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abstract | When X-rays are projected to an X-ray sensor through a grid, a pitch of slits on the grid has a relationship such that a length obtained by multiplying an odd number to a half pitch of a projection image on the X-ray sensor is equal to a pitch of detection pixels of the X-ray sensor. X-rays passing through a sample to be measured via the grid are detected by the X-ray sensor. Levels of the detected X-ray detection signals are inputted into an operation process portion and subjected to an equalizing process for every pixel groups, each having even number of the detection pixels, continuously lined up in a pitch direction of the grid. As a result, irregularities of the levels of the X-ray detection signals can be corrected, and moires generated on an output screen of an image display portion can be removed. |
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043538630 | summary | This invention relates to a method for localizing a leaking rod in a nuclear fuel assembly, notably an irradiated assembly. Nuclear fuel is generally in the shape of sealed tubes enclosing a pellet stacking, and one or a plurality of plenums for collecting the gaseous fission products which are released from the pellets during the nuclear reactor operation. Said tubes which are called "rods" in this description, are assembled in clusters according to a regular array with a square or triangular geometry for instance, the whole unit forming a rod assembly. Under producing conditions, the nuclear reactor is stopped regularly to unload part of the assemblies, the most used ones, and replace same by green assemblies. For various reasons some rods may lose the tightness thereof during the reactor operation. Said rods then release radio-active fission products the accumulation of which in the primary cooling circuit of the reactor would cause the access thereto to be more and more difficult. This is one reason why the users of nuclear power plants perform an overhauling of said assemblies as they are removed from the reactors, notably when the radio-activity of the primary circuit thereof exceeds some predetermined standards. During such overhauling the leaking assemblies are separated from the safe assemblies. By "leaking assemblies" is thus meant such assemblies as defined above at least one rod of which does not have the required tightness. So-called "wet sipping" or "dry sipping" sweating methods are generally used to perform such an overhauling. Such methods are well known, notably from French Pat. Nos. 2,389,202 and 4,147,587. The assembly to be overhauled is arranged under such conditions that the contaminating by the radio-active gaseous fission products, of that water or gas which has directly contacted said rods, may be measured either by having said water or air pass a radiation detector, or by drawing gas or water samples in which the radio-activity is measured. As a rule the leaking assemblies even as they are not completely spent, are not loaded back in the nuclear reactor. Consequently the presence of a leaking rod may penalize a complete assembly, that is about 300 rods in a PWR-type reactor ("pressurized water reactor"), about 50 rods in a BWR-type reactor ("boiling water reactor"), and about 250 rods in a FBR-type reactor ("fast breeder reactor"). The presence of such leaking rods in some assemblies has thus a substantial financial influence on the operating costs of a nuclear power plant. Another problem which is perhaps of less financial importance but which will cause heavier and heavier safety restraints in the future, is the conveying of leaking assemblies and the receiving thereof in retreatment works. One essential object of this invention is to provide a method allowing to obviate the drawbacks which have been sketched above. For this purpose according to the invention, for each rod in an assembly, the radio-activity in at least two discrete rod rows in which said rod lies is measured and a leaking rod is localized by sensing a varying of the radio-activity in the tested rows where said rod lies relative to the radio-activity in an identical row of non-leaking rods. In a preferred embodiment of the invention, the radio-activity of the gaseous fission products accumulated in the rod plenum(s) is measured. Advantageously the .gamma.-radiation generated by said fission products is measured, but according to the invention, the method may also be applied when adding gaseous radio-active tracers, and in such a case the .gamma.-radiation generated by such tracers is measured. Said latter method is generally applied for a single rod (U.K. Pat. No. 1,499,113 and Belgian Pat. No. 640,220). The invention also pertains to an equipment for the working of the above method which comprises at least one radio-activity sensor arranged behind such a collimator that only the rod plenums lie in the viewing area of the sensor. In a particular embodiment according to the invention, the sensor and the assembly are so mounted as to be movable relative to one another along a direction substantially at right angle to the rod axis. |
abstract | In a method and device for facilitating a uniform loading condition for a plurality of support members supporting a steam dryer in a nuclear reactor, the device may include at least one or more actuators. Each actuator may be provided between a corresponding support member and a lower bearing surface of a portion of the dryer for lifting its corresponding dryer portion lower bearing surface relative to the support member. The device may include at least one or more measurement units. Each measurement unit may correspond to a given support member for measuring a displacement value between the corresponding support member and the lower bearing surface of its corresponding dryer portion. |
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040244202 | summary | BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a semiconductor atomic batteries and a method of making the same. 2. Description of the Prior Art Batteries were the first source of harnassed electric energy used by man and are still one of the most practiced sources of portable electric energy. Most batteries operate on the general principle of converting chemical energy directly into electric energy. As a result of this dependence on chemical reactors, the performance of most batteries can be affected adversely by temperature and pressure changes. In addition, the shelf life of such chemical batteries is relatively limited. Moreover, as a result of the build-up of chemical reaction products from the chemical reactions being utilized to produce electric current, the internal resistance of a chemical battery increases with use so that an increasing share of the electrical energy is dissipated as wasted energy in the battery itself rather than as useful energy in an external load. Another limitation of chemical batteries is the storage capacity of such batteries in terms of available electric energy per unit volume or per unit weight of a battery. For example, electric-powered vehicles have been generally impractical because of this factor. Many chemical batteries must be discarded after use. Those that can be recharged require inconveniently long charging times and can only be subjected to a limited number of charging and discharging cycles. Chemical batteries can be irreparably damaged by accidental short circuiting resulting from failure in the load circuit or structural failures in the battery itself from vibrations or severe accelerational forces. In the 1950's, a beta-ray radiosotropic battery was developed which was superior in a number of characteristics to the conventional chemical battery. Beta rays consist of a stream of high energy electrons. A beta-ray radio isotope battery can be constructed by using an emitter anode coated with a radio isotope that emits beta-rays (electrons) to a collector cathode that collects the electrons emitted from the radioactive anode. The emitter anode becomes positively charged as beta-rays (electrons with negative charges) leave it and the collector cathode becomes negatively charged as it absorbs these high energy electrons. Because the beta-rays have considerable energy and thus are able to overcome moderate electric field forces, such cells are capable of producing a high voltage if enough time elapses for charges to build up. With a large capacitor in parallel with the beta-ray radioisotope battery, enough charge can be accumulated to give output currents of 40 amps at zero voltage and lower currents at maximum voltages of 6000 volts after two months. Other means of transforming the energy emitted in radioactive decay into electrical energy have been developed in recent years. Flourescence/Photoelectric batteries achieve an indirect nuclear to electrical energy conversion by using radiation to excite fluorescent material and using the generated light to operate a photoelectric cell. The overall efficiency of this battery is very low because it utilizes two low efficiency processes. Thermoelectric type batteries use the heat output from a highly radioactive source and the thermoelectric effect to generate electrictty. These cells are generally designed to use radioactive sources of thousands of curies. Because of the low penetration ability of alpha particles, alpha particle emitters are used in these cells so that low radioactivity levels outside of the cell are obtainable without excess shielding. Gas ionization batteries have also been developed using particles emitted from a radioactive source to generate numerous ion pairs in the gas, the "electrolyte" of the battery. The anode and the cathode are metals that have a large contact potential difference between them so that an electric field exists between the anode and cathode. This field separates the positive and negative ions and causes them to drift to opposite electrodes where they are discharged and cause a current in the external circuit of the battery. The output of this type of cell gives about 1/2 volt and several microamps. Thermionic batteries have been constructed using the heat output from a radioactive source to liberate electrons from an anode with a low work function and to collect these same thermal electrons on a cold cathode. Efficiencies of up to 15 percent are possible with this type of battery. P-N junction batteries have been made by irradiating a P-N junction with Beta particles. The electron-hole pairs formed by the absorption of the high energy beta particles are separated by the built in field of the P-N junction and thereby produce a current. Relatively high efficiencies are possible because each high energy beta particle produce many electron-hole pairs. Finally, Compton scattering batteries have been made which employ gamma rays from a gamma emitter. In this battery the anode and the cathode are separated by an insulating material. Gamma rays emitted from a radioactive source separated from the anode knock electrons out of the insulator material with a preferential forward direction onto the anode where they are collected. The efficiency of this battery is very low. An object of this invention is to provide a new and improved semiconductor atomic battery which overcomes the deficiencies of the prior art. An object of this invention is to provide a new and improved semiconductor atomic battery which utilizes gamma ray and x-ray emissions from radioactive isotopes to generate electrical energy. Another object of this invention is to provide a new and improved battery which will operate at low temperatures. Another object of this invention is to provide a new and improved battery with a very long life. Another object of this invention is to provide a new and improved battery which can be recharged quickly by a simple exchange of fuel elements. Another object of this invention is to provide a new and improved battery unaffected by vibrations or accelerations. Another object of this invention is to provide a new and improved battery which will not be damaged by an accidental short circuit. Another object of this invention is to provide a new and improved battery which is light and small in size relative to the energy it produces. Another object of this invention is to provide a new and improved battery which is very rugged and extremely reliable and which is unaffected by environments such as vacuums, high pressures, corrosive atmospheres and the such and is undamaged by temporary exposures to high temperatures. Another object of this invention is to provide a new and improved battery whose internal resistances does not change with time. Another object of this invention is to provide a new and improved battery which is suitable for use as a power supply in an integrated circuit chip. Other objects of this invention will, in part, be obvious and will, in part, appear hereinafter. BRIEF DESCRIPTION OF THE INVENTION In accordance with the teachings of this invention, there is provided a deep diode, or semiconductor, atomic battery comprising a body of semiconductor material. The body has walls defining a central cavity to contain a radioactive gamma or x-ray emitter, a plurality of regions of first type conductivity and selective resistivity and a plurality of regions of second type conductivity and selected resistivity. The material of the second regions is recrystallized semiconductor material of the body and of the first regions and contains a substantially uniform level of an dopant impurity material throughout each second region and is sufficient to impart the second and opposite type conductivity thereto. P-N junctions are formed by the contiguous surfaces of pairs of regions of opposite type conductivity. Electrical contacts are affixed to the respective regions of first type conductivity and to the regions of second type conductivity which becomes the anode and cathode of the battery. The semiconductor atomic battery is energized by inserting a radioactive gamma or x-ray source into the central activity in the semiconductor body. The dimensions of the semiconductor body are large enough so that a large proportion of the gamma or x-rays emitted from the central cavity in the semiconductor body are observed by the semiconductor body thereby enabling the battery to have a high efficiency and a low level radioactivity level at its external major surfaces. The dimensions and geometry of the regions of first type conductivity and regions of second type conductivity are chosen so that the distance from any point in the regions of first or second type conductivities to the nearest P-N junction formed by the contiguous surfaces of these regions is less than the minority carrier diffusion length in these regions. The radioactive source has a high specific activity and the energy level of the gamma or x-rays is selected to be less than the energy necessary to cause displacement of atoms in the semiconductor material of which the battery is comprised to avoid radiation damage to the semiconductor body. The semiconductor atomic battery operates by the conversion of the gamma or x-rays emitted from the sources in the semiconductor body into electron-hole pairs on absorption by the surrounding semiconductor body. Because all points in the semiconductor body are within a minority carrier diffusion distance of a P-N junction, the majority of electron-hole pairs are separated by the the built-in field of the P-N junction before they recombine. The separated electron-hole pairs forward bias the P-N junction and thus deliver power to an electrical load connected to the battery. Each absorbed gamma ray produces a plurality of electron-hole pairs to boost the current of the battery. |
claims | 1. A spent fuel housing square pipe for housing a spent fuel aggregate therein, the square pipe comprising: four walls and four corners arranged so as to form a square cross section, the four walls including neutron-absorbing material and having a thickness capable of preventing the spent fuel inserted therein from reaching criticality and capable of ensuring sufficient strength at a time of falling down; and a connecting section formed on each of the four corners, at which diagonally adjacent square pipes are contacted with each other, wherein the connecting section is formed into a terrace shape having a plurality of steps, and when the steps of the terrace shape are formed to butt against the steps of adjacent square pipes when the square pipes are assembled in a staggered arrangement. 2. The spent fuel housing square pipe according to claim 1 , wherein an engaging portion which prevents an offset in a direction perpendicular to an axis of the square pipe is formed on a wall of each step. claim 1 3. The spent fuel housing square pipe according to claim 1 , wherein a flux trap structure is obtained by providing a space between an inner and an outer surfaces of the wall of the square pipe. claim 1 4. The spent fuel housing square pipe according to claim 3 , wherein a space is provided between an inner and an outer surfaces of the wall of the square pipe at the corners of the square pipe. claim 3 5. The spent fuel housing square pipe according to claim 4 , wherein a wall between the flux trap placed inside the terrace portion and the flux trap placed inside the side face is allowed to become thicker toward the butted side. claim 4 6. The spent fuel housing square pipe according to claim 1 , wherein a corner of the step has a sharp edge with the radius of the sharp edge being set to at least not more than one-half of thickness of a plate with which the square pipe is formed. claim 1 7. The spent fuel housing square pipe according to claim 1 , wherein a corner of the step is molded so as to have a sharper edge than the inside of the corner. claim 1 8. The spent fuel housing square pipe according to claim 6 , wherein the radius of the sharp edge is set to not more than 0.5 mm. claim 6 9. The spent fuel housing square pipe according to claim 7 , wherein the radius of the sharp edge is set to riot more than 0.5 mm. claim 7 10. The spent fuel housing square pipe according to claim 6 , wherein the sharp edge has a chamfered shape, with the chamfered dimension being set to at least not more than one-half of thickness of a plate with which the square pipe is formed. claim 6 11. The spent fuel housing square pipe according to claim 7 , wherein the sharp edge has a chamfered shape, with the chamfered dimension being set to at least not more than one-half of thickness of a plate with which the square pipe is formed. claim 7 12. The spent fuel housing square pipe according to claim 7 , wherein the sharp edge has a chamfered shape, with the chamfered dimension being set to not more than 0.5 mm. claim 7 13. The spent fuel housing square pipe according to claim 7 , wherein the sharp edge has a chamfered shape, with the chamfered dimension being set to not more than 0.5 mm. claim 7 14. The spent fuel housing square pipe according to claim 1 , wherein the square pipe is made of aluminum alloy to which at least enriched boron has been added. claim 1 15. A basket comprising: a plurality of square pipes according to claim 1 assembled in a staggered arrangement, wherein a cell for housing a spent fuel aggregate is formed in a space defined by walls of the square pipes. claim 1 16. The spent fuel housing square pipe according to claim 15 , wherein at least two adjacent connecting sections of the connecting sections formed on the four corners of the square pipe have engaging directions having a difference of 90 degrees. claim 15 17. The spent fuel housing square pipe according to claim 15 , wherein a flux trap structure is obtained by providing a space between an inner and an outer surfaces of the wall of the square pipe. claim 15 18. The spent fuel housing square pipe according to claim 17 , wherein a space is provided between an inner and an outer surfaces of the wall of the square pipe at the corners of the square pipe. claim 17 19. The spent fuel housing square pipe according to claim 18 , wherein a wall between the flux trap placed inside the terrace portion and the flux trap placed inside the side face is allowed to become thicker toward the butted side. claim 18 20. The spent fuel housing square pipe according to claim 15 , wherein a corner of the step has a sharp edge with the radius of the sharp edge being set to at least not more than one-half of thickness of a plate with which the square pipe is formed. claim 15 21. The spent fuel housing square pipe according to claim 15 , wherein a corner of the step is molded so as to have a sharper edge than the inside of the corner. claim 15 22. The spent fuel housing square pipe according to claim 20 , wherein the radius of the sharp edge is set to not more than 0.5 mm. claim 20 23. The spent fuel housing square pipe according to claim 21 , wherein the radius of the sharp edge is set to not more than 0.5 mm. claim 21 24. The spent fuel housing square pipe according to claim 20 , wherein the sharp edge has a chamfered shape, with the chamfered dimension being set to at least not more than one-half of thickness of a plate with which the square pipe is formed. claim 20 25. The spent fuel housing square pipe according to claim 21 , wherein the sharp edge has a chamfered shape, with the chamfered dimension being set to at least not more than one-half of thickness of a plate with which the square pipe is formed. claim 21 26. The spent fuel housing square pipe according to claim 20 , wherein the sharp edge has a chamfered shape, with the chamfered dimension being set to not more than 0.5 mm. claim 20 27. The spent fuel housing square pipe according to claim 21 , wherein the sharp edge has a chamfered shape, with the chamfered dimension being set to not more than 0.5 mm. claim 21 28. The spent fuel housing square pipe according to claim 15 , wherein the square pipe is made of aluminum alloy to which at least enriched boron has been added. claim 15 29. A spent fuel housing square pipe comprising: a plurality of square pipes assembled in a staggered arrangement, wherein a spent fuel aggregate is housed inside the square pipes and in a space defined by walls of the square pipes, wherein corners of walls of each square pipe is formed into a terrace shape having a plurality of steps and when assembling the square pipes the steps of the terrace shape of adjacent square pipes are butted against each other, and wherein a flux trap structure, which fits to the shape of the terrace portion, is formed inside of the square pipe is at least the wall or the terrace portion of the square pipe. 30. The spent fuel housing square pipe according to claim 29 , wherein a corner of the step has a sharp edge with the radius of the sharp edge being set to at least not more than one-half of thickness of a plate with which the square pipe is formed. claim 29 31. The spent fuel housing square pipe according to claim 29 , wherein a corner of the step is molded so as to have a sharper edge than the inside of the corner. claim 29 32. The spent fuel housing square pipe according to claim 30 , wherein the radius of the sharp edge is set to not more than 0.5 mm. claim 30 33. The spent fuel housing square pipe according to claim 31 , wherein the radius of the sharp edge is set to not more than 0.5 mm. claim 31 34. The spent fuel housing square pipe according to claim 30 , wherein the sharp edge has a chamfered shape, with the chamfered dimension being set to at least not more than one-half of thickness of a plate with which the square pipe is formed. claim 30 35. The spent fuel housing square pipe according to claim 31 , wherein the sharp edge has a chamfered shape, with the chamfered dimension being set to at least not more than one-half of thickness of a plate with which the square pipe is formed. claim 31 36. The spent fuel housing square pipe according to claim 30 , wherein the sharp edge has a chamfered shape, with the chamfered dimension being set to not more than 0.5 mm. claim 30 37. The spent fuel housing square pipe according to claim 31 , wherein the sharp edge has a chamfered shape, with the chamfered dimension being set to not more than 0.5 mm. claim 31 38. The spent fuel housing square pipe according to claim 29 , wherein the square pipe is made of aluminum alloy to which at least enriched boron has been added. claim 29 39. A spent fuel housing square pipe comprising: four walls and four corners arranged so as to form a square cross section, the four walls including neutron-absorbing material and having a thickness capable of preventing the spent fuel inserted therein from reaching criticality and capable of ensuring sufficient strength at a time of falling down; and combining section formed on each of the four corners at which diagonally adjacent square pipes are contacted with each other so that a plurality of square pipes are assembled in a staggered arrangement, for housing a spent fuel aggregate inside the square pipe and in a space defined by walls of the square pipes, wherein the combining section is formed into a terrace shape having a plurality of steps, and the steps of the terrace share are formed to butt against the steps of adjacent square pipes when the square pipes are assembled in a staggered arrangement. |
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claims | 1. An optical system, comprising:a Bragg reflector configured to diffract incident light having a wavelength between about 0.1 nm and about 0.7 nm; anda diffraction grating comprising parallel lines engraved on a surface of the Bragg reflector, wherein the diffraction grating is configured to diffract incident light having a wavelength between about 0.6 nm and about 150 nm. 2. The optical system of claim 1, wherein the Bragg reflector comprises a crystal. 3. The optical system of claim 2, wherein the crystal comprises a silicon monocrystal. 4. The optical system of claim 2, further comprising a metallic layer which covers the diffraction grating. 5. The optical system of claim 1, further comprising a metallic layer which covers the diffraction grating. 6. An optical measuring device, comprising: an optical system, comprising:a Bragg reflector configured to diffract incident light having a wavelength between about 0.1 nm and about 0.7 nm; anda diffraction grating comprising parallel lines engraved on a surface of the Bragg reflector, wherein the diffraction grating is configured to diffract incident light having a wavelength between about 0.6 nm and about 150 nm;means for emitting at least one incident light beam toward the surface of the diffraction grating, the at least one incident light beam having a wavelength between about 0.1 nm and about 150 nm;means for collecting at least one returned light beam from the surface of the optical system; andmeans for rotating the optical system with respect to the at least one incident light beam so that the returned light beam results from the diffraction of the at least one incident light beam by the optical system. 7. The optical measuring device of claim 6, wherein the Bragg reflector comprises a crystal. 8. The optical measuring device of claim 7, wherein the crystal comprises a silicon monocrystal. 9. The optical measuring device of claim 7, wherein the optical system further comprises a metallic layer which covers the diffraction grating. 10. The optical measuring device of claim 6, wherein the optical system further comprises a metallic layer which covers the diffraction grating. 11. The optical measuring device of claim 6, wherein the means emitting emits a polychromatic light. 12. A light diffraction optical method using an optical measuring device, wherein the optical medical device comprises: an optical system, comprising: a Bragg reflector configured to diffract incident light having a wavelength between about 0.1 nm and about 0.7 nm; and a diffraction grating comprising parallel lines engraved on a surface of the Bragg reflector, wherein the surface of the Bragg reflector defines a normal axis, and the diffraction grating is configured to diffract incident light having a wavelength between about 0.6 nm and about 150 nm; means for emitting at least one incident light beam toward a surface of the diffraction grating, the at least one incident light beam having a wavelength between about 0.1 nm and about 150 nm; means for collecting at least one returned light beam from the surface of the optical system; and means for rotating the optical system with respect to the at least one incident light beam so that the returned light beam results from the diffraction of the at least one incident light beam by the optical system, the method comprising the steps of:emitting the at least one incident light beam in a direction of incidence forming an angle of incidence relative to the normal axis; andcollecting the at least one returned beam from the optical system in a returned direction forming a return angle with respect to the normal axis. 13. The method of claim 12, wherein the angle of incidence is between about 5° and about 80° when the wavelength of the at least one incident light beam is between about 0.1 nm and about 0.7 nm, and wherein the angle of incidence is at least about 70° when the wavelength of the at least one incident light beam is between about 0.6 nm and about 150 nm. 14. An optical system, comprising:a Bragg reflector configured to diffract incident light having a wavelength between 0.1 nm and 0.6 nm; anda diffraction grating comprising parallel lines engraved on a surface of the Bragg reflector, wherein the diffraction grating is configured to diffract incident light having a wavelength that is greater than 0.6 nm and is less than or equal to about 150 nm. |
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061040347 | summary | The invention relates to an objective lens for influencing a particle beam, provided particularly an electron beam, with a magnetic single-pole lens and an electrostatic lens having a first and a second electrode which can be supplied with different potentials. BACKGROUND OF THE INVENTION Objective lenses of the general class to which the invention relates are used for example in electron beam probing and in other spheres of application of electron beam devices, such as microscopy, inspection, lithography, etc. The high-resolution objective lenses should have low aberration coefficients particularly in the low-voltage range. Therefore combined electric-magnetic pole piece objective lenses are known in the art which have low aberration coefficients and accordingly good low-voltage properties. An improvement to these known objective lenses is disclosed in EP-A-0 790 634, in which the magnetic lens is formed by a single-pole lens, an electrostatic retarding lens being disposed within the magnetic lens. The object of the invention is to improve the known objective lenses in such a way that even lower aberration coefficients are achieved. SUMMARY OF THE INVENTION According to the invention this object is achieved by disposing the electrostatic lens downstream of the magnetic single-pole lens in the direction of the particle. In a preferred embodiment the two electrodes of the electrostatic lens are constructed as tube electrodes, the first electrode being passed through the single-pole lens and the second electrode being disposed coaxially with the first electrode. By a slotted construction of one of the two electrodes, electrical multi-pole elements can be formed in a simple manner which can be connected and used for example as electrostatic deflectors, stigmators or other correcting elements. |
claims | 1. A pattern observation method for observing a pattern formed on an insulating film and having a concave pattern and a convex pattern, the method comprising:irradiating both of the concave pattern and the convex pattern in the pattern with a first observing charged particle beam, to obtain a temporary image of the pattern having region information of a convex pattern region corresponding to the convex pattern and region information of a concave pattern region corresponding to the concave pattern;irradiating the convex pattern region in the pattern with a first electric field forming charged particle beam having a first incident voltage for forming an electric field in the convex pattern region and irradiating the concave pattern region in the pattern with a second electric field forming charged particle beam having a second incident voltage for forming an electric field in the concave pattern region, wherein the second incident voltage is different from the first incident voltage, based on the region information of the convex pattern region and the region information of the concave pattern region respectively, thereby forming an electric field between a top surface of the convex pattern and a bottom surface of the concave pattern so that charged particles emitted from the bottom surface of the concave pattern when the bottom surface is irradiated with the charged particle beam may be drawn out of the pattern; andirradiating both of the concave pattern and the convex pattern in the pattern with a second observing charged particle beam after the electric field is formed, to obtain an image of the pattern having the information of the bottom surface of the concave pattern. 2. The pattern observation method according to claim 1, comprising:when irradiating the convex pattern region with the electric field forming charged particle beam having the first incident voltage based on a dimension of the convex pattern which is contained in the region information of the convex pattern region, shifting a focus position of the electric field forming charged particle beam having the first incident voltage toward an inside of the pattern so that a first beam diameter on the top surface of the convex pattern may be equal to the dimension of the convex pattern; andwhen irradiating the concave pattern region with the electric field forming charged particle beam having the second incident voltage based on a dimension of the concave pattern which is contained in the region information of the concave pattern region, shifting a focus position of the electric field forming charged particle beam having the second incident voltage toward an inside of the pattern so that a second beam diameter on the bottom surface of the concave pattern may be equal to the dimension of the concave pattern. 3. The pattern observation method according to claim 2, wherein as the charged particle beam, an electron beam is used. 4. The pattern observation method according to claim 1, wherein as the charged particle beam, an electron beam is used. 5. The pattern observation method according to claim 4, whereinthe first incident voltage has a secondary electron emission coefficient larger than one, andthe second incident voltage has a secondary electron emission coefficient smaller than one. 6. The pattern observation method according to claim 4, wherein the first observing charged particle beam and/or the second observing charged particle beam have the incident voltage whose secondary electron emission coefficient is one. 7. The pattern observation method according to claim 4, whereinthe insulating film is a silicon oxide film,the first incident voltage is higher than 100 V and lower than 2000 V, andthe second incident voltage is lower than 100 V or higher than 2000 V. 8. The pattern observation method of claim 1, wherein the bottom surface of the concave pattern region is insulated. 9. A pattern observation method for observing a line and space pattern formed on an insulating film and having a line pattern and a space pattern, the method comprising:irradiating both of the line pattern and the space pattern in the line and space pattern with a first observing electron beam, to obtain a temporary image of the line and space pattern having region information of a line pattern region corresponding to the line pattern and region information of a space pattern region corresponding to the space pattern;irradiating the line pattern region with a first electric field forming electron beam having a first incident voltage for forming an electric field in the line pattern region and irradiating the space pattern region with a second electric field forming electron beam having a second incident voltage for forming an electric field in the space pattern region, wherein the second incident voltage results in a smaller secondary electron emission coefficient than that by the first incident voltage, based on the region information of the line pattern region and the region information of the space pattern region respectively, thereby forming an electric field between a top surface of the line pattern and a bottom surface of the space pattern so that secondary electrons emitted from the bottom surface of the space pattern when the bottom surface is irradiated with the electron beam may be drawn out of the line and space pattern; andirradiating both of the line pattern and the space pattern in the line and space pattern with a second observing electron beam after the electric field is formed, to obtain an image of the line and space pattern having the information of the bottom surface of the space pattern. 10. The pattern observation method according to claim 9, comprising:when irradiating the line pattern region with the electric field forming electron beam having the first incident voltage based on a line width of the line pattern which is contained in the region information of the line pattern region, shifting a focus position of the electric field forming electron beam having the first incident voltage toward an inside of the line and space pattern so that a first beam diameter on the top surface of the line pattern may be equal to the line width of the line pattern; andwhen irradiating the space pattern region with the electric field forming electron beam having the second incident voltage based on a line width of the space pattern which is contained in the region information of the space pattern region, shifting a focus position of the electric field forming electron beam having the second incident voltage toward an inside of the line and space pattern so that a second beam diameter on the bottom surface of the space pattern may be equal to the line width of the space pattern. 11. The pattern observation method according to claim 10, whereinthe first incident voltage has a secondary electron emission coefficient larger than one, andthe second incident voltage has a secondary electron emission coefficient smaller than one. 12. The pattern observation method according to claim 10, wherein the first observing electron beam and/or the second observing electron beam have the incident voltage whose secondary electron emission coefficient is one. 13. The pattern observation method according to claim 10 whereinthe insulating film is a silicon oxide film,the first incident voltage is higher than 100 V and lower than 2000 V, andthe second incident voltage is lower than 100 V or higher than 2000 V. 14. The pattern observation method according to claim 9, whereinthe first incident voltage has a secondary electron emission coefficient larger than one, andthe second incident voltage has a secondary electron emission coefficient smaller than one. 15. The pattern observation method according to claim 9, wherein the first observing electron beam and/or the second observing electron beam have the incident voltage whose secondary electron emission coefficient is one. 16. The pattern observation method according to claim 9, whereinthe insulating film is a silicon oxide film,the first incident voltage is higher than 100 V and lower than 2000 V, andthe second incident voltage is less than 100 V or higher than 2000 V. 17. The pattern observation method of claim 9, wherein the bottom surface of the space pattern region is insulated. 18. A pattern observation method for observing a two-step hole pattern formed on an insulating film and having a first hole pattern and a second hole pattern formed in a bottom surface of the first hole pattern, the method comprising:irradiating an entire observation region in the two-step hole pattern with a first observing electron beam, to obtain a temporary image of the two-step hole pattern having region information of a first region corresponding to a top surface of the two-step hole pattern, region information of a second region corresponding to a bottom surface of the first hole pattern, and region information of a third region corresponding to a bottom surface of the second hole pattern;irradiating the first region with a first electric field forming electron beam having a first incident voltage for forming an electric field in the first region, the second region with a second electric field forming electron beam having a second incident voltage for forming an electric field in the second region, wherein the second incident voltage results in a secondary electron emission coefficient smaller than that by the first incident voltage, and the third region with a third electric field forming electron beam having a third incident voltage for forming an electric field in the third region, wherein the third incident voltage results in which gives a secondary electron emission coefficient smaller than that by the second incident voltage, based on the region information of the first region, the region information of the second region, and the region information of the third region, to thereby form an electric field between the top surface of the two-step hole pattern and the bottom surface of the first hole pattern and an electric field between the bottom surface of the first hole pattern and the bottom surface of the second hole pattern so that secondary electrons emitted from the bottom surface of the first hole pattern and the bottom surface of the second hole pattern when they are irradiated with the electron beam may be drawn out to an outside of the two-step hole pattern; andirradiating the entire observation region in the two-step hole pattern with a second observing electron beam after the electric field is formed, to obtain an image of the two-step hole pattern having the information of the bottom surface of the first hole pattern and the bottom surface of the second hole pattern. 19. The pattern observation method according to claim 18, wherein the first observing electron beam and/or the second observing electron beam have the incident voltage whose secondary electron emission coefficient is one. 20. The pattern observation method of claim 18, wherein the bottom surface of the second hole pattern is insulated. |
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abstract | A portable and modular shielding system having various modular wall components that can be interconnect to form a custom designed wall configuration, wherein the resulting wall provides shielding from radiation at its joints of two adjacent modular wall components as well as along its entire length. The principal modular wall component has a main container being generally rectangular in shape and a connector container being an elongated cylinder having a cross section that is generally circular in shape and being integrally connected to the second end of the main container. The first end of the main container is concave in shape and adapted to correspond to the generally circular shape of the connector container. A shielding wall is formed by interconnecting a connector container of a first modular wall component into a first end of a second modular wall component. The main container and connector container are hollow and are adapted to be filled with a filler material. |
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description | This application is a national stage application of PCT-application number PCT/CA2017/050689 filed on Jun. 6, 2017, which claims priority of Canadian patent application No. 2,955,469 filed on Jan. 20, 2017, both of which disclosures are incorporated herein by reference. This invention relates to hazardous materials, for example radiopharmaceuticals. In particular this invention relates to a pig for storing, transporting and dispensing of liquid and capsules formulations of biohazardous products and substances in liquid and solid form, for example radiopharmaceuticals. The transportation of biohazardous materials and substances, for example radioactive materials or biological substances such as pathogens, presents a potentially dangerous situation and must be subject to strict controls. For example, radioactive pharmaceutical products, commonly known as “radiopharmaceuticals,” are prepared for patient injection, ingestion or other forms of administration in specially equipped and controlled facilities. Radiopharmaceuticals are well known for use as markers in nuclear medicine diagnostic procedures, and to treat certain diseases. Unless properly shielded, such products become a radiation hazard for individuals handling the product. For example, radioiodine pills or capsules that can be used for treating certain pathologies such as thyroid diseases or in conjunction with a diagnostic procedure to diagnose certain types of illnesses, are stored before use in a container typically made of plastic, for example a polyethylene pill bottle. In the case of a liquid radiopharmaceutical the container is typically a glass vial. Neither of these containers have any radioactivity-shielding properties. Therefore the storage, transportation and dispensing of radiopharmaceuticals is carefully controlled by rules designed to regulate the handling of such materials in a manner that reduces the radiation hazard. Each metered (for example assayed or calibrated) dose of the radiopharmaceutical product, for example in the case of a treatment for thyroid issues a radioiodine pill, or in the case of isotopes used in Nuclear Medicine (SPECT) and positron emission tomography (PET) diagnostic procedures a liquid, is placed by the manufacturer into the container to be shipped to a qualified facility for administration to a particular patient or patient category. At the radiopharmacy stock vials of different radiopharmaceuticals are dispensed as unit doses. This represents the first opportunity for hazardous exposure to the radioactive contents, and accordingly is effected at the manufacturer in a shielded booth or other enclosure, or under other radioactivity-shielded conditions. The container containing the radiopharmaceutical must then be shipped to the destination hospital or clinic for administration to the patient. To effect this safely, the container is dropped into a radioactivity-shielding container commonly known as a “pig” for interim storage and delivery to the destination. A conventional pig comprises a two-part vessel which is either formed from a radioactivity-shielding material, for example lead or tungsten, or has an exterior shell encasing a radiopharmaceutical container compartment that is lined with a radioactivity-shielding material such as lead or tungsten. A non-limiting example is described and illustrated in U.S. Pat. No. 6,586,758 issued Jul. 1, 2003 to Martin, which is incorporated herein by reference in its entirety. When the pig is assembled, the radiopharmaceutical container compartment is sealed in order to contain the radiation and thus minimize human exposure to the radioactive contents of the radiopharmaceutical compartment. The compartment is sized to accommodate the radiopharmaceutical product, in the ingestible radioiodine example a pill or dissolving capsule, or in the case of a liquid of radiopharmaceutical a vial, syringe, ampule or other glass container. In each case the radiopharmaceutical compartment would be dimensioned accordingly. Once the radiopharmaceutical container has been placed into the radiopharmaceutical compartment and the pig assembled, the pig is ready to be shipped to the patient's location. Because this part of the delivery process occurs entirely within the confines of the manufacturing plant, which is specifically designed and staffed so as to meet all regulatory guidelines and procedures, there is less chance of human exposure to the radioactive radiopharmaceutical product up to the point that the pill, capsule, vial, syringe or the like is sealed in the radiopharmaceutical container compartment of the pig. As is well known, the pig is designed to provide optimal shielding so as to reduce exposure during shipping. The transportation phase is a second opportunity for exposure to the radioactive contents of the radiopharmaceutical container, posing an occupational exposure opportunity for the driver/courier. At the destination staff trained in handling radioactive substances, for example a nuclear medicine technologist or technician, opens the pig and then removes the closure from the radiopharmaceutical container to vent the container bottle. This is the third opportunity for exposure to the radioactive contents of the radiopharmaceutical container, in the presence of hospital or clinic staff. The technologist must transfer the radiopharmaceutical to a Dose Calibrator to assay (measure) the activity of the radiopharmaceutical, which must be within 10% of prescribed activity. After recording the assay, the technologist must retrieve container containing the radiopharmaceutical and return the radiopharmaceutical container to the pig's radiopharmaceutical container compartment, which is the third opportunity for exposure to radioactivity. The technologist then applies the lid to the pig for delivery to the patient. The pig is opened in the patient's presence in order to gain access to the radiopharmaceutical container and remove the container closure for administration of the radiopharmaceutical product to the patient, providing a fourth opportunity for exposure to the radioactive contents of the radiopharmaceutical container. In this step exposure of radioactivity to the ambient environment is unavoidable in order to access the radiopharmaceutical product for administration to the patient, so great care must be taken to handle the unshielded radiopharmaceutical product using proper safety equipment and procedures. However, the assaying process, and the venting of the container in the case of certain volatile radioactive substances which produce radioactive iodine vapours such as 131 Iodine capsules, can present unnecessary points of risk of exposure to the technologist and other staff. Although the types of destination facilities to which these products are shipped are equipped to properly handle radiopharmaceutical products and the staff at such facilities are well trained in safety policies and procedures, this step in particular can increase the risk of human exposure to the radioactive contents of the radiopharmaceutical product. There is accordingly a need for a radiopharmaceutical pig that reduces opportunities for human exposure to the contents of the container when the pig reaches a hospital or clinic setting and the product in the container is exposed to the ambient environment. In accordance with an aspect of the invention, there is provided a pig for transporting a container of biohazardous material, wherein the container comprises a bottle and a bottle closure, the pig comprising: a body comprising a compartment dimensioned to receive the container; a cap attachable to the body for closing the compartment thereby to shieldingly contain the biohazardous material in the container, the cap comprising: a collar sealingly engageable with the body and having an opening therethrough in communication with the compartment thereby to provide access to the bottle closure; a cap closure sealingly engageable within the opening of the collar to sealingly close the opening and cause the bottle closure to be gripped within the cap, wherein when the collar is disengaged from the body while the cap closure is engaged within the opening of the collar, the container remains gripped within the cap. In an embodiment, the pig comprises a compression member dimensioned to be positioned intermediate the bottle closure and the annulus, the compression member being compressed against the bottle closure by the annulus while the cap closure is sealingly engaged within the opening of the collar. According to another aspect of the invention, there is provided a system for transporting and providing access to a biohazardous material, the system comprising the pig; and an insert sealingly engageable within the opening of the collar while the cap closure is removed, the insert comprising an injection port extending fully therethrough in axial alignment with the compartment thereby to guide insertion of a syringe centrally through the container closure and into the container. According to another aspect of the invention, there is provided a compression member for insertion into a pig for transporting a container of biohazardous materials, the compression member comprising: a flange; and spaced apart fingers supported by the flange and together forming a circle, the fingers each having a substantially vertical component extending upwards from the flange and a substantially horizontal component extending inwards from an end of the substantially vertical component distal from the flange, the spaced apart fingers resiliently compressible inwardly against the container by compressive engagement of a complementary annulus of the pig into which the compression member is dimensioned to be inserted. The invention relates to a pig 20 for transporting a container 10 containing a biohazardous product. The advantages of the invention are particularly applicable in the case of radiopharmaceuticals, whether in solid or liquid form. However, the pig 20 may be configured to be suitable for transporting virtually any type of radiopharmaceutical product, and is also suitable for transporting other types of biohazardous products or substances such as biological pathogens. One or more advantages can be obtained in the use of a pig according to the invention for storing and transporting any kind of biohazardous product where access to the internal (non-protective) container holding the biohazardous product is required intermittently. The embodiments of the invention described herein are for purposes of example only and the invention is not intended to be limited to the specific embodiments described. A biohazardous materials container, for example a radiopharmaceutical container 10 as shown, comprises a bottle 12 and a closure 14 for sealing the bottle 12. The container 10 may be made of any suitable material, typically plastic or glass depending upon the type and form of radiopharmaceutical contained therein. For example in the embodiment shown in FIG. 2 the container 12 is a glass vial containing a liquid radiopharmaceutical 2. The cap 30 of the pig 20 is configured 1) to allow the container 10 to be removed from the body 22 of the pig 20 while secured to (and thus in part shielded by) the cap 30, and 2) to allow the closure 14 to be removed from the bottle 12 without opening the pig 20 in order to avoid exposing the user to the radioactive contents of the product, as described in detail below. In the embodiment shown the bottle 12 comprises a bead 12a about its neck, and the closure 14 is a stopper-type closure having a body 14a which closes the neck of the bottle 12 in an interference fit. In other containers 10 the closure may be clinched to the neck of the bottle 12. In the case of liquids the closure 14 is typically provided with a generally central septum 14b (see FIG. 12) for penetration by a syringe in order to extract the contents of the bottle 12. The pig 20 in the embodiment illustrated a radiopharmaceutical pig 20, comprises a cylindrical body 22 and a complementary cylindrical cap 30 for attachment to the body 22. The components of the radiopharmaceutical pig 20 shown may be formed from a radioactivity-shielding material such as lead or tungsten, or may be formed from any suitably strong metal or plastic. In the case of the radiopharmaceutical pig 20 shown the portions surrounding the compartment 24 are lined with a suitably radioactivity-resistant liner formed from a material such as lead or tungsten. If the pig is used to transport toxins, biological pathogens or other non-radioactive products or substances, the compartment 24 may be hermetically sealed when the pig 20 is closed to prevent exposure to the ambient environment. The body 22 comprises a recess concentric with and overlying the radiopharmaceutical container compartment 24, forming a throat 23 which provides projecting cams 25 along its interior wall, as best seen in FIG. 4. The cap 30 comprises a two-stage closure for sealing the biohazardous container compartment 24 against radioactivity leakage. The first body closure stage comprises an outer collar 30a that fits within the throat 23 of the body, which when secured to the body 22 extends into and sealingly engages with the throat 23. In the embodiment illustrated the collar 30a comprises a projecting collar neck portion 31 that provides external projecting cams 31a, best seen in FIG. 5, which are complementary to the cams 25 about the throat 23 and positioned so that when the neck 31 of the collar 30a is secured into the throat 23 above the biohazardous materials container compartment 24 by partial (e.g. 60 degree) rotation in a ‘bayonet’ connection, the lower edge 31b of the neck 31 sealingly engages against the floor 27 of the throat 23 around its periphery and prevents radioactivity from escaping around the collar 30a. The collar 30a comprises an orifice 29 extending through the body and neck 31 of the collar 30a, in communication with the biohazardous materials container compartment 24. The upper portion of the orifice 29 provides a larger diameter and projecting cams 31d (see FIG. 7) disposed about its interior surface, for receiving the cap closure 30b as described below. The orifice 29 narrows as it approaches the neck 31, creating a ledge 31c at an intermediate point for sealing engagement by the cap closure 30b. In some embodiments the narrower lower portion of the orifice 29 is adapted to receive a compression, or “grip”, member 50 that functions to grip closure 14 as will be described below. The cap closure 30b provides a cap closure neck 33 that fits into the orifice 29. In the embodiment illustrated the cap closure 30b comprises a projecting closure neck portion 33 that provides external projecting cams 33a, best seen in FIG. 6, that are complementary to the cams 31d and positioned so that when the closure neck 33 is secured into the orifice 29 by partial (e.g. 60 degree) rotation in a ‘bayonet’ connection, the lower surface 33b of the neck 33 sealingly engages against the ledge 31c of the orifice 29 around its periphery and prevents radioactivity from escaping through the orifice 29. The cap closure 30b attaches to the collar 30a in a compressive motion, such that the container closure 14 is gripped by the annulus 35 of the closure 30b. Although a bayonet fitting arrangement is a particularly convenient means of compressively attaching the cap closure 30b to the collar 30a, these components may be attached together in any other suitable manner that provides a compressive motion of the cap closure 30b relative to the collar 30a, for example by threading. Also, in the embodiment shown the body 22 and cap 30 have a cylindrical exterior, which simplifies the provision of a bayonet connection, however any other convenient configuration may be used with a closure mechanism suitable for substantially preventing leakage of radioactivity from the pig 20. To improve the gripping action of the cap closure 30b compressed against the collar 30a, the somewhat resilient grip 50 may be disposed in the orifice. In the embodiment shown the grip 50 comprises a flange 51 supporting spaced apart fingers 54 that form a circle complementary to the inner wall of the annulus 35, as best seen in FIG. 6. The fingers 54 each have a substantially vertical component extending upwards from the flange 51 and a substantially horizontal component extending inwards from the end of the substantially vertical component thereby to overlap the container closure 14 to a degree as illustrated. In this embodiment the annulus 35 projects from the lower edge 33b of the closure neck 33 into the narrower portion of the orifice 29 in a clearance fit, as shown in FIG. 6, and instead of engaging the container closure 14 directly the annulus 35 defines a recess 35a adapted to engage the grip 50, best seen in FIGS. 6 to 10. In particular, when the cap closure 30b is attached to the collar 30a the annulus 35 compressively engages the fingers 54 of grip 50 to collapse the fingers 54 toward each other against their tendency to remain substantially vertical (that is, to tilt fingers 54 inwardly against their bias) and grip the container closure 14, as shown in FIG. 12. When the cap closure 30b is disengaged from the collar 30a the annulus 35 does not compress the fingers 54 inwards against the container closure 14 thus permitting fingers 54 to spread apart again as per the resiliency to remain substantially vertical (that is to enable fingers 54 to tilt outwardly again to the substantially vertical orientation to which they are biased) enabling the top of container closure 14 to be more exposed through the orifice. The grip 50 may be formed from a semi-compressible material such as plastic (such as a thermoplastic such as Delrin™ available from Dupont Corporation of Wilmington, Del., U.S.A. or polypropylene) or silicone, and has an external profile allowing it to fit snugly within the recess 35a of the annulus 35, and an internal profile allowing the closure 14 of the biohazardous container 10 to fit snugly within the grip 50, as shown in FIG. 12. The grip 50 may be provided with a pattern of openings, increasing the overall compressibility of the grip 50 and reducing its cost. The lower end of the annulus 35 has a slightly diverging wall which is drawn downwardly against the grip 50 as the collar 30a is engaged to the body 22, compressing the grip 50 slightly. The grip 50 thus provides a buffer between the incompressible interior surface of the annulus 35 and the container closure 14, which in the example shown is a stopper engaged with the neck of the container 12 in an interference fit thereby capping the container 12. This both allows the closure 14 to be held securely by the cap 30 and, where the biohazardous container 10 is made of glass, potentially avoids breakage. As in the embodiment illustrated the grip 50 may be frictionally and secured to the collar by lugs 52 projecting into complementary bores 31e formed in the lower edge of the neck 31 of the collar 30a thereby to inhibit rotation and translational exit from the bores 31e. In other embodiments (not shown) the periphery of the flange 51 may snap-fit onto the recess 37 formed in the bottom surface of the collar 30a (see FIG. 6), for example by proving a slight reverse-chamfer in the recess wall so it converges toward the lower limit of the collar 30a, retaining the flange 51, which avoids having to line up the lugs 52 with bores 31e. The grip 50 can be supplied in a single-use sterile package for the plastic piece, or can be pre-loaded to vial and both sterilized together. Different sizes of vial would dictate a corresponding change in the diameter of the compartment 24, but such vials tend to have a standard neck and same septum circumference and in such cases the same size of cap 30 and grip 50 can be used. In the case of the radiopharmaceutical pig 20 shown, the assembled cap 30 and body 22 thus provide a radioactively-shielded compartment 24, for shielding the radioactive contents of the radiopharmaceutical container 10 contained when sealed into the radiopharmaceutical compartment 24. In the embodiment shown the compartment 24 is defined by a cavity formed largely within the body 22 which is sized to receive the bottle 12 in a close fit, preferably a clearance fit but alternatively an interference fit, however the compartment 24 may be formed by defined by suitably sized and aligned adjoining cavities formed respectively in the body 22 and the cap 30. Thus, when the closure remover 34 is seated over the compartment 24 it closes the cap opening 32 in order to radioactively seal the radiopharmaceutical compartment 24. Also, when the cap 30 is removed from the body 22 it is possible to manipulate the sealed container 10 by handling only the cap 30, thereby shielding the technologist's extremities from radiation. To preserve a radiopharmaceutical pill (not shown), the bottle 12 optionally may be provided with fins (not shown) that confine the pill 2 to an axially central portion of the container 10 and thus reduce the amount of pill surface touching the bottle 12. In use of the embodiment shown, a radiopharmaceutical liquid or solid material (e.g. a pill) is placed into the bottle 12 using conventional techniques and equipment to avoid exposure to staff. A radioisotope solution 2 in a glass bottle 12 is illustrated in FIG. 2. In the case of a liquid radiopharmaceutical product the vial typically arrives already filled with the radioactive liquid. The closure 14 may optionally be designed to accommodate a desiccant or other product-stability material or method (not shown) in order to control the humidity within the container 10. The closure 14 is applied to the container 10 which is then placed into the container compartment 24. The cap 30 is placed on the body 22 of the pig 20 and rotated in the closing direction to engage the cams 25, 31a and to seal the cap 30 tightly to the body 22, confining radioactivity from the pill 2 within the container compartment 24. The pig 20 can then be transported to the patient's facility for administration of the biohazardous material, in the example shown a liquid radioisotope. When the pig 20 arrives at the destination, the pig 20 is taken to a room designed to contain the radioactivity and protect staff, as is conventional. The technician grasps the collar 30a and ensures that the cap closure 30b is fully rotated in the direction that locks it to the collar 30a, clockwise in the embodiment illustrated as indicated by the ‘pick up vial’ arrow in FIG. 1. This lodges the container closure 14 into the annulus 35, where a grip 50 is used squeezing the grip 50 against the container closure 14, to lock the container 10 to the cap 30. The technician then grasps the body 22 and rotates the cap 30 collar (30a and cap closure 30b together) to remove the cap 30 from the body 22 with the container closure 14 lodged in the annulus 35 (or where a grip 50 is used, in the grip 50), and lifts the cap 30 off the body 22 as shown in FIG. 3. Where the biohazardous material is a liquid and the cap 14 of the bottle (typically a vial) 12 provides a septum 14b or other entry orifice for a syringe (not shown), the closure 30b can be removed from the collar 30a to expose the top of the container closure 14 and allow the insertion of a syringe without releasing the vial from the collar 30a. A tungsten insert 60, for example as shown in FIG. 13A, may be provided to replace the cap closure 30b. The insert 60 comprises a head 62 and a neck 64 that fits into the orifice 29 in the collar 30a. In the embodiment illustrated the neck 64 of the insert 60 provides external projecting cams 66 that are complementary to the cams 31d and positioned so that when the insert 60 is secured into the orifice 29 by partial (e.g. 60 degree) rotation in a ‘bayonet’ connection, the lower surface of the neck 64 sealingly engages against the ledge 31c of the orifice 29 around its periphery. The syringe may be inserted into the septum through an injection port 68 extending fully through the insert 60 in axial alignment with the compartment 24 of the body 22. In this embodiment, the injection port 68 is cylindrical and has a single diameter throughout its length. The insert 60 provides enhanced radiation protection while dispensing from multi dose vial (stock) due to its smaller-diameter injection port 68 through a head 62 and neck 64 of tungsten, as well as guidance for a syringe to be inserted centrally into the container 10 through the container closure 14. In alternative embodiments, the injection port may be frustoconical. An alternative tungsten insert 60A is shown in FIG. 13B. In this embodiment, tungsten insert 60A has an injection port 68A that has an upper portion 68A_U extending partway through the insert 60A (substantially the height of head 62A) with a larger maximum diameter than does injection port 68 of insert 60, and a lower portion 68A_L extending from the upper portion 68A_U through the rest of the insert 60A (substantially the height of neck 64A) with a smaller diameter (in this embodiment, similar to the diameter of injection port 68 of insert 60). This larger diameter of the upper portion 68A_U permits the ease of insertion and angling of multiple outlet or inlet conduits (such as other syringes or needles thereof) while also permitting a user sufficient room to insert a syringe for withdrawing contents of the container 10. It will be noted that the thickness of a tungsten neck 64A is suitable for sufficient radiation protection in many instances such that there need not be significant concern about the head 62A accommodating the larger upper portion 68A_U of the injection port 68A rather than providing the additional shielding. In this embodiment, each of upper portion 68A_U and lower portion 68A_L are cylindrical. However, in an alternative embodiment, one or both of upper portion 68A_U and lower portion 68A_L of injection port 68A may be frustoconical in shape. Still further, in another alternative embodiment, the upper and lower portions 68A_U and 68A_L of injection port 68A may be replaced by a single, frustoconical injection port with the widest end having a diameter similar to that shown in FIG. 18B at the upper end of the insert 60A. The container 10 can be released by grasping the collar 30a and fully rotating the cap closure 30b in the direction that unlocks it from the collar 30a, counter-clockwise in the embodiment illustrated as indicated by the ‘release vial’ arrow in FIG. 1. In use, the biohazardous material is placed in the container 10 by the manufacturer, placed in the container compartment 24 of the pig 20, and shipped to the destination. A technician at the destination removes the cap 30 with the container 10 attached, moves the container 10 to a dose calibrator (not shown) and, while grasping the collar 30a, rotates the cap closure 30b to release the container closure 14 and (typically using tongs) insert the container 10 into the dose calibrator to measure (assay) amount of radioactivity. The bottle 12 is vented in the dose calibrator, if required (typically only in the case of radioiodine capsules). The container 10 can then be re-sealed and the closure 14 reinserted into the grip 50. The technician while grasping the collar 30a rotates the cap closure 30b in the locking direction to secure the container closure 14 to the grip 50. The cap 30 is then replaced in the manner described above, and delivered to the patient for administration by a qualified professional. At the patient site, in the case of a liquid the technician removes the cap closure 30b from the collar 30a and secures the insert 60 or insert 60A to the collar 30a by interlocking cams 66 and 25 in a bayonet fashion. The technician then inserts a syringe through the orifice 80 and the septum 14b to aspirate the liquid 2 from the bottle 12. The insert 60 or 60A can then be removed and the cap closure 30b replaced on the collar 30a to shield the residual radioactivity in the bottle 12. The pig according to the invention can be used for any type of radioisotope, including those used for so-called “theranostics.” Although tungsten shields gamma rays effectively, optionally a Lucite (Trademark) or Aluminum tube can be used to line the compartment 24 for materials having high beta emissions, for example to shield beta emissions from a radioisotope such as I-131. Bremsstrahlung occurs as beta particles strike a dense material like tungsten or steel, and the Lucite tube thus serves as a ‘pillow’ to reduce or eliminate bremsstrahlung x-rays. FIG. 14 is a front perspective view of a pig 200 according to an alternative embodiment and a handle assembly 300 for the pig 200. In this embodiment, pig 200 is very similar to pig 20 described above, but the outer dimensions (in this embodiment, diameter) of the body 220 of pig 200 is larger than the outer dimensions of the collar 30a of the cap 30 of pig 200 and thereby presents a ledge extending laterally outwards from below collar 30a to the periphery of body 220. As will be described, handle assembly 300 is configurable for carrying pig 200, for supporting pig 200 during extraction of contents of bottle contained within, and for inhibiting unintended removal of cap 30 particularly during transportation of pig 200. In this embodiment, handle assembly 300 includes an upper collar 310 and a lower collar 320 maintained in a fixed spaced relationship by two struts 330a, 330b located opposite each other with respect to pig 200 and extending between the upper collar 310 and the lower collar 320. Upper collar 310 includes a ring 312 with a central opening 314 and an outer diameter that is slightly larger than the outer diameter of body 220 of pig 200, and a wall 316 depends downwards at right angles to the ring 312 about its periphery. The diameter of the central opening 314 is slightly larger than the diameter of collar 30a so that the upper collar 310 can be associated with the body 220 of pig 200 by being placed atop the body 220 such that the ring 312 of upper collar 310 directly faces the ledge of body 220 with the wall 316 of the upper collar 310 extending down a short distance along the exterior of body 220. In this embodiment, lower collar 320 is identical to upper collar 310, but is oriented upward thereby to be associated with the bottom of body 220 by receiving the bottom of body 220 within its peripheral wall 326. It will be understood that, while upper and lower collars 310, 320 are identical in this embodiment, the lower collar 320 in this embodiment does not really need its own central opening 322 to fulfil its function since the bottom of body 220 does not have a corresponding feature. In this embodiment, upper collar 310 and lower collar 320 are made of Delrin™—a high-load thermoplastic available from Dupont™ Corporation of Wilmington, Del., U.S.A. or distributors thereof. Each of struts 330a, 33b is connected at a proximate end to the wall 316 of upper collar 310 and at a distal end to the wall 326 of lower collar 320. In this embodiment, channels 318a, 318b, 328a and 328b in the outer face of the peripheral walls 316, 326 of each of upper and lower collars 310, 320 receives corresponding proximate and distal ends of a strut 330a or 330b, and the proximate and distal ends of the strut 330a or 330b are locked within the corresponding channels 318a, 318b, 328a, 328b with fasteners F. In this way, the upper and lower collars 310, 320 contain body 220 of pig 200 such that it is not separable from the upper and lower collars 310, 320 unless these fasteners F are removed. Each of struts 330a, 330b has an outward-facing threaded aperture along its outward-facing surface and intermediate its proximate and distal ends for receiving the threaded end of a corresponding knob 340a or 340b via a corresponding washer 341a, 341b. A U-shaped handle 350 has elongate arms 352a and 352b each depending from a cross member 354, and each of the elongate arms 352a, 352b has therethrough an elongate channel 356a, 356b. The handle 350 is connectable to the struts 330a, 330b by passing knob 340a, 340b through a respective elongate channel 356a, 356b threading the knobs 340a, 340b into its corresponding threaded aperture in the strut 330a, 330b. In this configuration, if both of the knobs 340a, 340b are not fully threaded into corresponding threaded apertures, they do not compress respective arms 352a, 352b against the corresponding strut 330a, 330b, such that the channel 356a, 356b and correspondingly the handle 350 can be both freely rotated about and freely slid along the corresponding knob 340a, 340b while remaining generally connected to the rest of the handle assembly 300. In this way, the handle 350 can be moved between various rotational and extensional orientations with respect to the body 220 of pig 200. If any or both of the knobs 340a, 340b are tightened so as to press the arms 352, 352b against the struts 330a, 330b, the handle is held frictionally in position and is thereby prevented from rotating or sliding with respect to the struts 330a, 330b. It is preferred that the operator tighten both knobs 340a, 340b when intending to maintain the handle 350 in a particular fixed position with respect to the body 220, since the body 220 and the closure 30, being formed with dense, thick walls of tungsten, can be quite heavy. FIG. 15 is a perspective view of the pig 200 and handle assembly 300 of FIG. 14, with the handle 350 having been slid along knobs 340a, 340b to a position in which the cross member 354 is resting atop the cap 30 of the pig 200. In this position, the handle 350 serves to further inhibit removal of the cap 30 thereby providing an extra measure of security for transportation. Cap 30 cannot be lifted from body 220 while handle 350 is in this position (and knobs 340a, 340b are tightened), even if it is rotated somewhat with respect to body 220. In this respect, body 220 can be rotated somewhat within collars 310 and 320 if urged to do so either manually or during jostling in transportation, because, while handle assembly 300 encapsulates body 220, it is not fastened directly to it in this embodiment. The surface of cross member 354 facing the top of cap 30 is generally smooth such that cap 30 is free to rotate along with body 220 even when handle 350 is in the position shown in FIG. 15. In this way, handle 350 is not easily positioned with respect to cap 30 in a way that will result in handle 350 inadvertently loosening cap 30. In an alternative embodiment, body 220 is non-cylindrical such as square-based and handle assembly 300 is of a complementary shape, thus inhibiting any rotation of one with respect to the other. FIG. 16 is a perspective view of the pig 200 and handle assembly 300 of FIG. 14, with the handle 350 having been slid and rotated along knobs 340a, 340b to a position in which the cross member 354 is underneath and spaced from the bottom of lower collar 320. In this position, handle 350 can be used to hold pig 200 either manually or on a hook (not shown) in preparation for removal of the contents of pig 200. FIG. 17 is an exploded perspective view of the handle assembly 300 for the pig 200 in isolation. In this view, compression washers 341a and 341b, in this embodiment formed of rubber, are viewable. These are positioned adjacent to the threaded apertures in struts 330a, 330b for knobs 340a and 340b in order to improve their grip against handle arms 352a, 352b via their channels 356a, 356b, particularly during jostling in transport but also for handling. FIG. 18 is a perspective top view of an alternative compression member, or grip 500, for assisting in securing a container closure 14 to the cap 30. In the embodiment shown the grip 500 comprises a flange 510 supporting a sleeve 505 that is integrated with and encompasses spaced apart fingers 540 that form a circle complementary to the inner wall of the annulus 35. The fingers 540 each have a substantially vertical component extending vertically with the sleeve 505 from the flange 510 and a substantially horizontal component extending inwards with the sleeve 505 from the end of the substantially vertical component thereby to overlap the container closure 14 to a degree in a similar manner as has been described above with respect to grip 50. Extending between each pair of fingers 540 of grip 500, however, is a respective web 542 integrated also with sleeve 505 that is made of a material as will be described that permits flexibility of the fingers 540 inwards and outwards and accordingly towards and away from each other, while providing a more unitary overall structure for surrounding a container closure 14. In this embodiment, flange 510 is formed of a semi-compressible material such as plastic (such as a thermoplastic such as Delrin™ available from Dupont Corporation of Wilmington, Del., U.S.A. or polypropylene). In this embodiment, flange 510 is not circular, but is instead substantially a square with significantly rounded corners 512. Furthermore, flange 510, as best seen in the side elevation view of FIG. 19, has a sloped edge S spanning the entire periphery of the flange 510. Both the rounded corners 512 and the sloped edge S contribute to permit flange 510 to be snapped into, and retained frictionally within, corresponding sloped structure at a correspondingly sloped lower edge of the neck 31 of collar 30a of the cap 30. While flange 510 is retained within such a correspondingly sloped lower edge of neck 31, when desired, flange 510 may be manually snapped out of the lower edge of neck 31 of collar 30a for disposal of grip 500 and a new grip 500 snapped into place as a replacement. It will be noted that, unlike grip 50, grip 500 does not have posts 52. However, in an alternative embodiment the combination of such posts and the sloped edge S of flange 510 may be employed. In this embodiment, fingers 540 are formed of the same rigid material as flange 510, while sleeve 505 and webs 542 are formed of a more flexible but resilient material such as silicone that is fused at its boundaries with flange 510 and fingers 540. While a grip 500 of two integrated materials exhibiting the two different properties (rigid and flexible) can be very useful, it can be expensive to manufacture. As such, in alternative embodiments grip 500 may be manufactured from a single material for the sleeve 505, fingers 540 and webs 542 with the relative rigidity and flexibility produced through differing thicknesses at different points throughout the grip 500 of the one material rather than necessarily from different materials. For example, the interfaces between the webs 542 and the fingers 540 and flange 510 may incorporate less of the material than between the fingers 540 and the flange 510 thereby to permit webs 542 to be flexed relative to the flange 510 and fingers 540 more than the fingers 540 can flex relative to the flange 510. In this way, the resilience of fingers 540 with respect to flange 510 can be maintained while reducing the rigidifying effect of the webs 542 between the fingers 540. FIG. 20 is a top plan view of the grip 500, FIG. 21 is a bottom plan view of the grip 500, FIG. 22 is a perspective bottom view of the grip 500, FIG. 23 is a perspective top view, partially sectioned, of the grip 500, FIG. 24 is a perspective bottom view, partially sectioned, of the grip 500, FIG. 25 is another perspective top view, partially sectioned below the horizontal components of the sleeve 505, the fingers 540 and the webs 542, of the grip 500, FIG. 26 is another perspective bottom view, partially sectioned, of the compression member of FIG. 18. The radiopharmaceutical pigs 20 and 200 described and illustrated are particularly suitable for transporting radioactive substances such as liquid and solid radiopharmaceuticals due to the radioactivity-shielding character of the container 24, but can be adapted to transport other biohazardous products and materials without the use of radioactivity shielding by hermetically sealing the container 24. Various embodiments of the present invention comprising been thus described in detail by way of example, it will be apparent to those skilled in the art that variations and modifications may be made without departing from the invention. The invention includes all such variations and modifications as fall within the scope of the appended claims. For example, while embodiments described herein involve the compartment 24 of body 22 or body 220 being dimensioned to receive only a container of the biohazardous material, embodiments are contemplated in which the compartment 24 is dimensioned to receive a container in addition to a sponge, such as a cellulose sponge, for physically absorbing liquid originally contained within the received container should it escape from the container during transportation or other handling. Some regulators require that there be provided a quantity of sponge that is capable of absorbing twice the volume of liquid to be contained within the container. Such a cellulose sponge may be formed as a slab and positioned at the bottom of compartment 24 underneath the container, but may alternatively be formed as a cup having a bottom and a sleeve dimensioned to receive the container and, in turn, to be received within compartment 24. The cellulose sponge slab or sleeve would be a consumable. Furthermore, while handle assembly depicted and describe herein has two struts, alternatives are contemplated having more than two struts, or other structures for encapsulating the body within the handle assembly. Still further, very thin layers of rubber or other frictional material may be placed at the interfaces between collar 30a and cap closure 30b and collar 30a and body 22 in order to resist inadvertent relative movements when being transported to thereby resist inadvertent exposure to the contents of the container 10. |
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summary | ||
summary | ||
043895719 | claims | 1. In an electron beam device having a source of electrons, the improvement in the device for correcting higher order aberration, comprising: first and second sextupoles, each for focusing a beam in an image plane, and each having a second-order astigmatism distribution, an intermediate lens positioned between said first and said second sextupoles for focusing the beam to a point in the center of said second, sextupole, a first lens for focusing the beam to a point in the center of said first, sextupole, and a second lens positioned in said image plane of said second, sextu-pole for focusing the beam to a point in a final image plane. 2. The device of claim 1 wherein said first and said second focusing means comprise first and second sextupoles, respectively. 3. The device of claim 2, wherein said second sextupole is located downstream of said first sextupole and has between 40% and 80% of the strength of said first sextupole. 4. The device of claim 2, further including steering means for aligning said beam along the optical axis of the device. 5. The device of claim 4 wherein said steering means includes two pairs of steering coils with one pair of coils positioned upstream of said first sextupole and the second pair of coils positioned downstream of said second sextupole. 6. The device of claim 3, wherein said second lens has a focal length of 1 mm, a value of spherical aberration coefficient of 0.4 mm, and the source produces 75,000 volt electrons. |
claims | 1. An ion beam processing apparatus comprising:a first sample stage that holds a sample;an ion source that generates an ion beam;an ion beam irradiation optical system that irradiates the ion beam along an ion beam irradiation axis to the sample held on the first sample stage;an electron beam irradiation optical system that irradiates an electron beam along an electron beam irradiation axis to the sample;a probe that carries a test piece extracted from the sample by performing ion beam processing; anda second sample stage on which the test piece is mounted,wherein the ion beam processing apparatus is configured to have a tilting ability to vary an angle of irradiation, at which the ion beam is irradiated to the sample, by tilting the second sample stage;the ion beam irradiation optical system comprises an irradiation optical system that irradiates the ion beam to the sample through a mask including an opening of a d rectangular shape to form a rectangular ion beam; andthe ion beam processing apparatus further comprises a control device configured to control widths of edges of an intensity profile representing edges of the rectangular beam so that a width of an edge of the intensity profile representing an edge of the rectangular ion beam, which is irradiated to the sample, in a direction perpendicular to a direction in which a tilting axis of the second sample stage is projected on the second sample stage surface will be smaller than a width of an edge of an intensity profile representing another edge of the rectangular ion beam in a direction parallel to the direction in which the tilting axis of the second sample stage is projected on the second sample stage surface,wherein said control device controls said widths of said edges of the intensity profile independently of the shape of the rectangular ion beam, andwherein said control device includes at least one of an ion source aperture plate and a stencil mask. 2. The ion beam processing apparatus according to claim 1,wherein the electron beam irradiation axis and the ion beam irradiation axis intersect substantially above the sample. 3. The ion beam processing apparatus according to claim 1,wherein a tilt angle at which both the electron beam irradiation axis and the ion beam irradiation axis are tilted relative to the first sample stage is substantially 45°. 4. An ion beam processing apparatus comprising:a first sample stage that holds a sample;an ion source that generates a first ion beam;a first ion beam irradiation optical system that irradiates the first ion beam along a first ion beam irradiation axis to the sample held on the first sample stage;a second ion beam irradiation optical system that irradiates a second ion beam along a second ion beam irradiation axis to the sample from a field ionization ion source;a probe means that carries a test piece extracted from the sample by performing ion beam processing; anda second sample stage on which the test piece is mounted,wherein the ion beam processing apparatus is configured to have a tilting ability to vary an angle of irradiation, at which the first ion beam is irradiated to the sample, by tilting the second sample stage;the first ion beam irradiation optical system comprises an irradiation optical system that irradiates the first ion beam to the sample through a mask including an opening of a rectangular shape to form a rectangular ion beam; andthe ion beam processing apparatus further comprises a control device configured to control widths of edges of an intensity profile representing edges of the rectangular beam so that a width of an edge of the intensity profile representing an edge of the rectangular ion beam, which is irradiated to the sample, in a direction perpendicular to a direction in which a tilting axis of the second sample stage is projected on the second sample stage surface will be smaller than a width of an edge of an intensity profile representing another edge of the rectangular ion beam in a direction parallel to the direction in which the tilting axis of the second sample stage is projected on the second sample stage surface,wherein said control device controls said widths of said edges of the intensity profile independently of the shape of the rectangular ion beam, andwherein said control device includes at least one of an ion source aperture plate and a stencil mask. 5. The ion beam processing apparatus according to claim 4,wherein the second ion beam irradiation axis and the first ion beam irradiation axis intersect substantially above the sample. 6. The ion beam processing apparatus according to claim 4,wherein a tilt angle at which both the second ion beam irradiation axis and the first ion beam irradiation axis are tilted relative to the first sample stage is substantially 45°. 7. The ion beam processing apparatus according to claim 1, wherein the width of the edge of the intensity profile representing an edge of the rectangular ion beam is a distance between a point indicating a first percentage of maximum beam intensity and a point indicating a second higher percentage of a maximum beam intensity to quantitatively indicate a steepness of the edge of the rectangular ion beam. 8. The ion beam processing apparatus according to claim 2, wherein the width of the edge of the intensity profile representing an edge of the rectangular ion beam is a distance between a point indicating a first percentage of maximum beam intensity and a point indicating a second higher percentage of a maximum beam intensity to quantitatively indicate a steepness of the edge of the rectangular ion beam. 9. The ion beam processing apparatus according to claim 3, wherein the width of the edge of the intensity profile representing an edge of the rectangular ion beam is a distance between a point indicating a first percentage of maximum beam intensity and a point indicating a second higher percentage of a maximum beam intensity to quantitatively indicate a steepness of the edge of the rectangular ion beam. 10. The ion beam processing apparatus according to claim 4, wherein the width of the edge of the intensity profile representing an edge of the rectangular ion beam is a distance between a point indicating a first percentage of maximum beam intensity and a point indicating a second higher percentage of a maximum beam intensity to quantitatively indicate a steepness of the edge of the rectangular ion beam. 11. The ion beam processing apparatus according to claim 5, wherein the width of the edge of the intensity profile representing an edge of the rectangular ion beam is a distance between a point indicating a first percentage of maximum beam intensity and a point indicating a second higher percentage of a maximum beam intensity to quantitatively indicate a steepness of the edge of the rectangular ion beam. 12. The ion beam processing apparatus according to claim 6, wherein the width of the edge of the intensity profile representing an edge of the rectangular ion beam is a distance between a point indicating a first percentage of maximum beam intensity and a point indicating a second higher percentage of a maximum beam intensity to quantitatively indicate a steepness of the edge of the rectangular ion beam. 13. The ion beam processing apparatus according to claim 7, wherein the first percentage is substantially 16% and the second percentage is substantially 84%. 14. The ion beam processing apparatus according to claim 8, wherein the first percentage is substantially 16% and the second percentage is substantially 84%. 15. The ion beam processing apparatus according to claim 9, wherein the first percentage is substantially 16% and the second percentage is substantially 84%. 16. The ion beam processing apparatus according to claim 10, wherein the first percentage is substantially 16% and the second percentage is substantially 84%. 17. The ion beam processing apparatus according to claim 11, wherein the first percentage is substantially 16% and the second percentage is substantially 84%. 18. The ion beam processing apparatus according to claim 12, wherein the first percentage is substantially 16% and the second percentage is substantially 84%. 19. The ion beam processing apparatus according to claim 1, wherein the control device further comprises a condenser lens for projecting the ion source aperture plate or the stencil mask onto the sample. 20. The ion beam processing apparatus according to claim 4, wherein the control device further comprises a condenser lens for projecting the ion source aperture plate or the stencil mask onto the sample. |
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description | The present invention relates to a radiation protection equipment configured to reduce the amount of radiation exposure of a medical staff, and a radiation protection system including the radiation protection equipment. In Patent Literature 1, there is disclosed a radiation protection system configured to cover a patient on an X-ray table and separate a working area from an X-ray emitter having a C-shaped arm. The radiation protection system includes a radiation shielding wall, a radiation shielding screen on the X-ray table, and a flexible interface for radiation shielding, which is configured to connect the radiation shielding screen and the X-ray table to the radiation shielding wall. Further, the radiation shielding screen includes a plurality of screen support parts mounted to the X-ray table and radiation-resistant partition walls mounted to the screen support parts. When the radiation shielding screen is in an extended state, the radiation shielding screen covers the X-ray table in the working area, and the radiation-resistant partition wall is interposed between the patient and a doctor. Further, when fluoroscopic treatment is performed, the radiation shielding screen is extended from a leg part of the X-ray table to a central abdominal portion of the patient. The radiation shielding screen can be folded when the screen support parts slide along the X-ray table. The radiation shielding screen includes access ports so that the doctor can give treatment to the patient through use of a surgical instrument. Each access port is covered with a radiation shielding cloak attached to the radiation shielding screen. The radiation shielding cloak assists protection of the doctor giving treatment on a periphery of the X-ray table from radiation scattering through each access port. PTL 1: Japanese Patent No. 5016774 According to the radiation protection system of Patent Literature 1, a medical staff can be protected from scattering radiation. However, for example, when an endoscopic spinal operation is performed, the working area is narrowed by the radiation shielding walls, with the result that there is difficulty in performing the operation. Further, the size of each component of the radiation protection system is large, and each component includes a shielding material containing lead or the like, with the result that the weight of the component becomes heavier. Further, it takes time to install the radiation protection system, and it requires labor to put away the components of the radiation protection system after the operation. In order to solve the above-mentioned problem, according to one embodiment of the present invention, there is provided a radiation protection equipment, including: a first protection sheet arranged on a periphery of a radiation source device and configured to shield radiation; a second protection sheet formed separately from the first protection sheet, arranged on a side of an operation table, and configured to shield radiation; and a third protection sheet formed separately from the first protection sheet and the second protection sheet, arranged on a periphery of a surgical field so as to expose the surgical field, and configured to shield the radiation. Further, according to another embodiment of the present invention, there is provided a radiation protection system, including: an imaging apparatus including a radiation source device and a detector; and the above-mentioned radiation protection equipment. With this, the amount of radiation exposure of the medical staff can be significantly reduced, and a large working area can be ensured during an operation. Further, the size of each component of the radiation protection equipment can be reduced, and hence the weight thereof can be decreased. Further, the radiation protection equipment can be provided, which can be installed within a short time period before an operation and enables the components to be easily put away after the operation. Further features of the present invention are apparent from the following description of exemplary embodiments with reference to the attached drawings. Exemplary embodiments for carrying out the present invention are now described in detail with reference to the drawings. However, for example, the dimensions, materials, shapes, and relative positions of the components, which are described in the following embodiments, may be suitably set and changed based on the configuration of the system to which the present invention is applied or based on various conditions. Unless otherwise noted, the scope of the present invention is not limited to the embodiments specifically described herein. Vertical directions herein respectively correspond to an upward direction and a downward direction with respect to the direction of gravity. Further, horizontal directions correspond to directions parallel to a floor surface on which an operation table is installed. [First Embodiment] A radiation protection system 100 according to a first embodiment of the present invention is described with reference to FIG. 1. FIG. 1 is a schematic perspective view of the radiation protection system 100 and is an illustration of a state as viewed from a foot side of an operation table 9. In FIG. 1, the right side of the operation table 9 corresponds to a foot side of a patient, and the left side of the operation table 9 corresponds to a head side of the patient. As illustrated in FIG. 1, the radiation protection system 100 includes an imaging apparatus 110 and the operation table 9. The imaging apparatus 100 includes a radiation source device 101 and a detector 102. On the operation table 9, a patient to be subjected to an operation lies down. Further, in FIG. 1, first sheet support part 5 and second sheet support part 6, which are configured to support protection sheets of a radiation protection equipment 10, are illustrated. In FIG. 1, for convenience of description, illustration of the protection sheets is omitted, and only a second side surface sheet 12 of a first protection sheet and a foot side sheet 24 of a second protection sheet are illustrated with the dotted lines. As the imaging apparatus 110, there are given various medical imaging apparatus using radiation. In the following, an X-ray imaging apparatus (surgical image pickup apparatus) is described below as an example. The imaging apparatus 110 includes the radiation source device 101 including an X-ray tube and an X-ray diaphragm device (not shown). The X-ray tube is configured to generate an X-ray through use of a high voltage to be supplied thereto. Further, the X-ray diaphragm device is configured to shield a part of the X-ray generated by the X-ray tube to control an irradiation field. Further, the imaging apparatus 110 includes the detector 102. The detector 102 is configured to detect radiation (X-ray), which is radiated from the radiation source device 101 and transmitted through the patient on the operation table 9, through conversion into an electric charge. Further, the imaging apparatus 110 includes a C-shaped arm configured to support the radiation source device 101 and the detector 102. A imaging position may often be changed for a plurality of times in one operation. Therefore, the arm can perform various operations such as the movement in the vertical directions, the rotation around an axis of the arm, the slide movement along a curved direction of the arm, and the like. When an operation is performed, an operator (medical staff) stands on the right side of FIG. 1, that is, the foot side of the patient with respect to the radiation source device 101, or on the left side of FIG. 1, that is, the head side of the patient with respect to the radiation source device 101 to perform the operation. Therefore, in order to protect the operator from radiation, the first protection sheet configured to shield radiation radiated from the radiation source device 101 is arranged on a periphery of the radiation source device 101. In FIG. 1, only the second side surface sheet 12 described later is illustrated with the dotted lines. Further, in order to shield scattering radiation which comes out from the patient, the second protection sheet is arranged also between the operator and the patient, that is, on the side of the operation table 9. In FIG. 1, only the foot side sheet 24 described later is illustrated with the dotted lines. Further, in order to shield scattering radiation which comes out from the vicinity of a surgical field, a third protection sheet (not shown) is arranged also on the periphery of the surgical field. In order to support those protection sheets, the radiation protection equipment 10 includes the first sheet support part 5 and the second sheet support part 6. The first sheet support part 5 includes a pair of sheet support parts arranged so that the radiation source device 101 is placed therebetween. Similarly, the second sheet support parts 6 include a pair of sheet support parts arranged so that the detector 102 is placed therebetween. Each of the sheet support parts includes a fixing part to be fixed to the operation table 9 and a pole serving as a main body. The first sheet support part 5 and the second sheet support part 6 have the same configuration except for the shape of the main body of the sheet support part. Therefore, the first sheet support part 5 is described below. A fixing part 56 of the first sheet support part 5 may be formed of a pole clamp into which a lower end portion of the pole of the first sheet support part 5 can be inserted. The fixing part 56 includes a receiving part having a substantially U-shape in cross-section on the operation table 9 side. When the receiving part is inserted to a rail arranged on the operation table 9, the fixing part 56 is mounted to the operation table 9. With this, the fixing part 56 is mounted so as to be movable along a longitudinal direction of the operation table 9. Therefore, the distance from the radiation source device 101 or the detector 102 to the first sheet support part 5 can be appropriately adjusted. Further, an insertion hole into which the lower end portion of the pole can be inserted is formed in the fixing part 56. When a lever 57 is rotated after the lower end portion is inserted into the insertion hole, the lower end portion can be held and fixed in the fixing part 56. Further, when the lever 57 is loosened, the first sheet support part 5 can be moved along the vertical directions. With this, the height of the first sheet support part 5 with respect to the operation table 9 can be appropriately adjusted. Further, the first sheet support part 5 includes a first extension part 51 extending in the horizontal direction A (an emitting direction of radiation) of FIG. 1. Further, the first sheet support part 5 includes a second extension part 52 continuing from the first extension part 51, and the second extension part 52 extends in the vertical direction B (a downward direction) of FIG. 1. Further, the first sheet support part 5 can be rotated about the fixing part 56 in the horizontal direction. When the lever 57 is loosened, the orientation of the first extension part 51 can be changed, and the position thereof can be appropriately adjusted. The pole of the first sheet support part 5 can be formed by bending a stainless steel pipe having a diameter of from 13 mm to 14 mm and a length of 145 cm. In the first sheet support part 5, one sheet support part arranged on the foot side of the patient includes the first extension part 51 of 45 cm and the second extension part 52 of 50 cm formed so as to be bent downward at 90° from the first extension part 51. Further, the one sheet support part includes a third extension part 53 of 20 cm formed so as to be bent in the emitting direction at 90° from the second extension part 52, a fourth extension part 54 of 15 cm formed so as to be bent toward the foot side at 90° along the longitudinal direction of the operation table 9, and a fifth extension part 55 of 15 cm formed so as to be bent downward at 90° from the fourth extension part 54. Further, another sheet support part of the first sheet support part 5 has a shape symmetrical to that of the one sheet support part with respect to the radiation source device 101. That is, the another sheet support part includes the first extension part 51 of 45 cm, the second extension part 52 of 50 cm formed so as to be bent downward at 90° from the first extension part, the third extension part 53 of 20 cm formed so as to be bent in the emitting direction at 90° from the second extension part 52, the fourth extension part 54 of 15 cm formed so as to be bent toward the head side at 90° along the longitudinal direction of the operation table 9, and the fifth extension part 55 of 15 cm formed so as to be bent downward at 90° from the fourth extension part 54. Meanwhile, the pole of the second sheet support part 6 can be formed by bending a stainless steel pipe having a diameter of from 13 mm to 14 mm and a length of 110 cm. Each pole of the second sheet support part 6 has a substantially L-shape. That is, the second sheet support part 6 includes a first extension part 61 of 45 cm extending in the emitting direction of radiation, and a second extension part 62 of 65 cm formed so as to be bent downward at 90° from the first extension part 61. A hook-and-loop fastener 68 configured to mount the protection sheet is mounted to the first extension part 61 of the second sheet support part 6. Further, an end portion of the second extension part 62 of the second sheet support part 6 is also inserted into the fixing part (pole clamp) mounted to the operation table 9 and fixed. The fixing parts of the first sheet support part 5 and the second sheet support part 6 are not limited to pole clamps. For example, the fixing part can also be formed of a pin that can be inserted into a hole formed in the pole of the sheet support part. Subsequently, mounting of the first to third protection sheets is described with reference to FIG. 2A, FIG. 2B, FIG. 3A, FIG. 3B, and FIG. 4. FIG. 2A, FIG. 3A, and FIG. 4 are views for illustrating states of the protection sheets in a developed state, as viewed from above. The right side corresponds to the foot side of the patient, and the left side corresponds to the head side of the patient. Further, FIG. 2B and FIG. 3B are views for illustrating the protection sheets in a hanging state after being mounted, as viewed from above. The radiation protection equipment 10 includes a first protection sheet 1 arranged on the periphery of the radiation source device 101 and configured to shield radiation, a second protection sheet 2 arranged between the operator and the patient and configured to shield radiation, and a third protection sheet 3 arranged on the periphery of a surgical field so as to expose the surgical field and configured to shield radiation. The first protection sheet 1, the second protection sheet 2, and the third protection sheet 3 are formed separately from each other. Each protection sheet includes a surface material and a shielding material for radiation. The shielding material is arranged on an inner side of the surface material. For example, the protection sheet is formed of a sheet having a lead equivalent of 0.25 mmPb and has a shielding ability to shield radiation by about 80% to about 99%. When such protection sheet is folded and stored, there is a risk in that the shielding material in a folded portion may be damaged to cause degradation of the shielding ability. Therefore, even when the protection sheet has a large size, the protection sheet cannot be folded, and it is necessary to ensure a large storage space. In this respect, according to the first embodiment, the first protection sheet 1, the second protection sheet 2, and the third protection sheet 3 are formed separately from each other. With this, the size of each protection sheet can be reduced, thereby being capable of stacking the protection sheets for storage without folding the protection sheets. Therefore, it is not necessary to ensure a large storage space, and there is no risk of damage to the shielding material in the folded portion. Further, the first protection sheet 1, the second protection sheet 2, and the third protection sheet 3 are formed separately from each other, and hence the weight of each protection sheet can be reduced. For example, in the case of a protection sheet having dimensions of 200 cm×70 cm, the weight of the protection sheet is from about 5.4 kg to about 10.0 kg, and it cannot be easily mounted. Meanwhile, in the case of a protection sheet having dimensions of 100 cm×70 cm, the weight of the protection sheet is a half of the protection sheet having dimensions of 200 cm×70 cm, and it can be relatively easily mounted. When the radiation protection equipment 10 is mounted to the operation table 9, the second sheet support part 6 (FIG. 1) is first mounted to the operation table 9. The second sheet support part 6 is mounted so that the first extension part 61 is positioned above the operation table 9 (above a patient). Then, the first sheet support part 5 (FIG. 1) is mounted to the operation table 9. The first sheet support part 5 is mounted so that the radiation source device 101 is placed between the first extension parts 51. Next, as illustrated in FIG. 2A, the first protection sheet 1 (first protection sheet set) is arranged on the periphery of the radiation source device 101. The first protection sheet 1 includes a first side surface sheet 11 facing a first side surface of the radiation source device 101, a second side surface sheet 12 facing a second side surface on an opposite side to the first side surface of the radiation source device 101, and a back surface sheet 13 facing a back surface and an upper surface of the radiation source device 101. The back surface of the radiation source device 101 is a surface on an opposite side to a side facing the detector 102. The first side surface sheet 11, the second side surface sheet 12, and the back surface sheet 13 can be formed separately from each other. With this, the size of each protection sheet can be further reduced, and the weight of each protection sheet can be even further decreased. The first side surface sheet 11 is mounted to the first extension part 51 of the first sheet support part 5. The first side surface sheet 11 has a rectangular shape having dimensions of 100 cm×70 cm, and a pair of upper edge hook-and-loop fasteners 111 are arranged in an upper end portion of the first side surface sheet 11. When mounting the first side surface sheet 11, the pair of upper edge hook-and-loop fasteners 111 are first joined to each other so that the upper end portion is bent to have a substantially ring shape in cross-section. Then, the first extension part 51 of the one sheet support part of the first sheet support part 5 is inserted into an inner side of the ring shape, to thereby mount the first side surface sheet 11 to the first extension part 51. Similarly, the second side surface sheet 12 is mounted to the first extension part 51. The second side surface sheet 12 is a rectangular protection sheet having dimensions of 110 cm×70 cm, and a pair of upper edge hook-and-loop fasteners 121 are arranged in an upper end portion of the second side surface sheet 12. When mounting the second side surface sheet 12, the pair of upper edge hook-and-loop fasteners 121 are first joined to each other so that the upper end portion is bent to have a substantially ring shape in cross-section. Then, the first extension part 51 of the another sheet support part of the first sheet support part 5 is inserted into an inner side of the ring shape, to thereby mount the second side surface sheet 12 to the first extension part 51. Further, the back surface sheet 13 is mounted to the first side surface sheet 11 and the second side surface sheet 12. The back surface sheet 13 is a rectangular protection sheet having dimensions of 130 cm×30 cm. A pair of side edge hook-and-loop fasteners 131 are arranged on back surfaces of both side edge portions of the back surface sheet 13. Further, a side edge hook-and-loop fastener 112 is arranged on the first side surface sheet 11, and a side edge hook-and-loop fastener 122 is arranged also on the second side surface sheet 12. When the back surface sheet 13 is mounted to the first side surface sheet 11 and the second side surface sheet 12, the side edge hook-and-loop fasteners 131 of the back surface sheet 13 are joined to the side edge hook-and-loop fastener 112 of the first side surface sheet 11 and to the side edge hook-and-loop fastener 122 of the second side surface sheet 12. The side edge hook-and-loop fasteners 131 arranged on the back surface are illustrated with the dotted lines. As illustrated in FIG. 2B, the first side surface sheet 11 and the second side surface sheet 12, which have been mounted, are positioned on both sides of the radiation source device 101. The first side surface sheet 11 and the second side surface sheet 12 are supported by the first sheet support part 5, and hang down on the floor surface side. Further, the back surface sheet 13, which has been mounted, is positioned on a back side and an upper side of the radiation source device 101. The back surface sheet 13 is supported by the first sheet support part 5 through intermediation of the first side surface sheet 11 and the second side surface sheet 12, and hangs down on the floor surface side. Further, end portions of the first side surface sheet 11, the second side surface sheet 12, and the back surface sheet 13 are superposed and joined to each other so that the first side surface sheet 11, the second side surface sheet 12, and the back surface sheet 13 are arranged without a gap. Next, the second protection sheet 2 (second protection sheet set) is arranged between the operator and the patient (operation table 9). As illustrated in FIG. 3A, the second protection sheet 2 includes the foot side sheet 24 arranged on the foot side of the patient with respect to the radiation source device 101 and a head side sheet 25 arranged on the head side of the patient with respect to the radiation source device 101. The foot side sheet 24 and the head side sheet 25 can be formed separately from each other. With this, the size of each protection sheet can be even further reduced, and the weight thereof can be even further decreased. The foot side sheet 24 is mounted to the side of the operation table 9. The foot side sheet 24 is a rectangular protection sheet having dimensions of 50 cm×70 cm, and an upper edge hook-and-loop fastener 241 is arranged in an upper end portion of the foot side sheet 24. When mounting the foot side sheet 24, the upper edge hook-and-loop fastener 241 is joined to a hook-and-loop fastener 91 (FIG. 1) arranged on the operation table 9. The upper edge hook-and-loop fastener 241 arranged on the back surface is illustrated with the dotted lines. The head side sheet 25 is mounted to the first side surface sheet 11 and to the first extension part 61 of the second sheet support part 6. The head side sheet 25 is a rectangular protection sheet having dimensions of 110 cm×80 cm. A side edge hook-and-loop fastener 251 is arranged on a back side of a side edge portion of the head side sheet 25. Further, the hook-and-loop fastener 68 (FIG. 1) is arranged on the first extension part 61. Further, an upper edge hook-and-loop fastener 252 is arranged on a back side of an upper edge portion of the head side sheet 25. Further, a side edge hook-and-loop fastener 113 (FIG. 2A) is arranged in a side edge portion of the first side surface sheet 11 on the operation table 9 side. When mounting the head side sheet 25, the side edge hook-and-loop fastener 251 is joined to the side edge hook-and-loop fastener 113 of the first side surface sheet 11. At the same time, the upper edge hook-and-loop fastener 252 is joined to the hook-and-loop fastener 68 of the first extension part 61. The side edge hook-and-loop fastener 251 and the upper edge hook-and-loop fastener 252 arranged on the back surface are illustrated with the dotted lines. As illustrated in FIG. 3B, the head side sheet 25, which has been mounted, is supported by the first extension part 61 and the first side surface sheet 11. Further, the head side sheet 25 is arranged between the first side surface sheet 11 and the operation table 9 so that a part of the head side sheet 25 is positioned on the side of the operation table 9, and another part of the head side sheet 25 covers a part of the patient. Further, end portions of the foot side sheet 24 and the second side surface sheet 12 are superposed on each other, and end portions of the head side sheet 25 and the first side surface sheet 11 are superposed on each other. Thereby, the foot side sheet 24 and the second side surface sheet 12 are arranged without a gap, and the head side sheet 25 and the first side surface sheet 11 are arranged without a gap. The second protection sheet 2 may be arranged only on one side. However, a plurality of medical staffs are generally involved in an operation, and hence the second protection sheet 2 is arranged on both sides of the radiation source device 101. Next, as illustrated in FIG. 4, the third protection sheet 3 (third protection sheet set) is arranged on the periphery of a surgical field S. The third protection sheet 3 includes at least two sheets that are combined so as to expose a rectangular region. The third protection sheet 3 according to the first embodiment includes four protection sheets (first to fourth surgical field sheets) that surround the surgical field S. The first to fourth surgical field sheets are formed separately from each other. With this, the size of each protection sheet can be even further reduced, and the weight thereof can be even further decreased. The surgical field S is a rectangular region having a side of, for example, from 15 cm to 45 cm. Further, an edge of each of the first to fourth surgical field sheets on the surgical field S side defines each side of the rectangular surgical field S. After the third protection sheet 3 is arranged, the third protection sheet 3 is covered with a sterilized cover cloth (not shown), and the cover cloth is attached to the body of the patient with a tape. Therefore, the cover cloth is positioned between the third protection sheet 3 and the surgical field S. With this, during an operation, the third protection sheet 3 is prevented from being placed over the surgical field S. Further, the third protection sheet 3, in place of the cover cloth, may be sterilized and attached to the body of the patient. Further, the third protection sheet 3 may be accommodated into a sterilized cover and attached to the body of the patient. When the third protection sheet 3 is arranged, a first surgical field sheet 36 is first placed on the first sheet support part 5 and the second sheet support part 6. The first surgical field sheet 36 is a rectangular protection sheet having dimensions of 140 cm×90 cm. When the first surgical field sheet 36 is arranged, the first surgical field sheet 36 is arranged so as to cover the radiation source device 101 and to be placed over a part of a patient P. Further, the first surgical field sheet 36 is superposed on the first protection sheet 1 (first side surface sheet 11, second side surface sheet 12, and back surface sheet 13) and on a part of the head side sheet 25. That is, the first surgical field sheet 36 is placed on the first sheet support part 5 through intermediation of the first side surface sheet 11, the second side surface sheet 12, and the back surface sheet 13. Further, the first surgical field sheet 36 is placed on the second sheet support part 6 through intermediation of the head side sheet 25. Subsequently, the second surgical field sheet 37 is mounted to the second sheet support part 6. In this case, the second surgical field sheet 37 is arranged so as to be placed over a part of the patient P. The second surgical field sheet 37 is a rectangular protection sheet having dimensions of 70 cm×50 cm, and a hook-and-loop fastener (not shown) is arranged in a part of the second surgical field sheet 37. When mounting the second surgical field sheet 37, the hook-and-loop fastener of the second surgical field sheet 37 is joined to the hook-and-loop fastener 68 of the first extension part 61. With this, the second surgical field sheet 37 is mounted to the second sheet support part 6. Subsequently, a third surgical field sheet 38 is placed on the second sheet support part 6. The third surgical field sheet 38 is a rectangular protection sheet having dimensions of 50 cm×60 cm. When the third surgical field sheet 38 is arranged, the third surgical field sheet 38 is arranged so as to be superposed on a part of the first surgical field sheet 36 and the second surgical field sheet 37 and placed over a part of the patient P. That is, the third surgical field sheet 38 is placed on the first sheet support part 5 through intermediation of the first surgical field sheet 36 and placed on the second sheet support part 6 through intermediation of the second surgical field sheet 37. A fourth surgical field sheet 39 is placed on the second sheet support part 6. The fourth surgical field sheet 39 is a rectangular protection sheet having dimensions of 50 cm×25 cm. When the fourth surgical field sheet 39 is arranged, the fourth surgical field sheet 39 is arranged so as to be superposed on a part of the first surgical field sheet 36, the second surgical field sheet 37, and the head side sheet 25 and placed over a part of the patient P. That is, the fourth surgical field sheet 39 is placed on the second sheet support part 6 through intermediation of the second surgical field sheet 37 and the head side sheet 25. Thus, the third protection sheet 3 includes a plurality of protection sheets which are formed separately from each other and surround the surgical field S, and hence the third protection sheet 3 can expose the surgical field S having suitable area and shape. That is, the area and shape of the surgical field S to be exposed can be changed by changing the degree of superposition of the first surgical field sheet 36, the second surgical field sheet 37, the third surgical field sheet 38, and the fourth surgical field sheet 39. Thus, even when the area of the surgical field S varies depending on the body shape of the patient or the operation type, the surgical field S can be surrounded by the protection sheets. With the radiation protection equipment 10 according to the first embodiment, the amount of radiation exposure of the medical staff can be significantly reduced. Specifically, as a result of measurement for the amount of radiation exposure through use of the radiation protection equipment 10, it has been found that the effective dose equivalent can be reduced to about 1/20 of that of the related art. Further, with the radiation protection equipment 10 according to the first embodiment, a large working area can be ensured during an operation. Further, the size of each component of the radiation protection equipment 10 can be reduced, thereby being capable of decreasing the weight thereof. Further, the radiation protection equipment 10 can be installed within a short time period before the operation, and each component can be easily put away after the operation. [Second Embodiment] Subsequently, a radiation protection equipment 10 according to a second embodiment of the present invention is described with reference to FIG. 5. FIG. 5 is a view for illustrating mounting of a third protection sheet 203, and the first protection sheet 1 and the second protection sheet 2 are not shown. Further, FIG. 5 is a view for illustrating the third protection sheet 203 in a developed state as viewed from above. In FIG. 5, the right side corresponds to the foot side of the patient, and the left side corresponds to the head side of the patient. In the description of the second embodiment, differences from the first embodiment are described. The components described in the first embodiment are denoted by the same reference symbols, and descriptions thereof are therefore omitted. Unless otherwise noted, the components denoted by the same reference symbols have substantially the same operation and function, and actions and effects thereof are also substantially the same. In the second embodiment, the shape of the third protection sheet 203 is different from that of the first embodiment. Specifically, the third protection sheet 203 includes two protection sheets including a first surgical field sheet 236 and a second surgical field sheet 237, which surround the surgical field S. The first surgical field sheet 236 and the second surgical field sheet 237 both have a substantially L-shape. Also with the third protection sheet 203 according to the second embodiment, the first surgical field sheet 236 and the second surgical field sheet 237 can be combined so as to expose a rectangular region. Further, the first surgical field sheet 236 and the second surgical field sheet 237 are formed separately from each other. With this, the size of each protection sheet can be even further reduced, and the weight thereof can be even further decreased. Two edges on the surgical field S side of each of the first surgical field sheet 236 and the second surgical field sheet 237 define each side of the rectangular surgical field S. Also in the second embodiment, the third protection sheet 203 is covered with a sterilized cover cloth (not shown), and the cover cloth is attached to the body of the patient P with a tape. Further, the third protection sheet 203, in place of the cover cloth, may be sterilized and attached to the body of the patient. Further, the third protection sheet 203 may be accommodated into a sterilized cover and attached to the body of the patient. When the third protection sheet 203 is arranged, the first surgical field sheet 236 is first placed on the first sheet support part 5 and mounted to the second sheet support part 6. The first surgical field sheet 236 is a substantially L-shaped protection sheet, and has a shape obtained by cutting away a rectangle having dimensions of 30 cm×60 cm from a rectangle having dimensions of 180 cm×90 cm. Further, a hook-and-loop fastener (not shown) is arranged in a part of the first surgical field sheet 236. When the first surgical field sheet 236 is arranged, the first surgical field sheet 236 is arranged so as to cover the radiation source device 101 and to be superposed on the first protection sheet 1 (not shown) and a part of the foot side sheet 25 (not shown), and placed over a part of the patient P. That is, the first surgical field sheet 236 is placed on the first sheet support part 5 through intermediation of the first protection sheet 1. At the same time, the hook-and-loop fastener of the first surgical field sheet 236 is joined to the hook-and-loop fastener 68 of the second sheet support part 6. With this, the first surgical field sheet 236 is mounted to the second sheet support part 6. Subsequently, the second surgical field sheet 237 is mounted to the second sheet support part 6. In this case, the second surgical field sheet 237 is arranged so as to be superposed on a part of the foot side sheet 25 (not shown) and placed over a part of the patient P. The second surgical field sheet 237 is a substantially L-shaped protection sheet, and has a shape obtained by cutting away a rectangle having dimensions of 50 cm×40 cm from a rectangle having dimensions of 100 cm×85 cm. Further, a hook-and-loop fastener (not shown) is arranged in a part of the second surgical field sheet 237. When mounting the second surgical field sheet 237, the hook-and-loop fastener of the second surgical field sheet 237 is joined to the hook-and-loop fastener 68 of the second sheet support part 6. With this, the second surgical field sheet 237 is mounted to the second sheet support part 6. As described above, the third protection sheet 203 according to the second embodiment includes a plurality of protection sheets which are formed separately from each other and surround the surgical field S, and hence the third protection sheet 3 can expose the surgical field S having suitable area and shape. That is, the area and shape of the surgical field S to be exposed can be changed by changing the degree of superposition of the first surgical field sheet 236 and the second surgical field sheet 237. Thus, even when the area of the surgical field S varies depending on the body shape of the patient or the operation type, the surgical field S can be surrounded by the protection sheets. Also with the radiation protection equipment 10 according to the second embodiment, the amount of radiation exposure of the medical staff can be significantly reduced, and a large working area can be ensured during an operation. Further, the size of each component of the radiation protection equipment 10 can be reduced, thereby being capable of decreasing the weight thereof. Further, the radiation protection equipment 10 can be installed within a short time period before the operation, and each component can be easily put away after the operation. The present invention is described above by way of each embodiment, but the present invention is not limited to the above-mentioned embodiments. The present invention also encompasses the invention modified within the scope of the present invention, and the invention equivalent to the present invention. Each of the above-mentioned embodiments and each modification example can be appropriately combined within the scope of the present invention. For example, the size of each protection sheet can be suitably changed depending on the dimensions and the like of the imaging apparatus 110. In particular, the lengths of the first side surface sheet 11 and the second side surface sheet 12 can be appropriately set depending on the height of the radiation source device 101. Further, the first protection sheet 1 may include four or more protection sheets or two protection sheets. The second protection sheet 2 may include three or more protection sheets. Further, the third protection sheet 3 may include five or more protection sheets. Further, the first surgical field sheet 36 of the third protection sheet 3 covers an upper portion of the radiation source device 101, but the first surgical field sheet 36 may be formed to dimensions that do not cover the radiation source device 101. Further, the first sheet support part 5 can be formed to a substantially L-shape in the same manner as in the second sheet support part 6. Further, it is only necessary that the first sheet support part 5 and the second sheet support part 6 have a shape capable of supporting the protection sheets, and the first sheet support part 5 and the second sheet support part 6 may be formed of a pipe curved in an arc shape. Further, the first sheet support part 5 and the second sheet support part 6 may be formed of a stainless steel plate having a planar shape. However, a large sheet support part such as a screen has a risk of falling down. Thus, it is preferred that a relatively small sheet support part capable of being fixed to the operation table 9 be employed. Further, means for mounting the protection sheet to the sheet support part is not limited to the hook-and-loop fastener. The protection sheet can be mounted through use of means such as a snap button, a belt, and an adhesive tape. Further, a tubular mounting part may be arranged on the protection sheet so that the protection sheet is mounted to the sheet support part with the mounting part. This application claims the benefit of priority from Japanese Patent Application No. 2014-194643, filed on Sep. 25, 2014, the content of which is incorporated herein by reference. 1: first protection sheet, 2: second protection sheet, 3: third protection sheet, 5: first sheet support part, 6: second sheet support part, 9: operation table, 10: radiation protection equipment, 11: first side surface sheet, 12: second side surface sheet, 13: back surface sheet, 51: first extension part, 52: second extension part, 56: fixing part, 61: first extension part, 62: second extension part, 100: radiation protection system, 101: radiation source device, 102: detector, 110: imaging apparatus, S: surgical field |
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description | Objects such as wafers are manufactured by a highly complex manufacturing process. The wafer may be evaluated during the manufacturing process and even after the completion of the manufacturing process. The evaluation of the integrated circuit may include inspecting the integrated circuit, reviewing the wafer and/or measuring structural elements of the integrated circuit. Scanning electron microscopes exhibit a nanometric resolution but are slow and have relatively large footprints. There is a growing need to provide fast and compact systems and method for evaluating objects such as integrated circuits. There may be provided a system. The system may include (a) evaluation units, (b) an object distribution system for receiving the objects and distributing the objects between the evaluation units, and (c) at least one controller. Each evaluation unit may include (i) a chamber housing that has an inner space, (ii) a chuck, (iii) a movement system that is conFigured to move the chuck, and (iv) a charged particle module that is conFigured to irradiate the object with a charged particle beam, and to detect particles emitted from the object. In each evaluation unit, a length of the inner space is smaller than twice a length of the object, and a width of the inner space is smaller than twice a width of the object. There may be provided a method. The method may include (a) receiving objects by an object distribution system, (b) distributing the objects, by the object distribution system, between evaluation units, and (c) evaluating the objects by the evaluation units. The evaluating of the objects by the evaluation units may include evaluating at least two objects by at least two evaluation units in parallel. The evaluating of an object of the objects by an evaluation unit of the evaluation units may include (i) positioning the object on a chuck of the evaluation unit and within an inner space that is defined by a chamber housing of the evaluation unit, (ii) sealing the inner space from a movement system of the evaluation unit, (iii) irradiating, by a charged particle module of the evaluation unit, the object with a charged particle beam, and (iv) detecting, by the charged particle module, particles emitted from the object. For each evaluation unit of the evaluation units, a length of the inner space is smaller than twice a length of the object and a width of the inner space is smaller than twice a width of the object. It will be appreciated that for simplicity and clarity of illustration, elements shown in the Figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the Figures to indicate corresponding or analogous elements. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the disclosure. However, it will be understood by those skilled in the art that the present embodiments of the disclosure may be practiced without these specific details. In other instances, well-known methods, procedures, and components have not been described in detail so as not to obscure the present embodiments of the disclosure. Any reference in the specification to a method should be applied mutatis mutandis to a system capable of executing the method. Any reference in the specification to a system should be applied mutatis mutandis to a method that may be executed by the system. The assignment of the same reference numbers to various components may indicate that these components are similar to each other. FIG. 1 illustrates an example of system 11 for evaluation of objects. FIG. 1 also illustrates object 190. System 11 includes five evaluation units 106, an object distribution system, at least one controller 107 and processor 1181. The number of evaluation units per system may be two, three, four or may exceed five. The evaluation units 106 may work independently from each other. In order to increase throughput, at least two evaluation units 106 operate in parallel to each other. Parallel means in an overlapping or in a partial overlapping manner. The object distribution system is configured to receive objects and distribute the objects between evaluation units 106. The object distribution system may receive at least one object at a time. The object distribution system may distribute at least one object at a time. In FIG. 1 the object distribution system is illustrated as including factory interface unit 103, outside transfer robot 102, load lock 104, transfer chamber 109 and inside transfer robot 108. The outside transfer robot 102 may be located inside factory interface unit 103. Inside transfer robot 108 may be located within transfer chamber 109. In system 11 objects such as wafers may be transported in a cassette 101. The cassette 101 is loaded on load ports of the factory interface unit 103. The factory interface unit 103 is an interface that is configured to receive objects. The outside transfer robot 102 transfers the objects from the cassette 101 to load lock 104. One or more vacuum pumps (not shown) connected to the load lock 104 may pump down the load lock 104 to a desired pressure level that may approximate the pressure level in transfer chamber 109. An external gate 116 of the load lock and internal gate 117 between the load lock 104 and the transfer chamber 109 as well as vacuum pumps and venting system (not shown) provide necessary vent/pump cycle of the load lock 104. The load lock 104 may include a support module 1041 for receiving and supporting an object. Inside transfer robot 108 picks up an object from the load lock 104 and loads the object into any of the evaluation units 106. The object may be transferred from the load lock 104 to any evaluation unit 106, and from one evaluation unit 106 to another evaluation unit 106 under a controlled pressure level, including various levels of vacuum. The pressure levels within the load lock 104, the transfer chamber 109, and each of the evaluation units 106 may be maintained at substantially the same or different pressure levels, as desired. Internal gates 117 may be mounted between transfer chamber 109 and the evaluation units 106. The internal gates 117 provide prevention of the objects cross-contamination. In FIG. 1, each evaluation unit includes a charged particle module such as a scanning electron microscope column 111, optical microscope 112 and chamber 113. The optical microscope 112 may be used for detecting suspected defects, navigating towards suspected defects and the like. Each evaluation unit 106 is compact in the sense that (a) a width 171 of space 411 which is an inner space defined by the chamber 113 does not exceed twice a width 181 of object 190, and (b) a length 172 of space 411 defined by the chamber 113 does not exceed twice a length 182 of object 190. The evaluation unit 106 may be compact by evaluating only one region of the object 190 at a time. The object 190 is moved between an evaluation of one region to the other—in order to expose different regions of the object to the scanning electron microscope at a time. FIG. 1 also illustrates vibration dumping elements such as bellows 110 that are coupled between the evaluation units 106 and the transfer chamber 109 of the object distribution system. The evaluation of an object by an evaluation unit may involve moving the object. A movement of the object by one evaluation unit may vibrate another evaluation unit. Vibration dumpling elements may be any mechanical elements that dump (attenuate) the vibration generated by one evaluation unit. Especially—attenuate the vibrations before the vibrations reach another evaluation unit. FIG. 1 further illustrates one or more processors such as processor 1181. The one or more processors may be conFigured to process images or any other detection signals received from the evaluation units. The one or more processors may be any combination of hardware processors, image processors, accelerators, general-purpose computers, and the like. The one or more processors may be included in the evaluation units 106, located outside the evaluation units 106, and the like. FIG. 2 is a cross-sectional view of a part of system 11. FIG. 2 also illustrates object 190. System 11 is shown as including: a. Transfer chamber 109. b. Inside transfer robot 108. c. Evaluation unit 106 that includes chamber 113, scanning electron microscope column 111, optical microscope 112 and first vibration isolation system 2071. d. Legs 119. e. Base 120. f. Bellows 110. Transfer chamber 109 is supported by legs 119. Chamber 113 is supported by a first vibration isolation system 2071. Legs 119 and first vibration isolation system 2071 are positioned on base 120. Base 120 may be a part of a chassis. FIG. 3 illustrates an example of system 19 for evaluation of objects. System 19 includes five evaluation units 106, an object distribution system, at least one controller (not shown) and at least one processor (not shown). FIG. 3 differs from FIG. 1 by providing a more detailed example of bellows 110. FIG. 4 is a cross-sectional view of a part of system 19. System 19 is shown as including: a. Cassette 101. b. Factory interface unit 103. c. Outside transfer robot 102. d. Load lock 104. Load lock 104 has an external gate 116. e. Inside transfer robot 108. f. Transfer chamber 109. g. Bellows 110. h. Internal gates 117 between the transfer chamber and each one of the load lock 104 and the evaluation units 106. i. Pre-liner module 209. j. Second chassis 201. k. Second vibration isolation system 202. l. Transfer chamber 109. Transfer chamber 109 is mounted on the second vibration isolation system 202. Second vibration isolation system 202 is installed on the second chassis 201. m. Evaluation unit 106. Evaluation unit 106 includes a chamber 113 that includes a cover 203 and a sidewall. Evaluation unit 106 also includes a chuck (electrostatic or mechanical) 215, and movement system (for example, XY stage, XYZ stage, XYZ⊖ stage, ⊖ stage or R⊖Z stage) 206. n. Scanning electron microscope column 111. o. Optical microscope 112 that is installed on the cover 203. P. First chassis 208. q. First vibration isolation system 2071 that is installed on first chassis 208. Chamber 113 may be compact design because, for example, the 300 mm wafer is positioned on top of a substrate motion system. The movement system is configured to move along each one of X-axis and Y axis is by up to 75 mm per direction. A quarter turn of the substrate may be done by a rotary stage (⊖ stage) of movement system 206, or by the pre-liner module 209 that may be mounted, for example, in the load lock 104. FIG. 5 illustrates an example of system 12 for evaluation of objects. System 12 differs from system 11 of FIG. 1 by having evaluation units 106 that do not include optical microscopes. FIG. 6 illustrates an example of system 13 for evaluation of objects. System 13 differs from system 11 of FIG. 1 by not including bellows 110. FIG. 7 illustrates an example of system 14 for evaluation of objects. System 14 differs from system 11 of FIG. 1 by: a. Having four evaluation units 106 and not five evaluation units 106. b. Having an additional load lock 104′. Load lock 104 and additional load lock 104′ are connected between factory interface unit 103 and transfer chamber 109. Using multiple load locks may increase the rate of exchanging objects between factory interface unit 103 and transfer chamber 109. FIG. 8 illustrates an example of system 15 for evaluation of objects. System 15 differs from system 11 of FIG. 1 by: a. Having three evaluation units 106 and not five evaluation units 106. b. Having two cassettes 101 instead of three cassettes. FIG. 9 illustrates an example of system 16 for evaluation of objects. System 16 differs from system 11 of FIG. 1 by having four evaluation units 106 and not five evaluation units 106. Any combination of any components of any system illustrated in any of the Figures may be provided. The number of each component is each of the system may differ from those illustrated in any of the Figures. For example the number of load locks per system may exceed one. FIG. 10 illustrates an example of method 220. Method 220 may include the following steps: a. Receiving (222) objects by an object distribution system. The objects may be received simultaneously, one at a time or some at a time. For example, objects may be received from one or more cassettes, housings and the like. The receiving may include receiving one or more objects by one or more outside transfer robots, and transferring the object via one or more load lock and to the inner transfer robot. b. Distributing (224) the objects, by the object distribution system, between evaluation units. The distributing may include providing one or more objected by one or more inner transfer robot to one or more evaluation units, transfecting an object from one evaluation unit to another. c. Evaluating (226) the objects by the evaluation units. The evaluating may include at least one out of inspecting, reviewing or performing a metrology operation. d. Dumping (228) dumping vibrations. Especially, dumping vibrations by vibration dumping elements that are coupled between the evaluation units and the object distribution system. The receiving (222), distributing (224) and the evaluation (226) may be executed in a sequential manner, in a pipelined manner, in an overlapping manner, in a non-overlapping manner, in a partially overlapping manner and the like. For example, two substrates may be fed to two evaluation units while a third evaluation unit is being fed by a third substrate. The dumping can be executed in parallel to the evaluating. For each evaluation unit of the evaluation units, the length of the inner space may be smaller than twice the length of the object. The length of the inner space may be measured within an imaginary plane in which the object is positioned during the evaluation of the object. The imaginary plane may be positioned slightly above the chuck. For each evaluation unit of the evaluation units, the width of the inner space may be smaller than twice the width of the object. The width of the inner space may be measured within the imaginary plane in which the object is positioned during the evaluation of the object. For each evaluation unit of the evaluation units, the length of the inner space may be smaller than twice the length of the object but may exceed 1.5 times of the length of the object. For each evaluation unit of the evaluation units, the width of the inner space may be smaller than twice the width of the object but may exceed 1.5 times of the width of the object. The evaluating (226) may include executing one or more steps of method 900 of FIG. 16. The evaluating (226) may include repeating, for each region of the object out of a plurality of regions of the object: a. Rotating the chuck, by the movement system, to position a given portion of the region of the object within a field of view of the charged particle module; and b. Moving the chuck, by the movement system, in relation to the charged particle module to position additional portions of the region of the object within the field of view of the charged particle module. The object can have a radial symmetry, and the plurality of regions may include four regions. Method 220 may include comparing (230) between evaluation results generated by different evaluation units. The evaluation results may refer to the same object or to different objects. The comparing may be used for various purposes including defect detection, calibration of stations, evaluating process variations and the like. FIG. 11 is an example of a cross-sectional view of system 11. The cross-section is taken along an imaginary plane that does not cross the center of system 11. FIG. 11 illustrates: a. Cassette 101. b. Outside transfer robot 102. c. Factory interface unit 103. d. Load lock 140. Load lock 104 includes external gate 116, internal gate 117, and support module 1041 for receiving and supporting an object. e. Second vibration isolation system 202, which is installed on the second chassis 201. The second vibration isolation system 202 supports the transfer chamber 109. Such configuration allows reaching a high-resolution image of the object features and improves the quality of treatment in process chambers. f. Evaluation unit 106. g. Inside transfer robot 108. h. Transfer chamber 109. i. Scanning electron microscope column 111. j. Optical microscope 112. k. A housing of the evaluation unit that includes cover 203 and sidewalls 204. l. Chuck 205. Chuck 205 may be an electrostatic chuck or a mechanical chuck. Chuck 205 may support an object. m. Movement system 206. n. Sealing plate 207. o. Module 400 which is an air bearing/differential pumping module. p. Vacuumed space 411 that is defined by the housing of the evaluation unit and the sealing plate 207. q. Movement system base 2081. The movement system 206 includes a rotation stage (also referred to as theta stage) for rotating the object, a Z stage and may also include one stage such as an XY stage or a R stage. FIG. 12 is an example of a rear view of the evaluation unit 106. The movement system base 208 has brackets 301. The brackets 301 are connected to the sidewalls 204 of the evaluation unit 106. FIG. 12 also illustrates second chassis 201, sealing plate 207, movement system 206, and movement system base 2081. The evaluation unit 106 prevents sources of contamination from contaminating an object. The object, during evaluation processes or manufacturing processes, is located in a vacuumed space in which predetermined conditions (contamination level, vacuum level, temperature and the like) are maintained even when the object is moved by the movement system 206. The movement system 206 may be located in atmosphere environment. Cables, control device and various other components can be located in atmosphere in order to reduce and even eliminate the amount of contaminating elements generated within the atmosphere. The chamber can be free of moving parts. The vacuumed space can be isolated from atmosphere environment by using one or more dynamic seals, such as dynamic seals 440 of FIGS. 13 and 14. Contamination which is generated by the movement system 206, by bearing and from plastic cables may be prevented from reaching the vacuumed space 411 due to a positive air flow formed by the dynamic seal. The dynamic seal can be arranged to generate an air flow directed towards the atmosphere and thus repel contamination from entering the vacuum chamber. FIG. 13 is a cross-sectional view of the area of a module 400 that illustrates a dynamic seal 440. The seal is dynamic in the sense that it requires to circulate air. The module 400 is mechanically connected to sidewall 204 and forms a dynamic seal 440 between the bottom surface of module 400 and sealing plate 207. The module 400 may include one or more sealing elements such as first vacuum conduit 402, second vacuum conduit 403 and third vacuum conduit 404, each of which is connected with its vacuum pump (not shown in the Figure). The bottom surface of module 400 includes the three vacuum grooves 405, 406 and 407 and atmospheric pressure gas groove 408 which is a differential pumping unit. In addition, the bottom part of module 400 may include several orifices 409 which form an air bearing unit. The manner in which a gas cushion (dynamic seal) is formed is illustrated, for example, in U.S. Pat. No. 6,899,765 which is incorporated herein by reference in its entirety. Different conduits can provide gas at different pressure and/or vacuum levels. Module 400 may be mechanically connected to sidewall 204 by a clamping mechanism 401. The clamping mechanism 401 is arranged around the perimeter of module 400 and are adapted to provide sufficient force to compensate for the force of the pressure differential between the module 400 and the atmosphere. FIGS. 14 and 15 illustrate various parts of the system 11 such as cover 203, scanning electron microscope column 111, optical microscope 112, chuck 205, support element 410, sealing plate 207, first opening 431, second opening 432, first bellows 412 and second bellows 414. Support element 410 supports chuck 205 and mechanically coupled chuck 205 to the movement system 206. FIGS. 14 and 15 also illustrate dynamic seals 440. First bellows 412 and second bellows 414 surround the support element 410 in order to prevent a leakage of particles from the movement system 206 into vacuumed space 411. First opening 431 and second opening 432 are formed in cover 203. A lower part of scanning electron microscope column 111 is inserted through first opening 431. A lower part of optical microscope 112 is inserted through second opening 432. The sealing plate 207 of FIG. 13 is positioned in a different position than the sealing plate 207 of FIG. 5, due to a movement of the sealing plate 207 (as well as the support element 410 and the chuck 205) by the movement system. FIG. 16 illustrates an example of object 500, first region 501, second region 502, third region 503, fourth region 504, portions 511 of first region 501, portions 512 of second region 502, portions 513 of third region 503 and portions 514 of fourth region 504. Object 500 has a symmetrical symmetry and first region 501, second region 502, third region 503, fourth region 504 have a quadrant shape. The evaluation unit may evaluate object 500 by four iterations. A single region may be evaluated during each iteration of the four iterations. Each iteration may start by rotating the object 500 by ninety degrees in order to reach the region that should be evaluated during the iteration. Reaching regions means that portions of the region can be positioned within the field of view of the scanning electron microscope and/or within the field of view of the optical microscope by moving the chuck. The field of view of the scanning electron microscope may be smaller than the region but additional movements of the chuck (for example raster scan movement or any other movements) and/or scanning by at the scanning electron microscope may cover the entire region. The same applies to the optical microscope. The movements of the chuck are limited to movements that should not cause another region of the object to be positioned within the field of view of the scanning electron microscope and/or within the field of view of the optical microscope. During a first iteration, portions 511 of first region 501 may be positioned within the within the field of view of the scanning electron microscope and/or within the field of view of the optical microscope. During a second iteration, portions 512 of second region 502 may be positioned within the within the field of view of the scanning electron microscope and/or within the field of view of the optical microscope. During a third iteration, portions 513 of third region 503 may be positioned within the within the field of view of the scanning electron microscope and/or within the field of view of the optical microscope. During a fourth iteration, portions 514 of fourth region 504 may be positioned within the within the field of view of the scanning electron microscope and/or within the field of view of the optical microscope. FIG. 17 is an example of method 800 for moving an object within a chamber that includes a chamber housing. Method 800 may start by step 810 of positioning an object on a chuck that is positioned within the chamber. The chuck is mechanically coupled to a movement system. Step 810 may be followed by step 820 of sealing the chamber from the movement system by forming, by at least one sealing element, a dynamic seal between an intermediate element and the chamber housing. The intermediate element is positioned between the chamber housing and the movement system. Step 810 may also be followed by repeating, for each region of the object out of a plurality of regions of the object, steps 830 and 840. Step 830 may include rotating the chuck, by the movement system, to position a given portion of the region of the object within a field of view that is related to an opening of the chamber housing. The field of view is related to the opening in the sense that (a) an evaluation tool that has a field of view may be partially inserted through the opening, and/or (b) an evaluation tool that has a field of view may view the object through the opening. Step 830 may include using a rotary stage of the movement system to rotate the chuck. Step 830 may be followed by step 840 of moving the chuck, by the movement system, in relation to the opening to position additional portions of the region of the object within the field of view that is related to the opening. Step 830 and 840 may be executed in parallel to step 820. The object may have a radial symmetry and the plurality of regions may include four regions—or any other number of regions. Step 840 may include at least one of the following: a. Using an XY (X-axis and Y-axis) stage of the movement system. b. Moving the intermediate element in relation to the chamber housing while moving the chuck in relation to the opening. c. Moving the intermediate element by up to a maximal distance in any direction, wherein the maximal distance does not exceed one hundred and twenty percent of a radius of the object. FIG. 18 is an example of method 900 for moving an object within a chamber that includes a chamber housing. Method 900 may start by step 810 of positioning an object on a chuck that is positioned within the chamber. The chuck is mechanically coupled to a movement system. Step 810 may be followed by step 820 of sealing the chamber from the movement system by forming, by at least one sealing element, a dynamic seal between an intermediate element and the chamber housing. The intermediate element is positioned between the chamber housing and the movement system. Step 810 may also be followed by repeating, for each region of the object out of a plurality of regions of the object, steps 930, 940 and 950. Step 930 may include rotating the chuck, by the movement system, to position a given portion of the region of the object within a field of view of a microscope. Step 930 may be followed by step 940 of moving the chuck, by the movement system, in relation to the opening to position additional portions of the region of the object within the field of view of the microscope. Step 940 may be followed by step 950 of evaluating, using the microscope, suspected defects of the objects that are positioned in the additional portions of the region of the object. The microscope may be a scanning electron microscope. Step 950 may include finding the suspected defects using an optical microscope and scanning the suspected defects by the scanning electron microscope. The evaluation unit is compact and can be integrated with various tools that differ from any of the systems illustrated in any of the previous Figures. The evaluation unit may include a review tool such as a scanning electron microscope reviews defects of an object positioned within the chamber. The evaluation unit may be included in an optical inspection system. The evaluation tool may be configured to perform immediate, object to object comparison and accurate control of a processing of the object. The object may be, for example, a mask or a wafer. The processing of the object may include, for example, at least one out of etch, deposition, copper mechanical polishing, and Implant. The scanning electron microscope may be configured to perform at least one of the following tasks: detect defect, review defects, measure dimensions, measure layer to layer location, measure pattern positioning and edge placement accuracy. The scanning electron microscope, after completing a task may be configured to provide immediate feedback to a processing tool. Any of the systems may be integrated with one or more processing tool. For example—one or more of the evaluation units of the system may be replaced by a processing tool. Accordingly—the processing tool and the evaluation tool may belong to the same system. Hence immediate and automated tuning of the processing tool may be provided. The integration of the evaluation tool with a process tool allows to perform evaluations of layers or features of an object during manufacturing steps that limit the provision of the object outside of the process environment defined by the processing tool. The limit may result, for example, due to oxidation. The inclusion of a processing tool in a system that includes one or more evaluation units may provide (a) fast fault response and root cause analysis, (b) improve process quality and process uniformity along the object, (c) improve process chamber to process chamber matching. Most of the wafer fabrication systems include multiple process chambers which perform the same operations. (same chemistry, thermal effects, material flows, irradiances and the like). However, there are small differences among the exact process parameters of the process chambers. The differences will cause fabrication process differences and the final result will be physical differences among wafers due to their history location in the specific process chamber. The evaluation tool will enable to define the differences and to perform immediate parameters tuning which will bring the process chambers to match to other and hence to reduce the process differences associated with the differences among process chambers. The evaluation unit facilitates non-destructive inspection, metrology, compositional analysis of moisture, atmosphere and time sensitivity nanofilms and structures. In the foregoing specification, the embodiments of the disclosure has been described with reference to specific examples of embodiments of the disclosure. It will, however, be evident that various modifications and changes may be made therein without departing from the broader spirit and scope of the embodiments of the disclosure as set forth in the appended claims. Moreover, the terms “front,” “back,” “top,” “bottom,” “over,” “under” and the like in the description and in the claims, if any, are used for descriptive purposes and not necessarily for describing permanent relative positions. It is understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the disclosure described herein are, for example, capable of step in other orientations than those illustrated or otherwise described herein. The connections as discussed herein may be any type of connection suitable to transfer signals from or to the respective nodes, units or devices, for example via intermediate devices. Accordingly, unless implied or stated otherwise, the connections may for example be direct connections or indirect connections. The connections may be illustrated or described in reference to being a single connection, a plurality of connections, unidirectional connections, or bidirectional connections. However, different embodiments may vary the implementation of the connections. For example, separate unidirectional connections may be used rather than bidirectional connections and vice versa. Also, plurality of connections may be replaced with a single connection that transfers multiple signals serially or in a time multiplexed manner. Likewise, single connections carrying multiple signals may be separated out into various different connections carrying subsets of these signals. Therefore, many options exist for transferring signals. Although specific conductivity types or polarity of potentials have been described in the examples, it will be appreciated that conductivity types and polarities of potentials may be reversed. Those skilled in the art will recognize that the boundaries between logic blocks are merely illustrative and that alternative embodiments may merge logic blocks or circuit elements or impose an alternate decomposition of functionality upon various logic blocks or circuit elements. Thus, it is to be understood that the architectures depicted herein are merely exemplary, and that in fact many other architectures may be implemented which achieve the same functionality. Any arrangement of components to achieve the same functionality is effectively “associated” such that the desired functionality is achieved. Hence, any two components herein combined to achieve a particular functionality may be seen as “associated with” each other such that the desired functionality is achieved, irrespective of architectures or intermedial components. Likewise, any two components so associated can also be viewed as being “operably connected,” or “operably coupled,” to each other to achieve the desired functionality. Furthermore, those skilled in the art will recognize that boundaries between the above described steps are merely illustrative. The multiple may be combined into a single step, a single step may be distributed in additional steps and steps may be executed at least partially overlapping in time. Moreover, alternative embodiments may include multiple instances of a particular step, and the order of steps may be altered in various other embodiments. Also for example, in one embodiment, the illustrated examples may be implemented as circuitry located on a single integrated circuit or within a same device. Alternatively, the examples may be implemented as any number of separate integrated circuits or separate devices interconnected with each other in a suitable manner. However, other modifications, variations and alternatives are also possible. The specifications and drawings are, accordingly, to be regarded in an illustrative rather than in a restrictive sense. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word ‘comprising’ does not exclude the presence of other elements or steps then those listed in a claim. Furthermore, the terms “a” or “an,” as used herein, are defined as one or more than one. Also, the use of introductory phrases such as “at least one” and “one or more” in the claims should not be construed to imply that the introduction of another claim element by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim element to embodiments of the disclosures containing only one such element, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an.” The same holds true for the use of definite articles. Unless stated otherwise, terms such as “first” and “second” are used to arbitrarily distinguish between the elements such terms describe. Thus, these terms are not necessarily intended to indicate temporal or other prioritization of such elements. The mere fact that certain measures are recited in mutually different claims does not indicate that a combination of these measures cannot be used to advantage. While certain features of the embodiments of the disclosure have been illustrated and described herein, many modifications, substitutions, changes, and equivalents will now occur to those of ordinary skill in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the embodiments of the disclosure. |
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abstract | A collimator for an X-ray inspection apparatus is provided comprising a carrier having a planar top surface; an arcuate base disposed on the carrier, comprising at least one arcuate bar section made from a radio-opaque material; and a plurality of radio-opaque collimator plates disposed on the arcuate base in a radial array with a bottom edge of each collimator plate in contact with the top surface of the arcuate base. A method for assembling such a collimator is also provided, as well as an alignment fixture useful for practicing the described method. The described structure, method, and alignment fixture permit the construction of large collimator assemblies while maintaining precision and minimizing cost. |
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047479981 | claims | 1. A thermally actuated thermionic switch which responds electrically to an increase in temperature of thermionic material therein by changing from a high impedance to a low impedance at a predetermined temperature set point, comprising: an emitter constituting an outer casing of said switch and adapted to be in contact with an associated medium which may undergo a change in temperature, said outer casing having a closed end and an open end, a collector positioned totally within said emitter and separated therefrom by a gap, said collector including a hollow longitudinally extending annular section and a hollow reduced diameter section, said collector being electrically isolated from said emitter and retained within said emitter by an insulator member positioned within said emitter, said insulator member being located intermediate said reduced diameter section of said collector and an inner surface of said emitter, means for closing said open end of said outer casing formed by said emitter for defining a closed volume within said emitter, electrical lead means connected to said inner surface of said emitter and to said reduced diameter section of said collector and extending through said means for closing said outer casing for connection to an associated power supply and to an associated point of use, and a quantity of thermionic material held in a matrix in a graphite block reservoir, and which is located within said emitter, said thermionic material consisting of metal which ionizes when heated to a temperature above said set point, for electrically connecting said emitter and collector when said thermionic material is ionized, whereby upon said thermionic material ionizing, said switch changes from high impedance to low impedance allowing the conduction of large electrical currents therethrough. said thermionic switch containing a quantity of thermionic material which ionizes when heated to a predetermined temperature above said set point, said thermionic material constituting a metal held in a matrix in a graphite block reservoir, said switch additionally including: an emitter electrode defining an outer body of said switch and adapted to be in contact with an associated coolant, said outer body having a closed end and an open end, said graphite block reservoir being secured to an inner surface of said emitter electrode. a collector electrode located totally within and spaced from said emitter electrode, said collector electrode including a hollow longitudinally extending annular section and a hollow reduced diameter end section, an insulator member secured to an inner surface of said emitter electrode and secured to an outer surface of said collector electrode for retaining said collector electrode within said emitter electrode and for electrically isolating same, means containing insulative material for closing said open end of said emitter electrode for forming a closed volume therein, and electrical lead means connected to said inner surface of said emitter electrode and to said collector electrode and extending through said closing means and adapted to be connected to an associated electrical circuit for controlling same, said quantity of thermionic material being located within said emitter electrode for electrically connecting said emitter electrode and collector electrode when said material is ionized so as to change said switch from high impedance to low impedance allowing the conduction of electrical current therethrough. an emitter electrode constructed to define an outer casing having an open end and a closed end and constructed to form a space therein, means comprising an insulator member for closing said open end of said emitter electrode for defining a closed volume, a collector electrode located totally within said space and spaced from said emitter electrode so as to form a gap therebetween, said collector electrode including a hollow longitudinally extending annular section and a hollow reduced diameter section, insulator means positioned totally within said space formed by said emitter electrode for retaining said collector electrode within said emitter electrode and for electrically isolating said collector electrode from said emitter electrode, said insulator means being positioned intermediate an outer surface of said collector electrode and an inner surface of said emitter electrode, electric lead means connected to said inner surface of said emitter electrode and to said reduced diameter section of said collector electrode, extending through said closing means, and adapted to be connected to an associated power supply and to an associated point of use, and a quantity of thermionic material selected from the group consisting of cesium, sodium, potassium and rubidium, which ionizes upon being heated to a predetermined temperature, located within said emitter electrode and held in a matrix in a graphite block reservoir so as to be adjacent said emitter electrode for electrically connecting said emitter electrode and said collector electrode when said material ionizes, such that large electrical currents are allowed to pass through said switch from an associated power supply to an associated point of use due to said switch changing from a high impedance to a low impedance at a predetermined temperature. 2. The thermionic switch of claim 1, wherein said thermionic material is a metal which is liquid at a desired operation temperature. 3. The thermionic switch of claim 1, wherein said metal is selected from the group consisting of cesium, sodium potassium and rubidium. 4. The thermionic switch of claim 1, wherein said set point is in a range of about 565.degree.-570.degree. C., and wherein said thermionic material consists of a cesium loaded graphite block secured to an inner surface of said emitter. 5. The thermionic switch of claim 1, wherein said means for closing said outer casing comprises a member containing insulative material secured in and extending into said emitter, through which said electrical lead means extend. 6. A thermionic switch which responds electrically upon an increase in temperature, which ionizes thermionic material therein, by changing from a high impedance to a low impedance at a predetermined temperature set point and adapted to be responsive to coolant temperature: 7. The improvement of claim 6, wherein said temperature set point is in the range of about 565.degree.-570.degree. C., and wherein said quantity of thermionic material consists of a cesium loaded graphite block. 8. The improvement of claim 6, wherein said metal is cesium, and wherein said temperature set point is in a range of about 565.degree.-570.degree. C. 9. A thermally actuated thermionic switch which changes from a high impedance to a low impedance upon ionization of thermionic material therein at a predetermined temperature such that large electrical currents are allowed to flow therethrough, comprising: 10. The thermionic switch of claim 9, wherein said emitter electrode is constructed to include a longitudinally extending annular section, a closed end section and an open end section, said collector electrode and said insulator means being located within said longitudinally extending annular section of said emitter electrode, said thermionic material being located in said closed end section of said emitter electrode and said insulator member through which said electrical lead means extend being located in said open end section of said emitter electrode. 11. The thermionic switch of claim 6, wherein said quantity of thermionic material is selected from the group consisting of cesium, sodium, potassium and rubidium. |
041486862 | claims | 1. An auxiliary cooling device for absorbing residual energy in a primary fluid heat exchanger of a nuclear reactor which continues to generate energy after shut down, said exchanger comprising a casing for conveying a flow of primary fluid heated in the reactor and a nest of tubes disposed inside the casing for conveying a secondary cooling fluid in thermal contact with the primary fluid, said auxiliary cooling device comprising a jacket disposed around the casing and including inlet means and outlet means for an auxiliary cooling fluid, and auxiliary heat exchange surfaces projecting from said casing into the space around the casing inside said jacket. 2. An auxiliary cooling device according to claim 1 wherein the auxiliary cooling fluid is air. 3. An auxiliary cooling device according to claim 1 wherein the auxiliary heat exchange surfaces are constituted by spikes. 4. An auxiliary cooling device according to claim 1 wherein the auxiliary cooling fluid inlet and outlet means include means for providing a forced flow of auxiliary cooling fluid. 5. An auxiliary cooling device according to claim 1 wherein the auxiliary cooling fluid is free to flow by convection. 6. An assembly of auxiliary cooling devices according to claim 4 comprising a plurality of primary heat exchangers connected in parallel each equipped with an auxiliary cooling device wherein the auxiliary cooling devices are connected to a common source of forced flow for the auxiliary cooling fluid. 7. A primary fluid heat exchanger for a nuclear reactor which continues to generate energy after shut down, said exchanger comprising a casing for conveying a flow of primary fluid heated in the reactor and a nest of tubes disposed inside the casing for conveying a secondary cooling fluid in thermal contact with the primary fluid and the auxiliary cooling device of claim 1. 8. A primary fluid heat exchanger according to claim 7 wherein the secondary cooling fluid is water which is heated to superheated steam. 9. A primary fluid heat exchanger according to claim 7 including a primary fluid jacket over portions of the casing adjacent each of its ends, the jacket of the auxiliary cooling device being disposed intermediate the portions of the primary fluid jacket. 10. A rapid neutron nuclear reactor installation including the heat exchanger of claim 7. 11. A reactor installation according to claim 10 wherein the primary fluid heated by the reactor is an alkaline metal. 12. An auxiliary cooling device according to claim 1 including a primary fluid jacket over portions of the casing adjacent each of its ends, the jacket of the auxiliary cooling device being disposed intermediate the portions of the primary fluid jacket. 13. An auxiliary cooling device according to claim 1 wherein the secondary cooling fluid is water which is heated to superheated steam. |
claims | 1. A method of generating radiological images comprising:generating a first image by collimating radiation from a continuously pulsed radiation source onto an imaged zone using a first collimating configuration causing the first image to be refreshed at a first rate;generating a second image by collimating the radiation from the continuously pulsed radiation source onto only a part of the imaged zone using a second collimating configuration causing the second image at be refreshed a second rate,wherein the first rate is lower than the second rate, the radiation is pulsed at a pulse rate corresponding to a pulse period, and a duration of opening or of shutting a collimating system used to collimate the radiation is longer than at least one pulse period. 2. The method according to claim 1, wherein the first image is displayed on a first display screen, and the second image is displayed on a second display screen distinct from the first display screen. 3. The method according to claim 1, wherein the second image is a zoom of a part of the first image. 4. The method according to claim 1, wherein the second image is displayed over a larger or equal screen area than the first image. 5. The method according to claim 1, wherein a box framing the second image is displayed in the first image. 6. The method according to claim 1, wherein the imaged zone is a part of a body of a human being. 7. The method according to claim 1, wherein the imaged zone is imaged by a medical X-ray imaging. 8. The method according to claim 1, wherein the imaged zone is imaged by a medical dynamic X-ray imaging. 9. The method according to claim 1, wherein the duration of opening or of shutting the collimating system used to collimate the radiation is longer than two pulse periods. 10. The method according to claim 1, wherein one or more pulses are not sent during the opening and the shutting of the collimating system. 11. The method according to claim 1, wherein the first image is a combination of captured images, wherein some of the captured images contain only a part of the imaged zone. 12. The method according to claim 1, wherein the first image is a single and full capture of the imaged zone. 13. The method according to claim 1, wherein at least an image processing correction is applied on the second image only and not on the first image. 14. The method according to claim 1, comprising displaying the first image in a first display window and displaying he second image in a second display window distinct from the first display window. 15. An image generation system comprising:a collimator comprising:a first configuration for collimating radiation from a continuously pulsed radiation source onto an imaged zone to generate a first image; anda second configuration for collimating the radiation from the continuously pulsed radiation source onto only a part of the imaged zone to generate a second image,wherein the first collimating configuration is operable to cause the first image to be refreshed at a first rate and the second collimating configuration is operable to cause the second image be refreshed at a second rate that is higher than the first rate, the radiation is pulsed at a pulse rate corresponding to a pulse period, and a duration of opening or of shutting a collimating system used to collimate the radiation is longer than at least one pulse period. 16. The image generation system of claim 15, comprising a first display window for displaying the first image and a second display window distinct from the first display window for displaying the second image. 17. An image system comprising:a continuously pulsed radiation source;a collimating system comprising:a first configuration for collimating radiation from the continuously pulsed radiation source onto an imaged zone to generate a first image; anda second configuration for collimating the radiation from the continuously pulsed radiation source onto only a part of the imaged zone to generate a second image,wherein the first collimating configuration is operable to cause the first image to be refreshed at a first rate and the second collimating configuration is operable to cause the second image be refreshed at a second rate that is higher than the first rate, the radiation is pulsed at a pulse rate corresponding to a pulse period, and a duration of opening or of shutting a collimating system used to collimate the radiation is longer than at least one pulse period; andan image display system comprising:a first display window configured to display the first image; anda second display window, distinct from the first display window, configured to display the second image. |
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abstract | A method for replacing a cesium trap includes freezing the cesium trap which partially contains cesium and is located within a shielded cell and. The cesium trap is then decoupled and removed from the shielded cell. A second cesium trap is inserted into the shielded cell and attached to the shielded cell. |
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claims | 1. A conformal coating composition, comprising: an amount of high Z shielding particles densely packed at a concentration greater than 60% by volume in a first binder; and an amount of low Z shielding particles densely packed at a concentration greater than 60% by volume in a second binder, wherein said amount of high Z shielding particles and said amount of low Z shielding particles are sufficient to shield an object from receiving an amount of radiation greater than a total dose tolerance of said object. 2. The composition of claim 1 , wherein said object is an integrated circuit. claim 1 3. The composition of claim 1 , wherein said high Z shielding particles are selected from the group consisting of tungsten, osmium, iridium, platinum, tantalum, and gold. claim 1 4. The composition of claim 1 , wherein said low Z shielding particles are selected from the group consisting of copper, nickel, carbon, titanium, chromium, cobalt, boron, silicon, iron, and nitrogen. claim 1 5. The composition of claim 1 , wherein said first and second binders are selected from the group consisting of latex, urethane, and epoxy. claim 1 6. A flexible shielding composition, comprising: a fabric; and an amount of high Z shielding particles densely packed at a concentration greater than 60% by volume in a first flexible binder impregnated into said fabric; and an amount of low Z shielding particles densely packed at a concentration greater than 60% by volume in a second flexible binder impregnated into said fabric, wherein said amount of high Z shielding particles and said amount of low Z shielding particles are sufficient to shield an object from receiving an amount of radiation greater than a total dose tolerance of said object. 7. The composition of claim 6 , wherein said flexible shielding composition is clothing for shielding a living object. claim 6 8. The composition of claim 6 , wherein said flexible shielding composition is gasket material. claim 6 9. The composition of claim 6 , wherein said fabric is selected from the group consisting of cotton, polyester, Kevlar, and Teflon. claim 6 10. The composition of claim 6 , wherein said high Z shielding particles are selected from the group consisting of tungsten, osmium, iridium, platinum, tantalum, and gold. claim 6 11. The composition of claim 6 , wherein said low Z shielding particles are selected from the group consisting of copper, nickel, carbon, titanium, chromium, cobalt, boron, silicon, iron, and nitrogen. claim 6 12. The composition of claim 6 , wherein said first and second binders are selected from the group consisting of latex, urethane, and epoxy. claim 6 13. A method of designing a shielding composition, comprising: determining the radiation tolerance of the object to be shielded; determining the radiation requirement for the particular application; and determining the amount of said shielding composition required to bring said object within tolerance relative to said determined radiation tolerance of said object and said determined radiation requirement of said application, wherein said shielding composition consists of an amount of high Z particles densely packed at a concentration greater than 60% by volume in a first binder and an amount of low z particles densely packed at a concentration greater than 60% by volume in a second binder. 14. The method of claim 13 , wherein said object is an integrated circuit. claim 13 15. The method of claim 13 , wherein said object is a living thing. claim 13 16. The method of claim 13 , wherein said high Z shielding particles are selected from the group consisting of tungsten, osmium, iridium, platinum, tantalum, and gold. claim 13 17. The method of claim 13 , wherein said low Z shielding particles are selected from the group consisting of copper, nickel, carbon, titanium, chromium, cobalt, boron, silicon, iron, and nitrogen. claim 13 18. The method of claim 13 , wherein said first and second binders are selected from the group consisting of latex, urethane, and epoxy. claim 13 19. A method of designing a shielding composition, comprising: estimating the amount of shielding composition required to bring an object within a tolerance, wherein said shielding composition consists of an amount of high Z particles densely packed at a concentration greater than 60% by volume in a first binder and an amount of low Z particles densely packed at a concentration greater than 60% by volume in a second binder. 20. The method of claim 19 , wherein said object is an integrated circuit. claim 19 21. The method of claim 19 , wherein said object is a living thing. claim 19 22. The method of claim 19 , wherein said high Z shielding particles are selected from the group consisting of tungsten, osmium, iridium, platinum, tantalum, and gold. claim 19 23. The method of claim 19 , wherein said low Z shielding particles are selected from the group consisting of copper, nickel, carbon, titanium, chromium, cobalt, boron, silicon, iron, and nitrogen. claim 19 24. The method of claim 19 , wherein said first and second binders are selected from the group consisting of latex, urethane, and epoxy. claim 19 25. A method of shielding an object, comprising: applying a conformal coating composition composed of an amount of high Z shielding particles densely packed at a concentration greater than 60% by volume in a first binder an amount of low Z shielding particles densely packed at a concentration greater than 60% by volume in a second binder, wherein said amount of shielding particles are sufficient to shield an object from receiving an amount of radiation greater than a total dose tolerance of said object. 26. The method of claim 25 , wherein said object is an integrated circuit. claim 25 27. The method of claim 25 , wherein said object is a living thing. claim 25 28. The method of claim 25 , wherein said shielding composition is applied to the exterior of said object. claim 25 29. The method of claim 25 , wherein said shielding composition is applied equally in all axial directions. claim 25 30. The method of claim 25 , wherein said high Z shielding particles are selected from the group consisting of tungsten, osmium, iridium, platinum, tantalum, and gold. claim 25 31. The method of claim 25 , wherein said low Z shielding particles are selected from the group consisting of copper, nickel, carbon, titanium, chromium, cobalt, boron, silicon, iron, and nitrogen. claim 25 32. The method of claim 25 , wherein said first and second binders are selected from the group consisting of latex, urethane, and epoxy. claim 25 33. A method of shielding an object, comprising: inserting said object into an injection mold; and injecting a conformal coating composition composed of an amount of high Z shielding particles densely packed at a concentration greater than 60% by volume in a first binder and an amount of low Z shielding particles densely packed at a concentration greater than 60% by volume in a second binder into said injection sold containing said object, wherein said amount of high Z shielding particles and said amount of low Z shielding particles are sufficient to shield said object from receiving an amount of radiation greater than a total dose tolerance of said object. 34. The method of claim 33 , wherein said object is an integrated circuit. claim 33 35. The method of claim 33 , wherein said shielding composition is applied to the exterior of said object. claim 33 36. The method of claim 33 , wherein said shielding composition is applied equally in all axial directions. claim 33 37. The method of claim 33 , wherein said high Z shielding particles are selected from the group consisting of tungsten, osmium, iridium, platinum, tantalum, and gold. claim 33 38. The method of claim 33 , wherein said low Z shielding particles are selected from the group consisting of copper, nickel, carbon, titanium, chromium, cobalt, boron, silicon, iron, and nitrogen. claim 33 39. The method of claim 33 , wherein said first and second binders are selected from the group consisting of latex, urethane, and epoxy. claim 33 |
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claims | 1. A modular reactor head area assembly installed on a reactor head, the modular reactor head area assembly comprising;a seismic support structure comprising a seismic cap plate that supports an upper portion of a control rod driving apparatus inserted thereinto, and a seismic support ring beam coupled to and surrounding an outer circumference surface of the seismic cap plate;an upper module that is an assembly of components located at an upper portion of the seismic support structure and comprises an upper shroud shell detachably coupled to the seismic support ring beam, a plenum disposed on an upper portion of the upper shroud shell, a cooling fan disposed on the plenum, a shackle coupled to the plenum, and a tripod coupled to the shackle;a lower module that is an assembly of components located at a lower portion of the seismic support structure and of which an upper portion is coupled to the seismic support structure; anda main column accommodated in the upper module and lower module, and of which a first end is detachably coupled to the reactor head and a second end is detachably coupled to the tripod. 2. The modular reactor head area assembly of claim 1, wherein the upper module comprises:an upper baffle that is disposed in the upper shroud shell, forms an air path along with the upper shroud shell, and is coupled to the seismic support ring beam. 3. The modular reactor head area assembly of claim 1, wherein the lower module comprises:a lower shroud shell formed as a cylinder with open upper and lower ends;a lower baffle disposed in the lower shroud shell and forming an air path along with lower shroud shell; anda plurality of control rod driving apparatuses coupled to the reactor head. 4. The modular reactor head area assembly of claim 1, wherein a flange is disposed on a lower end portion of the upper shroud shell to protrude outwards, and is coupled to the seismic support ring beam via a bolt. 5. The modular reactor head area assembly of claim 1, further comprising:a cable support ring beam coupled to an external side of the upper shroud shell; anda plurality of cable support wires coupled to the cable support ring beam, wherein a first end of each of the cable support wires is coupled to the cable support ring beam, and a second end is coupled to the cable support ring beam through the upper shroud shell. 6. The modular reactor head area assembly of claim 1, further comprising a cable connection plate disposed on an external side of the upper shroud shell and coupled to a cable extending from the control rod driving apparatus. |
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claims | 1. A method for safe removal of buried waste comprising:a) enclosing the buried waste in a casing;b) providing a system for grinding and mixing the buried waste with surrounding soil to form a mixturec) permitting chemical reactions to occur during mixing to stabilize the mixture;d) testing the mixture for radio isotopes ande) providing a retrieval mechanism for removal of the buried wastewhereby the mixture is stabilized underground without the possibility of surface contamination, tested and safely removed for disposal. 2. The method of claim 1 wherein an enclosure base is used for centering the casing over the buried waste. 3. The method of claim 1 wherein the casing is mechanically driven to enclose the buried waste. 4. The method of claim 1 wherein the grinding mechanism is a rotating augering tool that is housed in an augering tool enclosure concentrically fitted over the casing via an interface enclosure that is fitted over the enclosure base. 5. The method of claim 1 wherein the rotating motion of the augering tool is provided by a drilling rig. 6. The method of claim 1 wherein dust is controlled by using dust control chemicals inserted through one or more openings provided in the interface enclosure. 7. The method of claim 1 wherein the augering tool is cleaned prior to removal by using high pressure water through openings provided in the interface enclosure. 8. The method of claim 1 wherein testing the mixture is done by inserting a detector through a hollow stem auger. 9. The method of claim 8 wherein the detector tests for the presence of radio isotopes in the mixture in situ as the hollow stem auger is rotating in the mixture. 10. The method of claim 9 wherein test results are remotely monitored for classification as transuranic or not transuranic waste. 11. The method of claim 1 wherein a retrieval enclosure is mounted over the enclosure base. 12. The method of claim 1 wherein the retrieval mechanism for transuranic waste is provided by a retrieval bucket attached that scoops out the mixture and removes it into the retrieval enclosure for safe disposal. 13. The method of claim 12 wherein the retrieval bucket is moved axially into the casing by the drilling rig. 14. The method of claim 12 where in the retrieval enclosure contains a hopper and conveyor to transport the mixture into drums for disposal. 15. The method of claim 10 wherein grout is injected through the hollow stem auger for waste that is not transuranic. 16. The method of claim 15 wherein the hollow stem auger is removed by the drilling rig and the grout allowed to cure with the mixture to form a monolith. |
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abstract | An apparatus includes an x-ray source operable to generate x-ray beams, a collimator comprising one or more leaves configured to modify the x-ray beams, a motorized system operable to move the one or more leaves of the collimator independently in or out of the x-ray beams, and a controller configured to synchronize operation of the x-ray source and the motorized system, allowing modification of the x-ray beams substantially in real time with generation of the x-ray beams. At least one leaf or each of the leaves of the collimator may be configured to modulate a beam quality of the x-ray beams. |
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summary | ||
06297419& | summary | BACKGROUND The present invention relates to a method of treating zirconium based metal waste particularly, though not exclusively, waste resulting from nuclear fuel reprocessing. Fuel rods for nuclear plants comprise a core of enriched uranium material having an outer can or cladding of a zirconium based alloy. Presently, when the spent fuel rods are reprocessed, they are chopped up into shorter lengths and treated with nitric acid to dissolve out the spent fuel core, leaving behind the cladding since it is not attacked by the nitric acid. The pieces of zirconium alloy constitute so-called intermediate level waste which needs to be contained and stored safely for many years. One current method of dealing with this waste is to crush the pieces and store it encapsulated as the metal in concrete grout in drums. A further problem with reprocessing irradiated fuel is that associated with isolating and dealing with the fission products generated during the nuclear reaction process. Normally, the fission products are separated from the uranium and plutonium, the latter two elements being reprocessed for further use. However, it is necessary to contain and safely store the fission by-products as they constitute so-called high-level waste. One method of dealing with this waste is by encapsulation by vitrification. Dealing with the zirconium waste and the fission product waste currently constitutes two separate stages of the reprocessing cycle and are both extremely costly in both plant and in running costs. It is an object of the present invention to provide a process for dealing more economically with zirconium waste. It is a further object to provide an alternative and more cost effective means of dealing with and storing the fission product waste. The present invention relates to a process for treating zirconuim based metal waste, the process including the steps of converting at least some of said zirconium based metal into an oxide (as herein defined). As hereafter described in more detail, the oxide is used in the production of a green body, for example by pressing, and the green body is sintered. According to a first aspect of the present invention there is provided a process for treating zirconium based metal waste, said waste comprising at least some of the zirconium based metal in solution, the process including the steps of converting at least said solution of said metal into an oxide of said zirconium based metal; and, sintering said oxide to form solid articles. One zirconium based mental alloy currently is use is known as "Zircalloy" (trade name) and comprises in excess of 95 wt % zirconium. The step of bringing the zirconium based metal into solution by chemical or electrochemical means is known in the prior art and provides a stable solution, e.g., a nitrate and oxide residues. See, for example, "Use of Electrochemical Processes in Aqueous Reprocessing of Nuclear Fuels" by F. Baumgarter and H. Schmeider, Radiochemical Acta, Vol. 25 pp 191-210 (1978). In this specification the terms "zirconium oxide" and "oxide of zirconium" and similar terms are frequently used. The actual chemical compositions resulting from the processes described herein may not have chemical compositions which correspond exactly either to a pure zirconium oxide or to zirconia, ZrO.sub.2, since the sintered materials in question will contain impurities and/or intentionally added materials and contaminants which it is desired to encapsulate, and/or to stabilize the crystal phase and which may also modify the crystal structure. Examples of such stabilizing and modifying additions may include, for example, metal oxides such as yttria, Y.sub.2 O.sub.3 to stabilize the crystal phase of zirconium oxide. Furthermore, in embodiments to be described below, particles of zirconium oxide powder are embodied in a matrix also containing aluminum and/or silicon atoms. Therefore, any reference herein to "zirconium oxide" or similar terms are to be taken as generic terms encompassing the resulting matrix of the sintered product or intermediate material in all embodiments and variations of the invention described herein howsoever arrived at. The zirconium based metal may constitute waste resulting from irradiated fuel rods from nuclear plants for example. The zirconium based metal may be brought into solution by electrochemical dissolution wherein the metal is made anodic in a electrolyte or nitric acid so converting the metal to a nitrate. In this method, a substantial proportion, perhaps about 85% of the zirconium metal, is converted directly to the oxide which forms a sludge in the dissolution vessel. The remaining nitrate may be thermally treated to decompose the nitrate to the oxide in a known manner. The resulting oxide may be separated, dried and milled to break down friable flakes if necessary; the resulting powder being pressed, cast or extruded for example into "green" compacts and sintered to solid bodies in known manner at temperatures up to about 1800.degree. C. Those steps in the ceramics art normally associated with the pressing and sintering of refractory oxide materials may be employed as desired and include such steps as appropriate as mixing with resin binders and/or lubricating waxes and preliminary burn-off treatments to remove such resins and waxes for example prior to sintering. Such steps are described in standard texts such as "Enlargement and Compaction of Particulate Solids", Ed. Nayland G. Stanley-Wood, Butterworths & Co. Ltd. 1983, particularly chapters 7 and 11; "Principles of Powder Technology", Ed. Martin Rhodes, Wiley, 1994, chapter 10; and "Principles of Ceramic Processing", J S Reed, Wiley Inter-science 1995, chapters 12, 17, 20, 22, and 29. In practicing the present invention, where the zirconium based metal constitutes the cladding of a nuclear fuel rod, the whole fuel rod, including the irradiated uranium fuel, is preferable brought into solution in nitric acid. Thus, the solution will contain nitrates of uranium, plutonium, zirconium and also the fission products in the spent fuel. The uranium and plutonium may then be separated from the solution by one of the known so called "PUREX" processes which are essentially solvent extraction techniques. See for example, "The Chemistry of the Purex Process" by J. Malvyn McKibben, Radiochinica Acta 36 (1984) 3-15. This results in the solution retaining the fission by-products which are normally treated as a separate waste product. Again, the resulting nitrates may be thermally treated to decompose and convert them to oxide, including those of at least some of the fission products. The zirconium based metal may alternatively be brought into solution by a route other than one of the so-called "PUREX" processes. For example, the zirconium metal waste may by converted to ZrX, where "X" is a halide, using an intensified fluorination technique such as by a fluidised bed with hydrogen fluoride. Other fluorinating agents such as nitrofluor (NOF:3HF) may also be used. The zirconium halides thus prepared may be readily converted to oxides. Alternatively, oxides of the fission products may be separately treated and subsequently blended with the zirconium oxide powder in a preferred proportion. A major advantage of the latter option is that the fission products are effectively encapsulated in the resulting sintered zirconium oxide body and a separate treatment stage for the fission products is removed from the process with a consequently great cost saving. Zirconium oxide is a particularly stable ceramic and has the necessary chemical durability to allow it to form the matrix for encapsulation of the high-level waste fission products. Furthermore, the melting point of zirconium oxide is greatly in excess of glass which forms the matrix in current verification encapsulation processes. The sintered bodies may be stored in drums in concrete grout for example. A further advantage conferred by the nature of zirconium oxide compared with glass is that it may allow higher levels of fission product waste to be incorporated into the ceramic encapsulate than is achievable with glass. The sintered zirconium oxide material may also by used to encapsulate some or all of the plutonium arising from the nuclear reaction process in the same manner as described with reference to the fission products above. The irradiated fuel rods may be processed as complete units without prior dicing into shorter lengths so improving the efficiency and ease of automation of the process and also reducing the contamination attributable to the dicing or slicing process. This again improves the economics of the process as a complete plant dedicated to cutting and handling of the fuel rod pieces may be dispensed with. BRIEF SUMMARY In a first aspect, the present invention is characterized in that the zirconium oxide, either alone or including at least some of the fission products, is mixed with a sol or a solution of a gel forming chemical, and a green body is produced from the mixture and subsequently sintered. Examples of suitable chemicals are aluminum secondary butoxide and aluminum iso-propoxide which form complementary phases with the zirconium oxide. The gel forming chemical may be treated with a modifying agent such as an alkanolamine, an example of which is triothanolamine, to stabilize them. This is due to metal alkoxides being readily precipitated in the presence of moisture. When stabilized a polycondensation reaction occurs promoting gelation on hydrolysis. This results in a stable cross-linked inorganic polymer gel. The modified chemical is mixed with the zirconium oxide to form a slurry, the proportion of zirconium oxide being added such that the resulting mixture is still workable and the density is as high as possible to minimize shrinkage during subsequent processing. The proportion of water added to the slurry controls the gelation time. The slurry so formed is then cast into a mold or otherwise formed into desired shapes such as by extrusion for example, and allowed to set. Once set, the green bodies are removed from their mold, if appropriate, and slowly dried so as to minimize cracking during shrinkage. The dried green bodies are then sintered to densify and increase the strength of the articles for long term storage in a repository. A hydrolyzed zirconium salt or other metal salt such as a chromium salt may be used instead of the aluminum alkoxide. In a second aspect, the present invention is characterized in that the oxide is mixed with a material which is a chemical or a combination of chemicals which gels and hardens by heat (rather than by hydrolysis), and a green body is produced from the mixture and subsequently sintered. Examples of suitable materials include zirconium acetate, zirconium acetate/citric acid, zirconium nitrate/citric acid and zirconium acrylamide. A particular advantage of the present invention in its second aspect is that after the drying process bonds are formed between the zirconium oxide particles and the residual material resulting from either the aluminum alkoxide or from the zirconium sol for example; this residual material comprises aluminum, zirconium and oxygen, as appropriate, on a molecular scale. Due to this residual material being on a substantially molecular scale, the necessary sintering reaction is greatly enhanced. It is expected that the temperature will be generally lower than those normally needed for sintering similar zirconia powder bodies. In a third aspect, the present invention is characterized in that the zirconium oxide, either alone or including at least some fission product, is mixed with a gel which is freeze castable, and a green body is produced from the mixture and subsequently sintered. That is, the oxide is initially bound together by the so-called freeze-casting technique utilizing a sol-gel method. Gelation takes place by dehydration of the sol during freezing and, at a critical concentration, the sol particles form chemical bonds. The result of this is that when an oxide mass which was previously a slurry, is brought back to room temperature from its freezing temperature, it remains in the green state in a stable solid and handleable form. Due to the formation of ice crystals as a result of the freezing process, the ceramic particles take up space between the ice crystals and form a continuous matrix around the crystals. On sintering of the thawed and dried green body, very little shrinkage occurs. Furthermore, due to the strong bonding produced during sol-gel freeze-casting, sintering temperatures are relatively low thus promoting relatively little shrinkage and consequent cracking. A particular advantage of the freeze-casting technique is that it is essentially solvent free thus, reducing the hazardous and consequent on-costs by way of more complex plant usually associated with the use of solvents. Prior technology related to the use of the freeze-casting technique is applicable to the second preferred embodiment. In the third aspect of the present invention utilizing the freeze-casting technique, the zirconium oxide and fission products may be combined with a silica sol, or alternatively, with a zirconia sol. In the invention, in any of the first, second and third aspects, filler powders such a zircon (ZiSiO.sub.4) for example may be added to the zirconium oxide waste and sol to control shrinkage on sintering. Other ceramic filler powders may also be added as appropriate. The role of filler powder may be fulfilled by suitable content levels of the zirconium oxide waste powder itself. The use of filler powders also applies to the process of the first preferred embodiment. The present invention also provides a process for the disposal of nuclear waste comprising converting at least said zirconium based metal into a sintered body according to any of the first second and third aspects and storing said body. The present invention also contemplates the encapsulation of fission product oxides within the sintered zirconium oxide body. |
061538094 | description | DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved process and product for immobilizing waste in a chemically bonded phosphate ceramic (CBPC) waste form. As described in detail in the background section above, although methods for fabricating CBPC products encapsulating waste materials are well known, the known CBPC encapsulation methods are ineffective for containing wastes having a high concentration of salt. The present invention modifies known CBPC encapsulation methods and products to include a unique immobilization step that specifically addresses problems experienced in the art due to the presence of soluble salt anions in the waste stream. According to the present invention, a polymer coating is applied to the exterior surface of the CBPC product to infiltrate the complex surface structure of the CBPC product and bond and/or adhere thereto, such that salt waste is effectively macro-encapsulated with in phosphate ceramic matrix and isolated from the environment. Advantageously, the polymer surface coating protects the CBPC waste form from environmental stresses by providing a greater resistance to air, water, organic liquids, acids, and alkalis, among other conditions. The polymer surface coated CBPC waste form also has improved mechanical properties, such as greater hardness and high abrasion resistance. The polymer coating has three main components: the binder, the pigment, and the solvent. The binder provides adhesion and cohesion between the coating and the CBPC surface, the pigment is a fine powder that provides the coating with color and hardness, and the solvent is a volatile liquid for dissolving solid or semi-solid binders. The pigment has considerable influence on the consistency of the properties of the polymer coating and contributes to its abrasion and weather resistance. A feature of the invention is the inclusion of at least one inorganic metal compound in the binder component of the polymer coating. Preferred inorganic metal compounds are inorganic metal oxides, such as magnesium oxide (MgO) and/or silicon oxide (SiO.sub.2). These inorganic metal compounds may be in the form of magnesite (MgCO.sub.3), talc (Mg.sub.2 (Si.sub.2 O.sub.5).sub.2.Mg(OH).sub.2), or borosilicate glass (i.e., silicate glass with at last 5% boron oxide). These ceramic materials provide an excellent interface adhesion between the polymer coating and the surface and infiltrated structure of the CBPC product, apparently caused by mechanical and chemical interactions between the phosphate ester comprising the CBPC product and the ceramic coating composition. Polymer coating materials that do not contain ceramic, inorganic metal compounds peel off of the surface of the phosphate ceramic product after curing. The most preferred polymer material is a commercially available thermoset polyester resin that is comprised of a polyester resin binder, magnesite, talc, or soda-lime glass pigment, a styrene monomer solvent, and also a benzoyl peroxide initiator. Generally preferred polymer coatings are comprised of unsaturated polyester resins that are straight-chain polymers having reactive double bonds at intervals along the chain. In their popular form, unsaturated polyester resins are supplied as solutions in vinyl monomer (e.g., styrene), and copolymerization is activated by the addition of an initiator (e.g., organic peroxides or hydroperoxides) and promoters (e.g., metallic dryers, cobalt octoate, naphthenate). Copolymerization results in the cross-linking of polyester chains by the formation of polmerized vinyl monomors. According to the preferred method of the present invention, the polymer material is applied to the exterior surface of a phosphate ceramic product as a thin film by adding the initiator to the pigment and the binder, mixing the initiator-pigment-binder composition for a few minutes to form a slurry, uniformly coating the exterior surface of the phosphate ceramic product with the slurry, and chemically drying the coating by allowing sufficient time for the slurry to infiltrate the phosphate ceramic product surface, such that the slurry completely wets and adheres to the surface. Although the polymer coating hardens in about ten minutes, a curing time of 24 hours is preferred. The polymer coating is subjected to a chemical drying step, e.g., curing, a process in which the molecules of the binder chemically react with one other to form bonds within the film by primary valences. These bonds are very strong and not susceptible to dissolution by the action of solvents. Thus, a feature of the invention is the subjection of the surface coated CBPC product to a chemical drying step that converts the coating from a fluid to a solid state, wherein chemical reactions occur to anchor the thin film coating to the CBPC surface. Table II below provides the results of the American Nuclear Society's ANS 16.1 Standard Test for nitrate and chloride loaded polymer coated MKP ceramic products. Generally, the ANS 16.1 Standard Test studies leachability of contaminants contained in matrices in an aqueous environment over time and evaluates retention rates by calculating a leachability index value from the test data. (The leachability index is the negative logarithm of the effective diffusivity coefficient). Sample polymer coated salt loaded MKP ceramic products were placed in the leaching solution for a fixed period of time, after which the leaching solution was analyzed for specific ions. As shown in Table II, the chloride leaching was excessively low, with the chloride ion reading below the detection limit even after a cumulative 96 hours of exposure. The nitrate leaching was relatively higher. FNT (ND indicates None Detected; * indicates test in progress). TABLE II ______________________________________ Cumulative Leaching of Chloride and Nitrate Ions from Polymer Coated MKP Ceramic Products Cumulative Chloride Ion (Cl.sup.-) Nitrate Ion (NO.sub.3.sup.-) Time (hours) (ppm) (ppm) ______________________________________ 2 ND 3.96 7 ND 5.28 24 ND 2.20 48 ND 3.08 72 2.64 96 ND 2.20 456 3.4 13.20 1128 * 43.12 2136 * 176.00 ______________________________________ ND indicates None Detected; *indicates test in progress. Salt waste is generally highly reactive and therefore its flammability is of concern, in view of transportation and storage issues. Department of Transportation (DOT) oxidation tests conducted on polymer coated salt loaded phosphate ceramic products demonstrated that because phosphate ceramics are inorganic ceramic-type materials, they advantageously inhibit the spread of flames and are an excellent solidification medium for flammable salt waste. The resulting phosphate ceramic materials may be used to produce building and construction materials, e.g., engineering barrier systems. EXAMPLE Nitrate Loaded Polymer Coated MKP Ceramic Product Surrogate waste having the composition listed below in Table III was prepared in the laboratory and mixed for 72 hours using mixing rollers. The surrogate waste was chemically treated by mixing the surrogate waste first with an aqueous solution containing a small amount of sodium monosulfide (Na.sub.2 S) for about 8 to 10 minutes to efficiently convert mercury (Hg) into its most stable form of mercury sulfide (HgS), and next treating the surrogate waste with tin chloride (SnCl.sub.2) for about 5 minutes to reduce the valency of chromium from +6 to a less toxic, less water soluble oxidation state of +3. TABLE III ______________________________________ Surrogate Waste Composition Constituent wt % Contaminant ppm ______________________________________ Fe.sub.2 O.sub.3 6.0 PbO 1000 Al.sub.2 (OH).sub.3 4.0 CrO.sub.3 1000 Na.sub.3 PO.sub.4 2.0 HgO l000 Mg(OH).sub.2 4.0 CdO 1000 CaSiO.sub.3 8.0 NiO 1000 Portland Cement 2.0 H.sub.2 O 14.0 NaNO.sub.3 (nitrate salt) 60.0 ______________________________________ Magnesium potassium phosphate (MKP) ceramic waste products incorporating the surrogate waste were fabricated by methods generally shown in FIG. 1 for waste loadings of 58% and 70%. Accordingly, a binder was formed by spontaneously reacting a stoichiometric amount of well mixed, calcined magnesium oxide (MgO) powder and monopotassium phosphate (KH.sub.2 PO.sub.4), under aqueous conditions and constant stirring, in four successive batches at one minute intervals, to produce magnesium potassium phosphate (MgKPO.sub.4.6H.sub.2 O), according to Equation (3) above. The resulting binder has a highly crystalline ceramic structure and a solubility product constant as low as 10.sup.-12. The chemically treated surrogate waste and binder were combined to form a slurry that initially experienced a few degrees decrease in temperature due to the dissolution of the phosphate crystals in the water. Upon dissolution of the phosphate, the temperature increased to about 35.degree. C., and the slurry having a pH of about 6 to 7 was stirred thoroughly for about 18 to 20 minutes, or until the slurry started to set. The slurry was hardened in molds for about 2 to 5 hours, resulting in dense, monolithic, chemically bonded phosphate ceramic (CBPC) waste products. After 14 days of curing, the CBPC waste products were subjected to variance performance tests, including strength, leaching and characterization. FIG. 2 is a high magnification (2000.times.) scanning electron microscopy (SEM) photomicrograph of a fractured surface of a magnesium potassium phosphate (MKP) ceramic waste product loaded with 58% surrogate salt waste. The photomicrograph shows a very dense, crystalline structure with a small amount of pores. Pores allow water to penetrate the waste form, causing nitrates to (e.g., NaNO.sub.3) to dissolve and leach into the environment. According to the present invention, a select number of the CBPC waste products were coated with an unsaturated polyester resin system to further immobilize the surrogate waste within the CBPC waste products. FIGS. 3 and 4 show high (2000.times.) and very high (7500.times.) magnification SEM photomicrographs, respectively, of the polymer coated surface of a CBPC waste product. The photomicrographs show a very smooth, substantially pore free surface structure, demonstrating a very low possibility for water to penetrate into the polymer coated CBPC waste product through its surface structure, and the prevention of nitrate dissolution and subsequent leaching. FIGS. 5 and 6 show low (350.times.) and high (2000.times.) magnification SEM micrographs of the interface between a CBPC waste product loaded with surrogate waste and a polymer coating applied thereon. As shown in FIGS. 5 and 6, the polymer coating has completely wet and adhered to the phosphate ceramic surface, resulting in a CBPC waste product having superior leaching performance. The polymer coating-CBPC waste product interface also appears to be essentially free of cracks demonstrating high compression strength and excellent compatibility between the polymer coating and the CBPC waste product. Table IV below provides the results of density and compression strength tests conducted on the uncoated and polymer coated magnesium potassium phosphate (MKP) ceramic products loaded with 58 weight percent and 70 weight percent nitrate salts. The compression strength of the waste forms are well above of the Nuclear Regulatory Commission (NRC) minimum requirement of 500 psi. TABLE IV ______________________________________ Structure Properties of MKP and Nitrate Waste Products Uncoated Uncoated Polymer Coated 58 wt % Salt 70 wt % Salt 58 wt % Salt Property Waste Waste Waste ______________________________________ Density (g/cc) 1.893 2.000 1.691 Compression Strength 1400 .+-. 160 1900 .+-. 180 1970 (PSI) ______________________________________ FIG. 7 is a graphical illustration of cumulative nitrate leaching for nitrate loaded MKP ceramic products with and without the polymer (unsaturated polyester resin) coating. As depicted, the polymer coated nitrate loaded MKP ceramic product immobilized the nitrate ions significantly more effectively than the uncoated nitrate loaded MKP ceramic product. A comparison of the leachability index for the polymer coated nitrate loaded MKP ceramic product versus an uncoated nitrate loaded MKP ceramic product is provided in Table V, below. The calculated leachability index for the polymer coated nitrate loaded MKP ceramic product was greater than 12, substantially above the ANS 16.1 standard leachability index of at least 6.0. Generally, the leachability index is related to the effective diffusivity in that the higher the leachability index, the lower is the effective diffusivity, resulting in a more favorable retention of a contaminant within a matrix. These results demonstrate that the essentially pore free surface structure of the polymer coated salt waste loaded MKP ceramic product provides superior immobilization of the waste salts than uncoated salt loaded phosphate ceramic products currently known in the art. TABLE V ______________________________________ ANS 16.1 Results for Various Waste Containment Products NO.sub.3.sup.- in Waste Fraction Waste Containment of NO.sub.3.sup.- Effective Containment Product Leached Diffusivity Leachability Product (ppm) Out (cm.sup.2 /s) Index (LI) ______________________________________ Uncoated, 58 wt % 218700 0.33 6.31 .times. 10.sup.-8 7.20 Loaded Uncoated, 70 wt % 260600 0.35 5.82 .times. 10.sup.-8 7.24 Loaded Polymer Coated 218700 0.0169 6.87 .times. 10.sup.-13 12.16 58 wt % Loaded ______________________________________ Alternative coating systems were tested, including fly ash coatings, epoxy resins, and rubber derivatives. The fly ash coating system exhibited excellent film integrity and good waste form compatibility, while the epoxy resin and rubber derivative coating systems demonstrated very poor film integrity and waste form compatibility. The foregoing description of a preferred embodiment of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments described explain the principles of the invention and practical applications and should enable others skilled in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. While the invention has been described with reference to details of the illustrated embodiment, these details are not intended to limit the scope of the invention, rather the scope of the invention is to be defined by the claims appended hereto. |
055524559 | description | DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1, a typical RAM coating, indicated by numeral 10, is illustrated covering a substrate 12. When a radar wave, indicated by numeral 14, impinges the top surface 16 of the RAM coating 10 at an angle .theta..sub.i, it splits into two components. One component reflects off the top surface 14 as a primary reflection coefficient 14A. The other component 14B is refracted at an angle et and travels into the coating 10 until it hits the interface 18 between the ram coating 10 and substrate 12 and is reflected back to the top surface 16 and out thereof as a secondary reflection component 14C. Ram coatings used for specular reflection absorbers must balance the primary and secondary component magnitudes and achieve the proper phase shift between the two components to accomplish good radar attenuation. Traveling wave absorbers must minimize the front face reflection coefficient and absorb most of the radar energy internally before it reaches an impedance mismatch and gets reflected back. The effective reflection coefficient defines the attenuation of a RAM coating on top of a conductive substrate. The cosine of the refraction (transmission) angle .theta..sub.t is calculated from the equation: ##EQU1## where .xi. is the permittivity .mu. is the permeability .theta..sub.i is the incidence angle (refraction angle) PA1 1. The real permittivity decreases with an overall shape similar to the change in the real permeability. PA1 2. The real permeability increases at lower frequencies and decreases less with increasing frequency than non sorted material. PA1 3. The real permittivity, real permeability, and imaginary permeability increase faster than the imaginary permittivity. PA1 4. The overall electrical properties of the sorted particles are better than the non-sorted particles as the percolation factor increases. PA1 Measured true density of iron is 7.60 g/cc PA1 Measured tap density is 4.402 g/cc PA1 Volume fraction of iron for optimum packing is PA1 Volume fraction of binder at optimal packing is EQU 1-0.5792=0.4208 PA1 For 99 percolation factor need to add additional binder EQU 1/0.99=1.0101 PA1 Calculate volumes required: PA1 Volume fraction of iron=0.5792 cc/1.0101 cc=0.57341 PA1 Volume fraction of binder=0.4309 cc/1.0101 cc=0.42659 PA1 Calculate weight basis for mixture: PA1 Weight fraction of iron=4.3637 g/4.754 g=0.9179 PA1 Weight fraction of binder=0.3903 g/4.754 g=0.0821 PA1 .rho. the density PA1 (beginning radius--end radius of segment)/2) PA1 1. Lighter and thinner specular coatings having broad band high level attenuation. PA1 2. Thinner traveling wave absorbers requiring less thickness length because of higher imaginary permeability and less back scatter because of a significantly lower front face reflection coefficient. PA1 3. A reduction in weight by the addition of light weight spheres without causing any detrimental change in the electrical properties of existing RAM coatings. PA1 4. Combined specular and traveling wave RAM coatings that provide superior overall radar signature reductions PA1 5. The elimination of small particles under two microns in size provides a RAM coating with better physical properties by significantly reducing the surface area required to be wetted by the polymer binder. the primary reflection coefficient .GAMMA. for parallel polarization is calculated from the equation: ##EQU2## The electrical attenuation coating thickness t.sub..theta. is calculated from the equation: ##EQU3## where t=the physical thickness of the RAM coating and the effective reflection coefficient .GAMMA..sub.eff. is calculated from the equation: ##EQU4## where k=a constant dependent on units. f=frequency A Ram coating must be light in weight and have a high attenuation level over a broad frequency range. The technique for obtaining high attenuation is to have the primary reflection coefficient be equal in magnitude to the secondary reflection coefficient and have both coefficients be 180 degrees out of phase. The band width of maximum attenuation is increased by having about one third of the energy reflected as the primary reflection coefficient, two thirds of the energy absorbed in the coating as a result of phase cancellation between the primary and secondary reflections. The loss within the RAM coating is determined by the exponential term in the effective reflection coefficient equation. The energy reflected from the RAM coating surface is determined from the primary and secondary reflections. The effective reflection coefficient calculates all of the quantities in one equation and solves for the attenuation. As can be seen in the equations, the primary reflection coefficient F for vertical polarized electromagnetic waves is controlled by the quantity .mu./.xi. and is generally lowest on low observable aircraft when ##EQU5## approaches 1. RAM coatings have real .xi. values of 20 or more to keep them thin and light weight while providing adequate attenuation. As can be seen in FIG. 2A, the real permeability of a typical RAM coating decreases rapidly from 1 through 6 GHz then decreases at a constant rate from 6 through 18 GHz. As can be seen in FIG. 2B, the real permittivity of a typical RAM coating either remains constant through the 2 to 18 GHz range or has a slight linear decrease from 2 through 18 GHz. This causes the front face reflection coefficient to change rapidly because of the disproportional change in .xi. and .mu. as the frequency goes from 18 GHz to 2 GHz; the phase angle changes because the permittivity/permeability product decreases at a slower rate than the wave length decreases; and the peak attenuation band width decrease with decreasing frequency. As further seen in FIGS. 2A and 2B, increased loading of magnetic fillers in a typical RAM coating without regard to size sorting results in a disproportionately large increase in the real permittivity compared to the real permeability. This causes a decrease in .mu./.xi. which increases the primary reflection coefficient and decreases effective attenuation. It also results in both high real and high imaginary permittivity which indicates that particles are shorting and that conductivity is increasing. Increased conductivity causes the effective skin depth of the coating to decrease which in turn reduces energy penetration into the RAM coating and makes it look more like a reflecting metal surface. It is believed that the increased conductivity is caused by small metal particles creating electrical contact between larger closely packed particles. Proper sorting and sizing of magnetic particles enables close packing to improve real permittivity and permeability without causing the undesirable shorting and high conductivity. Proper sizing is achieved by using two different size particles. Referring to FIGS. 3 and 4, it can be seen that if eight spheres 30A-H with a diameter D.sub.L are closely packed together so that they are in contact, they will occupy a square box 28, having sides with a length of 2 D.sub.L. The distances between the centers of the spheres 30A-H will, of course, be D.sub.L (forming a square box 34), except for those along the diagonal Z. which will have a length L equal to D.sub.L plus D.sub.S Solving for D.sub.S is provided by the simple equation: ##EQU6## Thus in a two sphere system, the smaller sphere is 0.73 times the diameter of larger sphere. Of course, smaller and smaller particles can be added, but this results, as will be subsequently discussed, in poorer performance. It is also readily apparent that, in the above example, if N.sub.L equals the number of large spheres, the number of small spheres N.sub.S is equal to: ##EQU7## However, when N.sub.L is very large, as in the case of any RAM coating applied to a vehicle, N.sub.S .congruent.N.sub.L. For example, if N.sub.L equals 1,000,000 spheres there is only a 2.3 percent error, at 10,000,000 the error is less than 0.2 percent. As additionally shown in FIGS. 2A and 2B, the proper percolation factor produces a RAM coating with the following advantages: Measurements indicate that permeability's of size sorted RAM coatings can be increased to higher values than non-size sorted RAM coatings and that the increase occurs at magnetic particle volume loadings which do not cause poor coating physical properties. This is the result of removing small diameter particles with their disproportionately high surface areas for a unit particle volume. Examining the changes in permeability and permittivity with frequency and the equations which calculate attenuation, the .xi. and .mu. terms of the low percolation factor sorted coatings change their relation to each other as the frequency changes. The permeability changing much more rapidly at lower frequencies than the permittivity. This causes the .mu./.xi. term in the primary reflection coefficient to change with frequency. This change upsets the relation between the primary and secondary reflection coefficients in the RAM coating resulting in limited band width at peak attenuation. The .xi. and .mu. values of the high percolation sorted coatings change in a proportional way with frequency and keep the primary reflection coefficient relatively constant with frequency change. Additionally the loss (exponential) term in the effective reflection coefficient equation is affected by the electrical thickness of the coating. In addition, the loss and phase change are related to the wavelength of the wave which is the speed of light in vacuum divided by the frequency. This is reflected by the use of the f (frequency) term in the effective reflection coefficient exponential. The relative change in the values of the .xi. and .mu. terms of the low percolation factor Ram coatings indicate that the internal loss will decrease more rapidly as the frequency decreases than in high percolation factor RAM coatings. Electrical measurements also indicate that higher permeability's with equal magnetic particle volume loading are possible. Generally permeability's of mixtures of materials are a function of the effective particle permeability and the volume of particles loaded into the mixture. The effective particle permeability is a function of the geometry of the particle with a value of approximately 3.0 for a sphere of ferromagnetic material to much higher permeability's for fibers. The measurement of high mixture permeability with spherical particle loading using size sorted particles and the increase in real permittivity without a proportionate increase in the imaginary permittivity indicates that some unique phenomenon is occurring when sorted particles are used. This phenomenon appears to be related to making the spherical particles look like non spherical particles caused by electrical contact of a controlled number of the magnetic spheres which have a higher effective permittivity than electrically isolated spheres. This controlled electrical contact is another unique phenomenon of using size sorted magnetic spheres to improve RAM coating performance as a function of weight. The bulk of the formulations evaluated to date were fabricated using size sorted iron spheres dispersed in melted paraffin wax. Paraffin was used because it is easy to handle. Of course, actual ram material would use resins or ceramics and the like. Upon receipt of various quantities and sizes of spherical iron particles from suppliers they are sorted by centrifugal type separators into specific size cuts. Particle size distribution is measured on the sized iron and calculations are made to control the number of large and small particles using a weight basis and the measured particle size distribution. Appropriate amounts of sizes of iron particles are mixed together and measurements are made of their tap density and true density. The measured tap and true densities of the iron particles and the true density of the binder are used to calculate how much matrix binder is required to attain a given theoretical percolation factor. Percolation factor is defined as the volume of all particles when optimally packed divided by the volume of particles and binder after the RAM coating cures and optimal packing occurs when all particles touch and therefore occupy a minimum volume. An example of the calculations used to determine the formulation for a 99 percolation factor material is as follows: Tap Density/True Density (4.402 g/cc)/(7.60 g/cc)=0.5792 ______________________________________ Iron 0.5792 cc = 0.5792 cc Binder 0.420 cc + .0101 cc = 0.4309 cc Total 1.0101 cc ______________________________________ ______________________________________ Iron 0.57341 cc (7.610 g/cc) = 4.637 g Binder 0.42659 cc (0.915 g/cc) = 0.3903 g Total = 4.7540 g ______________________________________ Ideally, the procedure to determine the weights of particles that must be mixed to get optimum packing assumes two groups of perfect uni-size particles with the smaller diameter group having a diameter which is 0.73 times the larger diameter group particle size. Mixing an equal number of particles is accomplished by calculating the weights of large and small particles as follows: Assuming their densities are the same, the volume ratios will be the same as the weight ratios. If the volume densities are not the same then the volume ratios must be multiplied by the ratio of the densities. The weight ratios (W.sub.L /W.sub.S) is as follows: ##EQU8## where V.sub.L and V.sub.S are the volumes of the large and small spheres R.sub.L and R.sub.S are the radius of the large and small spheres This means that 2.5706 pounds of large diameter sorted material must be mixed with one pound of small diameter sorted material to get equal numbers of particles with a size ratio of 1 to 0.73 in the resultant mix. However, iron particles available from suppliers have a distribution that typically varies from less than one micron to over ten microns in size. Even after the iron particles are separated by size using a centrifuge, a Gaussian distribution exists. Mixing these Gaussian distribution size separated materials using the 2.5707 weight ratio may not provide optimum or repeatable results This requires that the small and large particle size distributions be measured so that a "best" fit can be used to determine the optimum weight ratios. A procedure used to accomplish this follows: FIG. 5 presents typical size distributions of the small diameter and large diameter size cuts made with a Coulter LS particle size analyzer after centrifugal separation. The dissimilarities in the shape of the two distributions is typical of actual sorts. The number of particles in a measured segment (N) is calculated using an average particle radius and equating it to the segment radius. ##EQU9## where: V.sub.F is the Volume fraction R is the average radius in each volume segment. Calculations are made by assuming a unit volume of one cc and dividing it into fractions equal to the measured volume fractions. The number of particles in a given fraction is then calculated by dividing the fractional cc volume by the volume of one particle calculated by using the average measured diameter within the volume fraction. The data for the first segment of the larger diameter sort size is interpreted as 0.030 volume percent is between 1.047 and 1.149 microns in diameter. ##EQU10## This process is repeated for all the fractions of each particle size and then plotted as shown in FIGS. 6 and 7. A visual technique is used to compare plots of the number of particles in the smaller diameter size cut to the number of particles in the larger diameter size cut. Before visual comparisons are performed the distribution of the number of particles in the size cuts must be normalized. The normalization is accomplished by multiplying the large particle sizes by 0.73 and displacing the original large diameter sort particle number distribution to lower diameters as shown in FIG. 8. The normalized particle number distribution curve of the larger diameter sort is visually compared to the non normalized particle distribution curve of the smaller diameter sort. In a similar manner the smaller diameter particle number distribution can be normalized by dividing its diameters by 0.73 and comparing the resultant curve to the non normalized particle number distribution curve of the larger diameter sort. Thus in the above example the sort shown in FIG. 6 is normalized by multiplying by 0.73 and multiplied by a multiplication factor providing the distribution curve shown in FIG. 8. Typically, the normalized distribution curve must be repeatably multiplied by a series of multiplication factors until the "best fit" shown occurs. The distribution curve shown in FIG. 8 is then overlaid on the distribution curve for the smaller diameter particles shown in FIG. 7 to provide a visual fit. This "best" visual fit is shown in FIG. 9 and results in a mixture of 2.125 pounds of the larger diameter sort particles for each pound of smaller diameter sort particles. This procedure can be computerized and a sample flow chart for a suitable computer program is illustrated in FIG. 10. Thereafter the binder, in the form of a resin or ceramic, is added in the proper amount to the mixture of particles and solidified by curing. In this step, the mixture of binder and particles maybe cast in a mold, formed into sheets. It may even be sprayed on to a surface as a coating. The imparting of a higher frequency dependent real permittivity with controlled imaginary permittivity and a high real and imaginary permeability using particle size sorting offers the following improvements compared to non particle size sorted RAM coatings. While the invention has been described with reference to a particular embodiment, it should be understood that the embodiment is merely illustrative as there are numerous variations and modifications which may be made by those skilled in the art. Thus, the invention is to be construed as being limited only by the spirit and scope of the appended claims. INDUSTRIAL APPLICABILITY The invention has applicability to military vehicles and structures that require reduced radar cross-sections. Thus, for example, the invention would have application to the military aircraft and ship industries. |
description | This application is an application based on International Application No. PCT/JP2011/063886, filed on Jun. 17, 2011, entitled “SCINTILLATOR MATERIAL AND SCINTILLATION DETECTOR”, which claims priority based on Article 8 of Patent Cooperation Treaty from prior Japanese Patent Application No. 2010-151330, filed on Jul. 1, 2010, the entire contents of which are incorporated herein by reference. The present invention relates to a scintillator material that emits fluorescence in response to an incident radiation. The present invention also relates to a scintillation detector that includes a scintillator made of such scintillator material. Scintillation detectors expose their scintillator to ionization radiation such as X rays, γ rays, and α rays, which causes the scintillator to emit fluorescence. The fluorescence is amplified by a photomultiplier tube for detection. One application of such scintillation detector is PET (Positron Emission Tomography) devices, which detect γ rays emitted in process of positrons annihilation. PET devices use coincidence to detect γ rays, which are comparatively higher in energy, and for this purpose, employ scintillation detectors that are high in sensitivity and in response speed. In recent years, attempts are underway to develop next generation PET devices of TOF (Time-Of-Flight) type and other types. These next generation PET devices require high time resolution, which necessitates scintillators of particularly short fluorescence lifetime. Zinc-oxide single crystal is a currently used material (scintillator material) for such scintillators. Zinc-oxide single crystal is short in fluorescence lifetime compared with other scintillator materials made of BaF2 or the like. Due to having no deliquescency, zinc-oxide single crystal is stable in air and therefore easy to handle. Additionally, use of a hydrothermal method ensures production of the zinc-oxide single crystal in large quantities. For example, patent document 1 discloses a scintillator material made of a zinc-oxide single crystal doped with Al, Ga, In, and the like. The scintillator material disclosed in patent document 1 emits fluorescence of approximately 600-ps fluorescence lifetime in response to an incident radiation. Patent document 2 discloses a scintillator material made of a zinc-oxide single crystal that is doped with Sb, Bi, In, or Ge as donor impurity and doped with Li as acceptor impurity. In response to an incident radiation, the scintillator material disclosed in patent document 2 emits fluorescence that includes two components, one with 30 to 60-ps fluorescence lifetime and the other with 250 to 800-ps fluorescence lifetime. The 30 to 60-ps fluorescence lifetime of the one component is significantly shorter than the 600-ps fluorescence lifetime of the fluorescence that the scintillator material disclosed in patent document 1 emits. Accordingly, the scintillator material disclosed in patent document 2 is shorter in fluorescence lifetime than the scintillator material disclosed in patent document 1, and therefore, is a suitable material for the scintillators of next generation PET devices requiring high time resolution. [Patent Document 1] WO2005/114256. [Patent Document 2] JP2009-286856A. As described above, next generation PET devices require high time resolution. The time resolution improves as the fluorescence lifetime of the scintillator becomes shorter, and in view of this, there is a need for a scintillator material of a further shortened fluorescence lifetime. Specifically, there is a need for a scintillator material that emits fluorescence of less than 20-ps fluorescence lifetime in response to an incident radiation. The present invention has been made in view of the above-described circumstances, and it is an object of the present invention to provide a scintillator material of a shorter fluorescence lifetime and to provide a scintillation detector that includes a scintillator made of the scintillator material. A scintillator material according to the present invention emits fluorescence in response to an incident radiation. The scintillator material is made of a zinc-oxide single crystal grown on a +C surface or a −C surface of a plate-shaped seed crystal of zinc oxide including a C surface as a main surface. The zinc-oxide single crystal contains In and Li. The fluorescence has a fluorescence lifetime of less than 20 ps. As used herein, the term fluorescence lifetime refers to a period of time over which the intensity of the fluorescence reaches its maximum and then attenuates to 1/exp of the maximum. In the scintillator material according to the present invention, donor-acceptor pair luminescence (DAP luminescence) is observed as the fluorescence emitted in response to an incident radiation. Specifically, when a radiation is incident on the scintillator material, electrons are excited from the valence band into the conduction band, with the result that free electrons are generated in the conduction band while positive holes are generated in the valence band. The free electrons are trapped at the donor level formed by In, while at the same time the positive holes are trapped at the acceptor level formed by Li. Then, the free electrons and the positive holes recombine with each other to emit light. This phenomenon is referred to as DAP luminescence. In the scintillator material according to the present invention, the DAP luminescence observed in response to an incident radiation includes a component of less than 20-ps fluorescence lifetime. The fluorescence lifetime of this component is shorter than the 30 to 60-ps fluorescence lifetime of the one component of the fluorescence that the conventional scintillator material made of zinc-oxide single crystal emits in response to an incident radiation. Thus, the scintillator material according to the present invention ensures a shorter fluorescence lifetime compared with conventional scintillator materials that emit fluorescence made up of a plurality of components having 30-ps or longer fluorescence lifetimes. In the scintillator material according to the present invention, the fluorescence that the scintillator material emits in response to an incident radiation preferably is made up of only a single component of less than 20-ps fluorescence lifetime. This further shortens the fluorescence lifetime of the fluorescence that the scintillator material emits. In the scintillator material according to the present invention, Li concentration in the zinc-oxide single crystal is preferably in a range of 0.15 to 11 times In concentration in the zinc-oxide single crystal, particularly preferably in a range of 0.15 to 6.74 times In concentration in the zinc-oxide single crystal. A zinc-oxide single crystal in which Li concentration is in the range of 0.15 to 11 times In concentration can be produced in a high quality state, with decreased crystal defects, by a hydrothermal method or other method. A scintillation detector according to the present invention includes a scintillator made of the above-described scintillator material according to the present invention. The scintillation detector according to the present invention includes a scintillator made of the scintillator material according to the present invention, and thus has high time resolution. The present invention provides a scintillator material of a shorter fluorescence lifetime and provides a scintillation detector that includes a scintillator made of the scintillator material. The scintillator material according to this embodiment is made of a zinc-oxide single crystal containing In and Li. In view of this, description will be made below with regard to a method for producing the zinc-oxide single crystal constituting the scintillator material according to the present invention. <Method for Producing the Scintillator Material> —Configuration of Single Crystal Growth Furnace— First, description will be made below with regard to a configuration of a single crystal growth furnace (hereinafter simply referred to as growth furnace). The growth furnace is where single crystals are grown using a single crystal growth solution (hereinafter simply referred to as growth solution) by a hydrothermal method. As shown in FIG. 1, a growth furnace 1 includes a furnace main body 2 and an electric furnace 3 disposed over the outer circumference of the furnace main body 2. The electric furnace 3 heats the furnace main body 2. The furnace main body 2 has a cylindrical shape open at an upper portion and closed at a bottom portion. An upper end opening 21 accepts a lid 22 to hermetically seal the interior of the furnace main body 2. The lid 22 is attached with a pressure gauge 22a to measure the pressure inside the furnace main body 2. The furnace main body 2 accommodates a cylindrical growth container 24 made of platinum. The growth container 24 has a hermetically sealed inner space 4. At a vertically intermediate position of the inner space 4, a convection regulation plate 23 is disposed. The convection regulation plate 23 separates the inner space 4 of the growth container 24 into a raw material section 41 on the lower side and a growth section 42 on the upper side. The raw material section 41 accommodates zinc-oxide single crystal raw materials 5, which are used for growth. The growth section 42 accommodates a plurality of seed crystals 6 supported on a single crystal growth shelf 61. The inner space 4 of the growth container 24 is filled with a growth solution (alkali solution). The single crystal raw material 5 used in this embodiment was a mixture of zinc oxide powder of 1 to 10 μm in diameter and indium oxide (In2O3) powder of 1 to 25 μm in diameter. The mixture was shaped into form on a press machine, and then sintered into a sintered body in an oxygen atmosphere of 1000 to 1400° C. or in atmosphere. The seed crystal 6 used was a plate-shaped zinc-oxide single crystal with a C surface as a main surface. The plate-shaped zinc-oxide single crystal was cut from a hexagonal crystal with the C surface in parallel to a (0001) surface, which is a C surface of the hexagonal crystal. The growth solution used was a KOH aqueous solution to which Li or a Li compound (for example, LiOH) was added. Instead of KOH, the growth solution may also be an aqueous solution of alkali such as NaOH, Na2CO3, or K2CO3 to which Li or a Li compound was added. —Single Crystal Growth Operation— Description will be made below with regard to a single crystal growth operation of the growth furnace 1, which accommodates the single crystal raw materials 5 and the seed crystals 6 and which is filled with the growth solution in the manner described above. In the growth operation, the electric furnace 3 heats the furnace main body 2. A heating condition is that the raw material section 41 is set at a temperature higher than a temperature of the growth section 42. The resulting difference in temperature causes natural convection of the growth solution between the raw material section 41 and the growth section 42 under high temperature and high pressure. By the natural convection, the growth solution in which the single crystal raw materials 5 are dissolved moves from the raw material section 41 to the growth section 42. Here, the growth solution in which the single crystal raw materials 5 are dissolved is cooled in the growth section 42 to be brought into supersaturation state. This makes the single crystal raw materials 5 deposited and grown on the seed crystals 6. This operation continues for a predetermined period of time to obtain zinc-oxide single crystals each of a predetermined size. The zinc-oxide single crystals thus obtained were cut so as to remove a part of each zinc-oxide single crystal grown on a (0001) surface, which is a +C surface of the corresponding seed crystal 6, or grown on a (000-1) surface, which is a −C surface of the seed crystal 6. This part of the zinc-oxide single crystal was used as a scintillator material. A scintillator made of this scintillator material was mounted in the scintillation detector. Next, the scintillator material according to the embodiment of the present invention will be described in detail by referring to examples. Description will be made below with regard to fluorescence characteristics of scintillator materials according to examples 1 to 6 of the embodiment produced by the above-described method for production, by way of comparison with conventional scintillator materials according to comparative examples 1 to 6. The scintillator materials according to comparative examples 1 to 6 are each made of a zinc-oxide single crystal grown on an M surface, which is a main surface, of a seed crystal. Specifically, the seed crystal 6 used was a plate-shaped zinc-oxide single crystal with an M surface as a main surface. The plate-shaped zinc-oxide single crystal was cut from a hexagonal crystal with the M surface in parallel to a (10-10) surface, which is an M surface of the hexagonal crystal. A zinc-oxide single crystal was obtained by the above-described method for production, and the obtained zinc-oxide single crystal was cut to remove a part grown on the M surface. This part of the zinc-oxide single crystal was used as the scintillator materials according to comparative examples 1 to 6. The zinc-oxide single crystals constituting the scintillator materials according to examples 1 to 6 are higher in quality, with decreased crystal defects, than the zinc-oxide single crystals constituting the scintillator materials according to comparative examples 1 to 6. Among these zinc-oxide single crystals, the zinc-oxide single crystals constituting the scintillator materials according to examples 1 to 5 are particularly superior in quality, with significantly decreased crystal defects. Table 1 below shows the atomic ratio between Li and In contained in the zinc-oxide single crystal of each of the scintillator materials according to examples 1 to 6 and the scintillator materials according to comparative examples 1 to 6, and shows the fluorescence lifetime of fluorescence that each scintillator material emits in response to an incident radiation. TABLE 1Fluorescence lifetimeComponent percentageLi/In(Ps)(%)(atomic ratio)Component 1Component 2Component 1Component 2Example 10.1517.2—1000Example 21.9010.7—1000Example 32.3215.2—1000Example 43.0016.5—1000Example 56.7412.7—1000Example 610.8112.1—1000Comparative0.14122.06005941Example 1Comparative0.20102.02378812Example 2Comparative0.4390.82918515Example 3Comparative6.73103.06256535Example 4Comparative64.6991.44035050Example 5Comparative323.6962.71337624Example 6 The Li/In (atomic ratio) shown in Table 1 is the ratio of the Li concentration (atoms/cm3) to the In concentration (atoms/cm3) in the zinc-oxide single crystal. The In concentration and the Li concentration in the zinc-oxide single crystal were analyzed by secondary ion mass spectrometry using a secondary ion mass spectrometer (ims6F, available from CAMECA). A streak camera (HAMAMATSU C1587) was used to measure the fluorescence lifetime of the fluorescence that the scintillator material according to each of examples 1 to 6 and each of comparative examples 1 to 6 emitted in response to an incident radiation. In the case of a plurality of components constituting the fluorescence, the fluorescence lifetimes of the respective components are shown as well as percentages of the components. FIG. 2 shows a relationship between the Li/In (atomic ratio) and the fluorescence lifetime. In FIG. 2, the plotted square dots are for the scintillator materials according to examples 1 to 6, while the plotted round dots are for the scintillator materials according to comparative examples 1 to 6. The case of a plurality of components constituting the emitted fluorescence is represented by the component of shortest fluorescence lifetime, showing a relationship between the shortest fluorescence lifetime and this component's Li/In (atomic ratio). Table 1 and FIG. 2 show that in the scintillator materials according to examples 1 to 6, each of which is made of a zinc-oxide single crystal grown on the +C surface or the −C surface of a seed crystal, the components constituting the emitted fluorescence have fluorescence lifetimes of less than 20 ps. The less than 20-ps fluorescence lifetimes of these components are observed to be shorter than any of the fluorescence lifetimes of the components of the fluorescence emitted by the scintillator materials according to comparative examples 1 to 6, each of which is grown on the M surface of a seed crystal. The scintillator materials according to examples 1 to 6 are mutually different in respect of the Li/In (atomic ratio) in zinc-oxide single crystal within the range of 0.15 to 11. These scintillator materials are observed to emit fluorescence made up of components of fluorescence lifetimes as short as 10.7 ps to 17.2 ps, without depending on the Li/In (atomic ratio). Additionally, the fluorescence that the scintillator materials according to examples 1 to 6 emitted in response to an incident radiation is observed to be made up of only a single component. Whereas, the fluorescence that the scintillator materials according to comparative examples 1 to 6 emitted in response to an incident radiation is observed to be made up of two components. Description will be made below with regard to a relationship between the intensity of the fluorescence and the fluorescence lifetime(s) of the component(s) constituting the fluorescence. The intensity of the fluorescence made up of only a single component (hereinafter referred to as component 1) is represented by the following Equation 1. In Equation 1, I denotes the emission intensity with its maximum set at 1, τ1 denotes the fluorescence lifetime of the component 1, and t denotes a period of time that elapsed after the emission intensity reached its maximum.I=exp(−t/τ1) [Equation 1] The following Equation 2 represents the intensity of fluorescence made up of the component 1 and another component (hereinafter referred to as component 2) having a longer fluorescence lifetime than the fluorescence lifetime of the component 1. In Equation 2, I denotes the emission intensity with its maximum set at 1, τ1 denotes the fluorescence lifetime of the component 1, τ2 denotes the fluorescence lifetime of the component 2, and t denotes a period of time that elapsed after the emission intensity reached its maximum. In addition, C1 denotes the presence ratio of the component 1 to the total of the component 1 and the component 2, and C2 denotes the presence ratio of the component 2 to the total of the component 1 and the component 2. It is noted that C1+C2=1.I=C1*exp(−t/τ1)+C2*exp(−t/τ2) [Equation 2] For example, Table 1 shows that the fluorescence that the scintillator material according to comparative example 5 emits in response to an incident radiation is made up of a component 1 of 91.4-ps fluorescence lifetime τ1 and a component 2 of 403-ps fluorescence lifetime τ2 at a presence ratio of 50:50 (that is, C1=0.5, C2=0.5). The emission intensity of the fluorescence that the scintillator material according to comparative example 5 emits changes over time, as shown in FIG. 3A. According to Equation 2, when the fluorescence of the component 1 reaches the end of its fluorescence lifetime (that is, when t=τ1=91.4), the emission intensity is considered higher than 1/exp of its maximum, because of the existence of the fluorescence of the component 2. Specifically, the fluorescence made up of the component 1 and the component 2 has a longer fluorescence lifetime than the fluorescence lifetime of the component 1. Hence, in the scintillator materials according to comparative examples 1 to 5 each emitting fluorescence made up of the component 1 and the component 2, the fluorescence lifetimes of these scintillator materials are considered longer than the 62.7-ps to 122-ps fluorescence lifetime of the component 1. Contrarily, the fluorescence that the scintillator material according to example 1 emits in response to an incident radiation is made up of only the component 1 of 17.2-ps fluorescence lifetime τ1, as shown in Table 1. The emission intensity of the fluorescence that the scintillator material according to example 1 emits changes over time, as shown in FIG. 3B. According to Equation 1, when the component 1 reaches the end of its fluorescence lifetime (that is, when t=τ1=17.2 ps), the emission intensity is considered to be at 1/exp of its maximum. Specifically, fluorescence made up of only the component 1 has the same fluorescence lifetime as the fluorescence lifetime of the component 1. Hence, in the scintillator materials according to examples 1 to 6 each emitting fluorescence made up of only the component 1, the fluorescence lifetimes of these scintillator materials are considered to be less than 20 ps, similarly to the fluorescence lifetime of the component 1, specifically 10.7 ps to 17.2 ps. That is, a comparison between FIG. 3A and FIG. 3B shows that the fluorescence that the scintillator materials according to examples 1 to 6 emit is considered higher in speed of attenuation of the emission intensity than the fluorescence that the scintillator materials according to comparative examples 1 to 6 emit, resulting in shorter fluorescence lifetimes. Additionally, fluorescence made up of only the component 1 is not a combination of the component 1 and the component 2, which has a longer fluorescence lifetime than the fluorescence lifetime of the component 1. This prevents the fluorescence from having a longer fluorescence lifetime than the fluorescence lifetime of the component 1. Hence, in the scintillator materials according to examples 1 to 6 emitting fluorescence made up of only the component 1, the fluorescence lifetimes of these scintillator materials are considered significantly shorter than the fluorescence lifetimes of the fluorescence that is made up of the component 1 and the component 2 and that the scintillator materials according to comparative examples 1 to 6 emit. As has been described hereinbefore, the fluorescence that the scintillator materials according to examples 1 to 6 emit in response to an incident radiation has a fluorescence lifetime of less than 20-ps. Thus, the scintillator materials according to examples 1 to 6 are considered to ensure a shorter fluorescence lifetime compared with the conventional scintillator materials according to comparative examples 1 to 6 that emit the fluorescence made up of a plurality of components having the equal to or more than 30-ps fluorescence lifetime. Thus, providing a scintillation detector with a scintillator made of any of the scintillator materials according to examples 1 to 6 improves the time resolution of the scintillation detector. Incidentally, it is believed from the following Equations 3 and 4 that the fluorescence lifetime of a zinc-oxide single crystal constituting a scintillator material is related to the lifetime of quenching, in which electrons excited from the valence band to the conduction band return to the valence band without emitting light. Equation 3 represents the fluorescence lifetime of the zinc-oxide single crystal, τall. The symbol τrad denotes the lifetime of the light emitted in process which of the electrons excited from the valence band to the conduction band return to the valence band, and τdef denotes the lifetime of the quenching.1/τall==1/τrad+1/τdef [Equation 3]That is, the fluorescence lifetime τall of the zinc-oxide single crystal is represented by Equation 4.τall=τradτdef/(τrad+τdef)=τdef/(1+τdef/τrad) [Equation 4] Equation 4 leads to a conclusion such that when the lifetime τdef of the quenching is significantly shorter than the lifetime τrad of the emitted light, the fluorescence lifetime τall of the zinc-oxide single crystal becomes approximately equal to the lifetime τdef of the quenching. That is, it is possible to say that the fluorescence lifetime τall of the zinc-oxide single crystal is determined by the lifetime τdef of the quenching. Thus, the scintillator materials according to examples 1 to 6 have shorter lifetimes of quenching, and this presumably makes the resulting fluorescence lifetimes as short as 10.7 ps to 17.2 ps. In the above-described method for producing the scintillator material according to the embodiment, the single crystal raw material 5 used is a sintered body of a mixture of zinc oxide powder and indium oxide powder, that is, a raw material containing Zn and In. The growth solution used is a KOH aqueous solution to which Li is added. To ensure better crystallinity of the finally obtained zinc-oxide single crystal, it is possible to contain at least one of Al, Fe, Ga, Ce, and Pr in the single crystal raw material or in the growth solution. That is, the scintillator material according to the present invention may contain, in its zinc-oxide single crystal, at least one of Al, Fe, Ga, Ce, and Pr. The present invention can be embodied and practiced in other different forms without departing from the spirit and essential characteristics of the present invention. Therefore, the above-described embodiments are considered in all respects as illustrative and not restrictive. The scope of the invention is indicated by the appended claims rather than by the foregoing description. All variations and modifications falling within the equivalency range of the appended claims are intended to be embraced therein. This application claims priority to Patent Application No. 2010-151330 filed in Japan on Jul. 1, 2010, which is hereby incorporated by reference in its entirety by claiming the priority. The present invention is applicable to scintillation detectors that expose their scintillator to ionization radiation such as X rays, γ rays, and α rays so as to cause the scintillator to emit fluorescence, and that amplify the fluorescence by a photomultiplier tube to detect the fluorescence, or the present invention is applicable to scintillator materials of such scintillation detectors. 1 Growth furnace 2 Furnace main body 21 Upper end opening 22 Lid 22a Pressure gauge 23 Convection regulation plate 24 Growth container 3 Electric furnace 4 Inner space 41 Raw material section 42 Growth section 5 Single crystal raw material 6 Seed crystal |
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054882290 | abstract | A high resolution, deep UV photolithography system includes a deep UV radiation source for generating a beam of narrow wavelength deep ultraviolet radiation along a path, mask receiving structure in the path, a first optical system in the path for homogenizing and shaping the deep UV energy in the path; and a second optical system in the path for directing radiation energy onto the surface of a substrate to be processed, the second optical system including large area mirror structure having a numerical aperture of at least 0.3 and a plurality of refractive elements disposed between the mask receiving structure and the substrate for compensating (reducing) image curvature introduced into the system by the large area mirror structure. |
description | The present invention relates to a nuclear fuel rod spacer grid for a fuel assembly, of the type comprising at least two meshed grid parts which are to be superposed in a longitudinal direction, each grid part extending in a transverse plane, the grid parts being movable relative to one another in at least one transverse direction between an open configuration for insertion of nuclear fuel rods in the longitudinal direction through the grid parts, and a closed configuration allowing each rod inserted through the grid parts to be clamped transversely between the grid parts. FR 2 639 139 A1 describes a nuclear fuel rod spacer grid for a light water reactor, comprising two grid parts with dimples and one grid part with springs, which grid parts can be offset for the longitudinal insertion of the rods through the grid or aligned in order to clamp the rods between the grid parts. The grid comprises an outer frame produced in two parts for holding the grid parts in the rod clamping configuration. The use of this grid requires a special tool for holding the grid parts in the rod insertion configuration and in the rod clamping configuration, and for fixing the frame. An object of the invention is to provide a nuclear fuel rod spacer grid which is easy to use. To that end, the invention provides a nuclear fuel rod spacer grid of the type mentioned above, characterized in that it comprises elements for transversely immobilizing the grid parts in the closed configuration, which elements are arranged to come into engagement as the superposed grid parts are brought together in the longitudinal direction. According to other embodiments of the invention, the nuclear fuel rod spacer grid has one or more of the following features, taken in isolation or in any technically possible combinations: the grid parts have members for locking the grid parts longitudinally in the closed configuration; locking members are fixed to one grid part and are capable of snapping onto the other grid part as the grid parts are brought together in the longitudinal direction; immobilization elements comprise peripheral walls which are fixed to one grid part and define, between them and with that grid part, a space for receiving the other grid part, into which space the other grid part can be fitted; when viewed in the longitudinal direction, the grid parts have a polygonal peripheral contour, the peripheral walls comprising at least one pair of peripheral walls which are fixed to one grid part and extend along opposite sides of that grid part; at least one peripheral wall fixed to one grid part carries a tooth for locking the grid parts in the closed configuration, which tooth is capable of snapping onto the other grid part as the grid parts are brought together; the grid parts define at least one passage for a guide thimble for receiving a cluster rod, at least one of the grid parts being capable of receiving the or each guide thimble with transverse clearance in at least one transverse direction of clamping of the rods between the grid parts; each grid part is formed of first plates and second plates which intersect with the first plates; it comprises a first pair of grid parts provided for clamping rods in a first transverse direction, and a second pair of grid parts for clamping those rods in a second transverse direction that is different from the first transverse direction; one grid part of the first pair of grid parts is fixed to one grid part of the second pair of grid parts. The invention relates also provides a nuclear fuel rod spacer framework for a nuclear fuel assembly, comprising a plurality of spacer grids for rods of a bundle of rods, which spacer grids are to be distributed along the rods at a distance from one another, characterized in that at least one of the spacer grids is a spacer grid as defined above. The invention also provides a nuclear fuel assembly comprising a bundle of nuclear fuel rods and a spacer framework for the rods as defined above. In order to illustrate the context of the invention, FIG. 1 shows, in diagrammatic form, a nuclear fuel assembly 2 for a pressurized water reactor. In this type of reactor, during operation, light water serves as the moderator for the nuclear reaction and as the coolant for the heat exchanges. The assembly 2 extends in a longitudinal direction L, which is intended to be vertical when the assembly 2 is disposed in the core of a nuclear reactor. That direction is the main direction of flow of the water. The assembly 2 comprises, in known manner, a bundle of nuclear fuel rods 4 containing the fissile material, and a framework 6 for supporting and holding the rods 4. The framework 6 conventionally comprises a bottom end-piece 8, a top end-piece 10, guide thimbles 12, and grids 14 for holding the rods 4. The bottom end-piece 8 and the top end-piece 10 are arranged at the longitudinal ends of the assembly 2. The guide thimbles 12 extend longitudinally between the end-pieces 8, 10 and are fixed at their longitudinal ends to the end-pieces 8, 10. Accordingly, the guide thimbles 12 connect the end-pieces 8 and 10 together. In a conventional manner, the guide thimbles 12 are to receive, through their open top ends, cluster rods which do not contain fissile material, the presence or insertion of which to a greater or lesser extent allows the nuclear reaction to be controlled. In an alternative embodiment, at least one of the guide thimbles is replaced by an instrumentation tube which is to permit the insertion, through its open bottom end, of a reactor instrumentation device. The grids 14 are fixed to the guide thimbles 12 and distributed along the guide thimbles 12, between the end-pieces 8, 10. The grids 14 have analogous structures and can exhibit variations according to their longitudinal position: presence or absence of mixing vanes, guide vanes, outer straps, etc. The rods 4 are disposed longitudinally in a bundle and pass through the grids 14. The grids 14 serve to hold the rods 4 on the frame 6. The rods 4 terminate at a distance from the end-pieces 8, 10. The grids 14 keep the rods 4 and the guide thimbles 12 apart in order to allow pressurized water to flow in direction L, through the assembly, between the rods 4. A conventional grid for a pressurized water reactor fuel assembly defining a square-base system has, for example, between 14 and 19 cells on each of its sides, a plurality of cells for receiving guide thimbles distributed in the system, and, optionally, a central cell for receiving an instrumentation tube. A conventional grid for a boiling water reactor fuel assembly defining a square-base system has, for example, between 6 and 13 cells on each of its sides and at least one cell for receiving a water channel which replaces from 1 and up to 5×5 fuel rods and is generally disposed relatively centrally. The invention will now be described with reference to FIGS. 2 to 8, which show a grid 14 which is analogous to those of FIG. 1 but is limited, for reasons of clarity of the drawings, to one system designed to receive a smaller number of rods as compared with a conventional grid. As shown in FIGS. 2 and 3, the grid 14 comprises a first grid part 16 and a second grid part 18, which parts are separate. The grid parts 16, 18 are movable relative to one another in direction L, between an open configuration (FIG. 2) for insertion of nuclear fuel rods through the grid 14 in direction L, and a closed configuration (FIG. 3) for clamping the nuclear fuel rods between the grid parts 16, 18. As shown in FIG. 2, each of the grid parts 16, 18 is of the meshed type and defines a system of cells comprising cells 20 for receiving nuclear fuel rods, and a cell 22 for receiving a guide thimble 12. In the example shown, each grid part 16, 18 defines a square-base system having five cells on each of its sides. The cell 22 for receiving a guide thimble 12 is the central cell, and the other cells 20 are cells for receiving nuclear fuel rods. In the open configuration, a rod 4 is able to pass through each cell 20 substantially without being clamped. In the open configuration (FIG. 2), the grid parts 16 and 18 extend transversely to direction L and are superposed in direction L, so that each cell 20 of one grid part is superposed with a cell 20 of the other grid part in order to allow a nuclear fuel rod to be inserted in direction L through each pair of superposed cells 20. Each grid part 16, 18 comprises first inner spacer plates 24 which intersect with second inner support plates 26, defining between them the cell system. The spacer plates 24 are substantially flat and extend in a first transverse direction T1. The support plates 26 have a curved shape and extend generally in a second transverse direction T2, which is perpendicular to direction T1. In the example shown, each of the support plates 26 comprises a plurality of substantially semi-cylindrical support portions 28, the axis of which is parallel to direction L. Each support portion 28 has a support face which defines in part a wall of a cell 20 and is to come to bear on a rod in order to clamp it. The support faces of the support portions 28 are here their concave faces. The support faces of the support portions 28 of a support plate 26 are oriented on the same side of the plate 26, and the support faces of the support portions 28 of the support plates 26 of one grid part 16, 18 are oriented in the same transverse direction. The spacer plates 24 cross the support plates 26 between the support portions 28 and maintain the spacing between the support plates 26. As shown in FIG. 4, which is an exploded perspective view of the second grid part 18, the support plates 26 and the spacer plates 24 are equipped with complementary notches 30, which allow them to be fitted together. The cell 22 of the second grid part 18 is larger than the guide thimble 12, in particular in direction T1, so that the second grid part 18 can be threaded onto the guide thimble 12 with transverse clearance. As shown in FIG. 5, the first grid part 16 comprises two tabs 31 on two of the first plates 24 delimiting the cell 22. The tabs 31 are in the form of portions of a cylinder whose axis is parallel to direction L. The tabs 31 are integral with the plates 24. By way of variation, the tabs 31 are attached and fixed to the plates 24. The tabs 31 are to receive the guide thimble 12 between them, substantially without transverse clearance, so that the first grid part 16 is transversely stationary relative to the guide thimble 12. As shown in FIG. 2, the grid 14 comprises means for transversely immobilizing the grid parts 16, 18 relative to one another when the grid parts 16, 18 are in the closed configuration. In the example shown, the transverse immobilization means comprise peripheral plates 32, 34 which surround the inner plates 24, 26 of the first grid part 16 and are fixed thereto. The peripheral plates 32, 34 are fixed to the ends of the inner plates 24, 26. Each peripheral plate 32, 34 extends on one side of the first grid part 16. The peripheral plates 32, 34 terminate at a distance from one another and are not connected directly to one another at the corners of the first grid part 16. The peripheral cells 20 of the first grid part 16 are closed laterally by the peripheral plates 32, 34, with the exception of two corner cells 20, which are open laterally (on the right in FIG. 2). By way of variation, the peripheral plates 32, 34 meet and are connected together, for example by welding, the four corner cells are closed. As a result, the rods received in the corner cells will be protected during handling operations. The peripheral plates 32, 34 extend beyond the inner plates 24, 26 of the first grid part 16, in the direction towards the second grid part 18 disposed in the open configuration. They define, between them and with the upper edges of the inner plates 24, 26 of the first grid part 16, a space 36 for receiving the second grid part 18. The space 36 is complementary to the outer contour of the second grid part 18. In the closed configuration (FIG. 3), the second grid part 18 is inserted in direction L into the space 36 and is immobilized transversely relative to the first grid part 16 by the peripheral plates 32, 34. In the example shown, the peripheral plates 32, 34 extend over the whole of the height of the inner plates 24, 26 of the first grid part 16 and of the second grid part 18. The grid 14 comprises locking means which are capable of fixing the grid parts 16, 18 longitudinally relative to one another and which are active when the grid 14 is in the closed configuration. In the example shown, the locking means comprise locking teeth 38 which are provided to snap onto the upper edges of the inner plates 24, 26 of the second grid part 18 in the closed configuration (FIG. 3). The teeth 38 are disposed on the top edges of a pair of peripheral walls 32 extending along opposite sides of the first grid part 16. The peripheral plates 32 project over a height (in direction L) which is slightly greater than the height of the plates 24, 26 of the second grid part 18. The second grid part 18 does not have peripheral walls. Accordingly, the peripheral cells 20 of the second grid part 18 are open laterally in the open configuration (FIG. 2). Some of the peripheral cells 20 are closed by the peripheral walls 32, 34 of the first grid part 16 in the closed configuration (FIG. 3). In a variant where the peripheral plates 32, 34 meet at the four corners of the first grid part 16, the peripheral cells 20 of the second grid part 18 are all closed laterally. Optionally, the peripheral plates 32, 34 comprise guide vanes which project from their bottom edge and/or from their top edge and which are inclined towards the centre of the grid, in order to effect guiding of the grid with the surrounding objects during handling operations. The insertion of fuel rods through the grid 14 is described hereinbelow with reference to FIGS. 2, 3 and 6 to 8. In order to join the two grid parts 16, 18 and insert the rods 4, the first grid part 16 and the second grid part 18 are threaded onto the guide thimble 12 and disposed in the open configuration (FIG. 2). The grid parts 16 and 18 are oriented about direction L so that for each pair of cells 20 superposed in direction L of the grid parts, and the support faces of the support portions 28 delimiting the cells of said pair of cells are facing. The tabs 31 are welded to the guide thimble 12. Accordingly, the first grid part 16 is longitudinally and transversely stationary relative to the guide thimble 12. The second grid part 18 slides longitudinally and is transversely movable at least in direction T1 relative to the guide thimble 12. The second grid part 18 is then shifted transversely in direction T1 so that the support faces of the support portions 28 of the cells 20 of each pair of superposed cells 20 are moved apart in direction T1 in order to allow a rod 4 to be inserted, substantially without being clamped between the support faces of the support portions 28 (FIG. 6). To that end, the spacing between the support faces is greater than the diameter of the rods 4. Each rod 4 is inserted in direction L through a pair of superposed cells 20. The grid parts 16 and 18 are then brought together in direction L until the second grid part 18 is inserted into the corresponding space 36 of the first grid part 16 (FIG. 8). During the insertion, the peripheral walls 32, 34 guide the second grid part 18 so that the opposing support faces of the support portions 28 of the cells 20 of each pair of superposed cells 20 are brought together in direction T1 and clamp between them the rod 4 passing through those two cells 20 (FIG. 7). The peripheral walls 32 are deformed resiliently and move apart during the insertion in order to allow the teeth 38 to slide along the first grid part 18 until the teeth 38 snap onto the first grid part 18 and oppose a reverse spreading movement of the grid parts 16 and 18. It will be noted in FIGS. 6 and 7 that the support portions 28 have a radius of curvature, on their supporting face side, that is greater than the radius of curvature of the outer surface 40 of the rods 4. This ensures that the rod 4 is centred as the support portions 28 are brought together. FIG. 8 shows the grid 14 in the closed configuration, the rods 4 passing through the grid 14. In the embodiment of FIGS. 2 to 8, each rod 4 is clamped in a transverse direction (direction T1) between a support plate 26 of one of the grid parts 16, 18 and a support plate 26 of the other grid part. The insertion of the rods 4 in the open configuration of the grid parts 16, 18 without clamping avoids friction of the rods 4 against the grid parts 16, 18 and the formation of recessed chips on the outer surface of the rods 4, which can impair the strength and longevity of the rods 4. During movement in the closed configuration, the second grid part 18 moves longitudinally along the rods 4 and gradually clamps them. Nevertheless, this is effected over a reduced length, which is here substantially equal to the height of the second grid part 18. The grid 14 is easy to install because the grid parts 16, 18 are joined simply by being brought together longitudinally, which causes the rods 4 to be clamped and the means for transversely immobilizing the grid parts 16, 18 in the closed clamping configuration (peripheral walls 32, 34) to be brought into engagement. Bringing the grid parts 16, 18 together also causes the engagement of the means for locking the grid parts 16 and 18 in the closed clamping configuration (for example the teeth 38). By way of variation or optionally, longitudinal locking of the grid parts 16, 18 is obtained by fixing them together so that the grid cannot be taken apart, for example by welding the peripheral plates 32, 34 of the first grid part 16 to one or more inner plates of the second grid part 18 in several places. As shown in FIGS. 9 and 10, where references to elements similar to those in FIGS. 1 to 8 have been retained, two grids 44, 42 identical to the grid 14 of FIGS. 2 to 8 are superposed and offset by an angle of 90° about direction L in order to clamp the rods 4 in two different transverse directions. As shown in FIG. 10, in an assembly, the grids 42, 44 are spaced in direction L. Furthermore, the grid 44 is turned round so that the second grid part 18 of the grid 42 fits into the corresponding first grid part 16 from the top, while the second grid part 18 of the grid 44 fits into the corresponding first grid part 16 from the bottom. This facilitates the movement of the second grid parts 18 in the clamping configuration when the longitudinal spacing between the grids 42, 44 is small. As shown in FIGS. 11 and 12, a grid 46 corresponds to the joining of the grids 42, 44 of FIGS. 9 and 10. There is accordingly obtained a grid 46 having two stages 48, 50, each of which is formed by a first grid part 16 and a second grid part 18 which are capable of cooperating in order to clamp each rod in a transverse direction, the two stages being capable of clamping the rods in different (here perpendicular) directions. Optionally, and as shown in FIGS. 11 and 12, the grid 46 has vanes 52 for mixing a coolant flowing between the rods 4, the vanes 52 projecting upwards from the grid 46. More precisely, the vanes 52 are fixed to the second grid part 18 of the top stage 48, to the top edges of the spacer plates 24 and to the top edges of substantially flat auxiliary vane support plates 54, and extend perpendicularly to the spacer plates 24. The provision of mixing vanes is not limited to grids having two stages. Vanes may optionally also be provided on a grid having a single stage, such as that of FIG. 8. The shape of the support portions 28 according to the example of FIGS. 2 to 8 allows a large support surface to be obtained while the loss of pressure of the grid 14 is limited, i.e. its resistance to the flow of a fluid through the grid 14 is limited. However, the shape of the support portions 28 is not limited to the example of FIGS. 2 to 8. The support portions 28 can have different shapes. The support portions 28 of two grid parts of a grid can be different. This is illustrated in FIGS. 13 to 18. As shown in FIG. 13, where references to elements similar to those of FIGS. 2 to 8 have been retained, a grid 14 differs from the grid of FIGS. 2 to 8 in the shape of the support portions 28 of the grid parts 16 and 18. As can be seen more clearly in FIG. 14, in a view in direction L, each support portion 28 has the general shape of a rounded W. The support face comprises a concave support zone 56 surrounded by two convex zones 58. When a rod 4 is inserted into aligned cells 20 of the grid parts 16, 18, and when the grid parts 16, 18 are in the closed configuration, the grid 14 bears on the rod 4 in two diametrically opposite zones 60. In a variant shown in FIG. 15, the support portions 28 are different. When viewed in direction L, each of the support portions 28 of the first grid part 16 has on its support face two spaced concave support zones 62, and each of the support portions 28 of the second grid part 18 has on its support face a concave support zone 64. When a rod 4 is inserted into aligned cells 20 of the grid parts 16, 18, and when the grid parts 16, 18 are in the closed configuration, the grid 14 bears on the rod 4 in three zones 66 which are spaced circumferentially. FIG. 16 shows a grid having two stages, analogous to that of FIGS. 11 and 12, the grid parts 16, 18 of which have support portions 28 which are identical to those of FIG. 14. FIG. 17 shows a two-stage grid having two second grid parts 18 equipped with support portions 28 which are identical to those of FIG. 14, which has a certain degree of resilience radially to the rod 4 and forms springs, and two first grid parts 18 equipped with support portions each having a single flat support zone 68, which is similar to a boss, which are more rigid than the springs. FIG. 18 shows a two-stage grid, the grid parts of which have support portions 28, each of which has, on its support face, a concave support zone 70 provided with a slot 72 which extends in direction L (perpendicular to the plane of FIG. 18). The presence of the slot 72 allows the resilience of the support portion 28 to be adjusted. The grid parts are made of any suitable material, especially of metal, such as zirconium-based alloys, nickel-based alloys etc. The invention is not limited to the examples which have been described. In particular, the walls or the support zones defining bosses and springs can have any suitable shapes. Furthermore, the grid parts of a grid are locked in the closed configuration by any suitable means, such as by snap-in raised portions (teeth 38) or by welding. The invention is applicable to grids for a nuclear fuel assembly for a light water nuclear reactor, such as pressurized water reactors (PWR) and boiling water reactors (BWR). In the latter case, each grid defines at least one longitudinal passage for a water flow channel, for example by replacing a guide thimble of a grid for a PWR-type assembly. |
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summary | ||
claims | 1. An X-ray phase-contrast imaging (PCI) system, comprising:an X-ray source;a detector;a first grating disposed between the X-ray source and the detector; anda second grating disposed between the first grating and the detector,wherein the first grating is a quasi-periodical phase grating such that a period of the first grating varies across the first grating and changes equally in both lateral directions. 2. The system according to claim 1, wherein the second grating is an analyzer grating. 3. The system according to claim 1, wherein the detector is flat. 4. The system according to claim 3, wherein the detector is a flat detector array. 5. The system according to claim 1, wherein the second grating is flat. 6. The system according to claim 1, wherein the first grating is curved. 7. The system according to claim 6, wherein the first grating is a cylindrical grating or a spherical grating. 8. The system according to claim 1, wherein the detector is flat,wherein the second grating is flat, andwherein the first grating is a cylindrical grating or a spherical grating. 9. The system according to claim 1, further comprising a source grating disposed between the X-ray source and the first grating. 10. The system according to claim 9, wherein the source grating is a cylindrical grating or a spherical grating. 11. The system according to claim 1, wherein the period of the first grating varies the same way in both lateral directions as an angle is varied positively or negatively by the same amount from a point on the first grating where X-rays from the X-ray source are centered during imaging. 12. A method of performing X-ray phase-contrast imaging, comprising:providing the imaging system according to claim 1;positioning an object to be imaged between the X-ray source and the first grating; andimaging the object using the system. 13. The method according to claim 12, wherein the detector is flat,wherein the second grating is flat, andwherein the first grating is a cylindrical grating or a spherical grating. 14. The method according to claim 13, wherein the second grating is an analyzer grating. 15. The method according to claim 13, wherein the imaging system further comprises a source grating disposed between the X-ray source and the first grating,wherein the source grating is a cylindrical grating or a spherical grating,and wherein the object is positioned between the source grating and the first grating for imaging of the object. 16. The system according to claim 1, wherein the first grating is disposed closer to the detector than it is to the X-ray source such that the system is configured so the first grating is disposed between the detector and an object to be imaged. |
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claims | 1. An operation method of a plant including a secondary system of a pressurized-water-type nuclear power plant, which has a low-pressure feed water heater, a deaerator and a high-pressure feed water heater sequentially arranged in a feed water pipe reaching a steam generator from a condenser, and leads high-temperature feed water to a steam or a feed water system of a thermal power plant which has a low-pressure feed water heater, a deaerator and a high-pressure feed water heater sequentially arranged in a feed water pipe reaching a boiler from a condenser, and leads high-temperature feed water to a pressure reaction vessel, the operation method of the plant comprising:forming an oxide film for suppressing an elution of an element constituting a structural material of at least one of the feed water pipe, the low-pressure feed water heater, the deaerator and the high-pressure feed water heater which come in contact with the high-temperature feed water, on a surface of the structural material by injecting an oxidant into the high-temperature feed water of which pH is adjusted to 9 to 10 during generation of power; anddepositing a corrosion suppression substance on the oxide film formed on the surface of the structural material in a region in which the corrosion accelerated by a flow of a feed water occurs, by introducing the corrosion suppression substance into the feed water, the corrosion suppression substance being oxide or hydroxide containing one or more elements selected from Ti, Zr, Ce, Nb, La, Nd and Y. 2. The plant operation method according to claim 1, wherein the oxide film is formed by injecting at least one oxidant selected from a group of oxygen, hydrogen peroxide and ozone into the high-temperature feed water. 3. The plant operation method according to claim 2, wherein the oxidant is injected in a downstream side of the condenser and in an upstream side of the low-pressure feed water heater in the feed water pipe. 4. The plant operation method according to claim 2, wherein the oxidant to be injected into the feed water for forming the film is injected so as to make a dissolved oxygen concentration in the feed water 5 ppb or more. 5. The plant operation method according to claim 2, wherein an injection amount of the oxidant to be injected into the feed water is controlled by monitoring a corrosion potential of the feed water. 6. The plant operation method according to claim 1, wherein the corrosion suppression substance is titanium oxide and 5 μg/cm2 or more of the titanium oxide is deposited on the surface of the structural material. 7. The plant operation method according to claim 1, wherein the corrosion suppression substance is in a state of colloid or slurry having a fine particle diameter and is deposited on the surface of the structural material by spraying, thermal spraying or injection into the feed water. 8. The plant operation method according to claim 1, wherein the corrosion suppression substance is introduced in a downstream side of the condenser and in an upstream side of the high-pressure feed water heater in the feed water pipe. 9. The plant operation method according to claim 1, wherein the feed water flowing in an inside of the structural material of the feed water pipe has a temperature of 15° C. or higher and 350° C. or lower. 10. The plant operation method according to claim 1, wherein a flow of the feed water, which accelerates corrosion, has a flow velocity of 1 msec or more and 20 msec or less. 11. The plant operation method according to claim 1, wherein hydrogen is injected in the feed water flowing in an inside of the structural material of the feed water pipe. 12. The plant operation method according to claim 11, wherein the hydrogen is injected so as to make a dissolved hydrogen concentration in the feed water 1 ppb or more. 13. An operation system of a secondary system of a pressurized-water-type nuclear power plant which has a low-pressure feed water heater, a deaerator and a high-pressure feed water heater sequentially arranged in a feed water pipe reaching a steam generator from a condenser, and leads high-temperature feed water of which pH is adjusted to 9 to 10 to the steam generator, the plant operation system comprising:an oxidant injection unit which is provided in a downstream side of the condenser and in an upstream side of the low-pressure feed water heater in the feed water pipe, and during generation of power injects an oxidant for forming an oxide film into the high-temperature feed water, the oxide film suppressing an elution of an element constituting a structural material of at least one of the feed water pipe, the low-pressure feed water heater, the deaerator and the high-pressure feed water heater, which come in contact with the high-temperature feed water, onto a surface of the structural material; anda corrosion suppression substance introduction unit which is provided in a downstream side of the deaerator and in an upstream side of the high-pressure feed water heater in the feed water pipe, and introduces a corrosion suppression substance so as to deposit the corrosion suppression substance on the oxide film formed on the surface of the structural material in a region in which corrosion accelerated by a flow of the feed water occurs. 14. An operation system of a thermal power plant which has a low-pressure feed water heater and a high-pressure feed water heater sequentially arranged in a feed water pipe reaching a boiler from a condenser, and leads high-temperature feed water of which pH is adjusted to 9 to 10 to the boiler,the plant operation system including an injection unit which is provided in a downstream side of the condenser and in an upstream side of the low-pressure feed water heater in the feed water pipe, and during generation of power injects an oxidant for forming an oxide film into the high-temperature feed water, the oxide film suppressing an elution of an element constituting a structural material of at least one of the feed water pipe, the low-pressure feed water heater and the high-pressure feed water heater, which come in contact with high-temperature feed water, onto a surface of the structural material, and a corrosion suppression substance for depositing the corrosion suppression substance into a feed water, the corrosion suppression substance being oxide or hydroxide containing one or more elements selected from Ti, Zr, Ce, Nb, La, Nd and Y, onto the oxide film formed on the surface of the structural material in a region in which corrosion accelerated by a flow of the feed water occurs. |
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description | This invention was made with government support under Contract No. DE-AC02-06CH11357 awarded by the United States Department of Energy to UChicago Argonne, LLC, operator of Argonne National Laboratory. The government has certain rights in the invention. This invention relates to a method to produce salts containing a metal halide and more specifically, this invention relates to a low temperature, scalable system with minimal to no waste discharge and a method for dissolving a metal halide in a matrix halide salt by halogenation of the metal, with a halogen gas. The molten form of metal halides is a typical component in pyro-chemical processes as it is important in the reprocessing of spent nuclear fuels. Numerous synthesis methods exist for producing small quantities of such halides, including uranium chlorides. For example, existing reaction pathways utilize a chlorine compound and typically require purification via a secondary reaction sequence. These pathways do not efficiently eliminate residual lower or higher valent uranium chlorides. Synthesis pathways that yield unwanted lower or higher valent compounds of uranium could lead to ancillary oxidation or reduction reactions occurring in the final salt that could contaminate the salt with unwanted metals or metal halides. Furthermore, the current reaction pathways to uranium chloride are not operated at 100 percent efficiency nor are they capable of producing large quantities of the salt in a single batch process. Finally, state of the art methods for producing metal halides use higher melting metals such as cadmium, which then must be further processed to obtain the target metal halide. This creates additional process steps, and disposal issues. Methods which utilize HCl or Cl2 as the chlorinating agent result in extensive levels of corrosion in ferrous metal containers and any associated ferrous-based process equipment. This corrosion side reaction limits the quantity of uranium chloride which may be produced at a given point in time. Further the current methods of chloride salt synthesis are not used as stand-alone processes, but typically as adjuncts in other processes or operations. Other chlorinating methods based on organic chlorides such as CCl4, CH2Cl2, etc., result in unwanted reaction products including phosgene gas that must be treated before disposal as waste. As a component in the process used in molten salt reactors, chloride salts (and NaCl in particular) were previously thought to have good nuclear, chemical, and physical properties. However, NaCl has a high melting point, requiring it to be blended with other salts such as KCl, CsCl, MgCl2 or CaCl2 to form lower melting solutions. These additions often result in the addition of actinide trichlorides so that the mixture becomes eutectic. A eutectic mixture is preferred over the binary chlorides within this process because it leads to a lower liquid temperature for the fluid, thus mitigating corrosion reactions and allowing the use of less costly structural materials. In pyro-processing applications, molten LiCl is considered a promising option for the electrochemical reduction process for a myriad of reasons: the operating temperature is lower than other commonly used salts such as CaCl2; a high current efficiency may be achieved; and it is compatible with the other electrochemical processes such as electro-refining in which actinides are separated from fission products found in used nuclear fuel. A eutectic mixture of LiCl— UCl3 used in the electrorefining process enables a more efficient method for fuel recycling and minimizes the amount of salt waste discharged from the overall treatment process. Chemistries for this process include those depicted in Equations 1-4, infra: Electroreduction:Cathode Reaction UO2(solid)→U(solid)+2O2−(liquid in LiCl—Li2O) (1)Anode Reaction 2O2−(liquid in LiCl—Li2O)+C(solid)→CO2(gas) (2) ElectrorefiningAnode Reaction U(solid,impure)→U3+(liquid in LiCl—UCl3)+3e− (3)Cathode Reaction U3+(liquid in LiCl—UCl3)+3e−→U(solid,pure) (4) A need exists in the art for a process to produce actinide halides which does not generate reactive or hazardous waste streams. The process should be highly scalable for industrial applications. The system should be useable as a stand-alone process or incorporated as a component in another existing process such as electrorefining. Also, the process should be highly efficient to minimize the need for off-gas treatment (e.g., unreacted chlorine gas) while generating a minimal waste stream. An object of the invention is to provide a system and method for producing uranium chloride which overcomes many of the drawbacks of the prior art. A primary object of the invention is to provide a method for producing a metal halide. A feature of the method is halogenation of the metal in the first step of the process. (The metal, which is initially a constituent of a low melting alloy, is halogenated with a halogen gas.) Another feature is that the method utilizes direct chlorination of a binary eutectic mixture in a second step. An advantage of the method is that it does not require extreme temperatures and is readily scalable. Another advantage is that the method eliminates the need for a chlorine carrying metal, such as CdCl2 to transport chlorine to the pure target metal that is ultimately to be halogenated. Another object of the invention is to provide a system to efficiently produce large quantities of salts containing uranium chloride in either a continuous or batch process. A feature of the invention is utilization of a crucible containing a low melting point alloy submerged within a matrix salt. Another feature of the invention is the introduction of a reactant metal (e.g., uranium) during the process to keep the metal alloy in a molten phase throughout processing by replenishing the metal (e.g., uranium) reacting with the chlorine gas. An advantage is that minimal to no excess chlorine is released. Also, this method eliminates the salt trace impurities by sequestering them in the alloy. Another advantage is that the process utilizes direct chlorination of a binary eutectic alloy via chlorine gas injection (and so eliminating the need for a chlorine carrying metal that is soluble in the molten salt solution) thereby more efficiently chlorinating uranium. The process treats a binary eutectic salt mixture via chlorine gas injection to more efficiently yield a mixture of metal halides in the salt. Still another object of the invention is to provide a system for producing salts containing uranium chloride without the use of temperatures above about 825° C. A feature of the invention is chlorinating metal halide species to form a solution, whereby the solution resides within a matrix salt. An advantage of the invention is that it yields a high purity product when high purity feed materials are used. Another advantage is that the system may operate as an individual process or be incorporated into another process operation such as in an electrorefiner or in a molten salt reactor. Yet another object of the present invention is to provide a method for producing large quantities of uranium chloride salt for nuclear energy applications. A feature of the method is a two-step method to produce a eutectic mixture of uranium salt comprising NaCl— UCl3— UCl4. An advantage of the invention is that it yields large quantities of uranium salts while minimizing the waste impurity contamination and the generation of secondary waste streams. Another advantage is that it allows for the removal of the liquid metal alloy from the salt bath simultaneous with the halogen gas continually fed to the system until the desired composition of NaCl—UCl3—UCl4 is achieved. Briefly, the invention provides a method for producing salts of uranium halide, the method comprising: establishing a molten salt bath; confining uranium metal alloy within a specific region within the bath wherein the specific region is in constant fluid communication with the salt bath; contacting the alloy with a halogen gas in a first reaction to halogenate the uranium; and contacting the halogenated uranium with the salt bath in a second reaction to form a eutectic mixture comprising the mixed valent uranium salts. Also provided is a method for producing a metal halide, the method comprising submerging a liquid alloy containing an element of the halide in a molten salt bath; contacting the alloy with halogen in a first reaction to form a first metal halide, wherein the element is more electropositive than the halogen; and contacting the first metal halide with the molten salt bath in a second reaction to form a second metal halide. The invention further provides a system for producing metal halides, the system comprising: a heated vessel; wherein the vessel is maintained in a dry inert atmosphere; a chemically inert crucible positioned within the heated vessel, the crucible adapted to receive uranium alloy; a sparge tube with a first depending end positioned within the crucible and a second superior end in fluid communication with a halogen gas supply; a molten salt bath covering the crucible; and; a bale for retrieving the crucible from the salt bath. The foregoing summary, as well as the following detailed description of certain embodiments of the present invention, will be better understood when read in conjunction with the appended drawings. All numeric values are herein assumed to be modified by the term “about”, whether or not explicitly indicated. The term “about” generally refers to a range of numbers that one of skill in the art would consider equivalent to the recited value (e.g., having the same function or result). In many instances, the terms “about” may include numbers that are rounded to the nearest significant figure. The recitation of numerical ranges by endpoints includes all numbers within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5). The following detailed description should be read with reference to the drawings in which similar elements in different drawings are numbered the same. The drawings, which are not necessarily to scale, depict illustrative embodiments and are not intended to limit the scope of the invention. As used herein, an element or step recited in the singular and preceded with the word “a” or “an” should be understood as not excluding plural said elements or steps, unless such exclusion is explicitly stated. As used in this specification and the appended claims, the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise. Furthermore, references to “one embodiment” of the present invention are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Moreover, unless explicitly stated to the contrary, embodiments “comprising” or “having” an element or a plurality of elements having a particular property may include additional such elements not having that property. The invention provides a method to produce metal halide MXn. The feedstock M is originally supplied as a liquid alloy and then mixed with halogen gas for a time sufficient to form the metal halide MX. Chemistry for the invented method is depicted in Equation 5, infra: M ( liquid alloy ) + n 2 X 2 ( g ) → MX n ( liquid salt ) Equation 5 For example, the invention provides high yield, efficient production of salts containing uranium chloride. The invented system utilizes a salt (e.g., NaCl) matrix in continual fluid communication with a liquid uranium nickel alloy as the uranium feedstock. (Aside from nickel, other alloying meals are suitable, including, but not limited to Bi, Ga, Fe, Al, and combinations thereof.) The liquid uranium nickel alloy is confined to a crucible submerged in the matrix salt. Chlorine gas is then sparged into the liquid uranium nickel alloy. The metal halide MXn product remains in chemical communication with the metal M within the alloy, such that the metal halide formed will be the stable halide with the smallest value of n for that system in equilibrium with the metal M. In this embodiment, the metal is uranium and the alloy is molten U—Ni, the halide formed by sparging chlorine gas into the molten salt alloy will be UCl3. The sparge rate and concentration of the halide can be determined empirically and controlled such that the reaction occurs at 100 percent efficiency. If it is desired to achieve a higher valent metal halide to achieve a desired chemistry in the end use or mixture of a higher valent halide with MXn in the molten salt solution, the metal alloy is removed from the system and chlorine gas is sparged directly into the molten salt solution. This provides a means for converting MXn to a higher valent halide. The ultimate composition of the molten salt solution is achieved by controlling the pressure and time for chlorination. The system may be maintained in a dry inert atmosphere (e.g., argon or helium) to maintain product purity and eliminate unwanted side reactions with the atmosphere or its impurities. Dry in this case would be approximately one hundred of ppm of water or less, depending on the reacting metal utilized. Such atmospheres may be supplied via a glovebox, blast box or other similar enclosure chemically isolated from ambient pressures, temperatures and atmospheres. The reaction may occur at any chlorine pressure. As long as the uranium chloride product is in equilibrium with the uranium metal, the halide will have the lowest value of n. If all the uranium is consumed to form a chloride, then the valence state of uranium will continue to increase with the amount of chlorine added to the system. The process produces essentially no waste stream and is scalable for industrial application. The process may be used as a stand-alone process or incorporated as a component in another process operation such as in an electrorefiner or in a molten salt reactor. The process minimizes the need for off-gas treatment of unreacted chlorine gas. This compares favorably to state of the art processes which require a secondary reaction to eliminate the residual lower or higher valent uranium chlorides to further purify the chloride product. FIG. 1A is a schematic diagram of the invented system, generally designated as numeral 100. The system comprises a first crucible 125, constructed from graphite, glass carbon, or other salt resistant material, and a second crucible 130, constructed for example from tungsten that is compatible with the liquid alloy and salt, wherein the second crucible 130 is positioned within the first crucible 125. The second crucible may or may not contact the bottom or sides of the first crucible. A first volume of molten salt 110 is contained within the first crucible 125 to a level sufficient to submerge the second crucible 130. The second crucible 130 may or may not be permeable to some of the reactants utilized in the invented method and system. Metal comprising the metal constituent of the product metal halide is initially supplied to the second, submerged crucible 130 as a metal alloy. For example, uranium nickel alloy is placed within the submerged crucible via a dedicated conduit therefor so as to allow for continuous operation. Alternatively, the crucible is loaded with an initial charge of the alloy in the inert atmosphere enclosure, then lowered into the molten salt. Halogen gas 140 is then contacted with the crucible-contained alloy for a time sufficient to effect the reaction depicted in Equation 5, supra. Composition adjustments (i.e., adding uranium) to the alloy are made throughout the process. This approach allows for long production runs (or even continuous production runs) to produce the halide salt. Temperatures within the first crucible 125 can range between 250° C. and 850° C. depending on the melting point of the salt matrix and alloy, and preferably between 300° C. and 825° C. Preferably, temperatures are not higher than 900° C. Preferably, the crucible 130 is submerged within the molten salt base 110 so when the halogen gas 140 reacts with the liquid uranium nickel alloy 120 to generate a metal halide 160, UCl3; the UCl3 diffuses into the molten salt matrix 110. Halogen gas 140, Cl2, is fed into the system 100 by a sparge tube 145, which feeds directly into the liquid uranium nickel alloy 120 contained in an alloy crucible 130. Generally, the sparge tube 145 comprises a heat resistant material capable of withstanding temperatures of approximately 850° C. For example, the sparge tube 145 may consist of an outer W or Ta sheath and an inner BeO tube. The W or Ta sheath confers heat and corrosion resistance to the matrix salt while the inner BeO tube provides heat and corrosion resistance from pure chlorine gas. The molten uranium 120 and halogen gas 140 react to generate the metal halide 160 UCl3, which is sparingly soluble in the molten alloy and diffuses up to the molten NaCl base salt 100. To keep the liquid uranium-nickel alloy 120 liquid, small amounts of uranium metal 150 are periodically added to the alloy crucible 130 to replenish the converted uranium and keep the alloy in liquid phase at operating temperature. Alternatively, nickel could precipitate from the liquid alloy as uranium from the alloy is depleted, but then it is re-dissolved when more uranium is added. A preferred operation is to keep the alloy in liquid phase throughout the process. Only the molten UCl3 dissolves into the molten salt mixture 110. The amounts of halogen gas 140 and metal uranium 150 added depending on the amount of UCl3 that is to be generated. When the target amount of UCl3 has been generated to form a UCl3—NaCl eutectic mixture (approximately 31 mole percent UCl3 in NaCl) the crucible 130 and the halogen gas sparge tube 145 is lifted out of the salt mixture by a bale 126. The resulting salt composition can be monitored in situ by electroanalytical methods or a grab sample can be analyzed off-line. Also, mass flow meters may be used to monitor the amount of chlorine added to the system to monitor UCl3 production. Some of the UCl3—NaCl mixture may be retained as a separate product, but most of the mixture is further reacted to generate batches of UCl3—UCl4—NaCl eutectic mixed salt compositions. The conversion of UCl3 to UCl4 is done by immersing the sparge tube 145 into the UCl3—NaCl eutectic mixture to continue the reaction converting UCl3 to UCl4 until the desired salt composition is achieved. Ultimately, the aforementioned “desired salt composition” is the target salt, which is to say the target salt is the eutectic mixture of the now formed actinide chloride(s) with NaCl. The entire batch of salt is therefore removed from the vessel for further processing. Metal Alloy Detail The liquid alloy contains actinide metals M selected from the group consisting of Th, U, Np, Pu, Am, Cm, and combinations thereof. The metal M (i.e., uranium) to be halogenated is initially alloyed with another more noble metal (i.e., Bi, Ga, Ni, Fe) to form a lower melting metal alloy. The second metal and the composition of the alloy is selected such that the alloy is molten at a temperature equal to or less than the melting point of the matrix salt, discussed infra. Since the alloy is a liquid, the halogen gas can be sparged into the molten metal alloy to form the metal halide, MXn. The metal alloy composition is maintained in a range where the alloy is a liquid at process temperatures (e.g., ranging from between 740° C. and 825° C. for uranium chloride synthesis by this method) by periodic additions of M to the metal alloy as the concentration of M decreases due to its halogenation. Regarding the composition of the U—Ni alloy, at a temperature of 800° C. the composition of the liquid alloy can range from about 28 to 42 mole percent Ni. Preferably, the starting composition for the alloy is 33 mole percent Ni given its lowest melting point (740° C.). Liquid alloy comprises an element selected from group consisting of cobalt, iron, nickel, bismuth, gallium, aluminum, cadmium and combinations thereof, contains a lanthanide or transition metal element resulting in formation of a lanthanide or transition metal halide dissolved in a matrix salt. Salt Base Detail Generally, the salt bath is comprised of alkali and alkaline earth salts comprising alkali and alkaline earth fluorides, chlorides, bromides, iodides or combinations thereof. NaCl is the preferred salt base 110 due to its abundance in nature. However other salts may be employed so long as they contain certain characteristics. Generally, the salt matrices are thermodynamically and kinetically stable with uranium compounds. As such, halides are selected which have a more negative free energy than the uranium chloride. Preferably, the salt has a melting point below about 800° C. in the pure or dissolved state. Further, the salt has stability against atmospheric constituents, high thermal heat conductivity and specific heat capacity, low fuel salt viscosity, is non-toxic, and has good corrosion properties if possible. The chemical stability of alkali chlorides (e.g., KCl and CsCl) and alkaline earth chlorides (e.g., MgCl2 and CaCl2), and combinations thereof are favorable alternatives to NaCl as the salt base 110. The carrier salt may be comprised of LiCl, NaCl, CsCl, KCl, CaCl2, or MgCl2 and actinide salts. Suitable actinide salts include, but are not limited to PuCl4, UCl3, ThCl4, UCl4, NpCl3, Npl4, AmCl3, AmCl2, or CmCl3, and any combinations thereof. FIG. 1B depicts an example embodiment of an alloy crucible 130. Crucible permeability is not required so long as there is interfacial contact between the salt matrix and alloy. A permeable crucible could be used if it is chemically compatible (i.e., chemically inert) with the alloy and base salt. The molten uranium alloy pool 120 and chlorine gas 140 react to generate UCl3, which is sparingly soluble in the molten alloy pool 120, such that it diffuses into the molten salt matrix 110. Metal uranium 150 can be periodically added to the molten uranium—nickel alloy in the alloy crucible 130 to replenish the converted uranium and prevent the uranium—nickel alloy from solidifying. Any nickel will remain in the alloy crucible 130 after the UCl3 diffuses into the molten salt matrix 110. The alloy crucible 130 may be repositioned or removed from the system 100 using a bale 126 within the salt matrix. The bale may comprise an elongated, heat and corrosion tolerant structure such as a bar, tube, or handle that is attached to a peripheral region of the inner crucible 130. The sparge tube 145 may be removed from the alloy crucible 130 and resubmerged into the molten salt matrix 110 and continue to feed halogen gas 140 into the system at will to allow for UCl3 to react and form UCl4. The UCl3 will continue to react with the sparged gas 140 until the desired final composition nears that of a eutectic mixture of UCl3—UCl4—NaCl. In another embodiment, the alloy crucible 130 may be porous 135, to allow for the liquid uranium nickel alloy 120 and halogen gas 140 to enter the system 100 by a steady drip system kept under pressure. Pore sizes should allow the UCl3 salt to diffuse through to contact the matrix salt and dissolve. The alloy should be maintained within the crucible so that it can be replenished with uranium to remain molten. FIG. 2 depicts a two-step process to produce a eutectic mixture of NaCl—UCl3— UCl4 uranium chloride salt for nuclear application. The process is carried out in a heated vessel under a dry (e.g., 100 ppm of water or less) inert atmosphere such as a furnace that is attached to or contained in a dry, inert atmosphere glovebox. Step 1 (designated as 210) comprises producing a eutectic mixture of NaCl—UCl3 formed by sparging chlorine gas into a molten U—Ni alloy contained in a chemically inert crucible submerged in molten NaCl. The crucible is initially maintained at a temperature greater than the melting point of the salt matrix, so in the case of NaCl, 801° C. The UCl3 formed in the liquid metal is less dense than the U—Ni alloy and moves to the molten metal-molten salt interface to dissolve in the molten NaCl. When the desired amount of uranium has been chlorinated and dissolved in the molten NaCl as UCl3, the crucible with the U—Ni alloy can be removed from the molten salt prior to beginning the second step (designated as 220). In the second step (220), the UCl3 in the molten NaCl—UCl3 can be reacted with additional chlorine gas to generate UCl4 such that a salt mixture near the UCl3—UCl4—NaCl ternary eutectic composition is produced. FIG. 2 shows that the UCl3—NaCl binary and near-ternary eutectic mixtures have much lower melting points, 508° C. and approximately 340° C. respectively, compared to the reagents NaCl (801° C.), UCl3 (837° C.), and UCl4 (590° C.). As the UCl4 content increases in the salt solution, the melting temperature decreases from near 508° C. for the initial UCl3—NaCl eutectic to approximately 340° C. for the near ternary eutectic composition. Conversion of the UCl3—NaCl binary to UCl3—UCl4—NaCl ternary can be completed at 550° C. FIG. 3 depicts a flow chart of a method to produce salts containing uranium chloride. A molten NaCl salt bath is established in the first graphite crucible 125. A separate, second crucible 130 containing liquid uranium-nickel alloy 310 is submerged in the molten salt bath and may be positioned therein or removed using the bale 320. A depending end of the sparge tube 145 is placed within the second crucible 130 so that the depending end feeds into the crucible with the liquid uranium alloy and a second, upstream end is free above the system 100 and in fluid communication with a halogen gas supply. Preferably, the sparge tube is submerged beneath the surface of the uranium alloy pool. The sparge tube 145 introduces Cl2 gas 140 into the liquid uranium-nickel alloy within the crucible 330. As the Cl2 gas 140 is introduced into the alloy crucible 130, sparingly soluble product UCl3 rises to the surface of the uranium-nickel alloy pool and dissolves into the surrounding salt matrix pool 110, 340. Any remaining nickel remains in the second crucible 130. In the molten salt matrix, UCl3 dissolves, causing a eutectic solution within the matrix to form. While the reaction occurs 355, a reactant metal U 150 is periodically added to the liquid uranium nickel alloy in the second crucible 130, keeping the alloy molten throughout the process 345. The solution formed within the surround salt matrix comprises a eutectic mixture of NaCl—UCl3 350. The UCl3—NaCl mixture may be retained as a separate product at this point or, the liquid metal alloy 120 may be removed from the salt bath 360, or sparging may be modified, until a desired composition of NaCl— UCl3—UCl4 is achieved 370. The salt product can be transferred from the graphite crucible by pumping, vacuum transfer or pouring. The eutectic forming reaction 355 is carried out in the salt base matrix. Aside from Na, the salt cation may be Li, K, Cs, Ba, Ca, Mg, or Be and the anion may be F, Br, or I. The reaction 355, is the further chlorination of the metal halide species, in this embodiment UCl3, dissolving in the matrix to form a solution 350 comprising UCl3—NaCl, approximately 31 mol % UCl3 in NaCl. The addition of a reactant metal U 345, replenishes the converted molten metal within the second crucible 130 and prevents the alloy from solidifying, thereby providing a means for preventing excess chlorine from escaping the system 100. Chlorine gas escape is further minimized when the gas is introduced into the second crucible via a sparge tube, wherein the sparge tube is submerged beneath the surface of the liquid alloy confined within the crucible to prevent off gassing of the halogen gas. The invented system and method can be used in electrorefining processes of separating uranium from other fuel components such as plutonium or thorium. The fuel segments are chopped and loaded into an anode basket, which is lowered into a molten salt, usually LiCl—KCl containing a small quantity of UCl3 (e.g., 5 weight percent UCl3). An electric potential is applied between the anode and cathode of the refiner, which results in dissolution of the solid metal fuel. The actinides, fission products (FP), and sodium are dissolved in the salt, which is maintained at 500° C., allowing the uranium to be recovered on the cathode, while the sodium and active metals react and displace UCl3 from the molten salt. Periodically, the UCl3 needs to be replenished in the electrorefiner system so a salt comprising a eutectic composition of LiCl—KCl—UCl3 is added to the refiner. Production of the LiCl—KCl—UCl3 eutectic salt is accomplished using the synthesis method described. It is to be understood that the above description is intended to be illustrative, and not restrictive. For example, the above-described embodiments (and/or aspects thereof) may be used in combination with each other. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its scope. While the dimensions and types of materials described herein are intended to define the parameters of the invention, they are by no means limiting, but are instead exemplary embodiments. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. In the appended claims, the terms “including” and “in which” are used as the plain-English equivalents of the terms “comprising” and “wherein.” Moreover, in the following claims, the terms “first,” “second,” and “third,” are used merely as labels, and are not intended to impose numerical requirements on their objects. Further, the limitations of the following claims are not written in means-plus-function format and are not intended to be interpreted based on 35 U.S.C. § 112, sixth paragraph, unless and until such claim limitations expressly use the phrase “means for” followed by a statement of function void of further structure. As will be understood by one skilled in the art, for any and all purposes, particularly in terms of providing a written description, all ranges disclosed herein also encompass any and all possible subranges and combinations of subranges thereof. Any listed range can be easily recognized as sufficiently describing and enabling the same range being broken down into at least equal halves, thirds, quarters, fifths, tenths, etc. As a non-limiting example, each range discussed herein can be readily broken down into a lower third, middle third and upper third, etc. As will also be understood by one skilled in the art all language such as “up to,” “at least,” “greater than,” “less than,” “more than” and the like include the number recited and refer to ranges which can be subsequently broken down into subranges as discussed above. In the same manner, all ratios disclosed herein also include all subratios falling within the broader ratio. |
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052308588 | claims | 1. In a fuel bundle for boiling water nuclear reactor, said fuel bundle including a matrix of upstanding fuel rods for undergoing nuclear reaction and generating steam, a lower tie plate for supporting the matrix of fuel rods and admitting liquid water moderator to the fuel bundle from the lower portion of said fuel bundle, an upper tie plate for fastening to at least some of the fuel rods and permitting the outflow of liquid and vapor water moderator from the upper portion of said fuel bundle, a channel surrounding said upper and lower tie plates and said fuel rods therebetween for confining moderator flow between said tie plates and around said fuel rods, and a plurality of vertically spaced apart fuel rod spacers, each said spacer surrounding each said fuel rod at the particular elevation of said spacer for maintaining said fuel rods in side-by-side relation, and a water rod for installation to said fuel bundle for supplying liquid moderator to the upper two phase region of said fuel bundle, the improvement to said water rod comprising: said water rod having a first upper compartment, and a second lower compartment, said upper compartment isolated from said lower compartment; said first upper compartment defining an open, upwardly exposed end for receiving and maintaining water in said upper water rod compartment during the power generating operation of said fuel bundle will fill with liquid by gravity flow from above; means communicated to the bottom portion of said lower compartment for receiving water from said lower portion of said fuel bundle; and, means communicated to the upper portion of said lower compartment for discharging water to the interior of said fuel bundle below the upper most spacer of said fuel bundle whereby discharge to said fuel bundle occurs in said upper two phase region of said bundle. a matrix of upstanding fuel rods for undergoing nuclear reaction and generating steam; a lower tie plate for supporting the matrix of fuel rods and admitting liquid water moderator tot eh fuel bundle from the lower portion of said fuel bundle; an upper tie plate for fastening to at least some of the fuel rods and permitting the outflow of liquid and vapor water moderator from the upper portion of said fuel bundle; a channel surrounding said upper and lower tie plates and said fuel rods therebetween for confining moderator flow between said tie plates and around said fuel rods; a plurality of vertically spaced apart fuel rod spacers, each said spacer surrounding each said fuel rod at the particular elevation of said spacer for maintaining said fuel rods in side-by-side relation; a water rod for installation to said fuel bundle for supplying liquid moderator to the upper two phase region of said fuel bundle; a first upper compartment in said water rod, said first upper compartment defining an open, upwardly exposed end for receiving and maintaining water in said upper water rod compartment during the power generating operation of said fuel bundle; a second lower compartment in said water rod, said water rod has said upper compartment isolated from said lower compartment; means communicated to the bottom portion of said lower compartment for receiving water from said lower portion of said fuel bundle; and, means communicated to the upper portion of said lower compartment for discharging water to the interior of said fuel bundle below the upper most spacer of said fuel bundle whereby discharge to said bundle occurs in said upper two phase region of said bundle. a matrix of upstanding fuel rods for undergoing nuclear reaction and generating steam; a lower tie plate for supporting the matrix of fuel rods and admitting liquid water moderator to teh fuel bundle from the lower portion of said fuel bundle; an upper tie plate for fastening to at least some of the fuel rods and permitting the outflow of liquid and vapor water moderator from the upper portion of said fuel bundle; a channel surrounding said upper and lower tie plates and said fuel rods therebetween for confining moderator flow between said tie plates and around said fuel rods; a plurality of vertically spaced apart fuel rod spacers, each said spacer surrounding each said fuel rod at the particular elevation of said spacer for maintaining said fuel rods in side-by-side relation; a water rod for installation to said fuel bundle for supplying liquid moderator to the upper two phase region of said fuel bundle; a process of supplying said water rod with liquid moderator comprising the steps of: providing a first upper compartment in said water rod; opening said first upper compartment to receive and maintain water in said upper water rod compartment during the power generating operation of said fuel bundle; providing a second lower compartment in said water rod, said water rod having said upper compartment isolated from said lower compartment; communicating in flowing water to the bottom portion of said lower compartment for receiving water from said lower portion of said fuel bundle; and, discharging from the upper portion of said lower compartment to the interior of said fuel bundle below the upper most spacer whereby water discharge to said fuel bundle occurs in said upper two phase region of said bundle. 2. The fuel bundle of claim 1 and wherein said means communicated to the upper portion of said lower compartment discharges water to the interior of the fuel bundle occurs between the first and second spacer. 3. The fuel bundle of claim 1 and wherein said means communicated to the upper portion of said lower compartment discharges water to the interior of the fuel bundle occurs between the second and third spacer. 4. The fuel bundle of claim 1 and wherein said fuel bundle has one large central water rod. 5. A fuel bundle for boiling water nuclear reactor, said fuel bundle comprising: 6. In a fuel bundle for a boiling water nuclear reactor, said fuel bundle comprising: 7. The process of claim 6 and wherein said discharging water to the interior of the fuel bundle occurs between the first and second spacer. 8. The process of claim 6 and wherein said discharging water to the interior of the fuel bundle occurs between the second and third spacer. |
description | This U.S. patent application is a continuation of U.S. application Ser. No. 14/180,824 filed Feb. 14, 2014, which claimed the priority under the Paris Convention of Japanese Patent Application No. 2013-38774 filed on Feb. 28, 2013, the entirety of both applications are incorporated herein by reference. 1. Field of the Invention The present invention relates to deposition substrates and to scintillator panels used in the formation of radiographic images of subjects. 2. Description of the Related Art Radiographic images such as X-ray images have been widely used in medical diagnosis of disease conditions. In particular, radiographic images based on intensifying screen-film combinations have undergone enhancements in terms of sensitivity and image quality during a long history and consequently remain in use in the medical field worldwide as the imaging system with high reliability and excellent cost performance. However, this image information is analogue and thus cannot be processed freely or transmitted instantaneously in contrast to digital image information which has been developed currently. Recently, digital radiographic image detectors such as computed radiography (CR) systems and flat panel detectors (FPDs) have come in use. These radiographic image detectors directly give digital radiographic images and allow the images to be directly displayed on displays such as cathode ray tube panels and liquid crystal panels. Thus, there is no need for the images to be created on photographic films. Consequently, the digital X-ray image detectors have decreased a need for the image formation by silver halide photography and have significantly enhanced diagnostic convenience at hospitals and clinics. The computed radiography (CR) is one of the digital X-ray image techniques currently used in medical practice. However, CR X-ray images are less sharp and are insufficient in spatial resolution as compared to screen film system images such as by silver halide photography, and the level of their image quality compares unfavorably to the quality level of screen film system images. Thus, new digital X-ray image techniques, for example, flat panel detectors (FPDs) involving a thin film transistor (TFT) have been developed (see, for example, Non Patent Literatures 1 and 2). In principle, a FPD converts X-rays into visible light. For this purpose, a scintillator panel is used which has a scintillator layer made of an X-ray phosphor that, when illuminated with X-rays, convert the radiations into visible light that is emitted. In X-ray photography using a low-dose X-ray source, it is necessary to use a scintillator panel with high luminous efficiency (X-ray to visible light conversion) in order to enhance the ratio (the SN ratio) of signal to noise detected from the scintillator panel. In general, the luminous efficiency of scintillator panels is determined by the thickness of the scintillator layer (the phosphor layer) and the X-ray absorption coefficient of the phosphor. The light produced in the phosphor layer upon illumination with X-rays is scattered more markedly in the scintillator layer with increasing thickness of the phosphor layer, and consequently the sharpness of X-ray images obtained via the scintillator panel is lowered. Thus, setting of the sharpness required for the quality of X-ray images automatically determines the critical thickness of the phosphor layer in the scintillator panel. On the other hand, some kinds of phosphors permit the critical thickness of phosphor layers in scintillator panels to be increased. Cesium iodide (CsI) is a phosphor that has a relatively high X-rays to visible light conversion ratio and is easily deposited to form a columnar phosphor crystal layer which can suppress the scattering of light in the phosphor crystals (namely, in the scintillator layer) by light guide effects. Thus, the thickness of the phosphor layer can be increased corresponding to the amount of suppressed scattering. Because the luminous efficiency obtained with CsI alone is low, however, an approach to increasing the visible light conversion efficiency of the scintillator layers is generally adopted. For example, (1) CsI crystals and a sodium compound activator, (2) CsI crystals and a thallium compound activator, or (3) CsI crystals and an indium compound activator are deposited onto substrates to form scintillator layers, and the scintillator layers are annealed in the subsequent step. Other approaches which have been proposed to increase the optical output of scintillator panels include a method in which scintillator layers are formed on reflective substrates (see, for example, Patent Literature 1), a method in which reflective layers are provided on substrates by depositing metal films (see, for example, Patent Literature 2), and a method in which reflective thin metal films are provided on substrates and coated with transparent organic films, and scintillator layers are formed on the transparent organic films (see, for example, Patent Literature 3). Although scintillator panels obtained by these methods achieve an increase in optical output, the light produced in the scintillator layer is scattered at the interface between the reflective layer and the scintillator layer, with the result that the X-ray image data obtained via the scintillator panels are disturbed and the sharpness of the obtainable X-ray images is markedly deteriorated. Meanwhile, methods are proposed in which X-ray image detectors are manufactured by arranging scintillator panels on the surface of planar light-receiving elements (see, for example, Patent Literatures 4 and 5). However, the productivity of such detectors is low because of the need that the scintillator panels have to be produced in different sizes in accordance with various sizes of the planar light-receiving elements. Further, such an approach does not solve the aforementioned problem that the sharpness of X-ray images is deteriorated by the scattering of light at the interface between the reflective layer and the scintillator layer. In the conventional production of scintillator panels by a gas-phase method, it is a general practice to form a scintillator layer on a rigid substrate made of such a material as aluminum or amorphous carbon, and cover the entire surface of the scintillator with a protective film (see, for example, Patent Literature 6). However, such scintillator panels having a scintillator layer on an inflexible and rigid substrate cause a difficulty in obtaining a uniform contact between the scintillator panel and a planar light-receiving element when they are bonded to each other. In detail, such a scintillator panel has irregularities ascribed to the unevenness of the substrate itself as well as to different heights of the columnar phosphor crystals in the scintillator layer, and the inflexible substrate significantly reflects the influence of such irregularities (a flexible substrate may cancel the irregularities by deformation) to make it difficult for the scintillator panel to be tightly and uniformly attached to a planar light-receiving element. To solve this problem, methods are proposed in which a spacer is used at the plane of contact between the scintillator panel and a planar light-receiving element (see, for example, Patent Literatures 4 and 5). However, this approach, which prioritizes the solution of problematic attachment between the scintillator panel and a planar light-receiving element over productivity, has a problem in that because the scintillator panel and the planar light-receiving element are spaced apart by a gap, the light produced in the scintillator layer of the scintillator panel is scattered in the gap to inevitably deteriorate the sharpness of the obtainable X-ray images. This problem has become more serious with the recent enlargement of flat panel detectors. In order to solve the problems of loose attachment between scintillator panels and planar light-receiving elements as well as the problems associated with the use of spacers, methods have been generally adopted in which a scintillator layer is directly formed on an imaging element by deposition or in which a less sharp but flexible material such as a medical intensifying screen is used instead of a scintillator panel. Further, a method has been adopted in which a flexible protective layer made of such a material as a polyparaxylylene is used to protect layers such as scintillator layers in scintillator panels (see, for example, Patent Literature 7). However, the substrates used in the above method are rigid materials such as aluminum and amorphous carbon. Even if the protective layer is formed with a thickness of about 10 μm on the scintillator layer or the substrate, the surface of the protective layer will show irregularities ascribed to the unevenness of the substrate itself as well as to different heights of the columnar phosphor crystals in the scintillator layer. Thus, even the adoption of such protective layers with the above thickness does not eliminate the influences of the irregularities on the substrates or the scintillator layers, and it remains difficult to achieve a uniform and close contact between the surface of the scintillator panel and the surface of a planar light-receiving element. On the other hand, increasing the thickness of the flexible protective layer increases the gap between the scintillator panel and a planar light-receiving element, resulting in a deterioration of the sharpness of the obtainable X-ray images. Under such circumstances, there has been a demand for the development of radiographic flat panel detectors that have excellent luminous efficiency of scintillator panels and have small deteriorations in the sharpness of X-ray images due to factors such as the size of the gap between the scintillator panel and a planar light-receiving element. Patent Literature 8 discloses a scintillator panel which includes a reflective layer on a substrate and a scintillator layer formed on the top by deposition, the reflective layer including a white pigment and a binder resin. Patent Literature 8 also discloses that because the reflective layer is formed of a white pigment and a binder resin, the scintillator panel exhibits high light-emitting efficiency and consequently sharp X-ray images are obtained. This scintillator panel can solve the aforementioned problem. That is, even when this scintillator panel is used in combination with a planar light-receiving element, the sharpness of X-ray images is negligibly decreased by factors such as the scattering of the emitted light at the interface between the scintillator panel and the planar light-receiving element. However, the scintillator panels disclosed in Patent Literature 8 are still rife with possibilities for improvements such as in terms of the prevention of the separation of the scintillator layers during the cutting of the scintillator panels. [Patent Literature 1] JP-B-H07-21560 [Patent Literature 2] JP-A-H01-240887 [Patent Literature 3] JP-A-2000-356679 [Patent Literature 4] JP-A-H05-312961 [Patent Literature 5] JP-A-H06-331749 [Patent Literature 6] Japanese Patent No. 3566926 [Patent Literature 7] JP-A-2002-116258 [Patent Literature 8] JP-A-2008-209124 [Non Patent Literature 1] John Rowlands, “Amorphous Semiconductor Usher in Digital X-ray Imaging”, Physics Today, November issue, 24 (1997) [Non Patent Literature 2] L. E. Antonuk, “Development of a High-Resolution Active-Matrix Flat-Panel Imager with Enhanced Fill Factor”, SPIE, 32, 2 (1997) The present invention is aimed at solving the above problems. In more detail, an object of the invention is to provide a scintillator panel which exhibits excellent cuttability and can be cut without the occurrence of problems such as the separation of a scintillator layer, and which can give radiographic images such as X-ray images with excellent sensitivity and sharpness. Another object of the invention is to provide a deposition substrate that allows for the manufacturing of such scintillator panels, exhibits excellent cuttability and is free from problems such as the separation of a reflective layer even when subjected to a cutting treatment. The present inventors carried out extensive studies in order to achieve the above objects. As a result, the present inventors have found that a deposition substrate which includes a support and a reflective layer disposed on the support wherein the reflective layer includes light-scattering particles and a binder resin with a specific glass transition temperature (Tg) and has a specific film thickness exhibits excellent cuttability and realizes a scintillator panel capable of giving radiographic images such as X-ray images with excellent sensitivity and sharpness as well as capable of excellent cuttability. In more detail, the present inventors have found the following. It has been found that the binder resin having a specific Tg in the deposition substrate exhibits excellent adhesion with respect to the support and excellently follows deformation experienced during cutting. As a result, the deposition substrate and a scintillator panel including the deposition substrate do not suffer problems such as the separation of the reflective layer even when subjected to cutting, and the scintillator panel is free from problems such as the separation of a scintillator layer even when subjected to cutting. It has been further found that the specific thickness of the reflective layer in the deposition substrate ensures that the reflective layer will not become separated from the support because of the thickness being so small that the reflective layer cannot withstand the impact applied during cutting as well as ensures that cracks will not be generated during film production because of the thickness being so large and accordingly there will occur no abnormal growth of phosphor crystals during deposition, thus resulting in the realization of excellent sharpness of radiographic images obtained via a scintillator panel including the deposition substrate. Furthermore, it has been found that the sharpness of radiographic images obtained via a scintillator panel including the deposition substrate is further improved when the volatile content in the reflective layer in the deposition substrate is in a specific range. With respect to a scintillator panel in which a scintillator layer is disposed on the surface of the reflective layer (the surface of the reflective layer opposite to the support side) of the deposition substrate, the present inventors have also found that the heights of crystals forming the scintillator layer can be aligned without any deteriorations in the characteristics of the crystals by the application of a specific pressure to the scintillator panel at a temperature not less than the Tg of the binder resin, thus further enhancing the sharpness of radiographic images obtained via the scintillator panel. To solve the aforementioned problems, a deposition substrate according to the present invention includes a support and a reflective layer disposed on the support, the reflective layer including light-scattering particles and a binder resin with a glass transition temperature of −100° C. to 60° C., the thickness of the reflective layer being 5 to 300 μm. In the deposition substrate of the invention, it is preferable that the light-scattering particles include at least one selected from alumina, yttrium oxide, zirconium oxide, titanium dioxide, barium sulfate, silica, zinc oxide, calcium carbonate, glasses and resins. In the deposition substrate of the invention, it is preferable that the light-scattering particles include at least one type of particles selected from hollow particles having a hollow portion within the particle, multi-hollow particles having a number of hollow portions within the particle, and porous particles. In the deposition substrate of the invention, it is preferable that the light-scattering particles include at least titanium dioxide. In the deposition substrate of the invention, it is preferable that the volatile content in the reflective layer be not more than 0.5 mg/m2. In the deposition substrate of the invention, it is preferable that the support include a resin as a main component and the reflective layer be disposed on the support. In the deposition substrate of the invention, it is preferable that the resin be polyimide. Preferably, the deposition substrate of the invention further includes a light-absorbing layer on the side opposite to the deposition surface (hereinafter, also referred to as the “scintillator layer formation scheduled surface”) of the reflective layer. To solve the aforementioned problems, a deposition substrate production method according to the present invention includes forming a reflective layer including a binder resin on a support, and cutting the deposition substrate after the formation of the reflective layer. In the deposition substrate production method of the invention, it is preferable that the glass transition temperature of the binder resin be −100 to 60° C. and the thickness of the reflective layer be 5 to 300 μm. To solve the aforementioned problems, a scintillator panel according to the present invention includes a support, a reflective layer disposed on the support, and a scintillator layer formed on the reflective layer by deposition, the reflective layer including light-scattering particles and a binder resin with a glass transition temperature of −100° C. to 60° C., the thickness of the reflective layer being 5 to 300 μm. The scintillator panel of the invention is preferably obtained by forming a scintillator layer by deposition on a scintillator layer formation scheduled surface of the deposition substrate. In the scintillator panel of the invention, it is preferable that the light-scattering particles include at least one selected from alumina, yttrium oxide, zirconium oxide, titanium dioxide, barium sulfate, silica, zinc oxide, calcium carbonate, glasses and resins. In the scintillator panel of the invention, it is preferable that the light-scattering particles include at least one type of particles selected from hollow particles having a hollow portion within the particle, multi-hollow particles having a number of hollow portions within the particle, and porous particles. In the scintillator panel of the invention, it is preferable that the light-scattering particles include at least titanium dioxide. In the scintillator panel of the invention, it is preferable that the support include a resin as a main component and the reflective layer be disposed on the support. In the scintillator panel of the invention, it is preferable that the resin be polyimide. Preferably, the scintillator panel of the invention further includes a light-absorbing layer on the side opposite to the surface of the reflective layer on which the scintillator layer is disposed. In the scintillator panel of the invention, it is preferable that the scintillator layer have a columnar crystal structure formed by depositing raw materials including cesium iodide and one or more activators including at least thallium. In the scintillator panel of the invention, it is preferable that the surface of the scintillator layer be covered with a protective film. In the scintillator panel of the invention, it is preferable that the protective film be a polyparaxylylene film. In the scintillator panel of the invention, it is preferable that the scintillator layer include columnar crystals grown from an interface between the reflective layer and the scintillator layer. The scintillator panel of the invention is preferably supported on a support plate having higher rigidity than the deposition substrate. To solve the aforementioned problems, a scintillator panel manufacturing method according to the present invention includes forming a reflective layer including a binder resin on a support, and forming a scintillator layer on the reflective layer by deposition, wherein the heights of columnar crystals forming the scintillator layer are aligned by applying a pressure of 1,000 to 10,000,000 Pa to the surface of the scintillator panel at a temperature not less than the glass transition temperature of the binder resin. In the scintillator panel manufacturing method of the invention, it is preferable that the glass transition temperature of the binder resin be −100 to 60° C. and the thickness of the reflective layer be 5 to 300 μm. The deposition substrates according to the present invention have excellent cuttability and may be cut without the separation of the reflective layer. Further, the inventive deposition substrates realize scintillator panels which exhibit excellent cuttability and are free from the separation of the scintillator layer during cutting and which can give radiographic images such as X-ray images with excellent sensitivity and sharpness. The scintillator panels according to the present invention are suppressed from the separation of the scintillator layer during cutting and can give radiographic images such as X-ray images with excellent sensitivity and sharpness. According to the scintillator panel manufacturing method of the invention, the heights of columnar crystals are aligned under specific conditions so as to allow for the manufacturing of scintillator panels realizing further enhanced sharpness of the obtainable radiographic images. Hereinbelow, deposition substrates and scintillator panels according to the present invention will be described in detail. The scope of the invention is not limited to the embodiments described below, and various modifications are possible without departing from the scope of the invention. The deposition substrates of the invention include a support and a specific reflective layer disposed on the support. The scintillator panels of the invention include the support, the reflective layer, and a scintillator layer formed by deposition. Hereinbelow, configurations of the invention will be described. The term “phosphors (scintillators)” in the invention refers to fluorescent materials that absorb energy of incident invisible radiations (the wavelengths are usually 10 nm or less) such as X-rays and γ-rays and emit electromagnetic waves having wavelengths of 300 nm to 800 nm, namely, electromagnetic waves (lights) mainly in the visible light region from ultraviolet light to infrared light. 1. Deposition Substrates A deposition substrate of the invention includes a support and a reflective layer disposed on the support. The reflective layer includes light-scattering particles and a binder resin with a glass transition temperature of −100° C. to 60° C. The thickness of the reflective layer is 5 to 300 μm. The glass transition temperature of the binder resin and the thickness of the reflective layer which are in the above ranges ensure that the deposition substrate exhibits excellent cuttability and the reflective layer is not separated during cutting. From the viewpoints of handling properties and cuttability, the thickness of the entirety of the deposition substrate is preferably 10 to 1,000 μm. 1-1. Reflective Layers In the deposition substrates of the invention, a reflective layer is disposed on a support and includes light-scattering particles and a specific binder resin. In the deposition substrates of the invention, the support and the reflective layer may be each comprised of a single layer, or two or more layers. In order for the deposition substrates and scintillator panels produced therewith to achieve excellent cuttability as well as from the viewpoint of the adhesion with respect to the surface of a light-receiving element used for radiography in combination with the scintillator panel, the thickness of the reflective layer is usually 5 to 300 μm, preferably 15 to 150 μm, and more preferably 30 to 100 μm. If the thickness of the reflective layer is less than 5 μm, separation tends to occur at the interface between the support and the reflective layer because of the failure of the reflective layer to follow deformation experienced during cutting. In a scintillator panel in which a scintillator layer is disposed on the scintillator layer formation scheduled surface of such an excessively thin reflective layer in the deposition substrate, the reflective layer similarly fails to follow deformation during cutting and tends to be separated at the interface between the support and the reflective layer or at the interface between the scintillator layer and the reflective layer. If the thickness of the reflective layer exceeds 300 μm, the deposition substrate tends to exhibit large warpage due to the residual stress after film production. Depositing a scintillator layer onto such a deposition substrate tends to result in the occurrence of cracks in the scintillator layer and consequent deteriorations in image quality (in particular, sharpness) of the obtainable radiographic images. In order to ensure that a phosphor having excellent crystallinity (crystalline order) will be formed on the surface of the reflective layer in the deposition substrate (the surface of the reflective layer opposite to the surface in contact with the support), the volatile content in the reflective layer is preferably not more than 0.7 mg/m2, and more preferably not more than 0.5 mg/m2. (The measurement method will be described later.) Examples of the volatile components include residual solvents and water. The reflective layer is preferably disposed on a support including a resin as a main component. According to this configuration, the deposition substrate advantageously exhibits excellent cuttability. The resin will be described in detail later. From the viewpoint of cuttability of the deposition substrate and a scintillator panel including the deposition substrate, it is particularly preferable that the reflective layer be disposed on a support including polyimide as a main component. As used herein, the term “main component” indicates that the component represents 50 to 100 wt % of the total of component(s) constituting the support taken as 100 wt %. In the deposition substrates of the invention, the surface of the reflective layer opposite to the surface in contact with the support is defined as the “scintillator layer formation scheduled surface. In the deposition substrate of the invention, the reflective layer disposed on the support includes a binder resin with a specific Tg and has a specific thickness. With this configuration, the deposition substrate can realize a device such as a scintillator panel exhibiting excellent cuttability and capable of giving excellently sharp radiographic images. The reflective layer may contain additives described later such as fluorescent whitening agents, coloring materials for controlling the reflectance (such as carbon black and titanium black), and UV absorbers. From the viewpoint of transmission of radiations such as X-rays, the reflective layer in the deposition substrate of the invention may have voids, such as those formed by a method described later. In this case, the void volume in the reflective layer (the proportion of the volume of the voids to the volume of the reflective layer) is preferably 5% to 30% from the above viewpoint. The void volume may be easily calculated based on the difference between the theoretical density (without voids) and the actual density of the reflective layer. From viewpoints such as the brightness and the sharpness of the obtainable radiographic images, the reflectance of the reflective layer in the deposition substrate of the invention is preferably 5% to 98%. Herein, the reflectance of the reflective layer is calculated from the spectral reflectivity in the 400 to 700 nm wavelength band with spectrocolorimeter SE-2000 (manufactured by NIPPON DENSHOKU INDUSTRIES CO., LTD.) in accordance with JIS Z-8722. The reflectance is a value at 550 nm wavelength in the absence of any indication of reflection wavelength. 1-1-1. Light-Scattering Particles The light-scattering particles present in the reflective layer in the inventive deposition substrate serve to prevent the light produced in the scintillator layer from being diffused in the reflective layer as well as to effectively return the light which has reached the reflective layer into the columnar crystals of the scintillator layer. Such light-scattering particles may be commercial products or may be produced by known methods as will be described later. The light-scattering particles are not particularly limited as long as the particle material has a different refractive index from the binder resin which in combination therewith constitutes the reflective layer. Examples of such materials include alumina, yttrium oxide, zirconium oxide, titanium dioxide, barium sulfate, silica, zinc oxide, calcium carbonate, glasses and resins. These materials may be used singly, or two or more may be used as a mixture. (The mixture may include two or more materials belonging to different categories such as a glass and a resin; two or more materials belonging to the same category such as an acrylic resin and a polyester resin; or one or more materials belonging to a category and one or more materials belonging to another category such as a glass, an acrylic resin and a polyester resin.) Of the above materials, for example, glass beads and resin beads, in particular, glass beads are preferable because the refractive index can be set to a desired value more freely and thus optical diffusion characteristics can be controlled more easily than metal oxides. Glass beads having a higher refractive index are more preferable. Examples thereof include BK7 (n (relative refractive index, the same applies hereinafter)=about 1.5); LaSFN9 (n=about 1.9); SF11 (n=about 1.8); F2 (n=about 1.6); BaK1 (n=about 1.6); barium titanate (n=about 1.9); high refractive index blue glass (n=about 1.6 to 1.7); TiO2—BaO (n=about 1.9 to 2.2); borosilicate (n=about 1.6); and chalcogenide glass (n=about 2 or more). Examples of the resin beads include acrylic particles, polyester resin particles, polyolefin particles and silicone particles, with specific suitable examples including CHEMISNOW (registered trademark) (manufactured by Soken Chemical & Engineering Co., Ltd.), Silicone Resins KR Series (manufactured by Shin-Etsu Chemical Co., Ltd.), and TECHPOLYMER (registered trademark) (manufactured by SEKISUI PLASTICS CO., LTD.). White pigments such as titanium dioxide (TiO2) have high opacifying properties and a high refractive index, and can easily scatter the light emitted from the scintillator by reflecting and refracting the light. Thus, the use of such pigments allows for marked improvements in the sensitivity of devices such as radiographic image conversion panels including scintillator panels in which scintillator layers are disposed on the inventive deposition substrates. The light-scattering particles are particularly preferably titanium dioxide (TiO2) in view of the facts that this material is easily available and has a high refractive index. When titanium dioxide is used as the light-scattering particles, the titanium dioxide may be one which has been surface treated with inorganic compounds or organic compounds in order to improve dispersibility and workability. For example, the surface-treated titanium dioxide and the surface treatment methods are disclosed in JP-A-S52-35625, JP-A-S55-10865, JP-A-S57-35855, JP-A-S62-25753, JP-A-S62-103635 and JP-A-H09-050093. For the surface treatments, inorganic compounds such as aluminum oxide hydrate, hydrous zinc oxide and silicon dioxide, and organic compounds such as dihydric to tetrahydric alcohols, trimethylolamine, titanate coupling agents and silane coupling agents may be preferably used as surface-treatment agents. The amounts of the surface-treatment agents may be determined appropriately in accordance with the purposes as described in the above patent literatures. The crystal structure of the titanium dioxide may be any of rutile, brookite and anatase forms. However, the rutile form is particularly preferable because its refractive index has a high ratio to that of resins to realize high brightness as well as from the viewpoint of the reflectance with respect to visible light. Specific examples of titanium oxides include those produced by a hydrochloric acid process such as CR-50, CR-50-2, CR-57, CR-80, CR-90, CR-93, CR-95, CR-97, CR-60-2, CR-63, CR-67, CR-58, CR-58-2 and CR-85; and those produced by a sulfuric acid process such as R-820, R-830, R-930, R-550, R-630, R-680, R-670, R-580, R-780, R-780-2, R-850, R-855, A-100, A-220 and W-10 (product names, manufactured by ISHIHARA SANGYO KAISHA, LTD.). From the viewpoint of reflectance, the area average particle diameter of the titanium oxide is preferably 0.1 to 10.0 μm, more preferably 0.1 to 5.0 μm, still more preferably 0.2 to 3.0 μm, and particularly preferably 0.2 to 0.3 μm. In order to improve the affinity and dispersibility for polymers as well as to suppress a degradation of polymers, the titanium oxide is particularly preferably one which has been surface treated with oxides of metals such as Al, Si, Zr and Zn. The use of titanium oxide as the light-scattering particles tends to cause a decrease in the reflectance to light with wavelengths of 400 nm or less and also a degradation of the binder due to the photocatalytic action of titanium oxide. In view of these facts, it is preferable to use the titanium oxide in combination with at least one kind of light-scattering particles selected from barium sulfate, alumina, yttrium oxide and zirconium oxide which have a high reflectance even to light with wavelengths of at least 400 nm or less. Barium sulfate is more preferable because its reflectance in the wavelengths of 400 nm or less is particularly high. For the same reason, the mass ratio of barium sulfate to titanium dioxide is preferably 95:5 to 5:95, more preferably 20:80 to 5:95, and particularly preferably 20:80 to 80:20. Further, it is preferable that the light-scattering particles include at least one selected from solid particles and void particles. The void particles are not particularly limited as long as the particles have voids. Examples thereof include single-hollow particles having one hollow portion within the particle, multi-hollow particles having a number of hollow portions within the particle, and porous particles. These particles may be selected appropriately in accordance with the purpose. Of the void particles, single-hollow particles and multi-hollow particles are preferable because they are free from the risk that the voids will be filled with the binder resin. Here, the term “void particles” refers to particles having voids such as hollow portions and pores. The term “hollow portions” refers to holes (air layers) in the inside of particles. Due to the difference in refractive index between the holes (the air layers) and the shells (such as resin layers), the hollow particles can add optical reflection and diffusion characteristics to the reflective layer which cannot be obtained with solid particles. The term “multi-hollow particles” refers to particles having a plurality of such holes in the inside of particles. The term “porous particles” refers to particles having pores in the particle. The term “pores” refers to portions that are inwardly curved or recessed from the surface toward the inside of the particle. Examples of the shapes of the pores include cavities, and needle-like shapes or curved shapes which are tapered or choked toward the inside or the core of the particles. The pores may be present across the particles. The sizes and the volumes of the pores may be variable and are not particularly limited. The materials of the void particles are not particularly limited and may be selected appropriately in accordance with the purpose. Examples thereof include the aforementioned materials. In particular, suitable examples include thermoplastic resins such as styrene/acryl copolymers. The void particles may be appropriately produced or are available in the market. Examples of the commercially available products include ROPAQUE HP1055 and ROPAQUE HP433J (manufactured by ZEON CORPORATION), and SX866 (manufactured by JSR Corporation). Suitable examples of the multi-hollow particles include Sylosphere (registered trademark) and Sylophobic (registered trademark) manufactured by FUJI SILYSIA CHEMICAL LTD. Of the void particles, single-hollow particles are particularly preferable in terms of void content. When the void particles are used as the light-scattering particles, the light-scattering particles may be a collection of a single form of the above particles or may include two or more kinds of void particles. The void particles may be used in combination with solid particles. The void particles may be advantageously used in combination with white pigments such as titanium dioxide, alumina, yttrium oxide, zirconium oxide and barium sulfate. This combined use prevents deteriorations in scintillator characteristics due to the white pigments adsorbing water (H2O) and carbon dioxide (CO2) to their surface and releasing them when exposed to heat or X-ray energy. That is, the combined use of the void particles and the white pigments suppresses the release of impurity gases such as water (H2O) and carbon dioxide (CO2) from the white pigments and thus prevents deteriorations in scintillator characteristics. Alternatively, deteriorations in scintillator characteristics due to the detachment of water (H2O) and carbon dioxide (CO2) from the surface of white pigments may be effectively prevented by forming a large number of bubbles in the reflective layer including a white pigment and a binder resin. According to this method, the white pigment and the bubbles having a large difference in refractive index are placed in contact with each other in the reflective layer, and the reflectance of the reflective layer is improved by this increased difference in refractive index between the materials constituting the reflective layer. Details are described in the section of “Deposition substrate production methods”. From viewpoints such as the reflectance of the reflective layer, the occurrence of cracks on the surface of the reflective layer, and the stability of a coating liquid prepared for the formation of the reflective layer (hereinafter, also referred to as “reflective coating liquid”, the same applies to coating liquids for other purposes), the area average particle diameter of the light-scattering particles is preferably 0.1 μm to 10.0 μm, and more preferably 0.1 μm to 5.0 μm. This area average particle diameter of the light-scattering particles ensures that optical scattering occurs efficiently in the reflective layer to lower the transparency and increase the reflectance, as well as that the reflective coating liquid exhibits improved stability over time and the occurrence of cracks in the dry reflective layer is avoided. From the viewpoint of the dispersibility of the light-scattering particles in the reflective layer, the grain size distribution of the light-scattering particles is preferably in the range of 0.05 μm to 10.0 μm. The volume fraction of the light-scattering particles is preferably 3 to 70 vol %, and more preferably 10 to 50 vol % in 100 vol % of the total volume of the components constituting the reflective layer. This fraction of the light-scattering particles in the reflective layer ensures not only that the reflectance of the reflective layer as well as the sensitivity of a scintillator panel having a scintillator layer on the deposition substrate are improved, but also that the adhesion with respect to the support or the phosphor layer is enhanced to suppress the separation of the reflective layer during cutting. When the content of the light-scattering particles in the reflective layer is not more than 70 vol %, the reflective layer can follow deformation experienced during cutting and is thus not separated at the interface between the support and the reflective layer. Further, the above volume fraction is also advantageous in that the reflective layer can similarly follow deformation experienced during cutting of a scintillator panel in which a scintillator layer is disposed on the scintillator layer formation scheduled surface of the reflective layer in the deposition substrate, and consequently no separation occurs at the interface between the support and the reflective layer or at the interface between the scintillator layer and the reflective layer. Further, it is preferable that the reflective layer in the inventive deposition substrate contain voids in a proportion of 5 to 30 vol %. 1-1-2. Binder Resins The binder resins are not particularly limited as long as the objects of the invention are not deteriorated. The binder resins may be appropriately purchased or produced. From the viewpoint of the cuttability of the deposition substrate, the glass transition temperature (Tg) of the binder resin measured by the method specified in JIS K 7121-1987 is −100° C. to 60° C., preferably −50° C. to 50° C., and more preferably −20° C. to 40° C. If the glass transition temperature (Tg) of the binder resin is below −100° C., it tends to be that the surface of the reflective layer comes to exhibit high tackiness and easily collects foreign substances during production, thus increasing the occurrence of image defects in radiographic images obtained via a scintillator panel in which a scintillator layer is disposed on the scintillator layer formation scheduled surface of the deposition substrate. Further, such a reflective layer tends to fail to withstand the heat (usually 150° C. or more) applied thereto during the deposition of a scintillator layer on the scintillator layer formation scheduled surface of the reflective layer; as a result, cracks are produced in the reflective layer to let phosphor crystals grow abnormally and thereby to deteriorate the image quality (in particular, sharpness) of radiographic images obtained via the scintillator panel in which the scintillator layer is disposed on the scintillator layer formation scheduled surface of the deposition substrate. If the glass transition temperature (Tg) of the binder resin is above 60° C., it tends to be that the reflective layer fails to follow deformation experienced during cutting and is separated at the interface between the support and the reflective layer. Further, such an excessively high glass transition temperature is also disadvantageous in that the reflective layer similarly tends to fail to follow deformation experienced during cutting of a scintillator panel in which a scintillator layer is disposed on the scintillator layer formation scheduled surface of the reflective layer in the deposition substrate, and consequently the reflective layer is separated at the interface between the support and the reflective layer or at the interface between the scintillator layer and the reflective layer. Examples of the binder resins include polyurethane resins, vinyl chloride copolymers, vinyl chloride vinyl acetate copolymers, vinyl chloride vinylidene chloride copolymers, vinyl chloride acrylonitrile copolymers, butadiene acrylonitrile copolymers, polyamide resins, polyvinylbutyrals, polyester resins, cellulose derivatives (such as nitrocellulose), styrene butadiene copolymers, various synthetic rubber resins, phenolic resins, epoxy resins, urea resins, melamine resins, phenoxy resins, silicone resins, acrylic resins and urea formamide resins. Of these, hydrophobic resins such as polyester resins, polyurethane resins and acrylic resins are preferable, and polyester resins and polyurethane resins are more preferable because of excellent interlayer adherability with respect to columnar phosphor crystals formed by deposition and to the support. From the viewpoint of the cuttability of the deposition substrate, polyester resins having the aforementioned glass transition temperature are particularly preferable. In the invention, the binder resin having a glass transition temperature (Tg) of −100° C. to 60° C. represents 5 to 100 wt %, preferably 30 to 100 wt %, more preferably 50 to 100 wt %, and particularly preferably 100 wt % relative to the total of the binder resin(s) present in the reflective layer. The binder resins contained in the refractive layer preferably contain at least two binder resins showing different glass-transition temperatures of not less than 5° C., and more preferably 10 to 100° C., from the viewpoint that the film properties of the refractive layer may be easily controlled. Here, the plurality of binder resins may belong to an identical category or different categories as long as their glass transition temperatures are different. 1-2. Supports Exemplary materials of the supports include various glasses, ceramic materials, semiconductor materials, polymer materials and metals which are transmissive to radiations such as X-rays. Specific examples include plate glasses such as quartz, borosilicate glass and chemically reinforced glass; ceramics such as amorphous carbon, sapphire, silicon nitride and silicon carbide; semiconductors such as silicon, germanium, gallium arsenide, gallium phosphide and gallium nitride; polymer films (plastic films) such as cellulose acetate films, polyester resin films, polyethylene terephthalate films, polyamide films, polyimide films, triacetate films, polycarbonate films and carbon fiber-reinforced resin sheets; metal sheets such as aluminum sheets, iron sheets and copper sheets, as well as metal sheets having layers of oxides of the metals; and bio-nanofiber films. These materials may be used singly or in the form of a stack of materials. From the viewpoint of processability, the materials for the supports in the invention are preferably flexible. Here, the term “flexible” indicates that the materials can be processed from roll to roll. Such materials preferably have a film thickness of 1 to 1,000 μm and an elastic modulus of 0.1 to 100 GPa, and more preferably a film thickness of 50 to 500 μm and an elastic modulus of 1 to 30 GPa. In the invention, the “elastic modulus” is a value obtained by testing a JIS-C2318 sample with a tensile tester in accordance with JIS K 7161, and calculating the ratio of the stress over the strain indicated by the gauge marks on the sample, in the range in which the strain stress curve shows a straight relationship. This ratio is called the Young's modulus. In the specification, this Young's modulus is defined as the elastic modulus. The support materials in the invention are preferably flexible polymer films. Examples of the flexible polymer films include polymer films formed of polyethylene naphthalate (7 GPa), polyethylene terephthalate (4 GPa), polycarbonate (2 GPa), polyimide (7 GPa), polyetherimide (3 GPa), aramid (12 GPa), polysulfone (2 GPa) and polyether sulfone (2 GPa). (The values in parenthesis are elastic moduli). From the viewpoint of heat resistance during deposition, polyimide is particularly preferable. The values of elastic moduli are variable even in polymer films of the same material, and the values in parenthesis are not absolutely correct and should be considered as a guide. The flexible polymer film may be a single polymer film, a film of a mixture of the above polymers, or a stack of two or more identical or different polymer layers. In particular, polymer films including polyimide or polyethylene naphthalate are suitable in the case where columnar crystals of a phosphor (scintillator) are formed on the reflective layer by a gas-phase method using cesium iodide as the raw material. The use of a bio-nanofiber film as the support provides benefits in terms of support characteristics and environmental friendliness because the bio-nanofiber films have characteristics which are not possessed by existing glasses or plastics such as (i) low weight, (ii) strength five times or more greater than iron (high strength), (iii) resistance to swelling by heat (low thermal expansion properties), (iv) being flexible (excellent flexibility), (v) feasibility of various treatments such as mixing, coating and film production, and (vi) combustibility of plant fiber materials. The support of the deposition substrate is advantageously a polymer film having a thickness of 50 μm to 500 μm. Such a support allows a scintillator panel including the deposition substrate to be bonded to a planar light-receiving element in such a manner that the scintillator panel changes its shape in accordance with the shape of the surface of the planar light-receiving element. Thus, the scintillator panel can be uniformly bonded tightly to the planar light-receiving element even in the presence of deformation or warpage of the deposition substrate caused by deposition. The resultant flat panel detectors can achieve uniform sharpness of radiographic images in the entirety of the light-receiving plane. (Because the bonding between the scintillator panel and the planar light-receiving element is tight and uniform, the entire light-receiving plane of the flat panel detector provides uniform sharpness in the obtainable radiographic images.) In order to, for example, adjust the reflectance of the support, the support may include a light-shielding layer and/or a light-absorbing layer in addition to the layer of the aforementioned material. Further, the support itself may have light-shielding properties or light-absorbing properties, or may be a colored support. Examples of the supports having light-shielding properties include various metal plates. Examples of the supports having light-absorbing properties include amorphous carbon plates and films of polymers such as polyimide, polyether imide and aramid. From the viewpoint of adjusting the reflectance of the deposition substrates, preferred colored supports are resin films containing coloring materials such as pigments and dyes (pigments are more preferable). Examples of such resins include general thermoplastic resins. Examples of the pigments include common organic and inorganic coloring pigments such as hardly soluble (usually less than 1 g is dissolved in 100 g of water at 20° C.) azo pigments, phthalocyanine blue and titanium black. Specific examples include insoluble azo pigments such as First Yellow, Disazo Yellow, Pyrazolone Orange, Lake Red 4R and Naphthol Red; condensed azo pigments such as Cromophtal Yellow and Cromophtal Red; azo lake pigments such as Lithol Red, Lake Red C, Watching Red, Brilliant Carmine 6B and Bordeaux 10B; nitroso pigments such as Naphthol Green B; nitro pigments such as Naphthol Yellow S; phthalocyanine pigments such as Phthalocyanine Blue, First Sky Blue and Phthalocyanine Green; threne pigments such as Anthrapyrimidine Yellow, Perinone Orange, Perylene Red, Thioindigo Red and Indanthrone Blue; quinacridone pigments such as Quinacridone Red and Quinacridone Violet; dioxadine pigments such as Dioxadine Violet; isoindolinone pigments such as Isoindolinone Yellow; acidic dye lakes such as Peacock Blue Lake and Alkali Blue Lake; and basic dye lakes such as Rhodamine Lake, Methyl Violet Lake and Malachite Green Lake. The pigments are preferably used in amounts of 0.01 to 10 parts by weight with respect to 100 parts by weight of the binder resin. This amount of the pigments ensures sufficient coloring of the films and prevents deteriorations in mechanical properties such as elongation and strength of the support resin due to excessive addition of the pigments over the saturated coloration. 1-3. Additional Layers Where necessary, the deposition substrates may include additional layers in addition to the reflective layer and the support. In a scintillator panel obtained by forming a scintillator layer on the deposition substrate, it is generally preferable that the luminous efficiency of the scintillator and the sharpness of the obtainable radiographic images be adjusted to desired levels in accordance with the purpose of use of the radiographic image detector. In oral radiography as an example, radiographic images with high sharpness are required because the imaging subjects include dental nerves having fine and complicated structures. Further, the scintillators are required to have high luminous efficiency in pediatric radiography in order to minimally reduce radiation exposure on children susceptible to radiation effects. According to the invention, the reflectance of the deposition substrates is adjusted as required in the following manner, whereby the scintillator luminous efficiency of scintillator panels obtained by forming scintillator layers on the deposition substrates and the sharpness of the obtainable radiographic images can be adjusted to desired levels. For example, the reflectance of the deposition substrate may be adjusted by providing at least one of light-shielding layers and light-absorbing layers containing light-absorbing pigments or the like, in addition to the reflective layer and the support. Alternatively, the reflectance of the deposition substrate may be adjusted by coloring the reflective layer or the support layer in the deposition substrate so as to obtain an appropriate reflectance. In a configuration in which a light-shielding layer or a light-absorbing layer is provided in the deposition substrate, the light-shielding layer or the light-absorbing layer is disposed on the side of the reflective layer opposite to the deposition surface (hereinafter, also referred to as the “scintillator layer formation scheduled surface”). The light-shielding layer or the light-absorbing layer may be provided by stacking a film including a light-shielding layer or a light-absorbing layer. The reflectance of the deposition substrates may also be adjusted by adopting a support which itself has light-shielding properties or light-absorbing properties. Alternatively, as mentioned earlier, the reflectance of the deposition substrates may be adjusted by coloring the reflective layer or the support with a coloring material. Details in these cases of reflectance adjustment are as described in the sections of “Supports” and “Reflective layers”. In particular, the reflectance is more preferably adjusted by coloring the reflective layer itself with a coloring material because this adjustment may be performed by a simple method in which the coloring material is added to the dispersion of the white pigment and the binder resin, and the resultant coating liquid is applied onto the support. The above techniques for adjusting the reflectance of the deposition substrates may be adopted singly. However, at least two techniques are preferably adopted in combination for reasons such as that the reflectance of the deposition substrates may be accurately adjusted to a desired value more easily. When both the light-shielding layer and the pigment layer are used, they are preferably disposed in the order of the light-shielding layer and the pigment layer from the support side for the same reason as above. Hereinbelow, the light-shielding layers and the light-absorbing layers will be described. The light-absorbing layers are not particularly limited as long as the layers have light-absorbing properties and are colored. For example, layers including a pigment and a binder resin may be used. The pigments in the light-absorbing layers may be any known pigments. Suitable pigments are those capable of absorbing long-wavelength red light which is more prone to scatter, and blue pigments are preferred, with preferred examples including ultramarine blue and Prussian blue (iron ferrocyanide). Further, organic blue pigments such as phthalocyanine, anthraquinone, indigoid and carbonium may also be used. Of these, phthalocyanine is preferable from viewpoints such as radiation durability and UV durability of the light-absorbing layers. Furthermore, titanium black that is a titanium-containing black pigment may be suitably used. Titanium black is a black substance resulting from partial removal of oxygen from titanium dioxide. Because its specific gravity is the same as titanium dioxide, a reflective coating liquid including titanium dioxide as the light-scattering particles and titanium black exhibits high stability. The reflectance of the deposition substrate can be advantageously adjusted easily by regulating the mixing ratio of titanium dioxide and titanium black. Examples of the binder resins in the light-absorbing layers include those described in the section of “Reflective layers”. The pigments are preferably used in amounts of 0.01 to 30 parts by weight, and more preferably 0.01 to 10 parts by weight with respect to 100 parts by weight of the binder resin from the viewpoint of the light-absorbing properties of the light-absorbing layer. From the viewpoint of light-absorbing properties, the thickness of the light-absorbing layer is preferably 1 to 500 μm. The light-shielding layers include materials having light-shielding properties. Preferred light-shielding materials for the light-shielding layers are stainless steel and metal materials including one, or two or more elements of aluminum, silver, platinum, palladium, gold, copper, iron, nickel, chromium and cobalt from the viewpoint of the adjustment of the reflectance of the deposition substrates. In particular, aluminum- or silver-based metal materials are particularly preferable because such light-shielding layers exhibit excellent light-shielding properties and corrosion resistance. The light-shielding layer may be comprised of a single film of the metal material, or may include two or more films of the metal materials. In order to increase the adhesion between the support and the light-shielding layer, an intermediate layer is preferably disposed between the support and the light-shielding layer. Examples of the materials of the intermediate layer include general adhesive polymers (such as polyester resins, polyurethane resins and acrylic resins), as well as metals different from the metals in the light-shielding layers (dissimilar metals). Examples of the dissimilar metals include nickel, cobalt, chromium, palladium, titanium, zirconium, molybdenum and tungsten. The intermediate layer may include one, or two or more kinds of these dissimilar metals. In particular, it is preferable that nickel or chromium, or both of these metals be contained from the viewpoint of the light-shielding properties of the light-shielding layer. From the viewpoint of light-shielding properties, the thickness of the light-shielding layer is preferably 1 to 500 μm. The light-shielding layer made of such a metal material also serves as an antistatic layer and thus may be suitably used for antistatic purposes. Such an antistatic layer may be formed instead of or in combination with the addition of an antistatic agent to the reflective layer. In this case, from the viewpoint of antistatic properties of the deposition substrates, the surface resistivity measured with respect to the surface of the reflective layer opposite to the surface in contact with the support is preferably not more than 1.0×1012Ω/□, more preferably not more than 1.0×1011Ω/□, and most preferably not more than 1.0×1010Ω/□ (□ in the unit Ω/□ means square and has no dimension. The same applies hereinafter.) As discussed above, the deposition substrates of the invention include the support and the reflective layer disposed on the support, and the reflective layer includes the light-scattering particles and the binder resin with a specific glass transition temperature (Tg) and has a specific thickness. With this configuration, the deposition substrates of the invention exhibit excellent cuttability and realize scintillator panels exhibiting excellent cuttability and giving radiographic images such as X-ray images with excellent sensitivity and sharpness. In the inventive deposition substrate, the binder resin which has a specific Tg exhibits excellent adhesion with respect to the support and excellently follows deformation experienced during cutting. As a result, the deposition substrate and a scintillator panel including the deposition substrate achieve excellent cuttability, and the deposition substrate does not suffer problems such as the separation of the reflective layer even when subjected to cutting, and the scintillator panel is free from problems such as the separation of a scintillator layer even when subjected to cutting. Further, the reflective layer in the inventive deposition substrate has a specific thickness to ensure that the reflective layer will not become separated from the support because of the thickness being so small that the reflective layer cannot withstand the impact applied during cutting as well as to ensure that cracks will not be generated during film production because of the thickness being so large and accordingly there will occur no abnormal growth of phosphor crystals during deposition, thus resulting in the realization of excellent sharpness of radiographic images obtained via a scintillator panel including the deposition substrate. Furthermore, the sharpness of radiographic images obtained via a scintillator panel including the deposition substrate is further improved when the volatile content in the reflective layer in the deposition substrate is in the specific range. Furthermore, the deposition substrates and scintillator panels including the substrates may be manufactured in a specific size without the need for fabricating individual deposition substrates with the specific size separately, and may be manufactured in such a manner that the deposition substrates and scintillator panels are manufactured with a larger size than the desired size and are thereafter cut into individual deposition substrates or scintillator panels having the desired size. Thus, the deposition substrates and scintillator panels including the substrates ensure uniform quality within the lot or between the lots. After the formation of a scintillator layer on the inventive deposition substrate, the layer configuration is in the order of the support, the reflective layer and the scintillator layer. This layer configuration permits the scintillator panel to be freely attached to and removed (detached) from a planar light-receiving element. Thus, in the event of any problems in the planar light-receiving element or the scintillator panel, the loss caused by such problems can be minimized. 2. Scintillator Panels A scintillator panel according to the present invention includes a support, a reflective layer disposed on the support, and a scintillator layer formed on the reflective layer by deposition. The reflective layer includes light-scattering particles and a binder resin with a glass transition temperature of −100° C. to 60° C. The thickness of the reflective layer is 5 to 300 μm. In the scintillator panel of the invention, it is preferable that a protective layer described later be provided in addition to the reflective layer and the scintillator layer. In the inventive scintillator panel, a light-absorbing layer may be disposed on the side of the reflective layer opposite to the surface on which the scintillator layer is disposed. Further, the scintillator panel of the invention may be supported on a support plate having higher rigidity than the deposition substrate. Hereinbelow, constituents such as layers and elements in the inventive scintillator panels will be described. 2-1. Supports and Reflective Layers In contrast to the case described in the deposition substrate above, the order of the arrangement of the support and the reflective layer may be changed appropriately in accordance with the purpose. The supports and the reflective layers are similar to those in the deposition substrates, and thus will not be described anew. In the scintillator panel of the invention, it is preferable that the reflective layer be located between the support and the scintillator layer and include the light-scattering particles and the binder resin. With this configuration, the luminous efficiency of the scintillator panel is advantageously increased. 2-2. Scintillator Layers In the scintillator panel of the invention, the scintillator layer is preferably formed by the growth of columnar crystals from the surface of the reflective layer. Examples of the materials for the scintillator layers include known phosphors such as NaF, NaCl, NaBr, NaI, KF, KCl, KBr, KI, RbF, RbCl, RbBr, RbI, CsF, CsCl, CsBr and CsI. Of these, cesium iodide (CsI) is preferable from the viewpoints that the X-rays to visible light conversion ratio is relatively high, that columnar crystals can be formed easily by deposition, and that the scattering of light in the crystals is suppressed by the light guide effects ascribed to the crystal structure and consequently the thickness of the phosphor layer can be increased corresponding to the amount of suppressed scattering. However, because the luminous efficiency obtained with CsI alone is low, the scintillator layer preferably includes CsI in combination with any of various activators. Examples of such scintillator layers include a scintillator layer disclosed in JP-B-S54-35060 which contains CsI and sodium iodide (NaI) in an appropriate molar ratio. Further, an example of preferred scintillator layers is one disclosed in JP-A-2001-59899 which contains CsI and activators such as thallium (Tl), europium (Eu), indium (In), lithium (Li), potassium (K), rubidium (Rb) and sodium (Na) in an appropriate molar ratio. In the scintillator panel of the invention, a particularly preferred scintillator layer includes cesium iodide and an activator(s) including one or more thallium compounds. In particular, thallium-activated cesium iodide (CsI:Tl) is preferable because this material has a wide emission wavelength range from 300 nm to 750 nm. Various thallium compounds (thallium (I) compounds and thallium (III) compounds) may be used, with examples including thallium iodide (TlI), thallium bromide (TlBr), thallium chloride (TlCl) and thallium fluoride (TlF and TlF3). In particular, thallium iodide (TlI) is preferable because CsI is activated to a higher degree. The thallium compounds preferably have a melting point in the range of 400 to 700° C. This melting point of the thallium compounds ensures that the activator is uniformly distributed in the columnar crystals in the scintillator layer formed by deposition, resulting in an improvement in luminous efficiency. Herein, the melting point is measured at normal pressure (usually about 0.101 MPa). In the scintillator panel of the invention, the relative content of the activators in the scintillator layer is preferably 0.1 to 5 mol %. Herein, the relative content of the activators is the molar percentage of the activators relative to 1 mole of the phosphor matrix compound taken as 100 mol %. The term “phosphor matrix compound” refers to the phosphor itself such as CsI that is not activated with activators. The raw materials for the scintillator layers such as the phosphor matrix compounds and the activators are collectively referred to as phosphor raw materials. The scintillator layer may be comprised of a single layer or may include a scintillator main layer and a scintillator underlayer which has a higher void content than the scintillator main layer. (The scintillator underlayer is disposed between the scintillator main layer and the reflective layer.) Herein, the term “void content” refers to the ratio of the total cross sectional area of voids to the total cross sectional area of the columnar phosphor crystals plus the voids with respect to a cross section of the scintillator layer that has been cut parallel to the plane of the support at an arbitrary position in the columnar phosphor crystals including the scintillator underlayer. The void content may be determined by cutting the phosphor layer of the scintillator panel parallel to the plane of the support, and analyzing a scanning electron micrograph of the cross section with use of an image processing software to obtain the cross sectional areas of the phosphor portions and the voids. In the scintillator underlayer, the relative content of the activator is preferably 0.01 to 1 mol %, and more preferably 0.1 to 0.7 mol %. In particular, the relative content of the activator in the underlayer is highly preferably not less than 0.01 mol % in terms of the enhancement of emission brightness as well as the storage properties of the scintillator panels. In the invention, it is highly preferable that the relative content of the activator in the scintillator underlayer be lower than the relative content of the activator in the scintillator main layer. The ratio of the relative content of the activator in the scintillator underlayer to the relative content of the activator in the scintillator main layer ((relative content of activator in scintillator underlayer)/(relative content of activator in scintillator main layer)) is preferably 0.1 to 0.7. From viewpoints such as the luminous efficiency of the scintillator layer, the degree of orientation based on an X-ray diffraction spectrum with respect to a plane of the phosphor in the scintillator layer having a certain plane index is preferably in the range of 80 to 100% at any position in the direction of layer thickness. For example, the plane index in the columnar crystals of thallium-activated cesium iodide (CsI:Tl) may be any of indices including (100), (110), (111), (200), (211), (220) and (311), and is preferably (200). (For the plane indices, refer to X-Sen Kaiseki Nyuumon (Introduction to X-ray analysis) (Tokyo Kagaku Dojin), pp. 42-46.) Herein, the “degree of orientation based on an X-ray diffraction spectrum with respect to a plane having a certain plane index” indicates the proportion of the intensity Ix of the certain plane index relative to the total intensity I of the total including planes with other plane indices. For example, the degree of orientation of the intensity I200 of the (200) plane in an X-ray diffraction spectrum is obtained by: “Degree of orientation=I200/I”. For example, the plane indices for the determination of the orientation degree may be measured by X-ray diffractometry (XRD) (crystal X-ray diffractometry or powder X-ray diffractometry). The X-ray diffractometry is a versatile analytical technique capable of identifying substances or giving information about structures such as crystal phase structures by utilizing a phenomenon in which a characteristic X-ray having a specific wavelength is diffracted by crystalline substances according to the Bragg's equation. The illumination targets may be Cu, Fe and Co, and the illumination outputs are generally about 0 to 50 mA and about 0 to 50 kV in accordance with the performance of the apparatus. The columnar phosphor crystals may be formed by a gas-phase method. Examples of the gas-phase methods include deposition and sputtering. Several gas-phase methods may be performed in combination. For example, the phosphor matrix (CsI) may be vaporized and deposited by deposition and the activator raw material by sputtering. Even activator raw materials having a high melting point (compounds having a melting point of 1000° C. or above and are hardly vaporized by deposition) may be used by adopting sputtering for the vaporization of the activator raw materials. The thickness of the scintillator layer is preferably 100 to 800 μm, and more preferably 120 to 700 μm because this thickness ensures that a good balance is obtained between the brightness of the scintillator panel and the sharpness of the obtainable radiographic images. The thickness of the scintillator underlayer is preferably 0.1 μm to 50 μm, and more preferably 5 μm to 40 μm from the viewpoints of high brightness of the scintillator panel and ensuring the sharpness of the obtainable radiographic images. 2-2. Protective Layers Where necessary, the scintillator panels of the invention may have a protective layer which physically or chemically protects the phosphor layer. From viewpoints such as the prevention of deliquescence of the scintillator in the scintillator layer described later, it is preferable that the entire surface of the phosphor layer opposite to the support side be covered with a continuous protective layer, and it is more preferable that the entire surface of the scintillator layer and a portion of the reflective layer of the scintillator panel be covered with a continuous protective layer. Here, the “entire surface of the phosphor (scintillator) layer” refers to all the regions of the columnar phosphor crystal scintillator layer including the surface opposite to the surface in contact with the substrate as well as the lateral sides (in other words, all the surfaces which are not in contact with the substrate). Further, the “portion of the reflective layer” refers to all the regions of the reflective layer which are not in contact with the scintillator layer or the support and are exposed to the atmosphere (in other words, the lateral sides of the reflective layer). The term “continuous protective layer” means that the protective layer covers the region completely without any exposure or whatsoever. The protective layer may be formed of a single material, a mixed material, or a plurality of films or the like including different materials. As mentioned above, the main purpose of the protective layer in the invention is to protect the scintillator layer. In detail, cesium iodide (CsI) as an example of the phosphors is highly hygroscopic and deliquesces when left in the air by absorbing vapor in the air. To prevent this, the protective layer is disposed in the scintillator panel. The protective layer also functions to block substances (such as halogen ions) released from the phosphor in the scintillator panel and to prevent the corrosion of a light-receiving element placed in contact with the scintillator layer. In a configuration in which the columnar phosphor crystal scintillator layer of the scintillator panel and a photoelectric light-receiving element are coupled together through a medium such as an adhesive or an optical oil, the protective layer also serves as an anti-penetration layer preventing the penetration of the adhesive or the optical oil between the columnar phosphor crystals. As will be described below, the protective layer may be directly formed on the scintillator layer by a CVD method or a coating method, or may be provided by stacking a preliminarily prepared polymer film (or protective film) onto the scintillator layer. When the protective layer is directly formed on the scintillator layer by a CVD method or a coating method, preferred materials for forming the protective layer include polyolefin resins, polyacetal resins, epoxy resins, polyimide resins, silicone resins and polyparaxylylene resins. The polyparaxylylene resins may be applied by a CVD method, and the other materials may be applied by a coating method. Examples of the polyparaxylylene resins include polyparaxylylene, polymonochloroparaxylylene, polydichloroparaxylylene, polytetrachloroparaxylylene, polyfluoroparaxylylene, polydimethylparaxylylene and polydiethylparaxylylene. From the viewpoints of appropriate protection of the scintillator layer as well as the strength and the flexibility of the scintillator panel, the thickness of the protective layer is preferably 0.1 μm to 2000 μm. In the case where the protective layer is a film including a polyparaxylylene resin, the film thickness is preferably 2 μm to 15 μm from the viewpoints of the sharpness of radiographic images and the moisture proofness of the protective layer. In the case where the protective layer is bonded to a light-receiving element, the thickness of the adhesive layer is preferably not less than 5 μm, and more preferably not less than 10 μm in order to ensure adhesion, and the total thickness of the protective layer and the adhesive layer is preferably not more than 20 μm. When the total thickness of the polyparaxylylene layer and the adhesive layer is not more than 20 μm, the protective layer and a light-receiving element may be bonded while the scattering of light in the gap between the planar light-receiving element and the scintillator panel is suppressed and thus a decrease in sharpness can be advantageously prevented. Examples of the polymer films which may be disposed on the scintillator layer include polyester films, polymethacrylate films, nitrocellulose films, cellulose acetate films, polypropylene films, polyethylene terephthalate films and polyethylene naphthalate films. These polymer films are easily available in the market. In terms of transparency and strength, these polymer films may be suitably used as the protective layers in the inventive scintillator panels. The polymer film may be preferably applied onto the scintillator layer (onto all the surfaces of the scintillator layer which are not in contact with other surfaces such as the reflective layer and are exposed to the atmosphere, or further onto the exposed portion of the reflective layer) by a method in which the polymer film is bonded to the scintillator surface through the adhesive layer, or a method in which the polymer films larger than the scintillator panel are arranged to vertically interpose the scintillator panel therebetween, and the regions of the upper and lower polymer films outside of the periphery of the scintillator panel are bonded together by fusion or with an adhesive in a vacuum environment. The thickness of the polymer film is preferably 12 μm to 120 μm, and more preferably 20 μm to 80 μm from viewpoints such as the protection and moisture proofness for the scintillator layer, the sharpness of the obtainable radiographic images, and the workability during the production of scintillator panels. In another embodiment, a hot melt resin layer may be formed on the phosphor layer so as to serve as a protective layer. In this case, the hot melt resin also functions to bond the surface of the scintillator layer of the scintillator panel to the surface of a light-receiving element, in addition to the function as a protective layer. Herein, the term “hot melt resin” refers to an adhesive resin which is free from water or solvents and is solid at room temperature (usually about 25° C.) and which includes a nonvolatile thermoplastic material. The hot melt resins become molten when the resin temperature is raised to or above the melting onset temperature by heating or the like, and become solid when the resin temperature falls to or below the solidification temperature. Further, the hot melt resins exhibit tackiness in the thermally molten state and have no tackiness (become non-tacky) in the solid state when the resin temperature is decreased to or below the solidification temperature (for example, to normal temperature). Suitable hot melt resins are those based on polyolefin resins, polyester resins or polyamide resins, but are not limited thereto. Of these, polyolefin resins are more preferable in view of light transmission properties. From viewpoints such as continuous use characteristics and the prevention of adhesive separation in planar light-receiving elements such as thin film transistors (TFTs), the melting onset temperature of the hot melt resins is preferably 60° C. to 150° C. The melting onset temperature of the hot melt resins may be adjusted by the addition of plasticizers. The thickness of the hot melt resin is preferably not more than 50 μm, and more preferably not more than 30 μm. Preferably, the entirety of the top and lateral sides of the scintillator layer as well as the peripheral surface of the reflective layer in the deposition substrate is covered with polyparaxylylene. According to this configuration, high moisture proofness is obtained. The haze of the protective layer is preferably 3% to 40%, and more preferably 3% to 10% in view of factors such as the sharpness and uniformity in the obtainable radiographic images, as well as the production stability and workability in the production of scintillator panels. (The haze is a value measured with NDH5000W manufactured by NIPPON DENSHOKU INDUSTRIES CO., LTD.) Materials having a haze in the above range may be easily selected from such polymer films in the market, or may be fabricated in accordance with appropriate manufacturing methods. The optical transmittance of the protective layer is preferably not less than 70% with respect to 550 nm light in view of factors such as the photoelectric conversion efficiency of the scintillator panels and the emission wavelengths of the phosphors (scintillators). Because materials (such as films) having an optical transmittance of 99% or more are difficult to obtain in the industry, however, a practical preferred range of the optical transmittance is from 99% to 70%. The moisture permeability of the protective layer measured at 40° C. and 90% RH in accordance with JIS Z 0208 is preferably not more than 50 g/m2·day, and more preferably not more than 10 g/m2·day from viewpoints such as the protection of the scintillator layer and the prevention of deliquescence. Because films having a moisture permeability of 0.01 g/m2·day or less are difficult to obtain in the industry, however, a practical preferred range of the moisture permeability is from 0.01 g/m2·day to 50 g/m2·day, and more preferably from 0.1 g/m2·day to 10 g/m2·day. 2-3. Support Plates When it is desired that the scintillator panel of the invention do not exhibit flexibility in accordance with the purpose of use or the like, the scintillator panel may be held on a support plate having higher rigidity than the deposition substrate. Here, the term “rigidity” refers to the degree of resistance to dimensional changes (deformation) when materials are subjected to a bending or torsional force. Higher (greater) rigidity permits a smaller deformation by such a force, and lower (smaller) rigidity causes a larger deformation. In terms of the selection of materials, the rigidity may be increased by using materials having a high elastic modulus. The elastic modulus is defined as described hereinabove. In order to make sure that the scintillator panel will not exhibit flexibility (in other words, the scintillator panel will exhibit high rigidity), the elastic modulus of the support plate on which the scintillator panel is held is preferably not less than 10 GPa, and more preferably not less than 30 GPa. Specifically, any materials such as metals, glasses, carbons and composite materials may be suitably used without limitation. From the viewpoint of transmission of radiations such as X-rays, the thickness of the support plate is preferably adjusted such that the X-ray transmittance will be 80% or more when the scintillator panel is illuminated with X-rays at a tube voltage of 80 kV. In detail, the thickness is preferably about 0.3 mm to 2.0 mm for amorphous carbon plates, and about 0.3 mm to 1.0 mm for glass plates. As discussed above, the scintillator panels of the invention do not suffer the separation of the scintillator layer during cutting and can give radiographic images such as X-ray images with excellent sharpness and sensitivity. In the inventive scintillator panel, the binder resin which has a specific Tg exhibits excellent adhesion with respect to the support and the scintillator layer, and excellently follows deformation experienced during cutting. As a result, the scintillator panel does not suffer problems such as the separation of the scintillator layer even when subjected to cutting. Further, the reflective layer in the inventive scintillator panel has a specific thickness to ensure that the reflective layer will not become separated from the support because of the thickness being so small that the reflective layer cannot withstand the impact applied during cutting as well as to ensure that cracks will not be generated during film production because of the thickness being so large and accordingly there will occur no abnormal growth of crystals during deposition, thus resulting in the realization of excellent sharpness of the obtainable radiographic images. Furthermore, the sharpness of radiographic images obtained via the scintillator panel is further improved when the volatile content in the reflective layer is in the specific range. Furthermore, the scintillator panels of the invention may be manufactured in a specific size without the need for fabricating individual scintillator panels with the specific size separately, and may be manufactured in such a manner that the scintillator panels are manufactured with a larger size than the desired size and are thereafter cut into individual scintillator panels having the desired size. Thus, the scintillator panels ensure uniform quality within the lot or between the lots. In the scintillator panel of the invention, the layer configuration may be in the order of the support, the reflective layer and the scintillator layer. This layer configuration permits the scintillator panel to be freely attached to and removed (detached) from a planar light-receiving element. Thus, in the event of any problems in the planar light-receiving element or the scintillator panel, the loss caused by such problems can be minimized. 3. Deposition Substrate Production Methods 3-1. Procedures in Deposition Substrate Production Methods Next, methods for producing the deposition substrates of the invention will be described. The deposition substrates of the invention may be produced by adopting an appropriate known method in accordance with the purpose. Here, a typical example will be described with reference to FIG. 7. FIG. 7 is a schematic view illustrating a typical example of the methods for producing the deposition substrates of the invention. In the typical example of the deposition substrate production methods, a deposition substrate production apparatus 109 schematically illustrated in FIG. 7 is used. The deposition substrate production method involving the production apparatus 109 preferably includes a workpiece (support) feed step 29, an application step 39, drying steps 49 and 79, a heat treatment step 59, and a recovery step 69. In the feed step 29, a feeder (not shown) is used. In the feed step 29, a roll 202 of a support 201 wound around a core is dispensed by the feeder and the support is fed to the subsequent application step 39. In the application step 39, an applicator 304 is used which includes a backup roll 301, an application head 302, and a vacuum chamber 303 disposed upstream the application head 302. In the application step 39, the support 201 continuously fed by the feeder in the feed step 29 is held by the backup roll 301, and the application head 302 applies a reflective coating liquid to the support 201, the reflective coating liquid including light-scattering particles, a binder resin, additives and a solvent. The reflective coating liquid is applied to the support 201 in such a manner that the vacuum chamber 303 disposed upstream the application head 302 generates a vacuum to stabilize the bead (a pool of the coating liquid) formed during the application between the support 201 and the coating liquid supplied from the application head 302. The vacuum chamber 303 is configured such that the degree of vacuum can be adjusted. The vacuum chamber 303 is connected to a vacuum blower (not shown), which evacuates the inside of the vacuum chamber. The vacuum chamber 303 is airtight, is located adjacent to the backup roll 301 with a small gap, and is evacuated to an appropriate degree of vacuum to suction the upstream of the bead (on the feeder side relative to the application head), thus allowing the coating liquid to form a stable bead. The flow rate of the coating liquid ejected from the application head 302 is adjusted as required via a pump (not shown). Although extrusion coating is illustrated above as an example of the application methods, any of other known application methods may also be used, with examples including gravure coating, roll coating, spin coating, reverse coating, bar coating, screen coating, blade coating, air knife coating and dipping. In the drying step 49, a dryer 401 is used. In the drying step 49, the reflective coating film layer formed by the application of the reflective coating liquid onto the support 201 in the application step 39 is dried by the dryer 401. The drying step 49 is usually performed such that the surface temperature of the reflective coating film layer is raised to 80 to 200° C. In the drying step 49, the reflective coating film layer is dried with a drying gas. The drying gas is introduced through a drying gas inlet 402 and is discharged through an outlet 403. The dryer 401 is configured such that the temperature and the flow rate of the drying air including the drying gas can be determined appropriately. The drying step 79 has the same configuration as in the drying step 49, and thus detailed description thereof will be omitted. The drying step 79, in combination with the drying step 49, allows for the adjustment of the speed of drying of the reflective coating film layer. In the heat treatment step 59, the support 201 having the reflective coating film layer is heat treated with a heat treatment apparatus 501 to remove volatile components in the reflective coating film layer. The heat treatment is usually performed such that the surface temperature of the reflective coating film layer reaches 150° C. to 250° C. In the heat treatment step, the reflective coating film layer is heat treated with a heat treatment gas. The heat treatment gas is introduced through an inlet 502 and is discharged through an outlet 503. The heat treatment apparatus 501 is configured such that the temperature and the flow rate of the heat treatment gas can be determined appropriately. Although not illustrated in FIG. 7, the heat treatment step 59 may be followed by a cooling step in which the support having the reflective layer (the deposition substrate) is cooled. In the recovery step 69, the support 201 on which the reflective coating film layer has been formed is wound with a winding machine (not shown). The reference sign 601 in FIG. 7 indicates a recovered roll of the support wound on a core. In the above steps, the support 201 having the coating film is conveyed on conveyor rolls a to d. In the case where the reflective layer is produced in a multilayer structure or additional layers other than those described above are formed by application, the support on which a first reflective layer has been formed may be wound into a roll in the recovery step 69, and the wound support 601 may be again set as a support 201 in the feed step 29 and be subjected to the steps in which a reflective coating liquid is applied onto the reflective layer, dried and heat treated to form the reflective layer including two or more layers. Where necessary, the obtained deposition substrate may be heat treated to increase the adhesion of the interface between the two or more layers in the reflective layer. In the method for producing the deposition substrates of the invention, the surface temperature of the reflective coating film layer is raised to 80° C. to 200° C. in the drying steps 49 and 79, and is elevated to 150° C. to 250° C. in the heat treatment step 59. In this manner, the amount of volatile components (the volatile content) in the deposition substrate (the support having the reflective layer) may be reduced to less than 5%. One of the characteristics of the inventive deposition substrate production methods is that the heat treatment step is carried out after the drying steps to remove volatile components. The surface temperature of the reflective coating film layer formed on the support 201 may be measured with a known non-contact thermometer such as a laser thermometer or an infrared thermometer. The temperature and the flow rate of the gases in the drying steps 49 and 79 and in the heat treatment step 59 are not particularly limited and may be appropriately adjusted based on the results of measurement with a non-contact thermometer such that the surface temperature of the coating film will fall in the above prescribed temperature range. In the drying steps 49 and 79, it is preferable that the gas flow at a relative speed of 1 to 3 m/sec with respect to the support 201 in a direction parallel to the plane of the support, as measured at a position 5 mm above the surface of the coating film on the support 201. When the relative speed of the gas to the support 201 at a position 5 mm above the coating film surface is in the above range, the reflective layer can be dried without suffering problems such as roughening of the dried surface. In the heat treatment step 59, the surface of the coating film may be heated with the heat treatment gas in combination with an infrared heater. Such a combined heat treatment advantageously increases the effects of the heat treatment on the reflective layer on the support. By the inventive deposition substrate production methods described above, deposition substrates having small amounts of residual solvents and small amounts of gases adsorbed to the light-scattering particles may be obtained. 3-2. Materials Used in Deposition Substrate Production Methods Hereinbelow, the supports and the reflective coating liquids used in the methods for producing the inventive deposition substrates will be described. 3-2-1. Supports The materials of the supports used in the inventive deposition substrates are as described hereinabove. In particular, polymer films are preferable from viewpoints such as that the production apparatus 109 illustrated in FIG. 7 may be suitably used, that the polymer films can be easily processed from roll to roll, and that the flexibility of the polymer films allows the scintillator panels to be intimately coupled to planar light-receiving elements. In order to prevent the deformation of the supports by heat applied during the deposition of phosphors onto the polymer films, the glass transition temperature of the polymer films is preferably not less than 100° C. In detail, suitable such polymer films are polyimide films. Where necessary, additional layers such as the aforementioned light-shielding layers and light-absorbing layers may be appropriately disposed on the support. Further, the support itself may have light-shielding properties or light-absorbing properties as required. The light-shielding layer may be provided on the support by any methods without limitation such as deposition, sputtering and metal foil lamination. From the viewpoint of the adhesion of the light-shielding layer with the support, sputtering is most preferable. For example, the light-absorbing layer may be provided on the support by applying a coating liquid containing components such as a light-absorbing pigment onto the support and drying the coating. 3-2-2. Reflective Coating Liquids The reflective coating liquid may be prepared by dispersing or dissolving in a solvent individual components or a mixture of the components including light-scattering particles, a binder resin and optional additives such as coloring materials including pigments, UV absorbers, fluorescent whitening agents, antistatic agents and dispersants. The procedures such as the sequence of the addition of the components are not particularly limited as long as the objects of the invention are not deteriorated. The light-scattering particles, the binder resin and the additives may be dispersed or dissolved by any known dispersion or dissolution methods. Exemplary dispersing machines which may be suitably used include sand mills, Attritor, Pearl Mill, Super Mill, ball mills, impellers, dispersers, KD mills, colloid mills, Dynatron mills, three roll mills and pressure kneaders. The details of the light-scattering particles, the binder resin, the coloring materials such as pigments, the UV absorbers and the fluorescent whitening agents are as described hereinabove. The dispersants are added in order to help the light-scattering particles be dispersed in the binder resin. Various dispersants may be used in accordance with the binder resin and the light-scattering particles used. Examples thereof include polyhydric alcohols, amines, silicones, phthalic acid, stearic acid, caproic acid, and lipophilic surfactants. The dispersants may remain in or may be removed from the reflective layer that has been formed. The dispersants are preferably used in amounts of 0.05 to 10 parts by weight, and more preferably 1 to 5 parts by weight with respect to 100 parts by weight of the binder resin. The light-scattering particles, the binder resin and the additives may be dispersed or dissolved in any solvents without limitation. Examples of the solvents include lower alcohols (preferably alcohols having 1 to 6 carbon atoms) such as methanol, ethanol, n-propanol and n-butanol; chlorinated hydrocarbons such as methylene chloride and ethylene chloride; ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone; aromatic compounds such as toluene, benzene, cyclohexane, cyclohexanone and xylene; esters of lower fatty acids with lower alcohols such as methyl acetate, ethyl acetate and butyl acetate; ethers such as dioxane, ethylene glycol monoethyl ether, ethylene glycol monomethyl ether and propylene glycol monomethyl ether acetate; and mixtures of these solvents. The light-scattering particles, the binder resin and the additives may exhibit insufficient dispersibility in a single solvent. Further, the use of a single solvent may cause difficulties in controlling the solvent evaporation rate in the drying steps and tends to result in a reflective layer having a roughened surface. To prevent such problems, it is preferable to use a mixed solvent including a plurality of compatible solvents having different amounts of evaporation heat. In particular, a mixed solvent including toluene, methyl ethyl ketone (MEK) and cyclohexanone is preferable. When voids are introduced into the reflective layer in the inventive deposition substrate, the methods for forming such voids are not particularly limited and may be selected appropriately in accordance with the purpose. Examples of the methods include (I) void particles are added to the reflective layer, and (II) a reflective coating liquid containing bubbles or a foaming agent is applied onto the support to form a reflective layer having a porous structure. In particular, the method (I) of adding void particles is preferable from the viewpoint of the easiness in the formation of the coating film. From the viewpoint of the void volume, the method (II) utilizing bubbles is preferable. In the method (II) utilizing bubbles, the foaming agents may be appropriately selected from known foaming agents in accordance with the purpose. Suitable examples include carbon dioxide-generating compounds, nitrogen gas-generating compounds, oxygen gas-generating compounds, and microcapsule foaming agents. Examples of the carbon dioxide-generating compounds include bicarbonates such as sodium hydrogencarbonate. Examples of the nitrogen gas-generating compounds include a mixture of NaNO2 and NH4Cl; azo compounds such as azobisisobutylonitrile and diazoaminobenzene; and diazonium salts such as p-diazodimethylaniline chloride zinc chloride, morpholinobenzenediazonium chloride zinc chloride, morpholinobenzenediazonium chloride fluoroborate, p-diazoethylaniline chloride zinc chloride, 4-(p-methylbenzoylamino)-2,5-diethoxybenzenediazonium zinc chloride, and sodium 1,2-diazonaphthol-5-sulfonate. Examples of the oxygen gas-generating compounds include peroxides. Examples of the microcapsule foaming agents include microcapsule particulate foaming agents encapsulating low-boiling substances vaporized at low temperatures (which may be liquid or solid at normal temperature). Specific examples of the microcapsule foaming agents include microcapsules 10 to 20 μm in diameter in which low-boiling vaporizable substances such as propane, butane, neopentane, neohexane, isopentane and isobutylene are encapsulated in microcapsules made of polystyrene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyacrylate ester, polyacrylonitrile, polybutadiene or any copolymer of these polymers. The content of the foaming agents in the binder resin cannot be specified because it is variable in accordance with the types of the foaming agents. However, it is generally preferable that the content be 1 to 50 wt %. In the method (I) in which void particles are added, the void volume in the reflective layer may be adjusted by adding the void particles to, for example, the reflective coating liquid in such an amount that the void particles will represent 5 to 30 vol % relative to the entirety of the reflective layer taken as 100 vol %. In the method (II) utilizing bubbles, the void volume in the reflective layer may be adjusted by adding the foaming agent to, for example, the reflective coating liquid in such an amount that 1 to 50 wt % of the foaming agent is added to the reflective layer relative to the binder resin taken as 100 wt %. Voids may be introduced into the reflective layer with the aforementioned volume fraction relative to the volume of the reflective layer by any of these methods. From the viewpoint of X-ray transmission properties of the deposition substrates, part of or all the voids are preferably formed of hollow particles. The reflectance of the deposition substrates may be adjusted by, for example, the following methods. (1) On the support, a light-shielding layer is provided which is formed of stainless steel or a material including one, or two or more elements of aluminum, silver, platinum, palladium, gold, copper, iron, nickel, chromium and cobalt. (2) A light-absorbing layer is provided on the support. (3) A light-shielding layer, a light-absorbing layer, or a film including at least one of these layers is stacked onto the support. (4) Light-absorbing properties are imparted to the support. (5) Light-reflecting properties are imparted to the support. (6) The reflective layer is colored. (7) The content of light-scattering particles in the reflective layer, or the thickness of the reflective layer is controlled. (8) At least two of the methods (1) to (7) are combined. By combining the methods (1) to (7), the reflectance and the absorptance of the inventive deposition substrates with respect to the light (produced in the scintillator layer) may be adjusted freely. Further, the sensitivity of radiographic image detectors may be enhanced by increasing the optical reflectance of the deposition substrates. By increasing the optical absorptance of the deposition substrates, radiographic image detectors that include scintillator panels obtained by forming scintillator layers on the inventive deposition substrates may provide radiographic images with improved sharpness. When a metallic light-shielding layer is provided as the aforementioned light-shielding layer and the obtained deposition substrate is used in a scintillator panel, advantages are obtained in that because the deposition substrate has a lowered optical transmittance, it becomes possible to prevent the entry of external light or electromagnetic waves through the surface of the support opposite to the surface in contact with the reflective layer as well as to prevent the leakage of the light produced in the scintillator layer to the outside of the scintillator panel. In particular, the use of a highly reflective metal such as aluminum or silver as the aforementioned light-shielding layer is advantageous in that the reflectance of the reflective layer including the light-scattering particles and the binder resin can be further increased. A light-shielding layer including the aforementioned metal material may be formed on surfaces such as the support by any methods without limitation such as deposition, sputtering and metal foil lamination. From the viewpoint of adhesion, sputtering is most preferable. The reflective layer itself may be colored with a coloring material by any methods without limitation. From viewpoints such as simplicity, a colored reflective layer is more preferably formed on the support by adding the aforementioned coloring material to the reflective coating liquid and applying the resultant reflective coating liquid to the support. Preferred pigments which may be added to the reflective coating liquid include titanium black that is a titanium-containing black pigment. Examples of the titanium blacks suitably used in the invention include Titanium Black S type, M type and M-C type manufactured by Mitsubishi Materials Corporation. A light-absorbing layer may be provided on the support or a film to be stacked on the support in a similar manner as above. That is, a light-absorbing layer may be formed easily by dispersing or dissolving the aforementioned coloring material and other components such as a binder resin in a solvent, and applying the resultant coating liquid onto the support or the film followed by drying. At the start of the deposition for the formation of the scintillator layer on the inventive deposition substrate, the volatile content in the reflective layer is preferably less than 7.5%, more preferably less than 5%, still more preferably less than 2.5%, and further preferably less than 1% relative to the total mass of the reflective layer. This volatile content ensures that the abnormal growth of columnar phosphor crystals can be prevented. Herein, the volatile content is defined by the following equation.Volatile content (mass %)=[(M−N)/N]×100 M is the total mass of the reflective layer before heat treatment, and N is the total mass of the reflective layer after being heat treated at 200° C. for 3 minutes. When the volatile content is in the aforementioned range, the release of gas by volatilization from the reflective layer is reduced during the process in which columnar phosphor crystals are grown by deposition under high temperature and high vacuum conditions. Thus, it becomes possible to suppress the abnormal growth of columnar phosphor crystals in portions from which the volatile components have flown out. Consequently, deteriorations in the sharpness and the uniformity of sharpness in the obtainable radiographic images can be prevented. When the volatile content in the reflective layer of the deposition substrate is outside the aforementioned range, the deposition substrate may be subjected to a volatile component removal step to reduce the volatile content in the reflective layer to the above range. The volatile component removal step is a step in which the volatile components in the reflective layer of the deposition substrate are removed in vacuum and/or at a high temperature. In the step, any known methods may be used as long as the volatile components can be removed. Due to easy operations, a more preferred method is performed in such a manner that the inventive deposition substrate is set to a substrate holder of a deposition apparatus, thereafter the substrate holder is heated to 100° C. or above and at the same time the deposition apparatus is evacuated to a vacuum of 100 Pa or less, and the reflective layer of the deposition substrate is heat treated for several minutes to several hours. The volatile components are mainly residual solvents in the reflective layer formed by the application and drying of the reflective coating liquid, and also gases that have been adsorbed to the white pigment used as a raw material. In particular, gases such as vapor (H2O) and carbon dioxide (CO2) are easily adsorbed to the white pigment even in a low humidity environment. Thus, the volatile component removal step is more preferably performed immediately before the scintillator layer is formed by deposition. 3-3. Cutting of Deposition Substrates The inventive deposition substrate, after being cut as required to the size of a substrate holder of a deposition apparatus, is set to the substrate holder and is subjected to deposition to forma scintillator layer on the reflective layer. The deposition substrate may be cut by any known cutting methods without limitation. From viewpoints such as workability and cutting accuracy, a cutting method using a force-cutting blade, a decorative cutting machine, a punching machine, a laser or the like is preferable. Because of its excellent cuttability, the inventive deposition substrate can be cut without the occurrence of problems such as the separation of the reflective layer under conditions where the cutting environment temperature is around room temperature (usually 25° C.). Thus, the deposition substrate production method involving the step of cutting the inventive deposition substrate entails less thermal energy for the implementation of cutting and is thus advantageous in terms of aspects such as production cost, production efficiency, work safety and work efficiency. From the above viewpoint, the cutting temperature is preferably 20° C. to 40° C. Because the above cutting method can perform cutting of the inventive deposition substrates while avoiding defects, if any, present in the deposition substrates, the deposition substrate production method utilizing the deposition substrate cutting method achieves excellent productivity. 4. Scintillator Panel Manufacturing Methods The scintillator panels of the invention may be manufactured by any methods without limitation as long as the objects of the invention are not deteriorated. Preferably, the scintillator panels are manufactured by a deposition method which utilizes a deposition apparatus having a deposition source and a support rotating mechanism in a vacuum container and which includes a step in which the deposition substrate is set to the support rotating mechanism such that the support side of the deposition substrate is in contact with the mounting surface of the support rotating mechanism, and a phosphor raw material is deposited onto the scintillator layer formation scheduled surface of the deposition substrate while rotating the deposition substrate having the support. A typical example of the methods for manufacturing the inventive scintillator panels will be described with reference to FIGS. 1 to 3. FIG. 1 is a schematic sectional view illustrating a configuration of a scintillator panel 10 as an example of the inventive scintillator panels. FIG. 2 is an enlarged sectional view of the scintillator panel 10 in FIG. 1. FIG. 3 is a schematic view illustrating a configuration of a deposition apparatus 81 as an example of the deposition apparatuses. The scintillator panels of the invention may be preferably manufactured by a method utilizing the deposition apparatus 81 described in detail below. Hereinafter, a method for manufacturing radiographic scintillator panels 10 using the deposition apparatus 81 will be described. 4-1. Deposition Apparatuses As illustrated in FIG. 3, the deposition apparatus 81 has a box-shaped vacuum container 82. Near the bottom of the inside of the vacuum container 82, deposition sources 88a and 88b for vacuum deposition are arranged opposite to each other on the circumference of a circle about the central line perpendicular to a deposition substrate 84. The deposition sources 88a and 88b are members into which a deposition material is packed. Electrodes are connected to the deposition sources 88a and 88b. In this case, the gap between the deposition substrate 84 and the deposition sources 88a and 88b is preferably 100 to 1500 mm, and more preferably 200 to 1000 mm. The gap between the central line perpendicular to the deposition substrate 84 and the deposition sources 88a and 88b is preferably 100 to 1500 mm, and more preferably 200 to 1000 mm. The deposition apparatus 81 is configured such that the deposition sources 88a and 88b generate heat by Joule heating by the passage of an electric current through the deposition sources 88a and 88b via the electrodes. In the manufacturing of the radiographic scintillator panels 10, a mixture including cesium iodide and an activator compound is packed in the deposition sources 88a and 88b, and the mixture is heated and vaporized by the passage of an electric current through the deposition sources 88a and 88b. Three or more (for example, eight, sixteen or twenty four) deposition sources 88 may be provided. The deposition sources 88 may be arranged at regular or irregular intervals. The radius of the circle about the central line perpendicular to the deposition substrate 84 may be selected freely. In order to heat the phosphor contained therein by resistance heating, the deposition sources 88a and 88b may be comprised of alumina crucibles wrapped with a heater, or may be comprised of boats or heaters including high-melting metals or similar materials. The phosphor heating method is not limited to resistance heating and may be any of other methods such as electron beam heating and high frequency induced heating. However, a resistance heating method by the direct application of an electric current, or an indirect resistance heating method by indirect heating of the crucibles with a surrounding heater is preferable because of advantages such as that the method has a relatively simple configuration and is easy to operate, inexpensive and applicable to a very wide range of substances. The deposition sources 88a and 88b may be configured utilizing molecular beam sources according to molecular beam epitaxy. In the inside of the vacuum container 82, a holder 85 configured to hold the deposition substrate 84 is arranged above the deposition sources 88a and 88b. The holder 85 is provided with a heater (not shown) and is configured to heat the deposition substrate 84 attached to the holder 85 by the operation of the heater. The deposition apparatus 81 is configured, by performing heating of the deposition substrate 84, to detach or remove substances adsorbed to the surface of the deposition substrate 84, to prevent an impurity layer from occurring between the deposition substrate 84 and a scintillator layer (a phosphor layer) formed on the substrate surface, to increase the adhesion between the deposition substrate 84 and the scintillator layer formed on the substrate surface, and to control the quality of the scintillator layer formed on the surface of the deposition substrate 84. The holder 85 is configured to hold the deposition substrate 84 such that the scintillator layer formation scheduled surface of the deposition substrate 84 is opposed to the bottom of the vacuum container 82 and in parallel to the bottom of the vacuum container 82. The holder 85 is provided with a rotating mechanism 86 capable of rotating the deposition substrate 84 together with the holder 85 in a horizontal direction. The rotating mechanism 86 is comprised of a rotating shaft 87 which supports the holder 85 and rotates the deposition substrate 84, and a motor (not shown) which is arranged outside the vacuum container 82 and serves as a power supply driving the rotating shaft 87. The deposition apparatus 81 is configured such that driving of the motor causes the rotation of the rotating shaft 87 and consequently the rotation of the holder 85 while keeping the holder 85 opposed to the deposition sources 88a and 88b. Preferably, the holder 85 is fitted with a heater (not shown) for heating the deposition substrate 84. By heating the deposition substrate 84 with the heater, the adhesion of the support of the deposition substrate 84 with respect to the holder 85 can be increased, and the quality of the phosphor layer can be controlled. Such heating also detaches or removes substances which have been adsorbed to the surface of the deposition substrate 84, and prevents an impurity layer from occurring between the surface of the deposition substrate 84 and the phosphor layer. Further, the holder 85 may have a warm or hot medium circulating mechanism (not shown) as a unit for heating the deposition substrate 84. This heating unit is suitable when the temperature of the deposition substrate 84 is maintained at a relatively low temperature such as 50 to 150° C. during the deposition of the phosphor. Furthermore, the holder 85 may have a halogen lamp (not shown) as a unit for heating the deposition substrate 84. This heating element is suited when the temperature of the deposition substrate 84 is maintained at a relatively high temperature such as 150° C. or above during the deposition of the phosphor. In addition to the above configuration, the deposition apparatus 81 includes a vacuum pump 83 connected to the vacuum container 82. The vacuum pump 83 evacuates the vacuum container 82 and introduces a gas to the inside of the vacuum container 82. The inside of the vacuum container 82 can be maintained in a constant pressure gas atmosphere by the operation of the vacuum pump 83. In order to evacuate the vacuum container 82 to a high vacuum, two or more types of vacuum pumps having different operating pressure ranges may be arranged. Examples of the vacuum pumps include rotary pumps, turbo-molecular pumps, cryogenic pumps, diffusion pumps and mechanical boosters. The deposition apparatus 81 includes a mechanism configured to introduce a gas into the vacuum container 82 in order to adjust the pressure in the chamber. The gas introduced here is generally an inert gas such as Ne, Ar or Kr. The pressure in the vacuum container 82 may be adjusted by introducing the gas to the desired pressure while evacuating the vacuum container 82 with the vacuum pump 83, or may be adjusted in such a manner that the vacuum container 82 is evacuated to a vacuum lower than the desired pressure, the evacuation is then terminated, and the gas is introduced to the desired pressure. The pressure in the vacuum container 82 may be adjusted by another approach, for example, by providing a pressure control valve between the vacuum container 82 and the vacuum pump 83 so as to adjust the amount of gas evacuated by the pump. Between the deposition substrate 84 and the deposition sources 88a and 88b, a shutter 89 is provided which can be opened and closed in a horizontal direction to block the space extending from the deposition sources 88a and 88b to the deposition substrate 84. The shutter 89 is closed at the initial stage of deposition, whereby even in the event that impurities, if any, which have become attached to the surface of the phosphor contained in the deposition sources 88a and 88b are vaporized at the initial stage of deposition, the attachment of such impurities to the deposition substrate 84 can be prevented. The shutter 89 is opened after the above purpose is fulfilled, and the phosphor raw material is successfully deposited to form a scintillator layer without allowing any impurities to be deposited to the deposition substrate 84. 4-2. Formation of Scintillator Layers The deposition substrate 84 having the reflective layer 3 on the support 1 is set to the holder 85, whilst the deposition sources 88a and 88b are arranged near the bottom of the vacuum container 82 on the circumference of a circle about the central line perpendicular to the deposition substrate 84. Next, the same number of containers such as crucibles or boats as the deposition sources (two in this case) are filled with a phosphor raw material such as a powdery mixture including a phosphor matrix compound such as cesium iodide and an activator such as thallium iodide, and the filled containers are packed into the deposition sources 88a and 88b (preparation step). In the case where a scintillator underlayer and a scintillator main layer are sequentially formed on the reflective layer, the phosphor matrix compound such as cesium iodide and the activator such as thallium iodide may be separately packed into the deposition sources. In any of these cases, it is preferable that the gap between the surface of the reflective layer of the deposition substrate 84 and the deposition sources 88a and 88b be set to 100 to 1500 mm and the deposition step described later be performed while keeping the gap in the range that has been set. Where necessary, preliminary heating may be performed prior to the deposition in order to remove impurities in the packed phosphor matrix and activator. The preliminary heating temperature is desirably not more than the melting point of the materials used. For example, the preliminary heating temperature is preferably 50 to 550° C., and more preferably 100 to 500° C. in the case of CsI, and is preferably 50 to 500° C., and more preferably 100 to 500° C. in the case of TlI. To prevent the impurities from being deposited to the deposition substrate 84, the preliminary heating is preferably performed with the shutter 89 closed. After the preparation step, the vacuum pump 83 is activated to evacuate the vacuum container 82 and the inside of the vacuum container 82 is brought to a vacuum atmosphere of 0.5 Pa or less, and preferably 0.1 Pa or less (vacuum atmosphere creating step). Here, the term “vacuum atmosphere” refers to an atmosphere in a pressure of not more than 100 Pa, and the vacuum container 82 is preferably evacuated to a vacuum atmosphere in a pressure of not more than 0.1 Pa. Thereafter, the inert gas such as Ar is introduced into the vacuum container 82, and the inside of the vacuum container 82 is maintained in a vacuum atmosphere at 0.1 Pa or less. Next, the heater of the holder 85 as well as the motor of the rotating mechanism are driven, and thereby the deposition substrate 84 mounted to the holder 85 is rotated and heated while being opposed to the deposition sources 88a and 88b. (The rotational speed (rpm) is variable depending on the size of the apparatus, but is preferably 2 to 15 rpm, and more preferably 4 to 10 rpm.) Next, the phosphor is deposited. For example, the phosphor such as CsI may be activated by a method in which the phosphor such as CsI and the activator such as a sodium compound, a thallium compound, an indium compound or a europium compound are vaporized simultaneously in the deposition apparatus and are deposited onto the deposition substrate. Particularly, in this method of deposition through the simultaneous vaporization of the phosphor and the activator, the phosphor is preferably CsI from viewpoints such as that the columnar crystal structure provides light guide effects, and the activator compound is preferably an iodide such as sodium iodide (NaI), thallium iodide (TlI) or indium iodide (InI) from viewpoints such as that these iodides do not inhibit the growth of columnar CsI crystals. Alternatively, the phosphor may be activated by a method in which an activator-free scintillator layer comprised of columnar crystals of the phosphor such as CsI is formed first by deposition on the deposition substrate, thereafter the substrate having the scintillator layer is placed in a closed space such as in a deposition apparatus together with the activator compound such as a sodium compound, a thallium compound, an indium compound or a europium compound, and the activator compound is heated to or above its sublimation temperature to activate the phosphor such as CsI, namely, to activate the scintillator layer. In this method in which the substrate having the scintillator layer is heat treated together with the activator, it is preferable that the substrate placed in the closed space, specifically, the scintillator layer formed of the phosphor such as CsI have been heated to a temperature of 100 to 350° C. The phosphor is preferably CsI from viewpoints such as that the columnar crystal structure provides light guide effects, and the activator compound is, although not particularly limited, preferably one having a low sublimation temperature for easy handling. In an embodiment, the phosphor that is deposited first may be CsI which has been activated with a specific compound (for example, thallium iodide (TlI)). According to such an embodiment, the resultant scintillator layer contains different kinds of activators between the inside and the surface of the CsI columnar crystals. In particular, the decay time of the radiation emitted from the scintillator layer may be shortened by using a europium compound as the activator. When any scintillator underlayer is not formed on the reflective layer, an electric current is passed through the deposition sources 88a and 88b via the electrodes while the deposition substrate 84 is being heated and rotated, and thereby the phosphor raw material such as a mixture including cesium iodide and thallium iodide is vaporized by being heated at about 700° C. to 800° C. for a prescribed time. As a result, a great number of columnar phosphor crystals 2a are gradually grown on the surface of the deposition substrate 84, thus forming a scintillator layer 2 with a desired thickness (deposition step). The thickness of the scintillator layer may be variable in accordance with the purpose, but is preferably 120 to 700 μm. When a scintillator underlayer is formed on the reflective layer, a crucible containing the phosphor matrix compound (such as CsI without activators (pure)) may be heated to allow the phosphor to be deposited into a scintillator underlayer (a first phosphor layer). In this process, the temperature of the deposition substrate 84 is preferably 5 to 200° C., more preferably 5 to 100° C., and particularly preferably 15 to 50° C. The thickness of the scintillator underlayer may be variable depending on the crystal diameters or the thickness of the phosphor layers, but is preferably 0.1 to 50 μm. Subsequently, heating of the deposition substrate 84 is initiated to raise the temperature of the deposition substrate 84 to 150 to 250° C., and operations are started to vaporize a phosphor raw material including the remaining portion of the phosphor matrix compound (such as CsI without activators (pure)) and the activator (such as TlI), thus forming a scintillator main layer (a second phosphor layer). During this process, the activator is migrated by heat from the scintillator main layer to the scintillator underlayer, and consequently the relative content of the activator in the scintillator underlayer is adjusted to 0.01 to 1 mol %. In this process, it is preferable from the viewpoint of productivity that the phosphor matrix compound be deposited at a higher deposition rate than that in the formation of the underlayer. Although variable depending on the thicknesses of the scintillator underlayer and the scintillator main layer, the rate of this deposition is preferably 5 to 100 times higher, and more preferably 10 to 50 times higher than the rate of deposition of the scintillator underlayer. The activator may be vaporized in such a manner that the activator alone is vaporized or that a deposition source including a mixture of CsI and TlI is prepared and heated to a temperature (for example, 500° C.) at which CsI is not vaporized but TlI is vaporized. Because the deposition substrate 84 heated during the deposition is hot, its temperature needs to be cooled for the substrate to be removed. In the cooling step, the deposition substrate 84 may be cooled to 80° C. at an average cooling rate in the range of 0.5° C. to 10° C./min. This cooling rate advantageously ensures that the cooling can be performed without causing damages to the deposition substrate 84 due to the thermal shrinkage of the support by quenching. The cooling of the deposition substrate 84 under this condition is particularly effective when, for example, the support in the deposition substrate 84 is a relatively thin film such as a polymer film having a thickness of 50 μm to 500 μm. In order to avoid any discoloration of the scintillator layer, this cooling step is particularly preferably performed in an atmosphere having a vacuum degree of 1×10−5 Pa to 0.1 Pa. During the cooling step, an inert gas such as Ar or He may be introduced into the vacuum container of the deposition apparatus. Here, the average cooling rate is determined by continuously measuring the time and the temperature from the start of the cooling (the completion of the deposition) to when the temperature is cooled to 80° C., and calculating the cooling rate per 1 minute. In the deposition method, reactive deposition may be carried out by introducing a gas such as O2 or H2 as required. Of the aforementioned columnar phosphor crystal formation methods, the manufacturing method preferably includes a step in which a scintillator underlayer having a higher void content than a phosphor main layer is formed on the surface of the substrate, and a step in which the phosphor is deposited by a gas-phase deposition method on the surface of the scintillator underlayer to form the scintillator main layer. This configuration is preferable in order to satisfy the aforementioned requirement regarding the plane index. The scintillator panels of the invention may be manufactured in the manner described above. The formation of the scintillator layer on the reflective layer under the aforementioned deposition conditions is advantageous in that the scintillator layer is formed by the growth of columnar phosphor crystals at the interface thereof with the reflective layer. According to the scintillator panel manufacturing method using the deposition apparatus 81, the arrangement of a plurality of deposition sources 88a and 88b allows the vapors from the deposition sources 88a and 88b to be corrected or put in order at their confluence with the result that the crystallinity of the phosphor deposited on the surface of the deposition substrate 84 becomes uniform. Increasing the number of deposition sources increases the number of confluences at which correction occurs, thus resulting in uniform crystallinity of the phosphor over a wider range. By the arrangement of the deposition sources 88a and 88b on the circumference of a circle about the central line perpendicular to the deposition substrate 84, the effects of the correction of vapors providing uniform crystallinity can be obtained isotropically on the surface of the deposition substrate 84. From the viewpoints described later, the obtained scintillator panels are preferably subjected to post treatments such as the heat treatment and the pressure treatment described below. 4-3. Heat Treatment for Scintillator Layers Preferably, the scintillator layer formed on the reflective layer of the deposition substrate is placed in a closed space evacuated to 1.0 Pa or below together with one or more activators selected from sodium compounds, thallium compounds, europium compounds and indium compounds, and is subjected to additional activation by heating the activator compound(s) to or above the sublimation temperature to vaporize the compound(s). By this heat treatment, the emission characteristics of the scintillator layer may be adjusted. In this case, the phosphor such as CsI deposited on the deposition substrate is preliminarily heated to a temperature of 250° C. After the additional activation is performed for 1 hour, the deposition substrate having the additionally activated scintillator layer is cooled to 50° C. or below (preferably at an average cooling rate of 0.5° C. to 10° C./min) and the scintillator panel is removed from the closed space in the deposition apparatus. In this manner, scintillator panels having an additionally activated scintillator layer may be obtained. Without the use of any activator compounds, the heat treatment may be performed singly for 1 hour according to the similar procedures. In this case, the activator that has been added during the deposition is activated, and a scintillator panel having high emission intensity may be obtained. 4-4. Pressure Treatment for Scintillator Layers When a scintillator layer is deposited on the reflective layer of the inventive deposition substrate, the layer formed is usually a collection of columnar phosphor crystals having a uniform height from the interface thereof with the reflective layer. However, problems such as the abnormal growth of phosphor crystals may take place locally and consequently the scintillator layer may have less uniform heights of the columnar phosphor crystals (but the objects of the invention are still achieved). For example, such abnormal growth of columnar phosphor crystals may be caused by factors such as dusts suspended in the deposition apparatus, splash during deposition, and substrate defects such as scratches or attachment of foreign substances. Here, the term “splash” during deposition indicates a phenomenon in which molecules of solid CsI are emitted before vaporization and become attached to the deposition substrate (see, for example, JP-A-2006-335887). The abnormally grown columnar phosphor crystals can be a factor deteriorating the properties such as sharpness of radiographic images obtained through the scintillator panels (but the objects of the invention are still achieved). Thus, it is desirable to perform the following pressure treatment so that the abnormally grown columnar phosphor crystals will not be left as such. It is needless to mention that even when there are no abnormally grown columnar phosphor crystals, the implementation of the following pressure treatment is more preferable in order to obtain scintillator panels having a more uniform height of columnar crystals from the interface between the crystals and the reflective layer. The surface of the scintillator layer of the scintillator panel obtained as described above is subjected to a pressure treatment to align the heights of the columnar phosphor crystals in the scintillator layer from the interface with the reflective layer. By the treatment, it becomes possible to obtain scintillator panels which have a scintillator layer comprised of a collection of more uniform columnar phosphor crystals. Here, the term “heights from the interface with the reflective layer” indicates the heights from a middle line (JIS B 0601-2001) at half the height of roughness on the surface of the reflective layer. Here, the term “aligned” indicates that the differences in height of the columnar crystals forming the scintillator layer as measured from the interface with the reflective layer are 20 μm or less. Although the heights of the columnar crystals forming the scintillator layer are defined as extending from the interface with the reflective layer, portions of the columnar crystals other than the portions above the interface with the reflective layer may be present in the inside of the reflective layer (portions of the columnar crystals may be buried in the binder resin in the reflective layer). When the scintillator layer of the scintillator panel is brought into close contact with (or is bonded to) a light-receiving element, the reflective layer in the scintillator panel exhibits flexibility so as to absorb irregularities on the surface of the scintillator layer (the irregularities on the scintillator layer are smoothed by the force applied when the light-receiving element is closely contacted with the scintillator panel, and the reflective layer is deformed in accordance with the smoothing), with the result that the uniformity in resolution in the entire light-receiving plane is improved. In order to further enhance the uniformity in close contact between the scintillator and the light-receiving element, it is advantageous to align the heights of the columnar crystals by pressing the scintillator surface with a flat surface such as a roller or a flat glass before the inventive scintillator is brought into close contact with (or is bonded to) the light-receiving element. From the viewpoints described above, the pressure treatment is preferably carried out such that the maximum difference in the heights of the columnar crystals forming the scintillator layer will be about 20 μm. In detail, the pressure treatment may be performed by a method in which the surface of the scintillator layer of the scintillator panel is pressed with a roller or a flat surface such as glass so as to crush the abnormal protrusions and thereby to align the heights of the columnar phosphor crystals, or may be performed by a method utilizing atmospheric pressure. However, the methods are not particularly limited thereto as long as uniform pressurization is feasible. (The magnitude of the pressure may be adjusted appropriately so that the purpose of this treatment can be achieved.) Particularly in the case where the heights of the columnar phosphor crystals are aligned by pressing the scintillator surface with a roller or a flat plate such as glass, the treatment is more preferably performed while giving a constant pressure force to the roller or the glass plate due to reasons which will be described later. The roller or the glass plate may be preliminarily heated to 80° C. to 200° C. Further, the treatment may involve a flat glass plate which is given quick oscillations by a device such as an ultrasonic vibrator. In this manner, the heights of the ends of the columnar phosphor crystals may be aligned with a less force. In a more specific example of the methods for aligning the heights of the columnar phosphor crystals, a flat glass plate is placed in close contact with the surface of the scintillator layer of the scintillator panel, then resin films are arranged on and under the scintillator panel-glass assembly and the peripheries of the resin films are fusion bonded together in vacuum to seal the assembly; after the scintillator panel-glass assembly is sealed in the resin films, the scintillator panel in that state is heat treated at 50° C. to 200° C. for about 0.5 to 100 hours. This method is preferable from the viewpoint of the easiness of the pressure treatment. Through the pressure treatment for the scintillator layer at a temperature not less than the glass transition temperature of the binder resin, the abnormally grown columnar phosphor crystals are pushed into the reflective layer and consequently the scintillator layer attains uniform aligned heights of the columnar phosphor crystals (the differences in height are within 20 μm). That is, the reflective layer in the invention contains the binder resin with the specific glass transition temperature and has the specific thickness so as to be easily plastically deformed by pressure and absorb the abnormally grown columnar phosphor crystals. The pressure treatment for aligning the heights of the columnar phosphor crystals surpasses other methods such as adjusting the heights by grinding the abnormally grown portions of columnar phosphor crystals, in terms of the facts that high productivity is obtained because there is no generation of wastes such as dusts by the destruction of the columnar phosphor crystals and thus there are no needs for the removal of such wastes, as well as that the quality can be controlled in an advantageous manner. According to the scintillator panel manufacturing methods of the invention, scintillator panels can be provided which exhibit excellent cuttability and do not suffer problems such as the separation of the reflective layer or the scintillator layer even when subjected to a cutting operation and which have uniform crystallinity of the phosphor in the scintillator layer. Such scintillator panels may provide devices such as flat panel detectors which show uniform image quality in the light-receiving plane and can give radiographic images excellent in sharpness and uniformity of sharpness as well as in sensitivity. Further, because the inventive scintillator panel manufacturing methods can produce scintillator panels that do not suffer problems such as the separation of the reflective layer or the scintillator layer even when subjected to a cutting operation, advantages such as excellent productivity can be obtained by performing the deposition in any scale possible in the deposition apparatus (preferably in the largest scale possible in view of the merits described later) and thereafter cutting the produced scintillator panels into desired sizes as required. According to the inventive scintillator panel manufacturing methods, the scintillator panel may be freely attached to and removed (detached) from a planar light-receiving element. Thus, in the event of any problems in the planar light-receiving element or the scintillator panel, the loss caused by such problems can be minimized. 4-5. Scintillator Panel Cutting Methods In the case where the area of the scintillator panel of the invention is larger than the area of the surface of a photoelectric element such as a light-receiving element, the scintillator panel is cut to a size corresponding to the area of the surface of the light-receiving element as required. Because the cutting takes place after the scintillator layer is formed on the reflective layer of the deposition substrate, there are no complicated procedures involved such as those encountered when a plurality of deposition substrates having different sizes are provided in conformity to the sizes of light-receiving elements in radiographic image detectors and these deposition substrates with respective sizes are separately subjected to the phosphor deposition. That is, the deposition may be performed in any scale possible in the deposition apparatus (preferably in the largest scale possible in view of the merits described below) and thereafter the produced scintillator panels may be cut into desired sizes as required. This provides merits in, for example, productivity, adherence to delivery deadlines, and uniformity in quality between the lots or within the lot. Because of its excellent cuttability, the inventive scintillator panel can be cut without the occurrence of problems such as the separation of the reflective layer in the deposition substrate or the separation of the scintillator layer from the deposition substrate under conditions where the cutting environment temperature is around room temperature (usually 25° C.). Thus, the scintillator panel manufacturing method involving the step of cutting the inventive scintillator panel entails less thermal energy for the implementation of cutting and is thus advantageous in terms of aspects such as production cost, production efficiency, work safety and work efficiency. Further, the heights of columnar crystals are aligned under specific conditions during the manufacturing of scintillator panels and consequently the sharpness of the obtainable radiographic images can be further improved. From the above viewpoint, the cutting temperature is preferably 20° C. to 40° C. A typical example of the methods used in the cutting step for cutting the inventive scintillator panels will be described. (Methods using a force-cutting blade will be described in EXAMPLES later, and thus the description thereof is omitted here.) FIGS. 8A and 8B illustrate an example of cutting of a scintillator panel 10 by blade dicing. The scintillator panel 10 is arranged on a dicing table 322 of a dicing apparatus 32 such that a scintillator layer 2 comes downward in contact with the dicing table 322. The scintillator panel 10 is cut with a blade 321 inserted from the support 1 side (the side opposite to the scintillator layer 2 side). The blade 321 cuts the scintillator panel 10 by rotating about a rotational shaft 321a. The dicing table 322 has a groove 221 for receiving the blade 321 which has penetrated the scintillator panel 10. On both sides of the blade 321, support members 324 are provided in order to fix the blade 321. To cool the frictional heat generated during the cutting of the scintillator panel 10 with the blade 321, cooling air is blown to the cut from nozzles 323 disposed on both sides of the blade 321. The temperature of the cooling air is usually not more than 4° C. To prevent condensation, the indoor humidity is usually controlled to not more than 20%. Blade dicing may be suitably adopted when the supports in the scintillator panels are based on carbon, aluminum and glass. FIG. 9 illustrates an example of laser cutting in which a scintillator panel 10 is cut with a laser. A laser cutting apparatus 33 includes a box-shaped purge chamber 333. The purge chamber 333 defines a substantially airtight space protected from the entry of dusts or whatsoever suspended in the outside space. The inside of the purge chamber 333 is preferably a low-humidity environment. The top face of the purge chamber 333 has a translucent window 335 through which a laser beam is transmitted. Further, the purge chamber 333 is fitted with a discharge pipe 334 through which suspended substances such as dusts are introduced to the outside of the purge chamber 333. The scintillator panel 10 is mounted on a support table 332 of the laser cutting apparatus 33. In this case, the scintillator panel 10 may be mounted with the scintillator layer 2 upside or downside. The scintillator panel 10 is held on the support table 332 by suction. The scintillator panel 10 mounted on the support table 332 is guided by a support table moving unit (not shown) to a position immediately below a laser of a laser beam generator 331. The scintillator panel 10 is cut by the application of a laser beam from the laser beam generator 331. Usual laser beam application conditions are YAG-UV (yttrium aluminum garnet crystal, wavelength 266 nm) pulse laser beam, oscillation frequency 5000 Hz, beam diameter 20 μm, and output 300 mW. When the portion of the scintillator panel 10 illuminated with the laser beam has been cut, the scintillator panel 10 is moved by the support table moving unit (not shown) to slide the laser beam illumination position and another portion of the scintillator panel 10 is cut. These operations are repeated to cut the entire scintillator panel to desired shapes. The laser beam used in the cutting of the inventive scintillator panels is desirably an ultraviolet laser beam having a wavelength of about 266 nm such as one described above. A laser beam having a wavelength of about 266 nm is capable of machining the workpiece by the heating action as well as dissociating molecular bonds in organic materials such as C—H bonds and C—C bonds. That is, when the support is, for example, a resin film such as a polyimide film, cutting of such a scintillator panel takes place in such a manner that the scintillator layer is cut by the heating action while the support comprised of a resin film such as a polyimide film is cut by the dissociation of molecular bonds. Thus, the resin film as the support is not thermally deformed. Consequently, no stress will be applied to the joint between the deposition substrate and the scintillator layer, and the occurrence of crystal breakage at the cut can be prevented. Laser cutting may be suitably adopted particularly when the support of the scintillator panel is a resin film. 4-6. Methods for Forming Protective Layers in Scintillator Panels A protective layer may be provided in the scintillator panel. The protective layer may be formed by directly coating the surface of the scintillator layer with a protective coating liquid including the aforementioned materials for the protective layer, or may be provided by stacking or bonding via an adhesive a separately prepared protective layer onto the phosphor layer. Alternatively, the materials for the protective layer may be deposited onto the scintillator panel to form the protective layer. Compact detectors such as dental detectors used for oral radiography require washing or alcohol disinfection as a whole including the housings due to their use in the mouth. Thus, the housings themselves have high moisture proofness. The protective layers in the scintillator panels are not necessarily required in such cases. When the protective layer is provided in the inventive scintillator panel, it is preferable to form the protective layer such that the entire surface of the scintillator layer and a portion of the reflective layer are covered with the continuous protective layer. From viewpoints such as easy production and easy processing of the film, it is particularly preferable that polyparaxylylene be deposited by a chemical vapor deposition (CVD) method to form a polyparaxylylene film as the protective layer on the scintillator panel. Further, a polyparaxylylene film as the protective layer may be advantageously formed on the scintillator panel such that the surface roughness (Ra) will be 0.5 μm to 5.0 μm. In an embodiment in which the scintillator panel is coupled to a light-receiving element, this configuration makes it possible to effectively prevent the optical diffusion of light due to regular reflection and total reflection by the plane of the scintillator and the plane of the light-receiving element. FIG. 10 illustrates an example of the formation of a polyparaxylylene film as the protective layer on the surface of a phosphor layer 2 of a scintillator panel 10. A CVD apparatus 50 includes a vaporization chamber 551 into which diparaxylylene that is the raw material for the polyparaxylylene is fed and vaporized, a pyrolysis chamber 552 in which the vaporized diparaxylylene is heated and converted into radicals, a deposition chamber 553 in which the radicals of diparaxylylene are deposited onto the scintillator panel 10 having a scintillator, a cooling chamber 554 for performing deodorization and cooling, and an evacuation system 555 having a vacuum pump. Here, as illustrated in FIG. 10, the deposition chamber 553 has an inlet 553a through which the radicals of diparaxylylene from the pyrolysis chamber 552 are introduced, an outlet 553b through which excess polyparaxylylene is discharged, and a turntable (a deposition table) 553c configured to support the workpiece during the deposition of the polyparaxylylene film. The scintillator panel 10 is placed on the turntable 553c in the deposition chamber 553 such that the scintillator layer 2 comes upward. Next, the radicals of diparaxylylene generated by vaporization at 175° C. in the vaporization chamber 551 and heating at 690° C. in the pyrolysis chamber 552 are introduced through the inlet 553a into the deposition chamber 553 and are deposited in a thickness of 2 to 15 μm to form a protective layer (a polyparaxylylene film) for the scintillator layer 2. Here, the inside of the deposition chamber 553 is maintained at a vacuum degree of, for example, 1 to 100 Pa, (preferably 13 Pa). The turntable 553c is rotated at a speed of, for example, 0.5 to 20 rpm (preferably 4 rpm). The excess polyparaxylylene is discharged through the outlet 553b to the cooling chamber 554 for performing deodorization and cooling, and the evacuation system 555 having a vacuum pump. In another embodiment, a hot melt resin may be used as the material for the protective layer. The hot melt resin may also serve as an adhesive for bonding the scintillator panel to the surface of a planar light-receiving element. The protective layer of a hot melt resin may be formed by any of the following methods which are described as examples. A release sheet coated with a releasing agent is provided, and a hot melt resin is applied onto the release sheet. The side coated with the hot melt resin is arranged on the surface of the phosphor layer of the scintillator panel, and the layers are bonded to each other under the application of a pressure with a hot roller. After cooling, the release sheet is removed. In another method, the sheet coated with a hot melt resin is arranged on the surface of the scintillator layer, and resin films are arranged on respective other surfaces (meaning not in contact with each other) of the hot melt resin-coated sheet and the scintillator layer. After the peripheral portions of the resin films are sealed (tightly closed) under a reduced pressure, the assembly is heat treated at atmospheric pressure. In the latter method, the resin films are suitably sealant films or polyethylene terephthalate (PET) dry laminate films. Such films are more advantageous in that uniform bond pressure by atmospheric pressure is obtained in the entire plane of contact between the hot melt resin and the scintillator layer. When the protective layer is disposed on the scintillator panel, a layer including an inorganic substance such as SiC, SiO2, SiN or Al2O2 may be stacked on the protective layer by a method such as deposition or sputtering. Since the performances of the scintillator panels are evaluated with respect to radiographic image detectors in which units of the scintillator panels and light-receiving elements described later have been incorporated, the evaluation of such performances will be discussed in detail after the radiographic image detectors are described. 5. Evaluation and Use Application of Deposition Substrates and Scintillator Panels In the deposition substrates of the invention, the reflective layer includes the binder resin with a specific Tg and has a specific thickness, and the deposition substrates thus exhibit excellent cuttability. Further, the deposition substrates realize scintillator panels which can give radiographic images with excellent sensitivity and sharpness and which exhibit excellent cuttability. With these characteristics, the deposition substrates are suitably used in applications such as scintillator panels (for radiographic detectors). The scintillator panels of the invention can give radiographic images such as X-ray images with excellent sensitivity and sharpness, and exhibit excellent cuttability. With these characteristics, for example, the scintillator panels may be suitably coupled to light-receiving elements for use in applications such as radiographic image detectors. As mentioned above, the deposition substrates of the invention may be used in scintillator panel applications. Further, as will be described below, the scintillator panels of the invention may be coupled to light-receiving elements for use in radiographic image detector applications. Furthermore, the methods for evaluating the performances of the scintillator panels with respect to radiographic image detectors will be described below. 5-1. Radiographic Image Detectors 5-1-1. Coupling of Scintillator Panels to Light-Receiving Elements The scintillator panel of the invention may be coupled to a light-receiving element which has a plurality of two-dimensionally arranged light-receiving pixels and is configured to convert light produced in the scintillator panel into electricity. The light-receiving element may have a film which separates the light-receiving element from the scintillator panel. Hereinafter, light-receiving elements having such films and light-receiving elements having no such films will be collectively referred to as “light-receiving elements”. The scintillator panel of the invention is preferably coupled to a planar light-receiving element by a coupling method which can suppress deteriorations in the sharpness of the obtainable radiographic images due to optical diffusion at the plane of contact. A general method for coupling the scintillator panel to the planar light-receiving element is to bring the scintillator surface of the scintillator panel and the surface of the light-receiving element into intimate contact together by any pressing technique, or to couple the two components with a jointing agent, for example, an adhesive or an optical oil, which has an intermediate refractive index between the refractive index of the scintillator of the scintillator panel and the refractive index of the light-receiving section of the planar light-receiving element. (In the case where a protective layer is disposed on the scintillator layer of the scintillator panel, the “scintillator surface” will be appropriately interpreted as the “surface of the protective layer” unless otherwise mentioned. The same applies hereinafter.) Examples of the adhesives for coupling the scintillator surface of the scintillator panel to the surface of the light-receiving element include room-temperature vulcanizing (RTV) adhesives such as acrylic adhesives, epoxy adhesives and silicone adhesives. In particular, examples of elastic adhesive resins include rubber adhesives. Exemplary resins of the rubber adhesives include block copolymers such as styrene isoprene styrene, synthetic rubbers such as polybutadiene and polybutylene, and natural rubbers. Suitable examples of commercially available rubber adhesives include one-part RTV rubber KE420 (manufactured by Shin-Etsu Chemical Co., Ltd.). Examples of the silicone adhesives include silicone adhesives of peroxide-crosslinking type or addition condensation type. These adhesives may be used singly or as a mixture. Further, the adhesives may be mixed together with acrylic or rubber-based pressure-sensitive adhesives. Furthermore, adhesives may be used in which silicone components have been introduced as pendant groups to the polymer main chain or side chains of acrylic adhesives. Optical greases are also usable. Further, other materials such as optical oils which exhibit tackiness with respect to the scintillator panels and the light-receiving elements are also usable. Any known optical oils having tackiness and high transparency may be used. Suitable examples of commercially available optical oils include KF96H (1000000 CS, manufactured by Shin-Etsu Chemical Co., Ltd.) and Cargille Immersion Oil Type 37 (manufactured by Cargille Laboratories, Inc., refractive index fluid). Any known optical greases having tackiness and high transparency may be used. Suitable examples of commercially available optical greases include silicone oil KF96H (1000000 CS, manufactured by Shin-Etsu Chemical Co., Ltd.). When the scintillator panel is coupled to the light-receiving element via an adhesive, a pressure of 10 to 10,000 gf/cm2, and more preferably 10 to 500 gf/cm2 is applied until the adhesive solidifies. By the application of pressure, air bubbles are removed from the adhesive layer. In the case where a hot melt resin has been used as the protective layer, the scintillator panel and the light-receiving element are placed in contact with each other, and, under a pressure of 10 to 10,000 gf/cm2, are heated to a temperature that is 10° C. or more higher than the melting onset temperature of the hot melt resin, then allowed to stand for 1 to 2 hours, and gradually cooled. Quenching tends to result in damages to the light-receiving element due to the stress of shrinkage of the hot melt resin. Preferably, the temperature is cooled to 50° C. or below at a rate of not more than 20° C./hour. Of the above methods, however, the method of bringing the surfaces into intimate contact together by any pressing technique has an inconvenience in that the light emitted from the scintillator panel inevitably causes unfavorable effects by being scattered in the gap (the air layer) at the joint between the scintillator surface of the scintillator panel and the surface of the light-receiving element. Even when the other method is adopted by coupling the scintillator panel and the light-receiving element via a jointing agent having an intermediate refractive index between the scintillator of the scintillator panel and the light-receiving element, it is difficult to equate all the refractive indexes of the scintillator of the scintillator panel, the jointing agent and the light-receiving element, with the result that light is scattered at the interface between the scintillator and the jointing agent and at the interface between the jointing agent and the light-receiving element. The scattering of light emitted from the scintillator panel deteriorates the sharpness of the obtainable radiographic images (but the objects of the invention are still achieved). These problematic deteriorations in the sharpness of radiographic images may be remedied by subjecting the scintillator surface of the scintillator panel and the surface of the light-receiving element to an anti-scattering treatment, for example, by providing an anti-optical diffusion layer on the scintillator surface of the scintillator panel, by providing an antireflection layer on at least one of the scintillator surface of the scintillator panel and the surface of the light-receiving element, or by controlling the surface roughness (Ra) of either or both of the opposed surfaces, namely, the scintillator surface and the surface of the light-receiving element to 0.5 μm to 5.0 μm. The implementation of the above known coupling method in combination with any of these anti-scattering treatments makes it possible to effectively prevent the scattering of light and to obtain radiographic images with excellent sharpness and excellent uniformity of sharpness. Here, the anti-optical diffusion layer is a layer which has an optical transmittance of 60% to 99% with respect to 550 nm wavelength light and is disposed on the scintillator panel to serve also as a protective layer. This layer has a function to attenuate the intensity of light propagating through the protective layer (the anti-optical diffusion layer). While the intensity of the light emitted from the scintillator toward the light-receiving element is not substantially decreased because the optical path of such light in the anti-optical diffusion layer is sufficiently short, the anti-optical diffusion layer effectively removes scattered light traveling a long optical path within the anti-optical diffusion layer at an angle nearly parallel to the surface of the light-receiving element. The antireflection layer prevents a phenomenon in which the light emitted from the scintillator of the scintillator panel is repeatedly reflected and propagated between the scintillator surface of the scintillator panel and the surface of the light-receiving element, and consequently prevents a failure of the light to be detected by the light-receiving element. The antireflection layer is a resin layer having a lower refractive index than the scintillator when it is disposed on the scintillator surface, and is a resin layer having a lower refractive index than the light-receiving element when it is disposed on the surface of the light-receiving element. By providing such an antireflection layer on at least one of the scintillator surface of the scintillator panel and the surface of the light-receiving element, the emitted light is allowed to be propagated in the antireflection layer at an angle smaller than the angle of incident from the scintillator side and to be propagated to the light-receiving element at an angle larger than the above angle, thereby preventing repeated reflection of the emitted light between the scintillator surface and the surface of the light-receiving element. More preferably, the antireflection layer is designed such that its optical transmittance with respect to 550 nm wavelength light will be 60% to 99% in order to add effects similar to those obtained with the aforementioned protective layer serving also as the anti-optical diffusion layer. Further, controlling the surface roughness (Ra) of either or both of the opposed surfaces of the scintillator and of the light-receiving element to 0.5 μm to 5.0 μm suppresses the occurrence of regular reflection and total reflection by irregularities in the light incidence plane. As a result, it becomes possible to effectively prevent the optical diffusion of the light emitted from the scintillator between the scintillator surface and the surface of the light-receiving element. In order to obtain combined effects in the prevention of optical diffusion, it is more preferable that the anti-optical diffusion layer and the antireflection layer disposed on the scintillator surface and the surface of the light-receiving element be treated such that the arithmetic average surface roughness of their planes (surfaces) placed in contact with the surface of the scintillator panel or the light-receiving element will be 0.5 μm to 5.0 μm. Examples of the anti-optical diffusion layers and the antireflection layers include layers containing materials such as polyparaxylylenes, polyurethanes, vinyl chloride copolymers, vinyl chloride vinyl acetate copolymers, vinyl chloride vinylidene chloride copolymers, vinyl chloride acrylonitrile copolymers, butadiene acrylonitrile copolymers, polyamide resins, polyvinyl butyrals, polyester resins, cellulose derivatives (such as nitrocellulose), styrene butadiene copolymers, various synthetic rubber resins, phenolic resins, epoxy resins, urea resins, melamine resins, phenoxy resins, silicone resins, acrylic resins and urea formamide resins. These materials may be used singly, or two or more may be mixed together. The anti-optical diffusion layer and the antireflection layer are preferably polyparaxylylene films formed by, in particular, a chemical vapor deposition (CVD) method from viewpoints such as that such layers may be easily formed on the scintillator surface of the scintillator panel or the surface of the light-receiving element, and that such layers also have a function as protective layers for the scintillator. (In this case, a separate protective layer is not necessarily provided because the polyparaxylylene film serves as a protective layer, an anti-optical diffusion layer and an antireflection layer.) When the optical transmittance of the anti-optical diffusion layer is adjusted by the addition of a coloring material, a blue coloring material is preferably used from the viewpoint that the blue coloring materials absorb long-wavelength red light which is more prone to scatter than other wavelength light. Examples of the blue coloring materials include ultramarine blue, Prussian blue (iron ferrocyanide), phthalocyanine, anthraquinone, indigoid and carbonium. 5-1-2. Radiographic Image Detectors Including Imaging Panels Incorporating Scintillator Panels Coupled with Light-Receiving Elements Hereinbelow, an example of the applications of the inventive scintillator panels will be described with reference to FIGS. 4 and 5 illustrating a radiographic image detector 100 including a radiographic scintillator panel 10. In the radiographic image detector 100, the scintillator panel coupled with a light-receiving element is incorporated in an imaging panel. FIG. 4 is a partially broken schematic perspective view illustrating a configuration of the radiographic image detector 100. FIG. 5 is an enlarged sectional view of the imaging panel 51. As illustrated in FIG. 4, the radiographic image detector 100 includes the imaging panel 51, a control section 52 configured to control the operations of the radiographic image detector 100, a memory section 53 configured to store image signals output from the imaging panel 51 in a medium such as a rewritable special memory (for example, a flash memory), and a power supply section 54 that supplies electrical power required to drive the imaging panel 51 and to acquire image signals. These and other components are accommodated in a housing 55. The housing 55 is provided with a communication connector 56 for establishing a communication between the radiographic image detector 100 and an external device as required, an operation section 57 for switching the operations of the radiographic image detector 100, and a display section 58 configured to display messages such as that the radiographic image detector is ready for imaging, or that the memory section 53 has stored a predetermined volume of image signals. The radiographic image detector 100 including the power supply section 54 and the memory section 53 capable of storing radiographic image signals may be detachably connected via the connector 56 to a computer to which the images will be forwarded. According to this configuration, the radiographic image detector 100 does not have to be located at a fixed position with the computer and may be transported from one place to another. As illustrated in FIG. 5, the imaging panel 51 includes the radiographic scintillator panel 10, and an output substrate 20 that absorbs electromagnetic waves from the radiographic scintillator panel 10 and outputs the image signals. In the imaging panel 51, the radiographic scintillator panel 10 is arranged such that the scintillator layer is in contact with the light-receiving element, and is configured to emit electromagnetic waves corresponding to the intensities of the incident radiations. The output substrate 20 is disposed opposite to the radiation-illuminated side of the radiographic scintillator panel 10, and includes a separator film 20a, the light-receiving element 20b, an image signal output layer 20c, and a base 20d sequentially in the order of increasing distance from the radiographic scintillator panel 10. The separator film 20a separates the radiographic scintillator panel 10 and the adjacent layers (in the imaging panel 51, the output substrate 20). The light-receiving element 20b includes a transparent electrode 21, a charge generation layer 22 that generates electric charges by being excited by the electromagnetic waves incident thereon through the transparent electrode 21, and a counter electrode 23 that makes a pair with the transparent electrode 21. These are disposed in the order of the transparent electrode 21, the charge generation layer 22 and the counter electrode 23 as viewed from the separator film 20a side. The transparent electrode 21 is capable of transmitting electromagnetic waves which are to be photoelectric converted and is made of, for example, a conductive transparent material such as indium tin oxide (ITO), SnO2 or ZnO. The charge generation layer 22 is disposed in the form of a thin film on the surface of the transparent electrode 21 opposite to the surface in contact with the separator film 20a. The charge generation layer 22 includes photoelectric conversion compounds, namely, organic compounds that undergo charge separation when illuminated with light. The organic compounds which produce charge separation are a conductive compound serving as an electron donor by donating electric charges, and another conductive compound serving as an electron acceptor. When electromagnetic waves such as radiations are incident on the charge generation layer 22, the electron donor is excited to release electrons, and the released electrons are transferred to the electron acceptor. In this manner, charges, namely, hole and electron carriers are generated in the charge generation layer 22. Examples of the conductive compounds as the electron donors include p-type conductive polymer compounds. Preferred p-type conductive polymer compounds are those compounds having a basic skeleton of polyphenylene vinylene, polythiophene, poly(thiophene vinylene), polyacetylene, polypyrrole, polyfluorene, poly(p-phenylene) or polyaniline. Examples of the conductive compounds as the electron acceptors include n-type conductive polymer compounds. Preferred n-type conductive polymer compounds are those compounds having a basic skeleton of polypyridine, and particularly preferred compounds are those having a basic skeleton of poly(p-pyridyl vinylene). The thickness of the charge generation layer 22 is preferably not less than 10 nm (particularly not less than 100 nm) in order to ensure a sufficient amount of optical absorption, and is preferably not more than 1 μm (particularly not more than 300 nm) in order to avoid an excessively high electric resistance. The counter electrode 23 is disposed on the surface of the charge generation layer 22 opposite to the surface on which the electromagnetic waves (the light emitted from the scintillator layer 2 of the radiographic scintillator panel 10) are incident. For example, the counter electrode 23 may be selected from general metal electrodes such as gold, silver, aluminum and chromium as well as from transparent electrodes similar to the transparent electrode 21. In order to achieve good characteristics, the electrode is preferably formed from a material with a low work function (not more than 4.5 eV) selected from metals, alloys, electrical conductive compounds and mixtures of these substances. Between the charge generation layer 22 and each of the electrodes (the transparent electrode 21 and the counter electrode 23), a buffer layer may be disposed which serves as a buffer zone preventing the reaction between the charge generation layer 22 and the electrodes. For example, the buffer layers may be formed using such materials as lithium fluoride, and poly(3,4-ethylenedioxythiophene):poly(4-styrene sulfonate) or 2,9-dimethyl-4,7-diphenyl[1,10]phenanthroline. The image signal output layer 20c stores the charges generated in the light-receiving element 20b, and outputs signals based on the stored charges. This layer is comprised of capacitors 24 that are charge storage elements for storing the charges generated in the light-receiving element 20b with respect to each pixel, and transistors 25 that are image signal output elements outputting the stored charges as signals. Examples of the transistors 25 include thin film transistors (TFTs). The TFTs may be inorganic semiconductor TFTs utilized in devices such as liquid crystal displays or may be organic semiconductor TFTs. TFTs formed on plastic films are preferable. Examples of the TFTs formed on plastic films include amorphous silicon semiconductor TFTs on plastic films, and TFTs obtained utilizing the fluidic self assembly (FSA) technology developed by Alien Technology Corp., USA, specifically, TFTs on flexible plastic films obtained by arranging fine single crystal silicon CMOS (Nanoblocks) on embossed plastic films. Further, TFTs including organic semiconductors described in literature such as Science, 283, 822 (1999), Appl. Phys. Lett., 771488 (1998), and Nature, 403, 521 (2000) may be utilized. The transistors 25 used in the invention are preferably TFTs fabricated by the FSA technology or organic semiconductor TFTs, and are particularly preferably organic semiconductor TFTs. The fabrication of organic semiconductor TFTs does not entail large facilities such as vacuum deposition apparatuses in contrast to silicon TFTs, and may be accomplished at low costs by utilizing a printing technology or an inkjet technology. Further, organic semiconductor TFTs allow the processing temperature to be decreased, and thus may be formed on heat-labile plastic substrates. To the transistor 25 are electrically connected the capacitor 24 for storing the charges generated in the light-receiving element 20b, and a collector electrode (not shown) serving as one of the electrodes of the capacitor 24. The capacitor 24 stores the charges generated in the light-receiving element 20b, and the stored charges are read out by the driving of the transistor 25. That is, the signals of the respective pixels for the radiographic image may be output by the driving of the transistors 25. The base 20d serves as a support of the imaging panel 51, and may be comprised of a material similar to the support 1. Next, there will be described the mechanism in which the radiographic image detector 100 detects a radiographic image. First, the radiographic image detector 100 is illuminated with radiations such as X-rays incident from the radiographic scintillator panel 10 side toward the base 20d side of the imaging panel 51. The radiations incident on the radiographic image detector 100 are absorbed as radiation energy by the scintillator layer 2 of the radiographic scintillator panel 10 in the radiographic image detector 100. The radiations are then converted into visible light in the scintillator layer 2, and the visible light (electromagnetic waves) corresponding to the intensities of the radiations is emitted from the scintillator layer 2. A portion of the emitted visible light (electromagnetic waves) enters the output substrate 20 and reaches the charge generation layer 22 through the separator film 20a and the transparent electrode 21 of the output substrate 20. The visible light (electromagnetic waves) is absorbed in the charge generation layer 22, and hole-electron pairs (charge separation) are formed in accordance with the intensities of the absorbed visible light (electromagnetic waves). The holes and the electrons generated in the charge generation layer 22 are transported to the respective electrodes (the transparent electrode 21 and the counter electrode 23) by the action of an internal electric field produced by the application of bias voltage from the power supply section 54, resulting in the passage of photocurrent. The holes transported to the counter electrode 23 side are stored in the capacitors 24 of the image signal output layer 20c. When the transistors 25 connected to the capacitors 24 are driven, the stored holes are output as image signals, which are then stored in the memory section 53. Because of the incorporation of the radiographic scintillator panel 10, the radiographic image detector 100 achieves a high photoelectric conversion efficiency and an improved S/N ratio during low-dose imaging of radiographic images, and can eliminate (or reduce) image unevenness and linear noise. 5-3. Methods for Evaluating Performances of Deposition Substrates and Scintillator Panels 5-3-1. Method for Evaluating Cuttability of Deposition Substrate The cuttability of the deposition substrate is evaluated in accordance with the evaluation method described later in EXAMPLES. First, the deposition substrate is cut with a force-cutting blade, and the length of separation of the reflective layer from the support is measured with an optical microscope. The cuttability of the deposition substrate is evaluated based on the following criteria. The cuttability is evaluated to be acceptable for product performance when the length of separation of the reflective layer is 100 μm or less. TABLE 1⊙Not more than 10 μm◯More than 10 μm to not more than 50 μmΔMore than 50 μm to not more than 100 μmXMore than 100 μm5-3-2. Method for Evaluating Cuttability of Scintillator Panel The cuttability of the scintillator panel is evaluated in accordance with the evaluation method described later in EXAMPLES. First, the scintillator panel is cut with a force-cutting blade, and the length of separation of the scintillator layer from the reflective layer is measured with an optical microscope. The cuttability of the scintillator panel is evaluated based on the following criteria. The cuttability is evaluated to be acceptable for product performance when the length of separation of the scintillator layer is 100 μm or less. TABLE 2⊙Not more than 10 μm◯More than 10 μm to not more than 50 μmΔMore than 50 μm to not more than 100 μmXMore than 100 μm5-4-3. Method for Evaluating Sensitivity (Brightness) of Scintillator Panel The sensitivity (brightness) of the scintillator panel is evaluated in accordance with the evaluation method described later in EXAMPLES. With an X-ray illuminator having a tube voltage of 80 kVp, X-rays are applied to the light-receiving plane of a FPD including the radiographic image detector. The obtained X-ray image data is analyzed to determine the average signal value of the entirety of the X-ray image, thereby evaluating the sensitivity of the scintillator panel. The average signal value of the radiographic image detector including the scintillator panel No. 1 is taken as 100. 5-3-4. Method for Evaluating Sharpness of Scintillator Panel With an X-ray illuminator having a tube voltage of 80 kVp, X-rays are applied to the backside (the surface without the scintillator layer) of the scintillator panel through a lead MTF chart, and the image data detected at a CMOS flat panel is recorded on a hard disk. Thereafter, the image data recorded on the hard disk is analyzed with a computer to determine the MTF value (at a spatial frequency of 1 cycle/mm) of the X-ray image recorded on the hard disk, as the indicator of sharpness. A larger value of MTF, which is an abbreviation for modulation transfer function, indicates higher sharpness of the X-ray image. The present invention will be described in detail based on examples hereinbelow without limiting the scope of the invention. Hereinafter, the term “average particle diameter” indicates “area average particle diameter”. 40 Parts by mass in total of rutile-form titanium dioxide (CR93 manufactured by ISHIHARA SANGYO KAISHA, LTD., average particle diameter 0.28 μm) as light-scattering particles and a polyester resin (VYLON 550 manufactured by TOYOBO CO., LTD., Tg: −15° C.) as a binder resin, and 30 parts by mass of cyclohexanone and 30 parts by mass of methyl ethyl ketone (MEK) as solvents were mixed together. The mixture was dispersed with a sand mill to give a first resin coating liquid (a reflective coating liquid 1). The light-scattering particles and the binder resin were used in a solid content ratio (vol %) of 20/80. The first resin coating liquid was applied onto a 500 mm wide polyimide film support (UPILEX S manufactured by UBE INDUSTRIES, LTD., 125 μm thick) with a comma coater. The first resin coating liquid was then dried at 180° C. for 3 minutes to form a resin layer on the support. Thus, a deposition substrate No. 1 was fabricated which included the support and the reflective layer described in Table 5. Deposition substrates Nos. 2 to 5 with the thicknesses described in Table 5 were fabricated in the same manner as in EXAMPLE 1, except that the binder in EXAMPLE 1 was changed as described in Table 5. Deposition substrates Nos. 6 to 9 with the thicknesses described in Table 5 were fabricated in the same manner as in EXAMPLE 2, except that the thickness of the reflective layer in EXAMPLE 2 was changed as described in Table 5. A deposition substrate No. 10 with the thickness described in Table 5 was fabricated in the same manner as in EXAMPLE 2, except that the type of light-scattering particles in EXAMPLE 2 was changed to hollow particles (SX866 manufactured by JSR Corporation, average particle diameter 0.3 μm). A deposition substrate No. 11 with the thickness described in Table 5 was fabricated in the same manner as in EXAMPLE 2, except that the light-scattering particles/binder resin ratio in EXAMPLE 2 was changed as described in Table 5. A deposition substrate No. 12 with the thickness described in Table 5 was fabricated in the same manner as in EXAMPLE 2, except that the light-scattering particles/binder resin ratio in EXAMPLE 2 was changed as described in Table 5. A deposition substrate No. 13 with the thickness described in Table 5 was fabricated in the same manner as in EXAMPLE 2, except that the time of drying after the application in EXAMPLE 2 was reduced to 2 minutes. A deposition substrate No. 14 with the thickness described in Table 5 was fabricated in the same manner as in EXAMPLE 2, except that the reflective coating liquid in EXAMPLE 2 was applied onto a 500 mm square aluminum support with a spin coater and the coating was dried at 180° C. for 5 minutes. Deposition substrates Nos. 15 and 16 with the thicknesses described in Table 5 were fabricated in the same manner as in EXAMPLE 10, except that the material of the support in EXAMPLE 10 was changed as described in Table 5. Deposition substrates Nos. 17 and 18 with the thicknesses described in Table 5 were fabricated in the same manner as in EXAMPLE 1, except that the resin of the reflective layer in EXAMPLE 1 was changed as described in Table 5. The deposition substrates Nos. 1 to 4, 7, 8, 10, 11 and 13 to 18 represent examples, and the deposition substrates Nos. 5, 6, 9 and 12 represent comparative examples. The deposition substrates Nos. 1 to 13, 17 and 18 were cut with a force-cutting blade, and the deposition substrates Nos. 14 to 16 were cut with a dicing blade. The length of separation of the reflective layer from the support was measured with an optical microscope, and the cuttability of the deposition substrate was evaluated based on the following criteria. The cuttability was evaluated to be acceptable for product performance when the length of separation of the reflective layer was 100 μm or less. TABLE 3⊙Not more than 10 μm◯More than 10 μm to not more than 50 μmΔMore than 50 μm to not more than 100 μmXMore than 100 μm (Formation of Scintillator Layer) The deposition substrates Nos. 1 to 18 were each cut to a 400 mm square piece with a force-cutting blade or a dicing blade. Each piece was set to a substrate holder 85 of a deposition apparatus illustrated in FIG. 3, and a phosphor was deposited onto the scintillator layer formation scheduled surface of the reflective layer sample as described below. Thus, scintillator panels Nos. 1 to 18 were fabricated in which a scintillator (phosphor) layer was disposed on the reflective layer sample. (The scintillator panels Nos. 1 to 4, 7, 8, 10, 11 and 13 to 18 represent examples, and the scintillator panels Nos. 5, 6, 9 and 12 represent comparative examples.) A phosphor raw material (CsI) was packed as a deposition material into resistance-heating crucibles, thus preparing deposition sources 88. The reflective layer sample (the deposition substrate) was placed onto the rotatable holder 85 such that the surface of the support of the reflective layer sample was in contact with the holder 85. The gap between the reflective layer sample (the deposition substrate) and the deposition sources 88 was adjusted to 400 mm. Next, the deposition apparatus was evacuated, and the degree of vacuum in the deposition apparatus was adjusted to 0.5 Pa by introducing Ar gas. While rotating the reflective layer sample (the deposition substrate) together with the holder 85 at 10 rpm, the holder 85 was heated to maintain the temperature of the reflective layer sample (the deposition substrate) at 200° C. Next, the resistance-heating crucibles (the deposition sources 88) were heated to allow the phosphor to be deposited on the scintillator layer formation scheduled surface of the reflective layer sample (the deposition substrate), thereby forming a scintillator layer. The deposition was terminated when the thickness of the scintillator layer became 500 μm. Thus, a scintillator panel was obtained in which the scintillator layer was formed in the prescribed thickness on the scintillator layer formation scheduled surface of the reflective layer sample (the deposition substrate). Next, the scintillator panel was cut into four 130 mm square pieces with a force-cutting blade or a dicing blade. Next, the scintillator panel which had been cut was placed into a deposition chamber of a CVD apparatus and was exposed to a vapor formed by the sublimation of a raw material for polyparaxylylene. In this manner, scintillator panels Nos. 1 to 18 were obtained in which the surface of the phosphor layer was covered with a polyparaxylylene resin film with a thickness of 10 μm. The scintillator panel No. 4 was subjected to the following pressure treatment. A flat glass plate was placed in close contact with the surface of the scintillator layer of the scintillator panel, then resin films were arranged on and under the scintillator panel-glass assembly and the peripheries of the resin films were fusion bonded together in vacuum to seal the assembly; after the scintillator panel-glass assembly was sealed in the resin films, the scintillator panel in that state was heat treated at 100° C. for 1 hour. The obtained samples were each set to a CMOS flat panel (X-ray CMOS camera system Shad-o-Box 4KEV manufactured by Teledyne Rad-icon Imaging Corporation). With the obtained 12 bit output data, the sharpness of the X-ray image obtained via the scintillator flat panel was measured by the following method. The measured sharpness was evaluated by the method described below. Sponge sheets were applied to the carbon plate of the radiation incident window of the CMOS flat panel as well as to the radiation incident side (the side without the scintillator layer) of the scintillator panel, and the surface of the scintillator panel and the surface of the planar light-receiving element disposed in the CMOS flat panel were lightly pressed against each other to fix the scintillator panel to the planar light-receiving element. (Method for Evaluating Sensitivity of Scintillator Panel) With an X-ray illuminator having a tube voltage of 80 kVp, X-rays were applied to the light-receiving plane of a FPD including the radiographic image detector. The obtained X-ray image data was analyzed to determine the average signal value of the entirety of the X-ray image, thereby evaluating the sensitivity of the scintillator panel. The average signal value of the radiographic image detector including the scintillator panel No. 1 was taken as 100. (Method for Evaluating Sharpness of Scintillator Panel) With an X-ray illuminator having a tube voltage of 80 kVp, X-rays were applied to the backside (the surface without the scintillator layer) of the scintillator panel through a lead MTF chart, and the image data detected at the CMOS flat panel was recorded on a hard disk. Thereafter, the image data recorded on the hard disk was analyzed with a computer to determine the MTF value (at a spatial frequency of 1 cycle/mm) of the X-ray image recorded on the hard disk, as the indicator of sharpness. A larger value of MTF, which is an abbreviation for modulation transfer function, indicates higher sharpness of the X-ray image. (Evaluation of Cuttability of Scintillator Panel) The scintillator panels Nos. 1 to 18 were cut with a force-cutting blade or a dicing blade. The length of separation of the scintillator layer from the reflective layer was measured with an optical microscope, and the cuttability of the scintillator panel was evaluated based on the following criteria. The cuttability was evaluated to be acceptable for product performance when the length of separation of the scintillator layer was 100 μm or less. TABLE 4⊙Not more than 10 μm◯More than 10 μm to not more than 50 μmΔMore than 50 μm to not more than 100 μmXMore than 100 μm The evaluation results are described in Table 5. TABLE 5Configurations of deposition substrates used for fabrication of scintillator panelsDepositionReflective layerssubstratesScintillatorSupportsResins*5Light-absorbingVolatilepanelsMaterialsThicknessLSP*3TgRatio*4ThicknesslayerscontentPressureNos.*1TypesμmTypesTypes° C.vol %/vol %μmPresence or absencemg/m2treatment1Polyimide125TiO2VYLON 550−1540/6050Present (PI)0.2Not performed2Polyimide125TiO2VYLON GK1402040/6050Present (PI)0.2Not performed3Polyimide125TiO2VYLON GK6004740/6050Present (PI)0.2Not performed4Polyimide125TiO2VYLON GK1402040/6050Present (PI)0.2Performed5Polyimide125TiO2VYLON 20SS6740/6050Present (PI)0.2Not performed6Polyimide125TiO2VYLON GK1402040/603Present (PI)0.1Not performed7Polyimide125TiO2VYLON GK1402040/6010Present (PI)0.1Not performed8Polyimide125TiO2VYLON GK1402040/60250Present (PI)0.5Not performed9Polyimide125TiO2VYLON GK1402040/60350Present (PI)0.9Not performed10Polyimide125HollowVYLON GK1402040/6050Present (PI)0.2Not performedparticles11Polyimide125TiO2VYLON GK1402015/8550Present (PI)0.2Not performed12Polyimide125—VYLON GK14020 0/10050Present (PI)0.2Not performed13Polyimide125TiO2VYLON GK1402040/6050Present (PI)0.7Not performed14Aluminum500TiO2VYLON GK1402015/8550Absent0.2Not performed15Glass500TiO2VYLON GK1402015/8550Absent0.2Not performed16a-C*2500TiO2VYLON GK1402015/8550Present (a-C)0.2Not performed17Polyimide125TiO2VYLON UR8700−2240/6050Present (PI)0.2Not performed18Polyimide125TiO2N-3022−3840/6050Present (PI)0.2Not performedEvaluations of deposition substrates and scintillator panelsEvaluationsCuttabilityNos.Deposition substratesScintillator panelsSensitivitySharpnessRemarks1⊙⊙1000.63EXAMPLES 1 and 152⊙⊙1020.64EXAMPLES 2 and 163◯◯1010.63EXAMPLES 3 and 174⊙⊙1020.67EXAMPLES 4 and 185XX1000.63COMPARATIVE EXAMPLES 1 and 56XX760.68COMPARATIVE EXAMPLES 2 and 67◯◯850.67EXAMPLES 5 and 198⊙⊙1060.55EXAMPLES 6 and 209⊙⊙1080.43COMPARATIVE EXAMPLES 3 and 710⊙⊙820.61EXAMPLES 7 and 2111⊙⊙960.68EXAMPLES 8 and 2212⊙⊙530.71COMPARATIVE EXAMPLES 4 and 813⊙⊙1010.60EXAMPLES 9 and 2314ΔΔ970.57EXAMPLES 10 and 2415ΔΔ970.59EXAMPLES 11 and 2516ΔΔ950.67EXAMPLES 12 and 2617⊙⊙990.61EXAMPLES 13 and 2718⊙⊙1000.59EXAMPLES 14 and 28*1The numbers of the deposition substrates and the numbers of the scintillator panels (The numbers are common.)*2a-C = amorphous carbon*3LSP = light-scattering particles*4light-scattering particles/binder resin ratio*5VYLON 550, VYLON GK140, VYLON GK600 and VYLON 20SS: amorphous polyester resins manufactured by TOYOBO CO., LTD., VYLON UR8700: polyurethane resin manufactured by TOYOBO CO., LTD., N-3022: polyurethane resin manufactured by NIPPON POLYURETHANE INDUSTRY CO., LTD.Notes:The support made of polyimide (PI) or amorphous carbon also serves as a light-absorbing layer because PI or amorphous carbon is colored. As clear from the results illustrated in Table 5, EXAMPLES in accordance with the invention achieved excellent cuttability without deteriorations in sharpness or sensitivity compared to COMPARATIVE EXAMPLES. 10: SCINTILLATOR PANEL 1: SUPPORT 2: SCINTILLATOR LAYER 2a: COLUMNAR PHOSPHOR CRYSTAL 3: REFLECTIVE LAYER 61: MIDDLE LINE 62: LIGHT-SCATTERING PARTICLE 63: BINDER RESIN 81: DEPOSITION APPARATUS 82: VACUUM CONTAINER 83: VACUUM PUMP 84: DEPOSITION SUBSTRATE 85: HOLDER 86: ROTATING MECHANISM 87: ROTATING SHAFT 88 (88a and 88b): DEPOSITION SOURCES 89: SHUTTER 29: FEED STEP 39: APPLICATION STEP 49: DRYING STEP 59: HEAT TREATMENT STEP 69: RECOVERY STEP 79: DRYING STEP 109: PRODUCTION APPARATUS 201: SUPPORT 202: ROLL OF SUPPORT WOUND AROUND CORE 301: BACKUP ROLL 302: APPLICATION HEAD 303: VACUUM CHAMBER 304: APPLICATOR 401: DRYER 402: INLET 403: OUTLET 801: DRYER 802: INLET 803: OUTLET 501: HEAT TREATMENT APPARATUS 502: HEAT TREATMENT GAS INLET 503: OUTLET 601: RECOVERED ROLL OF SUPPORT WOUND AROUND CORE a: CONVEYOR ROLL b: CONVEYOR ROLL c: CONVEYOR ROLL d: CONVEYOR ROLL 32: DICING APPARATUS 221: GROOVE 321: BLADE 321a: ROTATIONAL SHAFT 322: DICING TABLE 323: NOZZLE 324: SUPPORT MEMBER 33: LASER CUTTING APPARATUS 331: LASER BEAM GENERATOR 332: SUPPORT TABLE 333: PURGE CHAMBER 334: DISCHARGE PIPE 335: TRANSLUCENT WINDOW 50: DEPOSITION APPARATUS 551: VAPORIZATION CHAMBER 552: PYROLYSIS CHAMBER 553: DEPOSITION CHAMBER 553a: INLET 553b: OUTLET 553c: TURNTABLE (DEPOSITION TABLE) 554: COOLING CHAMBER 555: EVACUATION SYSTEM 512: DEPOSITION OF PROTECTIVE LAYER (POLYPARAXYLYLENE FILM) 100: RADIOGRAPHIC IMAGE DETECTOR 51: IMAGING PANEL 52: CONTROL SECTION 53: MEMORY SECTION 54: POWER SUPPLY SECTION 55: HOUSING 56: CONNECTOR 57: OPERATION SECTION 58: DISPLAY SECTION 20: OUTPUT SUBSTRATE 20a: SEPARATOR FILM 20b: LIGHT-RECEIVING ELEMENT 20c: IMAGE SIGNAL OUTPUT LAYER 20d: BASE 21: TRANSPARENT ELECTRODE 22: CHARGE GENERATION LAYER 23: COUNTER ELECTRODE 24: CAPACITOR 25: TRANSISTOR |
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claims | 1. A method of providing a repair to a hazardous waste canister (HWC) having a perimeter wall with an outer surface, the HWC being received in a chamber defined by an inner surface of an overpack container, the method comprising:providing an application system including:a cold spray apparatus configured to generate a high-pressure gas flow carrying particles, the cold spray apparatus including a nozzle having an outlet from which a stream of gas and powder particles exits the cold spray apparatus; anda mobile applicator apparatus configured to carry at least the nozzle of the cold spray apparatus to a cold spray application site, the mobile applicator apparatus including a mobile base with a frame and a plurality of wheels rotatably mounted on the frame;positioning the nozzle of the cold spray apparatus in a gap between the outer surface of the perimeter wall of the HWC and the inner surface of the overpack container by at least one wheel of the plurality of wheels holding the mobile applicator apparatus against one of the surfaces forming the gap;emitting a substantially linear flow of particles of a powder from the nozzle of the cold spray apparatus toward an area in the compromised region of the outer surface of the perimeter wall to impact the particles of the powder against the area of the outer surface of the perimeter wall in a manner effective to cause the particles of the powder to bond to the outer surface of the perimeter wall to produce a coating on the area of the outer surface of the perimeter wall; andoperating the mobile applicator apparatus to move the nozzle of the cold spray apparatus and the substantially linear flow of particles emitted from the nozzle in a direction substantially parallel to the outer surface of the perimeter wall to cause the particles of the powder to impact an additional area of the outer surface of the perimeter wall to cause the particles of the powder to bond to the additional area of the outer surface of the perimeter wall and create a substantially continuous coating in an extended area which includes the area and the additional area of the outer surface of the perimeter wall. 2. The method of claim 1 additionally comprising:impacting the substantially linear flow of particles of the powder sprayed from the nozzle of the cold spray apparatus against the area in the compromised region of the outer surface of the perimeter wall in a manner effective to cause the particles of the powder to remove material from the outer surface of the perimeter wall prior to material deposition on the outer surface of the perimeter wall; andmoving the nozzle of the cold spray apparatus in the gap with respect to the outer surface of the perimeter wall from one position adjacent to the compromised region of the outer surface of the perimeter wall to another position adjacent to the compromised region of the outer surface of the perimeter wall to thereby cause the particles of the powder to impact the additional area of the compromised region of the outer surface of the perimeter wall and remove material from the outer surface of the additional area of the compromised region of the perimeter wall. 3. The method of claim 1 wherein the compromised region of the outer surface of the perimeter wall of the canister comprises a portion of the outer surface of the perimeter wall which exhibits damage to the perimeter wall. 4. The method of claim 1 wherein the compromised region of the outer surface of the perimeter wall the canister includes a portion of the outer surface of the perimeter wall which exhibits at least one characteristic selected from the group of corrosion, cracking, stress corrosion cracking, fretting, wear, scratching, pitting, and chlorine induced stress corrosion cracking. 5. The method of claim 1 wherein the compromised region includes at least one of a welded joint, a heat affected area of a welded joint, and a portion of the outer surface of the perimeter wall susceptible to corrosion and stress corrosion cracking. 6. The method of claim 5 wherein impacting the substantially linear flow of the particles of the powder against the extended area of the outer surface of the perimeter wall is performed in a manner creating compressive residual stress in the extended area of the outer surface of the HWC. 7. The method of claim 1 including selecting a material for the particles of the powder that is less susceptible to corrosion damage than a material forming the outer surface of the perimeter wall of the HWC. 8. The method of claim 1 wherein impacting the substantially linear flow of the particles of the powder against the extended area of the outer surface of the perimeter wall is performed prior to positioning waste material in an interior of the HWC. 9. The method of claim 1 wherein impacting the substantially linear flow of the particles of the powder against the extended area of the outer surface of the perimeter wall is performed while waste material is positioned in an interior of the HWC. 10. The method of claim 1 wherein the cold spray apparatus further includes:elements for generating the high-pressure gas flow carrying the particles of the flow, the elements being positioned outside of the overpack container; anda conduit extending between the elements and the nozzle carried on the mobile applicator apparatus positioned in the gap to provide the nozzle with the high-pressure gas flow carrying the particles. 11. The method of claim 1 wherein the mobile applicator apparatus further includes:a motivating element operatively connected to the at least one wheel of the plurality of wheels to rotate the at least one wheel and cause movement of the mobile base in the gap between the outer surface of the perimeter wall of the HWC and the inner surface of the overpack container. 12. The method of claim 1 wherein the at least one wheel of the plurality of wheels of the mobile applicator apparatus is magnetic in character. 13. The method of claim 2 wherein impacting the particles of the powder against the area of the outer surface of the perimeter wall to cause removal of material from the outer surface of the perimeter wall is performed at a first velocity; andwherein impacting the particles of the powder against the area of the outer surface of the perimeter wall to cause bonding of the particles to the outer surface of the perimeter wall is performed at a second velocity capable of causing cold spray bonding of the particles to the outer surface of the perimeter wall; andwherein the first velocity is lower relative to the second velocity. 14. The method of claim 1 wherein said moving includes moving the nozzle in portions of the gap located between the top and bottom of the HWC. 15. A method of forming a coating on a hazardous waste canister (HWC) positioned in a chamber of an overpack container, the chamber of the overpack container being defined by an inner surface of the overpack container, the HWC having a perimeter wall with an outer surface positioned in opposition to the inner surface of the overpack container to define an annular gap between the outer surface of the perimeter wall and the inner surface of the overpack container, the gap extending from a bottom of the HWC to a top of the HWC, the method comprising:providing an application system including:a cold spray apparatus configured to generate a high-pressure gas flow carrying particles, the cold spray apparatus including a nozzle having an outlet from which a stream of gas and powder particles exits the cold spray apparatus; anda mobile applicator apparatus configured to carry at least the nozzle of the cold spray apparatus, the mobile applicator apparatus including a mobile base with a frame and a plurality of wheels rotatably mounted on the frame to contact and traverse the outer surface of the perimeter wall of the HWC;accessing the outer surface of the perimeter wall of the HWC by positioning the mobile applicator apparatus in the annular gap between the outer surface of the perimeter wall of the HWC and the inner surface of the overpack container;identifying a compromised region on the outer surface of the perimeter wall of the canister for material application to the outer surface of the perimeter wall;positioning the nozzle of the cold spray apparatus in the annular gap between the inner surface of the overpack container and the outer surface of the perimeter wall of the HWC at a first position adjacent to the compromised region of the outer surface of the perimeter wall;emitting, at the first position of the nozzle in the annular gap, a substantially linear flow of particles of a powder from the nozzle of the cold spray apparatus toward an area in the compromised region of the outer surface of the perimeter wall to impact the particles of the powder against the area in a manner effective to cause the particles of the powder to bond to the outer surface of the perimeter wall to produce a coating on the area of the compromised region of the outer surface of the perimeter wall; andmoving the nozzle of the cold spray apparatus in the gap with respect to the outer surface of the perimeter wall from the first position to a second position adjacent to the compromised region of the outer surface of the perimeter wall;emitting, at the second positon of the nozzle in the annular gap, a substantially linear flow of particles of the powder from the nozzle of the cold spray apparatus toward an additional area in the compromised region of the outer surface of the perimeter wall to impact the particles of the powder against the additional area in a manner effective to cause the particles of the powder to bond to the additional area of the outer surface of the perimeter wall to produce a further coating on the additional area of the compromised region of the outer surface of the perimeter wall;wherein said moving of the nozzle of the cold spray apparatus is performed without moving the HWC with respect to the overpack container. 16. The method of claim 15 wherein the step of moving the nozzle of the cold spray apparatus includes moving the substantially linear flow of particles emitted from the nozzle in a direction substantially parallel to the outer surface of the perimeter wall to cause the particles of the powder to impact the additional area of the compromised region of the outer surface of the perimeter wall at the second position to cause the particles of the powder to bond to the outer surface of the additional area of the perimeter wall and create a substantially continuous coating in an extended area which includes the area and the additional area of the compromised region of the outer surface of the perimeter wall. 17. The method of claim 15 wherein the gap between the outer surface of the perimeter wall of the HWC and the inner surface of the overpack container is thin relative to a thickness of a peripheral wall of the overpack container. 18. The method of claim 15 wherein the gap between the outer surface of the perimeter wall of the HWC and the inner surface of the overpack container is substantially uniform in width from a bottom of the HWC to a top of the HWC. 19. The method of claim 15 wherein the overpack container has a vent in communication with the gap between the outer surface of the perimeter wall of the HWC and the inner surface of the overpack container, and additionally including:moving the mobile applicator apparatus through the vent in the overpack to position the mobile applicator with the nozzle of the cold spray apparatus in the gap between the outer surface of the perimeter wall of the HWC and the inner surface of the overpack container. |
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abstract | Among the existent X-ray phase-contrast modalities, grating interferometry appears as a promising technique for commercial applications, since it is compatible with conventional X-ray tubes. However, since applications such as medical imaging and homeland security demand covering a considerable field of view, the fabrication of challenging and expensive large-area gratings would be needed. A scanning setup is a good solution, because it uses cheaper line detectors instead of large-area 2D detectors and would require smaller gratings. In this setup, the phase-retrieval using the conventional phase-stepping approach would be slow, so having a faster method to record the signals becomes fundamental. To tackle this problem, a scanning-mode grating interferometer configuration is used, in which a grating is tilted to form Moire fringes perpendicular to the grating lines. The sample is then translated along the fringes, so each line detector records a different phase step for each slice of the sample. |
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summary | ||
abstract | Disclosed is a medical particle irradiation apparatus comprising a rotating gantry 1 including an irradiation unit 4 emitting particle beams; an annular frame 16 located within and supported by the rotating gantry 1 such that it can rotate relative to the rotating gantry 1; an annular frame 15 fixedly located opposite the annular frame 16; an anti-corotation mechanism 34 being in contact with both the annular frames 16 and 15 to prevent the annular frame 16 from rotating together with the rotating gantry 1 during rotation of the rotating gantry 1; and a flexible moving floor 17 interposed between the annular frames 15 and 16, the flexible moving floor 17 being engaged with the annular frames 15 and 16 in such a manner as to move freely such that its bottom is substantially level and that it moves as the rotating gantry rotates. |
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055043445 | description | DESCRIPTION OF PREFERRED EMBODIMENTS Referring now more specifically to the drawings, FIGS. 1 and 2 are intended to schematically represent a typical radiation source containment vessel or container 10 and a closure or sealing unit 12 for an access opening or port 14 within the container 10. As will be recognized, the closure, particularly in the larger more bulky assemblies, must be readily assembled to, and removed from, the container 10 by remote and/or robotic means without binding or jamming. This, particularly when considering what might be substantial expansion and contraction of the two components 10 and 12, necessitates what, with regard to radiation flow, comprises a substantial gap between the peripheral walls of the container and closure. The radiation shield 16 of the invention reduces radiation streaming from the generated isotropic radiation flux of a source within the container 10 to a degree substantially beyond what has heretofore been achieved by conventional shield member interface configurations. The radiation shield 16 of the invention restricts, and in fact prevents laterally dispersed or angled photon flow from the radiation source outwardly through the gap, and limits the flow to only those photons which are collimated. This is achieved by providing each of the surfaces defined by the peripheral wall of the port 14 and the peripheral wall of the closure 12 with a series of alternating ridges 18 and grooves or valleys 20 uniformly configured for a complementary and mating engagement of the port wall surface with the closure wall surface. As suggested in the drawings, the respective heights and depths of the ridges and valleys are such as to provide for a substantial interdigitation or mating interlock whereby no unimpeded lateral, i.e., non-collimated photon, flow within the formed gap is possible, notwithstanding substantial gap tolerances and variations thereof due to expansion and contraction as required by the nature of the components. The relationship between the interdigitated surfaces will be readily apparent from the enlarged cross-sectional details of the principal trigonal interface of FIGS. 7 and 8 and the alternate configurations of FIGS. 9, 10 and 11 which respectively illustrate a rectangular interface, a circular interface and a parabolic interface. As previously indicated, FIG. 5 schematically illustrates the unimpeded photon flow between opposed planar surfaces of a conventional shield interface. In contrast, the schematic illustration of the radiation shield 16 of the invention, as illustrated in FIG. 7, clearly demonstrates the effectiveness of the shield wherein photons other than those few specifically collimated relative to the ridges 18 and valleys 20, will encounter immediately adjacent ridges for collision with and absorption by the material, e.g., steel, of the ridges and valleys at the point of engagement therewith before reaching the target point. Due to minimal reflection of photons, e.g., an albedo in the order of 1%, and continued collision and absorption, the streaming of photons outwardly of the source container will be substantially eliminated. With continued reference to the schematic illustration of FIG. 7, it will be appreciated that the greater the length of the radiation shield in the direction from a radiation source in the container to ambient, the greater the likelihood of collision with and thus absorption of photons within the ridges with corresponding reduction of streaming by any photons other than those exactly collimated or paralleling the interdigitated ridges and valleys. Referring again to the exemplary embodiment of FIG. 2 with respect to a containing vessel 10, it will be recognized that the parallel ridges and valleys of the radiation shield 16, extending parallel to the direction of movement of the closure 12 relative to the containing vessel 10, allow for a smooth unimpeded engagement of the closure and subsequent removal of the closure. As desired, appropriate locating means, stops or the like can be provided to define or limit inward travel of the closure within the containing vessel. For example, a prior art stepped shield, as in FIG. 3, can be used in conjunction with the radiation shield of the invention both to provide a locating means and to even further enhance the efficiency of the shielding effect. In such a combination of shield configurations, as suggested in FIG. 13, it will be appreciated that the ridge and valley shield of the invention will be defined between all opposed parallel faces of the container and closure surfaces. Referring to FIG. 12, the triagonal interface therein has been illustrated with ridge and valley angles of 90 degrees. This particular geometry results in a situation where the gap between the shield surfaces is only 70.7% of the "tolerance" distance between shield sections. This means that the tolerance difference between sections can be 41.4% greater than the gap set. This is an important advantage as one wants to reduce the gap as much as possible to restrict the radiation streaming, while at the same time increase the tolerance distance as much as possible to accommodate changes such as the thermal expansion of the components, and also to compensate for manufacturing intolerances. If the 90 degree angle is increased or decreased, this particular advantage will decline until the gap is equal to the tolerance distance. From the foregoing, it will be recognized that a significant advance has been made with regard to radiation shielding within necessarily occurring joinder gaps. The enhanced photon absorption effectiveness, and thus anti-streaming characteristic, is achieved without interference with the ability of the components to be assembled and disassembled in the conventional manner, such normally being effected remotely in a secured environment, possibly by robotic means which necessitates a degree of tolerance between the components sufficient to avoid jamming or misalignment. The shield of the invention effectively eliminates radiation streaming other than that which is collimated or travelling strictly in a linear direction along the interdigitated ridges and valleys. When optionally combined with a stepped shield interface, as suggested in FIG. 13, the minuscule streaming of remaining collimated photon flow can itself be further reduced, if not in fact practically eliminated. The foregoing described embodiments of the ridge and valley shield are illustrative of the invention. As other embodiments incorporating the inventive features may occur to those skilled in the art, the disclosed embodiments are not to be considered as a limitation on the scope of the invention. |
052672913 | claims | 1. In a fuel bundle for a boiling water nuclear reactor, including a plurality of side-by-side vertically disposed sealed nuclear fuel rods, said fuel rods arrayed in a square section, a lower tie plate for supporting said fuel rods and permitting the entrance of water moderator to said fuel bundle between said fuel rods, an upper tie plate with at least some of the fuel rods fastened thereto and permitting the exit of water and generated steam from said fuel bundle, a plurality of vertically separated spacers surrounding each said fuel rod at the elevation of said spacer to hold said fuel rods in designed spaced apart relation as a unitary mass at the elevation of said spacers, each said spacer including a peripheral band having four sides, each of said sides corresponding to one of said sides of said square section, and a channel surrounding said lower tie plate, said upper tie plate and said fuel rods and spacers there between, said channel defining a complimentary and larger square section with respect to said square section of said square array of fuel rods, said channel during operation of said reactor defining a flow boundary between a core bypass region containing water moderator on the outside and a steam generating flow path through said fuel bundle between said tie plates on the inside, the improvement to the peripheral band of at least one spacer for maintaining required spatial separation between said fuel rods and channel for neutron moderation and steam generation comprising: two first adjacent spacer sides defining at least two full dimension outward protrusions occupying the entire interval necessary to maintain the fuel rods adjacent all four sides at their full optimal spacing from the interior channel walls whereby said fuel rods adjoining said two adjacent spacer sides are maintained at an optimal spacing from said channel wall to assure optimum neutron moderation and moderator flow around said fuel rods to maintain optimum critical power on fuel rods adjacent said channel; two second and remaining adjacent spacer sides defining lesser dimension outward protrusions occupying a sufficient and lesser interval to prevent inadvertent closing of the fuel rods adjacent said second and remaining adjacent spacer sides to the channel sides beyond said lesser interval, said lesser interval chosen to provide the peripheral fuel rods adjacent said second and remaining spacer sides with adequate clearance from said channel wall to maintain a safe level of neutron moderation and avoid a worst case critical power limitation; and spring means on said two second and remaining adjacent sides of the peripheral spacer band acting on the channel wall given sufficient force to bias the fuel rod matrix at the spacer away from the channel wall at said two second and remaining adjacent sides to register the full dimension outward protrusions at the first and adjacent spacer sides to the channel wall at the opposite sides of the spacer whereby said fuel rods adjoining said all spacer sides are maintained at an optimal spacing from said channel wall to assure optimum neutron moderation and moderator flow around said fuel rods to maintain optimum critical power on fuel rods adjacent said channel. a plurality of side-by-side sealed vertically disposed nuclear fuel rods, said fuel rods arrayed in a square section; a lower tie plate for supporting said fuel rods and permitting the entrance of water moderator to said fuel bundle between said fuel rods; an upper tie plate with at least some of the fuel rods fastened thereto and permitting the exit of water and generated steam from said fuel bundle; a plurality of vertically separated spacers surrounding each said fuel rod at the elevation of said spacer to hold said fuel rods in designed spaced apart relation as a unitary mass at the elevation of said spacers, each said spacer including a peripheral band having four adjacent sides; and, a channel surrounding said lower tie plate, said upper tie plate and said fuel rods and spacers there between, said channel defining a complimentary and larger square section with respect to said square section of said square array of fuel rods, said channel during operation of said reactor defining a flow boundary between a core bypass region containing water moderator on the outside and a steam generating flow path through said fuel bundle between said tie plates on the inside; the peripheral band of at least one spacer having two first adjacent spacer sides defining at least two full dimension outward protrusions occupying the entire interval necessary to maintain the fuel rods adjacent all four sides at their full optimal spacing from the interior channel walls whereby said fuel rods adjoining said two adjacent spacer sides are maintained at an optimal spacing from said channel wall to assure optimum neutron moderation and moderator flow around said fuel rods to maintain optimum critical power on fuel rods adjacent said channel; said peripheral band further including two second and remaining adjacent spacer sides defining lesser dimension outward protrusions occupying a sufficient and lesser interval to prevent inadvertent closing of the fuel rods adjacent said second and remaining adjacent spacer sides to the channel sides beyond said lesser interval, said lesser interval chosen to provide the peripheral fuel rods adjacent said second and remaining spacer sides with adequate clearance from said channel wall to maintain a safe level of neutron moderation and avoid a worst case critical power limitation; and, spring means on said two second and remaining adjacent sides of the peripheral spacer band acting on the channel wall given sufficient force to bias the fuel rod matrix at the spacer away from the channel wall at said two second and remaining adjacent sides to register the full dimension outward protrusions at the first and adjacent spacer sides to the channel wall at the opposite sides of the spacer whereby said fuel rods adjoining said all spacer sides are maintained at an optimal spacing from said channel wall to assure optimum neutron moderation and moderator flow around said fuel rods to maintain optimum critical power on fuel rods adjacent said channel. a spacer body for placement at a selected elevation between said tie plates, said spacer body for defining about each said fuel rod at a spacer position between said tie plates separation between said fuel rods for maintaining said fuel rods in designed side-by-side relation; each said spacer including a square sectioned peripheral band having four sides; two first adjacent spacer sides defining at least two full dimension outward protrusions occupying the entire interval necessary to maintain the fuel rods adjacent all four sides at their full optimal spacing from the interior channel walls whereby said fuel rods adjoining said two adjacent spacer sides are maintained at an optimal spacing from said channel wall to assure optimum neutron moderation and moderator flow around said fuel rods to maintain optimum critical power on fuel rods adjacent said channel; two second and remaining adjacent spacer sides defining lesser dimension outward protrusions occupying a sufficient and lesser interval to prevent inadvertent closing of the fuel rods adjacent said second and remaining adjacent spacer sides to the channel sides beyond said lesser interval, said lesser interval chosen to provide the peripheral fuel rods adjacent said second and remaining spacer sides with adequate clearance from said channel wall to maintain a safe level of neutron moderation and avoid a worst case critical power limitation; and spring means on said two second and remaining adjacent sides of the peripheral spacer band acting on the channel given sufficient force to bias the fuel rod matrix at the spacer away from the channel wall at said two second and remaining adjacent sides to register the full dimension outward protrusions at the first and adjacent spacer sides to the channel wall at the opposite sides of the spacer whereby said fuel rods adjoining said all spacer sides are maintained at an optimal spacing from said channel wall to assure optimum neutron moderation and moderator flow around said fuel rods to maintain optimum critical power on fuel rods adjacent said channel. 2. The fuel bundle of claim 1 wherein said spring means includes a leaf spring. 3. The fuel bundle of claim 2 and wherein said leaf spring is placed adjacent the corner of said channel. 4. The fuel bundle of claim 1 and wherein each peripheral band at said remaining sides includes paired spring means. 5. A fuel bundle for a boiling water nuclear reactor, comprising: 6. The fuel bundle of claim 5 and wherein said spring means includes a leaf spring. 7. The fuel bundle of claim 6 and wherein said leaf spring is placed adjacent the corner of said channel. 8. In a spacer for fuel bundle for a boiling water nuclear reactor fuel bundle, said fuel bundle including a plurality of side-by-side vertically disposed sealed nuclear fuel rods, said fuel rods arrayed in a square section, a lower tie plate for supporting said fuel rods and permitting the entrance of water moderator to said fuel bundle between said fuel rods, and upper tie plate with at least some of the fuel rods fastened thereto and permitting the exit of water and generated steam from said fuel bundle, a channel surrounding said lower tie plate, said upper tie plate and said fuel rods and spacers there between, said channel defining a complimentary and larger square section with respect to said square section of said square array of fuel rods, said channel during operation of said reactor defining a flow boundary between a core bypass region containing water moderator on the outside and a steam generating flow path through said fuel bundle between said tie plates on the inside, said spacer comprising: 9. The fuel bundle of claim 8 and wherein each peripheral band at said remaining sides includes paired spring means. |
048896632 | claims | 1. A method of manufacturing sintered pellets, comprising the steps of: preparing fine UO.sub.2 powder by dry conversion of UF.sub.6 ; manufacturing reactive U.sub.3 O.sub.8 powder having a grain size less than 350 .mu.m by oxidation in air of part of the UO.sub.2 as obtained by dry conversion, at a temperature less than 800.degree. C.; preparing an intimate mixture of said UO.sub.2 powder and of a proportion of from 5% to 25% by weight of said reactive U.sub.3 O.sub.8 powder; cold compressing the mixture into green pellets; and sintering said green pellets. 2. Method according to claim 1, wherein the oxidation temperature is between 250.degree. C. and 350.degree. C. 3. Method according to claim 2, wherein the mixture additionally contains one at least of the elements Pu, Th and Gd in dioxide form and Gd as Gd.sub.2 O.sub.3. 4. Method according to claim 1, wherein sintering is carried out at a temperature of from 1200.degree. C. to 1300.degree. C. in a slightly oxidizing atmosphere. 5. Method according to claim 1, wherein said intimate mixture is granulated by precompression and crushing into grains prior to said cold compressing of said mixture into pellets. 6. A method of manufacturing sintered nuclear fuel pellets, comprising the steps of: preparing fine UO.sub.2 by dry conversion of UF.sub.6 ; manufacturing reactive U.sub.3 O.sub.8 powder having a grain size less than 350 .mu.m by oxidation in air of part of said UO.sub.2 powder at a temperature between 250.degree. C. and 350.degree. C.; preparing an intimate mixture of said UO.sub.2 powder and a proportion of from 5 to 25% by weight of said reactive U.sub.3 O.sub.8 powder; cold compressing the mixture into green pellets; and sintering said green pellets at a temperature between 1500.degree. and 1800.degree. C. in a reducing atmosphere. |
abstract | An apparatus for inspecting overlapping figures includes a chip overlap inspection unit configured to input a data file on each chip of a plurality of chips arranged in a writing pattern, and inspect an existence of an overlap between a plurality of chips, based on arrangement data on each region of the plurality of chips, a setting unit configured to set, with respect to the plurality of chips, a plurality of hierarchies and a plurality of cell regions of each of the plurality of hierarchies, an extraction unit configured to extract, with respect to a plurality of chips where the overlap occurs, a cell region where the overlap is located, from a higher hierarchy level to a lower hierarchy level in order, a figure overlap judging unit configured to judge an existence of an overlap between a figure in the cell region extracted and a figure in the other cell region extracted, and an output unit configured to output data on a plurality of figures overlapping. |
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description | This application is a divisional of U.S. application Ser. No. 13/724,474, filed Dec. 21, 2012, the entire contents of which is incorporated herein by reference. Example embodiments relate generally to nuclear Boiling Water Reactors (BWRs), and more particularly to a system and a method for injecting hydrogen into reactor support systems during periods of reactor startup and shutdown. The system is capable of providing hydrogen at variable pressures (including high pressures of about 1,100 psig) in order to match the changing operating pressures of the support systems throughout the startup and shutdown modes. Conventionally, Hydrogen Water Chemistry (HWC) systems 1 (see FIG. 1) inject hydrogen into feedwater systems at the suction of the condensate booster pumps or at the suction of the feedwater pumps (see injection point 2) of a Boiling Water Reactor (BWR). Injection of hydrogen into these locations helps mitigate Inter-Granular Stress Corrosion Cracking (IGSCC) in the recirculation piping and reactor internals. Specifically, the injected hydrogen causes a reduction in dissolved oxygen by lowering the radiolytic net production of hydrogen and oxygen in the core region of the reactor. The conventional HWC system 1 includes a hydrogen source 4 which may be a liquid storage tank (with compressors and vaporizers) or bottles of hydrogen. The hydrogen source may also be electrolytically generated. A hydrogen filter 6 may filter the hydrogen prior to the hydrogen passing through a series of valves, which may include a pressure control valve 8, excess flow check valve 11, shutoff valves 10 and bypass valves 12. An air-operated control valve 14 may be used to isolate the hydrogen before entering a hydrogen injection module 16 that discharges hydrogen to conventional hydrogen injection points 2. Purge connections 70 throughout the system 1 are generally used for maintenance and safety purposes. The conventional hydrogen injection points 2 are injection points located in lower-pressure systems (relative to the reactor), such as the suctions of the condensate booster pumps (85-160 psig) and the suctions of the feedwater pumps (400-650 psig). Because the pumps of these lower-pressure systems are not in service during the full reactor startup or shutdown (including emergency reactor shutdown, such as a reactor SCRAM), hydrogen therefore may not be injected at these conventional locations during startup and shutdown, as doing so would not allow hydrogen dissolution for efficient transport to the recirculation piping and/or reactor internals. Because IGSCC corrosion is more prevalent at lower operating temperatures (of about 200° F. to about 450° F., during reactor startup/heat-up to about 5% power), the reactor (and the reactor support systems) is at greater risk during startup and shutdown modes, thereby exacerbating the effects that are caused by an inability to inject hydrogen into the conventional injection points 2 during reactor startup and shutdown modes. Example embodiments provide a startup/shutdown hydrogen injection system (and associated method) for injecting hydrogen into BWR reactor support systems during periods of reactor startup and shutdown. Because the reactor (and the reactor support systems) experience temperatures and pressures that vary greatly as the reactor cycles through startup and shutdown modes (as a result of the reactor heat-up and cool-down), the hydrogen injection system provides hydrogen at a variable pressure that may match the operating pressures of these support systems at any period of time. Because the hydrogen injection system provides hydrogen to reactor support systems that also operate at potentially high pressures, the hydrogen injection system may boost the pressure of hydrogen beyond pressure levels normally associated with conventional HWC systems. Detailed example embodiments are disclosed herein. However, specific structural and functional details disclosed herein are merely representative for purposes of describing example embodiments. Example embodiments may, however, be embodied in many alternate forms and should not be construed as limited to only the embodiments set forth herein. Accordingly, while example embodiments are capable of various modifications and alternative forms, embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that there is no intent to limit example embodiments to the particular forms disclosed, but to the contrary, example embodiments are to cover all modifications, equivalents, and alternatives falling within the scope of example embodiments. Like numbers refer to like elements throughout the description of the figures. It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of example embodiments. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. It will be understood that when an element is referred to as being “connected” or “coupled” to another element, it may be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being “directly connected” or “directly coupled” to another element, there are no intervening elements present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between”, “adjacent” versus “directly adjacent”, etc.). The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises”, “comprising,”, “includes” and/or “including”, when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. It should also be noted that in some alternative implementations, the functions/acts noted may occur out of the order noted in the figures. For example, two figures shown in succession may in fact be executed substantially concurrently or may sometimes be executed in the reverse order, depending upon the functionality/acts involved. FIG. 2 is a P&ID diagram of a startup/shutdown hydrogen injection system 30, in accordance with an example embodiment. The system may include one or more hydrogen sources. For instance, an optional dedicated hydrogen gas source 32 may be provided for the hydrogen injection system 30. The dedicated hydrogen gas source 32 may be small hydrogen gas bottles, a hydrogen gas truck, or liquid storage containing hydrogen. Alternative to a dedicated hydrogen gas source 32 (or, in addition to a dedicated hydrogen gas source 32), a connection 20 may be provided which may connect to an existing HWC system 1 (see optional connection points 20 on FIG. 1, which may, for instance, connect to HWC system 1 either upstream or downstream of air-operated valve 14, and inside or outside of the plant wall). If a connection 20 between an existing HWC system 1 and the startup/shutdown hydrogen injection system 30 is used to supply hydrogen, flow control equipment may be provided on the connection 20. For instance, a pressure control valve 34, a pressure transmitter 36, a local flow indicator 38, a flow control valve 40 and an air-operated valve 42 may be provided in the connection line 20 to control the flowrate and pressure of hydrogen coming from the existing HWC system 1 into the startup/shutdown hydrogen injection system 30. A shutoff valve 44 may also be included to shut-off the flow of hydrogen into the hydrogen injection system 30. Whether a connection between an existing HWC system 1 and the startup/shutdown hydrogen injection system 30 is used, or whether a dedicated hydrogen gas source 32 for the hydrogen injection system 30 is used, a hydrogen filter 46 may be provided to filter hydrogen gas prior to any pressurization of the hydrogen. The hydrogen injection system 30 may further include a hydrogen gas booster 48 that may significantly increase the pressure of hydrogen which is to be injected into hydrogen injection point 50. The hydrogen gas booster 48 may be hydraulic or air-driven (pneumatic), and may be capable of increasing hydrogen pressure to any of a wide range of pressures, varying from about 0 psig to about 1,100 psig. By providing the hydrogen gas booster 48, the hydrogen injection system 30 may provide hydrogen to reactor support systems that experience a reactor water flow (at potentially high operating pressures of about 1,100 psig, and operating temperatures as low as about 200° F. when oxygen concentration in the reactor water is relatively elevated) during reactor startup and/or shutdown conditions (reactor “shutdown” including reactor scrams, hot/standby and/or hot/shutdown modes). For instance, hydrogen injection point 50 may include injections points in reactor support systems such as the reactor water cleanup (RWCU) return line or the feedwater recirculation lines of the BWR. Because these example reactor support systems experience reactor water flow during reactor startup and/or shutdown, and because these systems experience a wide range of pressures as the reactor cycles through startup and/or shutdown, the hydrogen gas booster 48 is particularly well equipped in increasing hydrogen pressure that is appropriate for these example service points. The hydrogen gas booster 48 may be located downstream of the flow controls (including any one of the pressure control valve 34, pressure transmitter 36, flow indicator 38, flow control valve 40 and air operated valve 42), as doing so allows the flow control equipment to be a lower pressure class (and thereby less expensive). The hydrogen gas booster 48 may be pneumatically operated via a plant service air 56 connection. A pressure control valve 58 may be used to control the pressure of service air entering the hydrogen gas booster 48. An air filter may be used to filter the inlet air. Service air shutoff valves 62a/62b may be included in the air inlet line to close the air inlet line (to service the hydrogen gas booster 48, for instance). The hydrogen gas booster 48 may include a air flow control valve 72 to throttle the air flow to the booster to subsequently increase the hydrogen pressure out of the booster 48. The flow control valve 72 may be automatically or manually controlled. A number of system shut-off valves 54a-54g may be provided to manage hydrogen flow through desired portions of the system 30 for added flexibility. For instance, when hydrogen is being injected to systems requiring relatively lower pressure, the hydrogen gas booster 48 may not be required. In such a scenario, if the conventional hydrogen source 4 (FIG. 1) is being used to supply hydrogen to injection point 50, shutoff valves 54c, 54e and 54f may be closed, while shutoff valves 54d and 54g may be opened. Alternatively, dedicated hydrogen gas source 32 may be used to supply lower-pressure hydrogen by closing shutoff valves 54b, 54e and 54f (to bypass hydrogen gas booster 48), and opening shutoff valves 54a, 54c, 54d and 54g to hydrogen in injection point 50. In scenarios where higher-pressure hydrogen service is desired, shutoff valve 54b may be opened, allowing hydrogen from hydrogen source 4 (through opened shutoff valve 54c) or hydrogen source 32 (through opened shutoff valve 54a) to enter the hydrogen gas booster 48. Hydrogen leaving the hydrogen gas booster 48 may be directed to hydrogen injection point 50 through shutoff valves 54e, 54f and 54g. Local pressure indicators 64a-64c may be included to confirm the operating pressure of hydrogen and/or service air within the system. Especially in the case of high pressure hydrogen injection points 50, a check valve 66 may be included in the hydrogen injection line 50 to ensure that fluids from the high pressure systems to not backup into the hydrogen injection system. The startup/shutdown hydrogen injection system 30 may be provided on two separate skids 30a/30b for convenience, with the relatively lower pressure hydrogen equipment being predominantly included on one skid 30a and the relatively higher pressure hydrogen equipment being predominantly included on the other skid 30b. A safety-relief valve 68 may be provided on the hydrogen gas booster 48 to vent hydrogen (to vent line 52) at times when the hydrogen gas booster 48 may become over-pressurized. Purge connections 70 throughout the system 30 may also be provided for maintenance and safety purposes. FIG. 3 is a flowchart of a method of making and using a startup/shutdown hydrogen injection system 30, in accordance with an example embodiment. The method may include a step S80 of fluidly connecting at least one hydrogen source to a BWR reactor support system in operation during periods of reactor startup and/or shutdown. This may be accomplished, for instance, by providing piping or tubing between the hydrogen source and the BWR reactor support system. It should be understood that a support system which is “in operation” during startup and/or shutdown relates to a system which provides a reactor water fluid flow through the system during periods when the reactor is starting up and shutting down (thereby offering a transport medium for the injected hydrogen to then be transported to the recirculation piping and/or reactor internals during startup and/or shutdown modes). The method may further include a step S82 of directing a hydrogen flow from the at least one hydrogen source to the reactor support system. This may be accomplished, for instance, by opening valve connections in piping/tubing located between the hydrogen source and the reactor support system. The opening of the valve(s) may be accomplished via a controller, such as PLC 60 (see FIG. 2). The method may further include a step S84 of regulating a pressure of the hydrogen flow from the at least one hydrogen source to the reactor support system, based on an operating pressure of the reactor support system. Specifically, the pressure of the hydrogen flow may be regulated to match the operating pressure of the reactor support system, with the understanding that the operating pressure may change while the reactor cycles through the startup and/or shutdown modes. The regulating of the pressure of the hydrogen flow may be accomplished via a controller, such as PLC 60 (see FIG. 2), which may compare a measured pressure at hydrogen injection point 50 against measured pressures at the pressure transmitter 36 or pressure indicator 64c (for instance) in order to regulate the pressure of the hydrogen being directed to the hydrogen injection point 50. The hydrogen injection system 1 may include a programmable logic controller (PLC) and/or data acquisition system 60 that may be used to determine the rate and pressure for supplying hydrogen to injection point 50 (based upon a measure of the required injection point 50 pressure). Therefore, the PLC and/or data acquisition system 60 may be in communication with the control hardware shown in both the lower and higher pressure skids 30a/30b (not all connections shown in FIG. 2). The PLC and/or data acquisition system 60 may also control the hydrogen gas booster 48 and any system valves within the hydrogen injection system 30. Example embodiments having thus been described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the intended spirit and scope of example embodiments, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims. |
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062018469 | claims | 1. A method of jacketing a cylindrical body of uranium within an aluminum cylindrical jacket having a cup-shaped body having an open mouth at one end and a plug cap effecting closure at said end comprising the following steps: inserting the cup-shaped aluminum body into a tightly fitting cup-shaped steel sleeve coterminous therewith; flaring slightly the mouth of said cup-shaped body to seal the mouth of the body against the mouth of the sleeve by pressing a metal ball of larger diameter than said bodies into the concentric mouths and thereafter removing the ball; immersing said assembly in a molten bonding bath of aluminum silicon having a silicon content of 11.2 to 11.5 percent at 590-596.degree. C., allowing the aluminum body to fill with molten bonding material; dipping the uranium into the bonding bath; inserting the uranium into the open end of said assembly while under the surface of the bonding bath; inserting the plug cap in the open end of the assembly while under the surface of the bonding bath; removing the complete assembly from the bonding bath; quenching in cold water; and removing the sleeve. 2. A method of jacketing a cylindrical body of fissionable material within a cylindrical aluminum jacket having a cup-shaped body having an open mouth at one end and a plug cap effecting closure at said end comprising the following steps: inserting the cup-shaped body into a tightly fitting cup-shaped sleeve coterminous therewith; flaring slightly the mouth of said cup-shaped body to seal the mouth of the body against the mouth of the sleeve by pressing a metal ball of larger diameter than said bodies into the concentric mouths and thereafter removing the ball; completely submerging said assembly in a molten bonding bath consisting of an alloy of aluminum and silicon, allowing the inner body to fill with molten bonding material; dipping the fissionable body into the bonding bath; inserting the fissionable body into the open end of said assembly while under the surface of the bonding bath; inserting the plug cap in the open end of the assembly while under the surface of the bonding bath; removing the complete assembly from the boding bath; quenching in cold water; and removing the sleeve. 3. A method of jacketing a body of fissionable material within a nonfissionable jacket having a cup-shaped body open at one end and a cap effecting closure at said end comprising the following steps: inserting the cup-shaped body into a tightly fitting cup-shaped sleeve; completely submerging said assembly in a bonding bath of a molten metallic bonding material, allowing the inner body to fill with molten bonding material; dipping the fissionable body into the bonding bath; inserting the fissionable body into the open end of said assembly while under the surface of the bonding bath; closing the open end of the assembly with the cap while under the surface of the bonding bath; removing the complete assembly from the bonding bath; quenching in cold water; and removing the sleeve. 4. In a process of jacketing a body of uranium within, and bonding said body to, an aluminum jacket, the steps of completely submerging the body and the jacket in a bath of molten bonding material consisting of an aluminum-silicon alloy having a silicon content of 11.2 to 11.5 percent at a temperature of 590-596.degree. C., inserting the uranium body into the aluminum jacket, both of said elements being so submerged during substantially all of said insertion, withdrawing the assembly so made from the bath, and solidifying the molten bonding material. 5. In a process of jacketing a body of uranium within, and bonding said body to, an aluminum jacket, the steps of completely submerging the jacket and the body in a bath of molten bonding material consisting of an aluminum-silicon alloy, withdrawing the uranium body from the bath, substantially simultaneously withdrawing a small opening portion of the jacket from the bath to permit viewing thereof, immediately inserting a small portion of the end of the body into said opening, immediately thereafter completely submerging said body and jacket and completing the insertion of the body into the jacket, withdrawing the assembly so made from the bath, and solidifying the molten bonding material. 6. A method of jacketing a body of fissionable material within an aluminum jacket comprising the following steps: completely submerging a jacket, enclosed in a tightly fitting sleeve, the jacket having a flange sealing any clearance between the jacket and the sleeve, in a molten bath consisting of an alloy of aluminum and silicon; inserting the fissionable body into the jacket, said fissionable body and jacket being under the surface of the bath during substantially all of said insertion; removing the assembly from the bonding bath; solidifying the molten bonding material; and removing said sleeve. |
description | This application is a continuation of co-pending U.S. application Ser. No. 11/389,183, filed Mar. 27, 2006 and entitled “APPARATUS FOR GENERATING FOCUSED ELECTROMAGNETIC RADIATION,” which is a continuation of U.S. application Ser. No. 09/786,507, filed May 1, 2001, which is the U.S. national phase of international application PCT/GB1999/002943, filed 6 Sep. 1999, designating the U.S. and claiming priority from GB 9819504.3, filed 7 Sep. 1998, the entire contents of each of which are hereby incorporated by reference. The present invention relates to the generation of electromagnetic radiation and, more particularly, to an apparatus and method of generating focused pulses of electromagnetic radiation over a wide range of frequencies. More particularly it relates to an apparatus and method for generating pulses of non-spherically decaying electromagnetic radiation. The present apparatus and method are based on the emission of electromagnetic radiation by rapidly varying polarisation or magnetisation current distributions rather than by conduction or convection electric currents. Such currents can have distribution patterns that move with arbitrary speeds (including speeds exceeding the speed of light in vacuo), and so can radiate more intensely over a much wider range of frequencies than their conventional counterparts. The spectrum of the radiation they generate could extend to frequencies that are by many orders of magnitude higher than the characteristic frequency of the fluctuations of the source itself. Furthermore, intensities of normal emissions decay at a rate of R−2, where R is the distance from the source. It has been noted, however, that the intensities of certain pulses of electromagnetic radiation can decay spatially at a lower rate than that predicted by this inverse square law (see Myers et al., Phys. World, November 1990, p. 39). The new solution of Maxwell's equations set out below, for example, predicts that the electromagnetic radiation emitted from superluminally, circularly moving charged patterns decays at a rate of R−1. Another example is the electromagnetic radiation emitted from superluminally, rectilinearly moving charged patterns which decays at a rate of R - 2 3 . This emission process can be exploited, moreover, to generate waves which do not form themselves into a focused pulse until they arrive at their intended destination and which subsequently remain in focus only for an adjustable interval of time. It will be widely appreciated that being able to employ such emissions for signal transmission, amongst other applications, would have significant commercial value, given that it would enable the employment of lower power transmitters and/or larger transmission ranges, the use of signals that cannot be intercepted by third parties, and the exploitation of higher bandwidth. The near-field component of the radiation in question has many features in common with, and so can be used as an alternative to, synchrotron radiation. The present invention provides a method and apparatus for generating such emissions. According to the present invention there is provided an apparatus for generating electromagnetic radiation comprising: a polarizable or magnetizable medium; and means of generating, in a controlled manner, a polarisation or magnetisation current with a rapidly moving, accelerating distribution pattern such that the moving source in question generates electromagnetic radiation. The speed of the moving distribution pattern may be superluminal so that the apparatus generates both a non-spherically decaying component and an intense spherically decaying component of electromagnetic radiation. The apparatus may comprise a dielectric substrate, a plurality of electrodes positioned adjacent to the substrate, and the means for applying a voltage to the electrodes sequentially at a rate sufficient to induce a polarised region in the substrate which moves along the substrate with a speed exceeding the speed of light. The dielectric substrate may have either a rectilinear or a circular shape. The wavelength of the generated electromagnetic radiation may be in any range from the radio to a minimum determined only by the lower limit to the acceleration of the source (potentially optical, ultraviolet or even x-ray). Examples of the present invention will now be described with reference to the accompanying drawings, in which: Prior to description of the invention, it is appropriate to discuss the principles underlying it. Bolotovskii and Ginzburg (Soviet Phys. Usp. 15, 184, 1972) and Bolotovskii and Bykov (Sovet Phys. Usp. 33, 477, 1990) have shown that the coordinated motion of aggregates of charged particles can give rise to extended electric charges and currents whose distribution patterns propagate with a phase speed exceeding the speed of light in vacuo and that, once created, such propagating charged patterns act as sources of the electromagnetic fields in precisely the same way as any other moving sources of these fields. That the distribution patterns of these sources travel faster than light is not, of course, in any way incompatible with the requirements of special relativity. The superluminally moving pattern is created by the coordinated motion of aggregates of subluminally moving particles. We have solved Maxwell's equations for the electromagnetic field that is generated by an extended source distribution pattern of this type in the case where the charged pattern rotates about a fixed axis with a constant angular frequency. There are solutions of the homogeneous wave equation referred to, inter alia, as non-diffracting radiation beams, focus wave modes or electromagnetic missiles, which describe signals that propagate through space with unexpectedly slow rates of decay or spreading. The potential practical significance of such signals is clearly enormous. The search for physically realizable sources of them, however, has so far remained unsuccessful. Our calculation pinpoints a concrete example of the sources that are currently looked for in this field by establishing a physically tenable inhomogeneous solution of Maxwell's equations with the same characteristics. Investigation of the present emission process was originally motivated by the observational data on pulsars. The radiation received from these celestial sources of radio waves consists of highly coherent pulses (with as high a brightness temperature as 1030° K) which recur periodically (with stable periods of the order of 1 sec). The intense magnetic field (˜1012 G) of the central neutron star in a pulsar affects a coupling between the rotation of this star and that of the distribution pattern of the plasma surrounding it, so that the magnetospheric charges and currents in these objects are of the same type as those described above. The effect responsible for the extreme degree of coherence of the observed emission from pulsars, therefore, may well be the violation of the inverse square law that is here predicted by our calculation. The present analysis is relevant also to the mathematically similar problem of the generation of acoustic radiation by supersonic propellers and helicopter rotors, although this is not discussed in detail here. We begin by considering the waves that are emitted by an element of the distribution pattern of the superluminally rotating source from the standpoint of geometrical optics. Next, we calculate the amplitudes of these waves, i.e. the Green's function for the problem, from the retarded potential. We then specify the bifurcation surface of the observer and proceed to calculate the electromagnetic radiation arising from an extended source with a superluminally moving distribution pattern. The singularities of the integrands of the radiation integrals that occur on the bifurcation surface are here handled by means of the theory of generalised functions: the electric and magnetic fields are given by the Hadamard's finite parts of the divergent integrals that result from differentiating the retarded potential under the integral sign. The theory is then concluded with a descriptive account of the analysed emission process in more physical terms, the description of examples of the apparatus, and an outline of the applications of the invention. Consider a point source (an element of the propagating distribution pattern of a volume source) which moves on a circle of radius r with the constant angular velocity ωêz, i.e. whose path x(t) is given, in terms of the cylindrical polar coordinates (r,φ,z), byr=const., z=const., φ={circumflex over (φ)}+ωt, (1)where êz is the basis vector associated with z, and {circumflex over (φ)} the initial value of φ. The wave fronts that are emitted by this point source in an empty and unbounded space are described by|xP−x(t)|=c(tP−t), (2)where the constant c denotes the wave speed, and the coordinates (xP, tP)=(rP,φP,zP,tP) mark the spacetime of observation points. The distance R between the observation point xP and a source point x is given by x P - x ] ≡ R ( φ ) = [ ( z P - z ) 2 + r P 2 + r 2 - 2 r P r cos ( φ P - φ ) ] 1 2 , ( 3 ) so that inserting (1) in (2) we obtain R ( t ) ≡ [ ( z P - z ) 2 + r P 2 + r 2 - 2 r p r cos ( φ P - φ ^ - ω t ) ] 1 2 = c ( t P - t ) . ( 4 ) These wave fronts are expanding spheres of radii c(tP−t) whose fixed centres (rP=rP,φP={circumflex over (φ)}+ωt,zP=z) depend on their emission times t (see FIG. 1). Introducing the natural length scale of the problem, c/ω and using tP=(φ−{circumflex over (φ)})/ω to eliminate t in favour of φ, we can express (4) in terms of dimensionless variables asg≡φ−φP+{circumflex over (R)}(φ)=φ, (5)in which {circumflex over (R)}≡Rω/c, andφ≡{circumflex over (φ)}−{circumflex over (φ)}P (6)stands for the difference between the positions {circumflex over (φ)}=φ−ωt of the source point and {circumflex over (φ)}p≡φp−ωtp of the observation point in the (r, {circumflex over (φ)}, z)-space. The Lagrangian coordinate {circumflex over (φ)} in (5) lies within an interval of length 2π (e.g. −π<{circumflex over (φ)}≤π), while the angle φ, which denotes the azimuthal position of the source point at the retarded time t, ranges over (−∞, ∞). FIG. 1 depicts the wave fronts described by (5) for fixed values of (r,{circumflex over (φ)},z) and of φ (or tp), and a discrete set of values of φ (or t). [In this figure, the heavier curves show the cross section of the envelope with the plane of the orbit of the source distribution pattern. The larger of the two dotted circles designates the orbit (at r=3c/ω) and the smaller the light cylinder (rp=c/ω).] These wave fronts possess an envelope because when r>c/ω, and so the speed of the source distribution pattern exceeds the wave speed, several wave fronts with differing emission times can pass through a single observation point simultaneously. Or stated mathematically, for certain values of the coordinates (rp, {circumflex over (φ)}p, zp; r, z) the function g(φ) shown in FIG. 2 is oscillatory and so can equal ø at more than one value of the retarded position φ: a horizontal line φ=constant intersects the curve (a) in FIG. 2 at either one or three points. [FIG. 2 is drawn for φp0, {circumflex over (r)}p=3, {circumflex over (r)}=2 and (a) {circumflex over (z)}={circumflex over (z)}p, inside the envelope, (b) {circumflex over (z)}={circumflex over (z)}c, on the cusp curve of the envelope, (c) {circumflex over (z)}=2{circumflex over (z)}c−{circumflex over (z)}p, outside the envelope. The marked adjacent turning points of curve (a) have the coordinates ((φ±, φ±), and φout represents the solution of g(φ)=φ0 for a φ0 that tends to φ− from below.] Wave fronts become tangent to one another and so form an envelope at those points (rp, {circumflex over (φ)}p, zp) for which two roots of g(φ)=φ coincide. The equation describing this envelope can therefore be obtained by eliminating φ between g=φ and ∂g/∂φ=0 Thus, the values of φ on the envelope of the wave fronts are given by∂g/∂φ=1−{circumflex over (r)}{circumflex over (r)}P sin(φP−φ)/{circumflex over (R)}(φ)=0. (7)When the curve representing g(φ) is as in (a) of FIG. 2 (i.e. {circumflex over (r)}>1 and Δ>0), equation this has the doubly infinite set of solutions φ=φ±+2nπ, where φ ± = φ P + 2 π - arccos [ ( 1 ∓ Δ 1 2 ) / ( r ^ r ^ P ) ] , ( 8 ) Δ ≡ ( r ^ P 2 - 1 ) ( r ^ 2 - 1 ) - ( z ^ - z ^ P ) 2 , ( 9 ) n is an integer, and ({circumflex over (r)}, {circumflex over (z)},{circumflex over (r)}p,{circumflex over (z)}p) stand for the dimensionless coordinates rω/c, zω/c, rpcω/c and zpω/c, respectively. The function g(φ) is locally maximum at φ+2nπ and minimum at φ. +2nπ. Inserting φ=φ±(5) and solving the resulting equation for ø as a function of ({circumflex over (r)}p, {circumflex over (z)}p), we find that the envelope of the wave fronts is composed of two sheets: ϕ = ϕ ± ≡ g ( φ ± ) = 2 π - arccos [ ( 1 ∓ Δ 1 2 ) / ( r ^ r ^ P ) ] + R ^ ± , ( 10 ) in which R ^ ± ≡ [ ( z ^ - z ^ P ) 2 + r ^ 2 + r ^ P 2 - 2 ( 1 ∓ Δ 1 2 ) ] 1 2 ( 11 ) are the values of {circumflex over (R)} at φ=φ±. For a fixed source point (r, {circumflex over (φ)}, z), equation (10) describes a tube-like spiralling surface in the (rp, {circumflex over (φ)}p, zp)-space of observation points that extends from the speed-of-light cylinder {circumflex over (r)}p=1 to infinity. [A three-dimensional view of the light cylinder and the envelope of the wave fronts for the same source point (S) as that in FIG. 1 is presented in FIG. 3A (only those parts of these surfaces are shown which lie within the cylindrical volume {circumflex over (r)}p≤9, −2.25≤{circumflex over (z)}p−{circumflex over (z)}≤2.25).] The two sheets φ=φ± of this envelope meet at a cusp. The cusp occurs along the curve ϕ = 2 π - arccos [ 1 / ( r ^ r ^ P ) ] + ( r ^ P 2 r ^ 2 - 1 ) 1 2 ≡ ϕ c , ( 12 a ) z ^ = z ^ P ± ( r ^ P 2 - 1 ) 1 2 ( r ^ 2 - 1 ) 1 2 ≡ z ^ c , ( 12 b ) shown in FIG. 4 and constitutues the locus of points at which three different wave fronts intersect tangentially. [FIG. 4 depicts the segment −15≤{circumflex over (z)}P−{circumflex over (z)}≤15 of the cusp curve of the envelope shown in FIG. 3A. This curve touches—and is tangent to—the light cylinder at the point ({circumflex over (r)}P=1, {circumflex over (z)}P={circumflex over (z)}, φ=φc|{circumflex over (r)}P=1) on the plane of the orbit.] On the cusp curve φ=φc, z=zc, the function g(φ) has a point of inflection [(b) of FIGS. 2] and ∂2g/∂φ2, as well as ∂g/∂φ, and g vanish atφ=φP+2π−arccos [1/({circumflex over (r)}{circumflex over (r)}P)]≡φc, (12c)This, in conjunction with t=(φ−{circumflex over (φ)})/ω, represents the common emission time of the three wave fronts that are mutually tangential at the cusp curve of the envelope. In the highly superluminal regime, where {circumflex over (r)}>>1, the separation of the ordinates φ+ and φ− of adjacent maxima and minima in (a) of FIG. 2 can be greater than 2π. A horizontal line φ=constant will then intersect the curve representing g(φ) at more than three points, and so give rise to simultaneously received contributions that are made at 5, 7, . . . , distinct values of the retarded time. In such cases, the sheet φ− of the envelope (issuing from the conical apex of this surface) undergoes a number of intersections with the sheet φ+ before reaching the cusp curve. We shall be concerned in this paper, however, mainly with source elements whose distances from the rotation axis do not appreciably exceed the radius c/w of the speed-of-light cylinder and so for which the equation g(φ)=φ has at most three solutions. At points of tangency of their fronts, the waves which interfere constructively to form the envelope propagate normal to the sheets φ=φ± (rp, zp) of this surface, in the directions n ^ ± ≡ ( c / ω ) ∇ P ( ϕ ± - ϕ ) = e ^ rp [ r ^ P - r ^ P - 1 ( 1 ∓ Δ 1 2 ) ] / R ^ ± + e ^ φ p / r ^ P + e ^ zp ( z ^ P - z ^ ) / R ^ ± , ( 13 ) with the speed c. (êr p, êφp and êz p are the unit vectors associated with the cylindrical coordinates rp, φp and zp of the observation point, respectively.) Nevertheless, the resulting envelope is a rigidly rotating surface whose shape does not change with time: in the (rp, {circumflex over (φ)}p and zp)-space, its conical apex is stationary at (r, {circumflex over (φ)}, z), and its form and dimensions only depend on the constant parameter {circumflex over (r)}. The set of waves that superpose coherently to form a particular section of the envelope or its cusp, therefore, cannot be the same (i.e. cannot have the same emission times) at different observation times. The packet of focused waves constituting any given segment of the cusp curve of the envelope, for instance, is constantly dispersed and reconstructed out of other waves. This one-dimensional caustic would not be unlimited in its extent, as shown in FIG. 4, unless the source distribution pattern is infinitely long-lived: only then would the duration of the source distribution pattern encompass the required intervals of emission time for every one of its constituent segments. Our discussion has been restricted so far to the geometrical features of the emitted wave fronts. In this section we proceed to find the Lienard-Wechert potential for these waves. The scalar potential arising from a volume element of the moving distribution pattern of the source we have been considering is given by the retarded solution of the wave equation∇′2G0−∂2G0/∂(ct′)2=−4πρ0, (14a)in whichρ0(r′, φ′, z′, t′)=δ(r′−r)δ(φ′−ωt′−{circumflex over (φ)})δ(z′−z)/r′ (14b)is the density of a point source of unit strength with the trajectory (1). In the absence of boundaries, therefore, this potential has the value G 0 ( x P , t P ) = ∫ d 3 x ′ dt ′ ρ 0 ( x ′ , t ′ ) δ ( t P - t ′ - x P - x ′ / c ) / x P - x ′ ( 15 a ) = ∫ - ∞ + ∞ dt ′ δ [ t P - t ′ R ( t ′ ) / c ] / R ( t ′ ) , ( 15 b ) where R(t′) is the function defined in (4) (see e.g. Jackson, Classical Electrodynamics, Wiley, New York 1975). If we use (1) to change the integration variable t′ in (15b) to φ, and express the resulting integrand in terms of the quantities introduced in (3), (5) and (6), we arrive atG0(r, rP, {circumflex over (φ)}−{circumflex over (φ)}P, z−zP)=∫−∞+∞dφδ[g(φ)−φ]/R(φ). (16)This can then be rewritten, by formally evaluating the integral, as G 0 = ∑ φ = φ i 1 R ∂ g / ∂ φ , ( 17 ) where the angles φj are the solutions of the transcendental equation g(φ)=φ in −∞<φ<+∞ and correspond, in conjunction with (1), to the retarded times at which the source point (r, {circumflex over (φ)}, z) makes its contribution towards the value of G0 at the observation point (rp, {circumflex over (φ)}p, zp). Equation (17) shows, in the light of FIG. 2, that the potential G0 of a point source is discontinuous on the envelope of the wave fronts: if we approach the envelope from outside, the sum in (17) has only a single term and yields a finite value for G0, but if we approach this surface from inside, two of the φj s coalesce at an extremum of g and (17) yields a divergent value for G0. Approaching the sheet φ=φ+ or φ=φ− of the envelope from inside this surface corresponds, in FIG. 2, to raising or lowering a horizontal line φ=φ0=const., with φ−≤φ0≤φ+ until it intersects the curve (a) of this figure at its maximum or minimum tangentially. At an observation point thus approached, the sum in (17) has three terms, two of which tend to infinity. On the other hand, approaching a neighbouring observation point just outside the sheet φ=φ− (say) of the envelope corresponds, in FIG. 2, to raising a horizontal line φ=φ0=const., with φ0≤φ− towards a limiting position in which it tends to touch curve (a) at its minimum. So long as it has not yet reached the limit, such a line intersects curve (a) at one point only. The equation g(φ)=φ therefore has only a single solution φ=φout in this case which is different from both φ+ and φ− and so at which ∂g/∂φ is non-zero (see FIG. 2). The contribution that the source distribution pattern makes when located at φ=φout is received by both observers, but the constructively interfering waves that are emitted at the two retarded positions approaching φ. only reach the observer inside the envelope. The function G0 has an even stronger singularity at the cusp curve of the envelope. On this curve, all three of the φjs coalesce [(b) of FIG. 2] and each denominator in the expression in (17) both vanishes and has a vanishing derivative (∂g/∂φ=∂2g/∂φ2=0). There is a standard asymptotic technique for evaluating radiation integrals with coalescing critical points that describe caustics. By applying this technique—which we have outlined in Appendix A—to the integral in (16), we can obtain a uniform asymptotic approximation to G0 for small |φ+−φ−|, i.e. for points close to the cusp curve of the envelope where G0 is most singular. The result is G 0 i n ~ 2 c 1 - 2 ( 1 - χ 2 ) - 1 2 [ p 0 cos ( 1 3 arcsin χ ) - c 1 q 0 sin ( 2 3 arcsin χ ) ] , χ < 1 , ( 18 ) and G 0 out ~ c 1 - 2 ( χ 2 - 1 ) - 1 2 [ p 0 sinh ( 1 3 arc cosh χ ) + c 1 q 0 sgn ( χ ) sinh ( 2 3 arc cosh χ ) ] , χ > 1 , ( 19 ) where c1, p0, q0 and X are the functions of (r, z) defined in (A2), (A5), (A6) and (A10), and approximated in (A23)-(A30). The superscripts ‘in’ and ‘out’ designate the values of G0 inside and outside the envelope, and the variable X equals +1 and −1 on the sheets φ=φ+ and φ=φ− of this surface, respectively. The function G0out is indeterminate but finite on the envelope [cf. (A39)], whereas G0in diverges like 3 c 1 - 2 ( p 0 ∓ c 1 q 0 ) / ( 1 - χ 2 ) 1 2 as χ -> ± 1. The singularity structure of G0in close to the cusp curve is explicitly exhibited by G 0 i n ~ 2 3 1 6 ( ω / c ) ( r ^ 2 r ^ P 2 - 1 ) - 1 2 c 0 1 2 ( z ^ c - z ^ ) 1 2 / [ c 0 3 ( z ^ c - z ^ ) 3 - ( ϕ c - ϕ ) 2 ] 1 2 , ( 20 ) in which 0≤{circumflex over (z)}e−{circumflex over (z)}<<1, |φe−φ|<<1 and c 0 ≡ 2 3 2 3 ( r ^ 2 r ^ P 2 - 1 ) - 1 ( r ^ P 2 - 1 ) 1 2 ( r ^ 2 - 1 ) 1 2 ( 21 ) [see (18) and (A22)-(A26)]. It can be seen from this expression that both the singularity on the envelope (at which the quantity inside the square brackets vanishes) and the singularity at the cusp curve (at which {circumflex over (z)}c−{circumflex over (z)} and φc−φ vanish) are integrable singularities. The potential of a volume source, which is given by the superposition of the potentials G0 of its constituent volume elements, and so involves integrations with respect to (r, {circumflex over (φ)}, z), is therefore finite. Since they are created by the coordinated motion of aggregates of particles, the types of source distribution patterns we have been considering cannot, of course, be point-like. It is only in the physically unrealizable case where the distribution pattern of a superluminal source is point-like that its potential has the extended singularities described above. In fact, not only is the potential of an extended source with a superluminally moving distribution pattern singularity free, but it decays in the far zone like the potential of any other source. The following alternative form of the retarded solution to the wave equation ∇2A0−∂2A0/∂(ct)2=−4πρ[which may be obtained from (15a) by performing the integration with respect to time]:A0=∫d3xρ(x, tP−|x−xP|/c)/|x−xP| (22)shows that if the density ρ of the source is finite and vanishes outside a finite volume, then the potential A0 decays like |xp|−1 as the distance |xp−x|≅|xp| of the observer from the source tends to infinity. Let us now consider an extended source distribution pattern which rotates about the z-axis with the constant angular frequency ω. The density of such a source—when it has a distribution with an unchanging pattern—is given byρ(r,φ,z,t)=ρ(r,{circumflex over (φ)},z), (23)where the Lagrangian variable {circumflex over (φ)} is defined by φ−ωt as in (1), and ρ can be any function of (r, {circumflex over (φ)}, z) that vanishes outside a finite volume. If we insert this density in the expression for the retarded scalar potential and change the variables of integration from (r,{circumflex over (φ)},z,t) to (r,{circumflex over (φ)},z,t), we obtain A 0 ( x P , t P ) = ∫ d 3 xdt ρ ( x , t ) δ ( t P - t - x - x P / c ) / x - x P ( 24 a ) = ∫ rdrd φ ^ dz ρ ( r , φ ^ , z ) G 0 ( r , r P , φ ^ - φ ^ P , z - z P ) , ( 24 b ) where G0 is the function defined in (16) which represents the scalar potential of a corresponding point source. That the potential of the extended source distribution pattern in question is given by the superposition of the potentials of the moving source points that constitute the distribution pattern is an advantage that is gained by marking the space of source points with the natural coordinates (r,{circumflex over (φ)},z) of the source distribution pattern. This advantage is lost if we use any other coordinates. In Sec. II, where the distribution pattern of the source was point-like, the coordinates (r,{circumflex over (φ)},z) of the source point in G0(r, rp, {circumflex over (φ)}−{circumflex over (φ)}p, z−zp) were held fixed and we were concerned with the behaviour of this potential as a function of the coordinates (rp, {circumflex over (φ)}p, zp) of the observation point. When we superpose the potentials of the volume elements that constitute an extended source distribution pattern, on the other hand, the coordinates (rp, {circumflex over (φ)}p, zp) are held fixed and we are primarily concerned with the behaviour of G0 as a function of the integration variables (r, {circumflex over (φ)}, z). Because G0 is invariant under the interchange of (r, {circumflex over (φ)}, z) and (rP, {circumflex over (φ)}P, zP) if φ is at the same time changed to −φ[see (5) and (16)], the singularity of G0 occurs on a surface in the (r, {circumflex over (φ)}, z)-space of source points which has the same shape as the envelope shown in FIG. 3A but issues from the fixed point (rP, {circumflex over (φ)}P, zP) and spirals around the z-axis in the opposite direction to the envelope. [FIG. 5 in which the light cylinder and the bifurcation surface associated with the observation point P are shown for a counterclockwise motion of the source distribution pattern. In this figure P is located at {circumflex over (r)}P=9, and only those parts of these surfaces are shown which lie within the cylindrical volume {circumflex over (r)}≤11, −1.5≤{circumflex over (z)}−{circumflex over (z)}P≤1.5. The two sheets φ=φ±(r,z) of the bifurcation surface meet along a cusp (a curve of the same shape as that shown in FIG. 4) that is tangent to the light cylinder. For an observation point in the far zone ({circumflex over (r)}P>>1), the spiralling surface that issues from P undergoes a large number of turns—in which its two sheets intersect one another—before reaching the light cylinder.] In this paper, we refer to this locus of singularities of G0 as the bifurcation surface of the observation point P. Consider an observation point P for which the bifurcation surface intersects the source distribution pattern, as in FIG. 6. [In FIG. 6, the full curves depict the cross section, with the cylinder {circumflex over (r)}=1.5, of the bifurcation surface of an observer located at {circumflex over (r)}p=3. (The motion of the source distribution pattern is counterclockwise.) Projection of the cusp curve of this bifurcation surface onto the cylinder {circumflex over (r)}=1.5 is shown as a dotted curve, and the region occupied by the source distribution pattern as a dotted area. In this figure the observer's position is such that one of the points (φ=φc, z=zc) at which the cusp curve in question intersects the cylinder {circumflex over (r)}=1.5—the one with zc>0—is located within the source distribution pattern. As the radial position rp of the observation point tends to infinity, the separation—at a finite distance zc−z from ((φc, zc)—of the shown cross sections decreases like r p - 3 2 . ] The envelope of the wave fronts emanating from a volume element of the part of the source distribution pattern that lies within this bifurcation surface encloses the point P, but P is exterior to the envelope associated with an element of the source distribution pattern that lies outside the bifurcation surface. We have seen that three wave fronts—propagating in different directions—simultaneously pass an observer who is located inside the envelope of the waves emanating from a point source, and only one wavefront passes an observer outside this surface. Hence, in contrast to the elements of the source distribution pattern outside the bifurcation surface which influence the potential at P at only a single value of the retarded time, this potential receives contributions from each of the elements inside the bifurcation surface at three distinct values of the retarded time. The elements of the source distribution pattern inside but adjacent to the bifurcation surface, for which G0 diverges, are sources of the constructively interfering waves that not only arrive at P simultaneously but also are emitted at the same (retarded) time. These elements of the source distribution pattern approach the observer along the radiation direction xp−x with the wave speed at the retarded time, i.e. are located at distances R(t) from the observer for which dR dt t = t P - R / c = - c ( 25 ) [see (4), (7) and (8)]. Their accelerations at the retarded time, d 2 R dt 2 t = t P - R / c = ∓ c ωΔ 1 2 R ^ ± , ( 26 ) are positive on the sheet φ=φ− of the bifurcation surface and negative on φ=φ+. The elements of the source distribution pattern on the cusp curve of the bifurcation surface, for which Δ=0 and all three of the contributing retarded times coincide, approach the observer—according to (26)—with zero acceleration as well as with the wave speed. From a radiative point of view, the most effective volume elements of the distribution pattern of the superluminal source in question are those that approach the observer along the radiation direction with the wave speed and zero acceleration at the retarded time, since the ratio of the emission to reception time intervals for the waves that are generated by these particular elements of the source distribution pattern generally exceeds unity by several orders of magnitude. On each constituent ring of the source distribution pattern that lies outside the light cylinder (r=c/ω) in a plane of rotation containing the observation point, there are two volume elements that approach the observer with the wave speed at the retarded time: one whose distance from the observer diminishes with positive acceleration, and another for which this acceleration is negative. These two elements are closer to one another the smaller the radius of the ring. For the smallest of such constituent rings, i.e. for the one that lies on the light cylinder, the two volume elements in question coincide and approach the observer also with zero acceleration. The other constituent rings of the source distribution pattern (those on the planes of rotation which do not pass through the observation point) likewise contain two such elements if their radii are large enough for their velocity rωeφ to have a component along the radiation direction equal to c. On the smallest possible ring in each plane, there is again a single volume element—at the limiting position of the two coalescing volume elements of the neighbouring larger rings—that moves towards the observer not only with the wave speed but also with zero acceleration. For any given observation point P, the efficiently radiating pairs of volume elements on various constituent rings of the source distribution pattern collectively form a surface: the part of the bifurcation surface associated with P which intersects the source distribution pattern. The locus of the coincident pairs of volume elements, which is tangent to the light cylinder at the point where it crosses the plane of rotation containing the observer, constitutes the segment of the cusp curve of this bifurcation surface that lies within the source distribution pattern. Thus the bifurcation surface associated with any given observation point divides the volume of the source distribution pattern into two sets of elements with differing influences on the observed field. As in (18) and (19), the potentials G0in and G0out of the source distribution pattern's elements inside and outside the bifurcation surface have different forms: the boundary |χ(r, rP, {circumflex over (φ)}−{circumflex over (φ)}P, z−zP)|=1 between the domains of validity of (18) and (19) delineates the envelope of wave fronts when the source point (r, {circumflex over (φ)}, z) is fixed and the coordinates (rp, {circumflex over (φ)}p, zp) of the observation point are variable, and describes the bifurcation surface when the observation point (rp, {circumflex over (φ)}p, zp) is fixed and the coordinates (r, {circumflex over (φ)}, z) of the source point sweep a volume. The expression (24b) for the scalar potential correspondingly splits into the following two terms when the observation point is such that the bifurcation surface intersects the source distribution pattern: A 0 = ∫ dV ρ G 0 ( 27 a ) = ∫ V in dV ρ G 0 in + ∫ V out dV ρ G 0 out , ( 27 b ) where dV ≡ rdrd{circumflex over (φ)} dz, Vin and Vout designate the portions of the source distribution pattern which fall inside and outside the bifurcation surface (see FIG. 6), and G0in and G0out denote the different expressions for G0 in these two regions. Note that the boundaries of the volume Vin depend on the position (rp, {circumflex over (φ)}p, zp) of the observer: the parameter {circumflex over (r)}p fixes the shape and size of the bifurcation surface, and the position (rp, {circumflex over (φ)}p, zp) of the observer specifies the location of the conical apex of this surface. When the observation point is such that the cusp curve of the bifurcation surface intersects the source distribution pattern, the volume Vin is bounded by φ=φ., φ=φ+ and the part of the boundary ρ(r, {circumflex over (φ)}, z)=0 of the distribution pattern that falls within the bifurcation surface. The corresponding volume Vout is bounded by the same patches of the two sheets of the bifurcation surface and by the remainder of the boundary of the source distribution pattern. In the vicinity of the cusp curve (12), i.e. for |φc−φ|<<1 and 0≤{circumflex over (z)}c−{circumflex over (z)}<<1, the cross section of the bifurcation surface with a cylinder {circumflex over (r)}=constant is described by ϕ ± - ϕ c ≃ - ( r ^ 2 - 1 ) 1 2 ( r ^ P 2 - 1 ) 1 2 ( r ^ 2 r ^ P 2 - 1 ) - 1 2 ( z ^ c - z ^ ) ± 2 3 2 3 ( r ^ 2 - 1 ) 3 4 ( r ^ P 2 - 1 ) 3 4 ( r ^ P 2 r ^ 2 - 1 ) - 3 2 ( z ^ c - z ^ ) 3 2 ( 28 ) [see (10)-(12) and (A26)]. This cross section, which is shown in FIG. 6, has two branches meeting at the intersections of the cusp curve with the cylinder {circumflex over (r)}=constant whose separation φ—at a given ({circumflex over (z)}c−{circumflex over (z)})—diminishes like r ^ P - 3 2 in the limit {circumflex over (r)}p→∞. Thus, at finite distances {circumflex over (z)}c−{circumflex over (z)} from the cusp curve, the two sheets φ=φ− and φ=φ+ of the bifurcation surface coalesce and become coincident with the surface ϕ = 1 2 ( ϕ - + ϕ + ) ≡ c 2 as r ^ P → ∞ . That is to say, the volume Vin vanishes like r ^ P - 3 2 . Because the dominant contributions towards the value of the radiation field come from those source distribution pattern's elements that approach the observer—along the radiation direction—with the wave speed and zero acceleration at the retarded time, in what follows, we shall be primarily interested in far-field observers the cusp curves of whose bifurcation surfaces intersect the source distribution pattern. For such observers, the Green's function lim r ^ p → ∞ G 0 undergoes a jump discontinuity across the coalescing sheets of the bifurcation surface: the values of X on the sheets φ=φ± and hence the functions G0out|φ=φ− and G0out|φ=φ+ remain different even in the limit where φ=φ− and φ=φ− coincide [cf. (A10) and (A39)]. In this section we begin the calculation of the electric and magnetic fields by finding the gradient of the scalar potential A0, i.e. by calculating the derivatives of the integral in (27a) with respect to the coordinates (rp, {circumflex over (φ)}p, zp) of the observation point. If we regard its singular kernel G0 as a classical function, then the integral in (27a) is improper and cannot be differentiated under the integral sign without characterizing and duly handling the singularities of its integrand. On the other hand, if we regard G0 as a generalized function, then it would be mathematically permissible to interchange the orders of differentiation and integration when calculating .gradient ∇PA0. This interchange results in a new kernel .gradient ∇PG0 whose singularities are non-integrable. However, the theory of generalized functions prescribes a well-defined procedure for obtaining the physically relevant value of the resulting divergent integral, a procedure involving integration by parts which extracts the so-called Hadamard's finite part of this integral (see e.g. Hoskins, Generalised Functions, Ellis Horwood, London 1979). Hadamard's finite part of the divergent integral representing ∇PA0.yields the value that we would have obtained if we had first evaluated the original integral for A0 as an explicit function of (rp, {circumflex over (φ)}p, zp) and then differentiated it. From the standpoint of the theory of generalized functions, therefore, differentiation of (27a) yields∇PA0=∫dVρ∇PG0=(∇PA0)in+(∇PA0)out, (29a)in which(∇PA0)in,out≡∫Vin,outdvρ∇PG0in,out, (29b)Since ρ vanishes outside a finite volume, the integral in (27a) extends over all values of (r,{circumflex over (φ)}, z) and so there is no contribution from the limits of integration towards the derivative of this integral. The kernels ∇PG0in,out of the above integrals may be obtained from (16). Applying ∇P to the right-hand side of (16) and interchanging the orders of differentiation and integration, we obtain an integral representation of ∇PG0 consisting of two terms: one arising from the differentiation of R which decays like rp−2 as rp→∞ and so makes no contribution to the field in the radiation zone, and another that arises from the differentiation of the Dirac delta function and decays less rapidly than rp−2. For an observation point in the radiation zone, we may discard terms of the order of rp−2 and write∇PG0≅(ω/c)∫−∞+∞dφR−1δ′(g−φ){circumflex over (n)}, {circumflex over (r)}P>>1, (30)in which δ′ is the derivative of the Dirac delta function with respect to its argument and{circumflex over (n)}≡êrP[{circumflex over (r)}P−{circumflex over (r)} cos(φ−φP)]/{circumflex over (R)}+êφP/{circumflex over (r)}P+êzP({circumflex over (z)}P−{circumflex over (z)})/{circumflex over (R)}. (31)Equation (30) yields ∇PG0in or .gradient ∇PG0out depending on whether φ lies within the interval (φ−, φ+) or outside it. If we now insert (30) in (29b) and perform the integrations with respect to {circumflex over (φ)} by parts, we find that ( ∇ p A 0 ) in ≃ ( ω / c ) ∫ S rdrdz { - [ ρG 1 in ] ϕ = ϕ - ϕ = ϕ + + ∫ ϕ - ϕ + d ϕ ∂ ρ / ∂ φ ^ G 1 in } , r ^ P ⪢ 1 , ( 32 ) and ( ∇ p A 0 ) out ≃ ( ω / c ) ∫ S rdrdz { [ ρ G 1 out ] ϕ = ϕ - ϕ = ϕ + + ( ∫ - π ϕ - + ∫ ϕ + + π ) d ϕ ∂ ρ / ∂ φ ^ G 1 out } , r ^ P ⪢ 1 , ( 33 ) in which S stands for the projection of Vin onto the (r, z)-plane, and G1in and G1out are given by the values of G 1 = ∫ - ∞ + ∞ d φ R - 1 δ ( g - ϕ ) n ^ = ∑ φ = φ i R - 1 ∂ g / ∂ φ - 1 n ^ ( 34 ) for φ inside and outside the interval (φ−, φ+), respectively. Like G0in, the Green's function G1in diverges on the bifurcation surface φ=φ± where ∂g/∂φ vanishes, but this singularity of G0in is integrable so that the value of the second integral in (32) is finite (see Sec. II and Appendix A). Hadamard's finite part of (∇PA0)in (denoted by the prefix Fp) is obtained by simply discarding those ‘integrated’ or boundary terms in (32) which diverge. Hence, the physically relevant quantity Fp{(∇PA0)in} consists—in the far zone—of the volume integral in (32). Let us choose an observation point for which the cusp curve of the bifurcation surface intersects the source distribution pattern (see FIG. 6). When the dimensions (˜L) of the source are negligibly smaller than those of the bifurcation surface (i.e. when L<<rp and so zc−z<<rp throughout the source distribution pattern) the functions G1in,out in (32) and (33) can be approximated by their asymptotic values (A34) and (A35) in the vicinity of the cusp curve (see Appendix A). According to (A34), (A36) and (A44), G1in decays like p1/c12=O(1) at points interior to the bifurcation surface where lim R P → ∞ χremains finite. since the separation of the two sheets of the bifurcation surface diminishes like r ^ P - 3 2 within the source distribution pattern [see (28)], it therefore follows that the volume integral in (32) is of the order of 1 × r ^ P - 3 2 ,a result which can also be inferred from the far-field version of (A34) by explicit integration. Hence, Fp { ( ∇ P A 0 ) in } = O ( r ^ P - 3 2 ) , r ^ P ⪢ 1 , ( 35 ) decays too rapidly to make any contribution towards the value of the electric field in the radiation zone. Because G1out is, in contrast to G1in, finite on the bifurcation surface, both the surface and the volume integrals on the right-hand side of (33) have finite values. Each component of the second term has the same structure as the expression for the potential itself and so decays like rp−1 (see the ultimate paragraph of Sec. II). But the first term—which would have cancelled the corresponding boundary term in (32) and so would not have survived in the expression for ∇PA0 had the Green's function G1 been continuous—behaves differently from any conventional contribution to a radiation field. Insertion of (A39) in (33) yields the following expression for the asymptotic value of this boundary term in the limit where the observer is located in the far zone and the source distribution pattern is localized about the cusp curve of his (her) bifurcation surface: ∫ rdrdz [ ρ G 1 out ] ϕ - ϕ + ∼ 1 3 c 1 - 2 ∫ rdrdz [ p 1 ( ρ ϕ + - ρ ϕ - ) + 2 c 1 q 1 ( ρ ϕ + - ρ ϕ - ) ] . ( 36 ) In this limit, the two sheets of the bifurcation surface are essentially coincident throughout the domain of integration in (36) [see (28)]. So the difference between the values of the source density on these two sheets of the bifurcation surface is negligibly small ( ∼ r ^ P - 3 2 )for a smoothly distributed source pattern and the functions ρ|φ35 appearing in the integrand of (36) may correspondingly be approximated by their common limiting value ρbs(r, z) on these coalescing sheets. Once the functions ρ|φ± are approximated by ρbs(r, z) and q1 by (A41), equation (36) yields an expression which can be written, to within the leading order in the far-field approximation {circumflex over (r)}p<<1 [see (A44) and (A45)], as ∫ S rdrdz [ ρ G 1 out ] ϕ - ϕ + ∼ 2 3 2 ( c / ω ) 2 r ^ P - 3 2 ∫ r ^ < r ^ > d r ^ ( r ^ 2 - 1 ) - 1 4 n 1 × ∫ z ^ c - L z ^ ω / c z ^ c d z ^ ( z ^ c - z ^ ) - 1 2 ρ bs ( r , z ) ∼ 2 5 2 ( c / ω ) 2 r ^ P - 3 2 ∫ r ^ < r ^ > d r ^ ( r ^ 2 - 1 ) - 1 4 n 1 ( L z ^ ω / c ) 1 2 〈 ρ bs 〉 , ( 37 ) with 〈 ρ bs 〉 ( r ) ≡ ∫ 0 1 d ηρ bs ( r , z ) z = z c - η 2 L z ^ , ( 38 ) where zc−L2(r)≤z≤zc and r<≤r≤r< are the intervals over which the bifurcation surface intersects the source distribution pattern (see FIG. 6). The quantity (ρbs) (r) may be interpreted, at any given r, as a weighted average—over the intersection of the coalescing sheets of the bifurcation surface with the plane z=zc−η2L{circumflex over (z)}→ of the source density ρ. The right-hand side of (37) decays like rp - 3 2 as rp → ∞ . The second term in (33) thus dominates the first term in this equation, and so the quantity (∇PA0)out itself decays like rp−1 in the far zone. Inasmuch as the charge density (23) has an unchanging distribution pattern in the (r, {circumflex over (φ)}, z)-frame, the electric current density associated with the moving source distribution pattern we have been considering is given byj(x,t)=rωρ(r,{circumflex over (φ)},z)êφ, (39)in which rωêφ=rω[− sin(φ−φP)êrP+ cos(φ−φP)êφP] is the velocity of the element of the source distribution pattern that is located at (r, {circumflex over (φ)}, z). This current satisfies the continuity equation ∂ρ/∂(ct)+∇·j=0 automatically. In the Lorentz gauge, the retarded vector potential corresponding to (24a) has the formA(xP,tP)=c−1∫d3xdtj(x,t)δ(tP−t−|x−xP|/c)/|x−xP|. (40)If we insert (39) in (40) and change the variables of integration from (r, φ, z, t) to (r, φ, z, {circumflex over (φ)}), as in (24), we obtainA=∫dV{circumflex over (r)}ρ(r, {circumflex over (φ)}, z)G2(r, rP, {circumflex over (φ)}−{circumflex over (φ)}P, z−zP), (41)in which dV=rdrd{circumflex over (φ)} dz, the vector G2—which plays the role of a Green's function—is given by G 2 ≡ ∫ - ∞ + ∞ d φ e ^ φ δ [ g ( φ ) - ϕ ] / R ( φ ) = ∑ φ = φ j R - 1 ∂ g / ∂ φ - 1 e ^ φ , ( 42 ) and g and φjs are the same quantities as those appearing in (17) (see also FIG. 2). Because (17), (34) and (42) have the factor |∂g/∂φ|−1 in common, the function G2 has the same singularity structure as those of G0 and G1: it diverges on the bifurcation surface ∂g/∂φ=0 if this surface is approached from inside, and it is most singular on the cusp curve of the bifurcation surface where in addition ∂2g/∂φ2=0. It is, moreover, described by two different expressions, G2in and G2out, inside and outside the bifurcation surface whose asymptotic values in the neighbourhood of the cusp curve have exactly the same functional forms as those found in (18) and (19); the only difference being that p0 and q0 in these expressions are replaced by the p2 and q2 given in (A37) (see Appendix A). As in (29), therefore, the time derivative of the vector potential has the form ∂A/∂tP=(∂A/∂tP)in+(∂A/∂tP)out with(∂A/∂tP)in,out≡−ω∫Vin,outdV{circumflex over (r)}ρ∂G2in,out/∂{circumflex over (φ)}P (43)when the observation point is such that the bifurcation surface intersects the source distribution pattern. The functions G2in,out depend on {circumflex over (φ)}p and {circumflex over (φ)} in the combination {circumflex over (φ)}−{circumflex over (φ)}p only. We can therefore replace ∂/∂{circumflex over (φ)}p in (43) by—∂/∂{circumflex over (φ)} and perform the integration with respect to {circumflex over (φ)} by parts to arrive at ( ∂ α / ∂ t p ) in = c ∫ S drdz r ^ 2 { [ ρ G 2 in ] ϕ = ϕ - ϕ = ϕ + - ∫ ϕ - ϕ + d ϕ ∂ ρ / ∂ φ ^ G 2 in } , ( 44 ) and ( ∂ α / ∂ t p ) out = - c ∫ S drdz r ^ 2 { [ ρ G 2 out ] ϕ = ϕ - ϕ = ϕ + + ( ∫ - ϕ - + ∫ ϕ + + ) d ϕ ∂ ρ / ∂ φ ^ G 2 out } . ( 45 ) For the same reasons as those given in the paragraphs following (32) and (33), Hadamard's finite part of (∂A/∂tp)in consists of the volume integral in (44) and is of the order of r ^ p - 3 2 [note that according to (A37) and (A42), p2>>c1q2 and p2/c12=O(i)]. The volume integral in (45), moreover, decays like r ^ p - 1 ,as does its counterpart in (33). The part of ∂A/∂tp that decays more slowly than conventional contributions to a radiation field is the boundary term in (45). The asymptotic value of this term is given by an expression similar to that appearing in (36), except that p1 and q1 are replaced by p2 and q2. Once the quantities and ρ|φ± in the expression in question are approximated by ρbs and by (A42), as before, it follows that ( ∂ α / ∂ t p ) out ~ - c ∫ S drdz r ^ 2 [ ρ G 2 out ] ϕ - ϕ + ∼ - 4 3 c ∫ S drdz r ^ 2 ρ bs c 1 - 1 q 2 ∼ - 2 3 2 3 ( c 2 / ω ) r ^ p - 1 e ^ φp ∫ r ^ < r ^ > d r ^ r ^ 2 ( r ^ 2 - 1 ) - 1 4 ∫ z ^ c - L z ^ ω / c z ^ c d z ^ ( z ^ c - z ^ ) - 1 2 ρ bs . ( 46 ) This behaves like r ^ p - 1 2 .as {circumflex over (r)}p→∞ since the {circumflex over (z)}-quadrature in (46) has the finite value 2 ( L z ^ ω / c ) 1 2 〈 ρ bs 〉 in this limit [see (37) et seq.]. Hence, the electric field vector of the radiation E = - ∇ p A 0 - ∂ α / ∂ ( ct p ) ∼ - c - 1 ( ∂ α / ∂ t p ) out ∼ 2 τ 2 3 ( c / ω ) r ^ p - 1 2 e ^ φ p ∫ r ^ < r ^ > d r ^ r ^ 2 ( r ^ 2 - 1 ) - 1 4 ( L z ^ ω / c ) 1 2 〈 ρ bs 〉 ( 47 ) itself decays like r p - 1 2 in the far zone: as we have already seen in Sec. IV(A), the term ∇PA0 has the conventional rate of decay rp−1 and so is negligible relative to (∂A/∂tp)out. There are no contributions from the limits of integration towards the curl of the integral in (41) because ρ vanishes outside a finite volume and so the integral in this equation extends over all values of (r, {circumflex over (φ)}, z). Hence, differentiation of (41) yieldsB=∇P×A=Bin+Bout, (48a)in whichBin,out≡∫Vin,outdV{circumflex over (r)}ρ∇P×G2in,out. (48b)Operating with ∇P× on the first member of (42) and ignoring the term that decays like rp−2, as in (30), we find that the kernels. ∇P×G2in and ∇P×G2out of (48b) are given—in the radiation zone—by the values of∇P×G2≅(ω/c)∫−∞+∞dφR−1δ′(g−φ){circumflex over (n)}×êφ, {circumflex over (r)}P>>1, (49)for φ inside and outside the interval (φ−, φ+), respectively. [{circumflex over (n)} is the unit vector defined in (31).] Insertion of (49) in (48) now yields expressions whose {circumflex over (φ)}-quadratures can be evaluated by parts to arrive at Β in ≃ ∫ S drdz r ^ 2 { - [ ρG 3 in ] ϕ = ϕ - ϕ = ϕ + + ∫ ϕ - ϕ + d ϕ ∂ ρ / ∂ φ ^ G 3 in } , r ^ p ⪢ 1 , ( 50 ) and Β out ≃ ∫ S drdz r ^ 2 { [ ρ G 3 out ] ϕ = ϕ - ϕ = ϕ + + ( ∫ - ϕ - + ∫ ϕ + + ) d ϕ ∂ ρ / ∂ φ ^ G 3 out } , r ^ p ⪢ 1 , ( 51 ) where G3in and G3out stand for the values of G 3 = ∫ - ∞ + ∞ d φ R - 1 δ ( g - ϕ ) n ^ × e ^ φ = ∑ φ = φ j R - 1 ∂ g / ∂ φ - 1 n ^ × e ^ φ ( 52 ) inside and outside the bifurcation surface. Once again, owing to the presence of the factor |∂g/∂φ|−1 in G3in, the first term in (50) is divergent so that the Hadamard's finite part of Bin consists of the volume integral in this equation, an integral whose magnitude is of the order of r ^ p - 3 2 [see the paragraph containing (35) and note that, according to (A38) and (A44), p3>>c1 q3 and p3/c12=O(1)]. The second term in (51) has—like those in (33) and (45)—the conventional rate of decay {circumflex over (r)}P−1. Moreover, the surface integral in (51)—which would have had the same magnitude as the surface integral in (50) and so would have cancelled out of the expression for B had G3in and G3out matched smoothly across the bifurcation surface—decays as slowly as the corresponding term in (45). The asymptotic value of G3 for source points close to the cusp curve of the bifurcation surface has been calculated in Appendix A. It follows from this value of G3 and from (51), (52), (A40), (A44) and (A45) that, in the radiation zone, Β ∼ ∫ S drdz r ^ 2 [ ρ G 3 out ] ϕ - ϕ + ∼ 4 3 ∫ S drdz r ^ 2 ρ bs c 1 - 1 q 3 ∼ 2 3 2 3 ( c / ω ) r ^ P - 1 2 ∫ r ^ < r ^ > d r ^ r ^ 2 ( r ^ 2 - 1 ) - 1 4 ∫ z ^ c - L z ^ ω / c z ^ c d z ^ ( z ^ c - z ^ ) - 1 2 ρ bs n 3 ( 53 ) to within the order of the approximation entering (37) and (46). The far-field version of the radial unit vector defined in (31) assumes the form lim r P → ∞ n ^ ϕ = ϕ c , z ^ = z ^ c = r ^ - 1 e ^ r P - ( 1 - r ^ - 2 ) 1 2 e ^ z P ( 54 ) on the cusp curve of the bifurcation surface [see (12b), (13) and (A27), and note that the position of the observer is here assumed to be such that the segment of the cusp curve lying within the source distribution pattern is described by the expression with the plus sign in (12b), as in FIG. 6]. So, n3 equals {circumflex over (n)}×êφP in the regime of validity of (53) [see (A45)]. Moreover, {circumflex over (n)} can be replaced by its far-field value{circumflex over (n)}≅(rPêrP+zPêzP)/RP, RP→∞, (55)if it is borne in mind that (53) holds true only for an observer the cusp curve of whose bifurcation surface intersects the source distribution pattern. Once n3 in (53) is approximated by {circumflex over (n)}×êφP and the resulting {circumflex over (z)}-quadrature is expressed in terms of ρbs [see (38)], this equation reduces toB˜{circumflex over (n)}×E, (56),where E is the electric field vector earlier found in (47). Equations (47) and (56) jointly describe a radiation field whose polarization vector lies along the direction of motion of the source distribution pattern, êφP. Note that there has been no contribution toward the values of E and B from inside the bifurcation surface. These quantities have arisen in the above calculation solely from the jump discontinuities in the values of the Green's functions G1out, G2out and G3out across the coalescing sheets of the bifurcation surface. We would have obtained the same results had we simply excised the vanishingly small volume limrp→∞Vin from the domains of integration in (29), (43) and (48). Note also that the way in which the familiar relation (56) has emerged from the present analysis is altogether different from that in which it appears in conventional radiation theory. Essential though it is to the physical requirement that the directions of propagation of the waves and of their energy should be the same, (56) expresses a relationship between fields that are here given by non-spherically decaying surface integrals rather than by the conventional volume integrals that decay like rp−1. Expressions (47) and (56) for the electric and magnetic fields of the radiation that arises from a charge-current density with the components (23) and (39) imply the following Poynting vector: S ∼ 2 5 3 2 π - 1 c ( c / ω ) 2 rp - 1 [ ∫ r ^ < r ^ > d r ^ r ^ 2 ( r ^ 2 - 1 ) - 1 4 ( L z ^ ω / c ) 1 2 〈 ρ bs 〉 ] 2 n ^ . ( 57 ) In contrast, the magnitude of the Poynting vector for the coherent cyclotron radiation that would be generated by a macroscopic lump of charge, if it moved subluminally with a centripetal acceleration cw is of the order of (ρL3)2ω2/(cRP2) according to the Larmor formula, where L3 represents the volume of the source distribution pattern and ρ its average charge density. The intensity of the present emission is therefore greater than that of even a coherent conventional radiation by a factor of the order of (L{circumflex over (z)}/L)(Lω/c)−4(RP/L), a factor that ranges from 1016 to 1030 in the case of pulsars for instance. The reason this ratio has so large a value in the far field (RP/L>>1) is that the radiative characteristics of a volume-distributed source pattern which moves faster than the waves it emits are radically different from those of a corresponding source that moves more slowly than the waves it emits. There are elements of the distirbution pattern of the source in the former case that approach the observer along the radiation direction with the wave speed at the retarded time. These lie on the intersection of the source distribution pattern with what we have here called the bifurcation surface of the observer (see FIGS. 5 and 6): a surface issuing from the position of the observer which has the same shape as the envelope of the wave fronts emanating from an element of the source distribution pattern (FIGS. 1 and 3A) but which spirals around the rotation axis in the opposite direction to this envelope and resides in the space of source points instead of the space of observation points. The elements of the source distribution pattern inside the bifurcation surface of an observer make their contributions towards the observed field at three distinct instants of the retarded time. The values of two of these retarded times coincide for an interior element of the source distribution pattern that lies next to the bifurcation surface. This limiting value of the coincident retarded times represents the instant at which the component of the velocity of the element in question of the source distribution pattern equals the wave speed c in the direction of the observer. The third retarded time at which an element of the source distribution pattern adjacent to—just inside—the bifurcation surface makes a contribution is the same as the single retarded time at which its neighbouring element of the source distribution pattern just outside the bifurcation surface makes its contribution towards the observed field. (The elements of the source distribution pattern outside the bifurcation surface make their contributions at only a single instant of the retarded time). At the instant marked by this third value of the retarded time, the two neighbouring elements of the source distribution pattern—just interior and just exterior to the bifurcation surface—have the same velocity, but a velocity whose component along the radiation direction is different from c. The velocities of these two neighbouring elements are, of course, equal at any time. However, at the time they approach the observer with the wave speed, the element inside the bifurcation surface makes a contribution towards the observed field while the one outside this surface does not: the observer is located just inside the envelope of the wave fronts that emanate from the interior element of the source distribution pattern but just outside the envelope of the wave fronts that emanate from the exterior one. Thus, the constructive interference of the waves that are emitted by the element of the source distribution pattern just outside the bifurcation surface takes place along a caustic which at no point propagates past the observer at the conical apex of the bifurcation surface in question. On the other hand, the radiation effectiveness of an element of the distribution pattern of the source which approaches the observer with the wave speed at the retarded time is much greater than that of a neighbouring element the component of whose velocity along the radiation direction is subliminal or superluminal at this time. This is because the piling up of the emitted wave fronts along the line joining the source and the observer makes the ratio of emission to reception time intervals for the contributions of the luminally moving elements of the source distribution pattern by many orders of magnitude greater than that for the contributions of any other elements. As a result, the radiation effectiveness of the various constituent elements of the source distribution pattern (i.e. the Green's function for the emission process) undergoes a discontinuity across the boundary set by the bifurcation surface of the observer. The integral representing the superposition of the contributions of the various volume elements of the source distribution pattern to the potential thus entails a discontinuous integrand. When this volume integral is differentiated to obtain the field, the discontinuity in question gives rise to a boundary contribution in the form of a surface integral over its locus. This integral receives contributions from opposite faces of each sheet of the bifurcation surface which do not cancel one another. Moreover, the contributions arising from the exterior faces of the two sheets of the bifurcation surface do not have the same value even in the limit Rp→∞. where this surface is infinitely large and so its two sheets are—throughout a localized source distribution pattern that intersects the cusp—coalescent. Thus the resulting expression for the field in the radiation zone entails a surface integral such as that which would arise if the source distribution pattern were two-dimensional, i.e. if the source distribution pattern were concentrated into an infinitely thin sheet that coincided with the intersection of the coalescing sheets of the bifurcation surface with the source distribution pattern. For a two-dimensional source distribution pattern of this type—whether it be real or a virtual one whose field is described by a surface integral—the near zone (the Fresnel regime) of the radiation can extend to infinity, so that the amplitudes of the emitted waves are not necessarily subject to the spherical spreading that normally occurs in the far zone (the Fraunhofer regime). The Fresnel distance which marks the boundary between these two zones is given by RF˜L⊥2/L∥, in which L⊥ and L∥ are the dimensions of the source distribution pattern perpendicular and parallel to the radiation direction. If the distribution pattern of the source is distributed over a surface and so has a dimension L∥ that is vanishingly small, therefore, the Fresnel distance RF tends to infinity. In the present case, the surface integral which arises from the discontinuity in the radiation effectiveness of the source elements across the bifurcation surface has an integrand that is in turn singular on the cusp curve of this surface. This has to do with the fact that the elements the source distribution pattern on the cusp curve of the bifurcation surface approach the observer along the radiation direction not only with the wave speed but also with zero acceleration. The ratio of the emission to reception time intervals for the signals generated by these elements is by several orders of magnitude greater even than that for the elements on the bifurcation surface. When the contributions of these elements are included in the surface integral in question, i.e. when the observation point is such that the cusp curve of the bifurcation surface intersects the source distribution pattern (as shown in FIG. 6), the value of the resulting improper integral turns out to have the dependence Rp−1/2, rather than Rp−1, on the distance Rp of the observer from the source distribution pattern. This non-spherically decaying component of the radiation is in addition to the conventional component that is concurrently generated by the remaining volume elements of the source distribution pattern. It is detectable only at those observation points the cusp curves of whose bifurcation surfaces intersect the source distribution pattern. It appears, therefore, as a spiral-shaped wave packet with the same azimuthal width as the {circumflex over (φ)}-extent of the source distribution pattern. For a source distribution pattern whose superluminal portion extends from {circumflex over (r)}=1 to {circumflex over (r)}={circumflex over (r)}>>1, this wave packet is detectable—by an observer at infinity—within the angles 1 2 π - arccos r ^ > - 1 ≤ θ p ≤ 1 2 π + arccos r ^ > - 1 from the rotation axis: projection (12b) of the cusp curve of the bifurcation surface onto the (r, z)-plane reduces to cot θ p = ( r ^ 2 - 1 ) 1 2 in the limit RP→∞, where θP≡arctan(rP/zP) [also see (54)]. Because it comprises a collection of the spiralling cusps of the envelopes of the wave fronts that are emitted by various elements of the source distribution pattern, this wave packet has a cross section with the plane of rotation whose extent and shape match those of the source distribution pattern. It is a diffraction-free propagating caustic that—when detected by a far-field observer—would appear as a pulse of duration Δ{circumflex over (φ)}/ω, where Δ{circumflex over (φ)} is the azimuthal extent of the source distribution pattern. Note that the waves that interfere constructively to form each cusp, and hence the observed pulse, are different at different observation times: the constituent waves propagate in the radiation direction {circumflex over (n)} with the speed c, whereas the propagating caustic that is observed, i.e. the segment of the cusp curve that passes through the observation point at the observation time, propagates in the azimuthal direction êφP with the phase speed rpw. The fact that the intensity of the pulse decays more slowly than predicted by the inverse square law is not therefore incompatible with the conservation of energy, for it is not the same wave packet that is observed at different distances from the source distribution pattern: the wave packet in question is constantly dispersed and re-constructed out of other waves. The cusp curve of the envelope of the wavefronts emanating from an infinitely long-lived source distribution pattern is detectable in the radiation zone not because any segment of this curve can be identified with a caustic that has formed at the source and has subsequently travelled as an isolated wavepacket to the radiation zone, but because certain set of waves superpose coherently only at infinity. Relative phases of the set of waves that are emitted during a limited time interval is such that these waves do not, in general, interfere constructively to form a cusped envelope until they have propagated some distance away from the source distribution pattern. The period in which this set of waves has a cusped envelope and so is detectable as a periodic train of non-spherically decaying pulses, would of course have a limited duration if the source distribution pattern is short-lived. Thus, pulses of focused waves may be generated by the present emission process which not only are stronger in the far field than any previously studied class of signals, but which can in addition be beamed at only a select set of observers for a limited interval of time. An apparatus can be designed for generating such pulses, in accordance with the above theory, which basically entails the simple components shown in FIGS. 7A and 7B. Referring to the example of FIG. 7A, a linear dielectric rod 1 of length/is provided with an array of electrodes 2, 3 arranged opposite one another along its length with n/l electrodes per unit length. In use, a voltage potential is applied across the dielectric rod 1 by the electrodes 2, 3, with each pair of electrodes 2, 3, in the array being activated in turn to generate a polarisation region with the fronts 5. By rapid application and removal of a potential voltage to electrodes 2, 3, the distribution pattern of this polarised region can be set in accelerated motion with a superluminal velocity. Creating a voltage across a pair of electrodes polarises the material in the rod between the electrodes. The electrodes can be controlled independently, so that the distribution pattern of polarisation of the rod as a function of length along the rod is controlled. By varying the voltage across the electrode pairs as a function of time, this polarisation pattern is set in motion. For example, neighbouring electrode pairs can be turned on with a time interval of Δt between them, starting from one end of the rod. Thus, at a snapshot in time, part of the rod is polarised (that part lying between electrode pairs with a voltage across them) and part of it is not polarised (that part lying between electrode pairs without a voltage across them). These regions are separated by “polarisation fronts” which move with a speed of l/(nΔt). With suitable choices of n and Δt the polarisation fronts can be made to move at any speed (including speeds faster than the speed of light in vacuo). The polarisation fronts can be accelerated through the speed of light by changing Δt with time. High-frequency radiation may be generated by modulating the amplitude of the resulting polarisation current with a frequency Ω that exceeds a/c, where a is the acceleration of the source distribution pattern. The spectrum of the spherically decaying component of the radiation would then extend to frequencies that would be by a factor of the order of (cΩ/a)2 higher than Ω. The required modulation may be achieved by varying the amplitudes of the voltages that are applied across various electrode pairs all in phase. FIG. 7B shows another example of the invention, the one analysed above. In this example, the dielectric rod is formed in the shape of a ring. FIG. 7B is a plan view showing electrodes 2, and has electrodes 3 disposed below the rod 1. For a ring of radius r and a polarisation pattern that moves around the ring with an angular frequency ω, the velocity of the charged region is rω. In this example, rω is greater than the speed of light c so that the moving polarisation pattern emits the radiation described with reference to FIGS. 1 to 6. FIGS. 3B and 3C depict representative three dimensional plots of the radiation pattern of the entire source of FIG. 7B at a frequency of 2.4 GHz and a phase difference between adjacent electrodes between 15 degrees and 5 degrees respectively. An azimuthal or radial polarisation current may be produced by displacing the plates of each electrode pair relative to one another. The voltages across neighbouring electrode pairs have the same time dependence (their period is 2π/ω) but, as in the rectilinear case, there is a time difference of Δt between them. The polarisation distribution pattern must move coherently around the ring, i.e. must move rigidly with an unchanging shape; this would be the case if nΔt=2πN/ω, where n is the number of electrodes around the ring and N an integer. Within the confines of this condition, the time dependence of the voltage across each pair of electrodes can be chosen at will. The exact form of the adopted time dependence would allow, for example, the generation of harmonic content and structure in the source distribution pattern. As in the rectilinear case, modulation of the amplitude of this source distribution pattern at a frequency Ω would result in a radiation whose spectrum would contain frequencies of the order of (Ω/ω)2Ω. The electrodes are driven by an array of similar oscillators, an array in which the phase difference between successive oscillators has a fixed value. There are several ways of implementing this: a single oscillator may be used to drive each electrode through progressively longer delay lines; each electrode pair may be driven by an individual oscillator in an array of phase-locked oscillators; or the electrode pairs may be connected to points around a circle of radius r which lies within—and is coplanar with—an annular waveguide, a waveguide whose normal modes include an electromagnetic wave train that propagates longitudinally around the circle with an angular frequency ω>c/r. For a dielectric rod in the shape of a ring of diameter 1 m, oscillators operating at a frequency of 100 MHz would generate a superluminally moving polarisation distribution pattern. The required oscillator frequencies are easily obtainable using standard laboratory equipment, and any material with an appreciable polarizability at MHz frequencies would do for the medium. If the amplitude of the resulting polarisation current is in addition modulated at 1 GHz, then the device would radiate at ˜100 GHz. The efficiency of this emission process is expected to be as high as a few percent. With oscillators operating at frequencies of 1 GHz (also available), the size of the device would be about 10 cm across; applications demanding portability are therefore viable. The present invention may be exploited to generate waves which do not form themselves into a focused pulse until they arrive at their intended destination and which subsequently remain in focus only for an adjustable interval of time, a property that allows for applications in various areas of medical practice and biomedical research. Examples of its use in therapeutic medicine are: (i) the selective irradiation of deep tumours whilst sparing surrounding normal tissue, and (ii) the radiation pressure or thermocautery removal of thrombotic and embolic vascular lesions that may result from abnormalities in blood clotting without invasive surgery. Examples of its use in diagnostic medicine are absorption spectroscopy (focusing a broadband pulse within a tissue some frequencies of which would be absorbed) and three-dimensional tomography (mapping specifiable regions of interest within the body to high levels of resolution). In biomedical research, it provides a more powerful alternative to confocal scanning microscopy; with a single aerial being used as an X-ray source for imaging purposes. An example of an apparatus required for generating the pulses in question is that shown in FIG. 7A. It consists of a linear dielectric rod, an array of electrode pairs positioned opposite to each other along the rod, and the means for applying a voltage to the electrodes sequentially at a rate sufficient to induce a polarization current whose distribution pattern moves along the rod with a constant acceleration at speeds exceeding the speed of light in vacuo. The envelope of the wave fronts emanating from a volume element of the superluminally moving distribution pattern thus produced is shown in FIG. 8. It consists of a two-sheeted closed surface when the duration of the source includes the instant at which the distribution pattern of the source becomes superluminal. The two sheets of this envelope are tangent to one another and form a cusp along an expanding circle. If the source distribution pattern has a limited duration, the envelope in question is correspondingly limited [as in FIG. 9D] to only a truncated section of the surface shown in FIG. 8. The snapshots in FIGS. 9A-9F trace the evolution in time of the relative positions of a particular set of wave fronts that are emitted during a short time interval. They include times at which the envelope has not yet developed a cusp [9A and 9B], has a cusp [9C-9E], and has already lost its cusp 9F. A source distribution pattern with the life span 0<t<T gives rise to a caustic, i.e. to a set of tangential wave fronts with a cusped envelope, only during the following finite interval of observation time:M(M2−1)l/c≤tP≤M[M2(1+aT/u)3−1]l/c, (58)where M≡u/c and l≡c2/a with u, c, and a standing for the speed of the distribution pattern of the source at t=0, the wave speed, and the constant acceleration of the distribution pattern of the source, respectively. For a T/u<<1, therefore, the duration of the caustic, 3M2T, is proportional to that of the source distribution pattern. Moreover, a cusped envelope begins to form in the case of a short-lived source distribution pattern only after the waves have propagated a finite distance away from the source. The distance of the caustic from the position of the source distribution pattern at the retarded time is given by R ~ p = β p 1 3 ( β p 2 3 - 1 ) l , ( 59 ) where βP≡(u+atP)/c and tp is the observation time. This distance can be long even when the duration of the source distribution pattern is short because there is no upper limit on the value of the length l(≡c2/a) that enters (58) and (59):/tends to infinity for a→0 and is as large as 1018 cm when a equals the acceleration of gravity. Thus RP can be rendered arbitrarily large, by a suitable choice of the parameter I, without requiring either the duration of the source (T) or the retarded value ( β p 1 3 c )of the speed of the source distribution pattern to be correspondingly large. This means that, when either M or I is large, the waves emitted by a short-lived source do not focus to such an extent as to form a cusped envelope until they have travelled a long distance away from the source. The period during which they then do so can be controlled by adjusting the parameters M and T. The collection of the cusp curves of the envelopes that are associated with various elements of the distribution pattern of the source constitutes a ring-shaped wave packet. This wave packet is intercepted only by those observers who are located, during its life time (58), on its trajectory ξ = ( β p 2 3 - 1 ) 3 2 , ζ = 1 2 β p 2 - 3 2 β p 3 2 + 1 , ( 60 ) where ξ represents the distance (in units of I) of the observer from the rectilinear path of the source, say the z-axis, and ζ stands for the difference between the Lagrangian coordinates z ~ = z - ut - 1 2 at 2 of the source point and z ~ P = z P - utp - 1 2 atp 2 of the observation point. It is possible to limit the spatial extent of the wave packet embodying the large-amplitude pulse by enclosing the path of the source distribution pattern within an opaque cylindrical surface which has a narrow slit parallel to its axis, a slit acting as an aperture that would only allow an arc of the ring-shaped wave packet to propagate to the far field. The volume occupied by the resulting wave packet could then be chosen at will by adjusting the width of the aperture and the longitudinal extent of the source distribution pattern. In the near zone, the radiation that is generated by the invention can be arranged to have many features in common with synchrotron radiation. Most experiments presently carried out at large-scale synchrotron facilities could potentially be performed by means of a polarization synchrotron, i.e. the compact device described in Sec. VI. This device has applications, as a source of intense broadband radiation, in many scientific and industrial areas, e.g. in spectroscopy, in semiconductor lithography at very fine length scales, and in silicon chip manufacture involving UV techniques. The spectrum of the radiation generated in a polarization synchrotron extends to frequencies that are by a factor of the order of (cΩ/a)2 higher than the characteristic frequency Ω of the fluctuations of the source distribution pattern itself (c and a are the speed of light and the acceleration of the source distribution pattern, respectively). For a polarizable medium consisting of a 1 m arc of a circular rod whose diameter is ˜10 m [see FIG. 7B], superluminal source distribution pattern motion is achieved by an applied voltage that oscillates with the frequency ˜10 MHz. If the amplitude of the resulting polarization current is in addition modulated at ˜500 MHz, then the device would radiate at ˜1 THz. In the case of the source distribution pattern elements that approach the observer with the wave speed and zero acceleration, the interval of retarded time δt during which a set of waves are emitted is significantly longer than the interval of observation time δtP during which the same set of waves are received. For a rectilinearly moving superluminal source distribution pattern, the ratio δt/δtP is given by 2 1 3 ( u 2 / c 2 - 1 ) 1 3 ( a δ tp / c ) - 2 3 ,where u is the retarded speed of the source distribution pattern and a its constant acceleration. This ratio increases without bound as a approaches zero. Regardless of what the characteristic frequency of the temporal fluctuations of the source may be, therefore, it is possible to push the upper bound to the spectrum of the emitted radiation to arbitrarily high frequencies by making the acceleration a small. [Note that the emission process described here remains different from the Ĉerenkov process, in which a exactly equals zero, even in the limit a→0.] The relationship between δt and δtP is δ tp ≃ 1 6 ω 2 ( δ t ) 3 if the source distribution pattern moves circularly with the angular frequency w. Thus the spectrum of the spherically decaying part of the radiation that is generated by a source with an accelerated superluminal distribution pattern extends to frequencies which are by a factor of the order of (cΩ/a)2 or (Ω/ω)2 higher than the characteristic frequency Ω of the modulations of the amplitude of the source distribution pattern. There are at present no known antennas in which the emitting electric current is both volume distributed and has the time dependence of a travelling wave with an accelerated superluminal motion. A travelling wave antenna of this type, designed on the basis of the principles underlying the present invention, generates focused pulses that not only are stronger in the far field than any previously studied class of signals, but can in addition be beamed at only a select set of observers for a limited interval of time: the constituent waves whose constructive interference gives rise to the propagating wave packet embodying a given pulse come into focus (develop a cusped envelope or a caustic) only long after they have emanated from the source and then only for a finite period (FIGS. 9A-9F). The intensity of the waves generated by this novel type of antenna decay much more slowly over distance than that of conventional radio or light signals. In the case of conventional sources, including lasers, if the transmitter (source) to receiver (destination) distance doubles, the power of the signal is reduced by a factor of four. With the present invention, the same doubling of distance only halves the available signal. Thus the power required to send a radio signal from the Earth to the Moon by the present transmitter would be 100 million times smaller than that which is needed in the case of a conventional antenna. The emission mechanism in question can therefore be used to convey telephonic, visual and other electronic data over very long distances without significant attenuation. In the case of ground-to-satellite communications, the power required to beam a signal would be greatly reduced, implying that either far fewer satellites would be required for the same bandwidth or each satellite could handle a much wider range of signals for the same power output. A combined effect of the slow decay rate and the beaming of the new radiation is that a network of suitably constructed antennae could expand the useable spectrum of terrestrial electromagnetic broadcasts by a factor of a thousand or more, thus dispensing with the need for cable or optical fibre for high-bandwidth communications. The evolution of the Internet, real-time television conferencing and related information-intense communication media means that there is a growing demand for cheap high-bandwidth aerials. Highly compact aerials for hand-held portable phones and/or television/Internet connections based on the present invention can handle, not only much longer transmitter-to-receiver distances than those currently available in cellular phone systems, but also much higher bandwidth. Far fewer ground based aerial structures are required to obtain the same area coverage. Because there would be no cross-talk between any pairs of transmitter and receiver, the effective bandwidth of free space could be increased many thousand-fold, thus allowing, say, for video transmission between hand-held units. In this Appendix, we calculate the leading terms in the asymptotic expansions of the integrals (16), (34), (42) and (52) for small φ+-φ−, i.e. for points close to the cusp curve (12) of the bifurcation surface (or of the envelope of the wavefronts). The method—originally due to Chester et al. (Proc. Camb. Phil. Soc., 54, 599, 1957)—which we use is a standard one that has been specifically developed for the evaluation of radiation integrals involving caustics (see Ludwig, Comm. Pure Appl. Maths, 19, 215, 1966). The integrals evaluated below all have a phase function g(φ) whose extrema (φ=φ±) coalesce at the caustic (12). As long as the observation point does not coincide with the source point, the function g(φ) is analytic and the following transformation of the integration variables in (16) is permissible: g ( φ ) = 1 3 v 3 - c 1 2 v + c 2 , ( A1 ) where v is the new variable of integration and the coefficients c 1 ≡ ( 3 4 ) 1 3 ( ϕ + - ϕ - ) 1 3 and c 2 ≡ 1 2 ( ϕ + + ϕ - ) ( A2 ) are chosen such that the values of the two functions on opposite sides of (A1) coincide at their extrema. Thus an alternative exact expression for G0 is G 0 = ∫ - ∞ + ∞ dvf 0 ( v ) δ ( 1 3 v 3 - c 1 2 v + c 2 - ϕ ) , ( A3 ) in whichf0(v)≡R−1dφ/dv. (A4) Close to the cusp curve (12), at which c1 vanishes and the extrema v=±c1 of the above cubic function are coincident, f0(v) may be approximated by p0+q0v, with p 0 = 1 2 ( f 0 v = c 1 + f 0 v = - c 1 ) , and ( A5 ) q 0 = 1 2 c 1 - 1 ( f 0 v = c 1 - f 0 v = - c 1 ) . ( A6 ) The resulting expression G 0 ∼ ∫ - ∞ + ∞ dv ( p 0 + q 0 v ) δ ( 1 3 v 3 - c 1 2 v + c 2 - ϕ ) ( A7 ) will then constitute, according to the general theory, the leading term in the asymptotic expansion of G0 for small c1. To evaluate the integral in (A7), we need to know the roots of the cubic equation that follows from the vanishing of the argument of the Dirac delta function in this expression. Depending on whether the observation point is located inside or outside the bifurcation surface (the envelope), the roots of 1 3 ν 3 - c 1 2 ν + c 2 = 0 ( A8 ) are given by ν = 2 c 1 cos ( 2 3 n π + 1 3 arccos χ ) , χ < 1 , ( A9 a ) for n=0, 1 and 2, or by ν = 2 c 1 sgn ( χ ) cosh ( 1 3 arc cosh χ ) , χ > 1 , ( A9 b ) respectively, where: χ ≡ [ ϕ - 1 2 ( ϕ + + ϕ - ) ] / [ 1 2 ( ϕ + - ϕ - ) ] = 3 2 ( ϕ - c 2 ) / c 1 3 . ( A10 ) Note that X equals +1 on the sheet φ=φ+ of the bifurcation surface (the envelope) and −1 on φ=φ−. The integral in (A7), therefore, has the following value when the observation point lies inside the bifurcation surface (the envelope): ∫ - ∞ + ∞ d νδ ( 1 3 ν 3 - c 1 2 ν + c 2 ) = ∑ n = 0 2 c 1 - 2 4 cos 2 ( 2 3 n π + 1 3 arccos χ ) - 1 - 1 , χ < 1. ( A11 ) Using the trignometric identity 4 cos2 α−1=sin 3α/sin α, we can write this as ∫ - ∞ + ∞ d νδ ( 1 3 ν 3 - c 1 2 ν + c 2 ) = c 1 - 2 ( 1 - χ 2 ) - 1 2 ∑ n = 0 2 sin ( 2 3 n π + 1 3 arccos χ ) = 2 c 1 - 2 ( 1 - χ 2 ) - 1 2 cos ( 1 3 arcsin χ ) , χ < 1 , ( A12 ) in which we have evaluated the sum by adding the sine functions two at a time. When the observation point lies outside the bifurcation surface (the envelope), the above integral receives a contribution only from the single value v given in (A9b) and we obtain ∫ - ∞ + ∞ d νδ ( 1 3 ν 3 - c 1 2 ν + c 2 ) = c 1 - 2 ( χ 2 - 1 ) - 1 2 sinh ( 1 3 arc cosh χ ) , χ > 1 , ( A13 ) where this time we have used the identity 4 cos h2 α−1=sin h 3α/sin hα. The second part of the integral in (A7) can be evaluated in exactly the same way. It has the value ∫ - ∞ + ∞ d ννδ ( 1 3 ν 3 - c 1 2 ν + c 2 ) = 2 c 1 - 1 ( 1 - χ 2 ) - 1 2 ∑ n = 0 2 sin ( 2 3 n π + 1 3 arccos χ ) × cos ( 2 3 n π + 1 3 arccos χ ) = - 2 c 1 - 1 ( 1 - χ 2 ) - 1 2 sin ( 2 3 arcsin χ ) , χ < 1 , ( A14 ) when the observation point lies inside the bifurcation surface (the envelope), and the value ∫ - ∞ + ∞ d ννδ ( 1 3 ν 3 - c 1 2 ν + c 2 ) = c 1 - 1 ( χ 2 - 1 ) - 1 2 sgn ( χ ) sinh ( 2 3 arc cosh χ ) , χ > 1 , ( A15 ) when the observation point lies outside the bifurcation surface (the envelope). Inserting (A12)-(A15) in (A7), and denoting the values of G0 inside and outside the bifurcation surface (the envelope) by G0in and G0out, we obtain G 0 in ∼ 2 c 1 - 2 ( 1 - χ 2 ) - 1 2 [ p 0 cos ( 1 3 arcsin χ ) - c 1 q 0 sin ( 2 3 arcsin χ ) ] , χ < 1 , and ( A16 ) G 0 out ∼ c 1 - 2 ( χ 2 - 1 ) - 1 2 [ p 0 sinh ( 1 3 arc cosh χ ) + c 1 q 0 sgn ( χ ) sinh ( 2 3 arc cosh χ ) ] , χ > 1 , ( A17 ) for the leading terms in the asymptotic approximation to G0 for small c1. The function f0(v) in terms of which the coefficients p0 and q0 are defined is indeterminate at v=c1 and v=−c1: differentiation of (A1) yields dφ/dυ=(υ2−c12)/(∂g/∂φ) the zeros of whose denominator at φ=φ− and φ=φ+ respectively coincide with those of its numerator at v=+c1 and v=−c1. This indeterminacy can be removed by means of l′Hopital's rule by noting that d φ d ν | ν = ± c 1 = ν 2 - c 1 2 ∂ g ∂ φ | ν = ± c 1 = 2 ν ( ∂ 2 g ∂ φ 2 ) ( d φ d ν ) | ν = ± c 1 , i . e . that ( A18 ) d φ d ν | ν = ± c 1 = ( ± 2 c 1 ∂ 2 g ∂ φ 2 ) 1 2 | φ = φ ∓ = ( 2 c 1 R . ∓ ) 1 2 Δ 1 2 , ( A19 ) in which we have calculated (∂2g/∂φ2) from (7) and (8). The right-hand side of (A19) is, in turn, indeterminate on the cusp curve of the bifurcation surface (the envelope) where c1=Δ=0. Removing this indeterminacy by expanding the numerator in this expression in powers of Δ 1 4 ,we find that dφ/dυ assumes the value 2 1 3 at the cusp curve. Hence, the coefficients p0 and q0 that appear in the expressions (A8) and (A9) for G0 are explicitly given by p 0 = ( ω / c ) ( 1 2 c 1 ) 1 2 ( R ^ - - 1 2 + R ^ + - 1 2 ) Δ - 1 4 and ( A20 ) ) q 0 = ( ω / c ) ( 2 c 1 ) - 1 2 ( R ^ - - 1 2 - R ^ + - 1 2 ) Δ - 1 4 ( A21 ) [see (A4)-(A6) and (A19)]. In the regime of validity of (A8) and (A9), where Δ is much smaller than ( r ^ p 2 r ^ 2 - 1 ⋓ ) 1 2 ,the leading terms in the expressions for {circumflex over (R)}±, c1, p0 and q0 are R ^ ± = ( r ^ p 2 r ^ 2 - 1 ) 1 2 ± ( r ^ p 2 r ^ 2 - 1 ) - 1 2 Δ 1 2 + O ( Δ ) , ( A22 ) c 1 = 2 - 1 3 ( r ^ p 2 r ^ 2 - 1 ) - 1 2 Δ 1 2 + O ( Δ ) , ( A23 ) p 0 = 2 1 3 ( w / c ) ( r ^ 2 r ^ p 2 - 1 ) - 1 2 + O ( Δ 1 2 ) , and ( A 24 ) q 0 = 2 - 1 3 ( w / c ) ( r ^ 2 r ^ p 2 - 1 ) - 1 + O ( Δ 1 2 ) . ( A25 ) These may be obtained by using (9) to express {circumflex over (z)} everywhere in (10), (11) and (A2) in terms of Δ and {circumflex over (r)}, and expanding the resulting expressions in powers of Δ 1 2 .The quantity Δ in turn has the following value at points 0 ^ ≤ z ^ c - z ^ ⪡ ( r ^ p 2 - 1 ) 1 2 ( r ^ 2 - 1 ) 1 2 : Δ = 2 ( r ^ p 2 - 1 ) 1 2 ( r ^ 2 - 1 ) 1 2 ( z ^ c - z ^ ) + O [ ( z ^ c - z ^ ) 2 ] , ( A26 ) in which {circumflex over (z)}c is given by the expression with the plus sign in (12b). For an observation point in the far zone ({circumflex over (r)}P>>1)the above expressions reduce to R ^ ± ≃ r ^ r ^ p , c 1 ≃ 2 1 6 ( r ^ r ^ p ) - 1 2 ( 1 - r ^ - 2 ) 1 4 ( z ^ c - z ^ ) 2 , ( A27 ) Δ ≃ 2 r ^ p ( r ^ 2 - 1 ) 1 2 ( z ^ c - z ^ ) , ( A28 ) p 0 ≃ 2 1 3 ( ω / c ) ( r ^ p r ^ ) - 1 , q 0 ≃ 2 - 1 3 ( ω / c ) ( r ^ p r ^ ) - 2 , and ( A29 ) X ≃ 3 ( 1 2 r ^ r ^ p ) 3 2 ( 1 - r ^ - 2 ) - 3 4 ( ϕ - ϕ c ) / ( z ~ c - z ~ ) 3 2 , ( A30 ) in which {circumflex over (z)}c−{circumflex over (z)} has been assumed to be finite. Evaluation of the other Green's functions, G1, G2 and G3, entails calculations which have many steps in common with that of G0. Since the integrals in (34), (42) and (52) differ from that in (16) only in that their integrands respectively contain the extra factors {circumflex over (n)}, êφ and {circumflex over (n)}×êφ, they can be rewritten as integrals of the form (A3) in which the functionsf1(v)≡{circumflex over (n)}f0, f2(v)≡êφf0 and f3(v)≡{circumflex over (n)}×êφf0 (A31)replace the f0(v) given by (A4). If p0 and q0 are correspondingly replaced, in accordance with (A5) and (A6), by p k = 1 2 ( f k ❘ v ❘ = c 1 + f k ❘ v = - c 1 ) , k = 1 , 2 , 3 , and ( A32 ) q k = 1 2 c 1 - 1 ( f k ❘ v = c 1 - f k ❘ v = - c 1 ) , k = 1 , 2 , 3 ( A33 ) then every step of the analysis that led from (A7) to (A8) and (A9) would be equally applicable to the evaluation of Gk. It follows, therefore, that G k in ~ 2 c 1 - 2 ( 1 - χ 2 ) - 1 2 [ p k cos ( 1 3 arcsin χ ) - c 1 q k sin ( 2 3 arcsin χ ) ] , χ < 1 , and ( A34 ) G k out ∼ c 1 - 2 ( χ 2 - 1 ) - 1 2 [ p k sinh ( 1 3 arc cosh χ ) + c 1 q k sgn ( χ ) sinh ( 2 3 arc cosh χ ) ] , χ > 1 , ( A35 ) constitute the uniform asymptotic approximations to the functions Gk inside and outside the bifurcation surface (the envelope) |x|=1. Explicit expressions for pk and qk as functions of (r, z) may be found from (8), (A19), and (A31)-(A33) jointly. The result is p 1 q 1 = 2 - 1 2 ( ω / c ) c 1 ± 1 2 Δ - 1 4 { { ( r ^ p - r ^ p - 1 ) ( R ^ - - 3 2 ± R ^ + - 3 2 ) - r ^ p - 1 Δ 1 2 ( R ^ - - 3 2 ∓ R ^ + - 3 2 ) ] e ^ rp + r ^ P - 1 ( R ^ - - 1 2 ± R ^ + - 1 2 ) e ^ φ p + ( z ^ p - z ^ ) ( R ^ - - 3 2 ± R ^ + - 3 2 ) e ^ z p } , ( A36 ) p 2 q 2 = 2 - 1 2 ( ω / c ) ( r ^ r ^ p ) - 1 c 1 ± 1 2 Δ - 1 4 { ( R ^ - 1 2 ± R ^ + 1 2 ) e ^ rp + [ R ^ - - 1 2 ± R ^ + - 1 2 + Δ 1 2 ( R ^ - - 1 2 ∓ R ^ + - 1 2 ) ] e ^ φ p } , and ( A37 ) p 3 q 3 = 2 - 1 2 ( ω / c ) ( r ^ r ^ p ) - 1 c 1 ± 1 2 Δ - 1 4 { - ( z ^ p - z ^ ) [ R ^ - - 3 2 ± R ^ + - 3 2 + Δ 1 2 ( R ^ - - 3 2 ∓ R ^ + - 3 2 ) ] e ^ rp + ( z ^ p - z ^ ) ( R ^ - - 1 2 ± R ^ + - 1 2 ) e ^ φ p + r ^ p [ Δ 1 2 ( R ^ - - 3 2 ∓ R ^ + - 3 2 ) - ( r ^ 2 - 1 ) ( R ^ - - 3 2 ± R ^ + - 3 2 ) ] e ^ zp } , ( A38 ) where use has been made of the fact êφ=−sin(φ−φP)êr p+cos(φ−φP)êφt. Here, the expressions with the upper signs yield the pk and those with the lower signs the qk. The asymptotic value of each Gkout is indeterminate on the bifurcation surface (the envelope). If we expand the numerator of (A35) in powers of its denominator and cancel out the common factor ( x 2 - 1 ) ❘ 1 2 prior to evaluating the ratio in this equation, we obtainGkout|φ=φ±=Gkout|X=±1˜(pk±2c1qk)/(3c12). (A39)This shows that Gkout|φ=φ− and Gkout|φ=φ+ remain different even in the limit where the surfaces φ=φ− and φ=φ+ coalesce. The coefficients qk that specify the strengths of the discontinuities G k out ❘ ϕ = ϕ + - G k out ❘ ϕ = ϕ - ∼ 4 3 q k / c 1 ( A40 ) reduce to q 1 ≃ 3 2 1 3 ( ω / c ) ( r ^ r ^ p ) - 3 [ ( 1 - 2 3 r ^ 2 ) r ^ p e ^ rp + ( z ^ p - z ^ ) e ^ zp ] , ( A41 ) q 2 ≃ 2 2 3 ( ω / c ) ( r ^ r ^ p ) - 1 e ^ φ p , and ( A42 ) q 3 ≃ - 2 2 3 ( ω / c ) ( r ^ r ^ p ) - 2 [ ( z ^ p - z ^ ) e ^ rp - r ^ p e ^ zp ] ( A43 ) in the regime of validity of (A27) and (A28). When 0 ≤ z ^ c - z ^ ⪡ ( r ^ 2 - 1 ) 1 2 r ^ p the expressions (A41) and (A43) further reduce to q 1 ≃ 3 2 1 3 ( ω / c ) ( r ^ r ^ p ) - 2 n 1 , and q 3 ≃ 2 2 3 ( ω / c ) ( r ^ r ^ p ) - 1 n 3 ( A44 ) with n 1 ≡ ( r ^ - 1 - 2 3 r ^ ) e ^ rp - ( 1 - r ^ - 2 ) 1 2 e ^ zp and n 3 ≡ ( 1 - r ^ - 2 ) 1 2 e ^ rp + r ^ - 1 e ^ zp , ( A45 ) for in this case (12b)—with the adopted plus sign—can be used to replace z ^ - z ^ p by ( r ^ 2 - 1 ) 1 2 r ^ p . |
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description | The invention generally relates to nuclear reactors. More specifically, the invention relates to a nuclear reactor, of the type comprising: a vessel. a core provided in the vessel. at least one plate heat exchanger provided in the vessel, at least one duct for supplying a secondary fluid to the heat exchanger and a duct for discharging the secondary fluid from the heat exchanger, the discharge duct extending through the vessel. In the rest of the text, the term “plate heat exchanger” is considered to cover the following two concepts: plate exchangers; micro-channel exchangers. For a low- or medium-power electricity production nuclear reactor, non-limitingly around 100 MW and up to 500 MW, the economic viability is based on the time and investment optimization of the manufacture and maintenance of the reactor. One of the avenues considered in order to improve the viability of this type of reactor is to design certain parts (modules) such that they can be at least partially manufactured, equipped and tested in the plant, then transported to the site to be assembled to other modules there. In this respect, it is necessary to increase the compactness of the different internal modules making up the reactor so that those modules are transportable. Embodiments of the invention therefore target the dimensional optimization of the reactor vessel and its inner parts. FR 2348458 describes a nuclear reactor including a plurality of heat exchangers distributed in the vessel around the core of the nuclear reactor. The exchangers proposed in this document have a design based on plate compartment groups, with upstream and downstream collectors for the secondary fluid respectively connected to upstream and downstream bent tube elements having a vertically oriented end. The vertical bulk of the vessel in FR 2348458 for this type of reactor is not optimal, and a new architecture is provided herein, with the aim of meeting the aforementioned requirements of configurability and compactness. In that context, a nuclear reactor of the aforementioned type is provided, characterized in that the reactor comprises a device for attaching the heat exchanger to an area of the vessel through which the discharge duct extends. Thus, the same zone of the vessel allows both the attachment of the heat exchanger and the passage of the discharge duct. This contributes to making the nuclear reactor particularly compact. In particular, the secondary fluid discharge duct is particularly short. That duct therefore takes up practically no space inside the vessel, which frees up space to house other inner parts of the reactor. This is in particular the case when the heat exchanger has a secondary fluid outlet orifice connected to the secondary fluid discharge duct, the attachment device comprising a plurality of attachment members distributed from the outlet orifice. Thus, the same members make it possible to attach the heat exchanger to the vessel and to connect the outlet orifice to the discharge duct. Such an arrangement is particularly compact. In that case, the heat exchanger advantageously includes a flange for attaching the heat exchanger to the vessel, surrounding the secondary fluid outlet. Such a fastening method is particularly robust and compact. The nuclear reactor comprises one or more plate exchangers, for example a least four plate exchangers. In specific embodiments, it includes four or six plate exchangers, all provided in the vessel. This heat exchanger is provided near the vessel, and is preferably attached by a single attaching device that is cantilevered relative to the wall of the vessel. Such an attachment method makes it possible to free the central zone of the vessel so as to install other equipment there, or partitions making it possible to channel the flow of the primary fluid. The nuclear reactor is for example a pressurized water reactor. The primary fluid of the reactor is then water, as is the secondary fluid. In that case, the heat exchanger is a steam generator, the secondary fluid penetrating the vessel in the liquid state, and being vaporized in the heat exchanger under the effect of the heat ceded by the primary fluid. The primary and/or secondary fluids could be different from water, and for example a liquid metal such as sodium or a gas. The heat exchanger may be different from a steam generator. The vessel is typically at least partially filled with the primary fluid. The primary fluid is heated in the core of the reactor, and flows from the core to one or more primary fluid inlets formed in the plate exchanger(s). After passing through the plate exchanger, the primary fluid circulates as far as a suction inlet of the primary pump, which discharges the primary liquid to the core. Typically, the moving part of the primary pump is housed inside the vessel. Alternatively, the primary pump is completely situated outside the vessel and connected to the vessel by ducts. The vessel includes inner partitions making it possible to channel the flow of the primary fluid between the core, the heat exchanger, and the primary pump(s). As indicated above, the heat exchanger is typically attached to the vessel by a plurality of attachment members, positioned around a downstream crossing making it possible to discharge the secondary fluid through the vessel and around the secondary fluid outlet orifice of the exchanger. In one non-preferred alternative, the attachment members for attaching the heat exchanger to the vessel are not placed around the downstream crossing and the orifice. They can for example be positioned in an area adjacent to the crossing. The device for attaching the heat exchanger to a zone of the vessel here refers to the device provided to bear the weight of the exchanger, as well as the main thermomechanical stresses, and to pass them on to the vessel. Typically, the attachment device situated in the zone of the vessel passed through by the discharge duct bears at least 70% of the weight of the exchanger. Advantageously, it bears 100% of the weight of the exchanger. Thus, in that case, the heat exchanger is fully supported by the attachment device connected to the zone of the vessel passed through by the discharge duct. It is therefore attached to a single zone of the vessel. This is particularly advantageous, since the heat exchanger can expand thermally. This is particularly important due to the fact that the heat exchanger is of the plate type, and therefore has a relatively solid metallic structure. Advantageously, the vessel has a substantially vertical central axis, the attachment device attaching an upper end of the heat exchanger to the vessel. Thus, the upper end of the exchanger constituting a stationary point, the thermal expansion of the heat exchanger is done in a downward direction. This contributes to minimizing the stresses in the heat exchanger. Preferably, the nuclear reactor comprises a guide device suitable for limiting the travel of the lower part of the heat exchanger in a horizontal plane, and allowing a movement of said lower part in the vertical direction relative to the vessel. Thus, the heat exchangers are guided in the lower part, so as to prevent them from pivoting or toppling in the event of a bias of the impact or earthquake type. However, because the lower part is free in the vertical direction, the thermal expansion of the heat exchanger remains possible. Advantageously, the attachment device removably attaches the heat exchanger to the vessel. Thus, it is easy to remove the heat exchanger from the vessel, for example for maintenance purposes. The attachment device is for example of the screw or tie rod type, or any other suitable type. Advantageously, the attachment device comprises a plurality of attachment members attaching the heat exchanger to the vessel, said attachment members being able to be disassembled from outside the vessel. Thus, it is not necessary to insert remotely controlled tools inside the vessel to disassemble the heat exchanger. This makes the disassembly of the heat exchanger faster and more convenient. Furthermore, the attachment members are easier to access from outside the vessel, the inside of the vessel generally being cluttered by the inner members of the nuclear reactor. Typically, the heat exchanger comprises a plurality of plates stacked parallel to one another, the discharge duct passing through the vessel in a substantially radial direction relative to a central axis of the vessel, the plates being substantially perpendicular to said radial direction. Thus, the plates are provided so as to be tangent to a circle centered on the central axis of the vessel. Such an arrangement makes it possible to arrange the collector collecting the secondary fluid leaving the heat exchanger, here called downstream secondary collector, easily such that it is aligned with the discharge duct. In fact, the secondary fluid discharge duct typically includes a downstream crossing provided in an orifice of the vessel. That downstream crossing inwardly delimits a passage for the secondary fluid leaving the heat exchanger. It is fluidly connected to the secondary circuit of the reactor. That passage extends substantially radially relative to the central axis of the vessel. Due to the orientation of the plates, the downstream secondary collector also has a substantially radial orientation and can easily be placed immediately next to the discharge duct. The discharge duct is thus kept minimal. Advantageously, the downstream secondary collector extends through the plates. It is typically made up of openings cut into the plates and placed so as to coincide with each other. This makes it possible to build a collector with a radial orientation easily, and contributes to increasing the compactness of the exchanger. In one non-preferred alternative, it is attached on the plates, for example outside the plate mass. A crossing here refers to a solid part, rigidly attached to the vessel. Typically, the attachment device attaches the heat exchanger directly to the crossing. This makes it possible to arrange the attachment device more easily, in particular the orifices allowing the passage of screws or tie rods. Typically, the attachment members are distributed around the passage formed in the crossing. The flange placed around the outlet of the heat exchanger is pressed against an inner face of the crossing. The attachment members are attached to the flange by one end. Typically, they extend completely through the crossing and have a head accessible from the outside of the vessel. Preferably, at least one sealing gasket is interposed between the flange and the inner face of the crossing. Typically, one or more pairs of annular seals are provided around the inner passage at the crossing. Leak detection channels advantageously emerge between each pair of seals. Preferably, these attachment members and the downstream crossing can be removed from the vessel from the outside of the vessel. The downstream crossing is in that case for example engaged in an orifice of the vessel and attached to the outer surface of the vessel so as to be able to be disassembled. It is for example attached using a device of the screw or tie rod type, or any other suitable type. This makes it possible to access the sealing gaskets interposed between the flange and the inner face of the crossing, in particular for maintenance thereof. These seals are advantageously secured to the crossing, and are removed from the vessel with the crossing. Preferably, the reactor comprises a ring provided to keep the heat exchanger suspended from the vessel after the downstream crossing has been removed from the vessel. That ring normally surrounds both the flange of the exchanger and the inner end of the crossing. It is engaged in the receiving orifice of the crossing. Alternatively, the attachment device attaches the heat exchanger directly to the vessel, around or next to the crossing. Advantageously, the supply duct supplying the heat exchanger with secondary fluid comprises an upstream crossing extending through the vessel, and a plurality of flexible ducts connecting the upstream crossing to the heat exchanger. A flexible duct here refers to ducts with small diameters, able to deform elastically under the effect of the thermal expansion of the plate exchanger. A single duct connecting the upstream crossing to the heat exchanger would have a larger diameter and higher stiffness than several ducts with smaller diameters. The crossing and the plate heat exchanger are two solid parts. It is necessary to create a flexible link between those two parts so as to allow the plate exchanger to travel relative to the crossing. That travel is obtained through deformation of the flexible ducts. The flexible ducts may in particular include bends, which contribute to increasing the flexibility of the ducts under the effect of the relative movements of the attachment points or ends of the ducts. Such bends are more difficult to obtain on ducts with large diameters. Typically, the heat exchanger comprises at least one upstream secondary collector supplying the heat exchanger with secondary fluid, that upstream secondary collector and the upstream crossing being connected to each other by the flexible ducts. The upstream secondary connector extends through the plates. It is typically made up of openings cut into the plates and placed so as to coincide with each other. A plate exchanger typically has channels, in particular micro-channels. It comprises primary and secondary plates alternatingly stacked around each other. The primary plates each have a first large face in which flow channels are hollowed out for the primary fluid, called primary channels, and a second large face without channels. The primary channels are open at the first large face. Likewise, the secondary plates each have a first large face in which flow channels are hollowed out for the secondary fluid, called secondary channels, and a second large face without channels. The secondary channels are open at their first large face. When the plates are assembled to each other, the first large faces of the primary plates are pressed against the second large faces of the secondary plates. The primary channels are therefore closed off at the first large faces. Likewise, the first large faces of the secondary plates are pressed against second large faces of the primary plates. The secondary channels are also closed off at the first large faces. Such an architecture makes it possible to obtain a very compact and very robust exchanger. Typically, the primary and secondary channels are etched. Such a method for obtaining channels is very convenient, in particular when it is necessary to produce a large number of channels with small sections. In one non-preferred alternative, the plate exchangers are not of the etched plate type. The channels are mechanically or laser machined or are formed by inserts placed between the plates. Alternatively, the channels are made by hollowing out the two large faces across from the primary and secondary plates. In this alternative, the two large faces of each primary and secondary plate bear half-channels. According to still another alternative, the exchanger does not include channels, the primary and secondary fluids circulating between the plates without being channeled in channels. Preferably, the primary and secondary plates are welded to each other by diffusion. This assembly method makes it possible to obtain a very robust link between the plates, and allows the exchanger to withstand significant pressure differences between the primary side and the secondary side. In one non-preferred alternative, the plates are assembled to each other by other means. They may be welded inside plates, or assembled by screws or tie rods. Advantageously, the heat exchanger comprises a plurality of primary channels delimited between the plates and traveled by the primary fluid, each primary channel having a main inlet and a main outlet, the exchanger having at least one hood delimiting a water tank, in which the main inlets or the main outlets emerge. The heat exchanger may include only one hood, covering the main inlets. It may also include only one hood, covering the main outlets. It may also include two hoods, one covering the main inlets and the other covering the main outlets. The hood covering the main inlets serves, inter alia, to distribute the primary fluid uniformly in the different primary channels. It has an orifice emerging in the inner volume of the vessel, through which the primary fluid penetrates the water tank. The purpose of the hood covering the primary outlets is to capture the primary fluid having come out of the primary channels, and to channel it toward a duct, for example toward the primary pumps. As indicated above, the heat exchangers are typically elongated in the vertical direction. The main inlets emerge at one of the ends of the heat exchanger, for example the upper end. The main outlets emerge at the other end of the exchanger, for example the lower end. The hood(s) are therefore positioned at the upper and/or lower ends of the heat exchanger. Alternatively, the primary fluid flows from bottom to top, the main inlets and outlets respectively emerging at the lower and upper ends of the exchanger. The hood(s) are typically attached on the block made up of the plates assembled to each other. It is advantageously provided to be able to be disassembled, so as to allow the inspection or operations of the primary channels. It is for example screwed on the plates. Alternatively, it is welded on the plates. According to a first embodiment, the vessel includes a shroud and a cover attached on the shroud so as to be able to be disassembled, the heat exchanger(s) being attached to the cover. Thus, it is particularly easy to remove the heat exchangers from the vessel of the reactor. They are discharged in one piece with the cover. According to a second embodiment, the reactor comprises absorbers for controlling the reactivity of the core, which are vertically movable relative to the core, the absorbers being situated above the core and the heat exchanger(s) being situated above the absorbers. The absorbers are clusters, crosses or any other suitable shape. More specifically, the absorbers can be moved between a first position removed outside the core, in which the absorbers are situated vertically between the heat exchangers and the core, and a plurality of positions in which those absorbers are partially or completely inserted inside the core. In that case, the reactor comprises mechanisms provided to maneuver the absorbers selectively, the mechanisms for maneuvering the absorbers comprising actuators placed vertically above the heat exchangers, and rods connecting the actuators to the absorbers, the nuclear reactor having several heat exchangers distributed around the rods. Typically, the actuators are placed above the cover of the vessel and are supported by the cover. The heat exchangers are placed along the shroud of the vessel, which frees a significant free volume in the middle of the vessel to allow the rods to pass. In the first embodiment, the mechanisms for maneuvering the absorbers for controlling the reactivity of the core are housed vertically between the heat exchangers and the core. The nuclear reactor 1 partially shown in FIG. 1 is of the PWR type. It comprises: a vessel 3; a core 5, provided in the vessel 3; four one plate heat exchangers 7 provided in the vessel 3; a secondary circuit 9, comprising, inter alia, for each heat exchanger, a duct 11 for supplying a secondary fluid to the heat exchanger and a duct 13 for discharging the secondary fluid from the heat exchanger; members ensuring the flow of the primary fluid inside the vessel 3, in particular pumps 14 and inner partitions. The vessel 3 is oriented vertically, and has a vertical central axis X. It includes, in the lower part, a shroud 15, which is only partially shown in FIG. 1, and a lower bottom, shown diagrammatically, secured to the shroud. The vessel 3 also includes a cover 17 removably attached on the upper peripheral edge 19 of the shroud 15. The cover 17 in turn includes a peripheral wall 21, coaxial to the axis X, and an upper bottom 23 closing the wall 21 at an upper end thereof. The exchangers 7 are exchangers of the etched plate type. As shown in FIGS. 4 and 5, each heat exchanger 7 includes a plurality of primary plates 25 and a plurality of secondary plates 27, stacked alternating on one another. Each primary plate 25 has a first large face in which flow channels 29 are hollowed out for the primary fluid. The second large face does not have channels. Likewise, each secondary plate 27 has a first large face in which a plurality of channels 31 are hollowed out that are provided for the flow of the secondary fluid. The second large face does not include channels. Thus, the channels hollowed in a given primary plate 25 are closed off laterally by the second large face of the secondary plates 27 situated immediately higher in the stack. Likewise, the secondary channels 31 in a given plate are close to the second large face of the primary plate 25 situated immediately higher in the stack. The primary and secondary plates are welded to each other by diffusion. The heat exchanger 7 includes an upstream secondary collector 33 (FIG. 3) supplying the secondary channels 31 with secondary fluid, and a downstream secondary collector 35 collecting the secondary fluid leaving the secondary channels 31. The upstream secondary collector 33 is made up of openings (not shown) cut into the primary and secondary plates 25, 27 and placed coinciding with each other. The downstream secondary collector 35 is also made up of openings 37, visible in FIG. 5, cut into to the primary and secondary plates and placed matching each other. The secondary channels 31 each emerge at an upstream end in the upstream secondary collector 33, and emerge at a downstream end in the downstream secondary collector 35. Each exchanger 7 also includes four other plates 39 and 41. The plates 39 also cover the large faces of the primary or secondary plates situated highest and lowest in the stack of plates in the illustration of FIG. 4, and one of the outer plates 39 covers the first large face of the primary plate situated at the apex of the stack. The other outer plate 39 covers the second large face of the primary plate situated at the very bottom of the stack of plates. As shown in FIG. 3, however, the plates have an elongated shape in the vertical direction. The downstream secondary collector 35 extends through an upper end of the plates, the upstream secondary collector 33 extending through a lower end of the plates. The plates are therefore each delimited (FIG. 5) by an upper edge 43 turned upward, by a lower edge (not shown) turned downward, and by two opposite lateral edges 45. The lateral outer plates 41 cover the lateral edges 45 of the primary and secondary plates 25, 27. The upstream and downstream secondary collectors 33 and 35 are elongated in a direction perpendicular to the primary and secondary plates 25, 27 and the outer plates 39. The upstream secondary collector 33 is closed at the two outer plates 39. The downstream secondary collector 35 is closed at the plates 39 but extends through the other outer plate 39 by an outlet orifice 47, shown in FIG. 3. The outer plate 39 has, around the orifice 47, a boss 49 forming a flange for attaching the exchanger 7 to the wall 21 of the cover. The primary channels 25 each have an inlet end emerging at the upper edge 43 of the primary plates, and an outlet end emerging at the lower edge of the primary plates. As shown in FIG. 3, the lateral plates 39 each have an extension 51 extending past the upper edges 43 of the primary and secondary plates. The exchanger also includes an upper hood 53 delimiting, with the two extensions 51, a water tank 54 that caps the upper edges 43 of the plates. The primary channels 29 emerge by their respective inlet ends in the water tank. Furthermore, the upper hood 53 includes an inlet 55 putting the water tank in communication with the inside of the vessel. One thus obtains a homogenous distribution of the primary fluid in the different primary channels 29. In other words, the primary fluid flow rate in the different primary channels is substantially the same. In the illustrated alternative embodiment, the exchanger does not include a hood on the lower side. The primary channels 29 emerge by their respective outlet ends directly in the inner volume of the vessel. The secondary supply duct 11 includes, as shown in FIGS. 1 and 3, an upstream wall crossing 57 and a plurality of flexible ducts 59. The peripheral wall 21 of the vessel cover includes an orifice in which the wall crossing 57 is engaged. The latter is rigidly attached to the vessel cover and is sealably linked to the edge of the orifice. The crossing 57 has an inner passage 61 through which the secondary fluid extends through the wall 21. The inner passage 61 is fluidly connected in the upstream direction to a secondary fluid flow pump. The inner passage 61 is fluidly connected in the downstream direction to the flexible duct 59. The secondary fluid extending through the wall 21 via the passage 61 is distributed in the different flexible ducts 59. As shown in FIGS. 1 and 3, the flexible ducts 59 are tubes with small diameters for example in light of the cross-section of the exchanger 7. They are each in the general shape of an asymmetrical U. Each duct 59 has, from the crossing 57, a first branch 61 extending downward, then a substantially horizontal intermediate part 63, and lastly a second branch 65 that is much shorter than the first branch 61, rising upward from the horizontal part 63. The second branch 65 emerges in the secondary upstream collector 33. The first branch 61 has several bends with strong curve radii. Each discharge duct for the secondary fluid 13 also includes a wall crossing 67, mounted in an orifice of the peripheral wall 21 of the cover. As shown in FIG. 2, the crossing 67 includes a cylindrical main segment 69 engaged in the orifice 71 of the wall 21, inwardly delimiting a passage 73 for the secondary fluid. The main segment 69 protrudes both toward the inside of the vessel by an inner end, and toward the outside of the vessel. The crossing 67 also includes a flange 75, in a single piece with the segment 69, extending radially around the outer end of the main segment 69. The passage 73 extends in a substantially radial direction relative to the vertical central axis X of the vessel. The collar 75 is pressed against the outer surface of the vessel cover and rigidly attached to that cover by tie rods 78. The main segment 69 extends toward the outside of the vessel, beyond the collar 75, by a mushroom head 79. The mushroom head 79 ends with a flange 81. The passage 73 extends completely through the mushroom head 79 and emerges at the center of the flange 81. The flange 81 makes it possible to connect the crossing to a line (not shown) connecting the heat exchanger to a steam turbine. The main segment 69 of the crossing is delimited toward the inside of the vessel by an annular surface 83 surrounding the passage 73. The annular surface 83 extends in a plane substantially perpendicular to said radial direction along which the passage 73 extends. It forms a bearing step for the flange 49. Furthermore, a device 85 ensures the attachment of the heat exchanger 7 to the vessel. This device 85 includes a plurality of tie rods 87 securing the exchanger 7 to the crossing 67. The tie rods each have one end screwed into an orifice 89 formed in the flange 49. They extend over the entire length of the main segment 69, through the latter, and protrude on the face of the collar 75 turned toward the outside of the vessel. Nuts 91 are screwed on the protruding ends 93 of the tie rods. The tie rods 87 are regularly distributed around the passage 73 and the orifice 47. The tie rods 87 thus bias the flange 49 against the annular surface 83 of the crossing. In that position, shown in FIG. 2, the passage 73 is placed coinciding with the outlet 47. More specifically, the downstream secondary collector 35 is aligned with the passage 73, in a radial direction. The downstream secondary collector 35 and the passage 73 are both rectilinear, and placed in the extension of one another. Annular sealing gaskets 131 are interposed between the flange 49 and the annular surface 83. In the illustrated example, two pairs of seals 131 are positioned around the passage 73. A leak detection channel 133 emerges between each pair of seals. The seals 131 are each placed in a groove, formed on the annular surface 83, and are secured to the surface. At least one pair of annular sealing gaskets 135 is interposed between the flange 75 and the outer surface of the cover of the vessel. As indicated above, the tie rods 78 and the tie rods 87 are can be disassembled from the outside of the vessel 3. Once the tie rods are removed, it is possible to remove the wall crossing 67 outside the orifice 71 of the vessel, in particular to perform maintenance on the sealing gaskets 131 and 135. A ring 137 is provided to keep the heat exchanger suspended from the vessel cover once the crossing 67 is removed from the orifice. That ring 135 normally surrounds both the flange 49 and the end of the main segment 69 of the crossing. It is engaged in the orifice 71 and interposed radially between the segment 69 and the wall of the orifice. During the period of time where the crossing 67 is removed from the orifice, the exchanger 3 is radially wedged between the inner partitions and the vessel, and is supported and maintained in the axis of the crossing by the ring 137. In that situation, the heat exchanger 7 is mounted cantilevered, in the immediate vicinity of the peripheral wall 21 of the vessel cover. As shown in FIG. 1, the four heat exchangers 7 are positioned around the axis X at 90° from each other. The central zone 95 of the vessel, between the four exchangers 7, is thus freed and allows the flow of the primary fluid from the core of the reactor upward, to the upper bottom 23. The volume 97 situated immediately below the upper bottom 23 is free, the primary fluid flowing from that volume into the water tanks 54 of the four exchangers through the orifices 55. The secondary flow ducts 11 are positioned in the volumes 99 of the vessel situated between two exchangers 7. These volumes 99 are delimited radially toward the outside by the peripheral wall 21 and are delimited toward the inside of the vessel by the lateral plates 41 of the two exchangers 7. The nuclear reactor also includes inner partitionings such as the partitions 101 shown in FIG. 2, arranged to guide the flow of the primary fluid inside the vessel. The partitions 101 in particular guide the flow of the primary fluid from the core through the volume 95 up to the volume 97, from the elements of the primary channels to the sections of the primary pumps, and also from the discharge of the primary pumps to the core. Only part of these partitions is shown in FIGS. 1 and 2. Each exchanger 7 is fastened to the side wall 21 using only the flange 49. In other words, each exchanger 7 is rigidly attached to the vessel by its upper end, its lower end not being rigidly attached to the vessel. However, the exchanger is guided in the lower part so as to prevent pivoting of the exchanger around a vertical axis or toppling in case of bias of the impact or earthquake type. To that end, the outer lateral plates 41 each bear a raised portion 103. This raised portion assumes the shape of a vertically elongated stick. The raised portions 103 cooperate with guideways (not shown), for example borne by inner partitions 101. The raised portions 103 are free to slide in the vertical direction inside the guideways, thus allowing the downward expansion of the exchanger. When the reactor is operating, the primary fluid is heated in the core 5 of the reactor. After having crossed through the core 5 of the reactor, it flows toward the top of the vessel, in particular through the volume 95 to the volume 97 situated below the upper bottom of the cover. It penetrates the water tanks 54 of the heat exchangers 7 through the orifices 55 and is distributed in the primary channels 29. It leaves the primary channels of the lower end of the heat exchangers 7 and is channeled by the partitions 101 to the sections of the primary pumps 14. The primary pumps 14 discharge the primary fluid to the core 5 of the reactor. The secondary fluid penetrates the vessel 3 of the reactor through the passages 61 formed in the upstream crossings 57. At the outlet of passages 61, it is distributed in the flexible ducts 59. The flexible ducts 59 conduct the secondary fluid to the upstream secondary collectors 33. In each exchanger 7, the secondary fluid is distributed by the upstream secondary collector 33 in the secondary channels 31 of the heat exchanger. The secondary fluid is vaporized under the effect of the heat ceded by the primary fluid. The steam is collected by the downstream secondary collector 35, flows in the passage 73 and exits the vessel. It then flows to the turbine, then is condensed. A secondary pump next discharges the secondary fluid to the crossing 57. In the first embodiment of the invention, the heat exchangers 7 are secured to the cover 3 of the vessel, such that the heat exchangers 7 are removed in a single piece with the vessel cover. A second embodiment of the invention will now be outlined, in reference to FIGS. 6 and 7. Only the differences between the second embodiment and the first will be described below. Identical elements or performing elements the same function both embodiments will be designated using the same references. The nuclear reactor of FIG. 6 includes six heat exchangers 7, distributed circumferentially at 60° from each other around the axis of the vessel. The heat exchangers 7 are each attached by an attachment device 85 to the shroud 19 of the vessel, and not to the cover. Each heat exchanger 7 includes a hood 105 (FIG. 7) in its lower part. It does not include a hood 53 in its upper part. In this second embodiment, the outer plates 39 of the heat exchanger protrude downward relative to the primary and secondary plates. They delimit a water tank with the hood 105. The water tank covers the outlet ends of the primary channels 29, those elements emerging in the water tank. The hood 105 makes it possible to capture the primary fluid leaving the heat exchanger and to orient it toward the suction of the primary pump 107 shown in FIG. 7. To that end, the hood 105 has an outlet orifice 109 emerging in a duct delimited by inner partitions 111 provided in the vessel. The primary pump 107 includes a rotor 112 embedded in the duct. It also includes a motor 113, and a shaft 115 driving the rotor 112. The motor 113 is provided outside the vessel, the shaft 115 extending through said vessel. In the nuclear reactor illustrated in FIG. 6, the core 117 of the reactor is situated in the lower part of the vessel. The nuclear reactor also includes a plurality of absorbers 119 that can be moved relative to the vessel, and provided to control the reactivity of the core. The absorbers 119 can each be moved selectively in the vertical direction between a plurality of insertion positions inside the core 117. In the low position, the absorbers 119 are completely inserted inside the core 117. In the upper position, the absorbers 119 are completely removed outside the core. They are then situated above the core 117. As shown in FIG. 6, the heat exchangers 7 are positioned so as to be situated above the absorbers 119. The nuclear reactor also includes a mechanism 121 provided to maneuver the absorbers 119. This mechanism comprises actuators 123, and rods 125 with vertical orientations secured to the absorbers 119. The actuators 123 are arranged to move the rods 125 in the vertical direction. The heat exchangers 7 are positioned on the periphery of the vessel, along the shroud 15. They delimit a central passage between them in which the rods 125 are provided. The actuators 123 are supported by the cover 17. In the embodiment of FIGS. 1 to 5, the heat exchangers 7 are positioned in the vessel cover 17. The maneuvering mechanisms of the absorbers for controlling the reactivity of the core are situated below the heat exchangers. In the second embodiment, illustrated in FIGS. 6 and 7, the procedure for removing the heat exchangers 7 from the vessel is as follows. The cover 17 is first disassembled and separated from the shroud 19. The actuators 123 and at least part of the rods 125 are removed in a single piece with the cover. Then, the tie rods 87 attaching each exchanger to the vessel are disassembled and each exchanger is individually removed from the vessel. |
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abstract | Disclosed are a zirconium alloy for a nuclear fuel cladding having a good oxidation resistance in reactor accident conditions, a zirconium alloy nuclear fuel cladding prepared by using thereof and a method of preparing the same. The zirconium alloy includes 1.0 to 1.2 wt % of niobium (Nb); at least one element selected from tin (Sn), iron (Fe) and chromium (Cr); 0.02 to 0.1 wt % of copper (Cu); 0.1 to 0.15 wt % of oxygen (O); 0.008 to 0.012 wt % of silicon (Si) and a remaining amount of zirconium (Zr). The amount of Sn is 0.1 to 0.3 wt %, the amount of Fe is 0.3 to 0.8 wt %, and the amount of Cr is 0.1 to 0.3 wt %. A good oxidation resistance of the nuclear fuel cladding may be confirmed under accident conditions as well as normal operating conditions of a reactor, thereby improving economic efficiency and safety. |
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description | This application claims the benefit of U.S. Provisional Application No. 61/792,235 filed Mar. 15, 2013 and titled “CRDM DESIGNS WITH SEPARATE SCRAM LATCH ENGAGEMENT AND LOCKING”. U.S. Provisional Application No. 61/792,235 filed Mar. 15, 2013 and titled “CRDM DESIGNS WITH SEPARATE SCRAM LATCH ENGAGEMENT AND LOCKING” is hereby incorporated by reference in its entirety into the specification of this application. This invention was made with Government support under Contract No. DE-NE0000583 awarded by the Department of Energy. The Government has certain rights in this invention. DeSantis et al., U.S. Pub. No. 2011/0222640 A1 published Sep. 15, 2011 and incorporated herein by reference in its entirety discloses (among other subject matter) a CRDM for a nuclear reactor employing a lead screw (sometimes referred to as a ball screw herein denoting specific lead screw embodiments employing ball nuts disposed between the screw and nut threadings) engaged by a motor to provide controlled vertical translation, in which a separate latch assembly connected with the lead screw latches to the lifting rod of a control rod (or to the lifting rod of a control rod assembly comprising plural control rods connected by a yoke or spider to the lifting rod). The latch is actively closed to connect the translating assembly comprising the lifting rod and the control rod(s) so that the translating assembly translates with the lead screw under control of the CRDM motor. Upon removal of the closing force, e.g. during a SCRAM, the latch opens to release the lifting rod and SCRAM the control rod(s), while the lead screw remains engaged with the CRDM motor and does not fall. In some illustrative embodiments, the latches are actively closed by cam bars that are lifted by a hydraulic piston, solenoid, or other lifting mechanism, where each cam bar is part of a four-bar linkage that moves the cam bar horizontally in response to the lifting in order to cam the latches shut. In DeSantis et al., U.S. Pub. No. 2011/0222640 A1, the four-bar linkage is arranged such that under gravity the four-bar linkage operates to move the cam bars outward so as to release the latch. By way of non-limiting illustrative example, FIGS. 1 and 2 correspond to drawing sheets 1 and 16, respectively, of DeSantis et al., U.S. Pub. No. 2011/0222640 A1. With reference to FIG. 1, an illustrative nuclear reactor vessel of the pressurized water reactor (PWR) type is diagrammatically depicted. An illustrated primary vessel 10 contains a reactor core 12, internal steam generator(s) 14, and internal control rods 20. The illustrative reactor vessel includes four major components, namely: 1) a lower vessel 22, 2) upper internals 24, 3) an upper vessel 26 and 4) an upper vessel head 28. A mid-flange 29 is disposed between the lower and upper vessel sections 22, 26. Other vessel configurations are also contemplated. Note that FIG. 1 is diagrammatic and does not include details such as pressure vessel penetrations for flow of secondary coolant into and out of the steam generators, electrical penetrations for electrical components, and so forth. The lower vessel 22 of the illustrative reactor vessel 10 of FIG. 1 contains the reactor core 12, which can have substantially any suitable configuration. The illustrative upper vessel 26 houses the steam generator 14 for this illustrative PWR which has an internal steam generator design (sometimes referred to as an integral PWR design). In FIG. 1, the steam generator 14 is diagrammatically shown. In a typical circulation pattern the primary coolant is heated by the reactor core 12 and rises through the central riser region 32 to exit the top of the shroud 30 whereupon the primary coolant flows back down via the downcomer region 34 and across the steam generators 14. Such primary coolant flow may be driven by natural convection, by internal or external primary coolant pumps (not illustrated), or by a combination of pump-assisted natural convection. Although an integral PWR design is illustrated, it is also contemplated for the reactor vessel to have an external steam generator (not illustrated), in which case pressure vessel penetrations allow for transfer of primary coolant to and from the external steam generator. The illustrative upper vessel head 28 is a separate component, but it is also contemplated for the vessel head to be integral with the upper vessel 26. While FIG. 1 illustrates an integral PWR, in other embodiments the PWR may not be an integral PWR, that is, in some embodiments the illustrated internal steam generators may be omitted in favor of one or more external steam generators. Still further, the illustrative PWR is an example, and in other embodiments a boiling water reactor (BWR) or other reactor design may be employed, with either internal or external steam generators. With reference to FIG. 2, a control rod system embodiment is described, e.g. suitably part of the upper internals 24 of the nuclear reactor of FIG. 1, which provides electromagnetic gray rod functionality (i.e. continuously adjustable control rod positioning) and a hydraulic latch system providing SCRAM functionality (i.e. in an emergency, the control rods can be fully inserted in order to quickly quench the nuclear reaction, an operation known in the art as a SCRAM). The control rod system of FIG. 2 allows for failsafe SCRAM of the control rod cluster without scramming the lead screw. A motor/ball nut assembly is employed, such that a lead screw 40 is permanently engaged to a ball-nut assembly 42 which provides for axial translation of the lead screw 40 by driving a motor 44. The illustrative motor 44 is mounted on a standoff 45 that positions and bottom-supports the motor 44 in the support structure of the upper internals 24; other support arrangements are contemplated. A control rod cluster (not shown) is connected to the lead screw 40 via a lifting/connecting rod or lifting/connecting rod assembly 46 and a latch assembly 48. The lead screw 40 is substantially hollow, and the lifting/connecting rod 46 fits coaxially inside the inner diameter of the lead screw 40 and is free to translate vertically within the lead screw 40. The latch assembly 48, with spring loaded latches, is attached to (i.e. mounted on) the top of the lead screw 40. When the latches of the latch assembly 48 are engaged with the lifting rod 46 they couple the lifting/connecting rod 46 to the lead screw 40 and when the latches are disengaged they release the lifting/connecting rod 46 from the lead screw 40. In the illustrated embodiment, latch engagements and disengagements are achieved by using a four-bar linkage cam system including two cam bars 50 and at least two cam bar links 52 per cam bar 50. Additional cam bar links may be added to provide further support for the cam bar. When the cam bars 50 move upward the cam bar links 52 of the four-bar linkage also cam the cam bars 50 inward so as to cause the latches of the latch assembly 48 to rotate into engagement with the lifting/connecting rod 46. In the illustrated embodiment, a hydraulic lift assembly 56 is used to raise the cam bar assemblies 50. In an alternative embodiment (not illustrated), an electric solenoid lift system is used to raise the cam bar assemblies. When a lift force is applied to the cam system, the upward and inwardly-cammed motion of the cam bars 50 rotates the latches into engagement thereby coupling the lifting/connecting rod 46 to the lead screw 40. This causes the control rod cluster to follow lead screw motion. When the lift force is removed, the cam bars 50 swing down and are cammed outward by the cam bar links 52 of the four-bar linkage allowing the latches of the latch assembly 48 to rotate out of engagement with the lifting/connecting rod 46. This de-couples the lifting/connecting rod 46 from the lead screw 40 which causes the control rod cluster to SCRAM. During a SCRAM, the lead screw 40 remains at its current hold position. After the SCRAM event, the lead screw 40 is driven to the bottom of its stroke via the electric motor 44. When the lift force is reapplied to the cam system via the hydraulic lift assembly 56, the latches of the latch assembly 48 are re-engaged and the lifting rod 46 is re-coupled to the lead screw 40, and normal operation can resume. Other latch drive modalities are contemplated, such as a pneumatic latch drive in which pneumatic pressure replaces hydraulic pressure in the illustrated lift assembly 56. In FIG. 2, the lead screw 40 is arbitrarily depicted in a partially withdrawn position for illustration purposes. The latching assembly 48 is attached to (i.e. mounted on) the top of the lead screw 40. The ball nut 42 and motor 44 are at the bottom of the control rod drive mechanism (CDRM), the latch cam bars 50 extend for the full length of mechanism stroke, and the hydraulic lift system 56 is located at the top of the mechanism. In some embodiments, the CRDM of FIG. 2 is an integral CDRM in which the entire mechanism, including the electric motor 44 and ball nut 42, and the latching assembly 48 are located within the reactor pressure vessel 10 (see FIG. 1) at full operating temperature and pressure conditions. Further illustrative embodiments of CRDM designs employing the cam bars with four-bar linkages are described in DeSantis et al., U.S. Pub. No. 2011/0222640 A1, which is incorporated herein by reference in its entirety. In some illustrative embodiments, a control rod drive mechanism (CRDM) comprises: a lead screw engaged by a CRDM motor; a lifting rod supporting at least one control rod; latches secured to the lead screw and configured to latch an upper end of the lifting rod to the lead screw; a latch engagement mechanism configured to close the latches onto the upper end of the lifting rod; and a latch holding mechanism configured to hold the latches closed; wherein the latch holding mechanism is separate from the latch engagement mechanism. In some embodiments the CRDM further comprises a four-bar linkage including cam bars, the four-bar linkage configured to drive the cam bars inward to cam the latches closed responsive to operation of the latch engagement mechanism, the latch holding mechanism configured to hold the cam bars in the inward position to keep the latches closed. In some such embodiments the four-bar linkage is configured to bias the latches closed under force of gravity. In some embodiments the latch engagement mechanism operates responsive to lowering the latches over the upper end of the lifting rod and is not effective to keep the latches closed when the latches are raised again after the latch engagement mechanism operates. In some illustrative embodiments, a control rod drive mechanism (CRDM) comprises: a lead screw engaged by a CRDM motor; a lifting rod supporting at least one control rod; latches secured to the lead screw and configured to latch an upper end of the lifting rod to the lead screw; a latch engagement mechanism configured to close the latches onto the upper end of the lifting rod; and a latch holding mechanism configured to hold the latches closed; wherein the latch engagement mechanism is not effective to keep the latches closed when the latches are supporting the weight of the lifting rod and supported at least one control rod. In some embodiments the latch holding mechanism is not effective to close the latches. In some embodiments the CRDM further comprises a four-bar linkage including cam bars, the four-bar linkage configured to drive the cam bars inward to cam the latches closed responsive to operation of the latch engagement mechanism, the latch holding mechanism configured to hold the cam bars in the inward position to keep the latches closed. In some such embodiments the four-bar linkage is configured to bias the latches closed under force of gravity. In some embodiments the latch engagement mechanism operates responsive to lowering the latches over the upper end of the lifting rod and is not effective to keep the latches closed when the latches are raised again after the latch engagement mechanism operates. In some illustrative embodiments, a control rod drive mechanism (CRDM) comprises: a lead screw engaged by a CRDM motor; a lifting rod supporting at least one control rod; latches secured to the lead screw and configured to latch an upper end of the lifting rod to the lead screw; and a four bar linkage including cam bars, the four bar linkage configured to drive the cam bars inward to cam the latches closed responsive to operation of a latch engagement mechanism; wherein the four bar linkage is configured to bias the latches closed under force of gravity. In some illustrative embodiments, a control rod drive mechanism (CRDM) includes: a CRDM motor; an element translated under control of the CRDM motor; a latch configured to latch a lifting rod supporting at least one control rod with the element translated under control of the CRDM motor; a latch engagement mechanism configured to close the latch onto the lifting rod; and a latch holding mechanism, separate from the latch engagement mechanism, configured to hold the latch in its closed position. In some illustrative embodiments, a control rod drive mechanism (CRDM) includes: a CRDM motor; an element translated under control of the CRDM motor; a latch configured to latch a lifting rod supporting at least one control rod with the element translated under control of the CRDM motor; and a four bar linkage including cam bars, the four bar linkage configured to cam the latches closed responsive to operation of a latch engagement mechanism; wherein the four bar linkage is configured to bias the latches closed under force of gravity. In some illustrative embodiments, a control rod drive mechanism (CRDM) is configured to latch onto the lifting rod of a control rod assembly and includes separate latch engagement and latch holding mechanisms. In some illustrative embodiments, a control rod drive mechanism (CRDM) is configured to latch onto the lifting rod of a control rod assembly and includes a four-bar linkage closing the latch, wherein the four-bar linkage biases the latch closed under force of gravity. Disclosed herein are improvements upon CRDM designs of DeSantis et al., U.S. Pub. No. 2011/0222640 A1 employing the cam bars with four-bar linkages. In one aspect, the CRDM is improved by separating the latch engagement and latch holding functions. This may entail increasing the number of CRDM components since a separate latch engagement mechanism and latch holding mechanism are provided. However, it is recognized herein that this increase in parts is offset by improved energy efficiency. This is because the latch engagement is a momentary event that occurs very infrequently (possibly only once per fuel cycle). In contrast, the latch holding operation is performed over the entire fuel cycle (barring any SCRAM events). By employing separate latch engagement and holding mechanisms, the latch holding mechanism is not required to perform the relatively higher-energy operation of moving the latches from the unlatched position to the latched position. Accordingly, the latch holding mechanism can be made more energy efficient. In another aspect, the latch engagement mechanism, which no longer needs to perform the latch holding function, can be substantially improved. In one embodiment (see FIGS. 3-6), the latch engagement mechanism comprises a lower camming link built into the lower portion of the CRDM, which is engaged by the latch box or housing as it is lowered toward the lifting rod (which, due to its not currently being latched, is typically located at its lowermost position corresponding to maximum insertion of the control rods into the nuclear reactor core). The lowering latch housing engages the lower camming link which is curved and mounted pivotally so that an end distal from the end cammed by the latch housing is caused to drive the cam bars inward, into the latched position. Once in the latched position, the separate latch holding mechanism is engaged, and thereafter when the latch housing is raised by the CRDM motor and lead screw the lower camming link disengages but the latch remains closed by action of the separate latch holding mechanism. In another aspect, the latch engagement mechanism is implemented as a self-engaging cam/latch system (see FIGS. 7-18). This approach is achieved by modifying the four-bar linkage such that under gravity the four-bar linkage operates to move the cam bars inward so as to engage the latch. Similar to the latch engagement of FIGS. 3-6, this latch engagement activates upon lowering the latch housing over the upper end of the lifting rod. In the self-engaging approach, the latch is normally closed due to the four-bar linkage defaulting to moving the cam bars inward under force of gravity, and the upper end of the lifting rod includes a camming surface that cams the latch open as the latch housing is lowered over the upper end of the lifting rod. Once over the camming surface of the upper end, the latch again closes under force of gravity due to the orientation of the four-bar linkage. The separate latch holding mechanism is then activated to hold the cam bars in the inward position to keep the latch closed. Surprisingly, this embodiment is capable of reliable SCRAM even though the four-bar linkage is biasing the latch closed under gravity. This is because the four-bar linkage is designed with its links at large angles and of relatively long length so that the force necessary to open the latches against the gravitational closing bias of the four-bar linkage is quite modest. (See FIGS. 7-18 and related discussion for details). Accordingly, the weight of the translating assembly (i.e. the lifting rod and the attached control rod or rods and optional spider or yoke) is sufficient to easily overcome the closing bias of the four-bar linkage. In further disclosed aspects, various embodiments of the latch holding mechanism are disclosed. See FIG. 19 and following. In the CRDM system of FIG. 2, the lift system 56 (hydraulic as shown, or alternatively an electric solenoid) supports both latch actuation and long term engagement during hold and translational operations. In the variant embodiments described in the following, features of like functionality to the CRDM of FIG. 2 (for example, the cam bars 50 and the cam bar links 52 of the four-bar linkage) are labeled with like reference numbers. With reference to FIGS. 3-6 and with contextual reference to FIG. 2, a CRDM embodiment is described in which latch activation and long term hold/translation functions are separated, resulting in reduction of operational power requirements. The CRDM comprises a mechanically actuated latching device. FIG. 3 shows an isometric view of the CRDM with the control rod (not shown) fully inserted. FIGS. 4 and 5 show isometric and side cutaway views, respectively, with the latching device disengaged. FIG. 6 shows a side cutaway view with the latch engaged. The latching mechanism utilizes the CRDM motor 44, the lead screw 40 (e.g. threadedly engaged with the CRDM motor 44 via the ball screw 42 as shown in FIG. 2) and a latch box 102 to engage the latches 104 to the top of the connecting (i.e. lifting) rod 46. Springs 106 bias the latches 104 open. The latch box 102 and spring-biased latches 104 form a latch assembly corresponding to the latch assembly 48 of FIG. 2. In FIGS. 3-6, a mounting feature 108 is shown via which the latch box 102 is mounted to the top of the lead screw 40, but the lead screw itself is omitted in FIGS. 3-6. Similarly, only the top of the lifting rod 46 is shown in FIGS. 3-6, but it is to be understood that the lifting rod 46 extends downward as shown in contextual FIG. 2.) In this operation, the control rod or rods are initially fully inserted and the upper end of the lifting rod 46 is disengaged from the latches 104. The CRDM motor 44 is then operated to cause the lead screw 40 to translate downward, thus lowering the latch box 102 toward the upper end of the lifting rod 46. The downward force supplied by the CRDM motor 44 through the ball screw 42 moves the latch box 102 into contact with a lower camming link 110 built into a lower portion 112 of the CRDM. FIGS. 4 and 5 show isometric cutaway and side cutaway views, respectively, of the state in which the latch box 102 is just beginning to contact the lower camming link 110 at a contact area 114. As seen in FIG. 6, the continued application of motor torque forces the latch box 102 downward so as to press the lower camming link 110 downward resulting in a rotary action about a pivot point 116. This rotary action lifts and translates the cam bars 50 into the engaged position so as to cam against and close the latches 104 in the latch box 102. A separate holding mechanism (not shown in FIGS. 3-6 but embodiments of which are disclosed elsewhere in this application) keeps the cam bars 50 engaged as the latch box 102 is translated back upward after the latch engagement so as to lift the lifting rod 46 and attached control rod(s) upward. (Note that the control rods are not shown in FIGS. 3-6). This approach of the embodiment of FIGS. 3-6 separates latch activation and long term hold/translation functions of the CRDM, resulting in reduction of operational power requirements. (Again, FIGS. 3-6 illustrate only the latch activation—suitable embodiments of the long term hold/translation component are described elsewhere in this application.) The separation of latch activation and long term hold/translation functions simplifies the latching assembly making it easier to manufacture and less expensive. The mechanically actuated latching device described with reference to FIGS. 3-6 is electrically operated (assuming the lead screw 40 is driven by the electric CRDM motor 44 as per FIG. 2). In combination with an electrically operated holding mechanism (again, disclosed elsewhere in this application), this constitutes an all-electric CRDM. With reference to FIGS. 7-18, a CRDM embodiment with self-engaging cam/latch system and electromagnetic holding is described. In these CRDM embodiments, the four-bar linkage is modified such that under gravity the four-bar linkage operates to move the cam bars 50 inward so as to engage the latch. These CRDM embodiments also include a holding mechanism that only holds the latch and does not perform the engagement. With reference to FIG. 7, the CRDM is shown in combination with a control rod assembly 140 connected by the lifting/connecting rod 46 via the lead (or ball) screw 40 to the CRDM which includes the motor assembly 44, a modified cam assembly 144 (with a modified four-bar linkage) and latch assembly 148. With reference to FIG. 8, an enlarged view of the CRDM of FIG. 7 is shown, including the motor 44 mounted on the standoff 45, the cam assembly 144 with modified four-bar linkage, the latch assembly 148, and an optional position sensor 149. The illustrative CRDM also includes an electromagnet holding system 150 at the top of the cam assembly 144. With reference to FIGS. 9 and 10, which show cutaway perspective view of the CRDM in SCRAM mode (fully inserted) and in normal operating mode (translating or holding the control rods), respectively, the CRDM allows for failsafe SCRAM of the control rod (or control rod cluster) 140 without the need to SCRAM the lead screw 40. The lead screw/ball nut assembly is permanently attached to the electric motor 44 (only the top of which is visible in FIG. 9) which provides for its axial translation. The control rod cluster 140 is connected to the lead screw 40 via a connecting (i.e. lifting) rod 46 and the latch assembly 148 (see FIG. 7). As seen in FIG. 9, the lead screw 40 is hollow, and the lifting rod 46 fits inside the lead screw inner diameter (ID) and is free to translate vertically within the lead screw 40. The latch assembly, with two latches 154 (although three or more latches are contemplated), is secured to the top of the lead screw 40 by a lead screw/latch assembly coupling 156 (e.g., a latch housing mounted to the upper end of the lead screw). When the latches 154 are engaged with the lifting rod 46 they couple the lifting rod 46 to the lead screw 40 (normal operation) so that the lead screw 40 and lifting rod 46 move together. When the latches 154 are disengaged they release the lifting rod 46 from the lead screw 40 (an event referred to as SCRAM). Latch engagements and disengagements are achieved by using the four-bar linkage cam system 144 with a cam bar assembly provided for each latch including a cam bar 160 and cam bar links 162. However, unlike the embodiment of FIG. 2, in the CRDM embodiments of FIGS. 7-18 the cam bar links 162 are oriented such that when gravity causes the cam bars 160 to move downward the four-bar linkage action rotates the cam bars 160 inward thereby causing the latches 154 to rotate into engagement with the lifting rod 46. Because of this self-engaging feature, there is no action required to engage the latches 154 to the lifting rod 46 (other than operating the CRDM motor 44 to lower the latch assembly 148 over the upper end of the lifting rod 46) and there are no springs for biasing the latches 154 (compare with springs 106 of the embodiment of FIGS. 3-6). Thus, force of gravity is sufficient to cause the cam bars 160 to cam the latches 154 to engage the lifting rod 46 when the lifting rod is in its lowermost position (corresponding to the control rods being fully inserted). However, force of gravity is not capable of keeping the latches 154 engaged when the CRDM of FIGS. 7-18 is operated to lift the control rod assembly 140 via the lifting rod 46. Thus, the separate holding mechanism 150 is provided, which includes electromagnets 170 and magnetic couplers 172 each connected with the upper end of a respective one of the cam bars 160. In the embodiments described herein with reference to FIGS. 7-18, the illustrative electromagnet holding system 150 is incorporated to hold the cam bars 160, and thus the latches 154, in full engagement for long term hold and translational operations. When power is removed from the electromagnets 170 (as per FIG. 9) the weight of the translating assembly 140, 46 is sufficient to rotate the latches 154 and cams bars 160 out of engagement thereby causing the CRDM to SCRAM. (The term “translating assembly” or similar phraseology refers to the combination of the lifting rod 46 and the control rod assembly 140 including a set of control rods connected with the lifting rod 46 by a yoke or spider.) While the electromagnet holding mechanism embodiment 150 is described for illustrative purposes in FIGS. 7-18, elsewhere in this application other holding mechanism embodiments are disclosed that may be substituted for the holding mechanism 150. After the SCRAM event the lead screw 40 is driven back to the bottom of its stroke via the electric CRDM motor. As the latch assembly nears the bottom of the stroke it automatically re-engages with the lifting rod 46 by cam action against the conical surface 176 of the upper end of the connecting rod 46. The same automatic re-engagement action could also be used to re-engage in the event that a control rod becomes stuck and the SCRAM does not complete. The overall CRDM assembly is shown in FIGS. 7-8. Note that the lead screw 40 may also be referred to as a “ball screw”, which is an equivalent term when the threaded engagement employs a ball nut (that is, a threaded nut/screw coupling with ball bearings disposed in the threads). The layout of the CRDM of FIGS. 7-18 is similar to illustrative CRDMs described with reference to FIG. 2. However, in the CRDM of FIGS. 7-18 the electromagnet holding system 150 at the top of the CRDM has replaced the hydraulic (or solenoid) lift assembly 56 of CRDM embodiments of FIG. 2. FIG. 9 illustrates the CRDM of FIGS. 7-18 in full SCRAM mode with the ball screw 40 and control rod assembly fully inserted. In FIG. 9 only the upper end of the lifting rod 46 (also sometimes called a connecting rod) is visible. The reversed (as compared with embodiments of FIG. 2) cam link orientation causes the four-bar linkage action under downward gravitational weight of the cam bars 160 to rotate the cam bars 160 inward into full engagement thereby causing the latches 154 to be fully engaged with (the upper end of) the lifting rod 46 of the translating assembly. This is the normal self-engaged cam bar position with no load on the latches from the translating assembly and no electromagnet holding force applied by the electromagnet holding system 150. FIG. 10 illustrates normal CRDM operation (either long term hold mode or translation of the control rod assembly under control of the CRDM motor). For this operating condition the electromagnets 170 are powered on to hold the cam bars 160, and thus the latches 154, in full engagement so that they can carry the maximum translating assembly weight force. As seen in FIG. 10, the cam bars 160 extend above the top plate of the cam housing where the magnetic couplers 172 are attached. These couplers 172, made of 410 SS magnetic material in a suitable embodiment, complete the magnetic circuit for optimum electromagnet holding force. FIG. 11 shows the CRDM of FIGS. 7-18 at the start of SCRAM. The latches 154 have been rotated out of engagement by the downward force due to the weight of the translating assembly. The latch heels, which are in contact with the cam bars 160, push the cam bars outward thereby allowing the connecting rod to SCRAM. This action is designated by the force annotation 180 in FIG. 11. FIG. 11 shows the latches 154 in the land-on-land (LOL) position just riding over the outside diameter of the upper end of the connecting rod 46. FIG. 12 illustrates the CRDM of FIGS. 7-18 with the latches 154 and cam bars 160 in the fully disengaged position. This orientation is a non-operational position that could occur if the latches 154 are “kicked” outward by the downward movement of the translating assembly during SCRAM. Although this is a non-operational position with the self-engaged cam bar design of FIGS. 7-18, it illustrates that there is ample clearance between the inside surface of the latches 154 and the connecting rod 46 for SCRAM reliability. This is shown in the inset of FIG. 12, where the clearance dclearance is indicated. FIG. 13 illustrates the force balance for SCRAM operation. In FIG. 13, the weight of the translating assembly is denoted WTA, the force pushing the cam bars outward is denoted Fpush, and the weight of the cam bars is denoted WCam Bar. In the illustrative design, the maximum force needed to push each cam bar assembly outward for SCRAM (that is, the maximum required Fpush) is only a few pounds. This lateral force component of the cam bar assembly weight WCam Bar can be minimized by increasing the orientation angle of the cam link 162, e.g. to a minimum angle of about 70° in some calculated designs. In general, making the cam link 162 longer or at a larger angle (relative to the horizontal) reduces the maximum force needed to push out the cam bars. The minimum force available to push each cam bar 160 outward is produced by latch rotation due to the downward weight force of the translating assembly. This minimum available force is based on the translating assembly weight WTA minus worst-case assumed mechanical friction drag in the control rod channel and worst-case friction at all contact surfaces. SCRAM reliability is assured since the minimum available force Fpush for SCRAM is significantly larger than the force needed for SCRAM. Advantageously, the SCRAM is totally driven by gravity with no other loads required. FIG. 14 illustrates the force balance for normal operation. Sufficient lateral force Fhold must be applied at the heel of each latch 154 to hold the translating assembly weight WTA for various modes of operation. In the illustrative embodiment of FIGS. 7-18, this force is provided by the electromagnet holding system 150 at the top of the CRDM. Since the cam bars 160 are self-engaged, the cam bar side load reduces the needed electromagnetic force. The minimum holding force FMag needed at the holding magnet 170 to maintain latch engagement during translation of the control rod assembly is computed based on translating assembly weight WTA plus worst-case assumed mechanical friction drag in the control rod channel. In calculated designs, there is ample holding force margin for all normal operating conditions. FIG. 15 illustrates isometric views of the electromagnet holding system 150 at the top of the CRDM. FIG. 15 shows the fully engaged operational configuration (top view, power to magnet 170 either on or off), the SCRAM operational configuration (middle view, power to magnet 170 off) and the fully disengaged operational configuration (bottom view, power to magnet 170 off). In the fully engaged mode (top view), either with or without electromagnet holding force, the magnetic couplers 172 are seated against the electromagnet housings 170. This seat provides the inward stop for the cam bars 160 and for the latches for full operational engagement. FIG. 16 shows plan views corresponding to the isometric views of FIG. 15. It is seen from FIG. 16 that for all operating modes the electromagnet holding system 150 fits well within the CRDM space envelope. FIG. 17 illustrates an enlarged cutaway view of the electromagnet holding system 150 for the fully engaged condition. The electromagnets 170 are suitably hermetically sealed by welding and potted for high temperature use inside the reactor pressure vessel. Some suitable materials for the components are as follows: for the electromagnet 170, the electromagnet housing may be alloy 625 non-magnetic material, the electromagnet core may be 410 stainless steel magnetic material, and the electromagnet winding may be 24 gauge copper wire; and the magnet couplers 172 may suitably be 410 stainless steel magnetic material. Designs with these materials are estimated to provide a calculated 310 lbs of holding force. These are merely illustrative examples, and other materials and/or design-basis holding force may be employed depending upon the reactor design. FIG. 18 illustrates the latch re-engagement action. The views are labeled: (1) top left view; (2) top middle view; (3) top right view; (4) bottom left view; (5) bottom middle view; and (6) bottom right view. After a SCRAM event, when re-engagement is desired, the ball screw is driven back to the bottom by the CRDM motor. The latches 154 automatically re-engage with the lifting/connecting rod 46 as the latching assembly reaches bottom. For this purpose, a conical cam surface 176 is incorporated into the configuration of the upper end of the connecting rod 46. As the latch assembly is driven back down, the inboard surfaces of the latches 154 slide down over the top of the connecting rod 46, being cammed open by the conical cam surface 176 against the gravitational bias toward closure driven by the four-bar linkage, until the self-engaged latches 154 snap back into the normal engagement pocket. Normal operation can then resume. The same latch auto re-engagement action, as illustrated in FIG. 18, can also be used to re-engage a control rod (or bank of control rods) that becomes stuck during SCRAM. The latch assembly is driven down over the upper end of the connecting rod 46 of the stuck rod (or rod bank) until the latches 154 snap into the normal engagement pocket. If it is desired to fully insert the rods into the reactor core (as is typically the case in the event of a SCRAM), then the latching assembly is driven downward by the ball screw and motor with the latches 154 pushing downward on the stuck rod. In that scenario, the bottom surfaces of the latches 154 contact the flat portion of the engaging pocket in the connecting rod 46. As load is applied, the eccentricity of the contact surfaces causes the latches 154 to remain engaged without any additional holding system. As the motor drives the ball screw down, the latches drive the stuck rod in. With reference to FIGS. 19-22, another holding mechanism embodiment for a CRDM is described. In this regard, FIGS. 3-6 and 7-18 illustrate embodiments in which latch activation and long term hold/translation functions are separated, resulting in reduction of operational power requirements. FIGS. 3-6 illustrate an embodiment of the latch activation, while FIGS. 7-18 illustrate an embodiment of the latch activation (the self-engaging cam/latch system) in combination with an embodiment 150 of the long term hold/translation function. FIGS. 19-22 illustrate another embodiment of the long term hold/translation function, which may be used in combination with the embodiment of FIGS. 3-6 or substituted for the holding mechanism 150 of the embodiment of FIGS. 7-18. FIG. 19 shows an isometric view of the latch hold mechanism of FIGS. 19-22 operating in conjunction with the cam assembly of FIGS. 2-6, i.e. with cam bars 50. FIGS. 20 and 21 show side view and cutaway side views, respectively, of the latch hold mechanism in its disengaged position. FIG. 22 shows a side cutaway view of the latch hold mechanism in its engaged position. The holding mechanism illustrated in FIGS. 19-22 utilizes a large electromagnet 200, coupled with a magnetic hanger 202 connected with the upper ends of the cam bars 50 by pins 204, as shown in FIG. 19. The electromagnet 200 is spaced apart from the hanger 202 by support posts 206 extending from a base plate 208 secured to (or forming) the top of the cam bar assembly 144. With the CRDM engaged by an engagement mechanism (such as that described with reference to FIGS. 3-6, in illustrative FIGS. 19-22), the electromagnet 200 is activated, causing a magnetic attraction between the hanger 202 and the electromagnet 200 that holds the hanger 202 in contact with the electromagnet 200 as shown in FIG. 22 (or, in alternative embodiments, into contact with a landing surface interposed between the electromagnet and the hanger). The raised hanger bar 202 holds the cam bars 50 in their raised (i.e. engaged) position via the pins 204. When power is cut to the electromagnet 200 the attractive force between the magnet 200 and the hanger 202 is severed, causing the hanger 200 and cam bars 50 to fall to the disengaged position shown in FIGS. 20 and 21. Pin slots 210 in the hanger 202 accommodate the lateral motion of the cam bars 50 due to the four-bar linkage. The sectional views of FIGS. 21 and 22 illustrate the copper windings 212 of the electromagnet 200. By separating latch activation and long term hold/translation functions of the latch of the CRDM, it is recognized herein that the operational power requirements can be reduced, since the holding mechanism is not required to actually lift the cam bars, but merely maintains the cam bars in the lifted position after the (different) engagement mechanism operates. The separation of features simplifies the holding feature making it easier to manufacture and less expensive. With reference to FIGS. 23-32, another holding mechanism embodiment for a CRDM is described, which may be used in combination with the embodiment of FIGS. 3-6 or substituted for the holding mechanism 150 of the embodiment of FIGS. 7-18. FIGS. 23-25 show two isometric views and a plan view, respectively, of the holding mechanism in the fully engaged position. FIGS. 26-28 show two isometric views and a plan view, respectively, of the holding mechanism in the SCRAM position. FIGS. 29-31 show two isometric views and a plan view, respectively, of the holding mechanism in the fully disengaged position. The isometric view of FIGS. 23, 26, and 29 show the top region of the CRDM including the holding mechanism at a viewing angle of approximately 45°. The isometric view of FIGS. 24, 27, and 30 show the top region of the CRDM including the holding mechanism at a more oblique viewing angle than 45°. FIG. 32 illustrates a plan view of the holding mechanism with annotations of the electromagnet holding force FElect for applying a force FCam Bar sufficient to hold the cam bars 160. The holding mechanism of FIGS. 19-28 utilizes horizontal holding arms 230 that have slots 232 into which pins 234 at the tops of the cam bars 160 (e.g. cam bar pins 234) fit. When the cam bars 160 are moved to the engaged position by an engagement mechanism (e.g. such as the one described with reference to FIGS. 3-6, or the self-engaging cam/latch system of the embodiment of FIGS. 7-18), the cam bar pin 234 in each pin slot 232 pushes the holding arm 230 to rotate to a point where it is in close proximity with an electromagnet 240. The rotation is about an arm pivot point 242, and the various components of the holding mechanism are mounted on a baseplate 244 that is secured to (or forms) the top of the cam bar assembly 144. When power is applied to the electromagnets 240 they attract and hold the arms 230 which are made of magnetic material. The restrained arms, in turn, hold the cam bars 160 in the engaged position via the cam bar pins 234 in the pin slots 232 and thereby maintain latch engagement. FIGS. 23-25 shows two alternative isometric views and a top view, respectively, of the holding mechanism in this fully engaged position. With reference to FIGS. 26-28 (SCRAM mode) and FIGS. 29-31 (fully disengaged mode), when power is cut to the electromagnets 240, the attractive force between the electromagnets 240 and the arms 230 is severed, allowing the arms 230 to rotate out of engagement. The weight of the translating assembly is sufficient to disengage the latches and move the cam bars 160 away (i.e. outward) for SCRAM. During this action, the holding arms 230 freely move out of the way. With particular reference to FIG. 32, the holding mechanism of FIGS. 23-32 provides a mechanical advantage due to the configuration of the holding arms 230. This is accomplished by the relative positions of the arm pivot point 242, the cam bar contact point (i.e. the engagement between the cam bar pin 234 and the pin slot 232) and the electromagnet holding force contact point (corresponding to the location of the electromagnet 240), suitably quantified by the distance dmag between the magnet 240 and the pivot point 242 and the distance dpin between the cam bar contact point (approximately the cam bar pin 234) and the pivot point 242. Because of this mechanical advantage, the holding force FElect provided by the electromagnets 240 can be reduced to provide a given force FCam Bar for holding the cam bars 160. This facilitates the use of smaller, less complex electromagnets as the electromagnets 240, as well as lower power demands for operation. The configuration of the electromagnetic holding mechanism of FIGS. 23-32 will vary somewhat depending on the configuration of the cam bars 160 and the four bar linkage. The pin slot 232 is arranged to accommodate the horizontal cam bar travel while providing the appropriate engagement to rotate the horizontal holding arms 230. In a variant embodiment, magnets are embedded into the holding arms to provide added holding strength. In some embodiments, this added force is expected to be enough to enable the holding mechanism of FIGS. 23-32 to perform both the engagement and holding operations, and could, for example, be used in place of the hydraulic lifting assembly 56 of the embodiment of FIG. 2. By way of review, FIGS. 23-25 show the cam bars 160 and holding arms 230 in the fully engaged position, either held by the electromagnets 240 or engaged by an outside means (e.g. such as the one described with reference to FIGS. 3-6, or the self-engaging cam/latch system of the embodiment of FIGS. 7-18) prior to powering the electromagnets 240. FIGS. 26-28 show the SCRAM mode, in which the arms 230 and thus the cam bars 160 have moved sufficiently for the latches to completely release the connecting (i.e. lifting) rod and control rod assembly. FIGS. 29-31 show the fully disengaged position. Due to the 4-bar linkage action, the cam bars 160 rise and fall as they are moved laterally from engaged to disengaged positions. This action is best seen in the isometric view of FIGS. 24, 27, and 30. Since the holding arms 230 pivot about fixed support posts (the pivot arm points 242), the pin slots 232 are incorporated into the holding arms 230 to accommodate the rise and fall of the cam bars 160. These slots 232 should be sized and positioned to accommodate both the rise and fall of the cam bars 160 and the lateral motion of the cam bars 160 due the four-bar linkage action responding to the rise/fall of the cam bars 160. When used in conjunction with the self-engaging cam/latch system described herein with reference to FIGS. 7-18, the direct mechanical advantage for the illustrated locations of the holding arm pivot points 242 has been estimated to be approximately 4.5:1 (corresponding to the ratio dmag/dpin in FIG. 32). However, there is not a direct relationship between this mechanical advantage and the holding force needed since the holding arms 230 do not pull in line with the plane of collapse of the cam bars 160. A force correction is needed that is proportional to the cosine of the holding arm angle. The net effect for the configuration shown herein is an effective mechanical advantage of 2.4:1. This force balance, along with the effective mechanical advantage, is diagrammatically illustrated in FIG. 32. The holding mechanism of FIGS. 23-32 has the benefit of a mechanical advantage provided by the configuration of the holding arms. With reference to FIGS. 33-38, another holding mechanism embodiment for a CRDM is described, which may be used in combination with the embodiment of FIGS. 3-6 or substituted for the holding mechanism 150 of the embodiment of FIGS. 7-18. FIGS. 33-35 show two isometric views at different viewing angles and a top view, respectively, of the top of the CRDM (and more particularly the top of the cam assembly and the holding mechanism) with the cam system in the unlatched position. FIGS. 36-38 show two isometric views at different viewing angles and a top view, respectively, of the top of the CRDM including the holding mechanism with the cam system in the latched position. Illustrative FIGS. 33-38 show the holding mechanism in combination with the embodiment of FIGS. 3-6, and hence the cam bars are labeled cam bars 50 in FIGS. 33-38. Once the cam system is in the engaged (i.e. “latched”) position the holding mechanism of FIGS. 33-38 holds the cam bars 50 such that they engage the latches and maintain latching of the connecting (i.e. lifting) rod. The holding mechanism of FIGS. 33-38 includes two high temperature magnets 260 and magnetic links 262 attached to the upper end of each of the two cam bars 50 at the top end of the CRDM. The two canned high temperature electromagnets are suitably wired in a parallel fashion. When the cam system transitions from the unlatched position (FIGS. 33-35) to the engaged (latched) position (FIGS. 36-38), the upper ends of the cam bars 50 engaging the magnetic links 262 rotate the magnetic links 262 about pivots 264 so that the ends 270 of the magnetic links 262 distal from the cam bar/magnetic link joint 272 are moved by the inward movement of the cam bars 50 to be in close proximity to the electromagnets 260. When the electromagnets 260 are energized these distal ends 270 of the magnetic links 262 are held against the magnets 270, and the cam bar 50 at the opposite end of the link 262 is prevented from moving. This holds the latch in the latched position. The holding power of the electromagnets 260 is adequate to hold the weight of the cam bars 50 as well as the force exerted on the cam bars 50 by the latches. The latched state is shown in alternative isometric views (FIGS. 36 and 37) and a plan view (FIG. 38). Slots 276 in a base plate 278 secured to (or forming) the top of the cam bar assembly and supporting the hold mechanism components accommodate the lateral motion of the cam bars 50 during unlatched/latched transitions. When used in conjunction with the embodiment of FIGS. 3-6 (as illustrated in FIGS. 33-38), operation is as follows. When the electromagnets 260 are de-energized the magnetic links 262 are decoupled from the electromagnets 260 and the cam bars 50 are free to fall under their own weight and swing into the unlatched position. In the unlatched position the cam bars 50 are disengaged from the latches and the latches can then rotate out of engagement with the connecting rod. When the cam bars 50 are disengaged from the latches, the latches can be rotated out of engagement with the connecting rod by the latch springs 106 (for the embodiment of FIGS. 3-6). Therefore, in the unlatched position the cam bars 50 are not engaged with the latches, the latches are not engaged with the lifting rod and the translating assembly (including the lifting rod and the attached control rod or rods) can then fall under its own weight (SCRAM). The holding mechanism of FIGS. 33-38 is fail-safe in the sense that if power is lost to the electromagnets 260 the connecting rod will SCRAM due to gravity. Operation of the holding mechanism of FIGS. 33-38 in conjunction with the cam arrangement of FIGS. 7-18 (self-latching) is similar, except that when the electromagnets 260 are de-energized the cam bars 160 do not open under gravity, but rather are cammed open by the cam surface at the upper end of the lifting rod 46 of the falling translating assembly. (See description of FIGS. 7-18 for details). Again, the de-energizing of the electromagnets 260 allows the magnetic links 262, and hence the cam bars 160, to freely move to perform the SCRAM. With reference to FIGS. 39-48, another holding mechanism embodiment for a CRDM is described, which may be used in combination with the embodiment of FIGS. 3-6 or substituted for the holding mechanism 150 of the embodiment of FIGS. 7-18. The embodiment of FIGS. 39-48 is illustrated in conjunction with a four-bar linkage with cam bars and cam bar links oriented as in the embodiments of FIGS. 2-6; accordingly, in FIGS. 39-48 the cam bars and cam bar links are labeled as cam bars 50 and cam bar links 52, respectively. The embodiment of FIGS. 39-48 illustrates a variant latching mechanism located beneath the cam assembly, in which a hydraulic cylinder 300 (or, alternatively, an electric solenoid) raises a lift plunger or piston 302 upward to engage cam bar lift rollers 304 at the bottom ends of the cam bars 50 so as to raise the cam bars 50—by action of the four-bar linkage provided by cam bar links 52 this raising of the cam bars 50 simultaneously moves the cam bars 50 inward to engage the latch. (By comparison, in the embodiment described with reference to FIG. 2, the hydraulic lift assembly 56 located above the cam assembly lifts the upper ends of the cam bars 50 to engage the latches). The embodiment of FIGS. 39-48 also illustrates a holding mechanism located above the cam assembly, where a base plate 308 secured to (or forming) the top of the cam bar assembly supports the hold mechanism components. FIG. 39 shows a diagrammatic side view of the cam assembly, in which the lift system (comprising electric solenoid or hydraulic cylinder 300 and piston 302 in conjunction with cam bar lift rollers 304) is deactivated and the hold mechanism (diagrammatically shown in a tilted view) is also deactivated. FIG. 40 shows a top view of the deactivated hold mechanism corresponding to FIG. 39. FIG. 41 shows a diagrammatic side view of the cam assembly in which the lift system is activated and the hold mechanism is still deactivated. FIG. 42 shows a top view of the deactivated hold mechanism corresponding to FIG. 41. FIG. 43 shows a diagrammatic side view of the cam assembly in which both the lift system and the hold mechanism are activated, and FIG. 44 shows a corresponding top view of the activated hold mechanism. FIG. 45 shows a diagrammatic side view of the cam assembly in which the lift system is deactivated and the hold mechanism is still activated, and FIG. 46 shows a corresponding top view of the activated hold mechanism. FIGS. 47 and 48 illustrate geometric aspects of the hold mechanism. The hold mechanism of the embodiment of FIGS. 39-48 keeps the four-bar linkage cam system 50, 52 in the engaged position during rod translation and hold functions, and provides the SCRAM functionality when subsequently deactivated. It also structurally internalizes the majority of the cam bar retention force required to hold the latches in the engaged position, and utilizes mechanical advantage to minimize the remaining hold force, resulting in a structurally efficient unit. FIGS. 39 and 40 illustrate the holding mechanism (and associated lift system in FIG. 39) both in the deactivated state. The holding mechanism including a rotary hold bar 310, a hold-solenoid 312 (where the housing of the solenoid 312 is visible), a hold-solenoid plunger 314, and hold-bar rollers 316, is located at the top or base plate 308 of the cam bar assembly. FIGS. 39 and 40 illustrate the hold mechanism deactivated at startup. Prior to startup, the lift system (electric solenoid or hydraulic), which includes the electric solenoid or hydraulic cylinder 300 and the lift plunger or piston 302, is also deactivated. Therefore, the latches are not engaged by the four-bar cam system 50, 52, rendering the connecting rod and attached control rods in the fully inserted position. As best seen in the top view of FIG. 40, in the unlatched state of the four-bar linkage 50, 52 the cam bars 50 are in their outboard positions (i.e., moved outward and away from the latches). Also note that the base plate 308 includes slots to accommodate movement of the upper ends of the cam bars 50 between their inboard (i.e. moved in) and outboard (i.e. moved out) horizontal positions. With reference to FIGS. 41 and 42, upon activation of the lift system (shown in FIG. 41), the lift plunger or piston 302 raises the cam bars 50 into the latch engagement position by contact with the cam bar lift rollers 304. At initial engagement of the lift mechanism, the hold mechanism is still deactivated as depicted in FIGS. 41 and 42. Because of activation of the lift system, the latches are now engaged with the connecting rod which is resting with the attached control rods at the fully inserted position. As best seen in FIG. 42, the lifting of the cam bars 50 also moves the cam bars 50 into their inboard positions by action of the four-bar linkage, and this inward movement is what engages the latches, as described in more detail with reference to the embodiments of FIGS. 2-6. With reference to FIGS. 43 and 44, subsequently following activation of the lift system, the hold solenoid 312 of the hold mechanism is activated, resulting in extension of the solenoid plunger 314, which rotates the hold bar 310 about a pivoting engagement 318 of the hold bar 310 with the base plate 308. At full extension of the solenoid plunger 314, the hold-bar rollers 316 are rotated into position behind the upper extremity (i.e. upper ends) of the cam bars 50 (note again that the upper ends of the cam bars 50 protrude through the slots in the base plate 308), so as to function in the hold capacity. It is noted that the hold solenoid 312 is free to pivot about a post mount 320 that secures the solenoid 312 on the base plate 308. It is also noted that the solenoid plunger 314 is pin-connected to the hold bar 310, which provides rotational freedom for operation. The relative orientations of all the pertinent components at this phase of operation are illustrated in FIGS. 43 and 44. With reference to FIGS. 45 and 46, with the hold mechanism activated the lift system can be deactivated, with the hold system thereafter keeping the latches engaged. Upon deactivation of the lift system, the lift plunger or piston 302 is released, and therefore, no longer (bottom) supports the cam bars 50. At this point, the cam bars 50 are retained in the engaged position solely by the hold mechanism. The four-bar cam system 50, 52 is now being retained for long-term retention of the connecting rod by the hold mechanism. With reference to FIG. 47, there exists an eccentricity Econtact between the center of rotation of the hold bar 310 and the line of action of the contact force between (the upper end of) the cam bar 50 and the hold-bar roller 316. This eccentricity Econtact results in a force-moment imbalance on the hold bar 310 when the force applied by the hold solenoid 312 is removed. This moment imbalance at power loss to the hold solenoid 312 is the driving mechanism for rapidly rotating the hold bar 310 and the attached rollers 316 out of contact with the cam bars 50—resulting in SCRAM (rapid release of connecting rod). In order to create a smooth rolling action of the hold-bar rollers 316 on the contact surface of the cam bars 50, the contact surface is contoured to the arc of the rolling-contact point. With continuing reference to FIG. 47 and with further reference to FIG. 48, the desired lower power consumption of the hold mechanism is a product of the significant mechanical advantage of the unit. The moment arm Eplunger of the hold solenoid plunger 314, relative to the pivot center of the hold bar 310, is significantly larger than the moment arm of the contact force of the cam bar 50 at the hold-bar roller 316, as illustrated in FIGS. 47 and 48. Therefore, the force required by the hold solenoid 312 is significantly less than the latch-to-cam bar contact force required to support the connecting rod load. Of further advantage, internalization of the majority of the cam bar retention forces as equal and opposite loads reacted through the hold bar 310 eliminates force reaction through the remainder of the hold mechanism, resulting in a structurally efficient unit. As previously stated, the hold mechanism described with reference to FIGS. 39-48 separates latch activation and long term hold/translation functions, resulting in reduction of operational power requirements. The hold mechanism keeps the four-bar linkage cam system in the engaged position during rod translation and hold functions, and provides the SCRAM functionality when subsequently deactivated. It also structurally internalizes the majority of the cam bar retention force required to hold the latches in the engaged position, and utilizes mechanical advantage to minimize the remaining hold force, resulting in a structurally efficient unit. With reference to FIGS. 49-52, another holding mechanism embodiment for a CRDM is described, which may be used in combination with the embodiment of FIGS. 3-6 or substituted for the holding mechanism 150 of the embodiment of FIGS. 7-18. FIG. 49 shows an isometric view of the top region of the CRDM including the holding mechanism with the vertical linkage engaged to raise the cam bars. FIG. 50 shows a corresponding isometric view with the vertical linkage disengaged to allow the cam bars to fall. FIG. 51 corresponds to the engaged view of FIG. 49 but includes a partial cutaway, and similarly FIG. 52 corresponds to the disengaged view of FIG. 50 but includes the partial cutaway. The latch holding mechanism of FIGS. 49-52 utilizes a vertical linkage system including vertical links 340 connected to a hanger 342 disposed between (the upper ends of) the cam bars 160 of FIGS. 7-18 (as shown; or, alternatively, the cam bars 50 of FIGS. 2-6) and (in the engaged position shown in FIGS. 49 and 51) held in the engaged position by electromagnets 344. When the cam bars 160 are moved to the engaged position by the separate latch engagement mechanism (e.g. as in the embodiment of FIGS. 3-6, or the embodiment of FIGS. 7-18), it causes the hanger 342 to move up which, in turn, raises the vertical links 340 to a position where horizontal drive members 348 are in close proximity with the electromagnets 344. When power is applied to the electromagnets 344 they attract and hold magnets that are embedded into the horizontal drive members 348. (Alternatively, the horizontal members 348 may be made of steel or another ferromagnetic material but not include magnets). The restrained vertical links 340, in turn, hold the hanger 342, and thus the cam bars 160, in the engaged position and thereby maintain latch engagement. When power is cut to the electromagnets 344, the attractive force between the electromagnets 344 and the horizontal drive members 348 is severed, allowing the vertical links 340 to drop out of engagement, as seen in FIGS. 50 and 52. The weight of the translating assembly is sufficient to disengage the latches and move the cam bars 160 away for SCRAM. During this action, the linkage system freely moves downward out of the way. To recap, FIGS. 49 and 50 show isometric views of the top region of the CRDM at a viewing angle of approximately 45° for the engaged and disengaged states, respectively. FIG. 49 shows the vertical linkage system in the fully engaged (full up) position, either held by the electromagnets 344 or engaged by an outside means prior to powering the electromagnets. For the SCRAM mode, shown in FIG. 50, the linkage system has moved full down for the latches to completely release the connecting rod and control rod assembly. FIGS. 51 and 52 show isometric cutaway views of the top region of the CRDM for the engaged and disengaged states, respectively. FIG. 51 shows the vertical linkage system in the fully engaged (full up) position, either held by the electromagnets 344 or engaged by an outside means prior to powering the electromagnets 344. FIG. 52 shows the linkage system in the full down (SCRAM) position. In the illustrative embodiment, the minimum angle of the vertical links 340, in the fully engaged position (FIGS. 49 and 51), is set to about 10° which is expected to assure an adequate SCRAM reliability margin. In the disengaged position (FIGS. 50 and 52) the vertical links 340 collapse to a maximum angle of about 40° in the illustrative embodiment. The latch holding mechanism described with reference to FIGS. 49-52 provides a mechanical advantage due to the configuration of the linkage system. This is due to the relative positions and size of the vertical link 340 lengths compared to the horizontal drive member 348. In addition, the permanent magnet that is embedded in the horizontal arm 348 provides added holding force. The true mechanical advantage for this disclosed vertical linkage system is calculated to be 2.9:1 at the minimum link angle. However, the effective mechanical advantage is higher, estimated to be closer to 4.0:1, when an assumed permanent magnet force per link assembly is added. Because of this mechanical advantage, the required holding force needed by the electromagnets is reduced. This results in smaller, less complex electromagnets, as well as lower power demands for operation. Illustrative embodiments including the preferred embodiments have been described. While specific embodiments have been shown and described in detail to illustrate the application and principles of the invention and methods, it will be understood that it is not intended that the present invention be limited thereto and that the invention may be embodied otherwise without departing from such principles. In some embodiments of the invention, certain features of the invention may sometimes be used to advantage without a corresponding use of the other features. Accordingly, all such changes and embodiments properly fall within the scope of the following claims. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the present disclosure be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof. |
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description | This application is a divisional under 35 U.S.C. 121 of U.S. application Ser. No. 12/071,455, filed Feb. 21, 2008, now U.S. Pat. No. 8,437,443, issued May 7, 2013. 1. Field Example embodiments generally relate to radioisotopes having medical applications and apparatuses and methods for production thereof in nuclear reactors. 2. Description of Related Art Radioisotopes have a variety of medical applications stemming from their ability to emit discreet amounts and types of ionizing radiation. This ability makes radioisotopes useful in cancer-related therapy, medical imaging and labeling technology, cancer and other disease diagnosis, and medical sterilization. Short-term radioisotopes, having half-lives on the order of days or even hours, are of particular importance in cancer and other medical therapy for their ability to produce a unique radiation profile and yet quickly decay into harmless, stable isotopes excreted from the body after the radiation dose is delivered in the specific application. However, the short half-lives of these short-term radioisotopes also make their acquisition and handling difficult. Short-term radioisotopes are conventionally produced by bombarding stable parent isotopes in accelerators or low-power reactors with neutrons on-site at medical facilities or at nearby production facilities. These radioisotopes are quickly transported due to the relatively quick decay time and the exact amounts of radioisotopes needed in particular applications. Further, production of medical short-term radioisotopes generally requires cumbersome and expensive irradiation and extraction equipment, which may be cost-, space-, and/or safety-prohibited at medical facilities. Several short-term radioisotopes having medical applications may be generated through nuclear fission, and thus in large quantities at nuclear power plants. For example, fission of Uranium-235 in nuclear fuel may produce large amounts of Technetium-99, which is useful in multiple imaging and cancer diagnosis applications. However, the short-term radioisotopes produced in nuclear fuel may be intermixed with a wide spectrum of other nuclear fission byproducts. Extraction of the useful short-term radioisotopes may have unacceptable radiation and chemical exposure hazards and/or may require an amount of time in which the short-term radioisotopes may decay to unusable amounts. Because of difficulties with production and the lifespan of short-term radioisotopes, demand for such radioisotopes may far outweigh supply, particularly for those radioisotopes having significant medical applications in persistent disease areas such as cancer. The cost of effective short-term radioisotopes may become prohibitively high compared to typical healthcare costs for diseases such as cancer. Example embodiments are directed to methods of producing radioisotopes, useable in medical applications, in commercial nuclear reactors and associated apparatuses. Example methods may utilize instrumentation tubes conventionally found in nuclear reactor vessels to expose irradiation targets to neutron flux found in the operating nuclear reactor. Short-term radioisotopes may be produced in the irradiation targets due to the flux. These short-term radioisotopes may then be relatively quickly and simply harvested by removing the irradiation targets from the instrumentation tube and reactor containment, without shutting down the reactor or requiring chemical extraction processes. The short-term radioisotopes may then be immediately transported to medical facilities for use in, for example, cancer therapy. Example embodiments may include apparatuses for producing radioisotopes in nuclear reactors and instrumentation tubes thereof. Example embodiments may include one or more subsystems configured to insert and remove irradiation targets from an instrumentation tube of an operating commercial nuclear reactor. Example embodiments may include a tube subsystem, an irradiation target drive subsystem, and/or an irradiation target storage and removal subsystem for inserting and removing irradiation targets from an instrumentation tube. Example embodiments may preserve a linear order of irradiation targets used therein to permit tracking and measurement of radioisotopes produced in example embodiment irradiation targets. Detailed illustrative embodiments of example embodiments are disclosed herein. However, specific structural and functional details disclosed herein are merely representative for purposes of describing example embodiments. The example embodiments may, however, be embodied in many alternate forms and should not be construed as limited to only example embodiments set forth herein. It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of example embodiments. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. It will be understood that when an element is referred to as being “connected,” “coupled,” “mated,” “attached,” or “fixed” to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being “directly connected” or “directly coupled” to another element, there are no intervening elements present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between”, “adjacent” versus “directly adjacent”, etc.). The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the language explicitly indicates otherwise. It will be further understood that the terms “comprises”, “comprising,”, “includes” and/or “including”, when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. It should also be noted that in some alternative implementations, the functions/acts noted may occur out of the order noted in the figures. For example, two figures shown in succession may in fact be executed substantially and concurrently or may sometimes be executed in the reverse order, depending upon the functionality/acts involved. FIG. 1 is an illustration of a conventional reactor pressure vessel 10 usable with example embodiments and example methods. Reactor pressure vessel 10 may be used in at least a 100 MWe commercial light water nuclear reactor conventionally used for electricity generation throughout the world. Reactor pressure vessel 10 may be positioned within a containment structure 411 that serves to contain radioactivity in the case of an accident and prevent access to reactor 10 during operation of the reactor 10. A cavity below the reactor vessel 10, known as a drywell 20, serves to house equipment servicing the vessel such as pumps, drains, instrumentation tubes, and/or control rod drives. As shown in FIG. 1, at least one instrumentation tube 50 extends vertically into the vessel 10 and well into or through core 15 containing nuclear fuel and relatively high amounts of neutron flux during operation of the core 15. Instrumentation tubes 50 may be generally cylindrical and widen with height of the vessel 10; however, other instrumentation tube geometries are commonly encountered in the industry. An instrumentation tube 50 may have an inner diameter and/or clearance of about 1 inch, for example. The instrumentation tubes 50 may terminate below the reactor vessel 10 in the drywell 20. Conventionally, instrumentation tubes 50 may permit neutron detectors, and other types of detectors, to be inserted therein through an opening at a lower end in the drywell 20. These detectors may extend up through instrumentation tubes 50 to monitor conditions in the core 15. Examples of conventional monitor types include wide range detectors (WRNM), source range monitors (SRM), intermediate range monitors (IRM), and/or Local Power Range Monitors (LPRM). Access to the instrumentation tubes 50 and any monitoring devices inserted therein is conventionally restricted to operational outages due to containment and radiation hazards. Although vessel 10 is illustrated with components commonly found in a commercial Boiling Water Reactor, example embodiments and methods may be useable with several different types of reactors having instrumentation tubes 50 or other access tubes that extend into the reactor. For example, Pressurized Water Reactors, Heavy-Water Reactors, Graphite-Moderated Reactors, etc. having a power rating from below 100 Megawatts-electric to several Gigawatts-electric and having instrumentation tubes at several different positions from those shown in FIG. 1 may be useable with example embodiments and methods. As such, instrumentation tubes useable in example methods may be any protruding feature at any geometry about the core that allows enclosed access to the flux of the nuclear core of various types of reactors. Applicants have recognized that instrumentation tubes 50 may be useable to quickly and constantly generate short-term radioisotopes on a large-scale basis without the need for chemical or isotopic separation and/or waiting for reactor shutdown of commercial reactors. Example methods may include inserting irradiation targets into instrumentation tubes 50 and exposing the irradiation targets to the core 15 while operating, thereby exposing the irradiation targets to the neutron flux commonly encountered in the operating core 15. The core flux may convert a substantial portion of the irradiation targets to a useful radioisotope, including short-term radioisotopes useable in medical applications. Irradiation targets may then be withdrawn from the instrumentation tubes 50, even during ongoing operation of the core 15, and removed for medical and/or industrial use. Example embodiments that enable example methods are discussed below, including further details of example methods enabled by the example embodiments. FIG. 2 is an illustration of an example embodiment system for producing radioisotopes in a nuclear reactor. Example embodiment radioisotope generation system 100 is shown in FIG. 2 positioned below an instrumentation tube 50 in drywell 20, below reactor pressure vessel 10. Example embodiment radioisotope generation system 100 may insert and remove irradiation targets 250 into/from instrumentation tube 50 for irradiation in the operating vessel 10. Example embodiment radioisotope generation system 100 may include three different subsystems, each discussed in turn below—instrumentation tube subsystem 200; irradiation target drive subsystem 300; and/or irradiation target storage and removal subsystem 400. Irradiation targets 250 and their use in example embodiments and methods are discussed lastly below. Tube Subsystem FIG. 3 is an illustration of an example embodiment instrumentation tube subsystem 200. As shown in FIG. 3, instrumentation tube 50, as also shown in FIGS. 1-2, extends from a lower position in the drywell 20 into reactor vessel 10 and nuclear core 15 containing nuclear fuel. Irradiation targets 250 may be linearly pushed into and removed from instrumentation tube 50 via instrumentation tube opening 51 by irradiation drive subsystem 300 (FIG. 5). Instrumentation tube 50 may extend to near a top 16 of the core 15. Thus, irradiation targets 250 may be linearly positioned and held through the vertical length of the nuclear core 15 in instrumentation tube 50. The neutron flux in the core 15 may be known and may be sufficiently high to convert a substantial amount of the irradiation targets 250 in the tube 50 into useful short-term radioisotopes. As will be discussed below with reference to FIGS. 8A and 8B, the type of target 250 and vertical position in the nuclear core 15 may allow precise exposure time and radioisotope generation rate calculation to maximize radioisotope generation and activity. A sleeve 260 may be inserted into instrumentation tube 50 in order to provide further containment, shielding, and geometry matching of the irradiation targets 250. Sleeve 260 may be generally rigid and fabricated from a material that substantially maintains its physical characteristics when exposed to an operating nuclear core 15. Sleeve 260 may be fabricated of, for example, stainless steel, aluminum, a zirconium alloy, Inconel, nickel, titanium, etc. Sleeve 260 may extend beyond opening 51 of instrumentation tube 50 to provide guidance and alignment beyond instrumentation tube 50. For example, sleeve 260 may extend downward and terminate closer to irradiation target drive subsystem 300 in order to properly guide irradiation targets 250 into and out of the irradiation target drive subsystem 300, which may be located further below vessel 10 than opening 51. Sleeve 260 may provide a smooth, constant inner surface to facilitate irradiation target 250 insertion and removal into/from instrumentation tube 50. As discussed above, instrumentation tube 50 may have a variety of geometries and/or change width with vertical distance into vessel 10. Sleeve 260 may have a varying outer diameter to account for the geometry of instrumentation tube 50 but may have a uniform inner diameter associated with the size of irradiation targets 250. For example, the sleeve 260 may have an inner diameter narrow enough to prevent irradiation targets 250 from shifting or changing position in line through instrumentation tube 50, to allow preservation of irradiation target order, to allow order-based identification, etc. In an example embodiment, sleeve 260 may be modular and consist of several pieces that permit assembly and insertion into instrumentation tube 50. As shown in FIGS. 4A and 4B, several different components may form a modular sleeve 260. In FIG. 4A, segments 261 of a sleeve 260 are shown. Each segment 261 may include a mating element 264 and/or 265 that may join each segment 261 to another segment 261 and permit irradiation target 250 to pass through segments 261 by being hollow. Mating elements 264 and 265 may include, for example, a hollow threaded end and hole or a hollow tang and receptor. Segments 261 may have varying outer diameters 262 to meet or mirror the geometry of instrumentation tube 50 yet small enough to pass through opening 51. Segments 261 may include inner diameters 263 that are relatively constant and of a width compatible with receiving irradiation targets 250. Thus, if segments 261 are inserted into instrumentation tube 50 individually, segments 261 may be assembled inside instrumentation tube 50 to provide a continuous, linear inner diameter for irradiation targets 250 inserted into tube 50 and sleeve 260. Alternatively, as shown in FIG. 4B, sleeve 260 may have a substantially constant inner and outer diameter, and one or more modular collets 266 may be coupled to sleeve 260 to provide a fit between instrumentation tube 50 and sleeve 260/collet 266. Thus, collets 266 may be inserted and assembled around sleeve 260 in instrumentation tube 50 to provide a continuous inner diameter for irradiation targets 250 inserted into tube 50 and sleeve 260 surrounded by modular collets 266. Irradiation Target Drive Subsystem FIG. 5 is an illustration of an example embodiment irradiation target drive subsystem 300. As shown in FIG. 5, two driving gears 310a and 310b may receive and/or transmit irradiation targets 250 from/to sleeve 260 or opening 51 of instrumentation tube 50. Driving gears 310a and 310b may be positioned opposite each other. Driving gears 310a and 310b may be positioned below and on either side of instrumentation tube 50 in drywell 20 below vessel 10. By sizing and positioning driving gears 310a and 310b and target drive subsystem 300 based on the amount of space in drywell 20 below vessel 10, radioisotope generation system 100 may fit entirely within drywell 20 of many current operating nuclear reactors worldwide. Driving gears 310a and 310b may have specially-shaped circumferential or lateral surfaces 311a and/or 311b that complement the shape of irradiation targets 250 so as to securely grab and hold or fit with irradiation targets 250 coming between driving gears 310a and 310b. For example, as shown in FIG. 5, surfaces 311a and 311b may have a scalloped shape in order to mate with spherical irradiation targets 250. The scallops in surfaces 311a and 311b may have radii substantially similar to that of irradiation targets 250 to securely hold and move irradiation targets 250 coming between driving gears 310a and 310b while maintaining the same linear order of irradiation targets 250 into and out of instrumentation tube 50. Alternatively, surfaces 311a and 311b may have other shapes to match and/or mate with alternately-shaped irradiation targets as may be substituted by one skilled in the art. Driving gears 310a and 310b may rotate in opposite directions about parallel axes perpendicular to instrumentation tube 50, so as raise or lower irradiation targets 250 passing therebetween. For example, as shown in FIG. 5, if driving gear 310a rotates in a clockwise direction and driving gear 310b in a counter-clockwise direction, irradiation targets 250 between and below the axes of rotation of the driving gears 310a and 310b may be elevated from storage and removal subsystem 400 into tube subsystem 200. Oppositely, if driving gears 310a and 310b are rotated in the reverse directions, such that driving gear 310a is rotated in a counter-clockwise direction and driving gear 310b is rotated in a clockwise direction, irradiation targets 250 may be lowered from tube subsystem 200 into removal subsystem 400. Driving gears 310a and 310b and other example driving mechanisms useable in irradiation target drive subsystem 300 may preserve the linear order of irradiation targets 250 passing between tube subsystem 200 and irradiation target storage and removal subsystem 400. In this way, overall linear order of irradiation targets 250 may be preserved throughout example embodiment system 100, and any irradiation target monitoring dependent upon irradiation target 250 vertical order within tube 50 may be successfully carried out. As shown in FIG. 5, driving gears 310a and 310b may be driven by a driving power subsystem 390 that allows synchronous movement between driving gears 310a and 310b. The example embodiment shown in FIG. 5 shows a plurality of individual gears transferring motion from a power drive shaft 325 to driving gears 310a and 310b. Power drive shaft 325 may connect to toothed lower transfer gears 391a and 391b that mesh with a toothed area of upper transfer gears 392a and 392b, respectively, so that upper transfer gears 392a and 392b may be rotated by rotation of power drive shaft 325. Upper transfer gears 392a and 392b may include threaded or interlocking ends 393a and 393b, respectively, that mesh or otherwise interlock with driving gears 310a and 310b, respectively. In this way, both driving gears 310a and 310b may be rotated by rotation of power drive shaft 325. As shown in FIG. 5, lower transfer gears 391a and 391b may mesh with opposite orientations to driving gears 310b and 310a, respectively, so as to rotate driving gears 310a and 310b in opposite directions as described above. Upper transfer gears 392a and 392b may have similar radii and mesh with driving gears 310b and 310a at similar radii so as to impart symmetrical angular motion (driving gears 310a and 310b may have negative angular motions of each other) to driving gears 310a and 310b. Thus, if driving gears 310a and 310b possess similar outer radii of surfaces 311a and 311b, irradiation targets 250 may fit at a constant circumferential position within surfaces 311a and 311b so as to enable the holding and fitting of irradiation targets 250 through driving gears 310a and 310b described above. It is understood that any known method of arranging gears and/or providing power to driving gears 310a and 310b may be used in example embodiments. For example, although a worm gear system is shown on upper transfer gears 392a and 392b to drive driving gears 310a and 310b, other interfaces, including a conventional toothed-gear and/or friction plate interface, may be used. Alternatively, for example, driving gears 310a and 310b may be directly powered by electric motors without the need for driving power subsystem 390 and power drive shaft 325. Power drive shaft 325 may be powered locally by a variety of means including a motor 921, from gearings off primary circulation pumps, etc., or may be powered remotely. As shown in FIG. 5, power drive shaft 325 may be connected to a motor 921 capable of rotating power drive shaft 325. A digital counter 911 may be further connected to power drive shaft 325 in order to detect a position, number of rotations, and/or angular velocity of power drive shaft 325. Both digital counter 911 and motor 921 may be communicatively connected to a computer 900. Computer 900 may be appropriately programmed, input with, or have access to pertinent system information including, for example, radii of and connection among gears used in example embodiment system 100, position of gears an irradiation targets in other subsystems 200 and 400, reactor axial flux profile, irradiation target dimensions, makeup, and linear order, and/or information from digital counter 911 and motor 921. With this information, computer 900 may automatically actuate motor 921 and move irradiation targets 250 through example embodiment system 100. Such automatic actuation may be based on the known system and reactor information, including online status. In this way, computer 900 may connect with and coordinate other subsystems, including irradiation target storage and removal subsystem 400, described below, so as to permit synchronization throughout example embodiment system 100. Irradiation target drive subsystem 300 may insert and remove irradiation targets 250 from tube subsystem 200 at any desired speed, depending on the rotation rate of driving gears 310a and 310b and radii of driving gears 310a and 310b. Further, driving gears 310a and 310b may serve to maintain the axial position of irradiation targets 250 within tube subsystem 200. As driving gears 310a and 310b may be held in place by, for example, a worm gear system used on threaded ends 393a and 393b of upper transfer gears 392a and 392b and driving gears 310a and 310b, irradiation targets 250 may be held in axial position with no room to escape between locked driving gears 310a and 310b and tube 50 and/or sleeve 260. That is, threaded or interlocking ends 393a and 393b may include screws that interface with driving gears 310a and 310b so as to provide motion to and rotate driving gears 310a and 310b but prevent driving gears 310a and 310b from driving the driving power subsystem 390. By preserving both axial order of irradiation targets 250 in the instrumentation tube 50 and order of irradiation targets 250 inserted or removed from the core 15, tracking and identification of irradiation targets 250 passing through irradiation target drive subsystem 300 may be enabled. Although irradiation target drive subsystem is illustrated as a series of gears in FIG. 5, other mechanisms of raising and/or lowering irradiation targets 250 between subsystems 200 and 400 may be used as will be appreciated by one skilled in the art. For example, an actuator or pneumatic drive between subsystems 200 and 400 may serve to move and hold irradiation targets 250 between these subsystems. In this way other mechanisms may be used for target drive subsystem 300 while still permitting example embodiment radioisotope generation system 100 to function in inserting and removing irradiation targets into instrumentation tubes 50 of operating nuclear reactors. Irradiation Target Storage and Removal Subsystem FIG. 6 is an illustration of an example embodiment irradiation target storage and removal subsystem 300. As shown in FIG. 6, irradiation targets 250 may enter or leave the irradiation target drive subsystem 300 near the top of storage and removal subsystem 400. Irradiation targets 250 may enter/leave storage subsystem 300 from a holding tube 420 running from an outlet of irradiation target drive subsystem 300 down into a lower location in drywell 20. Holding tube 420 may be a rigid tube fabricated of a material designed to substantially maintain its physical characteristics when exposed to radiation present near an operating nuclear reactor, including, for example, stainless steel, nickel-based allow, titanium, etc. Unirradiated (fresh) irradiation targets 250 may travel up through holding tube 420 to be loaded into irradiation target drive subsystem 300 and/or irradiated irradiation targets 250 (now containing short-term radioisotopes from being exposed to core neutron flux) may travel down into holding tube 420 to be stored in holding tube 420 after removal from the operating reactor by the irradiation target drive subsystem 300. Holding tube 420 may include an exit tube 410 located near a gap in holding tube 420 and a removal mechanism 415, which is described below with respect to FIG. 7. Removal mechanism 415 may push irradiation targets 250 from the holding tube 420 into an exit tube 410. Exit tube 410 may then pass through containment 411 to an exterior holding area 412, where irradiation targets 250 may be harvested for use as radioisotopes. Exit tube 410 may pass through containment 411 in a variety of ways, including through known piping and/or hatchways in the drywell 20 that exits containment 411 and/or through a specially-designed passage through containment 411. Such a passage may be specially designed to sustain containment pressurization and/or security. FIG. 7 is an illustration of an example embodiment removal mechanism 415. As shown in FIG. 7, example embodiment removal mechanism 415 may include a push bar 418 connected to a shaft 417 and drive wheel 416 in a piston/wheel configuration. Drive wheel 416 may be driven by removal gearing 414 to rotate and push irradiation targets 250 into exit tube 410 from holding tube 420. Removal gearing 414 may be a conventional cog connected to drive wheel 416 or may be a screw and worm gear configuration as shown in FIG. 7. Removal gearing 414 may be connected to driving power subsystem 390 and/or power drive shaft 325 (FIG. 5) at desired times in order to synchronously extract irradiation targets as they are moved by irradiation target drive subsystem 300. In this way, exact location and irradiation target 250 identification may be possible between subsystems, by maintaining target order and/or synchronously moving targets 250 through example embodiment radioisotope generation system 100. Alternatively, a motor 922 and/or digital counter 912 may be attached to drive shaft 325 in order to provide rotary location and timing to the computer 900. Such a system may be similar to the motor 921/digital counter 911 combination discussed above in FIG. 5 and may relay similar information to shared computer 900 to facilitate synchronization of irradiation target 250 movement and removal within/from example embodiment system 100. Although example embodiment removal mechanism 415 is shown as a piston/wheel configuration, other types of removal mechanisms may be useable with example embodiments. For example, removal mechanism 415 may include a remotely operated actuator that simply pushes irradiation targets 250 into exit tube 410 upon actuation. Other types of removal mechanisms known in the art may be substituted for removal mechanism 415 as would be known to one skilled in the art. As shown in FIG. 6, irradiation targets 250 may fill holding tube 420 down to a flow control mechanism 450. A make-up tube 460 may extend upward and around subsystems 400 and/or 300 to an irradiation target reservoir 419 in a spiral fashion. In this way, gravity may drive irradiation targets 250 down through make-up tube 460 to flow control mechanism 450. Although make-up tube 460 is shown as a spiral, any number of configurations may be used, including a straight or upward path from reservoir 419 aided by an additional drive system to push irradiation targets to flow control mechanism 450. Flow control mechanism 450 may be a set of toothed and/or specially-surfaced gears similar to the drive gears 310a and 310b of irradiation target drive subsystem 300 (FIG. 5), and descriptions of redundant portions of these omitted. Flow control mechanism may include a horizontal pair of gears instead of being vertical as drive gears 310a and 310b. Similar to the gears 310a and 310b, the flow control mechanism 450 may be moved by worm gears connected to drive shaft by connecting gears. A drive shaft may be connected to a motor and/or counter, both of which may be connected to computer 900, which may further coordinate and control movement of irradiation targets 250 with flow control mechanism 450. Flow control mechanism 450 may hold and/or move irradiation targets between make-up tube 460 and holding tube 420, which may both have openings near flow control mechanism 450. Because irradiation targets may be gravity-driven from reservoir 490, flow control mechanism 450 may serve to block irradiation targets from pushing up into holding tube 420 at undesired times. Flow control mechanism 450 may be driven by the same gear set 320 and/or power drive 325 as the irradiation target drive subsystem 300 (FIG. 5) so as to simplify and preserve synchrony of example embodiment radioisotope generation system 100. Software on computer 900 controlling flow control mechanism 450 may maintain synchronicity between all subsystems 200, 300, and 400. Flow control mechanism 450 is shown as a set of toothed gears; however, several different types of blocking devices, such as actuators, valves, etc., may be used to control irradiation target movement between make-up tube 460 and holding tube 250. By the configuration of example embodiment storage and removal system 400, irradiation target 250 order and linearity may be preserved from insertion to removal from example embodiment radioisotope generation system 100. For example, as irradiation targets 250 are fed into holding tube 420 from irradiation drive system 300 after being irradiated in the core, targets may be backed up and/or be driven into make-up tube 460 until all irradiation tubes are removed from instrumentation tube subsystem 200. Due to the gravity-driven nature of make-up tube 460, flow control mechanism 450 may permit the irradiated irradiation targets 250 to return up to removal mechanism 415, which may synchronously extract the queued irradiated irradiation targets 250 to the exit tube 410. In this way, the exact vertical order of irradiation targets, from topmost to bottommost position in tube 50, may be preserved as the irradiated irradiation targets 250 are directed outside containment 411. Neutron flux within the core 15 is generally known or determinable to one skilled in the art. By preserving the linear order of irradiation targets in the core, example embodiment system 100 may provide maximum specific activity in irradiation targets 250. In this way, specific activity of irradiation targets 250 may be maximized by allowing targets ready for discharge to be placed at an axial position with flux conducive to generate a required specific activity for medical and/or industrial usage of irradiation target 250. Further, by the configuration shown in FIG. 6, make-up tube 460 may have a length approximately equal to a length of instrumentation tube 50, thus preventing an incorrect count or overflow of irradiation targets into irradiation target drive subsystem 300 or tube subsystem 200. Reservoir 419 may store additional irradiation targets that may be released into make-up tube 460 after all previous, irradiated irradiation targets 250 have passed into holding tube 420. In this way, reservoir 419 may continuously provide irradiation targets 250 into example embodiment radioisotope generation system 100 and may maximize radioisotope production. Reservoir 419 may act both as a target makeup repository and a repository for the placement of targets 250 exiting the stacked loop 460. When subsystem 300 and/or flow control mechanism 450 are advancing targets into the reactor core, additional targets 250 may be allowed to exit repository 419 by gravity and enter make-up tube 460. When targets are withdrawn from the reactor core, targets may move back into repository reservoir 419. Reservoir 419 may be a variety of shapes permitting such irradiation target movement, including, for example, a funnel-shaped reservoir. The example embodiment irradiation target storage and removal subsystem 400 shown in FIG. 6 may facilitate ordered removal and/or storage of irradiation targets 250 containing short-term radioisotopes useable in medical and industrial applications; however, other example embodiment subsystems may successfully allow removal of irradiated irradiation targets 250 from the radioisotope generation system 100. For example, removal subsystem 300 may consist entirely of an exit tube directed outside of containment, such that irradiation targets 250 may directly exit the vessel 10 from irradiation target drive systems and/or be directly loaded into the vessel 10 therefrom. Radioisotope Generation System Operation Example embodiment radioisotope generation systems being described above, it is possible to summarize the operation of such example embodiments to achieve example methods. Fresh irradiation targets 250 may be stored in reservoir 419 (FIG. 6) and/or held in makeup tube 460 by flow control mechanism 450. Upon release or activation of flow control mechanism 450, irradiation targets 250 may move up through holding tube 420, driven by gravity due to the reservoir 419 being above holding tube 420 and or by flow control mechanism. Once a sufficient amount of irradiation targets 250 have been passed into holding tube 420, irradiation targets 250 may exit holding tube 420 near driving gears 310a and 310b (FIG. 5). Driving gears 310a and 310b may be rotated to mate with the irradiation targets 250 emerging from holding tube 420. Driving gears 310a and 310b may sequentially move the irradiation targets 250 into sleeve 260 (FIG. 3) while preserving the order of irradiation targets 250. Irradiation targets 250 may be continually driven into sleeve 260 so as to pass into instrumentation tube 50 through opening 51 and up into core 15. Once instrumentation tube 50 and sleeve 260 are filled with irradiation targets, driving gears 310a and 310b may hold the irradiation targets in place in the tube 50. The core 15 may be operation at some point while irradiation targets are held in the tube 50 and core 15. Knowing the axial flux profile of the core 15 and the irradiation target 250 makeup, irradiation targets may be held within core 15 for a time period to substantially convert irradiation targets 250 into desired radioisotopes. Upon completion of the desired time period, driving gears 310a and 310b may stop holding the targets 250 within tube 50 and sleeve 260 and/or reverse direction in order to allow irradiation targets to pass from the sleeve 260 back into holding tube 420. This downward drive of the irradiation targets 250 may back up other irradiation targets in holding tube 420 or makeup tube 460 further back into makeup tube 460. Holding mechanism 450 may further aid in backing irradiation targets into makeup tube 460 or, alternately, may prevent any irradiation targets from entering holding tube or remove those targets 250 that do such that holding tube 420 is empty when irradiated irradiation targets 250 pass down into holding tube 420. Once all irradiated irradiation targets 250 are emptied from sleeve 260 into holding tube 420, holding mechanism 450 may drive, or allow gravity to drive, the irradiated irradiation targets 250 into an exit tube 410 (FIG. 7). A removal mechanism 415 may synchronously push the irradiation targets 250 into exit tube 410 with their movement by holding mechanism 450. From exit tube 410, irradiated irradiation targets 250 may be removed from containment 411 and harvested for medical or industrial use. Throughout the operation of example embodiment systems, irradiation targets 250 maintain a linear order. The entire process described above may be automated by remote user or computer 900 that drives the various subsystems as described above with regard to each subsystem. For example, a remote computer 900 may initiate target 250 insertion into the core 15 and may calculate the axial flux profile of the core 15 and the neutronic characteristics of the irradiation targets 250 being placed in the core 15. Knowing the linear order of the irradiation targets and hence their axial placement in the core, the computer may calculate a desired exposure time. Upon passage of the exposure time, the computer may initiate target 250 removal from the core and, once all targets 250 are removed from core 15, the computer 900 may initiate removal of targets 250 from example embodiment systems and containment 411. The exact activity and radiation properties of each irradiation target 250 may be calculated in its linear order upon removal, allowing harvesting and use of radioisotopes present in irradiated irradiation targets 250. Irradiation Targets FIGS. 8A and 8B are illustrations of example embodiment irradiation targets 250a and 250b. As shown in FIG. 8A, irradiation target 250a may be roughly spherical so as to permit rotation and rolling through example embodiment apparatuses. However, as discussed above, irradiation targets may be other shapes as well. For example, hexahedrons and/or cylinders may be useable as irradiation targets 250 in order to prevent rolling in some or all directions or to accommodate different instrumentation tube 50 geometries and/or locations. Surfaces of driving gears and tube shapes may be varied to match these different irradiation target geometries. As shown in FIG. 8A, irradiation target 250a may be generally solid and fabricated from a material that converts to a useful radioisotope when exposed to neutron flux present in an operating commercial nuclear reactor. Alternatively, different materials may be plated or layered at different radii in irradiation target 250a to allow easier handling and harvesting of radioisotopes from irradiation target 250a. Alternatively, as shown in FIG. 8B, irradiation target 250b may be generally hollow and include a liquid, gaseous, and/or solid material that converts to a useful gaseous, liquid, and/or solid radioisotope when exposed to neutron flux present in an operating commercial nuclear reactor. A shell 251 may surround and contain the solid liquid, or gaseous target material 252, the shell 251 having negligible physical changes when exposed to a neutron flux, including, for example, stainless steel and/or aluminum. An access port 253 may permit access through shell 251 for harvesting radioisotopes produced in irradiation target 250b. For example, access port 253 may be welded or threaded into shell 251 so as to provide a seal for the gaseous/liquid/solid target material 252 and produced radioisotope. Access port 253 may include a frangible area 255 that readily tears, is easily punctured, etc. when subjected to an appropriate outside force when the gaseous/liquid/solid radioisotope is ready to be harvested. Although example embodiment radioisotope generation system 100 has been described in detail as an apparatus useable to perform example methods of producing and harvesting short-term isotopes, it is understood that other apparatuses may be used to perform example methods. For example, a closed sleeve containing irradiation targets may be inserted and removed from instrumentation tubes of operating commercial reactors in a “cartridge”-like fashion at various intervals in order to properly expose the irradiation targets to neutron flux sufficient to create useable short-term radioisotopes. Several different radioisotopes may be generated in example embodiments and example methods. Example embodiments and example methods may have a particular advantage in that they permit generation and harvesting of short-term radioisotopes in a relatively fast timescale compared to the half-lives of the produced radioisotopes, without shutting down a commercial reactor, a potentially costly process, and without hazardous and lengthy isotopic and/or chemical extraction processes. Although short-term radioisotopes having diagnostic and/or theraputic applications are producible with example apparatuses and methods, radioisotopes having industrial applications and/or long-lived half-lives may also be generated. Irradiation targets 250 and amount of exposure time in instrumentation tube 50 may be selected in example methods and apparatuses to determine the type and concentration of radioisotope produced. That is, as discussed above, because axial flux levels are known within an operating reactor, and because example embodiments may permit precise control of axial position of irradiation targets 250 used in example embodiment apparatuses and methods, the type and size of irradiation target 250 and exposure time may be used to determine the resulting radioisotopes and their strength. It is known to one skilled in the art and from reference to conventional decay and cross-section charts what types of irradiation targets 250 will produce desired radioisotopes given exposure to a particular amount of neutron flux. Further, irradiation targets 250 may be chosen based on their relatively smaller neutron cross-section, so as to not interfere substantially with the nuclear chain reaction occurring in an operating commercial nuclear reactor core. For example, it is known that Molybdenum-99 may be converted into Technetium-99m having a half-life of approximately 6 hours when exposed to a particular amount of neutron flux. Technetium-99m has several specialized medical uses, including medical imaging and cancer diagnosis, and a short-term half-life. Using irradiation targets 250 fabricated from Molybdnenum-99 and exposed to neutron flux in an operating reactor based on the size of target 250, Technetium-99m may be generated and harvested in example embodiment apparatuses and methods by determining the size of the irradiation target containing Mo-99, the axial position of the target in the operational nuclear core, the axial profile of the operational nuclear core, and the amount of time of exposure of the irradiation target. Table 1 below lists several short-term radioisotopes that may be generated in example methods using an appropriate irradiation target 250. The longest half-life of the listed short-term radioisotopes may be approximately 75 days. Given that reactor shutdown and spent fuel extraction may occur as infrequently as two years, with radioisotope extraction and harvesting from fuel requiring significant process and cool-down times, the radioisotopes listed below may not be viably produced and harvested from conventional spent nuclear fuel. TABLE 1List of potential radioisotopes producedRadioisotopeHalf-LifeParent MaterialProduced(approx)Potential UseMolybdenum-Technetium-6hoursImaging of cancer &9999mpoorly permiatedorgansChromium-50Chromium-5128daysLabel blood cellsand gasto-intestinaldisordersCopper-63Copper-6413hoursStudy of Wilson's &Menke's diseasesDysprosium-Dysprosium-2hoursSynovectomy164165treatment ofarthritisErbium-168Erbium-1699.4daysRelief of arthritispainHolmium-165Holmium-16627hoursHepatic cancer andtumor treatmentIodide-130Iodine-1318daysThyroid cancer anduse in beta therapyIridium-191Iridium-19274daysInternalradiotherapy cancertreatmentIron-58Iron-5946daysStudy of ironmetabolism andsplenaic disordersLutetium-176Lutetium-1776.7daysImagine andtreatment ofendocrine tumorsPalladium-102Palladium-10317daysBrachytherapy forprostate cancerPhosphorus-31Phosphorous-14daysPolycythemia vera32treatmentPotassium-41Potassium-4212hoursStudy of coronaryblood flowRhenium-185Rhenium-1863.7daysBone cancer therapySamarium-152Samarium-15346hoursPain relief forsecondary cancersSelenium-74Selenium-75120daysStudy of digestiveenzymesSodium-23Sodium-2415hoursStudy of electrolytesStrontium-88Strontium-8951daysPain relief forprostate and bonecancerYtterbium-168Ytterbium-16932daysStudy ofcerebrospinal fluidYtterbium-176Ytterbium-1771.9hoursUsed to produce Lu-177Yttrium-89Yttrium-9064hoursCancerbrachytherapy Table 1 is not a complete list of radioisotopes that may be produced in example embodiments and example methods but rather is illustrative of some radioisotopes useable with medical therapies including cancer treatment. With proper target selection, almost any short-term radioisotope may be produced and harvested for use through example embodiments and methods. Example embodiments thus being described, it will be appreciated by one skilled in the art that example embodiments may be varied through routine experimentation and without further inventive activity. Variations are not to be regarded as departure from the spirit and scope of the exemplary embodiments, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims. |
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abstract | A bath containing nickel ions and formic acid is injected into a film-forming aqueous solution flowing in a circulation pipe connected to feed water pipe made of carbon steel in a BWR plant. This film-forming aqueous solution is supplied into the feed water pipe through the circulation pipe, and then, a nickel metal film is formed on an inner surface of the feed water pipe. After the nickel metal film is formed, a film-forming aqueous solution containing iron (II) ions, formic acid, nickel ions, hydrogen peroxide, and hydrazine is supplied to the feed water pipe. A nickel ferrite film is formed on the surface of the nickel metal film in the feed water pipe. Then, the nickel ferrite film is come into contact with water containing dissolved-oxygen at 150° C. or above to transform the nickel metal film into a nickel ferrite film. A thick nickel ferrite film is formed on the inner surface of the feed water pipe. Corrosion of the carbon steel member composing the plant can further reduce. |
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052710475 | claims | 1. A method of acting remotely on a nuclear power station site, said method comprising the steps of: placing lengths of waveguide end-to-end by means of at least one carriage and remotely controlling the carriage by a line of waveguide lengths defined by said end-to-end lengths of waveguide, said carriage being provided with handling equipment for laying said lengths of waveguide and with at least one robot arm, and said method further comprises connecting said lengths of waveguide together by said at least one robot arm under control of a control station which includes a signal generator and a signal receiver, whereby said line of waveguide lengths may be laid from said control station to the site to be inspected and optionally treated. 2. A method according to claim 1, wherein said at least one carriage is loaded with a certain number of lengths of waveguide and wherein the line of waveguide lengths is laid by repeating the following cycle of operations until the site is reached: said at least one carriage is displaced along the last length to have been laid; said at least one carriage is stopped close to the end of said length; and the next length is laid and connected. 3. A method according to claim 2, wherein the cycles of operations are interrupted when all of the lengths loaded on the carriage have been laid, said at least one carriage then being returned to the beginning of the line of waveguide lengths, being reloaded with a certain number of lengths, and then being returned to the end of the line that has already been implemented. 4. A method according to claim 1, wherein positioning and inspection are performed using a rotary television camera installed on an elevator arm on the carriage. 5. A method according to claim 1, wherein said at least one carriage comprises two carriages, and said method comprises controlling movement of said two carriages via said line of waveguide lengths. 6. A method according to claim 1, wherein once the line of waveguide lengths has been installed all the way to the site, treatment tooling is installed on the carriage. 7. A method according to claim 1, wherein said at least one carriage comprises multiple special robot carriages and said method further comprises remotely controlling said special robot carriages on the site using said line of waveguide lengths. |
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041750039 | claims | 1. A grid for a nuclear reactor fuel assembly comprising: a multiplicity of straps interleaved with each other to form a structure of egg-crate configuration which includes individual cells adapted to contain fuel rods and control rod guide tubes; a spring projecting inwardly into each cell designated to hold a fuel rod from that portion of each strap which cooperates with the other three strap portion to define the four walls of each cell; each of said springs being pressed from said strap portion and having its top and bottom ends merging directly into the material of said strap; each of the four springs projecting inwardly into each cell further being of generally sinusoidal shape and having at least one surface thereon arranged to contact the surface of a fuel rod adapted to extend through a cell; thereby providing at least a four point resilient support for a fuel adapted to extend through said cell to thereby permit fuel rod axial and radial expansion and contraction without distortion. one section on each of the other two springs projects into said one cell and the two sections on each of said other two springs respectively project into separate adjacent cells; the arrangement being such that all cells in the grid may contain the sections of four springs spaced at 90.degree. intervals which serve to provide support for a fuel rod adapted to extend through each of said cells. 2. The combination according to claim 1 wherein each of said springs includes three sections which lie outside the plane of the strap wall, the arrangement being such that each cell contains spring sections positioned to contact at 90.degree. intervals at least four sides of a fuel rod adapted to extend axially through said cell. 3. The combination according to claim 2 wherein two sections of at least two springs project into separate adjacent cells; and 4. The combination according to claim 3 wherein said two spring sections of two springs contact the fuel rod along its axial length, and the springs having said one section projecting into a cell, contact the fuel rod surface at a point intermediate the two sections on the springs. |
047117583 | abstract | A cask for storing spent nuclear fuel after removal from a pool of water includes a container with a cylindrical cavity and a basket which is inserted into the container. The basket includes disk-like grid assemblies which provide spent fuel storage slots and which are coaxially mounted at spaced-apart positions, each grid assembly having a diameter that is slightly less than the one above it. If fuel assemblies are to be stored, hollow cells are affixed to one of the grid assemblies and positioned in the others by heat-conducting wedges which permit the basket and cells to expand at different rates. Rings which project slightly into the interior of the container are provided on the container walls, each ring being positioned to be in alignment with the periphery of a corresponding grid assembly after the basket is inserted into the container. Like the grid assemblies, each ring has a diameter that is slightly less than the ring above it, and moreover the diameter of each ring is slightly greater than the diameter of the corresponding grid assembly. These stepped diameters reduce the possibility that the basket might become jammed during the insertion process due to slight misalignment of the basket. After insertion, temperature changes expand the grid assemblies into pressing contact with the rings in order to transfer heat from the spent fuel to the container walls. |
claims | 1. Method of protecting a radiation detector in a charged particle beam apparatus, the apparatus including a source for producing a beam of charged particles, a condenser system including lenses for illuminating a sample, a projection system including lenses for forming a magnified image of the sample on a detector system, the detector system including a radiation detector, the method comprising:exposing the detector to radiation using a first set of parameters, the set of parameters including condenser lens settings, projection lens settings, charged particle beam energy and beam current,predicting the flux density to which the detector will be exposed at a changed parameters before implementing said change in parameters, the prediction based on an optical model and/or a look-up table with one or more input variables from the group of condenser lens settings, projection lens settings, charged particle beam energy, beam current as input, andcomparing the predicted flux density with a predetermined value, and, depending on the comparison, eitherImplement said change of parameters when the predicted flux density is below the predetermined value, orAvoid exposure of the detector to the flux density associated with the requested change in parameters when the predicted flux density is above the predetermined value. 2. The method of claim 1 in which comparing the predicted flux density with a predetermined value includes generating a warning or an error message when the predicted flux density exceeds said predetermined value. 3. The method of claim 1 in which the detector is a direct electron detector, the radiation comprises electrons and the flux density is a current density. 4. The method of claim 3 in which the detector is equipped to detect electrons transmitted through a sample. 5. The method of claim 2 in which, when an error message or a warning is generated, the excitation of the lenses and the beam energy are not changed. 6. The method of claim 2 in which, when an error message or a warning is generated, the beam is blanked by a beam blanker. 7. The method of claim 1 in which the beam is blanked by a beam blanker when changing the parameters. 8. The method of claim 1 in which exposure of the detector to a dose exceeding the predetermined value results in permanent damage to the detector. 9. The method of claim 1 in which the detector is equipped with a CMOS chip or a CCD chip for direct detection of electrons. 10. The method of claim 1, the method further comprising, prior to exposing the detector to radiation using a first set of parameters, calibrating the optical model and/or Look-Up Table by measuring the beam current for different sets of parameters. 11. Software carrier carrying program code for programming a charged particle beam apparatus comprising a programmable controller to perform the method of claim 1. 12. A method of protecting a radiation detector in a charged particle beam apparatus, comprising:exposing the detector to radiation using a first set of parameters, the set of parameters including condenser lens settings, projection lens settings, charged particle beam energy and beam current,predicting the flux density to which the detector will be exposed at a changed parameters before implementing said change in parameters, the prediction based on an optical model and/or a look-up table with one or more input variables from the group of condenser lens settings, projection lens settings, charged particle beam energy, beam current as input, andcomparing the predicted flux density with a predetermined value,when the predicted flux density is below the predetermined value, implementing said change of parameters, andwhen the predicted flux density is above the predetermined value, avoiding exposure of the detector to the flux density associated with the requested change in parameters. 13. The method of claim 12 in which avoiding exposure of the detector to the flux density associated with the requested change in parameters includes blanking the beam. 14. The method of claim 12 further comprising generating a warning or an error message when the predicted flux density exceeds said predetermined value. 15. The method of claim 12 in which the detector is equipped with a CMOS chip or a CCD chip for direct detection of electrons. 16. The method of claim 12 in which the detector is equipped to detect electrons transmitted through a sample. 17. The method of claim 12 in which the detector is a direct electron detector, the radiation comprises electrons and the flux density is a current density. |
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abstract | A liquid reactant metal alloy includes at least one chemically active metal for reacting with non-radioactive material in a mixed waste stream being treated. The reactant alloy also includes at least one radiation absorbing metal. Radioactive isotopes in the waste stream alloy with, or disperse in, the chemically active and radiation absorbing metals such that the radiation absorbing metals are able to absorb a significant portion of the radioactive emissions associated with the isotopes. Non-radioactive constituents in the waste material are broken down into harmless and useful constituents, leaving the alloyed radioactive isotopes in the liquid reactant alloy. The reactant alloy may then be cooled to form one or more ingots in which the radioactive isotopes are effectively isolated and surrounded by the radiation absorbing metals. These ingots comprise the storage products for the radioactive isotopes. The ingots may be encapsulated in one or more layers of radiation absorbing material and then stored. |
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description | FIG. 1 shows a surgeon wearing a surgical mask 10 of the present invention. The surgical mask 10 has a facial portion 12 which covers the surgeon""s mouth and nose as well as straps 14 which holds the surgical mask 10 onto the surgeon""s face. As shown in FIGS. 2 and 3, the facial portion 12 of the surgical mask is primarily made up of three plies: an interior ply 20 situated next to the surgeon""s face, an exterior ply 22 situated on the outside of the mask and a central liner 24. In its common, disposable form, the interior 20 and exterior 22 plies of the surgical mask 10 are made of paper and the central liner 24 is made of a breathable cloth material, such as gauze. Plastic or metal stays 26 are typically provided at the top, bottom and middle of the surgical mask 10 to help the surgical mask 10 retain its shape and enhance its seal. As described thus far, the surgical mask 10 shown in FIGS. 1-3 is of conventional construction. A distinguishing aspect of the present invention is inexpensively imparting radiopaque qualities to such a surgical mask 10 without significantly diminishing its lightweight usability. These radiopaque qualities can be imparted in a number of ways. In one preferred embodiment, the surgical mask of the present invention can be given radiopaque qualities by, prior to assembly, soaking or dipping its liner 24 in a high concentration solution of a relatively lightweight radiopaque compound, such as barium sulfate, or the reagents used to form the relatively lightweight radiopaque compound, such as barium chloride and sulfuric acid reagents to form a barium sulfate lightweight radiopaque compound. In the case of barium sulfate, this solution might advantageously be a 1 or 2 molar aqueous solution of barium sulfate precipitate (although other concentrations would also work). After the barium sulfate precipitate has been given an opportunity to thoroughly impregnate the liner 24 (e.g., by soaking overnight), the liner 24 can be removed from the barium sulfate solution and air dried. Drying can also be accomplished through use of a drying lamp or a microwave assembly. The impregnated liner 24 can then be placed between interior 20 and exterior 22 plies and sewn or sealed into the surgical mask 10 in a manner that is well known in the art. Since barium sulfate is capable of blocking x-rays, the impregnation of barium sulfate into a surgical mask liner 24 gives an otherwise conventionally constructed surgical mask 10 the ability to block x-rays from harming the surgeon""s face, while still allowing breathability. To improve the efficiency of the impregnation process, various additives can advantageously be used. These additives can include adhesives, fixatives and/or emulsifiers to enhance the adhesion and/or thicken the solution of the lightweight radiopaque compound. For example, an adhesive, such as Gum Arabic or Guar Gum, might be added to the previously mentioned barium sulfate solution to both thicken the solution and increase the adhesion of barium sulfate to the mask material. Alternatively, the adhesive might be added to the mask material, rather than the barium sulfate solution. The pre-treated mask material would then be soaked or dipped in the barium sulfate solution. In addition to being soaked or dipped in a premade solution containing lightweight radiopaque compounds, the relatively lightweight radiopaque materials of the present invention can also be impregnated into the liner 24 of a surgical mask 10 using alternative techniques. Where the radiopaque material is in particulate form in solution (e.g., as a precipitate), one alternative technique is to choose a liner with pores that are smaller in size than the particles of radiopaque material but larger in size than the solvent (e.g., water or alcohol) used for the radiopaque solution. The radiopaque solution can then be passed through the surgical mask liner 24 in a manner where the liner will act as a filter to filter out the radiopaque particles while allowing the solvent to pass through. In the case of an aqueous solution containing barium sulfate precipitate, the filter pore size should be on the order of 2 microns and correspond to Whatman""s pore size 5. Similarly, the solution of radiopaque particles can be sprayed onto the liner. Again, after the liner 24 has been sufficiently impregnated with the radiopaque compound, it can then be dried and assembled into a surgical mask in the conventional manner. In an second alternative embodiment, a reaction chamber can be created with a solution of one reagent used to create the radiopaque compound on one side, a solution of the complementary reagent used to create the radiopaque compound on the other side and a liner 24 placed in the middle. In the case of a barium sulfate radiopaque compound, these reagents might be barium chloride and sulfuric acid. In this barium sulfate example, because of the natural attraction of barium chloride to sulfuric acid, a chemical reaction will occur within liner 24 between the barium chloride and sulfuric acid which will leave behind a barium sulfate precipitate in liner 24. In a third alternative, the liner 24 can be formed with one reagent incorporated within the liner 24 (e.g., as either a compound or free radical) and then exposed to the other reagent in order to create a resulting radiopaque impregnation. Again, in the case of a barium sulfate radiopaque compound, the liner 24 might advantageously be formed with barium or sulfate as part of the liner 24 and then exposed to the other compound in order to create the barium sulfate impregnation. Barium sulfate is a preferred radiopaque precipitate for the present invention because, as compared with lead, for example, it is lighter in weight, inexpensive, promotes breathability and has fewer known heath hazards. Other lightweight radiopaque materials can also used to impregnate fabric for the present invention in a manner similar to that already described. These other lightweight radiopaque materials include, but are not limited to, barium, other barium compounds (e.g., barium chloride), tungsten, tungsten compounds (e.g., tungsten carbide and tungsten oxide), bismuth, bismuth compounds, HYPAQUE(trademark), Acetrizoate Sodium, Bunamiodyl Sodium, Diatrizoate Sodium, Ethiodized Oil, Iobenzamic Acid, Iocarmic Acid, ocetamic Acid, Iodipamide, Iodixanol, Iodized Oil, Iodoalphionic Acid, o-Iodohippurate Sodium, Iodophthalein Sodium, Iodopyracet, Ioglycamic Acid, Iohexol, Iomeglamic Acid, Iopamidol, Iopanoic Acid, Iopentol, Iophendylate, Iophenoxic Acid, Iopromide, Iopronic Acid, Iopydol, Iopydone, Iothalamic Acid, Iotrolan, Ioversol, Ioxaglic Acid, Ioxilan, Ipodate, Meglumine Acetrizoate, Meglumine Ditrizoate Methiodal Sodium, Metrizamide, Metrizoic Acid, Phenobutiodil, Phentetiothalein Sodium, Propryliodone, Sodium Iodomethamate, Sozoiodolic Acid, Thorium Oxide and Trypanoate Sodium. These radiopaque materials for the present invention can be purchased from a variety of chemical supply companies such as Fisher Scientific, P.O. Box 4829, Norcross, Ga. 30091 (Telephone: 1-800-766-7000), Aldrich Chemical Company, P.O. Box 2060, Milwaukee, Wis. (Telephone: 1-800-558-9160) and Sigma, P.O. Box 14508, St. Louis, Mo. 63178 (Telephone: 1-800-325-3010). Those of skill in the art will readily recognize that other relatively lightweight radiation protective materials incorporating the same metals can be used interchangeably with the ones previously listed. While the radiopaque impregnation examples provided thus far have been for a surgical mask liner 24, those of skill in the art will recognize that the principles of this invention can also be applied to a wide range of other applications. For example, rather than just the liner 24, the entire surgical mask 10 could be impregnated with a radiopaque compound of the present invention (e.g., barium sulfate or HYPAQUE(trademark)) in the manner previously described. It should be noted that this is a less preferred embodiment because the side of the surgical mask which comes in contact with the user""s face should preferably be left untreated. Besides surgical masks, any number of other garments such as hoods, gowns, gloves, patient drapes, coverings, booties, jumpsuits, uniforms, fatigues etc. could be given radiopaque qualities in the manner previously described. A manufacturing technique that is particularly suited for mass production of relatively lightweight radiopaque fabrics or other flat, pliable materials for use in garments and other articles involves mixing relatively lightweight radiopaque compounds with polymers and then applying the polymerized mixture to the fabrics or other materials. FIG. 4 illustrates one preferred embodiment of such a process. The FIG. 4 process begins with one or more rolls 30, 32 of fabric or other flat, pliable material 34, 36 to which the polymer mixture will be applied. A non-woven, polymeric fabric, such a polypropylene, polyethylene, rayon or any mixture of these is preferred for this process because these polymeric fabrics have been found to bind well with the liquid polymeric mixture. Alternatively, this process may also be accomplished using woven fabrics and other flat, pliable materials, such sheets of paper or films. To enhance the ability of the fabric or other material 34, 36 to bind with the polymer mixture, an electrostatic charge may be applied to the fabric or other material by one or more corona treaters 38, 39. In this process, the liquid polymer mixture is applied to one side of the unwound fabric or other material 34 through the use of an applicating unit 40. This applicating unit 40 would typically have a roller 42 to roll a thin layer (e.g., preferably 0.1-20 millimeters in thickness) of the liquid polymeric mixture onto one side of an unwound fabric or other material 34. The liquid polymeric mixture preferably includes a polymer, a radiopaque compound and one or more additives. The liquid polymer may be selected from a broad range of plastics including, but not limited to, polyurethane, polyamide, polyvinyl chloride, polyvinyl alcohol, natural latex, polyethylene, polypropylene, ethylene vinyl acetate and polyester. The additives are typically chemicals to improve the flexibility, strength, durability or other properties of the end product and/or to help insure that the polymeric mixture has an appropriate uniformity and consistency. These additives might be, in appropriate cases, plasticizers (e.g., epoxy soybean oil, ethylene glycol, propylene glycol, etc.), emulsifiers, surfactants, suspension agents, leveling agents, drying promoters, flow enhancers etc. Those skilled in the plastic processing arts are familiar with the selection and use of such additives. The proportions of these various polymeric mixture ingredients can vary. Using a greater proportion of radiopaque compound will generally impart greater radiation protection. Nonetheless, if the proportion of radiopaque compound is too high, the polymeric mixture will become brittle when dried and easily crumble apart. The inventors have found from their work with barium sulfate that over 50% of the polymeric mixture, by weight, can be barium sulfate or other lightweight radiopaque compounds, with most of the rest of the mixture consisting of the polymer. In one case, the inventors created a polymeric mixture of 85% by weight of barium sulfate and 15% by weight of polymer. After the applicating unit 40, the polymerized fabric 44 is then preferably passed through a hot air oven 46 to partially dry the thin layer of polymeric mixture before it is sent into a laminating unit 48. At the laminating unit 48, the coated fabric 44 is preferably combined under heat and pressure with a second sheet of fabric or other material 36 to create a sandwich-like radiation protective product 50. The sandwich-like radiation protective fabric or other material can then be perforated and/or embossed, as desired, in a perforating/embossing unit 52. Typically, the finished radiation protective product will then be wound into a final roll 54 to be shipped to a suitable location for use in fabricating garments or other articles. While two layers of fabric or other material 34, 36 have been shown in this FIG. 4 example, one could alternatively apply the polymeric mixture to a single sheet of fabric or other material 34 (i.e., like an open faced sandwich). A sandwich-like radiation protective fabric product 50 of the type produced using the FIG. 4 process is illustrated in a cross-sectional view in FIG. 6. In the FIG. 6 illustration, an intermediate polymeric layer 60, which includes radiopaque materials in addition to the polymers, is sandwiched between two layers of fabric or other material 34, 36. In the illustration of FIG. 6, the intermediate polymeric layer 60 includes several types of radiopaque compounds 62, 64, 66, 68. These radiopaque compounds 62, 64, 66, 68 could be, for example, a barium compound 62, a tungsten compound 64, a bismuth compound 66 and an iodine compound 68. By using a plurality of different radiopaque compounds, the radiation protective article can be more effective in blocking different forms of radiation than a similar article with a single radiopaque compound. For example, some radiopaque compounds might be more effective in blocking beta rays, while others will be more effective in blocking gamma rays. By using both types of radiopaque compounds in the radiation protective fabric or other material of the present invention, the article will have a greater ability to block both beta and gamma rays. In this regard, it may be appropriate to consider the use of lead as one of the radiopaque compounds for such a hybrid application, or even more generally for the type of plasticized articles disclosed herein. While, because of its heavy weight and potential health hazards, lead would not be as preferred as the relatively lightweight radiopaque compounds previously listed, lead nonetheless might have a role in a plasticized radiopaque compound mixture or in certain other plastic film applications. FIG. 8 shows a second approach to enhancing radiation protection through a particular multi-layer construction 80. Each of the layers 81, 82, 83 of this multi-layer product 80 have different thicknesses. While a layer of one thickness 81 might be capable of stopping radioactive particles 84 with certain wave characteristics, it might allow radioactive particles of different wave characteristics 86 to pass right through. Nonetheless, by backing up the first layer 81 with additional layers of different thicknesses, there is a greater chance of stopping radioactive particles regardless of their wave characteristics. As those in the art will recognize, a synergistic effect might be achieved by combining the different radiopaque compounds 62, 64, 66, 68 as shown in FIG. 6 with the use of layers of different thicknesses 81, 82, 83 as shown in FIG. 8 in order to create a radiation protective article that offers the maximum amount of radiation protection for a given weight and thickness. Turning now to FIG. 5, an alternative mass production process is shown. In the FIG. 5 process, the polymeric mixture ingredients 70 are placed into the hopper 71 of a first extruder 72. As before, the polymeric mixture would preferably include a polymer, a radiopaque material and one or more additives. In this process, these polymeric mixture ingredients 70 can enter the hopper 71 in a solid form. As the hopper 71 feeds the polymeric mixture ingredients 70 into the first extruder 72, the polymeric mixture ingredients are preferably heated into a viscous liquid state and mixed together through the turning action of the motorized extruder screw 73. As this motorized extruder screw 73 pushes the polymeric mixture ingredients out of the first extruder 72, the combination of a perforated plate and rotary cutter 74 chops the exiting polymeric mixture into pellets 75. These pellets 75 are then preferably inserted into the hopper 76 of a second extruder 77. Again, through heating and a motorized screw 78, the polymeric mixture is melted. This time, when the polymeric mixture ingredients are pushed out of the extruder 77, a slotted plate at the end of the second extruder 79 is used to extrude a thin film of liquefied polymeric mixture 100. This thin film might advantageously be on the order of 0.1-20 millimeters thick. In order to simplify the process steps, this thin film 100 could be produced by the first extruder 72 alone. Nonetheless, by eliminating the second extruder 77, there is a greater chance that the polymeric mixture will not be evenly mixed before it is extruded. As with the preferred FIG. 4 process, the liquefied polymeric mixture in the FIG. 5 process is sandwiched between two sheets of fabric or other material 90, 92. As before, the fabric sheets are preferably unwound from fabric rolls 94, 96. Corona treaters 96, 98 may again be used to apply an electrostatic charge to enhance the binding process. In this case, the thin film of liquefied polymeric mixture 100 is applied simultaneously between both sheets of fabric or other material 90, 92. Once the thin film of liquefied polymeric mixture 100 is inserted between the two sheets 90, 92, the two sheets are then preferably compressed and heated between the rollers of a laminating unit 102 and perforated and/or embossed, as desired, in a perforating/embossing unit 104. For convenient storage, the finished radiation protective fabric or other material 106 can then be wound into a final roll 108. Turning now to FIG. 10, a process is shown for forming a free standing film of radiation protective polymer, which does not need to be attached to a fabric or other material. Like the FIG. 5 process, this protective film process preferably starts by putting a mixture of a suitable polymer, radiopaque compound and any appropriate additives 132 in the hopper 134 of an extruder 130. As the hopper 134 feeds the polymer mixture into the extruder 130, the polymer mixture is heated into a viscous liquid state and churned by the motorized extruder screw 136. As the motorized extruder screw 136 pushes the polymeric mixture out of the extruder 130, a slotted plate at the end of the extruder 138 produces a film of radiation protective polymer which is deposited on endless conveyor belt 142 and cooled. The endless conveyor belt preferably has a polished metal or TEFLON(trademark) coating in order to prevent the film from needlessly sticking to the conveyor belt 142. To speed up the cooling process, a fan, blower or refrigeration unit (not shown) may be used. When the radiation protective film 140 has sufficiently cooled, it can be wound into a final roll 144 for convenient storage. The final roll of radiation protective film 140 can then be used for any number of the applications discussed herein, including the manufacture of garments, tents, envelopes, wallpaper, liners, house sidings etc. FIG. 11 shows a variation of the process illustrated in FIG. 10. Like the FIG. 10 process, the FIG. 11 process begins by putting the polymeric mixture 132 into the hopper 134 of an extruder 130. As the hopper 134 feeds the polymer mixture into the extruder 130, the polymer mixture is again heated and churned by the motorized extruder screw 136. This time, though, the polymer mixture is preferably heated to the consistency of a paste, rather than into a viscous liquid state. As the motorized extruder screw 136 pushes the polymeric mixture out of the extruder 130, a slotted plate at the end of the extruder 138 again produces a film of radiation protective polymer 148 which is deposited on endless conveyor belt 142. This time, when the pasty film 148 exits the endless conveyor belt 142, it is fed into calender rollers 150, 152 which simultaneously heat and compress the pasty film 148. During this calendering process, the polymer molecules will typically cross-polymerize to form even stronger polymer molecules. After leaving the calender rollers 150, 152, the finished film 154 is pulled by take up rollers 155, 156 and then preferably wound into a final roll 158 for convenient storage and later use. Thus far, techniques have been described for imparting radiopaque qualities into a fabric or other material through impregnation with relatively lightweight radiopaque materials, with or without the use of polymers. In another alternative embodiment, sheets of radiopaque materials, such as aluminum, can be inserted between the plies of an article to impart radiopaque qualities. For example, liner 24 of surgical mask 10 could be a sheet of aluminum foil. To provide breathability, this sheet of aluminum foil could be perforated with multiple holes (not shown). Breathability and protection can also be provided by staggering partial layers of radiopaque sheets with layers of porous cloth liners or staggering perforated radiopaque sheets. One staggering embodiment is illustrated in FIG. 7. As shown in FIG. 7, two sheets of fabric or other material 110, 112 incorporating radiopaque materials are separated by a gap 114. Both of these two sheets 110, 112 have been perforated to create patterns of holes 116, 118, 120. By offsetting the holes 116, 118, 120 in the two sheets 110, 112 as shown in FIG. 7, radioactive particles, which travel in an essentially straight line, would be blocked by at least one of the two sheets while air, which can bend around obstructions, will still be allowed to pass through. This staggering approach can be particularly useful for applications that demand breathability, such as the surgical mask 10 shown in FIG. 1. In the same vein, the radiopaque material, such as the polymeric mixtures previously described or aluminum, could be formed into tubes, cylinders or threads and woven into a garment or interwoven with conventional garment material, such as cloth, to provide both the flexibility of a cloth garment and the x-ray protection of metallic garment. The radiopaque material could also be incorporated within a variety of clear plastics or glass to create, for example, a clear eye shield with radiopaque qualities. In the foregoing specification, the invention has been described with reference to specific preferred embodiments and methods. It will, however, be evident to those of skill in the art that various modifications and changes may be made without departing from the broader spirit and scope of the invention as set forth in the appended claims. For example, a number of the preferred embodiments previously described have been in the field of medicine. Nonetheless, those of skill in the art know that radiation problems occur in many other fields, such as nuclear and electrical power, aviation and the military. For example, the amount of radiation a passenger is exposed to in a cross-country airplane flight is actually greater than the radiation exposure of a chest x-ray. To protect such airline passengers and, more urgently, the people who operate such airplanes on a daily basis, the type of plasticized radiation protective fabrics produced by the processes shown in FIGS. 4 and 5 or plasticized radiation protective films produced by the processes shown in FIGS. 10 and 11 could, for example, be glued as an interior liner into airplane cabins. Similarly, the glass used for airplanes windows could be manufactured to incorporate the type of lightweight radiopaque materials described herein. The plasticized radiation protective fabrics or other materials of the present invention could also be formed into envelopes or pouches to protect radiation sensitive materials (e.g., photographic film, electronics) from being damaged when they are x-rayed at airports. These pouches or envelopes could also be used to safely transport radioactive materials, such as radioactive products or nuclear waste. As another example, FIG. 9 shows how the lightweight radiopaque materials of the present invention could be incorporated into common drywall 120. In this case, the relatively lightweight radiopaque materials of the present invention, such as barium sulfate, could be mixed with the gypsum commonly used in drywall and then inserted 122 between two layers of cardboard 124, 126. As a further example, FIG. 12 shows a jumpsuit 160 which is constructed with the relatively lightweight radiation protective materials of the present invention. In one preferred embodiment, the radiation protective fabrics produced by the processes shown in FIGS. 4 and 5 or the radiation protective films produced by the processes shown in FIGS. 10 and 11 could be used to manufacture such a radiation protective jumpsuit. To provide the most protection, the jumpsuit 160 should probably be a one-piece jumpsuit which covers nearly every portion of the human body. Elastic bands 161, 163 can be used around the hand and foot areas to help insure a tight fit. Alternatively, the gloves 162, booties 164 and hood 166 could be separate pieces which overlap with the rest of the jumpsuit in a way which leaves no skin surface exposed. The hood 166 preferably includes drawstrings 168 so that it can be fit tightly against the wearer""s head. A transparent eye shield 170 is preferably included with the jumpsuit 160 to provide protection for the face. As previously discussed, this eye shield 170 can be manufactured with the same sorts of radiation protective polymeric mixtures that have been used in the previous embodiments to produce rolls of radiation protective fabric or other materials. In the case of clear eye shields, though, an injection molding process of the type well known in the plastic arts would be preferable to the continuous roll processes previously discussed. For convenience, the eye shield 170 could be hinged, such as with corner rivets 172, in order to allow the user to flip the shield 170 up and down. Alternatively, the eye protection could be a stand alone device, such as safety glasses. The jumpsuit 160 can also include a VELCRO(trademark) or zipper flap 174 to allow the user to easily enter the jumpsuit 160, while still providing radiation protection. Pockets 176 can also be included to hold useful items, such as a Geiger counter. As a still further example, the lightweight radiopaque materials of the present invention could be finely ground up and mixed into latex or oil based paints. Emulsifiers, binding agents or suspension agents may be added to such paints to keep the lightweight radiopaque materials well mixed so that they do not precipitate out of solution, emulsion or suspension. Through the addition of such radiopaque materials, radiation protection can be painted or coated onto any number of surfaces in order to provide protection from the dangers of radiation. Those of skill in the art will readily understand that the principles and techniques described in this application are applicable to any field where radiation is present. The specification and drawings are, accordingly, to be regarded in an illustrative, rather than restrictive sense; the invention being limited only by the appended claims. |
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abstract | A method of determining the spatially corrected inverse count ratio (SCICR) used to determine reactor criticality, which subtracts a background noise signal from the source range detector output. The method monitors the source range detector signal at two different core temperature levels during a transient portion of the detector output as the power output of the reactor is increased in the source range. This information is employed to analytically determine the background noise signal, which is then subtracted from the detector outputs to obtain the SCICR reactivity measurement. |
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053596340 | summary | BACKGROUND AND SUMMARY OF THE INVENTION The present invention relates to a reactor core for a boiling water nuclear reactor with a plurality of vertical fuel assemblies, each fuel assembly containing a plurality of vertical fuel rods with enriched nuclear fuel material, which fuel rods are arranged between a bottom tie plate and a top tie plate in a surrounding vertical fuel channel. Each fuel assembly is formed with an inlet for water for conducting water in through the bottom tie plate, through the space between the fuel rods in the vertical fuel channel, and out through the top tie plate. Further, each fuel assembly is arranged with intermediate gaps with respect to adjoining fuel assemblies and possibly with a channel, internally arranged in the fuel assembly, for conducting water through the gaps and through the internal channel (if any) in the vertical direction from below and upwards through the core. Usually, each fuel rod in a fuel assembly of the kind described above is arranged with the same enrichment content of fissile material (hereinafter referred to as enrichment only) in its entire length. During operation of a bailing water nuclear reactor with a core containing several fuel assemblies of the above-mentioned kind, there may be a risk of so-called dryout, that is, that the water film present on the surface of each fuel rod disappears or is broken down in restricted areas, which locally leads to a considerably deteriorated heat transfer between the fuel rod and the water conducted through the fuel assembly, resulting in a greatly increased wall temperature of the fuel rod. The increased wall temperature may result in damage with serious consequences arising on the fuel rod. In current designs with the same enrichment in the whole length of each fuel rod, in order to achieve a sufficient dryout margin, the requirements for the effect which is otherwise attainable are lowered. The present invention makes it possible to improve the dryout margin without deteriorating the attainable effect. The favourable result is achieved according to the invention by a redistribution of the fuel while achieving a special enrichment distribution in the longitudinal direction of the fuel rods. What more particularly characterizes the present invention is that each one of at least the main part of the fuel rods, central rods, which in a fuel assembly are surrounded by fuel rods, edge rods, which are located close to a water gap or an internal water channel, is arranged with a ratio of the enrichment in the central rod in question to the medium enrichment for the central rods and the edge rods in a horizontal section, which is lower for an upper part than for a lower part of the central rod. Preferably, each one of at least the main part of the edge rods is arranged with a ratio of the enrichment in the edge rod in question to the medium enrichment for the central rods and the edge rods in a horizontal section, which is higher for the upper part than for the lower part of the edge rod. The length of the upper part suitably constitutes one-fourth to two-thirds, preferably one-third to two-thirds, of the active length of tile fuel rod and the lower part the remainder of the active length of the fuel rod. By the active length of the fuel rod is meant that axial part of the fuel rod which contains nuclear fuel material. According to an advantageous embodiment of the invention, which provides a good shutdown margin for the reactor, the medium enrichment of the central rods and the edge rods in a horizontal section is 5-15% lower in the area of the upper part of the fuel rods than in tile area of the lower part of the fuel rods. It is known per se to arrange fuel rods with different enrichments in different parts of the length of the fuel rods in order to influence, in other ways than those stated above, the properties of the reactor core and the operation of a nuclear reactor. |
claims | 1. A method, comprising:acquiring a first dataset of a first region of interest of an imaging subject in a first scan by transmitting a radiation beam to the imaging subject via a first filter, wherein the first filter is determined based on an anatomy of the first region of interest;switching to a second filter after acquiring the first dataset, wherein the first filter and the second filter are different filters; andacquiring a second dataset of a different, second region of interest of the imaging subject in a second scan by transmitting the radiation beam to the imaging subject via the second filter;wherein the second filter is determined based on anatomy of the second region of interest;wherein switching from the first filter of the first scan to the second filter of the second scan is time sensitive; andwherein switching from the first filter to the second filter takes less than two seconds. 2. The method of claim 1, wherein both the first filter and the second filter are non-deformable. 3. The method of claim 1, wherein the first filter and the second filter are bowtie filters. 4. The method of claim 1, wherein the first region of interest of the imaging subject and the second region of interest of the imaging subject are of different anatomies. 5. The method of claim 1, wherein switching to the second filter includes operating one or more motors coupled to the first filter and the second filter to translate the first filter out of the radiation beam and translate the second filter into the radiation beam. 6. A method, comprising:responsive to a contrast enhancement of an injected contrast agent within an imaging subject, acquiring a first dataset of a first region of interest of the imaging subject in a first scan, wherein the first dataset is acquired by transmitting an X-ray beam to the first region of interest of the imaging subject via a first filter wherein the first filter is determined based on an anatomy of the first region of interest;switching to a second filter after acquiring the first dataset; andacquiring a second dataset of a different, second region of interest of the imaging subject in a second scan by transmitting the X-ray beam to the second region of interest of the imaging subject via the second filter;wherein the first filter and the second filter are different filters;wherein the second filter is determined based on the second region of interest;wherein switching from the first filter of the first scan to the second filter of the second scan is time sensitive; andwherein switching from the first filter to the second filter takes less than two seconds. 7. The method of claim 6, further comprising determining a time point to start acquiring each of the first and the second datasets based on the contrast enhancement of the injected contrast agent within the imaging subject. 8. The method of claim 6, wherein the first filter and the second filter are bowtie filters. |
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description | The development of matrix-assisted laser desorption/ionization (“MALDI”) techniques has greatly increased the range of biomolecules that can be studied with mass analyzers. MALDI techniques allow normally nonvolatile molecules to be ionized to produce intact molecular ions in a gas phase that are suitable for analysis. One class of MALDI instrument, which have found particular use in the study of biomolecules, are MALDI tandem time-of-flight mass spectrometers, referred to as MALDI-TOF MS/MS instruments hereafter. A traditional tandem mass spectrometer (MS/MS) instrument uses multiple mass separators in series. An MS/MS instrument can be use, for example, to determine structural information, such as, e.g., the sequence of a protein. Traditional MS/MS techniques use the first mass separator (often referred to as the first dimension of mass spectrometry) to transmit molecular ions in a selected mass-to-charge (m/z) range (often referred to as “the parent ions” or “the precursor ions”) to an ion fragmentor (e.g., a collision cell, photodissociation region, etc.) to produce fragment ions (often referred to as “daughter ions”) of which a mass spectrum is obtained using a second mass separator (often referred to as the second dimension of mass spectrometry). Time-of-flight (TOF) mass spectrometers distinguish ions on the basis of the ratio of the mass of the ion to the charge of the ion, often abbreviated as m/z. Traditional TOF techniques rely upon the fact that ions of different mass-to-charge ratios (m/z) achieve different velocities if they are all exposed to the same electrical field; and as a result, the time it takes an ion to reach the detector (called the ion arrival time or time of flight) is representative of the ion mass. In theory, each ion of a given mass-to-charge ratio should have a unique arrival time. As a result, a mixture of ions of different mass should produce a spectrum of arrival time signals each corresponding to a different ion mass. Such spectra are commonly referred to as arrival time spectra or simply, mass spectra. In practice, however, achieving accurate results is not easy, and the greater the accuracy required in the analysis, the more difficult the task. Several operational configurations of MALDI mass spectrometers which have found particular use in the study of biomolecules, are linear time-of-flight (“TOF”) mass spectrometers, reflectron TOF mass spectrometers, and tandem TOF mass spectrometers referred to as MS/MS TOF instruments hereafter. Each of these configurations has its own advantages and disadvantages depending, e.g., on the biomolecules of interest, the nature of the study, etc. Accordingly, commercial instruments exist which are configured so that an investigator can switch from one operational mode (linear TOF, reflectron TOF, and MS/MS TOF) to another. Although instruments exist where the mode of operation can be switched, the instrument configurations and operational conditions that provide good resolution and sensitivity for one mode of operation (e.g., linear TOF, reflectron TOF, and MS/MS TOF) can significantly decrease the resolution and sensitivity for other operational modes. As a result, conventional instruments often must comprise the resolution and/or sensitivity of at least one of these three operational modes to provide an instrument that has acceptable resolution and sensitivity in all three modes. In many biomolecule studies (such as, e.g., proteomics studies) that employ mass analyzers the biomolecule masses of interest can readily span two or more orders of magnitude. In addition, in many biological studies there is a limited amount of sample available for study (such as, e.g., rare proteins, forensic samples, archeological samples). In a tandem mass spectrometer (MS/MS), it is also generally desirable to control the collision energy of the ions prior to the ions entering the ion fragmentor, e.g., a collision cell. Typically, this is done in a TOF/TOF tandem mass spectrometer by first accelerating the ions from the first TOF region (first dimension of MS) to an initial energy and then decelerating the ions to the desired collision energy by adjusting the electrical potential on the collision cell entrance. In general, it is simple to optimize an ion optical system for a single collision energy that provides good focusing into the second TOF region following the collision cell, however, it is considerably more difficult to provide an ion optical system that provides good focusing into the second TOF region across a range of collision energies, without compromising ion transmission efficiency and thereby instrument sensitivity. MALDI-TOF MS/MS instruments can also be very complex machines requiring the accurate alignment and interaction of myriad components for useful operation. Mass spectrometry requires ion optics to focus, accelerate, decelerate, steer and select ions. Misalignment of theses and non-uniformity in their electrical fields can significantly degrade the performance of a mass spectrometry instrument. The ion optical elements are positively positioned in the X, Y and Z directions with respect to each other and other components of the instrument. Once positioned, subsequent movements of the ion optical elements can significantly degrade instrument performance. For example, if an element moves out of alignment after an instrument has been tuned, the instrument's mass accuracy, sensitivity and resolution can be adversely affected. Traditional ion optics stack assemblies have used assembly jigs, where possible, to position the ion optical elements followed by securing the optics in place with threaded fasteners. For example, a series of optical elements is stacked up, some using assembly jigs and some having self-aligning features, an end plate is bolted over the end of the stack, and the bolts tightened to compress the optical elements with the end plate and secure the stack. In addition, such traditional methods of assembly often require the assembler to tighten the bolts in both a specific pattern and with specific torques to properly align the ion optical elements, e.g. without warping. Such procedures, however, can be time-consuming and can require a skilled assembler to perform. In addition, as the alignment tolerances of instruments decrease (e.g., to improve sensitivity, decrease instrument size, etc.) misalignment errors become less and less noticeable to the naked eye and harder to detect by the less skilled assembler. The present teachings relate to MALDI-TOF instruments, instrument components, and methods of operation thereof. In various aspects, the MALDI-TOF instrument can serve and be operated as a MS/MS instrument. In various embodiments, provided are MALDI-TOF instruments, and methods of operating one or more components of a MALDI-TOF instrument, that facilitate one or more of increasing sensitivity, increasing resolution, increasing dynamic mass range, increasing sample support throughput, and decreasing operational downtime. In various aspects, the present teachings provide systems for providing sample ions, methods for providing sample ions, sample support handling mechanisms, ion sources methods for focusing ions from a delayed extraction ion source, methods for operating a time-of-flight mass analyzer, In various aspects, the present teaching provide mass analyzer systems comprising one or more of the systems for providing sample ions, methods for providing sample ions, sample support handling mechanisms, ion sources, methods for focusing ions from a delayed extraction ion source, methods for operating a time-of-flight mass analyzer, methods for focusing ions for an ion fragmentor, methods for operating an ion optics assembly, ion optical assemblies, and systems for mounting and aligning ion optic components of the present teachings. Sample Handling Mechanisms In various aspects, the present teachings relate to sample support handling mechanisms for a mass analyzer system. In various embodiments, the sample support comprises a plate, e.g., a 3.4″×5″ plate, a microtiter sized MALDI plate, etc. The sample support handling mechanisms of the present teachings comprising a sample support transfer mechanism portion and a sample support changing mechanism portion, where the sample support changing mechanism portion is disposed in a vacuum lock chamber. In various embodiments, the sample support transfer mechanism comprises a base member having a substantially planar front face and a left arm and a right arm which extend from the base member in a direction X substantially perpendicular to the front face and are spaced apart from each other in a direction Y substantially parallel to the front face a distance sufficient to fit a sample support between them. The left arm and the right arm each having a bearing support structure. In various embodiments, the left arm and right arm each have a retention projection extending in the Y direction towards the other arm a distance smaller than the distance between the arms. In various embodiments, a sample support is retained within a frame member. It is to be understood that in the present teachings that the descriptions of handling (e.g., capture, engagement, disengagement, etc.) and registration of a sample support are equally applicable to a sample support retained in a frame member where, e.g., are the various structures of the sample transfer and changing mechanism are in direct contact with the frame member and do not necessarily directly contact the sample support retained therein. In various embodiments, a sample support is retained on a frame such as described in U.S. Pat. Nos. 6,844,545 and 6,825,478, the entire contents of which are hereby incorporated by reference. In various embodiments, a frame member has a perimeter ridge portion, which, for example, can engage (e.g., slip over) at least a portion of the perimeter of capture mechanism of a sample changing mechanism of the present teachings to facilitate, e.g., retaining a sample support in an unload region of the changing mechanism. The sample support transfer mechanism further comprises an engagement member situated between the left and the right arms, where in a first position the engagement member is configured to urge a front end of a sample support into registration with the front face of the base member and to urge the front end of the sample support into registration in a direction Z (the direction Z being substantially perpendicular to both the X and Y directions), and the left and right bearing support structures are configured in a first position to urge a back end of a sample support into registration in a direction Z. In various embodiments, the sample support transfer mechanism comprises three cam structures, a left cam structure, a right cam structure, and a central cam structure disposed between the left and right cam structures. Between the left and central cam structures is a sample support loading region and between the central and right cam structures is a sample support unloading region. The sample support loading region comprises a first disengagement member capable of urging the engagement member to a second position and a registration member capable of urging a sample support against the front face and the left arm. The left cam structure being capable of (a) slideably engaging the left arm bearing support structure to urge the left arm bearing support structure to a second position; and (b) engaging the registration member and causing the registration member to urge a sample support against the front face and the left arm. The central cam structure being capable of slideably engaging the right arm bearing support structure to urge the right arm bearing support structure to a second position, so when the engagement member, the left arm bearing support structure and the right arm bearing support structure are in their respective second positions, the sample support transfer mechanism is capable of engaging a sample support between the left and right arms of the sample support transfer mechanism. The sample support unloading region comprises a second disengagement member capable of urging the engagement member to a third position and a sample support capture mechanism configured to retain a sample support in the sample support unloading region after it is disengaged from the sample support transfer mechanism. The central cam structure being capable of slideably engaging the left arm bearing support structure to urge the left arm bearing support structure to a third position and the right cam structure capable of slideably engaging the right arm bearing support structure to urge the right arm bearing support structure to a third position, so when the engagement member, the left arm bearing support structure and the right arm bearing support structure are in their respective third positions, the sample support transfer mechanism is capable of disengaging a sample support from between the left right arms of the sample support transfer mechanism. In various embodiments, the engagement member of the sample transfer handling mechanism comprises a latch attached to the base member. In various embodiments, the latch comprises a roller which contacts the second disengagement member and allows the sample support to slowly disengage from the sample support transfer mechanism. In various embodiments, the sample support transfer mechanism comprises a frame having an electrically conductive surface. In various embodiments, such a frame facilitating the reduction of electrical field line discontinuity at and/or near the edges of a sample support. In various embodiments, the sample support transfer mechanism transfers a sample support from a region of low vacuum (e.g., the vacuum lock chamber) to a region of higher vacuum (e.g., a sample chamber). In various embodiments, the sample chamber is configured to achieve a pressure of less than or equal to about 10−6 Torr. In various embodiments, the sample chamber is configured to achieve a pressure of less than or equal to about 10−7 Torr. As such, in various embodiments, the sample support transfer mechanism is made of vacuum compatible materials. In various embodiments, the sample support handling mechanism facilitates providing consistent positioning of a sample support for subsequent ion generation by MALDI. In various embodiments, the sample support handling mechanism is configured such that a sample support is registered to a position in the sample transfer mechanism to: (a) within about ±0.005″ in the Z direction; (b) within about ±0.01″ in the X direction; (c) within about ±0.01″ in the Y direction; (d) or combinations thereof. In various embodiments, the sample support handling mechanism is configured such that a sample support is registered to a position in the sample transfer mechanism to: (a) within about ±0.002″ in the Z direction; (b) within about ±0.005″ in the X direction; (c) within about ±0.005″ in the Y direction; (d) or combinations thereof. In various aspects, the present teachings provide a system for providing sample ions comprising a vacuum lock chamber and a sample chamber connected to the vacuum lock chamber, where disposed in the vacuum lock chamber is a sample support changing mechanism and disposed in the sample chamber is a sample support transfer mechanism. The sample support transfer mechanism being configured to extract a sample support from a loading region of the sample support changing mechanism such that the sample support is registered in the sample support transfer mechanism. In various embodiments, the sample support is registered to within about ±0.005″ in a Z direction, to within about ±0.01″ in a X direction, and to within about ±0.01″ in a Y direction, wherein the X, Y and Z directions are mutually orthogonal. In various embodiments, the sample support is registered to within about ±0.002″ in a Z direction, to within about ±0.005″ in a X direction, and to within about ±0.005″ in a Y direction, wherein the X, Y and Z directions are mutually orthogonal. In various embodiments, the sample support is registered within a frame in the sample support transfer mechanism. The sample support transfer mechanism also being mounted on a multiaxis translation stage such that the sample support can be translated to a position where sample ions can be generated by laser irradiation of a sample on the surface of the sample support while said sample support is held in the sample support transfer mechanism and said sample ions extracted into a mass analyzer system in a direction substantially perpendicular to the surface of the sample support. In various embodiments, the Z direction being substantially perpendicular to the surface of the sample support. In various embodiments, sample ions are extracted in a direction substantially perpendicular to the surface of the sample support along a first ion optical axis which is substantially coaxial with the laser irradiation. For example, in various embodiments, a system for providing sample ions is configured such that sample ions are extracted from the sample chamber along a direction that is substantially coaxial with the Poynting vector of the pulse of laser energy striking the sample which generated the sample ions. In various embodiments, the first ion optical axis forms an angle that is within about 5 degrees or less of the normal of the sample surface. In various embodiments, the first ion optical axis forms an angle that is within about 1 degree or less of the normal of the sample surface. In various embodiments, a frame member has an electrically conductive surface, at least on the surface facing the ion extraction direction. In various embodiments, such a frame facilitates reducing electrical field line discontinuities at and/or near the edges of a sample support. In various aspects, the present teachings provide methods for providing sample ions for mass analysis comprising: supporting a plurality of samples on a surface of a sample support; providing a vacuum lock chamber having a region for loading a sample support and a region for unloading a sample support; and providing a sample chamber having a sample transfer mechanism disposed therein. The methods extract the sample support disposed in the region for loading with the sample transfer mechanism such that the sample support is registered in the sample support transfer mechanism. In various embodiments, the sample support is registered within a frame in the sample support transfer mechanism. In various embodiments, the sample support is registered to within about ±0.005″ in a Z direction, to within about ±0.01″ in a X direction, and to within about ±0.01″ in a Y direction, wherein the X, Y and Z directions are mutually orthogonal and the direction Z is substantially perpendicular to the surface of the sample support. In various embodiments, the sample support is registered to within about ±0.002″ in a Z direction, to within about ±0.005″ in a X direction, and to within about ±0.005″ in a Y direction, wherein the X, Y and Z directions are mutually orthogonal. The sample support is translated to a first position within the sample chamber where a first sample on the surface of the sample support is irradiated with a pulse of energy to form a first group of sample ions while the sample support is being held by the sample transfer mechanism and at least a portion of the first group of sample ions is extracted in the Z direction. The sample support is then translated to a second position within the sample chamber where a second sample on the surface of the sample support is irradiated with a with a pulse of energy to form a second group of sample ions while the sample support is being held by the sample transfer mechanism and at least a portion of the second group of sample ions is extracted in the Z direction. Further samples can be analyzed on the sample support prior to the sample support being placed by the sample support transfer mechanism in the region for unloading a sample support. The methods continue with repeating the steps of extracting a sample support followed by the steps of translating, irradiating and extracting for at least two samples. In various embodiments, at least one of the steps of irradiating a sample with a pulse of energy comprises irradiating the sample at an irradiation angle that is within 5 degrees or less of the normal of the surface of the sample support to form sample ions by matrix-assisted laser desorption/ionization. In various embodiments, at least one of steps irradiating a sample with a pulse of energy comprises irradiating the sample at an irradiation angle that is within 1 degree or less of the normal of the surface of the sample support to form sample ions by matrix-assisted laser desorption/ionization. In various embodiments, at least one of the steps of extracting at least a portion of the sample ions comprises extracting sample ions in the Z direction along a first ion optical axis, wherein the first ion optical axis is substantially coaxial with the pulse of energy. Ion Sources In various aspects, the present teachings relate to ion sources for TOF instruments, and methods of operation thereof. In various embodiments, the present teachings relate to matrix-assisted laser desorption/ionization (MALDI) ion sources and methods of MALDI ion source operation, for use with mass analyzers. In various aspects, provided are ion sources and methods of operation thereof that facilitate increasing one or more of sensitivity and resolution of a TOF mass analyzer configured for multiple modes of operation. In a general purpose MALDI TOF mass spectrometer, it is desirable to change the position of the velocity space focus plane of the ion source such that optimal resolution is attained for different modes of operation, i.e., linear, reflector (ion mirror), and precursor (parent ion) selection for MS/MS. A typical two-stage Wiley McLaren type source employing delayed extraction can be designed to provide ideal focusing for any singular mode of operation. However, it is more difficult to design a singular geometry that provides optimized performance in more than one mode of operation without sacrificing performance elsewhere. In particular, to optimize the source for a focal plane close to the source, such as can be required for timed ion selection for MS/MS, the spatial focusing of the beam (in x, y) is degraded to the point where significant portions of the ion beam are not transmitted through critical apertures; and hence, a substantial loss of instrument sensitivity is observed. The present teachings, in various embodiments, provide novel three-stage ion sources that allow for an adjustable velocity space focus plane and improved x,y spatial focus characteristics of the ion beam compared to conventional two-stage ion sources. In various embodiments, the ion source facilitates compensating for the spread in ion arrival times due to initial ion velocity without substantially degrading the radial spatial focusing of the ions. The skilled artisan will recognize that the concepts described herein using the terms “velocity space focus” and “x,y spatial focus” can be described using different terms. As delayed extraction can be used to bring ions with different initial velocities, but the same m/z value, to a particular plane in space at substantially the same time, this process has been referred to by several terms in the art including, “time focusing” and “space focusing,” “velocity focusing” and “time-lag focusing.” In addition, for example, the terms “space focus,” “space focus plane,” “space focal plane,” “time focus,” “velocity focusing” and “time focus plane” have all been used in the art to refer to one or more of what are referred to herein as the velocity space focus plane. Unfortunately, the terms “time focusing,” “temporal focusing,” “space focus,” “space focus plane,” “space focal plane,” “time focus” and “time focus plane” have also been used in the art of time-of-flight mass spectrometry to describe processes that are fundamentally different from the velocity space focusing of an ion source using delayed extraction. As x,y spatial focusing can narrow the diameter of an ion beam in a direction perpendicular to its primary propagation direction, z, this process has also been referred to in the art by the term “radial focusing.” However, the terms “spatial focusing” and “radial focusing” have also been used in the art of time-of-flight mass spectrometry to describe processes that are fundamentally different from the x,y spatial focusing of the present teachings. Accordingly, given the complex usage of terminology found in the mass spectrometry art, the terms “velocity space focus” and “x,y spatial focus” used herein were chosen for conciseness and consistency in explanation only and should not be construed out of the context of the present teachings to limit the subject matter described in any way. In various aspects, a three-stage ion source of the present teachings comprises a first electrode spaced apart from a sample support having a sample surface, a second electrode spaced apart from the first electrode in a direction opposite the sample support, and a third electrode spaced apart from the second electrode in a direction opposite the first electrode. The sample support, first, second and third electrodes are electrically coupled to a power source which is adapted to: (a) apply a first potential to the sample surface and a second potential to at least one of the first electrode and the second electrode to establish a non-extracting electric field at a first predetermined time substantially prior to striking a sample on the sample surface with a pulse of energy to form sample ions, the non-extracting electrical field substantially not accelerating sample ions in a direction away from the sample surface; (b) change the electrical potential of at least one of the sample surface and the first electrode to establish a first extraction electric field at a second predetermined time subsequent to the first predetermined time, the first extraction electric field accelerating sample ions in a first direction away from the sample surface; and (c) apply a third potential to the second electrode to focus ions in a direction substantially perpendicular to the first direction. In various embodiments, the non-extracting electrical field can be a retardation electrical field which retards the motion of sample ions in a direction away from the sample surface. In various embodiments, the non-extracting electrical field can be a substantially zero electrical field, e.g., a substantially electrical field free region is established. A substantially zero electrical field can be established, e.g., when the first potential and the second potential are substantially equal. In various embodiments, the first direction is substantially coaxial with the pulse of energy. For example, in various embodiments, sample ions are extracted along a first direction which is substantially coaxial with the Poynting vector of the pulse of energy striking the sample which generated the sample ions. In various embodiments, the first direction forms an angle that is within about 5 degrees or less of the normal of the sample surface. In various embodiments, the first direction forms an angle that is within about 1 degree or less of the normal of the sample surface Application of a potential difference between the sample support and first electrode that accelerates sample ions away from the sample surface can be delayed by a predetermined time subsequent to generation of the pulse of laser energy to perform, for example, delayed extraction. In some embodiments, delayed extraction is performed to provide time-lag focusing to correct for the initial sample ion velocity distribution, for example, as described in U.S. Pat. No. 5,625,184 filed May 19, 1995, and issued Apr. 29, 1997; U.S. Pat. No. 5,627,369, filed Jun. 7, 1995, and issued May 6, 1997; U.S. Pat. No. 6,002,127 filed Apr. 10, 1998, and issued Dec. 14, 1999; U.S. Pat. No. 6,541,765 filed May 29, 1998, and issued Apr. 1, 2003; U.S. Pat. No. 6,057,543, filed Jul. 13, 1999, and issued May 2, 2000; and U.S. Pat. No. 6,281,493 filed Mar. 16, 2000, and issued Aug. 28, 2001; and U.S. application Ser. No. 10/308,889 filed Dec. 3, 2002; the entire contents of all of which are herein incorporated by reference. In other embodiments, extraction can be performed to correct for the initial sample ion spatial distribution, for example, as described in W. C. Wiley and I. H. McLaren, Time-of-Flight Mass Spectrometer with Improved Resolution, Review of Scientific Instruments, Vol. 26, No. 12, pages 1150-1157, (December 1955), the entire contents of which are herein incorporated by reference. In various embodiments of operation, a sample is irradiated with a pulse of laser energy at an irradiation angle to produce sample ions by MALDI. After any previous sample ion extraction and during the irradiation of the sample with the pulse of laser energy, the power source applies a first potential to the sample support and a second potential to at least one of the first electrode and the second electrode to establish a first electrical field at a first predetermined time relative to the generation of the pulse of energy, the first electrical field substantially not accelerating sample ions in a direction away from the sample support. In some embodiments, the first potential is more negative than the second potential when measuring positive sample ions, and the first potential is less negative than the second potential when measuring negative sample ions, to thereby produce a retarding electrical field prior to sample ion extraction. In various embodiments, the first electrical field can be a substantially zero electrical field, e.g., a substantially electrical field free region is established. A substantially zero electrical field can be established, e.g., when the first potential and the second potential are substantially equal. In various embodiments, at a second predetermined time subsequent to the generation of the pulse of laser energy, the power source changes a potential on at least one of the sample support and the first electrode to establish a second electrical field that accelerates sample ions away from the sample support to extract the sample ions and applies a third potential to the second electrode to provide x,y spatial focusing. A wide variety of structures can be used to control the timing of the generation of the potentials. For example, a photodetector can be used to detect the pulse of laser energy and generate an electrical signal synchronously timed to the pulse of energy. A delay generator with an input responsive to the synchronously timed signal can be used to provide an output electrical signal, delayed by a predetermined time with respect to the synchronously timed signal, for the power source to trigger or control the application of the various potentials. In various embodiments, a three-stage ion source of the present teachings is configured to extract sample ions in a direction substantially normal to the sample surface and includes an optical system configured to irradiate a sample on the sample surface of a sample support with a pulse of laser energy at an angle substantially normal to the sample surface. In various embodiments, the first electrode and second electrode, each have an aperture. The first and second electrodes are in some embodiments arranged such that a first ion optical axis (defined by the line between the center of the aperture in the first electrode and the center of the aperture in the second electrode) intersects the sample surface at an angle substantially normal of the sample surface. In various embodiments, the optical system is configured to substantially coaxially align the pulse of laser energy with the first ion optical axis. In various aspects, three-stage ion sources which facilitate reducing material deposition on electrodes in the ion beam path are provided. Reducing material deposition on electrodes in the ion beam path can facilitate, for example, increased mass analyzer sensitivity, resolution, or both, and facilitate decreasing the operational downtime of a mass analyzer. In one aspect, a three-stage ion source can be provided where one or more of the elements of the ion source are connected to a heater system; and a temperature-controlled surface is disposed substantially around at least a portion of the three-stage ion source. Suitable heater systems include, but are not limited to, resistive heaters and radiative heaters. In some embodiments, the heater system can raise the temperature of one or more of the elements in the ion source to a temperature sufficient to desorb matrix material. In various embodiments, the heater system includes a heater capable of heating one or more of the elements in the ion source to a temperature greater than about 70° C. The temperature of the temperature-controlled surface can be actively controlled, for example, by a heating/cooling unit, or passively controlled, such as, for example, by the thermal mass of the temperature-controlled surface, placing the temperature-controlled surface in thermal contact with a heat sink, or combinations thereof. In other various aspects, three-stage ion sources for, and methods of, providing sample ions for mass analysis are provided. In various embodiments, the ion sources and methods are suitable for providing sample ions for mass analysis by time-of-flight mass spectrometry, including, but not limited to, multi-dimensional mass spectrometry. Examples of suitable time-of-flight mass analysis systems and methods are described, for example, in U.S. Pat. No. 6,348,688, filed Jan. 19, 1999, and issued Feb. 19, 2002; U.S. application Ser. No. 10/023,203 filed Dec. 17, 2001; U.S. application Ser. No. 10/198,371 filed Jul. 18, 2002; and U.S. application Ser. No. 10/327,971 filed Dec. 20, 2002; the entire contents of all of which are herein incorporated by reference. In various aspects, the present teachings provide methods for focusing ions from an ion source. In various embodiments, the ion source comprises a delayed extraction ion source. In various embodiments, the methods focus ions from an ion source having a sample support, a first electrode spaced apart from the sample support, a second electrode spaced apart from the first electrode in a direction opposite the sample support holder, and a third electrode spaced apart from the second electrode in a direction opposite the first electrode. Samples for ionization are disposed on a sample surface of the sample support and the energy of the ions can be established by an electrical potential difference between the sample surface and the third electrode. In various embodiments, ions are focused by selecting the position of a time-focus plane of the ion source in a direction z by application of an electrical potential difference between the sample surface and the first electrode, where this potential difference is established by applying a first electrical potential to the sample surface and a second electrical potential to the first electrode; and focusing ions in a direction substantially perpendicular to the direction z by application of a third electrical potential to the second electrode. In various aspects, the present teachings provide methods for operating a time-of-flight (TOF) mass analyzer having two or more modes of operation, and an ion source. Examples of modes of operation include, but are not limited to, linear TOF, reflectron TOF, and MS/MS TOF. In various embodiments, the ion source having a sample support, a first electrode spaced apart from the sample support, a second electrode spaced apart from the first electrode in a direction opposite the sample support holder, and a third electrode spaced apart from the second electrode in a direction opposite the first electrode. In various embodiments, the methods for operating of a TOF mass analyzer having two or more modes of operation comprise: (a) establishing an ion energy by selecting an electrical potential difference between the sample surface and the third electrode; (b) selecting for a first mode of operation the position of a time-focus plane in a direction z by applying a first electrical potential to the sample surface and a second electrical potential to the first electrode; and (c) focusing for the first mode of operation ions in a direction substantially perpendicular to the direction z by applying a third electrical potential to the second electrode. In various embodiments, the methods further comprise: (d) changing the mode of operation of the time-of-flight mass analyzer to a second mode of operation; (e) selecting for the second mode of operation the position of a time-focus plane in a direction z by changing the electrical potential applied to the first electrode; and (f) focusing for the second mode of operation ions in a direction substantially perpendicular to the direction z by changing the electrical potential applied to the second electrode. In various embodiments, the time-focus plane is a time-focus plane of a delayed extraction ion source. In various embodiments of focusing ions from an ion source, of operating a time-of-flight (TOF) mass analyzer having two or more modes of operation, or combinations thereof, sample ions are produced by irradiating a sample with a pulse of laser energy where the irradiation angle is substantially normal to the sample surface. In some embodiments, the sample ions so produced are extracted in an extraction direction that is substantially normal to the sample surface and the pulse of laser energy is substantially aligned with the extraction direction. In various embodiments, sample ions are produced by irradiating a sample with a pulse of laser energy where the Poynting vector of the pulse of energy intersecting the sample surface is substantially coaxial with the ion extraction direction. For example, in various embodiments, sample ions are extracted along a first ion optical axis in a direction substantially normal to the sample surface and the pulse of energy is substantially coincident with the first ion optical axis. For example, in various embodiments, the methods comprise irradiating a sample on the sample surface with a pulse of energy at an irradiation angle that is within 1 degree or less of the normal of the sample support surface to form sample ions by matrix-assisted laser desorption/ionization and extracting sample ions along a first ion optical axis in a direction substantially normal to the sample support surface by application of an electrical potential difference between the sample support surface and the first electrode at a predetermined time. In various embodiments, the first ion optical axis is substantially coaxial with the pulse of energy. Ion Optics In various aspects, the present teachings provide methods for focusing ions for an ion fragmentor and methods for operating an ion optical assembly comprising an ion fragmentor. In various embodiments, the present teachings provide methods that substantially maintain the position of the focal point of the an incoming ion beam over a wide range of collision energies, and thereby provide a collimated ion beam for a collision cell over a wide range of energies. In various embodiments, the present teachings provide methods that facilitate decreasing ion transmission losses over a wide range of collision energies. In various aspects, an ion optics assembly of the methods comprises a first ion lens disposed between a retarding lens and an entrance to a collision cell. In various embodiments, the retarding lens and first ion lens comprise multiple elements, and can share elements. For example, in various embodiments, the retarding lens comprises a first electrode, a second electrode and a third electrode; and the first ion lens comprises the third electrode, a fourth electrode and a fifth electrode. In various embodiments, sample ions are substantially focused to a focal point between the third electrode and the fourth electrode to form a substantially collimated ion beam after the focal point and before the entrance to the collision cell. In various aspects, the present teachings provide methods for operating an ion optics assembly comprising a first ion lens disposed between a retarding lens and an entrance to a collision cell, comprising the steps of: focusing sample ions at a focal point within the first ion lens a distance F from an entrance to the retarding lens and forming a substantially collimated ion beam of sample ions at a first collision energy of the sample ions with respect to a neutral gas in a collision cell; and maintaining the focal point substantially at the distance F for collision energies different from the first collision energy by substantially maintaining the electrical potential on the retarding ion lens and changing an electrical potential on the first ion lens. In various aspects, the present teachings provide methods for focusing ions for an ion fragmentor; the methods using an ion optics assembly comprising a first ion lens disposed between a retarding lens and an entrance to an ion fragmentor. In various embodiments, the methods apply a decelerating electrical potential to the retarding lens, apply an accelerating electrical potential difference between the retarding lens and the first ion lens; and apply a decelerating electrical potential difference between the first ion lens and the entrance to the collision cell. In various embodiments, sample ions are substantially focused to a focal point within the first ion lens, e.g., to form a substantially collimated ion beam after the focal point and before the entrance to the collision cell. In various embodiments, the position of this focal point is maintained for different collision energies by changing the accelerating electrical potential difference between the retarding lens and the first ion lens while substantially maintaining the decelerating electrical potential applied to the retarding lens. In various embodiments, methods of the present teachings for operating an ion optics assembly comprising a first ion lens disposed between a retarding lens and an entrance to a collision cell, comprise: (a) at a first collision energy substantially focusing sample ions to a focal point in the first ion lens and forming after the focal point in the first ion lens and before the entrance to the collision cell a substantially collimated ion beam of sample ions by: (i) establishing a decelerating electrical field to decelerate sample ions entering the retarding lens by applying a first electrical potential to an electrode of the retarding lens; (ii) establishing an accelerating electrical field between the retarding lens and the first ion lens to accelerate sample ions from the retarding lens and into the first ion lens by applying a second electrical potential to an electrode of the first ion lens; and (iii) establishing a decelerating electrical field between the first ion lens and the entrance of the collision cell to decelerate sample ions from the first ion lens by applying a third electrical potential to the entrance of the collision cell. The methods proceed with (b) changing the first collision energy to a second collision energy different from the first collision energy. Sample ions for are then (c) at the second collision energy substantially focusing sample ions to the focal point in the first ion lens and forming after the focal point in the first ion lens and before the entrance to the collision cell a substantially collimated ion beam of sample ions by: (i) establishing a decelerating electrical field to decelerate sample ion entering the retarding lens by applying a fourth electrical potential to an electrode of the retarding lens, the fourth electrical potential being substantially equal to the first electrical potential; (ii) establishing an accelerating electrical field between the retarding lens and the first ion lens to accelerate sample ions from the retarding lens and into the first ion lens by applying a fifth electrical potential to an electrode of the first ion lens; and (iii) establishing a decelerating electrical field between the first ion lens and the entrance of the collision cell to decelerate sample ions from the first ion lens by applying a sixth electrical potential to the entrance of the collision cell. In various embodiments, sample ions are substantially focused to a focal point a distance F from an entrance to the retarding lens. In various embodiments when the difference between the first collision energy and the second collision energy is less than about 5000 electron volts, the distance F varies within less than about: (a) ±4%; (b) ±2%; and/or (c) ±1%. In various embodiments, the fourth electrical potential is within about ±5% or less of the first electrical potential. For example, in various embodiments, the fourth electrical potential is within about ±2.5% or less of the first electrical potential. Ion Optics Assemblies In various aspects, the present teachings provide ion optical assemblies with features that facilitate the alignment of ion optical elements. In various embodiments, provided are ion optical assemblies comprising a first plurality of ion optical elements disposed between a front member and a front side of a mounting body. The front member is attached to the mounting body by at least one attachment member and the front member has a threaded opening configured to accept a threaded surface of a front securing member. The threaded opening of the front member is configured such that when the threaded surface of the front securing member is engaged in the threaded opening of the front member, a contact face of the front securing member can contact an ion optical element of the first plurality and apply a compressive force against the first plurality of ion optical elements. Each ion optical element of the first plurality has a recess structure adapted to receive a complimentary registration structure, a registration structure aligning an ion optical element of the first plurality with respect to at least one other ion optical element of the first plurality when the registration structure is registered in a complimentary recess structure when the compressive force is applied by the front securing member. In various embodiments, the alignment of the ion optical elements by compressing them with the securing members, as described in the present teachings, can simplify the alignment and assembly of ion optical elements. In the present teachings, no torque pattern is required to compress and align the ion optical elements. In various embodiments, the securing members can lock the ion optics elements in place, so no additional parts are required to secure the ion optic assembly for shipping. In various aspects, the present teachings provide systems for mounting and aligning ion optic components that facilitate their alignment. In various embodiments, provided are systems comprising a mounting base having a plurality of pairs of protrusions protruding from a mounting surface of the base and one or more mounting structures associated with each pair of protrusions. At least one electrical connection element is associated with each pair of protrusions, the connection elements passing through the mounting base from a back surface to the mounting surface. The systems further comprise two or more ion optic component supports, where each ion optic component support has a pair of recesses configured to receive one or more of the plurality of pairs of protrusions. The recess are configured such that when the pair of recesses of an ion optic component support is brought into registration with the corresponding pair of protrusions (by mounting an ion optic component to the mounting base using the one or more mounting structures associated with the pair of protrusions) an ion optics component mounted in the support is substantially aligned with another ion optics component so mounted and an electrical connection site on said ion optics component is proximate to a corresponding electrical connection element. In various embodiments, the plurality of pairs of protrusions are configured such that only one orientation of an ion optic component support will enable the corresponding recesses in an ion optic component support to be brought into registration with the corresponding pair of protrusions. For example, in various embodiments, unique recess and protrusion patterns can be used to orient an ion optic component support. In various embodiments, the pairs of protrusions are configured to have different shapes for different ion optic components. In various embodiments, the systems for mounting and aligning ion optic components facilitating, for example, the rapid change out of optical components without fear of interchanging components or misorienting them. Mass Analyzer Systems In various aspects, the present teachings provide MALDI-TOF mass analyzer systems. In various embodiments, a mass analyzer system comprises (a) an optical system configured to irradiate a sample on a sample surface with a pulse of energy such that the pulse of energy strikes a sample on the sample surface at an angle substantially normal to the sample surface; (b) a MALDI ion source of the present teachings; (c) an ion deflector configured to deflect ions from a first ion optical axis along which ions are extracted into the mass analyzer system and onto a second ion optical axis; (d) a first substantially field free region positioned between the ion deflector and a timed ion selector, the timed ion selector being positioned between the first substantially field free region and a collision cell; (e) a second time-of-flight positioned between the collision cell and a first ion detector; (f) an ion mirror positioned between the second time-of-flight and the first ion detector; and (g) a second time-of-flight positioned between the ion mirror and a second ion detector. The timed ion selector is positioned to receive ions traveling along the second ion optical axis and is configured to select ions for transmittal to the collision cell. In various embodiments, the MALDI ion source comprises a first electrode spaced a part from a sample support having a sample surface, a second electrode spaced apart from the first electrode in a direction opposite the sample support, and a third electrode spaced apart from the second electrode in a direction opposite the first electrode. The sample support, first, second and third electrodes are electrically coupled to a power source which is adapted to: (a) apply a first potential to the sample surface and a second potential to at least one of the first electrode and the second electrode to establish a non-extracting electric field at a first predetermined time substantially prior to striking a sample on the sample surface with a pulse of energy to form sample ions, the non-extracting electrical field substantially not accelerating sample ions in a direction away from the sample surface; (b) change the electrical potential of at least one of the sample surface and the first electrode to establish a first extraction electric field at a second predetermined time subsequent to the first predetermined time, the first extraction electric field accelerating sample ions in a first direction away from the sample surface; and (c) apply a third potential to the second electrode to focus ions in a direction substantially perpendicular to the first direction. In various embodiments, the non-extracting electrical field can be a retardation electrical field which retards the motion of sample ions in a direction away from the sample surface. In various embodiments, the non-extracting electrical field can be a substantially zero electrical field, e.g., a substantially electrical field free region is established. A substantially zero electrical field can be established, e.g., when the first potential and the second potential are substantially equal. In various embodiments, a mass analyzer system further comprises a vacuum lock chamber and a sample chamber connected to the vacuum lock chamber. A sample support changing mechanism is disposed in the vacuum lock chamber and a sample support transfer mechanism is disposed in the sample chamber. The sample support transfer mechanism configured to extract a sample support from a loading region of the sample support changing mechanism such that the sample support is registered within a frame in the sample support transfer mechanism. The sample support transfer mechanism is mounted on a multi-axis translation stage such that the sample support can be translated to a position where sample ions can be generated by laser irradiation of a sample on the surface of the sample support by a pulse of energy while said sample support is held in the sample support transfer mechanism, the sample support transfer mechanism is in the sample chamber, and said sample ions can be extracted along the first ion optical axis. In various embodiments, a mass analyzer system further comprises one or more temperature controlled surfaces disposed therein. In various embodiments, the timed ion selector and the collision cell comprise portions of an ion optical assembly, the ion optical assembly comprising a first plurality of ion optical elements disposed between a front member and a front side of a mounting body. The front member is attached to the mounting body by at least one attachment member and the front member has a threaded opening configured to accept a threaded surface of a front securing member. The mounting body contains the collision cell and the timed ion selector comprises at least one of the ion optical elements. The threaded opening of the front member is configured such that when the threaded surface of the front securing member is engaged in the threaded opening of the front member, a contact face of the front securing member can contact an ion optical element of the first plurality and apply a compressive force against the first plurality of ion optical elements. Each ion optical element of the first plurality has a recess structure adapted to receive a complimentary registration structure, a registration structure aligning an ion optical element of the first plurality with respect to at least one other ion optical element of the first plurality when the registration structure is registered in a complimentary recess structure when the compressive force is applied by the front securing member. In various aspects, the present teachings provide methods for operating MALDI-TOF mass analyzer systems having two or more modes of operation and an ion source comprising a sample support having a sample surface, a first electrode spaced apart from the sample support, a second electrode spaced apart from the first electrode in a direction opposite the sample support holder, and a third electrode spaced apart from the second electrode in a direction opposite the first electrode. In various embodiments, the methods for a first mode of operation (a) select for the first mode of operation the position of a time-focus plane of the ion source in a direction z by application of an electrical potential difference between the sample surface and the first electrode, where this potential difference is established by applying a first electrical potential to the sample surface and a second electrical potential to the first electrode; and focusing ions in a direction substantially perpendicular to the direction z by application of a third electrical potential to the second electrode; (b) irradiate a sample on the sample surface with a pulse of energy at an irradiation angle that is substantially normal to the sample surface to form sample ions by matrix-assisted laser desorption/ionization; (c) extract sample ions in a direction substantially normal to the sample surface along a first ion optical axis which is substantially coaxial and substantially coincident with the pulse of energy; and (d) deflect sample ions from the first ion optical axis and onto a second ion optical axis for mass analysis using the first mode of operation. The mode of operation of the mass analyzer system is then changed to a second mode of operation; and the methods (a) select for the second mode of operation the position of a time-focus plane of the ion source in a direction z by application of an electrical potential difference between the sample surface and the first electrode, where this potential difference is established by applying a fourth electrical potential to the sample surface which is substantially equal to the first electrical potential, and applying a fifth electrical potential to the first electrode; and focusing ions in a direction substantially perpendicular to the direction z by application of a sixth electrical potential to the second electrode; (b) irradiate a sample on the sample surface with a pulse of energy at an irradiation angle that is substantially normal to the sample surface to form sample ions by matrix-assisted laser desorption/ionization; (c) extract sample ions in a direction substantially normal to the sample surface along a first ion optical axis which is substantially coaxial and substantially coincident with the pulse of energy; and (d) deflect sample ions from the first ion optical axis and onto a second ion optical axis for mass analysis using the second mode of operation. In various embodiments where one of the modes of operation comprises collision induced dissociation, the methods for operating MALDI-TOF mass analyzer systems can include various embodiments of the present teachings of methods for focusing ions for a collision cell of the and can include various embodiments of the present teachings of methods for operating an ion optics assembly. In various aspects, the present teachings provide novel MALDI-TOF systems. In various embodiments, provided are novel MALDI-TOF systems comprising one or more novel components such as, for example, sample support handling mechanisms, ion sources, ion optics and ion optical assemblies. In various embodiments, provided are novel methods for use with a mass spectrometry system to, for example, provide sample ions, focus sample ions, operate a mass spectrometry system in different operational modes, and operate ion fragmentors. FIGS. 1A-1D depict substantially to scale views of a MALDI-TOF system 100 in accordance with various embodiments of the present teachings. FIG. 1A depicting a front sectional view, FIG. 1B a side sectional view, and FIGS. 1C and 1D presenting expanded views of portions of FIGS. 1A and 1B, respectively. To facilitate the viewing of FIGS. 1A-1D, the system 100 can be oriented such that the floor is in direction 101, the ceiling in direction 102, and the “front” of the instrument can be considered to be from viewpoint 103. The various embodiments illustrated by FIGS. 1A-1D are not intended to be limiting. For example, a MALDI-TOF system in accordance with the present teachings can comprise fewer system components than illustrated or more system components than illustrated in FIGS. 1A-1D. In addition, the MALDI-TOF systems of the present teachings are not necessarily limited to the arrangement of the parts illustrated in FIGS. 1A-1D; rather, the illustrated arrangements are but some of the many modes of practicing the present teachings. For example, various embodiments of the systems illustrated in FIGS. 1A-1D can be operated in various modes, such as, e.g., linear MS operation, ion mirror MS operation, MS/MS operation, etc. In various embodiments, a MALDI-TOF system 100 of the present teachings comprises a sample support handling system 105 comprising a vacuum lock chamber 106, through which sample supports can be loaded and removed, and a sample support transfer mechanism 108 configured to transport sample supports from the vacuum lock chamber 106 to an ion region 111. The sample support transfer mechanism can comprise a translation mechanism for translating the sample support in one or more dimensions within the ion source region to, for example, facilitate the serial analysis of two or more samples on the sample support. In various embodiments, the translation mechanism comprises an multi-axis (e.g., two dimension, x-y; three dimension x-y, -z) translational stage 112. The mass spectrometry system can comprise a viewing system 113 to view along a line of sight 114, e.g., the samples on the surface of a sample support when the sample support is positioned for ion formation in the ion source region. The various embodiments of a MALDI-TOF system illustrated in FIGS. 1A-1D can be operated in various modes, e.g., linear MS operation, ion mirror MS operation, MS/MS operation, etc., and can comprise one or more regions substantially free of electrical fields 120, 122, 124. For example, in various embodiments, the TOF system can be operated as a linear TOF mass spectrometer. In linear TOF operational mode, ions produced in the ion source region 111 are extracted by electrical fields established by one or more ion source electrodes into a first region substantially free of electrical fields (a first field free region) 120 and travel to a first detector 125. In various embodiments, the TOF system can be operated as a reflectron TOF mass spectrometer. In ion mirror TOF operational mode, after drifting through one more substantially electrical field free regions 120, 122, ions enter an ion mirror to, e.g., correct for differences in ion kinetic energy. The ions exiting the ion mirror 130 can then drift through another field free region 124 to a detector 135. In various aspects, the MALDI-TOF system can serve and be operated as a MS/MS instrument. For example, in various embodiments, the MALDI TOF system comprises an ion fragmentor 140. Ions produced in the ion source region 111 are extracted by electrical fields established by one or more ion source electrodes into a first region substantially free of electrical fields (a first field free region) 120 and a timed ion selector 142 can be used to select ions for transmittal to, e.g., a collision cell 144, of the ion fragmentor, and fragment ions extracted into a second region substantially free of electrical fields (a second field free region) 122 to travel to a first detector 125, e.g., when performing linear-linear TOF, or travel to a second detector 135, e.g., when performing linear-reflector TOF. In various aspects and embodiments, the present teachings utilize a pulse of energy to form sample ions. The pulse of energy can be coherent, incoherent, or a combination thereof. In various embodiments the pulse of energy is a pulse of laser energy. A pulse of laser energy can be provided by a laser system 150, for example, by a pulsed laser or continuous wave (cw) laser. The output of a cw laser can be modulated to produce pulses using, for example, acoustic optical modulators (AOM), crossed polarizers, rotating choppers, and shutters. Any type of laser of suitable irradiation wavelength for producing sample ions of interest by MALDI can be used with the present teachings, including, but not limited to, gas lasers (e.g., argon ion, helium-neon), dye lasers, chemical lasers, solid state lasers (e.g., ruby, neodinium based), excimer lasers, diode lasers, and combination thereof (e.g., pumped laser systems). Sample Handling Mechanisms Mass spectrometer systems can be complex instruments requiring accurate and repeatable alignment of components. One area where accurate and repeatable alignment is generally required is in the ion source. In MALDI-TOF mass analyzer systems, variations in the positioning of samples in the direction of ion extraction (referred herein as the Z direction) lead to variations in flight length (flight time), which can decrease mass resolution. In addition, variations in Z position, as well as X and Y position, can lead to formation of sample ions at positions where the ion optics of the instrument have not be tuned, which can decrease ion signal and resolution. These variations can be of even greater concern when investigations require the analysis of large numbers of samples necessitating repeated loading and unloading of samples, typically carried on sample supports such as, e.g., MALDI plates, from the ion source region of the mass analyzer system. In various aspects, the present teachings provide sample support handling mechanisms. In various embodiments, the sample support handling mechanisms comprise a sample support changing mechanism and a sample support transfer mechanism, that can be configured to allow a user to place a sample support in the changing mechanism, which when captured by a sample support transfer mechanism for transfer to an ion source region, is registered in the X, Y and Z directions, facilitating the accurate and repeatable alignment of the samples in the X, Y and Z directions in the ion source. In various embodiments, the sample support handling mechanism is configured such that a sample support is registered to a position in the sample support transfer mechanism to: (a) within about ±0.002″ in the Z direction; (b) within about ±0.005″ in the X direction; (c) within about ±0.005″ in the Y direction; (d) or combinations thereof. In various embodiments, the sample support handling mechanism is configured such that a sample support is registered to a position in the sample transfer mechanism to: (a) within about ±0.005″ in the Z direction; (b) within about ±0.01″ in the X direction; (c) within about ±0.01″ in the Y direction; (d) or combinations thereof. In various embodiments, the sample support is capable of holding a plurality of samples. In various embodiments, a sample support comprises a plate, e.g., a 3.4″×5″ plate, a microtiter sized MALDI plate, etc. Suitable sample supports include, but are not limited to, 64 spot, 96 spot and 384 spot plates. An electrically insulating layer can be interposed between the sample and sample surface of the sample support. The sample can include a matrix material that absorbs at a wavelength of the pulse of laser energy and which facilitates the desorption and ionization of molecules of interest in the sample. In addition to misalignment of sample support positions, distortions in the electrical field lines near a sample undergoing ionization can also lead to decreased ion signal and resolution. For example, discontinuities in electrical field lines close to samples undergoing MALDI can disturb the ion extraction electrical field lines, causing the path of the ion plume to deviate from the desired flight to an extraction electrode. In various embodiments, the sample support handling mechanisms of the present teachings provide a frame having an electrically conductive surface and which substantially surrounds the sample support to extend the electrically conductive area around the sample support. Referring to FIG. 2, in various embodiments, a sample support handling mechanism of the present teachings comprises a sample support transfer mechanism 200 disposed in a sampling chamber 205 and a sample support changing mechanism 210 disposed in a vacuum lock chamber 215. In various embodiments, the sample support transfer mechanism 200 comprises a translation stage 217 (e.g. a two axis or three axis stage). The sample support transfer mechanism is disposed in the sample chamber but can extend a portion into the vacuum lock chamber to extract a sample support from and return a sample support to the sample support changing mechanism. In operation, a sample support can be placed in a loading region 220 (e.g., onto a load pad) of the changing mechanism 210 in the vacuum lock chamber 215, and the vacuum lock chamber door 225 closed. The vacuum lock chamber is pumped down (e.g., to about 80 mTorr or lower) and a sample chamber door (e.g., a gate valve) between the vacuum lock and sample chambers opened. The sample support transfer mechanism can be translated in a Y direction until a left arm 232 is sufficiently aligned with a left cam structure 234 of the changing mechanism and a right arm 236 is sufficiently aligned with a central cam structure 238 of the changing mechanism. The sample transfer mechanism can be then translated in the X direction so the left and right arms 232, 236 can engage and capture the sample support (not shown in FIG. 2 for the sake of clarity in illustrating other structures) in the loading region 220. As the left and right arms approach the sample support, the left cam structure 234 and central cam structure 238 engaging, respectively, left and right bearing support structures of, respectively, the left and right arms, urging them to a second position (e.g., pushing them down) and a first disengagement member 239 urges an engagement member 240 to a second position (e.g., pushing it down) allowing a sample support to be engaged against a front face of the transfer mechanism. In various embodiments, a frame for the sample support (not shown in FIG. 2 for the sake of clarity in illustrating other structures) can be between the left and right arms prior to engagement of a sample support in the loading region, or on the sample support in the loading region. When, e.g., the frame is between the left and right arms (see, e.g., FIG. 3) the transfer mechanism is aligned in such a manner that the frame is slightly above the sample support to allow the frame to pass over the sample support without substantially contacting samples of interest thereon. In various embodiments, the sample support (not shown in FIG. 2 for the sake of clarity in illustrating other structures) can be in a frame when it is loaded into the loading region, the sample transfer mechanism engaging and loading the framed sample support. When, e.g., the sample support is in a frame prior to engagement by the sample transfer mechanism, the frame can be registered within the transfer mechanism. After capture of the sample support, the sample support can be translated into the sample chamber, the sample chamber door closed, the sample chamber pumped down to a pressure suitable for ion formation, and the formation of ions begun by, e.g., MALDI. In the illustrated sample chamber of FIG. 2, sample ions are extracted from the sample chamber substantially in the direction Z. The X, Y and Z directions in the isometric view of FIG. 2 being schematically illustrated by the inset coordinates 241. In operation, to remove a sample support, e.g., after MALDI analysis, the sample transfer stage can be translated in the Y direction until the left arm 232 is sufficiently aligned with a central cam structure 234 of the changing mechanism and the right arm 236 is sufficiently aligned with a right cam structure 242 of the changing mechanism. The sample transfer mechanism can be then translated in the X direction so the left and right arms 232, 236 can engage, respectively, the central 238 and right cam structures 242 and a second disengagement member 243 can disengage the engagement member 240 on the transfer mechanism. In various embodiments, the engagement member comprises rollers that can follow the surface (e.g., the under surface of the disengagement member 243) of a sloped second disengagement member 243, thereby allowing a sample support to slowly disengage (e.g., without abruptly dropping) into the unloading region 245 and depressing a sample support capture member 250. As the sample transfer mechanism continues to travel in the X direction the sample support becomes fully disengaged from the left and right arms of the transfer mechanism, the leading edge (the edge furthest into the unloading region) of the sample support (and/or frame member in which it may be retained) places pressure against the capture member, and the engagement member 240 becomes fully disengaged from the sample support. In various embodiments, when the leading edge of the sample support (and/or frame member in which it may be retained) clears the outer edge of the capture member 250, the capture member engages (e.g., springs up) the sample support (and/or frame member in which it may be retained) preventing the sample support from being withdrawn with the transfer mechanism. FIG. 3 depicts an expanded portion of a sample support transfer mechanism 300, in accordance with various embodiments of a sample handling mechanism of the present teachings, showing a captured sample support 305 and a frame 310. The X, Y and Z directions in the isometric view of FIG. 3 being schematically illustrated by the inset coordinates 311. Referring to FIG. 3, the sample support transfer mechanism comprises a base 315, a left arm 320 and a right arm 330 which are substantially perpendicular to a front face (obscured by the sample support 305 and frame 310 in this illustration). In various embodiments, the base 315 of the transfer mechanism attaches to an X-Y translation stage within the sample chamber. The translation stage can be used to move samples to an ion formation region as well as transferring the sample support between the vacuum lock and sample chambers. In various embodiments, the right arm bearing support structure comprises a pivot arm 340 and a clamp arm 345. During translation into a loading region or unloading region of the changing mechanism, the central cam structure (loading operation) or right cam structure (unloading operation) of the changing mechanism engage the pivot arm 340 urging from a first position and down into a second position (loading operation) or third position (unloading operation), which in turn pushes down the clamp mechanism 345 allowing the right arm to engage a sample support (loading operation) or disengage a sample support (unloading operation). For example, in various embodiments, in a loading operation as the transfer stage is driven in the X direction into the loading region, the left arm 330 of the sample support handling mechanism actuates the registration member (a rocker arm in FIG. 4B) of the loading region. The registration member pushes the sample support into the corner of the sample support transfer mechanism where the left arm meets the front face of the base 315. As the transfer mechanism continues in the X direction into the loading region, the pivot 340 arm is released, and the clamp arm 345 pushes the sample support against the retaining structures 350 on the frame, registering the back side (i.e., the side of the sample support farther from the front face of the base) of the sample support plate in the Z direction. In various embodiments, the frame comprises an electrically conductive surface on at least the surface which faces the ion extraction electrode(s) of the ion source. In various embodiments, extending the electrically conductive area around the sample support facilitates reducing electrical field line discontinuity between the sample support and extraction electrode(s). In various embodiments, the corners of the frame up against which a sample support can be registered in the Z direction, have a low profile to facilitate reducing electrical field disturbance. In various embodiments, the pivot arm and clamp arm are substantially duplicated on both the right arm 330 and the left arm 320 of the transfer mechanism, e.g., for actuation from either side. Motion can be transferred from an active side to a slave side by, e.g., a solid rod 355 at the pivot point. In an unloading operation, for example, the transfer mechanism can be driven in the X direction into the unloading region, one or more of the cam structures engaging one or more of the bearing support structures to disengage the clamping arms, and a second disengagement member disengages the engagement member, allowing the sample support to drop out from between the left and right arms of the transfer mechanism. As the transfer mechanism retracts from the unloading region, a capture mechanism (illustrated as a stripper plate in FIG. 4B) prevents the sample support from following the sample support transfer mechanism as it retracts. Referring to FIGS. 4A and 4B, expanded views of a sample support transfer mechanism portion (FIG. 4A) and a sample support changing mechanism portion (FIG. 4B), in accordance with various embodiments of a sample handling mechanism of the present teachings, are shown. The sample support handling mechanism comprises a sample support transfer mechanism 400 and a sample support changing mechanism 405, the sample changing mechanism being disposed in a vacuum lock chamber. Sample supports can be input and output through the vacuum lock chamber. For example, in operation, a sample support can be placed in a loading region 410 of the changing mechanism 405 and the vacuum lock chamber door closed. The vacuum lock chamber is pumped down and when a desired vacuum is reached in the vacuum lock chamber, a door 412 separating the two chambers (e.g., a gate valve) can be opened. Once the sample transfer mechanism is aligned in the Y direction with the loading region 410 it can be translated into the loading region 410 in the X direction. As the left and right arms approach the sample support, a left cam structure 415 and central cam structure 420 engaging, respectively, the left 425 and right 430 bearing support structures urging them to a second position (e.g., pushing them down) and a first disengagement member 435 urges the engagement member 440 to a second position (e.g., pushing it down). In various embodiments, the engagement member comprises an angled surface 442 sloped away from the front face 455 of the base member to facilitate, e.g., smooth registration of a sample support. In various embodiments, the front face 455 of the base member comprises bearings to facilitate, e.g., smooth registration of a sample support. As the transfer mechanism continues into the loading region, the left arm 445 engages the registration member 450 (illustrated as a rocker arm), e.g., on the left cam side of the rocker arm pivot 452, pivoting the rocker arm which in turn pushes the sample support against the front face 455 and left arm 445, and, in various embodiments, registers the sample support in the X-Y direction up against the left arm 445 and the front face 455 of the base. As the transfer mechanism continues into the loading region in the X direction, the engagement member reaches 440 reaches the end of the disengagement member 435, and the engagement member returns to its first position (e.g., springs up) registering the front side of the sample support (i.e., the side of the sample support nearer the front face of the base) in the Z direction and securing it in the X direction. In various embodiments, the sample support is registered in the Z direction against a retention projection (e.g., ledge) of the left arm 456 a retention projection (e.g., ledge) of the right arm 457. The retention projections extending in the Y direction only a portion of the distance between the two arms. As the transfer mechanism retracts from the loading region back into the sample chamber, the bearings support blocks spring back up (return to their respective first positions) and register the back side of the plate in the Z direction. The X, Y and Z directions in the isometric views of FIGS. 4A and 4B being schematically illustrated by the inset coordinates 458. In operation, unloading of a sample support can proceed, for example, as follows. When a desired vacuum is reached in the vacuum lock chamber the door separating 412 the two chambers (e.g., a gate valve) can be opened. Once the sample transfer mechanism is aligned in the Y direction with the unloading region 460 it can be translated into the unloading region 460 in the X direction. As the left and right arms of the transfer mechanism approach they enter the unloading region, the central cam structure 420 and a right cam structure 464 engage, respectively, the left 425 and right 430 bearing support structures urging them to a third position (e.g., pushing them down) and a second disengagement 465 member urges the engagement member 440 to a third position (e.g., letting it disengage). In various embodiments, a ramp 465 slowly drops the engagement member 440 and the sample support engages a sample support capture mechanism 470 (e.g., illustrated as a spring loaded stripper plate in FIG. 4A) urging it from a first position to a second position (e.g., pushing it down). In various embodiments, the engagement member 440 comprises roller 472 which engage the second disengagement member 465. As the leading edge of the sample support passes over the outer edge 475 of the stripper plate 470, the stripper plate springs back up (e.g., to a third position) which retains the sample support in the unloading region as the transfer mechanism retracts back into the sample chamber. In various aspects, the present teachings provide methods for providing sample ions for mass analysis. Referring to FIGS. 1A-4B, in various embodiments, the methods comprise supporting a plurality of samples 370 on a sample surface 375 of a sample support 305; providing a vacuum lock chamber 106, 215 having a region for loading a sample support 220 and a region for unloading a sample support 245; and providing a sample chamber 160, 205 having a sample transfer mechanism 108, 200 disposed therein The methods extract a sample support disposed in the region for loading 220 with the sample transfer mechanism 108, 200 such that the sample support is registered within a frame 310 in the sample support transfer mechanism, e.g., to within about ±0.002″ in a Z direction, to within about ±0.005″ in a X direction, and to within about ±0.005″ in a Y direction, wherein the X, Y and Z directions are mutually orthogonal and the direction Z is substantially perpendicular to the surface of the sample support. The sample support is translated to a first position (e.g., to align a first sample on the sample surface with an ion source extraction electrode 162) within the sample chamber 160, 205 where a first sample on the surface of the sample support is irradiated with a with a pulse of energy 164 to form a first group of sample ions while the sample support is being held by the sample transfer mechanism and at least a portion of the first group of sample ions is extracted in the Z direction 166. The sample support is then translated to a second position (e.g., to align a second sample on the sample surface with an ion source extraction electrode 162) within the sample chamber where a second sample on the surface of the sample support is irradiated with a with a pulse of energy 164 to form a second group of sample ions while the sample support is being held by the sample transfer mechanism and at least a portion of the second group of sample ions is extracted in the Z direction 166. Further samples can be analyzed on the sample support prior to the sample support being placed by the sample support transfer mechanism in the region for unloading 245 a sample support. The methods continue with repeating the steps of extracting at least one other sample support followed by the steps of translating, irradiating and extracting for at least two samples on the sample support. In various embodiments, at least one of the steps of irradiating a sample with a pulse of energy comprises irradiating the sample at an irradiation angle that is within 5 degrees or less of the normal of the surface of the sample support to form sample ions by matrix-assisted laser desorption/ionization. In various embodiments, at least one of steps irradiating a sample with a pulse of energy comprises irradiating the sample at an irradiation angle that is within 1 degree or less of the normal of the surface of the sample support to form sample ions by matrix-assisted laser desorption/ionization. In various embodiments, at least one of the steps of extracting at least a portion of the sample ions comprises extracting sample ions in the Z direction along a first ion optical axis, wherein the first ion optical axis is substantially coaxial with the pulse of energy. For example, referring to FIGS. 1A-1D, in various embodiments, sample ions are extracted along a first ion optical axis 168 which is substantially coaxial and substantially coincident with the pulse of energy 164. Ion Sources In various aspects, the present teachings relate to MALDI ion sources and methods of MALDI ion source operation, for use with mass analyzers. In various aspects, the present teachings provide three-stage ion sources that, in various embodiments, facilitate compensating for the spread in ion arrival times due to initial ion velocity without substantially degrading the radial spatial focusing of the ions and while allowing for an adjustable velocity space focus plane. As is generally understood by those of ordinary skill in the art, the desired position of the velocity space focus plane is primarily determined by the mode of operation of a TOF instrument. Referring to FIG. 5, a three-stage ion source 500 of the present teachings comprises a sample support 502 having a sample surface 504, a first electrode 506, a second electrode 508, and a third electrode 510. In various embodiments, the first-stage 520 being defined by the sample surface 504 and first electrode 506, the second-stage 522 being defined by the first electrode 506 and the second electrode 508, and the third-stage 524 defined by the second electrode 508 and the third electrode 510. In various embodiments, the first-stage 520 being defined by the sample surface 504 and second electrode 508, the second-stage 522 being defined by the first electrode 506 and the second electrode 508, and the third-stage 524 defined by the second electrode 508 and the third electrode 510. A variety of electrode shapes and configurations can be used including, but not limited to, plates, grids, cones, and combinations thereof. For example, the first electrode 506 can be in the form of a skimmer, having a conical portion 511. In various embodiments, the methods for operating of a TOF mass analyzer having two or more modes of operation comprise establishing an ion energy by setting an electrical potential difference between the sample surface 504 and the third electrode 510, and focusing ions by variation of the electrical potentials on one the first electrode 506 and the second electrode 508. In various embodiments, in a first mode of operation the position of a time-focus plane in a direction z is selected by applying a first electrical potential to the sample surface 504 and a second electrical potential to the first electrode 506 and ions are focused in a direction substantially perpendicular to the direction z by applying a third electrical potential to the second electrode 508. The refocusing of the TOF mass analyzer comprises the position of a time-focus plane in a direction z for the second mode of operation is selected by changing the electrical potential applied to the first electrode 506; and ions are focused in a direction substantially perpendicular to the direction z by changing the electrical potential applied to the second electrode 508. Sample ions can be generated by irradiating a sample disposed on a sample surface of the holder with a pulse of energy. In various embodiments, to provide a velocity space focus plane and x, y spatial focusing, the three-stage ion source comprises a power source, electrically coupled to the sample support, first, second and third electrodes, which is adapted to: (a) apply a first potential to the sample surface and a second potential to at least one of the first electrode and the second electrode to establish a non-extracting electric field at a first predetermined time substantially prior to striking a sample on the sample surface with a pulse of energy to form sample ions, the non-extracting electrical field substantially not accelerating sample ions in a direction away from the sample surface; (b) change the electrical potential of at least one of the sample surface, the first electrode and the second electrode to establish a first extraction electric field at a second predetermined time subsequent to the first predetermined time, the first extraction electric field accelerating sample ions in a first direction away from the sample surface; and (c) apply a third potential to the second electrode to focus ions in a direction substantially perpendicular to the first direction. An electrical potential applied to one or more of the sample surface, first electrode, and second electrode to establish a non-extracting electrical field can be a zero potential. An electrical potential applied to one or more of the sample surface, first electrode, second electrode, and third electrode to establish one or more of the first extraction electrical field and to focus ions in a direction substantially perpendicular to the first direction, can be a zero potential. In various embodiments, the non-extracting electrical field can be a retardation electrical field, the retardation electrical field retarding the motion of sample ions in a direction away from the sample surface. In various embodiments, the non-extracting electrical field can be a substantially zero electrical field, e.g., a substantially electrical field free region is established. A substantially zero electrical field can be established, e.g., when the first potential and the second potential are substantially equal. Referring to FIG. 5, an example of the relative electrical potentials on the sample surface, first electrode, second electrode, and third electrode at the second predetermined time are illustrated in the inset schematic plot 550 of electrical potential 555 as a function of the z coordinate 557. The coordinate system for FIG. 1 and the data of Table 1 is shown by the inset coordinate system reference 560 where the z axis lies along the ion extraction axis 570, the y axis is perpendicular to the z axis in the plane of the figure and the x axis is perpendicular to the z axis out of the plane of the figure, and the origin is at the intersection 575 of the ion extraction axis 570 with the sample surface 504. In some embodiments, both the first and second electrodes have apertures. In various embodiments, sample ions are extracted along a first ion optical axis 570 defined by the axis running through the centers of apertures in the first electrode 506 and the second electrode 508. In various embodiments, an optical system is configured to substantially align the pulse of laser energy with the first ion optical axis. For example, in various embodiments, sample ions are extracted along a first ion optical axis in a direction substantially normal to the sample surface and the pulse of energy is substantially coincident with the first ion optical axis. The third electrode can be an apertured electrode that is a substantially planar plate or grid. In various embodiments, the third electrode is positioned so the centers of the apertures of the first, second, third apertured electrodes substantially fall on a common axis. Where the apertures in the first and second electrodes are substantially centered on the sample being irradiated and the first and second electrodes are substantially symmetric about the normal to the sample surface, the first ion optical axis will intersect the sample surface at an angle substantially normal to the sample surface, the extraction direction will be substantially normal to the sample surface, the extraction direction will be substantially parallel to the first ion optical axis, and sample ions will be extracted along the first ion optical axis. The three-stage ion source of the present teachings can introduce an additional adjustable parameter for the ion source which can be used to compensate for changes to the x,y spatial focus characteristics of the ion beam due to optimizing the velocity space focus plane at particular position (in z). This additional parameter can allow the operator of a three-stage ion source of the present teachings to change the effective length of the second-stage of the ion source electrostatically; thus facilitating the optimization of the x,y space focus characteristics of the ion beam without compromising the position of the velocity space focus plane, which position is primarily dictated by the voltage ratio and geometry of the first-stage of the ion source. The behavior of a two-stage ion source and its operation to form a velocity space focus plane has been previously described, see for example, M. Vestal and P. Juhasz, J. American Soc. Mass Spec., 9, 892-911 (1998), the entire contents of which are hereby incorporated by reference. Tables 1-6 compare ion beam characteristics for a three-stage ion source substantially as illustrated in FIG. 1 with a two-stage ion source (i.e., the source configuration of FIG. 1 operated without a potential on the third electrode). The data of Tables 1-6 was calculated using SIMION (v7.0, Idaho National Engineering and Environmental Laboratory) with the input parameters: d1 580 equaled 2 mm, d2 582 equaled 13.675 mm and, d3 584 equaled 3.175 mm, initial ion velocity equaled 300 m/s. Tables 1-6 compare ion beam divergence a (i.e., the angular deviation of the ion beam α at the source exit 586) (column 5) and the ion beam radial position (e.g., x or y) at two z positions, the source exit 588 (column 3) and at 74.4 mm 590 (column 4), for ions formed with various initial velocity vectors angles (column 1) with respect to the normal to the surface of the sample support. Column 2 lists the potential applied to the third electrode, the zero potential data corresponding in this case to two-stage operation of the ion source. Tables 1-3 compare results for ions formed at the origin 575 with initial velocity vectors at 0, 15, 30 and 45 degrees with respect to the normal to the surface of the sample support. Tables 4-6 compare results for ions formed at +50 microns in the y direction initial velocity vectors at 0, 15, 30 and 45 degrees with respect to the normal to the surface of the sample support. Tables 1-6 also compare ion beam characteristics for three operation modes, linear TOF, ion mirror TOF, and MS/MS TOF where the ion source was operated to provide a velocity space focus plane. Tables 1 and 4 present results for linear TOF mode operation with a 20 kV potential on the sample support and a 19.1 kV potential on the first electrode, and where the time delay for delayed extraction was 370 ns. Tables 2 and 5 present results for ion mirror TOF mode operation with a 20 kV potential on the sample support and a 16 kV potential on the first electrode, and where the time delay for delayed extraction was 600 ns. Tables 3 and 6 present results for MS/MS TOF mode operation with a 8 kV potential on the sample support and a 7.3 kV potential on the first electrode, and where the time delay for delayed extraction was 460 ns. It is to be understood that although electrical potentials are given in Tables 1-6, that the absolute values of the potentials are not critical to the present teachings. Further, it is to be understood that although various electrical potentials are noted as zero or ground, this is purely for convenience of notation and conciseness in the equations appearing herein. One of skill in the art will readily recognize that it is not necessary to the present teachings that the potential at an electrode be at a true earth ground electrical potential. For example, the potential at the electrode can be a “floating ground” with an electrical potential significantly above (or below) true earth ground (e.g., by thousands of volts or more). Accordingly, the description of an electrical potential as zero or as ground herein should not be construed to limit the value of an electrical potential with respect to earth ground in any way. TABLE 1Linear TOF, On AxisInitial IonThirdIon BeamIon BeamTrajectoryElectrodeRadialRadialSpreadAnglePotentialPosition (mm)Position (mm)Angle(degrees)(V)Source Exitz = 74.4 mmα (degrees)2 Stage 000001500.05030.0123−0.0293000.08960.0257−0.0494500.10650.0297−0.0593 Stage 044000001544000.06790.0645−2.62 × 10−3 3044000.10810.11323.93 × 10−34544000.12660.13073.16 × 10−3 TABLE 2Ion Mirror TOF, On AxisInitial IonThirdIon BeamIon BeamTrajectoryElectrodeRadialRadialAnglePotentialPosition (mm)Position (mm)Spread Angle(degrees)(V)Source Exitz = 74.4 mmα (degrees)2 Stage 000001500.14210.44760.2353000.24110.77070.4084500.27410.88510.4713 Stage 01310000015131000.15280.16569.86 × 10−330131000.26610.28120.01645131000.31140.32460.01 TABLE 3MS/MS TOF, On AxisInitial IonThirdIon BeamIon BeamTrajectoryElectrodeRadialRadialAnglePotentialPosition (mm)Position (mm)Spread Angle(degrees)(V)Source Exitz = 74.4 mmα (degrees)2 Stage 000001500.11740.27440.1213000.19950.4740.2114500.23110.5450.2423 Stage 049000001549000.15280.16569.86 × 10−33049000.26610.28120.0164549000.31140.32460.01 TABLE 4Linear TOF, Off AxisInitial IonThirdIon BeamIon BeamTrajectoryElectrodeRadialRadialAnglePotentialPosition (mm)Position (mm)Spread Angle(degrees)(V)Source Exitz = 74.4 mmα (degrees)2 Stage 000.0147−0.1042−0.1191500.0624−0.0933−0.123000.1033−0.0798−0.1414500.1169−0.0757−0.1483 Stage 044000.0213−0.0662−0.0671544000.08340.00326.20 × 10−23044000.13170.0461−0.0664544000.15230.0638−0.068 TABLE 5Ion Mirror TOF, Off AxisInitial IonThirdIon BeamIon BeamTrajectoryElectrodeRadialRadialAnglePotentialPosition (mm)Position (mm)Spread Angle(degrees)(V)Source Exitz = 74.4 mmα (degrees)2 Stage 000.08510.23880.1181500.21940.68690.363000.32411.00620.5254500.3541.11270.5843 Stage 0131000.09940.0707−0.02215131000.25580.2283−2.10 × 10−230131000.36020.3412−0.01545131000.40370.3885−0.012 TABLE 6MS/MS TOF, Off AxisInitial IonThirdIon BeamIon BeamTrajectoryElectrodeRadialRadialAnglePotentialPosition (mm)Position (mm)Spread Angle(degrees)(V)Source Exitz = 74.4 mmα (degrees)2 Stage 000.04540.0242−0.0161500.16030.29530.1043000.24340.49160.1914500.27520.56630.2243 Stage 049000.06370.0128−0.0391549000.21640.1738−3.30 × 10−23049000.32830.2869−0.0324549000.36920.3304−0.03 A comparison of the data shows that the angular spread in the ion beam is about an order of magnitude or more lower for the three-stage ion source relative to the two-stage source for all operation modes. In Tables 1-6 the differences tend to be more pronounced for ions formed off the ion optical axis and for ion mirror TOF mode operation. Referring to FIG. 6, in various embodiments a three-field ion source 600 comprises a sample support 602, a first electrode 604, a second electrode 606, and a third electrode 608. A variety of electrode shapes and configurations can be used including, but not limited to, plates, grids, cones, and combinations thereof. For example, the first electrode can be in the form of a skimmer, having a conical portion 609. Sample ions can be generated by irradiating a sample 610 disposed on a sample surface 612 of the support 602 with a pulse of energy and sample ion energy established by selecting the potential difference between the surface 612 and the third electrode 608. An insulating layer can be interposed between the sample and sample surface. A power source 614, electrically coupled to each of the sample surface 612, first electrode 604, second electrode 606, and third electrode 608, is configured to establish a non-extracting electrical field in a first region 620 that does not substantially accelerate sample ions of interest in a direction away from the sample surface. In various embodiments, the non-extracting electrical field can be a retardation field that retards the motion of the sample ions of interest in a direction away from the sample surface. The power source can, for example, establish an retardation electrical field by applying a first electrical potential to the sample surface and a second electrical potential to the first electrode where: (a) the first electrical potential is more negative than the second electrical potential when the sample ions of interest are positive ions; and (b) the first electrical potential is more positive than the second electrical potential when the sample ions of interest are negative ions. In various embodiments, the non-extracting electrical field can be a substantially zero electrical field, e.g., a substantially electrical field free region is established. An electrical potential applied to one or more of the sample surface, first electrode, and second electrode to establish a non-extracting electrical field can be a zero potential. The power source is also configured to establish at least in a first region 620 a first extraction electric field at a predetermined time that accelerates sample ions of interest in a first direction 623 away from the sample surface and establish across one or more of the second region 622 and a third region 624 a spatial focus electrical field(s) that spatially focuses sample ions of interest in a direction substantially perpendicular to the first direction 623. The power source can, for example, establish the first extraction electric field by changing the potential on one or more of the sample surface 612, the first electrode 604 and the second electrode 606. An electrical potential applied to one or more of the sample surface, first electrode, second electrode, and third electrode to establish one or more of the first extraction electrical field and the spatial focus electrical field(s) can be a zero potential. For example, when the sample ions of interest are positive ions the power source can establish a first extraction electrical field by changing the electrical potential on one or more of the sample surface and the first electrode, such that the electrical potential of the sample surface is more positive than the electrical potential of the first electrode; and can establish a second extraction electrical field by establishing a potential difference between the second and third electrodes where the electrical potential on the second electrode is more positive than the electrical potential on the third electrode. For example, when the sample ions of interest are negative ions the power source can establish a first extraction electrical field by changing the electrical potential on one or more of the sample surface and the first electrode, such that the electrical potential of the sample surface is more negative than the electrical potential of the first electrode; and can establish a second extraction electrical field by establishing a potential difference between the second and third electrodes where the electrical potential on the second electrode is more negative than the electrical potential on the third electrode. The power source can comprise a single device, multiple stand-alone devices, multiple integrated devices, or combinations thereof. For example, a power source can comprise a first power supply electrically coupled to the sample support and the first electrode, a second power supply electrically coupled to the first electrode and the second electrode, and a third power supply electrically coupled to the second electrode and the third electrode. The power source can be, for example, manually controlled, electronically controlled, and/or programmable. The term “power source” is used herein to facilitate concise description and is not intended to be limiting. The term “power source” as used herein is not intended to imply that the power source necessarily comprises a single device or that where the power source comprises multiple devices that the sample support, first, second and third electrodes are each electrically coupled to each of the multiple devices. For example, referring again to FIG. 6, in various embodiments a power source 614 can comprise multiple power supplies 650, 652. The power source can be electrically coupled to another power supply, for example, to provide an electrical potential reference, such as, e.g., a floating ground. In various embodiments, a three-stage ion source of the present teachings includes an optical system configured to irradiate a sample on the sample surface of a sample support with a pulse of laser energy. In various embodiments, the optical system can comprise a lens or window. The optical system can also comprise a mirror or prism to direct the pulse of laser energy onto the sample. In various embodiments, the optical system is configured to substantially align the pulse of laser energy with the direction of ion extraction. Referring again to FIG. 6, in various embodiments, the three-stage ion source includes a temperature-controlled surface 660 disposed about at least a portion of the source, and a heater system 670 connected to and capable of heating one or more of the first, second and third electrodes. In some embodiments, the heater system 670 is connected to all the elements of the ion source about which the temperature-controlled surface 660 is disposed, the ion optic elements in the path of the neutral beam, or both. In various embodiments, the heater system 670 is connected to the first electrode 604, the second electrode 606, and the third electrode 608. In various embodiments, a heater system 670 is used to raise the temperature of one or more elements of the ion source to decrease the amount of neutrals deposited on elements of the source. The amount of neutral deposition can be reduced by heating elements of the ion source to, for example, decrease the sticking probability of neutrals on the heated surfaces, volatizing deposits, or both. In various embodiments, a temperature-controlled surface 660 is held at a temperature lower than that of one or more elements of the ion source and is used to capture neutral molecules and prevent their deposition on other surfaces. In various embodiments, the temperature-controlled surface is configured and used to capture neutral molecules and thereby reduce the amount of neutrals deposited on elements of the ion source. The amount of neutral deposition on the ion optics can be reduced by setting the temperature of the temperature-controlled surface lower than that of the elements of the ion source to, for example, increase the sticking probability of neutrals on the temperature controlled surface, capture desorbed neutrals, or both. In various embodiments, one or more the elements of the ion source are heated such that matrix molecules do not substantially stick to these elements; thereby reducing the buildup of insulating layers on these elements. The neutral plume generated in MALDI can contain a small amount of nonvolatile non-matrix material that can also build up an insulating layer, but the concentration of this non-matrix material is generally several orders of magnitude lower than that of the matrix. This generally results in a much longer time before non-matrix material deposits become significant. In addition, in various embodiments, heating an ion source element surface generally reduces the resistivity of such deposits and thus further facilitates diminishing the effect of asymmetric charging deflecting the ion beam. In various embodiments, the heater system includes a heater capable of heating the elements of the ion source which are heated to a temperature sufficient to desorb one or more the matrix materials listed in Table 7. The right column of Table 7 lists some of the typical uses for the associated matrix material in MALDI studies. TABLE 7Matrix MaterialTypical Uses2,5-dihydroxybenzoic acid (2,5-Peptides, neutral or basicDHB) MW 154.03 Dacarbohydrates, glycolipids, polarand nonpolar synthetic polymers,small moleculesSinapinic AcidPeptides and Proteins >MW 224.07 Da10,000 Daa-cyano-4-hydroxy cinnamic acidPeptides, proteins and PNAs <(aCHCA)10,000 DaMW 189.04 Da3-hydroxy-picolinic acid (3-HPA)Large oligonucleotides >MW 139.03 Da3,500 Da2,4,6-Trihydroxy acetophenoneSmall oligonucleotides < 3,500(THAP)Acidic carbohydrates, acidicMW 168.04 DaglycopeptidesDithranolNonpolar synthetic polymersMW 226.06 DaTrans-3-indoleacrylic acid (IAA)Nonpolar polymersMW 123.03 Da2-(4-hydroxyphenylazo)-benzoic acidProteins, Polar and nonpolar(HABA)synthetic polymersMW 242.07 Da2-aminobenzoic (anthranilic) acidOligonucleotides (negative ions)MW 137.05 Da In various embodiments, the heater system can raise the temperature of the elements of the ion source which are heated to a temperature sufficient to desorb matrix material. In various embodiments, the one or more of the elements of the ion source are heated periodically to a sufficiently high temperature to rapidly vaporize any deposits on the surfaces of these elements. In various embodiments, a “blank” or “dummy” sample support is substituted for the MALDI sample support so that the deposits formed, for example, on or more elements of the ion source can be redeposited on the blank (which can be removed from the instrument), the temperature-controlled surface, or both. In various embodiments, a three-stage ion source of the present teachings includes a fourth electrode. In some embodiments, the fourth electrode is a substantially planar plate or grid that is substantially parallel to the third electrode. The fourth electrode can be an apertured electrode that is a substantially planar plate or grid. In various embodiments, the fourth electrode is positioned so the centers of the apertures of the second and third apertured electrodes substantially fall on a common axis. In various other embodiments, the fourth electrode is positioned off the axis running through the centers of the apertures in the second and third electrodes. In various embodiments where the fourth electrode is positioned off the axis running through the centers of the apertures in the second and third electrodes, the fourth electrode is positioned such that neutral molecules traveling from the sample support along the extraction direction do not substantially collide with the fourth electrode. In various embodiments, a three-stage ion source of the present teachings includes a first ion deflector positioned to deflect sample ions in a direction different from the extraction direction. In various embodiments, the first ion deflector is positioned between the third electrode and a fourth electrode. In various embodiments, a fourth electrode is positioned off the axis running through the centers of the apertures in the second and third electrodes such that the fourth electrode can receive deflected sample ions; and in some embodiments, the fourth electrode is positioned such that it facilitates directing sample ions into a mass analyzer. Ion generation by MALDI produces a plume of neutral molecules in addition to ions. In various embodiments, a portion of this neutral plume passes through apertures in one or more electrodes and forms essentially a cone with an axis substantially along the extraction direction. The size of the aperture in the last electrode and the distance between the last electrode and the sample surface determines the half-angle δ of the cone about the neutral beam axis that travels beyond the last electrode. In various embodiments where an ion optical element (such as, for example, a fourth electrode) is positioned off the axis running through the centers of the apertures in the second and third electrodes, these ion optical elements can be positioned such that neutral molecules in the neutral beam do not substantially collide with the off-axis ion optical element. In various embodiments, such an off-axis ion optical element is positioned a distance L away from the neutral beam axis in a direction perpendicular to the neutral beam axis. In various embodiments, the off-axis optical element is positioned at a distance L such that the neutral beam intensity at L is at least less than: 14 percent of the neutral beam intensity at the neutral beam axis; 5 percent of the neutral beam intensity at the neutral beam axis; or 1 percent of the neutral beam intensity at the neutral beam axis. In various embodiments, the off-axis ion optical element is positioned such that L is at least a distance Lmin away where Lmin can be determined by,Lmin=Dz tan(δ), (1)where Dz is the distance in the extraction direction between the off-axis ion optical element and the sample surface, and δ is the half-angle of the neutral beam cone that travels beyond the last element that determines the half-angle δ of the neutral beam cone. FIGS. 7A and 7B depict substantially to scale views of a MALDI-TOF system 700 incorporating various embodiments of a three-stage ion source of the present teachings. FIG. 7A depicting a front sectional view and FIG. 7B a side sectional view. To facilitate the viewing of FIGS. 7A-7B, the system 700 can be oriented such that the floor is in direction 701, the ceiling in direction 702, and the “front” of the instrument can be considered to be from viewpoint 703. FIG. 7C depicts an expanded view of a portion of FIG. 7A. The various embodiments illustrated by FIGS. 7A-7C are not intended to be limiting. For example, a MALDI-TOF system incorporating an ion source of the present teachings can comprise fewer system components than illustrated or more system components than illustrated in FIGS. 7A-7C. In addition, the MALDI-TOF systems incorporating an ion source of the present teachings are not necessarily limited to the arrangement of the parts illustrated in FIGS. 7A-7C; rather, the illustrated arrangements are but some of the many modes of practicing the present teachings. Referring to FIGS. 7A-7C, the illustrated system comprises a sample support handling system 705 comprising a vacuum lock chamber 706, through which sample supports can be loaded and removed, and a sample support transfer mechanism 708 configured to transport sample supports from the vacuum lock chamber 706 to an ion source region 720. The sample support transfer mechanism can comprise a translation mechanism for translating the sample support in one or more dimensions within the ion source region to, for example, facilitate the serial analysis of two or more samples on the sample support. In some embodiments, the translation mechanism comprises an x-y (two dimensions) translational stage. Referring to FIG. 7C, the ion source region 720 can comprise a three-stage ion source in accordance with the present teachings comprising a sample support 722 having a sample surface 724, a first electrode 726 spaced a part from the sample support 722, a second electrode 728 spaced apart from the first electrode 726 in a direction opposite the sample support 722, and a third electrode 730 spaced apart from the second electrode 728 in a direction opposite the first electrode 726. In various embodiments, a three-stage ion source can provide an ion beam where the angle of the trajectory at the exit from an acceleration region of the ion source of sample ions substantially at the center of the ion beam is substantially independent of sample ion mass. In some embodiments, such a trajectory is provided by irradiating a sample on a sample surface of a sample support with a pulse of laser energy at an irradiation angle substantially normal to the sample surface and extracting the sample ions in a direction substantially normal to the sample surface to form the ion beam. In various embodiments, the pulse of energy is substantially coaxial with a first ion optical axis substantially parallel to the extraction direction. Examples of irradiation of a sample with a pulse of laser energy at an irradiation angle substantially normal to the sample surface and extraction of the sample ions in a direction substantially normal to the sample surface can be found in U.S. application Ser. No. 10/700,300 filed Oct. 31, 2003, the entire contents of which are herein incorporated by reference. The system illustrated in FIGS. 7A-7B can be operated in various modes, such as, e.g., linear TOF operation, ion mirror (reflectron) TOF operation, and MS/MS TOF operation. In linear TOF operational mode, ions produced in the ion source region 720 can be extracted (by electrical fields established by one or more ion source electrodes) into a first region substantially free of electrical fields (a first substantially field free region) 740 and drift to a first detector 742. It is to be understood that substantially field free region does not necessarily imply zero-electrical potential rather a substantially constant potential across the region. In linear TOF mode, no gas is added to the collision cell 750 and the ion mirror 760 is off. In linear TOF mode, the time focus plane of the ion source is typically set to coincide with the first detector 742. In ion mirror (reflectron) mode, ions produced in the ion source region 720 can be extracted (by electrical fields established by one or more ion source electrodes) into the first substantially field free region 740, drift to the ion mirror 760 and are reflected to a second detector 762. As in linear TOF mode, no gas is added to the collision cell 750 in ion mirror TOF mode. In ion mirror TOF mode, the time focus plane of the ion source is typically set to coincide with the focal plane of the ion mirror 760. As a result, the desired position of the time focal plane in ion mirror TOF mode is closer to the ion source than in linear TOF mode operation. In MS/MS TOF mode, ions produced in the ion source region 720 can be extracted (by electrical fields established by one or more ion source electrodes) into the first substantially field free region 740 and drift to a timed ion selector 770 that selects the parent ion m/z range transmitted to an ion fragmentor (here comprising a collision cell 750) by deflecting away ions outside this m/z range. In MS/MS TOF mode the collision cell 750 can be filled with an appropriate collision gas to fragment parent ions by collision induced dissociation (CID) and produce fragment ions. In various embodiments, fragment ions can be produced from unimolecular dissociation of sample ions, e.g., such unimolecular processes becoming more likely with increasing ion fluence. Fragments ions can be extracted by electrical fields established by one or more exit electrodes into another substantially field free region 772 and fragment ions can be, e.g., analyzed using the ion mirror 760 and detected using the second detector 762, or analyzed without using the ion mirror 760 and detected using the first detector 742. In MS/MS TOF mode, the time focus plane of the ion source is typically set to coincide with the timed ion selector 770. As a result, the desired position of the time focal plane in MS/MS TOF mode is closer to the ion source than in either ion mirror or linear TOF modes of operation. In various embodiments, a three-stage ion source includes an optical system configured to irradiate a sample on the sample surface 724 of a sample support 722 with a pulse of laser energy 780 at angle substantially normal to the sample surface. In various embodiments, the optical system can comprise a window 782 and a prism or mirror 784 to direct the pulse of laser energy onto the sample. The pulse of laser energy can be provided by a laser system 790, for example, by a pulsed laser or continuous wave (cw) laser. The output of a cw laser can be modulated to produce pulses using, for example, acoustic optical modulators (AOM), crossed polarizers, rotating choppers, and shutters. Any type of laser of suitable irradiation wavelength for producing sample ions of interest by MALDI can be used with the ion sources and mass analyzer systems of the present invention, including, but not limited to, gas lasers (e.g., argon ion, helium-neon), dye lasers, chemical lasers, solid state lasers (e.g., ruby, neodinium based), excimer lasers, diode lasers, and combination thereof (e.g., pumped laser systems). In various embodiments, a three-stage ion source is configured to extract sample ions in a direction substantially normal to the sample surface. In FIGS. 7A-7C, the ion source includes a first apertured electrode 726 and a second apertured electrode 728. The line between the center of the aperture in the first electrode and the center of the aperture in the second electrode can be used to define a first ion optical axis 792. Accordingly, in various embodiments, a three-stage ion source is configured such that the pulse of radiation and first ion optical axis are substantially coaxial and, in various embodiments, such that the pulse of radiation and first ion optical axis are substantially coincident. In various embodiments, the aperture in the first electrode is substantially centered on the sample being irradiated by moving the sample support 722. In some embodiments, the sample support 722 is held by a sample support transfer mechanism 794 capable of one-axis translational motion, x-y (2 axis) translational motion, or x-y-z (3 axis) translational motion to position a sample for irradiation. Where the aperture in the first electrode is substantially centered on the sample being irradiated and the first apertured electrode is substantially symmetric about the normal to the sample surface, the extraction direction will be substantially normal to the sample surface. In some embodiments, the sample support is capable of holding a plurality of samples. Suitable sample supports include, but are not limited to, 64 spot, 96 spot and 384 spot plates. The sample includes a matrix material that absorbs at a wavelength of the pulse of laser energy and which facilitates the desorption and ionization of molecules of interest in the sample. In various embodiments, a three-stage ion source includes a temperature-controlled surface disposed about at least a portion of the ion source, and a heater system 795 connected to one or more of the first electrode 726, the second electrode 728, the third electrode 730, and a first ion deflector 796. In some embodiments, the heater system is connected to all the ion source elements about which the temperature-controlled surface is disposed, the ion optic system elements in the path of the neutral beam, or both. In various embodiments, a first ion deflector 796 is positioned between the third electrode 730 and a fourth electrode 797 to deflect sample ions in a direction different from the extraction direction and onto a second ion optical axis 798. A tube or other suitable structure 799 can be used, for example, to shield the sample ions from stray electrical fields, maintain electrical field uniformity, or both, after deflection. In various embodiments, such a structure 799 can serve as a temperature-controlled surface, can be connected to a heater system, or both. A three-stage ion source of the present teachings may be used with a wide variety of mass analyzers and mass analyzer systems. The mass analyzer can be a single mass spectrometric instrument or multiple mass spectrometric instruments, employing, for example, tandem mass spectrometry (often referred to as MS/MS) or multidimensional mass spectrometry (often referred to as MSn). Suitable mass spectrometers, include, but are not limited to, time-of-flight (TOF) mass spectrometers, quadrupole mass spectrometers (QMS), and ion mobility spectrometers (IMS). Suitable mass analyzers systems can also include ion reflectors and/or ion fragmentors. Examples of suitable mass analyzers and suitable ion fragmentors also include, but are not limited to, those described elsewhere herein. Examples of suitable ion fragmentors include, but are not limited to, collision cells (in which ions are fragmented by causing them to collide with neutral gas molecules), photodissociation cells (in which ions are fragmented by irradiating them with a beam of photons), and surface dissociation fragmentors (in which ions are fragmented by colliding them with a solid or a liquid surface). Ion Optics In various aspects, the present teachings provide methods for focusing ions for an ion fragmentor and methods for operating an ion optical assembly comprising an ion fragmentor. In various embodiments, the present teachings provide methods that substantially maintain the position of the focal point of the an incoming ion beam over a wide range of collision energies, and thereby provide a collimated ion beam for a collision cell over a wide range of energies. Referring to FIGS. 8A and 9, in various embodiments, an ion optics assembly 800, 900 comprises a first ion lens 805, 905 disposed between a retarding lens 810, 910 and a collision cell 815, 915. The first ion lens is also referred to herein as a “focus lens” because in various embodiments a radial focal point exists for the ion beam within the first lens. The retarding lens 810, 910 and the focus lens 805, 905 can be composed of multiple lens elements, e.g., electrodes. A variety of electrode shapes and configurations can be used including, but not limited to, plates, grids, cones, and combinations thereof. The ion optics assembly can include a timed ion selector 907 for selecting sample ions for transmittal to the collision cell. The retarding lens and focus lens can share lens elements. For example, in various embodiments, the retarding lens 810, 910 comprises a first electrode 822, 922, a second electrode 824, 924, and a third electrode 826, 926, and the focus lens 805, 905 comprises the third electrode 826, 926, a fourth electrode 828, 928 and a fifth electrode 830, 930. In various embodiments, various electrodes are at substantially the same potential; for example, in various embodiments, the fifth electrode is at substantially the same potential as the collision cell entrance; in various embodiments, the first electrode is at substantially the same electrical potential as the second electrode; and in various embodiments, the third electrode is at substantially the same electrical potential as the fifth electrode. Referring to FIG. 8B, a schematic plot of electrical potential 832 as a function of the direction D 834 along an ion optic axis 835 of the ion optic assembly is illustrated. It should be understood that the absolute and relative values of the electrical potential are not to scale, FIG. 8B being only intended to illustrate whether the electrical potential increases or decreases as one proceeds in the direction D. Further, it should be understood that by typical convention, the electrical potential plot is drawn for the case where the sample ions of interest are positive ions, but that an illustration for negative ions can be had where the electrical potential is viewed as decreasing in the direction V 832. Referring to FIGS. 8A-9, in various aspects, the present teachings comprise methods for focusing sample ions formed at a source electrical potential. In various embodiments, the methods establish a first electrical field (a decelerating electrical field) with the retarding lens 810, to decelerate incoming sample ions, by applying a first electrical potential to an electrode of the retarding lens; establish a second electrical field (an accelerating electrical field) between the retarding lens 810 and the first ion lens 805 to accelerate sample ions away from the retarding lens and into the first ion lens by applying a second electrical potential to an electrode of the first ion lens; and establish a third electrical field (a decelerating electrical field) between the first ion lens 805 and the entrance 837 to the collision cell to decelerate sample ions prior to entry into the collision cell, by applying a third electrical potential to the entrance of the collision cell. For example, in various embodiments, a decelerating electrical potential can be applied to the retarding lens 810 by applying to one or more of a first electrode 822 and the second electrode 824 a decelerating electrical potential. For example, positive sample ions entering the retarding lens from a region with at an entry potential 840 (e.g., the electrical potential of a proceeding drift region, ion optical element, etc.) encounter a decelerating potential when the electrical potential of the first electrode 842 and/or the electrical potential of the second electrode 844 is greater than the entry potential 840. Although the electrical potentials on the first and second electrodes are illustrated as different in FIG. 8B, they can be the same. An accelerating electrical potential difference for positive sample ions can be established between the retarding lens 810 and first ion lens 805 by applying an electrical potential 846 to an electrode 828 of the first ion lens which is less than the potential 844 on the retarding lens. A decelerating electrical potential difference for positive sample ions can be established between the first ion lens 805 and the entrance 837 to the collision cell, by applying an electrical potential 848 to the entrance of the collision cell that is greater than the first ion lens potential 846. In various embodiments, various electrodes are at substantially the same potential; for example, in various embodiments, the third electrode, the fifth electrode and the collision cell entrance are at substantially the same electrical potential 848. In various embodiments, sample ions are substantially focused to a focal point a distance F from an entrance 852 to the retarding lens 810, 910. In various embodiments, the methods maintain the focal point of a collimated input ion beam at substantially the same position in the ion optic assembly over a range of collision energies by changing the electrical potential on the focus lens 805. In various embodiments, when the difference between a first collision energy and a second collision energy is less than about 5000 electron volts, the distance F varies within less than about: (a) ±4%; (b) ±2%; and/or (c) ±1%. Table 8 presents data on the position of the focal point at two different collision energies 500 electron volts (eV) and 1000 eV for a collimated input ion beam with an input diameter 860 focused to a focal point a distance F from the entrance 852 and forming a collimated ion beam 862 with an output diameter 864. In FIG. 8A, electrical potentials applied to an ion optical element 870 after the collision cell 815. Referring to Table 8, it can be seen that the calculated position of the focal point changes by less than 1% upon changing the collision energy from 500 eV to 1000 eV and changing the electrical potentials on the retarding lens 810 and the focus lens in accordance with the present teachings. Table 9 and FIG. 10A present data on the calculated electrical potentials for application to the retarding lens 810 and the focus lens 805 which maintain the focal point at a distance F substantially equal to 34 mm over a range of collision energies in accordance with various embodiments of the present teachings. Table 10 and FIG. 10B present data on the calculated electrical potentials for application to the retarding lens 810 and the focus lens 805 which maintain the focal point at a distance F substantially equal to 34 mm over a range of collision energies in accordance with various embodiments of the present teachings where the focal point is maintained substantially at the distance F=34 mm by substantially maintaining the electrical potential on the retarding ion lens 810 and changing the electrical potential on the first ion lens 805. For example, for the 500 eV collision energy data the retarding ion lens potential (6200 V) is within less than 2.5% of potential applied (6350 V) at the other collision energies. The data of Tables 8, 9 and 10 and FIGS. 10A and 10B was calculated using SIMION (v7.0, Idaho National Engineering and Environmental Laboratory) where input and output parameters are listed in the tables. Tables 9 and 10, respectively, provide the values plotted in FIGS. 10A and 10B. The structure used for the SIMION calculations was substantially that shown in FIG. 8A, where the structural elements are substantially to scale. Estimates of the absolute size of the structure in FIG. 8A can be made by noting that the distance between the entrance to the first electrode 822 and the focal point distance F is about 34 mm as illustrated in FIG. 8A. It is to be understood that although electrical potentials are given in Tables 8-10 and FIGS. 10A-10B, that the absolute values of the potentials are not critical to the present teachings. Further, it is to be understood that where various electrical potentials are noted as zero or ground, this is purely for convenience of notation and conciseness herein. One of skill in the art will readily recognize that it is not necessary to the present teachings that the potential at an electrode be at a true earth ground electrical potential. For example, the potential at the electrode can be a “floating ground” with an electrical potential significantly above (or below) true earth ground (e.g., by thousands of volts or more). Accordingly, the description of an electrical potential as zero or as ground herein should not be construed to limit the value of an electrical potential with respect to earth ground in any way. TABLE 8Focal Point Position and Ion Beam Diameter1000 eV500 eVCollisionCollisionEnergyEnergymass (Da)10001000source potential (V)80007500retarding lens: second electrode potential (V)63005750focus lens: fourth electrode potential (V)35005250collision cell entrance potential (V)70007000retarding focal point F (mm)34.034.3ion beam diameter at entrance (mm)2.12.1ion beam diameter at exit (mm)3.84.3 TABLE 9Source Potential Varied, Collision Cell Potential Constant at 7000 VRetarding LensFocus LensCollisionSecond ElectrodeFourth ElectrodeEnergy (eV)Source Potential (V)Potential (V)Potential (V)50075005750525010008000630035001500850067002000200090007100500250095007500−15003000100007875−3000 TABLE 10Source Potential Constant at 8000 V, Collision Cell Potential VariedCollision CellRetarding LensFocus LensCollisionEntranceSecond ElectrodeFourth ElectrodeEnergy (eV)Potential (V)Potential (V)Potential (V)50075006200570010007000635035001500650063501500200060006350−500250055006350−2500300050006350−4500Ion Optical Assemblies In various aspects, the present teachings provide ion optical assemblies with features that facilitate the alignment of ion optical elements. Referring to FIGS. 11 and 12, in various embodiments, an ion optics assembly 1100, 1200 of the present teachings comprises a mounting body 1105, 1205, a first plurality of ion optical elements 1110, 1210, a front member 1114, 1214, a front securing member 1118, (obscured by the front member in FIG. 12), second plurality of ion optical elements 1120, 1220, a back member 1124, 1224, and a back securing member 1128, 1228. The front member 1114, 1214 and back member 1124, 1224 are attached to the mounting body 1105 by at least one attachment member 1130, 1230. The end members (front member 1114, 1214 and back member 1124, 1224) are threaded such that when their associated securing members (front 1118 and back 1128, 1228, respectively) are engaged in them, a contact face of the securing member can contact an ion optical element of the associated plurality of elements (e.g., a front member contact face 1140 contacting an element 1142 of the first plurality, and a back member contact face 1144 contacting an element 1146 of the second plurality) and apply a compressive force against the plurality of ion optical elements. In various embodiments, each ion optical element comprises a recess structure adapted to receive a complimentary registration structure, the registration structure aligning an ion optical element with respect its neighbors when said registration structure is registered in the complimentary recess structure when a compressive force is applied by the respective securing member. For example, a recess structure 1150 can comprise, e.g., a slot, counter-bore, hole, etc., configured to receive a complimentary registration structure, e.g., a pin, spacer, etc., a recess structure 1152 can comprise a first surface intersecting the face of the ion optical element to form, e.g., a corner on the face of the element against which a neighboring ion optical element can register. In various embodiments, a registration structure can serve as a spacer 1154 (which can be electrically insulating) to properly space ion optical elements. In various embodiments, the registration structure is provided by the shape of the ion optical element, such as, e.g., a corner 1156 that can register against a corner on the face of a neighboring element. In the present teachings, ion optical elements are aligned by applying a compressive force with the respective securing member. The compressive force is applied by engaging the thread on the securing member with those on the respective end member. As used herein, the terms “threads” and “threaded” include, but are not limited to helical ridges, spiral ridges and circular ridges. Accordingly, these terms include, but are not limited to, parallel ridges that form complete circles or segments of a complete circle. The ridges can be continuous or interrupted. For example the ridges can be cut to facilitate pumping out gas trapped or out gassed in these spaces. In various embodiments where the threads comprise helical or spiral ridges, the securing member can be screwed into the respective end member to apply the compressive force. In various embodiments where the threads comprise circular ridges, the securing member is pushed into the respective end member (e.g., providing a snap fit) to apply the compressive force. In various embodiments, the securing members are self locking, which can, e.g., help prevent an ion optics lens stack from loosening due to shipping or instrument vibration. In various embodiments, the securing members are self-locking when a pre-selected torque is applied. In various embodiments, the securing members are self-locking when pushed in (e.g., giving a snap fit), which can also include turning the securing member, e.g., to rotate a structure on securing member (which passed through a cut in a thread when pushed in) to a position behind a thread, locking the securing member in place. The end members can be attached to the mounting body by any suitable means. The attachments can be permanent or reversible. FIG. 11 provides a non-limiting example of one attachment means, but those of ordinary skill in the art will recognize that many other means are available. For example, in various embodiments, the end members are attached using threaded rods one end of which is pushed or screwed into the mounting body and another which is attached to the end member by means of bolts. In various embodiments, the mounting body comprises a region for performing ion fragmentation. For example, in various embodiments, the mounting body comprises a collision cell 1170 having, e.g., a channel 1172 for the provision of a collision gas, and an opening 1176 for fluid communication with a vacuum pump. In various embodiments, the alignment of the ion optical elements by compressing them with the securing members, as described in the present teachings, can simplify the alignment and assembly of ion optical elements. In the present teachings, no torque pattern is required to compress and align the ion optical elements. In various embodiments, the securing members can lock the ion optics elements in place, so no additional parts are required to secure the ion optic assembly for shipping. In various aspects, the present teachings provide systems for mounting and aligning ion optic components. Referring to FIG. 12, in various embodiments, a mounting and aligning system comprises a mounting base 1240 having a mounting surface 1242 and a back surface 1244 opposite the mounting surface. A plurality of pairs of protrusions 1250 protrude from the mounting surface 1242, one or more mounting structures 1252 are associated with each pair of protrusions and at least one electrical connection element 1254 is associated with each pair of protrusions, where the element connection elements pass through the mounting base from the back surface to the mounting surface. The system also comprises two or more ion optic component supports 1260, each ion optic component support having a pair of recesses configured to receive one or more of the plurality of pairs of protrusions (the general location of each recess on the face of ion optic component support brought in contact with the mounting surface is indicated by a dashed line 1262 connecting to the corresponding protrusion). The positions of the pairs of protrusions on the mounting surface and their corresponding recesses are configured such that when the pair of recesses of an ion optic component support is brought into registration with the corresponding pair of protrusions by mounting an ion optic component to the mounting base using the one or more mounting structures associated with the pair of protrusions (e.g., using bolts 1270 to mount into a threaded hole mounting structure 1252), an ion optics component mounted in said ion optic component support is substantially aligned with other ion optics components so mounted and an electrical connection site (e.g., 1280) on said ion optics component is proximate to a corresponding electrical connection element associated with the corresponding pair of protrusions. A wide variety of protrusion and complimentary recess shapes can be used, including but not limited to pins mating to holes and/or slots. In various embodiments, the plurality of pairs of protrusions are configured such that only one orientation of an ion optic component support will enable the pair of recesses of the ion optic component support to be brought into registration with the corresponding pair of protrusions. For example, in various embodiments, unique recess and protrusion patterns can be used to orient an ion optic component support. In various embodiments, the pairs of protrusions are configured to have different shapes for different ion optic components. Mass Analyzer Systems In various aspects, the present teachings provide MALDI-TOF mass analyzer systems. Referring to FIGS. 1A-1D, 2, 3 and 7A-7C, in various embodiments, a mass analyzer system comprises: (a) an optical system 782, 784 configured to irradiate a sample 370 on a sample surface 192, 375 with a pulse of energy 165 such that the pulse of energy strikes a sample on the sample surface at an angle substantially normal to the sample surface; (b) a MALDI ion source 720 of the present teachings; (c) an ion deflector 796 configured to deflect ions from a first ion optical axis 166, 792 along which ions are extracted into the mass analyzer system and onto a second ion optical axis 194, 798; (d) a first substantially field free region 120, 740 positioned between the ion deflector 796 and a timed ion selector 142, 770, the timed ion selector being positioned between the first substantially field free region and a collision cell 144, 750; (e) a second substantially field free region 122 positioned between the collision cell and a first ion detector 125; (f) an ion mirror 130 positioned between the second substantially field free region and the first ion detector; and (g) a third substantially field free region 124 positioned between the ion mirror and a second ion detector 135. The timed ion selector is positioned to receive ions traveling along the second ion optical axis and is configured to select ions for transmittal to the collision cell. In various embodiments, the optical system can comprise a window 782 and a prism or mirror 784 to direct the pulse of laser energy onto the sample. In various embodiments, one or more structures 190 can be provided, for example, to shield the sample ions from stray electrical fields, maintain electrical field uniformity, or both, as they travel from the ion mirror 130 to the second detector 135. In various embodiments, the MALDI ion source 720 comprises a first electrode 726 spaced apart from the sample support 722; a second electrode 728 spaced apart from the first electrode in a direction opposite the sample support holder; and a third electrode 730 spaced apart from the second electrode in a direction opposite the first electrode; where a power source is electrically coupled to the sample support, the first electrode, the second electrode, and the third electrode and configured to: apply a first potential to the sample surface and a second potential to at least one of the first electrode and the second electrode to establish a non-extracting electric field at a first predetermined time substantially prior to striking a sample on the sample surface with a pulse of energy to form sample ions, the non-extracting electrical field substantially not accelerating sample ions in a direction away from the sample surface; change the electrical potential of at least one of the sample surface and the first electrode to establish a first extraction electric field at a second predetermined time subsequent to the first predetermined time, the first extraction electric field accelerating sample ions in a first direction away from the sample surface, the first extraction electric field accelerating sample ions in a first direction away from the sample surface along a first ion optical axis that is substantially coaxial with the pulse of energy; and apply a third potential to the second electrode to focus ions in a direction substantially perpendicular to the first direction. In various embodiments, a mass analyzer system further comprises a vacuum lock chamber 106 and a sample chamber 160 connected to the vacuum lock chamber. A sample support changing mechanism 210 is disposed in the vacuum lock chamber and a sample support transfer mechanism 108 is disposed in the sample chamber. The sample support transfer mechanism configured to extract a sample support from a loading region 220 of the sample support changing mechanism such that the sample support is registered within a frame 310 in the sample support transfer mechanism. The sample support transfer mechanism is mounted on a multi-axis translation stage 112 such that the sample support can be translated to a position where sample ions can be generated by laser irradiation of a sample on the surface of the sample support by a pulse of energy 164 while said sample support is held in the sample support transfer mechanism and the sample support transfer mechanism is in the sample chamber, and said sample ions extracted along the first ion optical axis 166, 792. In various embodiments, the non-extracting electrical field can be a retardation electrical field which retards the motion of sample ions in a direction away from the sample surface. In various embodiments, the non-extracting electrical field can be a substantially zero electrical field, e.g., a substantially electrical field free region is established. A substantially zero electrical field can be established, e.g., when the first potential and the second potential are substantially equal. In various embodiments, a mass analyzer system further comprises one or more temperature controlled surfaces disposed therein. In various embodiments, the timed ion selector 142, 770 and the collision cell comprise 144, 750 portions of an ion optical assembly 195, the ion optical assembly comprising a first plurality of ion optical elements 196 disposed between a front member 197 and a front side of a mounting body 198. The front member is attached to the mounting body by at least one attachment member 199 and the front member has a threaded opening configured to accept a threaded surface of a front securing member. The mounting body contains the collision cell and the timed ion selector comprises at least one of the ion optical elements. The threaded opening of the front member is configured such that when the threaded surface of the front securing member is engaged in the threaded opening of the front member, a contact face of the front securing member can contact an ion optical element of the first plurality and apply a compressive force against the first plurality of ion optical elements. Each ion optical element of the first plurality has a recess structure adapted to receive a complimentary registration structure, a registration structure aligning an ion optical element of the first plurality with respect to at least one other ion optical element of the first plurality when the registration structure is registered in a complimentary recess structure when the compressive force is applied by the front securing member. Ion generation by MALDI produces a plume of neutral molecules in addition to ions. In various embodiments where an ion optical element is positioned off the axis running through the centers of the apertures in the first ion optical axis 166, 792, these optical elements can be positioned such that neutral molecules in the neutral beam do not substantially collide with the off-axis ion optical element. In various embodiments, such an off-axis ion optical element is positioned a distance L away as can be determined by Equation (1). Mass Analyzers A wide variety of mass analyzers may be used with various aspects of the present teachings. The mass analyzer can be a single mass spectrometric instrument or multiple mass spectrometric instruments, employing, for example, tandem mass spectrometry (often referred to as MS/MS) or multidimensional mass spectrometry (often referred to as MSn). Suitable mass spectrometers, include, but are not limited to, time-of-flight (TOF) mass spectrometers, quadrupole mass spectrometers (QMS), and ion mobility spectrometers (IMS). Suitable mass analyzers systems can also include ion reflectors and/or ion fragmentors. Examples of suitable ion fragmentors include, but are not limited to, collision cells (in which ions are fragmented by causing them to collide with neutral gas molecules), photodissociation cells (in which ions are fragmented by irradiating them with a beam of photons), and surface dissociation fragmentors (in which ions are fragmented by colliding them with a solid or a liquid surface). In various embodiments, the mass analyzer comprises a triple quadrupole mass spectrometer for selecting a primary ion and/or detecting and analyzing fragment ions thereof. In various embodiments, the first quadrupole selects the primary ion. The second quadrupole is maintained at a sufficiently high pressure and voltage so that multiple low energy collisions occur causing some of the ions to fragment. The third quadrupole is scanned to analyze the fragment ion spectrum. In various embodiments, the mass analyzer comprises two quadrupole mass filters and a TOF mass spectrometer for selecting a primary ion and/or detecting and analyzing fragment ions thereof. In various embodiments, the first quadrupole selects the primary ion. The second quadrupole is maintained at a sufficiently high pressure and voltage so that multiple low energy collisions occur causing some of the ions to fragment, and the TOF mass spectrometer detects and analyzes the fragment ion spectrum. In various embodiments, a mass analyzer for use with the present teachings comprises two TOF mass analyzers and an ion fragmentor (such as, for example, CID or SID). In various embodiments, the first TOF selects the primary ion for introduction in the ion fragmentor and the second TOF mass spectrometer detects and analyzes the fragment ion spectrum. The TOF analyzers can be linear or reflecting analyzers. In various embodiments, the mass analyzer comprises a time-of-flight mass spectrometer and an ion reflector. The ion reflector is positioned at the end of a field-free drift region of the TOF and is used to compensate for the effects of the initial kinetic energy distribution by modifying the flight path of the ions. In various embodiments ion reflector consists of a series of rings biased with potentials that increase to a level slightly greater than an accelerating voltage. In operation, as the ions penetrate the reflector they are decelerated until their velocity in the direction of the field becomes zero. At the zero velocity point, the ions reverse direction and are accelerated back through the reflector. The ions exit the reflector with energies identical to their incoming energy but with velocities in the opposite direction. Ions with larger energies penetrate the reflector more deeply and consequently will remain in the reflector for a longer time. The potentials used in the reflector are selected to modify the flight paths of the ions such that ions of like mass and charge arrive at a detector at substantially the same time. In various embodiments, the mass analyzer comprises a tandem MS-MS instrument comprising a first field-free drift region having a timed ion selector to select a primary sample ion of interest, a fragmentation chamber (or ion fragmentor) to produce sample ion fragments, a mass analyzer to analyze the fragment ions. In various embodiments, the timed ion selector comprises a pulsed ion deflector. In various embodiments, the second ion deflector can be used as a pulsed ion deflector in versions of this tandem MS/MS instrument. In various embodiments of operation, the pulsed ion deflector allows only those ions within a selected mass-to-charge ratio range to be transmitted to the ion fragmentation chamber. In various embodiments, the mass analyzer is a time-of-flight mass spectrometer. The mass analyzer can include an ion reflector. In various embodiments, the fragmentation chamber is a collision cell designed to cause fragmentation of ions and to delay extraction. In various embodiments, the fragmentation chamber can also serve as a delayed extraction ion source for the analysis of the fragment ions by time-of-flight mass spectrometry. In various embodiments, the mass analyzer comprises a tandem TOF-MS having a first, a second, and a third TOF mass separator positioned along a path of the plurality of ions generated by the pulsed ion source. The first mass separator is positioned to receive the plurality of ions generated by the pulsed ion source. The first mass separator accelerates the plurality of ions generated by the pulsed ion source, separates the plurality of ions according to their mass-to-charge ratio, and selects a first group of ions based on their mass-to-charge ratio from the plurality of ions. The first mass separator also fragments at least a portion of the first group of ions. The second mass separator is positioned to receive the first group of ions and fragments thereof generated by the first mass separator. The second mass separator accelerates the first group of ions and fragments thereof, separates the first group of ions and fragments thereof according to their mass-to-charge ratio, and selects from the first group of ions and fragments thereof a second group of ions based on their mass-to-charge ratio. The second mass separator also fragments at least a portion of the second group of ions. The first and/or the second mass separator may also include an ion guide, an ion-focusing element, and/or an ion-steering element. In various embodiments, the second TOF mass separator decelerates the first group of ions and fragments thereof. In various embodiments, the second TOF mass separator includes a field-free region and an ion selector that selects ions having a mass-to-charge ratio that is substantially within a second predetermined range. In various embodiments, at least one of the first and the second TOF mass separator includes a timed-ion-selector that selects fragmented ions. In various embodiments, at least one of the first and the second mass separator includes an ion fragmentor. The third mass separator is positioned to receive the second group of ions and fragments thereof generated by the second mass separator. The third mass separator accelerates the second group of ions and fragments thereof and separates the second group of ions and fragments thereof according to their mass-to-charge ratio. In various embodiments, the third mass separator accelerates the second group of ions and fragments thereof using pulsed acceleration. In various embodiments, an ion detector positioned to receive the second group of ions and fragments thereof. In various embodiments, an ion reflector is positioned in a field-free region to correct the energy of at least one of the first or second group of ions and fragments thereof before they reach the ion detector. In various embodiments, the mass analyzer comprises a TOF mass analyzer having multiple flight paths, multiple modes of operation that can be performed simultaneously in time, or both. This TOF mass analyzer includes a path selecting ion deflector that directs ions selected from a packet of sample ions entering the mass analyzer along either a first ion path, a second ion path, or a third ion path. In some embodiments, even more ion paths may be employed. In various embodiments, the second ion deflector can be used as a path selecting ion deflector. A time-dependent voltage is applied to the path selecting ion deflector to select among the available ion paths and to allow ions having a mass-to-charge ratio within a predetermined mass-to-charge ratio range to propagate along a selected ion path. For example, in various embodiments of operation of a TOF mass analyzer having multiple flight paths, a first predetermined voltage is applied to the path selecting ion deflector for a first predetermined time interval that corresponds to a first predetermined mass-to-charge ratio range, thereby causing ions within first mass-to-charge ratio range to propagate along the first ion path. In various embodiments, this first predetermined voltage is zero allowing the ions to continue to propagate along the initial path. A second predetermined voltage is applied to the path selecting ion deflector for a second predetermined time range corresponding to a second predetermined mass-to-charge ratio range thereby causing ions within the second mass-to-charge ratio range to propagate along the second ion path. Additional time ranges and voltages including a third, fourth etc. can be employed to accommodate as many ion paths as are required for a particular measurement. The amplitude and polarity of the first predetermined voltage is chosen to deflect ions into the first ion path, and the amplitude and polarity of the second predetermined voltage is chosen to deflect ions into the second ion path. The first time interval is chosen to correspond to the time during which ions within the first predetermined mass-to-charge ratio range are propagating through the path selecting ion deflector and the second time interval is chosen to correspond to the time during which ions within the second predetermined mass-to-charge ratio range are propagating through the path selecting ion deflector. A first TOF mass separator is positioned to receive the packet of ions within the first mass-to-charge ratio range propagating along the first ion path. The first TOF mass separator separates ions within the first mass-to-charge ratio range according to their masses. A first detector is positioned to receive the first group of ions that are propagating along the first ion path. A second TOF mass separator is positioned to receive the portion of the packet of ions propagating along the second ion path. The second TOF mass separator separates ions within the second mass-to-charge ratio range according to their masses. A second detector is positioned to receive the second group of ions that are propagating along the second ion path. In some embodiments, additional mass separators and detectors including a third, fourth, etc. may be positioned to receive ions directed along the corresponding path. In one embodiment, a third ion path is employed that discards ions within the third predetermined mass range. The first and second mass separators can be any type of mass separator. For example, at least one of the first and the second mass separator can include a field-free drift region, an ion accelerator, an ion fragmentor, or a timed ion selector. The first and second mass separators can also include multiple mass separation devices. In various embodiments, an ion reflector is included and positioned to receive the first group of ions, whereby the ion reflector improves the resolving power of the TOF mass analyzer for the first group of ions. In various embodiments, an ion reflector is included and positioned to receive the second group of ions, whereby the ion reflector improves the resolving power of the TOF mass analyzer for the second group of ions. All literature and similar material cited in this application, including, patents, patent applications, articles, books, treatises, dissertations and web pages, regardless of the format of such literature and similar materials, are expressly incorporated by reference in their entirety. In the event that one or more of the incorporated literature and similar materials differs from or contradicts this application, including defined terms, term usage, described techniques, or the like, this application controls. The section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described in any way. While the present teachings have been described in conjunction with various embodiments and examples, it is not intended that the present teachings be limited to such embodiments or examples. On the contrary, the present teachings encompass various alternatives, modifications, and equivalents, as will be appreciated by those of skill in the art. The claims should not be read as limited to the described order or elements unless stated to that effect. While the inventions has been particularly shown and described with reference to specific illustrative embodiments, it should be understood that various changes in form and detail may be made without departing from the scope of the appended claims. By way of example, any of the disclosed features can be combined with any of the other disclosed features to, practice a method of MALDI ion formation or produce a mass analyzer system in accordance with various embodiments of the present teachings. For example, two or more of any of the various disclosed sample handling mechanisms, ion sources, optical systems, ion optical systems, heater systems, temperature-controlled surface configurations, ion optical assemblies, and mass analyzers can be combined to produce a mass analyzer system in accordance with various embodiments of the present teachings. Therefore, all embodiments that come within the scope and spirit of the following claims and equivalents thereto are claimed. |
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claims | 1. A method for decontaminating biological pathogens in a contaminated environment, comprising:tailoring x-ray radiation spectrum to match absorption characteristics of a contaminated environment;generating x-ray radiation having a diffused radiation angle by accelerating electrons from a cathode towards a concave surface of an anode and in accordance with the absorption characteristics of the contaminated environment; anddirecting the x-ray radiation towards the contaminated environment. 2. The method of claim 1 wherein tailoring x-ray radiation further comprises determining a photon energy for the x-ray radiation that adequately penetrates the absorption materials found in the contaminated environment. 3. The method of claim 1 wherein tailoring x-ray radiation further comprises determining a dose of x-ray radiation needed to kill a biological pathogen residing in the contaminated environment. 4. The method of claim 1 further comprising generating x-ray radiation having the diffused radiation angle by electrically grounding the cathode to eliminate any self-bias voltage. 5. The method of claim 1 further comprising generating x-ray radiation having the diffused radiation angle by disposing a secondary electrode proximate to the cathode for shaping the x-ray radiation. 6. A method for decontaminating biological pathogens in a contaminated environment, comprising:identifying a primary absorption material found in the contaminated environment;determining a dose of x-ray radiation needed to kill a biological pathogen residing in the contaminated environment, the x-ray radiation having a photon energy that penetrates the absorption material;generating x-ray radiation having a diffused radiation angle; anddirecting the diffused x-ray radiation towards the contaminated environment. 7. The method of claim 6 wherein determining a dose of x-ray radiation further comprisesplacing a known biological pathogen in a test environment;exposing the test environment to a calibrated dose of x-ray radiation; andmeasuring a survival rate of the biological pathogens in the test environment prior to decontaminating the contaminated environment. 8. The method of claim 7 further comprising placing an absorption material of interest between the source of x-ray radiation and the known biological pathogen. 9. The method of claim 6 further comprising generating the x-ray radiation having a photon energy approximately 8 keV when the absorption material in the contaminated environment is carpet. 10. The method of claim 6 further comprising generating the x-ray radiation having a photon energy approximately 18 keV when the absorption material in the contaminated environment is wood. 11. A method for decontaminating biological pathogens in a contaminated environment, comprising:identifying a primary absorption material found in the contaminated environment;determining a dose of x-ray radiation needed to kill a biological pathogen residing in the contaminated environment, the x-ray radiation having a photon energy that penetrates the absorption material;generating x-ray radiation having a diffused radiation angle by accelerating electrons from a cathode towards a concave surface of an anode, electrically grounding the cathode to eliminate self-bias voltage, and disposing a secondary electrode proximate to the cathode for shaping the radiation; anddirecting the diffused x-ray radiation towards the contaminated environment. |
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H00009148 | claims | 1. Apparatus for supporting at least one contactor stage for removing radioactive materials from aqueous solutions, the contactor stage having a housing, a rotor in the housing, a motor secured to the top of the housing for turning the rotor, and a drain in the bottom of the housing, said apparatus comprising a tubular, rectangular frame member having substantially flat, spaced top and bottom surfaces separated by substantially vertical side surfaces, said top and bottom surfaces each having an opening through which the housing may be placed, means for supporting said frame without substantially obstructing access to the contactor drain from three sides of the contactor stage, and means for securing said housing to said frame member, whereby the contactor stage is secured in a stable manner without obstructing access to the contactor drain. a tubular, rectangular frame member having substantially flat, spaced top and bottom surfaces separated by substantially vertical side surfaces, said top and bottom surfaces each having a separate opening through which each housing may be placed, means for supporting said frame without substantially obstructing access to the contactor drains from three sides of the contactors, and means for securing said housings to said frame member, whereby the contactors are secured in a stable manner without obstructing access to the contactor drains. 2. The apparatus of claim 1 wherein said frame supporting means comprises at least two horizontal footers placed on a ground surface perpendicular to the frame, one vertical leg extending to each footer, and a brace securing each footer to each leg. 3. The apparatus of claim 1 wherein said means for securing said housing comprises a weld. 4. Apparatus for supporting a plurality of contactor stages for removing radioactive materials from aqueous solutions, the contactor stages being arranged in a substantially straight row, each of the contactor stages having a housing, a rotor in the housing, a motor secured to the top of the housing for turning the rotor, a drain in the bottom of the housing, a plurality of first interconnect pipes for placing a first solution containing radioactive materials in the housing and removing solution containing radioactive materials from the housing, and a plurality of second embodiment pipes for placing a second solution containing organic materials in the housing and removing solution containing organic materials from the housing, said apparatus comprising 5. The apparatus of claim 4 wherein said frame supporting means comprises a series of horizontal footers placed on a ground surface perpendicular to the frame, a vertical leg extending from each of said footers, and a plurality of braces secured to said footers and said legs. 6. The apparatus of claim 5 wherein said legs extend below the first and second interconnect pipes. 7. The apparatus of claim 4 wherein said means for securing said housing comprises a weld. |
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claims | 1. A protection system for a nuclear boiling water reactor, the protection system comprising:a device configured to monitor reactor power;a device configured to monitor reactor pressure;a device configured to determine a first high reactor pressure setpoint that corresponds to 100% reactor power and at least one second high reactor pressure setpoint that corresponds to one or more values of percent reactor power in an operating domain of the reactor, based on the monitored reactor power; anda device configured to initiate a protection system action when the monitored reactor pressure is greater than the first high reactor pressure setpoint or the at least one second high reactor pressure setpoint;wherein the at least one second high reactor pressure setpoint is less than the first high reactor pressure setpoint. 2. The system of claim 1, wherein the device configured to initiate a protection system action initiates a reactor scram when the monitored reactor pressure is greater than the first high reactor pressure setpoint. 3. The system of claim 1, wherein the device configured to initiate a protection system action initiates a warning, an alarm, or a warning and an alarm when the monitored reactor pressure is greater than the first high reactor pressure setpoint. 4. The system of claim 1, wherein the device configured to initiate a protection system action initiates a reactor scram when the monitored reactor pressure is greater than the at Least one second high reactor pressure setpoint. 5. The system of claim 1, wherein the device configured to initiate a protection system action initiates a warning, an alarm, or a warning and an alarm when the monitored reactor pressure is greater than the at least one second high reactor pressure setpoint. 6. The system of claim 1, further comprising:one or more signals in the system that correspond to one or more values of percent reactor power;wherein the one or more signals in the system that correspond to one or more values of percent reactor power are delayed in time before the one or more signals in the system that correspond to one or more values of percent reactor power affect the at least one second high reactor pressure setpoint. 7. The system of claim 1, further comprising:one or more signals in the system that correspond to one or more values of percent reactor power; andone or more signals in the system that correspond to reactor pressure;wherein the one or more signals in the system that correspond to one or more values of percent reactor power are lagged relative to the one or more signals in the system that correspond to reactor pressure. |
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063013193 | summary | BACKGROUND OF THE INVENTION The invention relates to a method of sealing a reactor pressure vessel (RPV) and, more particularly, to a method for temporarily sealing a RPV submerged under twenty feet of water or more. Commercial nuclear reactors for generating electrical power must be taken off-line every one to two years in order to refuel the reactors. During such refuelings and other scheduled outages when the RPVs must be opened, the refueling cavities are flooded with water to depths of twenty (20) feet or more above the RPV circumferential flanges so that their removable upper heads may be safely removed. During such outages, periodic inspections, maintenance activities and repairs may be performed on the RPVs and/or on associated vessels and equipment such as steam generators, coolant circulating pumps and the like as well as the interconnecting piping. Certain of these inspections and other activities must be performed on dry surfaces. Accordingly, the RPVs or the balance of the loops must be sealed from the pools so that the loops can be at least partially drained. Temporary RPV heads have been designed to replace removed RPV heads in order to provide a seal between the internal portions of the RPVs (and the balance of the loops) and the pools of water in which the RPVs are submerged. These temporary RPV heads are large and heavy and expensive, special handling equipment is needed to transport them. It is desirable to employ existing on-site RPV internals lifting rigs to transport the temporary RPV heads and to guide them into position on RPV flanges. Such RPV internals lifting rigs are supported on the RPVs and normally used for transporting and positioning internal assemblies and fuel rod assemblies in the RPVS. However, the weight and/or the structural elements of the temporary RPV heads must be compatible with the lifting capabilities and/or structure of the existing lifting rigs if they are to be precisely positioned on the RPV flanges. The temporary RPV head designs may have pumping devices carried by their domed portions. These devices pump out water which may leak into the RPVs if the temporary RPV heads are not precisely positioned on the RPV flanges by the lifting rigs. Undesirably, such devices complicate the structure and use of the temporary RPV heads. SUMMARY OF THE INVENTION Thus, it is an object of the present invention to provide a method for installing a light weight, mechanically simple, temporary RPV head seal on a RPV submerged in a pool of water. It is a further object to provide method for testing the leak-tightness of such a temporary RPV seal. With these objects in view, the present invention resides in a method of sealing a RPV submerged in a pool of water, comprising the steps of: removing the RPV upper head; using a RPV internals lifting rig to position a temporary RPV head having an elliptical shaped dome with a circumferential flange retaining a pair of circumferential rings in spaced apart relationship onto a RPV circumferential flange to create a liquid-tight seal, the flanges and the rings defining a space between them; and then testing the leak-tightness of the space. In a preferred practice, the leak-tightness of the seal is determined by pressurizing the space between the two spaced rings. Most preferredly, the space is pressurized to a pressure of about 20 pounds/square inch and for about 5 minutes. |
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055286542 | description | DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The inventors of the present invention discovered and reported that Cr is capable of forming a uniform and continuous thin film having a thickness of around 10 .ANG. without condensation (Proc. SPIE Vol. 1720, p 208, 1992). As evident from the above, Cr is one of the materials suitable for the multilayer film of which high reflectivity can be expected for a light of shorter wavelength. However, when optical constants of each of Cr and Co to a light of wavelength 100 .ANG. or less are compared, (Henke et al. At. Data Nucl. Data Tables, Vol. 27, p. 1, 1982), Co exhibits greater differences in the refractive index from that of various materials having larger refractive indices, that is, light elements, than the difference that Cr shows. Thus, if a uniform and continuous Co thin film having a thickness 30 .ANG. or less can be formed, the formed multilayer ought to have higher reflectivity than that of a multilayer film using the thin film of Cr. FIG. 2 illustrates, for example, variations of reflectivity calculated in accordance with the number of layers i.e. the number of layer pairs. The readings show the dependence of the reflectivity on the number of layers in the multilayer films in which the combination of materials are Co/C and Cr/C, respectively, optimized in a case of a wavelength of 45 .ANG.. As shown in FIG. 2, the reflectivity of the Co/C multilayer film is greater than that of the multilayer film of Cr/C when both multilayers have the same number of layers. Moreover, in order to obtain the same reflectivity, the Co/C multilayer needs a lesser number of layers. It means that Co/C multilayer film has the following advantages as well as being easier to produce. Generally, in a multilayer film, the range of the wavelength which can be reflected is limited within a band width determined in accordance with the structure of the multilayer film. The band width is in approximately inverse proportion to the number of layers of the multilayer film. In other words, the band width narrows in accordance with the increasing of the number of layers. Therefore, if the multilayer film can be formed with the smaller number of layers, the multilayer film has a greater integral reflectivity to the incident light. A multilayer film with a greater integral reflectivity has the effect of improving efficiency of an optical apparatus using the multilayer film, as for example, increasing of throughput of an X-ray exposure apparatus. The inventors of the present invention succeeded in producing a multilayer film with high optical quality in which the layer structure is uniform and continuous. And in suppressing condensation of the material even with a thickness of 30 .ANG. or less, by using an alloy of Co having excellent optical constants and Cr having excellent interfacial smoothness, as a material of thin film having lower refractive index in the multilayer. Further, the inventors of the present invention have found that, uniform and continuous layers consisting of CoCr can be formed when a mole fraction of Co is under 0.8 or less as a component of the alloy. Moreover, the inventors of the present invention have found that in order to obtain high reflectivity, the mole fraction of Co should be over 0.3 as the component of the above alloy. In summation, the multilayer film for X-rays is most effective when CoCr alloy is used as a material for the thin film having smaller refractive index and having the formula Co.sub.x Cr.sub.1-x, where, x is within 0.3-0.8. It is needless to say that not only an alloy of Co and Cr but also the thin film may also consist of three or more elements in the above formula, and be equally efficient. As the material for the thin layer having the higher refractive index with which the layer having the lower refractive index is combined in the multilayer film, where the CoCr alloy is used as the layer having lower refractive index in the present invention, various elements can be selected in accordance with the wavelengths. In Table 1, preferable examples of the elements and compounds of the elements are shown. TABLE 1 ______________________________________ Range of wavelength (.ANG.) Elements ______________________________________ -24 Ba, Mg, Be 24-32 Sb, Ba, V, Te, Mg, Be 32-36 Sc, Ba, Mg, Be, Ti 36-44 Ca, Ba, Sc, Be, Mg 44-66 C, Ca, Ba, Sc 66-100 B, Ca, Zr, Sc, Ba, C ______________________________________ Table 2 shows examples of the calculated reflectivity of the multilayer film prepared under the optimized condition from materials containing elements in Table 1 in various wavelengths, with respect to several combinations of the materials. The reflectivity was calculated by a generally known method on the basis of Fresnel's reflection law which is generally known (for example, J. H. Underwood et al. Appl. Opt, Vol. 20, p 3027, 1981). Here, S-polarized reflectivity is calculated based on the number of layer pairs being 100, and perpendicular incident angle to the multilayer film. TABLE 2 ______________________________________ Wavelength Combination d.sub.CoCr d.sub.B Reflectivity (.ANG.) of materials (A) (A) (%) ______________________________________ 25 CoCr/V 6.14 6.39 4.7 32 CoCr/Sc 7.46 8.58 17.6 40 CoCr/CaF.sub.2 8.83 11.28 14.2 70 CoCr/B.sub.4 10.33 24.93 37.4 ______________________________________ where, d.sub.CoCr : thickness of CoCr thin film PA1 d.sub.B : thickness of the thin film having the higher refractive index The present invention will now be described in detail with reference to the following examples and related Figures. Example of a multilayer mirror FIG. 1 is a sectional view of a main part of a preferred embodiment of a multilayer mirror according to the present invention. The multilayer film for soft X-rays has a structure in which thin films A.sub.1 -A.sub.n in which material having the lower refractive index consist of an alloy of CoCr, and thin films B.sub.1 -B.sub.n in which the material having the higher refractive index consist of C are alternately formed on substrate 1. Here, the surface of substrate 1 on which the multilayer film is formed is processed to be sufficiently smooth with respect to a wavelength of the soft X-rays in order to prevent scattering of the soft X-rays on substrate 1. Thicknesses of each CoCr thin film and each C thin film are set at the value calculated on the basis of said Fresnel's reflection law for obtaining higher reflectivity. For example, when the Co/Cr alloy has the component Co.sub.0.5 Cr.sub.0.5, and the number of layer pairs are 100, they are set so that d.sub.CoCr =9.36 .ANG., d.sub.c =15.79 .ANG. in order to reflect a soft X-ray having a wavelength of 50 .ANG. at a perpendicular incident angle to the multilayer film. Next, the process for producing the multilayer film illustrated in FIG. 1 will be explained. The multilayer film was produced by using a magnetron sputtering method, which is well known. Initially, substrate 1 made from quartz was set in a substrate holder rotatable in a vacuum chamber. After the vacuum chamber was evacuated to vacuum degree of 5E-7 Torr, argon gas was introduced to the vacuum chamber so that the pressure within the chamber was 0.5 mTorr. Then, each thin film of Co/Cr alloy of A.sub.1 -A.sub.n and each carbon thin film of B.sub.1 -B.sub.n was deposited alternately on the substrate by electric discharge on targets of CoCr alloy and carbon (C) respectively. The thickness d.sub.CoCr of each of the CoCr alloy thin film and the thickness d.sub.c of each of C thin film were monitored by a quartz oscillator. The quantity of deposition was controlled by a deposition shutter. Upon sputtering, the deposition speed of CoCr alloy was 0.4 .ANG./sec, and the deposition speed of carbon was 0.3 .ANG./sec. The component of the alloy in CoCr thin film of the resultant multilayer film was analyzed by Auger electron spectroscopy (AES). And it was observed to correspond with the component of the CoCr alloy of the target within experimental error. The multilayer film of CoCr/C produced as above was evaluated in the periodicity and the diffraction intensity by small angle diffraction of X-rays of wavelength 1.54 .ANG.. FIG. 3 illustrates the results of the experiment. Here, the abscissa represents a period of each of the produced various multilayer films, and the ordinate axis represents a peak intensity of primary Bragg diffraction by the multilayer film. Curves 11 and 12 represent the diffraction intensities of the multilayer film produced with an alloy of composition Co.sub.0.8 Cr.sub.0.2, and Co.sub.0.5 Cr.sub.0.5, respectively. For comparison to the above results, FIG. 3 shows curve 13 of the measured values in the multilayer film of Co/C prepared in the same manner as above. Curve 13 shows that in the Co/C multilayer film, the diffraction intensity reduces more steeply when the period is shorter than 40 .ANG., and when the period is under 31 .ANG., the diffraction intensity was nearly zero. A cross section of the Co/C multilayer film having a period shorter than 40 .ANG. was observed by a transmission electron microscope of high resolving power. It was observed that desolation occurred in the layers of Co to form an island-like condition and the layers were not formed continuously. In contrast, as shown by curve 11, in the multilayer film using an alloy with component Co.sub.0.8 Cr.sub.0.2, prepared by adding 20 mole % Cr to Co, as a target, the diffraction intensity at a short period was remarkably improved, and the diffraction intensity was observed up to the period of 25 .ANG.. Moreover, curve 12 shows that in the multilayer film using an alloy with component Co.sub.0.5 Cr.sub.0.5 prepared by adding 50 mole % Cr to Co as a target, the diffraction intensity in shorter period was further improved, the characteristics of which are by no means inferior to those of the Cr/C multilayer film. Then, the reflectivity of the multilayer films prepared as above to the soft X-ray region was evaluated. A synchrotron radiation was used as a light source of the soft X-rays. Reflectivity of the multilayer film to the monochromatic soft X-rays of wavelengths 20-120 .ANG. was evaluated by obtaining spectra by a diffraction grating monochromater. The soft X-rays were incident with an incident angle 10.degree. to the multilayer films, and the reflectivity was calculated on the basis of the ratio of the intensity of the soft X-rays reflected from the multilayer film to the intensity of the incident soft X-rays. The wavelength dependence of the reflectivity measured as above was shown in FIG. 4. The multilayer film shown in FIG. 4 was formed using an alloy with the component Co.sub.0.5 Cr.sub.0.5 as a target for the thin film having lower refractive index, in which the thickness of CoCr thin film d.sub.CoCr =9.4 .ANG., the thickness of C thin film d.sub.c =16.3 .ANG., and the number of the layer pairs was 100. A peak of the reflection intensity was observed when the wavelength was near 50 .ANG., and the peak reflection intensity was 10.2%. With respect to a CoCr/C multilayer film having 100 layer pairs in which the peak of the reflection intensity exists at the wavelength near 60 .ANG., peak values of the reflectivity in various components of the CoCr alloy were calculated. The change in the values is shown in FIG. 5. FIG. 5 shows that in the multilayer formed by using an alloy Co.sub.0.8 Cr.sub.0.2 in which 20% of Cr was added to Co, the reflectivity in a normal incidence was remarkably improved. It is because the island-like deposition of Co thin layer was suppressed by adding Cr, and the roughness in the interfaces of the multilayer film was reduced. Though the reflectivity increases in accordance with rising of the concentration of Cr, it decreases from the time that the mole fraction exceeds 50%, due to the decreasing of concentration of Co, which is an advantage in the optical constant. In a multilayer film formed by using an alloy of which the mole fraction of Cr is over 70%, the reflectivity was as good as the Cr/C multilayer film. That is, the reflectivity was not improved. The above embodiment describes examples of the multilayer mirror for X-rays. However, the multilayer film of the present invention can be utilized also for reflection-type X-ray mask for lithography. FIG. 6 illustrates some examples of structures of the reflection-type X-ray mask. FIG. 6(A) is the mask in which the above described reflection multilayer film 11 is provided on a substrate 10, and further on the multilayer film, pattern 12 is provided which is formed from X-ray absorption material. In FIG. 6(B), a reflection pattern 13 of the multilayer film is directly formed on a substrate 10. In FIG. 6(C), non-reflective pattern 15 is formed by providing reflection multilayer film 14 on a substrate 10, then partially destroying the multilayer structure by irradiating an electron beam. PREFERRED EMBODIMENT OF AN EXPOSURE APPARATUS FIG. 7 illustrates an example of a reducing exposure apparatus utilizing the above multilayer mirror or reflection-type mask. In the apparatus, a beam from laser plasma X-ray source 33 which generates soft X-rays of wavelength of 4.5 nm, is condensed by two reflection mirror 27, 28 having the above described layer structure, and light reflection mask 29 on which the above pattern is formed. The mask 29 has one of the structures described in FIG. 6. The soft X-rays reflected by reflection-type mask 29 is reduced by an imaging optical system consisting of two reflection mirrors 30, 31 having the above multilayer structure, projected to the resist coated on wafer 32. A mask pattern is then exposed and transferred. Where, reducing rate is one fifth, the number of openings is 0.02, and a Schwarzschild optical system is composed. THE PREFERRED EMBODIMENT OF MANUFACTURING A DEVICE An embodiment of the present invention applied to a manufacturing method of a semiconductor device utilizing an exposure apparatus according to one of the preceding embodiments, will now be explained. FIG. 8 is a flow chart of the sequence of manufacturing a semiconductor device such as a semiconductor chip i.e. IC or LSI, a liquid crystal panel or a CCD, for example. Step 1 is a design process for designing the circuit of a semiconductor device. Step 2 is a process for manufacturing a mask on the basis of the circuit pattern design. Step 3 is a process for manufacturing a wafer by using a material such as silicon. Step 4 is a wafer process which is called a pre-process wherein, by using the prepared mask and wafer, circuits are formed on the wafer through lithography. Step 5 subsequent to this is an assembling step which is called a post-process wherein the wafer processed by step 4 is formed into semiconductor chips. This step includes assembling, i.e. dicing and bonding, and packaging i.e. chip sealing. Step 6 is an inspection step wherein operability check, durability check and so on of the semiconductor devices produced by step 5 are carried out. With these processes, semiconductor devices are finished and they are shipped Step 7. FIG. 9 is a flow chart showing details of the wafer process. Step 11 is an oxidation process for oxidizing the surface of a wafer. Step 12 is a CVD process for forming an insulating film on the wafer surface. Step 13 is an electrode forming process for forming electrodes on the wafer by vapor deposition. Step 14 is an ion implanting process for implanting ions to the wafer. Step 15 is a resist process for applying a resist which is a photosensitive material to the wafer. Step 16 is an exposure process for printing, by exposure, the circuit pattern of the mask on the wafer through the exposure apparatus described above. Step 17 is a developing process for developing the exposed wafer. Step 18 is an etching process for removing portions other than the developed resist image. Step 19 is a resist separation process for separating the resist material remaining on the wafer after being subjected to the etching process. By repeating these processes, circuit patterns are superposedly formed on the wafer. While the invention has been described with reference to the structure disclosed herein, it is not confined to the details set forth and this application is intended to cover such modifications or changes as may come within the purpose of the improvements or the scope of the following claims. |
description | This is a continuation application of U.S. Ser. No. 11/441,016, filed May 26, 2006 (now U.S. Pat. No. 7,482,603), which claims priority from Japanese Application No. 2005-154875 filed on May 27, 2005. The entire disclosures of all of the above-identified applications are hereby incorporated by reference. The present invention relates to an apparatus and a method of fabricating a specimen for observation of a structure, which is used to observe a cross sectional shape of a device or the like. There have been increased needs for examination and analysis of semiconductor devices, for which miniaturization is going to progress. In a failure analysis, which specifies the cause of failure, among the needs, it is an essential technology to directly observe a defect inside a device. Method of observing a section is shown in FIGS. 2A and 2B. In the beginning, focused ion beam (referred below to as FIB) 201 is used to process a rectangular hole 202, of which one side defines a position being requested for section observation. One side of the hole formed thereby defines a requested section 203, and the section is observed by a scanning electron microscope (referred below to as SEM). Since the section is formed by irradiating FIB 201 in parallel to the requested section, the section formed by FIB is essentially flat. On the other hand, SEM used for observation irradiates primary electrons in a position of observation and imaging, as contrast, the number of secondary electrons (or reflected electrons) generated from the position to thereby form an image to be observed. While the number of secondary electrons depends upon material of an object, it depends upon an irregular shape further than that. That is, since an observation section 203 formed by FIB is flat as described above and little irregular in shape, a difference in SEM image contrast consists of only a difference in secondary-electron yield attributable to a material. However, only a difference, in secondary-electron yield, attributable to a material is insufficient for that observation of a minute structure, the necessity of which has been increased in recent years, and so there is caused a problem that the image resolution is insufficient. Therefore, it is desirable to emphasize a contrast difference attributable to a structure. As measures for realizing this, there is used decoration of profile by forming irregularities every material of a structure. In SEM, when irregularities are present, boundaries of raised portions are observed to be bright since edges become large in secondary-electron yield, so that observation in high contrast is made possible. In order to provide for a difference in level every structure, a difference in processing sputtering yield, attributable to a material, is made use of. In case of FIB, since a difference in sputtering yield, attributable to a material, is present also in physical sputtering, irregularities 301, 302, 303 every material can be formed as shown in FIGS. 3A and 3B by irradiating FIB not in parallel to a section but obliquely at a certain angle to a section. FIG. 3B shows a section when a section indicated by a broken line in FIG. 3A is viewed along an arrow 304, and a left side thereof defines an outermost surface. For example, structures 301, 303 are made of Si and a structure 302 is made of SiO2. Here, the reason why FIB is irradiated obliquely is that since a section is defined by a side of a processed hole, irradiation perpendicular to the section is impossible. Since a difference in sputtering yield, attributable to a material, is relatively small, however, an intense processing on a section is needed to form sufficient irregularities by physical sputtering with FIB, which causes a problem in terms of damage. Therefore, methods of efficiently forming irregularities depending upon a material include a processing making use of chemical reaction. For example, Japanese Patent No. 3216881 indicates that irregularities due to differences in sputtering rate can be formed by performing a FIB processing while making fluorine-containing gases flow to a processed sample. Japanese Patent No. 3350374 discloses FIB assist-etchant measures, in which halogenated gases and halogenated hydrocarbon gases such as Cl2, XeF2, CF4, CHF4, C2F6, C3F8, C4F8, etc. are used as etch-assisting gases. U.S. Pat. No. 6,211,527 discloses measures to realize decoration of a section by means of FIB assist-etchant, in which halogenated hydrocarbon gases are used as etch-assisting gases. By performing FIB assist-etchant with the use of etch-assisting gases as in the related art, it is possible to vary a processing speed every material. As described above, a difference in level of irregularities is important in order to provide for a difference in contrast in SEM observation. However, an excessive processing with a view to forming a difference in contrast is not desirable. The reason for this is a fear that in case of FIB, since the presence of irregularities brings about an increase in sputtering rate at edge portions, the edge portions get out of shape to look differently in SEM observation from an original structure of a section. Further, digging much by means of FIB in order to provide for a difference in level means that a structural profile different from a section being essentially observed is observed in a device, which is varied in structure in a depthwise direction. Therefore, it is desirable to make an amount of processing as small as possible to form a necessary difference in level. Gases adopted in Japanese Patent Nos. 3216881 and 3350374 are in essence gaseous in a standard state. The standard state means 1 barometric pressure and 25° C. Essentially, these gases are those used in plasma etchant. In case of plasma etchant, gases themselves are ionized as plasma and ionized molecules are accelerated by plasma sheath formed on a surface of a sample, being a target of processing, to be irradiated on a surface of the sample, thereby performing etchant. However, FIB assist-etchant is different in reaction configuration in the following manner. Etch-assisting gases as supplied are first adsorbed by a sample surface. FIB is irradiated on the sample surface to inject energy thereinto to give thereto a reaction energy for reaction of a constituent material of a sample with gases, thereby generating a chemical reaction to subject a material of the sample to etchant. Therefore, in order to adequately cause the reaction, it is required that gases be sufficiently adsorbed by the sample surface. However, the probability that the gases being originally gaseous at room temperature are physically adsorbed by the sample surface is small as compared with a substance being originally solid, so that it is difficult to ensure a sufficient adsorbed amount. That is, gases used in plasma etchant is not necessarily suited to FIB etch-assisting gases. Further, a material accounting for a large part of a semiconductor device comprises silicon (Si) being a substrate material and an oxide silicon (SiO2, etc.) being an insulating material. While it is desirable to form a difference in level between Si and SiO2, the reason why the CF gases are used is as follows. Si reacts chemically with F to generate volatile SiF4 or the like to be etched. In this case, however, C remains whereby a substance, such as SiC, etc., being hard to be etched is formed to suppress etchant. On the other hand, with SiO2, Si volatilizes as SiF4 or the like as described above and C also reacts with O to volatilize as CO2 or the like, so that etchant is not suppressed like Si. Thereby, Si and SiO2 are varied in sputtering rate, so that it becomes possible to create a difference in level. CF gases, such as CO, COOH, etc., which contain O, are adopted in the U.S. Pat. No. 6,211,527. While SiC serves to suppress Si etchant in the reaction, O contained in etchant gases involves a fear that such suppressing effect is decreased. Therefore, there are needed an apparatus and a method of fabricating a section, in which the problems are solved, an effective difference in etchant is ensured, and a requested difference in level is fabricated in less processing to enable realizing a high contrast observation with SEM. In order to solve such problems, the invention provides a specimen fabricating apparatus and a specimen fabricating method described below. A specimen fabricating apparatus according to the invention comprises a movable specimen stage, on which a specimen is placed, a charged particle beam optical system that irradiates a charged particle beam on the specimen, an etchant material supplying source that supplies an etchant material, which contains fluorine and carbon in molecules thereof, does not contain oxygen in molecules thereof, and is solid or liquid in a standard state (1 barometric pressure and 25° C.), and a vacuum chamber that houses therein the specimen stage. Thereby, it becomes possible to fabricate a specimen profile of which is decorated. A specimen fabricating apparatus according to the invention comprises a movable specimen stage, on which a specimen is placed, a charged particle beam optical system that irradiates a charged particle beam on the specimen, an etchant material supplying source that supplies an etchant material, in molecules of which a ratio of fluorine to carbon in number is 2 or more and which is solid or liquid in a standard state (1 barometric pressure and 25° C.), to the specimen, and a vacuum chamber that houses therein the specimen stage. Thereby, since a further difference in sputter rate can be ensured, it becomes possible to effectively fabricate a specimen profile of which is decorated. A specimen fabricating method according to the invention comprises the steps of processing a hole in the vicinity of a requested region of a specimen by means of irradiation of charged particle beam, exposing the requested region by means of irradiation of charged particle beam, supplying an etchant material, which contains fluorine and carbon in molecules thereof, does not contain oxygen in molecules thereof, and is solid or liquid in a standard state (1 barometric pressure and 25° C.), to the requested region as exposed, and irradiating a charged particle beam on the requested region as exposed. Thereby, it is possible to realize fabrication of a specimen profile of which is decorated. A specimen fabricating method according to the invention comprises the steps of processing a hole in the vicinity of a requested region of a specimen by means of irradiation of charged particle beam, exposing the requested region by means of irradiation of charged particle beam, supplying an etchant material, in molecules of which a ratio of fluorine to carbon in number is 2 or more and which is solid or liquid in a standard state (1 barometric pressure and 25° C.), to the specimen, and irradiating a charged particle beam on the requested region as exposed. Thereby, since a further difference in sputter rate can be ensured, it becomes possible to effectively fabricate a specimen profile of which is decorated. According to the invention, a device section can be simply observed by means of SEM with high accuracy, so that it is possible to realize a failure analysis in a short time and to achieve an improvement in yield in semiconductor process. Other objects, features and advantages of the invention will become apparent from the following description of the embodiments of the invention taken in conjunction with the accompanying drawings. An explanation will be given below to concrete embodiments of an apparatus for fabricating a specimen and a method of fabricating a specimen, by which beam-assisting etchant with the use of effective etch-assisting gases can be used to fabricate minute irregularities every structure on a section of a specimen for a section SEM observation. FIG. 1 shows a construction of a specimen fabricating apparatus for fabricating an observe section making use of focused ion beam. The specimen fabricating apparatus comprises a movable specimen stage 102, on which a specimen substrate such as a semiconductor wafer 101, etc. is placed, a specimen position controller 103 that controls a position of the specimen stage 102 to observe the wafer 101 and specify a position of processing, an ion-bean irradiating optical system 105 that irradiates an ion beam 104 on the wafer 101 for processing, and a secondary-electron detector 106 that detects secondary electrons emitted from the wafer 101. The ion-bean irradiating optical system 105 is controlled by a controller 107 for the ion-beam irradiating optical system, and the secondary-electron detector 106 is controlled by a controller 108 for the secondary-electron detector. An etch-assisting gas supplying source 109, which supplies an etch-assisting gas for formation of irregularities on a section every material, that is, decoration of a section, is controlled by a controller 110 for the etch-assisting gas supplying source with respect to a position thereof, heater temperature, valve opening and closing, and the like. The controller 107 for the ion-beam irradiating optical system, the controller 108 for the secondary-electron detector, the controller 110 for the etch-assisting gas supplying source, the specimen position controller 103, etc. are controlled by a central processing unit 111. The specimen stage 102, the ion-bean irradiating optical system 105, the secondary-electron detector 106, the etch-assisting gas supplying source 109, etc. are arranged in a vacuum chamber 112. Here, a specimen is a wafer, and the fact that it is possible to observe in a state of a wafer is advantageous in that it is easy to control addresses of positions, of which observation is requested, and a wafer can be transferred as it is from an examining device. However, decoration of a section is possible for a chip specimen, and so a specimen chamber and a specimen stage may be constructed so that they can be formed to be small and simple. This case is advantageous in terms of device cost since manufacture is enabled at low cost. FIG. 4 shows a schematic construction of an etch-assisting gas source. According to the embodiment, a material being solid or liquid in a standard state is used as an etch-assisting gas material 401, and so there is provided a reservoir 402 that stores an etch-assisting gas material. An etch-assisting gas material used in the embodiment comprises perfluorododecane (F(CF2)12F) which is solid in a standard state. A heater 403 heats an etch-assisting gas material together with the reservoir to a requested temperature. The etch-assisting gas material heated and vaporized is fed to a specimen surface from a nozzle 404. Here, flow of a gas will be described with reference to FIG. 5 which is an enlarged view. The etch-assisting gas material (perfluorododecane) 401 heated by the heater 403 vaporizes to flow toward the nozzle 404 through a supplying hole 501. A valve 502 controls ON/OFF of supplying of the gas flowing into the nozzle 404, and ON/OFF of air pressure from an air tube 503 causes extension and contraction of a bellows 504 to enable control. Gas flow rate can be controlled by heating temperature by the heater, and perfluorododecane is heated to about 35° C. in the embodiment. A thermo sensor 405 monitors temperature of the reservoir 402 to effect feedback of the same to the heater 403, thus realizing stable heating. Here, a thermocouple is used as the thermo sensor 405. An air is introduced into the air tube 503 through a connector 406 shown in FIG. 4, and communication of electric signals of the heater 403 and the thermo sensor 405 is performed through a feedthrough 407. Connection to the vacuum chamber 112 which is a specimen chamber is effected through a connection flange 408. Here, while an explanation has been given to the case where an etch-assisting gas is solid, an etch-assisting gas material which is liquid can be likewise stored in the reservoir and heated by the heater to be vaporized and supplied. In the case where an etch-assisting gas material is liquid, however, sealing is needed to prevent the material from leaking into a gas supplying line as it is liquid, and so an etch-assisting gas material which is solid is easy in handling than the liquid. In either case, as compared with an etch-assisting gas material which is essentially gaseous, handling of an etch-assisting gas material which is solid or liquid is easy by virtue of easiness in storage and easiness in gas pressure regulation with temperature control. FIG. 6 shows the positional relationship between connection of the etch-assisting gas supplying source 109 to the vacuum chamber 112 which is a specimen chamber and a specimen. The etch-assisting gas supplying source 109 is fixed to a vacuum chamber wall 605 by the connection flange 408 as described above. A line 601 indicates an optical axis of the ion-bean irradiating optical system 105 and an intersecting point of the optical axis and the semiconductor wafer 101 defines a processed point, so that the nozzle 404 is caused to approach the intersecting point. While an adjustment mechanism for a position of the nozzle is omitted in the drawing, adjustment mechanisms in three directions are actually provided and it is possible to adjust a position of the nozzle close to a processed point. Actually, efficient gas supplying is enabled by causing a tip end of the nozzle 404 to approach a distance of several hundreds microns to a processed point. The etch-assisting gas supplying source 109 comprises a valve controller 602 that controls an air pressure for opening and closing of the valve, a heater controller 604, and a thermo sensor controller 603, and these controllers are controlled by the controller 110 for the etch-assisting gas supplying source. While not shown, in the case where a motor is provided to control a position of the nozzle, a nozzle position controller is also controlled by the controller 110 for the etch-assisting gas supplying source. The etch-assisting gas supplying source described above with reference to FIGS. 4 to 6 is needed to be removed from the connection flange 408 when an etch-assisting gas material is to be replenished. In case of using several kinds of etch-assisting gases to effect decoration of profile, it is troublesome to remove etch-assisting gas supplying sources one by one from the flange, so that the apparatus is decreased in operability. Further, in order to remove the etch-assisting gas supplying source from the flange, it is necessary to once open the vacuum chamber to the atmosphere, which is an obstacle to an improvement in throughput of specimen fabrication. Hereupon, an etch-assisting gas material can be readily replenished by making a system, which supplies a gas to the etch-assisting gas supplying source, a cartridge type. Details for this will be described below with reference to FIG. 7. An etch-assisting gas material 802 is stored in a cartridge 701 which is a portable type filling vessel, and the cartridge is inserted into a cartridge holder 804 to be connected to the etch-assisting gas supplying source. The cartridge holder 804 in the embodiment is cylindrical-shape with a side wall and a bottom cover 807 coupled together by a hinge. A heater 703 and a thermo sensor 704 are embedded in the cylindrical-shaped side wall and respectively connected to the heater controller 604 and the thermo sensor controller 603 through feeder lines. Therefore, connecting terminals are provided on a surface of the cartridge holder to connect the heater 703 and the thermo sensor 704, respectively, to the feeder lines. In addition, when the heater 703 is formed on an inner wall surface of the cartridge holder 804, efficiency at the time of heating the cartridge becomes higher than that with an embedded type. Further, a heater may be embedded in a cartridge. For the purpose of easy comprehension of the cartridge 701, FIG. 8 shows a state, in which the cartridge 701 and the cartridge holder 804 are separated from each other. The cartridge 701 comprises a body portion that stores an etch-assisting gas material 802, and a neck portion that connects the body portion and the cartridge holder 804 to each other. An opening is provided on an upper surface of the neck portion, and the opening is hermetically closed by a seal member such as a film 803, etc. The upper surface of the neck portion around the opening defines a joint surface to the cartridge holder 804 or the etch-assisting gas supplying source. Provided inside the cartridge holder 804 is a recess, into which the neck portion of the cartridge 701 is inserted, and the recess is provided with a projection 805. An O-ring 806 for vacuum sealing is provided at a root of the projection 805, that is, a bottom surface of the recess. When the cartridge 701 is inserted into the cartridge holder 804, the film 803 is torn by the projection 805. Further, the upper surface of the neck portion of the cartridge 701 and the bottom surface of the recess of the cartridge holder are vacuum-sealed by the O-ring 806. Thereby, a tube 702 in the etch-assisting gas supplying source and the cartridge 701 are coupled to each other. Finally, when the bottom cover 807 is closed, the cartridge 701 is fixed in the cartridge holder. The cartridge 701 is appropriately heated by the heater 703 and the thermo sensor 704 and gas is supplied to the tube 702. Air pressure is controlled by the valve 705 whereby ON/OFF of the gas is made. Further, a valve may be provided in the vicinity of the neck portion (toward the body portion or the cartridge holder), at which the body portion of the etch-assisting gas supplying source and the cartridge holder are connected to each other, to shield the etch-assisting gas, thereby making exhaust differentially relative to the valve 705. Since the cartridge 701 is heated, it is preferably formed from a material of good thermal conductivity. Further, in order to store the etch-assisting gas material 802 therein, an inner wall surface of the cartridge 701 is preferably coated with a material, which is hard to react with the etch-assisting gas material. A manner, in which the cartridge holder 804 and the cartridge are connected to each other, is not limited to the present system but may resort to fitting or screwing. In this case, while the cartridge can be fixed to the holder even without the bottom cover 807, the bottom cover is preferably provided in terms of thermal efficiency. Further, while the embodiment has been given by way of an example, in which the cartridge is shaped to comprise the neck portion and the body portion, it does not matter if the cartridge is shaped otherwise. Further, the term “etch-assisting gas supplying source” is used in the above descriptions for convenience, it goes without saying that the cartridge type mechanism described above is applicable to systems for supplying other gases than “etch-assisting gas”. As described above, the etch-assisting gas supplying source is made a cartridge type whereby it becomes not only easy to replenish a gas but also possible to quickly and readily exchange the gas for a preferable etch-assisting gas. Accordingly, the apparatus is improved in operability and fabrication of specimens is increased in throughput. Since quick exchange of kinds of etch-assisting gases is made possible, a plurality of kinds of gases can be made to flow through one gas supplying system without an increase in stress of a user for the apparatus. Accordingly, it is possible to reduce the number of gas supplying systems required to be provided in a specimen fabricating apparatus, thus enabling manufacture of an apparatus at low cost. In addition, while one cartridge holder is provided for the etch-assisting gas supplying source in the embodiment, the provision of a plurality of cartridge holders makes it possible to supply a plurality of kinds of gases without exchange. Both in the case where one cartridge holder is provided for the etch-assisting gas supplying source and in the case where a plurality of cartridge holders are provided, there is a possibility that when a kind of gas is replaced by another, a gas having been used remains as a contaminant in a gas path (tube). In order to eliminate the contaminant, cleaning is made by providing a device that heats the gas path, separately providing gas supplying means for flowing of inert gases, etc. through the gas path, or mounting/supplying a cartridge for inert gases. With the use of the specimen fabricating apparatus, irregularities every material can be formed on a section by performing a processing of a hole with FIB and FIB processing while supplying a gas to a requested section as formed. Details of processing sequences will be described in subsequent embodiments. A most simplified model will be described with respect to reactions of an etch-assisting gas with Si and SiO2. First, a CF etch-assisting gas material comprises CnFm. Here, n and m are positive integers. Here, m<4n is assumed. Further, reaction products comprise SiF4, CO2, O2, and SiC, which assume stable configurations. Among these substances, three substances, that is, SiF4, CO2, and O2 are volatile and are extinguished by evacuation. On the other hand, SiC remains on a specimen surface. Further, it is assumed that Si and SiO2 are the same in number of adsorption sites of an etch-assisting gas. Under the above assumptions, a chemical reaction formula of SiO2 is as follows.4nSiO2+4CnFm→mSiF4↑+4nCO2↑+(4n−m)Si (1)Also, a chemical reaction formula with Si is as follows.(m+4n)Si+4CnFm→mSiF4↑+4nSiC (2) When the formula (1) and the formula (2) are standardized per reaction adsorption site in order to make a comparison between rates, at which one Si and one SiO2 are removed, the formula (1) is converted into a formula (3) and the formula (2) is converted into a formula (4) SiO 2 + ( 1 n ) CnFm → ( m 4 n ) SiF 4 ↑ + CO 2 ↑ + ( ( 4 n - m ) 4 n ) Si ( 3 ) Si + ( 4 ( m + 4 n ) ) CnFm → ( m ( m + 4 n ) ) SiF 4 ↑ + ( 4 n ( m + 4 n ) ) SiC ( 4 ) That is, with SiO2, what is removed from one SiO2 is only a part of SiF4, so that a coefficient (m/4n) in the formula (3) indicates a rate as removed. Likewise, with Si, what is removed from one Si is a part of SiF4, so that a coefficient (m/(m+4n)) in the formula (4) indicates a rate as removed. Based on the results, a ratio of SiO2 and Si, which are removed by the reaction, is indicated by a formula (5) where N(SiO2) and N(Si), respectively, indicate removable numbers of SiO2 and Si per adsorption site. N ( SiO 2 ) N ( Si ) = ( m 4 n ) ( m ( m + 4 n ) ) = ( m + 4 n ) 4 n = 1 + m 4 n ( 5 ) Therefore, it is indicated that a sputter ratio in this reaction is surely larger than 1, that is, SiO2 is larger in sputter rate than Si. Further, it is found that m/n is preferably large in order to increase the sputter ratio. Further, in the case where O is contained in a CF etch-assisting gas material, in contrast to an effect that Si remains as SiC as indicated by the formula (2) and the sputter is constrained, there is a possibility that O possibly decomposes SiC and there is a fear that a sputter ratio of SiO2 and Si decreases. What is described above is a model assumed in most simplification and the model does not always react actually in this way, but it can be grasped as a tendency and so can be made use of as a search guideline for an etch-assisting gas material. Further, for adsorption of an etch-assisting gas, it is advantageously solid or liquid in a standard state to be able to adequately produce an effect of the chemical reaction. That is, it is found that an etch-assisting gas material which is solid or liquid in a standard state and does not contain O is advantageous to the section decoration. TABLE 1 indicates examples of CF gases. TABLE 1CHEMICALPRESENCE ORREACTIONSTANDARDABSENCE OFF/CNo.FORMULASTATEORATIO1F(CF2)12FsolidABSENT2.172(CF2)15F3NliquidABSENT2.203I(CF2)8IsolidABSENT2.004CF3CONH2solidPRESENT1.505CF3COOHliquidPRESENT1.506CF3CF2COOHliquidPRESENT1.677CF3COHCOOHsolidPRESENT1.008F(CF2)7COOHsolidPRESENT1.889CF3COFGASEOUSPRESENT2.0010CF3COCF3GASEOUSPRESENT2.0011CF4GASEOUSABSENT4.0012C4F8GASEOUSABSENT2.0013C5F8GASEOUSABSENT1.6014C3F6GASEOUSABSENT2.0015CHF3GASEOUSABSENT3.00 Nos. 4 to 15 among the examples represent gases already known as etch-assisting gases. It is found that No. 1, F(CF2)12F, which is being used in the embodiment satisfies the condition that it is solid in a standard state and does not contain O. Actually, favorable section decoration was confirmed by making an experiment with the present apparatus. Other than F(CF2)12F, No. 2, (CF2)15F3N, which is a kind of fluorinert and No. 3, I(CF2)8I, satisfy the condition that they are solid or liquid in a standard state and do not contain O and it was confirmed that favorable section decoration is possible. Further, a sputter ratio of 1.5 times or more is expected in an exceedingly ideal case from the formula (5) provided that m/n assumes 2 or more. Also, in this case, since adsorption of an etch-assisting gas is of course important, the condition that it is solid or liquid in a standard state and m/n is 2 or more becomes one of an efficient search guideline for an etch-assisting gas material. It is found that among the gases in TABLE 1, Nos. 1 to 3 conform to this condition and are effective in section decoration likewise as described above. As a result of confirmation by actual experiments, in case of F(CF2)12F, the sputter rate of SiO2 at the time of FIB etch-assisting is about 2.5 times that of Si, so that a difference in level can be readily formed by less FIB irradiation. Further, it has been confirmed by experiments that the sputter rate of No. 2, (CF2)15F15N, in TABLE 1 which is a kind of fluorinert is about 1.9 times that of Si and the sputter rate of No. 3, I(CF2)8I, is about 1.6 times. Since these substances need less ion beam irradiation, that is, less dose, it is possible to reduce damage to a section. Further, an effect of boundary discrimination with SEM is adequately produced when a difference in level between SiO2 and Si is formed to be 1 nm. In case of F(CF2)12F, section decoration can be made without little processing of a requested section and a section structure can be observed substantially as it is since there is only a need of processing of SiO2 by 1.6 nm and Si by 0.6 nm in a direction of section depth. In this case, while sediment containing C is formed on Si, there is a need of dose of an order of magnitude larger than that in the processing at this time in order that sediment is actually accumulated to enable observation with SEM, so that such sediment has no influence on SEM observation in the processing of section decoration in the embodiment with less dose. Further, since F(CF2)12F, (CF2)15F3N which is a kind of fluorinert, I(CF2)8I, etc. are solid or liquid in a standard state, they have less influences on an environment as compared with gases, and since they can be processed in a short time as described above, they have an advantage that it is possible to decrease a material consumption. The present embodiment has illustrated an etchant material, which contains fluorine and carbon in molecules thereof and does not contain oxygen and which is solid or liquid in a standard state, or an etchant material, in molecules of which a ratio of fluorine to carbon in number is 2 or more and which is solid or liquid in a standard state. By using, for example, F(CF2)12F, or (CF2)15F3N which is a kind of fluorinert, or I(CF2)8I, etc. as an etchant material, it becomes possible to ensure a large difference in sputter rate to effectively fabricate a specimen, profile of which is decorated. Further, by making an etch-assisting gas supplying source an apparatus of a cartridge type construction capable of exchanging an etch-assisting material, it becomes possible to readily replenish an etch-assisting material, thus enabling efficiently fabricating a specimen. With the use of the present specimen fabricating apparatus, it becomes possible to fabricating a section specimen which high contrast observation in a device section by SEM becomes possible. A method of fabricating a specimen, according to the invention, will be described. FIG. 9 illustrates flow of fabrication of a specimen. A specimen fabricating apparatus used here is the apparatus shown FIG. 1. (a) At the outset, FIB 104 processing is used to put marks 902, 903 indicative of a position, in which a requested section 901 is fabricated. (b) Subsequently, a rectangle, one side of which is defined by a line connecting between the marks, is set as FIB irradiation region and a hole 904 is processed by means of FIB processing. A length of a set rectangle along a requested section is determined by a region of the requested section, and a length in a direction perpendicular thereto is determined by a prospective angle of FIB irradiation at the time of section decoration described later and by a prospective angle at the time of SEM observation. At this time, since FIB actually has a finite beam diameter and beam flare or the like is involved, a processing is sometimes made over a region, for which irradiation is set. In this case, since there is a fear that the requested section disappears, it is requested that in view of influences thereby, a region of FIB irradiation be set apart a little from the marking line so as not to overlap the same at the time of hole processing. Further, a depth of hole processing is actually determined by a depth of a section structure, of which observation is requested. (c) A side wall 905 on a side of a requested section of a rectangular-shaped hole thus fabricated is processed and reduced by means of a thin FIB in parallel to the requested section to expose the requested section 901. (d) Subsequently, a specimen stage is inclined to enable irradiation of FIB at a certain angle on the requested section. In case of the embodiment, the specimen stage is inclined at 45 degrees so as to enable irradiation at an angle of 45 degrees to the section. Of course, the angle of inclination is not limited to 45 degrees. (e) In this state, an etch-assisting gas material 906 is supplied to the section. As described in the embodiment, the etch-assisting gas material is supplied through the nozzle 404 by opening the valve in a state, in which the reservoir of the etch-assisting gas supplying source is heated to gasify the material. It is requested that the nozzle 404 be as close to a specimen as possible within a region free of obstruction to irradiation of FIB, because supplying is enabled at high density, consumption of the gas supplying source is small, and the specimen chamber can be maintained high in degree of vacuum. (f) In a state, in which the etch-assisting gas is thus supplied, FIB 104 is irradiated on the requested section 905. It suffices that dose make it possible to fabricate a difference of around 1 nm in level between SiO2 and Si. In the procedure described above, it is possible to fabricate a specimen, in which a difference in level is formed every structure on the requested section. Here, while a requested region has been described as a section, whether a requested region is a flat surface in parallel to a specimen surface does not matter, and a difference in level can be also formed by irradiating FIB on an exposed flat surface while supplying the etch-assisting gas thereto in the same manner as described above. When a section of the specimen thus fabricated is observed with SEM, it is possible to obtain an image of structure observation in high contrast owing to the edge effect. An explanation will be given to a specimen fabricating apparatus for fabricating a specimen, a section of which is to be observed, from an extracted micro-sample according to the invention. FIG. 10 shows a specimen fabricating apparatus functioning to extract a micro-sample. The apparatus is substantially the same in fundamental construction as the specimen fabricating apparatus in FIG. 1 but is different therefrom in having a probe 1001 for extraction of a micro-sample. The probe comprises a minute tip end having a tip end diameter in the order of submicron. In the embodiment, a tungsten probe is used. The probe 1001 can be positioned by a probe driver 1002 and a probe controller 1003. Further, the apparatus comprises a deposition-gas supplying source 1004. The supplying source is substantially the same in construction as an etch-assisting gas supplying source 1005 but what is stored therein is a deposition-gas. In the embodiment, tungsten carbonyl (W(CO)6) is used as the deposition-gas material but the material is not limited thereto. Further, the apparatus comprises a sample-carrier holder 1006 that places thereon a sample-carrier for fixation of an extracted micro-sample. FIG. 11 illustrates a method of fabricating a specimen with the use of the apparatus. (a), (b) At the outset, FIB 1101 is used to process three rectangular holes 1102, 1103, 1104 along three sides around a requested section. (c) Subsequently, a micro-sample 1107 supported on an original sample only by a residual area 1106 can be fabricated by inclining a specimen stage and processing a trench 1105. (d) Subsequently, the specimen stage is returned to an original position from the inclined position and the probe driver 1002 brings a tip end of the probe 1001 into contact with the micro-sample 1107. Subsequently, FIB 1101 is irradiated on a region including the tip end of the probe while a deposition-gas 1108 is supplied from the deposition-gas supplying source 1004, whereby a deposition film 1109 (W film in the embodiment) can be formed and (e) the micro-sample 1107 and the probe 1001 can be fixed together. Thereafter, the micro-sample can be separated from the original sample by removing the residual area 1106 by means of FIB processing (f), (g). The micro-sample 1107 thus separated is brought into contact with a sample-carrier 1110 by driving of the probe (h). The micro-sample and the sample-carrier are fixed together by forming a deposition film 1111 on the contact in the same way as described above (i). Thereafter, the tip end of the probe is subjected to FIB processing to achieve separation of the probe whereby the micro-sample 1107 can be made independent. Subsequently, fabrication of a section will be described with reference to FIG. 12. (a), (b) FIB 1101 is irradiated in parallel to a requested section to perform a processing so as to expose the requested section 1201. (c) Finally, the sample-carrier holder is inclined to enable irradiation of FIB at a certain angle on the requested section. In the embodiment, nothing obstructs in front of the requested section unlike the case where one surface of the hole is made the requested section as in Embodiment 1, so that it is possible to irradiate FIB perpendicularly to the requested section (d), (e). A specimen, the requested section of which is decorated, can be fabricated by irradiating FIB 1101 in this posture to perform etch-assisting while supplying an etch-assisting gas 1202. The specimen thus fabricated can be observed in higher contrast than that in case of Embodiment 1. The reason for this is that since a section to be observed in Embodiment 1 is present in the hole, it is hard to take secondary electrons into the detector at the time of SEM observation and yield is poor. In contrast, since nothing obstructs in front of the requested section fabricated in the present embodiment, it is possible to efficiently detect secondary electrons to make observation in high contrast. Further, while an angle of SEM observation corresponds to oblique looking-into in Embodiment 1, observation from a vertical is enabled in the present embodiment. Thereby, since observation of an aspect ratio in actual size is enabled, it is possible to increase the resolving power especially in a longitudinal direction. Further, since primary electrons of SEM invade an interior of a section to some extent depending upon acceleration voltage, detection of secondary electrons makes estimated information in a region of invasion. With a semiconductor device to be observed, estimation in a direction perpendicular to a section does not cause an important problem since the structure is the same in a shallow region, but it is necessary to pay attention to understanding of a structure from an observed image since information is estimated in an oblique direction in the case where observation is made in oblique entrance as in Embodiment 1. In contrast, the present embodiment, which affords vertical observation, has an advantage that less care suffices. By using the specimen fabricating apparatus according to the present embodiment, it is possible to fabricate a specimen, which enables SEM observation from a vertical and of which a section is decorated. In the present embodiment, an explanation will be given to a FIB-SEM apparatus that affords SEM observation on the spot after a section is fabricated by FIB etch-assisting. FIG. 13 shows a construction of a FIB-SEM apparatus. The present apparatus is the same in fundamental construction as the specimen fabricating apparatus shown in FIGS. 1 and 10 but the present apparatus differs therefrom in that a scanning electron beam irradiating optical system 1301 is installed in the same specimen chamber. The SEM is obliquely provided relative to a specimen stage. This is because a section fabricated is made easy to observe without inclining the specimen stage and a section being subjected to FIB processing can be monitored by SEM at the time of formation of a requested section. Thereby, SEM observation can be made without exposing a specimen, a section of which is decorated, to the atmosphere and an observed image of a section with high reliability can be obtained without care for contamination in the atmosphere. Further, since observation can be made on the same spot without movement to a separate SEM apparatus, there is an advantage that time for analysis is shortened. Further, since a section being subjected to FIB processing can be monitored by SEM at the time of formation of a requested section, it becomes also possible to fabricate a requested section in a further correct position. Further, with the present apparatus, FIB irradiation for etch-assisting can be made perpendicularly to a requested section and SEM observation can be made even when a micro-sample is not transferred to a sample carrier as in Embodiment 3. The reason for this is that since a probe 1302 is provided to be able to extract a micro-sample in the same manner as in Embodiment 3 and a probe rotating mechanism is provided, it is possible to incline a micro-sample fixedly left on the probe and to arrange a requested section perpendicularly to FIB and SEM. This method will be described with reference to FIG. 14. (a), (b) The procedure up to extraction of a micro-sample 1401 is the same as that shown in FIG. 12. (c) A requested section 1402 while being fixed by the probe 1302 is processed by means of FIB 1404. (d) Thereafter, the probe 1302 is inclined. (e) Subsequently, a specimen with a section thereof decorated can be fabricated by irradiation of FIB 1404 while an etch-assisting gas 1403 is supplied. In this state, it is possible to irradiate FIB 1404 and to make SEM observation. With the use of FIB-SEM according to the present embodiment, it is possible to realize observation of a section in a short time and with a further high reliability. In the present embodiment, an explanation will be given to a FIB-SEM apparatus that affords SEM observation on the spot after a section is fabricated by FIB etch-assisting and comprises an inclined ion-beam irradiating optical system. FIG. 15 shows a construction of the FIB-SEM apparatus comprising an inclined ion-beam irradiating optical system 1501. A large difference in construction between the apparatus and the FIB-SEM apparatus, according to Embodiment 4, shown in FIG. 13 is that a specimen stage 1502 is not inclined. Thereby, the mechanism for the specimen stage is made simple and an area required for a specimen chamber 1503 can be substantially decreased in an apparatus conformed to a wafer having, for example, φ300 mm, so that the construction is advantageous in terms of cost and positional accuracy. In this case, however, when the FIB optical system is mounted perpendicularly to a specimen surface as in FIG. 13, a processing of a hole for exposure of a requested section is possible but FIB irradiation for etch-assisting for decoration of a section cannot be made at a certain angle to a requested section. Therefore, the construction comprises the ion-beam irradiating optical system 1501 inclined relative to a specimen surface as shown in FIG. 15. While an angle of inclination is optional, an inclination of, for example, 30 degrees is adopted in the present embodiment. Fabrication of a specimen with the use of the apparatus and a method of observing a section will be described with reference to FIG. 16. (a) First, a rectangular region, one side of which is defined by a requested section 1602, is set in order to expose the requested section, and irradiation of FIB 1601 is made. At this time, adjustment is accomplished by rotating the specimen stage so as to make the requested section be in parallel to a direction, in which the FIB optical system is inclined. Actually, as described with respect to Embodiment 2, a processed region is set apart a little from a position of the actual requested section so as not to include the position of the requested section. FIB processing in a rectangular shape can fabricate a processed hole 1603 in the form of a parallelogram as shown in the drawing, and a surface of the parallelogram is in parallel to the requested section. Successively, the requested section is processed and reduced by means of a thin FIB with the positional relationship as it is, and thus the requested section 1602 is exposed. (b) Thereafter, setting is accomplished by rotating the specimen stage by 90 degrees to enable irradiation of FIB 1601 on the requested section 1602. With the ion-beam optical system, which is inclined by 30 degrees, according to the present embodiment, FIB is irradiated at 60 degrees on the requested section. Section decoration is enabled by irradiating FIB 1601 in this state while supplying an etch-assisting gas 1604 to the requested section 1602 from a nozzle 1605 in the same manner as in the embodiment described above. Thereafter, the specimen stage is rotated back by 90 degrees to afford SEM observation of the decorated requested section 1602. The present apparatus can also be provided with a probe, extraction of a micro-sample becomes possible as in the Embodiments 3 and 4, and the same effect as that in the latter is expected. FIB-SEM in the present embodiment is used to enable decoration of a section by means of etch-assisting also in an apparatus without a mechanism for inclining a specimen stage. In the present embodiment, an explanation will be given to section decoration by etch-assisting with the use of a projection type ion-beam apparatus (referred below to as PJIB). FIG. 17 shows the PJIB apparatus. A projection mask 1702 capable of projecting a requested rectangular shape 1701 is selected and irradiation enables processing a rectangular hole. A difference to FIB is that no scanning is made owing to batch irradiation. Thereby, a large current processing becomes possible and a short time processing is realized. Of course, it is also possible to form a rectangular beam smaller than a requested rectangle and to perform scanning with such rectangular beam to form a target rectangular hole. Also in this case, a processing in a shorter time than that with FIB is enabled. An ion beam is irradiated on a requested section thus formed while an etch-assisting gas is supplied thereto, but there is a problem. In case of FIB, irradiation on the whole section is performed by basically exercising deflective control of a spot beam, and for a minute region corresponding to a FIB spot diameter, dead time corresponding to one frame of deflective scanning passes away until FIB is subsequently irradiated after FIB is once irradiated. During the time, the etch-assisting gas can be adsorbed. In case of PJIB, however, when batch irradiation is performed on a requested section, an ion beam is constantly irradiated on the requested section during the irradiation, so that it is not possible to gain time, during which an etch-assisting gas is adsorbed. In this case, a sufficient chemical reaction does not take place and physical sputtering becomes a main sputtering, so that a requested difference in sputtering rate cannot be obtained every material in a section structure and section decoration cannot be made efficiently. Therefore, also in case of the PJIB apparatus, etch-assisting is made possible by simulatively forming FIB. That is, FIB can be formed by inserting a pinhole aperture 1703 midway a PJIB optical system and forming a minute beam to perform scanning with a deflector. While a large current of PJIB is effective in hole processing in order to lessen a processing time, restriction of beam with the pinhole aperture does not cause a problem since a minute current is sufficient for an irradiation beam for etch-assisting used in section decoration. Thereby, section decoration can be realized by performing scanning and irradiation with a minute beam while supplying an etch-assisting gas in the same manner as in the embodiment described above. Also, decoration of a section can be accommodated by making a non-irradiation time with a blanker so that the gas is adsorbed. Further, in the present embodiment, a processing with a large current becomes possible also in case of argon beam, which becomes small in current density when used as FIB, and therefore, manufacture in non-contamination like this can be realized, so that it becomes possible to return a wafer after analysis to a semiconductor manufacturing process. Further, influences on a subsequent semiconductor manufacturing process can also be suppressed by filling the processed hole with, for example, a deposition film, etc. to return the same to the processing. With the PJIB apparatus according to the present embodiment, a high-speed hole processing is possible, so that it is possible to lessen time for analysis. Further, since a section for observation in non-contamination can be fabricated and influences on the semiconductor manufacturing process can be made small, in-line analysis becomes possible. In the present embodiment, an explanation will be given to section decoration with the use of an electron beam. FIG. 18 shows an electron beam apparatus. While the apparatus is the same in fundamental construction as SEM but difference is that an etch-assisting gas supplying source 1801 is mounted. Also with an electron beam 1802, a processing is enabled by the use of an etch-assisting gas. While a processing for exposure of a requested section is not impossible with the etch-assisting gas and irradiation of electron beam, the electron beam is not practical since electron is small in mass as compared with ion and an electron beam is extremely small in sputtering rate as compared with an ion beam. Therefore, in case of an independent electron beam apparatus as in the present embodiment, it is preferable to introduce a specimen, a requested section of which is exposed by a separate processing apparatus. The electron beam 1802 is irradiated to the section while supplying thereto an etch-assisting gas such as perfluorododecane, etc. from a nozzle. As described above, while the processing speed is small as compared with an ion beam, a difference in irregularities every material, which is as small as 1 nm, is effective for a requested section, for which section decoration is necessary, so that section decoration can be realized even with an electron beam. In particular, since an electron beam is negligibly small in physical sputtering, the reaction is almost purely composed of chemical etchant to enable sputtering further relying on a material. Therefore, it is possible to realize decoration of a minute section with lower damage. The section thus fabricated can be observed with the SEM function of the present apparatus. Further, since section decoration is possible even with an electron beam, it is also possible in FIB-SEM illustrated in the Embodiments 4 and 5 to make use of an electron beam of SEM for an etch-assisting section processing after the processing of a hole. A processing for decoration of a further minute section is made possible by the use of the electron beam etch-assisting apparatus according to the present embodiment. Since the invention produces an effect in examination and analysis of a semiconductor processing, it can be made use of for an improvement in yield in semiconductor manufacturing companies to contribute much to reduction in cost, or the like. It should be further understood by those skilled in the art that although the foregoing description has been made on embodiments of the invention, the invention is not limited thereto and various changes and modifications may be made without departing from the spirit of the invention and the scope of the appended claims. |
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abstract | An ion source is provided that utilizes a cooling plate and a gap interface to control the temperature of an ion source chamber. The gap interface is defined between the cooling plate and a wall of the chamber. A coolant gas is supplied to the interface at a given pressure where the pressure determines thermal conductivity from the cooling plate to the chamber to control the temperature of the interior of the chamber. |
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046559957 | summary | BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to boiling water reactor (BWR) fuel assemblies and more particularly to a BWR fuel assembly capable of reversible or inverted operation. 2. Description of the Prior Art The generation of a large amount of heat energy through nuclear fission in a nuclear reactor is well known. This energy is dissipated as heat in elongated nuclear fuel rods. A plurality of nuclear fuel rods are grouped together to form separately removable nuclear fuel assemblies. A number of such nuclear fuel assemblies are typically arranged in a matrix to form a nuclear reactor core capable of a self sustained, nuclear fission reaction. The core is typically submersed in a fluid, such as light water, that serves as a coolant for removing heat from the nuclear fuel rods and as a neutron moderator. A typical nuclear fuel assembly may be formed by an 8.times.8 array of spaced-apart, elongated rods supported between upper and lower tie plates. Examples of such typical nuclear fuel assemblies are depicted in and described in U.S. Pat. Nos. 3,350,275; 3,466,226; 3,802,995. In a typical BWR nuclear fuel assembly having an 8.times.8 rod array, the sixty four rods that form the 8.times.8 array may be either sixty four fuel rods or may have one or more nonfueled, water moderator rods with the remaining rods being fuel rods. A common problem in BWR reactors is the high fuel costs associated with the typical BWR fuel cycle. In BWR fuel assemblies, the fuel near the bottom of the fuel assemblies is "burned up" at a faster rate than the fuel near the top of the assembly. This is because in a BWR, the power spectrum is skewed towards the bottom of the fuel assembly. This skewing is a result of the change in void fraction in the fuel assembly from the top to the bottom. Boiling of coolant typically commences about one quarter of the way from the bottom of the fuel assembly. From that point upwards, the void fraction increases to as high as sixty to seventy percent at the top of the fuel assembly. Since the coolant acts as a neutron moderator, thermalizing fast neutrons, the low H/U ratio at the top of the core results in a situation where the top of the core is less reactive than the bottom and therefore generates less power. In typical BWR reactors, the control rods enter the core from the bottom for the purpose of limiting the skew and power distribution. However, even with control rod insertion, more power is produced and more burn up takes place at the bottom of the core. Thus, the fuel at the lower end of the core, where the water density is high, is more completely burned than the fuel at the top of the core. This results in less than optimum burn up of fuel and overall higher fuel costs. In copending, commonly assigned U.S. application Ser. No. 609,250 filed currently herewith, an improved (PWR) pressurized water reactor fuel assembly is disclosed having fuel rods with plenum zones for fission gases where some of the fuel rods have plenum zones at the bottom of the rod for the purpose of enhanced fuel utilization and reduced neutron leakage. In U.K. Pat. No. 923,633 there is disclosed a method of continuously charging a BWR in order to achieve a more uniform burn up of fuel. The method involves dividing the fuel assembly into axial and radial zones of differing mean burn up rate and then continuously transporting the fuel rods from zone to zone according to a complex schedule. Itoh et al and U.S. Pat. No. 4,119,489 discloses a nuclear fuel assembly design in which the tubular channel members surrounding the fuel assemblies is removably supported by the upper tie plate so that the channel member may be removed, turned upside down, and then reinserted over the fuel assemblies so as to minimize the effects of flow channel deformation. In the asssembly of Itoh et al, the fuel assemblies themselves are not moved nor are they reversible. Thus, the prior art fails to teach a BWR fuel assembly which is compatible with and which can be substituted for original fuel during refueling operations and which can achieve more complete burn up of the fuel. SUMMARY OF THE INVENTION It is therefore, an object of the present invention to provide an improved BWR fuel assembly. It is a further object of the present invention to provide and improve BWR fuel assembly capable of achieving higher rates of fuel burn up thus lowering overall fuel cycle costs. It is still a further object of the present invention to provide a new and improved method of operating a BWR reactor wherein more complete burn up of fuel is accomplished. To achieve these other objects of the present invention in accordance with the preferred embodiment of the invention there is provided a nuclear fuel assembly having a flow channel and a lower nozzle assembly structurally attached to the flow channel in order to form an external envelope into which a fuel bundle may be inserted. According to the present invention, the fuel bundle is configured to be inserted into the envelope in either of two axially reversible orientations. The fuel bundle comprises a plurality of elongated fuel rods held in a spaced lateral array between a top and a bottom tie plate. The top and bottom tie plates are substantially identical and each is supplied with a means for supporting the fuel bundle within the envelope. Preferably, the supporting means are provided with lifting slots to facilitate the removal of the fuel bundle from the fuel assembly and subsequent reinsertion of the inverted fuel assembly. Advantageously, each fuel bundle will comprise a plurality of fuel rods having tubular cladding containing nuclear fuel and a fission gas plenum disposed within the cladding for accommodating fission gases released during operation of the fuel assembly. A portion, preferably half of the fission gases plenums are disposed adjacent to the top tie plate and the remainder of the fission gas plenums are disposed adjacent to the bottom tie plate. For in assuring axial symmetry, it is preferable that each alternate fission gas plenum be disposed adjacent to top tie plate and the intervening alternate fission gas plenums be disposed adjacent to bottom tie plate. In accordance with another embodiment of present invention, there is disclosed a method of operating a nuclear reactor comprising inserting a substantially axially symmetrical nuclear fuel bundle into an external envelope from a flow channel to the bottom nozzle assembly and then operating the reactor for a period of time. After operation, the fuel bundle is withdrawn from the envelope and axially inverted. The axially inverted fuel bundle is then reinserted into the envelope after which reactor operation is continued for an additional period of time. |
052316548 | description | DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A radiation imager system 10, such as a medical computed tomography (CT) system, incorporating the device of the present invention is shown in schematic form in FIG. 1. CT system 10 comprises a radiation point source 20 and a radiation detector 30 comprising a plurality of radiation detector panels 40 and a plurality of collimators 50 disposed between radiation source 20, typically an x-ray source, and detector panels 40. Each detector plate comprises a plurality of detector elements (not shown) that convert incident radiation into electrical signals. The detector elements are typically arranged in a one- or two-dimensional array. The radiation detector elements are coupled to a signal processing circuit 60 and thence to an image analysis and display circuit 70. Detector panels 40 are mounted on a curved supporting surface 80 which is positioned at a substantially constant radius from radiation point source 20. This arrangement allows an object or subject 90 to be placed at a position between the radiation source and and the radiation detector for examination. Collimators 50 are positioned over radiation detector panels 40 to allow passage of radiation beams that emanate directly from radiation source 20, through exam subject 90, to radiation detector panels 40, while absorbing substantially all other beams of radiation that strike the collimator. The details of steps in the fabrication, and the resulting structure, of collimators 50 in accordance with this invention are set out below. FIG. 2 is a cross-sectional view of a representative portion of a collimator substrate 110. Substrate 110 comprises photosensitive material, i.e., a material that will react to exposure to light in a manner similar to photoresist, to allow etching of a pattern in the material. Such photosensitive material may lose its photosensitive characteristics after it has been exposed to light and processed. One example of this type of substrate material is the Corning, Inc. product known as Fotoform.RTM. glass. An optically opaque mask 112 is formed by conventional methods on a first surface 110a of collimator substrate 110. The pattern of openings in mask 112 corresponds to the pattern of detector elements in each radiation detector panel 40 (FIG. 1). For example, mask 112 would have a pattern generally mimicking the arrangement, e.g., rows and columns in a two-dimensional array, as well as the cross-sectional shapes of detector elements at the interface between radiation detector panel 40 and collimator 50 (FIG. 1). Alternatively, mask 112 need not be on the surface of the collimator substrate but can be positioned with respect to the substrate in accordance with known photolithographic techniques to provide the desired exposure of the photosensitive material in substrate 110. In any event, the pattern of the mask is selected to expose areas of photosensitive collimator substrate 110 of sufficient size and orientation so that, upon completion of the fabrication of collimator 50, the surface of each radiation detector element for receiving the radiation is exposed to radiation passing along the desired paths from the radiation source. In accordance with the present invention, collimator substrate 110 and mask 112 are exposed to light from light source 114. Light source 114 is preferably a laser, an ultraviolet light source, or the like, and is positioned with respect to collimator substrate 110 so that light beams pass through the openings in mask 112 and strike collimator substrate 110 along paths corresponding to direct paths between radiation point source 20 and radiation detector 30 (FIG. 1). As illustrated in FIG. 2, exemplar pairs of light beams 116a-b, 116c-d, and 116e-f define the boundaries of exposed photosensitive material shown in cross section. The light beams exposing the photosensitive material under each respective opening in mask 112 strike the collimator substrate at slightly different angles, the magnitude and orientation of which depend on the position along the length of the collimator substrate where the light strikes. For example, light beams 116a and 116b strike the collimator substrate at angles which differ in magnitude and orientation (i.e. left or right with respect to a perpendicular between the substrate and the light source) from light beams 116c-d and 116e-f. The light beams falling on photosensitive collimator substrate 110 define a plurality of respective exposed volumes 118 in the photosensitive material under each opening in the mask through which the light beams pass. Each exposed volume 118 has a longitudinal axis at a selected orientation angle corresponding to the angle at which the light beams emanating along a direct path from light source 114 strike the collimator substrate. Thus light beams 116a-b expose a volume that has a selected orientation angle .beta., whereas light beams 116e-f expose a volume having a different selected orientation angle, .differential.. The position of the collimator substrate with respect to light source 114 is selected to correspond with the distance that the collimator substrate will be from the radiation source in the assembled imager. Further, to ensure that the exposed volumes have the correct selected orientation angles required for collimating radiation in the assembled device, the plane of the collimator substrate is oriented at a "planar angle" so that the plane of the substrate has the same orientation with respect to the light source as the radiation detector panel with respect to the radiation source in the assembled device. Collimator substrate 110 is then etched using conventional techniques appropriate for the photosensitive material used in the substrate to remove the exposed volumes 118 of photosensitive material and create a pluraltiy of channels or passages 120 through the substrate, as illustrated in FIG. 3. Each of these channels has a longitudinal axis 122 aligned with the selected orientation angle defined when the photosensitive material was exposed to light source 114 (FIG. 2). Typically the selected orientation angles of the longitudinal axes of the channels range between about 0.degree. and 10.degree.. Each channel has a channel sidewall 124 which is substantially smooth along its length and has a substantially uniform slope formed when the photosensitive material exposed by the light beams in the previous step is removed in the etching process. The slope of the sidewalls is typically substantially aligned with the selected orientation angle of the channel defined by those sidewalls. The remaining portions of mask 112 may next removed to prepare the collimator substrate for the next step in the process of forming the collimator. A radiation absorbent material layer 130 (FIG. 3) is then applied on collimator substrate 110 so as to cover at least the surfaces of the substrate which will be exposed to incident radiation when assembled in an imager device. The radiation absorbent material at least covers all of the sidewalls defining the channel. The cross-sectional portion of the radiation absorbent material on the sidewalls and the top and bottom of substrate 110 is illustrated in FIG. 3 in cross-hatch, while the radiation absorbent material on the "back" sidewall of the channel is illustrated in alternating cross-hatch and dashed lines. The radiation absorbent material can be applied through known techniques, such as vapor deposition techniques. Radiation absorbent material 130 is selected to absorb radiation of the wavelength distribution emitted by radiation source 20 (FIG. 1) in the imager device. The radiation absorbent material typically has a relatively high atomic number, e.g., greater than about 72, and advantageously comprises tungsten, lead, or gold when the radiation used in the imager device is x-ray. The thickness of the radiation absorbent material layer is selected to provide efficient absorption of the incident radiation and depends on the type of incident radiation and the energy level of the radiation when it strikes the collimator. For example, in a typical CT system using an x-ray point radiation source of about 100 KeV positioned approximately one meter from the detector array, a total thickness in the range of about 30 to 40 mils of tungsten in one or more layers disposed along the path of the radiation will substantially absorb the x-rays emitted by the source. After application of the radiation absorbent material, the cross-sectional area of the opening or void space in the channel is substantially the same as the area for receiving radiation on the detector element which it adjoins so as to allow substantially all radiation rays emanating along direct paths from the radiation source to strike the detector element. Collimator 50 of FIG. 1, shown in an enlarged and simplified view in FIG. 4, comprises a collimator body 55 including at least one substrate 110 coated with radiation absorbent material 130. Collimator body 55 may comprise a plurality of substrates joined together as illustrated in FIG. 4. When two or more substrates are joined together to form the collimator body, the openings of the channels in the respective surfaces of the collimator substrates are aligned to form continuous channels through the collimator body The channel sidewalls are advantageously aligned so that the sidewalls of the respective channels in the adjoining substrates are contiguous. Dependent on the energy level and wavelength of the radiation to be collimated, different thicknesses of collimator bodies may be required. Once the necessary thickness has been determined, an appropriate thickness of collimator substrate, or plurality of substrates, can be selected and fabricated in accordance with this invention. For example, the thickness of a collimator for an imager system using x-rays, such as a CT system, may be only about 8 mm, but for an imager using gamma rays, the collimator preferably would be three to five times thicker than that used for x-ray radiation. In the assembled device, collimator body 55 is disposed to adjoin radiation detector panel 40, as illustrated in FIG. 4. Radiation detector elements 42 are positioned along detector panel 40 and typically comprise a scintillator coupled to a photodetector. Collimator body 55 is positioned to allow incident radiation on a direct path between the radiation source and one of the radiation detector elements 42 to pass through the channels in the collimator. Beams of radiation that are not aligned with such a direct path strike the collimator body and are absorbed. The collimator of the present invention is readily used with either a one-dimensional or a two-dimensional array of radiation detector elements. A plan view of a collimator fabricated in accordance with the present invention and showing a representative number of channels 120 appears in FIG. 5. The figure has been marked to show left, right, upper and lower edges solely to provide a reference for ease of discussion, and the selection and positioning of such references is not meant to constitute any limitation on the structure or positioning of the device of the invention. Openings 122 of channels 120 on the opposite surface of collimator body 55 are shown in phantom. In the two-dimensional array the center channel is in substantial vertical alignment with the radiation source, and the opening 122 of the channel on the side of the collimator body opposite the radiation source is aligned with the opening in the surface closest to the radiation source. As the radiation beams spread out as they emanate from the point source, each of openings 122 has a slightly larger cross-sectional area than the respective opening of the channel 120 in the surface of the collimator closest to the radiation source. Openings 122 for channels on the left, right, top, or bottom are slightly offset from being in vertical alignment with their respective openings in the upper surface of the substrate. The direct path from the radiation source to a radiation detector in the upper left hand corner, for example, is offset both to the left and the upper side of the array. The selected orientation angle of the axis of the channel is substantially aligned with this direct path, and the channel thus extends through the collimator body at this angle. The selected orientation angle for each channel is different from any other channel in the collimator. Such a structure, which would be extremely difficult and time consuming to construct with conventional collimator fabrication techniques, is readily produced in accordance with this invention. While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention. |
claims | 1. A weight compensation apparatus for compensating for a weight of a stage that is movable along a vertical reference plane, said apparatus comprising: a pulley having a pulley shaft; a belt which is wound around and supported by said pulley and has the stage at one end and a counter mass corresponding to the stage at the other end; a hydrostatic bearing which has an arcuated bearing portion and supports the pulley shaft by causing a fluid to flow into a bearing gap between the bearing portion and the pulley shaft; and a thrust bearing mechanism for resisting axial motion of said pulley by causing the fluid to flow into a gap between a thrust bearing portion and a side surface of said pulley. 2. The apparatus according to claim 1 , wherein claim 1 the bearing portion of said hydrostatic bearing includes a portion made of a porous material, and the fluid is supplied to the bearing gap via the porous material. 3. The apparatus according to claim 1 , wherein said hydrostatic bearing is made of a magnetic material. claim 1 4. The apparatus according to claim 1 , wherein said hydrostatic bearing comprises an electromagnet. claim 1 5. The apparatus according to claim 1 , further comprising plural sets of said pulley, said belt and said hydrostatic bearing, wherein the stage is movable two-dimensionally along the vertical reference plane. claim 1 6. A stage apparatus comprising: a stage which moves in at least a vertical direction along a vertical reference plane; a pulley disposed above said stage, said pulley having a pulley shaft; a belt which is wound around and supported by said pulley and has said stage at one end and a counter mass corresponding to said stage at the other end; a hydrostatic bearing which has an arcuated bearing portion and supports the pulley shaft by causing a fluid to flow into a bearing gap between the bearing portion and the pulley shaft; and a thrust bearing mechanism for resisting axial motion of said pulley by causing the fluid to flow into a gap between a thrust bearing portion and a side surface of said pulley. 7. The apparatus according to claim 6 , further comprising a damper for adjusting at least one of a tension and an effective length of said belt in order to provide damping in accordance with displacement of said stage. claim 6 8. The apparatus according to claim 6 , wherein claim 6 the bearing portion of said hydrostatic bearing includes a portion made of a porous material, and the fluid is supplied to the bearing gap via the porous material. 9. The apparatus according to claim 6 , wherein said hydrostatic bearing is made of a magnetic material. claim 6 10. The apparatus according to claim 6 , wherein said hydrostatic bearing comprises an electromagnet. claim 6 11. An exposure apparatus comprising: the stage apparatus defined in claim 6 ; claim 6 an exposure light source for generating exposure light; a first holder for holding a mask; a second holder for holding an object to be exposed on a stage; and an exposure controller for irradiating the object held by said second holder with the exposure light having passed through the mask held by said first holder, while moving the stage apparatus. 12. The apparatus according to claim 11 , claim 11 the exposure apparatus further comprising a display, a network interface, and a computer for executing network software, wherein maintenance information of the exposure apparatus is communicated via said computer network. 13. The apparatus according to claim 12 , wherein the network software is connected to an external network of a factory in which the exposure apparatus is installed, provides on said display a user interface for accessing a maintenance database provided by a vendor or user of the exposure apparatus, and enables obtaining information from the database via the external network. claim 12 14. A device manufacturing method comprising the steps of: installing a plurality of semiconductor manufacturing apparatuses including an exposure apparatus in a factory; and manufacturing a semiconductor device by using the plurality of semiconductor manufacturing apparatuses, wherein the exposure apparatus includes the stage apparatus defined in claim 7 , an exposure light source for generating exposure light, a first holder for holding a mask, a second holder for holding an object to be exposed on a stage, and an exposure controller for irradiating the object held by the second holder with the exposure light having passed through the mask held by the first holder, while moving the stage apparatus. claim 7 15. The method according to claim 14 , further comprising the steps of: claim 14 connecting the plurality of semiconductor manufacturing apparatuses by a local area network; connecting the local area network to an external network outside the factory; acquiring the information about an X-ray exposure apparatus from a database on the external network by using the local area network and the external network; and controlling the X-ray exposure apparatus on the basis of the acquired information. 16. The method according to claim 15 , wherein a database provided by a vendor or user of the exposure apparatus is accessed via the external network to obtain maintenance information of the manufacturing apparatus by data communication, or production management is performed by data communication between the semiconductor manufacturing factory and another semiconductor manufacturing factory via the external network. claim 15 17. A semiconductor manufacturing factory comprising: a plurality of semiconductor manufacturing apparatuses including an exposure apparatus; a local area network for connecting said plurality of semiconductor manufacturing apparatuses; and a gateway which allows the local area network to access an external network outside the factory, wherein the exposure apparatus includes the stage apparatus defined in claim 7 , an exposure light source for generating exposure light, a first holder for holding a mask, a second holder for holding an object to be exposed on a stage, and an exposure controller for irradiating the object held by the second holder with the exposure light having passed through the mask held by the first holder, while moving the stage apparatus. claim 7 18. An exposure apparatus maintenance method comprising the steps of: preparing a database for accumulating information about maintenance of the exposure apparatus, on an external network outside a factory in which an exposure apparatus is installed; connecting the exposure apparatus to a local area network in the factory; and maintaining the exposure apparatus on the basis of the information accumulated in the database by using the external network and the local area network, wherein the exposure apparatus includes the stage apparatus defined in claim 6 , an exposure light source for generating exposure light, a first holder for holding a mask, a second holder for holding an object to be exposed on a stage, and an exposure controller for irradiating the object held by the second holder with the exposure light having passed through the mask held by the first holder, while moving the stage apparatus. claim 6 19. The apparatus according to claim 6 , further comprising plural sets of said pulley, said belt and said hydrostatic bearing, wherein the stage is movable two-dimensionally along the vertical reference plane. claim 6 |
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abstract | In an electron microscope, focus correction is carried out automatically, an astigmatic difference amount is displayed and astigmatism correction is executed quantitatively. Enlarged specimen images obtained by irradiating an electron beam on a specimen while changing excitation currents of an objective lens and of a stigmator coil are picked up by a capturing unit comprised of an optical lens and a capturing device and image sharpness coefficients are calculated by means of an arithmetic logic unit. A suitable astigmatism correction direction is chosen on the basis of an angular component value of the obtained image sharpness coefficients and then, a correction excitation current is supplied to a stigmator coil to correct astigmatism and a correction excitation current is supplied to an objective lens coil to perform focus correction. |
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claims | 1. An apparatus structured to be received into a boiling water reactor (BWR) and to be usable to inspect at least a portion of a top guide of the BWR, the top guide having a plurality of beams arranged in a grid pattern, the top guide further having a number of receptacles, a receptacle of the number of receptacles being defined by and situated adjacent a subset of beams of the plurality of beams that comprises a first pair of beams of the plurality of beams and a second pair of beams of the plurality of beams, each beam of the plurality of beams having an upper edge, the apparatus comprising:a housing comprising a base and a pair of supports, the pair of supports being situated on the base, each support of the pair of supports having an engagement edge, the engagement edges being structured to be received atop the upper edges of one of the first pair of beams and the second pair of beams;an alignment assembly situated on the base and comprising a plurality of legs and an actuator, the actuator being operable to simultaneously move the plurality of legs between a retracted position wherein at least one of the legs of the plurality of legs is structured to be disengaged from the subset of beams and an extended position wherein all of the legs of the plurality of legs are structured to be engaged with the subset of beams; andan inspection system situated on the base and comprising at least a first inspection device that is structured to be situated in proximity to the upper edge of a beam of the other of the first pair of beams and the second pair of beams when the legs are in the extended position and the engagement edges are received atop the upper edges of the one of the first pair of beams and the second pair of beams. 2. The apparatus of claim 1 wherein the plurality of legs are each movably situated on the base, wherein the actuator is situated on the base, and wherein the alignment assembly comprises a plurality of links that extend between the actuator and the plurality of legs. 3. The apparatus of claim 1 wherein the inspection system further comprises a drive apparatus that is situated on the base, the at least first inspection device being situated on the drive apparatus, the drive apparatus being operable to translate the at least first inspection device along an inspection path between a first location adjacent a first support of the pair of supports and a second location adjacent a second support of the pair of supports. 4. The apparatus of claim 3 wherein the inspection system further comprises a second inspection device, the drive apparatus being operable to translate the second inspection device along another inspection path between another first location adjacent the first support and another second location adjacent the second support. 5. The apparatus of claim 3 wherein the at least first inspection device comprises a holder and an inspection element, the holder being situated on the drive apparatus, the inspection element being situated on the holder. 6. The apparatus of claim 5 wherein the pair of supports each extend away from the base in a first direction, and wherein the inspection element situated on the holder is spaced away from the base in the first direction. 7. The apparatus of claim 6 wherein each leg of the plurality of legs is of an L-shaped configuration having a first portion situated adjacent the base and having a second portion that extends in the first direction away from the first portion. 8. The apparatus of claim 7 wherein the first portions of a pair of legs of the plurality of legs extend in a direction generally away from the actuator and toward the pair of supports, and wherein the second portions of the pair of legs extend adjacent the pair of supports. 9. The apparatus of claim 8 wherein the first portions of another pair of legs of the plurality of legs extend in a direction generally away from the actuator and generally midway between the pair of supports, and wherein the second portions of the pair of legs extend generally midway between the pair of supports. 10. The apparatus of claim 6 wherein the holder comprises an extension mechanism that is structured to translate the inspection element between a first position disposed a first distance away from the base and a second position disposed a second distance away from the base greater than the first distance. 11. An apparatus structured to be received into a boiling water reactor (BWR) and to be usable to inspect at least a portion of a top guide of the BWR, the top guide having a plurality of beams arranged in a grid pattern, the top guide further having a number of receptacles, a receptacle of the number of receptacles being defined by and situated adjacent a subset of beams of the plurality of beams that comprises a first pair of beams of the plurality of beams and a second pair of beams of the plurality of beams, each beam of the plurality of beams having an upper edge, the apparatus comprising:a housing comprising a base and a pair of supports, the pair of supports being situated on the base, each support of the pair of supports having an engagement edge, the engagement edges being structured to be received atop the upper edges of one of the first pair of beams and the second pair of beams;an alignment assembly situated on the base, wherein the alignment assembly comprises a plurality of legs that are structured to be engaged with the subset of beams and an actuator operable to move at least one of the plurality of legs in relation to the base and the subset of beams;an inspection system situated on the base and comprising at least a first inspection device that is structured to be situated in proximity to the upper edge of a beam of the other of the first pair of beams and the second pair of beams when the engagement edges are received atop the upper edges of the one of the first pair of beams and the second pair of beams; andthe inspection system further comprising a drive apparatus that is situated on the base, the at least first inspection device being situated on the drive apparatus, the drive apparatus being operable to translate the at least first inspection device along an inspection path between a first location adjacent a first support of the pair of supports and a second location adjacent a second support of the pair of supports. |
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abstract | These teachings provide for administering a radiation treatment plan to a patient in a single radiation treatment session using a multi-leaf collimator that is comprised of pairs of selectively movable collimating leaves. By one approach this comprises administering a sequential plurality of modulated radiation doses to the patient, where the sequential plurality of modulated radiation doses comprises at least a substantial majority of a planned total radiation dose for the radiation treatment session and where each modulated radiation dose is administered while modulating a radiation beam with the multi-leaf collimator using a curtain pattern (or, perhaps more typically, a plurality of curtain patterns). |
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claims | 1. A method of servicing a nuclear reactor during a reactor outage, the reactor comprising a primary containment vessel and a reactor pressure vessel positioned in the primary containment vessel, said method comprising:positioning a servicing platform above the reactor pressure vessel, the servicing platform comprising:a frame comprising a plurality of interconnected beams;a support structure attached to the frame;a floor attached to a top of the frame, the floor comprising a reactor access opening sized to permit access to the reactor pressure vessel; andat least one auxiliary platform movably coupled to the frame and extending into the access opening, the at least one auxiliary platform movable along a perimeter of the access opening of the floor; andperforming predetermined servicing operations on the reactor. 2. A method in accordance with claim 1 wherein the servicing platform access opening has a circular, elliptical, or polygonal shape. 3. A method in accordance with claim 1 wherein the servicing platform comprises at least one of steel, aluminum, and a thermoplastic and fiber composite material. 4. A method in accordance with claim 1 wherein the reactor comprises at least two refuel bridges spaced apart and located in the primary containment above the reactor pressure vessel, and positioning a servicing platform above the reactor pressure vessel comprises positioning the servicing platform with the servicing platform support structure engaging the refuel bridges to suspend the servicing platform from the two spaced apart refuel bridges. 5. A method in accordance with claim 1 wherein the primary containment comprises a refuel floor located above the pressure vessel, the refuel floor comprising a plurality of crane rails, the support structure comprising a plurality of wheels, and positioning a servicing platform above the reactor pressure vessel comprises positioning the servicing platform with the servicing platform support structure wheels engaging the crane rails. 6. A method in accordance with claim 1 wherein the primary containment comprises a refueling floor located above the pressure vessel, and positioning a servicing platform above the reactor pressure vessel comprises positioning the servicing platform with the servicing platform support structure engaging the refueling floor to support the servicing platform above the pressure vessel. 7. A method in accordance with claim 6 wherein the refuel floor comprises a pressure vessel access opening and a ledge extending circumferentially around the pressure vessel access opening, and positioning a servicing platform above the reactor pressure vessel comprises positioning the servicing platform with the servicing platform support structure engaging the ledge to support the servicing platform above the pressure vessel. 8. A method in accordance with claim 1 wherein the servicing platform further comprises at least one lifting device movably coupled to the frame, the at least one lifting device movable along a perimeter of the access opening. 9. A method in accordance with claim 1 wherein positioning a servicing platform above the reactor pressure vessel comprises:assembling the reactor servicing platform inside the primary containment vessel; andmoving the reactor servicing platform into position above the reactor pressure vessel. 10. A method in accordance with claim 9 wherein assembling the reactor servicing platform inside the primary containment vessel comprises coupling modular sections of the reactor servicing platform together, each modular section comprising at least one of a portion of the frame, a portion of the support structure, and a portion of the floor. |
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description | The present invention relates to a technique for sensing a liquid level of a liquid held in a container. In a spent fuel storage pool, to ensure a radiation shielding effect of water, a liquid level is kept under surveillance so as not to fall below a reference level, e.g., a level a little over twice a length of spent fuel assemblies. The liquid level in a conventional spent fuel storage pool is measured by a float level switch installed in an upper end portion of the pool. Also, water temperature of the pool is measured by a thermometer installed separately from the float level switch. Cranes for use to replace fuel are placed above the spent fuel storage pool and configured to move over an entire surface of the pool, severely limiting space for installation of liquid level meters and thermometers. Also from the perspective of preventing pool water leakage, through-holes cannot be formed in a pool wall surface, making it impossible to adopt a typical differential pressure system as a liquid level meter. Furthermore, if foreign objects drop in the fuel storage pool, it is difficult to take them out, and thus it is also necessary to take measures to prevent foreign objects from getting into the pool. Under these circumstances, a sensor has been proposed which involves placing a heater in a neighborhood of one of two junctions of a thermocouple to sense a liquid level (e.g., Patent Document 1). Relying on the fact that there is a difference in thermal diffusivity between a water phase and gas phase, this technique determines in which of the water phase and gas phase a sensor portion is located, based on a temperature difference (electromotive force difference) between the two junctions. Patent Document 1: Japanese Patent Laid-Open No. 10-153681 Now, in the spent fuel storage pool, if a cooling function stops for a long period of time, disabling water supply, water temperature rises due to heat dissipation of the spent fuel, and the liquid level falls due to evaporation. If the liquid level falls in this way, the radiation shielding effect decreases, resulting in a deteriorated radiation environment. Thus, when the liquid level falls below a predetermined reference level, it is required to evaluate safety of the radiation environment by accurately keeping track of the liquid level. However, with the technique described in Patent Document 1, when the water temperature rises to boiling temperature, it is difficult to measure the temperature difference (electromotive force difference) between the two junctions of the thermocouple in a stable manner. Consequently, there is concern that sensing accuracy for the liquid level in the spent fuel storage pool may decrease. Also, since output signals of various sensors are processed digitally, meaning that the system is software-controlled, there is concern about vulnerability of nuclear facilities to contingencies. The present invention has been made in view of the above circumstances and has an object to provide a technique for sensing a liquid level reliably based solely on an analog process even if a liquid held in a container boils, causing the liquid level to fall. A liquid level sensing apparatus which measures a liquid level in a liquid holding vessel based on temperature signals from a plurality of probes placed at fixed intervals in a vertical direction of the liquid holding vessel, where each of the probes contains a temperature sensor and a heater enclosed in the probe and the heater is placed in a neighborhood of a detecting point of the temperature sensor, the liquid level sensing apparatus includes: a probe selection unit configured to select a probe whose heater is to be activated from among the plurality of probes; an input unit configured to receive an output of the temperature sensor of the probe selected by the probe selection unit, the output being received as a temperature signal directly in the form of an analog quantity; a signal processing unit configured to output a processing signal of the temperature signal in synchronization with activation of the heater; a calculation unit configured to arithmetically process the temperature signal and the processing signal and output a result; a gas/liquid discrimination unit configured to discriminate whether the detecting point exists in a gas phase or a liquid phase based on the output result of the arithmetic processing; and a display unit configured to indicate a discrimination result produced by the gas/liquid discrimination unit. The present invention provides a technique for sensing a liquid level reliably based solely on an analog process even if the liquid held in a container boils, causing the liquid level to fall. Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1A shows a spent fuel storage pool 1 to which a liquid level sensing apparatus 20 according to the embodiments is applied. A rack 2 adapted to store plural spent fuel assemblies 3 is placed in a spent fuel storage pool 1 (hereinafter also referred to as a “liquid holding vessel 1”). Furthermore, a circulation cooler (not shown) is placed in the spent fuel storage pool 1 to cool pool water 4 whose temperature is raised by decay heat of the spent fuel assemblies 3. If, for example, length a of the spent fuel assemblies 3 is approximately 4.5 m (a=approximately 4.5 m) and height b of the rack 2 is approximately 5 m (b=approximately 5 m), a liquid holding vessel 1 with a depth of about 12 m is required (d=approximately 12 m) and a liquid level of the pool water 4 is kept at a normal water level c=approximately 11 m. Consequently, a high-level of radiation released from the spent fuel assemblies 3 is blocked by the pool water 4 and kept from leaking out of the liquid holding vessel 1. In the liquid holding vessel 1, plural probes 10k (k=0 to n) are placed with their tip portions spaced from one another in a height direction. As shown in FIG. 1B, the probe 10k is made up of an enclosing tube 11 in which a temperature sensor 12 and a heater 14 are enclosed, the temperature sensor 12 being placed in a neighborhood of a detecting point 15 of the heater 14. The temperature sensor 12 is made up of a copper-constantan thermocouple and a sheath tube whose tip is closed, where wires 13 of the thermocouple are contained in the sheath tube. A space between the wires 13 and sheath tube is filled with magnesium oxide serving as an insulating material. A copper and constantan wires are welded together at the detecting point 15. Other ends of the wires 13 are led to a temperature detecting unit 21, and ambient temperature around the detecting point 15 is measured based on a thermo-electromotive force detected at these ends. In order to detect the liquid level of the pool water 4 in deep part of the liquid holding vessel 1, the wires 13 of the thermocouple need to be extended in length. In this case, however, a large load is placed on the wires 13 of the thermocouple, and thus superior mechanical properties are required of the wires 13 themselves. Furthermore, noise in the detected thermo-electromotive force increases as the wires 13 of the thermocouple get longer, and thus it is necessary to adopt a thermocouple with a large thermo-electromotive force to increase a signal to noise ratio. The wires 13 of the copper-constantan thermocouple are superior to those of a commonly-used chromel-alumel thermocouple in capability to produce a larger thermo-electromotive force and suitability for low-temperature measurement, but inferior in mechanical properties. Thus, a sheathed copper-constantan thermocouple is adopted as the temperature sensor 12 to ensure mechanical strength. The sheathed copper-constantan temperature sensor 12 is produced by inserting the wires of the copper-constantan thermocouple into the sheath tube before stretching, and then stretching the wires and sheath tube together. Being contained in the sheath tube, the wires 13 of the copper-constantan thermocouple does not become overloaded, which makes it possible to create the temperature sensor 12 elongated in shape. The enclosing tube 11 contains the temperature sensor 12 and heater 14. Also, the enclosing tube 11 is filled with magnesium oxide and externally placed in contact with the pool water 4 (liquid phase) and atmosphere (gas phase), where the magnesium oxide has a high heat conductivity. The temperature sensor 12 measures the temperatures of the pool water 4 (liquid phase) and atmosphere (gas phase) via the enclosing tube 11 and magnesium oxide while thermal energy from the heater 14 is released to the pool water 4 (liquid phase) and atmosphere (gas phase) by passing through the magnesium oxide and enclosing tube 11. A voltage output Vk (k=0 to n) on the order of millivolts is produced from the temperature sensor 12 of the probe 10k configured as described above. Joule heat generated when an electric current is passed through the heater 14 varies in thermal diffusivity depending on whether the detecting point 15 of the probe 10k (k=0 to n) is surrounded by a gas phase or liquid phase. This makes a difference in the voltage output Vk of the temperature sensor 12. The temperature detecting unit 21 converts the week voltage output Vk received from the probe 10k (k=0 to n) into a temperature signal VA(k) at a voltage level processible by an analog circuit and outputs the temperature signal to a determination unit 30. Specifically, a voltage range of the voltage output Vk corresponding to a temperature measurement range of 0 to 100 C.° of the probe 10k is converted into the temperature signal VA(k) corresponding to a voltage range of 1 to 5 V. A heat supply unit 22 generates Joule heat by activating the heater 14 of a selected probe 10k (k=0 to n) and thereby supplies thermal energy to around the detecting point 15 at a fixed flow rate. Note that a start time and duration t of the heat supply is controlled by the determination unit 30. As shown in FIG. 2 (see also FIG. 1 as appropriate), the determination unit 30 includes a probe selection unit 31 adapted to select a probe 10 whose heater 14 is to be activated from among the plural probes 10k (k=0 to n), an input unit 33 adapted to receive the voltage output Vk of the sensor 12 (FIG. 1) selected by the probe selection unit 31, as the temperature signal VA(k) directly in the form of an analog quantity, a signal processing unit 34 adapted to output a processing signal VB(k) of the temperature signal VA(k) in synchronization with activation of the heater, a calculation unit 35 adapted to arithmetically process the temperature signal VA(k) and processing signal VB(k) and output a result, a gas/liquid discrimination unit 37 adapted to discriminate whether the detecting point 15 exists in a gas phase or liquid phase based on the output result of the arithmetic processing, and a display unit 38 adapted to indicate a discrimination result produced by the gas/liquid discrimination unit 37. The probe selection unit 31 selects a probe 10 to be used for liquid discrimination in the liquid holding vessel 1 from among the plural probes 10k (k=0 to n). A heat supply control unit 32 causes thermal energy to be supplied to the heater 14 of the selected probe 10k at a fixed flow rate for the duration t and causes the signal processing unit 34 to start processing in synchronization with the start time of the heat supply. That is, the heat supply control unit 32 outputs a voltage signal to the heat supply unit 22 to activate and deactivate the heater, thereby prescribing the duration t of heat supply, and outputs a same level of a voltage signal to the signal processing unit 34 as well. The input unit 33 divides the received temperature signal VA(k) into two parts directly in the form of analog quantity and inputs one part directly to the calculation unit 35 and inputs another part to the signal processing unit 34. The signal processing unit (hold circuit) 34A accepts as input a synchronizing signal from the heat supply control unit 32, and outputs the processing signal VB(k) held at a level of the temperature signal VA(k) at the time of input. That is, when the synchronizing signal from the heat supply control unit 32 is set to OFF, the signal processing unit 34A outputs the received temperature signal VA(k) as it is. Then, when the synchronizing signal is switched to ON, the signal processing unit 34A continues to output the held processing signal VB(k) by maintaining an input voltage level of the temperature signal VA(k) inputted at that time until the synchronizing signal is switched to OFF again. The signal processing unit 34A is comprised, for example, of a hold circuit and the like, the hold circuit being made up of a combination of a switch contact and capacitor. A graph in FIG. 3 shows time variations of the temperature signal VA and the processing signal VB thereof when the detecting point 15 of the probe 10k is exposed to a gas phase and the synchronizing signal of the heat supply control unit 32 is switched from an OFF setting to an ON setting. When a tip of the probe 10k is exposed to a gas phase in this way, the thermal energy supplied from the heater 14 does not diffuse in the gas phase with low thermal diffusivity and thus greatly raises the ambient temperature around the detecting point 15. Consequently, the temperature signal VA(k) of the temperature sensor 12 increases with a time constant on the order of a few minutes and greatly diverges from the processing signal VB held at the level of the temperature signal VA(k) at the time of switching to ON. Next, a graph in FIG. 4 shows time variations of the temperature signal VA and the processing signal VV thereof when the detecting point 15 of the probe 10k is immersed in a liquid phase and the synchronizing signal of the heat supply control unit 32 is switched from an OFF setting to an ON setting. When the tip of the probe 10k is immersed in a liquid phase in this way, the thermal energy supplied from the heater 14 is diffused in the liquid phase with high thermal diffusivity, and thus the ambient temperature around the detecting point 15 does not rise much. Consequently, the temperature signal VA(k) of the temperature sensor 12 reaches a state of equilibrium without diverging much from the processing signal VB held at the level of the temperature signal VA(k) at the time of switching to ON. The calculation unit 35 (FIG. 2) applies a subtraction process to the temperature signal VA(k) and processing signal VB(k) thereof, and outputs a difference to a threshold comparison unit 36. During the duration t of heat supply, the threshold comparison unit 36 outputs a determination signal to the gas/liquid discrimination unit 37, indicating whether or not a relationship between the output of the calculation unit 35 and a threshold α satisfies determination formula (1) below. As the threshold α, an optimal value is established experimentally.α<VA(k)−VB(k) (1) When determination formula (1) is satisfied, the gas/liquid discrimination unit 37 determines that the tip of the probe 10k is exposed to a gas phase and when determination formula (1) is not satisfied, the gas/liquid discrimination unit 37 determines that the tip of the probe 10k is immersed in a liquid phase. The display unit 38 is designed to present a discrimination result to an operator, indicating whether the tip portion of the probe 10k is in a liquid phase or gas phase and is implemented, for example, by a function to turn on and off a lamp. As another operation example, the calculation unit 35 (FIG. 2) applies a division process to the temperature signal VA(k) and processing signal VB(k) thereof, and outputs a quotient to the threshold comparison unit 36. During the duration t of heat supply, the threshold comparison unit 36 outputs a determination signal to the gas/liquid discrimination unit 37, indicating whether or not a relationship between the output of the calculation unit 35 and a threshold β satisfies determination formula (2) below. As the threshold β, an optimal value is established experimentally.β<VA(k)/VB(k) (2) When determination formula (2) is satisfied, the gas/liquid discrimination unit 37 determines that the tip of the probe 10k is exposed to a gas phase and when determination formula (2) is not satisfied, the gas/liquid discrimination unit 37 determines that the tip of the probe 10k is immersed in a liquid phase. Referring now to FIG. 5, a second embodiment of the present invention will be described. The second embodiment differs from the first embodiment in that a signal processing unit 34B (34) of the determination unit 30 is a first order delay circuit adapted to output a first order delay response to a temperature signal. In FIG. 5, components same as or equivalent to those in FIG. 2 are denoted by the same reference numerals as the corresponding components in FIG. 2, and redundant description thereof will be omitted. In this way, since the signal processing unit 34B is configured as a first order delay circuit, a processing signal VB(k) for use in gas/liquid discrimination can be outputted to the calculation unit 35 in synchronization with heat supply without the need for a synchronizing signal from the heat supply control unit 32. Also, such a first order delay circuit can be implemented solely by a resistor and capacitor, eliminating the need for the threshold comparison unit 36 to recognize the start time of the duration t of heat supply and thereby allowing a determination to be made based on determination formula (1) or (2) described above without regard to time. Thus, the second embodiment allows configuration of the determination unit 30 to be simplified. A graph in FIG. 6 shows time variations of the temperature signal VA and the processing signal VB thereof when the detecting point 15 of the probe 10k according to the second embodiment is exposed to a gas phase and the heat supply control unit 32 is switched from an OFF setting to an ON setting. During a period when the heat supply control unit 32 is at an OFF setting, since the temperature signal VA(k) is in a steady state, the processing signal VB converges to the temperature signal VA(k). However, when the heat supply control unit 32 is switched to an ON setting, the temperature signal VA(k) from the gas phase rises greatly and shifts to a transient state. Then, the processing signal VB (k) which indicates a first order delay response to the transient state increases, following the temperature signal VA(k), but diverges greatly, being unable to keep up with a rate of change of the temperature signal VA(k). Next, a graph in FIG. 7 shows time variations of the temperature signal VA and the processing signal VB thereof when the detecting point 15 of the probe 10k according to the second embodiment is immersed in a liquid phase and the heat supply control unit 32 is switched from an OFF setting to an ON setting. During a period when the heat supply control unit 32 is at an OFF setting, since the temperature signal VA(k) is in a steady state, the processing signal VB converges to the temperature signal VA(k). Then, when the heat supply control unit 32 is switched to an ON setting, the temperature signal VA(k) from the liquid phase rises and shifts to a transient state, but has a low rate of change. Consequently, the processing signal VB(k) which indicates a first order delay response to the transient state increases, following the temperature signal VA(k) with a small divergence. A time constant of the first order delay is, for example, around 60 seconds. Operation of the liquid level sensing apparatus according to the above embodiments will be described with reference to a flowchart of FIG. 8 (also to FIG. 1 as appropriate). Plural probes 10k (k=0 to n) placed by varying their tip position in a height direction of the liquid holding vessel 1 are selected one at a time beginning at the top (S11 and S12). Then, heat supply to the heater 14 is started by inputting the output Vk from the temperature sensor 12 of the selected probe 10k as the temperature signal VA(k) directly in the form of an analog quantity (S13 and S14). The processing signal VB(k) (hold value or first order delay response) of the temperature signal VA(k) is outputted in synchronization with the heat supply (S15), and the temperature signal VA(k) and processing signal VB(k) thereof are arithmetically processed and results are outputted until the duration t of heat supply expires (No or Yes in S16). If the output result of the arithmetic processing satisfies determination formula (1) or (2) described above, a decision of a gas phase is made (Yes in S17; S18), and if the output result does not satisfy determination formula (1) or (2), a decision of a liquid phase is made (No in S17; S19). Furthermore, a determination as to a gas phase or liquid phase is made using a next probe 10k (No in S20), and the liquid level in the liquid holding vessel 1 is determined based on determination results produced using all the probes 10k (k=0 to n) (Yes in S20; S21). The liquid level sensing apparatus according to at least one of the embodiments described above can be made up solely of analog circuit, providing robustness against contingencies in nuclear facilities. Whereas a few embodiments of the present invention have been described, these embodiments are presented only by way of example, and not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, changes, and combinations can be made without departing from the spirit of the invention. Such embodiments and modifications thereof are included in the spirit and scope of the invention as well as in the invention set forth in the appended claims and the scope of equivalents thereof. For example, although the liquid level is sensed by the plural probes 10k (k=0 to n) mounted at fixed locations in the above embodiments, the liquid level may be sensed by moving the probes in a vertical direction. |
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abstract | A feedback controller for generating and using a normalized performance index for a feedback control loop is shown and described. The feedback controller is configured to generate an input for a control process, identify an error signal representing a difference between a setpoint and a feedback signal from the control process, compute a first exponentially-weighted moving average (EWMA) of a first function of the error signal and a second EWMA of a second function of the error signal, and to generate a normalized performance index using the first EWMA and the second EWMA. |
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041772415 | claims | 1. A process for recovering in solution form enriched nuclear fuel compounds from scrap materials, said process comprising the steps of: (a) calcining the scrap material that is readily combustible to yield an oxidized material; (b) comminuting the oxidized material to form a particulate material of particle size less than about 250 microns; (c) contacting the particulate material with an acid containing some recycled acid from step (g) in a mechanically agitated leaching zone of a slab-shaped nuclear-safe configuration to dissolve said compounds and yield an acid solution of said compounds; (d) mulching non-combustible material such as filter media so that it is in the form of particulate material; (e) contacting the mulched non-combustible material with the acid solution of (c); (f) filtering the nonsuspended insoluble solids from the acid solution in a filtering zone; (g) separating the suspended solids from the acid solution in a clarification zone; (h) recycling at least a portion of the acid solution of (g) from the clarification zone to the leaching zone; and (i) collecting the remainder of the acid solution for subsequent treatment. 2. A process according to claim 1 in which the calcination step is conducted at a temperature in the range of 750.degree. to 1000.degree. C. 3. A process according to claim 1 that further includes a step of screening the oxidized material so that particles of less than about 250 microns are directly contacted with the acid and particles of greater than about 250 microns are subjected to the comminuting step prior to contacting with the acid. 4. A process according to claim 1 in which the acid comprises nitric acid. 5. A process according to claim 4 in which the concentration of the acid is in the range of about 3 to about 8 normal. 6. A process according to claim 1 in which the separating step is performed in a wet pulp separator zone. 7. A process according to claim 1 in which the comminuting step yields a particulate material of particle size in the range of about 10 to about 250 microns. 8. A process according to claim 1 in which the nuclear fuel compound is an oxide compound. 9. A process according to claim 8 in which the oxide compound is a uranium oxide. 10. A process according to claim 8 in which the oxide compound is comprised of a mixture of uranium oxide and plutonium oxide. 11. A process according to claim 8 in which the oxide compound is uranium dioxide. |
055235158 | summary | BACKGROUND OF THE INVENTION The present invention relates to a method of separating and purifying a spent solvent discharged from a solvent extraction process in a nuclear fuel cycle, such as a reprocessing plant of spent nuclear fuel or nuclear fuel manufacturing plant. The present invention can preferably be utilized in regeneration and disposal processes of such a spent solvent as described above. A solvent prepared by diluting a phosphate, such as tributyl phosphate (TBP), and octylphenyl-N,N-diisobutylcarbamoyl methylphosphine oxide (CMPO), with a higher hydrocarbon, such as n-dodecane (hereinafter referred to simply as "dodecane") and kerosene, is widely used in a solvent extraction step of a reprocessing process of spent nuclear fuel or of wet recovery process of mixed-oxide fuel scrap in a nuclear fuel manufacturing plant. The spent solvent generated in the solvent extraction step contains deterioration products, such as dibutyl phosphate (DBP), formed as a result of degradation of a portion of TBP by an acid, heat, radioactive rays, etc. Such deterioration products adversely affect the extraction when the spent solvent is recycled for reuse. Therefore, the deterioration products are removed by alkali washing with an aqueous solution of sodium hydroxide or sodium carbonate. A radioactive waste containing the deterioration products thus removed, such as DBP, is converted into a vitrified solid or a bituminized solid by mixing the same with a vitrification additive or a bituminization additive. However, in order to stabilize a large amount of the sodium component incorporated by the alkali washing, it is necessary in this solidification treatment to use a large amount of these additives. Consequently, the development of a method of separating and purifying a spent solvent which enables deterioration products, such as DBP, to be removed from TBP without using any salts of sodium has been desired in the art. On the other hand, methods such as vacuum freeze-drying and low-temperature vacuum distillation wherein difference in vapor pressure is utilized have been used as a method of separating TBP, DBP and dodecane from a spent solvent. However, they are disadvantageous in that the treatment capacity is small because of the low vapor pressure. Consequently, the development of a separation method having a large treatment capacity for a spent solvent has been desired in the art. Moreover, when a spent solvent is heated under atmospheric pressure to conduct distillation into components, there occur problems involving the danger of fire or explosion and also the danger that volatile components undergo evaporation and sublimation upon heating, thus causing environmental contamination. The applicant of the present invention has proposed a method (hereinafter referred to as "cooling crystallization method") of separating and purifying a spent solvent containing a phosphate and a higher hydrocarbon, which comprising exposing the spent solvent at a temperature not greater than the freezing point of the higher hydrocarbon but not less than the freezing point of the phosphate to selectively freeze the higher hydrocarbon, and separating a resulting frozen solid mainly composed of the higher hydrocarbon from a remaining solution containing the phosphate in a higher concentration (see U.S. Pat. No. 5,110,507 corresponding to Japanese Patent Laid-open Specification No. 3-293595(1991)). However, the cooling crystallization method is not always satisfactory. This is because it is difficult to suitably control the temperature, cooling speed and other conditions in the course of the formation of the frozen solid, and TBP, DBP, etc., are incorporated into the frozen solid to form a solid/liquid mixture, whereby it becomes difficult to efficiently separate the higher hydrocarbon having a high purity. In addition, it is necessary to such a cryogenic temperature as -20.degree. C. or below for increasing the recovery of the higher hydrocarbon. SUMMARY OF THE INVENTION An object of the present invention is to provide a method of separating and purifying a spent solvent which enables the higher hydrocarbon to be efficiently separated from the phosphate without using any reagent including sodium and attains high safety because of freeness from the danger of fire or explosion. Another object of the present invention is to provide a method of separating and purifying a spent solvent which is free from the temperature control and the cryogenic temperature to thereby enable the treatment capacity to be enlarged and the required labor to be saved. A further object of the present invention is to provide a method of separating and purifying a spent solvent which enables the amount of generated radioactive waste to be reduced by virtue of possible recycling of the recovered solvent. According to the present invention, there is provided a method of separating and purifying a spent solvent generated in a nuclear fuel cycle and containing a higher hydrocarbon and a phosphate. This method comprises applying to the spent solvent a pressure high enough for allowing the crystallization of the higher hydrocarbon to thereby crystallize the higher hydrocarbon, and separating under pressure a resulting solid mainly composed of the higher hydrocarbon from a remaining solution containing the phosphate in a higher concentration. |
claims | 1. A control rod drive mechanism comprising:a shaft elongated along an axis and comprising engagement recesses formed along the axis on a circumference thereof;a supporting member defining an elongated channel for receiving the shaft, the supporting member comprising a latch opening therethrough;a latch assembly comprising a latch mechanism and a latch operably connected to the latch mechanism, the latch mechanism disposed outside the shaft in a radial direction from the axis, the latch comprising a latch tip extending into the elongated channel via the latch opening and configured to latch the shaft by engagement with one of the engagement recesses;a latch housing located outside the supporting member in the radial direction and housing the latch mechanism, wherein the latch housing comprises a latch housing wall disposed outside the latch assembly in the radial direction; anda plurality of coil housings disposed outside the latch assembly in the radial direction, each coil housing comprising an inner wall facing the shaft, the inner wall comprising a non-magnetic wall portion and a magnetic wall portion, wherein the plurality of coil housings are arranged along the axis together with the latch housing wall such that the inner walls of the plurality of coil housings and the latch housing wall together provide non-magnetic wall portions and magnetic wall portions that are alternatingly arranged along the axis while facing the shaft. 2. The control rod drive mechanism of claim 1, wherein each of the coil housings comprises an outer wall connected to the inner wall and facing away from the inner wall. 3. The control rod drive mechanism of claim 2, wherein non-magnetic wall portion of each coil housing overlaps a corresponding coil when viewed in a viewing direction perpendicular to the axis. 4. A control rod drive mechanism comprising:a shaft elongated along an axis and comprising engagement recesses formed along the axis on a circumference thereof;a latch assembly comprising a latch mechanism and a latch operably connected to the latch mechanism, the latch mechanism disposed outside the shaft in a radial direction from the axis, the latch comprising a latch tip extending toward the shaft and configured to latch the shaft by engagement with one of the engagement recesses;a latch housing located outside the latch mechanism in the radial direction and housing the latch mechanism, wherein the latch housing comprises non-magnetic wall portions and magnetic wall portions that are alternatingly arranged along the axis while facing the shaft; anda plurality of coil housings located outside the latch housing in the radial direction and arranged along the axis. |
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abstract | A method of decontaminating naturally occurring radioactive material (NORM) from downhole equipment may include injecting a NORM dissolver into an isolated region of a wellbore in which NORM-contaminated production equipment is located; and removing the NORM contaminants from the production equipment. The method may also include recommencing production of hydrocarbons following the decontamination. |
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abstract | A method is presented for collecting and removing radon from a confined area, a storage box or articles of clothing. The method includes collecting radon from the confined area or around a storage box via at least one collector, connecting each of a plurality of radon adsorbers to a corresponding power supply or power source such as a battery, capacitor, fuel cell, etc. diverting, via a plurality of valves, the collected radon or radon daughters through one or more of the plurality of radon adsorbers, and receiving, via a plurality of radon storage units, radon or radon daughters held by the plurality of radon adsorbers for a predetermined period of time. |
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abstract | Tropospheric volume elements enriched with vital elements and/or protective substances as well as procedures for their production and application. The term “vital elements” applies to all matter supporting the development of life within the earth's biosphere and the term “protective substances” means all those substances which contribute directly or indirectly to the prevention of harmful effects on the earth's biosphere and in particular on man. Tropospheric volume elements in the form of clouds which contain contaminants and which can escape from industrial facilities due to damage or malfunction are enriched with protective substances which prevent the organism from taking in radioactive elements and minimize the extent of the area affected by the clouds and possess additional warning and identification properties. |
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054188326 | claims | 1. A scanning radiographic system for producing images of a patient comprising: an x-ray source producing a fan beam of rays of x-rays directed toward the patient along a beam axis, the fan beam having a cross-sectional length and width measured in a plane perpendicular to the beam axis; a detector array positioned to receive the fan beam after the fan beam has passed through the patient so as to produce an attenuation signal related to the intensity of the received fan beam; a slot formed of a radiopaque material, having an aperture with a width and length substantially equal to that of the fan beam attached to move with the detector array and positioned on the same side of the patient as the detector array; a scanner attached to the slot to scan the slot over a volume of the patient in a direction generally perpendicular to the length of the fan beam; a grid, affixed to the slot and comprised of a set of radiopaque lamellae having a lamellae height measured along the beam axis greater than the lamellae width measured the cross-sectional length of the fan beam extending across the width of the slot so as to pass x-rays therebetween. 2. The scanning radiographic system of claim 1 wherein the lamellae extend diagonally across the width of the slot. 3. The scanning radiographic system of claim 2 wherein the lamellae are separated along the length of the slot by a repeat distance D' and wherein the lamellae extend at an angle with respect to the length of the slot of .theta. where: ##EQU2## where W is the width of the slot and n is a non-negative integer. 4. The scanning radiographic system of claim 2 wherein the lamellae are canted to reduce their cross-section measured perpendicularly to the rays of the fan beam. 5. The scanning radiographic system of claim 1 wherein the attenuation signal from the detector indicates the intensity of the received x-ray signal in two or more energy bands. 6. The scanning radiographic system of claim 1 wherein the detector array conforms in area substantially to the aperture of the slot. |
description | This application claims the benefit of German Patent Application Ser. No. DE 10 2005 057 700.8 filed on Nov. 25, 2005. The specification of this application is expressly incorporated by reference into this application in its entirety. The invention relates to X-ray optical elements which are generally provided with gradient multilayer mirrors. This involves an improved form of a side-by-side arrangement according to Montel. Such X-ray optics are able to collimate or focus the radiation from an X-ray beam source in both spatial directions and are usually used in conjunction with spatially resolving area counters (2D detectors) in X-ray diffractometry or small-angle scattering or for local excitation of fluorescent radiation in X-ray fluorescence analysis. The principle of side-by-side or arrangement according to Montel of two curved mirrors was described back in 1960 by Cosslett and Nixon; “X-Ray Microscopy”; Cambridge at the University Press; 1960, and in this form as an example also in DE 699 09 599 T2. Montel optics are distinguished by a high photon flux on the sample, a compact external form, virtually identical beam properties in the spatial directions perpendicular to the beam direction and easier handleability and adjustability compared with the arrangement—likewise cited by Cosslett and Nixon—of X-ray mirrors in Kirkpatrick-Baez geometry (KB arrangement). Instead of lying one behind another (KB arrangement), the two beam-shaping X-ray mirrors (elementary mirrors) in the Montel arrangement lie side-by-side and image the X-ray source. Each elementary mirror of the side-by-side arrangement or the KS arrangement has a cylindrically symmetrical surface contour, that is to say that said mirrors are embodied as a plane parabola (collimating or parallel beam optic) or plane ellipse (focussing optic). Two-dimensional beam shaping requires reflection at both elementary mirrors, which therefore means a total of two reflections (that is to say that the transmission of the optic is proportional to R2 if R denotes the reflectance of an elementary mirror). In the side-by-side optic according to Montel, the elementary mirrors are joined together at a right angle (90°) in order to ensure the exact imaging of the X-ray source, which is described both in Cosslett and Nixon and in DE 69909599 T2 (cf., in particular, Patent claim 1). The optimally adjusted mirrors in the KB arrangement also lie at right angles with respect to one another one behind another. In these two known arrangements, meridional and sagittal focal points of the optics coincide at a point in the beam direction. Both Cosslett and Nixon, and U. W. Arndt; “Focusing Optics for Laboratory Sources in X-ray Cristallography”; J. Appl. Cryst.; (1990) 23; pp. 161-168, describe the possibility of two-dimensional beam shaping with only one reflection at a paraboloidal or ellipsoidal surface that is simultaneously curved meridionally and sagittally. The advantage of this solution consists in the higher transmission—higher by the magnitude 1/R (R instead of R2)—of the optical element compared with the side-by-side arrangement according to Kirkpatrick-Baez, since the second reflection does not take place. It may be disadvantageous that the suppression of disturbing parts of the emission spectrum of the X-ray source likewise takes place only with R rather than with R2. When rotational symmetry is present, the meridional and sagittal focal points likewise coincide in the beam direction. The brilliance of the X-ray beam source is also significant in this case. It is all the higher, the higher the thermal power introduced on the anode. U. W. Arndt explains, inter alia, that there is a relationship between the form of the thermal tube focus and the thermal power introduced on the focal spot of the X-ray source. If x and y were the dimensions of the thermal focal spot on a Cu anode, a maximum thermal power of 460 W/mm would result given y/x=1 (the length indication relates to the lateral lengths of a quadrangle containing the area x*y=A), where an increase to 630 W/mm may be observed given a ratio where y/x=10. Owing to this fact, the laboratory X-ray tubes used nowadays have thermal focal spots which achieve a ratio y/x>10 (e.g. 8 mm/0.4 mm) and thus naturally a higher brilliance than is the case with comparable X-ray beam sources having a square thermal focal spot. If a thermal focal spot of an X-ray beam source is considered at the take-off angle α, there appears either in the y direction what is usually referred to as an optical point focal spot having the extent [x, z=y*sin(α)] or in the x direction a line focal spot having the extent [z=x*sin(α), y] (e.g. line 0.04 mm*8 mm, point 0.4 mm*0.8 mm). The geometric focal spots thus represent a projection of the thermal focal spot of the X-ray beam source into a geometric plane. Even if the projection supplies a square and hence symmetrical focal spot, the X-ray radiation nevertheless arises in the thermal focal spot which has a spatial extent in the beam direction, and it is thus advantageous for the imaging properties of an optic to take account of this particular feature of the arising of radiation. In the case of a line focal spot, the extent in the beam direction is negligibly small with respect to the acceptance of an elementary mirror at 0.4 mm or 0.04 mm, but it is very considerable in the case of point focal spots (8 mm to 0.8 mm). There is a discrepancy between the geometric focal point (optic focus) of elementary mirrors arranged side by side in the plane perpendicular to the beam direction and the real and non-symmetrical thermal focal point in the plane of the anode surface of the X-ray beam source, which on top of everything is inclined in relation to the plane perpendicular to the beam direction by the take-off angle 90°-α. It is not necessarily so that the identical elementary mirrors in side-by-side arrangement also have to generate a symmetrical beam cross section in the imaging of the thermal focal spot (square or circle) if the real X-ray tube focal point has different extents in the x and y directions. Rather, it is to be expected that a rectangular focal spot present in reality is also imaged into a rectangular focal point or an elliptical focal spot is again imaged into an ellipse. If the meridional and sagittal focal points coincide, then the geometric focal point (optic focus) of the X-ray optic does not, moreover, lie on the entire thermal focal spot, but rather only on a small segment thereof. The situation where locations having different levels of thermal loading and hence different brilliance are situated locally on the thermal focal spot cannot be precluded. If specific influences shift the position of the thermal focal spot on the anode relative to the geometric focal point of the optic, intensity fluctuations at the location of the sample may be the consequence. Accrrding to the invention, this object is achieved by means of X-ray optical elements. Advantageous refinements and developments can also be achieved. Therefore, in many points the solution according to the invention is constructed analogously to that known from DE 699 09 599 T2. In this case, the X-ray optical element according to the invention is formed anaolgously to the arrangement described by Moontel likewise with two elements such as elements 104, 106 of FIGS. 1-4 that reflect the X-ray radiation 108 of FIGS. 1, 3 and are arranged side-by-side. The reflect the surfaces 104, 106 of FIGS. 1-4 are curved in this case. This may be parabolic as shown in FIG. 4 or elliptical as shown in FIG. 2. However, it is also possible to form a combination of parabolic and elliltical curvanture at a respective one of the reflective elements. In this case, an X-ray beam emitted 108 by an X-ray beam souce 102 of FIGS. 1 and 3 is directed onto the two reflective elements 104, 106 that are arrangee side-by-side and preferbly connected to one another and is reflected in one axis by one reflective element and in a second axis by the other element. The X-ray beam source 102 may be between a line formed from points S1 and S2 and a line formed between S3 and S4. The line S1-S2 may be a substantially vertical line where the X-ray intersect prior to reflecting off the elements 104, 106. The line S3-S4 may be substantially perpendicular line to the line S1-S2 where the X-rays intersect prior to reflecting off the elements 104, 106. It should be noted that the line S1-S2 being disposed before the line S3-S4 is only exemplary an the line S3-S4 may be disposed prior to the line S1-S2. The Disposition of the X-ray beam source 102 may allow the X-rays from the souce 102 to form a tetraeder. Those skilled in the art wiil understand that the disposition of the reflective elements 104, 106 and an appropriate location of the X-ray beam source 102 allows the tetraeder to form according to the present invention. An improved astigmatic configuration of the X-ray arrangement according to the present invention may be had. Furthermore, the elongation of the X-ray radiation may be improved. With regard to the reflection, if the Xray beam 108 initially reflects off element 104, then the X-ray beam is subsequently reflected off element 106. The portion of the X-ray radiation that is reflected by the two reflective elements impinges on a further area—downstream in the beam path—of the respective other reflective element and is reflected there a second time, in this case in the other axis. In this case, the angles of curvature of the two reflective elements 104, 106 deviate from one another, so that they have a different focal length. For xample, in FIG. 2, element 104, 106 exhibit elliptical curvatures where foci 112 and 114, respectively, are situated in a different location. In another example, in FIG. 4, elements 104, 106 exhibit parabolic curvatures where foci 112 and 114, respectively, are situated in a different location. That is, the focal length for foci 112, 114 are different. This angular deviation may be keep small and lie within the range of 0.01 to a few tenths of a degree. Those skilled in the art will understand that with an elliptical curvature, the resulting reflections cause a convergence of the X-ray beam 108 such as end point 110 in FIG. 1. Thosr skilled in the art wiil also understand that with a parabolic curvature, the resulting reflections cause a divergence of the X-ray beam 108 such as end point 110 in FIG. 3. The targeted use of a “spatial dissociation” of the meridional and sagittal focal points affords better success in removing the abovementioned discrepancy and minimizing intensity fluctuations resulting from positional fluctuations of the thermal focal spot of X-ray beam sources. The use of different reflective elements makes it possible, in the case of focussing side-by-side arrangements, to influence the imaging ratio in the x and y directions in such a way that approximately a square or a circular beam cross section of the X-ray beam reflected by the two reflective elements and a corresponding focal spot geometry are formed at the sample location. The X-ray radiation reflected by the two reflective elements can be locally influenced with regard to one or more characteristics, and this can be achieved in two dimensions. After the reflection of the X-ray radiation, the latter is influenced by way of its cross section, and this can also be exploited at the imaging location, for example at a sample. Thus, the following characteristics of the X-ray radiation reflected according to the invention can be influenced: homogeneity, photon density distribution over the cross section of the reflected X-ray beam. Its cross-sectional form and the size of the cross-sectional area. The divergence can also be influenced. With the use of astigmatism, the source-side focal point of X-ray optical systems changes into a focal point volume that is extended in the beam direction and that better integrates the real thermal focal spot into the optical imaging. In the case of collimating optics, it is possible, by way of the targeted influencing of the parabola parameter, to match divergence differences in the two spatial axial directions. These usually result from the non-symmetrical form of focal spots of the X-ray radiation sources (rectangular, elliptical) which generally reach the imaging. The focal point becomes a focal point range between meridional and sagittal focal points. If the thermal focal spot is put into the focal point range by means of the differently curved reflective elements, that proportion of the area of the thermal focal spot which actually contributes to the imaging increases. Temporal fluctuations in the photon flux, resulting from local differences in brilliance on the thermal focal spot and the drifting thereof on the anode surface, can be virtually completely compensated for owing to the averaging of a larger area. Non-symmetrical beam cross sections of the X-ray radiation emitted by X-ray beam sources can be shaped into symmetrical cross sections and also be imaged in this way at the sample location if use is made of different reflective elements in a targeted manner. The improved homogeneity and symmetry of the beam cross section, its improved temporal stability and, at the same time, the optimum intensity in the imaged focal spot on the sample are advantageous. The realization of an “astigmatic” imaging which may be at least approximately symmetrical is realized by means of two different gradient multilayers in a side-by-side arrangement of two reflective elements. The distances between the source-side focal point and the centre of the two reflective elements differ in both reflective elements according to the sagittal or meridional focal point distance chosen. The distance between the centre of the two reflective elements and the focal point at the location of a sample being identical or being able to be identical especially in the case of the focussing arrangement. Even if the ellipse parameters a and b of the two reflective elements differ, it is nevertheless possible to comply with the symmetry of the convergence angle in the two axial directions perpendicular to the beam direction at the sample location. In the case of a collimating embodiment of X-ray optical elements, it is possible to achieve a symmetrical (square or circular) beam cross section by means of a suitable choice of the two parabola parameters p of the two reflective elements. The distances between focal points considered from the direction of the X-ray beam source and the centre of the reflective elements differ with regard to the meridional and sagittal focal point distances in both reflective elements in a preferred embodiment. When focussing in the direction of a sample, the distance of the focal points from the centre of the reflective elements to the sample location should be identical. The reflective elements are preferably provided with a gradient multilayer system at their surfaces, in which system the different thicknesses of individual layers are derived from the respectively locally different angles of incidence and the respective wavelength of the X-ray radiator. The Bragg condition λ=2deff*sin θ ought to be taken into account in order to achieve an increased reflectivity. Besides graded layer thickness distributions in a lateral direction, layer thickness distributions that are graded in their depth can also be realized at multilayer systems. Moreover, in contrast to the known solutions, the invention may advantageously be embodied such that the two reflective elements are oriented at an angle of less than 90° with respect to one another. An overlapping region of the X-ray radiation with increased intensity can thereby be achieved in the reflected imaging. In this case, the angular inclination may be chosen to be only slightly less than 90°. The text below will have recourse to figures for an exemplary elucidation. It becomes clear in this case that with an X-ray optical element according to the invention, the two focal points are arranged in the direction of the X-ray radiation reflected onto a sample within a focal point volume and, therefore, the two reflective elements have different focal lengths. |
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claims | 1. A method for decontaminating radiocontaminated grains, the method comprising: a pretreatment step of mixing radiocontaminated grains and a sodium phosphate-based dispersant; and a decontamination step of mixing the radiocontaminated grains processed by the pre-treatment step and paper sludge-derived sintered carbonized porous grains so as to incorporate radioactive 134Cs and 137Cs of the radiocontaminated grains in the sintered carbonized porous grains. 2. The method for decontaminating radiocontaminated grains according to claim 1, wherein the sodium phosphate-based dispersant contains at least one compound selected from the group consisting of sodium hexametaphosphate, sodium tripolyphosphate, and sodium tetrapyrophosphate. 3. The method for decontaminating radiocontaminated grains according to claim 1, wherein at least one ion-exchangeable compound selected from the group consisting of potassium chloride, magnesium sulfate, and copper sulfate is impregnated in the sintered carbonized porous grains, these sintered carbonized porous grains and the radiocontaminated grains processed by the pre-treatment step are mixed together, and the radioactive 134Cs and 137Cs of the radiocontaminated grains are incorporated in the sintered carbonized porous grains by ion-exchange. 4. The method for decontaminating radiocontaminated grains according to claim 2, wherein at least one ion-exchangeable compound selected from the group consisting of potassium chloride, magnesium sulfate, and copper sulfate is impregnated in the sintered carbonized porous grains, these sintered carbonized porous grains and the radiocontaminated grains processed by the pre-treatment step are mixed together, and the radioactive 134Cs and 137Cs of the radiocontaminated grains are incorporated in the sintered carbonized porous grains by ion-exchange. 5. The method for decontaminating radiocontaminated grains according to claim 2, wherein the sodium phosphate-based dispersant contains sodium hexametaphosphate. 6. The method for decontaminating radiocontaminated grains according to claim 2, wherein the sodium phosphate-based dispersant contains sodium tripolyphosphate. 7. The method for decontaminating radiocontaminated grains according to claim 2, wherein the sodium phosphate-based dispersant contains sodium tetrapyrophosphate. 8. The method for decontaminating radiocontaminated grains according to claim 3, wherein potassium chloride is impregnated in the sintered carbonized porous grains. 9. The method for decontaminating radiocontaminated grains according to claim 3, wherein magnesium sulfate is impregnated in the sintered carbonized porous grains. 10. The method for decontaminating radiocontaminated grains according to claim 3, wherein copper sulfate is impregnated in the sintered carbonized porous grains. 11. The method for decontaminating radiocontaminated grains according to claim 4, wherein potassium chloride is impregnated in the sintered carbonized porous grains. 12. The method for decontaminating radiocontaminated grains according to claim 4, wherein magnesium sulfate is impregnated in the sintered carbonized porous grains. 13. The method for decontaminating radiocontaminated grains according to claim 4, wherein copper sulfate is impregnated in the sintered carbonized porous grains. |
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