure structure (CES) 300 is entirely surrounded on all exposed above grade portions by the containment enclosure structure (CES) 300, which preferably is sufficiently tall to provide protection for the containment vessel against aircraft hazard or comparable projectile to preserve the structural integrity of the water mass in the annulus 313 surrounding the containment vessel. In one embodiment, as shown, the containment enclosure structure (CES) 300 extends vertically below grade to a substantial portion of the distance to the top of the base mat 304. The containment enclosure structure (CES) 300 may further include at least one rain-protected vent 317 which is in fluid communication with the head space 318 beneath the dome 316 and water-filled annulus 313 to allow water vapor to flow, escape, and vent to atmosphere. In one embodiment, the vent 317 may be located at the center of the dome 316. In other embodiments, a plurality of vents may be provided spaced (substantially) radially around the dome 316. The vent 317 may be formed by a short section of piping in some embodiments which is covered by a rain hood of any suitable configuration that allows steam to escape from the containment enclosure structure (CES) but minimizes the ingress of water. In some possible embodiments, the head space 318 between the dome 316 and top head 206 of the containment vessel 200 may be filled with an energy absorbing material or structure to minimize the impact load on the containment enclosure structure (CES) dome 316 from a crashing (falling) projecting (e.g. airliner, etc.). In one example, a plurality of tightly-packed undulating or corrugated deformable aluminum plates may be disposed in part or all of the head space to form a crumple zone which will help absorb and dissipate the impact forces on the dome 316. Referring primarily to FIGS. 1-5 and 8-17, the buried portions of the containment vessel 200 within the concrete foundation 301 below the base mat 304 may have a plain shell 204 without external features. Portions of the containment vessel shell 204 above the base mat 304, however, may include a plurality of longitudinal external (substantially) radial ribs or fins 220 which extend axially (substantially) parallel to vertical axis VA of the containment vessel-enclosure assembly 200-300. The external longitudinal fins 220 are spaced circumferentially around the perimeter of the containment vessel shell 204 and extend (substantially) radially outwards from the containment vessel. The ribs 220 serve multiple advantageous functions including without limitation (1) to stiffen the containment vessel shell 204, (2) prevent excessive “sloshing” of water reserve in annulus 313 in the occurrence of a seismic event, and (3) significantly to act as heat transfer “fins” to dissipate heat absorbed by conduction through the shell 204 to the environment of the annulus 313 in the situation of a fluid/steam release event in the containment vessel. Accordingly, in one embodiment to maximize the heat transfer effectiveness, the longitudinal fins 220 extend vertically for substantially the entire height of the water-filled annulus 313 covering the effective heat transfer surfaces of the containment vessel 200 (i.e. portions not buried in concrete foundation) to transfer heat from the containment vessel 200 to the water reservoir, as further described herein. In one embodiment, the external longitudinal fins 220 have upper horizontal ends 220a which terminate at or proximate to the underside or bottom of the larger diameter top portion 216 of the containment vessel 200, and lower horizontal ends 220b which terminate at or proximate to the base mat 304 of the concrete foundation 301. In one embodiment, the external longitudinal fins 220 may have a height H3 which is equal to or greater than one half of a total height of the shell of the containment vessel. In one embodiment, the upper horizontal ends 220a of the longitudinal fins 220 are free ends not permanently attached (e.g. welded) to the containment vessel 200 or other structure. At least part of the lower horizontal ends 220b of the longitudinal fins 220 may abuttingly contact and rest on a horizontal circumferential rib 222 welded to the exterior surface of the containment vessel shell 204 to help support the weight of the longitudinal fins 220 and minimize stresses on the longitudinal rib-to-shell welds. Circumferential rib 222 is annular in shape and may extend a full 360 degrees completely around the circumferential of the containment vessel shell 204. In one embodiment, the circumferential rib 222 is located to rest on the base mat 304 of the concrete foundation 301 which transfers the loads of the longitudinal fins 220 to the foundation. The longitudinal fins 220 may have a lateral extent or width that projects outwards beyond the outer peripheral edge of the circumferential rib 222. Accordingly, in this embodiment, only the inner portions of the lower horizontal end 220b of each rib 220 contacts the circumferential rib 222. In other possible embodiments, the circumferential rib 222 may extend (substantially) radially outwards far enough so that substantially the entire lower horizontal end 220b of each longitudinal rib 220 rests on the circumferential rib 222. The lower horizontal ends 220b may be welded to the circumferential rib 222 in some embodiments to further strengthen and stiffen the longitudinal fins 220. The external longitudinal fins 220 may be made of steel (e.g. low carbon steel), or other suitable metallic materials including alloys which are each welded on one of the longitudinally-extending sides to the exterior of the containment vessel shell 204. The opposing longitudinally-extending side of each rib 220 lies proximate to, but is preferably not permanently affixed to the interior of the inner shell 310 of the containment enclosure structure (CES) 300 to maximize the heat transfer surface of the ribs acting as heat dissipation fins. In one embodiment, the external longitudinal fins 220 extend (substantially) radially outwards beyond the larger diameter top portion 216 of the containment vessel 200 as shown. In one representative example, without limitation, steel ribs 220 may have a thickness of about 1 inch. Other suitable thickness of ribs may be used as appropriate. Accordingly, in some embodiments, the ribs 220 have a radial width that is more than 10 times the thickness of the ribs. In one embodiment, the longitudinal fins 220 are oriented at an oblique angle A1 to containment vessel shell 204 as best shown in FIGS. 2-3 and 5. This orientation forms a crumple zone extending 360 degrees around the circumference of the containment vessel 200 to better resist projectile impacts functioning in cooperation with the outer containment enclosure structure (CES) 300. Accordingly, an impact causing inward deformation of the containment enclosure structure (CES) shells 210, 211 will bend the longitudinal fins 220 which in the process will distribute the impact forces preferably without direct transfer to and rupturing of the inner containment vessel shell 204 as might possibly occur with ribs oriented 90 degrees to the containment vessel shell 204. In other possible embodiments, depending on the construction of the containment enclosure structure (CES) 300 and other factors, a perpendicular arrangement of ribs 220 to the containment vessel shell 204 may be appropriate. In one embodiment, referring to FIGS. 6-8, portions of the containment vessel shell 204 having and protected by the external (substantially) radial fins 220 against projectile impacts may extend below grade to provide protection against projectile strikes at or slightly below grade on the containment enclosure structure (CES) 300. Accordingly, the base mat 304 formed at the top of the vertically extending sidewalls 303 of the foundation 301 where the fins 220 terminate at their lower ends may be positioned a number of feet below grade to improve impact resistance of the nuclear reactor containment system. In one embodiment, the containment vessel 200 may optionally include a plurality of circumferentially spaced apart internal (substantially) radial fins 221 attached to the interior surface of the shell 204 (shown as dashed in FIGS. 2 and 3). Internal fins 221 extend (substantially) radially inwards from containment vessel shell 204 and longitudinally in a vertical direction of a suitable height. In one embodiment, the internal (substantially) radial fins 221 may have a height substantially coextensive with the height of the water-filled annulus 313 and extend from the base mat 304 to approximately the top of the shell 204. In one embodiment, without limitation, the internal fins 221 may be oriented substantially perpendicular (i.e. 90 degrees) to the containment vessel shell 204. Other suitable angles and oblique orientations may be used. The internal fins function to both increase the available heat transfer surface area and structurally reinforce the containment vessel shell against external impact (e.g. projectiles) or internal pressure increase within the containment vessel 200 in the event of a containment pressurization event (e.g. LOCA or reactor scram). In one embodiment, without limitation, the internal fins 221 may be made of steel. Referring to FIGS. 1-15, a plurality of vertical structural support columns 331 may be attached to the exterior surface of the containment vessel shell 204 to help support the diametrically larger top portion 216 of containment vessel 200 which has peripheral sides that are cantilevered (substantially) radially outwards beyond the shell 204. The support columns 331 are spaced circumferentially apart around the perimeter of containment vessel shell 204. In one embodiment, the support columns 331 may be formed of steel hollow structural members, for example without limitation C-shaped members in cross-section (i.e. structural channels), which are welded to the exterior surface of containment vessel shell 204. The two parallel legs of the channels may be vertically welded to the containment vessel shell 204 along the height of each support column 331 using either continuous or intermittent welds such as stitch welds. The support columns 331 extend vertically downwards from and may be welded at their top ends to the bottom/underside of the larger diameter top portion 216 of containment vessel housing the polar crane. The bottom ends of the support columns 331 rest on or are welded to the circumferential rib 222 which engages the base mat 304 of the concrete foundation 301 near the buried portion of the containment. The columns 331 help transfer part of the dead load or weight from the crane and the top portion 216 of the containment vessel 300 down to the foundation. In one embodiment, the hollow space inside the support columns may be filled with concrete (with or without rebar) to help stiffen and further support the dead load or weight. In other possible embodiments, other structural steel shapes including filled or unfilled box beams, I-beams, tubular, angles, etc. may be used. The longitudinal fins 220 may extend farther outwards in a (substantially) radial direction than the support columns 331 which serve a structural role rather than a heat transfer role as the ribs 220. In certain embodiments, the ribs 220 have a (substantially) radial width that is at least twice the (substantially) radial width of support columns. FIGS. 11-15 show various cross sections (both longitudinal and transverse) of containment vessel 200 with equipment shown therein. In one embodiment, the containment vessel 200 may be part of a small modular reactor (SMR) system such as SMR-160 by Holtec International. The equipment may generally include a nuclear reactor vessel 500 disposed in a wet well 504 and defining an interior space housing a nuclear fuel core inside and circulating primary coolant, and a steam generator 502 fluidly coupled to the reactor and circulating a secondary coolant which may form part of a Rankine power generation cycle. Such a system is described for example in PCT International Patent Application No. PCT/US13/66777 filed Oct. 25, 2013, which is incorporated herein by reference in its entirety. Other appurtenances and equipment may be provided to create a complete steam generation system. Steam generator 502 is more fully described in International PCT Application No. PCT/US13/38289 filed Apr. 25, 2013, which is incorporated herein by reference in its entirety. As described therein and shown in FIGS. 11, 12, and 23 of the present application, the steam generator 502 may be vertically oriented and axially elongated similarly to submerged bundle heat exchanger 620. The steam generator 502 may be comprised of a set of tubular heat exchangers arranged in a vertical stack configured to extract the reactor's decay heat from the primary coolant by gravity-driven passive flow means. The circulation flow loops of primary coolant (liquid water) and secondary coolant (liquid feedwater and steam) through the reactor vessel and steam generator during normal operation of the reactor and power plant with an available electric supply produced by the station turbine-generator (T-G) set is shown in FIG. 23 herein. The primary coolant flow between the fluidly coupled steam generator 502 and reactor vessel 500 forms a first closed flow loop for purposes of the present discussion. In one embodiment, the primary coolant flow is gravity-driven relying on the change in temperature and corresponding density of the coolant as it is heated in the reactor vessel 500 by nuclear fuel core 501, and then cooled in the steam generator 502 as heat is transferred to the secondary coolant loop of the Rankine cycle which drives the turbine-generator set. The pressure head created by the changing different densities of the primary coolant (i.e. hot—lower density and cold—higher density) induces flow or circulation through the reactor vessel-steam generating vessel system as shown by the directional flow arrows. In general with respect to a pressurized closed flow loop, the primary coolant is heated by the nuclear fuel core 501 and flows upwards in riser column 224. The primary coolant from the reactor vessel 500 then flows through the primary coolant fluid coupling 273 between the reactor vessel 500 and steam generator 502 and enters the steam generator. The primary coolant flows upward in the centrally located riser pipe 337 to a pressurizer 380 at the top of the steam generator. The primary coolant reverses direction and flows down through the tube side of the steam generator 502 and returns to the reactor vessel 500 through the fluid coupling 273 where it enters an annular downcomer 222 to complete the primary coolant flow loop. The steam generator 502 may include three vertically stacked heat transfer sections—from bottom up a preheater section 351, steam generator section 352, and superheater section 350 (see, e.g. FIGS. 11, 12, and 23). Secondary coolant flows on the shellside of the steam generator 502 vessel. Secondary coolant in the form of liquid feedwater from the turbine-generator (T-G) set of the Rankine cycle enters the steam generator at the bottom in the preheater section 351 and flows upwards through the steam generator section 352 being converted to steam. The steam flows upwards into the superheater section 350 and reaches superheat conditions. From there, the superheated steam is extracted and flows to the T-G set to produce electric power. Auxiliary Heat Dissipation System Referring primarily now to FIGS. 2-3, 16, and 18, the containment vessel 200 may further include an auxiliary heat dissipation system 340 comprising a discrete set or array of heat dissipater ducts 341 (HDD). In one embodiment, the auxiliary heat dissipation system 340 and associated heat dissipater ducts 341 may form part of a passive reactor core cooling system described in further detail below and shown in FIGS. 22 and 23. Heat dissipater ducts 341 include a plurality of internal longitudinal ducts (i.e. flow conduits) circumferentially spaced around the circumference of containment vessel shell 204. Ducts 341 extend vertically parallel to the vertical axis VA and in one embodiment are attached to the interior surface of shell 204. The ducts 341 may be made of metal such as steel and are welded to interior of the shell 204. In one possible configuration, without limitation, the ducts 341 may be comprised of vertically oriented C-shaped structural channels (in cross section) or half-sections of pipe/tube positioned so that the parallel legs of the channels or pipe/tubes are each seam welded to the shell 204 for their entire height to define a sealed vertical flow conduit. The fluid (liquid or steam phase) in the heat dissipater ducts in this embodiment therefore directly contacts the reactor containment vessel 200 to maximize heat transfer through the vessel to the water in the annular reservoir (primary annulus 313) which forms a heat sink for the reactor containment vessel 200 and the heat dissipater ducts. Other suitably shaped and configured heat dissipater ducts 341 may be provided for this type construction so long as the fluid conveyed in the ducts contacts at least a portion of the interior containment vessel shell 204 to transfer heat to the water-filled annulus 313. In other possible but less preferred acceptable embodiments, the heat dissipater ducts 341 may be formed from completely tubular walled flow conduits (e.g. full circumferential tube or pipe sections rather than half sections) which are welded to the interior containment vessel shell 204. In these type constructions, the fluid conveyed in the ducts 341 will transfer heat indirectly to the reactor containment vessel shell 204 through the wall of the ducts first, and then to the water-filled annulus 313. Any suitable number and arrangement of ducts 341 may be provided depending on the heat transfer surface area required for cooling the fluid flowing through the ducts. The ducts 341 may be uniformly or non-uniformly spaced on the interior of the containment vessel shell 204, and in some embodiments grouped clusters of ducts may be circumferentially distributed around the containment vessel. The ducts 341 may have any suitable cross-sectional dimensions depending on the flow rate of fluid carried by the ducts and heat transfer considerations. The open upper and lower ends 341a, 341b of the ducts 341 are each fluidly connected to a common upper inlet ring header 343 and lower outlet ring header 344. The annular shaped ring headers 343, 344 are vertically spaced apart and positioned at suitable elevations on the interior of the containment vessel 200 to maximize the transfer of heat between fluid flowing vertically inside ducts 341 and the shell 204 of the containment vessel in the active heat transfer zone defined by portions of the containment vessel having the external longitudinal fins 220 in the primary annulus 313. To take advantage of the primary water-filled annulus 313 for heat transfer, upper and lower ring headers 343, 344 may each respectively be located on the interior of the containment vessel shell 204 adjacent and near to the top and bottom of the annulus. In one embodiment, the ring headers 343, 344 may each be formed of half-sections of arcuately curved steel pipe as shown which are welded directly to the interior surface of containment vessel shell 204 in the manner shown. In other embodiments, the ring headers 343, 344 may be formed of complete sections of arcuately curved piping supported by and attached to the interior of the shell 204 by any suitable means. In one embodiment, the heat dissipation system 340 is fluidly connected to a source of steam that may be generated from a water mass inside the containment vessel 200 to reject radioactive material decay heat from the reactor core. The containment surface enclosed by the ducts 341 serves as the heat transfer surface to transmit the latent heat of the steam inside the ducts to the shell 204 of the containment vessel 200 for cooling via the external longitudinal fins 220 and water filled annulus 313. In operation, steam enters the inlet ring header 343 and is distributed to the open inlet ends of the ducts 341 penetrating the header. The steam enters the ducts 341 and flows downwards therein along the height of the containment vessel shell 204 interior and undergoes a phase change from steam to liquid. The condensed steam drains down by gravity in the ducts and is collected by the lower ring header 344 from which it is returned back to the source of steam also preferably by gravity in one embodiment. It should be noted that no pumps are involved or required in the foregoing process. It will be appreciated that in certain embodiments, more than one set or array of heat dissipater ducts 341 may be provided and arranged on the inside surface of the inner containment vessel 200 within the containment space defined by the vessel. Auxiliary Air Cooling System According to another aspect of the present disclosure, a secondary or backup passive air cooling system 400 is provided to initiate air cooling by natural convection of the containment vessel 200 if, for some reason, the water inventory in the primary annulus 313 were to be depleted during a thermal reactor related event (e.g. LOCA or reactor scram). Referring to FIG. 8, the air cooling system 400 may be comprised of a plurality of vertical inlet air conduits 401 spaced circumferentially around the containment vessel 200 in the primary annulus 313. Each air conduit 401 includes an inlet 402 which penetrates the sidewalls 320 of the containment enclosure structure (CES) 300 and is open to the atmosphere outside to draw in ambient cooling air. Inlets 402 are preferably positioned near the upper end of the containment enclosure structure's sidewalls 320. The air conduits 401 extend vertically downwards inside the annulus 313 and terminate a short distance above the base mat 304 of the foundation (e.g. approximately 1 foot) to allow air to escape from the open bottom ends of the conduits. Using the air conduits 401, a natural convection cooling airflow pathway is established in cooperation with the annulus 313. In the event the cooling water inventory in the primary annulus 313 is depleted by evaporation during a thermal event, air cooling automatically initiates by natural convection as the air inside the annulus will continue to be heated by the containment vessel 200. The heated air rises in the primary annulus 313, passes through the secondary annulus 330, enters the head space 318, and exits the dome 316 of the containment enclosure structure (CES) 300 through the vent 317 (see directional flow arrows, FIG. 8). The rising heated air creates a reduction in air pressure towards the bottom of the primary annulus 313 sufficient to draw in outside ambient downwards through the air conduits 401 thereby creating a natural air circulation pattern which continues to cool the heated containment vessel 200. Advantageously, this passive air cooling system and circulation may continue for an indefinite period of time to cool the containment vessel 200. It should be noted that the primary annulus 313 acts as the ultimate heat sink for the heat generated inside the containment vessel 200. The water in this annular reservoir also acts to maintain the temperature of all crane vertical support columns 331 (described earlier) at essentially the same temperature thus ensuring the levelness of the crane rails (not shown) at all times which are mounted in the larger portion 216 of the containment vessel 200. Operation of the reactor containment system 100 as a heat exchanger will now be briefly described with initial reference to FIG. 19. This figure is a simplified diagrammatic representation of the reactor containment system 100 without all of the appurtenances and structures described herein for clarity in describing the active heat transfer and rejection processes performed by the system. In the event of a loss-of-coolant (LOCA) accident, the high energy fluid or liquid coolant (which may typically be water) spills into the containment environment formed by the containment vessel 200. The liquid flashes instantaneously into steam and the vapor mixes with the air inside the containment and migrates to the inside surface of the containment vessel 200 sidewalls or shell 204 (since the shell of the containment is cooler due the water in the annulus 313). The vapor then condenses on the vertical shell walls by losing its latent heat to the containment structure metal which in turn rejects the heat to the water in the annulus 313 through the longitudinal fins 220 and exposed portions of the shell 204 inside the annulus. The water in the annulus 313 heats up and eventually evaporates forming a vapor which rises in the annulus and leaves the containment enclosure structure (CES) 300 through the secondary annulus 330, head space 318, and finally the vent 317 to atmosphere. As the water reservoir in annulus 313 is located outside the containment vessel environment, in some embodiments the water inventory may be easily replenished using external means if available to compensate for the evaporative loss of water. However, if no replenishment water is provided or available, then the height of the water column in the annulus 313 will begin to drop. As the water level in the annulus 313 drops, the containment vessel 200 also starts to heat the air in the annulus above the water level, thereby rejecting a portion of the heat to the air which rises and is vented from the containment enclosure structure (CES) 300 through vent 317 with the water vapor. When the water level drops sufficiently such that the open bottom ends of the air conduits 401 (see, e.g. FIG. 8) become exposed above the water line, fresh outside ambient air will then be pulled in from the air conduits 401 as described above to initiate a natural convection air circulation pattern that continues cooling the containment vessel 200. In one embodiment, provisions (e.g. water inlet line) are provided through the containment enclosure structure (CES) 300 for water replenishment in the annulus 313 although this is not required to insure adequate heat dissipation. The mass of water inventory in this annular reservoir is sized such that the decay heat produced in the containment vessel 200 has declined sufficiently such that the containment is capable of rejecting all its heat through air cooling alone once the water inventory is depleted. The containment vessel 200 preferably has sufficient heat rejection capability to limit the pressure and temperature of the vapor mix inside the containment vessel (within its design limits) by rejecting the thermal energy rapidly. In the event of a station blackout, the reactor core is forced into a “scram” and the passive core cooling systems will reject the decay heat of the core in the form of steam directed to upper inlet ring header 343 of heat dissipation system 340 already described herein (see, e.g. FIGS. 16 and 18). The steam then flowing downwards through the network of internal longitudinal ducts 341 comes in contact with the containment vessel shell 204 interior surface enclosed within the heat dissipation ducts and condenses by rejecting its latent heat to the containment structure metal, which in turn rejects the heat to the water in the annulus via heat transfer assistance provide by the longitudinal fins 220. The water in the annular reservoir (primary annulus 313) heats up eventually evaporating. The containment vessel 200 rejects the heat to the annulus by sensible heating and then by a combination of evaporation and air cooling, and then further eventually by natural convection air cooling only as described herein. As mentioned above, the reactor containment system 100 is designed and configured so that air cooling alone is sufficient to reject the decay heat once the effective water inventory in annulus 313 is entirely depleted. In both these foregoing scenarios, the heat rejection can continue indefinitely until alternate means are available to bring the plant back online. Not only does the system operate indefinitely, but the operation is entirely passive without the use of any pumps or operator intervention. Passive Reactor Cooling System According to another aspect of the invention, a passive gravity-driven nuclear reactor cooling system 600 is provided to reject the reactor's decay heat following a loss-of-coolant accident (LOCA) during which time the reactor is shutdown (e.g. “scram”). The cooling system does not rely on and suffer the drawbacks of pumps and motors which require an available electric supply. Accordingly, the reactor cooling system 600 can advantageously operate during a power plant blackout situation. Referring to FIGS. 20 and 21, the passive reactor cooling system 600 in one embodiment is an atmospheric pressure closed loop flow system in one embodiment comprised of three major fluidly coupled parts or sub-systems, namely (i) a reactor well 620, (ii) a discrete set or array of heat dissipater ducts 341 (HDD) integrally connected to the inner wall of the containment structure (described in detail above), and (iii) an in-containment reactor water storage tank 630 filled with a reserve of cooling water. The reactor cooling system 600 is configured to utilize cooling water flooded into the reactor well 620 from the storage tank to extract the thermal energy generated by the fuel core during a reactor shutdown and LOCA that can continue indefinitely in the absence of an available source of electric power, as further described herein. Although FIGS. 20 and 21 shows the reactor well 620 in the flooded condition, it should be noted that the reactor well is dry and empty during the normal power generation operating mode of the reactor prior to a LOCA event. Referring to FIGS. 20-23, the reactor vessel 500 containing the nuclear core 501 is disposed in reactor well 620 defined by a large concrete monolith 621. The monolith 621 is formed inside the inner containment vessel 200 (best shown in FIG. 21). Reactor vessel 500 is generally formed by a vertically elongated cylindrical shell (sidewall) and a closed bottom head 505. Accordingly, the reactor vessel 500 is vertically oriented with a majority of the height or length of the reactor vessel being positioned inside the reactor well as shown. The reactor well 620 is an annular vacant space surrounding the reactor vessel 500 and may be dry and unfilled during normal power generation operation of the reactor. The bottom head 505 of the reactor vessel 500 is spaced above the bottom of the reactor well 620. The top of the reactor well 620 may be partially or completely closed by a closure structure. In one embodiment, the closure structure may be formed at least in part by a ring-shaped reactor support flange 632 that extends circumferentially around the perimeter of the reactor vessel 500. The annular support flange may be supported by the concrete monolith 621. Additional structural and other elements (e.g. metal, concrete, seals/gaskets, etc.) may be provided to supplement the support flange 632 and to seal the top of the reactor well 630 if it is to be completely sealed for better capturing steam present in the reactor well which is directed to the auxiliary heat dissipation system 340, as further described herein. The outer wall of the reactor well 620 may be insulated by one or more layers of stainless steel liners 700 with small interstitial space or air gap formed between them (see, e.g. FIGS. 22, 22A, 22B). For additional cooling of the reactor well space, cold water may be circulated in the inter-liner spaces in some embodiments. The stainless steel liners 700 serve to block extensive heating of the concrete monolith 621 forming the reactor well. Referring to FIGS. 20 and 22 (including sub-parts A and B), the outside surface of the reactor vessel 500 may also be insulated by a liner assembly comprised of one or more layers of metal liners 701 with small interstitial spaces or air gaps therebetween which serve to retard the outflow of heat generated by the reactor core 501 during normal reactor operation. In some non-limiting examples, the liners may preferably be stainless steel or aluminum; however, other suitable metals for a reactor well environment may be used. Preferably, in one embodiment, the liners 701 may extend completely around the circumference and the entire height of the reactor vessel 500 that is positioned within the reactor well 620 including under the bottom head 505 of the reactor vessel. The entire perimeter of the reactor vessel 500 lying within the reactor well may therefore include the liners 701 such that a plurality of liners is disposed between the outside surface of the reactor vessel 500 and outermost liner 510. The insulating liner assembly comprised of liners 701 may include an array of one or more flow-holes which may be formed by top flow-hole nozzles 702 disposed in the upper sidewall (shell) region of the reactor vessel 500 and reactor well 620, preferably below the first pipe penetration into the reactor vessel in one embodiment. The nozzles 702 are in fluid communication with the air gaps (interstitial spaces) in the insulating liner assembly and space formed within the reactor well 620. The top flow-hole nozzles 702 are therefore disposed on the outside surface of the reactor vessel sidewall, but are not in fluid communication with the interior of the reactor vessel 500 and primary coolant therein. Although in some embodiments the nozzles 702 may be attached to outside surface of the reactor vessel for support, the nozzles are instead configured to be in fluid communication with the air gaps formed in the side liner 701 assembly on the outside of the reactor vessel as noted above. In one embodiment, for example, this may be accomplished by providing a plurality of lateral holes in the nozzles 702 adjacent the air gaps between the liners 701. The top flow-hole nozzles 702 are configured and operable to evacuate steam flowing within the liner assembly and discharge the steam to the reactor well, as further described herein. The top flow-hole nozzles 702 may be circumferentially spaced around the reactor vessel. In one non-limiting embodiment, four top flow-hole nozzles 702 may be provided at approximately the same elevation. Other arrangements and numbers of top flow-hole nozzles 702 may be provided. One or more bottom flow-hole nozzles 703 may also be provided for the vessel liners 701 adjacent the bottom head 505 of the reactor vessel 500. In one embodiment, a single larger nozzle 703 may be provided which is concentrically aligned with the centerline CL of the reactor vessel 500 at the lowest point on the arcuate bottom reactor vessel head 505. The nozzle 703 may be supported, configured, and arranged to form fluid communication with the air gaps (interstitial spaces) between the bottom liners 701 and reactor well 620 in similar fashion as the top flow-hole nozzles 702. Nozzle 703 may therefore be constructed and operate similarly to top flow-hole nozzles 702 being supported by, but not in fluid communication with the interior of the reactor vessel 500 and primary coolant therein. The bottom flow-hole nozzle 703 is configured and operable to admit cooling water in the reactor well from the water storage tank 630 into the lower portion of the insulating liner assembly, as further described herein. The top flow-hole nozzles 702 may have provisions such as closure flaps 704 which are designed to remain closed during normal operation of the reactor when the gaps between the reactor vessel 500 and the liners 701 are filled with air (see, e.g. FIG. 22A). The flap and nozzle combination forms a flap valve. The flaps 704 are each pivotably movable and connected to its respective nozzle 702 at a top end by a pivot 705. Any suitable type of pivot may be provided, such as without limitation a pinned joint or self-hinge wherein the flap is made of a flexible material such as a high temperature withstanding polymer. The flaps 704 may be made of any suitable metallic or non-metallic material. The vertical orientation and weight of the flap 704 holds it in the closed position against the free end of nozzle 702 by gravity. In other embodiments, a commercially available flap valve comprising a valve body and flap may instead be mounted on the free end of the top flow-hole nozzles 702 to provide the same functionality. The bottom flow-hole nozzles 703 are also normally each closed by a flap 706 during normal operation of the reactor when the gaps between the reactor vessel 500 and the liners 701 are filled with air (see, e.g. FIG. 22B). In one embodiment, the flaps 706 may be held closed via a float device including a buoyant float 709 rigidly connected to one end of the flap by a linkage arm 708. The flap 706 and linkage arm 708 assembly is pivotably coupled to a bottom nozzle 703 by a pivot 707, such as without limitation a pinned joint in one embodiment. Flap 706 is preferably made of a rigid metallic or non-metallic material in order to maintain its shape and seal against the free end of nozzle 703 when in its closed position. In operation, gravity acts downward on the float 709 when the reactor well 620 is empty during normal operation of the reactor. This rotates the float 709 and the flap 706 assembly in a counter-clockwise direction to force the flap against the free end of nozzle 703. When water floods the reactor well 620 from storage tank 630 during a LOCA event as further described herein, the rising water will cause the float 709 to rotate upwards now in a clockwise direction. This simultaneously rotates the flap clockwise and downward opening the nozzle 703 admitting water into the air gaps between the reactor vessel 500 metal shell wall and the stainless steel liners 701. When the cooling water W from water storage tank 630 enters the air gaps between the liners 701 and comes in contact with the metal reactor vessel 500 wall after the passive reactor cooling system 600 is activated, the water vaporizes producing steam which raises the pressure in the gap. This buildup of pressure forces the flaps 704 of the top flow-hole nozzles 702 to open and relieve the steam build up into the reactor well 620 which is subsequently routed to the heat dissipation ducts 341 of the auxiliary heat dissipation system 340, as further described herein. Accordingly, the cooling water W therefore enters the liners 701 through the open flap(s) 706 of the bottom flow-hole nozzle(s) 703 and is evacuated from the liner assembly through the top flow-hole nozzles 702 in the form of steam. Referring now to FIGS. 20 and 21, the concrete monolith 621 further defines a large in-containment cooling water storage tank 630 (i.e. within the inner containment vessel 200 also variously shown in FIGS. 1-19). The water tank 630 holds a reserve of cooling water W and is fluidly coupled and positioned to dump its contents into the reactor well 620 in the event of a LOCA. In one embodiment, water storage tank 630 is fluidly coupled to the reactor well 620 by an upper and lower flow conduit 633 in which dump valves 631 are positioned to control flow. At least one flow conduct 633 with dump valve 634 may be provided; however, in some embodiments more than two flow conduits with dump valves may be provided. The dump valve may be operated in a fully opened or closed mode, or alternatively if needed throttled in a partially open mode. During normal power generation operation of the reactor, the dump valves are normally closed to prevent cooling water W from flooding into the reactor well 620 through the flow conduits. The dump valves 631 may be automatically operated via electric or pneumatic valve operators. In one embodiment, the dump valves 631 may be configured to operate as “fail open” when power supply is lost to the valves to automatically flood the reactor well 620 with cooling water W. In some preferred non-limiting embodiments, the cooling water tank 630 has a volumetric capacity at least as large as or larger than the capacity of the reactor well 620 to optimize cooling the reactor core and replenishing any cooling water W in the reactor well which might be lost as steam to the containment space in designs where the top of the reactor well is either not intentionally fully enclosed and/or tightly sealed or may be damaged. A method for operating the passive reactor cooling system 600 will now be described with primary reference to FIGS. 20-22. As mentioned earlier in this disclosure, in the case of a LOCA, the pressure and temperature in the containment will rise. When the containment pressure (or temperature) reaches a pre-set threshold value, then the dump valves 631 connecting the water storage tank 630 and reactor well 620 are opened causing a rapid transfer of cooling water W and filling of the reactor well. The insulating liners 701 on the reactor vessel 500 protect it from rapid quenching (and high thermal stresses). After the water in the reactor well 620 reaches near the top flow-hole nozzle 702 in the liner 701 assembly (until then the reactor vessel is undergoing limited cooling thru the heat transfer across the liners to the reactor well water), then the cold cooling water W begins to fill the interstitial spaces between the liners and the reactor vessel thus significantly accelerating the extraction of decay heat from the reactor core 501 and reactor vessel. After some time, the temperature of the pool of deposited water in the reactor well 620 reaches the boiling point temperature and begins to boil. The steam thus produced rises by buoyancy action through inlet piping 603 to the bank of heat dissipater ducts 341 of the auxiliary heat dissipation system 340, as described above and shown in FIGS. 16, 18, and 21. These ducts 341 condense the steam generated in the reactor well pool and return the condensate to the reactor well 620 via outlet piping 603 with the latent heat of steam delivered to the external annular reservoir 313 holding water having a temperature lower than the steam to form a heat sink in thermal communication with the containment vessel 200. Accordingly, the heat from the spilled reactor cooling system primary coolant water (e.g. via a primary coolant piping failure) is thus removed by the containment, albeit less efficiently, as the water/air mixture rises and contacts the internal surface of the containment (which is equipped with large external and internal fins 220, 221 shown in FIG. 3 and described above) to facilitate the heat extraction. It should be noted that the flow of steam and condensate between the heat dissipater ducts 341 and reactor well 620 is advantageously driven solely by gravity due to the changing densities of the steam and condensate, without need for pumps and an available power supply. The heat dissipater ducts 341 are therefore preferably positioned on the inner containment vessel 200 wall at higher location than the reactor well 630 and the extraction point of steam from the reactor well. Flow of steam and condensate through the inlet and outlet piping 603 to and from the array of heat dissipater ducts 341 may be controlled by suitable valves 625 (see FIG. 20), which may be operated in an on/off mode, or throttled. Valves 625 may be configured to operate as “fail open” when power supply is lost to the valves which may have electric or pneumatic valve operators. This automatically opens and actuates the closed flow loop of the reactor cooling system 600 between the heat dissipater ducts 341 and reactor well 620. The inlet steam piping 603 to the heat dissipater ducts 341 may be fluidly coupled to the top portion of reactor well 620 to optimally capture the accumulating steam. The outlet condensate return piping 603 may be fluidly coupled to the top portion of water storage tank 630 to optimally capture the accumulating steam. The atmospheric closed flow loop of the reactor cooling system 600 between the reactor well 620 and heat dissipater ducts 341 may therefore flow through the water storage tank 630 (see FIG. 21). In the event of a LOCA, as the water inventory in the annular reservoir 313 between the inner containment vessel 200 and outer containment enclosure structure 300 evaporates, it may be readily replenished. However, if replenishment is not possible, then the receding water inventory in the reservoir 313 will actuate rejection of heat to the air by ventilation action using the passive air cooling system 400 described above. Once all the water has evaporated in the reservoir 313, the containment structure will continue to reject heat by air cooling alone. Air cooling after a prolonged period of water cooling is ideally sufficient to remove all the decay heat. This also passive gravity driven heat expulsion process driven by changing air densities can continue as long as necessary to cool the reactor. It will be appreciated that numerous variations of the foregoing method for operating the passive reactor cooling system 600 are possible. While the foregoing description and drawings represent some example systems, it will be understood that various additions, modifications and substitutions may be made therein without departing from the spirit and scope and range of equivalents of the accompanying claims. In particular, it will be clear to those skilled in the art that the present invention may be embodied in other forms, structures, arrangements, proportions, sizes, and with other elements, materials, and components, without departing from the spirit or essential characteristics thereof. In addition, numerous variations in the methods/processes described herein may be made. One skilled in the art will further appreciate that the invention may be used with many modifications of structure, arrangement, proportions, sizes, materials, and components and otherwise, used in the practice of the invention, which are particularly adapted to specific environments and operative requirements without departing from the principles of the present invention. The presently disclosed embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being defined by the appended claims and equivalents thereof, and not limited to the foregoing description or embodiments. Rather, the appended claims should be construed broadly, to include other variants and embodiments of the invention, which may be made by those skilled in the art without departing from the scope and range of equivalents of the invention.
040597695	description	For a better understanding of the present invention, the following are specific Examples illustrating the method of preparing the radiation source according to the invention. EXAMPLE 1 A weighed portion of 165 mg of ground Te.sup.124 was placed into a 100 ml beaker and mixed with 3 ml of a 5N solution of KOH. The mixture was heated to a temperature of 60 to 70.degree. C and a 30% solution of H.sub.2 O.sub.2 was added thereto under stirring. Therewith, an intensive oxidation of the tellurium occurred with the formation of K.sub.2 H.sub.4 TeO.sub.6 which is completed after 10-15 minutes; the excess of hydrogen peroxide is then decomposed by heating at reflux. The potassium tellurate solution was diluted with distilled water to 50 ml and gradually mixed with a solution of 1.63 g of magnesium sulphate (MgSO.sub.4.7 H.sub.2 O) in 30 ml of water. In doing so, a mixture of magnesium tellurate with magnesium hydroxide precipitated. To minimize the adsorption of impurities and enlargening of the precipitate particles, the mixture was boiled, right after precipitation, for 10-15 minutes and the residue, without allowing the mixture to be cooled, was separated on a dense paper filter under suction. The residue was washed with several portions of hot water till no SO.sub.4.sup.= ions were detected. Then, the residue was washed with 10 ml of absolute ethanol and 40-50 ml of diethyl ether, whereafter air was purged therethrough for 5-10 minutes. The residue was dried at a temperature of from 120.degree. to 140.degree. C, placed into a corundum crucible and calcined for 2 hours at a temperature within the range of from 900.degree. to 1,000.degree. C. The calcined residue of 5MgO.Te.sup.124 O.sub.3 was ground, sealed into a quartz ampule and irradiated for 360 hours in a reactor with a flux of 3 to 10.sup.13 thermal neutrons/cm.sup. 2 sec. The resulting 5MgO.Te.sup.125m O.sub.3 was annealed at a temperature within the range of from 900 to 1,000.degree. C for 6 hours, whereafter it was gradually cooled to room temperature. As a result, a radiation source was obtained with an activity of 100 mC and with a natural width of the emission line. EXAMPLE 2 A weighed portion of 500 mg of ground Te.sup.124 was taken for the experiment. Further operations were performed in accordance with the procedure of Example 1, excluding the manufacture of the source 5MgO.Te.sup.125m O.sub.3 per se. To this end, a weighed portion of 100 mg of 5MgO.Te.sup.124 O.sub.3 was placed into a quartz ampule. Irradiation was effected in the reactor with a flux of thermal neutrons of 8.multidot.10.sup.4 thermal neutrons/cm.sup. 2 sec for 500 hours. Annealing of the resulting 5MgO.Te.sup.125m O.sub.3 was conducted at a temperature of 800.degree. C for 7 hours. Further operations were similar to those of Example 1. Two sources were prepared from the thus-prepared active compound: the former with an activity of 1C for experiments of nuclear coherent dissipation on tellurium single cyrstals and the latter with an activity of 200 mC for experiments on resonance absorption. EXAMPLE 3 The experiments in this Example performed in accordance with the procedure of Example 1, with the only difference that annealing of 5MgO.Te.sup.125m O.sub.3 was conducted at a temperature of 600.degree. C for 10 hours. As a result, a radiation source was obtained with activity of 100 mC and with a width of the emission line slightly more than the natural one: 2 .GAMMA. = 6 mm/sec.
	description	The present invention relates to a terahertz wave generation device that generates terahertz waves in a direction satisfying non-collinear phase matching conditions by irradiating ultra-short pulse laser light inside a non-linear optical crystal, and a terahertz wave generating method. As conventional terahertz wave generating methods, Non-Patent Literature 1 discloses three methods, namely an antenna method, a non-linear effect method and a magnetic field application method. In the antenna element method, a voltage bias is applied on a photoconductive antenna that is a microstructure formed on a semiconductor substrate, and in that state ultra-short pulse laser light irradiates the photoconductive antenna, thereby generating terahertz waves. In the non-linear effect method, terahertz waves are generated by irradiating ultra-short pulse laser light on a material having a non-linear receptivity χ (2) on the basis of a light rectification effect. In the magnetic field application method, a magnetic field is applied in parallel on a semiconductor surface, and in that state ultra-short pulse laser light irradiates the semiconductor surface, thereby generating terahertz waves. Non-Patent Literature 2 discloses a method for tilting the wavefront of the laser light irradiating a non-linear optical crystal with respect to the surface of the non-linear optical crystal as a method of generating Cherenkov radiation in the non-linear optical crystal so as to obtain high-strength terahertz waves. With this method, the wavefront of the laser light is tilted by using a diffraction image transmission system composed of a diffraction grating and lens. In addition, as one terahertz wave generating method, there is a method of projecting a pump wave onto a nonlinear optical crystal capable of being used in parametric oscillation. FIG. 10 shows the terahertz wave generating principle under this method. With this method, when pulse laser light L is incident on a non-linear optical crystal 100 from a direction orthogonal to the optical axis Z of this non-linear optical crystal 100, a parametric interaction is occurred inside the non-linear optical crystal 100 and a terahertz wave T is generated in a direction A satisfying the non-collinear phase matching conditions. As this terahertz wave generating method, Patent Literature 1 discloses a method using two laser generators. Of these two, one laser generator is a YAG laser that outputs pulse laser light, and the pulse laser light here is set to a pulse width of 15 ns and a wavelength of 1064 nm. The other laser generator is a Yb fiber laser that outputs continuous laser light. The continuous laser light here is used as a terahertz wave injection seeder, and the wavelength is fixed at 1070.2 nm in order to improve terahertz wave strength. Patent Literature 1: Unexamined Japanese Patent Application KOKAI Publication No. 2002-72269. Non-Patent Literature 1: “Journal of the Spectroscopical Society of Japan”, The Spectroscopical Society of Japan, 2001, Vol. 50, No. 6. Non-Patent Literature 2: U.S. “Applied Physics Letters”, American Institute of Physics, 2007, Vol. 90, pp. 17121-1 to 17121-3. With the three terahertz wave generating methods described in Non-Patent Literature 1, the terahertz waves generated are weak, and for example, even in the case of the magnetic field application method, with which the highest strength can be obtained, the strength of the terahertz waves generated is around 8 J/pulse. Consequently, it is difficult to apply these terahertz wave generating methods to fields excluding prescribed spectroscopical measurements. In addition, with the method described in Non-Patent Literature 2, it is necessary to create a diffraction grating with a complex structure in the terahertz wave generation device. Moreover, it is necessary to form a diffraction image near the focal point of the lens, making adjustment of the transmission system difficult. In addition, with the method disclosed in Patent Literature 1, two laser generators are necessary as described above, and in order to stabilize the wavelength of the continuous laser light, it is necessary for the Yb fiber laser to be a mode-hop-free laser. With this method, only a terahertz wave having a time width on the order of nanoseconds can be generated. In addition, the manufacturing cost of the device becomes quite high. In consideration of the foregoing, it is an object of the present invention to provide a terahertz wave generation device which has a simple structure and which can generate high-strength terahertz waves, and a method of generating terahertz waves. In order to achieve the above object, the terahertz wave generation device according to a first aspect of the present invention is a terahertz wave generation device for generating terahertz waves in a direction satisfying non-collinear phase matching conditions by projecting ultra-short pulse laser light on a non-linear optical crystal, having a pulse light source for generating the ultra-short pulse laser light and an irradiation unit for discretely irradiating the ultra-short pulse laser light generated by the pulse light source on terahertz wave transmission line in the non-linear optical crystal so that the ultra-short pulse laser light is in synchronous with transmission of the terahertz wave. Preferably, the irradiation unit is provided with a plurality of optical fibers for receiving and transmitting the ultra-short pulse laser light generated by the pulse light source and projecting such toward the terahertz wave transmission line of the non-linear optical crystal so that the ultra-short pulse laser light is in synchronous with transmission of the terahertz wave, and the optical fibers have mutually differing optical path lengths. Preferably, the irradiation unit is provided with a light distributor for splitting the ultra-short pulse laser light generated by the pulse light source into a plurality of ultra-short pulse laser lights and transmitting such to the plurality of optical fibers. Preferably, the irradiation unit is provided with a length adjustment mechanism for adjusting the optical path lengths of the optical fibers, and this length adjustment mechanism is provided with drums around which the optical fibers are wound, and a tension changing unit for changing the tension of the optical fibers in a lengthwise direction by changing the diameter of the drums. Preferably, the pulse light source is provided for each optical fiber. Preferably, the irradiation unit is provided with a multi-core fiber having a plurality of cores as the transmission paths for receiving and transmitting the ultra-short pulse laser light generated by the pulse light source and projecting such toward the terahertz wave transmission line of the non-linear optical crystal so a that the ultra-short pulse laser light is in synchronous with transmission of the terahertz wave, and the plurality of cores have mutually differing optical path lengths. Preferably, the projection units of the plurality of cores are positioned parallel to the direction of the terahertz wave transmission line, and the end surface composed of the projection units of the plurality of cores is shaped so as to have a predetermined angle, and the optical path lengths of the cores are longer toward one side in a direction parallel to the projection units. Preferably, the pulse light source is provided for each of the cores. Preferably, each pulse light source is provided with a timing adjustment mechanism for adjusting the generation timing of the ultra-short pulse laser light. Preferably, at the projection unit of each of the transmission paths, a lens is provided for making desired values of the incident angle on the non-linear optical crystal and the spacing of arrival positions on the terahertz wave transmission line in the non-linear optical crystal of the ultra-short pulse laser light projected from the projection units. In order to achieve the above object, the terahertz wave generating method according to a second aspect of the present invention is a method for generating terahertz waves in a direction satisfying non-collinear phase matching conditions by making ultra-short pulse laser light incident on a non-linear optical crystal, and includes irradiating a pulse laser light group having a discrete wave surface composed of a plurality of ultra-short pulse laser lights of a single repeating frequency toward the non-linear optical crystal, and transmitting the ultra-short pulse laser lights of the pulse laser light group to successively shifted positions on the terahertz wave transmission line so that such arrive with a time difference. Preferably, the pulse laser light group is composed by the ultra-short pulse laser lights being transmitted via transmission paths and being projected from the projection units of the transmission paths toward the non-linear optical crystal; the shift in arrival positions of the ultra-short pulse laser lights on the transmission line is created by the projection units being parallel in one direction; and the difference in arrival times of the ultra-short pulse laser lights on the transmission line is created by the optical path lengths of the transmission paths being longer toward one side of the parallel direction of the projection units. With the terahertz wave generation device and generating method of the present invention, it is possible to generate high-strength terahertz waves with a simple structure and process. The preferred embodiments of the present invention are described in detail below with reference to the drawings. Identical or corresponding parts in the drawings are labeled with the same symbols, and explanation of such is not repeated. (First Embodiment) FIG. 1 shows the structure of a terahertz wave generation device according to a first embodiment. The terahertz wave generation device 1 according to the first embodiment has an ultra-short pulse laser light source 3, a distributor 5 and a fiber bundle 7. The ultra-short pulse laser light source 3 generates ultra-short pulse laser light having a single repeating frequency. The distributor 5 is connected to the ultra-short pulse laser light source 3 via one optical fiber 9. This distributor 5 splits the ultra-short pulse laser light projected from the ultra-short pulse laser light source 3 and also collimates this split ultra-short pulse laser light to less than the diameter of the transmission paths of the below-described optical fibers F1 to F5. The fiber bundle 7 is a bundle of the optical fibers F1 to F5, each of which is connected to the distributor 5. The ultra-short pulse laser lights split and collimated by the distributor 5 are simultaneously incident on the optical fibers F1 to F5. Furthermore, after transmitting the ultra-short pulse laser light, the optical fibers F1 to F5 project this ultra-short pulse laser light L from projection units 13 to an LN crystal 15 as a non-linear optical crystal (hereinafter simply called the LN crystal). The terahertz wave generation device 1 in this embodiment generates a terahertz wave T using the principle shown in FIG. 10, so the direction of the projection unit 13 of each optical fiber F1 to F5 is adjusted so that the ultra-short pulse laser light L is incident on the LN crystal 15 from a direction orthogonal to the optical axis of the LN crystal 15. Below, the optical fibers F1 to F5 are shown generally as optical fiber F. In addition, in the explanation of this embodiment, the number of optical fibers is taken to be 5, namely F1 to F5, but the number may be more than this. The straight line shown in FIG. 1 shows the transmission line along which the terahertz wave T generated in the LN crystal 15 by irradiation by the ultra-short pulse laser light L advances in a direction satisfying the non-collinear phase matching condition. The projection unit 13 of each optical fiber F is arranged so that the ultra-short pulse laser light L projected from these projection units 13 sequentially irradiate the terahertz wave transmission line A. The optical path length of each optical fiber F becomes longer in a direction parallel to the projection units 13, that is to say to one side in the direction of the terahertz wave transmission line A. Specifically, these becoming longer in the order F1, F2, F3, F4 and F5. In addition, condenser lenses 17 are provided at the projection units 13 of the optical fiber F. By adjusting the curved surface and position of these lenses 17, the ultra-short pulse laser light L projected from the projection units 13 is condensed so as to be orthogonally incident on the surface of the LN crystal 15, and the condensing point of the ultra-short pulse laser light L is positioned with a predetermined spacing on the terahertz wave transmission line A. With the terahertz wave generation device 1 having the above structure, each time the ultra-short pulse laser light source 3 projects ultra-short pulse laser light, the ultra-short pulse laser light is split and collimated by the distributor 5 and is simultaneously incident on the optical fiber F. Furthermore, after this split and collimated ultra-short pulse laser light L has been transmitted to the transmission paths of the optical fibers F, the light is projected from the projection unit 13 toward the LN crystal 15. As a result, a pulse laser light group C composed of the plurality of ultra-short pulse laser lights L and having a discrete wave surface advances toward the LN crystal 15. When the various ultra-short pulse laser lights L that compose the pulse laser light group C here pass through the transmission paths of the optical fibers F, a time delay can be bestowed. This time delay is generated from optical fiber F materials with high refractive index, the value thereof being determined in accordance with the optical path lengths of the transmission paths of the optical fibers F. In this embodiment, because the optical path lengths of the transmission paths of the optical fibers F1 to F5 become longer toward one side in the parallel direction of the projection units 13 (that is to say, in the direction of the terahertz wave transmission line A), the time delay is larger for ultra-short pulse laser light L projected from the optical fibers F close to one side in the parallel direction of the projection units 13 (that is to say, in the direction of the terahertz wave transmission line A). Consequently, when the ultra-short pulse laser light is simultaneously incident on the optical fibers F1 to F5 from the distributor 5, the wave front of the pulse laser light group C becomes tilted so as to be delayed toward one side in the parallel direction of the projection units 13 (that is to say, in the direction of the terahertz transmission line A). FIG. 2 shows an enlargement of the ultra-short pulse laser light group C incident on the LN crystal 15. Reference numbers L1 to L3 shown in FIG. 2 are the ultra-short pulse laser lights L contained in a single pulse laser light group C. L1 passes through the optical fiber F1 having the shortest transmission path, so the time delay is shortest. L2 passes through the optical fiber F2 having the second-shortest transmission path, so the time delay is second shortest. L3 passes through the optical fiber F3 with the third-shortest transmission path, so the time delay is third shortest. Out of the plurality of ultra-short pulse laser lights L that comprise the pulse laser light group C, the ultra-short pulse laser light L1 having the shortest time delay arrives first at the LN crystal 15. As a result, a terahertz wave T is generated in the LN crystal 15 through parametric fluorescence, and a portion of this terahertz wave T propagates in the direction of the transmission line A. Furthermore, when the terahertz wave T has advanced a predetermined distance dl in the direction of the transmission line A, the ultra-short pulse laser light L2 having the second shortest time delay arrives at the post-advancement position, and parametric amplification is created through parametric interaction. As a result, the strength of the terahertz wave T is amplified. Furthermore, when the terahertz wave T has advanced a predetermined distance d2 in the direction of the transmission line A, the ultra-short pulse laser light L3 having the third shortest time delay arrives at the post-advancement position and the strength of the terahertz wave T is again amplified. This process of amplifying strength is repeated until the ultra-short pulse laser light L having the longest time delay arrives at the LN crystal 15. As a result, the terahertz wave T becomes very strong. During the course of the terahertz wave T propagating inside the LN crystal 15, absorption of the terahertz wave T by the LN crystal occurs. For this reason, in the present embodiment, the pulse amplitude of the laser light generated by the ultra-short pulse laser light source 3 and the spacing of the ultra-short pulse laser lights L in the pulse laser light group C are adjusted so that the gain in strength of the terahertz wave T is larger than the absorption amount. With the present embodiment, as the pulse laser light group C composed of a plurality of ultra-short pulse laser lights L advances toward the LN crystal 15, the ultra-short pulse laser lights L in the pulse laser light group C arrive at positions successively shifted on the transmission line A of the terahertz wave A with time differences, so it is possible to successively irradiate each ultra-short pulse laser light L on the terahertz wave T created in the LN crystal 15. Through this, a very strong terahertz wave is generated. Furthermore, in addition to providing a plurality of optical fibers F in the terahertz wave generation device 1, the structure of the device obtained through adjusting the optical path length of the transmission path and the position of the projection units 13 of the various optical fibers F is simple. In addition, by adjusting the position of the projection units 13 and the optical path lengths of the transmission paths in the various optical fibers F, the position and timing of arrival of the ultra-short pulse laser lights L in the pulse laser light group C on the terahertz wave transmission line A can be adjusted. Through this, the shape of the LN crystal 15 and the relative positions of the LN crystal 15 and the terahertz wave generation device 1 can be arbitrarily set. In addition, by adjusting the position and curved surface of the lens 17, it is possible to condense the ultra-short pulse laser lights L projected from the various optical fibers F to the desired positions. Through this, it is possible to make the amplification of the terahertz wave through the ultra-short pulse laser lights L projected from the various optical fibers F certain. Through this, a very strong terahertz wave is generated with certainty. With this embodiment, the lens 17 may be omitted. In this case, the strength of the terahertz wave can be amplified by tilting the wave front of the pulse laser light group C (that is to say, giving sequential time delays to the various ultra-short pulse laser lights L of the pulse laser light group C) so that the beam-like ultra-short pulse laser lights L irradiate the terahertz wave in succession. (Second Embodiment) FIG. 3 is a block diagram showing the structure of a terahertz wave generation device 20 according to a second embodiment. This terahertz wave generation device 20 is provided with an ultra-short pulse fiber laser light source 21 and a distributor 23 instead of the ultra-short pulse laser light source 3 and the distributor 5 in the first embodiment. Differences from the first embodiment are explained below. The ultra-short pulse fiber laser light source 21 generates ultra-short pulse laser light of a single repeating frequency, and collimates the generated ultra-short pulse laser light to less than the diameter of the transmission path of the optical fibers F. The distributor 23 is connected to the ultra-short pulse fiber laser light source 21 via a single optical fiber 10. This distributor 21 splits the ultra-short pulse laser light projected from the ultra-short pulse fiber laser light source 21 into a plurality of ultra-short pulse laser lights, and projects the split ultra-short pulse laser lights simultaneously toward the various optical fibers F. In this embodiment, as in the first embodiment, the positions of the projection units 13 and the optical path lengths of the various optical fibers F, along with the curved surface and the position of the lens 17, can be adjusted, and consequently the same effect as in the first embodiment can be exhibited. (Third Embodiment) FIG. 4 is a block diagram showing the structure of a terahertz wave generation device 30 according to a third embodiment. This terahertz wave generation device 30 is the terahertz wave generation device 1 according to the first embodiment to which has been added a length adjustment mechanism 31 for adjusting the optical path lengths of the transmission paths of the optical fibers F. Differences from the first embodiment are explained below. The length adjustment mechanism 31 is provided with drums (unrepresented) around which the various optical fibers F1 to F5 are wound, and a piezoelectric unit (unrepresented) for changing the diameter of each drum. By changing the diameters of the drums, it is possible to change the tension in the lengthwise direction applied to the optical fibers F1 to F5. With this embodiment, by changing the tension in the lengthwise direction applied to the optical fibers F1 to F5 by operating the length adjustment mechanism 31, the lengths of the optical fibers F1 to F5 change, so it is possible to adjust the optical path lengths of the transmission paths in the optical fibers F1 to F5 to the desired lengths. Through this, it is possible to set the time delay given to the ultra-short pulse laser lights L projected from the optical fibers F1 to F5 within a wider range. Through this, the ultra-short pulse laser lights L projected from the optical fibers F1 to F5 can irradiate the terahertz wave on the terahertz wave transmission line A with certainty. More preferably, the piezoelectric unit is connected to a computer (unrepresented) and the drum diameters are changed based on signals from the computer. In this case, the computer can be electrically connected to a sensor (unrepresented) that measures the strength of the terahertz wave, and computes the amount of change in the diameters of the drums on the basis of the measured values from the sensor. Furthermore, the computer transmits signals that cause changes by the computed amounts to occur in the drums to the piezoelectric device. Through this, the optical path lengths of the transmission paths in the optical fibers F1 to F5 can be adjusted based on the current generation strength of the terahertz wave T, so it is possible to adjust the generation strength of the terahertz wave T to the desired value. (Fourth Embodiment) FIG. 5 is a block diagram showing the structure of a terahertz wave generation device 40 according to a fourth embodiment. This terahertz wave generation device 40 is the terahertz wave generation device 1 according to the first embodiment, further provided with a plurality of ultra-short pulse laser light sources 3. The ultra-short pulse laser lights L that comprise the pulse laser light group C are each generated by a different ultra-short pulse laser light source 3. Differences from the first embodiment are explained below. In the fourth embodiment, the distributor shown in FIG. 1 is omitted and the ultra-short pulse laser light sources 3 are provided for each optical fiber F of the fiber bundle 7. After the ultra-short pulse laser light generated by the corresponding ultra-short pulse laser light source 3 has been transmitted, each optical fiber F projects this ultra-short pulse laser light L toward the LN crystal 15. In addition, a timing adjustment mechanism 41 for adjusting the timing of generating the laser light is connected to each of the ultra-short pulse laser light sources 3. By operating this timing adjustment mechanism, each ultra-short pulse laser light source 3 projects ultra-short pulse laser light simultaneously to the corresponding optical fiber F. With the present embodiment, it is possible for the ultra-short pulse laser light to be simultaneously incident on each of the optical fibers F without providing the distributor 5. As in the present embodiment, when a plurality of ultra-short pulse laser light sources 3 are provided, the optical path lengths in the transmission paths of the optical fibers F may be set to a constant value. In this case, it is possible to provide the desired tilt to the wavefront of the pulse laser light group C by successively shifting the generation timing of the laser lights from the ultra-short pulse laser light sources 3 with an appropriate span. Each timing adjustment mechanism 41 can be controlled by a personal computer, so it is possible to adjust the light pulse projection unit timing from the corresponding ultra-short pulse laser light source 3 to the desired time. (Fifth Embodiment) FIG. 6 is a block diagram showing the structure of a terahertz wave generation device 50 according to a fifth embodiment. This terahertz wave generation device 50 is the terahertz wave generation device 1 according to the first embodiment to which a below-described high-output amp 51 has been added. Differences from the first embodiment are explained below. In the fifth embodiment, the high-output amp 51 is provided in order to increase the output of the ultra-short pulse laser light passing through the transmission path of each optical fiber F. With this embodiment, ultra-short pulse laser light L whose strength has been increased by the high-output amp 51 is projected from each optical fiber F toward the LN crystal 15. Consequently, when the ultra-short pulse laser light L projected from each optical fiber F irradiates the terahertz wave, the size of the strength amplitude of the terahertz wave becomes larger, so that a strong terahertz wave is generated. A variation on this embodiment is shown in FIG. 7. A terahertz wave generation device 53 according to this variation has the length adjustment mechanism 31 explained in the third embodiment provided on the optical fibers F1 to F5 so as to be positioned preceding the high-output amp 51. With this variation, it is possible to endow the ultra-short pulse laser light L whose strength has been increased by the high-output amp 51 with the desired time delay by causing the length adjustment mechanism 31 to adjust the optical path length of the optical fibers F1 to F5. Through this, it is possible for the high-strength ultra-short pulse laser light L to irradiate the terahertz wave on the terahertz wave transmission line A with certainty, thereby generating an even stronger terahertz wave. (Sixth Embodiment) FIG. 8 is a block diagram showing the structure of a terahertz wave generation device 60 according to a sixth embodiment. In this terahertz wave generation device 60, a coupler 61 and a multi-core fiber 63 are provided in place of the distributor 5 and the fiber bundle 7 of the first embodiment. Differences from the first embodiment are explained below. The coupler 61 is connected to the ultra-short pulse laser light source 3 via the optical fiber 65, and makes the strength of the ultra-short pulse laser light projected from the ultra-short pulse laser light source 3 uniform. The multi-core fiber 63 is composed of a plurality of transmission paths 67 and a clad unit (unlabeled) that covers the plurality of transmission paths 67. the transmission paths 67 are directly connected to the projection unit of the coupler 61 so that the ultra-short pulse laser light whose strength has been made uniform by the coupler 61 is simultaneously incident on the transmission paths 67. In addition, the orientation of the projection units 69 of the transmission paths 67 is adjusted so that the ultra-short pulse laser light L projected from the projection units 69 is incident on the LN crystal 15 from a direction orthogonal to the optical axis of the LN crystal 15. In addition, the projection units 69 of the transmission paths 67 are arranged so that the ultra-short pulse laser light L projected from the projection units 69 irradiates with successive shifts the terahertz wave transmission line A. In addition, because the projection unit side end surface of the multi-core fiber 63 is ground to a desired inclination, the optical path lengths of the transmission paths 67 becomes longer toward one side of the parallel direction of the projection units 69 (that is to say, in the direction of the terahertz wave transmission line A). In addition, condenser lenses 71 for condensing light are provided at the projection units 69. Here, by adjusting the curved surface and position of each lens 71, the ultra-short pulse laser light L projected from each projection unit 69 is condensed so as to be orthogonally incident on the surface of the LN crystal 15, and the focal point of each ultra-short pulse laser light L is positioned with a predetermined spacing on the terahertz wave transmission line A. With this embodiment, each time the ultra-short pulse laser light source 3 projects ultra-short pulse laser light L, this ultra-short pulse laser light L is simultaneously incident on the transmission paths of the multi-core fiber 63 after the strength has been made uniform by the coupler 61. Furthermore, the ultra-short pulse laser light L incident on the transmission paths 67 is projected from the projection units 69 toward the LN crystal 15. As a result, the pulse laser light group C having a discrete wave surface composed of a plurality of ultra-short pulse laser lights L advances toward the LN crystal 15, the same as in the first embodiment. Moreover, the optical path lengths of the transmission paths 67 of the multi-core fiber 63 become longer toward one side in the parallel direction of the projection units 69 (that is to say, in the direction of the terahertz wave transmission line A), so the wave front of the pulse laser light group C becomes inclined so as to be delayed toward one side of the parallel direction of the projection units 69 (that is to say, in the direction of the terahertz wave transmission line A). As a result, because the ultra-short pulse laser lights L of the pulse laser light group C arrive with a time difference at positions successively shifted on the terahertz wave transmission line A, it is possible to repeatedly irradiate the ultra-short pulse laser lights L on the terahertz wave T, the same as in the first embodiment. Through this, a very strong terahertz wave T is generated in the LN crystal 15. Furthermore, the structure of the device obtained by providing a multi-core fiber 63 and adjusting the positions of the projection units 69 of the transmission paths 67 and the optical path lengths of the transmission paths 67 in the multi-core fiber 63 is simple. In addition, by adjusting the positions of the projection units 69 of the transmission paths 67 and adjusting the grinding inclination of the projection unit side end surface of the multi-core fiber 63 in order to adjust the optical path lengths of the transmission paths 67, it is possible to adjust the arrival time and the position where the ultra-short pulse laser lights L of the pulse laser light group C are irradiated on the terahertz wave transmission line A. Through this, it is possible to arbitrarily set the relative positions of the LN crystal 15 and the terahertz wave generation device 60 and the shape of the LN crystal 15. In addition, by adjusting the curved surfaces and positions of the lenses 71, it is possible to condense the ultra-short pulse laser lights L projected from the transmission paths 67 to a desired location, so that a very strong terahertz wave T is generated with certainty. FIG. 9 shows a variation on this embodiment. In the terahertz wave generation device 73 of this variation, the transmission paths 67 of the multi-core fiber 63 are connected to the projection unit of the coupler 61 via optical fibers 75, and the ultra-short pulse laser lights are incident from the coupler via these optical fibers 75. In this terahertz wave generation device 73, the length adjustment mechanism 31 shown in the third embodiment is provided in a position subsequent to the coupler 61 with respect to the optical fibers 75. With this variation, by adjusting the optical path length of the optical fibers 75 using the length adjustment mechanism 31, it is possible to set the time delay given to the ultra-short pulse laser lights L projected from the transmission paths 67 in a wider range. Through this, the ultra-short pulse laser lights L projected from the transmission paths 67 irradiate the terahertz wave T on the terahertz wave transmission line A with certainty. In this embodiment, the ultra-short pulse laser light source 3 may be provided for each transmission path 67 of the multi-core fiber 63. In this case, the transmission paths 67 are connected to the ultra-short pulse laser light source 3 via optical fibers, and the ultra-short pulse laser lights are incident from the ultra-short pulse laser light source 3. In addition, in this case the timing adjustment mechanism 41 shown in FIG. 5 may be connected to the ultra-short pulse laser light source 3. Through this, it is possible to make the ultra-short pulse laser lights generated by the ultra-short pulse laser light source 3 simultaneously incident in the transmission paths 67 of the multi-core fiber 63. This application claims the benefit of Japanese Patent Application No. 2008-217385, filed Aug. 26, 2008, the entire disclosure of which is incorporated by reference herein. The present invention is a device for generating a very strong terahertz wave, and has extremely high industrial applicability, such as being usable for measuring multilayer automotive film thickness. 1, 20, 30, 40, 50, 53, 60, 73 terahertz wave generation device 7 fiber bundle 9, 10, 65, 75 optical fiber 3 ultra-short pulse laser light source 5, 23 distributor 13, 69 projection unit 15 LN crystal 17, 71 lens 21 ultra-short pulse fiber laser light source 31 length adjustment mechanism 41 timing adjustment mechanism 51 high-output amp 61 coupler 63 multi-core fiber 67 transmission path A terahertz wave transmission line C pulse laser light group F1 to F5 optical fibers L ultra-short pulse laser light T terahertz wave
062263420	description	DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1a shows a fuel assembly 1 of boiling-water type which comprises a long tubular container, of rectangular cross section, referred to as a fuel channel 2. The fuel channel 2 is open at both ends so as to form a continuous flow passage, through which the coolant of the reactor flows. The fuel assembly 1 comprises a large number of equally long tubular fuel rods 3 arranged in parallel in a bundle, in which pellets 4 of a nuclear fuel are arranged. The fuel rods 3 are arranged separated into four orthogonal sub-bundles by means of a cruciform support device 8, see also FIG. 1b. The respective sub-bundle of fuel rods 3 is retained at the top by a top tie plate 5 and at the bottom by a bottom tie plate 6. The fuel rods 3 in the respective sub-bundle are kept spaced-apart from each other by means of spacers 7 and are prevented from bending or vibrating when the reactor is in operation. The spacer 7 according to the invention may, of course, also be used in a reactor of boiling-water type which has no cruciform support device 8 but instead is provided with, for example, one or more water tubes. FIG. 2 shows a fuel assembly 1 of pressurized-water type which comprises a number of elongated tubular fuel rods 3 and control rod guide tubes 3a, arranged in parallel. In the fuel rods 3, pellets 4 of a nuclear fuel are arranged. The control rod guide tubes 3a are retained at the top by a top nozzle 5 and at the bottom by a bottom nozzle 6. The fuel rods 3 are kept spaced-apart from each other by means of spacers 7. FIGS. 3a, 3b show an embodiment of a ceramic retaining component, more particularly the spacer 7. The spacer 7 is formed as a lattice structure with sleeve-formed cells 9. At least some of the cells 9 are arranged to surround and position elongated elements in a fuel assembly according to the invention. The elongated element may comprise, for example, a fuel rod 3 or a control rod guide tube 3a. The cells 9 which are adapted to surround an elongated element 3 are provided with damping surfaces 10a and/or 10b, uniformly distributed around the periphery of the cell 9 and along the whole length of the cell 9. In a preferred embodiment, the number of damping surfaces 10a, 10b is four and they are arranged with a pitch angle of 90.degree.. Such a sleeve cell 9 with four damping surfaces 10a is shown in FIG. 3c. The damping surfaces 10a are thus formed as elongated grooves, the surface of which, facing inwards towards the center of the sleeve 9, is adapted to connect closely with the outer surface of an elongated element 3. FIG. 3d shows an alternative embodiment of a sleeve cell 9. This sleeve cell is provided with three damping surfaces 10b which are evenly distributed along the periphery of the sleeve 9. The damping surfaces 10b are formed as ridges extending along the whole axial extent of the sleeve. The ridges are formed with a surface facing inwards towards the center of the sleeve 9, which surface is concave for the purpose of connecting closely with the outer convex surface of an elongated element 3. The damping surfaces 10a, 10b are arranged so as to be situated very close to the elongated element 3, 3a extending through the cell 9, but without making contact therewith. When coolant flows upwards through the fuel assembly 1, a thin liquid film is formed between the elongated elements 3, 3a and the damping surfaces 10a, 10b. In this way, a spacer 7 with hydraulic damping of the movements of the respective elongated elements 3, 3a in the fuel assembly 1 is achieved. The above embodiments of a ceramic spacer 7 are manufactured by cutting ceramic tubes with damping surfaces 10a, 10b into tube sleeves 9 in suitable lengths. The tube sleeves 9 are then joined together into a spacer lattice with the aid of sintering with a powder of the same composition as that of the material in the tube sleeves 9. An alternative way of manufacturing ceramic parts for retaining a bundle of elongated elements in a nuclear fuel assembly is to start from a ceramic material in powdered state and shape and consolidate this by pressing at elevated pressure, combined with sintering at elevated temperature. Preferably, the ceramic powder has then been preformed, using a suitable method, into a green body, which is consolidated and sintered into an essentially tight ceramic body. The tight ceramic body has few internal defects by having been pressed isostatically at an elevated temperature, so-called hot-isostatic pressing, HIP. Examples of the above-mentioned parts are shown in FIGS. 4-6 and will be described in greater detail below. In the following, a more detailed description will be made of a preferred method for manufacturing a ceramic body which constitutes at least part of a retaining component in a fuel assembly 1 according to the invention. A ceramic powder, suitably a powder of a partially stabilized zirconium dioxide (PSZ), is mixed with an organic binder, such as wax or another polymer. The ceramic powdered material with addition of binder is then preformed into a porous body in a suitable way by slip casting, pressing, extrusion, injection moulding, etc., into a so-called green body. The mixture of binder and ceramic powder may also be preformed into a body by spray-drying, which may then be formed by means of pressing, extrusion or by being filled into a suitable mould. The porous green body is thereafter treated in a plant for driving off the temporary organic binder. Driving off the binder takes place by heating, vacuum treatment or by a combined heating and vacuum treatment. By heating, the green body shrinks linearly in the order of magnitude of 15% in such a way that the shape of the component is retained. To be able to consolidate the porous body, it must be degassed and enclosed in a continuous tight casing, which is impenetrable to the pressure medium used during the isostatic pressure. Usually, a glass casing is applied to the porous body, the porous body then being placed in a mould together with a powder of a glass or a glass-forming material. Before the isostatic pressing, the porous body and the glass powder are heated, whereby the powdered glass or glass-forming material forms a tight coherent casing around the porous body. Thereafter, the injection-moulded object is sintered and consolidated by hot-isostatic pressing in a high-pressure furnace, whereby the component is subjected to a high temperature at a high pressure. The encapsulation is then removed using a suitable method, leaching, blasting, etc. In certain cases, a subsequent processing with conventional methods is needed, such as, for example, grinding to give the product its final shape. This especially applies to slots and recesses which are not rotationally-symmetrical and grinding to fulfill given tolerance requirements. In an alternative embodiment, the component is pressed in cold state, whereby another encapsulating material, which is flexible at the pressing temperature, such as a plastic or a rubber material, which is impenetrable to the pressure medium used, is used. The cold-isostatically pressed body is then sintered in a conventional heating furnace. The advantage of forming a ceramic body by isostatic pressing is that the number of pores and other internal defects in the material are considerably reduced in relation to a corresponding body manufactured by common, linear pressing. Another advantage is less mechanical subsequent processing since, with isostatic pressing, bodies with a more complex shape may be manufactured. Subsequent treatment is usually needed only for non-rotationally symmetrical objects to be formed and for fulfilling certain tolerance requirements. It is less expensive to process into close tolerances than to try to check shrinkage, form filling etc. so accurately that the pressed body fulfils given tolerances. FIGS. 4a-d show alternative embodiments of a ceramic spacer 7 obtained according to the method stated above. The spacer 7 in FIG. 4a is formed in a manner corresponding to that shown in FIGS. 3a, 3b. However, the lattice structure in FIGS. 4a, 4b has been given a more open structure. The support surface 10 may be formed in a manner corresponding to that shown in FIGS. 3c and 3d, see reference numerals 10a and 10b, respectively. FIGS. 4c, 4d and 4e show another embodiment of a spacer 7 manufactured according to the method described above. The spacer 7 has the same open structure as the spacer 7 shown in FIG. 4b. The spacer 7 according to FIG. 4d comprises both elongated support surfaces 10, designed as described above, and springs 10c. The springs 10c are designed as a part projecting from the spacer structure, in the figure provided with reference numeral 10d, and an elongated part 10e. The springs 10c have a first end, which conforms to the structure, and a second free end. In the figure, the respective free ends are facing upstream in comparison with the coolant flowing upwards through the assembly. They may, of course, also be arranged with their free ends facing downstream. The springs 10c are formed such that their respective free ends are arranged nearer the center of the cell 9 than their first ends which conform to the structure. Further, the respective free ends are adapted to make contact with an elongated element 3, 3a extending through the cell 9. Two of the support surfaces suitably consist of elongated fixed supports 10 and two of resilient supports 10c, the supports being evenly distributed around the periphery of the cell 9. The springs 10e in the ceramic material may be utilized as springs up to the yield point of the material. This resilient capacity is sufficient to position the elongated elements 3 in the spacer 7. FIGS. 5a, 5b show an embodiment of another ceramic retaining component, more particularly a bottom tie plate 6, see also FIG. 1. The bottom tie plate 6 is made in one piece according to the method described above. The bottom tie plate 6 is formed with a plurality of substantially circular openings 11 for receiving elongated elements 3 (see FIG. 1) and for passage of the coolant flowing through the fuel assembly 1. FIG. 5b shows that the bottom tie plate 6 is provided with a diagonal opening 12. The diagonal opening 12 is formed during the injection moulding. In an alternative embodiment, the diagonal opening is formed by means of mechanical processing after the rest of the body has been completed in accordance with the method described above. FIGS. 6a, 6b show an embodiment of still another ceramic retaining component, more particularly a top tie plate 5, see also FIG. 1. The top tie plate 5 is formed with a plurality of substantially circular openings 13 for receiving elongated elements 3 and an open structure between these openings for passage of the coolant flowing upwards through the fuel assembly 1. The top tie plate 5 is manufactured according to the method described above. The bottom and top tie plates, respectively, shown in FIGS. 5 and 6 are intended for a boiling water reactor. For a pressurized-water reactor, the bottom and top tie plates, respectively, are formed in a corresponding way with openings and/or milled grooves.
	description	In order to describe the present invention in greater detail, the invention will be described with reference to the accompanying drawings. FIG. 1 is a structural diagram of a scanning tunnel microscope (STM) to which the present invention is applied. The nanotube probe needle 1 is fastened to a holder 2a to form a detection probe 2. The method of fastening will be described later. This holder 2a is inserted into the cut groove 3a of a holder setting part 3, and is fastened in place by means of spring pressure so that the holder 2a can be detached. A scanning driving part 4 comprises an X piezo-electric element 4x, a Y piezo-electric element 4y and a Z piezo-electric element 4z scans the holder setting part 3 by expanding and contracting in the X, Y and Z directions, and thus causes scanning of the nanotube probe needle 1 relative to the sample 5. The reference numeral 6 is a bias power supply, 7 is a tunnel current detection circuit, 8 is a Z-axis control circuit, 9 is an STM display device, and 10 is an XY scanning circuit. The Z axis control circuit controls the nanotube probe needle 1 by expansion and contraction in the Z direction so that the tunnel current remains constant at each XY position. This amount of movement corresponds to the amount of indentation or projection in the Z axis direction. As the nanotube probe needle 1 is scanned in the X and Y directions, a surface-atomic image of the sample 5 is displayed by the STM display device. When the nanotube probe needle 1 is replaced in the present invention, the holder 2a is removed from the holder setting part 3, and the probe 2 is replaced as a unit. FIG. 2 is a structural diagram of an atomic force microscope (AFM) to which the present invention is applied. The nanotube probe needle 1 is fastened to a holder 2a. The holder 2a is a pyramid-form member formed on the tip end of a cantilever 2b. The cross section of this pyramid is a right-angled triangle, and the probe needle 1 is fastened to the perpendicular surface; accordingly, the probe needle 1 contacts the sample surface more or less perpendicularly, so that the shape of the sample surface can be accurately read. The cantilever 2b is fastened to a substrate 2c and fastened in a detachable manner to a holder setting part (not shown). In this configuration, the nanotube probe needle 1, holder 2a, cantilever 2b and substrate 2c together constitute the probe 2; when the probe needle is replaced, the entire probe 2 is replaced. For example, if the conventional pyramid-form probe needle 87 shown in FIG. 27 is utilized as the holder 2a, the nanotube probe needle can be fastened to this by a method described later. The sample 5 is driven in the X, Y and Z directions by a scanning driving part which is a piezo-electric 30 element. 11 indicates a semiconductor laser device, 12 indicates a reflective mirror, 13 indicates a two-part split light detector, 14 indicates an XYZ scanning circuit, 15 indicates an AFM display device, and 16 indicates a Z axis detection circuit. The sample 5 is caused to approach the nanotube probe needle 1 in the direction of the Z axis until the sample 5 is in a position where a specified repulsive force is exerted; and afterward, the scanning driving part 4 is scanned in the X and Y directions by the scanning circuit 14 with the Z position in a fixed state. In this case, the cantilever 2b is caused to bend by the indentations and projections of the surface atoms, so that the reflected laser beam LB enters the two-part split light detector 13 after undergoing a positional displacement. The amount of displacement in the direction of the Z axis is calculated by the Z axis detection circuit 16 from the difference in the amounts of light detected by the upper and lower detectors 13a and 13b, and an image of the surface atoms is displayed by the AFM display device 15 with this amount of displacement as the aamount of indentation and projection of the atoms. This device is constructed so that the sample 5 is scanned in the X, Y and Z directions. However, it is also possible to scan the probe needle side, i.e., the probe 2, in the X, Y and Z directions. The nanotube probe needle 1 may be caused to vibrate so that it lightly strikes the surface of the sample 5. The nanotube probe needle 1 shown in FIGS. 1 and 2 is a nanotube itself, such as a carbon nanotube, BCN type nanotube or BN type nanotube, etc. Of these various types of nanotubes, the carbon nanotube (also referred to as xe2x80x9cCNTxe2x80x9d below) was discovered first. In the past, diamond, graphite and amorphous carbon have been known as stable allotropes of carbon. The structures of these allotropes were also in states that were more or less determined by X-ray analysis, etc. In 1985, however, fullerene, in which carbon atoms are arranged in the form of a soccer ball, was discovered in a vapor cooled product obtained by irradiating graphite with a high-energy laser, and this compound was expressed as C60. In 1991, furthermore, carbon nanotubes, in which carbon atoms are arranged in a tubular form, were discovered in a cathodic deposit produced by means of a DC arc discharge. BCN type nanotubes were synthesized on the basis of the discovery of such carbon nanotubes. For example, a mixed powder of amorphous boron and graphite is packed into a graphite rod, and is evaporated in nitrogen gas. Alternatively, a sintered BN rod is packed into a graphite rod, and is evaporated in helium gas. Furthermore, an arc discharge may be performed in helium gas with BC4N used as the anode and graphite used as the cathode. BCN type nanotubes in which some of the C atoms in a carbon nanotube are replaced by B atoms and N atoms have been synthesized by these methods, and multi-layer nanotubes in which BN layers and C layers are laminated in a concentric configuration have been synthesized. Very recently, furthermore, BN type nanotubes have been synthesized. These are nanotubes which contain almost no C atoms. For example, a carbon nanotube and powdered B2O3 are placed in a crucible and heated in nitrogen gas. As a result, the carbon nanotube can be converted into a BN type nanotube in which almost all of the C atoms of the carbon nanotube are replaced by B atoms and N atoms. Accordingly, not only carbon nanotubes, but also general nanotubes such as BCN type nanotubes or BN type nanotubes, etc., can be used as the nanotubes of the present invention. Since these nanotubes have more or less the same substance structure as carbon nanotubes, carbon nanotubes will be used as an example in the structural description below. Carbon nanotubes (CNT) is a cylindrical carbon substance with a quasi-one-dimensional structure which has a diameter of approximately 1 nm to several tens of nanometers, and a length of several microns. Carbon nanotubes of various shapes, as shown in FIG. 3, have been confirmed from transmission electron micrographs. In the case of FIG. 3(a), the tip end is closed by a polyhedron, while in the case of FIG. 3(b), the tip end is open. In the case of FIG. 3(c), the tip end is closed by a conical shape, while in the case of FIG. 3(c), the tip end is closed by a beak shape. In addition, half-donut type nanotubes are also known to exist. It is known that the atomic arrangement of a carbon nanotube is a cylinder which has a helical structure formed by shifting and rolling up a graphite sheet. It is known that the end surface of the cylinder of a CNT can be closed by inserting six five-member rings. The fact that there are diverse tip end shapes as shown in FIG. 3 is attributable to the fact that five-member rings can be arranged in various ways. FIG. 4 shows one example of the tip end structure of a carbon nanotube; it is seen that this structure varies from a flat plane to a curved surface as a result of six-member rings being arranged around a five-member ring, and that the tip end has a closed structure. Circles indicate carbon atoms, solid lines indicate the front side, and dotted lines indicate the back side. Since there are various possible arrangements of five-member rings, the tip end structures show diversity. Not only carbon nanotubes, but also general nanotubes show such a tube structure. Accordingly, nanotubes show an extremely strong rigidity in the central axial direction and in the bending direction; and at the same time, like other carbon allotropes, etc., nanotubes show extreme chemical and thermal stability. Accordingly, when nanotubes are used as probe needles, these nanotubes tend not to be damaged even if they collide with atomic projections on the sample surface during scanning. Furthermore, since the cross-sectional diameters of nanotubes are distributed over a range of approximately 1 nm to several tens of nanometers (as described above), such nanotubes are most suitable as materials of probe needles which can produce sharp images of fine structures at the atomic level (if a nanotube with a small curvature radius is selected). Furthermore, since there are many nanotubes that have conductivity, nanotubes can be utilized not only as AFM probe needles, but also as STM probe needles. Furthermore, since nanotubes are difficult to break, they can also be used as probe needles in other scanning probe microscopes such as leveling force microscopes, etc. Among nanotubes, carbon nanotubes are especially easy to manufacture, and are suited to inexpensive mass production. It is known that carbon nanotubes are produced in the cathodic deposit of an arc discharge. Furthermore, such carbon nanotubes are generally multi-layer tubes. Furthermore, it has been found that single-layer carbon nanotubes are obtained when the arc discharge method is modified and a catalytic metal is mixed with the anode. Besides the arc discharge method, carbon nanotubes can also be synthesized by CVD using fine particles of a catalytic metal such as nickel or cobalt, etc., as a substrate material. Furthermore, it is also known that single-layer carbon nanotubes can be synthesized by irradiating graphite containing a catalytic metal with high-output laser light at a high temperature. Furthermore, it has also been found that such carbon nanotubes include nanotubes that envelop a metal. Moreover, as described above, it has been found that BCN type nanotubes and BN type nanotubes, etc., can also be inexpensively manufactured using an arc discharge process or crucible heating process, etc., and techniques for enveloping metals in nanotubes are also being developed. However, for example, in the carbon nanotube manufacturing process, it is known that carbon nanotubes are not produced just by themselves; instead, such nanotubes are produced in a mixture with large quantities of carbon nanoparticles (hereafter also abbreviated to xe2x80x9cCPxe2x80x9d). Accordingly, the recovery of CNT from this mixture at a high density is a prerequisite for the present invention. In regard to this point, the present inventors have already provided a CNT purification method and purification apparatus based on an electrophoretic process in Japanese Patent Application No. 10-280431. In this method, CNTs can be purified by dispersing the carbon mixture in an electrophoretic solution, and applying a DC voltage or AC voltage. For example, if a DC voltage is applied, the CNTs are arranged in straight rows on the cathode. If an AC voltage is applied, the CNTs are arranged in straight rows on the cathode and anode as a result of the formation of a non-uniform electric field. Since the degree of electrophoresis of CPs is smaller than that of CNTs, CNTs can be purified by means of an electrophoretic process utilizing this difference. It has been confirmed that this electrophoretic method can be used to purify not only carbon nanotubes, but also BCN type nanotubes and BN type nanotubes. This electrophoretic method is also used in the working of the present invention. Specifically, nanotubes purified and recovered by the above-described method are dispersed in a separate clean electrophoretic solution. When metal plates such as knife edges, etc., are positioned facing each other as electrodes in this solution, and a DC voltage is applied to these electrodes, nanotubes adhere to the cathode (for example) in a perpendicular configuration. If the electrodes are positioned so that a non-uniform electric field is formed in cases where an AC voltage is applied, nanotubes will adhere to both electrodes in a perpendicular configuration. These electrodes with adhering nanotubes are utilized in the manufacturing process of the present invention. Of course, other methods of causing nanotubes to adhere to a knife-edge-form metal plate may also be used. The above-described electrophoretic solution may be any solution that is capable of dispersing the nanotubes so that the nanotubes undergo electrophoresis. Specifically, the solvent used is a dispersing liquid, and is at the same time an electrophoretic liquid. Solvents which can be used in this case include aqueous solvents, organic solvents and mixed solvents consisting of both types of solvents. For example, universally known solvents such as water, acidic solutions, alkaline solutions, alcohol, ethers, petroleum ethers, benzene, ethyl acetate and chloroform, etc., may be used. More concretely, all-purpose organic solvents such as isopropyl alcohol (IPA), ethyl alcohol, acetone and toluene, etc., may be utilized. For example, in the case of IPA, carboxyl groups are present as electrophoretic ion species. Thus, it is advisable to select the solvent used on the basis of a comprehensive evaluation of the electrophoretic performance and dispersion performance of the nanotubes, the stability of the dispersion, and safety, etc. FIG. 5 shows a case involving CNTs as one example of a DC electrophoretic process. The electrophoretic solution 20 in which the CNTs are dispersed is held inside a hole formed in a glass substrate 21. Knife edges 22 and 23 are positioned facing each other in the solution, and a DC power supply 18 is applied. Although not visible to the naked eye, countless extremely small carbon nanotubes (CNTs) are present in the electrophoretic solution. These CNTs adhere in a perpendicular configuration to the tip end edge 22a of the cathode knife edge 22. This can be confirmed under an electron microscope. In this apparatus, a non-uniform electric field in which the lines of electric force are bent in the direction perpendicular to the plane of the knife edges is formed between the two electrodes. However, this can be utilized as a DC electrophoresis apparatus even if a uniform electric field is formed. The reason for this is as follows: specifically, in the case of a non-uniform electric field, the rate of electrophoresis is merely non-uniform; electrophoresis is still possible. FIG. 6 shows a case involving CNTs as one example of an AC electrophoretic process. The electrophoretic solution 20 in which the CNTs are dispersed is held inside a hole formed in a glass substrate 21. Knife edges 22 and 23 are positioned facing each other in the solution, and an AC power supply 19 is applied via an amplifier 26. A non-uniform electric field similar to that of FIG. 5 acts between the electrodes. Even if a non-uniform electric field is not intentionally constructed, local non-uniform electric fields are actually formed, so that electrophoresis can be realized. In this figure, a 5 MHz, 90 V alternating current is applied. CNTs adhere in a perpendicular configuration to the tip end edges 22a and 23a of the knife edges of both electrodes. FIG. 7 is a schematic diagram showing states of adhesion of nanotubes 24 to the tip end edge 23a of a knife edge 23. The nanotubes 24 adhere to the tip end edge 23a in a more or less perpendicular configuration, but some of the nanotubes are inclined. Furthermore, there are also cases in which a plurality of nanotubes are gathered together so that they adhere in the form of bundles; these are referred to as NT bundles 25 (also called nanotube bundles). The curvature radii of the nanotubes are distributed over a range of approximately 1 nm to several tens of nanometers. In cases where excessively slender nanotubes are selected as probe needles, such probe needles offer the advantage of allowing fine observation of indentations and projections in the atomic surface; conversely, however, such nanotubes may begin to vibrate in a characteristic mode, and in such cases, the resolution drops. Here, if an NT bundle 25 is used as a probe needle, the nanotube that protrudes the furthest forward in this bundle fulfills the function of a direct probe needle, while the other nanotubes act to suppress vibration. Accordingly, such NT bundles 25 can also be used as probe needles. FIG. 8 is a computer image of a scanning electron microscope image of a knife edge with an adhering CNT. It is seen that CNTs can easily be caused to adhere to a knife edge merely by performing an electrophoretic operation. However, CNTs more commonly adhere to the tip end edge at an inclination rather than at right angles. The knife edge shown in FIG. 8 is subjected to a special treatment for the purpose of a strength test. This electron-microscopic apparatus contains considerable quantities of organic substances as impurities. Accordingly, it was found that when this knife edge is irradiated with an electron beam, a carbon film originating in the impurities is formed on the surface of the knife edge. The details of this phenomenon will be described later; however, this carbon film is formed on the knife edge surface so that it covers only some of the CNTs. In other words, the carbon film has the function of fastening CNTs to the knife edge that were merely adhering to the knife edge. Other nanotubes besides CNTs can be similarly treated. The mechanical strength of CNTs on the above-described knife edge was tested. The CNTs were pressed by a member with a sharpened tip. FIGS. 9 and 10 show computer images of scanning electron microscope images obtained before and after pressing. As is clearly seen from FIG. 10, the CNT has a bending elasticity which is such that there is no breakage of the CNT even when the CNT is bent into a semicircular shape. When pressing was stopped, the CNT returned to the state shown in FIG. 9. Such a high strength and high elasticity are the reason why CNTs are not damaged even if they contact the atomic surface or are dragged across the atomic surface. This also verifies that the carbon film strongly fastens the CNTs in place. Thus, the fastening force is sufficient so that the CNTs are not separated from the knife edge even if bent. General nanotubes also have such a high strength and high elasticity; this is a major advantage of using nanotubes as probe needles. FIG. 11 is a diagram of a device used to transfer a nanotube to the cantilever of an AFM holder. A holder 2a is caused to protrude in the form of a pyramid from the tip end of a cantilever 2b. This is a member made of silicon which is manufactured using a semiconductor planar technique. Ordinarily, such a pyramid-form protruding part is used as an AFM. However, in the present invention, this pyramid-form protruding part is converted to use as a holder 2a. A nanotube 24 on the knife edge 23 is transferred to this holder 2a, and this nanotube 24 is used as a probe needle. Since the nanotubes on the knife edge are merely adhering to the knife edge, they are naturally not fastened by a film. These operations are preformed under real-time observation inside a scanning electron microscope chamber 27. The cantilever 2b can be moved three-dimensionally in the X, Y and Z directions, and the knife edge can be move two-dimensionally in the X and Y directions. Accordingly, extremely minute operations are possible. The surface signal operating probe of the present invention is completed by transferring a nanotube adhering to the knife edge to a holder, and fastening this nanotube to the holder by a fastening means. In regard to this fastening means, two methods are used in the present invention. One is a coating film; in this case, the nanotube is fastened to the holder by means of a coating film. The second method uses a fusion-welded part; in this case, the nanotube is caused to adhere to the holder, and the contact portion is fused so that the two members are bonded to each other. Since nanotubes are extremely slender, the entire base end portion of the nanotube in contact with the holder tends to form the fusion-welded part. Fusion welding methods include fusion welding by means of an electric current and fusion welding by electron beam irradiation. Below, concrete examples of nanotube fastening means will be described as embodiments. Embodiment 1 [AFM Probe Fastened by a Coating Film] FIG. 12 is a layout diagram showing the state immediately prior to the transfer of the nanotube. While being observed under an electron microscope, the tip end of the holder 2a is caused to approach very close to the nanotube 24. The holder 2a is positioned so that the nanotube 24 is divided into a tip end portion length L and base end portion length B by the tip end of the holder 2a. Furthermore, a transfer DC power supply 28 is provided in order to promote this transfer, and the cantilever 2b is set on the cathode side. However, the polarity of the DC power supply also depends on the material of the nanotube; accordingly, the polarity is adjusted to the direction that promotes transfer. The transfer of the nanotube is promoted when this voltage is applied. A voltage of several volts to several tens of volts is sufficient. This voltage can be varied according to the transfer conditions. Furthermore, this power supply 28 may also be omitted. When the approach distance D becomes closer than a specified distance, an attractive force acts on both members, so that the nanotube 24 spontaneously jumps to the holder 2a. As the approach distance D becomes closer, the actual values of the lengths L and B approach the preset design values. This transfer may include cases in which the nanotube 24 contacts both the knife edge 23 and holder 2a; and these may be separated following the formation of the coating film. FIG. 13 is a layout diagram showing the state in which the nanotube 24 adheres to the holder 2a. The tip end portion 24a protrudes by the tip end portion length L, and the base end portion 24b adheres to the holder 2a by the base end portion length B. The tip end portion 24a constitutes the probe needle. It would also be possible to cause an NT bundle 25 to adhere to the holder instead of a single nanotube 24. Furthermore, if single nanotubes 24 are transferred and caused to adhere to the holder a number of times, an effect which is the same as causing an NT bundle 25 to adhere to the holder can be obtained. In cases where nanotubes are caused to adhere a number of times, the individual nanotubes can be caused to adhere after being arbitrarily adjusted. Accordingly, a stable, high-resolution probe can be manufactured in which the nanotube that protrudes furthest to the front acts as the probe needle, while the surrounding nanotubes suppress resonance of the probe needle as a whole. Next, a coating film is formed over a specified region including the base end portion 24b of the nanotube 24, so that the nanotube 24 is firmly fastened to the holder 2a. As seen from FIG. 14, the coating film 29 is formed so that it covers the base end portion 24a from above. As a result of this coating film 29, even if the tip end portion 24a constituting the probe needle should catch on an atomic projection, the probe needle will merely flex into a bent state as described above. Thus, damage such as breakage of the probe needle or removal of the probe needle from the holder 2a can be prevented. If this coating film 29 is absent, the nanotube 24 will separate from the holder 2a when the tip end portion 24a catches on a projection. Next, methods which can be used to form the coating film 29 will be described. As described above, one method which can be used is as follows: specifically, when the base end portion 24b is irradiated with an electron beam, carbon substances floating inside the electron microscope chamber 27 are deposited in the vicinity of the base end portion so that a carbon film is formed. This carbon film is used as a coating film. A second method is a method in which a very small amount of a reactive coating gas is introduced into the electron microscope chamber 27, and this gas is decomposed by means of an electron beam, so that a coating film of the desired substance is formed. In addition, general coating methods can also be employed. For example, CVD (also referred to as chemical vapor deposition) and PVD (also referred to as physical vapor deposition) can be utilized. In the case of a CVD process, the material is heated beforehand, and a reactive coating gas is caused to flow to this location, so that a coating film is reactively grown on the surface of the material. Furthermore, the low-temperature plasma method in which the reaction gas is converted into a plasma and a coating film is formed on the surface of the material is also one type of CVD method. Meanwhile, PVD methods include several types of methods ranging from simple vapor deposition methods to ion plating methods and sputtering methods, etc. These methods can be selectively used in the present invention, and can be widely used on coating film materials ranging from insulating materials to conductive materials in accordance with the application involved. FIG. 15 is a scanning electron microscope image of a completed probe. It is seen that a CNT is fastened to the holder in accordance with the design. The present inventors took AFM images of deoxyribonucleic acid (DNA) in order to measure the resolution and stability of this probe. FIG. 16 shows an AFM image of this DNA; and the crossing and twining of the DNA were clearly imaged. To the best knowledge of the inventors, this is the first time that such clear DNA images have been obtained. Judging from FIG. 16, it appears that the tip end curvature radius of this probe constructed according to the present invention is 1.2 nm or less; it will be understood that this is extremely effective in scientific research. Embodiment 2 [Reinforced AFM Probe Fastened by Coating Film] FIG. 17 shows another coating film formation method. In order to obtain high-resolution images, it is desirable that the curvature radius of the tip end of the nanotube 24 be small. However, as described above, there are cases in which the tip end portion undergoes microscopic vibrations if the nanotube is too slender, so that the images become blurred. Accordingly, in cases where a slender nanotube 24 is used, a coating film 30 is also formed on a region of the tip end portion 24a that is close to the base end portion 24b, i.e., on an intermediate portion 24c. As a result of this coating film 30, the intermediate portion 24c is made thicker and greater in diameter, so that an effect that suppresses microscopic vibrations is obtained. This coating film 30 may be formed from the same material as the coating film 29 at the same time that the coating film 29 is formed, or may be formed from a different material. In this way, a probe needle comprising a single nanotube in which the tip end of the nanotube 24 is slender and the root of the nanotube is thick can be constructed. In other words, a high-resolution, high-reliability probe needle can be constructed from a slender nanotube, without using an NT bundle 25. Embodiment 3 [STM Probe Fastened by Coating Film] FIG. 18 is a perspective view of the essential parts of a scanning tunnel microscope probe 2. The tip end portion 24a of a nanotube 24 is caused to protrude, and this portion constitutes the probe needle. The base end portion 24b is fastened to a holder 2a by means of a coating film 29. This probe may be easily understood by a comparison with the probe 2 in FIG. 1. The actions and effects of this probe are similar to those of Embodiment 1; accordingly, a detailed description is omitted. Embodiment 4 [Magnetic Probe Fastened by Coating Film] A probe similar to that shown in FIG. 18 can be utilized as an input-output probe in a magnetic disk drive. In this case, iron atoms are embedded in the tip end of the nanotube, so that the nanotube is endowed with a magnetic effect. Since a nanotube has a tubular structure, various types of atoms can be contained inside the tube. Among these atoms, magnetic atoms can be contained in the tube, so that the nanotube is endowed with magnetic sensitivity. Of course, ferromagnetic atoms other than iron atoms may also be used. Since the tip end curvature radius of a nanotube is extremely small, i.e., a value ranging from approximately 1 nm to several tens of nanometers, the input and output of data recorded at a high density in an extremely small space can be performed with high precision. Embodiment 5 [AFM Probe Fastened by Electric Current Fusion Welding] FIGS. 19 through 24 illustrate an embodiment of fusion-welding fastening of the nanotube. First, FIG. 19 is a layout diagram of the state immediately prior to fusion welding of the nanotube. The tip end of the holder 2a is caused to approach very closely to the nanotube 24 while being observed under an electron microscope. The holder 2a is positioned so that the nanotube 24 is divided into a tip end portion length L and base end portion length B by the tip end of the holder 2a. Furthermore, a high resistance R, a DC power supply 28 and a switch SW are connected between the knife edge 23 and cantilever 2b. For example, the resistance value of the high resistance R is 200 Mxcexa9, and the voltage of the DC power supply is 1 to 100 V. In FIG. 19, in which the members are in a close proximity, the switch SW is in an open state, and no current has yet been caused to flow. When the two members are caused to approach each other even more closely so that the nanotube 24 contacts the holder 2a, the state shown in FIG. 20 results. Here, the tip end portion 24a protrudes by an amount equal to the tip end portion length L, and the base end portion 24b adheres to the holder 2a for a length equal to the base end portion length B. When the switch SW is closed so that current flows in this stage, current flows between the nanotube 24 and the holder 2a, so that the base end portion 24b that is in contact with the holder 2a is fusion-welded to the holder 2a by current heating. In other words, the base end portion 24b is fused to form the fusion-welded part 24d indicated by a black color in the figure, and the nanotube 24 is firmly fastened to the holder 2a. It is also possible to use a process in which the switch SW is closed prior to the contact between the nanotube 24 and the holder 2a, after which the base end portion 24b is converted into the fusion-welded part 24d by the flow of current caused by contact, and then the holder 2a is moved away from the knife edge 23. In this electric current fusion welding treatment, not only is the fastening strong, but fusion welding can be reliably performed with the feeling of spot welding while confirming the object in the electron microscope, so that the product yield is increased. The DC power supply 28 may be replaced by an AC power supply or pulsed power supply. In the case of a DC power supply, fusion welding can be performed using a current of 10xe2x88x9210 to 10xe2x88x926 (ampere-seconds (Axc2x7s)). For example, in a case where the diameter of the carbon nanotube (CNT) is 10 nm, and the length B of the base end portion is 200 nm, stable fusion welding can be performed at 10xe2x88x929 to 10xe2x88x927 (Axc2x7s). However, the gist of the present invention lies in the fastening of the CNT by fusion welding, and the present invention is not limited to these numerical values. Embodiment 6 [AFM Probe Fastened by Electron Beam Fusion Welding] The second fusion welding method is the electron beam irradiation method. When the switch SW is closed in the non-contact state shown in FIG. 19, an electric field is formed between the holder 2a and the nanotube 24. When the respective members are caused to approach each other even more closely, the nanotube 24 is caused to fly onto the holder 2a by the force of this electric field. Afterward, when all or part of the base end portion 24b of the nanotube 24 is irradiated with an electron beam, the base end portion 24b melts and is fusion-welded to the holder 2a as the fusion-welded part 24d. In this case, the polarity of the DC power supply 28 depends on the material of the nanotube, etc. Thus, this polarity is not limited to the arrangement shown in the drawings; and the polarity is adjusted to the direction that promotes transfer. An electric field transfer method is used in the above-described method; however, it is also possible to perform a non-electric-field transfer with the switch SW open. Specifically, when the holder 2a is caused to approach the nanotube 24 within a certain distance, a van der Waals attractive force acts between the two members, and the nanotube 24 is caused to fly onto the holder 2a by this attractive force. The surface of the holder 2a may be coated with an adhesive agent such as an acrylic type adhesive agent, etc., in order to facilitate this transfer. Following this transfer, the base end portion 24b adhering to the holder 2a is fused by irradiation with an electron beam, so that the nanotube 24 is fastened to the holder 2a via a fusion-welded part 24d. Thus, a probe similar to that obtained by current fusion welding can also be obtained by electron beam fission welding. FIG. 21 is a schematic diagram of the completed probe following fusion welding. The tip end portion 24a constitutes the nanotube probe needle and can be used as a high-resolution probe with a tip end curvature radius of 10 nm or less. The nanotube 24 is firmly fastened to the holder 2a by means of the fusion-welded part 24d, so that the nanotube 24 does not break, bend or come loose even if subjected to a considerable impact. In the case of a carbon nanotube, it appears that the nanotube structure is destroyed and changed in amorphous carbon in the fusion-welded part 24d. If silicon is used as the material of the holder 2a, it appears that the carbon atoms that have been converted into an amorphous substance and the silicon atoms of the holder bond to form silicon carbide, so that the fusion-welded part 24d assumes a silicon carbide structure. However, detailed structural analysis of this part has not yet been completed, and this is merely conjecture at this point. In the case of BCN type nanotubes or BN type nanotubes, structural analysis of the fusion-welded part has not yet been performed. However, it has been experimentally confirmed that the members are strongly bonded by this fusion-welded part. As described above, in cases where the holder 2a is made of silicon, the holder 2a has a certain amount of conductivity since it is a semiconductor. Accordingly, since a voltage can be directly applied, current fusion welding is possible. Of course, the van der Waals transfer method or electron beam fusion welding method can also be used. However, in cases where the holder 2a is constructed from an insulator such as silicon nitride, the holder 2a has no conductivity. In such cases, therefore, the transfer method using the van der Waals attractive force or the electron beam fusion welding method is the optimal method. In cases where the current fusion welding method cannot be applied to an insulator, the following procedure may be used: An electrode is formed from a conductive substance on the surface of the CNT holder 2a or cantilever 2b. An electrode film is formed by means of, for instance, metal vapor deposition, etc. A voltage is applied to this film, resulting in that an electric current flows, the fusion welding phenomenon occurs, and a probe is thus obtained. Embodiment 7 [AFM Probe Fastened by Coating Film and Fusion Welding] In cases where a single nanotube 24 is used as a probe needle, if the tip end portion 24a of the nanotube is long and slender, it could happen that resonance occurs so that the tip end vibrates, thus causing a drop in resolution. In order to suppress such resonance, there is a method in which an additional coating film is formed on specified regions. As is clear from FIG. 22, if a coating film 30 is formed on the root side of the tip end portion 24a, this portion becomes thicker so that resonance tends not to occur. This coating region can be freely designed; accordingly, a coating film 29 which extends to the base end portion 24b may be formed. This coating film 29 has the effect of pressing the nanotube from above. Thus, together with the fusion-welded part 24d, the coating film reinforces the fastening of the nanotube 24 to the holder 2a. The thickness of the coating films 29 and 30 may be varied depending upon the case. Next, methods for forming the coating films 29 and 30 will be described. As described above, in one method, when the base end portion 24b and intermediate portion 24c are irradiated with an electron beam, not only do these portions melt, but carbon substances floating inside the electron microscope chamber 27 are deposited in the vicinity of the base end portion so that a carbon film is formed. This carbon film can be utilized as a coating film. In another method, a trace amount of a reactive coating gas is introduced into the electron microscope chamber 27, and this gas is broken down by an electron beam, so that a coating film of the desired substance is formed. In addition, general coating methods can also be employed. For example, the CVD (also called chemical vapor deposition) or PVD (also called physical vapor deposition) can be similarly utilized. Details of these methods are omitted here. It is also possible to fusion-weld an NT bundle 25 instead of fusion-welding a single nanotube 24. If a plurality of nanotubes 24 are fusion-welded one by one, the same effect as the fusion welding of an NT bundle 25 can be obtained. In cases where such fusion welding is performed one by one, the individual nanotube can be arbitrarily adjusted and fusion-welded. Accordingly, a stable, high-resolution probe can be obtained in which a nanotube that protrudes furthest forward acts as the probe needle, while the surrounding nanotubes suppress resonance of the probe needle as a whole. Embodiment 8 [STM Probe Fastened by Fusion Welding] FIG. 23 is a perspective view of the essential portion of a scanning tunnel microscope. The tip end portion 24a of a nanotube 24 is caused to protrude, and this portion acts as a probe needle. The base end portion 24b forms a fusion-welded part 24d and is fusion-welded to the holder 2a. This probe will be easily understood if compared with the probe 2 shown in FIG. 1. A metal such as tungsten or a platinum-iridium alloy, etc. can be used as the material of the holder 2a. The actions and effects of this probe are similar to those of Embodiment 5. Accordingly, details thereof are omitted. Embodiment 9 [STM Probe Fastened by Coating Film and Fusion Welding] FIG. 24 shows a probe 2 in which a coating film 30 is formed on the intermediate portion 24c of the nanotube 24. This coating film 30 is installed in order to prevent vibration of the probe needle. As in FIG. 22, a coating film 29 which covers the fusion-welded part 24d may be formed. Since the actions and effects of this probe are similar to those of Embodiment 7, details are omitted. Embodiment 10 [Magnetic Probe Fastened by Fusion Welding] A probe similar to that shown in FIG. 23 can be utilized as an input-output probe for a magnetic disk drive. In this case, iron atoms are embedded in the tip end of the nanotube, so that the nanotube is endowed with a magnetic effect. Since a nanotube has a tubular structure, various types of atoms can be contained inside the tube. As one example, ferromagnetic items can be contained in the tube, so that the nanotube is endowed with magnetic sensitivity. Of course, ferromagnetic atoms other than iron atoms may also be used. Since the tip end curvature radius of a nanotube is extremely small, i.e., approximately 1 nm to several tens of nanometers, processing such as the input and output of data recorded at a high density in a very small space, etc. can be performed with high precision. The present invention is not limited to the above-described embodiments; and various modifications and design changes, etc., within limits that involve no departure from the technical spirit of the present invention are included in the technical scope of the invention. As described in detail above, the present invention relates to an electronic device surface signal operating probe which comprises a nanotube, a holder which holds this nanotube, and a fastening means which fastens the base end portion of the nanotube to the surface of the holder in a manner that the tip end portion of the nanotube protrude, so that the tip end portion of the nanotube is used as a probe needle; and it also relates to a method for manufacturing the same. Since a nanotube is thus used as a probe needle, the tip end curvature radius is small. Accordingly, by way of using this probe needle in a scanning probe microscope, high-resolution images of surface atoms can be picked up. When this probe needle is used as the probe needle of a magnetic information processing device, the input and output of high-density magnetic information can be controlled with high precision. Since nanotubes have an extremely high rigidity and bending elasticity, no damage occurs to nanotubes even if they should contact neighboring objects. Accordingly, the useful life of the probe can be extended. Furthermore, carbon nanotubes are present in large quantities in the cathodic deposits of arc discharges, and other BCN type nanotubes and BN type nanotubes can easily be manufactured by similar methods. Accordingly, the cost of raw materials is extremely low. In the manufacturing method of the present invention, probes can be inexpensively mass-produced, so that the cost of such probes can be lowered, thus stimulating research and economic activity. In particular, STM and AFM probes with a long useful lives that are necessary for the creation of new substances can be provided inexpensively and in large quantities. Thus, the present invention can contribute to the promotion of technical development.
047073268	claims	1. In a reconstitutable fuel assembly having at least one control rod guide thimble and a top nozzle, said guide thimble including an upper end portion, said top nozzle including a lower adapter plate and an upper hold-down plate, said lower and upper plates having respectively an opening and passageway defined therethrough and aligned with one another, said opening in said lower plate receiving said guide thimble therethrough with its upper end portion extending above said lower plate and toward said passageway of said upper plate, an improved arrangement for mounting said top nozzle on said guide thimble, comprising: (a) alignment means extending between said plates and receiving said guide thimble upper end portion, said means at an upper end being inserted into said passageway of said upper hold-down plate and at a lower end resting on said adapter plate; and (b) complementary means formed on and interconnecting said alignment means and said guide thimble upper end portion so as to connect said alignment means and said guide thimble together, said complementary means including a primary interior annular groove formed on said alignment means and a primary exterior bulge formed on said guide thimble upper end portion and extending into said primary annular groove; (c) said complementary means further including a secondary interior annular groove formed on said alignment means at a location spaced below said primary annular groove, said secondary groove adapted to receive a secondary exterior bulge, being formed on said guide thimble upper end portion after severance of an upper segment of said guide thimble upper end portion containing said primary bulge followed by removal and receipt of said severed guide thimble upper end portion from and back in said alignment means, for reconnection of said alignment means and said severed guide thimble together; (d) said complementary means still further including a primary interior section on said alignment means which contains said primary annular groove and a secondary interior section on said alignment means which contains said secondary annular groove, said secondary section being disposed below said primary section and having an interior diameter larger than that of said primary section for facilitating receiving of said severed guide thimble upper end portion back into said alignment means for reconnection of said alignment means and said severed guide thimble together. a tertiary interior annular groove formed on said alignment means at a location spaced below said secondary annular groove, said tertiary groove adapted to receive a tertiary exterior bulge, being formed on said guide thimble upper end portion after a second severance of a second upper segment of said guide thimble upper end portion contianing said secondary bulge followed by removal and receipt of said twice severed guide thimble upper end portion from and back in said alignment means, for reconnection of said alignment means and said twice severed guide thimble together; and a tertiary interior section on said alignment means which contains said tertiary annular groove, said tertiary section being disposed below said secondary section and having an interior diameter larger than that of said secondary section for facilitating receiving of said twice severed guide thimble upper end portion back into said alignment means for reconnection of said alignment means and said twice severed guide thimble together. (a) alignment means extending between said plates, within said coil spring and receiving said guide thimble upper end portion, said means at an upper end being inserted into said passageway of said upper hold-down plate and at a lower end resting on said adapter plate in contact therewith but in an unattached relationship with respect thereto; (b) complementary means formed on and interconnecting said alignment means and said guide thimble upper end portion so as to connect said alignment means and said guide thimble together; and (c) an elongated shroud having a lower portion resting on said adapter plate in contact therewith but in an unattached relationship with respect thereto and underlying said coil spring and an upper portion extending along and surrounding a portion of said spring for protecting said spring from damage by coolant cross flow from adjacent fuel assemblies, said lower end of said alignment means and said lower portion of said shroud being interconnected together but unattached to said adapter plate. (a) a sleeve member including (b) complementary means formed on and interconnecting said inner alignment sleeve portion and said guide thimble upper end portion so as to connect said alignment sleeve portion and said guide thimble together, said complementary means including a primary interior annular groove formed on said alignment sleeve portion and a primary exterior bulge formed on said guide thimble upper end portion and extending into said primary annular groove. a primary interior section on said alignment sleeve portion which contains said primary annular groove; and a secondary interior section on said alignment sleeve portion which contains said secondary annular groove, said secondary section being disposed below said primary section and having an interior diameter larger than that of said primary section for facilitating receiving of said severed guide thimble upper end portion back into said alignment sleeve portion for reconnection of said alignment sleeve portion and said severed guide thimble together. a tertiary interior annular groove formed on said alignment sleeve portion at a location spaced below said secondary annular groove, said tertiary groove adapted to receive a tertiary exterior bulge, being formed on said guide thimble upper end portion after a second severance of a second upper segment of said guide thimble upper end portion containing said secondary bulge followed by removal and receipt of said twice severed guide thimble upper end portion from and back in said alignment sleeve portion, for reconnection of said alignment sleeve portion and said twice severed guide thimble together; and a tertiary interior section on said alignment sleeve portion which contains said tertiary annular groove, said tertiary section being disposed below said secondary section and having an interior diameter larger than that of said secondary section for facilitating receiving of said twice severed guide thimble upper end portion back into said alignment sleeve portion for reconnection of said alignment sleeve portion and said twice severed guide thimble together. (a) providing said sleeve with at least a pair of internal upper and lower annular grooves; (b) inserting said upper end portion of said guide thimble into said sleeve such that said upper end portion thereof extends adjacent said upper annular groove; (c) bulging an annular part of said guide thimble upper end portion outwardly into said upper annular groove in said alignment sleeve so as to connect said sleeve and guide thimble together; (d) circumferentially cutting said guide thimble upper end portion at a location below the level of its annular part bulged into said upper annular groove in said alignment sleeve and above the level of said lower annular groove in said alignment sleeve to sever an upper segment of said guide thimble upper end portion containing said bulged annular part from the remainder thereof; (e) removing said top nozzle, including said alignment sleeve with said upper guide thimble segment connected thereto, from said severed guide thimble upper end portion for facilitating reconstitution of said fuel assembly; (f) reinserting said severed upper end portion of said guide thimble into said sleeve such that said severed upper end portion thereof extends adjacent said lower annular groove; and (g) bulging another annular part of said severed guide thimble upper end portion outwardly into said lower annular groove in said alignment sleeve so as to connect said sleeve and guide thimble together. 2. The arrangement as recited in claim 1, wherein said complementary means further includes: 3. In a reconstitutable fuel assembly having at least one control rod guide thimble and a top nozzle, said guide thimble including an upper end portion, said top nozzle including a lower adapter plate and an upper hold-down plate, said lower and upper plates having respectively an opening and passageway defined therethrough and aligned with one another, said opening in said lower plate receiving said guide thimble therethrough with its upper end portion extending above said lower plate and toward said passageway of said upper plate, and a hold-down coil spring disposed about said guide thimble upper end portion and extending between said lower and upper plates for maintaining said upper plate in spaced relationship above said lower plate while allowing movement of said upper plate toward and away from said lower plate, an improved arrangement for mounting said top nozzle on said guide thimble, comprising: 4. In a reconstitutable fuel assembly having at least one control rod guide thimble and a top nozzle, said guide thimble including an upper end portion, said top nozzle including a lower adapter plate and an upper hold-down plate, said lower and upper plates having respectively an opening and passageway defined therethrough and aligned with one another, said opening in said lower plate receiving said guide thimble therethrough with its upper end portion extending above said lower plate and toward said passageway of said upper plate, a hold-down coil spring disposed about said guide thimble upper end portion and extending between said lower and upper plates for maintaining said upper plate in spaced relationship above said lower plate while allowing movement of said upper plate toward and away from said lower plate, means disposed between and interconnecting said lower and upper plates for defining the limits of movement of said plates toward and away from each other, an improved arrangement for attaching and detaching said top nozzle on and from said guide thimble, comprising: 5. The arrangement as recited in claim 4, wherein said complementary means further includes a secondary interior annular groove formed on said alignment sleeve portion at a location spaced below said primary annular groove, said secondary groove adapted to receive a secondary exterior bulge, being formed on said guide thimble upper end portion after severance of an upper segment of said guide thimble upper end portion containing said primary bulge followed by removal and receipt of said severed guide thimble upper end portion from and back in said alignment sleeve portion, for reconnection of said alignment sleeve portion and said severed guide thimble together. 6. The arrangement as recited in claim 5, wherein said complementary means also includes: 7. The arrangement as recited in claim 6, wherein said complementary means further includes: 8. In a method of making a nuclear fuel assembly reconstitutable, wherein said fuel assembly has at least one control rod guide thimble and a top nozzle, said guide thimble including an upper end portion, said top nozzle including a lower adapter plate and an upper hold-down plate, said lower and upper plates having respectively an opening and passageway defined therethrough and aligned with one another, said opening in said lower plate for receiving said guide thimble therethrough with its upper end portion extending above said lower plate and toward said passageway of said upper plate, and an alignment sleeve extending between said plates for receiving said guide thimble upper end portion, said sleeve at an upper end being inserted into said passageway of said upper hold-down plate and at a lower end resting on said adapter plate, said method comprising the steps of:
	abstract	Systems and methods for the conversion of energy of high-energy photons into electricity which utilize a series of materials with differing atomic charges to take advantage of the emission of a large multiplicity of electrons by a single high-energy photon via a cascade of Auger electron emissions. In one embodiment, a high-energy photon converter preferably includes a linearly layered nanometric-scaled wafer made up of layers of a first material sandwiched between layers of a second material having an atomic charge number differing from the atomic charge number of the first material. In other embodiments, the nanometric-scaled layers are configured in a tubular or shell-like configuration and/or include layers of a third insulator material.
	abstract	A method of wind turbine management includes receiving operational information on operational characteristics of a wind turbine. The operational information is analyzed based on a set of rules, and a determination is made as to whether a fault of the wind turbine is resettable. The set of rules may be configured based on operating configuration of the wind turbine. Advanced operational information may be received for conducting enhanced diagnostics and a determination is made as to whether a fault of the wind turbine is resettable.
	claims	1. An imaging system comprising:a detector configured to detect X-rays from an X-ray source and comprising a plurality of photodetector elements; andan anti-scatter grid disposed over the detector, wherein the anti-scatter grid comprises a plurality of radiation absorbing elements, at least a portion of one or more of the radiation absorbing elements of the plurality of radiation absorbing elements is disposed on each photodetector element, a total area of each respective portion of the one or more radiation absorbing elements disposed on each photodetector element is substantially equal, and each of the radiation absorbing elements is equally spaced apart relative to each other, wherein each photodetector element comprises a photosensing area, and at least some of the photosensing areas of the photodetector elements have different regions covered by the respective portion of the one or more radiation absorbing elements. 2. The imaging system of claim 1, wherein each of the photodetector elements comprise a substantially equal area. 3. The imaging system of claim 1, wherein the detector comprises a complementary metal-oxide semiconductor detector. 4. The imaging system of claim 1, wherein each of the radiation absorbing elements comprises a substantially equal width. 5. The imaging system of claim 1, wherein each photodetector element comprises an axis along a length or width of the photodetector element, and the respective portion of the one or more radiation absorbing elements disposed on each respective photodetector element is disposed at an angle relative to the axis, wherein the angle is greater than 0 degree and less than 180 degrees. 6. The imaging system of claim 5, wherein the plurality of photodetector element comprises a pixel pitch, and wherein a sum of a width of a single radiation absorbing element and a distance between adjacent radiation absorbing elements is less than the pixel pitch. 7. An imaging system comprising:a detector configured to detect X-rays from an X-ray source and comprising a plurality of photodetector elements having a pixel pitch p, wherein each photodetector element comprises an axis along a length or width of the photodetector element; andan anti-scatter grid disposed over the detector, wherein the anti-scatter grid comprises a plurality of radiation absorbing elements, at least a portion of one or more of the radiation absorbing elements of the plurality of radiation absorbing elements is disposed on each photodetector element, and a respective portion of the one or more radiation absorbing elements disposed on each respective photodetector element is disposed at an angle α relative to the axis, wherein the angle α is greater than 0 degree and less than 180 degrees, and the angle α is the same for each respective portion of the one or more radiation absorbing elements disposed on each respective photodetector element. 8. The imaging system of claim 7, wherein a sum of a width, d, of a single radiation absorbing element and a distance, D, between adjacent absorbing elements is less than the pixel pitch, p. 9. The imaging system of claim 8, wherein the pixel pitch, p, equals d × D cos ⁢ ⁢ α . 10. The imaging system of claim 8, wherein an area of a respective portion of the one or more radiation absorbing elements disposed on each respective photodetector element is equal to p × d cos ⁢ ⁢ α . 11. The imaging system of claim 10, wherein the area of each respective portion of the one or more radiation absorbing elements disposed on each photodetector element is substantially equal. 12. The imaging system of claim 7, wherein each photodetector element comprises a photosensing area, and at least some of the photosensing areas of the photodetector elements have different regions covered by a respective portion of the one or more radiation absorbing elements. 13. The imaging system of claim 7, wherein each of the photodetector elements comprise a substantially equal area. 14. The imaging system of claim 7, wherein the detector comprises a complementary metal-oxide semiconductor detector. 15. The imaging system of claim 7, wherein each of the radiation absorbing elements comprises an equal width. 16. The imaging system of claim 7, wherein each of the radiation absorbing elements is equally spaced apart relative to each other. 17. A method for assembling an X-ray detector comprising:providing a detector configured to detect X-rays from an X-ray source, wherein the detector comprises a plurality of photodetector elements having a pixel pitch p, wherein each photodetector element comprises an axis along a length or width of the photodetector element; anddisposing an anti-scatter grid over the detector at an angle α , wherein the anti-scatter grid comprises a plurality of radiation absorbing elements, at least a portion of one or more of the radiation absorbing elements of the plurality of radiation absorbing elements is disposed on each photodetector element, and a respective portion of the one or more radiation absorbing elements disposed on each respective photodetector element is disposed at the angle α relative to the axis, wherein the angle α is greater than 0 degree and less than 180 degrees, and the angle α is the same for each respective portion of the one or more radiation absorbing elements disposed on each respective photodetector element. 18. The method of claim 17, wherein a sum of a width, d, of a single radiation absorbing element and a distance, D, between adjacent absorbing elements is less than the pixel pitch, p. 19. The method of claim 18, wherein the pixel pitch, p, equals d × D cos ⁢ ⁢ α . 20. The method of claim 18, wherein an area of a respective portion of the one or more radiation absorbing elements disposed on each respective photodetector element is equal to p × d cos ⁢ ⁢ α . 21. The method of claim 17, wherein each photodetector element comprises a photosensing area, and at least some of the photosensing areas of the photodetector elements have different regions covered by a respective portion of the one or more radiation absorbing elements. 22. The method of claim 17, wherein each of the radiation absorbing elements comprises a substantially equal width. 23. The method of claim 17, wherein each of the radiation absorbing elements is equally spaced apart relative to each other.
052316548	summary	CROSS REFERENCE TO RELATED APPLICATIONS This application is related to the application of C. Y. Wei, R. F. Kwasnick, and G. E. Possin entitled "X-ray Collimator," Ser. No. 07/802,789, filed concurrently with this application, and assigned to the assignee of the present application. FIELD OF THE INVENTION This invention relates generally to radiation imagers, and in particular to focused collimators used in conjunction with radiation detection equipment. BACKGROUND OF THE INVENTION Collimators are used in a wide variety of equipment in which it is desired to permit only beams of radiation emanating along a particular path to pass beyond a selected point or plane. Collimators are frequently used in radiation imagers to ensure that only radiation beams emanating along a direct path from the known radiation source strike the detector, thereby minimizing detection of beams of scattered or secondary radiation. Collimator design affects the field-of-view, spatial resolution, and sensitivity of the imaging system. Particularly in radiation imagers used for medical diagnostic analysis or for non-destructive evaluation procedures, it is important that only radiation emitted from a known source and passing along a direct path from that source through the subject under examination be detected and processed by the imaging equipment. If the detector is struck by undesired radiation, i.e., radiation passing along non-direct paths to the detector, such as rays that have been scattered or generated in secondary reactions in the object under examination, performance of the imaging system is degraded. Performance is degraded by lessened spatial resolution and lessened energy resolution that result from noise in the signal processing circuits generated by the detection of the scattered or secondary radiation rays. Collimators are positioned to substantially absorb the undesired radiation before it reaches the detector. The collimator comprises a relatively high atomic number material placed so that radiation approaching the detector along a path other than one directly from the known radiation source strikes the body of the collimator and is absorbed before being able to strike the detector. In a typical detector system, the collimator includes barriers extending outwardly from the detector surface in the direction of the radiation source so as to form channels through which the radiation must pass in order to strike the detector surface. Some radiation imaging systems, such as computerized tomography (CT) systems used in medical diagnostic work, use a point (i.e. a relatively small, such as 1 mm in diameter or smaller) source of x-ray radiation to expose the subject under examination. The radiation passes through the subject and strikes a radiation detector positioned on the side of the subject opposite the radiation source. In a CT system the radiation detector typically comprises a number of one-dimensional arrays of detector elements. Each array is disposed on a flat panel or module, and the flat panels are typically arranged end to end along a curved surface to form a radiation detector arm. The distance to a given position on any of the separate panels, typically the center of the panel, on any one of the separate panels is the same, i.e., each panel is at substantially the same radius from the radiation source. On any given panel there is a difference from one end of the panel to the other in the angle of incidence of the radiation beams arriving from the point source. In any system using a "point source" of radiation and flat panels or modules of detector elements, some of the radiation beams that are desired to be detected, i.e., ones emanating directly from the radiation source to the detector surface, strike the detector surface at some angle offset from vertical. For example, in a common medical CT device, the detector is made up of a number of panels, each of which has dimensions of about 32 mm by 16 mm, positioned along a curved surface having a radius of about 1 meter from the radiation point source. Each panel has about 16 separate detector elements about 32 mm long by 1 mm wide arranged in a one-dimensional array, with collimator plates situated between the elements and extending outwardly from the panel to a height above the surface of the panel of about 8 mm. As the conventional CT device uses only a one-dimensional array (i.e., the detector elements are aligned along only one row or axis), the collimator plates need only be placed along one axis, between each adjoining detector element. Even in an arrangement with a panel of sixteen 1 mm-wide detector elements adjoining one another (making the panel about 16 mm across), if the collimator plates extend perpendicularly to the detector surface, there can be significant "shadowing" of the detector element by the collimator plates towards the ends of the panel. This shadowing results from some of the beams of incident radiation arriving along a path such that they strike the collimator before reaching the detector surface. Even in small arrays as mentioned above (i.e. detector panels about 16 mm across), when the source is about 1 meter from the panel with the panel positioned with respect to the point source so that a ray from the source strikes the middle of the panel at right angles, over 7.5% of the area of the end detector elements is shadowed by collimator plates that extend 8 mm vertically from the detector surface. Even shadowing of this extent can cause significant degradation in imager performance as it results in nonuniformity in the x-ray intensity and spectral distribution across the detector module. In the onedimensional array, the collimator plates can be adjusted slightly from the vertical to compensate for this variance in the angle of incidence of the radiation from the point source. Advanced CT technology, however, requires use of two-dimensional arrays, i.e., arrays of detector elements on each panel that are arranged in rows and columns. In such an array, a collimator must separate each detector element along both axes of the array. The radiation vectors from the point source to each detector on the array have different orientations, varying both in magnitude of the angle and direction of offset from the center of the array. Setting up collimator plates along two axes between each of the detector elements in two dimensional arrays would be extremely time consuming and difficult. Additionally, arrays larger than the one dimensional array discussed above may be advantageously used in imaging applications. As the length of any one panel supporting detector elements increases, the problem of the collimator structure shadowing large areas of the detector surface becomes more important. Accordingly, one object of the present invention is to provide a highly focused collimator for use in imagers having point radiation sources and an efficient method to readily fabricate such a collimator. Another object is to provide a readily-fabricated collimator for use with two-dimensional detector arrays in conjunction with a point radiation source. SUMMARY OF THE INVENTION In a radiation detecting system in which the radiation desired to be detected is emitted from a single point source, a collimator is provided which has channels that allow radiation emanating along a direct path from the point source to pass through to underlying radiation detectors while substantially all other radiation beams striking the collimator are absorbed. The axis of each channel has a selected orientation angle so that it is substantially aligned with the direct beam path between the radiation point source and the underlying radiation detector element. The sidewalls of the collimator are substantially smoothly shaped with a uniform slope and the channels preferably have a cross-sectional shape that corresponds to the shape of the adjoining detector element. The collimator body comprises at least one substrate made of a photosensitive material, the surfaces of which are coated with a radiation absorbent material. The radiation absorbent material is selected to absorb radiation of the energy level and wavelength emitted by the radiation source and typically comprises a material having a relatively large atomic number (i.e., about 72 or larger). The collimator body may be formed from two or more collimator substrates joined together so that the passages in each substrate are aligned to form channels through the assembled device that have the desired selected orientation angle. Such a collimator is advantageously used in an x-ray imager having a two-dimensional radiation detector array. A method of forming a collimator is also provided, including the steps of forming a mask corresponding to the pattern of radiation detector elements; exposing the photosensitive substrate through the mask to light beams passing along paths corresponding to those taken by light emitted from a point source, the light beams exposing the photosensitive substrate at respective selected orientation angles; etching the photosensitive material to form channels having the selected orientation angle; and coating the photosensitive collimator substrate with a radiation absorbent material.
044902875	claims	1. A process for the treatment of a substance contained in an aqueous solution or slurry containing radioactive waste whereby the substance is incorporated in a glass-like or ceramic material, which comprises: subjecting the solution or slurry containing radioactive waste to the influence of microwave radiation in a fluidized bed to dry the solution or slurry and thereby produce a fusible dried product; feeding particles of glass-formers to said fluidized bed to produce product particles of glass-formers coated with the fusible dried product formed from said solution or slurry containing the radioactive waste; scrubbing off-gases from the fluidized bed to remove dust by counter-currently contacting said off-gases with said particles entering the fluidized bed; heating said product particles to fuse them; and cooling the fused product particles to produce a glass-like or ceramic material comprising said substance. 2. A process according to claim 1 wherein said waste comprises a metal compound selected from the group consisting of nitrates and carbonates. 3. A process according to claim 2 wherein said metal compound is radioactive. 4. A process according to claim 1 wherein said radioactive waste comprises a member selected from the group consisting of uranium, transuranium elements, fission products, elements resulting from nuclear fuel reprocessing, and magnesium. 5. A process according to claim 1 wherein said fusing of said fusible dried product is effected by heating said fusible dried product with microwaves. 6. A process according to claim 1 wherein said glass-forming compound is present in said solution or slurry. 7. A process according to claim 1 wherein said fusible dried product comprises a glass-forming or ceramic forming material and wherein said glass-forming or ceramic-forming component comprises said material.
039895890	summary	BACKGROUND OF THE INVENTION 1. Field of the Invention: This invention pertains to control mechanisms for nuclear reactors, and more particularly to hydraulically operated drive mechanisms for a control rod having a positive mechanical latch arrangement for holding the control rod in a withdrawn position. 2. Description of the Prior Art: In accordance with the prior art, certain power reactors are controlled by a combination of chemical shim systems and rod cluster control systems. In pressurized water reactors of the type exemplified, the chemical shim system typically consists of adding boric acid to the reactor coolant. Boric acid has the effect of lowering the effective multiplication factor of the nuclear core to slightly above 1.0 so that the nuclear chain reaction is just capable of maintaining itself and does not become supercritical. There is significantly more boric acid present in the reactor coolant at beginning of core life than at the end of core life due to the differing amounts of fissile material present in the core during those times, respectively. Conceivably a pressurized water nuclear reactor may be completely controlled with a chemical shim system; however, the time factor involved in changing the concentration of boric acid makes this method of control impractical. As a result, a boric acid chemical shim is usually assisted by a rod cluster control system which permits rapid changes in reactivity of the nuclear core. The rod system is a mechanical system which generally comprises 16 to 20 control or neutron absorbing rods situated to be moved axially within cooperating guide tubes in selected fuel assemblies of the core. In the earlier prior art, all of the control rods associated with each of the fuel assemblies were attached to a single spider-like hub which in turn was attached to a drive shaft. Thus, all of the control rods were operated simultaneously and because of the relatively large worth of a single control rod assembly, the control rods were operated in discrete steps over the entire distance of travel. As indicated and explained in detail in U.S. Pat. No. 3,519,535 issued July 7, 1970 to Erling Frisch and Harry Andrews, A Nuclear Reactor, and assigned to the assignee of the present invention, reactors utilizing rod control systems or other incrementally movable control elements have several limiting characteristics. The worth of each control cluster is too great to be used for suppressing radial flux peaks. Partial insertion of a cluster can cause sever perturbations in the axial flux distribution and can lead to xenon cycling. As further explained in pending application Ser. No. 53,206, filed July 8, 1970 of E. Frisch and H. Andrews, Reactor Refueling Method, now Pat. No. 3,775,246 granted Nov. 27, 1973, and assigned to the present assignee, an optimum control system would accordingly have two primary characteristics. A wide disposal of individually movable low worth absorber rods; and no control configuration wherein certain control rods are partially inserted. Such a control system would result in appreciable savings due to more efficient usage of nuclear fuel. In this regard, a highly reliable drive mechanism which is capable of positioning a plurality of two position control elements is necessary to render such a desirable control system practical. A relatively large number of drive mechanisms would, however, be necessary; further, they must not be so large that they cannot be mounted side by side on a reactor vessel. A prior art solution to these problems is disclosed in U.S. Pat. No. 3,607,629 issued Sept. 21, 1971 by E. Frisch et al, Drive Mechanism For Control Elements, and assigned to the present assignee. The most recent prior art then, discloses a hydraulic control rod drive mechanism which utilizes the substantial pressure available in pressurized reactors to move the absorber or control rods relative to stationary fuel assemblies with which they are associated. The hydraulic mechanism allows independent movement of individual control rod drive shafts having one or more absorber rods attached thereto, to be fully withdrawn from or fully inserted into the core. Each mechanism has provision to accommodate a multiplicity of control rod drive shafts. A number of electromagnets are mounted to the hydraulic mechanism; one electromagnet being associated with each control rod drive shaft. A fully withdrawn control rod is held in this position by actuation of the respective electromagnet. Thus, in the prior art a mechanism is disclosed which allows a reactor to be controlled by a large and diverse pattern of low worth two position control rods and therefore to more nearly achieve the full potential of its fissile fuel. Even with these most recent developments, in the prior art, namely, hydraulic control rod drive mechanisms, the method of operation for full length control rods is, however, not considered satisfactory for part length control rods which are also required in today's large nuclear reactors. Part length control rods are utilized to trim the axial power distribution of the core and to prevent divergence of the xenon cycling within the core. In a typical large nuclear reactor, eight part length control rod assemblies each containing 20 individual control rods are interspersed throughout the core. For purposes of comparison, the same reactor example would also use 53 full length control rod assemblies, with each assembly containing 20 individual control rods. A part length control rod contains absorber material only in the lower part of its length. For example, in the same large reactor previously illustrated, the lower three feet of a control rod having a total length of twelve feet contains neutron absorbing material. Withdrawal of a part length control rod moves the absorber section from the lower to the upper part of the core and is therefore not totally removed or withdrawn from the core as is the case with the regular control rods. Tripping or rapidly inserting a part length control rod may actually increase core reactivity. Simultaneous tripping of several part length control rods may then result in an undesirable increase in reactor power level even though all full length control rods are tripped at the same time. Such an event is a distinct possibility in the prior art in reactors equipped with hydraulically operated control rod drive mechanisms by accidental deenergizing of an electromagnet holding coil bus. SUMMARY OF THE INVENTION The aforementioned problems of the prior art are overcome by providing a nuclear reactor having hydraulically operated control rod mechanisms wherein individual part length control rods are either fully inserted or fully withdrawn, and, while in the latter position, are retained by a positive mechanical latch arrangement. In an exemplary embodiment, the present invention utilizes a differential pressure to drive a piston which is connected to a control rod drive shaft having one or more individual part length control rods connected thereto. To withdraw a control rod, an electromagnetic valve is actuated which exposes one side of the piston to a variable source of pressure which is lower than the high constant pressure available in pressurized reactors and to which the other end of the piston is exposed. A single hydraulic control rod mechanism is capable of acting upon a multiplicity of control rod drive shafts, either singly or in concert. The part length control rod assemblies are retained in a fully withdrawn position by the mechanical engagement of coacting members; one engaging member being attached to the piston of a control rod drive shaft, and the other being integral with a latch mechanism provided within the control rod drive mechanism. When the piston is lifted by application of differential hydraulic pressure, the engaging member attached to the piston momentarily pushes aside and then engages the other engaging member. Insertion of a part length control rod is accomplished by actuating an electromagnet which disengages the latch mechanism and allows the control rod assembly to drop by gravity. On withdrawal, a control rod is smoothly decelerated from a relatively high velocity by a decelerating device before the engaging members impart. An envisioned decelerating device comprises a localized restriction in the cylinder wall located within the housing of the drive mechanism. When the piston reaches this restriction, the water trapped above the piston, is forced through the restriction creating a considerable over-pressure which slows down the movement of the piston. The combination of the above enumerated features constitutes a nuclear reactor which is controlled by a large and diverse pattern of low worth two position part length control elements and provides a latching means which positively holds the part length control rod in a withdrawn position .
	claims	1. An x-ray collimator comprising:a first subassembly with a first plurality of adjacent apertures with each of said adjacent apertures corresponding to a single selected x-ray focal spot of a plurality of x-ray focal spots reducing leakage of x-ray radiation through apertures other than said aperture corresponding to said single selected x-ray focal spot; anda second subassembly positioned between said first subassembly and an imaging object reducing amount of said x-ray radiation striking outside an x-ray detector, said second subassembly with a second plurality of apertures corresponding to said first plurality of apertures and said plurality of x-ray focal spots wherein entrances of said second plurality of apertures is smaller than exits of said second plurality of apertures and wherein size of said second plurality of apertures linearly increase through thickness of said second subassembly from smallest at said entrances of said second plurality of apertures to largest at said exits of said second plurality of apertures. 2. The x-ray collimator of claim 1 wherein said first subassembly is made from a material with an atomic number of at least 39. 3. The x-ray collimator of claim 1 wherein said first subassembly is made from a material with a value of Young's modulus of at least 200 GPa. 4. The x-ray collimator of claim 1 wherein said first subassembly is made from tungsten. 5. The x-ray collimator of claim 1 wherein said first subassembly is made from lead. 6. The x-ray collimator of claim 1 wherein said first subassembly further comprises material sheets with thickness of at least 0.5 millimeters. 7. The x-ray collimator of claim 1 wherein thickness of said first subassembly is at least 1 millimeter. 8. The x-ray collimator of claim 1 wherein said second subassembly further comprises material sheets with thickness of at least 0.5 millimeters. 9. The x-ray collimator of claim 8 wherein said second subassembly further comprises an air gap of at least 0.5 millimeters between said material sheets. 10. The x-ray collimator of claim 1 wherein said second subassembly is made from a material with an atomic number greater than 10 and less than 39. 11. The x-ray collimator of claim 1 wherein said second subassembly is made from a material with relative magnetic permeability of at least 10,000. 12. The x-ray collimator of claim 1 wherein said second subassembly is made from mu-metal. 13. The x-ray collimator of claim 1 wherein said second subassembly is made from brass. 14. The x-ray collimator of claim 1 wherein said second subassembly is made from steel. 15. The x-ray collimator of claim 1 wherein thickness of said second subassembly is at least 5 millimeters. 16. The x-ray collimator of claim 1 further comprising:a third subassembly positioned between said first subassembly and an x-ray source, said third subassembly with a third plurality of apertures and a thickness of at least 0.5 millimeters and made from a material with an element having an atomic number of at least 39. 17. The x-ray collimator of claim 1 further comprising:a fourth subassembly positioned between said second subassembly and said x-ray detector, said fourth subassembly with a fourth plurality of apertures and a thickness of at least 1 millimeter and made from a material with an element having an atomic number of at least 39. 18. The x-ray collimator of claim 17 wherein said fourth subassembly is separated from said second subassembly by an air gap of at least 0.5 millimeters. 19. A x-ray collimator of claim 17 wherein entrances of said fourth plurality of apertures is smaller than exits of said fourth plurality of apertures. 20. The x-ray collimator of claim 1 further comprising:a fourth subassembly positioned between said second subassembly and said x-ray detector, said fourth subassembly with a fourth plurality of apertures and a thickness of at least 1 millimeter and made from a material with an element having an atomic number greater than 10 and less than 39.
	abstract	A fault detector for detecting valve movement of a valve in a fuel injector of an engine system, the valve includes an electromagnetic actuator arranged to move the valve between first and second valve positions, the engine system includes a sensor for sensing a current through the actuator. The detector includes a controller arranged to control the sensor; receive sensor data related to the current through the actuator; analyze the received data for current discontinuities; and output a valve movement signal dependent upon the current discontinuities. The controller is arranged to sense current during a finite sampling window, move the sampling window from a first window position to a later window position for one or more subsequent injection events; determine a new sampling window position on based a valve movement signal output the two preceding windows; and feedback the new sampling window position for a subsequent injection event.
	description	This application claims the benefit of U.S. Provisional Application No. 62/681,731 filed Jun. 7, 2018, which is incorporated herein by reference in its entirety. The present invention relates generally to casks used to transport and store spent nuclear fuel created by nuclear generating plants or other facilities. In the operation of nuclear reactors, the nuclear energy source is in the form of hollow zircaloy tubes filled with enriched uranium, collectively arranged in assemblages referred to as fuel assemblies. When the energy in the fuel assembly has been depleted to a certain predetermined level, the fuel assembly is removed from the nuclear reactor. The standard structure used to package used or spent fuel assemblies discharged from light water reactors for off-site shipment or on-site dry storage is known as the fuel basket. The fuel basket is essentially an assemblage of prismatic storage cells each of which is sized to store one fuel assembly that comprises a plurality of individual spent nuclear fuel rods. The fuel basket is arranged inside a metallic storage canister which is placed into a ventilated outer overpack or cask for safe transport or storage of the multiple spent fuel assemblies within the inner fuel basket. The spent nuclear fuel (“SNF”) in the fuel assemblies is still highly radioactive and produces considerable heat which must be dissipated, in addition to concomitantly emitting dangerous ionizing neutron and gamma photons (i.e. neutron and gamma radiation) requiring protective shielding. Thus, caution must be exercised when the fuel assemblies are handled, transported, packaged and stored. Neutron radiation may be effectively attenuated with metallic and polymeric shielding materials typically containing boron. These boron-containing materials however are not effective at attenuating and shielding gamma radiation emitted from the fuel baskets. Effective gamma radiation shielding requires very dense materials, such as lead or others. A typical transfer cask features a main body designed to structurally protect the spent nuclear fuel stored in the fuel canister inside it. A common configuration consists of concentrically arranged steel shells filled with lead. Such a cask body made with high-density conductive materials has excellent heat conduction and gamma radiation shielding capabilities, but unfortunately possesses a relatively modest neutron capture capability. For capturing neutrons, a hydrogenous material is needed which is generally provided by a jacket filled with water or a solid resinous material integrally and permanently joined to the main cask body. This traditional transfer cask design suffers from several drawbacks which makes it marginal or unsuitable for loading canisters with high decay heat generation rates (i.e., in excess of 40 kW), in locations where the crane capacity is less than what is typically needed to load such a heavy transfer cask with inserted canister, or where the facility's cask loading area dimensions or spatial constraints prevent the placement of a traditional large-sized high-capacity transfer cask. Improvements in the traditional transfer cask design to extend the applicability and versatility of transfer casks which overcomes the foregoing crane capacity and spatial constraint situations noted above are desired. The present application provides a unique multi-component transfer cask comprised of two detachably coupled and separable nested containers. The transfer cask according to the present disclosure primarily comprises an outer neutron shield container or cylinder (NSC) and inner gamma blocker container or cylinder (GBC) removably insertable into the NSC. Unlike traditional transfer casks in which the neutron shielding material may be permanently incorporated with the gamma blocking material in the cask body, the present two-component transfer cask system with non-permanently mounted and separable GBC allows the spent fuel canister cask loading operations to be staged in a particular manner which can be accomplished within limited spatial constraints of the cask loading area (e.g. spent fuel pool) and within limited crane lifting capacities in situations where applicable. Otherwise, the weight of the fuel canister must be reduced by inserted fewer spent fuel assemblies than the full storage capacity of the canister which is inefficient and costly as more canisters must be employed. The main body of the inner GBC of the transfer cask has a gamma radiation blocking composition that is preferably comprised of high density and high thermal conductivity materials such as steel, lead, or copper to block gamma radiation which are effective at blocking gamma radiation and in combination to provide structural integrity to the cylinder. The shell of the GBC is thus constructed of materials having a higher thermal conductivity than the shell of the NSC whose role is to shield neutron radiation requiring generally different typically less dense materials with lower thermal conductivity properties for neutron shielding. The GBC main body has a cylindrical cavity which encloses and supports the nuclear spent fuel canister. The transfer cask has suitably sized flanges or other structural connections or elements to secure the NSC thereto. The GBC can be of non-cylindrical external profile in some embodiments to comport with the architecture of the cask loading area in the spent fuel pool where the GBC is staged for fuel loading. In one embodiment, the shell of the GBC has a cylindrical shape with circular transverse cross section. The outer NSC of the transfer cask serves the function of attenuating and absorbing (i.e., shielding) the neutrons emitted by the used fuel inside the canister and GBC. The NSC therefore has a solid or liquid neutron radiation blocking composition which may contain boron for neutron moderation. While it may also provide supplemental gamma shielding, its primary function is to provide shielding of neutrons. The NSC is separated from the cask's GBC main body at such times where the NSC's weight may exceed the available nuclear facility crane's lifting capacity, or its size may restrict loading operations in the facility's cask loading area (i.e., spent fuel pool) due to spatial constraints. The water-filled fuel canister with spent fuel assembly therein may be loaded into the GBC while submerged in the fuel pool. At the earliest convenient opportunity, following removal of the GBC from the cask loading area (with canister therein), the GBC and NSC are mated. At the time of the GBC removal from the spent fuel pool, the water filled in the fuel canister provides the neutron shielding until placement of the GBC in the outer NSC. The lighter lift weight of GBC and loaded water-filled fuel canister (without the NSC) is advantageously within the allowable crane capacity. When the operations in the cask loading area of the spent fuel pool are complete, the GBC is set down and the NSC and GBC are mated and coupled together as further described herein. The transfer cask assembly, now comprising the GBC and NSC, has the requisite shielding for the spent nuclear fuel in the canister to commence with traditional canister closure and transfer operations. Preferably, the NSC is installed prior to the dewatering of the canister in the GBC to assure no lapse in neutron shielding. Prior to lifting the transfer cask, now including the GBC, canister, and NSC, the canister preferably has been dewatered to reduce its overall lift weight to within the capacity of the crane (or other lifting device such as the cask, vertical transporter vehicle). With the NSC in place, there is no longer a need for the neutron protection afforded by the water inside the canister. The principal means of heat rejection in the two-piece transfer cask according to the present disclosure is the natural convective air flow ventilation action in a circumferentially and vertically extending air ventilation annulus formed between the GBC and NSC. The cooling air circulation is naturally driven and induced by the hot exterior surface of the GBC heated by decay heat emitting by the spent fuel assemblies in the canister located inside the GBC. The annulus extends for substantially the entire height of the cask having a bottom air inlet opening and top air outlet openings. The heat rejection may further be boosted and enhanced by providing an open and ventilated annular space inside the GBC at the canister-to-GBC interface for on-demand ventilation capacity. For optimal thermal and ALARA performance, the ability to keep this secondary inner annulus filled with water for additional neutron shielding when needed, or alternatively air ventilated at times for additional heat rejection is desirable during different stages of the spent fuel loading and transfer process. This drainable canister-to-GBC annular space is also valuable if it is desired to cool the canister more efficiently by spraying of the canister lid with cooling water to remove excess heat in some situations. The spray may be gravity fed and flows over and around the canister through the annular space for maximum reliability to protect the structural integrity of the canister and fuel assemblies therein. Calculations show that the spray mode can keep the water in the water-filled canister from boiling for an indefinite period which is critically important to deal with the scenario where a fuel bearing canister must remain water filled for an extended period of time such as for neutron shielding. The coupling arrangement between the separable NSC and GBC is unique and compensates for differential thermal expansion between these two cylinders. The inner GBC has a top mounting flange which is rigidly and detachably coupled to a top flange of the outer NSC such that the inner GBC is suspended and supported via the coupled flanges at the top in a cantilevered manner. In one preferred embodiment, there is no other rigid coupling engagement between the NSC and GBC below the coupled top flanges. Advantageously, this allows the hotter body of inner GBC (heated by decay nuclear fuel heat emitted from the canister inside the GBC) to thermally grow and expand vertically downwards in length from the coupled flanges to a greater degree than the relatively cooler outer NSC which is exposed to natural ambient cooling air. This avoids the formation of cracks between the GBC and NSC due to differential thermal expansion. In one embodiment, the two flanged may be bolted together by a plurality of threaded fasteners. In one aspect, a separable multi-component cask for spent nuclear fuel transport and storage comprises: a vertical longitudinal axis; a vertically elongated first cylinder having a neutron radiation shielding composition, the first cylinder defining a first cavity extending along the longitudinal axis; a vertically elongated second cylinder having a gamma radiation blocking composition, the second cylinder defining a second cavity extending along the longitudinal axis and configured to hold a spent nuclear fuel canister; the second cylinder detachably mounted inside the first cavity of the first cylinder; and an air ventilation annulus formed between the first and second cylinders, the air ventilation annulus defining a heat removal passage to remove heat emitted by the canister when placed inside the second cylinder. In one aspect, a multi-component transfer cask system for storage and transport of spent nuclear fuel comprises: a vertical longitudinal axis; a vertically elongated outer container having a neutron radiation shielding composition, the outer container comprising a top end including an annular top flange, a bottom end, and a cylindrical sidewall extending between the ends and defining a first cavity; a vertically elongated inner container having a gamma radiation blocking composition, the inner container comprising a top end including an annular mounting flange, a bottom end, and a sidewall extending between the ends and defining a second cavity configured to hold a spent nuclear fuel canister; the mounting flange of the inner container detachably coupled to the top flange of the outer the outer container such that the inner container is suspended and supported via the coupled flanges in a cantilevered manner; wherein the inner container is axially and slideably separable from the outer container. The suspended and cantilevered mounting of the inner container allows the container which is directly heated by a spent nuclear fuel canister when placed therein to grow at a higher differential thermal expansion rate than the cooler outer container, thereby avoiding thermal expansion cracking between the two containers. In one aspect, a method for transferring and transporting spent nuclear fuel comprises: providing a nuclear fuel transport cask comprising an outer neutron shield cylinder having an internal first cavity and an inner gamma block cylinder having an internal second cavity, the gamma block cylinder detachably coupled to and nested inside the first cavity of the neutron shield cylinder; separating the gamma block cylinder from the neutron shield cylinder; placing the gamma block cylinder on a support surface; loading a plurality of spent nuclear fuel assembles into the second cavity of the gamma block cylinder; lifting the gamma block cylinder over the neutron shield cylinder; and inserting the gamma block cylinder and fuel canister assembly into the neutron shield cylinder. Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. All drawings are schematic and not necessarily to scale. Features shown numbered in certain figures are the same features which may appear un-numbered in other figures unless noted otherwise herein. The features and benefits of the invention are illustrated and described herein by reference to exemplary embodiments. This description of exemplary embodiments is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description. Accordingly, the disclosure expressly should not be limited to such exemplary embodiments illustrating some possible non-limiting combination of features that may exist alone or in other combinations of features. In the description of embodiments disclosed herein, any reference to direction or orientation is merely intended for convenience of description and is not intended in any way to limit the scope of the present invention. Relative terms such as “lower,” “upper,” “horizontal,” “vertical,”, “above,” “below,” “up,” “down,” “top” and “bottom” as well as derivatives thereof (e.g., “horizontally,” “downwardly,” “upwardly,” etc.) should be construed to refer to the orientation as then described or as shown in the drawing under discussion. These relative terms are for convenience of description only and do not require that the apparatus be constructed or operated in a particular orientation. Terms such as “attached,” “affixed,” “connected,” “coupled,” “interconnected,” and similar refer to a relationship wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both movable or rigid attachments or relationships, unless expressly described otherwise. As used throughout, any ranges disclosed herein are used as shorthand for describing each and every value that is within the range. Any value within the range can be selected as the terminus of the range. In addition, all references cited herein are hereby incorporated by reference in their entireties. In the event of a conflict in a definition in the present disclosure and that of a cited reference, the present disclosure controls. FIGS. 1-13 depict a system for storing and transporting radioactive spent nuclear fuel comprising a cask 20. Cask 20 is vertically elongated defining a vertical longitudinal axis LA and includes outer neutron shield cylinder 21 (NSC) and inner gamma blocker cylinder 40 (GBC) detachably and removably positioned and inserted inside the outer cylinder. These cylinders may be variously referred to herein by their abbreviations/acronyms, full names, or simply inner and outer cylinders. Outer NSC 21 has an elongated body including a top end 22, a bottom end 23, cylindrical sidewall 24 extending between the ends, and an internal cavity 25. Cavity 25 extends completely through the cylinder 21 along the longitudinal axis from the top to bottom end. Cylinder 21 includes an interior surface 30 and opposing exterior surface 30. NSC 21 may be comprised of a single long cylinder body, or alternatively may be formed by a plurality of axially aligned and vertically stacked cylinder segments seal welded together at the joints between the segments to collectively form the cylinder body The bottom end 23 of neutron shield cylinder 21 may include a gusseted annular radial bottom support flange 26 for support of the NSC and stiffening of the sidewall 24 of the cylinder. The flange 26 may extend radially/laterally completely from the interior surface 30 of cylinder to the outer exposed exterior surface 31 in one non-limiting embodiment (see, e.g. FIG. 7). The flange 26 is configured and arranged to engage a platform 73 surrounding a receptacle 74 of a self-propelled wheeled or tracked vertical cask transport vehicle or crawler 75 used to transport the fully loaded cask 20 with loaded fuel canister, GBC, and NSC (represented schematically in FIGS. 13 and 14). Such cask transporters are well known in the art and commercially available from manufacturers such as Enerpac Heavy Lifting Technology and others. When the inner gamma block cylinder 40 loaded with a fuel canister 60 is mounted inside the outer NSC 21, the bottom end of the GBC projects downwards below support flange 26 into the upwardly open receptacle 74 and may not engage any structural surface of the transport vehicle for support. Accordingly, the bottom support flange 26 of the outer NSC supports the entire weight of the cask 20 and spent fuel therein. The top end 22 of the cylinder 21 may include an annular radial top flange 27 defining an upwardly open top recess 28. The flange 27 is configured to form a vertically-extending annular lip 27-1 extending circumferentially around the top end of the cylinder 21. In one embodiment, the flange 27 may be formed by an L-shaped metallic structural angle comprising a horizontal section 27-2 and adjoining vertical section which defines the annular lip 27-1 that defines a perimeter of the flange (see, e.g. FIG. 6). Both the top and bottom flanges 26 and 27 are rigidly coupled to the sidewall 24 of the neutron shield cylinder 21 such as via seal welding. Each flange 26, 27 may further protrude radially outward beyond the sidewall 24 of neutron shield cylinder 21 as shown in one non-limiting embodiment. In one embodiment, the top end 22 of the outer neutron shield cylinder 21 may be castellated in configuration including a plurality of castellations formed by raised spacer blocks 29 disposed in the top recess 28 of the cylinder created by top mounting flange 27 (see, e.g. FIG. 4). The spacer blocks 29 extend vertically upwards from a planar upward facing surface 27-1 of the top flange 27. Spacer blocks 29 may be rectangular or square cuboid in shape. Blocks 29 may be circumferentially spaced apart on the top flange 27 at preferably regular intervals in one embodiment to uniformly engage the mounting flange 70 of the inner gamma blocking cylinder 40 and support the cylinder, as further described herein. In one embodiment, the neutron shield cylinder 21 may have a composite wall construction including an inner cylindrical shell 33 and outer cylindrical shell 32 with a neutron attenuation shielding media 35 sandwiched therebetween (best shown in FIG. 7). The shells may be formed of a suitable metal of sufficient structural strength and thickness such as without limitation stainless steel for corrosion protection. The neutron shielding media 35 may be a boron-containing material for neutron attenuation. In one embodiment, the neutron shielding may be a solid material such as Holtite™ available from Holtec International of Camden, N.J. which is formulation comprising hydrogen rich polymer impregnated with uniformly dispersed boron carbide particles. Other boron containing materials may be used. In other embodiments, the neutron shielding media 35 may be liquid such as water containing boric acid. In either the case of a solid or liquid neutron shielding media, the media may be completely enclosed or encased between the walls 32, 33 and the top and bottom flanges 27, 26 of cylinder 21 as shown. The inner gamma blocking cylinder 40 will now be further described. Referring generally to FIGS. 1-13, the inner cylinder 40 has an elongated body including a top end 41, a bottom end 42, sidewall 43 extending between the ends, and an internal cavity 44. Sidewall 43 may be cylindrical with circular transverse cross section in some embodiments to match the cylindrical shape of the fuel canister 60. However, other non-cylindrical shaped sidewalls such as hexagonal or other for example. Cavity 44 of gamma block cylinder 40 extends completely through the body of the cylinder 40 along the longitudinal axis LA from the top to bottom ends 41, 42. Cavity 44 is configured to hold and support the nuclear spent fuel canister 60 therein. The cavity 44 of the gamma block cylinder 40 preferably has a transverse cross-sectional area configured to hold no more than a single spent nuclear fuel canister 60, which in turn holds a plurality of spent fuel assemblies which each contain the fuel rods. Canister 60 includes a sealable lid 61 to provide access to the interior of the canister and fuel assemblies stored therein. A typical nuclear fuel canister may hold approximately 89 fuel assemblies at full capacity. The inner cylinder 40 further includes an interior surface 45 and opposing exterior surface 46. The gamma block cylinder 40 may be comprised of a single long cylinder body, or alternatively may be formed by a plurality of axially aligned and vertically stacked cylinder segments seal welded together at the joints between the segments to collectively form the cylinder body. In one embodiment, the GBC 40 may have a composite wall construction including an inner cylindrical shell 47 and outer cylindrical shell 48 with a gamma blocking liner 49 interposed and sandwiched therebetween (best shown in FIG. 7). An annular bottom closure ring 51 may be provided to enclose and support the bottom ends of the two shells and liner. The shells 47, 48 may be formed of a suitable metal of sufficient structural strength and thickness such as without limitation stainless steel for corrosion protection. The gamma blocking liner 49 material is preferably constructed of a high density and high thermally conductive metallic material(s) selected and operable to block gamma radiation. Suitable materials which may be used that meet those criteria include steel, lead, or copper as some non-limiting examples. In one implementation, the composite wall construction may be steel/lead/steel—all of which serve to block gamma radiation emitted by the decaying nuclear fuel held inside the fuel canister 60 disposed in cavity 44 of the GBC. The cavity 44 at the bottom end 42 of GBC 40 may be closed by a detachable bottom lid 50 best shown in FIGS. 5, 7, and 8. Lid 50 protrudes vertically downwards below the bottom support flange 26 and bottom end 23 of the outer neutron shield cylinder 21 when the inner gamma block cylinder 40 is placed therein. The lid 50 is constructed to support the spent fuel canister 60 which rests on the planar horizontal top surface of lid, which is of suitable thickness for this purpose without undue deflection from the weight of the canister. Lid 50 may be removably coupled to the bottom closure ring 51 of cylinder 40 by suitable fasteners selected to form an interlocked arrangement between the ring and lid. In one embodiment, as best seen in FIGS. 9 and 10, a plurality of locking keys 53 at circumferentially spaced intervals around the perimeter of cylinder 40 and lid 50 may be used to couple the lid to the closure ring 51. The keys 53 are inserted into complementary configured locking slots 54; a half-portion of the slots being formed in each of the adjoining bottom closure ring 51 and lid 50 which collectively define the shape of the locking slot. Slots 54 are laterally open and extend radially inwards into the cylinder 40 towards longitudinal axis LA for a suitable distance. The keys 53 may be polygonal shaped, and preferably rectilinear polygon shaped in one non-limiting embodiment. In one embodiment, the keys 53 and mating slots 54 may be I-shaped as shown. Other shaped keys including non-polygonal shapes however may be used so long as an interlocked arrangement is formed between the bottom closure ring 51 and lid 50 of the GBC. The shape of the key is not limiting of the invention. To provide access to locking keys 53 when the inner gamma blocker cylinder 40 is inserted in the outer neutron shield cylinder 21, a plurality of radially extending and laterally open access slots 56 may be formed in the bottom flange 26 of the outer cylinder 21 (best shown in FIG. 9). Each key 53 has an associated access slot 56. In other possible implementations, threaded fasteners 55 (represented in dashed lines in FIG. 8) such as bolts may be used to detachably couple the lid 50 to the bottom closure ring 51 of the GBC. The fasteners 55 may be inserted at a diagonal orientation relative to the closure ring and lid as shown. In one embodiment, the interface between the lid 50 and bottom closure ring 51 may be sealed by an annular gasket or seal 52 formed of a suitable resiliently compressible elastomeric material or rubber. The seal is selected and configured to seal the internal cavity 44 of the gamma blocker cylinder 40 which holds the nuclear waste fuel canister 60 in an air-tight and liquid-tight manner. The bottom lid 50 preferably does not extend beyond the sidewall 43 of the gamma blocker cylinder 40 as best shown in FIG. 8. This provides unimpeded insertion of cylinder 40 into the outer neutron shield cylinder 21 and maintains clearances for formation of the cooling air ventilation annulus 34 between the inner and outer cylinders further described herein. To facilitate centering and insertion of the inner cylinder 40, a plurality of longitudinal guide ribs or splines 57 may provided on the interior surface 30 of the outer cylinder 21 in cavity 25. Guide splines 57 are circumferentially spaced and vertically elongated extending longitudinally along the longitudinal axis LA for preferably a majority or more preferably substantially the entirety of the longitudinal length of the cavity 25. Splines 57 extend radially inwards into the cavity 25 a short distance beyond the inner diameter of the NSC top flange 27 which circumscribes the top opening of the outer neutron shield cylinder 21 to ensure engagement with and guidance of the inner cylinder 40 as it is lowered therein. The top ends of the splines 57 may be obliquely angled to facilitate centering and entry of the inner cylinder 40 into the outer cylinder cavity 25, and smoothly engage the peripheral edges of the bottom lid 50 of the inner cylinder if not perfectly aligned coaxially with the longitudinal axis LA of the cask when lowered into the outer cylinder by a crane. It bears noting that the guide splines 57 further serve an important function of maintaining a substantially uniform cooling air ventilation annulus 34 between the inner and outer cylinders 40, 21. The guide splines 57 may be permanently attached to the outer neutron shield cylinder 21 by welding in one embodiment. With continuing reference generally to FIGS. 1-13, the top end 41 of the inner gamma block cylinder 40 may be terminated by an annular top mounting flange 70. Flange 70 projects radially/laterally outwards beyond the sidewall 43 of gamma blocker cylinder 40 (GBC) to engage the top flange 27 of the outer neutron shield cylinder 21 (NSC) as shown in FIGS. 5 and 6. The GBC mounting flange 41 is detachably mounted to the NSC top flange 27 by a plurality of mounting fasteners 71 such as threaded bolts in one non-limiting embodiment, thereby detachably coupling the inner and outer cylinders together (see also FIGS. 4 and 11). Fasteners 71 extend vertically completely through GBC mounting flange 70 and engage corresponding upwardly open threaded bores 72 formed in the NSC top flange 27. In one embodiment, the threaded bores 72 may be formed in spacer blocks 29 as best shown in FIG. 4. The spacer blocks 29 advantageously provide additional purchase or thickness of material to secure the mounting fasteners 71 to the NSC top flange 27 for structural strength. When the inner gamma block cylinder 40 is mounted in the outer neutron shield cylinder 21, the entire weight of the inner cylinder 40 with loaded spent fuel canister 60 therein is fully supported by the outer cylinder 21 in a cantilevered manner via engagement between the mounting flange 70 and top flange 27. This allows the inner cylinder 40 directly heated by the heat emitting fuel canister 60 therein to thermally grow in length independently of the outer neutron shield cylinder 21 to avoid cracking caused by differential thermal expansion. The bottom support flange 26 of outer neutron shield cylinder 21 in turn is supported by the vertical cask transport crawler or vehicle 75 described elsewhere herein. In one construction, the entire fully-loaded cask 20 including the outer neutron shield cylinder 21 and inner gamma block cylinder 40 with spent fuel canister 60 may be raised and lifted via the GBC mounting flange 70 and bolting alone. The flange 70 therefore has a sufficiently robust structure and thickness to support the entire cask weight. To lift the cask, at least one pair of lifting lug assemblies 76 shown in FIGS. 1-3 may be detachably mounted to the top of the mounting flange 70 via threaded lug fasteners 77 such as bolts. More lugs assemblies may be used in other embodiments depending on the desired rigging arrangement. In various embodiments, existing mounting fasteners 71 used to secure the mounting flange 70 to outer neutron shield cylinder 21 may be used as the lug fasteners. In other embodiments, separate threaded lug fasteners 77 may be used. FIG. 3 shows inner gamma block cylinder 40 in the process of being raised or lowered via the hoist 79 of a crane 80 to remove or insert cylinder 40 into outer neutron shield cylinder 21. A lifting harness 78 is coupled to the hoist above and to the lifting lug assemblies 76 below mounted to the gamma block cylinder. When the inner gamma block cylinder 40 is mounted to the outer neutron shield cylinder 21 via mounting fasteners 71 as noted above, the entire cask 20 will be lifted or lowered in the same manner shown. It bears noting that the crane 80 shown may be one inside the reactor containment structure with access to the nuclear spent fuel pool, or the one mounted on the vertical cask transporter vehicle 75 (see, e.g. FIG. 14). The inner gamma block cylinder 40 which holds the spent fuel canister 60 is heated by decay heat emanating from the spent nuclear fuel, which can be significant for a fairly long period of time. Provisions must therefore be made to effectively remove the decay heat to maintain the structural integrity of the cask components and its nuclear fuel contents. According to one aspect of the invention, a cooling air system is provided which utilizes available ambient cooling air and natural flow circulation created via the chimney effect which is induced by the heat emitted by the decaying nuclear fuel assemblies via the inner gamma block cylinder 21 vertical sidewall 43. Referring to FIGS. 5-8, 11, and 13, an open vertically-extending cooling air ventilation annulus 34 is provided by a space or gap between the exterior surface 46 of vertical sidewall 43 of the inner gamma block cylinder 40 and the interior surface 30 of the vertical sidewall 24 of the outer neutron shield cylinder 21. Cooling air ventilation annulus 34 extends for the full height of the cask 20 and circumferentially around the entire interface between the inner and outer cylinders 40, 21. As previously described herein, the air ventilation annulus 34 may have a substantially uniform transverse cross-sectional area created by the longitudinal splines 57 affixed to the interior surface of the outer neutron shield cylinder 21 (see also FIGS. 4 and 12). Air flows vertically upwards through the cooling air ventilation annulus 34 between the splines 57 which create a plurality of longitudinally-extending air passages 34-1 defined by the splines. Because the inner gamma block cylinder 40 is fully supported inside the outer neutron shield cylinder 21 from the top via engagement between the GBC mounting flange 70 and the NSC top flange 27, this allows the air ventilation annulus to extend completely through the bottom end of cask. This forms an annular lower cooling air inlet opening 34-2 into the air ventilation annulus 34 between the cylinders at the bottom of the cask (best shown in FIGS. 7-8). Air inlet opening 34-2 may be continuously open and uninterrupted for a full 360 degrees in some embodiments. Seating the top mounting flange 70 of the gamma block cylinder 40 on the spacer blocks 29 of the neutron shield cylinder top flange 27 in the manner previously described herein further forms a plurality of upper cooling air outlet openings 34-3 between the vertically spaced apart mating flanges which are in fluid communication with the air ventilation annulus 34 between the gamma block cylinder 40 and neutron shield cylinder 21. The vertically protruding raised annular lip 27-1 of the neutron shield cylinder top flange 27 and angled cross-sectional shape of the flange creates a circuitous air L-shaped outlet path which advantageously prevents direct streaming of neutrons to the external environment through the upper air outlet openings 34-3. This there is no direct line of sight from outside through the air outlet openings 34-3 into the interior portions of the cask 20 to prevent neutron streaming. In operation of the cooling air system, ambient cooling air enters the annular lower air inlet opening 34-2 vertically and flows vertically into and upwards through the air ventilation annulus 34 to the top of the cask 20 (parallel to longitudinal axis LA). The air in the open annulus 34 is directly heated by the inner gamma block cylinder sidewall 43. This draws the air inwards into the cask 20 via the lower air inlet opening 34-2 by natural convention. The heated cooling air then flows upwards in the air ventilation annulus, flows radially/laterally through the upper air outlet openings 34-3 (perpendicular to longitudinal axis LA), then turns vertically upwards flowing past the annular lip 27-1 of the outer NSC cylinder 21 and is discharged to the ambient atmosphere and environment. Referring to FIGS. 7 and 8, a circumferentially-extending radial annular space or gap G may preferably also be provided at the interface between the fuel canister 60 and the interior surface 45 of the gamma block cylinder 40. For optimal thermal and ALARA performance, the ability to keep this annular gap G either filled with water (for additional shielding) or air ventilated (for additional heat rejection capacity) is desirable during different stages the fuel loading scenario. The bottom lid 50 of the gamma block cylinder 40 may include a plurality of air inlet holes 62 configured to provide a passage for introducing ambient cooling ventilation upwards into annular gap G (see, e.g. FIGS. 7 and 9). Although air inlet holes 62 are formed in the lateral sides of the portion of the lid 50 which extend beneath the bottom support flange 26 of the neutron shield cylinder 21. Air inlet holes 62 may have an L-shape configuration, the holes may in other embodiments be vertically straight and drilled directly through the underside of the lid 50 and extend upwards to fluidly coupled to annular gap G. The air inlet holes 62 in the bottom lid are designed to be readily plugged, if needed, to keep the annular gap G instead filled with water if needed during certain phases of the cask fuel loading and handling operations. Thus, the drainable annular gap G surrounding the canister can be used to promote air ventilation or to keep filled with water, as needed, during the fuel loading and transfer operations. The annular gap G is upwardly open at the interface between the gamma block cylinder 40 and canister 60 forming an annular air outlet 63 (best shown in FIG. 6). Water can be introduced into the annular gap G via the air outlet 63 to cool the canister 60 if needed for additional neutron shielding instead of air cooling, as previously described above. If the canister 60 requires further active cooling to dissipate heat generated by the decaying nuclear fuel, the drainable annulus (gap G) advantageously provides the facility to spray water on the canister lid using gravity fed water drip to efficiently remove heat from the canister without resorting to an active cooling system. The physically detachable outer neutron shield cylinder 21 (NSC) separable at strategic times from the inner gamma block cylinder 40 (GBC) as previously described herein offers several advantages. One advantage is that by separating the thermally low conductivity part of transfer cask (i.e., NSC) from the thermally high conductive GBC, it is now possible to incorporate an air ventilation annulus 34 previously described herein between them. The hot external surface of the GBC, heated by the decay heat from fuel in the canister inside the GBC, drives an efficient natural convection air ventilation action to keep fuel from heating excessively. Another advantage is that in some cases (e.g., during the canister drying operation), it may desirable to keep the cask as hot as possible. In such a case, having the high thermal inertia neutron shield of the NSC separated from the GBC of the cask body or the ability to physically block the air ventilation is helpful in accelerating the drying operation. Another advantage is that the permissible weight of most transfer casks is limited by the rated lift capacity of the cask handling crane or the size of the cask loading area in the spent fuel pool. Under the present separable GBC and NSC approach, the GBC is made as heavy and as large in diameter as possible within the constraints of the plant's architecture and crane capacity. The NSC is likewise made as large as possible within the constraints of the load lifting device used to handle the transfer cask typically having a higher rated load lifting capacity than the cask handling crane in the nuclear facility cask loading area. These two features combine in a way to optimize the transfer cask's shielding performance. Yet another advantage is that the NSC may be made in the form of a single or multiple section annular cylinder containing water or a solid resinous neutron shielding material therein, such as Holtite™, contained in a steel exterior. Boric acid may be added to the water mass of the NSC for enhanced neutron capture. FIG. 14 is a schematic diagram of an example of a “wet” spent nuclear storage facility 100 for temporary holding of spent nuclear fuel—not to be confused with a “dry” independent spent fuel storage installation (ISFSI) for the longer interim storage of spent nuclear fuel. Wet storage facility 100 includes a structural building enclosure with roof 125, walls 123, and a steel reinforced concrete base mat 121 that defines a substantially horizontal operating deck 122 surrounding and extending over portions of a spent fuel pool 140 impounded with water W. Deck 122 may be at surrounding ground level or grade G to facilitate movement of motorized cask vehicles or carts into and out of the facility. An access bay 90 is defined by deck 122 adjacent to the fuel pool 140 for staging the present fuel transport cask 20 comprises of the outer neutron shield cylinder 21 and inner gamma block cylinder 40 as shown. In some embodiments, the building enclosure may be a reactor containment enclosure structure. Fuel pool 140 includes a base or floor 142 and plural vertical sidewalls 141 extending upwards therefrom to the operating deck 122. A water level WL is formed in the pool. Submerged in the pool 140 is a fuel storage rack 127 comprising a plurality of upwardly open storage cells 129 each configured to hold a single used or spent nuclear fuel assembly 128 removed from the reactor. The fuel assembles themselves comprise a plurality of fuel rods and upper and lower flow nozzles for primary coolant flow in the reactor; the design of the fuel assembly being well known to those skilled in the art without undue elaboration herein. A portion of the fuel pool 140 defines a cask loading area 150 for loading fuel assemblies from rack 127 into the canister 60 located inside the gamma block cylinder 40 as further described below. For the fuel assembly to canister loading operation and manipulating the transfer cask 20 components (GBC, NSC) and fuel canister, one or more overhead trolley cranes 80 previously described herein may be provided which are operable to lift a load and traverse the wet storage facility 100. A process or method for transferring and transporting spent nuclear fuel will now be briefly summarized with initial reference to FIG. 14. The first step is providing a nuclear fuel transport cask 20 comprising an outer neutron shield cylinder 21 having an internal first cavity 25 and an inner gamma block cylinder 40 having an internal second cavity 44. Initially, the gamma block cylinder is detachably coupled to and nested inside the first cavity of the neutron shield cylinder at the start of the process describe below. The cask 20 may be transported to the dry spent fuel storage facility 100 via the self-propelled wheeled or tracked crawler 75 having an overhead high lifting capacity crane 102 mounted high above platform 73 of the crawler by a pair of vertical columns 81 with the crane supported by a beam between the columns. Such cask transporters are well known in the art. The cask 20 may be moved via the heavy duty crawler 75 (e.g. about 170 ton lifting capacity) to a staging spot immediately outside the fuel storage facility 100 as shown. The tall height and weight of the crawler generally precludes it from entering the fuel storage facility. In one scenario, the entire cask 20 may be placed on a low profile wheeled cask transport cart 301 which typically move along a pair of continuous rails supported at ground level G outside the facility and the operating deck 122 inside the facility. The cask 20 is then moved inside the facility enclosure to the access bay 90 alongside the fuel pool 140. The next step in the process is separating the gamma block cylinder 40 from the outer neutron shield cylinder 21 using inside crane 80 as shown in FIG. 14. This is accomplished by first unbolting the mounting flange 70 of the gamma block cylinder 40 from the top flange 27 of the outer neutron shield cylinder 21. The gamma block cylinder 40 is then lifted/raised with the crane 80 and separated from neutron shield cylinder 21 via the lifting harness 78 and lifting lugs 78 attached to the top mounting flange 70 of the gamma block cylinder. An available empty fuel canister 60 may then be lifted by crane 80 and inserted vertically downwards into the gamma block cylinder 40 either outside of or in the fuel pool 140 (if not already placed therein previously). Alternatively, the canister may be placed inside the gamma block cylinder 40 before separation from the neutron shield cylinder 21. In an alternate possible but less preferred scenario, the gamma block cylinder 40 may be uncoupled and removed from the neutron shield cylinder 21 outside the fuel storage facility 100 by the crawler crane 102. The gamma block cylinder may then be moved alone on the cask transport cart 301 and moved into the facility. Next, the inside overhead crane 80 then lifts/raises the gamma block cylinder 40 and canister 60 assembly (assuming the canister is inserted in cylinder 40 outside the fuel pool 140), and places/lowers the assembly into the fuel pool 140 onto a support surface (e.g. fuel pool floor 142) in the cask loading area 150 of the pool. Water fills both the gamma block cylinder and canister (which has its lid 61 removed). The gamma block cylinder and canister 60 are submerged under water W to a depth sufficient to keep the fuel assembles 128 beneath the water level WL when loaded into the canister by crane 80. The fuel assemblies are then loaded into the canister and gamma block cylinder one at a time. After loaded with fuel assemblies, the next step is using crane 80 to lift/raise the loaded gamma block cylinder 40 and fuel canister 60 assembly out of the fuel pool 140. The gamma block cylinder 40 and fuel canister 60 assembly is maneuvered over top of the neutron shield cylinder 21 on the cart 301, and then lowered/inserted into the neutron shield cylinder. Because the neutron shield cylinder 21 is now in place for neutron radiation shielding, the canister may be optionally dewatered at this time. The next step is bolting the inner gamma block cylinder 40 to the outer neutron shield cylinder 21 via the mating mounting and top flanges 70, 26 of each vessel, respectively. The cart 301 with now fully re-assembled cask 20 is then moved back out of the facility. Using the crawler crane 102, the next step is lifting the cask 20 back onto the crawler 75 for further closure operations and transport to the dry storage facility. It bears noting that at the time of the gamma block cylinder 40 and canister 60 removal from the spent fuel pool 140, the water in the canister provides the necessary neutron shielding (the gamma block cylinder providing the gamma radiation shielding). The lift weight of gamma block cylinder and water filled canister (without the neutron shield cylinder 21) is within the allowable facility crane 80 lifting capacity. Once the gamma block cylinder 40 with water-laden canister 60 are inserted into the outer re-coupled neutron shield cylinder 21, the transfer cask 20 has the requisite neutron shielding to commence with the canister dewatering, closure, and transfer operations. The neutron shield cylinder 21 is thus preferably installed prior to the dewatering of the canister 60 to assure no lapse in neutron shielding. Prior to lifting the entire fully assembled transfer cask 20, now consisting of the gamma block cylinder 40, neutron shield cylinder 21, and canister 60, the now dewatered canister reduces the casks overall/cumulative lift weight to within the capacity of the crawler 75 crane (or other lifting device). Variations in the foregoing sequence of steps may be used in practice in other embodiments and does not limit the invention. While the foregoing description and drawings represent some example systems, it will be understood that various additions, modifications and substitutions may be made therein without departing from the spirit and scope and range of equivalents of the accompanying claims. In particular, it will be clear to those skilled in the art that the present invention may be embodied in other forms, structures, arrangements, proportions, sizes, and with other elements, materials, and components, without departing from the spirit or essential characteristics thereof. In addition, numerous variations in the methods/processes described herein may be made. One skilled in the art will further appreciate that the invention may be used with many modifications of structure, arrangement, proportions, sizes, materials, and components and otherwise, used in the practice of the invention, which are particularly adapted to specific environments and operative requirements without departing from the principles of the present invention. The presently disclosed embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being defined by the appended claims and equivalents thereof, and not limited to the foregoing description or embodiments. Rather, the appended claims should be construed broadly, to include other variants and embodiments of the invention, which may be made by those skilled in the art without departing from the scope and range of equivalents of the invention.
039403092	claims	1. An electromagnet coupling for supporting a safety rod and a control-and-safety rod in a nuclear reactor which coupling comprises a plurality of electromagnet means acting in parallel on a single armature common to all of them each of said electromagnet means being provided with an energizing winding adapted for being fed separately from the other; in which coupling a fraction only of the total number of electromagnet means is necessary for holding the suspended rod. 2. In a safety system for a nuclear reactor with vertical safety rods said system comprising three n sensing means of n variable quantities such as for example coolant temperature, fuel temperature and ratio of reactor power to coolant flow rate of the reactor operation, three n measuring means of said variable quantities each provided with limiting threshold 3, logic circuits to each of which one of the output signals from said three n measuring means is supplied, three amplifying means which are separately supplied with the three output signals from said logic circuits, a coupling means for releasably supporting each safety rod in the reactor which coupling means comprises six identical electromagnets with vertical axes arranged in pairs in a circular row at regular distances from one another around the rod axis, the electromagnets of each pair being disposed at diametrically opposed positions with respect to said axis and a single annular armature attached to said rod and located beneath said six electromagnets to contact the lower ends thereof; the windings of each pair of electromagnets being supplied in parallel by one of said amplifying means; said electromagnets being so dimensioned that two pairs of them are capable of holding the supported load comprising the rod while a single pair of electromagnets is not capable of holding the rod.
	summary
	claims	1. A semiconductor diode comprising:a first layer formed with a p-type semiconductor;a second layer formed with an n-type semiconductor;a third active depletion layer contained between the first and second regions, the third layer formed with a p-n type semiconductor;a fourth layer and a fifth layer each formed with a radioisotope between the first and third layers and the second and third layers, respectively, such that initial emission of beta particles begins in the fourth and fifth layers and substantially all of the emitted beta particles are contained within the first through fifth layers during operation. 2. The diode of claim 1 where the p-type and n-type layers have sufficient depth to contain substantially all of beta particles emitted from the fourth and fifth layers. 3. The diode of claim 2 where the depth of the p-type and n-type layers is substantially equal to or greater than the maximum beta emission depth of the radioisotope. 4. The diode of claim 3 including a scintillator layer formed on the p-type and n-type layers, respectively, for converting beta particles into light and reflecting the light back to the depletion layer. 5. The diode of claim 4 including a mirror coating formed on the respective scintillator layer for reflecting light back to the depletion layer. 6. A Schottky-type semiconductor diode comprising:a first Schottky contact layer;a second ohmic contact layer;a third active depletion layer contained between the first and second layers, the third layer formed with a radioisotope of p-type or n-type semiconductors such that initial emission of beta particles begins in the active depletion region and substantially all of the emitted beta particles are contained within the first, second and third layers during operation.
	claims	1. An ion implantation system suitable for use in implanting ions into one or more workpieces comprising:an ion source for producing a quantity of ions which can be extracted in the form of an ion beam, the ion beam having a beam current density;a beamline assembly downstream of the ion source to receive and direct the beam of ions;an end station downstream of the beamline assembly to hold the one or more workpieces toward which the ion beam is directed;a component downstream of the ion source for modulating the ion beam current density via at least one of a generated electric and magnetic field; anda measurement component for taking readings of beam current, the modulating component adjusting the beam current density in response to readings taken by the measurement component. 2. The system of claim 1, wherein the modulating component comprises one or more plates of an ion beam accelerator. 3. The system of claim 1, wherein the modulating component comprises a ground electrode. 4. The system of claim 1, wherein the modulating component comprises a set of electrically conductive plates located between the ion source and the beamline assembly. 5. The system of claim 1, wherein the beamline assembly includes an analyzer magnet to mass resolve ions within the beam, the modulating component comprising an electrode downstream of the analyzer magnet. 6. The system of claim 1, wherein the modulating component comprises a set of electrically conductive plates defining a resolving aperture of the beamline assembly. 7. The system of claim 1, wherein the modulating component comprises an electrode located downstream of a resolving aperture of the beamline assembly. 8. The system of claim 1, wherein the modulating component comprises an extraction suppression electrode located close to the ion source. 9. The system of claim 1, wherein the modulating component comprises a source magnet that assists with generating ions within the ion source, the source magnet located close to the ion source. 10. The system of claim 1, wherein the measurement component is utilized in developing implantation waveforms that are employed in modulating the beam current. 11. The system of claim 1, wherein the measurement component comprises at least one of a Faraday cup and terminal return current. 12. The system of claim 1 further comprising a controller for selectively controlling the modulating component in response to readings taken by the measurement component. 13. The system of claim 1, wherein the beam current is modulated between at least one of a frequency of about 1–1000 Hz and a range of about 10–20% of the beam current. 14. The system of claim 1, wherein the measurement component takes readings of beam current during the ion implantation process to facilitate feedback or closed-loop adjustments to the beam current. 15. The system of claim 1, wherein the measurement component takes readings of beam current prior to the ion implantation process to facilitate open loop adjustments to the beam current. 16. An ion implantation system suitable for use in implanting ions into one or more workpieces comprising:an ion source for producing a quantity of ions which can be extracted in the form of an ion beam, the ion beam having a beam current density;a beamline assembly downstream of the ion source to receive and direct the beam of ions;an end station downstream of the beamline assembly to hold the one or more workpieces toward which the ion beam is directed;a component downstream of the ion source for modulating the ion beam current density via at least one of a generated electric and magnetic field; anda measurement component for taking readings of beam current at one or more points during ion implantation, the modulating component adjusting the beam current density in response to readings taken by the measurement component,wherein the modulating component includes at least one ofone or more plates of an ion beam accelerator,a ground electrode,a set of electrically conductive plates located between the ion source and the beamline assembly,an electrode downstream of an analyzer magnet within the beamline assembly that mass resolves ions within the beam,a set of electrically conductive plates defining a resolving aperture of the beamline assembly,an electrode located downstream of a resolving aperture of the beamline assembly,an extraction suppression electrode located close to the ion source,a source magnet that assists with generating ions within the ion source, the source magnet located close to the ion source. 17. The system of claim 16, wherein the measurement component is utilized in developing implantation waveforms that are employed in modulating the beam current. 18. The system of claim 17, wherein the measurement component comprises at least one of a Faraday cup and terminal return current. 19. An acceleration system suitable for use in implanting ions into a workpiece comprising:an ion source for producing a quantity of ions which can be extracted in the form of an ion beam, the ion beam having a beam current density;a beamline assembly downstream of the ion source to receive and direct the beam of ions;an end station downstream of the beamline assembly to hold one or more workpieces onto which the ion beam is directed;a first modulating component associated with the ion source for modulating the beam current density via at least one of a generated electric and magnetic field; anda second modulating component downstream of the ion source for selectively modulating the ion beam current density via at least one of a generated electric and magnetic field. 20. The system of claim 19, wherein the first modulating component comprises a source magnet that assists with producing ions within the ion source. 21. The system of claim 19 further comprising:a measurement component for taking readings of beam current at one or more points during ion implantation; anda controller operatively coupled to the measurement component, the controller selectively adjusting at least one of the first and second modulating components in response to readings taken by the measurement component. 22. The system of claim 19, wherein the second modulating component comprises one or more electrically conductive members situated along the beam path.
	description	This application is a Divisional application of U.S. patent application Ser. No. 14/457,250, filed 12 Aug. 2014, which is a Continuation-in-Part application of PCT International Application Number PCT/IL2013/050121, filed 10 Feb. 2013, claiming priority from U.S. Provisional Patent Application No. 61/598,035, filed 13 Feb. 2012. All of these applications are hereby incorporated by reference in their entirety. This patent application relates to X-ray radiation delivery devices and methods, including X-ray radiation therapy devices and methods. X-ray radiation can be used for a wide range of applications, including X-ray therapy and X-ray surgery, various X-ray imaging applications, sensing and detection applications. In these and other applications, the X-ray radiation is directed to a target which can be a tissue or other object at a desired location. It is desirable to properly aim the X-ray beam to a desired point or location on the target in many applications. The techniques and devices described here use an X-ray imaging beam to image a target and use the obtained imaging information of the target to control or deliver another X-ray beam onto the desired location of the target. In one implementation, an X-ray system is provided to include one or more lenses configured to receive a first portion of X-ray radiation from an X-ray source and to direct treatment radiation to converge onto a target; a first shutter located in a path between the X-ray source and the target to receive a second portion of the X-ray radiation from the X-ray source to selectively allow imaging X-ray radiation to reach the target; and a detector configured to detect at least a portion of the imaging radiation after the imaging radiation has interacted with the target to provide imaging information of the target. In another implementation, a method is provided to include receiving X-ray radiation from an X-ray source at a first shutter located in a path between the X-ray source and a target; using the X-ray source to provide radiation to be directed by one or more lenses as treatment radiation onto the target; controlling an operation of the first shutter to selectively allow the X-ray radiation to reach the target as imaging radiation; receiving at least a portion of the imaging radiation at a detector after the imaging radiation has interacted with the target; and using imaging information of the target from the detector to control a property of the treatment radiation onto the target. In yet another implementation, a method is provided to include controlling an operation of a first X-ray source in an X-ray system to provide radiation to be directed by one or more lenses as treatment radiation onto a target at one or more converging angles; blocking radiation from the first X-ray source that is not incident upon the one or more lenses from reaching the target; controlling an operation of a second X-ray source in the X-ray system to provide imaging radiation that is incident upon the target; and receiving at least a portion of the imaging radiation at a detector after the imaging radiation has interacted with the target. These and other implementations of the techniques and devices are described in greater detail in the drawings, the description and the claims. Recent advances in X-ray technology enable effective use of X-ray imaging systems and methodologies in a variety of applications. These applications include, but are not limited to, a variety medical imaging techniques, ranging from plain X-ray imaging of the skeletal system and soft tissue, to fluoroscopy, radiation therapy and radiosurgery. Radiation therapy is commonly applied to cancerous tumors to control or impede cell growth. Ionizing radiation works by damaging the DNA of exposed tissue leading to cellular death. The use of X-ray systems for radiosurgery allows non-invasive treatment of benign and/or malignant tumors enabled by the localized, highly precise concentration of X-rays at the target lesion. During a radiosurgery session or a radiation therapy treatment it is important to minimize the amount of radiation absorbed by healthy tissue. This requires that the clinicians know precisely where the targeted volume is located before irradiation, and if possible during irradiation. This task is often made more difficult because tumors can change in size over time, especially between radiation courses of many days or weeks. Therefore, often patients are subjected to imaging procedures immediately before radiation sessions so as to determine the size, shape and location of the tumor. However, such procedures, which may include plane radiography using two dimensional imaging sensors, computed tomography (CT), magnetic resonance imaging (MRI) and the like, are costly and can be time consuming. In addition, the target, such as a cancerous tumor, can move and possibly change shape while the radiation therapy is actually taking place. Such a scenario can occur, for example, in a treatment session for prostate cancer, during which the prostate can move because of bladder filling and random movements of the bowels. The movement of a target lesion can also occur due to breathing and heart beating. The techniques and devices described here are based on imaging-guided delivery of X-ray radiation by using an X-ray imaging beam to image a target and using the obtained imaging information of the target to control and deliver another X-ray beam onto the desired location of the target. For example, the imaging information is used to accurately determine the location, size and other characteristics of a target during, before and after a radiation therapy or radiosurgery session while minimizing the associated complexity, cost and the time involved in acquiring such information. In this document, the word “exemplary” is used to mean serving as an example, instance, or illustration. Any embodiment or design described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments or designs. Rather, use of the word exemplary is intended to present concepts in a concrete manner. In X-ray therapy, in order to reduce the exposure of healthy tissue during radiation treatments, it is important to determine the exact location, size, shape and other characteristics of a target. To accomplish this task, a relatively new field called Image Guided Radiation Therapy (IGRT) has evolved to assist radiation oncologists to better deliver radiation therapy to the targeted areas. IGRT techniques often involve acquiring imaging data using, MRI, CT, positron emission tomography (PET), and other techniques immediately prior to the radiation therapy session in order to obtain the needed information regarding a target within the patient's body. Monitoring the position of a tumor during a therapy session can also be accomplished using what is often referred to as portal imaging. For example, portal imaging can include placing a two dimensional image sensor behind the patient so that the treating radiation exiting the patient can be imaged along with the tumor. This technique, however, can produce poor results since the tumor may not be differentiated well from its surroundings due to the low contrast of different parts of the body to the very high energy treatment X-rays typical to conventional radiation therapy. Another approach for obtaining information regarding a target prior to, or during, a course of radiation treatment is to utilize a conventional radiographic X-ray tube operating in the many tens of Kilovolt range and pointed at the tumor in a direction perpendicular to the axis between the irradiating source and the tumor. By aiming this additional X-ray radiation at the tumor region, detecting the radiation that is transmitted through the body using a two dimensional sensor, and rotating the additional X-ray source around the axis to obtain additional images, both plane images and two dimensional reconstructed images similar to a conventional CT image can be attained. Design of such systems, however, requires an extra gantry for the imaging radiation and, therefore, adds substantial cost and bulk to the x-ray system. In addition, such a system can limit the versatility of the irradiation source design. The disclosed embodiments relate to providing cost effective methods and systems for acquiring accurate information regarding a target prior to, during, or after, a radiation therapy and/or radiosurgery session. A target can include any normal or abnormal target region within a patient's body, including, but not limited to, cancerous and/or benign tumors, lesions and the like. A target can also include both normal and abnormal regions, such as in a scenario where a cancerous tumor and a limited region surrounding the tumor are the target of radian therapy or radiosurgery. To minimize, or to reduce, irradiating the tissue outside of the target, such as healthy skin or organs that surround a tumor, shaped radiation beams are often focused from several converging angles to intersect at the target. As a result, the target receives a concentrated radiation dosage from the converging beams while the surrounding tissue outside of the focal region receives a much lower radiation dosage. Such systems often utilize optical components with a crystal structure for guiding and/or focusing the X-ray beams based on Bragg or Laue diffraction principals. For example, germanium (Ge) or silicon (Si) curved crystals may be used to deflect diverging radiation from an X-ray source onto a target. Such crystals, which may be singly curved, doubly-curved or be shaped for use with any other technique related to Johansson and Johan geometries, can be utilized in what is called a Rowland circle configuration to provide focusing of the X-ray beams in two or three dimensions, respectively. For instance, a doubly-curved crystal may be used to focus the beams onto a relatively small (e.g., point) target. The crystals can also provide wavelength (or energy) selectivity and, therefore, can be used for filtering purposes to, for example, monochromatize the X-ray radiation. FIG. 1 illustrates an exemplary system 100 that is configured to focus X-ray radiation from a source 102 to a target 106 using a plurality of ring-like lenses 104(a), 104(b) and 104(c). The target 106 can be a tissue of a patient in an X-ray therapy system or other object when the system 100 is used for other applications. Each of the lenses 104(a), 104(b) and 104(c) are positioned on Rowland circles 122 and focus an incident bundle of X-ray beams onto the target 106 at a converging angle. The term “optical axis” is defined as the line connecting the source 102 with the target 106 passing through the center of the lenses 104(a), 104(b) and 104(c) and shutters 108 and 210. The lenses 104(a), 104(b) and 104(c) can be constructed in such a way to allow only a limited spectral portion of the incident X-ray radiation to reach the target 106. As such, the X-ray radiation that is directed by the lenses 104(a), 104(b) and 104(c) to the target 106 is sometimes referred to as monochromatic radiation. It should be noted that the term monochromatic in the present context is not necessarily indicative that such radiation only includes one spectral wavelength. But rather the term monochromatic is used to convey that such radiation includes fewer spectral components than unaltered X-ray radiation that is emanating from the X-ray source 102. Since such radiation in the configuration of FIG. 1 is used for radiation treatment, it may also be referred to as the treatment radiation. The exemplary system 100 of FIG. 1 illustrates only two small portions of each ring-like lens 104(a), 104(b) and 104(c) at the top and bottom of the corresponding Rowland circles 122 as examples. The lenses 104(a), 104(b) and 104(c) are ring-like structures that are appropriately positioned around the axis that connects the source 102 to the target 106. In other exemplary configurations, the number, shape and symmetry characteristics of the lenses 104(a), 104(b) and 104(c) may be altered to accommodate particular applications, cost targets or design goals. FIG. 1 further illustrates a stop 108 that is placed in the direct path between the source 102 and the target 106 to block X-ray radiation that would otherwise reach the target 106 unimpeded. The radiation that is incident upon the stop 108 may include the full spectral range of the X-ray source 102 (i.e., it is “polychromatic”) and may, therefore, harm the patient if not attenuated or blocked by the stop 108. FIG. 2 illustrates a system 200 that is configured to allow treatment as well as imaging of a target 106 in accordance with an exemplary embodiment. The system 200 enables imaging of the target 106 prior to, during and/or after treatment of the target 106 by allowing at least a portion of the X-ray radiation from the source 102 to directly reach the target 106. The boundaries of the imaging portion of the radiation are shown as 107. Such radiation can be used for imaging purposes and, therefore, is sometimes referred to herein as imaging radiation. Similar to the system 100 of FIG. 1 , the lenses 104(a), 104(b) and 104(c) of FIG. 2 can direct, focus and/or spectrally filter the incident X-ray that is delivered to the target 106 at, for example, high diverging angles. However, in contrast to FIG. 1, X-ray radiation that is not incident on the lenses 104(a), 104(b) and 104(c) is incident upon at least an imaging radiation shutter 208 that is located in the direct path between the source 102 and the target 106. In some example embodiments, the imaging radiation shutter 208, when closed, operates similar to the stop 108 that was described in connection with FIG. 1. As such, in one mode of operation, the imaging radiation shutter 208 can block (or greatly attenuate) the X-ray radiation in the direct path from the source 102 to the target 106. When the imaging radiation shutter 208 is at least partially open, all or a portion of the X-ray radiation 107 from that is incident upon the imaging radiation shutter 208 can reach the target 106. FIG. 2 also illustrates a detector 212 that is located, for example, behind the patient and can capture at least a portion of the imaging radiation 107 after the imaging radiation has interacted with the target. Such an interaction can include, but is not limited to, reflection, scattering, transmission, and combinations thereof. The detector 212 can include a single detector or a plurality of detector elements that are, for example, arranged to form a detector array. Through the use of at least the imaging radiation shutter 208 and the detector 212, the system 200 of FIG. 2 becomes capable of acquiring images of the target 106 during a treatment session, while the treatment radiation is also being directed to the target 106. In some embodiments, the radiation source 102, the lenses 104(a), 104(b) and 104(c), the shutter 208 and the detector 212 may be rotated around the body (and therefore the target) to irradiate the target 106 from different directions, thus enabling the acquisition of multiple images that can enable reconstruction of, for example, three-dimensional images of the target 106. In some embodiments, the detector 212 is positioned such that it receives the imaging radiation without receiving appreciable treatment radiation (i.e., radiation from the high divergence beams that are directed to the target 106 by the lenses 104(a), 104(b) and 104(c)). This is illustrated in FIG. 2, where the detector 212 is placed just outside of the path of high divergence beams. In other embodiments, the location and size of the detector 212 can readily adjusted within the system 200. In some embodiments, the treatment radiation may be blocked from reaching the detector 212 by using filters, shutters or other mechanisms. In one particular example, the detector 212 may be implemented as part of a movable mechanism or platform that allows the detector 212 to move inside and outside of the treatment radiation and/or imaging radiation path. Such a movable mechanism may also allow the detector to move within the treatment and/or imaging radiation path to provide images with proper characteristics, such as sharpness, contrast, brightness, and the like. In some embodiments, the imaging radiation is filtered to modify the spectral content and/or intensity of the X-ray radiation that is incident upon the target 106 so as to protect the non-target regions from harmful radiation. Moreover, filtering of the imaging radiation 107 may be adjusted to provide optimal contrast, brightness, sharpness and other characteristics of the acquired images. Filtering of the imaging radiation can be carried out using filters that are constructed from, for example, metal sheets that are placed in the imaging radiation path. In some example embodiments, such filters constitute separate components from the imaging radiation shutter 208. In some embodiments, however, the filters may be implemented as part of the imaging radiation shutter 208. According to some embodiments, a treatment radiation shutter 210 may be placed in the path between the X-ray source 102 and the lenses 104(a), 104(b) and 104(c) so as to block or attenuate the radiation that would normally reach the lenses 104(a), 104(b) and 104(c). A variety of shutter designs for both the imaging and treatment radiation can be used, including designs that are typically used in photographic cameras. In FIG. 2, the treatment radiation shutter 210 is illustrated as having a hollow central portion 214 to allow the imaging radiation 107 from the source 102 to propagate towards the target 106. The treatment radiation shutter 210 and the imaging radiation shutter 208 may be controlled independently from one another to enable simultaneous or time-multiplexed operations of the two shutters. For example, in one mode of operation, the treatment radiation shutter 210 is configured to block the treatment radiation, while the imaging radiation shutter 208 is configured to allow at least a portion of the imaging radiation 107 to reach the target 106. This exemplary mode of operation can, for example, be utilized prior to or after a treatment session, as well as during a treatment session when the treatment radiation is momentarily turned off. In another mode of operation, the treatment radiation shutter 210 is configured to allow the treatment radiation to reach the lenses 104(a), 104(b) and 104(c), while the imaging radiation shutter 208 is configured to block the imaging radiation 107. This exemplary mode of operation can, for example, be utilized during a treatment session when acquiring images of the target 106 is not needed. In another mode of operation, the treatment radiation shutter 210 is configured to allow the treatment radiation to reach the lenses 104(a), 104(b) and 104(c), while the imaging radiation shutter 208 is also configured to allow at least a portion of the imaging radiation 107 to reach the target 106. This exemplary mode of operation can, for example, be utilized during a treatment session to allow simultaneous treatment and imaging of the target. In another mode of operation, both the treatment radiation shutter 210 and imaging radiation shutter 208 may be configured to block the respective radiations. This exemplary mode of operation can, for example, be used when the X-ray system is turned off or is temporarily disabled to allow, for example, movement of the x-ray tube and/or the whole system configuration to a new position. By controlling the operations of the treatment radiation shutter 210 and the imaging radiation shutter 208, different modes of operations can be combined to, for example allow the treatment and imaging radiations to reach the target 106 in a time-multiplexed fashion in accordance with a desired duty cycle. The control signals that are provided to the treatment radiation shutter 210 and the imaging radiation shutter 208 can be controlled through additional components (not shown) that can be implemented as hardware, software, firmware or combinations thereof. In some implementations, a system control module 230 is provided in the system 200 to control the imaging-guided delivery of the treatment radiation onto the target 106. The control module 230 can be in communications with the detector 212 enabling the movement of the detector 212 (if needed), to receive imaging information of the target based on the received radiation at the detector 212, and to control the operations of the imaging radiation shutter 208, the treatment radiation shutter 210, and the X-ray source 102. The control module 230 can be used to automated controls of the source 102, the shutters 210 and 208 based on the imaging information from the detector 212. The control module 230 can also be used to control the lenses 104(a), 104(b) and 104(c), e.g., the positions or orientations of such lenses, to adjust the treatment radiation from the lenses 104(a), 104(b) and 104(c) onto the target based on the imaging information from the detector 212. This adjustment can be in the position, spectral contents, intensity, or focusing of the converged treatment radiation on the target 106. FIG. 3 illustrates a system 300 that is configured to allow treatment, as well as imaging of a target 106 in accordance with another exemplary embodiment. The exemplary system 300 of FIG. 3 includes similar components as the exemplary system 200 of FIG. 2, except for the treatment radiation shutter 310 that is located in the path between the lenses 104(a), 104(b) and 104(c) and the target 106. Such a configuration enables the use of a thinner and lighter treatment radiation shutter 310 since such a shutter operates on monochromatic X-ray radiation. Compared to the treatment radiation shutter 210 of FIG. 2, the hollow central portion 314 of the treatment radiation shutter 310, as well as the portions of the shutter 210 that modulate that treatment radiation, may need to be modified in size to enable for the propagation of sufficient imaging and treatment radiation through the treatment radiation shutter. Numeral 307 refers to boundaries of the imaging portion of the radiation. Moreover, compared to the treatment radiation shutter 210 of FIG. 2, the choice of placement of the treatment radiation shutter 310 may be limited to only a fraction of the distance between the lenses 104(a), 104(b) and 104(c) and the target 106 since the last portion of that distance is likely within the body of the patient. The detector 312 of FIG. 3 is also depicted as having a somewhat different size and location compared to its counterpart in FIG. 2. This change is merely done to illustrate that different detectors with different sizes and at different locations can be implemented as part of the disclosed embodiments. In some embodiments, the imaging radiation shutter and the treatment radiation shutter may be incorporated as part of a single composite shutter. In such a configuration, the central portion of the composite shutter operates as an imaging radiation shutter (with or without filtering capability), whereas the remaining portions of the composite shutter operate as a treatment radiation shutter. As discussed above in connection with FIGS. 2 and 3, the two shutters can be controlled independently from one another to enable simultaneous or time-multiplexed gating and/or modulation of the imaging and treatment radiations. The above described systems of the exemplary embodiments can be constructed in a very cost effective manner since they require only a single radiation source for both treatment and imaging purposes. Therefore, by adding one or more shutters, one or more filters (optional), an imaging detector and the associated electronic circuitry, an X-ray treatment system can be utilized to also produce accurate data describing the location and the size of a target. Moreover, in the above described systems of the exemplary embodiments in FIGS. 2 and 3, the imaging axis and treatment axis are substantially the same. The alignment of the treatment radiation and the imaging radiation simplifies the calibration (or mapping) of the position of the treatment radiation relative to the imaging radiation. In some embodiments an additional shutter 315 blocks the treatment X-rays and/or scattered X-rays from reaching the detector 312 such that only the imaging X-rays are collected by the detector. In some embodiments, the energy of the X-ray source, which can be used for imaging and treatment purposes, is below 1 Mega electron volt (Mev). In one particular example, the spectral range of the treatment radiation can be selected to be in the range of several tens of electron volts. Such a spectral range is also suitable for achieving high contrast imaging, which allows proper differentiation of different body parts. By selecting the imaging radiation to be somewhat centered in this spectral range, the choice and thickness of metal shutters and filters becomes quite cost effective, as is the mechanism for opening and closing the shutters. For example, the shutters can be produced using relatively thin sheets of material with properly selected atomic number Z values so as to provide the needed absorption of the respective radiation. This is in stark contrast to the expensive shuttering mechanisms needed in conventional radiation therapy equipment, such as the very thick metal components needed in Multi Leaf Collimators (MLC) to stop the typical high energy treatment beams in linear accelerators. In some exemplary embodiments, the X-ray treatment/imaging system is designed to be able to move the focal spot of the X-ray tube toward or away from the target. Such a capability provides varying degrees of magnification of the area of interest when the X-ray treatment/imaging system is used in imaging only mode. In addition, such a capability provides variability in selecting the size of the imaged area. FIG. 4 illustrates a system 500 that is configured to allow treatment, as well as imaging of a target 106 in accordance with another exemplary embodiment. The exemplary system 500 includes some components that are similar to those illustrated in FIG. 2, including the lenses 104(a), 104(b) and 104(c), the first radiation source 102, the stop 108, the treatment radiation shutter 210 and the target 106. The exemplary system 500 of FIG. 4 further includes an imaging system that guides the radiation outside the optical axis via path 507 reaching target 106 at an angle relative to the optical axis. The exemplary system 500 of FIG. 4 further includes an imaging radiation shutter 520 that is configured to control the imaging radiation 507 that is incident upon the target 106 through a plurality of reflectors 522, 524. In one example embodiment, the reflectors 522, 524 are double reflection reflectors. The detector 512 captures at least a portion of the imaging radiation after it has interacted with the target 106. The imaging radiation shutter 520 does not affect the radiation that is directed to the one or more lenses 104(a), 104(b) and 104(c) by, for example, including a hollow central portion. In contrast to FIG. 2, the imaging radiation of the exemplary system 500 of FIG. 5 does not traverse a direct path between the X-ray source 102 and the target 106. But, as illustrated in FIG. 4, the imaging radiation reaches the target 106 after reflections from the reflectors 522, 524. The reflectors 522 and 524 that are depicted in the exemplary system 500 of FIG. 4 can have the suitable geometry that is needed to allow proper reflection of the imaging radiation onto the target 106. For example, the reflectors 522, 524 can be concave, convex or flat (or combinations thereof) crystal reflectors. The exemplary system 500 of FIG. 4 can further include a filter in the imaging radiation path that operates to limit at least one of the intensity and/or spectral content of the radiation that irradiates the target. Similar to the operations of the exemplary systems in FIGS. 2 and 3, the first and second shutters can be controlled to enable simultaneous or time-multiplexed irradiation of the target 106 with the treatment and imaging radiation. In the exemplary system 500 of FIG. 4, the reflectors 522, 524 and the detector 512 form one reflector-detector set. In some embodiments, several reflector-detector sets are provided to enable the acquisition of multiple images from multiple angles. Alternatively, or additionally, the one or more reflector-detector sets can be rotated around the target in order to enable the acquisition of multiple images for construction of, for example, two and three-dimensional images by, for example, using Tomo Synthesis, simple CT techniques or other techniques. In some embodiments, where complete rotations around the target are not possible, only rotations within a particular angular cone (illustrated in FIG. 4, by the way of example, as a cone having an angle Θ) are carried out to acquire images of the target 106. The exemplary embodiments that are shown in FIGS. 1 to 4 illustrate X-ray treatment/imaging systems with components that operate based on Bragg diffraction principles. However, it is understood that the disclosed embodiments can additionally, or alternatively, utilize components that operate based on Laue diffraction principles. As such, filtering, focusing and guiding of the X-ray radiation can be carried out using transmissive and/or reflective components. Moreover, at least some of the imaging techniques and systems that are described herein can be used in non-X-ray treatment systems, such as in proton therapy or other radiation therapy systems. As such, the imaging techniques and components that are described in the present application may be used to enable imaging of a target before, during and after a non-X-ray treatment session. For example, FIG. 5 illustrates a system 600 that is configured to allow treatment, as well as imaging of a target 106 in accordance with another exemplary embodiment. Similar to the configuration of FIG. 4, the radiation from the source 602 is reflected by the reflectors 522, 524 and reaches the target 106 via path 507 as imaging radiation. At least a portion of the imaging radiation is received at the detector 512 after interacting with the target 106. The treatment system 602 can be a non-X-ray treatment system such as a proton therapy system. The radiation from the source 602 may be modulated and/or turned on/off using an imaging radiation shutter 618. Additionally, or alternatively, the operation of the source 602 may be controlled through a control module 618. In example embodiments that utilized the imaging radiation shutter 618, the operation of the imaging radiation shutter 620 can also be controlled by the control module 618. The control module 618 may also control the operation of the detector 512 and, optionally, the treatment system 602. For example, the control module 618 may sent or receive synchronization information and signals to/from the treatment system 602. The imaging radiation 507 may be optionally filtered to produce the desired intensity and/or spectral content of the imaging radiation that is received at the target 106. FIG. 6 illustrates a set of operations 700 that can be carried out to allow treatment, as well as imaging of a target in accordance with an exemplary embodiment. At 702, X-ray radiation from an X-ray source at a first shutter (i.e., the imaging radiation shutter) is received. The first shutter is located in a path between the X-ray source and the target, and the X-ray source also provides radiation to be directed by one or more lenses as treatment radiation onto a target at, for example, one or more converging angles. At 704, the operation of the first shutter is controlled to selectively allow the X-ray radiation to reach the target as imaging radiation. At 706, at least a portion of the imaging radiation is received at a detector, after the imaging radiation has interacted with the target. At 706, the imaging information of the target from the detector is used to control a property of the treatment radiation onto the target. In some embodiments, the operations 700 can further include (not shown) controlling a second shutter (i.e., treatment radiation shutter) to selectively allow the treatment radiation to reach the target. FIG. 7 illustrates a set of operations 800 that can be carried out to allow treatment, as well as imaging of a target in accordance with another exemplary embodiment. At 802, operation of the first X-ray source in an X-ray system is controlled. The first X-ray source provides radiation to be directed by one or more lenses as treatment radiation onto a target at one or more converging angles. The radiation from the first X-ray source that is not incident upon the one or more lenses is blocked from reaching the target by placing a stop in the direct path between the first X-ray source and the target. At 804, an operation of a second X-ray source in the X-ray system is controlled to provide imaging radiation that is incident upon the target. The second X-ray source is located between the target and the stop. At 806, at least a portion of the imaging radiation is received at the detector, after the imaging radiation has interacted with the target. The operation of the X-ray treatment/imaging systems that are described in the present application can require synchronous and/or asynchronous control of the treatment and imaging components, including but not limited to control of the X-ray source(s), filters, shutters, imaging detectors, focusing and targeting components, and the like. To this end, specific hardware, software and/or firmware components can be developed to provide the needed timing synchronization and control of the various components of the X-ray systems. For example, some or all of the needed operations can be implemented using a processor, a memory unit, and an interface that are communicatively connected to each other. In particular, the memory can be in communication with the processor, and at least one communication unit enables the exchange of data and information, directly or indirectly, through a communication link with other entities, devices, user interfaces, databases and networks. The communication unit can, for example, provide wired and/or wireless communication capabilities in accordance with one or more communication protocols, and therefore it may comprise the proper transmitter/receiver antennas, circuitry and ports, as well as the encoding/decoding capabilities that may be necessary for proper transmission and/or reception of data and other information. Moreover, at least some of the embodiments described herein are described in the general context of methods or processes, which may be implemented in one embodiment by a computer program product, embodied in a computer-readable medium, including computer-executable instructions, such as program code, executed by computers in networked environments. A computer-readable medium may include removable and non-removable storage devices including, but not limited to, Read Only Memory (ROM), Random Access Memory (RAM), compact discs (CDs), digital versatile discs (DVD), Blu-ray Discs, etc. Therefore, the computer-readable media described in the present application include non-transitory storage media. Generally, program modules may include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types. Computer-executable instructions, associated data structures, and program modules represent examples of program code for executing steps of the methods disclosed herein. The particular sequence of such executable instructions or associated data structures represents examples of corresponding acts for implementing the functions described in such steps or processes. The foregoing description of embodiments has been presented for purposes of illustration and description. The foregoing description is not intended to be exhaustive or to limit embodiments of the present invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of various embodiments. The embodiments discussed herein were chosen and described in order to explain the principles and the nature of various embodiments and its practical application to enable one skilled in the art to utilize the present invention in various embodiments and with various modifications as are suited to the particular use contemplated. The features of the embodiments described herein may be combined in all possible combinations of methods, apparatus, modules, systems, and computer program products.
	summary
054328292	claims	1. A fuel assembly comprising a number of fuel rods arrayed in a square lattice pattern, and at least one neutron moderating rod having a cross-sectional area of a moderator larger than a cross-sectional area of a unit lattice of the fuel rod array, wherein: (a) said fuel rods include a plurality of first fuel rods and one or more second fuel rods having a shorter fuel effective length than said first fuel rods; (b) said second fuel rods are arranged in an outermost layer of said fuel rod array in the square lattice pattern at positions other than corners of the outermost layer; and (c) among the fuel rods inside said outermost layer of said fuel rod array in the square lattice pattern and arranged in a layer adjacent to said outmost layer, all of the fuel rods adjacent to said second fuel rods in said outermost layer are said first fuel rods. (a) said fuel rods include a plurality of first fuel rods and one or more second fuel rods having a shorter fuel effective length than said first fuel rods; (b) said second fuel rods are arranged in an outermost layer of said fuel rod array in the square lattice pattern at positions other than corners of the outermost layer; and (c) all of the fuel rods inside said outermost layer of said fuel rod array in the square lattice pattern and arranged in a layer adjacent to said outermost layer are said first fuel rods. (a) said core includes a plurality of first fuel assemblies and a plurality of second fuel assemblies, said second fuel assemblies each comprise a number of fuel rods; (b) said first fuel assemblies each comprise a number of fuel rods arrayed in a square lattice pattern and at least one neutron moderating rod having a cross-sectional area of a moderator larger than a cross-sectional area of a unit lattice of the fuel rod array, said fuel rods including a plurality of first fuel rods and one or more second than said first fuel rods, said second fuel rods being arranged in an outermost layer of said fuel rod array in the square lattice pattern at positions other than corners of the outermost layer, among the fuel rods inside said outermost layer of said fuel rod array in the square lattice pattern and arranged in a layer adjacent to said outermost layer, all of the fuel rods adjacent to said second fuel rods in said outermost layer being said first fuel rods; and (c) said first fuel assemblies and said second fuel assemblies are loaded in a core central portion and a core circumferential portion, said first fuel assemblies having a smaller loading ratio in the core central portion than in the core circumferential portion. 2. A fuel assembly according to claim 1, wherein said second fuel rods in said outermost layer are arranged at positions other than the corners and positions adjacent to the corners. 3. A fuel assembly according to claim 1, wherein when said neutron moderating rod is projected in two directions orthogonal to each other in said fuel rod array in the square lattice pattern, said second fuel rods arranged in said outermost layer are located inside a projected range of said neutron moderating rod including the outermost opposite regions of the projected range. 4. A fuel assembly according to claim 1, wherein the cross-sectional area of the moderator in said neutron moderating rod is from 7 to 14 cm.sup.2. 5. A fuel assembly according to claim 1, wherein said neutron moderating rod is arranged in a region able to accommodate 7 to 12 said fuel rods. 6. A fuel assembly according to claim 1, wherein said fuel rods further comprise one or more third fuel rods having a shorter fuel effective length than said first fuel rods, said third fuel rods being arranged adjacent to said neutron moderating rod. 7. A fuel assembly according to claim 1, wherein the number of said second fuel rods arranged in said outer layer is larger than the number of said third fuel rods arranged adjacent to said neutron moderating rod. 8. A fuel assembly according to claim 1, wherein said fuel rods further comprise one or more third fuel rods having a shorter fuel effective length than said first fuel rods, said third fuel rods being arranged in a fuel rod layer adjacent to said outermost layer inside thereof at positions of corners of said fuel rod layer. 9. A fuel assembly according to claim 1, wherein said second fuel rods are arranged two adjacent to each other in said outermost layer. 10. A fuel assembly according to claim 1, wherein said second fuel rods have a fuel effective length in a range of 1/2 to 3/4 of the fuel effective length of said first fuel rods. 11. A fuel assembly according to claim 1, wherein said neutron moderating rod is circular in cross-section and arranged three in a lattice region of 4.times.4 at the center of said fuel assembly along a diagonal line of said lattice region. 12. A fuel assembly according to claim 1, wherein said neutron moderating rod is circular in cross-section and arranged two in a lattice region of 3.times.3 at the center of said fuel assembly along a diagonal line of said lattice region. 13. A fuel assembly according to claim 1, wherein said neutron moderating rod includes a spectral shift rod in which an axial water level is changed depending on a core flow rate. 14. A fuel assembly according to claim 1, wherein the fuel rods arranged inside said outermost layer of said fuel rod array in the square lattice pattern in one layer adjacent to said outermost layer and another one layer adjacent to said one layer are said first fuel rods. 15. A fuel assembly comprising a number of fuel rods arrayed in a square lattice pattern, and at least one neutron moderating rod having a cross-sectional area of a moderator larger than a cross-sectional area of a unit lattice of the fuel rod array, wherein: 16. A fuel assembly according to claim 15, wherein said second fuel rods in said outermost layer are arranged at positions other than the corners and positions adjacent to the corners. 17. A fuel assembly according to claim 15, wherein when said neutron moderating rod is projected in two directions orthogonal to each other in said fuel rod array in the square lattice pattern, said second fuel rods arranged in said outermost layer are located inside a projected range of said neutron moderating rod including the outermost opposite regions of the projected range. 18. A fuel assembly according to claim 15, wherein said neutron moderating rod is arranged in a region able to accommodate 7 to 12 said fuel rods. 19. A fuel assembly according to claim 15, wherein said fuel rods further comprise one or more third fuel rods having a shorter fuel effective length than said first fuel rods, said third fuel rods being arranged adjacent to said neutron moderating rod. 20. A fuel assembly according to claim 15, wherein the number of said second fuel rods arranged in said outer layer is larger than the number of said third fuel rods arranged adjacent to said neutron moderating rod. 21. A fuel assembly according to claim 15, wherein said second fuel rods are arranged two adjacent to each other in said outermost layer. 22. A fuel assembly according to claim 15, wherein said second fuel rods have a fuel effective length in a range of 1/2 to 3/4 of the fuel effective length of said first fuel rods. 23. A fuel assembly according to claim 15, wherein said neutron moderating rod is circular in cross-section and arranged three in a lattice region of 4.times.4 at the center of said fuel assembly along a diagonal line of said lattice region. 24. A fuel assembly according to claim 15, wherein said neutron moderating rod is circular in cross-section and arranged two in a lattice region of 3.times.3 at the center of said fuel assembly along a diagonal line of said lattice region. 25. A fuel assembly according to claim 15, wherein said neutron moderating rod includes a spectral shift rod in which an axial water level is changed depending on a core flow rate. 26. A fuel assembly according to claim 15, wherein the fuel rods arranged inside said outermost layer of said fuel rod array in the square lattice pattern in one layer adjacent to said outermost layer and another one layer adjacent to said one layer are said first fuel rods. 27. A fuel assembly according to claim 15, wherein the lattice pattern of said fuel rod array comprises 10 rows and 10 columns. 28. A reactor core using light water as a coolant, wherein: 29. A reactor core according to claim 28, wherein in said first fuel assemblies, said second fuel rods in said outermost layer are arranged at positions other than the corners and positions adjacent to the corners. 30. A reactor core according to claim 28, wherein said second fuel assemblies include no fuel rods having a shorter fuel effective length than said first fuel rods. 31. A reactor core according to claim 28, wherein said second fuel assemblies include one or more third fuel rods having a shorter fuel effective length than said first fuel rods, the number of said third fuel rods being smaller than the number of said second fuel rods.
	abstract	An intensifying screen, comprising a support, a phosphor layer disposed on the support and a protecting film disposed on the phosphor layer. The phosphor layer comprises a first phosphor layer formed on the support side and constituted of particles of the first phosphor having average particle diameter D1 and range coefficient k, which expresses a particle size distribution, in the range of 1.3 to 1.8, and a second phosphor layer formed on the protective film side and constituted of particles of the second phosphor having average particle diameter D2 ( greater than D1) and range coefficient k, which expresses a particle size distribution, in the range of 1.5 to 2.0. The ratio (CW1:CW2) of coating weight per unit area of the particles of the first phosphor in the first phosphor layer CW1 and coating weight per unit area of the particles of the second phosphor in the second phosphor layer CW2 is in the range of from 8:2 to 6:4. According to such intensifying screens, even when phosphors of, for instance, high emission efficiency are employed, while preventing lowering of speed and sharpness from occurring, granularity can be improved.
052727386	abstract	In a device for monitoring the atmosphere within the containment shell (1) of a reactor plant, a sample removal means (41) is provided in the containment shell, from which a gas mixture is led via a measuring line (42) through a measuring zone (14) and subsequently discarded. The concentration of the gas is reduced upstream of the measuring zone (14) in a dilution plant (40).
042382904	claims	1. A controllable valve for the live steam line extending from the inside to the outside of the containment of a nuclear reactor plant comprising: (a) a valve body having an inlet, an outlet and a valve seat, each with a cross section corresponding to that of the live steam line; (b) probe means in the live steam line for detecting the pressure therein in order to detect a leak in said steam line; (c) a movable valve disk disposed within said valve body; (d) operating means coupled to said probe means and responsive thereto for moving the valve disk to a closed position in the event of a leak in the live steam line, said operating means being further responsive to the application of the pressure on the valve disk in excess of the normal operating pressure of the live steam line to move the valve toward an open position; and (e) limiting means for limiting the reopening of the valve in response to said excessive pressure to a maximum of one half the outlet cross section, whereby after closing, in response to a leak in the live steam line, said valve will reopen to prevent a build-up of pressure on its inlet side to prevent damage to the nuclear reactor plant. 2. The valve of claim 1 in which the disk has retard means for holding it from opening for more than about 30% of said aperture cross section under the force of said excessive pressure, at least for a short time interval. 3. The valve of claim 2 in which said retard means is adjustable. 4. The valve of claim 3 in which the valve disk has an operating stem and the said retard means comprises an adjustable mechanical stop for the stem and powered means for adjusting the stop. 5. The valve of claim 1 in which said operating means is for sequentially partially closing and thereafter fully closing the valve disk on the valve seat, under said force which is overcome by said excessive pressure. 6. The valve of claim 5 in which said partial closing leaves the valve with a residual aperture cross section of from 5% to 20% of said maximum aperture cross section. 7. The valve of claim 5 in which said partial closing is adjustable. 8. The valve of claim 1 in which said valve disk and valve seat have conical surfaces differently angled to form an annular Venturi when the valve disk is partially closed on the seat. 9. The valve of claim 1 in which the fast-acting valve is inside said containment. 10. The valve of claim 1 in which said operating means has a statically stored energy source controllably connected thereto.
047598972	claims	1. Apparatus for determining external dimensional relationships of a nuclear fuel assembly including an array of elongated fuel rods engaged in transverse grids and extending between top and bottom nozzles, said apparatus comprising: support means, positioning means on said support means for fixedly positioning the fuel assembly in a selected orientation to establish a first portion of the fuel assembly as a reference, carriage means mounted on said support means for movement longitudinally of the fuel assembly substantially the entire length thereof when it is disposed in said selected orientation, measuring means on said carriage means, and drive means on said carriage means for moving said measuring means between a retracted condition and a measuring condition disposed in measuring engagement with a second portion of the fuel assembly to measure the position and orientation of said second portion relative to said reference, and processing means responsive to said measurements of said second portion for determining said external dimensional relationships of the fuel assembly. 2. The apparatus of claim 1, wherein said positioning means includes means for engaging the top and bottom nozzles for retaining the fuel assembly in said selected orientation. 3. The apparatus of claim 1, wherein said selected orientation is with the direction of elongation of the fuel assembly disposed substantially vertically. 4. The apparatus of claim 1, and further including control means coupled to said positioning means and said carriage means and said drive means for remotely controlling the operation thereof. 5. The apparatus of claim 4, wherein said control means includes video camera means mounted on said carriage means for viewing the measurement operation. 6. The apparatus of claim 1, wherein said measuring means includes a plurality of measuring gauges respectively engageable with the fuel assembly at a plurality of measurement points. 7. The apparatus of claim 6, wherein each of said measuring gauges measures the distance of its associated measuring point from a fixed reference plane. 8. Apparatus for determining external dimensional relationships of a nuclear fuel assembly including an array of elongated fuel rods engaged in transverse grids and extending between top and bottom nozzles, wherein each of said grids and nozzles has external planar faces arranged in a rectangular configuration, said apparatus comprising: support means, reference means mounted on said support means for cooperation therewith to define mutually perpendicular X and Y and Z reference axes and XZ and YZ reference planes, positioning means on said support means for fixedly positioning the fuel assembly in a selected orientation with the faces of the top nozzle disposed parallel to said Z axis, measuring means carried by said support means for establishing on adjacent faces of each of the grids and nozzles a plurality of measurement points in a measurement plane perpendicular to said Z axis and measuring the distances of said points from said XZ and YZ planes, and processing means for calculating from said measured distances the location of the centre of each of the grids and nozzles in its associated measurement plane and further calculating from said center locations the tilt of the fuel assembly and the bow and twist of the fuel assembly at each of the grids thereof. 9. The apparatus of claim 8, wherein said measuring means includes a plurality of measuring gauges respectively engageable with a selected one of said grids and nozzles at said measurement points thereon. 10. The apparatus of claim 9, wherein said measurement means includes two measurement gauges movable parallel to said XZ plane and disposed at predetermined distances from said YZ plane and two measurement gauges movable parallel to said YZ plane and disposed at predetermined distances from XZ plane, whereby the coordinates of said measurement points are determined by said predetermined distances and said measured distances. 11. The apparatus of claim 8, wherein said support means is disposed so that said Z axis is substantially vertical. 12. The apparatus of claim 8, wherein said processing means includes a computer under program control. 13. The apparatus of claim 8, and further including control means coupled to said positioning means and to said measuring means for remotely controlling the operation thereof. 14. The apparatus of claim 13, wherein said reference means includes carriage means movable parallel to said Z axis, said measuring means being mounted on said carriage means, said control means being coupled to said carriage means for remotely controlling the operation thereof. 15. Apparatus for determining external dimensional relationships of a nuclear fuel assembly including an array of elongated fuel rods engaged in transverse grids and extending between top and bottom nozzles, wherein each of said grids and nozzles has external planar faces arranged in a rectangular configuration, said apparatus comprising: support means, carriage means mounted on said support means for cooperation therewith to define mutually perpendicular X and Y and Z reference axes and XY and XZ and YZ reference planes, positioning means on said support means for fixedly positioning the fuel assembly in a selected orientation with the faces of the top nozzle disposed parallel to said Z axis, said carriage means and said XY plane being movable parallel to said Z axis and generally longitudinally of the fuel assembly among a plurality of measuring locations respectively disposed adjacent to said nozzles and said grids with said XY plane defining a measurement plane intersecting the faces of the adjacent nozzle or grid, a plurality of measuring means mounted on said carriage means for movement in said XY plane into and out of measuring engagement with intersecting faces of the adjacent nozzle or grid for establishing on the faces a plurality of measurement points and measuring the distances of said points from said XZ and YZ planes, control means for controlling the movement of said carriage means and said measuring means, and processing means for calculating from said measured distances the location of the center of each of the grids and nozzles in its associated measurement plane and further calculating from said center locations the tilt of the fuel assembly and the bow and twist of the fuel assembly at each of the grids thereof. 16. The apparatus of claim 15, wherein said positioning means includes means movable into engagement with the top and bottom nozzles for retaining said fuel assembly in said selected orientation. 17. The apparatus of claim 16, wherein said control means includes means coupled to said positioning means for controlling the operation thereof. 18. The apparatus of claim 15, and further including chain drive means coupled to said carriage means for effecting movement thereof, and fluid drive means coupled to said positioning means and to said measuring means for effecting movement thereof. 19. The apparatus of claim 15, wherein said support means includes adjusting means for adjusting the orientation of said Z axis. 20. The apparatus of claim 15, wherein said processing means includes computer means operating under program control.
	claims	1. A process for separating americium from other metal elements present in a phase P1, which comprises one or more operations each comprising putting the phase P1 in contact with a phase P2 which is not miscible with the phase P1, and then separating the phase P1 from the phase P2, one of the phases P1 and P2 being an acid aqueous phase and the other one of the phases P1 and P2 being an organic phase which comprises at least one extractant in an organic diluent, and in which the acid aqueous phase contains an ethylenediamine derivative fitting the general formula (I) hereafter:wherein A1, A2, A3 and A4, which are identical or different, represent a group of general formula (II) hereafter:wherein:either X represents a nitrogen atom, in which case one of the R1, R2 and R4 represent a complexing group selected from the groups —COOH, —SO3H, —PO3H2, —CONH2 and —CON(CH3)2, while the other ones of R1, R2 and R4 represent independently of each other, a hydrogen atom or a group selected from the groups —OH, —NH2, —N(CH3)2, —COOH, —COOCH3, —CONH2, —CON(CH3)2, —SO3H, —SO3CH3, —PO3H2, —PO(OCH3)2, —O(CH2CH2)n—OH and —O(CH2CH2)n—OCH3 wherein n is an integer equal to or greater than 1;or X represents a carbon atom bearing a hydrogen atom or a group R3, in which case one of R1, R2, R3 and R4 represents a complexing group selected from the groups —COOH, —SO3H, —PO3H2, —CONH2 and —CON(CH3)2, while the other ones of R1, R2, R3 and R4 represent, independently of each other, a hydrogen atom or a group selected from the groups —OH, —NH2, —N(CH3)2, —COOH, —COOCH3, —CONH2, —CON(CH3)2, —SO3H, —SO3CH3, —PO3H2, —PO(OCH3)2, —O(CH2CH2)n—OH and —O(CH2CH2)n—OCH3 wherein n is an integer equal to or greater than 1;or a salt of the ethylenediamine derivative. 2. The process according to claim 1, in which, in general formula (I), A1, A2, A3 and A4 all represent a group of general formula (II) wherein X represents a nitrogen atom, or a carbon atom bearing a hydrogen atom, a group —OH or a group —O(CH2CH2)n—OH wherein n is an integer equal to or greater than 1. 3. The process according to claim 1, in which, in general formula (II), R1 represents a complexing group —COOH. 4. The process according to claim 3, in which, in general formula (II), R2 and R4 represent a hydrogen atom. 5. The process according to claim 1, in which, in the general formula (I), A1, A2, A3 and A4 are identical with each other. 6. The process according to claim 1, in which the ethylenediamine derivative of general formula (I) is selected from:N,N,N′,N′-tetrakis[-carboxypyridin-2-yl)methyl]ethylenediamine;N,N,N′,N′-tetrakis[(6-carboxy-4-hydroxypyridin-2-yl)methyl]ethylene-diamine;N,N,N′,N′-tetrakis[(6-carboxy-4-polyethyleneglycolpyridin-2-yl)methyl]-ethylenediamines; andN,N,N′,N′-tetrakis[(6-carboxypyrazin-2-yl)methyl]ethylenediamine. 7. The process according to claim 1, in which the acid aqueous phase is a nitric aqueous phase comprising from 0.001 to 3 mol/L of nitric acid. 8. The process according to claim 1, in which the ethylenediamine derivative of general formula (I) or salt thereof is present in the acid aqueous phase at a concentration ranging from 10−5 to 10−1 mol/L. 9. The process according to claim 1, in which the extractant(s) present in the organic phase is (are) selected from solvating extractants and cation exchange extractants. 10. The process according to claim 9, in which the extractant(s) is (are) selected from malonamides, N,N,N′,N′-tetraalkyl-3,6-dioxaoctane-diamides, lipophilic diglycolamides, alkylphosphine oxides, carbamoylphosphine oxides, carbamoylphosphonates, dialkyl sulfides, substituted pyridines, 2,2′-dibenzimidazoles, bisphenylphosphonic acid alkyl esters, alkylphosphoric acids, alkyphosphonates, alkylphosphinic acids, lipophilic carboxylic acids, sulfonic acids, thiophosphoric acids, thiophosphonic acids, thiophosphinic acids, thiophosphinic acids, thiophosphorous acids, lipophilic hydroxyoximes and lipophilic β-diketones. 11. The process according to claim 1, in which the organic phase further comprises at least one phase modifying agent. 12. A process for selectively recovering americium from a first acid aqueous phase comprising americium and other metal elements, the process comprising a step of separating americium from the other metal elements present in a phase P1, which comprises one or more operations each comprising putting the phase P1 in contact with a phase P2 which is not miscible with the phase P1, and then separating the phase P1 from the phase P2, one of the phases P1 and P2 being the first acid aqueous phase or a second acid aqueous phase and the other one of the phases P1 and P2 being an organic phase which comprises at least one extractant in an organic diluent, and in which the first or second acid aqueous phase comprises an ethylenediamine derivative fitting general formula (I) hereafter:wherein A1, A2, A3 and A4, which are identical or different, represent a group of general formula (II) hereafter:wherein:either X represents a nitrogen atom, in which case one of the R1, R2 and R4 represent a complexing group selected from the groups —COOH, —SO3H, —PO3H2, —CONH2 and —CON(CH3)2, while the other ones of R1, R2 and R4 represent independently of each other, a hydrogen atom or a group selected from the groups —OH, —NH2, —N(CH3)2, —COOH, —COOCH3, —CONH2, —CON(CH3)2, —SO3H, —SO3CH3, —PO3H2, —PO(OCH3)2, —O(CH2CH2)n—OH and —O(CH2CH2)n—OCH3 wherein n is an integer equal to or greater than 1;or X represents a carbon atom bearing a hydrogen atom or a group R3, in which case one of R1, R2, R3 and R4 represents a complexing group selected from the groups —COOH, —SO3H, —PO3H2, —CONH2 and —CON(CH3)2, while the other ones of R1, R2, R3 and R4 represent, independently of each other, a hydrogen atom or a group selected from the groups —OH, —NH2, —N(CH3)2, —COOH, —COOCH3, —CONH2, —CON(CH3)2, —SO3H, —SO3CH3, —PO3H2, —PO(OCH3)2, —O(CH2CH2)n—OH and —O(CH2CH2)n—OCH3 wherein n is an integer equal to or greater than 1;or a salt of the ethylenediamine derivative. 13. The process according to claim 12, in which the first acid aqueous phase is a nitric aqueous phase which comprises as other metal elements at least curium and fission products including lanthanides, and is free of uranium, plutonium and neptunium or comprises uranium, plutonium and neptunium as trace amounts. 14. The process according to claim 13, in which the nitric aqueous phase is a raffinate stemming from a first purification cycle of a process for processing used nuclear fuels PUREX or COEX. 15. The process according to claim 12, which comprises at least the following steps:a) extraction of the americium and of all or part of the other metal elements from the first acid aqueous phase, the extraction comprising at least one operation in which the first acid aqueous phase is put into contact with an organic phase which is non-miscible with the first acid aqueous phase, the organic phase comprising at least one extractant in an organic diluent, and then the first acid aqueous phase is separated from the organic phase; andb) selective stripping of the americium from the organic phase stemming from step a), the stripping comprising at least one operation in which the organic phase is put into contact with the second acid aqueous phase, the second aqueous phase comprising the ethylenediamine derivative of general formula (I) or the salt thereof, and then the organic phase is separated from the second acid aqueous phase. 16. The process according to claim 15, in which the first acid aqueous phase subject to step a) comprises at least one complexing agent. 17. The process according to claim 15, in which:step a) further comprises, after the separation of the organic phase from the first acid aqueous phase, at least one operation of washing the organic phase with a third acid aqueous phase; and/orstep b) further comprises, after the separation of the organic phase from the second acid aqueous phase, at least one operation of washing the second acid aqueous phase with an organic phase having the same composition as the one organic phase used in step a). 18. The process according to claim 15, which further comprises a step c) of stripping the other metal elements from the organic phase stemming from step b), the stripping comprising at least one operation in which the organic phase is put into contact with a fourth acid aqueous phase and then the organic phase is separated from the fourth acid aqueous phase. 19. The process according to claim 15, in which the organic phase used in step a) comprises a mixture of a malonamide and of an alkylphosphoric acid, or a diglycolamide extractant. 20. The process according to claim 12, which comprises at least one step a) of selective extraction of all the other metal elements from the first acid aqueous phase, the extraction comprising at least one operation in which the first acid aqueous phase is put into contact with an organic phase which is non-miscible with the first acid aqueous phase, the organic phase comprising at least one extractant in an organic diluent, and then the first acid aqueous phase is separated from the organic phase, and the extraction being carried out after or simultaneously to an addition of the ethylenediamine derivative of general formula (I) or the salt thereof to the first acid aqueous phase. 21. The process according to claim 20, in which step a) further comprises, after the separation of the organic phase from the first acid aqueous phases, at least one operation of washing the organic phase, the washing comprising putting the organic phase in contact with a second acid aqueous phase comprising the ethylenediamine derivative of general formula (I) or the salt thereof and then separating the organic phase from the second acid aqueous phase. 22. The process according to claim 20, which further comprises a step b) of stripping the other metal elements from the organic phase stemming from step a), the stripping comprising at least one operation in which the organic phase is put into contact with a third acid aqueous phase, and then the organic phase is separated from this the third acid aqueous phase. 23. The process according to claim 22, in which the third acid aqueous phase used in step b) comprises at least one complexing agent. 24. The process according to claim 20, in which the organic phase used in step a) comprises a mixture of an alkylphosphoric acid extractant and of a phase modifying agent, or a diglycolamide extractant. 25. The process according to claim 12, characterized in that the ethylenediamine derivative of general formula (I) is N,N,N′,N′-tetrakis[(6-carboxypyridin-2-yl)methyl]ethylenediamine. 26. The process according to claim 12, characterized in that the ethylenediamine derivative of general formula (I) or the salt thereof is present in the first or second acid aqueous phase at a concentration ranging from 10−4 to 10−2 mol/L.
	description	This invention relates generally to nuclear reactors and more particularly to a heat removal system in a containment. One known boiling water nuclear reactor includes a reactor pressure vessel (RPV) positioned in a drywell, or containment, suppression pool (SP) and a passive containment cooling system (PCCS). The RPV contains a core, and the containment is designed to withstand design pressure defined by a loss of coolant accident (LOCA) and other loads associated with plant operation. The PCCS is configured to limit the containment pressure below the design value and to keep the RPV core substantially cool during a postulated loss of coolant accident. Typically the bottom floor of the containment vessel is part of the basemat of the reactor building. The basemat, in certain situations, rests on bedrock and typically supports the reactor building, containment vessel wall, suppression pool and reactor pedestal that supports the RPV including the internal components of the reactor. In the event of a severe accident in which the molten core is postulated to penetrate the lower head of the reactor, the molten core would flow into the region below the reactor pressure vessel and contacts the floor of the containment vessel that is lined with a stainless steel liner. There are several known methods of protecting the containment liner and basemat structure from the molten core debris. However, some methods do not include long-term stabilization by cooling the molten core debris. In one aspect, an assembly is provided that includes a base grid configured to be disposed below a pressure vessel and spaced vertically above a floor of a containment vessel to define a sump therebetween. The assembly further includes an annular wall extending vertically upwards from the floor and laterally bounding the base grid and the sump, the wall separates the sump from a suppression pool, at least one flow baffle extending into the sump from the wall, an inlet passage extending through the wall, the inlet passage providing flow communication between the sump and the suppression pool, and an outlet passage extending through the wall, the outlet passage providing flow communication between the sump and the suppression pool. In another aspect, an assembly is provided that includes a containment vessel, the containment vessel having a drywell and a floor, a reactor pressure vessel installed inside the containment vessel, a base grid disposed below the pressure vessel and spaced vertically above the floor of the containment vessel to define a sump therebetween, at least one flow baffle in the sump; an annular wall extending vertically upward from the base grid, the wall spaced inwardly from a sidewall of the containment vessel to define an annular channel therebetween, an inlet flow channel extending through the channel providing flow communication between the drywell and the sump, and an outlet flow channel extending through the channel providing flow communication between the sump and the drywell. In another aspect, a nuclear reactor is provided that includes a primary containment including a floor, a reactor pressure vessel located in the primary containment, a drywell located in the primary containment and disposed above the reactor pressure vessel, a suppression pool located in the primary containment and disposed adjacent to the reactor pressure vessel, and a core cooling system located in the primary containment and disposed below the reactor pressure vessel. The core cooling system including a base grid having a top plate and a bottom plate, the base grid is spaced vertically above the floor of the containment vessel to define a sump therebetween, a substantially sinuous flow path defined in the sump, an inlet passage providing flow communication between the sump and at least one of the drywell and the suppression pool, and an outlet passage providing flow communication between the sump and at least one of the drywell and the suppression pool, the inlet and outlet passages configured to circulate water between the sump and at least one of the drywell and the suppression pool through convection. FIG. 1 is a schematic depiction of a nuclear reactor system 10 in accordance with one embodiment of the present invention. Nuclear reactor system 10 includes a cylindrical reactor pressure vessel 12 (RPV) which encloses a reactor core 14. RPV 12 includes a cylindrical wall 16 sealed at one end by a top head 18 and at the other end by a bottom head 20. RPV 12 is housed in a primary containment vessel 22 (PCV). The inside surface of the primary containment vessel 22 is lined with a steel liner. Primary containment vessel 22 includes a drywell 24 and a wetwell 26. In one embodiment, drywell 24 is a concrete cylinder with a domed top, and wetwell 26 is an annular chamber formed by a RPV pedestal or wall 28 and primary containment vessel 22. A suppression pool of water 30 is located in wetwell 26, and RPV 12 is located in drywell 24. Connection between drywell 24 and wetwell 26 is provided by the drywell/wetwell vent system embedded within wall 28. During a severe accident, additional connection is activated between the lower drywell and the suppression pool 30 through a plurality of fusible valves 32 in the lower part of drywell wall 28. Downcomers or tubular channels (not shown) extend vertically within wall 28. One end of each downcomer is open to drywell 24 and the other end is coupled to horizontal nozzles 31 which are immersed in water of suppression pool 30. Drywell wall 28 extends vertically from a basemat 82 of PCV 22 and separates drywell 24 from suppression pool 30. In one embodiment, drywell wall 28 is annular. Valves 32 are fusible, and remain closed until the temperature in drywell 24 exceeds a predetermined temperature. At the predetermined temperature, valves 32 open to permit water to flow from suppression pool 30 into drywell 24. Additionally, a feedwater line 34 supplies water to RPV 12, and a steam line 36 carries steam away from RPV 12. Also shown in FIG. 1 are two primary containment cooling systems 38 and 40, sometimes referred to herein as PCCS 38 and 40. PCCS 38 and 40 include condensers, or heat exchangers, 42 and 44 that condense steam and transfer heat to water in a large condenser pool 46 which is vented to the atmosphere. Each condenser 42 and 44 is submerged in a respective compartment of condenser pool 46 located high in the reactor building at approximately the same elevation as the fuel pools. Condenser pool 46 is above and outside of PCV 22. In one embodiment, nuclear reactor system 10 does not include PCCS 38. Each condenser 42 and 44 is coupled to an upper drum 48 and a lower drum 50. Steam enters PCCS 38 and 40 through lines, or flowpaths, 52 and 54 respectively. A steam-gas mixture may also enter PCCS 38 through line, or flowpath, 56 from RPV 12. The steam is condensed in condensers 42 and 44 and falls to lower drum 50. From lower drum 50, the steam condensate and the noncondensable gases can be drained and vented through lines 58 and 60 having outlets which are submerged in suppression pool 30. Heat from PCCS 38 and 40 causes condenser pool 46 temperature to rise to a point where the condenser pool water will boil. The steam which is formed, being nonradioactive and having a slight positive pressure relative to station ambient pressure, is vented from the steam space above each PCCS 38 and 40 to outside the reactor building via discharge vents 62. A moisture separator may be installed at the entrance to discharge vents 62 to preclude excessive moisture carryover and loss of condenser pool water. In the event of a severe accident, the reactor core 14 may become overheated and the nuclear fuel therein, which includes uranium, may melt to form a liquid molten mass referred to herein as corium 70. Corium 70 will melt its way through bottom head 20 of pressure vessel 12 and drop to a corium protection assembly. In order to protect PCV 22 from the corium 70 and contain it therein, a corium protection assembly or core catcher 80 in accordance with one embodiment of the present invention is provided. Core catcher 80 is positioned proximate a basemat 82 of PCV 22 in a lower region of drywell 24. FIG. 2 is a schematic side view of one embodiment of core catcher 80. Core catcher 80 includes a base grid 84 disposed below the pressure vessel 12 and spaced vertically above basemat 82 of PCV 22 to define a gap or sump 86 therebetween. Drywell wall 28 lateral bounds base grid 84 and sump 86. Base grid 84 has a top plate 87 and a bottom plate 88. Base grid 84 has base grid shield walls 89 extending vertically from top plate 87 of base grid 84. In one embodiment, a plurality of columns 90 support a web of I-beams 92 on which is mounted base grid 84. The web defines openings between I-beams 92 facilitating fluid flow under base grid 84. In one embodiment, a plurality of layers of laterally adjoining protective blocks (not shown) are disposed on top plate 87 of base grid 84 and are sized and configured for protecting PCV 22 from corium 70. In another embodiment, base grid 84 includes a supported structure (not shown) made of a steel layer, which is covered on top plate 87 with a refractory material 85 and cooled by water 94. Water 94 may be provided by flooding the lower drywell 24 through a conduit 96 using either active (pumps) or passive (gravity) means. In another embodiment, bottom plate 88 and the side surface of cylindrical wall 89 are covered with insulation material 98 (or ceramic material) to prevent degradation of strength of core catcher 80 due to high temperatures from corium 70. Insulation material (or ceramic material) protects core catcher 80 to maintain its structural integrity such that corium 70 can be retained in core catcher 80 and cooled. Core catcher 80 includes at least one flow baffle 100 disposed in sump 86. In one embodiment, flow baffle 100 extends from wall 28. Flow baffle 100 has a base end 106 and a tip end 107, whereby base end 106 has a larger cross-sectional area than tip end 107. Flow baffle 100 has a flow inlet side 102 and a flow outlet side 104. In one embodiment, flow baffles 100 are configured to extend around existing I-beams 92 such that I-beams 92 are not changed to accommodate flow baffles 100. In a further embodiment, flow baffle 100 is annular and extends from wall 28 to define a flow baffle opening 108. As shown in FIG. 2, wall 28 includes an inlet flow passage 110 and an outlet flow passage 112 extending therethrough. Both inlet and outlet flow passages 110 and 112 provide flow communication between suppression pool 30 and sump 86. In one embodiment, inlet flow passage 110 is substantially parallel to basemat 82 and outlet flow passage 112 is angled upward from sump 86 to suppression pool 30. Inlet flow passage 110 is positioned in wall 28 to discharge water from suppression pool 30 into sump 86 proximate to flow inlet side 102 of flow baffle 100. Sump 86 is continually maintained to have a sufficient level of water to accomplish the objectives described herein. In the event of a core melt, water from a lower region (cooler water) of suppression pool 30 is drawn through inlet flow passage 110 to sump 86. Water enters sump 86 in a first flow path 120 and travels along flow inlet side 102 of flow baffle 100. As the water is heated by corium 70, the heated water/steam mixture exits sump 86 and travels in a second flow path 122 along flow outlet side 104 of flow baffle 100 by the process of natural convection. The heated water/steam mixture exits sump 86 through outlet flow passage 112 and is discharged, as indicated by arrow 124, to an upper region of suppression pool 30. Thus a substantially sinuous path of travel is provided to promote circulation of the cooling water. In one embodiment, base grid 84 of core catcher 80 is cone shaped to enhance flow along bottom plate 88. Alternatively, a small conical addition is coupled at the center of bottom plate 88 of base grid 84 to enhance the heat transfer near the center of base grid 84 (due to minimizing the stagnation point effects). In a further embodiment, base grid 84 has a generally convex shape to enhance flow along bottom plate 88. In addition, I-beams 92 may be perforated to enhance cooling water flow below base grid 84. FIG. 3 is a schematic side view of another embodiment of a core catcher 130. Components in core catcher 130 that are identical to components in core catcher 80 described above with regard to FIG. 2 are identified in FIG. 3 using the same reference numerals used in FIG. 2. Sump 86 could be either dry or filled with water during normal operations. If sump 86 were not filled during normal operation it could be filled during an accident through flooding the lower region of drywell 24. Shield walls 89 are spaced inwardly from wall 28 to define an annular channel 132 therebetween. Annular channel 132 has a flow opening 134 and includes an inlet flow channel 140 and an outlet flow channel 142 extending therethrough. In one embodiment, inlet and outlet flow channels 140 and 142 are annular and a partition 144 extends from flow outlet side 104 of flow baffle 100. Partition 144 extends into channel 132 and divides channel 132 into inlet flow channel 140 and outlet flow channel 142. In another embodiment, inlet flow channel 140 and outlet flow channel 142 extend substantially perpendicular to basemat 82 and are substantially parallel to each other. In the event of a core melt, water 94 from drywell 24 is circulated into flow opening 134, as indicated by arrow 146, and through inlet flow channel 140 in a first flow path 150. Water 94 travels in a second flow path 160 along flow inlet side 102 of flow baffle 100. As water 94 is heated by corium 70, the heated water/steam mixture travels in a third flow path 170 along flow outlet side 104 of flow baffle 100 by the process of natural convection. The heated water/steam mixture exits sump 86 in a fourth flow path 180 through outlet flow channel 104. The heated water/steam mixture is discharged through flow opening 134 and returned to drywell 24. Thus a substantially sinuous path of travel is provided to promote circulation of the cooling water. In the embodiments shown in FIGS. 2 and 3, the circulating water keeps the bottom and sides of core catcher 80 sufficiently cool to avoid melt through by corium 70. Core catchers 80 and 130 utilize passive designs to retain and cool the core melt masses within containment boundary under severe accident conditions. Core catchers 80 and 130 provide simultaneous bottom and top cooling of corium 70 through the optimization of the internal design of core catchers 80 and 130 which eliminates the interaction of corium 70 with the containment basemat 82 and walls 28 of PCV 22. The above-described core catcher retains and cools the corium, inhibits corium-concrete interaction and thereby minimizes the resulting pressure in the containment during a severe accident without damage to containment structures. While the invention has been described and illustrated in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.
	summary
	description	The invention relates to a reactor pressure vessel of a boiling water reactor, in which a separation device for steam/water separation is provided above a reactor core. The invention also relates to a method for steam/water separation in a reactor pressure vessel of this type. In a boiling water reactor, the cooling water which flows through the reactor core is heated in the reactor pressure vessel. The cooling water is partially converted into the steam phase, so that a mixture of steam and water flows out of the reactor core. Before the steam is fed to a steam turbine for generation of electrical energy, the steam is separated from the water with the aid of the separation device. WO 99/08287 has disclosed a separation device of this type which has a plurality of separators supported on an upper core grid of the reactor core, so that the steam/water mixture which flows out of the reactor core is introduced directly into the separators. After the separators, as seen in the direction of flow, dryers which have metal baffle or diverter plates are connected downstream of the individual separators. In the separator, the steam/water mixture is set in rotation in the manner of a cyclone, so that the heavy water particles accumulate in the outer region and the low-water steam accumulates in the central region. The low-water steam is then fed to the dryers and when it emerges from the latter has a residual water content of just 0.01% to 0.02% by mass. On account of the steam/water separation required within the reactor pressure vessel of a boiling water reactor, with the two-stage construction comprising a cyclone or separator device and a drying device connected downstream of it in the direction of flow, overall a very great overall height of the reactor pressure vessel and therefore also of a containment in which the reactor pressure vessel is arranged is required. The large overall height also entails considerable costs, on account of the high safety standards required of the containment and the reactor pressure vessel. The invention is based on the object of allowing a reactor pressure vessel to have a low overall height. According to the invention, the object is achieved by the reactor pressure vessel as claimed in claim 1, in which a flow space with a flow cross-sectional area which increases upstream of the separation device is present between the reactor core and the separation device. In this configuration, in operation the steam/water mixture flows out of the reactor core into the flow space, which has a predetermined flow cross-sectional area for the steam/water mixture. Before the mixture reaches the separation device, the flow cross-sectional area for the mixture increases in size. The heavy and therefore inert mass parts made up of water remain substantially in the central region, while the lightweight steam parts spread outward. As a result, initial separation already occurs. Therefore, this configuration is based on the idea of utilizing the different inertia of the water and steam fractions for preliminary separation even before entry into the actual separation device. Since this measure already partially separates the light steam fractions from the heavy water fractions, the subsequent units of the separation device can be correspondingly adapted to the altered conditions, which in particular means that on account of the preliminary separation the separation device can have a low overall height. To achieve a configuration which is as simple as possible, in an expedient refinement there is a component which initially reduces the flow cross-sectional area and then increases it again. The flow cross-sectional area is substantially defined by the internal cross-sectional area of the reactor pressure vessel. The component initially reduces this maximum flow cross-sectional area in a simple way, so that the mixture is accelerated in a central region. During the subsequent increase in the size of the flow cross-sectional area, which is in particular an abrupt increase to, for example, more than double the previous flow cross-sectional area, the flow velocity is reduced again and the lighter steam fractions flow from the central region into an edge region or outer region. The component is expediently a ring element with a central passage which defines the flow cross-sectional area and narrows on the entry side. On account of the narrowing, the flow cross-sectional area is initially continuously reduced, thereby preventing undesirable turbulence or pressure losses. After the passage, the flow cross-sectional area increases in size from a minimum value, preferably abruptly, to a maximum value, resulting in particularly efficient preliminary separation. Therefore, it is preferable for the passage to narrow continuously only on the entry side. Since the preliminary separation in the edge regions means that a low-water mixture is already present, it is provided in a preferred refinement that a separator or cyclone device be arranged only in the central region. At this separator or cyclone device, the separation of the water-rich mixture takes place in the customary way by building up a swirling or rotational flow, so that an encircling liquid ring surrounding a central, low-water steam region is formed in the respective cyclone or separator. The water of the liquid ring remains in the reactor pressure vessel, while the low-water steam region is passed, after a further separation stage, to a steam turbine. The cyclone device may in this case have a plurality of cyclones. The use of the cyclones in only a central subregion reduces costs. It is preferable for a drying device to be arranged in the annular space surrounding the centrally arranged cyclone device. Since a low-water mixture is already present in the edge regions, on account of the preliminary separation, it is sufficient for just one drying device, which may comprise a plurality of dryers, to be arranged in this edge region. Therefore, there is no need for two-stage separation by upstream cyclone and downstream dryer in this edge region. Rather, the first stage of the separation is achieved by the preliminary separation brought about by the increase in cross-sectional area upstream of the separation device. With a view to the desired reduction in the overall height of the reactor pressure vessel, it is particularly advantageous if the drying device is arranged exclusively next to the cyclone device and the steam/water mixture which emerges from the cyclone is passed via the drying device arranged at the edge side. In this configuration, therefore, there is no further dryer provided above the cyclone device. The overall height of the reactor pressure vessel is therefore determined, for example, by the upper height of the cyclone device. With a view to particularly efficient separation, the drying device preferably comprises a first dryer unit for the steam/water mixture emerging from the cyclone device and a second dryer unit for the remaining steam/water mixture, which flows out of the passage into the edge regions. This measure makes it possible to take into account differences in the water content of the mixture by using a different design of the two dryer units, in order to achieve the highest possible separation rate. In this context, it is expedient for the first dryer unit to be arranged between the cyclone device and the second dryer unit. In this case, the mixture which emerges from the cyclone device is introduced into the first dryer unit in particular via suitable metal diverter plates. After it has left the drying device, the steam, which is then dry, flows to a steam outlet connection piece, to which, in operation, a steam line leading to a turbine is connected. An exemplary embodiment of the invention is explained in more detail below with reference to the only drawing, which shows a highly simplified illustration of a reactor pressure vessel of a boiling water reactor. The reactor pressure vessel 2 extends along a longitudinal direction 4. A reactor core 6 is arranged in the bottom third and is followed by a flow space 8 and then a separation device 10. When the reactor is operating, cooling water W is fed from an outer edge region 14 to the centrally arranged reactor core 6 from below by means of coolant circulation pumps 12, flows through the reactor core 6 and leaves it as a steam/water mixture G. The mixture G flows through the separation device 10 and leaves it as dry steam D in the direction of a steam outlet connection piece 16. An annular component 18 with a central passage 20 is arranged in the flow space 8. From the reactor core 6, the passage 20 narrows continuously and in particular constantly in the longitudinal direction 4. The annular component 18 is therefore, for example, of conically narrowing design in this region. As a result, the flow cross-sectional area is continuously reduced. The maximum flow cross-sectional area approximately corresponds to the internal cross-sectional area of a core shroud which surrounds the area within the outer edge regions 14. This maximum flow cross-sectional area is reduced to a minimum flow cross-sectional area in the region of the passage 20. After the passage 20, the flow cross-sectional area suddenly widens again to the maximum flow cross-sectional area. The sudden cross-sectional widening brings about a first phase separation between water and steam; on account of the greater inertia of the heavy water particles, these water particles have less tendency to follow the sudden change in cross section than the light and therefore less inert steam fractions. Before the mixture G enters the separation device 10, therefore, an initial phase separation has already taken place, with a water-rich mixture being present in the central region adjoining the passage 20, and a low-water mixture being present in the edge region 22. This first phase separation on account of the different inertias is utilized by adapting the subsequent components of the separation device 10 to these different conditions. Specifically, a cyclone device 24 is provided only in the central region, and is surrounded by a drying device 26 in the form of a ring. This drying device has a first dryer unit 28 and a second dryer unit 30, which encloses the first dryer unit 28 between it and the cyclone device 24. On account of the preliminary separation, the mixture G is already sufficiently dry in the edge region 22, which means that a cyclone is no longer required at this location. Sufficient steam drying is achieved here simply by the provision of the drying device 26. Both the drying device 26 and the cyclone device 24 may include a multiplicity of individual dryers or cyclones. The same also applies to the first and second dryer units 28, 30, which may likewise be formed from a plurality of individual dryers. After it has flowed through the second dryer unit 30, the dry steam passes directly to the steam outlet connection piece 16. On the exit side at the top end of the cyclone device 24, the mixture G which flows through the cyclone device 24 is guided in the opposite direction to the longitudinal direction by a metal guide plate 32 and is fed via an inlet opening 34 to the first dryer device 28. Here, the mixture G is diverted again and flows through the first dryer unit 28 in the longitudinal direction 4, leaving it as dry steam D and then being fed to the steam outlet connection piece 16 together with the steam D emerging from the second dryer unit 30. The metal guide plate 32 is designed in the form of a hollow cylinder which concentrically surrounds the cyclone device 24, leaving clear a flow path 36. The dryer device 26 and the cyclone device 24 each have their entry sides aligned at the same height. The cyclone device 24 and the second dryer unit 30 each have an inlet for the mixture G oriented toward the flow space 8. The inlet into the first dryer unit 28 is exclusively from the flow path 36 via the inlet opening 34. The flow path 36 and the first dryer unit 28 are closed toward the flow space 8. As an alternative to this closed design, in an alternative configuration (not shown here), the flow path 36 and the first dryer unit 28 are open toward the flow space 8, so that the mixture G which leaves the cyclone device 24 enters the drying device 26 via the flow space 8. Also, the drying device 26 does not necessarily have to be divided into different dryer units. However, this division does have the advantage that the different dryer units 28, 30 are set to different water contents of the mixtures G flowing through them by virtue of suitable design measures, for example different heights. This ensures a high separation rate. Since the mixture in the edge region 22 close to the outer edge region 14 is driest, on account of the preliminary separation in the flow space 8, it is also possible to further differentiate the drying device 26, for example by providing a third dryer unit, which is provided at the outer edge for the mixture G which is already substantially dry. The in particular sudden cross-sectional widening in the flow space 8 makes advantageous use of the different inertia properties of water and steam to effect an initial phase separation, by virtue of the fact that the subsequent components are matched to the preliminary separation. It is in this context crucial that the cyclone device 24 is now only required in the central region. As a result, a space is left clear in the annular space around the cyclone device 24 and is used to fit the drying device 26, specifically in such a way that the drying device 26 is arranged exclusively in this annular space next to the cyclone device 24. This therefore obviates the hitherto customary arrangement of the drying device 26 on top of the cyclone device, as seen in the longitudinal direction 4, so that overall a reduction in the height of the reactor pressure vessel is achieved. List of designations 2Reactor pressure vessel 4Longitudinal direction 6Reactor core 8Build-up space10Separation device12Coolant circulation pump14Outer edge region16Steam outlet connection piece18Component20Passage22Edge region24Cyclone device26Drying device28First dryer unit30Second dryer unit32Metal guide plate34Inlet opening36Flow pathDSteamGMixtureWCooling water
	claims	1. An operating floor confinement that constitutes part of a nuclear plant, the nuclear plant including:a reactor pressure vessel that houses a core;a dry well housing the reactor pressure vessel and having a top slab;a wet well housing a suppression pool in its lower portion and a gas phase in its upper portion;a LOCA vent pipe connecting the dry well and the suppression pool;a containment vessel that includes at least the dry well, the LOCA vent pipe and the wet well;a containment vessel head;a main steam line; anda reactor building including an equipment area that houses a section of the main steam line, whereinthe operating floor confinement is fluidically isolated from the equipment area of the reactor building and forms a pressure boundary that has pressure resistance that is at least the same level as that of the containment vessel and a leakage protection function, wherein the operating floor confinement comprises:a reactor well that surrounds the containment vessel head and is in contact with the containment vessel via the containment vessel head,an operating floor that is provided around the reactor well, the operating floor having a larger area than a cross-sectional area of the dry well, wherein the operating floor constitutes a part of the pressure boundary and has no staircase, elevator, elevator shaft, or equipment hatch that communicates with the equipment area of the reactor building,a sidewall that surrounds the operating floor, the sidewall being arranged wider than the cross-sectional area of the dry well, wherein the sidewall constitutes a part of the pressure boundary and has no blowout panel,a ceiling that is provided on an upper portion of the sidewall, constitutes a part of the pressure boundary and has no blowout panel,a fuel pool extending horizontally beyond the top slab of the dry well and constituting a part of the pressure boundary,a dryer and separator pit extending horizontally beyond the top slab of the dry well and constituting a part of the pressure boundary,an equipment hatch that is provided on the sidewall,an air lock that is provided on the sidewall,a penetration line that passes through the sidewall, andan isolation valve that is provided on the penetration line. 2. The operating floor confinement according to claim 1, further comprisingan external venting system that includes an external vent pipe, which penetrates the pressure boundary of the operating floor confinement and communicates with outside, and an external vent isolation valve, which is provided on the external vent pipe in order to vent, to the outside, atmosphere of the operating floor confinement. 3. The operating floor confinement according to claim 1, further comprising:a reactor well overflow section that is provided between the reactor well and the fuel pool;a fuel pool overflow section that is provided on the fuel pool; andan operating floor drain pit that is provided inside the operating floor confinement in such a way as to make a dent in part of the operating floor. 4. The operating floor confinement according to claim 3, further comprising:a drain pipe having one end opened inside the operating floor drain pit while another end is connected to the wet well; anda drain isolation valve that is provided on the drain pipe. 5. The operating floor confinement according to claim 4, further comprising:a connecting vent pipe having one end opened in the atmosphere of the operating floor confinement while another end is connected to the containment vessel; anda connecting vent isolation valve that is provided on the connecting vent pipe, whereinan opening of the connecting vent pipe inside the operating floor confinement is located higher than an opening of the drain pipe inside the operating floor drain pit. 6. The operating floor confinement according to claim 1, wherein a portion of the sidewall includes the airlock and the equipment hatch, whereinthe portion of the sidewall is shared with an auxiliary access building that is built adjacent to the reactor building, whereineach floor of the auxiliary access building communicates with each floor of the equipment area of the reactor building,an elevator is provided in the auxiliary access building to allow operators to go upstairs and downstairs,a staircase is provided in the auxiliary access building to allow operators to go upstairs and downstairs,an equipment access lock is provided on a wall of the auxiliary access building,a shaft is provided in the auxiliary access building adjacent to the equipment access lock and through each floor of the auxiliary access building,an equipment hatch is provided on a top floor of the auxiliary access building, whereinequipment, as well as workers, can be moved in and out to the operating floor confinement via the auxiliary access building. 7. The operating floor confinement according to claim 6, whereinthe auxiliary access building further includes a blowout panel on a sidewall of the auxiliary access building. 8. A nuclear plant comprising:a core;a reactor pressure vessel that houses the core;a dry well housing the reactor pressure vessel and having a top slab;a wet well housing a suppression pool in its lower portion and a gas phase in its upper portion;a LOCA vent pipe connecting the dry well and the suppression pool;a containment vessel that includes at least the dry well, the LOCA vent pipe and the wet well;a containment vessel head;a main steam line;a reactor building including an equipment area that houses a section of the main steam line; andan operating floor confinement that is fluidically isolated from the equipment area of the reactor building and forms a pressure boundary that has pressure resistance that is at least the same level as that of the containment vessel and a leakage protection function, wherein the operating floor confinement includes:a reactor well that surrounds the containment vessel head, constitutes the pressure boundary and is in contact with the containment vessel via the containment vessel head,an operating floor that is provided around the reactor well, the operating floor having a larger area than a cross-sectional area of the dry well, wherein the operating floor constitutes a part of the pressure boundary and has no staircase, elevator, elevator shaft, or equipment hatch that communicate with the equipment area of the reactor building,a sidewall that surrounds the operating floor, the sidewall being arranged wider than the cross-sectional area of the dry well, wherein the sidewall constitutes a part of the pressure boundary and has no blowout panel,a ceiling that is provided on an upper portion of the sidewall, constitutes a part of the pressure boundary and has no blowout panel,a fuel pool extending horizontally beyond the top slab of the dry well and constituting a part of the pressure boundary,a dryer and separator pit extending horizontally beyond the top slab of the dry well and constituting a part of the pressure boundary,an equipment hatch that is provided on the sidewall,an air lock that is provided on the sidewall,a penetration line that passes through the sidewall, andan isolation valve that is provided on the penetration line.
048572624	abstract	A method and apparatus for separating the fuel rods (15) in a fuel element 8), whereby the former are retained in a bird cage arrangement (16, 18) between a head piece (19) and a foot piece (19'). The fuel elements (8) is located on a support table (6) with the help of a clamping arrangement (10). Before the fuel rods can be separated, the head piece and the foot piece are removed. In order to simplify removal of the fuel rods from the fuel element, to save space, and to minimize any risk of breakage after removal of the head piece (19) and the foot piece (19'), the bird cage arrangement (16,18) is progressively stripped from one layer of fuel rods to the next and from around the fuel rods. The exposed fuel rods are then lifted out of the fuel element (8) layer by layer and reshuffled in a more compact arrangement. A cutting tool (24), provided with a cutting disk head (26), is used to strip and separate the fuel rods with the help of a grappler (28). The grappler is used to bend the bird cage arrangement apart, bar by bar, after it is severed.
	claims	1. An X-ray inspecting device comprising:a sample stage on which an inspection target sample is placed;image observing means for observing an image of the sample placed on the sample stage;a positioning mechanism that is controlled based on an image observation result of the sample by the image observing means to move the sample stage in two orthogonal directions on a horizontal plane, a height direction, and an in-plane rotation direction;a goniometer including first and second rotation members that rotate independently of each other along a virtual plane perpendicular to a surface of the sample around a rotational axis contained in the same plane as the surface of the sample placed on the sample stage;an X-ray irradiation unit that is installed in the first rotation member and focuses and irradiates characteristic X-rays to an inspection position set in the same plane as the surface of the sample placed on the sample stage;an X-ray detector installed in the second rotation member, wherein the X-ray irradiation unit includes an X-ray tube for generating X-rays, and an X-ray optical element for receiving X-rays irradiated from the X-ray tube, extracting only characteristic X-rays of a specific wavelength and focusing the extracted characteristic X-rays on the inspection position, and the X-ray optical element includes a first X-ray optical element for focusing the characteristic X-rays so that a height of the characteristic X-rays decreases within a virtual vertical plane orthogonal to the surface of the sample and containing an optical axis, and a second X-ray optical element for focusing the characteristic X-rays so that a width of the characteristic X-rays decreases within a virtual plane orthogonal to the virtual vertical plane and containing the optical axis, and wherein the first X-ray optical element is constituted by a crystal material having high crystallinity, and the second X-ray optical element comprises a multilayer mirror; androcking curve measuring means for executing a method for measuring rocking curve on a sample in which a thin film crystal is epitaxially grown on a substrate crystal, wherein the rocking curve measuring means has a function of executing the following operations (I) to (VI):(I) selecting two equivalent asymmetrical reflection crystal lattice planes for the sample;(II) arranging the X-ray irradiation unit and the X-ray detector at angular positions for the sample surface determined based on a Bragg angle of the substrate crystal in the sample for one of the selected crystal lattice planes;(III) irradiating the sample surface with X-rays from the X-ray irradiation unit, and detecting a reflection angle and intensity of diffracted X-rays reflected from the sample by the X-ray detector;(V) arranging the X-ray irradiation unit and the X-ray detector at angular positions for the sample surface determined based on a Bragg angle of the substrate crystal in the sample for the other selected crystal lattice plane;(V) irradiating the sample surface with X-rays from the X-ray irradiation unit, and detecting a reflection angle and intensity of diffracted X-rays reflected from the sample by the X-ray detector; and(VI) obtaining a rocking curve based on the reflection angle and intensity of the diffracted X-rays detected by the X-ray detector, and analyzing data on the rocking curve,wherein the rocking curve measuring means further has a function of executing the following operations (VI-I) to (VI-IV) in the operation (VI):(VI-I) determining an angular difference between a diffraction peak in the substrate crystal of the sample and diffraction peaks of two equivalent asymmetric reflections in the thin film crystal of the sample;(VI-II) calculating a lattice constant of the thin film crystal of the sample from the angular difference of the diffraction peaks determined by the operation (VI-I);(VI-III) calculating, from a known elastic constant of the thin film crystal of the sample and the calculated lattice constant, at least one of a strain of the thin film crystal, a lattice constant under a state where a stress of the thin film crystal is released, a composition of the thin film crystal and the stress of the thin film crystal; and(VI-IV) outputting a calculation result obtained by the operation (VI-III). 2. The X-ray inspecting device according to claim 1, wherein the first X-ray optical element uses a crystal material and is configured to reflect X-rays by lattice planes having an inherent rocking curve width of 0.06° or less in the crystal material. 3. The X-ray inspecting device according to claim 1, wherein the X-ray irradiation unit includes a focusing angle control member for controlling a focusing angle of the characteristic X-rays in the virtual vertical plane orthogonal to the surface of the sample and containing the optical axis. 4. The X-ray inspecting device according to claim 3, wherein the focusing angle control member comprises a slit member having a slit for transmitting only a part having any width of the characteristic X-rays focused by the first X-ray optical element. 5. The X-ray inspecting device according to claim 4, wherein the X-ray irradiation unit is configured so that respective components of the X-ray tube, the X-ray optical element, and the slit member are incorporated in an unit main body that is rotatably installed in the first rotation member. 6. The X-ray inspecting device according to claim 1, wherein the X-ray detector comprises a one-dimensional X-ray detector or a two-dimensional X-ray detector. 7. A method for measuring rocking curve that uses the X-ray inspecting device according to claim 1 to perform a rocking curve measurement on a sample in which a thin film crystal is epitaxially grown on a substrate crystal and includes the following steps A to D:step A of selecting two equivalent asymmetric reflection crystal lattice planes for the sample;step B of arranging the X-ray irradiation unit and the X-ray detector at angular positions for the sample surface determined based on a Bragg angle of the substrate crystal in the sample for one of the selected crystal lattice planes;step C of irradiating the sample surface with X-rays from the X-ray irradiation unit, and detecting a reflection angle and intensity of diffracted X-rays reflected from the sample by the X-ray detector;step D of arranging the X-ray irradiation unit and the X-ray detector at angular positions for the sample surface determined based on a Bragg angle of the substrate crystal in the sample for the other selected crystal lattice plane;step E of irradiating the sample surface with X-rays from the X-ray irradiation unit, and detecting a reflection angle and intensity of diffracted X-rays reflected from the sample by the X-ray detector; andstep F of obtaining a rocking curve based on the reflection angle and intensity of the diffracted X-rays detected by the X-ray detector, and analyzing data on the rocking curve,wherein the step F further includes the following steps F-1 to F-4:step F-1 of determining an angular difference between a diffraction peak in the substrate crystal of the sample and diffraction peaks of two equivalent asymmetric reflections in the thin film crystal of the sample;step F-2 of calculating a lattice constant of the thin film crystal of the sample from the angular difference of the diffraction peaks determined by the operation of the step F-1;step F-3 of calculating, from a known elastic constant of the thin film crystal of the sample and the calculated lattice constant, at least one of a strain of the thin film crystal, a lattice constant under a state where a stress of the thin film crystal is released, a composition of the thin film crystal and the stress of the thin film crystal; andstep F-4 of outputting a calculation result obtained in the step F-3. 8. The X-ray inspecting device according to claim 1, wherein the X-ray irradiation unit includes a focusing angle control member for controlling a focusing angle of the characteristic X-rays in a virtual vertical plane orthogonal to the surface of the sample and containing the optical axis, sets a focusing angle of X-rays to be irradiated on the sample surface from the X-ray irradiation unit to 2° or more by the focusing angle control member, and irradiates the sample surface with X-rays in an angle range of 2° or more, and wherein the X-ray detector comprises a one-dimensional X-ray detector or a two-dimensional X-ray detector, and diffracted X-rays reflected from the sample are made incident to the X-ray detector to detect a reflection angle and intensity of the diffracted X-rays. 9. The X-ray inspecting device according to claim 8, wherein the X-ray irradiation unit is configured to oscillate in a virtual vertical plane orthogonal to the surface of the sample and containing the optical axis to irradiate the sample surface with X-rays. 10. The X-ray inspecting device according to claim 8, wherein the X-ray detector and the X-ray irradiation unit are scanned interlockingly with each other within a virtual vertical plane orthogonal to the surface of the sample and containing the optical axis to measure diffracted X-rays reflected from the sample by a scanning method based on a TDI Mode.
063109344	description	DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 4 is a diagram illustrating the entire configuration of an X-ray reduction projection exposure apparatus. In FIG. 4, X-rays (vacuum-ultraviolet rays or soft X-rays) are emitted from an undulator source 101, serving as a radiation source. The optical path of the X-rays is deflected by an illuminating system comprising a convex total-reflection mirror 102 and a concave multilayer-film reflecting mirror 103, and the X-rays are then projected onto a reflection mask 104. A multilayer film for effecting regular reflection of X-rays is formed on the reflection mask 104, and a predetermined circuit pattern is formed on the multilayer film. The X-rays reflected by the reflection mask 104 reach a wafer 106 after passing through a reduction projection optical system 105 having a plurality of reflection mirrors, to image the circuit pattern on the wafer 106 with a predetermined projection magnification (for example, 1/5). The reflection mask 104 is fixed and held on a mask stage 107, and the wafer 106 is fixed and held on a wafer stage 108. The reflection mask 104 and the wafer 106 are aligned with each other by the mask stage 107 and the wafer stage 108, respectively, and the scanning movement of the mask stage 107 holding the reflection mask 104 and the wafer stage 108 holding the wafer 106 is performed in a synchronized manner. Since the wavelength of the X-rays used for exposure is between about 20 nm and 4 nm, the theoretical resolution determined by the wavelength of the exposure light is improved. Since vacuum-ultraviolet rays and soft X-rays are greatly attenuated by a gas, the inside of the entire apparatus is held in a vacuum or in a reduced pressure of a light-element gas, such as helium or the like. In the present invention, an electrostatic chuck (unipolar type) which is suitable for the use in a vacuum or in a reduced pressure is used for a mechanism for fixing and holding the reflection mask 104 on the mask stage 107. The electrostatic chuck functions based on the principle that charges having a sign opposite to that of an electrode are excited on an insulator provided on the chuck's surface to cause a dielectric polarization phenomenon to occur, so that an electrostatic force is applied to an object to be attracted. The attracting force F of the electrostatic chuck is represented by the following expression: EQU F=S/2.times..di-elect cons..times.(V/d).sup.2, where S is the area of the electrode of the electrostatic chuck, .di-elect cons. is the dielectric constant of the insulator, V is the applied voltage, and d is the thickness of the insulator on the surface. The above-described expression may be modified in accordance with various conditions. In a bipolar electrostatic chuck which is easy to handle and in which an object to be attracted need not be grounded, the attracting force is less than half the value of the above-described electrostatic chuck (unipolar type). For example, when using high-purity Al.sub.2 O.sub.3, which is little contaminated with metal, for the insulator on the surface, the attracting force is about 25 g/cm.sup.2. If the pattern region of the reflection mask is 200 mm square with a thickness of a few .mu.m, and the base is 210 mm square with a thickness of 10 mm and is made of Si, the mass of the reflection mask is about 1 Kg. If a time period of 0.5 sec is required for exposure of one shot, it is necessary to scan a distance of 200 mm in a time period equal to or less than 0.5 sec. Hence, if a scanning speed of 400 mm/sec is obtained within 0.05 sec, the maximum acceleration of the mask stage is 8 m/sec.sup.2. When the mask is supported in a direction parallel to the direction of gravity, the maximum acceleration applied to the mask after adding the acceleration due to gravity is about 18 m/sec.sup.2, i.e., the force applied to the mask in the scanning direction is 18 N. Since the attracting force of the electrostatic chuck is 21.times.21.times.0.025.times.9.8=100 N, the coefficient of friction must be equal to or greater than 0.18 N in order to prevent the reflection mask from dropping. In general, the surface of the electrostatic chuck is very precisely processed to an excellent flatness, and therefore has a low coefficient of friction. Hence, the mask may drop in the worst case. Accordingly, in the present invention, the attracting force of the mask by the electrostatic chuck is changed in accordance with a situation in order to prevent the mask from dropping. A specific configuration for that purpose will now be described. First Embodiment FIG. 1 is a cross-sectional view as seen from the side, illustrating the configuration of a mask supporting device, which is used in a mask stage of an X-ray projection exposure apparatus, according to a first embodiment of the present invention. In FIG. 1, a reflection X-ray mask 1, serving as an optical element, comprises a base 1a comprising an Si substrate, and a pattern region 1b. The pattern region 1b is formed on the base 1a according to a thin-film forming method, such as magnetron sputtering, or the like. The pattern region 1b comprises a region having a low reflectivity for X-rays, such as vacuum-ultraviolet rays or soft X-rays, and a pattern portion having a high reflectivity for the X-rays. The pattern portion comprises an X-ray absorbing member (for example, made of gold or tungsten) formed on a patterned X-ray reflecting multilayer film obtained by alternately laminating at least two kinds of substances having different refractive indices for vacuum-ultraviolet rays or soft X-rays. The mask supporting device for holding the mask 1 comprises an electrostatic chuck 2 for attracting the mask 1, a plurality of pin-shaped projections 6 formed on portions thereof, a pressure sensor (attracting-force detection means) 11 for detecting an attracting force for the mask 1, an attraction control unit 12 for calculating the attracting force from the result of detection of the pressure sensor 11, a voltage control unit 10 for outputting a voltage for controlling the attracting force from the attracting force calculated by the attraction control unit 12, and a driving control unit 9 for effecting scanning movement of the mask 1. A supply tube 7 for supplying voids formed between the projections 6 with a cooling gas (such as helium or the like), and a recovering tube 8 for recovering the gas introduced into the voids are also provided. The electrostatic chuck 2 comprises a first insulating layer 3 and a second insulating layer 4. A first electrode 5a and a second electrode 5b for generating the attracting force are formed between the first insulating layer 3 and the second insulating layer 4, and the pin-shaped projections 6 are formed on the first insulating layer 3. In this configuration, when a voltage is applied from the voltage control unit 10 to the first electrode 5a and the second electrode 5b of the electrostatic chuck 2, static electricity is generated and charges having a sign different from that of the voltage are excited on the surface of the first insulating layer 3. At that time, the dielectric polarization phenomenon appears on the surface of the first insulating layer 3, and an electrostatic force is applied to the mask 1. The mask 1 is thereby attracted and fixed by being supported on the pin-shaped projections 6 formed on the electrostatic chuck 2. Since a so-called pin-chuck shape is provided in the above-described manner and the ratio of the area of portions of the distal ends of the pin-shaped projections 6 contacting the back of the mask 1 to the entire area of the mask 1 is arranged to be equal to or less than 10% (more preferably, <2%), the deformation of the mask 1 due to the presence of dust between the mask 1 and the electrostatic chuck 2 is prevented. In addition, since cooling gas flows in the voids between the projections 6, the mask 1, placed in a vacuum in which cooling is difficult to perform, is effectively cooled from the back to suppress the distortion of the mask pattern. The pressure sensor 11 for detecting the attracting force for the mask 1 is disposed on the surface of the electrostatic chuck 2, and the attracting force for the mask 1 is calculated by the attraction control unit 12 from a detection signal from the pressure sensor 11. In order to increase the illuminating region for the mask 1, the electrostatic chuck 2 is subjected to scanning movement by the control of the driving control unit 9. The attraction control unit 12 calculates the acceleration of the electrostatic chuck 2 from position information relating to the electrostatic chuck 2 detected by the driving control unit 9, and transmits an instruction to the voltage control unit 10 so that the following relationship is satisfied: EQU {(the mass of the mask).times.(acceleration due to gravity+the maximum acceleration of the mask while being moved)/(the makimum coefficient of static friction between the mask and the mask chuck)}.times.(safety factor)<the attracting force (1), wherein (the attracting force) is defined by:(the generating electrostatic force)-(the differential pressure between the pressure of the cooling gas and the atmosphere pressure of the inside of the entire apparatus). The voltage control unit 10 controls the attracting force by changing the voltage applied to the first electrode 5a and the second electrode 5b in accordance with the instruction from the attraction control unit 12. Expression (1) may be satisfied by controlling the attracting force to be constant and controlling the acceleration instead of the attracting force by providing an instruction from the attraction control unit 12 to the driving control unit 9. According to the above-described configuration, the drop of the mask 1 from the electrostatic mask 2 is prevented. Second Embodiment FIGS. 2(a) and 2(b) are diagrams illustrating the configuration of a mask supporting device according to a second embodiment of the present invention: FIG. 2(a) is a perspective view; and FIG. 2(b) is a cross-sectional view as seen from the side. In the mask supporting device of the first embodiment, a bipolar electrostatic chuck is used. In the mask supporting device of the second embodiment, a unipolar electrostatic chuck having a strong attracting force is used. By using such a unipolar electrostatic chuck, reliability in the attraction of the mask is improved. The second embodiment has the same structure as the first embodiment, except as noted below. In FIGS. 2(a) and 2(b), only the configuration of components added in the second embodiment which are not found in the first embodiment, is illustrated, and the attraction control unit, the voltage control unit and the driving control unit shown in the first embodiment are not illustrated. Since the operations of these units are the same as in the first embodiment, a description thereof will be omitted. When attracting a mask on the unipolar electrostatic chuck, the mask must be grounded. However, since the mask is conveyed within the exposure apparatus and is mounted on and detachable from the electrostatic chuck, it is difficult to always ground the mask. Accordingly, in the mask supporting device of the second embodiment, the mask is grounded only when it is attracted on the electrostatic chuck so as not to hinder the conveyance of the mask. In FIGS. 2(a ) and 2(b), a mask 21 comprises a base 21a comprising an Si substrate, and a pattern region 21b which is formed on the base 21a. The mask supporting device for attracting and holding the mask 21 comprises an electrostatic chuck 22 for attracting the mask 21, and an earth pawl 26 for grounding the mask 21. The electrostatic chuck 22 comprises a first insulating layer 23 and a second insulating layer 24, and an electrode 25, for generating an attracting force, is formed between the first insulating layer 23 and the second insulating layer 24. The earth pawl 26 is connected to a minus (-) terminal of a power supply 27, and a plus (+) terminal of the power supply 27 is connected to the electrode 25. In this configuration, when the plus (+) potential of the power supply 27 is applied to the electrode 25 of the electrostatic chuck 22, charges of a different sign are excited on the surface of the first insulating layer 23. At that time, the dielectric polarization phenomenon appears on the surface of the first insulating layer 23, and an electrostatic force is applied to the mask 21. The mask 21 is thereby attracted and fixed to the electrostatic chuck 22. The earth pawl 26 is fixed relative to the electrostatic chuck 22 so as to be movable in the z direction shown in FIG. 2(b) to contact the base 21a of the mask 21, so that the mask 21 can be grounded and masks having different thicknesses can be attracted. By disposing the earth pawl 26 at a side of the base 21a, the earth pawl 26 also has the function of preventing the mask 21 from dropping. An object which can be attracted by the electrostatic chuck 22 is a conductor or a semiconductor. When attracting a mask 21 having a base 21a made of an insulator, the mask 21 is attracted by forming a conductive layer of a metal on the back and the sides of the mask 21 by vacuum deposition or the like and contacting the conductive layer to the earth pawl 26. According to the above-described configuration, a unipolar electrostatic chuck having a strong attracting force can be used for the mask supporting device, and reliability in the attraction of the mask can be improved. Since a sufficient attracting force can be obtained even with a material having a relatively low dielectric constant, a material with low metal contamination can be adopted. When semiconductor devices are manufactured using an exposure apparatus including the mask supporting device of the second embodiment, the production yield of the devices can be increased. Furthermore, since masks having different thicknesses can be attracted, the tolerances in the thickness of the mask required in the manufacture of the mask can be increased. Hence, the cost in the manufacture of the mask can be reduced. Since the earth pawl 26 also has the function of preventing the mask 21 from dropping, reliability in the attraction of the mask is improved. In addition, since a grounding mechanism which does not hinder the conveyance of the mask 21 is adopted, reliability in the conveyance of the mask is also improved. Third Embodiment FIG. 3 is a cross-sectional view as seen from a side illustrating the configuration of a mask supporting device according to a third embodiment of the present invention. The mask supporting device of the third embodiment includes temperature control means for controlling an electrostatic chuck to be a desired temperature. The third embodiment has the same structure as the first embodiment, except as noted below. In FIG. 3, only the configuration of components added in the third embodiment, which are not found in the, first embodiment, is illustrated, and the attraction control unit and the voltage control unit shown in the first embodiment are not illustrated. Since the operations of these units are the same as in the first embodiment, a description thereof will be omitted. In FIG. 3, a mask 31 comprises a base 31a comprising a Si substrate, and a pattern region 31b which is formed on the base 31a. The mask supporting device for attracting and holding the mask 31 comprises an electrostatic chuck 32 for attracting the mask 31, a chuck base 38 having a low coefficient of linear expansion and high stiffness on which the electrostatic chuck 32 is fixed, a temperature sensor 37 for detecting the temperature of the chuck base 38, a temperature-adjusting-medium supply device 42 containing a temperature-adjusting or controlled medium for changing the temperature of the chuck base 38 by changing the temperature of the temperature adjusting or controlled medium, a temperature control unit 41 for controlling the temperature-adjusting-medium supply device 42 based on a detection signal from the temperature sensor 37, and a driving control unit 44 for effecting scanning movement of the electrostatic chuck 32. The electrostatic chuck 32 comprises a first insulating layer 33 and a second insulating layer 34. An electrode 35 for generating an attracting force is formed between the first insulating layer 33 and the second insulating layer 34. A plurality of pin-shaped projections 36 are formed on the surface of the first insulating layer 33. In addition, a supply tube 45 for supplying voids formed between projections 36 with a cooling gas, and a recovering tube 46 for recovering the gas introduced into the voids are provided. In this configuration, when a voltage is applied from a voltage control unit (not shown) to the electrode 35 of the electrostatic chuck 32, charges having a sign different from that of the voltage are excited on the surface of the first insulating layer 33. At that time, the dielectric polarization phenomenon appears on the surface of the first insulating layer 33, and an electrostatic force is applied to the mask 31. The mask 31 is thereby attracted and fixed on the pin-shaped projections 36 formed on the electrostatic chuck 32. The temperature sensor 37 comprises, for example, a platinum resistance temperature sensor, and has a resolution of about 0.01.degree. C. By being directly buried at a sufficiently deep position in the chuck base 38, the temperature sensor 37 can very precisely detect the temperature of the chuck base 38. A channel 39 is provided in the chuck base 38 in order to receive a temperature-adjusting or controlled medium subjected to temperature control. The temperature-adjusting or controlled medium is supplied from the temperature-adjusting-medium supply device 42 via flexible tubes 43 made of a metal or Teflon which has a low gas discharge rate in a vacuum. The chuck base 38 comprises, for example, a ceramic material, such as SiC, SiN or the like, or low-thermal-expansion glass, in which thermal strain is very small due to a low coefficient of linear expansion. The temperature control unit 41 controls the temperature-adjusting-medium supply device 42 based on an output signal from the temperature sensor 37 in order to control the temperature of the temperature-adjusting or controlled medium to be supplied to the chuck base 38. The electrostatic chuck 32 generates a sufficient force to attract the mask 31, and prevents the thermal expansion of the mask 31, having absorbed exposure light in lateral directions, by the attracting force x the coefficient of friction of the electrostatic chuck 32. In order to prevent position deviation in lateral directions due to thermal expansion, the temperature of the electrostatic chuck 32 is very precisely controlled. More specifically, variations in the temperature of the electrostatic chuck 32 are very precisely controlled within a range equal to or less than 0.01.degree. C. In general, in an exposure apparatus, exposure is performed after very precisely aligning a mask with a wafer. In order to precisely perform the alignment, as disclosed in Japanese Patent Laid-Open Application (Kokai) No. 2-100311 (1990), a fine movement mechanism using a displacement member, comprising an elastic member having a low stiffness, such as a leaf spring or the like, and an actuator, comprising a piezoelectric element, are required for a mechanism for driving the wafer or the mask. The fine movement mechanism vibrates when the temperature adjusting medium flows because of its low stiffness, thereby degrading accuracy in the line width of the transferred pattern. In order to solve such a problem, the mask supporting device of the third embodiment uses only a coarse movement mechanism having a high stiffness for the driving mechanism, and a fine movement mechanism is provided in a mechanism for driving the wafer. The device also includes means for measuring the amount of shift of the interval between patterns on the exposed wafer, and expanding or contracting the electrostatic chuck by changing the temperature of the electrostatic chuck so as to minimize the amount of the shift. When the electrostatic chuck 32 is expanded or contracted, since the mask 31, attracted and constrained thereon, is simultaneously expanded or contracted, it is possible to correct the position deviation of the pattern of the mask 31. The temperature of the electrostatic chuck 32 is corrected by measuring, in advance, the relationship between the amount of shift of the pattern of the wafer after exposure and the change in the temperature of the electrostatic chuck 32, and by controlling the temperature of the electrostatic chuck 32 by the temperature control unit 41 so as to minimize the amount of shift of the interval between patterns on the wafer based on the obtained data. The amount of shift of the interval between patterns on the wafer may be obtained from a signal from alignment adjusting means (not shown) for performing alignment between the mask and the wafer, instead of measuring the interval between exposed patterns. Instead of using a temperature adjusting medium, the temperature of the electrostatic chuck 32 may be adjusted by precisely controlling the temperature at a high speed using, for example, a Peltier-effect element as disclosed in Japanese Patent Laid-Open Application (Kokai) No. 5-21308 (1993). Embodiment of Device Manufacturing Method FIG. 5 is a flow chart of a method for manufacturing semiconductor devices (semiconductor chips of ICs (integrated circuits), LSIs (large scale integrated circuits) or the like, liquid-crystal panels, CCDs (charge-coupled devices) or the like) using the above-described X-ray projection exposure apparatus. In step 1 (circuit design), circuit design of semiconductor devices is performed. In step 2 (mask manufacture), masks, on which designed circuit patterns are formed, are manufactured. In step 3 (wafer manufacture), wafers are manufactured using a material, such as silicon or the like. Step 4 (wafer process) is called a preprocess, in which actual circuits are formed on the wafers by means of photolithography using the above-described masks and wafers. Step 5 (assembly) is called a postprocess which manufactures semiconductor chips. using the wafers manufactured in step 4, and includes an assembling process (dicing and bonding), a packaging process (chip encapsulation), and the like. In step 6 (inspection), inspection operations, such as operation-confirming tests, durability tests, and the like, of the semiconductor devices manufactured in step 5 are performed. The manufacture of semiconductor devices is completed after passing through the above-described processes, and the manufactured devices are shipped (step 7). FIG. 6 is a detailed flow diagram of the above-described wafer process (step 4). In step 11 (oxidation), the surface of the wafer is oxidized. In step 12 (CVD (chemical vapor deposition)), an insulating film is formed on the surface of the wafer. In step 13 (electrode formation), electrodes are formed on the surface of the wafer by vacuum deposition. In step 14 (ion implantation), ions are implanted into the wafer. In step 15 (resist process), a photosensitive material is coated on the wafer. In step 16 (exposure), the circuit pattern on the mask is exposed and printed on the wafer using the above-described X-ray projection exposure apparatus. In step 17 (development), the exposed wafer is developed. In step 18 (etching), portions other than the developed resist image are etched off. In step 19 (resist separation), the resist, which becomes unnecessary after the completion of the etching, is removed. By repeating these steps, a final circuit pattern made of multiple patterns is formed on the wafer. The individual components shown in outline or designated by blocks in the drawings are all well known in the X-ray projection exposure apparatus and device manufacturing method arts and their specific construction and operation are not critical to the operation or the best mode for carrying out the invention. While the present invention has been described with respect to what are presently considered to be preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, the present invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
	claims	1. A method of inspecting nuclear fuel comprising:providing a nuclear fuel rod to an inspection area, the nuclear fuel rod comprising nuclear fuel pellets disposed within the nuclear fuel rod along a long axis;irradiating the nuclear fuel rod with X-ray radiation to generate a series of angularly displaced images of the nuclear fuel rod via direct radiography, such that the circumference of the nuclear fuel pellets is substantially imaged;inspecting the series of angularly displaced images to detect nuclear fuel pellet defects;irradiating the nuclear fuel rod with additional X-ray radiation having a different energy to generate one or more additional images; andinspecting the one or more additional images to detect different nuclear fuel pellet defects. 2. The method of claim 1, wherein the X-ray radiation used to generate the series of angularly displaced images has a lower energy than the additional X-ray radiation. 3. The method of claim 1, wherein the series of angularly displaced images are inspected to detect tangential nuclear fuel pellet defects and the one or more additional images are inspected to detect internal nuclear fuel pellet defects. 4. The method of claim 1, wherein inspecting the series of angularly displaced images comprises executing one or more comparison and/or detection algorithms using one or more algorithms to facilitate the detection of nuclear fuel pellet defects, wherein irradiation and inspection occur in less than about 30 seconds. 5. The method of claim 1, comprising reducing unattenuated X-rays incident at a detector used to generate the series of angularly displaced images by positioning a masking fixture proximate the nuclear fuel rod. 6. The method of claim 1, wherein a rod positioning mechanism is used to rotate the nucelar fuel rod to produce the series of angularly displaced images. 7. The method of claim 1, wherein a detector comprising a scintillator and a diode array is used to generate the series of angularly displaced images of the nuclear fuel rod, the images comprising digital X-ray images. 8. A method of inspecting nuclear fuel comprising:providing a nuclear fuel rod to an inspection area, the nuclear fuel rod comprising nuclear fuel pellets disposed within the nuclear fuel rod along a long axis;irradiating the nuclear fuel rod with X-ray radiation to generate a series of angularly displaced images of the nuclear fuel rod via direct radiography, such that the circumference of the nuclear fuel pellets is substantially imaged;inspecting the series of angularly displaced images to detect nuclear fuel pellet defects;translating and/or rotating the nuclear fuel rod using a nuclear fuel rod positioning mechanism after producing the series of angularly displaced images;irradiating the nuclear fuel rod with an additional portion of X-ray radiation to produce a second set of angularly displaced images;dividing, using one or more algorithms executed by a processing circuit, each image of the set of angularly displaced images by the corresponding image of the second set to produce a digital representation of the quotient;inspecting the digital representation for any areas comprising a value less than or greater than one;wherein the nuclear fuel rod is translated between about 1 micron and about 1 centimeter, and/or the nuclear fuel rod is rotated less than about 3 degrees.
	summary
	abstract	A core spray sparger assembly for supplying coolant to a nuclear reactor. The nuclear reactor includes fuel assemblies, a top guide, coolant supply pipes and a shroud head. The core spray sparger assembly includes at least one coolant manifold, at least one coolant coupling in fluid communication with the coolant manifold, and at least one mounting device configured to couple the coolant manifold to the nuclear reactor. The core spray sparger assembly further includes a plurality of fluid conductors in a parallel array positioned above the fuel assemblies, the fluid conductors in fluid communication with the coolant manifold, and a plurality of nozzles in fluid communication with the fluid conductors.
	claims	1. A control rod coupling assembly for coupling a nuclear reactor control rod to a control rod drive mechanism, the control rod drive mechanism comprising an index tube and a bayonet head, said control rod coupling assembly comprising: a control rod comprising a longitudinal tube and at least one blade extending from the tube, said longitudinal tube extending the length of said control rod; a bayonet socket configured to receive the bayonet head; a shaft extending from said bayonet socket, said shaft extending longitudinally through said longitudinal tube of said control rod; and a handle extending from said shaft, said handle movable to rotate said bayonet socket without rotating said control rod. 2. A control rod coupling assembly in accordance with claim 1 wherein said shaft is removably attached to said handle. claim 1 3. A control rod coupling assembly in accordance with claim 1 wherein said shaft is removably attached to said bayonet socket. claim 1 4. A control rod coupling assembly in accordance with claim 1 wherein said handle comprises a roller mechanism. claim 1 5. A control rod coupling assembly in accordance with claim 1 wherein said handle comprises a plate and at least one opening. claim 1 6. A control rod coupling assembly in accordance with claim 1 wherein said bayonet socket further comprises a coupling cavity and an internal engagement flange defining an engagement aperture, said coupling cavity configured to receive the bayonet head through said engagement aperture, and said internal engagement flange configured to abut the bayonet head upon rotation of said bayonet socket. claim 1 7. A control rod apparatus in accordance with claim 6 wherein said internal engagement flange comprises four arcuate segments, each said segment subtending substantially about 45 degrees of radial arc. claim 6 8. A control rod apparatus in accordance with claim 7 wherein said segments comprise an internal face. claim 7 9. A control rod coupling assembly in accordance with claim 1 wherein said control rod coupling assembly further comprises an external hex nut rotatably and circumferentially enclosing said bayonet socket. claim 1 10. control rod coupling assembly in accordance with claim 1 wherein said control rod coupling further comprising at least one bearing coupled to said bayonet socket, said bearing disposed around said shaft. claim 1 11. A control rod apparatus comprising: a control rod comprising at least one blade and a longitudinal tube, said longitudinal tube extending the length of said control rod; a control rod drive mechanism comprising an index tube, said index tube having a first end, and a bayonet head secured to said first end, said bayonet head comprising a lower surface; and a coupling assembly comprising: a bayonet socket sized to receive said bayonet head; a shaft extending axially from said bayonet socket through said longitudinal tube; and a handle extending from said shaft distal from said bayonet socket, said handle movable to rotate said bayonet socket without rotating said control rod. 12. A control rod apparatus in accordance with claim 11 wherein said bayonet socket comprises a coupling cavity and an internal engagement flange defining an engagement aperture, said coupling cavity sized to receive said bayonet head through said engagement aperture and said internal engagement flange configured to abut said bayonet head upon rotation of said bayonet socket. claim 11 13. A control rod apparatus in accordance with claim 12 wherein said handle is substantially coplanar with said at least one blade when said internal engagement flange fully engages said lower surface of said bayonet head. claim 12 14. A control rod apparatus in accordance with claim 11 wherein said control rod drive mechanism further comprises at least one restraining device engaging said index tube so as to prevent rotation of said index tube. claim 11 15. A control rod apparatus in accordance with claim 14 wherein said restraining device comprises a roller key slidably engaged in an axial channel of said index tube so as to prevent rotation of said index tube. claim 14 16. A control rod apparatus in accordance with claim 11 wherein said coupling assembly further comprises an external hex nut rotatably and circumferentially enclosing said bayonet socket. claim 11 17. A control rod apparatus in accordance with claim 16 wherein said control rod further comprises a hub, said hub coupled to said external hex nut and to said at least one blade. claim 16 18. A control rod apparatus in accordance with claim 17 wherein said coupling assembly further comprising a bearing coupled to said bayonet socket and to said hub, to facilitate rotation of said bayonet socket. claim 17 19. A control rod apparatus in accordance with claim 11 wherein said at least one blade comprises a blade thickness, said handle comprises a handle thickness substantially equal to or less than said blade thickness. claim 11 20. A control rod apparatus in accordance with claim 11 wherein said handle comprises a roller mechanism. claim 11 21. A control rod apparatus in accordance with claim 11 wherein said handle comprises at least one opening. claim 11 22. A control rod apparatus in accordance with claim 12 wherein said bayonet head comprises four members in a cruciform configuration, each said member subtending substantially about 45 degrees of arc. claim 12 23. A control rod apparatus in accordance with claim 22 wherein said internal engagement flange comprises four arcuate segments, each said segment subtending substantially about 45 degrees of arc, complementary to said bayonet head. claim 22 24. A control rod apparatus comprising: a control rod comprising at least one generally planar blade, a longitudinal axis, and a longitudinal tube substantially aligned with said axis, said longitudinal tube extending the length of said control rod; a control rod drive mechanism comprising an index tube having a first end, a restraining device securing said index tube, and a bayonet head secured to said first end, said bayonet head comprising four members in a cruciform arrangement, each member subtending substantially about 45 degrees of arc, each of said members including a lower surface; and a coupling assembly comprising a shaft including a proximate end and a distal end, received in and extending axially through said longitudinal tube, a handle detachably secured to said distal end of said shaft, and a bayonet socket, detachably secured to said proximate end of said shaft, said bayonet socket including a coupling cavity and an internal engagement flange defining an engagement aperture comprising four arcuate segments, each segment subtending substantially about 45 degrees of arc, complementary to said members; said coupling cavity sized to receive said bayonet head through said engagement aperture, such that upon rotation of said handle, said shaft rotates in said tube and said bayonet socket rotates, said internal engagement flange engages said lower surface of said bayonet head with substantially no rotation of said control rod; said handle substantially co-planar with at least one blade of said control rod when said members fully engage said segments.
046577220	description	DETAILED DESCRIPTION OF THE INVENTION In FIG. 1, a conventional Marx Bank 14 applies a potential difference between grounded shell 15 and suspended electrode 16. The inner electrode 17 is attached to and supported by discharge tube 18 which comprises a series of washer-like rings. The cathode 11 discharges electrons to the anode 29 which comprises a bulkhead 24 that has a tapered channel 22 leading the electron beam to the target comprising, for example, a lead mass 26. The channel 22 is of dielectric material but has a conductive liner 23 and a flared entrance 21 graphite or other partially conductive material. In FIG. 2, the portion of the tubular anode 21 which is nearest to the cathode tip may be made of graphite or it can be an extension of the thin metal liner 23 which should preferably be made of a resistive alloy such as Inconel, or any one of many other resistive alloys, and should have such a thickness as to produce a potential drop along the length of the liner approaching a tenth the voltage of the cathode when the discharge current from the cathode has risen to more than half its maximum value. The liner 23 is supported by a dielectric sleeve 22 which in turn is supported by the bulkhead 24. The liner 23 is electrically grounded to the bulkhead at or near the target 26 which is also grounded to the bulkhead. If it is desired to accelerate clusters of mercury ions, the cathode 12 can be a hollow dielectric tube. A pool of mercury 13 provides the vapor which flows out of the cathode to be ionized, collected and accelerated by the electron beam. The collection chamber 27 is pumped by a mercury diffusion pump through pipe 28 and a mercury vapor trap can be used with this pump whose temperature is held at a suitable value to provide the desired flow of mercury vapor through the small aperture 25. This aperture is at an angle from the center line and is located near the side and away from the center line to avoid interfering with the beam and cluster impacting the target. The arrangement in FIG. 3 shows the apparatus rotated into a vertical position. An advantage of this arrangement is that liquid nitrogen or other coolent can easily be used for cooling the tubular anode 43 and its surrounding containing wall 51 for any applications where that is needed. Another difference is that the tubular anode 43 is self-supporting. In FIG. 4, a mercury pool is shown at 33 and the cathode at 32. A graphite section 41 of the tubular anode is mechanically and electrically connected to the resistive tubular section 43 which in turn is electrically connected to and supported at its lower end by the container 51. In order to be able to submerge the reduced diameter portion 51 of the container in a coolant, such as liquid nitrogen, it is convenient to connect this portion 51 to the main upper larger portion of the container by a thin metal wall section 48. In FIGS. 5 and 6, there is a Marx Bank similar to that in FIG. 1 which applies a potential difference across grounded shell 15 and suspended electrode 16. The inner electrode 17 is attached to and supported by discharge tube 18. The discharge tube 18 comprises a stack of washer-like rings, two of which 65 and 65 are of special construction since they carry the diaphragm 64 which in turn carries tubular graphite piece 66 which flares outwardly at its upper end. The tubular cathode 52 narrows as it approaches its discharge end, and has a mercury pool 63 which discharges mercury through the hole running downstreamwardly through the tubular cathode 52. The target 68 is positioned across the end of the anode which is farthest from the target. There is a return path for the electrons that reach the target 68; this return path comprising the grounded shell 15. The anode (which comprises parts 66, 67 and 68) comprises means for forming a potential trough that collects and accelerates ions toward the target. Sub-nuclear products, such as mesons, neutrons, neutrinos, and hadrons, are produced by the collision of ions with the target 68. To achieve this result two things are involved, first, the target 68 is composed of material whose mass number is at least 70; suitable materials such as, lead, bismuth, tin, tungsten, and alloys of one or more of the foregoing elements. Secondly, the potential applied between the cathode and the anode should preferably be so high as to give each ion of the cluster a kinetic energy sufficient to produce one or more of mesons, neutrons, neutrinos, hadrons, etc. Under these circumstances, the collision of the ions with the target will produce said sub-nuclear products. In FIGS. 5 and 6, for example, the distance from the free end of cathode 62 to the upper end of the tubular metal or graphite piece 66 would be about 5 to 20 centimeters. As the electrons and ions enter the tubular piece 66, pinching of the beam begins and during the next 20 or more centimeters of travel the electrons, that were separated from atoms during the producing of ions, are accelerated rapidly towards the target and that leaves behind a positive potential trough. However, in providing this positive potential trough, the magnetic field that accompanies the pinch deflects beam electrons towards the center-line of the beam and thereby locally produces a negative potential trough which collects and concentrates positive ions into a cluster of ions in the beam. These positive ions are accelerated from the point where the cluster is formed, toward the target (a distance that is preferably at least 8 centimeters) since they are in a negative potential trough that is accelerated toward the target. Assuming the distances, referred to in the immediately preceding paragraph, the required potential difference between the anode and the cathode would normally be at least five million volts. The impact of the cluster upon the target 68 can be looked upon in the following way. The impact of each such heavy ion in the cluster upon a target nucleus, after the ion has been accelerated to the same velocity as the electrons in the electron beam, produces collision processes in two parts, one of which includes the sub-nuclear products in a forward narrow cone, and the other which includes a collection of the fragments of both the projectile and target nuclei dispersing randomly about the moving center of mass of the two impacting particles. By virtue of the very high momentum of the projectile ion, the center of mass is moving at a velocity at nearly that of the velocity of light, and consequently, all of the products of the disintegration of the two impacting particles will also be moving (in the laboratory frame of reference) in a narrow forward cone. The products of the earlier collisions of the clusters upon the target, moving in narrow forward cones, immerse the target nuclei downstream so that the projectile nuclei which are also moving at approximately the velocity of light collide with target nuclei which are also immersed in said showers of sub-nuclear particles so that the particles in the collisions progressively lose their identity and in effect fuse in those collisions which occur deeper and deeper into the target. In order to achieve the beam, and the impact, as described above the apparatus shown in FIGS. 1 to 6 inclusive should be adjusted and operated as follows. First, the diameter of the cathode should be selected to avoid streamers in the discharge along the cathode and off of the end of the cathode. In order to accomplish this, a diameter for portion 12, 32 or 62 of the cathode should be selected at an approximate diameter of about 1 mm. for the last centimeter of the length of the cathode, namely, that particular 1 centimeter portion of the cathode which is closest to the anode. The preferred exact diameter is determined by substituting cathodes having various diameters for tube 12, etc. respectively, until the diameter is found which best avoids streamers. It is also desirable to adjust the rate of flow of the mercury from the pool 13 out the free end of the dielectric cathode portion 12. Here again, the adjustment of the flow rate of the mercury vapor out the end of tube 12 is accomplished by substituting different cathodes into the apparatus until the correct mercury flow rate is achieved. The correct rate will result in a density of mercury ions in the beam which will attract the electrons in the beam toward the center line of the beam with a force which is in excess of the force exerted on the ions toward the axis by virtue of the pinch effect. The rate of flow of the mercury vapor may be increased or decreased by either varying the internal diameter of, or the length of the dielectric tube 12 which projects into the vicinity of the mercury pool 13 and is also located inside the metal cathode holder 11. As stated above, the mercury ions will cause a force toward the center line to be exerted on the electrons toward the axis of the beam. The excess force, which results from the ions attracting the electrons in the beam, results from a higher density of positive ions than is required for the pinch effect. This is obtained by introducing an increased positive ion production (by means of mercury gas) in the vicinity of the beam. The extra force is produced by the positive mercury ions introduced in the vicinity of the beam. This causes an increase in the density of beam electrons near the center line and produces the local potential trough which is attractive to the cluster of mercury ions which overlie this potential trough and are moving forward and backward in the potential trough. The mercury ions that are not as highly ionized or as well located as to be held firmly in the cluster in the potential trough will drift rearwardly from the potential trough, toward the cathode, and be lost. This purging of the cluster of the less firmly held ions is essential to the formation of a cluster of ions which will follow the potential trough and be accelerated progressively towards the anode by increasing in velocity. The potential trough cannot run away from the cluster of ions because the potential trough is produced mainly by the cluster. In order to collect, concentrate and accelerate heavy ion clusters as accomplished in this invention, it is necessary to produce and sustain a very intense pinch effect in the relativistic electron beam particularly in the portion of the electron beam nearer to the target and within the tubular anode whose diameter is much reduced below the diameter of the tube around the cathode. In order to produce the pinch effect along the entire length of the beam, it is necessary to apply a continually accelerating applied electric field along the entire beam. This has been accomplished in the various designs and methods disclosed in my previous application Ser. No. 149,163 by virtue of the penetration of the applied electric field into the hollow tubular anodes of the various designs. The basic improvement in the design of the tubular anode as described above makes this invention fully effective in a much broader range of kinds of applications. One mercury ion moving at the same velocity as the electrons in a 10,000,000 volt beam has an energy of over 4.10.sup.12 eV (4000 GeV) which is greater than the highest energy ever given an ion of any element by a man-made machine. The effects of the impact of the nucleus of such a high energy mercury ion on a nucleus in a solid state heavy element like lead should include the production of many more varieties of nuclear fragments and mesons including neutrons, neutrinos and hadrons, and also including those of much greater energy than are seen in the figures shown in "Annual Review of Nuclear and Particle Science", Vol., 28, pages 164 and 166, 1978. (Annual Reviews, Inc., 4139 El Camino Way, Palo Alto, Calif. 94306, in an article by Goldhaber and Heckman). FIG. 1 shown on page 164 shows products from a 72 GeV argon nucleus colliding with a silver nucleus in the emulsion. The argon projectile is shattered into 5 helium nuclei in the forward narrow cone with about the same velocity as the argon nucleus had. There is also a negative pion particle in the same forward cone which comes to rest and forms a three-pronged star. The target silver nucleus is shattered into comparatively low velocity fragments in random directions about the moving center of mass of the argon and silver combination. FIG. 2 shown on page 166 of the reference shows the interaction of 72 GeV argon projectile nucleus striking a lead target nucleus. There are at least 63 product particles including protrons, neutrons, light fragments and pions including at least one negative pion. There is also a forward cone of high energy products as in FIG. 1. These figures show a much lower projectile energy (72 GeV instead of 4000 GeV) and a much smaller nuclear mass (40 instead of about 200) than in the example mentioned above of the mercury ion at the velocity of the electrons in a 10,000,000 volt beam. A far greater difference is that there is only one projectile nucleus in the above examples instead of the order of 10.sup.8 heavy nuclei in a compact cluster as is inherent in this method and process. Although there are many more nuclear and sub-nuclear fragments in the forward cone, there is a much more important difference when a compact cluster is the projectile, instead to single ions well separated from any other ions. The jets in narrow cones of very high energy sub-nuclear and nucleonic products from those collisions of ions occurring earlier upon entry of the cluster into the target will envelop and immerse the colliding nuclei farther into the target so that those later colliding have begun to lose their identity and to fuse by the time each later arriving projectile has fully engaged the strongly activated target nucleus. Throughout the history of the developing physics of heavy ion collisions, each increase by several times of the energy of the projectile ion, or the mass of either or both of the projectile ion or target ion, has resulted in the production of new kinds of particles as for example the recent recognition of what are called "anomolons" which have collision cross-sections an order of magnitude greater than any of the high energy secondary products of lower energy collisions of such ions. (See Physics Today, pages 17-19, April 1982). It should be apparent from the above description that this new method for accelerating clusters of heavy nuclei provides for the first time the capability of producing the following new nuclear processes: (1) the production of strong concentrated directed beam yields of neutrons and neutrinos from heavy nuclei; (2) the production of shock waves and Mach cones in nucleus-nucleus collisions with the attendant production of compressed nuclear matter with consequences of kinds suggested by recent astrophysical discoveries; (3) during this transition fusion of the composite nucleus of atomic mass of the order of 400, by virtue of the coherent induced radiation of neutrinos and electrons, analogous to the coherent induced optical radiation in lasers, the production of stable and quasi-stable elements at the so-called stable islands of atomic number much above any presently known element; (4) the containment and utilization of the highly energetic and actinic yields from heavy ion fusion in the production of nuclear power as is done deep inside the sun and which can never be accomplished with the current attempts here on earth to produce fusion power using ionizesd low atomic number gases or multiple laser beams. The description contained in the next three paragraphs is applicable to each of FIGS. 1 to 7. The electron beam from the cathode 12, 32 or 62 to the anode 29, 43 or 66 collects ions from the vicinity of the cathode tip 12, 32 or 62 and begins to concentrate them in a cluser en route to the tapared metal or graphite piece 21, 41 or 66. This further concentrates the cluster en route towards the target, 26, 46 or 68 while accelerating the cluster of accelerated ions up to the velocity of the electrons in the beam and impelling that cluster into the target at that velocity. Near the cathode 12, 32 or 62, gas atoms are ionized and the electrons are accelerated away from the cathode 12, 32 or 62 while the ions are initially accelerated towards the cathode 12, 32 or 62 at a much slower rate, thus allowing an excess of positive ions to accumulate, thus producing locally a positive potential trough. This trough in combination with the pinch effect, deflects the on-coming electrons towards the center line of the beam until the above positioned positive potential trough is reversed to a negative potential trough which collects positive ions and accelerates them away from the cathode. This occurs only in a small section of the beam near the center line and does not reverse the electric field over most of the space in front of the cathode. The collection of the cluster of ions occurs in the negative potential trough just before the electrons in the beam are deflected towards the center line of the beam. The cluster of ions collects adjacent to, and slightly overlapping, the moving negative potential trough. The interaction of the positive and negative potential troughs continues to intensify and accelerate during their movement toward the target while approaching the velocity of the beam electrons. The formation of the positive and negative troughs, and the function of the negative trough in accelerating ions toward the target, has been explained above. However, in at least some cases it is desirable to have an electric field to sustain the beam with said troughs therein. The electric field may also increase the acceleration of the ions toward the target. The means and method of providing this electric field will now be explained. In FIG. 2, electrons from cathode 12 strike graphite piece 21 and these electrons will flow along that piece and then through the partially conductive tubular member 23 to the target 26. This current flow creates a potential difference between (1) the end of graphite piece 21 that is closest to the target, and (2) the target. This potential difference creates the electric field referred to above. Similarly, in FIG. 4, electrons from cathode 32 strike graphite piece 41 and then flow along the partially conductive wall of tube 43 to the target 46, thereby creating a potential difference along parts 41 and 43, in turn creating the desired electric field. FIG. 6 works in the same overall manner as FIGS. 2 and 4, except that there is a departure so far as generating the potential difference is concerned. In this figure, electrons from the cathode 62 are intercepted by graphite piece 66 and fed to diaphragm 64 and then flow along paralled wires 67 to grounded ring 70. The potential difference between graphite piece 66 and grounded ring 70 creates the desired electric field. In FIG. 2, chamber 27 is an optional addition to the system. It is a partially evacuated ionization chamber, partially exhausted through outlet 28. Chamber 27 contains a low pressure gas containing mercury ions and some of this gas leaks through hole 25 in target 26 to provide ionized gas in the vicinity of the point where the beam strikes the target. This enhances the pinch of the beam. All three forms of the invention may work in the following modified manner if a number of ions exist, or are formed, directly in front of the cathode. The application of a high voltage negative pulse to the cathode in the presence of a low density gas such as mercury vapor projects electrons from the cathode tip into the gas. The electrons ionize the gas with an efficiency which rises next to the cathode tip to a maximum at a distance where the potential difference from the cathode tip is about 50 to 100 volts, and then decreases from there on as the potential difference increases. Thus, there is a thin region surrounding the cathode tip where there is an increased density of ionizing collisions. The electrons separated from the ions in these ionizations are swept downstream away from the cathode leaving behind the ions so produced which are swept upstream much more slowly due to the greater mass of the ions. The ions contribute a positive charge to the beam which acts as a weak positive potential trough. This potential trough extends along the beam and attracts the beam electrons towards the centerline of the beam. Some of the beam electrons that are deflected toward, and pass the centerline of the beam, are deflected so much that they go past the centerline and keep going thus leaving the beam. Where the density of those beam electrons which are deflected toward the centerline build up to a maximum there is a negative potential trough which builds up. As soon as this negative potential trough has built up enough, it is capable of entrapping some of the more slowly moving ions which move forward and drop into the negative potential trough. As the electrons responsible for the negative potential trough increase in density, the trough increases in speed and the entrapped positive ions pick up speed to the same degree. The pinch effect in the beam over the length of the potential trough increases in strength and pinches down the diameter of the trough and the cluster of ions that have been entrapped increases in speed. Thus, the diameter of the cluster decreases or in other words is pinched. In this way the progress of the negative potential trough and its entrapped cluster of positive ions speed up with the result that ions have increased energy, the cluster is increasingly concentrated and the rate of increase of the kinetic energy of the ions also increases.
	abstract	A method of generating a single photon, includes preparing an optical resonator including a resonator mode of a resonance angular frequency ωc, preparing a material contained in the optical resonator, including a low energy state \|g> and a high energy state \|e>, and including a transition angular frequency ωa between \|g>−\|e> that is varied by an external field, applying, to the material, light of an angular frequency ωl different from the resonance angular frequency ωc, and applying a first external field to the material to vary the transition angular frequency ωa to resonate with the angular frequency ωl, such that a state of the material is changed to \|e>, and then applying a second external field to the material to vary the transition angular frequency ωa to resonate with the resonance angular frequency ωc, such that the state of the material is restored to \|g>.
053316789	description	DESCRIPTION OF THE PREFERRED EMBODIMENT FIGS. 1-3 show a portion of a nuclear fuel assembly grid strip 10, which represents one of a plurality of orthogonally inter-engaged strips 10, 100, 200, 300 that would make up an egg-crate type fuel assembly grid with cells as shown in FIGS. 4-7 for supporting a plurality of nuclear fuel rods. Each strip 10 is initially sized and annealed as a substantially rectangular flat plate having length, height, and width dimensions. The plate is then stamped to form a plurality of cut outs, slots, and projections. The present invention is preferably implemented with strips 10, that are made from a zirconium alloy, especially Zircaloy. Such a strip 10 has a plurality of slots 12,14 extending along the height dimension at regular intervals along the length dimension, thereby defining successive cell walls 16,18,20 between successive slots along the length dimension. A plurality of strips can thus be interengaged orthogonally at the slots to form the well-known egg-crate configuration. Each cell wall such as 16, has fuel rod support features or structure. In a preferred embodiment of the present invention, there are three fuel rod support features 22,24,26 per cell wall 16, located respectively in upper 28, central 30, and lower regions 32 of the cell wall. Each region includes a substantially flat base area 34,36,38, and cold-formed fuel rod support structure 22,24,26 projecting integrally from the base area along the width dimension of the strip. The support structure 22,26 in each of the upper 28 and lower regions 32 includes a relatively stiff, arched stop which projects in a first direction, and the support structure 24 in the central region includes a relatively soft, arched spring, which projects in a second direction opposite the first direction. In accordance with the invention, the spring 24 includes spaced apart pedestals 40,42 or similar projections formed in the base area 36 of the central region 30 and projecting in the second direction. A resilient beam 44 extends between and is rigidly supported by the pedestals 40,42, so as to project in the second direction beyond the projection of the pedestals. Preferably, each pedestal forms an arch that curves along the length dimension of the strip, and the beam forms a shallow peak or arch that bends or curves along the height dimension of the strip. The cut-outs 46,48 are formed adjacent to the locations of the pedestals 40,42 and beam 44. Moreover, additional cut-outs 50,52 and 54,56 are provided to facilitate the forming of the arches in the upper and lower regions, which project in a direction opposite to that of the spring. Preferably, each of the arch stops 22,26 is formed between a pair of longitudinal cut-outs 50,52 and 54,56 that extend along the length dimension of the strip. The beam 44 is formed between a pair of transverse cut-outs 46,48 that extend along the height dimension of the strip, and each pedestal such as 40 is formed between one longitudinal cut-out 52 and the pair of transverse cut-outs 46,48. The pedestals 40,42 project from the central region base area 36 a first distance d.sub.1, and the beam 44 has a crown 58 which projects from the central region base area a second distance d.sub.2 which is less than twice the first distance. Preferably, the beam 44 has a length 60 extending between the pedestals 40,42, that is at least about ten times greater than the distance d.sub.3 that the crown projects into the cell relative to the distance which the pedestal projects into the cell (i.e. d.sub.3 =d.sub.2 -d.sub.1). In other words, the length 60 of the beam 44 is at least about ten times greater than the difference d.sub.3 between the projection of the crown 44 relative to the base area 36 and the projection of the pedestals 40,42 relative to the base area 36. All the fuel rod support features as described in connection with FIGS. 1-7, can be formed during a single stamping operation, which cold-works the material constituting the projections. The base regions 34,36,38 are in a condition corresponding to the annealing of the strip 10, before the cutting of the slots 12,14 and cut-outs 46,48,50,52,54,56. The projecting structure 22,24,26, however, necessarily experience a certain amount of straining (cold working) during formation. The more highly strained portions of the strip, undergo greater elongation and relaxation during exposure to radiation in the reactor core. It can be appreciated from inspection of FIGS. 1 and 2, that since beam 44 has been cold worked, whereas the base area 36 has not, the relatively greater elongation of the beam would give rise to axial compression stresses, acting inwardly toward the crown 58, which thereby urge the crown further into the cell. The strips of the type shown in FIGS. 1-3, are assembled into an egg crate structure that results in the creation of grid cells with the geometry shown in FIGS. 4 and 5. Insertion of a fuel rod 500 into a grid cell produces the geometry shown in FIGS. 6 and 7. In the initial geometry of the cell as shown in FIGS. 4 and 5, the horizontal distance between each spring 24,324 and its opposing arch stops 222,226 and 122, 126 is less than the diameter of the fuel rod 500. Therefore, insertion of the fuel rod into the cell as shown in FIGS. 6 and 7, deflects each spring and thus preloads the rod against the arch stops. The preload prevents relative motion between the rod and grid during handling and shipment. During reactor operation the preload is reduced due to the short-term and long-term mechanisms described previously. Particularly with conventional Zircaloy grids, reactor operation can result in the complete loss of grid spring preload and the possible generation of gaps between the fuel rod and the rod support features. However, the inventive configuration of the spring and its supports minimizes or eliminates these gaps by using the lateral amplification of the axial compression of a nearly straight beam. As shown in FIG. 8, a more complex forming process of the spring 24' and its support projections 40'42' can further enhance the amplification effects between the beam and the base area. This is achieved by additionally straining only the spring 24 during or after the strip of FIGS. 1 and 2 has been stamped (overforming, then forcing back) and allowing a slight cant of the pedestals 40' 42' away from each other, i e , away from the crown 58' of the beam spring. The axial compression of the spring 24' can result from relaxation of the residual stresses associated with the cant of the support projections 40'42 or from the cold-worked spring being restrained from growing by the fully annealed strip. As with any virtually straight member, axial compression of the spring, however slight, results in a much larger lateral deflection. This lateral deflection of the spring is toward the rod, thus eliminating or minimizing any gap. Another desirable feature which can be implemented with the present invention, is shown in FIGS. 1 and 2. The arch stops 22,26 in the first and second regions can be formed with vertical extensions 62,64 and 66,68 for contacting the rod and preventing scratching of the rod as it is inserted into the cell. The vertical contact length increases the rod-to-arch contact area, thus decreasing rod wear by lowering the contact pressure.
	claims	1. A multilayer structure for reflecting x-rays comprising: at least one triad of layers including a first layer, a second layer, and a third layer; wherein the first layer includes one of lanthanum (La), lanthanum oxide (La 2 O 3 ), or a lanthanum-based alloy, the second layer includes one of carbon (C), boron (B), silicon (Si), boron carbide (B 4 C) or silicon carbide (SiC), and the third layer includes one of boron (B) or boron carbide (B 4 C), and wherein the second layer is disposed between the first layer and the third layer. 2. The multilayer structure of claim 1 wherein the first layer includes one of lanthanum (La) or lanthanum oxide (La 2 O 3 ). claim 1 3. The multilayer structure of claim 1 wherein the third layer consists of boron carbide (B 4 C). claim 1 4. The multilayer structure of claim 1 wherein the second layer includes one of carbon (C), boron (B), or silicon (Si). claim 1 5. The multilayer structure of claim 1 wherein the second layer includes one of boron carbide (B 4 C) or silicon carbide (SiC). claim 1 6. The multilayer structure of claim 1 wherein the first layer consists of lanthanum (La), the second layer consists of silicon carbide (SiC), and the third layer consists of boron carbide (B 4 C). claim 1 7. The multilayer structure of claim 1 wherein the first layer consists of lanthanum oxide (La 2 O 3 ), the second layer consists of silicon (Si), and the third layer consisting of boron carbide (B 4 C). claim 1 8. The multilayer structure of claim 1 wherein the first layer consists of lanthanum oxide (La 2 O 3 ), the second layer consists of carbon (C) and the third layer consists of boron carbide (B 4 C). claim 1 9. The multilayer structure of claim 1 characterized in that the structure consists of between 1 and 100 of the triads of layers. claim 1 10. The multilayer structure of claim 1 characterized in that the structure consists of between 30 and 60 of the triads of layers. claim 1 11. The multilayer structure of claim 1 characterized in that the structure is laterally graded. claim 1 12. The multilayer structure of claim 1 characterized in that the structure is depth graded. claim 1 13. The multilayer structure of claim 1 wherein a thickness of the first layer, a thickness of the second layer, and a thickness of the third layer are substantially identical. claim 1 14. The multilayer structure of claim 1 wherein a thickness of the first layer, a thickness of the second layer, and a thickness of the third layer are variable. claim 1 15. The multilayer structure of claim 1 characterized in that the structure is elliptically curved. claim 1 16. The multilayer structure of claim 1 characterized in that the structure is parabolically curved. claim 1 17. The multilayer structure of claim 1 characterized in that the structure is spherically curved. claim 1 18. The multilayer structure of claim 1 wherein the at least one triad of layers is between 5 and 60 nanometers in thickness. claim 1 19. A method of x-ray fluorescence spectroscopy comprising: providing a field x-ray radiation; irradiating a sample to be analyzed with the field of x-ray radiation, thereby inducing a field of fluorescence radiation; directing the field of fluorescence radiation from a multilayer reflector including at least one triad of layers, the at least one triad of layers including a first layer, a second layer, and a third layer, the first layer including one of lanthanum (La), lanthanum oxide (La 2 O 3 ), or a lanthanum-based alloy, the second layer including one of carbon (C), boron (B), silicon (Si), boron carbide (B 4 C) or silicon carbide (SiC), and the third layer including one of boron (B) or boron carbide (B 4 C). 20. The method of claim 19 further comprising the step of analyzing the field of fluorescence radiation after it has irradiated the sample. claim 19 21. An x-ray fluorescence spectroscopy system comprising: an x-ray source emitting an x-ray radiation field on a sample; a multilayer structure having at least one period of individual layers, wherein the number of individual layers in the period is either three or four, a first layer including one of lanthanum (La), lanthanum oxide (La 2 O 3 ), or a lanthanum-based alloy, a second layer including one of carbon (C), boron (B), silicon (Si), boron carbide (B 4 C) or silicon carbide (SiC), and a third layer including one of boron (B) or boron carbide (B 4 C); wherein the sample emits a fluorescent radiation field in response to the x-ray radiation field, and wherein further the multilayer structure selectively reflects the fluorescent radiation field. 22. A multilayer structure for reflecting x-rays comprising: at least one quartet of layers; wherein a first layer includes one of lanthanum (La), lanthanum oxide (La 2 O 3 ), or a lanthanum-based alloy, a second layer includes one of boron (B) or boron carbide (B 4 C), a third layer includes one of carbon (C), boron (B), silicon (Si), boron carbide (B 4 C) or silicon carbide (SiC), and a fourth layer includes one of carbon (C), boron (B), silicon (Si), boron carbide (B 4 C) or silicon carbide (Sic); and wherein the third layer is disposed between the first layer and the second layer, end wherein the second layer is disposed between the third layer and the fourth layer. 23. The multilayer structure of claim 22 , characterized in that the structure consists of between 1 and 100 of the quartets of layers. claim 22 24. The multilayer structure of claim 22 characterized in that the structure consists of between 80 and 60 of the quartets of layers. claim 22 25. The multilayer structure of claim 22 characterized in that the structure is laterally graded. claim 22 26. The multilayer structure of claim 22 characterized in that the structure is depth graded. claim 22 27. The multilayer structure of claim 22 wherein a thickness of the first layer, a thickness of the second layer, a thickness of the third layer, and a thickness of the fourth layer are substantially identical. claim 22 28. The multilayer structure of claim 22 , wherein a thickness of the first layer, a thickness of the second layer, a thickness of the third layer, and a thickness of the fourth layer are variable. claim 22 29. The multilayer structure of claim 22 characterized in that the structure is elliptically curved. claim 22 30. The multilayer structure of claim 22 characterized in that the structure is parabolically curved. claim 22 31. The multilayer structure of claim 22 characterized in that the structure is spherically curved. claim 22 32. The multilayer structure of claim 22 wherein the at least one quartet of layers is between 5 and 60 nanometers in thickness. claim 22
	claims	1. A method of treating a particle beam, the particle beam including positive ions, including the step of passing the particle beam through a charge exchange cell, the charge exchange cell containing a gaseous target material, the gaseous target material being a material that is electrically insulating at room temperature and pressure, at least some of the positive ions of the particle beam being converted to negative ions by interaction with the gaseous target material, the particle beam incident at the charge exchange cell further including molecules and/or molecular ions which interact with the same gaseous target material in the same charge exchange cell to reduce the concentration of molecules as a result of repeated collisions with particles of the gaseous target material thereby to provide a treated particle beam, wherein the negative ions are selected from the treated particle beam for subsequent analysis. 2. The method according to claim 1 wherein the gaseous target material includes a component that is matched in terms of atomic weight to a species in the particle beam to be detected. 3. The method according to claim 1 wherein the gaseous target material used in the charge exchange cell includes at least one of hydrogen, helium, nitrogen, argon, methane, butane, ethane, isobutane and propane, or a mixture thereof. 4. The method according to claim 1 wherein the gaseous target material is energetically-pumped. 5. A method for performing mass spectrometry on an analyte sample including the steps of:generating a particle beam using the analyte sample, the particle beam including positive ions;passing the particle beam through a charge exchange cell, the charge exchange cell containing a gaseous target material, the gaseous target material being a material that is electrically insulating at room temperature and pressure, at least some of the positive ions of the particle beam being converted to negative ions by interaction with the gaseous target material, the particle beam incident at the charge exchange cell further including molecules and/or molecular ions which interact with the same gaseous target material in the same charge exchange cell to reduce the concentration of molecules as a result of repeated collisions with particles of the gaseous target material thereby to provide a treated particle beam; andpassing the treated particle beam to a particle detector configured to detect at least some of said negative ions. 6. The method according to claim 5 used for radiocarbon detection, wherein the beam generated from the analyte sample includes at least one of 14C+, 14C2+, and 14C3+. 7. The method according to claim 6 wherein the treated particle beam is passed through a mass spectrometer to select 14C−, and receiving the selected portion of the beam at the particle detector configured to detect 14C−. 8. The method according to claim 5 wherein the incident particle beam is subjected to selection using a first mass spectrometer before reaching the charge exchange cell. 9. The method according to claim 8 wherein the incident particle beam is subjected to selection so that it consists primarily of 14C2+ and incidental interferences. 10. The method according to claim 6 wherein the positive ions in the particle beam are generated using an electron cyclotron resonance (ECR) ion source. 11. The method according to claim 10 wherein the plasma in the ECR ion source is manipulated by the addition of a carrier or by addition of excess sample material, in order that the ECR ion source operates to discriminate against the production of ions of some constituents. 12. The method according to claim 11 wherein a helium carrier gas is added to suppress the production of hydrocarbon molecules where the sample is a CO2 sample. 13. The method according to claim 6 wherein, in the charge exchange cell, the gaseous target material suppresses at least one interfering species by repeated collision with the gaseous target material. 14. The method according to claim 8 wherein, following the charge exchange cell, the treated particle beam is further subjected to selection using a second mass spectrometer. 15. The method according to claim 14 wherein the selected part of the treated particle beam reaches the particle detector configured to detect at least some of said negative ions. 16. A method for performing mass spectrometry on a carbon-based analyte sample including the steps of:generating a particle beam from the analyte sample using an electron cyclotron resonance ion source operated to generate 14C2+;selecting the 14C2+ portion, and remaining interferences, using a first mass spectrometer;passing the particle beam through a charge exchange cell containing a gaseous target material selected from a group comprising one or more of hydrogen, helium, nitrogen, argon, methane, butane, ethane, isobutene, propane, and a mixture thereof to convert positive incident 14C ions to negative ions by interaction with the gaseous target material and to suppress 13CH and 12CH2 interferences as a result of repeated collisions with particles of the gaseous target material in the same charge exchange cell thereby to provide a treated particle beam containing negative ions;passing the treated particle beam through a second mass spectrometer to select 14C−; andreceiving the selected portion of the treated particle beam at the particle detector to detect 14C−. 17. A mass spectrometry system suitable for performing mass spectrometry on an analyte sample, the system including:a particle beam generator for generating a particle beam using the analyte sample, the particle beam including positive ions;a charge exchange cell, the charge exchange cell configurable to contain a gaseous target material the gaseous target material being a material that is electrically insulating at room temperature and pressure, the charge exchange cell being operable so that at least some of the positive ions of the particle beam are converted to negative ions by interaction with the gaseous target material the charge exchange cell further being operable so that molecules and/or molecular ions present in the particle beam incident at the charge exchange cell interact with the same gaseous target material in the same charge exchange cell to reduce the concentration of molecules as a result of repeated collisions with particles of the gaseous target material, thereby to provide a treated particle beam; anda particle detector configured to detect at least some of said negative ions in said treated particle beam. 18. The mass spectrometry system according to claim 17 including mass flow gas controllers for controlling the gas formulation in the charge exchange cell at room temperature.
	claims	1. A scanning electron microscope, comprising:an electrode which is located under an objective lens, and to which a voltage can be applied independently, anda sample stage which is located under said electrode, and to which a voltage can be applied independently, said sample stage being used for mounting a sample thereon,wherein said sample is set up between said electrode and said sample stage such that an arbitrary equipotential surface and the surface of said sample coincide with each other, said arbitrary equipotential surface being formed by a parallel electric potential, said parallel electric potential being generated between said electrode and said sample stage by applying each of said voltages to said electrode and said sample stage. 2. The scanning electron microscope according to claim 1, wherein said sample is a sample whose substrate is formed of an insulating substance, said insulating substance being exposed on a part or the whole of said surface of said sample. 3. The scanning electron microscope according to claim 1, wherein said electrode is a flat-plate electrode having a hole through which an electron beam can pass, said hole provided in said flat-plate electrode being of a size which prevents a potential over said flat-plate electrode from being substantially exerted on said sample surface, relationship between D and L satisfying D/L≦1.5 when letting diameter of said hole be D and distance between said flat-plate electrode and said sample be L. 4. The scanning electron microscope according to claim 1, wherein said sample stage is larger than area of said sample. 5. The scanning electron microscope according to claim 1, wherein said sample stage is geometrically similar to shape of said sample. 6. The scanning electron microscope according to claim 1, wherein the upper surface of said sample stage or a specific surface thereof on which said sample is mounted is formed into a structure, said structure being planarized over an area larger than said sample and having no projections and depressions within said surface, said upper surface or said specific surface being a surface which is directly opposed to the bottom surface of said sample. 7. The scanning electron microscope according to claim 1, wherein depth of an excavated structure or height of a spacing structure is smaller than one-half of thickness of said sample, said excavated structure or said spacing structure being provided in said sample stage so as to mount said sample therein or thereon. 8. A sample observation method, comprising a step of, when said sample whose substrate is formed of an insulating substance such as glass or quartz is observed in said scanning electron microscope according to claim 1, setting a voltage which is to be applied to said electrode, at a voltage which becomes positive with reference to a potential on said sample stage, and which becomes positive by a few V to a few tens of V with reference to a potential on said sample surface. 9. The sample observation method according to claim 8, further comprising a step of changing said voltage, which has been applied to said electrode, in a range in a continuous manner or in a step-by-step manner in the midst of irradiating an electron beam onto said sample, said range ranging from a few V to a few tens of V in a direction which is negative with reference to said initial value of said voltage. 10. The sample observation method according to claim 9, wherein an irradiation area of said electron beam on said sample in the midst of changing said voltage applied to said electrode is sufficiently larger as compared with an area to be observed. 11. A scanning electron microscope capable of automatically changing said voltage applied to said electrode in said sample observation method according to claim 9, said scanning electron microscope, comprising means for measuring secondary-electron quantity or reflected-electron quantity generated from said sample, wherein, if said secondary-electron quantity or said reflected-electron quantity has become larger or smaller than threshold values determined in advance, said scanning electron microscope automatically terminates said change in said voltage applied to said electrode, and sets said voltage at that time as said initial value of said voltage. 12. A scanning electron microscope, comprising means for measuring secondary-electron quantity or reflected-electron quantity generated from said sample in said sample observation method according to claim 9, wherein, if said secondary-electron quantity or said reflected-electron quantity has become larger or smaller than threshold values determined in advance, said scanning electron microscope automatically terminates said change in said voltage applied to said electrode. 13. The scanning electron microscope according to claim 11, wherein said threshold values according to claim 11 are specific luminance of an image and number of pixels belonging to said specific luminance, said image being formed based on secondary-electron signals or reflected-electron signals. 14. The scanning electron microscope according to claim 12, wherein said threshold values are specific luminance of an image and number of pixels belonging to said specific luminance, said image being formed based on secondary-electron signals or reflected-electron signals. 15. The scanning electron microscope according to claim 12, wherein said means according to claim 12 for measuring said secondary-electron quantity or said reflected-electron quantity is an electron detector, said electron detector being a Wien filter including an electric field and a magnetic field, or a potential-blockage type energy filter equipped with an electrode, said electrode being capable of generating a potential which turns out to become a barrier against energy possessed by said secondary electrons or said reflected electrons.
	claims	1. A steel composition comprising:Cr at between about 10.0 wt% and about 13.0 wt%;C at between about 0.17 wt% and about 0.23 wt%;Mo at between about 0.80 wt% and about 1.2 wt%;Si less than or equal to about 0.5 wt%;Mn less than or equal to about 1.0 wt%;V at between about 0.25 wt% and about 0.35 wt%;W at between about 0.40 wt% and about 0.60 wt%; andFe at least 80 wt%;wherein the processing of the steel composition includes transforming at least some of the steel composition into an austenite phase by heating the steel composition to a temperature from 1100° C. to 1300° C. for 40-60 hours. 2. The steel composition of claim 1,wherein the steel composition has been processed so that it exhibits a swelling of less than 0.9% by volume at a depth between 500-700 nm below the surface after dual-beam Fe++ and He++ irradiation to doses of 188 displacements per atom (dpa) with 0.2 appm He/dpa, as calculated using the Stopping Range in Matter simulation with the K-P option for damage cascades and a 40 eV displacement energy, created by irradiating the steel composition at 460° C. with a defocused beam of 5 MeV Fe++ ions and a raster-scanned beam of ˜2 MeV He++ ions transmitted through a thin Al foil for scattering and energy reduction to create a uniform He profile at the irradiation depth of a sample of the steel composition. 3. The steel composition of claim 2, wherein the steel composition exhibits a swelling of less than 0.75% by volume. 4. The steel composition of claim 2, wherein the steel composition exhibits a swelling of less than 0.5% by volume. 5. The steel composition of claim 2, wherein the steel composition exhibits a swelling of less than 0.3% by volume. 6. The steel composition of claim 1, wherein the steel composition is an HT9 steel. 7. A fuel element made of the steel composition of claim 1. 8. A component of a fuel assembly made of the steel composition of claim 1. 9. A steel composition comprising:(Fe)a(Cr)b(Mo, Ni, Mn, W, V)cNd;whereina, b, c, and d are each a number greater than zero representing a weight percentage;b is between 11 and 13;c is between about 0.25 and about 0.9;d is between about 0.01 and about 0.04; andbalanced by a; andwherein the processing of the steel composition includes transforming at least some of the steel composition into an austenite phase by heating the steel composition to a temperature from 1100° C. to 1300° C. for 40-60 hours. 10. The steel composition of claim 9, wherein b is between 11.5 and 12.5. 11. The steel composition of claim 9,wherein the steel composition has been processed so that it exhibits a swelling of less than 0.9% by volume at a depth between 500-700 nm below the surface after dual-beam Fe++ and He++ irradiation to doses of 188 displacements per atom (dpa) with 0.2 appm He/dpa, as calculated using the Stopping Range in Matter simulation with the K-P option for damage cascades and a 40 eV displacement energy, created by irradiating the steel composition at 460° C. with a defocused beam of 5 MeV Fe++ ions and a raster-scanned beam of ˜2 MeV He++ ions transmitted through a thin Al foil for scattering and energy reduction to create a uniform He profile at the irradiation depth of a sample of the steel composition. 12. The steel composition of claim 11, wherein the steel composition exhibits a swelling of less than 0.75% by volume. 13. The steel composition of claim 11, wherein the steel composition exhibits a swelling of less than 0.5% by volume. 14. The steel composition of claim 11, wherein the steel composition exhibits a swelling of less than 0.3% by volume. 15. The steel composition of claim 9, wherein the steel composition is an HT9 steel. 16. A fuel element made of the steel composition of claim 9. 17. A component of a fuel assembly made of the steel composition of claim 9. 18. The steel composition of claim 1, wherein:Cr is at between about 10.0 wt% and about 12.5 wt%;C at between about 0.17 wt% and about 0.22 wt%;Mo at between about 0.80 wt% and about 1.2 wt%;Si less than or equal to about 0.5 wt%;Mn less than or equal to about 1.0 wt%;V at between about 0.25 wt% and about 0.35 wt%;W at between about 0.40 wt% and about 0.60 wt%;P less than or equal to about 0.5 wt%;S less than or equal to about 0.5 wt%; andFe at least 80 wt%. 19. The steel composition of claim 1, further comprising:Ni at between about 0.3 wt% and about 0.7 wt%. 20. The steel composition of claim 1, wherein at least substantially all of the composition is in the martensite phase.
	abstract	Disclosed is a spacer grid assembly with mixing vanes supporting fuel rods of nuclear fuel assemblies and mixing coolant that flows around the fuel rods, and more particularly, a spacer grid equipped with mixing vanes that mix coolant flowing around fuel rods.
	description	The present disclosure relates generally to an apparatus and method for doping semiconductor material based on the nuclear transmutation process. In the production of semiconductor components, it is necessary to be able to set the electrical conductivity of the semiconductor material as precisely as possible according to the desired purpose of the semiconductor components. Semiconductor material for power electronics especially requires unique material characteristics because of the high blocking capability of semiconductor material and the high currents flowing in the semiconductor material. Semiconductor material with non-uniform electrical properties may render the power devices unstable and potentially dangerous. The electrical characteristics of a semiconductor material are set by doping it with suitable impurity atoms. For power devices to work at designated power levels and voltage readings it is necessary to dope the semiconductor material with impurities that enable sufficient blocking capability and homogeneous current flow through the bulk of the semiconductor material. One effective and accurate doping technique used for high power semiconductor material is the Neutron Transmutation Doping (NTD) process. The conventional NTD process is implemented by irradiating semiconductor ingot rods in a nuclear reactor with neutrons of suitable energy for a suitable time period. Silicon is by far the most common semiconductor material used for power semiconductor devices today. As applied to silicon, the conventional NTD process provides effective doping control and removal of non-uniformities in high resistivity silicon crystal. When silicon material is exposed to thermal neutron irradiation, phosphorous dopant atoms are induced within the silicon material thereby changing the resistivity of the silicon material. Specifically, when a neutron collides and merges with a 30Si isotope, an unstable 31Si isotope is formed, which subsequently transmutes to a 31P atom by beta decay, resulting in n type impurity doping in the silicon material. However, since the neutrons are absorbed in the silicon, the conventional NTD process results in an undesired radial gradient of the resulting n-doping, which results in a lateral variation of the electrical characteristics of the power semiconductor devices manufactured from the silicon ingot rod. In order to minimize this effect of inhomogeneity, the silicon ingot rods can, for example, be rotated in the nuclear reactor, so that the neutron irradiation is performed from all sides of the silicon ingot rod. However, despite such measures substantial lateral variations still occur in silicon ingot rods having a diameter of about for example 300 mm or larger due to the above described absorption effects. Lateral doping uniformity of ingot rods having a diameter of about 300 mm or greater has been a challenge using conventional NTD. Further, the conventional NTD process is implemented with a nuclear reactor which is undesirable. It is difficult to adapt existing nuclear reactors to accommodate larger diameter semiconductor ingots. For example, ingots having a diameter larger than about 200 mm cannot be irradiated in many existing nuclear reactors. In various embodiments, a method of processing one or more semiconductor wafers is provided. The method includes positioning the one or more semiconductor wafers in an irradiation chamber, generating a neutron flux in a spallation chamber coupled to the irradiation chamber, moderating the neutron flux to produce a thermal neutron flux, and exposing the one or more semiconductor wafers to the thermal neutron flux to thereby induce the creation of dopant atoms in the one or more semiconductor wafers. Various embodiments of the invention are explained in greater detail below, with reference to the accompanying figures. However, the invention is not restricted to the embodiments specifically described, but rather can be more suitably modified and altered. It lies within the scope of the invention to combine individual features and feature combinations of one embodiment with features and feature combinations of another embodiment in order to arrive at further embodiments according to the invention. Identical elements are provided with the same or similar reference signs in the figures. A repeated description of these elements has been dispensed with in order to avoid repetition. The basic principle presented here will be elucidated on the basis of the examples given below. In accordance with various embodiments, semiconductor ingots having a large diameter (e.g., ranging from about 300 mm to about 1,000 mm) can achieve a homogenous and reproducible doping. In various embodiments, a semiconductor ingot having a diameter of about 300 mm or greater may be processed into a plurality of semiconductor wafers each having an area greater than about 70,685 mm2, a doping in the region of n doping below 2×1013 cm−3 can be achieved. This doping level is interesting e.g. for high-voltage components. Typical fields of application would be for example high blocking insulated gate bipolar transistors (IGBTs) or diodes. FIG. 1 illustrates a typical configuration for an NTD process. Referring to FIG. 1, an NTD reactor 1 includes a nuclear reactor 80 that provides thermal neutron flux 82 directed upwards or sidewards from the nuclear reactor 80 and a rotating tube 84 disposed over the nuclear reactor 80. An undoped silicon ingot rod 86 is loaded into the rotating tube 84 and positioned so that it is in the thermal neutron flux 82. The central axis of the silicon ingot rod 86 may be perpendicular to the direction of the thermal neutron flux 82. The duration of irradiation is determined based on the power of the nuclear reactor 80 and the initial and target ingot resistivity. However, due to the neutron absorption effect of silicon, the NTD process is usually more suitable for cylindrical ingot rods having a diameter less than or equal to about 200 mm. In various embodiments, a proton beam generator and a neutron producing material may be used instead of a nuclear reactor to generate neutrons that can be used for the NTD process. Nuclear spallation is one of the processes by which a particle accelerator may be used to produce a beam of neutrons. For example, a neutron producing material may be a material that can undergo a spallation when bombarded by energetic particles. In nuclear spallation, neutrons are generated through the spallation of nuclei by charged particles such as protons accelerated by a particle accelerator. Neutrons may be emitted when a spallation target composed of material such as boron-compounds, lithium, tungsten, tantalum, uranium, or compounds and alloys thereof is struck with protons with an energy of 100 keV up to about 1 GeV, depending on the spallation target material. For example, neutrons are emitted when a spallation target composed of a material such as lithium or boron nitride is struck with protons with an energy in the range from 1 MeV up to about 10 MeV. A particle accelerator such as a proton or ion implanter commonly used in the manufacturing of semiconductor devices may be used to irradiate such a target with highly energetic protons to thereby generate a well-defined neutron flow. Neutron yield data of the neutron producing material versus incident energy are necessary in order to select the proper incident energy and irradiation time and for estimating the intensity and duration of the incident proton current. FIG. 2 illustrates a cross-sectional view of a non-nuclear NTD reactor 101 in accordance with at least one embodiment. Referring to FIG. 2, the reactor 101 may include a proton beam generator 110 (not shown) configured to emit a proton beam to a neutron generation chamber 102 which is coupled to an irradiation chamber 104. The neutron generation chamber 102 may include an aperture 121 followed by a neutron producing target 120 mounted on a target mount 122 which is followed by a neutron moderator 126. The proton beam generator 110 is configured so that an emitted proton beam enters the aperture 121 to strike the neutron producing target 120. The irradiation chamber 104 is configured to house one or preferentially more semiconductor wafers 140 rather than a semiconductor ingot. The irradiation chamber 104 includes an aperture 141 which can be sealed by chamber door 150. In various embodiments, the one or more semiconductor wafers 140 are held upright on a removable wafer rack 142. Operationally, referring to FIG. 2, the proton beam generator 110 emits an ion or proton beam 119 that interacts with the neutron producing target 120 to generate a flow of neutrons 129 including “hot” neutrons, above the thermal energy range. The flow of neutrons 129 is guided to the neutron moderator 126 which reduces the thermal energy of the neutrons as they pass through the neutron moderator. The flow of moderated neutrons which is composed substantially of “cold” neutrons in the thermal energy range, i.e., thermal neutrons 149, is used to irradiate the one or more semiconductor wafers 140 housed in the irradiation chamber 104. Referring to FIG. 2, the proton beam generator 110 may be a conventional proton or ion implanter which can provide proton (H+) beam current currents (i.e., dose rate), for example in the range from about 1 mA to a about 100 mA and provide implantation energies (i.e., acceleration voltage) in the region up to about 10 MeV, for example, in the range from about 2 MeV to about 10 MeV. The beam current may be limited by the thermal energy input of the neutron producing target. In various embodiments, the acceleration voltage may be about 2 MeV. In various embodiment, the acceleration voltage may be less than or equal to about 4 MeV. In various embodiments, a proton-implanter in a parameter region of up to about 5 MeV and about 0.5 mA may be used. The proton beam current and the irradiation energy are key parameters for an accelerator useful for a NTD reaction. The target area may be determined by the spot size of the proton beam. The approximate spot size of a typical ion implanter is in the order of 1 to several cm2, however systems with ion beams as broad as the irradiated target can also be achieved. In various embodiments, a proton beam may be generated by a high current H+ implanter. For example, a high current H+ implanter may generate proton energies up to about 2 MeV and beam currents up to about 100 mA. A corresponding upscaling of the energy is technically possible. In various embodiments, a proton implanter having the capability to implant an inhomogeneous dose in a targeted radial manner may also be used. This capability could be used e.g. in case effects of different dopings would be desired in a targeted manner. Referring to FIG. 2, the proton beam generator 110 emits a proton beam 119 that may interact with the neutron producing target 120 to create a flow of neutrons 129 through various (p,n) type reactions or similar types of reactions. In various embodiments, a neutron flow of approximately 1e12 cm−2s−1 should be generated. Thus, the target material selected should allow a high-efficiency generation of neutrons. For example, such a target material may be lithium, lithium/carbon mixture, tungsten, or boron and boron compounds (for example boron nitride). The neutron producing target 120 may be in the form of a circular disc or it may be provided in any other shape, including rectangular, elliptical, conical, toroidal, etc. The neutron producing material of the neutron producing target 120 may be in solid phase or be in liquid phase pumped through a target chamber made of steel. The thickness of the neutron producing target material should be sufficient to slow protons past the reaction threshold. For example, in various embodiments, a beam of protons may be used to bombard a thick lithium-7 target to generate neutrons via the 7Li(p,n)7Be reaction. The lithium-7 target may be a circular puck of lithium-7 in a solid phase that is approximately 1 mm thick and having a diameter of at least 1 cm2 The neutron yield is dependent on the proton beam current density. The neutron yield between the 7Li target and the neutron moderator 126 should be approximately 1e11 n/cm2/mA. This would correspond to a 1e12 n/cm2s neutron flow when a 10 mA proton beam is used and a 1e13 n/cm2s neutron flow when a 100 mA proton beam is used. The neutron yield at the wafers for a 100 mA proton current may range from about 2e12/cm2s and 6e12/cm2s. The actual neutron yield may further depend on various factors including the design of the irradiation chamber and the proton implanter. FIG. 4 is a graph showing the basic ohmic characteristic of an initially undoped wafer dependent on the irradiation period for various neutron flows. In the semiconductor industry, the resistivity rather than the dopant concentration is usually used. Therefore, the relationship between the resistivity and the dopant concentration should be established first. For n type silicon doping, the resistivity (Ωcm) is given by ρ = 1 [ D ] ⁢ μ ⁢ ⁢ ɛ where [D] is the dopant atomic concentration in cm−3, ε is the electron charge, 1.602×10−19 C, and μ is the drift mobility of the electrons in the silicon crystal lattice. Electron mobility depends on the temperature, and it may be in the range of 1220˜1500 cm2/V·s. In normal conditions at 300 K, it should be usually 1350 cm2/V·s for silicon. As shown in FIG. 4, the use of a higher power proton beam may reduce the irradiation period. However, this may also increase the temperature in the active target area of the neutron producing target. For example, a proton beam of about 2 MeV at about 100 mA may heat the active target area on the order of about 100 kW/cm2. The efficient removal of heat from the active target area may be a limiting factor on the intensity of the proton beam and the duration of the irradiation period. Due to the high energy input of the protons, the neutron producing target 120 should to be cooled effectively. Up to 500 kW/cm3/mA of thermal energy may need to be discharged from neutron producing target 120. This is due to the correspondingly small input cross section for the targeted proton reaction. Therefore, the neutron producing target 120 should have a good heat conductivity and/or should be correspondingly cooled. The target mount 122 is configured such that it allows an efficient cooling of the neutron producing target 120. The cooling should be performed so that the neutrons produced by the neutron producing target 120 are not absorbed. In various embodiments, the target mount 122 may include a copper plate for cooling. Alternatively, a target mount 122 may include a liquid coolant. For example, in various embodiments, heavy water (D2O) may be used and configured for injection cooling. Heavy water is an effective coolant with a minimal absorption coefficient, i.e., heavy water is not likely to absorb neutrons. Additionally, heavy water is a good moderating material. In various embodiments, depending on the target material the liquid coolant may be a liquid metal. The uniformity of coverage of the generated neutron flux is another aspect in the NTD reaction. For example, in the NTD of silicon, the induced 31P concentration is proportional to the irradiated neutron fluence, which is a product of the neutron flux, time of irradiation with a constant neutron flux, and the reaction cross-section. As the neutron cross-section varies by neutron energy, it is influenced from the neutron spectrum in the irradiation site. The energy spectra and angular distribution of the generated neutron flow is dependent on the incident beam energy of the proton beam, the incident angle of the proton beam, and the space angle behind the neutron producing target 120. As the protons lose energy traveling through the neutron producing target, the energy spectra and angular distribution of the neutrons generated change. For example, FIGS. 6A and 6B show a distribution of the energy spectrum and the emission angles of the neutron yield for a proton beam striking a lithium target at an incidence angle of 0° for various incident beam energies. Consequently, the irradiation of the neutron producing target 120 with protons should be carried out such that the neutron flow is distributed homogeneously over the cross sectional areas of the neutron generation chamber 2 and the irradiation chamber 104. In various embodiments, homogeneity is determined by the uniformity of the neutron flux in the irradiation chamber over the volume of the plurality of wafers and by the purity of the grown crystals. Neutron fluence monitors may be installed in the irradiation chamber to monitor neutron spectra and cross sectional reaction area. This information may be used to reconfigure the NTP reactor to achieve a desired doping. In various embodiments, the proton beam may be configured to scan or trace a pattern over the neutron producing target 120. This may homogenize the neutron flux depending on the material of the neutron producing target 120. This may also minimize local heating of the neutron producing target 120. Alternatively, the target mount 122 may be adjustable. In various embodiments, the target mount 122 may be configured to modify the position of the neutron producing target 120 to achieve a homogeneous distribution of the neutron flow or to minimize local heating of the neutron producing target 120. The angular distribution of the neutron flow may also be dependent on the reflectivity of the walls of the chambers so that stray neutrons striking the walls are redirected towards the irradiation chamber 104. The walls 130a and 130b of the neutron generation chamber 102 and the irradiation chamber 104 act as neutron guides and are made of material which is suitable as a neutron reflector. For example, beryllium, tungsten, nickel, steel, graphite, or other suitable chemical compounds may be used. Referring to FIG. 2, the inner walls 130a and 130b of the neutron generation chamber 102 and the irradiation chamber 104 should act as neutron guides to guide the flow of neutrons from the neutron producing target 120 to the one or more wafers 140 in the irradiation chamber 104. The inner walls 130a and 130b may be made of a neutron reflecting material. For example, a neutron reflecting material may include solids, such as beryllium, carbon, steel, or silicon, with polished surfaces. As another example, a neutron reflecting material may be a neutron mirror including a layer of nickel, titanium, silicon, or nickel/titanium alloy on a substrate of glass or steel. As another example, a neutron reflecting material may be a neutron multilayer mirror or neutron supermirror. The thickness of the chamber walls depend on the reflecting material that is used to construct the chambers. In various embodiments, the walls 130a and 130b of the neutron generation chamber and irradiation chamber may be manufactured from a solid cylindrical block of beryllium having a bore through the center of the block. The diameter of the bore may be slightly greater than the diameter of the semiconductor wafers. For example, in in various embodiment, the diameter of the bores may be about 500 mm which is large enough to accommodate semiconductor wafers that have a diameter of about 450 mm or less. The length of the block of beryllium may be about 120 cm. The thickness of these beryllium reflector walls may be about 60 cm. The generated neutrons may be classified according to their energies as thermal (En<0.5 eV), epithermal (0.5 eV<En<10 keV), or fast (En>10 keV) neutrons. A neutron producing target 120 may generate a flow of neutrons including epithermal and fast neutrons. For example, the energy of the neutrons emitted from a lithium target may have a neutron flux spectra be in the range from about 25 keV to about 100 keV. Thermal neutrons are required to initiate the neutron capture that triggers the NTD reaction and epithermal and fast neutrons may damage the wafers. The epithermal and fast neutrons (i.e., “hot” neutrons) may be cooled to thermal neutrons (i.e., “cold” neutrons) by means of a moderating material before they are used to irradiate semiconductor wafers. The neutron moderator 126 receives a flow of neutrons 129 including epithermal neutrons and/or fast neutrons from the neutron producing target 120 and outputs a flow of thermal neutrons 149 to the one or more wafers 140 by reducing the energy of neutrons passing through it. As epithermal neutrons and fast neutrons travel through the neutron moderator, they lose energy and fall into the thermal range through repeated collisions with the moderating material. The neutron moderating material may be solid, liquid (with suitable chamber), or gaseous (with suitable chamber). The material used as the moderator should result in a moderation (i.e., reduces neutron energy via elastic scattering) without any substantial absorption of neutrons. Various material may be suitable as moderating material. A moderating material should have low neutron absorption, high neutron moderation, and low reflectivity to maximize the number of neutrons that reach the semiconductor wafers. Heavy water (D2O) is very effective as a moderator. Carbon or carbon compounds (e.g., methan) may also be suitable as a moderator. The volume (width, thickness, height) of the neutron moderator 126 may be calculated by means of the corresponding elastic scattering cross sections (or Fermi-age). Referring to FIG. 2, in various embodiments, the neutron moderator 126 may be made of carbon having a thickness of 30 cm and a diameter that is larger than the diameter of the neutron generation chamber 102. In order for the neutron moderator 126 to cool neutrons effectively, it has to be maintained at room temperature. The flow of thermal neutrons 149 is guided to the irradiation chamber 104 coupled to the neutron generation chamber 102. The direction of the thermal neutron flux in the irradiation chamber is along the axial direction of the irradiation chamber. The irradiation chamber 104 houses one or more semiconductor wafers 140 to be irradiated. The one or more semiconductor wafers may be arranged so that the top and bottom surfaces of each wafer is perpendicular to the direction of the thermal neutron flux and axially aligned with the irradiation chamber. In various embodiments, the number of semiconductor wafers 140 housed in the irradiation chamber 104 may range from about 10 wafers to about 100 wafers. The number of semiconductor wafers that may be simultaneously irradiated may be calculated based on the thickness dw of a wafer. In a conventional NTD reactor, a 200 mm diameter silicon ingot may be irradiated in a radial direction without significant risk of absorption effects for the case that the wafer is rotated during the irradiation. Thus, for example, assuming 100 mm as a maximum distance between the first and last silicon wafers and a silicon wafer thickness of 750 μm, 100 mm/dw silicon wafers, i.e., more than 100 silicon wafers, can be simultaneously irradiated in the irradiation chamber. In various embodiments, the semiconductor wafers may be arranged on a wafer rack that is placed into an irradiation chamber. The wafer rack may be removable and the irradiation chamber may include a slide and rail assembly for mounting a removable wafer rack. In various embodiments, the irradiation chamber 104 is maintained in a clean room environment in order to reduce environmental pollutants that may interact with the semiconductor material of the wafers. Referring to FIG. 2, in various embodiments, the chamber door 150 is configured to provide repeated access to the irradiation chamber 104. It may be made of various layers of neutron absorbers. The construction of chamber door 150 should be in compliance with the valid laws. For example, in various embodiments, the chamber door 150 may include three layers. Materials suitable as a first layer may include boron and its compounds thereof, paraffin wax, and water (very good absorber). A material suitable as a second layer may be lead. A material suitable as a third layer may be ferro concrete, which may also serve as structural support. FIG. 5 illustrates a flow chart of a method 300 for providing uniform doping of semiconductor wafers having large diameters in accordance with at least one embodiment. This homogeneous doping procedure results in a scattering of the doping level across the wafer which is less than 8%. In other embodiments, it may be less than 5% or less than 3% or even less than 2%. Referring to FIG. 5, at step 302 one or more semiconductor wafers are cut from a semiconductor ingot that is undoped or that has low doping. In other embodiments, the semiconductor ingot may be cut into logs having a length for example of about 100 mm for irradiation in the chamber and the logs are processed into wafers after the NTP process. At step 304, the semiconductor wafers are cleaned and cladded with an oxide. For example, silicon wafers may be cleaned and cladded with silicon dioxide (SiO2) or just cleaned using state of the art silicon wafer cleaning technology. At step 306, the semiconductor wafers are arranged in the irradiation chamber. The semiconductor wafers may be positioned so that the centers of the wafers are axially aligned with each other and the faces of the semiconductor wafers are perpendicular to the direction of neutron flow. The semiconductor wafers for example may be evenly spaced from each other. The space between each wafer should be large enough to allow the loading and unloading of the wafers without scratching a neighboring wafer, yet should be small enough to minimize contamination by atmospheric impurities. The distance between the neutron producing target and the wafer to be irradiated may be variably configured depending on the requirements of the processing, however, it should usually be as low as possible in order to ensure a shortest possible process duration. At step 308, a proton beam is generated and is directed to a neutron producing target to generate a flow of neutrons, i.e., neutron flux, in a direction towards the irradiation chamber. At step 310, the incident angle and/or energy of the proton beam may be adjusted to obtain a neutron flux having uniform coverage in the neutron generation chamber and the irradiation chamber. The adjustment may be made based on the diameter of irradiation chamber since the uniform coverage may depend on a cross-sectional area of the irradiation chamber. At step 312, the neutron flux passes through a neutron moderator which moderates the epithermal and fast neutrons in the neutron flux to obtain a thermal neutron flux. At step 314, the thermal neutron flux having uniform coverage is guided to the irradiation chamber. The direction of the thermal neutron flux in the irradiation chamber is along the axial direction of the irradiation chamber. The wafers are irradiated for a suitable period. For example, in various embodiments including a lithium target and silicon wafers, the irradiation time should be approximately 10 hours at 1e12 n/cm2s to achieve a resistivity of 60 Ωcm Si. At step 316, to ensure a more homogeneous distribution of the irradiation from wafer to wafer or to increase the number of wafers to be irradiated, the wafer rack may be removed from the irradiation chamber at the end of the first half of the irradiation period, reversed front to back, and then placed back in the irradiation chamber for the second half of the irradiation period. Thus, the wafers that were closer to the neutron moderator become closer to the chamber door, and vice versa. At step 318, at the end of the irradiation period, the one or more wafers are removed and rinsed. At step 320, the irradiated wafers are stored so that the irradiated semiconductor material has time to undergo the transmutation nuclear reaction that produces the dopant atoms. Since this nuclear reaction produces gamma radiation, the irradiated wafers are stored in a cooled and shielded chamber. The chamber may be a double walled steel vessel filled with chilled water. The storage time depends on the semiconductor material and the half-life of the NTP reaction producing the dopant atoms. For silicon semiconductor material, the nuclear conversion producing phosphorous dopant atoms has a half-life of 2.62 hours. Consequently, irradiated silicon wafers should be stored in a cooled and shielded chamber for approximately three days. Parasitic nuclear conversions may occur. For example,31Si(n,γ)32Si→(β−)32P(T1/2=˜172y)→(β−)32S(T1/2=14.3d);32P(n,γ)32P→(β−)32S(T1/2=14.3d).However, this may be neglected for sufficiently short irradiation times. Carbon and oxygen are not affected by the NTD process and remain as oxygen and carbon in the silicon. At step 322, after a suitable amount of time in storage (3 days for silicon semiconductor material), each semiconductor wafer should be surveyed to determine if there is any residual radiation. At step 324, after the wafers clear the radiation inspection, any oxide cladding if present may be etched away from each wafer by means of for example hydrogen fluoride. At step 326, the uncladded semiconductor wafers may then be placed in an annealing chamber to repair any radiation-induced crystal damage. The annealing chamber may be a state-of-the-art furnace capable of accommodating large diameter ingots and wafers. In accordance with various embodiments, a plurality of silicon wafers may be simultaneously irradiated with neutrons in the irradiation chamber. The plurality of silicon wafers may be arranged so that the top and bottom surfaces of each wafer are perpendicular to the direction of neutron flux and the number of wafers is determined so that there is no risk of significant absorption effects. Since the silicon material is irradiated as a wafer in an axial direction rather than as an ingot in a radial direction, the achievable radial homogeneity can be tightly controlled and optimized. For example, in various embodiments, a silicon wafer having a diameter of about 300 mm or greater may be irradiated with neutrons to obtain a uniform base resistivity in the range from about 100 Ohm/cm to about 1,000 Ohm/cm. In various embodiments, a uniform base resistivity in the range from about 200 Ohm/cm to about 700 Ohm/cm can be obtained. For example, a wafer may have a target base resistivity value selected from the range from about 100 Ohm/cm to about 1,000 Ohm/cm and the uniformity of the actual base resistivity value should be ±8.0% or better. In some embodiments, the uniformity of the base resistivity may be ±3.0% or better. In other embodiments, the uniformity of the base resistivity may be ±1.0% or better. For another example, a wafer may have a target base resistivity value selected from the range from about 200 Ohm/cm to about 700 Ohm/cm and the uniformity (max/min value) of the actual base resistivity value should better than ±8.0%. In other embodiments, the uniformity of the base resistivity may be ±2.5% or better. In other embodiments, the uniformity of the base resistivity may be ±1.0% or better. To ensure the security and health of the staff, the handling of the semiconductor wafers may be performed completely automatically starting from the beginning of the irradiation until the semiconductor wafers are cleared of radiation. In the event of an emergency shutdown of the proton beam generator 110, the semiconductor wafers may remain in the irradiation chamber 104 until a re-start occurs. In case the plurality of semiconductor wafers 140 has to be removed, an emergency energy supply of the redundantly configured handling robot should then be provided. At suitable positions outside the NTD reactor, neutron detectors and gamma ray detectors should be mounted. In the event of an emergency shutdown, it should be possible to temporarily completely close off the site. Alpha particles which may be generated during the longer operation of the site may be guided to a getter target (e.g. paraffin) by means of a magnetic field. In various embodiments, the cooling water and the semiconductor wafers should not be radioactive after the process and can be used again after filtering (dirt/discontinuities; avoiding the contamination of the wafers for further processing). In various embodiments, a variety of monitoring or measurement sensors may be mounted in the neutron generation chamber and irradiation chamber for continuous monitoring or for periodic probing. For example, the chambers may include one or more cameras for visual inspection and/or one or more sensors for measuring or monitoring neutron flux (e.g., neutron detectors), temperature (e.g., temperature sensors), or proton flux (e.g., proton detectors). In various embodiments, an NTP reactor may include one proton beam generator and two neutron generation/irradiation chamber assemblies, where each neutron generation/irradiation chamber assembly may be similar to the ones depicted in FIGS. 2 and 3. For example, each neutron generation/irradiation chamber assembly may be positioned next to each other so that the apertures into each of the neutron generation chambers are similarly oriented and a single proton beam generator may be configured to direct proton beams to each of the neutron generation/irradiation chamber assemblies so that at least one irradiation chamber may be irradiated at any time. This configuration allows the loading and unloading of wafers in one of the irradiation chambers without interrupting the proton beam for wafer handling. In various embodiments, a proton beam may be generated by a laser ion accelerator. For example, the proton beam generator 110 may be a laser directed at a target made of proton producing material. More specifically, a laser producing a beam of high energy short time pulses may be used to irradiate a proton producing material which emits high energy protons thereby generating a proton beam. For example, in various embodiments, the laser ion accelerator may include a petawatt laser that generates a pulse beam having an energy of more than about 100 TW for a duration of more than about 100 femtoseconds and a foil target made of a proton producing metal such as aluminum or gold. The generated ions are accelerated in the direction perpendicular to the target surface. The intensity of the ion beam may be controlled by the duration of the laser pulse and the thickness of the target. A typical ion or proton implanter operates in a vacuum sealed environment. The vacuum sealed environment should be extended to include the neutron producing target. For example, the neutron producing target may be made of material that is highly reactive to air and should be enclosed in a vacuum sealed environment. The vacuum sealed environment may further be extended to the moderator. For example, the neutron producing target may be mechanically fragile and so the vacuum sealed environment may extend to the moderator which should be a rigid structure. In various embodiments, a vacuum pump may be positioned between aperture 121 and neutron producing target 120. The vacuum pump removes particles that may interfere with the proton beam generator 110. For example, when a solid lithium target is bombarded by protons, lithium atoms may be sputtered off or secondary reactions creating helium atoms may occur. In various embodiments, the surface of the neutron moderator may be modified so that the reflection of neutrons back to the neutron source is minimized. For example, surface of the moderating material or its casing should not be polished. A rather rough surface helps in reducing the reflection of neutrons. In various embodiments, there may be ports in the chamber walls to permit access to the neutron producing target or the neutron moderator or both. FIG. 5 illustrates a cross-section top view of various embodiments of the non-nuclear NTD reactor 201. Referring to FIG. 5, the non-nuclear NTD reactor 201 is similar to the non-nuclear NTD reactor 101 except that the neutron generation chamber 202 is coupled to the irradiation chamber 204 at about a 90° degree angle. The neutron moderator 226 is further configured to redirect the neutron flow. One surface of the neutron moderator 226 may be configured to include a mirror. The price of a semiconductor wafer should be significantly lower since the new NTD process provides a very high success rate with relative simplicity. In accordance with various embodiments, it would be possible to achieve a higher wafer quality and homogeneity at comparable costs. In various embodiments, the plurality of semiconductor wafers may be made of germanium (Ge) or gallium (Ga) or compounds thereof. For example, when natural germanium is irradiated by thermal neutrons gallium-31 can be formed by electron capture and some β-decay according to the following reaction: 70Ge+n→71Ge→(EC)71Ga. Since 71Ga is an impurity from group 13 in the periodic table, p type impurity doping is possible by the neutron irradiation of germanium. In the following, various aspects of this disclosure will be illustrated: Example 1 is a method of processing one or more semiconductor wafers. The method includes positioning the one or more semiconductor wafers in an irradiation chamber, generating a neutron flux in a spallation chamber coupled to the irradiation chamber, moderating the neutron flux to produce a thermal neutron flux, and exposing the one or more semiconductor wafers to the thermal neutron flux to thereby induce the creation of dopant atoms in the one or more semiconductor wafers. In Example 2, the subject matter of Example 1 can optionally include that the generating the neutron flux includes generating a proton beam, and directing the proton beam at a neutron producing target to thereby generate the neutron flux. In Example 3, the subject matter of Example 2 can optionally include that the directing further includes adjusting a space angle between the proton beam and the neutron producing target according to the diameter of the irradiation chamber. In Example 4, the subject matter of any one of Examples 2 or 3 can optionally include that the generating the proton beam includes directing a laser beam at a proton producing target to thereby generate the proton beam. In Example 5, the subject matter of any one of Examples 1 to 4 can optionally include that the method further includes arranging the one or more semiconductor wafers in a carrier for positioning in the irradiation chamber, and repositioning the carrier in the irradiation chamber after a first exposure period. In Example 6, the subject matter of any one of Examples 1 to 5 can optionally include that the method further includes cooling the neutron producing target. In Example 7, the subject matter of any one of Examples 1 to 6 can optionally include that the method further includes positioning the one or more semiconductor wafers so that the top and bottom surfaces of each semiconductor wafer are perpendicular to the thermal neutron flux. Example 8 is an apparatus for processing one or more semiconductor wafers. The apparatus includes a spallation chamber, a neutron producing material mounted in the spallation chamber, a neutron moderator mounted in the spallation chamber, and an irradiation chamber coupled to the spallation chamber, the irradiation chamber accommodates one or more semiconductor wafers. In Example 9, the subject matter of Example 8 can optionally include that the neutron producing material includes or essentially consists of lithium, lithium/carbon mixture, tungsten, boron, and/or boron compounds. In Example 10, the subject matter of any one of Examples 8 or 9 can optionally include that the apparatus further includes an adjustable mount. The neutron producing material is mounted on the adjustable mount. In Example 11, the subject matter of any one of Examples 8 to 10 can optionally include that the apparatus further includes a proton beam generator directed at the neutron producing material. In Example 12, the subject matter of Example 11 can optionally include that the proton beam generator is a proton implanter. In Example 13, the subject matter of any one of Examples 11 or 12 can optionally include that the proton beam generator includes a proton producing material, and a laser generator directed at the proton producing material. The laser generator is configured to output a laser beam. In Example 14, the subject matter of any one of Examples 11 to 13 can optionally include that the apparatus further includes a vacuum pump disposed adjacent to a surface of the neutron producing material that faces the proton beam generator. In Example 15, the subject matter of any one of Examples 8 to 14 can optionally include that the apparatus further includes a cooling unit coupled to the neutron producing material. In Example 16, the subject matter of any one of Examples 8 to 15 can optionally include that the neutron moderator includes or essentially consists of heavy water, carbon, or carbon compounds. In Example 17, the subject matter of any one of Examples 8 to 16 can optionally include that the irradiation chamber accommodates one or more semiconductor wafers that are axially aligned with the irradiation chamber. In Example 18, the subject matter of any one of Examples 8 to 17 can optionally include that the apparatus further includes one or more sensors mounted in the irradiation chamber, the one or more sensors configured to monitor neutron flux. Example 19 is a semiconductor wafer having a diameter of about 300 mm or greater, and a uniform base resistivity in the range from about 100 Ohm/cm to about 1,000 Ohm/cm, wherein the uniformity of the base resistivity is within about ±8% (max/min value). In Example 20, the subject matter of Example 19 can optionally include that the uniform base resistivity is in the range from about 200 Ohm/cm to about 700 Ohm/cm, wherein the uniformity (max/min value) of the base resistivity is within about ±2.5%. While the invention has been particularly shown and described with reference to specific embodiments, it should be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. The scope of the invention is thus indicated by the appended claims and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced.
056489951	description	DESCRIPTION OF PREFERRED EMBODIMENTS EXAMPLE 1 Intermediate treatments: 2 hours at 580.degree. C. PA1 Final treatment: 2 hours at 580.degree. C. PA1 Intermediate treatments: 2 hours at 700.degree. C. PA1 Final treatment: 2 hours at 580.degree. C. PA1 Intermediate treatments: 2 hours at 700.degree. C. PA1 Final treatment: 2 hours at 700.degree. C. PA1 Example 1: 48 mg/dm.sup.2 PA1 Example 2: 57 mg/dm.sup.2 PA1 Example 3: 63 mg/dm.sup.2 PA1 quenching in water after heating for 1 hour at 1050.degree. C.; PA1 machining a billet having an outside diameter of 168 mm and an inside diameter of 48 mm; PA1 extrusion after induction heating to 650.degree. C. to obtain an outside diameter of 80 mm and an inside diameter of 48 mm; PA1 rolling tubes in five cycles, including intermediate heat treatments for 2 hours at 580.degree. C.; and PA1 final heat treatments for 2 hours at 580.degree. C. PA1 Zr: 1% Nb, 150 ppm Fe, recrystallized: 0.5; PA1 "Zircaloy 4" recrystallized from a composition that is optimal from the creep point of view: .ltoreq.1.0%. EXAMPLE 2 EXAMPLE 3 The mass increases during autoclave testing were as follows: The samples in all three examples had an iron content of 150 ppm. It was observed that the alloy presented a "memory" phenomenon such that the effect of a single treatment at above 620.degree. C. applied to the alloy later than the first pass was never completely "forgotten". In general, the intermediate heat treatments should be performed at a set temperature lying in the range 565.degree. C. to 605.degree. C.; a temperature greater than 580.degree. C. for the intermediate treatments and a temperature of about 580.degree. C. for the final treatment have been found to be particularly satisfactory for most compositions. A tube can be manufactured from an extruded blank in particular by performing four or five passes separated by heat treatments in the range 560.degree. C. to 620.degree. C., and advantageously close to 620.degree. C. An oxygen content of about 1200 ppm has been found satisfactory to obtain a favorable effect on the resistance to creep in a recrystallized alloy. The invention also proposes a sheathing or guidance tube for a fuel assembly for a nuclear reactor that is cooled and moderated by pressurized water, the tube being made of a zirconium-based alloy in the fully recrystallized state, having 50 ppm to 250 ppm iron, 0.8% to 1.3% by weight niobium, 1000 ppm to 1600 ppm oxygen, less than 200 ppm carbon, less than 120 ppm silicon, the balance being zirconium, excepting unavoidable impurities. When the alloy made in this way is examined, it can be seen that there are no alignments of .beta. Zr precipitates, which are harmful from the corrosion point of view. Comparative tests have been performed on alloys having niobium contents lying in the range 0.86% to 1.3% and iron contents lying in the range 100 ppm to 150 ppm. A representative manufacturing range, starting from a forged bar having a diameter of 177 mm, is as follows: Tests showed generalized corrosion resistance in a high temperature aqueous medium representative of conditions in a high pressure water reactor comparable to those of known Zr-Nb alloys having a high niobium content; they also showed hot creep strength much better than that of known alloys and very comparable to that of the best "Zircaloy 4" alloys: thus, after 240 hours at 400.degree. C. under 130 MPa, the following creepage diameter deformations were measured:
	abstract	A system and method for calibrating a radiation imaging system include a dual use variable thickness radiation filter having a slit in one part thereof such that in a first position a radiation beam passing through is not attenuated and in a second position the radiation beam is attenuated according to the total filter thickness in the path of the radiation beam. The filter may be formed of multiple movable plates or a single piece of stepped high density material.
043084605	summary	BACKGROUND OF THE INVENTION Storage containers for radioactive material are common place and widely used to transport spent fuel pins from nuclear powder reactors and to transport radioisotopes for use in medicine and industry. Containers suitable for transporting radioactive material must be designed to withstand severe impact yet retain their integrity to prevent unacceptable nuclear contamination if the container is involved in an accident. Such transportation type containers are generally heavy and bulky and are inapplicable for use in the laboratory where small amounts of radioactive material must be stored, yet be readily available for inventory or use. Such a laboratory storage container should provide adequate shielding to prevent workers from being exposed to harmful radiation and also to prevent the escape of radioactive material. On the otherhand, because the radioactive material is often used for experimental purposes, the container should be designed for ready access to the material not only for day-to-day experimental use but also for inventory control. Because plutonium as well as enriched uranium is often used in experimental facilities, a criticality problem exists which must be taken into account in the container design to prevent container stacking which may result in a critical mass being formed. Accordingly, containers suitable for laboratory use which meet all the requirements described above would generally not be suitable for transporting radioactive material by common carrier. Representative literature pertinent to transportation containers include the Allen U.S. Pat. No. 3,113,215 issued Dec. 3, 1963 for Cask Construction For Radioactive Material. This patent discloses a cask construction for radioactive material including a screwed down top plate with a gasket seal. The Bonilla et al. U.S. Pat. No. 3,229,096 issued Jan. 11, 1966 for Shipping Container For Spent Nuclear Reactor Fuel Elements discloses a container including a screwed down cover with a vent and with a ring handle. The Lecuyer U.S. Pat. No. 3,560,749 issued Feb. 2, 1971 for Container Means For a Radioactive Element discloses a container having interchangeable storage bodies formed of a radioactive shielding material. The Peterson et al. U.S. Pat. No. 3,731,101 issued May. 1, 1973 for Shipping Container For Radioactive Material discloses a container with a gasket seal at the top of the container and screws for maintaining the top in place. The Backus U.S. Pat. No. 3,770,964 issued Nov. 6, 1973 for Shipping Container for Radioactive Material discloses a cask with a screw down top plate and annular gasket sealing same. The Czaplinski et al. U.S. Pat. No. 4,084,097 issued Apr. 11, 1978 for Shielded Container discloses a container having a handle pivoted thereto which includes means for measuring the radioactivity of the solution stored therewithin. Other patents generally pertinent to the subject matter include the Anderson et al. U.S. Pat. No. 3,569,714 issued Mar. 9, 1971 for Protected Radioisotopic Heat Source which discloses a protected radioisotopic heat source including a cover fitted on a plate on which the source rests and the Johnson U.S. Pat. No. 3,953,288 issued Apr. 27, 1976 for Gas Venting discloses containers housing radioactive material which utilize the passageways between interbonded impervious laminae. SUMMARY OF THE INVENTION The present invention relates to a storage system for storing radioactive material in the laboratory particularly adapted fior plutonium and enriched uranium which segregates the radioactive material preventing formation of critical masses, yet provides easy access thereto. An important object of the present invention is to provide a fuel storage system comprising a flat base plate having a groove in one surface thereof and a hollow pedestal extending perpendicularly away from the other surface thereof, a gasket in the groove, a cover having a filtered vent therein dimensioned to fit over the one surface of the plate and to form therewith a fuel storage area, the cover having a flange overlying the groove and the gasket, and clamp means for maintaining the cover and the plate together in sealed relation, whereby the plate and the cover and the clamp means cooperate to provide a storage system for radioactive material readily accessible for use or inventory. A further object of the present invention is to provide a fuel storage system of the type set forth in which vertically spaced apart wall mounting receptacles are provided for storing the system at preselected points along a wall. Another object of the present invention is to provide a fuel storage system of the type set forth including a floor stand including a flat plate and upstanding shaft for accepting the hollow pedestal to allow the system to be used in the laboratory where access to the stored radioactive material is desired. The invention both as to the attainment of its aforesaid objects and the operation thereof may more readily be understood by reference to the following specification and the accompanying drawings, in which:
060977906	description	DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an X-ray extraction window E.sub.1 comprising a partition wall according to an embodiment of the present invention, as well as a portion of an X-ray exposure apparatus having the partition. The X-ray window E.sub.1 is disposed between an exposure chamber 1 and a beam duct 2. As will be described later, a beam of X-rays L.sub.1 such as synchrotron X-rays produced from a light source 3 (FIG. 3) such as a charged particle accumulation ring, for example, passes through the beam duct 2, being kept in a ultra-high vacuum, and it is introduced into the exposure chamber 1 through the X-ray window E.sub.1. The inside of the exposure chamber 1 is controlled to be occupied by a reduced pressure ambience of helium gas, for example, of about 0.2 Pa, for example. This is to prevent attenuation of X-rays and, with convection of helium gas, to facilitate heat radiation from a wafer W.sub.1, for example. The X-ray window E.sub.1 includes a beryllium film 11, comprising a thin film of several microns or several tens of microns in thickness, and a flange (supporting means) 12 for supporting the outside peripheral edge of the film. The outside peripheral edge of the beryllium film 11 is fixed to the flange 12 by means of a bonding ring 13. The flange 12 is fixedly mounted to a flange 2a, for example, of the beam duct 2 by means of an O-ring 14 and bolts 15. As described, the beryllium film 11 should have mechanical strength sufficient sufficient to bear a pressure difference AP between a pressure P.sub.1 of the beam duct 2, being kept in a high vacuum, and a pressure P.sub.2 of the exposure chamber, being kept in a reduced pressure ambience of helium gas. Additionally, it should have a high X-ray transmissivity. Thus, it is desirable to reduce the thickness of the beryllium film 11 as much as possible, within the limit of the required mechanical strength. Thus, the thickness T.sub.1 of the beryllium film 11 may be determined, from the tension stress .sigma..sub.1 to be produced at the central portion of the film 11 as flexure is produced in the film 11 in response to the tolerance value for the pressure difference .DELTA.P, that is, to a design pressure P.sub.0, and in accordance with equation (4) having been mentioned. However, there is a possibility that, even when the central tension stress .sigma..sub.1 does not exceed the breaking stress .sigma..sub.0, the outside peripheral portion of the beryllium film 11 is broken due to the stress concentration at the contact portion between the beryllium film 11 and the flange 12. In consideration of this, the flange 12 is provided at its inside peripheral edge with a curved portion (curvature support) 12a of a ring-like shape, having a predetermined curvature radius R. This curved portion 12a contacts the outside peripheral edge portion of the beryllium film 11 to bend it along the curved face of the curvature support. This effectively prevents stress concentration and, thus, breakage of the beryllium film 11. As the outside peripheral portion of the beryllium film is curved along the curvature portion 12a, a tension stress .sigma.f produced thereby is added to the tension stress .sigma..sub.2 to be produced by deflection caused by the pressure difference .DELTA.P between the exposure chamber 1 and the beam duct 2. Thus, the curvature radius R of the curvature portion 12a of the flange 12 may be determined as follows. When, as shown in FIG. 2, deflection is produced in the beryllium film 11 due to a pressure difference .DELTA.P and the outside peripheral edge portion of the beryllium film 11 is curved along the curvature portion 12a of the flange 12, the tension stress .sigma.t produced at the outside peripheral portion of the film 11 corresponds to the sum of (i) a tension stress .sigma..sub.2 produced by deflection resulting from the pressure difference .DELTA.P and (ii) a tension stress .sigma.f produced by flexure of the film along the curvature portion 12a of the flange 12. Namely: EQU .sigma.t=.sigma..sub.2 +.sigma.f (5) The tension stress .sigma.f can be calculated from the curvature radius R of the curved portion 12a and the thickness T.sub.1 of the beryllium film 11, in accordance with the following equation: EQU .sigma.f=0.5.multidot.E.multidot.T.sub.1 /R (6) From equations (6) and (2), it follows that: EQU .sigma.t=0.328(E.multidot..DELTA.P.sup.1/2 .multidot.a.sup.1/2 /T.sub.1.sup.2).sup.1/3 +0.5.multidot.E.multidot.T.sub.1 /R(7) In order to assure that the tension stress .sigma.t produced at the outside peripheral portion of the beryllium film 11 is smaller than the tension stress .sigma..sub.1 produced at the center of the film 11, on an occasion when the pressure difference .DELTA.P is equal to the design pressure P.sub.0, from equations (7) and (1) it follows that: EQU R>5.263.multidot.(E.sup.2 .multidot.T.sub.1.sup.5 /P.sub.0.sup.2 /a.sup.2).sup.1/3 (8) Namely, the curvature radius R of the curvature portion 12a of the flange 12 may well be selected to satisfy equation (8). Practically, a larger tension stress is produced at a portion slightly inside the outside peripheral edge of the beryllium film, than at the outside peripheral edge, and preferably the curvature radius of the curvature portion 12a of the flange 12 may be gradually enlarged toward the inside edge thereof. When the outside peripheral portion of the beryllium film 11 is bent along the curvature portion having a curvature radius determined as described above, there is no possibility that a tension stress larger than that at the center of the beryllium film is produced in the outside peripheral portion thereof. Since breakage of the beryllium film can be avoided as the film thickness is designed on the basis of the tension stress at the central portion of the film, there is no necessity of using an unnecessarily enlarged safety factor as in the conventional example. Thus, the required beryllium film thickness can be reduced and the X-ray transmissivity of the film can be improved significantly. FIG. 3 shows a general structure of an X-ray exposure apparatus. Light source 3 projects a beam of X-rays L.sub.1, comprising sheet-beam-like synchrotron radiation, and it is expanded by a convex mirror 4 in a direction perpendicular to the orbital plane of the radiation light. The X-ray beam L.sub.1 being reflectively expanded by the convex mirror 4 passes through the X-ray window E.sub.1, and it is introduced into the exposure chamber 1. Then, by means of a shutter (not shown), the X-ray beam is adjusted to provide a uniform exposure amount within an exposure region. The X-ray beam L.sub.1 passing the unshown shutter is projected to a mask M.sub.1. A wafer (substrate) W.sub.1 is held vertically by a wafer chuck (substrate holding means) 5. An exposure pattern formed on the mask M.sub.1 is transferred, by exposure, onto the wafer W.sub.1 in accordance with a step-and-repeat procedure, for example. The wafer chuck 5 can be positioned precisely with respect to five directions, by means of a wafer stage 6, which comprises a fine-motion stage 6a and a rough-motion stage 6b. Next, an embodiment of a semiconductor device manufacturing method which uses an X-ray exposure apparatus such as described above, will be explained. FIG. 4 is a flow chart of a procedure for the manufacture of semiconductor devices such as semiconductor chips (e.g., ICs or LSIs), liquid crystal panels, CCDs, thin film magnetic heads or micro-machines, for example. Step S11 is a design process for designing a circuit of a semiconductor device. Step S12 is a process for making a mask on the basis of the circuit pattern design. Step S13 is a process for preparing a wafer by using a material such as silicon. Step S14 is a wafer process which is called a pre-process wherein, by using the so prepared mask and wafer, circuits are practically formed on the wafer through lithography. Step S15 subsequent to this is an assembling step which is called a post-process wherein the wafer having been processed by step S14 is formed into semiconductor chips. This step includes an assembling (dicing and bonding) process and a packaging (chip sealing) process. Step S16 is an inspection step wherein an operation check, a durability check and so on for the semiconductor devices provided by step S15, are carried out. With these processes, semiconductor devices are completed and they are shipped (step S17). FIG. 5 is a flow chart showing details of the wafer process. Step S21 is an oxidation process for oxidizing the surface of a wafer. Step S22 is a CVD process for forming an insulating film on the wafer surface. Step S23 is an electrode forming process for forming electrodes upon the wafer by vapor deposition. Step S24 is an ion implanting process for implanting ions to the wafer. Step S25 is a resist process for applying a resist (photosensitive material) to the wafer. Step S26 is an exposure process for printing, by exposure, the circuit pattern of the mask on the wafer through the exposure apparatus described above. Step S27 is a developing process for developing the exposed wafer. Step S28 is an etching process for removing portions other than the developed resist image. Step S29 is a resist separation process for separating the resist material remaining on the wafer after being subjected to the etching process. By repeating these processes, circuit patterns are superposedly formed on the wafer. With these processes, high density microdevices can be manufactured. While the invention has been described with reference to the structures disclosed herein, it is not confined to the details set forth and this application is intended to cover such modifications or changes as may come within the purposes of the improvements or the scope of the following claims.
	description	The present invention teaches a novel low-energy ion implant method involving the separation of the charged ion beam from the uncharged neutralized particles. FIG. 2 is a diagram of the current invention. The diagram of the ion beam implant system includes the ion source 105, the mass analyzer magnet assembly 125, beamline chamber 140, post analysis deceleration electrode assembly 135, plasma shower 145, and target chamber 150 for implanting a target wafer 120 with an ion beam 110. Under normal operation, the ion beam is mass-selected and decelerated by the decel electrode assembly 135, and is transported to the target wafer 120. The plasma shower 145 helps to reduce the space charge of the decelerated ion beam 110 and increase the beam transportation efficiency from the decel electrode assembly 135 to the wafer 120. As the ion beam 110 travels through the resolving chamber 140 some charged particles may be neutralized through the process of charge exchange with residual gas in the beamline. The deceleration voltage will not decelerate these neutralized particles because they do not carry any charge. The speed and direction of the neutral particles are not affected by the electric field. When these neutral particles with higher energy reach the target wafer 120 together with the decelerated ion beam, they will cause energy contamination with deeper implant profile. Separating the neutral particle beam and the ion beam to prevent the neutral beam from reaching the wafer is the most effective way to eliminate the energy contamination. In this invention, the beam is steered downward (FIG. 3a) or upward (FIG. 3b) in decel-mode by displacing one or several of the decel electrodes off the beam line symmetric axis on the dispersive plane defined by the mass analyzer magnet The non-symmetric electric field bends the ion beam with an off-axis angle as a function of the decel electrode displacements and the decel electrode voltages. After passing through the decel electrode assembly 135, the path of the neutralized particles and the charged particles are therefore separated during deceleration and become two separate beams 110-1 and 110-2. The neutralized particle beam 110-1 travels along a straight line while the charged ion beam 110-2 is travels along a path with a slightly downward (or upward) angle, in a range of three to fifteen degrees, such that the beam is directed at the target wafer 120. Note that the angle can be different depending on a particular system configuration. A beam stopper 155 is employed in the path of the neutralized particle beam 110-1 to block the neutralized beam 110-1 from reaching the target wafer 120. The target wafer 120 is tilted with a small slant angle relative to the vertical axis such that the wafer normal is parallel to the incident ion beam 110-2. The wafer is also moved downward (or upward) from the normal implant position as shown in FIG. 2 to a new position as shown in FIG. 3a (or FIG. 3b) to accept the steered ion beam. The invention discloses an ion implantation method that requires the use of a target chamber for containing a target for implantation and an ion source chamber that includes an ion source with a mass analyzer for generating an ion beam with specific mass at original energy. The ion source chamber further includes beam deceleration optics for decelerating the ion beam from the original energy to the desired final energy. The beam deceleration optics further includes an ion beam steering means for generating an electrostatic field. The electrostatic field is applied to steer the ions to the targeted ion-beam direction that is slightly different from the original ion beam direction. The targeted ion-beam direction has a small downward (or upward) angle, in a range from three to fifteen degrees, while the neutralized beam particles are unaffected by the deceleration and steering means and travel in the original beam direction. The target chamber containing the target for implantation is tilted backward (or forward), as shown in FIG. 3a and 3b, at a small angle in a range from three to fifteen degrees toward the ion-source chamber whereby the target for implantation may be perpendicular to the ion beam. A beam stopper is provided in the neutralized beam path to prevent the neutralized beam from reaching the implant target in the target chamber. The energy contamination from high-energy neutral particles is therefore eliminated regardless how many neutral particles are created from ion beam interaction with the residual gas molecules. Low energy contamination of less than 0.1% can be achieved even low vacuum environment exists in the beamline. In a specific embodiment, the ion source chamber is provided with a vacuum in the range of 10xe2x88x925 Torr and the ion beam may be decelerated to an energy level as low as 200 eV with a beam energy contamination of less than 0.1%. The original beam is required to have small beam width for separating the decelerated and steered ion beam with the neutralized beam in a position not far from the deceleration region to significantly reduce energy contamination Assume that the steering angle is xcex8o, the beam width is w for both the neutralized beam and decelerated ion beam, and the travel distance for completely separating the neutralized beam and the steered ion beam is L. The steering angle xcex8o should be maintained small, usually from three degrees to fifteen degrees, to minimize corresponding wafer position change and possible beam current loss. The travel distance L should be short to maximize beam current delivery to the wafer when space charge blow-up occurs for low energy and high current beam. Since the relation among these parameters is approximately w=L tanxcex8o, the beam width is required to be small, too. For instance, when xcex8o is equal to 6 degrees and L equal 30 cm, w will become 3.2 cm. Considering that large beam cross section is required to minimize space charge blow-up for low energy and high current beam, the beam height should be increased when the beam width is limited to be small. In other words, an ion beam with large aspect ratio (or large height-to-width ratio) is required in the deceleration and steering region for successfully separating the decelerated and steered ion beam from the neutralized beam, and transporting the production worthy low energy beam currents. An aspect ratio of 4 is considered to be the minimum requirement for separation of a low energy and high current ion beam from the corresponding neutralized beam. Since the beam width is usually larger than 25 cm, the beam height would be at least 10 cm. After the neutralized beam is separated from the decelerated ion beam, a beam stopper can be applied in the neutralized beam path to prevent the neutrals with higher energy from reaching the wafer and therefore minimize energy contamination. For an ion source with a narrow extraction aperture, the aspect ratio of an ion beam usually decreases when the beam travels from the ion source/extraction region to the deceleration and steering region because the space charge blow-up is more severe in the dispersive plane than in the non-dispersive plane defined by the analyzer magnet To obtain an ion beam with aspect ratio larger than 4 in the deceleration and steering region, the aspect ratio of the ion source extraction aperture should be several times larger than 4. We consider that the aspect ratio of the ion source extraction aperture is at least equal to 20 to provide high aspect ratio beams in the region of deceleration and steering for successful separation of the decelerated and steered ion beam and the neutralized beam. According to FIGS. 2 and 3, this invention discloses a method for performing an ion implantation. The method includes steps of a) providing a target chamber for containing a target for implantation and an ion source chamber including an ion source for generating an ion beam; b) providing a beam deceleration optics that includes a beam deceleration means in the ion source chamber for decelerating the ion beam for producing a low energy ion beam; c) providing a beam steering means to the beam deceleration optics to separate neutralized particles out of the ion beam by keeping the neutralized particles propagating in a neutralized-particle direction slightly different from a steered targeted ion-beam direction; and d) employing the ion-beam deceleration optics for transmitting the ion beam along the targeted ion-beam direction to the target for implantation and for blocking the neutralized particles from reaching the target for implantation. In a preferred embodiment, the method further includes a step of e) providing an analyzer magnet to the ion source chamber for mass filtering. In a preferred embodiment, the step of employing the beam deceleration means further includes a step of providing a deceleration electric-field means for generating a deceleration electric-field for decelerating the ion beam for producing a low energy ion beam. In a preferred embodiment, the step of employing the ion beam steering means for generating an electrostatic field for keeping the neutralized particle to transmit along a trajectory different than the ion beam carrying electric charges comprising a step of steering the ion beam to transmit in a targeted ion-beam direction slightly different from the neutralized-particle direction. In a preferred embodiment, the step of employing an ion-beam deceleration optics further includes a step of employing a neutralized beam blocking means for blocking the neutralized particle from reaching the target of implantation in the target chamber. In a preferred embodiment, the step of providing an ion source in an ion source chamber is a step of providing an ion source for generating a positive charged ion beam. And, the step of employing the beam deceleration means includes the step of employing a deceleration electric-field means for generating a negative electric-field for decelerating the ion beam for producing a low energy ion beam. In a preferred embodiment, the step of employing the ion beam steering means comprising a step of steering the ion beam carrying electric charges to transmit in the targeted ion-beam direction at a small deflected angle. In a preferred embodiment, the step of employing the ion beam steering means to steer the ion beam carrying electric charges to transmit in the targeted ion-beam direction comprising a step of steering the ion beam at a small deflected angle in a range of three to fifteen degrees relative to the horizontal axis. In a preferred embodiment, the step of providing the ion source in the ion source chamber comprising a step of providing the ion source chamber and the target chamber with a vacuum in the range of 10xe2x88x925 Torr. And, the step of employing the ion beam deceleration means comprising a step of decelerating the ion beam to an energy level as low as about 200 eV with an energy contamination of less than about 0.1%. In essence, this invention discloses a method for generating an implantation ion beam from an ion source projecting a plurality of ions. The method includes steps of a) employing a beam deceleration means for decelerating the ions projected from the ion source; b) employing a beam steering means for generating an electrostatic field for separating a plurality of neutralized particles from the ion ions by keeping the neutralized particles propagating in a neutralized-particle direction slightly different from a targeted ion-beam direction of the ions. In a preferred embodiment, the method further includes a step c) arranging a wafer implant position corresponding to the targeted ion-beam direction for accepting the ions projected thereto. In a preferred embodiment, the step of employing a means for transmitting the ions to a target of implantation comprising a step of employing a means for blocking the neutralized particles from reaching the target of implantation. In a preferred embodiment, the step of separating the neutralized particles from the ions comprising a step of providing a charged particle deflection means for deflecting the trajectory of the ions at a small angle from the trajectory of the neutralized particles. In a preferred embodiment, the method further comprising a step of configuring the ion beam deceleration means for decelerating and processing the ions into an ion beam having a large beam-height to beam-width ratio. In another preferred embodiment, the method further comprising a step of providing a beam block for blocking the neutralized particles propagating in the neutralized-particle direction. In a preferred embodiment, the method further includes a step of projecting the ions in forming the implantation ion beam with high beam current and low and a ratio of a beam height to a beam width equal or larger than 20. In another preferred embodiment, the step of forming the implantation ion beam having a ratio of a beam height to a height to a beam width equal or larger than 20 comprising a step of providing an extraction aperture for the ion source with an aspect ratio equal or larger than 20. In another preferred embodiment, the step of configuring the ion beam deceleration means for decelerating and processing the ions into an ion beam having a large beam-height to beam-width ratio comprising a step of processing the ions into an ion beam having a beam-height to beam-width ratio equal or greater than 4. And, the step of processing the ions into an ion beam having a beam-height to beam-width ratio equal or greater than 4 comprising a step of providing an aperture of a deceleration and steering optics having a beam-height to beam-width ratio equal or greater than 4. In a preferred embodiment, the step of providing a charged particle deflection means for deflecting the trajectory of the ions at a small angle from the trajectory of the neutralized particles comprising a step of deflecting the trajectory of the ions at an angle in the range of three to fifteen degrees. Therefore, the present invention provides a new low energy implant method used to form shallow p-type and n-type junctions in semiconductor devices. Specifically, a new ion beam deceleration method is disclosed for decelerating a charged ion beam and for separating a neutralized beam from the ion beam. The neutral beam is composed of neutral particles propagating at energies higher than the desired energy. The neutral beam is separated and stopped by a neutral-particle-stopping block so that it is unable to reach the target wafer. The problem of energy contamination in very low energy implants using decel-mode is thus resolved using this invention. Although the present invention has been described in terms of the presently preferred embodiment, it is to be understood that such disclosure is not to be interpreted as limiting. Various alterations and modifications will no doubt become apparent to those skilled in the art after reading the above disclosure. Accordingly, it is intended that the appended claims be interpreted as covering all alterations and modifications as fall within the true spirit and scope of the invention.
043009832	description	DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows a core catcher 1 provided with cooling pipes 2 and having disposed therein blocks 3 consisting of a wrapper enclosing a water soluble borate. The reactor core catcher is arranged within a reactor containment 7 of, for example, a 1000 MWe gas cooled breeder reactor. The core catcher 1 has at its inner surface 4 a protective layer 5 consisting preferably of graphite which layer 5, however, is not part of the present invention. The water-soluble borate of the blocks 3 comprises preferably the easily soluble alkali borates i.e. lithium-, potassium-, sodium-, rubidium, and cesium-borates. In connection with gas cooled breeder reactors, however, Na.sub.2 B.sub.4 O.sub.7, borax is preferred because of its availability and because of its advantageous physical and chemical properties. As a wrapper material, steel is suitable. But also other metals such as iron, nickel and also metal alloys are usable. Through selection of the material of the wrapper or rather their melting points, as well as the size of the blocks 3, the penetration pattern of a core melt can be determined. The steel included in the core melt of a 1000 MWe gas cooled breeder reactor--if evenly distributed over a core catcher floor of 50 m.sup.2 --would form a layer of about 1011 cm thickness. In order to facilitate removal of such a metallic layer from the core catcher, there are provided at the bottom of the core catcher 1, that is below the borate blocks, bins 6 of graphite which have side walls extending upwardly above the expected height of the metallic layer. Borate blocks 3 may also be disposed within the bins 6. A heat shield 10 is provided above the borate blocks 3 for the protection of the cooled walls of the core catcher 1 against excessive heat radiation from the molten core materials flowing down into the core catcher 1. FIG. 2 illustrates the penetration of the core melt through the borate layer in the core catcher. The figure is based on time values calculated for the borate layer to reach the melting point of steel (about 1427.degree. C.) under the assumption of certain conditions. The weight ratio of sodium borate to the oxidic part of the core melt is preferably selected to be at least about 1:1. For the calculations of penetration times as given in FIG. 2, the ratio of Na.sub.2 B.sub.4 O.sub.7 :core melt was assumed to be about 4:3. Because of the relatively low atomic weights of sodium and boron as compared to uranium, the molar or atomic ratio is even greater. Such greater borate to core melt weight ratio is necessary if it is to be insured that the solid solution remains water leachable, even after a complete reaction with the core catcher material. It is, for example, possible that chemical reactions occur in the core melt which form Na.sub.3 UO.sub.4 (sodium uranate) and UO.sub.2 (BO.sub.2).sub.2 (uranyl-borate). Na.sub.3 UO.sub.4 immediately absorbs water and CO.sub.2 when only exposed to air; when exposed to water total hydrolysis will be the result. UO.sub.2 (BO.sub.2).sub.2 is also hydrolized with water by forming UO.sub.3.2H.sub.2 O. From this it can be learned that, if sufficient water soluble materials are present in the core catcher, the mixture of core catcher materials and core melt can be dissolved or hydrolized. The remainder of the oxidic part of the core melt assumes the state of a fine powder which can be rinsed from the containment as a slurry simply by suction. The dissolution and hydrolization can be achieved in a circuit in which the water is evaporated from the solution, any particles suspended in the solution are removed by filtration, and the water is continuously returned to the containment. With the method according to the present invention, it becomes unnecessary to provide remotely controlled machinery in the reactor containment for the removal of a core melt after solidification. Instead, there are provided merely water inlets 8, 8a and suction lines 9, 9a which are not necessarily permanently installed but may be introduced into the containment after a core melt-down accident. Also, the hydrolized core melt when removed from the water solution is obtained in a form well suited for reprocessing. Although the present invention was developed in connection with a gas-cooled breeder reactor, it should be understood that the invention can also find application, with certain modifications, in connection with water-cooled or sodium-cooled reactors. In the case of a light water reactor, provisions must be made that, during an accident, the water will not wash the water-soluble borate layer away from its location under the core. This can be achieved by fully enclosing the borate layer in the core catcher or rather encapsulating the layer. In connection with sodium-cooled reactors (such as breeder reactors) a borate is preferred which is essentially inactive chemically with regard to sodium, such as Na.sub.2 BO.sub.2, sodium metaborate. In connection with sodium-cooled reactors there must be provisions excluding the in-flows of water into the reactor containment in order to avoid its reaction with the sodium and the formation of hydrogen. With light water reactors no hydrogen or hardly any hydrogen will develop if the borate is in the form of blocks 3 enclosed in wrappers since, after melting of the wrappers of the uppermost blocks, the borate will prevent a direct contact between steel and water or steam. If, during an accident, only some of the blocks are melted, the undamaged blocks are removed in the normal manner and the remaining damaged blocks are removed by dissolution in a solvent circulated through the core catcher. If a large part of the blocks is damaged it is preferred to first expose the core catcher to the solution for dissolution of the damaged block material. The undamaged blocks can be removed afterwards. Dissolution of the core melt and core layer material and its removal by pumping the solution out of the containment provides for an easy and safe clean-up operation after a core melt-down accident and this operation can be initiated soon after an accident has occurred. With the arrangement according to the present invention it is furthermore insured that the decay heat still generated after a core melt-down can safely be absorbed by the core catcher without any additional active means. Also, the exposure of the containment and the reactor to heat and radiation is reduced. However, the additional safety measures have really no influence on the reactor design itself. They are simple and inexpensive. There is no disadvantage generated for the reactor and the containment by inclusion of an arrangement according to the present invention in a reactor installation. The arrangement according to the invention will also insure that the metallic part of the core melt will have only little contact with any water or steam present in the reactor containment as it readily melts into the top layer of blocks, which, upon melting cover the metallic part of the core melt so as to protect it from any water and steam in the containment. The blocks which as mentioned consist of water soluble alkali borates enclosed in a casing, may be arranged in layers of different thicknesses. Each layer includes preferably the same type or the same mixture of borates. Different layers may include different types of borates or different mixtures of borates. Different layers may also have blocks of different casing materials. The block casings generally consist of metal or metal alloys such as steel, iron, cast iron, nickel, iron alloys, or nickel alloys. But the casings may also consist of ceramic materials or glasses having a relatively high melting temperature however below the temperature of the core melt. The amount of core catcher material (alkali borates) arranged in layers in the core catcher is, by weight about equal the amount of the oxidic part of the core melt possibly to be received in the core catcher. Principally, during a core melt-down accident the molten core material flowing from the core penetrates the core catcher material layer by layer by melting the core catcher materials while being dissolved therein. This process consumes a large amount of heat thus taking up the residual decay heat and cooling the core melt. Once the solution of core material and core catcher materials has become solid and relatively cool, water may be introduced into the core catcher to leach the water soluble core catcher materials (borates) from the solid solution which leaves the oxidic part of the core melt in the form of a powder that may be washed out of the core catcher and sucked out of the reactor containment without the need for humans to be exposed to radiation during such clean-up operations.
	abstract	Methods, tools, systems and computer readable media for compliance testing instrumentation and/or software. Data from one or more analytical instruments and/or software is inputted, and calculations are performed on the data to produce one or more outputs. At least one of the outputs may be compared to first and second test limits, and compliance status of the at least one output relative to the first and second test limits is reported.
	description	1. Field of the Invention The invention is concerned with ion beam adjustment, and directed particularly to adjust the ion beam between a mass analyzer and a workpiece by using one or more specific shaped magnetic fields. 2. Description of Related Art Ion implantation is a ballistic process used to introduce into a substrate with ions, atoms or molecules, generally referred to as dopants, to make materials with useful properties. Of particular interest, ion implantation is a common process used in making modem integrated circuits. Ion implantation may also be used for other purpose, like thin film deposition or formation with controlled thickness and predefined surface properties for manufacturing optical display devices such as flat panel displays. In general, an ion implanter has at least an ion source, a mass analyzer and a substrate holder. The ion source is used to ionize one or more material to generate numerous ions, and the mass analyzer is used to filter these ions so that the selected ion beam has only substantially ions with desired specific mass-to-charge ratio. Then, the workpiece held by the substrate holder is implanted by the selected ion beam. Herein, the workpiece can be a semiconductor substrate, a glass plate or other bulk materials. In general, without further focusing or adjusting, the ion beam just exited from the mass analyzer would not have a desired shape and property other than corrected beam current and energy. For example, the cross-sectional shape of ion beam may be irregular, and the ion beam current distribution on the cross section may be non-uniform or far away from Gaussian distribution. Moreover, different implantations applications may prefer different ion beams with different shapes. For example, a narrower ion beam may be beneficial than a wider ion beam for implanting a region with more defined boundary on a workpiece. Accordingly, the ion implanter usually has one or more control assemblies which are capable of applying the magnetic field or the electromagnetic field on the ion beam in a region between the mass analyzer and the substrate holder. The trajectory of each charged particle, such as ion, in the ion beam will be affected by the applied magnetic/electromagnetic field, and then the properties of ion beam may be adjusted. For example, a diverse ion beam may be collimated, a ribbon shape ion beam may be focused to form a spot beam at the surface of the workpiece, and the ion beam current density distribution may be modified to become Gaussian-like distribution with beam width and height in the preferred rang by controlling the ion beam envelope. There is a number of conventional control assemblies used in ion implanter. For example, as shown in FIG. 1A, one popular conventional control assembly has two mutual parallel straight bar magnets 11/12 having the coils 13 uniformly disposed on the straight support rods 14. Hence, by adjusting separately the electrical current directions through the coils 13, different magnet fields may elongate or compress the ion beam 15 (direction into the paper and vertical to the two straight bar magnets 11/12) when the ion beam is directed through a space between the straight bar magnets 11/12. Another conventional control assembly, as shown in FIG. 1B, is similar with the above except that the coils 13 are non-uniformly disposed on the straight support rods 14. Still another conventional control assembly, as shown in FIG. 1C, is similar with the above except that one additional straight bar magnet 16 is configured to mechanically connect the two straight bar magnets 11/12 for forming a U-shape magnet structure. Herein, the coils 13 may be uniformly or non-uniformly disposed on the additional straight bar magnet 16. One more conventional control assembly, as shown in FIG. 1D, is similar with the above except that two additional straight bar magnets 16/17 are configured to mechanically connect the two straight bar magnets 11/12 for forming a rectangle magnet structure. Herein, the coils 13 may be uniformly or non-uniformly disposed on the two additional straight bar magnets 16/17. Moreover, one or more electric element 18 may be disposed on one or two additional straight bar magnets 16/17 for further tuning the direction of the ion beam 15. However, as well-known by the one skilled in the art, all conventional control assemblies have limitations for all potential implementations on a workpiece to cover the beam optics requirements to transportion beam at various beam current from light to heavy mass species and for ion energy from several tens keV down to as low as few hundred eV. Therefore, there is a need existed to propose a novel apparatus for adjusting an ion beam, after the ion beam is exited from the mass analyzer and before the workpiece on the substrate holder. The present invention provides ion implanter capable of adjusting an ion beam by using one or more bended bar magnets. For example, arch-shaped bar magnet, curved bar magnet, zigzag shaped bar magnet and so on. The fundamental difference between the proposed bended bar magnet(s) and the conventional straight bar magnet(s) is the capability to elongate or compress an ion beam not only along horizontal or perpendicular direction relative to ion beam path with different amplitude but also along different directions to change ion beam shape to a desired shape and beam size. One feature of the invention is directed to an ion implanter having at least an ion source, a mass analyzer, a substrate holder and a control assembly. Both the functions and the structures of the ion source, the mass analyzer and the substrate holder can be similar with the conventional ion technologies, and the control assembly is capable of adjusting the ion beam within the adjustment space between the mass analyzer and the substrate holder. The control assembly has at least a first bended bar magnet having a first bended support rod and one or more first coils dispensed on the first bended support rod with one or more first currents flowing through the first coils, and a second bended bar magnet having a second bended support rod and one or more second coils dispensed on the second bended support rod with one or more second currents flowing through the second coils. Herein, the first bended bar magnet is at a gap from the second bended bar magnet to form the adjustment space between the first bended bar magnet and the second bended bar magnet. The bended bar magnet(s) is proposed to replace the conventional straight bar magnet(s), i.e., to form a control assembly having the bended bar magnet(s). The differences between the bended bar magnet and the straight bar magnet naturally induce different ratios of horizontal and vertical Lorentz forces, and then may adjust differently the ion beam. The ratio may be changed more significantly by changing the gap width between the two bended bar magnets, by changing the curvatures of these bended bar magnets, and/or by changing the currents flowing through the two bended bar magnets. FIG. 2A illustrates qualitatively both the magnetic field flux and the magnetic field induced by two conventional straight bar magnets as shown in FIG. 1A. Herein, two straight bar magnets 21 and 22 are located on two opposite sides of a predetermined ion path so that an adjustment space is partially surrounded. Moreover, one straight bar magnet 21 has disposed clockwise coils and another straight bar magnet 22 has disposed counter-clockwise coils, and the current directions (expressed by arrow) through the two coils are opposite when the current amount is same. Further, to simplify the figures, the cross-sectional shape of the ion beam is expressed as a rectangular. Therefore, two sets of magnetic fields are induced with essentially opposite directions (refer to the fluxes 23 and 24) so that a total magnetic field is formed with a specific distribution. Refer to the arrows 25 illustrating qualitatively how the direction and the amplitude of the total magnetic field are varied. FIG. 2B illustrates qualitatively the corresponding Lorentz force direction on an ion beam travelling into the paper and how the ion beam is elongated along a perpendicular direction and compressed along a horizontal direction. Herein, the arrows 26 show qualitatively how the direction and the amplitude of the Lorentz force are varied. Along the vertical direction (the beam height direction) and the horizontal direction (the beam width direction), the amplitude of the Lorentz force is largest on the edges and lowest on the center of the entered ion beam 27. Accordingly, after the entered ion beam 27 is adjusted by the corresponding Lorentz force applied by the two straight bar magnets 21 and 22, the exited ion beam 28 is elongated along the vertical direction and compressed along the horizontal direction. In other words, the ion beam becomes narrower and taller after traveling through the adjustment space partially surrounded by the two straight bar magnets 21 and 22. As illustrated qualitatively in FIG. 3A and FIG. 3B, one embodiment of the invention uses two concave bar magnets 31/32 to replace the two conventional straight bar magnets 21/22. The distance between the neighboring top ends (or neighboring bottom ends) of the two concave bar magnets 31/32 is equal to the distance between the two straight bar magnets 21/22, and the two concave bar magnets 31/32 are symmetrical around a centerline of a gap between the two concave bar magnets 31/32. Herein, a concave bended bar magnet indicates that a midpoint of the concave bended bar magnet is farther from the centerline of the gap than two ends (even other portions) of the concave bended bar magnet. Reasonably, due to the wider gap width at the middle portion of the gap, the distribution of the two sets of magnetic fields (refer to the fluxes 33 and 34) induced respectively by the two concave bar magnets 31/32 will be less densely in the middle portion of the gap than that induced by the two straight bar magnets 21/22, when the distribution of the two sets of magnetic fields (refer to the fluxes 33 and 34) induced respectively by the two concave bar magnets 31/32 in the top/bottom ends of the gap will be essentially similar with that induced by the two straight bar magnets 21/22. Accordingly, the total magnetic field 35 is weaker in the middle comparing to the total magnetic field 35 close to the top and bottom ends of the two concave bar magnets 31/32, so that the ion beam tends to be compressed less along horizontal direction than to be elongated along vertical direction by the Lorentz force 36. Therefore, the exited ion beam 38 is taller and less narrower than the entered ion beam 37 after the entered ion beam 37 traveling through the adjustment space partially surrounded by the concave bar magnets 31/32. Especially, to compare with the FIG. 2B, the exited ion beam is wider than the exited ion beam 28, which is a main characteristic of this embodiment. As illustrated qualitatively in FIG. 4A and FIG. 4B, another embodiment of the invention uses two convex bar magnets 41/42 to replace the two conventional straight bar magnets 21/22. The distance between the middle portions of the two convex bar magnets 41/42 is equal to the distance between the two straight bar magnets 21/22, and the two convex bar magnets 41/42 are symmetrical around a centerline of a gap between the two convex bar magnets 41/42. Herein, a convex bended bar magnet indicates that the midpoint of the convex bended bar magnet is closer to the centerline of the gap than the two ends (even other portions) of the convex bended bar magnet. Reasonably, due to the opposite geometric characteristic, the effect of the convex bar magnets 41/42 is opposite to the effect of the concave bar magnets 31/32. Hence, due to the larger gap width at the top/bottom portions of the gap, to compare with the distribution of the magnetic field induced by the straight bar magnets 21/22, the distribution of the two sets of magnetic fields (refer to the fluxes 43 and 44) induced respectively by the two convex bar magnets 41/42 will be less densely in the top/bottom portions of the gap but will be essentially similar with in the middle portions of the gap. Accordingly, the total magnetic field 45 is weaker in the top/bottom portions comparing to the total magnetic field 45 in the middle portion. Therefore, the exited ion beam 48 is narrower and taller than the entered ion beam 47, after the entered ion beam 47 traveling through the adjustment space partially surrounded by the convex bar magnets 41/42 and being adjusted by the Lorentz force 46. Especially, to compare with the FIG. 2B, the exited ion beam 38 is shorter than the exited ion beam 28, which is a main characteristic of this embodiment. Besides, in the above embodiments, except that the shape of the bar magnets is changed, other parameters are kept as constant as possible. For example, the current flowing the coils disposed on different bar magnets with same direction and same amount, the density and the outline of the coils disposed on different bar magnets are equivalent, the two bended bar magnets are symmetric around a centerline of the gap there between, the shape of each bar magnet is a combination of three straight segments, the distance between two bended bar magnets is equal essentially to the distance between two straight bar magnets, and so on. However, all these parameters may be adjusted without violating the mechanism of the bended bar magnets. For example, other non-illustrated embodiments may have two concave bar magnets where the distance between the middle portions of the two concave bar magnets is equal to the distance between the two straight bar magnets 21/22, and may have two convex bar magnets where the distance between the neighboring top ends (or neighboring bottom ends) of the two convex bar magnets is equal to the distance between the two straight bar magnets 21/22. FIG. 5 illustrates qualitatively an embodiment being similar with the embodiment shown in FIGS. 4A and 4B except the gap width is twice larger. Herein, similar items are labeled by similar numbers, and the related description is omitted. Clearly, the relative strength of horizontal and perpendicular Lorentz forces is changed when the gap width between two bar magnets is adjusted. Hence, the ratio of amplitudes of an ion beam elongation and compression along horizontal and perpendicular direction is correspondingly changed after the ion beam traveling through the bar magnets. As shown in FIG. 5, the larger gap width induces a less densely magnetic field, so that a less narrower and less taller exited ion beam 58 is acquired. As a short summary, the embodiments shown in FIG. 3A to FIG. 5 may be applied to adjust the size, especially the ratio between the horizontal direction and the perpendicular direction, of an ion beam. Hence, even the operations of both the ion source and the mass analyzer are fixed, the size/shape of the final ion beam implanted to the workpiece may be adjusted flexibly to meet the different requirements of different implantations. FIG. 6 and FIG. 7 illustrate qualitatively two embodiments being similar with the above embodiments except that the two bended bar magnets are not symmetric around the centerline of the gap between the two bended bar magnets. Herein, FIG. 6 shows the situation that the bended bar magnets 61/62 are asymmetric distributed around the centerline of the gap, and FIG. 7 shows the situation that two bended bar magnets 71/72 are concave and convex respectively. Again, similar items are labeled by similar numbers, and the related description is omitted. Reasonably, due to the specific configuration of the bended bar magnets 61/62/71/72, the ion beam will deviate from the symmetric ion beam axis so that the ion beam shape will be changed non-symmetrical. In the situation shown in FIG. 6, the asymmetric concave bar magnets 61/62 changes the size of the entered ion beam 67 and twists slightly the entered ion beam 67 as well, so that the exited ion beam has a taller, less narrower and deformed shape. In the situation shown in FIG. 7, the concave and the convex bar magnets 71 and 72 changes the size of the entered ion beam 77 and bends the entered ion beam 77 slightly at both top and bottom portions of the entered ion beam 77, so that the exited ion beam 78 has a more obvious curvature than the entered ion beam 77. Reasonably, the embodiments shown in FIG. 6 and FIG. 7 may be applied to improve the ion beam outputted from the mass analyzer even the operations of both the ion source and the mass analyzer are fixed. For example, a twisted ion beam outputted from the mass analyzer may be straightened by the situation shown in FIG. 6 and a banana ion beam outputted from the mass analyzer may be straightened by the situation shown in FIG. 7. Furthermore, for some ion implantation applications, the ion beam outputted from the mass analyzer has to be non-uniformly adjusted before the workpiece being implanted. For example, the cross-sectional shape of the outputted ion beam is partially non-uniform, so that a non-uniform adjustment is useful to separately elongate/compress different portions of the outputted ion beam for achieving an adjusted ion beam with a more uniform cross-sectional shape. In such condition, different coils of the conventional straight bar magnets have to be electrically coupled with different current sources, so that different coils may generate different magnetic fields with different amplitudes. Then, even these coils are disposed along two straight lines, the net magnetic field generated by the two straight bar magnets may be non-uniformly distributed. In contrast, because the coils of the bended bar magnets are not disposed along two straight lines, the net magnetic field generated by the two bended bar magnets may be non-uniformly distributed even the amplitude of the magnetic fields induced by different coils may be uniformly, or only slightly non-uniform. In other words, these coils of each bended bar magnet may be electrically coupled with one and only one power source, or may be electrically coupled with a few power sources. Accordingly, to compare with the conventional straight bar magnets, the proposed bended bar magnets may reduce the cost and simplify the operation because less power sources being required, at least may provide an alternative option on the design/operation of the ion implanter. FIG. 8A and FIG. 8B illustrate quantitatively an ion implanter uses the proposed bended bar magnets. The proposed ion implanter 800 has at least an ion source 801 capable of generating an ion beam 805, a mass analyzer 802 capable of directing the ion beam 805 (ribbon beam, spot beam or any type ion beam) with numerous ions having desired mass-to-charge ratio, a substrate holder 803 capable of holding a workpiece (not shown) to be implanted by the ion beam 805, and a control assembly 804 capable of adjusting the ion beam 805 in an adjustment space between the mass analyzer 802 and the substrate holder 803. Moreover, each of the ion source 801, the mass analyzer 802 and the substrate holder 803 may be manufactured by the conventional technologies and then are not further discussed. Besides, the control assembly 804 has at least a first bended bar magnet 8041 having a first bended support rod 8042 and one or more coils 8043 dispensed on the first bended support rod 8042 with one or more first currents flowing through said first coils, and a second bended bar magnet 8044 having a second bended support rod 8045 and one or more coils 8046 dispensed on the second bended support rod 8045 with one or more second currents flowing through said first coils. The first bended bar magnet 8041 is at a gap from the second bended bar magnet 8044, so that the adjustment space is formed between the two bended bar magnets 8041/8044. In this embodiment, both bended bar magnets 8041/8042 are convex and bended continuously. However, as shown in FIG. 3A to FIG. 7 and discussed above, the bended bar magnets used to form the control assembly 804 are not limited by the shape, the size, the gap width, the construction, and so on. For example, each of the bended bar magnet 8041/8042 may have an arc shape, a curve shape, a zigzag shape, or a shape consisting of several straight segments. For example, the curvature of the bended bar magnet is not limited. FIG. 9A and FIG. 9B illustrate qualitatively two embodiments with bended bar magnets of different bending curvature. Both control assemblies in these two embodiments have convex bar magnets 8041/8044 with uniformly disposed coils, but the curvature of the convex bar magnets 8041/8044 in FIG. 9A is clearly smaller than that in FIG. 9B. Differences in the curvature will directly affect the magnetic field distribution in the region surrounded by two magnet bars at same coil current. Hence, the deformation ratio on the ion beam shape between the perpendicular direction and the horizontal direction of the ion beam 805, as illustrated in FIGS. 9A and 9B, will be different. In other words, different adjustments on the ion beam may be achieved by using different control assemblies having bended bar magnets with different curvatures. Reasonably, even not illustrated in any drawing, to use lesser power source(s) to supply current(s) to more coils on the bended bar magnets, the control assembly 804 may be configured according to at least one of the following: these first coils are electrically coupled with one and only one first power source, these first coils are electrically coupled with two or more first power sources, these second coils are electrically coupled with one and only one second power source, and these second coils are electrically coupled with two or more second power sources. Also, the control assembly 804 may be configured according to at least one of the following: different first power sources are separately operated (each provides an individual current), different second power sources are separately operated (each provides an individual current), these first power sources and these second power sources are separately operated (each provides an individual current), these first power sources behaves as one and only one power source (all provide the same current), these second power sources behave as one and only one power source (all provide the same current), and both these first power sources and these second power sources behaves as one and only one power source (all provide the same current). In addition, although not shown in any drawing, some embodiments may adjust flexibly the shape of one or more bended bar magnets. In other words, one or more bended bar magnets may have an adjustable shape, so that the control assembly may be more suitable for many different adjusted ion beams required by different ion implantations. The adjustments of the bended bar magnet(s) may be achieved when the ion implanter is performance maintained or during the operation of the ion implanter. How to adjust the shape of the bended bar magnet(s) is not limited. For example, it may be achieved by replacing an original bended bar magnet by a new bended bar magnet, and it may be achieved by rotating the bearing used to mechanically connect different segments of one bended bar magnet. Of course, to more flexibly adjust the ion beam, some other embodiments without any drawings may adjust other parameters, but not adjust the shape of the bended bar magnet(s). For example, the gap width between neighboring bended bar magnets may be adjusted flexibly, the curvature of each bended bar magnet may be adjusted flexibly, even the current flowing through each bended bar magnet may be adjusted flexibly. It should be noted that two or more parameters may be adjusted flexibly simultaneously or in sequence. Moreover, whether the coils are disposed uniformly or non-uniformly on any bended bar magnet also is not limited. Different configuration of the disposed coils may be used to induce different induced magnetic fields. Note that different current amounts flowing through the coils may change directly the amplitude of the induced magnetic field but the configuration of the coils on the bended bar magnet(s) may control directly how the induced magnetic field is distributed. Further, although not shown in any drawings, some embodiments may non-uniformly turn on (or turn off) one or more of the coils disposed on one or more bended support rod. Hence, to compare with the situation having disposed uniformly coils on same bended support rod, the total magnetic field induced by the control assembly may have more different variations, even may be adjusted more flexibly. Accordingly, the available adjustments on the ion beam passing through the adjustment space are significantly increased. Although specific embodiments have been illustrated and described, it will be appreciated by those skilled in the art that various modifications may be made without departing from the scope of the present invention, which is intended to be limited solely by the appended claims.
	description	This application is related to, and claims priority from, the following U.S. Provisional patent applications: (1) Application No. 60/783,696, entitled “Apparatus and Methods for Optimizing Alignment Performance and Productivity in a Fleet of Exposure Tools”, by Mike Adel et al., filed Mar. 16, 2006. (2) Application No. 60/891,209, entitled “Apparatus and Methods for Optimizing Alignment Performance and Productivity in a Fleet of Exposure Tools”, by Mike Adel et al., filed Feb. 22, 2007. These applications are herein incorporated by reference in their entirety. The invention described herein pertains to methods and approaches used to optimize the alignment performance and the productivity of a fleet of exposure tools in a lithography cell of a semiconductor fabrication facility. As the density and complexity of microcircuits continue to increase, the photolithographic processes used to print circuit patterns becomes more and more challenging. Previous technologies and thinking in the art has required denser and more complex patterns to achieve the formation of the denser circuits consisting of smaller pattern elements packed more closely together. Such patterns push the resolution limits of available lithography tools and processes and place ever increasing burdens on the photolithography processes used to form the many layers of a semiconductor wafer design pattern. One of the most time consuming and labor intensive tasks undertaken in the lithography cell of a high productivity semiconductor manufacturing plant is that of ensuring good quality alignment performance of a stepper or scanner with minimal impact on fleet productivity. The basic problem resides in the fact that even the most advanced patterning exposure tools possess an intrinsic unique pattern placement error signature, both at the full wafer (sometimes called grid) level and at the individual field (sometimes call shot) level. This is due to residual imperfections in both the optical and mechanical systems of the patterning tool (also referred to herein as an exposure system) which differ from tool to tool, varying by tool identity, by tool model, by tool generation, by tool vendor, and even by tool component and illumination conditions. In order to meet ever shrinking alignment control requirements, the exposure tools require more and more sophisticated control methodologies. In an effort to meet these demands, exposure systems include an ever increasing array of adjustment features with more and more degrees of freedom, all directed toward error compensation. In an ordinary process an exposure system is obtained by an end user and then calibrated such that it performs within its manufacturer specifications. Only then can such systems take their place in the manufacturing fleet. However, the inventors point out that even though such systems are calibrated to within manufacturer specifications, each tool demonstrates some degree of pattern distortion and misalignments making it imperfect. Ordinarily such imperfections are not particularly troublesome. However, with the pressure to obtain ever shrinking feature sizes and the associated need for greater precision, such systems are under pressure to demonstrate improved precision. Thus, increasingly even systems calibrated to manufacturer specifications are under increased pressure for greater fidelity. The presence of these residual errors can be compounded when combined with other tools which have their own intrinsic errors. Accordingly, metrology tools are currently used in the art to measure and quantify errors, distortions, and misalignments in each exposure system. Commonly, the exposure systems will be calibrated using highly precise test wafers featuring many alignment targets and a peerless surface. The exposure systems are used to form lithographic patterns on the test wafers. The test wafers are then subject to metrology testing (overlay alignment metrology and the like) to determine the degree of fidelity possible with each exposure system. The degree of error present in each machine is determined. It turns out that machines demonstrate a few general categories of error propagation. Accordingly, machines having similar error propagation properties are typically grouped together so that pattern alignment can be maintained to a reasonable degree. This principle is depicted in the extremely simplified illustration of FIG. 1. An intended pattern 101 is depicted here as a square pattern. A fleet of exposure systems (A, B, C, D, E, F) is also shown. Each exposure system includes its own distortion signature causing it to deviate from a perfect replication of the intended pattern 101. As mentioned above, the systems frequently demonstrate distortion signatures that are similar to each other. For example, exposure systems A, B, & C of Group 1 have somewhat similar distortions signatures. Also, exposure systems D, E, & F of Group 2 have somewhat similar distortions signatures. However, it is noted that the signatures of the Group 1 systems vary rather more substantially from the signatures of the Group 2 systems. As a result, the Group 1 systems generally are used together and the Group 2 systems are used together. For example, in fabricating lithography layers on a lot of wafers, layer one is formed using system A, layer two is then formed using system B, and layer three is then formed using system C. Thus, relatively good alignment can be maintained using the systems grouped this way. There are some drawbacks to such a system. For example, when a fourth layer is desired to be formed, the wafer is loaded again onto system A and a fourth layer is formed. However, if none of the Group 1 tools are available (i.e., they are currently in use) the process has a bottleneck. The Group 2 tools can not be used because of the variance in signature between the Group 1 and Group 2 systems. Thus, it is possible, for the process to come to a halt, and additionally, the Group 2 systems may lie unused for an extended period of time. Although, on its surface this may seem like a relatively minor problem, one must consider that in many cases, the exposure systems cost $40,000,000 or more each. The cost for idling such an expensive tool is astronomical. Currently, that is the current state of the art. In some cases adjustments at the set-up stage can be used to harmonize the distortion caused by each machine as much as possible to attempt to overcome the intrinsic mismatches between different exposure tools in the fleet. In some existing methods one may perform so-called “mix & match” activity during the initial ramp up of an exposure fleet prior to, or in parallel, to bringing exposure systems on-line in a manufacturing environment. Since no “absolute” grid reference exists, back to which the relative displacements of the individual exposure tools can be compared, a “golden exposure tool” and a “golden reticle” or both may be selected, and the golden tool and reticle are then used in various scenarios to generate a mix & match database of discrepancies for each exposure tool relative to the golden exposure tool. This technique generally require a lengthy sequence of exposures and subsequent processing of test wafers, followed by intensive high density overlay metrology using a tool such as the Archer AIM overlay metrology tool manufactured by KLA-Tencor on the test wafers. A description of such a procedure is given in the following reference: S. J. DeMoor, J. M. Brown, J. C. Robinson, S. Chang, and C. Tan, “Scanner overlay mix and match matrix generation: capturing all sources of variation” Proc. SPIE Int. Soc. Opt. Eng. 5375, 66 (2004), which document is incorporated herein by reference it its entirety for all purposes. This practice suffers from a number of deficiencies, including time consuming labor intensive non-automated analysis, risk of errors, and that over time, the database can become an inaccurate reflection of the current status of the tool set due to drifts or maintenance induced modifications. Improved methods for optimizing alignment in a fleet of exposure systems is needed. Among other things, this disclosure seeks to provide solutions to this problem. Accordingly, the embodiments of invention present substantial advances over the existing methodologies and overcome many limitations of the existing pattern fabrication arts. These and other inventive aspects of the invention will be discussed herein below. In accordance with the principles of the present invention, methods and systems for achieving optimized alignment performance in a fleet of lithographic exposure systems are disclosed. Numerous aspects of the present invention are described in detail in the following description and drawings set forth hereinbelow. In one embodiment, a method for optimizing alignment performance and productivity of a fleet of exposure systems is disclosed. The method involves characterizing each exposure system in a fleet of exposure systems to generate a set of distinctive distortion profiles associated with each exposure system. The set of distinctive distortion profiles are stored in a database. A wafer having reference pattern formed thereon is provided for further pattern fabrication and an exposure system is selected from the fleet to fabricate a next layer on the wafer. Linear and higher order parameters of the selected exposure system are adjusted to model the distortion of the reference pattern and/or the systems used to make the reference pattern. Once the exposure system is adjusted, it is used to form a lithographic pattern on the wafer. Embodiments of the invention also enable updating the distortion profile information. For example, production metrology information concerning the lithographic patterns formed on wafers can be obtained by measuring production wafers metrology tools and using the metrology information to update the distortion profile information regarding the exposure systems. Method embodiments of the invention include the acquisition and storing of context information. Such information can be obtained during pre-production characterization and is used to generate distinctive distortion profiles that include linear distortion effects and high order distortion effects attributable to at least one of: distortions attributable to different reticles, distortions attributable to different exposure systems, distortions attributable to different stages of an exposure system, distortions attributable to different scan directions used in fabricating layers with exposure systems, distortions attributable to different chuck systems employed with exposure systems, distortions attributable to different illumination conditions. Another embodiment includes computer program products used to implement methodologies described herein. Also, a computer controlled network of exposure systems and inspection tools arranged to enable real-time adjustments of higher order distortion parameters is disclosed. One architecture embodiment of this type includes a group of lithography exposure systems linked to an exposure system control server enabling control of the exposure systems and a group of metrology tools linked to a metrology system control server. Additionally, the architecture includes databases of accumulated distortion profiles characteristic of each of the exposure systems. The databases store exposure system distortion information characterizable by higher order distortion models or included in look-up tables stored in the databases. Such databases can be stored on one of said servers. The architecture is further configured to include a direct link between the exposure system control server and the metrology system control server that enables the transmission of exposure system distortion profile information between the exposure system control server and the metrology system control server. This direct link can enable real-time adjustment of high order parameters or look up table information for the exposure systems during production. These and other aspects of the present invention are described in greater detail in the detailed description of the drawings set forth hereinbelow. It is to be understood that, in the drawings, like reference numerals designate like structural elements. Also, it is understood that the depictions in the Figures are not necessarily to scale. The present invention has been particularly shown and described with respect to certain embodiments and specific features thereof. The embodiments set forth herein below are to be taken as illustrative rather than limiting. It should be readily apparent to those of ordinary skill in the art that various changes and modifications in form and detail may be made without departing from the spirit and scope of the invention. The following detailed description describes various embodiments of a method and approach for optimizing alignment among the exposure systems of a fleet of exposure systems. The methods disclosed herein the rapid selection and adjustment of exposure based on real-time considerations present in mass production manufacturing environment such as in a factory setting. The disclosed invention enables the use of initial characterization information to make parameter adjustments to selected tools to enable selected systems in the fleet to be employed in fabrication processes on an as needed basis. The system and approach disclosed herein is flexible, fast, and enables optimized utility in a fleet of exposure systems. Many embodiments are disclosed herein however the invention is not intended to be limited to only the disclosed embodiments. As hinted at above, one of the problems presently encountered by present fabrication technologies (particularly photolithography) is that they are approaching a level of fabrication accuracy that is challenging the accuracy of current fleet management approaches. The present inventions disclosed herein offer solutions to some of these problems and represent a significant improvement in the art. It should be noted that distortions caused by fabrication systems are well studied in the art. In general such errors and distortions can be characterized as linear distortions and higher order distortions. Generally, when a wafer layer is fabricated it is subject to metrology (e.g., overlay metrology and so on) processes to determine the fidelity of the fabricated layer. Such metrology examines many features to make a determination of layer fabrication suitability. One feature is alignment accuracy. A series of measurements of the fabricated layer are made and compared with a series of alignment targets and other associated features to determine the accuracy of the layer fabrication process. The information received by these metrology measurements can be mapped and modeled to produce a model of exposure system performance. Such models can describe exposure system performance on both the field and wafer levels. The modeling can be used to describe the fabrication alignment distortion in linear terms and higher order terms. Alternately, the distortions may be described by a look up table approach, in which, for instance, the linear field distortion terms for each field are described independently for each field. Linear terms describe such things as simple pattern translation in an x or y direction, pattern rotation, scaling problems, and are generally of the same order of magnitude across the modeled surface (be it field or wafer, depending on the extent of the modeled surface). FIG. 2 presents one simplified embodiment of a linear distortion or displacement error. The displaced pattern 202 (depicted with dashed lines) is shown superimposed over the intended position 201. The displaced is a translation in both the x and y directions and can typically be corrected using existing technologies. However, lithography patterns are also fraught with numerous “higher order” distortions. Such “higher order” distortions are distortion patterns that demonstrate non-linear behavior. Typical “higher order” distortions include, but are not limited to, second order distortions (where the distortions vary with respect to the square of the distance), third order distortions (where the distortions vary with respect to the cube of the distance), trapezoidal distortion patterns, s- and c-shaped distortion patterns, bowed patterns, 4th, 5th and 6th order distortions, and many more essentially any non-linear distortion pattern. A non-exclusive list of such distortion patterns is provided as part of Appendix A. An important point to be made here is that most modern exposure systems include adjustable parameters capable of being varied to account for these effects. In the prior art such adjustments are done once when the machines are received at the factory floor and adjusted to meet manufacturer specifications. What is not done in the previous art is a further optimization of the exposure tool parameters to enable the systems to adjust to optimize an entire fleet of systems for maximized performance. Reference will now be made in detail to a specific embodiment of the invention. An example of this embodiment is illustrated in the accompanying drawings. While the invention will be described in conjunction with this specific embodiment, it will be understood that it is not intended to limit the invention to one embodiment. On the contrary, it is intended to cover alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. The present invention may be practiced without some or all of these specific details. In other instances, well known process operations have not been described in detail in order not to unnecessarily obscure the present invention. In one approach a methodology for optimizing exposure systems of the fleet is described. Reference is now made to the illustrative flow diagram of FIG. 3. Upon introduction of an exposure system to the fleet, the system is characterized (Step 301). Typically, this involves using the exposure system to fabricate a layer on a target wafer using a desired mask reticle. This target wafer is of course a specially prepared wafer having many metrology targets and other alignment sites to enable high quality metrology measurements to be obtained. The layer is then subjected to many metrology measurements to obtain highly detailed alignment information. For example, using an Archer AIM overlay metrology tool produced by KLA-Tencor of San Jose, Calif. One particularly useful implementation of the principles of this invention relates to applications of the instant principles to integrated metrology tools. Such integrated metrology tools can include metrology tools (e.g., overlay tools) that are integrated into fabrications tools (like, scanners and steppers and so on). As such, these integrated metrology tools are particularly well suited to maximize the principles of the present invention. Such integrated metrology tools are new and include such concepts as those embodied in tools like the iArcher overlay metrology tool conceived of by KLA-Tencor of San Jose, Calif. Additionally, the reticle itself can be analyzed to determine errors in the reticle (which can be used elsewhere in the process to correct for reticle induced pattern distortions). The metrology information is then used to model the distortion pattern on the surface. This model can be corrected for errors present in the reticle. Additionally, the metrology information can be used to model the distortion caused by the exposure system. Unlike methodologies known in the prior art. Many different aspects of the exposure system can be modeled and separately inventoried and stored. For example, layers can be formed using the same exposure system but the illumination conditions can be changed. For example, measurements can be made on layers formed using annular illumination, quadrapole illumination, and so on. Thus, each relevant illumination condition for the system can be modeled. A separate data file can be generated for each variable distortion causing parameter in an exposure system (Step 303). For example, a distortion profile can be generated and stored for each illumination condition of the exposure system. Specifically, the database can be made more granular. In multi-stage exposure systems, measurements can be made of layers formed with each stage of the exposure system. Also, layers and associated measurements can be made for each chuck used in an exposure system. Additionally, layers and associated measurements can be made for each scan direction used in an exposure system. In this way, the databases can be enhanced to include distortion profiles that capture the distortion effects caused by variation in scan direction in an exposure tool. Also, each of these layers and measurements can be repeated for each combination of variables listed above as well as any others deemed relevant. Also, the measurements can be modeled on a per field basis or on a per wafer basis. This information can be stored as a set of distinctive distortion profiles that characterize each exposure system. The distortion profiles can also include reticle information that includes the amount of distortion introduced be each specific reticle. The databases can also be stored as distortion profiles that are basically differences information (“delta's”) that define the amount of change induced by the presence of one or more of the above referenced confounding factors. Additionally, the data can be enhanced by dynamic sampling which will be discussed in greater detail elsewhere in this patent. Thus, the initial calibration to manufacturer specification is also expanded to characterize the exposure system in a plurality of exposure profiles that is distinct to each system and its subsystems (illumination, stage motion properties, chuck effects, and so on). Once the initial characterization is complete and a wafer is provided for further fabrication (Step 305). The stored distortion profiles for the exposure systems can be used to enhance the fabrication of wafer patterns. Once a wafer has a pattern formed thereon by a specified exposure tool (under known fabrication conditions which are tracked by the system), the distortion profiles can be used to determine the degree of distortion in the pattern formed by a specific exposure system (including reticle distortion effects, illumination distortion effects, stage effects and so on). Thus, much history is known about the distortion pattern of previous patterning steps. Once a wafer is received and a reference pattern is identified (a reference pattern being a pattern to which other subsequently formed layers are aligned), the exposure system to be used for further fabrication is selected from the fleet of exposure systems (Step 307). This exposure system can be a system that has a distortion pattern that is generally similar to that of the reference pattern already formed on the wafer (such as indicated in e.g., FIG. 1)). Or it can be any of the exposure systems in the fleet. For example, it can be the first available system. The selection of the exposure system can be using a so-called “best-fit” system whereby the original calibration specification information is known and the tool that best matches the distortion properties of the reference layer is chosen. Using the finer granularity of adjustment possible with the present invention, such a best fit system can take into consideration many distortion factors including, but not limited to, illumination conditions, stage ID, chuck ID, stage scan motion direction, and even in some cases, the reticle used. Thus, a system that best models the desired distortion signature can be used. However, in many situations the chosen exposure system will merely be the first available tool. In the prior art once an exposure tool was calibrated to within the manufacturer's specification that was the end of adjustment. Not so in the present invention. The inventors specifically contemplate further adjusting the adjustable parameters of the selected exposure system so that the selected exposure system distortion models the distortion present in the previously formed reference pattern (Step 309). Typically, this means that the pattern can be adjusted for first order distortions and errors such that the first order distortion of the selected exposure system is similar to the first order distortion present in the reference pattern. Still more significantly, the high order parameters are adjusted to so that the selected exposure system has high order distortion that models (or is otherwise similar to) the high order distortion pattern of the previously formed reference pattern. This can include the deliberate introduction of distortion into an exposure tool so that the distortion models that of the tool used form the reference pattern. This is new. Additionally, these changes to the high order parameters can be done in “real-time” just as needed upon the selection of the exposure tool to be used. Aspects of the system architecture facilitate such a real-time implementation and are discussed herein below with respect to FIG. 4. Once the parameters are suitably adjusted, the selected exposure system forms a desired lithographic pattern on the wafer (Step 311). This process can be repeated as necessary to fabricate as many layers as needed. FIG. 4 illustrates, in a simplified block diagram, a network architecture suitable for implementing embodiments of the invention. A fleet of exposure systems 411, 412, 413 (embodiments of the invention can implement a fleet having any number of systems) suitably equipped with reticles, stages, chucks, and all the other accouterments of lithographic patterning is in communication with an exposure system control server 401. Such communication can be established by any number or linking technologies (internet, intranet, WAN, LAN, wireless or wired connections and so on). Additionally, a group of metrology tools 421, 422, 423 (the embodiments of the invention contemplate any number of tools) in communication with a metrology system control server 402. Additionally, the databases 404 of accumulated distortion profile information (that characterizes each of the exposure systems) is stored on at least one of the servers 401, 402. The metrology system control server 402 is in direct communication 403 with the exposure system control server 401. This enables high speed communication between the two servers and also enables high speed communication between the databases and the exposure and metrology tools. Accordingly, such an architecture enables the real time transmission of information to the fleet of exposure tools enabling real-adjustment of high order distortion parameters. A user interface 405 enables control and input of data to the system if desired. Another aspect of the invention is further disclosed with respect to the optional steps (Steps 313, 315) disclosed in FIG. 3. The system is not forced to rely on characterization information provided using test wafers only. Because the system employs metrology devices to continuously test production wafers (Step 313), the system is awash in production data which can be used to influence parameter adjustments. This continuous stream of metrology measurements of production wafers can provide information that can be used to gauge the drift in measurements over time. Thus, exposure systems which begin to drift to far out of alignment can be recognized. Once recognized, these tools can be subjected to a re-characterization process wherein test wafers are run with a suspect exposure tool to determine if the initial distortion correction parameter settings are correct. Alternatively, such re-characterization can reveal that there is a need to adjust the system parameters to recalibrate the distortion profiles thereby enabling the exposure system to again provide satisfactory output (Step 315). In one other implementation, the production metrology data can be used to update the profiles without the need for re-characterization using test wafers. The data obtain from production wafer metrology is typically corrected for reticle error, existing error in the reference pattern, and surface topology related errors caused by the presence of preexisting surface layers. Also, certain corrections must be made to deal with the lower signal-to-noise ratios experienced when using production wafer information. The inventors point out that in one specific example of a proposed methodology, the mix & match database of distortion profiles can be dynamically updated over time, instead of remaining a static set of correctibles that is constant over time. In one implementation, this can be accomplished by using the overlay data that is collected on product wafers to refresh the database contents. In one scenario, a mix & match (M&M) database contains an array of up to L2×N2 correctible sets where N is the number of exposure tools and L the number of illumination conditions in the exposure tool fleet. Thus, one basic element of the database is a combination of exposure tool and illumination condition which indicates the sequence of subsequent layer exposures and not a specific exposure tool and illumination condition representing a specific exposure event. Although this substantially enlarges the size of the database, it significantly improves the functionality of the database and obviates the need to know which scanner in a sequence of two subsequent exposures is responsible for the drift or change. As indicated above, an added database refinement expands the database to store data from different reticle sets, i.e. different product separately. An alternative to this is described in the section below on reticle errors. A practical aspect to implement such a technique in a timely and efficient fashion comprises utilizing the direct data exchange link between the metrology server and the exposure tool fleet control server. As pointed out briefly above, production data can be used to update the distortion profiles in the database. However, one issue with using such data is that errors and distortions in product reticles must be taken into account or compensated for. This is because these effects can vary from reticle to reticle and from wafer lot to wafer lot independently of the exposure tool sequence. Therefore, in one implementation, the distortions and errors in each reticle used are independently characterized by an alternative method. For example, direct reticle feature placement metrology can be performed on all of the reticles participating in the exposure sequence. Such can be conducted using, for example, a reticle metrology tool such as a Leica iPRO system available from Leica Microsystems, Inc. of Chantilly, Va. Once the reticles are characterized, the reticle error can be removed from information obtained during production metrology data prior to incorporation of the data in the data base. Additionally, instead of taking into consideration only the errors introduced by the presently patterning reticle, the production data can be made more accurate by taking into account the existence of feature placement errors in the product reticles used in the previous product exposures. Thus, compensation data can account for errors in the underlying reference pattern (e.g., reticle errors in the reticle used to form the reference pattern) as well as errors in the reticle being used to fabricate the current layer. Such reticle error data can be made available in a number of ways including through access to a reticle data base that includes all such data as part of the distortion profile data base, or direct file input of the reticle data, or by accessing a fabrication facility host computing system. As an aside, the inventors point out that the nature of the linear errors discrepancies between different scanners can easily be corrected for. It is common practice today to routinely correct for the linear overlay errors between subsequent exposure steps leaving the higher order terms to be managed by different strategies. By linear error, we mean (as indicated above) that overlay errors between two subsequent patterning steps that can be modeled as a linear function of the spatial location across a field or across a wafer. These are supplemented by the high order distortion information that remains after linear corrections are implemented. With further reference to FIG. 3, the operations identified by Steps 313 and 315 enable an evolving data base of distortion profiles to be generated. For example, an initial set of set of distortion profiles is obtained from the pre-production characterization using target wafers. This data could then used to generate an initial differential mix and match database by subtracting results from all combinations if desired. Many other ways of employing such data will be apparent to those of ordinary skill. In one embodiment, this initial database can then used as the basis from which an evolving database is generated as new production data becomes available. The updated database can make available a steadily improving set improved set of correction parameters applicable to subsequent production. The inventors point out that, since the production wafer overlay is also impacted by previous and current layer reticle errors, they must be accounted for. In one implementation, these errors are superimposed on the improved set of correction parameters from the database before application to an exposure system. After exposure, further overlay metrology is performed and the data is used to update the database. However, this data is typically imperfect and can be “contaminated” by reticle previous and present reticle distortions. The data can be “corrected” to account for these reticle induced distortions prior to entry into the database. Additionally, if desired, two separate databases can be used, one the mix & match database where each element in the database is a particular exposure tool/illumination combination generated by on wafer overlay metrology and the other a reticle error database generated by direct feature placement metrology on the reticle. Since the production data is of finite accuracy and precision, it may also be desirable to keep production “correctibles” (or correction data) generated by metrology tools in the database, but to generate modified correctibles by using noise reduction techniques (one example being to use a “moving average” of the production data). Additionally, the inventors contemplate the employment of sampling methodologies to enhance the accuracy of the distortion profile database and otherwise enhance the data. Such sampling can be employed at the front end when the exposure systems are characterized and also to the metrology data obtained during the production stage. In order to enable high order parameter correction data to be extracted from production data, enhanced sampling is implemented beyond that currently used in standard production metrology. Standard overlay metrology sample plans are designed to enable linear models and hence typically use only 4 to 5 alignment sites (e.g., overlay targets) per field and perhaps up to 9 fields per wafer. As explained herein, the methodologies disclosed herein correct for high order distortion. In order for production data to be useful in modeling such high order distortion, more overlay metrology (e.g., misregistration monitoring) sites are generally required. For example, if up to 3rd order polynomial spatial behavior is to be modeled then a minimum of 10 sites per field are typically used to enable twenty or so free parameters that are used in the model of high order distortion behavior. In practice, much higher density sampling would be used in order to achieve reasonable levels of statistical uncertainty in the high order model. A similar situation exists for the wafer level high order sampling. It should be noted however, that if certain specific information is available about the sources of variation in the overlay data in advance, then this can be used to generate an optimized sample plan to best characterize these sources of variation. By way of example, if it is known that the high order field dependence of the overlay is different for different scan directions in the case of a scanner, then the sample plan should ensure coverage of fields printed with all combinations of scan directions of the two subsequent exposure steps. Again, the information regarding the direction of scan as well as other lithographic data of significance in determining the sample plan can be made available by a direct link between the database device and the exposure tool fleet management system. In one embodiment, the sampling can be used to obtain only data from a select group of wafers. For example, when used in initial characterization, a group of test wafers is provided and patterns are formed thereon using exposure tools. The wafers are then subject to metrology to determine the degree of distortion in the exposure systems (reticles, stages, chucks, illumination conditions and so on). However, rather than just randomly select the wafers to use in obtaining the characterization data, only selected wafers will be used in such analysis. For example, the degree of alignment with overlay targets can be determined. In one example, a set of wafers demonstrates a varying degree of alignment with the targets. A first wafer is aligned with respect to 99% of the targets, a second wafer to 99% of the targets and so on until all of the wafers in a lot are characterized. In the following examples, the alignment of a group of wafers includes alignment percentages as follows: 99, 98, 99, 81, 65, 99. A threshold can be chosen by the process engineer. For example, the threshold can be set to accept only wafers having an alignment with 99% of the targets or better. Alternatively, different alignment criteria could be used (e.g., only wafers having alignment of 85% or less, if a worse case scenario is desired). Thus, a first group of wafers is selected to meet the threshold criteria. Only the wafers meeting the threshold criteria are then evaluated. Thus, in the above case, the highly aligned wafers can be used to provide a highly accurate data concerning exposure system distortion. Under such circumstances the 99% group provides a group of wafers having satisfactory alignment. Additionally, where production data is used (instead of target wafers) a similar threshold concept can be used to select the production wafers that will be used. This is where it becomes advantageous to have production wafers having a large number of alignment targets as, for example, indicated above. Thus, the best wafers are used to obtain the most representative distortion information. Also, poorly aligned production wafers can be used to give indications of the worst-case distortion scenarios. By monitoring the evolution of the scanner matching database over time, it is possible to monitor the stability of the exposure tools and to use this data to generate preventive maintenance when certain parameters go beyond control boundaries. Although production data always contains overlay signatures resultant from two subsequent exposures, by summing (or any other reasonable algebraic operator) over all data from a single exposure tool, it is generally possible to differentiate effects from different tools and to identify problematic exposure systems. In one approach, the distortion profile information can be updated in accordance with a predetermined schedule. Perhaps every three months a re-characterization of the exposure system is conducted using an analysis of a new batch of test wafers. Additionally, the post-production metrology analysis of wafer pattern alignment can be used to identify a time-based drift in a fabricated wafer pattern. Once the drift extends beyond a specified threshold re-characterization can be done. Additionally, under such circumstances the inventors contemplate that the distortion profile information can be updated using production metrology information. One concern in the use of metrology data from production wafers is that the quality of the metrology data may be influenced by the significant additional processing applied to these wafers compared with test wafers. In order to mitigate this risk, one option is to apply a weighting function or even reject production data based on metrology diagnostic data. One example of such a process is disclosed in U.S. Pat. No. 6,928,628 issued 9 Aug. 2005 by Seligson et al., which is directed to target diagnostics. The aforementioned patent is incorporated herein by reference in its entirety for all purposes. The invention employs a combination of hardware and software components. The software can be embodied as computer readable code (or computer program code) on a computer readable medium. The computer readable medium is any data storage device that can store data which can thereafter be read by a computer system. Examples of the computer readable medium include read-only memory, random-access memory, CD-ROMs, magnetic tape, and optical data storage devices. The computer readable medium can also be distributed over a network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion. In one implementation the computer readable medium comprises memory of the server systems 401, 402 of FIG. 4. The many features and advantages of the present invention are apparent from the written description, and thus, it is intended by the appended claims to cover all such features and advantages of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation as illustrated and described. Hence, all suitable modifications and equivalents may be resorted to as falling within the scope of the invention.
	abstract	An elongated control rod guide thimble for a nuclear reactor having a tube-in-tube dashpot design that has circumferential slots in the dashpot walls that align with spaced openings in the guide thimble sheath. The dashpot tube has an end plug with a threaded opening extending axially therethrough which is captured by a thimble screw that extend through an opening in the bottom nozzle and sandwiches an end plug attached to the guide thimble sheath between the dashpot tube end plug and the bottom nozzle.
043137970	description	BEST MODE FOR CARRYING OUT THE INVENTION FIG. 1 illustrates a fuel assembly 10, oriented with its longitudinal axis in the vertical plane. Said assembly has a lower end fitting 11 and an upper end fitting 12, vertically supporting a plurality of longitudinally extending parallel members, including fuel rods 13, guide tubes 14 and an instrument tube (not shown). The fuel rods 13 and guide tubes 14 are laterally braced and spaced by spacer grids 15. As shown in FIG. 2, each spacer grid is made of a plurality of grid plates 21 and 22 which are slotted and fitted together in "egg-crate" fashion. The intersecting grid plates form a plurality of cellular voids, each void accommodating the extension therethrough of a parallel member. Cellular void 23 accommodates a fuel rod 13 while cellular void 24 accommodates a guide tube 14. Because the fuel assembly 10 typically contains more fuel rods than guide tubes, spacer grid 15 contains more voids 23 than voids 24, a single void 24 being surrounded by a plurality of voids 23. Each cellular void has four walls, said walls being comprised of those sections of intersecting grid plates which define and face the void. For example, FIG. 2 shows the walls 30 of cellular void 23. The walls of void 23 contain appendages, like indentations 25, which engage and support the fuel rod 13. The walls of cellular void 24 have appendages, like indentations 26, which are called saddles. As shown, the saddles 26 have a concave surface to accommodate the cylindrical guide tube. Note that the guide tube 14 has a larger diameter than the fuel rod 13, this difference in size being responsible for the different configuration of void 23 vis-a-vis void 24. Despite this difference in configuration, the center-to-center distance L.sub.1 between adjacent voids accommodating fuel rods is equal to the center-to-center distance L.sub.2 between a void accommodating a guide tube and an adjacent void accommodating a fuel rod. FIGS. 3 and 4 illustrate guide tube sleeve 100, including deflecting tabs 101 and openings 102. Tabs 101 are made of rectangular segments of the sleeve wall which are folded outwardly. Openings 102 accommodate tab-making tools, thus facilitating the formation of said tabs. FIGS. 3 and 5 illustrate notched-slot 110 which is a square shaped notch 111 superimposed over a slot 112. That part of the sleeve between two adjacent slots is called a finger 113. The notched-slot 110 is located at either end of the sleeve 100, and is used to anchor the sleeve to a spacer grid as illustrated in FIGS. 6, 7 and 8. Slots 112 give the fingers 113 a measure of flexibility. To install the sleeve, the fingers 113 are flexed inwardly slightly while the notched-slot end of the sleeve is pushed into void 24. The sleeve is pushed into the void 24 until the notch 111 fully surrounds a saddle 26, as shown in FIGS. 6 & 7. In the engaged position, each corner of void 24 accommodates the top of a finger 113, as shown in FIG. 8. Secured in this manner, vertical, horizontal and rotational movement of the sleeve is precluded. For purposes of clarification, it should be noted that FIG. 2 shows a guide tube without its surrounding sleeve while FIG. 8 shows a sleeve without its surrounded guide tube. Each sleeve, except for the notched-slot end extending partway into the supporting spacer grid, is no longer than the vertical distance between two adjacent spacer grids. There may be more than one sleeve per guide tube, each sleeve being disposed between a pair of adjacent spacer grids. Therefore, if desired, a guide tube may be covered throughout its entire length by a series of sleeves arranged end-to-end. FIG. 1 illustrates longitudinal flow channels 80 and 81, being the space between adjacent parallel members. A coolant, usually water, is circulated through the flow channels, the coolant usually entering from the b 5 of the fuel assembly and exiting at the top of said assembly. The size of the flow channel depends upon the type of members which define said channel. For example, in FIG. 9, the cross-sectional area of flow channel 81 is defined by 4 adjacent fuel rods 13. Contrast the size of flow channel 81 to the size of flow channel 80 shown in FIG. 10. Flow channel 80 is defined by 3 fuel rods 13 and a guide tube 14. Because the diameter of the guide tube is larger than that of the fuel rod, and because all the cellular voids of the spacer grid have equal center-to-center distances, the size of channel 80 is smaller than that of 81. This difference in size affects the flow of coolant, there being more flow in channel 81 than in channel 80. Coolant flow is also affected by gap size. Gap size is the shortest distance between two adjacent parallel members. In FIG. 9, the gap between two fuel rods is designated by numeral 41. In FIG. 10, the gap designated by numeral 40 is the distance between a fuel rod 13 and a guide tube 14. Gap 40 is smaller than gap 41 for the same reasons given above concerning the relative sizes of flow channels 81 and 80. Because of this difference in gap size, there will be more coolant flow through gap 41 than through gap 40. The tabs 101 projecting from sleeve 100 serve to increase the rate of coolant flow through tap 40 and through flow channel 80. The tabs also serve to otherwise modify the flow of coolant, causing a mixing action in the immediate area surrounding the guide tubes. The increased rate of coolant flow as well as the mixing action results in an increased heat transfer rate and a general enhancement of the coolant's effectiveness thereby increasing the operating capacity of the reactor. FIG. 3 shows the preferred embodiment of tab 101, that being a flat tab inclined 30.degree. from the vertical. FIG. 6 shows an alternative embodiment of tab 101, said tab having a slight twist. While in accordance with the provisions of the statutes, there is illustrated and described herein a specific embodiment of the invention, those skilled in the art will understand that changes may be made in the form of the invention covered by the claims and that certain features of the invention may sometimes be used to advantage without a corresponding use of the other features.
	summary
	abstract	A control rod drive mechanism (CRDM) configured to latch onto the lifting rod of a control rod assembly and including separate latch engagement and latch holding mechanisms. A CRDM configured to latch onto the lifting rod of a control rod assembly and including a four-bar linkage closing the latch, wherein the four-bar linkage biases the latch closed under force of gravity.
	claims	1. An illumination optical unit configured to illuminate an object field in which an object to be imaged is arrangeable, the illumination optical unit comprising:a field facet mirror comprising a plurality of field facets arranged in a region of a field plane of the illumination optical unit;a pupil facet mirror comprising a plurality of pupil facets in a region of a pupil plane of the illumination optical unit;a correction control device; andcorrection actuators,wherein:each of the field facets is configured to transfer used illumination light from a light source to respectively one of the pupil facets;the illumination optical unit is configured so that, during use of the illumination optical unit via respectively one illumination channel, a respective used illumination light partial beam is guided between the light source and the object field via exactly one field facet and exactly one pupil facet;a transfer optical unit is downstream of the field facet in the respective illumination channel;the transfer optical unit is configured to superimposedly image the field facets into the object field;for each illumination channel, the transfer optical unit respectively includes one of the pupil facets to transfer the illumination light partial beam from the field facet toward the object field;at least some pupil facets, which are usable as correction pupil facets, are arranged in the beam path of the illumination light partial beam impinging thereon so that an image of the light source arises at an image location which lies at a distance from the pupil facet along the illumination channel;the correction control device is configured to controlledly displace at least some of the field facets, which are assigned to the correction pupil facets via the respective illumination channels and which are usable as correction field facets, via the correction actuators which are connected to the correction field facets;the correction control device and the correction actuators are configured so that a correction displacement travel of the correction field facets in a correction displacement range is so large that a respective correction illumination channel is cut off by an edge of the correction pupil facet so that the illumination light partial beam is not transferred in the entirety thereof from the correction pupil facet into the object field; andthe illumination optical unit an EUV lithography illumination optical unit. 2. The illumination optical unit of claim 1, wherein the correction actuators are configured to continuously displace the correction field facets. 3. The illumination optical unit of claim 2, wherein the correction actuators are configured to displace the correction field facets about two mutually perpendicular axes. 4. The illumination optical unit of claim 2, wherein:the object is displaceable along an object displacement direction; andan arrangement geometry of guiding the illumination light via the illumination channels is such that a cross section of the respective illumination channel on the correction pupil facets has a marginal contour so that, over a variable of the correction displacement path, the cross section in a direction perpendicular to the object displacement direction is marginal trimmed or cut off during use of the illumination optical unit. 5. The illumination optical unit of claim 2, wherein:the object is displaceable along an object displacement direction; andan arrangement geometry of guiding the illumination light via the illumination channels is such that a cross section of the respective illumination channel on the correction pupil facets has a marginal contour so that, over a variable of the correction displacement path, the cross section in a direction parallel to the object displacement direction is marginal trimmed or cut off during use of the illumination optical unit. 6. The illumination optical unit of claim 2, wherein the illumination optical unit is configured to determining, by way of a direction of the correction displacement path, whether trimming of the cross section of the illumination channel is carried out centrally or marginally when seen in a dimension perpendicular to a trimmed or cut off edge or margin. 7. The illumination optical unit of claim 2, wherein the field facets comprise arcuate field facets. 8. The illumination optical unit of claim 1, wherein the correction actuators are configured to displace the correction field facets about two mutually perpendicular axes. 9. The illumination optical unit of claim 1, wherein:the object is displaceable along an object displacement direction; andan arrangement geometry of guiding the illumination light via the illumination channels is such that a cross section of the respective illumination channel on the correction pupil facets has a marginal contour so that, over a variable of the correction displacement path, the cross section in a direction perpendicular to the object displacement direction is marginal trimmed or cut off during use of the illumination optical unit. 10. The illumination optical unit of claim 1, wherein:the object is displaceable along an object displacement direction; andan arrangement geometry of guiding the illumination light via the illumination channels is such that a cross section of the respective illumination channel on the correction pupil facets has a marginal contour so that, over a variable of the correction displacement path, the cross section in a direction parallel to the object displacement direction is marginal trimmed or cut off during use of the illumination optical unit. 11. The illumination optical unit of claim 1, wherein the illumination optical unit is configured to determining, by way of a direction of the correction displacement path, whether trimming of the cross section of the illumination channel is carried out centrally or marginally when seen in a dimension perpendicular to a trimmed or cut off edge or margin. 12. The illumination optical unit of claim 1, wherein the field facets comprise arcuate field facets. 13. An illumination system, comprising:an illumination optical unit according to claim 1; anda light source configured to produce the illumination light. 14. An optical system, comprising:an illumination optical unit, comprising:an illumination optical unit according to claim 1; anda light source configured to produce the illumination light; anda projection optical unit configured to image the object field into an image field. 15. An optical system, comprising:an illumination optical unit, comprising:an illumination optical unit according to claim 2; anda light source configured to produce the illumination light; anda projection optical unit configured to image the object field into an image field. 16. An apparatus, comprising:an illumination optical system, comprising:an illumination optical unit according to claim 1; anda light source configured to produce the illumination light;a projection optical unit configured to image the object field into an image field;an object holder comprising an object displacement drive configured to displace the object along an object displacement direction; anda wafer holder comprising a wafer displacement drive configured to displace a wafer in a manner synchronized with the object displacement drive,wherein the apparatus is a projection exposure apparatus. 17. A method of using a projection exposure apparatus comprising an illumination optical unit and a projection optical unit, the method comprising:using the illumination optical unit to illuminate at least a portion of an object in an object field; andusing the projection optical unit to project at least a portion of the illuminated object into an image field,wherein the illumination optical unit is an illumination optical unit according to claim 1. 18. A method for prescribing an intended distribution of an illumination light intensity over a field height of an object field of a projection exposure apparatus including an illumination optical unit for illuminating the object field, in which an object to be imaged that is displaceable transversely to the field height in an object displacement direction is arrangeable, a field facet mirror comprising a plurality of field facets being arranged in a region of a field plane of the illumination optical unit, a pupil facet mirror comprising a plurality of pupil facets arranged in a region of a pupil plane of the illumination optical unit, each of the field facets configured to transfer used illumination light from a light source to respectively one of the pupil facets, via respectively one illumination channel, a respective used illumination light partial beam being guided between the light source and the object field via exactly one field facet and exactly one pupil facet, a transfer optical unit downstream of the field facet in the respective illumination channel and configured to superposedly image the field facets into the object field, for each illumination channel the transfer optical unit respectively comprising one of the pupil facets for transferring the illumination light partial beam from the field facet toward the object field, the method comprising:using at least some pupil facets as correction pupil facets, which are arranged in the beam path of the illumination light partial beam impinging thereon in such a way that an image of the light source arises at an image location which lies at a distance from the pupil facet along the illumination channel;displacing, in a controlled manner, at least some of the field facets as correction field facets, which are assigned to the correction pupil facets via the respective illumination channels, with a correction control device via correction actuators that are connected to the correction field facets; andselecting a correction displacement travel of the correction field facets within a correction displacement range in such a way that a respective correction illumination channel is cut off by an edge of the correction pupil facet so that the illumination light partial beam is not transferred in the entirety thereof from the correction pupil facet into the object field. 19. A method for prescribing a minimum illumination intensity of illumination light over a transverse field coordinate of an object field of an illumination optical unit for projection lithography, an object to be imaged being arrangeable in the object field, the transverse field coordinate extending transversely to an object displacement direction along which the object is displaceable, the illumination optical unit comprising two facet mirrors arranged in succession in the beam path of the illumination light so that, via respectively one illumination channel, a respective used illumination light partial beam is guided between a light source and the object field via exactly one facet of the first facet mirror and exactly one facet of the second facet mirror, the method comprising:identifying a minimum intensity transverse field coordinate at which the overall illumination intensity of the illumination light partial beams that are guided via all illumination channels is minimal;identifying at least one illumination channel in which a variation of a marginal trimming or cut off of the illumination light partial beam, which is guided thereover, at the second facet leads to an increase in an illumination intensity of this illumination light partial beam at the minimum intensity transverse field coordinate; andaligning the first facet of this illumination channel for increasing the illumination intensity thereof at the minimum intensity transverse field coordinate. 20. The method of 19, further comprising:identifying at least one illumination channel, in which a variation of a marginal trimming or cut off of the illumination light partial beam, which is guided thereover, at the second facet leads to an increase in a minimum illumination intensity of this illumination light partial beam over the transverse field coordinate; andaligning the first facet of this illumination channel for increasing this minimum illumination intensity.
	summary
	summary
	summary
	description	The present invention relates to a composition for transmuting a radioactive substance into a non-radioactive substance using complex microorganisms and a method for preparing the composition. A fundamental solution to safe disposal of spent nuclear fuel as high-level radioactive nuclear waste as well as intermediate-level and low-level radioactive waste from nuclear power plants is a prerequisite for continuous utilization of nuclear power plants as large-scale energy sources. Despite this situation, a satisfactory fundamental solution to the disposal of radioactive waste has not been proposed so far. Long-term storage in safe places is accepted as the only way to dispose of radioactive waste. However, radioactive waste disposal facilities do not provide a fundamental solution to radioactive waste disposal due to their limited storage capacity. No approach can be considered as a fundamental solution to nuclear waste disposal as long as radioactive substances remain untransmuted while emitting radioactive rays. A fundamental solution to this situation is required to drastically reduce radioactive waste. For example, techniques for transmuting Cs-137 as a radionuclide into safe, non-radioactive elements Ba-137 or Ba-138 can be considered. However, no satisfactory techniques have yet been put to practical use. Transmutation of radionuclides is observed mainly in radioactive substances with high atomic number. According to recent studies on cold nuclear fusion, transmutation with very low energy input at room temperature is observed. This phenomenon is not described by current nuclear physics theories. In the academic literature, transmutation is represented by neologisms such as “low energy nuclear reaction (LENR)”, “lattice assisted nuclear reaction (LANR)”, “condensed matter nuclear science (CMNS)”, and “chemically assisted nuclear reaction (CANR)”, which are used to distinguish transmutation from conventional nuclear reactions. In connection with radioactive waste disposal using microorganisms, several techniques have been reported in South Korea. For example, Korean Patent No. 10-1754790 discloses the use of microorganisms for the capture of radioactive substances to prevent groundwater from being contaminated by the diffusion of radioactive substances. The purpose of this technique is to transmute a radioactive substance (cesium ion) into a sparingly water soluble substance (pautovite) to prevent the diffusion of contamination. However, this technique fails to transmute a radioactive substance into a safe element and cannot fundamentally reduce the risk of radioactive contamination. Thus, successful transmutation of radioactive elements in radioactive waste into safe elements can provide a fundamental solution to radioactive waste disposal. It is an aspect of the present invention to provide a composition for transmuting a radioactive substance into a non-radioactive substance comprising complex microorganisms. It is another aspect of the present invention to provide a method for preparing a composition for transmuting a radioactive substance into a non-radioactive substance. It is a further aspect of the present invention to provide a method for transmuting a radioactive substance into a non-radioactive substance, comprising bringing the composition described herein into contact with a radioactive substance. One aspect of the present invention relates to a composition for transmuting a radioactive substance into a non-radioactive substance comprising complex microorganisms. The complex microorganisms may include two or more species selected from the group consisting of radiation-resistant microorganisms, yeast, fungi, photosynthetic bacteria, and green algae. As an example, the complex microorganisms may include at least three, more specifically at least four species selected from the group consisting of radiation-resistant microorganisms, yeast, fungi, photosynthetic bacteria, and green algae. The complex microorganisms include a radiation-resistant microorganism, yeast, a fungus, a photosynthetic bacterial species, and a green alga, which is preferred in terms of transmutation efficiency. As a further example, the complex microorganisms essentially include a radiation-resistant microorganism and a photosynthetic bacterial species and may optionally further include at least one species selected from the group consisting of yeast, fungi, and green algae. As another example, the complex microorganisms essentially include a radiation-resistant microorganism, a photosynthetic bacterial species, and yeast and may optionally further include at least one species selected from the group consisting of fungi and green algae. As another example, the complex microorganisms essentially include a radiation-resistant microorganism, a photosynthetic bacterial species, and a fungus and may optionally further include at least one species selected from the group consisting of yeast and green algae. As another example, the complex microorganisms essentially include a radiation-resistant microorganism, a photosynthetic bacterial species, and a green alga and may optionally further include at least one species selected from the group consisting of fungi and yeast. In the present invention, it was found that the microorganisms have no ability to transmute a radioactive substance into a non-radioactive substance when used alone but have the ability to transmute a radioactive substance into a non-radioactive substance when used in combination. Any radiation-resistant microorganism that can survive even in the presence of radioactive substances may be used in the present invention. The radiation-resistant microorganism may be, for example, Deinococcus sp., Cryptococcus sp. or Bacillus sp. Specifically, the radiation-resistant microorganism may be Deinococcus radiodurans, Bacillus safensis or Bacillus pumilus but is not limited thereto. As an example, the radiation-resistant microorganism may be a Bacillus safensis strain (KCCM12163P) or a Bacillus pumilus strain (KCCM12165P). The two strains were deposited with the Korean Culture Center of Microorganisms (120-861, Hongje-2ga-Gil, Seodaemun-Ku, Seoul, Korea) on Nov. 10, 2017, respectively. Any yeast that has antioxidant activity may be used in the present invention. The yeast may be, for example, Cryptococcus sp., Saccharomyces sp. or Trichosporon sp. Specifically, the yeast may be Saccharomyces boulardii, Saccharomyces servazzii, Saccharomyces cerevisiae, Trichosporon cutaneum and/or Trichosporon loubieri but is not limited thereto. As an example, the yeast may be a Saccharomyces servazzii strain (KCCM12157P) and/or a Trichosporon loubieri strain (KCTC10876BP). The Trichosporon loubieri strain (KCTC10876BP) is known from U.S. Pat. No. 8,034,605B2, the entire disclosure of which is hereby incorporated by reference. The Saccharomyces servazzii strain (KCCM12157P) was deposited with the Korean Culture Center of Microorganisms (120-861, Hongje-2ga-Gil, Seodaemun-Ku, Seoul, Korea) on Nov. 10, 2017. Any fungus that has antioxidant activity may be used in the present invention. The fungus may be, for example, Irpex sp. or Phanerochaete sp. Specifically, the fungus may be Irpex lacteus, Irpex hydnoides, Phanerochaete chrysosporium or Phanerochaete sordida but is not limited thereto. The Phanerochaete chrysosporium strain (KCCM10725P) is known from Korean Patent No. 10-0903666, the entire disclosure of which is hereby incorporated by reference. Any photosynthetic bacterial species that can use light energy to assimilate carbon dioxide may be used in the present invention. The photosynthetic bacterial species may be, for example, Rhodobacter sp., Chlorobium sp., Chromatium sp., Rhodospirillum sp., or Rhodopseudomonas sp. More specifically, the photosynthetic bacterial species may be Rhodobacter sphaeroides or Rhodobacter capsulatus but is not limited thereto. Without being bound by theory, since the photosynthetic bacterial species uses protons (H+) for carbon dioxide assimilation, the function of the photosynthetic bacterial species is assumed to play an important role in the ability of the complex microorganisms to transmute a radioactive substance into a non-radioactive substance. Any green alga that has a green color due to the presence of chlorophyll may be used in the present invention. The green algae may be, for example, Trebouxia sp., Stichococcus sp., Ehptochloris sp. or Coccomyxa sp. Specifically, the green algae may be Coccomyxa viridis or Stichococcus sp. but is not limited thereto. The complex microorganisms may be used in the form of culture broths including their respective cultures. The supernatants may be removed from the culture broths before use. Alternatively, the culture broths may be concentrated and mixed before use. The composition of each culture may further include not only one or more ingredients necessary for the culture of the corresponding microorganism but also one or more ingredients exerting a synergistic effect on the growth of the microorganism. The composition of each culture can be readily determined by those skilled in the art. Each of the complex microorganisms may be present at a concentration of 0.5×102 CFU/ml to 2.5×1010 CFU/ml, specifically 5×103 CFU/ml to 5×1010 CFU/ml, more specifically 1×105 CFU/ml to 5×109 CFU/ml in the composition. The complex microorganisms may be present in a total amount of 0.05% by weight to 60% by weight, specifically 5% by weight to 50% by weight, more specifically 10% by weight to 40% by weight, based on the weight of the composition. The radioactive substance refers to a substance capable of emitting radioactive rays such as α, β or γ-rays. For example, the radioactive substance may be cesium (Cs), uranium, iodine, strontium, iridium, radium or plutonium. In the present invention, it was found that the radioactive substance is transmuted into a non-radioactive substance by the complex microorganisms. The weight ratio of the complex microorganisms to the radioactive substance may be from 9.9:0.1 to 0.1:9.9, specifically from 8:2 to 2:8, more specifically from 7:3 to 3:7. The composition and/or the complex microorganisms may be in a liquid or dry state, specifically in the form of a dry powder. The composition may further include an environmentally acceptable carrier. In this case, the composition may be formulated with the carrier to dispose of radioactive waste or to treat soil, groundwater and/or wastewater, contaminated with radioactive substances. The term “environmentally acceptable carrier” as used herein refers to a carrier or diluent that causes no environmental damage and does not deteriorate the biological activity and properties of the complex microorganisms. When formulated into a liquid solution, the acceptable carrier may be selected from saline solution, sterilized water, buffered saline, dextrose solution, maltodextrin solution, glycerol, and mixtures thereof that are suitable as nutrients for the complex microorganisms. If necessary, one or more general additives, such as antioxidants, buffer solutions, and bacteriostatic agents may be added to the composition. The composition of the present invention may be formulated into a liquid preparation such as an aqueous solution, suspension or emulsion or a solid preparation such as a powder. In this case, the composition of the present invention may further include one or more additives selected from diluents, dispersants, surfactants, binders, and lubricants. A binding agent, an emulsifier or a preservative may be further added to the composition to prevent the quality of the composition from deteriorating. Another aspect of the present invention relates to a method for preparing a composition for transmuting a radioactive substance into a non-radioactive substance comprising complex microorganisms. The complex microorganisms may include two or more species selected from the group consisting of radiation-resistant microorganisms, yeast, fungi, photosynthetic bacteria, and green algae. As an example, the complex microorganisms may include at least three, more specifically at least four species selected from the group consisting of radiation-resistant microorganisms, yeast, fungi, photosynthetic bacteria, and green algae. The complex microorganisms include a radiation-resistant microorganism, yeast, a fungus, a photosynthetic bacterial species, and a green alga, which is preferred in terms of transmutation efficiency. As a further example, the complex microorganisms essentially include a radiation-resistant microorganism and a photosynthetic bacterial species and may optionally further include at least one species selected from the group consisting of yeast, fungi, and green algae. As another example, the complex microorganisms essentially include a radiation-resistant microorganism, a photosynthetic bacterial species, and yeast and may optionally further include at least one species selected from the group consisting of fungi and green algae. As another example, the complex microorganisms essentially include a radiation-resistant microorganism, a photosynthetic bacterial species, and a fungus and may optionally further include at least one species selected from the group consisting of yeast and green algae. As another example, the complex microorganisms essentially include a radiation-resistant microorganism, a photosynthetic bacterial species, and a green alga and may optionally further include at least one species selected from the group consisting of fungi and yeast. Details of the complex microorganisms, the carrier, and the kinds and contents of the ingredients are the same as those described for the composition. The method may include culturing complex microorganisms individually or at least partially together. The individual microorganisms can be cultured by suitable methods known in the art. Natural or synthetic media can be used to culture the complex microorganisms. Examples of carbon sources of the media include, but are not limited to, glucose, sucrose, dextrin, glycerol, and starch. Examples of nitrogen sources of the media include, but are not limited to, peptone, meat extract, whole milk powder, yeast extract, dried yeast, soybean, ammonium salt, nitrate and other organic and inorganic nitrogenous compounds, and sulfur-containing compounds. One or more inorganic salts may be added to each medium. Examples of such inorganic salts include, but are not limited to, magnesium, manganese, calcium, iron, potassium, sodium, boron, molybdenum, copper, cobalt, and zinc salts. Each medium may further include one or more compounds selected from amino acids, vitamins, nucleic acids, and compounds related thereto. The microorganisms may be cultured at a temperature of 20° C. to 40° C. or 25° C. to 35° C. for 12 hours to 7 days or 12 hours to 5 days. The complex microorganisms may be in the form of a mixture of culture solutions obtained by individual culture of the respective strains or a mixture of culture solutions obtained by co-culture of the strains. Alternatively, the complex microorganisms may be in the form of a mixture of the strains isolated from the culture solutions. The method may further include adding an environmentally acceptable carrier to the complex microorganisms or a culture solution, mixture or dried product thereof. The complex microorganisms can be formulated with the carrier to dispose of radioactive waste or to treat soil, groundwater and/or wastewater contaminated with radioactive substances. Next, the method may include formulating the composition into a liquid or solid preparation. When formulated into a liquid solution, the acceptable carrier may be selected from saline solution, sterilized water, buffered saline, dextrose solution, maltodextrin solution, glycerol, and mixtures thereof that are suitable as nutrients for the complex microorganisms. If necessary, one or more general additives, such as antioxidants, buffer solutions, and bacteriostatic agents may be added to the composition. The composition of the present invention may be formulated into a liquid preparation such as an aqueous solution, suspension or emulsion or a solid preparation such as a powder. In this case, the composition of the present invention may further include one or more additives selected from diluents, dispersants, surfactants, binders, and lubricants. A further aspect of the present invention relates to a method for transmuting a radioactive substance into a non-radioactive substance, comprising bringing the composition described herein into contact with a radioactive substance. The contact includes mixing the composition comprising complex microorganisms with the radioactive substance, culturing the composition with the radioactive substance, adding the radioactive substance to the composition, or placing the composition and the radioactive substance in the same reaction system, but is not limited thereto. In one embodiment, the contact may include mixing the composition and the radioactive substance with stirring. The contact may be continued in the temperature range of 20° C. to 40° C. or 25° C. to 35° C. for 12 hours to 3 months, 12 hours to 2 months, 24 hours to 60 days or 36 hours to 56 days. The complex microorganisms used in the method of the present invention have an outstanding ability to convert radioactive substances into non-radioactive substances and are of great utility in radioactive waste disposal. In addition, the complex microorganisms are suitable for use in the treatment of soil or groundwater contaminated with radioactive substances or cooling water or wastewater from nuclear power plants. The present invention will be described in more detail with reference to the following examples. However, these examples are provided for illustrative purposes only and the present invention is not limited thereto. A composition comprising complex microorganisms was prepared in the same manner as in Example 1, except that only four of the five culture solutions were used. The four culture solutions were obtained from Bacillus pumilus KCCM12165P, Saccharomyces servazzii KCCM12157P, Phanerochaete chrysosporium KCCM10725P, and Rhodobacter capsulatus. The composition was divided into two groups (“Composition 1” and “Composition 2”), each of which had a concentration of 1×107-109 cfu/ml. A composition was prepared in the same manner as in Example 1, except that only the culture solution of Stichococcus sp. was used. 100 ml of each of Compositions 1 and 2 prepared in Example 1 and Compositions 1 and 2 prepared in Example 2 was mixed with 400 ml of a liquid sample of Cs-137 (half-life: (30.05±0.08) year, 0.1 M HCl aqueous solution, 50 kBq on Mar. 3, 2018, 0.159 mL). 500 ml of the resulting sample was irradiated with light at 12-h intervals while shaking at ˜120 rpm in a shaking incubator at 25° C. Radioactivities from the sample were measured at 24-h intervals. The sample was closed with a lid made of air-permeable, hydrophobic silicon with less water evaporation. The sample including the complex microorganisms and the radioactive isotope was placed on a shaker (DAIHAN Scientific model SHO-2D) and was shaken continuously at ˜100 RPM except for ˜30 min for radiation intensity measurement. The laboratory temperature was maintained at 21-25° C. without artificial temperature control over the entire experimental period. In the laboratory, fluorescent lamps remained turned on during the experiment and turned off after 6 p.m. Two p-type high-purity Ge detectors with relative efficiencies of ˜70% were used to measure radiation intensities. A detection part of each of the Ge detectors is encapsulated in a structure surrounded by a shield to shield gamma rays from the outside. The shield is lined with a 10 cm thick lead plate and a 2 mm thick copper plate. The detector is installed in a vertical cooling system. A sample (or beam source) holder is used to observe the intensities of radiation from the sample with time. The sample holder is designed such that the position of the sample is kept in place relative to the detector. The sample holder is made of an acrylic cylinder and a plate. The sample holder fixes the vertical position of the sample relative to the bottom of the shield. The inner diameter of the cylinder is adapted to the outer diameter of an Erlenmeyer flask containing the sample to fix the horizontal position of the sample. The holder is spaced a distance from the outer periphery of the detector. The detector is fitted into the holder such that the center of the cylinder of the holder coincides with the center of the detector. To this end, the holder is made by cutting an acrylic resin into a doughnut shape. The distances between the upper sides of the detectors and the bottom of the Erlenmeyer flask containing the sample are ˜5 mm and ˜55 mm (FIG. 2). After contact of the complex microorganisms with cesium for a total of 49 days, the count rates of gamma rays per second were measured. The results are shown in FIGS. 3 and 4. Trend lines were plotted based on the above experimental results. When calculated using the trend lines, the effective initial half-life was estimated to be 39 days from the increased count rates of gamma rays from the radioactive isotope 137C with a half-life of 30 years (from April 12 to April 17) and the effective elimination half-life was estimated to be 87 days from the decreased count rates (from April 18 to May 31). These results support the assumption that the increased count rates of gamma rays at the initial stage are due to the decay of Cs-173 and the decreased count rates of gamma rays are because the microorganisms directly biotransmuted Cs-137 into stable isotopes Ba-137 or Ba-138 without accelerating radioactive decay. After contact of the composition including only one microorganism with cesium in each of Comparative Examples 1-7, the count rates of gamma rays per second were measured. The results are shown in FIGS. 6-12. No significant decrease in the count rate of gamma rays was observed when only one microorganism was used, unlike when the complex microorganisms were used. To determine whether transmuAtation occurred, cesium was treated with the microorganisms, as in Experimental Example 1. After storage for 60 days, the solutions were sampled. The concentrations of 137Ba and 138Ba in the samples were analyzed using a high resolution inductively coupled plasma mass spectrometer (HR-ICP-MS). The results are shown in Table 1. TABLE 1Bal37Bal38SampleConcentrationRSDConcentrationRSDNo.name(μg/L)(%)(μg/L)(%)1Control0.17411.640.1240.502D17.1960.8017.0340.833DX23.9740.4723.8380.35D: Composition of Example 2 including the complex microorganisms + average cesium concentration;DX: Composition of Example 1 including the complex microorganisms + average cesium concentration;Control: Cesium-containing composition As can be shown from the results in Table 1, the concentrations of 137Ba and 138Ba in D and DX were ˜100-140 times and ˜142-194 times higher than those in the control containing only cesium without complex microorganisms. These results demonstrate that the radioactive substance 137Cs can be transmuted into non-radioactive substances 137Ba and 138Ba by the complex microorganisms. To determine the viabilities of the microorganisms, cesium was treated with the microorganisms, as in Experimental Example 1. After storage for 60 days, the solutions were sampled. 10 ml of each of the samples was diluted 104-fold with sterile physiological saline. The viability and growth of the strains in solid media (NA, MRS, TSA, PDA) supplemented with different nutrients depending on the strains were observed (see FIG. 5). These results concluded that even when contaminated with a high concentration (50,000 becquerels) of radioactive 137Cs, the complex microorganisms added at the initial stage remained viable at a high concentration (>1×105 cfu/ml).
	claims	1. A radiation image conversion panel comprising a support and provided thereon, a phosphor layer comprising phosphor having a columnar crystal structure,wherein a region in which no phosphor layer is provided on a surface of the support is within 0.5 mm from an edge of the support, and columnar crystals at an edge of the phosphor layer are fused via heat generated by cutting. 2. The radiation image conversion panel of claim 1,wherein the support and provided thereon, the phosphor layer are cut by laser light. 3. The radiation image conversion panel of claim 2,wherein the laser light is UV laser. 4. The radiation image conversion panel of claim 1,wherein the support comprises a metal-coated polymer film. 5. The radiation image conversion panel of claim 4,wherein the metal comprises aluminum or silver as a principal component. 6. The radiation image conversion panel of claim 4,wherein the polymer film is made of any one of polyimide, polyethylene naphthalate, polyethersulfone and polysulfone as a principal component. 7. The radiation image conversion panel of claim 1,wherein the phosphor layer contains the phosphor comprising alkali halide represented by Formula (1) as a principal substance:M1X·aM2X′2·bM3X″3: eA Formula (1)wherein M1 is at least one alkali metal atom selected from the group consisting of Li, Na, K, Rb and Cs; M2 is at least one divalent metal atom selected from the group consisting of Be, Mg, Ca, Sr, Ba, Zn, Cd, Cu and Ni; M3 is at least one trivalent metal atom selected from the group consisting of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Al, Ga and In; X, X′ and X″ each are at least one halogen selected from the group consisting of F, Cl, Br and I; A is at least one metal atom selected from the group consisting of Eu, Tb, In, Cs, Ce, Tm, Dy, Pr, Ho, Nd, Yb, Er, Gd, Lu, Sm, Y, Tl, Na, Ag, Cu and Mg; and a, b and e each are a value within the range of 0≦a <0.5, 0≦b <0.5 and 0<e ≦0.2, respectively. 8. The radiation image conversion panel of claim 1,wherein the phosphor comprises stimulable phosphor 9. A cassette comprising the radiation image conversion panel of claim 1.
	abstract	A process for an intensity-modulated proton therapy of a predetermined volume within an object includes discretising the predetermined volume into a number of iso-energy layers each corresponding to a determined energy of the proton beam. A final target dose distribution is determined for each iso-energy layer. The final target dose distribution or at least a predetermined part of this final target dose distribution is applied by parallel beam scanning by controlling the respective beam sweepers, thereby scanning one iso-energy layer after the other using an intensity-modulated proton beam while scanning a predetermined iso-energy layer.
054066000	claims	1. A container for containing and transporting spent nuclear fuel, comprising: a structural shell defining a cavity for receiving spent nuclear fuel and first and second end apertures opening into the cavity, the shell having a first end portion formed of a first material and a second end portion formed of a second material, the first end portion being joined to the second end portion, wherein the first material has a higher load-bearing strength than the second material; a bearing surface defined on the first end portion and engageable to enable hoisting of the container; a first closure securable to the first end portion of the shell to seal the first end aperture; a second closure securable to the second end portion of the shell to seal the second end aperture; and a radiation absorbing shield layer affixed to the shell. the shell has a tubular configuration; the first end portion of the shell has a tubular configuration and is formed from a first metal; and the second end portion of the shell has a tubular configuration and is formed from a second metal, the first end portion being welded end to end to the second end portion. first and second trunnion mounting structures secured in opposing disposition to the first end portion of the shell; and first and second trunnions, each defining a base and a bearing surface, the base of each trunnion being releasably securable to a corresponding one of the trunnion mounting structures, whereby the bearing surfaces of the trunnions can be grasped to hoist the container. the second closure comprises a second closure plate welded proximate its perimeter to the second ends of the inner shell and the structural shell to create airtight joints therewith; and the first closure comprises: the first closure comprises a first closure plate that is releasably securable to the first end portion of the shell, whereby when secured to the shell the first end aperture of the shell is sealed and when released from the shell permitting loading and unloading of spent nuclear fuel through the first end aperture into the cavity; and the second closure comprises: a second closure plate secured to the second end portion of the shell to seal the second end aperture of the shell, the second closure plate defining a central access aperture; and an access cover plate releasably securable to the second closure plate, whereby when secured to the second closure plate the access aperture is sealed, and when released from the second closure plate permitting access through the access aperture into the cavity of the shell to facilitate unloading of spent nuclear fuel through the first end aperture of the shell. the access aperture shield assembly comprises an annular first shield member filled with a neutron absorbing shield material and defining a central aperture therethrough, the first shield member being releasably securable to the second closure plate to block a perimeter region of the access aperture, thereby reducing its effective width; and a second shield member selectively securable to the first shield member to shield the central aperture defined in the first shield member. 2. The container of claim 1, wherein: 3. The container of claim 2, wherein the first metal comprises a high alloy stainless steel. 4. The container of claim 1, further comprising: 5. The container of claim 4, wherein the first and second trunnion mounting structures each comprise an annular sleeve secured to the first end portion of the shell, the base of each of the first and second trunnions having a cylindrical configuration and being receivable within the corresponding sleeve. 6. The container of claim 5, further comprising third and fourth trunnion mounting structures secured to the shell at a location spaced along a length of the shell from the first and second trunnion mounting structures, and third and fourth trunnions releasably securable to the third and fourth trunnion mounting structures. 7. The container of claim 5, wherein each of the first and second annular sleeves is formed from the first material used to form the first end portion of the shell. 8. The container of claim 5, wherein each of the first and second trunnions defines an internal trunnion cavity, the trunnion cavity being filled with a neutron absorbing shielding material. 9. The container of claim 8, wherein the internal trunnion cavity of each of the first and second trunnions is defined by a recess formed through the base of the trunnion, the neutron absorbing shielding material being enclosed within the trunnion cavity by a backing plate secured within and covering the recess. 10. The container of claim 1, further comprising a key way secured to an exterior surface of the shell, the key way being formed from perimeter frame members that are secured to the shell, thereby defining an engaging structure for use in securing the container during transportation, wherein at least a portion of the perimeter frame members are formed from the first material used to form the first end portion of the shell. 11. The container of claim 1, wherein the structural shell has a tubular configuration and first and second ends defining the first and second end apertures, further comprising a tubular inner shell having first and second ends, the structural shell being assembled coaxially over the inner shell to define an annular space there between, wherein the first closure is secured to the first ends of the structural shell and the inner shell and the second closure is releasably securable to the second ends of the structural and inner shells. 12. The container of claim 11, wherein: 13. The container of claim 12, wherein the first annular sealing surface on the annular member comprises a hardened metal inlay. 14. The container of claim 11, wherein the annular space between the structural shell and the inner shell is filled with a gamma absorbing shield material. 15. The container of claim 14, wherein the radiation absorbing shield layer comprises a jacket secured about an exterior surface of the structural shell and filled with a neutron shielding material. 16. The container of claim 1, wherein the first end portion of the shell defines a first annular sealing surface and the first closure defines a corresponding second annular sealing surface, wherein the first annular sealing surface comprises a hardened metal inlay. 17. The container of claim 16, wherein an annular groove is formed in the second annular sealing surface on the first closure, the annular groove having a half-dovetailed cross section. 18. The container of claim 1, wherein the radiation absorbing shield layer comprises a shield jacket comprising a jacket skin secured about an exterior surface of the shell, the jacket skin being filled with a neutron absorbing shield material. 19. The container of claim 18, wherein the shell defines a longitudinal axis, further comprising a plurality of elongate reinforcing members, embedded within the neutron shield material between the exterior surface of the shell and the jacket skin in a disposition parallel to the longitudinal axis of the shell, each reinforcing member being bent lengthwise along a longitudinal axis to define a corner edge and first and second free edges, wherein the first and second free edges of the elongate member contact one of the structural shell and the jacket skin and the corner edge of the reinforcing member contacts the other of the structural shell and the jacket skin. 20. The container of claim 1, wherein: 21. The container of claim 20, further comprising an access aperture shield assembly containing a neutron absorbing shield material, the access aperture shield assembly being securable to cover the access aperture when the access cover plate is removed from the second closure plate, thereby reducing streaming of neutron particles through the access aperture. 22. The container of claim 21, wherein: 23. The container of claim 1, wherein the structural shell defines a longitudinal axis, further comprising at least one elongate rail member secured within the cavity to an interior surface of the cavity and disposed in parallel relationship to the longitudinal axis of the shell, the rail member being constructed from a hardened, low friction metal.
	summary
049903047	claims	1. In a fuel assembly having a instrumentation tube with a hollow interior and a flux thimble tube inserted in said hollow interior of said instrumentation tube for taking flux measurements, said flux thimble tube radially spaced inwardly at its exterior surface from an interior surface of said instrumentation tube so as to define a coolant flow annulus therebetween, means for reducing coolant flow-inducing vibration of said thimble tube, comprising: a plurality of mechanical elements defined on said interior surface of said instrumentation tube in said hollow interior of said instrumentation tube at a plurality of axially spaced points therealong for engaging said exterior surface of said flux thimble tube within said instrumentation tube and inducing a controlled elastic sinuous deflection of said thimble tube to reduce vibration thereof induced by coolant flow in said annulus between said instrumentation and thimble tubes. a plurality of mechanical elements defined on said interior surface of said instrumentation tube in said hollow interior of said instrumentation tube at a plurality of axially spaced points therealong for engaging said exterior surface of said flux thimble tube within said instrumentation tube and inducing a controlled elastic sinuous deflection of said thimble tube to reduce vibration thereof induced by coolant flow in said annulus between said instrumentation and thimble tubes, said elements being disposed at the elevations of said grids along said instrumentation tube. 2. The fuel assembly as recited in claim 1, wherein said mechanical elements are int he form of dimples formed in sad interior surface of said instrumentation tube and projecting radially inwardly therefrom. 3. The fuel assembly as recited in claim 2, wherein said dimples are bulged from a wall of said instrumentation tube. 4. The fuel assembly as recited in claim 1, wherein said mechanical elements are in the form of cantilevered spring fingers formed in said interior surface of said instrumentation tube and projecting radially inwardly therefrom. 5. The fuel assembly as recited in claim 4, wherein said spring fingers are cut out from a wall of said instrumentation tube. 6. The fuel assembly as recited in claim 1, wherein said mechanical elements are formed at a plurality of points on said instrumentation tube interior surface staggered on a single diametral plane through said tube. 7. The fuel assembly as recited in claim 6, wherein said points are at spaced axially and 180 degrees from one to the next. 8. The fuel assembly as recited in claim 1, wherein said mechanical elements are defined by an undulating longitudinal configuration of said instrumentation tube. 9. The fuel assembly as recited in claim 1, wherein said mechanical elements are defined by a spiral configuration of said instrumentation tube. 10. The fuel assembly as recited in claim 1, wherein said mechanical elements are defined by a zig-zag configuration of said instrumentation tube. 11. In a fuel assembly having a skeleton including a plurality of fuel rod-supporting grids being spaced apart from one another along an axis of said skeleton, a instrumentation tube extending through said grids and having a hollow interior, and a flux thimble tue inserted in said hollow interior of said instrumentation tube for taking flux measurements, said flux thimble tube radially spaced inwardly at its exterior surface from an interior surface of said instrumentation tube so as to define a coolant flow annulus therebetween, means for reducing coolant flow-inducing vibration of said thimble tube, comprising: 12. The fuel assembly as recited in claim 11, wherein said mechanical elements are in the form of spring fingers formed in said interior surface of said instrumentation tube by being cut out lengthwise and projecting radially inwardly therefrom. 13. The fuel assembly as recited in claim 12, wherein said spring fingers by being cut out from said instrumentation tube leave holes in said tube which are substantially covered by said grids. 14. The fuel assembly as recited in claim 11, wherein said mechanical elements are formed at a plurality of points on said instrumentation tube interior surface staggered on a single diametral plane through said tube. 15. The fuel assembly as recited in claim 14, wherein said points are at spaced axially and 180 degrees from one to the next.
	description	The invention relates to hunting blind, more particularly to a molded hunting blind. Hunting blinds are important for hunting and nature photography. Hunting blinds hide occupants from view so that wild animals can be viewed in a relatively undisturbed condition. According to one aspect, a molded hunting blind includes a one piece molded body. The molded hunting blind also includes a molded door and a plurality of windows; and at least one of: an archery door with a taper configured to limit movement; and a gun door with a gun rest and an arm rest. In one embodiment, the one piece molded body includes walls which slant inward towards a roof. In another embodiment, the walls slant inward towards the roof at an angle of between about 1 degree and about 18 degrees. In yet another embodiment, two or more of the one piece molded bodies are configured to be nestably stackable. In yet another embodiment, the archery window and the gun window are configured to open inwardly to minimize detection by wildlife. In yet another embodiment, the archery door and the gun door are recessed in a wall of the molded hunting blind. In yet another embodiment, the one piece body further includes a plurality of outwardly protruding molded sections configured to house an inwardly open window or door. In yet another embodiment, the archery door includes a vertical taper of between about 1 degree and 8 degrees off vertical. In yet another embodiment, the one piece body further includes a plurality of outwardly protruding molded sections configured to mechanically strengthen the molded hunting blind. In yet another embodiment, the one piece molded body includes molded brackets configured to accept the arm rest. In yet another embodiment, the arm rest is configurable to a right hand or left hand shooter. In yet another embodiment, the molded hunting blind further includes a molded gun rack. In yet another embodiment, the molded hunting blind further includes a molded shelf. In yet another embodiment, a color is died into a plastic of the one piece molded body. In yet another embodiment, an outside surface of the one piece molded body includes a light color and inside surface of the one piece molded body includes a dark color for use in warm or hot temperature applications. In yet another embodiment, an outside surface of the one piece molded body includes a dark color and inside surface of the one piece molded body includes a dark color for use in cool or cold temperature applications. In yet another embodiment, the molded hunting blind further includes handles configured for carrying and positioning the hunting blind. In yet another embodiment, the molded hunting blind further includes holes in a base flange configured for anchoring the hunting blind. In yet another embodiment, the one piece molded body is seamless. According to another aspect, a process for molding a one piece molded hunting blind including the steps of: providing a mold of the one piece molded hunting blind; providing a molding material; and molding the one piece molded body. In one embodiment, the step of molding includes molding simultaneously a plurality of hunting blind components using a common mold. In another embodiment, the step of providing a molding material includes providing a molding material including a first molding material having a first color for forming an outer surface of the molded hunting blind and a second molding material having a second color for forming an inner surface of the molded hunting blind. 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. 1A shows a drawing of one embodiment of a molded hunting blind. The molded body can be provided as a one piece main body unit with no assembly of the main body or seams to the (seamless) main body. Molded hunting blinds as described herein can be conveniently stacked one within the other for shipping, storage, and transport in numbers to one or more hunting sites. The structure design allows such molded hunting blinds to be built for durability, such as with a relatively heavy gauge one piece molded plastic for strength, while remaining light enough in weight to move into position using handles. Multi-purpose molded hunting blind can be used for, for example, archery hunting, gun hunting, ice fishing, and filming. There can also be molded rain gutters over the windows and doors. The rain gutters are important for extended occupancy over hours to days during rain or snow. Keeping rain or melting snow water out of the hunting blind is important both for a general state of well-being of the hunter and/or photographer as well as to minimize damage to expensive hunting gear including hunting rifles and/or still or video cameras and other electronic equipment. Holes or other suitable openings in a lower flange can be used to secure the hunting blind against undesired movement. FIG. 1B shows the roof of the exemplary hunting blind of FIG. 1A. The molded hunting blind can be vented for better air circulation. Doors and windows can be provided as molded parts that can be assembled onto the main body. The exemplary embodiment includes an archery window with a taper to limit movement and a gun window with a gun rest, and an elbow/arm rest for shooting. A low profile Archery window is shaped specifically for archery hunters. The archery window can be tapered to limit movement and made elongated for more room to draw the bow without being spotted. The archery window can also be tapered wider at the top for adequate shooting room and narrow at the bottom to limit visibility from being spotted. The archery door vertical taper typically ranges from about 1 degree to about 8 degrees off vertical, preferably less than about 5 degrees. The exemplary embodiment also includes filming windows for still and/or video photography use. One exemplary embodiment includes gun windows with a gun rest lip. Windows can be made to open inward and down allowing more room when open and less chance of being spotted when opening. Prior art hunting shelters or hunting blinds typically do not have an arm rest. One exemplary embodiment also includes an elbow/arm shooting rest. In most embodiments, the arm rest is slid into brackets in the one piece molded body. By installing the arm rest in one end or side or the other end or side of the hunting blind, the arm rest can accommodate left hand and right hand shooters. As compared with fixed non-movable arm rests, there is more room in the hunting blind, because only arm rests in actual use (right or left handed as desired) are typically installed near a gun door in active use. The interior can include molded attachable shelves. The interior can also include one or more molded attachable gun racks. The molded hunting blind can be made to reduce heat for hunting in warmer climates. For example, a lighter color can be used on the outside and a darker color on the inside for use in summer and/or warm or hot temperature applications. Similarly, the outside can be made darker for better solar heating in winter and/or cold weather applications. The colors can be died into the surfaces of the plastic. Also, a darker inside color helps the hunter or photographer from being spotted. For example, by making the shelter darker to blend in with camouflage that the hunter will be wearing making movement by the hunter harder to detect. In the southern United States, for example, the shelter can be a lighter color on the outside to blend in with the terrain. If colored on the inside with the same lighter color, movement inside the shelter would likely be quickly spotted. FIG. 1C shows an end view of the molded hunting blind of FIG. 1A having a one piece molded body 1. FIG. 1D shows a side view of the molded hunting blind of FIG. 1A. Archery door 3 having an archery window is shown on a side wall. The molded hunting blind can be vented by roof vent 4 for better air circulation. The gun door and archery door can be hinged by a hinge 7. Handles 10 allow for convenient loading and unloading for transport as well as for placing the molded hunting blind in a use location, typically outdoors on any suitable ground surface. FIG. 1E shows another end view of the molded hunting blind of FIG. 1A. A main door 6 is shown having a gun door handle 12. Filming window 17 can be seen next to the main door 6. FIG. 1D shows another side view of the molded hunting blind of FIG. 1A having an archery window 13, a gun door 16, and a filming window 17. FIG. 1G shows a view of the interior of one end side molded hunting blind of FIG. 1A. Rest 11 can be seen near open gun door 16 and archery door 3. Main door 6 is open about hinges 9. Archery door 3 can open about hinges 7. Gun rack 18 can be seen in an out of the way upper location. FIG. 1H shows a view of the interior of the other end side molded hunting blind of FIG. 1A. Filming window 17 can be seen in more detail with hinges 9. Shelf 122 can also be seen in an out of the way upper location. FIG. 1J shows a detailed underside isometric cut away view of molded hunting blind of FIG. 1A. Filming window 17 can be seen with latch mechanism 21 and hook 22. Seat 30 is affixed to the molded body 1. One end of a gun rack 18 is also affixed to the molded body 1. FIG. 1K shows a more detailed cut away view latch mechanism 21 and hook 22. FIG. 2A shows an isometric view of another embodiment of an exemplary molded hunting blind. FIG. 2B shows an end view of the molded hunting blind of FIG. 2A. FIG. 2C shows a side view of the molded hunting blind of FIG. 2A. FIG. 2D shows another end view of the molded hunting blind of FIG. 2A. FIG. 2E shows the roof of the hunting blind of FIG. 2A. FIG. 2F shows a view of the interior of one end of the molded hunting blind of FIG. 2A. FIG. 2G shows a view of the interior of one side of the molded hunting blind of FIG. 2A. Components which can be fitted into the one piece molded hunting blind structure are now shown in more detail. Each of these components can also be formed using similar molding processes, such as for example as molded plastic parts. Gun door: FIG. 3A shows an isometric view of a gun door. FIG. 3B shows a top view of the gun door of FIG. 3A. FIG. 3C shows a front view of the gun door of FIG. 3A. FIG. 3D shows a side view of the gun door of FIG. 3A. FIG. 3E shows a top view of the gun door of FIG. 3A showing mounting holes for the door hinges. FIG. 3F shows a section view of the gun door of FIG. 3E in a horizontal plane. FIG. 3G shows a section view of the gun door which is cut vertically in the center of the part of the gun door of FIG. 3A. In most embodiments, the gun door can easily open downward on hinges as a flip down door. In most embodiments, there are 2 drip edges on doors and windows, one over the window, the other at the bottom. Filming windows: In most embodiments filming windows can be substantially the same as gun doors. One Archery door and one window could be sufficient for hunting. However, it was realized that additional filming windows could be added as a safety feature to avoid a potential hazardous situations, such as, for example, filming and shooting from the same window. These additional filming windows allow the shooter to shoot from one window (e.g. a gun door) on one end and to perform filming from another filming window. This was done to avoid a potentially dangerous situation where both the shooter and the filming are done through one common door or window. Archery door: FIG. 4A shows an isometric view of an archery door. FIG. 4B shows an exterior front view of the archery door of FIG. 4A. FIG. 4C shows an interior view of the archery door of FIG. 4A. FIG. 4D shows a top view of the archery door of FIG. 4A. FIG. 4E shows a section view with more detail of the archery door of FIG. 4A. FIG. 4F shows a side view of the archery door of FIG. 4A. FIG. 4G shows more detail in a side view of the archery door of FIG. 4A. Main door: FIG. 5A shows an isometric view of the exterior of the main door. FIG. 5B shows an isometric view of the interior of the main door of FIG. 5A. FIG. 5C shows a top view of the main door of FIG. 5A. FIG. 5D shows a front view of the main door of FIG. 5A. FIG. 5E shows a side view of the main door of FIG. 5A. FIG. 5F shows an interior view of the main door of FIG. 5A. FIG. 5G shows another side view of the main door of FIG. 5A. FIG. 5H shows a detailed section view of the main door of FIG. 5A. FIG. 5I shows a detailed front cut away view of holes for the door handle of the main door of FIG. 5A. FIG. 5J shows a detailed interior cut away view of the interior section of FIG. 5I. FIG. 5K shows another more detailed section view of the main door of FIG. 5A. Gun rack: FIG. 6A shows an isometric view of a gun rack bracket, such as to support the barrel of a long gun. FIG. 6B shows a side view of the gun rack bracket of FIG. 6A. FIG. 6C shows a front view of the gun rack bracket of FIG. 6A. FIG. 6D shows a top view of the gun rack bracket of FIG. 6A. FIG. 6E shows an isometric view of another gun rack bracket, such as to support the stock of a long gun. FIG. 6F shows a side view of the gun rack bracket of FIG. 6E. FIG. 6G shows a front view of the gun rack bracket of FIG. 6E. FIG. 6H shows a top view of the gun rack bracket of FIG. 6E. Inward opening doors: As can be seen, for example, in FIG. 1A and FIG. 1J, filming windows and gun doors can be opened inwardly and downward into expanded protruding sections of the main body. The expanded outwardly molded protruding sections of the main body can accept the inwardly open windows, thus substantially maintaining the interior space of the hunting blind. In most embodiments, such as can also be seen in FIG. 1A, windows and archery doors are recessed inward to block wind and to help conceal a shooter and/or a photographer. The wall and roof structural features, such as the recessed window frames and expanded outwardly molded protruding sections of the main body, also help to mechanically or physically strengthen the structure as compared to a flat surfaced shelter. Carrying handle: FIG. 7A shows an isometric view of an exemplary carrying handle. FIG. 7B shows a top view of the carrying handle of FIG. 7A. FIG. 7C shows a side view of the carrying handle of FIG. 7A. FIG. 7D shows an end view of the carrying handle of FIG. 7A. FIG. 7E shows a bottom view of the carrying handle of FIG. 7A. Seat: FIG. 8A shows an isometric view of an exemplary seat. FIG. 8B shows a top view of the seat of FIG. 8A. FIG. 8C shows a bottom view of the seat of FIG. 8A. FIG. 8D shows a side view of the seat of FIG. 8A. FIG. 8E shows another side view of the seat of FIG. 8A. FIG. 8F shows yet another side view of the seat of FIG. 8A. FIG. 8G shows a detailed section view of the seat of FIG. 8A. Shelf: FIG. 9A shows an isometric view of an exemplary shelf. FIG. 9B shows a side view of the shelf of FIG. 9A. FIG. 9C shows another side view of the shelf of FIG. 9A. FIG. 9D shows a top view of the shelf of FIG. 9A. Roof vent: FIG. 10A shows an isometric view of an exemplary roof vent. FIG. 10B shows a top view of the roof vent of FIG. 10A. FIG. 10C shows a side view of the roof vent of FIG. 10A. FIG. 10D shows another side view of the roof vent of FIG. 10A. Hardware: FIG. 11A shows an isometric view of an exemplary door handle. FIG. 11B shows an isometric view of an exemplary hook. FIG. 11C shows an isometric view of an exemplary latch mechanism. Stacking: It was realized that the body can be slanted inwards toward the center of the unit, typically at an angle of between about 1 degree to 18 degrees off vertical, preferably between about 3 degrees and 6 degrees, to make stacking the one piece molded bodies partially nested (e.g. stacking household cups) possible. The roof and walls of the hunting blinds described herein are slanted inwards towards the roof to allow such stacking. Considerations for stacking include window shapes, window movement direction, gun rests, and window ledges. For example, the outwardly protruding sections are angled in towards the roof off vertical, similar to how the walls are slanted into towards the roof. Similarly, slant angles, such as, for example, the angles of the sides of the archery window also allow for nestable stacking. FIG. 12A shows an isometric view of exemplary stacked hunting blind bodies. Exemplary one piece molded body 121 is shown nestingly stacked over one piece molded body 122. It is understood that additional one piece molded bodies can be so stacked, limited only by considerations of total weight and height of the nested stack. In the exemplary embodiment of FIG. 12A, a recess 123 can be seen which will later accept one side of a window or door hinge (e.g. hinge 9, FIG. 1J). FIG. 12B shows a side view of the stacked hunting blind bodies of FIG. 12A. As can be seen in FIG. 12B, using the angular ranges described herein above for the walls, windows, and other slanted and/or protruded wall features (e.g. bowed out), nestable stacking can be efficient in stacked height. For example, in the exemplary stack of FIG. 12B, the added height for each additional nestably stacked hunting blind body can be seen to be less than about 5% to 10% of the height of a single one piece hunting blind body. FIG. 12C shows an end view of the stacked hunting blind bodies of FIG. 12A. FIG. 12D shows an over-head cut-away view of the inside of the stacked hunting blind bodies of FIG. 12A. FIG. 12E shows an over-head cut-away view of the inside end portion of the stacked hunting blind bodies of FIG. 12A. Expanded protruding sections 126, 125 of the main bodies 121, 122 respectively can be seen to nest within each other, enhancing the stability of the stacked structure. FIG. 12F shows an over-head cut-away view of the inside lower portion of the body of the stacked hunting blind bodies of FIG. 12A. Arm and elbow rest: In addition to the gun rest an arm rest can accommodate both left and right hand shooters. One problem was that the tapered design of the unit seemingly did not allow for room to accommodate an arm rest. The Arm rest should stick out about 24 inches from the window and about 12 inches from the wall. Ideally, up to four arm rests can be installed at each window. However, four separate arm rests limited the space inside the shelter. To allow for arm rests, window operation the up (because of the taper) and side-ways directions (because of the arm rest location) was also problematic. Another concern was accessibility and to still allow room for filming and a second person in the hunting blind. The solution was to extend the main body by about two inches on each end. Brackets can be molded with main body of the mold. The brackets also allow arm rests not in use to be removed (e.g. when only one arm rest is needed, the other three can be removed). In some embodiments, the arm rest can be inserted into the bracket attached to the main body. Also, the same arm rest can work for all windows. Thus, in many uses, one arm rest can be used, eliminating the need for a permanently installed arm rest at each window. The arm rest solution described hereinabove significantly improves the working space within the hunting blind. Also, a user can slide the arm rest out and place it at the other end depending on if the user is a right hand or left hand shooter. The arm rest solution described hereinabove significantly improves the working space within the hunting blind. Also, use of the arm rest set in brackets for a right handed or left handed shooter allows for more accurate shots. Manufacturing: Typically, most accessory parts can be molded in the same mold and at the same time as the main body is molded. However in a typical molding manufacturing processes, one of the largest accessory parts, the main door, can be more conveniently manufactured using a separate mold. A mold polyethylene can be used as the molding material. A color can be dyed into at least one side of the molding material. In one embodiment of a manufacturing process, the outer color can be provided by mixing a pigment into a natural powdered polyethylene at a rate of 1 gram per pound, and mixing in a mixer until all of the powder is coated. For an inner layer of black color, natural pellets can be melted in an extruder with a black pigment pellet at a rate of around ¾%. The material can be mixed by the extruder screw and extruded into thin rods which are cut into pellets and then ground into powder. Using such manufacturing techniques, the color can be added throughout the material thickness. In one embodiment, the outer color is added to the mold as a powder which melts with heat, becoming a solid. The inner color is then applied using a second shot hopper. It is also a powder that melts with the heat and forms an inside layer. The composite one piece molded hunting blind body ends up with an outside distinct color layer and an inside distinct color layer. Thus, the process to make the one piece molded body can include providing a first molding material having a first dyed color which will form the outer surface of the molded hunting blind and a second molding material having a second dyed color which will provide the inner surface of the molded hunting blind. Following such a molding process, the result is a composite two colored one piece molded hunting blind body. Transport: In some embodiments, a hunting blind as described hereinabove can have a width suitable to fit in the back of a full size pick-up truck, yet big enough to easily draw a bow back while shooting a bow out of the archery door to the front or to the back of the shelter. Shooting from end to end (the length of the hunting blind) was not an issue for drawing a bow, however shooting from front to back (the width) can been problematic, because of the length of a draw on a bow is substantial. Being able to easily load hunting blinds as described hereinabove into the back of a pick-up truck solves the problem of transporting the hunting blind to hunting spots, while maintaining the ability to draw a bow front to back. While the present invention has been particularly shown and described with reference to the preferred mode as illustrated in the drawing, it will be understood by one skilled in the art that various changes in detail may be affected therein without departing from the spirit and scope of the invention as defined by the claims.
	claims	1. An X-ray examination apparatus, comprising: an X-ray source, an X-ray detector, a filter arranged between said source and said detector, said filter comprising an array of filter elements having X-ray absorbtivities that can be adjusted by means of control voltages, a control circuit for supplying said control voltages to said filter elements, an object support arranged between said filter and said detector, said station being adapted to support an object to be exposed to X-ray radiation emanating from said source, the transmitted X-ray radiation being detected by said detector, and a signal processing assembly receiving detector signals from said X-ray detector, said detector signals being group-wise arranged in accord with the supply of said control voltages to groups of adjacent filter elements, said control circuit being adapted to supply said control voltages in single-sequence fashion to said groups of adjacent filter elements. 2. The apparatus as claimed in claim 1 , in which said groups are evenly and regularly distributed over the filter. claim 1 3. The apparatus as claimed in claim 1 , in which each filter element comprises an X-ray absorbing element coupled with an actuator controlled by a respective control voltage, thus controlling the effective X-ray absorbtivity of said filter element. claim 1 4. The apparatus as claimed in claim 3 , in which said X-ray absorbing element comprises a heavy element. claim 3 5. The apparatus as claimed in claim 1 , in which filter element comprises a liquid crystal element controlled by a respective control voltage for controlling the effective X-ray absorbtivity of said filter. claim 1 6. The apparatus as claimed in claim 1 , in which each filter element comprises a capillary tube connected to a reservoir for X-ray absorbing liquid, the inner surface of said capillary tube at least partly being coated with an electrically conductive layer connected with said control circuit for receiving a respective control voltage for adjusting the amount of X-ray absorbing liquid present in said capillary tube thus controlling the effective X-ray absorbtivity of said filter element. claim 1 7. The apparatus as claimed in claim 1 , wherein said groups of detector signals being supplied to a memory means, said signal processing assembly being adapted to reconstruct an image by comparing pixel-wise said respective groups of detector signals stored in said memory means and using only every pixel value which is larger than the signal values of the corresponding pixel of every other group. claim 1
042882915	description	DESCRIPTION OF THE PREFERRED EMBODIMENT The multi-sensor detector assembly 10 shown in FIG. 1 will typically comprise a dust cap 12, a connector adapter 14, and a first section of sheathing 16 connected to a seal plug 18 which is itself connected to a second sheathing portion 17. The second sheathing portion 17 may further be divided into five sections for purposes of the present invention as shown in FIG. 1 as sections 19, 20, 22, 24 and 26. These five sections are used to visually indicate that for each of the five sensors, the actual sensing portion (41, 43, 45 or 47), that is, the rhodium emitter portion of the sensor, is located at a different lengthwise position along the second sheathing portion 17. For example, a first emitter element 41 may be located in section 19, the emitter element 43 of the second sensor 52 assembly may be located lengthwise in section 20, the actual emitter element 45 of the third sensor assembly may be located within the section 22 and so forth. Each emitter element is approximately 15 inches long and of the same diameter as the lead wire. In the preferred embodiment, the background detector which consists of a length of wire (of the same diameter and material as all other lead wires) only (i.e., it has no rhodium emitter) is located in the section 26. In this manner, the level of radiation may be monitored at various positions within the core of the reactor. The background sensor 48 is used to detect the background level of radiation as averaged over the length of the background sensor element shown as 48 in FIG. 2. At the end of the second sheathing portion 17, or at the end of section 26 and forming the end of the multi-sensor detector assembly, there is a nose portion 28. This portion is suitably shaped and contoured so that it will not easily snag on any of the internal walls of the path used to guide the detector assembly through the reactor. FIG. 2 shows the cross-section as appears in the detector section 19 of FIG. 1. The sheathing 17 is shown to enclose the star-shaped common conductor 30 of the various sensor assemblies. This common conductor 30 may be made of stainless steel. The thickness of the common conductor 30 is carefully chosen such that it is thick enough to shield the sensors from one another (i.e., minimize cross talk) and yet thin enough to permit the detector assembly to negotiate the tight turns in the paths provided in nuclear reactors. This star-shaped common conductor divides the interior of the sheathing portion 17 into five equally sized wedge-shaped compartments which are each filled with a silicon dioxide insulator designated 32. The silicon dioxide is provided in the form of a slurry and is extruded over the sensors and fitted into the wedge-shaped sections. A vacuum pump and heat is used to remove moisture from the assembly. Within each of the five wedge-shaped sections there is located a sensor assembly, and the lead wires as indicated at 40, 42, 44 46, or 48. The cross-section as shown in FIG. 2 will change along the length of the sheath 17 to reflect the presence of the rhodium emitter element at the particular section where the cross-section may be taken. Thus, as shown in FIG. 1, the cross-section which comprises FIG. 2 has been taken at the portion of the section 19 wherein the rhodium emitter element is attached to the lead wire 40. The remaining lead wires 42, 44, and 46, as shown in FIG. 2, are comprised of a suitable conductive material such as nickel, Inconel or stainless steel. The final sensor assembly is the background sensor 58 and it is comprised of a wire 48 of the same material as the rhodium lead wires along its full length, and thus will appear the same regardless of the position at which the cross-sectional view is taken. If the cross-sectional view corresponding to the view of FIG. 2 were taken in the section labeled detector section number 22, then the sensor assembly number 54 would at that point be comprised of rhodium rather than the stainless steel or Inconel as shown in FIG. 2. It should be noted with particularity that the five sensors comprise the sensor assemblies 50, 52, 54, 56 and 58, each of which is located within a dielectric 32 and separated from its conducting element 30, which conducting element is common to each of the sensor assemblies 50 through 58. Because of the shape of the common conductor 30 and the extrusion method of manufacture, the multiple sensor assemblies are all held in proper parallel axial alignment throughout the active detecting length of the multi-sensor detector assembly 10. The relative location of the various rhodium emitters is schematically illustrated in FIG. 3. The exterior sheath 17 houses five detector assemblies 50, 52, 54, 56 and 58, four of which comprise a pair of lead wires (40, 42, 44 and 46 respectively) and an emitter element (41, 43, 45 and 47 respectively); the fifth detector 58 comprising the background detector lead wire 48. In order to facilitate extrusion of the silicon dioxide dielectric over the lead wire and rhodium emitter, the outer diameter of the lead wire and rhodium emitter are identical. Each respective rhodium emitter element is disposed at a different distance along the length of the overall lance assembly 10. In this manner the radiation level may be monitored at different locations within the reactor. Each sensor assembly, including the background detector, is connected to a common conductor element 30, through the dielectric insulator element 32. Although the present invention has been described with reference to the particular embodiment best illustrated by FIGS. 2 and 3, it is to be expressly understood that various modification may be made to that device by those having ordinary skill in the art without departing from the intended spirit and scope of the invention. For example, it should be obvious that instead of using a common center conductor to divide the interior of the sheath into five portions, a suitably shaped conductor could be used to divide the interior of the sheath into a greater or lesser number of compartments as desired. Also the detector assembly may be constructed of any suitable materials and the detectors themselves may be constructed of any material that emits sufficient charged particles under the influence of nuclear radiation. The present invention is only to be viewed as limited by the attached claims and not limited to the specific embodiments discussed herein. There has thus been provided a multi-sensor detector assembly wherein all of the detector assemblies use a common conductor element which serves to divide the multi-sensor detector assembly into a plurality of equally spaced and properly aligned wedge-shaped compartments so as to maintain the sensor assemblies in proper co-axial and parallel alignment throughout the length of the active radiation detecting zone of the detector assembly. The common conductor also serves to shield each detector against the emissions of its neighbors thus minimizing cross talk among the detectors of the assembly.
	claims	1. A support grid for a nuclear fuel assembly, said nuclear fuel assembly structured to support a generally cylindrical fuel rod with an outer diameter, said support grid comprising:a frame assembly having a plurality of outer straps and a plurality of helical frame members;wherein each said helical frame member has a helical contact portion and at least one fluted helical fuel rod contact portion, said helical contact portion having a greater diameter than the diameter of the at least one helical fuel rod contact portion, the helical contact portion structured to contact one of an adjacent helical frame member or one said outer strap, said contact portion and said fuel rod contact portion joined by a transition portion, said at least one helical fuel rod contact portion diameter being generally equivalent to said fuel rod outer diameter such that, if a fuel rod was disposed in said helical frame member, said fuel rod outer diameter would engage said helical fuel rod contact portion;wherein, if a fuel rod was disposed in said helical frame member, said at least one helical fuel rod contact portion defines an inner passage between the rod and the helical frame member, said inner passage having a helical shape;each said helical frame members coupled to an adjacent helical frame member at a contact portion, said plurality of helical frame members forming a grid;said plurality of outer straps disposed about the perimeter of said helical frame members; andsaid plurality of outer straps being coupled to said contact portion of each helical frame member disposed immediately adjacent to an outer strap. 2. The support grid of claim 1 wherein said helical frame members have a wall with a uniform thickness. 3. The support grid of claim 1 wherein said helical frame members are coupled to each other at 90 degree intervals about the perimeter of each helical frame member. 4. The support grid of claim 1 wherein said at least one helical fuel rod contact portion extends 360 degrees about said helical frame member. 5. The support grid of claim 4 wherein said transition portion is a generally smooth curve. 6. The support grid of claim 1 wherein said at least one helical fuel rod contact portion includes two helical fuel rod contact portions. 7. The support grid of claim 6 wherein each said helical fuel rod contact portion extends 180 degrees about said helical frame member. 8. The support grid of claim 6 wherein each said helical fuel rod contact portion extends 90 degrees about said helical frame member. 9. The support grid of claim 8 wherein said transition portion is a generally smooth curve. 10. The support grid of claim 1 wherein said at least one helical fuel rod contact portion includes four helical fuel rod contact portions. 11. The support grid of claim 10 wherein each said helical fuel rod contact portion extends 90 degrees about said helical frame member. 12. The support grid of claim 11 wherein said transition portion is a generally smooth curve. 13. The support grid of claim 1 wherein said at least one helical fuel rod contact portion defines a helical outer passage. 14. The support grid of claim 1 wherein said helical frame member is a tubular member having at least one flute. 15. The support grid of claim 14 wherein said helical frame member is a tubular member having two flutes. 16. The support grid of claim 14 wherein said helical frame member is a tubular member having four flutes.
	description	This application claims the benefit under 35 U.S.C. 119(e) of U.S. Provisional Application No. 60/749,493, filed on Dec. 9, 2005 which is incorporated herein by reference in its entirety. X-ray microscopy is a technique that offers unique imaging through its combination of resolution, penetrating power, analytical sensitivity, compatibility with wet specimens, and ease of image interpretation. In the past, high resolution X-ray microscopy has been restricted to a few synchrotron radiation laboratories around the world. The emergence of laboratory source-based x-ray microscopes holds the opportunity to make this imaging modality much more widely available. Such laboratory-source x-ray microscopes, however, rely on the availability of high brightness x-ray sources for high performance. Resolution and throughput are two important parameters defining the performance of a microscope. The former defines smallest features that can be imaged, while the later defines how fast useful information can be obtained. For a full field x-ray microscope, the exposure time T is inversely proportional to the flux F incident on the object:F=ηBcL2Δθ2, (Ex. 1) where Bc, L, and Δθ are the beam brightness, the field of view, and the divergence of the illumination beam at the object, respectively; η the efficiency of the focusing optics. Expression (1) shows that for a given field of view L, divergence Δθ, focusing efficiency η, F is proportional to the source brightness Bc. Therefore, a brighter x-ray source means shorter exposure time and thus higher throughput. A brighter x-ray source also permits higher resolution for a given exposure time. The dependence of exposure time T on resolution δ is approximately given byT=a/δ4, (Ex. 2) where “a” is a parameter independent of resolution and related to image contrast and the imaging system efficiency. Expressions (1) and (2) show that for a given exposure time and imaging objective, the resolution can be improved by a factor of B1/4 for a brighter source. This factor equals to 1.56 for a 6× brighter source. The most widely deployed laboratory sources generate x-rays by bombarding energetic electrons into a target (anode), similar to how Roentgen first generated x-rays in his laboratory. The resulting x-rays consist of narrow-band characteristic x-rays resulting from ionization and de-excitation of core electrons and continuous Bremsstrahlung (braking) radiation resulting from the deceleration of the energetic electrons. Except for commercial x-ray applications requiring sources with a high intensity as the main requirement such as medical radiography and medical CT, or luggage scanners, a significant number of applications such as x-ray microscopy, protein crystallography, and small angle scattering, requires a source with high brightness for the characteristic x-rays. The key limiting factor for increasing brightness of this type of source is the melting of the anode target. Two well-established approaches have been developed to overcome this limitation and are used in current high brightness laboratory x-rays sources. The first method facilitates thermal dissipation by using a fast rotating anode target to distribute the heat flux over a large area to prevent the target from melting. X-ray sources based on this method constitute the most powerful x-ray sources widely used in a home-lab environment. The second method uses a micro-sized electron spot (microfocus source) to reduce the thermal path to produce a large thermal gradient for better thermal dissipation. Several other approaches have been explored in recent years to produce high brightness laboratory x-ray sources. One method involves innovations based on various forms of accelerator-based technologies and two miniature synchrotron sources have been demonstrated recently. The accelerator and miniature synchrotron sources are currently expensive. Another method uses a high power laser beam focused to a small spot on a target to produce high temperature plasmas that emit high brightness x-rays. However, this method is limited to soft x-rays and not well suited for multi-kiloelectron Volts (KeV) x-rays that are desired for most for imaging. The present invention concerns an x-ray source, anode target design and x-ray microscope. The designs are based on the realization that the effectiveness (yield) of high energy electrons in producing characteristic x-rays decreases rapidly with decreasing energy. In the standard configuration of an x-ray source, all the energy of the energetic electrons including inefficient lower energy ones are deposited in the target within a small interaction volume. Embodiments of the present invention include a structured anode that has a thin top layer made of the desired target material and a thick bottom layer made of low atomic number and low density materials with good thermal properties. This structured target design allows for the use of efficient high energy electrons for the efficient generation of characteristic x-rays per unit energy deposited in the top layer and the use of the bottom layer as a thermal sink. This anode design can be applied to substantially increase the brightness of stationary, rotating anode or other electron bombardment-based sources where brightness is defined as number of x-rays per unit area and unit solid angle emitted by a source and is a key figure of merit for a source. In one example, the anode comprises a target layer of copper with an optimal thickness deposited on a substrate layer of beryllium or carbon/diamond substrate. In other examples, the target layer is chromium, tungsten, platinum, or gold. This target will used to replace the anode in a commercially available x-ray source. The present source can substantially improve the performance of many well established x-ray techniques, including x-ray microscopy, protein crystallography for determination of crystallographic structures of proteins and viruses, and small angle scattering for studying macromolecules in native solution. The above and other features of the invention including various novel details of construction and combinations of parts, and other advantages, will now be more particularly described with reference to the accompanying drawings and pointed out in the claims. It will be understood that the particular method and device embodying the invention are shown by way of illustration and not as a limitation of the invention. The principles and features of this invention may be employed in various and numerous embodiments without departing from the scope of the invention. Roentgen discovered in 1896 that when energetic electrons hit a target, x-rays are generated. This basic principle is still used in almost all commercial laboratory x-ray sources. The generated x-rays do not all have the same energy (and equivalently wavelength), but have a spectral distribution that contains a broad Bremsstrahlung (braking radiation) component and very narrow x-ray spectral lines known as the characteristic radiation. Many applications use the combined x-ray output e.g. medical radiography. However, applications that require strictly quasi-monochromatic (single wavelength) x-rays can only use the narrow x-ray lines of the characteristic radiation. For these applications, which include x-ray diffraction, small angle scattering, or x-ray microscopy using zone plates, the Bremsstrahlung component yields unwanted background and is suppressed by energy filtering or eliminated by monochromators. The following discussions only focus on characteristic x-ray radiation, and only on a particular x-ray fluorescence line of interest, e.g. CuKα. The energy (or wavelength) of the characteristic radiation is dependent on the target anode material. For example a copper anode will emit Cu—Kα radiation at an energy of 8.05 KeV (or wavelength of 1.54 Å) if bombarded with electrons of energy greater than 8.98 KeV, the critical excitation energy. The source brightness B is the most important figure of merit for an x-ray source for many x-ray techniques that include x-ray microscopy, diffraction, and small angle scattering. The source brightness is proportional to the x-ray flux F of the characteristic radiation emitted, and inversely proportional to the source area A, from which x-rays are emitted: B ∝ ϕ A ( Ex ⁢ ⁢ 3 ) where φαP≡IU and P is the Power loading Expression (3) shows that a high brightness source requires a lot of x-rays to be generated over a small area. In existing high brightness electron bombardment based x-ray sources, development efforts have been focused on increasing electron current density and optimizing x-ray production by optimizing electron energy. It has been found that the optimal electron beam energy U is in the range of 3-6 times the atomic shell ionization energy U0 of the characteristic x-ray line. The parameter U/U0 is called the overvoltage and is a convenient dimensionless parameter to use. The exact optimum choice of overvoltage depends heavily on the target material, the take-off angle of the x-rays and the self absorption within the target. Accepting the optimum value of the overvoltage which fixes the x-ray yield for a given current, the brightness of a conventional source is determined by the current density I/A, as the generation of x-rays is proportional to number of electrons: B Solid ⁡ ( U U 0 = Constant ) ⁢ α ⁢ P A ( Ex ⁢ ⁢ 4 ) The practical limit to the increase of the electron beam current density is the melting of the target anode due to heat deposited by the electron beam, or in some cases such as Cr, the sublimation temperature which further limits the electron beam current. It is known that the allowable electron beam power increases linearly with the electron spot diameter, which favors small spot sizes for high brightness. To reduce the problem of thermal load, modern sources operate either at a low (˜6-15 degrees) take-off angle (micro-focus sources) to allow spreading the electron beam heat load along a line or they use a rotating anode target to spread the heat load over a line on the rotating cylinder surface. While the rotating anode typically produces a much larger total x-ray flux, microfocus x-ray sources can be substantially brighter than rotating anode sources due to a small source spot. For example, the maximum thermal loading of a widely deployed rotating anode is quoted as 1.2 kiloWatts (kW) over an electron spot size of 100 micrometers and that of a microfocus x-ray source is quoted 5 W and 10 W over an electron spot size of 4 and 7 micrometers, respectively. This corresponds to relative brightness of 0.12, 0.3 and 0.2 W/μm2 respectively. Accepting that the thermal load constitutes the practical limit for the electron beam current density, a solution has to be sought by minimizing the heat load in the target and maximizing the x-ray yield for a given thermal load. FIG. 1(a) shows clearly, for the example of a copper target, that for electrons with low overvoltages a lot of heat is dissipated in the target per unit path length. However, the x-ray generation per unit path length, which is proportional to the ionization cross section, as depicted in FIG. 1(b) shows that the x-ray generation is fairly constant even at high overvoltages. This is summarized in FIG. 1(c), which illustrates that the x-ray generation per unit energy deposited increases monotonically as a function of overvoltage. However, for a conventional solid, uniform target this fact cannot be utilized. The preferred embodiment of the present invention utilizes high overvoltages to minimize heat generation in the target for equivalent x-ray output and a micrometer size excitation spot to maximize the brightness of the x-ray source. Specifically, in the preferred embodiment, the electron beam energy U is more than 6 times the atomic shell ionization energy U0 of the characteristic x-ray line of interest. In the preferred embodiment electron beam energy U is more than 8-10 times the atomic shell ionization energy U0 and can be as high as 15 or more in some embodiments. To only use high overvoltages, the chosen target anode material must be a thin foil. In this case, the electrons lose only a small amount of energy after transmission through the foil. This is illustrated in FIG. 2a with the example of a 4 micrometer (μm) thick copper foil that is struck by electrons of 120 KeV energy. As shown in the energy distribution of the transmitted electrons in FIG. 2b, the average energy loss of the electrons is only 10% in the Copper foil. Therefore the ratio of x-ray generation versus heat generation is 10 times higher than for low overvoltages (cf. FIG. 1c). As can be seen, the cross section rises rapidly over the ionization threshold and then drops off very gradually towards high overvoltages. The additional benefit of a thin foil is that the electrons stay tightly collimated, opening only to a full width half maximum (FWHM) of 2 μm due to scattering when exiting the foil, which satisfies the requirement for a high brightness source. On the other hand, it is clear that a thin foil target by itself dissipates heat quite poorly, so a “heat sink” that is in intimate contact to the copper foil is provided. The requirements for this “heat sink” are: 1) very weak interaction with the electron beam to minimize heating and spread the energy of the transmitted electrons over a large volume; 2) high heat conductivity to efficiently remove the heat from the copper foil and the residual heat generated from the electrons inside the “heat sink” itself; 3) good x-ray transmission for the x-ray line of the primary anode target foil (if used in a transmission source geometry); and 4) poor x-ray generation efficiency of the “heat sink” itself, which would contribute to the background x-rays. In one embodiment, beryllium is used as the substrate for the foil target since this element provides a good fit and compromise for all of these requirements. In another embodiment, diamond (crystallized carbon) is used as the substrate since it offers superior melting point and thermal conductivity properties. The table shows the melting points and thermal conductivity at room temperature of copper, beryllium and diamond. TABLE 1Melting points and thermal conductivity of materialsMelting PointThermal Conductivity atin (° C.)room temperature (W/cm/K)Beryllium12872.01Copper10854.01Diamond444011 It is recognized that Copper and Beryllium require an additional, thin (˜20 nanometer (nm)) diffusion barrier material such as Titanium, Chromium or Tungsten between them to prevent the formation of alloys. But this will not impact the thermal properties of the structured target. FIG. 3 shows a simulation of electron trajectories from electron beam 156 for a 4 μm copper foil target 150 in intimate contact with a thick Beryllium substrate 154, with an optional intervening barrier layer 152. It can be seen that the electrons that leave the copper foil 150 generally do not return, because of the low backscattering in the beryllium substrate 154. Therefore, the tight collimation of the electrons in the copper foil 150 is preserved. Secondly, the differential energy loss in the beryllium is small resulting in a deep penetration into the beryllium spreading the residual kinetic energy of the electrons over a large interaction volume (sphere ˜100 μm diameter). The foregoing assumes that the continuum radiation is minimized which is an additional advantage of the proposed x-ray source. Firstly, as opposed to a thick solid target of conventional sources, the thin film of copper 150 in which only about 10% of the electron energy is deposited, minimizes the production of the continuum radiation. Secondly from Kramer's law, we know that the continuum is directly proportional to Z. Since beryllium has a very low atomic number (Z=4), production of continuum radiation by the thick beryllium substrate 154 is smaller by about a factor of 7 as compared to a thick Copper target. The spectral output then would have a significant peak to continuum ratio as compared to conventional targets. FIG. 4 shows finite element analysis results, which assume an incident electron beam power of 8 W of which 0.8 W dissipate in the 4 μm copper layer and 7.2 W dissipate in the beryllium. The heated shapes have been assumed to be a cylinder 156 with 2 μm diameter in the copper 150 and a sphere 150 with diameter 100 μm in the beryllium 154. Under the simulated conditions the highest temperature reached in the system is 437 degree Centigrade, approximately half the melting point temperature of copper. To compute the generated x-ray flux, one can use empirical formulae for solid and thin targets respectively or alternatively use a Monte-Carlo simulation for both cases. If one considers a Copper target, the calculations show that for a given electron beam current, the generated x-ray flux is approximately the same for a solid Copper target bombarded with 40 KeV electrons and a 4 μm thick Copper target bombarded with 120 KeV electrons. The table below compares the allowable operating parameters of a conventional Copper microfocus x-ray source with the proposed structured target. TABLE 2Solid4 um Copper/Target TypeCopper TargetBeryllium backingElectron Beam Energy40 KeV120 KeVMaximum Linear Power0.4 W/um4 W/umLoading2Source Size Achievable4 um2 umMaximum Power For Spot Size1.6 W8 WMaximum Electron Current40 uA66 umRelative X-ray Brightness12.516.51This is given as the ratio of the electron current and x-ray focal spot area. It has been shown with empirical calculations and Monte-Carlo simulations that under these two target/beam conditions the generated x-ray output is the same for a given electron beam current.2Maximum heating power per linear micrometer that can be tolerated by the target. It results in a maximum temperature increase to half the melting point of Copper. The important conclusion from this calculation is that the maximum x-ray brightness of the source corresponds directly to the highest electron beam current density that can be supported by the target. This comparison shows that a brightness increase of more than a factor of 6 can be expected with the proposed structured target. A structured target as shown in FIG. 3 comprises a top layer of Copper 150 with a thickness of 1-8 μm and preferably about 3-5 μm and a bottom layer made of a beryllium or diamond of about 100 to 1000 μm and preferably about 200 to 300 μm. The copper thickness corresponds to the depth that 120 KeV electrons lose about 5-15% or about 10% of its energy. Thus different energies or targets would yield different target layer thicknesses. The beryllium or diamond thickness is sufficiently thick to stop all the electrons and has negligible absorption of the Cu Ka x-rays. The thin barrier layer 152 is preferably added between the target material and the substrate material. To obtain optimum source brightness, the copper film has a high thermal conductivity close to its bulk value. Depending on deposition method and conditions of the Cu film, the thermal conductivity can change by up to 25%. Film deposited by sputtering offers the highest attainable film densities and thus higher thermal conductivity. Although various methods are preferably used to optimize the thermal conductivity, such as annealing and ion assisted sputtering. Both beryllium and diamond are good candidates for the bottom layer. Beryllium is a low atomic number and low mass density material and has reasonably good thermal conductivity and relatively high melting point. Diamond is also a low atomic number and low mass density material but has much higher thermal conductivity and melting point. However, beryllium foil with the required thickness is more cost effective than a comparable diamond foil. Preventing diffusion and alloying of copper and beryllium is an important reliability issue for the proposed structured target. Alloying between beryllium and copper will decrease the attainable power loading by reducing both the melting point and thermal conductivity of the target region whose values are given in Table 1. In the preferred embodiment, a thin barrier layer is deposited between the beryllium and copper, such as Cr or Ti. The electron beam preferably has the following characteristics: acceleration voltage greater than 80 and preferably greater than 100-120 kV, focal spot size of less than 5 μm, and preferably less than about 2-3 μm, beam current less than 60 microAmperes (μA). FIG. 5 is a schematic diagram of an X-ray microscope 1 using a x-ray source, which has been constructed according to the principles of the present invention. Specifically, in the current embodiment, the electron bombardment laboratory X-ray source 20 comprises an electron gun 22 that generates an electron beam 24, as described above, that is directed at the target 26. The target 26 is as describe above having a thin copper target layer 150. In other embodiments, the target layer is selected from the group of: chromium, tungsten, platinum, or gold. The target 26 also comprises a low Z material substrate such a beryllium or carbon (diamond). The barrier layer 152 is also used in some embodiments. This bombardment of the target 26 generates X-ray radiation 28 by the process of x-ray fluorescence. The radiation is emitted, typically at a 6-45 degree, take-off angle. A condenser system 100 preferably provided, such as a capillary tube-based system. In some example, a monochromator 155 is added to reduce background radiation levels. The radiation is converted into a converging cone of radiation, directed at the sample 10. The sample 10 is preferably held on a stage 120, which allows for its controlled positioning along the optical axis A, or z-axis direction, and the x and y axes, which are orthogonal to the optical axis A. Some of the radiation is absorbed, phase-shifted, or diffracted in the sample, whereas other radiation is transmitted completely through the sample 10. The transmitted radiation is received at a zone plate lens 122. This zone plate collects the diverging cone of radiation, and converts it into a converging hollow cone of radiation in the direction of a detector 128. In the typical embodiment, an intervening scintillator 124 and optical system 126 are used. Generally, the scintillator 124 is required when the detector 128 was not responsive to the radiation generated by the source. This is especially common for shorter wavelength X-rays and hard X-rays. Charge coupled devices (CCDs) are not responsive to this form of radiation since it will pass entirely through the device. As a result, the scintillator 124 generates radiation in the optical wavelengths, which are then focused or imaged by the optical system 126 onto the detector 128, such as a CCD or film. In zone plate systems, the radiation that is used to illuminate the sample 10 preferably has a hollow cone profile. That is, there is substantially no radiation being transmitted along the optical axis A. This is because zone plates are only approximately 20% efficient in diffracting radiation to the detector. Thus radiation traveling along the optical axis is dominated by undiffracted radiation, which carries little information about the sample 10. As a result, in the preferred embodiment, a center stop 116 is located between the source 10 and the detector 128. Preferably the center stop is located near or in the capillary optic 110. In the preferred embodiment, it is located at the capillary optics exit aperture. In the preferred embodiment, the center stop 116 is attached to a membrane 140, which is transmissive to radiation, such as silicon nitride. This silicon nitride membrane is then adhered or bonded to the exit aperture of the capillary tube 110. To further improve the signal to noise ratio, a pinhole aperture 118 is preferably provided between the source 10 and the detector 128 to further decrease system background radiation. The pinhole stop 118 is preferably located on a separate stage. In an embodiment, the capillary optic is approximately 3 millimeters (mm) in diameter. The exit aperture is approximately 200 micrometers in diameter. The numerical aperture of the condenser 110 preferably matched to the zone plate lens. The zone plate lens is thus fully filled and therefore, efficiently used. In still other implementations, where the source size is smaller than the field of view of the x-ray microscope, the condenser is used in a magnifying geometry to achieve suitable illumination of the object. This design allows the use of a source with a small source size which typically provides higher source brightness and thus typically higher throughput. While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.
	abstract	A collimation device for an X-ray beam, an optical device for analyzing a specimen by the scattering of an X-ray beam, and a collimator for an X-ray beam. The collimation device includes an enclosure configured to be under a vacuum or a controlled atmosphere, the enclosure including an inlet and an outlet for the X-ray beam and at least one plate made of a material having a diffracting periodic structure, the plate including two main faces and at least one flared aperture between the faces.
	claims	1. A pattern inspection method for inspecting a circuit pattern of an electronic device, comprising:a step of acquiring a reflection electron image and a secondary electron image of the electron device;a division step of dividing a region in the reflection electron image based on brightness values of pixels of the reflection electron image;an association step of associating the region in the reflection electron image divided in the division step and a region in the secondary electron image; andan inspection step of inspecting a circuit pattern in the secondary electron image using a result in the association step. 2. The pattern inspection method according to claim 1, whereinthe division step comprises dividing the brightness values of the pixels of the reflection electron image into two or more brightness value ranges and uniformly correcting brightness values of pixels included in a same division; andthe association step comprises associating the region in the reflection electron image after the correction and the region in the secondary electron image. 3. The pattern inspection method according to claim 2, wherein the division step comprises dividing the brightness values of the pixels of the reflection electron image into the two or more brightness value ranges based on appearance frequencies of the brightness values and replacing brightness values of pixels belonging to respective divisions with brightness values having highest appearance frequencies in respective divisions. 4. The pattern inspection method according to claim 2, wherein the association step comprises correcting a brightness value of a pixel of the region in the secondary electron image corresponding to the region belonging to the division in the reflection electron image, so as to clarify a boundary with other regions. 5. The pattern inspection method according to claim 1, further comprising a step of generating a synthetic reflection electron image by acquiring reflection electrons in two or more different space positions, acquiring two or more reflection electron images and synthesizing the two or more reflection electron images,wherein the division step and the association step comprise using the synthetic reflection electron image instead of the reflection electron image. 6. The pattern inspection method according to claim 5 wherein, in the step of generating the synthetic reflection electron image, a maximum brightness value among brightness values of pixels in a same position of the two or more reflection electron images is adopted and set as a brightness value of a corresponding pixel of the synthetic reflection electron image, or an average value of brightness values of pixels in a same position of the two or more reflection electron images is set as a brightness value of a corresponding pixel of the synthetic reflection electron image. 7. The pattern inspection method according to claim 1, further comprising:a step of evaluating an overlapping degree between a boundary part of the region belonging to the division in the reflection electron image and a boundary part of the region in the secondary electron image; anda step of correcting a position of the reflection electron image or the secondary electron image such that the reflection electron image and the secondary electron image overlap in a position in which the overlapping degree is highest. 8. The pattern inspection method according to claim 1, further comprising:a step of detecting a boundary part of the region belonging to the division in the reflection electron image and creating contour data;a step of detecting a boundary part of the region in the secondary electron image; anda step of searching for a position in which the contour data in the reflection electron image and the boundary part in the secondary electron image overlap, and aligning positions of the reflection electron image and the secondary electron image. 9. The pattern inspection method according to claim 1, further comprising a step of correcting a position of the reflection electron image or the secondary electron image by a predetermined amount and aligning positions of the secondary electron image and the reflection electron image. 10. The pattern inspection method according to claim 4, wherein the association step comprises correcting brightness values of pixels of the secondary electron image by contrast correction or gamma correction of the pixels of the secondary electron image. 11. The pattern inspection method according to claim 1, wherein the association step comprises specifying an inspection position in the secondary electron image by performing pattern matching using an image of the region belonging to the division in the reflection electron image. 12. The pattern inspection method according to claim 11, wherein the association step comprises specifying an inspection position in the secondary electron image by performing pattern matching between the region belonging to the division in the reflection electron image and the circuit pattern on design data. 13. The pattern inspection method according to claim 11, further comprising a step of generating a synthetic reflection electron image by acquiring reflection electrons in two or more different space positions, acquiring two or more reflection electron images and synthesizing the two or more reflection electron images,wherein the division step and the association step comprise using the synthetic reflection electron image instead of the reflection electron image. 14. The pattern inspection method according to claim 13, wherein, in the step of generating the synthetic reflection electron image, a maximum brightness value among brightness values of pixels in a same position of the two or more reflection electron images is adopted and set as a brightness value of a corresponding pixel of the synthetic reflection electron image, or an average value of brightness values of pixels in a same position of the two or more reflection electron images is set as a brightness value of a corresponding pixel of the synthetic reflection electron image. 15. The pattern inspection method according to claim 1, wherein the inspection step comprises inspecting the circuit pattern based on whether a shape of an edge part in the secondary electron image and a shape of contour data of the circuit pattern in design data are matched with each other. 16. The pattern inspection method according to claim 15, wherein the inspection step comprises searching for a position in which an edge part of a circuit pattern in an inspection target part of the reflection electron image and an edge part of a circuit pattern in an inspection target part of the secondary electron image overlap, and inspecting the circuit pattern on the secondary electron image in the position found as a result. 17. A pattern inspection program causing a computer to execute the pattern inspection method according to claim 1. 18. An electron device inspection apparatus comprising:a charged particle sending unit that sends a charged particle radiation to an electronic device;a reflection electron detector that detects a reflection electron generated from the electron device;a secondary electron detector that detects a secondary electron generated from the electronic device;an observation image acquiring unit that acquires a reflection electron image and a secondary electron image based on detection results in the reflection electron detector and the secondary electron detector; anda computing unit that executes the pattern inspection method according to claim 1.
	summary
RE0347086	description	DESCRIPTION OF THE PREFERRED EMBODIMENT The Scanning Ion Conductance Microscope (SICM) of the present invention is shown in simplified form in a preferred embodiment in FIG. 2 where it is generally indicated as 22. As depicted in FIG. 2, the SICM 22 is in the process of determining surface topography of the sample 14. The sample 14 is disposed in a reservoir 24 filled with an electrolyte 26. In the SICM 22, the scanning is accomplished by a micropipette 28 which is scanned by apparatus 30 according to techniques well known in the art as mentioned above. Again as in the prior art, the micropipette 28 could be stationary and the reservoir 24 holding the sample 14 moved by the scanning apparatus 30. The micropipette 28 (which is non-conductive and preferably of glass) has one electrode 32 disposed therein while a second electrode 32 is disposed in the electrolyte 26 within the reservoir 24. To complete the ion conductance path at the micropipette 28, the micropipette 28 is also filled with the electrolyte 26. A voltage source 34 is connected to the electrodes 32 and a current measuring transducer 36 is placed in series with the voltage source 34 to measure the current flowing and provide an indicative signal thereof to the control logic 38 on line 40. The control logic 38 performs two functions. First, it controls the scanning apparatus 30 over line 42. Second, by receiving a z-positional feedback signal from the scanning apparatus 30 it outputs the data on line 44 employed to visualize the scan results according to techniques well known in the art which, per se, form no part of the invention. In operation, the micropipette 28 is filled with electrolyte 26 and lowered through the reservoir 24 toward the surface 12 of the sample 14 while the conductance between the electrode 32 inside the micropipette 28 and the electrode 32 in the reservoir 24 is monitored. As the tip of the micropipette approaches the surface 12, the ion conductance decreases because the space through which ions can flow is decreased. The micropipette 28 is then scanned laterally over the surface 12 while the feedback system comprising the scanning apparatus 30 and the control logic 38 as described above raises and lowers it to keep the conductance constant. The path of the tip, as indicated by the dashed line in FIG. 2, follows the topography of the surface 12, therefore. As in prior art scanning microscopes, the z-directional signal developed in the process can be employed to display the surface topography in an manner desired as, for example, by displaying on a CRT (with or without color and/or other enhancements) or by plotting on a plotter, or the like. With respect to the micropipettes as employed by the inventors in tested embodiments to date, the early micropipettes were made from 1.5 mm outer diameter, 0.75 mm inner diameter Omega Dot capillary capillary tubing. Later micropipettes were made with similar tubing on a Brown-Flaming puller. The micropipette tip diameters were estimated using a non-destructive bubble pressure method which correlates the pipette's outer diameter to the internal pressure required for the pipette to produce a fine stream of bubbles in a liquid bath. The ratio of outer diameter to inner diameter has been found to be essentially constant along the entire length of the pipette. Inner diameters were thus estimated from the OD/ID ratio of the unpulled capillary tubing. Typically recently employed micropipettes have had tips with outer diameters of order 0.1 to 0.2 .mu.m and inner diameters of order 0.05 to 0.1 .mu.m. Samples were glued onto glass substrates or directly onto electrodes and then covered with a few drops of 0.1M NaCl. The micropipette tips were allowed to fill by capillary action and then their shafts were backfilled with a syringe. The 0.1M NaCl was also employed in the micropipettes to avoid concentration cell potentials and liquid junction potentials. Reversible Ag/AgCl microelectrode holders and bath electrodes provided the necessary stability for reliable current and topographic imaging. In their testing, the inventors herein applied DC voltages of 0.03 to 0.4 V and measured DC currents (typically 1 to 10 nA) to find the conductance: generally 10-8 to 10-7S. The microscope was operated with conductances 0.9 to 0.98 of the conductance when the tip was far from the surface. At smaller conductances, the inventors found that the micropipette tip was sometimes actually pressing into the sample surface. The inventors generated topographic images of their test samples by measuring the voltage that the feedback system applied to the z-axis of a single-tube x,y,z piezoelectric translator to keep the conductance constant. For ion current images, the local current was monitored as the micropipette 28 was scanned over the surface 12 at a constant height (i.e. at a constant z, being a plane parallel to the sample 14) as depicted in FIG. 3. A digital scanner supplied the x and y scan voltages for both topographic and ion current images. The z values (or ion currents) together with their x and y coordinates were recorded on a video cassette recorder via a digital data acquisition system. A program developed at the University of California Santa Barbara was used to filter the resulting image and added shading or color scales to allow surface features to be seen more easily. The inventors found that the method of statistical differences, which enhances features on their local background while suppressing noise, was especially useful for processing ion current images. The resolution of the SICM as a function of pipette diameter was measured with a large-scale model. A glass pipette, inner diameter 0.71 mm, outer diameter 1.00 mm, was scanned at a constant height over plastic blocks with regularly spaced grooves 0.71 mm deep. The height was set by lowering the pipette until the ion conductance went from 4.2.times.10-5S, its value far from the surface, down to 4.0.times.10-5S. These conductances were measured at a frequency of 10 KHz. This resolution test showed that it should be possible, in principle at least, to resolve features as small as the micropipette's inner diameter if the noise on the ion conductance signal could be reduced below 1%. So far, in practice the inventors have resolved features down to several times the micropipette's inner diameter of 0.05 to 0.2 .mu.m. There is a compromise between averaging the ion conductance signal from a long time to reduce noise and obtaining entire images in a reasonable time. The inventors have chosen to acquire their images in about five minutes and found that in so doing the smallest resolvable features are of order 0.2 .mu.m. The most promising application for the SICM is not simply imaging the topography of surfaces at submicron resolution. As mentioned above with respect to FIG. 3, the SICM 22' shown therein can image not only the topography but also the local ion currents coming out through pores in a surface. Comparison of topographic and ion current images can give a more detailed picture of the type of surface features that correlate with ion channels. This will be important in the evaluation of biological samples where not every hole is an ion channel. For images of the local ion currents, the micropipette 28 was scanned over the surface 12 at a preselected height, as indicated by the dashed line in FIG. 3, without moving up and down. It was also possible to hold the micropipette 28 over various locations on the imaged surface and measure local electrical properties. Thermal drift was small enough, approximately 0.004 .mu.m/minute, so that it was possible to look, for example, at the time dependence of the ion currents above a pore. While the current was constant for the model system employed, it would be more subtle for biological samples. As should now be appreciated from the foregoing description, the SICM of this invention is the first microscope that offers both high resolution topographic and ion current images of non-conductors. Much of the necessary apparatus employed in the SICM such as the micropipettes, microelectrodes, and current amplifiers, are already used routinely by electrophysiologists. Most of the rest of it is substantially the same as used in scanning tunneling microscopy and is readily available commercially. Because the SICM operates in a saline solution or other ionic solution, the microscope is well suited for bilogical applications. As also depicted in FIG. 3, an exciting extension of the basic SICM would be to use a scanning head 46 employing multiple barrel micropipettes 28 with ion-specific electrodes 32',32". The total current into all barrels (or the current into one barrel with a non-specific electrode provided for the purpose) could be used for feedback while the microscope could simultaneously measure and image the flow of different ions. It is anticipated by the inventors herein that such a technique will prove invaluable in the future to electrophysiologists to combine spatially resolved ion flow measurements and topological imaging of biological membranes. Another version of the SICM is depicted in FIG. 4 wherein it is labelled as 22". As with the embodiment of FIG. 4, there is a scanning head 46 employing multiple barrel micropipettes 28 with ion-specific electrodes 32', 32" and a non-specific electrode 32. The free electrode 32 (i.e. the electrode 32 in the reservoir 24) of the previous embodiments is replaced by the non-specific electrode 32 in one of the micropipettes 28 in the scanning head 46. All the active electrodes 32,32',32" . . . are, therefore, included in the scanning head 46. In this way, the scanning head 46 becomes self contained and only needs electrical connections thereto. This could be of particular interest in an arrangement where the scanning head 46 was fixed and the reservoir 24 containing the sample 14 is moved to create the scanning action of the micropipettes 28 over the surface 12 of the sample 14.
	claims	1. A diaphragm unit for use in an x-ray device of the type having an x-ray emitter positioned in a housing, comprising an assembly unit allowing for rotational movement of the diaphragm unit about the housing, so that the assembly unit isocentrically translates the diaphragm unit in its entirety about a source point of the x-ray emitter, allowing an asymmetrical part of an examination area to be irradiated by the x-ray emitter using the diaphragm unit. 2. The diaphragm unit according to claim 1, wherein the assembly unit includes a guide rail for moving the diaphragm unit along a path always equidistant from the source point of the x-ray emitter. 3. The diaphragm unit according to claim 1, further comprising an electric motor for powering rotational movement of the diaphragm unit about the housing. 4. An x-ray device, comprising:an x-ray emitter; anda diaphragm unit arranged on an assembly unit and facing the x-ray emitter for fading in an examination area, wherein the assembly unit is configured to isocentrically rotate the diaphragm unit about the x-ray emitter so that an asymmetrical examination area is irradiated by the x-ray emitter. 5. The x-ray device according to claim 4, wherein components of the diaphragm unit do not change position relative to one another while the assembly unit is rotated. 6. The x-ray device according to claim 4,wherein the x-ray emitter includes a source point from which an axis of symmetry extends;wherein x-rays travel from the source point; along the axis of symmetry and through an exit opening of the emitter; andwherein the diaphragm unit and the x-ray emitter form one integrated unit which can be tilted in the entirety about the source point to thereby rotate the axis of symmetry. 7. The x-ray device according to claim 6, further including a housing surrounding the emitter and a hanger assembly connecting the emitter to the housing to effect tilting of the integrated unit about the source point so that an asymmetrical part of an examination area to be irradiated by the x-ray emitter can be exposed to the x-ray emitter. 8. The x-ray device according to claim 7, wherein the hanger assembly includes a swivel arm for tilting the integrated unit. 9. The diaphragm unit according to claim 4, further comprising a guide rail for moving the diaphragm unit. 10. The diaphragm unit according to claim 9, wherein the guide rail is arranged isocentrically relative to the source point of the x-ray emitter. 11. The x-ray device according to claim 4, further comprising an electric motor for powering isocentric rotation of the diaphragm unit about the x-ray emitter. 12. A method of adjusting a diaphragm unit of the type which receives radiation from an x-ray emitter in order to effect fading in an examination area to be irradiated by the x-ray emitter, the method including the steps of:connecting an assembly unit to provide a rotational path about a source point of the emitter; andconnecting the diaphragm unit to the assembly unit for movement along the rotational path and about the x-ray emitter so that an asymmetrical part of the examination area is exposed to the radiation by moving the diaphragm unit.
051475987	summary	CROSS REFERENCE TO RELATED APPLICATION Reference is hereby made to the following copending patent application dealing with related subject matter and assigned to the assignee of the present invention: 1. "Fuel Assembly Containing Fuel Rods Having Standardized-Length Burnable Absorber Integral With Fuel Pellets And Method Of Customizing Fuel Assembly" by Barry F. Cooney, U.S. Ser. No. 07/270,560, filed Nov. 14, 1988. Abandoned on Aug. 2, 1990. 2. "Nuclear Fuel With Helium Release-Reducing Burnable Absorber Coating" by Charles A. Bly, U.S. Ser. No. 345,859, filed May 1, 1989. Abandoned on Aug. 20, 1991. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to nuclear reactors and, more particularly, is concerned with a nuclear reactor core having nuclear fuel and composite burnable absorber arranged for power peaking and moderator temperature coefficient control. 2. Description of the Prior Art In a typical nuclear reactor, such as a pressurized water reactor (PWR), the reactor core includes a large number of fuel assemblies each of which is composed of a plurality of elongated fuel elements or rods. The fuel rods each contain fissile material in the form of a stack of nuclear fuel pellets The fuel rods are grouped together in an array which is organized to provide a neutron flux in the core sufficient to support a high rate of nuclear fission and thus the release of a large amount of energy in the form of heat. A liquid coolant, such as water, is pumped upwardly through the core in order to extract some of the heat generated in the core for the production of useful work. In the operation of a PWR it is desirable to prolong the life of the reactor core as long as feasible to better utilize the uranium fuel and thereby reduce fuel costs. To attain this objective, it is common practice to provide an excess of reactivity initially in the reactor core and, at the same time, maintain the reactivity relatively constant over its lifetime. In a PWR, initial excess reactivity is controlled primarily by use of soluble boron in the coolant water and power peaking is controlled primarily by use of burnable absorber. For long cycles, the control of initial excess reactivity by soluble boron alone would require high boron concentrations in water, which would lead to positive moderator coefficient Therefore, in addition to power peaking control, burnable absorber is used to hold down some of the excess reactivity, so that the soluble boron concentration is appropriate to maintain the moderator temperature coefficient within the technical specifications. In one prior art approach, a burnable absorber is mixed directly with the fissionable material of the fuel pellets and integrated therewith to enable the use of an excessive amount of fuel in the reactor core during the initial life of the fuel. In another prior art approach, a burnable absorber coating is applied to the surface of fuel pellets. For example, in U.S. Pat. No. 3,427,222 to Biancheria et al, assigned to the assignee of the present invention, the fuel pellets have a fusion-bonded coating on the surface of each pellet Each fuel pellet is a cylindrical body composed of sintered particles of fissionable material, such as enriched uranium oxide, and an outer coating of predetermined thickness containing a burnable absorber or poison material, such as boron, cadmium, gadolinium, samarium, and europium Examples of boron-containing compounds used are boron carbide, boron nitride and zirconium boride or zirconium diboride. The burnable absorber coating approach has been successfully applied in an integral fuel burnable absorber (IFBA) rod, manufactured and marketed by the assignee of the present invention and used in a PWR fuel assembly known commercially as the VANTAGE 5. Up to the present, the same burnable absorber, such as zirconium diboride employed in IFBA rods, has been used for controlling both power peaking and moderator temperature coefficient. For long cycles, with high initial excess reactivity, a number of IFBA rods are used for power peaking control and oftentimes additional IFBA rods are needed for moderator temperature coefficient control. The latter is done indirectly by reducing the concentration of boron in water (used to surpress excess core reactivity) by providing for increased absorption through burnable absorber rods. This situation leads to the use of a large number of IFBA rods and a higher residual penalty. Consequently, a need exists for a different approach to controlling both power peaking and moderator temperature coefficient than by use of a large number of IFBA rods in the nuclear reactor core as has been the practice heretofore. SUMMARY OF THE INVENTION The present invention provides a nuclear reactor core having nuclear fuel rods and composite fuel and burnable absorber rods in an arrangement designed to satisfy the aforementioned needs. In accordance with the present invention, power peaking and moderator temperature coefficient are controlled by using two different absorber materials in the composite fuel and burnable absorber rods, one material tailored primarily for controlling power peaking and the other material tailored primarily for controlling moderator temperature coefficient. The result is a significant reduction in the number of composite fuel and burnable absorber rods, and reduction in the residual penalty without any loss in peaking factor or moderator temperature coefficient control. Boron in the zirconium diboride coated on the nuclear fuel is the preferred material for power peaking control in view of its well-known advantages of no moderator displacement and very low residual penalty. Erbium has nuclear absorption resonances around 0.5 ev, providing effective moderator temperature coefficient control through increased absorption in the resonances as moderator temperature rises leading to reduction in moderator density Erbium coated on or mixed in the nuclear fuel is the preferred material for moderator temperature coefficient control. It eliminates the need to use additional zirconium diboride or other burnable absorber material for moderator temperature coefficient control. The combination of zirconium diboride and erbium takes advantage of the strength of both of these absorbers. For power peaking control, erbium by itself would require its use in high concentrations, with the attendant residual poison penalty. Boron by itself controls moderator temperature coefficient indirectly by reducing the soluble boron concentration in the coolant water, thus requiring a large number of absorber rods. The combination of the two, on the other hand, uses each one for the control of the parameter that it is most effective for, i.e., Erbium controlling the moderator temperature coefficient directly and effectively through resonance absorption and zirconium diboride controlling power peaking utilizing high absorption in Boron. The combination is thus better than the sum of each or the use of each separately. Accordingly, the present invention is directed to a nuclear reactor core having a first group of fuel rods containing fissionable material and no burnable absorber, and a second group of fuel rods containing fissionable material and two burnable absorber materials. The groups of fuel rods are arranged in the core for controlling power peaking and moderator temperature coefficient. The number of fuel rods in the first group are greater than the number in the second group. More particularly, the two burnable absorber materials can be provided as separate coatings or a mixture. One burnable absorber material is an erbium-bearing material such as erbium oxide and the other is a boron-bearing material such as zirconium diboride. Alternatively, the erbium-bearing material can be interspersed or mixed with the fissionable material. These and other features and advantages of the present invention will become apparent to those skilled in the art upon a reading of the following detailed description when taken in conjunction with the drawings wherein there is shown and described an illustrative embodiment of the invention.
	summary
	summary
043483550	description	DESCRIPTION OF PREFERRED EMBODIMENT In the Figures, the numeral 1 designates cruciform control rods. Between a group of four of these control rods there is arranged a group of four fuel assemblies 2. Each fuel assembly comprises four boxes 2a, 2b, 2c and 2d of square cross-section, each of these boxes containing a respective bundle of fuel rods 3. These fuel rods comprise fuel pellets in sheathing tubes. The boxes 2a-2d of the fuel assembly are connected at the bottom to a common bottom portion 4, which is connected to an assembly supporting plate of the core and distributes the cooling water to the four boxes of the assembly. At the top, the boxes are connected to a common top portion or unit 5. Between the bottom portion 4 and the top unit 5, the boxes 2a-2d may be connected to each other in one or more places by means of connecting elements 6. As shown in FIG. 3, which shows one of the boxes (box 2a), it can be seen that each of the boxes 2a-2d may be formed with corners of large radius and the four fuel rods 3a adjacent the corners of a box may be of smaller diameter than the other fuel rods 3b. By employing a fuel assembly with four boxes 2a-2d having a common bottom portion 4 and a common top unit 5, it is possible to improve the fuel economy of both new reactors and reactors already in operation. Previously known and tested devices may be employed for supporting the fuel assemblies. Because of the cruciform gap 8 between the four boxes 2a-2d of a fuel assembly, a steam-free quantity of water is obtained which results in an increased moderating ability, and thus in a more even neutron flux over the cross-section of the fuel assembly, as well as a more even power developement and burn-up. The need to vary the degree of fuel enrichment within the fuel rod bundle is reduced or eliminated. Since the gaps 9 and 10 between two adjacent fuel assemblies 2 are larger than the gap 8 between the boxes 2a-2d, the neutron flux is somewhat greater nearest the gaps 9 and 10, and thus also the power development. By re-arrangement of the boxes containing the fuel rods or transfer of fuel rod bundles between boxes, as shown by the arrows 11 in FIG. 1, an uneven burn-up may be prevented. As shown, the boxes 2a and 2c change positions and the boxes 2b and 2d change positions. One further possibility of achieving an equalization of the neutron flux, the power development and the burn-up is to replace a fuel rod with an empty tube 7 (see FIG. 3) through which the cooling water and the moderator water pass freely. A rod may be placed in the centre of the fuel assembly, which rod connects and retains the bottom portion 4 and the top unit 5 of the fuel assembly. In a design of a fuel assembly in which the four boxes of the assembly are connected to each other, the fuel assembly may comprise a cruciform temporary absorber rod 12 or individual absorber plates with a burnable absorber which may be removed after a certain time in connection with fuel transfer or refuelling. The bottom portion of the fuel assembly is preferably formed with a cruciform divider 13 which extends down into or through a throttle opening in the bottom portion 4 and the core bottom orifice. The bottom portion 4 is thus divided into four throttled channels, which ensures that the water volume through the four boxes becomes equal and stable even if the flow resistance in the boxes should be different. By the division of a fuel assembly box into four smaller ones, a larger box surface is obtained. However, because the dimensions are smaller, the bending stresses will be reduced to such an extent that the thickness of the metallic sheet material from which the boxes are made may be reduced by more than 50 percent. The amount of box material is considerably reduced, and thus also the undesired neutron absorption. At the same time, a larger space is obtained for a steam-free water volume and a more even distribution thereof.
	summary
052672824	summary	BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to a device for monitoring the stack exit air in a reactor installation, essentially consisting of a pressure relief line which connects the containment vessel to the stack and in which a filter unit is located, a sampling point being provided downstream of the filter, from where gas mixture is branched off via a sampling line, passed through a measurement section and then returned to the stack exit air. 2. Discussion of Background The atmosphere in the containment vessel of a nuclear power station consists as a rule of air, steam, hydrogen, CO.sub.2, rare gases, iodine and aerosols. In normal operation of the installation, this mixture, which has an activity of about 10.sup.3 Bq/m.sup.3, is discharged from the containment vessel via a venting unit directly into the stack. In the event of an accident with a small leakage in the primary system, during which the activity is between 10.sup.3 Bq/m.sup.3 and 10.sup.8 Bq/m.sup.3, the gas is likewise discharged via the venting unit directly into the stack. In the event of a major accident with, for example, core meltdown, the activity can become greater than 10.sup.14 Bq/m.sup.3. During a major accident, the venting unit is isolated, whereupon the pressure in the containment vessel rises. To avoid an unduly great pressure rise, the containment vessel is relieved via a filter unit. In this filter unit (for example a dry filter or wet filter), the activity of iodine and aerosols is reduced by a factor of at least 1,000. Downstream of the filter unit, the activity of the gas is then determined in a measurement section. Because of the remaining very high activity in the downstream pure-gas line leading to the stack, the measuring apparatus used for normal operation, such as balancing filters and aerosol monitors cannot be used, since the measuring range would be exceeded and handling of the balancing filter would not be ensured. For this reason, special instruments having a wider measuring range and involved screenings as well as complicated devices for handling the balancing filter are normally used. SUMMARY OF THE INVENTION The invention attempts to avoid these disadvantages. Accordingly, one object of this invention is to provide, in an installation of the type described at the outset, for operation of the installation with the existing measuring instruments and apparatus even in the event of an accident. According to the invention, this is achieved when the activity concentration of the gas is reduced in a dilution unit upstream of the measurement section. The advantages of the invention are to be seen, inter alia, in the elimination of the hitherto usual heavy screenings around the entire measurement section. Screening for the transport of the balancing filter to be measured is also eliminated, whereby the hazard for the operating personnel is greatly reduced. It is particularly advantageous, if the gas sample in the sampling line is protected from cooling by means of a heater, before it is diluted. This avoids, on the one hand, condensation of steam in the sampling line and measurement section and an associated erroneous measurement due to precipitation of iodine and aerosols.
	description	FIG. 1 shows diagrammatically an X-ray apparatus with a filter according to the invention. The X-ray source 1 emits an X-ray beam 2 whereto an object 3, for example a patient to be examined, is exposed. Due to local differences in the absorption of X-rays in the object 3, an X-ray image is formed on the X-ray detector 4, being an image intensifier pick-up chain in the present example. The X-ray image is formed on the entrance screen 5 of the X-ray image intensifier 6 and is converted into an optical image on the exit window 7 which is imaged on a video camera 9 by means of a system of lenses 8. The video camera 9 forms an electronic image signal from the optical image. For example, for the purpose of further processing the electronic image signal is applied to an image processing unit 10 or to a monitor 11 on which the image information contained in the X-ray image is displayed. A filter 12 for locally attenuating the X-ray beam 2 is arranged between the X-ray source 1 and the object 3. The filter 12 includes a plurality of tubular filter elements 13, the X-ray absorptivity of which is adjustable by application, by way of an adjusting circuit 14, of electric voltages to the wall of the filter elements. The electric voltages are adjusted, for example, on the basis of the setting of the X-ray source 1 with the power supply 15 of the X-ray source and/or on the basis of, for example, brightness values of the X-ray image which can be derived from the signal present at the output terminal 16 of the video camera 9. The general construction of such a filter 12 and the composition of the absorption liquid are described in detail in United States patent U.S. Pat. No. 5,625,665 (PHN 15.044). FIG. 2a is a diagrammatic sectional view of a tubular filter element 13 of a filter as shown in FIG. 1. Via the supply channel 20 the filter element 13 is filled with the liquid filling 22 which is electrically conductive and X-ray absorbing. For each filter element there are defined the longitudinal direction z and the internal volume 21, the latter being bounded by the walls 28 of the filter element. Each filter element includes the first electrode 23 in the form of an electrically conductive layer which is electrically insulated, by means of an insulation layer 34, from the liquid filling present in the internal volume 21, an inert cover layer 24 which is provided on an inner side of the walls 28, and a second electrode 29 for applying an electric potential to the liquid filling. The electrically conductive layer 23 of the filter element 13 is coupled to a switching element which is in this case formed by a drain contact 30 of a field effect transistor 25, its source contact 31 being coupled to a voltage line 26. The field effect transistor 25 is turned on, that is, the switching element is closed by means of a control voltage which is applied to a gate contact 32 of the field effect transistor 25 via the control line 27. The electric voltage of the voltage line 26 is applied to the electrically conductive layer 23 by closing the switching element. When the voltage line is adjusted to the value of the xe2x80x9cfillingxe2x80x9d voltage, the contact angle xcex8 of the liquid filling 22 relative to the inert cover layer 24 decreases and the relevant filter element is filled with the liquid filling. FIG. 2b is a diagrammatic sectional view of the tubular filter element 113 of a filter as shown in FIG. 1, the filter element now being filled with the liquid filling consisting of an electrically conductive liquid component 122 and an X-ray absorbing liquid component 124. The liquid components are supplied via respective supply channels 120 and 121. The further functional parts of the filter element 113 are substantially identical to those of the filter element 13, so that the control chart for the electrically conductive liquid component can be similar. This control chart determines the level of the electrically conductive liquid component 122 in the internal volume 21 of the filter element 113 which itself determines the level of the X-ray absorbing liquid component 124 in the filter element 113, because the respective components constitute one common liquid column with an interface 130. The degree of X-ray absorption is in this case determined by the degree of filling of the filter element 113 with the X-ray absorbing component 124. FIG. 3 is a 360xc2x0 view of the electrode segments 23 on a substrate 38 in a first embodiment of the filter element 13 according to the invention, the electrode segments bearing even sequence numbers 40 in the series and the electrode segments bearing odd sequence numbers 41 in the series constituting respective sub-groups and the electrical device being provided with switches 25 for controlling said sub-groups. The field effect transistors in this embodiment again act as switching elements. It is an advantage of the present embodiment that the electrical wiring is simplified. For optimum transport of the liquid filling in the longitudinal direction z of the filter element, in this embodiment a given time overlap is desired between the pulses of the electric xe2x80x9cfillingxe2x80x9d voltages applied to both sub-groups. As soon as the meniscus of the liquid filling is present in the Nth electrode segment to be filled, the voltage applied to the electrode segments of the other sub-group must be adjusted to the value of the xe2x80x9cdrainingxe2x80x9d voltage, unless transport to the N+1th electrode segment is required. In order to make the latter switching superfluous, a second embodiment of the filter element 13 is presented in which each electrode segment is connected to the electrical device via a respective connection. FIG. 4 is a 360xc2x0 view of the projection of the electrode segments 23 on a substrate 38 in this embodiment. For optimum transport of the liquid filling in the longitudinal direction z of the filter element, a given time overlap is desired between the pulses of the electric xe2x80x9cfillingxe2x80x9d voltages applied to both sub-groups in this embodiment. FIG. 5 is a diagrammatic 360xc2x0 view of the electrode segments of the filter element 13 in a fourth embodiment according to the invention, wherein the facing edges of directly successive electrode segments are provided with meshing teeth. This step enhances the reliability of the transport of the liquid filling in the longitudinal direction z of the filter element. FIG. 5a shows an example of the crenellation-like teeth 37 and 39 of the electrode segments of the type 123. FIG. 5b shows an example of the sawtooth-like teeth 50 of the electrode segment of the type 223.
	summary

Subsets and Splits

No community queries yet

The top public SQL queries from the community will appear here once available.