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	abstract	An emergency spent nuclear fuel pool cooling system that requires no external electrical power source and relies on the expansion of a cryogenic fluid through an evaporator/heat exchanger submerged within the spent fuel pool, to power various components used to cool the spent fuel pool and adjacent areas and provide makeup water to the spent fuel pool. Other than the evaporator/heat exchanger to which the cryogenic fluid is connected, the remaining components employed to cool the pool and the surrounding area and provide makeup water can be contained in a relatively small, readily transportable skid.
	description	1. Field The present disclosure relates to methods of adding oxygen to reactor water sample flows. 2. Description of Related Art In certain reactor situations, the addition of oxygen to a reactor water sample flow is desired. Conventionally, the addition of oxygen in such situations involves the bubbling of oxygen gas into the reactor water sample flow, wherein the oxygen gas is supplied from a compressed source (e.g., bottled oxygen). However, the use of bottled oxygen raises serious safety concerns because of its relatively highly pressurized state. Example embodiments of the present invention relate to a method of adjusting an oxygen concentration of a reactor water side stream in a nuclear plant. The method may include injecting demineralized water into the reactor water side stream to produce an oxygenated stream with an increased oxygen concentration. The injecting demineralized water step may include adding demineralized water with a known oxygen concentration of at least 20 times more oxygen than the reactor water side stream. The injecting demineralized water step may include adding demineralized water to the reactor water side stream, the reactor water side stream having less than 100 ppb oxygen. The injecting demineralized water step may include adding demineralized water with at least 2000 ppb oxygen to the reactor water side stream. The injecting demineralized water step may include adjusting a flow rate of the demineralized water such that a temperature of the oxygenated stream is at least 400° F. after injecting the demineralized water. The injecting demineralized water step may include adjusting a flow rate of the demineralized water such that a hydrogen-to-oxygen molar ratio in the oxygenated stream is greater than 2 after injecting the demineralized water. The injecting demineralized water step may include adding the demineralized water at a point downstream from a reactor and upstream from a clean-up system. The injecting demineralized water step may include adding the demineralized water at a point downstream from a reactor and upstream from a recirculation system. The injecting demineralized water step may include adding the demineralized water at a point upstream from a catalytic mitigation monitoring system (MMS). The injecting demineralized water step may include adding the demineralized water into a pipe carrying the reactor water side stream at a point that is a distance of at least 10 times a diameter of the pipe upstream from an electrochemical corrosion potential (ECP) sensor. The injecting demineralized water step may include adding the demineralized water at a flow rate that is 10% or less of a flow rate of the reactor water side stream. The injecting demineralized water step may include adding the demineralized water before an injection of a noble metal and while an electrochemical corrosion potential (ECP) is being measured so as to determine a catalytic effect of the noble metal. The injecting demineralized water step may include adding the demineralized water during an injection of a noble metal and while an electrochemical corrosion potential (ECP) is being measured so as to determine a catalytic effect of the noble metal. The injecting demineralized water step may include adding the demineralized water after an injection of a noble metal and while an electrochemical corrosion potential (ECP) is being measured so as to determine a catalytic effect of the noble metal. The injecting demineralized water step may include adding demineralized water in liquid form. The injecting demineralized water step may include adding demineralized water that has been produced on site at the nuclear plant. The injecting demineralized water step may include pumping the demineralized water into the reactor water side stream with a positive displacement pump. Example embodiments of the present invention also relate to a method of determining a catalytic effect of a noble metal deposited within a reactor system. The method may include injecting demineralized water into a reactor water side stream to produce an oxygenated stream with an increased oxygen concentration such that a hydrogen-to-oxygen molar ratio of the oxygenated stream is less than infinity; and performing a plurality of electrochemical corrosion potential (ECP) measurements on the oxygenated stream to determine the catalytic effect of the noble metal deposited within the reactor system. It should be understood that when an element or layer is referred to as being “on,” “connected to,” “coupled to,” or “covering” another element or layer, it may be directly on, connected to, coupled to, or covering the other element or layer or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly connected to,” or “directly coupled to” another element or layer, there are no intervening elements or layers present. Like numbers refer to like elements throughout the specification. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. It should be understood that, although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers, and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, or section from another region, layer, or section. Thus, a first element, component, region, layer, or section discussed below could be termed a second element, component, region, layer, or section without departing from the teachings of example embodiments. Spatially relative terms (e.g., “beneath,” “below,” “lower,” “above,” “upper,” and the like) may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It should be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the term “below” may encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. The terminology used herein is for the purpose of describing various embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “includes,” “including,” “comprises,” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. Example embodiments are described herein with reference to cross-sectional illustrations that are schematic illustrations of idealized embodiments (and intermediate structures) of example embodiments. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, example embodiments should not be construed as limited to the shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. For example, an implanted region illustrated as a rectangle will, typically, have rounded or curved features and/or a gradient of implant concentration at its edges rather than a binary change from implanted to non-implanted region. Likewise, a buried region formed by implantation may result in some implantation in the region between the buried region and the surface through which the implantation takes place. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the actual shape of a region of a device and are not intended to limit the scope of example embodiments. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which example embodiments belong. It will be further understood that terms, including those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. Example embodiments of the present invention relate to the addition of oxygen to reactor water samples. In particular, the methods according to example embodiments utilize demineralized water to adjust an oxygen concentration of a reactor water side stream, wherein the reactor water side stream may be a reactor water sample flow. It should be understood that demineralized water is also known to those ordinarily skilled in the art as deionized (DI) water. Demineralized or deionized water is water that has had its mineral ions removed (such as cations from sodium, calcium, iron, copper and anions such as chloride and bromide). Water may be demineralized or deionized using ion exchange resins which bind to and filter out the mineral salts from the water. As used herein, it should be understood that demineralized water means deionized water and vice versa. FIG. 1 is a flow chart showing a method of adjusting an oxygen concentration of a reactor water side stream according to a non-limiting embodiment of the present invention. Referring to step S100 in FIG. 1, demineralized water may be injected into a reactor water side stream to produce an oxygenated stream. It should be understood that the demineralized water is injected in liquid form (as opposed to a gaseous state). The demineralized water may be injected at a point downstream from a reactor and upstream from a clean-up system. The demineralized water may also be injected at a point downstream from a reactor and upstream from a recirculation system. The presence of the additional oxygen introduced by the demineralized water and a subsequent change in the concentration of the oxygen may be measured and analyzed. As indicated in step S120 of FIG. 1, the oxygenated stream may be tested to determine the effect of a process treatment on the reactor system. FIG. 2 is a diagram illustrating a method of adjusting an oxygen concentration of a reactor water side stream according to a non-limiting embodiment of the present invention. In a nuclear plant, a method of adjusting an oxygen concentration of a reactor water side stream may involve injecting demineralized water into the reactor water side stream to produce an oxygenated stream with an increased oxygen concentration. Referring to FIG. 2, a nuclear plant may include a reactor water piping 200 that runs from a reactor (not shown) to a monitoring system 230. For instance, the reactor water piping 200 may be connected to the bottom of the reactor (not shown). A reactor water side stream 202 flows from the reactor (not shown) to the monitoring system 230 by way of the reactor water piping 200. The reactor water side stream 202 may be used as a sample flow. A demineralized water piping 212 runs from a demineralized water supply (not shown) to the reactor water piping 200. The demineralized water supply (not shown) is produced on site at the nuclear plant. The demineralized water supply (not shown) may be produced specifically to provide a demineralized water stream 214 in the demineralized water piping 212. Alternatively, the demineralized water supply (not shown) may be an existing supply that provides demineralized water for various uses within the nuclear plant, wherein a portion of the supply is diverted by the demineralized water piping 212. Compared to untreated water, demineralized water has a higher resistivity and lower conductivity due to the removal of the mineral ions therein. For instance, demineralized water may have a resistivity of at least 0.1 MΩ·cm and a conductivity of at most 10 μS·cm−1. In another instance, demineralized water may have a resistivity of at least 1.0 MΩ·cm and a conductivity of at most 1 μiS·cm−1. Demineralized water also has a relatively high oxygen content compared to untreated water. For instance, demineralized water may have at least 2000 ppb O2 and up to 8000 ppb O2 when air saturated. The demineralized water piping 212 is connected to the reactor water piping 200 at an injection point 220. During injection of the demineralized water, the demineralized water stream 214 may be introduced into the reactor water side stream 202 with a pump 210. The pump 210 may be a positive displacement pump, although example embodiments are not limited thereto. The demineralized water may be pumped into the reactor water piping 200 at pressures ranging from 100 psig to over 1000 psig (e.g., 1100 psig). Assuming the reactor water piping 200 has a certain diameter at the injection point 220, the mixing of the reactor water side stream 202 and the demineralized water stream 214 may be complete about 10 to 20 diameters downstream from the injection point 220 to produce an oxygenated stream 224. Thus, the mixing may be complete at an oxygenated point 222 which is downstream from the injection point 220 and upstream from the monitoring system 230. That being said, the length of the reactor water piping 200 extending from the injection point 220 to the monitoring system 230 will be longer than the length of the reactor water piping 200 extending from the injection point 220 to the oxygenated point 222. Stated more clearly, a minimum length of the portion of the reactor water piping 200 that is downstream from the injection point 220 is the distance between the injection point 220 and the oxygenated point 222. The reactor water side stream 202 may have an oxygen concentration that is less than about 100 ppb. In contrast, the demineralized water stream 214 may have an oxygen concentration ranging from about 2000 to 8000 ppb (e.g., 5000 ppb). Thus, the demineralized water stream 214 may have a known oxygen concentration that is 20 to 80 times higher than that of the reactor water side stream 202. That being said, the addition of a relatively small amount of demineralized water to the reactor water side stream 202 can increase the oxygen concentration of the resulting mixture rather significantly. For example, the demineralized water stream 214 may be added at a flow rate that is 10% or less of a flow rate of the reactor water side stream 202. In a non-limiting embodiment, to add 100 ppb oxygen to the reactor water side stream 202, a demineralized water stream 214 with 8000 ppb oxygen may be added at a flow rate that is about 1.25% that of the reactor water side stream 202. The resulting temperature of the oxygenated stream 224 may also be taken into account to ensure proper functioning of the monitoring system 230. For instance, the flow rate of the demineralized water stream 214 may be adjusted such that a temperature of the oxygenated stream 224 is at least 400° F. after injecting the demineralized water, although example embodiments are not limited thereto. In a non-limiting embodiment, the temperature of the reactor water side stream 202 may be about 520° F., while the temperature of the demineralized water stream 214 may be less than about 200° F. (e.g., 100° F.). Accordingly, the flow rate of the demineralized water stream 214 may be adjusted such that a resulting temperature of the oxygenated stream 224 exceeds what is needed for accurate operation of the monitoring system 230. The monitoring system 230 may be a catalytic mitigation monitoring system (MMS). In a reactor system such as a boiling water reactor (BWR) system, oxygen ions (O2−) are present as a result of the reactor environment and may react with the metal piping in the system so as to cause stress corrosion cracking. One solution for addressing the issue of stress corrosion cracking is an On-line NobleChem (OLNC) process. During an On-line NobleChem process, a chemical containing a noble metal such as platinum is injected into the reactor water where the chemical decomposes and releases the platinum so as to form platinum deposits on inner surfaces of the system piping. As a result, the platinum acts as a catalyst for the recombination of the hydrogen ions (H+) and oxygen ions (O2−) to form water (H2O), thereby reducing the amount of oxygen ions (O2−) in the system, which, in turn, mitigates or prevents the occurrence of stress corrosion cracking. An On-line NobleChem process may be performed as frequently as needed (e.g., every year) to ensure that the inner surfaces of the system piping (as well as any new cracks) have been adequately coated with the platinum. To evaluate the effectiveness of an On-line NobleChem process, a monitoring system 230 may be used, which may be in the form of a catalytic mitigation monitoring system. The monitoring system 230 may include sensors for measuring various properties, including an electrochemical corrosion potential (ECP), of the reactor water. For instance, the electrochemical corrosion potential of the reactor water may be −200 mV before platinum injection and −500 mV after platinum injection, although example embodiments are not limited thereto. However, in certain situations, the electrochemical corrosion potential may already be −500 mV before the platinum injection. In other situations, the electrochemical corrosion potential may remain unchanged even after the platinum injection. In the above situations, it is believed that the line length and/or flow rate may be such that a majority or all of the oxygen in the reactor water may have already been consumed (e.g., by the piping) before the oxygen even has a chance to reach the monitoring system. Thus, a subsequent electrochemical corrosion potential measurement by the monitoring system may be relatively low due to the lack of oxygen in the reactor water as opposed to the catalytic recombination of the oxygen with hydrogen. In view of the above, to ensure that an electrochemical corrosion potential measurement of the reactor water side stream 202 can be used as a direct assessment of mitigation, oxygen may be added to the reactor water side stream 202 by way of the demineralized water stream 214. In particular, the oxygen addition would increase the electrochemical corrosion potential of the oxygenated stream 224 before the platinum injection, thereby allowing a subsequent decrease in the electrochemical corrosion potential to be associated with the catalytic effect provided by the platinum injection. As a result, the effectiveness of an On-line NobleChem process may be evaluated. The demineralized water stream 214 may be introduced into the reactor water side stream 202 before an injection of a noble metal and while an electrochemical corrosion potential is being measured so as to determine a catalytic effect of the noble metal. Additionally, the demineralized water stream 214 may be introduced into the reactor water side stream 202 during an injection of a noble metal and while an electrochemical corrosion potential (ECP) is being measured so as to determine a catalytic effect of the noble metal. Furthermore, the demineralized water stream 214 may be introduced into the reactor water side stream 202 after an injection of a noble metal and while an electrochemical corrosion potential (ECP) is being measured so as to determine a catalytic effect of the noble metal. It should be understood that the demineralized water addition may be performed for a desired duration (e.g., a few minutes) every week or month during normal operation and/or performed continuously or hourly during a noble metal injection. While the above example has been described in connection with an On-line NobleChem process, it should be understood that example embodiments are not limited thereto and may be applied in other instances where oxygen addition is needed. The flow rate of the demineralized water stream 214 may be adjusted such that a hydrogen-to-oxygen molar ratio in the oxygenated stream 224 is greater than 2 (e.g., ratio of 3 or 4). In a non-limiting embodiment, the hydrogen-to-oxygen molar ratio may be range from 5 to 10 and even up to 15 to 20. To ensure adequate mixing, the demineralized water stream 214 may be introduced into the reactor water piping 200 such that the injection point 220 is at a distance of at least 10 times a diameter of the reactor water piping 200 upstream from an electrochemical corrosion potential sensor in the monitoring system 230. The flow rate of the oxygenated stream 224 into the monitoring system 230 may be about 5 gpm, although example embodiments are not limited thereto. A method of determining a catalytic effect of a noble metal deposited within a reactor system may include injecting a demineralized water stream 214 into a reactor water side stream 202 to produce an oxygenated stream 224 with an increased oxygen concentration such that a hydrogen-to-oxygen molar ratio of the oxygenated stream 224 is less than infinity. A plurality of electrochemical corrosion potential measurements may then be performed on the oxygenated stream 224 to determine the catalytic effect of the noble metal deposited within the reactor system. In view of the above, example embodiments of the present invention provide a relatively safe, simple, and effective way of adding oxygen to a reactor water stream of a nuclear plant. While a number of example embodiments have been disclosed herein, it should be understood that other variations may be possible. Such variations are not to be regarded as a departure from the spirit and scope of the present disclosure, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.
	claims	1. A method for evaluating at least one quantity relative to the distortion of a nuclear fuel assembly, the method comprising the following steps:placing the nuclear fuel assembly in a volume of water bounded by a free upper surface;placing a camera outside the volume of water, above the free upper surface;taking at least one image of at least one lateral face of the nuclear fuel assembly with the camera while the camera is above the free upper surface of the volume of water; andgraphically analyzing the at least one image and deducing the at least one quantity relative to the distortion of the nuclear fuel assembly therefrom. 2. The evaluation method according to claim 1 wherein the at least one image taken by the camera shows the entire lateral face of the nuclear fuel assembly. 3. The evaluation method according to claim 1 wherein the nuclear fuel assembly comprises: a plurality of longitudinally elongated nuclear fuel rods; and a plurality of grids for maintaining the nuclear fuel rods in position, the plurality of grids being distributed longitudinally along the nuclear fuel rods, the at least one quantity relative to the distortion of the nuclear fuel assembly being respective shifts of the grids in a transverse plane perpendicular to a longitudinal direction. 4. The evaluation method according to claim 3 wherein the camera has an optical axis forming an angle between 10° and 40° relative to a vertical at a time of a shot. 5. The evaluation method according to claim 3 wherein the camera and the nuclear fuel assembly are spaced apart from each other when the image is taken by a distance between 1 meter and 4 meters in a horizontal plane. 6. The evaluation method according to claim 3 wherein the nuclear fuel assembly comprises an upper and a lower maintenance grid situated near opposite ends of the nuclear fuel rods; and a plurality of intermediate maintenance grids distributed between the upper and the lower maintenance grids, wherein the step for graphic analysis comprises the following sub-steps:materializing, on the image, at least one substantially longitudinal reference line extending from the upper or lower maintenance grid to the other upper or lower maintenance grid; anddetermining, on the image, a transverse shift of each of the intermediate grids relative to the at least one reference line. 7. The evaluation method according to claim 6 wherein the upper, lower and intermediate maintenance grids or the fuel rods near the maintenance grids can have respective visual references substantially aligned longitudinally when the upper, lower and intermediate maintenance grids are not shifted transversely, the reference line passing through the visual references relative to the upper and lower maintenance grids, the transverse shift of each intermediate maintenance grid being determined by estimating, on the image, the transverse shift between the visual reference relative to the intermediate maintenance grid and the reference line. 8. The evaluation method according to claim 3 wherein at least one image is taken of each of the two lateral faces perpendicular to each other of the nuclear fuel assembly, and the respective shifts of the maintenance grids are determined in two directions perpendicular to each other and perpendicular to the longitudinal direction. 9. The evaluation method according to claim 1 wherein the nuclear fuel assembly comprises upper and lower caps, wherein the quantity relative to the distortion of the nuclear fuel assembly is the rotation of the upper and lower caps relative to each other around a longitudinal direction. 10. The evaluation method according to claim 9 wherein the camera presents an optical axis forming an angle between 1° and 10° relative to a vertical when the image is taken. 11. The evaluation method according to claim 9 wherein, when the image is taken, the camera and the nuclear fuel assembly are spaced apart from each other by a distance smaller than 1 meter in a horizontal plane. 12. The evaluation method according to claim 9 wherein the upper and lower caps have determined respective geometric lines normally parallel to each other when the upper and lower caps do not have any rotation relative to each other around the longitudinal direction, wherein the step for graphic analysis of the image comprises the following sub-steps:determining, in the image, the two geometric lines; anddetermining, in the image, a relative angle between the two geometric lines. 13. The method according to claim 1 wherein the camera has a determined optical axis, and a shielding window being placed on the free surface and inserted on the optical axis of the camera.
	claims	1. An end effector for supporting an ultrasonic testing probe on a robot arm having a robot mounting bracket, comprising: a wrist assembly having a rotatable wrist shaft; said wrist assembly coupled to said robot mounting bracket; a probe assembly rotatably coupled to said wrist shaft; said probe assembly structured to floatably support an ultrasonic testing probe having a body with a diameter and at least one projection; said probe assembly comprising: a probe carriage assembly having a hollow cylindrical body and an interior surface; at least one longitudinal slot having a length and width on said interior surface; said interior surface having an interior diameter that is larger than said probe diameter; said at least one projection disposed within said at least one slot; and said at least one projection having a smaller diameter than said length and width of said slot. 2. An end effector for supporting an ultrasonic testing probe within a nuclear reactor pressure vessel on a robot arm having a robot mounting bracket, comprising: a wrist assembly having a rotatable wrist shaft; said wrist assembly coupled to said robot mounting bracket; a probe assembly rotatably coupled to said wrist shaft; said probe assembly structured to floatably support an ultrasonic testing probe having a body with a diameter and at least one projection; said probe assembly comprising: a probe carriage assembly having a hollow cylindrical body and an interior surface; at least one longitudinal slot having a length and width on said interior surface; said interior surface having an interior diameter that is larger than said probe diameter; said at least one projection disposed within said at least one slot; and said at least one projection having a smaller diameter than said length and width of said slot. 3. The end effector of claim 2 wherein said probe has a body having a cross-sectional area and said carriage assembly hollow body has a cross-sectional area that is larger than the probe cross-sectional area. claim 2 4. The end effector of claim 3 wherein said probe carriage assembly has a front end; and claim 3 further includes a means disposed within said probe carriage assembly structured to bias a probe toward said front end of said carriage assembly. 5. The end effector of claim 2 wherein said probe carriage assembly has a front end, and claim 2 further includes a spring disposed within said carriage assembly structured to bias a probe toward said front end of said carriage assembly. 6. The end effector of claim 5 wherein said probe assembly includes a camera assembly disposed above said probe assembly. claim 5 7. The end effector of claim 5 , wherein said probe carriage assembly is rotatable about a longitudinal axis. claim 5 8. The end effector of claim 7 wherein said probe assembly further includes: claim 7 a frame member coupled to said wrist shaft; said frame member having a front end and a back end; a hollow cylindrical probe carriage housing integral to said frame member front end; said probe carriage assembly rotatably disposed within said probe carriage housing. 9. The end effector of claim 8 , wherein said probe assembly includes: claim 8 a pin extending from said probe carriage housing adjacent to said probe carriage back end; said probe carriage assembly having a back end with at least one stop pin extending therefrom; during rotation of said probe carriage assembly, said at least one stop pin contacts said probe carriage housing pin limiting rotation of said probe carriage assembly to less than 360xc2x0 within said probe carriage housing. 10. The end effector of claim 7 , wherein said probe assembly includes a carriage assembly rotation motor coupled to said probe carriage assembly. claim 7 11. The end effector of claim 10 , wherein said probe carriage assembly has a back end coupling arm extending therefrom; claim 10 said coupling arm attached to said carriage assembly rotation motor. 12. The end effector of claim 11 , wherein said coupling arm has a notch to provide access for cables connected to a probe disposed within said probe assembly. claim 11 13. The end effector of claim 12 wherein said probe assembly further includes: claim 12 a frame member coupled to said wrist shaft; said frame member having a front end and a back end; a hollow cylindrical probe carriage housing integral to said frame member front end; said probe carriage assembly rotatably disposed within said probe carriage housing. 14. The end effector of claim 13 , wherein said probe assembly includes: claim 13 a pin extending from said probe carriage housing adjacent to said probe carriage back end; said probe carriage assembly including at least one stop pin extending from said probe carriage back end; during rotation of said probe carriage assembly, said at least one stop pin contacts said probe carriage housing pin limiting rotation of said probe carriage assembly to less than 360xc2x0 within said probe carriage housing. 15. The end effector of claim 14 , wherein said probe assembly and a camera assembly is disposed above said probe assembly. claim 14 16. An end effector for supporting an ultrasonic testing probe on a robot arm having a robot mounting bracket, comprising: a wrist assembly having a rotatable wrist shaft; said wrist assembly coupled to said robot mounting bracket; a probe assembly rotatably coupled to said wrist shaft, including a clutch assembly releasably coupling said probe assembly to said wrist shaft wherein said clutch assembly comprises: a clutch pin; said wrist shaft having a lower end and said lower end having a detent; and a means to bias said clutch pin against said lower end detent; said probe assembly structured to floatably support an ultrasonic testing probe. 17. The end effector of claim 16 wherein said clutch assembly further includes: claim 16 a clutch assembly housing having a back plate; said clutch assembly housing being rotatably attached to said wrist assembly and fixedly attached to said probe assembly; clutch pin housing; a clutch pin spring; said shaft lower end disposed within said clutch assembly housing; said clutch pin housing fixedly attached to said clutch assembly housing back plate; said clutch pin spring and said clutch pin disposed within said clutch pin housing; said clutch pin spring biasing said clutch pin against said lower end detent. 18. The end effector of claim 17 wherein said wrist assembly comprises: claim 17 a wrist motor; a resolver integral to said wrist motor; a mounting bracket attached to said wrist motor and coupled with said robot mounting bracket. 19. The end effector of claim 18 , wherein said probe assembly includes a camera assembly attached to said frame member. claim 18 20. A method of ultrasonically inspecting a bolt, comprising the steps of: positioning a robotic arm end effector adjacent to a bolt head having a lock bar, said end effector having wrist assembly which supports a probe assembly, said probe assembly floatably supporting an ultrasonic probe and biasing said probe toward said bolt head, said probe having a mating surface with a groove; rotating said wrist in a first plane to grossly align said ultrasonic probe with said bolt head; rotating said ultrasonic probe in a second plane to grossly align said groove with said lock bar; bringing said ultrasonic probe into contact with said bolt head; allowing floatable probe to align flush with said bolt head; and performing ultrasonic testing. 21. The method of claim 20 wherein said robotic arm has a camera assembly to provide visual feedback to aid in aligning said ultrasonic probe with said bolt head and lock bar, and wherein said gross alignment is performed using visual feed back. claim 20
	summary
	description	The present invention relates to a radiation image storage panel employable in a radiation image recording and reproducing method utilizing an energy storable phosphor. The invention also relates to a process for reading a radiation image information recorded and stored in the radiation image storage panel. When the energy storable phosphor (e.g., stimulable phosphor, which gives off stimulated emission) is exposed to radiation such as X-rays, it absorbs and stores a portion of the radiation energy. The phosphor then emits stimulated emission according to the level of the stored energy when exposed to electromagnetic wave such as visible or infrared light (i.e., stimulating light). A radiation image recording and reproducing method utilizing the energy storable phosphor has been widely employed in practice. In that method, a radiation image storage panel, which is a sheet comprising the energy storable phosphor, is used. The method comprises the steps of: exposing the storage panel to radiation having passed through an object or having radiated from an object, so that radiation image of the object is temporarily recorded in the storage panel; sequentially scanning the storage panel with a stimulating light such as a laser beam to emit a stimulated light; and photoelectrically detecting the emitted light to obtain electric image signals. The storage panel thus processed is then subjected to a step for erasing radiation energy remaining therein, and then stored for the use in the next recording and reproducing procedure. Thus, the radiation image storage panel can be repeatedly used. The radiation image storage panel (often referred to as energy storable phosphor sheet) used in the radiation image recording and reproducing method has a basic structure comprising a support and a phosphor layer provided thereon. However, if the phosphor layer is self-supporting, the support may be omitted. Further, a protective layer is generally provided on the free surface (surface not facing the support) of the phosphor layer to keep the phosphor layer from chemical deterioration or physical shock. Various kinds of phosphor layer are known and used. For example, a phosphor layer comprising a binder and an energy storable phosphor dispersed therein is generally used, and a phosphor layer comprising agglomerate of an energy storable phosphor without binder is also known. The latter layer can be formed by a gas phase-accumulation method or by a firing method. Further, still also known is a phosphor layer comprising energy storable phosphor agglomerate impregnated with a polymer material. Japanese Patent Provisional Publication 2001-255610 discloses a variation of the radiation image recording and reproducing method. While an energy storable phosphor of the storage panel used in the conventional type plays both roles of radiation-absorbing function and energy storable function, those two functions are separated in the disclosed method. In the method, a radiation image storage panel comprising at least an energy storable phosphor (which stores radiation energy) is used in combination with a phosphor screen comprising another phosphor (radiation-absorbing phosphor) which absorbs radiation and emits ultraviolet or visible light. The disclosed method comprises the steps of: causing the radiation-absorbing phosphor of the screen or the panel to absorb and convert radiation having passed through an object or having radiated from an object into ultraviolet or visible light; causing the energy storable phosphor of the panel to store the energy of the converted light as radiation image information; sequentially scanning the panel with a stimulating light to emit stimulated light; and photoelectrically detecting the emitted light to obtain electric image signals. The radiation image recording and reproducing method (or radiation image forming method) has various advantages as described above. However, it is still desired that the radiation image storage panel used in the method have as high sensitivity as possible and, at the same time, give a reproduced radiation image of high quality (in regard to sharpness and graininess). In order to improve the sensitivity and the image quality, it is proposed that the phosphor layer of the storage panel be prepared by a gas phase-accumulation method such as vacuum vapor deposition, sputtering or chemical vapor deposition (CVD). The process of vacuum vapor deposition, for example, comprises the steps of: heating to vaporize an evaporation source comprising a phosphor or materials thereof by means of a resistance heater or an electron beam, and depositing and accumulating the vapor on a substrate such as a metal sheet to form a layer of the phosphor in the form of columnar crystals. The phosphor layer formed by the gas phase-accumulation method contains no binder and consists of the phosphor only, and there are cracks among the columnar crystals of the phosphor. Because of the cracks, the stimulating light can stimulate the phosphor efficiently and the emitted light can be collected efficiently, too. Accordingly, a radiation image storage panel having that phosphor layer has high sensitivity. At the same time, since the cracks prevent the stimulating light from diffusing parallel to the phosphor layer, the storage panel can give a reproduced image of high sharpness. As a process for reading out radiation image information from the storage panel, a line-scanning reading method is proposed so as to shorten the time of read-out, to downsize the apparatus and to reduce the cost. Japanese Patent Provisional Publication 2001-350230 discloses a radiation image information-reading apparatus for the line-scanning reading method. The disclosed apparatus comprises a line light source which irradiates the storage panel linearly with stimulating lights to cause stimulated emission, a stimulated emission-detecting means which receives and photoelectrically converts the stimulated emission given off by the panel from the area linearly exposed to the stimulating lights, a scanning means by which the storage panel and a combination of the light source and the detecting means are relatively moved in a direction (secondary direction of scanning) different from the longitudinal direction of the linearly exposed area (primary direction of scanning), and a reading means by which signals output from the detecting means are read in accordance with the movement. The detecting means comprises a linear light-receiving face whose width in the direction perpendicular to the longitudinal direction (that is, generally, a dimension of the face in the secondary direction of scanning) is designed so that 30 to 90% of the stimulated emission can be detected even though the emission is spread or diffused. Japanese Patent Provisional Publication 2001-350230 also discloses a graph showing a relationship between the diffusion of stimulated emission and the distribution of diffused emission intensity. The graph indicates that the storage panel processed in the above apparatus gives a stimulated emission of about 400 μm luminescence width (full width at half maximum, i.e., half-width). An object of the present invention is to provide a radiation image storage panel improved in sensitivity and in sharpness. Another object of the invention is to provide a process for reading radiation image information from an radiation image-stored storage panel, whereby a radiation image of high quality can be obtained. The present inventors have studied a radiation image storage panel comprising a phosphor layer formed by the gas phase-accumulation method, and have finally found that, if the storage panel gives off stimulated emission of a specific luminescence width, both sensitivity and sharpness can be improved when the emission is observed with a line-scanning detecting means comprising pixels whose sizes are designed for medical diagnoses. It is also found that, if the pixel of the detecting means has a specific size in the primary direction of scanning, a radiation image of high quality can be obtained. The present invention resides in a radiation image storage panel comprising an energy storable phosphor layer formed by a gas phase-accumulation method, wherein the energy storable phosphor layer gives off an emission having a luminescence width in terms of d in the range of 150 to 395 μm (preferably 150 to 380 μm, more preferably 290 to 380 μm) when it is exposed to radiation and then excited with a stimulating light of 50 μm half-width. In the specification, the term “luminescence width in terms of d” means a half-width (i.e., full width at half maximum) in an emission profile obtained by the steps of: applying a stimulating light of about 50 μm half-width onto a radiation image storage panel having been exposed to X-rays in the manner that the stimulating light impinges at an angle of about 15° to the normal of the panel surface, to make the storage panel give off emission; focusing the emission with a SELFOC lens array placed perpendicularly to the normal of the storage panel; leading the emission through an optical filter which cuts the stimulating light but which transmits the emission; and detecting the emission by means of a two-dimensional CCD sensor array comprising about 800×800 pixels having a size of about 7 μm. The invention also resides a process for reading out a radiation image stored in a radiation image storage panel which comprises the steps of: moving a radiation image storage panel of the invention in which the radiation image is stored, relatively to a set of a stimulating means and a light-detecting means in which the stimulating means applies to one surface of the storage panel a stimulating light extended linearly in a width direction of the storage panel and in which the light-detecting means is equipped with an isometric erect image-forming means and comprises a plurality of photoelectrically converting pixels aligned in the width direction of the storage panel, each of the pixels having a size in terms of D under such conditions that 25 μm≦D≦400 μm and 0.5≦d/D≦4 in the width direction of the storage panel; applying the stimulating light to one surface of the storage panel linearly in the width direction of the storage panel and detecting a stimulated emission given off by the storage panel by the light-detecting means through the equivalent erect image-forming means to produce a series of electric signals; and processing the electric signals in relation to an information of the relative movement between the storage panel and the set of a stimulating means and a light-detecting means, to obtain a reproduced radiation image in the form of a series of electric image signals. The radiation image storage panel of the invention, which gives off stimulated emission having a luminescence width in a specific range, has high sensitivity and gives a radiation image of high sharpness, and hence is balanced and suitable for medical diagnoses. Further, the process of the invention for read-out of radiation image information, in which the detecting means comprises pixels of a size in a specific range, gives a radiation image of high sharpness with high sensitivity. The energy storable phosphor used in the radiation image storage panel of the invention preferably is a stimulable alkali metal halide phosphor represented by the following formula (I). In the formula (I), it is preferred that MI is Cs, X is Br, A is Eu, and z is a number satisfying the condition of 1×10−4≦z≦0.1.MIX.aMIIX′2.bMIIIX″3:zA (I)[in which MI is at least one alkali metal selected from the group consisting of Li, Na, K, Rb and Cs; MII is at least one alkaline earth metal or divalent metal selected from the group consisting of Be, Mg, Ca, Sr, Ba, Ni, Cu, Zn and Cd; MIII is at least one rare earth element or trivalent metal 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; each of X, X′ and X″ is independently at least one halogen selected from the group consisting of F, Cl, Br and I; A is at least one rare earth element or metal selected from the group consisting of Y, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Cu, Ag, Tl and Bi; and a, b and z are numbers satisfying the conditions of 0≦a<0.5, 0≦b<0.5 and 0<z<1.0, respectively]. In the process of the invention for read-out of radiation image information, the light-detecting means preferably is a line sensor which comprises plural photoelectric converting elements arranged linearly. Each pixel of the light-detecting means preferably one-to-one corresponds to each photoelectric converting element. In the following description, the radiation image storage panel of the invention is explained in detail with reference to the attached drawings. The radiation image storage panel of the invention comprises an energy storable phosphor layer formed by a gas phase-accumulation method, and gives off stimulated emission having a luminescence width (d) of 150 to 380 μm. The luminescence width d (half-width, i.e., full width at half maximum) can be determined on the basis of an emission profile, as shown in FIG. 1. FIG. 1 is a graph showing a relationship between distribution and intensity of stimulated emission, namely, an emission profile. The emission profile of FIG. 1 is obtained in the following manner. First, a storage panel comprising a support and a CsBr:Eu stimulable phosphor layer formed by vapor deposition is exposed to X-rays (tube voltage: 80 kVp, amount: 100 mR), and then excited with a semiconductor laser beam (wavelength: 660 nm). Before applied onto the storage panel, the laser beam was focused though a lens so that the half-width would be set to 50 μm. As shown in FIG. 2, the focused beam (J) is applied onto the top surface (phosphor layer-side surface) of the storage panel 10 so that the beam would is impinged at an angle (b) of about 15° to the normal (a), to cause the storage panel 10 to give off emission (K). The emission (K) is focused with a SELFOC lens array 11 placed perpendicularly to the normal (a), that is, parallel to the storage panel 10; led through an optical filter 12 [B410, HOYA Corporation] which cuts the stimulating light but which transmits the emission; and detects by means of a two-dimensional CCD sensor array 13 comprising about 800×800 pixels (size: about 7 μm), to obtain the emission profile. If the luminescence width (d, half-width, i.e., full width at half maximum) is in the range of 150 to 395 μm (particularly, 150 to 380 μm, more particularly 290 to 380 μm), the radiation image storage panel of the invention is excellent in both sensitivity and sharpness. FIG. 3 is a graph showing a relationship between the luminescence width (d) and the amount of stimulated emission (relative value). Various radiation image storage panels having vapor-deposited CsBr:Eu phosphor layers were produced (in Examples described later), and the stimulated emission given off by each storage panel was determined using a detecting means having the pixel size of 200 μm, which is generally required for medical diagnoses, to obtain the relationship. The graph of FIG. 3 indicates that the amount of stimulated emission, which corresponds to sensitivity, is highest when the luminescence width (d) is within the range of 150 to 600 μm. FIG. 4 is a graph showing a relation between the luminescence width (d) and the modulation transfer function (MTF) of radiation image. The graph of FIG. 4 was also obtained from the above storage panels (Examples) using the detecting means having the pixel size of 200 μm. It is clearly shown in FIG. 4 that high MTF, which corresponds to high sharpness, can be obtained when the luminescence width (d) is 395 μm or shorter (particularly, 380 μm or shorter). In the following description, the process for preparation of the radiation image storage panel of the invention is explained in detail, by way of example, utilizing a case where a resistance-heating process is used in the gas phase-accumulation method. The resistance-heating process can be carried out under medium vacuum, and thereby a favorable columnar crystal-deposited layer can be easily formed. The substrate on which the vapor is to be deposited can be as such used as a support of the radiation image storage panel, and hence can be optionally selected from known materials conventionally used as a support of a radiation image storage panel. The substrate preferably is a sheet of quartz glass, sapphire glass; metal such as aluminum, iron, tin or chromium; or heat-resistant resin such as aramide. Particularly preferred are an aluminum plate and quartz glass. For improving the sensitivity or the image quality (e.g., sharpness and graininess), a conventional radiation image storage panel often has a light-reflecting layer containing a light-reflecting material such as titanium dioxide or a light-absorbing layer containing a light-absorbing material such as carbon black. These auxiliary layers can be provided on the radiation image storage panel of the invention. Further, in order to accelerate growth of the columnar crystals, a great number of very small convexes or concaves may be provided on the substrate surface on which the vapor is deposited. If an auxiliary layer such as a subbing layer (e.g., adhesive layer), a light-reflecting layer or a light-absorbing layer is formed on the deposited-side surface of the substrate, the convexes or concaves may be provided on the surface of the auxiliary layer. The energy storable phosphor preferably is a stimulable phosphor giving off stimulated emission in the wavelength region of 300 to 500 nm when exposed to a stimulating light in the wavelength region of 400 to 900 nm. The phosphor is particularly preferably an alkali metal halide stimulable phosphor represented by the following formula (I):MIX·aMIIX′2·bMIIIX″3:zA (I)In the formula (I), MI is at least one alkali metal selected from the group consisting of Li, Na, K, Rb and Cs; MII is at least one alkaline earth metal or divalent metal selected from the group consisting of Be, Mg, Ca, Sr, Ba, Ni, Cu, Zn and Cd; MIII is at least one rare earth element or trivalent metal 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; each of X, X′ and X″ is independently at least one halogen selected from the group consisting of F, Cl, Br and I; A is at least one rare earth element or metal selected from the group consisting of Y, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Cu, Ag, Tl and Bi; and a, b and z are numbers satisfying the conditions of 0≦a<0.5, 0≦b<0.5 and 0<z<1.0, respectively. In the formula (I), z preferably is a number satisfying the condition of 1×10−4≦z≦0.1; MI preferably comprises at least Cs; X preferably comprises at least Br; and A preferably is Eu or Bi, more preferably Eu. The phosphor represented by the formula (I) may further contain metal oxides such as aluminum oxide, silicone dioxide and zirconium oxide as additives in an amount of 0.5 mol or less based on one mol of MIX. As the phosphor, it is also preferred to use a rare earth activated alkaline earth metal fluoride halide stimulable phosphor represented by the following formula (II):MIIFX:aLn (II)in which MII is at least one alkaline earth metal selected from the group consisting of Ba, Sr and Ca; Ln is at least one rare earth element selected from the group consisting of Ce, Pr, Sm, Eu, Tb, Dy, Ho, Nd, Er, Tm and Yb; X is at least one halogen selected from the group consisting of Cl, Br and I; and z is a number satisfying the condition of 0<z≦0.2. In the formula (II), MII preferably comprises Ba more than half of the total amount of MII, and Ln preferably is Eu or Ce. The MIIFX in the formula (II) forms a matrix crystal structure of BaFX type, and it by no means indicates stoichiometrical composition of the phosphor. Accordingly, the molar ratio of F:X is not always 1:1. It is generally preferred that the BaFX type crystal have many F+(X−) centers corresponding to vacant lattice points of X− ions since they increase the efficiency of stimulated emission in the wavelength region of 600 to 700 nm. In that case, F often is in slight excess of X. Although omitted from the formula (II), one or more additives such as bA, wNI, xNII and yNIII may be incorporated into the phosphor of the formula (II). A is a metal oxide such as Al2O3, SiO2 or ZrO2. In order to prevent MIIFX particles from sintering, the metal oxide preferably has low reactivity with MIIFX, and the primary particles of the oxide are preferably super-fine particles of 0.1 μm or less diameter. NI is a compound of at least one alkali metal selected from the group consisting of Li, Na, K, Rb and Cs; NII is a compound of alkaline earth metal(s) Mg and/or Be; and NIII is a compound of at least one trivalent metal selected from the group consisting of Al, Ga, In, Tl, Sc, Y, La, Gd and Lu. The metal compounds preferably are halides, but are not restricted to them. b, w, x and y represent amounts of the additives incorporated into the starting materials, provided that the amount of MIIFX is assumed to be one mol. They are numbers satisfying the conditions of 0≦b≦0.5, 0≦w≦2, 0≦x≦0.3 and 0≦y≦0.3. These numbers by no means represent the contents in the resultant phosphor because the additives possibly decrease during the steps of firing and washing performed thereafter. Some additives remain in the resultant phosphor as they are added to the materials, but the others react with MIIFX or emigrates into the matrix. In addition, the phosphor of the formula (II) may further contain Zn and Cd compounds; metal oxides such as TiO2, BeO, MgO, CaO, SrO, BaO, ZnO, Y2O3, La2O3, In2O3, GeO2, SnO2, Nb2O5, Ta2O5 and ThO2; Zr and Sc compounds; B compounds; As and Si compounds; tetrafluoro-borate compounds; hexafluoro compounds such as monovalent or divalent salts of hexa-fluorosilicic acid, hexafluoro-titanic acid and hexa-fluorozirconic acid; or compounds of transition metals such as V, Cr, Mn, Fe, Co and Ni. The phosphor usable in the invention is not restricted to the above-mentioned phosphor, and any phosphors that can be essentially regarded as rare earth activated alkaline earth metal fluoride halide stimulable phosphors can be used. It is still also preferred to use a rare earth activated alkaline earth metal sulfide stimulable phosphor represented by the following formula (III):MIIS:A,Sm (II)in which MII is at least one alkaline earth metal selected from the group consisting of Mg, Ca and Sr; and A is preferably Eu and/or Ce. Further, yet another preferred phosphor is a cerium activated trivalent metal oxide halide stimulable phosphor represented by the following formula (IV):MIIIOX:Ce (IV)in which MIII is at least one rare earth element or trivalent metal selected from the group consisting of Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb and Bi; and X is at least one halogen selected from the group consisting of Cl, Br and I. In the case where the vapor-deposited layer is formed by multi-vapor deposition (co-deposition), at least two evaporation sources are used. One of the sources contains a matrix material of the energy storable phosphor, and the other contains an activator material. The multi-vapor deposition is preferred because the vaporization rate of each source can be independently controlled to incorporate the activator uniformly in the matrix even if the materials have very different melting points or vapor pressures. According to the composition of the desired phosphor, each evaporation source may consist of the matrix material or the activator material only or otherwise may be a mixture of the matrix material and additives. Three or more sources may be used. For example, in addition to the above sources, an evaporation source containing additives may be used. The matrix material of the phosphor may be either the matrix compound itself or a mixture of two or more substances that react with each other to produce the matrix compound. The activator material generally is a compound containing an activating element, for example, a halide or oxide of the activating element. If the activator is Eu, the Eu-containing compound of the activator material preferably contains Eu in a content of 70% or more by molar ratio because the desired stimulated emission (or instant emission) is emitted from the phosphor activated by Eu2+ although the Eu-containing compound generally contains both Eu2+ and Eu3+. The Eu-containing compound is preferably represented by EuXm (X: halogen) in which m is a number preferably satisfying the condition of 2.0≦m≦2.3. It is desired that the value of m should be 2.0. However, oxygen is liable to emigrate into the compound, if the value of m reaches 2.0. The compound is, therefore, practically stable when m is approximately 2.2. The evaporation source preferably has a water content of not more than 0.5 wt. %. For preventing the source from bumping, it is particularly important to control the water content in the above low range if the material of matrix or activator is a hygroscopic substance such as EuBr or CsBr. The materials are preferably dried by heating at 100 to 300° C. under reduced pressure. Otherwise, the materials may be heated under dry atmosphere such as nitrogen gas atmosphere to melt at a temperature above the melting point for several minutes to several hours. The evaporation source, particularly the source containing the matrix material, can contain impurities of alkali metal (alkali metals other than ones constituting the phosphor) preferably in a content of 10 ppm or less and impurities of alkaline earth metal (alkaline earth metals other than ones constituting the phosphor) preferably in a content of 5 ppm or less (by weight). That is particularly preferred if the phosphor is an alkali metal halide stimulable phosphor represented by the formula (I). Such preferred evaporation source can be prepared from materials containing little impurities. The two or more evaporation sources and the substrate are placed in a vacuum evaporation-deposition apparatus. The apparatus is then evacuated to give a medium vacuum of 0.05 to 10 Pa. In order to narrow the luminescence width (d), a low degree of vacuum is preferred. The degree of vacuum preferably is in the range of 0.05 to 5 Pa. In addition, it is particularly preferred that, after the apparatus is evacuated to a high vacuum of 1×10−5 to 1×10−2 Pa, an inert gas such as Ar, Ne or N2 gas be introduced into the apparatus so the inner pressure may be the medium vacuum. If this is desired, partial pressures of water and oxygen can be reduced. The apparatus can be evacuated by means of an optional combination of, for example, a rotary pump, a turbo molecular pump, a cryo pump, a diffusion pump and a mechanical buster. For heating the evaporation sources, electric currents are then supplied to resistance heaters. The sources of matrix and activator materials are thus heated, vaporized, and reacted with each other to form the phosphor, which is deposited on the substrate. The space between the substrate and the sources depends upon various conditions such as the size of substrate, but generally is in the range of 10 to 1,000 mm. In order to narrow the luminescence width (d), a small space is preferred. The space, therefore, is preferably in the range of 50 to 500 mm. The space between the sources is generally in the range of 10 to 1,000 mm. In this step, the substrate may be heated or cooled. The temperature of the substrate generally is in the range of 20 to 350° C. In order to narrow the luminescence width (d), a low substrate temperature is preferred. The temperature, therefore, preferably is in the range of 20 to 250° C. The deposition rate, which means how fast the formed phosphor is deposited and accumulated on the substrate, can be controlled by adjusting the electric currents supplied to the heaters. The deposition rate generally is in the range of 0.1 to 1,000 μm/min., preferably in the range of 1 to 100 μm/min. The heating with resistance heaters may be repeated twice or more to form two or more phosphor layers. After the deposition procedure is complete, the deposited layer may be subjected to heating treatment (annealing treatment), which is carried out generally at a temperature of 100 to 300° C. for 0.5 to 3 hours, preferably at a temperature of 150 to 250° C. for 0.5 to 2 hours, under inert gas atmosphere which may contain a small amount of oxygen gas or hydrogen gas. Before preparing the above deposited film (layer) of stimulable phosphor, another deposited film (layer) consisting of the phosphor matrix alone may be beforehand formed. The layer of the phosphor matrix alone generally comprises agglomerate of columnar or spherical crystals, and the phosphor layer formed thereon is well crystallized in the form of columnar shape. The matrix alone-deposited layer also serves as a light-reflecting layer, and increase the amount of emission given off from the surface of the phosphor layer. In addition, if the matrix layer has a relative density in the range of 80 to 98%, it further serves as a stress-relaxing layer to enhance the adhesion between the support and the phosphor layer. In the thus-formed layers, the additives such as the activator contained in the phosphor-deposited layer are often diffused into the matrix alone-deposited layer while they are heated during the deposition and/or during the heating treatment performed after the deposition, and consequently the interface between the layers is not always apparent. In the case where the phosphor layer is produced by mono-vapor deposition, only one evaporation source containing the above stimulable phosphor or a mixture of materials thereof is heated by means of a single resistance heater. The evaporation source is beforehand prepared so that it may contain the activator in a desired amount. Otherwise, in consideration of the gap of vapor pressure between the matrix components and the activator, the deposition procedure may be carried out while the matrix components are being supplied to the evaporation source. Thus produced phosphor layer consists of a stimulable phosphor in the form of columnar crystals grown almost in the thickness direction. The phosphor layer contains no binder and consists of the stimulable phosphor only, and there are cracks among the columnar crystals. The thickness of the phosphor layer depends on, for example, aimed characters of the panel, conditions and process of the deposition, but generally is in the range of 50 μm to 1 mm, preferably in the range of 200 to 700 μm. Generally, the narrower luminescence width (d) can be obtained if the phosphor layer has a smaller thickness and a lower density. Accordingly, the phosphor layer giving a narrow luminescence width can be prepared by, for example, lowering the temperature of substrate in deposition, reducing the degree of vacuum (increasing the pressure of introduced inert gas) in the apparatus, or reducing the space between the evaporation source and the substrate. The phosphor layer of the radiation image storage panel of the invention preferably has a thickness in the range of 130 to 800 μm. The packing ratio of the phosphor layer preferably is in the range of 80 to 90%. The density of the phosphor layer preferably is in the range of 3.6 to 4.0 g/cm3. The gas phase-accumulation method employable in the invention is not restricted to the above-described resistance heating process, and various other known processes such as an electron beam-application process, a sputtering process and a CVD process can be used. It is not necessary that a substrate on which the phosphor layer is deposited is the same as a support of the radiation image storage panel. For example, after formed on the substrate, the deposited phosphor film is peeled from the substrate and then laminated on a support with an adhesive to prepare the phosphor layer. Otherwise, the support (substrate) may be omitted. It is preferred to provide a protective layer on the surface of the phosphor layer, so as to ensure good handling of the storage panel in transportation and to avoid deterioration. The protective layer preferably is transparent so as not to prevent the stimulating light from coming in or not to prevent the emission from coming out. Further, for protecting the storage panel from chemical deterioration and physical damage, the protective layer preferably is chemically stable, physically strong, and of high moisture proof. The protective layer can be provided by coating the stimulable phosphor layer with a solution in which an organic polymer such as cellulose derivatives, polymethyl methacrylate or fluororesins soluble in organic solvents is dissolved in a solvent, by placing a beforehand prepared sheet for the protective layer (e.g., a film of organic polymer such as polyethylene terephthalate, a transparent glass plate) on the phosphor layer with an adhesive, or by depositing vapor of inorganic compounds on the phosphor layer. Various additives may be dispersed in the protective layer. Examples of the additives include light-scattering fine particles (e.g., particles of magnesium oxide, zinc oxide, titanium dioxide and alumina), a slipping agent (e.g., powders of perfluoroolefin resin and silicone resin) and a crosslinking agent (e.g., polyisocyanate). The thickness of the protective layer generally is in the range of about 0.1 to 20 μm if the layer is made of polymer material or in the range of about 100 to 1,000 μm if the layer is made of inorganic material such as glassy material. For enhancing the resistance to stain, a fluororesin layer may be further provided on the protective layer. The fluororesin layer can be form by coating the surface of the protective layer with a solution in which a fluororesin is dissolved (or dispersed) in an organic solvent, and drying the coated solution. The fluororesin may be used singly, but a mixture of the fluororesin and a film-forming resin is generally employed. In the mixture, an oligomer having polysiloxane structure or perfluoroalkyl group can be further incorporated. In the fluororesin layer, fine particle filler may be incorporated to reduce blotches caused by interference and to improve the quality of the resultant image. The thickness of the fluororesin layer generally is in the range of 0.5 to 20 μm. For forming the fluororesin layer, additives such as a crosslinking agent, a film-hardening agent and an anti-yellowing agent can be used. In particular, the crosslinking agent is advantageously employed to improve durability of the fluororesin layer. Thus, a radiation image storage panel of the invention can be produced. The radiation image storage panel of the invention may be in known various structures. For example, in order to improve the sharpness of the resultant image, at least one of the constitutional films (or layers) may be colored with a colorant which does not absorb the stimulated emission but the stimulating light. Below, the process of the invention for read-out of radiation image information is explained in detail with reference to the attached drawings. FIG. 5 is a sketch showing a radiation image information-reading apparatus for performing the process of the invention. FIG. 6 is a sectional view of the apparatus shown in FIG. 5 sectioned with I—I line. FIG. 7 schematically illustrates the line-sensor 28 in detail. The radiation image storage panel 20 in FIGS. 5 and 6 comprises a support and an energy storable phosphor layer formed on the support by a gas phase-accumulation method, and it can gives off stimulated emission having a luminescence width (d) of 150 to 395 μm. The storage panel 20 is beforehand exposed to radiation (such as X-rays) having passed through an object, and hence radiation image of the object is recorded and stored in the storage panel 20. The storage panel 20 is put on the transferring belt 40 so that the phosphor layer-side may be upside. The transferring belt 40 moves in the direction shown by an arrow Y, and thereby the storage panel 20 is transferred in that direction. The transferring rate of the storage panel 20 is identical with the moving rate of the belt 40, which is beforehand input into an image-reading means 30. A broad area laser (hereinafter often referred to as BLD) 21 linearly gives off stimulating light L almost parallel to the surface of the panel 20. The stimulating light L is focused through a cylindrical lens 22, and reflected by a dichroic mirror 24 placed at an angle of 45° to the storage panel 20. The light reflected by the mirror 44 then advances perpendicularly to the storage panel 20, and passes through a distributed index lens array (an array of many distributed index lenses, hereinafter referred to as “first SELFOC lens array”) 25 to be focused on the storage panel 20 linearly in the direction shown by an arrow X. The storage panel 20 is thus exposed to the stimulating light L in a linear area whose width (namely, the width of the laser beam) generally is in the range of 10 to 200 μm. The length of the area is preferably longer than or the same as the width of the storage panel 20. The linearly focused stimulating light L is perpendicularly applied to the storage panel 20, and thereby a stimulated emission M is emitted from an area enclosing the applied area and neighbor thereof. The emission M has an intensity according to the stored radiation image information. The stimulated emission M is converted into parallel light through the first SELFOC lens array 25, and passes through the dichroic mirror 24. The emitted light M then passes through a second SELFOC lens array 26, to be focused on light-receiving faces of photoelectric converting elements 29 constituting a line sensor 28 placed just above the area on which the stimulating light is focused. In this way, an image on the storage panel 20 is isometrically focused on the elements 29. As shown in FIG. 7, the line sensor 28 comprises many (for example, 1,000 or more) photoelectric converting elements 29 regularly aligned in the direction X. Examples of the photoelectric converting element 29 include an amorphous silicon sensor, a CCD sensor, a CCD with back illuminator and MOS image sensor. Each converting element one-to-one corresponds to each pixel, and has a light-receiving face of, for example, 200 μm×200 μm in size. In the present invention, for ensuring the resultant image quality, the pixel satisfies the conditions of 25≦D≦400 and 0.5≦d/D≦4 where D stands for the pixel size (μm) in the direction X (primary direction of scanning). In the line sensor 28 of FIG. 7, the pixel size D corresponds to an X-directional size of the light-receiving face in each photoelectric converting element 29. The line sensor 28 has the converting element 29 satisfying the above conditions. Also in the direction Y (secondary direction of scanning), each pixel (namely, light-receiving face in each element 29) preferably has a size (μm) satisfying the above-mentioned conditions. Since the line sensor 28 is placed right above the area on which the stimulating light L is focused, the stimulated emission coming almost perpendicularly can be efficiently collected. That is particularly remarkable because the converting elements 29 have small light-receiving faces. The stimulated emission M having passed through the second SELFOC lens array 26 is slightly contaminated with the stimulating light L reflected by the surface of the panel 20, and hence the contaminating light L is cut off by means of a stimulating light-cutting filter 27. The filter 27 does not transmit the stimulating light L but the stimulated emission M. The stimulated emission M received by each converting element 29 is photoelectrically converted into signals S, which are then sent to the image-reading means 30. In the image-reading means 20, the signals S are processed on the basis of the moving speed of the transferring belt 40 to obtain image data according to the position of the storage panel 20. Thus obtained image data are supplied into an image-processing apparatus (not shown). The radiation image information-reading apparatus used in the invention is not restricted to the embodiment shown in FIGS. 5 to 7. Each part of the apparatus (such as the light source, the light-collecting optical system between the light source and the storage panel, the optical system between the storage panel and the line sensor, and the line sensor) may have various known constitution. The line sensor may consist of two or three rows of photoelectric converting elements, as well as the above-described single row of the elements. Further, according to the desired pixel size and the size of light-receiving face in each element, two or more elements may correspond to one pixel. As the line light source, a light source itself having a linear shape may be used. Further, a fluorescent lamp, a cold cathode fluorescent lamp and a LED (light-emitting diode) array can be also used. The line light source may give off the stimulating lights either continuously or intermittently in the form of pulses. In consideration of lowering noises, the stimulating lights are preferably in the form of pulses with high power. The radiation image storage panel is preferably transferred almost perpendicularly to the longitudinal direction of the line light source and the line sensor. However, as long as almost all of the surface of the panel is evenly exposed to the stimulating lights, the panel may be transferred diagonally or in a zigzag. In the above embodiment, the optical path of the stimulating lights L and that of the stimulated emission M are partly overlapped to downsize the apparatus. However, the path of the stimulating lights L may be completely different from that of the emission M. Further, in the above embodiment, the radiation image information is read out while the storage panel is being transferred. However, the information may be read out while not the panel but the line light source and the line sensor are being moved parallel to the surface of the panel. If the panel has a transparent support, another line sensor may be placed on the bottom side in addition to the line sensor on the top side so that the emission can be detected from both top and bottom of the panel. Otherwise in that case, the emission may be observed only from the bottom. In the above reading system, an image-processing apparatus, in which image data signals sent from the radiation image information-reading apparatus are subjected to various signal processing, may be installed. Further, an erasing means, in which radiation energy remaining in the panel after reading is adequately released, may be combined. (1) Evaporation Source As the evaporation sources, powdery cesium bromide (CsBr, purity: 4N or more) and powdery europium bromide (EuBrm, m is approx. 2.2, purity: 3N or more) were prepared. Each of them was analyzed according to ICP-MS method (Inductively Coupled Plasma Mass Spectrometry), to find impurities. As a result, the CsBr powder contained each of the alkali metals (Li, Na, K, Rb) other than Cs in an amount of 10 ppm or less and other elements such as alkaline earth metals (Mg, Ca, Sr, Ba) in amounts of 2 ppm or less. The EuBrm powder contained each of the rare earth elements other than Eu in an amount of 20 ppm or less and other elements in amounts of 10 ppm or less. The powders are very hygroscopic, and hence were stored in a desiccator keeping a dry condition whose dew point was −20° C. or below. Immediately before used, they were taken out of the desiccator. (2) Preparation of Phosphor Layer A synthetic quartz substrate as a support was washed successively with an aqueous alkaline solution, purified water and IPA (isopropyl alcohol). The thus-treated substrate was mounted to a substrate holder in an evaporation-deposition apparatus. Each of the CsBr and EuBrm evaporation sources was placed in a crucible. The apparatus was evacuated to make the inner pressure 1×10−3 Pa by means a combination of a rotary pump, mechanical booster and turbo molecular pump, and then Ar gas (purity: 5N) was introduced to set the inner pressure at 0.8 Pa (Ar gas pressure). The distance between the substrate and each source was 200 mm. The substrate was then heated to 100° C. by means of a sheath heater placed on the back side (the opposite side to the face which the vapor is to be deposited on). Each evaporation source was also heated with a resistance heater, so that CsBr:Eu stimulable phosphor was accumulated on the surface of the substrate at a deposition rate of 10 μm/min. for 15 minute. During the deposition, the electric currents supplied to the heaters were controlled so that the molar ratio of Eu/Cs in the stimulable phosphor might be 0.003/1. Each source was first covered with a shutter, which was then opened to start the evaporation of CsBr or EuBr. After the evaporation-deposition was complete, the inner pressure was returned to atmospheric pressure and then the substrate was taken out of the apparatus. On the substrate, a deposited layer (thickness: approx. 200 μm, area: 10 cm×10 cm) consisting of columnar phosphor crystals aligned densely and almost perpendicularly was formed. Thus, a radiation image storage panel of the invention comprising the support and the phosphor layer was produced by multi-vapor deposition. The procedures of Example 1 were repeated except that the period for deposition in Example 1 (2) was change as set forth in Table, to prepare radiation image storage panels having a phosphor layer having different thickness. The procedures of Example 1 were repeated except that the Ar gas pressure was set to 0.5 Pa, the substrate temperature was set to 30° C., and the deposition period was set to 45 min., to give a radiation image storage panel having a thickness differing from that of the storage panel of Example 1. The procedures of Example 1 were repeated except that the Ar gas pressure was set to 0.5 Pa, the substrate temperature was set to 60° C., and the deposition period was set to 60 min., to give a radiation image storage panel having a thickness and a density differing from those of the storage panel of Example 1. The procedures of Example 1 were repeated except that the Ar gas pressure was set to 1 Pa, the substrate temperature was set to 60° C., and the deposition period was set to 50 min., to give a radiation image storage panel having a thickness and a density differing from those of the storage panel of Example 1. The procedures of Example 1 were repeated except that, the time for deposition in Example 1 (2) was changed as set forth in Table 1, to give a radiation image storage panel having a thickness differing from that of the storage panel of Example 1. The procedures of Example 1 were repeated except that the Ar gas pressure was set to 0.5 Pa and the deposition period was set to 30 min., to give a radiation image storage panel having a thickness and a density differing from those of the storage panel of Example 1. The procedures of Example 1 were repeated except that the Ar gas pressure was set to 1×10−3 Pa and the deposition period was set to 50 min., to give a radiation image storage panel having a thickness and a density differing from those of the storage panel of Example 1. The procedures of Example 1 were repeated except that the Ar gas pressure was set to 2 Pa, the substrate temperature was set to 30° C., and the deposition period was set to 60 min., to give a radiation image storage panel having a thickness and a density differing from those of the storage panel of Example 1. With respect to each produced radiation image storage panel, the density and the packing degree of the phosphor layer were measured and then the luminescence width (d) was determined in the above-described manner. In addition, the sensitivity and the sharpness given by each panel were evaluated in the following manner. (1) Sensitivity Each radiation image storage panel was encased in a room light-shielding cassette and then exposed to X-rays (voltage: 80 kvp, current: 16 mA). After the storage panel was taken out of the cassette, the stimulated emission was released and detected by means of the aforementioned reading apparatus shown in FIGS. 5 to 7 [stimulating lights: broad area laser beam, width of beam (half-width of stimulating light): 50 μm, size of CCD light-receiving face=pixel size D: approx. 200 μm], to measure the amount of the stimulated emission. On the basis of the obtained amount (relative value) of stimulated emission, the sensitivity of the panel was estimated. (2) Sharpness (MTF) Each radiation image storage panel was exposed through a CTF chart to the above X-rays, and then the image data was obtained in the same manner as described above. The obtained image data was processed by an image reproducing apparatus into an image film, from which intensity at each spatial frequency was measured to determine a modulation transfer function (MTF) at the spatial frequency of 1 c/mm. The results are shown in Table 1. TABLE 1Ex.(1)(2)(3)(4)(5)(6)(7)(8)(9)Ex. 10.8100151503.885.8155170.87Ex. 20.8100202003.885.8183190.86Ex. 30.8100353553.885.8216280.81Ex. 40.8100505303.885.8304300.66Ex. 50.8100606113.885.8297350.67Ex. 60.8100656503.885.8304370.66Ex. 70.8100757703.885.8318420.63Ex. 80.530454663.885.8338500.60Ex. 90.560606003.988.0358450.59Ex. 10160505113.783.5296400.65Con10.81005503.885.880110.97Con20.8100101003.885.8135130.92Con30.5100606004.192.6500220.32Con21 × 10−3100505004.499.3865110.03Con3230605863.476.7400300.49Remarks: (1) Ar gas pressure (Pa) (2) Temperature (° C.) of substrate (3) Period (min.) of deposition (4) Thickness (μm) of deposited phosphor layer (5) Density (g/cm3) of deposited phosphor layer (6) Packing ratio (%) of deposited phosphor layer (7) Luminescence width d (μm) (8) Sensitivity (relative value) (9) Sharpness The results shown in Table 1 indicate that the radiation image storage panels of the invention (Examples 1 to 10, total evaluation: good), each of which gives off the stimulated emission with a luminescence width (d) of 150 to 395 μm (particularly, 150 to 380 μm), have much higher sensitivities and give reproduced images of higher sharpness than a radiation image storage panel for comparison (Comparison Example 4, total evaluation: bad) giving off the emission with a large luminescence width. It is also evident from the results that the storage panels of the invention have higher sensitivity and give higher sharpness than other radiation image storage panels for comparison (Comparison Example 1 and 2, total evaluation: bad), each of which gives a narrow luminescence width of less than 150 μm or than still another panel for comparison (Comparison Examples 3 and 5, total evaluation: bad) giving a luminescence width as large as 500 μm.
	claims	1. A method for treating tritium water-containing raw water by which tritium water-containing raw water is treated by a first alkali water electrolysis step comprising the steps of:(1) supplying a part of raw water containing tritium water and alkali water to a circulation tank;(2) mixing the raw water with the alkali water in the circulation tank to obtain an electrolyte adjusted so as to have a desired alkali concentration, supplying the electrolyte to an alkali water electrolysis device, and performing electrolysis treatment;(3) supplying the raw water continuously to the circulation tank in an amount which corresponds to raw water lost by the above electrolysis treatment to maintain alkali concentration at an adjusted initial concentration, and continuing the electrolysis treatment while circulating the electrolyte in order to continuously perform the alkali water electrolysis treatment;(4) gasifying the raw water to tritium-containing hydrogen gas and oxygen gas so that tritium concentration is diluted to 1/1,244 relative to tritium concentration in the raw water; and(5) reducing the volume of the raw water. 2. The method for treating tritium water-containing raw water according to claim 1, wherein the tritium-containing hydrogen gas generated by the first alkali water electrolysis step is taken out to open air. 3. The method for treating tritium water-containing raw water according to claim 1, wherein the tritium-containing hydrogen gas generated by the first alkali water electrolysis step is sent to a catalyst tower, the tritium-containing hydrogen gas is reacted with water vapor on a catalyst filled in the catalyst tower, and the tritium is recovered as concentrated tritium water-containing water. 4. The method for treating tritium water-containing raw water according to claim 1, the method comprising:the first alkali water electrolysis step for performing continuously the alkali water electrolysis treatment;a second distillation step in which, after completion of the first alkali water electrolysis step, the entire amount of the electrolyte remained in the first alkali water electrolysis step is supplied to an evaporator, an alkali component in the electrolyte is recovered as alkali salt slurry, and simultaneously, tritium water-containing water distilled by the evaporator is taken out; anda second alkali water electrolysis step in which the tritium water-containing water taken out by the second distillation step and new alkali water are supplied to a circulation tank, the tritium water-containing water is mixed with the new alkali water in the circulation tank so as to have an electrolyte solution with a desired alkali concentration, electrolysis capacity of an alkali water electrolysis device is adjusted to the capacity suitable for a treatment amount of the electrolyte, an alkali water electrolysis treatment is performed followed by batch treatment, the tritium water-containing water is gasified and converted to tritium-containing hydrogen gas and oxygen gas so that tritium concentration is diluted to 1/1,244 relative to tritium concentration in the tritium water-containing water, and the volume of the raw water is reduced,if necessary, further comprising a step of repeating several times the second distillation step and the second alkali water electrolysis step until the completion of the batch treatment in which, at the time of repeating several times, the capacity of the alkali water electrolysis device used for the second alkali water electrolysis step is gradually reduced and the treatment is repeated. 5. The method for treating tritium water-containing raw water according to claim 1, wherein, when raw water which contains impurities including a large amount of chloride ions is used as the tritium water-containing raw water, a first distillation step for removing the impurities is further provided as a pre-step of the first alkali water electrolysis step, and in the first distillation step, the raw water which contains impurities including the chloride ions is supplied to the evaporator and the impurities are removed as salt slurry, and simultaneously, the tritium water-containing raw water after removing the impurities is taken out and then continuously supplied to be treated by the first alkali water electrolysis step. 6. The method for treating tritium water-containing raw water according to claim 4, wherein, when raw water which contains impurities including a large amount of chloride ions is used as the tritium water-containing raw water, a first distillation step for removing the impurities is provided as a pre-step of the first alkali water electrolysis step, and in the first distillation step, the raw water which contains impurities including the chloride ions is supplied to the evaporator and the impurities are removed as salt slurry, and simultaneously, the tritium water-containing raw water after removing the impurities is taken out and then continuously supplied to be treated by the first alkali water electrolysis step. 7. The method for treating tritium water-containing raw water according to claim 5, wherein, in the first distillation step, the salt slurry is concentrated and then separated and recovered as a solid matter. 8. The method for treating tritium water-containing raw water according to claim 4, wherein, in the second distillation step, the alkali salt slurry is concentrated and then separated and recovered as a solid matter. 9. The method for treating tritium water-containing raw water according to claim 4, wherein, in the first alkali water electrolysis step, alkali water with relatively high concentration is used as the alkali water and the electrolysis treatment is performed at relatively high current density, and in the second alkali water electrolysis step, alkali water with relatively low concentration is used as the alkali water and the electrolysis treatment is performed at relatively low current density. 10. The method for treating tritium water-containing raw water according to claim 1, wherein, in the first alkali water electrolysis step, 15% by mass or more of alkali water is used as the alkali water, and the electrolysis treatment is performed at current density of 15 A/dm2 or higher. 11. The method for treating tritium water-containing raw water according to claim 4, wherein, in the second alkali water electrolysis step, 2 to 10% by mass of alkali water is used as the alkali water, and the electrolysis treatment is performed at current density of 5 to 20 A/dm2.
	claims	1. A method for monitoring telemetry from a host computer system to detect degradation in a remote storage device, comprising:monitoring performance parameters from a host computer system which accesses the remote storage device, wherein the performance parameters relate to interactions between the host computer system and the remote storage device;for each of the monitored performance parameters:using a moving window with varying window width for the monitored performance parameter and moving windows with varying window widths for each of the other monitored performance parameters to slide through the monitored performance parameter and each of the other monitored performance parameters;varying an alignment between the moving window for the monitored performance parameter and the moving windows for each of the other monitored performance parameters to optimize a degree of association between the monitored performance parameter and each of the other monitored performance parameters;determining the degree of association by determining a set of F-statistic values for the monitored performance parameter for each of the other monitored performance parameters, wherein an F-statistic value for each of the other monitored performance parameters indicates a correlation between the monitored performance parameter and each of the other monitored performance parameters; andusing the set of F-statistic values to discard one or more monitored performance parameters that are correlated by more than a predetermined amount;determining whether the monitored performance parameters have deviated from predicted values for the performance parameters; andif so, generating a signal indicating that the remote storage device has degraded. 2. The method of claim 1, wherein prior to determining whether the performance parameters have deviated from predicted values, the method further comprises using a non linear non parametric regression technique to generate the predicted values for the monitored performance parameters based on a model of the host computer system which was generated while the remote storage device was operating in a non degraded state. 3. The method of claim 2, wherein the non linear non parametric regression technique is a multivariate state estimation technique (MSET). 4. The method of claim 2, wherein prior to using the non linear non parametric regression technique to generate predicted values for the monitored performance parameters, the method further comprises preprocessing the monitored performance parameters to remove outlying and flat data. 5. The method of claim 2, wherein prior to monitoring the performance parameters, the method further comprises generating the model during a training phase by:monitoring the performance parameters from the host computer system while the remote storage device is operating in a non degraded state;preprocessing the monitored performance parameters to remove outlying and flat data; andusing the non linear non parametric regression technique to build the model. 6. The method of claim 1, wherein determining whether the performance parameters have deviated from predicted values involves determining whether the monitored performance parameters have deviated a specified amount from the predicted values. 7. The method of claim 1, wherein determining whether the performance parameters have deviated from predicted values involves using a sequential probability ratio test (SPRT). 8. The method of claim 1, wherein the remote storage device can include:a hard disk drive; ora storage array. 9. The method of claim 1, wherein the performance parameters can include disk related metrics, which can include:average service time;average response time;number of kilobytes (kB) read per second;number of kB written per second;number of read requests per second;number of write requests per second; andnumber of soft errors per second. 10. The method of claim 1, wherein the performance parameters can include software variables, which can include:load metrics;CPU utilization;idle time;memory utilization;transaction latencies; andother performance metrics reported by the operating system. 11. The method of claim 1, wherein the performance parameters can include hardware variables, which can include:temperature;voltage;current; andfan speed. 12. A computer-readable storage medium storing instructions that when executed by a computer cause the computer to perform a method for monitoring telemetry from a host computer system to detect degradation in a remote storage device, wherein the method comprises:monitoring performance parameters from a host computer system which accesses the remote storage device, wherein the performance parameters relate to interactions between the host computer system and the remote storage device;for each of the monitored performance parameters:using a moving window with varying window width for the monitored performance parameter and moving windows with varying window widths for each of the other monitored performance parameters to slide through the monitored performance parameter and the other monitored performance parameters;varying an alignment between the moving window for the monitored performance parameter and the moving windows for each of the other monitored performance parameters to optimize a degree of association between the monitored performance parameter and each of the other monitored performance parameters;determining the degree of association by determining a set of F-statistic values for the monitored performance parameter for each of the other monitored performance parameters, wherein an F-statistic value for each of the other monitored performance parameters indicates a correlation between the monitored performance parameter and each of the other monitored performance parameters; andusing the set of F-statistic values to discard one or more monitored performance parameters that are correlated by more than a predetermined amount;determining whether the monitored performance parameters have deviated from predicted values for the performance parameters; andif so, generating a signal indicating that the remote storage device has degraded. 13. The computer-readable storage medium of claim 12, wherein prior to determining whether the performance parameters have deviated from predicted values, the method further comprises using a non linear non parametric regression technique to generate the predicted values for the monitored performance parameters based on a model of the host computer system which was generated while the remote storage device was operating in a non degraded state. 14. The computer-readable storage medium of claim 13, wherein the non linear non parametric regression technique is a multivariate state estimation technique (MSET). 15. The computer-readable storage medium of claim 13, wherein prior to using the non linear non parametric regression technique to generate predicted values for the monitored performance parameters, the method further comprises preprocessing the monitored performance parameters to remove outlying and flat data. 16. The computer-readable storage medium of claim 13, wherein prior to monitoring the performance parameters, the method further comprises generating the model during a training phase by:monitoring the performance parameters from the host computer system while the remote storage device is operating in a non degraded state;preprocessing the monitored performance parameters to remove outlying and flat data; andusing the non linear non parametric regression technique to build the model. 17. The computer-readable storage medium of claim 12, wherein determining whether the performance parameters have deviated from predicted values involves determining whether the monitored performance parameters have deviated a specified amount from the predicted values. 18. The computer-readable storage medium of claim 12, wherein determining whether the performance parameters have deviated from predicted values involves using a sequential probability ratio test (SPRT). 19. The computer-readable storage medium of claim 12, wherein the remote storage device can include:a hard disk drive; ora storage array. 20. The computer-readable storage medium of claim 12, wherein the performance parameters can include disk related metrics, which can include:average service time;average response time;number of kilobytes (kB) read per second;number of kB written per second;number of read requests per second;number of write requests per second; andnumber of soft errors per second. 21. The computer-readable storage medium of claim 12, wherein the performance parameters can include software variables, which can include:load metrics;CPU utilization;idle time;memory utilization;transaction latencies; andother performance metrics reported by the operating system. 22. The computer-readable storage medium of claim 12, wherein the performance parameters can include hardware variables, which can include:temperature;voltage;current; andfan speed. 23. An apparatus that monitors telemetry from a host computer system to detect degradation in a remote storage device, comprising:a monitoring mechanism, which is configured to:monitor performance parameters from a host computer system, wherein the performance parameters relate to the interactions between the host computer system and a remote storage device;for each of the monitored performance parameters:use a moving window with varying window width for the monitored performance parameter and moving windows with varying window widths for each of the other monitored performance parameters to slide through the monitored performance parameter and the other monitored performance parameters;vary an alignment between the moving window for the monitored performance parameter and the moving windows for each of the other monitored performance parameters to optimize a degree of association between the monitored performance parameter and each of the other monitored performance parameters;determine the degree of association by determining a set of F-statistic values for the monitored performance parameter for each of the other monitored performance parameters, wherein an F-statistic value for each of the other monitored performance parameters indicates a correlation between the monitored performance parameter and each of the other monitored performance parameters; anduse the set of F-statistic values to discard one or more monitored performance parameters that are correlated by more than a predetermined amount;determine whether the monitored performance parameters have deviated from predicted values for the performance parameters; andif so, to generate a signal indicating that the remote storage device has degraded.
061817600	abstract	The invention relates to a sensor for a measuring an electrochemical corrosion potential comprising a sensor tip, a conductor electrically connected to the sensor tip, an insulating member which surrounds the conductor, a connecting member which surrounds the conductor; and a sleeve which fits over the sensor tip, the insulating member, and the connecting member, the sleeve having inner threads which engage with corresponding outer threads on at least one of the sensor tip and the connecting member.
	summary
	summary
046541918	claims	1. In a containment for a nuclear reactor, a pressure release arrangement comprising: a break structure adapted to provide a pressure relief opening in the containment wall upon occurrence of a predetermined overpressurization, said break structure having a design break area of limited size with an operating bar mechanically connected with the break structure between spaced sections of the containment wall so as to cause rupture of said break structure upon stretching within the plastic deformation range of said containment walls by overpressurization of the containment. 2. A pressure release arrangement for a nuclear reactor pressure container, comprising: a pressure release pipe extending through the container wall and having an inner end provided with a closure plate disposed essentially normal to the wall of said container and arranged adjacent thereto, said pipe having a circumferential groove providing for a reduced thickness pipe area forming a design breaking point, and a drawbar having one end operatively connected to the end of said pipe at said closure plate and the other end to a distant point of the container wall, said drawbar being mounted with a free motion length sufficient only to permit stretching of the container wall by not more than about 0.5% and to cause rupture of the pipe at said breaking point by said drawbar upon further stretching of the container walls while they remain within the plastic deformation range. 3. A pressure release arrangement according to claim 2, wherein a U-shaped mounting structure with legs of unequal length is provided with the longer of said legs having its free end welded to the container wall and said pressure release pipe extends through said longer leg and is welded thereto whereas the pipe closure plate is welded to said shorter leg and the pipe design breaking point is disposed between the legs of said mounting structure, said drawbar having its one end connected to the free end of the shorter leg of said U-shaped mounting structure. 4. A pressure release arrangement according to claim 3, wherein the U bent area of said mounting structure includes a flex joint area of reduced thickness. 5. A pressure release arrangement according to claim 2, wherein the other end of said drawbar is mounted on a wall bracket adapted to move together with the container wall. 6. A pressure release arrangement according to claim 5, wherein said container is spherical, said pipe's inner end is disposed adjacent the container wall and said drawbar forms, with respect to the spherical container walls, essentially a chord between said wall bracket and the inner end of said pressure release pipe.
	description	The invention provides an EUVL multilayer coating that has high reflectivity, high thermal stability and controlled reaction or interdiffusion between the two different materials at their interface. Such a multilayer consists of alternating layers of an absorber layer (e.g., molybdenum) and a spacer layer (e.g., silicon). The invention is a thin layer of a third compound, e.g., boron carbide (B4C), placed on both interfaces (Mo-on-Si and Si-on-Mo interface). This third layer comprises boron carbide and other carbon and boron based compounds characterized as having a low absorption in EUV wavelengths and soft X-ray wavelengths. Thus, a multilayer film comprising alternating layers of Mo and Si includes a thin interlayer of boron carbide (e.g., B4C) and/or boron based compounds between each layer. The interlayer changes the surface (interface) chemistry, resulting in an increase of the reflectance and increased thermal stability. A unique feature of a Mo/Si multilayer system is that the interlayer regions are asymmetric. For example, the Mo-on-Si interface is considerably thicker than Si-on-Mo interface. This seems to be an intrinsic property of Mo/Si multilayers and has been observed in multilayers grown by magnetron sputtering [1], ion beam sputtering [2] and by electron beam evaporation [3,4]. The present invention also contemplates depositing a thicker layer of the interlayer material on the Mo-on-Si interface and a thinner layer of the interlayer material on the Si-on-Mo interface. The present inventors experimentally confirmed that a thicker boron carbide layer on the Mo-on-Si interface and a thinner layer of boron carbide on the Si-on-Mo interface gave the best reflectivity results. FIG. 1 shows multilayer design of a Mo/Si multilayer with a thicker B4C layer on the Mo-on-Si interface (where Mo is referred to as 12 and Si is referred to as 14) and a thinner B4C layer 16 on the Si-on-Mo interface (where Si is referred to as 18 and Mo is referred to as 12). The interface layer can be deposited using the same methods as for depositing Mo and Si. These methods include magnetron sputtering, ion beam sputtering, electron evaporation and any combination thereof. FIG. 2 shows the reflectance as a function of wavelength for this design, which achieved a peak reflectance of 69.9% at about 13.4 nm. The present inventors also performed time stability testing of these multilayers. Interdiffusion in a Mo/Si multilayer was prevented by depositing B4C on the interfaces once the initial reaction from a Mo, Si, B, C amorphous layer occurred. The interfaces between the three component layers in these structures remained sharp after 2.5 years and the multilayer structurexe2x80x94(Mo/Mo, Si, B, C/Si/Mo, Si, B, C/ remained unchanged. The reflectivity on a high reflectance multilayer dropped by only 0.4% (absolute) in 2.5 years (FIG. 3). The observed reflectance drop is due to surface oxidation of the last Si layer that occurs within a couple of months after the deposition. This multilayer structure (Mo/Si with B4C on interfaces) is stable in reflectance as well as in wavelength over long periods of time. FIG. 4 shows a schematic representation of an embodiment of a multilayer structure of the present invention. FIG. 5 shows a high magnification cross-section TEM of a Mo/B4C/Si/B4C multilayer fabricated by magnetron sputtering. The deposited thickness are: Mo=26.2 xc3x85, Si=42.72 xc3x85, B4C=2.55/2.55 xc3x85. The TEM thicknesses are: Mo=21.2 xc3x85, Si=34 xc3x85, B37Si31Mo23C9=7.35/7.35 xc3x85. The non-crystalline reacted zones at the Mo/B4C/Si interfaces are clearly shown in this magnification TEM of surface layers in the multilayer. Typically, the sharpness of the Mo on Si interface 50 would be about 2.5 times worse than that of the Si on Mo interface; however, due to the deposition of the interlayer of B4C in the Mo on Si interface, such interface sharpness is comparable to that of the Si on Mo interface. The multilayer was terminated with a Si layer that subsequently formed SiO2 on the top ambient surface. Highest reflectance multilayers are achieved with very thin B4C layers (0.1-0.35 nm). Improved lifetime stability of these multilayers can be achieved with 0.2-0.25 nm B4C thick interfaces. To make the multilayer thermally stable at higher temperatures ( greater than 300 degrees Celsius) thicker B4C layers are needed (0.3 nm or thicker). Referring again to FIG. 1, optimum performance is obtained where the thickness for the interlayer 10 is between 0.1 and 1.0 nm and interlayer 16 is between 0.1 and 0.5 nm Another important property of the multilayers is residual stress. Residual stress of Mo/Si multilayers with boron carbide interfaces is about 30% higher than the residual stress of Mo/Si multilayers with no boron carbide on the interfaces. The measured residual stress of Mo/Si multilayers with B4C interfaces is about xe2x88x92560 MPa. Annealing at about 150 degrees Celsius for about 3 hours reduces the residual stress substantially. The present invention contemplates that the residual stress of annealed Mo/Si multilayers with B4C interfaces is less than or equal to the residual stress of Mo/Si multilayers with no B4C on the interfaces. Still another aspect of the invention is that the annealing does not reduce the peak reflectance and does not change the peak wavelength. References: [1] A. K. Petford-Long, R. S. Rosen, M. B. Stearns, C. -H. Chang, S. R. Nutt, D. G. Stearns, N. M. Ceglio, and A. M. Hawryluk, J. Appl. Phys. 61, 1422, 1987. [2] A. Ulyanenkov, R. Matsuo, K. Omote, K. Inaba, and J. Harada, J. Appl. Phys. 87,7255 (2000). [3] J. M. Slaughter, D. W. Schulze, C. R. Hills, A. Mirone, R. Stalio, R. N. Watts, C. Tarrio, T. B. Lucatorto, M. Krumrey, P. Mueller, C. M. Falco, J. Appl. Phys. 76, 2144 (1994). [4] M. B. Stearns, C. -H. Chang, D. G. Stearns, J. Appl. Phys. 71, 187 (1992). The foregoing description of the invention has been presented for purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. The embodiments disclosed were meant only to explain the principles of the invention and its practical application to thereby enable others skilled in the art to best use the invention in various embodiments and with various modifications suited to the particular use contemplated. The scope of the invention is to be defined by the following claims.
	abstract	Radiosurgery systems are described that are configured to deliver a therapeutic dose of radiation to a target structure in a patient. In some embodiments, inflammatory ocular disorders are treated, and in some embodiments, other disorders or tissues of a body are treated with the dose of radiation. In some embodiments, target tissues are placed in a global coordinate system based on ocular imaging. In some embodiments, a fiducial marker is used to identify the location of the target tissues.
	abstract	A detector assembly is provided that includes a semiconductor detector, a collimator and a processing unit. The semiconductor detector has a first surface and a second surface opposed to each other. The first surface includes pixels (which in turn comprise corresponding pixelated anodes), and the second surface includes a cathode electrode. The collimator includes openings, with each opening associated with a single corresponding pixel of the semiconductor detector. The processing unit is configured to identify detected events within virtual sub-pixels distributed along a length and width of the semiconductor detector. Each pixel includes (e.g., has associated therewith) a plurality of corresponding virtual sub-pixels, with absorbed photons are counted as events in a corresponding virtual sub-pixel. Absorbed photons are counted as events within a thickness of the semiconductor detector at a distance corresponding to an energy window width used to identify the events as photon impacts.
	abstract	A diffractometer, having variable center and suitable for performing analysis on hidden or hardly accessible bodies or specimens is described. Said variable center diffractometer is equipped with an analytical unit that comprises: a circle arc structure, called Euler cradle; a radiation beam source and a detector of the said radiation beam; devices for the pointing of the analytical unit; devices for the movements of said analytical unit in the space; devices for rotation of said source and detector along the Euler cradle; characterized by the fact that it comprises also: devices able to rotate said source and detector with respect to an orthogonal axis to the plane containing the Euler cradle; collimators or deflectors firmly placed on the said radiation source and detector.
	abstract	A method of storing nuclear fuel is described. In some cases, the method includes submerging at least a portion of a nuclear fuel rod in a storage pool containing an aqueous solution including at least one of polyhedral boron hydride anions or carborane anions. In some cases, the method includes adding a salt having a polyhedral boron hydride anion or carborane anion to a storage pool containing water and at least a portion of a nuclear fuel rod submerged in it. The method may include both of these. A storage pool is also described. The storage pool includes an aqueous solution having at least one of polyhedral boron hydride anions or carborane anions with at least a portion of a nuclear fuel rod submerged in the aqueous solution. A method of servicing a nuclear reactor core is also described.
043671845	summary	Fuels in the form of sintered microspheres containing a high percentage of U.sup.235 have come into general use for nuclear power generation. However, such microspheres can readily be processed to provide fissile material for use in atomic weapons. To promote nuclear weapon control, the nuclear reactor fuel supplied to countries in need of nuclear power generating plants should be in a form that can only be diverted into use in atomic weapons by means of uranium-enriching facilities not generally available. A preferred form of nuclear fuel that can safely be supplied to energy-poor countries consists of high density microspheres produced from 20% enriched uranium and containing up to 30 mole percent UC.sub.2 with the remainder in the form of UO.sub.2. PRIOR ART Extensive investigations have been conducted to determine the nature of the uranium-carbon-oxygen nuclear fuel system with which the present invention is involved. The phase diagram for the system at temperatures in the range of 1300.degree.-1750.degree. C. has been developed in detail, and the preferred process embodiment of this invention will be described by reference to this diagram. The same U-C-O diagram has been previously considered in an article titled "The Application of Thermochemical Principles to the Production of Nuclear Fuel Materials" and published by G. R. Chilton in 1976 as Special Publication No. 30 of The Chemical Society, Burlington House, London, England. Carbothermic reduction of uranium dioxide, which is utilized in the preferred process of this invention, is also described in the aforesaid publication and in an article titled "Carbon Monoxide Equilibrium Pressures and Phase Relations During the Carbothermic Reduction of Uranium Dioxide" and published by J. F. A. Hennecke and H. L. Scherff in 1971 in the Journal of Nuclear Materials 38, North-Holland Publishing Company, Amsterdam, Holland. SUMMARY OF THE INVENTION It is an object of this invention to form microspheres containing uranium compounds in chemical forms and proportions suitable for use as nuclear reactor fuel but not conveniently adaptable for use in atomic weapons. Another object of the invention is to provide a method for making nuclear fuel microspheres consisting essentially of about 1-30 mole percent uranium dicarbide and 70-99 mole percent uranium dioxide and the fuel having a density of about 10.2 to 11.0 g/cm.sup.3. These objects are attained by a preferred process embodiment of the invention wherein microspheres containing uranium dioxide and uncombined carbon are first sintered at a temperature of 1550.degree. C. in an atmosphere containing about 0.5 to 1 mole percent of carbon monoxide and then sintered at the same temperature in an atmosphere containing about 3 mole percent of carbon monoxide.
	description	1. Field of the Invention The present invention relates to a soft X-ray microscope, and more particularly, to a soft X-ray microscope that uses a liquid target that is not affected by target fragments and that has excellent monochromaticity so that the soft X-ray microscope can be easily used in a laboratory and has spatial resolution of no more than 100 nm. 2. Description of the Related Art In general, a microscope refers to an apparatus for enlarging a minute part of an object (hereinafter, referred to as a sample) to observe the minute part and may include an electronic microscope that uses electrons as a light source or an optical microscope that uses visible rays as a light source. In the case of the electronic microscope, since the sample must be put under vacuum and must be physically and chemically pre-processed, it is not possible to observe a living sample such as the cells of an organism. In the case of the optical microscope, it is possible to observe a living sample; however, since the visible rays are used as the light source, the resolution is limited to about 200 nm due to the diffraction limitation of the light source according to the current technology. Recently, a soft X-ray microscope using an X-ray wavelength region referred to as window of water (λ=2.3 to 4.4 nm) has been studied. In the region of the window of water, since there exists large X-ray absorption differences between water and protein that constitutes the living sample, it is possible to observe protein through a water layer of a thickness of several microns and to observe the inside of the living sample due to the permeability of X-ray. The above-described soft X-ray microscope includes a light source chamber in which a solid target made of tantalum is provided, a light source for focusing pulse light on the solid target to generate X-ray so that the X-ray is radiated onto the living sample, a sample chamber in which the living sample is provided, a mirror chamber for leading the X-ray that transmits the sample to capturing device, and the capturing device for capturing the X-ray image that is scattered by the living sample or that transmits the living sample. The operation of the soft X-ray microscope having the above structure will be described as follows. When the pulse light is emitted from the light source to the solid target, the pulse light collides with the target to generate a predetermined X-ray. The generated X-ray is radiated onto the living sample provided in the sample chamber to be scattered by the living sample and to transmit the image of the living sample. The capturing device captures the light that is scattered by the living sample and that transmits the image of the living sample so that the living sample can be observed. However, since the target onto which the pulse light is radiated is solid, minute pieces are generated in the part onto which the pulse light is radiated and the generated pieces are attached to the internal surface of the light source chamber that remains vacuous in which the solid target is provided so that the vacuum degree is damaged. In particular, the pieces attached to the internal surface of the light source chamber prevent the X-ray from being precisely generated so that it is difficult to repeatedly use the soft X-ray microscope for a long time. Furthermore, the solid target damaged by the radiation of the pulse light must be frequently exchanged in order to precisely generate the X-ray so that the light source chamber in which the solid target is provided must be released and reset under vacuum. Therefore, work time and maintenance and repair expenses increase. The mirror chamber that leads the X-ray generated by the light source chamber to pass through the living sample includes mirrors on both sides of the living sample, that is, an illuminating mirror for illuminating the living sample before the pulse light passes through the living sample and an amplifying mirror for enlarging and amplifying the light that passed through the living sample illuminated by the illuminating mirror by the capturing device. The X-ray generated by the light source chamber is illuminated and enlarged by the mirrors and passes through the living sample and the capturing device captures the X-ray image to obtain an image. However, in the above case, in order to enlarge and photograph the light that passed through the living sample by the capturing device in accordance with the optical enlargement magnification formula, the distance between the sample chamber and the capturing device is 3 to 4 m on the average, the magnification is about 286, and resolution is about 200 nm, which is similar to the resolution of the optical microscope. As described above, the soft X-ray microscope in which the distance between the sample chamber and the capturing device is 3 to 4 m on the average in order to obtain an image of high magnification as mentioned above is preferably horizontally installed rather than vertically installed so that the use area of the soft X-ray microscope increases and that the space efficiency of a work place deteriorates. Therefore, a work place for the exclusive use of the soft X-ray microscope must be additionally provided, which causes inconvenience and inefficiency. In order to solve the above problem, it is an object of the present invention to provide a soft X-ray microscope in which a liquid target with no target pieces and having excellent monochromaticity (λ/Δλ), that is, liquefied nitrogen is used so that the soft X-ray microscope has spatial resolution of no more than 100 nm and can be continuously used for a long time. It is another object of the present invention to provide a soft X-ray microscope that includes a mirror chamber made of a dual oval illuminating mirror and a Fresnel diffraction zone plate such that the living sample is illuminated by the illuminating mirror and the light penetrated the living sample is amplified and obtained by the Fresnel diffraction zone plate so that the resolution of no more than 100 nm and an expanded image more than 1000× magnification are provided, the distance from the mirror chamber to the image capturing device is minimized, and the microscope can be minimized. It is still another object of the present invention to provide a soft X-ray microscope in which the respective devices are vertically provided to minimize the installation space thereof so that it is possible to maximize the space efficiency, to increase the application range of the soft X-ray microscope, and to conveniently install the soft X-ray microscope. In order to achieve the above objects, there is provided a soft X-ray microscope including: a table; a housing installed to the upper side of the table and having a partition; a light source chamber installed lower than the partition of the housing to project a light to liquid jetted under a high pressure to generate plasma; a mirror chamber, installed above the partition of the housing, in which first and second mirror are respectively installed to upper and lower sides of a holder for storing a living sample, the soft X-ray generated by the plasma generated in the light source chamber illuminates the living sample, and the soft X-ray penetrated the living sample is amplified to obtain an image in an image capturing chamber; and an image capturing chamber installed to the upper side of the housing to amplify a light image signal amplified through the mirror chamber and to capture the light image on an external screen to allow distinguishing the light image from exterior. Preferably, the soft X-ray microscope further includes a telemicroscope installed to the side of the light source chamber to allow watching the procedure of projecting the soft X-ray to the high-pressure liquid to form the plasma from the exterior. The light source chamber includes a nozzle part for jetting liquid nitrogen supplied from the exterior under a high pressure, a discharge part provided opposite to the nozzle part to suction the liquid nitrogen and to discharge the liquid nitrogen to the exterior; a light source for projecting a light to the liquid nitrogen jetted from the nozzle part to form the plasma; and a light source vacuum pump for vacuuming the inside of the housing in which the light source is installed and for maintaining vacuum of the housing. The nozzle part includes a capillary tube for receiving the high-pressure nitrogen gas from the exterior to jet the high-pressure nitrogen gas, and an outer tube for surrounding the outer circumference of the capillary tube and for receiving the high-pressure liquid nitrogen from the exterior to be filled up and to liquefy the high-pressure nitrogen gas jet through the capillary tube. Preferably, the light source includes a diode pump solid laser having an average power of 12 W and a repetition rate of 300 Hz. Preferably, the light source vacuum pump includes a turbo molecular pump having a vacuum degree of more than 500 L/S. The mirror chamber includes: a first base plate fixed to the upper side of the partition of the housing and having a first transmission hole formed in the central portion thereof; a first mirror including a first transporting device installed on the first base plate, and a condenser mirror installed in the central portion of the first transporting device to amplify the light and to illuminate the living sample; a second base plate positioned above the first mirror, supported by a plurality of supporting rods to maintain the distance from the first base plate, and having a second transmission hole formed in the central portion thereof; a holder part including a second transporting device installed on the second base plate, and a coupling for separating and coupling the holder storing the living sample from and to the central portion of the second transporting device; a second mirror including a third transporting device installed on the second base plate, and a Fresnel diffraction zone plate installed in the central portion of the third transporting device and positioned above the holder; and a vacuuming device for vacuuming the inside of the housing having the mirror chamber and for maintaining vacuum. The soft X-ray microscope further includes a rod lock chamber provided at the side of the mirror chamber and to transport the holder such that vacuum of the mirror chamber is not damaged and the holder storing the living sample is coupled with and separated from the coupling of the holder part. The soft X-ray microscope further includes an optical aligning device for checking whether the first mirror, the holder part, and the second mirror are aligned in the optical axis direction, and for aligning the same. Preferably, the condenser mirror includes first and second oval-shaped hedrons symmetrical to each other and having an optical axis-directional length 136 mm, an inner diameter of 50 mm, and a depth of 42 mm, and a pin hole formed in the center portion in the longitudinal direction, and the first and second oval-shaped hedrons are formed by ovals having a longitudinal directional center as a focal point, a distance of 160 mm from the focal point to another focal points, and symmetrical to each other with respect to the central focal point. The holder part includes: a holder including a sample part having sample windows made of a silicon nitride layer (Si3N4) with a thickness of 90 nm to 120 nm to cover ends of the living sample and viton plates for covering ends of the sample windows, a sample plate, on which the sample part is placed, having a transmission hole formed in the center and a locking hook formed in a side, a cover plate for covering the upper side of the sample plate on which the sample part is placed and having a transmission hole formed in the center thereof, and an O-ring for maintaining sealing between the sample plate and the cover plate; a coupling including a plurality of supporting plates having a plurality of ball plungers to support outer circumference of the sample plate, and an opened portion enabling the holder to separate; and a second transporting device provided at the side of the coupling and transported in the three directions of the X-axis, the Y-axis, and the Z-axis by a motor. The Fresnel diffraction zone plate is manufactured by forming gold (Au) having a thickness of 100 nm to 160 nm on a silicon nitride layer (Si3N4) substrate, and has an outmost zone width of 30 mm to 40 mm a diameter of 60 mm to 70 mm, and the number of Fresnel diffraction zone plate is 200 to 300. The vacuuming device includes at least one turbo molecular pump of 210 L/S and at least one ion pump of 120 L/S. The rod lock chamber includes a vacuuming device for preventing vacuum generated in the mirror chamber from being damaged when the holder storing the living sample is separated from and coupled with the mirror chamber, wherein the vacuuming device includes a turbo molecular pump of 60 L/S and an ion pump of 30 L/S. The soft X-ray microscope further includes a filter installed in the lower side of the first base plate to filter the light transmitted to the mirror chamber through the plasma generated by the light source chamber and to separate the vacuum of the light source chamber and the mirror chamber, and made of titanium. The soft X-ray microscope further includes a shielding device installed to the lower side of the second base plate to interrupt a direct light, which is not amplified by the condenser mirror, to directly illuminate the living sample when illuminating the illuminated through the condenser mirror, and including a through-hole formed in a supporting plate supported by a fourth transporting device, and a focal point interrupting plate installed in the center of the through-hole to interrupt the direct light. The image capturing chamber includes a multi-channel plate for converting a light image signal obtained through the light amplified by the second mirror into an electric signal, and a CCD for amplifying the electric signal converted by the multi-channel plate and for converting the amplified electric signal into a visible light using a fluorophor such that the converted visible light forms an image on the external screen through an optical lens. Hereinafter, the present invention will be described in detail with reference to the attached drawings. A soft X-ray microscope includes a light source chamber for generating a soft X-ray wavelength area using light projected from a light source, a mirror chamber provided to a side of the light source chamber to illuminate an living sample using the soft X-ray generated by the light source chamber and to expand the light illuminated to the living sample such that an image capturing chamber captures an image, and the image capturing chamber provided to a side of the mirror chamber to convert the image capture in the mirror chamber such that an external device can discern the converted image, wherein the light source chamber, the mirror chamber, and the image capturing chamber are controlled an integrated operating program and an optical aligning algorithm. FIG. 1 schematically illustrates the external appearance of a soft X-ray microscope according to the present invention, and FIG. 2 is a sectional view of the soft X-ray microscope according to the present invention. Referring to the drawings, the soft X-ray microscope includes a table 10, a housing 20 installed in the table 10, a light source chamber 30 installed in the lower side of the housing 20, a mirror chamber 40 installed above the light source chamber 30, and an image capturing chamber 50 installed at the upper side of the housing 20. The soft X-ray microscope is installed in the vertical direction so that radius of the soft X-ray microscope is optimized and the efficiency of the space for installation is maximized. The table 10 can use any device that is not affected by external vibrations, and preferably is implemented by a cradle type optical table. The housing 20 is a hollow cylinder and includes a partition installed at a predetermined depth thereof. Moreover, the housing, as shown in the drawings, includes a ring-shaped locking step 24 provided at a predetermined height of the outer circumference of the housing 20, a blade 26 fixed to the ring-shaped locking step 24, and is structured such that a plurality of interval maintaining devices 12 is fixed to the lower side of the blade 26 so that the table 10 and the housing 20 are spaced apart from each other by the interval maintaining devices 12. This is to minimize the affects due to vibrations in spite of installing the housing 20 on the table 10. The light source chamber 30 is installed below the partition 22 of the housing 20. Since the partition 22 of the housing 20 is closed by a first base plate 440 of the mirror chamber 40 and the lower side of the housing 20 is closed by a light source vacuum pump 340, the interior of the housing 20 in which the light source chamber 30 is installed can be maintained in a vacuum. FIG. 3 is a plan view of the light source chamber. Referring to the drawing, the light source chamber 30 includes a discharge part 320 aligned with a nozzle part 310 provided at a side of the light source chamber 30, a light source 330 installed between the nozzle part 310 and the discharge part 320 to project light, and a tele-microscope 60 for allowing a user to check an operation state of the nozzle part 310, the discharge part 320, and the light source 330. The nozzle part 310 is a device for jetting high-pressure liquid to form a liquid target, and preferably includes a capillary tube 312 for jetting nitrogen gas supplied from an exterior to the housing and an outer tube 314 for surrounding the capillary tube 312 and for receiving high-pressure liquid nitrogen from an exterior to liquefy the nitrogen gas jetted through the capillary tube 312. Of course, according to circumstances, only liquid nitrogen may be used. Moreover, the light source 330 preferably utilizes a high power laser such as a diode pump solid laser of average 12 W and a repetition rate of 300 Hz. In other words, the liquid nitrogen jetted through the capillary tub 312 of the nozzle part 310 becomes the liquid target serving as a medium and the laser beam projected from the light source 330 is projected to the liquid target so that plasma of the soft X-ray laser having a wavelength of 2.3 nm to 4.4 nm is generated. Meanwhile, the inside of the housing 20 can be vacuumed or the vacuum state of the housing 20 can be maintained by the light source vacuum pump 340 for closing the lower side of the housing 20. In this case, the light source vacuum pump 340 is preferably implemented by a turbo molecular pump having a vacuuming capacity of more than 500 L/S. In addition, the housing 20 includes at least one window 24 to enable a user to check the inside of the housing 20. FIG. 4 is an exploded perspective view of a first base plate and a first mirror according to the present invention, and FIG. 5 is a plan sectional view of a mirror chamber provided in a housing according to the present invention. The mirror chamber 40 is installed above the partition 22 of the housing 20, and includes a first base plate 440 fixed to the upper side of the partition 22, a first mirror 410 installed on the upper side of the first base plate 440, a second base plate 450 positioned above the first mirror 410, a holder part 420 installed on the second base plate 450, and a second mirror 430 positioned above the holder part 420. The first base plate 440 is fixed to the upper side of the partition 22 of the housing 20 by a plurality of fastening devices, has a first transmission hole 442 formed in the central portion thereof such that the soft X-ray passes through the first transmission hole 442 according to the generation of plasma in the light source chamber 30, and a filter 470 installed in the lower side of the first transmission hole 442, that is, in the lower side of the first base plate 440 so that wavelength of the soft X-ray is filtered through the filter 470 and vacuum of the light source chamber 30 and the mirror chamber 40 are separated from each other. Additionally, the filter 470 is made of titanium and preferably has a thickness of about 100 nm to 200 nm. Particularly, the filter 470 is made to be exchanged. The first mirror includes a first transporting device 412 installed on the first base plate 440 and a condenser mirror 414 installed to the first transporting device 412 and that can have its position adjusted. Additionally, the position of the first transporting device 412 is adjusted in multiple directions of the X-axis direction, the Y-axis direction, and the Z-axis direction, and preferably includes separate motors installed in the respective axes to move along the respective axes. FIG. 6 is an enlarged sectional view of the condenser mirror. As shown in the drawing, the condenser mirror 414 is an illuminating mirror for amplifying a wavelength of the soft X-ray obtained through the plasma generated in the light source chamber 30 and for illuminating the living sample with the amplified soft X-ray. The condenser mirror 414 amplifies the wavelength of the soft X-ray to illuminate the living sample using symmetric oval-shaped hedron. Additionally, the condenser mirror 414 includes first and second oval-shaped hedrons 414a and 414b symmetrical to each other and having an optical axis-directional length 136 mm, an inner diameter of 50 mm, and a depth of 42 mm, and a pin hole 414 formed in the center portion in the longitudinal direction. Moreover, the first and second oval-shaped hedrons 414a and 414b are preferably formed by ovals having a longitudinal directional center as a focal point P, a distance of 160 mm from the focal point P to another focal points P′ and P″, and symmetrical to each other with respect to the central focal point P. Referring to FIG. 6, in view of the principle that the length of a line started from a focal point and terminated to another focal point after reflected by the oval is identical, as shown in the drawing, it can be learned that all lines passing through two focal points P-P′ or P-P″ are identical. Preferably, in the condenser mirror 414 using the principle, one focal point P′ is positioned in the first transmission hole 442 of the first base plate 440 and the opposite another focal point P″ is positioned on the living sample. By doing so, the soft X-ray passing through the first transmission hole 442 passes through one focal point P′, is reflected by the first oval-shaped hedron 414a, passes through the central focal point P, and is collected to another focal point P″ after reflected by the second oval-shaped hedron 414b, so that the soft X-ray illuminates the living sample placed on the focal point P″. Additionally, the wavelength of the soft X-ray is reflected by the first and second oval-shaped hedrons 414a and 414b and is amplified. The wavelength of the soft X-ray that is not reflected by one focal point P′ or the first and second oval-shaped hedrons 414a and 414b is interrupted by the pin hole 414c formed in the center of the condenser mirror 414. Moreover, a direct light passing through the pin hole 414c is interrupted by a shielding device 480, described later, installed in the lower side of the second base plate 450. FIG. 7 is an exploded perspective view of the second base plate 450, the holder 420, and the second mirror 430 according to the present invention. The second base plate 450 has a second transmission hole 454 formed in the center thereof and a plurality of supporting rods 452 fixed to the lower side to support the lower side thereof. The supporting rods 452 maintain a predetermined distance between the second base plate 450 and the first base plate 440. Additionally, on the lower side of the second base plate 450, that is, in the lower side where the second transmission hole 454 is formed, the shielding device is installed. Here, the shielding device 480 includes a through-hole 484a formed in a supporting plate 484 supported by a fourth transporting device 482, and a focal point interrupting plate 486 installed in the center of the through-hole 484a to interrupt the direct light. Preferably, the focal point interrupting plate 486 is positioned in the center of the through-hole 484a, and includes a plurality of fixing pins 488 such that the focal point interrupting plate 486 is fixed in the through-hole 484a. Meanwhile, on the second base plate 450, the holder part 420 and the second mirror 430 are installed. FIG. 8 is an exploded perspective view of the holder. The holder part 420 includes the second transporting device 422 installed on the upper side of the second base plate 450, a holder 424 for storing the living sample, and a coupling 426 installed on the second transporting device 422 to separate and couple the holder 424. The holder 424 includes a sample part 4210 having sample windows 4212 made of a silicon nitride layer. (Si3N4) with a thickness of 90 nm to 120 nm to cover ends of the living sample and viton plates 4214 for covering ends of the sample windows 4212, a sample plate 4220, on which the sample part 4210 is placed, having a transmission hole 4222 formed in the center and a locking hook 4224 formed in a side, a cover plate 4230 for covering the upper side of the sample plate 4220 on which the sample part 4210 is placed and having a transmission hole 4232 formed in the center thereof, and an O-ring 4240 for maintaining sealing between the sample plate 4220 and the cover plate 4230. Thus, the holder 424 prevents moisture contained in the living sample from evaporating to protect the living sample. The coupling 426 includes a plurality of supporting plates 426a having a plurality of ball plungers 426b to support an outer circumference of the sample plate 4220. Each of the supporting plates 426a has an opened portion where the ball plungers 426b do not interfere such that the holder 424 supported by the ball plungers 426b may be separated and coupled in one direction. The direction of the opened portion of the supporting plates 426a is preferably the axial direction where the holder 424 is transported by a rod lock chamber 70 described later. Moreover, the second transporting device 422 is provided at the side of the coupling 426 and is preferably transported in the three directions of the X-axis, the Y-axis, and the Z-axis by a motor. FIG. 9 is a side view of the rod lock chamber. The rod lock chamber 70 is provided at the side of the housing 20 and is structured to transport the holder part 420 such that vacuum of the mirror chamber 40 in the housing 20 is not damaged and the holder 424 storing the living sample is coupled with and separated from the coupling 426 of the holder part 420. Additionally, the rod lock chamber 70 includes a vacuuming device 72 for preventing vacuum generated in the mirror chamber 40 from being damaged when the holder 424 storing the living sample is separated from and coupled with the mirror chamber 40. The vacuuming device 72 preferably includes a turbo molecular pump of 60 L/S and an ion pump of 30 L/S. Here, the rod lock chamber 70 includes a chamber 74 fixed to a flange provided at the housing 20, a rod shaft 76 provided in the chamber 74 and moved forward and backward by a driving device 76b, and having a locking part 76a, formed in the side thereof, to which one side of the holder 424 is fixed, and the vacuuming device 72 provided at the side of the chamber 74 to vacuum the inside of the chamber 74 and to maintain vacuum of the chamber 74. Particularly, since the chamber 74 has an opening and closing window 78 formed at the side thereof, the holder 424 can be coupled with or separated from the locking part 76a of the rod shaft 76 through the window 78. The window 78 has a transparent indicating window. The second mirror 430 includes a third transporting device 432 installed on the second base plate 450, and a supporting plate 436 installed in the center of the third transporting device 432 and having a Fresnel diffraction zone plate 434 placed thereon to position above the holder 424. Additionally, the Fresnel diffraction zone plate 434 is generally called as a zone plate, and is preferably manufactured by forming gold (Au) having a thickness of 100 nm to 160 nm on a silicon nitride layer (Si3N4) substrate. The Fresnel diffraction zone plate 434 has an outmost zone width of 30 mm to 40 mm and a diameter of 60 mm to 70 mm. Preferably, the number of Fresnel diffraction zone plate is 200 to 300. The Fresnel diffraction zone plate 434 is installed to maintain the distance 0.8 mm from the living sample stored in the holder 424, and preferably, the distance between the Fresnel diffraction zone plate 434 and the image capturing chamber 50 is 800 mm. According to the optical magnification formula 1 a + 1 b = 1 f ,the optical magnification is changed according to the difference between the distance from the living sample to the Fresnel diffraction zone plate and the distance the Fresnel diffraction zone plate to the image capturing chamber. It can be understood that the magnification of 1000× can be obtained in the above case. At the side of the mirror chamber 40, an optical aligning device 80 is further provided. The optical aligning device 80 checks whether the first mirror 410, the holder part 420, and the second mirror 430 are aligned in the optical axis direction, and automatically aligns them. The optical aligning device 80 projects a visible light, and the projected visible light is refracted by an objective lens and is projected to the second mirror 430 positioned at the lower side, the holder part 420, and the first mirror 410. The visible light refracted by the second mirror 430, the holder part 420, and the first mirror 410 is inputted to the optical aligning device through the objective lens such that the optical aligning device 80 performs calculation and automatically aligns second mirror 430, the holder part 420, and the first mirror 410. At the side of the optical aligning device 80, a CCD camera is installed to watch the light path of the visible light and the automatic aligning through an external screen. Additionally, a vacuuming device 460 is installed in the housing 20 in which the mirror chamber 40 is installed. Preferably, the vacuuming device 460 includes at least one turbo molecular pump of 210 L/S and at least one ion pump of 120 L/S. The image capturing chamber 50 includes a cover plate 540 fixed by a plurality of fastening devices to cover the upper side of the housing 20, a multi-channel plate 510 installed at the upper side of the cover plate 540, and a CCD 520. The multi-channel plate 510 converts an optical image signal obtained through the light amplified by the second mirror 430 into an electric signal. The CCD 520 amplifies the electric signal converted by the multi-channel plate 510 and the amplified electric signal is converted into a visible light by a fluorophor such that the converted visible light forms an image on the external screen through an optical lens. In this case, preferably, a vacuum chamber 530 for maintaining the distance between the multi-channel plate 510 of the image capturing chamber 50 and the Fresnel diffraction zone plate 434 is provided. The operation of the soft X-ray microscope structured as described above will be described. FIG. 10 is a flowchart of the soft X-ray microscope according to the present invention. Referring to the drawing, firstly, an optical aligning step S10 is a procedural step of checking whether the second mirror in the mirror chamber, the holder, and the first mirror are aligned in the optical axis direction and of automatically aligning the second mirror, the holder, and the first mirror if the second mirror, the holder, and the first mirror are not aligned yet. The optical aligning step S10 is carried out by the optical aligning device 80 installed at the side of the mirror chamber 40. In other words, the visible light projected from the optical aligning device 80 is refracted downward through the objective lens, the refracted visible light passes through the Fresnel diffraction zone plate 434 of the second mirror 430, the holder 424 of the holder part 420 and the condenser mirror 414 of the first mirror 410 and the positions are measured. The measured positions are calculated, if necessary to compensate, a signal is transmitted to an integrally driving program so that the transporting devices installed in the respective devices automatically align the respective devices in the optical axis direction. Of course, the automatic alignment can be watched from exterior through the CCD provided at the side of the optical aligning device 80. A living sample placing step S20 is a procedural step of placing the living sample in the soft X-ray microscope, and is carried out by the rod lock chamber 70 provided at the side of the mirror chamber 40. In this case, after positioning a predetermined sized living sample between a plurality of the sample windows 4212, the sample windows 4212 are stacked and the outer sides of the sample windows 4212 are covered by the viton plates 4214. The sample part 4212 structured as such is positioned on the sample plate 4220 and the cover plate 4230 is fastened on the sample plate 4220. At that time, the O-ring 4240 is provided between the sample plate 4220 and the cover plate 4230 so as to maintain sealing force so that evaporation of moisture contained in the living sample under vacuum is minimized. The holder 424, in which the living sample is stored in the above procedures, opens the window 78 of the rod lock chamber 70 and locks and fixes the locking hook 4224 of the holder 424 to the end of the rod shaft 76. After that, the opened window 78 is closed and the vacuuming device 72 of the rod lock chamber 70 performs vacuuming. This is to transport the holder 424 storing the living sample to the mirror chamber 40 without damaging vacuum of the housing 20 because the housing 20 including the light source chamber 30 maintains vacuum. Although not depicted and described, a shielding layer is formed between the rod lock chamber 70 and the housing 20, due to the shielding layer, vacuum between the rod lock chamber 70 and the housing 20 is maintained, and additionally, the window 78 is automatically opened when transporting the holder 424 from the rod lock chamber 70 to the housing 20. This is general technique. When finished the vacuuming of the rod lock chamber 70, the shielding layer is opened and the rod shaft 76 is advanced into the housing 20 by the driving device 76a such that the holder 424 is placed on the coupling 426 of the holder part 420 in the mirror chamber 40. The holder 424 is positioned inside the supporting plates 426a of the coupling 426 and is supported by the ball plungers 426b of the supporting plates 426a. The rod shaft 76 transported the holder 424 is transported in the reverse direction by the driving device 76a and is positioned at the rod lock chamber 70. When the holder 424 storing the living sample is placed in the mirror chamber 40, the soft X-ray microscope is operated to watch the living sample. According to circumstances, the alignment of the mirror chamber 40 can be checked again by the optical aligning device 80. A plasma generating step S30 is a procedural step of generating plasma having a wavelength range of the soft X-ray by projecting a laser beam to the liquid target. In this step, nitrogen gas is jetted through the capillary tube 312 of the nozzle part 310 installed in the light source chamber 30 and the jetted nitrogen gas is liquefied due to liquid nitrogen filled in the outer tube 314 for surrounding the capillary tube 312 so that the liquid target is generated. The light source 330 projects the high power laser to the liquid target so as to generate plasma having a wavelength of 2.3 nm to 4.4 nm of the soft X-ray by the light source 330. Moreover, the liquid nitrogen jetted from the nozzle part 310 is suctioned into the discharge part 320 and discharged to the exterior so that the housing 20 including the light source chamber 30 can be prevented from being contaminated due to the liquid nitrogen and the continuous recycling is enabled. As such, it can solve the problems that fine solid fragments are generated from a solid target projected by a laser beam when using the solid target and the fine solid fragments are suctioned into the light source chamber so that the suctioned fragments disturb the generation of the soft X-ray from the light source chamber, cause malfunction of the chamber, and restrict the continuous use of the chamber. A living sample illuminating step S40 is a procedural step of amplifying the wavelength of the soft X-ray generated from the light source chamber and of illuminating the lower side of the living sample. In this step, the wavelength of the soft X-ray having an excellent monochromaticity is filtered through the liquid target of the light source chamber 30 by the filter 470 provided in the lower side of the first base plate 440, and a light penetrating the first transporting device 412 of the first base plate 440 is amplified by passing through the oval-shaped hedrons 414a and 414b of the condenser mirror 414 to illuminate the living sample. Like the above description of the condenser mirror 414, the amplification of the wavelength of the soft X-ray by the condenser mirror 414 is carried out such that a light passing through one focal point P′ is reflected by the oval-shaped hedron 414a and the reflected light passes through the central focal point P of the pin hole 414c and is reflected again by the oval-shaped hedron 414b positioned in the symmetric direction, so that the amplified light illuminates the living sample positioned at the another focal point P″. In this case, a light does not pass through the focal points P′, P, and P″ of the condenser mirror 414 is interrupted by the pin hole 414c or the shielding device 480 so that the living sample is prevented from being illuminated by the direct light generated from the light source chamber 30. By doing so, the illumination efficiency to the living sample by the condenser mirror 414 is enhanced. A light expanding step S50 is a procedural step of amplifying and expanding a light illuminated to the living sample to obtain an image of the living sample from the image capturing chamber. In the step, the soft X-ray amplified by the condenser mirror 414 of the first mirror 410 illuminates the living sample, and the illuminated light is expanded to form an image on the multi-channel plate 510 of the image capturing chamber 50. This is to amplify and expand a light using the Fresnel diffraction zone plate 434 of the second mirror 430. In other words, the light penetrated the living sample is diffracted by the 200 to 300 Fresnel diffraction zone plates of the Fresnel diffraction zone plate 434 and is collected to the focal distance. In other words, the living sample and the Fresnel diffraction zone plate 434 maintains the distance of 0.8 mm and the Fresnel diffraction zone plate 434 and the image capturing chamber 50 maintain the distance of 800 mm so that an image of magnification of 1000× can be obtained in the image capturing chamber 50 through the light illuminated to the living sample. An image obtaining step S60 is a procedural step of converting a light image expanded through the Fresnel diffraction zone plate into an electric signal to allow to watch the light image through an external screen or to print the light image. In this step, the light image is converted into the electric signal by the multi-channel plate 510 on which the light image amplified by maximum 1000× magnification through the Fresnel diffraction zone plate 434 of the second mirror 430 is collected. The CCD 520 amplifies the converted electric signal and the amplified electric signal is converted into a visible light by the fluorophor such that the converted visible light forms an image on the external screen through an optical lens. Thus, the image of the living sample can be watched from exterior. According to circumstances, the image of the living sample obtained through the CCD 520 is outputted on a monitor, in the form of a computer file, or printed on paper to allow watching the image. As described above, the soft X-ray microscope according to the present invention uses a liquid target with no target pieces and having excellent monochromaticity (λ/Δλ=1000), has spatial resolution of no more than 100 nm, and can be continuously used for a long time. Moreover, the soft X-ray microscope includes a mirror chamber made of a dual oval illuminating mirror and a Fresnel diffraction zone plate such that the living sample is illuminated by the illuminating mirror and the light penetrated the living sample is amplified and obtained by the Fresnel diffraction zone plate so that the resolution of no more than 100 nm and an expanded image more than 1000× magnification are provided, the distance from the mirror chamber to the image capturing device is minimized, and the microscope can be minimized. Moreover, according to the soft X-ray microscope, the respective devices are vertically provided to minimize the installation space thereof so that it is possible to maximize the space efficiency, to increase the application range of the soft X-ray microscope, and to conveniently install the soft X-ray microscope. Although the preferred embodiment of the soft X-ray microscope of the present invention has been described, it will be understood by those skilled in the art that the present invention should not be limited to the described preferred embodiment, but various changes and modifications can be made within the spirit and scope of the present invention as defined by the appended claims.
	description	This application is a continuation of U.S. application Ser. No. 11/245,072 filed on Oct. 7, 2005, now U.S. Pat. 7,238,956, which is a continuation of U.S. application Ser. No. 10/494,031 filed on May 7, 2004, now abandoned, which is a National Stage of PCT/FR02/03937 filed on Nov. 18, 2002, all of which claim priority to French Patent Application No. 01/14990 filed on Nov. 20, 2001. The contents of each of these documents are incorporated herein by reference. The present invention relates to an adjusting device of an apparatus for generating a beam of charged particles. The invention particularly relates to an adjusting device of an apparatus for generating an ion beam and more particularly to an adjusting device of an instrument for nanomanufacturing with an ion beam. One tries to adjust in particular the size of an ionic probe i.e. the size of the focused ion beam which is sent onto a target, as well as the shape of the ion distribution in this ionic probe at the target are attempted. The invention is in particular applied to the manufacture of structures with very small sizes, less than 50 nm, and more particularly to the manufacture of nanostructures with sizes of the order of 10 nm or less. The invention finds applications in various fields such as electronics (in particular with regard to single electron devices—for example single electron transistors), ultra high density data storage (using nanostructures formed on magnetic materials) and ultra high speed semiconductor devices (using nanostructures formed on semiconducting materials). The present invention is in particular applied to adjusting an ion beam emitted by an apparatus comprising an ion point source, i.e., an ion source with a very bright emissive point area. Further, this ion point source is preferably an LMIS, i.e., a liquid metal ion source. Concerning liquid metal ion sources, one may refer to the following documents: [1] International application PCT/FR 95/00903, International publication NO. WO 96/02065, invention of Jacques Gierak and Gérard Ben Assayag, corresponding to patent U.S. Pat. No. 5,936,251. [2] U.S. Pat. No. 4,426,582, invention of J. H. Orloff and L. W. Swanson. In addition, apparatuses generating ion beams called FIB and producing focused ion beams are known. But it should be noted that with these FIBs, it is not possible to manufacture good quality nanostructures with sizes less than 50 nm. Further, a device for adjusting the shape of a focused ion beam is known from the following document: [3] U.S. Pat. No. 4,704,726, invention of H. Kyogoku and T. Kaito (Seiko Instruments and Electronics Ltd.). The adjusting technique disclosed in this document [3] is only a transposition of the adjusting technique conventionally used in scanning electron microscopy or ion beam lithography. Such a technique cannot be used in the nanometric range. Further, this known technique requires the preliminary manufacturing of costly and fragile calibration markers which are not reusable. In addition, according to a known technique, for adjusting an apparatus generating an ion beam, it is the operator himself/herself who checks the various operating parameters of the ion optical system of the apparatus and who should make sure that the results of the adjustments give a theoretical resolution which is consistent with the intended use for the ion beam. This step is delicate as it is subject to interpretation and compromise. The operator is sometimes provided with tabulated data to facilitate his/her task, for example, the values of the ionic optical system's resolution versus the ionic probe current values for various distances between this ionic optical system (comprising a set of electrostatic lenses) and the target of the ion beam. However, adjusting the apparatus remains delicate. The object of the present invention is to find a remedy to the above drawbacks. The invention in particular is directed to adding self-adjustment, self-diagnose and self-calibration capacity to an apparatus for generating an ion beam. By adding such capacities to the apparatus, it is possible to improve and to widen the field of applications of this apparatus as well as the productivity of the latter, by almost totally excluding the intervention of an operator, i.e. a user of the apparatus. More generally, the present invention proposes an adjusting device of an apparatus for generating a charge particle beam, with which the intervention of an operator is almost totally excluded. Specifically, the object of the present invention, is an adjusting device of an apparatus for generating a beam of charge particles, in particular an ion or electron beam, wherein this beam is for interacting with a target, this device comprising means for: storing the desired characteristics for the particle beam, as determined by the user of the apparatus, determining the values of the adjustment parameters of the apparatus according to these characteristics and storing these values, and giving these stored values to the adjustment parameters of the apparatus. According to a particular embodiment of the invention, the adjustment means are additionally for: continually or periodically measuring these parameters, when the beam of charged particles interacts with a target and determining the characteristics of the beam from these measurements: comparing the thereby determined characteristics with the stored characteristics, and if at least one of the thereby determined characteristics lies outside a predefined amplitude range, centered on the corresponding stored characteristic, changing the adjustment parameters of the apparatus and/or informing the user of the apparatus. According to a preferred embodiment of the invention, the charged particles are ions, the target is a substrate, the apparatus comprises an ion source, means for accelerating these ions and means for focusing these ions, this apparatus is for manufacturing a structure, in particular a nanostructure, on the substrate, the ion beam is capable of eroding this substrate, and the adjustment means are for: storing the desired characteristics for the ion beam, as determined by the user of the apparatus according to the structure to be manufactured, determining the values of the adjustment parameters of the apparatus according to these characteristics and storing these values, and giving these stored values to the adjustment parameters of the apparatus. Preferably, the adjustment means are further for: continually or periodically measuring these parameters, during the manufacturing of the structure, and determining the characteristics of the beam from these measurements, comparing the thereby determined characteristics to the stored characteristics, and if at least one of the thereby determined characteristics lies outside a predefined amplitude interval, centered on the corresponding stored characteristic, changing the adjustment parameters of the apparatus and/or informing the user of the apparatus. The characteristics of the ion beam may comprise the size and the current density of this ion beam. According to a particular first embodiment of the invention, the adjustment means are further for: measuring the adjustment parameters of the apparatus at any time or periodically during the manufacturing of the structure, and if at least one of the parameters drifts and therefore leaves a predefined amplitude range, centered on the corresponding stored parameter, changing the measured parameter so that it is again found in this range. According to a particular second embodiment, the adjustment means are further for: measuring the adjustment parameters of the apparatus at any time or periodically during the manufacturing of the structure, and in the event of any instability of at least one of these parameters, interrupting the manufacturing process and informing the user and/or calibrating the apparatus for adjusting this parameter again. The adjustment parameters may comprise the emission current of the ion source, the energy of the ions, the focusing of the ion beam, the amplitude of the writing field on the substrate, the correction of stigmatism and the distance between the apparatus and the substrate. In this FIGURE, an example of an apparatus 2 for generating an ion beam to which the invention may be applied, is illustrated schematically. This apparatus 2 comprises an ion source 4 for example with a liquid metal, which is for producing an ion beam, for example, formed with gallium ions, a system 6 for extracting and accelerating the produced ion beam, a source support 8 and an electrostatic optical system 10. The axis of the system 10 is marked as Z1 and the axis of the ion beam 12 emitted by the source 4 as Z, axes Z and Z1 being parallel. The assembly formed by the source 4, its support 8 and the system 10 forms the focused ion column of the apparatus 2. System 10 essentially consists of electrostatic lenses (not illustrated) for focusing the beam 12 in order to form a focused ion beam 14. In order to align the central axis Z of the emission cone of the ion beam 12 (axis of the source 4) with the optical axis Z1 of the electrostatic optical system 10, the source support is provided with a set 16 of micrometric stages. This set 16 symbolized by dot and dash lines in the figure allows the support 8 to be displaced along an X axis and a Y axis which are perpendicular to each other as well as to the Z axis. The FIGURE also shows a substrate 18 to be treated by the focused beam 14 and forming a target for this beam (which is capable of eroding this substrate 18). This substrate is mounted on a stage 20 which may be displaced along three axes respectively perpendicular to axes X, Y and Z. The apparatus 2 is for manufacturing a nanostructure on the substrate 18. Additionally, a control system 22 or an operating system of the device 2 for generating an ion beam is seen. This system 22 comprises: means 24 for controlling the ion source 4, means 26 for controlling the system 6 for extracting and accelerating the ion beam 12, means 28 for controlling the electrostatic optical system 10, and means 29 for controlling the assembly 16 of micrometric stages. Means 30 for controlling the displacement of the substrate bearing stage 20 are also seen. A technique is considered in the following which is directed to solving the basic problem of the adjustment of the parameters of an ion column providing an ionic probe at the scale of tens of nanometers, in order to form nanometric size structures by controlled ion irradiation. The geometrical shape (size), the profile (a more or less sharp decrease in the number of particles when moving away from the central axis of the beam) dominate, as well as the sphericity of the distribution in the ionic probe at the target. At a scale of a few nanometers, the problems are all the more complicated. This technique is directed to providing a very accurate and fast adjustment of the profile of this ionic probe. The relevant points are: focusing (concentration) of the ion beam 12 under the action of the electrostatic lenses of the apparatus 2, at the target formed by the substrate 18, into a spot (impact) with nanometric dimensions, correcting the lack of sphericity of the incident ionic probe, and calibrating the writing field (a field which may be addressed by the beam under the action of electrostatic deflectors which the electrostatic optical system 10 comprises) at the surface of the target, so that the relative position is always accurately known within a few nanometers. Use of an ion beam focused into a 10 nm spot for nanomanufacturing applications has specific constraints: the sputtering effect induced by energetic ions which bombard the target, sooner or later leads to the destruction of the calibration structures (generally gold markers on silicon) which are conventionally used in electron beam lithography, for example). Moreover, calibrated structures of a few tens of nanometers are delicate to manufacture, very brittle and expensive above all. The period of use of the ion beam may attain several hours, which imposes periodic checks on the characteristics of this ion beam in order to limit the influence of drifts and transient instabilities. The reduced working distances which are required for obtaining a geometrical magnification of the source spot less than 1, all the more reduce the usable depth of field. Moreover, certain substrates include patterns with heights which highly differ from one another, so that these patterns are not all located at the ideal focal distance. In the latter case, an ion which falls on such a substrate at the optical axis (Z1 axis) covers a much shorter path than another ion which has been deflected from this axis by several millimeters. This optical path difference causes the occurrence of defects or aberrations. In order to limit these aberrations to an acceptable value, the writing size is limited in a field of the order of a hundred micrometers. Thus, without any appended device, the FIB nanomanufacturing technique can only form small elementary patterns When an ultra accurate displacement of substrate 18 is used, the possibility of linking up several elementary substructures occurs for defining a large size pattern. But this remains dependent on strict calibration of the size of the FIB elementary writing field. Indeed, a most complete match as possible between the coordinates of the points defined within a scanning field and the displacement coordinates of the substrate bearing stage 20 is required. All this is complex because the scanning of the ionic probe is obtained by means of a CAD (computer-aided design) generator of the digital/analog type (contained in the control means 28) whereas the stage 20, as far as it is concerned, is driven by control means 30 formed by a specific and independent interface 30. It should also be noted that any variation in the distance between the substrate and the ionic column, in the energy of the ions or the nature of the latter, changes the value of the amplitude of the scanning field. The proposed device particularly tends to improve and make the adjustment more effective of the parameters of a unique ionic column delivering an ionic probe at the scale of tens of nanometers, in order to form nanometric sized structures by controlled ion irradiation. In particular, different levels of assistance are proposed to the user of an apparatus for generating a beam of charged particles and more particularly a beam of ions: Determination of the optimal parameters for utilizing the apparatus according to the required operating conditions, i.e.: selection of an optical mode for obtaining the required resolution (for example, the energizing voltage of the focusing lenses, working distance, semidivergent mode, semiconvergent mode or collimated mode (in the optical system) or the need for a “cross over” i.e. a crossing of charged particles, in particular, ions in the optical system), size of the writing field, detection of distortion effects and quantification of these effects, and then, in connection with the computer program of the pattern scanning generator (contained in the operating system 22 of apparatus 2), validation of these parameters or further detection of the impossibilities or conflicts between parameters (for example, the precision level of the scanning or the incident ion dose). Determination of the parameterization of the ionic probe provided by the optical system: characteristic of the current distribution (for example, width or standard deviation) value of the transported current checking the adjustments of the apparatus: An example of a device according to the invention is provided hereafter. It is assumed that the intention is to accomplish a certain sequence of nanomanufacturing with apparatus 2. According to the invention, the system 22 is completed by an adjustment module 40 or computation module. This module 40, essentially including a computer, provides information to the operator (the user of the apparatus) via the display means 38. The operator, as far as he/she is concerned, is led to provide information (in particular data) to module 40, information which is symbolized by the arrow 42 in the figure. Furthermore, for implementing the invention, the adjustment module 40 is connected to various control means 24, 26, 28, 29 and 30, which the operating system 22 of the apparatus 2 includes, in order to control these means 24, 26, 29 and 30. The latter are equipped with suitable sensors (not shown) which allow them to know the state of various units 4, 6, 10, 16 and 20, which they control. In addition, module 40 is connected to detection means 32 and electronic processing means 36 in order to control the operation of the apparatus in the scanning ion microscopy mode and to exploit the results from this operation. According to the invention, adjustments are proposed to the operator, these adjustments being determined by the computation module. Then the operator starts the nanomanufacturing sequence. Module 40 then continually (or periodically but then with a high frequency) computes the properties of the ionic probe (ion beam 14) during this nanomanufacturing sequence and compares the computational result to pre-established values, stored in this module 40. If the values obtained during the calculation are different from these pre-established values, the module undertakes corrective measures by adjusting the parameters for adjusting the apparatus or, if the difference between the results of a calculation and the pre-established values is too large, module 40 informs the operator via the display means 38. More specifically, according to the invention, the adjustment module 40 stores the desired characteristics for the ion beam 14, as determined beforehand by the user of the apparatus 2 according to the structure to be manufactured on the substrate 18. Next, module 40 determines the values of the adjustment parameters of apparatus 2 according to these characteristics and stores these values. And then the module gives these values which it has stored, to the adjustment parameters of the apparatus 2 via the control means 24, 26, 28 and 30, to which module 40 sends control signals enabling the desired adjustments to be made. The characteristics of the ion beam 14 are the size of this ion beam and the current density in this beam. The adjustment parameters of the ion column, as for them, are the following: the emission current of the ion source 4, the energy of the ions, the voltages applied to the focusing lenses, the amplitude of the scanning field, i.e., the amplitude of the writing field, the correction of stigmatism of the ion beam 14, the distance between the apparatus and the target 18, this distance being adjusted by displacing the stage 20 parallel with the Z1 axis. It should be noted that when the operator wants to make a too large correction of stigmatism, the computation module 40 informs this operator about this via the display means 38. Moreover, during the manufacturing of the structure on the substrate 18, module 40 may measure these parameters either continually or periodically (preferably with a high frequency) and determine the characteristics of the beam 14 from these measurements (which are made via means 24, 26, 28 and 30). The module then compares the thereby determined characteristics with the stored characteristics. When one or more of these thereby determined characteristics differ (by a predefined percentage, for example ranging from −10% to +10%) from the corresponding stored characteristic, the module informs the operator and changes the adjustment parameters of the apparatus to obtain again the proper characteristics for beam 14. If the differences are too large, module 40 may simply inform the operator and wait for instructions from the latter for proceeding with the manufacturing. Further, module 40 may be programmed so as to act on the apparatus (via control means 24, 26 and 28 in the event of any drift of one or more parameters). Indeed, it should be noted that a manufacturing sequence generally lasts a long time, for example 2 hours. As module 40 is able to (continually or periodically) measure the parameters, it may detect the drift of the latter and remedy it. Moreover, module 40 may be programmed so that it interrupts the manufacturing sequence (and informs the operator about it) in the event of an instability of one or more parameters, i.e., in the event of a sudden change of the latter. Further, it should be noted that the nanomanufacturing process takes place at a very low pressure; for one reason or another, this pressure may increase very rapidly; also, a problem of an electrical nature is liable to affect the apparatus 2; in such cases, the module 40 cannot act by itself and requires intervention of the operator. The present invention is not limited to the adjustment of an apparatus for generating a (positive or negative) ion beam. It also applies to the adjustment of other apparatuses for generating beams of charged particles such as electron microscopes, the particles then being electrons.
06058159&	summary	FIELD OF THE INVENTION The present invention relates to the field of relatively compact scanner apparatus and methods and more particularly to apparatus and methods for scanning objects which are transported by a conveyor belt through a temporarily sealed tunnel, such as in contraband detection systems. BACKGROUND OF THE INVENTION Scanners, particularly "compact" scanners, are used for detecting contraband at schools, correctional mail screening, courthouse security, airport hand parcels, and industrial processing applications. These scanners employ tunnel housing, an isolating device, a conveyor device, a bed assembly housing in which the conveyor device is substantially located, and framing. The tunnel housing typically has a top portion, and side portions which together with a top portion from the bed assembly housing, form a substantially enclosed area. The tunnel housing is also provided with entrance and exit openings to the substantially enclosed area. The isolating device substantially covers the entrance and exit openings and is typically in the form of two separate lead curtains. One lead preferably fabric curtain is bolted to flat framing at the entrance opening, and the other lead preferably curtain is bolted to flat framing located at the exit opening. Isolating devices permit the passage of conveyed objects into the substantially enclosed area of formed by the tunnel housing and the top portion of the bed assembly housing, which is typically X-ray scatter lead shielded, and may also substantially exclude light, noise, heat, cold, moisture, dryness, electrostatic or electromagnetic fields, dust gasses or chemical vapors while the conveyed objects are being analyzed. Scanners analyze objects which are brought into the enclosed area of formed by the tunnel housing and the top portion of the bed assembly housing by the conveyor device. The conveyor devices are typically comprised of relatively short lengthed conveyor belts. Short lengthed conveyor belts, particularly those with a relatively low length to width ratio, such as of less than twelve to one, 12 to 1, often mistrack causing damage to the conveyor belts, objects being scanned, and other parts of the system. Currently, expensive and elaborate tracking mechanisms such as precise construction of components, toothed or perforated belting to mesh with drive gears or belt grooves, raised profile rails, servo-drive tracking adjustment mechanisms, and reliance on a human attendant are used for tracking conveyor belts. The framing provided to structurally connect the tunnel housing, the bed assembly housing, the conveyor device and the isolating device is often elaborate, wasteful, and space consuming. Scanners are needed which are more compact in overall width and length without sacrificing the width of the enclosed area inside the tunnel housing. SUMMARY OF THE INVENTION A compact and reliable scanning apparatus and method is provided. The scanner in one embodiment comprises a conveyor device, a tunnel housing, a bed assembly housing, an isolating device, and one or more analysis devices. The tunnel housing is comprised of top and side portions which together with a top portion from the bed assembly housing form a substantially enclosed area for analyzing objects. The bed assembly housing encloses most of the components of the conveyor device. The conveyor device is typically comprised of a conveyor belt, rollers and a conveyor tracking device. The conveyor tracking device is comprised of first and second channels formed in first and second rails. The conveyor belt, preferably includes a first edge and a second edge, and an inner surface and an outer surface. The first and second edges of the conveyor belt typically pass through the first and second channels formed in the first and second rails, respectively. The first and second rails inhibit the conveyor belt from misaligning. The conveyor belt preferably traverses a forward path and a return path and the first and second rails are preferably provided in the return path. The first and second rails are preferably opposite one another. The isolating device is preferably comprised of separate first and second curtains which extend outward from separate first and second rods, respectively. The first and second rods and curtains are preferably adaptable for insertion into first and second slots, respectively, located in the top portion of the tunnel housing, near the entrance and exit openings, respectively. The slots can also be called slits. The rods, the curtains, and the slots of the housing, are typically adaptable so that the curtains can be inserted into and through the appropriate slot but the rods cannot be inserted through the appropriate slot. After the rods and curtains have been inserted into their respective slot each curtain should entirely the cover either the exit or the entrance opening. The isolating device preferably temporarily seals off the substantially enclosed area bounded by the tunnel housing and the top portion of the bed assembly housing so that no X-rays will leak out. In one embodiment of the present invention the tunnel housing, the bed assembly housing, the conveyor device, the one or more analysis devices, and the isolating device are constructed in a manner which provides a largely frameless scanner apparatus. The bed assembly housing preferably comprises a top portion which is used as with the tunnel housing to form a substantially enclosed area. The bed assembly housing further preferably comprises first and second side portions which are preferably fixed to the first and second side portions of the tunnel housing providing structural support and reducing the need for framing. One of the analysis devices may be comprised of a substantially steel member which is used to further connect the tunnel housing with the bed assembly housing. The analysis devices may be various types including X-ray or electromagnetic generators and detectors and optimal vapour detectors. The efficient construction of the conveyor device, the isolating device, the tunnel housing, the bed assembly housing, and the one or more analysis devices of the scanner maximizes the cross sectional area, and the width and height for the enclosed area of formed by tunnel housing and the top portion of the bed assembly housing of the scanner for a given overall cross sectional width and height.
048805963	summary	The invention relates to control systems for nuclear reactors, and, more particularly, to a self-actuated control system responsive to temperature increase or over-power conditions of a reactor. The use of control systems to regulate the reactivity of a nuclear reactor by varying the location of control (neutron absorber) elements or rods with respect to the reactive core is well known. With a view toward the possibility of an emergency condition arising, as by an unexpected drop in coolant flow, increase in temperature, or rise in reactivity, such control systems include arrangements for "scramming" the control rods, i.e., for rapid insert of the absorber elements into the core to quickly shut down the reactor. With the advent of the liquid metal fast breeder reactor (LMFBR) and the Gas-Cooled Fast Reactor (GCFR), a need for faster, less complex, more reliable control rod scram or shutdown systems has become apparent, whereby the reactivity of the reactor can be quickly shut down. More recent efforts have been directed to the desirability of utilizing secondary or alternate control systems of the self-actuating type which would make an LMFBR or GCFR inherently safe. Such alternate or self-actuating systems provide control without reliance on the primary reactor control system or plant operators, while being capable of actuation by the plant operators. These efforts have resulted in systems which sense the reactor flow rate and actuate when the flow drops below a predetermined level, measure the temperature of the coolant and actuate when the temperature exceeds a specified point, or measure the flux or reactivity level of the reactor and actuate when the reactivity exceeds a specified level. The following exemplifies various operator-actuated and/or self-actuated prior art control systems. U.S. Pat. No. 4,158,602 issued June 19, 1979, to L. E. Minnick discloses a self-actuating scram system triggered by a loss of primary coolant flow which supports the absorber rods above the reactor core region. A loss of primary coolant flow causes a decrease in the supporting pressure on the absorber rods allowing the rods to fall into the core region, thus scramming the reactor. U.S. Pat. No. 3,359,172 issued Dec. 19, 1967, to C. S. Olsson discloses a reactor shutdown system employing an electromagnet-operated valve to terminate coolant flow. Absorber rods, normally suspended above the core, will fall into the core region upon loss of coolant flow. U.S. Pat. No. 2,931,763 issued Apr. 6, 1960, to J. A. Dever discloses a control apparatus incorporating electromagnetically held control rods. The control rods are released upon a signal initiated within an ionization chamber. Electron tubes conduct sufficient current to retain the control rods as long as the neutron flux remains below a predetermined level. U.S. Pat. No. 2,781,308 issued Feb. 12, 1957, to E. C. Creutz et al discloses a neutronic reactor control system in which voltage produced by an ionization chamber effects release of absorber rods from an electromagnetic latching mechanism. U.S. Pat. No. 3,940,309 issued Feb. 24, 1976, to F. Imperiali discloses a self-actuated scram system utilizing electromagnetic means to suspend and release absorber material into the reactor core region. U.S. Pat. No. 2,867,727 issued Jan. 6, 1959, to H. Welker et al discloses a neutron-sensing device in which neutrons, penetrating a semiconductor, create electron-hole pairs which produce a voltage which can be monitored. U.S. Pat. No. 4,085,004 issued Apr. 18, 1978, to J. c. Fletcher et al discloses a control device for a nuclear thermionic power source. Actual neutron flux is compared to a linear function of current supplied by a thermionic converter. U.S. Pat. No. 3,970,007 issued July 20, 1976, to J. R. Klein discloses a neutron detection device utilizing uranium hydride as a neutron sensor. Radiation causes the uranium hydride to fission, releasing heat and hydrogen gas. The gas pressure breaks a normally closed circuit causing activation of a safety device. U.S. Pat. No. 3,177,124 issued Apr. 6, 1965, to D. T. Eggen et al discloses a reactor control device triggered by the melting of a solder joint. Upon experiencing an increase in neutron flux a layer of uranium abutting the solder joint begins to heat the joint until it melts, releasing absorber material. U.S. Pat. No. 2,904,487 issued Sept. 15, 1959, to J. J. Dickson discloses a reactor control system employing a temperature responsive transducer actuated by heat generated from a uranium strip. Neutron flux causes the uranium strip to fission and heat a bimetallic transducer which generates an automatic control signal. Thus, while various approaches have been developed for reactor control, a need still exists for a simple self-actuated control system which is failsafe, reliable, testable in the core at shutdown, resettable and capable of actuating upon sensing either the initiation of a transient coolant temperature increase event or a transient over-power (increased reactivity) event, as well as being capable of actuation by plant operators. The above-cited art fulfills certain of these requirements in various ways, but involves complex apparatus and is not fully responsive to both or either of these reactor conditions by use of simple control apparatus. RELATED APPLICATION The present invention is in the same general field of art as U.S. application Ser. No. 270,672, filed June 4, 1981, and assigned to the assignee of this application. SUMMARY OF THE INVENTION It is an object of the present invention to provide a self-actuated control system for nuclear reactors. It is a further object of the invention to provide a self-actuated shutdown system for a reactor which is responsive to coolant temperature increase and/or over-power (increased reactivity) conditions of the reactor. A further object of the invention is to provide a self-actuating reactor shutdown system, particularly applicable for liquid metal cooled fast breeder reactors (LMFBR) and gas-cooled fast reactors (GCFR). Another object of the invention is to provide a self-actuated shutdown system for a reactor which utilizes a thermionic switched electromagnetic latch arrangement responsive to reactor neutron flux changes and to reactor coolant temperature changes. Another object of the invention is to provide a thermionic switched, electromagnetic latched self-actuating reactor shutdown system which utilizes a thermionic diode for actuating the electromagnetic latch for releasing absorber elements into a reactor core. The self-actuating shutdown system (SASS) of the present invention, which utilizes a thermionic sensing device, acts directly to cause release (scram) of the control rod (absorber element) without a reference or signal from the main reactor plant protection and control systems. The thermionic trigger or switch acts in conjunction with, but independent of, the plant control and protective system and therefore provides separate and redundant reactor shutdown capability for selected off-normal conditions. To optimize both the temperature and neutron flux effects, the invention utilizes two separate detectors which are tailored to their specialized positions and functions, as follows: 1. Self-actuation in response to a temperature increase of the reactor coolant occurs by heating of a thermionic sensor to a selected set trigger point by the coolant as it emerges from fuel assemblies adjacent to the SASS and impinges on the sensor mounted above the reactor fuel assemblies. As the reactor coolant temperature increases, the temperature of the thermionic sensor is raised to a point where it conducts current (changes from a high impedance to a very low impedance) generating the signal used for shutdown. 2. Self-actuation in response to reactor neutron flux increase is achieved by placing the thermionic sensor near the reactor core or flux region. The thermionic sensor is made responsive to the reactor flux by the attachment of uranium, or other material which heats from neutron bombardment, to its emitter or by enclosing the emitter of the sensor inside a blanket of these materials. When the reactor neutron flux is increased, the uranium or other heating material responds by heating the thermionic sensor to the selected trigger point where it conducts current generating a shutdown signal. The present invention broadly encompasses a self-actuated reactor shutdown system wherein an electromagnetically actuated latch mechanism retains the control rod (neutron absorber element) in a ready or cocked position exterior of the reactor core region, and upon an increase in coolant temperature beyond a selected point and/or upon an increase in neutron flux (over-power) beyond a selected point, a thermionic device connected electrically to the electromagnetic latch mechanism is heated so as to conduct current which effects a short-circuit of the electromagnet causing same to lose holding power which releases the control rod to drop by gravitational force into the reactor core causing shutdown of the reactor. The thermionic device may, for example, constitute a thermionic diode connected electrically in parallel with the electromagnet.
	description	The invention relates to a multi-beam source for generating a plurality of beamlets of energetic charged particles, the multi-beam source comprising an illumination system and a beam forming system. Furthermore, the invention is related to an electrical zone plate for use in such a multi-beam source and an apparatus for multi-beam lithography for irradiating a target by means of a beam of energetic electrically charged particles, employing such a multi-beam source. Multi-beam sources of the above mentioned kind can be used for a variety of applications, like lithography and microscopy systems. Some of the systems employing multi-beam sources use a single source generating one beam which is subsequently split into a plurality of beamlets. The charged particle sources used in such systems typically emit a charged particle beam with a defined opening angle, i.e. a diverging beam. The diverging beam often needs to be collimated, i.e. transformed into a homogeneous beam. In most applications a lens or lens assembly is used to refract the diverging beam emitted. Improvements of such multi-beam sources are currently the subject of intensive research activities all over the world. A typical application of a multi-beam source is a multi-beam lithography system, e.g. in the semiconductor industry, for producing patterns on different substrate materials. Such apparatus usually comprise an illumination system with a particle source, generating a diverging beam of energetic particles and a lens system for forming said beam into a telecentric beam which illuminates different means for splitting the broad beam into a plurality of sub-beams. By means of an optical projection system the sub-beams are focused on a target which is typically some kind of substrate, e.g. a silicone wafer. Systems of that kind are disclosed in the US 2005/0161621 A1, US 2005/0211921 A1 and two documents by the applicant/assignee, namely the U.S. Pat. No. 6,989,546 B2 and the U.S. Pat. No. 6,768,125. However these systems have certain drawbacks since optical systems, regardless of whether they are light-optical or particle-optical systems, produce imaging aberrations and distortions. Therefore sub-beams projected on the target will get blurred and the spot size of the sub-beam is no longer well-defined, which results in a blurry pattern or image. It is known and general practice for particle-optical imaging systems to use electro-static lenses in the form of two or three rotationally symmetrical annular electrodes, which are formed as a tube, ring or diaphragm, or rather arrangements of such elements in rows, where a beam passes through the middle of said annular electrodes which lie at least partly at different electric potentials. Lenses of this type always have a positive refractive power and are thus focusing lenses; furthermore without exception they have significant aberrations of the third (or higher) order which can only be slightly influenced by the shape of the lens geometry. A system employing such a lens setup is disclosed in the U.S. Pat. No. 5,801,388 by the applicant/assignee. By using diverging lenses (negative refracting power) it is possible to ensure that the aberrations produced by the arrangement of combined focusing lenses and diverging lenses are to a great extent compensated by cancellation of the contributions to the third (or higher) order aberrations of the focusing and diverging lenses, the other coefficients of aberration are also maintained as small as possible. It is not possible by means of annular electrodes alone to achieve a lens of negative refracting power; on the contrary, it is necessary to use a plate or control grid electrode through which the beam passes. A system using the mask of a lithography apparatus to form diverging lenses in combination with annular electrodes located in front of and after the mask, respectively, is disclosed in the U.S. Pat. No. 6,326,632 B1 by the applicant/assignee. As a result of the lens errors of focusing lenses, an illumination system which comprises focusing lenses and which produces a substantially telecentric ion beam has the characteristic that, for example, although the beams in the proximity of the axis are parallel to the optical axis, the beams remote from the axis are somewhat convergent or divergent. In the outer regions of the mask this would lead to image defects, especially if used in conjunction with a large reduction optical system (such as described in U.S. Pat. No. 6,768,125) where the angular errors at the object plane (aperture plate system) lead to significant landing angle errors at the substrate, or if used in conjunction with a parallel multi-column array, where the angular alignment of each beam in each column is very critical. One solution for avoiding these shadow effects is the production of structure orifices which are inclined accordingly with respect to the axis; however this is extremely expensive from the technology point of view. An additional diverging lens disposed downstream of the focusing lens arrangement can render it possible to correct these errors and the excessive convergence of the beams remote from the axis can be compensated. Such a solution is described in the article “Development of a multi-electron-beam source for sub-10 nm electron beam induced deposition”, J. Vac. Sci. Technol. B 23(6) (2005), pp. 2833-2839, by M. J. van Bruggen et. al. The authors therein describe a multi-beam source, where a broad beam of particles is split into 100 sub-beams with an aperture plate. The sub-beams are individually focused by a micro-lens array, creating a negative lens effect together with a subsequent electrode. Van Bruggen et. al. aim on compensating for both the third-order geometric and first-order chromatic aberration inherent in the system, however such a system can not provide for correction of the individual beams and aberrations due to insufficient illumination of the aperture plate. The US 2004/0232349 A1 discloses a multi-beam source of the type the invention is related to. It comprises a particle source, a converging means and a lens array, placed between the source and the converging means to avoid the negative influences of the chromatic aberrations of the optical system. The lens array is substantially a plate with holes, interacting with annular electrodes placed before and/or after the lens array. In a variant of the invention as disclosed in the US 2004/0232349 A1, at least one deflector array with holes and deflectors aligned with the beamlets can be additionally included, which allows for asserting a deflecting effect proportional to the distance of a deflector from an optical axis of the respective beam. By virtue of such an arrangement, the beamlets can be controlled individually. However this solution has the significant drawback of requiring specifically shaped lens arrays, e.g. convex plates or stacks of multiple plates allotting inclined holes to account for the slope of the beamlets. Furthermore the lens arrays can scarcely be adapted to changing circumstances concerning the beamlets. A comparable approach is described in the U.S. Pat. No. 7,084,411 B2 by the applicant/assignee, disclosing a pattern definition device for use in a particle-exposure apparatus. In said device a beam of energetic charged particles is patterned by a system of pattern definition means of substantially plate-like shape, each comprising a plurality of apertures, into a plurality of sub-beams. In order to correct for the individual aberrations that may be present in a particle-exposure apparatus, for each aperture at least two deflecting electrodes are provided for correcting the path of the sub-beam. The electrodes can be controlled individually or in groups. In the WO 2006/084298 by the applicant/assignee, a solution for the above mentioned imaging aberrations and distortions in a charged particle exposure apparatus is proposed. The solution is applicable for instance in the IMS-concept PML2 (short for “Projection Mask-Less Lithography”) as described in the U.S. Pat. No. 6,768,125 by the applicant/assignee, in which a multi-beam direct write concept using a programmable aperture plate system for structuring an electron beam is disclosed. The WO 2006/084298 describes the provision of a diverging lens that is able to compensate for aberration errors of higher rank than third order and/or distortions, or to correct specific aberration coefficients, or to correct for misalignment. The lens is realized as a plate electrode means with a plurality of apertures, comprising a composite electrode composed of a number of partial electrodes, being adapted to be applied different electrostatic potentials. This plate electrode means realizes an electrostatic zone plate (EZP), which provides a simple and yet efficient means to implement a diverging lens and/or specific compensation for the imaging problems discussed above. The present invention provides a multi-beam source producing a set of particle beamlets with low emittance and homogeneous current distribution, the multi-beam source being adapted to reduce the various aberration effects present in existing multi-beam applications. Emittance here denotes a measure of the parallelism of a beam, a low-emittance particle beam is a beam where all individual beamlets seem to emerge from a common virtual source not significantly larger than the virtual source of an individual beam, which means that the beamlets are emerging from a small area, or, in case of a telecentric beam, are substantially parallel (virtual source infinitely far away). Beamlets with a low emittance thus have small components of transverse velocity and a reduced spread in angle relative to an axis of propagation. It is another goal of the present invention to provide a multi-beam source which is correctable/controllable with respect to deviations from the ideal angles of the beamlets to compensate imaging errors of consecutive lens systems, as for a example a projection system or multi-lens array. These aims are met by a multi-beam source as stated in the beginning, wherein the illumination system is adapted to generate energetic electrically charged particles and to form said particles into a wide illuminating beam, and the beam forming system is configured to be illuminated by the illuminating beam emerging from the illumination system and is adapted to form a plurality of beamlets of energetic particles out of the beam, said beam forming system comprising a beam-splitting means, having a plurality of apertures transparent to the energetic particles of the particle beam to form a plurality of beamlets out of the beam, and an electrical zone device, said electrical zone device comprising a composite electrode being positioned along a two-dimensional plane oriented orthogonally to an optical axis of the electrical zone device and having lateral dimensions covering at least an area permeated by the particle beam, said composite electrode being composed of a number of substantially planar partial electrodes, said partial electrodes being arranged adjoining to each other according to a partitioning of the surface area of the electrical zone device and said partial electrodes being adapted to be applied different electrostatic potentials, the electrical zone device further comprising a plurality of openings transparent to the energetic particles of the particle beam. The composite electrode of the electrical zone device, particularly the partial electrodes, are preferably made of electrically conductive material such as metal. However, any material can be chosen which gives rise to a well-defined electrostatic boundary if placed in an electrostatic environment with presence of electrostatic fields. One alternative to metal could be a semiconducting material with sufficient doping. Though the partial electrodes are arranged adjoining to each other, they are usually separated by small gaps. The invention provides an effective solution to remedy insufficient illumination of beam-splitting devices frequently appearing in beam-manipulating devices. The illuminating beam irradiating the beam forming system is sufficiently wide to illuminate all of the beam forming system, i.e. also the parts remote from the optical axis of the beam forming system. The current emitted by the particle source can be processed more efficiently. Further it allows for the treatment of distortions and aberration errors of optical systems of the abovementioned kind. In general the invention presents a means to control and/or correct the beamlets of a multi-beam application with respect either to their radial and circular image distortions or to their direction. Since the beam forming system is separated from the illumination system, the multi-beam source has an augmented tolerance towards deviations of the openings with respect to the beamlet-axes. The invention allows for correction of the illuminating particle beam before the beam splitting means (aberration errors of the illuminating system) as well as for the beam after the beam splitting device (aberration errors of the projection system). The multi-beam source according to the invention produces a plurality of beamlets that is either homocentric, i.e. seemingly emerging from a common virtual source, convergent, i.e. converging to a crossover situated somewhere below the multi-beam source as seen in the direction of the beam, or telecentric/parallel. The aims of the invention are also met by an electrical zone device for use in a multi-beam source as mentioned above, said electrical zone device comprising a composite electrode having lateral dimensions covering the whole of the electrical zone device, said composite electrode being composed of a number of substantially planar partial electrodes, said partial electrodes being arranged adjoining to each other according to a partitioning of the surface area of the electrical zone device and said partial electrodes being adapted to be applied different electrostatic potentials, the electrical zone device further comprising a plurality of openings. Likewise, these aims are met by an apparatus for multi-beam lithography for irradiating a target by means of a beam of energetic electrically charged particles, comprising a multi-beam source as described above for generating a plurality of substantially telecentric/parallel beamlets out of the beam of energetic electrically charged particles, and a multi-beam optical system positioned after the multi-beam source as seen in the direction of the beam for focusing the beamlets onto the surface of a target. Preferably, the beam-splitting means and the electrical zone device are arranged in consecutive order and the openings of the electrical zone device are aligned with the apertures of the beam-splitting means. The electrical zone device can be arranged before or after the beam-splitting means, in the first case it allows for correction of the particle beam before it irradiates the beam-splitting means, in the second case it allows for correction of errors of individual beamlets or groups of beamlets, the errors being caused by the beam-splitting means or by the illumination system of the multi-beam source. In a variant of the invention, the beam-splitting means may be integrated in the electrical zone device, e.g. in an arrangement with a plate-like shape. Thus the size of the multi-beam source could be reduced. Depending on the application of the multi-beam source, the beamlets produced can be either homocentric, i.e. seemingly emerging from a common virtual source, or telecentric. Both variants are feasible. Preferably, the electrically charged particles used in the multi-beam source are ions. These can be, for instance, helium ions, hydrogen ions or heavy ions, the term ‘heavy’ here referring to ions of elements heavier than C, such as O, N or the noble gases Ne, Ar, Kr and Xe. Protons or electrons may be used as well. Due to the extremely short wavelength of ions, their use offers various advantageous features with respect to the imaging quality, in particular a very low numerical aperture, e.g. when the multi-beam source is used in combination with an ion optical system. In such a case the distance between the optical system and a substrate can be enlarged substantially so as to allow plenty of space for, e.g. a deflection unit, as well as enhance the decoupling of the wafer plane from the optics system. In one advantageous realization of the invention at least one additional electrode is provided, in particular an annular electrode, said electrode being positioned in proximity of the electrical zone device but out of plane of the composite electrode of said electrical zone device. The annular electrode can be used to correct for image distortions by forming an electrostatic lens in combination with an electrical zone device. The annular electrode may be positioned before or after the electrical zone device as seen in the direction of the particle beam. Preferably, the at least one additional electrode comprises at least one multi-pole electrode, the at least one multi-pole electrode being positioned out of plane of the composite electrode of the electrical zone device. In a preferred embodiment of the invention, the partial electrodes of the electrical zone device are arranged such that each opening of the electrical zone device is associated with a set of partial electrodes being located adjoining to the respective opening. Advantageously, the set of partial electrodes comprises four partial electrodes. Such a lay-out of partial electrodes, arranged comparably to ‘lily pads’ around the openings, allows for individual control of the beamlets crossing the respective opening and thus for the correction of various imaging problems. The sets of partial electrodes are set up only to influence the beamlet crossing the opening the set is associated with. As a consequence, the partial electrodes forming a set have small dimensions. Since the diameter of the openings is small compared to their mutual distance, this means that in the setup at hand, the composite electrode of the electrical zone device is divided into a multitude of partial electrodes being arranged in sets, wherein the sets are associated with an opening of the electrical zone device each, the distance between neighboring sets being large. In another embodiment of the invention, the partial electrodes of the composite electrode of the at least one electrical zone device are shaped as concentric rings, centered at an optical axis of the electrical zone device. By virtue of this solution, a plurality of openings of the electrical zone device may be influenced by applying different electric potentials to the partial electrodes of the electrical zone device. Various arrangements of the partial electrodes of the electrical zone device are possible and useful depending on the specific function. For instance, they may be shaped as sectors arranged around an optical axis of the electrical zone device. The sector-shaped partial electrodes may be arranged around a central area of the electrical zone device, said central area being formed by at least one further partial electrode. Preferably, a resistive material is provided in the gaps between neighboring partial electrodes of the at least one electrical zone device. By virtue of this solution, the effect of stray electric fields between the partial electrodes may be reduced. By using an insulating, dielectric material the different potentials of neighboring partial electrodes may be separated and a dielectric polarization may be produced that reduces the total stray field at the position of neighboring openings. A simple way to rule out effects of the stray fields occurring at the edges of partial electrodes is realized by positioning the openings of the electrical zone device such that they are present only within the areas of each of the partial electrodes of the electrical zone device. By keeping the openings remote from the gaps between neighboring partial electrodes, negative effects of the stray fields can be avoided. In order to control the partial electrodes of the electrical zone device, a CMOS-layer containing electronic circuitry is provided within the electrical zone device which is adapted to control the partial electrodes by applying different electrostatic potentials. The provision of such a layer facilitates the production of the electrical zone device, respectively the multi-beam source, since the production of a CMOS-layer of the aforementioned kind is a well known and established technique. In a variant of the invention direct wiring may be used to apply different electrostatic potentials to the partial electrodes for controlling them. In an advantageous embodiment of the invention, at least one of said electrical zone devices is positioned immediately in front of or after a beam-splitting means as seen along the direction of the particle beam. By combining such an electrical zone device with an additional electrode, it is possible to form an electrostatic lens to allow for the correction of image distortions. By applying different potentials to the electrical zone device and the beam splitting means such an effect may be realized without the provision of an additional electrode. In yet another embodiment of the invention, a first electrical zone device is positioned immediately in front of the beam-splitting means (the first one, if more than one are present) as seen along the direction of the particle beam and a second electrical zone device is positioned immediately after the beam-splitting means (the last one, if more than one are present) as seen along the direction of the particle beam. Such an arrangement improves the performance of a multi-beam source considerably, since the first electrical zone device allows for optimizing the illumination of the beam-splitting means, i.e. the plurality of apertures. The second electrical zone device may be used to correct for imaging aberrations caused by the beam-splitting means. Preferably, the partial electrodes of the electrical zone device are arranged such that each opening of the electrical zone device is associated with a set of partial electrodes being located adjoining to the respective opening. By employing at least one electrical zone device with such a ‘lily pads’-arrangement the illumination and/or the correction of the imaging aberrations can be accomplished more effectively. The invention furthermore pertains to a multi-beam source comprising a blanking device for switching off the passage of selected beamlets, said blanking device being realized in a substantially plate-like shape, comprising a plurality of openings, each opening being provided with a controllable deflection means for deflecting particles radiated through the opening off their nominal path. The openings of the blanking device are preferably aligned with the other openings present in the multi-beam source, e.g. of the electrical zone device or the beam-splitting means. Advantageously, the blanking device is provided with a CMOS-layer for controlling the deflection means. An absorbing surface may be provided to collect the particles that are deflected off their path. It is favorable if the multi-beam source comprises at least one correction lens arrangement for the correction of geometric aberrations of the multi-beam source, the correction lens arrangement being realized having substantially a plate-like shape and comprising a plurality of orifices, the orifices widening to opening spaces at the beginning or the end of the orifices as seen in the direction of the particle beam, said opening spaces configured to act as correction lenses upon receiving the respective beamlets, said opening spaces further having a width varying over the area of the correction lens arrangement, thus defining a varying correction lens strength, the correction lens arrangement being located in front of or after the electrical zone device as seen in the direction of the particle beam. Such a correction lens arrangement is useful to correct for optical defects such as a curvature of the image field. Since the geometric aberrations are known to vary with the distance from the optical axis of the correction lens arrangement, the width of the opening spaces of the orifices varies across the device depending on the lateral position of the corresponding orifice. The correction lens arrangement may be situated in front of the beam-splitting means as seen in the direction of the particle beam, thus locally changing the angle of incidence of the particles onto the apertures of the beam-splitting means. Alternatively, the correction lens arrangement may be positioned after the beam-splitting means as seen in the direction of the particle beam, in which case it can be used to shift the focusing length of the multi-beam source. Preferably, the correction lens arrangement is located adjacent to an electrical zone device, the electrical zone device being arranged in front of or after the correction lens arrangement as seen along the direction of the particle beam. When the correction lens arrangement and the electrical zone device are held on different electric potentials, a correction lens can be realized. By choosing the width of the opening spaces of the orifices of the correction lens arrangement and the potential difference accordingly, a correction lens of predefined focus can be realized to allow for the correction of image distortions. To be less prone to damage caused by the impingent beam of highly energetic particles, the electrical zone device which is closest to the illumination system may be provided with a cover layer to protect the subsequent structures of the electrical zone device from the impingent particle beam. Preferably, the cover layer is made of electrically conductive material. As mentioned above, the invention also pertains to an electrical zone device for use in a multi-beam source of abovementioned kind. In an advantageous embodiment of such a device, the partial electrodes of the electrical zone device are arranged such that each opening of the plurality of openings of the electrical zone device is associated with a set of partial electrodes being located adjoining to the respective opening. Preferably, the set of partial electrodes comprises four partial electrodes, thus realizing a ‘lily pads’-like arrangement of the electrodes. Various arrangements of the partial electrodes of the electrical zone device are possible and useful depending on the specific function. For instance, they may be shaped as concentric rings, as sectors arranged around an optical axis of the electrical zone device. The sector-shaped partial electrodes may be arranged around a central area of the electrical zone device, said central area being formed by at least one further partial electrode. Good results can be obtained when a resistive material is provided in the gaps between neighboring partial electrodes. The provision of such a material allows for reducing the stray fields forming at the edges of the partial electrodes. The negative effects of such stray fields may also be reduced by positioning the openings of the plurality of openings of the electrical zone device only within the areas of each of the partial electrodes of the electrical zone device and not in the gaps between the partial electrodes. Preferably, a CMOS-layer is provided within the electrical zone device to allow for controlling the partial electrodes of the electrical zone device by applying different electrostatic potentials. In yet another variant of the invention, the partial electrodes are controlled via direct wiring which is adapted to apply different electrostatic potentials to the partial electrodes. In order to allow for protecting subsequent structures, the electrical zone device may be provided with a cover layer. Preferably, the cover layer is made of electrically conductive material. The invention furthermore relates to an apparatus for multi-beam lithography of abovementioned kind, comprising a multi-beam source for the generation of a plurality of beamlets of energetic electrically charged particles and a multi-beam optical system for focusing the beamlets onto a target. Such a target may be a silicon-on-isolator (SOI) wafer coated with a resistive layer, for instance. In one advantageous realization of the invention, the apparatus for multi-beam lithography comprises at least one blanking means for switching off the passage of selected beamlets, said blanking means having a plurality of openings, each opening being aligned with the respective openings/apertures of the multi-beam source described above, each opening further being provided with a controllable deflection means for deflecting particles radiated through the opening off their path to an absorbing surface within the multi-beam lithography apparatus, said blanking means being located before the multi-beam optical system as seen in the direction of the particle beam and/or being integrated in the multi-beam optical system. In a variant of the invention, the apparatus for multi-beam lithography comprises a multi-beam source as described above, wherein a blanking device in a substantially plate-like shape is provided within the source. Due to the very accurate positioning of the beamlets on the target to be structured, the use of a blanking means allows a relaxed requirement on the accuracy for the mechanical positioning on the wafer stage. This reduces the production expenditures and simplifies adjustment of the components of the lithography setup as well as controlling during operation. In another realization of the invention, for each beamlet a deflection unit is provided, said deflection unit being positioned within or before the multi-beam optical system as seen in the direction of the beam, said deflection unit being adapted to correct individual imaging aberrations of its respective beamlet with respect to a desired position on the target and/or to position its respective beamlet during a writing process on the target. With said realization of the invention it is also possible to blank selected beamlets by deflecting them off their regular path. A deflection unit may be realized as an electrostatic multi-pole. In one beneficial realization of the invention, an electrostatic lens array is placed within the multi-beam optical system. This lens array serves to adjust the beam diameter at the substrate surface. Preferably, for each beamlet an electrostatic lens arrangement is provided as a means to adjust the diameter of the beamlet and/or the position of the beamlet on the target. This facilitates the adjustment of the beamlets substantially so as to render them equivalent to each other. Such electrostatic lenses, either in the form of an array or of an arrangement for each beamlet, allow for compensation of imaging aberrations. Suitably, for instance to reduce the total space required for the optical column, this electrostatic lens arrangement is integrated within one respective lens of the multi-beam optical system. It should be appreciated that the invention is not restricted to the embodiments discussed in the following, which merely represent possible implementations of the invention. Generally it has to be said that the embodiments depicted here are only some of many different embodiments possible and are thus not intended to restrict the scope of the invention. FIG. 1 shows a multi-beam source 101 according to the invention, comprising an illumination system 102 and a beam-forming system 103, arranged consecutively as seen in the direction of the particle beam, which propagates vertically downward in FIG. 1. The lateral dimensions of the figures are not to scale. The illumination system 102 comprises a particle source 104 and an extractor lens array 105. Preferably, the electrically charged particles used in the multi-beam source are ions such as helium ions, but also heavier ions can be used. Protons or electrons can be used as well. The particles, emerging from the particle source 104, are formed into a diverging beam 106 by the extractor lens array 105. A collimating lens 107, which is usually realized as an electrostatic or electromagnetic lens, produces a substantially homogenous beam 106′ of particles, emerging from the illumination system 102. The use of lenses has the drawback of causing chromatic and spherical aberrations, thus deteriorating the quality of the particle beam. Due to this fact the particle trajectories of the substantially homogeneous beam 106′ near the outer boundary are slightly inclined against the optical axis 113 of the multi-beam source 101. The beam-forming system 103 comprises an annular electrode 108 and an electrical zone device 109. The beam-forming system 103 forms a plurality of beamlets 112 out of the substantially homogeneous particle beam 106′ emerging from the illumination system 102. The particle beam 106′ is preferably homogenous over its width so as to have a particle flow sufficiently uniform within the allowed tolerances for all individual beamlets 112 which are produced from the beam. The annular electrode 108 together with the electrical zone device 109 forms a lens of negative diffracting power (divergent lens) or positive diffracting power (convergent lens), depending on the potential applied. The annular electrode 108 may be realized as a multi-pole electrode. The electrical zone device 109 comprises a composite electrode 110 (shown only symbolically in FIG. 1) being positioned along a two-dimensional plane oriented perpendicular to the optical axis 113 of the multi-beam source 101. Furthermore the electrical zone device 109 comprises a plurality of openings to allow passage of the particles of the homogeneous particle beam 106′ through the electrical zone device 109 and thus forming the beamlets 112 emerging from the multi-beam source 101. The beamlets shown in FIGS. 1-3 are only representative for a usually huge number of beamlets produced in the beam-forming system 103. The composite electrode 110 is composed of a number of partial electrodes, being arranged adjoining to each other, whereas a gap is provided between the partial electrodes as discussed in further detail below. The partial electrodes are adapted to be applied different electrostatic potentials, so as to form, together with the annular electrode 108, an electrostatic lens and influence the particles passing through the openings of the electrical zone device 109. The composite electrode 110 extends over the whole area of the electrical zone device 109, irrespective of the fact that only part of the electrical zone device 109 may be irradiated by the homogeneous particle beam 106′. The partial electrodes may extend over large fractions of the area of the electrical zone device 109 (see FIGS. 4a-4c), containing a multitude of openings aligned with the openings of the electrical zone device 109 which are thus influenced simultaneously when an electrostatic potential is applied to the respective partial electrode. However it is worth-while to mention that embodiments are possible where each partial electrode is associated to only one opening and the composite electrode 110 composed of said partial electrodes is restricted to a small region of the area of the electrical zone device 109, e.g. the region of the electrical zone device 109 where the openings are situated. The beamlets 112 emerging from the multi-beam source 101 are homocentric, i.e. seemingly emerging from a virtual source 145 which is located above the particle source 104 as seen in the direction of the beam, which propagates vertically downward in FIG. 1. The seeming emergence of the beamlets 112 from a common virtual source 145 results in the beamlets 112 being inclined against the optical axis 113 of the multi-beam source 101, the angle of inclination increasing with the distance of the beamlet from the optical axis 113. FIG. 1a shows a multi-beam source 101′ with an illumination system 102′ and a beam-forming system 103′, the setup being exactly the same as in FIG. 1. However, in FIG. 1a the beam-forming system 103′ is configured in a way that the beamlets 112′ emerging from the multi-beam source 101′ are substantially telecentric/parallel. It is, however, possible to arrange a collimating lens 107, an annular electrode 108 and an electrical zone device 109 in such a way, that the beamlets 112 emerging from the multi-beam source 101 are convergent, i.e. converging in a crossover being located somewhere below the multi-beam source 101, as seen in the direction of the beam. FIG. 2 depicts a variant of the multi-beam source 201, again comprising an illumination system 202 and a beam-forming system 203. The illumination system 202 is comparable to the one depicted in FIG. 1, comprising a particle source 204, an extractor lens array 205 and a collimating lens 207 for a diverging beam 206. However, the beam forming system 203 is different: In addition to an annular electrode 208 and an electrical zone device 209 with a composite electrode 210 it comprises a beam-splitting means 211 which is arranged consecutively as seen in the direction of the particle beam. The beam-splitting means 211 has a substantially plate-like shape and comprises a plurality of apertures transparent to the energetic particles of the particle beam. The beam-splitting means 211 and the electrical zone device 209 are arranged such that each opening of the plurality of openings of the electrical zone device 209 is aligned with an aperture of the plurality of apertures of the beam-splitting means 211. As discussed in reference to FIG. 1, the collimating lens 207 causes optical aberrations which is illustrated in FIG. 2 by the substantially homogeneous beam 206′ being inclined against the optical axis 213 of the multi-beam source 201. The combination of annular electrode 208 and electrical zone device 209 provides for correction of the imaging errors introduced by the lenses of the illumination system 202. Also it allows for homogenous illumination of the beam-splitting means 211, thus solving a common problem of particle-optical systems namely that the illumination decreases with increasing distance from the optical axis 113, resulting in shadow effects. Since the electrical zone device 209 serves to improve illumination of subsequent devices and the forming of the substantially telecentric/parallel beamlets 212 is carried out by the subsequent beam-splitting means 211, the width of the openings of the electrical zone device 209 is usually larger than the width of the apertures of the beam-splitting means 211. This ensures sufficient illumination of the apertures of the beam-splitting means 211. FIG. 3 shows yet another variant of the multi-beam source 301, comprising an illumination system 302 and a beam-forming system 303. The illumination system 302 is formed by a particle source 304 and an extractor lens array 305, forming a diverging beam 306 which is collimated by a collimating lens 307. An annular electrode 308 together with an electrical zone device 309 provides for substantially homogeneous illumination of a blanking device 314, the annular electrode 308, the electrical zone device 309 and the blanking device 314 being arranged in consecutive order as seen in the direction of the particle beam. In contrast to FIG. 2, the forming of substantially telecentric/parallel beamlets 312 is here provided by a blanking device 314, which allows for additional treatment of the respective beamlets 312, 317. The blanking device 314 is realized in a substantially plate-like shape and comprises a plurality of openings allowing for the particles of the particle beam to pass through the blanking device 314. The blanking device 314 is arranged such that its openings align with the respective openings of the electrical zone device 309. Every opening of the blanking device 314 is associated with a pair of electrodes 315, 316 being adapted to deflect the particle-beamlet passing through the respective opening. For this purpose, one electrode acts as active deflecting electrode 316 and the other electrode acts as ground electrode 315. When the deflecting electrode 316 is energized, i.e. voltage is applied to the electrode, the beamlet passing by the deflecting electrode 316 is deflected off its nominal path. The electrodes may be organized in groups, so that the controlling of the beamlets may be performed synchronously for all groups. This reduces the supply and controlling elements for the electrodes, and at the same time reduces the risk of cross-talk effects. FIG. 3 shows exemplarily a number of undeflected parallel beamlets 312 and two distracted beamlets 317 that are deflected by their respective pair of electrodes 315, 316, which are thus inclined against the optical axis 313 of the multi-beam source 301. The electrodes 315, 316 are located in a depression that is formed around the opening with which the electrodes are associated. Their height is chosen such that they do not protrude over the surface of the blanking device 314 they are manufactured in. The electrodes 315, 316 may be formed by well established lithography techniques. The sequence of components of the beam-forming systems 103, 203, 303 in FIGS. 1-3 are only a few of many possible arrangements, variants thereof are depicted in FIGS. 9-13. The electrical zone device 109, 209, 309 can be realized in different ways. FIGS. 4a-4c show different exemplary variants. FIG. 4a depicts a plan view of an electrical zone device 409. It features a planar, basically two-dimensional composite electrode that is composed of circular concentric partial electrodes 418 around a central partial electrode 419. The plurality of openings of the electrical zone device 409 is located in a field 420 which includes the central partial electrode 419. For the sake of clarity, no openings are depicted in FIG. 4a. Different electrostatic potentials can be applied to the partial electrodes 418, 419. For mutual insulation, and to reduce the influence of stray fields, there are gaps 421 provided between the partial electrodes 418, 419. FIG. 4b shows a different arrangement of the partial electrodes 418′ of an electrical zone device 409′. The area of the composite electrode here is divided into sector electrodes 418′ extending into the field 420′ in which the openings are located and separated by gaps 421′. The plan view of FIG. 4c shows yet another variant of an electrical zone device 409″ with a mosaic-shaped assemblage of partial electrodes 418″. The rectangular partial electrodes 418″ cover the area within and preferably also beyond the field 420″ the openings are located in. The electrical field can be controlled in both dimensions of the electrical zone device 409″, i.e. xy-direction, assuming a two-dimensional coordinate system being assigned to the electrical zone device 409″. A schematic setup of an electrical zone device 509 is depicted in FIG. 5. It shows a detail of a longitudinal section view of such a device. In order to facilitate the description of the device, the terms topside TS and bottom side BS are used here. These terms of the two sides are not related to the orientation of the electrical zone device with regard to the incoming particle beam—either side may be directed towards the impingent beam. The bulk of the electrical zone device 509 is formed by a silicon plate 523, covered with three layers 524, 525, 526. Located on top, e.g. on the topside TS, is the composite electrode in the form of a segmented electrode layer 524. It realizes the partial electrodes 518 to which different electrostatic potentials can be applied in order to influence the path of the beamlets that pass through the openings 522 of the electrical zone device 509. Some possible arrangements of partial electrodes are depicted in FIGS. 4a-4c, however the invention is not restricted to these embodiments. In the electrode layer 524, gaps 521 are provided between the zones covered by the different partial electrodes 518. These gaps make for reducing the mutual influence of neighboring partial electrodes 518 that produce stray fields when an electrostatic potential is applied to them. Another way of coping with said stray fields is realized by filling the gaps 521 with a resistive material 521′. By virtue of this solution, the effect of stray electric fields forming between the partial electrodes may be reduced. By using an insulating, dielectric material the different potentials of neighboring partial electrodes 518 may be separated and a dielectric polarization may be produced that reduces the total stray field at the position of neighboring openings 522. For the sake of clarity, FIG. 5 shows gaps 521 that are left empty as well as gaps 521 filled with a resistive material 521′. Usually only one of the two variants will be implemented on one device, however, it is also possible to realize a combination of the two variants. Beneath the electrode layer 524 an isolating layer 525 is located. The thickness of this layer is chosen sufficient so it can accommodate also the supplying lines (not shown) for applying electrostatic potentials to the partial electrodes of the electrode layer 524. Typically a CMOS-layer is used for that purpose. However, it is also possible to supply the partial electrodes 518 with the electrostatic potentials via direct wiring (not shown). Direct wiring here indicates every electrode being provided with its own feed line for applying an electric potential. In this case an isolating material with a smaller thickness may be used for the isolating layer 525, since no supply lines have to be accommodated. Below the isolating layer 525 a conductive layer 526 is situated which shields the partial electrodes 518 from any electrical field that may emerge from the direction of the bottom side BS. FIGS. 4a-4c show embodiments of an electrical zone device where the composite electrode extends over the whole surface of the device and the partial electrodes are arranged adjoining to each other, with only small gaps in between. FIG. 6 depicts yet another embodiment: The composite electrode of the electrical zone device 609 is realized as a multitude of partial electrodes in the form of pads 641. For the sake of better understanding, partial electrodes in said form will be called ‘pads’ in the following. In FIG. 6 the pads 641 are located only within the field 620 where the openings of the electrical zone device 609 are located. Size and number of the openings and the partial electrodes are not to scale in FIG. 6 for the sake of visibility. Every opening of the plurality of openings of the electrical zone device 609 is provided with a set of pads 641, forming the partial electrodes. The pads 641 belonging to such a set are arranged adjoining to each other and are adapted to be applied an electrostatic potential. Every pad 641 can be supplied with an electrostatic potential independently. The pads 641 are adapted to influence a particle-beamlet crossing the opening of the electrical zone device 609 the pads 641 are located on. Depending on the electrostatic potential applied to an electrode, it either repels or attracts a beamlet. By virtue of this solution it is possible to individually influence the path of a beamlet and correct chromatic or spherical aberrations or other deficiencies of the beamlet, e.g. when its path is affected by an opening that is not exactly parallel to the optical axis of the electrical zone device. It is not necessary to provide an additional annular electrode as is the case for the embodiments shown in FIGS. 4a-4c. FIG. 6a shows yet another embodiment of an electrical zone device 609′. It comprises composite electrodes according to two aspects of the invention at the same time. The first composite electrode is realized as a substantially two-dimensional layer, consisting of a number of circular concentric partial electrodes 618 which are separated from each other by small gaps 621 to reduce the effects of stray fields. A second composite electrode is formed by a multitude of partial electrodes in the form of pads 641′, being located in a field 620′. The pads 641′ are formed on top of the circular concentric partial electrodes 618, however advantageously an isolating layer is provided between them. Each pad 641′ is associated with an opening of the electrical zone device 609′. For the sake of clarity it is mentioned that in the direct proximity of a gap 621 between partial electrodes 618 of the first composite electrode, neither openings nor pads 641′ are located. In order to fully exploit the advantageous features of the electrical zone device 609′ depicted in FIG. 6a, it should be combined with an annular electrode. FIG. 7 shows a detail of a plan view of the field 620 of an electrical zone device 609 as depicted in FIG. 6. FIG. 7 shows a sample of openings 722 with their respective sets of pads 741. In the present example, a set contains four pads 741. The openings 722 have a quadratic shape and the pads 741 are arranged on each side of the openings 722, the arrangement resembling ‘lily pads’. However it should be appreciated that the invention is not restricted to the embodiment discussed in the following, which merely represents one of the possible implementations. Different numbers of pads 741 per set are possible as well as other shapes of the openings 722, like circular or rectangular. The area between neighbored sets of pads 741 can either be left empty or be provided with an isolating or dielectric material. FIG. 7a shows a longitudinal section detail of an electrical zone device 709 taken along the line A-A of FIG. 7. A silicon plate 723 is covered with three layers 742, 725, 726: A conductive layer 726 shields the other layers from any electric field that may emerge from the silicon plate 723. An isolating layer 725 accommodates the supply lines 727, e.g. in the form of strip conductors, that are needed to control and supply the pads 741 that form the ‘lily pad’-layer 742. Each of the pads 741 is associated with an opening 722 that reaches through the electrical zone device 709 and allows for the transition of energetic particles in the form of beamlets. The path of the beamlets can be influenced by applying an electrostatic potential to the respective pads 741. Preferably, the isolating layer 725 is realized as a CMOS-layer which is best suited to accommodate the wiring, also the production of such a CMOS-layer is a well established process in the semiconductor industry. In order to shield the supply lines 727 from any electric field, screening conductors 728 are provided above and below the supply lines 727. The setup depicted in FIGS. 7 and 7a allows for the individual handling of each beamlet passing through a respective opening 722 of the electrical zone device 709. Thus displacements of the beamlets, e.g. due to mechanical deficiencies of the openings of the electrical zone device 709, can be corrected. FIG. 8 shows a detail of a plan view of the field 620′ of an electrical zone device 609′ as depicted in FIG. 6a. The partial electrodes 818 of the first composite electrode are here separated by a small gap 821. On top of the partial electrodes 818, the pads 841 are located, arranged in ‘lily pad’-like sets of four around each opening 822. The width of the gap 821 usually amounts to about 1 μm, which is typically much smaller than the distance between the apertures usually arranged in a regular 2D translational array. The small gap 821 may also be positioned right in between the apertures without breaking the translational symmetry across the gap area (as for example shown in FIG. 5 where the aperture spacing is not changed by the gap), possibly meandering through the space between the apertures or ‘lily pads’. FIG. 8a shows a longitudinal section detail of an electrical zone device 809 from the plan view of FIG. 8 along the line B-B. A silicon plate 823 is covered with different layers which are explained bottom up according to the arrangement depicted in FIG. 8a: A conductive layer 826 shields the other layers from any electric field that may emerge from the silicon plate 823. An isolating layer 825 accommodates the wiring for the partial electrodes 818 and the ‘lily pads’ 841. Only the supply lines 827 for the ‘lily pads’ 841 are shown in FIG. 8a, the wiring for the partial electrodes 818 is not shown, though located in the isolating layer 825 as well. Screening conductors 828 are provided above and below the supply lines 827 to shield them from any electric field. Similar screening devices are provided for the wiring of the partial electrodes 818, however they are not depicted in FIG. 8a for the sake of clarity. Preferably, the isolating layer is realized as a CMOS-layer. On top of the isolating layer, an electrode layer 824 is provided, forming the first composite electrode, thus containing the partial electrodes 818 which are separated by gaps 821. Between the electrode layer 824 and the ‘lily pad’-layer 842, a second isolating layer 843 is provided to prevent the ‘lily pads’ 841 from being influenced by the electric field of the partial electrodes 818. Each of the ‘lily pads’ 841 is associated with an opening 822 of the electrical zone device 809, the openings 822 allowing for energetic particles to pass through the electrical zone device 809. The combination of extended partial electrodes 818, covering many openings 822 of the electrical zone device 809, with sets of ‘lily pads’ 841, each set being associated with only one opening 822, allows for the correction of imaging aberrations of the whole beam/all beamlets as well as of small displacements of individual beamlets. FIGS. 9 to 13 show different embodiments of a beam-forming system of a multi-beam source according to the invention. In FIG. 9, a substantially homogenous beam 906′ of charged particles passes through a first annular electrode 908 and impinges upon an electrical zone device 909, formed according to, for instance, one of the embodiments discussed above. In order to protect the different layers of the electrical zone device 909 from the energetic particles of the impinging beam, a protective layer (not shown) may be provided on top of the other layers, closest to the impingent beam. The electrical zone device 909 in combination with the annular electrode 908 corrects for optical aberrations of the beam 906′ and simultaneously forms the substantially homogeneous beam 906′ into a number of beamlets. Further it is suited to improve the illumination of the subsequent beam-splitting means 911 which is arranged after the electrical zone device 909, as seen in the direction of the particle beam. The beam-splitting means 911 forms a multitude of substantially telecentric/parallel beamlets of energetic particles with a desired diameter. The beamlets pass through a second electrical zone device 909′ that is combined with a second annular electrode 908′ to form an electrostatic lens. This lens allows for the correction of imaging aberrations. Depending on the variant of the electrical zone device used it is even possible to influence the path of individual beamlets, e.g. when an electrical zone device employing the ‘lily pads’-arrangement is used. FIG. 10 shows a sectional view of an arrangement with a correction lens arrangement 1029 and an electrical zone device 1009. Instead of an annular electrode the electrical zone device 1009 in combination with the correction lens arrangement 1029 forms an electrostatic lens for correction of geometric aberrations of the illumination system. For that purpose, the correction lens arrangement 1029 and the electrical zone device 1009 are kept on different electrostatic potentials. The correction lens arrangement 1029 has a substantially plate-like shape with a number of orifices, each orifice being aligned with a respective opening of the plurality of openings of the electrical zone device 1009 which is located subsequently to the correction lens arrangement 1029 as seen in the direction of the beam. FIG. 10a shows a detail of a correction lens arrangement 1029′ as depicted in FIG. 10 with some orifices 1044. The width of the orifices changes across the section of the arrangement. A first width w1 in the part of the orifice 1044 that is directed towards the incoming beam is much smaller than a second width w2, located on the opposite surface. The ratio of the first width w1 and the second width w2 and the thickness t1 as well as the electrostatic potentials applied to the correction lens arrangement 1029, 1029′ and the electrical zone device 1009 define the strength of the lens that is formed by the combination of the latter two. The more offset from the optical axis of the correction lens arrangement 1029′ an orifice 1044 is located, the more the axis of the beamlet passing through it may be declined against the optical axis of the electrical zone device, necessitating a correction. Therefore the widths w1, w2 of the orifices may vary across the area of the electrical zone device depending on the lateral position of the corresponding orifice. In the embodiment depicted in FIG. 10, where the correction lens arrangement is situated in front of the electrical zone device 1009, it locally changes the angle of incidence of the particles onto the electrical zone device. By virtue of this solution it is possible to ameliorate the illumination of the electrical zone device and allow for correction of imaging aberrations. FIGS. 11-13 show different embodiments of a beam-forming system employing a blanking means, used to adjust the nominal path of selected beamlets. Every embodiment contains a first annular electrode, a first electrical zone device, a beam-splitting means, a second electrical zone device and a second annular electrode. The sequence of the parts of the beam-forming system is basically the same in FIGS. 11-13, however it has to be pointed out that this is not intended to restrict the invention in any kind, since other sequences are possible as well. FIG. 11 displays a beam-forming system 1103 wherein a broad beam of charged particles 1106′ passes through a first annular electrode 1108 and irradiates an electrical zone device 1109. After the electrical zone device as seen in the direction of the beam, a beam-splitting means 1111 is located. The beam-splitting means is followed by a second electrical zone device 1109′, combined with a second annular electrode 1108′. Every aperture of the beam-splitting means 1111 is associated with a pair of electrodes 1115, 1116 which are adapted to be applied different electrostatic potentials, thereby producing an electrical field which influences the path of the beamlet that passes through the respective aperture. One of the electrodes 1115, 1116 acts as ground electrode 1115, whereas the other electrode is the active deflecting electrode 1116. The electrodes are preferably located on the surface of the beam-splitting means 1111 that is oriented away from the incoming beamlets. By means of the electrodes 1115, 1116 it is possible to blank out selected beamlets by directing them off the nominal path that leads through the opening of the second electrical zone device 1109′, causing them to hit the second electrical zone device 1109′ and be absorbed there. For that purpose an absorbing layer (not shown) may be provided on the surface of the second electrical zone device 1109′ that is directed towards the incoming beamlets. In another possible embodiment, a separate absorbing layer (not shown) may be provided for that purpose. In FIG. 11 the electrodes 1115, 1116 are depicted as being located ‘on’ the surface of the beam-splitting means 1111, in the sense of not-being an integral part of said means. Such electrodes could be formed by perpendicular growth employing state-of-the-art electroplating techniques. The blanking means depicted in the arrangements of FIGS. 12 and 13 are formed differently. FIG. 12 shows a beam-forming system 1203 containing the same parts as the arrangement in FIG. 11, but the beam-splitting means 1211 features recesses 1230 around each aperture, accommodating the electrodes 1215, 1216. The electrodes 1215, 1216 in this embodiment may be formed e.g. by application of known etching techniques. FIG. 13 depicts a beam-forming system 1303 wherein the electrodes and the respective recesses are formed in the first electrical zone device 1309. For the sake of clarity it is pointed out that it is also possible to include a separate blanking device in the beam-forming systems, a variant that is not depicted in the figures. Also it has to be mentioned that in each of the cases described, the beam splitting could be taken over by the electrical zone device, thus rendering obsolete a self-contained beam-splitting means by providing a combined ‘beam-splitting electrical zone device’. Multi-beam sources of the kind as described above are suitable for a lot of different purposes. One possible application is in a multi-beam lithography system, e.g. in the semiconductor industry, for producing patterns on different substrate materials. FIG. 14 shows such a lithography system 1431 as disclosed in the U.S. Pat. No. 6,768,125 B2 by the applicant/assignee. The concept, dubbed PML2 (short for ‘Projection Mask-Less Lithography #2’), basically comprises an illumination system 1402, a pattern definition device 1432, a projecting system 1434 and a target station 1435 with a substrate 1433. For the sake of clarity, the components are not shown to size in FIG. 14. The illumination system 1402 produces a lithography beam which propagates vertically downwards in FIG. 14. The beam may consist of electrically charged particles of different kind—apart from electrons these can be, for instance, helium ions, hydrogen ions or heavy ions, here referring to ions of elements heavier than C, such as O, N or the noble gases Ne, Ar, Kr, Xe. The pattern definition device 1432 comprises a number of plates stacked on top of the other, among them an aperture array means (aperture plate) and a deflector array means (blanking plate). The plates each comprise a multitude of openings, the openings of the different plates aligning with each other. The separate plates are mounted together at defined distances, for instance in a casing. The pattern definition device 1432 defines a beam pattern, consisting of beamlets, to be projected on the substrate 1433. With the deflector array means beamlets can be deflected off their nominal path, thus being blanked and not reaching the target surface. The beamlets may be deflected such that they are absorbed by a stop plate 1436. By means of electrostatic or electromagnetic lenses the projecting system 1434 displays the pattern provided by the pattern definition device 1432 on the substrate 1433. Lithography apparatus of the abovementioned kind have various problems, e.g. the illumination of the plates of the pattern definition device 1432 may be insufficient, especially in the regions remote from the optical axis 1413 of the lithography system 1431. Also the use of electrostatic or electromagnetic lenses causes optical errors like spherical and chromatic aberrations. Said problems may be reduced to a great extent when a multi-beam source according to the invention is used instead of the illumination system 1402. Such an arrangement is shown in FIG. 15, where a multi-beam lithography system 1531 is depicted—the components are not shown to size here for the sake of clarity. A multi-beam source 1501 is provided to produce a multitude of beamlets that is projected on a substrate 1533 in a target station 1535 by a projecting system 1534. In principle any of the multi-beam sources 1501 described above can be used here. In the embodiment depicted in FIG. 15 the provision of an electrical zone device 1509 together with an annular electrode 1508 allows for amelioration of the illumination of the beam-splitting means 1511 that is arranged consecutively to the electrical zone device 1509 as seen in the direction of the beam. The beam-splitting means 1511 may comprise a blanking means as in FIGS. 11-13 to allow for the blanking of selected beamlets. FIG. 16 shows yet another multi-beam lithography system 1631 of prior art. Such a system is disclosed in the U.S. Pat. No. 6,989,546 B2 by the applicant/assignee. The lithography apparatus 1631 is adapted to write structures on a resist-covered wafer substrate 1633 that is located on a target station 1635. The apparatus comprises an illumination system 1602 with a particle source 1604 and a collimator optics system producing an illuminating beam of electrically charged particles. A multi-beam optical system 1637 is located after the illumination system 1602, comprising an arrangement of electrostatic aperture plates 1638 with additional imaging elements. The aperture plates 1638 form the beam into a plurality of beamlets, wherein the aperture plates 1638 are designed in such a way that that each of the beamlets is successively focused into a concentrated intensity on the wafer substrate 1633. For the sake of clearness only a reduced number of beamlets is shown in FIG. 16. In order to adjust the focusing properties of the beamlets individually, e.g. with respect to the beam diameter, and correct for any aberrations introduced by the illumination system 1602, an arrangement of electrostatic lenses 1639 is provided, for instance between the aperture plates 1638. A multi-pole arrangement 1640, comprising an individual deflection unit for each beamlet, which is arranged after the aperture plates 1638 as seen in the direction of the beam, allows to further adjust the beamlets, e.g. with respect to the position on the wafer substrate 1633. The arrangement depicted in FIG. 16 allows for the correction of individual imaging aberrations of the respective beamlets. However, the performance of the lithography system 1631 may be ameliorated by using a multi-beam source according to the invention instead of the illumination system 1602. FIG. 17 depicts an improved multi-beam lithography apparatus 1731 comprising a multi-beam source 1701, a multi-beam optical system 1737 with a number of electrostatic aperture plates 1738 with additional imaging elements and a wafer substrate 1733 on a target station 1735. The use of a multi-beam source 1701 according to the invention allows for an ameliorated illumination of the electrostatic aperture plates 1738 as well as for reduced imaging aberrations that arise in an arrangement as depicted in FIG. 16 where the illumination system is combined with a collimator optics system employing electrostatic or electromagnetic lenses. Even though the provision of a multi-beam source according to the invention seems to render obsolete an arrangement of electrostatic lenses 1739, it is still employed ion FIG. 17 since it allows to correct for any remaining imaging aberrations as well as for errors that may be introduced by mechanical deficiencies of any of the plates or devices employed. Such a deficiency could be the axis of an opening or aperture not being exactly parallel to the optical axis 1713 of the multi-beam lithography apparatus 1731 or alignment errors of the different plates and devices. Also a multi-pole arrangement 1740, comprising an individual deflection unit for each beamlet, is provided to allow for accurate positioning of the beamlets on the substrate 1733. It is to be understood that the above description is included to illustrate the operation of the preferred embodiments and is not meant to limit the scope of the invention. From the above discussion, many variations will be apparent to one skilled in the art that would yet be encompassed by the spirit and scope of the present invention.
	claims	1. A limiting device (9) for limiting electromagnetic radiation (3;5;7), which device includes an essentially flat beam cross-section limiter (10) which at least partly encloses at least one passage aperture (l2;13) for beams (5;7), characterized in that the device (9) includes at least a second beam cross-section limiter (14) which, in the active position, constitutes at least one component extending at an angle, which is not zero, to the first beam cross-section limiter (10). 2. A device as claimed in claim 1, characterized in that the second beam cross-section limiter (14) extends perpendicularly to the first beam cross-section limiter (10). 3. A device as claimed in claim 1, characterized in that the first beam cross-section limiter (10) includes two mutually intersecting passage apertures (12;l3) for beams (5;7). 4. A device as claimed in claim 1, characterized in that the second beam cross-section limiter (14) includes a passage aperture (16) for beams (5;7) which commences in an edge zone and is only partly enclosed. 5. A device as claimed in claim 1, characterized in that the passage apertures (12;13;16) of the first and the second beam cross-section limiter (10;14) are formed by respective sectors of a circle. 6. A device as claimed in claim 1, characterized in that the first passage aperture (12) of the first beam cross-section limiter (10) constitutes in projection at least approximately a circle in conjunction with the passage aperture (16) of the second beam cross-section limiter (14). 7. A device as claimed in claim 6, characterized in that the circular contour is such that a beam (5) which enters perpendicularly thereto reaches only edge faces of the first passage aperture (12) of the first beam cross-section limiter (10) as well as the passage aperture (16) of the second beam cross-section limiter (14). 8. A device as claimed in claim 1, characterized in that the second passage aperture (13) of the first beam cross-section limiter (10) constitutes in projection a circle in conjunction with the passage aperture (16) of the second beam cross-section limiter (14). 9. A device as claimed in claim 8, characterized in that the circular contour is such that a beam (7) which is incident on or emanates from this contour at right angles reaches only edge zones of the second passage aperture (13) of the first beam cross-section limiter (10) as well as the passage aperture (16) of the second beam cross-section limiter (14), and that reflected or secondary rays (22) which originate from boundaries of the first passage aperture (12) of the first beam cross-section limiter (10) do not invade the beam (7) emanating from said passage apertures (13;16). 10. A device as claim in claim 1, characterized in that the fist beam cross-section limiter (10) and the second beam cross-section limiter (14) can be detachably connected to one another. 11. An analysis device (A) for the examination of material samples (6) by means of electromagnetic radiation (3; 5; 7), characterized in that the analysis device (A) includes at least one limiting device (9) as claimed in claim 1. 12. An analysis device as claimed in claim 11, characterized in that the limiting device (9) is built into the analysis device (A) in such a manner that a beam (5) which is incident on an optical element, and directed onto a sample (6) passes through the aperture of incidence which is enclosed by the boundaries of the first passage aperture (12) of the first beam cross-section limiter (10) and the boundary of the passage aperture (16) of the second beam cross-section limiter (14) and that a beam (7) which originates from the optical element, traverses the exit aperture which is limited by the boundaries of the second passage aperture (13) of the first beam cross-section limiter (10) and the passage aperture (16) of the second beam cross-section limiter (14). 13. An analysis device as claimed in claim 12, characterized in that the incident beam (5;21) contacts merely edge zones of the first passage aperture (12) of the first beam cross-section limiter (10) and the passage aperture (16) of the second beam cross-section limiter (14). 14. An analysis device as claimed in claim 12, characterized in that secondary rays (22) which are reflected by the first passage aperture of the first beam cross-section limiter (10) or are produced at that area do not traverse the exit aperture formed by the second passage aperture (13) of the first beam cross-section limiter (10) and the passage aperture (16) of the second beam cross-section limiter (14). 15. An analysis device as claimed in claim 11, characterized in that the first passage aperture (12) and the second passage aperture (13) of the first beam cross-section limiter (10) are of different size. 16. A limiting device (9) for limiting electromagnetic radiation (3;5;7), which device includes an essentially flat beam cross-section limiter (10) which at least partly encloses two mutually intersecting passage apertures (12;13) for beams (5;7), characterized in that the device (9) includes a second beam cross-section limiter (14) which includes a passage aperture (16) far beams (5;7) which commences in an edge zone and is only partly enclosed.
	claims	1. A method of regulating a dose of energy produced during continuous burst mode of an EUV light source comprising:(a) beginning a burst having a predetermined energy dose target;(b) timing by the laser controller a trigger to pulse a laser beam to irradiate a droplet during the burst;(c) sensing EUV energy generated by the droplet;(d) calculating by the laser controller a current dose error for the droplet based on the sensed EUV energy and the energy dose target;(e) accumulating by the laser controller a burst error based on the current dose error and a running burst error calculated for one or more preceding droplet during the burst;(f) repeating steps (b)-(e) for a next droplet when the burst is not finished and the accumulated burst error does not meet or exceed a threshold burst error;(g) mistiming by the laser controller the trigger to pulse the laser beam to not irradiate the next droplet when the burst is not finished and the accumulated burst error meets or exceeds the threshold burst error; and(h) repeating steps (c)-(g) until the burst is finished. 2. The method of claim 1 wherein the current dose error equals the sensed EUV energy minus the energy dose target. 3. The method of claim 2 wherein the accumulated burst error equalsrunning burst error+(gaindose error). 4. The method of claim 3 wherein the gain is 1. 5. The method of claim 1 wherein the current dose error equals the energy dose target minus the sensed EUV energy. 6. The method of claim 5 wherein the accumulated burst error equalsrunning burst error+(gaindose error). 7. The method of claim 6 wherein the gain is −1. 8. A system for regulating a dose of energy produced during continuous burst firing of an EUV light source configured to generate an energy dose target comprising:a drive laser configured to pulse a laser beam when a trigger is received;a sensor configured to sense EUV energy generated by irradiation of a droplet; anda controller configured to:(a) time the trigger to pulse a laser beam to irradiate a droplet during the burst;(b) calculate a current dose error for the droplet based on the sensed EUV energy and the energy dose target;(c) accumulate a burst error based on the current dose error and a running burst error calculated for one or more preceding droplet during the burst;(d) repeat steps (a)-(c) for a next droplet when the burst is not finished and the accumulated burst error does not meet or exceed a threshold burst error;(e) mistime the trigger to pulse the laser beam to not irradiate the next droplet when the burst is not finished and the accumulated burst error meets or exceeds a threshold burst error; and(f) repeat steps (b)-(e) until the burst is finished. 9. The system of claim 8 wherein the current dose error equals the sensed EUV energy minus the energy dose target. 10. The system of claim 9 wherein the accumulated burst error equalsrunning burst error+(gaindose error). 11. The system of claim 10 wherein the gain is equal to 1. 12. The system of claim 8 wherein the current dose error equals the energy dose target minus the sensed EUV energy. 13. The system of claim 12 wherein the accumulated burst error equalsrunning burst error+(gaindose error). 14. The system of claim 13 wherein the gain is −1.
	description	A simplified block diagram of an ion beam system in accordance with a first embodiment of the invention is shown in FIG. 1. An ion beam generator 10 generates an ion beam of a desired species, accelerates ions in the ion beam to desired energies, performs mass/energy analysis of the ion beam to remove energy and mass contaminants and supplies an energetic ion beam 12. A scanner 20 deflects the ion beam 12 to produce a scanned ion beam having a fan-shaped beam envelope 30 with a scan origin 34. Scanner 20 is part of a beam scanning apparatus as described below. A semiconductor wafer 32 or other workpiece is positioned in the path of the scanned ion beam, such that ions of the desired species are implanted into semiconductor wafer 32. An angle corrector (not shown) may be utilized to direct the ions in the scanned ion beam along parallel trajectories. The ion beam system shown in FIG. 1 may represent an ion implanter. The ion implanter may include additional components well known to those skilled in the art. For example, semiconductor wafer 32 is typically supported in an end station which includes automated wafer handling equipment, a dose measuring system, an electron flood gun, etc. Ion beam generator 10 may include an ion source, a beam accelerator and a mass analyzer. It will be understood that the entire path traversed by the ion beam is evacuated during ion implantation. Scanner 20 includes a first scan element 40 and a second scan element 42. Scan elements 40 and 42 are spaced apart and define a gap 44 through which ion beam 12 is directed. In one embodiment, scanner 20 is an electrostatic scanner, and scan elements 40 and 42 are electrostatic scan plates. The ion beam 12 passes through gap 44 between the electrostatic scan plates and is deflected by electric fields in gap 44. In the case of electrostatic scanning, the ion beam 12 is deflected in the direction of the electric field between the scan plates. Thus, horizontally-spaced scan plates are utilized to perform horizontal beam scanning. In another embodiment, scanner 20 is a magnetic scanner, typically implemented as an electromagnet. The electromagnet includes magnetic polepieces, which correspond to the scan elements 40 and 42, and a magnet coil for energizing the magnetic polepieces. The ion beam 12 passes through gap 44 between the magnetic polepieces and is deflected by magnetic fields in gap 44. In the case of magnetic scanning, the ion beam is deflected perpendicular to the direction of the magnetic field between the magnetic polepieces. Thus, vertically-spaced magnetic polepieces are utilized to perform horizontal beam scanning. The beam scanning apparatus of FIG. 1 further includes a scan signal generator 50 which provides scan signals to scan elements 40 and 42. In the case of an electrostatic scanner, scan signal generator 50 supplies scan voltages to the scan plates. The scan voltages, which may comprise sawtooth waveforms, produce electric fields between scan elements 40 and 42 for scanning the ion beam. In the case of a magnetic scanner, scan signal generator 50 supplies a scan current to the magnet coil of the electromagnet that constitutes the magnetic scanner. The scan signal generator 50 is controlled by a system controller 64 in response to user-selected beam parameters and other implant parameters. The beam scanning apparatus of FIG. 1 further includes a scan element positioner 60 for positioning scan element 40 and a scan element positioner 62 for positioning scan element 42. Scan element positioners 60 and 62 may each include a mechanical drive system, such as a motor and a mechanical coupling between the motor and the scan element, for controlling the positions of scan elements 40 and 42. Scan element positioners 60 and 62 are controlled by system controller 64 in response to user-selected beam parameters, such as ion beam energy and ion beam species. As described below, scan element positioners 60 and 62 adjust the spacing between scan elements 40 and 42, may move scan elements 40 and 42 axially with respect to ion beam 12 toward or away from ion beam generator 10, may rotate scan elements 40 and 42, or may provide combinations of these movements under the control of system controller 64. The scan element positioners 60 and 62 may establish a continuous range of positions of scan elements 40 and 42 or may establish two or more discrete positions of scan elements 40 and 42. In one embodiment, scan elements 40 and 42 are moved along paths 70 and 72, respectively, which are inclined at angles +xcex1 and xe2x88x92xcex1, respectively, with respect to ion beam 12. In particular, as the spacing between scan elements 40 and 42 is increased, scan elements 40 and 42 are moved upstream with respect to ion beam 12 toward ion beam generator 10. As described below, paths 70 and 72 may be selected to ensure that scan origin 34 remains in a fixed position as scan elements 40 and 42 are moved. A first example of an electrostatic scanner for use in the ion beam apparatus of FIG. 1 is described with reference to FIGS. 2 and 3. An electrostatic scanner 100 includes scan plates 110 and 112 spaced apart by a gap 114. Scan plates 110 and 112 correspond to scan elements 40 and 42 in FIG. 1. Scan plates 110 and 112 may include upstream plate portions 110a and 112a, which may have a spacing S that is constant or slightly diverging in the downstream direction, and diverging downstream plate portions 110b and 112b. The scan plates are shaped and positioned to provide electric fields suitable for scanning ion beam 12. A fan-shaped beam envelope 116 of the scanned ion beam increases in width in the downstream direction through scan plates 110 and 112. Typically the divergence of scan plates 110 and 112 corresponds to the shape of beam envelope 116. Scan plates 110 and 112 deflect ion beam 12 in one dimension. In some cases, a complete scanner may include a second set of scan plates for deflecting the ion beam 12 in a second dimension to cover the entire surface of wafer 32. In other cases, scanning in the second dimension is achieved by mechanical movement of wafer 32. Scan plates 110 and 112 are connected to scan element positioners 60 and 62, respectively, and to scan signal generator 50 as shown in FIG. 1. The scan signal generator 50 applies scan voltages to scan plates 110 and 112 for deflecting ion beam 12. The scan voltages may have different amplitudes, frequencies and waveforms. Although a sawtooth scan waveform is typically utilized, the waveform may be modified to adjust the uniformity of the ion dose applied to the semiconductor wafer. The amplitude of the scan voltage depends on the ion species and energy, as well as the length and spacing of scan plates 110 and 112. By way of example only, the frequency of the scan voltage waveform may be on the order of 1 KHz. In accordance with an aspect of the invention, the spacing S between scan plates 110 and 112 may be adjusted as a function of one or more ion beam parameters, such as ion beam energy. FIG. 2 illustrates a case of relatively high ion beam energy. For high ion beam energy, an intense electric field is required to deflect the ion beam. Therefore, the scan voltage amplitudes must be relatively high and the spacing S between scan plates 110 and 112 must be relatively small to achieve an intense electric field in the region between scan plates 110 and 112. For low ion beam energies, the amplitudes of the scan voltages applied to scan plates 110 and 112 may be reduced. However, as noted above, low energy ion beams tend to expand due to the space charge effect, and a significant fraction of the ion beam may not pass between scan plates 110 and 112 having a small spacing S. As a result, the ion beam current delivered to the wafer is significantly reduced. This causes implant times to be increased and throughput to be reduced. The scanner is conventionally characterized by a beam acceptance, which represents the fraction of the ion beam that passes through the scanner for given ion beam and scanner parameters. As shown in FIG. 3, reduced beam acceptance at low energies may be overcome, at least in part, by increasing the spacing S between scan plates 110 and 112. The scan voltages are adjusted to provide the desired bam deflection at the selected spacing between scan plates 110 and 112. Beam envelope 116 is characterized by a scan origin 120. Scan origin 120 is a point where the ion trajectories in beam envelope 116 intersect. As the spacing S between scan plates 110 and 112 is adjusted to accommodate different ion beam parameters, the scan origin 120 moves along the axis of ion beam 12. As shown in FIGS. 2 and 3, scan origin 120 moves downstream away from ion beam generator 110 by a distance 122 as the spacing between scan plates 110 and 112 is increased by moving the scan plates perpendicular to ion beam 12. The shift in scan origin 120 may create problems in certain ion implanter configurations. For example, ion implanters typically utilize an angle corrector positioned downstream of the scanner. The angle corrector converts the diverging ion trajectories produced by the scanner into parallel ion trajectories for incidence on semiconductor wafer 32. The angle corrector is designed and positioned based on a particular location of the scan origin. When the scan origin shifts, the ion trajectories output by the angle corrector may no longer be parallel. In accordance with a further aspect of the invention, the movement of scan plates 110 and 112 may include both a lateral component and an axial component. The lateral component is perpendicular to ion beam 12 and the axial component is parallel to ion beam 12. In particular, scan plates 110 and 112 may be moved upstream with respect to ion beam 12 as the spacing between scan plates 110 and 112 is increased, along paths 70 and 72. As shown in FIG. 1, paths 70 and 72 are oriented at angles of +xcex1 and xe2x88x92xcex1, respectively, with respect to the axis of ion beam 12. The lateral component of scan plate movement, which produces a change in spacing S, is selected to provide a desired beam deflection and beam acceptance. The axial component of scan plate movement is selected to provide a desired position of scan origin 120. In a preferred embodiment, the axial movement is selected to maintain scan origin 120 of the beam envelope 116 in a fixed position as the spacing S between scan plates is varied. By way of example, the configuration of FIG. 2 may utilize a spacing S between scan plates 110 and 112 of 12 millimeters (mm) for an ion beam having an energy of 1.55 MeV. The configuration of FIG. 3 may utilize a spacing S between scan plates 110 and 112 of 40 mm for a beam energy of 750 keV. In this example, scan origin 120 shifts along ion beam 12 by approximately 37 mm, thus requiring an axial component of scan plate movement of 37 mm. A graph of scan origin position in millimeters as a function of plate spacing in millimeters for one example of scan plate geometry is shown in FIG. 4. A line 140 represents the shift in scan origin 120 as a function of scan plate spacing for a given scan plate geometry. It will be understood that the graph of FIG. 4 represents a particular scan plate geometry and that other scan plate geometries would be represented by different lines. A second example of an electrostatic scanner for use in the ion beam apparatus of FIG. 1 is described with reference to FIGS. 5 and 6. An electrostatic scanner 148 includes scan plates 150 and 152 spaced apart by a gap 154. Scan plates 150 and 152, which correspond to scan elements 40 and 42 shown in FIG. 1, have a spacing S that diverges in the downstream direction of ion beam 12. FIG. 5 represents a configuration suitable for a relatively high energy ion beam, and FIG. 6 represents a configuration suitable for a relatively low energy ion beam. For the low energy ion beam, as shown in FIG. 6, the spacing S between scan plates 150 and 152 is increased, and the downstream portions of scan plates 150 and 152 are rotated away from ion beam 12. The increase in spacing S combined with rotation of scan plates 150 and 152 has the combined effect of increasing beam acceptance and controlling scan origin shift. In particular, the rotation of scan plates 150 and 152 may be selected for a given change in spacing S to achieve a fixed position of the scan origin of the beam envelope. A graph of scan origin location as a function of scan plate angle for different scan plate spacings is shown in FIG. 7. In particular, line 160 represents scan origin position as a function of scan plate angle for a spacing between scan plates 150 and 152 of 29 mm. Similarly, lines 162, 164, 166 and 168 represent scan origin position as a function of scan plate angle for plate spacings of 33 mm, 43 mm, 57 mm and 77 mm, respectively. It will be understood that the graph of FIG. 7 represents a particular scan plate geometry and other scan plate geometries would be represented by different sets of lines. The control of scan element position as described above may be manual or automatic. When control is automatic, system controller 64 (FIG. 1) determines the required positions of scan elements 40 and 42 based on the user-selected parameters of the ion beam. Such parameters may include ion beam species and energy. The system controller 64 determines the required positions of scan elements 40 and 42 based on the selected beam parameters and provides position control signals to scan element positioners 60 and 62. Scan element positioners 60 and 62 in turn adjust the positions of scan elements 40 and 42. In a manual mode, the user provides desired scan element positions to system controller 64, and system controller 64 provides corresponding position control signals to scan element positioners 60 and 62. It will be understood that the positions of scan elements 40 and 42 are typically adjusted during the setup period for an implant with ion beam generator 10 turned off. A simplified block diagram of an ion beam system in accordance with a second embodiment of the invention is shown in FIG. 8. An ion beam generator 210 generates an ion beam of a desired species, accelerates ions in the ion beam to desired energies, performs mass/energy analysis of the ion beam to remove energy and mass contaminants, and supplies an energetic ion beam 212. A scanner 220 deflects the ion beam 212 to produce a scanned ion beam having a beam envelope 230 with a scan origin 232. Scanner 220 is part of a beam scanning apparatus as described below. A semiconductor wafer 234 or other workpiece is positioned in the path of ion beam 212. Scanner 220 includes a first set of scan elements 240 and 242, and a second set of scan elements 250 and 252. Scan elements 240 and 242 are spaced apart and define a gap 244 through which ion beam 212 is directed. Scan elements 250 and 252 are spaced apart and define a gap 254 through which ion beam 212 is directed. Scan elements 240 and 242 and scan elements 250 and 252 are positioned for deflecting ion beam 212 in one dimension, as distinguished from sets of scan plates which are orthogonally positioned with respect to the ion beam and which perform two-dimensional scanning of an ion beam. It will be understood that scanner 220 may include more than two sets of scan plates. In one embodiment, scanner 220 is an electrostatic scanner, and scan elements 240, 242, 250, 252 are electrostatic scan plates. As previously noted, the scan plates in each set are horizontally spaced for horizontal beam scanning. In another embodiment, scanner 220 is a magnetic scanner, and scan elements 240 and 242 are magnetic polepieces of a first electromagnet, and scan elements 250 and 252 are magnetic polepieces of a second electromagnet. As previously noted, the magnetic polepieces of each electromagnet are vertically spaced for horizontal beam scanning. The beam scanning apparatus of FIG. 8 further includes a system controller 260, a scan signal generator 262 and a scan signal controller 264. System controller 260 receives beam parameters selected by a user and provides control signals to scan signal generator 262 and scan signal controller 264. Scan signal generator 262 generates scan signals, which may be scan voltages in the case of an electrostatic scanner or a scan current in the case of a magnetic scanner. Scan signal controller 264 provides scan signals to first scan elements 240 and 242 and second scan elements 250 and 252. Scan signal generator 262 and scan signal controller 264 constitute a scan generator 266. The scan signals provided to first scan elements 240 and 242 and to second scan elements 250 and 252 are individually controlled. Thus, scan signal controller 264 may vary the scan signals provided to first scan elements 240 and 242 and to second scan elements 250 and 252 between zero and maximum values to achieve a desired result. In one example, the ratio of the scan signals supplied to scan elements 240 and 242 and to scan elements 250 and 252 may be adjusted so as to control the position of scan origin 232. In another example, one set of scan elements, such as scan elements 240 and 242, may be grounded electrically when low energy ion beams are being utilized. The beam scanning apparatus of FIG. 8 may ether include a scan element positioner 270 connected to scan element 240, a scan element positioner 272 connected to scan element 242, a scan element positioner 280 connected to scan element 250 and a scan element positioner 282 connected to scan element 252. The scan element positioners 270, 272, 280 and 282 adjust 15 the positions of the respective scan elements under control of system controller 260. System controller 260 provides position control signals as a function of beam parameters such as species and energy. Scan element positioners 270 and 272 may move scan elements 240 and 242, respectively, with respect to ion beam 212 so as to adjust gap 244. Scan element positioners 280 and 282 may move scan elements 250 and 252, respectively, with respect to ion beam 212 so as to adjust gap 254. A first example of an electrostatic scanner for use in the ion beam apparatus of FIG. 8 is described with reference to FIG. 9. An electrostatic scanner 300 includes a first set of scan plates 310 and 312 spaced apart by a gap 314 and a second set of scan plates 320 and 322 spaced apart by a gap 324. Scan plates 310 and 320 are positioned on one side of ion beam 212 and are electrically isolated from each other. Scan plates 312 and 322 are positioned on the opposite side of ion beam 212 and are electrically isolated from each other. Scan plates 310 and 312 and scan plates 320 and 322 have a spacing that diverges in the downstream direction and produce electric fields suitable for scanning ion beam 212 in one dimension in response to scan voltages. A fan-shaped beam envelope 330 having a scan origin 332 increases in width in the downstream direction through scanner 300. Scanner 300 may be controlled by adjusting the positions of the scan plates in one or both sets of scan plates, by adjusting the relative scan voltages applied to the sets of scan plates, or both. For example, the spacing between scan plates 310 and 312 may be increased, and the spacing between scan plates 320 and 322 may be increased to accommodate low energy beams. Furthermore, the ratio of the scan voltages applied to scan plates 310 and 312 and scan plates 320 and 322 may be adjusted to control the position of scan origin 332 as the spacing between scan plates is adjusted. In particular, the scan voltages applied to upstream scan plates 310 and 312 are increased relative to the scan voltages applied to downstream scan plates 320 and 322 as the spacing between scan plates is increased. It will be understood that a wide dynamic range and a high degree of flexibility can be obtained by adjusting the positions of the scan plates in one or both sets of scan plates and by adjusting the relative scan voltages applied to the sets of scan plates. Adjustment of scan plate position and adjustment of relative scan plate voltages may be utilized separately or in combination. A second example of an electrostatic scanner for use in the ion beam apparatus of FIG. 8 is described with reference to FIG. 10. An electrostatic scanner 400 includes a first set of scan plates 410 and 412 separated by a gap 414, a second set of scan plates 420 and 422 separated by a gap 422 and a third set of scan plates 430 and 432 separated by a gap 434. Scan plates 410, 420 and 430 are positioned on one side of ion beam 212, and scan plates 412,422 and 432 are positioned on the opposite side of ion beam 212. The scan plates have a spacing that diverges in the downstream direction and produce electric fields suitable for scanning ion beam 212 in one dimension. A fan-shaped beam envelope 440 having a scan origin 442 increases in width in the downstream direction. As described above, the spacing between the scan plates in one or both sets of scan plates may be adjusted, and the relative scan voltages applied to the sets of scan plates may be adjusted to achieve a desired operation. For high energy operation, the scan plates are positioned with small spacing, and all scan plates of the same polarity are connected together. For low energy operation, the spacing between scan plates is increased, allowing a relatively large diameter ion beam to pass. Scan plates 410 and 412 and scan plates 430 and 434 are electrically grounded (zero scan voltage), and only scan plates 420 and 422 are used. By appropriate choice of scan plate geometry, the scan origin position for high energy and low energy operation may be the same. That is, the scan origin position for scan plates 420 and 422 with a relatively large spacing may be the same as the scan origin position for scan plates 410, 412, 420, 422, 430 and 432 with a relatively small spacing. It may be observed that the effective length of scanner 400 is reduced when one or more sets of scan plates is grounded. This reduction in effective length of the scanner serves to lessen the space charge forces that reduce beam transmission to the wafer. A preferred embodiment uses only electrically grounded or negatively biased scan plates for positive ion beam scanning at low energy. This minimizes space charge forces on the beam and provides, with large plate spacing, high beam transmission to the wafer. Such space charge forces have the undesired effect of increasing the beam size, which in turn can reduce the transmission of the beam to the wafer. While there have been shown and described what are at present considered the preferred embodiments of the present invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the invention as defined by the appended claims.
	claims	1. A method of treating a workpiece having an internal cavity with an interior surface, the method comprising:positioning the workpiece in a charged particle beam processing system configured to produce a charged particle beam;positioning a beam deflector inside the internal cavity of the workpiece;exposing the workpiece to said charged particle beam; andre-directing said charged particle beam toward the interior surface of the workpiece using a beam deflector surface of said beam deflector. 2. The method of claim 1, wherein said positioning the workpiece in said charged particle beam processing system further comprises:positioning the workpiece in a gas cluster ion beam (GCIB) processing system configured to produce a GCIB. 3. The method of claim 2, wherein the workpiece is a tubular workpiece, and positioning the workpiece in the GCIB processing system comprises:positioning said tubular workpiece within said GCIB processing system. 4. The method of claim 2, wherein the workpiece is an accelerator member, and positioning the workpiece in the GCIB processing system comprises:positioning said accelerator member within said GCIB processing system. 5. The method of claim 2, wherein the workpiece is a waveguide member, and positioning the workpiece in the GCIB processing system comprises:positioning said waveguide member within said GCIB processing system. 6. The method of claim 2, further comprising:adjusting the position of the workpiece relative to said GCIB. 7. The method of claim 2, further comprising:adjusting the position of said beam deflector relative to the workpiece. 8. The method of claim 7, wherein adjusting the position of said beam deflector further comprises:translating said beam deflector relative to the workpiece or rotating said beam deflector relative to the workpiece or a combination thereof. 9. The method of claim 2, wherein re-directing said GCIB comprises:electrically biasing said beam deflector such that said beam deflector surface of said beam deflector electrostatically deflects said GCIB toward the interior surface. 10. The method of claim 2, further comprising:disposing a shield member between said beam deflector and the interior surface of the workpiece, andcommunicating said GCIB from said beam deflector surface to the interior surface through an aperture in said shield member. 11. The method of claim 10, further comprising:controlling the temperature of said shield member. 12. A processing system configured to treat a workpiece having an internal cavity with an interior surface, said processing system comprising:a vacuum vessel;a charged particle beam source disposed in the vacuum vessel, said charged particle beam source configured to produce a charged particle beam;a workpiece holder configured to support the workpiece inside said vacuum vessel for treatment by said charged particle beam;a beam deflector disposed in said vacuum vessel, said beam deflector including a beam deflector surface; anda positioning system mechanically coupled with said beam deflector, said positioning system configured to position said beam deflector surface of said beam deflector inside the internal cavity of the workpiece, and said positioning system configured to move said beam deflector relative to the internal cavity of the workpiece so that said beam deflector surface intercepts and re-directs said charged particle beam toward the interior surface. 13. The processing system of claim 12, wherein said charged particle beam source comprises a gas cluster ion beam (GCIB) source configured to produce a GCIB. 14. The processing system of claim 13, wherein said beam deflector comprises:an arm member configured to extend into the internal cavity of the workpiece, said arm member carrying the beam deflector surface; andan electrical bias system electrically coupled to said arm member, said electrical bias system configured to electrically bias said arm member so that said GCIB is electrostatically re-directed by said beam deflector surface toward the interior surface of the workpiece. 15. The processing system of claim 14, wherein said positioning system is configured to adjust the position of said beam deflector surface relative to the interior surface and said GCIB by translating said arm member relative to the workpiece or rotating said arm member relative to the workpiece or both. 16. The processing system of claim 14, further comprising:a shield member disposed between said arm member and the interior surface, said shield member including an aperture positioned to communicate said GCIB from said beam deflector surface to the interior surface. 17. The processing system of claim 16, further comprising:a temperature control system coupled to said shield member, said temperature control system configured to cool or heat said shield member. 18. The processing system of claim 14, wherein said source is an inert source or a reactive source. 19. The processing system of claim 14, further comprising:a controller electrically coupled to said GCIB processing system, electrically coupled to said workpiece holder, electrically coupled to said electrical bias system, and electrically coupled to said positioning system, said controller configured to coordinate the operation of said GCIB processing system, said workpiece holder, said electrical bias system, and said positioning system according to a process recipe for treating the interior surface of the workpiece. 20. A beam deflector for use in a gas cluster ion beam (GCIB) processing system to treat a workpiece having an internal cavity with an interior surface, said beam deflector comprising:an arm member including a beam deflector surface; anda positioning system mechanically coupled with said arm member, said positioning system configured to position said arm member such that said beam deflector surface is inside the internal cavity of the workpiece, and said positioning system configured to move said arm member relative to the internal cavity of the workpiece so that said beam deflector surface intercepts and re-directs said GCIB toward the interior surface. 21. The beam deflector of claim 20, further comprising:an electrical bias system electrically coupled to said arm member, said electrical bias system configured to electrically bias said arm member so that said GCIB is electrostatically re-directed by said beam deflector surface toward the interior surface of the workpiece. 22. The beam deflector of claim 20, wherein said positioning system is configured to adjust the position of said beam deflector surface relative to the interior surface by translating said arm member relative to the workpiece or rotating said arm member relative to the workpiece or both. 23. The beam deflector of claim 20, further comprising:a shield member between said arm member and the interior surface, said shield member including an aperture positioned to communicate said GCIB from said beam deflector surface to the interior surface.
	summary
	abstract	An X-ray optical system for small angle scattering has a parabolic multilayer mirror and, so that switching to other X-ray incident optical systems for X-ray analysis can be easily performed. A parabolic multilayer mirror, an optical-path selecting slit device, a small-angle selecting slit device and a Soller slit are arranged between an X-ray source and a specimen-side slit. An X-ray beam having passed through the first aperture of an aperture slit plate is interrupted by the optical-path selecting slit. An X-ray beam having passed through the second aperture of the aperture slit plate is reflected at the reflecting surface of the multilayer mirror to become a parallel beam. This parallel beam passes through an aperture of the optical-path selecting slit device. The beam width is restricted by a narrow slit of the small-angle selecting slit device.
043495060	summary	A tokomak magnetic confinement fusion reactor confines a plasma within a toroidal plasma region by the use of a group of field coils that each encircle the plasma region. When the plasma, which may consist of deuterium and tritium, is "ignited," the plasma generates heat by nuclear fusion. Some of the heat escapes the plasma region and may be used to generate electricity. Successful operation of the reactor requires that sufficient heat escape to prevent such a high plasma temperature that the plasma becomes magnetohydrodynamically unstable and causes complete loss of plasma. At the same time, excessive heat should not escape from the plasma that could quench the fusion reaction. A mechanism is required to control heat loss from the plasma to maintain it at a desired operation point. A major source of heat loss from the plasma arises from ion heat conduction due to ripple in the toroidal magnetic field that confines the plasma. Toroidal field ripple is the amount of variation of the toroidal magnetic field as measured along a circular path extending along the toroidal plasma region. The principal contribution to field ripple is the geometrical arrangement of the field coils which encircle the toroidal plasma region, and arises because of the spacing between of the outer legs of the field coils from one another. It is generally desirable to enable operation of the reactor with minimal field ripple to minimize heat losses during starting up of the reactor. A mechanism which enables controllable variations of magnetic field ripple, and which does not require large amounts of additional space within the already-filled space of typical magnetic confinement reactors, would be of considerable value. OBJECTS AND SUMMARY OF THE INVENTION One object of the present invention is to provide an apparatus for controlling the energy state of the plasma in a magnetic confinement fusion reactor. Another object is to provide an apparatus for controlling magnetic field ripple in a tokamak type of fusion reactor. Another object is to provide an apparatus for controlling the heat flow out of magnetic confinement fusion reactors. Another object is to decrease the ripple in a magnetic containment fusion reactor during startup, and then to increase the ripple to enhance heat propagation from the plasma during normal operation. Another object is to provide a method for controlling the energy state of a magnetic confinement fusion reactor. In accordance with one embodiment of the present invention, an apparatus is provided for controlling the plasma energy state in a tokamak-type fusion reactor, which requires minimal additional space within the reactor. The apparatus includes a magnetic shield structure lying radially between the plasma region and the toroidal field coils of the reactor, with the shields constructed of a magnetic material which has a temperature-dependent saturation magnetization. The apparatus also includes a mechanism for controlling the temperature of the shields, to thereby vary their influence on the magnetic field ripple in the reactor and therefore the heat loss from the plasma. The shield can include primary shield sectors lying directly between the outer leg of each toroidal field coil and the plasma, so that the magnetic ripple produced by the primary sectors counters the ripple produced by the spaced toroidal field coils. The range of values of ripple achievable can be increased by means of additional secondary magnetic shield sectors placed in the spaces between the primary shield sectors. An entire shield structure which includes the primary and secondary shields, is a largely self supporting keystoned shell. In optimal designs, the attraction between adjacent magnetic shield sectors overcomes the outward force due to radially adjacent toroidal field coils, so that a relatively modest net inward force is created which keeps the sectors under compression. Temperature control of the shields can be produced by heat transfer fluids, such as cold water for rapidly cooling the shields and steam or pressurized hot water for heating them. The novel features of the invention are set forth with particularity in the appended claims. The invention will best be understood from the following description read in conjunction with the accompanying drawings.
	abstract	A composition of matter includes water, at least one acid, at least one surfactant, at least one fluoride salt, and ammonium nitrate. A method of decontaminating a surface includes exposing a surface to such a composition and removing the composition from the surface. Other compositions of matter include water, a fatty alcohol ether sulfate, nitrilotriacetic acid, at least one of hydrochloric acid and nitric acid, sodium fluoride, potassium fluoride, ammonium nitrate, and gelatin.
	claims	1. A portable, versatile, self supporting and weight bearing means and system for construction of Portable Nuclear Radioactive Fallout Protection Shelters & Preservation and storage of Potable Water Storage that effectively prevents nuclear radioactive rays (more technically referred to as electromagnetic radiation that includes X-rays and gamma rays) from penetrating through water filled jugs that comprise walls, barriers, and shelters, said means comprising:a plurality of stand-alone interlocking jugs,each jug comprising a plurality of individual jug design features that includes a plurality of male studs and female slots that fit snugly into and around the recessed female slots and the male studs, respectively, of jugs of the same design when mated with one another, a protruding handle on one side that fits snugly into a recessed handle port of a jug of the same design when the jugs are mated with one another, and protruding watertight fill spouts that fit snugly into the recessed female slots of jugs of the same design when mated with one another. 2. The system of claim 1 wherein the system effectively prevents nuclear radioactive rays from penetrating through the walls, barriers, and shelters means that in addition to the jugs being filled with water, such is accomplished by the overlapping stacking and the interlocking means of assembling three containers abreast totaling a thickness totaling 36″ that supplies the necessary thickness of water to be an effective barrier to shield occupants of the shelter from radioactive rays while also greatly enhancing the strength and weight bearing capacity of barrier walls and completed shelters. 3. The system of claim 1 wherein the jugs are placed to form walls inside an existing structures that is either above or partially under ground and has one, two, three, or four existing walls, with or without a ceiling, and is constructed of sundry kinds and thicknesses of materials that are known to act as a partial or sufficient barriers to radioactive rays depending upon their density and thickness. 4. The system of claim 1 wherein said jugs are manufactured using materials having properties selected from the group of being strong, resistant to natural and manmade environments, chemicals and substances, according to specifications necessary for specific installations and elements to which they will be subjected including being bullet proof. 5. The system relative to any of the preceding claims wherein the weights and measures of each individual “jug” are: volume—1 square foot, gallons of water=7.48, and weight, not including the weight of the jug,=62.30 pounds. 6. The system claimed in any of the preceding claims and further comprising support beams, and/or vertical support posts, of sufficient strength and plywood of sufficient thickness that will be placed across the top of barrier walls or shelters leaving enough space between any existing ceiling and the top of the beams and plywood for the placement of three layers of “jugs” or fewer layers if the existing ceiling offers protective radiation blockage that will make up the difference for less than three layers being applied. 7. The system of claim 6 relevant to beams and plywood used to support top jugs must be of sufficient length and strength to safely support the weight of the ceilings made of water-filled jugs; supporting vertical beams are also placed inside the shelter between the weight bearing walls depending upon the span between them. 8. The system of claim 7 further including guidelines to be supplied to builders relative to safe construction of shelters; all necessary instructions and safety warning labels to insure safe, easy and quick assembly by unskilled laborers including a statement stipulating that if the assembler doesn't understand the instructions supplied to enlist the aid of someone who does. 9. The system of claim 1, further comprising a plurality of additional jugs, in numbers mandated by the specifications of each barrier wall or shelter, arranged to form air vents using inner or outer wall “L” shaped arrangements that allow air to flow in and out as it follows the pathway of said “L” while not allowing radioactive rays from entering because radioactive rays i.e. gamma and X-ray travel only in straight lines from their source. 10. The system of claim 1, further comprising a plurality of additional jugs, in numbers mandated by the specifications of each barrier wall or shelter, arranged to form maze entrances, “L” shaped arrangements that allow easy entrance and exit of people into and from sheltered areas while not allowing radioactive rays from entering because radioactive rays i.e. gamma and X-ray travel only in straight lines from their source. 11. The system of claim 4, wherein the jugs are color coded or marked to indicate the material from which they are formed. 12. The system of claim 4, wherein the jugs are manufactured from new materials. 13. The system of claim 4, wherein the jugs are manufactured from recycled materials. 14. The system of claim 4, wherein the jugs are manufactured by blow molding.
	summary
	abstract	The present specification discloses a beam chopping apparatus, and more specifically, a helical shutter for an electron beam system that is employed in radiation-based scanning systems, and more specifically, a beam chopping apparatus that allows for variability in both velocity and beam spot size by modifying the physical characteristics or geometry of the beam chopper apparatus. The present specification also discloses a beam chopping apparatus which provides a vertically moving beam spot with substantially constant size and velocity to allow for substantially equal illumination of the target. In addition, the present specification is a beam chopping apparatus that is lightweight and does not cause an X-ray source assembly employing the beam chopper to become heavy and difficult to deploy.
052971759	claims	1. An assembling machine for nuclear fuel assembly comprising: a base, formed in a plate shape, which is arranged in an inclined manner to extend in an inclined direction; a plurality of supporting posts, disposed linearly on the base along with its inclined direction, each of which supports a supporting grid, each supporting grid including at least one grid cell, and wherein said plurality of supporting posts support said supporting grids such that said at least one grid cell is directed along the inclined direction; a fuel magazine, provided at an upper portion of the base in its inclined direction, which holds a fuel rod along the inclined direction in a free-engaged state; a stopper, fixed in the vicinity of a lower edge portion of the fuel magazine in the inclined direction, which regulates a fall-down movement of the fuel rod; and a releasing mechanism which drives the stopper so as to release a regulation of the stopper applied to the fuel rod. an inclined base plate extending in an inclined direction and having a plurality of supporting posts disposed therealong, each supporting post supporting a supporting grid, each supporting grid including at least one grid cell, and wherein said supporting posts support said supporting grids such that said at least one grid cell has an opening extending in the inclined direction; a movable supporting plate including means for moving said supporting plate such that said supporting plate is disposed at a position above said inclined base plate; a fuel magazine disposed on said supporting plate, said fuel magazine having an open bottom end; a stopper disposed adjacent said open bottom end of said fuel magazine for regulating movement of fuel rods through said open bottom end toward said base plate; and a releasing mechanism for moving said stopper. 2. An assembling machine for nuclear fuel assembly as defined in claim 1 wherein said supporting posts are disposed on an upper surface of the base. 3. An assembling machine for nuclear fuel assembly as defined in claim 1 wherein said stopper is formed approximately in a plate-like shape and this stopper is arranged to be faced with a lower edge surface of the fuel magazine in the inclined direction. 4. An assembling machine for nuclear fuel assembly as defined in claim 1 or 3 wherein said releasing mechanism is constructed by a cylinder which moves the stopper in a direction crossing a moving direction of the fuel rod. 5. An assembling machine for nuclear fuel assembly as defined in claim 1 further including a rotating mechanism for rotating the base about an approximately horizontal axis which crosses approximately perpendicular to a moving direction of the fuel rod. 6. An assembling machine for nuclear fuel assembly as defined in claim 1 further including a rotating mechanism for rotating the fuel magazine about an approximately horizontal axis which crosses approximately perpendicular to a moving direction of the fuel rod. 7. An assembling machine for nuclear fuel assembly as defined in claim 6 wherein a regulating member for regulating a rotation angle of the fuel magazine is further attached to the base at a position which faces with the fuel magazine. 8. An assembling machine for nuclear fuel assembly as defined in claim 6 further including a vertical lifting mechanism which lifts up or down both of the rotating mechanism and the fuel magazine. 9. An assembling machine for nuclear fuel assembly as defined in claim 8 further including a mobile mechanism which moves the fuel magazine in a direction having a horizontal component. 10. An assembling machine for nuclear fuel assembly as defined in claim 1 wherein a regulating plate for avoiding the fall-down movement of the fuel rod inserted in the supporting grid is further located at a position facing with a lower surface of the supporting post which is located at the lowest position among the supporting posts. 11. The assembling machine of claim 1, wherein said base includes a base plate having said plurality of supporting posts disposed therealong, said base further including a separate support plate upon which said fuel magazine is disposed. 12. The assembling machine of claim 11, further including means for vertically lifting said support plate. 13. The assembling machine of claim 12, further including means for varying an inclination angle of said support plate, said means for varying an inclination angle disposed above said means for vertically lifting. 14. The assembling machine of claim 11, further including a fitting member for connecting said base plate to said support plate. 15. The assembling machine of claim 14, further including means for moving said fitting member. 16. An assembling machine for nuclear fuel assembly comprising: 17. The assembling machine of claim 16, further including first means for varying an inclination angle of said inclined base plate and second means for varying an inclination angle of said movable support plate.
	description	This application is a National Phase of PCT/EP2010/068611, filed Dec. 1, 2010, entitled, “NUCLEAR FUEL ROD AND METHOD FOR MANUFACTURING PELLETS FOR SUCH A FUEL ROD”, which claims the benefit of French Patent Application No. 09 58661, filed Dec. 4, 2009, the contents of which are incorporated herein by reference in their entirety. The invention relates to a new type of nuclear fuel rod. Applications targeted for this new type of nuclear fuel rod include nuclear Pressurised Water Reactors (PWR) and Gas-Cooled Fast Reactors (GCFR), called 4th generation reactors. For the purposes of this entire application, “nuclear reactors” refer to the normal sense of this term at the present time, namely power stations generating energy based on nuclear fission reactions using fuel elements in which fission reactions occur that release power in the form of heat, this power being extracted from elements by heat exchange with a coolant that cools the elements. For the purposes of this entire application, “nuclear fuel rod” refers to the official sense as defined for example in the Nuclear Sciences and Techniques dictionary, namely a small diameter narrow tube closed at its two ends, forming the core of a nuclear reactor and containing fissile material. This forms a “nuclear fuel pin”, for which the preferred term used in the description of this invention is nuclear fuel rod. The invention thus discloses a new design of nuclear fuel rods with improved thermomechanical behaviour during mechanical interactions between fuel pellets and the cladding. There are different types of fuel elements depending on operating conditions and reactor performances. So-called 3rd generation power stations, and particularly PWR reactors, use rod type fuel elements with a circular cross-section. The inventor has envisaged an improvement to a fuel element concept. He started by attempting to understand the design principles and identify the functional limits of all known fuel elements. The main functions that a fuel element has to perform are: the density of its fissile atoms must be compatible with neutron functioning conditions and the power density per unit volume of the reactive volume, it must transfer heat between the fuel material and the heat transporting fluid, it must confine solid and gas fission products released by the fuel during operation of the reactor. Fission reactions within the fuel generate solid and gas fission products that cause potentially significant swelling of the structure of the material. The swelling phenomenon, particularly gaseous, is activated by heat that also induces mechanisms by which fission gases are released outside the fuel material. Therefore the cladding of the fuel element needs to be capable of accommodating these deformations and gaseous releases from the fuel without losing its integrity. The density of fission reactions within the fuel is directly correlated to the power per unit volume to be evacuated to the coolant through the cladding. Therefore it is essential to minimise thermal resistance between the heat source and the coolant in order to limit maximum fuel temperature and effects induced by this heat flux; gradient in the materials and differential expansions between the fuel and the cladding. The density of fissile material in the reactive volume depends principally on the shape of the elements that limits their capability of being arranged in a given volume by aiming at a maximum filling ratio while maintaining the necessary permeability to the coolant to evacuate power generated by the elements with an acceptable pressure loss. Basic fuel elements conventionally encountered in nuclear installations may be classified into three types, specifically plate type element (all shapes), cylindrical type element slender along the direction of the axis (usually a circular or annular section) that forms an element of a rod, and a spherical type element, usually in the form of a small diameter particle (about a millimeter). Furthermore, composite fuel elements generated from spherical particles encased in an inert matrix exist in the three geometric forms mentioned above, namely balls, plates and compact shapes in high temperature reactors (HTR). Each of these three types of fuel elements combines different solutions to the problems that arise and a compromise has to be made between design choices for its operating domain. The operating domain of each fuel element is actually limited by the performances of the selected design. Thus, plates comprise cladding that behaves like shells with a very high slenderness (ratio between the free length of the shell and its thickness). Due to its ductility, the geometry of the cladding material adapts itself to the geometry of the central part of the fuel which means that the differential transverse deformations (swelling and expansion) in the fuel material and the cladding can be accommodated, at a very low stress level. However, this plate structure has a poor ability to constrain deformations imposed on it by the fuel in the direction of the thickness due to the very low stiffness of the cladding transverse to its plane. This freedom allows the fuel to deform anisotropically and preferentially in this direction. The structure is also very unstable in buckling in the case in which compression forces are applied in the plane of the structure, either globally or locally (for example at a hot point), particularly in cases in which the fuel core is not connected to the cladding or is only weakly connected to it. Good thermal contact between the fuel and the cladding is required to keep the fuel within a sufficiently low temperature range so that it does not release its gas fission products under any operating circumstances. Therefore, plate elements are only used for cold fuels, in other words within the temperature range in which the fuel material does not release its gases and at moderate levels of power per unit volume. Plate optimisation parameters for a targeted power per unit volume usually apply to the thickness of the plate and the quality of the fuel/cladding contact, control of corrosion of the cladding and non-degradation of its ductility properties during operation. The main failure modes of these elements are either related to a lack of the cladding ductility under imposed deformation (corrosion degradation or irradiation hardening), or an increase in the thermal resistance between the fuel and the coolant (for example resistive corroded zone on the cladding, decohesion between the fuel and the cladding with a clearance being formed by local buckling of the cladding) causing an increase in the fuel temperature and release of fission gases and internal pressure in the cladding building up causing failure by unstable deformation of the cladding. The cylindrical elements comprise for example cartridges used in graphite/gas reactors, rods used in pressurised water reactors (PWR) or pins in fast reactors (FR). There is a radial clearance inherent to the construction of these cylindrical elements between the fuel in the form of pellets and the cladding inside which the pellets are stacked, which allows accommodation of differential deformations between the fuel material and the cladding; this clearance is capable of at least compensating for differential expansions during the first power buildup of the element and the proportion of swelling of the fuel that cannot be resorbed by itself by creep and redensification on its internal cavities, in other words cavities composed of the central hole and its pores. The fuel material must also operate at a temperature at which it can activate these mechanisms for accommodation of its deformations. On the other hand, it releases some of its fission gases. A second expansion volume is formed in the cladding at the end of the stack of fuel pellets in order to limit the internal pressure in the element. The main optimisation parameters of these cylindrical elements are the initial radial clearance between the fuel and the cladding, in other words the radial clearance at assembly, the quality of the fluid making the thermal connection between the fuel and the cladding (gas seal or molten metal seal), the effective filling density of the fuel in the section of the cladding defined by the radial clearance, pores, voids such as the central hole and/or lenticular dishings at the longitudinal ends of the pellet, the stiffness of the cladding (thickness) and the mechanical properties (maximum strength and ductility) and behaviour laws (swelling and creep) of the cladding and fuel materials. The radial clearance between the pellet and the cladding full of gas and the thickness of the cladding form a radial thermal resistance that controls the heat transfer between the coolant and fuel pellets. The thermal resistance is variable during operation because there is a variation of the radial clearance and degradation of the conductivity due to the release of fission gases. This variation in the thermal resistance complicates control over the maximum fuel temperature, which is controlled by the fact that the fuel material must not reach its melting point under any operating situations. Furthermore, use of this type of element in a “pressure containment” implies the use of material capable of holding the element mechanically in place with no risk of sudden failure (instantaneous and/or delayed) under pressure. To achieve this, the circular section is usually adopted because it has the best resistance to pressure; thus in a situation of mechanical interaction between the fuel and the cladding, the cladding opposes high hoop stiffness by being in hoop tension, the fuel is then blocked in its two radial directions and only its axial direction is partially free, this partial freedom depending on the adhesion between the pellets and the cladding. This circumferential pressure applied by the cladding on the fuel activates its re-arrangement mechanisms on itself, in other words redensification on itself. Therefore the choice of the cladding material is of overriding importance because it must provide sufficient ultimate strength in the targeted operating temperature range, ductility in plasticity and thermal creep and sufficient toughness, typically more than 20 MPa. √m within a temperature range corresponding to the entire range in which fuel elements operate. Therefore limiting operating conditions of these elements (temperature and power per unit volume) are fixed by the choice of the cladding (instantaneous ultimate strength and creep strength as a function of the temperature) and the fuel material (melting temperature). The main residual failure mode associated with this type of element is the mechanical instantaneous interaction between the fuel and the cladding exceeding the deformation capability of the cladding, for example in situations in which reactor power rises to a higher level than the previous operating level or in an operating condition in which the fuel temperature does not activate its mechanisms of auto-accommodation of its own deformations or only activates them slightly. Finally, in spherical elements such as elements comprising particles used in high temperature reactors (HTR), different coating layers are successively deposited on a fissile core that must be centred. This is achieved by creating voids in the form of pores within the fissile core and in an intermediate layer called the “buffer” with very high porosity, and that maintains the initial continuity between the fissile core and the cladding layers. Differential deformations between the fuel and the cladding, in other words the coating layer, are accommodated by filling in the voids; during operation, progressive densification of the buffer under neutron flux releases a radial clearance that prevents strong mechanical interaction between the fissile core and cladding layers. Furthermore, free internal volumes in the cladding retain fission gases released by the fissile material; the spherical shape of the cladding is then well adapted to resist the internal pressure that builds up. Elementary particle optimisation parameters are essentially in the choice of the materials (nature, structure, properties and behaviour laws under neutron flux and temperature) and the thickness of the different layers. These spherical fuel elements are only used in high temperature thermal flux and gas cooled reactors (HTR). Their main residual failure mode corresponds to strong interaction between the fissile core and the cladding layers (creation of tension in imposed deformation of the cladding) that can cause failure of the confinement cladding; from this point of view, the worst shape of the cladding is spherical because it leaves no direction for deformation of the fuel material (beyond its maximum densification), to relieve interaction forces (creation of hydrostatic pressure in the internal volume of the cladding). This type of spherical fuel element is also used in miscellaneous composite forms diluting the particles with a very small content of the fissile material in the reactive volume of the reactor per unit volume, of the order of a few %, in a matrix through which heat is transferred to the coolant. Furthermore by design, the risk of a cladding failure at high values of nuclear combustion (or burnup) is reduced. Thus, considering the above, the inventor considered that each of the three types of fuel element has its own advantages that can summarised as follows: plates have good heat transfer and accommodation qualities when there is mechanical interaction between the fuel pellets and the cladding, cylindrical elements (rods) and spherical elements have good resistance to pressure from gas fission products. On the other hand, considering the above, it can also be seen that the currently used cylindrical type element (rod) has the major disadvantage that its thermomechanical behaviour when there is a mechanical interaction between the fuel pellets and the cladding may be uncontrollable. Therefore, the inventor sets himself the prime objective of improving the thermomechanical behaviour of rod type fuel elements in the presence of mechanical interaction between fuel pellets and the cladding, currently used in 2nd and 3rd generation reactors. These new elements could also be used for 4th generation gas fast reactors. A more general purpose of the invention is to propose a rod type fuel element that combines the advantages specific to the different types of existing fuel elements like those mentioned above, and that would make it possible to satisfy the following specification: 1/ reach fuel fractions per unit volume equal to fuel fractions used in existing rods with circular section, 2/ achieve optimum heat transfer from fuel pellets to the coolant throughout the life, and achieving values comparable to heat transfer with a plate (exchange preferably on 2 opposite faces), 3/ avoid the risk of a cladding failure by controlling the mechanical interaction between fuel pellets and the cladding. Another purpose of the invention is to propose a rod type fuel element for which the fabrication process is not completely foreign to the industrial facility that has been set up to fabricate current rod type fuel elements with a circular section. To achieve this, the purpose of the invention is a nuclear fuel rod extending along a longitudinal direction comprising a plurality of fuel pellets stacked on each other and a cladding made of a material transparent to neutrons surrounding the stack of pellets, in which in the section transverse to the longitudinal direction: the cladding is elliptical in shape and the inside surface has a major axis with length 2a and a minor axis with length 2b, each nuclear fuel pellet is generally elliptical in shape truncated at the ends of the major axis of the cladding, the minor axis of each pellet being of length 2b′ equal to length 2b of the minor axis of the inside surface of the cladding except for the assembly clearance j of the pellets in the cladding, the difference in length between half of the truncated major axis of the pellets and half of the major axis of the cladding (c-a) being very much larger than the assembly clearance. For the purposes of this invention, “very” much larger than the assembly clearance means a value larger than an assembly clearance such that void volumes can be arranged to enable the fuel to swell without any circumferential interaction with the cladding as explained below. To achieve the solution according to the invention, the inventor attempted to identify mechanical phenomena that occur in the case of uncontrolled pellet/cladding mechanical interaction, in other words in instantaneous mechanical interaction situations beyond the deformation capability of the cladding. These situations may occur for example when the power in the reactor builds up to a level greater than the previous operating power or in an operating condition in which the fuel temperature does not activate its re-arrangement mechanisms on itself, in other words auto-accommodation of its own deformations, or activates them only slightly. In these situations, an existing fuel rod with a circular section has very strong mechanical interaction between the pellets and the cladding. The solid circular pellets in these situations have a thermal gradient that decreases from their centre towards their periphery; in other words, the cold periphery of the pellet imposes a radial stiffness that forms a sort of hoop binding stiffness. Furthermore, since the pellet is only very slightly accommodating by itself, there is no radial flexibility. Thus in these situations, the cladding has a hoop binding stiffness called the membrane stiffness imposed by the larger proportion of radial deformations of the fuel pellet. In other words, hoop binding occurs in this radial interaction direction. The pellet then only has one possible direction of relaxation, namely the axial or longitudinal direction, which enables local creep towards the dishings formed for this purpose at the ends of each pellet. The inventor also reached the conclusion that the following solutions will have to be implemented if the thermomechanical behaviour of a fuel rod is to be improved in a situation with very strong pellet/cladding mechanical interaction: reduce the stiffness of the cladding by changing its hoop binding method, ovalling of the cladding in the case of a circular section. The mechanical radial pellet/cladding interaction has to be made non-axisymmetric. Therefore, an initially oval section has to be defined with a possible mechanical contact between the pellets and the cladding only in the direction of a small diameter and space has to be created to allow movement, in other words expansion of the fuel, between the pellets and the cladding in the direction of the major diameter, correspondingly reduce the stiffness of the cold periphery of the pellet by making it oval in shape which means that the interaction surfaces can be localised making them only orthogonal to the small diameter by stressing the pellet in an ovalling mode, create a non-axisymmetric thermal gradient of the pellet, by having a thermal gradient more like that of a plate cooled on two faces. A non-axisymmetric thermal gradient of the fuel can reduce the hoop stiffness of the cold periphery of a currently used pellet with a circular section, by creating hotter portions at the ends of the major axis of the oval pellet. This thermal effect contributes to the reduction in the ovalling stiffness that the pellet will have along its minor axis, create a larger volume of voids in the cross-section so that the fuel that swells and expands can re-arrange itself by creep in its own section without generating any other stress or pellet/cladding interaction. This re-arrangement by creep is only possible if these voids are adjacent to the hottest portions of the pellet and the reaction forces applied to the pellet during a pellet/cladding interaction act on these hottest portions, maintain the mechanical equilibrium of the cross-section of the rod to which external coolant pressure is applied. Under very strong pellet/cladding mechanical interaction conditions, the resulting ovalling stiffness must be sufficient to maintain the geometry of the cross-section in stable equilibrium. The inventor also proposes firstly to make the cross section of the fuel rod elliptical to improve its thermomechanical behaviour in situations of mechanical interaction between fuel pellets and the cladding. The inventor then attempted to understand other phenomena that occur in nuclear fuel elements during normal operation of the reactors in which they are used. In existing reactors such as pressurised water reactors, the rod type fuel elements are composed of circular cylindrical shaped fuel pellets stacked individually on each other and placed inside cladding in a tube longer than the stack, to leave expansion volumes necessary to limit progressive increase in pressure in the stack of fuel elements under the effect of release of fission gases, at the ends of the column. Heat transfer between fuel pellets and the coolant takes place radially through a thermal resistance composed of the radial clearance between the pellets and the cladding at assembly filled with gas at the beginning of life, and the thickness of the cladding. Controlling this thermal resistance throughout the life of the element guarantees that acceptable fuel temperature limits are respected. The inventor thus considered that the following factors have to be adopted for the design of new fuel rods: heat transfer through a radial gas seal calibrated at the beginning of life, free volumes formed in the direction transverse to the direction of heat transfer. Usual plate type fuel elements are capable of accommodating deformations imposed by the fuel through “ductility” of their cladding with very low stress in the cladding, while maintaining heat transfer in the direction of the deformation. The inventor thus believed that fuel elements have to be made very slender, in other words they need to have a high width to thickness ratio so that they can accommodate deformations imposed by the fuel in the direction of the thickness at a very low stress in the cladding. Consequently, the inventor reached the conclusion that a fuel rod with an elliptical section according to the invention must advantageously use the three solution factors mentioned above, in other words it must have: an elliptical cross-section with its major axis with length 2a and minor axis with length 2b with a slenderness factor of the section equal to a/b, the shape of the pellet should also be elliptical creating a radial clearance in assembly between the pellets and the calibrated cladding comparable to what already exists in standard rods with a circular cross-section, the presence of free volumes at the ends of the major axis of the pellet obtained by truncating said axis. The inventor thus arrived at the solution disclosed in the invention, namely pellets with an elliptical cross-section truncated along their major axis stacked individually on each other in an elliptically shaped cladding with a radial clearance formed during assembly along the non-truncated portion of the pellets, and fission gas expansion chambers at the truncated ends. The result obtained with this new rod cross-section is the targeted improvement in the thermomechanical behaviour under very strong mechanical interaction between the pellets and the cladding since: the interaction is limited to the portions of the pellet/cladding mechanical contact orthogonal to the minor axis of the cross-section enabling the cladding to accommodate deformations imposed by the pellet by reducing its ovality and thus only generating bending stresses within the thickness of the cladding located in its end portions along its major axis 2a, a temperature gradient in the pellets facilitating a more flexible mechanical behaviour of the pellet during interactions, the combination of the generally elliptical shape of the pellet and the presence of large gas seals at its major axis ends creates heat exchanges preferentially oriented along the direction of the minor axis with a hot core of the pellet extending along the major axis and the cold peripheral parts limited to portions in contact with the cladding. The mechanical stiffness that the pellet forms during an interaction in the direction of its minor axis will be very much reduced by the almost complete absence of an arch effect created by the cold peripheral portions of the pellet, the local resistance to heat exchange between the pellets and the cladding at the truncated ends of the pellet, in other words along the major axes, increases the temperature of surface portions of the pellet in this zone. Thus, in a mechanical interaction with the cladding, the fuel pellet is subject to compression essentially along its small diameter, the presence of a hot zone as far as its surface at the ends of the major axis, means that it can deform by creep preferentially along this axis. This degree of freedom in extrusion by creep towards the transverse end voids enables the pellet to accommodate its volume increases by deformation of creep preferentially along this direction, correspondingly minimising the deformation imposed by the mechanical interaction with the cladding along its minor axis. Those skilled in the art will attempt to achieve geometric stability of the elliptical section of the rod under the action of pressure forces external to the coolant applied during normal operation of a reactor in which the rods according to the invention are used, by adjusting the stiffness parameters applied by the fuel pellet to oppose flattening of the cross section. These parameters can be defined as follows: the slenderness factor of the cross-section (ratio between the major and minor axes) controls the thermal properties of the pellet and therefore its stiffness to compression along its minor axis, the dimensions of the transverse end cavities along the major truncated axis c of the pellet control the temperature and therefore the creep deformation rate of the pellet along this direction (stiffness against extrusion towards the cavities partly determining the stiffness of the pellet to compression along its minor axis). Therefore the new rod geometry proposed by the invention gives geometric stability of the cross-section guaranteeing control over the gradient and heat exchanges of the pellet during normal operation while enabling accommodation of deformations imposed by the pellet onto the cladding under a mechanical interaction situation by adjusting the slenderness factor of the section and by the design of truncation of the pellet and therefore dishings at the ends, which minimises stresses in the cladding due to the distribution of imposed deformations between the pellet and the cladding and due to the way in which the cladding is stressed in bending by ovalling. Preferably, the assembly clearance j of the pellets in the cladding over the length of the truncated major axis c is less than or equal to 10% of the length of the major axis 2a of the cladding. When the rod according to the invention is designed for a pressurised water reactor (PWR), the cladding is preferably made of a zirconium alloy or an M5 alloy (ZrNbO), and the fuel pellets are preferably made of ceramic materials such as UO2, (U, Pu)O2, or a mixture based on uranium oxide and retreated plutonium oxides. When the rod according to the invention is intended for use in a gas-cooled fast reactor (GCFR), the cladding is preferably made of a refractory or semi-refractory metallic material, for example like Vanadium-based alloys or a ductile ceramic, for example such as MAX-phases of the Ti3SiC2 type, and the fuel pellets are preferably made of ceramic materials like (U, Pu) C, (U, Pu)O2. The invention also relates to a nuclear fuel assembly comprising a plurality of fuel rods like those described above and arranged together in a lattice. The invention also relates to cladding made of a material transparent to neutrons extending along a longitudinal direction and with an elliptical section transverse to its longitudinal direction. The invention also relates to a nuclear fuel pellet that extends along a longitudinal direction and with a generally truncated elliptical shape with a truncated major axis in the section transverse to its longitudinal direction. The invention also relates to a method of manufacturing a fuel pellet with height H along its longitudinal direction and with a generally truncated elliptical shape with a truncated major axis with length 2c and a minor axis with length 2b′ in its section transverse to the longitudinal direction, in which the following steps are performed: prepare the fuel powder in the so-called pelleting step, compress the fuel powder on the edge of the raw pellet, in a set of dies with height H and with a truncated elliptical cross section with a major length 2c and a minor length 2b′, sinter the compressed fuel pellet. Note that the term “raw pellet” means a pellet that has not been sintered. Advantageously, the H/(2c) ratio between the height H and the major length 2c is equal to at least 1.2. Thus, the new fuel rod geometry disclosed according to the invention also enables potential improvements in terms of fabricating the fuel rods. The truncated elliptical shape of the cross-section of the fuel pellets means that the two improvements in the manufacturing method described above can be envisaged as formulated differently below: concerning the pellet compression method: the new shape of the pellets means that the compression axis could be along the direction of the minor axis of the elliptical section (instead of a compression axis along the axis of the cylinder as it is for known pellets with a circular section). This new compression method can give better control over uniformity of the compression density and therefore the geometry of the sintered pellet, elimination of grinding to adjust the pellet diameter: the new elliptical shape of the cross-section of the rod means that the cladding is forced into contact onto the faces of the pellet (orthogonal to the minor axis) due to the effect of external pressure the first time that the coolant temperature rises in the reactor. Therefore, the thermal properties of the pellet are insensitive to the initial assembly clearance between the pellets and the cladding. Thus, unlike the situation in the state of the art, there is no need to adjust the pellet dimensions since the geometric tolerances obtained by sintering become acceptable (particularly with the improvement in the compression method envisaged above). The invention also relates to a method of stacking fuel pellets in a cladding made of a material transparent to neutrons so as to make a nuclear fuel rod, in which as-sintered fuel pellets made directly using the fabrication process described above are stacked inside a generally elliptical shaped cladding in which the length of the minor axis of the inside surface is equal to 2b and is the same as the length 2b′ of the minor axis of the pellets except for the assembly clearance, the difference in length between half of the truncated major axis of the pellets and half of the major axis of the cladding (c-a) being very much larger than the assembly clearance j. For reasons of clarity, the longitudinal axes along which the pellets 6 and the cladding 2 and the rod 1 composed of these elements will extend, are all referenced XX′. Note that: dimensions a and b are inside dimensions of the elliptical cladding 2, dimensions A and B are outside dimensions of the elliptical cladding 2, dimensions a′ and b′ are applicable to a non-truncated pellet 6, dimension 2c is the major length of the fuel pellet 6 truncated according to the invention. FIG. 1 shows a nuclear fuel rod 1 according to the invention represented in its configuration ready for use in a nuclear reactor, in other words in the vertical position with pellets 6 near the bottom part as specified below. The rod 1 is composed of a cladding 2 made of zirconium alloy closed at each of its ends by an upper plug 3 and a lower plug 4. The inside of the cladding is essentially divided into two compartments, one 5 of which is in the top part forming a gas expansion chamber, and the other 6 houses the fissile column formed by the stack of nuclear fuel pellets 6, each of which extends along the longitudinal direction XX′ of the rod 1. In the stack shown, each pellet 6 has approximately the same height H. A helical compression spring 7 is placed in the expansion chamber 5 with its lower end bearing on the stack of pellets 6 and its other end bearing on the upper plug 3. This spring 7 holds the stack of pellets 6 in position along the longitudinal axis XX′ and “absorbs” longitudinal swelling of the pellets 6 during time, and it also prevents buckling of the cladding section in its ovalling mode. In other words, it prevents extreme ovalling of the cladding section. FIG. 1A shows a straight cross-section of the rod 1 in FIG. 1. Cladding 2 according to the invention has a constant thickness around its entire periphery and is generally elliptical in shape. More precisely, the inside surface 200 of the elliptical shaped cladding 2 has a major axis with length 2a and a minor axis with length 2b. The fuel pellet 6 also has a truncated elliptical shape at each end of the major axis of the cladding. In other words, the pellet 6 has a truncated major axis with length 2c and a minor axis with length 2b′. Note that the dimension c defines the distance of the truncation plane of the pellet 6 from its centre. A uniform radial assembly clearance j between the pellet 6 and the cladding 2 is defined on the elliptical sides of the pellet, in other words over the entire length 2c of the pellet. In other words, once fabricated and before use as a fissile material in a nuclear reactor, each fuel pellet 6 has a truncated elliptical cross-section in which the length of the half minor axis b′ is approximately equal to the length of half the minor axis b of the inside surface 200 of the cladding 2, except for the assembly clearance j. Free volumes or expansion voids 60 are thus located at the two ends of the truncated major axis of the pellet 6, in other words between the truncated edges 61 of the pellet 6 and the inside surface 200 of the cladding 2. Thus, the parameter settings for the cross section of the fuel rod 1 are expressed based on the characteristics of the pellet 6 defined as follows: its ovalling factor or slenderness factor “a/b′”, where a′=a-j, its truncation ratio “c/a”. The inventor considers that the slenderness factor a′/b′ should be equal to at least 1.5 in order to achieve satisfactory thermal behaviour, typically values for a plate as disclosed in application WO2007/017503. It would be possible to use the rod 1 with an elliptical section according to the invention in two categories of nuclear reactors functioning with a core coolant maintained under higher pressure than the fuel elements. The first targeted application is use specific to operating conditions in pressurised water reactors (PWR). The rod can then a priori be made from the same constituent materials as those used for the design of existing standard fuel elements, such as rods with a circular section like those known at the present time; zirconium alloys or an M5 alloy (ZrNbO) for the cladding and UO2 ceramic or a mixture based on uranium oxide and retreated plutonium oxides for the fuel pellets. The second targeted application is use specific to gas-cooled fast reactors (GCFR), conditions under which cladding temperatures are high within the range from 300° C. to 900° C. and the fast neutron fluence is high. The constituent materials used to make the rod can then be refractory or semi-refractory metal such as Vanadium based alloys or ductile ceramic, like MAX-phases of the Ti3SiC2 type for the cladding and ceramic (U, Pu) C or (U, Pu) O2 for the fuel pellets. One particular embodiment of a rod with an elliptical section according to the invention is described below. In this embodiment, the rod 1 is designed to satisfy operating conditions of a standard pressurised water reactor (PWR). The geometries, materials and operating conditions of a standard PWR reactor used for reference purposes are as follows: Dimensions of a rod with known circular section: Cladding: outside diameter Dext=9.5 mm, inside diameter Dint=8.36 mm, Fuel pellets: diameter=8.2 mm, Materials: Cladding made of M5 alloy, UO2 fuel pellets, Operating Conditions: Temperature at the outside surface of the cladding, T=342° C., Coolant pressure P=155 bars, Power per unit volume of the fuel=320 W/cm3, Burnup rate=60 000 MWd/t. Based on these reference data for a rod with a known circular section, the inventor proposes the following dimensions for a new elliptical rod according to the invention: section of the pellet the same as a pellet with standard circular section; ovality factor a′/b′=1.8; truncation ratio equal to c/a′=0.9, namely the following dimensions a′, b′, c as shown for rod 1: a′=5.61 mm; b′=3.115 mm; c=5.05 mm. cladding thickness 0.57 mm equal to the thickness of the standard section cladding; radial assembly clearance equal to the radial assembly clearance between the pellets and the cladding in a rod with a standard circular section in which j=0.08 mm (this assembly clearance j between pellets 6 and cladding 2 in the rod according to the invention is measured along the minor axis b of the ellipse in which the dimensions of the elliptical section of the cladding are as follows: large inside diameter 2a=5.69 mm; small inside diameter 2b=3.195 mm; large outside diameter 2A=6.26 mm; small outside diameter 2B=3.765 mm. In comparison with the reference geometry of a rod with a standard circular section for a pressurised water reactor (PWR), the total section of the rod 1 with an elliptical section according to the invention is increased by the order of 4.4% and the area of the fuel occupies about 92.5% of the cladding. Thus, the total void j, 60 composed of the initial radial assembly clearance j between the pellets 6 and the cladding 2 and by truncations 61 of the ends of the pellet 6 (void space 60 between truncated edges 61 and the inside surface of the cladding 20) represents about 7.47% of the internal cross-section of the cladding equal to Πab. There are no particular fabrication problems in making cladding 2 with an elliptical section. A different compression operation could also be envisaged to make the pellet 6. The slenderness a′/b′ considered in the invention equal to 1.8 with the dimensions given above, means that it would be possible to envisage compression of each pellet orthogonally, in other words along the direction of the minor axis a′ of its elliptical section or in other words on its edge delimited by its height H, instead of along its cylindrical axis XX′ as is done at the moment for rods with a circular cross section. The elliptical shape of the cladding also means that as-sintered pellets can be put in the cladding. The inventor believes that compression of the fuel pellet along its edge H must result in less dispersion of thicknesses of sintered pellets due to better uniformity of the compression densities within the pellet. As mentioned above, during operation of a PWR reactor, the elliptical shape of the cladding will mean that contact will be made between the faces of the pellets and the cladding (except at the end voids 60), in other words over the entire length 2*c, as soon as the coolant is pressurised. Even at the beginning of its life, the thermal properties of the pellets 6 no longer depend on the initial assembly clearance between the pellets 6 and cladding 2. The analysis of the thermal and thermomechanical behaviour of a rod 1 with an elliptical section according to the invention under PWR reference operating conditions was made by digital simulation using the CAST3M finite element program. This simulation was based on the assumption of constant fuel power throughout the life, a variation in the physical properties of M5 cladding materials and the UO2 fuel as a function of the temperature, the viscoelastic behaviour of the cladding material and the fuel (thermal and irradiation creep), swelling of materials under irradiation and a release rate of fission gases produced by the fuel of the order of 6% (which is a typical value found for rods with circular section for burnup of 60000 MWd/t). The results show the following for operation with this burnup rate of 60000 MWd/t: good control of fuel temperatures throughout its life; as soon as power is first generated, the radial clearance j between the pellets 6 and the cladding 2 closes and the maximum fuel temperature changes between a life start temperature of 683° C. to a life end temperature of 904° C. This change is due to a deterioration in the conductivity of the fuel by irradiation and presence of fission gases released by the fuel that degrade the heat exchange coefficient between the pellets 6 and the cladding 2. Due to the elliptical shape of the section, since the size of the pellet along the direction of the heat exchange (its small diameter) is smaller than the diameter of a circular pellet with the same surface area, the maximum temperature inside the fuel is lower than in a rod with a standard circular section. good global thermomechanical behaviour on the cross-section of the fuel pellet. This provides control over deformations of the section, since creep of the elliptical section of the fuel pellet is controlled by the surface temperature achieved due to the thermal resistance formed by the voids 60 created at the truncated ends 61 of the pellet. At the start of life, the local temperature increase (at the edges 61) is 136° C. higher than the temperature of the exchange surfaces (at portions 62) in contact with the cladding. At the end of life, the local temperature increase (between the truncated edges 61 and portions 62) is 220° C. This thermal equilibrium that controls the mechanical stability of the section is obtained by optimising the geometric parameters of the section, namely its ovality factor a/b and its truncation ratio c/a. Obviously, these parameters depend on each use and their optimisation depends on operating conditions of each fuel pellet and the mechanical properties of the component materials, and particularly thermal creep and irradiation behaviour laws. Good thermomechanical behaviour also results in good control over the internal pressure in the rod created by fission gases released by the fuel. The presence of voids 60 at the truncated ends 61 of the pellet forms additional expansion chambers that are not present in a rod with a standard circular section. Finally, the good thermomechanical behaviour creates mechanical interaction between the pellets 6 and the cladding 2 that bends the cladding. The induced bending stresses are located in the end sectors 200 of the cladding facing the truncations 61 of the fuel pellet. Creep in the cladding 2 limits these stresses to values of less than 100 MPa during operation. Therefore, the cladding is actually only stressed in bending on its ovalling mode; it is not subject to hoop binding mode as can happen with rod cladding with a standard circular section. The deformations in the section of the fuel pellet 6 are adapted mainly by creep extrusion towards the end voids 60 under the action of ovalling stiffnesses of the truncated elliptical section of the pellet that thus oppose expansion and swelling deformations. Other improvements and modifications could be envisaged without going outside the framework of the invention: for application in pressurised water reactors (PWR) currently in service, it would be possible to use standard materials, namely a zirconium alloy cladding 2 and UO2 fuel pellets 6, or a mixture based on depleted uranium oxides and retreated plutonium oxides, also called MOx. Rod performances can be optimised by controlling creep behaviours of cladding materials and the fuel in the rod with an elliptical section according to the invention, for application in gas-cooled fast reactors (GCFR), the use of a ductile cladding is desirable from the range of ductile metallic and ceramic materials as described above.
	description	This application is a Continuation of application Ser. No. 10/734,247, filed on Dec. 15, 2003 now abandoned, and for which priority is claimed under 35 U.S.C. § 120; and this application claims priority of Application No. 0215935 filed in France on Dec. 16, 2002 under 35 U.S.C. § 119; the entire contents of all are hereby incorporated by reference. The present invention relates to a method and to a device for handling a pressurized water nuclear reactor upper internals guide tube. Pressurized water reactors comprise, inside a vessel, the nuclear reactor core which consists of assemblies of prismatic shape arranged with their axis vertical and, over the core, upper internals comprising, in particular, a collection of vertical guide tubes for guiding the rod cluster control assembly consisting of bundles of rods placed parallel to one another and containing a neutron-absorbing material. The nuclear reaction that produces the supply of heat transmitted to the heat transfer fluid consisting of pressurized water is controlled or shut down using rod cluster control assemblies that are introduced into the guide tubes of a fuel assembly arranged inside the array of fuel rods of the assembly, these guide tubes also constituting part of the framework of this assembly. The rod cluster control assemblies are moved in the reactor core in its vertical direction to control the nuclear reactor, as a function of the depletion of the enriched uranium of the pellets contained in the fuel rods and the variations in power demand from the grid. The movement of the rod cluster control assemblies in the axial direction of the guide tube of the fuel assemblies is performed by control mechanisms placed on the head of the reactor vessel containing the core. The guide tubes that guide the rod cluster control assemblies are each formed of an upper tube and of a lower tube which are connected to the upper support plate (PSTG) by assembly means comprising flanges attached to each other and fixed using screws. The upper tube of the guide tube is intended to be placed above the lower tube, above the upper support plate. The upper and lower tubes of the guide tube are internally equipped with guide plates secured to these tubes and arranged such that they are spaced apart in the axial direction of the guide tube. Each of these guide plates has guide openings for guiding the corresponding rod cluster control assembly. The lower tube at its bottom end has a flange equipped with two centring pins that serve to position the guide tube on the nuclear reactor upper core plate. The screws that pass through the flanges of the upper and lower tubes of the guide tubes serve to fix the guide tubes into the upper internals on the upper support plate. While the nuclear reactor core is shut down, the guide tubes are sometimes removed, either in order to replace them with new guide tubes, or to fit them with new centring pins. To do that, the guide tubes are extracted from the upper internals arranged in the bottom of the reactor pit, on a storage and maintenance stand. The operators work from a working platform situated over the water of the pit and each guide tube is equipped with a gripping and handling tool that allows the two tubes of each guide tube to be secured together to hold it together mechanically while it is being handled once the connecting screws that join these two tubes have been removed. For this, the gripping and handling tool enters the guide tube from above and passes through its entire height to bear against its underside. This tool in particular passes through the lower tube of the guide tube which comprises horizontal guide plates in its discontinuous guidance region and continuous guidance at its lower part. As a result, introducing the tool over the entire height of the guide tube increases the risks that this tool will catch on the guide plates. This risk therefore dictates that, on completion of the operations of handling and refitting the guide tubes, the interior of the guide tube and all the horizontal guide plates together with the continuous guide part be systematically inspected. In consequence, apart from the significant amount of time needed to introduce the gripping and handling tool, there also has to be added the time needed for the inspection. These operations are therefore expensive and any damage that might be caused could lead to the replacement or repair of the damaged elements. In addition, given the great length of the gripping and handling tool, it is not easy for the operators situated on the working platform to use, either for its assembly of the two parts of the guide tubes or for the operations of handling and of introduction into the guide tube. It is an object of the invention to propose a method and a device for handling a nuclear reactor upper internals guide tube that avoids the aforementioned drawbacks. The subject of the invention is therefore a method for handling a guide tube for the upper internals of a nuclear reactor arranged under water in a pit, the said guide tube comprising two independent tubes, an upper one and a lower one, in each of which there are fixed horizontal guide plates arranged such that they are spaced apart in the axial direction of the guide tube and comprising a central cavity and guide openings for guiding a rod cluster control assembly that controls the reactivity in the core of the reactor, in which method a gripper equipped at a first end with two opposed arms that can be moved between a retracted position and a deployed position and, at a second end, with a control member for controlling the said arms is introduced into the central cavity of the horizontal guide plates of the upper tube, characterized in that: the first end of the gripper is placed under one of the two upper guide plates of the lower tube, the arms are deployed by means of the control member, using this control member the two arms are applied under the said upper guide plate of the lower tube on the one hand and the second end of the gripper is applied to the upper end of the upper tube on the other hand, and the gripper is used to simultaneously raise the upper and lower tubes of the guide tube. According to another feature of the invention, the gripper is rotated about its longitudinal axis into a given position according to marks formed on the upper end of the upper tube when the first end of the gripper is placed under the second upper guide plate. Another subject of the invention is a device for handling a guide tube for the upper internals of a nuclear reactor arranged under water in a pit, the said guide tube comprising two independent tubes, an upper one and a lower one, in each of which there are fixed horizontal guide plates arranged such that they are spaced apart in the axial direction of the guide tube and comprising a central cavity and guide openings for guiding a rod cluster control assembly that controls the reactivity in the core of the reactor, the said device being formed of a gripper comprising a tubular body equipped at one end with two opposed arms that can be moved between a retracted position and a deployed position and, at a second end, with a control member for controlling the said arms, characterized in that the length of the tubular body of the gripper is greater than the distance separating the upper end of the upper tube and the first guide plate of the lower tube and less than the distance separating the said upper end and the third guide plate of the said lower tube. According to other features of the invention: the tubular body has, at its second end, a bearing piece for bearing against the upper end of the upper tube, the said bearing piece supporting the said control member, the said control member, first of all, deploys the arms then, secondly, brings these arms closer to the bearing piece, the bearing piece comprises, on its face in contact with the upper end of the upper tube, at least one elastic washer, the control member comprises a load-limiting spring and is connected to the arms by a screw-nut system. FIG. 1 schematically depicts a pressurized water reactor vessel denoted by the general reference 1. In the conventional way, inside the nuclear reactor vessel 1 is the core 2 consisting of fuel assemblies 3 of straight prismatic shape placed side by side in such a way that the longitudinal axes of the fuel assemblies are vertical. The reactor core 2 is arranged inside the lower internals of the reactor which in particular comprise the core baffle assembly 4. The upper internals 5 rest on the upper part of the core assemblies via an upper core plate 6. The upper internals 5 comprise a guide tube support plate 7 known as the upper support plate (PSTG) parallel to the upper core plate 6 constituting the lower part of the upper internals which part is produced in such a way as to fix the upper internals inside the vessel in which there is also suspended a casing containing the baffle assembly 4 and the core 2 of the reactor, at the lower end of which is fixed a lower plate for supporting the assemblies of the core. When the reactor is shut down for repair and for refuelling, the upper internals 5 are extracted from the reactor vessel 1 and placed on the storage stand 10 (FIG. 2), these upper internals 5 resting via the upper support plate 7 on the vertical supports of the stand 10 which themselves rest on the bottom 11 of the pit 12. This pit 12 of the reactor is filled with water to its upper level and the various operations are usually performed from a pit bridge arranged over the upper level of this pit 12. As shown in FIGS. 1 to 3, the upper internals 5 comprise guide tubes each denoted by the general reference 15, which are vertical and provide guidance to rod cluster control assemblies that control the reactivity in the reactor core, each rod cluster control assembly being formed of bundles of rods placed parallel to one another and containing a neutron-absorbing material. As depicted in FIGS. 2 and 3, each guide tube 15 comprises, above the upper support plate 7 of the upper internals, an upper guide tube 16 of circular cross section and, between the upper support plate 7 supporting the upper internals 5 and the upper core plate 6, a lower guide tube 17 with a roughly square cross section with rounded corners. Each of the lower tubes 17 is axially aligned with an upper tube 16 and these two tubes, 16 and 17 respectively, constitute a guide tube 15 for the upper internals 5 allowing a rod cluster control assembly that controls the reactivity to be moved vertically in the reactor core, this rod cluster control assembly being connected to a suspension and movement rod whose movement in the vertical direction is given by a mechanism 8 situated above the head 1a of the vessel 1 (FIG. 1). Between the support plate 7, the upper internals 5 and the upper core plate 6 there are placed, in addition to the lower tubes 17, spacer columns 9 that hold the upper core plate 6 away from the upper support plate 7 supporting the upper internals 5. As depicted in FIG. 3, the upper 16 and lower 17 tubes of each guide tube 15 are connected together by assembly means denoted by the general reference 20. In a conventional way, these assembly means 20 comprise an upper flange 21 secured to the upper tube 16 and a lower flange 22 secured to the lower tube 17 and which are attached to one another and assembled using screws 23. The upper tube 16 arranged above the support plate 7 contains discontinuous guide elements consisting of horizontal guide plates 24 of circular cross section, as shown in FIG. 4. These guide plates 24 are arranged spaced apart in the axial direction of the guide tube 15 and each comprises a central cavity 24a and radially directed openings 24b each opening at its inner end into the said central cavity. Each of the radially directed openings at its outmost end has a roughly circular opening for guiding the absorber rod of a rod cluster control assembly. The lower tube 17 of the guide tube 15 of roughly square cross section, placed between the upper support plate 7 supporting the internals 5 and the upper core plate 6, comprises an upper part in which the rod cluster control assembly has discontinuous guidance, like in the upper tube 16, via horizontal guide plates 25 as depicted in FIG. 5. Each horizontal guide plate 25 comprises a central cavity 25a and radially directed openings 25b opening at their inner end into the central cavity 25a of the said guide plate 25. The circular openings 25b provide guidance for the absorber rods in the same way as the openings 24b of the guide plates 24. The lower part of the lower tube 17 of the guide tube 15 constitutes a continuous guidance region in which elements for guiding the absorber rods of the rod cluster control assembly are fixed, which elements consist of continuous guide sleeves and of split tubes, not depicted. As shown in FIG. 3, the lower tube 17 of the guide tube 15 comprises, from top to bottom, a first horizontal guide plate referenced 25A, a second horizontal guide plate referenced 25B, a third horizontal guide plate referenced 25C and so on over the entire height of the first part of the lower tube 17. In the description that follows, the guide plate 25A will be known as the first upper guide plate 25A, the guide plate 25B will be known as the second upper guide plate 25B and the third guide plate 25C will be known as the third upper guide plate 25C. In the conventional way, the first upper guide plate 25A is positioned in a spot face formed on the upper face of the flange 22 and this guide plate 25A is fixed to the said flange 22 by screwing elements, not depicted, consisting, for example, of screws the heads of which are embedded in the thickness of the said guide plate 25A. The second upper guide plate 25B is fixed to the lower tube 17 by welding. To remove a guide tube 15 from the upper internals 5, the operators, having removed the fixing elements 23 on the upper support plate 7 supporting the guide tubes 15, use a handling device formed of a gripper denoted by the general reference 30 and depicted in FIG. 6. This gripper 30 is formed of a tubular body 31 equipped, at a first end, with two opposed arms 32 and, at a second end, with a control member 37 for moving the arms 32 between a retracted position and a deployed position, as will be seen later. In the exemplary embodiment depicted in FIG. 6, the control member 37 consists of a hexagon socket head 38 and is connected to the arms 32 by a screw-nut system 39 of known type. Each arm 32 comprises an end 32a mounted articulated at the end of the screw of the screw-nut system 39 and an end 39b mounted articulated on a link rod 33 which is itself mounted articulated at the end of the tubular body 31. This tubular body 31 is equipped at its opposite end to the arms 32 with a piece 40 intended to bear against the upper end of the upper tube 16 of the guide tube 15 to be handled, and this piece 40 supports the control member 37. The piece 40 is also equipped, on its face in contact with the upper end of the upper tube 16, with at least one elastic washer 41. Finally, the control member 37 is equipped with a spring 42 to limit the load when the screw-nut system 39 is tightened. In general, the length “1” of the tubular body 31 (FIG. 6) is greater than the distance “d1” separating the upper end of the upper tube 16 and the first guide plate 25A of the lower tube 17 (FIG. 3) and less than the distance “d2” separating the said first end and the third guide plate 25C of the said lower tube (FIG. 3). To remove the guide tube 15, the operators, for example using a pole, not depicted, introduce the tubular body 31 of the gripper 30 into the central cavity 24a of each horizontal guide plate 24 of the upper tube 16, the arms 32 being in the retracted position as shown in FIG. 7A. The elastic washer 41 of the bearing piece 40 rests against the upper end of the upper tube 16. Next, the operators use a motorized tool, not depicted, comprising a turning element that positions itself in the hexagon socket head 38 to turn the screw-nut system 39. First of all, the turning of the screw-nut system 39 causes the arms 32 to move into the deployed position (FIG. 7B), and then, secondly, causes these arms 32 to move closer to the bearing piece 40. Preferably and as depicted in FIGS. 7A and 7B, the arms 32 are applied against the first upper guide plate 25A of the lower tube 17 all the parts of which are rigid and which is connected to the lower tube 17 by screwing elements. The grip of the gripper 30 on the upper end of the upper tube 16 and against the upper guide plate 25A is limited by the spring 42. According to an alternative form depicted in FIGS. 8A and 8B, the end of the tubular body 31 carrying the arms 32 is placed under the second guide plate 25B of the lower tube 17 (FIG. 8A). As the screw-nut system 39 is turned, the arms 32 move first of all into a deployed position. In this case, the operator, having placed the arms 32 under the guide plate 25B and deployed these arms 32, turns the gripper 30 about its longitudinal axis into a position determined according to marks formed on the upper end of the upper tube 16. This turning has the purpose of bringing the arms 32 under a rigid region of the said guide plate 25B. Secondly, these arms 32 are applied against the second upper guide plate 25B, as shown in FIG. 8B. The gripper 30 therefore allows the upper 16 and lower 17 tubes to be secured together so as to mechanically hold the guide tube 15 together as it is handled. The gripper 30 has the advantage of being easy to manipulate on site by operators situated on the working platform of the stand, thus making the operations less tiresome for these operators. The time taken to introduce into the guide tube is reduced, which means that the intervention time is shorter. In addition, the risks of catching on the inside of the guide tube are reduced and the inspection of the interior of the guide tube after the intervention can be confined to the upper tube and, at most, to the first two guide plates of the lower tube, making it possible to reduce the inspection time. As a preference, the guide tube is handled by applying the arms of the gripper against the first upper guide plate of the lower tube, because the magnitudes of the forces applied to the fixing screws that secure this guide plate are known. Furthermore, this guide plate has the advantage of being removable, making it possible to envisage possibilities of removing it in order to perform an analysis and/or a replacement if the forces incurred are higher than the permissible forces.
058870440	summary	BACKGROUND OF THE INVENTION The secure and timely disposal of transuranic materials (primarily plutonium) has been the subject of intense debate in recent years. The two primary sources of transuranics are disassembled nuclear weapons and spent fuel from existing power reactors. Large quantities of weapons-grade plutonium currently exist in U.S. and C.I.S. weapons stockpiles which are to be dismantled in accordance with current arms reduction treaties. This material must be closely safeguarded to prevent its diversion for use in nuclear weapons. The weapons-grade material can be quickly put into a form which is not readily usable for nuclear weapons by diluting the material and introducing radioactivity, thus rendering it difficult to handle. However, this short-term "disposal" of weapons material does not remove the long-term proliferation risk, and such denatured material requires perpetual active safeguarding. Therefore, the only enduring solution is to actively safeguard the denatured weapons material in the short-term and eventually destroy the material. Even larger quantities of transuranics are contained in the spent fuel inventories of existing nuclear reactors. This material does not pose an immediate proliferation concern because it already exists in a dilute (transuranics constitute about 1% of the total heavy metal mass) and radioactive form. The current U.S. waste management strategy calls for direct disposal of the LWR spent fuel in a centralized repository. However, direct disposal of LWR spent fuel in a centralized repository is complicated by the presence of the transuranics, which dominate the long-term radiotoxicity of LWR spent fuel. Thus, from a waste management perspective it is desirable to process the LWR spent fuel to remove the transuranics and process the remaining waste material into a more stable form. Subsequent destruction of the separated transuranic material reduces its long-term radiological and proliferation hazards. Therefore, sufficient motivation exists for eventual destruction of the transuranics from both disassembled weapons and spent fuel: i.e., the reduction of proliferation and radiotoxicity hazards. Destruction by fission is the only means available to permanently destroy the transuranics. Although fission creates radioactive fission products which have a higher short-term hazard than the original fuel material, the fission products decay much more rapidly, so the long-term hazard is significantly reduced. Furthermore, the energy produced by the fission reactions can be converted to electrical power (the fission of 1MT of actinides yields enough energy to produce approximately 1GWe-year of electricity), and the sale of this power allows revenue recovery for the disposition activity. In all conventional fission nuclear reactor systems, the transuranic destruction rate is mitigated by in-situ production of Pu-239 (by U-238 neutron capture). The available range of destruction/production characteristics in metal-fueled cores allows a flexible transuranic management strategy. Conventional fast reactor cores maintain or even increase the transuranic inventory (conversion ratio of 1.0-1.3); this allows sustained power production from a fixed transuranic inventory. By removing fertile material and/or altering the neutron balance, the conversion ratio can be reduced. Core designs with conversion ratios between 0.5 and 1.0 have been investigated; further reductions in the conversion ratio would require transuranic contents greater than 30 weight percent, as previously investigated in the Integral Fast Reactor (IFR) metal fuels testing program. The partial burner core designs, with 0.5-1.0 conversion ratios, are referred to as conventional burner designs because they utilize conventional IFR metallic fuel alloys. Because the minimal conversion ratio of conventional burners is 0.5, they can achieve transuranic consumption rates of roughly half the maximum value (1/2.times.1 g/MW.sub.t d). To allow more rapid destruction of the transuranics, non-conventional metal fuel alloys are required; to achieve the maximum transuranic consumption rate of 1.0 g/MW.sub.t d, a non-uranium fuel form is required. Preliminary neutronic investigations of non-uranium core designs (called pure burners because they achieve the maximum destruction rate) have been discussed in R. N. Hill, D. C. Wade, E. K. Fujita, and H. Khalil, "Physics Studies of Higher Actinide Consumption in an LMR." International Conference on the Physics of Reactors Marseille, France, Apr. 23-27, 1990, p.1-83; R. N. Hill, "An Evaluation of Reactivity Coefficients for Transuranic Burning Fast Reactor Designs," Transactions of the American Nuclear Society, Vol. 65, p. 450 (1992); and GE Nuclear Energy, "Plutonium Disposition Study," GEFR-00919, May 1993. However, the fuel material design properties and behavior were not investigated in any detail. SUMMARY OF THE INVENTION Pu--Zr and Pu--Zr--Hf alloys are proposed for maximum Pu destruction in a metal-fueled advanced liquid metal reactor (ALMR). An assessment of the expected properties of Pu--28Zr indicate that the fuel alloy should have acceptable properties and irradiation behavior. In order to achieve the maximum destruction rate, the fuel alloy can have no U-238 as does the Integral Fast Reactor (IFR) U--Pu--Zr alloy. Hf is the alloying element which provides resonance capture and reduction in burnup swing normally provided by U-238. Incorporating Hf into the fuel alloy should have no adverse impact on thermophysical properties. However, sufficient Zr is required in a Pu--Zr--Hf alloy to maintain acceptable solidus temperatures and to mitigate possible Fuel Cladding Chemical Interactions (FCCI). A fuel element composed of a Pu--Zr--Hf fuel alloy injection cast into a Hf--Zr sheath and Na-bonded to HT9 cladding is one aspect of the invention. A thermal analysis for a Pu--28Zr-fueled subassembly in Experimental Breeder Reactor-II indicates that fuel temperatures during steady state operation or unlikely transients will not exceed the approximately 1090.degree. C. solidus temperature. Zr depletion and axial growth behavior are not expected to be of concern. The invention consists of certain novel features and a combination of parts hereinafter fully described, illustrated in the accompanying drawings, and particularly pointed out in the appended claims, it being understood that various changes in the details may be made without departing from the spirit, or sacrificing any of the advantages of the present invention.
060312416	claims	1. A method of operating a capillary discharge source in the approximately 11 nm to approximately 14 nm wavelength region comprising the steps of: (a) forming a discharge within a capillary source having a bore size of approximately 1 mm, and at least one radiating gas, with a discharge current of approximately 2000 to approximately 10,000 amperes; and (b) radiating selected wavelength regions between approximately 11 to approximately 14 nm from the discharge source. xenon. an oxygen containing molecule to provide oxygen as the one radiating gas. a buffer gas. approximately 0.1 to approximately 50 Torr. approximately 0.1 to approximately 20 Torr. a metal vapor radiating the selected wavelength regions. approximately 0.1 to approximately 20 Torr. lithium. lithium radiating the selected wavelength region between approximately 11 to approximately 14 nm; and helium as a buffer gas. (a) forming a discharge across a capillary source having a bore size of approximately 0.5 to approximately 3 mm, and at least one radiating gas, with a discharge current density of up to approximately 1,300,000 Amperes/cm.sup.2 ; and (b) radiating selected wavelength regions between approximately 11 to approximately 14 nm from the discharge source. a length of approximately 1 to approximately 10 mm. xenon. an oxygen containing molecule to provide oxygen as the one radiating gas. a buffer gas. approximately 0.1 to approximately 50 Torr. pre-conditioning interior bore surface walls of a capillary discharge source that operates in the ultraviolet region; and continuing the pre-conditioning until a selected impulse value is reached. a heat source. laser. focussing the laser within the bore; and operating the laser at a focussed intensity in the range of approximately 10.sup.7 to approximately 10.sup.11 Watts/cm.sup.2. an excimer laser, a Nd:Yag laser, and a Copper Vapor laser. less than approximately 20 Torr-.mu.s. initiating discharge current discharge pulses within the capillary with a second gas having a pressure range of approximately 1 to approximately 20 Torr. approximately 3000 pulses. a capillary constructed from a nonconducting and an insulating material; and at least one gaseous species inserted in the capillary, wherein the capillary is used to generate ultraviolet discharges. a metallic conductor on opposite sides of the capillary. quartz, saphire, aluminum nitride, silicon carbide, and alumina. a segmented bore of alternating conductive and nonconductive materials. a capillary; a first electrode on one side of the capillary; a second electrode on a second side of the capillary opposite to the first side; a pipe having a first end for supporting the second electrode and a second end; a discharge port connected to the second end of the pipe; a wick passing through the pipe from the discharge port to an portion of the pipe adjacent to but not within the capillary; and means for operating the capillary as a discharge source for generating ultraviolet wavelengths signals. a lithium wetted mesh for operation as a heat pipe. 2. The method of operating the capillary discharge source of claim 1, wherein the gas includes: 3. The method of operating the capillary discharge source of claim 1, wherein the gas includes: 4. The method of operating the capillary discharge source of claim 1, further comprising: 5. The method of operating the capillary discharge source of claim 1, wherein total pressure in the capillary is within the range of: 6. The method of operating the capillary discharge source of claim 1, wherein the gas radiating the selected wavelength regions has a pressure of: 7. The method of operating the capillary discharge source of claim 1, wherein the gas includes: 8. The method of operating the capillary discharge source of claim 7, wherein the metal vapor has a pressure of: 9. The method of operating the capillary discharge source of claim 7, wherein the metal vapor is: 10. The method of operating the capillary discharge source of claim 1, wherein the gas includes: 11. A method of operating a capillary discharge source in the approximately 11 to approximately 14 nm wavelength region comprising the steps of: 12. The method of operating the capillary discharge source of claim 11, wherein the bore size further includes: 13. The method of operating the capillary discharge source of claim 11, wherein the gas includes: 14. The method operating the capillary discharge source of claim 11, wherein the gas includes: 15. The method of operating the capillary discharge source of claim 11, further comprising: 16. The method of operating the capillary discharge source of claim 11, wherein total pressure in the capillary is within the range of: 17. A method of pre-processing a capillary discharge source having an optical element that operates in the ultraviolet region, prior to operating the source, in order to prevent rupturing of the optical element or contaminating mirrors that receive radiation, comprising the steps of: 18. The method of pre-processing the capillary discharge source of claim 17, wherein the pre-conditioning step further includes: 19. The method of pre-processing the capillary discharge source of claim 18, wherein the heat source includes: 20. The method of pre-processing the capillary discharge source of claim 19, further including the steps of: 21. The method of pre-processing the capillary discharge source of claim 18, wherein the laser is chosen from one of: 22. The method of pre-processing the capillary discharge source of claim 17, wherein the selected value is: 23. The method of pre-processing the capillary discharge source of claim 17, wherein the pre-conditioning step further includes the step of: 24. The method of pre-processing the capillary discharge source of claim 17, wherein the pre-operation pulses includes: 25. A capillary discharge lamp source operating in the ultraviolet wavelength region, comprising: 26. The capillary discharge lamp source of claim 25, further including 27. The capillary discharge lamp source of claim 26, wherein the metallic conductor is chosen from one of: molybdenum, Kovar, and stainless steel. 28. The capillary discharge lamp source of claim 25, wherein the nonconducting and the insulating material is chosen from one of: 29. The capillary discharge lamp source of claim 25, wherein the capillary is 30. A discharge lamp source operating the ultraviolet wavelength region comprising: 31. The capillary discharge source of claim 30, wherein the means for operating includes
06233302&	summary	BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nuclear reactor core arrangement. More particularly, this invention relates to a nuclear reactor core arrangement which is adapted to combust plutonium along with uranium fuels and which utilizes a plurality of fuel assemblies that include mixed-oxide (MOX) fuel rods. 2. Discussion of the Related Art The Department of Energy (DOE) has a large excess of plutonium resulting from the retirement of nuclear weapons and is considering options for its disposal. One option recommended by the National Academy of Sciences (NAS) for the disposal of the excess weapons-grade plutonium is conversion to spent fuel. In this approach, the excess weapons plutonium is converted to plutonium oxide (PuO.sub.2) and used in a mixed oxide (PuO.sub.2 --UO.sub.2) form without reprocessing as fuel for existing nuclear reactors. This results in a spent fuel form which is "proliferation resistant" and that meets the "spent fuel standard" which is recommended by the NAS and which is being used by the DOE. However, this mixed oxide (MOX) approach requires: 1) conservative, realistic core performance characteristics which are similar to those for current uranium core designs; 2) that the technique minimize licensing risks by avoiding any erosion of safety margins compared to those for currently licensed conventional uranium core designs; 3) that impacts on plant operation be minimized or totally avoided; and 4) that the energy extracted from the MOX fuel be maximized, thus providing the best economics. Accordingly, ground rules were established by the DOE in light of the above objective. Namely, it is required that: There is no mixing of MOX and burnable absorber in the same fuel rod. This allows manufacture of lead test assemblies in existing European MOX fuel fabrication facilities. PA1 The fuel and core designs are developed using existing fuel and core design methodologies. PA1 The equilibrium cycle core design characteristics using MOX matches current uranium oxide (UO.sub.2) reload core design characteristics as much as possible. PA1 The cycle length of the MOX core design is essentially the same as that of the UO.sub.2 core design. PA1 There is no significant (if any) plant modifications necessary. PA1 There is no significant impact on plant systems or operation. PA1 Plant parameters should remain within existing plant technical specifications to the greatest extent possible. Accordingly, there exists a need for a nuclear core arrangement which can used in existing facilities and which enables an acceptably high throughput of plutonium in the form of MOX, while remaining within the above constraints. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a novel core design that allows the use of mixed oxide (MOX) fuel containing weapons-grade plutonium in an existing nuclear reactor. Another object of the present invention is to provide a novel reload core design that enables the disposal of a large quantity of weapons-grade material in existing nuclear reactors with no significant plant modifications or impact on plant systems or plant operation. Another object of the present invention is to provide novel core designs for pressurized water reactor which uses MOX fuel, which maximizes the loading and throughput of weapons-grade plutonium and which is capable of disposing of a predetermined amount of weapons-grade plutonium in a given number of years of plant operation. Another object of the present invention is to provide a novel reload MOX core design that has essentially the same cycle length and combustion characteristics as existing UO.sub.2 core designs. Another object of the present invention is to provide a novel core design that would ensure that fuel assemblies can be manufactured in existing MOX fuel fabrication facilities and meet the requirement that the MOX and a burnable absorber are not present in the same fuel rod. Another object of the present invention is to provide a novel reload MOX core design that will allow plant parameters to remain within the existing plant technical specifications to the greatest extent possible. In brief, in order to achieve the above objects and to use up the above mentioned stockpile of weapons-grade plutonium, the plutonium is converted into a mixed oxide (MOX) fuel form wherein it can be disposed in a plurality of different fuel assembly designs. Depending on the equilibrium cycle that is required, a predetermined number of one or more of the fuel assembly types is selected and arranged in the core of the reactor in accordance with a selected loading schedule. Each of the fuel assemblies is designed to produce different combustion characteristics whereby the appropriate selection and disposition in the core enables the resulting equilibrium cycle to closely resemble that which is produced using conventional urania fuel. The arrangement of the MOX fuel and burnable absorber rods within each of the fuel assemblies, in combination with a selective control of the amount of plutonium which is contained in each of the MOX rods, is used to tailor the combustion characteristics of the assembly. More specifically, a first aspect of the invention resides in a fuel assembly for use in a nuclear reactor comprising: a plurality of MOX fuel rods; and a plurality of burnable absorber rods; each of the MOX fuel rods and each of the burnable absorber rods being disposed at a predetermined location within the fuel rod assembly. A second aspect of the invention resides in an equilibrium cycle core arrangement of a nuclear reactor comprising: a plurality of fuel assembly types, each type comprising: a plurality of MOX fuel rods, and a plurality of burnable absorber rods, each of the MOX fuel rods and each of the absorber rods being disposed at a predetermined location within a rod matrix for that type; wherein each fuel assembly type has a different number of MOX fuel rods and burnable absorber rods, respectively. A further aspect of the invention resides in a nuclear reactor core comprising a first predetermined number of mixed oxide (MOX) fuel assemblies which are arranged in a predetermined pattern in the core; each of the fuel assemblies being selected from a plurality of different fuel assembly designs wherein the MOX fuel is arranged differently and which, when arranged in the predetermined pattern, combust to produce an equilibrium cycle which is essentially the same as an equilibrium cycle produced using fuel assemblies containing only urania fuel. Another aspect of the invention comes in a method of fueling a nuclear reactor comprising the steps of: loading a first group of fresh unburnt MOX fuel rod assemblies into a first set of predetermined positions in a core of the reactor, in accordance with a predetermined location schedule; loading a second group of MOX fuel rod assemblies which have been burned once, into a second set of predetermined positions which are selectively arranged in the core with respect to the first set of predetermined positions, in accordance with the predetermined location schedule; and loading a third group of MOX fuel rod assemblies which have been burned twice, into a third set of predetermined positions which are selectively arranged in the core with respect to the first and second set of predetermined positions, in accordance with the predetermined location schedule. An important feature of the above method comes in the step of selecting the first group of fuel rod assemblies so as to comprise one or more of a plurality of predetermined octantly symmetrical assembly designs which each contain different amounts of plutonium and/or wherein the plutonium is distributed between the fuel rods of the assembly in a manner wherein an equilibrium cycle for the core exhibits a predetermined relationship with a predetermined equilibrium cycle produced using urania fuel. Another important feature of the above method comes in the step of distributing the amount of plutonium which is contained in the fuel rods of each of the plurality of octantly symmetrical assembly designs in accordance with a plurality of predetermined distribution schedules. Yet another aspect of the invention resides in a nuclear reactor core comprising: a first group of fresh MOX fuel rod assemblies which are unburnt and which are loaded into a first set of predetermined positions in the core, in accordance with a predetermined location schedule; a second group of MOX fuel rod assemblies which have been burned once, and which are loaded into a second set of predetermined positions which are selectively arranged in the core with respect to the first set of predetermined positions, in accordance with the predetermined location schedule; and a third group of MOX fuel rods assemblies which have been burned twice, and which are loaded into a third set of predetermined positions which are selectively arranged in the core with respect to the first and second set of predetermined positions, in accordance with the predetermined location schedule. An important feature of the above structure comes in that the first group of fuel rod assemblies comprise one or more of a plurality of predetermined octantly symmetrical assembly designs which each contain different amounts of plutonium, and so that an equilibrium cycle for the core exhibits a predetermined relationship with a predetermined equilibrium cycle produced using urania fuel. A further important feature of the above structure comes in that the amount of plutonium, which is contained in the fuel rods of each of the plurality of octantly symmetrical assembly designs, is distributed in accordance with a respective plurality of predetermined distribution schedules.
	summary
	summary
	claims	1. A head assembly for a reactor pressure vessel, comprising:a reactor pressure vessel closure head;a seismic support platform spaced from the closure head;an array of control rod drive mechanisms, each control rod drive mechanism including an electro-magnetic coil stack assembly and having a lower end supported by the reactor pressure vessel and an upper end extending through the seismic support platform;a lower shroud surrounding the electro-magnetic coil stack assemblies and having an upper end spaced from the seismic support platform in air flow communication with the atmosphere around the control rod drive mechanisms;a plurality of internal ducts disposed between control rod drive mechanisms within the array of control rod drive mechanisms, each duct having a lower end extending below the electro-magnetic coil stack assemblies and in air flow communication with the lower shroud and each duct having an upper end extending above the seismic support platform;an upper plenum disposed above the seismic support platform having inlet air openings in air flow communication with the upper ends of the internal ducts;a missile shield assembly disposed within the upper plenum, the missile shield having a plate superposed over and spaced from the inlet air openings of the upper plenum in air flow communication with the upper ends of the internal ducts;a plurality of fan assemblies disposed on the upper plenum in air flow communication with the upper plenum; andlift legs connected with the reactor pressure vessel closure head and supporting the seismic support platform, the upper plenum and the missile shield assembly for removal of the head assembly as an integral assembly. 2. A head assembly for a reactor pressure vessel, comprising:a reactor pressure vessel closure head;a seismic support platform spaced from the closure head;an array of control rod drive mechanisms, each control rod drive mechanism including an electro-magnetic coil stack assembly and having a lower end supported by the reactor pressure vessel and an upper end extending through the seismic support platform;a lower shroud surrounding the electro-magnetic coil stack assemblies and having an upper end spaced from the seismic support platform in air flow communication with the atmosphere around the control rod drive mechanisms;a plurality of internal ducts disposed within the array of control rod drive mechanisms, wherein each duct has a lower end extending below the electro-magnetic coil stack assemblies disposed in air flow communication with the lower shroud and each duck has an upper end, and wherein the internal ducts extend within the array of control rod drive mechanisms through the seismic support platform and have internal plates in the section of the ducts disposed in the seismic support platform;an upper plenum disposed above the seismic support platform having inlet air openings in air flow communication with the upper ends of the internal ducts;a missile shield assembly disposed within the upper plenum, the missile shield having a plate superposed over and spaced from the inlet air openings of the upper plenum in air flow communication with the upper ends of the internal ducts;a plurality of fan assemblies disposed on the upper plenum in air flow communication with the upper plenum; andlift legs connected with the reactor pressure vessel closure head and supporting the seismic support platform, the upper plenum and the missile shield assembly for removal of the head assembly as an integral assembly. 3. The head assembly of claim 1, wherein the internal ducts are bolted to the upper plenum and wherein each lift leg comprises an upper leg member attached by a clevis assembly to a lower leg member with the upper plenum supported by the upper leg member and with the seismic support platform supported by the lower leg member. 4. The head assembly of claim 1, wherein the internal ducts are a backfit into an existing head assembly. 5. A head assembly for a reactor pressure vessel, comprising:a reactor pressure vessel closure head;a seismic support platform spaced from the closure head;an array of control rod drive mechanisms, each control rod drive mechanism including an electro-magnetic coil stack assembly and having a lower end supported by the reactor pressure vessel and an upper end extending through the seismic support platform;a lower shroud surrounding the electro-magnetic coil stack assemblies and having an upper end spaced from the seismic support platform in air flow communication with the atmosphere around the control rod drive mechanisms;a control rod drive mechanism plenum disposed between the closure head and the lower shroud;a plurality of internal ducts disposed between control rod drive mechanisms within the array of control rod drive mechanisms, each duct having a lower end disposed in the control rod drive mechanism plenum and each duct having an upper end extending above the seismic support platform;an upper plenum disposed above the seismic support platform having inlet air openings in air flow communication with the upper ends of the internal ducts;a missile shield assembly disposed within the upper plenum, the missile shield having a plate superposed over and spaced from the inlet air openings of the upper plenum in air flow communication with the upper ends of the internal ducts;a plurality of fan assemblies disposed on the upper plenum in air flow communication with the upper plenum; andlift legs connected with the reactor pressure vessel closure head and supporting the seismic support platform, the upper plenum and the missile shield assembly for removal of the head assembly as an integral assembly. 6. The head assembly of claim 5, wherein the internal ducts have an L shaped cross-section within the seismic support platform. 7. The head assembly of claim 5, wherein the internal ducts have a rectangular shaped cross-section.
062698737	description	DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling heat exchange, particularly heat exchange in a nuclear reactor, typically of the pressurized water type. In contradistinction to prior art methods which involve the opening and closing of mechanical valves on the pipes, the method of the present invention utilizes a different type of device which makes it possible to modify the heat exchange conditions at the exchanger in the pool in which the heat exchanger is immersed. The method of the present invention makes it possible to eliminate valves on the circuit and thereby increases reliability. More particularly, the present invention relates to a method for controlling a heat exchange system by means of a thermal valve. The system comprises at least one heat exchanger immersed in a pool containing a fluid. Present in the pool is a container which confines the heat exchanger(s); the container has at least one opening in an upper part and means for introducing the fluid though a lower part of the container. Also present are means for partially or totally opening or closing the opening in the upper part of the container as well as means for partially or totally opening or closing the means for introducing the fluid through the lower part of the container. When the heat exchanger is connected to a loop through which a coolant flows, the use of the thermal valve eliminates the need for any mechanical valves to control the coolant flow in the loop. Thus, the thermal valve employed in the method of the present invention will control the heat exchange between the coolant in the loop and the fluid of the pool confined in the container. In order to prevent heat exchange from occurring, the upper opening of the container or the fluid introduction means in the lower part of the container is closed and the fluid of the pool confined within the container is heated by the exchanger and then commences boiling, thereby generating vapor or steam within the container. Heat exchange between the exchanger is then significantly decreased almost to the point of total cessation of the heat exchange. In order to permit re-occurrence of the heat exchange, the upper opening of the container or the fluid introduction means in the lower part of the container is opened. According to one embodiment of the invention, one or more valves are present at an outlet of the opening of the upper part of the container. Indeed, there may be several valves arranged in parallel at the outlet of the opening of the upper part of the container. In addition, a bell can be disposed above such valve(s) so that the outlet of each valve is positioned above the lower edge of the bell. The means for introducing the fluid through a lower part of the container may comprise one or more openings created in the lower part of the container by one or more tubes for supplying fluid to lower part of the container. According to another embodiment of the invention, one or more valves are positioned either directly at the inlet of the opening(s) made in the lower part of the container or on the tube(s) for supplying the fluid to the lower part of the container. The thermal valve employed in the method of the invention can thereby also have means for preventing an entry of fluid through the opening made in the upper part of the container. The thermal valve may also be provided with means for preventing an entry of fluid through the opening made in the upper part of the container. DETAILED DESCRIPTION OF THE DRAWINGS AND THE PREFERRED EMBODIMENTS OF THE INVENTION FIG. 1 depicts a prior art assembly for removal of residual power from a pressurized water reactor, having as its cold source a heat exchanger immersed in a pool. This cold source is based on reactors described in the literature such as AP600 or SIR (Safe Integral Reactor). FIG. 1 shows the vessel 1 of a pressurized water reactor and one of the main loops A of the primary circuit constituted by a hot branch 2, the vapor or steam generator 3, the pump 4 and the cold branch 5. A pressurizer 6 is located on the hot branch of one of the main loops. A heat exchanger 7 is placed within vessel 1 for evacuating the residual power produced by the core 8. Heat exchanger 7 forms part of a loop B having a hot branch 9 on which is disposed an expansion tank 10. Branch 9 penetrates a pool 11 filled with water and supplies a heat exchanger 12 disposed in pool 11. Discharge from heat exchanger 12 occurs by means of a pipe 13 which forms the cold branch and which returns to heat exchanger 7. Therefore, the cold source for removing the residual power from core 8 comprises the immersed heat exchanger 12. Typically, heat exchanger 12 comprises a bundle of tubes having a downward flow. Other types of heat exchangers can also be used, e.g. heat exchangers containing inverted U-tubes, bayonet tubes or plate tubes. Pump 14 on pipe 13 is not indispensable, but is advantageous in that it improves convection in loop B. However, pump 14 may be eliminated if natural convection is adequate. Loop B is only used for the removal of low levels of power, such as residual power, when such removal becomes necessary. Therefore, one or more valves are typically placed on loop B in order to check and control the flow rate of the coolant in the loop. For simplicity, only one mechanical valve 15 on branch 9 is shown in FIG. 1. Thus, valve 15 is generally closed down during normal operation and is opened when the reactor is shutdown, so as to permit a flow of coolant in loop B necessary for removal of the residual power from core 8. The main disadvantage of the system shown in FIG. 1 is that high thermal stresses are present which can damage the system. Thus, in the case of electrogenic nuclear reactors, the temperature of the water in vessel 1 is generally close to 300.degree. C. under high pressure conditions (approximately 150 bar for a pressurized water reactor), whereas that present in pool 11 is about 20-40.degree. C. at a pressure close to atmospheric pressure. When valve 15 is closed, one of the branches of loop B is in contact with a hot zone, in this case heat exchanger 7, while the remaining branch is in contact with a cold zone, in this case heat exchanger 12. Thus the loop has two zones at significantly different temperatures, i.e., a hot zone at about 300.degree. C. and a cold zone at about 40.degree. C. If the coolant is water, which is generally the case in pressurized water reactors, there is a risk of partial vaporization of the coolant due to the internal pressure of the loop. This is particularly the case if the pressure in the loop is too low, thereby entailing the use of multiple valves on the loop (which are not shown in FIG. 1). Loop B participates in the residual power removal from core 8, and therefore possesses a critical safety function. Any complexity in loop B serves to reduce the reliability of the loop. When opening one or more of valve(s) 15, the displacement of the coolant creates thermal shocks on the components of the system due to the cold and hot locks present in the loop when the valve(s) is (are) closed. If the fluid in loop B is of a two-phase nature, on startup, considerable oscillations of the fluid can occur as a result of the sudden condensation of vapor locks on the cold walls. Such oscillations are clearly disadvantageous for the operation of the system and can create locally significant thermal stresses on the components of the system. In FIG. 2, reference numerals identical to those in FIG. 1, designate the same components. Thus, FIG. 2 illustrates reactor core 8 and the heat exchanger 7 for removal of residual power, as described above with reference to FIG. 1. However, in FIG. 2, mechanical valve 15 and been eliminated and replaced by thermal valve system 25 whose components and mode of operation are described below. Thermal valve system 25 possesses a container 26 in the form of an inverted tank or "bell", positioned above, and confining, heat exchanger 22. In the upper part of container 26, there is located one or more openings 28 by which vapor or steam can escape; the escape of the vapor or steam may be controlled by valve 27 positioned above opening 28. In normal operation, of a nuclear reactor, fluid flowing in loop C is maintained under pressure and its temperature is generally in the range of about 250 to 330.degree. C. The water in pool 11 is at a pressure close to atmospheric pressure and at a low temperature of about 20 to 40.degree. C. To the extent necessary, heat exchanger 18 cools the water in pool 11. The system employed in the method of the present invention functions as a "thermal valve" in that it controls the heat exchange between the hot water in loop C and the cold water of pool 11. Thus, when cessation of heat exchange is desired, valve 27 is closed and the water of the pool confined beneath bell 26 is heated by heat exchanger 22 and boils, thereby forming a vapor cushion beneath bell 26. The excess liquid water forced back by the vapor cushion returns to pool 11, passing beneath bell 26, by means of opening 29 at the base (or lower part thereof), e.g., in the form of a ring. Heat exchanger 22 is then in a gaseous atmosphere mode, thereby sharply reducing further heat exchange. In order to allow heat exchange to resume, it is merely necessary to open valve 27. The vapor trapped by bell 26 escapes through opening 28 and valve 27 into the water of pool 11 and enables the cold water in pool 11 to enter inverted tank 26 through opening 29. This cold water contacts heat exchanger 22 and is heated. A natural convection is established in pool 11 between the hot source (heat exchanger 22) and the cold source (water of pool 11) through valve 27. In order to insure an adequate amount of convection, opening 28 and valve 27 are appropriately sized. Optionally, several valves in parallel may be installed to increase the size of the opening. If the temperature in bell 26 approaches the saturation temperature, heat transfer takes place by boiling therein adjacent to heat exchanger 22. The uniqueness of such a "thermal valve" system is that it eliminates the need for valves on loop C between heat exchanger 7 and heat exchanger 22 and it permits a permanent temperature conditioning of loop C. Such conditioning is accomplished either by force convection with the aid of pump 24, or natural convection with a slight flow rate in loop C at a substantially uniform temperature, thereby avoiding any thermal stresses on the components and pipes of the system. Note that in the embodiment described in respect to FIG. 2, the concept of the "thermal valve" has been applied to heat exchanger 22 on independent loop C containing a single-phase fluid kept under pressure by expansion tank 10. In FIG. 3, a further exemplified application of the concept of the "thermal valve" will be described with reference to a loop branched in respect to a main loop and with a two-phase fluid. In FIG. 3, the "thermal valve" is not applied to a single independent loop (such as loop C in FIG. 2) but to a loop D branched to the main supply loop of a steam or vapor generator of a nuclear reactor. FIG. 3 shows a steam generator 34 of the inverted U-tube type which is used in many electrogenic nuclear reactors, with its water supply pipe 30 and steam or vapor outlet tube 31 (to a turbine which is not shown). Valves 32 and 33 are disposed on tubes 30 and 31, respectively, thereby making it possible to isolate steam generator 34, if a situation so requires such isolation. The main loop is constituted by pipe 30, steam generator 34 and pipe 31. An auxiliary loop D is constituted by a pipe 44 connected to pipe 31, a heat exchanger 45 and a return pipe 46 to steam generator 34. In the system shown in FIG. 3, heat exchanger 45 is constituted by bayonet tubes, e.g. two coaxial tubes. Central tube 48 carries the incoming fluid which, in this case, is the steam which exits steam generator 34. External tube 50, closed at one end, is used for return of the fluid and permits heat exchange to occur. This particular type of heat exchanger is employed is various types of prior art processes and will not therefore be described in any further detail. Suffice it to say, this type of heat exchanger is depicted for exemplary purposes and is not indispensable for the use of the "thermal valve" employed in the method of the present invention and other types of heat exchangers may also be used. Heat exchanger 45 is located in pool 11 containing a liquid which, for exemplary purposes is water. Heat exchanger 45 is surmounted by container 56 in the form of an inverted tank or bell and having in an upper part thereof, an opening 53 and a valve 57. Heat exchanger 18 makes it possible to maintain the desired temperature in pool 11. In normal operation, i.e., when heat is transmitted to the turbine to produce electricity and no heat is transmitted through loop D, valve 57 is closed and valves 32 and 33 are open. Pressurized steam exiting steam generator 34 at a temperature of about 250 to 300.degree. C. is supplied to the turbine through pipe 31 and part of such steam is transmitted to heat exchanger 45 by means of pipe 44. Since valve 57 is closed, the water confined beneath bell 56 undergoes a temperature rise and is transformed into steam at about 100.degree. C. (such temperature is dependent on the pressure of the water in pool 11, which is, e.g., 1 bar). The remaining liquid water is then discharged into pool 11 through the lower opening 62 of bell 56. When heat exchanger 45 contains only steam confined beneath bell 56, heat exchange ceases. Thus, all the heat produced by steam generator 34 is directed to the turbine. If an operational situation requires an extraction of power through loop D, particularly when the main loop is unavailable with valves 32 and 33 closed, it is merely necessary to open valve 57 above bell 56. Steam contained in bell 56 will then escape via valve 57 and condenses in pool 11. The water level rises in bell 56 and again submerges the tube bundle in heat exchanger 45, thereby permitting heat exchange to occur. Steam transmitted from steam generator 34 via pipe 44 then condenses in heat exchanger 45 and returns to steam generator 34 via pipe 46. The significance of the method of the invention which makes use of the "thermal valve" concept is that it eliminates the need to utilize valves on auxiliary loops and keeps such loops constantly hot. On auxiliary loops shown in the prior art, there is generally at least one valve located on each such auxiliary loop in order to block the circulation of fluid with in the loop. Due to the temperature levels (i.e. 250 to 300.degree. C. for the hot fluid and 20 to 50.degree. C. for the cold fluid of the pool), only a limited amount of natural convection can occur with the same pipe, thereby resulting in thermal gradients which can significantly impair the reliability of the system components. In the method of the present invention, the thermal gradient is transferred to a gaseous volume having poor heat exchange capability. Mechanical valves are no longer necessary and the loop which is kept constantly hot by a slight flow leakage, is no longer subject to deleterious thermal gradients. In order to reduce heat leakage when bell 56 is filled with steam, the bell may be internally and/or externally lined by thermal insulant 58 in order to reduce convection movements of steam within the bell. In a similar manner, thermal insulant 59 may be provided at the inlet of pipes 44 and 46 into pool 11. In the embodiments shown in FIG. 2 and FIG. 3, the container, i.e., the bell, has been shown without any support. It should be understood, however, that the bell can be maintained in any desired random manner, e.g., in the manner as shown in FIG. 4. It may be attached to the pool by its lower part with the aid of fasteners, e.g., screws, or with welds, or other manner as desired. In the case of such attachment, the opening in the lower part of the bell (i.e., 29 and 62 in FIG. 2 and FIG. 3, respectively) is no longer a ring-like space, but instead consists of a series of openings 64 in the lower part of the container (or bell) 66, as shown in FIG. 4. Reference numeral 59 designates a thermal insulant at the intake of the pipes into the pool, while reference numerals 63 and 67 designate an opening and a valve, respectively in the upper part of container 66. Valve 67 is of a variable nature. For precise applications, e.g., for nuclear reactors requiring reliable systems, several valves may be arranged in parallel. As the need arises, the desired setting for power extraction may be accomplished by a partial opening of the valve or multiplicity of valves. Here again for security purposes, if the need arises, the valves can be designed to open automatically in the case of a failure of supply of control fluid or electricity. In order to insure good natural convection of the fluid in the pool and, as shown in FIG. 4, the outlet of valve 67 can be located beneath the free level 70 of the pool. However, if for any reason, the outlet of valve 67 is not or is no longer located beneath the level 70, the "thermal valve" is still operational. Under such conditions, the fluid contained in pool 11 would exit in vapor form if the temperature level so permitted and would be discharged to the outside of the pool. FIGS. 2 to 4 show the "thermal valve" employed in the method of the invention with the heat exchanger and its incoming and outgoing supply pipes penetrating the bell through the lower part of the pool. Such arrangement has been designed for simplicity purposes. However, if for any reason, and as illustrated in FIG. 5, the supply pipe(s) 82 must enter container 86 through its side or top, the "thermal valve" would still be operational. However, in order to maintain a good level of efficiency for the "thermal valve", the pipe(s) 81 through container 86 should have a minimum degree of leakage between the interior of bell 86 and the water of pool 11. If, for certain operating conditions, it is necessary for valve 87 to have a large cross-sectional passageway, it could happen that water enters through such valve when the power to be removed is well below the power level for which the "thermal valve" has been dimensioned. Thus, at a low power level, the vapor flow rate will be low and the water of pool 11 can enter bell 86 through valve 87, while the vapor concurrently exits through the same valve. The vapor will then flow in an upward direction, while the water will flow in a downward direction. If avoidance of such countercurrent flow in the valve is desired, it is possible to position a small bell 93 above valve 87, as is shown in FIG. 5, so that the bottom 94 of bell 93 is below outlet 95 of valve 87. Bell 93 creates a baffle for the vapor or steam, preventing any re-entry of the cold water of pool 11. There is no significant operational criticality to the shape or volume of the inverted tank, i.e., the container. All that is necessary is that it be capable of confining the heat exchanger and the vapor bubble for the modification of the heat exchange coefficient. The thermal valve" employed in the method of the present invention is operational independent of the construction of the inverted tank. Thus, if for any reason, compartmentalization of the pool is required, one of the compartments could fulfill the function of the inverted tank (i.e., the container) as shown in FIG. 6. FIG. 6 depicts partitions 100 for forming a compartment 101 having a heat exchanger 102. Compartment 101 has at least two openings 103 in its upper part surmounted by valves 107 and 104 in the lower part of the compartment. Thus, compartment 101 fulfills the same function as inverted tank 26 or 56 of FIG. 2 or FIG. 3, respectively. If for any reason it is not possible to position valve 107 at the top of the inverted tank or the compartment 101, it can be positioned directly at the intake of the opening(s) in the lower part, as shown in FIG. 7. In order to avoid the entry of any water through the upper opening, it is possible to use the device 93 shown in FIG. 5, or a pipe 110 bent in the shape of a gunstock, as shown in FIG. 7. For efficiency purposes, it is preferred that outlet 109 of pipe 110 be located lower than bend 108. With valve 117 placed in the lower part, the operation of the resultant device is similar to that where valve 107 is placed in the upper part. When valve 117 is closed, fluid contained in the compartment is heated on contact with heat exchanger 102 and is transformed into steam, assuming the temperature and pressure conditions would so permit, thereby significantly reducing heat exchange as is the case with the inverted tank described in FIGS. 2 to 5. Return to a good heat exchange coefficient will re-occur by opening valve 117. A special arrangement of the opening through which water of the pool enters the compartment is possible if the opening cannot be located in the lower part. Thus, as shown in FIGS. 8 and 9, there may be a compartment 111 having heat exchanger 112 at the bottom of pool 11. The openings 113 and 114 are located in the upper part of compartment 111 defined by partition 116. Intake opening 114 is connected to tube 115 in the interior of the compartment for supplying water from the pool to the bottom of the compartment. A mechanical valve for controlling the heat flux can be located on one of the openings, as is shown by valve 127 in FIG. 8 or valve 137 in FIG. 9. If the valve is positioned on the intake opening 114, device 120, similar to device 110 of FIG. 7, must be used to prevent the water from entering through outlet opening 113. Alternatively, a device such as bell 93 of FIG. 5 can be used, in which case its opening would be directed towards the opening of the upper part 113 of the compartment, and a pipe fixed at the outlet of such opening would issue into the internal space of the bell. In the above description, for simplicity purposes, only a single valve at the inlet or outlet of the compartment or a single pipe 115 has been shown. However, the "thermal valve" and its use in the method of the present invention will not be adversely affected if it is deemed necessary to employ several valves or pipes instead. The "thermal valve" employed in the method of the present invention has been applied to water reactor systems operating at a high temperature of 250 to 300.degree. C. leading to the formation of a vapor or steam bubble beneath the inverted tank, i.e., the bell. For other applications or in the case of reactors operating at lower temperatures, no vapor bubble is formed, the "thermal valve" would still be operational. Thus when the valve is closed, the liquid contained in the bell heats up and tends to rise by natural convection. This hot liquid cannot escape from the bell, because the valve is closed. The temperature attained by such liquid than corresponds to the temperature of the coolant flowing in the heat exchanger. As a consequence, heat exchange ceases, and resumes when the valve is again opened.
	claims	1. A process for making an aluminum alloy comprising:a) providing an aluminum composite powder having an aluminum microstructure with an ultra-fine grain size and aluminum oxide particles distributed throughout the aluminum microstructure; andb) mixing a ceramic particulate with the aluminum powder to form a powder mixture, the ceramic particulate is selected from the group consisting of silica, silicon carbide, boron carbide, boron nitride, titanium oxide, titanium diboride, and mixtures thereof. 2. The process of claim 1, wherein the powder mixture comprises about 5 wt. % to about 40 wt. % of the ceramic particulate. 3. The process of claim 1, wherein the ceramic particulate is boron carbide having a particle size distribution of 100% less than about 250 microns and the boron carbide is nuclear grade. 4. The process of claim 1, wherein the aluminum composite powder has a particle size that is less than about 30 microns. 5. The process of claim 1, wherein subsequent to step b), the powder mixture is sintered to form a billet. 6. The process of claim 5, wherein the billet is subsequently extruded. 7. The process of claim 1, wherein the ultra-fine grain size is about 200 nm. 8. An aluminum alloy comprising a sintered blend of:an aluminum composite powder having an aluminum microstructure with an ultra-fine grain size; anda ceramic particulate selected from the group consisting of silica, silicon carbide, boron carbide, boron nitride, titanium oxide, titanium diboride, and mixtures thereof. 9. The aluminum alloy of claim 8, wherein the sintered blend comprises about 7 wt. % to about 40 wt. % of the ceramic particulate. 10. The aluminum alloy of claim 8, wherein the ceramic particulate is boron carbide having a particle size distribution of 100% less than about 250 microns and the boron carbide is nuclear grade. 11. The aluminum alloy of claim 8, wherein the aluminum composite powder comprises aluminum oxide particles distributed throughout the aluminum microstructure. 12. The aluminum alloy of claim 11, wherein the oxide content of the aluminum composite powder ranges from about 0.1 wt. % to about 4.5 wt. %. 13. The aluminum alloy of claim 11, wherein the ultra-fine grain size is about 200 nm. 14. The aluminum alloy of claim 8, wherein the aluminum composite powder has a particle size that is less than about 30 microns. 15. A radiation shield comprising the aluminum alloy of claim 8. 16. A process for making an aluminum nano-composite comprising:a) providing an aluminum powder having an oxide content between about 0.1 wt. % and 4.5 wt. %; andb) hot-working the aluminum powder such that a microstructure grain size of the aluminum powder is reduced by a factor of at least 10 to form an aluminum nano-composite. 17. The process of claim 16, wherein the hot-working is performed at a temperature below the recrystallization temperature of the aluminum powder. 18. The process of claim 16, wherein the oxide content is derived from a natural aluminum oxide formation layer on the aluminum powder. 19. The process of claim 16, wherein during step b) the natural aluminum oxide is distributed throughout a microstructure of the aluminum powder. 20. The process of claim 16, wherein the aluminum nano-composite is subsequently formed into a radiation shield.
	summary
	description	This patent application claims the benefit of and priority to U.S. Provisional Patent Application No. 61/777,480, filed on Mar. 12, 2013, the contents of which are hereby incorporated by reference in their entirety. The invention described herein was made in the performance of work under a NASA contract and by employees of the United States Government and is subject to the provisions of Public Law 96-517 (35 U.S.C. §202) and may be manufactured and used by or for the Government for governmental purposes without the payment of any royalties thereon or therefore. In accordance with 35 U.S.C. §202, the contractor elected not to retain title. Ionizing radiation, and in particular neutrons, pose a hazard to crew, passengers, and equipment in the aerospace and other industries. For example, research indicates that for flights within the commercial height range, aircrew and frequent flying passengers may be subject to radiation dose levels significantly above that permitted for members of the public under statutory recommendations. Equipment and crews on spacecraft that for part or all of their flight profile enter into low earth orbit, or travel beyond low earth orbit, are subjected to even higher radiation risks than aircraft at commercial height ranges. One hazard of neutron radiation is neutron activation, i.e., the ability of neutron radiation to induce radioactivity in most substances it encounters, including a person's body tissues. The risk posed by radiation has long been recognized as one of the major challenges to frequent and long duration spaceflight. To help address the risks posed by neutron radiation, effective neutron radiation absorbers and detectors are needed. However, materials for neutron radiation detection have rarely been studied extensively. The present invention provides methods for making a neutron converter layer. The various embodiment methods enable the formation of a single layer neutron converter material. The single layer neutron converter material formed according to the various embodiments may have a high neutron absorption cross-section, tailored resistivity providing a good electric field penetration with submicron particles, and a high secondary electron emission coefficient. In an embodiment method a neutron converter layer may be formed by sequential supercritical fluid metallization of a porous nanostructure aerogel or polyimide film. In another embodiment method a neutron converter layer may be formed by simultaneous supercritical fluid metallization of a porous nanostructure aerogel or polyimide film. In a further embodiment method a neutron converter layer may be formed by in-situ metalized aerogel nanostructure development. These and other features, advantages, and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims, and appended drawings. For purposes of description herein, it is to be understood that the specific devices and processes illustrated in the attached drawings, and described in the following specification, are simply exemplary embodiments of the inventive concepts defined in the appended claims. Hence, specific dimensions and other physical characteristics relating to the embodiments disclosed herein are not to be considered as limiting, unless the claims expressly state otherwise. The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any implementation described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other implementations. The various embodiments will be described in detail with reference to the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. References made to particular examples and implementations are for illustrative purposes, and are not intended to limit the scope of the invention or the claims. As used herein “a high neutron absorption cross-section” may be a neutron absorption cross-section at or above 1.9 barns. For comparison purposes, the neutron absorption cross-sections of various materials are illustrated in Table 1. TABLE 1Neutron Abs x-sectionsMaterialDensity (g/cm3)(barns)Aluminum2.70.212BoronBN (2.27); BNNT (1.37)710 (10B: 3835)Gadolinium7949000Lead11.34 0.28Titanium4.545.0Nitrogengas1.9Hydrogengas0.33Carbon1.8-3.50.0035 As used herein “a high electron emission coefficient” may be a secondary electron emission coefficient (“SEE”) greater than 1. As used herein “tailored resistivity” may be resistivity greater than or equal to 107 Ohms/cm and less than or equal to 109 Ohms/cm. Materials for neutron radiation detection that can provide a high neutron absorption cross-section, high electron emission coefficient, and tailored resistivity have rarely been studied. Multiple layers have been used to attempt to achieve a high neutron absorption cross-section, high electron emission coefficient, and tailored resistivity, but there are a number of disadvantages to using multiple layers, in particular, the inability to achieve a material with a high neutron absorption cross-section, high electron emission coefficient, and tailored resistivity without disrupting other functions of the material. Multiple layer material has required the use of large amounts of filler material to achieve a high neutron absorption cross-section, high electron emission coefficient, and tailored resistivity. The use of filler material has resulted in increasing the weight of the multiple layer material because fillers are generally denser than the matrix of the multiple layer material, complexity in manufacture of the multiple layer material, and cost increases for the multiple layer material as larger amounts of neutron attenuating filler material are added. Additionally, processability of the multiple layer material decreases as filler volume increases and negative impacts on other desirable properties of the multiple layer material occur as filler volume increases. The present invention provides methods for making a neutron converter layer. The various embodiment methods enable the formation of a single layer neutron converter material. The various embodiments may enable the development of a neutron converter layer formed as a one layer porous nanostructure or a one layer solid film. The single layer neutron converter material formed according to the various embodiments may have a high neutron absorption cross-section, tailored resistivity providing a good electric field penetration with submicron particles, and a high electron emission coefficient. In some embodiments, a high neutron absorption cross-section may be achieved by the use of lithium (Li), boron (B), and/or gadolinium (Gd) as precursors. In some embodiments, a high electron emission coefficient may be achieved by the use of Magnesium Oxide (MgO) and/or Cesium Iodide (CsI) as precursors. Neutron shielding materials for aerospace applications are being developed under the Materials International Space Station Experiments (“MISSE”) program. Emerging materials such as boron nitride nanotubes (“BNNT”) and single wall carbon nanotubes (“SWCNT”) as well as B, hexagonal boron nitride (h-BN), and Gd nanoparticles have been studied using a neutron exposure lab with a 1 Curie (Ci) americium/beryllium source. The preliminary study indicates that BNNT, h-BN, and Gd exhibited excellent neutron radiation shielding effectiveness compared with polyethylene. Polymers containing high nitrogen (N) composition, such as polyimides, showed good neutron shielding effectiveness compared with non-nitrogen containing polymers. All N, B, and Gd possess high neutron absorption cross-sections compared with other elements and exhibited excellent neutron shielding effectiveness (i.e., above 0.1 mm−1) as illustrated in the graph shown in FIG. 1. Tailoring physical properties of nanocomposites has been the main focus of research activities, such as private industry (“PI”) research activities, throughout the last decade to generate multifunctionalities for specific aerospace applications of interest. Especially for sensor and actuator applications, electrical conductivity and dielectric properties were effectively controlled as a function of the degree of dispersion, concentration, and orientation of the nanoinclusions. For example, the electrical conductivity can be controlled by several orders of magnitude with less than a 0.05% volume of carbon nanotubes as seen in FIG. 2. Supercritical fluid (“SCF”) metal infusion has been studied and a novel metallized nanotube polymer composites (“MNPC”) has been developed to incorporate functional metals on the nanotube surface preferentially inside of a polymer matrix. Various metals (such as silver (Ag), gold (Au), platinum (Pt), palladium (Pd), iron (Fe), cobalt (Co), and nickel (Ni)) have been successfully metalized inside of a polymer and a SWCNT polymer composite. The metal particle size, infusion depth, and distribution may be controlled as a function of the SCF infusion conditions (e.g., time, temperature, and pressure). A silver nanoparticle infused SWCNT polymer composite morphology is shown in FIG. 3. Bright round dots represent reduced silver nanoparticles deposited on the SWCNT surface predominantly. The following section describes embodiment methods to develop a nanostructure with high neutron absorption cross-section, high electron emission coefficient, and tailored resistivity. In the various embodiment methods a porous aerogel nanostructure (e.g. silica) with nanoparticles offering three functions may be processed systematically. Different approaches are performed to achieve the proposed nanostructure. In an embodiment method a neutron converter layer may be formed by sequential supercritical fluid metallization of a porous nanostructure aerogel or polyimide film. In another embodiment method a neutron converter layer may be formed by simultaneous supercritical fluid metallization of a porous nanostructure aerogel or polyimide film. In a further embodiment method a neutron converter layer may be formed by in-situ metalized aerogel nanostructure development. FIG. 4 is a process flow diagram illustrating an embodiment method 400 for forming a neutron converter layer by sequential supercritical fluid metallization of a porous nanostructure aerogel or polyimide film. In step 402a nanostructured aerogel or polymer matrix (e.g., a commercially purchased nanostructured aerogel or polyimide film) may be machined to a selected (e.g., appropriate to the intended application) dimension for the converter layer. In step 404 neutron hardening precursors (e.g., B and/or Gd) may be dissolved in a supercritical carbon dioxide (CO2) fluid above 31.1 degrees Celsius and 7.29 MPa (72.0 bar). In step 406 the supercritical CO2 fluid with the precursors dissolved in it may be infused into the aerogel or polymer (i.e., polymide) matrix. In step 408 the pressure may be lowered, thereby trapping the infused metal precursors into the internal pores and surfaces of the aerogel or polymer matrix uniformly while the highly diffusive CO2 escapes rapidly. In step 410 the trapped and deposited metal precursors may be reduced at an elevated temperature to create nanoparticles. In step 412 conductive precursors may be infused, and in step 414 high SEE element precursors (e.g., MgO and/or CsI) may be infused to provide appropriate conductivity and SEE, respectively to the neutron converter layer. FIG. 5 is a process flow diagram illustrating an embodiment method 500 for forming a neutron converter layer by simultaneous supercritical fluid metallization of a porous nanostructure aerogel or polyimide film. Method 500 is similar to method 400 described above with reference to FIG. 4, except that in method 500 the neutron hardening, conductive, and SEE element precursors are applied together. In step 502 neutron hardening precursors (e.g., B and/or Gd), conductive, and SEE element precursors (e.g., MgO and/or CsI) may be dissolved in a supercritical carbon dioxide (CO2) fluid above 31.1 degrees Celsius and 7.29 MPa (72.0 bar). Because the neutron hardening, conductive, and SEE element precursors are applied together, steps 412 and 414 may not be required in method 500. FIG. 6 is a process flow diagram illustrating an embodiment method 600 for forming a neutron converter layer by in-situ metalized aerogel nanostructure development. In method 600 the aerogel may be created via a sol-gel process in the presence of metal precursors (e.g., Gd2O3, B2O3, MgO, and/or CsI). In step 602a solution of alkoxide solution, water, alcohol, and basic catalyst may be formed in the presence of the metal precursors. In optional step 604 the resistivity of the metalized aerogel may be adjusted by adding a small quantity of carbon nanotubes or other metal precursors. In step 606 the composition of alkoxide solution, water, alcohol, and basic catalyst may be adjusted to control the rate of hydrolysis and condensation. The radiation hardened nanoparticles (e.g., B and/or Gd) and the high SEE nanoparticles (e.g., MgO and/or CsI) may uniformly form inside of the aerogel structure. In step 608 supercritical carbon dioxide (CO2) fluid at 31.1 degrees Celsius and 7.29 MPa (72.0 bar) may employed to dry the condensed gel with the nanoparticles. Method 600 may provide uniformly distributed functional nanoparticles incorporated into an aerogel nanostructure. All cited patents, patent applications, and other references are incorporated herein by reference in their entirety. However, if a term in the present application contradicts or conflicts with a term in the incorporated reference, the term from the present application takes precedence over the conflicting term from the incorporated reference. All ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other. Each range disclosed herein constitutes a disclosure of any point or sub-range lying within the disclosed range. The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. “Or” means “and/or.” As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. As also used herein, the term “combinations thereof” includes combinations having at least one of the associated listed items, wherein the combination can further include additional, like non-listed items. Further, the terms “first,” “second,” and the like herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The modifier “about” used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context (e.g., it includes the degree of error associated with measurement of the particular quantity). Reference throughout the specification to “another embodiment”, “an embodiment”, “some embodiments”, and so forth, means that a particular element (e.g., feature, structure, and/or characteristic) described in connection with the embodiment is included in at least one embodiment described herein, and can or cannot be present in other embodiments. In addition, it is to be understood that the described elements can be combined in any suitable manner in the various embodiments and are not limited to the specific combination in which they are discussed. The preceding description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the following claims and the principles and novel features disclosed herein.
	description	This invention relates to a process that produces ultra clean radiopharmaceutical reusable shipping canisters which are generally referred to as pigs; and more particularly for cleaning pigs utilized for shipping radioactive drugs having relatively short half lives, typically on the order of no more than a few days. This invention is an improvement on the process disclosed and claimed in U.S. Pat. No. 7,825,392 to Rodney Wayne Prosser, the inventor in the present application, entitled Cleaning Process for Radiopharmaceutical Reusable Pigs; the disclosure and content of which patent (hereafter the “Prior Prosser Patent”) is hereby incorporated by reference. Radioactive drugs are typically shipped by pharmacies to hospitals, clinics and medical offices, frequently for diagnostic purposes; but are at times utilized in “ultra clean” areas where a patient has internal tissues exposed, such as operating rooms, surgical suites or interventional procedure suites; or where the patient is otherwise at a greater than normal risk of contracting an infection. These ultra clean areas have filtered air and other features to minimize the presence of harmful microorganisms. The personnel working in these areas follow strict protocols to reduce the presence of pathogens that can cause harm to patients. These protocols include hand hygiene, gowning procedures, use of sterile gloves, and cleaning procedures for the room and equipment brought into the room. This is done to maintain a sterile or clean operating or procedure field and to greatly reduce the risk of infection. The radioactive drugs are shipped in pigs, each of which has a lead surround for radiation shielding and an inner chamber that may contain a syringe or vial which is suitable for dispensing an individual dose of a radioactive drug. The radiopharmaceutical pig typically is a two-part assembly, with an upper portion or cap threadably attached to the lower portion. The structure of a typical pig is shown in FIGS. 2 and 3 of the Prior Prosser Patent and described in the specification thereof, which also describes the manner in which the pig is utilized for transportation of the radioactive drug which is contained in a syringe or vial within the pig. After the pig is delivered to the utilization site and the syringe or vial is removed and used, the syringe or vial is usually put back in the pig and the spent pig is returned to the pharmacy from which it came, for reprocessing. Reprocessing of the spent pig is preferably done by the process described and claimed in the Prior Prosser Patent. This process results in a pig decontaminated to a level of cleanliness which is acceptable for most applications. However, a significantly higher level of cleanliness is required for use in ultra clean areas. A known approach to improving the cleanliness of the reprocessed pigs is to place the syringe or vial in a protective plastic insert within the internal cavity of the pig. See, for example, the article entitled The Incidence of Blood Contamination of Lead Unit Dose Containers With and Without Single-Use Protective Inserts Used with Commercially Prepared Radiopharmaceutical Unit Doses, by Martha W. Pickett, Judith E. Kosegi, Kathleen S. Thomas and Kristen M. Water-stram-Rich, Journal of Nuclear Medicine Technology, Volume 26, Number 3, September 1998, pages 200-203. However, this approach, while improving cleanliness, does not provide as high a level of cleanliness as is desirable for use in ultra clean areas. Accordingly, an object of the present invention is to provide an improved process for cleaning radiopharmaceutical pigs that is better suited for use in ultra clean areas. As described herein, a process is provided for further cleaning a radiopharmaceutical reusable pig after it has been cleaned by the process of the Prior Prosser Patent, by transporting the cleaned pig to a drug preparation area suitable for dispensing a drug for human use, and within the drug preparation area, inserting a syringe or vial containing a radioactive drug into the containment enclosure, after which the cap is assembled to the lower portion of the pig. Then, still within the drug preparation area, the assembled pig containing the drug is placed in a protective outer container to protect the pig from external contamination during handling and transportation. The protective outer container containing the pig is then placed in a transportation receptacle. Referring to the FIGURE, a spent pig containing used syringes and vials is returned to the pharmacy. At Step 1 the pig is processed according to the Prior Prosser Patent to reduce any radiation from it to background level and to remove contaminants and microorganisms. At Step 2 the cleaned, radiation-free pig is transported to a drug preparation area suitable for dispensing a drug for human use. Such an area is usually a clean room with filtered air, or a laminar flow hood. At Step 3, the already sanitized pig may be sanitized a second time while it is in the drug preparation area. Sanitization may be accomplished by placing the pig in an autoclave, high temperature wash, a chemical wash, or by any other suitable method that will destroy microorganisms. This step may be omitted if the resulting slightly lower level of cleanliness is acceptable for the place of use. For example, a nuclear medicine department in a hospital might not require the level of cleanliness that the operating room requires. At Step 4 while still in the drug preparation area, a syringe or vial containing a radioactive drug to be utilized at a treatment site, including a site that requires a higher level of cleanliness such as an operating room, surgical suite, or interventional procedure suite, is inserted into the lower portion of the pig and the pig cap is assembled to the lower portion thereof. At Step 5, while still in the drug preparation area, the assembled pig containing the drug syringe or vial is placed in a protective outer cover to protect the pig from external contamination during transportation. The protective outer cover is preferably a self sealing pre-sterilized sterility maintenance cover or bag which is intended to cover wrapped or enclosed items after sterilization to provide protection from environmental factors which could compromise sterility. A suitable Sterility Maintenance Cover is made of a medical grade polyolefin material such as polyethylene and is commercially available from General Econopak, Inc., 1725 North Sixth Street, Philadelphia, Pa. 19122 under Reorder No. 3315ST. At Step 6 the protective outer container containing the pig and drug syringe or vial is placed in a federal Department of Transportation approved transportation receptacle for delivery to the place where the drug is to be used. At the destination, the protective outer container (still containing the pig and drug syringe or vial within the pig) is removed from the transportation receptacle and delivered to a utilization site which may be an operating room, surgical suite or interventional procedure room, or other area designated as a clean environment. While in that area, the outer container is removed, the cap is removed from the pig, and the syringe or vial is removed and utilized. Therefore the syringe or vial is, at all times that it is associated with the pig, kept in a protected clean environment. For an even higher level of protection, the protective outer container can be sanitized at the site of use prior to the user touching it. Then the pig can be removed from the outer container, to expose the ultra clean pig.
	description	The present application is a Continuation of U.S. application Ser. No. 11/521,465, filed Sep. 15, 2006, now U.S. Pat. No. 7,462,838 which claims priority from Japanese application JP2005-270660 filed on Sep. 16, 2005, the contents of which are hereby incorporated by reference into this application. The present invention relates to an electrostatic deflection circuit and method for controlling the deflection of an electronic beam in an electronic beam measuring apparatus which scans a sample by an electron beam (electronic beam) and measures minute patterns. The electronic beam measuring apparatus such as a scanning electron microscope generates an electronic beam from an electron gun and converges it on a sample, and at the same time applies a force on this electronic beam using a deflector, scans on the sample by deflecting irradiation points and collects information of the sample, and it is used, for example, for the check of the minute circuit patterns, etc. The electronic beam measuring apparatus is generally requested to satisfy the conditions such as to be able to obtain an image of high precision with high resolution and minimum aberration such as noise and distortion, to be able to obtain a desired magnification, to have a wide field of vision, and that the apparatus is small and its structure is simple. In the electronic beam measuring apparatus, as described above, the deflector plays an important role with regard to the deflection of the electronic beam and the scan and there are the types of electromagnetic deflector and electrostatic deflector, but as these have different characteristics they have been used separately according to the use object or the use mode. For example, the electrostatic deflector, compared with the electromagnetic deflector, has characteristics such as to be able to obtain a large amount of deflection with small size and to be able to have a high speed scan rate because a high speed deflection is possible. Thus, conventionally a focused ion beam device (the first conventional apparatus) has been proposed in which the electrostatic deflector and the electromagnetic deflector are arranged shifted in the direction of the light axis, and which performs the scan by the ion beam by the electromagnetic deflector with high magnification and performs the scan by the ion beam by the electrostatic deflector with low magnification (for example, refer to JP-A-10-199460, paragraphs 0018-0022, FIG. 2). Also, a focused ion beam device (the second conventional apparatus) has been proposed which is provided with an electrostatic deflector in which each deflecting factor of the deflector is divided into two parts of the upstream side and the downstream side of the ion beam, and which switches the state in which both of the deflector of the upstream side and the deflector of the downstream side are connected to the deflecting power supply and the state in which only the deflector of the downstream side is connected to the deflecting power supply (for example, refer to JP-A-2002-117796, paragraph 0025, FIG. 6). However, in the case of the first conventional apparatus described above, it is provided with both of the electrostatic deflector and the electromagnetic deflector and the electromagnetic deflector includes a coil and it generates the electromagnetic induction. Therefore, in this apparatus even while the deflection is being performed by the electrostatic deflector the beam passes through within the electromagnetic deflector and it is affected by the electromagnetic induction. For this reason, there has been a problem that it is difficult to obtain an image of high precision or high magnification because the center of the field of vision is shifted with the change of the scan magnification or the aberration such as a distortion is generated on the beam. Also, as it is provided with two kinds of deflectors there have been problems that it is difficult to mechanically match the light axes of the deflectors each other, moreover, that the structure of the entire deflector would be complicated, large, and expensive. Also, in the second conventional apparatus described above, as the deflector is divided into 2 parts in the direction of the light axis, it is as the same structure as which is provided with substantially two sets of electrostatic deflectors. In this structure when the magnification is high only the deflector of the downstream side is used and the deflector of the upstream side is not used. For this reason, compared with an apparatus provided with a single deflector, there have been problems that the structure of the deflector itself would be complicated, at the same time the structure of the deflecting power supply would be double and the apparatus would be complicated, large, and expensive. Further, in this apparatus, there has been a problem that the control of the beam would be difficult and it is difficult to obtain an image of high precision and high magnification because the path length of the beam would be long, at the same time the beam possibly would be affected unexpectedly by the electrostatic deflector of the upstream side (the side to which the voltage is not applied). Thus, the present invention, in consideration of the problems described above, is aimed to provide an electrostatic deflection circuit and method of an electronic beam measuring apparatus which can achieve the high precision of the electronic beam measuring and at the same time contribute to the simplification of the structure of the apparatus. The electrostatic deflection circuit of the electronic beam measuring apparatus according to the present invention outputs a deflection signal to the electrostatic deflector to deflect the electronic beam to scan on the sample, includes a deflection circuit for low magnification comprising a first operational amplifier of a first amplification factor which amplifies the deflection signal by the first operational amplifier, a deflection circuit for high magnification comprising a second operational amplifier of a second amplification factor which is lower than the first amplification factor which amplifies the deflection signal by the second operational amplifier, and a switch circuit which switches to the deflection circuit for low magnification and outputs the deflection signal to the electrostatic deflector when a scan magnification of the electronic beam measuring apparatus is no more than a given value, and switches to the deflection circuit for high magnification and outputs the deflection signal to the electrostatic deflector when the scan magnification is over the given value. Also, the electrostatic deflection method of the electronic beam measuring apparatus according to the present invention outputs a deflection signal to the electrostatic deflector to deflect the electronic beam to scan on the sample, includes a deflection process for low magnification with a first operational amplifier of a first amplification factor amplifying the deflection signal by the first operational amplifier, a deflection process for high magnification with a second operational amplifier of a second amplification factor which is lower than the first amplification factor amplifying the deflection signal by the second operational amplifier, and a switching process which switches to the deflection process for low magnification and outputs the deflection signal to the electrostatic deflector when a scan magnification of the electronic beam measuring apparatus is no more than a given value, and switches to the deflection process for high magnification and outputs the deflection signal to the electrostatic deflector when the scan magnification is over the given value. According to the electrostatic deflection circuit and method of the electronic beam measuring apparatus of the present invention, it is possible to achieve the high precision of the electronic beam measuring and to contribute to the simplification of the structure of the apparatus because the deflection circuit for low magnification and the deflection circuit for high magnification are to be switched corresponding to the scan magnification. Other objects, features and advantages of the invention will become apparent from the following description of the embodiments of the invention taken in conjunction with the accompanying drawings. Next, an embodiment of the present invention will be explained in detail referring to the drawings. FIG. 1 is a principle structure diagram of an electronic beam measuring apparatus according to an embodiment of the present invention. The electronic beam measuring apparatus is typically a scanning electron microscope (SEM) or such an apparatus provided with an additional function. More specifically, the electronic beam measuring apparatus is provided with an electron source 101 which generates an electron beam (electronic beam), a condenser lens 6 which once converges the electronic beam generated at the electron source 101, a deflector 3 which deflects the electronic beam by generating an electrostatic field, an electrostatic deflection circuit (corresponding to an “electrostatic deflection circuit” stated in the claims) 100 which supplies a deflection voltage to the deflector 3, an object lens 5 which focuses the electronic beam on a sample P by the object lens 5, a secondary electron detector 6 which detects a secondary electron radiated resulting from the electronic beam being irradiated on the sample P, an amplifier 107 which amplifies a detection signal which is output when the secondary electron detector 106 detects the secondary electron, a signal processing part 108 which generates an image data (or an image signal) of the sample P based on the amplified detection signal, and an observation monitor 109 which displays an image of the sample P based on the generated image data (or image signal). FIG. 2 is a block diagram showing a functional structure of the electrostatic deflection circuit 100 and the deflector 3 provided in the electronic beam measuring apparatus 10. The electrostatic deflection circuit 100 and the deflector 3 also can be used for another charged particle beam such as a focused ion beam (FIB), etc. instead of being used for the electron beam (electronic beam). Also, it may be applied to a processing apparatus, etc. other than the measuring apparatus such as the electronic beam measuring apparatus 10. The electrostatic deflection circuit 100 is for controlling the deflection direction and the deflection amount of the electronic beam (electron probe) which is radiated from an electronic beam generator (not shown) and has a desired current value converged by an electron lens (not shown) to scan a given area of the surface of the sample with a given pitch. The electrostatic deflection circuit 100 is provided with a control part 4 which outputs deflection data Dd representing information of the scanning pattern of the electron probe as well as outputs a magnification switch signal Sd showing a low magnification or a high magnification corresponding to the setting of the electronic beam measuring apparatus, a D-A (Digital to Analog) conversion part 1 which converts the deflection data Dd from digital to analog and outputs it as a X deflection signal Sx and a Y deflection signal Sy, and an analog operation part 2 which applies a deflection voltage to each of electrostatic deflecting boards (described later) of the deflector 3 based on the magnification switch signal Sd, the X deflection signal Sx, and the Y deflection signal Sy. FIG. 3 is a block diagram showing the analog operation part 2 in detail. The analog operation part 2 is provided with analog arithmetic circuits 2x1-2x4, 2y1-2y4. To the analog arithmetic circuits 2x1-2x4, 2y1-2y4 the magnification switch signal Sd is input from the control part 4 as well as the X deflection signal Sx and the Y deflection signal Sy are input from the D-A conversion part 1. Also, the deflection voltages X1-X4, Y1-Y4 output from the analog arithmetic circuits 2x1-2x4, 2y1-2y4 are applied to the electrostatic deflecting boards 3x1-3x4, 3y1-3y4 (described later) of the deflector 3 respectively. FIG. 4 is an explanatory diagram showing the deflector 3 in detail. The deflector 3 comprises a plurality of electrostatic deflecting boards 3x1-3x4, 3y1-3y4 which work as deflecting factors for the electronic beam, and these are arranged in a ring around the light axis (a central axis along the forward direction of the electronic beam). Namely, as shown in FIG. 1, the electronic beam (electron probe) with the given current value passes within the ring of the deflector 3 and receives an influence of the electrostatic field in the ring and gets deflected at any of point on the path of being radiated out from the electron source 1, converged by the condenser lens 6, and focused on the sample P by the object lens 5. Returning to FIG. 4, in this embodiment, for example from the point of view that the large amount of deflection can be obtained and the precision is good, as the deflector 3, an example using an 8 poles deflector which is provided with 8 electrostatic deflecting boards 3x1-3x4, 3y1-3y4 will be explained. Of course, the 8 poles deflector is an example and as the deflector 3 an electrostatic deflector which has another structure corresponding to the use object or mode, for example, a 4 poles deflector which is provided with 4 electrostatic deflecting boards X+, X−, Y+, and Y− (neither of them is shown) and has a simpler structure, etc. may be used. FIG. 5 is a block diagram showing an example of the structure of the analog arithmetic circuit 2x1 included in the analog operation part 2 in detail. The structures of the analog arithmetic circuits 2x1-2x4, 2y1-2y4 are the same structures except that the multiplication rates of multipliers 21x and 21y (described later) are different. The analog arithmetic circuit 2x1 is provided with a multiplier 21x which has the X deflection signal Sx input and multiplies its voltage (X deflection voltage Vx) by given times and output it, a multiplier 21y which has the Y deflection signal Sy input and multiplies its voltage (Y deflection voltage Vy) by given times and output it, an adder 22 which outputs a voltage which results from adding the output voltage of the multiplier 21x and the output voltage of the multiplier 21y, a high gain amplifier 23q and a low gain amplifier 23p which amplify the output voltage of the adder 22 by given gain and output it, a relay with contact 25 which switches either of the output of the high gain amplifier 23q or the output of the low gain amplifier 23p and output it to the electrostatic deflecting board 3x1, and a relay driving circuit 24 which drives the relay with contact 25. The multipliers 21x, 21y are both operational amplifiers. The multipliers 21x, 21y of each of the analog arithmetic circuits 2x1-2x4, 2y1-2y4 amplify the voltage (the X deflection voltage Vx or the Y deflection voltage Vy) of the input signal (the X deflection signal Sx or the Y deflection signal Sy) by the following multiplication rate and output it. The multiplication rate α, β are set to add the main deflection signal and the deflection signal of its 90 degree direction to obtain a uniform electrostatic field in the deflector 3. multiplicationmultiplicationsign of analograte ofrate ofarithmetic circuitmultiplier 21xmultiplier 21y2x1+α+β2x2+α−β2x3−α+β2x4−α−β2y1+β+α2y2−β+α2y3+β−α2y4−β−α The adder 22 is structured including an operational amplifier. The output voltages of the adders 22 of each of the analog arithmetic circuits 2x1-2x4, 2y1-2y4 are as the followings. sign of analogarithmetic circuitoutput voltage of adder 222x1+αVx+βVy2x2+αVx−βVy2x3−αVx+βVy2x4−αVx−βVy2y1+βVx+αVy2y2−βVx+αVy2y3+βVx−αVy2y4−βVx−αVy The low gain amplifier 23p is an operational amplifier including a differential amplifier circuit, a level shift circuit, an output circuit (either of them are not shown). The low gain amplifier 23p has a function to linearly amplify and output the input voltage from the adder 22, and when the input signal from the adder 22 is no input the output voltage is 0. The low gain amplifier 23p has a relatively small amplification factor, but as its noise-figure (NF) is small (therefore the noise rate in the output signal is small), its linearity is good and its offset voltage is low, it can perform the highly precise amplification. The high gain amplifier 23q is a similar circuit to the low gain amplifier 23p, but it is a so-called power operational amplifier and although the amplification factor and the output can be greater, the characteristics such as the noise figure, the linearity, and the lowness of the offset voltage are slightly worse than the low gain amplifier 23p. The low gain amplifier 23p and the high gain amplifier 23q can be obtained at a low price and easily as a uniform one by using an appropriate kind from among the ones on the market as a packaged IC (Integrated Circuit) and by doing so a trouble of design or packaging can be saved. Of course the circuit may be implemented by combining the discrete devices. Assuming that the amplification factor of the high gain amplifier 23q is A1, the output voltages of the high gain amplifiers 23q of each of the analog arithmetic circuits 2x1-2x4, 2y1-2y4 are the value which is the output voltage of the adder 22 multiplied by A1. Also, assuming that the amplification factor of the low gain amplifier 23p is A2, the output voltages of the low gain amplifiers 23p of each of the analog arithmetic circuits 2x1-2x4, 2y1-2y4 are the value which is the output voltage of the adder 22 multiplied by A2. The relay with contact 25 is a relay of a 1a1b contact (c contact) mode relay which has mechanical contacts, and is provided with an ordinarily open contact (a contact) 25a connected to the low gain amplifier 23p, an ordinarily closed contact (b contact) 25b connected to the high gain amplifier 23q, a movable contact piece 25m consisting of a magnetic alloy and connected to the electrostatic deflecting board 3x1, and a coil 25h which generates a magnetic force when the operating current is supplied. As the relay with contact 25 theoretically has no leakage current and its ON resistance is for example as small as a few tens mΩ, it has an advantage that it can retain a good symmetry of the opposite electrostatic deflecting boards each other in the deflector 3. As shown in FIG. 5, when the operating current is not supplied to the coil 25h, by the movable contact piece 25m returning to the ordinarily closed contact 25b side by a spring (not shown) or the elasticity of the movable contact piece 25m itself or a magnetic force of a magnet (not shown), between the ordinarily closed contact 25b and the movable contact piece 25m it is closed and at the same time the ordinarily open contact 25a is released. Also, when the operating current is supplied to the coil 25h, a magnetic force is generated to the coil 25h and by the movable contact piece 25m operating to the ordinarily open contact 25a side, between the ordinarily open contact 25a and the movable contact piece 25m it is closed and at the same time the ordinarily closed contact 25b is released. From the point of view of avoiding the interference of the signal at the time of high magnification and the signal at the time of low magnification, the relay with contact 25 is preferably of the c contact mode, but a circuit which has a similar function may be implemented by combining a plurality of relays of 1a contact mode or 1b contact mode, or by using a part of multi-contact relay. The relay driving circuit 24 drives the relay with contact 25 according to the magnification switch signal Sd input from the control part 4. That is, the relay driving circuit 24 does not supply the operating current to the coil 25h when the magnification switch signal Sd indicates the “low magnification”. At this time, the output side of the high gain amplifier 23q is connected to the electrostatic deflecting board 3x1 and the output voltage (the deflection voltage X1) of the high gain amplifier 23q is applied to the electrostatic deflecting board 3x1. In the same way, the summary about the other analog arithmetic circuits 2x2-2x4, 2y1-2y4 is as the following. Here, the amplification factor of the high gain amplifier 23q is assumed to be A1. sign ofsign ofelectrostaticanalogoutput voltage ofdeflecting boardarithmeticanalog arithmeticof outputcircuitcircuitdestination2x1X1 = A1 (+αVx +βVy)3x12x2X2 = A1 (+αVx −βVy)3x22x3X3 = A1 (−αVx +βVy)3x32x4X4 = A1 (−αVx −βVy)3x42y1Y1 = A1 (+βVx +αVy)3y12y2Y2 = A1 (−βVx +αVy)3y22y3Y3 = A1 (+βVx −αVy)3y32y4Y4 = A1 (−βVx −αVy)3y4 Also, the relay driving circuit 24 supplies the operating current to the coil 25h when the magnification switch signal Sd indicates the “high magnification”. At this time, the output side of the low gain amplifier 23p is connected to the electrostatic deflecting board 3x1 and the output voltage (the deflection voltage X1) of the low gain amplifier 23p is applied to the electrostatic deflecting board 3x1. In the same way, the summary about the other analog arithmetic circuits 2x2-2x4, 2y1-2y4 is as the following. Here, the amplification factor of the low gain amplifier 23p is assumed to be A2. sign ofsign ofelectrostaticanalogoutput voltage ofdeflecting boardarithmeticanalog arithmeticof outputcircuitcircuitdestination2x1X1 = A2 (+αVx +βVy)3x12x2X2 = A2 (+αVx −βVy)3x22x3X3 = A2 (−αVx +βVy)3x32x4X4 = A2 (−αVx −βVy)3x42y1Y1 = A2 (+βVx +αVy)3y12y2Y2 = A2 (−βVx +αVy)3y22y3Y3 = A2 (+βVx −αVy)3y32y4Y4 = A2 (−βVx −αVy)3y4 In this way, by inputting the necessary X deflection signal Sx and Y deflection signal Sy to the analog operation part 2, it is possible to create a desired electrostatic field within the ring of the deflector 3, and by changing the X deflection voltage Vx and the Y deflection voltage Vy by time, it is possible to change the deflection direction and the deflection amount of the electronic beam to scan on the sample. Further, by switching the magnification switch signal Sd to “low magnification” or “high magnification”, the scan magnification can be switched to the low magnification or the high magnification. The electronic beam measuring apparatus of this embodiment can be used with the scan magnification of low magnification and high magnification. As the deflection voltage when the scan magnification is low magnification is, for example, a few hundreds V at the most, the output circuit (not shown) of the high gain amplifier 23q needs to have a high pressure resistance to resist this voltage. Also, as the deflection voltage when the scan magnification is high magnification is, for example, a few V—a few hundreds mV at the most, the output circuit (not shown) of the low gain amplifier 23p only needs to have the pressure resistance for this pressure. Also, in the case when the image obtained by the measuring is displayed for example using an image display device (not shown) of 512 pixel×512 pixel, as the deflection voltage per 1 pixel at the low magnification is a few hundreds mV/pixel—a few V/pixel, the deflection system for low magnification including the high gain amplifier 23q only needs to have the precision corresponding to this. Also, as the deflection voltage per 1 pixel at the high magnification is about a few mV/pixel, the deflection system for high magnification including the low gain amplifier 23p is supposed to have a high precision corresponding to this. The so-called power operational amplifier device has the noise element at the used frequency of for example a few tens μV, namely about 1 percent of the deflection voltage per 1 pixel at the high magnification. Therefore, the power operational amplifier device can obtain a sufficient scan waveform precision as for the deflection voltage output when the magnification is low, but as for the deflection voltage output when the magnification is high it cannot obtain sufficient scan waveform precision. Further, the deflection voltage per 1 pixel when the magnification is high is, for example, a few mV/pixel, and it is almost equal to the offset voltage of the power operational amplifier device (here, the offset voltage is also amplified by the gain of the power operational amplifier device). Therefore, it is generated the pixel shift (image shift) by this offset voltage from the intended beam irradiation location. In this way, when the offset voltage is large, it becomes difficult to irradiate accurately the electronic beam to the surface of the sample. For example, if the design rule of the integrated circuit to be a sample is 200 nm, the pattern measuring would be performed with the magnification of 200 thousands times, and the deflection voltage per 1 pixel at that time would be about 3.4 mV/pixel. Also, if the design rule is 90 nm, the pattern measuring would be performed with the magnification of 400 thousands times, and the deflection voltage per 1 pixel at that time would be about ½ of that of when the magnification is 200 thousands times, namely about 1.7 mV/pixel. The value of the deflection voltage at this time is almost equal to the noise level or the offset voltage of the power operational amplifier device. In this embodiment, the problems described above are solved by switching to the output from the high gain amplifier 23q which has a high pressure resistance and high output by the relay with contact 25 at the time of low magnification when it is necessary to output a high deflection voltage to the deflector 3, and by switching to the output from the low gain amplifier 23p with low noise and low offset voltage by the relay with contact 25 at the time of high magnification when it is necessary to output a high precision deflection voltage waveform to the deflector 3. Therefore, when the magnification is low as the deflection signal is amplified by the high gain amplifier 23q the electronic beam measuring of wide field of view can be performed with sufficient precision, and when the magnification is high as the deflection signal is amplified by the low gain amplifier 23p the electronic beam measuring with small noise and aberration and with high precision can be performed. On switching to the low magnification or to the high magnification, if it is configured to be performed with the magnification with which the deflection voltage per 1 pixel would be greater than the offset voltage of the high gain amplifier 23q, the image shift resulting from the switching of the low magnification and the high magnification is rarely generated. By this configuration, it is possible to omit the offset adjustment of the high gain amplifier 23q. Also, by performing the switching by the relay with contact 25, as the structure of the analog arithmetic circuits 2x1-2x4, 2y1-2y4 except the high gain amplifier 23q and the low gain amplifier 23p can be used in common at the time of the low magnification and the high magnification, the deterioration of the precision by the device scattering can be restrained as well as the circuit can be simplified. Also, as the deflection of the electronic beam at the time of the low magnification and the high magnification can be performed by one deflector 3, the deflection mechanism of the electronic beam such as the deflector 3 can be simplified. FIG. 6 is a block diagram showing an analog arithmetic circuit 2bx1 included in an analog operation part 2b of a deformed example in detail. The analog operation part 2b can be used instead of the analog operation part 2 and has the similar function. The analog operation part 2b is provided with, instead of the analog arithmetic circuits 2x1-2x4, 2y1-2y4 (see FIG. 3), analog arithmetic circuits 2bx1-2bx4, 2by1-2by4 which have the similar function. The analog arithmetic circuit 2bx1 has the similar structure to the analog arithmetic circuit 2x1 except that it is provided with an optical MOS relay 26 instead of the relay with contact 25 and a relay driving circuit 24b instead of the relay driving circuit 24. Also, as the analog arithmetic circuits 2bx2-2bx4, 2by1-2by4 have the similar structure to the analog arithmetic circuit 2bx1, their illustration is omitted. The optical MOS relay 26 is provided with an ordinarily open device 26a including a light receiving device and a power MOSFET, a light emitting device 26c on the side of the ordinarily open device 26a, an ordinarily closed device 26b including a light receiving device and a power MOSFET, and a light emitting device 26d on the side of the ordinarily closed device 26b. The relay driving circuit 24b, when the magnification switch signal Sd indicates the “low magnification”, puts the light emitting device 26c off and puts the ordinarily open device 26a in a non-conductive state, as well as lights the light emitting device 26d and puts the ordinarily closed device 26b in a conductive state. Thereby, the output voltage (the deflection voltage X1) of the high gain amplifier 23q is applied to the electrostatic deflecting board 3x1. Also, the relay driving circuit 24b, when the magnification switch signal Sd indicates the “high magnification”, lights the light emitting device 26c and puts the ordinarily open device 26a in a conductive state, as well as puts the light emitting device 26d off and puts the ordinarily closed device 26b in a non-conductive state. Thereby, the output voltage (the deflection voltage X1) of the low gain amplifier 23p is applied to the electrostatic deflecting board 3x1. By using the optical MOS relay 26, it is possible to switch the low magnification and the high magnification at a high speed and it has an advantage that as it does not have the mechanical contact it has a longer life and the reliability of the contact is enhanced. Instead of the optical MOS relay 26, a semiconductor relay without contact of another form may be used. Further, it is possible to use another device which has a switching function such as a hybrid relay or a switching device. FIG. 7 is a block diagram showing an analog arithmetic circuit 2cx1 included in an analog operation part 2c of another embodiment in detail. In this analog arithmetic circuit 2cx1 it does not have the function of switching the low magnification and the high magnification and it amplifies the input voltage from the adder 22 by one amplifier 23 and applies it to the electrostatic deflecting board 3x1. In the case when this electronic beam measuring apparatus is made to be usable with the low magnification, it is necessary to use an operational amplifier which has high output capacity and high pressure resistance capacity for the amplifier 23. For this reason, when it is used with the high magnification the noise or the offset voltage will be large and a high precision image may not be obtained. Also, in the case when this electronic beam measuring apparatus is made to be suitable to the usage with the high magnification, it is necessary to use a high precision operational amplifier for the amplifier 23. For this reason, when the magnification is low, it may not be used because the pressure resistance and the high output may be insufficient. It should be further understood by those skilled in the art that although the foregoing description has been made on embodiments of the invention, the invention is not limited thereto and various changes and modifications may be made without departing from the spirit of the invention and the scope of the appended claims.
044341300	claims	1. In a fusion reactor, the combination comprising: (a) means including coaxial electrodes spaced apart to establish an annular reaction zone with a voltage thereacross to establish a spiral beam of electrons traveling along a common spiral path through an annular reaction zone free from any applied magnetic field to form a cylindrical electron sheath which rotates as a whole about a common sheath axis; and (b) means to project oppositely directed beams of fusible ions longitudinally through said electron sheath to force ions in both ion beams into linear paths in a common thin cylindrical zone located where the potential gradient in electron sheath is minimum. (a) means including coaxial electrodes spaced apart with a voltage thereacross to establish an annular reaction zone free from any applied magnetic field with means to maintain a beam of flowing electrons as a cylindrical spiral electron sheath which rotates as a whole about a common sheath axis having a transverse electron distribution such that the potential gradient across said sheath exhibits a minimum within said sheath; and (b) ion sources for projecting oppositely directed beams of fusible ions through said electron sheath to force the ions in both beams to follow paths where the potential gradient in electron sheath is minimum. (a) electrode structure forming boundaries for an annular cylindrical chamber with a voltage thereacross; (b) means to establish and maintain spiral beam of electrons in said chamber in the form of a cylindrical electron sheath which rotates as a whole about a common sheath axis free from any applied magnetic field; and (c) means to project oppositely directed beams of fusible ions through said electron sheath in said chamber to force said ions into linear paths where the potential gradient in electron sheath is minimum for enhancing head-on collisions between ions in said oppositely directed beams. (a) establishing an annular reaction zone bounded by coaxial cylindrical walls with a voltage thereacross; (b) accelerating and focusing a stream of electrons for spiral flow to form a cylindrical electron sheath which rotates as a whole about a common sheath axis free from any applied magnetic field; (c) projecting high energy ions from a first source along through said sheath in a first direction; (d) projecting high energy ions from a second source through said sheath in direction opposite to said first direction wherein ions from both sources respond to the electric fields in said sheath to settle into paths at the radius at which the potential gradient in said sheath is minimum. (a) establishing a spiral flow of electrons to form a cylindrical electron sheath in an annulus between a pair of coaxial electrodes across which a voltage is applied and which flow rotates as a whole about a common sheath axis free from any applied magnetic field; (b) projecting high energy ions from a first source through said sheath in a first direction; (c) projecting high energy ions from a second source through said sheath in direction opposite to said first direction; (d) the ratio of the total number of electrons forming said sheath to the total number of ions in said sheath being at least equal to the ratio of the average ion mass to the mass of the electron whereby said ions respond to the electric fields in said sheath to settle into paths at a radius in said sheath at which the potential gradient is minimum. (a) means including coaxial electrodes spaced apart with a voltage connected between said electrodes to establish an annular reaction zone with means to establish spiral flow of electrons along paths whose locus is a cylinder thereby forming an electron sheath which rotates as a whole about a common sheath axis free from any applied magnetic field; and (b) means to project oppositely directed beams of fusible ions along substantially linear paths parallel to the length of said cylinder and through said spiral flow to force the ions in both beams into a common thin cylindrical path located where the potential gradient due to said electron flow is minimum. (a) means including coaxial electrodes spaced apart with a voltage connected between said electrodes to establish an annular reaction zone with means to maintain a spiral flow of electrons to form a cylindrical electron sheath which rotates as a whole about a common sheath axis having radial electron distribution such that the potential gradient across said sheath exhibits a minimum free from any applied magnetic field; and (b) ion sources for projecting oppositely directed beams of fusible ions along paths whose locus is a cylinder and which paths pass through said electron sheath to force the ions in both beams to follow paths where the potential gradient in electron sheath is minimum. 2. A system for promotion of nuclear fusion comprising: 3. The combination set forth in claim 2 wherein said sheath is cylindrical wherein said electrons flow in spiral paths. 4. The combination set forth in claim 3 wherein said ions travel in opposite directions along linear paths substantially perpendicular to the direction of travel of said electrons. 5. A system for promotion of nuclear fusion comprising: 6. A method for promoting fusion of atomic particles which comprises: 7. The method of claim 6 whereinsaid electrons emerge from a circular source symmetrical to an axis common to said sheath and wherein said electrons are magnetically deflected and electrostatically focused into spiral paths to form said sheath. 8. The method of claim 6 wherein the ratio of the total number of electrons forming said sheath bears a predetermined relation to the ratio of the mass of the electron to the average mass of the ions in said sheath. 9. A method of claim 6 wherein the ratio of the total number of electrons forming said sheath to the total number of ions in said sheath is at least equal to the ratio of the average ion mass to the mass of the electron. 10. A method for promoting fusion of atomic particles which comprises: 11. In a fusion reactor, the combination comprising: 12. The system according to claim 11 in which the first means establishes spiral flow of electrons is in our direction only. 13. The system according to claim 11 in which the first means establishes spiral flow of electrons in two directions. 14. The system according to claim 13 in which the first means establishes electron flow in one direction at a first radius and in the opposite direction in a second radius slightly different from the first radius. 15. A system for promotion of nuclear fusion comprising: 16. The system of claim 15 in which the means to maintain said spiral flow comprises two sources of electrons, one adjacent to each of said ion sources, and wherein electrons from one of said sources are of velocity different from the velocity of electrons from the other source.
043137954	claims	1. A nuclear power plant comprising: a. a containment vessel having: b. power generating means connected to said containment vessel for generating electric power by use of said drive medium. a. compressing wet steam at a first temperature and pressure to a second temperature and pressure less than the saturation point of the wet steam; b. adding heat from an external source comprising solid state heat transfer conductors having a first portion in contact with a heat transfer medium of a nuclear reactor core and a second portion in contact with the steam, said heat transfer conductor remaining in a solid state condition during operation of the cycle to the wet steam wherein the steam maintains a substantially constant second temperature and pressure to the superheated point wherein the steam is dry; c. adding additional heat from said external source to the dry steam, superheating the dry steam wherein the temperature of the steam at the second pressure is raised to a third temperature; d. extracting work from the steam at the second pressure, and third temperature reducing the steam to approximately the first temperature and pressure; e. extracting heat from the steam at the first temperature and pressure for return of the steam to the conditions of the first step. 2. The nuclear power plant of claim 1 wherein said solid state heat transfer conductors comprise a plurality of elongated thermally conductive rods arranged in an array wherein said rods are spaced from one another. 3. The nuclear power plant of claim 1 wherein said plant comprises further a reactor core storage dump connected to and directly below said containment vessel for storage of spent nuclear reactor cores, said containment vessel having means for dropping a spent reactor core together with a portion of molten core-coolant heat transfer medium into said dump from said first portion of said containment vessel. 4. The nuclear power plant of claim 3 wherein said reactor core storage dump comprises an elongated third portion of said containment vessel oriented below said first portion of said containment vessel and separable therefrom, said third portion having a capacity to contain and store a plurality of spent reactor cores and a quantity of core-coolant, heat transfer medium. 5. The nuclear power plant of claim 3 wherein said reactor core storage dump comprises an elongated column of container vessels, said container vessels being substantially spherical in configuration and vertically oriented wherein said container vessels comprise a bottom vessel and upper vessels arranged in a series and supported on said bottom vessels, said upper vessels having top and bottom openings, and said bottom vessel having a top opening wherein wastes deposited in said upper vessels pass to said bottom vessel for storage. 6. The nuclear power plant of claim 5 wherein said column of container vessels is located in a salt pack means for maintaining the stability of the column. 7. The nuclear power plant of claim 1 wherein said power generating drive medium comprises a heated gas, for use with other low grade fuels in conventional boilers. 8. The nuclear power plant of claim 7 wherein said power generating means comprises a turbine having means connected to said second portion of said containment vessel for receiving heated pressurized gas from said containment vessel, an electric generator mechanically connected to said gas turbine, and a gas compressor mechanically connected to said gas turbine having means connected to said gas turbine and said second portion of said containment vessel for receiving gas discharged from said gas turbine, and returning such gas after compression by said compressor to said second portion of said containment vessel. 9. The nuclear power plant of claim 8 wherein said gas compressor includes a gas conditioner means for reducing the heat content of gas received by the compressor. 10. The nuclear power plant of claim 8 wherein said heated gas comprises a superheated steam. 11. A method for producing useable power with steam comprising the cycle steps of:
	description	The present invention relates to fluid filled devices, and in particular to those devices comprising a sealed cavity. The present invention is particularly suitable for use in electrowetting devices. Fluid filled devices are devices that contain at least two fluids (i.e. multi-fluid filled devices), with the device typically being arranged to perform a function by displacing (changing the position or shape of) a volume of at least one of the fluids. Optical fluid filled devices can for instance function as lenses, diaphragms, gratings, shutters, optical switches or filters. Examples of optical fluid filled devices, as well as different possible methods of displacing the fluids such as by using electrowetting, are described within WO 02/069016. Electrowetting devices are devices that utilise the electrowetting phenomenon to operate. In electrowetting, the three-phase contact angle is changed with applied voltage. The three-phases constitute two fluids and a solid. The term fluid encompasses both liquids and gases. Typically, at least the first fluid is a liquid; the second fluid may be a liquid, or a gas or vapour. EP 1,069,450 describes an optical device that utilises the electrowetting effect so as to act as a variable density optical filter. FIG. 1 is a cross-sectional view of such a typical optical device 90. The optical device 90 has two immiscible fluids 80, 87 confined in a sealed space 92, (i.e. a chamber, or cavity). The term immiscible indicates that the two fluids do not mix. The first fluid 80 is an insulator (e.g. silicone oil) and the second fluid 87 electroconductive (e.g. a mixture of water and ethyl alcohol). The first fluid 80 and the second fluid 87 have different light transmittances. A voltage from a voltage supply 40 can be applied to the two electrodes 41, 42 so as to produce an electric field between the fluid 87 and the electrode 42 (an insulating layer 50 prevents the second electrode 42 contacting the conductive second fluid). By varying the voltage applied to the second fluid 87, the shape of an interface 85 between the first fluid 80 and the second fluid 87 is altered, so as to change the overall transmittance of the optical element. It is also known to provide a variable lens utilising a similar configuration, but with the two fluids 80, 87 having different refractive indices. The device 90 in FIG. 1 has a water-repellent film 60 of diameter D1 on the insulating layer 50, surrounded by a ring of a hydrophilic agent 70 so as to locate the first fluid 20. The shape of the interface 85 changes during the operation of the device. The change in shape may result in the fluid 80 extending from the water-repellent layer 60 to the opposite surface of the sealed space. In order to prevent the first fluid 80 adhering to the opposite surface, a portion of the opposite surface is coated with a layer of hydrophilic film 72 of diameter D2. In order to limit the action of gravity upon the interface 25, the two fluids 80, 87 may be of equal density. It is an aim of embodiments of the present invention to provide an improved electrowetting device. It is an aim of embodiments of the present invention to provide an electrowetting device that has improved stability, particularly when subjected to accelerative forces. In one aspect, the present invention provides a device comprising a sealed cavity containing n volumes of fluids, where n is an integer and n≧2, each volume of fluid being substantially immiscible with every contiguous volume of fluid, the cavity being defined by an interior surface divided into n continuous areas, each continuous area corresponding to and being in contact with a respective one of the volumes of fluid, the wettability of each area being such that each volume of fluid preferentially adheres to the corresponding continuous area rather than any one of the continuous areas adjacent to the corresponding area. By providing a sealed cavity having such a structure, the likelihood of a volume of fluid adhering to an incorrect portion of the internal surface of the cavity is greatly diminished. Consequently, the stability of the device when subjected to accelerative forces is improved. Further, any small amounts of one fluid that have dissolved in another fluid are prevented from condensing on an incorrect surface. In another aspect, the present invention provides an optical scanning device for scanning an information layer of an optical record carrier, the device comprising a radiation source for generating a radiation beam and an objective system for converging the radiation beam on the information layer, wherein the optical scanning device comprises a device comprising a sealed cavity containing n volumes of fluids, where n is an integer and n≧2, each volume of fluid being substantially immiscible with every contiguous volume of fluid, the cavity being defined by an interior surface divided into n continuous areas, each continuous area corresponding to and being in contact with a respective one of the volumes of fluid, the wettability of each area being such that each volume of fluid preferentially adheres to the corresponding continuous area rather than any one of the continuous areas adjacent to the corresponding area. In a further aspect, the present invention provides a method of manufacturing a device, the method comprising: providing a cavity having an interior surface divided into n continuous areas, where n is an integer and n≧2; filling the cavity with n volumes of fluid, each volume of fluid being substantially immiscible with every contiguous volume of fluid such that each continuous area corresponds to and is in contact with a respective one of the volumes of fluid; and sealing the cavity, wherein the wettability of each area is such that each volume of fluid preferentially adheres to the corresponding continuous area rather than any one of the continuous areas adjacent to the corresponding area. In another aspect, the present invention provides a method of manufacturing an optical scanning device for scanning an information layer of an optical record carrier, the method comprising the steps of: providing a radiation source for generating a radiation beam; providing a device, the device comprising a sealed cavity containing n volumes of fluids, where n is an integer and n≧2, each volume of fluid being substantially immiscible with every contiguous volume of fluid, the cavity being defined by an interior surface divided into n continuous areas, each continuous area corresponding to and being in contact with a respective one of the volumes of fluid, the wettability of each area being such that each volume of fluid preferentially adheres to the corresponding continuous area rather than any one of the continuous areas adjacent to the corresponding area. The present inventors have realised that it is possible for the device 90 shown in FIG. 1 to be disturbed, such that both bodies of liquids do not stay entirely in the desired positions. For instance, a portion 81 of the fluid 80 might become lodged in a corner of the device, as shown in FIG. 2. This situation could arise if the two liquids were not completely immiscible. For instance, small (e.g. sub-micrometer sized) droplets of the fluid 20 within the fluid 30 might stick to, and accumulate on, a portion of the interior surface of the device 10. Alternatively, the situation could arise if the device 90 was subjected to accelerative forces e.g. it was shaken or dropped. Displacing a portion of the liquid from its desired location (or, indeed, the entire liquid) is undesirable, as it will effect the performance of the device. The shape of the interface 85 between the two fluids 80, 87 is partly dependent upon the volume of the first fluid 80. Consequently, if the volume of the first fluid 80 is decreased, then the shape of the interface 85 as a function of the applied voltage will be effected. This will change the performance of the device 90, and impair the function of the device as a variable filter (or as a lens, depending upon the properties of the fluids 20, 30). The present inventors have realised that, for such a two fluid system, this problem can be overcome by dividing the complete interior surface into two separate areas, each area corresponding to and preferentially attracting one of the two respective fluids. This is achieved by providing areas of the device having different wettabilities for each fluid, such that each fluid will be attracted to a respective area. Wettability is the extent by which a solid is wetted (covered) by a fluid. The term “divided into” means that the surface areas are adjacent or contiguous, (i.e. substantially without intermediate areas) as well as continuous (i.e. each of the areas does not include any substantial intervening areas arranged to attract another fluid). The maximum width of such intermediate or intervening areas is smaller than the diameter of a droplet that could be formed in the fluids. Preferably, the maximum width of such areas is less than 100 μm, and more preferably less than 10 μm. Consequently, if such a droplet would touch such an intermediate area, it would not adhere because the intermediate area does not provide sufficient contact area with the droplet. FIG. 3 illustrates a cross-sectional view of a device 100 in accordance with a first embodiment of the present invention. The device 100 generally corresponds to the device 90 illustrated in FIGS. 1 and 2, with identical reference numerals indicating similar features. The device 100 has an area of diameter D1 of a hydrophobic surface 60 arranged to attract the non-conducting non-polar first fluid 80. The remainder of the interior surface is covered with a hydrophilic coating 170 that is preferentially wetted by (i.e. it attracts) the conducting polar fluid 87. This prevents the situation shown in FIG. 2 of a portion of the liquid volume 80 adhering in an undesired manner to a portion of the interior cavity. Instead, if undesired droplets are formed, the droplets will not adhere to undesired parts of the interior surface, but keep moving about until they coalesce with the volume of liquid from which they were split off, thereby returning to the desired configuration of the fluids. In this particular embodiment, the electrode 41 is in electrical contact with the conducting polar fluid 87, whilst the surface of the electrode (which forms a portion of the interior surface of the sealed cavity) is hydrophilic. The surface of the electrode may be naturally hydrophilic. Alternatively, a conductive hydrophilic coating may be applied to the complete surface area 170, or only to the electrode (or the portion of the electrode that forms part of the interior surface of the cavity). In other embodiments, the coating covering the electrode 41 is not electrically conducting i.e. it is an insulator. For instance, the hydrophilic insulator Silicon Oxide could be used. Electrowetting will still occur due to capacitive coupling, but at a somewhat higher voltage. If the insulating coating is thin compared to the insulating layer covering the counter electrode 42, then the required voltage increase will be minimal. FIG. 4 illustrates a device 200 in accordance with a further embodiment of the present invention. The device 200 is again an optical device (i.e. it is arranged to alter the properties of light incident upon the device), and in this instance the device 200 is arranged to act as a variable-focus lens. The device 200 comprises a first fluid 220 and a second fluid 230, the two fluids being immiscible. The first fluid 220 is a non-conducting non-polar liquid, such as a silicone oil or an alkane. The second fluid 230 is a conducting or polar liquid such as water containing a salt solution (or a mixture of water and ethylene glycol). The two fluids 220, 230 are preferably arranged to have an equal density, so as to minimise the gravitational effects between the two liquids such that the lens functions independently of orientation. The two fluids 220, 230 have different refractive indices, such that the interface 225 between the two fluids will act as a lens. Varying the shape of the interface 225 will vary the focal length of the lens. The shape of the interface 225 is adjusted by the electrowetting phenomenon, by applying a voltage between the electrodes 260 and the electrode 242 so as to alter the contact angle of the fluid and the walls of the device 200. So as to allow the transmission of light through the device, at least opposite faces of the device (in the orientation shown in the figure, top and bottom surfaces) are transparent. In this particular embodiment, the device takes the form of a cylinder 210, with light entering and exiting through the transparent ends 212, 214 of the cylinder. The fluids 220, 230 are enclosed within the sealed space defined by the cylinder 210. One end 260 of the interior surface of the cylinder 210 is hydrophilic so as to attract the polar fluid 230. The remainder of the cylinder 210 (i.e. the opposite end, and the interior side walls) is coated with a hydrophobic coating 270. The hydrophilic area 260 may be formed entirely of a hydrophilic material (e.g. glass), or alternatively coated with a hydrophilic layer (e.g. silicon dioxide). In this particular embodiment, the hydrophilic area 260 of the interior surface is completely covered by a transparent hydrophilic conductor (e.g. Indium Tin Oxide), so as to form an electrode. A voltage is supplied from variable voltage source 240 across the polar liquid 230 by the transparent electrode 260 and an annular electrode 242 extending around the device 200 in proximity to the three-phase line. The electrode 242 is not in conductive contact with the polar fluid 230. By arranging for one area of the interior surface of the cylinder to be hydrophilic, with the remainder of the interior surface being hydrophobic, then it will be appreciated that in this two fluid system the stability of the device will be greatly enhanced. The polar fluid will not adhere to any portion of the interior surface where it is desired to have only the non-polar fluid, and vice versa. It should be noted that this condition does not prohibit the polar fluid 230 being in contact with part of the hydrophobic coating 270. The purpose of the hydrophilic layer is to locate the polar fluid i.e. to keep the polar fluid in a desired position (with the position often defining at least in part the shape). Thus, a relatively small hydrophilic area may be suitable for this purpose. For instance, the whole of the interior surface of a device could be hydrophobic, apart from those areas in which it is necessary to keep the polar fluid(s) in a certain shape or position. Electrowetting can be used to increase the wettability of a polar or conducting fluid on a surface. If this wettability is initially small (for a polar liquid this is usually termed a hydrophobic surface, e.g. a Teflon-like surface), a voltage can be used to make it larger. If the wettability is initially large (for a polar liquid this is usually called a hydrophilic surface, e.g. silicon dioxide) then applying voltage will have relatively little effect. It is therefore preferable that in electrowetting devices the three-phase line is initially in contact with a hydrophobic layer. It will also be appreciated that the present invention can be applied to electrowetting devices comprising more than two fluids, as shown by way of example in FIGS. 5 and 6. The present invention can be applied to any device having n volumes of fluid, where n≧2, n being the number of intended volumes of fluid according to the design of the device. FIG. 5 illustrates an electrowetting device 300 comprising two volumes of polar fluids 330, 332, separated by a volume of non-polar fluid 320. The polar fluids 330, 332 may be identical, or alternatively different fluids. Preferably, each fluid is non-miscible with the adjacent fluid with which it forms an interface 325a, 325b. More preferably, all of the fluids are immiscible with respect to each other. Preferably, each fluid is of substantially similar density. The interior surface of the device 300 is divided up into three distinct areas 360, 370, 362, with each area corresponding to a respective volume of fluid 330, 320, 332. The properties of each continuous area 360, 370, 362 are such that each area will preferentially attract the corresponding fluid rather than the adjacent connecting fluid. For instance, areas 360, 362 will be hydrophilic, whilst area 370 will be hydrophobic. It is appreciated that this arrangement of interior surfaces will not completely prohibit the incorrect positioning of the fluids e.g. a portion of the volume of fluid 330 may end up adhering to the hydrophilic layer 362 if the device 300 is violently shaken. However, due to the arrangement of the interior surfaces, for any portion of the polar fluid 330 to contact the area 362, it would first need to traverse the volume of fluid 320 surrounded by the area 370. Thus, the likelihood of the fluid 330 adhering to an undesired portion of the interior surface of the device 300 is greatly diminished, so as to provide a relatively stable device. FIG. 6 shows an example of an electrowetting device 400 comprising four separate fluids 420, 430, 422, 432. Each volume of fluid is immiscible with the adjacent fluid. Further, each volume of fluid is in contact with a respective area to which that volume of fluid preferentially adheres (rather than to any one of the continuous areas adjacent to the corresponding area). For instance, fluid volume 432 preferentially adheres to the annular interior surface area 462, rather than to either of the adjacent areas 477, 470. Equally, fluid 430 preferentially adheres to the area 460 rather than to the adjacent area 470 (which corresponds to fluid 420). For convenience, no electrodes are illustrated with respect to either the electrowetting device 300 illustrated in FIG. 5, or the electrowetting device 400 illustrated in FIG. 6. It will be appreciated that the above embodiments are provided by way of example only. It will be appreciated that the areas of different wettability can be formed entirely from a hydrophobic or a hydrophilic material. Alternatively, the areas can be formed by coating other materials with hydrophobic or hydrophilic substances e.g. by dip coating or by chemical vapour deposition. The devices may be any multi-fluid filled devices, and are not limited to devices that utilise the electrowetting phenomenon to operate. The devices can comprise any desired shape. For instance, an electrowetting device in accordance with the present invention could be shaped as described within WO 00/58763. The devices may be optical devices, or form part of optical devices or indeed any other type of device. FIG. 7 illustrates a device 1 for scanning an optical record carrier 2, including an objective lens system lens 18 comprising a variable focus lens in accordance with an embodiment of the present invention. In this particular embodiment, the variable focus lens 18 corresponds to the electrowetting device 200 illustrated in FIG. 4. However, it will be appreciated that other embodiments may use other fluid filled devices to perform any desired optical functions. For instance, a suitable device could be used as any lens having an adjustable strength, or as an adjustable diaphragm, or as a wavefront correcting element (e.g. for introducing an adjustable amount of spherical aberration in the radiation beam passing through the element) in a scanning device. FIG. 7 shows a device 1 for scanning an optical record carrier 2, including an objective lens 18. The record carrier comprises a transparent layer 3, on one side of which an information layer 4 is arranged. The side of the information layer facing away from the transparent layer is protected from environmental influences by a protection layer 5. The side of the transparent layer facing the device is called the entrance face 6. The transparent layer 3 acts as a substrate for the record carrier by providing mechanical support for the information layer. Alternatively, the transparent layer may have the sole function of protecting the information layer, while the mechanical support is provided by a layer on the other side of the information layer, for instance by the protection layer 5 or by a further information layer and a transparent layer connected to the information layer 4. Information may be stored in the information layer 4 of the record carrier in the form of optically detectable marks arranged in substantially parallel, concentric or spiral tracks, not indicated in the Figure. The marks may be in any optically readable form, e.g. in the form of pits, or areas with a reflection coefficient or a direction of magnetisation different from their surroundings, or a combination of these forms. The scanning device 1 comprises a radiation source 11 that can emit a radiation beam 12. The radiation source may be a semiconductor laser. A beam splitter 13 reflects the diverging radiation beam 12 towards a collimator lens 14, which converts the diverging beam 12 into a collimated beam 15. The collimated beam 15 is incident on an objective system 18. The objective system may comprise one or more lenses and/or a grating. The objective system 18 has an optical axis 19. The objective system 18 changes the beam 17 to a converging beam 20, incident on the entrance face 6 of the record carrier 2. The objective system has a spherical aberration correction adapted for passage of the radiation beam through the thickness of the transparent layer 3. The converging beam 20 forms a spot 21 on the information layer 4. Radiation reflected by the information layer 4 forms a diverging beam 22, transformed into a substantially collimated beam 23 by the objective system 18 and subsequently into a converging beam 24 by the collimator lens 14. The beam splitter 13 separates the forward and reflected beams by transmitting at least part of the converging beam 24 towards a detection system 25. The detection system captures the radiation and converts it into electrical output signals 26. A signal processor 27 converts these output signals to various other signals. One of the signals is an information signal 28, the value of which represents information read from the information layer 4. The information signal is processed by an information processing unit for error correction 29. Other signals from the signal processor 27 are the focus error signal and radial error signal 30. The focus error signal represents the axial difference in height between the spot 21 and the information layer 4. The radial error signal represents the distance in the plane of the information layer 4 between the spot 21 and the centre of a track in the information layer to be followed by the spot. The focus error signal and the radial error signal are fed into a servo circuit 31, which converts these signals to servo control signals 32 for controlling a focus actuator and a radial actuator respectively. The actuators are not shown in the Figure. The focus actuator controls the position of the objective system 18 in the focus direction 33, thereby controlling the actual position of the spot 21 such that it coincides substantially with the plane of the information layer 4. The radial actuator controls the position of the objective lens 18 in a radial direction 34, thereby controlling the radial position of the spot 21 such that it coincides substantially with the central line of track to be followed in the information layer 4. The tracks in the Figure run in a direction perpendicular to the plane of the Figure. The device of FIG. 7 in this particular embodiment is adapted to scan also a second type of record carrier having a thicker transparent layer than the record carrier 2. The device may use the radiation beam 12 or a radiation beam having a different wavelength for scanning the record carrier of the second type. The NA of this radiation beam may be adapted to the type of record carrier. The spherical aberration compensation of the objective system must be adapted accordingly. By providing a device having such an interior surface as described above, the likelihood of the volume of fluid adhering to an incorrect portion of the internal surface of the device is greatly diminished. Consequently, the stability of the device is improved. This is particularly advantageous if the device is used in a portable unit such as a portable CD (Compact Disc) or DVD (Digital Versatile Disc) player.
	claims	1. An X-ray computerized tomography apparatus comprising: an X-ray detection unit for detecting transmission X-rays from a plurality of directions irradiated from an X-ray beam generation source and transmitted through a subject; a data acquisition unit for acquiring transmission data according to the transmission X-rays detected by the X-ray detection unit: an object position detection unit for detecting a position of an object inside the subject, according to a part of the transmission data acquired by the data acquisition unit; a reconstructing range determining unit for determining a slice to be Image-reconstructed, according to the position detected by the object position detection unit; and an image reconstruction unit for reconstructing a tomographic image of a slice in which the object exists, according to transmission data acquired by the data acquisition unit, the transmission data being acquired in the slice determined by the reconstruction range determining unit. 2. The X-ray computerized tomography apparatus according to claim 1 , wherein claim 1 the object position detection unit includes: a transmission data extraction unit for extracting transmission data at a predetermined tube position of the X-ray beam generation source, for each slice, from the transmission data acquired by the data acquisition unit, whereby to detect a position of the object according to the extracted transmission data. 3. The X-ray computerized tomography apparatus according to claim 1 , wherein claim 1 the object position detection unit detects a position of the object by deciding a presence of the object by using a predetermined threshold of an X-ray absorption value. 4. The X-ray computerized tomography apparatus according to claim 3 , wherein claim 3 when the object is an insertion object, and when the transmission data within the threshold for showing a tip of the insertion object exists in the slice displayed previously, the object position detection unit decides whether or not there is the transmission data within the threshold in an adjacent slice in a positive proceeding direction of the insertion object, and when there is no transmission data within the threshold in the slice displayed previously, the object position detection unit decides whether or not there is the transmission data within the threshold in an adjacent slice in a negative proceeding direction of the insertion object, so as to detect the tip of the insertion object in correspondence with the proceeding direction of the insertion object. 5. The X-ray computerized tomography apparatus according to claim 1 , wherein claim 1 the object position detection unit detects a position of the object by deciding a presence of the object by using a shape recognition. 6. The X-ray computerized tomography apparatus according to claim 1 , wherein claim 1 the object position detection unit detects a position of the object according to transmission data of a plurality of slices acquired by the data acquisition unit. 7. The X-ray computerized tomography apparatus according to claim 6 , wherein claim 6 the transmission data of the plurality of slices is obtained by scanning at a plurality of positions of a couch or a gantry, or by volume scanning using a two-dimensional detector having detecting elements laid out by a plurality of rows in a slice direction. 8. The X-ray computerized tomography apparatus according to claim 2 , further comprising: claim 2 a tube position determining unit for determining the predetermined tube position of the X-ray beam generation source, based on the transmission data of a plurality of slices from a plurality of directions acquired by the data acquisition unit, and for sending data indicating a determined tube position to the transmission data extraction unit. 9. The X-ray computerized tomography apparatus according to claim 8 , wherein claim 8 when the object is an insertion object, the tube position determining unit sets a tube position where the insertion object has the largest length on the transmission data from among the tube positions of a plurality of directions, as the tube position. 10. The X-ray computerized tomography apparatus according to claim 1 , further comprising: claim 1 a display unit for visualizing the tomographic image reconstructed by the image reconstruction unit. 11. The X-ray computerized tomography apparatus according to claim 10 , wherein claim 10 when the object is an insertion object, the display unit visualizes the tomographic image of the subject in a slice in which the tip of the insertion object exists. 12. The X-ray computerized tomography apparatus according to claim 10 , wherein claim 10 when the object is an insertion object, the display unit forms a stacked display image of an image in a slice in which an object previously designated exists and an image in a slice in which the tip of the insertion object exists. 13. The X-ray computerized tomography apparatus according to claim 11 , further comprising: claim 11 an operation controlling unit for instructing the X-ray detection unit and the data acquisition unit to acquire transmission data so as to make these units detect a position of the tip of an insertion object, based on an input by an operator, when the tip of the insertion object has deviated from an image displayed by the display unit. 14. The X-ray computerized tomography apparatus according to claim 11 , wherein claim 11 the display unit always displays a tomographic image of the subject in a slice in which the tip of the insertion object exists, according to a position of the insertion object detected by the object position detecting unit. 15. An X-ray computerized tomography apparatus, comprising: an X-ray detection unit for detecting transmission X-rays from a plurality of directions irradiated from an X-ray beam generation source and transmitted through a subject; a data acquisition unit for acquiring transmission data according to the transmission X-rays detected by the X-ray detection unit; an object position detection unit for detecting a position of an object inside the subject, according to a part of the transmission data acquired by the data acquisition unit; a visualizing-range detection unit for determining a slice in which an image should be visualized, according to the position detected by the object position detection unit; an image reconstruction unit for reconstructing a tomographic image, according to the transmission data acquired by the data acquisition unit; and a display unit for visualizing the tomographic image of a slice determined by the visualizing-range detection unit. 16. An X-ray computerized tomography apparatus, comprising: an X-ray detection unit for detecting transmission X-rays from a plurality of directions irradiated from an X-ray beam generation source and transmitted through a subject; a data acquisition unit for acquiring transmission data according to the transmission X-rays detected by the X-ray detection unit; an object position detection unit for detecting a position of an object inside the subject, according to a part of the transmission data acquired by the data acquisition unit; and a scanning range determining unit for determining a range in which the subject is to be scanned, according to the position detected by the object position detection unit. 17. The X-ray computerized tomography apparatus according to claim 16 , further comprising: claim 16 a position controlling unit for controlling a position of a couch or a gantry according to a range to be scanned determined by the scanning range determining unit. 18. The X-ray computerized tomography apparatus according to claim 16 , further comprising: claim 16 an X-ray collimator provided between the X-ray source and a subject, and having at least one X-ray shielding plate moving along a slice direction; and a collimator controlling unit for controlling a width of the X-ray shielding plate of the X-ray collimator, according to the range to be scanned determined by the scanning range determining unit. 19. The X-ray computerized tomography apparatus according to claim 16 , wherein claim 16 the object position detection unit includes: a transmission data extraction unit for extracting transmission data at a predetermined tube position of the X-ray beam generation source, for each slice, from the transmission data acquired by the data acquisition unit, whereby to detect a position of the target object according to the extracted transmission data. 20. The X-ray computerized tomography apparatus according to claim 16 , wherein claim 16 the object position detection unit detects a position of the object by deciding a presence of the object by using a predetermined threshold of an X-ray absorption value. 21. The X-ray computerized tomography apparatus according to claim 20 , wherein claim 20 when the object is an insertion object, and when the transmission data within the threshold for showing the tip of the insertion object exists in the slice displayed previously, the object position detection unit decides whether or not there is the transmission data within the threshold in an adjacent slice in a positive proceeding direction of the insertion object, and when there is no transmission data within the threshold in the slice displayed previously, the object position detection unit decides whether or not there is the transmission data within the threshold in an adjacent slice in a negative proceeding direction of the insertion object, so as to detect the tip of the insertion object in correspondence with the proceeding direction of the insertion object. 22. The X-ray computerized tomography apparatus according to claim 16 , wherein claim 16 the object position detection unit detects a position of the object by deciding a presence of the object by using a shape recognition. 23. The X-ray computerized tomography apparatus according to claim 16 , wherein claim 16 the object position detection unit detects a position of the object according to transmission data of a plurality of slices acquired by the data acquisition unit. 24. The X-ray computerized tomography apparatus according to claim 23 , wherein claim 23 the transmission data of the plurality of slices is obtained by scanning at a plurality of positions of a couch or a gantry, or by volume scanning using a two-dimensional detector having detecting elements laid out by a plurality of rows in a slice direction. 25. The X-ray computerized tomography apparatus according to claim 17 , further comprising: claim 17 a tube position determining unit for determining the predetermined tube position of the X-ray beam generation source, based on the transmission data of a plurality of slices from a plurality of directions acquired by the data acquisition unit, and for sending data indicating a determined tube position to the transmission data extraction unit. 26. The X-ray computerized tomography apparatus according to claim 25 , wherein claim 25 when the object is an insertion object, the tube position determining unit sets a tube position where the insertion object has the largest length on the transmission data from among the tube positions of a plurality of directions, as the tube position. 27. The X-ray computerized tomography apparatus according to claim 16 , further comprising: claim 16 a display unit for visualizing the tomographic image reconstructed by the image reconstruction unit. 28. The X-ray computerized tomography apparatus according to claim 27 , wherein claim 27 when the object is an insertion object, the display unit visualizes the tomographic image of the subject in a slice in which the tip of the insertion object exists. 29. The X-ray computerized tomography apparatus according to claim 27 , wherein claim 27 when the object is an insertion object, the display unit forms a stacked display image of an image in a slice in which an object previously designated exists and an image in a slice in which the tip of the insertion object exists. 30. The X-ray computerized tomography apparatus according to claim 28 , further comprising: claim 28 an operation controlling unit for instructing the X-ray detection unit and the data acquisition unit to acquire transmission data so as to make these units detect a position of the tip of an insertion object, based on an input by an operator, when the tip of the insertion object has deviated from an image displayed by the display unit. 31. The X-ray computerized tomography apparatus according to claim 27 , wherein claim 27 the display unit always displays a tomographic image of the subject in a slice in which the tip of the insertion object exists, according to a position of the insertion object detected by the object position detecting unit. 32. The X-ray computerized tomography apparatus according to claim 16 , further comprising: claim 16 a scan controlling unit for controlling the scanning of the subject in a scanning range determined by the scanning range determining unit, in correspondence with an input by an operator with respect to a portion inside the subject to be photographed. 33. An X-ray computerized tomography apparatus, comprising: an X-ray detection unit having detecting elements laid out in a plurality of rows in a slice direction, for detecting transmission X-rays from a plurality of directions irradiated from an X-ray beam generation source and transmitted through a subject; a data acquisition unit for collecting transmission data according to the transmission X-rays detected by the X-ray detection unit; an image reconstruction unit for reconstructing a tomographic image of a slice in which an object inside the subject exists, according to the transmission data acquired by the data acquisition unit; and a display unit for displaying an image of transmission data at a predetermined tube position of the X-ray beam generation source from among the transmission data acquired by the data acquisition unit, together with the tomographic image reconstructed by the image reconstruction unit. 34. The X-ray computerized tomography apparatus according to claim 33 , further comprising: claim 33 a data selection unit for selecting transmission data at a plurality of predetermined tube positions, based on the transmission data acquired by the data acquisition unit; wherein the display unit displays the transmission data at a plurality of predetermined tube positions selected by the data selection unit, together with the transmission data reconstructed by the image reconstruction unit. 35. An X-ray computerized tomography apparatus, comprising: an X-ray detection unit having detecting elements laid out in a plurality of rows in a slice direction, for detecting transmission X-rays for a plurality of slices from a plurality of directions irradiated from an X-ray beam generation source and transmitted through a subject; a data acquisition unit for acquiring transmission data according to the transmission X-rays detected by the X-ray detection unit; an object position detection unit for detecting a position of an object inside the subject, according to transmission data at a predetermined tube position of the X-ray beam generation source out of the transmission data for a plurality of slices acquired by the data acquisition unit; a visualizing-range detection unit for determining a slice in which an image should be visualized, according to the position detected by the object position detection unit; an image reconstruction unit for reconstructing a tomographic image, according to the transmission data acquired by the data acquisition unit; and a display unit for visualizing the tomographic image of a slice determined by the visualizing-range detection unit. 36. An X-ray computerized tomography apparatus, comprising: a scan unit for scanning a subject to obtain projection data of the subject; an object position detection unit, configured to said scan unit, for detecting a position of an object inside the subject, according to at least a part of the projection data; and an image reconstruction unit, configured to said object position detection unit, for reconstructing at least one of a plurality of tomographic images in which the object is included according to the position. 37. An X-ray computerized tomography apparatus, comprising: a scan unit for scanning a subject to obtain projection data of the subject; an object position detection unit, configured to said scan unit, for detecting a position of an object inside the subject, according to at least a part of the projection data; and a scan range determining unit, configured to said object position detection unit, for determining a range in which the subject is to be scanned, according to the position. 38. The X-ray computerized tomography apparatus according to claim 1 , further comprising: claim 1 a visualizing range detection unit for determining a slice in which an image should be visualized, according to the position detected by the object position detection unit and a display unit for visualizing the tomographic image of a slice determined by the visualizing-range detection unit. 39. The X-ray computerized tomography apparatus according to claim 1 , further comprising: claim 1 a display unit for displaying an image of transmission data at a predetermined tube position of the X-ray beam generation source from among the transmission data acquired by the data acquisition unit, together with the tomographic image reconstructed by the image reconstruction unit. 40. The X-ray computerized tomography apparatus according to claim 39 , further comprising: claim 39 a data selection unit for selecting transmission data at a plurality of predetermined tube positions, based on the transmission data acquired by the data acquisition unit wherein the display unit displays the transmission data at a plurality of predetermined tube positions selected by the data selection unit, together with the transmission data reconstructed by the image reconstruction unit. 41. The X-ray computerized tomography apparatus according to claim 1 , further comprising: claim 1 a visualizing-range detection unit for determining a slice in which an image should be visualized, according to the position detected by the object position detection unit; and a display unit for visualizing the tomographic image of a slice determined by the visualizing-range detection unit, wherein said object position detection unit detects a position of an object inside the subject, according to transmission data at a predetermined tube position of the X-ray beam generation source out of the transmission data for a plurality of slices acquired by the data acquisition unit. 42. An X-ray computerized tomography apparatus, comprising: a scan unit configured to scan a subject to obtain projection data of the subject; an object position detection unit configured to detect a position of an object inside the subject, according to at least a part of the projection data; and an image reconstruction unit configured to reconstruct at least one of a plurality of tomographic images in which the object is included according to the position. 43. An X-ray computerized tomography apparatus, comprising: a scan unit configured to scan a subject to obtain projection data of the subject; an object position detection configured to detect a position of an object inside the subject, according to at least a part of the projection data; and a scan range determining unit configured to determine a range in which the subject is to be scanned, according to the position. 44. The X-ray computerized tomography apparatus according to claim 1 , further comprising: claim 1 a visualizing-range detection unit configured to determine a slice in which an image should be visualized, according to the position detected by the object position detection unit and a display unit configured to visualize the tomographic image of a slice determined by the visualizing-range detection unit. 45. The X-ray computerized tomography apparatus according to claim 1 , further comprising: claim 1 a display unit configured to display an image of transmission data at a predetermined tube position of the X-ray beam generation source from among the transmission data acquired by the data acquisition unit, together with the tomographic image reconstructed by the image reconstruction unit. 46. The X-ray computerized tomography apparatus according to claim 39 , further comprising: claim 39 a data selection unit configured to detect transmission data at a plurality of predetermined tube positions, based on the transmission data acquired by the data acquisition unit wherein the display unit displays the transmission data at a plurality of predetermined tube positions selected by the data selection unit, together with the transmission data reconstructed by the image reconstruction unit. 47. The X-ray computerized tomography apparatus according to claim 1 , further comprising: claim 1 a visualizing-range detection unit configured to determine a slice in which an image should be visualized, according to the position detected, by the object position detection unit; and a display unit configured to visualize the tomographic image of a slice determined by the visualizing-range detection unit, wherein said object position detection unit detects a position of an object inside the subject, according to transmission data at a predetermined tube position of the X-ray beam generation source out of the transmission data for a plurality of slices acquired by the data acquisition unit.
	abstract	Various embodiments of a decay heat conversion to electricity system and related methods are disclosed. According to one exemplary embodiment, a decay heat conversion to electricity system may include a spent fuel rack configured to pressurize spent fuel bundles to obtain superheated vapor to drive a turbine-driven pump and fast alternator all submerged with the spent fuel rack and positioned at the bottom of the spent fuel pool for conversion of electricity distributed outside of the spent fuel pool via cables without impairing spent fuel pool operations.
	description
044977670	summary	BACKGROUND OF THE INVENTION This invention relates to compression hubs of the type that are employable in cooperative association with a plurality of magnets in a fusion reactor system, and, more particularly, to such a compression hub which is equipped with eddy current prevent means operable to impede the circulation therethrough of eddy currents induced by changes in the magnetic flux field. One form of fusion reactor that has been proposed for use by the prior art is the so-called Tokamak-type reactor. In accordance with the mode of operation of this type of reactor, thermal power is generated as a consequence of the ignition of plasma. There exists, however, in this type of reactor not only a need to ignite the plasma, but also a need for effecting control over the plasma. One technique which has been proposed for use for purposes of effecting control over the plasma is that of magnetic confinement. More specifically, it has been proposed to employ for this purpose a plurality of superconducting magnets operating at cryogenic temperatures. Through the use of such magnets, it is possible to attain intense magnetic fields of a strength sufficient to effect the desired confinement of the plasma. To produce the desired result, the superconducting magnets are preferably arranged relative to each other so that they extend outwardly from a common point, in a manner similar to that of the spokes of a wheel. These magnets generate intense forces, tending to draw them together to the common point. Thus, there is a need created to provide means operative to resist the forces tending to draw the magnets together. One means contemplated for use for this purpose is a compression hub, also commonly referred to as a bucking post. One form of a compression hub, which is suitable for use for the afore-described purpose, comprises the subject matter of my earlier U.S. Pat. No. 4,174,254, which issued on Nov. 13, 1979, and which is assigned to the same assignee as the present invention. As discussed therein, a compression hub, in order to be suitable for use for the purpose described above, must be susceptible to being cooled to the same relative temperature as the superconducting magnets, i.e., to cryogenic temperatures. In addition, this cooling of the compression hub must be capable of being accomplished while at the same time ensuring that the structural adequacy of the compression hub is maintained. Regarding the matter of cooling, as set forth in my aforementioned earlier issued U.S. patent, the normal operative temperature range for the superconducting magnets is 4.2.degree. to 4.9.degree. kelvin. To achieve this range of temperatures, the magnets are preferably cooled by liquid helium, which boils at 4.2.degree. kelvin at atmospheric pressure. Because of the criticality of the operating temperature, it is necessary that the compression hub, which is cooperatively associated with the superconducting magnets, be cooled also to the same temperature as the magnets. Otherwise, heat transfer in the form of a heat loss could take place between the compression hub and the magnets cooperatively associated therewith whereby the operating effectiveness of the magnets would be seriously impaired. Not only is it necessary that the operating temperature of the compression hub be maintained at the same operating temperature as the superconducting magnets, but also it is important that the compression hub be capable of being cooled to the desired operating temperature of 4.2.degree. kelvin in a relatively short period of time. One method of effecting the desired cooling of the compression hub is to depend on the cooling effect of the magnets to remove heat from the compression hub. However, this could take an inordinate amount of time to achieve, which would be totally unacceptable from the standpoint of how long it takes to render the system operative, particularly in a start-up situation. The reason for this, as discussed in my aforementioned earlier issued U.S. patent, is that at these very low temperatures the thermal gradient between the compression hub and the magnets cooperatively associated therewith is so small that virtually no cooling of the compression hub is effected. It, therefore, becomes necessary to supply coolant to the compression hub itself. More specifically, fluid flow paths must be established for coolant in the compresion hub. However, as noted previously hereinabove, the coolant flow paths in the compression hub must be provided in such a manner as to not adversely affect the structural adequacy of the compression hub, i.e., the ability of the compression hub to resist the forces tending to draw the magnets together to a common point. One form of compression hub, which fulfills the above-stated requirements for a compression hub employable in a Tokamak-type fusion reactor system, has been described and illustrated in my aforementioned earlier issued U.S. patent. In addition, an alternative form of construction for a compression hub, which also satisfies the above-stated requirements, comprises the subject matter of Penfield patent application, Ser. No. 000,047, filed on Jan. 2, 1979, which issued on Sept. 1, 1981 as U.S. Pat. No. 4,287,022, and assigned to the same assignee as the present invention. To summarize, these two alternative forms of construction for a compression hub are deemed to be equally suitable for use in a Tokamak-type fusion reactor system insofar as concerns fulfilling those requirements for such a structure, which have been stated hereinbefore. However, in addition to those requirements that have been set forth above, it is also desirable that a compression hub embody means operable for impeding the circulation therethrough of eddy currents. The latter, as is known to those skilled in the art, comprise those currents which are induced in the body of a conducting mass as a consequence of a variation in magnetic flux. The presence of circulating eddy currents would disadvantageously characterize the compression hub, insofar as concerns the ability of the latter to provide the type of performance being sought therefrom, when the latter is being employed in cooperative association with a plurality of superconducting magnets in a Tokamak-type fusion reactor system. Accordingly, it is contemplated in accord with the present invention to interrupt the surface of the elements that collectively comprise the compression hub so as to prohibit the circulation through the latter of the aforedescribed eddy currents. However, there is a need to accomplish the aforesaid interruption in the surfaces of the elements without adversely affecting either the strength of the compression hub, i.e., the capability of the latter to successfully resist the forces tending to draw the magnets thereagainst, or the ability of the compression hub to be cooled to a satisfactory level, i.e., the existence of a sufficient flow of coolant through the compression hub so as to enable the latter to be cooled to a temperature of 4.2.degree. kelvin. In summary, there has been deemed to exist a need to provide a compression hub with suitable means to insure that the latter will not be disadvantageously characterized as a result of the inducement therein of eddy currents that would otherwise be free to circulate therethrough. It is, therefore, an object of the present invention to provide a compression hub that is designed to be cooperatively associated with a plurality of superconducting magnets in a Tokamak-type fusion reactor system. It is another object of the present invention to provide such a compression hub which embodies sufficient structural strength as to be capable of resisting the intense forces produced by the superconducting magnets that tend to draw the latter together towards a common point whereat the compression hub is located. It is still another object of the present invention to provide such a compression hub which embodies a construction that permits the latter to be cooled to a temperature that is commensurate with the operating temperature of the superconducting magnets, while yet enabling the compression hub to retain the structural strength required thereof. A further object of the present invention is to provide such a compression hub which embodies means operative to impede the circulation of eddy currents therethrough, while yet possessing the strength and cooling characteristics desired therefrom. A still further object of the present invention is to provide a compression hub embodying such eddy current prevent means wherein the latter consists of an interruption provided in the surface of the elements that collectively comprise the compression hub. Yet another object of the present invention is to provide such a compression hub embodying eddy current prevent means wherein the interruption provided in the surface of the elements takes the form of a radial cut in which an insulative material is inserted. Yet still another object of the present invention is to provide a compression hub embodying eddy current means wherein the interruption provided in the surface of the elements is effected by fabricating the elements from multiple segments that in the assembled state are separated one from another by means of insulative material. SUMMARY OF THE INVENTION In accordance with the present invention, there is provided a new and improved form of compression hub that is designed to be cooperatively associated with a plurality of superconducting magnets in a Tokamak-type fusion reactor system. The subject compression hub is operative to resist the intense forces brought to bear thereagainst by the superconducting magnets, whilst yet possessing the capability of being cooled to a temperature commensurate with the operating temperature of the superconducting magnets. Further, the subject compression hub embodies means operative to impede the circulation of eddy currents therethrough. To this end, the compression hub comprises a multiplicity of compression plates that are polygonal in configuration, and which are arranged in vertically stacked, substantially abutting relation to each other. The aforementioned eddy current prevent means consists of an interruption that is provided in the surface of the compression plates. In accord with one aspect of the present invention, the interruption is in the form of a radial cut in which insulative material in inserted. In accord with another aspect of the invention, the interruption is effected by fabricating the compression plates from multiple segments which in the assembled state are separated one from another through the use of layers of insulative material.
	claims	1. A polycrystalline scintillator comprising:sintered crystalline semiconductor particles, the crystalline semiconductor particles formed of a radiation absorption region of a first semiconductor material and a spatially discrete radiative carrier recombination region of a second semiconductor material operable to receive carriers produced in the radiation absorption region. 2. The polycrystalline scintillator of claim 1, wherein the crystalline semiconductor particles have core-shell architecture. 3. The polycrystalline scintillator of claim 2, wherein the radiative carrier recombination region is at the core of the semiconductor particles and the radiative absorption region is part of the shell surrounding the core. 4. The polycrystalline scintillator of claim 3, wherein shells of the sintered crystalline semiconductor particles form a continuous radiation absorption matrix with radiative carrier recombination regions dispersed in the continuous radiation absorption matrix. 5. The polycrystalline scintillator of claim 2, wherein the crystalline semiconductor particles have a size ranging from about 20 nm to about 100 μm. 6. The polycrystalline scintillator of claim 2, wherein the radiation absorption region of one or more of the crystalline semiconductor particles has a size ranging from about 10 nm to about 500 nm. 7. The polycrystalline scintillator of claim 1, wherein the radiation absorption region has a carrier mobility of at least about 1·10−4 cm2/V·s. 8. The polycrystalline scintillator of claim 1, wherein the radiation absorption region has a carrier mobility ranging from about 1·10−4 cm2/V·s to about 1000 cm2/V·s. 9. The polycrystalline scintillator of claim 1, wherein the radiation absorption region has a carrier mobility ranging from about 1·10−2 cm2/V·s to about 100 cm2/V·s. 10. The polycrystalline scintillator of claim 1, wherein the first semiconductor material is a II/VI semiconductor. 11. The polycrystalline scintillator of claim 1, wherein the second semiconductor material is a II/VI semiconductor material. 12. The polycrystalline scintillator of claim 1, wherein the first semiconductor material and the second semiconductor material are binary II/VI semiconductors. 13. A method of making a polycrystalline scintillator comprising:providing crystalline semiconductor particles, the crystalline semiconductor particles formed of a radiation absorption region of a first semiconductor material and a spatially discrete radiative carrier recombination region of a second semiconductor material operable to receive carriers produced in the radiation absorption region; andsintering the crystalline semiconductor particles. 14. The method of claim 13, wherein the crystalline semiconductor particles have core-shell architecture. 15. The method of claim 14, wherein the radiative carrier recombination region is at the core of the semiconductor particles and the radiative absorption region is part of the shell surrounding the core. 16. The method of claim 15, wherein sintering the crystalline semiconductor particles forms a continuous radiation absorption matrix with radiative carrier recombination regions dispersed in the continuous radiation absorption matrix. 17. The method of claim 14, wherein the crystalline semiconductor particles have a size ranging from about 20 nm to about 100 μm. 18. The method of claim 14, wherein the radiation absorption region of one or more of the crystalline semiconductor particles has a size ranging from about 10 nm to about 500 nm. 19. The method of claim 13, wherein the radiation absorption region has a carrier mobility of at least about 1·10−4 cm2/V·s. 20. The method of claim 13, wherein the radiation absorption region has a carrier mobility ranging from about 1·10−4 cm2/V·s to about 1000 cm2/V·s.
054127009	claims	1. A system for contaminate recovery for a nuclear reactor during reactor refueling comprising: a relatively flat closure head connected to said nuclear reactor, said closure head having a predetermined number of penetrations for fuel rods, control rods, gadolinium injection piping and instrumentation; a barrier plate sandwiched between said nuclear reactor and said closure head forming a primary containment boundary; a refueling guard plate sandwiched between said closure head and said barrier plate; said refueling guard plate and barrier plate defining an annular chamber containing instrumentation and gadolinium injection piping; and a means for sealing connected to said closure head and said barrier plate creating a secondary containment boundary. a plurality of penetrations; and said penetrations having means for sealing said penetrations once said fuel rods, control rods, gadolinium injection piping and instrumentation are removed. a closure head connected to said nuclear reactor, said closure head having a predetermined limited number of penetrations; a barrier plate sandwiched between said nuclear reactor and said closure head forming a primary containment boundary; said barrier plate having a plurality of penetrations for containing a plurality of fuel assemblies disposed in and extending from said penetrations; said penetrations having means for sealing said penetrations once said fuel assemblies are removed thereby providing a secondary containment boundary; and said means for sealing being a seal having the ability to act as a flap and inhibits heavy water evaporation through said barrier plate penetration. said guard plate has a plurality of penetrations and with a predetermined number of said penetrations axially aligned with said penetrations of said barrier plate. lifting said closure head to disengage a drive mechanism; evacuating said secondary boundary area; removing said closure head to remove said upper portion of said drive mechanism from said lower portion, while preventing release of gases within said nuclear reactor to the atmosphere; and replacing a fuel assembly in said reactor. at least one screw jack sandwiched by said closure head and said barrier plate, whereby said screw jack is adapted to allow for the raising and lowering of said closure head; and means for sealing said drive mechanism having the abiltiy to seal a barrier plate penetration once said drive mechanism has been removed. an elastomer seal connected to said closure head and said barrier plate. removing an instrumentation plug from said fuel assembly; replacing said fuel assembly and said instrumentation plug. 2. A system for contaminate recovery for a nuclear reactor during reactor refueling as recited in claim 1 wherein said barrier plate comprises: 3. A system for contaminate recovery for a nuclear reactor during refueling comprising: 4. A system for contaminate recovery for a nuclear reactor during reactor refueling as recited in claim 3 wherein 5. A system for contaminate recovery for a nuclear reactor during reactor refueling as recited in claim 4 having at least one drive mechanism having an upper and lower portion, whereby said drive mechanism is disposed in and extends from said penetration in said closure head. 6. A system for contaminate recovery for a nuclear reactor during reactor refueling as recited in claim 5 having means for lifting and sealing said closure head. 7. A system for contaminate recovery for a nuclear reactor during reactor refueling as recited in claim 6 wherein said means for sealing said closure head comprises an elastomer bellows seal which allows said closure head to be lifted to disengage said upper portion of said drive mechanism from said lower portion, while preventing release of gases within said nuclear reactor to the atmosphere. 8. A system for contaminate recovery for a nuclear reactor during reactor refueling as recited in claim 6 wherein said means for lifting includes at least one screw jack sandwiched by said closure head and said barrier plate. 9. A system for contaminate recovery for a nuclear reactor during reactor refueling as recited in claim 6 further comprising means for exhausting said secondary boundary area whereby when said upper portion of said drive mechanism is disengaged said secondary boundary area is evacuated by said means for exhausting prior to the removal of said upper portion of said drive mechanism thereby preventing the uncontrolled release of gases to the atmosphere. 10. A method of refueling a nuclear reactor having a closure head connected to said nuclear reactor, said closure head having a predetermined limited number of penetrations, a barrier plate sandwiched between said nuclear reactor and said closure head forming a primary containment boundary, a means for sealing connected to said closure head and said barrier plate creating a secondary containment boundary comprising the steps of: 11. A method of refueling a nuclear reactor as recited in claim 10 wherein said step of lifting said closure head to disengage said drive mechanism comprises: 12. A method of refueling a nuclear reactor as recited in claim 11 wherein said means for sealing connected to said closure head and said barrier plate comprises: 13. A method of refueling a nuclear reactor as recited in claim 12 wherein said step of replacing a fuel assembly comprises:
	summary
	claims	1. A method of automatically correcting a charged-particle beam, comprising the steps of:irradiating a sample with the charged-particle beam via an aberration corrector and an objective lens, the aberration corrector having multipole elements;obtaining information about a cross section of the charged-particle beam based on plural images of a surface of the irradiated sample;calculating an amount of axial deviation of the optical axis of the charged-particle beam relative to the center of a multipole field in the aberration corrector based on the obtained information about the cross section of the beam; andautomatically applying feedback to the aberration corrector or to the objective lens according to the calculated amount of axial deviation. 2. An apparatus for automatically correcting a charged-particle beam, comprising:an aberration corrector equipped with multipole elements;irradiation means for irradiating a sample with the charged-particle beam via the aberration corrector and an objective lens;cross-sectional information-obtaining means for obtaining information about a cross section of the charged-particle beam based on plural images of a surface of the irradiated sample;calculation means for calculating an amount of axial deviation of the optical axis of the charged-particle beam relative to the center of a multipole field in the aberration corrector, based on the obtained information about the cross section of the beam; andfeedback means for automatically applying feedback to the aberration corrector or to the objective lens according to the calculated amount of axial deviation. 3. An apparatus for automatically correcting a charged-particle beam as set forth in claim 2, wherein the number of used images of the surface of the sample is any one of two, three, and five. 4. An apparatus for automatically correcting a charged-particle beam as set forth in claim 3, wherein the number of the used images of the surface of the sample is two, and wherein a first one of the images is obtained when the focusing strength of the aberration corrector is set to a first value and a second one of the images is obtained when the focusing strength is set to a second value shifted from the first value by a given amount. 5. An apparatus for automatically correcting a charged-particle beam as set forth in claim 3, wherein the number of the used images of the surface of the sample is three, and wherein a first one of the images is obtained when the focusing strength of the aberration corrector is set to a first value, a second one of the images is obtained when the focusing strength is set to a second value changed from the first value by a first given amount in an X-direction, and a third one of the images is obtained when the focusing strength is set to a third value changed from the first value by a second given amount in a Y-direction. 6. An apparatus for automatically correcting a charged-particle beam as set forth in claim 3, wherein the number of the used images of the surface of the sample is five, and wherein a first one of the images is obtained when the focusing strength of the aberration corrector is set to a first value, a second one of the images is obtained when the focusing strength is set to a second value changed from the first value by a first positive given amount in an X-direction, a third one of the images is obtained when the focusing strength is set to a third value changed from the first value by a second negative given amount in the X-direction, a fourth one of the images is obtained when the focusing strength is set to a fourth value changed from the first value by a third positive given amount in a Y-direction, and a fifth one of the images is obtained when the focusing strength is set to a fifth value changed from the first value by a fourth negative given amount in the Y-direction. 7. An apparatus for automatically correcting a charged-particle beam as set forth in claim 2, wherein said aberration corrector is equipped with four stages of multipole elements. 8. An apparatus for automatically correcting a charged-particle beam as set forth in claim 7, wherein each of the four stages of multipole elements constituting said aberration corrector has at least four pole elements. 9. A method of automatically correcting a charged-particle beam as set forth in claim 1, wherein said aberration corrector is equipped with four stages of multipole elements, and wherein any one of dipole field produced by the stages of multipole elements in the aberration corrector, quadrupole field produced by the stages of multipole elements, hexapole field produced by the stages of multipole elements, octupole field produced by the stages of multipole elements, and focusing field produced by the objective lens is changed in strength. 10. A method of automatically correcting a charged-particle beam as set forth in claim 9, wherein each image of the surface of the sample is obtained in synchronism with the changing of the strength of any one of the fields. 11. An apparatus for automatically correcting a charged-particle beam as set forth in claim 2, wherein information about one or two cross sections of the charged-particle beam is obtained, and wherein said amount of axial deviation is calculated by multiplying the difference between the center of gravity of distribution of particle densities contained in the obtained information about one or two cross sections of the beam and the position of the origin contained in the information about the cross sections by a constant value. 12. An apparatus for automatically correcting a charged-particle beam as set forth in claim 2, wherein information about one or two cross sections of the charged-particle beam is obtained, and wherein said amount of axial deviation is calculated by multiplying the difference between the center position of the cross-sectional contour of the beam contained in the obtained information about one or two cross sections of the beam and the position of the origin contained in the information about the cross sections by a constant value. 13. An apparatus for automatically correcting a charged-particle beam as set forth in claim 2, wherein feedback is applied to the aberration corrector or to the objective lens in proportion to the obtained amount of axial deviation. 14. An apparatus for automatically correcting a charged-particle beam as set forth in claim 13, wherein said aberration corrector is equipped with four stages of multipole elements, and wherein feedback is applied to any one of dipole field produced by the stages of multipole elements in the aberration corrector, quadrupole field produced by the stages of multipole elements, and focusing field produced by the objective lens. 15. An apparatus for automatically correcting a charged-particle beam as set forth in claim 2, wherein a decision as to whether the optical axis of the charged-particle beam has been corrected so as to enter a given range is automatically made by comparing the amount of axial deviation with a threshold value. 16. An apparatus for automatically correcting a charged-particle beam as set forth in claim 15, wherein processing for automated correction is repeated until said amount of axial deviation falls below the threshold value. 17. An apparatus for automatically correcting a charged-particle beam as set forth in claim 2, wherein said sample is a reference sample, and wherein the sample is moved between a first position in a sample chamber where the sample is irradiated with the charged-particle beam and a second position where the sample is on standby for transfer to the first position. 18. An apparatus for automatically correcting a charged-particle beam as set forth in claim 2, wherein said sample is a reference sample, and wherein the sample is a particle having a circular cross-sectional contour. 19. An apparatus for automatically correcting a charged-particle beam as set forth in claim 2, wherein said sample is a reference sample, and wherein the sample can be a spherical particle made of gold or resin. 20. An apparatus for automatically correcting a charged-particle beam as set forth in claim 2, wherein the axial deviation is corrected in X- and Y-directions independently. 21. An apparatus for automatically correcting a charged-particle beam as set forth in claim 2, wherein the obtained information about the cross sections of the charged-particle beam and the calculated amount of axial deviation are displayed. 22. An apparatus for automatically correcting a charged-particle beam, said apparatus comprising:an aberration corrector equipped with multipole elements and acting to correct aberration in the charged-particle beam;an aberration correction controller for controlling the strength of a multipole field produced by the aberration corrector;an objective lens;a control unit for supplying a control signal to the aberration correction controller or to the objective lens;cross-sectional information-obtaining device for obtaining a SEM image in synchronism with operation of the control unit and obtaining information about a cross section of the charged-particle beam;an axial deviation quantification device for quantifying the amount of the axial deviation of the optical axis of the beam from the obtained information about the cross section of the beam;a decision unit for making a decision from the quantified amount of axial deviation as to whether automated correction is completed; anda feedback device for outputting an amount of feedback to the aberration correction controller or to the objective lens from the quantified amount of axial deviation. 23. A method of controlling an aberration corrector for a charged-particle beam, the corrector being made up of plural stages of multipole elements, wherein a control unit controls the whole aberration corrector as a single lens, and wherein during the control, the lens strength ratio of the stages of multipole lenses is kept constant. 24. A method of controlling an aberration corrector for a charged-particle beam, the corrector being made up of plural stages of multipole elements, wherein a control unit controls the whole aberration corrector as a single lens, and wherein during the control, the lens strength ratio of the stages of multipole lenses and the objective lens is kept constant. 25. A method of controlling an aberration corrector for a charged-particle beam as set forth in claim 23, wherein feedback is applied by said control unit either to a lens formed in such a way that the lens strength ratio of the stages of multipole elements in the aberration corrector is kept constant or to a lens formed in such a way that the lens strength ratio of the stages of multipole elements and objective lens is kept constant. 26. A method of controlling an aberration corrector for a charged-particle beam as set forth in claim 24, wherein feedback is applied by said control unit either to a lens formed in such a way that the lens strength ratio of the stages of multipole elements in the aberration corrector is kept constant or to a lens formed in such a way that the lens strength ratio of the stages of multipole elements and objective lens is kept constant.
	abstract	The disclosure relates to an amplifying optical cavity of the Fabry-Perot type that can be used in combination with a high-rate picosecond pumped laser for generating monochromatic X-rays. The disclosure relates to an amplifying optical cavity of the Fabry-Perot type that can be used for obtaining a strongly focused pumped laser beam having a high stability at the average power PMOY. The disclosure more particularly relates to an amplifying optical cavity of the Fabry-Perot type for generating monochromatic X-rays by the Compton reaction between a high-rate picosecond pumped laser beam and a synchronised electron beam, the cavity including a closed enclosure that can be placed under a vacuum and through which extends an electron beam tube, the enclosure including a laser beam input means, a means for maintaining and positioning two planar optical reflectors, and a means for maintaining and positioning two spherical optical reflectors capable of focusing the laser beam at an interaction point with the electron beam. The means for maintaining and positioning the optical reflectors are arranged so that said optical reflectors substantially define the vertexes of a tetrahedron.
	description	The present invention relates to a radiation measurement instrument calibration facility capable of lowering scattered radiation and shielding background radiation, and more particularly, to a calibration facility capable of providing a suitable environment for performing performance test, calibration and experiment upon a radiation measurement instrument. In an embodiment, the calibration facility comprises: a shielding device, a collimator, a multi-source irradiator, a radiation baffle, a carrier, an electric door unit and a control unit, using that not only the affection of background radiation existing in the ambient environment of the facility can be reduced, but also the affection of scattered radiation resulting from the emission of the multi-source irradiator can be lowered by the use of the collimator as it is used for enabling the radiation field size of the radiation beam to be smaller than the apertures on the travelling path of the same, and thus the accuracy of the instrument performance test, calibration and experiment is prevented from being adversely affected by the scattered radiation. Moreover, as there are illuminators, video monitors and environment sensors, such as thermometers, hygrometers, and pressure meters, being mounted inside the shielding device, the measurement of an instrument being calibrated by the use of the calibration facility can be monitored and displayed in a real time manner. Generally, the operation of a conventional apparatus for calibrating radiation measurement instruments comprises the following steps: a radiation measurement instrument that is to be calibrated in a radiation field produced from a standard radiation source; recording and analyzing the readout values of the to-be-calibrated instrument so as to obtain a calibration factor or test parameter for the to-be-calibrated instrument. However, it is noted that using the aforesaid conventional calibration apparatus, the interference of the background radiation and scatter radiation toward the readout values of the to-be-calibrated instrument is generally unpreventable, and consequently, not only the radiation measurement accuracy of the radiation measurement instrument that is calibrated using the conventional calibration apparatus without necessary correction is questionable, but also the safety of radiation professionals may be endangered by the incorrect radiation readout. Thus, it is in need of an improved radiation measurement instrument calibration facility that is capable of effectively reducing the interference of the background radiation and scatter radiation toward the instrument and thus uplifting the measurement accuracy. In addition, the establishment of such a facility can also to be used for providing a suitable environment for performing performance test, calibration and experiment upon the radiation measurement instruments. Please refer to FIG. 1, which is a schematic diagram showing a conventional apparatus for calibrating radiation measurement instruments. As shown in FIG. 1, the conventional calibration apparatus is installed inside a laboratory 1, while allowing a to-be-calibrated instrument 11 to be disposed on a cart 12 that is mounted on a rail 13 so as to be moved along therewith, and thus enabling the to-be-calibrated instrument 11 to move to a specific location for allowing the same to be irradiated by a primary radiation beam emitted from a radiation source 141 of irradiator 14. It is noted that, operationally, the readout values of the to-be-calibrated instrument 11 are interfered by the background radiation 15 and scatter radiation 16 of the primary radiation beam inside the laboratory 1. In the regulation specified in ISO 4037-1 Standard (1996), the amount of scatter radiation 16 should not exceed 5% of the primary radiation beam. However, the conventional calibration apparatuses are not able to ensure to lower their scatter radiation to meet the ISO 4037-1 (1996) requirement due to the space limitation and structural design of the laboratory where they are installed. In addition, although the background radiation 15 of most conventional calibration apparatuses can be neglected while operating in medium and high dose rate radiation field, but while operating in low dose rate radiation field, the measurement accuracy can be severely affected by the background radiation 15 since its amount can achieve more than 20% of the primary radiation beam. Thus, the improved radiation measurement instrument calibration facility of the present invention is designed to overcome the aforesaid shortcomings in view of enhancing the accuracy of measurement or calibration for the instrument. In view of the disadvantages of prior art, the primary object of the present invention is to provide a radiation measurement instrument calibration facility with the abilities of lowering scattered radiation and shielding background radiation, that is capable of providing a suitable environment for performing performance test, calibration and experiment upon a radiation measurement instrument. In an embodiment, the calibration facility comprises: a shielding device, a collimator, a multi-source irradiator, a radiation baffle, a carrier, an electric door unit and a control unit, using that not only the affection of background radiation existing in the ambient environment of the facility can be reduced, but also the affection of scattered radiation resulting from the emission of the multi-source irradiator can be lowered by the use of the collimator as it is used for enabling the radiation field size of the radiation beam to be smaller than the apertures on the travelling path of the same, and thus the accuracy of the instrument performance test, calibration and experiment is prevented from being adversely affected by the scattered radiation. Moreover, as there are illuminators, video monitors and environment sensors, such as thermometers hygrometers, and pressure meters, being mounted inside the shielding device, the measurement of an instrument being calibrated by the use of the calibration facility can be monitored and displayed in a real time manner. To achieve the object, the present invention provides a radiation measurement instrument calibration facility capable of lowering scattered radiation and background radiation, which is adapted to be disposed inside a laboratory, and comprises: a shielding device, for shielding the scattered radiation and background radiation inside the laboratory, being configured with an inlet, an outlet and a cavity in a manner that the inlet, the outlet and the cavity are arranged in communication with each other while the to-be-calibrated instrument being placed in the cavity and the cavity being in communication with two openings formed respectively on two sides of the shielding device that are perpendicular to the inlet and the outlet; an electric door unit, for positioning the to-be-calibrated instrument in the shielding device as well as controlling the movement of two door panels for enabling the two to wall the two openings of the shielding device; a control unit, for controlling the operation of the electric door unit; a multi-source irradiator, configured with several radiation sources of different intensity, capable of emitting a primary radiation beam while allowing the radiation intensity of the same to be variable according to the radiation source that is selected from the irradiator for the emission; a collimator, for controlling the radiation field size of the primary radiation beam while enabling the primary radiation beam to travel into the shielding device through the inlet and out of the same through the outlet; a carrier, for carrying the shielding device and the electric door unit while adjusting the levels of the two; and a radiation baffle, for reducing the amount of background radiation entering the shielding device through the outlet. Moreover, the present invention further provide an operation method for the aforesaid radiation measurement instrument calibration facility capable of lowering scattered radiation and background radiation, which comprises the steps of: (A1) adjusting the carrier for leveling the shielding device and the electric door; (A2) enabling the collimator to operate for controlling the radiation field size of the primary radiation beam to an extent that it is smaller than the inlet and the outlet so as to reduce the amount of scatter radiation generated from the interaction between the primary radiation beam and the inside of shielding device; (A3) arranging the radiation baffle to be disposed at a position outside the outlet for reducing the amount of background radiation entering the shielding device through the outlet; (A4) using a fixing rack of the electric door unit to position the to-be-calibrated instrument while using the control unit to remotely control a step motor of the electric door unit for enabling the two door panels to move along a rail until walling the shielding device; (A5) selecting a radiation source from the multi-source irradiator to be used for producing a suitable radiation field upon the to-be-calibrated instrument for performing performance test, calibration and experiment upon the same, while using illuminators, video monitors, thermometers, hygrometers, and pressure meters that are being mounted inside the shielding device, to collect, record and analyze environmental monitoring data as well as data relating to the readouts of the to-be-calibrated instrument; and (A6) opening the two door panels for retrieving the to-be-calibrated instrument out of the calibration facility. Further scope of applicability of the present application will become more apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. For your esteemed members of reviewing committee to further understand and recognize the fulfilled functions and structural characteristics of the invention, several exemplary embodiments cooperating with detailed description are presented as the follows. 1. Please refer to FIG. 2 and FIG. 3, which show a radiation measurement instrument calibration facility capable of lowering scattered radiation and shielding background radiation according to an embodiment of the invention. In the embodiment shown in FIG. 2 and FIG. 3, the radiation measurement instrument calibration facility, that is installed inside a laboratory 2, comprises: a shielding device 6, for shielding the scattered radiation 94 and background radiation 93 inside the laboratory 2, being configured with an inlet 61, an outlet 62 and a cavity 63 in a manner that the inlet 61, the outlet 62 and the cavity 63 are arranged in communication with each other while the to-be-calibrated instrument 3 being placed in the cavity 63 and the cavity 63 being in communication with two openings formed respectively on two sides of the shielding device 6 that are perpendicular to the inlet 61 and the outlet 62; an electric door unit 91, for positioning the shielding device 6 and the to-be-calibrated instrument 3 as well as controlling the movement of two door panels 911 for enabling the two to wall the two openings of the shielding device 6. The electric door unit 91 further comprises: a rail 912, for guiding the two door panels 911 to move along therewith; and a step motor, for power and driving the two door panels 911 to move; a control unit 92, for controlling the operation of the electric door unit 91 in a remote manner; a multi-source irradiator 5, configured with several radiation sources 51 of different intensity, capable of emitting a primary radiation beam 52 while allowing the radiation intensity of the same to be variable according to the radiation source 51 that is selected from the irradiator for the emission; a collimator 7, for controlling the radiation field of the primary radiation beam 52 while enabling the primary radiation beam 52 to travel into the shielding device 6 through the inlet 61 and out of the same through the outlet 62; a carrier 4, for carrying the shielding device 6 and the electric door unit 91 while adjusting the levels of the two; and a radiation baffle 8, for reducing the amount of background radiation entering the shielding device 6 through the outlet 62; wherein, the to-be-calibrated instrument 3 is received inside the cavity 63 of the shielding device 6, while allowing the to-be-calibrated instrument 3 to be fixed securely by the use of the fixing rack that are mounted on the external of the to-be-calibrated instrument 3; and the cavity 63 of the shield device 6 further has an illuminator, a video monitor, and environment sensors, such as thermometer, hygrometer, and pressure meter that are mounted inside the cavity 63 of the shielding device 6. Please refer to FIG. 4, which is a flow chart depicting steps of a method for calibrating radiation measurement instruments according to the present invention. As shown in FIG. 4, the operation method for calibrating radiation measurement instruments comprises the steps of: (A1) adjusting the carrier for leveling the shielding device and the electric door; (A2) enabling the collimator to operate for controlling the radiation field size of the primary radiation beam to an extent that it is smaller than the inlet and the outlet so as to reduce the amount of scatter radiation generated from the interaction between the primary radiation beam and the inside of shielding device; (A3) arranging the radiation baffle to be disposed at a position outside the outlet for reducing the amount of background radiation entering the shielding device through the outlet; (A4) using a fixing rack of the electric door unit to position the to-be-calibrated instrument while using the control unit to remotely control a step motor of the electric door unit for enabling the two door panels to move along a rail until walling the shielding device; (A5) selecting a radiation source from the multi-source irradiator to be used for producing a suitable radiation field upon the to-be-calibrated instrument, while using illuminators, video monitors, thermometers, hygrometers, and pressure meters that are being mounted inside the shielding device, to monitor, collect and record environmental data as well as data relating to the readouts of the to-be-calibrated instrument; and (A6) analyzing the environmental monitoring data and the data relating to the readouts of the to-be-calibrated instrument so as to calculate and obtain a calibration factor or a test parameter for the to-be-calibrated instrument; (A7) opening the two door panels for retrieving the to-be-calibrated instrument out of the calibration facility after calibration. Comparing with those conventional calibration apparatuses, the calibration facility of the present invention is featured by the following characteristics: (1) By the addition of the shielding device that is formed with the inlet and the outlet for enabling the same work cooperatively with the two door panels, the interference coming from the background radiation and scattered radiation in the laboratory during the calibration can be effectively reduced. (2) By the use of the collimator to control the radiation field size of the primary radiation beam to an extent that it is smaller than the diameters of the inlet and the outlet, the scattering coming from radiation interaction with the shielding device can be reduced, and simultaneously, by the cooperation with the radiation baffle, the and background radiation can further be reduced. (3) By the addition of a video monitor, an illuminator and a control unit, the instrument positioning, on-site measurement and data observation/recording can be performed in a remote manner. (4) With the design of the calibration facility of the present invention, the instrument calibration and testing can be performed in radiation fields of low-, medium- and high-dose rate levels. With respect to the above description then, it is to be realized that the optimum dimensional relationships for the parts of the invention, to include variations in size, materials, shape, form, function and manner of operation, assembly and use, are deemed readily apparent and obvious to one skilled in the art, and all equivalent relationships to those illustrated in the drawings and described in the specification are intended to be encompassed by the present invention.
044420285	claims	1. A method for incorporating radioactive phosphoric acid solutions in concrete comprising: (a) first neutralizing a phosphoric acid solution containing Cobalt-60 with Ca(OH).sub.2 and thereby forming a precipitate, said precipitate having the formula Ca.sub.10 (PO.sub.4).sub.6 (OH).sub.2 and the crystal structure of hydroxyapatite, and then (b) mixing said precipitate with portland cement and thereby forming concrete. 2. The method of claim 1 wherein said phosphoric acid solution contains 6% phosphoric acid. 3. The method of claim 1 wherein said precipitation is carried out at a pH of from 7.5 to 8.5. 4. The method of claim 1 wherein the precipitate and the portland cement are mixed in proportions by weight ranging from 3:1 to 1:1. 5. The method of claim 1 wherein the precipitate is separated from the supernate and dried before the mixing with portland cement.
044366957	summary	This invention pertains to a nuclear reactor system for producing useful thermal energy and valuable nuclear materials, such as plutonium, uranium enriched in U.sup.233, or tritium, by irradiating suitable target materials with neutrons produced in a large containing chamber by explosions or other neutron-producing bursts occurring seriatim. Useful thermal energy produced by the explosions is absorbed by substantial quantities of very lean molten sodium slurry, much of which is introduced into the chamber in a pattern substantially surrounding the centroidal nuclear explosion. Heat exchangers permit this energy to be extracted and used. In addition, desired materials are preferably precipitated from the slurry and processed for the fabrication of a large free-falling mass and two high velocity slugs which are introduced into the chamber and concur to produce a fission explosion near the center of the large containing chamber. In prior art system designs, it has been necessary to pay special attention to two important considerations. These are the positioning of adequate quantities of slurry in suitable locations around the explosion and the fine control of the concurrence of the masses and/or slugs producing the explosion or other burst. The proper positioning of slurry in the chamber becomes a more serious concern as the magnitude of the contained explosion and of the containing chamber are increased. This is shown by the following illustrative example: Assume a stream of liquid which enters a substantially evacuated chamber with a downward velocity of 3.0 meters/second has a cross-sectional area of 1.0 dm.sup.2 so that 30 liters of liquid enters the chamber each second. In the first second, the liquid falls about 7.9 meters; in the second second, it falls about 17.7 meters; and in the third second, it falls about 27.5 meters. In the third second, 30 liters of liquid will be distributed within a volume of about 275 liters (assuming no sideways scattering) so that the "destiny" of liquid is about 10.9% of what it was when it first entered the chamber. In my prior reactor designs, this decrease in stream density has been countered by the "bunching" of such stream-sprays. The stream-sprays are given both a downward velocity and a horizontal velocity toward the center-line of the chamber. Note that if the stream-sprays come from an area with a radius of 8 meters from the center-line and are "bunched" into an area which has a radius of 4 meters, the liquid density therein is increased by a factor of four. As the size of the chamber is increased because of larger contained explosions, the volume of the chamber increases as the cube of the diameter but the surface area increases but as the square of the diameter. The quantity of liquid from a single opening of fixed size that can be falling within the chamber increases as the square root of the diameter. Also the energy and equipment needed to pump the working fluid greater distances with larger chambers increases as the diameter of the chamber. It may be desirable to increase the flow rate of the slurry to introduce more fluid into the chamber in a shorter time. However, such an increase in velocity of the lean slurry working fluid causes a much greater increase in erosion of conduit surfaces while the slurry falling a greater distance will cause more erosion of the bottom portions of the larger chambers. In the practice of these contained explosion reactor systems wherein the working fluids are of slurries, erosion not only "wears out" the reactor system sooner but also causes build-up of undesirable materials worn from the conduit walls within the slurry and/or the precipitates from the slurry. It should also be noted that the eroded materials in the slurries act to cause a still more rapid rate of erosion. Thus, with more erosion, there is the need for both more frequent and more complex processing of the precipitates and of the sodium remaining which contains materials dissolved therein. It will be readily recognized that fine and precise control of concurring masses which are to produce a prescribed nuclear explosion, or other, less energetic neutron-producting burst, is vital to the successful operation of a reactor of the type disclosed herein. If the masses are improperly fabricated or the timing of their travelings are so incorrect that the resulting concurrence of the three masses results in an assembly which is not super-critical, there will be no energetic neutron-producing burst and the masses will fall to the bottom of the chamber. However, if the timing of their travelings is moderately off, there will be an energetic neutron-producing burst of less than desired magntiude but yet of sufficient magnitude to atomize the masses and to produce some useful thermal energy. Likewise, if the velocities of the concurring masses are lower than optimum, the desired explosion will be of lower magnitude than desired and there will be less production of energy and isotopes. With projectiles being fired to intercept a free-falling mass, the importance of this control consideration is further highlighted. Because of the higher projectile velocities required, a high rate of acceleration must be used for the projectiles. Also, the start and rate of acceleration must be precisely timed with respect to the earlier release of the free-falling mass. The reactor system of this invention deals with these and other concerns of prior art systems. As in the abovementioned U.S. Pat. application Ser. No. 40,849, the preferred embodiment of this invention utilizes a contained fission explosion with a lean sodium slurry as the working fluid. However, the present system is designed to be a breeder of plutonium instead of U.sup.233 enriched uranium. The reactor of this invention preferably produces about 3.times.10.sup.12 joules every 30 seconds. While the explosion is three times the magnitude of the prior application, the power produced is but doubled. To assure that sufficient quantities of the lean slurry surround the center of the chamber at the instant of explosion or burst, slurry is pumped to the top of the chamber and into large containers. At a prescribed moment before each explosion, a bottom holding means of such containers is removed with sufficient speed to not interfere with the free-fall of the liquid which falls in the form of column-globs of great size. By providing each column-glob with a sufficient cross-sectional area and preventing the containing bottom holding means from interfering with the liquid by being withdrawn faster than the free-liquid will fall, the effects of liquid viscosity, surface tension, and adhesion of liquid to containing walls is minimal. By using such column-globs in combination with "bunching" spray streams and fine sprays, more working fluid can be positioned nearer the contained nuclear explosion at the required instant in each cycle. Hence, a smaller containing chamber and less pumping power are needed. Precise control of the projected slugs of this invention is also accomplished. The slugs contain much UH.sub.3. By maintaining the slugs at cryogenic temperatures, this UH.sub.3 can be maintained in a ferromagnetic state. As a result, very fine control of the velocity of the slugs can be obtained as the slugs are being propelled into the chamber toward concurrence with the large mass by careful regulation of magnetic fields along the initial flight paths of the slugs. This enables the intensity of any neutron burst or explosion resulting from concurrence of the two slugs with the free-falling mass to be very precisely controlled as to time and location as well as magnitude. Thus, the large contained burst reactor system of this invention has a substantial advantage over prior art systems both in providing means for placing substantially greater quantities of working fluid in close proximity to the centroidal explosion and through a larger and more precise explosion or burst being obtainable as a result of the finer control provided for the concurring slugs. The reactor system of this invention provides a great technological contribution toward the development of massive fusion explosion systems, such as were disclosed in my application Ser. No. 40,849, by teaching a method by which much greater quantities of working fluid can be positioned in closer proximity to a centroidal nuclear explosion so that an explosion-containing chamber of less volume than previously required can be utilized. With a fusion explosion system for the breeding of U.sup.233 enriched uranium with an energy output of 10.sup.13 joules per explosion-cycle, the free-falling column-globs of very lean slurry can be used in order to avoid the need for much larger containing chamber or to avoid more complex and more expensive means of containing explosions in a less voluminous chamber. The use of massive column-globs in an explosion-containing chamber as disclosed in this invention is not limited to nuclear explosion reactor systems, nor is such use limited to the containment of explosions for such column-globs themselves can be a cause of a highly energetic, explosion-like effect. Specifically, a large chamber may be provided with a small opening in an upper portion through which a meteor-like mass can enter and collide with the column-globs which are released at a coordinated time for producing useful thermal energy and desired chemical reactions, such as is disclosed in my U.S. Pat. application Ser. No. 119,516 filed Feb. 7, 1980. Note that the kinetic energy of an object "falling" from near the moon has about 23 times the energy needed to " lift" it from the moon.
050088416	claims	1. A non-invasive monitoring system for a valve of the type including a housing and a movable element mounted in the housing for movement between an open position and a closed position and intermediate positions between the open and closed positions comprising: (a) first means for both detecting acoustic energy produced by the valve during a monitoring interval and generating data representative of the detected acoustic energy; (b) second means for both detecting signals indicative of the position of the movable element during the monitoring interval and generating data representative of the detected signals; and (c) third means coupled to the first and second means for simultaneously receiving the data generated by the first and second means and providing data from which a condition of the valve can be determined by a user. (a) computer means programmed to identify significant data corresponding to impacts of internal elements of the valve resulting from movement of the movable element and corresponding to the position of the movable element at times that substantially coincide with the internal impacts; and (b) display means coupled to the computer means and responsive to the significant data to provide a display of the significant data. (a) analog to digital converter means for converting the analog voltage signals generated by the first and second means to digital voltage signals; (b) digital signal processing means coupled to the analog to digital converter means and programmed to locate digital voltage signals corresponding to impacts of internal elements of the valve resulting from movement of the movable element and corresponding to the position of the movable element at times that substantially coincide with the internal impacts; and (c) display means operatively coupled to the digital signal processing means and responsive to the located digital voltage signals to provide a display of the located digital voltage signals. (a) detecting acoustic energy produced by the valve during a monitoring interval and generating data representative of the detected acoustic energy; (b) detecting signals indicative of the position of the movable element during the monitoring interval and generating data representative of the detected signals; and (c) processing the data generated in steps (a) and (b) to place the data generated in steps (a) and (b) in a form for detecting various conditions within the valve. (i) identifying significant data corresponding to impacts of internal elements of the valve resulting from movement of the movable element and corresponding to the position of the movable element at times that substantially coincide with the internal impacts; and (ii) displaying said significant data. (a) detecting acoustic energy produced by the valve during a monitoring interval and generating data representative of the detected acoustic energy; (b) detecting signals indicative of the position of the movable element during the monitoring internal and generating data representative of the detected signals; and (c) recording the data generated in steps (a) and (b) for subsequent analysis. (d) processing the data recorded in step (c) to place the recorded data in a form for analysis. (e) analyzing the data processed in step (d) to detect various conditions within the valve. (a) mounting an accelerometer and a Hall effect generator on the exterior of the housing; and (b) processing the output signals of the accelerometer and the Hall effect generator to place the same in a form for detecting various conditions within the valve. (i) locating output signals of the accelerometer corresponding to internal impacts resulting from movement of the movable element; (ii) locating output signals of the Hall effect generator corresponding to the position of the movable element at times that substantially coincide with the internal impacts; and (iii) displaying the located output signals of the accelerometer and the Hall effect generator for analysis. (a) mounting a piezoelectric accelerometer and a Hall effect generator on the exterior of the housing; (b) effecting movement of the movable element; and (c) during step (b) simultaneously recording the output signals of the accelerometer and the output signals of the Hall effect generator. (d) processing the recorded output signals of the accelerometer and the recorded output signals of the Hall effect generator to place the same in a form for analysis. (i) identifying significant output signals of the accelerometer corresponding to impacts of internal elements of the valve resulting from movement of the movable element and identifying significant output signals of the Hall effect generator corresponding to the position of the movable element at times that substantially coincide with the internal impacts; and (ii) displaying the significant output signals of the accelerometer and Hall effect generator for analysis. (e) analyzing the data processed in step (d) to detect various conditions within the valve. 2. A non-invasive monitoring system according to claim 1 wherein the third means comprises recording means for recording the data generated by the first and second means. 3. A non-invasive monitoring system according to claim 1 wherein the third means comprises data processing means for processing the data generated by the first and second means to place the data generated by the first and second means in a form for analysis. 4. A non-invasive monitoring system according to claim 3 wherein the data processing means comprises: 5. A non-invasive monitoring system according to claim 1 wherein the first means comprises an accelerometer. 6. A non-invasive monitoring system according the claim 5 wherein the accelerometer comprises a piezoelectric crystal accelerometer. 7. A non-invasive monitoring system according to claim 1 wherein the second means comprises magnetic field generating means mounted on the movable element for movement therewith to provide a varying magnetic field as the position of the movable element changes, and magnetic field strength sensing means for detecting the strength of the magnetic field provided by the magnetic field generating means and for generating signals proportional to the strength of the magnetic field detected thereby. 8. A non-invasive monitoring system according to claim 7 wherein said magnetic field generating means comprises a permanent magnet and said magnetic field strength sensing means comprises a Hall effect generator. 9. A non-invasive monitoring system according the claim 1 wherein the first means comprises a piezoelectric crystal accelerometer and the second means comprises a permanent magnet mounted on the movable element for movement therewith and a Hall effect generator. 10. A non-invasive monitoring system according to claim 9 wherein the piezoelectric crystal accelerometer and the Hall effect generator are disposed within a single container, the container being mounted on the exterior of the valve housing. 11. A non-invasive monitoring system according to claim 1 wherein the first means generates data in the form of analog voltage signals representative of the detected acoustic energy; the second means generates data in the form of analog voltage signals representative of the detected signals; and wherein the third means comprises data processing means for processing the data generated by the first and second means to place the data generated by the first and second means in a form for analysis; the data processing means comprising: 12. A non-invasive method of monitoring a valve of the type having a housing and an internal element mounted in the housing for movement between open and closed positions and intermediate positions between the open and closed positions comprising the steps of: 13. A non-invasive method of monitoring a valve according to claim 12 wherein step (c) comprises: 14. A non-invasive method of monitoring a valve of the type having a housing and an internal element mounted in the housing for movement between open and closed positions and intermediate positions between the open and closed positions comprising the steps of: 15. A non-invasive method of monitoring a valve according to claim 14 further comprising the step of: 16. A non-invasive method of monitoring a valve according to claim 15 further comprising the step of: 17. A non-invasive method of monitoring a valve of the type having a housing and an interval element mounted in the housing for movement between open and closed positions and intermediate positions between the open and closed positions, the moveable element having a permanent magnet located thereon for movement therewith, comprising the steps of: 18. A non-invasive method of monitoring a valve according to claim 17 wherein step (b) comprises: 19. A non-invasive method of monitoring a valve of the type having a housing and an internal element mounted in the housing for movement between open and closed positions and intermediate positions between the open and closed positions, the movable element having a permanent magnet located thereon for movement therewith, comprising the steps of: 20. A non-invasive method of monitoring a valve according to claim 19 further comprising the step of: 21. A non-invasive method of monitoring a valve according to claim 20 wherein step (d) comprises: 22. A non-invasive method of monitoring a valve according to claim 21 further comprising the step of:
	summary
048030449	claims	1. A fuel assembly for a boiling water reactor comprising a group of vertical, parallel, elongated fuel rods containing a fissionable material, and an outer flow channel surrounding said fuel rods, said assembly having a critical heat transfer zone in its upper portion; at least one inner flow channel having substantially rectilinear sides spanning at least several fuel tubes, said inner channel being constructed and arranged to receive cooling water near the lower end of said assembly, said inner channel extending upwardly through said assembly parallel to said fuel rods and closed at its upper end; a closure in the upper portion of said inner channel; an inner tube having an opening through said closure, and an opening adjacent to the top of said inner channel; at least one opening in said central tube, adjacent said closure, and upper openings in said inner channel above said closure, and located within said critical heat flux zone, whereby cooling water will flow upwardly through said inner channel, upwardly through said inner tube, then downwardly through said inner channel and outwardly through said upper openings into the critical heat flux zone. 2. An assembly as defined and claim 1, and further including at least one intermediate egress opening in said inner channel adjacent to the lower end of said critical heat transfer zone. 3. An assembly as defined in claim 2, wherein said intermediate egress opening is located in the range of about 50 percent to about 65 percent of the height of the assembly measured from the bottom. 4. An assembly as defined in claim 3, wherein said upper exit opening is located in the range of about 65 percent to about 75 percent of the height of the assembly measured from the bottom, said intermediate and upper opening being spaced a substantial distance apart. 5. An assembly as defined in claim 1, wherein said inner channel is cruciform in shape with its arms extending from side to side of said fuel assembly, at about the midpoint of the sides thereof. 6. An assembly as defined in claim 5, wherein said inner tube is located at the crossing point of the arms of said cruciform flow channel. 7. An assembly as defined in claim 1, wherein said inner flow channel is a substantially rectangular member centrally positioned in said fuel assembly.
	claims	1. A passively-cooled spent nuclear fuel pool system, the system comprising:a containment vessel comprising a thermally-conductive cylindrical shell formed of metal;an annular reservoir surrounding the cylindrical shell of the containment vessel, the annular reservoir holding a coolant that defines a heat sink;a spent fuel pool disposed in the containment vessel, the fuel pool comprising:a floor and a peripheral sidewall extending upwards from the floor that collectively define an interior cavity;a body of water disposed in the interior cavity and having a surface level, at least one spent nuclear fuel rod submerged in the body of water that heats the water to form water vapor via evaporation; anda removable lid covering the spent fuel pool to form a sealed vapor space between the surface level of the body of water and the lid;a passive heat exchange sub-system comprising an assembly of:a primary riser section fluidly coupled to the vapor space;at least one downcomer fluidly coupled to the primary riser section for receiving the water vapor from the primary riser section, the water vapor condensing within the at least one downcomer to form a condensed water vapor; andat least one return conduit fluidly coupled to the at least one downcomer, the at least one return conduit having an outlet located within the body of liquid water for returning the condensed water vapor to the body of liquid water;wherein the peripheral sidewall of the fuel pool is formed by a portion of the cylindrical shell of the containment vessel adjacent to the spent fuel pool which defines a shared heat transfer wall, the heat transfer wall operable to transfer heat from the body of water in the spent fuel pool to the heat sink for cooling the body of water. 2. The system according to claim 1, wherein the at least one downcomer is attached to the cylindrical shell of the containment vessel for transferring heat to the heat sink. 3. The system according to claim 1, wherein the annular reservoir contains water as the liquid coolant having a lower temperature than the body of water in the fuel pool. 4. The system according to claim 1, wherein the heat transfer wall has an arcuate shape in top plan view. 5. The system according to claim 1, further comprising a vertically oriented flow partition plate disposed at least in a portion of the annular reservoir adjacent the heat transfer wall, the flow partition plate spaced radially apart from the heat transfer wall and configured to define a convective flow path that induces natural gravity circulation of the liquid coolant in the annular reservoir. 6. The system according to claim 5, wherein the flow partition plate includes a bottom spaced above a base mat of the annular reservoir and a top spaced apart below a top end of the annular reservoir such that a liquid coolant circulation flow path is formed over and under the flow partition plate. 7. The system according to claim 5, further comprising a plurality of heat exchange fins extending radially outwards from cylindrical shell of the containment vessel into the annular reservoir, and wherein the flow partition plate is supported by the heat exchange fins. 8. The system according to claim 7, wherein the flow partition plate is comprised of a plurality of segments each attached between a pair of heat exchange fins. 9. The system according to claim 1, further comprising a vertically oriented flow partition wall disposed in the fuel pool between a spent fuel rack storage area on the floor and the heat transfer wall, the flow partition wall configured to define a convective flow path that induces natural gravity circulation of the body of water in the fuel pool. 10. The system according to claim 1, wherein the heat transfer wall has an arcuate shape in top plan view. 11. The system according to claim 1, wherein the annular reservoir is vented to atmosphere for cooling the liquid coolant via evaporative loss.
	abstract	A lithographic apparatus includes an illumination system configured to condition a radiation beam, a projection system configured to project the radiation beam onto a substrate, and a filter system for filtering debris particles out of the radiation beam. The filter system includes a plurality of foils for trapping the debris particles, a support for holding the plurality of foils, and a cooling system having a surface that is arranged to be cooled. The cooling system and the support are positioned with respect to each other such that a gap is formed between the surface of the cooling system and the support. The cooling system is further arranged to inject gas into the gap.
	abstract	This X-ray imaging apparatus for rounds includes inside a cart a battery, a charging circuit adapted to limit charging current flowing through the battery, and a control circuit, in which the control circuit includes: a power supply voltage detecting part adapted to detect power supply voltage supplied from an external power supply; a charged voltage detecting part adapted to detect the charged voltage of the battery; a charging current detecting part adapted to detect charging current at the time when the battery is charged; and a charging current value control part adapted to, depending on a variation in the power supply voltage detected by the power supply voltage detecting part, control a charging current value set for the charging circuit.
	summary
	abstract	An improved method and apparatus for transporting a syringe containing radioactive material that provides many advantages, including the safe enclosure of the syringe both before and after use, which reduces the possibility of contamination of the radiopharmaceutical pig. The present invention also provides a radiopharmaceutical pig that eliminates the need for a protective plastic outer shell and has a convenient grip. Finally, the present invention allows the user to readily determine if a syringe within a closed sharps container is full or spent without handling the container.
06278756&	summary	FIELD OF THE INVENTION The present invention relates generally to nuclear reactors, and more particularly to an electrochemical corrosion potential sensor for sensing the electrochemical corrosion potential of materials exposed to high temperature water. BACKGROUND A nuclear power plant includes a nuclear reactor for heating water to generate steam which is routed to a steam turbine. The steam turbine extracts energy from the steam to power an electrical generator which produces electrical power. The nuclear reactor is typically in the form of a boiling water reactor having nuclear fuel disposed in a reactor pressure vessel in which water is heated. The water and steam are carried through various components and piping which are typically formed of stainless steel, with other materials such as iron based alloys and nickel based alloys being used for various components inside the reactor pressure vessel. It has been found that these materials tend to undergo intergranular stress corrosion cracking depending on the chemistry of the material, the degree of sensitization, the presence of tensile stress, and the chemistry of the reactor water. By controlling one or more of these critical factors, it is possible to control the propensity of a material to undergo intergranular stress corrosion cracking. However, it is conventionally known that intergranular stress corrosion cracking may be controlled or mitigated by controlling a single critical parameter called the electrochemical corrosion potential (ECP) of the material. Thus, considerable efforts have been made in the past decade to measure the electrochemical corrosion potential of the materials of interest during operation of the reactor. This measurement, however, is not a trivial task, because the electrochemical corrosion potential of the material varies depending on the location of the material in the reactor circuit. As an example, a material in the reactor core region is likely to be more susceptible to radiation assisted stress corrosion cracking than the same material exposed to an out-of-core region. The increased susceptibility occurs because the material in the core region is exposed to the highly oxidizing species generated by the radiolysis of water by both gamma and neutron radiation under normal water chemistry conditions in addition to the effect of direct radiation assisted stress corrosion cracking. The oxidizing species increase the electrochemical corrosion potential of the material, which in turn increases its propensity to undergo intergranular stress corrosion cracking or radiation assisted stress corrosion cracking. Thus, a suppression of the oxidizing species is desirable in controlling intergranular stress corrosion cracking. An effective method of suppressing the oxidizing species coming into contact with the material involves the injection of hydrogen into the reactor water via the feedwater system so that recombination of the oxidants with hydrogen occurs within the reactor circuit. The recombination results in an overall reduction in the oxidant concentration present in the reactor which in turn mitigates intergranular stress corrosion cracking of the materials if the oxidant concentration is suppressed to low levels. This method is conventionally called hydrogen water chemistry and is widely practiced for mitigating intergranular stress corrosion cracking of materials in boiling water reactors. When hydrogen water chemistry is practiced in a boiling water reactor, the electrochemical corrosion potential of the stainless steel material typically decreases from a positive value generally in the range of 0.050 to 0.200 V (SHE) under normal water chemistry to a value less than -0.230 V (SHE), where SHE stands for the standard hydrogen electrode. There is considerable evidence that when the electrochemical corrosion potential is below -0.230 V (SHE), intergranular stress corrosion cracking of materials such as stainless steel can be mitigated, and the initiation of intergranular stress corrosion cracking can be largely prevented. Thus, considerable efforts have been made to develop reliable electrochemical corrosion potential sensors to be used as reference electrodes for determining the electrochemical corrosion potential of operating surfaces. These sensors are being used in boiling water reactors worldwide, with a high degree of success, which has enabled the determination of the minimum feedwater hydrogen injection rate required to achieve electrochemical corrosion potentials of reactor internal surfaces and piping below the desired negative value, -0.230 mV (SHE). However, the sensors typically have a limited lifetime, in that some have failed after only a few months of use, while most have shown evidence of successful operation for approximately six to nine months. Only a few sensors have shown successful operation over a period of one fuel cycle, e.g. eighteen months in a US boiling water reactor. Recent experience with boiling water reactors in the United States has shown that the two major modes of failure of the sensor have been cracking and corrosive attack in the ceramic-to-metal braze used at the sensor tip, and the dissolution of the sapphire insulating material used to electrically isolate the sensor tip from the metal conductor cable for platinum or stainless steel type sensors. The electrochemical corrosion potential sensors may be mounted either directly in the reactor core region for directly monitoring electrochemical corrosion potential of in-core surfaces, or may be mounted outside the reactor core to monitor the electrochemical corrosion potential of out-of-core surfaces. However, the typical electrochemical corrosion potential sensor nevertheless experiences a severe operating environment in view of the high temperature of water, typically exceeding 288.degree. C., relatively high flow rates, e.g up to several meters per second (m/s) or more, and the effects of high nuclear radiation in the core region. This environment complicates the design of the sensor, since suitable materials are required for this hostile environment, preferably configured to provide a water-tight assembly for a beneficial useful lifetime. As indicated above, experience with the typical platinum electrochemical corrosion potential sensor has uncovered shortcomings leading to premature failure before expiration of a typical fuel cycle. Accordingly, it is desired to improve the design of electrochemical corrosion potential sensors to increase their useful life, e.g. to at least one fuel cycle. SUMMARY The invention relates to a sensor for a measuring an electrochemical corrosion potential comprising a sensor tip, a conductor electrically connected to the sensor tip, an insulating member which surrounds the conductor, a connecting member which surrounds the conductor, and a sleeve which fits over the sensor tip, the insulating member, and the connecting member, the sleeve having inner threads which engage with corresponding outer threads on at least one of the sensor tip and the connecting member. The invention also relates to a method of making an electrochemical corrosion potential sensor comprising the steps of providing a sensor tip, connecting a conductor to the sensor tip, providing an insulating member around the conductor, providing a connecting member around the conductor, providing a sleeve which fits over the insulating member, a portion of the connecting member, and a portion of the sensor tip, forming inner threads on the sleeve, forming outer threads on at least one of the sensor tip and the connecting member, and engaging the inner threads with the outer threads. The sensor sleeve can be preformed to have a high mechanical strength and high density, which provides excellent protection to the insulating member and braze joints of the sensor in the high temperature water environment. Exemplary embodiments of the sensor typically have a significantly increased lifetime which allows data on electrochemical corrosion potential to be acquired over a complete fuel cycle.
	description	This application claims the benefit of priority under 35 U.S.C. § 119 (a) and (b) to U.S. Provisional Application No. 62/802,860, filed Feb. 8, 2019, the entire contents of which are incorporated herein by reference. A steam methane reformer (SMR) is an industrial apparatus that utilizes heat, pressure, and a catalyst to convert methane (CH4) and steam (H2O) into hydrogen (3H2) and carbon monoxide (CO). The CH4 and H2O react with each other in catalyst-filled tubes that are enclosed within a furnace which provides heat to the endothermic reaction that forms H2 and CO. In order for this endothermic reaction to proceed, a very high furnace temperature is required. Typically, the temperature will be within 700-1,000° C. (1,292-1,832° F.), while the pressure may typically range from 3 to 25 bar. Some companies manufacture thermocouples that can be inserted into reactor tubes, by which the temperature can be measured along the length of the tube. Knowing this inside-of-SMR-tube temperature is valuable, so that the SMR reaction can be monitored, the process can be optimized, and the tube failure can be predicted. Installing these inside-of-SMR-tube thermocouples can be challenging because they need to be installed before catalyst is installed around them. This invention outlines an apparatus by which the inside-of-reactor tube thermocouple is installed and centered, and then catalyst is loaded into the tube afterwards. A device for centering a temperature measurement device inside a reactor tube that will be filled with catalyst, including multiple inflatable bladders mechanically and fluidically attached to a centering ring. 101=reactor tube (SMR tube) 102=tube inner surface 103=centering ring 104=multiple inflatable bladders 106=temperature measurement device 107=pressurized gas conduit 109=area between multiple inflatable bladders (for catalyst filling) 110=multiple bladder positioning system (including centering ring 103 and multiple inflatable bladders 104) 112=catalyst 113=bottom (distal end) of the reactor tube 114=top (proximal end) of the reactor tube 115=catalyst springs 116=centering ring and catalyst springs tether 117=vibration device 118=compressed gas source 119=compressed gas source valve 122=compressed air bleed valve 123=distal end mesh disk Illustrative embodiments of the invention are described below. While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developer's specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure. The term “about 1 foot” means as close to one foot as is reasonable given the conditions. As used herein, “about 1 foot” is defined as meaning 12 inches plus or minus 20%. Likewise, “about 5 feet” is defined as 60 inches plus or minus 20%. The term “essentially vertical orientation” means as close to vertical is reasonable given the conditions. The term “essentially vertical orientation” means sufficiently vertical such that the performance of the instant invention, from the perspective of one with ordinary skill in the art, is the same as if the tubes were precisely vertical. As used herein, “essentially vertical orientation” is defined as within 10 degrees from true vertical, preferably within 5 degrees of true vertical. As an overview, a method is provided that uses a dense catalyst loading technique. A centering ring is centered within the reformer tube using multiple inflatable bladders (typically 3) that will allow the catalyst to pass between them through the openings and into the lower empty space of the reactor tube. To start, the bladders are positioned above the tube's catalyst layer. Or, if the tube is completely empty, the bladders are positioned above the end of the tube. The distance above the tube end (or catalyst layer) may vary, but about 12 inches is typical. The bladders are inflated, typically using nitrogen or dry service air. Then a “dense loading” technique is used to introduce the catalyst to just below the height of the bladders. The bladders are then repositioned, typically 1 foot above catalyst layer, and the process is repeated until the tube is fully loaded with catalyst. FIG. 1 and FIG. 2 represent a cross-sectional view of steam methane reformer (SMR) tube 101 utilizing the instant device and method. Each of at least three inflatable bladders 104 are attached at one end to, and preferably spaced evenly around, the perimeter of centering ring 103. As indicated in FIG. 6a (cross-sectional view, uninflated), FIG. 6b (isometric view, uninflated), and FIG. 7 (cross-sectional view, inflated), for ease of explanation, this assembly will be referred to as multiple bladder positioning system 110. As indicated in FIGS. 6a, 6b, and 7, within centering ring 103 are at least temperature measurement device 106 and pressurized gas conduit 107. Pressurized gas conduit 107 introduces and evacuates the gas used to inflate and deflate multiple inflatable bladders 104. Pressurized gas conduit 107 connects directly to with multiple inflatable bladders 104, thus allowing them to be inflated and deflated. When inflated (as indicated in FIG. 2), multiple inflatable bladders 104 make at least partial contact with reactor tube wall inner surface 102, and act to locate centering ring 103 centrally within reactor tube wall inner surface 102. Temperature measurement device 106 is located inside of centering ring 103, and after inflation of multiple inflatable bladders 104 is also positioned near the axial center of reactor tube 101. Although only one temperature measurement device 106 is indicated in the figures, it is understood that two or more temperature measurement devices 106 may be located inside centering ring 103 (not shown). This embodiment may be better understood with reference to FIGS. 2-12. In a typical catalyst dense loading procedure, radial springs (or brushes) 115 are positioned at a predetermined spacing down the length of reactor tube 101. Reactor tube 101 may be an SMR tube. Springs 115 radiate from a generally central circular ring and act to impede the catalyst as it falls down the length of reactor tube 101. Springs 115 act to slow down the catalyst as it falls and helps prevent the catalyst from being damaged. It is understood that springs 115 may be used along with the instant invention. Springs 115 may be distributed along reactor tube 101, in circular rings above the instant invention. These circular rings encompass temperature measurement device 106 and pressurized gas conduit 107. These rings are sequentially withdrawn as the instant invention moves up reactor tube 101. These circular rings, from which springs 115 emanate, are connected to each other, and to positioning system 110 by tethers 116. Before the filling of reactor tube 101 with catalyst may commence, the tube is positioned in an essentially vertical orientation, and a sieve has been located at the distal end of the reactor tube, in order to keep the catalyst within the reactor tube. It is preferred that the inside of the tube be inspected to ensure that undesired objects or foreign material not be present. In some cases, a Boroscope (not shown) is used to determine that the inside of the reactor tube is clean. First, temperature measurement device 106 is attached to distal end mesh disk 123. This helps secure temperature measurement device in place when catalyst 112 is loaded above it. This keeps temperature measurement device 106 from migrating up reactor tube 101 during the subsequent steps. Starting at proximal end 114, temperature measurement device 106 is then inserted down the length of the empty reactor tube. Temperature measurement device 106 and pressurized gas conduit 107 are inserted into the center of centering ring 103, and centering ring tether 116 is attached to centering ring 103. While two centering ring tethers 116 are shown in the figures, temperature measurement device 106 may be fitted with one or multiple centering ring tethers 116. Pressurized gas conduit 107 may be inserted through centering ring 103, or pressurized gas conduit 107 may not be inserted through centering ring 103. Pressurized gas conduit 107 may be left outside centering ring 103 if desired (not shown). Then, while holding and extending centering ring tether 116, lower multiple bladder positioning system 110 into reactor tube 101. Then, lower multiple bladder positioning system 110 until it touches the bottom of reactor tube 101. At this time, it is recommended that centering ring tether 116 is marked to indicate the level at proximal end 114 of the tube, as a point of reference. Temperature measurement device 106 may be any device known to the art, suitable for this purpose. Temperature measurement device 106 may be a single thermocouple as indicated in FIG. 3a. Temperature measurement device 106 may be a strand of multiple thermocouple sensors as indicated in FIG. 3b. Multiple bladder positioning system 110 is then raised a first distance H1 from the end of reactor tube 101. H1 is entirely discretionary, but a typical value would be about one foot. This distance may be determined from the mark previously made on centering ring tether 116. An additional reference mark may be made at this time on centering ring tether 116 with reference to proximal end 114, to indicate the new location of multiple bladder positioning system 110. When uninflated, Multiple inflatable bladders 104 are simultaneously inflated, thereby at least partially contacting tube wall inner surface 102 and locating centering ring 103 centrally within reactor tube 101. Any available and suitable compressed gas source 118 may be used for inflating the bladders, such as compressed nitrogen or dry service or plant air. Temperature measurement device 106, which may be approximately the same length as reactor tube 101, is essentially centered within reactor tube 101. A predetermined, or calculated amount of catalyst 112 is added to reactor tube 101. Catalyst 112 passes through open area 107 between multiple inflatable bladders 104, centering ring 103, and tube wall inner surface 102. Utilizing a dense loading technique, catalyst 112 may be added at a prescribed filling rate to reactor tube 101 by any such system known in the art. As catalyst 112 is added to reactor tube 101, it falls through the spaces between the multiple inflatable bladders 104 and settles into the void below. In order to promote better catalyst packing, and to help avoid unwanted voids in the catalyst, reactor tube 101 may be vibrated 117 while filling. When an amount sufficient to approximately fill this void has been added, filling stops and multiple inflatable bladders 104 are deflated. Multiple bladder positioning system 110 is then raised a predetermined distance H2 and the process is repeated. Predetermined distance H2 may be any distance useful or meaningful to the installer, for example three feet. Again, this distance may be determined from the mark previously made on centering ring tether 116, and an additional reference mark may be made at this time on centering ring tether 116. Care must be taken not to overfill with catalyst and covering device 110. In the second, and subsequent, iterations, catalyst 112 is allowed to fill the space below multiple inflatable bladders 104 as well. This ensures that catalyst 112 fully fills reactor tube 101, and the temperature measurement device 106 remains centered. This process is repeated to the desired location within reactor tube 101, which may be a desired distance from the top of the tube. Reactor tube 101 is now fully reloaded and full of fresh catalyst, and temperature measurement device 106 is centrally located and able to provide accurate and meaningful readings of temperature along the length of reactor tube 101. It will be understood that many additional changes in the details, materials, steps and arrangement of parts, which have been herein described in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims. Thus, the present invention is not intended to be limited to the specific embodiments in the examples given above.
	claims	1. A collimator comprising:a pair of first plate members having X-ray absorbability, being movable symmetrically with each other in a direction parallel to surfaces thereof, and defining an X-ray passing aperture by a spacing between respective end faces opposed to each other;a second plate member spaced from the first plate members in a direction perpendicular to the surfaces of the first plate members, having X-ray absorbability, and being movable in a direction parallel to a surface thereof and parallel to the moving direction of the first plate members;a pair of third plate members spaced from the first plate members and the second plate member in a direction perpendicular to the surfaces of the first plate members and the second plate member, having X-ray absorbability, being movable symmetrically with each other in a direction parallel to surfaces thereof and perpendicular to the moving direction of the first plate members, and defining an X-ray passing aperture by a spacing between respective end faces opposed to each other; anda fourth plate member spaced from the first plate members, the second plate member, and the third plate members in a direction perpendicular to the surfaces of the first plate members, the second plate member, and the third plate members, having X-ray absorbability, and being movable in a direction parallel to a surface thereof and parallel to the moving direction of the third plate members. 2. A collimator according to claim 1, wherein the second plate member and the fourth plate member are movable independently of each other. 3. A collimator according to claim 1, wherein the first plate members and the second plate member are constructed as a unitized combination, and the third plate members and the fourth plate member are also constructed as a unitized combination. 4. A collimator according to claim 3, wherein the unitized combination of the first plate members and the second plate member is subunitized for each of the first plate members and the second plate member, and the unitized combination of the third plate members and the fourth plate member is subunitized for each of the third plate members and the fourth plate member. 5. An X-ray irradiator comprising:an X-ray tube; anda collimator for collimating an X-ray generated from the X-ray tube;the collimator comprising:a pair of first plate members having X-ray absorbability, being movable symmetrically with each other in a direction parallel to surfaces thereof, and defining an X-ray passing aperture by a spacing between respective end faces opposed to each other;a second plate member spaced from the first plate members in a direction perpendicular to the surfaces of the first plate members, having X-ray absorbability, and being movable in a direction parallel to a surface thereof and parallel to the moving direction of the first plate members;a pair of third plate members spaced from the first plate members and the second plate member in a direction perpendicular to the surfaces of the first plate members and the second plate member, having X-ray absorbability, being movable symmetrically with each other in a direction parallel to surfaces thereof and perpendicular to the moving direction of the first plate members, and defining an X-ray passing aperture by a spacing between respective end faces opposed to each other; anda fourth plate member spaced from the first plate members, the second plate member, and the third plate members in a direction perpendicular to the surfaces of the first plate members, the second plate member, and the third plate members, having X-ray absorbability, and being movable in a direction parallel to a surface thereof and parallel to the moving direction of the third plate members. 6. An X-ray irradiator according to claim 5, wherein the second plate member and the fourth plate member are movable independently of each other. 7. An X-ray irradiator according to claim 5, wherein the first plate members and the second plate member are constructed as a unitized combination, and the third plate members and the fourth plate member are also constructed as a unitized combination. 8. An X-ray irradiator according to claim 7, wherein the unitized combination of the first plate members and the second plate member is subunitized for each of the first plate members and the second plate member, and the unitized combination of the third plate members and the fourth plate member is subunitized for each of the third plate members and the fourth plate member. 9. An X-ray apparatus comprising:an X-ray tube;a collimator for collimating an X-ray generated from the X-ray tube and applying the collimated X-ray to an object to be radiographed; anda detector device for detecting the X-ray which has passed through the object to be radiographed,the collimator comprising:a pair of first plate members having X-ray absorbability, being movable symmetrically with each other in a direction parallel to surfaces thereof, and defining an X-ray passing aperture by a spacing between respective end faces opposed to each other;a second plate member spaced from the first plate members in a direction perpendicular to the surfaces of the first plate members, having X-ray absorbability, and being movable in a direction parallel to a surface thereof and parallel to the moving direction of the first plate members;a pair of third plate members spaced from the first plate members and the second plate member in a direction perpendicular to the surfaces of the first plate members and the second plate member, having X-ray absorbability, being movable symmetrically with each other in a direction parallel to surfaces thereof and perpendicular to the moving direction of the first plate members, and defining an X-ray passing aperture by a spacing between respective end faces opposed to each other; anda fourth plate member spaced from the first plate members, the second plate member, and the third plate members in a direction perpendicular to the surfaces of the first plate members, the second plate member, and the third plate members, having X-ray absorbability, and being movable in a direction parallel to a surface thereof and parallel to the moving direction of the third plate members. 10. An X-ray apparatus according to claim 9, wherein the second plate member and the fourth plate member are movable independently of each other. 11. An X-ray apparatus according to claim 9, wherein the first plate members and the second plate member are constructed as a unitized combination, and the third plate members and the fourth plate member are also constructed as a unitized combination. 12. An X-ray apparatus according to claim 11, wherein the unitized combination of the first plate members and the second plate member is subunitized for each of the first plate members and the second plate member, and the unitized combination of the third plate members and the fourth plate member is subunitized for each of the third plate members and the fourth plate member.
	description	Reference is now made in detail to a specific embodiment of the present invention which illustrates the best mode presently contemplated by the inventors for practicing the invention. Initially, reference is made to the article xe2x80x9cFilter Optimization for X-ray Inspection of Surface-Mounted ICsxe2x80x9d, pages 377-379, by Richard C. Blish II, Susan Xi, and David Ledtonen, published April, 2002 at IEEE 40th Annual International Reliability Physics Symposium, Dallas, Texas, which material is herein incorporated by reference. FIG. 6 is similar to FIG. 1, but further including a filter 100 as will now be described As shown in FIG. 6 (rotated 90 degrees clockwise from a conventional orientation of elements therein), a semiconductor device 120 is placed on an inspection tray 122 of for example polyimide material. This typical semiconductor device 120 includes a silicon body 124 having a protective coating 125 of molding compound (in FIG. 6 shown lying on the tray 122), the silicon body 124 having an active region 124A and an inactive region 124B secured to a substrate 126 by a silver-organic material adhesive 128 (wire bonds connecting silicon body 124 and substrate 126 not shown). The substrate 126 includes organic portions (for example dielectric layers 130, 132) and patterned copper layers (one shown at 134), which copper layer 134 communicates with the active region 124A of the silicon body 124 (approximately 1 xcexcm in thickness and oriented most adjacent the tray 122) and solder balls 136 (commonly lead/tin but which may consist of a lead-free composition, usually tin-rich) which connect to a layer of copper traces 138 on an organic material (for example polyimide, epoxy, polyethylene, or glass fiber) printed circuit board 140. As previously described, it will be understood that the particular configuration of the semiconductor device 120 is for purposes of illustration, and that such device 120 may be configured in a wide variety of ways, including for example a number of levels of copper layers 134 and dielectric layers 130, 132, with appropriate vias connecting the copper layers. As in the previous example, the following typical thicknesses are given: In the present embodiment, a filter 100 in the form of a zinc foil is positioned between a source of x-rays 142 and the tray 122, such plate 100 having a thickness of for example 300 xcexcm. FIG. 7 is a graph showing x-ray absorption coefficient vs. x-ray energy level for silicon, copper, tin and lead (similar to FIG. 2), but also showing x-ray absorption coefficient vs. x-ray energy level for zinc. Zinc has an atomic number of 30, one greater than the atomic number of copper, which results in the K edge of zinc lying to the right of the K edge of copper, i.e., at a higher energy level (FIG. 7). The importance of this feature will be described further on. During x-ray inspection, x-rays including a wide range of energy levels are provided from the source 142 through the tray 122 and into and through the semiconductor device 120. FIGS. 8 and 9 are graphical representation of the structure of FIG. 6 for x-ray energy levels of 3 KeV and 9 KeV respectively. With reference to FIG. 8, for x-ray energy at the 3 KeV level, i.e., that x-ray energy level wherein silicon has a high coefficient absorption, the zinc filter 100 causes the intensity of the x-ray bean to drop significantly prior to passing through the tray 122 and reaching the silicon body 124. Thus, the intensity of the x-ray beam presented to the silicon body 124 is substantially lower th in the prior art, and the change in intensity of the x-ray beam through the silicon body 124, corresponding to the absorption of x-ray energy by the silicon body 124, is substantially lower than in the prior art, due to the inclusion of the zinc filer 100 (compare FIG. 3 and 8). With this low level of absorption of x-ray energy by the silicon body 124 as compared to the prior art, the problem of ionization of the silicon body 124 in the active region 124A, as described above, is overcome. Meanwhile, the thin adhesive 128 and dielectric layer 130, having low absorption, allow significant x-ray intensity to reach the high absorption copper layer 134. After a high degree of absorption by the copper layer 134, x-ray energy passes through the dielectric layer 132 (low absorption), solder balls 136 (high absorption), copper layer 138 (high absorption) and printed circuit board 140 (low absorption), so that the copper layers and solder balls are properly imaged as a radiograph at the image detector 144 at the 3 KeV x-ray energy level. FIG. 9 is a graphical representation similar to that of FIG. 8, but for the 9 KeV x-ray energy level. At this energy level, absorption by the zinc filter 100 is lower than as shown in FIG. 8 but is still considerable (see absorption coefficients of zinc for various x-ray energy levels in FIG. 7). Meanwhile, the silicon body 124 is substantially less absorbing at this energy level (again see FIG. 7), so that the problem of ionization of silicon is again avoided. Meanwhile, because the atomic number of the zinc filter 100 is greater than the atomic number of copper (in this case one atomic number greater), resulting in the offset in the K lines of copper and zinc in the region of 9 KeV of x-ray energy as shown, the copper is substantially more energy absorbing than the zinc at this energy level, so that the zinc filter 100 transmits a significant amount of x-ray energy to the copper (which at this energy level has significant absorption), providing for highly effective imaging of the copper layers. An important factor in being able to properly image a layer (copper in the examples given) is the selection of filter material with an atomic number greater than a specified layer to be imaged. This determines the offset between the K lines of the layer to be imaged and filter material (greater difference in these numbers determining greater offset between these K lines, and vice versa), which provides a xe2x80x9cwindowxe2x80x9d between these K lines at approximately the 9 KeV energy level, so that proper imaging at this energy level is achieved. It is to be noted that this is achieved along with proper shielding of the silicon body by the filter material as described above. It will be understood that this approach is not limited to copper and zinc, but is highly useful in imaging a wide variety of materials, wherein the material of the filter has a slightly higher atomic number than the material to be imaged. For example, in the situation where copper is to 4he be imaged, filter 100 may with advantage be made up of or include a material having an atomic number ranging from 30 through 35 inclusive, i.e. zinc (atomic number 30), gallium (atomic number 31), germanium (atomic number 32), arsenic (atomic number 33), selenium (atomic number 34), or bromine (atomic number 35). While this approach provides proper imaging of the copper, which is normally difficult or impossible to achieve, imaging of the thick solder balls, which are an import target in the imaging process, is easily accomplished in the normal approach described above, i.e., regardless of the presence or absence of a filter of a particular atomic number. The foregoing description of the embodiment of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Other modifications or variations are possible in light of the above teachings. The embodiment was chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill of the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally and equitably entitled.
	abstract	A method of carrying out a reactor vessel according to the present invention includes removing an overhead traveling crane in a reactor containment vessel of a pressurized water reactor. Alternatively, in an area where an overhead traveling crane is installed, operating the overhead traveling crane to move aside for creating a space, through which the reactor vessel is able to pass. Then the reactor vessel is carried out through an opening provided in a top portion of the reactor containment vessel. With the present method, the reactor vessel of the pressurized water reactor can be carried out in a short period of time with high efficiency.
	claims	1. A system comprising:a nuclear reactor reactivity control system, the nuclear reactor reactivity control system constructed to:control a rate of reactivity change resulting from power changes through all ranges of power levels as required by NRC regulations in effect on Nov. 1, 2015; andhold a core of a nuclear reactor controllable by the nuclear reactor reactivity control system in a subcritical state under cold conditions solely via movement of a single pair of blocks neutron reflector/moderator blocks; andwherein, the nuclear reactor reactivity control system comprises the single pair of neutron reflector/moderator blocks, the pair of neutron reflector/moderator blocks external to and partially surrounding the nuclear reactor, each of the pair of neutron reflector/moderator blocks comprising neutron reflective material with moderation properties. 2. The system of claim 1, further comprising:the nuclear reactor. 3. The system of claim 1, further comprising:a reactor containment structure that substantially surrounds the nuclear reactor. 4. The system of claim 1, further comprising:a core power detector coupled to a control system of the nuclear reactor, the control system constructed to, responsive to a signal from the core power detector, move the pair of neutron reflector/moderator blocks relative to an activated portion of the core of the nuclear reactor. 5. The system of claim 1, wherein:the pair of neutron reflector/moderator blocks is, via at least one motor, movable both vertically and horizontally relative to a core of the nuclear reactor. 6. The system of claim 1, wherein:suspension rod braces limit movement of the pair of neutron reflector/moderator blocks relative to a core of the nuclear reactor. 7. The system of claim 1, wherein:the pair of neutron reflector/moderator blocks comprises carbon black. 8. The system of claim 1, wherein:a position of the pair of neutron reflector/moderator blocks relative to a core of the nuclear reactor is manually controllable. 9. The system of claim 1, wherein:the pair of neutron reflector/moderator blocks is coupled to a vertical gearing rod, the vertical gearing rod, via a vertical gearing rod motor, constructed to move the pair of neutron reflector/moderator blocks vertically relative to the nuclear reactor. 10. The system of claim 1, wherein:the pair of neutron reflector/moderator blocks is coupled to a carriage, the carriage, via a carriage brace motor, constructed to cause the pair of neutron reflector/moderator blocks to reduce neutron reflection relative to the nuclear reactor by laterally traversing the pair of neutron reflector/moderator blocks. 11. The system of claim 1, wherein:the pair of neutron reflector/moderator blocks is coupled to a carriage, the carriage, via a carriage brace motor, constructed to cause the pair of neutron reflector/moderator blocks move away from the nuclear reactor. 12. The system of claim 1, wherein:the pair of neutron reflector/moderator blocks is suspended from a carriage brace by suspension rods, the carriage brace comprising two separate halves that are coupled together via center gearing, the pair of neutron reflector/moderator blocks positioned with a vertical gearing rod substantially through a center of each block and coupled to a suspension carriage, the suspension carriage engaged with the carriage brace, a carriage brace motor causing teeth of the carriage brace to move the carriage and thereby move the pair of neutron reflector/moderator blocks relative to a core of the nuclear reactor. 13. The system of claim 1, wherein:the pair of neutron reflector/moderator blocks is electrically controlled by a control logic system of the nuclear reactor. 14. The system of claim 1, wherein:the pair of neutron reflector/moderator blocks are suspended on suspension rods at core height of the nuclear reactor. 15. The system of claim 1, wherein:vertical gearing rods are substantially in the center of the pair of neutron reflector/moderator blocks and allow for vertical positioning of the pair of neutron reflector/moderator blocks. 16. The system of claim 1, wherein:the pair of neutron reflector/moderator blocks comprises petals like a flower. 17. The system of claim 1, wherein:the pair of neutron reflector/moderator blocks shaped in a configuration like an iris of a camera. 18. The system of claim 1, wherein:a shutdown feature of the nuclear reactor reactivity control system uses a separation of release locks to a vertical gearing rod, which allows the pair of neutron reflector/moderator blocks to drop down and away from the core to cause a shutdown condition for the core due to the removal of the pair of neutron reflector/moderator blocks, which increases fast and thermal neutron leakage from the core such that the core is no longer coupled neutronically and is shutdown.
052079759	claims	1. A hydraulic control rod driving system provided with a cylinder installed on a reactor vessel cover and a driving shaft which is coupled with a control rod cluster, extends into said cylinder while penetrating through said reactor vessel cover and has a piston portion at an upper end thereof, in which said driving shaft is moved vertically by controlling fluid pressure above and under said piston portion, characterized in that: radial clearance is formed between said piston portion and said cylinder; step portions each composed of a cylindrical upper part having a large diameter and a cylindrical lower part having a small diameter arranged adjacent to the lower side of said upper part are provided on said piston portion along an axial direction thereof; circumferential grooves for partitioning said respective step portions are provided; and a ratio of the length of each step portion to the maximum outside diameter of said piston portion is set at 0.5 to 1.0. 2. A hydraulic control rod driving system according to claim (1), wherein at least two or more step portions are provided.
048662801	abstract	An objective lens of an electron beam apparatus in which an electron beam emitted from an electron gun is converged onto a specimen, the reflected electron from the specimen or the secondary electron emitted therefrom is detected, and a fine pattern on the specimen is measured, comprises: a magnetic circuit consisting of an upper magnetic pole member having an opening adapted to transmit the electron beam to be converted which was emitted from the electron gun, a lower magnetic pole member provided so as to face the upper magnetic pole member, and a magnetic path member to connect the outer peripheral edges of the upper and lower magnetic pole members; a coil, provided for a part of the magnetic circuit, for generating the magnetic fluxes passing through the upper and lower magnetic pole members, the magnetic path member, and the space between the opening edge and the lower magnetic pole member when this coil is excited; and a moving apparatus which is disposed on the surface of the lower magnetic pole member opposite to the upper magnetic pole member and is movable on the plane perpendicular to the electron beam in the magnetic circuit in the state in which the specimen is put on the upper surface of the moving apparatus.
	claims	1. A radiation detection apparatus comprising a sensor panel and a scintillator panel, the scintillator panel including:a substrate;a scintillator disposed on the substrate; anda scintillator protective film that has a first organic protective layer and an inorganic protective layer, and covers the scintillator, whereinthe scintillator protective film is located between the sensor panel and the scintillator,the first organic protective layer is located on a scintillator side from the inorganic protective layer, anda surface on a sensor panel side of the scintillator is partially in contact with the inorganic protective layer. 2. The apparatus according to claim 1, wherein the scintillator comprises a set of columnar crystals, and tips of the columnar crystals penetrate the first organic protective layer and are in contact with the inorganic protective layer. 3. The apparatus according to claim 1, wherein the scintillator protective film further comprises a second organic protective layer,the second organic protective layer is located on the sensor panel side from the inorganic protective layer,the inorganic protective layer and the scintillator are bonded by the first organic protective layer, andthe inorganic protective layer and the sensor panel are bonded by the second organic protective layer. 4. The apparatus according to claim 3, whereinthe sensor panel comprises semiconductor members and electrically conductive members forming a pixel array, andat least some of the semiconductor members and at least some of the electrically conductive members have a part that is in contact with the second organic protective layer. 5. The apparatus according to claim 4, wherein at least some of the semiconductor members and at least some of the electrically conductive members have a part that penetrates the second organic protective layer and is in contact with the inorganic protective layer. 6. The apparatus according to claim 3, wherein the sensor panel comprises semiconductor members and electrically conductive members forming a pixel array, and a sensor panel protective film covering the semiconductor members and the electrically conductive members, andthe sensor panel protective film has a part that is in contact with the second organic protective layer. 7. The apparatus according to claim 6, wherein a part of the sensor panel protective film that covers the semiconductor members and the electrically conductive members includes a part that penetrates the second organic protective layer and is in contact with the inorganic protective layer. 8. The apparatus according to claim 3, wherein a temperature for bringing the first organic protective layer into a softened state and a temperature for bringing the second organic protective layer into a softened state both are lower than a temperature for bringing the inorganic protective layer into a softened state. 9. The apparatus according to claim 3, wherein the first organic protective layer and the second organic protective layer are organic resin films, and the inorganic protective layer is an oxide film or a nitride film. 10. A radiation detection system comprising:the radiation detection apparatus according to claim 1; anda signal processing unit for processing a signal obtained by the radiation detection apparatus. 11. A scintillator panel comprisinga substrate;a scintillator disposed on the substrate; anda scintillator protective film that has an organic protective layer and an inorganic protective layer, and covers the scintillator, whereinthe organic protective layer is located on a scintillator side from the inorganic protective layer, anda surface on an opposite side to a surface on a substrate side, of the scintillator is partially in contact with the inorganic protective layer. 12. A method for manufacturing a radiation detection apparatus, comprising:forming a scintillator on a substrate;preparing a scintillator protective film having an organic protective layer and an inorganic protective layer;covering the scintillator with the scintillator protective film so that the organic protective layer is in contact with the scintillator;bonding, by thermocompression bonding, the scintillator protective film to the scintillator; andlaminating the scintillator covered with the scintillator protective film and a sensor panel,wherein in the laminating, a surface on an opposite side to a surface on a substrate side, of the scintillator that enters partially the organic protective layer reaches the inorganic protective layer and stops. 13. A method for manufacturing a scintillator panel comprising:forming a scintillator on a substrate;preparing a scintillator protective film having an organic protective layer and an inorganic protective layer;covering the scintillator with the scintillator protective film so that the organic protective layer is in contact with the scintillator; andbonding, by thermocompression bonding, the scintillator protective film to the scintillator,wherein in the bonding by thermocompression bonding, a surface on a side opposite to a surface on a substrate side, of the scintillator that enters partially the organic protective layer reaches the inorganic protective layer and stops. 14. A method for manufacturing a scintillator panel comprising:preparing a scintillator protective film having an organic protective layer and an inorganic protective layer; andcovering a scintillator formed on a substrate with the scintillator protective film so that the organic protective layer is in contact with the scintillator. 15. The method according to claim 14, further comprising:bonding, by thermocompression bonding, the scintillator protective film to the scintillator,wherein in the bonding by thermocompression bonding, a surface on a side opposite to a surface on a substrate side, of the scintillator that enters partially the organic protective layer reaches the inorganic protective layer and stops. 16. The method according to claim 15, wherein the scintillator comprises a set of columnar crystals, and tips of the columnar crystals penetrate the first organic protective layer and are in contact with the inorganic protective layer. 17. The method according to claim 15, whereinthe scintillator protective film further comprises a second organic protective layer,the second organic protective layer is located on the inorganic protective layer, andthe inorganic protective layer and the scintillator are bonded by the first organic protective layer. 18. The method according to claim 15, wherein the first organic protective layer and the second organic protective layer are organic resin films, and the inorganic protective layer is an oxide film or a nitride film.
	summary
	claims	1. A support device for a polycapillary optic, said support device comprising: a unitary housing having a central opening passing therethrough, said central opening having an axis; at least two locating structures formed within said housing adjacent to said central opening therethrough, wherein each locating structure is sized and positioned to accommodate a polycapillary positioning component within said housing, and wherein each locating structure is aligned about said axis; and wherein said at least two locating structures facilitate positioning of at least two polycapillary positioning components to be disposed within said housing for holding polycapillaries of said polycapillary optic. 2. A support device of claim 1 , further comprising said at least two polycapillary positioning components, wherein said polycapillary positioning components, when disposed at said locating structures, orient said polycapillaries such that radiation from one of a divergent beam, a focused beam, or a parallel beam can be collected by said polycapillary optic, and such that said polycapillary optic can output one of a collimated beam, a focused beam or a divergent beam. claim 1 3. The support device of claim 2 , wherein each polycapillary positioning component comprises a positioning screen having at least one opening therein for accommodating a polycapillary of said polycapillary optic. claim 2 4. The support device of claim 2 , wherein each polycapillary positioning component comprises a positioning screen having multiple openings therein for accommodating multiple polycapillaries of said polycapillary optic. claim 2 5. The support device of claim 4 , wherein said multiple openings of at least some of said at least two polycapillary positioning components are disposed differently within said respective polycapillary positioning components to facilitate orienting of said polycapillaries such that radiation from said one of a divergent beam, a focused beam, or a parallel beam can be collected, or to facilitate said polycapillary optic outputting said one of a collimated beam, a focused beam, or a divergent beam. claim 4 6. The support device of claim 1 , wherein said at least two locating structures comprise at least two shoulders formed integral with an internal surface of said housing defining said central opening. claim 1 7. A support device for a polycapillary optic, said support device comprising: a housing having a central opening passing therethrough, said central opening having an axis; at least two locating structures formed within said housing adjacent to said central opening therethrough, wherein each locating structure is sized and positioned to accommodate a polycapillary positioning component within said housing, and wherein each locating structure is aligned about said axis; and wherein said at least two locating structures facilitate positioning of at least two polycapillary positioning components to be disposed within said housing for holding polycapillaries of said polycapillary optic; wherein said housing comprises a unitary structure, and said at least two polycapillary positioning components comprise positioning screens each with at least one fiber positioning hole passing therethrough, each said at least one fiber positioning hole being located within said screen relative to a periphery thereof to a tolerance of less than 100 microns. 8. The support device of claim 7 , wherein within at least one screen, location of said at least one fiber positioning hole determines whether an output of said polycapillary optic is converging, diverging, or parallel. claim 7 9. The support device of claim 1 , wherein said housing comprises an open frame structure having said central opening passing therethrough, said open frame structure comprising multiple ring sections fixedly interconnected, each ring section having one locating structure of said at least two locating structures for facilitating positioning of a corresponding polycapillary positioning component within the support device. claim 1 10. The support device of claim 9 , wherein said at least two locating structures each comprises a shoulder for facilitating positioning of one of said polycapillary positioning components, each shoulder being associated with one of said ring sections of said open frame. claim 9 11. The support device of claim 1 , wherein said polycapillary optic comprises a lens for focusing x-ray or neutron radiation. claim 1 12. The support device of claim 1 , wherein a diameter of said central opening varies along a length of said housing. claim 1 13. The support device of claim 1 , wherein said housing further comprises placement holes for accommodating a fastener to allow for positioning and alignment of the support device relative to a source or an output focal point. claim 1 14. A polycapillary optic assembly comprising: at least one polycapillary of said polycapillary optic; a support device for said at least one polycapillary, said support device comprising: a unitary housing having a central opening passing therethrough, said central opening having an axis; at least two locating structures formed within said housing adjacent to said central opening therethrough, wherein each locating structure is sized and positioned to accommodate a polycapillary positioning component within said housing, and wherein each locating structure is aligned about said axis; and wherein said at least two locating structures facilitate positioning of at least two polycapillary positioning components to be disposed within said housing for holding said at least one polycapillary therein. 15. The polycapillary optic assembly of claim 14 , further comprising said at least two polycapillary positioning components, wherein said polycapillary positioning components, when disposed at said locating structures, orient said at least one polycapillary such that radiation from one of a divergent beam, a focused beam, or a parallel beam can be collected by said polycapillary optic, and such that said polycapillary optic assembly can output one of a collimated beam, a focused beam or a divergent beam. claim 14 16. The polycapillary optic assembly of claim 15 , wherein each polycapillary positioning component comprises a screen having at least one opening therein for accommodating a polycapillary of said polycapillary optic. claim 15 17. The polycapillary optic assembly of claim 16 , wherein said at least one opening in each screen comprises multiple openings, and wherein said multiple openings of at least some of said at least two polycapillary positioning components are disposed differently within said respective polycapillary positioning components to change orientation of said polycapillaries between an input and an output of said polycapillary optic assembly. claim 16 18. A polycapillary optic assembly comprising: at least one polycapillary of said polycapillary optic; a support device for said at least one polycapillary, said support device comprising: a housing having a central opening passing therethrough, said central opening having an axis; at least two locating structures formed within said housing adjacent to said central opening therethrough, wherein each locating structure is sized and positioned to accommodate a polycapillary positioning component within said housing, and wherein each locating structure is aligned about said axis; and wherein said at least two locating structures facilitate positioning of at least two polycapillary positioning components to be disposed within said housing for holding said at least one polycapillary therein; wherein said housing comprises a unitary structure, and wherein said at least two locating structures comprise at least two shoulders formed integral with an internal surface of said unitary housing. 19. The polycapillary optic assembly of claim 14 , wherein said at least one polycapillary comprises a lens for focusing x-ray or neutron radiation. claim 14 20. A method for fabricating a support device for a polycapillary optic, said method comprising: providing a housing and forming a central opening within said housing, said forming of said central opening comprising machining a central opening through said housing such that said central opening is defined by at least one coaxial bore, said central opening having an axis; and defining at least two locating structures within said housing adjacent to said central opening therethrough and aligned about said axis, wherein each locating structure is sized and positioned to accommodate a polycapillary positioning component within the housing, said polycapillary positioning components to be disposed within said housing for holding polycapillaries of said polycapillary optic. 21. The method of claim 20 , further comprising positioning said at least two polycapillary positioning components within said housing using said at least two locating structures, wherein said polycapillary positioning components, when disposed at said locating structures, orient said polycapillaries such that radiation from one of a divergent beam, a focused beam, or a parallel beam can be collected by the polycapillary optic, and such that the polycapillary optic can output one of a collimated beam, a focused beam or a divergent beam. claim 20 22. The method of claim 20 , further comprising boring said central opening such that said at least two locating structures comprise at least two shoulders defined on an inner surface of said housing surrounding said central opening. claim 20
	abstract	The neutron monitoring system measures neutrons by counting both the negative pulse signals and the positive noise pulse signals output from a neutron detector 1, and subtracts the positive pulse count from the negative pulse count per unit time, thereby measuring the neutrons.
	description	This application is a non-provisional application claiming the benefit of priority of the provisional applications Nos. 61/202,560 filed on Mar. 12, 2009 and 61/272,894 filed on Nov. 16, 2009, the entire contents of which are incorporated herein by reference. 1. Filed An embodiment according to the present invention relates to an optical integrator, illumination optical system, exposure apparatus, and device manufacturing method. More particularly, an embodiment according to the present invention relates to an optical integrator used in an illumination optical system of an exposure apparatus used in manufacturing devices such as semiconductor devices, imaging devices, liquid crystal display devices, and thin film magnetic heads by lithography. 2. Explanation of Related Art The conventional exposure apparatus used in manufacturing the semiconductor devices and others is configured to project and transfer a circuit pattern formed on a mask (reticle), onto a photosensitive substrate (e.g., a wafer) through a projection optical system. The photosensitive substrate is coated with a resist, and the resist is exposed to light by projection exposure through the projection optical system, thereby forming a resist pattern corresponding to the mask pattern. The resolving power of exposure apparatus is dependent on the wavelength of exposure light and the numerical aperture of the projection optical system. Therefore, in order to improve the resolving power of exposure apparatus, it is necessary to decrease the wavelength of exposure light and increase the numerical aperture of the projection optical system. In general, it is difficult in terms of optical design to increase the numerical aperture of the projection optical system beyond a certain value, and it is thus necessary to decrease the wavelength of exposure light to a shorter wavelength. Therefore, the technique of EUVL (Extreme UltraViolet Lithography) is drawing attention as a next-generation photolithography method of semiconductor patterning (exposure apparatus). The EUVL exposure apparatus uses the EUV (Extreme UltraViolet) light (radiation) having the wavelength in the range of about 5 to 20 nm. When the EUV light is used as exposure light, there is no available optical material that can transmit the light. For this reason, the EUVL exposure apparatus has to use a reflection type optical integrator, a reflection type mask, and a reflection type (catopric type) projection optical system. In the general exposure apparatus, as well as the EUVL exposure apparatus, it is desirable to form a uniform and rotationally symmetric light intensity distribution (which will also be referred to hereinafter as “pupil intensity distribution”) on an illumination pupil of an illumination optical system. The applicant of the present application proposed the technology of forming an almost uniform and rotationally symmetric pupil intensity distribution on the illumination pupil, by devising a correspondence relation between a plurality of first optical elements in a first fly's eye optical system and a plurality of second optical elements in a second fly's eye optical system in the reflection type optical integrator (See U.S. Pat. Published Application No. 2007/0273859) The optical integrator disclosed in U.S. Pat. Published Application No. 2007/0273859 is configured so that the plurality of first optical elements in the first fly's eye optical system and the plurality of second optical elements in the second fly's eye optical system are set in optical correspondence in a nearly random form. Illumination fields formed on an illumination target surface by a plurality of beams obtained by wavefront division by the plurality of first optical elements are formed as deviating from a desired superimposed illumination region because of influence of various aberrations of the illumination optical system and (image rotation due to) projection or the like, so as to cause a light quantity loss due to so-called superposition errors of the illumination fields. An embodiment according to the present invention has been accomplished in view of the foregoing problem and it is an object of embodiments according to the present invention to provide an optical integrator capable of keeping the light quantity loss small. A first aspect of an embodiment according to the present invention provides an optical integrator used in an illumination optical system for illuminating an illumination target surface on the basis of light from a light source, the optical integrator comprising: a first fly's eye optical system having a plurality of first optical elements arranged in parallel at a position optically conjugate with the illumination target surface in an optical path between the light source and the illumination target surface; and a second fly's eye optical system having a plurality of second optical elements arranged in parallel so as to correspond to the plurality of first optical elements in an optical path between the first fly's eye optical system and the illumination target surface, wherein at least one first optical element out of the plurality of first optical elements, and another first optical element different from the at least one first optical element have respective postures different from each other about an optical axis of the illumination optical system or about an axis parallel to the optical axis. A second aspect of an embodiment according to the present invention provides an optical integrator used in an illumination optical system for illuminating an illumination target surface on the basis of light from a light source, the optical integrator comprising: a first fly's eye optical system having a plurality of first optical elements arranged in parallel at a position optically conjugate with the illumination target surface in an optical path between the light source and the illumination target surface; and a second fly's eye optical system having a plurality of second optical elements arranged in parallel so as to correspond to the plurality of first optical elements in an optical path between the first fly's eye optical system and the illumination target surface, wherein at least one first optical element out of the plurality of first optical elements, and another first optical element different from the at least one first optical element have respective lengths along a predetermined direction different from each other. A third aspect of an embodiment according to the present invention provides an optical integrator used in an illumination optical system for illuminating an illumination target surface on the basis of light from a light source, the optical integrator comprising: a first fly's eye optical system having a plurality of first optical elements arranged in parallel at a position optically conjugate with the illumination target surface in an optical path between the light source and the illumination target surface; and a second fly's eye optical system having a plurality of second optical elements arranged in parallel so as to correspond to the plurality of first optical elements in an optical path between the first fly's eye optical system and the illumination target surface, wherein at least one second optical element out of the plurality of second optical elements is arranged on a standard array surface of the plurality of second optical elements, and wherein another second optical element different from the at least one second optical element out of the plurality of second optical elements is arranged with a required level difference from the standard array surface. A fourth aspect of an embodiment according to the present invention provides an optical integrator used in an illumination optical system for illuminating an illumination target surface on the basis of light from a light source, the optical integrator comprising: a first fly's eye optical system having a plurality of first optical elements arranged in parallel at a position optically conjugate with the illumination target surface in an optical path between the light source and the illumination target surface; and a second fly's eye optical system having a plurality of second optical elements arranged in parallel so as to correspond to the plurality of first optical elements in an optical path between the first fly's eye optical system and the illumination target surface, wherein a size of the first fly's eye optical system and a distance between a center of an array surface of the plurality of first optical elements and a center of a standard array surface of the plurality of second optical elements are determined so that each illumination region formed on the illumination target surface by a beam traveling via each first optical element and corresponding second optical element becomes close to a desired superimposed illumination region. A fifth aspect of an embodiment according to the present invention provides an optical integrator used in an illumination optical system for illuminating an illumination target surface on the basis of light from a light source, the optical integrator comprising: a first fly's eye optical system having a plurality of first optical elements arranged in parallel at a position optically conjugate with the illumination target, surface in an optical path between the light source and the illumination target surface; and a second fly's eye optical system having a plurality of second optical elements arranged in parallel so as to correspond to the plurality of first optical elements in an optical path between the first fly's eye optical system and the illumination target surface, wherein a size D of the first fly's eye optical system and a distance K between a center of an array surface of the plurality of first optical elements and a center of a standard array surface of the plurality of second optical elements satisfy the following condition:0.17<D/K<1.64. A sixth aspect of an embodiment according to the present invention provides an optical integrator used in an illumination optical system for illuminating an illumination target surface on the basis of light from a light source, the optical integrator comprising: a first fly's eye optical system having a plurality of first optical elements arranged in parallel at a position optically conjugate with the illumination target surface in an optical path between the light source and the illumination target surface; and a second fly's eye optical system having a plurality of second optical elements arranged in parallel so as to correspond to the plurality of first optical elements in an optical path between the first fly's eye optical system and the illumination target surface, wherein at least either of postures and lengths of at least one first optical element out of the plurality of first optical elements and another first optical element different from the at least one first optical element, and at least either one of a distance between the at least one first optical element and the corresponding second optical element and a distance between the other first optical element and the corresponding second optical element are determined so as to reduce a superposition error between a first illumination region formed on the illumination target surface by a first beam traveling via the at least one first optical element and corresponding second optical element and a second illumination region formed on the illumination target surface by a second beam traveling via the other first optical element and corresponding second optical element. A seventh aspect of an embodiment according to the present invention provides an illumination optical system for illuminating an illumination target surface on the basis of light from a light source, the illumination optical system comprising the optical integrator of the first aspect, the second aspect, the third aspect, the fourth aspect, the fifth aspect, or the sixth aspect. An eighth aspect of an embodiment according to the present invention provides an exposure apparatus comprising the illumination optical system of the seventh aspect for illuminating a predetermined pattern, the exposure apparatus implementing exposure of the predetermined pattern on a photosensitive substrate. A ninth aspect of an embodiment according to the present invention provides a device manufacturing method comprising: implementing the exposure of the predetermined pattern on the photosensitive substrate, using the exposure apparatus of the eighth aspect; developing the photosensitive substrate with the predetermined pattern transferred, and forming a mask layer in a shape corresponding to the predetermined pattern, on a surface of the photosensitive substrate; and processing the surface of the photosensitive substrate through the mask layer. Embodiments of the present invention will be described on the basis of the accompanying drawings. FIG. 1 is a drawing schematically showing an overall configuration of an exposure apparatus according to an embodiment of the present invention. FIG. 2 is a drawing schematically showing internal configurations of a light source (radiation source), an illumination optical system, and a projection optical system shown in FIG. 1. In FIG. 1, the Z-axis is set along a direction of a normal to a surface (exposure surface) of a wafer W being a photosensitive substrate, the Y-axis along a direction parallel to the plane of FIG. 1 in the surface of the wafer W, and the X-axis along a direction perpendicular to the plane of FIG. 1 in the surface of the wafer W. Referring to FIG. 1, exposure (illumination) light (radiation) is supplied from a light source 1 in the exposure apparatus of the present embodiment. The light source 1 to be used herein can be, for example, a laser plasma light source. The light emitted from the light source 1 travels through a wavelength selecting filter (not shown) to enter an illumination optical system 2. The wavelength selecting filter has a property to selectively transmit only EUV light of a predetermined wavelength (e.g., 13.4 nm), out of the light supplied from the light source 1, and to block transmission of light at the other wavelengths. The EUV light 3 transmitted by the wavelength selecting filter travels via the illumination optical system 2 and a plane reflecting mirror 4 as a path deflecting mirror to illuminate a reflection type mask (reticle) M on which a pattern to be transferred is formed. The mask M is held by a mask stage 5 movable along the Y-direction, in such a state that its pattern surface extends along the XY plane. Movement of the mask stage 5 is measured by a laser interferometer 6 having a well-known configuration. Light from the pattern on the mask M thus illuminated travels via a reflection type projection optical system PL to form an image of the mask pattern on the wafer W being a photosensitive substrate. Namely, for example, a static exposure region (effective exposure region) of an arcuate shape symmetric with respect to the Y-axis is formed on the wafer W, as described below. The wafer W is held by a wafer stage 7 two-dimensionally movable along the X-direction and the Y-direction, in such a state that its exposure surface extends along the XY plane. Movement of the wafer stage 7 is measured by a laser interferometer 8 having a well-known configuration. As so configured, the pattern on the mask M is transferred onto a rectangular shot area on the wafer W by performing scanning exposure (scan photolithography) with movement of the mask stage 5 and the wafer stage 7 along the Y-direction, i.e., with movement of the mask M and the wafer W relative to the projection optical system PL along the Y-direction. At this time, when the projection (transfer) magnification (lateral magnification) of the projection optical system PL is, for example, ¼, synchronous scanning is carried out while a moving speed of the wafer stage 7 is set to be quarter of a moving speed of the mask stage 5. By repeating the scanning exposure with two-dimensional step movement of the wafer stage 7 along the X-direction and the Y-direction, the pattern on the mask M is sequentially transferred onto each of shot areas on the wafer W. Referring to FIG. 2, the laser plasma light source 1 has a laser light source 11, a condensing lens 12, a nozzle 14, an ellipsoidal reflecting mirror 15, and a duct 16. In the light source 1, for example, a high-pressure gas consisting of xenon (Xe) is supplied from the nozzle 14 and the gas jetted out from the nozzle 14 forms a gas target 13. Light (non-EUV light) emitted from the laser light source 11 travels through the condensing lens 12 to be focused on the gas target 13. The gas target 13 acquires energy from the focused laser beam to create plasma, from which EUV light is emitted. The gas target 13 is positioned at the first focus of the ellipsoidal reflecting mirror 15. Therefore, the EUV light emitted from the laser plasma light source 1 is focused at the second focus of the ellipsoidal reflecting mirror 15. On the other hand, the gas after the emission of light is suctioned through the duct 16 to be guided to the outside. The EUV light focused at the second focus of the ellipsoidal reflecting mirror 15 travels via a concave reflecting mirror 17 to become a flux of nearly parallel light to be guided to an optical integrator 18 consisting of a pair of fly's eye optical systems 18a and 18b. Configurations and actions of the first fly's eye optical system 18a and the second fly's eye optical system 18b will be described later. In this manner, a substantial surface illuminant (pupil intensity distribution) having a predetermined shape is formed at a position near an exit surface of the optical integrator 18, i.e., near a reflecting surface of the second fly's eye optical system 18b (or at a position of an illumination pupil). Light from the substantial surface illuminant travels via a condenser optical system 19 composed of a convex reflecting mirror 19a and a concave reflecting mirror 19b, to emerge from the illumination optical system 2. The illumination pupil of the illumination optical system 2 is an entrance pupil of the projection optical system PL, or a position optically conjugate with the entrance pupil of the projection optical system PL. The light emerging from the illumination optical system 2 is deflected by the plane reflecting mirror 4 and then travels through an arcuate aperture (light transmitting portion) of a field stop 21 arranged substantially in parallel and in proximity to the mask M, to form an arcuate illumination region on the mask M. As described above, the light source 1 (11-16), the illumination optical system 2 (17-19), the plane reflecting mirror 4, and the field stop 21 constitute an illumination system that illuminates the pattern on the mask M by Köhler illumination with the light from the pupil intensity distribution formed on the illumination pupil. Light from the pattern on the mask M thus illuminated travels via the projection optical system PL to form an image of the mask pattern in an arcuate static exposure region on the wafer W. The projection optical system PL is composed of a first reflecting imaging optical system for forming an intermediate image of the pattern on the mask M, and a second reflecting imaging optical system for forming an image of the intermediate image of the mask pattern (secondary image of the pattern on the mask M) on the wafer W. The first reflecting imaging optical system is composed of four reflecting mirrors M1-M4 and the second reflecting imaging optical system is composed of two reflecting mirrors M5 and M6. The projection optical system PL is an optical system telecentric on the wafer side (image side). FIG. 3 is a drawing schematically illustrating one scanning exposure in the present embodiment. Referring to FIG. 3, in the exposure apparatus of the present embodiment, a static exposure region ER of an arcuate shape symmetric with respect to the Y-axis is formed on the surface of the wafer W and an illumination region of the same arcuate shape symmetric with respect to the Y-axis is formed on the pattern surface of the mask M so as to correspond to the effective image region and effective field of the arcuate shape of the projection optical system PL. This arcuate exposure region ER moves from a scan start position indicated by solid lines in the drawing, to a scan end position indicated by dashed lines in the drawing, during transferring the pattern of the mask M onto one rectangular shot area SR on the wafer W by one scanning exposure (scan photolithography). FIGS. 4 and 5 are drawings schematically showing the configuration of the optical integrator in the present embodiment. In the optical integrator 18, the first fly's eye optical system 18a is provided with a plurality of first concave reflector elements (first optical elements) 18aa, as shown in FIG. 4. The plurality of first concave reflector elements 18aa are arranged in parallel at a position optically conjugate with the pattern surface of the mask M which is an illumination target surface of the illumination optical system 2. The second fly's eye optical system 18b is provided with a plurality of second concave reflector elements (second optical elements) 18ba, as shown in FIG. 5. The plurality of second concave reflector elements 18ba are arranged in parallel so as to be optically in one-to-one correspondence in a nearly random form to the plurality of first concave reflector elements 18aa. In FIG. 4, the x-direction is set along a direction corresponding to the X-direction in an entrance surface of the first fly's eye optical system 18a and the y-direction along a direction perpendicular to the x-direction in the entrance surface of the first fly's eye optical system 18a. Similarly, in FIG. 5, the x-direction is set along a direction corresponding to the X-direction in an entrance surface of the second fly's eye optical system 18b and the y-direction along a direction perpendicular to the x-direction in the entrance surface of the second fly's eye optical system 18b. Namely, the y-directions in FIGS. 4 and 5 correspond to the scanning direction (Y-direction) of the mask M and the wafer W. It is also noted that FIGS. 4 and 5 are depicted with the numbers of concave reflector elements 18aa, 18ba constituting the pair of fly's eye optical systems 18a, 18b smaller than the actual numbers thereof, for clarity of the drawings. The first fly's eye optical system 18a, as shown in FIG. 4, is constructed by vertically and horizontally arranging the first concave reflector elements 18aa having an arcuate contour. The first concave reflector elements 18aa have the arcuate contour in order to form the arcuate illumination region on the mask M and eventually form the arcuate static exposure region ER on the wafer W, corresponding to the effective image region and effective field of the arcuate shape of the projection optical system PL, as described above. On the other hand, the second fly's eye optical system 18b, as shown in FIG. 5, is constructed by vertically and horizontally arranging the second concave reflector elements 18ba having a rectangular contour, for example, close to a square shape. The second concave reflector elements 18ba have the rectangular contour close to a square because a small illuminant of a nearly circular shape is formed at or near a surface of each second concave reflector element 18ba. A contour of the entrance surface of the first fly's eye optical system 18a is close to a circular shape because a sectional shape of a beam entering the optical integrator 18 (i.e., a beam entering the first fly's eye optical system 18a) is approximately circular, and it enhances illumination efficiency. A contour of the entrance surface of the second fly's eye optical system 18b is close to a circular shape because a contour of the pupil intensity distribution (substantial surface illuminant) formed on the illumination pupil near the exit surface of the optical integrator 18 (i.e., near the exit surface of the second fly's eye optical system 18b) is approximately circular. In the present embodiment, the beam entering the optical integrator 18 is subjected to wavefront division by the plurality of first concave reflector elements 18aa in the first fly's eye optical system 18a. Beams reflected by the respective first concave reflector elements 18aa are incident to the corresponding second concave reflector elements 18ba in the second fly's eye optical system 18b. The beams reflected by the respective second concave reflector elements 18ba travel via the condenser optical system 19 as a waveguide optical system to illuminate an arcuate illumination region on the mask M in a superimposed manner. The disadvantage of the conventional technology and each of techniques of an embodiment will be described below on the basis of an optical integrator having a configuration simpler than the configuration shown in FIGS. 4 and 5. FIG. 6 is a drawing to illustrate a state in which superposition errors of illumination fields are caused by influence of image rotation or rotational strain due to projection of the illumination optical system in a case where a plurality of first concave reflector elements in the first fly's eye optical system are arrayed in accordance with the conventional technology. In the conventional technology, as shown in the upper part of FIG. 6, a group of first concave reflector elements 61a having an arcuate contour are arrayed in the y-direction (direction corresponding to the Y-direction being the scanning direction of the mask M and the wafer W) in a standard posture so that their arcuate sides are adjacent to each other. In proximity on the left side in the drawing to the group of first concave reflector elements 61a, a group of first concave reflector elements 61b having an arcuate contour are arrayed in the y-direction in the standard posture so that their arcuate sides are adjacent to each other. Furthermore, in proximity on the right side in the drawing to the group of first concave reflector elements 61a, a group of first concave reflector elements 61c having an arcuate contour are arrayed in the y-direction in the standard posture so that their arcuate sides are adjacent to each other. FIG. 6 shows the optical integrator in a three-group configuration in which each group includes four first concave reflector elements, as a simplified model. The standard posture herein refers to a posture in which the contour of the first concave reflector element is optically conjugate with a desired arcuate superimposed illumination region to be formed in a superimposed manner on the illumination target surface (the pattern surface of the mask M and, in turn, the exposure surface of the wafer W) by beams obtained by wavefront division by the plurality of first concave reflector elements 61a-61c, i.e., a posture in which the arcuate contour of the first concave reflector elements 61a-61c becomes symmetric with respect to the y-axis. In other words, as long as the rear optical system consisting of the optical integrator (including the plurality of first concave reflector elements 61a-61c) and the condenser optical system is in an aberration-free ideal state, the beams obtained by wavefront division by the plurality of first concave reflector elements 61a-61c arrayed in the standard posture in accordance with the conventional technology in the first fly's eye optical system form the desired arcuate superimposed illumination region while being almost perfectly superimposed on the illumination target surface. In practice, however, superposition errors of illumination fields are caused by various aberrations of the rear optical system, particularly, by influence of image rotation or rotational strain due to projection, as schematically shown in the lower part of FIG. 6. Referring to FIG. 6, each of beams traveling via the first group of first concave reflector elements 61a located in the center along the x-direction (direction corresponding to the X-direction perpendicular to the scanning direction of the mask M and the wafer W) out of the plurality of first concave reflector elements 61a-61c, is less affected than the beams traveling via the first concave reflector elements 61b, 61c, by the image rotation or rotational strain due to projection of the rear optical system, and forms an arcuate illumination field 62a in a substantially identical orientation (or in a substantially identical posture) with the desired arcuate superimposed illumination region 60 on the illumination target surface. In contrast to it, beams traveling via the second group of first concave reflector elements 61b and the third group of first concave reflector elements 61c located off the center along the x-direction, are affected by the image rotation or rotational strain due to projection of the rear optical system and tend to form arcuate illumination fields 62b and 62c in orientations different from that of the desired superimposed illumination region 60. According to a typical example, the arcuate illumination field 62b formed by each of beams traveling via the second group of first concave reflector elements 61b tends to be formed in such an orientation that the desired superimposed illumination region 60 is rotated counterclockwise (or clockwise) in FIG. 6. On the other hand, the arcuate illumination field 62c formed by each of beams traveling via the third group of first concave reflector elements 61c tends to be formed in such an orientation that the desired superimposed illumination region 60 is rotated clockwise (or counterclockwise) in FIG. 6. An angle of inclination of the arcuate illumination field 62b and an angle of inclination of the arcuate illumination field 62c relative to the desired superimposed illumination region 60 tend to be almost equal to each other. It is assumed hereinafter that the arcuate illumination field 62b and the arcuate illumination field 62c are inclined in directions opposite to each other and their inclination angles are equal to each other. In this case, an overlapping illumination field 63 formed in common on the illumination target surface by the plurality of beams obtained by wavefront division by the plurality of first concave reflector elements 61a-61c has a distorted contour and an arcuate illumination region IR corresponding to the arcuate static exposure region ER has to be set in a relatively small area in the overlapping illumination field 63. This means that the field stop arranged in proximity to the mask M blocks light traveling toward the outside of the arcuate illumination region IR, out of the light wavefront-divided by the plurality of first concave reflector elements 61a-61c and traveling toward the mask M, and the blocked light does not contribute to illumination of the pattern on the mask M (and to scanning exposure on the wafer W eventually); that is, there occurs a light quantity loss due to the superposition errors of the illumination fields 62a-62c. Since the reflectance of each of multilayer reflecting films used in the optical systems is relatively small, about 0.7, in the EUVL exposure apparatus, it is important to avoid reduction in throughput of scanning exposure by minimizing the light quantity loss caused by the superposition errors of illumination fields. An example of the first technique of an embodiment is to change the posture of the second group of first concave reflector elements 61b so that the orientation of the arcuate illumination field (illumination region) 62b formed on the illumination target surface by the beams traveling via the second group of first concave reflector elements 61b and the corresponding second concave reflector elements becomes closer to the orientation of the desired superimposed illumination region 60. Similarly, the posture of the third group of first concave reflector elements 61c is also changed so that the orientation of the arcuate illumination field 62c formed on the illumination target surface by the beams traveling via the third group of first concave reflector elements 61c and the corresponding second concave reflector elements becomes closer to the orientation of the desired superimposed illumination region 60. Specifically, as shown in the upper part of FIG. 7, the first concave reflector elements 61a of the first group are arranged in the standard posture, the first concave reflector elements 61b of the second group are arranged in a first tilt posture, and the first concave reflector elements 61c of the third group are arranged in a second tilt posture. The first tilt posture is a posture obtained by rotating the standard posture by a required angle in a required direction, for example, about a required axis (the optical axis or an axis parallel to the optical axis) perpendicular to the array surface (xy plane) of the plurality of first concave reflector elements 61a-61c. On the other hand, the second tilt posture is a posture obtained by rotating the standard posture in a direction opposite to that of the first tilt posture and by the same angle as the angle of the first tilt posture, about the required axis perpendicular to the array surface. Namely, the first tilt posture and the second tilt posture are symmetric with respect to a straight line extending along the y-direction. In this case, as schematically shown in the lower part of FIG. 7, each of beams traveling via the second group of first concave reflector elements 61b set in the first tilt posture and each of beams traveling via the third group of first concave reflector elements 61c set in the second tilt posture form arcuate illumination fields 62a-62c in an almost identical orientation (or in an almost identical posture) with the desired arcuate superimposed illumination region 60 on the illumination target surface as well as each of the beams traveling via the first group of first concave reflector elements 61a set in the standard posture does. As a result, a relatively large arcuate illumination region IR can be secured in the arcuate overlapping illumination field 63 formed in common on the illumination target surface by the plurality of beams obtained by wavefront division by the plurality of first concave reflector elements 61a-61c. Namely, the superposition errors of the illumination fields 62a-62c are kept small and in turn the light quantity loss caused by the superposition errors of the illumination fields 62a-62c is also kept small. In general, the first technique of an embodiment is to set at least one first optical element and another first optical element out of a plurality of first optical elements (corresponding to the first concave reflector elements 61a-61c) in the first fly's eye optical system, in mutually different postures about the optical axis of the illumination optical system or about an axis parallel to the optical axis. In other words, at least two first optical elements are set in mutually different postures about a predetermined axis. For example, the foregoing postures of the at least two first optical elements are determined so that orientations of illumination regions formed on the illumination target surface by beams traveling via the first optical elements and corresponding second optical elements become close to the orientation of the desired superimposed illumination region. For example, in a case where a first direction and a second direction perpendicular thereto are set for an illumination region, an orientation of the illumination region can be defined as a direction in which the length of the illumination region is larger. Where a first direction and a second direction perpendicular thereto are set for the desired superimposed illumination region, an orientation of the desired superimposed illumination region can be defined as a direction in which the length of the desired superimposed illumination region is larger. In other words, the postures of the at least two first optical elements are determined so as to make smaller the superposition error between the illumination regions formed on the illumination target surface by the beams traveling via the first optical elements and corresponding second optical elements. In the case where the first fly's eye optical system is composed of the plurality of arcuate first concave reflector elements 61a-61c, as shown in the example of FIG. 7, a required average posture along the array surface thereof can be determined for each group of the plurality of first concave reflector elements arrayed in the y-direction. In this case, even when the second group of first concave reflector elements 61b and the third group of first concave reflector elements 61c are arranged in the tilt postures, there occurs no clearance between a pair of adjacent optical elements and the optical quantity loss in the first fly's eye optical system can be avoided eventually. It is also possible to individually set a required number of first concave reflector elements, out of the plurality of arcuate first concave reflector elements 61a-61c constituting the first fly's eye optical system, in required tilt postures (without always having to be limited to the postures along the array surface), different from the example of FIG. 7. In this case, however, there occurs a clearance between a pair of adjacent optical elements and this results in causing a light quantity loss in the first fly's eye optical system. When the first technique of an embodiment is applied to the present embodiment, an example of application can be to determine a required average posture along the array surface, for each group consisting of a plurality of first concave reflector elements 18aa arrayed in the y-direction. Specifically, in the six-group configuration shown in FIG. 4, the two groups in the center are set in respective required tilt postures obtained by rotating the standard posture in opposite directions by an identical angle. The two groups adjacent to the two center groups along the x-direction are set in respective required tilt postures obtained by rotating the standard posture in opposite directions by an identical angle larger than the tilt angle of the two center groups. Furthermore, the two groups located at the outermost positions along the x-direction are set in respective required tilt postures obtained by rotating the standard posture in opposite directions by an identical angle larger than the tilt angle of the adjacent groups. This is because the influence of image rotation or rotational strain due to projection becomes greater with distance from the center in the x-direction. The example schematically shown in FIG. 4 is the configuration in which the first fly's eye optical system is composed of the even number of groups, but in configurations where it is composed of an odd number of groups, a group located in the center in the x-direction can be set in the standard posture. When the first technique of an embodiment is applied to the optical integrator 18 of the present embodiment, it is feasible to make small the superposition errors of the illumination fields formed on the pattern surface of the mask M by the plurality of beams obtained by wavefront division by the plurality of first concave reflector elements 18aa and, in turn, to make small the light quantity loss caused by the superposition errors of the illumination fields. As a consequence, the illumination optical system 2 of the present embodiment is able to illuminate the mask M under a required illumination condition with high luminous efficiency while keeping small the light quantity loss caused by the superposition errors of the illumination fields. Furthermore, the exposure apparatus of the present embodiment is able to perform excellent exposure under a good illumination condition, using the illumination optical system 2 which illuminates the pattern of the mask M under the required illumination condition with high luminous efficiency while suppressing the light quantity loss. FIG. 8 is a drawing to illustrate a state in which superposition errors of illumination fields are caused by magnification differences among the optical elements in the optical integrator. In the conventional technology disclosed in Patent Document 1, the plurality of first concave reflector elements in the first fly's eye optical system and the plurality of second concave reflector elements in the second fly's eye optical system are set in optical correspondence in a nearly random form. In an embodiment, this setting of optical correspondence in the nearly random form between the plurality of first concave reflector elements in the first fly's eye optical system and the plurality of second concave reflector elements in the second fly's eye optical system will be called a random method. In the configuration of the random method, as schematically shown in the upper part of FIG. 8, for example, one first concave reflector element 61ba among the second group of first concave reflector elements 61b in the first fly's eye optical system corresponds to a second concave reflector element 81 as in the second fly's eye optical system. One first concave reflector element 61 as among the first group of first concave reflector elements 61a corresponds to a second concave reflector element 81ba in the second fly's eye optical system. Furthermore, one first concave reflector element 61ca among the third group of first concave reflector elements 61c corresponds to a second concave reflector element 81ca in the second fly's eye optical system. In general, in the configuration of the random method, the plurality of first concave reflector elements (first optical elements) in the first fly's eye optical system and the plurality of second concave reflector elements (second optical elements) in the second fly's eye optical system are in one-to-one correspondence according to such a relation that at least a pair of projected line segments intersect when a plurality of line segments connecting corresponding paired optical elements are projected onto a certain plane. In this case, a magnification of an illumination field formed on the illumination target surface by a beam traveling via one first concave reflector element in the first fly's eye optical system and a corresponding second concave reflector element (length in a predetermined direction of the illumination field/length in a predetermined direction of a reflecting surface of the first concave reflector element), β, is represented by Eq (a) below, using a focal length fe of an element optical system consisting of the first concave reflector element and the corresponding second concave reflector element, and a focal length fc of the condenser optical system.β=fc/fe (a) Furthermore, the magnification β of the illumination field is also represented by Eq (b) below, using an optical path length L1 between the corresponding pair of optical elements, and an optical path length L2 from the second concave reflector element to the condenser optical system.β=L2/L1 (b) In a case where the second fly's eye optical system is configured to also function as the condenser optical system, by arraying the plurality of second concave reflector elements (second optical elements) along a predetermined curved surface, the optical path length L2 in Eq (b) above is replaced by an optical path length from the second concave reflector element to the illumination target surface. In the conventional technology wherein the first fly's eye optical system is composed of the plurality of arcuate first concave reflector elements having the same size (standard size) as shown in the upper part of FIG. 6, even when there is no influence of aberration and others at all, magnifications (sizes) of the illumination fields 62a-62c formed on the illumination target surface by the beams traveling via the plurality of first concave reflector elements 61a-61c are different among the optical elements and there occur so-called superposition errors of the illumination fields due to the magnification differences among the optical elements. The superposition errors of this kind are prominent, particularly, in the configuration of the random method, but they also occur in a regular configuration wherein the optical elements are set in such one-to-one correspondence as to avoid intersection of the aforementioned pair of projected line segments. For easier understanding of the description, it is assumed hereinafter that, as schematically shown in the lower part of FIG. 8, an arcuate illumination field 62ba formed by a beam traveling via the first concave reflector element 61ba and second concave reflector element 81aa is formed in a size larger than the desired arcuate superimposed illumination region 60. Furthermore, an arcuate illumination field 62ca formed by a beam traveling via the first concave reflector element 61ca and second concave reflector element 81ca is assumed to be formed in a size larger than the arcuate illumination field 62ba. It is further assumed that arcuate illumination fields formed by beams traveling via the other first concave reflector elements including the first concave reflector element 61aa are formed in a size approximately identical with the shape of the desired arcuate superimposed illumination region 60. In this simple case, the overlapping illumination field 63 formed in common on the illumination target surface by the plurality of beams obtained by wavefront division by the plurality of first concave reflector elements 61a-61c is approximately coincident with the desired superimposed illumination region 60 and approximately coincident with the arcuate illumination region IR eventually. Of the light subjected to the wavefront division by the first concave reflector elements 61ba and 61ca and traveling toward the mask M, the light traveling toward the outside of the arcuate illumination region IR does not contribute to illumination of the pattern on the mask M (and eventually to the scanning exposure on the wafer W) and a light quantity loss is caused by the superposition errors of the illumination fields due to the magnification differences among the optical elements. In practice, it is generally the case that the illumination fields formed via some first concave reflector elements become smaller than the desired superimposed illumination region 60, the illumination fields formed via some first concave reflector elements become approximately identical in size with the desired superimposed illumination region 60, and the illumination fields formed via some first concave reflector elements become larger than the desired superimposed illumination region 60. Therefore, the light quantity loss caused by the superposition errors of illumination fields due to the magnification differences among the optical elements is unignorable, particularly, in the configuration of the random method. The second technique of an embodiment is to set at least one first optical element and another first optical element out of the plurality of first optical elements (corresponding to the first concave reflector elements 61a-61c) in the first fly's eye optical system so that their lengths along a predetermined direction are different from each other. In other words, at least two first optical elements are set so that their lengths in the predetermined direction are different from each other. The predetermined direction can be selected, for example, to be the y-direction in the upper part of FIG. 6, i.e., the direction in which the plurality of first concave reflector elements 61a-61c are arrayed so that their arcuate sides are adjacent to each other. The y-direction in the upper part of FIG. 6 corresponds to the Y-direction being the scanning direction of the mask M and the wafer W, as described above. The lengths in the predetermined direction of the foregoing at least two first optical elements are determined so that lengths in the predetermined direction of illumination fields formed on the illumination target surface by beams traveling via the first optical elements and corresponding second optical element become close to the length in the predetermined direction of the desired superimposed illumination region. In other words, the lengths along the predetermined direction of the at least one first optical element and other first optical element are determined so as to make small the superposition errors of the illumination regions formed on the illumination target surface by the beams traveling via the first optical elements and the corresponding second optical elements. When the second technique of an embodiment is applied to the simple example shown in FIG. 8, the length along the y-direction of one first concave reflector element 61ba among the second group of first concave reflector elements 61b and the length along the y-direction of one first concave reflector element 61ca among the third group of first concave reflector elements 61c in the first fly's eye optical system are adjusted as shown in the upper part of FIG. 9. In the upper part of FIG. 9, the y-directional length of the first concave reflector element 61ba is adjusted so as to be smaller than the standard length in the y-direction of the first concave reflector elements and the y-directional length of the first concave reflector element 61ca is adjusted so as to be smaller than the length in the y-direction of the first concave reflector element 61ba. In this manner, as schematically shown in the lower part of FIG. 9, lengths in the Y-direction (vertical direction in the lower part of FIG. 9; scanning direction) of the arcuate illumination fields 62ba and 62ca formed by beams traveling via the first concave reflector elements 61ba and 61ca become closer to the length in the Y-direction of the desired superimposed illumination region 60, so as to keep small the superposition errors of the illumination fields due to the magnification differences among the optical elements. In the case where only the y-directional lengths of the first concave reflector elements are adjusted, two-dimensional array adjustment of the plurality of first concave reflector elements is simple and easy. In the example shown in FIG. 9, because the y-directional lengths of the first concave reflector elements 61ba and 61ca are set to be smaller than the standard length, small arcuate clearances are made along the arcuate sides of the optical elements adjusted in length when the overall contour of the first fly's eye optical system is maintained. In this case, if necessary, the small arcuate clearances may be filled with additional arcuate first concave reflector elements. On the other hand, in cases where the x-directional lengths of the first concave reflector elements are adjusted or where the x-directional lengths and the y-directional lengths of the first concave reflector elements both are adjusted, the two-dimensional array adjustment of the plurality of first concave reflector elements becomes complicated. When the second technique of an embodiment is applied to the optical integrator 18 of the present embodiment, we can enjoy the same effect as in the case of application of the first technique. The third technique of an embodiment is to arrange at least one second optical element out of the plurality of second optical elements in the second fly's eye optical system (second concave reflector elements 18ba in FIG. 5; the second concave reflector elements 81aa, 81ba, 81ca, etc. in the upper part of FIG. 8) on a standard array surface and arrange another second optical element on a surface with a required level difference from the standard array surface. The standard array surface herein refers to a plane on which the plurality of second optical elements are to be arrayed, for example, according to the technique of the conventional technology. The required level difference to be given to the specific second optical element is determined so that the size of the illumination field formed on the illumination target surface by a beam traveling via the first optical element corresponding to the second optical element, and via the second optical element becomes close to the size of the desired superimposed illumination region. In other words, the level difference between the aforementioned at least one second optical element and other second optical element, or a distance between the at least one first optical element and corresponding second optical element and a distance between the other first optical element and corresponding second optical element are determined so as to make smaller the superposition errors of the illumination regions formed on the illumination target surface by the beams traveling via the first optical elements and the corresponding second optical elements. When the third technique of an embodiment is applied to the simple example shown in FIG. 8, a reflecting surface of the second concave reflector element 81ba is arranged on the standard array surface and a reflecting surface of the second concave reflector element 81aa and a reflecting surface of the second concave reflector element 81ca are arranged with their respective required level differences from the standard array surface, as shown in the upper part of FIG. 10. When the reflecting surface of the second concave reflector element 81aa is arranged with the required level difference from the standard array surface, an optical path length L1b between the first concave reflector element 61ba and the second concave reflector element 81aa and an optical path length L2b from the second concave reflector element 81aa to the illumination target surface are adjusted. Similarly, when the reflecting surface of the second concave reflector element 81ca is arranged with the required level difference from the standard array surface, an optical path length L1c between the first concave reflector element 61ca and the second concave reflector element 81ca and an optical path length L2c from the second concave reflector element 81ca to the illumination target surface are adjusted. In contrast to it, the reflecting surface of the second concave reflector element 81ba is arranged on the standard array surface without any level difference, and therefore an optical path length L1a between the first concave reflector element 61aa and the second concave reflector element 81ba and an optical path length L2a from the second concave reflector element 81ba to the illumination target surface are not adjusted. As a result, as seen with reference to the aforementioned Eq (b), the magnification of the arcuate illumination field 62ba formed by the beam traveling via the first concave reflector element 61ba and the second concave reflector element 81aa and the magnification of the arcuate illumination field 62ca formed by the beam traveling via the first concave reflector element 61ca and the second concave reflector element 81 ca vary according to the level differences thus given. On the other hand, the magnification of the arcuate illumination field 62aa formed by the beam traveling via the first concave reflector element 61aa and the second concave reflector element 81ba (i.e., the illumination field originally having the small superposition error relative to the desired arcuate superimposed illumination region 60) is invariant because the reflecting surface of the second concave reflector element 81ba is given no level difference. In this manner, as schematically shown in the lower part of FIG. 10, the sizes of the other arcuate illumination fields 62ba and 62ca as well as the arcuate illumination field 62aa become close to the size of the desired superimposed illumination region 60 (and the illumination region IR eventually), so as to keep small the superposition errors of the illumination fields due to the magnification differences among the optical elements. Namely, when the third technique of an embodiment is applied to the optical integrator 18 of the present embodiment, the same effect is also achieved as in the case of application of the first technique and in the case of application of the second technique. Furthermore, by applying one or more techniques selected from the first technique, the second technique, and the third technique of an embodiment to the optical integrator 18 of the present embodiment, it is feasible to keep small the superposition errors of the illumination fields formed on the illumination target surface by the plurality of beams obtained by wavefront division. The fourth technique of an embodiment will be described below on the basis of an exposure apparatus of an inverse pupil type as shown in FIG. 11, i.e., on the basis of the exposure apparatus provided with the projection optical system PL configured as an inverse pupil optical system. The exposure apparatus of the inverse pupil type shown in FIG. 11 has a configuration similar to the exposure apparatus of the normal pupil type shown in FIGS. 1 and 2, but is different from the exposure apparatus of the normal pupil type in that the illumination optical system 2 is composed of only the optical integrator 18. In the exposure apparatus of the normal pupil type the entrance pupil of the projection optical system is located on the projection optical system side with respect to the object plane, whereas in the exposure apparatus of the inverse pupil type the entrance pupil of the projection optical system is located on the opposite side to the projection optical system with respect to the object plane. In FIG. 11, elements with the same functions as the constituent elements shown in FIGS. 1 and 2 are denoted by the same reference symbols as those in FIGS. 1 and 2. The configuration and action of the exposure apparatus of the inverse pupil type shown in FIG. 11 will be described below with focus on differences from the exposure apparatus of the normal pupil type. The teachings of the U.S. Pat. No. 6,781,671 is incorporated by reference. In the exposure apparatus of the inverse pupil type shown in FIG. 11, the light from the light source 1 is once focused and thereafter incident to the optical integrator 18 in the illumination optical system 2. Namely, the light from the light source 1 is incident to the first fly's eye optical system 18a of the optical integrator 18, without traveling via any optical member having a power (e.g., an optical member like the concave reflecting mirror 17 shown in FIG. 2). The power of the optical member is the inverse of the focal length of the optical member. It is a matter of course that an optical member having a power can be interposed. The beams obtained by wavefront division by the plurality of arcuate first concave reflector elements 18aa (not shown in FIG. 11) in the first fly's eye optical system 18a are reflected by the corresponding rectangular second concave reflector elements 18ba (not shown in FIG. 11) in the second fly's eye optical system 18b and thereafter emitted from the illumination optical system 2. The light emerging from the illumination optical system 2 travels via an oblique incidence mirror (plane reflecting mirror) 4 to form an arcuate illumination region on the mask M. Namely, the light traveling via the second fly's eye optical system 18b of the optical integrator 18 is guided to the pattern surface of the mask M as an illumination target surface, without traveling via any optical member having a power (e.g., an optical member like the condenser optical system 19 shown in FIG. 2). In the exposure apparatus of the inverse pupil type, a substantial surface illuminant (pupil intensity distribution) having a predetermined shape is also formed at a position (position of the illumination pupil) near the exit surface of the optical integrator 18, i.e., near the reflecting surface of the second fly's eye optical system 18b. This substantial surface illuminant is formed at the position of the exit pupil of the illumination optical system 2 consisting of the pair of fly's eye optical systems 18a and 18b. The position of the exit pupil of the illumination optical system 2 (i.e., the position near the reflecting surface of the second fly's eye optical system 18b) is coincident with the position of the entrance pupil of the projection optical system PL. As described above, the projection optical system PL is the inverse pupil optical system having the entrance pupil at the position apart by a predetermined distance on the opposite side to the projection optical system PL with respect to the object plane where the mask M is arranged. In the exposure apparatus of the inverse pupil type, the number of reflections of the EUV light in the illumination optical system 2 is smaller than that in the exposure apparatus of the normal pupil type, and therefore the luminous efficiency is improved when compared with the exposure apparatus of the normal pupil type. Prior to specific description of the fourth technique of an embodiment, consideration will be given to influence of a distance K between a center of the array surface of the plurality of first concave reflector elements (generally, first optical elements) 18aa in the first fly's eye optical system 18a and a center of the standard array surface of the plurality of second concave reflector elements (generally, second optical elements) 18ba in the second fly's eye optical system 18b, with reference to FIG. 12. As described above, the standard array surface of the plurality of second concave reflector elements 18ba is a plane where the plurality of second concave reflector elements 18ba are arrayed according to the technique of the conventional technology. For easier understanding of the description, FIG. 12 shows only the first concave reflector element 61ac arranged in the center of the plurality of first concave reflector elements 18aa and the second concave reflector element 81ac arranged in the center of the plurality of second concave reflector elements 18ba. Furthermore, for easier understanding of the description, it is assumed in FIG. 12 that the second concave reflector element 81 ac is arranged on the standard array surface, the array surface of the plurality of first concave reflector elements 18aa is approximately parallel to the standard array surface of the plurality of second concave reflector elements 18ba, and the light reflected by the first concave reflector element 61ac is incident to the second concave reflector element 81ac. In this case, the center-center distance K between the two array surfaces is nothing but a distance between the center of the reflecting surface of the first concave reflector element 61ac and the center of the reflecting surface of the second concave reflector element 81ac. When an offset amount along the array surfaces between the first concave reflector element 61ac and the second concave reflector element 81ac (and, therefore, an offset amount between the first fly's eye optical system 18a and the second fly's eye optical system 18b), C, is constant, the angle of incidence of the light to the reflecting surface of the first concave reflector element 61ac and the angle of incidence of the light to the reflecting surface of the second concave reflector element 81ac are smaller in a configuration where the distance K is set to be relatively large as shown in FIG. 12 (a) than in a configuration where the distance K is set to be relatively small as shown in FIG. 12 (b). As also readily seen by analogy from FIG. 12, the angles of incidence of light to the reflecting surfaces of the other first concave reflector elements 18aa and the angles of incidence of light to the reflecting surfaces of the other second concave reflector elements 18ba are also smaller in the configuration where the distance K is set to be large. When the distance K is set large as described above, the angles of incidence of the light to the reflecting surfaces of the concave reflector elements 18aa, 18ba can be kept small, and it is thus feasible to secure large reflectance of multilayer reflecting films forming the reflecting surfaces of the concave reflector elements 18aa, 18ba. This is because film-forming steps of the multilayer reflecting films are carried out for each predetermined angular range. When the distance K is set large, the angles of incidence of light to the reflecting surfaces of the concave reflector elements 18aa, 18ba are kept small, whereby occurrence of aberration in the optical integrator 18 is kept small, so as to make small the superposition errors of illumination fields due to aberration. When the distance K is set large as described above, various effects are achieved including improvement in reflectance, reduction in film-forming time, and reduction of superposition errors of illumination fields. However, when only the distance K were simply set large in practical design, various adverse effects could be caused. It is also possible to keep small the angles of incidence of light to the reflecting surfaces of the concave reflector elements 18aa, 18ba by setting the offset amount C small, but there is naturally a limit to setting the offset amount C small, in order to avoid interference between the incident beam to the first fly's eye optical system 18a and the second fly's eye optical system 18b and interference between the emerging beam from the second fly's eye optical system 18b and the first fly's eye optical system 18a. FIG. 13 is a drawing for explaining the fourth technique of an embodiment, which is a drawing corresponding to FIG. 8. FIG. 13 shows a first concave reflector element 61 ac arranged in the center of the plurality of first concave reflector elements 18aa, a pair of first concave reflector elements 61bc and 61cc arranged on both sides thereof, a second concave reflector element 81ac arranged in the center of the plurality of the second concave reflector elements 18ba, and a pair of second concave reflector elements 81bc and 81cc arranged on both sides thereof. The first concave reflector element 61bc corresponds to the second concave reflector element 81ac, the first concave reflector element 61ac to the second concave reflector element 81bc, and the first concave reflector element 61cc to the second concave reflector element 81cc. In the case of the exposure apparatus of the inverse pupil type where there is no condenser optical system interposed between the optical integrator 18 and the mask M, as described in association with Eq (b), the magnification of the illumination field formed on the illumination target surface (pattern surface of the mask M) by a beam traveling via one first concave reflector element in the first fly's eye optical system and a corresponding second concave reflector element (length in the predetermined direction of the illumination field/length in the predetermined direction of the reflecting surface of the first concave reflector element), β, is represented by Eq (c) below, using an optical path length L1 between the corresponding pair of optical elements and an optical path length L3 from the second concave reflector element to the illumination target surface.β=L3/L1 (c) Specifically, with reference to FIG. 13, an optical path length between the first concave reflector element 61bc and the second concave reflector element 81ac is a1, an optical path length between the first concave reflector element 61 ac and the second concave reflector element 81bc is a2, and an optical path length between the first concave reflector element 61cc and the second concave reflector element 81cc is a3. Furthermore, an optical path length from the second concave reflector element 81ac to the mask M is b1, an optical path length from the second concave reflector element 81bc to the mask M is b2, and an optical path length from the second concave reflector element 81cc to the mask M is b3. The optical path lengths (distances) a1-a3 correspond to the optical path length L1 between the optical elements and the optical path lengths (distances) b1-b3 correspond to the optical path length L3 from the second concave reflector element to the illumination target surface. Therefore, the magnification β1 of the illumination field (illumination region) formed by the beam traveling via the first concave reflector element 61bc and corresponding second concave reflector element 81ac, the magnification β2 of the illumination field formed by the beam traveling via the first concave reflector element 61ac and corresponding second concave reflector element 81bc, and the magnification β3 of the illumination field formed by the beam traveling via the first concave reflector element 61cc and corresponding second concave reflector element 81cc are represented by Eqs (d1), (d2), and (d3), respectively, below.β1=b1/a1 (d1)β2=b2/a2 (d2)β3=b3/a3 (d3) It is seen with reference to Eqs (d1) to (d3) that, in order to keep small the so-called superposition errors of the illumination fields due to the magnification differences among the optical elements, it is important to keep small variation in bi/ai (i=1-3 in FIG. 13; i=1−n in general (where n is a total number of first concave reflector elements)). While consideration is given to the fact that the optical path length bi is longer than the optical path length ai and, therefore, that the variation in the optical path length bi is smaller than the variation in the optical path length ai, it is seen that, in order to keep small the variation in bi/ai (dispersion of magnification βi), it is effective to set the center-center distance K between two array surfaces large and thereby to keep small the variation in the optical path length ai. The effectiveness of setting the distance K large is as described with reference to FIG. 12, but only the distance K cannot be simply set large in practical design, as described above. Now, let us consider an appropriate range of the distance K. As described previously, the entrance surface of the first fly's eye optical system 18a has the contour close to the circular shape in order to enhance the illumination efficiency because the sectional shape of the beam incident to the optical integrator 18 (i.e., the beam incident to the first fly's eye optical system 18a) is approximately circular. Therefore, when the length along the x-direction of the first fly's eye optical system 18a shown in FIG. 4 is designated by D, the length D corresponds to the diameter of a circle inscribed in the entrance surface of the first fly's eye optical system 18a and the length D can be called the size of the first fly's eye optical system 18a. A length along the x-direction of each first concave reflector element 18aa forming the first fly's eye optical system 18a is represented by D/s, using the number s of divisions along the x-direction of the first fly's eye optical system 18a (s=6 in FIG. 4). In the simplified model shown in FIG. 13, the number s of divisions is 3, the overall size in the horizontal direction in the drawing of the three first concave reflector elements 61bc, 61ac, and 61cc is designated by D, and each element size by D/s. Furthermore, d represents a required length along the X-direction (longitudinal direction) of the arcuate illumination region to be formed on the mask M, and P a distance (optical path length) from the center of the entrance surface of the second fly's eye optical system 18b to the center of the arcuate illumination region. In the simplified model shown in FIG. 13, the distance P is nothing but the optical path length bi from the second concave reflector element 81ac to the mask M. In this case, a1-a3 in Eqs (d1)-(d3) (ai in general) are approximated by the distance K, b1-b3 (bi in general) by the distance P, and β1-β3 (βi in general) by d/(D/s). As a consequence, an approximate expression represented by Formula (e1) below holds. The approximate expression (e1) can be modified to approximate expression (e2) below.d/(D/s)≈P/K (e1)D/K≈sd/P (e2) If D/K in approximate expression (e2) is too smaller than sd/P, the actual length along the X-direction of the arcuate illumination region formed on the mask M becomes too smaller than the required length d and, in turn, the actual length along the X-direction of the arcuate static exposure region ER formed on the wafer W becomes too smaller than the required length, which will make implementation of required exposure itself impossible. On the other hand, when D/K is too larger than sd/P, the actual length along the X-direction of the illumination region becomes too larger than the required length d and, in turn, the actual length along the X-direction of the static exposure region ER becomes too larger than the required length, which will cause reduction of throughput due to an excess light quantity loss. In practical typical design examples, the number s of divisions along the x-direction of the first fly's eye optical system 18a is, for example, approximately 5 to 7. The required length d along the X-direction of the arcuate illumination region is, for example, approximately 104 mm-130 mm in a case where the projection magnification of the projection optical system PL is ¼; it is, for example, approximately 156 mm-182 mm in a case where the projection magnification is ⅙; it is, for example, approximately 208 mm-234 mm in a case where the projection magnification is ⅛. The distance P from the center of the entrance surface of the second fly's eye optical system 18b to the center of the arcuate illumination region is, for example, approximately 1300 mm-3000 mm in the case where the projection magnification is ¼; it is, for example, approximately 1000 mm-3000 mm in the case where the projection magnification is ⅙ or ⅛. In cases where the projection magnification of the projection optical system PL, the number s of divisions, the length d, and the distance P are assumed to vary in these numerical ranges, values of D/K satisfying the relation of D/K=sd/P are given as shown in Table (1) below. TABLE 1s = 5s = 6s = 7with the projection magnification of ¼ and d = 104 mm,P = 13000.400.480.56P = 17000.310.370.43P = 22000.240.280.33P = 30000.170.210.24with the projection magnification of ¼ and d = 130 mm,P = 13000.500.600.70P = 17000.380.460.54P = 22000.300.350.41P = 30000.220.260.30with the projection magnification of ⅙ and d = 156 mm,P = 10000.780.941.09P = 13000.600.720.84P = 17000.460.550.64P = 22000.350.430.50P = 30000.260.310.36with the projection magnification of ⅙ and d = 182 mm,P = 10000.911.091.27P = 13000.700.840.98P = 17000.540.640.75P = 22000.410.500.58P = 30000.300.360.42with the projection magnification of ⅛ and d = 208 mm,P = 10001.041.251.46P = 13000.800.961.12P = 17000.610.730.86P = 22000.470.570.66P = 30000.350.420.49with the projection magnification of ⅛ and d = 234 mm,P = 10001.171.401.64P = 13000.901.081.26P = 17000.690.830.96P = 22000.530.640.74P = 30000.390.470.55 As shown in Table (1), when the projection magnification of the projection optical system PL, the number s of divisions, the length d, and the distance P in the practical typical design examples are assumed to vary within the aforementioned numerical ranges, it is seen that the values of D/K satisfying the relation of D/K=sd/P fall within the range of 0.17 to 1.64. This means that when the size D of the first fly's eye optical system 18a and the distance K between the center of the array surface of the plurality of first concave reflector elements (first optical elements) 18aa and the center of the standard array surface of the plurality of second concave reflector elements (second optical elements) 18ba satisfy Condition (1) below, the magnification differences among the optical elements can be kept small and, in turn, each illumination region formed by the beam traveling via each first concave reflector element 18aa and corresponding second concave reflector element 18ba can be made close to the desired superimposed illumination region. However, for example, when values of the length d vary over a wider range, the range of values of D/K satisfying the relation of D/K=sd/P will also vary.0.17<D/K<1.64 (1) For keeping the magnification differences among the optical elements smaller and, therefore, for making each illumination region closer to the desired superimposed illumination region, Condition (1A) below instead of Condition (1) may be satisfied and Condition (1B) below instead of Condition (1A) may be satisfied. Incidentally, when the projection magnification of the projection optical system PL is ¼, the range of Condition (1A) corresponds to the range of values of D/K satisfying the relation of D/K=sd/P. With the projection magnification of the projection optical system PL being ¼, P being approximately 1700 mm-2200 mm, and s being 5 or 6, the range of Condition (1B) corresponds to the range of values of D/K satisfying the relation of D/K=sd/P.0.17<D/K<0.70 (1A)0.24<D/K<0.46 (1B) The fourth technique of an embodiment is to keep small the superposition errors of illumination fields due to the magnification differences among the optical elements and to make each illumination region close to the desired superimposed illumination region eventually when the size D of the first fly's eye optical system 18a and the center-center distance K between the two array surfaces satisfy Condition (1), (1A), or (1B). In other words, the fourth technique of an embodiment is to determine the size D of the first fly's eye optical system 18a and the center-center distance K between the two array surfaces so that each illumination region becomes close to the desired superimposed illumination region, thereby keeping small the superposition errors of illumination fields due to the magnification differences among the optical elements. When the distance K is set relatively large within the range satisfying Condition (1), (1A), or (1B), the additional effects are achieved including the improvement in reflectance, reduction in film-forming time, and reduction in superposition errors of illumination fields, as described with reference to FIG. 12. As described above, when the fourth technique of an embodiment is applied to the optical integrator 18 of the present embodiment, the same effect is also achieved as in the case of application of the first technique, in the case of application of the second technique, and in the case of application of the third technique. Furthermore, when one or more techniques selected from the first technique, second technique, third technique, and fourth technique of an embodiment are applied to the optical integrator 18 of the present embodiment, it is feasible to keep small the superposition errors of the illumination fields formed on the illumination target surface by the plurality of beams obtained by wavefront division. Now, based on the exposure apparatus of the inverse pupil type shown in FIG. 11, let us further consider the suppression of the superposition errors of the illumination fields with reference to the simplified model shown in FIG. 13 and others. Let us first assume that the sizes and shapes of the respective first concave reflector elements 61ac, 61bc, 61cc in FIG. 13 are equal to each other as shown in FIG. 14, the length thereof along the x-direction is Ex, and the length thereof along the y-direction is Ey. In this case, the lengths along the X-direction of the respective illumination regions 65a, 65b, and 65c formed corresponding to the respective first concave reflector elements 61ac, 61bc, and 61cc are Iax, Ibx, and Icx and the lengths along the Y-direction thereof are Iay, thy, and Icy. The lengths of the illumination regions 65a, 65b, and 65c are represented by Eqs (f1) to (f6) below, using the magnifications β1 (=b1/a1), β2 (=b2/a2), and β3 (=b3/a3) between the optical elements, and influence factors A, B such as various aberrations of the illumination optical system and the image rotation due to projection.Iax=Ex×β2+A (f1)Ibx=Ex×β1+A (f2)Icx=Ex×β3+A (f3)Iay=Ey×β2+B (f4)Iby=Ey×β1+B (f5)Icy=Ey×β2+B (f6) For keeping the superposition errors of illumination fields small, it is important to prevent the lengths of the respective illumination regions from varying among the first concave reflector elements. Then, the second technique of an embodiment proposed the adjustment of the lengths Ex and Ey for each first concave reflector element, in order to prevent the lengths of the respective illumination regions from varying among the first concave reflector elements. In this case, as described with reference to FIG. 9, it is a practical method to adjust the y-directional lengths of the first concave reflector elements. However, as shown in FIG. 15, it is also possible to adjust the x-directional lengths as well as the y-directional lengths for the required number of first concave reflector elements and to locate various sensors 91 or the like by making use of spaces made by the adjustment of the x-directional lengths. FIG. 15 shows adjustment of the y-directional length and the x-directional length of first concave reflector element 61ca′ in a configuration corresponding to FIG. 9. For keeping the superposition errors of illumination fields small, it is important to keep small the variation in magnification βi among the optical elements. Then, the third technique of an embodiment proposed the provision of the required level differences among the second concave reflector elements, in order to prevent the variation in magnification β among the optical elements. The fourth technique of an embodiment proposed Condition (1), (1A), or (1B) to be satisfied, in order to prevent the variation in magnification β among the optical elements. In practice, these techniques may be optionally carried out in combination, in order to suppress the superposition errors of the illumination fields. Furthermore, with reference to Eqs (f4) to (f6), for keeping small the variation in the Y-directional lengths of the respective illumination regions, it is important to keep small the variation in magnification βi among the optical elements and to keep small the variation in the y-directional lengths of the respective first concave reflector elements. Namely, in the second technique of an embodiment, variance t2 of the y-directional lengths of the plurality of first concave reflector elements 18aa, which is defined by Σ(Ta−Ti)2/n, where Ti (i=1−n) is the y-directional length of each element out of the plurality of (n) first concave reflector elements (first optical elements) 18aa, Ta an average of the y-directional lengths of the n first concave reflector elements 18aa, and Σ a summation from i=1 to i=n, may satisfy Condition (2) below.0.05<t2<0.35 (2) When the variance is larger than the upper limit of Condition (2), the variation of the y-directional lengths of the first concave reflector elements 18aa becomes too large, so as to result in increase in the superposition errors of the illumination fields and increase in the light quantity loss eventually. On the other hand, when the variance is smaller than the lower limit of Condition (2), the variation of the y-directional lengths of the first concave reflector elements 18aa becomes too small, so as to result in decrease in the offset amount between the first fly's eye optical system 18a and the second fly's eye optical system 18b and increase in the possibility of mechanical interference between the first fly's eye optical system 18a and the mask M. For easier understanding, the description about the fourth technique of an embodiment and the description about Condition (2) were given based on the exposure apparatus of the inverse pupil type. It is, however, noted that the fourth technique of an embodiment and Condition (2) can also be applied similarly to the optical integrator used in the exposure apparatus of the normal pupil type, without having to be limited to the exposure apparatus of the inverse pupil type. In the above description, the first concave reflector elements 18aa in the first fly's eye optical system 18a have the arcuate contour and the second concave reflector elements 18ba in the second fly's eye optical system 18b have the rectangular contour. However, without having to be limited to this example, various forms can be contemplated as to the contours of the reflectors and the positive and negative arrangement of the powers of the reflectors. In the above description an embodiment was applied to the reflection type optical integrator, but, without having to be limited to it, an embodiment can also be applied, for example, to refraction type and diffraction type optical integrators. When an embodiment is applied to a refraction type optical integrator, the first fly's eye optical system and the second fly's eye optical system are constructed by arranging optical elements, e.g., microscopic lens elements in parallel. In this case, the first fly's eye optical system and the second fly's eye optical system may be formed in an integral form or in separate forms. The refraction type optical integrator with the first fly's eye optical system and the second fly's eye optical system formed in separate forms is disclosed, for example, in Japanese Patent Application Laid-open No. 08-262367 and U.S. Pat. No. 5,760,963 corresponding thereto or in Japanese Patent Application Laid-open No. 8-31736 and U.S. Pat. No. 5,594,526 corresponding thereto. The teachings of the U.S. Pat. Nos. 5,760,963 and 5,594,526 are incorporated by reference. In the aforementioned embodiment, the mask can be replaced with a variable pattern forming device for forming a predetermined pattern based on predetermined electronic data. Use of this variable pattern forming device minimizes the effect on synchronization accuracy even if the pattern surface is set vertical. The variable pattern forming device can be, for example, a DMD (Digital Micromirror Device) including a plurality of reflective elements driven based on predetermined electronic data. The exposure apparatus with the DMD is disclosed, for example, in Japanese Patent Application Laid-open No. 2004-304135 or in International Publication WO2006/080285 and U.S Pat. Published Application No. 2007/0296936 corresponding thereto. The teachings of the U.S Pat. Published Application No. 2007/0296936 are incorporated by reference. Besides the non-emission type reflective spatial optical modulators like the DMD, it is also possible to use a transmissive spatial optical modulator or a self-emission type image display device. The variable pattern forming device may be used in the case where the pattern surface is set horizontal. The exposure apparatus of the foregoing embodiment is manufactured by assembling various sub-systems containing their respective components as set forth in the scope of claims in the present application, so as to maintain predetermined mechanical accuracy, electrical accuracy, and optical accuracy. For ensuring these various accuracies, the following adjustments are carried out before and after the assembling: adjustment for achieving the optical accuracy for various optical systems; adjustment for achieving the mechanical accuracy for various mechanical systems; adjustment for achieving the electrical accuracy for various electrical systems. The assembling steps from the various sub-systems into the exposure apparatus include mechanical connections, wire connections of electric circuits, pipe connections of pneumatic circuits, etc. between the various sub-systems. It is needless to mention that there are assembling steps of the individual sub-systems, before the assembling steps from the various sub-systems into the exposure apparatus. After completion of the assembling steps from the various sub-systems into the exposure apparatus, overall adjustment is carried out to ensure various accuracies as the entire exposure apparatus. The manufacture of exposure apparatus is desirably performed in a clean room in which the temperature, cleanliness, etc. are controlled. The following will describe a device manufacturing method using the exposure apparatus according to the above-described embodiment. FIG. 16 is a flowchart showing manufacturing blocks of semiconductor devices. As shown in FIG. 16, the manufacturing blocks of semiconductor devices include depositing a metal film on a wafer W to become a substrate of semiconductor devices (block S40) and applying a photoresist as a photosensitive material onto the deposited metal film (block S42). The subsequent blocks include transferring a pattern formed on a mask (reticle) M, into each shot area on the wafer W, using the exposure apparatus of the above embodiment (block S44: exposure block), and developing the wafer W after completion of the transfer, i.e., developing the photoresist to which the pattern has been transferred (block S46: development block). Thereafter, using the resist pattern made on the surface of the wafer W in block S46, as a mask, processing such as etching is carried out on the surface of the wafer W (block S48: processing block). The resist pattern herein is a photoresist layer in which depressions and projections are formed in a shape corresponding to the pattern transferred by the exposure apparatus of the above embodiment and which the depressions penetrate throughout. Block S48 is to process the surface of the wafer W through this resist pattern. The processing carried out in block S48 includes, for example, at least either etching of the surface of the wafer W or deposition of a metal film or the like. In block S44, the exposure apparatus of the above embodiment performs the transfer of the pattern onto the wafer W coated with the photoresist, as a photosensitive substrate. The above embodiment uses the laser plasma X-ray source as a light source for supplying the EUV light. Without having to be limited to this, however, it is also possible, for example, to adopt a synchrotron orbit radiation (SOR) as the EUV light. The above embodiment is the application of an embodiment to the exposure apparatus having the light source to supply the EUV light. Without having to be limited to this, however, an embodiment is also applicable to exposure apparatus having a light source to supply any wavelength light other than the EUV light. The aforementioned embodiment is the application of an embodiment to the illumination optical system of the EUVL exposure apparatus using the reflection type mask M, but, without having to be limited to this, an embodiment can also be applied to a generally-used illumination optical system which illuminates an illumination target surface on the basis of light from a light source. According to one aspect of an embodiment, at least two first optical elements out of the plurality of first optical elements constituting the first fly's eye optical system are set so that the postures thereof about the optical axis of the illumination optical system or about the axis parallel to the optical axis are different from each other. For example, the postures of the at least two first optical elements are determined so that orientations of the illumination regions formed on the illumination target surface by beams traveling via the first optical elements and corresponding second optical elements become close to the orientation of the desired superimposed illumination region. As a result, the optical integrator according to one aspect of an embodiment is able to keep small the superposition errors of the illumination fields formed on the illumination target surface by the plurality of beams obtained by wavefront division by the plurality of first optical elements. The illumination optical system according to an embodiment is able to illuminate the illumination target surface under the required illumination condition with high luminous efficiency while keeping small the light quantity loss due to the superposition errors of the illumination fields, using the optical integrator which keeps the superposition errors of the illumination fields small. The exposure apparatus according to an embodiment is able to manufacture devices with excellent performance by implementing excellent exposure under a good illumination condition, using the illumination optical system which illuminates a pattern on an illumination target surface under a required illumination condition with high luminous efficiency while suppressing the light quantity loss. It should be noted that the embodiments given above were described for facilitating the understanding of the present invention but not for limiting the present invention. Therefore, the elements disclosed in the above embodiments are intended to embrace all design changes and equivalents belonging to the technical scope of the present invention. The invention is not limited to the fore going embodiments but various changes and modifications of its components may be made without departing from the scope of the present invention. Also, the components disclosed in the embodiments may be assembled in any combination for embodying the present invention. For example, some of the components may be omitted from all components disclosed in the embodiments. Further, components in different embodiments may be appropriately combined.
055966110	description	DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention comprises a method for producing medical isotopes through the use of a small reactor wherein the fission products come out in the form of a liquid or gas. The reactor can be an aqueous-homogeneous or water boiler or a gas-cooled type reactor, wherein the fissionable material comprises U-235, Pu-239 or U-233. The characteristics of the reactor used in conjunction with the present invention include the following: a power level near the 200 kilowatt range, 20 liters of uranyl nitrate solution containing approximately 1000 grams of U-235 in a 93% enriched uranium, and a container configured as an approximate right cylinder. An alternate embodiment of the invention can use 100 liters of uranyl nitrate solution containing 20% U-235 rather than 93% enriched uranium. For the aqueous-homogeneous or water boiler type reactor, the reactor uses a solution of uranium salts, i.e. uranyl nitrate in water contained within a reflected container. For the gas-cooled reactor, the fissionable material is supported on very thin foils or wires so that all fission products are released into the gas stream. The moderating material is separately deployed. The extraction of the desired fission products for medical isotopes such as Mo-99 are provided by a method of the present invention comprising subjecting the uranyl nitrate solution or in the case of the gas-cooled reactor, the gas stream, to sorption columns of alumina for a period of time ranging from about 12 to about 36 hours. After the fission products have been circulated through the columns of alumina, these products are subjected to a subsequent purification with organic chemicals which can be in the form of an aqueous solution and, preferably, the reaction products are removed from the columns of alumina by elution with a sodium or ammonium hydroxide solution. After purification, the fission products are further processed by circulation through ion exchange columns to produce the resultant medical isotopes, such as Mo-99, attached to the material of the column. Preferably, the resulting elutriant from the sodium hydroxide solution is precipitated with an organic chemical such as alpha-benzoinoxime which collects the Mo-99 by forming a precipitate, leaving other fission products in solution. The precipitate (Mo-99) may again be dissolved and the process repeated for greater purity. The uranyl nitrate solution is reused in the reactor by adding nitric acid in the solution to achieve a pH in a range of about 2 to about 5. After the nitric acid addition, the uranyl nitrate solution is passed back into the reactor for reuse without further processing. Referring to the drawing, the system for practicing the present invention generally designated 10 comprises a container or enclosure shown schematically at 12 for containing a pool of water, for example, 3.times.3 meters by 7 meters high, in which a vessel 14 is immersed, for example, a 20 liter right cylindrical vessel having fins 16 for heat transfer to the pool of water to form passive cooling with enhanced safety and to remove dependency on active pumping. For the embodiment of the invention using 100 liters of solution containing a lower proportion of pure U-235, a larger pool can be used with the suitably larger cylindrical vessel. According to the present invention, a small amount of the uranyl nitrate, for example, at a rate of about 0.1 to 1.0 ml/second is removed from vessel 14 along a conduit 18. Eventually, this entire amount of solution is returned to vessel 14 through a return conduit 20, after acid, for example, nitric acid, has been added to the solution at 22, to bring the solution to a pH of about 2 to 5. Within vessel 14, which forms the reactor, the solution forms the homogeneous fissionable material which, among other things, forms the Molybdenum-99, as well as other fission products such as iodine or palladium. The reactor with 20 liters volume in vessel 14 and 1000 grams of enriched uranium, is capable of generating about 200 kilowatts of power. The Mo-99 extraction portion of the invention is generally designated 30 and includes a first valve 32 which is capable for diverting the 0.1 to 1.0 ml/second flow of uranyl nitrate solution either through a conduit 34 to an alumina column A, at numeral 36 or, in a second position, to a second alumina column B, shown at numeral 38. When column 36 is being supplied with solution from line 18, a second valve 40 is positioned to pass the solution over a connecting conduit 42 to the return conduit 20. According the present invention, the flow of solution over conduits 18, 34, 42 and 20, through column 36 and past valves 32 and 40, is maintained for about 12 to 36 hours during which Mo-99 and some of the other fission products attach to the alumina in column 36. After this time, the position of valve 32 is changed to divert the flow of solution to a conduit 44, which supplies the solution to the second column 38 and through a further valve 50 to a connecting conduit 52 and again, back to the return conduit 20. At the same time, valve 40 is rotated to disconnect column 36 from connecting conduit 42 and connect the outlet of column 36 to an outlet conduit 54. This is followed by a washing step of approximately 30 minutes during which water from a water supply 60 is supplied through a suitably positioned valve 62 to a washing conduit 64 for passing washing water through column 36, through valve 40, along outlet conduit 54, passed a further valve 66, to a drain line 68. This serves to wash away removed materials from column A which have not been fixed to the alumina. After this washing period, valve 62 is rotated to close the flow of water to conduit 64 and valve 66 is rotated to divert flow to a further conduit 70. Another valve 72 connected to a source of hydroxide 74, for example, sodium hydroxide or ammonium hydroxide, is rotated to open a passage to a hydroxide conduit 76 for supplying hydroxide to and through column 36, passed valve 40 and from valve 66 to conduit 70 and extraction process shown only schematically at 80. The hydroxide serves to remove, that is elude Molybdenum-99 and other fission products from column 36. Subsequently, chemical processing in process 80 takes place by adding an organic solution such as alpha-benzoinoxime, which causes the Molybdenum-99 to form a precipitate, leaving the other fission products solution. The precipitate is then filtered. The precipitate may also be dissolved again and the process repeated for greater purity. After the uranyl nitrate solution has passed for the suitable time period through column B at 38, the positions of valves 32, 62, 72, 40, 50 and an outlet valve 86 can be changed to suitably wash, extract, precipitate and optionally purify the Mo-99, from column 38. The use of two columns avoids wasted time while Mo-99 is being extracted from the other column. While a schematic example of the valving and connections between the washing apparatus, the hydroxide apparatus and the extraction process are shown in the figure, any other suitable valving is also possible as long as the various function needed according to the invention can be achieved. A second embodiment of the present invention is a method used in gas-cooled reactors wherein very small particles of fissionable material in the form of uranium metal or a uranium compound, such as uranium carbide or uranium oxide, are subjected to the fission process in the reactor. Typically, the uranium should be a U-235 isotope. These fine particles of fissionable material are cooled by a gas stream such as a helium-xenon mixture or another inert gas or carbon dioxide. The fission products produced, when the uranium fissions in the critical reactor, are taken up in the gas stream and removed from the reactor. This gas stream containing the fission products is passed through a gas adsorbing bed, such as activated charcoal or carbon, for adsorbing the fission products from the gas stream. The gas adsorbing bed can then be removed and the absorbed fission products separated from the absorbing bed through separation means such as heating, and in turn dissolved in an aqueous solution by a process such as bubbling the gas through the solution. The solution containing the fission products could then be treated by known conventional means such as passing the solution through an alumina column for collecting the medical isotopes like Mo-99. A third embodiment of the present invention comprises a method wherein the fission products created, as described above, are mixed with carbon or other gas-adsorbing materials which, when heated by the fission fragments, elute the fission products into the gas stream for the separation treatment indicated above. A fourth embodiment of the present invention comprises mixing the small particles of fissionable material with a moderating material such as small particles of polyethylene to act as a neutron moderator and catcher of fission products which are in turn taken into the gas stream and subjected to the separation treatment indicated above. A fifth embodiment of the present invention comprises passing a solution of uranium salts through porous polyethylene rods such that the uranium salts adhere to the surface of the porous polyethylene. These rods are then assembled into a reactor configuration which can achieve critically. The uranium fissions and the fission products are then taken up into a gas stream which cools the reactor and sweeps out the fission products for the separation treatment indicated above. While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.
	claims	1. A method of producing a coating resistant to hydration on at least one surface of a cladding tube for nuclear fuel for use for use in a light water reactor, the cladding tube comprising a liner layer on an inside of the tube, the liner layer comprising zirconium or a zirconium alloy, the method comprising: forming a coating at least on a surface of the liner layer that faces an inner space of the cladding tube by subjecting the cladding tube to a treatment with a gas mixture while heating the cladding tube, the treatment being performed at a temperature of about 450xc2x0 C. to about 650xc2x0 C. and substantially at atmospheric pressure, the gas mixture comprising water steam and both oxygen gas and nitrogen gas, wherein the coating is formed such that it has a thickness of at least one xcexcm, such that the coating at least forms an innermost surface facing the inner space of the cladding tube. 2. The method according to claim 1 , wherein the coating is produced by making at least one of the oxygen gas and nitrogen gas of the gas mixture react with at least one material located in the surface of the liner layer. claim 1 3. The method according to claim 1 , wherein the coating comprises by at least one of an oxide and a nitride of zirconium. claim 1 4. The method according to claim 1 , wherein the treatment is controlled by adding at least one gas that is inert at the temperature and pressure of the treatment. claim 1 5. The method according to claim 4 , wherein the inert gases comprise at least one of argon, helium and neon. claim 4 6. The method according to claim 1 , wherein the treatment is controlled by varying the amount of water steam in the gas mixture. claim 1 7. The method according to claim 1 , wherein the coating formed on the surface or the surfaces of the cladding tube during the treatment comprises at least one of zirconium dioxide and zircondium nitride. claim 1 8. The method according to claim 1 , wherein the cladding tube is annealed a plurality of times prior to the treatment in order to confer mechanical strength, and that the treatment represents a final annealing performed in the same plant as the plurality of annealings. claim 1 9. A method according to claim 1 , characterized in that the gas mixture contains air. claim 1 10. A method according to claim 1 , characterized in that the gas mixture comprises further carbon dioxide (CO 2 ). claim 1 11. A method according to claim 1 , characterized in that the gas mixture comprises further mixtures of carbon monoxide (CO) and carbon dioxide (CO 2 ). claim 1 12. A method according to claim 1 , characterized in that the gas mixture comprises further dinitrogen oxide (N 2 O). claim 1 13. The method according to claim 1 , wherein the treatment is performed for a period of 1 to 10 hours. claim 1
	abstract	An ion implantation method and system that incorporate beam neutralization to mitigate beam blowup, which can be particularly problematic in low-energy, high-current ion beams. The beam neutralization component can be located in the system where blowup is likely to occur. The neutralization component includes a varying energizing field generating component that generates plasma that neutralizes the ion beam and thereby mitigates beam blowup. The energizing field is generated with varying frequency and/or field strength in order to maintain the neutralizing plasma while mitigating the creation of plasma sheaths that reduce the effects of the neutralizing plasma.
051606976	abstract	The lower connector comprises an adaptor plate of square shape, traversed by water passage orifices, and a filtration plate pierced with holes of small dimensions and abutting against the adaptor plate. The water passage orifices of the adaptor plate are arranged completely symmetrically in relation to the medians and to the diagonals of the adaptor plate. The set of orifices in each of the zones of the adaptor plate limited by a diagonal and a median comprises orifices have an oblong cross-section and, if appropriate, water passage orifices of a different shape. The filtration plate comprises sets of holes of small dimensions arranged in the zones of the plate which come into alignment with the oblong orifices of the adaptor plate.
047553464	description	DETAILED DESCRIPTION OF THE INVENTION The device which will now be described by way of example beongs to the control mechanism of a set of two clusters of control elements movable vertically for engaging them more or less deeper inside a same fuel assembly. For simplifying and since this mechanism comprises two coaxial shafts, that cluster which is controlled by the displacement and securing device will be designated by the term "internal cluster", because its control shaft is surrounded by the other. The other cluster will correlatively be called "external cluster". But it should of course be understood that this terminology is only used for more simplicity. Referring to FIG. 1, there is very schematicaly shown the coaxial mounting of two control clusters associated with a mechanism whose general construction is similar to the one described in French Pat. No. 2 537 764, to which reference may be made. The external cluster comprises sixteen elements 10 supported by a cross shaped bracket 12 fast with a pommel or enlarged end 14 provided for coupling a terminal expandable sleeve 16 of a drive shaft 18. The cluster is guided in its movement by a guide tube 20 belonging to the upper internal equipment of the reactor, which equipment is supported by the upper core plate (not shown). Shaft 18 is itself guided by a sleeve 22 passing through the cover of the vessel of the reactor and fluid-tight with said cover on which it is fixed. The external cluster is actuated by an electromagnetic gripper type drive device, only a single coil 24 of which is shown in FIG. 8a. This device may be identical to the one described in French Pat. No. 2 537 764 already mentioned. In general, the elements 10 of the external cluster will contain a neutron absorbing material, such as a boron compound, and the external cluster will be used for controlling the reactor by introducing a greater or lesser length of the cluster into the assembly. In the embodiment appearing on the Figures, the internal cluster comprises forty elements 26 divided into four groups offset by 90.degree. around the vertical axis of the cluster. Each group will be designated hereafter by the term sub-group or sub-cluster. Each sub-group comprises a head 28 in the form of a radially disposed plate. The device providing vertical displacement of the subgroups comprises a cross shaped bracket 30 having a pommel 32 in which may be locked the endmost resilient fingers of a sleeve 34 belonging to the displacement shaft 36 (FIG. 5). Four slides 19 (FIG. 3) are provided on tube 20 for guiding the pommel 32. Shaft 36 is controlled by a lifting device using the pressure of the moderating and cooling fluid (light water in a pressurized water reactor). For that, the endmost part 40 of shaft 18 forms a plunger fluid-tightly projecting into a decompression chamber 38 having an outlet duct 64 connected to a valve 65 for controlling the pressure which prevails in the chamber. Elements 26 will for example contain fertile material. When the cluster of fertile elements is used for modifying the energy spectrum of the neutrons during the life of the reactor, the internal cluster will be completely introduced into the core when the assemblies are new (position shown in FIG. 5). But, during operation of the reactor, it will be required to extract some internal clusters and secure them in the top position illustrated on FIG. 2. The head 28 of each sub-cluster is adapted for cooperating with one or other of two resilient securing blades one belonging to the cross shaped bracket 30 and the other to a block for securing the sub-clusters in the top position. The four resilient blades 42 (one per sub-cluster) carried by pommel 32 are each disposed at the end of an arm of bracket 30. These resilient blades 42 are intended to prevent sub-clusters blow-up when the internal shaft 36 is in the low position. Each blade 42 ends in a nose piece which engages in a notch 44 in the head 28 of the corresponding sub-cluster and prevents raising. When pommel 32 is housed in the upper end piece 46 of the corresponding assembly (FIG. 5), the flexible blades 42 are held laterally by the end piece, cannot bend and positively retain the sub-clusters. Since this locking effect disappears when the pommel is outside end piece 46, the bending resistance of blades 42 must be sufficient to avoid untimely escape and raising of the sub-clusters. Like the guide tube, the end piece has centering slides 47 so that pommel 32 cannot free itself from one set of slides 47 and 19 before being engaged in the other. The block for securing the sub-clusters in the top position (FIGS. 2 to 4) also comprises one flexible blade 48 per sub-cluster. These four flexible blades are carried by a plate 50 mounted at the end of the guide tube 20. In this plate slides an annular bolt 52 ending in an enlarged portion 54. A spring 56 tends to force this bolt back to a low position in which it prevents blades 48 from bending inwardly while freeing the path of an end tooth 58 on head 28 (FIG. 2b). The pommel 14 of the external cluster has a projection 60 intended to come into abutment against the enlarged portion of bolt 54 and to raise it (FIG. 2a) so as to release blades 48, when shaft 18 goes beyond the highest position which it may take for controlling the reactor, that is to say when the shaft undergoes an upward over-travel. The complete operation will be described further on. It may however already be mentioned that, when the flexible blades 48 are released by bolt 52, the heads 28 of the sub-clusters may engage in the respective housings formed in the latching block by bending blades 48. The upward movement of the sub-clusters under the action of shaft 36 is limited by the abutment of pommel 32 against the latching block (FIG. 2a). In this abutment position, the heads 28 are slightly above their permanent securing position (shown in FIGS. 2b). The device of the invention comprises a device for detecting the presence of the sub-clusters in the latching block. This device comprises a thermal protection muff 62 which, instead of being fixed, is mounted in sleeve 22 for sliding between a low position (when the sub-clusters are in the assembly) and a raised position (FIG. 8a). The detection means operate by determining the arrival of the muff in its top position. In the embodiment shown in FIGS. 8a and 8b, these means comprise a set of permanent magnets 70 which, in their rest position shown with a dot dash line, are situated below a set of electric contacts 72 placed in fluid-tight bulbs and adapted for closing when muff 62 is raised. Muff 62 ends in a tulip 66 resting on a counter weight 68, supported, through pushers 69, by the heads 28 of the sub-clusters. The counter weight 68 and muff 62 thus tend to urge the sub-clusters from their top latched position upon unlocking and guarantee that the internal cluster drops when the corresponding shaft is or comes into a low position and when the latching block is unlocked. The shaft 36 controlling the internal cluster is preferably provided with means for detecting the presence of this shaft at the top end of its travel. In the embodiment shown in FIGS. 9a and 9b, these means comprise an end ferromagnetic section 78 which, when it comes inside a detection coil 80, appreciably modifies the inductance thereof. These detection means confirm the presence of the sub-clusters in the latching block, also detected by raising of the thermal muff. Similarly, detection coils 82 (FIGS. 9a and 9b) may be provided for determining the positon of the shaft 18 controlling the external cluster, during its last steps of movement in excessive upward travel. Pommel 32 of the external cluster is equipped with a multi purpose shock abosrber. This shock absorber must protect the fuel assembly against accidental dropping of the external cluster as well as of the internal cluster. For that purpose, it comprises a plunger 90 intended to come into abutment against the bottom of end piece 46 and two concentric springs which tend to maintain a collar of plunger 90 against an internal shoulder 88 of the pommel. This latter also has an external shoulder 86 which receives the impact of the bracket or spider 12 of the external cluster should this latter fall. The shock absorbing capacity provided by springs 83 and 84 will be increased by hydraulic shock absorption, controlled in sizing the holes 85 through which water escapes from the internal chamber of the pommel. A possible sequence will now be described for securing the internal cluster in the top position and for releasing the bracket 30, allowing pommel 32 and the corresponding shaft 36 to move down again and leaving full freedom of manoeuvre for the external cluster, formed of absorbent elements 10. The external cluster of absorbent elements is first of all brought to the end of its upward over-travel i.e. in the position shown in FIGS. 2a, 8a and 9a, by electromagnetic displacement means, comprising a coil 24. This end of over-travel corresponds to the engagement, in the last groove of shaft 18, of catches, (not shown) fitted to the fixed sleeve 22. The securing block is at that moment unlocked, the blades 48 being released because bolt 52 is raised by projections 60 (FIG. 2a). The detection coils 82 allow a check to be made that the external cluster has reached the end of its upward over-travel. The sub-clusters of the internal cluster may then be raised by means of shaft 36, actuated by decompression of chamber 38. Raising is usually caused by bringing the pressure in chamber 38 to a value 15 to 20 bars lower than that which prevails in the reactor. Shaft 36 then comes into the position shown in FIGS. 2a, 8a and 9a. The heads 28 of the sub-clusters are fully engaged in the housings provided in the latching block, slightly above the final securing level (FIG. 2a). In this position, the heads 28 raise the pushers 69, the counterweight 68 and muff 62. The presence of the sub-clusters in the latching block may consequently be detected in two different ways. On one hand, the switches contained in the bulbs 72 are closed by magnet 70; on the other hand, the presence of shaft 36 in its top endmost position is detected by coil 80, opposite to the magnetic portion 78. For locking the sub-clusters in the latching block, shaft 18 is lowered by a height h.sub.O (FIG. 9b). The amplitude of the downward movement is determined both by counting the number of advancing steps of the electromagnetic means and by using the detection coils 82. The parts should be dimensioned so that, after lowering shaft 18 by amplitude h.sub.O, this latter is still fluid-tightly engaged in the decompression chamber 38. A height h.sub.O may more particularly be adopted equal to 5 advancing steps and a height h.sub.1 over which the shaft is still engaged which is equal to two steps. During this downward operation, the depression in chamber 38 is maintained at the value to which it was previously brought. Shaft 36, from which the internal cluster is suspended, is therefore still in the top position. But bolt 54, since it is no longer pushed upwardly, comes into abutment against the endmost enlarged portion of blades 48 and applies these blades against the teeth 58 of the sub-clusters. The depression which prevails in the compression chamber 38 is then gradually reduced. The control shaft 36 moves down. The sub-clusters are immobilized as soon as heads 28 come into the position shown in FIG. 2b. This beginning of the drop of sahft 36 is indicated by the change of the signal supplied by coil 80. With the continuing drop of shaft 36 and pommel 32, the anti-blow up blades 42 carried by the pommel leave notches 44, while being deformed so as to pass from the position shown with a broken line to the position shown with a full line in FIG. 2b. Then these blades slide along the edge of heads 28 of the sub-clusters and then resume their rest position (FIG. 1). The end of the drop of the pommel is slowed down by the shock absorber incoporated in the pommel (FIG. 5). It can be immediately seen that the sub-clusters have indeed remained secured by checking that all the switches in the bulbs 72 are still closed; Once the securing has been effected and pommel 32 completely lowered, it can be seen that manoeuvering the external cluster is completely free. The release of the sub-clusters and positioning thereof in the fuel assembly are provided by operations substantially the reverse of those which have just been described. It should be noted that shaft 36 is raised by controlling the depression in the depression chamber 38 to a sufficiently low value so that the shaft rises at a moderate speed. The depression in chamber 38 is then increased to its maximum, before unlocking by manoeuvering shaft 18. The embodiment of the device which has just been described by way of example is in no way limitative. The device may comprise additional members, more particularly for providing greater detection reliability. In particular, additional sensors for checking the presence of the sub-clusters at the bottom end of travel may be placed in the assembly end pieces. An additional hydraulic shock absorber may be provided for limiting shocks.
052456455	summary	The invention relates to a structural part for a nuclear reactor fuel assembly, in particular a cladding or casing tube for a nuclear fuel-filled fuel rod or a spacer for such fuel rods, and to a method for producing the structural part. German Published, Non-Prosecuted Application DE-OS 34 28 954 discloses a cladding or casing tube made of a zirconium alloy for a nuclear reactor fuel rod that can be filled with nuclear fuel. The zirconium alloy may be Zircaloy-2, containing from 1.2 to 1.7% by weight tin, 0.07 to 0.2% by weight iron, 0.05 to 0.15% by weight chromium, 0.03 to 0.08% by weight nickel, 0.07 to 0.15% by weight oxygen, and zirconium for the remainder. The geometric mean value of the grain diameter of the zirconium alloy is less than or equal to 3 .mu.m. In particular, the geometric mean value is from 2.5 to 2 .mu.m. Such a cladding tube is supposed to possess great resistance to stress corrosion cracking. Stress corrosion cracking is a corrosion mechanism on the inside of the cladding or casing tube in the nuclear reactor, for which the expansion of the of the cladding or casing tube resulting from the swelling of the nuclear fuel filling it and from nuclear fission products such as iodine liberated from the nuclear fuel are responsible. Stress corrosion cracking plays a particular role in nuclear ractor fuel rods that are used in boiling water reactors. There, abrupt changes in power of the nuclear reactor, in particular, can cause breaching of the cladding or casing tube walls of the nuclear reactor fuel rods from stress corrosion cracking. The grain diameter in a zirconium alloy can be determined by A.S.T.M. (American Society for Testing Materials) designation E 112-61. The geometric mean value of n diameters is defined as X.sup.G =(d.sub.1 .d.sub.2 . . . d.sub.i .d.sub.n).sup.1/n, where d.sub.i is the i.sup.th diameter. It is accordingly an object of the invention to provide a structural part for a nuclear reactor fuel assembly and a method for producing this structural part, which overcome the hereinafore-mentioned disadvantages of the heretofore-known methods and devices of this general type, and which include a zirconium alloy that has a high corrosion resistance not only to the nuclear fuel or nuclear fission products but also to the coolant which is water in a nuclear reactor, even at relatively high prevailing temperatures, for instance in a pressurized water reactor, which is higher than in a boiling water reactor. With the foregoing and other objects in view there is provided, in accordance with the invention, a structural part being formed of a cladding or casing tube of a nuclear fuel-filled fuel rod or a spacer for a fuel rod for a nuclear reactor fuel assembly, comprising: a) a zirconium alloy material having at least one alloy ingredient selected from the group consisting of oxygen and silicon, a tin alloy ingredient, at least one alloy ingredient selected from the group consisting of iron, chromium and nickel, and a remainder of zirconium and unavoidable contaminants; b) the zirconium alloy material having a content of the oxygen in a range of substantially from 700 to 2000 ppm, a content of the silicon of substantially up to 150 ppm, a content of the iron in a range of substantially from 0.07 to 0.5% by weight, a content of the chromium in a range of substantially from 0.05 to 0.35% by weight, a content of the nickel of substantially up to 0.1% by weight, and a content of the tin in a range of substantially from 0.8 to 1.7% by weight; c) the alloy ingredients selected from the group consisting of iron, chromium and nickel being precipitated out of a matrix of the zirconium alloy as secondary phases, having a diameter with a geometric mean value in a range of substantially from 0.1 to 0.3 .mu.m; and d) the degree of recrystallization of the zirconium alloy being less than or equal to 10% and a sample of the zirconium alloy, after a recrystallization annealing with a degree of recrystallization of 97.+-.2%, having a grain size with a geometric mean value less than or substantially equal to 3 .mu.m. In accordance with another feature of the invention, the content of iron in accordance with characteristic (b) is in a range of substantially from 0.07 to 0.3% by weight, and the content of chromium is in a range of substantially from 0.05 to 0.15% by weight, in the zirconium alloy. The diameter of secondary phases, that is independent crystallites of alloy components precipitated out of the zirconium alloy, can be determined either with high accuracy by using a transmission electron microscope, or with an accuracy which is not as high by using a scanning electron microscope. The geometric mean value of these diameters is defined in correspondence with the definition of the geometric diameter of particle or grain diameters. The degree of recrystallization is defined as the percentage of recrystallized crystal matrix in the zirconium alloy. The relatively low content of tin in the zirconium alloy in accordance with characteristic (b) mentioned above and the relatively high geometric mean value of the diameter of the secondary phases precipitated out of the matrix of the zirconium alloy in accordance with characteristic (c), in particular, bring about the increased corrosion resistance with respect to water. In accordance with a further feature of the invention, the zirconium alloy has a texture with a Kearns parameter f.sub.r wherein 0.6.ltoreq.f.sub.r .ltoreq.1 and preferably 0.6.ltoreq.f.sub.r .ltoreq.0.8. An even further increased corrosion resistance to both nuclear fuel or nuclear fission products and to water at increased temperatures can be attained in this way. A body of a zirconium alloy has a texture, if the hexagonal crystallites of this body have a 3-dimensional ordered alignment (for instance attainable by mechanical deformation), as compared with a purely random alignment (for instance virtually attainable by .beta.-quenching). One measure for the alignment of the crystallites which form right angles with the surface of the body being formed of the zirconium alloy and thus for the texture, is the Kearns parameter f.sub.r, which can be calculated in accordance with "Metallurgical Transactions A", Volume 10A, April 1979, pages 483 through 487. The necessary measurements are carried out in a goniometer with the aid of directional X-radiation. In accordance with an added feature of the invention, the content of tin in the zirconium alloy is in a range of substantially from 0.9 to 1.1 % by weight. In accordance with an additional feature of the invention, the contents of the alloy ingredients iron and chromium in the zirconium alloy are in a ratio of substantially 2:1, and/or the contents of the alloy ingredients iron and chromium have a sum of substantially 0.4 to 0.6% by weight. In this way, the structural parts being formed of the zirconium alloy can be given an optimal corrosion resistance to water at elevated temperatures. In accordance with yet another feature of the invention, the contents of the alloy ingredients iron and chromium have a sum of substantially 0.4 % by weight. In accordance with yet a further feature of the invention, in accordance with characteristic (b), the content of oxygen is in a range of substantially from 1000 to 1800 ppm, the content of silicon is in a range of substantially from 80 to 120 ppm, the content of iron is in a range of substantially from 0.35 to 0.45% by weight, the content of chromium is in a range of substantially from 0.2 to 0.3% by weight, and the content of tin is in a range of substantially from 1 to 1.2% by weight. In accordance with yet an added feature of the invention, the zirconium alloy is Zircaloy-2 or Zircaloy-4. With the objects of the invention in view, there is also provided a method for producing a structural part, which comprises: a) annealing a starting body of a zirconium alloy at a temperature in the .beta. range below the melting temperature to dissolve precipitated-out alloy ingredients, then quenching the starting body at a quenching rate of at least 30 K/s at a surface of the starting body, at a temperature transition through the .alpha.+.beta. range; b) then annealing the starting body at a first temperature in the .alpha. range until formation of precipitates of the alloy ingredients having a precipitate diameter with a geometric mean value in a range of substantially from 0.1 to 0.3 .mu.m; c) hot-forging the starting body into a forged part at a second temperature in the .alpha. range below the first temperature; d) then hot-rolling or hot-extruding the forged part at a temperature in the .alpha. range below the first temperature; and e) then cold-rolling the hot-rolled forged part in at least two rolling steps having recrystallization annealing carried out between two rolling steps with a degree of recrystallization in a range of substantially from 95% to 99% at an annealing temperature in the .alpha. range, while cold-pilgering the hot-extruded forged part in at least two pilgering steps, with a recrystallization annealing carried out between two pilgering steps with a degree of recrystallization in a range of substantially from 95% to 99% at an annealing temperature in the .alpha. range. With the objects of the invention in view, there is additionally provided a method for producing a structural part, which comprises: a) annealing a starting body of a zirconium alloy at a temperature in the .beta. range below the melting temperature to dissolve precipitated-out alloy ingredients, then quenching the starting body at a quenching rate of at least 30 K/s at a surface of the starting body, at a temperature transition through the .alpha.+.beta. range; b) hot-forging the starting body into a forged part at a first temperature in the .alpha. range; c) then heating the forged part to a second temperature in the .alpha. range above the first temperature, until formation of precipitations of the alloy ingredients having a precipitation diameter with a the geometric mean value in a range of substantially from 0.1 to 0.3 .mu.m; d) then hot-rolling or hot-extruding the forged part at a temperature in the .alpha. range below the second temperature; and e) then cold-rolling the hot-rolled forged part in at least two rolling steps having recrystallization annealing carried out between two rolling steps with a degree of recrystallization in a range of substantially from 95% to 99% at an annealing temperature in the .alpha. range, while the hot-extruded forged part is cold-pilgered in at least two pilgering steps, with a recrystallization annealing carried out between two pilgering steps with a degree of recrystallization in a range of substantially from 95% to 99%, at an annealing temperature in the .alpha. range In accordance with another mode of the invention, there is provided a method which comprises performing a final pilgering step and pilgering steps preceding the final pilgering step in the at least two pilgering steps, selecting a logarithmic cold work of at least 1.0 in the pilgering steps preceding the final pilgering step, and selecting a logarithmic cold work of at least 1.6 in the final pilgering step. In accordance with a further mode of the invention, there is provided a method which comprises performing a final pilgering step and pilgering steps preceding the final pilgering step in the at least two pilgering steps, selecting a quotient of a logarithmic wall thickness variation to a logarithmic diameter variation of at least 1 in the pilgering steps preceding the final pilgering step, and selecting a quotient of a logarithmic wall thickness variation to a logarithmic diameter variation of at least 5 in the final pilgering step. In accordance with a concomitant mode of the invention, there is provided a method which comprises performing a final rolling step and a final pilgering step, performing a final annealing following the final rolling step or the final pilgering step, and performing the final stress relief annealing with a degree of recrystallization of a maximum of 10%. The logarithmic wall thickness variation .epsilon..sub.S is the natural logarithm of the quotient S.sub.o /S of the wall thickness of a tube before (S.sub.o) and after (S) a pilgering step. The logarithmic diameter variation .epsilon..sub.D is the natural logarithm of the quotient D.sub.o /D of the mean diameter (between the inside and outside diameter) of this tube before (D.sub.o) and after (D) the same pilgering step. The logarithmic cold work value .phi. of the tube effected by this pilgering step is defined as .phi.=.epsilon..sub.S +.epsilon..sub.D, and a cold-deformation C.sub.W associated with the pilgering step is C.sub.W =100 (1-exp-.phi.) in percent. The .alpha. range of a zirconium alloy is the temperature range in which the crystal of the zirconium alloy has a hexagonal structure. The .beta. range is the temperature range in which the crystal of the zirconium alloy has a cubically body-centered structure. The (.alpha.+.beta.) range is the temperature transition range in which both of these crystal structures are present in the zirconium alloy. Other features which are considered as characteristic for the invention are set forth in the appended claims. Although the invention is illustrated and described herein as embodied in the manufacture of two cladding tubes for a nuclear reactor fuel assembly, for instance for a UO.sub.2 -filled fuel rod in a fuel assembly, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.
044029047	claims	1. A method for testing the clad integrity of a nuclear fuel rod comprising the steps of: (a) fabricating a sealed nuclear fuel rod with a cap seal at one end, the cap having a cavity therein, said cavity having connected therewithin a wad of fibrous zirconium or zirconium ferrite; (b) externally scanning the rod with an eddy current probe at the location of the wad to establish a probe output signal characteristic of the moisture-free rod; (c) placing the rod in a water environment in which the external water pressure is greater than the internal pressure of the rod; (d) externally scanning the rod with an eddy current probe at the location of the wad; (e) comparing the probe output signals of steps (b) and (d) to determine whether the conductivity of the wad has changed, indicating the ingress of water through the clad. (a) fabricating a plurality of sealed nuclear fuel rods, each having a cap seal at one end, the cap having a cavity therein, said cavity having connected therewithin a wad of fibrous zirconium or zirconium ferrite; (b) fabricating a fuel assembly by securing together said plurality of fuel rods in spaced parallel relationship; (c) externally scanning said one end of at least one fuel rod with an eddy current probe to establish a probe output signal characteristic of a moisture-free fuel rod; (d) irradiating the fuel assembly in a water cooled nuclear power reactor; (e) externally scanning said one end of each of the fuel rods in the assembly with an eddy current probe; (f) comparing the probe output signals from step (e) with the characteristic signal for a moisture free rod as established in step (c); (g) identifying any leaking fuel rods in the fuel assembly by the affect on the probe signal due to the permanent change in wad conductivity resulting from the oxidation of said wad material. 2. A method for identifying perforated nuclear fuel rods in a nuclear fuel assembly comprising the steps of:
	claims	1. A method to determine an operational period for a filter in a filtration device comprising:determining an initial remaining operational period based on an installation date of the filter and an initial expected operational period, wherein the initial expected operational period is determined before the filter starts filtration;periodically calculating a remaining actual operational period of the filter based on the remaining operational period based and an elapsed operational period of the filtration;monitoring an opacity of gases through the filter, andperiodically adjusting the calculated remaining actual operational period based on the monitored opacity. 2. The method of claim 1 wherein the filtration device is a bag house and the filter is an array of bag filters, and further comprising replacing the bag filters at or before the expiration of the adjusted remaining actual operational period. 3. The method of claim 1 wherein the operational period is a filter life. 4. A method for dynamically determining a remaining actual operational life a bag filter in a bag house having a controller, the method comprising:entering into the controller bag filter data and an installation date of the bag filter in the bag house;determining an initial bag filter life based on the bag filter data;decrementing the initial bag filter life to determine a remaining actual bag filter life and periodically decrementing the remaining actual bag filter life;monitoring a bag house operating condition, wherein the operating condition includes the opacity of a gas having passed through the bag filter;adjusting the remaining actual bag filter life based on the monitored bag house operating condition and periodically decrementing the remaining actual bag filter life, andreplacing the bag filter at a time based on the decremented, adjusted remaining actual bag filter life. 5. The method of claim 4 wherein bag house operating condition is the pressure differential and the pressure differential is determined promptly after a bag filter cleaning operation. 6. The method of claim 4 wherein the bag house operating condition is the particulate level and the method further comprises:determining a difference between the particulate level and a baseline particulate level, wherein the baseline particulate level is a function of remaining bag life, andadjusting the remaining bag life to reduce the difference. 7. The method of claim 4 wherein the remaining actual bag life is displayed on a user terminal in communication with the controller. 8. An apparatus for dynamically determining a remaining actual operational life of a filter in a filtration device, comprising:a non-transitory electronic storage containing data including an installation date of the filter, and data indicating an initial filter life;a sensor monitoring a particulate level in an outlet gas flow from the filtration device, and the sensor includes an exhaust gas opacity sensor in the outlet gas flow from the filtration device;a computer controller including an executable program stored on the electronic storage, wherein the execution of the program causes the controller to determine a remaining actual operational filter life based on a difference between a sensed level exhaust gas opacity provided by the opacity sensor and an expected opacity level, wherein the expected opacity level is determined by the controller based on opacity data stored in the electronic storage correlating the expected opacity level to an operational period of the filter, anda user terminal indicating the remaining actual filter life. 9. The apparatus as in claim 8 further comprising a filter cleaning device coupled to the filter and the executable program periodically commands the filter cleaning devices to remove dust and particles from the filter. 10. The apparatus as in claim 8 wherein the filtration device is a bag house and the filter is at least one bag filter. 11. The apparatus as in claim 8 wherein the opacity data is a lookup table which correlates various periods of expected remaining life to various opacity levels. 12. The apparatus as in claim 8 wherein the wherein the filter is an array of bag filters arranged in the device. 13. The apparatus as in claim 8 wherein the filter is a porous material.
	description	1. Field of the Invention Example embodiment(s) of the present invention are directed to methods of improving the energy output of a nuclear reactor, while satisfying a minimum subcritical bank withdrawal position (MSBWP) safety condition, to a method for determining fuel rods to be subject to an extended natural uranium blanket layer, so as to employ a variable natural blanket for selectable fuel rods in one or more fuel bundle(s) of the reactor, and to a fuel bundle which has a variable natural uranium blanket. 2. Description of the Related Art FIG. 1 illustrates a conventional boiling water reactor (BWR); FIG. 2 illustrates a fuel bundle in the core of a reactor vessel; and FIG. 3 represents an x-y map distribution of a 10×10 array of fuel rods and water rods in a fuel bundle located in one quadrant of a control blade. As show in FIG. 1, a pump 110 supplies water via a conduit (e.g., in the direction of arrow from pump 110 towards the containment vessel 114) to a reactor vessel 112 housed within the containment vessel 114. The core of the reactor vessel includes a number of fuel bundles B at locations. Controlled nuclear fission takes place at the fuel bundles (e.g., fuel bundles B of FIG. 2) in the core and generates heat which turns the supplied water (not shown)—flowing between fuel rods—into steam. Referring to FIG. 1, steam (not shown) is supplied from the reactor vessel 112 to turbines 118 for powering a power generator 120, which in turn outputs electrical energy. The steam supplied to the turbines 118 is condensed back into water at condenser 122. The water from the condensed steam is recycled back to pump 110. The above process repeats itself (for a number of cycles) to generate electricity from the BWR. A typical core of the reactor vessel may contain anywhere from about 200 to about 900 of fuel bundles B. Of course, different configurations as well as different numbers of fuel bundles may be used, so long as such configurations satisfy the safety and energy output requirements of a nuclear reactor. As shown in FIG. 2, a given fuel bundle B includes an outer channel C surrounding a plurality of fuel rods 100 extending generally parallel to one another between an upper plate U and a lower tie plate L. In general, the fuel rods 100 are provided in a generally rectilinear matrix as illustrated in FIG. 3. The fuel rods 100 are maintained laterally spaced from one another by a plurality of spacers S which are vertically separated from one other along the length of the fuel rods 100 within the channel C. FIG. 3 illustrates a 10×10 array of fuel rods 100 surrounded by the fuel channel C. The fuel rods 100 are arranged in orthogonally related rows to surround one or more water rods 130, with two water rods 130 shown in FIG. 3. Other configurations may be used. Reactor coolant (other than the water in the water rods) flows between fuel rods 100 and collects the heat generated from nuclear reactions occurring within the fuel rod(s) of the fuel bundle(s). In FIG. 3, a given fuel bundle B is arranged in one quadrant of a cruciform control blade 132 (e.g., only one of four quadrants is shown in this example); a cruciform control blade is a conventionally-known control blade configuration for a BWR. A given fuel bundle B is typically arranged in each of the other three quadrants of the control blade 132, as is known. Movement of control blade(s) 132 up (and down) between the bundles B controls the amount of nuclear reactivity occurring in the bundles B. FIGS. 1-3 illustrate just one conventional arrangement of rods 100 within a bundle of a reactor core of a BWR; other arrangements may be used as is evident to one skilled in the art. In a given fuel rod 100, the fuel rod 100 is typically filled along various locations within its vertical span in a bundle with uranium (e.g., pellets containing the isotopes 238U and 235U), where the amount of 235U may be enriched (as desired) to account for safe operating conditions in a nuclear reactor. The isotope 235U is naturally found in uranium at a concentration of 0.711% (by weight) with the remainder of the uranium being the isotope 238U. Accordingly, as used hereafter, 0.71 represents the concentration of natural uranium. After going through a process of enriching, the enriched uranium may contain from about 2% (or just above 2% by weight) to about 5% (by weight) 235U with the remainder of the uranium being isotope 238U. Although amounts greater than about 5% (by weight) of 235U in enriched uranium could be used, commercial power-producing nuclear reactors have traditionally been limited to 5% enriched uranium fuels. As discussed above, fuel rod 100 may be filled with pellets of natural uranium in some parts of rod 100 and pellets of enriched uranium in other parts of rod 100, along the vertical (axial) height of the fuel rod 100. Some of the pellets may contain only natural uranium while other pellets may contain a combination of natural uranium and enriched uranium. Additionally, some pellets may contain only enriched uranium (a concentration of 235U above that found in natural uranium, i.e., >0.71). Typically, the uranium pellets may be about a half inch in height. A typical fuel rod may 100 contain up to about 240 pellets. Also, in some parts, the fuel rod 100 may contain no pellets providing a void space (designated as V as further described herein) or the fuel rod 100 may have a truncated height (designated as E as further described herein). Thus, given fuel rod(s) 100 may be shorter than other fuel rods within a given fuel rod bundle B. FIG. 4 is a representation of various axial sections of a given fuel rod 100. With reference to bundle B in FIGS. 2 and 3, the 10×10 array of fuel rods 100 and water rods 130 can be represented by a x-y map distribution (or radial lattice) cutting across a (e.g., horizontal) cross-section of fuel bundle B. In FIG. 4, a typical fuel rod 100 has a height of about 150 inches. FIG. 4 illustrates seven x-y map distributions along the vertical height of a rod 100, from 0 to 150 inches. Each 6-inch segment of a fuel rod 100 may be referred to as a node; thus there are 25 nodes in a 150 inch rod, with node 1 representing the bottom 6 inches of rod 100 and node 25 representing the segment between 144 to 150 inches of fuel rod 100 from its bottom. These x-y map distributions, starting from the bottom of the fuel rod 100, are identified in FIG. 4 as the following: (a) 26868 (extending from height=0 inches to 6 inches, node 1); (b) 26869 (extending from height=6 inches to 54 inches, nodes 2 to 9); (c) 26870 (extending from height=54 inches to 84 inches, nodes 10 to 14); (d) 26871 (extending from height=84 inches to 96 inches, nodes 15 and 16); (e) 26872 (extending from height=96 inches to 138 inches, nodes 17 to 23); (f) 26873 (extending from height=138 inches to 144 inches, node 24); and (g) 26874 (extending from height=144 inches to 150 inches, node 25). FIGS. 5-11 illustrate x-y map distributions corresponding to (a) through (g) above for all fuel rods 100 of a given fuel rod bundle B at each of the seven specified locations between 0 to 150 inches of fuel rod height. The x-y map distributions of FIGS. 5-11 should be read in conjunction with FIG. 4. In FIGS. 5-11, a cell (fuel rod) with a “V” indicates that a fuel rod 100 does not exist at all at the cell position depicted in the corresponding x-y map distribution, and an “E” indicates that while the shell of a fuel rod 100 is present, the shell (of fuel rod 100) is empty at the corresponding cell position depicted in the corresponding x-y map distribution. FIGS. 5-11 should be referred to for the following discussion. FIG. 5 illustrates the x-y map distribution (e.g., 26868) for all fuel rods of a given fuel rod bundle at a location between height=0 to 6 inches. In FIG. 5, the number “0.71” reflects the concentration (in percent by weight) of the amount of 235U present in the fuel rod at the corresponding cell position (A1-J10) between height=0 inches and 6 inches, or in other words, rods 100 at that location or node (node 1) which have natural uranium. In FIG. 5, the cells D6, D7, E6 and E7 constitute a water rod (WR) corresponding to the circle identified as 130 in FIG. 3, with the second water rod 130 of FIG. 3 denoted by cells F4, F5, G4 and G5. As all fuel rods 100 at node 1 (0 to 6 inches from bottom) have a natural uranium concentration at that location, the x-y map distribution of FIG. 5 thus shows the formation of an all “natural” blanket layer at the bottom of the all fuel rods in a given bundle B at node 1. This 6-inch natural blanket at the bottom of a fuel bundle B is provided to help ensure safe nuclear reactor operation within specified safety and/or operating limits. FIGS. 6-9 show x-y map distributions corresponding to positions or nodes indicated in (b) through (e) above, and are provided merely for comparative reference. FIG. 10 is an x-y map distribution (e.g., 26873) of the composition of a fuel rod bundle at a location between height=138 (or >138) to 144 inches; and FIG. 11 is an x-y map distribution (e.g., 26874) of the composition of a fuel rod bundle at a location between height=144 (or >144) to 150 inches. Conventionally in a BWR, another all “natural” blanket layer is provided at the top of the fuel rods 100 within a given bundle B at a height between 138 and 150 inches as reflected in FIGS. 10 and 11 (x-y map distributions 26873 and 26874). This 12-inch natural blanket at nodes 24 and 25 is also typically provided to ensure safe nuclear reactor operation within specified safety limits. The use of a natural blanket at the bottom node 1 (6 inches of natural uranium) and at the top nodes (either a 6 inch blanket at node 25 (top) or a 12-inch blanket at nodes 24 and 25) is the conventional design choice for plant designers. The use of these natural blankets allows an overall reduction in bundle enrichment by reducing neutron leakage from the top and bottom of the core. Yet the larger 12-inch blanket at the top results in an effectively shorter fuel bundle, which can reduce thermal margins in non-peripheral portions of the core and hence lower thermal output. Moreover, in addition to being able to satisfy limits for thermal parameters such as MFLPD (Maximum Fraction of Limiting Power Density), MAPRAT (the ratio of MAPLHGR or Maximum Average Planar Linear Heat Generation compared to its limit), MFLCPR (Maximum Fraction of Limiting Critical Power Ratio), and limits for reactivity parameters (cold shutdown margin (CSDM) and hot excess reactivity (HOTX)), use of the larger 12-inch blanket may complicate satisfying the limit or condition for the reactivity parameter known as the maximum subcritical banked withdrawal position (MSBWP). An example embodiment of the present invention is directed to a method for improving the energy generating output of a nuclear reactor containing one or more fuel rods in one or more fuel rod bundles while satisfying a maximum subcritical banked withdrawal position (MSBWP) reactivity limit. In the method, enrichments of individual fuel rods in an axial cross-section of a lattice being evaluated at the top of the fuel bundle are ranked, and the fuel pins of the highest ranked rod location in the lattice are replaced with pins containing natural uranium. A core simulation is then performed to determine whether there is any margin to a MSBWP reactivity limit. For each lower ranked candidate rod position, the pin replacing and core simulation functions are repeated until no rod location violates the MSBWP reactivity limit, so as to achieve a desired lattice design for the top of the fuel bundle. Another example embodiment is directed to a method of determining a natural uranium blanket layer for a fuel bundle in a nuclear reactor. The method includes evaluating rod enrichments in all fuel rod locations in the bundle at an axial location that represents a cross-section of the top six inches of the bundle. A 6-inch blanket of natural uranium is provided in rod locations which have an enrichment exceeding a rod enrichment concentration threshold. Otherwise, a 12-inch blanket of natural uranium is provided in rod locations which have an enrichment less than or equal to the rod enrichment concentration threshold. Another example embodiment is directed to a fuel bundle of a nuclear reactor. The fuel bundle includes a six-inch natural uranium blanket layer at a bottom end of the bundle. In the bundle, one or more selectable rod locations at an axial cross-section at the top end of the bundle with fuel rod enrichments there at exceeding a rod enrichment threshold value have a six-inch natural uranium blanket layer therein. One or more selectable rod locations in the axial cross-section which have fuel rod enrichments less than or equal to the rod enrichment threshold value have a twelve-inch natural uranium blanket layer therein. In an example embodiment to be described in detail hereafter, there is described a method of improving the energy generating output of a nuclear reactor while satisfying the MSBWP reactivity limit. As will be seen below, certain example embodiments are directed to a method of identifying and/or enriching selected fuel rods in the 2nd top most six inches of nuclear reactor fuel bundles (e.g., between height=138 to 144 inches) with 235U which satisfies the MSBWP reactivity limit/constraint or safety condition. Other variations are possible within the scope of the present invention. For example, instead of 235U, another fissionable fuel may be used as appropriate. Other variations are also contemplated to be within the scope of the present invention as are recognized by those of ordinary skill in the art. An aspect of the present invention relates to the design of fresh fuel bundles which satisfy the MSBWP reactivity limit criteria/safety condition and also improve the energy output of a nuclear reactor. To appreciate various aspects of the present invention and for explanation of the various lattice designs shown in the figures, reference is made to FIG. 6. FIG. 6 is an x-y map distribution (e.g., 26869) of the composition of a fuel rod bundle at a location between height=6 (or >6) to 54 inches. This corresponds to the nodes between 6 and 54′ in the fuel rod 100 shown in FIG. 4. In FIG. 6, each of the cells in the lattice design (A1 to J10) contain an amount of 235U (in terms of percent by weight) reflected by the particular percent by weight value recited in each relevant cell position. Thus, for example, cell A1 of FIG. 6 is marked with the number 1.60. This means that between height=6 inches to 54 inches (consistent with the height or axial location of map distribution 26869 in FIG. 4), the fuel rod 100 contains 1.60% (by weight) of 235U. In other words, reading x-y map 26869 (of FIG. 6) in conjunction with FIG. 4 indicates exactly where in the fuel rod 100 one will find 1.60% by weight of 235U. Likewise, referring to cell D3 of FIG. 6, the amount of 235U is 4.40% by weight. At cell D4 of FIG. 6, however, two numbers are listed. The upper number reflects the amount of 235U present (e.g., 4.90% by weight) and the lower number reflects the amount of gadolinium present (e.g., 7.00% by weight). Gadolinium acts to slow down nuclear reactions by absorbing neutrons. Thus, gadolinium provides a means of controlling the local power and global reactivity of a nuclear reactor as a function of cycle exposure. Note, however, that gadolinium depletes or “burns out” over operational time. As discussed above, each of FIGS. 6-10 (and FIGS. 13-15 to be discussed later herein) illustrate the uranium and/or gadolinium distributions for a fresh bundle design of a 10×10 fuel rod assembly. Displayed are the radial lattices (e.g., typically homogeneous sections of the bundle) at various specified axial (vertical) elevations. As noted with FIGS. 4 and 5, each lattice is a two-dimensional x-y map distribution showing the composition of each fuel rod location (e.g., cells A1-J10). As noted, locations that are designated as “V” indicate that the fuel rod is vanished at that location (i.e. a partial length fuel rod that does not extend the full height of the bundle). Also as noted, locations designated as “E” indicate that the fuel rod is empty (i.e. a space is left in the rod, for example, to accommodate fission gas release). As previously noted, a single number corresponds to the natural (0.71) or enriched 235U (>0.71 concentration), while two numbers in a single cell correspond to the uranium (top number) and gadolinium (bottom number) concentrations, respectively. Fresh bundle design determines the distribution, both axially (vertically) and radially (horizontally), of enriched uranium and/or gadolinium burnable poison within the fuel rods of the fuel bundle. Typical uranium distributions range from natural (0.711 wt. %) to about 5.0 wt. % for a light water reactor. The higher the enrichment, the greater the nuclear fission rate and the power produced by a given fuel rod. While other time frames may be suitable, a BWR such as illustrated in FIG. 1 operates for a period of typically one, one and a half or two years. The core of the reactor is designed to generate a certain amount of energy measured in gigawatt days per short ton of uranium (GWD/ST). At the completion of a fuel cycle, approximately ¼ to ½ of the least reactive (and typically the most depleted) fuel is removed and replaced with fresh fuel. A rearrangement of the exposed fuel bundles is also typically performed as a means of maximizing (or improving) the energy production of the core while satisfying thermal and reactivity limits, which are Nuclear Regulatory Commission (NRC) imposed constraints that assure the integrity of the fuel and the safety of the plant. The design of the core loading involves the placement of the exposed fuel bundles as well as the design and placement of the fresh bundles. In addition, a control blade operational strategy (e.g., control blade placements and notch positions) and core flow, as a function of cycle exposure, are also typically determined as part of the design. Core Simulation Programs In addition to determining the core loading and control blade operational strategy design, all thermal and reactivity parameters for a given core loading are typically determined via reactor simulation utilizing NRC licensed computer codes, such as the codes TGBLA and PANACEA. These TGBLA and PANACEA codes are well known in the art and are incorporated herein by reference in their entirety. Equivalents of the TGBLA and/or PANACEA codes may be used. TGBLA models the behavior of a given bundle lattice while PANACEA models the behavior of the bundles (comprised of individual lattices) within the core loading pattern. Reactor simulation also involves assessing the impact of the control blade operational and core flow strategy as a function of cycle exposure. Thermal Parameters & Limits Enriched uranium and gadolinium (used as “poison” as one aspect of controlling fission reactions with a nuclear reactor) distributions within the fresh bundle are designed to satisfy thermal and reactivity limits within the core as a function of cycle exposure. Examples of thermal parameters are MFLPD (Maximum Fraction of Limiting Power Density), MAPRAT (the ratio of MAPLHGR or Maximum Average Planar Linear Heat Generation compared to its limit), and MFLCPR (Maximum Fraction of Limiting Critical Power Ratio). Examples of reactivity parameters are cold shutdown margin (CSDM), hot excess reactivity (HOTX) and maximum subcritical banked withdrawal position (MSBWP). MFLPD may be defined as the maximum of the ratio of local rod power or linear heat generation rate (LHGR) (i.e. kilowatts per unit length) in a given bundle at a given elevation, as compared to the limiting value. MAPLHGR is the maximum average LHGR over the plane in a given bundle at a given elevation. MAPRAT may be understood as the ratio of MAPLHGR to the limiting value. LHGR limits protect the fuel against the phenomena of fuel cladding plastic strain, fuel pellet centerline melting, and lift-off, which is bulging of the clad exceeding the expansion of the pellet. This is due primarily to fission gas build-up. Lift-off degrades the heat transfer from the pellet across the clad to the coolant. MAPRAT limits protect the fuel during postulated loss of coolant in an accident while MFLPD limits protect the fuel during normal operation. MFLCPR limits protect the fuel against the phenomena of ‘film dryout’. In a BWR heat transfer, a thin film of water on the surface of the fuel rod assures adequate removal of the heat generated in the fuel rod as the water is converted into steam. This mechanism, also known as nucleate boiling, will continue as the power in the fuel rod is increased up until a point known as transition boiling. During transition boiling, heat transfer degrades rapidly leading to the elimination of the thin film and ultimately film dryout, at which time the cladding surface temperature increases rapidly leading to cladding failure. The critical power of the bundle is the power at which a given fuel bundle achieves film dryout, and is determined from experimental tests. The Critical Power Ratio (CPR) is the ratio of the critical power to the actual bundle power. MFLCPR is simply the maximum over all bundles' of the fraction of each bundles CPR to the limiting value. Reactivity Parameters & Limits CSDM is defined as the reactivity margin to the limit for the reactor in a cold state, with all control blades inserted with the exception of the single most reactive control blade. CSDM is determined for each time (exposure) state-point during the cycle. HOTX is defined as the core reactivity for the reactor in the hot state, at rated power, with all control blades removed, at each exposure state-point during the cycle. MSBWP is defined as the maximum notch position, applied to all control blades, at which the core remains in a subcritical state for the reactor in a cold state as a function of cycle exposure. The MSBWP Reactivity Parameter Typically, to satisfy the MSBWP parameter condition or limit, it has been an industry standard to use, for example, the x-y map distribution 26874 of FIG. 11 not only between the fuel rod height=144 to 150 inches (node 25), but also between the fuel rod height=138 to 144 inches (node 24). In effect, and referring to FIG. 10, the x-y map distribution at node 24 is changed so that the x-y map distribution 26873 between height=138 to 144 inches is replaced with x-y map distribution 26874. In other words, the x-y map distribution of map 26874 (see FIG. 11) is extended to the top 12 inches of each fuel rod 100 in the bundle B. When such a configuration is used in conjunction with the distribution of x-y map 26868 between the fuel rod height=0 to 6 inches (see FIG. 5, at node 1), a “blanket” of natural uranium is formed in accordance with x-y map 26874 (FIG. 11) at the top 12 inches of the fuel rod 100 and in accordance with x-y map 26868 (FIG. 5) at the bottom 6 inches of the fuel rod 100. While doing so permits satisfaction of the MSBWP limit, the use of the full natural uranium blanket extended at node 24 (between the height=138 and 144 inches) results in more peaked power distributions (i.e. less thermal margin) and adds restrictions on the fuel loading which may require additional fuel bundle design changes in order to satisfy cycle energy requirements. According to an example embodiment, the MSBWP limit is determined from a reactor simulation utilizing NRC licensed computer codes. In an example, this calculation involves performing a simulation at various cycle exposure statepoints (e.g., from 0 to about 16000 cycle exposures MWd/ST, see FIG. 20), with the reactor in a simulated cold shutdown condition (e.g. 68° F.), and with all control blades inserted at the same notch position. Notch positions are discrete values representing a fraction of total control blade 132 insertion (or withdrawal). In a BWR, the control blades 132 are inserted from the bottom of the core. Thus, for example, notch ‘0’ represents full control blade 132 insertion into the core, notch ‘24’ represents half-way withdrawn, and notch ‘48’ represents the control blade 132 as fully withdrawn from the bottom of the core. These are typically of standard General Electric BWRs. Other notch value representations are possible, such as ‘0’ to ‘100’ as in the ABB or GE Advanced BWR reactor design (representing continuous control blade motion). Typical notch values for calculating the MSBWP limit would be a notch position at ‘2’ or ‘4’ (for a range of ‘0’ to ‘48’ for a control rod stroke of 144 inches in length), which forms the basis of technical specifications required for plant operation. For a given fuel cycle design, the validity of the MSBWP notch value would be confirmed by performing a series of reactor simulations, and confirming that sufficient reactivity margin existed to assure subcriticality (MSBWP) at cold shutdown conditions. As discussed above, in a BWR the control blades 132 are inserted from the bottom of the reactor. Thus, a fully inserted control blade 132 represents a blade that completely covers the length of the fuel rods 100 within the bundles B with respect to reactivity control. An MSBWP calculation for a notch value of ‘2’ (over the range of ‘0’ to ‘48’) would place all control blades 132 at axial positions slightly below the top of the active fuel. For a 150 inch length fuel rod 100, this corresponds to 6 inches of uncontrolled fuel at the top. An MSBWP notch value of ‘4’ would eliminate control of the top 12 inches of active fuel, and so on. Conventional core design practice is to reduce the enrichment in all fuel rods at the top and bottom of the fuel as a means of reducing the fuel cost (e.g., lower enriching or separative work costs) and/or improving neutron economy, e.g., lower neutron leakage). Referred to as axial ‘blankets’, the top and bottom lattices within the fresh bundle have enrichment distributions that range from natural (0.71) to 2.0 wt. %. As discussed previously, blankets are typically 6 inches at the bottom and 6 or 12 inches at the top, depending on the MSBWP criteria. It is appreciated from the definition of the MSBWP calculation that increasing the height of the top blanket results in increased MSBWP reactivity margin to the MSBWP limit, but conversely may cause undesirable peaked power distributions (i.e. less thermal margin) and additional fuel loading restriction. On the other hand, reducing the height of the top blanket may result in reduced (or lack of) MSBWP reactivity margin. The conventional art specifies a fixed height of the top blanket (e.g., all natural in all cells of the x-y map distribution such as depicted in map 26868 (FIG. 5), map 26874 (FIG. 11), or map 72017 (FIG. 12), etc.) as being necessary to satisfy the MSBWP reactivity margin (safety condition) requirements. However, by specifying a fixed height of the top blanket (that satisfies MSBWP) prior to the start of the fuel cycle design, the fuel cycle design may be performed in a slightly more constrained manner (from a design freedom perspective) while allowing MSBWP to be ignored, as the fixed height of the top blanket inherently assures that MSBWP is satisfied. The extended length of the top blanket would effectively eliminate MSBWP as an active design constraint, allowing the core designer to focus on other thermal and reactivity parameters such as MFLCPR, MFLPD, CSDM and/or HOTX. In such instances, the MSBWP simulation would be performed only as a validation check once the final design (e.g., with regard to MFLCPR, MFLPD, CSDM and/or HOTX) has been set. However, as the MSBWP reactivity parameter must be accounted for in design analysis, this alternative is not desirable. For example, a MSBWP notch value of ‘2’ or ‘4’ might require a 12-inch natural blanket for a given fresh bundle design. These correlations would be arrived at based on historical design and operating experience for a given plant. In the example described, a fresh fuel bundle design composed of uranium enrichment and gadolinium distributions would be determined within the constraint of a 12-inch top natural blanket. By specifying a 12-inch top natural blanket, satisfying MSBWP is all but assured. An alternate approach described herein is to address and incorporate the MSBWP criteria, not by extending the height of the top blanket (across the entire x-y map) but by extending the blanket within only a certain number of fuel rods or fuel rod subsets within a given bundle. Bundle Design for MSBWP The proposed approach in accordance with the example embodiments begins by assuming a minimum top axial blanket (at node 24 or 25) for the design. In most cases, this would correspond to 6-inches of top axial blanket at node 25. The fuel cycle design would proceed with determining the exposed fuel placement and fresh fuel placement, the fresh bundle design (consisting of the enriched uranium and gadolinium distributions), and control blade and flow operational strategy. The constraints for the design would consist of each of the limits on the thermal and reactivity parameters, such as MFLCPR, MFLPD, and CSDM, but the design analysis would exclude the constraint on MSBWP. The details of performing a fuel cycle design in the absence of MSBWP are known in the art and may consist of manual design methods as well as automated optimization techniques. In its basic form, the fuel cycle design process is an iterative process that involves 1) specifying the set of design variables, 2) performing a simulation, 3) evaluating the thermal and reactivity parameters output from the simulation with respect to limits, 4) performing one or multiple design variable changes to address one or more constraint violations and 5) repeating the process of simulation and evaluation until all limits are satisfied while maximizing (or improving) energy production. As known from experience, certain design variable changes affect certain output parameters. Variable changes may be localized or global in nature. For example, increasing the enrichment in a particular rod of a fresh bundle increases the power in the rod locally, thus increasing MFLPD while at the same time increasing HOTX. In another example, moving the exposed fuel towards the periphery will decrease neutron leakage, and thus increase energy production, albeit at the expense of an increase in power among all bundles located towards the core interior. Combining global with local variable changes allows the designer to achieve the highest degree of optimization while satisfying thermal and reactivity limits. Upon completion of the fuel cycle design in the absence of the MSBWP criteria, a simulation is performed to determine the reactivity margin (or lack thereof) that exists for the MSBWP calculation. With respect to the simulation, control blades 132 are inserted at the MSBWP technical specification limit with the reactor in a cold state. Several exposure statepoints during the cycle are simulated. Output results may be ASCII text or graphical in nature, for example. To meet the MSBWP criteria, design variable modifications are performed with respect to the fresh fuel bundle design by extending the top axial zone of selected, individual fuel rods downward to the lattice immediately below the top blanket lattice (at 144 to 150 inches), i.e., to the 12 inch blanket position. An assessment of potential fuel rod modifications may proceed as follows. First, a list of candidate rod changes is created based on a ranking of enrichments, from lowest enrichment to highest value (corresponding to the lowest to highest ranked rod locations), within the lattice immediately below the top blanket lattice. For example, in the axial view of the rod 100 in FIG. 4, eliminate lattice 26873 (also referenced as x-y map in FIG. 10) and extend lattice 26872 (FIG. 9) up to height 144.0 inches. Referring to lattice 26872 in FIG. 4 and FIG. 9, the first ranked enrichment (from lowest to highest enrichment) would correspond to the upper left corner cell ‘A-1’ of 1.6 wt %, the second and third ranked enrichments would correspond to the edge cells ‘A-2’ and ‘B-1’, etc. Once the ranked list of rod locations has been determined, the following functions may be performed with respect to the lattice: 1) identify the rod location based on the ranked list, 2) replace the uranium enrichment and gadolinium in identified location with the top blanket (e.g., x-y map 26874 of FIG. 11) enrichment, 3) perform a core simulation, 3) evaluate the MSBWP reactivity margin output from the simulation, 4) advance to next element of the ranked list and repeat the process of simulation and evaluation until the MSBWP criteria is satisfied for all cell locations. Accordingly, as described above, an example embodiment is directed to a method of improving the energy generating output of a nuclear reactor containing one or more fuel rods in one or more fuel rod bundles, while satisfying a minimum subcritical bank withdrawal position (MSBWP) safety condition. In the method, rod enrichments at individual fuel rod locations in a axial cross-section of the bundle lattice at the top of the fuel bundle may be ranked, in order from lowest to highest enrichment. The fuel pins of the highest ranked rod location in the lattice may be replaced with pins containing natural uranium, and a core simulation may be performed in order to determine whether there is any margin to a MSBWP reactivity limit. The replacing and performing functions may be repeated for each lower ranked candidate rod position until no rod location violates the MSBWP reactivity limit, so as to achieve a desired lattice design for the top of the fuel bundle. A reactor core having the fuel bundle(s) configured with the desired lattice design at the top end thereof may then be loaded for eventual reactor operation. In an example, the fuel bundle includes a 6 inch natural uranium blanket lattice at the top inches of the fuel bundle, and the axial cross section of the fuel bundle lattice being evaluated is a 6-inch lattice segment cross-section of the bundle immediately below the top 6-inch blanket. In an example as described above, the lattice being evaluated may be between 138 to 144 inches from the bottom of the fuel bundle, i.e., the 24th node. The above systematic ranking, replacement and evaluation methodology was applied to certain lattice designs (see FIGS. 12-15) to determine the effect of the lattice design on the MSBWP limit as well as on other thermal and reactivity limits for a fuel cycle design. FIGS. 13-15 illustrate three different lattice designs at the node 24 location for comparison against the conventional full natural uranium blanket lattice design of FIG. 12. FIG. 12 is an x-y map distribution (e.g., 72017) of the lattice cross-section of a fuel rod bundle at a location between height=138 (or >138) to 144 inches, in which all rods of the fuel bundle at this axial location (node 24) have a natural uranium concentration of 0.71. All of the fuel bundle lattices in FIGS. 12-15 have the same fuel rod designs with the exception of the 24th node (138-144 inches in the axial position of the rods). In the alternative lattice designs, FIG. 13 is an x-y map distribution (e.g., 70017) of the lattice cross-section of a fuel rod bundle at a location between height=138 (or >138) to 144 inches, in which 33% of the bundle at node 24 is natural uranium, the remainder enriched uranium. FIG. 14 shows an x-y map distribution (e.g., 73017) of the lattice cross-section of a fuel rod bundle at a location between height=138 (or >138) to 144 inches, in which 24% of the bundle at this node 24 is natural uranium, with the remainder enriched uranium. FIG. 15 shows another x-y map distribution (e.g., 75017) of the lattice cross-section of a fuel rod bundle at a location between height=138 (or >138) to 144 inches, in which 0% of the bundle at this location is natural uranium; this represents a fully enriched uranium node. As will be seen by the data gathered from simulations of the lattice designs, the lattice designs of FIGS. 13-15 had a favorable impact on various thermal and reactivity parameters considered, as compared to the conventional full blanket case of FIG. 12. FIG. 16 is a graph of hot excess reactivity for the four fuel bundle lattice designs illustrated in FIGS. 12-15. FIG. 16 shows a plot of Delta-K (change in core average hot excess, or HOTX) versus cycle exposure in terms of mega watt days per short ton (MWd/ST) for four different fuel bundle lattice designs shown at node 24 (138-144″) in FIGS. 12-15. A change in Delta-K of 0.001 corresponds to a change of 100 MWd/ST. The simulation used was conducted based on the TGBLA code for generating nuclear cross sections and used the PANACEA core simulation software. The data used to plot the curves in FIG. 16 corresponds to the control blade 132 being between notch ‘2’ (144 inches) and notch ‘4’ (138 inches). Thus, there is shown delta HOTX curves corresponding to FIG. 12 (78 fuel rods natural (0.71 wt. % 235U) at node 24 except where noted by V (vacant) and water rods); FIG. 13 (26 rods natural, all others enriched at node 24 except as noted by V or water rods); FIG. 14 (19 rods natural, all other rods enriched at node 24 or otherwise V or water rods); and FIG. 15 (0 rods natural, this is the fully enriched bundle (0.71 wt. % 235U)) when placed between height=138 to 144. The impact on cycle energy can be seen by comparing the change in HOTX for the various lattices in FIGS. 12-15. As shown in FIG. 16, an increase in HOTX of greater than 0.03 Delta-K is possible with the alternative lattices designs in FIGS. 13-15, relative to the full blanket extension of FIG. 12, which may translate into several weeks of additional energy for the selected bundle design. FIG. 17 is a graph of cold shutdown margin (CSDM) for the four fuel bundles illustrated in FIGS. 12-15. FIG. 17 is a plot of Delta-K (change in CSDM versus cycle exposure in terms of mega watt days per short ton (MWd/ST) for the four different fuel bundles shown in FIGS. 12-15 (e.g., 72017; 70017; 73017; and 75017) when placed between height=138 to 144 inches corresponding to node 24, or between notch ‘2’ (144 inches) and notch ‘4’ (138 inches). The simulation used was based on the TGBLA code for generating nuclear cross sections and used the PANACEA core simulation software. As can be seen from FIG. 17, the impact on CSDM of using a partially-enriched or fully enriched bundle cross section at node 24 in the various lattices of FIGS. 13-15, as compared to the present case lattice design at node 24 in FIG. 12, is slight. The variation in CSDM shows a worst case variation of ±0.002 Delta-K over the cycle (for the x-y map distribution of FIG. 15). This represents a minimal impact on CSDM. FIG. 18 is a graph of MFLCPR impact on core loading for the four fuel bundle lattice designs illustrated in FIGS. 12-15. FIG. 18 shows a plot of Delta MFLCPR (change in maximum fraction of limiting critical power ratio) versus cycle exposure in terms of MWd/ST for the four different fuel bundle lattice designs of FIGS. 12-15 (e.g., 72017; 70017; 73017; and 75017) when placed between height=138 to 144 inches corresponding to notch ‘2’ (144 inches) and notch ‘4’ (138 inches). The simulation used was based on the TGBLA code for generating nuclear cross sections and used the PANACEA core simulation software. FIG. 18 actually shows improvement as to the margin available to the thermal parameter MFLCPR, as compared to the conventional lattice design at node 24 shown in FIG. 12. FIG. 18 shows an additional margin between 0.007 and 0.015 at the end of the cycle for the lattice designs in FIGS. 13-15. FIG. 19 is a graph of MFLPD impact on core loading for the four fuel bundle lattice designs illustrated in FIGS. 12-15. FIG. 19 shows a plot of cycle exposure in terms of MWd/ST versus Delta MFLPD (change in maximum fraction of limiting power density) for the four different fuel bundle lattice designs shown in FIGS. 12-15 (e.g., 72017; 70017; 73017; and 75017) when placed between height=138 to 144 inches corresponding to between notch ‘2’ (144 inches) and notch ‘4’ (138 inches). The simulation was based on the TGBLA code for generating nuclear cross sections and employed the PANACEA core simulation software. FIG. 19 also shows improvement as to the margin available to the thermal parameter MFLPD for the lattice designs in FIGS. 13-15, as compared to the conventional lattice design at the 24th node, as shown in FIG. 12. FIG. 19 shows an additional margin between about 0.018 and 0.029 at the end of the cycle for the lattice designs in FIGS. 13-15. FIG. 20 is a graph of impact on MSBWP for the four fuel bundle lattice designs illustrated in FIGS. 12-15. FIG. 20 shows a plot of Delta K (change in maximum subcritical banked withdrawal position (MSBWP)) versus cycle exposure in terms of MWd/ST for the four different fuel bundle lattice designs at node 24 in FIGS. 12-15 (e.g., 72017; 70017; 73017; and 75017) when placed between height=138 to 144 inches corresponding to between notch ‘2’ (144 inches) and notch ‘4’ (138 inches). The simulation was based on the TGBLA code for generating nuclear cross sections and used the PANACEA core simulation software. The impact on the MSBWP can be readily seen in FIG. 20 for various stages of the example design process. In FIG. 20, comparisons of the lattices in FIGS. 13-15 are made against the full blanket extension as shown in the lattice design of FIG. 12. For a required MSBWP reactivity margin, for example, set at −0.0325 Delta-K (see dashed line marking MSBWP in FIG. 20), relative to the full blanket extension, there exist many possible designs that satisfy MSBWP, with only a subset of fuel rods in a given lattice design at the top of the core (between 138 and 150 inches) having an extended blanket (12 inch blanket) versus all fuel rods having an extended 12 inch blanket at nodes 24 and 25. For example, when Delta-K is set at −0.0325 for MSBWP, enrichment of 235U at the 24th node (height=138 to 144 inches), the MSBWP safety condition is satisfied for the entire cycle by x-y maps 70017 (FIG. 13), 73017 (FIG. 14) and up to about 12000 cycles for the fully enriched map 75017 (FIG. 15) as indicated in FIG. 20. As in the other simulations for FIGS. 16-19, the control blades 132 are inserted up to notch=2 (all except the top six inches of the fuel rod(s)). In other words, variations of the top blanket between 138 to 144 inches (e.g., enrichment greater than the all natural uranium blanket shown in x-y map 72017 of FIG. 12) may be used to improve energy output, while still satisfying the MSBWP condition. Upon meeting the MSBWP criteria, a number of changes within the enrichment distribution of the second to top lattice (nodes 24 and 25) will have been made and identified. In contrast to the conventional art, this number of changes corresponds to a small subset of fuel rods within the blanket lattice, versus a wholesale change of all fuel rods within the lattice (i.e. a complete extension downward of the top axial blanket). Natural Uranium Blanket Determination-Top End of Bundle In light of the above, it is possible to determine the blanket at the top end of the bundle on a rod location-by-rod location basis. In an example, this may be done by comparing the rod enrichments in the 24th and/or 25th nodes to some threshold rod enrichment value. In an example, this enrichment may equal the enrichment of natural uranium (0.71). As an example, rod enrichments in all fuel rod locations in the bundle at an axial location that represents a cross-section of the top six inches of the bundle may be evaluated against the rod enrichment threshold. For those rod locations having an enrichment exceeding the rod enrichment concentration threshold, a 6-inch blanket of natural uranium may be provided. Those rod locations having an enrichment less than or equal to the rod enrichment concentration threshold would have a 12-inch segment of natural uranium therein; a 12-inch blanket. Since most of the low enrichment fuel rods are clustered in vicinity of the control blades 132, such a change would result in relatively small changes in thermal margins, exposure capabilities and HOTX results, while potentially having a dramatic effect on the results of calculations for the MSBWP limit. It follows that the example embodiments additionally provide a fuel bundle of a nuclear reactor that is configured to have a variable natural uranium blanket at a top end thereof. The fuel bundle may include a six-inch natural uranium blanket at a bottom end of the bundle. Selectable rod locations at an axial cross-section at a top end of the bundle having fuel rod enrichments which exceed a rod enrichment threshold value are provided with a six-inch natural uranium blanket therein. Those selectable rod locations in the axial cross-section having fuel rod enrichments which are less than or equal to the rod enrichment threshold value may be provided with a twelve-inch natural uranium blanket therein. As discussed above, each rod location is evaluated so as to satisfy a MSBWP reactivity limit within an acceptable margin thereto. The following additional example embodiment is also, provided, directed to a method for improving the energy generating output of a nuclear reactor containing one or more fuel rods in one or more fuel rod bundles while satisfying a safety condition. This example method may include (a) simulating the variation of enrichment in one or more fuel rods in one or more fuel rod bundles with fissionable material at a selected axial (vertical) region and a selected radial (horizontal) region of the fuel rod and fuel rod bundle; and (b) calculating if the safety condition is satisfied, Steps (a) and (b) can be repeated until the highest enrichment level of fissionable material (or substantially highest enrichment level) in one or more fuel rods in one or more fuel bundles is identified which still satisfies the safety condition. An indication of the highest enrichment level (or substantially highest enrichment level) that satisfies the safety condition can then be output to a user or designer. In the above noted additional embodiment, the fissionable material may be 235U or an equivalent thereof. Also, the safety condition may be the MSBWP safety condition. The selected axial region may be at a height between about 0 inches and 150 inches of the one or more fuel rods in the one or more fuel bundles. Other suitable axial regions may be at a height between 0 and 6 inches, between 138 and 144 inches and/or between 144 and 150 inches measured from the bottom of the fuel rod(s). According to another embodiment, the above-noted method may also include the step (e) of causing the one or more fuel rods in one or more fuel rod bundles to be enriched above natural (e.g., above about 0.71% by weight 235U) and up to and/or including the highest or substantially highest enrichment level identified in step (c) which satisfies the safety condition (e.g., MSBWP safety condition). The exemplary embodiments being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as departure from the exemplary embodiments, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the appended claims.
052767213	description	Referring now in detail to FIGS. 1 and 2 of the drawing as a whole, there are seen fuel rods 4 which are disposed at an inside or inner surface 3 of an upper end plate 2, are filled with nuclear fuel, and have longitudinal axes at right angles to the inner surface 3 of the upper grid plate 2. While ends of these fuel rods 4 are spaced apart from the inner surface 3, control rod guide tubes 5, which are parallel to the fuel rods 4, are firmly screwed to both the inner surface 3 of the upper end plate 2 and the inner surface of a non-illustrated lower end plate. At the lower end plate, the ends of the fuel rods 4 are likewise spaced apart from the inner surface of the lower end plate. The control rod guide tubes 5 are each guided through a hole or space in non-illustrated gridlike spacers, which are located between the two end plates and are form-lockingly secured to individual control rod guide tubes. A form-locking connection is one which connects two elements together due to the shape of the elements themselves, as opposed to a force-locking connection, which locks the elements together by force external to the elements. Each fuel rod 4 is likewise extended through one hole of the gridlike spacer and is retained force-lockingly inside this hole with the aid of compression springs. The upper end plate 2 is square in cross section, and one leaf spring 11 is assigned to each edge of an outside or outer surface 12 of the upper end plate 2. A leaf spring 11 of this kind is bent at an acute angle 13. A first leg 14 of the leaf spring 11 rests perpendicularly on the outer surface 12 of the end plate 2, where it loosely engages an elongated guide groove 15 in the outer surface 12. The longitudinal direction of this guide groove 15 is parallel to the edge of the outer surface 12 on which the leaf spring 11 is located. An end of a second leg 16 of the leaf spring 11 meets the outer surface 12 of the upper end plate 2 at an acute angle. This end of the second leg 16 is fastened between the outer surface 12 and an angle element 17 firmly screwed to the outer surface 12, and is thus rigidly retained. The two legs 14 and 16 define a plane that is parallel to the edge of the outer surface 12 on which the leaf spring 11 is located. This plane is also perpendicular to the outer surface 12. A supplementary leaf spring 21 is likewise bent at an acute angle 23 and is disposed between the two legs 14 and 16 of the leaf spring 11. One end 24 of the supplementary leaf spring 21 has a fork which fits loosely around the leg 14 of the leaf spring 11. Another end 26 of the supplementary leaf spring 21 is bent outward in hooklike fashion in the plane defined by the legs 14 and 16 and is reduced to the width of the leg 14 of the leaf spring 11. With this end 26 bent in hooklike fashion, the supplementary leaf spring loosely engages the elongated guide groove 15. In order to install the leaf spring 11, its first leg 14, which has a crosswise strut 14a on its end, is first inserted by that end into the guide groove 15 through an insertion bore 12a and moved away from the insertion bore 12a, so that the crosswise strut 14a fits behind a shoulder 15a that narrows the guide groove 15 at the top of the outer surface 12. The second leg 16 of the leaf spring 11 is then rigidly secured to the outer surface 12 of the upper end plate 2 by screwing the angle element 17 onto the outer surface 12. This produces prestressing of the spring 11. In order to install the supplementary leaf spring 21, it is prestressed by narrowing the distance between its two legs having the ends 24 and 26. This accordingly prestressed supplementary leaf spring 21 is then inserted between the leg 16 of the leaf spring 11 and the outer surface 12 of the upper end plate 2. Next, the two legs having the ends 24 and 26 are freed so that the end 26 which is curved in hooklike fashion locks into place between the shoulders 15a of the elongated guide groove 15, and the leg 14 of the leaf spring 11 locks into place inside the fork at the end 24 of the supplementary leaf spring 21. Arrows 30 symbolize forces with which an upper core grid plate in a nuclear reactor presses the fuel assembly against a lower core grid plate in the direction of the longitudinal axes of the fuel rods 4. Under the influence of these forces, the leg 14 of each of the four leaf springs 11 in the applicable guide groove 15 moves away from the end of the other leg 16 of the applicable leaf spring 11 that is rigidly secured to the outer surface 12, thereby increasing the prestressing of the applicable leaf spring 11. At the same time, there is a decrease in the spacing between the legs of the supplementary leaf springs 21 having the ends 24 and 26. As a result, these springs are prestressed as well and they act with their spring force parallel to the spring force of the leaf springs 11.
052079783	description	DESCRIPTION OF PREFERRED EMBODIMENT The reactor partially shown schematically in FIG. 1 has a general construction which is well-known at the present time and is, for instance, as disclosed in U.S. Pat. No. 4,092,216. It will therefore be described only. The core is formed of mutually juxtaposed fuel assemblies and contained in a pressure vessel 10 closed by a lid 12. A shroud 14, supported by the vessel, defines an annular space through which the coolant admitted by nozzles (not shown), flows down to the space formed under a lower plate carrying the core. The coolant then rises through the core and leaves it through passages formed in an upper core plate 16 belonging to the upper internals of the reactor. The internals also comprise a support plate 18, supported by the vessel, connected to the core plate by structural columns (not shown), and by guide devices 20, each for receiving a control cluster. The clusters are formed of a bundle of elongated elements containing neutron absorbent material, e.g., twenty-four in number suspended from a "spider" fixed to a drive shaft 22. Each device 20 comprises, between plates 16 and 18, a tubular casing 24, of approximately square section as shown and, above the support plate 18, an extension having a closure plate 25, formed with a hole for passage of the drive shaft 22 therethrough. Horizontal guide plates 26 are evenly spaced apart along casing 24. They are fixed to the casing by external projections of the plates engaged in slots of the casing 24, and generally by welding. Those plates 26 which are situated at the upper part of casing 24, six in number in the embodiment shown in FIG. 1, have an internal cut-out such that the plates guide the elements and leave the arms of the spider free to move. The elements are thus guided discontinuously, at intervals corresponding to the spacing between plates 26. The lower plates, four in number in the embodiment shown in FIG. 1, are connected together and to the foot 28 of casing 24 by continuous guide means, and are securely connected to the casing, for instance by welding. As shown in FIG. 3, the guide means are formed as split tubes 30, each intended to receive an element, such as the element shown at 32, and as sleeves 34 and 36 each guiding a pair of elements carried by a same arm of the spider. Openings 38, elongated in the vertical direction, are formed in casing 24 in the continuous guide zone. These openings 38 constitute a path for the coolant from the core into the manifold defined by plates 16 and 18 and by shroud 14; from there, the coolant flows out of the reactor through nozzles 40. Finally, the guide device comprises a frusto-conical guide 42 for centering the drive shaft 22, when lid 12 is being positioned on the vessel. In general, the pressures are not balanced across the closure plate 25, which causes a turbulent flow in the annular clearance, between the wall of the hole in the plate and shaft 22. This flow may be upward or downward. When it is upward, it forms a jet which, before being diffused, is subjected to a double reversal, as shown by arrows f on FIG. 6. The turbulence of such a flow causes considerable excitation of the shaft which is communicated to the elements by the spider. The guide device according to the invention, a specific construction of which is shown in FIG. 2, considerably reduces the wear phenomenon due to vibrations of the elements. The device of FIG. 2, where the elements corresponding to those of FIG. 1 have the same reference numbers to which the index A has been added, may often replace that of FIG. 1 in an existing reactor as a retrofit. Again, it comprises a casing 28a to which horizontal guide plates 26a are fixed. The four lower plates 26a and the foot 28a of the device are again connected together by continuous guide means, formed of tubes 30a, and sleeves 34a and 36a (top part of FIG. 3) which pass through the plates, and connected to casing 24a, for instance by welding. As shown in FIG. 2a, the openings 38a have an approximately rectangular shape and are placed just below those plates 26a which are in the continuous guide zone. Each opening 38a extends as far as the plate 26a placed above it. To better distribute the flow which leaves the core among the superposed openings 38a, the three uppermost plates of the continuous guide zone are preferably formed so that they offer a coolant cross-sectional flow area smaller than the cross-sectional area of the lowest plate. To this end, the internal periphery of the three upper plates may preferably have the cut-out shape shown in the upper half of FIG. 3, while the lowest plate keeps the usual cut-out shape shown in the lower half of FIG. 3. It can be seen that the flow cross-sectional area is reduced in the upper plates by extending the plate inwardly along four sleeves 34a, placed at 90.degree. from each other. As a result, flow occurs in a passage consisting of a central zone and four radially directed zones having a width which only slightly increases radially outwardly. In a modified embodiment, the plate may extend inwardly along all sleeves, for giving a substantially constant width to the radial zones. To reduce the coolant speed between the sleeves and the pressure fluctuations, the internal end of the sleeves, in the radial direction, is advantageously rounded as shown in FIG. 3. To generate a pressure differential which applies the elements against the tube wall, each split tube may have a wall without any orifice other than the slit. Sleeves 34a are without apertures in their upper portion, above the second plate, only three elongate apertures 44 (FIG. 5) being left. Sleeves 36a likewise have apertures 46 at their lower part only. These apertures may be completed by two sets of three aligned holes 48, in the low part of the sleeves and in the vicinity of the slit. All these arrangements significantly reduce the risks of vibrations caused by the flow along the elongated elements. To reduce the vibrations induced by the flow along drive shaft 22, apertures 50 each in the form of a slit are formed in conical guide 42 to upward flow coolant. The apertures 50 may be in the form of slits spaced evenly angularly apart, elongated in the longitudinal direction and formed at the top part of the guide. Thus, the upward flow takes place in the direction of arrows fa in FIG. 6. Sixteen apertures 50 may typically be used, only three of these being shown schematically in FIG. 6.
053902270	description	DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a major portion of the exposure apparatus according to an embodiment of the present invention, and it best shows the feature of this embodiment. A mask MSK includes a pattern SLN corresponding to the scribe line of the mask MSK, and a pattern PTN of a semiconductor device circuit to be printed on an unshown semiconductor wafer and, an alignment mark AMK on the scribe line pattern SLN. The apparatus includes an alignment unit AAU1 for projecting an alignment beam AMB onto the alignment mark AMK to detect the deviation between the alignment mark on an unshown wafer and the alignment mark AMK on the mask MSK, a supporting member SPT on which the alignment unit AAU1 is fixedly supported, a semiconductor laser accommodating portion LD which is a light source for the alignment beam AMB, and a photosensor accommodating portion SEN for accommodating a photosensor for converting an optical deviation signal from the alignment mark AMK to an electric signal. The alignment unit AAU1 includes a collimator lens, a beam splitter means, a light receiving lens or other optical element. A blade BLD1 functions to limit the irradiation area of the mask MSK by the exposure beam EXB supplied in the direction indicated by an arrow (Z axis direction). The blade BLD1 is in the form of a rectangular plate and is securedly fixed on the supporting member SPT through an arm ARM. The blade BLD1 is provided with pipes CLI and CLO for cooling function, and cooling passages are formed in the blade. The apparatus includes a stage unit STG constituted by guiding and driving means movable in two orthogonal axes (X and Y axes) and position detecting means. The supporting member SPT is coupled with the stage unit STG so that the alignment beam ABM is positioned on the alignment mark AMK of the mask MSK. In the apparatus, four of the above-described alignment units are provided, corresponding to the alignment marks AMK in the four scribed lines around the pattern PTN. Therefore, one exposure apparatus is provided with four blades (BLD1, BLD2, BLD3 and BLD4) and four alignment units (AAU1, AAU2, AAU3 and AAU4). In the following description, therefore, the reference character for the blade is "BLD", and that for the alignment unit is "AAU", unless a particular one of them is referred to. FIGS. 2(A) and 2(B) a relationship between the blade and the exposure beam of the apparatus of FIG. 1, as seen in the direction y. As shown, the exposure beam EXB is a divergent beam having a point of origin O and having a divergent angle .theta.. In this embodiment, the exposure beam is X-rays contained in synchrotron orbital radiation. The exposure beam EXB is confined or limited first by a fixed aperture stop FAP. The limited beam is indicated by a reference EXBF. In FIG. 2(A), l.sub.max indicates the maximum exposure angle range of view on the mask MSK. The size of the aperture of the fixed aperture stop FAP is determined so that the exposure beam EXBF irradiates slightly beyond the maximum exposure view angle, as shown by chain lines. The exposure beam EXBF having passed through the fixed aperture FAP is further confined or limited by the blade BLD fixed on the alignment unit AAU. FIG. 3 shows the arrangement of the blades BLD1-BLD4 on the alignment unit AAU, as seen from the light (radiation) source, that is, in the direction of the z axis. The adjacent blades, for example, the blade BL1 and the blade BL2 are at different levels (positions in the z axis direction), and therefore, they do not interfere with each other irrespective of the size of the view angle. The description will be made as to the relation between the size of the view angle and the blade mounting position in this structure. In FIG. 2(A) shows the state wherein a spot SPT formed by the alignment beam AMB accesses the scribe line in the case of the maximum view angle l.sub.max, and FIG. 2(B) shows a state wherein the spot SPT by the alignment beam AMB accesses the scribe line in the case of the minimum view angle l.sub.min. The respective blades are fixed to the associated alignment unit AAU so that the exposure beam is incident slightly beyond the outer edges of the scribe lines. In order to accomplish this, the blade is projected beyond the outer edge of the scribe line into the view angle range in a direction parallel to the X-Y plane, more particularly, in the X axis direction in this figure, by the amount d.sub.max in FIG. 2(A) and d.sub.min in FIG. 2(B). The amount d of the projection of the blade BLD, is EQU d=L.sub.A .times.(l/2L.sub.M) (1) where l is a size of the view angle in the X (Y) axis direction, L.sub.M is a distance from the point of origin O of the exposure beam having a divergence angle .theta. to the mask MSK measured in the Z axis direction; and L.sub.A is a distance from the edge ADG of the blade BLD to the mask MSK measured in the Z axis direction. Therefore, d.sub.max and d.sub.min are: EQU d.sub.max =L.sub.A .times.(l.sub.max /2L.sub.M) (2) EQU d.sub.min =L.sub.A .times.(l.sub.min /2L.sub.M) (3) If, for example, L.sub.A =150 mm, L.sub.M =50000 mm, l.sub.max =30 mm, l.sub.min =15 mm, then d.sub.max =0.45 mm, and d.sub.min =0.225 mm. In consideration of the blade function, it is preferable that the blade edge EDG provides a boundary between the exposure area and the non-exposure area, which is as close to the outer edge of the scribe line as possible. However, if the blade BLD is set in consideration only of the maximum view angle shown in FIG. 2(A), then the light blocking area extends into the view angle l.sub.min as shown in FIG. 4, in the case of the minimum view angle. Therefore, the required view angle cannot be obtained. Therefore, when the blade BLD is fixed to the alignment unit AAU, the blade is set to meet the minimum view angle l.sub.min, and the amount d of the projection is not more than EQU L.sub.A .times.l.sub.min /2.times.L.sub.M. By disposing the blade at such a position and by fixing the blade BLD on the alignment unit AAU, the blade BLD can be moved to a proper position in accordance with the view angle size without the necessity of employing the positioning means exclusively for the blade. Generally, the alignment between the alignment mark AMK and the alignment beam spot SPT is as accurate as not more than 10 microns, and therefore, the positioning of the blade BLD is automatically very high. It is possible for the blade BLD to block almost all of the exposure beam that is not desired to reach the mask MSK. Referring to FIGS. 5 and 6, the description will be made as to the cooling of the blade BLD. In FIG. 5, there are provided cooling water containers TNK1 and TNK2, which contain water maintained at 23.5.degree. C. and 10.degree. C., respectively. The cooling water delivered from the cooling water tank TNK1 is subjected to a heat exchanging operation by a heat exchanger TEX with the cooling water delivered from the cooling water container 2, so that the temperature of the cooling water from the container TNK1 is decreased to a temperature T.sub.B .degree.C. which is lower than 23.5.degree. C. It is then passed through the passage CLP in the blade BLD, and is returned to the container TNK1. The cooling water containers TNK1 and TNK2 are disposed at such a position as is sufficiently away from the unit wherein the alignment is performed, by which the alignment operation is not influenced by heat. Temperature sensors TSNI and TSNO are disposed adjacent to an inlet and outlet of the cooling passage in the blade BLD. The sensor may include a thin film resistance element of platinum or a thermistor. The outputs of the temperature sensor TSNI and TSNO are supplied to a controller CNT, and are used as data for controlling a degree of opening of a proportional controlling valve LNV. From the cooling water container TNK2, a constant rate of the cooling water is supplied, and the proportional control valve LNV controls a ratio of the rate of the cooling water flowing to a by-pass pipe BP and the rate flowing into the heat exchanger TEX, by which the temperature T.sub.B of the cooling water supplied into the passage of the blade BLD is controlled to be the set temperature by the controller CNT. The exposure operation will be described. Generally, the exposure beam is projected onto the mask MSK for a predetermined period of time controlled by a shutter or the like, and therefore, thermal energy is produced in the blade BLD as shown by a curve L1 in FIG. 6(A). For example, when the exposure period is 1 sec, and the energy absorbed by the blade BLD is 50 mJ, approximately 1.22 cc/sec of the water flows to suppress the temperature rise to be approximately 1/100.degree. C. by constant rate of the cooling water having the constant temperature of 23.degree. C. In view of the fact that the cooling is necessary only during the exposure operation, it is effective to decrease the temperature of the cooling water down to less than 23.degree. C. in timed relation with the exposure operation, as shown by a line L3 in FIG. 6(B). This is accomplished by the control of the controller CNT in timed relation with the exposure operation using the signal SIN from the main controller, as shown in FIG. 5. The energy absorbed by the blade BLD changes in accordance with the size of the view angle and the change in the intensity of the beam source. When, for example, a constant rate of the cooling water having the constant temperature of 23.degree. C. is supplied during the exposure operation, the temperature sensor TSNO produces a temperature change output as shown by a reference L2 in FIG. 6, and a control table for the proportional control valve ALV is made on the basis of the data. As described in the foregoing, according to this embodiment, even when the exposure beam is not reflected, as in the case of X-rays, and the exposure beam energy is converted into thermal energy in the blade BLD, the produced heat is transmitted outside the apparatus, using cooling water, and therefore, the heat transfer around the blade is suppressed, to enable the highly precise alignment of the blade to be accomplished. In this embodiment, the temperatures of the two cooling water systems are 23.5.degree. C. and 10.degree. C., but the present invention is not limited to those values. From the standpoint of suppressing the heat transfer from the blade BLD to the other member, the blade mounting portion may be made of low thermal conductivity material such as ceramic material, by which the temperature is more easily controlled. Referring to FIG. 7, another embodiment of the present invention will be described. This Figure shows the portion of the blade BLD having connectors for the cooling type in FIG. 1, as seen from the radiation source side. As contrasted to FIG. 1, a parallel link PLK for supporting the blade BLD for movement in the Y (X) axis direction and an inch worm INC are connected through a rod ROD to the back side of the blade BLD in series. The unit is mounted on the alignment unit AAU by four screws SCR. In the embodiment of FIG. 1 wherein an exposure beam having a divergence angle is used, an inside edge of the beam blocking area formed by an edge EDG of the blade BLD fixed on the alignment unit AAU approaches the outside edge of the scribe line, and therefore, the blade BLD on the alignment unit AAU is set to meet the minimum view angle l.sub.min for safety. In order for the distance between the inside edge of the beam blocking area provided by the edge EDG and the outside edge of the scribe line to be constant, the amount of projection of the blade is corrected in consideration of the equation (1). Using the dimensions of the FIG. 1 embodiment, that is, d.sub.min =0.225 mm, and d.sub.max =0.45 mm, the difference is 0.225 mm. This is a stroke required to be corrected in the amount of blade projection in consideration of the size of the view angle. In this embodiment, the actuator is constituted by the inch worm INC, and the guiding mechanism is constituted by a parallel link PLK, and therefore, sufficient stroke and accuracy required for the correction can be provided. In addition, the parallel link PLK does not have a scribing portion, and therefore, no particles are produced. The inch worm INC used for the actuator hardly produces heat after the positioning, so that it does not influence the other constituent elements. FIG. 8 shows another example of a mechanism for correcting the amount of projection of the blade. In this Figure, blade BLD is seen in the y direction. In this Figure, a reference BO designates a common rotational center of the blade BLD and the worm wheel WH. The blade edge EDG is rotatable about this center by operation of a small size motor MTR with a reduction mechanism. When, for example, the distance from the blade edge EDG to the rotational center BOl is 20 mm, and the stroke required for the correction is 0.225 mm (same as the above), a necessary stroke can be obtained by rotating the blade BLD by approximately .theta.=8.6.degree.. In this example, the amount of projection of the blade edge EDG relative to the exposure beam can be controlled without use of an expensive linear movement guide. As described in the foregoing, according to this embodiment, the means for detecting the deviation between the substrate and the original and the means for limiting the exposure beam are made integral, so that they are integrally positioned. This eliminates the necessity of positioning means exclusively for the exposure beam limiting means. Therefore, the size of the apparatus is reduced, and the reliability of the apparatus is improved. Furthermore, when the exposure beam limiting means is made integral with the deviation detecting means, the unnecessary irradiation area of the exposure beam projected on the original is minimized, and in addition, the beam blocking area does not extend into the pattern, for any size of the view angle, and therefore, the unnecessary energy absorbed by the original can be minimized. The exposure beam limiting means is provided with cooling means to externally transmit the exposure beam energy absorbed by the exposure beam limiting means, and therefore, the thermal deformation is prevented, thus improving the alignment accuracy and reducing the line width of the exposure pattern which can be produced by the apparatus. FIG. 9 shows the relationship between the blade BLD and the exposure beam EXB, and it is a schematic view as seen in the direction y. The exposure beam EXB is first limited by the fixed aperture stop FAP, so that the view angle is limited from l.sub.EXB to l.sub.EX. The limited exposure beam is indicated by a reference EXBF. The maximum exposure view angle of this apparatus is indicated by l.sub.max. The size of the aperture of the fixed aperture stop FAP is so determined that the limited exposure beam EXBF irradiates slightly beyond the maximum exposure view angle. The exposure beam EXBF having passed through the fixed aperture FAP is further limited by the blade BLD fixed on the alignment unit AAU. The further limited exposure beam is depicted by a reference EXDB. The size of the view angle of the further limited exposure beam EXBB is l.sub.EXBB on the mask MSK. FIGS. 11(A) and 11(B) show the relationship between the alignment mark and the blade. FIG. 11(A) is a top plan view as seen from the radiation source side; and FIG. 11(B) is a side view thereof. When the alignment unit AAU is placed at such a position that the alignment beam ABM accesses the alignment mark AMK in the scribe line SLN, the exposure beam EXBB is blocked by the blade edge EDG at a position slightly outside the outer edge of the scribe line SLN. The blade BLD is fixedly mounted on the alignment unit AAU in the manner described in the foregoing so as to satisfy this. In FIG. 11(A), a center of the alignment mark AMK in the scribe line SLN is within an area l.sub.STG. The blade BLD has a length l.sub.w measured along the edge EDG, that is, in the Y axis direction in this Figure, wherein the length l.sub.w is l.sub.max +l.sub.STG +.alpha., when the maximum exposure view angle is l.sub.max .times.l.sub.max. Also, the blade BLD has a length l.sub.B measured in the direction perpendicular to the edge EDG, that is, in the X axis direction in this Figure, wherein the length l.sub.B =(l.sub.EX -l.sub.min)/2+.alpha., where the minimum exposure view angle is l.sub.min .times.l.sub.min. A length .alpha. is determined in consideration of an assembly error, a positioning error and diffraction or the like. As an example, .alpha. is equal to approximately 1 mm. When the view angle changes in the structure described above, the scribe line SLN moves in the direction perpendicular to the blade edge EDG in accordance with the change of the view angle, and simultaneously, the alignment mark AMK on the scribe line also moves in the direction perpendicular to the blade edge EDG. FIG. 10(A) shows the position of the blade BLD at the time of the maximum exposure view angle l.sub.max ; and FIG. 10(B) shows the position of the blade BLD at the time of the minimum exposure view angle l.sub.min. As shown in this Figure, since the length l.sub.B is (l.sub.EX -l.sub.min)/2+.alpha., the edge EDG can block the exposure beam while maintaining the relationship between the alignment mark AMK and the exposure beam EXBB shown in FIG. 3, when the alignment unit AAU is moved, and the blade BLD is positioned in accordance with the size of the view angle. At the time of the minimum exposure view angle, an edge EDGB opposite from the edge EDG of the blade BLD does not extend into the view angle l.sub.EX .times.l.sub.EX defined by the fixed aperture FAP, so that the portion outside the exposure view angle is completely blocked. The description will be made as to the case where the position of the alignment mark AMK in the scribe line SLN changes along the scribe line SLN. When the position where the alignment mark AMK is formed moves along the scribe line SLN, the alignment unit AAU also moves in parallel with the scribe line SLN, and the blade BLD fixed integrally on the alignment unit AAU also moves, similarly to the blade BLD. FIGS. 12(A)-12(C) movement of the blade BLD fixed on the alignment unit AAU, in accordance with the position of the alignment mark AMK. The adjacent blades are placed at different levels, as shown in FIG. 1, to avoid interference therebetween. For the simplicity of explanation, only one blade BLD1 of the four blades is moved. In this Figure, the "solid triangle" indicates the central position of the alignment mark AMK. FIG. 12(A) shows the state wherein the alignment mark is at the leftmost position; 12(B) shows the state wherein it is generally at the center; and 12(C) shows the state wherein it is at the rightmost position. In those Figures, the exposure view angle is maximum. As described in the foregoing, the longitudinal dimension of the blade BLD1, measured in the X axis direction in this Figure, l.sub.w is l.sub.max +l.sub.STG +.alpha., and therefore, the four blades BLD1, BLD2, BLD3 and BLD4 establish a regular square having a length l.sub.max of the sides by the overlapping of the adjacent edges, irrespective of the position of the alignment mark at the maximum exposure view angle. On the basis of the relationship between the exposure beam EXDB and the scribe line SLN shown in FIG. 11, the exposure beam is limited. Since the exposure beam is limited properly at the time of the maximum exposure view angle, the exposure beam can be also properly limited when the exposure view angle is a regular square or another rectangular shape having a length of side which is not more than l.sub.max. The size l.sub.EX .times.l.sub.EX of the fixed aperture FAP is only slightly larger than the maximum exposure view angle l.sub.max .times.l.sub.max, and therefore, almost all of the unnecessary exposure beam is blocked by the fixed aperture FAP, and the region corresponding to the change of the view angle is blocked by the blades BLD fixed on the alignment unit AAU, the area of the blade BLD being minimized. When the exposure beam source produces X-rays, the radiation incident on the exposure beam limiting means is not reflected but is absorbed, and therefore, it is converted to thermal energy. However, according to this embodiment, almost all of the unnecessary portion of the exposure beam is absorbed by the fixed aperture FAP, and only a minimum amount of an unnecessary portion of the exposure beam is absorbed by the blade BLD fixed on the alignment unit AAU. Therefore, the heat production attributable to absorption of the X-rays adjacent to the alignment unit AAU wherein the spatial positions of optical elements therein have to be maintained accurately, can be minimized. As described in the foregoing, according to this embodiment, the area of the blade moved and positioned integrally with the alignment unit for limiting the exposure beam is minimized in consideration of the moving region of the alignment unit and the view angle. Therefore, the space around the alignment unit is enlarged for accommodation of other parts, while maintaining the sufficient exposure beam limiting function. 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.
	abstract	A neutron absorber system for a nuclear fuel storage rack includes a neutron absorber, which is adapted to attach to a plurality of cell walls of a cell of the nuclear fuel storage rack. The neutron absorber is adapted to elastically deform to cause the attaching. A system for inserting a neutron absorber into the nuclear fuel storage rack includes means for applying at least one stress to the neutron absorber and means for releasing the at least one stress to cause the neutron absorber to attach to the plurality of cell walls of the cell of the nuclear fuel storage rack.
039768880	abstract	Fissionable uranium formed into a foil is bombarded with thermal neutrons in the presence of deuterium-tritium gas. The resulting fission fragments impart energy to accelerate deuterium and tritium particles which in turn provide approximately 14 MeV neutrons by the reactions t(d,n).sup.4 He and d(t,n).sup.4 He.
055368964	description	The depicted apparatus comprises the following units and works in the following fashion. Solid waste is fed to a first pyrolysis reactor 1 of the gravity type via a feed 2. After pyrolysis of the solid waste in said reactor 1, the solid pyrolysis residue (ash) is drawn off via a screw 3 to a container 4, which optionally contains a compressing device for said residue. The gas formed during pyrolysis in reactor 1 is afterwards conducted via a ceramic filter 5 and a conduit 6 to a second pyrolysis reactor 7, where it is subjected to pyrolysis under the earlier stated conditions. In the depicted embodiment of the apparatus of the invention, a condenser 8 is additionally present, which is connected up as necessary if the gas contains tar products which need to be condensed out before pyrolysis reactor 7. In such a case, these tar products are drawn off from the condenser 8 via a withdrawal conduit 9. The gas pyrolysed in reactor 7 is conducted via conduit 10 to a reductant bed of carbon 11 where sulphur oxides present are reduced to hydrogen sulphide and carbon disulphide. The reduced gas from bed 11 is then transferred via conduit 12 to a bed 13 of sulphur-forming metal, e.g. iron. The metal sulphide formed can then be drawn off via conduit 14 from the bottom of said bed 13. If iron is used as a metal in the bed, this means that the withdrawn metal sulphide principally comprises pyrite. The depicted embodiment of the apparatus of the invention additionally comprises a burner 15 for the final oxidation or combustion of the exhaust gases and a pump 16, which in this embodiment is placed between bed 13 and burner 15 and which is intended to provide negative pressure in the apparatus.

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