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051851040	abstract	A method of treatment of a high-level radioactive waste comprising heating the radioactive waste at a high temperature of about 500.degree. to 3000.degree. C. to vaporize part of the elements contained in the radioactive waste, and cooling the resultant vapor to separately collect the elements. In one embodiment, the heating step is replaced by a reduction-heating step wherein heating is carried out in the presence of a reducing agent, e.g. hydrogen. In another embodiment, the heating step may be followed by the reduction-heating step.
056152450	claims	1. A monochromator for radiant X-rays comprising a first crystal which has a surface of incidence having a concave letter V-shaped groove and cooling means for flowing a cooling material behind the surface of incidence along the letter V-shaped groove, and a second crystal which has a letter V-shaped convex having a convex letter V-shape to fit the concave letter V-shaped groove. 2. A monochromator for radiant X-rays according to claim 1, wherein said first crystal and said second crystal are arranged in such a manner that the bottom portion of the concave letter V-shaped groove and the tip portion of the letter V-shaped convex are positioned on substantially the same line. 3. A monochromator for radiant X-rays according to claim 1, wherein the angle of the letter V in the letter V-shaped groove and the letter V-shaped convex is substantially 90 degrees. 4. A monochromator for radiant X-rays according to claim 1, wherein the cooling means extends from the bottom portion of said first crystal to a portion just under the bottom portion of the concave letter V-shaped groove, branches off from the portion just under the bottom portion in opposite directions, and extends behind a surface of incidence along the concave letter V-shaped groove. 5. A monochromator for radiant X-rays according to claim 1, wherein the cooling means includes a tubular member which is formed of material having pressure and heat resistance. 6. A monochromator for radiant X-rays according to claim 1, wherein the cooling means uses water and/or liquid metal as a cooling material. 7. A monochromator for radiant X-rays according to claim 6, wherein liquid gallium is used as the liquid metal. 8. A monochromator for radiant X-rays according to claim 1, wherein the cooling means provides a water jet.
	description	This application claims priority under 35 U.S.C. §119(e) from Provisional Application Ser. No. 61/645,117, entitled “Simplified Tubesheet Gripping Mechanism,” filed May 10, 2012. 1. Field This invention generally concerns robotic systems and is specifically concerned with an improved gripping mechanism for lightweight robotic systems for servicing heat exchanger tubes of a nuclear steam generator. 2. Related Art In a pressurized water nuclear power electric generating system, the heat generated by the nuclear reaction is absorbed by a primary coolant that circulates through the reactor core and is utilized to generate steam in a heat exchanger commonly referred to as a steam generator. The steam generator typically is an upright cylindrical pressure vessel with hemispherical end sections. A transverse plate called a tubesheet, located at the lower end of the cylindrical section, divides the steam generator into a primary side, which is the lower hemispherical section below the tubesheet, and a secondary side above the tubesheet. A vertical wall bisects the primary side into an inlet section and an outlet section. The tubesheet is a thick carbon steel plate with an array of thousands of holes into which are inserted the ends of U-shaped tubes. One end of each U-shaped tube is inserted into a hole within the tubesheet which communicates with the inlet section of the primary side and the other end is inserted in a hole within the tubesheet which communicates with the outlet section. The primary coolant is introduced under pressure into the inlet section of the primary side, circulates through the U-shaped tube and exits through the outlet section. Water introduced into the secondary side of the steam generator circulates around the U-shaped tubes and is transformed into steam by heat given up by the primary coolant. Typically, there are thousands of small diameter U-shaped tubes which provide a large surface area for heat transfer. The number of tubes in a steam generator range from about 4,000 to 15,000. Some steam generators utilize straight length tubes each about 60 feet long. Most of the steam generators are constructed of U-shaped tubing or long vertical sections with two 90° bends joined by a shorter horizontal length tubing. During plant operation, the high pressure water that flows through the reactor core transports some amount of radioactive particles through the steam generators and some particles become deposited on the interior surface of the tubes. After plant operation, the steam generators become a source of radiation. Occasionally, during the operation of the steam generator, degradation occurs in some of the tubes. This is undesirable because the primary coolant is radioactive and any leakage of the reactor coolant into the secondary side of the generator contaminates the steam. It is generally not practical, however, to replace degraded tubing, but instead the steam generator is periodically inspected and the affected tubes are plugged at both ends. In view of the thousands of tubes in the steam generator, plugging of a few tubes does not appreciably affect the efficiency of the heat transfer. Because of the radiation hazard present in steam generators used in a nuclear power utility, the heat exchanger tubes of such steam generators must be, for the most part, remotely serviced to avoid exposing maintenance personnel to potentially harmful radiation. Consequently, a number of robotic systems have been developed for remotely performing repair and maintenance operations on these heat exchanger tubes. These robotic systems typically include some sort of robotic delivery arm in combination with any one of a number of specialized tools designed to be carried by the robotic arm, which are known in the art as “end effectors.” Some of the common robotic systems for this task utilize the holes in the tubesheet to anchor the robot via number of camlocks (typically four or more), for example, as shown in U.S. Pat. No. 7,314,343, assigned to the Assignee of this invention. Each charlock consists of a cylindrical arrangement of flexible “fingers” that protrude into a single tube and are expanded by a central cam actuated to engage the tube inner diameter surface. They thereby achieve anchoring from the resulting frictional force of the fingers on the tube inside diameter. This anchoring method is effective, but the problems are that the camlocks are costly, complex devices and they may release unexpectedly if the actuation force is lost. Accordingly, it is an object of this invention to provide a simpler gripper capable of anchoring a robot to the underside of a tubesheet without the use of camlocks. It is a further object of this invention to provide a single mechanism that provides both anchoring and rotational alignment. It is an additional object of this invention to provide such a mechanism that supplies a very high gripping force through a mechanical advantage. It is a further object of this invention to provide such a mechanism that automatically locks in place and requires no actuation force to stay locked. It is a further object of this invention to provide such a mechanism that can release and re-grip very quickly. It is an additional object of this invention to provide such a mechanism that is self-aligning and provides accurate locating. These and other objects are achieved by a tool having an actuator for gripping a tubesheet of a heat exchanger having a plurality of heat exchange tubes extending at least partially through thru-holes in the tubesheet, with each of the heat exchange tubes having a central axis extending along a length thereof. The actuator includes a first elongated finger sized to have a first end of the first elongated finger inserted at least partially within a first of the thru-holes within the tubesheet. A second elongated finger is sized to have a first end of the second elongated finger inserted at least partially within a second of the thru-holes in the tubesheet. The second elongated finger is spaced from the first elongated finger to substantially align with the second of the thru-holes when the first elongated finger is substantially aligned with the first of the thru-holes. A tie rod is connected between the first elongated finger and the second elongated finger at a first elevation along the first elongated finger and the second elongated finger that is spaced from the first ends. The connection of the tie rod between the first elongated finger and the second elongated finger is configured to restrain movement at the first elevation of the first elongated finger and the second elongated finger in at least a first of two lateral directions, either toward each other or away from each other. The actuator also includes an actuation arm connected between the first elongated finger and the second elongated finger at a second elevation along the first elongated finger and the second elongated finger that is spaced from the first elevation and spaced from the first ends. The connection of the actuation arm between the first elongated finger and the second elongated finger is configured to move the first elongated finger in at least one of two lateral directions and cant at least one of the first elongated finger and second elongated finger relative to the axis of a corresponding tube or through a hole in which it is designed to be inserted to pressure the one of the first elongated finger and the second elongated finger against an inner wall of the corresponding tube or through a hole and hold that position until the actuation arm is positively released. In one embodiment, the actuation arm cants both the first elongated finger and the second elongated finger relative to the axis of the corresponding tube or thru-hole in which it is designed to be inserted to pressure the first elongated finger and the second elongated finger against the corresponding tube in which it is inserted. Preferably, the actuation arm toggles between a locked position in which at least one of the first elongated finger and the second elongated finger is canted relative to the axis of the corresponding tube or thru-hole in which it is designed to be inserted and an unlocked position in which the first elongated finger and the second elongated finger are not pressured against the inner wall of the corresponding tube or thru-hole. In another embodiment, both the first elongated finger and the second elongated finger are pressured against the inner wall of the corresponding tube or thru-hole when the actuation arm moves in the at least one of the two lateral directions. In still another embodiment wherein the first elevation is between the first ends and the second elevation, the tie rod restrains movement of the first elongated finger and the second elongated finger towards each other. In an alternate embodiment, the tie rod restrains movement of the first elongated finger and the second elongated finger away from each other. In an additional embodiment, the second elevation is between the first ends and the first elevation and the tie rod restrains movement of the first elongated finger and the second elongated finger towards each other. Alternately, the tie rod restrains movement of the first elongated finger and the second elongated finger away from each other. In a further embodiment the first elongated finger and the second elongated finger are configured to move a distance vertically independent of the actuation arm. Preferably, the actuation arm includes a compensator that is configured to accommodate a variation in spacing of the thru-holes while maintaining an approximately constant clamping force. The compensator may be an air spring, for example. The invention also contemplates a method of supporting a tool from the underside of a heat exchange tubesheet having a plurality of openings extending through an underside. The method includes the step of inserting a portion of a first finger into a first opening in the underside of the tubesheet and inserting a portion of a second finger into a second opening in the underside of the tubesheet. The method leverages the first finger off the second finger to clamp at least a part of the portion of either the first finger or the second finger that is inserted into the corresponding opening against a wall of the opening and locks the first finger and the second finger in their clamped position. In one embodiment the method leverages both the first finger and the second finger against the wall of the corresponding opening. Preferably the leveraging step cants either the first finger or the second finger or both relative to an axis of the corresponding opening in which it is inserted. The method also includes the step of suspending the tool from the first and second finger. The method may also include the step of moving the first finger and the second finger in a vertical direction independent of a mechanism for performing the leveraging step. Further, the method may additionally include the step of compensating for a variation in the distance between openings in the underside of the tubesheet while substantially maintaining a constant clamping force. Occasionally it is necessary to inspect steam generator tubes for surface and volume flaws by using a robot that can position an inspection probe within the tubes to be inspected and support the equipment employed to facilitate the probe's travel through the tube. The invention claimed hereafter and the embodiments thereof described herein provide a simplified anchor for supporting such a robot from the underside of the tubesheet. Referring to FIG. 1, a steam generator is referred to generally by reference character 10 and comprises a generally cylindrical outer shell 12 having a cylindrical upper portion 14 and a cylindrical lower portion 16. Disposed in the upper portion 14 is moisture separating means 18 for separating a steam-water mixture so that entrained water is removed from the steam-water mixture. Disposed in lower portion 16 is an inner shell 20 which is closed at its top end except for a plurality of openings disposed in its top end for allowing passage of the steam-water mixture from the inner shell 20 to the moisture separating means 18. Inner shell 20 is open at its bottom end, which inner shell 20 defines an annulus 21 between the inner shell 20 and the lower portion 16 of the outer shell 12. Disposed in the inner shell 20 is a vertical steam generator tube bundle 22 having a plurality of vertical, U-shaped steam generator tubes 24 therein. Disposed at various locations along the length of the tube bundle 22 are a plurality of horizontal circular tube support plates 26, having holes therein for receiving each tube of the tube bundle 22, for laterally supporting the tubes and for reducing flow-induced vibration in the tubes. Additional support for the tubes in the tube bundle 22 is provided in the U-bend region of the tube bundle 22 by a plurality of anti-vibration bars 28. Still referring to FIG. 1, disposed in a lower portion 16 of the outer shell 12, below a bottom most support plate 52 is a horizontal, circular tubesheet 30 having a plurality of vertical apertures 32 therethrough for receiving the ends of the tubes of the tube bundle 22, which ends of the tubes extend a predetermined distance through the apertures 32. Tubesheet 30 is sealingly attached, which may be by welding, around a circumferential edge to a hemispherical channel head 34. Disposed in channel head 34 is a vertical, semi-circular divider plate 36 sealingly attached, which may be by welding, to the channel head 34 along the circumferential edge of the divider plate 36. Divider plate 36 is also sealingly attached, which may be by welding, to tubesheet 30 along the flat edge of the divider plate 36. Divider plate 36 divides the channel head 34 into an inlet plenum chamber 38 and an outlet plenum chamber 40. Referring again to FIG. 1, disposed on the outer shell 12 below the tubesheet 30 are a first inlet nozzle 42 and a first outlet nozzle 44 in fluid communication with inlet plenum 38 and with outlet plenum chamber 40, respectively. A plurality of manway holes 46 are disposed on the outer shell 12 below the tubesheet 30 for providing access to the inlet plenum chamber 38 and outlet plenum chamber 40. Disposed on the outer shell 12 above the tube bundle 22 is a second inlet nozzle 48, which is connected to a perforated horizontal and generally toroidal feedwater ring 50 disposed in the upper portion 14 of the outer shell 12 for allowing entry of nonradioactive secondary fluid or feedwater into the upper portion 14 through inlet nozzle 48 and through the perforations (not shown) of feedwater ring 50. A second outlet nozzle 54 is disposed on top of the upper portion 14 for exit of steam from the steam generator 10. During operation of the steam generator 10, radioactive primary fluid from the reactor, which may obtain a temperature of approximately 620° F. (327° C.) enters inlet plenum 38 through first inlet nozzle 42 and flows through the tube bundle 22 to the outlet plenum 40 where the primary fluid exits the steam generator 10 through the first outlet nozzle 44. The secondary fluid, which is water, enters the feedwater ring 50 through the second inlet nozzle 48 which is connected to the feedwater ring 50 and flows downwardly from the perforations (not shown) of the feedwater ring 50 through the annulus 21 until the secondary fluid is in fluid communication with the tubesheet 30. The secondary fluid then leaves annulus 21 flowing upwardly by natural convection through the tube bundle 22 where the secondary fluid boils and vaporizes into a steam-water mixture due to conductive heat transfer from the primary fluid to the secondary fluid through the walls of the tube bundle 22 which functions as heat conductors. The steam-water mixture flows upwardly from the tube bundle 22 and is separated by moisture separating means 18 into saturated water and dry saturated steam which may obtain a minimal quality of approximately 99.75%. The saturated water flows downwardly from the moisture separating means 18 and mixes with the secondary fluid. Thus, as the secondary fluid enters second inlet nozzle 48 dry saturated steam exits steam generator 10 through the steam outlet nozzle 54. In a manner well known in the art, the dry saturated steam is ultimately transported to perform useful work such as drive turbine generators for the production of electricity. Moreover, as previously mentioned, in a nuclear reactor, the primary fluid is radioactive; therefore, steam generator 10 is designed such that the primary fluid is nowhere in direct communication with the secondary fluid in order that the nonradioactive secondary fluid is not radioactively contaminated by intermixing with the radioactive primary fluid. Occasionally, due to tube wall defects or tube wall cracking caused by stress and corrosion, some tubes within the tube bundle 22, for example, a suspect steam generator tube (see FIG. 2), may develop surface and volume flaws and thus may not remain leak tight. Therefore, it is customary to inspect the steam generator tubes such as tube 56 to detect the location and extent of flaws or irregularities so that corrective action may be taken, preferably before a leak develops. A determination of whether tube 56 has flaws or irregularities sufficient to require corrective action may be obtained by examining tube 56 using a nondestructive examination scanning device (not shown). Naturally, the scanning device should be suitably moved without slip or creep along the inside surface of the tube 56 so that the tube may be thoroughly scanned for flaws or irregularities. Referring now to FIG. 2, there is illustrated a probe carrier drive assembly, generally referred to by reference character 58, for suitably moving a probe carrier 60 in the tube 56. As previously mentioned, a robotic arm 62 supported from two or more of the tubesheet holes 32 with the aid of camlocks has been employed to support the drive assembly 58 during this process. This invention, as claimed hereafter, several embodiments of which will be described herein, provides a single simplified mechanism for supporting such a robot on the underside of the tubesheet that provides lockable anchoring with rotational stability that would require at least two of the prior art camlocks. One preferred embodiment is shown in FIG. 3. Instead of engaging a single tube hole with the camlock as in the prior art, this mechanism engages two separate tube holes 64 and 66 spaced one or more pitches apart. When the linkage mechanism 68 is actuated it spreads first and second gripper fingers 70 and 72 and engages one surface of each tube 64 and 66 (or corresponding hole where the tubes do not fully penetrate the hole) inside diameter. Due to the geometry, the finger engagement will align the mechanism with the two holes, 64 and 66, thereby providing a fixed rotational reference, and will provide an anchoring force by way of friction with the tube inside diameter surface. The linkage mechanism 68 provides a significant mechanical advantage such that the engagement force is much larger than the actuation force, and with proper dimensioning and compliance, the linkage will toggle into a locked position such that the mechanism will stay gripped even after the actuation force is removed. As can be seen in FIG. 3, the fingers 70 and 72 have a first end 74 and 76 that are inserted at least partially within the tubesheet openings of heat exchange tubes 64 and 66. The distal ends of the fingers 70 and 72 are restrained against laterally moving outward by a tie bar or rod 78 which extends through an opening 80 and 82, respectively, in the distal ends of the fingers 70 and 72 and is captured by an enlarged end or nut 96 at either end. Preferably, the tie rod loosely fits through the openings 80 and 82 or the tie bar or rods 78 is flexible so that the fingers 70 and 72 can cant (slant) against the side walls of the openings in the tubes 64 and 66 when the actuation arm 68 is activated to the horizontal position in which it is locked. The robotic arm 62 that supports the tool (shown in FIG. 2) can be supported from either finger 70, 72 or the tie rod 78. The actuation arm is mainly formed by the two links 84 and 86 which are connected at the center by a pivot pin 92 and at the ends by pivot brackets 88 and 90. An actuation grip 94 is provided that can be accessed using a remote tool, such as a pole, which is manipulated from outside of one of the manways 46. FIG. 4 shows an alternate embodiment in which the actuation linkages 84, 86 of the actuation arm 68 are arranged as tension members. As explained with regard to FIG. 3, the mechanism is self-aligning with the holes, has significant mechanical advantage in gripping force, and is capable of toggling into a locked state. Like reference characters are used to identify corresponding components among the various figures. In this embodiment, the ends of the tie rods 78 are screwed into openings 80 and 82 in the distal ends of the fingers 70 and 72. The linkages 84 and 86 on the actuation arm 68 extend through openings 98, 100, respectively, in the fingers 70 and 72. The distal ends of the linkages 84 and 86 are captured by nuts 102, 104 on the other side of the openings 98 and 100. Thus, when the actuation disk 106 is rotated in the counterclockwise direction, the linkages 84 and 86 will be placed in tension drawing the fingers 70 and 72 towards each other and bracing the distal ends 74 and 76 against the inner walls of the tube openings 64 and 66. It should be appreciated that a similar result could be obtained by attaching the distal ends of the linkages 84 and 86 directly to the inside surfaces of the fingers 70 and 72 as was done in the embodiment illustrated in FIG. 3 and the actuation disk rotated in a clockwise direction to place the linkages 84 and 86 in compression and cant the ends 74 and 76 of the fingers 70 and 72 outward against the walls of the openings 64 and 66. FIGS. 5 and 6 show other embodiments in which the fulcrum (tie rod 78) is moved to the upper position and the fingers 70 and 72 are operated as levers from actuation linkages 84, 86 at the bottom or distal ends of the fingers, arranged as either compression or tension members. As before, the mechanism is self-aligning with the tube holes, has a significant mechanical advantage in applying the gripping force, and is capable of toggling into a locked state. It should be appreciated that a variety of support structures can house this mechanism and be supported from the tubesheet to perform any number of mechanical tasks such as inspecting the heat exchange tubes, plugging the ends of the tubes, rolling the ends of the tubes, welding tube sections, etc. In addition, if the connections to the fingers 70, 72 are slotted it will be possible to slide the fingers vertically into and out of the tubesheet when the mechanism is not actively gripped, thus providing a way to disengage the mechanism from the tubesheet, i.e., one or both of the tie rod and the actuation arm being connected to the fingers loosely through slots. An example of the latter arrangement is shown in FIG. 7. FIG. 7 shows still another embodiment of this invention that includes two additional features not included in the above embodiments. The first additional feature provides clearance slots 108, and 110, respectively in the fingers 72 and 70, that permit the fingers to move vertically, relative to one or both of the tie rod 78 and the actuation links 84 and 86, into or out of the tubesheet 30. This enables the tie rod 78 and/or the activation linkages 84, 86, to be separately supported while the fingers move into the tubes in the tubesheet 30 prior to gripping or out of the tubesheet after gripping. The second feature includes an air spring 120 between the primary cam lever 116 and the clamping lever 118 to accommodate dimensional variations. In the embodiment shown in FIG. 7 the two fingers 70 and 72 can be lifted into the tubesheet 30 using the common bar 130, while the tie rod 78 and actuation links 84 and 86 are separately supported, such as by a robot 62. The fingers 70 and 72 can be moved vertically by a pneumatic or hydraulic cylinder 136. As the fingers 70 and 72 are raised or lowered, the slots 110 and 108 move over the actuation linkages 84 and 86, respectively. The linkages 84 and 86 are provided with notches 126 which are captured within the slots 110 and 108 by the enlarged ends 112 and 114 of the linkages 84 and 86, i.e., as compared to the notches 126. Similarly the tie rod 78 may ride in similar slots, though it is not necessary unless the tie rod 78 and the linkages 84 and 86 are supported together, for example by the back plate 148. Alternately, the actuation linkages 84 and 86 can be provided with openings in their ends through which notches in the finger pass and move vertically in a similar manner. Alternately, in this latter embodiment, the actuation linkages 84 and 86 can be flat bars with clearance holes towards the peripheral ends of the bars for the passage of the fingers. In this embodiment the lower tie rod 78 is optional as the common lift bar 130, used to raise and lower the fingers, may also be used to restrain the bottom of the fingers. The actuation mechanism 68 comprises a cam and a series of interconnected actuation linkages. The actuation linkages 116 and 118 are connected to the back plate 148 respectively with pivot couplings 138 and 140 and the cam is connected to the back plate 148 with rotatable coupling 142. A pin 132 protrudes from the surface of the cam and rides against the curve surface of the hook 134 at the lower end of the actuation linkage 116, over at least of portion of the travel of the cam. The actuation linkage 116 is connected to one end of the actuation link 118 through an air spring 120 which is pivotally connected at its ends respectively to an intermediate segment of actuation link 116 and one end of actuation link 118. Actuation link 84 is pivotally coupled to an intermediate segment of actuation link 118 through bracket 124 which is rigidly attached to actuation link 84. Similarly actuation link 86 is pivotally coupled to an end portion of actuation link 118 through bracket 122 which is rigidly connected to actuation link 86. Once the fingers are in the up position inside the appropriate tubesheet tubes, rotating the cam pushes the actuation linkage lever 116 to compress the air spring 120, in turn moving the actuation link clamp lever 118 to inwardly tilt the ends 74 and 76 of the fingers 70 and 72 to engage the side walls of the tubesheet tubes 64 and 66. As the cam 106 continues motion in a clockwise direction it compresses the air spring 120 thus providing the clamping action. The cam 106 rotation continues until it reaches the curved hook 134 on the actuation lever arm 116 at which point the geometry causes a detent to occur (i.e., the cam cannot be back driven by the air spring). The use of the air spring 120 allows the clamping mechanism to accommodate small dimensional variations in the tube spacing while achieving a nearly constant clamping force. It should be appreciated that the fingers need not have a round cross-section and two contact points provide better self-alignment with the tubesheet openings. In addition, the tips of the fingers 70, 72 may be provided with elastomeric sheaths 150 (shown in FIG. 7) to protect the heat exchange tubes. While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular embodiments disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the appended claims and any and all equivalents thereof.
044477333	summary	CROSS REFERENCE TO RELATED APPLICATIONS The present application is related to our application Ser. No. 243,627 filed Mar. 13, 1981 as well as to the commonly assigned copending application Ser. No. 243,562 filed Mar. 13, 1981 by two of the present joint inventors and which is in turn related to an application Ser. No. 120,108 filed Feb. 8, 1980 (now U.S. Pat. No. 4,274,007), Ser. No. 966,951 filed Dec. 6, 1978 (now U.S. Pat. No. 4,278,892) and Ser. No. 940,856 of Sept. 8, 1978 (now U.S. Pat. No. 4,272,683). Certain of these applications were copending with application Ser. No. 940,098 corresponding to U.S. Pat. No. 4,234,798 and Ser. No. 107,276 filed Sept. 26, 1979 (now U.S. Pat. No. 4,288,698). Still earlier related applications culminated in U.S. Pat. Nos. 4,229,316 and 4,235,739 which are also considered material to the present application. For the construction of radiation-shieldng transport and storage containers, for details as to the radiation-shielding properties thereof and for the use of such vessels, these commonly owned prior applications and patents are hereby incorporated by reference in their entirety and it is noted that the prior art known to applicants to be the most relevant is the prior art represented by these patents to the extent that they are prior art, and the art of record of said applications. FIELD OF THE INVENTION Our present invention relates to radiation-shielding transport and storage containers and, more particularly, to containers for the transport and storage of radioactive materials which are capable of absorbing radiation from the packaged material and hence prevent significant escape of radiation into the environment. The invention also relates to an improved method of packaging such material. BACKGROUND OF THE INVENTION From the aforementioned patents and the art mentioned therein it is known to provide for the transport and storage of radioactive wastes, containers or vessels of radiation-shielding material and which may be provided with channels or compartments to contain radiation-blocking and radiant-energy-attenuating material and with ribs or the like to promote heat exchange with ambient air. Radioactive material can be placed in such containers and sealed by cover arrangements including a shielding cover which can have a plug configuration, i.e. which is comparatively massive so that it functions as a radiation-absorbing wall, the seal between this cover and the vessel being labyrinth or multiple seal having sealing rings between surfaces which are stepped or at angles to one another to minimize the probability that a radio nucleide particle can pass between the cover and the vessel and thereby escape. The vessel can have a mouth formed with a recessed seat receiving the plug-type inner cover which can have a frustoconical portion and a cylindrical portion fitting into correspondingly shaped parts of the seat and sealed relative to the latter with elastomeric seals, generally O-rings. Above this inner cover, an outer cover was mounted on the vessel as a protective member. Seals could be provided between this outer cover and the vessel as well and an important feature in the packaging of the radioactive material was the including of a control gas whose composition could be monitored or "sniffed" to verify the security of the seals. Between the outer cover and the inner cover, therefore, a control space was provided and this space was monitored to detect the stability of the seal. Both the vessel and the plug-type cover can be composed of cast iron, especially spherolytic cast iron or cast steel and the plug-type cover can be sealed to the vessel with an inner seal which can be of the single-stage or multiple-stage type. The safety cover, which is disposed above the shielding cover and defines a control-gas compartment therewith, is formed with the outer seal and can be overlain by a further protective cover, if desired. While packaging of the afordescribed type has proved to be effective for the transportation and long term storage of radioactive waste, monitoring of the integrity of the package, i.e. the integrity of the seals, has required monitoring of the presence in the control-gas compartment of radioactive species whose presence can signal a defect in the inner seal. Repair of the system, by removal of the outer cover, removal of the safety cover, and resealing the plug-type cover may result in release of any radioactive components in the control space between the safety cover and the plug-type cover. Furthermore, the detection of a failure is effected by analytical means requiring sniffing with sensitive species-discriminating detectors which may not always be reliable. Earlier techniques did not adequately signal a failure of the outer seal, i.e. the seal between the atmosphere and the control space. OBJECTS OF THE INVENTION It is the principal object of the present invention to provide an improved radiation-shield transport and storage container whereby the disadvantages described above are eliminated and, especially, the integrity of the seals can be maintained with less danger of release of radioactive species into the environment, with greater reliability and with the capacity to discriminate between failure of the outer seal or the inner seal. Another object of this invention is to provide an improved method of packaging radioactive wastes so that a failure or defect in the inner seal can be detected long before radioactive gases or vagabond radioactive species or gas containing same can enter the control space or the gas barrier compartment between the plug-type cover and the safety cover. SUMMARY OF THE INVENTION These objects and others which will become apparent hereinafter are obtained in accordance with the present invention in a container of the aforedescribed type, i.e. comprising a thick-wall vessel of spherolytic cast iron or cast steel, a plug-type absorption cover recessed in the mass of this vessel and provided with a multiple seal thereagainst, the multiple seal forming an inner seal and a safety cover fitted into the vessel and sealed thereagainst by the outer seal whereby the safety cover defines a control space with the plug-type seal. According to the invention, the control gas in the control or barrier space is sealed in the latter with a pressure significantly greater than the pressure in the storage compartment of the vessel and greater than atmospheric pressure, the container being provided with a monitoring device which responds to a pressure drop in the control gas in this compartment below a particular determined threshold value. When the storage chamber of the vessel is at a pressure of 0.8 to 1.5 bar, the control gas can be provided with pressure of 6 bar. Under these conditions the failure of the inner seal will result in the induction of control gas through the failed seal into the interior of the vessel from the control space. This is because the pressure in this space is higher than that in the vessel and the volume of the control space is small by comparison to the volume in the vessel. As a consequence the pressure in the control space will drop sharply and this drop in pressure can signal an alert. Of course, a pressure drop to atmospheric pressure will signal a failure of the outer seal as well. Naturally, the compartment can be "sniffed", (i.e. subjected to gas analysis by a species-sensitive detector) upon the detection of such a pressure drop to facilitate determination of whether it is the inner seal or the outer seal which has become defective. If an inner seal failure is detected, an additional cover can be applied so that the previous outer barrier then forms an inner barrier while the additional cover provides an outer barrier. A failure of the outer seal is extraordinary but is readily repaired by removal of the outer cover and the sealing cover and replacement of the sealing elements. Any release of radioactive material into the environment will be minimum because of the small size of the barrier compartment.
	claims	1. A shield for protecting a tool portion having an irradiance damage threshold from high-irradiance radiation from a light source when irradiating a workpiece, said shield arranged between the light source and the tool portion and having an irradiance damage threshold, an absorption coefficient, a volume and a thickness, and designed to absorb in said volume, a portion of said high-irradiance radiation that would otherwise be incident the tool portion, wherein the shield maintains said absorbed high-irradiance radiation below said shield irradiance damage threshold, and wherein radiation exiting the shield and incident the tool portion has an irradiance below the irradiance damage threshold of the tool portion. 2. A shield according to claim 1 , wherein said shield is arranged between the workpiece and the tool portion. claim 1 3. A shield according to claim 1 , wherein said shield is made of a partially transmitting glass. claim 1 4. A shield having an irradiance damage threshold I DT for protecting a tool portion from damage due to high-irradiance radiation I R from a light source when irradiating a workpiece, said shield arranged between the light source and the tool portion and having a volume damage threshold I DS , an absorption coefficient a, and a thickness t such that an irradiance I ABS absorbed by said shield from said high-irradiance radiation I R that would otherwise be incident the tool portion satisfies the condition: I ABS =I R a (1xe2x88x92exp(xe2x88x92at)) less than I DS , and wherein radiation exiting the shield and incident the tool portion has an irradiance I T which satisfies the condition: I T =I R (exp(xe2x88x92at)) less than I DT . 5. A shield according to claim 4 , wherein said shield is arranged between the workpiece and the tool portion. claim 4 6. An apparatus that prevents a tool portion having an irradiance damage threshold from being irradiated by high-irradiance radiation from a light source while irradiating a workpiece, the apparatus comprising: a workpiece support member for supporting a workpiece; and the shield according to claim 1 arranged between the light source and the tool portion. claim 1 7. An apparatus that prevents a tool portion having an irradiance damage threshold I DT from being irradiated by high-irradiance radiation of irradiance I R from a light source while irradiating a workpiece, the apparatus comprising: a workpiece support member for supporting a workpiece; and the shield according to claim 3 arranged between the light source and the tool portion. claim 3 8. A workpiece support member for supporting a workpiece having a workpiece outer edge, the workpiece support member being capable of protecting a tool portion having an irradiance damage threshold from high-irradiance radiation while irradiating the workpiece, the workpiece support member comprising: a body with an outer surface and an upper surface with an outer edge, said upper surface capable of supporting the workpiece so that the workpiece outer edge extends beyond said workpiece support member outer edge; and the shield according to claim 1 arranged between the workpiece and the tool portion around said outer surface. claim 1 9. A workpiece support member according to claim 8 , further including a lip on said workpiece support member body outer surface for supporting said shield. claim 8 10. A workpiece support member for supporting a workpiece having a workpiece outer edge and capable of protecting a tool portion having an irradiance damage threshold I DT from high-irradiance spillover radiation of irradiance I R while irradiating the workpiece, the workpiece support member comprising: a body with an outer surface and an upper surface with an outer edge, said upper surface capable of supporting the workpiece so that the workpiece outer edge extends beyond said workpiece support member outer edge; and A shield according to claim 3 arranged between the workpiece and the tool portion around said outer surface. claim 3 11. A workpiece support member according to claim 10 , further including a lip on said workpiece support member body outer surface for supporting said shield. claim 10 12. A shield for protecting a tool portion having an irradiance damage threshold from high-irradiance radiation from a light source when irradiating a workpiece, said shield arranged between the light source and the tool portion and having an irradiance damage threshold, a scattering coefficient, a volume and a thickness, and designed to scatter in said volume portion of said high-irradiance radiation that would otherwise be incident said tool portion, wherein said shield maintains said scattered high-irradiance radiation below said shield irradiance damage threshold, and wherein radiation exiting the shield and incident the tool portion has an irradiance below the irradiance damage threshold of the tool portion. 13. A shield according to claim 12 , wherein said shield is arranged between the workpiece and the tool portion. claim 12 14. A shield for protecting a tool portion having an irradiance damage threshold I DT from damage due to high-irradiance radiation I R from a light source when irradiating a workpiece, said shield arranged between the light source and the tool portion and separated from the tool portion by a distance d, and having a scattering coefficient "THgr", a scattering area A and a thickness t, wherein radiation exiting the shield and incident the tool portion has an irradiance I T satisfying the condition: I T =I R A/("THgr"d 2 ) less than I DT . 15. A shield according to claim 14 , wherein said shield is arranged between the workpiece and the tool portion. claim 14 16. A shield according to claim 14 , further having an absorption coefficient a and a shield irradiance damage threshold I DS , and wherein said shield absorbs an irradiance I ABS given by: claim 14 I ABS =I R a(1xe2x88x92exp(xe2x88x92at)) less than I DS . 17. A shield according to claim 12 , wherein said shield comprises one of a turbid media and a opal glass. claim 12 18. An apparatus that prevents a tool portion having an irradiance damage threshold from being irradiated by high-irradiance radiation from a light source while irradiating a workpiece, the apparatus comprising: a workpiece support member for supporting a workpiece; and the shield according to claim 12 arranged between the light source and the tool portion. claim 12 19. An apparatus for irradiating a workpiece with a high-irradiance irradiation I R and that prevents a tool portion having an irradiance damage threshold I DT from being irradiated by the high-irradiance radiation, the apparatus comprising: a workpiece support member for supporting a workpiece; and the shield according to claim 14 arranged between the light source and the tool portion. claim 14 20. A workpiece support member for supporting a workpiece having an outer edge and capable of protecting a tool portion having an irradiance damage threshold from high-irradiance radiation otherwise incident the tool portion while irradiating the workpiece, the workpiece support member comprising: a body with an outer surface and an upper surface with an outer edge, said upper surface capable of supporting the workpiece so that the workpiece outer edge extends beyond said workpiece support member outer edge; and the shield according to claim 12 arranged between the light source and the tool portion. claim 12 21. A workpiece support member according to claim 20 , further including a lip on said outer surface for supporting said shield. claim 20 22. A workpiece support member for supporting a workpiece having an outer edge, capable of protecting a tool portion having an irradiance damage threshold I DT from high-irradiance radiation of irradiance I R otherwise incident the tool portion while irradiating the workpiece, the workpiece support member comprising: a body with an outer surface and an upper surface with an outer edge, said upper surface capable of supporting the workpiece so that the workpiece outer edge extends beyond said workpiece support member outer edge: and the shield according to claim 14 arranged between the light source and the tool portion. claim 14 23. A workpiece support member according to claim 22 , further including a lip on said outer surface for supporting said shield. claim 22 24. A shield for protecting a tool portion having an irradiance damage threshold from high-irradiance radiation from a light source wherein irradiating a workpiece, said shield arranged between the light source and the tool portion and having an irradiance damage threshold, an absorption coefficient, a volume, a scattering coefficient and a thickness, wherein said shield is designed to absorb and scatter in said volume a portion of the high-irradiance irradiation, wherein the shield maintains said absorbed high-irradiance radiation below said shield irradiance damage threshold, and wherein radiation exiting the shield and incident the tool portion has an irradiance below the irradiance damage threshold of the tool portion. 25. A shield according to claim 24 , wherein said shield is arranged between the workpiece and the tool portion. claim 24 26. A shield according to claim 24 , wherein said shield comprises opal glass. claim 24 27. A shield for protecting a tool portion having an irradiance damage threshold I DT , from damage due to high-irradiance radiation of irradiance I R from a light source when irradiating a workpiece, said shield arranged between the workpiece and the tool portion and separated from the tool portion by a distance d, and having an irradiance damage threshold I DS , an absorption coefficient a, a scattering coefficient "THgr", a scattering area A, and a thickness t such that an irradiance I ABS absorbed by said shield from the high-irradiance radiation satisfies the condition: I ABS =I R a (1xe2x88x92exp(xe2x88x92at)), and radiation transmitted through the shield and incident the tool portion has an irradiance I T satisfying the condition: I T =I R (exp(xe2x88x92at)) A/(d 2 "THgr"). 28. A shield according to claim 27 arranged between the workpiece and the tool portion. claim 27 29. An apparatus that prevents a tool portion having an irradiance damage threshold from being irradiated by high-irradiance radiation from a light source while irradiating a workpiece, the apparatus comprising: a workpiece support member for supporting a workpiece; and the shield according to claim 24 arranged between the light source and the tool portion. claim 24 30. An apparatus that prevents a tool portion having an irradiance damage threshold I DT from being irradiated by high-irradiance radiation from a light source while irradiating a workpiece, the apparatus comprising: a workpiece support member for supporting a workpiece; and the shield according to claim 26 arranged between the light source and the tool portion. claim 26 31. An apparatus supporting a workpiece having an outer edge, capable of protecting a tool portion from high-irradiance radiation otherwise incident the tool portion while irradiating the workpiece, comprising: a body with an outer surface and an upper surface with an outer edge, said upper surface capable of supporting the workpiece so that the workpiece outer edge extends beyond said workpiece support member outer edge: and the shield according to claim 24 arranged around said workpiece support member body outer surface and extending beyond the outer edge of said workpiece so as to intercept radiation passing said workpiece outer edge. claim 24 32. An apparatus according to claim 31 , further including a lip on said workpiece support member body outer surface for supporting said shield. claim 31 33. An apparatus supporting a workpiece having an outer edge, capable of protecting a tool portion from high-irradiance radiation otherwise incident the tool portion while irradiating the workpiece, comprising: a body with an outer surface and an upper surface with an outer edge, said upper surface capable of supporting the workpiece so that the workpiece outer edge extends beyond said workpiece support member outer edge: and the shield according to claim 26 arranged around said workpiece support member body outer surface and extending beyond the outer edge of said workpiece so as to intercept radiation passing said workpiece outer edge. claim 26 34. An apparatus according to claim 33 , further including a lip on said outer surface. claim 33 35. A method of attenuating high-irradiance radiation from a light source incident a tool portion of a tool while processing the workpiece, the tool portion having an irradiance damage threshold, the method comprising the steps of: a) arranging a shield between the light source and the tool portion, said shield having a volume and capable of absorbing a portion of the high-irradiance radiation within said volume; and b) absorbing a portion of the high-irradiance radiation that would be incident the tool portion within said volume of said shield so that radiation leaving said shield and incident said tool portion has an irradiance below the irradiance damage threshold of the tool portion. 36. A method according to claim 35 , wherein said arranging step a) further includes positioning said shield between the workpiece and the tool portion. claim 35 37. A method of attenuating high-irradiance radiation from a light source incident a tool portion of a tool while processing the workpiece, the tool portion having an irradiance damage threshold, the method comprising the steps of: a) arranging a shield between the light source and the tool portion, said shield having a volume and capable of scattering a portion of the high-irradiance radiation within said volume; and b) scattering a portion of the high-irradiance radiation that would be incident the tool portion within said volume of said shield so that radiation leaving said shield and incident said tool portion has an irradiance below the irradiance damage threshold of the tool portion. 38. A method according to claim 37 , wherein arranging step a. further includes positioning said shield between the workpiece and the tool portion. claim 37 39. A method of attenuating high-irradiance radiation from a light source incident a tool portion of a tool while processing the workpiece, the tool portion having an irradiance damage threshold, the method comprising the steps of: a) arranging a shield between the light source and the tool portion, said shield having a volume and capable of absorbing and scattering a portion of the high-irradiance radiation within said volume; and b) absorbing and scattering a portion of the high-irradiance radiation that would be incident the tool portion within said volume of said shield so that radiation leaving said shield and incident said tool portion has an irradiance below the irradiance damage threshold of the tool portion. 40. A method according to claim 39 , wherein arranging step a. further includes positioning said shield between the workpiece and the tool portion. claim 39 41. A method of processing a workpiece with high-irradiance radiation from a light source using a tool having a tool portion with an irradiance damage threshold, comprising the steps of: a) supporting the workpiece on a workpiece support member; b) arranging a shield according to claim 1 between the light source and workpiece so as to intercept any of the high-irradiance radiation that would otherwise be incident the tool portion; and claim 1 c) irradiating the workpiece with the high-irradiance radiation. 42. A method of processing a workpiece with high-irradiance radiation from a light source using a workpiece processing tool having a tool portion with an irradiance damage threshold, comprising the steps of: a) supporting the workpiece on a workpiece support member; b) arranging a shield according to claim 12 between the light source and workpiece so as to intercept any of the high-irradiance radiation that would otherwise be incident the tool portion; and claim 12 c) irradiating the workpiece with high-irradiance radiation. 43. A method of processing a workpiece with high-irradiance radiation from a light source using a workpiece processing tool having a tool portion with an irradiance damage threshold, comprising the steps of: a) supporting the workpiece on a workpiece support member; b) arranging a shield according to claim 24 between the light source and workpiece so as to intercept any of the high-irradiance radiation that would otherwise be incident the tool portion; and claim 24 c) irradiating the workpiece with high-irradiance radiation.
061577014	abstract	An X-ray generating apparatus in which X-rays are emitted from laser plasma, the X-ray generating apparatus including a strong magnetic field generating device for generating a magnetic field component substantially parallel with the target surface in the vicinity of the laser plasma. The magnetic field component is arranged to generate a magnetic force which acts directly on charged particles in the laser plasma to bend the tracks of the charged particles, causing the charged particles to be confined in a magnetic field formed by the magnetic field component. The magnetic flux of the strong magnetic field is directed to a direction which is different from the direction in which the laser plasma is generated. An X-ray supply object is disposed in the laser plasma generating direction. Charged particles, liable to be directed to the X-ray supply object, are mainly confined in the strong magnetic field.
	summary
	abstract	The present invention includes a method to print patterns with improved edge acuity. The method for printing fine patterns comprises the actions of: providing an SLM and providing a pixel layout pattern with different categories of modulating elements, the categories differing in the phase of the complex amplitude.
	abstract	The application provides a self-diagnosis and accident-handling unmanned nuclear reactor, which: can passively cool down excessively generated heat without an operation of an operator when a malfunction of the nuclear reactor has occurred, wherein a cooling operation for safety measures can be carried out in a completely passive manner without a separate control command by a change in environmental conditions such as the structure and pressure of the nuclear reactor; and has a simpler structure compared to that of a conventional nuclear reactor safety system. It also provides a self-diagnosis and accident-handling unmanned nuclear reactor, which performs heat exchange by using a two-phase heat transfer mechanism, wherein heat exchange performance is maximized by introducing a spray-type heat exchanger having an optimized structure in which channels are three-dimensionally arranged, and can also easily and passively control heat exchange without a separate control means by using saturated steam pressure.
044877110	abstract	Disclosed is a process for making a cinder aggregate from neutralized PUREX waste. The PUREX waste is concentrated to about 30 to about 40 percent solids and a colloid of such de-alcoholated alkoxides of silicon, boron, and aluminum are added to the PUREX waste as are necessary to produce a mixture containing about 0.0001 to about 1 percent aluminum hydroxide, about 5 to about 15 percent silica, and about 1 to about 3 percent boric oxide. The resulting mixture is heated to about 400 to about 700.degree. C. which produces a cinder. The cinder will be transported to a vitrification center where it can be disintegrated in ammonium hydroxide and the nuclear waste can be permanently encapsulated in glass.
	description	This patent application claims the benefit of U.S. Provisional Application No. 60/604,374, filed Aug. 25, 2004, which is hereby incorporated by reference herein in its entirety. Large machinery, such as power generation equipment, is typically very expensive to purchase, install, maintain and operate. Accordingly, determining whether such equipment is operating within desired operating parameters is important. Detecting conditions that indicate that the equipment is operating outside these desired parameters, which may result in damage to the equipment is, therefore, also important. In order to detect such conditions, sensors are typically used to measure operating parameters, such as pressure, temperature, etc., of various components and, if a predetermined threshold for a particular parameter is crossed by a particular measurement, a fault is declared. Recently, learning techniques for fault detection systems have become more prevalent in attempts to improve the accuracy of determining whether a fault exists. Well-known techniques, such as neural networks, multivariate state estimation techniques (MSET) and fuzzy logic have been used for such purposes. All such methods use historical data, collected by a plurality of sensors and indicative of past normal operations and fault conditions, to generate a model that is used to monitor future data generated by operations of the equipment. If the future data deviates too much from the historical data model, an alarm is generated and a fault is declared. Prior fault detection methods typically relied on historical data to generate estimates of observed operational values expected to be measured by a particular sensor. Then, actual operational values were measured by the sensors and compared to the estimates. The sensor residue, or the difference between the estimate and the observed value, is then calculated and, if the residue is higher than a desired threshold, a fault is declared. However, in such prior sensor estimation techniques, estimates of a particular sensor were frequently affected by measurements taken by faulty sensors. Specifically, typical prior estimation techniques relied on measurements from several sensors measuring the same characteristic (e.g., multiple sensors measuring blade temperature in a turbine engine) to produce an estimate of the expected value from an individual sensor. Such a measurement derived from several sensors is referred to herein as a vector. These techniques typically minimized errors between the estimates and original values and, therefore, tended to spread any deviations between the values of the individual sensors among all the sensors. As a result, if one sensor was faulty and, therefore, produced a significant error in its measurement, that error would be shared by all of the non-faulty sensors, thus reducing the accuracy of the overall estimate from each of the sensors. This sharing of error is referred to herein as the spillover effect. In order to reduce such spillover, various estimation techniques have been used, such as techniques using the well-known gradient descent functions to search for solutions. For examples of such methods, see P. J. Huber, “Robust Statistics”, Wiley-Interscience, 1981. However, these methods require the selection of a control parameter to control how quickly the function converged. Selecting such control parameters accurately is difficult. Additionally, such methods tended to converge to an optimal estimate slowly and, therefore, are impractical in many operational uses. Other attempts at reducing the effect of spillover include methods involving regression, such as the well-known kernel regression or multivariate state estimation techniques (MSET). Such techniques are described more fully in A. V. Gribok, J. W. Hines and R/E. Uhrig, “Use of Kernel Based Techniques for Sensor Validation”, Int'l Topical Meeting on Nuclear Plant Instrumentation, Controls, and Human-Machine Interface Technologies, Washington D.C., November, 2000, which is hereby incorporated by reference herein in its entirety. However, these regression methods are computationally intensive, requiring a number of regression networks equal to the number of sensors. Additionally, such regression models are inaccurate when faulty sensors are present. The present inventors have invented a method and apparatus for detecting faults in equipment using sensor confidence and an improved method of identifying the normal operating range of the power generation equipment as measured by those sensors. Specifically, in accordance with one embodiment of the present invention, a confidence is assigned to a sensor in proportion to the residue associated with that sensor. If the sensor has high residue, a small confidence is assigned to the sensor. If a sensor has a low residue, a high confidence is assigned to that sensor, and appropriate weighting of that sensor with other sensors is provided. This confidence is then used to produce a revised estimate of an observed value of a characteristic of power generation equipment. In accordance with another embodiment of the present invention, a feature space trajectory (FST) method is used to model the normal operating range curve distribution of power generation equipment characteristics. In particular, such an FST method is illustratively used in conjunction with a minimum spanning tree (MST) method to identify a plurality of nodes and to then connect those with line segments that approximate a curve. Once this curve is approximated, the methods for determining sensor confidence, discussed above, can be used to determine and an improved sensor estimate. These and other advantages of the invention will be apparent to those of ordinary skill in the art by reference to the following detailed description and the accompanying drawings. FIG. 1 shows an illustrative plot of sensor vector estimates and observed values collected by a monitoring system, and how those estimates/values can be compared to the normal operating range of, for example, the temperature of a component in a turbine engine used to generate power. Specifically, referring to FIG. 1, two sensors, herein designated as sensor 1 122 and sensor 2 124 are part of a monitoring system 120. Sensor 1 122 is, for example, a faulty sensor and sensor 2 124 is, for example, a sensor that is not faulty. These sensors 122 and 124 are, for example, sensors positioned to monitor an operational characteristic of the aforementioned turbine engine, such as, illustratively, the blade path temperature of the blades in a turbine engine. As one skilled in the art will recognize, and as can be seen by FIG. 1, multiple temperature measurements, such as measurements taken by sensor 1 122 and sensor 2 124, respectively, can be represented by vectors 102 and 103. Specifically, vectors 102 and 103 in the vertical direction and the horizontal direction, respectively, represent the measurement of, for example, the blade path temperature measurements x1 (measured by sensor 1 122) and x2 (measured by sensor 2 124). Thus, instead of using a simple one-dimensional range of temperature measurements from a single sensor, the measurements form a two-dimensional graph that is a function of the temperature measurements x1 and x2 from sensor 1 122 and sensor 2 124, respectively. Accordingly, each point in FIG. 1 represents a vertical component representing one or more measurements taken by sensor 1 122 and a horizontal component representing one or more measurements taken by sensor 2 124. Normal operating range 101 is a curve representing the normal operating range of, for example, power generation equipment and is determined through well-known learning techniques in which historical data associated with the operation of that power generation equipment can be collected by sensors placed at desired locations on that equipment. This data, or a portion of this data, is used to estimate and characterize the normal operating range of the equipment using well-known statistical modeling techniques. In operations of the equipment, if a measurement significantly deviates from the calculated normal operating range, a fault could be declared. Determining the normal operating range curve 101 of the power generation equipment is also discussed further herein below. Referring once again to FIG. 1, once the normal operating range 101 is determined, a measurement of the operational characteristic (such as temperature) can then be taken by sensor 1 122 and sensor 2 124. Vector x 107 represents the position of an ideal estimate of the temperature values measured by sensor 1 122 and sensor 2 124 or, in other words, the actual operating blade path temperature. However, assume once again that sensor 1 122 is a faulty sensor and, hence its measurement will be inaccurate. As shown in FIG. 1, in such a case, the result of these measurements taken by sensor 1 122 and sensor 2 124 is observed vector y 110. As can be seen, vector y 110 is offset in the vertical direction from ideal estimate x 107 by an amount attributable to the error introduced by faulty sensor 1 122. This vertical offset is referred to herein as the sensor residue of sensor 2 124 and is directly attributable to the fault in sensor 1 122. In prior fault detection systems, once an observed value, such as sensor vector y, was measured, an attempt was typically made to minimize any errors in the measured value. This attempt usually involved mapping the observed vector to the closest point in the normal operating range and treating that closest point as the actual measured value. Referring to FIG. 1, the error represented by vector y 110 with respect to the normal operating range of the equipment is minimized, according to this method, by determining the closest point on normal operating range 101 to vector y 110. This closest point is represented by {tilde over (x)} 109, which is the point located on normal operating range 101 at the minimum distance 104 from vector y 110. Point {tilde over (x)} 109 is offset from ideal estimate x 107 in both the vertical and horizontal directions by distances 105 and 106, respectively. One skilled in the art will observe that, while the original observed vector y 110 was not offset with respect to x 107 in the horizontal direction, point {tilde over (x)} 109 is offset by distance 106. Distance 106 is referred to herein as the spillover error of sensor 2 124 which, as discussed above, is the error introduced into the measurements of a normally-operating sensor by faulty sensor 1 122. In this case, the spillover results directly from attempting to map the observed vector y 110, which is erroneous due to faulty sensor 1 122, onto the normal operating range. In accordance with the principles of the present invention, the spillover problem is substantially eliminated. In particular, in accordance with one embodiment of the present invention, a confidence is assigned to a sensor in proportion to the residue associated with that sensor. If the sensor has high residue, a small confidence is assigned to the sensor. If a sensor has a low residue, a high confidence is assigned to that sensor, and appropriate weighting of that sensor with other sensors is provided. In particular, a confidence, wi, is defined for the i-th sensor:wi=g(di) Equation 1where wi is the confidence of the i-th sensor, and di is the normalized absolute difference between the observed sensor value and the estimated sensor value for the i-th sensor. As the difference between the sensor value and the estimated value increases for a particular sensor increases, the residue associated with that sensor increases. In particular, di is defined as: d i =  x ~ i - y i   x ~ - y  Equation ⁢ ⁢ 2 where, once again, {tilde over (x)} is the estimate of a sensor vector from all sensors combined using traditional statistical modeling; {tilde over (x)}i is the estimate of a sensor vector using such modeling from the i-th sensor; yi is the observed sensor vector at the i-th sensor; and y is the observed sensor vector as measured from all sensors combined. This normalized absolute difference is used to reduce scaling effects of the residues for different sensors. FIG. 2 shows an illustrative graph of one illustrative confidence function 201 useful in assigning confidence to sensors in accordance with the method described herein. Referring to FIG. 2 again, as one skilled in the art will recognize, the confidence g(di) along the vertical axis 202 assigned to a sensor is a decreasing function from 1 to 0 as di increases, as represented by the horizontal axis 203. In particular, FIG. 2 shows an illustrative confidence function g(d) defined by the equation:g(d)=exp(γd2) Equation 3where d is as defined above and γ is a selected convergence where γ<0. Illustratively, as shown by the graph of FIG. 2, γ is selected illustratively in a way such that g(1)=0.001. By using such a confidence function, an updated, more accurate estimate {circumflex over (x)} of a sensor vector can be obtained. In particular, {circumflex over (x)}i for the i-th sensor such an improved estimate of a sensor vector can be calculated by:{circumflex over (x)}i=wi·yi+(1−wi)·{tilde over (x)}i Equation 4where the variables in equation 4 are as described above. As can be seen in FIG. 1, the new updated {circumflex over (x)} is significantly horizontally closer to the ideal estimate x and, as a result, the spillover effect attributed to the faulty sensor 1 is greatly reduced. FIG. 3 shows a method in accordance with one embodiment of the present invention whereby an improved estimate of x is obtained using the above equations and the sensor confidence function of FIG. 2. Specifically, referring to FIG. 3, at step 301, observed sensor vector y is input into Equation 2 in order to calculate the normalized absolute difference, di, between the observed sensor value y and the estimated sensor value {tilde over (x)}. Next, at step 302, this calculated value of di is then mapped to a particular confidence level wi=g(di) using the illustrative confidence function represented by FIG. 2 and as discussed above. Once the value of wi is determined, at step 303, the observed sensor vector yi and the original estimated value {tilde over (x)}i are entered into the equation 4 to obtain the value of {circumflex over (x)}i as discussed above. Once this value is calculated for each sensor, at step 304, a new {circumflex over (x)} is calculated which is an improved estimate of the observed sensor vector that has been refined to take into account the reduced confidence assigned to sensor 1. Next, at step 305, this new value of {circumflex over (x)} is then entered into the statistical model to determine a new, updated value of {tilde over (x)}. At step 306, a determination is made whether the distance from the new {tilde over (x)} to the previously computed {tilde over (x)} is smaller than a desired threshold. If so, then at step 307, the current value of {tilde over (x)} is used as the best value of the ideal estimate x. If, on the other hand, at step 305, the distance from the new {tilde over (x)} is larger than a desired threshold, then the process returns to step 301 and the new value of {tilde over (x)} is then used to calculate an updated di according to equation 2 and, a new value for {circumflex over (x)}i. The process continues as described above until the distance from the current value of {tilde over (x)} to the previous value of {tilde over (x)} is less than the desired threshold. In this manner, a confidence level is assigned to a sensor, thus significantly reducing the spillover of faulty sensor measurements on normally operating sensors. In order to ensure that the sensor confidence method described above is accurate, it is necessary to ensure that the identification of the normal operating range, such as curve 101 in FIG. 1, is accurately identified. The present inventors have recognized that, in many instances, operational equipment, such as power generation equipment, has one or more sets of highly correlated sensors, such as the aforementioned blade path temperature sensors in a turbine engine. These sensors are termed highly correlated because these sensors are physically located in known positions relative to one another and future measurements from one sensor can be relatively accurately predicted, absent faults, by the measurements from another sensor. As one skilled in the art will recognize, due to this correlation, the distribution of any pair of highly correlated sensors in a two-dimensional space resembles a curve. Due to this correlation, it can be assumed that the distribution of sensor vectors consisting of measurements taken by these sensors is also a curve. In order to produce a curve based on historical sensor measurements and, therefore, to obtain a normal operating range curve of the power generation equipment, well-known methods using principle curves and their equally well-known variations have been employed. Specifically, such methods involve determining a curve that passes through the center of the training data in the sensor vector space. However, such methods are frequently inadequate as they do not converge properly to a desired curve, especially when the curve is a complex shape. As a result, a specific curve representing the normal operating range of the power generation equipment is sometimes difficult to determine. Therefore, the present inventors have recognized that feature space trajectory methods can be employed to model the normal operating range curve distribution of power generation equipment characteristics. Such feature space methods are generally well known in other fields, such as image recognition and, therefore, will only be described herein as necessary to understand the principles of the present invention. Such FST methods are generally useful to identify a plurality of nodes and to then connect those with line segments that approximate a curve. FIG. 4 shows one illustrative FST model, further discussed below, which in this case consists of three line segments v1v2, v2v3 and v3v4. Test input vector y is used once again to statistically obtain the value for {tilde over (x)}, as described above, which, in this illustrative example, is the estimate producing the smallest distance 401 between y and the line segments. As discussed previously, once the value {tilde over (x)} is determined, sensor confidence can be determined and an improved sensor estimate can be iteratively produced. In order to compute an FST, such as the FST 400 of FIG. 4, typically the nodes, such as nodes v1, v2, v3 and v4 in FIG. 4 must be known and the order of those nodes must also be known such that the nodes are connected one by one to form a curve. However, in the present case, both nodes in the training data and their order are unknown and, therefore, this information must be derived from the set of training sensor vector data. Therefore, the present inventors have recognized that k-mean clustering can be used to determine the sensor vectors that are present in the training data and to then derive nodes for use in the FST. In such k-mean clustering, a plurality of centroid positions are identified in a set of data by determining the distance between data points in a set of data (e.g., sensor training data) and the centroid positions and grouping data points based on the minimum distance between each point and one of the centroids. Such clustering is well-known and will not be described further herein. Once the nodes have been identified, it is necessary to determine the order of the nodes and to connect them according to that order. In accordance with one embodiment of the principles of the present invention, a minimum spanning tree (MST) algorithm is used to accomplish this task. As is well-known, MST algorithms are useful in connecting a plurality of points in a way such that the sum of the lengths of the connections (the span) is a minimum. The result is frequently graphically portrayed as a tree-like graph. However, in the present case, the desired tree is intended to model the normal operating range of the power generation equipment. As such, the present inventors have recognized that, by applying certain constraints to the functions of the MST algorithm, it is possible to connect the nodes generated by the FST method described above and accurately model the normal operating range curve. Specifically, FIG. 5 shows a method in accordance with one embodiment of the present invention whereby the FST of FIG. 4 is developed. In particular, at step 501, an initial number k of nodes to be connected is identified, in this case k=3. This number corresponds to the number of centroids to be initially identified in the training data and is also the minimum number of points necessary to model a curve (two points would only result in a straight line connecting those two points. Next at step 502, a k-mean algorithm is applied to identify the three centroid positions. Referring to FIG. 6, using the training data represented by the curve in FIG. 4, three centroid positions v′1, v′2 and v′3 are illustratively identified. Next, at step 503, the MST algorithm is applied, as described above, to these k-nodes to connect them in order, represented by lines 601 and 602 in FIG. 6. However, in order to ensure these nodes form a curve, at step 504 a determination is made whether there are two end nodes belonging to one edge (i.e., are connected to only one other node). If yes, at step 505, a determination is made whether all remaining nodes (e.g., between the two edge nodes) belong to two edges (i.e., are connected to two and only two other nodes). Steps 504 and 505 function to ensure that the nodes form a model of a curve and not some other shape, such as a tree with separate individual segments. If, at step 505, the determination is made that each middle node belongs to two edges, then, at step 506, a further determination is made whether the angle θ formed between adjacent edges is greater than a predefined angle such as, illustratively, 30 degrees. This is to prevent the MST from forming a boundary to the training data having jagged edges. If the determination at step 506 is yes, then, at step 507, k is revised to k=k+1, in this case k=4, and the process returns to step 502. In this case, when k=4 the illustrative FST of FIG. 4 would be developed having line segments v1v2, v2v3 and v3v4. As will be obvious to one skilled in the art, the greater the number of nodes complying with the above constraints, the more precise the estimation of the normal operating range 101 of FIG. 1. Therefore, the above process iteratively continues with increasing values of k until one of the determinations at steps 504, 505 or 506 is no. In this case, at step 508, the results of the MST process are output as the final representation of the normal operating range of the power generation equipment as determined by the training data. One skilled in the art will recognize that a monitoring system using sensor confidence values and/or an FST/MST method for determining the normal operating range of power generation equipment, such as that discussed above may be implemented on a programmable computer adapted to perform the steps of a computer program to calculate the functions of the confidence values and/or the FST/MST. Referring to FIG. 7, such a monitoring system 700 may be implemented on any suitable computer adapted to receive, store and transmit data such as the aforementioned phonebook information. Specifically, illustrative monitoring system 700 may have, for example, a processor 702 (or multiple processors) which controls the overall operation of the monitoring system 700. Such operation is defined by computer program instructions stored in a memory 703 and executed by processor 702. The memory 703 may be any type of computer readable medium, including without limitation electronic, magnetic, or optical media. Further, while one memory unit 703 is shown in FIG. 7, it is to be understood that memory unit 703 could comprise multiple memory units, with such memory units comprising any type of memory. Monitoring system 700 also comprises illustrative modem 701 and network interface 704. Monitoring system 700 also illustratively comprises a storage medium, such as a computer hard disk drive 705 for storing, for example, data and computer programs adapted for use in accordance with the principles of the present invention as described hereinabove. Finally, monitoring system 700 also illustratively comprises one or more input/output devices, represented in FIG. 7 as terminal 706, for allowing interaction with, for example, a technician or database administrator. One skilled in the art will recognize that address monitoring system 700 is merely illustrative in nature and that various hardware and software components may be adapted for equally advantageous use in a computer in accordance with the principles of the present invention. The foregoing Detailed Description is to be understood as being in every respect illustrative and exemplary, but not restrictive, and the scope of the invention disclosed herein is not to be determined from the Detailed Description, but rather from the claims as interpreted according to the full breadth permitted by the patent laws. It is to be understood that the embodiments shown and described herein are only illustrative of the principles of the present invention and that various modifications may be implemented by those skilled in the art without departing from the scope and spirit of the invention. Those skilled in the art could implement various other feature combinations without departing from the scope and spirit of the invention.
	description	The present invention relates to a control apparatus for an injection molding machine, wherein the apparatus uses a neural network. Injection molding machines allow resin products to be manufactured while molding conditions are adjusted. When unsatisfactory products have been produced, the molding conditions are corrected to ensure that satisfactory products are obtained. The molding control method that uses a neural network and is disclosed, for example, in Japanese Patent Laid-Open Publication No. HEI-5-309711 is proposed as a technique for correcting molding conditions. The use of a neural network makes it possible to efficiently deal with nonuniform monitor values and to reduce the time and cost of test runs. The principle of a neural network is described below with reference to FIG. 6 hereof. FIG. 6 shows an example of a layered neural network configured from an input layer 100 composed of four input units, an intermediate layer 110 composed of one layer having five units, and an output layer 120 composed of one output unit. In the input layer 100, for example, a monitor value S1 related to the farthest forward location of injection as determined by a sensor provided to the injection molding machine, a monitor value S2 related to the location at the start of weighing, a monitor value S3 related to the temperature of the opening through which material falls, and a monitor value S4 related to peak loading pressure are inputted, respectively, to first, second, third, and fourth input units 101, 102, 103, and 104. The value of the first unit 111 of the intermediate layer 110 is determined by processing the monitor values S1, S2, S3, and S4 with the aid of a threshold value and the weighting factors determined for each input. The value of the second unit 112 of the intermediate layer 110 is determined by processing the monitor values S1, S2, S3, and S4 with the aid of another threshold value and the weighting factors determined for each input. The values of the third through fifth units 113 through 115 are determined in the same manner. The output unit 121 of the output layer 120 is determined by processing the values of the first through fifth units 111 through 115 of the intermediate layer 110 with the aid of yet another threshold and the weighting factors determined for each of the first through fifth units 111 through 115. This output unit 121 has a predicted weight obtained from the predicted quality value of the molded articles in this example. Since the neural network is a function, the monitor values S1 through S4 inputted to the input layer 100 and the output layer 120 can be assumed to be known quantities, and the weighting factors and thresholds in the function can be assumed to be unknown quantities. Specifically, the monitor values S1 through S4 are provided to the input layer 100, and the measured weight of the molded articles is provided to the output layer 120. The weight predicted by a computer is repeatedly calculated while revising the weighting factors and the thresholds until the predicted weight matches the measured weight. When the predicted weight satisfactorily matches the measured weight, the weighting factors and the thresholds are determined. When the weighting factors and the thresholds are determined, the function, or, specifically, the quality prediction function, is established. Thus, if a neural network is used, a quality prediction function can be established by estimating the weighting factors and the thresholds in addition to calculating the predicted weights. The inventors conducted confirmation experiments using an injection molding machine having a neural network with the object of confirming the precision of the neural network. Summaries of the experiments are as follows. (1) Molding conditions are set with a high probability that satisfactory products will be obtained. (2) 20 shots are conducted. At this time, the monitor values are obtained by a sensor in the injection molding machine. (3) The weight of the molded article is measured for each shot. (4) The weighting factors and the thresholds in the neural network are determined using the monitor values as the input of the neural network, and the weights of the molded articles as the output of the neural network. The weighting factor and threshold used in one shot are corrected for the next text molding. Repeating such corrections is referred to as “learning.” (5) The neural network (quality prediction function) is established by means of the learning in these 20 shots. This neural network (quality prediction function) can also be said to be a weight prediction function in which the weighting factors and the thresholds are determined. Therefore, predicted weights can be outputted when the monitor values are inputted to the weight prediction function. (6) Mass-production molding begins with the 21st shot. The weight prediction function is not revised with mass-production molding. The monitor values continue to be obtained by the sensor in the injection molding machine in mass-production molding. (7) The weights of the molded articles are then measured. The weights as measured are referred to as the measured weights. (8) The predicted weights are calculated by inputting the monitor values obtained in (6) to the neural network (weight prediction function) in which the learning process has been completed. (9) The measured weights and the predicted weights Ws are compared to determine the “probability” of the predicted weights Ws. The results of the confirmation test described above are shown in FIG. 7. The horizontal axis indicates the number of shots, the vertical axis indicates the weight of the molded articles, the bold-line graph represents the measured weights Wact, and the thin-line graph represents the predicted weights Ws. The numbers 0 to 20 along the horizontal axis indicate the range of test moldings, and the numbers 21 and up indicate the range of mass-production moldings. The weight prediction function is determined in the shots 1 through 20. In the shots 21 through 50, the monitor values are inputted to the determined weight prediction function, and the predicted weights Ws are outputted, whereupon the predicted weights Ws are found to be very close to the measured weights Wact. In the shots 51 through 110, the monitor values are inputted to the weight prediction function, and the predicted weights Ws are outputted, whereupon the predicted weights Ws are found deviate considerably from the measured weights Wact. The shots 51 through 110 are believed to be affected by changes over time and by slight revisions in the molding conditions during mass-production molding. It is necessary to avoid any loss in the predicted precision starting at a certain point in time in order to be able to continuously conduct multiple shots with an injection molding machine, and improved techniques are needed. According to an aspect of the present invention, there is provided a control apparatus for an injection molding machine, the apparatus having a neural network and operating so that information on test molding is inputted to the neural networks, a quality prediction function is determined by repeating the estimation of weight factors and thresholds on the neural networks as many times as the number of test molding cycles, and mass-production molding is begun with this quality prediction function, the control apparatus further comprising: an upper/lower control limit determination unit for setting an upper control limit and a lower control limit for each of the monitor values that indicate the state in each part of a molding machine; and a function revision need determining unit for setting the range between the upper control limit and lower control limit set by the upper/lower control limit determination unit as the control range, and outputting a revision command for the quality prediction function and/or generating an alarm signal from an alarm signal generating unit when the monitor values acquired during mass-production molding have deviated from the control range. Since the control apparatus includes a function revision need determining unit, the quality prediction function can be revised by the control apparatus when the monitor values have changed by a specific amount or greater during mass-production molding. The reliability of quality prediction can be improved by revising the quality prediction function during mass-production molding. Also, an alarm signal can be generated by the alarm signal generating unit when the monitor values have changed by a specific amount or greater, which can encourage the operator to review the quality prediction function. It is preferable that the upper control limit be a maximum value selected from the monitor group obtained by test molding, and that the lower control limit be a minimum value selected from the monitor group obtained by test molding. The system is easily managed because the maximum value and the minimum value are determined in an unambiguous manner. It is preferable that the control apparatus perform control wherein an alarm signal is generated from the alarm signal generating unit when the monitor values acquired during mass-production molding have deviated from the control range, and the quality prediction function is revised and/or the operation of the molding machine is stopped either when this alarm signal has continued for a specific number of times or when the cumulative number of alarm signals has reached a specific number. An alarm signal is produced when the monitor values have deviated from the control range. The control apparatus revises the function either when this alarm signal has continued for a specific number of times or when the cumulative number of signals has reached a specific number. When the monitor values have deviated from the control range because of a disturbance in the signal system, it is believed that the monitor values will subsequently return to the control range. On this assumption, an alarm is produced in the first stage, and the function is revised in the second stage. If the process does not advance to the second stage, then the load of the control apparatus can be reduced because there is no need for the control apparatus to revise the function. It is preferable that the control device include a calculation unit for predicting quality values by providing the monitor values to the quality prediction function, and a satisfactory product determination unit for ascertaining that the molded articles are satisfactory when the quality prediction value predicted by the calculation unit is within the required quality, and ascertaining that the molded articles are unsatisfactory when the quality prediction value does not comply with the required quality. During mass-production molding, it is possible to determine whether products are satisfactory without measuring the molded articles. Since the molded articles do not need to be measured individually, measuring costs can be eliminated, and molding costs can be reduced. As shown in FIG. 1, an injection molding machine 10 includes a clamping device 12 for clamping a metal mold 11, and an injecting device 13 for injecting a resin into the clamped metal mold 11, and also a control apparatus 20 that has a neural network as its main element. The control apparatus 20 includes a molding machine communication function unit 21 that has a function for interfacing with external devices, an upper/lower control limit determination unit 22 for receiving various monitor values M related to the operating state of the injection molding machine 10 and setting a maximum value that consists of an upper control limit and a minimum value that consists of a lower control limit for each of the monitor values M, memory 23 attached to the upper/lower control limit determination unit 22 and used for storing groups of monitor values M, a function revision need determining unit 24 for determining whether there is a need to revise the quality prediction function Qpf, an alarm signal generating unit 25 for generating an alarm signal As when the function revision need determining unit 24 has produced a function revision instruction signal Fc, a first neural network 26 and second neural network 27, a calculating unit 28 for calculating a quality prediction value Qp by providing the monitor values M to the quality prediction function Qpf determined by the first neural network 26 and the second neural network 27, and a satisfactory product determination unit 29 for comparing the quality prediction value Qp calculated by the calculating unit 28 with a required quality Dq and determining product quality. The calculating unit 28 also requires a neural network, but instead of a neural network being provided independently, the first neural network 26 and the second neural network 27 can be utilized. The operation of the control apparatus 20 having the configuration described above will now be described with reference to FIG. 1 and to the flowchart shown in FIG. 2. Step (hereinafter abbreviated as ST) 01: Molding conditions that have a high probability of resulting in satisfactory products are predicted and set empirically. ST02: About 20 shots are conducted. ST03: The monitor values M determined by the sensors provided to each part of the injection molding machine 10 are read. ST04: A quality prediction value Qm (FIG. 1) derived from the weight (measured weight) of the molded articles obtained in the test moldings is read. ST05: The first neural network 26 determines weighting factors and thresholds by using the various monitor values M read in ST03 as input conditions and the measured weights read in ST04 as output conditions. Specifically, the weighting factor and threshold used in one shot are revised in the next shot. Repeating such revision is referred to as “learning.” ST06: The first neural network 26 determines whether or not to end the test molding. If they are not to be ended, the process returns to ST02 and the test moldings are continued. ST07: If it has been determined in ST06 that the test moldings are to be ended, then the quality prediction function Qpf is determined. Specifically, the weighting factors and thresholds in the first neural network 26 are determined. ST08: A maximum value M1 and a minimum value M2 are selected from the group of monitor values M read in ST03. This process is performed for each type of monitor value. Preparations for mass-production molding are thereby considered to be completed. ST09: Mass-production molding is performed. ST10: The monitor values M3 in mass-production molding are read. ST11: A determination is made as to whether the monitor values M3 that are read in ST10 lie between the maximum value M1 and the minimum value M2 selected in ST08 (this range is referred to as the control range). If not, the process advances to ST13 where the function is revised, and then the process returns to ST09 and mass-production molding is continued. ST12: A determination is made as to whether mass-production molding is to be ended if the monitor values M3 fall between the maximum value M1 and the minimum value M2 in ST11. If not, mass-production molding is continued. Next, the process of revising the function in ST13 and onward is described in the flowchart shown in FIG. 3. ST13: If the determination is negative in ST11 above, a message is produced indicating that the function is to be revised. This message may be either textual or audio. ST14: The weights of the molded articles that have been molded at this time are measured and the measured weights are read on the basis of the signal indicating that the function must be revised. ST15: The second neural network 27 revises the weighting factors and the thresholds by using the monitor values M3 that are read in ST10 as input conditions and the measured weights that are read in ST14 as output conditions. ST16: The second neural network 27 determines the revised function (revised quality prediction function). ST17: The quality prediction function that has been used up to this point is replaced with the revised function. The process then returns to ST09. Test molding and mass-production molding were performed by the injection molding machine 10 capable of executing control based on the flowchart described above. The results are described with reference to FIG. 4. In this figure, the horizontal axis indicates the number of shots, the vertical axis indicates the weight of the molded articles, the bold-line graph represents the measured weights Wact, and the thin-line graph represents the predicted weights Ws. The numbers 0 to 20 on the horizontal axis are the range of the test molding, and the numbers 21 onward are the range of mass-production molding. The weights Ws predicted by the neural networks form a slightly vertically displaced graph because the monitor values vary. The measured weights Wact have fluctuated in the several initial shots, but have then since stabilized and moved very close to the predicted weights Ws by the 50th shot. However, the measured weights Wact suddenly decreased near the 50th shot. Nevertheless, the predicted weights Ws were revised to lower values to be near the measured weights Wact because the control apparatus of the present invention had revised the function near the 50th shot. The same revision was conducted near the 80th and 110th shots, and it was confirmed that the predicted weights Ws were still very close to the measured weights Wact. Specifically, in mass-production molding as well, it greatly increased the reliability of the predicted weights Ws by revising the function in ST13 through ST17, when it was determined in ST11 that the function (quality prediction function) had to be revised. However, aside from revising the quality prediction function, it is possible to determine whether products are satisfactory by whether or not the weight of the molded articles falls within the acceptable range. An example of this satisfactory determination process is described with reference to the flowchart shown in FIG. 5. ST18: The upper limit (upper limit of the allowable range) G1 and the lower limit (lower limit of the allowable range) G2 of the weights are read from the required quality Dq inputted in advance. ST19: The monitor values M3 read in ST10 are entered into the quality prediction function Qpf, and a predicted weight G3 is calculated, which is one quality prediction value Qp. ST20: A determination is made as to whether the predicted weight G3 is between the upper limit G1 and the lower limit G2, or, specifically, whether the required quality Dq is met. ST21: The molded articles are determined to be satisfactory if the predicted weight G3 is between the upper limit G1 and the lower limit G2. ST22: The molded articles are determined to be unsatisfactory if the determination in ST20 is negative. In other words, the satisfactory product determination unit 29 shown in FIG. 1 outputs satisfactory/unsatisfactory information Qinf on the basis of the required quality Dq and the quality prediction value Qp, and this information Qinf is sent to the injection molding machine 10. This process makes it possible to determine whether molded articles in mass-production molding are satisfactory without measuring the weight of the molded articles. As a result, the step of measuring the weight of the molded articles can be omitted, and production costs can be reduced. The weight, dimensions, shapes and other such features of the molded articles have no bearing on their quality. Also, in the present embodiment, the maximum value and minimum value of the monitor items were used in unmodified form for the upper control limit and lower control limit, but the present invention is not limited thereto, and the values can be arbitrarily set with consideration to the degree to which monitor values occur. For example, when the precision of prediction in the quality prediction function needs to be improved during mass-production molding, the degree of revision is intentionally increased by setting the upper control limit and/or the lower control limit to be lower than the maximum value and higher than the minimum value. The precision of prediction in the quality prediction function can thereby be improved by reviewing the quality prediction function. Therefore, precision of prediction in the quality prediction function can be maintained despite fluctuation in the monitor items or changes in the molding conditions over time. As a result, the frequency with which the quality prediction function must be reviewed can be reduced. Obviously, various minor changes and modifications of the present invention are possible in the light of the above teaching. It is therefore to be understood that within the scope of the appended claims the invention may be practice otherwise than as specifically described.
	abstract	Certain exemplary embodiments can provide a system comprising a substantially transparent radiation shield, which comprises transparent ammonium metatungstate. The transparent ammonium metatungstate can have a density of greater than 1.5 gram/(cubic centimeter). The substantially transparent radiation shield can be installed on tanks and/or pressure vessels, used as a transparent radiation shield in medical shielding/devices, used as windows in glove boxes, and any application where effective radiation shielding is needed with transparency. The substantially transparent radiation shield can be used in one or more articles worn by a human.
	description	1. Field of the Invention The present invention relates to a laser irradiation apparatus in which a pulsed laser beam emitted from a first laser light source and a pulsed laser beam emitted from a second laser light source are guided to pass through the same optical path for irradiation of an object to be irradiated with the laser beams. 2. Description of the Related Art Conventionally, a laser irradiation apparatus in which two laser light sources (laser resonators) each which emit a pulsed laser beam with a predetermined frequency are provided and a desired range of an object to be irradiated with a laser beam (e.g., a semiconductor substrate) is irradiated with a pulsed laser beam by using the two laser light sources has been developed (e.g., Patent Document 1 (Japanese Published Patent Application No. 2007-110064)). FIG. 9 shows a structural example of such a laser irradiation apparatus. As shown in FIG. 9, the laser irradiation apparatus is provided with a first laser resonator 31, a second laser resonator 32, a pulse control device 33, an optical path combining optical member 35, a beam expander 37, a cylindrical lens array 39, and a condenser lens 41. The first laser resonator 31 emits a linearly-polarized pulse laser beam, of which the polarization direction is perpendicular on the plane of the paper of FIG. 9, with a predetermined frequency. The second laser resonator 32 emits a linearly-polarized pulse laser beam, of which the polarization direction is in an up and down direction on the plane of the paper of FIG. 9, with a predetermined frequency. The pulse control device 33 controls the first laser resonator 31 and the second laser resonator 32 so as not to synchronize timing of emission of pulsed laser beams from the first laser resonator 31 and the second laser resonator 32. The optical path combining optical member 35 can guide the pulsed laser beams to pass through the same optical path using the fact that the polarization directions of the pulsed laser beams from the first laser resonator 31 and the second laser resonator 32 are at 90° to each other. The optical path combining optical member 35 is a polarization beam splitter, for example, which reflects a pulsed laser beam polarized linearly in a perpendicular direction on the plane of the paper of FIG. 9 and transmits a pulsed laser beam polarized linearly in an up and down direction on the plane of the paper of FIG. 9. In this manner, with the use of the optical path combining optical member 35, the pulsed laser beams from the first laser resonator 31 and the second laser resonator 32 are guided to pass through the same optical path; accordingly, the frequency of a pulsed laser beam can be doubled and the power of a pulsed laser beam can be increased. The beam expander 37 adjusts each of pulsed laser beams from the optical path combining optical member 35 so that the shapes thereof have an elongated shape. Each of the pulsed laser beams which have passed through the beam expander 37 is adjusted so that they have a cross-section with an elongated shape (e.g., a linear shape or a rectangular shape) in a direction perpendicular to the traveling direction of the pulsed laser beams on the surface to be irradiated with the laser beam of the object to be irradiated with the laser beam (e.g., a semiconductor substrate). In FIG. 9, the cross-sectional shapes are adjusted to have an elongated shape in an up and down direction in FIG. 9. The cylindrical lens array 39 divides an incident pulsed laser beam into plural beams. The condenser lens 41 superimposes these divided beams on the surface to be irradiated with the laser beam of the object to be irradiated with the laser beam. Note that the reference numeral 43 denotes a short-side direction condenser lens which concentrates the pulsed laser beam on the surface to be irradiated with the laser beam with respect to a perpendicular direction on the plane of the paper of FIG. 9. While the surface of the semiconductor substrate is irradiated successively with a pulsed laser beam with the above-described laser irradiation apparatus, the semiconductor substrate is transferred in a perpendicular direction on the plane of the paper of FIG. 9. In this manner, a desired range of the surface of the semiconductor substrate can be irradiated with the pulsed laser beam. Note that as an example of a prior art reference other than Patent Document 1, Patent Document 2 (Japanese Published Patent Application No. 2004-95792) can be given. In the case where a semiconductor substrate is irradiated with a laser beam with the use of the laser irradiation apparatus in FIG. 9 for laser annealing treatment of the semiconductor substrate, there is a possibility that an object to be irradiated with a laser beam may be adversely affected by the difference in the polarization state between pulsed laser beams. An average size of crystal grains in a crystallized semiconductor is different between the case where laser annealing is performed by irradiating a desired range of a surface to be irradiated with a laser beam of a substrate on a surface of which an amorphous semiconductor is provided (hereinafter also referred to as an “amorphous semiconductor substrate”) with only an s-polarized pulse laser beam and the case where laser annealing is performed by irradiating a desired range of a surface to be irradiated with a laser beam of an amorphous semiconductor substrate with only a p-polarized pulse laser beam. Here, the term “s-polarized” means a polarization state in which the direction of the electric field of a beam intersects with the traveling direction of a laser beam and is parallel to an up and down direction of the plane of the paper of FIG. 9 on a surface to be irradiated with a laser beam. The term “p-polarized” means a polarization state in which the direction of the electric field of a beam intersects with the traveling direction of the laser beam and is parallel to a perpendicular direction on the plane of the paper of FIG. 9 on a surface to be irradiated with a laser beam. FIG. 10 is a graph showing such a difference. In FIG. 10, the horizontal axis represents the energy density of a pulse laser beam with which a surface of an amorphous semiconductor substrate is irradiated, and the vertical axis represents the average size of crystal grains in a semiconductor crystallized by laser annealing. The squares represent measurement results in the case where the amorphous semiconductor substrate is irradiated with only an s-polarized pulse laser beam, and the diamonds represent measurement results in the case where the amorphous semiconductor substrate is irradiated with only a p-polarized pulse laser beam. As shown in FIG. 10, the size of crystal grains in a semiconductor, which are grown with an s-polarized pulse laser beam, is different from the size of crystal grains in a semiconductor, which are grown by a p-polarized pulse laser beam. Thus, when an amorphous semiconductor substrate is alternately irradiated with an s-polarized pulse laser beam and a p-polarized pulse laser beam, regions which are irradiated with only an s-polarized pulse laser beam and regions which are irradiated with only a p-polarized pulse laser beam are generated in some cases. As a result, there is a possibility that the size of crystal grains may be nonuniform; accordingly, a stable crystalline semiconductor cannot be obtained. As described above, there is a possibility that an object to be irradiated with a laser beam may be adversely affected by the difference in the polarization state between pulsed laser beams. Accordingly, an object of a mode of the present invention is to provide a laser irradiation apparatus in which when pulsed laser beams from two laser light sources are guided to pass through the same optical path for irradiation of an object to be irradiated with the laser beams, the occurrence of adverse effects on the object to be irradiated with the laser beam due to the difference in the polarization state between the pulsed laser beams can be prevented or significantly reduced. In order to achieve the above object, according to a mode of the present invention, a laser irradiation apparatus is provided which includes a first laser light source which emits a polarized pulse laser beam; a second laser light source which emits a polarized pulse laser beam of which the polarization state is different from the polarization state of the polarized pulse laser beam emitted from the first laser light source; an optical path combining optical member which guides the pulsed laser beam emitted from the first laser light source and the pulsed laser beam emitted from the second laser light source to pass through the same optical path; a polarization control member which is arranged in an arrangement direction perpendicular to a traveling direction of the pulsed laser beam from the optical path combining optical member and which includes a first polarization control portion which controls a polarization state of beam components of the pulsed laser beam from the optical path combining optical member and a second polarization control portion which controls a polarization state of the beam components of the pulsed laser beam from the optical path combining optical member so that the polarization state of the beam components of the pulsed laser beam from the optical path combining optical member is different from the polarization state of the first polarization control portion; and a laser beam superimposing optical member which superimposes the pulsed laser beam which has passed through the first polarization control portion and the pulsed laser beam which has passed through the second polarization control portion on each other on a surface to be irradiated with a laser beam of an object to be irradiated with a laser beam. In the above-described structure, in the case where pulsed laser beams which are in different polarization states and are emitted from the first laser light source and the second laser light source are guided to pass through the same optical path for irradiation of an object to be irradiated with a laser beam, each of the pulsed laser beams emitted from the first laser light source and the second laser light source is divided into plural beam components in different polarization states (the first polarization state and the second polarization state) by the polarization control member, and the beam components in different polarization states are superimposed on each other on the surface to be irradiated with the laser beam of the object to be irradiated with the laser beam by the laser beam superimposing optical member. Accordingly, both of the pulsed laser beams are in a state in which the first polarization state and the second polarization state are mixed on the surface to be irradiated with the laser beam. Thus, the occurrence of adverse effects on the object to be irradiated with the laser beam due to the difference in the polarization state between pulsed laser beams can be prevented or significantly reduced. Further, according to a mode of the present invention, in addition to the above-described structure, the laser irradiation apparatus may also include a pulse control device which controls the first laser light source and the second laser light source so as not to synchronize timing of emission of pulsed laser beams from the first laser light source and the second laser light source. Furthermore, according to a mode of the present invention, in addition to the above-described structure, the laser irradiation apparatus may also include a beam expander which adjusts a shape of the pulsed laser beam from the optical path combining optical member to have an elongated shape and sends the pulsed laser beam having an elongated shape to the polarization control member. According to a preferred embodiment mode of the present invention, the length of the first polarization control portion in the arrangement direction and the length of the second polarization control portion in the arrangement direction are set so that the total amount of energy of the beam components that have passed through the first polarization control portion is equal to or substantially equal to that of the beam components that have passed through the second polarization control portion. As described above, since the length of the first polarization control portion in the arrangement direction and the length of the second polarization control portion in the arrangement direction are set so that the total amount of energy of the beam components that have passed through the first polarization control portion is equal to or substantially equal to that of the beam components that have passed through the second polarization control portion, in both of the pulsed laser beams emitted from the first laser light source and the second laser light source, the total amount of energy of the beam components in a first polarization state can be equal to or substantially equal to that of the beam components in a second polarization state on a surface to be irradiated with a laser beam. Accordingly, laser irradiation (e.g., laser annealing of a semiconductor substrate) can be performed more stably. According to a preferred embodiment mode of the present invention, at least one of the first polarization control portion and the second polarization control portion is divided into plural parts so as to sandwich all or a part of the other in the arrangement direction. As described above, at least one of the first polarization control portion and the second polarization control portion may be divided into plural parts so as to sandwich all or a part of the other in the arrangement direction. Even in the case of this structure, effects similar to the above-described effects can be obtained. According to a preferred embodiment mode of the present invention, the polarization directions of linearly-polarized pulse laser beams emitted from the first laser light source and the second laser light source are at 90° to each other. The first polarization control portion is a half wave plate which rotates the polarization directions of beam components emitted from the first laser light source and the second laser light source by 90°. The second polarization control portion is a wave plate which does not change the polarization states of beam components emitted from the first laser light source and the second laser light source. As described above, the polarization direction of the beam components which have passed through the half wave plate of the first polarization control portion is rotated by 90°, and the polarization state of the beam components which have passed through the second polarization control portion is not changed. Accordingly, the polarization state of beam components of the pulsed laser beam which have passed through the first polarization control portion can be different from that of beam components of the pulsed laser beam which have passed through the second polarization control portion. According to an another embodiment mode of the present invention, the polarization directions of linearly-polarized pulse laser beams emitted from the first laser light source and the second laser light source are at 90° to each other. The first polarization control portion and the second polarization control portion are quarter wave plates which each have an optical axis at an angle of 45° with respect to each of the polarization directions of the pulsed laser beams emitted from the first laser light source and the second laser light source. The optical axes of the first polarization control portion and the second polarization control portion are at 90° to each other. When an optical axis of a quarter wave plate makes an angle of 45° on one side with the polarization direction of a linearly-polarized laser beam, the quarter wave plate changes the laser beam passing through it to circularly polarized light whose polarization direction is rotated in a first direction. When an optical axis of a quarter wave plate makes an angle of 45° on the other side with the polarization direction of the linearly-polarized laser beam, the quarter wave plate changes the laser beam passing through it to circularly polarized light rotating in a direction opposite to the first direction. Thus, in the above-described structure, the first polarization control portion and the second polarization control portion are quarter wave plates which each have an optical axis at an angle of 45° with respect to each of the polarization directions of the pulsed laser beams emitted from the first laser light source and the second laser light source, and the optical axes of the first polarization control portion and the second polarization control portion are at 90° to each other. Therefore, the beam components which have passed through the first polarization control portion and the beam components which have passed through the second polarization control portion can be in circular polarization states in which their polarization directions rotate in directions opposite to each other. Accordingly, the beam components which have passed through the first polarization control portion and the beam components which have passed through the second polarization control portion can be in different polarization states. It is preferable that the optical path length of the pulsed laser beam inside the second polarization control portion be equal to or substantially equal to that of the pulsed laser beam inside the first polarization control portion. As described above, since the optical path length of the pulsed laser beam inside the second polarization control portion is equal to or substantially equal to that of the pulsed laser beam inside the first polarization control portion, difference in the optical path length of the pulsed laser beam does not occur between the first polarization control portion and the second polarization control portion. Accordingly, adverse effects due to the difference in the optical path length (e.g., image position error on a surface to be irradiated with a laser beam) can be prevented. According to a mode of the present invention described above, in the case where pulsed laser beams from two laser light sources are guided to pass through the same optical path for irradiation of an object to be irradiated with the laser beams, the occurrence of adverse effects on the object to be irradiated with the laser beam due to the difference in the polarization state between the pulsed laser beams can be prevented or significantly reduced. Accordingly, by performing laser irradiation of a semiconductor substrate with the use of a laser irradiation apparatus which is a mode of the present invention, a stable crystalline semiconductor can be obtained. The modes for carrying out the present invention will be described with reference to the accompanying drawings. Note that in the drawings, the same portions or portions having similar functions are denoted by the same reference numerals, and repeated description thereof is omitted. FIG. 1 is a structural view of a laser irradiation apparatus according to Embodiment Mode 1 of the present invention. FIG. 2 is an enlarged view of a portion II in FIG. 1. As shown in FIG. 1, a laser irradiation apparatus 10 is provided with a first laser light source 3, a second laser light source 4, a pulse control device 5, an optical path combining optical member 7, a beam expander 8, a polarization control member 9, and a laser beam superimposing optical member 11. The first laser light source 3 is a laser resonator which emits a polarized pulse laser beam with a predetermined frequency. The second laser light source 4 is a laser resonator which emits, with a predetermined frequency, a pulsed laser beam which is polarized differently from the pulsed laser beam emitted from the first laser light source 3. In this example, the frequency of the pulsed laser beam emitted from the first laser light source 3 is equal to or substantially equal to that of the pulsed laser beam emitted from the second laser light source 4. In this embodiment mode, the first laser light source 3 emits a pulsed laser beam polarized linearly in a perpendicular direction on the plane of the paper of FIGS. 1 and 2 (hereinafter referred to as a “first linearly-polarized state”) with a predetermined frequency. The second laser light source 4 emits a pulsed laser beam polarized linearly in an up and down direction on the plane of the paper of FIGS. 1 and 2 (hereinafter referred to as a “second linearly-polarized state”) with a predetermined frequency. The pulse control device 5 controls the first laser light source 3 and the second laser light source 4 so as not to synchronize timing of emission of pulsed laser beams from the first laser light source 3 and the second laser light source 4. The optical path combining optical member 7 guides the pulsed laser beams emitted from the first laser light source 3 and the second laser light source 4 to pass through the same optical path. Thus, the frequency of a pulsed laser beam can be doubled and the power of a pulsed laser beam can be increased. The optical path combining optical member 7 may be the same as the optical path combining optical member 35 shown in FIG. 9. In an example of FIG. 1, the optical path combining optical member 7 is a polarization beam splitter which reflects the pulsed laser beam emitted from the first laser light source 3 and transmits the pulsed laser beam emitted from the second laser light source 4. The beam expander 8 adjusts each of pulsed laser beams from the optical path combining optical member 7 so that the shapes thereof have an elongated shape. Each of the pulsed laser beams which have passed through the beam expander 8 is adjusted so that they have a cross-section with an elongated shape (e.g., a linear shape or a rectangular shape) in a direction perpendicular to the traveling direction of the pulsed laser beams on the surface to be irradiated with the laser beam of the object to be irradiated with the laser beam. In FIGS. 1 and 2, the cross-sectional shapes are adjusted to have an elongated shape in an up and down direction in FIGS. 1 and 2. The polarization control member 9 controls the polarization state of the pulsed laser beam from the optical path combining optical member 7 and the beam expander 8. The polarization control member 9 is arranged in the arrangement direction perpendicular to the traveling direction of the pulsed laser beam (an up and down direction in FIG. 2) and is provided with a first polarization control portion 13 and a second polarization control portion 15 through which beam components of the pulsed laser beam from the optical path combining optical member 7 pass. The first polarization control portion 13 and the second polarization control portion 15 are formed so that the polarization states of the beam components which have passed through the first polarization control portion 13 (hatched portions in FIG. 2) and the beam components which have passed through the second polarization control portion 15 are different polarization states of the first polarization state and the second polarization state. At least one of the first polarization control portion 13 and the second polarization control portion 15 may be divided into plural parts so as to sandwich all or a part of the other in the arrangement direction. In an example of FIG. 2, the first polarization control portion 13 is divided into three polarization control elements 13a, 13b, and 13c. The second polarization control portion 15 is divided into two polarization control elements 15a and 15b. The polarization control element 15a is sandwiched between the polarization control elements 13a and 13b in the arrangement direction. The polarization control element 15b is sandwiched between the polarization control elements 13a and 13c in the arrangement direction. The polarization control element 13a is sandwiched between the polarization control elements 15a and 15b in the arrangement direction. In this embodiment mode, the length of the first polarization control portion 13 in the arrangement direction and the length of the second polarization control portion 15 in the arrangement direction are set so that the total amount of energy of the beam components that have passed through the first polarization control portion 13 is equal to or substantially equal to that of the beam components that have passed through the second polarization control portion 15. In addition, in this embodiment mode, the first polarization control portion 13 (the polarization control elements 13a, 13b, and 13c) is a half wave plate, and the second polarization control portion 15 (the polarization control elements 15a and 15b) is a wave plate which does not change the polarization state of beam components which pass through it (a whole wave plate) or a quartz plate. The half wave plate is arranged so as to rotate the polarization direction of the pulsed laser beam emitted from the first laser light source 3 by 90° and also rotate the polarization direction of the pulsed laser beam emitted from the second laser light source 4 by 90°. That is, an optical axis of the half wave plate makes an angle of 45° with the polarization direction of the pulsed laser beam emitted from the first laser light source 3 and also makes an angle of 45° with the polarization direction of the pulsed laser beam emitted from the second laser light source 4 so that the polarization directions of the pulsed laser beams emitted from the first laser light source 3 and the second laser light source 4 are rotated by 90° by the half wave plate. Accordingly, when beam components in the first linearly-polarized state pass through the half wave plate, the polarization state is changed to the second linearly-polarized state from the first linearly-polarized state. When beam components in the second linearly-polarized state pass through the half wave plate, the polarization state is changed to the first linearly-polarized state from the second linearly-polarized state. The second polarization control portion 15 (the polarization control elements 15a and 15b) transmits the pulsed laser beam, and the second polarization control portion 15 is formed using a material such that the optical path length of the pulsed laser beam inside the second polarization control portion 15 is formed using the same material as that of the optical path length of the pulsed laser beam inside the first polarization control portion 13. That is, the material of the second polarization control portion 15 is the same as that of the first polarization control portion 13. For example, the second polarization control portion 15 may be a whole wave plate or a quartz plate made of quartz. Thus, when beam components in the first linearly-polarized state pass through the second polarization control portion 15, the polarization state remains the first linearly-polarized state. When beam components in the second linearly-polarized state pass through the second polarization control portion 15, the polarization state remains the second linearly-polarized state. The laser beam superimposing optical member 11 superimposes beam components in the first polarization state and beam components in the second polarization state on each other on the surface to be irradiated with the laser beam of the object to be irradiated with the laser beam. In this embodiment mode, the laser beam superimposing optical member 11 includes a cylindrical lens array 17 and a condenser lens 18. The cylindrical lens array 17 includes a plurality of convex cylindrical lenses 17a arranged in the arrangement direction. Thus, the pulsed laser beam that enters the cylindrical lens array 17 is divided into plural laser beams by the plurality of convex cylindrical lenses 17a. The plural divided laser beams are superimposed on each other on the surface to be irradiated with the laser beam of the object to be irradiated with the laser beam by the condenser lens 18. Thus, even if the pulsed laser beam has nonuniform energy density distribution before passing through the laser beam superimposing optical member 11, the pulsed laser beam comes to have uniform or nearly uniform energy density distribution on the surface to be irradiated with the laser beam of the object to be irradiated with the laser beam. In an example of FIG. 2, the convex cylindrical lenses 17a as many as the polarization control elements 13a, 13b, 13c, 15a, and 15b are provided. Accordingly, an entire laser irradiation region of the surface to be irradiated with the laser beam is irradiated with beam components from the polarization control elements, which pass through the convex cylindrical lenses 17a. Note that the object to be irradiated with the laser beam is a semiconductor substrate in this embodiment mode. The term “semiconductor substrate” means a substrate which is formed of a semiconductor such as a silicon wafer or an insulating substrate over the surface of which a semiconductor film is formed. In addition, the reference numeral 12 denotes a short-side direction condenser lens which concentrates the pulsed laser beam on the surface to be irradiated with the laser beam with respect to a perpendicular direction on the plane of the paper of FIG. 1. Next, the function of the laser irradiation apparatus 10 with the above-described structure will be described. The surface to be irradiated with the laser beam is irradiated with beam components in the first polarization state and beam components in the second polarization state from the polarization control member 9 so as to even out an energy density distribution over an entire laser irradiation region of the surface to be irradiated with the laser beam. Accordingly, in each position of the laser irradiation region, the first polarization state and the second polarization state are mixed. As described above, when beam components in the first linearly-polarized state pass through the half wave plate (the polarization control elements 13a, 13b, and 13c), the polarization state is changed to the second linearly-polarized state. When beam components in the second linearly-polarized state pass through the half wave plate, the polarization state is changed to the first linearly-polarized state. On the other hand, the polarization control elements 15a and 15b do not change the polarization state of beam components which pass through them. Thus, both of the pulsed laser beam in the first linearly-polarized state and the pulsed laser beam in the second linearly-polarized state come to have both of beam components in the first linearly-polarized state and beam components in the second linearly-polarized state by passing through the polarization control member 9. In FIG. 2, an energy density distribution of the pulsed laser beam before passing through the polarization control member 9 is shown corresponding to positions of the polarization control elements 13a, 13b, 13c, 15a, and 15b. FIGS. 3A to 3E show energy density distributions of beam components which have passed through the polarization control elements 13a, 13b, 13c, 15a, and 15b, respectively, on a surface to be irradiated with a laser beam in the case where the pulsed laser beam that has the energy density distribution shown in FIG. 2 and is in the first linearly-polarized state passes through the polarization control member 9. In this case, the energy density distribution is affected by the laser beam superimposing optical member 11. In FIGS. 3A to 3F, the vertical axes represent arrangement directions on the surface to be irradiated with the laser beam, and the horizontal axes represent energy density distributions of beam components. Specifically, FIG. 3A shows an energy density distribution of beam components which passes through the polarization control element 13a and is in the second linearly-polarized state on the surface to be irradiated with the laser beam. FIG. 3B shows an energy density distribution of beam components which passes through the polarization control element 13b and is in the second linearly-polarized state on the surface to be irradiated with the laser beam. FIG. 3C shows an energy density distribution of beam components which passes through the polarization control element 13c and is in the second linearly-polarized state on the surface to be irradiated with the laser beam. FIG. 3D shows an energy density distribution of beam components which passes through the polarization control element 15a and is in the first linearly-polarized state on the surface to be irradiated with the laser beam. FIG. 3E shows an energy density distribution of beam components which passes through the polarization control element 15b and is in the first linearly-polarized state on the surface to be irradiated with the laser beam. FIG. 3F shows a schematic energy density distribution in which energy density distributions shown in FIGS. 3A to 3F are superimposed on each other. As shown in this energy density distribution, the first linearly-polarized state and the second linearly-polarized state are mixed in each position of the laser irradiation region of the surface to be irradiated with the laser beam. Further, in this embodiment mode, the total amount of energy shown in FIGS. 3A to 3C and the total amount of energy shown in FIGS. 3D and 3E are the same. Furthermore, although FIG. 2 and FIGS. 3A to 3F show the case where the pulsed laser beam in the first linearly-polarized state passes through the polarization control member 9, the same can apply to the case where the pulsed laser beam in the second linearly-polarized state passes through the polarization control member 9. In this case, FIG. 3A shows an energy density distribution of beam components which passes through the polarization control element 13a and is in the first linearly-polarized state. FIG. 3B shows an energy density distribution of beam components which passes through the polarization control element 13b and is in the first linearly-polarized state. FIG. 3C shows an energy density distribution of beam components which passes through the polarization control element 13c and is in the first linearly-polarized state. FIG. 3D shows an energy density distribution of beam components which passes through the polarization control element 15a and is in the second linearly-polarized state. FIG. 3E shows an energy density distribution of beam components which passes through the polarization control element 15b and is in the second linearly-polarized state. Note that the object to be irradiated with the laser beam is transferred in a perpendicular direction on the plane of the paper of FIGS. 1 and 2 by a transport device (not shown) while the surface to be irradiated with the laser beam of the object to be irradiated with the laser beam is irradiated with the pulsed laser beam by the laser irradiation apparatus 10. Accordingly, a desired range of the object to be irradiated with the laser beam is irradiated with the pulsed laser beam. In the laser irradiation apparatus 10 of the above Embodiment Mode 1 of the present invention, in the case where pulsed laser beams which are in different polarization states and are emitted from the first laser light source 3 and the second laser light source 4 are guided to pass through the same optical path for irradiation of the object to be irradiated with the laser beams, each of the pulsed laser beams emitted from the first laser light source 3 and the second laser light source 4 is divided into plural beam components in different polarization states (the first polarization state and the second polarization state) by the polarization control member 9, and the beam components in different polarization states are superimposed on each other on the surface to be irradiated with the laser beam of the object to be irradiated with the laser beam by the laser beam superimposing optical member 11. Accordingly, both of the pulsed laser beams are in a state in which the first polarization state and the second polarization state are mixed on the surface to be irradiated with the laser beam. Thus, the occurrence of adverse effects on the object to be irradiated with the laser beam due to the difference in the polarization state between the pulsed laser beams can be prevented or significantly reduced. Further, the length of the first polarization control portion 13 in the arrangement direction and the length of the second polarization control portion 15 in the arrangement direction are set so that the total amount of energy of the beam components that have passed through the first polarization control portion 13 is equal to or substantially equal to that of the beam components that have passed through the second polarization control portion 15; accordingly, in both of the pulsed laser beams emitted from the first laser light source 3 and the second laser light source 4, the total amount of energy of the beam components in the first polarization state can be equal to or substantially equal to that of the beam components in the second polarization state on the surface to be irradiated with the laser beam. Accordingly, laser irradiation (e.g., laser annealing of a semiconductor substrate) can be performed more stably. Furthermore, since the second polarization control portion 15 is formed using a material such that the optical path length of the pulsed laser beam inside the second polarization control portion 15 is formed using the same material as that of the optical path length of the pulsed laser beam inside the first polarization control portion 13, difference in the optical path length of the pulsed laser beam does not occur between the second polarization control portion 15 and the first polarization control portion 13. Accordingly, adverse effects due to difference in the optical path length (e.g., image position error on a surface to be irradiated with a laser beam) can be prevented. FIGS. 4A to 4F and FIGS. 5A to 5F each are images of a surface irradiated with a laser beam in order to show effects obtained according to Embodiment Mode 1. FIGS. 4A to 4F are electron microscope images. FIGS. 5A to 5F are optical microscope images. FIGS. 4A to 4C and FIGS. 5A to 5C each are images of a surface irradiated with a laser beam of a semiconductor substrate which is obtained by laser irradiation of the semiconductor substrate without using the polarization control member 9. FIG. 4A and FIG. 5A show the case of irradiation with a p-polarized pulse laser beam. FIG. 4B and FIG. 5B show the case of irradiation with an s-polarized pulse laser beam. FIG. 4C and FIG. 5C are low magnification images showing the case of laser irradiation with a composition of a p-polarized pulse laser beam and an s-polarized pulse laser beam (that is, the case where laser irradiation is performed using a structure in which the polarization control member 9 is omitted in FIG. 1). On the other hand, FIGS. 4D to 4F and FIGS. 5D to 5F each are images of a surface irradiated with a laser beam of a semiconductor substrate which is obtained by laser irradiation of the semiconductor substrate by using the polarization control member 9. FIG. 4D and FIG. 5D show the case of laser irradiation with a p-polarized pulse laser beam (that is, the case where only the first laser light source 3 is used of the first laser light source 3 and the second laser light source 4 in FIG. 1). FIG. 4E and FIG. 5E show the case of laser irradiation with an s-polarized pulse laser beam (that is, the case where only the second laser light source 4 is used of the first laser light source 3 and the second laser light source 4 in FIG. 1). FIG. 4F and FIG. 5F are low magnification images showing the case of laser irradiation with a composition of a p-polarized pulse laser beam and an s-polarized pulse laser beam (that is, the case where laser irradiation is performed using a structure of FIG. 1). FIGS. 4A to 4F and FIGS. 5A to 5F are compared to each other. Between FIGS. 4A and 5A and FIGS. 4B and 5B, there is a difference in the polarization state. Thus, as shown in FIG. 4C and FIG. 5C, unevenness due to difference in the polarization state is caused when a combined pulse laser beam is used for laser irradiation. On the other hand, in the case of this embodiment mode, between FIGS. 4D and 5D and FIGS. 4E and 5E, there is little difference in the polarization state. Thus, as shown in FIG. 4F and FIG. 5F, unevenness due to difference in the polarization state is not caused when a combined pulse laser beam is used for laser irradiation. The structure of a polarization control member of a laser irradiation apparatus according to Embodiment Mode 2 of the present invention is different from that of the polarization control member 9 of Embodiment Mode 1. The other structures of Embodiment Mode 2 may be the same as those of Embodiment Mode 1. FIG. 6 is an enlarged view of a portion II in FIG. 1 and shows a case of Embodiment Mode 2. Parts of the structure of a polarization control member 19, which are similar to those of the structure of Embodiment Mode 1, will be described. As shown in FIG. 6, the polarization control member 19 controls the polarization state of the pulsed laser beam from the optical path combining optical member 7. The polarization control member 19 is arranged in an arrangement direction (an up and down direction in FIG. 6). The polarization control member 19 is provided with a first polarization control portion 21 and a second polarization control portion 23, through which beam components of the pulsed laser beam from the optical path combining optical member 7 pass. The first polarization control portion 21 and the second polarization control portion 23 are formed so that the polarization states of the beam components that have passed through the first polarization control portion 21 and the beam components that have passed through the second polarization control portion 23 are different polarization states of the first polarization state and the second polarization state. At least one of the first polarization control portion 21 and the second polarization control portion 23 may be divided into plural parts so as to sandwich all or a part of the other in the arrangement direction. In an example of FIG. 6, the first polarization control portion 21 is divided into three polarization control elements 21a, 21b, and 21c. The second polarization control portion 23 is divided into two polarization control elements 23a and 23b. The polarization control element 23a is sandwiched between the polarization control elements 21a and 21b in the arrangement direction. The polarization control element 23b is sandwiched between the polarization control elements 21a and 21c in the arrangement direction. The polarization control element 21a is sandwiched between the polarization control elements 23a and 23b in the arrangement direction. In addition, the length of the first polarization control portion 21 in the arrangement direction and the length of the second polarization control portion 23 in the arrangement direction are set so that the total amount of energy of the beam components that have passed through the first polarization control portion 21 is equal to or substantially equal to that of the beam components that have passed through the second polarization control portion 23. Parts of the structure of the polarization control member 19, which are different from those of the structure of Embodiment Mode 1, will be described. According to Embodiment Mode 2, the first polarization control portion 21 and the second polarization control portion 23 of the polarization control member 19 are each quarter wave plates which have an optical axis at an angle of 45° with respect to each of the polarization directions of the pulsed laser beam emitted from the first laser light source 3 (a perpendicular direction on the plane of the paper of FIG. 6) and the pulsed laser beam emitted from the second laser light source 4 (an up and down direction on the plane of the paper of FIG. 6). The optical axes of the first polarization control portion 21 and the second polarization control portion 23 are at 90° to each other. Thus, when beam components which are emitted from the first laser light source 3 and are in the first linearly-polarized state pass through the first polarization control portion 21, the beam components are changed to beam components of circularly polarized light whose polarization direction rotates in a direction denoted by an arrow A in FIG. 6. Further, when beam components which are emitted from the first laser light source 3 and are in the first linearly-polarized state pass through the second polarization control portion 23, the beam components are changed to beam components of circularly polarized light whose polarization direction rotates in a direction denoted by an arrow B in FIG. 6, which is an opposite direction to the direction denoted by the arrow A. That is, the beam components of circularly polarized light that rotates in the direction denoted by the arrow A are in the first polarization state, and the beam components of circularly polarized light that rotates in the direction denoted by the arrow B are in the second polarization state. FIG. 6 shows a case where the pulsed laser beam in the first linearly-polarized state enters the polarization control member 19. In the case where beam components which are emitted from the second laser light source 4 and are in the second linearly-polarized state pass through the first polarization control portion 21, the beam components are changed to beam components of circularly polarized light whose polarization direction rotates in the direction denoted by the arrow B in FIG. 6, which is an opposite direction to the direction denoted by the arrow A. Further, in the case where beam components which are emitted from the second laser light source 4 and are in the second linearly-polarized state pass through the second polarization control portion 23, the beam components are changed to beam components of circularly polarized light whose polarization direction rotates in the direction denoted by the arrow A in FIG. 6. That is, the beam components of circularly polarized light that rotates in the direction denoted by the arrow B are in the first polarization state, and the beam components of circularly polarized light that rotates in the direction denoted by the arrow A are in the second polarization state. According to the laser irradiation apparatus of the above Embodiment Mode 2, each of the pulsed laser beams emitted from the first laser light source 3 and the second laser light source 4 is divided into beam components in the first polarization state and beam components in the second polarization state by the optical path combining optical member 7, and the beam components in the first polarization state and the beam components in the second polarization state are superimposed on each other on the surface to be irradiated with the laser beam of the object to be irradiated with the laser beam by the laser beam superimposing optical member 11. Accordingly, both of the pulsed laser beams are in a state in which the first polarization state and the second polarization state are mixed on the surface to be irradiated with the laser beam. Thus, the occurrence of adverse effects on the object to be irradiated with the laser beam due to the difference in the polarization state between the pulsed laser beams can be prevented or significantly reduced. As for other effects, effects and functions which are similar to those of the laser irradiation apparatus 10 described in the above Embodiment Mode 1 can also be obtained in Embodiment Mode 2. In Embodiment Mode 1 or Embodiment Mode 2, a modified example, which is described below, can be employed. A modified example of Embodiment Mode 1 will be described below; however, the same modified example can be employed for Embodiment Mode 2. The polarization control member 9 of Embodiment Mode 1 may include polarization control elements 13a and 13b and polarization control elements 15a, 15b, and 15c as shown in FIGS. 7A to 7C. FIG. 7A shows a polarization control member 9 that includes two polarization control elements 13a and 13b and one polarization control element 15a. FIG. 7B shows a polarization control member 9 that includes one polarization control element 13a and one polarization control element 15a. FIG. 7C shows a polarization control member 9 that includes two polarization control elements 13a and 13b and three polarization control elements 15a, 15b, and 15c. In FIGS. 7A to 7C, the length of the first polarization control portion 13 including the polarization control elements 13a and 13b in the arrangement direction and the length of the second polarization control portion 15 including the polarization control elements 15a, 15b, and 15c in the arrangement direction are set so that the total amount of energy of the beam components that have passed through the first polarization control portion 13 is equal to or substantially equal to that of the beam components that have passed through the second polarization control portion 15, as described above. Further, in Embodiment Mode 1, as shown in FIG. 8, the first polarization control portion 13 may include one polarization control element 13a, and the second polarization control portion 15 may include one polarization control element 15a. A width Wa1 of the polarization control element 13a in an arrangement direction and a width Wa2 of the polarization control element 15b in an arrangement direction (Wa1=Wa2 in FIG. 8) can be n times as large as a width Wb of the convex cylindrical lens 17a of the cylindrical lens array 17 (note that n is an integer more than one). In this case, it is preferable that a width Wc of the pulsed laser beam at an incidence plane when entering the polarization control member 9 in an arrangement direction be m times as large as the width Wb of the convex cylindrical lens 17a (note that m is an integer more than one). Accordingly, the number of the polarization control element 13a and the polarization control element 15a can be reduced. Furthermore, an entire laser irradiation region of the surface to be irradiated with the laser beam can be irradiated with beam components which have passed through the polarization control element 13a and the polarization control element 15a in an arrangement direction. Thus, even if the number of the polarization control element 13a and the polarization control element 15a is reduced, generation of a portion which has relatively high energy density of the pulsed laser beams in the first polarization state or the second polarization state in the laser irradiation region can be prevented. FIG. 8 shows an example of a case where one polarization control element 13a and one polarization control element 15a are provided. In the case where other numbers of polarization control elements are provided, the formulas “Wa1=n1×Wb, Wa2=n2×Wb, and Wc=m×Wb” are satisfied (note that n1, n2, and m are integers more than one) so that similar effects can be obtained. The present invention is not limited to the above embodiment modes, and it is needless to say that the mode and details can be changed in various ways without departing from the scope and spirit of the present invention. For example, although the structure in which the first polarization control portion 13 (the polarization control elements 13a to 13c) and the second polarization control portion 15 (the polarization control elements 15a and 15b) are arranged in an up and down direction in FIG. 2 is described, the structure is not limited thereto. For example, in the case where the cross-sectional shape of the pulsed laser beam that enters the polarization control member 9, which is perpendicular to the traveling direction of the pulsed laser beam, is also expanded in a perpendicular direction on the plane of the paper of FIG. 2, the first polarization control portion 13 (the polarization control elements 13a to 13c) and the second polarization control portion 15 (the polarization control elements 15a and 15b) can also be arranged in a perpendicular direction on the plane of the paper of FIG. 2 as in the case of an up and down direction in FIG. 2. The same can apply to other cases such as FIG. 6. This application is based on Japanese Patent Application serial No. 2008-075027 filed with Japan Patent Office on Mar. 24, 2008, the entire contents of which are hereby incorporated by reference.
	abstract	A laser wake-field acceleration (LWFA)-based nuclear fission system and related techniques are disclosed. In accordance with some embodiments, the disclosed system may be configured to accelerate charged particles, such as protons, to velocities close to the speed of light utilizing LWFA. The system also may be configured, in accordance with some embodiments, to use these high-energy relativistic charged particles in causing nuclear fission of a given downstream fissionable target, thereby releasing large amounts of harvestable energy. Optionally, the system further may be configured, in accordance with some embodiments, to utilize charged particles resulting from the fission in producing electrical energy.
047926880	description	DETAILED DESCRIPTION FIG. 1 illustrates, in block diagram form, a particle beam lithography system 10 for processing a workpiece 12, such as a semiconductor wafer or mask. This particle beam lithography system 10 also includes a differentially pumped seal apparatus 14 of this invention, hereinafter simply called "the seal apparatus", mounted at the output of a beam column 16. The beam column 16 includes an electron or ionized particle source, demagnification optics and projection and deflection optics which generate a finally focused beam 20 and may also include illumination and shaping optics when a shaped beam is utilized. A central tube 22 (shown in phantom) is within the column 16 and is traversed by the beam 20 and maintained at a high vacuum by a high vacuum pump 24 coupled to the column 16. The beam 20 passes through the seal apparatus 14 and impinges on the workpiece 12. The workpiece 12 is supported and held in position on a movable stage 26 which is translated in an X-Y direction by an X and Y axis drive system 30 and the position of the stage is sensed by X and Y position sensors 32 which are typically laser interferometers. The X and Y axis define a horizontal plane while the Z axis coincides with the axis of the beam. The complete lithography system 10 further includes a computer (controller), and associated electronics which controls the beam, the drive system, the vacuum system, the wafer handling system and stores pattern data and provides beam control signals. The relationship between the seal apparatus 14 and the workpiece 12 is illustrated in FIG. 2. The seal apparatus 14 includes a plurality of conically shaped sleeves 34, 36 and 40, partially shown in FIG. 2, which terminate in a generally planar tip 42 positioned, during processing, slightly above the workpiece 12. The position of the tip 42 relative to the workpiece 12 is referred to as a gap G and is important to the operation of the sealing apparatus 14 and the graded seal obtained thereby. As mentioned above, the seal apparatus 14 has increased vacuum conductance, provides a gap on the order of 12 to 15 microns, + or -3 microns, which is smaller than that used in the prior art, and a high vacuum on the order of 10.sup.-6 Torr which is lower than that of the prior art. As shown, the sleeves 34, 36 and 40 define a plurality of apertures. The first aperture 44 is annular and coupled to a first stage vacuum pump 46 which reduces the pressure around the two inner sleeves to a low vacuum level on the order of 1.0 Torr. The second aperture 48, inside the first aperture 44, is annular and coupled to a second stage vacuum pump 50 which reduces the pressure to an intermediate vacuum level on the order of 10.sup.-3 Torr. The third and central aperture 52 is coupled to a second high vacuum pump 54. This aperture 52 is maintained at a high vacuum corresponding to the vacuum in the central tube 22 which is on the order of 10.sup.-6 Torr and the beam 20 is scanned over the region of the workpiece 12 within the central aperture 52 as the workpiece 12 moves relative to the aperture. The construction of the seal apparatus 14 which accomplishes the reduction in vacuum and smaller gap size is shown in detail in FIGS. 3-7. The seal apparatus 14 is shown assembled in FIGS. 4-7 while the individual elements of the seal apparatus 14 are shown separately in FIG. 3. As shown, the seal apparatus 14 comprises three sectors of a circular cylinder (shown as a right circular cylinder) designated herein as a rough port nozzle R (of approximately 180 degrees), a medium port nozzle M (of approximately 90 degrees) and a high port nozzle H (of approximately 90 degrees). The term "approximate" is used herein to signify that any one of the nozzle sectors may vary in its angular extent so long as the total of 360 degrees for a circular cylinder is maintained and the terms "rough", "medium" and "high" are used to describe the degree of vacuum in each nozzle. When assembled, as in FIGS. 4-7, the seal apparatus 14 defines a circular, apertured, top 56 which is relatively thin as compared to an integral depending cylinder 58 of a lesser outer diameter. The latter terminates in the apertured sleeve 34 which is frustoconical in form and integral with the depending cylinder 58. As most clearly shown in FIG. 3, the rough port nozzle R is 180 degree sector of essentially three parts; a relatively flat top part 56 R with a depending cylindrical part 58 R, both of 180 degrees, and the frustoconical sleeve 34 of 360 degrees as shown in FIGS. 6 and 7. This sleeve 34 extends slightly below the depending cylindrical part 58 R, as at 60, is relatively flat and thin and with its aperture 44, being the largest of the three apertures, has its center on the center line of the seal apparatus 14. The wall of the depending cylindrical part 58 R is provided with a relatively large, radially oriented, channel 62 opening into the area of the sleeve 34 (see FIGS. 5 and 6). As will be apparent from the further description herein, this large channel 62 provides direct and unimpeded access to the aperture 44 when the seal apparatus is fully assembled. The top of sleeve 34 is also provided with an alignment ring or rib 64 of 180 degrees which is used to hold the other nozzles in place during assembly of the seal apparatus 14. The medium port nozzle M, shown separately in FIG. 3, is of essentially four parts although only a 90 degree sector. This nozzle M has a relatively flat top part 56 M with a depending cylindrical part 58 M and an inner circular integral cylinder part 66 which terminates in sleeve 36 which is also frustoconical with its aperture 48 on the center line of the seal apparatus 14. Cylindrical part 66 is thin walled and of a diameter less than the diameter of the depending cylindrical part 58 M to fit within the inner wall of the depending cylindrical part 58 R of the rough port nozzle R. The aperture 48 is on the center line of the seal apparatus 14 and is smaller than the aperture of the rough port nozzle R and concentric with the frustoconical sleeve 34 of the rough port nozzle R, when assembled. The inner cylindrical part 66 has a cut away portion 70, the width and depth of which will allow the high port nozzle H to be inserted therein. The wall of the depending cylindrical part 58 M is provided with a relatively large, radially oriented, channel 72, opening into the inner cylinder 66, to provide direct and unimpeded access to the aperture 48. The bottom wall of the depending cylindrical part 58 M has a downwardly extending ring 74 whose inner diameter is larger than the aligning ring 64 on the rough port nozzle R to facilitate assembly. The high port nozzle H, shown separately in FIG. 3, is also a sector of 90 degrees and essentially three parts; a top part 56 H with a depending cylindrical part 58 H and the conical sleeve part 40 of 360 degrees. This sleeve part 40 has the highest degree of taper and terminates in aperture 52 which is the smallest of the three apertures. The depending cylindrical part 58 H is also provided with a relatively large, radially oriented, channel 76 directly accessing the aperture 52. The bottom wall of the depending cylindrical part 58 H has a downwardly extending ring 80 whose inner diameter is larger than the aligning ring 64 on the rough port nozzle R to facilitate assembly. As in the prior art, the seal apparatus 14 is assembled and brazed to connect the nozzle sectors together. When the medium port nozzle M is placed on the aligning bar 64 so that the conical sleeve 36 is concentric with the conical sleeve 34 of the rough port nozzle R, the cylindrical inner sleeve part 66 is spaced from an inner cylindrical wall 82 of the depending cylindrical part 58 R thereby forming a rough vacuum chamber of 360 degrees which communicates with sleeve aperture 44 of 360 degrees and the relatively large radial channel 62. Thereafter, the high port nozzle H is placed on the aligning bar 64 in the cutaway 70, so that the conical sleeve 40 is in alignment with the other conical sleeves. Thus assembled, the inside vertical cylindrical wall 84 of the inner cylindrical part 66 forms, with the outside wall 86 of the conical sleeve 40, a tapered medium vacuum chamber of 270 degrees which communicates with sleeve aperture 48 and with the relatively large channel 72. The medium vacuum chamber is tapered due to the disposition of the walls 84 and 86. With the high port nozzle in place, the tapered high vacuum chamber of 360 degrees is formed by the inner wall 90 of the sleeve 40 which is in communication with sleeve aperture 52 of 360 degrees and with the relatively large channel 76. From the foregoing, it can be seen that air entering the rather restricted sleeve apertures and narrow gap will immediately enter passages which are large both horizontally and vertically as shown in FIG. 7 by arrows 92 thus producing a high vacuum conductance which, with a gap less than used in the prior art, increases the vacuum within the sealing apparatus and permits smaller vacuum pumps to be used. It should be apparent that, while the prior art seal apparatus is higher, (about 1.2 inches) and wider (about 3.25 inches) than the seal apparatus of this invention (which is 0.5 inches high and 1.34 inches wide), each port and passageway of the seal apparatus of this invention is higher than the prior art seal apparatus because the ports and pathways of the prior art seal apparatus are vertically stacked and some of the height is taken up by the thickness of the nested upper and lower plate members. Also, while only three port nozzles R, M and H are shown as the preferred embodiment, more than three nozzles may be designed utilizing the teachings of this invention; the only limitation being the balance of the vacuum conductance obtainable and the size of the passageways and channels within a 360 degree structure. When there is shown or described what is presently considered the preferred embodiment of the invention, it will occur 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 in the appended claims.
045338329	description	DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1-3, an assembled modular radiation attenuation system embodying the invention is designated generally by the reference numeral 10. The modular radiation attenuation system or radiation attenuator 10 is shown assembled around a pipe or nozzle 12 such as an inlet or outlet pipe of a boiling water reactor, and includes a plurality of modules 14. Boiling water reactors have a plurality of inlet and outlet pipes, typically two large inlets and twelve outlet pipes. An opening 15 is provided around each of the pipes, which opening can be as large as five feet by five feet. Each module 14 generally includes a skin 16 which maintains a stackable preformed shape of the modules 14 and which retains a radiation attenuation medium therein. The skin 16 is substantially dimensionally stable, but is flexible enough to conform to the skin of an adjacent module or the outer irregular surface of the pipe 12 or other radiation emitting object. Each of the modules 14 is preferably of a generally rectangular shape, which allows them to be conveniently stacked upon one another to form the system 10. The modules 14 are assembled and conformed to one another, the pipe 12 and to a shielding wall 18 which is part of a concrete wall formed around the reactor. This provides a substantial gross elimination of radiation exposure through the opening 15. The modules 14 can also be considered soft bricks and also can be stacked inside of the pipe 12, if it is open, to eliminate radiation therefrom. The modules 14 are stacked around the pipe 12 or other radiating emitting object in any convenient manner; however, the modules 14 provide the maximum radiation attenuation when aligned in the direction of the radiation path as illustrated in FIG. 3. Referring to FIGS. 4-7, the modules 14 can include a flexible inner liner or skin portion 20, which is placed in a mold 22. The liner 20 can be a section of a plastic or pvc tubing, preferably at least 20 mils thick. A wall piece 24 of the same or similar material is then secured to the portion 20 by a heating element 26 or by sewing or adhesive. The sealed pieces 20 and 24 are then inserted in the mold and filled with a radiation attenuation medium 28, such as lead shot. The medium 28 can also be compressed steel wool, in a single piece, in layers or slabs. The inner liner 20 is also useful in the case of the compressed lead wool, since the wool has a lot of fine particles or pieces and the liner prevents migration of the pieces from the module. In the case of lead particles or shot, the flexible inner liner provides a method of containing the particles during assembly and provides shock relief for the modules 14 after assembly. When utilizing the lead particles, a binding medium can be preferable, since it reduces or completely eliminates the free migration of the particles if the modules 14 are ruptured. The binding medium can be a water soluble paste-like binder, which hardens when exposed to air. The binding medium provides a number of benefits. The medium fills the spaces between the particles without increasing the total volume of the modules 14 and without decreasing the shielding efficiency of the modules 14. The material adds as much as twenty-five to thirty percent volume to the modules 14 by filling in the spaces, while only adding about five percent to the total weight of the modules 14. The particles as mentioned above, are also prevented from migrating by the binding medium and it makes the modules self sealing when torn or ripped since it hardens when exposed to air. One convenient medium is a latex caulking material, which is compatible with the austenitic stainless steel found in some generating plants. As illustratd in FIG. 8, the attenuation medium 28 is then sealed in by a second wall piece 30, in a similar manner as the piece 24. The sealed pieces provide an integral flexible inner liner or skin 32 as illustrated in FIG. 9. The skin 32 includes a lip 34, which can be heat sealed and sewn if desired. An outer skin 36, preferably is then secured around the inner skin 32 to complete the module 14. The outer skin 36 is sewn and/or heat sealed around the skin 32 as illustrated in FIG. 11, to form the module 14 as illustrated in FIG. 12. The skin 36, preferably is formed from a fairly rigid material such as reinforced, laminated or coated pvc or nylon or polyester inner weave so that the modules 14 maintain a dimensionally stable form. The skin 36 preferably is double sewn and inverted so only one outside closing seam 37 is exposed. A second module embodiment 14' is best illustrated in FIG. 13. The steps of forming the inner skin 32 can be the same as those described above; however, an outer skin 38 is formed by a unitary plastic material, such as by coating or dipping the liner in plastic. The system 10 can be free standing, since the modules 14 are stackable on one another; however, if desired a frame 40 can be utilized such as illustrated in FIGS. 14-16. The frame 40 can include a bottom support plate 42 and a pair of side plates 44 and 46. When utilized with a nozzle or the pipe 12, the frame 40 can include a pair of retainer plates 48 and 50. A rectangular frame unit 52 can be utilized to frame the pipe 12. The unit 52 includes bottom and top shelf plates 54 and 56, respectively, and a pair of side retainer plates 58 and 60. The unit 52 sets on the bottom support plate 42 forming a cavity 62 which can be filled with the modules 14. Once the cavity 62 is filled, a pair of perimeter retaining plates 64 and 66 can be secured to form the finished frame 40. The shape and configuration of the frame 40 can be varied as desired in accordance with the configuration of the radiation emitting object to be shielded. The assembled system 10' utilizing the frame 40 is best illustrated in FIGS. 16 and 17. The frame 40 provides faster assembly and disassembly of the modules 14, as well as a fixed location and framework for the assembly which facilitates the proper placement and conforming of the modules 14 to substantially eliminate radiation exposure. The assembly 10 is especially useful in reducing radiation exposure in set up and disassembly, but also provides for maximum protection while the assembly 10' is in place, such as when working on the pipe 12. Many modifications and variations of the present invention are possible in light of the above teachings. The skin can be formed from any flexible, yet substantially rigid material which can provide the stackable dimensionally stable module form, but allows for some flexiblity. The skin can be formed out of numerous impervious materials, such as 30 mil pvc, reinforced pvc or nylon, fiberglass, rubber or laminates of the materials, such as reinforced, rubberized or plasticized cloth. The modules can be designed for any desired shape, height and width, although one convenient size is two inches by three inches by six inches. Such a size permits the modules to weigh an easily manageable weight of about ten pounds, which is less than half as heavy as a conventional solid lead precision brick. The shielding efficiency of the modules 14 with lead shot or wool is approximately sixty percent of that of solid lead. Therefore a mean free path length through the modules of about six and one half inches is equivalent to four inches of solid lead. It is therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.
052788768	description	DESCRIPTION OF THE PREFERRED EMBODIMENT(S) Illustrated schematically in FIG. 1 is an exemplary boiling water nuclear reactor 10 which includes an annular pressure vessel 12 having a longitudinal centerline axis 14. Disposed inside the pressure vessel 12 is a conventional nuclear reactor core 16 submerged in reactor water 18 and effective for generating heat to boil the water 18 for generating steam 18a. Disposed above the core 16 is a conventional assembly of steam separators 20 and in turn a steam dryer assembly 22 to remove moisture from the steam 18a. The pressure vessel conventionally includes a cylindrical shell 24 and a lower head 26 conventionally welded to the bottom of the shell 24, and an upper head 28 conventionally bolted to the top of the shell 24 and including an integral vent line 30 in accordance with one embodiment of the present invention. The shell 24 also includes a main discharge nozzle 32 to which is conventionally joined a main steam outlet line 34 which channels the steam 18a to a conventional steam turbine-generator, for example, for generating electrical power. The upper portion of the pressure vessel 12 is illustrated in more particularity in FIG. 2. The upper head 28 includes an arcuate dome 36 suitably configured for withstanding the relatively high pressures generated in the pressure vessel 12 and conventionally includes an integral annular mounting or head flange 38 disposed coaxially with the centerline axis 14 and extending around the perimeter of the dome 36. The shell 24 includes an integral annular supporting or shell flange 40 also disposed coaxially about the centerline axis 14 and extending around the top of perimeter of the shell 24 for supporting the upper head 28. As shown in more particularity in FIG. 3, the head flange 38 includes an annular and flat head mating surface 42 at its bottom which faces downwardly for sealingly mating with the shell 24 upon assembly therewith. More specifically, the shell flange 40 includes an annular and flat shell mating surface 44 at its top which faces upwardly for sealingly mating with the head mating surface 42. At least one and preferably two annular conventional head seals 46 are conventionally disposed between the head and shell mating surfaces 42, 44 for providing an effective seal to prevent leakage of the high pressure steam from within the pressure vessel 12 from escaping therefrom between the head and shell flanges 38, 40. In the exemplary embodiment illustrated in FIG. 3, the head seals 46 are disposed in complementary recesses in the shell mating surface 44 and are suitably compressed by the head mating surface 42 when the upper head 28 is installed on the shell flange 40. As shown in FIGS. 2 and 4, a plurality of circumferentially spaced apart, conventional head bolts 48 extend downwardly through the head flange 38 and are threaded into the shell flange 48 for removably fixedly mounting the upper head 28 to the shell flange 40 at the top of the shell 24. In a conventional design, the upper head 28 is provided with an non-integral vent line which must be suitably disconnected from the upper head 28 prior to removing the upper head 28 from the shell 24. However, in accordance with the present invention, the vent line 30 as illustrated in FIG. 2, for example, is integrally joined to the upper head 28 and may be carried therewith when the head 28 is assembled to and disassembled from the shell 24. This may be accomplished in accordance with the present invention by suitably joining the vent line 30 in flow communication through the shell flange 40 to a stationary, primary vent line 50 conventionally fixedly joined to the shell flange 40. In this way, the primary vent line 50 remains joined to the shell flange 40, whereas the vent line 30 disposed integrally with the upper head 28 is removable therewith. As shown in more particularity in FIG. 3, the head flange 38 includes an internal head flow passage or conduit 52 extending through the head flange 38, with a first opening or port 52a being disposed on the head mating surface 42, and a second, opposite port 52b disposed on a top surface 54 of the head flange 38 spaced above the head mounting surface 42 and parallel therewith. The head flange top surface 54 is disposed outside the dome 36 and also provides the mounting surface against which the several bolts 48 are mounted. Similarly, the shell flange 40 includes an internal shell flow passage or conduit 56 extending through the shell flange 40 with a shell first port 56a being disposed on the shell mating surface 44 and aligned and disposed in flow communication with the head first port 52a. The shell internal passage 56 also includes a shell second port 56b disposed on a shell outer surface 58, which itself is disposed vertically and substantially perpendicularly to the shell mating surface 44. The vent line 30 includes a proximal end 30a disposed in flow communication with the head internal passage 52, and a distal end 30b disposed in flow communication with the inside of the dome 36 as shown in FIG. 2 for channeling a fluid 60 therebetween. In the exemplary embodiment illustrated in FIG. 2, the dome 36 includes an integral vent nozzle 62 at its top center which extends therethrough from a convex outer surface 36a of the dome 36 to a concave inner surface 36b of the dome 36. Also in the exemplary embodiment illustrated in FIG. 2, the vent line 30 is disposed externally of the dome 36 and extends along the dome outer surface 36a. More specifically, the vent line 30 extends between the top surface 54 of the head flange 38 as illustrated in FIG. 3 along the curvature of the dome 36 to the vent nozzle 62 as shown in FIG. 2. The vent line proximal end 30a is conventionally fixedly joined to the head flange 38, by welding for example, in flow communication with the second port 52b at the top surface 54 as shown in FIG. 3, and the distal end 30b as shown in FIG. 2 is disposed in flow communication with the dome nozzle 62 by being conventionally fixedly joined thereto by welding for example. In this way, the fluid 60, which for example may be non-condensable nitrogen gas, may be vented from inside the dome 36 by being channeled through the dome nozzle 62, through the vent line 30 and in turn through the head flange 38 and shell flange 40 through the respective internal passages 52 and 56 therein. The fluid 60 is discharged through the shell flange 40 through the primary vent line 50 joined thereto. Accordingly, the upper head 28 may be vented through the integral vent line 30 and in turn through the head and shell flanges 38, 40. Since the vent line 30 is fixedly joined to the dome 36 itself, it may be carried therewith when the upper head 28 is assembled to and disassembled from the shell 24. When the bolts 48 are removed from the head flange 38 the entire upper head 28 including the integral vent line 30 may be conventionally lifted away together, with the head first port 52a being automatically separated from the shell first port 56a breaking the connection therebetween. On reassembly of the upper head 28 to the shell flange 40, the head internal passage 52 is suitably realinged with the shell internal passage 56, with the respective first ports 52a, 56a thereof being realigned for reestablishing the flow connection therebetween. In the preferred embodiment of the invention illustrated in FIG. 3, the pressure vessel 12 further includes an annular vent seal 64 disposed between the head and shell mating surfaces 42, 44 around the respective first ports 52a, 56a thereof for restricting leakage of the fluid 60 from the vent line 30 and between the head and shell flanges 38, 40. In the exemplary embodiment illustrated, the vent seal 64 is suitably disposed in a complementary recess formed into the shell mating surface 44 which is effective for retaining the vent seal 64 therein during assembly and disassembly of the upper head 28, and which is suitably compressed upon assembly of the upper head 28 to the shell 24. Accordingly, the improved upper head 28 having the integral vent line 30 therein provides an effective vent for the pressure vessel 12 and has a continuous flow passage to carry the fluid 60 to the stationary primary vent line 50, while allowing disassembly of the upper head 28 with the vent line 30 being carried therewith. The vent line 30, itself, therefore does not require separate disconnection as in prior art designs, but is automatically disconnected from the primary vent line 50 upon disassembly of the cooperating head and shell flanges 38, 40. Illustrated in FIGS. 5 and 6 is an alternate embodiment of the present invention wherein the vent line 30 is disposed internally of the dome 36 and extends along the dome inner surface 36b. In this embodiment, the head flange 38 further includes an inside surface 66 facing radially inwardly and disposed above the head mating surface 42 and forms a portion of the dome inner surface 36b. And, the second port 52b of the head internal passage 52 is disposed on the inside surface 66 of the head flange 38. The vent line 30 extends from the flange inside surface 66 along the dome inner surface 36b preferably to the top center thereof as illustrated in FIG. 5, with the proximal end 30a being disposed in flow communication with the second port 52b at the flange inside surface 66 as shown in FIG. 6, and the distal end 30b being open inside the dome 36 in flow communication therewith as illustrated in FIG. 5. In this way, the fluid 60 is vented directly into the vent line distal end 30b and is carried through the vent line 30 and into the head internal passage 52 and in turn through the shell internal passage 56 for discharge through the primary vent line 50. In the exemplary embodiment illustrated in FIG. 6, the conventional head seals 46 are preferably spaced radially outwardly from the vent seals 64 for providing an additional barrier against leakage of the fluid 60 between the head and shell flanges 38, 40. The head seals 46 provide an effective barrier against leakage of the high pressure steam from inside the pressure vessel 12 through the joint between the head and shell flanges 38 and 40. By positioning the respective first ports 52a, 56a and the cooperating vent seals 64 radially inwardly of the head seals 46, any leakage therefrom will be further sealed by the head seals 46 themselves. In the embodiment of the invention illustrated in solid line in FIG. 3, the respective first ports 52a, 56a and vent seal 64 are disposed radially outwardly of the head seals 46. However, in an alternate embodiment shown in phantom, the head and shell internal passages 52, 56 may be suitably angled radially inwardly for positioning the respective first ports 52a, 56a radially inwardly of the head seals 46 as in the embodiment illustrated in FIG. 6 to provide improved sealing of the vent line 30 if desired. In the embodiments disclosed above, the internal or external vent lines 30 are fixedly joined to the upper head 28 and, therefore, are removable therewith during assembly and disassembly of the upper head 28 and the shell 24 with automatic disconnection between the head and shell internal passages 52, 56. This will decrease the amount of time required for removing and reinstalling the upper head 28 and therefore also reduces the time which maintenance personnel are subject to radiation exposure. Although the vent line 30 is preferably used for venting the fluid 60 from within the dome 36, it could also be used in alternate embodiments for providing a passage for channeling a fluid such as water for example into the pressure vessel 12 if desired. While there have been described herein what are considered to be preferred and exemplary embodiments of the present invention, other modifications of the invention shall be apparent to those skilled in the art from the teachings herein, and it is, therefore, desired to be secured in the appended claims all such modifications as fall within the true spirit and scope of the invention. Accordingly, what is desired to be secured by Letters Patent of the United States is the invention as defined and differentiated in the following claims:
	abstract	For a quasi-monochromatic x-ray radiation with high radiation intensity, an x-ray radiator generates quasi-monochromatic x-ray radiation to expose a subject from a point-shaped radiation source that emits a polychromatic x-ray radiation, and having a diffraction device to diffract the polychromatic x-ray radiation. The diffraction device has a super-mirror made of crystalline material with a flat surface. In the super-mirror, the crystalline material has at least one (in particular continuous) variation of the lattice plane spacing of the crystal lattice. The radiation source and the diffraction device are arranged such that quasi-monochromatic x-ray radiation is generated from the polychromatic x-ray radiation by partial reflection at the super-mirror.
	claims	1. An X-ray computed tomography apparatus comprising:an X-ray tube configured to generate X-rays;an X-ray detector configured to detect the X-rays generated from the X-ray tube and transmitted through an object;a top on which the object is placed;a rotation driving unit configured to rotate a rotating frame around the object, wherein the X-ray tube and the X-ray detector are mounted on the rotating frame;a movement driving unit configured to relatively reciprocate the rotating frame and the top over a plurality of times along a long-axis direction of the top; anda scan control unit configured to control the movement driving unit in relative reciprocal movement of the rotating frame and the top to coordinate a first plurality of moving loci of the X-ray tube with a first plurality of respective forward movements of at least one of the top and the rotating frame, and to coordinate a second plurality of moving loci of the X-ray tube with a second plurality of respective backward movements of at least one of the top and the rotating frame. 2. The X-ray computed tomography apparatus of claim 1, wherein the scan control unit is configured to determine velocity of the reciprocal movement based on imaging range information. 3. The X-ray computed tomography apparatus of claim 2, wherein the scan control unit is configured to determine acceleration of relative movement at a turnaround portion of the reciprocal movement based on the imaging range information. 4. The X-ray computed tomography apparatus of claim 3, wherein the scan control unit is configured to determine a time change pattern of acceleration based on an imaging range for the object. 5. The X-ray computed tomography apparatus of claim 2, wherein the scan control unit is configured to determine the velocity of the reciprocal movement in a constant-velocity interval based on the imaging range information. 6. The X-ray computed tomography apparatus of claim 2, wherein the scan control unit is configured to control the X-ray tube and the X-ray detector to generate the X-rays and acquire projection data in acceleration and deceleration intervals of a turnaround portion of the reciprocal movement.
042740070	description	SPECIFIC DESCRIPTION The radiation shielding transport and storage vessel 1 shown in the drawing is intended primarily to receive radioactive waste, especially nuclear-reactor fuel elements. The vessel comprises an upright wall structure 2 and a bottom 3 which is unitarily cast in one piece with the wall structure out of cast iron, especially spherolytic cast iron, cast steel or the like. The container, which has a central cavity or chamber 1a to receive the radioactive material, is closed at its upper end with a shielding cover 4 of a plug configuration. The cover has a downwardly convergent frustoconical portion 5 which is received in a downwardly tapered recess. The outwardly extending flange 6 of the plug-like cover rests upon the shoulder 7 at the mouth of the vessel. As is especially clear from FIG. 2, in the outer regions of the vertical wall 2 passages 9 are provided and receive a moderating material which is designed especially to capture neutrons which may be emitted from the stored radioactive material. These passages 9, filled with water, heavy water, paraffin or the like, are closed by a safety cover 8 which can be bolted to the wall 2, outwardly of the passage 6, which it overhangs. The wall 2 of the vessel is provided with unitary cast cooling or heat-dissipating ribs 10, as described in connection with applications 940,856 and 966,951, the ribs, having cut out or being erupted at 11 so that extension and contraction of individual rib sections is possible. Between the conical surface of the plug portion 5 and the conical face of the surrounding recess 13, sealing rings 14 and 15 are provided. Each of these sealing rings is an O-ring, which is partly trapped in an annular groove 16, which is of trapezoidal cross section. As shown in FIGS. 1 and 3, two such rings are provided in axial-spaced relation along the frustoconical portion of the cover, a further ring 15 between the flange 6 and the shoulder 7 and still another O-ring 18 between the shoulder 17 and an end face 4a of the cover. The interior of the vessel, after filling, receives a control gas which normally is excluded from the compartments 21 formed between the seals. The flange 6 is overhung by a peripheral portion 19 of the cover 8. This peripheral portion having another annular groove, receives an O-ring 20 which rests upon a shoulder 19a, flush with the top of the plug 6. Another control compartment 21 is provided between the O-rings 15 and 20. Passages 22 in the container wall run from a quick connect fitting 22a to the individual compartments 21 and can be coupled by the fitting to a gas closure 23 which monitors the security of the seal. Naturally, each of the compartments 21 can be connected by separate passage 22 to a separate fitting 22a, with the fittings monitored successively from the inner compartments to the outermost to ascertain whether any of the seals has leaked. In place of the O-ring between the flange 6 and the wall 2 and especially between the peripheral portion 19 and the shoulder 19a, a lip tight seal can be provided with welds 30 and 40, sealing the lips 31 and 32 and 41 and 42, which are set off by annular grooves. The advantages described in Ser. No. 966,951 are thereby gained here as well.
050248090	abstract	A nuclear fuel element for use in the core of a nuclear reactor is disclosed having an improved corrosion resistant cladding. The cladding is comprised of zirconium alloys containing in weight percent 0.5 to 2.0 percent tin, or 0.5 to 2.5 percent bismuth, or 0.5 to 2.5 percent bismuth and tin, and about 0.5 to 1.0 percent of a solute composed of a member selected from the group consisting of molybdenum, niobium, tellurium and mixtures thereof, and the balance zirconium. Composite claddings are disclosed having a surface layer of one of the corrosion resistant zirconium alloys metallurgically bonded to a Zircaloy alloy tube. Claddings may contain an inner barrier layer of a moderate purity zirconium metallurgically bonded on the inside surface of the cladding to provide protection from fission products and gaseous impurities generated by the enclosed nuclear fuel.
	abstract	Methods, apparatuses, devices, and systems for producing and controlling and fusion activities of nuclei. Hydrogen atoms or other neutral species (neutrals) are induced to rotational motion in a confinement region as a result of ion-neutral coupling, in which ions are driven by electric and magnetic fields. The controlled fusion activities cover a spectrum of reactions including aneutronic reactions such as proton-boron-11 fusion reactions.
	summary
06163588&	summary	BACKGROUND OF THE INVENTION This invention relates generally to nuclear reactors and more particularly, to core plate and reactor internal pump differential pressure lines for a boiling water reactor. A reactor pressure vessel (RPV) of a boiling water reactor (BWR) typically has a generally cylindrical shape and is closed at both ends, e.g., by a bottom head and a removable top head. A top guide typically is spaced above a core plate within the RPV. A core shroud, or shroud, typically surrounds the core plate and is supported by a shroud support structure. Particularly, the shroud has a generally cylindrical shape and surrounds both the core plate and the top guide. The core center axis is substantially coaxial with the center axis of the shroud, and the shroud is open at both ends so that water can flow up through the lower end of the shroud and out through the upper end of the shroud. The shroud, top guide, and core plate limit lateral movement of the core fuel bundles. The shroud, due to its large size, is formed by coupling a plurality of stainless steel cylindrical sections together, typically by welding. Shroud welds, however, increase the susceptibility of the shroud material to a detrimental effect known as inter-granular stress corrosion cracking (IGSCC). Typically, cracking may occur in the heat affected zone of the shroud welds. Currently, volumetric inspections are performed to detect and evaluate the extent of cracking. If the cracking is determined to be significant, repairs may be performed to re-establish the integrity of the weld joint, or the shroud is replaced. The RPV also includes reactor internal pumps located in the annulus between the shroud and the pressure vessel wall. The internal pumps provide circulation of water in the RPV. Typically differential pressure lines are used to measure the reactor internal pump flow and the flow of water through the reactor core located inside the shroud. The pressure lines are usually constructed using pipe and pipe fittings. The pressure lines enter the RPV through penetrations in the bottom head. The pressure lines extend along the inside of the shroud and are supported by brackets welded to the shroud. The brackets are required to prevent flow induced vibrations in the pressure lines. One reactor internal pump differential pressure line penetrates the shroud above pump impellers and the other terminates below the impellers inside of the shroud. The core differential pressure lines terminate above and below the core plate. Because the differential lines are welded to the shroud, replacement of shroud sections is difficult and time consuming. The pressure lines must first be removed from the shroud section before replacement of the shroud section. Also the differential pressure lines must be reinstalled, i.e., welded to the new shroud section. It would be desirable to provide a shroud that includes easily replaceable shroud sections. Particularly, it would be desirable to provide a shroud that includes replaceable shroud sections that can be removed without cutting pressure lines or pressure line supports, and that does not require welding pressure lines and/or pressure line supports to install a shroud section. BRIEF SUMMARY OF THE INVENTION These and other objects may be attained by a modular differential pressure measuring system for a boiling water nuclear reactor pressure vessel. The differential pressure measuring system permits the use of replaceable shroud sections because the modular pressure system does not require cutting the pressure lines or pressure line supports for replacement of the replaceable shroud sections. Additionally, the modular differential pressure system does not require welding of pressure lines and/or pressure line supports during installation of a replaceable shroud section. The modular differential pressure system includes a plurality of pressure lines with each pressure line including a plurality of pressure line sections. The modular system also includes a shroud having at least one replaceable shroud section. Each shroud section includes at least one pressure line section configured to connect to and disconnect from corresponding pressure line sections in adjacent shroud sections without welding. A shroud section may include at least one pressure line coupled to support brackets welded to the shroud section. The pressure line remains coupled to the shroud section and is removed or installed with the shroud section as a modular component. Connections of the pressure lines of one shroud section to an adjacent section are located at the flanged interface between shroud sections. Therefore, a separate flanged joint for the pressure line sections are not required, and welding of the connection is also not required. The modular system also includes a reactor bottom head petal section. The bottom head petal section is configured to support the shroud sections and includes a shroud support flange. The bottom head petal section also includes a plurality of bores defining pressure line sections. At least one pressure line section of the bottom head petal is configured to couple with a corresponding pressure line section of an adjacent shroud section. Particularly, a short vertical bore extends from the end of the horizontal bore to an outside surface of the shroud support flange. This vertical bore is configured to couple to a vertical bore in the lower shroud section, sometimes referred to as the shroud support. The vertical bore may extend vertically through several shroud sections, or the lower shroud vertical bore may include a short horizontal bore extending from the end of the bore to an outside surface of the lower shroud section. This horizontal bore may in turn be coupled to a vertical or horizontal pipe section of the pressure line extending along the inside surface of the shroud. In operation, the modular differential pressure system measures the pressure at two separate points within the reactor pressure vessel. The pressure differential is an indication of the flow between the two points within the reactor. Typically, the core flow is measured by measuring the pressure above and below the reactor core plate. Also the flow in the annulus of the reactor may be measured by measuring the pressure above and below the reactor internal pump impellers. Because the pressure system is modular, when a shroud section is removed for replacement, the modular pressure lines are removed with the shroud section. No cutting is required to disconnect a pressure line section from the corresponding pressure line section of an adjacent shroud section. The removed shroud section is then replaced with a shroud section that also includes integral pressure lines which re-couple to the pressure lines of an adjacent shroud section without welding. The above described modular differential pressure system permits the replacement of shroud sections without having to cut the differential pressure lines from the shroud. The modular differential pressure system also permits the installation of a replacement shroud section without having to reinstall the pressure lines by welding the lines to the core shroud. The modular system also simplifies and speeds up the process of replacing the core shroud in a nuclear reactor.
043839444	summary	BACKGROUND OF THE INVENTION The present invention relates to a method for producing molded bodies containing highly radioactive wastes wherein the wastes are mixed with molten glass or are melted together with glass formers, the resulting melt is converted to glass granules or glass powder and these granules or the powder are embedded in a matrix of pure metal or metal alloys. The necessity of providing long-term storage for solidified products containing highly radioactive wastes in, for example, salt stocks, brings about the following requirements for these final storage products: First, the product must be at an internal thermochemical equilibrium, i.e. it must be in a minimum energy state since this is presently the best assurance for thermochemical stability. Second, the product must be of such consistency that interactions with the environment cannot become a safety risk. Such interactions cannot be completely excluded since, due to the actual conditions of state and the possible changes in these conditions of state over a long period of time, it cannot be assured that an equilibrium remains in effect at the storage location between the final storage product and its environment. If these requirements are not met, changes in the product may adversely affect the interactions between various components or phase conversions or its properties, such as, for example, heat conductivity, corrosion resistance or strength, and chemical and/or mechanical interactions with the environment, such as leaching or mechanical stresses as a result of geologic pressure and shear forces, may destroy the final storage products wholly or in part. Such a destruction would involve the uncontrollable transfer of highly radioactive fission products into the biosphere. In order to solidify radioactive wastes for storage, it is well known to treat waste containing aqueous solutions by first reducing the volume of such wastes, thereby concentrating the radioactive substances, and then treating the concentrates by subjecting them together with glass formers to a heat treatment until the radioactive substances become distributed throughout the resulting glass melt, which is solidified into a solid body. Alternatively, the waste containing solution may be denitrated, spray dried, and calcined and the resulting calcinate may then be mixed in solid form with a glass former or with a ground, previously produced glass frit. In the course of prolonged storage, decomposition of the glass structure produced by the prior art methods may occur due to the continued emission of radiation and heat energy by the incorporated highly radioactive substances. As a result, the resistance of the glass structure to leaking deteriorates with time, and its ability to effectively retain radioactive materials is diminished, as compared with the nondecomposed glass structures which are highly resistant to leaching. In order to effectively increase the resistance to leaking of the well known waste and glass solidification products of the prior art, and to insure their physical stability for extended periods, German Offenlegungsschrift No. 2,524,169 discloses a process in which a glass melt containing the highly radioactive fission products is initially converted to glass granules and these granules are then filled into metal containers. Then, the empty space between the granules is filled with molten metal or a molten alloy, preferably of lead or lead alloys. This process is not supposed to result in an increase of the bulk volume of the waste granules within the containers. The surrounding or encasing of the glass granules with metal melts has the grave drawback, however, that a product is obtained in which the glass granules contact one another. Thus, it cannot be excluded that in the process according to German Offenlegungsschfrift No. 2,524,169: (a) the points of contact of the glass granules with one another react to mechanical stresses which causes constant brittle fracture; and (b) with respect to corrosion or leaching, there always exists access from the environment to all fission product-containing granules in the interior of the product. Moreover, in the process according to German Offenlegungsschrift No. 2,524,169, the selection of usable metal melts is limited to those whose wetting with the types of glass employed is satisfactory and whose coefficients of thermal expansion are sufficiently low compared to that of glass that contact at the metal-glass interface remains in existence at all times, even after cooling of the mixture from temperatures above the melting point of the metal. Contact between glass and metal must be maintained at least to an extent which assures the heat transfer to the metal phase during final storage. SUMMARY OF THE INVENTION It is an object of the present invention to provide a process for producing a solidification product of glass granules containing highly radioactive wastes which are embedded in a metal matrix, the solidification product being storable for extended or unlimited periods. It is another object of the present invention to embed the glass granules discontinuously in a continuous metallic matrix to prevent the glass granules from contacting one another. It is a further object of the present invention to produce a solidification product in which heat transfer from the glass phase to the metal phase during storage is assured. In order to achieve these objects, and in accordance with its purpose, the present invention provides a method for producing molded bodies containing highly radioactive wastes, in which the wastes are mixed with molten glass or are melted together with glass formers to form a melt, and the melt is converted into glass granules or glass powder comprising: (a) mixing the glass granules or glass powder with a powder of a metal selected from the group consisting of lead, iron, silver, cobalt, nickel, tin, and mixtures thereof, wherein the glass to metal ratio is selected so that the glass to metal ratio in the molded body is 20:1 to 1:6; and (b) condensing the mixture resulting from step (a) by subjecting the mixture to pressure of 25 Newtons/mm.sup.2 to 500 Newtons/mm.sup.2 to form a molded body. Preferably, the condensed mixture is sintered at a temperature below the melting point of the lowest melting metal present in the mixture, in order to increase the strength and density of the molded body. It is to be understood that both the foregoing general description, and the following detailed description are exemplary, but are not restrictive of the invention. DETAILED DESCRIPTION OF THE INVENTION The waste materials treated according to the present invention are the by-products of manufacturing, processing and reprocessing of nuclear fuels as well as the wastes of nuclear plants and the like. Typically, they are in water solution or suspension. The wastes treated according to the present invention generally are high activity waste solutions which comprise nitric acid solutions containing predominantly heavy metal nitrates, which are produced during the separation of fission products from spent nuclear fuels. The invention is also applicable to other wastes such as medium activity waste solutions, which are predominantly nitric acid solutions, generally containing a large amount of sodium nitrate, which are obtained during reprocessing of nuclear fuels and during decontamination processes in nuclear plants. The invention is also applicable to actinide concentrates, which are solutions or powders or combustion residues, which are obtained mainly as waste products during the processing and manufacture of nuclear fuels. The invention is further applicable to ashes and residues from the combustion of organic radioactive wastes which ashes and residues are fine-grained solid wastes and are suspended in water. A typical aqueous radioactive waste solution which can be treated is a highly radioactive aqueous waste solution (HAW) which is obtained during reprocessing of irradiated nuclear fuel and/or breeder materials after the common extraction of uranium and plutonium in the first extraction cycle of an extraction cycle. These solutions generally contain nitric acid and generally are denitrated before being spray dried and calcinated. In the process of the present invention, the radioactive waste is combined with glass so that the waste is distributed throughout the glass. This combination may be made by the techniques of the prior art in which the wastes are mixed with molten glass, or melted together with glass or glass formers. In one such method, a waste solution is evaporated to concentrate the radioactive substances. The concentrated wastes are then subjected with glass formers, such as SiO.sub.2, K.sub.2 O, and the like to heat treatments until the waste is distributed throughout the resulting glass melt, which is then solidified. In another process, the waste solution is denitrated, then spray dried and calcined to form a powder. The powder is mixed with glass formers or a previously produced ground, glass frit of known composition, and this mixture is melted in a crucible or furnace to form a homogeneous mass. The glass former or glass frit may also be added to the waste solution prior to spray drying and calcination. When this is done, a particularly pure and finely dispersed silicic acid known as Aerosil can be added to the waste solution in order to obtain a uniform mixture of the components being spray dried. This method is reported by J. Saidl in an article entitled "Verfestigung hochaktiver Spaltprodukte in Glas" (Solidification of Highly Active Fission Products in Glass), in the Annual Report for 1973-Department of Decontamination Operations; Report of the Gesellschaft fur Kernforschung mbH, No. KFK-2126, May 1975. The solidified glass containing the waste product is then converted to a glass powder or glass granules which may vary in size depending on the application. The glass powder or glass granules are obtained by mechanical crushing and milling the bulk glass compacts, where the general size distributions vary between .ltoreq.1 .mu.m up to .gtoreq.1-2 mm. These glass granules or glass powder are mixed with a powder of a metal selected from the group consisting of lead, iron, silver, cobalt, nickel, tin and mixtures thereof. The volume ratio of glass to metal should be selected so that the volume ratio in the molded body will be 20:1 to 1:6. The mixing of the glass granules or glass powder with the metal powder preferably is done mechanically, in a mixing media, or by coating the glass granules or glass powder with the metal powder, or by a combination of mechanical mixing in a mixing media and coating. Whatever method is used, thorough mixing should be assured. The mixture of metal particles and glass granules or glass powder is then condensed by pressing at pressures between 25 Newtons/mm.sup.2 and 500 Newtons/mm.sup.2 to form a molded body. This is generally done at ambient temperatures; room temperature (20.degree. C.-25.degree. C.) is preferred. In the case of lead, for example, pressing results in the formation of a solid, glass-metal molded body. In order to increase the strength and density of the molded bodies of the invention, sintering may take place after pressing, at a temperature below the melting point of the metal phase, or its lowest melting member, which results in little or no evaporation, particularly of radioactive waste fission products. Sintering should be used with iron, silver, cobalt, and nickel, and is optional with lead and tin. By proper selection of the glass-to-metal ratio, the size of the individual granules or of the powder particles and the mixing conditions, a product is obtained in which the glass granules or the glass powder containing the radioactive waste fission products are discontinuously embedded in a continuous metal matrix phase. The average interparticle space (.lambda.) for the glass granules is given by ##EQU1## where L.sub.3 is the average size (intercept length) of glass granules and V.sub.M is the volume content of the metal phase. The equation provides the interrelationship between .lambda., L.sub.3 and V.sub.M to keep a proper distance (.lambda..gtoreq.L.sub.3) between the discontinuously embedded glass granules. The time of mixing depends on the sort of powders. Generally good distributions of the glass granules in the metal matrices which is to say discontinuity of the glass particles--are obtained the more the condition is approached that ##EQU2## where .rho. means density. If there should exist access to a granule or a powder particle from outside the molded body by corrosion or leaching media, only this one granule or particle is in contact with the environment, while all others remain insulated. Substantial corrosion and leaching is thereby prevented. The metal matrix gives ductility to the molded body by allowing plastic deformation when the molded body is under mechanical stress, thereby avoiding destruction of the granules or of the particles. The glass granules or particles "float" in the metal matrix phase without contacting each other, and the product is no longer subject to brittle fracture. The drawbacks of the prior art processes are thus overcome by the use of powder technology in the present process for producing glass-metal products. Due to the low manufacturing temperatures of the molded body, which do not bring about a liquid phase, wetting between glass and metal, and difference in thermal expansion play no significant part in the contact at the glass-metal interface, so these factors will not influence the type of metal phase employed. The heat transfer from glass-to-metal is always assured. At the temperatures used, little or no evaporation, especially of radioactive waste fission products, occurs. Moreover, characteristics such as the heat conductivity can be varied with a given glass granule or glass powder concentration, by suitable selection of the shape and orientation of the granule or of the powder particles, and thus, optimized. The glass powder or granules can either approach spherical form or spheroidal shapes as platelets or cylindrical fibers. Highest thermal conductions in isotropic materials for example are achieved with spheres and fibers statistically oriented. The following example is given by way of illustration to further explain the principles of the invention. This example is merely illustrative and is not to be understood as limiting the scope and underlying principles of the invention in any way. All percentages referred to herein are by weight unless otherwise indicated.
040381331	claims	1. A nuclear reactor having a core comprising a plurality of laterally adjacent fuel assemblies, each assembly comprising a vertically elongated casing containing fuel rods and the casing having an upper end and extending downwardly therefrom and having an open lower end extending below said fuel rods, each casing having a vertical tubular suspension rod having an upper end with a supported connection above said casing and a lower end with a connection to the casing's said upper end so that the casing is suspended thereby, at least one of said connections being releasable, each assembly having a rod-like element having an upper end fixed above said casing, said rod-like element suspending from its said upper end downwardly and sliding by through said tubular suspension rod and the casing and having a lower end below the fuel rods and in the casing's said lower end, each fuel assembly independently of its said rod-like element being individually removable downwardly from the core by release of the releasable connection of its said suspension rod, failure of said suspension rod or its said connections in the case of any one of said assemblies causing an accidental release of such assembly so that it can fall from the core while its said rod-like element and any adjacent fuel assembly casing remain suspended so as to form vertically fixed parts relative to the released assembly, each of said casings having latch means for releasably normally latching its casing to one of said relatively fixed parts so that an accidentally released assembly cannot fall substantially relative to that one of the relatively fixed parts, said latch means having a latch release means on the inside of said lower end of the casing for actuation by tool means removably inserted upwardly via said lower end of any of said casings. 2. The reactor of claim 1 having releasable lock means for locking said latch release means against actuation, said lock means being releasable by said tool means. 3. The reactor of claim 1 in which said rod-like element forms said relatively fixed part. 4. The reactor of claim 1 in which said adjacent fuel assemblies form said relatively fixed parts. 5. The reactor of claim 2 in which said latch means comprises in each instance a plurality of interspaced annularly arranged latches having pivotal connections with said casing so the latches swing radially with respect to the casing, each latch having a latching surface extending towards said fixed part and the latter having a latch catch for each of said latching surfaces, each latch having a bottom portion forming a surface that angles downwardly for engagement by an upwardly moved tool for radially swinging the latch so as to disengage its latching surface from said latch catch, said lock means comprising a vertically movable locking inside of said casing's said lower end and normally in a down position engaging all of said latches and holding each in a latched position, said ring being movable to an up position by a tool inserted upwardly through said lower end, said up position releasing all of said latches for swinging to unlatched positions. 6. The reactor of claim 5 in which a mounting is fixed to said casing's said lower end concentrically therewith and has a vertical bore through which said rod-like element sliding depends with a lower end below said mounting and in which lower end an annular recess is formed to provide said latch catch, said latches swinging so they all engage and disengage with said latch catch, said locking ring encircling all of said latches, said latches having upper ends pivotally connected to said casing'said lower end via said mounting fixed thereto. 7. The reactor of claim 5 in which said casings have openings for each of said latches in their said lower porition and said latches have upper ends directly pivoted to said casing's said lower end with their said latching surfaces extending outwardly through said openings towards adjacent ones of said fuel asemblies, each of said casing's said lower ends having an external latch catch for each of said latching surfaces, said ring being positioned on the inside of said latches in each instance and normally holding the latches outwardly with their said latching surfaces engaging said latch catches of adjacent assemblies and normally locking all of said assemblies together.
044407190	abstract	The multistage injection of water into the pressure vessel of a nuclear reactor including the steam-driven injection of water using steam generated by the reactor, the stages of injection subject to the cooling of water heated by the steam, whereby the pressure level of the water injected is boosted in stages.
054250722	claims	1. A non-contact method of treating a surface of an object contaminated with radionuclides, the method comprising the steps of: applying at least one layer of a coating material to said surface; and passing a local area of intense heat across the coating material thereby providing a vitreous coating over the surface and fixing or sealing the radionuclides therein. 2. A method as claimed in claim 1, wherein the local area of intense heat has an energy level of at least 150 W/cm.sup.2. 3. A method as claimed in claim 2, wherein the intense heat is provided from a source comprising a laser means. 4. A method as claimed in claim 3, wherein the laser means includes a fibre optic cable through which the intense heat from the laser is applied. 5. A method as claimed in claim 3, wherein the laser means comprises a neodymium-yttrium aluminium garnet laser. 6. A method as claimed in claim 1, wherein the intense heat is passed across the surface by moving the object relative to the source of the intense heat. 7. A method as claimed in claim 6, wherein the source of the intense heat and the object are moved in overlapping manner. 8. A method as claimed in claim 1, wherein the surface comprises a metal, and the intense heat is such as to melt the surface. 9. A method as claimed in claim 1 and wherein a further layer of a coating material is applied to the surface after the application of the intense heat. 10. A method as claimed in claim 1, wherein the contaminated surface is a cementitious surface. 11. A method as claimed in claim 1, wherein the contaminated surface is a metallic surface. 12. A method as claimed in claim 1, wherein the coating comprises at least one of a refractory material, a cementitious material, a metal powder, a ceramic, and a mixture thereof. 13. A method as claimed in claim 3, wherein the laser means comprises one of a Nd-YAG laser, a CO.sub.2 laser, an eximer laser and a semiconductor laser.
	summary
	summary
052271269	claims	1. Internal structure of a fast neutron nuclear reactor comprising a main vessel, a core of said reactor and said internal structure being contained in said main vessel and immersed in a liquid metal for cooling said core, said internal structure comprising an internal vessel defining a zone of said main vessel for receiving hot liquid metal leaving said core and a zone for receiving cooled liquid metal, said internal vessel comprising a step shaped area having a substantially toroidal shape in the lower part thereof, a support element, termed a bed, for assemblies of said core and for the supply and distribution of said cooling liquid metal in said core, and a support element, termed plating, for supporting said bed and resting on a bottom of said main vessel, said step shaped area of said internal vessel having a lower portion directly fixed by welding to an upper part of said bed, means connected to said bed for supplying cooling liquid metal in a zone located at the periphery of said bed and outside said internal vessel and outside said plating, slidable bearing means interposed between said bed and said plating, said bed resting on said plating through the medium of said slidable bearing means, one of said slidable bearing means being located at the periphery of said bed and ensuring a sealing of said cooling liquid metal between said bed and said plating. 2. Internal structure according to claim 1, wherein said step shaped area of said internal vessel is constituted by a single wall. 3. Internal structure according to claim 1, comprising absorbent assemblies constituting a lateral neutronic protection of said reactor and fixed directly on said bed at the periphery of said core. 4. Internal structure according to claim 1, wherein said slidable bearing means comprise an annular bearing flange connected to a peripheral portion of said bed and a plurality of spherical bearing devices interposed between said bed and said plating. 5. Internal structure according to claim 1, further comprising a flange connected to said plating, and a central pivot connected to said bed and engaged in said flange for ensuring a transverse maintenance of said bed relative to said plating. 6. Internal structure according to claim 5, comprising a locking key engaged in an upper sole plate of said plating for locking said bed against rotation relative to said plating. 7. Internal structure according to claim 1, wherein said bed is constructed in the form of a cylindrical box structure which comprises an outer shell, a circular lower sole and a circular upper sole which are fixed by the periphery therof to said outer shell. 8. Internal structure according to claim 7, wherein said outer shell of said bed comprises an upper annular portion which projects from said upper sole, and said step shaped area of said inner vessel has an end which is welded onto said upper annular portion. 9. Internal structure according to claim 7, wherein said outer shell of said bed comprises an annular lower portion which projects below said lower sole, constitutes said peripheral slidable bearing means and rests on said plating through the medium of an adjusting packing piece. 10. Internal structure according to claim 9, comprising a hard covering provided on a lower bearing surface of said lower annular portion of said outer shell and on a respective bearing surface of said packing piece. 11. Internal structure according to claim 7, wherein said means for supplying cooling liquid metal to said bed comprise at least one piping connected to a respective nozzle welded to said outer shell around a throughway opening in said outer shell.
	abstract	Systems and methods are described herein for real-time data processing and for emergency planning. Scenario test data may be collected in real-time based on monitoring local or regional data to ascertain any anomaly phenomenon that may indicate an imminent danger or of concern. A computer-implemented method may include filtering a plurality of different test scenarios to identify a sub-set of test scenarios from the plurality of different test scenarios that may have similar behavior characteristics. A sub-set of test scenarios is provided to a trained neural network to identify one or more sub-set of test scenarios. The one or more identified sub-set of test scenarios may correspond to one or more anomaly test scenarios from the sub-set of test scenarios that is most likely to lead to an undesirable outcome. The neural network may be one of: a conventional neural network and a modular neural network.
061342904	summary	BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transport container of a fuel assembly of a light water reactor such as a boiling water reactor (hereinafter, referred simply to as BWR), a pressurized water reactor (hereinafter, referred simply to as PWR) or the like, and to a method of transporting the fuel assembly thereof. In particular, the present invention relates to a fuel assembly transport container and a fuel assembly transport method, which can transport the fuel assembly itself or a fuel protective container housing the fuel assembly while fixedly supporting a motion of the fuel assembly or the fuel protective container. 2. Description of the Prior Art A vibration generated in transporting a fuel assembly of a light water reactor such as BWR, PWR or other similar reactors, is a factor of causing wear in a metallic contact portion of the fuel assembly. In the fuel assembly, a spent fuel assembly has no problem as to somewhat of wear caused during transport because a waste disposal of the spent fuel assembly, reprocessing thereof and the like are carried out. Therefore, there is no need of subjecting a transport container of the spent fuel assembly to specific vibration measures for preventing vibrations of the fuel assembly, and the spent fuel assembly may be transported in a state of being safely accommodated in the transport container. As a result, in order to house a plurality of spent fuel assembly, a transport container, which has a large capacity and is compact in its structure, has been used. On the other hand, in the case of a transport container of a fuel assembly which is not used yet, since the fuel assembly is mounted to a reactor so that an operation of the reactor is carried out, it is very important that wear and damage should not be caused in a metallic contact portion or other similar portions of the fuel assembly which is not used yet by the vibration thereof during transporting the fuel assembly to the reactor, a store house or the like. So, when transporting the fuel assembly, a transport container of the fuel assembly is subjected to specific measures for preventing vibrations of the fuel assembly so that a reliability is maintained in the fuel assembly and a reactor using the fuel assembly. For preventing a vibration of the fuel assembly, there is a need of housing the fuel assembly in a fuel protective container (also, called as an inner container of a fuel transport container) in a state that a motion of the fuel assembly is fixedly supported, and further, housing the fuel protective container housing the fuel assembly in a basket of the transport container while fixedly supporting a motion of the fuel protective container. Here, FIGS. 25A and 25B show a conventional fuel protective container housing a fuel assembly in a state that the fuel assembly is fixedly supported. A fuel assembly 101 is constructed in the following manner. Specifically, a plurality of fuel rods are tied up in a bundle with a metallic upper tie-plate 102 which has a relatively large-mass and is situated on an upper portion when the fuel assembly 101 is accommodated in a reactor, and with a metallic lower tie-plate 103 which has a relatively large-mass and is situated on a lower portion when the fuel assembly 101 is accommodated in a reactor. The lower tie-plate 103 has step portions tapered toward the crosswise inner peripheral side surfaces 106c, 106c which are opposite each other, described hereinafter. This fuel assembly 101 has a square pillar shape having a square shape in its lateral cross section, and has a length of one side of the square cross section is substantially 4 m in a longitudinal direction of the fuel assembly 101. Further, bundled fuel rods (fuel rod group) constituting the fuel assembly 101 are supported by means of a fuel spacer 104 with a predetermined interval. A fuel protective container 105 comprises a container main body 106 having a substantially U shape in its lateral cross section, a cap member 107 which is detachably mounted on an upper portion (opening portion) of the container main body 106 which is transporting so as to cover the opening thereof, and protective members 108a.about.108d. The protective members 108a, 108b, 108c and 108d are formed along a bottom surface 106a of the container main body 106 along the horizontal direction when the container main body 106 is transported, longitudinally inner peripheral side surfaces 106b; 106b facing each other, crosswise inner peripheral side surfaces 106c; 106c which are opposite each other, and a lower surface 107a on the container main body side of the cap member 107, respectively. The fuel assembly 101 is accommodated in a fuel assembly housing space defined by the container main body 106 of the fuel protective container 105 and the cap member 107 so that the longitudinal direction of the fuel assembly 101 is parallel to the aforesaid horizontal direction during the transport of the container main body 106. In order to prevent a vibration when transporting the fuel protective container 105 in which the fuel assembly 101 is housed, several sets of transport (fastening) separators 110 are interposed between the fuel spacers 104, between the fuel spacer 104 and the upper tie-plate 102, and between the fuel spacer 104 and the lower tie-plate 103. These separators are arranged so that gaps between the separators and the protective members 108b mounted on the longitudinal inner peripheral side surfaces 106b; 106b are formed. That is, after the fuel assembly 101 is housed in the container main body 106, when the opening side upper portion of the container main body 106 is covered by the cap member 107 so as to be closed, the fuel assembly 101 is pressed down along a up and down direction (vertical direction) during the transport of the fuel assembly 101 by a fastening force of the cap 107 to the bottom surface 106a of the container main body 106 via the transport separator 110, and thus, is fixedly restricted therein. The fuel assembly 101 housed integrally with the fuel protective container 105 is transported while being fixedly supported by the fastening force via the transport separators arranged between the bottom surface 106a of the container main body 106 and the cap 107. However, in the aforesaid conventional fuel protective container 105 in which the fuel assembly 101 is fixedly supported, the fuel assembly 101 is merely fixedly supported by fastening the fuel assembly 101 from the vertical direction. As shown in FIGS. 25A and 25B, the fuel assembly 101 is not clamped in the horizontal direction along the crosswise direction. For this reason, the gap still exists between both sides of the fuel assembly 101 and the protective member 108b formed on the longitudinal inner peripheral side surfaces 106b, 106b of the container main body 106. As a result, there is the possibility that the fuel assembly 101 slides and moves on the protective member 108a formed on the bottom surface 106a of the container main body 106 along the aforesaid crosswise (lateral) direction. In this case, as a power of resistance to a relatively sliding motion between the fuel assembly 101 and the protective member 108a formed thereon, there are recited the own weight of the fuel assembly 101 and a frictional force between the fuel assembly 101 and the protective member 108a based on a fastening force by the cap 107. However, in the above power of resistance, concerning the fastening force by the cap member 107 recited as the frictional force, since the fastening portion is the transport separator 110 inserted into the fuel assembly 101, a compressive rigidity is small. When a great fastening force is applied on the transport separator 110, there is the possibility that the fuel assembly 101 is deformed; for this reason, a satisfied fastening force has not been provided by the cap member 107 on the transport separator 110. Therefore, concerning the frictional force resulting from the fastening force, a satisfied frictional force capable of preventing the sliding motion of the fuel assembly 101 has not been provided. Consequently, because a tightly restricting force of the fuel assembly 101 is short in the horizontal direction along the longitudinal direction with respect to the fuel protective container 105, there has arisen a problem that the fuel assembly 101 moves (vibrates) while sliding in the fuel protective container 105 according to a vibration of the horizontal direction of a relatively high acceleration during the transport of fuel protective container 105. In addition, a fastening force to the fuel assembly 101 is short in the horizontal direction along the longitudinal direction (axial direction) of the fuel assembly 101. Therefore, for example, in the case where a mixed-oxide fuel (MOX) assembly mixing a plutonium oxide (PuO.sub.2) and an uranium oxide (UO.sub.2) is used as the fuel assembly, during transport of the MOX fuel assembly, the MOX fuel assembly 101 is exothermic, and then, an elongation difference is caused due to a difference in thermal expansion between the MOX fuel assembly 101 and the fuel protective container 105. For this reason, a relatively positional shift is generated between the MOX fuel assembly 101 and the fuel protective container 105. In addition, a gap is defined between both end portions along the longitudinal direction (axial direction) of the MOX fuel assembly 101 and both side surfaces 106c of the fuel protective container 105 and between the MOX fuel assembly 101 and the bottom surface 106a of the fuel protective container 105. As a result, similar to the aforesaid case of the horizontal direction along the crosswise direction, there is the possibility that the fuel assembly 101 slides and moves (vibrates) on the protective member 108a formed on the bottom surface 106a of the container main body 106 along the longitudinal direction according to a vibration of the horizontal direction of relatively high acceleration which arises from transporting the fuel protective container 105. Moreover, in the conventional fuel protective container 105 in which the fuel assembly 101 is fixedly supported, since the fuel assembly 101 is fixedly supported by means of the transport separators 110 located between the fuel spacers 104, between the fuel spacer 104 and the upper tie-plate 102, and between the fuel spacer 104 and the lower tie-plate 103, a tightly fixing force is short in the attachment portions of the upper tie-plate 102 and the lower tie-plate 103 on both ends of the fuel assembly 101 in the longitudinal direction thereof. Therefore, resulting from mass of the upper tie-plate 102 and the lower tie-plate 103, there is the possibility that a remarkably different vibration is generated between the upper tie-plate 102 and the protective barrier 106 and between the lower tie-plate 103 and the same as compared with a vibration in the central portion of the fuel assembly 101 according to the aforesaid vibration of the horizontal direction during transport of the fuel protective container 105. As described above, because the tightly fixing force in the horizontal direction is short or the tightly fixing force on portions locating the upper and lower tie-plates 102 and 103 is short, the fuel assembly 101 has slid and vibrated in the fuel protective container 105 housing the fuel assembly 101. This sliding vibration of the fuel assembly 101 causes a problem of accelerating a wear of the metallic contact portion of the bundled fuel rods group. Furthermore, in the conventional fuel protective container 105 in which the fuel assembly 101 is fixedly supported, the fuel assembly 101, that is, the own weight of fuel rods group is supported by the transport separators 110. As a result, most of the own weight of fuel rods group are supported by a row of the fuel rods (the lowest row) which is closest to the bottom surface 106a of the fuel protective container 105 in the fuel rod groups. For this reason, in a transport process of the fuel assembly 101, when a transport container housing the fuel assembly 101 is loaded and unloaded with the use of a crane (hoist) or other similar machines, in the case where an instantaneous force having a relatively high acceleration is applied to the fuel assembly 101, there is the possibility that the fuel rods situated on the lowest row are plastically deformed. This causes a problem that a loading and unloading condition during transport of the fuel assembly 101 must be strictly limited. In particular, in a future fuel assembly, there is a tendency for a diameter of a fuel rod to be shortened. For this reason, there is the possibility that the loading and unloading restraint condition during the fuel assembly transporting process becomes further strict in future. Thus, it has been desired to present a proposal to immediately solve the above problem according to the deformation of the fuel assembly. On the other hand, the fuel assembly has long one side whose length is substantially 4 m in the longitudinal direction thereof; for this reason, vibration is not sufficiently prevented only by fixedly supporting both side portions of the fuel protective container in the longitudinal direction thereof. Therefore, in order to fixedly support the fuel protective container housing the fuel assembly in a basket of a transport container, there is a need of fixedly supporting an intermediate portion of the fuel protective container in the longitudinal direction thereof. However, specific fixedly supporting means for protecting the aforesaid fuel protective container has not been conventionally developed. Especially, the case of transporting the transport container which houses a plurality of fuel protective containers in the basket of the transport container, the fixedly supporting means basically needs to be provided for each fuel protective containers. However, conventionally, there is no existence of a small-size fixedly supporting means having a small spatial occupancy, and a spatial ratio occupied by the fixedly supporting means is large. This is the greatest factor of obstructing a development of a compact and large-capacity fuel transport container. Further, in the case where the MOX fuel assembly is used as the fuel assembly, since the MOX fuel assembly is exothermic during the transport of the MOX fuel assembly so that a temperature of the fuel protective container 105 becomes high, fixedly supporting means needs to be provided in order to maintain a high reliability under such a high temperature condition. However, there is a problem that fixedly supporting means having a high reliability under the high temperature condition has not been developed conventionally. Furthermore, according to the prior art, a plurality of fuel protective containers are fixedly supported in the basket of the transport container for each fuel protective container. For this reason, when the plurality of fuel protective containers are fixedly supported, manpower and time is much spent in accordance with the number of the fuel protective containers. Therefore, there has been strongly desired a development of a transport container having fixedly supporting means which is capable of reducing manpower and easily and fixedly supporting a plurality of fuel protective containers in a basket of the transport container in a short time. SUMMARY OF THE INVENTION The present invention is directed to overcome the foregoing problems. Accordingly, it is a first object of the present invention to provide a transport container of a fuel assembly and method of transporting the fuel assembly, which can prevent the fuel assembly from being slid and vibrated in an interior of a fuel protective container by improving (reinforcing) a tightly fixing (restricting) force of the horizontal direction along a crosswise direction and a longitudinal direction of the fuel assembly housed in the fuel protective container and a tightly fixing force of portions locating upper and lower tie-plates even if a relatively large-level vibration is generated during transporting the fuel protective container, making it possible to stably transport the fuel assembly. Further, a second object of the present invention is to provide a transport container of a fuel assembly and method of transporting the fuel assembly which can maintain a safety of a fuel assembly even in the case where a relatively high-acceleration instantaneous force is applied to the fuel assembly. Furthermore, a third object of the present invention is to provide a transport container of a fuel assembly and method of transporting the fuel assembly having fixedly supporting means which includes a small size and a low spatial occupancy, and is excellent in reliability under a high temperature condition thereby making the transport container compact and reducing the fixedly restriction work of the fuel assembly. To achieve the such objects, according to one aspect of the present invention, there is provided a transport container having at least one fuel assembly element including at least one fuel assembly for transporting the fuel assembly element, the transport container comprising container means having an inner surface portion to be fit to the at least one fuel assembly element for housing the at least one fuel assembly element, said inner surface portion having a predetermined shape substantially corresponding to a fit portion of the at least one fuel assembly element; and support means for pushing the at least one fuel assembly element against the inner surface portion of the container means along a fixedly support direction so as to fit the fit portion of the at least one fuel assembly element to the inner surface portion of the container means thereby fixedly supporting the at least one fuel assembly element to the container means. This aspect of the present invention has an arrangement that the container means is provided with a basket including at least one basket hole having the inner surface portion, said at least one basket hole having four inner side surfaces providing a substantially square-shaped cross section, said at least one fuel assembly element includes at least one fuel protective container in which the at least one fuel assembly is housed, said at least one fuel protective container having four outer side surfaces providing a substantially square-shaped cross section and being housed in the at least one basket hole so that the four outer side surfaces of the at least one fuel protective container are opposite to the four inner side surfaces of the at least one basket hole, respectively, said inner surface portion is formed by two inner side surfaces of the four inner side surfaces of the at least one basket hole which are adjacent each other so as to be shaped as a substantially V, said two inner side surfaces being set according to the fixedly support direction, and wherein said fit portion of the at least one fuel assembly element includes a corner portion defined by the two outer side surfaces of the four outer side surfaces of the at least one fuel protective container so as to be fitted in the V shaped inner surface portion. In preferred embodiment of this aspect, when the transport container is positioned along a horizontal plane in order to transport the transport container, the one of the two inner side surfaces of the at least one basket hole is inclined at a predetermined angle with respect to the horizontal plane or the one of the two inner side surfaces of the at least one basket hole is positioned along the horizontal plane. This aspect of the present invention has an arrangement that the support means is located so as to be interposed between remained two outer side surfaces of the four outer side surfaces of the at least one fuel protective container and remained two inner side surfaces of the four inner side surfaces of the at least one basket hole and is in contact with the remained two outer side surfaces and the remained two inner side surfaces so as to push the at least one protective container against the V shaped inner surface portion thereby fixedly supporting the corner portion of the at least one fuel protective container to the V shaped inner surface portion thereof. In preferred embodiment of this aspect, the basket has a substantially cylindrical shape and plurality of the basket holes arranged as a square shape and is divided into a plurality of basket portions in a longitudinal direction of the basket, said support means has a grid plate having substantially square shaped grid holes of a same arrangement as the plurality of basket holes, said grid plate being interposed between at least one adjacent basket portions and said at least one fuel protective container being inserted in at least one of the basket holes and at least one of the grid holes corresponding to the at least one of the basket holes and has a drive device for moving the grid plate along a diagonal direction of the at least one of the basket holes toward the V shaped inner surface portion thereof so as to push the at least one fuel protective container against the V shaped inner surface portion of the at least one of the basket holes thereby fixedly supporting the corner portion of the at least one fuel protective container to the V shaped inner surface portion thereof. This aspect of the present invention has an arrangement that the basket has a substantially cylindrical shape and plurality of the basket holes arranged as a square shape and is divided into a plurality of basket portions in a longitudinal direction of the basket, said support means has a pair of grid plates arranged so as to face each other each of which has substantially square shaped grid holes of a same arrangement as the plurality of basket holes, each of said grid plates being interposed between at least one adjacent basket portions and said at least one fuel protective container being inserted in at least one of the basket holes and at least one of the grid holes of each of the grid plates corresponding to the at least one of the basket holes and has a drive device for moving one of the grid plate along the one of the two inner side surface of the at least one of the basket holes toward the other of the two inner side surface thereof and moving other of the grid plate along the other of the two inner side surface thereof toward the one of the two inner side surface thereof so as to push the at least one fuel protective container against the V shaped inner surface portion of the at least one of the basket holes thereby fixedly supporting the corner portion of the at least one fuel protective container to the V shaped inner surface portion thereof. In order to achieve the such objects, according to another aspect of the present invention, there is provided a method of transporting at least one fuel assembly element including at least one fuel assembly, the method comprising the steps of providing a transport container including a basket which has at least one basket hole having an inner surface portion to be fit to the at least one fuel assembly element, said inner surface portion having a predetermined shape substantially corresponding to a fit portion of the at least one fuel assembly element; housing the at least one fuel assembly element in the at least one basket hole of the basket so that the fit portion of the at least one fuel assembly element is opposite to the inner surface portion of the at least one basket hole; and pushing the at least one fuel assembly element against the inner surface portion of the at least one basket hole along a fixedly support direction so as to fit the fit portion of the at least one fuel assembly element to the inner surface portion of the at least one basket hole thereby fixedly supporting the at least one fuel assembly element to the basket. In order to achieve the such objects, according to further aspect of the present invention, there is provided a method of transporting at least four fuel assemblies, the method comprising the steps of preparing at least one fuel protective container capable of housing at least four assemblies, housing the at least four fuel assemblies in the at least one fuel protective containers, preparing a transport container in which a basket is housed, said basket including at least one basket hole which is capable of accommodating the at least one fuel protective container and which has an inner surface portion to be fit to the at least one fuel protective container, said inner surface portion having a predetermined shape substantially corresponding to a fit portion of the at least one fuel protective container, housing the at least one fuel protective container in the at least one basket hole so that the fit portion of the at least one fuel protective container is opposite to the inner surface portion of the at least one basket hole and pushing the at least one fuel protective container against the inner surface portion of the at least one basket hole along a fixedly support direction so as to fit the fit portion of the at least one fuel assembly element to the inner surface portion of the at least one basket hole thereby fixedly supporting the at least one fuel assembly element to the basket. In order to achieve the such objects, according to further aspect of the present invention, there is provided a method comprising the steps of providing a transport container including a basket which has a plurality of basket holes arranged as a predetermined shape for housing at least one fuel assembly element in one of the basket holes, each of said basket holes being provided with an opening end portion preparing a fixing plate having a plurality of holes of a same arrangement as the plurality of basket holes attaching the fixing plate to the opening end portion of the basket holes so as to be detachable therefrom, said at least one fuel assembly element being housed in at least one of the basket holes and at least one of the holes of the fixing plate mounting a project portion on a position of the at least one fuel assembly element so that the project portion projecting toward the at least one of the basket holes, said mounted position of the at least one fuel assembly element being opposite to the opening end portion of the at least one of the basket holes and pushing the fixing plate against the project portion of the at least one fuel assembly element so as to fixedly support the at least one fuel assembly element to the fixing plate. In the above aspects of the present invention, the at least one fuel assembly element having a fit portion (corner portion) defined by two outer side surfaces thereof is pushed by the support means against the inner surface portions constituting the V shaped portion of the at least one basket hole of the basket which is opposite to the corner portion so that the corner portion of the at least one fuel assembly element is fit to the V shaped portion of the at least one basket hole whereby the at least one fuel assembly element is fixedly supported to the at least one basket hole of the basket. Therefore, the own weight of the fuel assembly element housing the fuel assembly is supported by the V shaped portion of the at least one basket hole of the basket and the movement of the at least one fuel assembly element is fixedly restriction by the supporting means, making it possible to prevent the at least one fuel assembly element from being slid and vibrated and to stably transport the fuel assembly element.
	description	The present invention refers to a method of operating a reactor of a nuclear plant in which the reactor comprises a reactor vessel enclosing a core having a plurality of fuel elements and a number of control rods, wherein each fuel element includes a plurality of elongated fuel rods, which each has an upper end and a lower end and includes a cladding and nuclear fuel in the form of fuel pellets enclosed in an inner space formed by the cladding, wherein the fuel pellets are arranged in the inner space to leave a free volume in the inner space, wherein the free volume comprises an upper plenum, containing no nuclear fuel and provided in the proximity of the upper end of the fuel rod, a lower plenum, containing no nuclear fuel and provided in the proximity of the lower end of the fuel rod, and a pellet-cladding gap between the fuel pellets and the cladding, wherein a reactor coolant, during operation of the reactor, is re-circulated as a coolant flow through the core in contact with the fuel rods and is added to the reactor via a feed-water conduit as feed-water having a normal feed-water temperature providing a sub-cooling of the reactor coolant, and wherein each of the control rods is displaceable a control rod distance to be inserted into and extracted from a respective position between respective fuel elements in the core, The reactor is a light water reactor and more precisely a boiling water reactor, BWR, or a pressurized water reactor, PWR. A method according to the prior art of this technical field is disclosed in WO 2005/122183. In such a reactor, each fuel rod comprises a cladding and nuclear fuel in the form of a stack of fuel pellets of substantially uranium dioxide. The fuel pellets do not fill the whole inner space but there is also a free volume in the inner space in which the fuel pellets are permitted to swell, i.e. through thermal and irradiation expansion. According to prior art, the free volume includes or is formed by a gap between the fuel pellets and the inner side of the cladding, and by an upper plenum. The free volume, i.e. the inner space that is not filled by fuel pellets, is filled with helium to improve heat transfer in operation and to facilitate defect detection at manufacturing. Each of the control rods is insertable to and extractable from a respective position between (BWR) or in (PWR) respective fuel elements in the core in order to influence the power of the reactor, i.e. to control the power of the reactor and/or to shut down the operation of the reactor. During unfortunate circumstances, it may happen that a smaller defect arises on the cladding of the fuel rod, a so-called primary defect. Such a primary defect can arise through wear from a foreign object. A small wear defect normally does not result in any significant dissolving and washing out of uranium dioxide from the fuel pellets of the fuel rod. A small primary defect may, however, result in a secondary degradation and the development of a larger secondary defect. When a primary defect has been established, there is a communication passage for the reactor coolant to the inner space of the fuel rod. This means that water and steam may penetrate the inner space of the fuel rod until the internal pressure in the fuel rod is the same as the system pressure of the reactor. During this process, the inner side of the cladding and the fuel pellets will oxidize while releasing hydrogen from the water molecules in the reactor coolant. This release of hydrogen leads to an environment with a high partial pressure of hydrogen at a distance from the primary defect; a phenomenon, which is called “oxygen starvation” or “steam starvation”. In such an environment, the inner side of the cladding is inclined to absorb hydrogen, so called hydriding, which is a basic material property of zirconium and zirconium-based alloys. This hydrogen absorption results in a locally very high hydrogen concentration in the cladding, which significantly deteriorates the mechanical properties of the cladding. The cladding then becomes brittle and this can due to self-induced stresses or due to external load, give rise to crack initiation, crack growth and the development of a secondary fuel defect. During normal operation of the reactor at principally full power, a primary defect can, as appears from above, arise in a fuel rod. It can be assumed that the defect fuel rod has an average load of for instance 20 kW/m, a certain pellet-cladding-gap, for instance 5-20 μm, and an internal pressure of for instance 5-100 bars. The internal pressure in fuel rods of a BWR lies during operation in the lower region of the interval, whereas the internal pressure in fuel rods of a PWR during operation can lie in the upper region of the interval. When the primary defect arises, the pressure difference between the internal pressure of the fuel rod and the system pressure will disappear, i.e. the internal pressure of the fuel rod will be the same as the system pressure. The system pressure in a BWR is typically about 70 bars, whereas the system pressure in a PWR typically is about 150 bars. When a primary defect occurs, the fill gas, which normally consists substantially of helium and fission gases from the fuel pellets, will be transported towards both the ends of the fuel rod. Steam will be introduced until the internal pressure of the fuel rod equals the system pressure. Before the fuel rod is taken into operation and the radiation is initiated, the fill gas of the fuel rod normally consists substantially of helium and the internal pressure of the fuel rod is at room temperature typically 1-40 bars. The internal pressure in fuel rods for a BWR typically lies in the lower region of the interval, whereas the internal pressure in fuel rods for a PWR normally lies in the upper region of the interval. During operation some fission gas is released from the pellets and mixed with the fill gas. The total pressure is then increased and may at end-of-life exceed the system pressure for some fuel rods. In case of a primary defect, the pressure equalizes also in these cases. It is of importance that the released fission gas also includes inert gases, e.g. He, Xe and Kr. As mentioned above, the steam will, after the occurrence of a primary defect and the introduction of water, react with the cladding and the fuel pellets during release of hydrogen from the water molecules, which react with the cladding or the fuel pellets. This means that an area with a very high partial pressure of hydrogen can be obtained at a distance from the primary defect. It is thus likely that very soon after the occurrence of the primary defect an area with fill gas has been formed at each of the two ends of the fuel rod. The free volumes, which are present directly adjacent to the ends, may initially contain substantially pure hydrogen gas, mixed with inert gases but free from steam. Since the partial pressure of hydrogen is very high in these areas directly after the occurrence of the primary defect, the risk for secondary degradation is high. However, if the partial pressure of hydrogen decreases and the partial pressure of steam increases, the local massive hydrogen absorption, and thus the risk for local secondary degradation will be reduced. The hydrogen absorption can take place more homogeneously over the whole inner side of the cladding wall. Steam has inferior heat transfer properties as compared to He. Consequently, the fuel pellets normally increases in temperature subsequent to the occurrence of a primary failure and the associated steam ingress. The thermal expansion that is connected to the increase of the temperature of the fuel pellets further reduces the pellet-cladding gap and reduces the gas communication within the rod. Oxidation of the cladding and the fuel pellets will have a similar restrictive effect by the formation of oxides with lower density and larger volume. WO 2005/122183 discloses a method according to which the risk for a secondary degradation can be reduced. More specifically, WO 2005/122/183 discloses a method for operating a reactor of a nuclear plant in which the reactor encloses a core having a plurality of fuel elements and a number of control rods. Each fuel element includes a plurality of fuel rods, which each includes a cladding and nuclear fuel in the form of fuel pellets enclosed in an inner space formed by the cladding. Each of the control rods is insertable to and extractable from a respective position between respective fuel elements in the core in order to influence the power of the reactor. The method includes the following steps: operating the reactor at a normal power during a normal state; monitoring the reactor for detecting a defect on the cladding of any of the fuel rods; reducing the power of the reactor after detecting such a defect; operating the reactor during a particular state during a limited time period during which the reactor at least periodically is operated at the reduced power in relation to the normal power; and extracting said inserted control rods after said time period for continuing operation of the reactor at substantially the normal state. Since the reactor according to WO 2005/122183, when a primary defect has been detected, is operated at a reduced power, the nuclear reaction in the fuel will decrease. The temperature in the fuel pellets will thus decrease, which reduces the thermal expansion of the fuel pellets. Consequently, the free volume and the communication paths in the inner space of the fuel rod increases. This means that even more steam may penetrate the inner space of the fuel rod for maintaining the pressure equalization between the inner space of the fuel rod and the system pressure. In addition, the reaction rates for the oxidation of the cladding and the fuel pellets, and for the hydriding of the cladding, will decrease when the reactor power is reduced and the fuel temperature decreases. Since the defect fuel rod, when the power is reduced, has a substantially lower fuel pellet temperature and a substantially larger free volume in the inner space, the gases, i.e. the fill gas, formed fission gases, hydrogen gas and steam, will be mixed through diffusion. Diffusion will take place also at higher pellet temperatures, but the oxidation and hydriding rates may then be so high that the diffusion will have no significant importance in comparison to the gas movements arising due to the pressure difference between the different parts of the fuel rod. Consequently, according to WO 2005/122183, the gas mixing via diffusion will be the dominating mechanism for significantly decreasing and distributing the consumption of oxygen and hydrogen in the fuel rod. During these conditions, a gas mixing is thus obtained in the inner space at the same time as the hydriding is relatively slow. When a proper mixture of hydrogen and water molecules has been obtained in the inner space of the fuel rod, the hydrogen absorption at a continuing operation will take place more homogeneously along the whole fuel rod. It is thus possible to avoid the creation of a zone of the cladding, which has significantly degraded mechanical properties as a consequence of a powerful local hydriding. The homogeneous hydrogen distribution makes the fuel rod significantly less sensitive to crack initiation, crack growth and the development of a secondary defect. Consequently, the limited time period, during which the reactor is operated, at least periodically, at a reduced power, leads to a significant increase of the probability that the reactor with the same set of fuel rods thereafter can be operated until the next scheduled normal revision outage without any additional shut downs for removing defect fuel and without requiring the introduction of control rods for locally reducing the power in the region of the core where the defect fuel rod is located. U.S. Pat. No. 5,537,450 discloses a device for detecting whether there is a fuel defect. The device is arranged to detect fuel defects during operation of the reactor by conveying a part of the off-gases from the reactor via a gamma spectrograph that continuously measures the nuclide composition and the activity level in the off-gases. It is also known to localize a fuel defect by a method called “flux-tilting”, which means that the control rods are operated one by one so that the power is changed locally in the core at the same time as the activity level in the off-gases is measured. An increase of the activity level in the off-gases can be correlated to control rod movements in the proximity of the fuel defect. In such a way the fuel defect can be localized. This method is time-consuming and during the time when the localization takes place, the power of the reactor is reduced to between 60 and 80% of full power. U.S. Pat. No. 6,298,108 discloses a fuel rod for a BWR. The fuel rod has an upper end and a lower end and includes a cladding and nuclear fuel in the form of fuel pellets enclosed in an inner space formed by the cladding. The fuel pellets are arranged in the inner space in such a way that an upper plenum, containing no nuclear fuel, is provided in the proximity of the upper end of the fuel rod, and a lower plenum, containing no nuclear fuel, is provided in the proximity of the lower end of the fuel rod. The axial length of the lower plenum is approximately 50% of the axial length of the upper plenum. The object of the present invention is to counteract degradation of a possible primary defect and thus reduce the risk of a secondary defect during a continuing operation of the reactor. This object is achieved by the method initially defined, which includes the following steps of operation: operating the reactor at a normal power and a normal sub-cooling during a normal state, monitoring the reactor for detecting a defect on the cladding of any of the fuel rods, changing the operation of the reactor to a particular state after detecting such a defect, wherein the particular state is configured to permit an increase of the free volume at least in the fuel rod in which a defect is detected, operating the reactor at the particular state during a limited time period, and operating, after said time period, the reactor at substantially the normal state. When a primary defect has been detected, the reactor is thus operated at the particular state increasing of the free volume and thus gas communication paths in the inner space of the fuel rod. During the particular state, the nuclear reaction in the fuel, and thus the temperature and the thermal expansion of the fuel pellets will decrease. The increased free volume, permits more steam to penetrate the inner space of the fuel rod, which will reduce the reaction rates for the oxidation of the cladding and the fuel pellets, and for the hydriding of the cladding. The gases, i.e. the fill gas, formed fission gases, hydrogen gas and steam, will be mixed through diffusion. The lower plenum enhances the gas mixing in the lower end of the fuel rod, while the upper plenum has the same effect in the upper end of the fuel rod. The steam in the mixture of gases in the lower plenum will, during the particular state, condense thanks to the reduction of the partial pressure of steam from approximately 70 bar to approximately 44 bar at a reduction of the temperature of the mixture of gases of approximately 30K. As a consequence thereof, even more steam may penetrate the inner space of the fuel rod than is possible with the method proposed in WO 2005/122183. According to a development of the method, the lower plenum has a longitudinal length along the elongated fuel rod and the upper plenum has a longitudinal length along the elongated fuel rod, wherein the longitudinal length of the lower plenum is significantly shorter than the longitudinal length of the upper plenum. In particularly, the longitudinal length of the lower plenum may be less than 30% of the total longitudinal length of the upper plenum and the lower plenum. According to a development of the method, the particular state comprises at least one of the following steps of operation: operating the reactor at a reduced power in relation to the normal power during the normal state, and operating the reactor at an increased sub-cooling of the reactor coolant in relation to the normal sub-cooling during the normal state in order to achieve a larger temperature gradient over the fuel rod. Along with the power reduction, at the particular state, the lower plenum will be cooled. The normal state of a BWR includes a system pressure of 70 bar and a reactor coolant temperature of approximately 286° C., i.e. saturation conditions. The core inlet temperature is normally about 10° C. below the saturation temperature, known as the sub-cooling. One way to reduce power is to reduce the core coolant flow in a BWR, which will increase the sub-cooling. The sub-cooling can be further enhanced by shutting off one or more of the preheaters in the feed-water preheating arrangement. According to a further development of the method, said reduced power and/or increased sub-cooling is obtained by reducing the coolant flow of the reactor coolant through the core. Such a power reduction can be performed very quickly and lead to a quick decrease of the temperature of the fuel pellets, which decreases their volume and thus increases the free volume and the gas communication paths in the inner space of the defect fuel rod. According to a further development of the method, the added reactor coolant is preheated outside the reactor during the normal state by means of a preheating arrangement, wherein said increased sub-cooling of the reactor coolant is obtained by reducing the preheating of the added reactor coolant, i.e. of the feed-water. Such an increased sub-cooling can be performed very quickly and efficiently. The normal feed-water temperature in the normal state of operation is approximately in the range from 180° to 240° C. By increasing the sub-cooling this feed-water temperature will be decreased by disconnecting one or several preheaters of the preheating arrangement. According to a further development of the method, said reduced power is obtained by displacing at least some of the control rods into the core at least a part of the control rod distance. Also such a power reduction can be performed very quickly and efficiently. According to a further development of the method, substantially all control rods are at least periodically displaced at least a part of the control rod distance during the particular state. In this case, a particularly significant power reduction is obtained for the important lower part of the fuel rods. This is particularly efficient in combination with the above mentioned increased sub-cooling. According to a further development of the method, said reduced power is obtained by displacing successively different groups of the control rods at least a part of the control rod distance, wherein each such group defines a respective specific part of the core. The particular state may thus also be established for different parts of the core in successive periods. Individual control rods or groups of control rods may then be used for the power reduction. This permits identification of the position of the defect fuel rod and limits the necessary power reduction. According to a further development of the method, the reactor is operated at the reduced power during the whole time period of the particular state. Advantageously, substantially all control rods may be displaced at least a part of the control rod distance during the whole time period of the particular state. According to a further embodiment of the method, the particular state is initiated at least within 72 h after the detection of a defect, preferably within 48 h after the detection of a defect, and more preferably within 24 h after the detection of a defect. Advantageously, the particular state is initiated substantially immediately after the detection of a defect. It is advantageous if the power reduction takes place quickly so that the desired mixture in the inner space is obtained as soon as possible after the occurrence of a defect. According to a further development of the method, the particular state involves that at least some of the control rods are alternately inserted into and extracted from the respective position for obtaining an alternating increase and decrease of the power. This may be advantageous when the position of the defect fuel rod has been identified. According to a further development of the method, said monitoring includes continuous monitoring during the operation of the reactor. The monitoring may then advantageously include sensing of a radioactive activity, or the presence of one or several fission gases, in a gas flow from the reactor. According to a further development of the method, the fuel rod comprises a hydrogen absorbing element provided in the upper plenum and/or a hydrogen absorbing element provided in the lower plenum. By means of such a hydrogen absorbing element, the risk for hydriding can be further reduced, since hydrogen present in the fill gas at least to a certain extent may be absorbed by the hydrogen absorbing element, and thus the percentage of hydrogen in the inner space of the cladding can decrease. According to a further development of the method, the hydrogen absorbing element comprises a hydrogen absorbing body having a surface coated with a layer of a substance that is non-oxidizing and permeable to hydrogen. Such a hydrogen absorbing element in at least one of the plenums will absorb hydrogen if the element is in an environment with a high partial pressure of hydrogen, i.e. in a zone where there is a high risk for hydriding, whereas the element, due to the non-oxidizing coating, will not react with water or steam in the environment. According to a further development of the method, the absorbing body is enclosed in an imaginary body having a substantially convex outer surface, and wherein the surface of the absorbing body is significantly greater than the outer surface of the imaginary body. With such a surface enlarging of the hydrogen element, the absorption ability is further increased. According to a further development of the method, the coating substance comprises at least one metal in the group consisting of palladium, rhodium, rhenium and alloys comprising one or more of these metals. According to a further development of the method, the absorbing body comprises at least one metal in the group consisting of zirconium, titanium, nickel and alloys comprising one or more of these metals. According to a further development of the method, the fuel rod comprises a distance element provided in the upper plenum and/or a distance element provided in the lower plenum. According to a further development of the method, at least one of the distance elements forms the absorbing element. According to a further development of the method, at least one of the distance elements is deformable for permitting swelling of the fuel pellets. FIG. 1 discloses a nuclear plant including a reactor 1, a discharge conduit 2 from the reactor 1, a utility device 3 and a feed-water conduit 4 from the utility device 3 back to the reactor 1. The reactor 1 may be a boiling water reactor, BWR, or a pressurized water reactor, PWR. In the example disclosed, it is referred to a BWR although the invention is applicable also to a PWR. The reactor 1 comprises a reactor vessel 6, which encloses a core with a plurality of fuel elements 7 and a number of control rods 8. Each fuel element 7 includes a plurality of elongated fuel rods 9, see FIG. 2, which each extends along a longitudinal axis between an upper end 9′ and a lower end 9″. Each fuel rod 9 includes a cladding 10 and nuclear fuel in the form of a pile of fuel pellets 11, which are enclosed in an inner space 12 formed by the cladding 10. Since the fuel pellets 11 do not take up the whole inner space 12, a free volume with no nuclear fuel is formed in the inner space 12 of the cladding 10. The size of the free volume varies with the temperature of the fuel pellets 11, and thus with the thermal expansion of the fuel pellets 11. The free volume is formed by a pellet-cladding gap, of for instance 5-20 μm, between the fuel pellets 11 and the inner side of the cladding 10, an upper plenum 12′ and a lower plenum 12″. The upper plenum 12′, containing no nuclear fuel, is provided in the proximity of the upper end 9′ of the fuel rod 9. The lower plenum 12, containing no nuclear fuel, is provided in the proximity of the lower end 9″ of the fuel rod 9. The total longitudinal length of the elongated fuel rod 9 is approximately 4 meters. The total longitudinal length of the plenums 12′, 12″ is approximately 25-40 cm. The lower plenum 12″ has a longitudinal length, which is significantly shorter than the longitudinal length of the upper plenum 12′. For instance, the longitudinal length of the lower plenum 12′ is less than 30%, preferably less than 20% and more preferably less than 10% of the total longitudinal length of the plenums 12′ and 12″. It is to be noted that each or some of the fuel rods 9 may also comprises one or more intermediate plenums (not disclosed), containing no nuclear fuel. Such one or more intermediate plenums are provided between the upper plenum 12′ and the lower plenum 12″. The one or more intermediate plenums are separated from each other and from the upper plenum 12′ and the lower plenum 12″ by some of the fuel pellets. The total longitudinal length of the plenums 12′, 12″ and the one or more intermediate plenums is still approximately 25-40 cm. Each of the control rods 8 is displaceable a control rod distance to be inserted to and extractable from a respective end position between respective fuel elements 7 in the core by means of drive members 13. The control rods 8 can be used, in a BWR, for influencing or controlling the power of the reactor 1. When the control rods 8 are extracted the nuclear chain reaction proceeds and when the control rods 8 are inserted to the respective end position in the core, the nuclear chain reaction stops at least in the proximity of the inserted control rods 8. During normal operation of the reactor, most of the control rods 8 are extracted, compare FIG. 1. In a BWR, the control rods 8 are displaceable to positions along the control rod distance between the end position and the extracted position in order to permit control of the power of the reactor. In a PWR, the control rods are displaceable to the fully inserted end position or to the fully extracted position, thereby influencing the power of the reactor. In a BWR, the reactor coolant is re-circulated in a primary system. The reactor coolant of the primary system is converted to steam in the reactor 1. The steam is separated from water and conveyed to the utility device 3 including a steam turbine and a condenser. From the condenser, in which the steam is converted to water, the reactor coolant is fed back to the reactor 1, as feed-water, via a preheating arrangement 14 and the feed-water conduit 4. The feed-water may be preheated in the preheating arrangement 14 to a normal feed-water temperature of approximately 180-240° C. before being conveyed back to the reactor 1 via the feed-water conduit 4. The preheating arrangement 14 may comprises one or more heat exchangers. The plant also includes an arrangement for catching and removing off-gases produced in the reactor 1. This arrangement may include an off-gas conduit 15. In, for instance, the off-gas conduit 15, a sensor 16 may be provided. The sensor 16 is arranged to detect radioactive nuclides formed at the reaction in the fuel rods 9. If a defect arises on a cladding 10, fission gases will leak out and be conveyed out from the primary system through the off-gas conduit 15. These fission gases include such radioactive nuclides that can be detected and give substantially immediate information indicating that a primary defect has occurred. During operation, the reactor coolant is also re-circulated as a coolant flow within the reactor 1 through the core in contact with the fuel rods 9, thereby influencing the power of the reactor 1. This re-circulation of reactor coolant is accomplished by means of a number a circulation pumps 17, normally provided in the proximity of the bottom of the reactor 1. In FIG. 1, merely two such circulation pumps 17 are schematically indicated. Also other arrangements of circulation pumps then those indicated herein may be used, e.g. in external loops or jet pumps internally in the reactor, which are driven by external feed pumps. Each fuel rod 9 also comprises a distance element 20′ provided in the upper plenum 12′ and a distance element 20″ provided in the lower plenum 20″. In the embodiment disclosed, the distance element 20′ in the upper plenum 12′ is configured as a plenum spring. The purpose of the distance element 20′ in the upper plenum 12′ is to maintain the fuel pellets 11 in a proper position in the inner space 12 of the cladding 10. Furthermore, the distance element 20′ of the upper plenum 12′ is configured to permit deformation or compression of the plenum spring in order to absorb swelling of the fuel pellets 11 during the operation of the reactor 1. The purpose of the distance element 20″ in the lower plenum 12″ is to maintain the fuel pellets 11 in a proper position in the inner space 12 of the cladding 10, and more precisely to carry the weight of the pile of fuel pellets 11. In the embodiment disclosed, the distance element 20″ in the lower plenum 12″ is configured as a rigid body, and more precisely as a short tube, see U.S. Pat. No. 6,298,108. The distance member 20″ of the lower plenum 12″ may be configured in a different manner as a rigid body of any suitable shape. Possibly, also the distance element 20″ of the lower plenum 12″ may be configured to permit deformation or compression of the plenum spring in order to absorb a part of the swelling of the fuel pellets 11 during the operation of the reactor 1. In case the fuel rod 9 comprises an intermediate plenum, a distance element is provided also in such an intermediate plenum. Furthermore, each or some of the fuel rods 9 may comprise a hydrogen absorbing element 21′ provided in the upper plenum 12′ and/or a hydrogen absorbing element 21″ provided in the lower plenum 12″. The hydrogen absorbing element 21′, 21″comprises a hydrogen absorbing body comprising or consisting of at least on metal in the group consisting of zirconium, titanium, nickel and alloys comprising one or more of these metals. These metals have a great ability to absorb hydrogen. The absorbing body has a surface coated with a layer of a substance that is permeable to hydrogen, but not permeable to substances consisting of molecules larger than hydrogen molecules. This substance of the layer comprises at least one metal in the group consisting of palladium, rhodium, rhenium and alloys comprising one or more of these metals. In the embodiment disclosed the absorbing body has a cylindrical shape. It is to be noted, that the absorbing body may have any suitable shape, for instance a spherical or a cubic shape, or a more complex shape with an outer contour with a relatively large surface area, which is advantageous. In order to achieve such a large surface area, the absorbing body may be enclosed in an imaginary body having a substantially convex outer surface, and wherein the surface of the absorbing body is significantly greater than the outer surface of the imaginary body. In a further embodiment, at least one of the distance elements 20′, 20″ forms the absorbing element. Especially the distance element 20″ of the lower plenum 12″ may be formed as a hydrogen absorbing element. In case the fuel rod 9 has an intermediate plenum, a hydrogen absorbing element may be provided in this intermediate plenum. According to an embodiment, the reactor 1 may be operated at a normal power, i.e. normally full power, during a normal state. During this normal operation, the reactor 1 is monitored frequently or continuously by means of the sensor 16 for detecting a possible defect on the cladding 10 of any of the fuel rods 9 in the core. The possible defect may be a primary defect, which for instance has been caused by mechanical wear. The defect is indicated in FIG. 2 at 30. If such a defect 30 has been detected, the operation of the reactor is changed to a particular state, comprising a reduced power of the reactor 1 and/or an increased sub-cooling of the reactor coolant. The change of the operation is made at least within 72 h, preferably within 48 h or more preferably within 24 h after the detection of the defect 30. Advantageously, the change of the operation to the particular state is made as soon as possible, for instance substantially immediately after the detection of the defect 30. The particular state may thus be obtained through one or a combination of the following measures. 1. The power may be reduced, in a BWR, by reducing the coolant flow of the reactor coolant through the core. Such a coolant flow reduction may be obtained by reducing the power or the speed of the one or more of the circulation pumps 17. 2. The power may be reduced, in a BWR or a PWR, by inserting at least some of the control rods to the respective position in the core. 3. The sub-cooling of the reactor coolant may be increased, in a BWR or a PWR, by reducing the preheating of the feed-water, for instance by shutting off one or more of the heat exchangers of the preheating arrangement 14. Especially in a BWR, the power may be reduced by displacing at least some of the control rods into the core at least a part of the control rod distance. For instance, the control rods 8 can be displaced a smaller distance, so that they covers at least approximately 15 cm, at least approximately 30 cm, or at least approximately 50 cm, of the fuel rod 9 from the bottom of the fuel rod 9. Upon the displacement of the control rods 8 into the core, by means of the drive members 13, the chain reaction is reduced and thus the power and temperature of the fuel pellets 11 in the fuel rods 9 decrease. If the control rods 8 are fully inserted to the respective end positions, a so called hot shut down is obtained, which means that the chain reaction substantially ceases but that the system pressure in the reactor 1 and the temperature of the coolant water in the reactor 1 are substantially maintained from residual heat generation from the fission products. The reactor 1 is then operated further at a reduced power and/or increased sub-cooling according to one or more of the measures 1-3 mentioned above, for instance with the control rods 8 inserted, during a particular state, which exists during a limited time period. The length of this limited time period may vary depending on a plurality of different factors, such as the size of the reactor 1, how many control rods 8 that has been inserted etc. During this time period, the power is thus substantially reduced in relation to the normal full power and a larger temperature gradient is established over the length of the fuel rod. The time period has to have at least such a length that the temperature of the fuel pellets decreases significantly. The limited time period may for instance rest from parts of an hour or some hours to 1, 2, 3 or 4 days. For instance, the limited time period may be at least 10, 20, 30, 40 or 50 minutes, or 1, 2, 3, 4, 5, 6, 7, 10, 14, 20 or more hours. The limited time period may maximally be 4, 3, 2 or 1 days. During the particular state, the thermal expansion of the fuel pellets 11 will decrease, and thus the free volume and the gas communication paths in the inner space 12 of the defect fuel rod 9 will increase. This volume increase means that further steam will penetrate the inner space 12 so that the pressure equalization between the inner space 12 and the system pressure is maintained. Furthermore, the lower temperature of the fuel pellets 11 means that the reaction rate for the oxidation of the cladding 10 and the fuel pellets 11 as well as for the hydriding of the cladding 10 decreases. Substantially immediately after this time period, when the equalization has taken place, the reactor 1 may again be operated at substantially full power with the same set of fuel rods 9. Consequently, the defect fuel rod 9 may be retained in the core until the next scheduled shut down for fuel exchange. It is to be noted that it may be possible during the defined time period to insert merely some of the control rods 8 to the respective position. The particular state may also be established for parts of the core in successive periods, wherein said reduction of the power is obtained through successive insertion of various groups of said control rods to respective position in the core. Each such group then advantageously defines a specific part of the core. It is also possible to imagine insertion of more than half of the control rods 8 for obtaining a power reduction influencing a greater fraction of the fuel elements of the reactor. According to a variant of the method the particular state includes that at least some or substantially all control rods 8 alternately are inserted to or extracted from the respective position for obtaining an alternating increase and decrease of the power. Analogously the sub-cooling can be alternated by changing the preheating of the feed-water. In such a way, the temperature and the thermal expansion of the fuel pellets 11 will also increase and decrease in an alternating manner, which means that the mixing of the gases in the inner space is accelerated. The invention is not limited to the embodiments disclosed but may be varied and modified within the scope of the following claims.
049960210	description	DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT; The numeral 10 in FIG. 1 generally designates a fuel assembly for a pressurized water nuclear reactor. The fuel assembly 10 includes an upper end fitting 12 and a lower end fitting 14 connected by a plurality of guide tubes or thimbles 16 for receipt of control elements in known manner. Cell-defining spacer grids 18, 20 and 22 have fuel or poison rod support features in the form of arches 24 and opposing springs 26, in known manner, and are secured at spaced intervals to the guide tubes 16 with their cells in register. The fuel rods or poison rods 30 are dotted-in in FIG. 2. The preferred embodiment of the invention is shown in FIGS. 3 and 4 in which the novel attachment of the zircaloy guide tube 16 to the stainless steel lower end fitting 14 is illustrated. The main feature of the attachment is a fastener 40 in the form of a stainless steel bolt having a head 42 configured for receipt of a hex key or wrench for torquing. A peripheral slot 44 can be used for staking to lock the bolt 40 against rotation. The shank of bolt 40 includes threads 46 through which a longitudinal slot or groove 48 is cut. The groove 48 creates a plurality of points 50 which tend to dig into mating threads in a zircaloy plug 52 having a threaded central passageway of threads mating with threads 46 to increase the frictional grip therebetween. The slot or groove 48 of the stainless steel fastener 40 further provides "give" to avoid cracking of either the plug 52 or guide tube 16 due to thermal dimensional changes during temperature recycling in the reactor. The end 54 of the fastener 40 opposite the headed end 42 and lower end fitting 14 into which it is countersunk in bore 56, has a transverse opening 58 in fluid communication with groove 48. This enhances coolant flow out of the guide tube 16 and flushes it, as well as giving it a "dashpot" or retarding function upon the insertion of a control rod. Between the zircaloy plug 52 and zircaloy guide tube 16 is the bottom of a stainless steel tube receiving cup 60. The cup 60 extends upwardly a distance sufficient to permit the lower grid 22, which is of stainless steel, to be attached to it. The aperture or bore 62 or cup 60 permits passage of the stainless steel fastener 40 therethrough to accomplish the fastening function. Because it is of stainless steel, as is the lower end fitting and the fastener itself, the thermal expansion characteristics of these three elements are substantially the same, thus permitting a firm and secure attachment between them even during temperature cycling. The end zircaloy guide tube 16 and zircaloy plug 52 are "captured" even though their expansion characteristics are different from the stainless steel elements. They are held firmly because of the increased friction and "give" afforded to the threaded connection by means of the groove 48 and sharp points 50 it forms with the threads 46 and their engagement with the corresponding threads in the plug 52.
048615200	summary	The present invention relates to a capsule for radioactive sources, and more particularly to such capsule which is drivable by way of a flexible cable from one point to another point. BACKGROUND OF THE INVENTION Radioactive sources are used in the art for both diagnosis and treatment of patients, especially human patients Such radioactive sources for such use are normally contained in a "safe" which avoids radiation hazard to technicians or physicians using the radioactive source in a diagnostic or treatment application. However, when the source is to be deployed, for example, in a human patient, the radioactive source must be driven from the safe to the place of diagnosis or treatment in the patient. To this end, the radioactive source is normally contained in a capsule and that capsule is attached to a drive member, most usually a flexible cable, so that the capsule and cable may be driven through a tubular guide from the safe to the point of disposition in the patient. This technique is referred to in the art as brachy therapy, e.g. intracavitary, intralumenal and interstitial radiotherapy, and this technique has become of increased importance in the treatment of certain diseases, especially cancer, in that the radiotherapy can be administered to very localized human body areas, as opposed to broad beam radiotherapy. To achieve this localized radiotherapy, the radioactive source must be placed in close proximity to the tissue being treated, since the radioactive source emits low levels of radiation at a distance from the locus of therapy and only high levels at the locus of therapy (the inverse square of the distance law). Thus, the application of the radiotherapy is normally achieved by guiding a radioactive source through at least one tubular guide until that source reaches the site of the tissue to be treated, e.g. cancerous tissue. A regiment of radiation is then administered according to a program defined for the particular cancerous tissue, and the therapy is, usually, periodically repeated until effective control of the cancerous tissue is achieved Since repeated treatments may be required, it is important that the technician or physician administering the treatment not be in close proximity to the patient during treatment, since the radioactive source, while emitting low levels of radiation at a distance from the source, emits high levels of radiation near the source, and over a period of time and with numerous patients this can result in dangerous total radiation to the technician or physician. To avoid such radiation hazard to the technician or physician, apparatus has been developed so that the radioactive source is not moved from the safe until the apparatus is fully in place on the patient and the technician or physician is not in close proximity to the patient during treatment, e.g. in a separate room. Such apparatus is known in the art as remote after loading apparatus for brachy therapy, e.g. intracavitary, intralumenal and interstitial radiotherapy. For example, when using such apparatus, a technician interstitially places a positioning member, e.g. a needle or canula at the site where radiotherapy is to be effected. This positioning member is then attached to one end of a tubular guide, and the tubular guide is attached at the other end thereof to a connection head of the remote after loading apparatus. After such positioning and connections are made, a technician, from a remote location, e.g. another room, can cause the apparatus to drive a cable with the radioactive source contained in a capsule attached to the cable from the safe, through the remote after loading apparatus, the tubular guide and into the positioning member for radiotherapy. Thus, the technician will not be in close proximity to the patient while the radioactive source is out of the safe and while administering the therapy. While apparatus of the above nature has been used for some time, a particular problem in connection therewith has been the ability of the capsule containing the radioactive source to be driven through the apparatus, especially the tubular guide, when that tubular guide is disposed in a tortuous path. The capsule, for safety reasons, must ensure that the radioactive source or sources contained therein are not dislodged from the capsule either while in the after loading apparatus or while passing through the tubular guide or while in the patient. To this end, the capsules are made of metal, and the radioactive source or sources are sealed in the metal capsule, usually by welding, to ensure that no dislodging of the radioactive sources will take place. Since the capsule is made of metal, the capsule is rigid, and when the capsule encounters a tortuous turn in the tubular guide, or other parts of the apparatus or in the patient, the capsule may not be able to traverse that tortuous turn and becomes lodged. As can be appreciated from the foregoing, it is therefore important that the length of the rigid capsule be as short as possible. Typically, the internal diameter of the tubular guide will only be about 1.5 millimeters or less and, consequently, the diameter of the capsule must be about 1.5 millimeters or less, usually about 1.1 millimeters. The capsules most often contain one or a plurality of radioactive sources, e.g. 4, 5, 6, 7, 8 or even 10 or more, and the length of the capsule is correspondingly increased with the number of sources. A typical capsule, containing seven radioactive sources, will have an overall length of approximately 7.2 millimeters. When a capsule of that length encounters a tortuous turn, e.g. in the tubular guide, the chances of the capsule binding in that turn significantly increases. As can be appreciated from the foregoing, even small deviations in the length of the capsule significantly affect the ability of the capsule to traverse such tortuous turns. In the usual and known method of manufacturing source capsules, a flexible transport cable is attached to the back end of the capsule. The front end of the capsule is open so that the required radioactive source or numbers of sources may be placed into the capsule. Thereafter, the front end of the capsule is sealed by inserting a rounded plug into the front end of the capsule, and that plug is then attached to the capsule, usually by welding. However, in such a welding operation, the plug must be held in position for welding by a holder having a pair of tongs or grippers with the result that the plug must have a certain minimum length in order to be securely held by such holder during the welding operation. In addition, the attachment, e.g. weld, is tested by a strong axial pull on the plug and the apparatus for gripping the plug for such pull test requires a plug of substantial relative length, e.g. about a minimum of 1.35 millimeters. As can be appreciated, this pull test is necessary in order to insure that the plug is well attached to the capsule, since if the plug dislodged from the capsule and allowed the source or sources to be lost in the apparatus, or much worse in the patient, disastrous results would ensue Consequently, the overall length of the capsule, with the plug attached, is increased beyond that necessary for the capsule containing the radioactive sources, and this increased length increases the chances of the capsule binding in the tubular guide or other parts of the apparatus during an attempted traverse of a tortuous turn. As can, therefore, be appreciated, it would be a substantial advantage to the art to provide a capsule which can contain the same number of radioactive sources as known capsules, but which capsule is of a significantly shorter length than the known capsules BRIEF DESCRIPTION OF THE INVENTION The present invention is based on three major discoveries and several subsidiary discoveries. First of all, it was found that if the capsule, in the form of a tubular body, is manufactured with the front end thereof in an appropriate configuration, e.g. a rounded configuration, then the necessity for providing the elongated plug at the front end for welding to the tubular body could simply be eliminated. By eliminating this welding step, the necessity for an increased length of the plug, as in the prior art devices, is also eliminated, since there is no requirement for the plug having a length adequate for holding by the holder during the welding process or adequate in length for a pull test, as described above. A second important discovery is that the welding to close the capsule in the form of a tubular body can take place at the back end of the tubular body. In this regard, a plug can be inserted into the back end of the tubular body, but if that plug is previously attached to the flexible drive cable, then the combination of the plug and drive cable provides far more than adequate length for securing in a holder during the welding operation and performing the pull test. Further, it has been found that when the tubular body has a uniformly shaped end, e.g. a rounded end, this provides a much more uniform field of radiation along the length of the capsule, since the relatively massive plug of the prior art is eliminated and therewith the radiation shielding which it effected. Also, it would be found that weldings of the present capsule could take place, very conveniently and very predictably, by use of laser or electron-beam welding and that such welding techniques, in combination with the source capsule, produced very predictably sealed capsules. Thus, the invention provides a drivable radioactive source capsule comprising a tubular body containing therein one or more radioactive sources. The tubular body has a first end (closed end), preferably a rounded first end, and a second end which is a terminus of the tubular body. A plug having an elongated closure portion with the diameter of the closure portion being substantially equal to the inside diameter of the tubular body is disposed within the tubular body such that the closure portion is passed through the second end of the tubular body and attached to the second end of the tubular body. The plug also has a connection portion adjacent the closure with the diameter of the connection portion being substantially equal to the outside diameter of the tubular body. An elongated flexible drive cable is connected to the connection portion of the plug. By this arrangement, radioactive sources may be placed in the tubular body and the tubular body is closed by disposing the closure of the plug into the second end of the tubular body and attaching the closure to the second end of the tubular body.
042886961	description	DESCRIPTION OF THE PREFERRED EMBODIMENT Referring initially to FIG. 1 a well logging system embodying the concepts of the present invention is illustrated schematically. A well borehole 11 is lined with a steel casing 12 and filled with a borehole fluid 15. The steel casing 12 is cemented in place by a cement layer 13 and effectively seals off earth formations 14 from communication with the borehole 11 except in instances where the steel casing and cement layer are perforated for oil production. A fluid tight, hollow body member or sonde 16 is suspended in the borehole 11 by a well logging cable 17 of the usual armored cable type known in the art. The logging cable 17 communicates electrical signals to and from the sonde to surface equipment. At the surface, the well logging cable 17 passes over a sheave wheel 18 which is electrically or mechanically linked, as indicated by the dotted line 20, to a well logging recorder 19. This linkage enables measurements made by the downhole sonde 16 to be recorded as a function of borehole depth by the recorder 19. Signals from the well logging cable 17 are provided to surface data processing circuits 21 which process measurement data to provide information which is supplied to the recorder 19 for recording as a function of borehole depth. Power supply 22, located at the surface, supplies power for the operation of the downhole equipment on cable 17 conductors. In the downhole sonde 16 equipment is provided for making pulsed neutron measurements. While not shown in the schematic drawing of FIG. 1 it will be understood that appropriate power supplies in the downhole instrument convert power source 22, power supplied from the surface into the necessary operating voltages for the equipment in the downhole sonde 16. Control circuits 23, which will be described in more detail subsequently, provide control functions for a neutron generator tube 27 and a high voltage power supply 28 associated therewith and which are located near the lower end of the sonde. Neutron shielding material 29 which may consist of alternate layers of iron, paraffin, cadmium and borated foils or the like is provided to shield the neutron generator 27 from the remainder of the instrumentation within the downhole sonde 16. A gamma ray detector in the form of a scintillation crystal 24 of thallium activated sodium iodide or the like is optically coupled to a photomultiplier tube 25. This provides for detecting gamma radiation originating in the earth formations in the vicinity of the borehole and resultant from neutron bombardment by the neutron generator 27. As is well known in the art the impingement of gamma rays upon the detector crystal 24 produces light flashes therein whose intensity is proportional to the energy of the gamma ray producing the scintillation. The photomultiplier tube 25 is optically coupled to the detector crystal 24 and amplifies the light flashes produced by the detector crystal 24 and converts them to electrical voltage pulses whose amplitude is proportional to the intensity of the light flashes. These electrical signals are further amplified in an amplifier 26 and conducted into the control circuit electronics 23 portion of the tool where they are appropriately supplied to conventional cable driving circuits (not shown) for transmission of the data processing circuits 21 located at the surface of the earth. The neutron output of a neutron generator tube 27 of FIG. 1 is illustrated in FIG. 3 as a function of time. In the illustration of FIG. 3 a pulsed neutron mode of operation of the neutron generator tube is contemplated. The high voltage power supply is on at all times in the system and bursts or pulses of neutrons are produced by applying voltage pulses illustrated at 46 of FIG. 2 to the ion source. The neutrons are produced by the neutron generator tube 27 as previously described. Voltage pulses 46 of a predetermined amplitude and duration are applied to the ion-source of the neutron generator tube 41. In this manner the neutron output of the tube may be made to vary as indicated in FIG. 3. That is to say, the neutron output will rapidly increase from essentially zero to N.sub.max, the maximum value of neutron output of which the generator tube is capable when a given magnitude voltage pulse is applied to the ion source. During this time an average value N.sub.avg will be emitted. In this manner a very rapid build up or pulse of neutron output from the generator tube 27 is accomplished as a function of time. Removing the voltage pulse from the ion source returns the neutron generator tube to the quiescent value of neutron output which is essentially zero. For typical well logging operations the on-time of the neutron generator tube in pulsed mode will usually not exceed a duty cycle of approximately 5-10% of its operating cycle. That is to say, the neutron generator tube will generally only be on from 5-10% of the time and the off periods of FIG. 3 will occupy approximately 90-95% of its time in a typical well logging operation. Neutron pulse durations of approximately 50 microseconds duration and repitition rates of from 1000-10,000 pulses per second are typical for pulsed neutron well logging techniques. The neutron generator control system of the present invention operates to maintain the average value N.sub.avg of the neutron output at a constant or predetermined value for the duration of a well logging run. Obviously such a system cannnot replace tritium in the tube which is used up in generating the neutron output. Long term deterioration of the neutron output is unavoidable in generator tubes which provide only deuterium in the replenisher. Tubes having a deuterium and tritium mixture can avoid such long term neutron output deterioration. The need for short term control of neutron output arises from the relationship between the replenisher current and the neutron output, which is a complicated function. Very small changes in the replenisher current can cause very large changes in the neutron output. By monitoring the target current (which is related to the neutron output) and correcting the replenisher current to hold the target current constant, the neutron output may be stabilized for short term variations such as could occur during a well logging job. Alternatively, it should be noted that the neutron generator 27 could be operated continuously for certain types of well logs. In such a case the values N.sub.avg and N.sub.max would be the same value. In this instance the control system of the present invention would maintain approximately a constant neutron output from the neutron generator 27 for the duration of a well logging job. Referring now to FIG. 2 a portion of the control circuitry 23 of FIG. 1 having to do with the control of the neutron output from a neutron generator tube is illustrated in more detail, but still schematically. Point A of the circuit is connected to the low side of the target high voltage power supply (which may typically be negative 125 kilovolts). The neutron generator tube 41 target beam current (which is sampled at Point A) flows to ground through resistor R.sub.1 generating a voltage V.sub.B at Point A which is related to the neutron output of the generator tube. The sampled voltage at Point A is used to regulate the drain current I.sub.D of the VMOS power field effect transistor 45 (labelled FET1). This current is also the replenisher current of the neutron generator tube 41, and is sampled at point 47. A variable resistor VR1 establishes a reference voltage for controlling the average neutron output of the generator tube 41. The setting of variable resistor VR1 is determined by the transfer characteristics of the VMOS power FET 45 and the relationship between the replenisher current and the neutron output of the generator tube. In general, the transfer characteristics will vary with each FET and generator tube. For the purpose of this description it will be assumed that the desired neutron output is obtained when the average target beam current is 100 microamperes and the replenisher current is 3 amperes. These are typical values encountered in the operation of neutron generator tubes in well logging usage. In this case, the variable resistor VR1 is adjusted until the replenisher current is 3 amperes and the target current is 100 microamperes giving a reference voltage V.sub.B at Point A, of 3 volts. This voltage establishes the average operating point of the neutron generator tube 41. Operational amplifier 44 is connected as an inverting voltage gain circuit with the gain determined by the ratio R3/R.sub.2. The output voltage V.sub.G of the operational amplifier 44 is applied to the gate of the field effect transistor 45. This gate voltage controls the drain current I.sub.D of the field effect transistor 45 which is supplied from a 5 ampere current supply 42. This drain current is sampled at point 47 and fed back through resistor R3 to establish the operating conditions of the operational amplifier 44 as previously described. The non-inverting input of the operational amplifier 44 is connected to the voltage setting provided by variable resistor VR1 through resistor R.sub.4. This voltage applied to the non-inverting input of the operational amplifier 44 plus the voltage developed across R.sub.1 determines the output voltage of the operational amplifier 44. If the average value of the neutron output N.sub.avg begins to decrease below the operating value as determined by the setting of VR1, the target beam current will decrease. This will cause the voltage V.sub.B to decrease. When V.sub.B decreases, this causes the output voltage V.sub.G of the operational amplifier 44 to increase. The increased voltage output V.sub.G of the operational amplifier 44 causes the replenisher current I.sub.D to increase. The increase in replenisher current I.sub.D tends to increase the target beam current as sampled at Point A. If the neutron output of the generator tube 41 begins to increase above predetermined average operating value N.sub.avg, the target beam current will increase. This causes the voltage V.sub.B across resistor R.sub.1 to increase. When V.sub.B increases, this causes the output voltage V.sub.G of the operational amplifier 44 to decrease. The decrease of V.sub.G, the gate voltage on field effect transistor 45, causes the replenisher current I.sub.D, as sample at point 47, to be reduced. This in turn reduces the output of the neutron generator tube 41 by cooling the replenisher heater element. A solid state switching integrated circuit 43 is used to apply and remove a control voltage source (0-15 volts) to variable resistor VR.sub.1. When the control voltage source is removed from the variable resistor VR.sub.1, the voltage applied to the non-inverting input of operational amplifier 44 goes to zero volts. When zero volts is applied to the non-inverting input of the operational amplifier 44, the voltage output of the operational amplifier is reduced sufficiently to insure that the field effect transistor 45 is completely turned off. This interrupts the replenisher current I.sub.D completely and effectively reduces the output of the neutron generator tube 41 to zero. The foregoing descriptions may make other alternative embodiments of the invention apparent to those skilled in the art. It is therefore the aim of the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.
	description	This application is a national phase application of International Application No. PCT/EP2012/070013, filed Oct. 10, 2012, designating the United States and claiming priority to European Patent Application No. 11184551.7, filed Oct. 10, 2011, which is incorporated by reference as if fully rewritten herein. The present invention concerns a method for producing a radioisotope and an installation for implementing this method. In nuclear medicine, positron emission tomography is an imaging technique requiring positron-emitting radioisotopes or molecules labelled with these same radioisotopes. The 18F radioisotope is one of the most frequently used radioisotopes. Other routinely used radioisotopes are: 13N; 15O; and 11C. The 18F radioisotope has a half-life time of 109.6 min and can therefore be conveyed to sites other than its production site. 18F is most often produced in its ion form. It is obtained by bombarding protons accelerated onto a target comprising 18O-enriched water. Numerous targets have been developed, all having the same objective of producing 18F in shorter time with better yield. In general, a device for producing radioisotopes comprises a proton accelerator and a target cooled by a cooling device. This target comprises a cavity hermetically sealed by a beam window to form a hermetic cell inside which a radioisotope precursor is contained in liquid or gas form. In general, the energy of the proton beam directed onto the target is in the order of a few MeV to about twenty MeV. Said beam energy causes heating of the target and vaporisation of the liquid containing the radioisotope precursor. Since the vapour phase has lower stopping power, a larger quantity of particles in the radiation beam passes through the hermetic cell without being absorbed by the radioisotope precursor, which not only reduces the radioisotope production yield but also causes further heating of the target. This well-known phenomenon is commonly called the <<tunnelling effect>>. It is known to reduce the magnitude of the tunnelling effect using a system to pressurise the hermetic cell as described for example in document WO2010007174. A said system pressurises the hermetic cell of the target with an inert gas so as to increase the evaporation temperature of the precursor liquid inside the hermetic cell. However this solution has the disadvantage of having to operate with a higher pressure inside the hermetic cell of the target, which requires a target designed to withstand higher pressures. A said target has the disadvantage of being provided with a wall of greater thickness than conventional targets. It therefore requires relatively high beam energy to irradiate the radioisotope precursor. Document JP2009103611 describes a device for producing radioisotopes comprising a system to pressurise the hermetic cell that is capable of maintaining a constant internal pressure inside the hermetic cell. To prevent rupture of the beam window subsequent to an increase in pressure, document JP 2009103611 proposes equipping the hermetic cell with a control valve allowing controlled discharge of the radioisotope precursor fluid if the pressure inside the hermetic cell exceeds a threshold value. This solution has the disadvantage in particular of causing loss of volume of the radioisotope precursor fluid contained in the hermetic cell. Yet some radioisotope precursor fluids may be very costly which means that undue discharges must be avoided at all costs. To prevent undue discharges the working pressure inside the hermetic cell of the target must be substantially lower than the discharge pressure. When the target intended for production of radioisotopes is daily irradiated by a proton beam for several hours, some regions of the target may become fragile over time. Heating of the irradiation cell may therefore damage seals sealing the cavity closed by the beam window, causing leakages. Leaks may also occur at the beam window. In addition, irradiation of the target produces secondary radiation which may damage neighbouring parts e.g. ducts, valves or pressure sensor equipping the target, also causing leaks. While the above-mentioned pressurising device has the advantage of maintaining the radioisotope precursor fluid in condensed or semi-condensed state, possible leaks in the irradiation cell and/or poor filling of the target due to a faulty valve for example cannot be detected in time. If the device monitoring internal pressure in the hermetic cell records a drop in this pressure, the pressurising device will normally inject inert gas into the target to re-increase its internal pressure. It is also to be noted that impurities resulting from washing of the target followed by incomplete drying may also cause overpressure, which may be masked by the above-mentioned pressurising device. When an insufficiently filled target is irradiated, in addition to the poor radioisotope yield obtained, some parts of the target may rapidly become heated on account of the tunnelling effect, going as far as deforming the target, the seals or beam window. Leaks may occur without being detected in time on account of the pressurisation system which re-increases the internal pressure of the target when the pressure varies. The greater the extent of filling of the hermetic cell with the radioisotope fluid precursor, the more the pressure inside the hermetic cell increases during irradiation. Yet if the internal pressure inside the hermetic cell exceeds a certain threshold, this may cause rupture of the beam window leading to extremely harmful consequences. Therefore, not only must rupture of the beam window be prevented further to an increase in pressure, but leakage problems or inadequate filling must also be detected in time. It is one objective of the present invention when producing radioisotopes to detect leakage problems or poor filling of a target in time, and to prevent deterioration of the target either via the said tunnelling effect or via an excessive increase in pressure. This objective is reached with the method described in claims 1 et seq. or the installation described in claims 10 et seq. More specifically, a method according to the invention comprises the steps known per se of irradiating a volume of radioisotope precursor fluid contained in a hermetic cell of a target, using a beam of particles of given current which is produced by a particle accelerator. The target is cooled and the internal pressure in the hermetic cell is measured. According to one aspect of the invention, the internal pressure (P) in the hermetic cell is allowed to be freely established during irradiation, without endeavouring to control the pressure by injecting a pressurising gas and/or using a depressurising valve, and irradiation is interrupted or its intensity is reduced when the internal pressure (P) in the hermetic cell moves out of a first tolerance range which is defined in relation to different parameters having an influence on changes in internal pressure in the hermetic cell during irradiation. Said parameters, for a given target and given radioisotope precursor fluid, particularly comprise the extent of filling of the hermetic cell, the cooling power of the target and beam current intensity (I). With this manner of operating, when the pressure falls below the lower limit of the first tolerance range, irradiation is interrupted or its intensity is reduced to avoid overheating the target. This lower limit corresponds to a difference that is too large compared with an optimal internal pressure determined for a hermetic cell containing a given volume of radioisotope precursor fluid and irradiated with a given beam current intensity. When the pressure exceeds the upper limits of the first tolerance range, irradiation is interrupted or its intensity is reduced also to prevent rupture of the beam window due to an excessive increase in pressure in the hermetic cell. This upper limit can be defined so that it affords sufficient safety in relation to the rupture pressure of the beam window. It will be appreciated that this manner of operating does not require any injection of a pressurising gas which would increase the total pressure inside the hermetic cell i.e. the nominal pressure designed for the target, and would also risk masking any leakages. Nor does it require depressurising via discharge causing loss of costly radioisotope precursor fluid. To interrupt irradiation or to reduce the intensity thereof, it is normally acted directly on the particle accelerator. However, it is also possible to act on the beam of particles (for example by deflecting the beam or inserting an obstacle on its pathway), or on the target (for example by moving it away from the pathway of the beam of particles). Preferably a curve P=f(I) is determined e.g. experimentally or using a mathematical model, giving the internal pressure (P) of the hermetic cell at different beam intensities (I), for a given target, a given volume of radioisotope precursor fluid and a given cooling power of the target. The first tolerance range then has a lower pressure limit and a higher pressure limit, defined for the given beam current intensity (I) on the basis of the curve P=f(I). The lower limit of internal pressure is defined so that it is lower, preferably between 5% and 20% lower, than the pressure value inferred from the said curve P=f(I) for the given beam intensity (I). The upper limit of internal pressure is a pressure between the pressure value inferred from the curve P=f(I) for the given beam intensity (I) and a nominal pressure value (Pmax) of the hermetic cell. This nominal pressure value (Pmax) is assumed to represent the maximum pressure value at which the hermetic cell is guaranteed. The upper limit of internal pressure in the first tolerance range is advantageously lower by at least 20% than the nominal pressure value (Pmax) of the hermetic cell. This normally affords sufficient safety against rupture of the beam window. Preferably, the upper limit of internal pressure in the first tolerance range is between 5 and 10 bars higher than the pressure value inferred from the curve P=f(I) for the given beam intensity (I) and its ceiling is a pressure value (P2) lower by a value of X bars than the nominal pressure value (Pmax) of the said hermetic cell. With this operating mode it is possible to detect poor filling of the hermetic cell or possible impurities derived from washing of the cell, and thereby to prevent too rapid rise in pressure when the beam intensity reaches high values. A control device advantageously triggers an alarm when the internal pressure (P) in the said hermetic cell moves out of a second tolerance range determined for the said given beam current intensity (I), a given volume of radioisotope precursor fluid and a given cooling power of the said target, this second tolerance range being included in the first tolerance range. The operator is thus alerted to a change in pressure in the hermetic cell which soon risks causing interruption of irradiation, and can optionally still prevent this automatic interruption. The second tolerance range has a lower pressure limit and a higher pressure limit, determined on the basis of the curve P=f(I), mentioned above. The lower limit of internal pressure in the second tolerance range is determined so that it is lower, preferably at least 2% lower, than the pressure value inferred from the said curve P=f(I) for the given beam current intensity (I) whilst remaining higher however than the lower limit of internal pressure in the first tolerance range. The upper limit of internal pressure in the second tolerance range is determined so that it is higher than the pressure value inferred from the curve P=f(I) for the given beam current intensity (I), whilst remaining lower than the upper limit of internal pressure in the first tolerance range. When the internal pressure (P) in the hermetic cell exceeds an upper limit of internal pressure which is determined so that it is higher than the pressure value inferred from the said curve P=f(I) for the given beam intensity (I), but lower than the upper limit of internal pressure in the first tolerance range, advantageously the beam current is reduced. In this manner it is optionally still possible to interrupt irradiation. The extent of filling of the hermetic cell is advantageously optimised so as to obtain a high yield of radioisotope production. The radioisotope precursor is advantageously a precursor of 11C, 13N, 15O or 18F. An installation is also presented for the implementation of the above-described method. This installation comprises a target with a hermetic cell capable of containing a volume of precursor fluid, this hermetic cell being guaranteed to withstand a nominal pressure (Pmax), a particle accelerator capable of producing and directing a beam of particles of given intensity (I) onto the target, a system for monitoring the internal pressure of the hermetic cell, and a control device programmed to interrupt the particle beam or to reduce the intensity thereof when the internal pressure (P) in the hermetic cell moves out of a determined first tolerance range in relation to different parameters having an influence on pressure changes inside the hermetic cell during irradiation. The control device is advantageously programmed to trigger an alarm when the internal pressure of the hermetic cell lies outside a second tolerance range included within the said first tolerance range. The control device may also advantageously be programmed to cause a reduction in the intensity of the beam current when the internal pressure (P) in the said hermetic cell exceeds an upper limit of internal pressure. In one preferred embodiment, the control device is programmed with a curve P=f(I) giving the internal pressure (P) of the hermetic cell at different beam current intensities (I), for a given volume of radioisotope precursor fluid and a given cooling power of the said target; this curve P=f(I) being used by the said control device to determine the said first tolerance range as a function of beam current intensity (I). One non-limiting embodiment of an installation 10 for producing radioisotopes according to the invention is illustrated on the basis of the schematic in FIG. 1. This installation 10 comprises a target, globally identified under reference number 12. This target 12 comprises a hermetic cell 14 containing a volume of radioisotope precursor fluid. As is known per se it is equipped with a cooling circuit 16. The installation 10 further comprises a particle accelerator 18 capable of producing a beam 20 of accelerated particles, which is directed onto the target 12 to irradiate the radioisotope precursor in the hermetic cell 14. The beam 20 enters the hermetic cell 14 via a beam window 22 having a thickness in the order of a few tens of micrometers. The maximum internal pressure that can be withstood by the target 12 is dependent in particular on the thickness of this beam window. The term nominal pressure (Pmax) of the target 12 is given to the maximum internal pressure in the hermetic cell 14 guaranteed by the manufacturer of the target. For as long as the internal pressure in the hermetic cell 14 remains lower than the nominal pressure (Pmax), it is guaranteed by the target manufacturer that the beam window 22 will be pressure-resistant. This nominal pressure (Pmax) is evidently a function of the geometry of the hermetic cell 14. The reference number 24 denotes a schematic illustration of a pressure sensor which measures the internal pressure inside the hermetic cell 14. A signal representing this measured pressure is transmitted via a data bus 26 for example to a control device 28. On the basis of this pressure signal, the control device 28 monitors the pressure inside the hermetic cell 14 continuously or almost continuously. The installation 10 advantageously comprises a multiple-way valve 30 which allows the hermetic cell 14 to communicate with different auxiliary equipment. A first port A of this valve 30 is connected for example to a three-way valve 32, itself connected to a reservoir 34 containing the radioisotope precursor and to a pipetting device 36 e.g. a syringe. A second port B is connected to a first port of the hermetic cell 14 via a duct 38 intended for filling and draining of the hermetic cell 14. A third port C is connected to a vessel 40 intended to receive the irradiated product when irradiation is completed. A fourth port D is connected to an overflow container 42 intended to collect excess fluid injected into the hermetic cell 14. A fifth port E is connected to a second port of the hermetic cell 14 via a duct 44. This duct 44 is used to evacuate the excess fluid injected into the hermetic cell and to add purge gas to the hermetic cell 14 respectively. This purge gas is contained in a reservoir 46 connected to a sixth port F. The control device 28 controls the different valves 30, 32, the pipetting device 36, the cooling device 16, the flow rate of the purge gas bottle 46 and the particle accelerator 18. During the filling of the hermetic cell 14, the valve 30 connects port A with port B and port D with port E. The three-way valve 32 connects the reservoir 34 containing the radioisotope precursor with the pipetting device 36 which draws a quantity of fluid containing the radioisotope precursor. The three-way valve 32 then connects the pipetting device 36 with port A of the valve 30. The pipetting device 36 is then able to inject the fluid containing the radioisotope precursor into the hermetic cell 14, any excess fluid being evacuated towards the overflow container 42. When the hermetic cell 14 is filled, the valve 30 closes all the ports and the accelerator 18 produces the beam to irradiate the target 12. When irradiation of the target 12 is completed, the valve 30 connects port F with port E, and port B with port C, so that the purge gas can be injected into the hermetic cell 14, and the irradiated fluid can be evacuated from the target 12 to be collected in the vessel for the irradiated product 40. It is to be noted that during the irradiation operation of the target 12, the internal pressure (P) is freely left to set itself up inside the hermetic cell 14. This means that there is no need for a device to regulate the internal pressure inside the hermetic cell 14, based on a pressurising system using a pressurising gas and a depressurising system using a purge valve. The internal pressure (P) inside the hermetic cell 14 is measured by the pressure sensor 24 and monitored by the control device 28. When the internal pressure (P) moves out of a first defined tolerance range, the controller 28 simply interrupts irradiation of the target 12 or reduces the intensity thereof. It is noted that, for a given target 12, this first tolerance range is defined specifically for the current intensity I of the beam 20, the volume V of radioisotope precursor fluid contained in the hermetic cell 14 and the cooling power of the target 12. (Normally, the cooling power is maintained constant). The control device 28 is therefore programmed to interrupt the irradiation of the target 12 when the internal pressure (P) in the hermetic cell 14 moves out of a first defined tolerance range. It is advantageously programmed to trigger a previous alarm and/or to reduce the intensity of irradiation when the internal pressure (P) of the hermetic cell 14 moves out of a second determined tolerance range which is included within the first tolerance range. One advantageous definition of these tolerance ranges will now be described with reference to FIG. 2 which in particular gives an experimental curve P=f(I) representing changes in internal pressure (P) inside the hermetic cell 14 as a function of beam current intensity (I), for a given target 12, a certain volume of radioisotope precursor fluid in the hermetic cell 14 and a certain cooling power of the target 12. The example of the curve P=f(I) illustrated in FIG. 2 was determined for example for a hermetic cell 14 of given geometry, having a volume of 3.5 ml, filled with a volume of 2.5 ml of radioisotope precursor fluid. To record this curve P=f(I) the beam intensity was gradually increased, measuring the internal pressure of the target using a pressure sensor 24. These measurements were performed until the nominal pressure value was reached (Pmax) guaranteed for the target 12 for a beam current intensity I of about 60 μA. Throughout all these measurements the flow rate of cooling liquid was maintained substantially constant, as was the input temperature of the cooling liquid into the target 12. It will be noted that the curve P=f(I) illustrated in FIG. 2 is not limiting for the invention. The curve P=f(I) varies in relation to the quality of the beam produced by the accelerator, the geometry of the target, cooling power, the volume and type of radioisotope precursor fluid. The curve P=f(I) can also be determined theoretically by simulation taking into account parameters of the beam, of the volume of radioisotope precursor fluid, the power of the cooling system, the geometry of the target 1 and the characteristics of the radioisotope precursor fluid. The first tolerance range has a lower pressure limit and a higher pressure limit, both defined for the said given beam current intensity (I) on the basis of the curve P=f(I). The lower limit of internal pressure is defined so that it is preferably between 5% and 20% lower than the pressure value inferred from the curve P=f(I) for the given beam current intensity (I). In FIG. 2, the curve f(I)=P−(0.2P) represents the case for example in which a lower internal pressure limit is defined so that it is 20% lower than the pressure value inferred from the curve P=f(I) for a given beam current intensity (I). The upper limit of internal pressure is a pressure between the pressure value inferred from the curve P=f(I) for the given beam current intensity and a nominal pressure value (Pmax) of the hermetic cell. It is advantageously between 5 and 10 bars higher than the pressure value inferred from the curve P=f(I) for a given beam intensity (I), and its ceiling is a pressure value (P2) lower than the nominal pressure value (Pmax) of the hermetic cell 14. The curve f(I)=P+5 in FIG. 2 represents the case for example in which an upper limit of internal pressure is determined so that it is 5 bars higher than the pressure inferred from the curve P=f(I) for a given beam intensity (I). In FIG. 2, the upper limit of internal pressure is preferably fixed at a value P2=30 bars, which represents 75% of the nominal pressure Pmax and is equal to 40 bars. The second tolerance range is included in the first tolerance range and is also positioned around the curve f(I)=P. The lower limit of internal pressure in the second tolerance range is defined so that it is lower, preferably at least 2% lower, than the pressure value inferred from the curve P=f(I) for the given beam intensity (I), whilst remaining higher than the lower limit of internal pressure in the first tolerance range. The upper limit of internal pressure in the second tolerance range is determined so that it is higher than the pressure value inferred from the curve P=f(I) for the given beam intensity (I) whilst remaining lower than the upper limit of internal pressure in the first tolerance range. An example of a second tolerance range is also illustrated in FIG. 2. The lower limit of internal pressure is illustrated by the curve f(I)=P−0.1P) and the upper limit of internal pressure is illustrated by the curve f(I)=P+2. The control device 28 which also controls the intensity of the beam current is advantageously programmed to cause a reduction in the intensity of the beam current when the internal pressure (P) in the hermetic cell 14 exceeds an upper limit of internal pressure. This upper limit is then defined so that it is higher than the pressure value inferred from the said curve P=f(I) for the given beam current intensity (I) but lower than the upper limit of internal pressure in the said first tolerance range. To optimise the method it is possible in particular to act on the extent of filling of the hermetic cell 14. To optimise the radioisotope production yield, it is useful to optimise the extent of filling of the hermetic cell. With knowledge of the nominal pressure value (Pmax) of the hermetic cell, whilst measuring the internal pressure of the hermetic cell, the target is irradiated with a beam current I for a defined period (e.g. two hours) with different volumes of radioisotope precursor fluid, so as not to exceed the nominal pressure (Pmax). The yield of radioisotope production for each of the volumes is then calculated. A yield curve of radioisotope production is plotted as a function of the extent of filling of the cell which in practice displays a constant yield over and above a critical volume filling, and a sharp drop in yield below this same critical volume filling. To minimise pressure constraints in the target whilst minimising the tunnelling effect, a volume filling of the hermetic cell is fixed which corresponds to this critical volume filling or to a slightly higher volume filling, and the pressure curve P is determined either experimentally or theoretically as a function of the beam current intensity I for this extent of volume filling of the hermetic cell. It remains to be noted that the described installation and method are particularly adapted for the production of radioisotopes such as 11C, 13N, 15O or 18F. 10 radioisotope production installation 12 target 14 hermetic cell 16 cooling circuit 18 particle accelerator 20 particle beam 22 beam window 24 pressure sensor 26 data bus 28 control device 30 multi-way valve 32 three-way valve 34 reservoir containing radioisotope precursor 36 pipetting device 38 duct 40 vessel to receive irradiated product 42 overflow container 44 duct 46 reservoir with purge gas
042008646	summary	BACKGROUND OF THE INVENTION The instant invention relates to a process control installation for mechanical elements such as pumps, valves, pulleys, control rod release stops, etc. More particularly, the invention may be utilized especially for controls in nuclear power plants, but is in no way limited to this application. It is known to utilize a process control installation for nuclear power plants in which a predetermined number of physical characteristics are detected or measured, each by several, (e.g., three independent sensors or probes), so that the measurement of each physical characteristic gives rise to a set of several (in this case three), measurement values. This known installation comprises, first, comparator circuits, each connected to one of the sensors and a reference transmitter, and each delivering at its output a signal the value of which is the difference between the value of reference and the value measured by the probe. Secondly, the installation comprises circuits for the reproduction of signals of the same value as the input signal, galvanically separated one with respect to the other and with respect to the input signal. Each reproduction circuit is connected to the output of a comparator circuit. In the third place, majority decision circuits are provided, each one associated with a physical characteristic. These majority decision circuits are connected to an output of each of the reproduction circuits which in turn receive signals from the comparator circuits connected to the probes measuring or detecting the same physical characteristic. If each physical characteristic is measured by three independent probes each majority decision circuit comprises three inputs. It is further possible to provide "two of three" majority decision circuits the output of which is not dependent on a single breakdown, but is sensitive to a double or triple breakdown. In the fourth place, the installation comprises two identical functional logic flow circuits at one or several outputs of and connected to the output of a majority decision circuit. These logic circuit trains may be very complex and comprise a variety of outputs designed to activate the different mechanical elements of the process control. Thus, in the fifth place, functional logic sets or circuits, each one connected to two corresponding outputs of the two circuit logic trains and influencing, as needed across the power circuits, one or several mechanical process control elements. It is useful at the point to briefly discuss the concept of the functional logic sets. This set is considered not in view of the output control signal, but in view of its final influence on the functioning of the process. For example, when the anticipated function is the opening of water valves in the event of a fire, if at least one of the logic circuit trains signal the beginning of a fire, a functional OR logic circuit can either open one valve by virtue of an electronic OR logic circuit, or an AND electronic logic circuit so that the signal to open the valve indicates the presence or absence of a fire. According to an alternative, the functional logic OR circuit can activate two valves disposed in parallel to open them, or open one of the two if one alone, or both, if the two logic circuit trains transmit the fire alarm. The known control installation, described hereinabove is highly reliable in normal operation, however, not being equipped with circuits for intrinsic security, partially loses this quality when one or the other of the two logic circuit trains is tested. Logic circuits for intrinsic security are described, for example, in the French Pat. Nos. 1,410,561, 1,461,822, 1,515,044 and 1,520,105. Furthermore, as is generally the case, when one of the logic circuit trains breaks down, the condition of the output represents the intervention of an urgency measure, for example, the sprinkling in case of a fire. This sprinkling can be initiated by a breakdown of a logic circuit train and may lead to the unnecessarily soaking of a costly installation. The same inconvenience results during an unexpected halt of a chemical process necessitating thereafter the cleaning of the polymerization tunnels and a delicate start up. SUMMARY The principal aim of the invention is to increase the security of the installation as a result of the utilization of logic circuits for intrinsic security and also to avoid untimely interruptions due to the breakdown of a single train of logic circuits. A subsidiary aim is the maintenance of the standard of security and insensitivity to accidental errors of one single logic circuit train during testing periods. The installation following the invention is characterized in that each of the identical logic circuit trains is replaced by two trains of identical logic circuits of which the corresponding outputs are connected to the functional AND logic circuit, the outputs of the AND logic circuit being connected to the input of an OR logic circuit. Preferably, all of the logic circuits are for intrinsic security. According to one subsidiary characteristic, a third set of two identical logic circuit trains is provided the corresponding outputs of which are connected to the functional AND logic circuits, the outputs of the AND logic functional circuits being connected to the inputs of a functional logic circuit, OR circuit, or majority decision circuit "two of three".
052992420	summary	BACKGROUND OF THE INVENTION This invention relates generally to a nuclear reactor control system and more particularly to a device for the control of a nuclear reactor in the form of two independently controlled, concentrically assembled, reflectors. Interest in the use of nuclear power sources for U.S. space programs has recently increased. The use of nuclear power in space has importance because spacecraft destined for deep-space exploration cannot effectively utilize solar power as an energy source due to their distance from the sun. Additionally, some satellites and planetary space probes operating close to the sun have electrical power design requirements that cannot withstand cyclical solar exposures or rely on rechargeable batteries. Furthermore, as the electrical power requirements for spacecraft increase, the capability of solar power to supply the electricity becomes limited by the sheer size of solar panels. Therefore, a reliable, long term supply of energy is needed in a low-mass form that requires minimal space. Nuclear power can supply this energy need. There are two types nuclear power sources used in space applications. One type, called radioisotope thermoelectric generators (RTGs), uses the decay of naturally radioactive elements to produce heat. The other type of nuclear power source uses nuclear reactors to produce heat. Space nuclear reactors employ several power conversion technologies. Among them are thermoelectrics and thermionics. In general, the thermoelectric nuclear reactor uses a circulating medium to transport heat from the reactor core to energy conversion devices located behind a radiation shield. In one reactor, the SP-100, a liquid metal (Li) is used in a pumped loop to transport the core heat to the conversion devices. The thermionic nuclear reactor concepts generally perform the energy conversion in the core and transport the waste heat via heat pipes or liquid metal loops. To achieve a maximum level of system reliability and redundancy in conventional reflector control systems employed in test reactors, like the Advanced Test Reactor (ATR) at the Idaho National Engineering Laboratory (INEL), or the SNAP and SP-100 space reactors, multiple and independently operated and controlled reflector elements are required. In the ATR, SNAP, and the Russian TOPAZ reactors, reflector drums are utilized around the perimeter of the core. In the SP-100 reactor, hinged "shutter" reflector segments are employed. In both of these systems, failure of one or more of the reflector drives or control systems may disable the reactor startup or shutdown, and at a minimum, will compromise full mission capability. A new space nuclear power concept has been developed by the INEL. This concept, the Small Ex-core Heat Pipe Thermionic Reactor (SEHPTR), has unique features and significant advantages for both defense and civilian space missions. SEHPTR was developed to meet needs for space nuclear power in the range of 10 to 40 kilowatts. In addition, other requirements that space nuclear power systems must meet to be acceptable to potential users have been identified. These requirements include safety of the system during launch and operation, and the ability to perform rigorous ground testing. Performance requirements dictate a high reliability and emphasize reduced system volume and mass. Additionally, several spacecraft developers have indicated a reluctance to incorporate into their spacecraft any primary power subsystem that has potential mission ending single point failures. It is therefore an object of the present invention to provide a reactor control device for a primary nuclear power subsystem which is subcritical in launch accident scenarios, and which eliminates credible mission ending single point failures. A further object of the present invention is to provide a reactor control device in which either of two reflectors are capable of independently controlling the reactor to provide redundancy. Yet another object of the present invention is to provide reliable reactor control for a space nuclear power system with a minimum of redundant hardware and minimum mass penalty. SUMMARY OF THE INVENTION This invention provides a nuclear reactor control system in a nuclear reactor having a core operating in the fast neutron energy spectrum where criticality control is achieved by neutron leakage. The control system includes dual annular, rotatable reflector rings. There are two reflector rings: an inner reflector ring and an outer reflector ring. The reflectors are concentrically assembled, surround the reactor core, and each reflector ring includes a plurality of openings. The openings in each ring are capable of being aligned or non-aligned with each other. Independent driving means for each of the annular reflector rings is provided so that reactor criticality can be initiated and controlled by rotation of either reflector ring in either direction such that the extent of alignment of the openings in each ring controls the reflection of neutrons from the core. The openings in each reflector ring are of a size to ensure that when the openings in each reflector are not aligned, the reactor is operational due to the reflection of neutrons back to the reactor core where the neutrons initiate and sustain the fission process, and when the openings in each reflector are aligned, the reactor is shutdown due to insufficient reflection of neutrons into the reactor core to allow the reactor to attain criticality. The means for independent driving of each reflector ring includes inner reflector drive means and outer reflector drive means. The inner reflector drive means and the outer reflector drive means each include a reflector drive shaft operably connected to a pinion and ring gear structurally connected to the inner or outer reflector, such that rotation of either drive shaft causes the pinion to turn its respective ring gear to thereby rotate the associated reflector to control neutron leakage from the reactor core.
060977876	summary	FIELD OF THE INVENTION The invention relates to a radiation emitting device, and more particularly to a system and method for calculating scatter radiation of the radiation emitting device. BACKGROUND OF THE INVENTION Radiation emitting devices are generally known and used, for instance, as radiation therapy devices for the treatment of patients. A radiation therapy device usually includes a gantry which can be swiveled around a horizontal axis of rotation in the course of therapeutic treatment. A linear accelerator is typically located in the gantry for generating a high-energy radiation beam for therapy. This high-energy radiation beam can be an electron radiation or photon (x-ray) beam. During treatment, this radiation beam is typically trained on a zone of a patient lying in the isocenter of the gantry rotation. In order to provide a proper dose of radiation to a patient, a dose chamber may be used. A dose chamber accumulates dose deliveries from the radiation beam. When the dose of the radiation beam reaches a given number of counts, then the radiation beam may be turned off. The unit with which the dose chamber counts is a "monitor unit". Determining how many monitor units to set the dose chamber so that the patient receives a proper dose is typically termed as dosimetry. Once a dose for a patient is determined, this dose typically needs to be translated into monitor units. There may be several factors in translating the dose into monitor units, such as attenuation through the patient, accounting for curvature of patient surface, and accounting of scattered radiation inside the patient. In determining a dose to a patient, a hypothetical plane, often referred to as a calculation plane, a patient plane, or an isocentric plane, directly above the patient may be used in determining the distribution of radiation intensity over the patient. The unit of measurement for radiation intensity is fluence, which is the number of photons per area per time. This calculation plane over the patient may be divided into squares, herein referred to as calculation squares. In determining the fluence over the calculation plane, only one calculation square above the immediate target is typically calculated for the fluence due to the complication of calculating fluence over all of the squares in the calculation plane. A problem with calculating the fluence in only one calculation square is that the approximation for the remaining calculation squares may be inaccurate. In particular, in the field of intensity modulation, this type of approximation for fluence of the calculation plane may be wholly inadequate. Intensity modulation typically improves the ratio of radiation dose to critical structures versus dose to target. Improving this ratio is highly desirable since it is assumed that non-target areas are receiving radiation. A common goal is to maximize the radiation dose to a target, such as the tumor, while minimizing the radiation dose to healthy tissue. Another method for calculating the fluence over the calculation plane attempts to calculate the fluence over each calculation square by using ray tracings through a thin aperture. A potential problem with this conventional calculation is that the volume of ray tracing calculations are typically substantial and a substantial amount of processing power is required. Additionally, a radiation aperture, such as a collimator, typically has enough of a thickness to effect the calculations. Accordingly, calculating with the assumption that the aperture is very thin may result in errors. It would be desirable to have a method for calculating the fluence over the calculation plane which is fast, efficient, and accurate. The present invention addresses such a need. SUMMARY OF THE INVENTION The present invention relates to a fast and accurate method for calculating fluence of a calculation plane over a patient. According to an embodiment of the present invention, only a subset of the collimator leaves are analyzed for the fluence calculation, thus reducing the number of calculations required. Additionally, pre-integrated values of scatter strips, associated with each point of the calculation plane, may be referenced in a lookup table. The use of these pre-integrated values allows the avoidance of adding the fluence contribution of each square on the scattering plane. Rather, pre-calculated values of a subset of the scattering plane (scatter strip) may be referenced and combined, thus reducing the number of calculations required for a final scatter contribution to a point on the calculation plane. Further, the thickness of the collimator leaves is considered in the fluence calculation, thus providing a more accurate model for the scatter contributions of points on the scattering plane. According to an embodiment of the present invention, for each square (herein referred to as a point) on the calculation plane, a subset of collimator leaves which may affect fluence calculation is determined. In addition, scatter strips in the scattering plane associated with the analyzed point on the calculation plane is determined. For every line that can be traced from the calculation point to each scatter strip, it is determined which leaves intersect the traced line on the bottom of the leaf and which leaves intersect the traced line on the top of the leaf, thus taking into consideration the thickness of the leaves within the determined subset of the leaves. Pre-integrated values of the scatter strips may then be referenced in a lookup table to assist in the performance of the fluence calculation over each calculation point in the calculation plane. A method according to an embodiment of the present invention for calculating scatter radiation is presented. The method comprises providing a scattering plane, wherein the scattering plane is divided into a plurality of sections. A scatter strip associated with the scattering plane is determined, wherein the scatter strip contains at least two of the plurality of sections. A fluence value associated with the scatter strip is also determined. A system according to an embodiment of the present invention for calculating scatter radiation is also presented. The system comprises a processor configured to provide a scattering plane, wherein the scattering plane is divided into a plurality of sections. The processor is also configured to determine a scatter strip associated with the scattering plane, wherein the scatter strip contains at least two of the plurality of sections. The processor is further configured to determine a fluence value associated with the scatter strip. A memory is coupled with the processor, wherein the memory is configured to provide the processor with instructions. Another method according to an embodiment for calculating scatter radiation is also provided. The method comprises determining a scatter strip associated with a scattering plane; determining a subset of collimator leaves; and calculating fluence, wherein the fluence calculation is related to the scatter strip and the subset of collimator leaves. Another system according to an embodiment of the present invention for calculating scatter radiation is also presented. The system comprises a processor configured to determine a scatter strip associated with a scattering plane, determine a subset of collimator leaves and calculate fluence, wherein the fluence calculation is related to the scatter strip and the subset of collimator leaves. The system also includes a memory coupled to the processor, the memory being configured to provide the processor with instructions. In another aspect of the invention, a method according to an embodiment of the present invention for calculating scatter radiation is presented. The method comprises providing a collimator leaf position and determining a subset of collimator leaves. The method also calculates fluence, wherein the fluence calculation is related to the subset of collimator leaves. A system according to an embodiment of the present invention for calculating scatter radiation is also presented. The system comprises a memory configured to provide a collimator leaf position and a processor coupled to the memory. The processor is configured to determine a subset of collimator leaves, and is also configured to calculate fluence, wherein the fluence calculation is related to the subset of collimator leaves. Another method according to an embodiment of the present invention for calculating scatter radiation is presented. The method comprises determining whether a ray traced from a calculation point to a portion of a scattering plane intersects a first portion of a collimator leaf or a second portion of the collimator leaf. The method also calculates fluence, wherein the fluence calculation is related to a first intersection, if the ray intersects the first portion; and wherein the fluence calculation is related to a second intersection, if the ray intersects the second portion. Yet another system according to an embodiment of the present invention for calculating scatter radiation is presented. The system comprises a processor configured to determine whether a ray traced from a calculation point to a portion of a scattering plane intersects a first portion of a collimator leaf or a second portion of the collimator leaf; the processor also being configured to calculate fluence, wherein the fluence calculation is related to a first intersection, if the ray intersects the first portion; and wherein the fluence calculation is related to a second intersection, if the ray intersects the second portion. A memory is coupled with the processor, the memory being configured to provide the processor with instructions.
043943454	claims	1. An apparatus for detecting cracks in the jet pump beam of a jet pump arrangement of a nuclear reactor, wherein said arrangement includes a downwardly directed jet pump having a nozzle for receiving pressurized driving water, a riser pipe positioned adjacent said jet pump for supplying said driving water, a pipe elbow connecting the top of said riser pipe to the inlet of said nozzle, and a removable jet pump beam assembly, including a jet pump beam bearing on said elbow to hold said elbow in place, said apparatus comprising an ultrasonic signal production means, and communicating means for communicating said signals from said production means to and from a jet pump beam, said communicating means being straddlingly mountable over a jet pump beam, and said ultrasonic signals being directionally oriented toward the upper surface of said jet pump beam, whereby incipient cracks appearing on said surface are timely ultrasonically detectable. 2. The apparatus of claim 1, wherein said communicating means includes at least one ultrasonic transducer and a transducer carriage for holding and positioning said at least one ultrasonic transducer for communication with said jet pump beam. 3. The apparatus of claim 1, further comprising transfer means transferring ultrasonic signals from said communicating means to a visual display, whereby electric signals indicative of cracking in said jet pump beam are conveniently displayed through a viewer. 4. The apparatus of claim 2, wherein at least two oppositely disposed ultrasonic transducers are held by said transducer carriage and one of said transducers sends ultrasonic signals and the other receives a portion of said signals. 5. The apparatus of claim 2, wherein the number of ultrasonic transducers is four, each of them being a member of a pair of oppositely disposed ultrasonic transducers. 6. The apparatus of claim 5, wherein one of said members of a pair is effective for sending and the other of said members is effective for receiving ultrasonic signals. 7. The apparatus of claim 5, wherein each of said transducers is effective for sending and receiving ultrasonic signals, whereby information indicative of cracking in said jet pump beam is produced. 8. The apparatus of claim 1 comprising positioning means for remotely positioning said communicating means and to straddlingly mount such jet pump beam including connection means for mechanically connecting said communicating means to said positioning means. 9. The apparatus of claim 8, wherein said connection means permits relative motion between said positioning means and said communicating means, whereby the vertical axis of said communicating means is adjustable to define an acute angle between the longitudinal axis of said positioning means and the vertical axis of said communicating means. 10. The apparatus of claim 8, wherein said positioning means is an elongated extension pole. 11. The apparatus of claim 1, wherein said communicating means defines a cavity fitting over a jet pump beam assembly and includes oppositely disposed extensions effective for straddling the sides of said jet pump beam assembly. 12. The apparatus of claim 11, wherein said communicating means is constructed in part from a block of aluminum. 13. An apparatus for detecting cracks in the jet pump beam of a jet pump arrangement of a nuclear reactor, wherein said arrangement includes a downwardly directed jet pump having a nozzle for receiving pressurized driving water, a riser pipe positioned adjacent said jet pump for supplying said driving water, a pipe elbow connecting the top of said riser pipe to the inlet of said nozzle, and a removable jet pump beam assembly including a jet pump beam bearing on said elbow to hold said elbow in place, said apparatus comprising: a plurality of transducers and electric circuitry for communicating an ultrasonic signal between a signal generator and a jet pump beam, said transducers arranged in oppositely disposed pairs; a carriage for positioning said plurality of transducers toward and in the proximity of said jet pump beam, and defining a cavity on its underside and including lateral extensions for cooperatively engaging the superstructure of a jet pump beam assembly including the jet pump beam; and pole means including adjustable connecting means connected to the upper portion of said carriage and responsive to the orientation of the jet pump beam assembly and the longitudinal axis of said pole means, whereby said pole means is effective for the remote positioning of said carriage and transducers on said jet pump beam assembly. a plurality of ultrasonic transducers directed at the upper surface of a jet pump beam, a transducer carriage for holding and directing said plurality of transducers, a positioning pole for remotely mounting said transducer carriage on said jet pump beam, an adjustable joint means connecting said positioning pole to the upper portion of said transducer carriage; whereby said transducer carriage is mounted on a jet pump beam and in ultrasonic communication therewith. 14. The apparatus of claim 13, wherein said carriage includes wings for mounting said transducers. 15. The apparatus of claim 13, wherein said transducers are mounted in said lateral extensions of said carriage. 16. The apparatus of claim 13, wherein said electric circuitry includes switching means permitting the manual selection between individual and pairs of transducers for sending and receiving ultrasonic signals in communication with said jet pump beam. 17. The apparatus of claim 13, wherein said extensions rest on trunions of said jet pump beam assembly and said extensions each include a recessed portion for cooperatively receiving one of said trunions. 18. The apparatus of claim 13, wherein the transducers are disposed to communicate an ultrasonic signal toward the jet pump beam and from above the upper surface of the jet pump beam. 19. The apparatus of claim 13, wherein the communicated ultrasonic signal penetrates the sides of the jet pump beam and examines the upper surface thereof. 20. The apparatus of claim 13, wherein the transducers are downwardly oriented about 60.degree. from the horizontal. 21. The apparatus of claim 13, wherein the transducers are upwardly oriented 10.degree. from the horizontal and inwardly 65.degree. from a vertical plane through the central axis of the jet pump beam. 22. An apparatus for detecting cracks in the jet pump beams of a jet pump arrangement of a nuclear reactor, wherein said arrangement includes a downwardly directed jet pump having a nozzle for receiving pressurized driving water, a riser pipe positioned adjacent said jet pump for supplying said driving water, a pipe elbow connecting the top of said riser pipe to the inlet of said nozzle, and a removable jet pump beam assembly, including a jet pump beam bearing on said elbow to hold said elbow in place, said apparatus comprising: 23. The apparatus of claim 22, wherein said adjustable joint means includes a swivel joint and a restraining means for providing an aligning bias between the vertical axis of the transducer carriage and the longitudinal axis of the positioning pole. 24. The method of examining the upper surface of a jet pump beam for incipient cracks, including the steps of remotely positioning a plurality of ultrasonic transducers near the jet pump beam while installed in a nuclear reactor, sending an ultrasonic signal toward the upper surface of said jet pump beam, receiving a portion of said signal, and visually displaying the received portion of the signal. 25. The method of claim 24, wherein the same transducer is effective for sending the ultrasonic signal and receiving a portion thereof. 26. The method of claim 24 including the step of inserting the plurality of transducers in a carriage and lowering said carriage into the reactor vessel for straddlingly mounting said jet pump beam.
	abstract	In an indirect cycle nuclear reactor, a size of the reactor containment vessel is decreased by removing decay heat inside the reactor pressure vessel without using any active component to improve the economic feasibility. A main steam pipe communicating with a heat exchanger of the indirect cycle nuclear reactor is branched in a position upstream of a main steam isolation valve to connect the branched pipe to a heat exchanger in a pressure suppression pool through an isolation valve. A feed water pipe is also branched in a position upstream of an isolation valve to connect the branched pipe to the heat exchanger through the isolation valve. Decay heat is dissipated from the heat exchanger into the pressure suppression pool, and condensed water condensed by heat dissipation is returned to the heat exchanger to cool the inside of the pressure vessel. Heat in the pressure suppression pool is transferred from a condensing type heat exchanger to a heat dissipater outside a containment vessel to be dissipated to the outside of the containment vessel.
	abstract	The invention relates to means for protecting the environment from the consequences of fires complicated by a radiation factor. A composition for dust suppression and containment of radioactive products of combustion after a fire with a radiation factor has been extinguished comprises, as a surfactant, a mixture of an anionic, a non-ionic and an amphoteric surfactant, and has the following ratio of components: 3.0-7.0% by weight of an aqueous solution of polyvinyl alcohol (in terms of a mass fraction of dry product); 0.1-0.3% by weight of plasticizer; 11.0-29.0% by weight of surfactant; with water making up the remainder. The invention makes it possible to carry out dust suppression and containment of radioactive products of combustion which are formed on surfaces, including at elevated temperatures, after a fire has been extinguished.
	abstract	An apparatus and method of manufacture of an extreme ultraviolet reflective element includes: a substrate; a multilayer stack on the substrate, the multilayer stack includes a plurality of reflective layer pairs having a first reflective layer formed from silicon and a second reflective layer formed from niobium or niobium carbide for forming a Bragg reflector; and a capping layer on and over the multilayer stack for protecting the multilayer stack by reducing oxidation and mechanical erosion.
061119288	abstract	A top mount canopy seal mechanical clamp assembly 20 for repair of a leaking canopy seal weld 16 between a nuclear reactor head penetration nozzle 12 and a mating part 14 has an annular housing 24 with insert support halves 28 and 30 for surrounding the nozzle. A top plate 34 is urged toward the support halves and housing by Belleville washers mounted on cap screws 42 threaded in bores 44 of the housing. A flexible graphite seal annulus 22 is compressed by the clamping action against the canopy seal weld 16 to create a flexible graphite leak stopping seal at the weld.
	description	This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2007-156183, filed on Jun. 13, 2007; the entire content of which is incorporated herein by reference. The present invention relates to a startup range neutron monitoring system for monitoring the output of a nuclear reactor at the time of starting up the nuclear reactor. More particularly, the invention relates to an apparatus for inspecting and testing the operating characteristic of a startup range neutron monitoring system. FIG. 3 shows a conventional startup range neutron monitoring system. The startup range neutron monitoring system shown in FIG. 3 includes a startup range neutron monitor (SRNM) detector 1, an SRNM preamplifier 2, and a monitor 3. The SRNM detector 1 measures any neutron flux existing in the pressure vessel provided in a nuclear reactor. The SRNM preamplifier 2 receives the electric signal from the SRNM detector 1 and amplifies the signal. The monitor 3 receives the electric signal from the SRNM preamplifier 2 and acquires necessary information from the signals, thus monitoring the output power of the nuclear reactor. The monitor 3 includes a pulse measurement unit 4, a Campbell measurement unit 5, a signal sorting unit 13, an arithmetic processing unit 6, a display unit 14, a diagnosis unit 15, an output unit 7, and a voltage setting unit 9. The pulse measurement unit 4 has discrimination-voltage setting unit 8 that sets voltage of a specific value. The pulse measurement unit 4 counts any pulse of a voltage higher than the voltage set by the discrimination-voltage setting unit 8. The Campbell measurement unit 5 measures the mean square value of pulsation at a frequency band of the electric signals output from the SRNM preamplifier 2. The signal sorting unit 13 sorts the electric signals from the SRNM preamplifier 2, some to the pulse measurement unit 4 and the others to the Campbell measurement unit 5. The arithmetic processing unit 6 calculates the output power of the nuclear reactor from the information supplied from the pulse measurement unit 4 and Campbell measurement unit 5. The display unit 14 displays the result of the calculation performed in the arithmetic processing unit 6. The diagnosis unit 15 diagnoses the other components of the monitor 3, for abnormality, if any, developing in the other components. The output unit 7 outputs the result of the calculation performed in the arithmetic processing unit 6, to an external apparatus. The voltage-setting unit 9 sets a high voltage, which will be applied to the SRNM detector 1. The arithmetic processing unit 6 has a CPU, which generates instructions. The unit 6 gives these instructions to the other components and collects data items from the other components, through a bus 16. The arithmetic processing unit 6 has a function of testing the characteristics of the startup range neutron monitoring system. The unit 6 determines, when necessary, the discrimination characteristic and Plateau characteristic of the startup range neutron monitoring system. This function is implemented by using software, as one of the various functions of the startup range neutron monitoring system. A radiation sensor exhibits an output-current characteristic with respect to the voltage applied to it. The output-current characteristic is generally called Plateau characteristic. Further, the radiation sensor exhibits one neutron-pulse sensitivity when the radiation contains gamma rays, and another neutron-pulse sensitivity when the radiation contains no gamma rays. The sensitivity characteristic due to the gamma rays is known as discrimination characteristic. Startup range neutron monitoring systems of the type described above are disclosed in, for example, the following references: Japanese Patent Application Laid-Open Publication Nos. 04-29085, 08-201526 and 2002-111654, the entire contents of which are incorporated herein by reference. In the conventional startup range neutron monitoring system described above, the arithmetic processing unit 6 determines the discrimination characteristic and Plateau characteristic based on the software installed in the monitor system. This software cannot be separated from the other arithmetic operation functions. Hence, even if a part of the software is altered, the whole monitor system must be tested for characteristics and be verified for reliability and safety. If only those parts of the software, which describe the function of determining the discrimination characteristic and Plateau characteristic, fail to work, they may adversely influence all arithmetic operation functions the arithmetic processing unit performs, because they cannot be separated from the other arithmetic operation functions. The present invention has been made to solve the problem specified above. An object of the invention is to provide an apparatus for inspecting and testing the operating characteristic of a startup range neutron monitoring system, which apparatus can determine the discrimination characteristic and Plateau characteristic of the system, without imposing any adverse influence on the arithmetic operation functions the arithmetic processing unit performs. According to an aspect of the present invention, there is provided an apparatus for inspecting and testing a startup range neutron monitoring system, the apparatus comprising: a neutron-flux detector that detects neutron flux existing in a pressure vessel of a nuclear reactor; a preamplifier that amplifies an electric signal output from the neutron-flux detector; a pulse measurement unit that counts times when electric signal output from the preamplifier exceeds a discrimination voltage; a discrimination-voltage setting unit that applies the discrimination voltage to the pulse measurement unit; a voltage-setting unit that applies a voltage to the neutron-flux detector; an arithmetic processing unit that calculates an output power of the nuclear reactor based upon an output signal of the pulse measurement unit; an output unit that outputs data representing the output power of the nuclear reactor, calculated by the arithmetic processing unit; and an inspecting/testing unit that sets the discrimination voltage and the voltage to be applied by the voltage-setting unit. According to another aspect of the present invention, there is provided an apparatus for inspecting and testing a startup range neutron monitoring system, the apparatus comprising: a neutron-flux detector that detects neutron flux existing in a pressure vessel of a nuclear reactor; a preamplifier that amplifies an electric signal output from the neutron-flux detector; a pulse measurement unit that counts times when electric signal output from the preamplifier exceeds a discrimination voltage; a Campbell measurement unit that measures mean square value of pulsation of the electric signal output from the preamplifier; a discrimination-voltage setting unit that applies the discrimination voltage to the pulse measurement unit; a voltage-setting unit that applies a voltage to the neutron-flux detector; an arithmetic processing unit that calculates an output power of the nuclear reactor based upon an output signal of the pulse measurement unit and an output of the Campbell measurement unit; an output unit that outputs data representing the output power of the nuclear reactor, calculated by the arithmetic processing unit; and an inspecting/testing unit that sets the discrimination voltage and the voltage to be applied by the voltage-setting unit. Embodiments of a startup range neutron monitoring system inspecting and testing apparatus according to the present invention will be described with reference to the accompanying drawings. A first embodiment according to the present invention will be described with reference to FIG. 1. A startup range neutron monitoring system according to a first embodiment includes a startup range neutron monitor (SRNM) detector 1, an SRNM preamplifier 2, and a monitor 3. The SRNM detector 1 detects the neutron fluxes existing in the pressure vessel provided in a nuclear reactor. The SRNM preamplifier 2 receives electric signals from the SRNM detector 1 and amplifies the signals. The monitor 3 receives the electric signals from the SRNM preamplifier 2 and acquires necessary information from the signals, thus monitoring the output power of the nuclear reactor. The monitor 3 includes a pulse measurement unit 4, a Campbell measurement unit 5, an arithmetic processing unit 6, an output unit 7, a discrimination-voltage setting unit 8, a voltage setting unit 9, and an inspecting/testing unit 10. The pulse measurement unit 4 counts any pulse of a voltage higher than a certain discrimination voltage set by the discrimination-voltage setting unit 8. The Campbell measurement unit 5 measures the mean square value of pulsation at a frequency band of the electric signals output from the SRNM preamplifier 2. The arithmetic processing unit 6 calculates the output power of the nuclear reactor from an output signal supplied from the pulse measurement unit 4 and Campbell measurement unit 5. The output unit 7 outputs the result of the calculation performed by the unit 6, to an external apparatus. The voltage-setting unit 9 sets a high voltage, which is applied to the SRNM detector 1. The inspecting/testing unit 10 can cause the discrimination-voltage setting unit 8 and voltage setting unit 9 to variably set a discrimination voltage and high voltage. In the first embodiment configured as above, when the nuclear reactor is activated, it emits a neutron flux. The SRNM detector 1 determines the output power of the nuclear reactor, or the neutron flux in the reactor pressure vessel. The detection output of the SRNM detector 1 is supplied to the SRNM preamplifier 2. The SRNM preamplifier 2 restricts the frequency band of the electric signal it has received from the SRNM detector 1. The SRNM preamplifier 2 then amplifies the electric signal, rectifies the waveform of the signal and supplies the signal to the pulse measurement unit 4 and the Campbell measurement unit 5. When the nuclear reactor is activated, its output power is 10−9% to 10−4% of that of normal operation, and the output of the SRNM detector 1, i.e., the intensity of the neutron flux, is small in magnitude. In this case, the pulse measurement unit 4 compares the wave-height value of the electric signal supplied from the SRNM preamplifier 2 with the wave-height value set in the discrimination-voltage setting unit 8. The number at which the wave-height value of the electric signal becomes greater than the wave-height value set by the discrimination-voltage setting unit 8 is regarded as the number of pulses output from SRNM detector 1. The data representing the number of pulses is supplied to the arithmetic processing unit 6. The arithmetic processing unit 6 converts the number of pulses to an output power level of the nuclear reactor, thus evaluating the output power the reactor produces during a low-power operation of the nuclear reactor. The value of the output power thus evaluated is supplied to the output unit 7. While the nuclear reactor is operating, generating an output power of 10−5% to 10% of normal operation, the output of the SRNM detector 1, i.e., the intensity of the neutron flux, is large. In this case, the Campbell measurement unit 5 performs a Campbell measurement based on the so-called Campbell, determining the power of a component that fluctuates due to the output pulses that overlap one another in the output of the SRNM detector 1. Thus, the unit 5 calculates the square mean value of pulsation at a restricted frequency band of the electric signals output from the SRNM detector 1. The square means value thus calculated is supplied to the arithmetic processing unit 6. The arithmetic processing unit 6 converts the square mean value of the measured output pulses to the output power of the nuclear reactor and then evaluates the output power of the reactor. The result of the evaluation is supplied to the output unit 7. The arithmetic processing unit 6 keeps monitoring and evaluating the output the nuclear reactor produces, at least throughout the startup phase. A certain voltage set by the voltage setting unit 9 is applied to the SRNM detector 1 through the SRNM preamplifier 2 so as to detect the neutron flux. The function and operation mode of the inspecting/testing unit 10 will be described. To determine the discrimination characteristic, the inspecting/testing unit 10 causes the discrimination-voltage setting unit 8 to automatically set different voltages (equivalent to wave-height values) sequentially at regular time intervals, one being higher or lower than the previously set voltage by a specific value. The inspecting/testing unit 10 determines the wave-height distribution characteristic of the electric signal input to the monitor 3, from the output power of the nuclear reactor, which has been so evaluated as described above. To determine the Plateau characteristic, the inspecting/testing unit 10 causes the SRNM detector 1 to automatically set different high voltages sequentially at regular time intervals, one being higher or lower than the previously set voltage by a specific value. The inspecting/testing unit 10 determines the Plateau characteristic of the electric signal input to the monitor 3, from the output power of the nuclear reactor, which has been evaluated as described above. The inspecting/testing unit 10 is designed to arbitrarily set a voltage range of voltages, voltage intervals, and time intervals at which the voltages are applied, for the voltage the discrimination-voltage setting unit 8 sets or for the high voltage the voltage setting unit 9 sets. The inspecting/testing unit 10 has the function of storing parameters, the data being processed, and the evaluated output power of the nuclear reactor, all supplied from the arithmetic processing unit 6 and output unit 7, so that the parameters, data and output may be used for calculations. In the first embodiment, the inspecting/testing function of determining the discrimination characteristic and the Plateau characteristic is separately provided from the function of performing arithmetic operations, such as the arithmetic processing unit 6. Hence, the startup range neutron monitoring system can be tested and inspected, without imposing any adverse influence on the function of performing arithmetic operations. Thus, the monitoring system can be efficiently verified for reliability and safety. Moreover, abnormality, if any, generated in the inspecting/testing unit 10 imposes no adverse influences on the function of performing arithmetic operations performed in the startup range neutron monitoring system. The output power of the nuclear reactor can therefore be monitored and evaluated continuously and reliably. The inspecting/testing unit 10 need not operate as long as the output power of the nuclear reactor is sequentially monitored and evaluated. The unit 10 needs to operate only when the discrimination characteristic or Plateau characteristic of the electric signal input must be determined. Therefore, the inspecting/testing unit 10 may be shared by, usually six to ten startup range neutron monitors in most, used in the system. This helps to save cost and to reduce the probability of failure. In addition, the inspecting/testing unit 10 can apply, to the discrimination-voltage setting unit 8, a discrimination voltage optimal for measuring the intensity of any neutron flux correctly, based on the wave-height distribution that represents the relation between the preset discrimination voltage and the evaluated output power of the nuclear reactor. Since the inspecting/testing unit 10 has the function of saving the any data being processed, it can easily perform both verification and analysis. A second embodiment of a startup range neutron monitoring system inspecting and testing apparatus according to the present invention will be described with reference to FIG. 2. The components identical or similar to those of the first embodiment are designated by the same reference numbers and will not be described here. The startup range neutron monitoring system inspecting and testing apparatus according to the present invention differs in configuration from the apparatus according to the first embodiment, in that a transfer unit 11 and a personal computer 12 are provided in addition the other components. The transfer unit 11 is provided to transfer data to an external apparatus. The personal computer 12 is connected to the transfer unit 11. In the second embodiment thus configured, the personal computer 12 controls the inspecting/testing unit 10 in order to determine discrimination characteristic. When controlled by the personal computer 12, the unit 10 causes the discrimination-voltage setting unit 8 to automatically set different voltages (equivalent to wave-height values) sequentially at regular time intervals, one being higher or lower than the previously set voltage by a specific value. The personal computer 12 determines the wave-height distribution of the electric signal input to the monitor 3, from the output power of the nuclear reactor, which has been evaluated. Further, the personal computer 12 displays the wave-height distribution and saves the data representing this distribution. To determine the Plateau characteristic, the personal computer 12 controls the inspecting/testing unit 10. When controlled by the personal computer 12, the unit 10 causes the SRNM detector 1 to automatically set different voltages sequentially at regular time intervals, one being higher or lower than the previously set voltage by a specific value. The personal computer 12 determines the Plateau characteristic of the electric signal input to the monitor 3 from the output power of the nuclear reactor, which has been evaluated. Further, the personal computer 12 displays the Plateau characteristic and saves the data representing this characteristic. The transfer unit 11 converts the signals coming from the personal computer 12 to the signals that will be supplied to the inspecting/testing unit 10. Thus, the transfer unit 11 insulates the signals coming from the personal computer 12, preventing them from adversely influencing any components of the monitor 3. With the second embodiment, the software stored in the personal computer 12 can convert the discrimination characteristic and Plateau characteristic to graphic information. Moreover, the graphic information can be saved in the large-capacity memory such as a built-in hard disk. As a result, data can be acquired directly from the inspecting/testing unit 10, and no printers need to be connected to the monitor 3. Hence, the second embodiment can inspect and test the startup range neutron monitoring system more efficiently. Through the use of the personal computer 12, the monitor 3 need not have a graphics function. Using a monitor having no complex functions, the present monitoring system can work for a long time. Furthermore, the data being processed and the evaluated output power data of the nuclear reactor can be saved for a long time in the large-capacity memory such as a hard disk incorporated in the personal computer 12. This facilitates the verification and analysis of the evaluation trend of the reactor output power. The embodiments explained above are merely examples, and the present invention is not restricted thereto. It is, therefore, to be understood that, within the scope of the appended claims, the present invention can be practiced in a manner other than as specifically described herein.
	claims	1. A method of constructing an X-ray collimator assembly, comprising: providing a carrier having a planar top surface; providing an arcuate base disposed on said top surface of said carrier, said arcuate base comprising an arcuate bar section, said bar section comprising a radio-opaque material and having an arcuate inner edge, an arcuate outer edge, and a planar top surface spaced away from a planar bottom surface, each of said inner and outer edges including a plurality of parallel grooves formed therein extending from said top surface to said bottom surface; providing a plurality of radio-opaque collimator plates, each of said plates being generally rectangular and having first and second alignment tabs extending downward from a bottom edge thereof, disposing said plurality of collimator plates on said arcuate base so that each of said first alignment tabs fits into one of said grooves in said inner edge of said arcuate base, and each of said second alignment tabs fits into one of said grooves in said outer edge of said arcuate base, such that said collimator plates are positioned in a radial array with respect to said arcuate base, and said bottom edge of each collimator plate is in contact with said top surface of said arcuate base; aligning said plurality of collimator plates perpendicular to said top surface of said arcuate base; and securing said collimator plates to said arcuate base. 2. The method of constructing an X-ray collimator assembly of claim 1 further comprising: claim 1 providing at least one circumferentially extending wire, said wire being received in at least one notch formed in an upper edge of each of said collimator plates; and securing said wire to said plurality of collimator plates. 3. The method of constructing an X-ray collimator assembly of claim 1 wherein said collimator plates are secured to said arcuate base using an adhesive. claim 1 4. The method of constructing an X-ray collimator assembly of claim 2 wherein said wire is secured to said plurality of collimator plates using an adhesive. claim 2 5. The method of constructing an X-ray collimator assembly of claim 1 further comprising providing additional arcuate bar sections, wherein each bar section has first and second circumferential edges, and the adjoining circumferential edges of adjacent bar sections extend in a direction which is not parallel to a line defining a radius of said arcuate base. claim 1 6. The method of constructing an X-ray collimator assembly of claim 1 wherein said step of aligning said plurality of collimator plates perpendicular to said top surface of said arcuate base includes engaging said plurality of collimator plates with an alignment fixture. claim 1 7. An alignment fixture for assembling an X-ray collimator which includes a plurality of collimator plates disposed in a radial array on an arcuate base, said alignment fixture comprising: a body including a plurality of ribs disposed on a bottom surface thereof for engaging said plurality of collimator plates, said ribs being arranged in a pattern corresponding to the desired positioning of said collimator plates; and means for aligning said alignment fixture in a circumferential direction with respect to said arcuate base. 8. The alignment fixture of claim 7 further comprising means for positioning said alignment fixture in a vertical direction with respect to said arcuate base. claim 7 9. The alignment fixture of claim 8 wherein said means for positioning said alignment fixture in a vertical direction comprise: claim 8 a first end cap disposed at an inner edge of said alignment fixture, said first end cap having a bottom surface disposed a selected distance from said bottom surface of said body; and a second end cap disposed at an outer edge of said alignment fixture, said second end cap having a bottom surface disposed a selected distance from said bottom surface of said body. 10. The alignment fixture of claim 7 wherein said ribs are disposed in a plurality of spaced-apart rows. claim 7 11. The alignment fixture of claim 7 wherein at least one access slot is formed through said body. claim 7 12. The alignment fixture of claim 9 wherein said first end cap has a horizontal portion and vertical portion, said vertical portion including a radially facing internal surface having an alignment rib formed thereon. claim 9 13. An X-ray collimator assembly, comprising: a carrier having a planar top surface; an arcuate base disposed on said carrier, said arcuate base comprising at least one radio-opaque arcuate bar section, said bar section having an arcuate inner edge, an arcuate outer edge; and a planar top surface spaced away from a planar bottom surface, each of said inner and outer edges including a plurality of parallel grooves extending from said top surface to said bottom surface; and a plurality of radio-opaque collimator plates disposed on said base in a radial array such that a bottom edge of each of said collimator plates is in contact with said top surface of said base, wherein each of said collimator plates includes first and second alignment tabs protruding downward from a bottom edge thereof, said first alignment tab being received in one of said grooves in said inner edge of said base, and said second alignment tab being received in one of said grooves in said outer edge of said base. 14. The X-ray collimator assembly of claim 13 further comprising a circumferentially extending wire spanning said plurality of collimator plates, said wire being received in a notch formed in a upper edge of each of said collimator plates. claim 13 15. The X-ray collimator assembly of claim 13 wherein each bar section has first and second circumferential edges, and the adjoining circumferential edges of adjacent bar sections extend in a direction which is not parallel to a line defining a radius of said arcuate base. claim 13 16. The X-ray collimator assembly of claim 13 wherein said collimator plates are secured to said arcuate base using an adhesive. claim 13 17. The X-ray collimator assembly of claim 14 wherein said wire is secured to said plurality of collimator plates using an adhesive. claim 14
	abstract	The invention deals with a method for precipitating at least one solute in a reactor comprising: a) a step in which a first liquid phase comprising the solute and a second liquid phase comprising a solute precipitation reagent are brought into contact in co-current in a reactor, as a result of which an emulsion mix is obtained comprising precipitate particles in suspension, and a third liquid phase forming a dispersing phase for said emulsion mix; and b) a step in which the mix mentioned in step a) is fluidized by the third phase.
039986942	abstract	Several digital sensing devices are described for use in automated production systems. The first described is for use in the automatic operation of a reactor. This device employs a binant electrometer using a quartz fiber mounted at one end but free to vibrate at the other in an AC field. The fiber oscillates if a charge is placed upon it. An optical slit replaces the ordinary eyepiece reticule scale. With the quartz fiber adjusted so its image is in focus at the optical slit, photoelectric signals are obtained at null charge on the fiber. The quartz fiber is repeatedly charged and allowed to discharge by collecting ions from a source under measurement. Each photoelectric signal causes a digital time reading to be taken. The time readings are used to evaluate the current due to the collected charge. The photoelectric signals, by feedback, also operate the electrometer for continuous or intermittent-continuous operation. Basically, the system is a current digitizer. Application is made to reactor monitoring and control as well as to other types of production systems. Finally, other types of sensing devices are also described and their use in automated controlled processes is shown.
052979172	description	DETAILED DESCRIPTION An undergound site, in particular for deep storage of radioactive wastes, comprises a shaft 2 connecting the surface 1 to a network of galleries 3 and fitted with an elevator 4. In the vicinity of the entrance to the shaft 2 there is a control station 5. The control station includes a microwave generator 10 and a cabinet 12 for receiving signals. The cabinet is connected to one or more television screens 14 disposed in a control panel facing a workstation for monitoring purposes. The control station 5 is connected by a coaxial cable 16 to a first waveguide line 6 connecting the control station 5 to the entrance 2A to the shaft 2. The shaft 2 is fitted with a second waveguide line 7 that extends vertically and that is connected at its top end by means of a coaxial cable 18 to the first line 6. A third waveguide line 8 is installed in each gallery 3 and is connected via a respective coaxial cable 20 to the second line 7 in the vicinity of the entrance 3A to the gallery 3. The elevator 4 is fitted with an antenna 10, FIG. 2, disposed facing the second line 7. This connection is used for remotely controlling and tracking the elevator 4 from the control station 5. The elevator 4 also includes a waveguide 11 which is disposed in the example shown in the floor of the elevator. The waveguide 11 is connected to the antenna 10 of the elevator. A robot carriage 9, possibly guided by rails, includes two antennas. One of the antennas 12, is disposed at the front of the carriage 9 while the other antenna, 13, is at the rear of the carriage. The antennas 12 and 13 are used for transmission between the carriage 9 and the control station 5 for tracking the carriage and for remotely controlling it: via the first line 6 on the surface 1; via the first line 6, the second line 7 and the waveguide 11 in the elevator when the carriage 9 is loaded in the elevator 4 and while the elevator is being lowered down the shaft; and via the first line 6, the second line 7, and the third line 8 when the carriage 9 is unloaded from the elevator 4 and while it is being caused to move along a gallery 3. By having two antennas 12 and 13, it is possible to maintain continuous connection between the carriage and the control station when loading and moving the carriage 9 inside and outside the elevator. During the periods of discontinuity between the first line 6 and the waveguide 11 and between the waveguide 11 and the third guide 8, at least one of the antennas 12 or 13 is always facing a corresponding one of the waveguides. In the elevator 4 and the gallery 3, the waveguides may be disposed on the floor, on the ceiling, or on the side walls, with the antennas 12 and 13 of the carriage 9 being disposed accordingly. It is thus possible to track and control a plurality of carriages 9 simultaneously. The capacity for remote action can be further increased by multiplying the number of waveguides that are installed, and operating them in parallel. The method of the invention is preferably intended for use in deep storage of radioactive wastes. Under such circumstances, the carriage 9 is provided with means 9A for transporting radioactive loads and means 2b for discharging said loads in a gallery 3. Such means 9A and 2b are remotely controlled from the control station 5. The carriage also includes a camera 22 providing a display at television screen 14 of the control station for control purposes. The carriage may also include measurement means 24, in particular for measuring the temperature of nuclear loads which may increase because of their residual energy. The invention serves to eliminate any mechanical connection or any connection involving friction between the remote control stations and the robot carriage while providing remote control signal transmission therebetween.
	description	The present invention relates, in general, to methods for manufacturing lens assemblies for electron beam microcolumns and lens assemblies manufactured by the methods and, more particularly, to a method for manufacturing a lens assembly for an electron beam microcolumn and the lens assembly which has a high resolution and is elaborate and is used in electron beam lithography and in electron microscopes. Electron emission sources operating under basic principles of scanning tunneling microscopes (STM) and electron beam microcolumns based on electron optical elements having microstructures were introduced in 1980. In electron beam microcolumns, microelements are elaborately assembled to minimize optical numerical values, thus forming improved electron columns. Furthermore, due to the microstructures, arrangements of a plurality of electron beam microcolumns are used in serial or parallel multi-electron columns. The microcolumns are high-aspect-ratio micromechanical structures including microlenses and deflectors. Microlens assemblies constituting the microcolumns are multi-layered silicon chips (with membranes windows for lens electrodes), or silicon membranes which are spaced apart from each other by insulating layers each having a thickness of 100 to 150 μm. The microlens assemblies of the microcolumns include bores having diameters of a few to several hundred micrometers. For optimum performance, the roundness of the bores must be in the nanometer range and the alignment error between elements is required to be within a range of less than 1 μm. FIG. 1 is a sectional view of a conventional 1 kV microcolumn based on the well-known STM aligned field emission (SAFE), showing a source lens part 1 and an Einzel lens part 3. An electron emission source 5, attached to a positioner of a scanning tunneling microscope (STM) type, emits an electron beam 6 toward a sample plane 25. The electron beam 6 first passes through the source lens 1, which is composed of silicon microlenses and, for example, an axially provided extractor 7 having a diameter of 5 μm, an accelerating electrode 11 having a 100 μm diameter hole, and a limiting aperture 13 with a 2.5 μm diameter hole. Three microlenses are separated by two insulating spacers 9. The insulating spacers 9 are preferably formed of Pyrex, but may be made of an insulating material, such as SD-2 glass made by Hoya. The source lens 1 is mounted on an aluminum base 15 having a deflector 17 which is composed of eight electrodes. Thereafter, the electron beam 6 passes through the Einzel lens 3. The Einzel lens 3 includes silicon microlenses 19 and 23 having 100 to 200 μm diameters. The silicon microlenses 19 and 23 each have at a center thereof a silicon hole unit 21 having a 1 to 2 μm thickness and a 1 mm×1 mm size. Silicon layers are separated by insulating spacers 9 to be spaced from each other at regular intervals. Thereafter, the electron beam 6 enters onto the sample plane 25 to emit a secondary electron. A channeltron detector 27 detects the secondary electron. To assemble the lens assembly of the conventional microcolumn, the microlenses, made of silicon, and the insulating Pyrex spacers are sequentially layered one after another. Thereafter, the layered lenses and insulating materials are anodic-bonded together. The anodic-bonding is an electrochemical process of coupling glass to metal and semiconductors, as shown in FIGS. 2 and 3. At high-temperature (300-600° C.), sodium and oxygen ions of Na2O in the Pyrex or other glass are activated. When an electric field is formed by applying voltage, supplied from a voltage source 52, between a silicon microlens layer 53 and a glass insulating layer 55, sodium ions in the glass migrate from an interface in a direction shown by the arrow 63. Oxygen anions 61 move toward an induced positive charge 59 in a silicon anode to form chemical bonds. This process was previously used for single sided bonding only. However, recently, this process has been extended to multilayer bonding. After the first silicon-to-glass bond, another silicon chip or membrane may be bonded to the free surface of the glass by reversing the applied voltage, as shown in FIG. 3. In this case, a second silicon layer 57 is placed on the glass insulating layer 55, while an opposite voltage is applied by the voltage source 52. At this time, the induced positive charge 59 moves the sodium ions in a direction indicated by the arrow 63 such that the oxygen anions 61 form chemical bonds with the second silicon layer 57. To achieve satisfactory multilayer bonding, controlling the temperature, the applied voltage, the bonding time, and, particularly, the surface condition of the layers is very significant. However, the above-mentioned anodic bonding is executed after a plurality of microlenses and insulating layers are alternately layered. Therefore, while a layered product of the lens assembly of the microcolumn, which requires high accuracy in alignment, is heated to a high temperature and cooled, the layers may become misaligned, and thereby, the accuracy may be deteriorated. Furthermore, for the anodic bonding, an upper electrode is connected into a contact point type using a wire. Accordingly, an excessively long time is required to anodic-bond the lens assembly through the whole area using wire voltage. In addition to the above-mentioned assembling method, a lens assembly of a microcolumn using laser spot bonding was proposed in Korean Patent Application No. 2001-7003679 (Filed: 22 Mar. 2001), which will be described herein with reference to FIG. 4 and will be quoted in the description of the present invention. FIG. 4 illustrates a lens assembly 93 of a microcolumn spot bonded by a laser, in which three microlenses 81, 85 and 89 and two insulating layers 77 and 87 are alternately layered. In the lens assembly 93, the first insulating layer 77 and the second insulating layer 87 each have two extension parts which horizontally protrude outwards from opposite edges of each of the first insulating layer 77 and the second insulating layer 87. That is, the first insulating layer 77 and the second insulating layer 87 have ear parts 79 and 88, respectively. Because a microlens aperture of the microcolumn has a diameter of 2 μm or less, it is imperative that multiple layers of the microcolumn be precisely aligned. When a laser beam is emitted from a laser, the laser beam substantially passes through the first insulating layer 77 to heat a surface of the second microlens 85. Thus, the first insulating layer and the surface of the microlens are instantaneously welded together. In the same manner, due to the laser beam passing through parts 84 to be welded, a surface of the second insulating layer 87 is instantaneously welded. In other words, while silicon of the microlenses is melted at a high temperature and, thereafter, recrystallized, an adjacent portion of the insulating layer is heated. At approximately 400 to 500° C., the glass insulating layer begins to flow. At this time, a micro-weld of approximately 100 μm-500 μm in diameter is formed between two layers at the location of a laser spot weld or micro-weld 84. [Technical Problem] However, in the case of the lens assembly of the microcolumn spot-bonded by the laser through the above-mentioned method, the lens assembly is maintained only by the welding parts 84 welded by the laser. Therefore, the lens assembly is problematic in that difficulty in maintenance of the arrangement exists, thus reducing stability. Furthermore, the lens assembly is problematic in that each insulating layer must have the ear part 79, 88 to provide a separate portion for laser welding. In addition, it is disadvantageous in that an action of layering the lenses using the designated portions (ear parts) must be sequentially executed from the bottom. [Technical Solution] Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a method for manufacturing a lens assembly of a microcolumn and the lens assembly, in which a microlens assembly set is formed by anodic-bonding a microlens and an insulating layer together in a preliminary process, so that bonding between two layers is stable, thus reducing assembling time. Another object of the present invention is to provide a method for manufacturing a lens assembly of a microcolumn and the lens assembly, in which the lens assembly of the microcolumn is formed by layering a plurality of microlens assembly sets, while spot bonding is executed by a laser to easily assemble the microlens assembly sets and, thereafter, anodic bonding is executed to provide the firm bonding, thus enhancing the stability of the lens assembly. A further object of the present invention is to provide a method for manufacturing a lens assembly of a microcolumn and the lens assembly, which ensures a wire path connected to each microlens and a stable wire connection, and is regardless of the order of layering microlenses, thus increasing the productivity of the lens assembly process. [Advantageous Effects] The present invention provides a lens assembly of a microcolumn, in which a plurality of microlens assembly sets is first prepared and, thereafter, the microlens assembly sets are simply layered on top of another, thus reducing the time required for layering the microlens assembly sets. In the present invention, a microlens and an insulating layer constituting each microlens assembly set are bonded together while the microlens is rotated on the insulating layer at a predetermined angle. Furthermore, the microlens assembly sets also are layered on top of one another while being rotated on each other at predetermined angles. Thus, laser spot bonding for maintenance of the arrangement can be easily executed. In addition, a laser beam can be simply scanned in a desired direction. Moreover, because anodic bonding is executed using a flat plate electrode, the arrangement of the bonded layers is stably maintained and, as well, the time for the anodic bonding is reduced. Although the preferred embodiments of the present invention will be explained for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. In an aspect, the present invention provides a method for manufacturing a lens assembly of an electron beam microcolumn having a plurality of microlenses each provided with a hole at a central position thereof, and a plurality of insulating layers alternately interposed between the microlenses. The method includes: forming at least one first microlens assembly set by anodic-bonding an insulating layer and a microlens together so that a part of a surface of the insulating layer is not covered by the microlens; layering the first microlens assembly set on a second microlens or a second microlens assembly set while aligning the holes of the microlenses, so that the second microlens or the microlens of the second microlens assembly set is in contact with the insulating layer of the first microlens assembly set, while the part of the insulating layer of the first microlens assembly set, not covered with the first microlens, is in contact with the second microlens or the microlens of the second microlens assembly set; and scanning a laser beam to bond the part of the insulating layer of the first microlens assembly set, not covered with the first microlens, to the second microlens or the microlens of the second microlens assembly set by passing the laser beam through the part of the insulating layer of the first microlens assembly set, thus welding the first microlens assembly set to the second microlens or the microlens of the second microlens assembly set. In another aspect, the lens assembly of the present invention manufactured through the above-mentioned method, includes a first microlens assembly set formed by anodic-bonding a microlens and an insulating layer together, so that a plurality of microlens assembly sets is laser-spot-bonded together by the scanning of a laser beam in a predetermined direction while a welding spot is formed between the insulating layer of the first microlens assembly set and a microlens of a second microlens assembly set. [Mode for Invention] Hereinafter, a method for manufacturing a lens assembly of an electron beam microcolumn will be described. First, the method for manufacturing the lens assembly of the electron beam microcolumn according to the present invention is as follows in brief. A microlens assembly set is formed by anodic-bonding a microlens and an insulating layer together using a flat plate electrode. Such microlens assembly sets are layered on top of another. Spot bonding using a laser is executed to bond the layered microlens assembly sets together. Thereafter, anodic bonding is executed to more stably bond the layered microlens assembly sets bonded together by the spot bonding. As shown in FIGS. 5 and 7, according to the preferred embodiment, a first microlens assembly set set_1 is formed. In detail, a microlens 102 and an insulating layer 101, which each comprise planar plates of the same size having a rectangular or square shape, are layered on top of one another while the microlens 102 is rotated on the insulating layer 101 at a predetermined angle, for example, at an angle of 45° C. or less. Thereafter, the layered microlens 102 and insulating layer 101 are anodic-bonded together using a flat plate electrode, thus forming the first microlens assembly set set_1. The anodic bonding of the first microlens assembly set set_1 will be explained in detail. As shown in FIG. 7, when voltage is applied, induced positive charges of a silicon microlens layer, which is placed on an anode support 117, is chemical-bonded to oxygen anions of the glass insulating layer which are generated by a flat plate electrode 115 placed on the first microlens assembly set set_1. At this time, an upper anode flat plate 115 is maintained in a contact state to rapidly bond the microlens in a precise arrangement, and simultaneously, the flat plate electrode 117 having a wide surface area applies anode voltage. In the preferred embodiment of the present invention, the wide contact is possible by using the flat plate electrode 115. Furthermore, by applying voltage through a wide area, a processing time of the anodic bonding is significantly reduced, compared with conventional anodic bonding using a wire electrode. In addition, the anodic bonding can be stably executed. At this time, the microlens and the insulating layer are arranged while aligning circular holes 108 which are provided at central positions on the microlens and the insulating layer. The holes 108 are used as a path for scanning an electron beam in the lens assembly of the completed microcolumn. Typically, the arrangement of the holes of the lens assembly of the microcolumn means the alignment of the holes of microlenses. The holes of the insulating layers are larger than the holes of the microlenses. Therefore, the hole arrangement of the microlens assembly set is formed in a short time, unlike the hole arrangement of the microlenses. That is, the holes of the microlens and the holes of the insulating layers can be aligned with the naked eye. After the arrangement of the holes, the anodic bonding is directly executed. As such, the formation of the microlens assembly set is attained in a short time. The description of the rotating angle is as follows. Each layer is rotated on a neighboring layer around each hole 108 at a predetermined angle to expose a predetermined portion to the outside, thus forming a passage of a laser beam during a laser spot bonding which will be described later herein. In the case of a rotating angle of 45°, as shown in FIG. 6, because the rotating angle is relatively large, sufficiently wide portions, on which welding spots are formed for laser spot bonding, are formed on each layer. In the case of FIG. 6, it is preferable that both the layering of the microlens assembly sets and the laser spot bonding are sequentially executed in the predetermined direction. In the case of a small rotating angle, as shown in FIG. 5, portions exposed to form welding spots for the laser beam are smaller than those of the case of FIG. 6. Therefore, it may be difficult to arrange the microlens assembly sets to execute the laser spot bonding. However, the advantage of the case of FIG. 5 is that a greater number of microlens assembly sets can be layered on top of one another and integrally treated by the laser spot bonding. If there are few microlens assembly sets, the provided portions for the laser spot bonding will be sufficient. As such, after the microlens assembly sets are prepared, a desired number of microlens assembly sets are layered on top of one another to manufacture a lens assembly of a microcolumn which has a predetermined thickness. According to the embodiment of the present invention, referring to FIGS. 8 and 9, a second microlens assembly set set_2 is layered on the first microlens assembly set set_1. At this time, the first and second microlens assembly sets set_1 and set_2 are arranged while the first microlens assembly set set_1 is rotated on the second microlens assembly set set_2 at the same angle and in the same direction as microlens 102 and 104 are rotated on insulating layers 101 and 103, at an angle of 45° or less. Thereafter, laser spot bonding is executed to maintain the arrangement between the first and second microlens assembly sets set_1 and set_2. When laser beams are scanned in a direction of the arrow of FIG. 9 at predetermined positions that are designated by reference marks ‘{circle around (x)}’ of FIG. 8, the laser beams pass through the transparent insulating layer 103 of the second microlens assembly set set_2. Then, the laser beams reach the microlens 102 of the first microlens assembly set set_1. Due to the laser beams, laser spot bonding is executed at four spots. Due to the laser spot bonding, the arrangement of the first and second microlens assembly set set_1 and set_2 is stably maintained. Furthermore, layering of the embodiment of FIG. 6 is simpler (not shown). In detail, first and second microlens assembly sets set_1 and set_2 are layered on top of one another such that each insulating layer and each microlens are nearly aligned with each other, unlike the embodiment of FIG. 8. Then, the portions to be scanned by the laser beam are widely formed, so that the arrangement of the first and second microlens assembly sets set_1 and set_2 is easy. In other words, the first and second microlens assembly sets set_1 and set_2 are layered on top of anther such that the microlens of the first microlens assembly set set_1 and the microlens of the second microlens assembly set set_2 cross at an angle of 45°. Continuously, in the same manner, more microlens assembly sets can be easily layered. As shown in FIGS. 10 and 11, three microlens assembly sets set_1, set_2 and set_3 are layered on top of one another while each microlens assembly set is rotated on a neighboring microlens assembly set around holes 108 at a predetermined angle, in the same manner as that described for the arrangement of the two microlens assembly sets set_1 and set_2. Thereafter, when laser beams are scanned in the direction of the arrow of FIG. 11 at predetermined positions that are designated by reference marks ‘{circle around (x)}’ of FIG. 10, both an insulating layer 105 of the third microlens assembly set set_3 and a microlens 104 of the second microlens assembly set set_2 form four welding spots 112 during the laser spot bonding. As well, both an insulating layer 103 of the second microlens assembly set set_2 and a microlens 102 of the first microlens assembly set set_1 form other welding spots 112 at four positions. Thus, the three microlens assembly sets set_1, set_2 and set_3 are bonded together. Substantially, the number of welding spot is not limited to four, but may be more or less, as the occasion demands. That is, the number of the welding spots can be selected such that the arrangement of bonded microlens assembly sets is not scattered. A method of layering circular microlenses and circular insulating layers on top of one another is shown in FIG. 12, according to a modification of the embodiment. In this modification, a microlens assembly set is previously prepared in the same manner as that of the above-mentioned embodiments. However, the microlens assembly set has circular shape, so that it is unnecessary to rotate the microlens assembly set on another microlens assembly set for the arrangement. Merely, because the microlens assembly sets are layered while reducing in diameter from the bottom one to the top one in a pyramidal shape, exposed portions to receive laser beams are formed as shown in FIG. 12. Therefore, in this case, sizes of each circular microlens and each circular insulating layer are previously set according to the order of layering them in a step of manufacturing the microlens assembly sets. In the meantime, after the lens assembly is completed by laser-spot-bonding the first, second and third microlens assembly sets set_1, set_2 and set_3, the whole microlens assembly sets set_1, set_2 and set_3 may be anodic-bonded using electrodes placed on upper and lower surfaces of the lens assembly, thus enhancing bonding force. Furthermore, in the lens assembly, to apply a desired bonding force to the microlens assembly sets through laser spot bonding, it is necessary to layer the microlens assembly sets such that a microlens is placed at each of the uppermost and lowermost layers. To achieve the above-mentioned purpose, a microlens is placed at the lowermost layer in place of the microlens assembly set. If the uppermost layer is an insulating layer, a microlens is placed at the uppermost layer in place of the microlens assembly set. In other words, in the embodiment of FIGS. 8 and 9 or FIGS. 10 and 11, the microlens assembly set set_1 and/or set_3 is replaced with a new microlens to achieve the above-mentioned purpose. In the same manner, in the embodiments of FIGS. 6 and 12, the above-mentioned purpose can also be achieved. Additionally, the insulating layers and the microlenses are layered on top of one another while being rotated on each other in the same direction and at the same angle, such that the microlenses are placed at the uppermost and lowermost layers. Thereafter, the layered lens assembly is anodic-bonded. Alternatively, a separately manufactured microlens assembly set, in which an insulating layer is interposed between two microlenses, may be used to form the lens assembly of the microcolumn. That is, a microlens assembly set is not limited to being formed by bonding one microlens and one insulating layer together in a preliminary step. Unimportant portions in the hole arrangement may be arranged in advance to form the microlens assembly set by a single anodic bonding process. However, in the case that the hole arrangement is important, it is preferable that the insulating layer and the microlens are preliminarily anodic-bonded. In the preferred embodiments of the present invention, both the microlens 102, 104, 106, 302, 202, 204 and the insulating layer 101, 103, 105, 301, 201, 203 have holes 108. Each hole 108 has a circular shape for ease of maintenance of the arrangement of the lens assembly. In detail, although each layer is rotated on a neighboring layer, because the holes 108 have a circular shape, the arrangement of the layers is stably maintained. As such, each hole 108 has a circular shape to prevent a rotating axis of the layers from undesirably shaking while the layers are rotated. The above-mentioned hole is provided according to the preferred embodiment of the present invention. However, the hole is not limited to a circular shape, but may have a polygonal shape, such as a triangular or rectangular shape. In the case of an equilateral polygonal hole, a microlens is layered on an insulating layer such that a polygonal hole of the microlens and a polygonal hole of the insulating layer correspond in shape to each other. Of course, microlens assembly sets are layered on top of one another so that polygonal holes of the microlens assembly sets correspond in shape to each other. In other words, the microlens assembly sets are arranged such that those polygonal holes correspond in shape to each other from the uppermost microlens to the lowermost rotated microlens. Thus, a laser beam can pass through the polygonal holes of the layered microlens assembly sets in the same manner as through those of the microlens assembly sets having the circular holes. With reference to an embodiment of FIG. 13, there is a phase angle difference of 45° between a square hole 308 of a microlens 302 of a first microlens assembly set set_1 and a square hole 309 of a microlens 304 of a second microlens assembly set set_2. Thus, when the microlens 302 of the first microlens assembly set set_1 and an insulating layer 303 of the second microlens assembly set set_2 are aligned with each other, the square holes 308 and 309 correspond to each other to allow laser spot bonding. To layer a plurality of microlens assembly sets, a plurality of first and second microlens assembly sets set_1 and set_2 is previously prepared. Thereafter, first and second microlens assembly sets set_1 and set_2 are alternately layered, in which each first microlens assembly set set_1 is layered on each second microlens assembly set set_2. Furthermore, in the case that a hole also has a triangular or polygonal shape, a predetermined angle, at which microlens assembly sets are rotated on each other, is previously determined. According to the determined angle, holes with a predetermined phase angle difference are formed on microlenses of the microlens assembly sets. Then, the microlens assembly sets can be layered on top of another in the same manner as that of the above-mentioned layering method. However, preferably, the holes have the phase angle difference equal to that of the embodiment of FIG. 13. In the arrangement of the hole of each microlens, if it is necessary to arrange the microlenses to be rotated at different angles, holes with different phase angle differences are formed on the microlenses. In addition, in the case that the hole does not have the equilateral polygonal shape but has an irregular polygonal shape, such as a rectangular shape, holes with a phase angle difference of 45° are previously formed on microlenses of first and second microlens assembly sets, in the same manner as that of the embodiment of FIG. 13. Then, the microlens assembly sets can be layered on top of another in the same manner as that of the above-mentioned layering method. Moreover, in the embodiment of FIG. 12, because the microlens assembly sets are not rotated, the microlens assembly sets can be layered on top of one another regardless of the shape of the holes of the microlenses. In the embodiments of the present invention, although the bond of three or less microlens assembly sets set_1, set_2 and set_3 has been explained, more microlens assembly sets may be layered and bonded together in the same manner. In the method for manufacturing the microlens and the lens assembly according to the present invention, a conventional wire path connected to each lens may be formed on the portions of each microlens, on which the laser spot bonding is executed. Thus, a stable wire connection is ensured. In other words, the wiring is accomplished using a conventional deposited gold pad on the microlens' portions for the laser spot bonding. Therefore, the wiring connection is physically and electrically stable. The wire path also is easily ensured. A lens assembly according to the present invention is utilized for a microcolumn which is used in an electron beam lithography and in an electron microscope.
	claims	1. A method of measuring waveforms of beam currents, for receiving ion beam scanned in an X direction and measuring the waveforms of the beam currents flowing into a plurality of beam detectors by a beam monitor in which the plurality of beam detectors for receiving the ion beam and detecting the beam currents are arranged at constant intervals in the X direction, the method comprising:connecting the plurality of beam detectors to a single current measurement apparatus through respective switches;measuring the waveforms of the beam currents flowing into the current measurement apparatus by receiving the ion beam by the beam monitor, under a condition in which a plurality of switches skipped by “n” in the switches are simultaneously switched on, wherein the “n” is an integer of 0≦n≦(p−2) and satisfying Equation 1 or an equation mathematically equivalent to the Equation 1, the Equation 1 is Wb<{n·Wf+(n+1)Ws}, a width of a beam incident hole of each of the beam detectors in the X direction is Wf, a gap between the beam incident holes of adjacent beam detectors in the X direction is Ws, a beam width of the ion beam in the X direction is Wb, a total number of beam detectors is “p”;switching the switches, which are simultaneously switched on, under the condition; andrepeating the steps of measuring and switching. 2. A method of measuring waveforms of beam currents, for receiving ion beam scanned in an X direction and measuring the waveforms of the beam currents flowing into a plurality of beam detectors by a beam monitor in which the plurality of beam detectors for receiving the ion beam and detecting the beam currents are arranged at constant intervals in the X direction, the method comprising:connecting the plurality of beam detectors to a single current measurement apparatus through respective switches;repeatedly performing a first measuring process of receiving the ion beam by the beam monitor and measuring the waveforms of the beam currents flowing into the current measurement apparatus in a state in which two switches in the switches are simultaneously switched on while sequentially shifting the two switches, which are simultaneously switched on, inward one by one from two switches connected to the beam detectors located at both ends of the beam monitor in the X direction, wherein the first measuring process is performed in a range satisfying Equation 2 or an equation mathematically equivalent to the Equation 2, the Equation 2 is Wb<{n·Wf+(n+1)Ws}, a width of a beam incident hole of each of the beam detectors in the X direction is Wf, a gap between the beam incident holes of adjacent beam detectors in the X direction is Ws, a beam width of the ion beam in the X direction is Wb, a total number of beam detectors is “p”, and the number of beam detectors interposed between the two beam detectors connected to the two switches, which are simultaneously switched on, is “n”, and “n” is 0≦n≦(p−2); andperforming a second measurement process of receiving the ion beam by the beam monitor and measuring the waveforms of the beam currents flowing into the current measurement apparatus in a state in which the remaining switches are switched on one by one, after the Equation 2 or the equation mathematically equivalent thereto does not become satisfied. 3. A method of measuring waveforms of beam currents, for receiving ion beam scanned in an X direction and measuring the waveforms of the beam currents flowing into a plurality of beam detectors by a beam monitor in which the plurality of beam detectors for receiving the ion beam and detecting the beam currents are arranged at constant intervals in the X direction, the method comprising:alternately grouping the beam detectors to a first group and a second group;connecting the beam detectors of the first group to a first current measurement apparatus through respective switches, and connecting the beam detectors of the second group to a second current measurement apparatus through respective switches;measuring the waveforms of the beam currents flowing into the first and second current measurement apparatus by receiving the ion beam by the beam monitor, under a condition in which the plurality of switches skipped by “n” for the beam detectors of the first group are simultaneously switched on, and the plurality of switches skipped by “m” for the beam detectors of the second group are simultaneously switched on, wherein “n” is an integer of 0≦n≦(q−2) and satisfying Equation 3 or an equation mathematically equivalent to the Equation 3, “m” is an integer 0≦n≦(r−2) and satisfying Equation 4 or an equation mathematically equivalent to the Equation 4, Equation 3 is Wb<{(2n+1)Wf+2(n+1)Ws}, Equation 4 is Wb<{(2m+1)Wf+2(m+1)Ws}, a width of a beam incident hole of each of the beam detectors in the X direction is Wf, a gap between the beam incident holes of adjacent beam detectors in the X direction is Ws , a beam width of the ion beam in the X direction is Wb, and total numbers of beam detectors of the first group and the second group are “q” and “r”;switching the switches, which are simultaneously switched on, under the condition, with respect to the switches for the beam detectors of the first group and the switches for the beam detectors of the second group; andrepeating the steps of measuring and switching. 4. A apparatus of measuring waveforms of beam currents, for receiving ion beam scanned in an X direction and measuring the waveforms of the beam currents flowing into a plurality of beam detectors by a beam monitor in which the plurality of beam detectors for receiving the ion beam and detecting the beam currents are arranged at the same interval in the X direction, wherein the beam detectors are alternately grouped to a first group and a second group, the beam detectors of the first group are connected to a first current measurement apparatus through respective switches, and the beam detectors of the second group are connected to a second current measurement apparatus through respective switches, the apparatus comprising:a control apparatus for controlling repetition of:(a) a measuring process of receiving the ion beam by the beam monitor, measuring the waveforms of the beam currents flowing into the first and second current measurement apparatus, and storing measurement data in a memory, in a condition in which the plurality of switches skipped by “n” for the beam detectors of the first group are simultaneously switched on, and the plurality of switches skipped by “m” for the beam detectors of the second group are simultaneously switched on, wherein “n” is an integer of 0≦n≦(q−2) and satisfying Equation 7 or an equation mathematically equivalent to the Equation 7, “m” is an integer 0≦m≦(r−2) and satisfying Equation 8 or an equation which is mathematically equivalent to the Equation 8, the Equation 7 is Wb<{(2n+1)Wf+2(n+1)Ws}, the Equation 8 is Wb<{(2m+1)Wf+2(m+1)Ws}, a width of a beam incident hole of each of the beam detectors in the X direction is Wf, a gap between the beam incident holes of adjacent beam detectors in the X direction is Ws, a beam width of the ion beam in the X direction is Wb, and total numbers of beam detectors of the first group and the second group are “q” and “r”, and(b) a switching process of switching the switches simultaneously switched on, under the condition, with respect to the switches for the beam detectors of the first group and the switches for the beam detectors of the second group.
047773626	abstract	A device to measure the extremely fast electrical waveform generated when atomic or subatomic particles of an identical type strike an electronic circuit or device. The device comprises a trigger element which signals the incidence of a particle on the electronic device and a picosecond sampler which receives the trigger signal and the waveform generated by the electronic device. The sampler obtains a measurement of a discrete point on the generated waveform each time a particle passes through the trigger element to the electronic device. The sampling point on the waveform can be moved by various techniques so that the entire waveform may be measured by the sampler.
	abstract	An ultraviolet (UV) light-emitting diode (LED) device for curing fluids such as inks, coatings, and adhesives, for example. In one embodiment, LEDs are positioned on faces defined by an inverted recess in a base portion. The LEDs are configured such that the light beams emitted from the LEDs converge at a single area or point to provide a single, focused area or point of amplified power from the LEDs. An optical culmination device may be used to further intensify the power output from the LEDs. The optical culmination device provides enhanced power output from the UV LED device which makes the curing process more efficient than previous curing systems.
	abstract	A filter assembly for a computed tomographic imaging system includes first and second endplates at opposite ends of the filter assembly. Also provided is a first moveable subassembly that includes at least a first x-ray filter and which is configured to move along an axis perpendicular to the first endplate between the first the second endplates. A second moveable subassembly is also provided that includes at least a second x-ray filter. The second moveable subassembly is configured to move along an axis perpendicular to the second endplate between the first and second endplates. The first moveable subassembly and the second moveable subassembly are independently movable to provide at least a small bowtie x-ray filter, a large bowtie x-ray filter, a medium bowtie x-ray filter, a flat filter, and a closed position for a radiation source positioned in a fixed position relative to the filter assembly.
	description	1. Field of the Invention The invention relates to a method and a system for appraising the wear of axles of a robot arm of an industrial robot. Methods for appraising the wear of axles on industrial robots that are based on the mechanical measurement of the axial backlash and appraise axial wear on the basis of the values measured are generally known. The appraisal is generally performed by the operating or service personnel, who can, on the basis of values obtained in their experience with handling the robots, interpret the measured values in such a way that on the one hand the state of wear is established, on the other hand a statement can be made as to whether and which measures have to be performed on the axles of the robot. 2. Summary of the Invention It is accordingly an object of the invention to provide a method and a system for appraising the wear of axles of a robot arm which overcome the above-mentioned disadvantages of the prior art methods and devices of this general type, with which wear can be determined in the simplest possible way. Accordingly, the method according to the invention for determining the wear of axles of a robot arm of an industrial robot has the following method steps. A torque profile of at least one axles during at least one working cycle of the industrial robot is taken as a basis for an analysis. The torque profile is analyzed for portions of the torque profile that leave a previously fixed torque band, and current axial wear is determined by assessing the frequency and/or the curve profile of the portions of the torque profile. One advantage of the method according to the invention is that only a torque profile of the axle to be considered of the industrial robot is required in order to appraise axial wear. It is of secondary importance here whether the torque profile is measured at the time or is read out from an earlier measurement that has been stored in a data memory. The proposed method considers in particular a working cycle or number of working cycles of the industrial robot. In principle, any time segment during the movement sequence of the industrial robot may be chosen as the working cycle. It is particularly meaningful, however, for a movement sequence of the industrial robot which the latter keeps repeating to be chosen as the working cycle, so that all the movements, all the tasks and all the loads that are performed during a repeat cycle, from the beginning of the performance of a task to the end of the performance of the task, are included. Such a working cycle therefore covers all the tasks and loads of the industrial robot. The wear appraisal for the axles concerned of a robot arm is accordingly accurate. The analysis of the torque profile for portions of the torque profile that leave a previously fixed torque band and the assessment of the frequency and/or the curve profile of the portions of the torque profile take place according to the invention in an automated manner. This dispenses entirely with the previously necessary interpretation by operating or service employees specializing in this. In this way, the amount of data considered for the torque profile can be increased and the accuracy of the wear determination is enhanced. Altogether, the method according to the invention is consequently quicker and more accurate than those previously known. An advantageous development of the method according to the invention is characterized in that the ratio of a maximum torque value to an averaged torque value in a previously defined time period within the working cycle considered is used for the assessment of the axial wear. In the analysis of the torque profile, individual portions of the torque profile having a maximum torque are analyzed in particular, the rotational direction of the torque being immaterial. The portions of the torque profile are analyzed as to whether they have a maximum that goes beyond a previously set torque band, with the result that a torque loading exceeding the torque band has occurred. These maximum or extreme torque values are one of the factors responsible for increased wear of the axles and are accordingly taken into account in the assessment. The ratio mentioned at the beginning of maximum torque values to averaged values can be adapted more closely to a weighting factor, which is empirically determined. A further form of the method according to the invention is characterized in that at least one curve profile, in particular the slope of the curve at a time directly before and possibly after an extreme, taken from the latter up to at least the next-following point of inflection of the torque curve, of a portion of the torque profile is used for the assessment of the axial wear. For the assessment, therefore the steeply rising or steeply falling torque profiles in particular lead to a different basis for the assessment of the axial wear than for example shallow curve profiles. This has to be taken into account for example by different assessment factors, which are included in the assessment formula. The set object is also achieved by a system for determining the wear of axles of a robot arm of an industrial robot, with a data module, which contains the data of a torque profile of at least one axle during at least one working cycle of the industrial robot, with an analysis module, with which portions of the torque profile that leave a previously fixed torque band can be selected, and with an assessment module, by which the frequency and/or the curve profile of the portions of the torque profile can be interpreted as axial wear, a data exchange between the data module, the analysis module and the assessment module being made possible. The system for determining the wear of axles of a robot arm has three different functional modules. The functional module referred to as the data module contains the data of the torque profile to be considered or of the torque profiles to be considered in the event that a number of axles are being considered. In the analysis module, specific data provided by the data module can be selected in the way specified. In particular, those portions of the torque profile that leave a previously fixed torque band, that is to say have comparatively high torque values, are to be used for the instances of axial wear that are then to be appraised in the assessment module. In this case, the torque band is generally defined such that the limits of the band correspond to the permissible axial loading of the respective axle, for example coinciding with the limit-value loading specifications of a robot manufacturer or adopted with other empirically established limit values. In an advantageous basic variant, the system according to the invention for determining wear requires no additional measured value pickups or other measuring devices that would not already be on the robot. Consequently, the construction is comparatively simple and the wear appraisal can be carried out particularly quickly and comparatively accurately on account of the automation of the system concerning the handling of the data, the analysis and the assessment of the data. In the basic variant as described above, the required data are taken from a robot control. A development of the system according to the invention is characterized in that at least one of the modules is disposed in a robot control. This additionally simplifies the equipment required. This is so because the robot control is a customary part of a robot system, so that the implementation of the module or modules in the robot control results in a particularly compact system. However, it is also quite possible for individual modules or all the modules to be integrated in an evaluation device, in particular a measuring computer. This achieves the advantage that the system according to the invention becomes mobile and is suitable for successive use on a number of industrial robots. Furthermore, it is immaterial for the system according to the invention whether the torque profile can be read out from the robot control as direct or indirect values. When indirect values of the torque profile are read out from the robot control, the torque values that are current at the time or else any stored torque values can be called up as the torque values. The system according to the invention can in this case detect a torque value or torque values without further data preparation. Indirect values refer to those values that are either available as an unscaled voltage value of the robot control or are made available as an analog voltage signal or other signal and first have to be interpreted or converted as a torque value. For this purpose, an analog-digital converter or some other transfer module may be disposed upstream of the system according to the invention. In an advantageous form of the system according to the invention, the modules are in each case configured as computer program products. 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 a method and a system for appraising the wear of axles of a robot arm, 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. Referring now to the figures of the drawing in detail and first, particularly, to FIG. 1 thereof, there is shown an example of a possibility for a connection between a robot controller 10, which controls a robot 12, and a system for wear appraisal 14. An interface 16 between the robot controller 10 and the system 14 is bordered by a frame of dashed lines and contains a number of interface points, which are denoted by X5, X6, X7 and X8. The interface 16 is in this case provided for tapping two signals of a robot axle, it being quite conceivable for a large number of signals of different axles to be sampled or removed via the interface 16. In the chosen example, the side of the interface 16 on which the robot 12 and its controller 10 are located is represented by the representation of the symbols for the robot 12 and its robot controller 10. On this side of the interface 16, a first data line 18 connects the connection point X6 to a first data selection switch 20 of the robot controller 10. In a comparable way, the connection point X5 is connected by a second data line 22 to a second data selection switch 24. Via a switching element 26, the first data line 18 can be switched either to a signal A1 of an absolute position of the robot axle or a torque signal A2 of the robot axle. In the chosen example, the switching element 26 connects the data line 18 to the signal A1 of the absolute position of the robot axle. As a difference from this, the second data line 22 is connected to the torque signal A2 for the axle of the robot 12. The connection points X7 to X8, which are assigned to the signal point X5 and X6, respectively, are connected to ground. The chosen example therefore shows the wiring of the interface 16 to data from the robot controller 10 merely concerning one axle. It is quite conceivable for the data of a number of axles or all the axles of the robot 12 to be connected to a corresponding interface, and that further signals can also be measured by the interface 16. The advantage of the wiring is that an absolute position of the axle can be assigned to each torque value, so that the absolute position of the axle can also be taken into account in an analysis of the torque values, for example for differentiating whether a high torque value has occurred as a result of a high load on the robot arm or as a result of an extreme position of the robot axle. For test purposes, as to whether the signals made available can also be transmitted without any errors to the interface 16, a first data selection switch 20, 26 and a second data selection switch 24 are respectively connected to a testing device 30 by third data lines 28. The interface 16 is also connected to the system for wear appraisal 14, here the measuring computer 14, which connection is indicated by a first arrow 32. Furthermore, the measuring computer 14 is connected by a fourth data line 34 to a server 36 and the latter is connected by a fifth data line 38 to a PC 40. In the example represented, the measuring computer 14 has the task of interpreting the voltage values of the robot axle made available at the interface 16 in analog form as values for a torque profile. The values correspondingly converted by the measuring computer 14 for the torque profile are transmitted to the data processing device 40 through the fifth data line 38, through the server 36 and through the fourth data line 34. With the configuration represented in FIG. 1 the method according to the invention proceeds as follows. Data signals A1 that are to be assessed as the absolute position of the axle are made available by the robot controller 10 at the connection point X6 via the first data line 18. In a comparable way, values A2 for the torque just applied at the axle of the robot 12 are transmitted by the robot controller 10 via the second data line 22. Both values A1, A2 are sensed together with a timing signal by the measuring computer 14 and initially stored. The signal value A1 for the absolute position of the first axle of the robot 12 is not absolutely necessary for the method according to the invention, but simplifies the interpretation of the measured values A2 for the torque for an expedient form of the method according to the invention. It is just as unnecessary that the measuring computer 14 stores the data received. These data could also be further processed immediately, that is online, and transmitted to the PC 40 for the results to be displayed. However, here too it is expedient initially to store the measured values A1, A2 received for comparison purposes or for later comparative calculations, in order in this way also to have a copy of the original data available. In this way, the entire torque profile of a complete working cycle of the robot 12 is transmitted to the PC 40. The latter also initially stores the received torque profile of the robot axle. In the chosen example, the working cycle of the robot 12 is to contain, in the first step, the action of moving to and gripping a work piece. The second working step is defined as the action of raising the work piece and subsequently bringing it to an end position for the work piece. Finally, the third working step for the robot 12 consists in that the work piece is released and the robot arm is moved back into its starting position, so that the then completed working cycle can be repeated. The working cycle defined by the working steps is initially represented as a torque profile on the display device of the PC 40. Each portion of the torque profile that leaves a previously fixed torque band, that is to say permissible minimum and maximum values for the torque band of this axle, is defined as such and analyzed and subjected to an assessment in a subsequent method step. In a simple assessment step, the frequency with which the torque band is left within a specific time, predetermined by the working cycle, is used as a measure for the assessment. Another possibility is that the curve profile in an analyzed portion of the torque profile is used for the assessment. Altogether, the frequency and/or the curve profile of the portions of the torque profile, possibly additionally provided with an empirically determined factor, is or are used to appraise the current axial wear caused by such a working cycle. The simplest axial wear that can be determined by the method according to the invention is therefore axial wear per working cycle. With the knowledge of the previously completed working cycles of the robot 12 from the historical operating data of the robot 12, the current state of wear of the robot 12, or of the axle or axles concerned, is then also determined according to the invention. On the basis of this appraisal, a statement relating to the time period for which this robot axle can continue to be operated with the present defined working cycle is then also made possible. In addition, recommendations as to how the loading of the robot axle in a working cycle can be reduced, and with it also the wear, can be calculated. The position signal 11 is also used for this purpose. FIG. 2 shows the example of a data flow from the robot controller 10 of the robot 12 via a TCP/IP interface 42, through which the data can be fed from the robot controller 10 to a TCP/IP server with a network 44. The TCP/IP network 44 therefore connects an evaluation device 46 to the robot controller 10. This example shows that the evaluation device 46 can be connected from the robot control 10 according to the invention by the network 44. In the chosen example, this is a standardized TCP/IP network. However, it is equally conceivable for the interface 42 to be integrated into an Internet interface, so that the network 44 is formed by the Internet, and the evaluation device 46 can consequently be disposed anywhere in the world without local restriction. In the example, the system according to the invention for appraising the wear of axles of a robot arm of an industrial robot is realized with all its modules in the evaluation device 46. The torque profile is accordingly passed in the form of the data made available to the robot controller 10 from the interface 42 via the network 44 to the evaluation device 46. There, the data obtained are initially received by a data collector 48 and recorded and possibly stored as torque data or other data, in particular also in their time sequence. In this way, it is possible for a processing module 50 to interpret the data made available by the data collector 48 as torques for a torque comparison, for the maximum value detection and for the representation of the data as curves. In a further module, an assessment module 52, the curve, the curve profile or specific aspects of the curve are assessed as wear, so that, at the end of the method according to the invention, a statement can be made concerning the extent to which a specific axle of the robot 12 is or has been exposed to particular, abnormal loads or loads exceeding specific permissible loads and of such a nature that a corresponding state of wear exists. These data with other data from production, servicing or the robot movement program, as indicated in FIG. 2 in the assessment module 52, altogether improve the quality of the statement concerning the wear appraisal or the state of the individual axles. Alternatively, the evaluation device 46 in whole or one or more of the component parts such as the data collector 48, the processing module 50 or the assessment module 52 can be contained within the robot controller 10 itself which is optionally shown in FIG. 2. FIG. 3 shows the representation of torque profiles of three different robot axles. Here, a first torque profile 54, a second torque profile 56 and a third torque profile 58 are represented on a time axis 60, which indicates the variation over time of the torque signals in seconds. The y-axis of the graph is plotted as a torque axis 62, normalized to a maximum value that corresponds to a percentage loading of 100%, in such a way that the different axles of the robot 12 can also be comparatively represented in a graph. The different axles of the robot 12 are usually configured completely differently with respect to their type of construction, their drive, their performance, their transmission and so on, so that, although plotting in absolute values would be possible, it would be very confusing and in any event lead to an unfavorable representation. Also entered in the graphs is an upper limit value 64 and a lower limit value 66, the limit values 64, 66, each at approximately 30%, that is on the one hand plus 30% on the other hand minus 30%, describing a torque band, which is also referred to as a normal band. Therefore, no particular wear is to be expected at the robot axles if the torque profile remains within the band described. For two 56, 58 of the three torque profiles 54, 56, 58, this is also always the case. The first torque profile 54, however, has a first point 68 and a second point 70 at which the band is left. These points are of particular interest for the wear appraisal of axles. The assessment of current axial wear can therefore be performed on the basis of various criteria. One possibility is to count the number of those points, such as the points 68, 70, which exceed or leave the normal band. The occurring frequency of these events is in this case a measure of the wear of the axle concerned. A further possibility is to use the maximum torque occurring in relation to a current torque with the inclusion of axle-specific parameters, that is empirical values, as a measure for assessment. To be regarded in particular as the current torque in this case is a mean value of torque values, which may be regarded as an arithmetic mean value over the entire measuring time period of the working cycle, or a selective mean value, which is obtained from the loading at rest, that is loading of the robot axle in the basic state of the robot without a work task. A further possibility of assessment is to use the number of opposing maximum values when moving to a coordinate within a working cycle as a measure of assessment for wear appraisal. Yet another possibility is to consider a trend comparison of the values of the friction of a powered unit, that is in particular the motor, transmission and robot arm, within a movement from one coordinate within the working cycle of the robot to a second coordinate. However, still further values and data from the robot control, not described here in any more detail, also have to be included in the consideration for this. The individual values to be considered are, however, familiar to a person skilled in the art. An axle 200 of the robot 12 is generally indicated using reference numeral 200 in FIG. 1. This application claims the priority, under 35 U.S.C. § 119, of German patent application No. 10 2004 028 559.4, filed Jun. 15, 2004; the entire disclosure of the prior application is herewith incorporated by reference.
045487839	summary	BACKGROUND OF INVENTION 1. Field of Invention This invention relates to a tool for servicing a nuclear reactor pressure vessel and specifically a tool for permitting closure of a normally submersed fluid outlet in a reactor pressure vessel. During a refueling and maintenance outage of a nuclear boiling water reactor, there is a need to facilitate isolation and drainage of the recirculation suction piping without draining the reactor vessel. In the past, maintenance and repair activity in the recirculation suction piping has required that the reactor vessel be drained to a level below the elevation of the side mounted recirculation outlet nozzle. Because the outlet nozzle is generally located at an elevation below the radioactive core, the entire core must be off loaded before the cooling fluid can be drained. This procedure is undesirable because it is costly, requires handling and storage of radioactive materials and is time consuming. 2. Description of the Prior Art In the past, valves in the outlet piping have been provided adjacent the outlet nozzle of the recirculation loop. However, such valves are in need of periodic maintenance which cannot be performed when such a valve is in use. Moreover, such valves have also been found to be subject to fluid leakage if not maintained. Heretofore, it has not been believed practical to provide means for closing off the submersed inlet to the first valve due to the relatively high pressures, close side wall tolerances of a reactor vessel and irregularities in the nozzle throat thought to prevent secure sealing and blockage. SUMMARY OF THE INVENTION According to the invention, an apparatus is provided for blocking the outlet nozzle coupled to a cooling fluid recirculation loop in a nuclear reactor pressure vessel for isolating the recirculation loop from the reactor which comprises a frusto-conical plug which mates the generally beveled seat of the outlet nozzle, gasket means mounted to the face portion of the plug which is sufficiently compliant to seal the plug against the possibly irregular seat surface, means for positioning the plug in confronting relation to the nozzle and means for remotely urging the plug into position abutting the nozzle. In specific embodiments, the gasket means is a double O-ring, each of which is remotely inflatable, and the urging means is a hydraulic jack with an end pad for abutting to a structural surface within the reactor pressure vessel which faces the nozzle. The apparatus is collapsible into a compact space which permits it to be lowered into the cooling fluid and deployed in the relatively tightly spaced region adjacent the nozzle. Cables are provided for suspending the apparatus, and fluid filled control lines are coupled to the apparatus for gasket inflation and jack extension functions. The invention will be better understood by reference to the following detailed description taken in connection with the accompanying drawings.
	claims	1. A method of reducing the point spread function for high resolution particle beam profile measurement, comprising:providing a substrate including a high atomic number material;creating a plurality of slotted openings through said high atomic number material;creating said plurality of slotted openings using a technique which provides a knife edge around a periphery of said slotted openings, where the radius of said knife edge ranges from about 1 nm to about 5 nm; andfinishing the surface of said knife edge so that the surface roughness of said surface is less than about 5 nm RMS. 2. A method in accordance with claim 1, wherein said particle beam is an electron beam, wherein a width of at least one of said slotted openings ranges from about 0.25 μm to about 2.5 μm, and a length of at least one of said slotted openings ranges from about 0.75 μm to about 20 μm. 3. A method in accordance with claim 1 or claim 2, wherein an angle is formed between a sidewall of said slotted opening and a horizontal substrate beneath said sidewalls which is at least 75°. 4. A method in accordance with claim 3, wherein said sidewall angle is formed to range between about 80° and about 89°. 5. A method in accordance with claim 4, wherein said sidewall angle is formed to range between about 84° and about 89°. 6. A method in accordance with claim 1, wherein said knife edge surface is finished to an RMS finish between about 1 nm and about 3 nm. 7. A method in accordance with claim 1, wherein said particle beam is selected from the group consisting of an electron beam, an ion beam, a laser beam, a proton beam, a neutron beam, or an X-ray. 8. A metrology array used to measure a beam profile of a particle beam, said metrology array comprising:a substrate including a high atomic number material;a plurality of slotted openings through said high atomic number material;a knife edge around a periphery of said slotted openings, where the radius of said knife edge ranges from about 1 nm to about 5 nm; anda surface finish on said knife edge which is less than about 5 nm RMS. 9. A metrology array in accordance with claim 8, wherein a width of at least one of said slotted openings ranges from about 0.25 μm to about 2.5 μm, and a length of at least one of said slotted openings ranges from about 0.75 μm to about 20 μm. 10. A metrology array in accordance with claim 8 or claim 9, wherein an angle between a sidewall of said slotted opening and a horizontal substrate beneath said sidewall is less than about 75°. 11. A metrology array in accordance with claim 10, wherein said sidewall angle ranges between about 80° and about 89°. 12. A metrology array in accordance with claim 11, wherein said sidewall angle ranges between about 84° and about 89°. 13. A metrology array in accordance with claim 8, wherein said knife edge surface exhibits an RMS finish between about 1 nm and about 3 nm.
052873900	summary	A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever. BACKGROUND OF THE INVENTION The present invention relates to apparatus and methods for monitoring and controlling the operation of commercial nuclear power plants. Conventionally, commercial nuclear power plants have a central control room containing equipment by which the operator collects, detects, reads, compares, copies, computes, compiles, analyzes, confirms, monitors, and/or verifies many bits of information from multiple indicators and alarms. Conventionally, the major operational systems in the control room have been installed and operate somewhat independently. These include the monitoring function, by which the components and the various processes in the plant are monitored; control, by which the components and the processes are intentionally altered or adjusted, and protection, by which a threat to the safety of the plant is identified and corrective measures immediately taken. The result of such conventional control room arrangement and functionality can sometimes be information overload or stimulus overload on the operator. That is, the amount of information and the variety and complexity of the equipment available to the operator for taking action based on such extensive information, can exceed the operator's cognitive limits, resulting in errors. The most famous example of the inability of operators to assimilate and act correctly based on the tremendous volume of information stimuli in the control room, particularly during unexpected or unusual plant transients, is the accident that occurred in 1978 at the Three Mile Island nuclear power plant. Since that event, the industry has focused considerable attention to increasing plant operability through improving control room operator performance. A key aspect of that improvement process is the use of human engineering design principles. Advances in computer technology since 1978 have enabled nuclear engineers and control room designers to display more information, in a greater variety of ways, but this can be counterproductive, because part of the problem is the overload of information. Improving "user friendliness" while maintaining the quantity and type of information at the operator's disposal has posed a formidable engineering challenge. SUMMARY OF THE INVENTION It is thus an object of the present invention to provide apparatus and method for nuclear power plant control and monitoring operations having the characteristics of concise information processing and display, reliable architecture and hardware, and easily maintainable components, while eliminating operator information overload. This objective should be accomplished while achieving enhanced reliability, ease of operation, and overall cost effectiveness of the control room complex. The solution to the problem is accomplished with the present invention by providing a number of features which are novel both individually and as integrated together in a control complex. The complex includes six major systems: (1) the control center panels, (2) the data processing system (DPS), (3) the discrete indication and alarm system (DIAS), (4) the component control system consisting of the engineered safeguard function component controls (ESFC) and the process component controls (PCC), (5) the plant protection system (PPS), and (6) the power control system (PCS). These six systems collect data from the plant, efficiently present the required information to the operator, perform all automatic functions and provide for direct manual control of the plant components. The control complex in accordance with the invention provides a top-down integrated information display and alarm approach that supports rapid assessment of high level critical plant safety and power production functions; provides guidance to the operator regarding the location of information to further diagnose high level assessments; and significantly reduces the number of display devices relative to conventional nuclear control complexes. The complex also significantly reduces the amount of data the operator must process at any one time; significantly reduces the operational impact of display equipment failures; provides fixed locations for important information; and eliminates display system equipment used only for off normal plant conditions. It is known that the nuclear steam supply system can be kept in a safe, stable state by maintaining a limited set of critical safety functions. The present invention extends the concept of the critical plant safety functions to include critical plant power production functions, in essence integrating the two functions so that the information presentation to the operator supports all high level critical plant functions necessary for power production as well as safety. The information display hierarchy in accordance with the invention includes a "big board" integrated process status overview screen (IPSO) at the apex, which provides a single dedicated location for rapid assessment of key information indicative of critical plant power production and safety functions. Further detail on the sources and trends of normal or abnormal parameter changes are provided by the DIAS. Both IPSO and the DIAS provide direct access and guidance to additional system and component status information contained on a hierarchy of CRT display pages which are driven by the DPS. The IPSO continually displays spatially dedicated information that provides the status of the plant's critical safety and power production functions. This information is presented using a small number of easily understood symbolic representations that are the results of highly processed data. This relieves the operator of the burden of correlating large quantities of individual parameter data, systems or component status, and alarms to ascertain the plant functional conditions. The IPSO presents the operator with high level effects of lower level component problems. The IPSO relies primarily on parameter trend direction, e.g., higher, lower, an alarm symbol color and shape, to convey key information. These are supplemented by values for selected parameters. The IPSO presents consolidated, simplified information to the operator in relatively small quantities of easily recognized and understood information. Furthermore, the IPSO compensates for the disadvantage inherent in recent industry trends towards presenting all information serially on CRTs, by enabling the operator to obtain an overview, or "feel" of the plant condition. Display of plant level overview on a large-format dedicated display addresses two additional operational concerns. First, operator tasks often require detailed diagnostics in very limited process areas. However, maintaining concurrent awareness of plant-wide performance is also necessary. Rather than relying on multiple operators in the control room to monitor respective indicators and the like on spatially separated panels, the IPSO can be viewed from anywhere in the control room and thus provides an operator a continuous indication of plant performance regardless of the detailed nature of the task that may be requiring the majority of his attention. In the preferred implementation, IPSO supports the assessment of the power and safety critical functions by providing for each function, key process parameters that indicate the functional status. For each function, key success paths are selected with the status of that success path displayed. The IPSO clearly relates functions to physical things in the plant. The critical functions are applied to power production, normal post trip actions, and optimal functional recovery procedures. The second level in the display information hierarchy in accordance with the present invention is the presentation of plant alarms from the DIAS. A limited number of fixed, discrete tiles are used with three levels of alarm priorities. Dynamic alarm processing uses information about the plant state (e.g., reactor power, reactor trip, refueling, shut-down, etc.) and information about system and equipment status to eliminate unnecessary and redundant alarms that would otherwise contribute to operator information overload. The alarm system provides a supplementary level of easily understood cueing into further information in the discrete indicators, CRTs and controls. Alarms are based on validated data, so that the alarms identify real plant process problems, not instrumentation and control system failures. The alarm features include providing a detailed message through a window to the operator upon the acknowledgment of an alarm and the ability to group the alarms without losing the individual messages. The tiles can dynamically display different priorities to the operator. The acknowledgment sequence insures that all alarms are acknowledged while at the same time reducing the operator task loading by providing momentary tones, then continuous alarm, followed by reminder tones to insure that the alarms are not forgotten. The operator has the ability to stop temporarily alarm flashing to avoid visual overload, and resume the flashing to insure that the alarm will eventually be acknowledged. The discrete indicators in the DIAS provide the third level of display in the hierarchy of the present invention. The flat panel displays compress many signal sources into a limited set of read-outs for frequently monitored key plant data. Signal validation and automatic selection of sensors with the most accurate signal ranges are also employed to reduce the number of control panel indicators. Information read-outs are by touch-screen to enhance operator interaction and include numeric parameter values, a bar form of analog display, and a plot trend. Various multi-range indicators are available on one display with automatic sensor selection and range display. The automatic calculation of a valid process representation parameter value, with the availability of individual sensor readings at the same display, avoids the need for separate backup displays, or different displays for normal operation versus accident or post-accident operation. Moreover, in another preferred feature of the invention, the parameter verification automatically distinguishes failed or multiple failed sensors, while allowing continued operation and accident mitigation information to the operator even if the CRT display is not available. Furthermore, the normal display information can be correlated to a qualified sensor, such as that used for post-accident monitoring purposes. At the information display level associated with control of specific components, dynamic "soft" controllers are provided with component status and control signal information necessary for operator control of these components. For the ESFC system, this information includes status lamp, on-off controls, modulation controls, open-closed controls, and logic controls. For the PCCS, the information includes confirm load, set points, operating range, process values, and control signal outputs. In the fourth level of the information hierarchy, dynamic CRT display pages are complementary to all levels of spatially dedicated control and information and can be accessed from any CRT location in the control room, technical support center, or emergency operations facility. These displays are grouped into a three level hierarchy that includes general monitoring (level 1), plant component and systems control (level 2), and component/process diagnostics (level 3). Display implementation is driven by the DPS and duplicates and verifies all discrete alarm and indicator processing performed in the DIAS. In the preferred implementation of the invention, the indicator, alarm, and control functions for a given major functional system of the plant are grouped together in a single, modularized panel. The panel can be made with cutouts that are spatially dedicated to each of the displays for the indicators, alarms, controls, and CRT, independent of the major plant functional system. This permits delivery, installation, and preliminary testing of the panels before finalization of the plant specific logic and algorithms, which can be software modified late in the plant construction schedule. This modularization is achievable because the space required on the panel is essentially independent of the major plant functional system to which the plant is dedicated. Both the alarms and indicators can be easily modified in software. The number of indicators and alarm tiles that can be displayed to the operator are not significantly limited by the available area of the panel, so that standardization of panel size and cutout locations for the display windows is possible.
	abstract	A soft starter system for monitoring and diagnosing electrical power system characteristics includes a motor controller including solid state switches for controlling application of power to a motor. A control circuit controls operation of the solid state switches. The control circuit includes a programmed processor for commanding operation of the solid state switches and for measuring electrical power system characteristics relating to operation of the solid state switches. A memory is connected to the programmed processor storing parameters of the measured electrical power system characteristics. An external monitoring and diagnostic device includes a memory for storing parameters of the measured electrical power system characteristics and an interface for communication with the motor controller. A monitoring and diagnostic program is operatively implemented in the external monitoring and diagnostic device for transferring parameters of the measured electrical power system characteristics from the control circuit to the external monitoring and diagnostic device to monitor electrical power system characteristics in real time.
	description	This application is a divisional of U.S. Nonprovisional patent application Ser. No. 12/815,965, filed Jun. 15, 2010, and claims the priority of JP Application serial no. 2009-150084, dated Jun. 24, 2009, the contents of which are herein incorporated by reference in its entirety. The present invention pertains to an ion implantation device; in particular, it pertains to a system which corrects the temperature of a wafer in an ion implantation device. Ion implantation is implemented in various steps in the semiconductor manufacturing process; for example, it is implemented during formation of the diffusion region of the source/drain of a MOS transistor and in the formation of a polysilicon gate electrode. For example, Japanese Kokai Patent Application No. Hei 9[1997]-213258 discloses a large current ion implantation device which can increase the beam current without degrading the device characteristics. Furthermore, Japanese Kokai Patent Application No. 2009-87603 discloses an ion implantation device which is capable of controlling the amount of ion implantation very precisely even when the divergence angle or the beam gradient of the ion beam changes. Methods for processing wafers with an ion implantation device can be broadly classified as a batch method or a single-substrate method. FIG. 1(a) shows an overview of a batch-type ion implantation device; FIG. 1(b) shows an overview of a single-substrate type ion implantation device. As shown in FIG. 1(a), a batch-type ion implantation device has a disk 1 on which are formed pedestals that respectively retain multiple wafers W which have been transported thereto. Disk 1 is rotated at a high speed of, for example, 1200 rpm and disk 1 is scanned mechanically in the vertical direction V, according to the amount of an ion beam B with which it is to be irradiated, from a more or less perpendicular or at an oblique angle with respect to disk 1, thus performing ion implantation of the wafers W. This method is primarily employed with high-current implantation devices. In particular, with a high-current process the wafers W are exposed to extremely high temperature, so that the wafers W must be cooled or the resist pattern formed on the wafers will be deformed by the heat, causing degradation of or variation in the device characteristics. Therefore, disk 1 is connected to a heat exchanger 3 via pipes 2A, 2B; water that is heated by disk 1 passes through pipe 2A and is cooled by heat exchanger 3, and cooled water is supplied to disk 1 through pipe 2B to cool wafers W. In addition, a chiller capable of temperature adjustment can be used in place of a heat exchanger. Furthermore, as shown in FIG. 1(b), a single-substrate ion implantation device has a platen 4 that supports a wafer W. With respect to wafer W retained on platen 4, ion implantation of said wafer W is performed by a scanning beam B that scans in the horizontal direction H and by mechanically controlling the scan in the vertical direction V of scanning beam B and platen 4. This method primarily is employed with medium-current implantation devices. As with the aforementioned disk, platen 4 is connected to a heat exchanger 3 via pipes 2A, 2B, and the wafer retained on platen 4 is cooled by cooling water or a gas. For both the batch-type and the single-substrate type methods shown in FIGS. 1(a) and (b), the temperature (the heat exchange efficiency) of a wafer W is a critical factor in the functioning of the implantation device, but the ion implantation device is not provided with a system to continuously monitor the wafer temperature. With both the batch processing method and the single-substrate processing method the pedestal and the wafer W are tightly adhered, or the platen and the wafer W are tightly adhered, and a basic premise is that heat exchange takes place normally between them. However, cooling systems these become completely ineffective when the pedestal or platen deteriorates or when contaminants or particles adhere to the pedestal or platen, causing wafer contact defects and resulting in an insufficient heat exchange, and in some cases the occurrence of a large number of product defects may not be noticed for a long time. The present invention solves the aforementioned problem of the prior art, and its objective is to provide an ion implantation device with which the wafer temperature can be continuously monitored and corrected. The ion implantation device according to the present invention is a device that implants ions in a substrate and that has: an irradiation means that radiates ions; a retention means that retains at least one substrate; a detection means that detects, in a noncontact state, temperature information pertaining to the temperature of a substrate retained by the aforementioned retention means; a supply means that supplies a cooling medium to the aforementioned retention means to enable heat exchange for the substrate retained by the aforementioned retention means; and a control means that calculates the surface temperature of the substrate retained by the aforementioned retention means based on the temperature information detected by the aforementioned detection means and determines whether the calculated substrate surface temperature is within a permissible temperature range. Preferably, the aforementioned control means halts the radiation of ions by the aforementioned irradiation means when it is determined that the aforementioned calculated substrate surface temperature is outside of the aforementioned permissible temperature range. Preferably, the aforementioned permissible temperature range is a temperature range permitted with the ion implantation process, and the aforementioned control means records information related to the permissible temperature range in a memory. Preferably, the aforementioned control means controls the aforementioned supply means based on the aforementioned calculated substrate surface temperature. Preferably, the aforementioned control means controls at least one of: the temperature of the cooling medium or the amount of cooling medium supplied by the aforementioned supply means. Preferably, the aforementioned control means records in a memory a correlation between the temperature information for a dummy silicon substrate and the surface temperature thereof, and the aforementioned control means calculates the surface temperature of a process silicon substrate based on the temperature information for the process silicon substrate and the aforementioned relational expression. Preferably, the aforementioned detection means includes an infrared sensor and the aforementioned temperature information is a voltage generated by the aforementioned infrared sensor according to the heat radiated from the substrate. Preferably, the surface temperature of the dummy silicon substrate included in the aforementioned correlation is a value observed on a thermo label attached to the surface of a dummy silicon substrate. Preferably, the aforementioned retention means includes a rotatable disk that retains multiple substrates and is used for batch processing, and the aforementioned disk exchanges heat by means of a cooling medium supplied by the aforementioned supply means. Preferably, the aforementioned retention means includes a retention member that retains one substrate and is used for single-substrate processing, and the aforementioned retention member exchanges heat by means of a cooling medium supplied by the aforementioned supply means. The method of the present invention for correcting the temperature of a substrate in an ion implantation device includes steps wherein: a dummy silicon substrate on which is attached a thermo label for the purpose of monitoring the substrate surface temperature is retained by a retention member; the temperature information for the dummy silicon substrate is detected when ion implantation is performed on the dummy silicon substrate, and the substrate surface temperature is monitored based on the aforementioned thermo label; the relationship between the temperature information for the aforementioned dummy silicon substrate and the observed substrate surface temperature is recorded; next, the temperature information for an actual process silicon substrate is detected when ion implantation will be performed or is being performed on the process silicon substrate; the surface temperature of the process silicon substrate is calculated based on the detected temperature information and the aforementioned recorded relationship; and it is determined whether the calculated surface temperature is within a permissible temperature range. Preferably, the temperature correction method further includes a step wherein implantation of ions in the process silicon substrate is halted when the aforementioned calculated surface temperature is outside of the aforementioned permissible temperature range. Preferably, the temperature correction method further includes a step wherein an alert is provided when the aforementioned calculated surface temperature is outside of the aforementioned permissible temperature range. Preferably, the temperature correction method controls the temperature of the aforementioned retention member based on the aforementioned calculated surface temperature and corrects the surface temperature of the process silicon substrate such that the surface temperature of the process silicon substrate is within the permissible temperature range. Preferably, the temperature correction method further includes a step wherein the calculated surface temperature of the process silicon substrate is displayed on a display in real time. In the figures 10 represents an ion implantation device, 112 represents a disk, 114 represents a rotary shaft, 116 represents a positioning mark, 118 represents a cover, 118A represents a through-hole, 119 represents a chamber, 122 represents an infrared sensor, P represents a measurement region, V represents a vertical scan, W represents a wafer By means of the present invention an ion implantation device can be provided that monitors and corrects the temperature of the substrate in real time. Therefore, variation in the manufacture of semiconductor devices can be reduced and the yield rate can be improved. In the following an embodiment of the present invention will be explained in detail with reference to the figures. However, the shape and the scale of the components recorded in the figures have been emphasized to facilitate an understanding of the invention, and it should be noted that they do not necessarily match those of an actual product. FIG. 2 is a schematic block diagram showing the configuration of an ion implantation device according to an embodiment of the present invention. As shown in FIG. 2, an ion implantation device 10 according to the present embodiment is configured to include: an ion irradiation unit 100 that irradiates a semiconductor wafer with ions; a wafer retention unit 110 that retains a semiconductor wafer; a temperature information detection unit 120 that detects temperature information for a semiconductor wafer retained by the wafer retention unit; a cooling medium supply unit 130 that supplies to wafer retention unit 110 a cooling medium, such as cooling water or a cooling gas, that enables heat exchange for the semiconductor wafer retained by wafer retention unit 110; a display unit 140 that displays various information; an input unit 150 that receives input from an operator; a data communication unit 160 that transmits and receives data using an external electronic device, external server, etc., in a wired or wireless manner; a control unit 170 that controls each unit; and a memory 180 that stores programs for execution by control unit 170, as well as other information. As is publicly known, ion irradiation unit 100 includes an ion source that generates ions to be implanted, an acceleration unit that accelerates the ions generated by the ion source, a deflection plate that deflects the accelerated ions, etc. Wafer retention unit 110 includes a disk for batch processing on which are formed pedestals that respectively retain multiple wafers, or a platen for single-wafer use. The following explanation will discuss batch processing. As shown in FIG. 3(a), a disk 112 is circular in shape and comprises electroconductive material, and can retain multiple semiconductor wafers W arranged circumferentially. Each pedestal is provided with a mechanism for clamping the edge of a semiconductor wafer W. The rotary shaft 114 of disk 112 is rotated by a motor not shown in the figure, and disk 112 can be moved in the vertical direction V. In addition, a positioning mark 116 is formed on the surface of disk 112, and positioning mark 116 is detected by a position detection sensor not shown in the figure. Thus, control unit 170 can identify the rotational angle of the wafer and the pedestal positions. Preferably, temperature information detection unit 120 measures the temperature of the wafer W retained on disk 112 in a noncontact manner. In the present embodiment an infrared sensor (thermopile) is used to measure heat radiated from the wafer. Generally, it is difficult to measure the temperature of a silicon wafer with a radiation thermometer, the primary reason being that many of the radiation wavelengths of the temperature measurement region pass through silicon. Consequently, the wafer is in a semi-translucent state with respect to the radiation measurement device, which ends up measuring extraneous energy other than that of the object to be measured. Furthermore, factors other than transmissivity which affect the measurement of the wafer temperature include emissivity, the visual field of measurement, responsiveness, resolution, etc. If a specific factor evaluation is preformed however, since many factors are stable, it can be said to be a suitable measurement environment. With regard to the transmissivity of silicon, the temperature of the back side is stable, and if the total energy can be determined then it is possible to determine the wafer temperature. For these reasons, the present embodiment utilizes a thermopile module used with a typical radiation measurement device. As shown in FIG. 3(b), a U-shaped cover 118 is mounted such that it faces the edge portion of the rotating disk 112. Cover 118 forms a chamber 119 in which disk 112 can be arranged. A small, cylindrical through-hole 118A is formed in a portion of cover 118 and a thermopile 122 is arranged in said though-hole 118A. The environment which includes disk 112 within chamber 119 and cover 118 is preferably a vacuum. As shown in FIG. 3(a), thermopile 122 measures a measurement region P of each wafer W on the circumference, but because through-hole 118A has a small radius and the distance between thermopile 122 and the wafers W is small, the field of view of thermopile 122 is small, so that the effect due to the measurement field of view can be limited. When disk 112 rotates, thermopile 122 measures the heat energy radiated by the wafers W placed on disk 112 and produces an electromotive force corresponding to that heat energy. Thermopile 122 is arranged within cover 118 such that the surfaces of the wafers W are parallel to the surface of thermopile 122. Furthermore, with the present embodiment a thermo label is used to obtain the relationship between the thermopile's output voltage and the substrate surface temperature of a wafer W. A thermo label exhibits a change in color when it reaches a specific temperature, and the change in color that occurs when it reaches that specific temperature is irreversible. With a thermo label the temperature can be viewed or checked in step widths of from 1 to 5 degrees. The thermo label cannot be attached to the actual product (wafer W); instead, as will be explained later, it is attached to a dummy wafer and the dummy wafer is used to determine the relationship between the thermopile's output voltage and the substrate surface temperature. Cooling medium supply unit 130 supplies cooling water or cooling gas to disk 112; for example, cooling medium supply unit 130 supplies the cooling medium to disk 112 via a pipe and collects the heat-exchanged cooling medium from disk 112 via a pipe. Cooling medium supply unit 130 can include a temperature sensor that detects the temperature of the cooling medium, a supply valve for adjusting the amount of cooling medium supplied, and a heat exchanger that adjusts the temperature of the cooling medium. Cooling medium supply unit 130 can adjust the temperature of the cooling medium and the amount of cooling medium supplied in response to commands from control unit 170. Display unit 140 includes a display and, for example, displays the substrate surface temperature of a semiconductor wafer in real time and displays information such as the process conditions for execution of ion implantation, the permissible substrate temperature for execution of ion implantation, and the characteristics of the semiconductor device being manufactured by ion implantation. Input unit 150 receives various information from an operator and transmits this to control unit 170. The operator can, for example, specify the beginning and end of ion implantation, and cans search for and select process conditions stored in memory 180. Data communication unit 160 can exchange data with other semiconductor manufacturing equipment and computer devices, and can exchange data with a server which manages the manufacturing process. For example, the ion implantation device can obtain process conditions from the server, with said process conditions including information such as the type of ions to be implanted, the ion beam power, and the permissible range of substrate surface temperature for ion implantation. Control unit 170 can control ion irradiation unit 100 in response to the received process conditions. Control unit 170 includes a device such as a central processing unit, microcomputer or arithmetic processor, and controls the various units. Memory 180 stores information required for execution of ion implantation, programs executed by control unit 170, etc. This information is prepared in advance or is received from the outside via data communication unit 160. Memory 180 stores, for example, the process conditions (including ion implantation conditions and the permissible wafer temperature during ion implantation) on a device-by-device basis, including information such as the formula for calculating the substrate surface temperature based on the temperature information detected by temperature information detection unit 120. Next, the operation of the ion implantation device according to the present embodiment will be explained with reference to the flow charts in FIGS. 4A and 4B. First, a dummy wafer is placed on a pedestal of disk 112 (step S101). The number of dummy wafers used does not necessarily have to be more than one. In addition, a thermo label which changes color when a specific temperature is attained is attached to the surface of the mounted dummy wafer. When multiple dummy wafers are mounted a thermo label can be attached to each dummy wafer. Next, control unit 170 rotates disk 112 at a fixed rotational velocity and the dummy wafer is subjected to ion implantation under actual process conditions (step S102). Control unit 170 reads the process conditions from memory 180 and controls the irradiation for the purpose of ion implantation by controlling the type of ion for ion irradiation unit 100, the ion beam power, etc. Next, temperature information detection unit 120 detects the dummy wafer temperature information—that is, the voltage generated in response to the radiant heat—in two stages and transmits the information to control unit 170 (step S103). First, temperature information detection unit 120 detects the mean temperature information for all dummy wafers on disk 112 being rotated at high speed in chamber 119 while ion implantation is being performed on the dummy wafers. In other words, the temperature within the batch is detected by thermopile 122. Next, ion implantation is stopped or paused, the rotational velocity of disk 112 is reduced, and when it becomes possible to detect individual dummy wafer temperature information, the temperature information for each dummy wafer is detected. Thus the two sets of information—the mean temperature information within the batch and the individual temperature information for the dummy wafers—are respectively stored in memory 180. On the other hand, the operator observes the substrate surface temperature from the thermo label attached to the surface of the dummy wafer. This observation is performed when the disk is rotating at high speed—in other words, during detection of mean temperature information for the batch—and when the disk's rotational velocity is reduced and temperature information is detected for each dummy wafer in the batch. Sampling of the information using dummy wafers is performed under multiple process conditions, and the information for each situation, such as the ion beam power, thermopile output voltage and the substrate surface temperature, are extracted. FIG. 5 is a table showing the relationship between the beam power (W), the thermopile output voltage (V), and the thermo label's substrate surface temperature (° C.) for sampling under multiple process conditions. FIG. 6 is a graph showing the relationship between the beam power, thermopile output voltage, and substrate surface temperature from the table of FIG. 5; the left vertical axis is the thermopile output voltage (V), the right vertical axis is the thermo label substrate surface temperature, and the horizontal axis is the beam power. The line shape obtained shows how the thermopile output voltage and the substrate surface temperature increase as the beam power increases. The correlation shown in FIG. 6 is created based on the mean temperature information within the batch and the individual temperature information for the dummy wafers. The substrate surface temperature observed by means of the thermo label is input by the operator at input unit 150, and control unit 170 can determine the correlation of the line shape shown in FIG. 6 based on the sample information by means of a prepared program, storing this in memory 180 (step S105). Next, the dummy wafers are removed from the disk and multiple process wafers are mounted (step S106). Control unit 170 rotates disk 112 at a fixed rotational velocity and controls ion irradiation unit 100 to perform ion implantation for the process wafers under actual process conditions (step S107). Just as with the dummy wafers, temperature information detection unit 120 detects the temperature information for the process wafers in two stages, outputting the information to control unit 170. First, temperature information detection unit 120 detects the mean temperature information for all process wafers on disk 112 being rotated at high speed in chamber 119 while ion implantation is performed. In other words, the temperature within the batch is detected by thermopile 122. Next, ion implantation is stopped or paused, the rotational velocity of disk 112 is reduced, and when it becomes possible to detect the individual process wafer temperature information, the temperature information for each process wafer is detected. Control unit 170 calculates substrate surface temperature information for the process wafers from the 2 output voltages for the process wafers—that is, the mean thermopile output voltage and the individual thermopile output voltage—and from the correlation obtained when the dummy wafers were sampled (step S108). FIG. 7 is a graph showing the relationship between the thermopile output voltage for process wafers and the calculated substrate surface temperature. A resist pattern and the like are formed on the surface of an actual process wafer, so that emissivity differs from that of a dummy wafer; in other words, with identical process conditions the thermopile output voltage detected with a process wafer differs from the thermopile output voltage detected with a dummy wafer. Therefore, a correlation is calculated wherein the corresponding substrate surface temperature has been sampled for the detected thermopile output voltage of the process wafer. Control unit 170 determines whether the mean temperature for each process wafer—that is, the temperature within the batch—is within the permissible temperature range for the corresponding process and the semiconductor devices manufactured with said process (step S109). Ion implantation continues (step S110) when the substrate surface temperature is within the permissible range. However, if the substrate surface temperature is outside of the permissible temperature range control unit 170 stops the operation of ion irradiation unit 100, pauses ion implantation (step S111), and displays an alert on display unit 140 indicating that a wafer temperature error has occurred (step S112). This alert is either a ‘Warning’ from which ion implantation is restarted or an ‘Alarm’ which cancels ion implantation. The difference between a ‘Warning’ and an ‘Alarm’, for example, can be set with a given temperature (60° C.) serving as the boundary, with anything at or above that being an ‘Alarm’ and anything below that being a ‘Warning’. In addition, the alert can be audible. When the alert is a ‘Warning’ the operator restarts ion implantation (S114) and the process returns to step S109. On the other hand, when the alert is an ‘Alarm’, ion implantation is stopped (S116). In addition, when ion implantation continues (S110), a determination is made regarding whether the specified ion implantation has been completed (S115); if it has not been completed the process returns to step S109, and if it has been completed, ion implantation is stopped (S116). When the ion implantation process is complete (step S116) the rotation of disk 112 is slowed enough to allow individual wafers to be identified, and the surface temperature is measured separately for each wafer while disk 112 is rotating (step S117). Then a determination is made regarding whether the surface temperature for each process wafer is within the permissible temperature range (step S118). If the surface temperature is within the permissible temperature range a new process wafer is mounted on disk 112 and the process repeats from step S106. On the other hand, if the surface temperature is not within the permissible temperature range an alert indicating that a wafer temperature error has occurred is displayed on display unit 140 (step S119), the device is stopped, and monitoring is complete. Preferably, control unit 170 detects positioning mark 116 on disk 112 with a position detection sensor during the aforementioned step S118 to identify which process wafer has a temperature error. This can be identified based on the time at which positioning mark 116 is detected and the angle between positioning mark 116 and each pedestal. The wafer temperature can thus be monitored on a per-wafer basis even for a batch. Furthermore, it is preferable that display unit 140 display the substrate surface temperature on a per-wafer basis in real time, with the operator confirming the wafer temperature. On the other hand, for a batch, the mean temperature within the batch can be monitored and corrected. By means of the present embodiment, it is possible when ion implantation is performed to correct the wafer temperature to a permissible temperature, so that variation in the characteristics of elements and circuits formed on the wafer can be limited and devices can be manufactured within the design margin. In particular, with a high-current ion implantation process it is well known that the wafer temperature has a significant effect on the amplification characteristic of the transistor (the HFE parameter). This is thought to be caused by an insufficient exchange of heat, which causes the wafer temperature to rise and increases crystal defects, thus hindering diffusion. In other words, the wafer temperature during processing is a critical factor not only with respect to product defects, but also with respect to variability in product quality. FIG. 8 is a diagram showing the relationship between wafer temperature and the HFE characteristic; the vertical axis is the amplification characteristic and the horizontal axis is the wafer temperature at the time of ion implantation. In this example, when the wafer temperature exceeds 60° C. a large variation in the HFE parameter begins to occur. Conversely, if the wafer temperature is too low (for example, 45° C.) the yield rate decreases. As with the current embodiment, correcting the wafer temperature within a permissible temperature range during ion implantation makes it possible to limit variability in the amplification characteristic of the transistor. Next, a second embodiment of the present invention will be explained with reference to the flow chart in FIG. 9. In the aforementioned embodiment, ion implantation is automatically stopped when the substrate surface temperature of the process wafer is outside of a permissible temperature range; however, in the second embodiment the substrate surface temperature is controlled such that it is within a permissible temperature range. First, control unit 170 determines whether the substrate surface temperature is outside of a permissible temperature range (step S201) and controls cooling medium supply unit 130 to increase the supply of cooling medium by a fixed amount (step S202). Cooling of disk 112 thus is promoted and the process wafer heat exchange efficiency is improved (step S203). Control unit 170 monitors the substrate surface temperature of process wafers based on temperature information from temperature information detection unit 120, and determines whether said temperature is within a permissible temperature range (step S204). If it is outside of the permissible temperature range, the flow rate of the cooling medium is further increased in the aforementioned step S202, and the heat exchange efficiency can be further improved. By means of the second embodiment the substrate surface temperature of the process wafer is corrected within a permissible range, enabling ion implantation to be performed continuously. A decrease in throughput can thus be prevented. In the case of the second embodiment, it is preferable that the permissible temperature be set such that it includes more of a margin than that of the first embodiment. Next, a third embodiment of the present invention will be explained with reference to the flow chart in FIG. 10. The second embodiment illustrated an example in which the flow rate of the cooling medium was adjusted, but here the temperature of the cooling medium is controlled. Control unit 170 determines whether the substrate surface temperature is outside of the permissible temperature range (step S301) and controls cooling medium supply unit 130, lowering the temperature of the cooling medium. Preferably the temperature of the cooling medium is detected with cooling medium supply unit 130 (step S302); next, the temperature of the cooling medium is lowered by a fixed amount (step S303) by means of a heat exchanger with which cooling medium supply unit 130 is provided. Cooling of the disk is thus promoted, and the heat exchange efficiency of the process wafer is improved (step S304). Control unit 170 monitors the substrate surface temperature of process wafers based on temperature information from temperature information detection unit 120 and determines whether the substrate surface temperature is within the permissible temperature range (step S305). If it is outside of the permissible temperature range, the temperature of the cooling medium is lowered by means of the aforementioned step S303, further improving heat exchange efficiency. In addition, control can be performed by combining the third embodiment and the second embodiment. The aforementioned embodiments involved a batch process ion implantation device, but the present invention can also be applied to a single-wafer ion implantation device. For the batch type a thermopile was used as a noncontact temperature detection means, but if the platen which retains the wafer in the single-wafer type does not rotate, the temperature detection means can be mounted on the platen itself. Furthermore, in the aforementioned embodiments, the examples for the batch type illustrated control involving detection of mean temperature information for dummy wafers and process wafers within a batch, but for the single-wafer type a thermopile (sensor) can track temperature information even during ion implantation, so it is not necessary to average the temperature within chamber 119. Accordingly, for the single wafer type it is possible to monitor the substrate surface temperature for the process wafer during ion implantation and to pause or stop ion implantation, or to control the cooling temperature of the process wafer in response to the detected temperature. Furthermore, the wafer retention method for the batch type or single-wafer type can use an electrostatic chuck or another adhesion method in addition to a mechanical clamp. Furthermore, the thermopile used to measure the radiant heat of the wafer was arranged in a vacuum environment, but instead of being in a vacuum the measurement can be performed from the outside through a special glass. The aforementioned embodiments illustrated an example whereby a dummy wafer is used to sample the relationship between the output voltage of a thermopile and the substrate surface temperature but when the relationship there-between (for example, a correlation such as that shown in FIG. 6) is already known, sampling of a dummy wafer is not always required if said correlation is stored in memory 180. For both the batch type and the single-wafer type it is possible to determine the temperature during processing by creating monitoring timing. For example, the ion implantation process includes cycles of ion implantation start, ion implantation hold, ion implantation start, and ion implantation end, and it is possible to determine the wafer temperature within these cycles. In the above a preferred embodiment of the present invention was described, but the present invention is not limited to a specific embodiment. Various modifications and changes are possible without departing from the scope of the invention recorded in the claims.
060834544	claims	1. An apparatus for forming uniformly sized and shaped spheres comprising: a crucible for containing a supply of a low viscosity liquid material, a stimulation means for applying a minute periodic disturbance to the low viscosity liquid material in the crucible, a pressure regulator means for applying a pressure to the low viscosity liquid material to force the low viscosity liquid material through at least one orifice in the crucible as a steady laminar stream, the stream breaking up into a plurality substantially uniformly sized spheres upon existing the orifice, a charging means for applying a charge to the stream of low viscosity liquid material as the stream exits the orifice and breaks up into the spheres, a deflection means for deflecting the charged spheres as the charged spheres pass through an electric field generated by the deflection means, and an enclosed controlled temperature solidification environment which defines a first or gaseous environment and which contains at least one heat transfer medium, the enclosed controlled temperature solidification receiving the stream of low viscosity liquid material and the spheres, the heat transfer medium in the first or gaseous environment absorbs the heat of fusion, cooling and substantially solidifying the spheres, the enclosed controlled temperature solidification environment further including a second or liquid environment which absorbs the specific heat of the spheres and cushions the spheres before the spheres contact a bottom of the enclosed controlled temperature solidification environment. 2. The apparatus of claim 1, wherein the second or liquid environment contains a supply of a second heat transfer medium comprising a liquefied gas or halo-carbon. 3. The apparatus of claim 1, further including an observation system to monitor the stream of material as the stream breaks into the spheres to provide information on the diameter and shape of the spheres. 4. The apparatus of claim 1, wherein a bottom of the enclosed controlled temperature solidification environment comprises a funnel. 5. The apparatus of claim 1, wherein the orifice has a diameter ranging from about 12 to 1000 microns. 6. The apparatus of claim 1, wherein a distance defined between the crucible orifice and a bottom of the enclosed controlled temperature solidification environment ranges from about 1 to about 5 meters. 7. The apparatus of claim 1, wherein the stimulation means comprises a piezoelectric actuator. 8. The apparatus of claim 7, wherein the piezoelectric actuator comprises a stack of piezoelectric crystals mounted on a top portion of the crucible. 9. The apparatus of claim 1, wherein the stimulation means comprises an electromechanical transducer. 10. The apparatus of claim 1, wherein the stimulation means comprises a nozzle with a fixed aspect ratio defining the orifice in the crucible. 11. The apparatus of claim 1, wherein the deflection means comprises two spatially separate surfaces and a voltage source for supplying an electrical force field between the surfaces.
051587416	claims	1. A passive cooling system for liquid metal cooled nuclear fission reactors comprising the combination of: a liquid metal cooled nuclear reactor plant comprising a satellite assembly with a reactor vessel component containing a heat producing core of fissionable fuel submerged in a pool of liquid metal coolant and having at least one primary heat transferring liquid metal coolant loop circuit including a pump component housed in a vessel paired with a heat exchanger component housed in a vessel, said components being connected in series by means of top entry loop conduits extending down into the component Vessels to provide for circulating liquid metal coolant in series from the reactor component vessel through the pump component vessel and the heat exchanger component vessel then back to the actor component vessel; and a passive cooling system including a series of spaced apart side-by-side partitions in generally concentric arrangement surrounding each component of the reactor satellite assembly forming a sequence of adjoining fluid flow space enclosures for the circulation of cooling fluid intermediate the partitions and heat transfer cooling through said space enclosures, the respective space enclosures around each assembly component being connected in fluid communication with the corresponding space enclosures of the other assembly components, said passive cooling system including a containment vessel substantially surrounding each of the vessels housing an assembly component in spaced apart relation, a cylindrical baffle wall substantially encircling each containment vessel of the assembly in spaced apart relation, a guard vessel substantially surrounding each containment vessel and cylindrical baffle wall of the assembly in spaced apart relation, a concrete silo substantially surrounding the guard vessels of the assembly in spaced apart relation, a fluid flow heat transferring circuit for the passage of air coolant extending downward from the ambient atmosphere above the reactor vessel and concrete silo into the space intermediate the guard vessel and cylindrical baffle wall of each assembly component and around the bottom edge of the cylindrical baffle wall and upward through the space intermediate the cylindrical baffle wall and the containment vessel of each assembly component and returning back out into the ambient atmosphere above the reactor vessel and concrete silo. a liquid metal cooled nuclear reactor plant including a satellite assembly with a reactor component comprising a primary vessel containing a heat producing core of fissionable fuel submerged in a pool of liquid metal coolant and having at least one primary heat transferring liquid metal coolant top entry loop circuit including a pump component housed in a primary vessel paired with a heat exchanger component housed in a primary vessel, said components being connected in series with top entry loop conduits providing for circulating liquid metal coolant in series from the primary vessel of the reactor component through the primary vessel of the pump component and the primary vessel of the heat exchanger component then back to the vessel of the reactor component: and a passive cooling system including a series of spaced apart side-by-side partitions in generally concentric arrangement surrounding each component of the reactor satellite assembly forming a sequence of adjoining fluid flow space enclosures for the circulation of fluid intermediate the partitions and heat transfer cooling through said space enclosures, the respective space enclosures around each satellite assembly component being connected in series fluid communication with the corresponding space enclosures of the other assembly paired component vessels, said passive cooling system including a containment vessel substantially surrounding each of the primary vessels housing an assembly component in spaced apart arrangement, a cylindrical baffle wall substantially encircling each containment vessel of the satellite assembly in spaced apart relation, a guard vessel having a cylindrical support substantially surrounding each containment vessel and cylindrical baffle wall of the reactor satellite assembly in spaced apart relation said guard vessel supports resting on a reactor base, a concrete silo substantially surrounding the satellite assembly of reactor components, and a reactor shield deck bridging overhead substantially across the concrete silo and each primary vessel and its surrounding containment vessel closing off the upper ends of each of said primary and containment vessels, the cylindrical supports of the guard vessels providing support and reinforcement to the overhead reactor shield deck, a fluid flow heat transferring circuit for the passage of air coolant through a duct extending downward from the ambient atmosphere above the reactor primary vessel and surrounding concrete silo into the space intermediate the guard vessel and cylindrical baffle wall of each assembly component and around a bottom edge of the cylindrical baffle wall and upward through the space intermediate the cylindrical baffle wall and the containment vessel of each assembly component for cooling the surface of the containment vessels by absorbing heat and returning air upward through a duct and out into the ambient atmosphere above the reactor vessel and concrete silo carrying the absorbed heat from reactor components. a liquid metal cooled nuclear reactor plant including a satellite assembly with a reactor component comprising a primary vessel containing a heat producing core of fissionable fuel submerged in a pool of liquid metal coolant and having at least one primary heat transferring liquid metal coolant top entry loop circuit including a pump component housed within a primary vessel paired with a heat exchanger component housed within a primary vessel, said components being connected in series with top entry loop conduits extending down into the component primary vessels from above to provide for circulating liquid metal coolant in series from the primary vessel of the reactor component through the primary vessel of the pump component and the primary vessel of the heat exchanger component then back to the vessel of the reactor component a passive cooling system including a series of spaced apart side-by-side partitions in generally concentric arrangement surrounding the primary vessel of each component of the reactor satellite assembly forming a sequence of adjoining fluid flow space enclosures, said respective space enclosures around each satellite assembly component primary vessel being connected in series fluid communication with corresponding space enclosures of the other assembly paired component vessels, the passive cooling system including containment vessel substantially surrounding each of the primary vessels housing an assembly component in spaced apart arrangement, a cylindrical baffle wall substantially encircling each containment vessel of the satellite assembly in spaced apart relation extending down substantially the length of the containment vessels, a guard vessel having underlying supports substantially surrounding each containment vessel and cylindrical baffle wall of the reactor satellite assembly in spaced apart relation, said guard vessel supports resting on a reactor base, a concrete silo substantially surrounding the satellite assembly of reactor components in spaced apart relation, and a reactor shield deck bridging overhead across the satellite assembly of reactor components closing off the upper ends of each of said primary and containment vessel sealing the space therebetween from retaining a gas therein, a fluid flow heat transferring circuit for the passage of air coolant through a passive cooling system comprising at least one duct extending downward from opening to the ambient atmosphere above the reactor satellite assembly into the space intermediate the guard vessel and cylindrical baffle wall of each assembly component and around a bottom edge of the cylindrical baffle wall and upward through the space intermediate the cylindrical baffle wall and the containment vessel of each assembly component and out into the atmosphere through at least one duct extending upward from said space intermediate the cylindrical baffle wall and containment vessel of each assembly component and opening into the atmosphere for cooling the surface of the containment vessels; and a secondary passive cooling system including at least one opening to the atmosphere between the concrete silo and the reactor satellite assembly and openings in the guard vessel supports whereby heating of the guard vessel will induce a cooling and heat carrying flow of air from the atmosphere into the concrete silo space surrounding the guard vessels through the opening and over the guard vessels and back out into the atmosphere through at least one air return opening to the atmosphere. 2. The passive cooling system for liquid metal cooled nuclear fission reactors of claim 1, wherein the satellite assembly comprising the reactor vessel component and the primary heat transferring liquid metal coolant loop pump and heat exchanger components are located substantially buried below ground level. 3. The passive cooling system for liquid metal cooled nuclear fission reactors of claim 1, wherein the liquid metal cooled nuclear reactor plant comprising a satellite assembly including a reactor component connected in fluid communication by means of top entry conduits in multiple primary heat transferring liquid metal coolant loop circuits each having a paired pump component housed in a vessel and heat exchanger component housed in a vessel. 4. The passive cooling system for liquid metal cooled nuclear fission reactors of claim 1, wherein the reactor vessel, containment vessel, cylindrical baffle and guard vessel are each circular in cross-section of respectively increasing diameter and concentrically arranged with their side walls providing spaced apart portions forming annular intermediate areas therebetween. 5. A passive cooling system for liquid metal cooled, top entry loop nuclear fission reactors comprising the combination of: 6. The passive cooling system for liquid metal cooled nuclear fission reactors of claim 5, wherein the satellite assembly comprising the reactor vessel component, and the primary heat transferring liquid metal coolant loop pump and heat exchanger components and housing vessels therefor are located substantially buried below ground level. 7. The passive cooling system for liquid metal cooled nuclear fission reactors of claim 5, wherein the primary vessel, the containment vessel, the cylindrical baffle and the guard vessel of each component of the satellite assembly ar circular in cross-section, sequentially of respectively increasing diameter and concentrically arranged with their side walls providing spaced apart partitions forming a series of annular intermediate areas therebetween. 8. The passive cooling system for liquid metal cooled nuclear fission reactors of claim 5, wherein the cylindrical supports of the guard vessels are resting upon a floor comprising the base for the reactor plant satellite assembly. 9. The passive cooling system for liquid metal cooled nuclear fission reactors of claim 5, wherein the cylindrical supports of the guard vessels are provided with openings in each cylinder below the bottom of the guard vessels to enable cooling fluid to flow through the cylinder supports across the bottom of the guard vessel. 10. A passive cooling system for liquid metal cooled, top entry loop nuclear fission reactors comprising the combination of:
06295332&	description	DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in the FIGURE, the novel method 10 of improving x-ray lithography in the sub 100 nm range to create high quality semiconductor devices comprises the steps of providing for the use and development horizontal beams from a synchrotron or point source of x-ray beams 11. The preparation of submicrometer, transverse horizontal and vertical stepper stages and frames 12 is next. This step develops stages and frames comprised of light weight, honeycomb structure constructed of composite materials. Also, used in this step includes using air or gaseous bearings, vacuum clamping and mating surfaces, active weight compensation; linear actuators and a fine alignment flexure stage for a all six degrees of freedom. The third step provides a stepper base frame for the proper housing and mating of the x-ray beam 13. Techniques and equipment used in this step include beam alignment, vibration insulation used when connecting to a stationary x-ray synchrotron or point source. The forth step is minimizing the effects of temperature and airflow by means of an environmental chamber 14. This unit is designed to control the temperature and humidity and, at the same time, minimize particle and molecular contamination. The fifth step is designed to transport, handle and prealign wafers and other similar items for tight process control 15. This step is required to produce high quality semiconductors. All critical wafer and mask handling and treating processes should be operated in a cluster like environment--the processes include coating, pre-baking, aligning and exposure, post baking and quality control. The sixth step is improving the control and sensing of positional accuracy through the use of differential variable reluctance transducers 16. The differential variable reluctance transducer provide a positional feedback for the six degrees of freedom alignment stage. The next step controls the continuous gap and all six degrees of freedom of the wafer being treated with a multiple variable stage control 17. The step uses an advanced multiple variable stage control that is designed as a cross coupled gantry in order to optimize the precise alignment of the device levels. Alignment systems are then incorporated using unambiguous targets in order to align one level to the next level 18. The alignment systems consist of multiple bright fields optical microscopes, normal to the plane of imaging to provide axis x, y and z, magnification and rotational data in order to align one level with the next level. Also, an additional imaging broad band interferometer alignment system is used to provide precise alignment of wafer levels and gap control during the x-ray exposure. The following step in the process is to use beam transport shaping or shaping devices to include x-ray point sources 19. This step uses steppers to interface an x-ray source mechanical interface and a vacuum or helium tight quick coupling. A beam transport chamber is used, either a snout design small unit or a large design integrated into the stepper base frame or as a full chamber designed for helium and or other low attenuation at atmosphere or lower pressure. The next step 20 uses an in line collimator or concentrator for collimating or concentrating the x-ray beams, along with the use of shutter and x-ray pulse controls. Mask magnification control is provided to allow for a mix and match with optical lithography levels and techniques. Finally, in the last step 21, the process images the pattern at the precise moment for optimum effectiveness. The whole process is repeated again to image the entire wafer or substrate with the mask pattern. The wafer or substrate is removed as in step number 15 and then repeated again and again until all wafers or substrates are imaged. While we have described our invention in connection with specific embodiments thereof, it is clearly to be understood that this is done only by way of example and not as a limitation to the scope of our invention as set forth in the objects thereof and in the appended claims.
045377413	description	DETAILED DESCRIPTION OF THE INVENTION This invention is directed to a funnel structure adapted to be arranged at the outer open end of a length of cladding which will ultimately contain fuel pellets as a nuclear fuel pin. It is utilized on a fuel pin subassembly which facilitates loading of fuel pellets within the cladding. A funnel is held in place by a length of shrink tubing that encircles both the funnel and cladding outer surfaces. The tubing serves as a protective cover about the encircled portion of the cladding outer surfaces. It also facilitates axial removal of the funnel after loading of the cladding. A completed fuel pin subassembly is shown in FIG. 2. The subassembly consists of a length of cladding 10 having a welded end cap 11, shown as the bottom end of the fuel pin, and internal non-contaminated fuel pin hardware (not shown) adjacent the welded end cap 11. A fuel loading funnel 12 is mounted to the remaining open end of the fuel cladding 10. As shown in FIG. 2, the funnel 12 has an enlarged outer open end that leads to a reduced diameter neck. A conical transition section connects the open end of funnel 12 to its neck. The smaller neck is at least partially inserted into the open axial end of the cladding as a coaxial extension of it. The fit between the funnel neck and the cladding interior should be reasonably close, and the thickness of the funnel neck should be minimal. The funnel 12 is held within the length of cladding 10 by a continuous length of plastic shrink tubing 4. After placement overlapping a portion of both the funnel and cladding, the tubing 14 is shrunk diametrically by proper application of heat. It tightly encircles and grips both the cladding 10 and funnel 12. It maintains them as a unit during reception of fuel into the cladding through the funnel 12. The funnel 12 is designed to be discarded after the length of cladding 10 has been charged with fuel pellets. Removal of the funnel is accomplished by pulling tubing 14 as cladding 10 is retracted axially. Removal is facilitated by providing a slidable collar or ring 13 that surrounds cladding 10 beneath the shrink tubing 14. The coaxial ring 13 presents a rear annular shoulder 19 which can be engaged to pull ring 13, tubing 14 and funnel 12 as a unit. If desired, the shoulder 19 could be presented as part of that portion of funnel 12 enveloped under the shrink tubing 14. The tubing 14 preferably extends along the outer surface of cladding 10 an an outer protective element. It provides a cylindrical surface for engagement by resilient or inflatable seals. Particles embedded in the tubing 14 as a result of such sealing will be discarded with the tubing when it is removed. This minimizes contamination of the cladding itself. It is to be understood that the funnel 12 could have many different interior or exterior configurations, so as to match the physical shape and requirements of particular pellet loading devices. These modifications are not believed to be pertinent to the present disclosure, since they will not change the manner by which the funnel is related to the length of cladding. The foregoing description of the preferred embodiments 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, and obviously many modifications and variations are possible in light of the above teaching. The embodiments discussed in detail were chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto.
	summary
	description	1. Field of the Invention This invention relates to a nozzle inspection tool, and more particularly, a nozzle inspection tool that can be used to inspect nozzles within a nuclear reactor. 2. Description of the Prior Art The use of nuclear energy to generate electricity began in the early 20th century after the discovery that radioactive elements such as radium release immense amounts of energy. Initially, however, harnessing such energy was impractical because intensely radioactive elements are very short-lived. By the late 1930s, experiments were being conducted with nuclear fusion. Those experiments in nuclear fusion led to the Manhattan Project, which led to the first nuclear weapons, which were used in World War II on the cities of Hiroshima and Nagasaki. After World War II, nuclear energy was used to generate power with the USSR's Obninsk Nuclear Power Plant becoming the world's first nuclear power plant to generate electricity for a power grid. The world's first commercial nuclear power plant was opened in 1956 in Sallafield, England. The first commercial nuclear generator to become operational in the United States was the Shipping Port Reactor in Pennsylvania in 1957. By 2005, 15% of the world's electricity was generated by nuclear power, with the United States, France and Japan accounting for 56% of the nuclear generated electricity. As of December 2009, the world had 436 nuclear reactors. While many different things have affected the number of nuclear reactors, the growth of nuclear power was impeded by (1) the Three-Mile Island accident in 1979, (2) Zhernobyl disaster in 1986, and (3) Wukushima Daiichi nuclear disaster in 2011. With these accidents, there has been an increased emphasis on safety and a decline in the growth rate of nuclear reactors. One of the areas of increased safety emphasis is in the containment vessel and in the lines flowing fluid to and from the nuclear power plant reactors. An item requiring inspection is the various welds and joints in (1) the containment vessel, (2) nuclear power reactors and (3) the lines leading and from such vessels. In the United States, there are approximately 104 operating nuclear reactors. Of those, sixty-nine are pressurized water reactors (PWR) and thirty-five are boiling water reactors (BWR). In both the PWR and BWR, fluid is converted to steam and the steam is used to turn a turbine that generates the electricity. The conduits taking the fluid or steam to or from the turbine have to be inspected, especially the welds occurring in the nozzles. In the United States, the Nuclear Regulatory Commission (NRC) is responsible for ensuring public health through licensing and inspection of nuclear power plants. One of the things that the NRC requires to be inspected are the welds that occur in the containment vessel and in the nozzles leading to and from the containment vessel. It is an object of the present invention to provide a tool for inspecting welds in the nozzle of a nuclear reactor. It is yet another object of the present invention to provide a submersible device that can enter the fluid contained in a nuclear reactor and go inside of the nozzles to inspect the welds contained therein. It is yet another object of the present invention to provide a tool that is self-contained and can directed itself inside of the nozzle of the nuclear reactor and position itself therein so that the welds in the nozzle can be inspected. It is still another object of the present invention to provide a tool that is buoyancy compensated with its own thrusters for properly locating itself inside the nozzles of the nuclear reactor for inspection of welds therein. It is even another object of the present invention to provide feet on a tool that will extend radially outward to center the tool in a nozzle of a nuclear reactor to allow for inspection of the weld there around. A main rail is provided with a buoyancy pack on either end thereof with thrusters for repositioning the entire device. On either end of the main rail between the buoyancy packs are located expandable feet that extend outwardly at approximately every 120° to contact around the nozzle and position the tool therein. While the expandable feet hold the tool in the nozzle, an expandable and rotating transducer package extends outward to a weld joint and radially rotates so a transducer package can inspect the entire weld. If there is more than one weld in the nozzle, (1) expanding and rotating transducer package is retracted, (2) expandable feet are refracted and (3) the device is moved to a position adjacent to another weld. The process is then repeated with the expandable feet expanding outward to secure the device. Thereafter, expandable and rotating transducer packages are expanded outward and rotated adjacent to the weld so that the entire weld is inspected. At the ends of each of the expandable feet are snubbers for securing the tool in position. An illustrative flow diagram for a nuclear power plant for generating electricity is shown in FIG. 1 and is represented generally by reference numeral 11. The nuclear power plant 11 has a reactor containment vessel 13 that has a Taurus 15 with an auxiliary water feed 17, which is a backup water supply for the nuclear power plant 11. Inside of the reactor containment vessel 13 is located a reactor pressure vessel 19. A bundle of fuel rods 21 absorb a neutron to cause nuclear fission on release of other neutrons. The nuclear fission heats the water contained within reactor pressure vessel 19 to convert it to steam. To ensure the bundle of fuel rods 21 remain immersed in water an internal reactor recirculation pump 23 continues to recirculate water over the bundle of fuel rods 21. Also, an external reactor recirculation pump 25 circulates water within the reactor pressure vessel 19 to ensure the bundle of fuel rods 21 remain cool and immersed in the water. While in the reactor pressure vessel 19 different fluids have been used, including gas, liquid metal or molten salts to ensure that the nuclear reaction does not run away. Control rods 27 are located in the bottom of the reactor pressure vessel 19. The control rods 27 absorb some of the released neutrons to prevent too large of a nuclear reaction with the bundle of fuel rods 21. Above the bundle of fuel rods 21 is located heat exchanger 29, which is used to convert the water to steam. Steam generated in the reactor pressure vessel 19 enters steam line 33 through outlet nozzle 31. The steam flows through the steam line 33 and the main steam isolation valve 35 to enter steam turbine 37. As the steam turns the steam turbine 37, steam turbine 37 turns generator 39, which generates electricity. After the steam flows through the steam turbine 37, a major portion of the steam flows through the main steam exit conduit 41 to condenser 43. Circulating through the condenser coil 45 is cooling water received from the cooling tower 47 via condenser cooling water pump 49, cooling water control valve 51 and cooling water inlet conduit 53. The cooling water returns to the cooling tower 47 via cooling water return conduit 55 and cooling water return valve 57. The cooling water can be of any convenient source such as lake water or river water. The cooling water does not have to be refined or processed. From condenser 43 through the feed water return conduit 59, the water is being pumped by condenser pump 61 through water return valve 63 into a feed water heater/preheater 65. The feed water flowing back to the reactor pressure vessel 19 is heated/preheated inside of feed water heater/preheater 65 which receives some of the steam flowing through steam turbine 37 through preheater steam conduit 67 and control valve 69 to feed water heater/preheater 65. The feed water heater/preheater 65 increases the temperature of the feed water significantly prior to returning to the reactor pressure vessel 19 via reactor feed pump 71, main feed water isolation valve 73 and main feed water return conduit 75. The main feed water is discharged into the reactor pressure vessel 19 through return nozzle 77. Any remaining portion of the preheater steam received in the feed water heater/preheater 65 flows to condenser 43 through preheater steam conduit 79 and preheater steam control valve 81. The outlet nozzle 31 and return nozzle 77 are very large in size and may vary anywhere from 24 inches to 46 inches in diameter. Also, there is more than one of the outlet nozzle 31 and the return nozzle 77. There are usually between two to six outlet nozzles 31 and return nozzles 77. These outlet nozzles 31 and return nozzles 77 handle extreme loads and extreme heat cycles. Pressure can be in the thousands of pounds per square inch (psi). Typically, the outlet nozzles 31 and return nozzles 77 are made by welding pipe together, which welds may be of the same type of metal or may be dissimilar metals. For example, the main feed water return conduit 75 may be of one type of metal, but the reactor pressure vessel 19 may be of a different type of metal. Different metals are used for a variety of different reasons, including strength, resistance to corrosion, or more economical. Because of the extremes of temperature and pressure through which the outlet nozzle 31 or the return nozzle 77 must endure, it is important to periodically check the welds to make sure the welds are holding. The present invention relates to a nozzle inspection tool 83 as shown pictorially in FIG. 2. The nozzle inspection tool 83 has a main rail 85 on which everything is mounted. The main rail 85 looks very similar to an I-beam. On each end of the main rail 85 are buoyancy packs 87. The buoyancy packs 87 are partially cut away so that thruster clusters 89 can be seen. The thruster clusters 89 are used to control the direction of movement of the nozzle inspection tool 83. The buoyancy packs 87 adjust the buoyancy of the nozzle inspection tool 83 so that the tool can be maintained at a particular depth. Mounted on either end of the main rail 85 are expandable foot clusters 91 and 93, which are identical. However, both expandable foot clusters 91 and 93 are independently moveable along the main rail 85. Between the expandable foot clusters 91 and 93 is located expanding/rotating transducer package 95. Referring to the perspective view of expandable foot cluster 91 in FIG. 3, operation of the expandable feet cluster 91 will be explained in more detail. Expandable foot cluster 91 is identical to expandable foot cluster 93. In the center of the expandable foot cluster 91 are linear bearings 97 that press against the main rail 85 (see FIG. 2). Linear bearings 97 are carried inside of expansion control ring 99. The linear bearings 97 are connected to a central frame 101 through which the main rail 85 may slide. Connected to the central frame 101 are cable bundle guides 103. The expansion control ring 99 is pivotally attached to central frame 101. Extending outwardly in a radial direction from the central frame 101 are expandable feet 105. There are three identical expandable feet 105 located at approximately 120° around the central frame 101 and extending radially outward from the central frame 101. Each of the expandable feet 105 have an adjustment bracket 107 connected to the central frame 101. Contained inside of the adjustment bracket 107 are air cylinders 109. Extending outwardly from the adjustment bracket 107 are adjustment rods 111. The adjustment rods 111 are telescopically received into adjustment bracket 107 with the outer end of the adjustment rods 111 being connected to a foot bracket 113. The foot bracket 113 is approximately perpendicular to the adjustment rods 111. On each end of the foot bracket 113 are located rollers 115. Between the rollers 115 and also mounted on the foot bracket 113 is a rubber snubber 117. The rubber snubber 117 extends radially outward slightly more than the rollers 115 on the expandable feet 105. A push rod 119 connects between the air cylinder 109 and the foot bracket 113 so that as the expandable foot 105 expands, push rod 119 would extend radially outward. As the expandable foot 105 retracts, push rod 119 would move radially inward. Since each of the expandable feet 105 may extend outward different amounts, expansion control ring 99 is rotatably carried on the central frame 101. As the expansion control ring 99 rotates, connecting rods 121 which connect from the expansion control ring 99 to the foot bracket 113 of each of the expandable feet 105, causes each expandable foot to also move. The expansion ring 99 with the connecting rod 121 ensures that the expandable foot cluster 91 is centered inside of a conduit in a manner as will be subsequently described. Also, a couple of the thrusters 123 and 125 of the thruster cluster 89 are shown attached to adjustment bracket 107. However, the thrusters 123 or 125 may be connected at other locations along the nozzle inspection tool 83. Referring back to FIG. 2, expandable foot clusters 91 and 93 are shown on each end of the main rail 85. The expanding/rotating transducer package 95 shown in FIG. 2, will be explained in more detail in the elevated view shown in FIG. 4 and the cross-sectional view of FIG. 5 taken along section lines 5-5 of FIG. 4. A transducer central frame 127 receives the main rail 85 there through. Linear bearings 129 allow the expandable/rotating transducer package 95 to move smoothly along main rail 85. Threadably connected to the transducer central frame 127 are lead screws 131. Lead screws 131 will adjust the expanding/rotating transducer package 95 linearly along the main rail 85 of the nozzle inspection tool 83. Rotatably connected to the transducer central frame 127 is external ring 133. A ring gear 135 is connected to external ring 133 so that when ring gear 135 is driven by drive gear 137, the external ring 133 and everything connected thereto will rotate about main rail 85 (see FIG. 2). Connected to the ring gear 133 at approximately 90° apart are linear guide mounts 139. Extending radially outward from the linear guide mounts 139 are linear guides 141. The linear guides 141 extend radially outward from linear guide mounts 139 with the outermost end of the linear guide mounts 141 connected to a transducer mounting bracket 143. The transducer mounting bracket 143 has mounted thereon a left transducer 145, center transducer 147 and a right transducer 149 to make up a transducer cluster referred to generally by reference numeral 151. Connecting to the center of the transducer mounting bracket 143 is a connecting rod 153 that connects between transducer mounting bracket 143 and air cylinder 155 secured inside of linear guide mounts 139. If the expanding/rotating transducer package 95 needs to be rotated, motor cam assembly 157 (shown in FIG. 5) will cause the rotation. Cable guide 159 (shown in FIG. 4) will protect the cabling that connects to transducers 145, 147 and 149 to prevent damage. While the electrical connections are not described in detail herein, electrical connections must connect to each of the transducers 145, 147, and 149 for signals to be transmitted to and from these transducers. Also, various control signals are used to control operation of nozzle inspection tool 83. Referring now to FIGS. 6A, 6B and 6C sequential views show the nozzle inspection tool 83 being used in a nozzle. Referring to FIG. 6A, the nozzle inspection tool 83 is shown in front of return nozzle 77, also sometimes called inlet nozzle. The return nozzle 77 has a tapered section 161 connecting between the return nozzle 77 and the main feed water return conduit 75 of the reactor pressure vessel 19 (see FIG. 1). The nozzle inspection tool 83 (shown in FIG. 6A) has the expandable foot clusters 91 and 93 as mounted on the main rail 85 in the retracted position. The expanding/rotating transducer packages 95 are also in the retracted position. The buoyancy packs 87 keep the nozzle inspection tool 83 at the desired depth while the thruster clusters 89 provide movement of the nozzle inspection tool 83. FIG. 6B illustrates movement of the nozzle inspection tool 83 inside of outlet nozzle 31. Outlet nozzle 31 has an inward shoulder 163 and an inward flair 165. The outlet nozzle 31 is connected to steam line 33 by weld 167. Weld 167 may be a weld of similar metals or it may be a weld of dissimilar metals. The object is for the nozzle inspection tool 183 to inspect weld 167. Referring now to FIG. 6C, the nozzle inspection tool 83 has moved inside of outlet nozzle 31 and the expandable foot clusters 91 and 93 have been expanded so that the rubber snubbers 117 are pressed against either the nozzle 31 or the steam line 33. The snubbers securely hold the inspection tool in position. While being held in position, the expanding/rotating transducer package 95 extends outward into a position immediately adjacent to weld 167. Now the electronic assembly nozzle inspection tool 83 is turned ON and the expanding/rotating transducer package 95 is rotated so that each of the transducer clusters 151 may check the integrity of the weld 167. Referring to FIG. 7, a general explanation as to the control system for nozzle inspection tool 83 is provided. Located on the nozzle inspection tool 83 near the buoyancy pack 87 is an inertia measurement unit 169. The inertia measurement unit 169 is used by applicant and sold under the brand name XSENS, Model MT. The inertia measurement unit 169 is a miniature gyro-enhanced altitude and heading reference system with a low-power signal processor that provides drift-free 3-D orientation, 3-D acceleration, 3-D rate of turn and 3-D earth-magnet field data. The inertia measurement unit 169 gives real time computed altitude/heading and inertia dynamic data. Also, the inertia measurement unit 169 either accepts or generates synchronization pulses. Also contained on board the nozzle inspection tool 83 is a camera 171 mounted near or on the buoyancy pack 87. While many different types of cameras can be used, a Mantis hi-definition camera is a typical example of a camera that can be used. By use of the camera 171, an operator of the nozzle inspection tool 83 can see the direction nozzle inspection tool 83 is moving. While the present nozzle inspection tool 83 only has one camera 171, multiple cameras could be used. The Mantis camera is an internally integrated digital camera that allows for image capture and documentation. The images being received by the Mantis camera can by simultaneously viewed optically and digitally. Also located on the nozzle inspection tool 83 are encoders 173 located on the backside of each of the motors (not shown) on nozzle inspection tool 83, excluding the motors contained in each of the thruster clusters 89. The encoders 173 that have been found suitable for the present invention are sold under the name Avago. The model that is found to be particularly suitable is the HELV-5540. These particular encoders are found to be very good for use in noisy environments. The Avago encoder provides precise positioning and velocity sensing information to servo motor feedback systems used in the operation nozzle inspection tool 83. Each of the inputs referred to generally as 175 connect to motor controllers 177. While different types of motor controllers can be used, a Maxon motor controller, Model EPOS 2 is found to be particularly suitable for the present invention. Motor controllers 177 are connected to a central processing unit 179 and receive and send communications thereto. In operation inputs 175 from the inertia measurement unit 179, camera 171, and encoders 173 located on the nozzle inspection tool 83 or are received through a cable connection 181 from the nozzle inspection tool 83 to the motor controllers 177. The motor controllers 177 provide feedback to the nozzle inspection tool 83 and the central processing unit 179. The operator then, through the central processing unit 179, may control operation of the nozzle inspection tool 83 via communications with the motor controllers 177. Through proper use of commands through the central processing unit 179, an individual can control operation of the nozzle inspection tool 83. Referring to FIGS. 6A, 6B, and 6C, the nozzle inspection tool 83 can be directed to any position desired in the outlet nozzle 31 or the steam line 33. Also, the nozzle inspection tool 83 may be directed into the return nozzle 77. Once the nozzle inspection tool 83 is in position, the expandable feet clusters 91 and 93 will extend outward to secure the nozzle inspection tool 83 into position. Once the expanding/rotating transducer package 95 is in position next to weld to be inspected, the expanding/rotating transducer package 95 will extend outward so that the transducers thereon are immediately adjacent to the weld to be inspected. Thereafter, the expanding/rotating transducer package 95 is rotated to inspect the weld.
	claims	1. A securing device for installation on an outer circumferential surface of a nuclear reactor core shroud and in contact with an inner circumferential surface of a nuclear reactor pressure vessel, the securing device comprising:a base configured for contacting the outer circumferential surface of the nuclear reactor core shroud; anda radial extender including an actuator, a stationary support section fixed to the base and a movable contact section, the radial extender being configured such that the movable contact section is movable along the stationary support section by the actuator to force the movable contact section radially into the inner circumferential surface of the pressure vessel,wherein the radial extender is configured such that an axial movement of the actuator moves the movable contact section radially,wherein the movable contact section includes an elongated hole formed therein, the actuator being radially movable in the elongated hole as the actuator moves the movable contact section radially. 2. The securing device as recited in claim 1 further comprising a plurality of fasteners for passing through the base into the nuclear reactor core shroud. 3. The securing device as recited in claim 1 wherein the stationary support section includes an axially extending hole formed therein, the actuator being movable in the axially extending hole to move the movable contact section radially. 4. The securing device as recited in claim 1 wherein the actuator is a bolt extending through the movable contact section and through the stationary support section. 5. The securing device as recited in claim 1 wherein the base includes a first radial contact section having a contact surface configured for radially contacting a first outer circumferential surface section of the nuclear reactor core shroud and a second radial contact section having a contact surface configured for radially contacting a second outer circumferential surface section of the nuclear reactor core shroud, the first radial contact section being radially offset from the second radial contact section. 6. The securing device as recited in claim 1 wherein the stationary support section and the movable contact section are connected together by the actuator. 7. The securing device as recited in claim 1 wherein the stationary support section includes a first wedge part and the movable contact section includes a second wedge part, the first wedge part being slidable along the second wedge part by the actuator to force the movable contact section radially into the inner circumferential surface of the pressure vessel. 8. The securing device as recited in claim 7 wherein the first wedge part includes a first sloped surface and the second wedge part includes a second sloped surface that is complementary to the first sloped surface. 9. A method for installing a securing device on an outer circumferential surface of a nuclear reactor core shroud and in contact with an inner circumferential surface of a pressure vessel, the method comprising:fixing a base of the securing device to outer circumferential surface of the nuclear reactor core shroud; andmoving an actuator of the securing device to force a movable contact section of the securing device along a stationary support section of the securing device to force the movable contact section radially into the inner circumferential surface of the pressure vessel,wherein the movable contact section includes an elongated hole therein, the moving of the actuator including moving the actuator radially within the elongated hole. 10. The method as recited in claim 9 wherein the fixing of the base to the outer circumferential surface of the nuclear reactor core shroud includes machining blind holes into the shroud and installing fasteners through the base and into the blind holes. 11. The method as recited in claim 9 wherein the stationary support section includes a first wedge part and the movable contact section includes a second wedge part, the moving of the actuator including sliding the second wedge part along the first wedge part via the actuator. 12. The method as recited in claim 9 wherein the stationary support section includes an axially extending hole, the moving of the actuator including moving the actuator axially within the axially extending hole. 13. A securing device for installation on an outer circumferential surface of a nuclear reactor core shroud and in contact with an inner circumferential surface of a nuclear reactor pressure vessel, the securing device comprising:a base configured for contacting the outer circumferential surface of the nuclear reactor core shroud; anda radial extender including an actuator, a stationary support section fixed to the base and a movable contact section, the radial extender being configured such that the movable contact section is movable along the stationary support section by the actuator to force the movable contact section radially into the inner circumferential surface of the pressure vessel,wherein the stationary support section includes a first wedge part and the movable contact section includes a second wedge part, the first wedge part being slidable along the second wedge part by the actuator to force the movable contact section radially into the inner circumferential surface of the pressure vessel. 14. The securing device as recited in claim 13 wherein the first wedge part includes a first sloped surface and the second wedge part includes a second sloped surface that is complementary to the first sloped surface.
049869590	description	DETAILED DESCRIPTION OF THE INVENTION In the following description, like references characters designate like or corresponding parts throughout the several views. Also in the following description, it is to be understood that such terms as "forward", "rearward", "left", "right", "upwardly", "downwardly", and the like, are words of convenience and are not to be construed as limiting terms. Referring now to the drawings, and particularly to FIG. 1, there is shown a fuel assembly, generally designated by the numeral 10, having an expandable top nozzle subassembly 12 constructed in accordance with the principles of the present invention. In addition to the top nozzle subassembly 12, the fuel assembly 10 basically includes a bottom nozzle 14 for supporting the fuel assembly on the lower core support plate (not shown) in the core region of a nuclear reactor (not shown) and a number of longitudinally extending control rod guide tubes or thimbles 16 projecting upwardly from the bottom nozzle 14 and attached at their upper and lower ends to the top nozzle subassembly 12 and bottom nozzle 14. Further, an organized array of fuel rods 18 are held in spaced relationship to one another by a number of transverse grids 20 spaced along the fuel assembly length and attached to the guide thimbles 16. An instrumentation tube 22 is located at the center of the fuel assembly 10. The top nozzle subassembly 12, bottom nozzle 14 and guide thimbles 16 together form an integral assembly capable of being conventionally handled without damaging the assembly parts. Referring to FIGS. 1-3, the expandable top nozzle subassembly 12 of the present invention has a construction which permits improved utilization of space for accommodating greater growth of fuel rods 18 of the fuel assembly 10 and higher fuel rod burnup. At the same time, the top nozzle subassembly 12 continues to allow the use of a conventional handling system for installing and removing the fuel assembly 10 in and from the reactor core. The expandable top nozzle subassembly 12 basically includes an upper structure 24, a lower adapter plate 26 and a plurality of resiliently-yieldable biasing devices 28. As shown alone and in greater detail in FIGS. 4-7, the upper structure 24 of the top nozzle subassembly 12 is composed of a top plate 30 and a sidewall enclosure 32 rigidly connected to and depending from the outer peripheral edge 30A of the top plate 30. The top plate 30 has an annular configuration defining a large central opening 34. Two diagonal ones of a plurality of corner portions 30B of the top plate 30 each has a hole 36 defined therethrough which permit insertion of components of the fuel assembly handling system (not shown) for engaging the lower surface 30C of the top plate 30 in order to lift the fuel assembly 10 in installing and removing it from the core. One of the other corner portions 30B has a hole 38 which provides a reference for properly orientating the fuel assembly 10 in the core. Also, a pair of holes 40 is defined through each corner portion 30B of the top plate 30 with each hole 40 surrounded on the lower surface 30C of the top plate by an annular recess 40A formed in the lower surface of the top plate. The sidewall enclosure 32 of the upper structure 24 is composed of four generally planar vertical wall portions 42 rigidly interconnected together at their opposite vertical edges to define the enclosure 32 in a generally square box-like configuration. At the lower peripheral edge of the sidewall enclosure 32, each wall portion 42 has a narrow inwardly-projecting retaining structure 44 composed of a series of spaced fingers 44A defining the retaining structure in a generally scalloped or serrated configuration. As shown alone and in greater detail in FIGS. 8-10, the lower adapter plate 26 of the top nozzle subassembly 12 is of generally square configuration and flat construction. The adapter plate 26 is formed of a plurality of cross-laced ligaments or bars 46 defining a plurality of coolant flow openings 48 of oblong shapes. Also, a plurality of circular through holes 50 corresponding in number and pattern to that of the guide thimbles 16 are provided through the adapter plate 26. The through holes 50 are of sufficient dimensional size to permit the adapter plate 26 to be installed over the upper ends of the guide thimbles 16. Further, a pair of circular recesses 52 are defined at each corner portion 26A of the lower adapter plate 26 in the upper surface 26B of the adapter plate. The pairs of recesses 52 are aligned below the pairs of holes 40 and annular recesses 40A in the top plate 24. In each recess 52, a series of coolant flow openings 54 in a generally square pattern are defined through the adapter plate 26. The outer peripheral edge of the adapter plate 26 is undercut to define a ledge or seat structure 56 overlying a continuous recess or groove 58. Referring to FIGS. 2, 3, 11 and 12, the resiliently-yieldable biasing devices 28 take the form of pairs of coil springs 60 being seated at their opposite upper and lower ends 60A, 60B in the respective recesses 44A, 52 formed at aligned corner portions of the 30A, 26A of the top plate 30 and lower adapter plate 26 located outside of an outer perimeter of the guide thimbles 16. The outer perimeter of the guide thimbles 16 is also aligned below an inner peripheral edge 30C defining the central opening 34 of the top plate 30. Also, a stabilizing or guide member 62 in the form of a short cylindrical plug or bar is secured to the top plate 30 in each of the holes 40 and extends within the corresponding coil spring 60. The guide members 62 provide lateral stabilization of the springs 60 and direct their expansion and compression along a generally vertical path. In the expanded states of the springs 60 seen in FIG. 11 the length of the guide members 62 is less than half the length of the springs. In the compressed state of the springs 60 as seen in FIG. 12, the lower ends of the guide members 62 are located adjacent to the adapter plate 26. FIG. 11 shows the top nozzle subassembly 12 in an expanded condition, whereas FIG. 12 shows it in a compressed condition. In both conditions of the top nozzle subassembly 12, the adapter plate 26 is stationarily secured in the same position on the upper ends of the guide thimbles 16 in a conventional manner by locking tubes 64. By way of example, the adapter plate 26 is disposed approximately 1 inch to 1.5 inches higher above the upper ends of the fuel rods 18 than is a conventional adapter plate heretofore. Also, the adapter plate 26 is slidably movably mounted within the interior of the sidewall enclosure 32. The sidewall enclosure 32 and adapter plate 26 are not rigidly connected to one another but instead are slidably movable relative to one another. The retaining structure 44 of the sidewall enclosure 32 and the seat structure 56 of the adapter plate 26 provide interengagable means on the lower edge of the enclosure 32 and on a peripheral edge of the adapter plate 26 for capturing and retaining the adapter plate 26 within the enclosure 32 upon movement of the enclosure relative to the adapter plate which, in turn, moves the top plate 30 away from the adapter plate 26. With such arrangement, the adapter plate 26 cannot become separated from the upper structure 24. To place the top nozzle subassembly 12 in the expanded condition seen in FIG. 11, the upper core support plate (not shown) is removed from imposing a downward bearing contact force upon the top plate 30 of the upper structure 24 of the top nozzle subassembly. The springs 60 are thus allowed to assume their expanded states in which they force the upper structure 24 away from adapter plate 26 and thus force the latter in resting or abutting relation at its annular seat structure 56 upon the fingers 44A of the retaining structure 44 on the enclosure 32 of the upper structure 24. The fingers 44A capture and retain the adapter plate 26 within the enclosure 32. The adapter plate 26 and top plate 30 are now spaced their maximum distance apart and provide sufficient space between them for insertion of the components of the fuel assembly handling system through the corner holes 36 in the top plate. To place the top nozzle subassembly 12 in the compressed condition seen in FIG. 12, the upper core support plate is installed upon the top plate 30 of the upper structure 24 of the top nozzle subassembly so as to reimpose the downward bearing contact force thereon. The top plate 30 is thus moved downward toward the lower adapter plate 26 forcing the springs 60 to their compressed states and slidably moving the sidewall enclosure 32 downwardly along and relative to the adapter plate 26 and lowering the retaining structure 44 on the enclosure away from the seat structure 56 on the adapter plate 26. The space between the top plate 30 and the adapter plate 26 is now reduced below that needed for insertion of the components of the fuel assembly handling system. However, this does not matter since the fuel assembly is never handled by the system while it is in the core with the upper core support plate placed on the top nozzle subassembly. Thus, the extra or "dead" space previously existing between the top plate 30 and adapter plate 26 has now been eliminated and is instead now being utilized by the higher mounting position of the adapter plate 26 on the guide thimbles 16 permitting greater distance between the adapter plate 26 and upper ends of the fuel rods 18 for increased growth and greater burnup of the fuel rods in the core. Later when the fuel assembly 10 is to be handled, the upper core plate is removed and the springs 60 moves the upper structure 24 upward to its position in FIG. 11 returning the top plate 30 and adapter plate 26 to their maximum spacing for providing the necessary space therebetween for the fuel assembly handling system components. The scalloped shape of the retaining structure 44 permits them to move downwardly past the upper ends of the fuel rods 18 to the position seen in FIG. 12. The central opening 34 of the top plate 30 accommodates passage of control rods (not shown) into the guide thimbles 16 in a conventional manner. The coil springs 60 transmit the necessary hold-down force from the upper core plate directly to the adapter plate 26. The number and arrangement of the coil springs 60 have the advantage of allowing the load from the upper core plate to be distributed much more evenly to the adapter plate, then in the case of prior hold-down arrangements, thus helping to prevent bow in the fuel assembly. It will be noted also that the sidewall enclosure 32 of the upper structure 24 completely encloses the springs 60 in both expanded and compressed conditions of the top nozzle subassembly 12, thus protecting and shielding the springs from imposition of lateral forces thereon by coolant flow. It should be realized, however, that other forms of biasing devices can be used, such as elongated leaf springs. In comparison of FIGS. 11 and 12, it can be understood that only the springs 60 extend between and engage both the top plate 30 and the lower adapter plate 26 and that the amount of reduction in the height of the top nozzle subassembly 12 in moving from its expanded to compressed condition is only limited by the amount of displacement the springs 60 can undergo in moving from their expanded to compressed states. It is thought that the expandable top nozzle subassembly of the present invention and many of its attendant advantages will be understood from the foregoing description and it will be apparent that various changes may be made in the form, construction and arrangement thereof without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the form hereinbefore described being merely a preferred or exemplary embodiment thereof.
	description	The present disclosure relates to neutron generators. Z-pinch plasma devices are used to study fusion as an energy source. A z-pinch plasma device that is used as an energy source typically employs aneutronic fusion to generate energy, and aims to produce more energy than the amount of energy the z-pinch plasma device consumes. Aneutronic fusion uses materials selected to produce few neutrons (e.g., as few as possible within operational constraints) since neutrons released from such experiments can be problematic. Z-pinch plasma devices that employ aneutronic fusion do not produce sufficient neutrons for neutron-based applications. In a particular implementation, a single-use neutron generator includes a power supply. The single-use neutron generator includes a fuel source configured to provide neutron-producing fuel. The single-use neutron generator includes a plasma confinement device coupled to the power supply and the fuel source and configured to generate a plasma pinch of the neutron-producing fuel. At least one component of the single-use neutron generator is configured for single use. In a particular implementation, a method of generating neutrons includes providing neutron-producing fuel within an interior of a plasma confinement device of a neutron generator. The method additionally includes applying power to the plasma confinement device to produce neutrons by generating a plasma pinch of the neutron-producing fuel within the plasma confinement device. The power exceeds an operational tolerance of at least one component of the neutron generator. In a particular implementation, a single-use neutron generator includes an outer electrode and an inner electrode within an interior of the outer electrode. The single-use neutron generator includes a power source electrically coupled to the outer electrode and the inner electrode. The power source is configured to generate a voltage differential between the outer electrode and the inner electrode. The single-use neutron generator includes a fuel source configured to provide neutron-producing fuel. The neutron-producing fuel is configured to undergo ionization to produce a plasma pinch. The plasma pinch is configured to undergo a thermonuclear fusion reaction. At least one component of the single-use neutron generator is configured for single use. The features, functions, and advantages described herein can be achieved independently in various embodiments or may be combined in yet other embodiments, further details of which are disclosed with reference to the following description and drawings. Particular embodiments of the present disclosure are described below with reference to the drawings. In the description, common features are designated by common reference numbers throughout the drawings. The figures and the following description illustrate specific exemplary embodiments. It will be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the principles described herein and are included within the scope of the claims that follow this description. Furthermore, any examples described herein are intended to aid in understanding the principles of the disclosure and are to be construed as being without limitation. As a result, this disclosure is not limited to the specific embodiments or examples described below, but by the claims and their equivalents. Examples of devices and methods described herein release, produce, radiate, propagate, or generate neutrons using plasma confinement of a neutron-producing fuel (e.g., gas). The neutron-producing fuel is compressed into compact plasma utilizing a self-reinforcing magnetic field referred to as a z-pinch. The plasma undergoes thermonuclear fusion (e.g., neutronic fusion), which releases, produces, radiates, propagates, or generates neutrons. FIGS. 1A and 1B illustrate block diagrams of an example of various stages of a single-use neutron generator 100 during generation of neutrons using a plasma pinch that is generated using a fuel source 102 (e.g., a gas fuel source). The single-use neutron generator 100 includes at least one component that is configured for single use as described in more detail below. The single-use neutron generator 100 includes a housing 148 to house the fuel source 102, a power supply 112, and a plasma confinement device 104. The fuel source 102, the power supply 112, the plasma confinement device 104, and the housing 148 are configured to be compact so that the single-use neutron generator 100 is a vehicle-deliverable package. The plasma confinement device 104 is coupled to the fuel source 102. The fuel source 102 is configured to provide or supply a neutron-producing fuel 106 to an interior 140 of the plasma confinement device 104. The neutron-producing fuel 106 is a gas that will experience a neutronic (e.g., as opposed to aneutronic) fusion reaction. In some examples, the neutron-producing fuel 106 includes or corresponds to deuterium, tritium, lithium, or a combination thereof. In some examples, the fuel source 102 corresponds to a neutron-producing fuel 106 stored in a container or other storage apparatus. The plasma confinement device 104 includes an inner electrode 108 and an outer electrode 110. The inner electrode 108 is located within an interior 140 of the outer electrode 110. In some examples, the inner electrode 108 is a hollow cylinder. Alternatively or additionally, in some examples the outer electrode 110 is a hollow cylinder. The power supply 112 is coupled to the outer electrode 110 and to the inner electrode 108. In some examples, the power supply 112 is a superconducting magnetic energy storage system 132, a plurality of ultra-capacitors 134, an explosive direct energy converter 136, or a flywheel energy storage device 138. An explosive direct energy converter includes an explosive and is configured to convert kinetic energy (from detonation or explosion of the explosive) into a voltage and/or current. In some examples, the power supply 112 is configured to apply approximately or at least one (1) GigaWatts of power to the plasma confinement device 104 during the single use. In some examples, the power supply 112 is configured to supply at least 500 kilo amps to the plasma confinement device 104 during the single use. In some examples, the power supply 112 is configured to apply power to the plasma confinement device 104 using a pulse having a duration of approximately one second. In other examples, the power supply 112 is configured to apply power to the plasma confinement device 104 using a pulse having a duration of less than one second or more than one second. The amount of power applied, generated, or supplied to the plasma confinement device 104 during the pulse will damage, destroy, or disable (e.g., beyond repair) at least one component of the single-use neutron generator 100 as described in more detail below. In some examples, prior to the single use, the power supply 112 is coupled to a power charger [not illustrated] to charge the power supply 112. In some examples, the charger is decoupled from the power supply 112 before the single-use neutron generator 100 is deployed for the single use. During operation, the neutron-producing fuel 106 is provided (e.g., injected or puffed) into the interior 140 of the outer electrode 110. Subsequent to or concurrent with providing the neutron-producing fuel 106 within the outer electrode 110, the power supply 112 is activated, causing the power supply 112 to apply a high voltage differential across the outer electrode 110 and the inner electrode 108. In response to application of the high voltage differential, an electric arc forms between the outer electrode 110 and the inner electrode 108, causing the neutron-producing fuel 106 within the plasma confinement device 104 to ionize into a plasma 114 that is capable of conducting current. Once the neutron-producing fuel 106 ionizes into the plasma 114, continued application of the high voltage differential causes a current to flow through the plasma 114. Current flowing through the plasma 114 creates a magnetic field 122 within the plasma confinement device 104 that squeezes or compresses portions of the plasma 114 to form a plasma pinch 116. The plasma pinch 116 is self-reinforcing, with the current flowing through the plasma 114 creating the magnetic field 122, and the magnetic field 122 in turn further compressing the plasma 114 formed from the neutron-producing fuel 106 in the region of the plasma pinch 116. Thus, the plasma confinement device 104 is configured to generate a plasma pinch 116 of the neutron-producing fuel 106. In some examples, the plasma pinch 116 is at least one half meter (0.5 m) in length. In some examples, the plasma pinch 116 corresponds to a sheared-flow stabilized z-pinch. A sheared-flow stabilized z-pinch is a z-pinch that is stabilized by a flow (e.g., a continuous flow) of gas (e.g., gas 130) outside (e.g., immediately outside) of the z-pinch 116. In these examples, the single-use neutron generator 100 is configured to inject the gas 130 (e.g., a neutral gas, such as hydrogen) into the interior 140 of the outer electrode 110. In some implementations of these examples, the single-use neutron generator 100 includes a flow-stabilizing gas source 153 to provide the gas 130. In other implementations, the gas 130 may be provided by the fuel source 102 (e.g., the gas 130 may correspond to the neutron-producing fuel 106), in which case the single-use neutron generator 100 does not include the flow stabilizing gas source 153 (e.g., the fuel source 102 serves as a flow stabilizing gas source). Flow of the injected gas 130 proximate to the z-pinch induces a sheared flow of the plasma 114 that stabilizes the z-pinch without using close fitting walls or axial magnetic fields, thereby enabling the z-pinch to remain stable. The flow of the injected gas 130 has a sheared flow velocity profile in the sense that the gas 130 flows at different velocity at the immediate edge of the z-pinch 116 than it does at radial distances farther from the z-pinch 116. In some examples, the z-pinch is stabilized during the duration of the single use (e.g., during the duration of the pulse described above). In some examples, the injected gas 130 fuels the z-pinch. In some implementations in which the injected gas 130 fuels the z-pinch, the gas 130 corresponds to or is formed of the same gas or gases that form the neutron-producing fuel 106. Application of the high voltage differential once the plasma 114 is formed causes the plasma 114 to experience heating. For example, the plasma pinch 116 progresses through stages in which different heating mechanics dominate. For example, the plasma pinch 116 may experience predominantly Ohmic heating during a first time period, predominantly adiabatic compression heating during a second time period, and predominantly alpha particle heating during a third time period. Particles within the plasma pinch 116 undergo neutronic fusion reactions (e.g., thermonuclear neutronic fusion reactions) when a temperature of the plasma pinch 116 is sufficiently high. In some examples, the neutronic fusion reactions release, produce, radiate, propagate, or generate neutrons N at a rate between 10{circumflex over ( )}19 neutrons per second and 10{circumflex over ( )}23 (or more) neutrons per second. The single-use neutron generator 100 of FIGS. 1A and 1B additionally includes a neutron modifying medium 145. In some examples, the neutron modifying medium 145 corresponds to a medium that increases a number of the neutrons N released, produced, radiated, propagated, or generated by the single-use neutron generator 100. In some implementations, the neutron modifying medium 145 corresponds to a medium that breeds (e.g., emits or releases) at least one gas of the neutron-producing fuel 106 when the neutron modifying medium 145 is struck by a neutron of the neutrons N. Thus, in these examples, the neutron modifying medium 145 increases the number of the neutrons N released, produced, propagated, or generated by the plasma pinch 116 as compared to the number of the neutrons N released, produced, propagated, or generated by the plasma pinch 116 when the single-use neutron generator 100 does not include the neutron modifying medium 145. As another example, in some implementations, the neutron modifying medium 145 corresponds to a neutron doubler that doubles each neutron of the neutrons N that strikes the neutron modifying medium 145. In these examples, the neutron modifying medium 145 causes the single-use neutron generator 100 to produce, propagate, or generate Y neutrons, where Y is greater than a number of the neutrons N released, produced, propagated, or generated by particles of the plasma pinch 116 that undergo a thermonuclear fusion reaction. In some examples, the neutron modifying medium 145 is formed of or includes lithium. In some examples, the neutron modifying medium 145 is embodied as a liner 147 (e.g., a neutron enhancing liner 147) that is disposed within the outer electrode 110 (e.g., that is disposed on an inner surface of the outer electrode 110), outside of the outer electrode 110 (e.g., on an outer surface of the outer electrode 110 or other surface of the plasma confinement device 104), or both. In some examples, the number of neutrons released, produced, radiated, propagated, or generated by the single-use neutron generator 100 is sufficient to make the single-use neutron generator 100 suitable to destroy or disable chemical, biological, or radiological weapons. At least one component (e.g., 108, 110, or 112) of the single-use neutron generator 100 is configured for single use, i.e. the neutron generator 100 is disposable or is self-destructive. In some examples, the at least one component includes the inner electrode 108 or the outer electrode 110. In these examples, the power supply 112 may be configured to apply an amount of power to the inner electrode 108 and to the outer electrode 110 that exceeds an operational tolerance of at least one of the inner electrode 108 or the outer electrode 110. An amount of power applied to the inner electrode 108 and to the outer electrode 110 exceeds an operational tolerance of at least one of the inner electrode 108 or the outer electrode 110 when application of the amount of power for the duration of the pulse is sufficient to damage, destroy, or disable (e.g., beyond repair) at least one of the inner electrode 108 or the outer electrode 110. In this example, the single-use neutron generator 100 is configured for single use because the single use damages (e.g., melts) at least a portion of at least one of the inner electrode 108 or the outer electrode 110. In other examples, the at least one component includes the power supply 112 or power transmission components. In these examples, the single-use neutron generator 100 is configured for single use in the sense that providing the power to the plasma confinement device 104 during the single use will damage, disable, or destroy the power supply 112 or power transmission components [not illustrated]. In some examples, the single-use neutron generator 100 is configured such that the power supply 112 or power transmission components and at least one of the inner electrode 108 and the outer electrode 110 are damaged, destroyed, or disabled based on application of or supplying the power to the plasma confinement device 104. In some implementations, the power supply 112 is configured to apply or supply power to the plasma confinement device 104 using the pulse described above (e.g., a pulse of approximately one second (or more) duration), and application or supply of the power during the pulse is sufficient to melt at least a portion of at least one of the inner electrode 108 or the outer electrode 110, to damage or disable the power supply 112 or power transmission components [not illustrated] of the power supply 112, or a combination thereof. FIGS. 2A-2C illustrate block diagrams of an example of various stages of a single-use neutron generator 200 during generation of neutrons using a plasma pinch that is generated using a fuel source 202 (e.g., a solid fuel source). The single-use neutron generator 200 includes at least one component that is configured for single use as described in more detail below. The single-use neutron generator 200 includes the housing 148 to house the fuel source 202, the power supply 112, and a plasma confinement device 104. The fuel source 202, the power supply 112, the plasma confinement device 104, and the housing 148 are configured to be compact so that the single-use neutron generator 200 is a vehicle-deliverable package. The fuel source 202 is disposed within the plasma confinement device 104. The fuel source 202 is configured to provide the neutron-producing fuel 106 responsive to current flow through the fuel source 202 as described in more detail below. In some examples, the fuel source 202 is a wire (e.g., a thin wire). In other examples, the fuel source 202 is an array of wires. The plasma confinement device 104 includes the inner electrode 108 and the outer electrode 110. The inner electrode 108 is located within the interior 140 of the outer electrode 110. The fuel source 202 is electrically coupled to the inner electrode 108. The power supply 112 is coupled to the outer electrode 110 and to the inner electrode 108. During operation, the power supply 112 is activated, causing the power supply 112 to apply a high voltage differential across the outer electrode 110 and the inner electrode 108. The high voltage differential results in a current flow along the fuel source 202 (e.g., along the wire or the wire array). The current flow along the fuel source 202 causes at least a portion of the fuel source 202 (e.g., at least a portion of the wire or the wire array) to vaporize into the neutron-producing fuel 106 of FIG. 2B and to ionize into the plasma 114 of FIG. 2C as described above with reference to FIG. 1B. Current flowing through the plasma 114 creates a magnetic field 122 within the plasma confinement device 104 that squeezes or compresses portions of the plasma 114 to form the plasma pinch 116 as described above with reference to FIG. 1B. In some examples, the plasma pinch 116 corresponds to a sheared-flow stabilized z-pinch as described above. In these examples, the single-use neutron generator 200 includes the flow stabilizing gas source 153 coupled to the plasma confinement device 104. The single-use neutron generator 200 is configured to inject the gas 130 (e.g., a neutral gas) from the flow stabilizing gas source 153 into the interior 140 of the outer electrode 110. Flow of the injected gas 130 proximate to the z-pinch stabilizes the z-pinch without using close fitting walls or axial magnetic fields, thereby enabling the z-pinch to remain stable. In some examples, the z-pinch is stabilized during the duration of the single use (e.g., during the duration of the pulse described above). In some examples, the injected gas 130 fuels the z-pinch. In some implementations in which the injected gas 130 fuels the z-pinch, the gas 130 corresponds to or is formed of the same gas or gases that form the neutron-producing fuel 106. Application of the high voltage differential after the plasma 114 is formed causes the plasma 114 to experience heating. For example, the plasma pinch 116 progresses through stages in which different heating mechanics dominate and in which neutrons are generated by neutronic fusion (e.g., thermonuclear fusion) as described above with references to FIGS. 1A and 1B. In some examples, the neutronic fusion reactions release, produce, radiate, propagate, or generate neutrons at a rate greater than 10{circumflex over ( )}19 neutrons per second. In some examples, the neutronic fusion reactions release, produce, radiate, propagate, or generate neutrons at a rate greater than 10{circumflex over ( )}23 neutrons per second. The single-use neutron generator 200 of FIGS. 2A, 2B, and 2C additionally includes the neutron modifying medium 145 described above with reference to FIGS. 1A and 1B. As described above with reference to FIGS. 1A and 1B, the neutron modifying medium 145 interacts with the neutrons N to provide additional fuel to the plasma pinch 116 or to double the neutrons N that are incident on the neutron modifying medium 145. In one aspect, FIG. 3 shows an example of a timing diagram during which the voltage differential described above with reference to FIGS. 1A and 1B is applied to the inner and outer electrodes 108 and 110, respectively, of the plasma confinement device 104 of FIGS. 1A and 1B. In this aspect, the timing diagram of FIG. 3 illustrates a time period beginning subsequent to or concurrent with injection of the neutron-producing fuel 106 into the interior 140 of the outer electrode 110. In the example illustrated in FIG. 3, the voltage differential is applied to the inner electrode 108 and the outer electrode 110 at T0. The voltage remains applied until T6 (represented by time period 302). Additionally the neutron-producing fuel 106 is injected into the outer electrode 110 at or prior to T0 (e.g, prior to a beginning of the time period 302). At time T1, the plasma pinch 116 forms within the outer electrode 110 as described above with reference to FIGS. 1A, 1B, and 1C. The elapsed time between the application of the voltage at T0 and formation of the plasma pinch 116 at T1 is represented by the time period 304 The plasma pinch 116 is maintained until time T5 (e.g., is maintained for a period of time 305). In some examples, the gas 130 is injected into the outer electrode 110 during the time period 305 to achieve shear flow stabilization of the plasma pinch 116. In some examples, the plasma pinch 116 is maintained for greater than one second (e.g., when the pulse described above is longer than one second). From time T1 to T2, (e.g., during a time period 306 of the pulse described above), the plasma pinch 116 experiences primarily Ohmic heating due to a relatively low temperature (e.g., relatively high resistance). From time T2 to T3, (e.g., during a time period 308 of the pulse described above), heating due to adiabatic compression of the plasma 114 causes the plasma pinch 116 to heat to a greater temperature than would be possible based on Ohmic heating alone. At time T3, the plasma pinch 116 reaches a sufficient temperature to cause particles within the plasma pinch 116 to experience thermonuclear fusion. Thermonuclear fusion of particles within the plasma pinch 116 continues until time T5 (e.g., thermonuclear reaction occurs during the time period 312). Between a time T4 and a time T5 (e.g., during the time period 310), the plasma pinch 116 experiences alpha particle heating and thermonuclear fusion reaction of particles within the plasma pinch 116 continues. At a beginning T5 of a time period 314, at least one component of the single-use neutron generator 100 experiences sufficient damage that prevents proper operation of the single-use neutron generator 100. Due to the damage, the single-use neutron generator 100 is unable to maintain the plasma pinch 116 and thus produce the neutrons N for the remainder of the pulse (e.g., for the time period 314) and thereafter. At a time T6, the single-use neutron generator 100 is damaged beyond repair. In another aspect, the timing diagram of FIG. 3 shows an example of a timing diagram during which the voltage differential described above with reference to FIGS. 2A 2B, and 2C is applied to the inner and outer electrodes 108 and 110, respectively, of the plasma confinement device 104 of FIGS. 2A, 2B, and 2C. In this aspect, the timing diagram of FIG. 3 illustrates a time period 302 during which the voltage differential described above with reference to FIGS. 2A, 2B, and 2C is applied. In the example illustrated in FIG. 3, the voltage differential is applied to the inner electrode 108 and the outer electrode 110 at T0. The voltage remains applied until T6 (represented by the time period 302). Between the time T0 and the time T1 (e.g., during the period of time 304), at least a portion of the fuel source 202 (e.g., the wire or the array of wires) vaporizes into the neutron-producing fuel 106. At time T1, the neutron-producing fuel 106 ionizes to form the plasma pinch 116 within the outer electrode 110 as described above with reference to FIGS. 2A, 2B, and 2C. The elapsed time between the application of the voltage at T0 and formation of the plasma pinch at T1 is represented by the period 304. The plasma pinch 116 is maintained until time T5 (e.g., is maintained for a period of time 305). In some examples, the gas 130 is injected into the outer electrode 110 during the time period 305 to achieve shear stabilization of the plasma pinch 116. In some examples, the plasma pinch 116 is maintained for approximately one second. From time T1 to T2, (e.g., during a time period 306 of the pulse described above), the plasma pinch 116 experiences primarily Ohmic heating due to a relatively low temperature (e.g., relatively high resistance). From time T2 to T4, (e.g., during a time period 308 of the pulse described above), heating due to adiabatic compression of the plasma 114 causes the plasma pinch 116 to heat to a greater temperature than would be possible based on Ohmic heating alone. At time T3, the plasma pinch 116 reaches a sufficient temperature to cause particles within the plasma pinch 116 to experience thermonuclear fusion. Thermonuclear fusion of particles within the plasma pinch 116 continues until time T5 (e.g., thermonuclear reaction occurs during the time period 312). Between a time T4 and a time T5 (e.g., during the time period 310), the plasma pinch 116 experiences alpha particle heating and thermonuclear fusion reaction of particles within the plasma pinch 116 continues. At a beginning T5 of the time period 314, at least one component of the single-use neutron generator 200 experiences sufficient damage that prevents proper operation of the single-use neutron generator 200. Due to the damage, the single-use neutron generator 200 is unable to maintain the plasma pinch 116 and thus produce the neutrons N for the remainder of the pulse (e.g., for the time period 314) and thereafter. At time T6, the single-use neutron generator 200 is damaged beyond repair. FIG. 4 illustrates a method 400 of generating neutrons. In some implementations, the method 400 of FIG. 4 is performed by the single-use neutron generator 100 of FIGS. 1A and 1B or the single-use neutron generator 200 of FIGS. 2A, 2B, and 2C. The method 400 of FIG. 4 includes, at 402, providing neutron-producing fuel within an interior of a plasma confinement device of a neutron generator (e.g., a single-use neutron generator). The neutron-producing fuel corresponds to the neutron-producing fuel 106 described above with reference to FIGS. 1A, 1B, 2A, 2B, and 2C, and the plasma confinement device corresponds to the plasma confinement device 104 of FIGS. 1A and 1B or to the plasma confinement device 104 of FIGS. 2A, 2B, and 2C. The neutron-producing fuel 106 is provided by a fuel source, such as the fuel source 102 of FIGS. 1A and 1B or the fuel source 202 of FIGS. 2A and 2B. In some examples, such as when the fuel source corresponds to stored neutron-producing fuel, the neutron-producing fuel is provided within the interior of the plasma confinement device by injecting the neutron-producing fuel into an interior of an outer electrode of the plasma confinement device as described above with reference to FIGS. 1A and 1B. The neutron-producing fuel is injected into the plasma confinement device using or more manifolds, ports and/or valves [not illustrated]. In other examples, such as when the fuel source corresponds to a wire or an array of wires, the neutron-producing fuel is provided within the interior of the plasma confinement device by vaporizing at least a portion of the fuel source. For example, as described above, the fuel source (e.g., the wire or the wire array) is at least partially vaporized responsive to current flow along the fuel source. The current flow is responsive to application of power from a power supply (e.g., the power supply 112 of FIGS. 1A, 1B, and 1C) to the plasma confinement device (e.g., to the inner and outer electrodes 108 and 110 of FIGS. 1A, 1B, and 1C. Thus, the neutron-producing fuel is provided within the interior of the plasma confinement device by injection of neutron-producing fuel into the interior of the plasma confinement device or by vaporizing a solid fuel source that is located within the plasma confinement device. The method 400 of FIG. 4 additionally includes, at 404, applying power to the plasma confinement device to produce neutrons by generating a plasma pinch of the neutron-producing fuel within the plasma confinement device. In some examples, the power is applied by the power supply 112 as described above with reference to FIGS. 1A, 1B, 2A, 2B, 2C, and 3. In some examples, the power is applied using a single pulse as described above with reference to FIGS. 1A, 1B, 2A, 2B, 2C, and 3. In some examples, the single pulse is approximately one second. The plasma pinch corresponds to the plasma pinch described above with reference to FIGS. 1A, 1B, 2A, 2B, and 2C and neutrons are produced by thermonuclear reaction of particles within the plasma pinch as described above with reference to FIGS. 1A, 1B, 2A, 2B, 2C and 3. In some examples, the neutrons are produced at a rate greater than 10{circumflex over ( )}19 neutrons per second. In some examples, the neutronic fusion reactions release, produce, radiate, propagate, or generate neutrons at a rate greater than 10{circumflex over ( )}23 neutrons per second. The power (applied or supplied to the plasma confinement device) exceeds an operational tolerance of at least one component of the neutron generator. The power exceeds an operational tolerance of the at least one component of the neutron generator when supplying, generation of, or application of the power damages, destroys, or disables the at least one component. In some examples, the power exceeds the operational tolerance of the at least one component when supplying, generation of, or application of the power damages, destroys, or disables the at least one component beyond repair. In some examples, the at least one component includes the power supply 112 or power transmission components, the inner electrode 108 of the plasma confinement device, the outer electrode 110 of the plasma confinement device, or a combination thereof as described above. Because the power applied exceeds the operational tolerance of the at least one component, application of the power will damage, destroy, or disable the at least one component. For example, application of the power from the power supply 112 may melt at least a portion of at least one of the inner electrode 108 or the outer electrode 110. As another example, application of the power to the plasma confinement device 104 may damage or destroy the power supply 112 or power transmission components (e.g., renders the power supply 112 inoperable). The plasma pinch experiences sufficient heating to cause particles of the plasma pinch to undergo a thermonuclear fusion reaction, thereby releasing, producing, radiating, propagating, or generating neutrons. Thus, at least some neutrons are released by particles of the plasma pinch that undergo thermonuclear fusion. In some examples, the neutrons are released, produced, radiated, propagated, or generated at a rate greater than 10{circumflex over ( )}19 neutrons per second. In some examples, the neutronic fusion reactions release, produce, radiate, propagate, or generate neutrons at a rate greater than 10{circumflex over ( )}23 neutrons per second. In some examples, the method 400 additionally includes increasing a number of neutrons released by the single-use neutron generator using a neutron enhancing liner 147 disposed within an outer electrode of the plasma confinement device as described above with reference to FIGS. 1A, 1B, 2A, 2B, and 2C. The illustrations of the examples described herein are intended to provide a general understanding of the structure of the various embodiments. The illustrations are not intended to serve as a complete description of all of the elements and features of apparatus and systems that utilize the structures or methods described herein. Many other embodiments may be apparent to those of skill in the art upon reviewing the disclosure. Other embodiments may be utilized and derived from the disclosure, such that structural and logical substitutions and changes may be made without departing from the scope of the disclosure. For example, method steps may be performed in a different order than shown in the figures or one or more method steps may be omitted. Accordingly, the disclosure and the figures are to be regarded as illustrative rather than restrictive. Moreover, although specific examples have been illustrated and described herein, it should be appreciated that any subsequent arrangement designed to achieve the same or similar results may be substituted for the specific embodiments shown. This disclosure is intended to cover any and all subsequent adaptations or variations of various embodiments. Combinations of the above embodiments, and other embodiments not specifically described herein, will be apparent to those of skill in the art upon reviewing the description. The Abstract of the Disclosure is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. In addition, in the foregoing Detailed Description, various features may be grouped together or described in a single embodiment for the purpose of streamlining the disclosure. As the following claims reflect, the claimed subject matter may be directed to less than all of the features of any of the disclosed examples. Examples described above illustrate but do not limit the disclosure. It should also be understood that numerous modifications and variations are possible in accordance with the principles of the present disclosure. Accordingly, the scope of the disclosure is defined by the following claims and their equivalents.
	description	The present application is a continuation application of U.S. patent application Ser. No. 10/614,425, filed Jul. 7, 2003, now U.S. Pat. No. 6,861,649,entitled, “BALANCED MOMENTUM PROBE HOLDER,” which is a continuation of U.S. patent application Ser. No. 09/766,555, filed Jan. 19, 2001, now U.S. Pat. No. 6,590,208 entitled, “BALANCED MOMENTUM PROBE HOLDER,” the disclosures of which are incorporated herein in their entirety. The present invention is generally directed to a balanced momentum probe holder for use in metrology systems, especially scanning probe microscopes used to measure sample surfaces down to the nanometer level. Specifically, the invention is directed to such systems employing nested-Z and non-nested parallel feedback loops, to achieve rapid, and highly accurate scanning of a sample surface. The invention also relates to methods of using such a probe holder in such systems. The ongoing miniaturization of components of a variety of devices makes high-resolution characterization of critical surfaces increasingly important. In the field of metrology, for example, surface-characterization devices such as stylus profilers and scanning probe microscopes (SPM) are routinely used to measure topography and other characteristics of critical samples. Stylus profilers and scanning probe microscopes are in fact frequently used as inspection tools to measure the critical surfaces of industrial devices like semiconductor chips and data storage devices during and after the manufacturing process. To be economically feasible, these profilers and scanning probe microscopes must complete their measurements as quickly, accurately, repeatably and as reliably as possible. The accuracy, precision, reproducibility, and reliability of such metrology instruments are especially critical in view of the ongoing desire that such surface-characterization instruments be capable of quickly and accurately characterizing dimensions smaller than those of the products and devices being fabricated, to assure manufacturing quality, and to provide accurate diagnoses of manufacturing problems. Because critical features continue to shrink in the manufacturing process, it is necessary to improve the accuracy and the speed of scanning probe microscopes and stylus profilers to keep up with the measurement demand. For the sake of convenience, the discussion that follows and throughout this patent specification will focus on Atomic Force Microscopes (AFMs). In this regard, it shall be understood that problems addressed and solutions presented by the present invention shall also be applicable to problems experienced by other measurement instruments including surface-modification instruments and micro-actuated devices. The typical AFM includes a probe which includes a flexible cantilever and a stylus mounted on the free end of the cantilever. The probe is mounted on a scanning stage that is typically mounted on a common support structure with the sample. A typical scanning stage may include an XY actuator assembly and a Z actuator, wherein “X” and “Y” represent what is typically the horizontal XY plane, and “Z” represents the vertical direction. “X” and “Y” and “Z” are mutually orthogonal directions. The XY actuator assembly drives the probe to move in an X-Y plane for scanning. The typical Z actuator mounted on the XY actuator and providing support for the probe, thus drives the probe to move along a Z axis which is disposed orthogonally relative to the X-Y plane. (The definition of the XYZ axes is convenient and typical, but the choice of axis name and orientation is of course arbitrary.) AFMs can be operated in different sample-characterization modes including contact-mode and Tapping™ mode. In contact-mode, the cantilever stylus is placed in contact with the sample surface, cantilever deflection is monitored as the stylus is scanned over the sample surface, and the resulting image is a topographical map of the surface of the sample. In Tapping™ mode (a trademark of Veeco Instruments, Inc.) sample characterization, the cantilever is oscillated mechanically at or near its resonant frequency so the stylus repeatedly taps the sample surface or otherwise interacts with the sample. See, e.g., U.S. Pat. Nos. 5,266,801; 5,412,980; and 5,519,212 to Elings et al., which are illustrative. In either sample-characterization mode, the interaction between the stylus and the sample surface induces a discernable effect on a probe-based operational parameter, such as the cantilever deflection oscillation amplitude, the phase or the frequency, all of which are detectable by a sensor. In this regard, the resultant sensor-generated signal is used as a feedback control signal for the Z actuator to maintain a designated probe operational parameter constant. In contact-mode, the designated parameter may be cantilever deflection. In Tapping™ mode, the designated parameter may be oscillation amplitude, phase or frequency. The feedback signal also provides a measurement of the surface characteristic of interest. For example, in Tapping™ mode, the feedback signal may be used to maintain the amplitude of cantilever oscillation constant to measure the height of the sample surface or other sample characteristics. In analyzing biological samples, polymers, photoresist, metals and insulators, thin films, silicon wafer surfaces, and other surfaces, the ability to accurately characterize a sample surface is often limited by the present ability of an AFM to move the stylus vertically relative to the surface at a rate sufficient to accurately measure the surface while scanning in either the X or Y direction. This ability is inadequate in present day devices for essentially two reasons. In order to accurately measure the height of all features, both large and small, on a sample surface, the Z actuator must have the ability to displace the stylus connected thereto over a large range of heights, i.e., it must have large vertical travel. This necessitates that the Z actuator, whether it is a scanning tube such as is on this assignee's Dimension series AFM heads or is a flexure such as is on this assignee's Metrology series AFM heads, must be large enough to move the stylus up and down sufficiently to measure even the largest surface features. Unfortunately, a necessary by-product of a larger Z actuator having greater range is associated greater mass which makes the actuator movement relatively slow. Slow actuators are not able to move the probe rapidly enough in Z while scanning in X or Y at anything more than modest speed without damaging the probe or sample or without sacrificing measurement accuracy. Because it is important while scanning to minimize the force of the stylus on the sample to prevent damage to the stylus and/or sample, the scan rate in X or Y must, of necessity, be reduced to a speed compatible with the Z actuator's ability to move the stylus up and over surface features without slamming into them, which is obviously undesirable. One present day technique to overcome this limitation and increase responsiveness of the Z-actuator is to increase the gain of its feedback loop. This works only to a limited degree because if the gain is increased more than a modest amount, the Z actuator begins to resonate and that resonance is passed into the AFM, creating parasitic oscillations, which in turn ruin image quality. In essence, a large mass, large displacement Z actuator cannot be made to overcome its inherent physical limitations. In another approach, one does not attempt to wring more performance from the large Z actuator than it is inherently able to deliver. Instead, a separate “fast” Z actuator is used, with its own feedback loop, to move the stylus quickly over small surface variations that the large Z actuator is too slow to react to, which enables one to obtain relatively high quality imaging at even high scan speeds. The fast Z actuator is smaller than and hence of significantly smaller mass than the slow Z actuator. As a result, it is advantageously driven in its own (or shared) fast feedback loop at speeds exceeding that of the slow Z actuator. Unfortunately, at high gain, the high speed of operation and momentum of the fast Z actuator can similarly cause parasitic oscillations which reduce image quality. A device and method which balances these inertial forces created by a fast Z actuator would be of great benefit and commercial interest. It is an object of the present invention to provide a novel balanced momentum probe holder for scanning probe microscopes and/or stylus profilers that permits the probe to measure the height of small surface features better than is presently possible with commercially available tools. It is specifically an object to provide such a probe holder for an improved atomic force microscope (AFM). Another object of the present invention is to provide a novel AFM that permits more accurate imaging of surface features at high scan rates. Still another object of this invention is to provide an AFM that can measure surface features at high scan rates without inducing parasitic oscillations in the AFM. A further object of this invention is to balance the momentum created by the fast Z actuator in an AFM to allow fast actuation without driving parasitic oscillations. Yet another object of this invention is to provide a fast actuator of sufficiently low mass to allow its use on the lower end of a scanning stylist AFM. Yet a further object of this invention is to provide an AFM with fast actuation optimized for operation in nested or parallel feedback loops. These and other objects are achieved according to the present invention by providing a new and improved AFM having a probe holder that includes a separate, fast Z actuator assembly operated in a fast feedback loop and that balances the momentum of the fast Z actuator assembly. The basic idea is to balance the momentum of the moving probe holder with the momentum of a counterbalance moving in synchronization with the probe holder, but in the opposite direction. In this case, the net momentum of the fast Z-actuator assembly is essentially zero, and thus the motion of the probe does not substantially excite parasitic resonances of the supporting structure and/or XYZ scan assembly. The fast Z actuator assembly is also of low mass and is therefore able to displace the probe in the Z direction more rapidly than a larger, higher mass conventional Z actuator which is part of the piezo tube or the flexure upon which the fast Z actuator assembly is mounted. In order to take advantage of the small size and low mass of the fast Z actuator assembly, it is operated in a fast feedback loop, either nested with the feedback loop of the conventional Z actuator or in a parallel feedback loop. The combination of a low mass fast Z-actuator and the balanced momentum enables extremely accurate scanning of even the smallest surface features and even at high scan speeds where conventional Z actuators perform sluggishly. The present invention, then, is generally directed to an apparatus having a probe for characterizing a surface of a sample. The apparatus may have an X actuator, a Y actuator and a first Z actuator as in an AFM but may also have only a Z actuator such as in a profilometer. The apparatus also has a second Z actuator assembly with the probe mounted on it. The second Z actuator assembly is coupled to the first Z actuator. The second Z actuator assembly is less massive and therefore quicker responding than the first Z actuator. When actuated to move the probe, the momentum of the second Z actuator assembly is balanced so that its motion does not transmit substantial vibration to other actuators or support members. The fast Z actuator assembly comprises first and second fast Z-actuators, sometimes referred to herein as the bottom actuator and the top actuator, respectively. The two actuators are arranged so that the fixed ends are attached to a common central support. Then the top end of the top actuator and the bottom end of the bottom actuator are both free to move. The measurement probe, for example an AFM cantilever probe, is attached directly or through intermediate mounting to the bottom or distal end of the bottom actuator which is proximate the sample. A counterbalance mass is attached to the top or distal end of the top actuator. The top and bottom fast Z-actuators are arranged so that they move in a synchronized manner, but in opposite directions. The probe mount, actuators, and counterbalance mass are arranged to match the momentum carried by the top and bottom actuators. In the simplest case, the mass of the top actuator is the same as the mass of the bottom actuator and the mass of the counterbalance mass matches the mass of the probe mount. Then the two actuators are arranged to move substantially the same distance (in opposite directions) at the same time. Since the motions are the same but opposite and the masses are matched, the net momentum is essentially zero, thus transmitting no vibration to surrounding members. In more complicated arrangements, the momentum can be matched by arranging a top actuator with say half the motion of the bottom actuator, but twice the moving mass, or suitable variations thereof that match combinations of velocity and mass of the top and bottom fast Z-actuators. In one embodiment, the first, bottom actuator includes a first piezo stack disposed between the common central support and the probe mount assembly, and the second, top actuator includes a second piezo stack disposed between the counterbalance and the common central support. In yet another embodiment, the balanced momentum probe holder is incorporated into a nested feedback control system. In still another embodiment, the balanced momentum probe holder is incorporated into a non-nested parallel feedback control system. In both feedback systems, when an error signal to move the probe vertically is sent to the fast Z actuator assembly, the first piezo stack extends or retracts to move the probe to the desired height while, simultaneously, the second piezo stack extends or retracts also. The momentum of the second piezo stack and its associated components balances the momentum of the first piezo stack and associated components including the probe. As a result, the net momentum, and therefore the net force acting upon the larger system is eliminated, thereby eliminating or substantially reducing parasitic oscillations. In a nested feedback control system, the error signal is processed by a control device such as a PID controller and sent to the fast Z actuator assembly to cause it to move the probe. Any residual error signal is sent to the slow Z actuator assembly to cause it to move the probe an additional amount needed. In this way, the probe is able to track, and therefore measure the height of surface features that are quite small, even at high scan speeds, while also being able to measure larger surface features as well. Throughout the drawings, like reference numerals refer to like parts. As suggested above, sample surfaces may be characterized by using probe-based instruments such as scanning probe microscopes, stylus profilers, or any other instrument capable of obtaining, recording, and manipulating sample surface information. While all of these applications are within the scope of the present invention, the preferred embodiment describes the invention as included in an Atomic Force Microscope (AFM) but does not exclude other SPMs. An AFM-based system which incorporates the balanced momentum probe holder of the present invention and which is capable of acquiring sample surface data, recording the surface data, and manipulating the data to perform desired tasks is schematically illustrated in FIG. 1. The AFM-based system (FIG. 1) includes an XYZ actuator 100 to which a cantilever arm 102 is operatively connected. A stylus 104 is mounted on the other end of the cantilever 102 for characterizing a surface 106 of a sample 108 releasably affixed to chuck 110. A displacement sensor 112 detects movement of the stylus 104 above the surface 106 and provides a signal that is related to a measured property of the sample surface, for example the shape of the sample surface. The output of the displacement sensor is sent to an AFM control/computer system 116 as is well known in the art. The control system 116 outputs scan and control signals to the XYZ actuator 100. AFMs are usually operated in a mode that attempts to maintain (and often minimize) a constant tracking force between the stylus 104 and the sample surface 106. This is usually accomplished by arranging a feedback loop to keep the output of the displacement sensor constant as the XYZ actuator scans the probe, and therefore the stylus, over an area of interest on the sample surface. To maintain the constant tracking force, the Z portion of the XYZ actuator 100 is raised up and down. In the current invention, this vertical motion is accomplished by either the Z portion of the XYZ actuator or the balanced momentum probe holder 114, or both, by raising or lowering the stylus 104 relative to the sample surface 106. The displacement sensor 112 includes a laser and a photodetector, both of which will be discussed in detail below in connection with FIGS. 8 and 9. Signals from the displacement sensor 112 may, for example, be used to determine the deflection, oscillation amplitude, frequency, or phase or similar parameter of the cantilever 102 and stylus 104 when they are moving in proximity or in contact with the sample surface 106. An image display device 118, operatively connected to the personal computer 116, is able to display video images in response to a signal from the personal computer 116. The computer also typically stores the sample images for later viewing and analysis. FIG. 2 is a side view illustrating the balanced momentum probe holder 114 of the present invention mounted on the XYZ actuator 100, in the form of a scanning tube as is referred to by this assignee as a Dimension tube scanner. The XYZ actuator 100 is a standard piezo tube scanner and includes a conventional XY actuator 120 consisting of cylindrical X and Y piezo elements and a Z actuator 122 consisting of a cylindrical Z piezo element. XY actuator 120 is adapted to move the stylus 104 relative to the sample surface 106 in the “X” and “Y” directions. Z actuator 122 is adapted to move the stylus 104 relative to the sample surface 106 in the “Z” (i.e., height) direction. The balanced momentum probe holder 114 is mounted on the lower end of Z actuator 122. FIG. 3 is a schematic of another embodiment of an XYZ actuator 100A, in the form of a flexure, referred to by this assignee as a Dimension Metrology scanner with which the inventive probe holder 114 may be used. Components of a preferred embodiment of XY actuator 120A include an X actuator 124 and a Y actuator 126. A Z actuator 122A is mounted on Y actuator 126, Y actuator 126 is mounted on X actuator 124, and X actuator 124 is mounted on a connector 128, for connecting the XYZ actuators 124, 126, and 122A to an apparatus for characterizing a surface of a sample. The balanced momentum probe holder 114 is mounted on the lower end of the Z actuator 122A. Each of the X, Y and Z actuators 124, 126, and 122A includes a respective piezo element or stack 130, 132, 134 mounted within respective flexures for moving the probe holder 114 relative to the sample surface as is standard. For this purpose, the X direction actuator piezo stack 130 and the Y direction actuator piezo stack 132, are each diagonally mounted respectively within their X, Y flexures 124, 126 while the Z direction piezo stack 134 is mounted in the Z direction within its flexure 122A as shown. In operation, a respective piezo element or stack 130, 132, 134 is energized, causing such piezo stack 130, 132 and/or 134 to expand or contract, bending its respective flexures for moving the balanced momentum probe holder 114 relative to the surface 106 of the sample 108. FIGS. 4 and 5 depict the Z actuator 122 of the piezo tube scanner as an elongated, hollow tube of conventional Z piezo material. A lower end portion 136 of the Z actuator 122 includes a plurality of pins 138 extending away from the end portion 136 of the Z actuator 122. The novel balanced momentum probe holder 114 includes a base or holder 140 which defines a corresponding plurality of apertures, or sockets, 142 dimensioned for receiving the pins 138 and for operatively connecting the Z actuator 122 and the base 140 together. Further in this regard and referring to FIG. 5, the base 140 defines a central, open portion 172 through which other components 146, 154 (described in detail below) of the probe holder 114 pass. Still further, the end portion 136 of the Z actuator 122 preferably includes a corresponding central, open portion 174 into which the probe holder 114 is disposed when actuator 100 is joined to the balanced momentum holder 114, as shown in FIG. 5. FIGS. 6 and 7 are exploded perspective views, based on FIGS. 2 and 4, and on an enlarged scale relative thereto, presenting a preferred embodiment of the balanced momentum probe holder of the present invention. The illustrated embodiment of the balanced momentum probe holder 114A of the present invention comprises the holder or base 140 (FIG. 5) connected to the actuator 100, and a common central support 144 connected to the holder or base 140. The base or holder 140 is not shown in FIG. 6 for purposes of clearly presenting the remainder of the components or elements of the first preferred embodiment of the balanced momentum probe holder 114 of the present invention. The balanced momentum probe holder 114A further comprises a first member 146 which preferably comprises a piezo stack 147. The first member 146 is carried by the common central support 144, in a central recessed portion 145 of the support. The first piezo stack 147 has a distal end 148 disposed toward the sample and which is extensible and retractable in the Z axis. The probe holder 114A further comprises a second member 150 which also preferably comprises a piezo stack 151. The second member 150 is carried on the opposite side 145′ of the common central support 144. The second piezo stack 151 has a free end 152 disposed away from the sample and which is extensible and retractable in the Z direction. First and second member 146 and 150 may alternatively comprise other piezo actuators such as piezo electric tubes or piezo electric bimorphs. First and second members 146, 150 may also comprise voice coil actuators, electrostatic actuators, electrorestrictive actuators or magnetorestrictive actuators, or other suitable actuators. The first and second actuator assemblies 146 and 150 each has a mass that is selected to provide minimal weight to the probe holder 114A yet achieve the desired sample surface characterization effect. In operation, the free ends 148 and 152 of the first and second actuator assemblies 146 and 150 either both extend or both retract synchronously in response to a signal from a detector, as is described in detail below. Moreover, in the preferred embodiment, the masses of the first and second actuator assemblies 146 and 150 are substantially equal, to balance the momentum of the piezo stacks 147 and 151 during operation of the balanced momentum probe holder 114A during surface characterization of a sample 108. In an alternate embodiment, the mass of the actuator assemblies can be different if the range of travel of the two actuators is different. For example, the upper actuator assembly 150 may have twice the mass of the lower actuator assembly 146 if the upper actuator assembly is arranged to move half the distance of the lower actuator assembly. Other effective combinations having matched mass times velocity products may be used as appropriate. Probe holder 114A further comprises a probe mount assembly 154 carried by the free end 148 of the lower actuator assembly 146. Probe mount assembly 154 comprises a probe mount 156 and a cantilever probe 158 carried by the mount 156, consisting of a cantilever substrate 160, and a cantilever arm 102 carried by the cantilever substrate, and disposed toward the sample. The cantilever probe 158 includes the cantilever arm 102 and stylus 104 (not shown), both of which are depicted in FIG. 1. Probe holder 114A further comprises a counterbalance 162 carried by the distal end 152 of the second member 150. The mount assembly 154 and counterbalance 162 have substantially equal masses or as indicated above are chosen to ensure that the momentums of the first and second actuator assemblies are balanced. When assembled, alumina insulating layers (not shown) may be placed between common central support 144 and the first piezo stack 147, between the common central support 144 and the second piezo stack 151, and between the first piezo stack 147 and the probe mount 156. The insulating layers are not necessary especially if the common central support is nonconducting. In operation, when activated by a Z actuation signal, each of the first and second piezo stacks 147, 151 will extend or retract in the Z direction (up or down by the conventional orientation and as oriented in the figures.) Further, the first and second piezo stacks 147, 151 are driven in opposite directions. This can be accomplished by orienting the piezo stacks so that the same control signal will cause them to move in opposite directions or by opposing control signals to two stacks that are oriented with the piezo polarity in the same direction. It may also be desirable to scale the control voltages going to each piezo stack to account for any difference in sensitivity (and therefore response) between the two piezo stacks. Accordingly, the momentum of extending and retracting actuator assemblies 146, 150 will be balanced, as will readily be appreciated by those skilled in the art. Additionally, to achieve Tapping™ mode operation, or other A.C. imaging modes such as MFM (magnetic mode microscopy) a signal at a frequency substantially equal to the resonant frequency of the cantilever arm 102 is fed to the first piezo stack 147 in combination with the Z actuation driving signal fed to that stack. In this way, first piezo stack not only causes the stylus 104 to move in the Z direction but to oscillate at resonance and tap the sample surface, or otherwise obtain sample information by various A.C. imaging modes. FIG. 7 is an exploded perspective view, presenting another embodiment of the balanced momentum probe holder of the invention. The base or holder 140 is not shown for purposes of clearly presenting the remainder of the components or elements of the second preferred embodiment of the balanced momentum probe holder 114B. The balanced momentum probe holder 114B of FIG. 7 is similar to the above-discussed embodiment of the balanced momentum probe holder of the present invention with the addition of a separate tapping piezo element. Thus in FIG. 7, the first member 146 preferably includes a first piezo stack 147 disposed between the common central support 144 and the probe mount assembly 154A. Similarly, second member 150 includes a second piezo stack 151 disposed between counterbalance 162A and the common central support 144. The mount assembly 154A illustrated in FIG. 7 further preferably includes an oscillation piezo element 180 which is disposed between the first piezo stack 147 and the probe mount 156. The oscillation piezo element 180 is typically used to oscillate the cantilever probe at or near its resonant frequency. Using a separate piezo element 180, excited with a signal at a frequency substantially equal to the resonant frequency of the cantilever arm 102, may provide additional robustness as compared to the apparatus of FIG. 6 which lacks a tapping piezo element and wherein tapping is achieved by combining the tapping signal with the fast Z actuation signal fed to the first piezo stack 147. Insulators, though not necessary, may be used as before in addition to one on either side of oscillation-piezo element 180. It should be noted that in the preferred embodiment the mass of the counterbalance 162A is substantially equal to the mass of the mount assembly 154A (which includes the tapping piezo element 180), to achieve the balanced momentum effect mentioned above. In an alternate embodiment, the masses of the counterbalance 162A and the probe mount assembly 154A can be different if the momentum of the assemblies are substantially balanced. For example if the counterbalance 162A had twice the mass of the probe mount 154A, the lower actuator would be moved roughly twice the distance of the upper actuator. Other effective combinations of mass and travel may be used as appropriate. A suitable commercially available adhesive material is preferably used to adhesively bond adjacent components of the balanced momentum probe holder 114A, 114B together or not. Said components may also be soldered, welded, braised, mechanically constrained, clamped or held together by any other equivalent method. FIG. 8 is a schematic illustrating one preferred embodiment of a method and apparatus in FIG. 1. The illustrated apparatus, in operation, includes the XYZ actuator 100 (FIG. 2), wherein the Z actuator portion 122 of the XYZ actuator 100 is extendable both toward and away from sample 108, alternatively, for characterizing the surface 106. As mentioned above, one preferred Z actuator is an elongated, tubular, hollow Z actuator 122. (See FIGS. 4 and 5.) The side wall of the hollow Z actuator 122 includes a sufficiently large cut-out portion 188 such that a beam 189 of light from a source (not shown) such as a laser is able to pass longitudinally through the hollow Z actuator 122, reflect off the cantilever arm 102 of the balanced momentum probe holder 114, and pass to detector 190. The detector 190 is adapted to produce a signal which is correlatable to the magnitude of displacement or oscillation of the stylus 104. FIG. 8 further depicts a nested feedback control system comprising the balanced momentum probe holder 114 discussed above, the detector 190, amplifier 196, difference amplifier 197, first and second control devices 192, 194, and optional amplifier 198. The first control device 192 is preferably a standard PID controller and is operatively connected to the output of the difference amplifier 197. Difference amplifier 197 has at its output the difference between the amplified output of the detector 190 and a set point voltage, as is standard. The first control device is connected to the first and second piezo stacks 147, 151 of the probe holder 114 through optional amplifier 198 for causing the distal ends 148, 152 of the first and the second piezo stacks 147, 151 to simultaneously extend or retract in response to the error signal from the amplifier 197 for moving the stylus 104 at a first predetermined rate either toward or away from the surface 106 of the sample 108. Simultaneous operation of the second piezo stack 151 with first piezo stack 147, balances the momentum generated by the piezo stack 147 when it extends or retracts. This advantageously eliminates unwanted detrimental parasitic oscillations in the device as a whole. The second control device 194 is also preferably a PID controller, operably connected to the output of first control device 192 and input to the XYZ actuator 100 for causing the extendable Z actuator portion 122 of actuator 100 to move the stylus 104 of probe holder 114 at a second predetermined rate either toward or away from the surface 106 of the sample 108 when the entire error signal is not reduced to zero by operation of the piezo stacks 147 and 151 of the probe holder 114, as discussed below. The first predetermined rate is greater than the second predetermined rate. In other words, the first piezo stack 147 (the fast Z actuator) of the balanced momentum probe holder 114 moves the stylus 104 toward and away from the sample 108 faster than does the Z actuator 122. This is possible because the probe holder 114 is significantly less massive than the Z actuator 122 and because the fast feedback loop operates at higher speed relative to the slower feedback loop of the Z actuator 122. The fast feedback loop comprises, operably coupled: the detector 190, the amplifier 196, the difference amplifier 197, the first controller 192, the optional amplifier 198 and the first piezo stack 147. The fast feedback loop operates at higher speed relative to the slower feedback loop of the Z actuator 122. The slower feedback loop comprises, operably coupled: the detector 190, the amplifier 196, the difference amplifier 197, the first controller 192, the second controller 194 and the slow Z actuator 122. The probe holder 114, by design, thus balances the momentum of its opposing ends, which is of significant interest because it keeps stray oscillations from probe holder 114 from coupling into the actuator 100 and the remainder of the apparatus. By current design, for the apparatus illustrated in FIGS. 8 and 9, the maximum range of travel for the Z actuator 122 in the direction toward and away from surface 106 is approximately 15 micrometers, and the maximum range of travel for the first piezo stack 147 of the probe holder 114 in the direction toward and away from the sample surface 106 is approximately 1 micrometer. Because the range of travel of the probe due to the first piezo stack of the probe holder 114 is limited to about 1 micrometer, it may not be able to move the probe the required amount to, for instance, clear a surface feature that is more than 500 nanometers high, which is about one-half of the total travel of the first piezo stack 147. In this situation, the error signal from difference amplifier 197 is not reduced to zero and a residual error signal will be input to the second control device 194 which will output a signal to the slow Z actuator 122 to move the probe the additional amount required to track or clear the surface feature being scanned. Preferably, the residual error signal input to the second control device 194 will be such as to cause the Z actuator 122 to keep the stylus 104 in the middle of the range of travel (1 micrometer) of the first piezo stack 147 on which the cantilever probe 158 including cantilever arm 102 and stylus 104 are mounted. In this way, probe holder 114, in particular the first piezo stack 147, will also have sufficient travel available, toward and away from the sample, to be able to move the probe rapidly in the Z direction to provide the fastest Z actuation possible. This ensures that the stylus will be able to accurately follow even the smallest surface features at high scan rates. Importantly, it will do so without inducing parasitic oscillations into the remainder of the apparatus because the second piezo stack 151 balances the momentum of the first piezo stack 147. FIG. 9 is a schematic illustrating another embodiment of a method and apparatus for characterizing the surface 106 of the sample 108 shown in FIG. 1. The illustrated apparatus (FIG. 9), in operation, includes the XYZ actuator 100 (FIG. 2), wherein the Z actuator portion 122 of the XYZ actuator 100 is extendable both toward and away from the sample 108, alternatively, for characterizing the surface 106 of the sample 108. Also, as discussed above in connection with FIG. 8, a light beam 189 from a source (not shown) reflects off the cantilever arm 102 of the holder 114, and passes to the detector 190, for determining either the displacement or the amount of oscillation of the cantilever arm 102 for controlling the relative force or distance between the sample surface 106 and the stylus 104. Further in that regard and for that purpose, FIG. 9 depicts a non-nested parallel feedback system comprising the novel probe holder 114 discussed above, the detector 190, amplifier 196A, difference amplifier 197A, high and low pass filters 200 and 202, and first and second control devices 192A, 194A. The components of the non-nested parallel feedback system (FIG. 9) are substantially as described above in connection with the nested feedback control system (FIG. 8), except as follows. The first control device 192A has as its input the error signal from difference amplifier 197A which has been high pass filtered by high pass filter 200. The output of the first control device 192A is fed through an amplifier 198A to the piezo stack 147 to move the stylus 104 at a first predetermined rate either toward or away from the sample surface 106. The second control device 194A has as its input the error signal from difference amplifier 197A which has been low pass filtered through low pass filter 202. The output of the second control device 194A is fed to the Z actuator 122 for causing the Z actuator 122 to move the stylus 104 at a second predetermined rate either toward or away from the sample surface 106. In operation, the first control device 192A produces a first control signal in response to the higher frequency components of the error signal from the high-pass filter 200, for causing the distal ends 148, 152 of the first and the second members 146, 150 (FIGS. 6, 7) either to extend or retract, for moving the stylus 104 relative to the sample surface 106 (FIG. 1) within a range of 1 micron and at a rapid rate. The second control device 194A produces a second control signal in response to the lower frequency components of the error signal from the low-pass filter 202, for moving the stylus 104 toward or away from the sample surface 106, within a range of 15 microns at a slower, conventional rate. In this regard, the outputs of the first and second control devices 192A and 194A cooperate to move the stylus to the appropriate height above the sample, through their respective Z actuators (piezo stack 147 and Z actuator 122, respectively), and with sufficient rapidity to ensure accurate measurement even at higher scan rates. As those skilled in the art can well appreciate, the first and second control devices 192, 192A, 194, 194A for the nested feedback control and non-nested parallel feedback control system may be micro computers or microprocessors, as desired. The invention thus allows relatively rapid high-precision sample scanning and characterization, resulting in significantly faster sample tracking than conventional systems can provide, without undesired system resonance and attendant system instability. What has been illustrated and described herein is a balanced momentum probe holder that can be used in a nested feedback control system or in a non-nested parallel feedback control system. However, as the balanced momentum probe holder system has been illustrated and described with reference to several preferred embodiments, it is to be understood that the invention is not to be limited to these embodiments. In particular, and as those skilled in the relevant art can appreciate, functional alternatives will become apparent after reviewing this patent specification. Accordingly, all such functional equivalents, alternatives, and/or modifications are to be considered as forming a part of the present invention insofar as they fall within the spirit and scope of the appended claims.
	claims	1. A method for constructing a graph from data representing an integrity measurement of a running computer program, the method comprising the steps of:decomposing the integrity measurement, using a microprocessor, into a plurality of distinct measurement classes, each measurement class representing a semantically related grouping of measurement variables which have been examined to produce a characterization of an isolated subset of a measurement target's state, the measurement variables identifying portions of a kernel of the computer program that are inspectable; andconnecting to each measurement class, using a microprocessor, a structured representation of the measurement of those measurement variables which contribute to the overall measurement of that class,wherein the structured representation is hierarchically organized to enable successive levels within the structured representation to provide contextual information to be employed for examining increasingly lower levels of classes until an indicated degree of completeness of examination is attained. 2. The method according to claim 1, the connecting step comprising the step of deriving the structured representation from the measurement target's in memory associations among the examined variables. 3. A machine for graphing data representing an integrity measurement of a running computer program comprising:a microprocessor coupled to a memory;wherein the microprocessor is programmed to construct a graph of the data by:decomposing the integrity measurement into a plurality of distinct measurement classes, each measurement class representing a semantically related grouping of measurement variables which have been examined to produce a characterization of an isolated subset of the running computer program's state, the measurement variables identifying portions of a kernel of the computer program that are inspectable; andconnecting to each measurement class a structured representation of the measurement of those measurement variables derived from the measurement target's in memory object graph which contribute to the overall measurement of that class,wherein the structured representation is hierarchically organized to enable successive levels within the structured representation to provide contextual information to be employed for examining increasingly lower levels of classes until an indicated degree of completeness of examination is attained.
	abstract	A holding fixture for assisting in assembly of a support grid for nuclear fuel rods and including a plurality of straps each having a plurality of slots extending approximately half a height of the straps and tabs formed beside or between the slots. The holding fixture includes an actuation plate, a support plate having a plurality of receiving members structured to receive therein straps of the support grid and having a plurality of cells, and a plurality of cam assemblies structured to move to deflect every other tab of the straps received in the plurality of receiving members. The cam assemblies are disposed in every other cell of the support plate.
040574636	summary	BACKGROUND OF THE INVENTION This invention pertains generally to the control of core operation of a nuclear reactor and more particularly to the control of the axial power distribution within the core. Generally nuclear reactors contain a reactive region commonly referred to as the core in which sustained fission reactions occur to generate heat. The core includes a plurality of elongated fuel rods comprising fissile material, positioned in assemblies and arranged in a prescribed geometry governed by the physics of the nuclear reaction. Neutrons bombarding the fissile material promote the fissionable reaction which in turn releases additional neutrons to maintain a sustained process. The heat generated in the core is carried away by a cooling medium, which circulates among the fuel assemblies and is conveyed to heat exchangers which in turn produce steam for the production of electricity. Commonly in pressurized water reactors a neutron absorbing element is included within the cooling medium (which also functions as a moderator) in controlled variable concentrations to modify the reactivity and thus the heat generated within the core, when required. In addition, control rods are interspersed among the fuel assemblies, longitudinally movable axially within the core, to control the cores reactivity and thus its power output. There are three types of control rods that are employed for various purposes. Full length rods, which extend in length to at least the axial height of the core, are normally employed for reactivity control. Part length control rods, which have an axial length substantially less than the height of the core, are normally used for axial power distribution control. In addition, reactor shutdown control rods are provided for ceasing the sustained fissionable reaction within the core and shutting down the reactor. The part length rods and full length control rods are arranged to be incrementally movable into and out of the core to obtain the degree of control desired. As a byproduct of the fissionable reaction, through a process of beta decay of radioactive iodine, xenon is created. Xenon has the property of having a large neutron absorption cross section and therefore has a significant effect on the power distribution within the core and reactivity control. While the other forms of reactivity management are directly responsive to control, the xenon concentration within the core creates serious problems in reactor control in that it exhibits a relatively long delay period and requires up to at least twenty hours after a power change to reach a steady-state value. While the radial power distribution of the core is fairly uniform, due to the prescribed arrangement of fuel assemblies and the positioning of control rods which are symmetrically situated radially throughout the core, the axial power distribution can vary greatly during reactor operation. Core axial power distribution has created many problems throughout the history of reactor operations for many reasons. Normally coolant flow through the fuel assemblies is directed from a lower portion of the core to the upper core regions, resulting in a temperature gradient axially along the core. Changes in the rate of the fissionable reaction, which is temperature dependent, will thus vary the axial power distribution. Secondly, the axial variation in the power distribution varies the xenon axial distribution, which further accentuates the variations in power axially along the core. Thirdly, insertion of the control rods from the top of the core, without proper consideration of the past operating history of the reactor can add to the axial power asymmetry. The change in reactor core power output which is required to accommodate a change in electrical output of an electrical generating plant is commonly referred to as load follow. One load follow control program currently recommended by reactor vendors utilizes the movement of the full length control rods for power level increases and decreases and the part length control rods to control axial oscillations and shape the axial power profile. Changes in reactivity associated with changes in the xenon concentration are generally compensated for by corresponding changes in the concentration of the neutron absorbing element within core coolant or moderator. In this mode of operation the part length rods are moved to maintain the axial offset within some required band, typically plus or minus 15%. The axial offset is a useful parameter for measuring the axial power distribution and is defined as: EQU A.O. = (P.sub.t -P.sub.b)/(P.sub.t +P.sub.b) where P.sub.t and P.sub.b denotes the fraction of power generated in the top half and the bottom half of the core respectively. No effort is made to maintain the inherent core axial power profile. The part length rods are moved to minimize and reduce the axial offset independent of the previously established steady-state axial offset. This process induces a constant fluctuation of the axial offset during sustained load follow operations which result in a number of undesirable operating conditions. For one thing power pinching, which is a large axially centered power peak, is likely to occur. Such power peaks result in a reactor power penalty which requires the reactor to be operated at a reduced level so that such peaks do not exceed specified magnitudes. Secondly, severe changes occur in the axial power profile of a transient nature during large load changes due to heavy insertion of control rods at reduced power levels. Thirdly, large xenon transients occur upon coming back to power resulting in occurrences such as axial power oscillations. Fourthly, the part length rod broad operating instructions are generally vague and require anticipation and interpretation by the reactor plant operator. Fifthly, increased hot channel factors result (which are hot spots which occur within the cooling channels among the fuel assemblies) and require reductions in the power rating of the reactor to accommodate these severe transients and/or adverse power profiles. Finally, no protection currently exists against severe pinching with small axial offsets. Due to the many adverse operating conditions experienced in operating a nuclear reactor during load follow many reactor vendors recommend operating the reactor at a constant power output without a load follow capability. Accordingly, a new method of operating a nuclear reactor is desired that will have a load follow capability without exhibiting the adverse operating conditions described above, thereby avoiding the necessity of imposing power penalties to compensate for axial power peaks. SUMMARY OF THE INVENTION Briefly, the method of this invention avoids the adverse operating characteristics experienced in the operation of a nuclear reactor according to prior practice by maintaining a substantially symmetric xenon axial profile. Implementation of the desired xenon distribution is obtained by monitoring the power generated in the core at a first and second axial location. The corepower parameters measured at the two locations are computed in accordance with a predetermined relationship to give a value indicative of the axial power distribution of the core. The reactivity control mechanisms of the reactor are manipulated in accordance with the monitored values to maintain a substantially symmetric axial power distribution within the core throughout reactor core operation including changes in reactor power output. Two separate embodiments are described which have the capability of complementing each other. In the first, the part length control rods remain withdrawn from the core while the neutron absorbing element within the core coolant or moderator is employed to assist adjusting the reactivity of the core associated with power changes and the full length control rods are manipulated to maintain the desired axial power profile. In the second embodiment the full length control rods are used to control the reactivity changes associated with changes in power in the core and the part length rods are employed to control the axial power distribution while the neutron absorbing element within the coolant or moderator compensates for reactivity changes due to xenon buildup or depletion. Each embodiment is capable of implementing the concepts of this invention and each has its respective distinct advantages.
	claims	1. A beam shaping filter for a CT imaging system, the filter comprising:a first end and a second end, each end having a circular cross-section;a body formed of radiation beam filtering material and extending between the first end and the second end, the body designed to be positioned in a path of x-rays emitted by an x-ray tube during radiographic imaging of a subject; anda pair of depressions formed in the body orthogonal from one another and defining a first body diameter and a second body diameter, wherein the first body diameter defines a minimum radiation beam filtering profile and the second body diameter defines a maximum radiation beam filtering profile and wherein the body further defines a number of radiation beam filtering profiles between the pair of depressions;wherein the pair of depressions defines a pair of filtering profiles and wherein a slope between a maximum point and a minimum point of one filtering profile is larger than a slope between a maximum point and a minimum point of the other filtering profile. 2. The beam shaping filter of claim 1 configured to rotate as a function of gantry view angle such that the first radiation beam filtering profile is presented when the filter is generally at a side of a subject and the second radiation beam filtering profile is presented when the filter is generally above the subject. 3. The beam shaping filter of claim 1 configured to minimize radiation dosage to a subject as a function of x-ray source view angle. 4. The beam shaping filter of claim 1 further comprising a shaft connectable to a motor at the first end and comprising a bearing assembly connected at the second end. 5. A CT system comprising:a rotatable gantry having an opening to receive a subject to be scanned and configured to rotate along a rotational path;a rotatable high frequency electromagnetic energy projection source configured to project a high frequency electromagnetic energy beam toward the subject at at least two view angles;a rotatable pre-subject filter having a static shape, wherein the filter is constructed to define at least two filtering profiles such that at a first view angle a first filtering profile filters the high frequency electromagnetic energy beam and at a second view angle rotated from the first view angle along the rotational path a second filtering profile different and rotated from the first filtering profile filters the high frequency electromagnetic energy beam without varying the shape of the filter between rotation between the first view angle and the second view angle, wherein the first filtering profile has a maximum point and a minimum point and the second filtering profile has a maximum point and a minimum point, and wherein a slope between the maximum point and the minimum point of the first filtering profile is larger than a slope between the maximum point and the minimum point of the second filtering profile;a scintillator array having a plurality of scintillator cells wherein each cell is configured to detect high frequency electromagnetic energy passing through the subject;a photodiode array optically coupled to the scintillator array and comprising a plurality of photodiodes configured to detect light output from a corresponding scintillator cell;a data acquisition system (DAS) connected to the photodiode array and configured to receive the photodiode outputs; andan image reconstructor connected to the DAS and configured to reconstruct an image of the subject from the photodiode outputs received by the DAS. 6. The CT system of claim 5 wherein the filter is a bowtie filter designed to reduce high frequency electromagnetic energy dosage to the subject as a function of projection source view angle. 7. The CT system of claim 5 wherein the filter includes a first end and a second end and a body extending therebetween, the body including at least a pair of depressions orthogonal from one another that defines a first body diameter and a second body diameter, respectively. 8. The CT system of claim 7 wherein the first body diameter is less than the second body diameter such that the slope between the maximum point and the minimum point of the first filtering profile defined by the first body diameter is larger than the slope between the maximum point and the minimum point of the second filtering profile defined by the second body diameter. 9. The CT system of claim 5 wherein the first view angle is orthogonal of the second view angle. 10. The CT system of claim 5 incorporated into at least one of a medical imaging system and a parcel inspection apparatus. 11. A method of reducing x-ray exposure during CT data acquisition comprising the steps of:positioning a subject to be scanned in a scanning bay, the scanning bay defined by a gantry having a bore therethrough and wherein the gantry includes an x-ray source and a multi-profile filter designed to rotate around the subject during an imaging session, the multi-profile filter having a first generally hour-glass cross-section and a second generally hour-glass cross-section different from the first cross-section and defined to be orthogonal from the first generally hour-glass cross-section;spinning the multi-profile filter to a first filtering profile position such that a first filtering profile defined by the first generally hour-glass cross-section is positioned between the x-ray source and the subject when the x-ray source is projecting x-rays at a first view angle;projecting x-rays toward the subject from the x-ray source at the first view angle;rotating the x-ray source to a second view angle;spinning the multi-profile filter to a second filtering profile position such that a second filtering profile defined by the second generally hour-glass cross-section is between the x-ray source and the subject when the x-ray source is projecting x-rays at the second view angle; andprojecting x-rays toward the subject from the x-ray source at the second view angle. 12. The method of claim 11 wherein the first view angle is orthogonal to the second view angle. 13. The method of claim 11 wherein a slope between a maximum point and a minimum point of the second filtering profile is larger than a slope between a maximum point and a minimum point of the first filtering profile. 14. The method of claim 13 wherein the first view angle is relatively above the subject and the second view angle is at a relative side of the subject. 15. The method of claim 11 further comprising the step of rotating the filter synchronously with rotation of the x-ray source. 16. The method of claim 11 wherein the filter is a beam shaping bowtie filter.
	description	This application is a US 371 Application from PCT/RU2015/000837 filed Dec. 1, 2015, which claims priority to Russia Application 2014153832 filed Dec. 30, 2014, the technical disclosures of which are hereby incorporated herein by reference. This invention relates to heat exchange devices used in thermal systems of various fields, including nuclear power industry; more specifically, this device is intended to space tubes of heat exchangers mostly designed for operations in the heavy liquid metal coolant medium. Various heat exchanger tube spacing devices are currently in use. For example, it is specified in USSR Inventor's Certificate No. 1556253 (issued on Jan. 15, 1994), Russian Patent No. 2153643 (issued on Jul. 27, 2000) and Russian Utility Model Patent No. 6224 (issued on Mar. 16, 1998) that tubes of the heat exchanger bundle are bound by profiled plates (dividers) which are rather difficult to make. Its closest analogue is a heat exchanger tube spacing device described in USSR Inventor's Certificate No. 515025 (issued on May 25, 1976). This device includes a supporting spacer grid which consists of two round-shaped coaxial cylindrical shells connected by an intermediate ring; each shell is provided with sleeves used to run the aforementioned heat exchange tubes through them; these sleeves are spaced apart at a preset gap and are bound with bridges, while sleeves of both shells are aligned in corners of equiangular triangles when observing along the shell axis. Russian Patents No. 2384807 (issued on Mar. 20, 2010) and No. 2386915 (issued on Apr. 20, 2010) describe similar solutions. USSR Inventor's Certificate No. 400797 (issued on Oct. 1, 1973) by V. S. Neevin, S. G. Khachaturyan, L. A. Dolgy, N. A. Georgiyevsky, D. I. Isbatyrov is known where a spacer grid was made of a solid piece, while its cells were mostly formed by milling cut. Reliability of fixation of heat exchanger tubes in such devices, especially under the effect of corrosion, vibration and high temperatures, is obviously insufficient due to the fact that sleeves of different shells are not interconnected, and the fixation of heat exchanger tubes in radial axis is not secure. Therefore, there is an objective which includes the development of a heat exchanger tube spacing device in order to ensure more reliable fixation of tubes with their simultaneous spacing. Implementation of this invention will lead to the following technical results: increased fixation reliability with simultaneous spacing of heat exchanger tubes; reliable fixation of heat exchanger tubes in radial axis; possibility to move heat exchanger tubes axially; independence of cells formed in the supporting spacer grid; high vibration resistance; high temperature resistance; The above technical results are achieved by the following distinctive features of the invention. To solve the aforementioned problem and to achieve the indicated technical result for the first object of this invention, a heat exchanger tube spacing device is proposed which includes at least one supporting spacer grid consisting of a cylindrical shell and at least two tiers of plates; these tiers are spaced apart at the preset gap; the width of each plate lies within the plane which is parallel to the shell axis; ends of all plates are fixed to the shell in such a way that plates of any tier are located at the preset gap being parallel to each other; plates of different tiers are criss-crossed at an angle of 60 degrees when observing along the shell axis, and are fastened together at the crossing points. The feature of this invention by the first option lies in the fact that the sum of the preset gap between plates and the thickness of each plate may be equal to the spacing of heat exchanger tubes. Moreover, it is possible to choose a preset gap between plates which is less than the heat exchanger tube diameter by a corresponding drilling or reaming allowance of each cell formed by criss-crossed plates of both tiers when observing along the shell axis. Another feature of the first option of this invention lies in fact that it is possible to use each supporting spacer grid independently, and the plates of both tiers have the same width. Finally, another feature of the first option of this invention lies in fact that it is possible to use every two supporting spacer grids in combination, and the width of plates of the same tier of each supporting spacer grid is less than that of plates of the other tier which are turned clockwise against narrower plates when observing along the shell axis, while both supporting spacer grids are coupled in such a way as to align ends of narrower plates. To solve the same objective and to achieve the same technical result for the second object of this invention, a heat exchanger tube spacing device is proposed which includes at least one supporting spacer grid consisting of a round-shaped cylindrical shell and two tiers of plates; these tiers are spaced apart at the preset gap and include three dividers running through the axis of the cylinder, while its ends are connected to the shell, and the distance between them makes an angle of 60 degrees; moreover, the width of each plate lies within the plane which is parallel to the shell axis, and ends of all plates of one section in each tier are connected either to the shell and one of the dividers, or to the adjacent dividers in such a way that plates of any section in each tier are spaced apart at a preset gap being parallel to each other, as well as to the divider with no planes connection; plates of both tiers are criss-crossed at an angle of 60 degrees when observing along the shell axis and are fastened together at crossing points. The feature of this invention by the second option lies in the fact that the sum of the preset gap between plates and the thickness of each plate may be equal to the spacing of heat exchanger tubes. Moreover, it is possible to choose a preset gap between plates which is less than the heat exchanger tube diameter by a corresponding drilling or reaming allowance of each cell formed by criss-crossed plates of both tiers when observing along the shell axis. Another feature of the first option of this invention lies in fact that it is possible to use each supporting spacer grid independently, and the plates of both tiers are of the same width. Another feature of the second option of this invention lies in fact that every two supporting spacer grids are used in combination, and the width of plates of the same tier of each supporting spacer grid is less than that of plates of the other tier which are turned clockwise against narrower plates when observing along the shell axis, while both supporting spacer grids are coupled in such a way as to align ends of narrower plates in the corresponding sections. Finally, another feature of the second option of this invention lies in fact that it is possible to design solid dividers in both tiers. The heat exchanger tube spacing device of the current invention is designed to ensure vibration resistance of steam-generating (evaporating) tubes which are made in a form of Field tubes well-known among experts (for instance, refer to Russian Patent No. 2534337 of Nov. 27, 2014). Since these tubes are intended to operate in the corrosive environment which is characterized by vibration, fretting and oxygen thermodynamic activity of heavy liquid metal coolant flowing around the tubes, it is very important to fix tubes properly. This invention ensures highly reliable fixation of heat exchanger tubes owing to their positioning within cells formed in the supporting spacer grid which is described in details below. The design of the heat exchanger tube spacing device of the first option of the present invention is presented in FIG. 1, as observed along the shell axis indicated with the cross. This device includes the supporting spacer grid indicated by a reference sign 1. Supporting spacer grid 1 consists of the cylindrical shell 2 (in FIG. 1 its inner surface is indicated with a dashed line) and two tiers of plates 3 and 4; plates 4 of the second tier are located behind plates 3 of the first tier. Plates 3 and 4 in each of these tiers are connected to the shell in such a way that they are spaced apart at a preset gap which is the same for both tiers; plates 3 of the first tier and plates 4 of the second tier are criss-crossed at an angle of 60 degrees when observing along the shell axis. The width of each plate 3 or 4 lies within the plane which is parallel to the shell axis; the thickness of each plate 3 or 4 is presented in FIG. 1. It should be noted that the sum of the preset gap between plates 3 or 4 and the thickness of each plate is equal to the spacing of the heat exchanger tubes (not indicated). Within the frames of this invention the preset gap between plates 3 or 4 is less than the heat exchanger tube diameter by a corresponding drilling or reaming allowance of each cell formed by criss-crossed plates of both tiers when observing along the shell axis. In FIG. 1 a spacing device for seven tubes is depicted, where the central cell is rhomb-shaped, while other cells are rounded, changing from one side into a rhomb-shaped angle which is the same as that of the central cell. None of the cells of FIG. 1 are drilled or reamed. FIG. 2 depicts a provisional diagram of plate connections at different tiers of the device as per FIG. 1. To simplify the drawing all plates 3 and 4 are two-dimensional along their full length up to the wall of shell 2. Connections 5 between plates 3 and 4 of different tiers are intentionally elongated, though in fact they could be considerably shorter or completely absent, i. e., plates 3 could be connected with plates 4 at their crossing points. Thus, the preset gap between the first and the second tiers of plates 3 and 4 may assume any value, depending on technological considerations. In FIG. 2 the width of plates 3 and 4 is approximately the same. In this design the device of the first option of the current invention can be used independently. However, there is another design of the supporting spacer grid 1 where plates 4 of the second tier are narrower than plates 3 of the first tier, for instance, by half. In this case, it is possible to combine two supporting spacer grids 1 in such a way as to put ends of narrower plates together. As in this case plates 3 of one tier of each supporting spacer grid 1 (wider plates) are turned, for instance, clockwise with regard to narrower plates when observing along the shell axis, the combination of two supporting spacer grids 1 will produce hexagonal tube cells. In FIG. 3 the heat exchanger tube spacing device of the second option of the present invention is depicted. This device includes the supporting spacer grid indicated by a reference sign 6, which consists of a round-shaped cylindrical shell 2 and two tiers of plates 3 and 4 spaced apart at a preset gap (the same as the supporting spacer grid in FIG. 1). Just as for the device in FIG. 1, FIG. 3 depicts plates 3 and 4 of each tier which are spaced apart at a preset gap, being the same for both tiers; plates 3 of the first tier and plates 4 of the second tier are criss-crossed at an angle of 60 degrees when observing along the shell axis. The width of each plate 3 or 4 lies within the plane which is parallel to the shell axis, while the thickness of each plate 3 or 4 is shown in FIG. 3. Just as for the device in FIG. 1, the sum of the preset gap between plates 3 or 4 and the thickness of each plate is equal to the spacing of the heat exchanger tubes (not indicated). The difference of the second option device of the current invention lies in the availability of three dividers 7 which run through the cylinder axis; their ends are connected to shell 2, being spaced from each other at an angle of 60 degrees. In each tier the ends of plates 3 or 4 of one section formed by two adjacent dividers 7 and an edge of shell 2 between them are connected either to shell 2 and one of the dividers 7 or to the adjacent dividers 7 in such a way that plates 3 or 4 of any section at each tier are spaced apart at a preset gap and are parallel to each other and to the divider 7 to which they are not connected. Plates of both tiers are criss-crossed at an angle of 60 when observing along the shell axis, and are fastened together at crossing points, similarly to the device in FIG. 1. It should be noted that dividers 7 in both tiers can be solid, i. e., running through the entire length of the cylindrical shell 2, though, it is also possible to separate dividers 7 of one tier from dividers of another tier. Just as in the first option of the invention, it is possible to use the second device option of the invention independently when plates 3 and 4 in both tiers are of the same width. However, there is another design of the supporting spacer grid 6 where plates 4 of the second tier are narrower than plates 3 of the first tier, for instance, by half. In this case, it is also possible to combine two supporting spacer grids 6 in such a way as to put together ends of narrower plates. Since plates 3 in one tier of each supporting spacer grid 6 (wider plates) are turned, for instance, clockwise with regard to narrower plates when observing along the shell axis, the combination of both supporting spacer grids 6 will produce hexagonal tube cells, resulting in better reliability of heat exchanger tube fixation. In FIG. 4 the heat exchanger tube spacing device with 3 plate tiers is depicted. Thus, any device option of this invention will result in more reliable fixation of heat exchanger tubes with their simultaneous spacing in cells formed by plates in two or three tiers.
	abstract	A container for a vial of radiopharmaceutical, made of polymethyl methacrylate consists of a receptacle, with a cavity capable of containing the vial of radiopharmaceutical, and of a lid screwed onto the receptacle for closing the container, said lid presenting a central through-hole. A set, in combination with this container with the vial of radiopharmaceutical, consisting of a bottle of saline solution and two infusion catheters, enhances the radioprotection during the infusion of a radiopharmaceutical in an infusion operation.
	summary
061455830	description	DETAILED DESCRIPTION OF THE INVENTION The present invention positions an inspection head into a flanged access port having a diameter of about six inches near the bottom of a steam generator. The device is mounted on a specially designed rail-like adapter to facilitate entry through a small opening. The device, designed for a vertical lift of about 30 feet or more, first extends horizontally into the steam generator through the flanged access port. The device rests near the base of the steam generator in the region known as the tube lane. The tube lane is the narrow area created by the innermost inverted U-tubes. Steam enters one side of the U-bend (the hot pipe). and travels around the U-bend of the pipe and is quenched by the cool water in the steam generator and proceeds around to the other side of the U-bend (the cool pipe). Once the tool is installed horizontally, it is raised to a vertical position through a flow slot in the support plates in the generator. The rail assembly is moved in or out as the tool is raised to keep the head aligned with the flow slot in each support plate. Support plates occur vertically throughout the height of the generator at three to six foot intervals. The device is then maneuvered into a vertical position through use manual cranking. The hydraulically-controlled telescoping assembly is then activated allowing the device to extend vertically to the desired height which may cause the device to proceed through the flow slots of successive support plates. Computer-controlled or manually controlled machinery extends the telescoping section to the height to be sensitively and accurately measured to assure an operator of the precise vertical location of the device head within the steam generator. Once the device is in the vertical position, the horizontal position location is verified visually and numerically by determining at which tube column the device is located. This is accomplished by mechanical distancing apparatuses, such as pulleys or gears, or may be done by using position sensors such as, for example, pattern recognition sensors, etc. A registration apparatus is then preferably pneumatically powered to extend sets of registration guides (which are finger-like projections) from a retracted position at rest. When each guide set is extended, one guide will contact the hot tube and one guide will contact the cool tube of the same U-tube. The probe camera at the end of an inspection wand is then raised, preferably by remote computer control of a direct motor drive, into the desired inspection position between specified tube columns. As the device is telescopically raised or lowered vertically, an upward facing head camera mounted in the top of the inspection head gives a view of the first tube row and the flowslot or lane. Preferably, the head of the device located atop the vertically telescoping section contains an additional camera or sensor facing the center of the generator to provide additional information on device location and generator condition. The device is therefore able to inspect both the top and bottom of tube support plates as well as the wrapper welds at the support plates, and other internal structures FIGS. 1-7 show one preferred embodiment of the present invention. Inspection device 1 comprises a telescoping boom assembly 12 with head assembly 18 attached. One (proximal) end of sensing wand 16 attaches to head assembly 18. The other (distal) end of the wand houses probe 20 which houses a camera and light assembly See FIGS. 17 and 18. First boom rail assembly 2 attaches to telescoping boom 12 at uprighting pivot clamp 3. The generator wall 4 has access port 5 to which access port mounting plate 6 attaches. Rack drive servo motor 7 attaches to mounting plate 6. Manual crank handle 31 drives gear 8 which is attached to rod 9. Rod 9 attaches to clamp 9a which is secured about telescoping boom 12. Manual crank handle 31 can be operated to deploy the second telescoping boom 12 and to retract telescoping boom 12 to the retracted position. Cable housing 14 attaches to head 18. Quick release feature 21 (FIG. 5) removably secures assembly 12 to head assembly 18. Registration guides 22, 24, 26, 28 are shown. See FIGS. 5-7. One end of registration links 30 attach to guides. The other end of the links 30 attach to the air cylinder attachment block 62 of air cylinder base 60. See FIG. 9. FIG. 3 shows the wand 16 in a deployed position. FIG. 4 shows wand 16 in a starting/retracted position. FIGS. 5-7 show an additional camera 40 in housing 42 at the proximal end of wand 16. Further top head camera 50 and side head camera 52 are positioned at the top housing 54 of head assembly 18. Air cylinder 44 provides pneumatic pressure to the registration guides. FIG. 8 shows a top view of one preferred embodiment of the present invention. Camera 40 positioned at the proximal end of wand 16 is shown along with side head camera 52, top head camera 50. Registration guides 26 and 28 are shown in their retracted position while guides 22 and 24 are shown extended. FIG. 9 shows an exploded view of the registration assembly. Air cylinder base 60 has driver block 62 fit over top post 64. Registration links 30 have through holes 66, through which link pins 68 extend and secure in driver block 62. Retainer caps 70 affix to link pins 68. Link pins 72 pass through links 30 and secure in guide openings 74. Link pins 76 pass through links 30 at openings 66 and secure in openings 78 in base 60. Elbow fitting 80 houses barb fitting 82 and is housed in pneumatic air cylinder 84. Fitting pins 86 fit into air cylinder. FIG. 10 shows an enlarged view of the wand 16. The wand 16 has an inner channel 90 and a support tube 92 both of which engage pivot arm fixture 94. Bearing gear 96 fits into bearing 98 which rests against pulley 100. Pivot arm 94 houses cable guide 102. Coupling 104 secures channel 90 and support tube 92. Probe head 106 houses camera and light assembly (not shown) and secures to inner channel 90 and support tube 92. FIG. 11 shows a cross-sectional top view of a longitudinal half of a steam generator bisected at the flow slot. Support plate 39 is shown with hundreds of tubes 79 and multiple flowslots 13 passing therethough. FIG. 12 shows the present invention deployed through access port 5 of generator wall 4. FIG. 12 depicts the present invention in both the horizontal retracted mode (position A) in which it passes through the access port, and the deployed vertical mode (position B). It is understood that for illustrative purposes, the generator is viewed across a longitudinally bisected line in the plane of the device (as shown in FIG. 11) to give a better view of the present invention. FIG. 13a shows the present invention deployed in the tube lane 81. The device is deployed vertically in the lane through the flowslot 83 in support plate 85. Wand 16 is in the retracted position. FIG. 13b shows wand 16 activated to inspect down the tube column into areas which could not be inspected using past methods and apparatuses. Cables 87 are visible, as are tubes 79, and support plates 85 and 89. FIG. 14 is a schematic partially exposed view of cable housing 14. Pulley 100 supports cable 220 which wraps about weighted pulley 222. Constant force spring 230 provides balance force to weighted pulley 222. FIG. 15 is a schematic block diagram of the preferred control layout of the present invention. Area monitor 300, control interface computer 302, optional auxiliary electronics 304, and hydraulic pump 306 are preferably positioned outside of a bioshield 308 and have their cables 310 directed to control electronics 312 and power and air supplies 314 which are set up adjacent the generator access opening 321. A rack and pinion drive 316 is attached to rail assembly 319 which is attached to pivot clamp 320 on device 10. Rail assembly 319 supports the device 10 as it is slid into position in the generator. FIG. 16 is a schematic representation of the preferred computer interface and circuitry provided to operate remotely the preferred inspection device of the present invention. FIG. 17 shows a cross-sectional enlarged view of the probe 20 of the wand assembly 16. Camera 400 is shown along with lamp 402, 404 and lamp lenses 406 and 408. FIG. 18 shows an end view 106 of the probe 20. In operation, the uprighting equipment comprises two major subsystems; the access port mounting equipment and the rail assembly. The access port mounting equipment comprises a backing plate 6, two cam roller support plates and a rack drive servo motor assembly 7. The backing plate 6 completely covers the face of the access port 5 and has slotted mounting holes to allow alignment with the tube lane, and has a relief cut in the backside in the area of the sealing surface of the access port to prevent damage to this surface. Preferably, six 1" diameter cam rollers are mounted on each of two cam roller support plates. These rollers support the first boom rail assembly 2 on all four horizontal edges. The rack drive servo motor 7 is controlled by the operator to precisely position the rail 2 within the steam generator. The rack drive servo motor housing 2 is mounted to one of the roller support plates by a pivot and preferably is held in place by a single locking, quick release pin. The rail can be installed and repositioned by hand by removing the locking pin and swinging the motor assembly up. The rail assembly 2 comprises two parallel, stainless steel bars, spaced by stainless steel blocks on both ends. For portability and ease of installation the assembly preferably comprises three sections. The primary purpose of the rail is to support and position the telescoping segment's uprighting mechanism, preferably a pivot clamp. Also the rail provides a means of tensioning the uprighting rod using a screw mechanism in the middle section. To move the rack assembly horizontally, a rack is embedded into the top of one of the two parallel stainless steel bars. This rack mates with the pinion on the end of the rack drive servo motor. The three rail assembly sections are joined by guide pins, preferably 1 inch (2.54 cm) in diameter, and preferably are locked together with the thumbscrews. In an alternative embodiment, air fittings for powering the telescoping segment locking pin release cylinder may be embedded into the ends of the sections and must be depressurized before a section can be removed from its mating section. The shaft sections link a removable handle at the end of the rail to the screw used for uprighting the segment. In one preferred embodiment, the inspection wand is made from thin section telescoping tubing actuated by a stainless steel 4-40 threaded rod driven by a servo motor. The probe head 20 itself, as shown in FIG. 17, preferably is made from an inert polymeric resin material, most preferably Delrin.RTM. or Teflon.RTM., and houses the inspection lighting 402 and 404 and camera, which is preferably a CCD camera 400. The inspection probe lighting intensity is set from the remote operator station or from the main control console as would be understood in the field of remote inspection devices. The wand 16 preferably pivots at the distal end of the telescoping segment, or shoulder joint. A set of bevel gears actuated by a servo motor powers the joint. The design of this pivot is such that when the device is de-energized, the motor can be freely back-driven. This safety measure helps to ensure that in the event of a tool failure, the probe can be removed without damaging the steam generator components. In one preferred embodiment, the wand further consists of a double-barrel outside tubular assembly with a double-barrel inside the tubular assembly and an internal screw. The inside assembly can be made to extend from and retract into the outside tubular assembly, making the total wand length shorter or longer as needed for inspection purposes and to negotiate the support plates during deployment into the tube columns. The distal end 19 of the inside tubular assembly attaches to the camera and light assembly probe 20, as shown in FIG. 19. The proximal end of the outside tubular assembly contains the screw (threaded rod), the drive motor, wand camera 40, and attachment shaft for attaching the wand to the head assembly. The attachment shaft rotates to position the wand at the desired angle in the steam generator tube column. In one preferred embodiment, the registration mechanism may be actuated to move in laterally forward or backward one tube at a time by extending one set of registration guides to an adjacent tube space, releasing the other set of registration guides, and moving the device to align between a new tube column. The registration guides 22, 24, 26, 28 prevent unwanted motion of the head while the inspection wand 16 is positioned between tube columns. The guides 22, 24, 26, 28 align vertically with the steam generator tubes. The guides 22, 24, 26, 28 are actuated by pneumatic air cylinders 29 and fail in the closed position when the device is deenergized. The guides 22, 24, 26, 28 are preferably coated with a material to eliminate the risk of damaging the tubes upon contact. Preferably, the registration guides 22, 24, 26, 28 comprise Delrin.RTM. and Teflon.RTM. or other highly resilient and adherent protective materials. An additional air cylinder arranged horizontally moves one registration guide with respect to the other to index the head to a particular column. By cycling the registration and indexing cylinders, the head can be effectively "walked" from one tube column to the next. When a series of several "walking" cycles are combined, the device can move across an entire flowslot width. For example, with reference to FIG. 7, guides 22 and 24 are extended and would contact the hot and cool tubes of a single U-bend tube in a generator. Air cylinder 29 would be activated to move the head 18 a distance sufficient to align guides 26 and 28 with the next tube. Guides 26 and 28 would be pneumatically extended while guides 22 and 24 would be retracted. Air cylinder 29 is again activated to push head 18 "ahead" until guides 22 and 24 are adjacent the next tube, and so forth. As the head is pushed or pulled in a direction along the tube row, an integrated tilt sensor senses that the second telescoping boom is out of verticality. The sensor sends a signal to the servo drive attached to the first boom rail assembly and advances or retracts a distance sufficient to reestablish second boom verticality. To assist in maintaining proper vertical positioning, a dual axis tilt sensor in the base of the telescoping segment provides operator feedback for +/-20 degrees of vertical tilt. Since the inspection probe is telescopic, a substantial length of cable must be managed and stored within the inspection head. A constant force spring 230 and a set of pulleys 100, 222, as shown in FIG. 14, rising in an enclosed track prevents the inspection camera cabling 220 from becoming tangled and potentially jammed while in operation. This guide also serves to protect the angle joint servo motor and provides a sturdy point to strain relieve the umbilical cable. The inspection head is linked to the main control console through a multi-function umbilical cable 87 (shown in FIG. 12). This umbilical cable 87 carries all electrical power, control and video signals. It additionally contains four small air lines for the pneumatic components. The primary electrical cable is internally reinforced with Kevlar filler strands for strength; the cable also serving as the emergency retrieval cable. The additional cameras 50, 52 used are preferably positioned on the head to look up and forward on the probe side. These cameras 50, 52 are used when installing and uprighting the system. These cameras 50, 52 also provide the operator views when traversing flowslots 13 of the support. The lighting and camera operation is preferably controlled by an operator at the computer interface. In one preferred embodiment, a plurality of proximity sensors, preferably eight, alert the operator to unexpected or undesirable operating conditions and also enable the computer to assume automatic control over the device. Further, in one preferred embodiment several tapered bumpers, preferably made from or coated with Delrin.RTM. help guide the head through the flowslot and ensure that the proximity sensors will be within an acceptable distance from the edge of the flowslot and to sense arrival at the preselected position. Other bumpers also serve to absorb potential impacts with support plates while traversing up through the steam generator. Due to the sensitive nature of the generators being inspected, the inspection device is preferably made from strong, non-reactive materials. Materials which include chlorides, fluorides and other halogens are inappropriate materials. The telescoping segment 12 of the present invention is more fully disclosed in commonly assigned U.S. Pat. No. 5,265,129 which is incorporated by reference herein. The segment 12 is a single acting, multi-sectioned telescopic cylinder, designed to deliver inspection head 20 and wand 16 through the flowslot openings in the generator. The segment 12 preferably uses hydraulic pressure as the motive force. The tubes preferably are made from stainless steel. Bronze bushings and aluminum pistons create the bearing surfaces for side loads with two cup seals present on each piston to limit fluid loss. Demineralized water is the preferred fluid, with the preferred maximum operating pressure being approximately 120 psi. The extended height of the tool may be measured by known gauges, but is preferably measured by a string wound take-up spool within the base of the telescoping segment. String tension is maintained by means of the torque supplied by an electric motor linked to the take-up spool via a set of spur gears. A magnetic rotary encoder 259 spinning on an axis common to the motor shaft provides quadrature output, which provides the feedback to a digital servo loop. The motor drive circuitry resides within the drive electronics 252 to limit motor current, thus preventing overheating and potential failure as would be understood by one skilled in the field. The distance the device moves, tube 79 column to tube column 79, down the tube lane within the generator is carefully calibrated such that, as the head of the device with the finger-like projections engages the tubes, the precise location of the device and the exact tube column being inspected is known with certainty. The inspection device, therefore may be made to move across the tube lanes 81 tube by tube if desired. The mechanism is preferably driven and computer controlled, and designed to step one tube at a time on command if desired, and send and receive positioning information allowing an operator to precisely and reliably know the precise area of the generator being inspected. The specially designed registration fingers or guides are made from materials which will not damage the tubes or any of the internal parts of the steam generator, but will also be durable enough to survive the harsh conditions. Preferable bumper materials include Teflon.RTM., and Delrin.RTM.. The guides are kept in place using either diverted pressure or spring tension from springs in the event air pressure is lost. A plurality of guides may be used, with two sets of positioning guides used on each side of the device head being particularly preferred. As mentioned above, the mounting rail can be made to automatically position the base of the device to maintain its vertical position to the next tube row. When the vertical telescoping assembly is mechanically raised to the predetermined desired location, an inspection wand 16 or arm is swung away from the body of the vertical structure perpendicular to the first boom 12 and rail assembly and at a progressive angle until the arm is positioned at a desired location between the desired tube columns, and at a desired specified height between said tube columns, as shown in FIG. 3. Preferably, the camera head comprises at least one radiation tolerant charge coupled device (CCD) color video camera. The camera preferably is fixed focus and is remotely computer controlled with the necessary circuitry and supporting wires and cables to receive positioning instructions, and to send back to the control station, and other various displays, transmissions from the camera in the form of pictures and location information, as would be readily understood by one skilled in the field of microcameras, robotics and circuitry. Therefore the system is controlled remotely by the computer once it is installed. The control station has the capability to record the output of the cameras on a VCR or other monitor. The device functions may be controlled by commands which may be given on even a lap top-type computer as would be readily understood by one skilled in the field. The operator interface provides information to the operator such as wand position, device height, registration position, tilt angle, tube row and column being viewed, as well as a number of other functions as may be desired. As mentioned above, the wand additionally is able to extend to a predetermined position on command by extending the wand length 276 in yet another telescoping fashion via a telescoping mechanism. In this way, the wand 17 and probe head 20 can move into any desired position in the steam generator (e.g. into the tube lanes, into the tube bundles between tube columns, beneath and above support plates, etc.) by combining the movements of the vertical telescoping boom 12 and the telescoping movements of the wand 17. The upper wand camera 40, near the wand pivot point, further allows the operator to view down the length of the wand as it is deployed. This feature allows the operator a view of the operation of the wand 16, as well as a view of the condition of the generator interior. Therefore the device of the present invention can deliver status updates of the generator inspection to an operator in numerical and graphical form if desired; specifically relaying precise probe location (probe is the housing containing the camera and lights at the distal end of the wand) such as support plate level, tube row, tube column, joint value, etc. In addition tilt sensor readings, proximity sensor readings, air and hydraulic pressure readings and registration guide condition can all be delivered to the operator and optionally recorded via the attached supporting computer 240. Once installed, all mechanical operations of the device of the present invention may be manually or automatically power driven through electric and pneumatic controls with the video inspection accomplished using high resolution miniature cameras with complementary lighting devices. In operation, system commands are relayed by the operator via the computer to give absolute, relative and jog commands for individual points. Further, automatic commands may be computer programmed to carry out a specific inspection sequence, giving automatic sequences to position the probe. As mentioned above, additional cameras 50, 52 can be positioned about the inspection device, some cameras carrying the wand and probe head in the field of view, to have a view of the device itself within the generator. Programs can be provided to the computer to allow for sophisticated camera switching at any desired time to deliver images to selected monitors as desired. It is understood that useful computer programs can be written and implemented to control the present device and to prevent the operator from inadvertently entering any commands which could damage the probe or the entire inspection device. Of course such safety measures could be written to be overridden in an emergency. Preferably, the control hardware for the present invention can be divided into primary control hardware and operator station hardware. The primary control hardware is set up at the steam generator platform and comprises two small suitcase-sized cases 312, 314 in FIG. 15. One case contains the main control console 312 and the second case 314 contains bulk power supplies. Plant supplied AC power and compressed air are required to be supplied to these cases for system operation. A switching-type power supply provides power to sensitive computer hardware from the main control console case. The main control console 302 provides the system manual control capability. Power for motor loads, lighting, cameras and support circuitry is supplied by the bulk power supply case 314. All system component connections terminate at the main control console 302. The operator station for the device preferably contains a control computer 302, running a Microsoft Windows based graphical user interface, associated control hardware 304, video monitoring 300 and recording equipment and audio communication equipment. In one preferred embodiment, audio communications link the steam generator platform and the operator station to assist in setup and installation. The control computer preferably is a PC/104, standard 80486, 25 MHz, PC compatible microprocessor. In one preferred embodiment, distributed off the common PC/104 bus are three additional devices; 1) a Win Systems 48 channel digital I/O 280, 2) a Win Systems analog I/O 250 providing eight 12 bit analog inputs and two 12 bit outputs and 3) a Motion Engineering 32 bit 4 axis motion controller 260. Three custom designed printed circuit boards interface each of these devices with associated components. The remaining applications to run the present system would be readily understood by one skilled in the field of remote inspection equipment. See FIG. 16 for the computer block diagram outlining one particularly preferred design. FIG. 16 shows a computer interface for remote operation. A sensor reading and lamp powering device 250 provides power to a probe lamp 256 through an amplifier 253 in the support electronics 252. The output of sensors, such as tilt sensors 257 and pressure sensors 258, are buffered by buffers 254 and read by the sensor reading and lamp powering device 250. The support electronics 252 also contain a motor driver 255 to run the encoder motor 259. The encoder's input 270 passes through amplifier 264 and buffer 263 from the motion controller 260. Feedback is provided by the encoder 270 to the motion controller 260. The motion controller 260 receives feedback from the rack drive 272, the wand angle 274, and the wand length 276 and provides control signals through corresponding amplifiers 265, 266, and 267. A digital I/O controller 280 through optical isolators and relay electronics 282 in the I/O support electronics 282 provide control signals to the registration guides 286, the lighting 288, the pumps 290, and the cameras 292 and receives control inputs 294. Interconnecting cable 242 connects the computer 240 with the analog sensor reading/lamp power/motor driver device 250, the motion controller 260, and the digital I/O controller 280. The working mechanism for the wand 16 of the present invention may be powered, hydraulically , pneumatically, etc., with a pneumatically controlled design being particularly preferred. The preferred hydraulic pump assembly 306 for the telescoping (second) boom of the present invention comprises a centrifugal vane pump, pressure relief valve, two proportional control valves, a solenoid block valve, a fluid reservoir and pressure gauges. Control power and signals are fed from the main control console 302 over a single cable and main 110V AC power to operate the pump 306 is obtained from a source local to the pump. As mentioned earlier, retrieval of the extended inspection device from the generator is a contingency which must be planned for in the event of a partial or complete system malfunction. The present invention depends upon gravity for retraction, and includes an emergency cable (the electrical and pneumatic cable bundle covered with a Kevlar sheath) to serve as a contingency recovery method. The cable 87 is securely attached within the head of the unit and extends the length of the device and out the access port 5. Therefore, the device can be forcibly extracted from the generator by lowering the device and retrieving the device with no lost parts from the device left in the generator after removal is complete. For example, use of exposed screws is avoided. When screws must be present they have retainer clips or safety wires attached. Where screws must be used it is preferable to recess the screws and fill the holes with a suitable filler to lock in the screws. Preferably, the emergency removal can be accomplished whether or not the wand 16 or 17 is in its extended position. Any workable camera may be used in connection with the present invention inspection device. Preferred devices are the charge coupled device (CCD) video cameras, for example as described in U.S. Pat. No. 5,265,129 which is incorporated by reference herein. The range of camera view can be increased to desired specifications by patching multiple cameras to the camera head on the wand 16 and elsewhere throughout the device including on the telescoping stem such that every aspect of the device can be viewed on the monitors. The materials selected for the device including the camera housings must be able to withstand harsh environmental conditions. It is understood that the camera will withstand excessive temperatures of at least about 50.degree. C., and may include passive or active cooling means. The probe camera cable system is preferably completely encased in a housing along the wand, preferably having constant cable tension during probe (wand) retraction. The cameras, according to one preferred embodiment, and as shown in the drawings, are preferably integrated into the wand along with the required lighting units as part of the camera structure. Preferred cameras are modified Toshiba QN401E 1/4" cameras, although other CCD cameras may be modified for use with the present invention as would be understood by one skilled in the electronics field. The primary function of the probe 20 is to house the cameras 400 along with supporting lighting fixtures 402, 404. The primary function of the wand 16 or 17 is to position the camera 400 for inspection. The wand 16 or 17 is preferably telescoping and wired to a computer to send and receive information for proper positioning. The wand preferably has an electromagnetic clutch attached to a de-couple drive, but could use any drive mechanism that can reliably move and position the wand as would be understood to one skilled in the field of drive mechanics. The device of the present invention will facilitate inspection of any closed vessel where maneuverability is critical and hard-to reach areas requiring visual inspection are required to keep the vessel in service. The entire device is designed to be a non-invasive device in the unlikely event of malfunction where careful retrieval and complete device removal would be required. As already mentioned, an in-bundle probe delivers the camera to the desired tube row with the device having at least one rotating joint and at least one telescoping vertical and at least one horizontal member. Many other modifications and variations of the present invention are possible to the skilled practitioner in the field in light of the teachings herein. It is therefore understood that, within the scope of the claims, the present invention can be practiced other than as herein specifically described.
040615340	claims	1. A nuclear reactor comprising a concrete shielding vessel with a steel lining, containing a freezable liquid metal coolant comprising the element sodium, a solid nuclear reactor core, a primary heat exchanger and a pump means all submerged in the coolant, the pump means being provided for circulating the coolant liquid within the vessel, cooling pipes within the vessel adjacent the inner surface of said vessel for effecting the freezing of the liquid coolant at the inner surface of the vessel, said cooling pipes containing a liquid metal cooling fluid, an interior wall adjacent the said inner surface, said interior wall comprising a frozen layer of the liquid coolant on and supported by the cooling pipes and the inner surface of the vessel, the said frozen layer interior wall being thin relative to the overall cross-section of the vessel. 2. A nuclear reactor according to claim 1, in which the pipes extending over the surface are closed loops, each loop including a cooler externally of the concrete and steel vessel, and a forced air cooling system for cooling the said liquid metal coolant in the closed loops at the cooler. 3. A nuclear reactor according to claim 1, including additional cooling pipes embedded in the concrete in proximity to the lining. 4. A nuclear reactor according to claim 3, including thermal insulation spaced from said surface. 5. A nuclear reactor according to claim 4, wherein said thermal insulation is located with runs of said cooling pipes disposed on both sides thereof. 6. A nuclear reactor according to claim 1, wherein the liquid coolant is sodium and the cooling fluid within the closed loops contains sodium-potassium alloy, and including further pipes embedded in the concrete and means for passing forced air therethrough. 7. A nuclear reactor according to claim 1, said interior wall being of sufficient thickness such that when the temperature of the liquid coolant inside is 400.degree. C, the temperature at the outer surface of the interior wall is approximately 50.degree. C.
	summary
062020382	summary	The present invention is related generally to a method and system for performing high sensitivity surveillance of various processes. More particularly the invention is related to a method and system for carrying out surveillance of any number of input signals and one or more sensors. In certain embodiments high sensitivity surveillance is performed utilizing a regression sequential probability ratio test involving two input signals which need not be redundant sensor signals, nor have similar noise distributions nor even involve signals from the same variable. In another form of the invention a bounded angle ratio test is utilized to carry out ultrasensitive surveillance. Conventional parameter-surveillance schemes are sensitive only to gross changes in the mean value of a process or to large steps or spikes that exceed some threshold limit check. These conventional methods suffer from either large numbers of false alarms (if thresholds are set too close to normal operating levels) or a large number of missed (or delayed) alarms (if the thresholds are set too expansively). Moreover, most conventional methods cannot perceive the onset of a process disturbance or sensor deviation which gives rise to a signal below the threshold level or an alarm condition. Most methods also do not account for the relationship between a measurement by one sensor relative to another sensor measurement. Another conventional methodology is a sequential probability ratio test (SPRT) which was originally developed in the 1940s for applications involving the testing of manufactured devices to determine the level of defects. These applications, before the advent of computers, were for manufactured items that could be counted manually. As an example, a company manufacturing toasters might sell a shipment of toasters under the stipulation that if greater than 8% of the toasters were defective, the entire lot of toasters would be rejected and replaced for free; and if less than 8% of the toasters were defective, the entire lot would be accepted by the company receiving them. Before the SPRT test was devised, the purchasing company would have to test most or all items in a shipment of toasters being received. For the toaster example, testing would continue until at least 92% of the toasters were confirmed to be good, or until at least 8% of the toasters were identified to be defective. In 1948 Abraham Wald devised a morelrigorous SPRT technique, which provided a formula by which the testing for defective manufactured items could be terminated earlier, and sometimes much earlier, while still attaining the terms of the procurement contract with any desired confidence level. In the foregoing example involving toasters, if the purchasing company were receiving 100 toasters and four of the first eight toasters tested were found to be defective, it is intuitively quite likely that the entire lot is going to be rejected and that testing could be terminated. Instead of going by intuition, however, Wald developed a simple, quantitative formula that would enable one to calculate, after each successive toaster is tested, the probability that the entire lot is going to be accepted or rejected. As soon as enough toasters are tested so that this probability reaches a pre-determined level, say 99.9% certainty, then a decision would be made and the testing could cease. In the 1980s, other researchers began exploring the adaptation of Wald's SPRT test for an entirely new application, namely, surveillance of digitized computer signals. Now, instead of monitoring manufactured hardware units, the SPRT methodology was adapted for testing the validity of packets of information streaming from real-time physical processes. See, for example, U.S. Pat. Nos. 5,223,207; 5,410,492; 5,586,066 and 5,629,872. These types of SPRT based surveillance systems have been finding many beneficial uses in a variety of application domains for signal validation and for sensor and equipment operability surveillance. As recited hereinbefore, conventional parameter-surveillance schemes are sensitive only to gross changes in the process mean, or to large steps or spikes that exceed some threshold limit check. These conventional methods suffer from either large false alarm rates (if thresholds are set too close) or large missed (or delayed) alarm rates (if the threshold are set too wide). The SPRT methodology therefore has provided a superior surveillance tool because it is sensitive not only to disturbances in the signal mean, but also to very subtle changes in the statistical quality (variance, skewness, bias) of the monitored signals. A SPRT-based system provides a human operator with very early annunciation of the onset of process anomalies, thereby enabling him to terminate or avoid events which might challenge safety guidelines for equipment-availability goals and, in many cases, to schedule corrective actions (sensor replacement or recalibration; component adjustment, alignment, or rebalancing; etc.) to be performed during a scheduled plant outage. When the noise distributions on the signals are gaussian and white, and when the signals under surveillance are uncorrelated, it can be mathematically proven that the SPRT methodology provides the earliest possible annunciation of the onset of subtle anomalous patterns in noisy process variables. For sudden, gross failures of sensors or system components the SPRT methodology would annunciate the disturbance at the same time as a conventional threshold limit check. However, for slow degradation that evolves over a long time period (gradual decalibration bias in a sensor, wearout or buildup of a radial rub in rotating machinery, build-in of a radiation source in the presence of a noisy background signal, etc), the SPRT methodology can alert the operator of the incipience or onset of the disturbance long before it would be apparent to visual inspection of strip chart or CRT signal traces, and well before conventional threshold limit checks would be tripped. Another feature of the SPRT technique that distinguishes it from conventional Methods is that it has built-in quantitative false-alarm and missed-alarm. probabilities. This is important in the context of safety-critical and mission-critical applications, because it makes it possible to apply formal reliability analysis methods to an overall expert system comprising many SPRT modules that are simultaneously monitoring a variety of plant variables. A variety of SPRT-based online surveillance and diagnosis systems have been developed for applications in utilities, manufacturing, robotics, transportation, aerospace and health monitoring. Most applications to date, however, have been limited to systems involving two or more redundant sensors, or two or more pieces of equipment deployed in parallel with identical sensors for each device. This limitation in applicability of SPRT surveillance tools arises because the conventional SPRT equation requires exactly two input signals, and both of these signals have to possess identical noise properties. It is therefore an object of the invention to provide an improved method and system for surveillance of a wide variety of industrial, financial, physical and biological systems. It is another object of the invention to provide a novel method and system utilizing an improved SPRT system allowing surveillance of any number of input signals with or without sensor redundancy. It is a further object of the invention to provide an improved method and system utilizing another improved SPRT type of system employing two input signals which need not come from redundant sensors, nor have similar noise distributions nor originate from the same physical variable but should have some degree of cross correlation. It is still another object of the system to provide a novel method and system selectively employing an improved SPRT methodology which monitors a system providing only a single signal and/or an improved SPRT methodology employing two or more input signals having cross correlation depending on the current status of relationship and correlation between or among signal sets. It is also a further object of the invention to provide an improved method and system employing a bounded angle ratio test. It is yet another object of the invention to provide a novel method and system for surveillance of signal sources having either correlated or uncorrelated behavior and detecting the state of the signal sources enabling responsive action thereto. It is an additional object of the invention to provide an improved method and system for surveillance of an on-line, real-time signals or off-line accumulated sensor data. It is yet a further object of the invention to provide a novel method and system for performing preliminary analysis of signal sources for alarm or state analysis prior to data input to a downstream SPRT type system. It is still an additional object of the invention to provide an improved method and system for ultrasensitive analysis and modification of systems and processes utilizing at least one of a single signal analytic technique, a two unique signal source technique and a bounded angle ratio test. It is an additional object of the invention to provide a novel method and system for generating an estimated signal for each sensor in a system that comprises three or more sensors. It is still another object of the invention to provide an improved method and system for automatically swapping in an estimated signal to replace a signal from a sensor identified to be degrading in a system comprising three or more signals. Other objects, features and advantages of the present invention will be readily apparent from the following description of the preferred embodiments thereof, taken in conjunction with the accompanying drawings described below.
054266815	summary	FIELD OF THE INVENTION This invention relates generally to protection systems for shutting down a boiling water reactor (BWR) and maintaining it in a safe condition in the event of a system transient or malfunction that might cause damage to the nuclear fuel core, most likely from overheating. In particular, the invention relates to emergency core-cooling systems (ECCS) for supplying water to the reactor core and containment systems for containing steam and radioactivity escaping from the reactor pressure vessel (RPV) in the event of a loss-of-coolant accident (LOCA) in a BWR. BACKGROUND OF THE INVENTION BWRs have conventionally utilized active safety systems to control and mitigate accident events. Those events varied from small break to design base accidents. Active systems, consisting of both high-pressure and low-pressure pumping equipment, have been the corner-stones of BWR/4 to BWR/6 safety systems product lines. A fully active three-division concept with N+1 capability (i.e., the capability to meet safety requirements despite one disabled division) is incorporated in the Advanced Boiling Water Reactor (ABWR). One alternative to the three active divisions concept is to use four active divisions. The four active divisions concept adds both more ECCS systems and supporting auxiliary systems, which require more maintenance to be performed. This is counter to the objective of reducing maintenance and improving safety. Another alternative to the three active divisions concept is to use passive systems. Totally passive safety systems have been studied for use in BWRs because of their merits in reducing maintenance and surveillance testing of the safety-related equipment, and in eliminating the need for AC power, thereby improving the reliability of BWR operation and safety. Simplified BWRs (SBWRs) have been designed with totally passive safety features that provide more resistance to human error in accident control and mitigation. There are, however, some tradeoffs when employing totally passive safety systems in BWRs. Due to their passive nature, the totally passive system--when designed in accordance with nuclear standards of system separation and diversity--would substantially add to plant size and cost. Therefore passive system applications to BWRs have been limited to small- and mediumsized plants having up to about 1000 MWe output. SUMMARY OF THE INVENTION The present invention is an improved system which combines the advantages of active and passive cooling systems. This invention combines active and passive systems in a single design that meets the safety requirements for BWRs. In addition, the design allows for a safety division out of service for on-line maintenance of the safety equipment during plant operation (N+2 capability). The preferred embodiment of the invention combines three active divisions with a passive fourth division to provide the N+2 capability. In accordance with the invention, an ECCS network is provided which has three active divisions (Divisions I through III) and a passive fourth division (Division IV). The selection of the fourth division to be passive provides diversity in systems and power supply with a resulting increase in plant reliability. The passive system also contains fewer parts so it provides the N+2 capability without a large increase in maintenance. From the licensing standpoint, a design with three active divisions and one passive division contains, at a minimum, the safety elements of the ABWR while introducing the passive features of the SSWR. The active systems include the traditional high-pressure and low-pressure safety systems that derive their power source from either reactor steam or from off-site AC power backed by on-site diesel generator power. The design of the active system divisions is similar to the known ABWR design. The passive division in accordance with the present invention derives its power supply from the plant battery bus. This division (as described herein) incorporates the following passive equipment: a gravity-driven cooling system (GDCS) for both short- and long-term reactor inventory supply; a primary containment cooling system (PCCS); a reactor heat removal condenser (RHR-CND) as a backup for the active reactor heat removal heat exchanger (RHR-HX) coupled to the suppression pool (SP), and the release valves (RLVs) connecting the RHR-CND to the RPV. Both the PCCS and RHR-CND are located in the condenser pool above the drywell. Multiple benefits accrue from combining the active and passive safety system divisions in a single design. First, the resulting system combines the individual merits of the active and passive systems. Second, the passive systems carry the load in the event that active systems are rendered inoperative and also share the load under plant degraded conditions. Therefore the passive systems serve the function of backing up the active systems. Third, the resulting design is feasible because it is based on the experience gained in the ABWR and SBWR designs. Lastly, the resulting reliability of the active/passive design concept is higher than the purely active concept of the ABWR. A BWR design combining the active safety systems of the ABWR with the passive safety features of the SBWR offers a new approach in combining the merits of both designs to provide diversity in core cooling, inventory makeup, depressurization and ultimate heat sink. In addition, the combined active/passive safety system of the invention provides increased plant reliability because of the diversity offered by the passive fourth division. The passive fourth division of the invention in turn incorporates a new system, the RHR-CND, which is used in conjunction with RLVs to provide backup depressurization of the RPV and backup heat removal and inventory control for events such as station blackout and reactor isolation. This is a medium-pressure system which is unique in operation compared to past isolation condenser (high pressure) and passive containment cooling (low pressure) systems. To improve plant availability and utilization of manpower, on-line maintenance is considered desirable for the ECCS network. By making the fourth division passive, on-line maintenance can be achieved without increasing the number of diesel generators, service systems and component cooling water systems.
047675934	summary	BACKGROUND OF THE PRIOR ART This invention relates generally to pressure vessels and in particular to pressure vessels for withstanding cyclic pressure and temperature extremes such as those found in nuclear reactor pressure vessels. Pressure vessels used for containing a nuclear reactor must be designed for operating conditions involving a combination of high temperatures and high pressures along with strong radiation in the form of neutrons and gamma rays. The pressure vessel must also be designed for emergency conditions such as Loss of Coolant Accidents (LOCA) and Pressurized Thermal Shock (PTS). The LOCA conditions may cause the vessel pressure to drop suddenly while the temperature may remain the same or even increase The PTS condition, which may be caused by the injection of cold "coolant" into the pressure vessel from the emergency core cooling system (ECCS), may cause steep temperature gradients, such as, a sudden drop in temperature of the inside surface of the pressure vessel and a portion of the vessel wall, while the pressure may remain constant or even increase. When pressure vessels are subjected to these pressure and temperature extremes, high tensile stresses are produced inside the vessel wall, particularly in the region of wall penetrations, such as, coolant inlet and outlet ports of the pressure vessel. During pressurized thermal shock (PTS) (as might be caused by a loss of coolant accident (LOCA)) where cold coolant is introduced to replace the lost coolant, steep thermal gradients in the vessel wall may cause large tensile stresses to occur in the crotch region of the vessel-outlet and vessel-inlet port intersections which may result in cracking of the vessel wall. In addition, crack initiation may be aided due to embrittlement of the vessel wall by the high level of neutron and gamma radiation being absorbed. To alleviate this condition, some multiple layer pressure vessels of the prior art utilized concentrically disposed multiple shell pressure vessels shrunk fit onto each other. Other pressure vessels utilized multiple layers of sheet metal spirally wrapped around the outside of an inner pressure vessel. In some of the pressure vessels using spaced apart shells, the space between the shell was filled with a neutron absorbing material. One prior art device utilized spaced apart pressure vessel shells filled with coolant or a low melting point material to effect a uniform pressure distribution. The filler material was not maintained under pressure. SUMMARY OF THE INVENTION The multiple shell pressure vessel of the present invention utilizes a set of concentrically disposed, spaced apart pressure vessel shells surrounding an inner pressure vessel, the spaces between the pressure vessel shells being filled with a low melting point, high boiling point material, selected from the group consisting of lead, tin, antimony, bismuth, or sodium and potassium, and mixtures thereof, pressurized to a pressure whereby the wall of the innermost pressure vessel shell is in compression or very low tension during steady state operation. Chemical compositions or compounds containing boron or cadmium may also be added to the molten filler material. The pressure vessel of the present invention may also include devices for maintaining the pressure in the space between the innermost pressure vessel shell and the next inner pressure vessel shell at a constant predetermined multiple of the pressure in the innermost pressure vessel The present invention also includes a configuration of concentric conduit pressure vessel penetration that reduces tensile stresses resulting from transient thermal and pressure variations. The present invention also includes a method of fabricating the multiple shell pressure vessel utilizing concentric, spaced apart pressure vessel shells and the subsequent (or simultaneous) introduction of molten filler materials and the pressurization thereof. It is, therefore, an object of the present invention to provide a pressure vessel offering greater safety with respect to initiation and propagation of cracking due to pressurized thermal shock (PTS) It is a further object of the present invention to provide a multiple shell pressure vessel in which the wall of the innermost pressure vessel shell is maintained in compression during steady state operation of the pressure vessel It is still another object of the present invention to provide a multiple shell pressure vessel in which the wall of the innermost pressure vessel is always maintained in compression or in low tension below the yield point of the wall material of the innermost pressure vessel during a temperature or pressure transient within the innermost pressure vessel shell It is yet a further object of the present invention to provide a multiple shell pressure vessel in which the spaces between the pressure vessel shells are filled with a low melting point, high boiling point material that is pressurized to a point whereby the wall of the innermost pressure vessel is maintained in compression during normal operation. It is also another object of the present invention to provide a device whereby the compression in the wall of the innermost pressure vessel shell is maintained relatively constant for variations in pressure within the innermost pressure vessel. It is yet another object of the present invention to provide a method of fabricating a multiple shell pressure vessel with pre-stressed (or pre-pressurized) fillers. These and other objects of the present invention will become manifest upon study of the following specification when taken together with the drawings .
	description	This is a Division of application Ser. No. 10/208,033 filed Jul. 31, 2002, now U.S. Pat. No. 6,665,051, which in turn is a Divisional of application Ser. No. 09/259,137 filed Feb. 26, 1999, now U.S. Pat. No. 6,452,661. The entire disclosure of the prior applications is hereby incorporated by reference herein in their entirety. The present invention relates to an illumination system capable of providing uniform illumination, and more particularly relates to an exposure apparatus incorporating the illumination system, and a semiconductor device manufacturing method using same. Conventional exposure apparatus for manufacturing semiconductor devices include an illumination system for illuminating a circuit pattern formed on a mask and projecting this pattern through a projection optical system onto a photosensitive substrate (e.g., a wafer) coated with photosensitive material (e.g., photoresist). One type of projection optical system employs an off-axis field (e.g., an arcuate field) and projects and transfers only a portion of the mask circuit pattern onto the wafer if the exposure were static. An exemplary projection optical system having such a field comprises two reflecting mirrors, a concave mirror and a convex mirror. In such projection optical systems, transfer of the entire mask circuit pattern onto the wafer is performed dynamically by simultaneously scanning the mask and wafer in a fixed direction. Scanning exposure has the advantage in that a high resolving power is obtained with a comparatively high throughput. In scanning-type exposure apparatus, an illumination system capable of uniformly illuminating with a fixed numerical aperture (NA) the entire arcuate field on the mask is highly desirable. Such an illumination system is disclosed in Japanese Patent Application Kokai No. Sho 60-232552. With reference to FIG. 1, an illumination system 10, disclosed therein, comprises, along an optical axis A, an ultrahigh-pressure mercury lamp 12, an elliptical mirror 14, and an optical integrator 16. With reference now also to FIG. 2, optical integrator 16 has an incident surface 16i, an exit surface 16e, and comprises a combination of four segmented cylindrical lenses 16a-16d. Lenses 16a and 16d are located at the respective ends of optical integrator 16, are oriented in the same direction, and have a focal length f1. Lenses 16b and 16c are located between lenses 16a and 16d and are each oriented in the same direction, which is substantially perpendicular to the orientation of lenses 16a and 16d. Adjacent optical integrator 16 is a first condenser optical system 18 and a slit plate 20. With reference now also to FIG. 3, the latter includes an arcuate aperture 20A having a width 20W and a cord 20C. Adjacent slit plate 20 is a condenser optical system 22 and a mask 24. Mercury lamp 12 generates a light beam 26 which is condensed by elliptical mirror 14 onto incident surface 16i of optical integrator 16. By virtue of having two different focal lengths, optical integrator 16 causes light beam 26, passing therethrough, to have different numerical apertures in orthogonal directions to the beam (e.g., in the plane and out of the plane of the paper, as viewed in FIG. 1). Light beam 26 is then condensed by condenser optical system 18 and illuminates slit plate 20 and arcuate aperture 20A. Light beam 26 then passes therethrough and is incident condenser optical system 22, which condenses the light beam to uniformly illuminate a portion of mask 24. With continuing reference to FIG. 3, a rectangular-shaped region 28 on slit plate 20 is illuminated so that at least arcuate aperture 20A is irradiated. Thus, light beam 26 is transformed from a rectangular cross-section beam to an arcuate illumination beam, corresponding to aperture 20A. Note that aperture 20A passes only a small part of the beam incident slit plate 20. Generally, arcuate cord 20C is made long to increase the size of the exposure field on the wafer. In addition, arcuate slit width 20W is set comparatively narrow to correspond to the corrected region of the projection optical system used in combination with illumination system 10. The illumination efficiency is determined by the ratio of surface area of arcuate aperture 20A to rectangular-shaped region 28. This ratio is small for illumination system 10, an indication that the system is very inefficient, which is disadvantageous. As a result, the amount of light reaching mask 24 is fixed at a relatively low level. Since the time of exposure of mask 24 is inversely proportional to the amount of light (i.e., intensity) at the mask (i.e., the more intense the light, the shorter the exposure time), the scanning speed of the mask is limited. This limits the exposure apparatus' ability to process an increasingly large number of wafers (e.g., to increase throughput). The present invention relates to an illumination system capable of providing uniform illumination, and more particularly relates to an exposure apparatus incorporating the illumination system, and a semiconductor device manufacturing method using same. Accordingly, the present invention has the goals of providing an illumination system capable of supporting higher throughput with an illumination efficiency markedly higher than heretofore obtained. Another goal is to maintain uniform illumination (e.g., uniform Köhler illumination). There has been a strong desire in recent years for a next-generation exposure apparatus capable of projecting and exposing a pattern having a much finer line width onto a photosensitive substrate by using a light source, such as a synchrotron, that supplies soft X-rays. However, prior art illumination systems are not capable of efficiently and uniformly illuminating a mask with X-ray wavelength light (“X-rays”). Consequently, the present invention has the further goal of supplying an illumination system and exposure apparatus capable of efficiently and uniformly illuminating a mask with X-rays, and further to provide a method for manufacturing semiconductor devices using X-rays. Accordingly, a first aspect of the invention is an illumination system for illuminating a surface over an illumination field having an arcuate shape. The system comprises a light source for providing a light beam and an optical integrator. The optical integrator includes a first reflective element group having an array of first optical elements each having an arcuate profile corresponding to the arcuate shape of the illumination field. Each first optical element also includes an eccentric reflecting surface comprising an off-axis section of a spherical reflecting surface or an off-axis section of an aspherical reflecting surface. The array of first optical elements is designed so as to form a plurality of arcuate light beams capable of forming multiple light source images. The illumination system further includes a condenser optical system designed so as to condense the plurality of arcuate light beams to illuminate the surface over the arcuate illumination field in an overlapping manner. A second aspect of the invention is the illumination system as described above, wherein the condenser optical system comprises a condenser mirror with a focal point, with the condenser mirror arranged such that the focal point substantially coincides with the surface to be illuminated. A third aspect of the invention is an illumination optical system as described above, further comprising a second reflective element group having a plurality of second optical elements. Each of the second optical elements has a rectangular shape and a predetermined second reflecting curved surface which is preferably an on-axis section of a spherical or aspherical reflective surface. The first and second reflecting element groups are opposingly arranged such that the multiple light source images are formed at the plurality of second optical elements when the light beam is incident the first reflecting element group. A fourth aspect of the invention is an exposure apparatus for exposing the image of a mask onto a photosensitive substrate. The apparatus comprises the illumination system as described above, a mask stage capable of supporting the mask, and a substrate stage capable of supporting the photosensitive substrate. A projection optical system is arranged between the mask stage and the substrate stage, and is designed so as to project a predetermined pattern formed on the mask onto the photosensitive substrate over an arcuate image field corresponding to the arcuate illumination field. A fifth aspect of the invention is an exposure apparatus as described above, and further including drive apparatus designed so as to synchronously move the mask stage and the wafer stage relative to the projection optical system. A sixth aspect of the invention is the exposure apparatus as described above, wherein the illumination system includes a first variable aperture stop having a first variable diameter. The projection optical system further includes a second variable aperture stop having a second variable diameter. First and second drive systems are operatively connected to the first and second variable aperture stops, respectively, so as to change the first and second variable diameters, respectively. A control apparatus is also preferably included. The control apparatus is electrically connected to the first and second drive units so as to control the coherence factor by varying the first and second variable aperture diameters. A seventh aspect of the invention is a method of patterning the surface of a photosensitive substrate with a pattern on a mask in the manufacturing of a semiconductor device. The method comprising the steps of first, providing an illumination light beam. The next (i.e., second) step is reflectively dividing the illumination light beam into a plurality of arcuate light beams corresponding to an arcuately shaped illumination field. The next step is condensing the arcuate light beams onto the mask over the arcuately shaped illumination field. The final step is projecting light from the mask onto the photosensitive substrate. The present method preferably further includes the steps in the above-mentioned second step, of first reflecting the light beam from a first array of reflecting elements each having an arcuate shape and a reflecting surface having an eccentric curvature, and forming a plurality of light source images, and then second, reflecting light from the plurality of light source images with a second array of reflecting elements opposingly arranged relative to the first array of reflecting elements. The present invention relates to an illumination system capable of providing uniform illumination, and more particularly relates to an exposure apparatus incorporating the illumination system, and a semiconductor device manufacturing method using same. With reference to FIGS. 4 and 5, exposure apparatus 50 comprises, along an optical axis AC, a light source 54 which supplies light of wavelength λ<200 nm. A preferred light source is a laser, such as an ArF excimer laser supplying light of wavelength λ=193 nm, or an F2 laser supplying light of wavelength λ=157. Alternatively, light source 54 may be an X-ray radiating apparatus such as a laser plasma X-ray source radiating X-rays of wavelength λ=10-15 nm or λ=5-20 nm, a synchrotron generating apparatus radiating light of wavelength λ=10-15 nm, λ=5-20 nm and the like. Exposure apparatus 50 further comprises an optical integrator (i.e., a multiple light source forming system) 56. Light beam 100 from light source 54 is directed to optical integrator 56. Optical integrator 56 is disposed in a predetermined position to receive light beam 100. Optical integrator 56 comprises a reflecting element group 60 having a plurality of reflecting elements E (FIG. 5) arranged two-dimensionally in dense formation (i.e., in an array) along a predetermined first reference plane P1 parallel to the Y-Z plane. Specifically, as shown in FIG. 5, reflecting elements E have reflecting curved surfaces with an arcuate shape (profile). In a preferred embodiment, reflecting elements E are arranged in a number of columns 62 (e.g., five columns, as shown) arranged along the Y-direction. Each column 62 comprises a plurality of reflecting elements E arranged along the Z-direction. Furthermore, columns 62 are designed such that together they roughly form a circular shape. The arcuate shape of reflecting elements E is similar to the shape of the arcuate illumination field formed on the mask, as discussed further below. With reference now to FIGS. 6 and 7, each reflecting element E comprises an arcuate section, removed from an optical axis AE, of a reflecting curved surface S of radius of curvature RE. Surface S is centered on optical axis AE and has an apex OE. Further, arcuate reflecting element E has a center CE removed from optical axis AE by a heigh hE. Accordingly, each reflecting element E comprises an eccentric reflecting surface RSE which is a section of reflecting curved surface S. Reflecting surface RSE is the effective reflecting region of reflecting element E that reflects light (e.g., light beam 100) from light source 54. With reference again to FIG. 4, exposure apparatus 50 further comprises a condenser optical system 64 having a condenser mirror 66 removed from optical axis AC. Condenser mirror 66 comprises a section of a spherical mirror 66′ (dashed line) centered on optical axis AC and having a radius of curvature RC (not shown). Optical axis AC passes through the center of a plane P2 located on optical axis AC. However, the focal point (not shown) of condenser mirror 66 is located on optical axis AC. The latter is also parallel to each optical axis AE of plurality of optical elements E in optical element group 60. Exposure apparatus 50 further comprises a fold mirror 68 for folding the optical path between condenser optical system 64 and a reflective mask M, and a mask stage MS for movably supporting the reflective mask M having a backside MB, and a reflective front side MF with a pattern (not shown), such as a circuit pattern. Mask stage MS is operatively connected to a mask stage drive system 72 for driving the mask stage in two-dimensional movement in the X-Y plane. A control system 74 is electrically connected to drive system 72 to control its operation. A projection optical system 76 is disposed in the optical path between reflective mask M and a photosensitive substrate such as wafer W. Projection optical system 76 includes an optical axis AP and is preferably an off-axis-type reduction system comprising, for example, four aspherical mirrors 78a-78d. The latter have effective reflecting surfaces at positions removed from optical axis AP. Mirrors 78a, 78c and 78d comprise concave aspherical mirrors, and mirror 78b comprises a convex aspherical mirror. A pupil position P is located at a reflecting surface SC of mirror 78c. An aperture stop (not shown) is provided at pupil position P. Exposure apparatus 50 further comprises a wafer stage WS for movably supporting a wafer W having a surface WS coated with a photosensitive material, such as photoresist. Wafer stage WS is connected to a wafer stage drive system 92 for driving the wafer stage in two-dimensional movement in the X-Y plane. Drive system 92 is also electrically connected to control system 74 which controls drive system 92 and also coordinates the relative driving of drive systems 72 and 92. The operation of exposure apparatus 50 is now described with reference to FIGS. 4 and 6. A light beam 100 having a wavefronts 105 and a beam diameter DB emanates from light source 54 and travels parallel to optical axis AC and also parallel to optical axis AE of reflecting element E (FIG. 6). Light beam 100 then reflects from each reflecting surface RSE of element E and is condensed at a focal point position FE (FIG. 6) on optical axis AE. A plurality of light source images I are formed corresponding to each reflecting element E (FIG. 6). If focal length fE of reflecting element E is equal to the distance between apex OE and focal point position FE, and RE is the radius of curvature of the reflecting curved surface S, then the relationship in condition (1) below holds:fE=−RE/2. (1) With continuing reference to FIGS. 4 and 6, wavefronts 105 of light beam 100 are incident reflecting element group 60 substantially perpendicular, thereby forming, upon reflection from reflecting elements E, a plurality of converging beams 108 each having an arcuate cross-section (hereinafter, “arcuate light beam”). This results in the formation of plurality of light source images I at plane P2. Light source images I are displaced from incident light beam 100 in direction perpendicular to optical axis AE. The number of light source images I corresponds to the number of reflecting elements E in reflecting element group 60. In other words, assuming light beam 100 is incident reflecting elements E from a direction parallel to each optical axis AE, light source images I are respectively formed in plane P2 through which focal point position FE passes. In this manner, reflecting element group 60 functions as an optical integrator, i.e., a multiple-light-source forming optical system capable of forming a plurality of secondary light sources. With continuing reference to FIG. 4, light beams 110 emanating from plurality of light source images I are respectively reflected and condensed by condenser mirror 66, which forms condensed light beams 116. The latter are deflected by deflection (fold) mirror 68 and arcuately illuminate front side MF of mask M in a superimposed manner. With reference now to FIG. 8, an arcuate illumination field IF, as formed on mask M when viewed from backside MB, has a center of curvature OIF on optical axis AP of projection optical system 76. If fold mirror 68 were to be removed, arcuate illumination field IF would be formed at position (plane) IP, and center of curvature OIF of arcuate illumination field IF would be located on optical axis AC. In exposure apparatus 50 of FIG. 4, optical axis AC is not deflected 90° by a fold mirror. However, if optical axis AC were so deflected by a hypothetical reflecting surface 68A, optical axis AC and optical axis AP would become coaxial and intersect mask M. Consequently, it can be said that optical axes AC and AP are optically coaxial. Accordingly, condenser mirror 66 and projection optical system 76 are arranged such that optical axes AC and AP optically pass through center of curvature OIF of arcuate illumination field IF. Light from condensed light beams 116 reflects from front side MF of mask M, thereby forming a light beam 118 which is incident projection optical system 76. The latter forms an image of the pattern present on mask front side MF over an arcuate image field IF′ on surface WS of wafer W. Mask stage MS moves two-dimensionally in the X-Y plane via drive system 72, and substrate stage WS moves two-dimensionally in the X-Y plane via drive system 92. Control system 74 controls the drive amount of drive systems 72 and 92. In particular, control system 74 moves mask stage MS and substrate stage WS synchronously in opposite directions (as indicated by arrows) via the two drive systems 72 and 92. This allows for the entire mask pattern to be scanned and exposed onto surface WS of wafer W through projection optical system 76. In this manner, semiconductor devices can be manufactured, since satisfactory circuit patterns are transferred (“patterned”) onto surface WS of wafer W. The operation of reflecting element group 60 is now explained in greater detail. With reference now to FIG. 9, reflecting element group 60 comprises, for the sake of explanation, three reflecting elements Ea-Ec arranged along plane P1 parallel to the Y-Z plane such that the position of the center of curvatures (the focal points) of each reflecting element Ea-Ec reside on plane P2. Light beam 100 comprises collimated light beams 100a and 100c comprising wavefronts 105a and 105c, respectively, that are incident reflecting elements Ea and Ec. The latter form, from light beams 100a and 100c, converging arcuate light beams 108a and 108c, respectively, which correspond to the profile shape of reflecting surface RSEA of reflecting element Ea and reflecting surface RSEC of reflecting element Ec. Arcuate light beams 108a and 108c converge to form light source images Ia and Ic, respectively, at plane P2. Subsequently, diverging light beams 110a and 110c emanate from light source images Ia and Ic and propagate toward condenser mirror 66. The latter condenses light beams 110a and 110c, thereby forming condensed light beams 116a (solid lines) and 116c (dashed lines). Light beams 116a and 116c are condensed by condenser mirror 66 such that they overlap (i.e., are super-imposed) and obliquely illuminate front side MF of mask M over arcuate illumination field IF. The Z-direction (i.e., the direction in the plane of the paper) along mask front side MF is the width direction of arcuate illumination field IF. Thus, light reflects from each reflecting element E in reflecting element group 60 and arcuately illuminates mask M over arcuate illumination field IF in an overlapping (i.e., superimposed) manner, allowing uniform illumination to be achieved. Uniform Köhler illumination is achieved when each light source image I formed by each reflecting element E is re-imaged at pupil position P of projection optical system 76 Even if the entire illumination system (i.e., elements 54 through 68) and projection optical system 76 includes only catoptric members and catoptric elements, an arcuate illumination field IF with uniform illumination intensity can be efficiently formed on mask M while substantially maintaining Köhler illumination. By making the projective relationship of condenser optical system 64 a positive projection, mask M can be illuminated with a uniform numerical aperture (NA), regardless of illumination direction. With reference again to FIG. 5, by densely arranging reflecting elements E such that reflecting element group 60 has a roughly circular outline, the outline (profile) of the secondary light sources formed by plurality of light source images I formed at position P2 is also roughly circular. Accordingly, by making the projective relationship of condenser mirror 66 a positive projection and by simultaneously setting the outline (profile) of plurality of light sources I, the spatial coherence inside arcuate illumination field IF formed on mask M can be rendered uniform regardless of the location and direction of incident beams 116 (see FIG. 9). Furthermore, by configuring the shape of reflecting surface RSE of each reflecting element E so that the projective relationship is identical to that of condenser mirror 66, the illumination intensity in arcuate illumination field IF can be rendered even more uniform, without generating distortion due to reflecting element group 60 and condenser mirror 66. With reference again to FIG. 8, an exemplary arcuate illumination field IF has a central arc 130 of radius RIF and an angle αIF=60°, ends IFa and IFb separated by a linear distance LIF=96 mm, a width WIF=6 mm, and an illumination numerical aperture NA=0.015 at mask M. Further, the inclination of the principle ray (not shown) of the illumination light with respect to the mask normal (not shown) is approximately 30 mrad (i.e., the entrance pupil position of projection optical system 76 is approximately 3119 mm from mask M), and diameter DB of light beam 100 from light source 54 is on the order of 42 mm (FIG. 4). The above description considered reflecting elements E and condenser mirror 66 both with eccentric spherical reflecting surfaces. However, these surfaces can also be aspherical surfaces. Below, specific numerical values for these surfaces as aspherical surfaces are provided. With reference now to FIG. 10, reflecting element E includes an arcuate section, removed from optical axis AE, of a reflecting curved aspherical surface ASE and a reference spherical surface SE having a common apex OE. Spherical surface SE has a center of curvature ORE. The X-axis passes through apex OE in the direction perpendicular to a plane PT tangential at apex OE (optical axis AE of reflecting element E is co-linear with the X-axis). The Y-axis passes through apex OE in the plane of the paper and is perpendicular to the X-axis. The origin of the X-Y coordinate system is apex OE. Accordingly, each reflecting element E comprises an eccentric aspherical reflecting surface ARSE which is a section of reflecting curved aspherical surface ASE. Aspherical reflecting surface ASE is described by the expression for an aspherical surface, below, wherein x(y) is the distance along the direction of the X-axis (optical axis AE) from the tangential plane at apex OE to the surface ASE, y is the distance along the direction of the Y-axis from the X-axis (optical axis AE) to reflecting surface ASE, RE is the radius of curvature of reference spherical surface SE ,-and C2, C4, C6, C8 and C10 are aspherical surface coefficients.x(y)=(y2/RE)/[1+(1−y2/RE2)0.5]+C2y2+C4y4+C6y6+C8y8+C10y10 An exemplary aspherical reflecting surface ASE has the following parameter values: RE=−183.3211 C2=−5.37852×10−4 C4=−4.67282×10−8 C6=−2.11339×10−10 C8=5.71431×10−12 C10=−5.18051×10−14 Each reflecting element E in reflecting element group 60 has a reflecting cross-sectional shape that interposes heights y1 and y2 from optical axis AE and comprises an arcuate aspherical eccentric mirror. In an exemplary illumination system 50 illustrated in FIG. 11, length LIF between ends IFa and IFb of arcuate illumination field IF at an arc open angle αE of 60° is approximately 5.25 mm (see FIG. 11), height y1 is approximately 5.085 mm, height y is approximately 5.25 mm, and height y2 is approximately 5.415 mm. In this case, plurality of light source images I (FIG. 10) formed by reflecting element E are formed at a position axially removed from apex OE by X1=76.56 mm, with height y=5.25 mm from the center diameter arc 130 (FIG. 11). The position of light source images I in a direction perpendicular to optical axis AE is removed by y1=5.085 mm from the inner diameter IFi of arcuate illumination field IF, and is removed by y2=5.415 mm from the outer diameter IFo. Thus, a satisfactory reflecting element group 60 (FIG. 5) can be constituted by arranging, in columns, a plurality of eccentric aspherical reflecting elements E having the above dimensions. Next, an exemplary condenser mirror 66 in condenser optical system 64, for the case where reflecting element group 60 comprises a plurality of eccentric aspherical reflecting elements E having the above dimensions, is discussed. With reference now to FIG. 12, condenser mirror 66 comprises, in a preferred embodiment, a section ARSC of reflective an aspherical surface ASC, with associated reference spherical surface SC having a common apex OC. Reference spherical surface SC has a center of curvature ORC. The X-axis is the direction perpendicular to a tangential plane P′T at apex OC (optical axis AC is the X-axis). The Y-axis is the direction parallel to tangential plane P′T at apex OC. The origin of the X-Y coordinate system is apex OC. Reflecting aspherical surface ASC associated with condenser mirror 66 is described by the expression for an aspherical surface below, wherein x(y) is the distance along the direction of the X-axis (optical axis AC) from tangential plane P′T at apex OC to reflecting aspherical surface ASC, y is the distance along the Y-axis from the X-axis (optical axis AC) to reflecting aspherical surface ASC, RC is the radius of curvature of reference spherical surface SC, and C2, C4, C6, C8 and C10 are aspherical surface coefficients.x(y)=(y2/RC)/[1+(1−y2/RC2)0.5]+C2y2+C4y4+C6y6+C8y8+C10y10 Specific numerical values for the present example are as follows: RC=−3518.74523 C2=−3.64753×10−5 C4=−1.71519×10−11 C6=1.03873×10−15 C8=−3.84891×10−20 C10=5.12369×10−25 With continuing reference to FIG. 12, light source images I formed by reflecting element group 60 are formed in plane P2 orthogonal to optical axis AC (see FIG. 4). In the present example, plane P2 is at a position removed by approximately x1C=2009.8 mm along optical axis AC from apex OC. Arcuate illumination field IF having a uniform illumination intensity distribution and spatial coherence is formed by condenser mirror 66 receiving diverging light beams 110 and forming converging light beams 116. Arcuate illumination field IF is formed by condenser mirror 66 at a position CIF removed by xM=1400 mm from apex OC (or plane P′T) and approximately yMC=96 mm from optical axis AC. By the abovementioned configuration, an arcuate illumination field IF having a uniform illumination intensity and spatial coherence can be formed on mask M. In a preferred embodiment of the present invention, condition (2) below, is satisfied:0.01<\|fF/fC\|<0.5 (2)wherein fF is the focal length of each reflecting element E in reflective element group 60 and fC is the focal length of condenser optical system 64 (e.g., the focal length of condenser mirror 66). If \|fF/fC\| exceeds the upper limit in condition (2), the focal length fC of condenser optical system 64 shortens in the extreme when an appropriate power is given to each reflecting element E. Consequently, it is difficult to form a uniform arcuate illumination field IF on mask M, since strong aberrations are generated by condenser optical system 64. On the other hand, if \|fF/fC\| falls below the lower limit in condition (2), the focal length fC of condenser optical system 64 increases excessively, with the result that the elements in the condenser optical system (e.g., condenser mirror 66) increase in size excessively. This makes it difficult to maintain a compact illumination system when the appropriate power is given to each reflecting element E. By way of example, for the case where each reflecting element E in reflecting element group 60 has radius of curvature RE=−183.3211 mm, the reference focal length fF=91.66055 mm (fF=−RE/2). In addition, for a corresponding condenser mirror 66 with a radius of curvature RC=−3518.74523 mm, reference focal length fC=1759.3726 mm (fC=−RC/2). Accordingly,\|fF/fC\|=0.052. Thus, condition (2) is satisfied and an illumination system can be compactly constituted while maintaining a satisfactory illumination region. The above first mode for carrying out the present invention shows an example wherein optical integrator 56 comprises one reflecting element group 60 (FIG. 4). In a second mode for carrying out the present invention, the optical integrator comprises two reflecting element groups, as described below. With reference now to FIG. 13, illumination system 200 comprises essentially the same components as illumination optical system 50 of FIG. 4, except that optical integrator 220, analogous to optical integrator 56 in system 50 of FIG. 4, comprises first and second opposingly arranged reflecting element groups 220a and 220b. First reflecting element group 220a is constituted so that a first plurality of reflecting elements E1 (not shown in FIG. 13) are densely arranged in two dimensions along a predetermined reference plane (first reference plane) Pa parallel to the Y-Z plane. Specifically, with reference to FIG. 14, first reflecting element group 220a includes a plurality of reflecting elements E1, each having an arcuate curved reflecting surface, arranged as described above in connection with elements E of reflecting element group 60. With reference now also to FIGS. 16 and 17, each reflecting element E1 in first reflecting element group 220a has an arcuate shape (profile) of one part of a reflecting curved surface S1 of radius of curvature RE1 in a region eccentric from optical axis AE1. Center CE1 of arcuate reflecting element E1 is positioned at height hE from optical axis AE1. Accordingly, the eccentric reflecting surface RSE1 of each reflecting element E1, as shown in FIGS. 16 and 17, comprises an eccentric spherical mirror having a radius of curvature RE1. Consequently, with reference to FIG. 17, a portion of light bean 100 impinging from an oblique direction with respect to optical axis AE1 is condensed to form a light source image I in plane PFO at a position removed from optical axis AE1 in a direction perpendicular to focal point position FE1 of reflecting element E1. Reflecting element E1 has a focal length fE1, which is the distance between apex OE1 and focal point position FE1. In a preferred embodiment of the present invention, condition (3), below, is satisfied:fE1=−RE1/2. (3) With reference again to FIG. 15, second reflecting element group 220b comprises a plurality of second reflecting elements E2 densely arranged in two dimensions along a predetermined reference plane (second reference plane) Pb parallel to the Y-Z plane. Specifically, second reflecting element group 220b includes a plurality of reflecting elements E2 having reflecting curved surfaces which have a rectangular profile (outline). Second reflecting element group 220b has along the Y-direction a plurality of columns 262 (e.g., five, as shown), each comprising a plurality of second reflecting elements E2 arranged in a row along the Z-direction. Furthermore, columns 262 of second reflecting elements are arranged to collectively form a near circular shape (i.e., outline). In other words, each of second reflecting elements E2 in second reflecting element group 220b is arranged in a row facing, in one-to-one correspondence, each of first reflecting elements E1 comprising first reflecting element group 220a. With reference now to FIGS. 18 and 19, each reflecting element E2 has a reflecting surface RSE2 having a rectangular profile (outline) that is one part of a reflecting curved surface S2 with a radius of curvature RE2 in a region including optical axis AE2. Accordingly, reflecting element E2 has a rectangular perimeter 270 and a center CE2 which coincides with optical axis AE2. Accordingly, reflecting surface RSE2 of each reflecting element E2 comprises a concentric spherical mirror with radius of curvature RE2. With reference again to FIG. 13, wavefronts 105 in beam 100 are incident first reflecting element group 220a obliquely from a predetermined direction and are split by the first reflecting element group into arcuately shaped segments by the reflecting action of plurality of reflecting elements E1. The latter form a plurality of light source images I (not shown) at plane (second reference plane) Pb, parallel to the Y-Z plane and displaced from incident light beam 100. The number of light source images I corresponds to the number of reflecting elements E1. Second reflecting element group 220b is arranged in plane Pb. Light beam 100 from light source 54, in addition to having a parallel component, also includes a dispersion angle of a certain range. Consequently, each light source image I having a certain size is formed in plane Pb by first reflecting element group 220a. Accordingly, second reflecting element group 220b functions as a field mirror group to effectively utilize light supplied from light source 54. In other words, each of the plurality of second reflecting elements E2 in second reflecting element group 220b functions as a field mirror. With continuing reference to FIG. 13, plurality of light source images I reflected by second reflecting element group 220b forms a plurality of light beams 310 which are incident condenser mirror 66 with a radius curvature Rc. The focal point position (not shown) of condenser mirror 66 coincides with secondary light source plane Pb. Center of curvature OC of condenser mirror 66 exists at the center position of plurality of light source images I formed on second reflecting element group 220b (i.e., the position wherein optical axis AC and plane Pb intersect, or the center of reflective element group 220b). Optical axis AC is parallel to each optical axis AE1 associated with each reflecting element E1 in first reflective element group 220a, but is not parallel to each optical axis AE2 associated with each reflecting optical element E2 in second reflective element group 220b. More particularly, each optical axis AE2 associated with reflecting optical elements E2 is preferably inclined at half the angle of incidence of the obliquely impinging light beam. With continuing reference to FIG. 13, light beams 310 from plurality of light source images I are each reflected and condensed by condenser mirror 66 thereby forming light beams 316. Light beams 316 are thus made to arcuately illuminate, in a superimposed manner, front side MF of mask M. Plane mirror 68, as discussed above in connection with apparatus 50 of FIG. 4, may be used as a deflecting mirror to fold the optical path. With reference again also to FIG. 8, arcuate illumination field IF is formed on mask M when viewed from the back side MB of mask M. Center of curvature OIF of arcuate illumination field IF exists on optical axis AP (FIG. 13). If plane mirror 68 in system 200 of FIG. 13 is temporarily eliminated, arcuate illumination field IF is formed at plane IP, and center of curvature OIF of arcuate illumination field IF exists on optical axis AC. With continuing reference to FIG. 13, optical axis AC of condenser optical system 64 is not deflected 90°. However, if optical axis AC were deflected 90° by hypothetical reflecting surface 68a, optical axis AC and optical axis AP would be coaxial on mask M. Consequently, it can be said that optical axes AC and AP are optically coaxial. Accordingly, as with exposure apparatus 50 of FIG. 4, condenser optical system 64 and projection optical system 76 of exposure apparatus 200 are arranged such that optical axes AC and AP optically pass through center of curvature OIF of arcuate illumination field IF. Light beam 118 reflected by front side MF of mask M passes through projection optical system 76, as described above, thereby forming an image of the mask pattern on surface WS of wafer W over an arcuate image field IF′ (not shown: see FIG. 4). Wafer surface WS is coated with photoresist and thus serves as a photosensitive substrate onto which the mask pattern, via the arcuately shaped image of mask M, is projected and transferred. As discussed above in connection with exposure apparatus 50 of FIG. 4, mask stage MS and substrate stage WS move synchronously in opposite directions (as indicated by arrows) via mask stage drive system 72 and wafer stage drive system 92. Drive systems 72 and 92 are controlled by control system 74 in a manner that allows the entire mask pattern on mask M to be scanned and exposed onto wafer surface WS through projection optical system 76. Consequently, satisfactory semiconductor devices can be manufactured, since satisfactory circuit patterns are transferred onto wafer W by a photolithography process that manufactures semiconductor devices. With reference now to FIG. 20, the operation of first and second reflecting element groups 220a and 220b are described in more detail. For ease of explanation, FIG. 20 omits plane mirror 68. Further, first reflecting element group 220a comprises only two reflecting elements Ea1 and Eb1, and second reflecting element group 220b comprises only two reflecting elements Ea2 and Eb2. Reflecting elements Ea1 and Eb1 are arranged along first reference plane Pa at a position substantially optically conjugate to mask M (an object plane of projection optical system 76) or photosensitive substrate W (an imaging plane of projection optical system 76). Reflecting elements Ea2 and Eb2 are arranged along a second reference plane Pb at a position substantially optically conjugate to the pupil of projection optical system 76. Light beam 100, which may be, for example, an X-ray beam, comprises light beams 100a and 100b (represented by the solid lines and dotted lines, respectively) each including wavefronts 105a and 105b, respectively, which impinge from respective directions onto reflecting element Ea1. Light beams 100a and 100b are then split into arcuate light beams 108a and 108b, respectively, corresponding to the profile shape of reflecting surface RSEA1 of reflecting element Ea1. Arcuate light beams 108a and 108b form light source images I1 and I2, respectively, at respective ends of reflecting element Ea2 in second reflecting element group 220b by the condensing action of reflecting surface RSEA1 of reflecting element Ea1. If the radiant light in light beam 100 spans the angular range between light beams 100a and 100b and is incident reflecting element Ea1, a light source image is formed whose size spans light source image I1 and light source image I2 on reflecting element Ea2 in second reflecting element group 220b. Subsequently, light beams 108a and 108b are condensed by the reflecting and condensing action of reflecting element Ea2 in second reflecting element group 220b, thereby forming light beams 310a and 310b which are directed toward condenser mirror 66. Light beams 310a and 310b are then further condensed by the reflecting and condensing action of condenser mirror 66, thereby forming light beams 316a (solid lines) and 316b (dotted lines). These beams arcuately illuminate mask M from two directions such that they superimpose at front side MF of mask M. The optical action due to reflecting element Eb1 and Eb2 in reflecting element groups 220a and 220b is the same as described above for reflecting elements Ea1 and Ea2. Thus, the light from plurality of light source images I (i.e., I1, I2, etc.) arcuately illuminate mask M in a superimposed manner, as described above. This allows for efficient and uniform illumination. Moreover, since light beams 108a and 108b are efficiently condensed due to the action of each reflecting element Ea2, Eb2, etc., in second reflecting element group 220b (i.e., by the action of these elements as field mirrors), condenser optical system 64 can be made compact. Since light source images I1, I2, etc., formed on the surface of each reflecting element Ea2, Eb2, etc., in second reflecting element group 220b are re-imaged at pupil position P (i.e., the entrance pupil) of projection optical system 76, Köhler illumination is achieved. As described above in connection with the second mode for carrying out the present invention, light having a certain dispersion angle and a particular wavelength, such as X-rays with a wavelength λ<100 nm, is preferably employed. The mask pattern is then exposed onto wafer surface WS as a photosensitive substrate with an arcuate image field IF′, as discussed above. The latter is efficiently formed with uniform illumination intensity while substantially maintaining the conditions of Köhler illumination, even if the illumination apparatus (elements 54-68 of exposure apparatus 200 of FIG. 13) and projection optical system 76 include only catoptric members. In the second mode for carrying out the present invention, as described above, reflecting elements E1 and E2 and condenser mirror 66 are eccentric spherical surfaces. However, these surfaces can be made aspherical surfaces, in a manner similar to that described above in connection with the first mode for carrying out the present invention. In the second mode for carrying out the present invention, as described above, condenser optical system 64 and projection optical system 76 are arranged so that optical axes AC and AP are orthogonal. However, with reference to FIG. 21 and exposure apparatus 350, condenser optical system 64, deflecting (plane) mirror 68 and projection optical system 76 may be arranged such that optical axes AC and AP are coaxial. Next, a preferred embodiment of the second mode for carrying out the present invention is explained with reference to FIGS. 22 and 23. In the present preferred embodiment, the illumination efficiency of first and second reflecting element groups 360a and 360b, as described below, is even greater than first and second reflecting element groups 220a and 220b (FIGS. 14 and 15). With reference to FIG. 22, first reflecting element group 360a has, along the Y-direction, three columns GE11-GEE13 of first reflecting elements E1 having a arcuate profile (outline) and arranged in a row (i.e., stacked) along the Z-direction. Reflecting element columns GE11-GE13 each comprise a plurality of reflecting elements E11a-E11v, E12a-E12y, and E13a-E13v, respectively. Each reflecting element columns GE11-GE13 are arranged such that certain reflecting elements therein are each rotated by just a prescribed amount about respective axes A1-A3 oriented parallel to the Z-axis and traversing the center of their respective columns. With reference now to FIG. 23, second reflecting element group 360b includes, along the Y-direction, nine columns C1-C9 each comprising a plurality of second reflecting elements E2 having a nearly rectangular profile (outline) and arranged in a row (i.e., stacked) along the Z-direction. Second reflecting element group 360b includes a first subgroup GE21 comprising columns C1-C3, a second subgroup GE22 comprising columns C4-C6, and a third subgroup GE23 comprising columns C7-C9. First and second reflecting element groups 360a and 360b are opposingly arranged, as described above in connection with apparatus 200 and first and second reflecting element groups 220a and 220b (see, e.g., FIG. 20). Reflecting elements E11a-E11v of first reflecting element column GE11 in first reflecting element group 360a condense light and form light source images I in the manner described above in connection with first reflecting element group 220a (see FIG. 20). In other words, light source images I formed by reflecting elements E11a-E11v are formed on the surfaces of reflecting elements E2 in first subgroup GE21. Likewise, additional light source images I are condensed by each reflecting element E12a-E12y of second reflecting element column GE12 in first reflecting element group 360b on the surfaces of reflecting elements E2 in second subgroup GE22. Further, additional light source images I are condensed by each reflecting element E13a-E13v of third reflecting element column GE13 in first reflecting element group on the surfaces of reflecting elements E2 in third subgroup GE23. With reference now also to FIG. 24, reflecting elements E11a-E11k in first reflecting element column GE11 are arranged such that arbitrary reflecting elements therein are rotated by just a prescribed amount about axis A1 oriented parallel to the Z-direction and traversing the center of the first reflecting element column (centers C1a-C1k of reflecting elements E11a-E11k). For example, reflecting element E11a is provided and fixed in a state wherein it is rotated by a prescribed amount counterclockwise about axis A1. This amount of rotation is preferably very small. Reflecting element E11a forms a circular-shaped light source image Ia having a certain size, on the uppermost reflecting element E2 of column C3 of first subgroup GE21. Likewise, reflecting element E11f is provided and fixed in a state wherein it is rotated by just a prescribed amount clockwise about axis A1. Reflecting element E11f forms a circular-shaped light source image If having a certain size, on the second reflecting element E2 from the top of first column C1 of first subgroup GE21. In addition, reflecting element E11k is provided and fixed without being rotated about axis A1. Reflecting element E11k forms a circular-shaped light source image Ik having a certain size, on the fourth reflecting element E2 from the top of second column C2 of first subgroup GE21. The optical axis (not shown) of reflecting element E11k and the optical axis (not shown) of each reflecting element in first subgroup GE21 are parallel to one another. The arrangement as described above with reference to first reflecting element column GE11 and first subgroup GE21 applies to that between second reflecting element column GE12 and second subgroup GE22, and that between third reflecting element column GE13 and third subgroup GE23, in first reflecting element group 360a. As described above, illumination efficiency can be improved if the configuration of the first and second reflecting element groups 360a and 360b (FIGS. 23 and 24) is adopted. This configuration has the advantage that light source images Ia, If, Ik, etc., are not easily obscured by the profile (outline) of the second reflecting elements, as compared to the configuration of the first and second reflecting elements in reflecting element groups 220a and 220b. In the above first and second modes for carrying out the present invention, reflecting elements E of reflecting element group 60, and reflecting elements E1 of reflecting element group 220a have an arcuate profile (outline) and having reflective surfaces RSE and RSE1 respectively, eccentric with respect to the optical axes AE, and AE1, respectively. Consequently, constraints from the standpoint of optical design are significantly relaxed as compared to non-eccentric reflecting elements. This is because aberrations need only be corrected in the arcuate region at a certain image height (i.e., a certain distance from the optical axis). Accordingly, aberrations generated by the reflecting elements in the first reflecting element group can be sufficiently controlled, resulting in very uniform arcuate illumination. Aberrations generated by condenser optical system 64 (FIGS. 4 and 13) can also be sufficiently controlled by configuring the condenser optical system as an eccentric mirror system. This allows the above advantages to be obtained synergistically. Furthermore, condenser optical system 64 can comprise one eccentric mirror (e.g., condenser mirror 66), or a plurality of such mirrors. First and second reflecting element groups in the present invention may be moved by a small amount independently or as a unit in a prescribed direction (e.g., axially or orthogonal thereto). Alternatively, first and second reflecting groups may be constituted such that at least one of the first reflecting element group and second reflecting element group is capable of being inclined by a small amount. This allows for the illumination intensity distribution in the arcuate illumination field IF formed on front side MF or wafer W (photosensitive substrate) to be adjusted. In addition, it is preferable that at least one eccentric mirror in condenser optical system 64 be capable of being moved or inclined by a minute amount in a prescribed direction (i.e., along optical axis AC or orthogonal thereto). In the present invention, it is advantageous to compactly configure the exposure apparatus while simultaneously maintaining a satisfactory arcuate illumination field IF. To this end, it is preferable in the present invention that the first reflecting element group (220a of FIG. 14 or 360a of FIG. 22) and condenser optical system 64 satisfy condition (2), discussed above. In addition, the above modes for carrying out the present invention included optical integrators 56, 220, and 360 comprising optical elements having reflective surfaces. However, the optical integrators of the present invention may also comprise refractive lens elements. In this case, the cross-sectional shape of such refractive lens elements constituting a first “refractive” element group are preferably arcuate. Furthermore, in the present invention, first and second reflecting element groups 220a and 220b and first and second reflective element groups 360a and 360b are depicted as having plurality of reflecting elements E1 and E2 which are densely in an array arranged with essentially no gaps between the individual elements. However, in the second reflective element groups 220b and 360b (FIG. 15 and FIG. 23), plurality of reflecting elements E2 need not be so densely arranged. This is because numerous light source images corresponding respectively to the reflecting elements E2 are formed on second reflective element group 220b and 360b, or in the vicinity thereof. Light loss does not occur to the extent that the light source images fit within the effective reflecting region of each reflecting element E2. Accordingly, if the numerous light source images are formed discretely, the numerous reflecting elements E2 in the second reflective element group can be arranged discretely with gaps. The same holds true for second reflective element group 360b. With reference now to FIG. 25, exposure apparatus 400 performs the exposure operation by a step-and-scan method according to the first mode for carrying out the present invention in a manner similar to that described in connection with exposure apparatus 50 of FIG. 4. The elements in exposure apparatus 400 having the same function as those in exposure apparatus 50 of FIG. 4 are assigned the same reference symbol. Exposure apparatus 400 uses, in a preferred embodiment, light in the soft X-ray region on the order of λ=5-20 nm EUV (Extreme Ultra Violet) light. In FIG. 25, the Z-direction is the direction of optical axis AP of projection optical system 76 that forms a reduced image of reflective mask M onto wafer W. The Y-direction is the direction within the paper surface and orthogonal to the Z-direction. The X-direction is the direction perpendicular to the paper surface and orthogonal to the Y-Z plane. Exposure apparatus 400 projects onto wafer W the image of one part of the circuit pattern (not shown) drawn on front side MF of mask M through projection optical system 76. The entire circuit pattern of mask M is transferred onto each of a plurality of exposure regions on wafer W by scanning mask M and wafer W in a one-dimensional direction (Y direction) relative to projection optical system 76. Since soft X-rays (EUV light) have a low transmittance through the atmosphere, the optical path through which this light passes is enclosed in vacuum chamber 410 and isolated from the outside air. With continuing reference to FIG. 25, light source 54 supplies light beam 100 having a high illumination intensity and a wavelength from the infrared region to the visible region. Light source 54 may be, for example, a YAG laser, an excimer laser or a semiconductor laser. Light beam 100 from light source 54 is condensed by condenser optical member 412 to a position 414. Nozzle 416 provides a jet of gaseous matter toward position 414, where it receives laser light beam 100 of a high illumination intensity. At this time, the jetted matter reaches a high temperature due to the energy of laser light beam 100, is excited into a plasma state, and discharges EUV light 419 when the gaseous matter transitions to a low-energy state. An elliptical mirror 418 is arranged at the periphery of position 414 such that its first focal point (not shown) nearly coincides with convergent position 414. A multilayer film is provided on the inner surface 418S of elliptical mirror 418 to reflect EUV light 419. The reflected EUV light 419 is condensed at a second focal point 420 of elliptical mirror 418 and then proceeds to a collimating mirror 422, which is preferably concave and may be paraboloidal. Collimating mirror 422 is positioned such that the focal point (not shown) thereof nearly coincides with second focal point 420 of elliptical mirror 418. A multilayer film is provided on the inner surface 422S of collimating mirror 422 to reflect EUV light 419. Condenser optical member 412, elliptical mirror 418 and collimating mirror 422 constitute a condenser optical system. Light source 54, and the condenser optical system constitute a light source unit LSU with optical axes AL1 and AL2. EUV light 419 reflected by collimating mirror 422 proceeds to optical integrator (e.g. reflecting type fly's eye system) 220 in a nearly collimated state. A multilayer film is provided onto the plurality of reflecting surfaces constituting first and second reflecting element groups 220a and 220b to enhance reflection of EUV light 419. Exposure apparatus 400 further includes a first variable aperture stop AS1 provided at the position of the reflecting surface of second reflecting element group 220b or in the vicinity thereof. Variable aperture stop AS1 is capable of varying the numerical aperture NA of the light illuminating mask M (i.e., the illumination numerical aperture). First variable aperture stop AS1 has a nearly circular variable aperture, the size of which is varied by a first drive system DR1 operatively connected thereto. A collimated EUV light beam 428 from collimating mirror 422 includes a wavefront 430 that is split by first reflecting element group 220a and is condensed to form a plurality of light source images (not shown), as discussed above. The plurality of reflecting elements E2 of second reflecting element group 220b are positioned in the vicinity of the location of the plurality of light source images. The plurality of reflecting elements E2 of second reflecting element group 220b substantially acts as field mirrors. In this manner, optical integrator 220 forms a plurality of light source images as secondary light sources from approximately parallel light beam 428. The EUV lightbeam 432 (comprising a plurality of light beams) from the secondary light sources formed by optical integrator 220 proceeds to condenser mirror 66 positioned such that the secondary light source images are formed at or near the focal point of the condenser mirror. Light beam 432 is reflected and condensed by condenser mirror 66, and is deflected to mask M by fold mirror 68. A multilayer film that reflects EUV light is provided on surface 66S of condenser mirror 66 and surface 68S of fold mirror 68. Condenser mirror 66 condenses EUV light in light beam 432 in a superimposed manner, forming an arcuate illumination field on front side MF of mask M. A multilayer film that reflects EUV light is provided on front side MF of mask M. Thus, EUV light incident thereon is reflected from mask M as light beam 434. The latter passes to projection system 76, which images mask M onto wafer W as the photosensitive substrate. In the present mode for carrying out the present invention, it is preferable to spatially separate the optical paths of light beam 432 that proceeds to mask M and light beam 434 reflected by the mask that proceeds to projection optical system 76. In this case, the illumination system is nontelecentric, and projection optical system 76 is also nontelecentric on the mask M side. Projection optical system 76 also includes multilayer films that reflects EUV light provided on the reflecting surfaces of the four mirrors 78a-78d for enhancing EUV light reflectivity. Mirror 78c in projection optical system 76 is arranged at the pupil position or in the vicinity thereof. A second variable aperture stop AS2 capable of varying the numerical aperture of projection optical system 76 is provided at the reflecting surface of mirror 78C or in the vicinity thereof. Second variable aperture stop AS2 has a nearly circular variable aperture, the diameter of which is capable of being varied by second drive system DR2 operatively connected thereto. The ratio of the numerical aperture of the illumination system NA1 to the numerical aperture NAP of projection optical system 76 is called the coherence factor, or σ value (i.e., σ=NAI/NAP). Due to the degree of fineness of the pattern on mask M to be transferred to wafer W and the process of transferring this pattern to wafer W, it is often necessary to adjust the resolving power and depth of focus and the like of projection optical system 76 by varying the σ value. Consequently, exposure information related to the exposure conditions of each wafer W sequentially mounted on wafer stage WS by a transport apparatus (not shown) (wafer transport map and the like that includes exposure information), and the mounting information of each type of mask M sequentially mounted on mask stage MS is input to a control apparatus MCU through input apparatus IU, such as a console electrically connected thereto. Control apparatus MCU is electrically connected to first and second drive systems DR1 and DR2. Based on the input information from input apparatus IU, each time a wafer W is mounted on substrate stage WS, control apparatus MCU determines whether to change the σ value. If control apparatus MCU determines that it is necessary to change the σ value, a signal is sent therefrom to at least one of two drive systems DR1 and DR2, to vary at least one aperture diameter among first variable aperture stop AS1 and second variable aperture stop AS2. Consequently, the appropriate exposure can be achieved under various exposure conditions. The light intensity distribution at a pupil position of projection optical system 76 is changed by using the illumination condition changing system including first variable aperture stop AS1, second variable aperture stop AS2 and drive systems DR1 and DR2. With continuing reference to FIG. 25, it is preferable in the present embodiment to replace collimating mirror 422 with a collimating mirror having a different focal length, in response to varying the aperture diameter of first variable aperture stop AS1. As a result, the diameter of EUV light beam 428 incident optical integrator 220 can be changed in accordance with the size of the opening of first variable aperture stop AS1. In this manner, illumination at an appropriate σ value is enabled while maintaining a high illumination efficiency. The light illumination intensity distribution on mask M or wafer W of exposure apparatus 400 may be nonuniform, in the sense that it is biased. In this case, this bias can be corrected by making light beam 428 eccentric prior to traversing reflecting element group 220a. For example, by making collimating mirror 422 slightly eccentric, the bias of the light illumination intensity distribution can be corrected. In other words, if the bias of the intensity distribution occurs in the lateral X-direction of the arcuate illumination field IF (or in arcuate image field IF′ on surface WS of wafer W), the bias can be corrected by moving collimating mirror 422 in the X-direction. If the illumination intensity in arcuate illumination field IF at the center part and peripheral part differs in the width direction, respectively, the bias of the light illumination intensity distribution can be corrected by moving collimating mirror 422 in the same direction. When varying at least one aperture diameter among first variable aperture stop AS1 and second variable aperture stop AS2, there are cases wherein the illumination deteriorates. For example, illumination non-uniformity occurs over the arcuate illumination field IF. In this case, it is preferable to correct illumination non-uniformity and the like over the arcuate illumination field IF by slightly moving at least one of collimating mirror 422, optical integrator 220 and condenser mirror 66. With reference now to FIG. 26, exposure apparatus 450, which is an alternate embodiment of exposure apparatus 400, is now described by highlighting the difference between these two apparatus. The first difference between exposure apparatus 400 and exposure apparatus 450 is that exposure apparatus includes a turret plate 452 instead of first variable aperture stop AS1. Turret plate 452 is connected to a drive shaft 454, connected to first drive system DR1. Turret plate 452 is thus rotatable about a rotational axis AR by first drive system DR1. With reference to FIG. 27, turret plate 452 comprises a plurality of aperture stops 456a-456f having different shapes and sizes. Turret plate 452 is discussed in more detail, below. With reference again to FIG. 26, exposure apparatus 450 further includes an adjustable annular light beam converting unit 460. The latter converts EUV light beam 428 having a circular cross-section to a light beam 428′ having an annular (ring-shaped) light beam cross section. Unit 460 is movably provided in the optical path (e.g., light beam 428) between collimating mirror 422 and first reflecting element group 220a of optical integrator 220. Annular light beam converting unit 460 has a first reflecting member 460a with a ring-shaped reflecting surface and second reflecting member 460b having a conical reflecting surface. To vary the ratio of the inner diameter of the ring to the outer diameter of (the so-called “annular ratio”) of light beam 428′, first reflecting member 460a and second reflecting member 460b are moved relative to one another. The insertion and removal of annular light beam converting unit 460 in and out of light beam 428 and the relative movement of first reflecting member 460a and second reflecting member 460b is performed by a third drive system DR3 in operable communication with annular light beam converting unit 460 and electrically connected to control apparatus MCU. With reference now again to FIG. 27, further details concerning turret plate 452 and annular light beam converting unit 460 are explained. Turret plate 452, as discussed briefly above, includes a plurality of different aperture stops 456a-456f and is rotatable about axis AR. Aperture stop 456a has an annular (donut-shaped) aperture, and aperture stops 456b and 456e have circular openings with different aperture diameters. Aperture stop 456c has four fan-shaped openings, and aperture stop 456d has four circular openings. Aperture stop 456f has an annular ratio (ratio of outer diameter rfo to inner diameter rfi of opening 456fo of the annular shape) different from that of aperture stop 456a (with outer diameter rao and inner diameter rai). In exposure apparatus 450, input apparatus IU is for inputting information necessary for selecting the method of illuminating mask M and exposing wafer W. For example, input apparatus IU inputs exposure information related to the exposure conditions of each wafer W sequentially mounted by an unillustrated transport apparatus (wafer transfer map and the like that includes the exposure information), and mounting information of each type of mask M sequentially mounted on mask stage MS. This information is based on the degree of fineness of the mask pattern to be transferred to wafer W and the process associated with transferring the pattern to wafer W. For example, control apparatus MCU can select illumination states such as “first annular illumination,” “second annular illumination,” “first normal illumination,” “second normal illumination,” “first special oblique illumination,” and “second special oblique illumination,” based on the information input into input apparatus IU. “Annular illumination” aims to improve the resolving power and depth of focus of projection optical system 76. It does so by illuminating EUV light onto mask M and wafer W from an oblique direction by setting the shape of the secondary light sources formed by optical integrator 220 to an annular shape. “Special oblique illumination” aims to further improve the resolving power and depth of focus of projection optical system 76. It does so by illuminating EUV light onto catoptric mask M and wafer W by making the secondary light sources formed by optical integrator 220 a discrete plurality of eccentric light sources. These light sources are made eccentric by just a predetermined distance from the center thereof. “Normal illumination” is one that aims to illuminate mask M and wafer W based on an optimal σ value by making the shape of the secondary light sources formed by optical integrator 220 nearly circular. Based on the input information from input apparatus IU, control apparatus MCU controls first drive system DR1 to rotate turret plate 452, second drive system DR2 to change the aperture diameter of aperture stop AS2 of projection optical system 76, and third drive system DR3 to insert and remove annular light beam converting unit 460 in and out light beam 428. Control apparatus MCU changes the relative spacing between the two reflecting members 460a and 460b in annular light beam converting unit 460. If the illumination state on mask M is set to normal illumination, control apparatus MCU selects “first normal illumination” or “second normal illumination,” based on the input information from input apparatus IU. “First normal illumination” and “second normal illumination” have different σ values. For example, if control apparatus MCU selects “first normal illumination,” control apparatus MCU rotates turret plate 452 by driving first drive system DR1 so that aperture stop 456e is positioned at the secondary light sources formed on exit side 220be of second reflective element group 220b. Simultaneously, control apparatus MCU changes, as needed, the aperture diameter of second aperture stop AS2 via second drive system DR2. At this point, if annular light beam converting unit 460 is set in light beam 428, control apparatus MCU withdraws this unit from the illumination optical path via third drive system DR3. If EUV light illuminates the mask pattern of mask M based on the set condition of the illumination system mentioned above, the pattern can be exposed onto wafer W through projection optical system 76 based on the appropriate “first normal illumination” condition (i.e., an appropriate σ value). If control apparatus MCU selects “second normal illumination,” control apparatus MCU rotates turret plate 452 by driving first drive system DR1 so that aperture stop 456b is positioned at the secondary light sources formed on exit side 220be of second reflective element group 220b. Simultaneously, control apparatus MCU changes, as needed, the aperture diameter of the second aperture stop AS2 via second drive system DR2. At this point, if annular light beam converting unit 460 is set in light beam 428, control apparatus MCU withdraws this unit from the illumination optical path via third drive system DR3. If EUV light illuminates the mask pattern of mask M based on the set condition of the illumination system mentioned above, the pattern can be exposed onto wafer W through projection optical system 76 based on the appropriate “second normal illumination” condition (i.e., σ value larger than that of first normal illumination). As mentioned in connection with exposure apparatus 400 (FIG. 25), it is preferable in exposure apparatus 450 (FIG. 26) to replace reflecting mirror 422 with a reflecting mirror having a focal length different therefrom in response to the varying of the aperture diameter of first variable aperture stop AS1. As a result, the beam diameter of light beam 428 can be changed in response to the size of the opening of first variable aperture stop AS1. Thus, illumination is enabled with an appropriate σ value while maintaining a high illumination efficiency. If the illumination with respect to mask M is set to oblique illumination, control apparatus MCU selects, based on the input information from input apparatus IU, one among “first annular illumination,” “second annular illumination,” “first special oblique illumination” and “second special oblique illumination.” “First annular illumination” and “second annular illumination” differ in that the annular ratios of the secondary light sources formed annularly are different. “First special oblique illumination” and “second special oblique illumination” differ in their secondary light source distributions. In other words, the secondary light source in “first special oblique illumination” is distributed in four fan-shaped regions (aperture stop 456c), and the secondary light sources in “second special oblique illumination” are distributed in four circular regions (aperture stop 456d). If “first annular illumination” is selected, control apparatus MCU rotates turret plate 452 by driving drive system DR1 so that aperture stop 456a is positioned at the position of the secondary light sources formed on exit side 220be of second reflective element group 220b. If “second annular illumination” is selected, control apparatus MCU rotates turret plate 452 by driving drive system DR1 so that aperture stop 456f is positioned at the position of the secondary light sources formed on exit side 220be of second reflective element group 220b. If “first special oblique illumination” is selected, control apparatus MCU rotates turret plate 452 by driving drive system DR1 so that aperture stop 456c is positioned at the position of the secondary light sources formed on exit side 220be of second reflective element group 220b. If “second special oblique illumination” is selected, control apparatus MCU rotates turret plate 452 by driving drive system DR1 so that aperture stop 456d is positioned at the position of the secondary light sources formed on exit side 220be of second reflective element group 220b. If one among the above four aperture stops 456a, 456c, 456d, and 456f is set in light beam 428, control apparatus MCU simultaneously changes, as needed, the aperture diameter of second aperture stop AS2 in projection optical system 76 via second drive system DR2. Next, control apparatus MCU sets annular light beam converting unit 460 in light beam 428 via third drive system DR3 and adjusts the unit. The operation of setting and adjusting annular light beam converting unit 460 is performed as described below. First, if annular light beam converting unit 460 is not set in light beam 428, control apparatus MCU sets the unit in the light beam via third drive system DR3. Next, control apparatus MCU changes the relative spacing of the two reflecting members 460a and 460b in annular light beam converting unit 460 via third drive system DR3 so that the annular light beam (now light beam 428′) is efficiently guided to the opening of one aperture stop among the four aperture stops 456a, 456c, 456d, and 456f set on exit side 220be of second reflective element group 220b. As a result, annular light beam converting unit 460 can convert light beam 428 incident thereon to annular light beam 428′ having an appropriate annular ratio. Secondary light sources (not shown) formed by optical integrator 220 can, by the setting and adjustment of the above annular light beam converting unit 460, be rendered annular secondary light sources having an appropriate annular ratio corresponding to the opening of each of the four aperture stops 456a, 456c, 456d, and 456f. Thus, oblique illumination of mask M and wafer W can be performed with a high illumination efficiency. The light intensity distribution at a pupil position of projection system 76 is changed by using the illumination condition changing system including turret plate 452 having plurality of aperture stops 456a-456f, second variable aperture stop AS2, annular light beam converting unit 460 and three drive systems DR1, DR2 and DR3. Thus, one of a plurality of aperture stops 456a-456f having mutually differing shapes and sizes can be set in the illumination optical path by rotating turret plate 452. Thus, the illumination state, such as illumination unevenness, of the arcuate illumination field IF or the arcuate image field IF′ may change. It is preferable to correct this illumination unevenness by slightly moving at least one of collimating mirror 422, optical integrator 220 and condenser mirror 66. With continuing reference to FIG. 26 and exposure apparatus 450, information like the illumination condition is input to control apparatus MCU via input apparatus IU. However, a detector (not shown) that reads the information on mask M may also be provided. Information related to the illumination method is recorded by, for example, a barcode and the like at a position outside the region of the mask pattern of mask M. The detector reads the information related to this illumination condition and transmits it to control apparatus MCU. The latter, based on the information related to the illumination condition, controls the three drive apparatus DR1-DR3, as described above, to set the illumination. In exposure apparatus 450, one of aperture stops 456a-456f is provided at exit side 220be of optical element group 220b (i.e., the position of the secondary light sources). However, illumination by aperture stops 456c and 456d having four eccentric openings need not be provided. Also, aperture stops 456a-456f formed on turret plate 452 are not essential to the present invention in the case of performing “annular illumination” or “normal illumination,” as will be understood by one skilled in the art from the theory of the present invention. Four eccentric light beams can be formed by constituting first reflecting member 460a, in annular light beam converting unit 460, by two pairs of plane mirror elements (not shown) arranged opposite one another and mutually inclined, and by constituting the reflecting surface of reflecting member 460a in a square column shape. As a result, the secondary light sources formed by optical integrator 220 can be rendered quadrupole secondary light sources eccentric to the center thereof. Accordingly, EUV light corresponding to the openings of aperture stops 456c and 456d having four eccentric openings can be formed. With reference now to FIG. 28, exposure apparatus 500, which is another modified version of exposure apparatus 400, is now described. In exposure apparatus 500, as well as in exposure apparatus 550 and 600 discussed below (FIGS. 29 and 30), elements AS1, 452, AS2, DR1, DR2, IU and MCU are included, as discussed above. However, these elements are not shown in FIGS. 28-36 for the sake of illustration. The difference between exposure apparatus 400 shown and exposure apparatus 500 of FIG. 28 is that the latter includes an auxiliary optical integrator 510. With reference also to FIGS. 29 and 30, auxiliary optical integrator 510 includes a first auxiliary reflecting element group 510a and a second auxiliary reflecting element group 510b. Exposure apparatus 500 further includes a relay mirror 514 as a relay optical system. Optical integrator 510 and mirror 514 are respectively arranged in the optical path between reflecting mirror 422 and optical integrator 220. Auxiliary optical integrator 510 is preferably a catoptric fly's eye system. If viewed in order from light source 54, auxiliary optical integrator 510 can be seen as a first optical integrator (i.e., first multiple light source forming optical system), and in combination with a second or main optical integrator 220. First auxiliary reflecting element group 510a comprises a plurality of reflecting elements E510a (FIG. 29) arranged on the entrance side 510ae of auxiliary optical integrator 120. Elements E510a are preferably formed in a shape similar to the overall shape (outline) of first reflecting element group 220a arranged on the entrance side of optical integrator 220 (see FIGS. 14 and 22). However, if reflecting elements E50a are constituted in a shape as shown in FIGS. 14 and 22, it is difficult to densely arrange the reflecting elements without gaps in between. Consequently, with reference to FIGS. 29 and 30, each of the reflecting elements E510a in first auxiliary reflecting element group 510a is nearly square in shape. Now, the cross section of light beam 428 incident first auxiliary reflecting element group 510a is nearly circular, and reflecting elements E510a are arranged in a row so that the overall shape (outline) of this group is nearly circular. As a result, first auxiliary reflecting element group 510a can form numerous light source images (secondary light sources) with high illumination efficiency at the position of second auxiliary reflecting element group 510b, or in the vicinity thereof. The overall shape (outline) of second auxiliary reflecting element group 510b arranged on the exit side of auxiliary optical integrator 510 is preferably formed in a similar shape to that of reflecting elements E2 comprising second reflecting element group 220b arranged on the exit side of optical integrator 220, as shown in FIGS. 15 and 23. Each reflecting element E510b in second auxiliary reflecting element group 510b is preferably shaped similar to the shape of the light source images formed by reflecting elements E510a in first auxiliary reflecting element group 510a so that it receives all the light source images. In exposure apparatus 500, main optical integrator 220 preferably comprises first and second reflecting element groups 360a and 360b (FIGS. 22 and 23) in place of reflecting element groups 220a and 220b (both reference numbers being used hereinafter to indicate either can be used for the first and second reflecting element groups of main optical integrator 220). Consequently, plurality of reflecting elements E2 in second reflecting element group 360b (220b) arranged on the exit side of optical integrator 220 have a shape that is nearly square, as shown in FIG. 23. With continuing reference to FIG. 28, the light source images (not shown) formed by each of the plurality of reflecting elements E510a comprising first auxiliary reflecting element group 510a in auxiliary optical integrator 510 are nearly circular. Thus, the shape of each reflecting element E510b of second auxiliary reflecting element group 510b is nearly square, as shown in FIG. 30. In addition, since the shape of each reflecting element E2 that comprises second reflecting element group 360b (220b) arranged on the exit side of main optical integrator 220 is nearly square, the reflecting elements therein are arranged in rows so that the overall shape (outline) of second auxiliary reflecting element group 510b is nearly square, as shown in FIG. 30. In this manner, in exposure apparatus 500 of FIG. 28, first and second auxiliary reflecting element groups 510a and 510b are preferably constituted by the same type of reflecting element group. This allows manufacturing costs to be controlled. It is also preferable that second reflecting element group 220b and condenser mirror 66 satisfy the relation in condition (2), discussed above. With continuing reference to FIG. 28, the action of optical integrators 220 and 510 are now explained in more detail. By the arrangement of optical integrators 220 and 510, a plurality of light source images (not shown) are formed. The number of light source images corresponds to the product of the number (N) of reflecting elements in one of the reflecting element groups in optical integrator 510 and the number (M) of reflecting elements in one of the reflecting element groups in main optical integrator 220. The plurality of light source images are formed on the surface of one of the second reflecting element groups 360b (220b) in main optical integrator 220, or in the vicinity thereof. Accordingly, many more light source images (tertiary light sources, not shown) than the light source images (secondary light sources) formed by auxiliary optical integrator 510 are formed on the surface of main reflecting element group 360b (220b), or in the vicinity thereof. Light from the tertiary light sources from main optical integrator 220 arcuately illuminate mask M in a superimposed manner. Thus, the illumination distribution in arcuate illumination field IF formed on mask M and arcuate image field IF′ formed on wafer W can be rendered more uniform, allowing for a much more stable exposure. Relay mirror 514 arranged between optical integrators 510 and 220 condenses light beam 520 from the numerous light source images (secondary light sources) from optical integrator 510, thereby forming a light beam 522 directed to optical integrator 220. Relay mirror 514 serves the function of making the near surface (i.e., entrance side 510ae) of reflecting element group 510a and the near surface (i.e., entrance side 220ae) of the reflecting element group 220a (360a) optically conjugate. Relay mirror 514 also serves the function of making the near surface (i.e., exit side 510be) of reflecting element group 510b and the near surface (i.e., exit side 220be) of the reflecting element group 360b (220b) optically conjugate. Surface 510ae and surface 220ae are optically conjugate mask M and wafer W. Also, surface 220be and surface 510be are optically conjugate the pupil of projection optical system 76 and the position of aperture stop AS2. With continuing reference to FIG. 28 and exposure apparatus 500, if the illumination intensity distribution in arcuate illumination field IF is biased, it is preferable to move auxiliary optical integrator 510 (i.e., move reflecting element groups 510a and 510b as a unit). If reflecting element groups 360a (220a) and 360b (220b) in main optical integrator 220 are made eccentric in the X-direction or Z-direction, the biased component of the illumination intensity distribution can be corrected and a uniform illumination intensity distribution can be obtained by the action of coma generated by main optical integrator 220. For example, if bias occurs in the illumination intensity distribution in the lateral direction (X-direction) of arcuate illumination field IF or in arcuate image field IF′, respectively, the bias can be corrected by moving optical integrator 510 in the X-direction. In addition, if the illumination intensity differs between the center part and peripheral part in the width direction of the arcuate illumination field IF or arcuate image field IF′, the bias in the illumination intensity distribution can be corrected by moving auxiliary optical integrator 510 in the same direction. For exposure apparatus 500 to properly form an image of mask M on wafer W, it is preferable to form a well-corrected image of the exit pupil of the illumination system at the center of the entrance pupil of projection optical system 76 (i.e., an image of tertiary light sources formed by optical integrator 220). If this condition is not satisfied, it is preferable to move the position of the exit pupil of the illumination system, to adjust the telecentricity of the illumination system, and to coordinate with the position of the entrance pupil of projection optical system 76. For example, by moving main optical integrator 220 (i.e., two reflecting element groups 360a (220a) and 360b (220b)) and first aperture stop AS1 as a unit, the telecentricity of the illumination system is adjusted, and the center of the exit pupil image of the illumination system is made to coincide with the center of the entrance pupil of projection optical system 76. However, if it is not necessary to provide aperture stop AS1 at the position of the tertiary light sources, then reflecting element groups 360a (220a) and 360b (220b) in main optical integrator 220 are preferably moved as a unit. In exposure apparatus 400 (FIG. 25) and exposure apparatus 450 (FIG. 26), discussed above, to match the image of the exit pupil of the illumination system to the center of the entrance pupil of projection optical system 76, the center of the exit pupil image of the illumination system can be made to coincide with the center of the entrance pupil of projection optical system 76 by moving optical integrator 220 and first aperture stop AS1 as a unit. If it is not necessary to provide aperture stop AS1 at the position of the secondary light sources, then reflecting element groups 360a (220a) and 360b (220b) are preferably moved as a unit. In exposure apparatus 400 (FIG. 25), 450 (FIG. 26) and 500 (FIG. 28), discussed above, light source unit LSU in practice generally occupies a considerable volume. It is a possibility that this volume can become equal to or larger than the exposure apparatus body unit (optical system and control system from optical integrator 220 to wafer stage WS). Consequently, it may be preferred to separate light source unit LSU and the exposure apparatus body unit, with light source unit LSU and the exposure apparatus body unit installed independently on a base. In this case, strain in the floor may occur due to, for example, vibration of the floor caused by people near the apparatus, or due to the weight of the light source unit and the exposure apparatus body unit themselves. Thus, there is a risk that the light source unit optical axes (AL1 and AL2) and the optical system axis (e.g., axis AP or AC) in the exposure apparatus body unit will become displaced, upsetting the adjustment state of the exposure apparatus. Accordingly, with reference to FIG. 28, it is preferable to arrange a photoelectric detector 528 in the optical path of the exposure apparatus body unit (i.e., in the optical path from optical integrator 220 to wafer stage WS). Photodetector 528 photoelectrically detects a relative displacement of light source unit optical axis AL1 and/or AL2, and provides a control signal to a detector control unit 530 that is operably connected to and controls the inclination of collimating mirror 422. Consequently, even if vibration of the floor due to walking and the like of operators or strain in the floor occurs, at least one of light source unit optical axes AL1 and AL2 and an optical axis (e.g., optical axis AP or AC) of the optical system inside the exposure apparatus body unit can be aligned automatically. Because it is difficult to obtain high reflectance for soft X-ray mirrors, it is desirable to reduce the number of mirrors in the optical system of a soft X-ray exposure apparatus. One technique to reduce the number of mirrors in the present invention involves eliminating condenser mirror 66. This is achieved by bending the entirety of one of second reflecting element group 360b (220b) in optical integrator 220 (FIG. 15 and FIG. 23). In other words, by constituting second reflecting element group 360b (220b) by arranging in a row numerous reflecting elements E2 within a reference spherical surface (reference curved surface) having a predetermined curvature, the function of condenser mirror 66 can be incorporated into second reflecting element group 360b (220b). Thus, with reference now to FIG. 31, and exposure apparatus 550 and also to FIG. 21, a second reflective element group 220c combines the function of condenser mirror 66 in one of second reflecting element group 360b (220b) in optical integrator 220. By modifying the configuration of second reflecting element group 360b (220b) of main optical integrator 220 of exposure apparatus 500 (FIG. 28), the function of condenser mirror 66 can be combined therein as well. Projection optical system 76 in FIG. 31 comprises six mirrors 78a-78f to still further improve imaging performance. Exposure apparatus 400 to 550 of the present invention preferably use a laser plasma light source. However, such a light source has the disadvantage of generating a spray of microscopic matter. If optical parts are contaminated by this fine spray, the performance of the optical system, which is based in part on mirror reflectance and reflection uniformity, deteriorates. Thus, with reference to FIG. 32 and exposure apparatus 600, it is preferable to arrange, with vacuum chamber 410, a sub-chamber 602 which houses a portion of nozzle 416, and elliptical mirror 418. Chamber 602 includes a filter window 604 capable of transmitting only soft X-rays while blocking transmission of the dispersed microscopic particles. A thin film of a light element (i.e., a membrane) may be used as filter 604. In the present arrangement, vacuum chamber 410 also includes a second window 606 capable of passing light from light source 54 into chamber 602. This arrangement may be used with any of exposure apparatus 400-550 of the present invention as well. If filter 604 is provided between elliptical mirror 418 and collimator collimating mirror 422, operating costs can be kept low by replacing elliptical mirror 418 and filter 604 when contamination occurs. Exposure apparatus 400-600 are enclosed in vacuum chamber 410, since the transmittance of soft X-rays through the atmosphere is relatively low. Nevertheless, it is difficult for the heat remaining in the optical parts to escape. As a result, the mirror surfaces tend to warp. Accordingly, it is preferable to provide a cooling mechanism (not shown) for each of the optical parts inside vacuum chamber 410. More preferably, if a plurality of cooling mechanisms is attached to each mirror and the temperature distribution inside the mirror controlled, then warping of the mirrors during the exposure operation can be further controlled. In addition, a multilayer film is provided on the reflecting surfaces in exposure apparatus 400-600. It is preferable that this multilayer film be formed by layering a plurality of materials from among molybdenum, lithium, rhodium, silicon and silicon oxide. As is apparent from the above description, the present invention has many advantages. A first advantage of the present invention is that a surface of an object, such as a mask surface, can be illuminated uniformly and efficiently over an arcuately shaped illumination field while maintaining a nearly fixed numerical aperture of the illumination light. A second advantage is that the illumination coherence can be varied to suit the particular pattern on the mask to be imaged onto the wafer by varying the size of the aperture stops in the illuminator and in the projection optical system. A third advantage is that the illumination beam can be altered through the use of an adjustable annular light beam converting unit. A fourth advantage is that one of a plurality of aperture stops can be inserted into the illumination system to alter the illumination coherence. A fifth advantage is that a bias in the illumination uniformity can be compensated by measuring the light beam uniformity and adjusting the collimating mirror in the illuminator based on the uniformity measurement. While the present invention has been described in connection with preferred embodiments, it will be understood that it is not so limited. On the contrary, it is intended to cover all alternatives, modifications and equivalents as may be included within the spirit and scope of the invention as defined in the appended claims.
	abstract	An embodiment of the present method may comprise: heating up at least one structural element beyond a change state temperature thereof; changing the configuration of the structural element from an extended configuration to a reduced size configuration; cooling the structural element to below the change state temperature thereof; covering the structural element with a thermal protection device; removing the thermal protection device to expose the structural element to heat radiation; and heating, via the heat radiation, at least a portion of the structural element to thereby cause the structural element to change from the reduced size configuration to the extended configuration. In one embodiment each of the structural elements is formed from a thin elastic memory composite material.
051986787	claims	1. A photopolymerization device for treating plastic dental parts, having an irradiation space in an irradiation chamber (1), the space being accessible via at least one pivotable or displaceable wall, and having a light conductor (2) and a radiation source unit (3), wherein the light conductor (2) feeds the radiation from the radiation source into the irradiation space of the irradiation chamber (1) and forms a releasable connection between the irradiation chamber and the radiation source unit, wherein said radiation source unit is a hand-held polymerization unit (3), having a housing part; said irradiation chamber (1) is coupled to a support frame (4) including a first support (6) and a second support (7), disposed on a support plate (5) forming a part of said support frame (4); and said hand-held polymerization unit (3) and said support frame (4) are formed with matching shapes adapted for rapid yet form-fitting engagement with one another to provide said releasable connection, said connection being formed upon engagement of said housing part in said first support (6) and of said light conductor (2) in said second support (7), said connection assuring fixation of the relative position of the polymerization unit and the chamber to thereby assure constant radiation conditions in said chamber. characterized in that the first support (6) is a platform-like part that has an opening (13) for receiving the hand-held polymerization unit (3). characterized in that the first support (6) has a slit (14) extending all the way from the opening (13) through to the outside. characterized in that the light conductor (2) has external sheathing that is connected to at least one of the irradiation chamber (1) and the hand-held polymerization unit (3). characterized in that the second support (7) holds the external sheathing of the light conductor (2), and the irradiation chamber (1) rests on the second support (7). characterized in that the irradiation chamber (1) is fastened to the support plate (5). characterized in that the irradiation chamber (1) has ribs (17) on its underside that partly enclose the outer contour of the support plate (5). characterized in that the hand-held polymerization unit (3) is retained in the first support (6) in a manner fixed against relative rotation. characterized in that the hand-held polymerization unit (3) has a protrusion (9) that engages the slit (14). characterized in that the hand-held polymerization unit (3) has an activation switch (12), the hand-held polymerization unit (3) being fixed in the support frame (4) in such a way that the activation switch (12) is located on a side remote from the support plate (5). characterized in that the support plate (5) forms the base plate of the support frame (4). characterized in that the axis of the light conductor (2) extends parallel to the support plate (5). characterized in that the light conductor (2) extends with its axis aligned horizontally. 2. The polymerization device of claim 1, 3. The polymerization device of claim 2, 4. The polymerization device of claim 1, 5. The polymerization device of claim 4, 6. The polymerization device of claim 1, 7. The polymerization device of claim 1, 8. The polymerization device of claim 1, 9. The polymerization device of claim 3, 10. The polymerization device of claim 1, 11. The polymerization device of claim 1, 12. The polymerization device of claim 1, 13. The polymerization device of claim 12,
053393406	claims	1. A baffle in combination with a containment vessel disposed inside a silo and wherein: said baffle comprises a perforate inner wall installed between said containment vessel and said silo, and an imperforate outer wall installed between said inner wall and said silo; said containment vessel contains a reactor vessel having a reactor core submerged in a liquid metal; said inner wall is spaced radially outwardly from said containment vessel to define an inner riser therebetween for channeling cooling air upwardly therein; said outer wall is spaced radially outwardly from said inner wall to define an outer riser therebetween for channeling cooling air upwardly therein; said outer wall is spaced radially inwardly from said silo to define a radially outer flow downcomer therebetween for channeling cooling air downwardly therein; and said downcomer is disposed in flow communication with both said inner and outer risers at bottom ends thereof for channeling downwardly flowing cooling air upwardly into both said inner and outer risers for cooling said containment vessel, said inner wall comprising a plurality of apertures spaced vertically and horizontally and sized for allowing a portion of thermal radiation from said containment vessel to pass laterally through said inner wall to said outer wall. said inner riser has an inner width laterally between said containment vessel and said inner wall; said outer riser has an outer width laterally between said inner wall and said outer wall; and said outer width is less than said inner width. said inner riser has an inlet at a bottom thereof, and an outlet at a top thereof; said outer riser has an inlet at a bottom thereof, and an outlet at a top thereof; said downcomer has an inlet at a top thereof, and an outlet at a bottom thereof disposed in flow communication with both said inlets of said inner and outer risers for channeling said cooling air thereto; and said inner and outer riser outlets discharge air heated therein vertically upwardly. a cylindrical inner wall arranged inside said annular volume and concentric with said containment vessel to form an inner riser therebetween for channeling cooling air upward; and a cylindrical outer wall arranged inside said annular volume and concentric with said containment vessel, said outer wall being arranged between said inner wall and said silo to form an outer riser between said inner wall and said outer wall for channeling cooling air upward, and to form a downcomer between said outer wall and said silo for channeling cooling air downward, wherein said inner wall comprises a plurality of apertures for allowing the passage of thermal radiation from said containment vessel to said outer wall. a cylindrical inner wall is arranged between and concentric with said containment vessel and said outer wall for dividing said riser into inner and outer risers, said inner wall comprising a plurality of apertures for allowing the passage of thermal radiation from said containment vessel to said outer wall. 2. A baffle combination according to claim 1 wherein: 3. A baffle combination according to claim 1 wherein said containment vessel, said inner wall, said outer wall, and said silo are annular and concentric. 4. A baffle combination according to claim 1 wherein said inner wall is joined to said outer wall by a plurality of spaced stud bolts. 5. A baffle combination according to claim 1 further comprising a plurality of vertically spaced horizontal boundary layer trips disposed on at least one of an outer surface of said containment vessel or an inner surface of said outer wall for increasing heat transfer to said cooling air flowing upwardly in said inner and outer risers, respectively. 6. A baffle combination according to claim 1 wherein said outer wall has an outer surface facing said silo characterized by the absence of thermal insulation thereon. 7. A baffle combination according to claim 1 wherein: 8. A baffle for enhancing air cooling of a containment vessel concentrically arranged inside a silo of a nuclear reactor with an annular volume therebetween, said containment vessel encircling a reactor vessel having a nuclear fuel core submerged in liquid coolant, comprising: 9. The baffle as defined in claim 8, wherein said downcomer is disposed in flow communication with both said inner and outer risers at bottom ends thereof for channeling downwardly flowing cooling air upwardly into both said inner and outer risers for cooling said containment vessel. 10. The baffle as defined in claim 8, wherein said inner wall is supported by said outer wall. 11. The baffle as defined in claim 8, wherein said outer wall has a radially outer circumferential surface facing said silo with no thermal insulation thereon. 12. The baffle as defined in claim 8, wherein said outer wall has a radially inner circumferential surface facing said inner wall with means for generating turbulence formed thereon. 13. The baffle as defined in claim 8, wherein said containment vessel has a radially outer circumferential surface facing said inner wall with means for generating turbulence formed thereon. 14. The baffle as defined in claim 8, wherein said apertures are circular. 15. In a nuclear reactor comprising a reactor vessel having a nuclear fuel core submerged in liquid coolant, a containment vessel encircling said reactor vessel, a baffle encircling said containment vessel for enhancing air cooling thereof, and a silo encircling said baffle, said baffle comprising a cylindrical outer wall arranged between and concentric with said containment vessel and said silo, said outer wall and said silo forming a downcomer therebetween for channeling cooling air downward, and said containment vessel and said outer wall forming a riser therebetween for channeling cooling air from said downcomer upward, the improvement wherein: 16. The baffle as defined in claim 15, wherein said inner wall is supported by said outer wall. 17. The baffle as defined in claim 15, wherein said outer wall has a radially outer circumferential surface facing said silo with no thermal insulation thereon. 18. The baffle as defined in claim 15, wherein said outer wall has a radially inner circumferential surface facing said inner wall with means for generating turbulence formed thereon. 19. The baffle as defined in claim 15, wherein said containment vessel has a radially outer circumferential surface facing said inner wall with means for generating turbulence formed thereon. 20. The baffle as defined in claim 15, wherein said apertures are circular.
051788241	description	Referring now to FIG. 1, a collection apparatus 10 is shown for collection of particulates from a grinding apparatus 12. The collection apparatus 10 comprises a vessel 14 having declivitous sides 15 descending to an outlet 16 connected to one side of a top valve 17. A tubular upright collection chamber 18 is connected at its upper end to the other side of the top valve 17, and is closable at its lower end by a lower valve 22. An ultrasonic sensor 24 is positioned just below the top valve 17 to monitor particulate level at that position in the chamber 18, and a compressed air inlet 25 into the chamber 18 locates between the sensor 24 and the top valve 17. An overflow 26 extends near the top of the vessel 14, and a recirculation circuit 28 including a pump 30 is connected between the declivitous sides 15 to a position above the grinding apparatus 12. The grinding apparatus 12 comprises parallel grinding wheels 34, 35 respectively located above a trough 36 which has a bottom outlet 38 extending so as to discharge into the vessel 14. In operation, nuclear fuel pellets 40 (eg uranium oxide) are fed between and along the grinding wheels 34, 35 to provide a required diameter of pellet 40. The recirculation circuit 28 discharges water over the grinding wheels 34, 35 and the water together with particulates 42 (eg 1 to 4 .mu.m) drop into the trough 36 and from there through the outlet 38 into the vessel 14. With the top valve 17 open and the lower valve 22 closed, the particulates 42 fall and settle in the chamber 18, whilst the water is recirculated by the recirculation circuit 28, any water flowing through the overflow 26 being collected and subsequently returned to the vessel 14. The particulates 42 gradually collect as a sludge 44 in the chamber 18 until they reach a level where they are detected by the sensor 24. The top valve 17 is then closed, the lower valve 22 opened, and compressed air introduced for a short period through the inlet 25 to eject the sludge 44 from the bottom of the chamber 18. The lower valve 22 is then closed, and the top valve 17 opened, to repeat the collection cycle in the chamber 18. Referring now to the modification shown in FIG. 2, the collection apparatus 50 shown is in many respects identical to the collection apparatus 12 of FIG. 1, except that in place of the recirculation circuit 28 of FIG. 1, a filter circuit 52 is used. The filter circuit 52 comprises an outlet pipe 54 from the vessel 14 connected to a pump 56 arranged to discharge to a conventional cross-flow filter 58. A clean water filtrate outlet 60 from the filter 58 is arranged to discharge between the grinding wheels 34, 35, whilst a through-flow outlet 62 from the filter 58 is returned into the vessel 14 above the outlet pipe 54. As an option, a flush-down pipe 66 (shown in broken line) may be connected between the through-flow outlet 62 and the side of the trough 36 to assist in flushing the particulates 42 from the trough 36 into the vessel 14. In order to inhibit rapid blocking of the filter 58 from the particulate 42, an initial feed of particulate U.sub.3 O.sub.8 may be introduced at 68 to form a permeable coating 70 (see FIG. 3) at the ingress side of filter element 72 of the filter 58. For example, particulate U.sub.3 .sub.8 having a size distribution of between 45 and 90 .mu.m at a loading of about 229 gm in 30 liters of water mixed with U.sub.3 O.sub.8 having a size distribution of 1<45 .mu.m at a loading of about 50 gm in 30 liters of water has been found suitable to provide an effective coating. An example of a suitable cross-flow filter 58 may be obtained from: Fairy Microfiltrex Limited PA1 Fareham Industrial Park PA1 Fareham PA1 Hampshire PA1 P016 8XO PA1 United Kingdom PA1 Bestobell Mobrey PA1 190-196 Bath Road PA1 Slough PA1 Berkshire PA1 SL1 4DN PA1 United Kingdom An example of a suitable sensor 24 to sense a sludge interface may be obtained from: It will be appreciated that the sensor may form part of a circuit for automatically operating the top valve 17, the lower valve 22, and the air inlet 25 in response to signals from the sensor. With some particulates and with frequent discharge of the sludge 44, the use of the air inlet 25 might be dispensed with. Although the invention has been described in relation to the manufacture of nuclear oxide fuels, the invention has applications with alternative nuclear fuels, and for non-nuclear materials. It will be understood that although obturating means in the form of valve means (eg ball valve means) have been described in relation to FIGS. 1 and 2, alternative suitable obturating means may be used preferably to provide a relatively clear axial path for the discharge of the sludge 44 therethrough.
	description	This application claims the benefit of U.S. Provisional Application No. 60/659,767 filed Mar. 7, 2005, which application is incorporated herein by reference. The invention relates generally to the field of plasma physics, and, in particular, to methods and apparati for confining plasma to enable nuclear fusion and for converting energy from fusion products into electricity. Fusion is the process by which two light nuclei combine to form a heavier one. The fusion process releases a tremendous amount of energy in the form of fast moving particles. Because atomic nuclei are positively charged—due to the protons contained therein—there is a repulsive electrostatic, or Coulomb, force between them. For two nuclei to fuse, this repulsive barrier must be overcome, which occurs when two nuclei are brought close enough together where the short-range nuclear forces become strong enough to overcome the Coulomb force and fuse the nuclei. The energy necessary for the nuclei to overcome the Coulomb barrier is provided by their thermal energies, which must be very high. For example, the fusion rate can be appreciable if the temperature is at least of the order of 104 eV—corresponding roughly to 100 million degrees Kelvin. The rate of a fusion reaction is a function of the temperature, and it is characterized by a quantity called reactivity. The reactivity of a D-T reaction, for example, has a broad peak between 30 keV and 100 keV. Typical fusion reactions include:D+D→He3(0.8 MeV)+n(2.5 MeV),D+T→α(3.6 MeV)+n(14.1 MeV),D+He3→α(3.7 MeV)+p(14.7 MeV), andp+B11→3α(8.7 MeV),where D indicates deuterium, T indicates tritium, α indicates a helium nucleus, n indicates a neutron, p indicates a proton, He indicates helium, and B11 indicates Boron-11. The numbers in parentheses in each equation indicate the kinetic energy of the fusion products. The first two reactions listed above—the D-D and D-T reactions—are neutronic, which means that most of the energy of their fusion products is carried by fast neutrons. The disadvantages of neutronic reactions are that (1) the flux of fast neutrons creates many problems, including structural damage of the reactor walls and high levels of radioactivity for most construction materials; and (2) the energy of fast neutrons is collected by converting their thermal energy to electric energy, which is very inefficient (less than 30%). The advantages of neutronic reactions are that (1) their reactivity peaks are at a relatively low temperature; and (2) their losses due to radiation are relatively low because the atomic numbers of deuterium and tritium are 1. The reactants in the other two equations—D-He3 and p-B11—are called advanced fuels. Instead of producing fast neutrons, as in the neutronic reactions, their fusion products are charged particles. One advantage of the advanced fuels is that they create much fewer neutrons and therefore suffer less from the disadvantages associated with them. In the case of D-He3, some fast neutrons are produced by secondary reactions, but these neutrons account for only about 10 percent of the energy of the fusion products. The p-B11 reaction is free of fast neutrons, although it does produce some slow neutrons that result from secondary reactions but create much fewer problems. Another advantage of the advanced fuels is that their fusion products comprise charged particles whose kinetic energy may be directly convertible to electricity. With an appropriate direct energy conversion process, the energy of advanced fuel fusion products may be collected with a high efficiency, possibly in excess of 90 percent. The advanced fuels have disadvantages, too. For example, the atomic numbers of the advanced fuels are higher (2 for He3 and 5 for B11). Therefore, their radiation losses are greater than in the neutronic reactions. Also, it is much more difficult to cause the advanced fuels to fuse. Their peak reactivities occur at much higher temperatures and do not reach as high as the reactivity for D-T. Causing a fusion reaction with the advanced fuels thus requires that they be brought to a higher energy state where their reactivity is significant. Accordingly, the advanced fuels must be contained for a longer time period wherein they can be brought to appropriate fusion conditions. The containment time for a plasma is Δt=r2/D, where r is a minimum plasma dimension and D is a diffusion coefficient. The classical value of the diffusion coefficient is Dc=ai2/τie, where ai is the ion gyroradius and τie is the ion-electron collision time. Diffusion according to the classical diffusion coefficient is called classical transport. The Bohm diffusion coefficient, attributed to short-wavelength instabilities, is DB=( 1/16)ai2Ωi, where Ωi is the ion gyrofrequency. Diffusion according to this relationship is called anomalous transport. For fusion conditions, DB/Dc=( 1/16)Ωiτie≅108, anomalous transport results in a much shorter containment time than does classical transport. This relation determines how large a plasma must be in a fusion reactor, by the requirement that the containment time for a given amount of plasma must be longer than the time for the plasma to have a nuclear fusion reaction. Therefore, classical transport condition is more desirable in a fusion reactor, allowing for smaller initial plasmas. In early experiments with toroidal confinement of plasma, a containment time of Δt≅r2/DB was observed. Progress in the last 40 years has increased the containment time to Δt≅1000 r2/DB. One existing fusion reactor concept is the Tokamak. For the past 30 years, fusion efforts have been focused on the Tokamak reactor using a D-T fuel. These efforts have culminated in the International Thermonuclear Experimental Reactor (ITER). Recent experiments with Tokamaks suggest that classical transport, Δt≅r2/Dc, is possible, in which case the minimum plasma dimension can be reduced from meters to centimeters. These experiments involved the injection of energetic beams (50 to 100 keV), to heat the plasma to temperatures of 10 to 30 keV. See W. Heidbrink & G. J. Sadler, 34 Nuclear Fusion 535 (1994). The energetic beam ions in these experiments were observed to slow down and diffuse classically while the thermal plasma continued to diffuse anomalously fast. The reason for this is that the energetic beam ions have a large gyroradius and, as such, are insensitive to fluctuations with wavelengths shorter than the ion gyroradius (λ<ai). The short-wavelength fluctuations tend to average over a cycle and thus cancel. Electrons, however, have a much smaller gyroradius, so they respond to the fluctuations and transport anomalously. Because of anomalous transport, the minimum dimension of the plasma must be at least 2.8 meters. Due to this dimension, the ITER was created 30 meters high and 30 meters in diameter. This is the smallest D-T Tokamak-type reactor that is feasible. For advanced fuels, such as D-He3 and p-B11, the Tokamak-type reactor would have to be much larger because the time for a fuel ion to have a nuclear reaction is much longer. A Tokamak reactor using D-T fuel has the additional problem that most of the energy of the fusion products energy is carried by 14 MeV neutrons, which cause radiation damage and induce reactivity in almost all construction materials due to the neutron flux. In addition, the conversion of their energy into electricity must be by a thermal process, which is not more than 30% efficient. Another proposed reactor configuration is a colliding beam reactor. In a colliding beam reactor, a background plasma is bombarded by beams of ions. The beams comprise ions with an energy that is much larger than the thermal plasma. Producing useful fusion reactions in this type of reactor has been infeasible because the background plasma slows down the ion beams. Various proposals have been made to reduce this problem and maximize the number of nuclear reactions. For example, U.S. Pat. No. 4,065,351 to Jassby et al. discloses a method of producing counterstreaming colliding beams of deuterons and tritons in a toroidal confinement system. In U.S. Pat. No. 4,057,462 to Jassby et al., electromagnetic energy is injected to counteract the effects of bulk equilibrium plasma drag on one of the ion species. The toroidal confinement system is identified as a Tokamak. In U.S. Pat. No. 4,894,199 to Rostoker, beams of deuterium and tritium are injected and trapped with the same average velocity in a Tokamak, mirror, or field reversed configuration. There is a low density cool background plasma for the sole purpose of trapping the beams. The beams react because they have a high temperature, and slowing down is mainly caused by electrons that accompany the injected ions. The electrons are heated by the ions in which case the slowing down is minimal. In none of these devices, however, does an equilibrium electric field play any part. Further, there is no attempt to reduce, or even consider, anomalous transport. Other patents consider electrostatic confinement of ions and, in some cases, magnetic confinement of electrons. These include U.S. Pat. No. 3,258,402 to Farnsworth and U.S. Pat. No. 3,386,883 to Farnsworth, which disclose electrostatic confinement of ions and inertial confinement of electrons; U.S. Pat. No. 3,530,036 to Hirsch et al. and U.S. Pat. No. 3,530,497 to Hirsch et al. are similar to Farnsworth; U.S. Pat. No. 4,233,537 to Limpaecher, which discloses electrostatic confinement of ions and magnetic confinement of electrons with multi-pole cusp reflecting walls; and U.S. Pat. No. 4,826,646 to Bussard, which is similar to Limpaecher and involves point cusps. None of these patents consider electrostatic confinement of electrons and magnetic confinement of ions. Although there have been many research projects on electrostatic confinement of ions, none of them have succeeded in establishing the required electrostatic fields when the ions have the required density for a fusion reactor. Lastly, none of the patents cited above discuss a field reversed configuration magnetic topology. The field reversed configuration (FRC) was discovered accidentally around 1960 at the Naval Research Laboratory during theta pinch experiments. A typical FRC topology, wherein the internal magnetic field reverses direction, is illustrated in FIG. 3 and FIG. 5, and particle orbits in a FRC are shown in FIG. 6 and FIG. 9. Regarding the FRC, many research programs have been supported in the United States and Japan. There is a comprehensive review paper on the theory and experiments of FRC research from 1960-1988. See M. Tuszewski, 28 Nuclear Fusion 2033, (1988). A white paper on FRC development describes the research in 1996 and recommendations for future research. See L. C. Steinhauer et al., 30 Fusion Technology 116 (1996). To this date, in FRC experiments the FRC has been formed with the theta pinch method. A consequence of this formation method is that the ions and electrons each carry half the current, which results in a negligible electrostatic field in the plasma and no electrostatic confinement. The ions and electrons in these FRCs were contained magnetically. In almost all FRC experiments anomalous transport has been assumed. See, e.g., Tuszewski, beginning of section 1.5.2, at page 2072. Thus, it is desirable to provide a fusion system having a containment system that tends to substantially reduce or eliminate anomalous transport of ions and electrons and an energy conversion system that converts the energy of fusion products to electricity with high efficiency. The present invention is directed to a system that facilitates controlled fusion in a magnetic field having a field-reversed topology and the direct conversion of fusion product energies to electric power. The system, referred to herein as a plasma-electric power generation (PEG) system, preferably includes a fusion reactor having a containment system that tends to substantially reduce or eliminate anomalous transport of ions and electrons. In addition, the PEG system includes an energy conversion system coupled to the reactor that directly converts fusion product energies to electricity with high efficiency. In one embodiment, anomalous transport for both ions and electrons tends to be substantially reduced or eliminated. The anomalous transport of ions tends to be avoided by magnetically confining the ions in a magnetic field of field reversed configuration (FRC). For electrons, the anomalous transport of energy is avoided by tuning an externally applied magnetic field to develop a strong electric field, which confines the electrons electrostatically in a deep potential well. As a result, fusion fuel plasmas that can be used with the present confinement apparatus and process are not limited to neutronic fuels, but also advantageously include advanced or aneutronic fuels. For aneutronic fuels, fusion reaction energy is almost entirely in the form of charged particles, i.e., energetic ions, that can be manipulated in a magnetic field and, depending on the fuel, cause little or no radioactivity. In a preferred embodiment, a fusion reactor's plasma containment system comprises a chamber, a magnetic field generator for applying a magnetic field in a direction substantially along a principle axis, and an annular plasma layer that comprises a circulating beam of ions. Ions of the annular plasma beam layer are substantially contained within the chamber magnetically in orbits and the electrons are substantially contained in an electrostatic energy well. In one preferred embodiment the magnetic field generator includes a current coil. Preferably, the magnetic field generator further comprises mirror coils near the ends of the chamber that increase the magnitude of the applied magnetic field at the ends of the chamber. The system also comprises one or more beam injectors for injecting neutralized ion beams into the magnetic field, wherein the beam enters an orbit due to the force caused by the magnetic field. In a preferred embodiment, the system forms a magnetic field having a topology of a field reversed configuration. In another preferred embodiment, an alternative chamber is provided that prevents the formation of azimuthal image currents in a central region of the chamber wall and enables magnetic flux to penetrate the chamber on a fast timescale. The chamber, which is primarily comprised of stainless steel to provide structural strength and good vacuum properties, includes axial insulating breaks in the chamber wall that run along almost the entire length of the chamber. Preferably, there are three breaks that are about 120 degrees apart from each other. The breaks include a slot or gap formed in the wall. An insert comprising an insulating material, preferably a ceramic or the like, is inserted into the slots or gaps. In the interior of the chamber, a metal shroud covers the insert. On the outside of the chamber, the insert is attached to a sealing panel, preferable formed from fiberglass or the like, that forms a vacuum barrier by means of an O-ring seal with the stainless steel surface of the chamber wall. In yet another preferred embodiment, an inductive plasma source is mountable within the chamber and includes a shock coil assembly, preferably a single turn shock coil, that is preferably fed by a high voltage (about 5-15 kV) power source (not shown). Neutral gas, such as Hydrogen (or other appropriate gaseous fusion fuel), is introduced into the source through direct gas feeds via a Laval nozzle. Once the gas emanates from the nozzle and distributes itself over the surface of the coil windings of the shock coil, the windings are energized. The ultra fast current and flux ramp-up in the low inductance shock coil leads to a very high electric field within the gas that causes breakdown, ionization and subsequent ejection of the formed plasma from the surface of the shock coil towards the center or mid-plane of the chamber. In a further preferred embodiment, a RF drive comprises a quadrupolar cyclotron located within the chamber and having four azimuthally symmetrical electrodes with gaps there between. The quadrupole cyclotron produces an electric potential wave that rotates in the same direction as the azimuthal velocity of ions, but at a greater velocity. Ions of appropriate speed can be trapped in this wave, and reflected periodically. This process increases the momentum and energy of the fuel ions and this increase is conveyed to the fuel ions that are not trapped by collisions. In another embodiment, a direct energy conversion system is used to convert the kinetic energy of the fusion products directly into electric power by slowing down the charged particles through an electromagnetic field. Advantageously, the direct energy conversion system of the present invention has the efficiencies, particle-energy tolerances and electronic ability to convert the frequency and phase of the fusion output power of about 5 MHz to match the frequency of an external 60 Hertz power grid. In a preferred embodiment, the energy conversion system comprises inverse cyclotron converters (ICC) coupled to opposing ends of the fusion reactor. The ICC have a hollow cylinder-like geometry formed from multiple, preferably four or more equal, semi-cylindrical electrodes with small, straight gaps extending there between. In operation, an oscillating potential is applied to the electrodes in an alternating fashion. The electric field E within the ICC has a multi-pole structure and vanishes on the symmetry axes and increases linearly with radius; the peak value being at the gap. In addition, the ICC includes a magnetic field generator for applying a uniform uni-directional magnetic field in a direction substantially opposite to the applied magnetic field of the fusion reactor's containment system. At an end furthest from the fusion reactor power core the ICC includes an ion collector. In between the power core and the ICC is a symmetric magnetic cusp wherein the magnetic field of the containment system merges with the magnetic field of the ICC. An annular shaped electron collector is positioned about the magnetic cusp and electrically coupled to the ion collector. In yet another preferred embodiment, product nuclei and charge-neutralizing electrons emerge as annular beams from both ends of the reactor power core with a density at which the magnetic cusp separates electrons and ions due to their energy differences. The electrons follow magnetic field lines to the electron collector and the ions pass through the cusp where the ion trajectories are modified to follow a substantially helical path along the length of the ICC. Energy is removed from the ions as they spiral past the electrodes, which are connected to a resonant circuit. The loss of perpendicular energy tends to be greatest for the highest energy ions that initially circulate close to the electrodes, where the electric field is strongest. Other aspects and features of the present invention will become apparent from consideration of the following description taken in conjunction with the accompanying drawings. As illustrated in the figures, a plasma-electric power generation (PEG) system of the present invention preferably includes a colliding beam fusion reactor (CBFR) coupled to a direct energy conversion system. As alluded to above, an ideal fusion reactor solves the problem of anomalous transport for both ions and electrons. The solution to the problem of anomalous transport found herein makes use of a containment system with a magnetic field having a field reversed configuration (FRC). The anomalous transport of ions is avoided by magnetic confinement in the FRC in such a way that the majority of the ions have large, non-adiabatic orbits, making them insensitive to short-wavelength fluctuations that cause anomalous transport of adiabatic ions. In particular, the existence of a region in the FRC where the magnetic field vanishes makes it possible to have a plasma comprising a majority of non-adiabatic ions. For electrons, the anomalous transport of energy is avoided by tuning the externally applied magnetic field to develop a strong electric field, which confines them electrostatically in a deep potential well. Fusion fuel plasmas that can be used with the present confinement apparatus and process are not limited to neutronic fuels such as D-D (Deuterium-Deuterium) or D-T (Deuterium-Tritium), but also advantageously include advanced or aneutronic fuels such as D-He3 (Deuterium-helium-3) or p-B11 (hydrogen-Boron-11). (For a discussion of advanced fuels, see R. Feldbacher & M. Heindler, Nuclear Instruments and Methods in Physics Research, A271(1988)JJ-64 (North Holland Amsterdam).) For such aneutronic fuels, the fusion reaction energy is almost entirely in the form of charged particles, i.e., energetic ions, that can be manipulated in a magnetic field and, depending on the fuel, cause little or no radioactivity. The D-He3 reaction produces an H ion and an He4 ion with 18.2 MeV energy while the p-B11 reaction produces three He4 ions and 8.7 MeV energy. Based on theoretical modeling for a fusion device utilizing aneutronic fuels, the output energy conversion efficiency may be as high as about 90%, as described by K. Yoshikawa, T. Noma and Y. Yamamoto in Fusion Technology, 19, 870 (1991), for example. Such efficiencies dramatically advance the prospects for aneutronic fusion, in a scalable (1-1000 MW), compact, low-cost configuration. In a direct energy conversion process of the present invention, the charged particles of fusion products can be slowed down and their kinetic energy converted directly to electricity. Advantageously, the direct energy conversion system of the present invention has the efficiencies, particle-energy tolerances and electronic ability to convert the frequency and phase of the fusion output power of about 5 MHz to match the frequency and phase of an external 60 Hertz power grid. Fusion Containment System FIG. 1 illustrates a preferred embodiment of a containment system 300 according to the present invention. The containment system 300 comprises a chamber wall 305 that defines therein a confining chamber 310. Preferably, the chamber 310 is cylindrical in shape, with principle axis 315 along the center of the chamber 310. For application of this containment system 300 to a fusion reactor, it is necessary to create a vacuum or near vacuum inside the chamber 310. Concentric with the principle axis 315 is a betatron flux coil 320, located within the chamber 310. The betatron flux coil 320 comprises an electrical current carrying medium adapted to direct current around a long coil, as shown, which preferably comprises parallel windings of multiple separate coils and, most preferably, parallel windings of about four separate coils, to form a long coil. Persons skilled in the art will appreciate that current through the betatron coil 320 will result in a magnetic field inside the betatron coil 320, substantially in the direction of the principle axis 315. Around the outside of the chamber wall 305 is an outer coil 325. The outer coil 325 produce a relatively constant magnetic field having flux substantially parallel with principle axis 315. This magnetic field is azimuthally symmetrical. The approximation that the magnetic field due to the outer coil 325 is constant and parallel to axis 315 is most valid away from the ends of the chamber 310. At each end of the chamber 310 is a mirror coil 330. The mirror coils 330 are adapted to produce an increased magnetic field inside the chamber 310 at each end, thus bending the magnetic field lines inward at each end. (See FIGS. 3 and 5.) As explained, this bending inward of the field lines helps to contain the plasma 335 in a containment region within the chamber 310 generally between the mirror coils 330 by pushing it away from the ends where it can escape the containment system 300. The mirror coils 330 can be adapted to produce an increased magnetic field at the ends by a variety of methods known in the art, including increasing the number of windings in the mirror coils 330, increasing the current through the mirror coils 330, or overlapping the mirror coils 330 with the outer coil 325. The outer coil 325 and mirror coils 330 are shown in FIG. 1 implemented outside the chamber wall 305; however, they may be inside the chamber 310. In cases where the chamber wall 305 is constructed of a conductive material such as metal, it may be advantageous to place the coils 325, 330 inside the chamber wall 305 because the time that it takes for the magnetic field to diffuse through the wall 305 may be relatively large and thus cause the system 300 to react sluggishly. Similarly, the chamber 310 may be of the shape of a hollow cylinder, the chamber wall 305 forming a long, annular ring. In such a case, the betatron flux coil 320 could be implemented outside of the chamber wall 305 in the center of that annular ring. Preferably, the inner wall forming the center of the annular ring may comprise a non-conducting material such as glass. As will become apparent, the chamber 310 must be of sufficient size and shape to allow the circulating plasma beam or layer 335 to rotate around the principle axis 315 at a given radius. The chamber wall 305 may be formed of a material having a high magnetic permeability, such as steel. In such a case, the chamber wall 305, due to induced countercurrents in the material, helps to keep the magnetic flux from escaping the chamber 310, “compressing” it. If the chamber wall were to be made of a material having low magnetic permeability, such as plexiglass, another device for containing the magnetic flux would be necessary. In such a case, a series of closed-loop, flat metal rings could be provided. These rings, known in the art as flux delimiters, would be provided within the outer coils 325 but outside the circulating plasma beam 335. Further, these flux delimiters could be passive or active, wherein the active flux delimiters would be driven with a predetermined current to greater facilitate the containment of magnetic flux within the chamber 310. Alternatively, the outer coils 325 themselves could serve as flux delimiters. As explained in further detail below, a circulating plasma beam 335, comprising charged particles, may be contained within the chamber 310 by the Lorentz force caused by the magnetic field due to the outer coil 325. As such, the ions in the plasma beam 335 are magnetically contained in large betatron orbits about the flux lines from the outer coil 325, which are parallel to the principle axis 315. One or more beam injection ports 340 are also provided for adding plasma ions to the circulating plasma beam 335 in the chamber 310. In a preferred embodiment, the injector ports 340 are adapted to inject an ion beam at about the same radial position from the principle axis 315 where the circulating plasma beam 335 is contained (i.e., around a null surface described below). Further, the injector ports 340 are adapted to inject ion beams 350 (See FIG. 17) tangent to and in the direction of the betatron orbit of the contained plasma beam 335. Also provided are one or more background plasma sources 345 for injecting a cloud of non-energetic plasma into the chamber 310. In a preferred embodiment, the background plasma sources 345 are adapted to direct plasma 335 toward the axial center of the chamber 310. It has been found that directing the plasma this way helps to better contain the plasma 335 and leads to a higher density of plasma 335 in the containment region within the chamber 310. Vacuum Chamber As described above, application of the containment system of a CBFR, it is necessary to create a vacuum or near vacuum inside the chamber. Since interactions (scattering, charge exchange) between neutrals and plasma fuel always present an energy loss channel, it is critical to limit the residual density in the reactor chamber. Furthermore, impurities resulting from poorly evacuated chambers can lead to contaminating side-reactions during operation and can drain an exorbitant amount of energy during startup as the system has to burn through these residuals. To achieve a good level vacuum usually involves the use of stainless steel chambers and ports as well as low outgassing materials. In the case of metals, the good vacuum properties are further paired with good structural characteristics. However, conductive materials such as stainless steel and the like, present various problems with regards to their electrical properties. Although these negative effects are all linked, they manifest themselves in different ways. Amongst the most negative characteristics are: Retarded diffusion of magnetic fields through chamber walls, accumulation of electrical charges on the surfaces, drastic alteration of response times of the system to transient signals as well as formation of image currents in the surfaces that impact the desired magnetic topology. Materials that do not have these undesirable characteristics and exhibit good vacuum properties are insulators such as ceramics, glass, quartz and to a lesser degree carbon-fibers. The primary problem with these materials is structural integrity as well as the potential for accidental damage. Fabrication problems such as poor machinability of ceramics are further limitations. In one embodiment, as depicted in FIGS. 2A, 2B, 2C and 2D, an alternative chamber 1310 is provided that minimizes these problems. The chamber 1310 of the CBFR is preferably primarily comprised of a metal, preferably stainless steel or the like, to provide structural strength and good vacuum properties. However, the cylindrical wall 1311 of the chamber 1310 includes axial insulating breaks 1360 in the wall 1311 that run along almost the entire length of the chamber 1310 in the central portion of the chamber 1310 or power core region of the CBFR. Preferably, as depicted in FIG. 2B, there are three breaks 1360 that are about 120 degrees apart from each other. The breaks 1360, as depicted in FIG. 2C, include a slot or gap 1362 in the wall 1311 of the chamber 1310 with a seal groove or seat 1369 formed about the periphery of the slot 1362. An O-ring seal 1367 is received in the groove 1369. The slots 1362, as depicted in FIG. 2D, extend almost the entire length of the chamber 1310 leaving sufficient stainless material forming an azimuthally continuous portion of the wall 1311 near the two ends to provide structural integrity and to allow for good quality vacuum seals at the ends. For improved structural integrity and the prevention of implosion, the chamber 1310, as depicted in FIG. 2A, preferably includes a plurality of sets of partial azimuthal ribs 1370 that are integrally formed with the chamber wall 1311 or coupled to the surface of the chamber wall 1311 by welding or the like. As depicted in FIG. 2C, the gap 1362 is filled with an insert 1364 formed of ceramic material. The insert 1364 extends slightly into the interior of the chamber 1310 and is covered on the inside by a metal shroud 1366 to prevent secondary plasma emission from collisions of primary plasma ions from the circulating plasma beam with the ceramic material. On the outside of the chamber 1310, the insert 1364 is attached to a sealing panel 1365 that forms a vacuum barrier by means of an O-ring seal 1367 with the stainless steel surface of the chamber wall 1311. To preserve desirable vacuum properties, the sealing panel 1365 is preferably formed from a substrate, preferably fiberglass or the like, which is more flexible and creates a tighter seal with the O-ring 1367 than a ceramic material would, especially when inward pressure slightly deforms the chamber 1310. The inserts or ceramic insulators 1364 inside the slots 1362 preferably prevent current from arching across the gaps 1362 and, thus, prevent the formation of azimuthal image currents in the chamber wall 1311. Image currents are a manifestation of Lenz's Law, which is nature's tendency to counteract any change in flux: for example, the change in flux that occurs in the flux coil 1320 during the formation of a FRC, as described below. Without slots 1362 in the cylindrical wall 1311 of the chamber 1310, the changing flux in the flux coil 1320 causes an equal and opposite inductively induced current to form in the stainless steel wall 1311 such as to cancel the magnetic flux change inside the chamber 1310. While the induced image currents would be weaker (due to inductive losses) than the current applied to the flux coil 1320, the image current tends to strongly reduce the applied or confinement magnetic field within the chamber 1310, which, when not addressed, tends to negatively impact the magnetic field topology and alter the confinement characteristics inside of the chamber 1310. The existence of the slots 1362 prevents azimuthal image currents from forming in the wall 1311 toward the mid-plane of the chamber 1310 away from the ends of the chamber 1310 in the azimuthally continuous portion of the wall 1311. The only image currents that can be carried by the chamber wall 1311 toward the mid-plane away from the ends of the chamber 1310 are very weak currents that flow parallel to the longitudinal axis of the slots 1362. Such currents have no impact on the axial magnetic confinement fields of the FRC as the magnetic image fields produced by the image currents longitudinally traversing the chamber wall 1311 only exhibit radial and azimuthal components. The azimuthal image currents formed in the azimuthally continuous conducting portion of the wall 1311 near the ends of the chamber 1310 tend not to negatively impact and/or alter the confinement characteristics inside of the chamber 1310 as the magnetic topology in this vicinity is not important to confinement of the plasma. In addition to preventing the formation of azimuthal image currents in the chamber wall 1311, the slots 1362 provide a way for magnetic flux from the field and mirror coils 1325 and 1330 to penetrate the chamber 1310 on a fast timescale. The slots 1362 enable sub-millisecond level fine-tuning and feedback control of the applied magnetic field as a result. Charged Particles in a FRC FIG. 3 shows a magnetic field of a FRC 70. The system has cylindrical symmetry with respect to its axis 78. In the FRC, there are two regions of magnetic field lines: open 80 and closed 82. The surface dividing the two regions is called the separatrix 84. The FRC forms a cylindrical null surface 86 in which the magnetic field vanishes. In the central part 88 of the FRC the magnetic field does not change appreciably in the axial direction. At the ends 90, the magnetic field does change appreciably in the axial direction. The magnetic field along the center axis 78 reverses direction in the FRC, which gives rise to the term “Reversed” in Field Reversed Configuration (FRC). In FIG. 4A, the magnetic field outside of the null surface 94 is in a first direction 96. The magnetic field inside the null surface 94 is in a second direction 98 opposite the first. If an ion moves in the direction 100, the Lorentz force 30 acting on it points towards the null surface 94. This is easily appreciated by applying the right-hand rule. For particles moving in the diamagnetic direction 102, the Lorentz force always points toward the null surface 94. This phenomenon gives rise to a particle orbit called betatron orbit, to be described below. FIG. 4B shows an ion moving in the counterdiamagnetic direction 104. The Lorentz force in this case points away from the null surface 94. This phenomenon gives rise to a type of orbit called a drift orbit, to be described below. The diamagnetic direction for ions is counterdiamagnetic for electrons, and vice versa. FIG. 5 shows a ring or annular layer of plasma 106 rotating in the ions' diamagnetic direction 102. The ring 106 is located around the null surface 86. The magnetic field 108 created by the annular plasma layer 106, in combination with an externally applied magnetic field 110, forms a magnetic field having the topology of a FRC (The topology is shown in FIG. 3). The ion beam that forms the plasma layer 106 has a temperature; therefore, the velocities of the ions form a Maxwell distribution in a frame rotating at the average angular velocity of the ion beam. Collisions between ions of different velocities lead to fusion reactions. For this reason, the plasma beam layer or power core 106 is called a colliding beam system. FIG. 6 shows the main type of ion orbits in a colliding beam system, called a betatron orbit 112. A betatron orbit 112 can be expressed as a sine wave centered on the null circle 114. As explained above, the magnetic field on the null circle 114 vanishes. The plane of the orbit 112 is perpendicular to the axis 78 of the FRC. Ions in this orbit 112 move in their diamagnetic direction 102 from a starting point 116. An ion in a betatron orbit has two motions: an oscillation in the radial direction (perpendicular to the null circle 114), and a translation along the null circle 114. FIG. 7A is a graph of the magnetic field 118 in a FRC. The horizontal axis of the graph represents the distance in centimeters from the FRC axis 78. The magnetic field is in kilogauss. As the graph depicts, the magnetic field 118 vanishes at the null circle radius 120. As shown in FIG. 7B, a particle moving near the null circle will see a gradient 126 of the magnetic field pointing away from the null surface 86. The magnetic field outside the null circle is in a first direction 122, while the magnetic field inside the null circle is in a second direction 124 opposite to the first. The direction of a gradient drift is given by the cross product {right arrow over (B)}×∇B, where ∇B is the gradient of the magnetic field; thus, it can be appreciated by applying the right-hand rule that the direction of the gradient drift is in the counterdiamagnetic direction, whether the ion is outside or inside the null circle 128. FIG. 8A is a graph of the electric field 130 in a FRC. The horizontal axis of the graph represents the distance in centimeters from the FRC axis 78. The electric field is in volts/cm. As the graph depicts, the electric field 130 vanishes close to the null circle radius 120. As shown if FIG. 8B, the electric field for ions is deconfining; it points in directions 132, 134 away from the null surface 86. The magnetic field, as before, is in opposite directions 122,124 inside and outside of the null surface 86. It can be appreciated by applying the right-hand rule that the direction of the {right arrow over (E)}×{right arrow over (B)} drift is in the diamagnetic direction 102, whether the ion is outside or inside the null surface 136. FIGS. 9A and 9B show another type of common orbit in a FRC, called a drift orbit 138. Drift orbits 138 can be outside of the null surface 114, as shown in FIG. 9A, or inside it, as shown in FIG. 9B. Drift orbits 138 rotate in the diamagnetic direction if the {right arrow over (E)}×{right arrow over (B)} drift dominates or in the counterdiamagnetic direction if the gradient drift dominates. The drift orbits 138 shown in FIGS. 9A and 9B rotate in the diamagnetic direction 102 from starting point 116. A drift orbit, as shown in FIG. 9C, can be thought of as a small circle rolling over a relatively bigger circle. The small circle 142 spins around its axis in the sense 144. It also rolls over the big circle 146 in the direction 102. The point 140 will trace in space a path similar to 138. FIGS. 10A and 10B show the direction of the Lorentz force at the ends of a FRC 151. In FIG. 10A, an ion is shown moving in the diamagnetic direction 102 with a velocity 148 in a magnetic field 150. It can be appreciated by applying the right-hand rule that the Lorentz force 152 tends to push the ion back into the region of closed field lines. In this case, therefore, the Lorentz force 152 is confining for the ions. In FIG. 10B, an ion is shown moving in the counterdiamagnetic direction with a velocity 148 in a magnetic field 150. It can be appreciated by applying the right-hand rule that the Lorentz force 152 tends to push the ion into the region of open field lines. In this case, therefore, the Lorentz force 152 is deconfining for the ions. Magnetic and Electrostatic Confinement in a FRC A plasma layer 106 (see FIG. 5) can be formed in a FRC by injecting energetic ion beams around the null surface 86 in the diamagnetic direction 102 of ions. (A detailed discussion of different methods of forming the FRC and plasma ring follows below.) In the circulating plasma layer 106, most of the ions have betatron orbits 112 (see FIG. 6), are energetic, and are non-adiabatic; thus, they are insensitive to short-wavelength fluctuations that cause anomalous transport. In a plasma layer 106 formed in a FRC and under equilibrium conditions, the conservation of momentum imposes a relation between the angular velocity of ions ωi and the angular velocity of electrons ωe. The relation is ω e = ω i ⁡ [ 1 - ω i Ω 0 ] , where ⁢ ⁢ Ω 0 = ZeB 0 m i ⁢ c . ( 1 ) In Eq. 1, Z is the ion atomic number, mi is the ion mass, e is the electron charge, B0 is the magnitude of the applied magnetic field, and c is the speed of light. There are three free parameters in this relation: the applied magnetic field B0, the electron angular velocity ωe, and the ion angular velocity ωi. If two of them are known, the third can be determined from Eq. 1. Because the plasma layer 106 is formed by injecting ion beams into the FRC, the angular velocity of ions ωi is determined by the injection kinetic energy of the beam Wi, which is given by W i = 1 2 ⁢ m i ⁢ V i 2 = 1 2 ⁢ m i ⁡ ( ω i ⁢ r o ) 2 ( 2 ) Here, Vi=ωir0, where Vi is the injection velocity of ions, ωi is the cyclotron frequency of ions, and r0 is the radius of the null surface 86. The kinetic energy of electrons in the beam has been ignored because the electron mass me is much smaller than the ion mass mi. For a fixed injection velocity of the beam (fixed ωi), the applied magnetic field B0 can be tuned so that different values of ωe are obtainable. As will be shown, tuning the external magnetic field B0 also gives rise to different values of the electrostatic field inside the plasma layer. This feature of the invention is illustrated in FIGS. 11A and 11B. FIG. 11A shows three plots of the electric field (in volts/cm) obtained for the same injection velocity, ωi=1.35×107s−1, but for three different values of the applied magnetic field B0: PlotApplied magnetic field (B0)electron angular velocity (ωe)154B0 = 2.77 kGωe = 0156B0 = 5.15 kGωe = 0.625 × 107 s−1158B0 = 15.5 kGωe = 1.11 × 107 s−1The values of ωe in the table above were determined according to Eq. 1. One can appreciate that ωe>0 means that Ω0>ωi in Eq. 1, so that electrons rotate in their counterdiamagnetic direction. FIG. 11B shows the electric potential (in volts) for the same set of values of B0 and ωe. The horizontal axis, in FIGS. 11A and 11B, represents the distance from the FRC axis 78, shown in the graph in centimeters. The electric field and electric potential depend strongly on ωe. The above results can be explained on simple physical grounds. When the ions rotate in the diamagnetic direction, the ions are confined magnetically by the Lorentz force. This was shown in FIG. 4A. For electrons, rotating in the same direction as the ions, the Lorentz force is in the opposite direction, so that electrons would not be confined. The electrons leave the plasma and, as a result, a surplus of positive charge is created. This sets up an electric field that prevents other electrons from leaving the plasma. The direction and the magnitude of this electric field, in equilibrium, is determined by the conservation of momentum. The electrostatic field plays an essential role on the transport of both electrons and ions. Accordingly, an important aspect of this invention is that a strong electrostatic field is created inside the plasma layer 106, the magnitude of this electrostatic field is controlled by the value of the applied magnetic field B0 which can be easily adjusted. As explained, the electrostatic field is confining for electrons if ωe>0. As shown in FIG. 11B, the depth of the well can be increased by tuning the applied magnetic field B0. Except for a very narrow region near the null circle, the electrons always have a small gyroradius. Therefore, electrons respond to short-wavelength fluctuations with an anomalously fast diffusion rate. This diffusion, in fact, helps maintain the potential well once the fusion reaction occurs. The fusion product ions, being of much higher energy, leave the plasma. To maintain charge quasi-neutrality, the fusion products must pull electrons out of the plasma with them, mainly taking the electrons from the surface of the plasma layer. The density of electrons at the surface of the plasma is very low, and the electrons that leave the plasma with the fusion products must be replaced; otherwise, the potential well would disappear. FIG. 12 shows a Maxwellian distribution 162 of electrons. Only very energetic electrons from the tail 160 of the Maxwell distribution can reach the surface of the plasma and leave with fusion ions. The tail 160 of the distribution 162 is thus continuously created by electron-electron collisions in the region of high density near the null surface. The energetic electrons still have a small gyroradius, so that anomalous diffusion permits them to reach the surface fast enough to accommodate the departing fusion product ions. The energetic electrons lose their energy ascending the potential well and leave with very little energy. Although the electrons can cross the magnetic field rapidly, due to anomalous transport, anomalous energy losses tend to be avoided because little energy is transported. Another consequence of the potential well is a strong cooling mechanism for electrons that is similar to evaporative cooling. For example, for water to evaporate, it must be supplied the latent heat of vaporization. This heat is supplied by the remaining liquid water and the surrounding medium, which then thermalize rapidly to a lower temperature faster than the heat transport processes can replace the energy. Similarly, for electrons, the potential well depth is equivalent to water's latent heat of vaporization. The electrons supply the energy required to ascend the potential well by the thermalization process that re-supplies the energy of the Maxwell tail so that the electrons can escape. The thermalization process thus results in a lower electron temperature, as it is much faster than any heating process. Because of the mass difference between electrons and protons, the energy transfer time from protons is about 1800 times less than the electron thermalization time. This cooling mechanism also reduces the radiation loss of electrons. This is particularly important for advanced fuels, where radiation losses are enhanced by fuel ions with an atomic number Z greater than 1;Z>1. The electrostatic field also affects ion transport. The majority of particle orbits in the plasma layer 106 are betatron orbits 112. Large-angle collisions, that is, collisions with scattering angles between 90° and 180°, can change a betatron orbit to a drift orbit. As described above, the direction of rotation of the drift orbit is determined by a competition between the {right arrow over (E)}×{right arrow over (B)} drift and the gradient drift. If the {right arrow over (E)}×{right arrow over (B)} drift dominates, the drift orbit rotates in the diamagnetic direction. If the gradient drift dominates, the drift orbit rotates in the counterdiamagnetic direction. This is shown in FIGS. 13A and 13B. FIG. 13A shows a transition from a betatron orbit to a drift orbit due to a 180° collision, which occurs at the point 172. The drift orbit continues to rotate in the diamagnetic direction because the {right arrow over (E)}×{right arrow over (B)} drift dominates. FIG. 13B shows another 180° collision, but in this case the electrostatic field is weak and the gradient drift dominates. The drift orbit thus rotates in the counterdiamagnetic direction. The direction of rotation of the drift orbit determines whether it is confined or not. A particle moving in a drift orbit will also have a velocity parallel to the FRC axis. The time it takes the particle to go from one end of the FRC to the other, as a result of its parallel motion, is called transit time; thus, the drift orbits reach an end of the FRC in a time of the order of the transit time. As shown in connection with FIG. 10A, the Lorentz force at the ends of the FRC is confining only for drift orbits rotating in the diamagnetic direction. After a transit time, therefore, ions in drift orbits rotating in the counterdiamagnetic direction are lost. This phenomenon accounts for a loss mechanism for ions, which is expected to have existed in all FRC experiments. In fact, in these experiments, the ions carried half of the current and the electrons carried the other half. In these conditions the electric field inside the plasma was negligible, and the gradient drift always dominated the {right arrow over (E)}×{right arrow over (B)} drift. Hence, all the drift orbits produced by large-angle collisions were lost after a transit time. These experiments reported ion diffusion rates that were faster than those predicted by classical diffusion estimates. If there is a strong electrostatic field, the {right arrow over (E)}×{right arrow over (B)} drift dominates the gradient drift, and the drift orbits rotate in the diamagnetic direction. This was shown above in connection with FIG. 13A. When these orbits reach the ends of the FRC, they are reflected back into the region of closed field lines by the Lorentz force; thus, they remain confined in the system. The electrostatic fields in the colliding beam system may be strong enough, so that the {right arrow over (E)}×{right arrow over (B)} drift dominates the gradient drift. Thus, the electrostatic field of the system would avoid ion transport by eliminating this ion loss mechanism, which is similar to a loss cone in a mirror device. Another aspect of ion diffusion can be appreciated by considering the effect of small-angle, electron-ion collisions on betatron orbits. FIG. 14A shows a betatron orbit 112; FIG. 14B shows the same orbit 112 when small-angle electron-ion collisions are considered 174; FIG. 14C shows the orbit of FIG. 14B followed for a time that is longer by a factor of ten 176; and FIG. 14D shows the orbit of FIG. 14B followed for a time longer by a factor of twenty 178. It can be seen that the topology of betatron orbits does not change due to small-angle, electron-ion collisions; however, the amplitude of their radial oscillations grows with time. In fact, the orbits shown in FIGS. 14A to 14D fatten out with time, which indicates classical diffusion. Formation of the FRC Conventional procedures used to form a FRC primarily employ the theta pinch-field reversal procedure. In this conventional method, a bias magnetic field is applied by external coils surrounding a neutral gas back-filled chamber. Once this has occurred, the gas is ionized and the bias magnetic field is frozen in the plasma. Next, the current in the external coils is rapidly reversed and the oppositely oriented magnetic field lines connect with the previously frozen lines to form the closed topology of the FRC (see FIG. 3). This formation process is largely empirical and there exists almost no means of controlling the formation of the FRC. The method has poor reproducibility and no tuning capability as a result. In contrast, the FRC formation methods of the present invention allow for ample control and provide a much more transparent and reproducible process. In fact, the FRC formed by the methods of the present invention can be tuned and its shape as well as other properties can be directly influenced by manipulation of the magnetic field applied by the outer field coils 325. Formation of the FRC by methods of the present inventions also results in the formation of the electric field and potential well in the manner described in detail above. Moreover, the present methods can be easily extended to accelerate the FRC to reactor level parameters and high-energy fuel currents, and advantageously enables the classical confinement of the ions. Furthermore, the technique can be employed in a compact device and is very robust as well as easy to implement—all highly desirable characteristics for reactor systems. In the present methods, FRC formation relates to the circulating plasma beam 335. It can be appreciated that the circulating plasma beam 335, because it is a current, creates a poloidal magnetic field, as would an electrical current in a circular wire. Inside the circulating plasma beam 335, the magnetic self-field that it induces opposes the externally applied magnetic field due to the outer coil 325. Outside the plasma beam 335, the magnetic self-field is in the same direction as the applied magnetic field. When the plasma ion current is sufficiently large, the self-field overcomes the applied field, and the magnetic field reverses inside the circulating plasma beam 335, thereby forming the FRC topology as shown in FIGS. 3 and 5. The requirements for field reversal can be estimated with a simple model. Consider an electric current IP carried by a ring of major radius r0 and minor radius a<<r0. The magnetic field at the center of the ring normal to the ring is Bp=2πIP/(cro). Assume that the ring current IP=Npe(Ω0/2π) is carried by Np ions that have an angular velocity Ω0. For a single ion circulating at radius r0=V0/Ω0,Ω0=eB0/mic is the cyclotron frequency for an external magnetic field B0. Assume V0 is the average velocity of the beam ions. Field reversal is defined as B p = N p ⁢ e ⁢ ⁢ Ω 0 r 0 ⁢ c ≥ 2 ⁢ B 0 , ( 3 ) which implies that Np>2r0/αi, and I p ≥ eV 0 π ⁢ ⁢ α i , ( 4 ) where αi=e2/mic2=1.57×10−16 cm and the ion beam energy is 1 2 ⁢ m i ⁢ V 0 2 . In the one-dimensional model, the magnetic field from the plasma current is Bp=(2π/c)ip, where ip is current per unit of length. The field reversal requirement is ip>eV0/πr0αi=0.225 kA/cm, where B 0 = 69.3 ⁢ ⁢ G ⁢ ⁢ and ⁢ ⁢ 1 2 ⁢ m i ⁢ V 0 2 = 100 ⁢ ⁢ eV . For a model with periodic rings and Bz is averaged over the axial coordinate <Bz>=(2π/c)(Ip/s) (s is the ring spacing), if s=r0, this model would have the same average magnetic field as the one dimensional model with ip=Ip/s.Combined Beam/Betatron Formation Technique A preferred method of forming a FRC within the confinement system 300 described above is herein termed the combined beam/betatron technique. This approach combines low energy beams of plasma ions with betatron acceleration using the betatron flux coil 320. The first step in this method is to inject a substantially annular cloud layer of background plasma in the chamber 310 using the background plasma sources 345. Outer coil 325 produces a magnetic field inside the chamber 310, which magnetizes the background plasma. At short intervals, low energy ion beams are injected into the chamber 310 through the injector ports 340 substantially transverse to the externally applied magnetic field within the chamber 310. As explained above, the ion beams are trapped within the chamber 310 in large betatron orbits by this magnetic field. The ion beams may be generated by an ion accelerator, such as an accelerator comprising an ion diode and a Marx generator. (see R. B. Miller, An Introduction to the Physics of Intense Charged Particle Beams, (1982)). As one of skill in the art can appreciate, the applied magnetic field will exert a Lorentz force on the injected ion beam as soon as it enters the chamber 310; however, it is desired that the beam not deflect, and thus not enter a betatron orbit, until the ion beam reaches the circulating plasma beam 335. To solve this problem, the ion beams are neutralized with electrons and, as illustrated in FIG. 15, when the ion beam 350 is directed through an appropriate magnetic field, such as the unidirectional applied magnetic field within the chamber 310, the positively charged ions and negatively charged electrons separate. The ion beam 350 thus acquires an electric self-polarization due to the magnetic field. This magnetic field also may be produced by, e.g., a permanent magnet or by an electromagnet along the path of the ion beam. When subsequently introduced into the confinement chamber 310, the resultant electric field balances the magnetic force on the beam particles, allowing the ion beam to drift undeflected. FIG. 16 shows a head-on view of the ion beam 350 as it contacts the plasma 335. As depicted, electrons from the plasma 335 travel along magnetic field lines into or out of the beam 350, which thereby drains the beam's electric polarization. When the beam is no longer electrically polarized, the beam joins the circulating plasma beam 335 in a betatron orbit around the principle axis 315, as shown in FIG. 1 (see also FIG. 5). When the plasma beam 335 travels in its betatron orbit, the moving ions comprise a current, which in turn gives rise to a poloidal magnetic self-field. To produce the FRC topology within the chamber 310, it is necessary to increase the velocity of the plasma beam 335, thus increasing the magnitude of the magnetic self-field that the plasma beam 335 causes. When the magnetic self-field is large enough, the direction of the magnetic field at radial distances from the axis 315 within the plasma beam 335 reverses, giving rise to a FRC. (See FIGS. 3 and 5). It can be appreciated that, to maintain the radial distance of the circulating plasma beam 335 in the betatron orbit, it is necessary to increase the applied magnetic field from the outer coil 325 as the circulating plasma beam 335 increases in velocity. A control system is thus provided for maintaining an appropriate applied magnetic field, dictated by the current through the outer coil 325. Alternatively, a second outer coil may be used to provide the additional applied magnetic field that is required to maintain the radius of the plasma beam's orbit as it is accelerated. To increase the velocity of the circulating plasma beam 335 in its orbit, the betatron flux coil 320 is provided. Referring to FIG. 17, it can be appreciated that increasing a current through the betatron flux coil 320, by Ampere's Law, induces an azimuthal electric field, E, inside the chamber 310. The positively charged ions in the plasma beam 335 are accelerated by this induced electric field, leading to field reversal as described above. When ion beams 350, which are neutralized and polarized as described above, are added to the circulating plasma beam 335, the plasma beam 335 depolarizes the ion beams. For field reversal, the circulating plasma beam 335 is preferably accelerated to a rotational energy of about 100 eV, and preferably in a range of about 75 eV to 125 eV. To reach fusion relevant conditions, the circulating plasma beam 335 is preferably accelerated to about 200 keV and preferably to a range of about 100 keV to 3.3 MeV. FRC formation was successfully demonstrated utilizing the combined beam/betatron formation technique. The combined beam/betatron formation technique was performed experimentally in a chamber 1 m in diameter and 1.5 m in length using an externally applied magnetic field of up to 500 G, a magnetic field from the rotating plasma induced by the betatron flux coil 320 of up to5 kG, and a vacuum of 1.2×10−5 torr. In the experiment, the background plasma had a density of 1013 cm−3 and the ion beam was a neutralized Hydrogen beam having a density of 1.2×1013 cm−3, a velocity of 2×107 cm/s, and a pulse length of around 20 μs (at half height). Field reversal was observed. Betatron Formation Technique Another preferred method of forming a FRC within the confinement system 300 is herein termed the betatron formation technique. This technique is based on driving the betatron induced current directly to accelerate a circulating plasma beam 335 using the betatron flux coil 320. A preferred embodiment of this technique uses the confinement system 300 depicted in FIG. 1, except that the injection of low energy ion beams is not necessary. As indicated, the main component in the betatron formation technique is the betatron flux coil 320 mounted in the center and along the axis of the chamber 310. Due to its separate parallel windings construction, the coil 320 exhibits very low inductance and, when coupled to an adequate power source, has a low LC time constant, which enables rapid ramp up of the current in the flux coil 320. Preferably, formation of the FRC commences by energizing the external field coils 325, 330. This provides an axial guide field as well as radial magnetic field components near the ends to axially confine the plasma injected into the chamber 310. Once sufficient magnetic field is established, the background plasma sources 345 are energized from their own power supplies. Plasma emanating from the guns streams along the axial guide field and spreads slightly due to its temperature. As the plasma reaches the mid-plane of the chamber 310, a continuous, axially extending, annular layer of cold, slowly moving plasma is established. At this point the betatron flux coil 320 is energized. The rapidly rising current in the coil 320 causes a fast changing axial flux in the coil's interior. By virtue of inductive effects this rapid increase in axial flux causes the generation of an azimuthal electric field E (see FIG. 18), which permeates the space around the flux coil. By Maxwell's equations, this electric field E is directly proportional to the change in strength of the magnetic flux inside the coil, i.e.: a faster betatron coil current ramp-up will lead to a stronger electric field. The inductively created electric field E couples to the charged particles in the plasma and causes a ponderomotive force, which accelerates the particles in the annular plasma layer. Electrons, by virtue of their smaller mass, are the first species to experience acceleration. The initial current formed by this process is, thus, primarily due to electrons. However, sufficient acceleration time (around hundreds of micro-seconds) will eventually also lead to ion current. Referring to FIG. 18, this electric field E accelerates the electrons and ions in opposite directions. Once both species reach their terminal velocities, current is carried about equally by ions and electrons. As noted above, the current carried by the rotating plasma gives rise to a self magnetic field. The creation of the actual FRC topology sets in when the self magnetic field created by the current in the plasma layer becomes comparable to the applied magnetic field from the external field coils 325, 330. At this point magnetic reconnection occurs and the open field lines of the initial externally produced magnetic field begin to close and form the FRC flux surfaces (see FIGS. 3 and 5). The base FRC established by this method exhibits modest magnetic field and particle energies that are typically not at reactor relevant operating parameters. However, the inductive electric acceleration field will persist, as long as the current in the betatron flux coil 320 continues to increase at a rapid rate. The effect of this process is that the energy and total magnetic field strength of the FRC continues to grow. The extent of this process is, thus, primarily limited by the flux coil power supply, as continued delivery of current requires a massive energy storage bank. However, it is, in principal, straightforward to accelerate the system to reactor relevant conditions. For field reversal, the circulating plasma beam 335 is preferably accelerated to a rotational energy of about 100 eV, and preferably in a range of about 75 eV to 125 eV. To reach fusion relevant conditions, the circulating plasma beam 335 is preferably accelerated to about 200 keV and preferably to a range of about 100 keV to 3.3 MeV. When ion beams are added to the circulating plasma beam 335, as described above, the plasma beam 335 depolarizes the ion beams. FRC formation utilizing the betatron formation technique was successfully demonstrated at the following parameter levels: Vacuum chamber dimensions: about 1 m diameter, 1.5 m length. Betatron coil radius of 10 cm. Plasma orbit radius of 20 cm. Mean external magnetic field produced in the vacuum chamber was up to 100 Gauss, with a ramp-up period of 150 μs and a mirror ratio of 2 to 1. (Source: Outer coils and betatron coils). The background plasma (substantially Hydrogen gas) was characterized by a mean density of about 1013 cm−3, kinetic temperature of less than 10 eV. The lifetime of the configuration was limited by the total energy stored in the experiment and generally was around 30 μs. The experiments proceeded by first injecting a background plasma layer by two sets of coaxial cable guns mounted in a circular fashion inside the chamber. Each collection of 8 guns was mounted on one of the two mirror coil assemblies. The guns were azimuthally spaced in an equidistant fashion and offset relative to the other set. This arrangement allowed for the guns to be fired simultaneously and thereby created an annular plasma layer. Upon establishment of this layer, the betatron flux coil was energized. Rising current in the betatron coil windings caused an increase in flux inside the coil, which gave rise to an azimuthal electric field curling around the betatron coil. Quick ramp-up and high current in the betatron flux coil produced a strong electric field, which accelerated the annular plasma layer and thereby induced a sizeable current. Sufficiently strong plasma current produced a magnetic self-field that altered the externally supplied field and caused the creation of the field reversed configuration. Detailed measurements with B-dot loops identified the extent, strength and duration of the FRC. An example of typical data is shown by the traces of B-dot probe signals in FIG. 19. The data curve A represents the absolute strength of the axial component of the magnetic field at the axial mid-plane (75 cm from either end plate) of the experimental chamber and at a radial position of 15 cm. The data curve B represents the absolute strength of the axial component of the magnetic field at the chamber axial mid-plane and at a radial position of 30 cm. The curve A data set, therefore, indicates magnetic field strength inside of the fuel plasma layer (between betatron coil and plasma) while the curve B data set depicts the magnetic field strength outside of the fuel plasma layer. The data clearly indicates that the inner magnetic field reverses orientation (is negative) between about 23 and 47 μs, while the outer field stays positive, i.e., does not reverse orientation. The time of reversal is limited by the ramp-up of current in the betatron coil. Once peak current is reached in the betatron coil, the induced current in the fuel plasma layer starts to decrease and the FRC rapidly decays. Up to now the lifetime of the FRC is limited by the energy that can be stored in the experiment. As with the injection and trapping experiments, the system can be upgraded to provide longer FRC lifetime and acceleration to reactor relevant parameters. Overall, this technique not only produces a compact FRC, but it is also robust and straightforward to implement. Most importantly, the base FRC created by this method can be easily accelerated to any desired level of rotational energy and magnetic field strength. This is crucial for fusion applications and classical confinement of high-energy fuel beams. Inductive Plasma Source The betatron and beam/betatron FRC formation techniques describe above, both rely on imparting energy to a background plasma via the flux coil 320. Analogous to a transformer, the flux coil performs the duties of the primary windings of the transformer, while the plasma acts as the secondary windings. For this inductive system to work efficiently, it is imperative that the plasma is a good conductor. Counter to typical conductors, such as metals, a plasma becomes less resistive and, thus, more conductive as its temperature increases. The temperature of plasma electrons, in particular, plays an important role and, to a large degree, determines dissipation, which is a function of electron-ion collisions. In essence, dissipation is due to resistance, which is caused by electron-ion collisions: the higher the collision frequency, the higher the resistivity. This is due to the collective phenomena in a plasma, where the coulomb collision cross-section is screened. The collision frequency (the rate at which successive collisions occur) is essentially a function of density, screened coulomb scattering cross-section and thermal (or average) velocity of the colliding/scattering charges, i.e.: νc=nσv. By definition v scales with T1/2, σ is proportional to v−4 or, thus, T−2. The collision frequency νc is, therefore, proportional to nT−3/2. The resistivity is related to the collision frequency by η=νcm/ne2. Hence, the resistivity is proportional to T−3/2 and, notably, independent of density—a direct result of the fact that even though the number of charge carriers increases with density, the number of scattering centers increases as well. Thus, higher temperature leads to higher plasma conductivity and less dissipative losses. To achieve better performance with regard to confinement in an FRC, a hot plasma is, therefore, highly desirable. In the case of the PEG system, enhanced electron temperature leads to improved FRC startup (the better a conductor the plasma becomes, the better the inductive coupling between the plasma and flux coil), better current sustainment (reduced plasma resistivity leads to less frictional/dissipative losses and hence less current loss) and higher magnetic field strength (the stronger the current, the more self-field). Adequate electron temperature during initial plasma formation and before the flux coil is engaged will lead to better coupling of the flux coil to the plasma (which advantageously tends to reduce the formation of azimuthal image currents in the chamber wall). This in turn will result in enhanced betatron acceleration (less resistivity leads to better inductive transfer of energy from flux coil to plasma) and plasma heating (some of the imparted directional energy as represented by the rotating current flow will thermalize and turn to random energy—ultimately leading to heating of the plasma by the flux coil), which will consequently increase the ion-electron collision time (due to higher temperature), reduce dissipation (less resistivity) and allow ultimately for the attainment of higher FRC fields (higher currents lead to stronger fields). To achieve better initial plasma temperature, an inductive plasma source is provided. As depicted in FIGS. 20A, 20B and 20C, the inductive plasma source 1010 is mountable within the chamber 310 about the end of the flux coil 320 and includes a single turn shock coil assembly 1030 that is preferably fed by a high voltage (about 5-15 kV) power source (not shown). Neutral gas, such as Hydrogen (or other appropriate gaseous fusion fuel), is introduced into the source 1010 through direct gas feeds via a Laval nozzle 1020. The gas flow is controlled preferably by sets of ultra fast puff valves to produce a clean shock front. Once the gas emanates from the nozzle 1020 and distributes itself over the surface of the coil windings 1040 of the shock coil 1030, the windings 1040 are energized. The ultra fast current and flux ramp-up in the low inductance shock coil 1030 leads to a very high electric field within the gas that causes breakdown, ionization and subsequent ejection of the formed plasma from the surface of the shock coil 1030 towards the center of the chamber 310. In a preferred embodiment, the shock coil 1030 comprises an annular disc shaped body 1032 bounded by an outer ring 1034 formed about its outer periphery and an annular hub 1036 formed about its inner periphery. The ring 1034 and hub 1036 extend axially beyond the surface of the body 1032 forming the edges of a open top annular channel 1035. The body 1032, ring 1034 and hub 1036 are preferably formed through unitary molded construction of an appropriate non-conductive material with good vacuum properties and low outgassing properties such as glass, plexiglass, pirex, quartz, ceramics or the like. A multi-sectioned shroud 1012 is preferably coupled to the ring 1034 of the shock coil 1030 to limit the produced plasma from drifting radially. Each section 1014 of the shroud 1012 includes a plurality of axially extending fingers 1016. The ends of each section 1014 include a mounting bracket 1015. The coil windings 1040 are preferably affixed to the face of the coil body 1032 in the channel 1035 using epoxy or some other appropriate adhesive. To obtain fast electro-magnetic characteristics of the shock coil 1030, it is important to keep its inductance as low as possible. This is achieved by using as few turns in the coil 1040 as possible, as well as building the coil 1040 up of multiple strands of wire 1042 that are wound in parallel. In an exemplary embodiment, the coil 1040 comprised 24 parallel strands of wire 1042, each of which executed one loop. The wires 1042 each begin at entry points 1044 that are located preferably about 15 degrees apart on the outer perimeter of the body 1032 and end after only one axis encircling turn at exit points 1046 on the inner radius of the body 1032. The coil windings 1040, therefore, cover the entire area between the inner and outer edges of channel 1035. Preferably, groups of strands 1042 are connected to the same capacitive storage bank. In general, power can be fed to all strands 1042 from the same capacitive storage bank or, as in an exemplary embodiment, 8 groups of 3 strands 1042 each are connected together and commonly fed by one of 2 separate capacitive storage banks. An annular disc-shaped nozzle body 1022 is coupled about its inner perimeter to the hub 1036 to form the Laval nozzle 1020. The surface 1024 of the nozzle body 1022 facing the hub 1036 has an expanding midsection profile defining an annular gas plenun 1025 between the surface 1024 and the face 1037 of the hub 1036. Adjacent the outer periphery of the nozzle body 1022, the surface 1024 has a contracting-to-expanding profile defining an azimuthally extending Laval-type nozzle outlet 1023 between the surface 1024 and the face 1037 of the hub 1036. Attached to the opposite side of the hub 1036 is a valve seat ring 1050 with several valve seats 1054 formed in the outer face of the ring 1050. The valve seats 1054 are aligned with gas feed channels 1052 formed through the hub 1036. In operation, neutral gas is feed through ultra fast puff valves in the valve seats 1054 to the gas channels 1052 extending through the hub 1036. Because of the constricting portion of the nozzle outlet 1023, the gas tends to feed into and fill the annular plenum 1025 prior to emanating from the nozzle 1020. Once the gas emanates from the nozzle 1020 and distributes itself over the surface of the coil windings 1040 of the shock coil 1030, the windings 1040 are energized. The ultra fast current and flux ramp-up in the low inductance shock coil 1030 leads to a very high electric field within the gas that causes breakdown, ionization and subsequent ejection of the formed plasma from the surface of the shock coil 1030 towards the center of the chamber 310. The current ramp-up is preferably well synchronized in all strands 1042 or groups of strands 1042 that are intended to be fired together. Another option that is possible and potentially advantageous, is to fire different groups of strands at different times. A delay can be deliberately instituted between engaging different groups of strands 1042 to fire different groups of strands at different times. When firing different groups of strands at different times it is important to group strands in a way so that the arrangement is azimuthally symmetric and provides sufficient coverage of the surface of the coil 1040 with current carrying wires 1042 at any given power pulse. In this fashion it is possible to create at least two consecutive but distinct plasma pulses. The delay between pulses is limited by how much neutral gas is available. In practice, it is possible to fire such pulses between about 5 and 600 micro-seconds apart. In practice, the input operating parameters are preferably as follows: Charging Voltage: about 10 to 25 kV split supply Current: up to about 50 kA total current through all windings combined Pulse/Rise Time: up to about 2 microseconds Gas Pressure: about −20 to 50 psi Plenum size: about 0.5 to 1 cm3 per valve—i.e.: about 4 to 8 cm3 total gas volume per shot In an exemplary embodiment, the input operating parameters were as follows: Charging Voltage: 12 to 17 kV split supply, i.e.: from −12 kV to +12 kV Current: 2 to 4.5 kA per group of 3 strands, i.e.: 16 to 36 kA total current through all windings combined Pulse/Rise Time: 1 to 1.5 microseconds Gas Pressure: −15 to 30 psi Plenum size: 0.5 to 1 cm3 per valve—i.e.: 4 to 8 cm3 total gas volume per shot The plasma created by this operational method of the inductive plasma source 1010 using the parameters noted above has the following advantageous characteristics: Density ˜4×1013cm−3 Temperature ˜10-20 eV Annular scale ˜40-50 cm diameter Axial drift velocity ˜5-10 eV. Due to the shape and orientation of the source 1010, the shape of the emerging plasma is annular and has a diameter tending to equal the rotating plasma annulus of the to be formed FRC. In a PEG present system two such inductive plasma sources 1010 are preferably placed on either axial end of the chamber 310 and preferably fired in parallel. The two formed plasma distributions drift axially towards the center of the chamber 310 where they form the annular layer of plasma that is then accelerated by the flux coil 320 as described above.RF Drive For Ions and Electrons in FRC A RF current drive, called a rotomak, has been employed for FRCs in which the current is carried mainly by electrons. It involves a rotating radial magnetic field produced by two phased antennas. The electrons are magnetized and frozen to the rotating magnetic field lines. This maintains the current until Coulomb collisions of the ions with electrons cause the ions to be accelerated and reduce the current. The rotomak, however, is not suitable for maintaining the current indefinitely, but it has been successful for milliseconds. In the FRCs of the present system the current is mainly carried by ions that are in betatron orbits which would not be frozen to rotating magnetic field lines. The large orbit ions are important for stability and classical diffusion. Instead of antennas, electrodes are employed as in cyclotrons and the ions are driven by an electrostatic wave. The problem is completely electrostatic because the frequency of the RF is less than 10 Megacycles so that the wavelength (30 m) is much longer than any dimension of the plasma. Electrostatic fields can penetrate the FRC plasma much more easily than electromagnetic waves. The electrostatic wave produced by the electrodes is designed to travel at a speed that is close to the average azimuthal velocity of the ions, or of the electrons. If the wave travels faster than the average speed of the ions, it will accelerate them and thereby compensate for the drag due to the ion-electron collisions. Electrons, however, are accelerated by Coulomb collisions with the ions. In this case the wave must have a speed slower than the electron average velocity and the electrons will accelerate the wave. The average electron velocity is less than the average ion velocity so that the electrons must be driven at two different frequencies. The higher frequency will be for ions and energy is preferably supplied by the external circuit. For electrons, energy can be extracted at the lower frequency. Electrode Systems A quadrupole RF drive system is shown in FIG. 21A and 21B. As depicted, the RF drive comprises a quadrupolar cyclotron 1110 located within the chamber 310 and having four elongate, azimuthally symmetrical electrodes 1112 with gaps 1114 there between. The quadrupole cyclotron 1110 preferably produces an electric potential wave that rotates in the same direction as the azimuthal velocity of ions, but at a greater velocity. Ions of appropriate speed can be trapped in this wave, and reflected periodically. This process increases the momentum and energy of the fuel ions and this increase is conveyed to the fuel ions that are not trapped by collisions. Fuel ions from the fuel plasma 335 may be replaced by injecting neutrals at any convenient velocity. An alternative and supplemental method to drive current is to augment the electrode system with additional magnetic field coils 1116 positioned about the flux coil 325 and quadrupole cyclotron 1110, and that are driven at half the frequency of the cyclotron electrodes 1112. The following discussion presented here, however, is dedicated to illustrate the electrode only version (without magnetic field coils 1116). In FIG. 21C electrodes are illustrated for two and four electrode configurations. The potential created by the electrodes with the indicated applied voltages are noted in FIG. 21C for vacuum in the space r<rb. The expressions are for the lowest harmonic. They are obtained by solving the Laplace equation ( 1 r ⁢ ∂ ∂ r ⁢ r ⁢ ∂ ∂ r + 1 r 2 ⁢ ∂ ∂ θ 2 ) ⁢ Φ ⁡ ( r , θ ; t ) = 0 ( 5 ) with appropriate boundary conditions. For example for the dipole cyclotron Φ ⁡ ( r b , t ) = - V o ⁢ cos ⁢ ⁢ ω ⁢ ⁢ t ⁢ ⁢ for ⁢ ⁢ 0 ≤ θ ≤ π ⁢ ⁢ = V o ⁢ cos ⁢ ⁢ ω ⁢ ⁢ t ⁢ ⁢ for ⁢ ⁢ π ≤ θ ≤ 2 ⁢ π ⁢ ⁢ Φ ⁡ ( r , θ ; t ) ⁢ ⁢ is ⁢ ⁢ ⁢ finite . ( 6 ) Since Φ(r, θ•, t) is periodic in θ with a period 2π, it can be expanded in a Fourier series, i.e.: Φ ⁡ ( r , θ ; t ) = ∑ n = - ∞ ∞ ⁢ u n ⁡ ( r , t ) ⁢ ⅇ ⅈ ⁢ ⁢ n ⁢ ⁢ θ ( 7 ) u n ⁡ ( r , t ) = 1 2 ⁢ π ⁢ ∫ 0 2 ⁢ π ⁢ ⅆ θ ′ ⁢ ⅇ - ⅈ ⁢ ⁢ n ⁢ ⁢ θ ′ ⁢ Φ ⁡ ( r , θ ′ ; t ) ( 8 ) and un satisfies the equation ( 1 r ⁢ ∂ ∂ r ⁢ r ⁢ ∂ ∂ r + n 2 r 2 ) ⁢ u n ⁡ ( r , t ) = 0 ⁢ ⁢ u n ⁡ ( r o , t ) = V o ⁢ cos ⁢ ⁢ ω ⁢ ⁢ t ⅈ ⁢ ⁢ n ⁢ ⁢ π ⁢ ( ⅇ - ⅈ ⁢ ⁢ n ⁢ ⁢ π - 1 ) = 0 ⁢ ⁢ if ⁢ ⁢ n = 2 , 4 ⁢ ⁢ … ⁢ ⁢ etc . ⁢ u n ⁡ ( 0 , t ) = 0 ( 9 ) Φ ⁡ ( r , θ ; t ) = 4 ⁢ V o ⁢ cos ⁢ ⁢ ω ⁢ ⁢ t π ⁢ ∑ l = 1 ∞ ⁢ sin ⁡ ( 2 ⁢ l - 1 ) ⁢ θ 2 ⁢ l - 1 ⁢ ( r r b ) 2 ⁢ l - 1 . ( 10 ) The lowest harmonic is Φ 1 ⁡ ( r , θ ; t ) = 2 ⁢ V o π ⁢ r r b ⁡ [ sin ⁡ ( ω ⁢ ⁢ t + θ ) - sin ⁡ ( ω ⁢ ⁢ t - θ ) ] ( 11 ) Higher harmonics are Φ l ⁡ ( r , θ ; t ) = 2 ⁢ V o π ⁢ ( r r b ) 2 ⁢ l - 1 ⁢ { sin ⁡ [ ω ⁢ ⁢ t + ( 2 ⁢ l - 1 ) ⁢ θ ] - sin ⁡ [ ω ⁢ ⁢ t - ( 2 ⁢ l - 1 ) ⁢ θ ] } ( 12 ) The wave speed in the azimuthal direction is {dot over (θ)}=±ω/(2l−1) so that the higher harmonics have a smaller phase velocity and amplitude. These comments apply to both cases in FIG. 21C. The frequency ω would be close to ωi the frequency of rotation of the ions in a rigid rotor equilibrium for the FRC. Thus {dot over (θ)}=ωi for l=1. For l=2 {dot over (θ)}=ωi/3 and the wave amplitude would be substantially lower; it is thus a good approximation to consider only the lowest harmonic. Plasma Effect The response of the plasma can be described by a dielectric tensor. The electric field produces plasma currents which produce charge separation according to the charge conservation equation ∇ · J → + ∂ ρ ∂ t = 0 ( 13 ) where {right arrow over (J)} is current density and ρ is charge density. The appropriate equation is∇·{right arrow over (E)}=4πρ=4π·{right arrow over (E)} (14)or∇··{right arrow over (E)}=−∇··∇Φ=0where =+4π is the dielectric tensor and χ is the polarizability. If only the contribution of the electrons is included the tensor is diagonal with one component ɛ ⊥ = 1 + 4 ⁢ π ⁢ ⁢ nmc 2 B 2 ( 15 ) where n is the density and B is the FRC magnetic field. n and B vary rapidly with r and B=0 on a surface at r=r0 within the plasma. The expression for ε⊥ is derived assuming electrons have a small gyroradius and the electric field changes slowly compared to Ωe=eB/mc, the gyrofrequency. This approximation breaks down near the null surface. The characteristic orbits change from drift orbits to betatron orbits which have a much smaller response to the electric field, i.e. ε⊥≅1 near the null surface at r=r0. The ions mainly have betatron orbits and for the drift orbits the response to the electric field is small because the electric field changes at the rate ω≅ωi. The net result is that the Laplace equation is replaced by 1 r ⁢ ∂ ∂ r ⁢ r ⁢ ∂ Φ ∂ r + 1 ɛ ⊥ ⁡ ( r ) ⁢ ⅆ ɛ ⊥ ⅆ r ⁢ ∂ Φ ∂ r + 1 r 2 ⁢ ∂ 2 ⁢ Φ ∂ r 2 = 0 ( 16 ) which must be solved numerically. The additional term vanishes near r=ro. The potential for the lowest harmonic of the quadrupole case has the form Φ = V o ⁢ F ⁡ ( r ) 2 ⁢ sin ⁡ ( 2 ⁢ θ - ω ⁢ ⁢ t ) ( 17 ) and a similar form for the dipole case. Waves traveling in the opposite direction to the ions (or electrons) will be neglected.Acceleration Due to Ions Trapped in an Electrostatic Wave We assume that ω=2ωi+Δω so that the wave {dot over (θ)}=ω/2=ωi+Δω/2 is a little faster than the ions. The standard rigid rotor distribution function is assumed for the ions f i ⁡ ( x → , v → ) = ( m i 2 ⁢ π ⁢ ⁢ T i ) 3 / 2 ⁢ n i ⁡ ( r ) ⁢ exp ⁢ { [ - m i 2 ⁢ T i ⁡ [ v r 2 + v z 2 + ( v θ - r ⁢ ⁢ ω i ) 2 ] ] } . ( 18 ) The reduced distribution function of interest is F i ⁡ ( r , v θ ) = ( m i 2 ⁢ π ⁢ ⁢ T i ) 1 / 2 ⁢ exp ⁡ [ - m i 2 ⁢ T i ⁢ ( v θ - r ⁢ ⁢ ω i ) 2 ] . The wave velocity of the electrostatic wave produced by the quadrupole cyclotron is νw=rω/2=rωi+Δνw Ions moving faster than the wave reflect if v θ - v w < 2 ⁢ ⅇΦ o m i . ( 19 ) This increases the wave energy, i.e., ⅆ W + ⅆ t = ∑ i = 1 , 2 ⁢ n i ⁢ m i λ ⁢ ∫ v θ = v w v θ = v w + 2 ⁢ ⅇΦ o m i ⁢ ⁢ ⅆ v θ ⁢ F i ⁡ ( r , v θ ) ⁡ [ v θ 2 2 - ( 2 ⁢ v w - v θ ) 2 2 ] ⁢ ( v θ - v w ) . ( 20 ) Ions moving slower than the wave reflect if v w - v θ < 2 ⁢ ⅇΦ o m i . and the wave loses energy at the rate ⅆ W - ⅆ t = ∑ i = 1 , 2 ⁢ n i ⁢ m i λ ⁢ ∫ v θ = v - 2 ⁢ ⅇΦ o m i v θ = v w ⁢ ⁢ ⅆ v θ ⁢ F i ⁡ ( r , v θ ) ⁡ [ v θ 2 2 - ( 2 ⁢ v w - v θ ) 2 2 ] ⁢ ( v w - v θ ) . ( 21 ) The net results is simplified with the change of variable v′θ=vθ−vw, i.e., ⅆ W ⅆ t = ⅆ W + ⅆ t - ⅆ W - ⅆ t = ∑ i = 1 , 2 ⁢ 2 ⁢ n i ⁢ m i ⁢ v w λ ⁢ ∫ 0 2 ⁢ ⅇΦ o m i ⁢ ⁢ ⅆ v θ ′ ⁡ ( v θ ′ ) 2 ⁡ [ F i ⁡ ( v w + v θ ′ ) - F i ⁡ ( v w - v θ ′ ) ] . ( 22 ) The approximation F i ⁡ [ v w ± v θ ] = F i ⁡ ( v w ) ± ∂ F i ∂ v θ  v w ⁢ v θ , ( 23 ) results in ⅆ W ⅆ t = ∑ i = 1 , 2 ⁢ 2 ⁢ n i ⁢ m i ⁢ v w λ ⁢ ( 2 ⁢ ⅇΦ o m i ) 2 ⁢ ∂ F i ∂ v θ ⁢ \| v θ = v w . ( 24 ) This has a form similar to Landau damping, but it is not physically the same because Landau damping (growth) is a linear phenomena and this is clearly non-linear. Since ∂ F i ∂ v θ ⁢ \| v w = ( m i 2 ⁢ π ⁢ ⁢ T i ) 1 / 2 ⁢ m i T o ⁢ ( v w - r ⁢ ⁢ ω o ) ⁢ exp ⁡ [ - m i 2 ⁢ T i ⁢ ( v w - r ⁢ ⁢ ω i ) 2 ] . ( 25 ) If νw=rωi there is no change in the wave energy. If ww>rωi or Δνw>0, the wave energy decreases; for Δνw<0 the wave energy increases. This is similar to the interpretation of Landau damping. In the first case Δνw>0, there are more ions going slower than the wave than faster. Therefore, the wave energy decreases. In the opposite case Δνw<0, the wave energy increases. The former case applies to maintaining the ion energy and momentum with a quadrupole cyclotron. This is current drive. The latter case provides the basis for a converter. Eqs. (22) and (24) can be used to evaluate the applicability to fusion reactor conditions. The power transferred to the ions when νw−rωi=Δνw≅νi, the ion thermal velocity, is P = 2 ⁢ π ⁢ ∫ 0 r b ⁢ ⅆ W ⅆ t ⁢ r ⁢ ⁢ ⅆ r ,where dW/dt is determined by Eqs. (24) and (25). To simplify the integration Φ0(r) is replaced by Φ0(r0), the value at the peak density which is a lower bound of the wave amplitude. P = ( 2 π ) 3 / 2 ⁢ ∑ i = 1 , 2 ⁢ ( N i ⁢ T i ) ⁢ ω i ⁡ [ 2 ⁢ e i ⁢ Φ o ⁡ ( r o ) T i ] 2 ( 26 ) Ni is the line density of ions. i=1,2 accommodates two types of ions which is usually the case in a reactor. Detailed calculations of F(r) indicate that the wave amplitude Φ0(r0) is about a factor of 10 less than the maximum gap voltage which is 2Vo. This will determine the limitations of this method of RF drive. Vo will be limited by the maximum gap voltage that can be sustained which is probably about 10 kVolts for a 1 cm gap. Reactor Requirements For current drive a power Pi is preferably transferred to the ions at frequency ωe and a power Pe is preferably transferred to the electrons at frequency ωe. This will compensate for the Coulomb interactions between electrons and ions, which reduces the ion velocity and increases the electron velocity. (In the absence of the power transfers, Coulomb collisions would lead to the same velocity for electrons and ions and no current). The average electric field to maintain the equilibrium of electrons and ions is given by2πr0<Eθ>=IR (27)where I = N e ⁢ e 2 ⁢ π ⁢ ( ω i - ω e ) is the current/unit length and R = ( 2 ⁢ π ⁢ ⁢ r 0 ) 2 ⁢ m N e ⁢ e 2 ⁢ ( N 1 ⁢ Z 1 ⁢ m 1 N e ⁢ t 1 ⁢ e + N 2 ⁢ Z 2 ⁢ m 2 N e ⁢ t 2 ⁢ e ) is the resistance/unit length. Ne, N1, N2 are line densities of electrons and ions Ne=N1Z1+N2Z2 where Z1, Z2 are atomic numbers of the ions; t1e and t2e are momentum transfer times from ions to electrons. The average electric field is the same for ions or electrons because Ne≅Ni for quasi-neutrality and the charge is opposite. The power that must be transferred to the ions isPi=2πr0Iiθ<Eθ> (28)and the power that can be extracted from electrons isPe=−\|2πr0Ieθ<Eθ>\| (29)where Iiθ=Neeωi/2π and Ieθ=Neeωe/2π. For refueling with the RF drive the fuel may be replaced at any energy atrates given by the fusion times tF1=1/n1<σν>1 and tF2=1/n2<σν>2;n1 and n2 are plasma ion densities and <σν> are reactivities. The magnitude will be seconds. The injected neutrals (to replace the fuel ions that burn and disappear) will ionize rapidly and accelerate due to Coulomb collisions up to the average ion velocity in a time of the order of milliseconds (for reactor densities of order 1015cm−3). However this requires an addition to <Eθ> and an addition to transfer of power to maintain a steady state. The addition is δ ⁢ 〈 E θ 〉 = V i ⁢ ⁢ θ - V b ⁢ ⁢ θ N e ⁢ e 2 ⁢ ( N 1 ⁢ Z 1 ⁢ m 1 t F ⁢ ⁢ 1 + N 2 ⁢ Z 2 ⁢ m 2 t F ⁢ ⁢ 2 ) ( 30 ) which will increase the required power transfer by about a factor of two (2). The power can be provided for current drive and refueling without exceeding the maximum gap voltage amplitude of 10 kVolts/cm. Considering that the frequency will be 1-10 Mega-Hertz and the magnetic field will be of order 100 kGauss no breakdown would be expected. The power that must be transferred for current drive and refueling is similar for any current drive method. However RF technology at 1-10 Mega-Hertz has been an established high-efficiency technology for many years. The method described that uses electrodes instead of antennas has a considerable advantage because the conditions for field penetration are much more relaxed than for electromagnetic waves. Therefore this method would have advantages with respect to circulating power and efficiency. Fusion Significantly, these two techniques for forming a FRC inside of a containment system 300 described above, or the like, can result in plasmas having properties suitable for causing nuclear fusion therein. More particularly, the FRC formed by these methods can be accelerated to any desired level of rotational energy and magnetic field strength. This is crucial for fusion applications and classical confinement of high-energy fuel beams. In the confinement system 300, therefore, it becomes possible to trap and confine high-energy plasma beams for sufficient periods of time to cause a fusion reaction therewith. To accommodate fusion, the FRC formed by these methods is preferably accelerated to appropriate levels of rotational energy and magnetic field strength by betatron acceleration. Fusion, however, tends to require a particular set of physical conditions for any reaction to take place. In addition, to achieve efficient burn-up of the fuel and obtain a positive energy balance, the fuel has to be kept in this state substantially unchanged for prolonged periods of time. This is important, as high kinetic temperature and/or energy characterize a fusion relevant state. Creation of this state, therefore, requires sizeable input of energy, which can only be recovered if most of the fuel undergoes fusion. As a consequence, the confinement time of the fuel has to be longer than its burn time. This leads to a positive energy balance and consequently net energy output. A significant advantage of the present invention is that the confinement system and plasma described herein are capable of long confinement times, i.e., confinement times that exceed fuel burn times. A typical state for fusion is, thus, characterized by the following physical conditions (which tend to vary based on fuel and operating mode): Average ion temperature: in a range of about 30 to 230 keV and preferably in a range of about 80 keV to 230 keV Average electron temperature: in a range of about 30 to 100 keV and preferably in a range of about 80 to 100 keV Coherent energy of the fuel beams (injected ion beams and circulating plasma beam): in a range of about 100 keV to 3.3 MeV and preferably in a range of about 300 keV to 3.3 MeV. Total magnetic field: in a range of about 47.5 to 120 kG and preferably in a range of about 95 to 120 kG (with the externally applied field in a range of about 2.5 to 15 kG and preferably in a range of about 5 to 15 kG). Classical Confinement time: greater than the fuel burn time and preferably in a range of about 10 to 100 seconds. Fuel ion density: in a range of about 1014 to less than 1016 cm−3 and preferably in a range of about 1014 to 1015 cm−3. Total Fusion Power: preferably in a range of about 50 to 450 kW/cm (power per cm of chamber length) To accommodate the fusion state illustrated above, the FRC is preferably accelerated to a level of coherent rotational energy preferably in a range of about 100 keV to 3.3 MeV, and more preferably in a range of about 300 keV to 3.3 MeV, and a level of magnetic field strength preferably in a range of about 45 to 120 kG, and more preferably in a range of about 90 to 115 kG. At these levels, high energy ion beams, which are neutralized and polarized as described above, can be injected into the FRC and trapped to form a plasma beam layer wherein the plasma beam ions are magnetically confined and the plasma beam electrons are electrostatically confined. Preferably, the electron temperature is kept as low as practically possible to reduce the amount of bremsstrahlung radiation, which can, otherwise, lead to radiative energy losses. The electrostatic energy well of the present invention provides an effective means of accomplishing this. The ion temperature is preferably kept at a level that provides for efficient burn-up since the fusion cross-section is a function of ion temperature. High direct energy of the fuel ion beams is essential to provide classical transport as discussed in this application. It also minimizes the effects of instabilities on the fuel plasma. The magnetic field is consistent with the beam rotation energy. It is partially created by the plasma beam (self-field) and in turn provides the support and force to keep the plasma beam on the desired orbit. Fusion Products The fusion products are born in the power core predominantly near the null surface 86 from where they emerge by diffusion towards the separatrix 84 (see FIGS. 3 and 5). This is due to collisions with electrons (as collisions with ions do not change the center of mass and therefore do not cause them to change field lines). Because of their high kinetic energy (fusion product ions have much higher energy than the fuel ions), the fusion products can readily cross the separatrix 84. Once they are beyond the separatrix 84, they can leave along the open field lines 80 provided that they experience scattering from ion-ion collisions. Although this collisional process does not lead to diffusion, it can change the direction of the ion velocity vector such that it points parallel to the magnetic field. These open field lines 80 connect the FRC topology of the core with the uniform applied field provided outside the FRC topology. Product ions emerge on different field lines, which they follow with a distribution of energies. Advantageously, the product ions and charge-neutralizing electrons emerge in the form of rotating annular beams from both ends of the fuel plasma. For example for a 50 MW design of a p-B11 reaction, these beams will have a radius of about 50 centimeters and a thickness of about 10 centimeters. In the strong magnetic fields found outside the separatrix 84 (typically around 100 kG), the product ions have an associated distribution of gyro-radii that varies from a minimum value of about 1 cm to a maximum of around 3 cm for the most energetic product ions. Initially the product ions have longitudinal as well as rotational energy characterized by ½ M(vpar)2 and ½ M(vperp)2. vperp is the azimuthal velocity associated with rotation around a field line as the orbital center. Since the field lines spread out after leaving the vicinity of the FRC topology, the rotational energy tends to decrease while the total energy remains constant. This is a consequence of the adiabatic invariance of the magnetic moment of the product ions. It is well known in the art that charged particles orbiting in a magnetic field have a magnetic moment associated with their motion. In the case of particles moving along a slow changing magnetic field, there also exists an adiabatic invariant of the motion described by ½ M(vperp)2/B. The product ions orbiting around their respective field lines have a magnetic moment and such an adiabatic invariant associated with their motion. Since B decreases by a factor of about 10 (indicated by the spreading of the field lines), it follows that vperp will likewise decrease by about 3.2. Thus, by the time the product ions arrive at the uniform field region their rotational energy would be less than 5% of their total energy; in other words almost all the energy is in the longitudinal component. Energy Conversion The direct energy conversion system of the present invention comprises an inverse cyclotron converter (ICC) 420 shown in FIGS. 22A and 23A coupled to a (partially illustrated) power core 436 of a colliding beam fusion reactor (CBFR) 410 to form a plasma-electric power generation system 400. A second ICC (not shown) may be disposed symmetrically to the left of the CBFR 410. A magnetic cusp 486 is located between the CBFR 410 and the ICC 420 and is formed when the CBFR 410 and ICC 420 magnetic fields merge. Before describing the ICC 420 and its operation in detail, a review of a typical cyclotron accelerator is provided. In conventional cyclotron accelerators, energetic ions with velocities perpendicular to a magnetic field rotate in circles. The orbit radius of the energetic ions is determined by the magnetic field strength and their charge-to-mass ratio, and increases with energy. However, the rotation frequency of the ions is independent of their energy. This fact has been exploited in the design of cyclotron accelerators. Referring to FIG. 24A, a conventional cyclotron accelerator 700 includes two mirror image C-shaped electrodes 710 forming mirror image D-shaped cavities placed in a homogenous magnetic field 720 having field lines perpendicular to the electrodes' plane of symmetry, i.e., the plane of the page. An oscillating electric potential is applied between the C-shaped electrodes (see FIG. 21B). Ions I are emitted from a source placed in the center of the cyclotron 700. The magnetic field 720 is adjusted so that the rotation frequency of the ions matches that of the electric potential and associated electric field. If an ion I crosses the gap 730 between the C-shaped electrodes 710 in the same direction as that of the electric field, it is accelerated. By accelerating the ion I, its energy and orbit radius increase. When the ion has traveled a half-circle arc (experiencing no increase in energy), it crosses the gap 730 again. Now the electric field between the C-shaped electrodes 710 has reversed direction. The ion I is again accelerated, and its energy is further increased. This process is repeated every time the ion crosses the gap 730 provided its rotation frequency continues to match that of the oscillating electric field (see FIG. 24C). If on the other hand a particle crosses the gap 730 when the electric field is in the opposite direction it will be decelerated and returned to the source at the center. Only particles with initial velocities perpendicular to the magnetic field 720 and that cross the gaps 730 in the proper phase of the oscillating electric field will be accelerated. Thus, proper phase matching is essential for acceleration. In principle, a cyclotron could be used to extract kinetic energy from a pencil beam of identical energetic ions. Deceleration of ions with a cyclotron, but without energy extraction has been observed for protons, as described by Bloch and Jeffries in Phys. Rev. 80, 305 (1950). The ions could be injected into the cavity such that they are brought into a decelerating phase relative to the oscillating field. All of the ions would then reverse the trajectory T of the accelerating ion shown in FIG. 24A. As the ions slow down due to interaction with the electric field, their kinetic energy is transformed into oscillating electric energy in the electric circuit of which the cyclotron is part. Direct conversion to electric energy would be achieved, tending to occur with very high efficiency. In practice, the ions of an ion beam would enter the cyclotron with all possible phases. Unless the varying phases are compensated for in the design of the cyclotron, half of the ions would be accelerated and the other half decelerated. As a result, the maximum conversion efficiency would effectively be 50%. Moreover the annular fusion product ion beams discussed above are of an unsuitable geometry for the conventional cyclotron. As discussed in greater detail below, the ICC of the present invention accommodates the annular character of the fusion product beams exiting the FRC of fusion reactor power core, and the random relative phase of the ions within the beam and the spread of their energies. Referring back to FIG. 22A, a portion of a power core 436 of the CBFR 410 is illustrated on the left side, wherein a plasma fuel core 435 is confined in a FRC 470 formed in part due to a magnetic field applied by outside field coils 425. The FRC 470 includes closed field lines 482, a separatrix 484 and open field lines 480, which, as noted above, determines the properties of the annular beam 437 of the fusion products. The open field lines 480 extend away from the power core 436 towards the magnetic cusp 486. As noted above, fusion products emerge from the power core 436 along open field lines 480 in the form of an annular beam 437 comprising energetic ions and charge neutralizing electrons. The geometry of the ICC 420 is like a hollow cylinder with a length of about five meters. Preferably, four or more equal, semi-cylindrical electrodes 494 with small, straight gaps 497 make up the cylinder surface. In operation, an oscillating potential is applied to the electrodes 494 in an alternating fashion. The electric field E within the converter has a quadrupole structure as indicated in the end view illustrated in FIG. 22B. The electric field E vanishes on the symmetry axis and increases linearly with the radius; the peak value is at the gap 497. In addition, the ICC 420 includes outside field coils 488 to form a uniform magnetic field within the ICC's hollow cylinder geometry. Because the current runs through the ICC field coils 488 in a direction opposite to the direction of the current running through the CBFR field coils 425, the field lines 496 in the ICC 420 run in a direction opposite to the direction of the open field lines 480 of the CBFR 410. At an end furthest from the power core 436 of the CBFR 410, the ICC 420 includes an ion collector 492. In between the CBFR 410 and the ICC 420 is a symmetric magnetic cusp 486 wherein the open field lines 480 of the CBFR 410 merge with the field lines 496 of the ICC 420. An annular shaped electron collector 490 is position about the magnetic cusp 486 and electrically coupled to the ion collector 498. As discussed below, the magnetic field of the magnetic cusps 486 converts the axial velocity of the beam 437 to a rotational velocity with high efficiency. FIG. 22C illustrates a typical ion orbit 422 within the converter 420. The CBFR 410 has a cylindrical symmetry. At its center is the fusion power core 436 with a fusion plasma core 435 contained in a FRC 470 magnetic field topology in which the fusion reactions take place. As noted, the product nuclei and charge-neutralizing electrons emerge as annular beams 437 from both ends of the fuel plasma 435. For example for a 50 MW design of a p-B11 reaction, these beams will have a radius of about 50 cm and a thickness of about 10 cm. The annular beam has a density n≅107−108 cm3. For such a density, the magnetic cusp 486 separates the electrons and ions. The electrons follow the magnetic field lines to the electron collector 490 and the ions pass through the cusp 486 where the ion trajectories are modified to follow a substantially helical path along the length of the ICC 420. Energy is removed from the ions as they spiral past the electrodes 494 connected to a resonant circuit (not shown). The loss of perpendicular energy is greatest for the highest energy ions that initially circulate close to the electrodes 494, where the electric field is strongest. The ions arrive at the magnetic cusp 486 with the rotational energy approximately equal to the initial total energy, i.e., ½Mvp2≅½Mv02. There is a distribution of ion energies and ion initial radii r0 when the ions reach the magnetic cusp 486. However, the initial radii r0 tends to be approximately proportional to the initial velocity v0. The radial magnetic field and the radial beam velocity produce a Lorentz force in the azimuthal direction. The magnetic field at the cusp 486 does not change the particle energy but converts the initial axial velocity vP≅v0 to a residual axial velocity vZ and an azimuthal velocity v⊥, where v02=vz2+v⊥2. The value of the azimuthal velocity v⊥ can be determined from the conservation of canonical momentum P θ = Mr 0 ⁢ v ⊥ - qB 0 ⁢ r 0 2 2 ⁢ c = qB 0 ⁢ r 0 2 2 ⁢ c ( 31 ) A beam ion enters the left hand side of the cusp 486 with Bz=B0, vz=v0, v⊥=0 and r=r0. It emerges on the right hand side of the cusp 486 with r=r0, Bz=−B0, v⊥=qB0r0/Mc and vz=√{square root over (v02−v⊥2)} v z v 0 = 1 - ( r 0 ⁢ Ω 0 v 0 ) 2 ( 32 ) where Ω 0 = qB 0 Mc is the cyclotron frequency. The rotation frequency of the ions is in a range of about 1-10 MHz, and preferably in a range of about 5-10 MHz, which is the frequency at which power generation takes place. In order for the ions to pass through the cusp 486, the effective ion gyro-radius must be greater than the width of the cusp 486 at the radius r0. It is quite feasible experimentally to reduce the axial velocity by a factor of 10 so that the residual axial energy will be reduced by a factor of 100. Then 99% of the ion energy will be converted to rotational energy. The ion beam has a distribution of values for v0 and r0. However, because r0 is proportional to v0 as previously indicated by the properties of the FRC based reactor, the conversion efficiency to rotational energy tends to be 99% for all ions. As depicted in FIG. 22B, the symmetrical electrode structure of the ICC 420 of the present invention preferably includes four electrodes 494. A tank circuit (not shown) is connected to the electrode structures 494 so that the instantaneous voltages and electric fields are as illustrated. The voltage and the tank circuit oscillate at a frequency of ω=Ω0. The azimuthal electric field E at the gaps 497 is illustrated in FIG. 22B and FIG. 25. FIG. 25 illustrates the electric field in the gaps 497 between electrodes 494 and the field an ion experiences as it rotates with angular velocity Ω0. It is apparent that in a complete revolution the particle will experience alternately acceleration and deceleration in an order determined by the initial phase. In addition to the azimuthal electric field Eθ there is also a radial electric field Er. The azimuthal field Eθ is maximum in the gaps 497 and decreases as the radius decreases. FIG. 22 assumes the particle rotates maintaining a constant radius. Because of the gradient in the electric field the deceleration will always dominate over the acceleration. The acceleration phase makes the ion radius increase so that when the ion next encounters a decelerating electric field the ion radius will be larger. The deceleration phase will dominate independent of the initial phase of the ion because the radial gradient of the azimuthal electric field Eθ is always positive. As a result, the energy conversion efficiency is not limited to 50% due to the initial phase problem associated with conventional cyclotrons. The electric field Er is also important. It also oscillates and produces a net effect in the radial direction that returns the beam trajectory to the original radius with zero velocity in the plane perpendicular to the axis as in FIG. 22C. The process by which ions are always decelerated is similar to the principle of strong focusing that is an essential feature of modern accelerators as described in U.S. Pat. No. 2,736,799. The combination of a positive (focusing) and negative lens (defocusing) is positive if the magnetic field has a positive gradient. A strong focusing quadrupole doublet lens is illustrated in FIG. 26. The first lens is focusing in the x-direction and defocusing in the y-direction. The second lens is similar with x and y properties interchanged. The magnetic field vanishes on the axis of symmetry and has a positive radial gradient. The net results for an ion beam passing through both lenses is focusing in all directions independent of the order of passage. Similar results have been reported for a beam passing through a resonant cavity containing a strong axial magnetic field and operating in the TE111 mode (see Yoshikawa et al.). This device is called a peniotron. In the TE111 mode the resonant cavity has standing waves in which the electric field has quadrupole symmetry. The results are qualitatively similar to some of the results described herein. There are quantitative differences in that the resonance cavity is much larger in size (10 meter length), and operates at a much higher frequency (155 MHz) and magnetic field (10 T). Energy extraction from the high frequency waves requires a rectenna. The energy spectrum of the beam reduces the efficiency of conversion. The existence of two kinds of ions is a more serious problem, but the efficiency of conversion is adequate for a D-He3 reactor that produces 15 MeV protons. A single particle orbit 422 for a particle within the ICC 420 is illustrated in FIG. 22C. This result was obtained by computer simulation and a similar result was obtained for the peniotron. An ion entering at some radius r0 spirals down the length of the ICC and after losing the initial rotational energy converges to a point on a circle of the same radius r0. The initial conditions are asymmetric; the final state reflects this asymmetry, but it is independent of the initial phase so that all particles are decelerated. The beam at the ion collector end of the ICC is again annular and of similar dimensions. The axial velocity would be reduced by a factor of 10 and the density correspondingly increased. For a single particle an extracting efficiency of 99% is feasible. However, various factors, such as perpendicular rotational energy of the annular beam before it enters the converter, may reduce this efficiency by about 5%. Electric power extraction would be at about 1-10 MHz and preferably about 5-10 MHz, with additional reduction in conversion efficiency due to power conditioning to connect to a power grid. As shown in FIGS. 23A and 23B, alternative embodiments of the electrode structures 494 in the ICC 420 may include two symmetrical semi-circular electrodes and/or tapered electrodes 494 that taper towards the ion collector 492. Adjustments to the ion dynamics inside the main magnetic field of the ICC 420 may be implemented using two auxiliary coil sets 500 and 510, as shown in FIGS. 27A and 24B. Both coil sets 500 and 510 involve adjacent conductors with oppositely directed currents, so the magnetic fields have a short range. A magnetic-field gradient, as schematically illustrated in FIG. 27A, will change the ion rotation frequency and phase. A multi-pole magnetic field, as schematically illustrated in FIG. 27B, will produce bunching, as in a linear accelerator. Reactor FIG. 28 illustrates a 100 MW reactor. The generator cut away illustrates a fusion power core region having superconducting coils to apply a uniform magnetic field and a flux coil for formation of a magnetic field with field-reversed topology. Adjacent opposing ends of the fusion power core region are ICC energy converters for direct conversion of the kinetic energy of the fusion products to electric power. The support equipment for such a reactor is illustrated in FIG. 29. Propulsion System Exploration of the solar system (and beyond) requires propulsion capabilities that far exceed the best available chemical or electric propulsion systems. For advanced propulsion applications, the present invention holds the most promise: design simplicity, high-thrust, high specific impulse, high specific power-density, low system mass, and fuels that produce little or no radio-activity. A plasma-thrust propulsion system, in accordance with the present invention, utilizes the high kinetic energy embedded in the fusion products as they are expelled axially out of the fusion plasma core. The system 800 is illustrated schematically in FIGS. 30 and 31. The system includes a FRC power core 836 colliding beam fusion reactor in which a fusion fuel core 835 is contained as described above. The reactor further comprises a magnetic field generator 825, a current coil (not shown) and ion beam injectors 840. An ICC direct-energy converter 820, as described above, is coupled to one end of the power core 836, and intercepts approximately half of the fusion product particles which emerge from both ends of the power core 836 in the form of annular beams 837. As described above, the ICC 820 decelerates them by an inverse cyclotron process, and converts their kinetic energy into electric energy. A magnetic nozzle 850 is positioned adjacent the other end of the power core 836 and directs the remaining fusion product particles into space as thrust T. The annular beam 837 of fusion products stream from one end of the fusion power core 836 along field lines 837 into the ICC 820 for energy conversion and from the other end of the power core 836 along field lines 837 out of the nozzle 850 for thrust T. Bremsstrahlung radiation is converted into electric energy by a thermoelectric-energy converter (TEC) 870. Bremsstrahlung energy that is not converted by the TEC 870 is passed to a Brayton-cycle heat engine 880. Waste heat is rejected to space. A power-control subsystem (810, see FIG. 32), monitors all sources and sinks of electric and heat energy to maintain system operation in the steady state and to provide an independent source of energy (i.e, fuel-cells, batteries, etc.) to initiate operation of the space craft and propulsion system from a non-operating state. Since the fusion products are charged α-particles, the system does not require the use of massive radiation and neutron shields and hence is characterized by significantly reduced system mass compared to other nuclear space propulsion systems. The performance of the plasma-thrust propulsion system 800 is characterized by the following kinetic parameters for a 100 MW p-B 11 fusion core example having a design as depicted in FIG. 31: Specific Impulse, Isp1.4 × 106 sThrust Power, PT50.8 MWThrust Power/Total Output Power, PT/Po0.51Thrust, T28.1 NThrust/Total Output Power, T/Po281 mN/MW The system 800 exhibits a very high specific impulse, which allows for high terminal velocities of a space craft utilizing the plasma-thrust propulsion system. A key mission performance/limitation metric for all space vehicles is system mass. The principal mass components in the plasma-thrust propulsion system 800 are illustrated in FIGS. 31 and 32. The fusion core 835 requires approximately 50 MW of injected power for steady-state operation. The system generates approximately 77 MW of nuclear (particle) power, half of which is recovered in the direct-energy converter 820 with up to 90% efficiency. Thus, an additional 11.5 MW is needed to sustain the reactor, which is provided by the TEC 870 and Brayton-heat engine 880. The principal source of heat in the plasma-thruster propulsion system 880 is due to Bremsstrahlung radiation. The TEC 870 recovers approximately 20% of the radiation, or 4.6MW, transferring approximately 18.2 MW to the closed-cycle, Brayton-heat engine 880. The Brayton-heat engine 880 comprises a heat exchanger 860, turbo-alternator 884, compressor 882, and radiators 886, as shown in FIG. 31. The Brayton engine 880 supplies the remaining 7 MW of power needed to sustain the reactor, another 11 MW is dumped directly to space by means of radiators. A closed-cycle, a Brayton-heat engine is a mature and efficient option to convert excess heat rejected by the TEC 870. In Brayton engines the maximum-cycle temperature is constrained by material considerations, which limits the maximum thermodynamic-cycle efficiency. Based on a standard performance map for the Brayton engine, several design points can be extracted. Typical efficiencies can reach up to 60%. For the present case, 7 MW is needed to be recovered, hence, only a 40% efficiency in converting waste heat is acceptable and well within currently attainable limits of conventional Brayton engines. The component mass for the entire Brayton engine (less the heat radiators) is calculated based on specific-mass parameters typical of advanced industrial technologies, i.e. in the range of 3 kg/kWe. Turbomachines, including compressors, power turbines, and heat exchangers, are combined for a total subsystem mass of 18 MT. The radiator mass is estimated to be 6 MT, preferably using heat-pipe panels with state-of-the-art high thermal conductivity. Significant system weight also comes from the magnets 825 confining the plasma core 835. The superconducting magnetic coils 825 are preferably made of Nb3Sn, which operates stably at 4.5K and at a field of 12.5-13.5 T. The cryogenic requirements for Nb3 Sn are less stringent than other materials considered. With a magnetic field requirement of 7 Tesla and a device length of approximately 7.5 meters, the coil needs about 1500 turns of wire carrying 56 kA of current. Using 0.5-cm radius wires, the total mass of this coil is about 3097 kg. The liquid helium cooling system is comprised of two pumps, one at each end of the main coil. The total mass of these pumps is approximately 60 kg. The outer structural shell is used to support the magnets and all internal components from outside. It is made of 0.01-m thick kevlar/carbon-carbon composite with a total mass of about 772 kg. The outermost layer is the insulation jacket to shield the interior from the large temperature variation in space is estimated at 643 kg. The total mass for the magnet subsystem 825 is, therefore, about 4.8 MT. At present, the ion injection system 840 most appropriate for space applications would be an induction linac or RFQ. Approximately 15 years ago an RFQ was flown on a scientific rocket and successfully demonstrated the use of high voltage power and the injection of ion beams into space. In a preferred embodiment, six injectors 840 distributed along the length of the CBFR, three for each species of ion. Each injector 840 is preferably a 30 beamlet RFQ with an overall dimension of 0.3 meters long and a 0.020-m radius. Each injector requires an ion source, preferaby 0.02-meters long and 0.020-meters radius, that supplies ionized hydrogen or boron. One source is needed for each accelerator. Both the injector and the source are well within currently attainable limits; with design refinements for space their total mass, including the sources and the accelerators, should be about 60 kg. The cone-shaped ICC direct energy converter 820 is located at one end of the reactor 836, which is preferably made of stainless steel. With a base radius of 0.5 meters and a length of 2 meters, the ICC mass is approximately 1690 kg. An RF power supply 820 (inverter/converter) recovers the directed-ion flow, converting it into electric power. The power supply mass is about 30 kg. A storage battery 812 is used to start/re-start the CBFR. The stored capacity is about 30 MJ. Its mass is about 500 kg. Alternately, a fuel cell could also be used. Additional control units coordinate operation of all the components. The control-subsystem mass is estimated to be 30 kg. The total energy converter/starter subsystem mass is, therefore, estimated at about 2.25 MT. A magnetic nozzle 850 is located at the other end of the fusion core 835. The nozzle 850 focuses the fusion product stream as a directed particle flow. It is estimated that the mass of the magnetic nozzle and the ICC are about equal; since both are comprised of superconducting magnets and relatively low-mass, structural components. The TEC 870 recovers energy from the electromagnetic emissions of the fusion core. It is preferably a thin-film structure made of 0.02-cm thick boron-carbide/silicon-germanium, which has a mass density of about 5 g/cm3. The TEC 870 is located at the first wall and preferably completely lines the inner surface of the reactor core; the mass of the TEC 870 is estimated at about 400 kg. The radiant flux onto the TEC 870 is 1.2 MW/m2 and its peak operating temperature is assumed to be less than 1800° K. The total plasma-thruster propulsion system mass is thus estimated at about 33 MT. This defines the remaining mission-critical parameters for the presently discussed 100 MW unit: Total Mass/Total Power, MT/Po0.33 × 10−3 kg/WThrust/Mass, T/MT0.85 × 10−3 N/kg While the invention is susceptible to various modifications and alternative forms, a specific example thereof has been shown in the drawings and is herein described in detail. It should be understood, however, that the invention is not to be limited to the particular form disclosed, but to the contrary, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the appended claims.
	description	This application is an national phase application based on PCT/IB2004/001738, filed May 27, 2004, the content of which is incorporated herein by reference, and claims the right to priority based on South African Application No. 2003/6376, filed Aug. 15, 2003. THIS INVENTION relates to a support arrangement. It also relates to a method of supporting a vessel. A problem which is encountered is the support of vessels which are subjected to temperature fluctuations. As a result of changes in temperature the shape and/or dimensions of the vessel may change and this can lead to undesirable stresses in the vessel and/or in the vessel support. This is particularly the case when the change in temperature is uneven. It is an object of this invention to provide means which the Inventor believes will at least alleviate this situation. According to one aspect of the invention there is provided a support arrangement which includes a vessel to be supported; a single vertical support for supporting the weight of the vessel; and lateral support means at least at an elevation which is above that of the single vertical support for providing lateral support to the vessel The Inventor believes that the invention will find application particularly, though not necessarily exclusively, in a high temperature gas cooled nuclear reactor. Accordingly the vessel may be a core barrel of a high temperature gas cooled nuclear reactor which includes a reactor pressure vessel within which the core barrel is housed, the vertical support including upper and lower support members which are connected respectively to the core barrel and the reactor pressure vessel, between which the vertical loads are transmitted. The core barrel may be generally cylindrical in shape and has an axis which extends generally vertically, the upper and lower support members defining centrally positioned oppositely disposed contact surfaces. At least one of the contact surfaces may be curved so that relative movement between the contact surfaces is achieved by rolling and not sliding thereby reducing wear and the risk of welding of the surfaces when operating in a helium environment. In a preferred embodiment of the invention both of the contact surfaces are curved. The upper support member may define a downwardly facing concave contact surface. The lower support member may define an upwardly facing convex contact surface. The contact surfaces may be part spherical. In a preferred embodiment of the invention, the radius of the convex contact surface is smaller than that of the concave contact surface. The vertical support may include an intermediate member interposed between the upper and lower support members. The intermediate member may define upper and lower contact surface which cooperate, respectively, with complementary contact surfaces of the upper and lower support members. The contact surfaces of the intermediate member may be convex with the complementary contact surfaces of the upper and lower support members being concave. In a preferred embodiment of the invention, each convex contact surface has a radius which is smaller than that of the complementary concave contact surface. The lateral support means may include a plurality of circumferentially spaced upper lateral supports positioned to support the core barrel laterally at or towards an operatively upper end thereof. Each upper lateral support may include a set of inner and outer upper lateral support members connected to the core barrel and the reactor pressure vessel respectively, at least one of the inner and outer upper lateral support members of each set being mounted on a resiliently deformable support. A roller element may be sandwiched between the inner and outer upper lateral support members of each upper lateral support to facilitate relative displacement between the inner and outer upper lateral support members and between the core barrel and the reactor pressure vessel to which they are connected. The roller and at least one of the inner and outer upper lateral support members may be provided with complementary teeth to ensure that relative displacement between the roller and complementary bearing surfaces of the inner and outer upper lateral support members is by rolling and not sliding. In addition to the use of the rollers, the bearing surfaces may be treated to inhibit welding. This treatment may include nitriding of the bearing surfaces. The bearing surfaces of the inner and outer upper lateral support members may be inclined. In particular, the bearing surfaces of the inner and outer upper lateral support members may be generally parallel and inclined outwardly upwardly. Each outer upper lateral support member may be mounted on a resiliently deformable support which, in turn, is mounted on an upper support ring secured to the reactor pressure vessel. The resiliently deformable support may include a pair of support posts connected to the upper support ring at spaced apart positions and an elastically deformable guide beam which extends between the support posts and on which the outer upper lateral support member is mounted. The position of the guide beam may be adjustable thereby permitting the relative positions of the inner and outer upper lateral support members to be adjusted. The lateral support means may include a plurality of circumferentially spaced lower lateral supports positioned to provide lateral support to the core barrel adjacent to a lower end thereof. Each lower lateral support may include an elastically deformable locating element extending radially between inner and outer receiving formations to transmit lateral loads between the core barrel and the reactor pressure vessel. The inner receiving formations may be provided on the upper support member and the outer receiving formations are protrusions which protrude radially inwardly from a lower support ring secured to the reactor pressure vessel. The support arrangement may include auxiliary support means for supporting the core barrel within the reactor pressure vessel when subjected to exceptional loads, eg as a result of a seismic event. In one embodiment of the invention, the upper support member includes a central member which extends downwardly from the bottom of the core barrel and a plurality of angularly spaced support beams connected to the bottom of the core barrel and to the central member and extending radially outwardly from the central member, the auxiliary support means including a lower auxiliary support including a plurality of circumferentially spaced radially inwardly facing slots in which radially outer ends of the support beams are receivable with little clearance. The slots may be defined on a radially inner surface of a lower support ring secured to the reactor pressure vessel. Shims may be used to obtain the desired clearance of the ends of the beams in the slots. In another embodiment of the invention, the upper support member includes a central member which extends downwardly from a bottom of the core barrel and a plurality of angularly spaced support beams connected to the bottom of the core barrel and to the central member and extending radially outwardly from the central member to an annular skirt which depends from the core barrel, the auxiliary support means including a lower auxiliary support which includes a plurality of circumferentially spaced protrusions which protrude radially inwardly from a lower support ring secured to the reactor pressure vessel and which are received with little clearance in complementary slots in the skirt Shims may be provided to obtain the desired clearance between the protrusions and the slots. According to another aspect of the invention there is provided a method of supporting a vessel which includes the steps of transmitting the weight of the vessel with its contents to a support arrangement through a single vertical support; and supporting the vessel laterally at least at a position which is at an elevation above that of the vertical support. When the vessel is in the form of a core barrel of a high temperature gas cooled nuclear reactor which includes a reactor pressure vessel within which the core barrel is supported, the method may include the steps of transmitting the weight of the core barrel and its contents to the reactor pressure vessel through a single vertical support; and transmitting lateral loads between the core barrel and the reactor pressure vessel through a lateral support positioned at an elevation above that of the vertical support. In the drawings, reference numeral 10 refers generally to a nuclear reactor incorporating a support arrangement in accordance with the invention. The reactor 10 includes a reactor pressure vessel 12 and a core barrel, generally indicated by reference numeral 14, contained within the reactor pressure vessel 12. The reactor 10 further includes a single vertical support, generally indicated by reference numeral 16, for transmitting vertical load from the core barrel to the reactor pressure vessel and lateral support means, generally indicated by reference numeral 18 (FIG. 7) for providing lateral support to the core barrel 14. The reactor pressure vessel 12 comprises a circular cylindrical side wall 20 and domed upper and lower ends 22, 24 respectively. The core barrel 14 includes a circular cylindrical side wall 26 having an axis 400 which extends vertically, a top 28 and a bottom 30. Positioned in the core barrel 14 are reflectors (not shown) which define between them a core or chamber 40 within which nuclear fuel is received. The operational detail of the reactor and the associated structural features are not essential to the understanding of the invention and are not shown or described in detail. Referring now in particular to FIGS. 2, 3 and 5 of the drawings, the vertical support 16 includes an upper support member 44 and a lower support member 46. The upper support member 44 includes a circular cylindrical centre member 48 which is connected to the bottom 30 of the core barrel 14 and extends downwardly therefrom coaxially with the core barrel 14. The centre member 48 defines a downwardly facing concave contact surface 50. The contact surface 50 is recessed so that it is surrounded by an annular shoulder 52. The upper support member 44 further includes a plurality of angularly spaced support beams 54 connected to the bottom 30 of the core barrel 14 and to the central member 48 and extending radially outwardly therefrom. Hence, the support beams 54 provide support to the bottom 30 and to the central member 48 and serve to transfer the weight of the core barrel 14 to the central member 48. The lower support member 46 as can best be seen in FIGS. 2 and 5 of the drawings, comprises a base 56 which is secured to the lower end 24 of the reactor pressure vessel 12 and a centrally disposed circular cylindrical portion 58 which protrudes upwardly from the base and defines a convex contact surface 60. The support member 46 is bolted to the reactor pressure vessel. These bolts do not have very large loads in view of the fact that it is the weight of the core barrel assembly which is transmitted through the vertical support 16 and the load is hence in a vertical downward direction. The diameter of the protruding portion 58 is smaller than the internal diameter of the annular shoulder 52 such that it is receivable therein with clearance. Further, the contact surface 50 has a radius of curvature which is larger than that of the contact surface 60. In one embodiment of the invention, the contact surface 50 has a radius of 5250 mm and the contact surface 60 has a radius of 4400 mm. Naturally, however, these radii may vary depending on the dimensions of the reactor and the optimum for a particular application can be determined by routine experimentation or empirical means. The curved surfaces are provided in order to ensure that relative movement occurs by rolling and not sliding. In addition, the relatively large radii are used in order to achieve a desired contact area. As can best be seen in FIGS. 7, 8 and 12 of the drawings, an upper ring 72 is secured in position in the reactor pressure vessel 12. In this regard, one or more torsion keys 74 may be used to secure the ring 72 in position. As can most clearly be seen in FIG. 12 of the drawings, the ring 72 and pressure vessel 12 are provided with complementary downwardly radially inwardly tapering surfaces 73, 75. In addition, an annular locking plate 77 is secured to the support ring 72 by welding or bolts, a radially outer edge portion of the locking plate 77 being received in an annular recess 79 in the reactor vessel 12. This arrangement serves to lock the ring 72 in position without the need for welding to the surface of the reactor pressure vessel 12. The lateral support means 18 includes a plurality of circumferentially spaced upper lateral supports 76 positioned to support the core barrel 14 at or towards an operatively upper end thereof. With reference also to FIG. 9 of the drawings, each upper lateral support 76 includes an inner upper lateral support member 78 and an outer upper lateral support member 80. The inner upper lateral support members 78 are secured to the core barrel 14 and the outer upper lateral support members 80 are connected to the upper ring 72 as described in more detail herebelow. The upper lateral support members 78, 80 define complementary inclined support or bearing surfaces 82, 84 which bear against a roller 86 positioned between the support members 78, 80. The roller 86 includes a circular cylindrical body 88 having a centrally disposed annular recess 90 therein. Further, a gear wheel 92 is provided at each end of the body and a circular cylindrical axial projection 94 projects from each of the gear wheels 92. Each of the inner and outer upper lateral support members 78, 80 is provided with a centrally disposed rib 96 which protrudes from the surfaces 82, 84 and is receivable in the recess 90. Further, on each side of each of the surfaces 82, 84 a set of gear teeth 98 complementary to those of the gear wheels 92 is provided. This arrangement serves to ensure that relative displacement of the inner lateral support member 78 and outer lateral support member 80 is achieved as a result of rolling of the roller 86. Further, each outer lateral support member 80 has a pair of cheek plates 100 which has a slot 102 provided therein. The slots 102 are parallel with the surface 84. The projections 94 are received with little clearance in the slots 102 and serve to restrict the extent of the movement of the roller 86 relative to the outer upper lateral support member 80. Each outer upper lateral support member 80 is mounted on a resiliently deformable support, generally indicated by reference numeral 104 (FIG. 8). Each support 104 includes a pair of guide posts 106 mounted on the upper ring 72 and an elastically deformable guide beam 108 which extends between the support posts 106. As can best be seen in FIG. 10 of the drawings, each support post 106 includes a base 110 which is secured to the upper ring 72 by welding and a slider 112. The base 110 and slider 112 have complementary lip and channel formations 113, 115 which permit relative displacement of the slider 112 on the base 110 in a vertical direction. Complementary semi-circular recesses 114, 116 are provided on the base 110 and the slider 112, respectively which together form a hole within which part of an adjusting screw 118 is positioned. The recess 116 is provided with a screw thread. Vertical displacement of the adjusting screw 118 is inhibited by a cover plate 120 which is mounted on the support base and held in position by screws 122. The cover plate 120 cooperates with a collar 124 on the adjusting screw 118 to inhibit vertical displacement of the adjusting screw 118. The cover plate 120 also serves to hold the slider 112 captive on the base 110 and permit a limited degree of vertical displacement of the slider 112 relative to the base 110 by rotation of the adjusting screw 118. The slider 112 defines a slot 126 within which an end portion of a guide beam 108 is receivable. The guide beam is accordingly supported on a pair of support posts 106 and is configured to permit a degree of resilient displacement of the guide beam 108, in the manner of a leaf spring, and hence the outer upper lateral support member 80 mounted thereon. Further, by adjusting the adjusting screws 118, the position of the guide beam and hence of the outer upper lateral support member 80 relative to the inner upper lateral support member 78 can be adjusted to obtain a desired preload. In the embodiment shown, the guide beams 108 are curved in order to fit within the space defined between the core barrel and the reactor pressure vessel. As will be described in more detail herebelow, the vertical support 16 and lateral support means 18 serve to support the core barrel 14 within the reactor pressure vessel 12 under normal operating conditions. However, the possibility exists that the reactor 10 is subjected to exceptional loads, e.g. as a result of a seismic event. The reactor 10 accordingly includes auxiliary support means. The auxiliary support means includes a lower auxiliary support, generally indicated by reference numeral 130 (FIGS. 3 and 4) and an upper auxiliary support, generally indicated by reference numeral 132 (FIG. 11). The lower auxiliary support 130 includes a lower support ring 134 which is secured to the reactor pressure vessel 12 adjacent to a lower end of the core barrel 14. The lower support ring 134 may be secured in position in the reactor pressure vessel 12 in a similar fashion to the upper support ring 72 as described above. A plurality of radially inwardly open slots 138 is provided at circumferentially spaced positions on the lower support ring 134. Radially outer end portions of the support beams 54 are received within the slots 138. The upper auxiliary support 132 includes a plurality of circumferentially spaced ribs 140 which are connected to and protrude outwardly from the side wall 26 of the core barrel 14. Complementary radially inwardly directed slots 142 are provided at circumferentially spaced positions on the upper support ring 72 within which slots portions of the ribs 140 are receivable. It will be appreciated that, in normal use, there will be some relative movement between the core barrel 14 and the reactor pressure vessel 12, e.g. as a result of changes in temperature, differential rates of expansion and the like. The clearance between the support beams 54 and the lower support ring 134 and between the ribs 140 and the upper support ring 72 will be selected to permit this relative movement. In order to obtain the desired clearance in the slots 138, 142, use is made of shims 144, one of which is shown in FIG. 6 of the drawings. The shims are machined to the required dimensions and installed on the lower support ring 134 and upper support ring 72 to provide the desired clearance between the ends of the support beams 54 and the ribs 140, respectively. As can best be seen in FIG. 6 of the drawings, each shim 144 includes an end plate 160 and a body portion 162 protruding from the end plate 160. Oppositely disposed parallel ribs 164 protrude laterally outwardly from the body 162 and are slidably receivable in complementary vertically extending oppositely inwardly disposed channel formations in the support rings 72, 134. The shims are retained in this position by means of screws 166 which extend through complementary holes 168 in protruding portions of the end plates 160. The core barrel typically has a length of about 22 meters and a circumference of about 18 meters. The core barrel heats up during operation and cools down during shut-down. In order to remain within the material temperature constraints, the core barrel has to be cooled down on the outside and to this end a core barrel cooling system is provided. However, it is unlikely that the core barrel sides will be at a uniform temperature all around the circumference at any given height. Variations in temperature can result from various factors such as an uneven flow of the core barrel cooling system gas around the circumference of the core barrel, an uneven gap between the side reflector and the core barrel sides, e.g. because of manufacturing tolerances, an uneven gap between the reactor pressure vessel and the core barrel due to manufacturing tolerances on both of these components, un-symmetrical placement of components such as inlet and outlet pipes, or the like. An uneven temperature distribution on the core barrel may result in some lateral deformation of the core barrel, e.g. slight bowing thereof. By supporting the weight of the core barrel on the single centrally disposed vertical support 16, the core barrel may bow without any exceptional stresses being induced in the core barrel or the support structure. This makes the core barrel insensitive to an uneven temperature distribution. A disadvantage with the prior art is that the core barrel is supported at a plurality of spaced apart vertical supports. As a result of movement of the core barrel uneven loading of the supports and hence of the core barrel can occur which can lead to undesirably high levels of stress. This problem is avoided by making use of the single centrally disposed vertical support 16. Further, naturally, as a result of differences in temperature as well as the materials used, the rates and extent of the expansion of the core barrel and the reactor pressure vessel may differ. In this regard, the upper lateral support 76 serves to support the upper end of the core barrel. As the core barrel heats up, it expands both vertically and radially. This results in the inner upper lateral support members 78 being displaced upwardly and radially outwardly relative to the outer upper lateral support members 80. However, the inclination of the support surfaces 82, 84 permits this expansion and maintains the support surfaces in contact with the surface of the roller 86. The natural resilience of the guide beams 108 also permits a degree of lateral movement. If, for some reason, the surfaces 82, 84 lose contact with the roller 86, the roller will be held in position by means of the gear teeth 92, 98. Should the separation between the surfaces 82, 84 become even greater such that the teeth 92, 98 lose contact, then the roller will roll down the surface 84 until the projections 94 are positioned in the bottom of the slots 102. This ensures that the rollers 86 do not fall down between the reactor pressure vessel 12 and core barrel 14. The surfaces 82, 84 are typically inclined at an angle of about 10° to the vertical. However, it will be appreciated, that this angle may vary with the optimum for a particular application being determined by routine experimentation or empirically. In the event of an unusual load being applied to the reactor 10, e.g. as a result of a seismic event, the single vertical support 16 will support the weight of the core barrel 14, however, the upper lateral supports 76 may be incapable of providing sufficient horizontal support to the core barrel 14 since the guide beams 108 will deform. If the deflection is sufficient, the gaps between the end portions of the support beams 54 and the slots 138 and between ribs 140 and the slots 142 will close thereby transmitting horizontal loads from the core barrel 14 to the reactor pressure vessel 12. After the seismic event, the guide beams 108 will centralize the core barrel 14 and open up the gaps between the ribs 140 and the slots 142. In this regard, it will be appreciated that the guide beams 108 are designed to handle this deformation and remain within the elastic region of the material from which they are manufactured. Naturally, certain variations of the support arrangement are possible. For example, the lower support member 46 can be connected to the reactor pressure vessel by means of a configuration of beams designed to spread the load transmitted thereto by the core barrel over a larger area of the reactor pressure vessel. Another variation of the support arrangement is illustrated in FIG. 13 of the drawings in which reference numeral 200 refers generally to part of another reactor incorporating a support arrangement in accordance with the invention and, unless otherwise indicated, the same reference numerals used above are used to designate similar parts. The main difference between the support arrangement of the reactor 200 and that of the reactor 10 is that, in the case of the reactor 200 the support arrangement includes an intermediate member 202 disposed between the upper support member 44 and the lower support member 46. The intermediate member 202 is generally oval in shape having convex upper and lower contact surface 204, 206. The upper support member 44 and lower support member 46 have concave support surfaces 208, 210. The radii of the support surfaces 208, 210 are larger than those of the support surfaces 204, 206. An advantage with this arrangement is that it is self-centering. Reference is now made to FIGS. 14 to 16 of the drawings, in which reference numeral 300 refers generally to part of another reactor incorporating a support arrangement in accordance with the invention and, unless otherwise indicated, the same reference numerals used above are used to designate similar parts. In this embodiment of the invention, an annular skirt 302 depends downwardly from the bottom 30 of the core barrel. The support beams 54 are connected to the bottom 30 of the core barrel 14 and to the central member 48 and extend radially outwardly therefrom, the radially outer ends of the support beams 54 being connected to the skirt 302. In addition, a plurality of, in the embodiment shown nine, protrusions 304 protrude radially inwardly from the lower support ring 134. The protrusions 304 extend through slots 306 provided in the skirt 302. Hence, the skirt 302 and protrusions 304 function as the lower auxiliary support 130 to support the core barrel in the event of its being subjected to an exceptional load, such as may be experienced during a seismic event. In order to obtain the desired clearance between the protrusions 304 and the slots 306, shims 308 may be used. Further, as can best be seen in FIG. 16 of the drawings, each protrusion 304 has convex sides 310 which, in the event of a seismic occurrence, make contact with the shims 308. The convex side 310 ensure that low contact stresses occur even if the skirt 302 should form a slight angle with the horizontal, e.g. as a result of bowing of the core barrel. In addition, in this embodiment of the invention, the lateral support means includes a lower lateral support comprising three elastically deformable locating elements or beams 312. Inner end portions of the beams 312 are located in inner receiving formations in the form of recesses 314 provided on the upper support member 48 and radially outer ends of the beams 312 are positioned in complementary recesses 316 provided on shims 318 mounted on three of the protrusions 304. The shims 318 are used to obtain a desired preload in the beams 312. The beams 312 are curved in order to obtain maximum deflection for minimum stresses in the beams during a seismic event, the beams 312 will deform sufficiently to permit the spaces between the protrusions 304 and shims 308 to close thereby transmitting transverse loads from the core barrel to the reactor pressure vessel. After the seismic event, the beams 312 will centralize the central member 48 and re-establish the gap between the protrusions 304 and the shims 308. The Inventor believes that when compared with prior art systems, the current invention will result in lower stresses on a vessel which is subjected to temperature fluctuations as well as on the support structure. Further, in the specific case of a reactor it allows a small amount of bowing of the core barrel without an increase in stresses. The core barrel is able to tolerate an uneven temperature distribution. Further, the core barrel can expand radially relative to the reactor pressure vessel as well as axially. By permitting adjustment of the supports 104, the lateral support of the core barrel adjacent its upper end can be adjusted to make sure that the core barrel is self-aligning and stable. Further, the shims which are provided on the upper and lower support rings are sized during installation and thereby ensure that the desired spacing or tolerances are achieved.
047175290	abstract	A thimble guide assembly for use in a nuclear reactor includes a lower element which can be screwed into a bore in a core plate and an upper element which can be screwed to the lower element. One of the screw-connections is right-handed while the other is left-handed. The length of the upper element is selected so that the exposed portion of a thimble tube, which extends through the thimble guide assembly and into a fuel assembly above it, is relatively modest, thereby minimizing the turbulence to which the thimble tube is exposed. The lower element of the thimble guide assembly is provided with a sleeve portion which extends through the bore in the core plate, and the tip of the upper element terminates in a planar, annular lip. Both elements are provided with surfaces for engagement by wrenches or other tools. The lower element has annular grooves for engagement by a lower spring clip which is welded to the core plate and an upper spring clip which is welded to the upper element.
052232077	summary	BACKGROUND OF THE INVENTION Reactor coolant pump degradation can produce severe economic penalties for nuclear power plants which have to shut down for extended periods of time in response to a possible coolant pump failure. As a result, there is a strong economic incentive to develop and commercialize an effective apparatus to provide for early detection of coolant pump problems. Early detection of a coolant pump degradation would allow the reactor operator to manually trip the reactor before major pump damage occurred as opposed to the operator experiencing an automatic rapid shutdown of the reactor due to the loss of coolant caused by a damaged pump or a false alarm caused by a defective sensor. A controlled response would allow maintenance to be performed on the pump prior to failure or severe damage or to pinpoint a sensor problem and thus, limit the reactor down time. The current general practice is to evaluate the condition of the reactor's coolant pump through the use of high/low limit checks of the pump's operating parameters. Using this system, when the coolant pump parameters read outside of a zone defined by the high/low values, an alarm is sounded, and the pump is shut down resulting in lost operating time. This type of analysis can result in a high number of false alarms and missed alarms when compared to an artificial intelligence technique which more closely analyzes the pump parameters as measured by a set of pump sensors. Artificial intelligence techniques in an expert system continually survey and diagnose pump performance and operability as a means of detecting the early stages of pump degradation. Since most pumps are equipped with numerous sensors to monitor the condition of the pump, the sensors provide a good data base for use by the expert system. Applicants' expert pump diagnosis system continuously monitors and compares the digitized signals representing a variety of variables associated with the physical condition of the coolant pump: speed, vibration level, power, and discharge pressure. Variation of these variables is a possible indication of off-normal operation of the pump. Applicants' invention uses an expert system based on a mathematical comparison and analysis of multiple signals from a pair of nuclear reactor coolant pumps to analyze the condition of the coolant pump using the aforementioned input signals. Accordingly, it is an object of this invention to provide an expert system for early detection of coolant pump degradation so as to provide the operator with information on this condition prior to pump failure. A further object of this invention is to provide an expert system for determining sensor degradation as opposed to pump failure. Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of instrumentalities and combinations particularly pointed out in the appended claims. SUMMARY OF THE INVENTION To achieve the foregoing and other objectives and in accordance with the purposes of the present invention, as embodied and broadly described herein, the present invention provides for a means to determine the degradation of a nuclear reactor cooling pump and the degradation of sensors used to measure various parameters associated with the cooling pump. Applicants' invention accomplishes this through the use of an expert system employing a sequential probability ratio test (SPRT) to evaluate parametric data associated with the function of the coolant pump. The SPRT technique requires the presence of duplicate sensors on each of two or more pumps. This system provides the reactor operator with an early warning system to allow an orderly shut down of the pump for sensor or pump degradation in lieu of a rapid emergency shut down of the pump.
043748015	summary	BACKGROUND OF THE INVENTION The invention concerns a method of handling fuel assemblies and rods in the reloading with fuel of a nuclear reactor containing assemblies with a framework closed by two caps inside which fuel rods are vertically disposed. After a certain working period, fuel assemblies disposed in the vessel of the reactor exhibit some wear, i.e. a nuclear fissionable fuel material of these assemblies is depleted to some extent, so that it is necessary to change some of these fuel assemblies which have become unsuitable for later use in the core of the nuclear reactor for the production of heat. In addition, the cladding material of some fuel rods can exhibit cracks after these rods have been used for some time, so that leakages of fission products into the cooling fluid of the reactor, in contact with these fuel rods, are possible. The core of the nuclear reactor is consequently reloaded with fuel at predetermined time intervals, during which used or defective fuel assemblies are removed and replaced. In most nuclear reactors, the fuel elements constituted by rods containing fuel material inside a tubular cladding of cladding material are disposed inside assemblies in which these rods are placed parallel to each other, in the axial direction of the core, i.e., generally in the vertical direction. Each of the fuel-rod assemblies constitutes a rigid assembly having a framework or skeleton inside which the fuel rods are disposed. The framework of the assembly is constituted by support tubes and caps which can be designed to allow de-mounting and remounting of the assembly if the framework is required to be reused when the fuel element of the fuel rods is used up. In the case of pressurized water nuclear reactors, the assemblies are disposed in the tank of the reactor and constitute its core. The assemblies are disposed in a lattice of square mesh, and some of these assemblies are equipped with a cluster of material absorbing the neutrons serving to control the reactor. During reloading of the reactor, the vessel of the nuclear reactor is open, and this vessel as well as the swimming pool around it is filled with water up to a certain level, allowing fuel rods to be moved between the reactor and the swimming pool, at a depth sufficient to assure the protection of the personnel carrying out the reloading operations. These operations consist firstly in moving fuel assemblies from one region of the reactor core to another, this core being divided into three regions inside which each of the fuel assemblies lies between two reloading operations. The most used assemblies are to be found in the third region of the reactor and are removed via the swimming pool for the fuel adjoining the reactor and replaced by new assemblies. When transferring assemblies from one position to another or replacing assemblies by new assemblies, it is necessary to carry out permutations of the control clusters, these clusters always staying in the same position in the core. The reloading operations also consist in replacing fuel assemblies having rods exhibiting leakages by new assemblies. Independently of the reloading operations, the used assemblies are removed after decay of their radio activity to reprocessing works, although a certain number of fuel rods inside these assemblies could be reutilized to reconstitute reloadable fuel assemblies in the nuclear reactor. Similarly, part of the fuel rods of the assemblies removed from the core of the nuclear reactor because they contain fuel rods exhibiting leakages or geometric deformations can be recovered to reconstitute reloadable assemblies in the core of the reactor. Methods of repairing fuel assemblies by replacing used fuel rods inside the assembly have also been proposed. In these methods, however, repair of the assembly is carried out, independently of the reloading operation, with a tool allowing the defective fuel rods to be removed one by one and replaced by new rods. Reloading is always carried out with whole assemblies, each used or defective assembly being replaced by a new or reconstituted assembly reconditioned in operations which are independent of the actual reloading operations. Known methods generally require reprocessing and storage of the whole of the assembly comprising both skeleton and fuel rods. The methods used to date consequently tend to increase the consumption of fuel material by removing fuel rods which could continue to be used, and to increase the number of de-mounting and handling operations carried out on fuel assemblies to recondition them before loading into the core. SUMMARY OF THE INVENTION The object of the invention is therefore a method of handling fuel assemblies and rods upon reloading with fuel of a nuclear reactor containing assemblies having a framework closed by two caps inside which fuel rods are disposed vertically, reloading being carried out with the vessel of the reactor open and the swimming pool around the vessel filled with water, and comprising transfers of fuel assemblies from one position to another inside the reactor, replacement of defective or used assemblies, by suitable assemblies and various tests, each assembly replaced being taken from the vessel of the reactor, placed in a transfer container and conveyed in a horizontal position into the swimming-pool for the fuel adjoining the reactor, this method allowing the best reuse of the fuel rods not completely used up in assemblies being replaced and use, on unloading, of frameworks or skeletons of these assemblies. To this end, the following operations are carried out in succession: the assembly is put in vertical position inverted relative to the position for service of this assembly in the core of the reactor, i.e., with its lower cap uppermost, PA1 the lower cap is de-mounted so that access can be had to the ends of the fuel rods, PA1 if necessary, the fuel rods to be replaced in the assembly are identified, if this identification has not been carried out in the reactor or in the swimming pool of the reactor, PA1 a set of rods to be replaced is taken up simultaneously, PA1 if necessary, the taking up of rods in sets is continued until all the rods to be replaced have been taken up, PA1 these sets of rods are deposited in a location for storing used rods, PA1 rods which are new or to be recycled corresponding exactly to the sets of rods to be replaced are taken up, PA1 these sets are deposited in the framework of the fuel assembly, PA1 the lower cap of the assembly is replaced and this assembly is conveyed into the vessel of the reactor in its new location.
	description	The present invention relates to a dimension measuring SEM system for measuring the dimensions of components of a circuit pattern formed on a semiconductor wafer by a photolithographic process to evaluate the circuit pattern, a pattern evaluating method of evaluating the shape of a circuit pattern and a pattern evaluating system for carrying out the pattern evaluating method. More specifically, the present invention relates to a pattern evaluating method of evaluating a circuit pattern formed on a semiconductor wafer through the comparison of the circuit pattern formed on the semiconductor wafer with a circuit pattern of a desired design, and a pattern evaluating system for carrying out the pattern evaluating method. A semiconductor device fabricating process forms an image of a device pattern or a circuit pattern, namely, a wiring pattern, designed by using a CAD system and formed on a photomask, namely, a reticle, on a wafer to form a semiconductor device. The recent advanced integrated circuit technology for forming miniaturized devices requires further dimensional reduction of wiring lines. The device miniaturization requires forming a circuit pattern having lines of a line width smaller than the wavelength of radiation radiated by an exposure light source. Thus printing a fine circuit pattern formed on a photomask on a resist film in a desired high resolution has become progressively difficult. Consequently, a resist pattern 102 formed by exposing a resist film through a photomask provided with a circuit pattern 101 to exposure radiation differs greatly from the circuit pattern 101 of the photomask as shown in FIG. 1. For example, a circular shape 104 is printed on the resist film when the resist film is exposed through a square shape 103 formed on a photomask, and a bent line 102 having rounded corners 106 are formed on the resist film when the resist film is exposed through a bent line 101 having rectangular corners 105. Moreover, a circuit pattern having regularly alternately arranged rectangular lines of predetermined dimensions and rectangular spaces of predetermined dimensions formed on a photomask is printed on a resist film in a circuit pattern having irregularly alternately arranged rectangular lines of dimensions different from those of the rectangular lines on the photomask and rectangular spaces of dimensions different from those of the spaces formed on the photomask. The shape deterioration of the resist pattern is due to a physical phenomenon called an optical proximity effect (OPE) The shape deterioration of the resist pattern causes the malfunction of semiconductor devices. Effort is made to form the resist pattern in an improved shape by intentionally properly deforming a mask pattern formed on the photomask. For example, to improve the resist pattern, a method forms a minute corrected circuit pattern that is not printed on the resist film contiguously with or in the proximity of the mask pattern formed on the photomask and another method forms a mask pattern having parts having dimensions greater or smaller than design dimensions on the photomask. Such correcting techniques will be called optical proximity correction techniques (OPC techniques). Resist patterns formed by the OPC techniques are used for forming extremely miniaturized semiconductor devices. The slight difference between the design shape of the mask pattern and the actual shape of the resist pattern affects significantly on the ability of semiconductor devices. Thus the difference between the mask pattern and the resist pattern is an important problem of quality control. To solve such a problem, the widths of the lines forming the circuit pattern formed on a wafer are measured by a length-measuring SEM system, and the measured widths of the lines are used for the optimization of photomask designing, exposure and process conditions. Further dimensional reduction of design circuit patterns is expected in the future. Therefore, there is a need for a measuring method and an evaluating method capable of grasping the minute condition of shapes of resist patterns. Techniques for evaluating circuit patterns formed on semiconductor wafers are disclosed in JP-A 2002-31525, JP-A 2002-353280 and JP-2004-228394. Related arts are disclosed in JP-A 8-160598, JP-A 200-58410, JP-A 2002-81914, JP-A 2003-16463 and JP-A 2003-21605. As mentioned above, the dimensional reduction of semiconductor devices and wiring lines has been achieved by the advanced integrated circuit technology relating with the semiconductor device fabricating process and the OPC technique relating with miniaturization techniques has been applied to forming circuit patterns. The geometrical features of minute circuit patterns, such as the roundness of corners of circuit patterns and distances between adjacent lines of circuit patterns, affect the ability of semiconductor devices. The quality of resist patterns cannot be satisfactorily evaluated through the dimensional measurement of the resist patterns by known measuring techniques. The present invention provides a dimension measuring SEM system, a method of evaluating the shape of a circuit pattern and a system for carrying out the method capable of evaluating the quality of a minute circuit pattern formed by the OPC technique, namely, a miniaturizing technique. The present invention provides a circuit pattern evaluating system, for carrying out a circuit pattern evaluating method of evaluating the shape of a circuit pattern, including an electronic or optical microscope for obtaining measured data on a printed circuit pattern corresponding to a mask pattern formed on a mask, namely, mask pattern, and formed on a substrate by an exposure process executed by an exposure system under predetermined exposure conditions; an input means for entering design data on the mask pattern provided by a CAD system or the like; and an evaluation index calculating means for processing the design data on the mask pattern and the measured data on the printed circuit pattern provided by the microscope by a superposition process and calculating evaluation indices for the evaluation of the OPC of the mask pattern (hereinafter, referred to as “OPC evaluation”) through the quantification of one- or two-dimensional geometrical features indicating the difference between the design data and the measured data. The present invention provides a dimension measuring SEM system, for obtaining measured data on a printed circuit pattern formed on a substrate by an exposure system under predetermined exposure conditions, including an input means for entering design data on a mask pattern provided by a CAD system or the like; and an evaluation index calculating means for processing the design data on the mask pattern entered by the input means and the measured data on the printed circuit pattern provided by the microscope by a superposition process and calculating evaluation indices for the OPC evaluation through the quantification of one- or two-dimensional geometrical features indicating the difference between the design data and the measured data. The dimension measuring SEM system according to the present invention further includes an input means for entering the exposure conditions and the design data on the mask pattern formed on the photomask, produced by a photomask designing unit; and a exposure simulator for calculating data on the printed circuit pattern formed by an exposure process based on the design data, on the mask pattern formed on the photomask, entered by the input means and the predetermined exposure conditions; wherein the evaluation index calculating means subjects the data on the printed circuit pattern obtained by the exposure simulator and the measured data on the printed circuit pattern provided by the pattern measuring SEM system to a matching process to calculate a position of data on a transfer circuit pattern in high correlation with the measured data on the printed circuit pattern provided by the pattern measuring SEM system through, for example, calculation of correlation, and the design data on the mask pattern and the measured data, on the printed circuit pattern, measured by the dimension measuring SEM system by replacing the calculated data on the printed circuit pattern with the design data on the mask pattern. The present invention calculates the accurate, specific evaluation indices necessary for OPC evaluation on the basis of a measured image of the printed circuit pattern, namely, a resist pattern. Thus, detailed evaluation of the circuit pattern which could not have hitherto been achieved can be achieved and the efficiency of photomask designing can be improved. Since the evaluation indices are quantitative, efficient evaluation is possible. These and other objects, features and advantages of the invention will become apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings. A dimension measuring SEM system capable of evaluating the quality of a minute resist pattern formed on a semiconductor wafer by a photolithographic process, a pattern shape evaluating system and a pattern shape evaluating method in preferred embodiments according to the present invention will be described with reference to the accompanying drawings. The present invention intends to quantify the difference between an image data, on a printed circuit pattern formed by a photolithographic process, measured by an electronic or optical microscope system and design data on a mask pattern and to calculate geometrical features representing the shape of a circuit pattern. Slight errors in a minute circuit pattern affect the performance of a semiconductor device. Therefore, the geometrical features of a resist pattern, namely, a printed circuit pattern formed by photolithography, must be accurately determined and hence it is desirable to superpose circuit pattern design data on a designed circuit pattern and measured pattern data on a resist pattern by an accurate a superposition process. However, in some cases, the shape of the resist pattern differs greatly from the design circuit pattern. In such a case, it is difficult to superpose the design circuit pattern and the resist pattern accurately. The present invention provides a superposing method capable of accurately superposing design data on the design circuit pattern and measured data on the resist pattern to calculate accurately geometrical features for the evaluation of the quality of a minute circuit pattern. OPC Evaluating Procedure FIG. 2 is a block diagram of an OPC evaluating procedure according to the present invention to be carried out by a photolithographic process. The flow of the steps of the OPC evaluating procedure will be described. A mask designing unit 517 shown in FIG. 5 designs a photomask pattern on the basis of design data 200 on a design circuit pattern of a desired design, taking into consideration an OPE in step 201. A photomask provided with the design circuit pattern is formed on the basis of the design data 200. An exposure system 519 shown in FIG. 5 exposes a resist film formed on a semiconductor wafer through the photomask to exposure radiation to form a latent image of the design circuit pattern in the resist film in step 202. The exposed resist film is processed by photolithography to form a resist pattern on the semiconductor wafer. A dimension measuring SEM system shown in FIG. 5 measures the resist pattern to obtain SEM image data in step 203. The dimension measuring SEM system is used to measure the resist pattern and to obtain the SEM image because the widths of component lines of the minute resist pattern formed on the semiconductor wafer are in the range of 80 to 100 nm or 30 to 65 nm. If the widths of the component lines are not less than about 100 nm, an image for dimensional measurement can be obtained by an optical microscope, such as an ultraviolet optical microscope. In step 204, an image processing unit 511 shown in FIG. 5 performs retrieving, collating and superposing operations to superpose a simulated circuit pattern provided by an exposure simulation process 206 based on the design data 200 provided by the photomask designing unit 517 or a CAD system and the SEM image provided by the dimension measuring SEM system in step 203 for a matching process. In step 205, the difference between the design circuit pattern conforming to the design data and the SEM image of the resist pattern is determined to evaluate the quality of the resist pattern. Results of evaluation of the resist pattern, namely, OPC evaluation indices for evaluating OPC points, are given to a workstation 515, namely, a controller. The results of evaluation are displayed on a screen of a GUI. If the resist pattern meets quality criteria, the semiconductor wafer is sent to the next process in step 209. If the resist pattern does not meet the quality criteria, information about the unacceptable resist pattern is fed back to the photomask designing unit 517 in step 208. Then steps 201 to 205 are repeated until a desired resist pattern is formed. The quality criteria are references for deciding whether or not the deviations of the data on the formed resist pattern from the design data are within the corresponding tolerances that ensure the normal operation of a desired circuit. The quality criteria are determined taking into consideration the operating characteristics of a designing circuit when the design data 200 is provided or in step 201 for designing the mask pattern. OPC evaluation will be described. CAD/SEM Superposing Process A method of positioning general measurement points on the dimension measuring SEM system stores the positional relation (directions and distances) of the evaluation points with respect to an aligned circuit pattern formed on the wafer and shifts a beam from the aligned circuit pattern to the evaluating point. When a high magnification, at which a measurement field is in the range of 0.5 to 5 μm, is used for OPC evaluation, the accuracy of superposition of the CAD data and the data on the resist pattern deteriorates due to an error in the movement of the stage or the beam from the alignment stage to the evaluation point. The CAD data and the data on the resist pattern are superposed by the following superposing process for the accurate superposition suitable for the minute OPC evaluation in an accuracy on the order of several nanometers. A superposing process for superposing the design data and the data on the SEM image of the resist pattern will be described. The evaluation of the quality of the resist pattern in step 205 shown in FIG. 2 is achieved through the determination of the difference between the design circuit pattern 300 defined by the design data and the SEM image 303 of the resist pattern. As shown in FIG. 3, the design circuit pattern 300 defined by the design data and the SEM image 303 of the resist pattern are superposed by a superposing step 304, and differences between the design circuit pattern 300 and the SEM image 303 are quantified. The superposing process is achieved by subjecting the design circuit pattern 300 and the SEM image 303 to a matching process. The design circuit pattern 300 and the SEM image are estranged greatly from each other in most cases due to the OPE of the exposure process. Consequently, in some cases, the superposition of the design circuit pattern 300 and the SEM image 304 results in failure or the design circuit pattern 300 defined by the design data and the SEM image 303 cannot be accurately superposed. It is desirable that the design circuit pattern 300 and the SEM image 303 of the resist pattern are accurately superposed. The present invention calculates a simulated circuit pattern 302 that may be formed when the resist film is exposed to exposure radiation through a photomask provided with the design circuit pattern 300 the by the exposure simulation process 206 (FIG. 2) executed by an exposure simulator included in the workstation 515. The simulated circuit pattern 302 and SEM image 303 of the resist pattern are subjected to a matching process 305 to improve the accuracy of positioning. The shape of the simulated circuit pattern 302 is closer to the SEM image 303 than that of the design circuit pattern 302 and hence the use of the simulated circuit pattern 302 instead of the design circuit pattern 300 is effective in improving the positioning accuracy. The superposing process will be described in connection with FIG. 3. The exposure simulator included in the workstation 515 calculates pattern data on the simulated circuit pattern 302 to be formed by simulation on the semiconductor wafer on the basis of the mask pattern data on a mask pattern 301 calculated by the photomask designing unit 517 on the basis of the design data defining the design circuit pattern 300. The calculated simulated circuit pattern 302 and the actual resist pattern 303 are subjected to the matching process to superpose the simulated circuit pattern 302 and the resist pattern 303 as indicated at 305. The positional relation between the simulated circuit pattern 302 calculated on the basis of the mask pattern 301, and the design circuit pattern 300 defined by the design data is known and is stored previously in the exposure simulator. For example, OPC evaluation to be made by the image processing unit 511 replaces the simulated circuit pattern 302 with the design circuit pattern 300 to superpose the design circuit pattern 300 and the resist pattern 303 as indicated at 304. A method of calculating the simulated circuit pattern formed by exposure simulation will be described with reference to FIG. 4. Mask data 401 and exposure conditions including the wavelength λ of exposure radiation, the numerical aperture NA of the objective lens, the apparent size σ of the light source (partial coherence) and at least one of conditions related with defocus are entered into the exposure simulator of the workstation 515 to calculate a light intensity distribution 403 when design photomask data is used for exposure. The exposure simulator included in the workstation 511 is provided with an input means for entering the mask data 401 and the exposure conditions. As shown in FIG. 5, the mask data 401 maybe entered by the photomask designing unit 517 through a network 516 into the exposure simulator of the workstation 515. The exposure conditions may be entered by the exposure system 519 through the network 516 into the exposure simulator of the workstation 515. The input means includes the photomask designing unit 517, the exposure system 519 and the network 516. The exposure simulator will be described. The exposure simulator calculates the light intensity distribution 403 shown in FIG. 4 that will occur when a design photomask, namely, a reticle, defined by the design photomask data is used on the basis of the mask data 401 on the photomask used for forming the resist pattern, namely, an object of measurement, and the exposure conditions. FIG. 13 shows an optical exposure system and an exposure simulation model. Light rays emerged from an illumination plane 1300 travel through a lens L1 (1301) and fall on a reticle 1302 provided with a mask pattern. The lens L1 (1301) and a lens L2 (1302) form an image of the illumination plane 1301 on a pupil plane 1304. The lens L2 (1303) and a lens L3 (1305) forms an image of the reticle 1302 on an object plane on an image plane 1306. The operations of the lenses of this optical system can be modeled by Fourier transform and inverse Fourier transform. A model from the illumination plane 1300 to the object plant 1302, a model from the pupil plane 1304 to the image plane 1306 correspond to Fourier transform and inverse Fourier transform, respectively. A picture surrounded by broken lines in FIG. 13 shows the flow of step of simulation based on such correspondence. Steps 1 to 6 of simulation will be described. Step 1: The shape 1307 of a light source is determined on the basis of conditions for illumination including the wavelength λ of light, the numerical aperture NA of the objective lens and the apparent size σ of the light source. Step 2: An illuminance distribution 1310 on the object plane is determined through the inverse Fourier transform of the shape 1307 of the light source. Step 3: The mask pattern 1309 (401) formed on the reticle is multiplied by the illuminance distribution 1310 calculated in step 2 to determine the illuminated state 1311 of the mask pattern. Step 4: The result of calculation in step 3 is subjected to Fourier transform 1312 to obtain a diffraction image 1314 of the mask pattern on the pupil plane. Step 5: The pupil plane 1313 is multiplied by the calculated data 1314 obtained in step 4 to determine a diffraction image 1315 behind the pupil plane. Step 6: The diffraction image 1315 determined in step 5 is subjected to inverse Fourier transform 1316 to obtain a circuit pattern 1317 on the image plane. The shape of the photomask formed on the reticle and the size of the pupil are specified optionally on the basis of the shape of illumination, the numerical aperture NA, the wavelength λ of the illuminating light, the apparent size σ of the light source and the design circuit pattern 300 defined by the design data. Then, the exposure simulator of the workstation 515 calculates the light intensity distribution 1317 (403) formed by exposure under the specified exposure conditions and using the photomask. The calculated light intensity distribution can be stored in, for example, a storage device 514. Description will be made of application of the calculated light intensity distribution 1317 (403) calculated by the exposure simulator of the workstation 515 shown in FIG. 5 to the superposition of the design data, namely, CAD data provided by the CAD system, and the SEM image. The exposure simulator of the workstation 515 slices of a part 402, corresponding to a light intensity, of the calculated light intensity distribution 1317 (403) and gives the sectional shape of the part 402 as a simulated circuit pattern 404 (302) to an image storage device 513. A CPU 512 included in the image processing unit (evaluation index calculating means) processes the simulated circuit pattern 404 stored in the image storage device 513 and the SEM image 303 of the resist pattern by a matching process to calculate superposing positions where the simulated circuit pattern and the resist pattern are superposed. A matching method to be carried out by the CPU 512 of the image processing unit 511, namely, the evaluation index calculating means, calculates an edge image from the images of the simulated circuit pattern and the SEM image, subjects the images to a matching process through the calculation of the correlation between the images, and uses a position that maximizes the value of correlation as a superposing position. Another method makes the exposure simulator of the workstation 515 take slices respectively corresponding to different light intensities 405 and calculate the sectional shapes of the slices, stores the sectional shapes in the image storage device 513, and makes the image processing unit 511 match each of the sectional shapes of the slices stored in the image storage deice 513 and the SEM image 303 of the resist pattern. This method is able to achieve matching the simulated circuit pattern 302 similar to the resist pattern and the SEM image 303 of the resist pattern. Thus the position of the simulated circuit pattern 302 for positioning the design circuit pattern 300 defined by the design data relative to the SEM image 303 of the resist pattern can be accurately determined and thereby the accuracy of superposition of the design circuit pattern 300 defined by the design data and the SEM image 303 of the resist pattern can be further improved. This matching method using image processing is not limitative. Thus the image processing unit 511 achieves the accurate superposition of the design circuit pattern 300 defined by the design data and the resist pattern 303. As shown in FIG. 4, the light intensity distribution 403 determined through exposure simulation is a light intensity distribution continuous in a surface of the wafer, namely, an X-Y plane in FIG. 4. The sectional shape 404 of a sliced part, corresponding to a proper light intensity, of the light intensity distribution 403, as compared with the design circuit pattern, is close to the SEM image (top-down view) of the resist pattern. The exposure simulator of the workstation 515 slices off parts of the light intensity distribution respectively corresponding to different light intensities and stores the sectional shapes of the sliced parts in the image storage device 513. The image processing unit 511 superposes the sectional shapes of the sliced parts on the SEM image of the resist pattern to select the sectional shape that is the closest to the SEM image. Accurate CAD-SEM superposition can be achieved by using the sectional shape thus selected for a CAD-SEM matching process for matching the design circuit pattern 300 defined by CAD data and the SEM image 303. More specifically, a light intensity at which a part of the light intensity distribution is sliced off is varied, edge images of the sections of sliced parts and an edge image of the SEM image of the resist pattern are matched for normalized correlation, and the result of matching of the SEM image of the resist pattern and the slice having the greatest value of correlation is used as a matching result. Dimension Measuring SEM System (Dimensional Circuit Pattern Evaluating System) A dimension measuring SEM system and peripheral devices for OPC evaluation according to the present invention will be described. FIG. 5 is a block diagram of the dimension measuring SEM system. In FIG. 5, components for exercising an OPC evaluating function of the dimension measuring SEM system are surrounded by broken lines. A resist pattern is formed by, for example, photolithography on a wafer 507 mounted on a stage 509. A SEM image of the resist pattern is formed. A primary electron beam 502 emitted by an electron gun 501 travels via a beam deflector 504, an ExB deflector 505 and an objective lens 506 and falls on the wafer 507 mounted on the stage 509. Then, the wafer 507 produces secondary electrons. The ExB deflector 505 deflects the secondary electrons produced by the wafer 507 and a secondary electron detector 508 detects the secondary electrons. A two-dimensional electron beam image, namely, a SEM image is formed by two-dimensional scanning with the primary electron beam 502 deflected by the deflector 504 or repetitive scanning in an X-direction by the electron beam deflected by the ExB deflector 505, and the detection of electrons produced by the wafer 507 provided with the resist pattern in synchronism with the continuous movement in a Y-direction of the stage 509 supporting the wafer 507 thereon. An A/D converter 510 converts a detection signal provided by the secondary electron detector 508 into a corresponding digital signal and sends the digital signal to an image processing unit 511. The image processing unit 511 has an image storage device 513 for temporarily storing a digital image represented by the digital signal, and a CPU 512 for calculating indices for OPC evaluation by using the image stored in the image storage device 513. A workstation 515 performs general control operations. Necessary operations of devices, exposure simulation (FIG. 13), and the confirmation of an OPC evaluation point input picture and calculated OPC evaluation indices can be achieved by a GUI. The storage device 514 and the workstation 515 are connected to an external network 516 to exchange data with external deices. The calculated OPC evaluation indices stored in the storage device 514 is fed back through the network 516 to the photomask designing unit 511 and the exposure system 519. Design data 601 on a design mask pattern provided by the CAD system, not shown, or the photomask designing unit 517 is stored in the storage device 514. Consequently, the image processing unit 511 can calculate the evaluation indices. Calculation of Evaluation Indices Evaluation indices to be calculated by the image processing unit 511 for detailed OPC evaluation will be described. Evaluation indices indicating the geometrical features of a resist pattern representing the quality of the resist pattern is needed in addition to the well-known dimensional measurement of the resist pattern, namely, the measurement of widths of lines forming the resist pattern. FIG. 6 shows evaluation indices by way of example. Referring to FIG. 6, a superposed image formed by superposing a SEM image 600 of a resist pattern stored in the image storage device 513 and a design circuit pattern 601 defined by design data stored in the storage device 514 is displayed on a display screen placed in the workstation 515. Evaluation indices 810 (FIG. 8) for OPC evaluation are, for example, a CD 602, a GAP 603, an interpattern distance 604, a rounding degree 605 of a corner (shape index) and a hole size 606. CDs 602 are the widths of lines forming the resist pattern. GAP 603 is the distance between a design position of an end part of a resist pattern and an actual position of the same end part receded from the design position due to OPE. Interpattern distance 604 is the distance between the adjacent circuit patterns. Rounding degree 605 is the degree of rounding of a corner of the resist pattern. Hole size 606 is the radius of a round hole or the major and the minor axis of an elliptic hole. These evaluation indices are only examples and any evaluation indices indicating the geometrical features of the resist pattern may be used. If the deviation of anyone of evaluation indices including a CD 602, a GAP 603, an interpattern distance 604, a rounding degree 605 of a corner and a hole size 606 from a design value is greater than a tolerance, it is possible that the device characteristics of a semiconductor device having a circuit formed by using the circuit pattern differ from desired device characteristics, the circuit malfunctions, the circuits on different layers of the semiconductor device are connected faultily and the circuit malfunctions. The present invention evaluates the quality of the resist pattern on the basis of the evaluation indices for detailed OPC evaluation. GUI Display Description will be made of input and output GUIs in, for example, the workstation 515 of the pattern measuring SEM system shown in FIG. 5, namely, a measuring instrument, for carrying out the method of OPC evaluation. Input Picture: Input of Measurement Points An input picture displayed by a measuring instrument for OPC evaluation will be described by way of example. That parts of a circuit pattern slight deviations of shapes of which from corresponding desired shapes cause fatal defects in device characteristics and unstable, fragile parts of a resist pattern susceptible to the variation of process conditions need to be inspected and evaluated. Those parts needing inspection and evaluation will be called fatal points. Fatal points are parts, having small process margin for forming a pattern that exhibits desired device characteristics that can be calculated through exposure simulation at the stage of designing a mask pattern. Positional information about the calculated fatal points on CAD data is stored in the storage device 514. When a resist pattern is evaluated after exposure, some or all of the fatal points are chosen as evaluation points. FIG. 7 shows an input picture to be displayed for the user is shown in FIG. 7 by way of example. The input picture shown in FIG. 7 includes a GUI 701 for assistance in choosing fatal points. A picture 718 of fatal points on design data is shown in GUI 701. An evaluation area 702 containing all or some of fatal points can be specified in the GUI 701. The input picture has an input GUI 707 for entering exposure conditions, including the wavelength λ of exposure light, the numerical aperture NA of the objective lens, the apparent size σ of the light source and at least one of conditions related with defocus, for simulation to achieve accurate matching of design data and a SEM image. The input picture has also an evaluation mode choosing picture 708. When an automatic measurement mode 709 is chosen, evaluation indices are calculated automatically from fatal points in the specified evaluation area 702. Optionally selected fatal points in the specified evaluation area 702 can be evaluated by specifying a measurement pattern type 711. For example, a measurement pattern type, namely, a line pattern 712 or a hole pattern 713, and measurement size, such as the widths of lines or the diameters of holes, can be specified. When the manual measurement mode 710 in the evaluation mode choosing picture 708 is chosen, fatal points to be measured and evaluation indices 714 can be manually specified. Thus OPC evaluation parts can be specified in the input picture. Output Picture: SEM-CAD Data Superposition and Evaluation Indices Indicating Method An evaluation indices indicating method of showing the calculated OPC evaluation indices to the user will be described. FIG. 8 shows a GUI output picture showing evaluation indices to be displayed on the screen of the workstation 515 by way of example. The present invention has an OPC evaluation information displaying function to display OPC evaluation information including all or some of displaying functions shown in FIG. 8. The output picture includes a SEM image 802 of a resist pattern, a design pattern 803 defined by design pattern data, results of simulation, and a GUI 801 indicating all or some of pattern tolerances in superposed images. The SEM image 802 is an image formed by measuring evaluation points of a resist pattern by the dimension measuring SEM system and stored in the image storage device 513. The design data 803 is superposed on the SEM image 802 on the basis of the result of superposition of the resist pattern and the SEM image 802 by the method illustrated in FIG. 3. The exposure simulator included in the workstation 515 shows the result of simulation in a superposed image of simulated circuit pattern 302 calculated on the basis of the mask pattern 301 and exposure conditions by the exposure simulator included in the workstation 515, and the SEM image 303. The GUI a picture formed by superposing a SEM image of the resist pattern, a maximum permissible pattern 901 and a minimum permissible pattern 902 as shown in FIG. 9 to facilitate recognizing pattern tolerances as OPC evaluation indices. The GUI 801 shown in FIG. 8 is also capable of displaying an image formed by superposing measurement points. Evaluation indices to be calculated for the measurement points, such as a CD 804, a GAP 805, an interpattern distance 807, a rounding degree 806 of a corner and a hole size 808, can be displayed in a partly or totally superposed image. All or selected one of evaluation indices, measurement points and measurements can be displayed. The output picture has also an evaluation mode choosing picture 809. When a photomask evaluation mode 816 is chosen, the calculated OPC evaluation indices are fed back to the photomask designing unit 517. When a process evaluation mode 817 is chosen, the calculated OPC evaluation indices are regarded as variations in the exposure conditions and, if the variations are greater than tolerances, an alarm signal is provided. A GUI 810 is used to specify evaluation indices to be calculated. Specified evaluation indices for the evaluation points determined by using the input picture are calculated. The calculated evaluation indices are displayed on the output picture. A GUI 815 is used to specify data to be displayed. Data that can be displayed in the GUI 815 are, for example, a SEM image 811, design data 812, simulation results 813 and pattern tolerances 814. The calculated evaluation indices are shown in the output picture or are stored in a storage medium. Thus the calculated OPC evaluation indices are displayed in the GUI. Process Evaluation A method of using the evaluation indices for process evaluation will be explained. In a mass-production line, deviation of parts of the SEM image of the resist pattern from the corresponding parts of a design pattern defined by the design data are quantitatively indicated by evaluation indices. FIG. 10 is a block diagram of a process evaluation procedure using evaluation indices. A semiconductor device fabricating process 1001 includes an exposure step 1002, a developing step 1003 and an etching step 1004. In a measuring step 1009, the dimension measuring SEM system measures a resist pattern formed on a wafer processed after the completion of the developing step 1003 and forms a SEM image of the resist pattern. In a superposing step 1010, the SEM image of the measured resist pattern is superposed on a design mask pattern 1006 defined by design data 1005. The superposing, step 1010 is similar to the method illustrated in FIG. 3. Differences of the superposed design data from the SEM image of the resist pattern are calculated. The calculated differences are used as evaluating values for evaluating the quality of the resist pattern. The quality of the resist pattern is evaluated on the basis of the evaluating values in an evaluating step 1011. When the formed resist pattern meets criteria, a step 1013 is executed. If the resist pattern does not meet the criteria for evaluation, the calculated differences are given to the exposure system 519 by a feedback operation 1012 to modify the exposure conditions or the evaluating values are given to the photomask designing unit 517 to modify the photomask design data. A reference numeral 1014 indicates the dimension measuring SEM system (the circuit pattern evaluating system) of the present invention having the OPC evaluating function. The criteria for evaluation are references for deciding whether or not the deviations of parts of the actual resist pattern from the corresponding parts of the design mask pattern defined by the design data are within the corresponding tolerances that ensure the normal operation of a circuit including a circuit pattern formed by using the resist pattern. FIG. 12 shows a resist pattern 1200 represented by evaluation indices within tolerances and a resist pattern 1205 represented by evaluation indices outside the tolerances by way of example. In the example shown in FIG. 12, the CD 1202 and the GAP 1203 are calculated. If deviations of parts of a resist pattern 1205 from corresponding parts of a design mask pattern 1206 defined by the design data are large and the CD 1207 and the GAP 1208 are outside the corresponding tolerances, it is decided that the resist pattern 1205 is unacceptable and the wafer provided with the unacceptable resist pattern is not sent to the next process. Then, a warning is given to warn the operator that the exposure conditions are inadequate and a defective resist pattern is formed. Information about the results of evaluation of the defective parts is displayed on the GUI. Names of the evaluation indices and evaluation indices are displayed. The operator corrects the exposure conditions defining the exposure process to be executed by the exposure system 519 with reference to the information about the results of evaluation. Thus the resist pattern can be minutely evaluated, the yield of mass-produced wafers can be improved, the calculated, detailed evaluation indices can be displayed on the GUI, the process can be efficiently evaluated and the load on the operator can be reduced. Superposition of Design Patterns Description will be made of a method of OPC evaluation in the present step (evaluating step) using measured data on the design pattern in the preceding or the succeeding step for OPC evaluation. Generally, a plurality of layered circuits are formed on a wafer. The circuit patterns on the different circuit layers need to be electrically connected to form a semiconductor device. The positional relation between the circuit patterns formed respectively by different circuit pattern forming processes is important. FIG. 11 shows parts of circuit patterns formed on different circuit layers by way of example. Referring to FIG. 11, a resist pattern 1105 represented by a SEM image is connected to a via hole 1100 formed in the succeeding process. The positional difference between the resist pattern 1105 and the via hole 1100 must be with in a tolerance. The OPC evaluating method of the present invention superposes a design pattern for the following process on the SEM image of the resist pattern to evaluate the connection of the circuit patterns on the different circuit layers. The superposition of the design pattern defined by the design data and the SEM image of the resist pattern is achieved by the foregoing superposing method to superpose the object resist pattern and the design data for the same layer on the resist pattern. The positional relation between the circuit patterns formed respectively on the different layers is included in the design data. Therefore, the design pattern defined by the design data for the following process can be superposed on the SEM image of the object resist pattern by replacing the design data with the design data for the layer to be processed by the preceding or succeeding process on the basis of the result of superposition of the resist pattern and the design data for the same layer. Evaluation indices include distances 1101 and 1102 between an end part 1100 of the resist pattern and a design pattern 1100 defined by the design data and the area 1103 of an overlapping part. The evaluation indices are examined to see if the evaluation indices are within the corresponding tolerances. Thus OPC evaluation can be achieved taking into consideration the connection of the patterns on the different layers. As apparent from the foregoing description, the present invention provides the dimension measuring SEM system capable of evaluating the shape of a pattern formed by lithography, proposes evaluation indices important for the miniaturization of design patterns for semiconductor devices, and provides a method of showing the operator the evaluation indices and a method of using the evaluation indices. The present invention achieves the accurate, minute OPC evaluation the importance of which is expected to increase with the miniaturization of design patterns for semiconductor devices, shows the result of evaluation so that the operator may be easily understand the results of evaluation to improve the efficiency of evaluation, and contributes to the early start of production of a variety of semiconductor devices in small lots. Thus the present invention has very high industrial applicability. The invention may be embodied in the specific forms without departing from the spirit or essential characteristics thereof. The present invention embodiment is therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. FIG. 2 200: Design data, 201: Mask formation, 202: Exposure, 203: Measurement, 204: Retrieval and collation, 205: Mask formation, 206: Exposure simulation, FIG. 3 1 (300) . . . Design data, 2 (301) . . . Mask pattern, 3 (302) . . . Simulated pattern (Result of simulation), 4 (303) . . . Resist pattern FIG. 4 1 . . . Light intensity FIG. 5 501: Electron gun, 502: Secondary electron beam, 503: Condenser lens, 504: Deflector, 505: ExB deflector, 506: Objective lens, 507: Wafer, 508: Secondary electron detector, 509: Stage, 510: A/D converter, 511: Image processing unit, 513: Image storage device, 519: Exposure system, 520: Controller, 517: Mask design processing unit FIG. 7 707: Exposure conditions, 708: Evaluation mode, 709: Automatic measurement, 710: Manual measurement, 711: Pattern type, 712: Pattern of lines, 713: Pattern of holes, 714: Evaluation index, 715: GAP, 716: CD, 717: Spacing 1 . . . Input list, 2 . . . Hot spot, 3 . . . Diameter of hole FIG. 8 809: Evaluation mode, 810: Evaluation index, 811: SEM Image, 812: Designd data (GDSII), 813: Result of simulation, 814: Pattern tolerance, 816: Mask evaluation, 817: Process evaluation 1 . . . Input table FIG. 10 1002: Exposure, 1003: Development, 1004: Etching, 1005: Design data, 106: Photomask pattern, 107: Exposure simulation, 108: Simulated pattern, 1009: Measurement, 1010: Superposition, 1011: Measurement FIG. 13 1307: Illumination, 1309: Mask, 1310: Luminance distribution on mask (?), 1311: Condition of illumination through mask (?), 1313: Pupil plane (Aberration/pupil) (?), 1314: Intensity distribution on pupil plane, 1315: Condition of illumination through pupil plane, 1317: Light intensity distribution
	summary
	summary
052079767	abstract	A fuel pellet surface defect inspection apparatus has an infeed conveyor, a discharge conveyor, and a slide and inspection assembly between the conveyors. The assembly includes a slide defining an inclined track having exit and entry ends adjacent the respective discharge and infeed conveyors. The entry end is at a higher elevation than the exit end. The assembly also includes an inspection station located along the track between its entry and exit ends. The station has lower and upper sound reflectors configured to define an annular inspection chamber through which a pellet moves as the pellet slides down the inclined track. The chamber completely encloses the cylindrical surface of the pellet as the pellet moves through the chamber. An ultrasonic inspection head is mounted at the station and transmits and receives sound energy to and from a pellet as it moves through the chamber such that the sound energy completely surrounds the moving pellet being inspected within the chamber. The inclined track has an upper portion extending to the inspection chamber and a lower portion extending from the inspection chamber and having a shallower slope than the upper portion to cause deceleration of a pellet as it moves from the upper portion to the lower portion. Deceleration reduces the velocity of the inspected pellet as it approaches the exit end of the track and thereby reduces the chance of impacts with the discharge conveyor that might otherwise produce chips and cracks in the pellets.

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