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claims | 1. A composite material heat controller for an object, the composite material heat controller comprising:a base material that radiates a larger amount of heat at a high-temperature relative to that of the heat radiated at a low-temperature, the base material having a surface adapted to thermally contact a surface of said object; anda phase-change substance overlying said base material having insulation properties at the high-temperature, metallic properties at the low-temperature, radiating a larger amount of heat at the high-temperature relative to a smaller amount of heat radiated at the low-temperature, and having a high reflectivity in the thermal infrared light region at the low-temperature;wherein said phase-change substance comprises a perovskite oxide or a corundum vanadium oxide and has a thickness in the range from about one to about thirty microns. 2. The composite material heat controller according to claim 1, wherein said base material comprises a thickness greater than a thickness of said phase-change substance. 3. The composite material heat controller according to claim 1, wherein said phase-change substance is a perovskite oxide. 4. The composite material heat controller according to claim 3, wherein said phase-change substance 1 is perovskite Mn oxide. 5. The composite material heat controller according to claim 1, wherein said base material comprises a thickness in the range from 10 to 100 μm. 6. The composite material heat controller according to claim 1, wherein said base material is selected from a group consisting of silicone, alumina, and partially stabilized-zirconia. 7. The composite material heat controller according to claim 1, wherein a reflective plate or reflective film each having reflectivity with respect to visible light is laminated onto said phase-change substance on a side opposite from a side on which said base material is laminated. 8. The composite material heat controller according to claim 1, wherein said surface of said base material of said composite material heat controller is affixed to the surface of the object either directly or via an intervening heat-conductive substance. 9. The composite material heat controller according to claim 8, wherein said composite material heat controller is thermally joined to said object, via an appropriate intervening adhesive. 10. The composite material heat controller according to claim 1, wherein said object comprises a non-flat surface. 11. The composite material heat controller according to claim 1, wherein said object includes an electronic circuit used in a space vehicle, including a man-made satellite and a spaceship. 12. A method for controlling heat in an object comprising:providing a base material that radiates a larger amount of heat at a high-temperature relative to that of the heat radiated at a low-temperature, the base material having at least a first surface and a second surface;attaching a phase-change substance on said first surface of said base material, said phase-changing substance having insulation properties at the high-temperature, metallic properties at the low-temperature, radiating a larger amount of heat at the high-temperature relative to a smaller amount of heat radiated at the low-temperature, and having a high reflectivity in the thermal infrared region at the low-temperature phase and comprising perovskite oxide or a corundum vanadium oxide and has a thickness in the range from about one to about thirty microns; andattaching said second surface of said base material to said object. 13. The method for controlling heat according to claim 12, wherein said base material comprises a thickness greater than a thickness of said phase-change substance. 14. The method for controlling heat according to claim 12, wherein said phase-change substance is a perovskite oxide. 15. The method for controlling heat according to claim 14, wherein said phase-change substance is perovskite Mn oxide. 16. The method for controlling heat according to claim 12, wherein said base material is selected from a group consisting of silicone, alumina and partially stabilized-zirconia. 17. The method for controlling heat according to claim 12, wherein either one of a reflective plate and a reflective film having reflectivity with respect to visible light is laminated onto said phase-change substance on a side opposite from a side attached to said first surface of said base material. 18. The method for controlling heat according to claim 12, wherein said composite material is attached to a surface of said object, either directly or via an intervening heat-conductive substance. 19. The method for controlling heat according to claim 12, wherein said object includes an electronic circuit used in a space vehicle, including a man-made satellite and a spaceship. |
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045129215 | abstract | An improved method for decontaminating the coolant system of water-cooled nuclear power reactors and for regenerating the decontamination solution. A small amount of one or more weak-acid organic complexing agents is added to the reactor coolant, and the pH is adjusted to form a decontamination solution which is circulated throughout the coolant system to dissolve metal oxides from the interior surfaces and complex the resulting metal ions and radionuclide ions. The coolant containing the complexed metal ions and radionuclide ions is passed through a strong-base anion exchange resin bed which has been presaturated with a solution containing the complexing agents in the same ratio and having the same pH as the decontamination solution. As the decontamination solution passes through the resin bed, metal-complexed anions are exchanged for the metal-ion-free anions on the bed, while metal-ion-free anions in the solution pass through the bed, thus removing the metal ions and regenerating the decontamination solution. |
description | This application is a divisional of U.S. application Ser. No. 15/616,423, filed Jun. 7, 2017, which is based upon and claims the benefit of priority from Japanese Patent Application No. 2016-115241, filed Jun. 9, 2016; the entire content of which is incorporated herein by reference. The embodiments of the present invention relate to a core catcher and a boiling water nuclear plant using the same. The core catcher is safety equipment designed to cope with severe accidents that may occur in the nuclear plant. Even if the molten core falls through the bottom of the reactor pressure vessel onto the floor of the containment vessel of the nuclear reactor, the core catcher receives the core debris (i.e., residues of the molten core), and keeps cooling the containment vessel of the nuclear reactor, thereby preserving the safety of the containment vessel and limiting the release of radioactive substances. As the radioactive substances existing in the core debris decay, they keep generating heat that amounts to about 1% of the nuclear reactor output power. Without cooling means, the core debris may melt through the base mat concrete of the containment vessel, and a great amount of radioactive substances may be released into the environment. To prevent such an event, it is planned that a core catcher having cooling channels should be installed in the boiling water reactor (BWR). The core catcher of the European ABWR (EU-ABWR), for example, has radial cooling channels. In the cooling channels, the cooling water in the upper part of the core catcher is recirculated, efficiently removing the decay heat generated in the debris. This recirculation of cooling water is natural circulation, and does not require active pumps. Further, the cooling water can be circulated uniformly in the cooling channels because the cooling channels extend in radial directions. Taking the conventional ABWR and the conventional European ABWR (EU-ABWR) for example, the containment vessel and core catcher used in the conventional boiling water reactor (BWR) will be outlined with reference to FIG. 9 to FIG. 16. (ABWR Shown in FIG. 9) FIG. 9 is an elevational, cross-sectional view of a containment vessel of a conventional ABWR. FIG. 10 is a plan view of the containment vessel of the conventional ABWR. As shown in FIG. 9, a core 1 is provided in a reactor pressure vessel 2. The reactor pressure vessel 2 is provided in the containment vessel 3. The containment vessel 3 is shaped like a hollow cylinder (see FIG. 10). The interior of the containment vessel 3 is partitioned into a dry well 4 and a wet well 5. The dry well 4 and the wet well 5 each constitutes a part of the containment vessel 3. The wet well 5 has a suppression pool 6 in it. The suppression pool 6 has a normal water level 6a of about 7 m. The suppression pool 6 holds pool water in a large amount, about 3,600 m3. Above the suppression pool 6, a wet-well gas phase 7 is provided. The wet-well gas phase 7 is about 12.3 m high. The outer wall parts of the dry well 4 and the wet well 5 are integrated, forming the hollow cylindrical outer wall 3a of the containment vessel 3. The ceiling part of the dry well 4 is a flat plate. This part is called a top slab 4a of the dry well 4. In the case of the ABWR, the containment vessel 3 is made of reinforced concrete. Therefore, the containment vessel 3 of the ABWR is called “reinforced-concrete containment vessel (RCCV).” To make the containment vessel gastight, steel liners (not shown) are laid on the inner surfaces of the containment vessel. FIG. 9 and FIG. 10 show an example of an RCCV. As seen from FIG. 10, the outer wall 3a of the containment vessel 3 is shaped like a hollow cylinder. The bottom part of the RCCV is constituted by a part 99a of a base mat 99. The RCCV is made of reinforced concrete. The base mat 99 constitutes the bottom part of the reactor building 100. It is proposed that the base mat 99 could be made of steel concrete composite (SC composite) in the future. As shown in FIG. 9, the reactor pressure vessel 2 is supported by a hollow cylindrical pedestal 61 through a vessel skirt 62 and a vessel support 63. The pedestal 61 is constituted by a hollow cylindrical sidewall (i.e., pedestal sidewall 61a). The pedestal sidewall 61a has a thickness of, for example, 1.7 m. The pedestal sidewall 61a is made of concrete, and has inner and outer layers made of steel. The outer layer made of steel is strong enough to support, almost by itself, the weight of the reactor pressure vessel 2. The bottom of the pedestal sidewall 61a contacts the base mat 99, and is supported by the base mat 99. Below the reactor pressure vessel 2 and the vessel skirt 62 in the dry well 4, a space is formed, surrounded by the hollow cylindrical pedestal sidewall 61a and the part 99a of the base mat 99. This space is called pedestal cavity 61b. In the RCCV of the ABWR, the pedestal sidewall 61a constitutes a boundary wall between the wet well 5 and the dry well 4. Particularly, the space of the pedestal cavity 61b is called lower dry well 4b. The height from the floor of this lower dry well 4b to the bottom of the reactor pressure vessel 2 is about 11.55 m. The upper space in the dry well 4, excluding the lower dry well 4b, is called upper dry well 4c. (Lower Dry Well Part Shown in FIG. 11) FIG. 11 is an enlarged view of the lower dry well (lower DW) 4b and peripherals. On the bottom of the lower dry well 4b, a concrete floor 67 is provided, having a thickness of about 1.6 m. The concrete floor 67 has sumps 68. The sumps 68 have a depth of about 1.3 m. The sumps 68 are configured to collect leakage water therein if the coolant leaks from the pipes or components connected to the reactor pressure vessel 2. The water levels in the sumps 68 are monitored in order to detect the leakage. Two sumps 68, a high conductivity waste sump 68a and a low conductivity waste sump 68b, are provided (see FIG. 10), but only one sump is shown in FIG. 9 and FIG. 11. Each sump 68 has a corium shield (i.e., a lid for preventing inflow of debris; not illustrated), which prevents the in-flow of core debris in case a severe accident occurs. Various types of corium shields have been devised, one of which is disclosed in Japanese Patent Application Laid-Open Publication 2015-190876, the entire content of which is incorporated by reference. In the lower dry well 4b, there are provided control rod drives 10 and a control rod drive handling equipment 11. The control rod drives 10 are connected to the bottom of the reactor pressure vessel 2. The control rod drive handling equipment 11 is arranged below the control rod drive 10. About 205 control rod drives 10 are used in all. The control rod drive handling equipment 11 takes the control rod drives 10, one by one, from the reactor pressure vessel 2, rotates each control rod drive 10 to a horizontal position and moves up the same again, so that the control rod drives 10 may be carried out of the containment vessel. The control rod drive handling equipment 11 is therefore indispensable for the maintenance of the nuclear reactor. The control rod drive handling equipment 11 can rotate, in its entirety, in the horizontal direction to be positioned with respect to each of the all control rod drives 10. This is why the upper surface of the control rod drive handling equipment 11 is also called a turntable 11a. The control rod drive handling equipment 11 has a height of about 4.6 m, and can hold the control rod drives 10 in it. On the turntable 11a operators may stand to perform maintenance work. Therefore, the lower ends of the control rod drives 10 are spaced from the turntable 11a by about 2.2 m. On the other hand, the lower end of the control rod drive handling equipment 11 is spaced away from the concrete floor 67 by about 10 cm only. Thus, a gap is scarcely provided between the concrete floor 67 and the lower end of the control rod drive handling equipment 11. The lower end of the control rod drive handling equipment 11 is about 1.7 m above the upper end of the part 99b of the base mat 99. The upper surface of the concrete floor 67 is about 1.6 m above the upper end of the part 99b of the base mat 99. No space is therefore available to arrange the core catcher, and the core catcher is not arranged there. In the conventional ABWR, the lower dry well 4b holds the control rod drives 10 and the control rod drive handling equipment 11, and cannot accommodate a core catcher. It is proposed that the lower dry well 4b should be used as a space for the core catcher and the device (i.e., hopper) associated with the core catcher (see, for example, Patent Application Laid-Open Publication 2008-241657, the entire content of which is incorporated by reference). In practice, however, the lower dry well 4b of the conventional ABWR has no extra clearance, and a core catcher (disclosed in Patent Application Laid-Open Publication 2008-241657) cannot be arranged there. The size and shape of the containment vessel of the conventional ABWR are standardized as described above. The height from the upper end of the part 99b of the base mat 99 to the lower end of the top slab 4a (i.e., total height of the containment vessel 3) is about 29.5 m. The dry well 4 and the suppression pool 6 are connected by LOCA vent pipes 8. Ten LOCA vent pipes 8, for example, are arranged (see FIG. 10), though only two LOCA vent pipes are shown in FIG. 9 and FIG. 11. Each of the LOCA vent pipes 8 has a plurality of horizontal vent pipes 8a submerged in the pool water and has openings in the pool water. In the case of the RCCV, three horizontal vent pipes 8a are provided for each of the LOCA vent pipes 8 and extend in the vertical direction. The uppermost horizontal vent pipe has its upper end located at the height of about 3.85 m from the part 99b of the base mat 99. If an accident occurs, the suppression pool 6 is used as water source for the safety system such as an emergency core cooling system. Even in such a case, the pool keeps holding water in such an amount that the water level never falls below the level of about 0.61 m to 1.0 m higher than the upper end of the uppermost horizontal vent pipe 8a. This measure is taken in order that the horizontal vent pipe 8a can keep a condensation function. Hence, in the event of an accident, the water in the suppression pool 6 can be maintained at a level of about 4.46 m to 4.85 m at the lowest. In the RCCV, the LOCA vent pipes 8 are arranged, extending in the interior of the pedestal sidewall 61a shaped like a hollow cylinder. The pedestal sidewall 61a is therefore called “vent wall 61c” if used in the case of the RCCV. As specified above, the vent wall 61c is about 1.7 m thick and made of concrete, and its inner and outer layers are made of steel. The outer layer made of steel can support, by itself, the weight of the reactor pressure vessel 2. The concrete part of the vent wall 61c reinforces the pedestal 61 and has the function of holding the LOCA vent pipes 8. The LOCA vent pipes 8 and the pedestal 61 constitute a part of the containment vessel 3. One of the methods of maintaining, in the suppression pool 6, water much enough to keep the water temperature low to cope with a severe accident is to supply water to the pool from an external water source. Various means (not shown) are available for supplying water to the suppression pool, such as a portable pump, a fire-fighting pump and an alternate water supply pump. The design pressure of the containment vessel 3 is about 3.16 kg/cm2 (0.310 MPa in terms of gauge pressure). The hollow cylindrical outer wall 3a and the top slab 4a are made of reinforced concrete and have thickness of about 2 m and a thickness of about 2.4 m, respectively. Their inner surfaces are lined with steel liners (not shown) for the purpose of limiting the leakage of radioactive substances. The base mat 99 has a thickness of about 5 m and is made of reinforced concrete, too. The containment vessel 3 has a design leakage rate of about 0.4% per day. Recently it is proposed that the hollow cylindrical outer wall 3a and the top slab 4a of the containment vessel 3 could be made of steel concrete composite (SC composite), not reinforced concrete. The SC composite comprises two steel frames secured to each other with ribs and concrete filled in the gap between the steel frames. The SC composite is advantageous in that rebars need not be laid and that it can be modularly assembled. Further, as the SC composite is stronger, raising the design pressure of the containment vessel 3 even higher is possible. An example of employing an SC composite in nuclear plants is the shield building of the AP1000 (registered trademark) of Westinghouse, Inc. (Eu-Abwr Shown in FIGS. 12 and 13) How an EU-ABWR core catcher is installed will be explained with reference to FIG. 12 and FIG. 13. FIG. 13 is an enlarged view of the lower dry well 4b. As shown in FIG. 12 and FIG. 13, a core catcher 30 is mounted on the part 99b of the base mat 99 provided at the lower part of the lower dry well 4b. The core catcher 30 is arranged eliminating the concrete floor 67 (FIG. 9 and FIG. 11) about 1.6 m thick provided in the conventional ABWR. Further, in the EU-ABWR, the lower dry well 4b is about 2.1 m higher than in the ordinary ABWR, and the space for the core catcher 30 has a height of about 3.7 m including the thickness of the eliminated concrete floor, i.e., 1.6 m. The core catcher 30 has height of about 2.45 m. Furthermore, a lid 31 is arranged above the core catcher 30. The upper end of the lid 31 lies about 3.6 m above the upper end of the base mat 99. The lid 31 has a sump 68. The sump 68 is about 1.3 m deep. The lid 31 is positioned so high that the sump 68 does not interfere with the core catcher 30. The lower end of the control rod drive handling equipment 11 is located about 3.7 m from the upper end of the base mat 99. Hence, the core catcher 30 having a height of about 2.45 m can be arranged together with the lid 31 having a height of about 3.6 m. (Fusible Valve) In the pedestal cavity 61b, fusible valves 64 and lower dry well flooding pipes 65 are provided to cope with a core meltdown that might occur. The lower dry well flooding pipes 65 extend from the LOCA vent pipes 8, penetrate the pedestal sidewall 61a and are connected to the fusible valve 64. One fusible valve 64 and one lower dry well flooding pipe 65 are provided on each of the LOCA vent pipes 8. Each fusible valve 64 has a plug part made of low-melting-point material, and opens by melting the plug part if the temperature in the lower dry well 4b rises to about 260 degrees centigrade. If a core meltdown occurs, the corium melts through the bottom of the reactor pressure vessel 2, falls down into the pedestal cavity 61b, melts through the control rod drive handling equipment 11, and is held in the core catcher 30 provided at the bottom of the pedestal cavity 61b. Accordingly, as the temperature abruptly rises in the pedestal cavity 61b, the fusible valves 64 open. The cooling water in the LOCA vent pipes 8 then flows through the lower dry well flooding pipes 65 into the pedestal cavity 61b, flooding and cooling the corium on the core catcher 30. The cooled corium partly becomes solidified core debris. The cooling water in the LOCA vent pipes 8 are supplied from the suppression pool 6 through the horizontal vent pipes 8a. The configuration of the core catcher of the conventional EU-ABWR will be described with reference to FIG. 14 to FIG. 16. FIG. 14 is a sectional view showing the configuration of the core catcher of the conventional EU-ABWR. FIG. 15 is a plan view showing the configuration of the core catcher of the conventional EU-ABWR. FIG. 16 is a perspective view of one of the cooling channels used in the core catcher of the conventional EU-ABWR. (Configuration of FIG. 14) As shown in FIG. 14, the core catcher 30 is provided on the bottom of the lower dry well 4b surrounded by the pedestal sidewall 61a and the part 99b of the base mat 99. The core catcher 30 is constituted by a dish-shaped basin 32. The basin 32 is made of steel and has a thickness of about 1 cm. In some cases, the thickness of the basin 32 may be about 5 cm, about 10 cm, or the like, depending on the strength the basin 32 must have. A refractory layer 33 is laid on the basin 32, and a sacrificial layer 34 is laid on the refractory layer 33. The refractory layer 33 is composed of refractory bricks glued together, and has a thickness of about 17.5 cm. The refractory bricks may be made of alumina (aluminum oxide) and zirconia (zirconium oxide). The sacrificial layer 34 is made of concrete and has thickness of about 5 cm. If core debris falls on to it, the sacrificial layer 34 is eroded with the heat of the core debris, preventing the refractory layer 33 from being heated over the allowable temperature, until the cooling water is supplied from the fusible valve 64 and starts cooling the core debris. The peripheral part of the basin 32 is connected to a circular annular riser sidewall 38a having an axis extending in the vertical direction. Around the riser sidewall 38a, a circular annular downcomer sidewall 39a is provided and spaced from the riser sidewall 38a by about 10 cm. The upper edge of the downcomer sidewall 39a lies at a height of about 2.45 m from the upper end of the part 99b of the base mat 99. The lid 31 is provided above the core catcher 30. The lid 31 lies at a height of about 3.6 m above the part 99b of the base mat 99. The lid 31 is configured to fall onto the sacrificial layer 34 immediately if the molten core falls from above. Thereafter, the lid 31 melts due to the high temperature of the core debris and becomes part of the debris. Below the basin 32, many radial cooling channels 35 are provided (see FIG. 15). The cooling channels 35 incline at about 10 degrees. The cooling channels 35 have a length of about 4 m. The cooling channels 35 are defined by many channel sidewalls (ribs) 35a provided below the basin 32 (see FIG. 15 and FIG. 16). The number of cooling channels 35 used is, for example, 16, and may be changed as needed. The channel sidewalls 35a perform the function of cooling fins and ribs supporting the basin 32. The channel sidewalls 35a are made of metal having high thermal conductivity, such as steel or copper. A distributor 36 shaped like a hollow cylinder and having a vertical axis is provided at the center of the radial cooling channels 35. The diameter of the distributor 36 is, for example, about 2 m. The diameter of the distributor 36 may be changed if necessary. To the distributor 36, the channel inlets 35b of the cooling channels 35 are connected. The cooling water can therefore be uniformly supplied to all cooling channels 35 from the distributor 36. The lower end of the distributor 36 is closed by a bottom plate 36a. The bottom plate 36a contacts the part 99b of the base mat 99. In the distributor 36, a distributor pillar 36b is provided as shown in FIG. 14. Alternatively, two or more distributor pillars may be provided as needed. The distributor pillar 36b contacts the basin 32, whereby the distributor 36 bears a part of the weight of the basin 32. The outlet ports of the radial cooling channels 35 are connected to a riser 38 that guides the cooling water upward in the vertical direction. The riser 38 is a flow passage provided between the riser sidewall 38a and the downcomer sidewall 39a, and has a width of about 10 cm. The upper end of the riser 38, i.e., riser outlet 38b, opens in the upper part of the core catcher 30. The cooling water rises in the riser 38 and flows through the riser outlet 38b into the upper part of the core catcher 30. Further, a circular annular downcomer 39 is provided, surrounding the riser 38. The downcomer 39 is a flow passage provided between the downcomer sidewall 39a and the pedestal sidewall 61a and has a width of about 30 cm. The upper end of the downcomer 39 opens in the upper part of the core catcher 30. The downcomer 39 extends down to the bottom of the lower dry well 4b and is connected to the cooling-water inlet ports 37a of cooling water injection pipes 37. Each of the cooling water injection pipes 37 has a cooling-water outlet port 37b, which is connected to the sidewall 36c of the distributor 36. In the configuration described above, the cooling water accumulated in the upper part of the core catcher 30 flows down again in the downcomer 39, reaches the distributor 36 through the cooling water injection pipes 37, and is used in the cooling channels 35. Thus, the cooling water in the upper part of the core catcher 30 is circulated again by the downcomer 39. The basin 32, the cooling channels 35, the distributor 36 and the cooling water injection pipes 37 are made watertight, and the cooling water would not leak from them. If the fusible valves 64 are melted with the heat generated in the core debris, the cooling water that floods the core debris existing above the basin 32 and cools the core debris is supplied from the LOCA vent pipes 8 through the lower dry well flooding pipes 65. Until the core debris becomes flooded by the cooling water, the sacrificial layer 34 protects the refractory layer 33 and the basin 32 from overheating, while the sacrificial layer 34 is melting. The main body 30a of the core catcher 30 is composed of the basin 32, the distributor 36, the cooling channels 35 and the riser 38. The refractory layer 33 and the sacrificial layer 34 have the function of protecting the main body 30a of the core catcher 30. The downcomer 39 and the cooling water injection pipes 37 have the function of circulating the cooling water and supplying the cooling water to the main body 30a. (Configuration of FIG. 15) FIG. 15 is a plan view of the core catcher used in the conventional EU-ABWR, specifying the positions of the cooling channels 35 of the core catcher. As shown in FIG. 15, the cooling channels 35 extend from the distributor 36 in radial directions. The cooling channels 35 are partitioned, one from another, by the channel sidewalls (ribs) 35a. Each channel sidewall 35a has an opening (not shown). In some case, the cooling water can flow from one cooling channel to another through the opening made in the channel sidewall 35a. More channel sidewalls (ribs) 35a may be provided in order to strengthen the peripheral part of the core catcher and to increase the number of heat transfer fins (see U.S. Pat. No. 8,358,732, the entire content of which is incorporated by reference). (Configuration of FIG. 16) FIG. 16 is a perspective view illustrating the configuration of the cooling channels 35 used in the core catcher of the conventional EU-ABWR. In FIG. 16, the thicknesses of the walls are not shown. Each cooling channel 35 is composed of a part 32a of the basin 32, a channel sidewall 35a, and a channel bottom wall 35c, and is shaped like a fan. The cooling channel 35 inclines, gradually upward to the outer circumference. The angle of inclination is about 10 degrees. The channel inlet 35b of the cooling channel 35 is connected to the sidewall 36c of the distributor 36. The other end of the cooling channel 35 is connected to the riser 38. The riser 38 is composed of a riser sidewall 38a, a riser rib 38c, and a downcomer sidewall 39a. The cooling water flows into the cooling channels 35 through the channel inlets 35b, is heated with the heat generated by the core debris, rises in the riser 38, and flows into the upper part of the core catcher 30 through the riser outlet 38b. Thereafter, again, the cooling water flows down through the downcomer 39, then flows from the cooling-water inlet port 37a into the cooling water injection pipe 37, and further flows from the cooling-water outlet port 37b into the distributor 36 (see FIG. 14 and FIG. 15). The cooling water supplied into the distributor 36 is circulated again in the cooling channels 35. The drive force recirculating the cooling water results from the water head of the cooling water in the downcomer 39, which is about 2.45 m high. In order to acquire this drive force, the core catcher of the conventional EU-ABWR has a height of about 2.45 m except the lid 31. The space below the channel bottom wall 35c is filled with concrete, embedding the cooling water injection pipe 37 therein. The channel bottom wall 35c can thereby withstand the load applied to the cooling channel 35. In some cases, a support member such as a rib may be used to support the channel bottom wall 35c, instead of filling the space with concrete. (Disadvantages of the Prior Art) In the containment vessel 3 of the EU-ABWR, the lower dry well 4b has a height about 2.1 m greater than the value used in the conventional ABWR. Hence, the levels of the reactor pressure vessel 2 and the core 1 are about 2.1 m higher than the conventional ABWR. This reduces the seismic resistance. The reduction of seismic resistance is not so problematic in, for example, Europe where earthquakes are not severe, but should be avoided in a country, such as Japan, which suffers from severe earthquakes. Further, the total height of the containment vessel 3 increases by about 2.1 m, and the total height of the reactor building 100 increases by about 2.1 m, too. This increases the amount of concrete used and worsens the economy. The containment vessel 3 of the EU-ABWR has a total height of about 31.6 m, from the upper end of the part 99b of the base mat 99 to the lower end of the top slab 4a. Accordingly, the core catcher 30 influences not only the lower dry well 4b, but also the entire plant including the containment vessel 3 and the reactor building 100. One of the methods of avoiding such a problem is to dig down the part 99b of the base mat 99, i.e., bottom of the lower dry well 4b, by about 2.1 m and put the core catcher 30 therein. The rebars that have been arranged in the conventional part 99b of the base mat 99, that is digged down, are to be cut and removed. In this case, however, the configuration of the base mat 99 becomes complicated, causing longer construction time and reducing the strength of the base mat 99 against earthquakes. In the containment vessel 3 of the conventional ABWR, the height of the lower dry well 4b is not increased about 2.1 m, unlike in the EU-ABWR. In view of the construction schedule and the structure strength, it is undesirable to dig down the part 99b of the base mat 99. Hence, if a gap of about 10 cm is secured between the core catcher 30 and the lower end of the control rod drive handling equipment 11, the height of the space for accommodating the core catcher 30 is limited to about 1.6 m, because this space is provided by removing a part of the concrete floor 67. As described above, the core catcher 30 of the EU-ABWR is about 2.45 m high and the upper end of the lid 31 is about 3.6 m high. Consequently, the core catcher 30 cannot be disposed in the ABWR core catcher space having a height of about 1.6 m. The core catcher 30 can be disposed in the ABWR core catcher space about 1.6 m high if the cooling channels 35 are inclined less, thereby reducing the thickness of the basin 32 and the height of the distributor 36 is also reduced, and so on. In such a case, however, the height of the downcomer 39 decreases from about 2.45 m to about 1.6 m. The height of the downcomer 39 determines the water head that is the drive force for circulating the water in the upper part of the core catcher 30 in the cooling water injection pipes 37, the distributor 36, the cooling channels 35 and the risers 38. Therefore, if the height of the downcomer 39 decreases to about 1.6 m, the flow rate of the cooling water flowing in the radial cooling channels 35 inevitably decreases, and the decay heat generated in the core debris cannot be sufficiently removed. The flow rate of recirculating the cooling water in the upper part of the core catcher 30 by the downcomer 39 is determined by the density difference between the cooling water in the radial cooling channels 35 and the riser 38, and the cooling water in the downcomer 39. The lower the temperature of the cooling water in the upper part of the core catcher 30 flowing into the downcomer 39, the larger the density difference will be. Generally speaking, however, the upper part of the core catcher 30 holds the hottest core debris, which heats the cooling water. It is therefore physically difficult to keep the cooling water flowing into the downcomer 39 at low temperature. Accordingly, the cooling water in the upper part of the core catcher 30 is heated to a high temperature as time passes, though it remains at low temperature immediately after the core debris has fallen. Consequently, there is a problem that the heated cooling water will impede a sufficient natural circulation flow rate. Since the cooling water recirculated by the downcomer 39 contacts the core debris existing in the upper part of the core catcher 30, part of the core debris may be released, flow into the downcomer 39 and move to the lower part of the core catcher 30. If this happens, the core catcher 30 would lose the function of holding and cooling the core debris. To prevent this, a filter is arranged in the opening made in the downcomer 39. The filter may be clogged with the loose parts scattered in the event of a severe accident. The core debris may melt through the bottom of the reactor pressure vessel 2, and may then fall onto the upper part of the core catcher 30. Accordingly in this process, the thermal insulators and such might become loose parts. Once the filter has been clogged with the loose parts, the cooling water may not be recirculated in a sufficient flow rate. In the conventional core catcher 30, the cooling water does not exist in the cooling channels 35 during the normal operation of the plant. If the core debris falls, raising the temperature in the lower dry well 4b and melting the fusible valves 64, the water in the LOCA vent pipes 8 submerges the core catcher 30 and the core debris, flows down in the downcomer 39, passes through the cooling water injection pipe 37 and distributor 36, and cools the cooling channels 35. Therefore, there is a time lag after the falling of the core debris until the cooling channels 35 start cooling the basin 32. During this time lag, the sacrificial layer 34 and the refractory layer 33 prevent the overheating of the basin 32. However, if the impact of the falling core debris damages the sacrificial layer 34 and the refractory layer 33, the core debris may contact the basin 32 directly and may melt a part of the basin 32. An object of the present embodiments is to provide a thin core catcher which has a main body about 1.6 m or less high and can be arranged in a lower dry well of a conventional ABWR without interfering with the control rod drive handling equipment. Another object of the present embodiments is to provide a core catcher which keeps cooling water in the cooling channels during normal operation and enables cooling channels to achieve cooling immediately if a sever accident occurred and core debris fell onto it. Yet another object of the present embodiments is to provide a thin core catcher which can, despite its small thickness, preserve the flow rate of cooling water flowing in the cooling channels by means of natural circulation. Yet another object of the present embodiments is to provide a core catcher in which the cooling water on the upper surface is not recirculated in the cooling channels, preventing the core debris and loose parts from flowing into the cooling channels. According to an embodiment, there is presented a core catcher for use in a boiling water nuclear plant which has: a base mat; a reactor building built on a part of the base mat; a containment vessel provided in the reactor building, built on the base mat and having a total height of not exceeding 29.5 m to a lower end of a top slab; a core; a reactor pressure vessel holding the core; a dry well constituting a part of the containment vessel and holding the reactor pressure vessel; a pedestal connected to the base mat and supporting the reactor pressure vessel through a vessel skirt and a vessel support; a wet well constituting a part of the containment vessel, the wet well being provided around the pedestal, holding a suppression pool in a lower part thereof, and having a wet well gas phase at an upper part thereof, LOCA vent pipes provided in a sidewall of the pedestal and connecting the dry well to the suppression pool; a lower dry well which is a space in the dry well, is located below the vessel skirt and the reactor pressure vessel and is surrounded by the sidewall of the hollow cylindrical pedestal and the part of the base mat, which lies inside the sidewall of the pedestal; control rod drives provided in the lower dry well and connected to a lower part of the reactor pressure vessel; and a control rod drive handling equipment provided in the lower dry well and below the control rod drives; the core catcher comprising: a main body including: a distributor arranged on the part of the base mat in the lower dry well, a basin arranged on the distributor, cooling channels arranged on a lower surface of the basin, having inlets connected to the distributor and extending in radial directions, and a riser connected to outlets of the cooling channels and extending upward in vertical direction; a lid connected to an upper end of the riser and covering the main body; a cooling water injection pipe open, at one end, to the suppression pool, penetrating the sidewall of the pedestal, connected at another end to the distributor, and configured to supply pool water to the distributor; and chimney pipes connected, at one end, to the riser, penetrating the sidewall of the pedestal, another end being located above the upper end of the riser and submerged and open in the pool water at a level lower than a minimum water level at a time of an accident, wherein the upper ends of the main body and the lid are at heights lower than lower end of the control rod drive handling equipment, as measured from upper end of the base mat. According to another embodiment, there is presented a boiling water nuclear power plant comprising: a base mat; a reactor building built on a part of the base mat; a containment vessel provided in the reactor building, built on the base mat and having a total height of not exceeding 29.5 m to a lower end of a top slab; a core; a reactor pressure vessel holding the core; a dry well constituting a part of the containment vessel and holding the reactor pressure vessel; a pedestal connected to the base mat and supporting the reactor pressure vessel through a vessel skirt and a vessel support; a wet well constituting a part of the containment vessel, the wet well being provided around the pedestal, holding a suppression pool in a lower part thereof, and having a wet well gas phase at an upper part thereof; LOCA vent pipes provided in a sidewall of the pedestal and connecting the dry well to the suppression pool; a lower dry well which is a space in the dry well, is located below the vessel skirt and the reactor pressure vessel and is surrounded by the sidewall of the hollow cylindrical pedestal and the part of the base mat, which lies inside the sidewall of the pedestal; control rod drives provided in the lower dry well and connected to a lower part of the reactor pressure vessel; a control rod drive handling equipment provided in the lower dry well and below the control rod drives; and a core catcher having: a main body including: a distributor arranged on the part of the base mat in the lower dry well, a basin arranged on the distributor, cooling channels arranged on a lower surface of the basin, having inlets connected to the distributor and extending in radial directions, and a riser connected to outlets of the cooling channels and extending upward in vertical direction; a lid connected to an upper end of the riser and covering the main body; a cooling water injection pipe open, at one end, to the suppression pool, penetrating the sidewall of the pedestal, connected at another end to the distributor, and configured to supply pool water to the distributor; and chimney pipes connected, at one end, to the riser, penetrating the sidewall of the pedestal, another end being located above the upper end of the riser and submerged and open in the pool water at a level lower than a minimum water level at a time of an accident, wherein the upper ends of the main body and the lid are at heights lower than lower end of the control rod drive handling equipment, as measured from upper end of the base mat. A first embodiment of the present invention will be described with reference to FIG. 1 to FIG. 6. Any components identical to ones shown in FIG. 9 to FIG. 16 are identified by the same numbers in FIG. 1 to FIG. 6, and will not be described repeatedly in the following description. (Configuration of FIGS. 1 and 2) FIG. 1 is a sectional view illustrating a situation where a core catcher according to the present invention is arranged in the containment vessel of an ordinary type ABWR. FIG. 2 is an enlarged view showing the position the core catcher takes in the lower dry well 4b of the containment vessel 3. In FIG. 1 and FIG. 2, the main body 30a of the core catcher 30 has a height of no more than about 1.6 m. The main body 30a of the core catcher 30 is arranged in a space provided by removing that part of a concrete floor 67 (see FIG. 11) having a height of about 1.6 m, at the bottom of the lower dry well 4b of the ABWR containment vessel 3. Therefore, none of the heights of the lower dry well 4b, the containment vessel 3 and the reactor building 100 are increased by about 2.1 m, unlike in the EU-ABWR. The total height of the containment vessel 3 is about 29.5 m, from the upper end of the part 99b of the base mat 99 to the lower end of the top slab 4a. The main body 30a of the core catcher 30 is provided below a control rod drive handling equipment 11 (about 1.7 m high), not contacting the lower end of the control rod drive handling equipment 11. A lid 31 is arranged also below the control rod drive handling equipment 11 (about 1.7 m high), not contacting the lower end of the control rod drive handling equipment 11. The upper end of the main body 30a of the core catcher 30 and the upper end of the lid 31 are below a height of 1.7 m from the upper end of the part 99b of the base mat 99. (Configuration of FIG. 3) The first embodiment of the present invention will be described with reference to FIG. 3 to FIG. 6. As shown in FIG. 3, the main body 30a of the core catcher 30 according to this embodiment includes a basin 32, a distributor 36, cooling channels 35 and a riser 38. This embodiment differs from the prior-art apparatus in several respects. First, the cooling channels 35 are inclined by, for example, 5 degrees (not 10 degrees as in the prior-art apparatus), and the main body 30a of the core catcher 30 is thin, having the total height of no more than about 1.6 m that is less than the height (1.7 m) of the control rod drive handling equipment 11. Second, the lid 31 is provided, contacting the upper end of the main body 30a of the core catcher 30 (i.e., the upper end of the riser 38). Third, the lid 31 is provided with no sumps. Fourth, no downcomers are provided. Fifth, the cooling water injection pipe 37 penetrates the vent wall 61c, and its distal end opens in the water in the suppression pool 6. Sixth, the upper end of the riser 38 is closed, not open to the upper part of the core catcher 30. Seventh, a chimney pipe 40 is provided and connected at one end to the riser 38. Eighth, the chimney pipe 40 penetrates the vent wall 61c, and its distal end opens in the water in the suppression pool 6. Finally, the chimney pipe 40 extends upward to a position higher than the riser 38. The chimney pipe 40 has an opening 40a in the suppression pool 6, at a height which is higher than the height (i.e., about 2.45 m) of the downcomer 39 of the core catcher 30 used in the conventional EU-ABWR and which is lower than the minimum water level (i.e., about 4.46 m to 4.85 m) in the suppression pool 6 in the event of an accident. For example, the upper end of the chimney pipe 40 may lie at a height of about 4 m. The cooling channels may be identical in structure to those shown in, for example, FIG. 16. FIG. 3 corresponds to a cross-sectional view of FIG. 4 taken along arrow C-C that runs through centers of the chimney pipes 40, but not centers of the LOCA vent pipes 8 (See FIG. 4). Chimney pipes 40 appear in FIG. 3. LOCA vent pipes 8, however, do not appear in FIG. 3 because LOCA vent pipes 8 do not exist on the cross section taken along arrow C-C in FIG. 4. For example, there are ten chimney pipes 40 in FIG. 4 in this embodiment. Therefore, five pieces of arrow C-C can be drawn in FIG. 4 crossing two pairing chimney pipes 40 although only one piece of arrow C-C is drawn for simplicity. FIG. 3 is identical to all the cooling channels 35, cooling water injection pipes 37 and chimney pipes 40 along all pieces of arrow C-C. (Configuration of FIG. 4) FIG. 4 is a plan view of a first embodiment of the core catcher according to the present invention. In FIG. 4, the cooling channels 35 are shown as exposed, but none of the lid 31, the sacrificial layer 34 made of concrete, the refractory layer 33 composed of refractory bricks and the basin 32 made of steel plate are not illustrated. As shown in FIG. 4, the number of cooling channels 35 provided is, for example, 10, and the number of LOCA vent pipes 8 used is, for example, 10. The number of the cooling channels 35 is not limited to 10, nevertheless. If eight LOCA vent pipes 8 are used, 8, 16 or 32 cooling channels 35 may be used in accordance with the cooling ability and structural strength that are desired. The chimney pipes 40 are positioned, not interfering with the LOCA vent pipes 8. In the configuration of FIG. 4, for example, each chimney pipe 40 is provided between two adjacent LOCA vent pipes 8. The chimney pipes 40 are arranged in the vent wall 61c (see FIG. 3). In the embodiment configured as described above, the cooling water injection pipes 37, the distributor 36, the cooling channels 35, the riser 38 and the chimney pipes 40 are kept communicated with the suppression pool 6 at all times, and always filled with the pool water of the suppression pool 6. During an accident, the pool water is supplied into the cooling channels 35 by virtue of the density difference between the water in the suppression pool 6 and the cooling water flowing in the cooling channels 35, the riser 38 and the chimney pipes 40. The chimney pipes 40 have an opening 40a at a height of about 4 m. Therefore, in each chimney pipe 40 up to about 4 m, exists low density cooling water heated to high temperature by the decay heat of the core debris. The water is vaporized, generating a two phase flow in each chimney pipe 40 in some cases. On the other hand, low-temperature, high-density water exists in the suppression pool 6 to a height of about 4 m. By virtue of the density difference between the respective water, the cooling water can be supplied into the cooling water injection pipe 37. The water head in the suppression pool 6 is about 4 m, much higher than the water head of about 2.45 m in the downcomer 39 of the conventional EU-ABWR core catcher. Therefore, much larger natural circulation flow rate can be obtained. The suppression pool 6 contains a large amount of pool water and can keep low temperature and high density of cooling water. Therefore, the large natural circulation flow rate can be maintained owing to the large density difference. A method for maintaining water at low temperature in the suppression pool 6 for a long time in the event of a severe accident may be to supply water from an external water source to the suppression pool 6, or to supply condensate from a passive containment cooling system to the suppression pool 6 (refer to WO2016/002224, the entire content of which is incorporated by reference). In the conventional core catcher 30, the density difference decreases because the downcomer 39 supplies the low-density, high-temperature water heated by the core debris above the basin 32. Consequently, it was difficult to keep a large flow rate of natural circulation. This problem can be solved in this embodiment. Further, the core catcher of the embodiment does not use for recirculation the contaminated water existing above the basin 32 that might contain some core debris and loose parts. Hence, it is possible to eliminate the possibility of loss of cooling function due to the clogging of the cooling channels 35 and so on. Furthermore, since the water is constantly supplied from the suppression pool 6 into the cooling channels 35 during the normal operation, the cooling of the basin 32 can be immediately started in an accident, even if the sacrificial layer 34 and the refractory layer 33 are damaged by an impact of core debris drop. Once the temperature of the basin 32 rises, the cooling water existing in the cooling channels 35 before the accident starts cooling the basin 32 naturally, and the cooling water is stably supplied thereafter by virtue of natural circulation. Thanks to the above cooling mechanism, the sacrificial layer 34 and the refractory layer 33 may be eliminated in the core catcher of this embodiment. The core debris existing above the core catcher 30 is cooled with the cooling water supplied from the lower dry well flooding pipes 65 through the fusible valves 64 that have been melted open (see FIG. 14). Since the chimney pipes 40 provide a water head of, for example, 4 m, the heights of the basin 32 and the riser 38 need not be increased. The main body 30a of the core catcher 30 can therefore be thin (or low in height). Hence, it is possible to provide a core catcher that can be arranged in the space with about 1.6 m height at the bottom of the lower dry well 4b, where is the only available space for the conventional ABWR to install a core catcher. Variations of the first embodiment of the present invention will be described with reference to FIG. 5 and FIG. 6. (Configuration of FIG. 5) As shown in FIG. 5, the chimney pipes 40 penetrate the pedestal sidewall 61a, each extending upward and slantwise. So shaped, the chimney pipes 40 have no elbow parts, reducing the flow resistance and increasing the natural flow rate of the cooling water. Alternatively, the chimney pipes 40 can have a smaller diameter for the same reason. (Configuration of FIG. 6) As shown in FIG. 6, the chimney pipes 40 penetrate the pedestal sidewall 61a in horizontal direction and then extend upward in the suppression pool 6. So shaped, the chimney pipes 40 have less elbow parts than otherwise. In addition, as they do not extend upward in the pedestal sidewall 61a the chimney pipes 40 can be installed more easily. A second embodiment of the core catcher according to the present invention will be described with reference to FIG. 7 and FIG. 8. (Configuration of FIG. 7) FIG. 7 is a plan view outlining the second embodiment of the core catcher according to the present invention. As shown in FIG. 7, two sumps 68, i.e., a high conductivity waste sump 68a and a low conductivity waste sump 68b, are arranged. In the vicinity of the sumps 68, a lid 31, a basin 32, a refractory layer 33, a sacrificial layer 34, cooling channels 35, channel sidewalls 35a, a riser 38, and chimney pipes 40 are configured to avoid interference with the sumps 68a and 68b and surround the peripheries of the sumps 68. The sumps 68a and 68b have a corium shield (not shown) each. In this embodiment, the core catcher 30 can be arranged without interfering with the sumps 68a and 68b. (Configuration of FIG. 8) FIG. 8 is an elevational sectional view outlining the second embodiment of the core catcher according to the present invention. FIG. 8 corresponds to a cross-sectional view of FIG. 7 taken along arrows A-A and B-B that run through centers of LOCA vent pipes 8 (See FIG. 7). LOCA vent pipes 8 appear in FIG. 8. Chimney pipes 40 and cooling water injection pipes 37, however, do not appear in FIG. 8 because they do not exist on the cross sections. Chimney pipes 40 and cooling water injection pipes 37 rather exist on the cross section taken along arrow C-C of FIG. 7 (See FIG. 7). A cross-sectional view of FIG. 7 taken along arrow C-C is exactly the same as FIG. 3. For example, there are ten chimney pipes 40 in FIG. 7 in this embodiment. Therefore, five pieces of arrow C-C can be drawn in FIG. 7 crossing two pairing chimney pipes 40 although only one piece of arrow C-C is drawn for simplicity. FIG. 3 is identical to all the cooling channels 35, cooling water injection pipes 37 and chimney pipes 40 along all pieces of arrow C-C also in the second embodiment (See FIG. 3). A sump riser 38d, a sump refractory layer 33a, and a sump sacrificial layer 34a are arranged along the sidewall of the sump 68. The core catcher 30 can therefore be arranged without interfering with the sumps 68a and 68b. While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions. |
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summary | ||
052705498 | claims | 1. A method of making an annular cylindrical multihole collimator for a radioisotope camera, comprising: forming a closed annular radio-opaque plate having a plurality of corrugations extending from the inner to the outer radius of the plate defining at least one collimator segment section and junction; stacking cylindrically, axially, a plurality of said plates on one another with their peaks and valleys aligned to form an annular cylindrical multihole collimator with at least one segment; and bonding each said plate to its adjacent plates. a plurality of closed annular radio-opaque plates each having a plurality of corrugations extending from the inner to the outer radius of the plate defining at least one collimator segment section and junction; and means for bonding said plates together with their peaks and valleys aligned to form an annular cylindrical multihole collimator with at least one segment. forming a closed annular radio-opaque plate having a plurality of corrugations extending from the inner to the outer radius of the plate defining at least one collimator segment section and junction; forming a closed annular flat radio-opaque plate; stacking cylindrically, axially, alternately a plurality of said flat and corrugated plates on one another to form an annular cylindrical multihole collimator with at least one segment; and bonding each said plate to its adjacent plates. a plurality of closed annular radio-opaque plates each having a plurality of corrugations extending from the inner to the outer radius of the plate defining at least one collimator segment section and junction; a plurality of closed, annular, flat radio-opaque plates; and means for bonding said flat and corrugated plates alternately together to form an annular cylindrical multihole collimator with at least one segment. 2. The method of making an annular cylindrical multihole collimator for a radioisotope camera of claim 1, further including applying a radio-opaque filler medium between said plates at the junction between segment sections. 3. The method of making an annular cylindrical multihole collimator for a radioisotope camera of claim 1 in which stacking includes arranging said plates on one another relative to alignment means. 4. The method of making an annular cylindrical multihole collimator for a radioisotope camera of claim 3 in which arranging includes aligning indicia on the plates with guide means. 5. The method of making an annular cylindrical multihole collimator for a radioisotope camera of claim 4 in which said indicia includes at least one hole. 6. The method of making an annular cylindrical multihole collimator for a radioisotope camera of claim 4 in which aligning said indicia includes registering a corrugation of a plate with a guide pin parallel to that corrugation. 7. The method of making an annular cylindrical multihole collimator for a radioisotope camera of claim 1 further including securing an end cap at each end of said collimator. 8. An annular cylindrical multihole collimator for a radioisotope camera, comprising: 9. The annular cylindrical multihole collimator of claim 8 further including a radio-opaque filler medium disposed between said plates at the junctions between segment sections. 10. The annular cylindrical multihole collimator of claim 8 further including an end cap mounted at each end of said collimator. 11. A method of making an annular cylindrical multihole collimator for a radioisotope camera, comprising: 12. The method of making an annular cylindrical multihole collimator for a radioisotope camera of claim 11, further including applying a radio-opaque filler medium between said plates at the junction between segment sections. 13. The method of making an annular cylindrical multihole collimator for a radioisotope camera of claim 11 in which stacking includes arranging said plates on one another relative to alignment means. 14. The method of making an annular cylindrical multihole collimator for a radioisotope camera of claim 13 in which arranging includes aligning indicia on the plates with guide means. 15. The method of making an annular cylindrical multihole collimator for a radioisotope camera of claim 14 in which said indicia includes at least one hole. 16. The method of making an annular cylindrical multihole collimator for a radioisotope camera of claim 14 in which aligning said indicia includes registering a corrugation of a plate with a guide pin parallel to that corrugation. 17. The method of making an annular cylindrical multihole collimator for a radioisotope camera of claim 11 further including securing an end cap at each end of said collimator. 18. An annular cylindrical multihole collimator for a radioisotope camera, comprising: 19. The annular cylindrical multihole collimator for a radioisotope camera of claim 18 further including a radio-opaque filler medium disposed between said plates at the junctions between segment sections. 20. The annular cylindrical multihole collimator for a radioisotope camera of claim 18 further including an end cap mounted at each end of said collimator. |
040173585 | abstract | An ion exchanger which allows flow in both directions along a selected flow-path. A separator plate divides the exchanger tank into two chambers each of which has a flow-conduit so that flow may enter or leave from either chamber while prohibiting the resin particles from migrating from one side of the tank to the other. This ion exchanger permits a dual-directional flow-process to be practiced which results in immediate changes in the boron concentration within a nuclear reactor coolant system even if the ion-exchanger resins have not been completely equilibrated during a previous operation. |
048896799 | abstract | Eddy current probe apparatus having an expansible sleeve thereon capable of hydraulically diametrically expanding a tubular member into engagement with an adjacent structure and capable of hydraulically diametrically expanding a tubular sealing member disposed in the tubular member into engagement with the interior wall of the tubular member, which probe is capable also of detecting the location of the structure and the extent of diametrical expansion of the sealing member and tubular member. The apparatus comprises a support body, expansion means sealingly attached to and surrounding the support body for diametrically expanding the tubular member or sealing member, and electromagnetic means connected to the support body for continuously electromagnetically detecting the variations in the electromagnetic characteristics of the tubular member, sealing member, and structure and the extent of diametrical expansion of the tubular member and sealing member. |
claims | 1. A system, comprising:(a) an apparatus that is deployed in a generally known geographical region, the deployed apparatus including,(i) an imaging component configured to capture an earthbound image of the sky from a terrestrial location,(ii) a chronometric component that measures time synchronously with standard time,(iii) a communication component configured to wirelessly transmit data representative of a captured earthbound image of the sky, and(iv) a controller that is,(A) arranged in electronic communication with said imaging component, said chronometric component, and said communication component, and(B) configured to cause,(I) an earthbound image of the sky to be captured using the imaging component at a time identified by the chronometric component, and(II) data representative of the captured earthbound image to be wirelessly transmitted; and(b) an apparatus for determining a terrestrial location of the deployed apparatus within the generally known geographical region comprising,(i) a computer, and(ii) a computer readable medium accessible by said computer and including,(A) data representative of a master mapping of the sky relative to the surface of the Earth, and(B) computer-executable instructions for determining a terrestrial location based on,(I) the data wirelessly transmitted from the deployed apparatus, and(II) the identified time at which the earthbound image was captured. 2. The system of claim 1, further comprising a plurality of deployed apparatus, each deployed apparatus including(i) an imaging component configured to capture an earthbound image of the sky from a terrestrial location,(ii) a chronometric component that measures time synchronously with standard time,(iii) a communication component configured to wirelessly transmit data representative of a captured earthbound image of the sky, and(iv) a controller that is,(A) arranged in electronic communication with said imaging component, said chronometric component, and said communication component, and(B) configured to cause,(I) an earthbound image of the sky to be captured using the imaging component at a time identified by the chronometric component, and(II) data representative of the captured earthbound image to be wirelessly transmitted. 3. The system of claim 2, wherein the plurality of deployed apparatus comprises sensors that are configured for monitoring of military troop movement. 4. The system of claim 3, wherein a sensor of at least one deployed apparatus comprises a motion detector. 5. The system of claim 3, wherein a sensor of at least one deployed apparatus comprises a microphone. 6. The system of claim 3, wherein a sensor of at least one deployed apparatus comprises a video camera. 7. The system of claim 2, wherein each of the plurality of deployed apparatus captures a plurality of earthbound images at predetermined time intervals. 8. The system of claim 2, wherein the plurality of deployed apparatus comprise triangulating sensors that are configured to triangulate the position of a transmitter, and wherein the computer-executable instructions determine a terrestrial location of the transmitter based on the triangulation by the triangulating sensors and the terrestrial location of each of the triangulating sensors based on the data wirelessly transmitted from each triangulating sensor and the identified time at which each earthbound image was captured. 9. The system of claim 2, wherein the plurality of deployed apparatus includes a global positioning system receiver. 10. The system of claim 1, wherein the controller is further configured to cause data representative of the identified time that the earthbound image of the sky is captured to be wirelessly transmitted in conjunction with the transmission of the data representative of the captured image. 11. The system of claim 1, wherein the deployed apparatus further comprises an internal power supply for powering of said imaging component, said chronometric component, said communication component, and said controller. 12. The system of claim 1, wherein the controller comprises a microcontroller. 13. The system of claim 1, wherein the controller comprises a microprocessor. 14. The system of claim 1, wherein the controller is configured to cause, in response to the occurrence of a predetermined event, an earthbound image of the sky to be captured using the imaging component, the time at which the earthbound image was captured to be identified using the chronometric component, and data representative of the captured earthbound image and identified time to be wirelessly transmitted. 15. The system of claim 1, wherein the controller is configured to cause, in response to the expiration of a predetermined period of time, an earthbound image of the sky to be captured using the imaging component, and data representative of the captured earthbound image to be wirelessly transmitted. 16. The system of claim 1, wherein the deployed apparatus further comprises a receiver for receiving wireless communications. 17. The system of claim 16, wherein the controller is configured to cause, in response to an instruction wirelessly received in a communication by the receiver, an earthbound image of the sky to be captured using the imaging component, the time at which the earthbound image was captured to be identified using the chronometric component, and data representative of the captured earthbound image and identified time to be wirelessly transmitted. 18. The system of claim 1, wherein said imaging component comprises a charge-coupled device (CCD). 19. The system of claim 18, wherein the CCD collects electromagnetic radiation at wavelengths below 2000 Angstroms. 20. The system of claim 18, wherein the CCD collects electromagnetic radiation at wavelengths above 7000 Angstroms. 21. The system of claim 1, wherein said imaging component is configured to process a captured earthbound image of the sky. 22. The system of claim 21, wherein the processing comprises homomorphic filtering. 23. The system of claim 1, wherein the imaging component is configured to capture an earthbound image of the sky at night. 24. The system of claim 1, wherein the deployed apparatus further comprises an accelerometer. 25. The system of claim 24, wherein the deployed apparatus further comprises a compass, wherein the deployed apparatus is mobile and wherein the controller is arranged in electronic communication with said accelerometer and said compass and is configured to cause data representative of movement of the deployed apparatus to be wirelessly transmitted in conjunction with the transmission of the data representative of the captured earthbound image. 26. The system of claim 25, wherein the compass is a gyrocompass. 27. The system of claim 1, wherein the imaging component is configured to capture an earthbound image of the sky during daylight hours. 28. The system of claim 27, wherein the controller is configured to cause a plurality of earthbound images of the sky to be captured using the imaging component at time intervals that are identified by the chronometric component, and is configured to cause data representative of the captured earthbound images to be wirelessly transmitted. 29. The system of claim 1, wherein the deployed apparatus is associated with an asset that is deployed within a generally known geographical region. 30. The system of claim 29, wherein the asset comprises a sensor. 31. The system of claim 1, wherein the computer-executable instructions for determining a terrestrial location based on the data wireless transmitted from the deployed apparatus and the identified time at which the earthbound image was captured performs a method comprising the steps of:(a) manipulating the master map of the sky into a model in which the shape of a sphere is disposed above the surface of the Earth;(b) projecting latitude and longitude lines perpendicularly from the surface of the Earth onto the master mapping of the sky;(c) comparing the captured earthbound image to said manipulated master mapping of the sky; and(d) matching said captured earthbound image to said manipulated master mapping of the sky and reading the latitude and longitude values on said manipulated master map of the sky at the point where said captured earthbound image most closely matches said manipulated master map of the sky,thereby determining the terrestrial location from which the earthbound image was captured by the deployed apparatus. 32. The system of claim 2, wherein the computer-executable instructions for determining a terrestrial location based on the data wireless transmitted from each respective deployed apparatus, and the identified time at which the earthbound image was captured by the respective deployed apparatus, perform a method comprising the steps of:(a) manipulating the master map of the sky into a model in which the shape of a sphere is disposed above the surface of the Earth;(b) projecting latitude and longitude lines perpendicularly from the surface of the Earth onto the master mapping of the sky;(c) comparing each captured earthbound image to said manipulated master mapping of the sky; and(d) matching each captured earthbound image to said manipulated master mapping of the sky and reading the latitude and longitude values on said manipulated master map of the sky at the point where each captured earthbound image most closely matches said manipulated master map of the sky, thereby determining a terrestrial location corresponding to a each captured earthbound image. |
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039376524 | claims | 1. A gas-cooled nuclear power installation comprising a nuclear reactor which includes a reactor core, at least one main boiler, at least one main coolant-gas circulator arranged to circulate coolant gas through the core and through the main boiler whereby to generate steam in the main boiler, a circulator-driving steam turbine arranged to drive said main coolant-gas circulator, and at least one main turbogenerator connected to be driven by steam generated in the main boiler, wherein the installation further comprises at least one auxiliary boiler, at least one auxiliary coolant-gas circulator arranged to circulate coolant gas through the core and the auxiliary boiler whereby to generate further steam in the auxiliary boiler and wherein the auxiliary boiler is connected to supply said further steam to said circulator-driving steam turbine. 2. A nuclear power installation as claimed in claim 1 and comprising at least one auxiliary steam turbogenerator connected to receive and be driven by said further steam exhausted from said circulator-driving steam turbine. 3. A nuclear power installation as claimed in claim 1 and comprising a plurality of main boilers, a plurality of main coolant-gas circulators each driven by a respective circulator-driving steam turbine and arranged to circulate coolant gas through the core and through a respective one of the main boilers, a plurality of auxiliary boilers each arranged to be heated by the coolant gas and to generate said further steam and connected to supply said further steam to at least one of the circulator-driving steam turbines, and a plurality of auxiliary coolant-gas circulators each arranged to circulate coolant gas through the core and through a respective one of the auxiliary boilers. 4. A nuclear power installation as claimed in claim 3 and comprising a prestressed concrete pressure vessel which contains the reactor core and the coolant gas and which includes a wall formed within its thickness with a plurality of cavities each communicating with the vessel interior, wherein each main boiler and its associated main coolant-gas circulator are housed in a respective one of said cavities and each auxiliary boiler and its associated auxiliary coolant-gas circulator are housed in a respective other one of said cavities. 5. A nuclear power installation comprising a nuclear reactor which includes a reactor core, at least one main boiler, at least one main coolant circulator arranged to circulate coolant fluid through the core and through the main boiler, and a circulator-driving steam turbine arranged to drive the main coolant circulator, wherein the installation further comprises at least one auxiliary boiler, which is arranged to be heated by the coolant fluid and to generate steam and which is connected to supply said steam to said circulator-driving steam turbine, at least one auxiliary steam turbogenerator connected to receive and be driven by steam exhausted from said circulator-driving steam turbine, and at least one steam reheater arranged to be heated by the reactor coolant fluid and interposed between said circulator-driving steam turbine and said auxiliary turbogenerator to receive steam exhausted from said circulator-driving steam turbine and, after reheating such steam, to feed it to the auxiliary turbogenerator. 6. A nuclear power installation comprising a nuclear reactor which includes a reactor core, a prestressed concrete pressure vessel which contains the reactor core and coolant fluid therefor and which includes a wall formed within its thickness with a plurality of first cavities and a plurality of second cavities each communicating with the vessel interior, a plurality of main boilers each housed in a respective one of said first cavities, a plurality of main coolant circulators each housed in a respective one of said first cavities and arranged to circulate coolant fluid through the respective main boiler therein and through the reactor core, a plurality of curculator-driving steam turbines each arrranged to drive a respective one of the main coolant circulators, a plurality of auxiliary boilers each housed in a respective one of said second cavities and each arranged to be heated by the coolant fluid and to generate steam and connected to supply said steam to at least one of the circulatordriving steam turbines, a plurality of auxiliary coolant circulators each housed in a respective one of said second cavities and arranged to circulate coolant fluid through the respective auxiliary boiler therein and through the reactor core, and a plurality of steam reheaters each housed in a respective one of said second cavities and each connected to receive steam exhausted from at least one of the circulator-driving steam turbines. |
051867648 | summary | BACKGROUND TO THE INVENTION 1. Field of the Invention This invention relates to the treatment of apertured plates with a gas. More specifically the invention has been developed for the treatment of apertured thin steel plates with a nitriding or nitrocarburising gaseous medium to form a layer of iron nitride on the surfaces of the plates. The invention provides apparatus for such treatment, a method of treatment and a fixture on which a multiplicity of plates can be supported for treatment. 2. Description of the Prior Art It is known from U.S. Pat. No. 4,793,871 assigned to Lucas Industries plc and issued Dec. 27th 1988 to treat steel plates to provide an iron nitride layer thereon by heating the plates in an inert atmosphere in a retort and then evacuating the inert atmosphere and introducing a nitrogen-containing gas which reacts with the heated plates to form the iron nitride layer on the surface thereof. In prior apparatus used for this purpose, the number of plates that could be accommodated in the retort so as to be properly treated was limited since one relied solely on the undirected circulation of the nitrogen-containing gas through the furnace by a fan. SUMMARY OF THE INVENTION It is an object of one aspect of the present invention to provide apparatus which will allow the effective treatment of a much greater number of plates than heretofore in the process described above. It is an object of another aspect of the invention to a provide an effective treatment method and it is an object of a third aspect of the invention to provide a fixture for the plates which will conveniently accommodate them for effective treatment by a gaseous medium. According to one aspect of the present invention we provide apparatus for treating a multiplicity of apertured plates with a gaseous medium comprising a chamber defined by opposite end walls and bottom, top and side walls extending between said end walls; means to circulate gaseous medium through said chamber in a general direction from one of said end walls to the other end wall, means to support said plates in the chamber in mutually spaced relation in a plurality of adjacent rows which extend generally parallel to said end walls so that faces of the plates lie parallel to said general direction of flow; and deflector means on at least some of said bottom, top and side walls for deflecting gas flowing along said walls to flow towards and between said rows so that the gas flow across all said plates is substantially uniform. The provision of the deflector means enables a large number of plates to be contained in the apparatus for treatment in an effective manner due to the uniformity of the gas flow across the plates. Preferably said deflector means comprise a plurality of deflecting members mounted on at least some of said bottom, top and side walls to project therefrom and so that the projection of the deflecting members from the wall on which they are mounted increases the nearer said deflecting members are to said other end wall of the chamber. The deflection of the gas is thus progressively increased as it flows through the chamber and this ensures the uniformity of the gas flow across the plates. More specifically the invention provides apparatus for treating a multiplicity of apertured plates with a gaseous medium comprising a chamber defined by opposite end walls and bottom, top and side walls extending between said end walls; means to circulate gaseous medium through said chamber in a general direction from one of said end walls to the other end wall; a fixture for supporting said plates in said chamber and comprising a base having opposed sides, a plurality of vertical columns mounted on each of said sides, each column of the plurality on one of said sides being aligned with a column of the plurality on the other of said sides to form a pair, a plurality of support bars each extending between a pair of columns so that the support bars are generally parallel to said end walls and so that a number of support bars engage each such pair of columns, each bar being adapted to be threaded through the apertures in a plurality of said plates to support the latter in rows and having locating means to hold the plates threaded thereon in fixed positions and in mutually spaced relation, an apertured end fitting at the end of each support bar, each such fitting having an aperture through which a column passes, and spacers on each column between the end fittings of adjacent support bars on the column to hold said support bars in vertically spaced relation on the column; and deflector means on at least some of said bottom, top and side walls for deflecting gas flowing along along said walls to flow towards and between rows of plates mounted on the support bars so that the gas flow across all said plates is substantially uniform. The provision of a fixture as set forth above together with the deflector means enables a large number of plates to be effectively treated with the gaseous medium One of said end walls may form a door and said chamber may include means whereby said fixture can be moved into and out of said chamber through the door. Said means for moving the fixture into and out of the chamber preferably includes a roller conveyor mounted on the bottom wall of the chamber. The invention also provides a method of treating plates with a gaseous medium in a chamber defined by opposite end walls and side walls extending between said end walls and in which the gaseous medium is circulated in a general direction from one of said end walls to the other, comprising mounting said plates in said chamber in fixed positions and in mutually spaced relation in a plurality of adjacent rows extending generally parallel to said end walls so that faces of the plates lie parallel to the general direction of flow of gaseous medium through the chamber and deflecting gaseous medium which flows along said walls so that said deflected gaseous medium flows towards and between said rows and so that the flow of gaseous medium across all of said plates is substantially uniform. The mounting of the plates so that their faces lie parallel to the general direction of gas flow through the chamber, together with the deflection of the gaseous medium ensure effective treatment of the plates. The plates are preferably apertured and are mounted in said rows with their apertures aligned, so that said deflected gaseous medium also flows into the aligned apertures of the rows of plates. The plates may be mounted in mutually spaced relation in notches on support bars which pass through the aligned apertures of each row of plates. Preferably the plates are of steel and are heated in the chamber in an inert atmosphere which is then evacuated and replaced by a gaseous medium which is a nitriding or nitrocarburising medium and is heated and circulated to form a surface layer of iron nitride on said plates. The invention also provides a fixture for supporting a multiplicity of apertured plates whilst undergoing treatment with a gaseous medium, the fixture comprising a base having opposed sides, a plurality of vertical columns mounted on each of said sides, each column of the plurality on one of said sides being aligned with a column of the plurality on the other of said sides to form a pair, a plurality of support bars each extending between a pair of columns so that a number of support bars engage each such pair of columns, each bar being adapted to be threaded through the apertures in a plurality of said plates to support the latter and having locating means to hold the plates threaded thereon in fixed positions and in mutually spaced relation, an apertured end fitting at the end of each support bar, each such fitting having an aperture through which a column passes, and spacers on each column between the end fittings of adjacent support bars on the column to hold said support bars in vertically spaced relation on the column. The locating means on the support bars may be notches, preferably of Vee-shape, to receive the edges of the apertures in the plates. The support bars may be of upwardly open Vee-section with said notches provided in opposed sides of the Vee. At least one tie bar may connect together the columns of each plurality adjacent the tops of the columns and may have apertures to receive the columns whilst being of angle section between said apertures. Each of said columns may consist of a plurality of separate parts which mutually and telescopically interfit. This enables the fixture to be built up as the plates are being mounted on it. |
claims | 1. A process for treating a waste water stream, to produce a useful water product said waste water stream comprising brackish ground waters, moderately saline water or waste from water purification processing, and containing less than about one percent by weight of dissolved salts of sodium, potassium, magnesium and/or calcium,said useful water product having reduced dissolved sodium and/or potassium content and increased dissolved magnesium and/or calcium content in comparison to said waste water stream, said process comprising the steps of:contacting said waste water stream with a cation exchange resin loaded with magnesium and/or calcium ions, to reduce the dissolved sodium and/or potassium ion content and increase the dissolved magnesium and/or calcium content thereof, andseparating said useful water product from said ion exchange resin. |
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039388450 | summary | In core reactors it is necessary from time to time to exchange the rod shaped fuel elements which means that it is necessary to pull out burned-off fuel elements from the reactor core, to convey the same to a storage place and there to place the same into a storage frame whereas new fuel elements have to be withdrawn from the storage place, conveyed to the core reactor and inserted into the same. Moreover, the control bars inserted in bores of fuel elements have to be pulled out from time to time from the burned-off fuel elements and to be inserted into other fuel elements. A charging device intended for this purpose has become disclosed in German Pat. No. 1,764,176 corresponding to U.S. Pat. No. 3,691,011--Kruger issued Sept. 12, 1972. This known device is characterized primarily by a vertically movable double gripper with an automatically operable control rod gripper and with a fuel element gripper. The fuel element gripper head is located at the lower end of a control bar guiding insert which is in vertical direction displaceably guided in a centering bell. This centering bell is in its turn vertically displaceably guided in a guiding post which extends downwardly from the carriage frame of the charging device. Within the guiding insert for the control bar there is vertically displaceably guided a control rod gripper lever system having at its lower end provided a control bar gripper head. The upper end of said control rod gripper lever system is engaged by a cable winch. By lifting said lever system by means of said winch, the control bar guiding insert which in this instance rests with its upper flange upon the control bar gripper head is lifted, while after a certain stroke, the centering bell is taken along. It is an object of the present invention to provide a gripper device of a lifting device for longitudinally extending bodies which pertain to at least two different groups with different functions, especially in a core reactor, for depositing and picking up fuel elements and control bars in a particularly simple and thus relatively inexpensive manner which is also practically foolproof. |
abstract | The invention relates to the automatic cleaning of ion sources inside mass spectrometers, especially the cleaning of ion sources where the ions are generated by matrix-assisted laser desorption (MALDI). |
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description | The present invention relates to a neutron shielding material composition. Further, the present invention relates to an epoxy resin composition for a neutron shielding material. The material is applied to a cask as a container for storing and transporting a spent nuclear fuel, exhibits improved heat resistance and has ensured neutron shielding performance. Nuclear fuels spent in nuclear facilities such as nuclear power plants are typically transported to reprocessing plants and then reprocessed. However, such spent nuclear fuels today are generated in an amount exceeding the reprocessing capacity. Thus, it is necessary to store spent nuclear fuels for a long period. In this case, spent nuclear fuels are cooled to a radioactivity level that makes the fuels suitable for transportation, and then placed in a cask as a nuclear shielding container and transported. Even at this stage, the spent nuclear fuels still emit radiation such as neutrons. Neutrons have high energy, and generate γ-rays to cause serious harm to the human body. For this reason, it is necessary to develop a neutron shielding material that can surely shield such neutrons. Neutrons are known to be absorbed by boron. To make boron absorb neutrons, it is necessary to moderate the neutrons. Hydrogen is known to be most suitable as a substance for moderating neutrons. Accordingly, a neutron shielding material composition must contain a large amount of boron atoms and hydrogen atoms. Further, since spent nuclear fuels or the like as a neutron source generate decay heat, the fuels are exothermically subjected to a high temperature when sealed in a cask for transportation or storage. The highest temperature varies depending upon the types of spent nuclear fuels, however, it is said that the temperature of spent nuclear fuels for high burnup may reach about 200° C. in a cask. For this reason, a nuclear shielding material for use preferably endures under such high-temperature conditions for about 60 years as a reference storage period for spent nuclear fuels. In this situation, use of a substance having a high hydrogen density, in particular, water as a shielding material has been proposed, and some of the proposals have been put into practice. However, water is difficult to be handled because it is a liquid, and is not suitable for a cask for transportation and storage, in particular. Moreover, when water is used, the internal temperature of a cask is 100° C. or more, and thus it is difficult to suppress boiling, disadvantageously. For this reason, conventionally, a resin composition has been used as a material for a neutron shielding material, and an epoxy resin has been used in one of such resin compositions. Generally, there is a reciprocal relationship between hydrogen content and heat resistance in a resin composition. A resin composition having a high hydrogen content tends to have low heat resistance, and a resin composition having high heat resistance tends to have a low hydrogen content. An epoxy resin exhibits excellent heat resistance and curability, but tends to contain only a small amount of hydrogens indispensable for moderating neutrons. Therefore, an amine curing agent having a high hydrogen content has been conventionally used to compensate this drawback. Japanese Patent Application Unexamined Publication No. 6-148388/1994 discloses a neutron shielding material composition containing a polyfunctional amine epoxy resin and having reduced viscosity for improving workability at ordinary temperature. The composition exhibits excellent pot life. Japanese Patent Application Unexamined Publication No. 9-176496/1997 discloses a neutron shielding material obtained by curing a composition comprising an acrylic resin, epoxy resin, silicone resin or the like with a polyamine curing agent. Sincethe amine has relatively high hydrogen content, the effect of moderating neutrons is improved. However, the amine moiety thereof is easily decomposed by heat. In addition, in order to compensate the lack of the hydrogen content in the epoxy component, a curing agent having a high hydrogen content but having rather lower heat resistance such as polyamine tends to be used, and the ratio of the curing agent component in the resin composition tends to be high. Accordingly, it has been demanded to develop a novel composition having sufficient durability necessary for storing a spent nuclear fuel for high burnup, rather than a conventional composition cured with an amine curing agent. An object of the present invention is to provide a neutron shielding material composition which exhibits heat resistance more excellent than that of a conventional composition, and has ensured neutron shielding capability. In order to achieve the above object, the present invention provides a neutron shielding material composition, comprising a hydrogenated bisphenol resin, a curing agent component, a boron compound and a density-increasing agent. The present invention also provides a neutron shielding material composition, comprising a hydrogenated bisphenol epoxy represented by the structural formula (1): wherein each of R1 to R4 is independently selected from the group consisting of CH3, H, F, Cl and Br, and n is from 0 to 2; a curing agent component having at least one ring structure and a plurality of amino groups; a boron compound; and a density-increasing agent. The composition may preferably further comprise one or more compounds selected from the group consisting of compounds having the structural formulas (2), (3), (6), and (9): wherein R5 is a C1-10 alkyl group or H, and n is from 1 to 24; wherein n is from 1 to 8; wherein each of R9 to R12 is independently selected from the group consisting of CH3, H, F, Cl and Br, and n is from 0 to 2; and The curing agent component may preferably comprise a compound represented by the structural formula (4): The curing agent component may preferably comprise one or more of the compounds represented by the structural formulas (5) and (8): wherein each of R6, R7 and R8 is independently a C1-18 alkyl group or H. The composition of the present invention may further comprise a filler and a refractory material. The refractory material may preferably comprise at least one of magnesium hydroxide and aluminum hydroxide. Magnesium hydroxide may be more preferably magnesium hydroxide obtained from seawater magnesium. The density-increasing agent may be preferably a metal powder having a density of 5.0 to 22.5 g/cm3, a metal oxide powder having a density of 5.0 to 22.5 g/cm3, or a combination thereof. The present invention can further provide a neutron shielding material and a neutron shielding container obtainable from the above-described neutron shielding material composition. Embodiments of the present invention will be described in detail below. The embodiments described below do not limit the present invention. Throughout the present invention, a hydrogenated bisphenol resin refers to a resin containing a polymer formed of a hydrogenated bisphenol A (2,2-bis(4′-(hydroxyphenyl)propane)) or a hydrogenated bisphenol F as a monomer. Examples of such a resin may include an epoxy resin and a polycarbonate resin. Specific examples may include a bisphenol A epoxy acrylate resin and a bisphenol A epoxy methacrylate resin. An epoxy component refers to a compound having an epoxy ring (hereinafter referred to as epoxy compound), and may comprise one epoxy compound or a mixture of two or more epoxy compounds. A curing agent component refers to one or more curing agents. A resin component refers to a combination of a hydrogenated bisphenol resin with a curing agent component, or a combination of an epoxy component with a curing agent component. In a conventional epoxy neutron shielding material, an amine compound mainly used as a curing agent component has particularly inferior heat resistance. This is because the bond is easily decomposed in the amine moiety of the cured resin under high-temperature conditions. The epoxy component in a conventional composition, however, has a low hydrogen content. Consequently, the composition contains a large amount of an amine curing agent having a high hydrogen content and low heat resistance to compensate the lack of the hydrogen content, whereby the necessary hydrogen content is ensured. Accordingly, the present invention provides a composition comprising, as a resin component, a hydrogenated bisphenol resin having a relatively high hydrogen content and a rigid structure. The present invention also provides the composition with high heat resistance and with an epoxy component having an increased hydrogen content, wherein the epoxy resin component comprises use of a compound having relatively high hydrogen content and a rigid structure or crosslinking structure. Still another embodiment of the present invention provides the composition with improved heat resistance and with only a small moiety to be decomposed by using a compound having a rigid structure as an amine curing agent and suppressing the ratio of the amine component in the whole resin composition. Yet another embodiment of the present invention provides the composition exhibiting an improved effect of moderating neutrons by use of an epoxy component having a high hydrogen content and a curing agent component having a high hydrogen content. The present invention can provide a composition comprising a hydrogenated bisphenol resin, a curing agent component, a boron compound as a neutron absorbent, a density-increasing agent, and a refractory material. More preferably, the present invention can provide a composition with excellent heat resistance and a high neutron shielding effect having a high hydrogen content, which comprises an epoxy component containing a hydrogenated bisphenol epoxy as a main component, a curing agent component, a boron compound as a neutron absorbent, a density-increasing agent, and a refractory material. Specifically, the composition of the present invention is cured into a resin, the resin may be required to have a temperature of 330° C. or more, and preferably 350° C. or more at which 90 wt % by weight of the resin remains by thermogravimetric analysis, and to have a hydrogen content of 9.8 wt % or more based on the total resin component. In addition to the above, more specifically, the cured resin having been subjected to thermal endurance at a high-temperature in a sealed environment for a long period can preferably keep a weight reduction and compressive strength as small as possible. For example, the cured resin after thermal endurance in a sealed environment at 190° C. for 1,000 hours may be required to keep a weight reduction not more than 0.5 wt %, preferably not more than 0.2 wt %, and to have compressive strength not being reduced, most preferably being increased instead. Each component will be described below. In the following description, an embodiment in which an epoxy component is used as a resin component will be particularly described. A hydrogenated bisphenol resin other than the above-described epoxy component, however, may be used as a resin component in the present invention. As the epoxy component of the present invention, an epoxy compound having an epoxy ring which can be cured with an amine curing agent can be used. The epoxy component may be one epoxy compound or a mixture of a plurality of epoxy compounds. The type or composition of the epoxy compound forming the epoxy component is selected so that the epoxy component can impart desired properties such as increased heat resistance and hydrogen content. To increase crosslinking density and improve heat resistance, the epoxy compound may be particularly preferably a compound having a plurality of epoxy rings. Additionally, when the epoxy compound contains many ring structures such as benzene rings, the compound has a rigid structure, and thus is suitable for improving heat resistance. Further, the compound may be required to have a high hydrogen content in order to moderate neutrons. The ring structure may preferably comprise a hydrogenated benzene ring, because a benzene ring is rigid and exhibits excellent heat resistance, but has only a low hydrogen content. The rigid structure that can impart heat resistance is preferably a structure containing the structural formula (10): but is more preferably a structure containing the structural formula (11): if taking a high hydrogen content into consideration. Taking these points into consideration, a hydrogenated bisphenol epoxy represented by the structural formula (1), for example, a hydrogenated bisphenol A epoxy or hydrogenated bisphenol F epoxy may be most suitable for the epoxy component in the composition of the present invention in terms of hydrogen content and heat resistance. Accordingly, the epoxy component of the present invention may comprise the structural formula (1) as an essential component. Further, the structural formula (3) or the structural formula (6) may be added as an epoxy component for imparting heat resistance. The structural formula (2) may be added as a component for improving heat resistance and hydrolysis resistance. Since the structural formula (9) retains the high hydrogen content and is expected to exhibit heat resistance, desirable properties can be imparted by adding this compound as an epoxy component. Accordingly, the epoxy component of the present invention may comprise all of the structural formulas (2), (3), (6), and (9), or may comprise only one of the structural formulas. One or more of these structural formulas may be selected according to viscosity of the composition or cost. The epoxy component of the present invention may comprise a hydrogenated bisphenol epoxy as a main component, and may comprise the structural formulas (2), (3), (6), and (9) in any possible combination of two or more. For example, the epoxy component of the present invention can be prepared by adding, to a compound of the structural formula (1), a combination of compounds of the structural formulas (2) and (3), a combination of compounds of the structural formula (2) and (6), a combination of compounds of the structural formula (2) and (9), a combination of compounds of the structural formula (3) and (6), a combination of compounds of the structural formula (3) and (9), a combination of compounds of the structural formula (6) and (9), a combination of compounds of the structural formula (2), (3), and (6), a combination of compounds of the structural formula (2), (3), and (9), a combination of compounds of the structural formula (2), (6), and (9) or a combination of compounds of the structural formula (3), (6), and (9). The epoxy component of the present invention comprising, as a main component, a hydrogenated bisphenol A epoxy of the structural formula (1), wherein R1 to R4 each represents a methyl group and n is from 0 to 2, can have a high hydrogen content and high heat resistance together in a suitable manner by itself, advantageously. A hydrogenated bisphenol F epoxy of the structural formula (1), wherein R1 to R4 are hydrogen and n is from 0 to 2, has a low viscosity, and is thus advantageously used in a mixture with a flaky epoxy of the structural formula (2). When the compound of the structural formulas (3), (6), and (9) are further added to the hydrogenated bisphenol F epoxy and a compound of the structural formula (2), a multi-component system having high heat resistance can be expected. One example of the epoxy component of the present invention may be an epoxy component comprising a hydrogenated bisphenol F epoxy and one or more compounds of the structural formula (2). In this case, the epoxy component may preferably have a composition in which one or more compounds of the structural formula (1) are 35 wt % to 90 wt % and one or more compounds of the structural formula (2) are 10 wt % to 65 wt %, respectively based on the total epoxy content. More preferably, the epoxy component may have a composition in which one or more compounds of the structural formula (1) are 50 wt % to 80 wt % and one or more compounds of the structural formula (2) are 20 wt % to 50 wt %, respectively based on the total epoxy content. The composition of the epoxy component can be determined so that the resin component contains sufficient amount of hydrogens for shielding neutrons, and preferably in an amount of 9.8 wt % or more. Neutron shielding performance of the neutron shielding material can be determined according to hydrogen content (density) of the neutron shielding material and thickness of the neutron shielding material. This value can be based on the hydrogen content required for the resin component, which is calculated with respect to the hydrogen content (density) required for the neutron shielding material, determined from neutron shielding performance required for a cask and the designed thickness of the neutron shield in the cask, taking into consideration the amounts of the refractory material or the neutron absorbent mixed to the neutron shielding material. Here, the epoxy component may comprise the structural formula (1) in an amount of preferably 35 wt % or more, more preferably 50 wt % or more, and most preferably 100 wt %. When the epoxy component comprises the structural formula (3), the content thereof in the epoxy component may be preferably 50 wt % or less, more preferably 30 wt % or less. When the epoxy component comprises a bisphenol epoxy represented by the structural formula (6), the content thereof may be preferably 50 wt % or less, more preferably 30 wt % or less. The compound represented by the structural formula (2) for imparting hydrolysis resistance and heat resistance may be added to the epoxy component in an amount of preferably 65 wt % or less, more preferably 50 wt % or less, still more preferably 30 wt % or less. This is because, if too large an amount of the structural formula (2) is added, viscosity may be increased, and it may be impossible to add a refractory material or the like. When the epoxy component comprises a hydrogenated bisphenol F epoxy as a main component, an increase in viscosity can be suppressed, and this is effective if a large amount of the structural formula (2) is added, accordingly. For example, the epoxy component comprising a hydrogenated bisphenol F epoxy as a main component and about 50 wt % of the structural formula (2) can have the same viscosity as in the epoxy component comprising a hydrogenated bisphenol A epoxy as a main component and about 35 wt % of the structural formula (2). As the curing component in the present invention which is reacted with the epoxy component to form a crosslinked structure, an amine compound can be used. To increase the crosslinking density, a compound having a plurality of amino groups may be preferably used. To further impart heat resistance, a curing agent component having one or more ring structures, and preferably two or more ring structures may be used. To further impart a neutron shielding effect, a compound having a high hydrogen content may be preferable. Preferable ring structures may include hydrocarbon cyclic structures such as a benzene ring, hexane ring and naphthalene ring; heat-stable 5- or 6-membered rings such as heterocyclic rings and a structure obtained by bonding these rings; and a complex cyclic structure containing these structures. Many such curing agents are described in various documents, and any of the curing agents can be applied taking into consideration the necessary amount thereof added stoichiometrically derived from the epoxy equivalent of the epoxy component, the hydrogen content, and the like. Menthenediamine, isophoronediamine, 1,3-diaminocyclohexane and the like can be used from the viewpoint of the hydrogen content, heat resistance, viscosity and the like. In particular, an amine compound having two ring structures, specifically, the structural formula (4) is preferably used in terms of heat resistance. The structural formula (5) can be added to the structural formula (4) as a by-component. Even a small amount of the structural formula (8) added functions as a curing agent and also functions as a curing promoter. Thus, the structural formula (8) is effective in reducing the amount of a curing agent component. When the curing agent component comprises two or more sub-components comprising the structural formula (4), for example, when the curing agent component contains two amine compounds of the structural formulas (4) and (5), the amine of the structural formula (4) may be added in an amount of preferably 80 wt % or less, more preferably 60 wt % or less based on the total curing agent component. The curing agent component may be added in an amount of preferably 25 wt % or less, more preferably 23 wt % or less based on the total resin component. However, the necessary amount to be added can be stoichiometrically derived from the epoxy equivalent of the epoxy component. The density-increasing agent may be any material that is dense and can increase the specific gravity of the neutron shield, unless the material adversely affects other components. Here, the density-increasing agent itself which effectively shields γ-rays may have a density of 5.0 g/cm3 or more, preferably 5.0 to 22.5 g/cm3, more preferably 6.0 to 15 g/cm3. If the density is less than 5.0 g/cm3, it may be difficult to effectively shield γ-rays without impairing neutron shielding capability. If the density is more than 22.5 g/cm3, an effect in proportion to the amount added cannot be observed. Specific examples of the density-increasing agent may include metal powders and metal oxide powders. Preferable examples of the density-increasing agent may include metals having a melting point of 350° C. or more such as Cr, Mn, Fe, Ni, Cu, Sb, Bi, U and W; and metal oxides having a melting point of 1,000° C. or more such as NiO, CuO, ZnO, ZrO2, SnO, SnO2, WO2, UO2, PbO, WO3 and lanthanoid oxides. Of these, Cu, WO2, WO3, ZrO2 and CeO2 may be particularly preferable. This is because they are advantageous in terms of cost. The density-increasing agent may be used singly or in a mixture of two or more. There are no specific limitations to the particle size of the density-increasing agent. However, if the particle size is large, the density-increasing agent may settle during manufacturing process. Therefore, the particle size may be preferably small to the extent that settling does not occur. The particle size that does not cause settling may largely depend on other conditions (for example, the temperature, viscosity, curing speed and the like of the composition), and thus cannot be numerically defined simply. By adding a density-increasing agent, the specific gravity of a neutron shield can be increased, and γ-rays can be more effectively shielded. By use of the above-described metal powder or metal oxide powder, fire resistance can also be improved. By replacing a part of an additive other than the resin component, mainly a part of the refractory material with the density-increasing agent, the hydrogen content may be increased. By replacing mainly a part of the refractory material with the density-increasing agent, the amount of the epoxy resin can be increased while maintaining a specific gravity of a neutron shielding material composition (1.62 to 1.72 g/cm3). Thus, a neutron shield having a high hydrogen content can be manufactured, and neutrons can be effectively shielded. Specifically, neutron shielding capability and γ-ray shielding can be achieved at the same time. The amount of the density-increasing agent to be added can be appropriately adjusted to maintain the specific gravity of the neutron shielding material composition (1.62 to 1.72 g/cm3). It is difficult to specifically define the amount, because the amount varies according to the type of the density-increasing agent used, the types and contents of other components, and the like. For example, the amount is 5 to 40 mass %, and preferably 9 to 35 mass % based on the total neutron shielding material composition. The amount is particularly preferably 15 to 20 mass % when using CeO2. If the amount is less than 5 mass %, it is difficult to observe the effect of adding the density-increasing agent. If the amount is more than 40 mass %, it is difficult to keep the specific gravity of the neutron shielding material composition in the range of 1.62 to 1.72 g/cm3. Examples of a boron compound added as the neutron absorbent may include boron carbide, boron nitride, boric acid anhydride, boron iron, colemanite, orthoboric acid and metaboric acid. Boron carbide may be most preferable. A powder can be used as the above-described boron compound without specific limitations to its particle size and amount added. When considering dispersibility in the epoxy resin of the matrix resin component and neutron shielding performance, the average particle size may range from preferably about 1 to 200 microns, more preferably about 10 to 100 microns, particularly preferably about 20 to 50 microns. On the other hand, the amount of the boron compound added may range from most preferably 0.5 to 20 wt % based on the total composition including the filler described below. If the amount is less than 0.5 wt %, the boron compound added may exhibit only a small effect as the neutron shielding material. If the amount is more than 20 wt %, it may be difficult to homogeneously disperse the boron compound. In the present invention, the filler may include a powder such as silica, alumina, calcium carbonate, antimony trioxide, titanium oxide, asbestos, clay, mica; or a glass fiber-. A carbon fiber or the like may be added if necessary. Further, if necessary, a releasing agent such as a natural wax, metallic salt of fatty acid, acid amides, or fatty acid esters; a flame retardant such as paraffin chloride, bromotoluene, hexabromobenzene, or antimony trioxide; a colorant such as carbon black, or iron oxide red; a silane coupling agent; a titanium coupling agent; or the like can be added. The refractory material used in the composition of the present invention aims to preserve a certain amount or more of the neutron shielding material so that neutron shielding capability can be maintained to a certain extent or higher even in case of fire. As such a refractory material, magnesium hydroxide or aluminum hydroxide is preferable. Of these, magnesium hydroxide may be particularly preferable, because it is present in a stable manner even at a high temperature of 170° C. or more. Magnesium hydroxide may be preferably magnesium hydroxide obtained from seawater magnesium. This is because magnesium in seawater has a high purity to make the hydrogen ratio in the composition relatively high. Seawater magnesium can be produced by a method such as a seawater method or ionic brine method. Otherwise, a commercially available product Kisuma 2SJ (product name, Kyowa Chemical Industry Co., Ltd.) may be purchased and used. However, commercially available magnesium hydroxide is not limited to this product. The refractory material may be added in an amount of preferably 20 to 70 wt %, particularly preferably 35 to 60 wt % based on the total composition. The composition of the present invention may be prepared by mixing epoxy components; then allowing the mixture to stand at room temperature; mixing a curing agent component with the mixture when the mixture is at about room temperature; and finally adding a density-increasing agent, a refractory material, a neutron absorbent and other additive components. Polymerization may be carried out at room temperature, but may be preferably carried out by heating. Although polymerization conditions may differ according to the composition of the resin component, heating may be preferably carried out at a temperature of 50° C. to 200° C. for 1 to 3 hours. Further, such heating treatment may be preferably carried out in two stages. It is preferable to carry out heating treatment at 60° C. to 90° C. for 1 to 2 hours, and then at 120° C. to 150° C. for 2 to 3 hours. A cask for storing and transporting a spent nuclear fuel can be produced using the above composition. Such a transportation cask can be produced by a known art. For example, in a cask disclosed in Japanese Patent Application Unexamined Publication No. 2000-9890, a location to be filled with a neutron shield is provided. Such a location can be filled with the composition of the present invention. The composition of the present invention can be used not only for such a neutron shield, but also for various places in apparatuses and facilities to prevent diffusion of neutrons, and can effectively shield neutrons. Specific examples of embodiments of the present invention using a resin component, a density-increasing agent and a refractory material will be further described in detail with reference to the drawings. Here, embodiments in which a boron compound or a filler is not added will be described for illustration, however, it should be construed that the present invention is limited to such embodiments. FIG. 1 is a conceptual view showing a configuration example of the neutron shield of the present embodiment. Specifically, as shown in FIG. 1, the neutron shield of the present embodiment is obtained by mixing a resin component 1 containing a hydrogenated bisphenol resin and a curing agent component with a refractory material 2 and a density-increasing agent 3 having a higher density than that of the refractory material 2. Here, the neutron shield is provided with an increased hydrogen content while maintaining the material density (in the range of 1.62 to 1.72 g/mL), by mixing a metal powder or metal oxide powder as the density-increasing agent 3, in particular. Density of the density-increasing agent 3 to be mixed is 5.0 g/mL or more, ranges from preferably 5.0 to 22.5 g/mL, more preferably 6.0 to 15 g/mL. Further, the density-increasing agent 3 to be mixed is preferably a metal powder having a melting point of 350° C. or more or a metal oxide powder having a melting point of 1,000° C. or more. Examples of a powder material corresponding to the density-increasing agent include metals such as Cr, Mn, Fe, Ni, Cu, Sb, Bi, U and W. Further examples thereof include metal oxides such as NiO, CuO, ZnO, ZrO2, SnO, SnO2, WO2, CeO2, UO2, PbO, PbO and WO3. Since the neutron shield of the present embodiment configured as above can be prepared by mixing the resin component 1, the refractory material 2, and the density-increasing agent 3 having a higher density than that of the refractory material 2, the neutron shield can have an increased hydrogen content while maintaining the material density at a certain value (in the range of 1.62 to 1.72 g/mL). Specifically, the refractory material 2 may have a slightly higher density and a slightly lower hydrogen content as compared with the resin component 1. Thus, a part of the refractory material 2 is replaced with the density-increasing agent 3 not containing hydrogen to make the material density equal. By calculating the density and the hydrogen content of each component and carrying out appropriate replacement, the refractory material 2 having a slightly lower hydrogen content is replaced with the resin component 1 having a high hydrogen content, so that the neutron shield can have an increased hydrogen content. As a result, the neutron shield can provide increased neutron dosage while maintaining secondary γ-ray shielding performance, and accordingly can have improved neutron radiation shielding performance without placing a structure for shielding γ-rays outside the main body of the neutron shield as in a conventional manner. In the neutron shield of the present embodiment, the density-increasing agent 3 to be mixed may have a density of 5.0 g/mL or more, preferably 5.0 to 22.5 g/mL, more preferably 6.0 to 15 g/mL. Therefore, the neutron shield can exhibit the above-described effect more significantly. FIG. 2 is a characteristic view showing the relation between the density of the density-increasing agent 3 and the hydrogen content. FIG. 2 shows hydrogen contents by changing the original neutron shield having a hydrogen content of 0.0969 g/mL, containing magnesium hydroxide as the refractory material 2 and containing the resin component 1 having a density of 1.64 g/mL, to the shields in which the refractory material 2 is replaced with the density-increasing agent 3 with the material density held constant. Magnesium hydroxide as the refractory material 2 has a density of 2.36 g/mL. As is clear from FIG. 2, the density-increasing agent 3 is effective only if the density of the density-increasing agent 3 reaches a density slightly higher than in the refractory material 2, not the density of the refractory material 2, although the effective density differs, depending on the types of the resin component 1 and the refractory material 2. Specifically, the density-increasing agent 3 is effective at a density of 5.0 g/mL or more, preferably 6.0 g/mL or more. If the density is more than 22.5 g/mL, an effect in proportion to the amount added cannot be observed. FIG. 3 is a characteristic view showing the relation between the density of the density-increasing agent 3 and the relative values for the sum of the neutron and secondary γ-ray doses outside the neutron shield. FIG. 3 shows a shielding effect of the neutron shield by changing original shield having a hydrogen content of 0.0969 g/mL, containing magnesium hydroxide as the refractory material 2 and containing the base resin 1 having a density of 1.64 g/mL, to the shields in which the refractory material 2 is replaced with the density-increasing agent 3 with the material density held constant. The dose outside the shield of the resin component 1 is defined as the relative value of “1”. As is clear from FIG. 3, the effect can be observed when the density-increasing agent 3 has a density of 5.0 g/mL or more, more preferably 6.0 g/mL or more. If the density is more than 22.5 g/mL, an effect in proportion to the amount added cannot be observed. Further, the neutron shield of the present embodiment can be provided with improved fire resistance by mixing a metal powder having a melting point of 350° C. or more (such as Cr, Mn, Fe, Ni, Cu, Sb, Bi, U or W) or a metal oxide powder having a melting point of 1000° C. or more (such as NiO, CuO, ZnO, ZrO2, SnO, SnO2, WO2, CeO2, UO2, PbO, PbO or WO3). As described above, the neutron shield of the present embodiment can have an increased hydrogen content while maintaining the material density at a certain value without any decrease, and accordingly can have improved neutron shielding performance without placing a structure for shielding γ-rays outside the main body of the neutron shield as in a conventional manner. As shown in the above FIG. 1, the neutron shield of the present embodiment is obtained by mixing a resin component 1 containing an epoxy resin and a curing agent with a refractory material 2 and a density-increasing agent 3 having a density higher than in the refractory material 2, and forming the mixture by curing. The density-increasing agent 3 to be mixed may have a density of 5.0 g/mL or more, preferably 5.0 to 22.5 g/mL, more preferably 6.0 to 15 g/mL. Further, the density-increasing agent 3 to be mixed may be preferably a metal powder having a melting point of 350° C. or more or a metal oxide powder having a melting point of 1,000° C. or more. Examples of a powder material corresponding to the density-increasing agent may include metals such as Cr, Mn, Fe, Ni, Cu, Sb, Bi, U and W. Further examples thereof include metal oxides such as NiO, CuO, ZnO, ZrO2, SnO, SnO2, WO2, CeO2, UO2, PbO, PbO and WO3. Since the neutron shield of the present embodiment configured as above is prepared by mixing the resin component 1, the refractory material 2, and the density-increasing agent 3 having a density higher than in the refractory material 2, the neutron shield can have an increased hydrogen content while maintaining the material density at a certain value (in the range of 1.62 to 1.72 g/mL). Specifically, the refractory material 2 may have a slightly higher density and a slightly lower hydrogen content as compared with the resin component 1. Thus, a part of the refractory material 2 is replaced with the density-increasing agent 3 not containing hydrogen to make the material density equal. By calculating the density and the hydrogen content of each component and carrying out appropriate replacement, the refractory material 2 having a slightly lower hydrogen content is replaced with the resin component 1 having a high hydrogen content, so that the neutron shield can have an increased hydrogen content. As a result, the neutron shield can provide an increased neutron dosage while maintaining secondary γ-ray shielding performance, and accordingly can have improved neutron radiation shielding performance without placing a structure for shielding γ-rays outside the main body of the neutron shielding material as in a conventional manner. In the neutron shielding material of the present embodiment, the density-increasing agent 3 to be mixed may have a density of 5.0 g/mL or more, preferably 5.0 to 22.5 g/mL, more preferably 6.0 to 15 g/mL. Therefore, the neutron shielding material can exhibit the above-described effect more significantly. FIG. 2 is a characteristic view showing the relation between the density of the density-increasing agent 3 and the hydrogen content. FIG. 2 shows hydrogen contents by changing the original neutron shield having a hydrogen content of 0.0969 g/mL, containing magnesium hydroxide as the refractory material 2 and containing the base resin 1 having a density of 1.64 g/mL, to the shields in which the refractory material 2 is replaced with the density-increasing agent 3 with the material density held constant. Magnesium hydroxide as the refractory material 2 has a density of 2.36 g/mL. As is clear from FIG. 2, the density-increasing agent 3 is effective only if the density of the density-increasing agent 3 reaches a density slightly higher than in the refractory material 2, not the density of the refractory material 2, although the effective density differs, depending on the types of the base resin 1 and the refractory material 2. Specifically, the density-increasing agent 3 is effective at a density of 5.0 g/mL or more, more preferably 6.0 g/mL or more. If the density is more than 22.5 g/mL, an effect in proportion to the amount added cannot be observed. FIG. 3 is a characteristic view showing the relation between the density of the density-increasing agent 3 and the relative values for the sum of the neutron and secondary γ-ray doses outside the neutron shield. FIG. 3 shows a shielding effect of the neutron shield by changing original shield having a hydrogen content of 0.0969 g/mL, containing magnesium hydroxide as the refractory material 2 and containing the base resin 1 having a density of 1.64 g/mL, to the shields in which the refractory material 2 is replaced with the density-increasing agent 3 with the material density held constant. The dose outside the shield of the base resin 1 is defined as the relative value of “1”. As is clear from FIG. 3, the effect can be observed when the density-increasing agent 3 has a density of 5.0 g/mL or more, and preferably 6.0 g/mL or more. If the density is more than 22.5 g/mL, an effect in proportion to the amount added cannot be observed. Further, the neutron shield of the present embodiment can be provided with improved fire resistance by mixing a metal powder having a melting point of 350° C. or more (such as Cr, Mn, Fe, Ni, Cu, Sb, Bi, U or W) or a metal oxide powder having a melting point of 1000° C. or more (such as NiO, CuO, ZnO, ZrO2, SnO, SnO2, WO2, CeO2, UO2, PbO, PbO or WO3). As described above, the neutron shield of the present embodiment also can have an increased hydrogen content while maintaining the material density at a certain value without any decrease, and accordingly can have improved neutron shielding performance without placing a structure for shielding γ-rays outside the main body of the neutron shield as in a conventional manner. Specifically, since the neutron shield can be more effective for shielding neutrons while maintaining γ-ray shielding performance by use of a density-increasing agent, it can be less necessary to place a heavy structure for shielding γ-rays outside the main body of the neutron shield as in a conventional manner. The present invention will be described in detail below with respect to examples. The examples below are not intended to limit the present invention. In the examples, the composition of the present invention was prepared, and the neutron shielding effect was examined. Typically, a resin composition for a neutron shielding material is mixed with copper as a density-increasing agent, aluminum hydroxide or magnesium hydroxide as a refractory material, and a boron compound such as boron carbide as a neutron absorbent, respectively in an amount of about 20 wt %, about 40 wt % and about 1 wt % based on the total resin composition to prepare a neutron shield. Compositions without the refractory material and the neutron absorbent are mainly described here in order to evaluate properties exhibited by a resin component, specifically, an epoxy component and a curing agent component, and a density-increasing agent. Properties required for the neutron shielding material include heat resistance (residual weight ratio, compressive strength, or the like), fire resistance and hydrogen content (the material must have a certain hydrogen content density or higher in order to be judged suitable for a neutron shield). Since fire resistance largely depends upon the refractory material, the resin composition for a neutron shielding material was evaluated for its heat resistance represented by a residual weight ratio and hydrogen content. The residual weight ratio was determined by measuring the weight change during heating to evaluate heat resistance of the composition. TGA was used for the measurement. The weight reduction by heat was measured under a condition where the composition was heated from room temperature to 600° C. at a rate of temperature rise of 10° C./min in a nitrogen atmosphere. A hydrogen content in a single resin of 9.8 wt % or more was defined as the standard hydrogen content required for the resin. Mixed were 59.47 g of a hydrogenated bisphenol A epoxy resin (manufactured by Yuka Shell Epoxy K. K., YL6663 (structural formula (1))) and 25.00 g of a polyfunctional alicyclic epoxy resin (manufactured by Daicel Chemical Industries, Ltd., EHPE3150 (structural formula (2)) as epoxy resins. The mixture was maintained at 110° C., and sufficiently stirred until EHPE3150 (solid) was dissolved. After dissolution of EHPE3150, the mixture was allowed to stand in an environment at room temperature. When the temperature of the mixture fell to about room temperature, 15.53 g of 1,3-BAC (manufactured by Mitsubishi Gas Chemical Company, Inc. (structural formula (5))) was mixed therewith as a curing agent, and the mixture was stirred. Fifty gram of copper having a density of 8.92 g/cm3 was mixed therewith as a density-increasing agent to prepare a resin composition used for a neutron shielding material. The hydrogen content of the resin composition for a neutron shielding material was measured by the componential analysis. As a result of the measurement, the hydrogen content was 9.8 wt % or more (about 10 wt % or more) which was above the standard value satisfactorily. The resin composition for a neutron shielding material was cured at 80° C. for 30 minutes and at 150° C. for 2 hours, and the weight reduction by heat of the cured product was measured by TGA. As a result of measuring the weight reduction by heat, the residual weight percentage at 200° C. was 99.5 wt % or more, and the temperature at a residual weight percentage of 90 wt % was 370° C. or more, which shows extremely good heat resistance and heat stability of the composition. Mixed were 48.81 g of a hydrogenated bisphenol A epoxy resin (YL6663 (structural formula (1))), 10.00 g of an alicyclic epoxy resin (manufactured by Daicel Chemical Industries, Ltd., Celloxide 2021P (structural formula (3))) and 25.00 g of a polyfunctional alicyclic epoxy resin (EHPE3150 (structural formula (2)) as epoxy resins. The mixture was kept at 110° C. and sufficiently stirred until EHPE3150 (solid) was dissolved. After dissolution of EHPE3150, the mixture was allowed to stand in an environment at room temperature. When the temperature of the mixture fell to about room temperature, 16.19 g of 1,3-BAC (structural formula (5)) was mixed therewith as a curing agent, and the mixture was stirred. Mixed therewith was 50 g of copper as a density-increasing agent to prepare a resin composition used for a neutron shielding material. As a result of measuring the hydrogen content in the resin composition, the hydrogen content was 9.8 wt % or more (about 10 wt % or more) which was above the standard satisfactorily. The resin composition for a neutron shielding material was cured at 80° C. for 30 minutes and at 150° C. for 2 hours to measure the weight reduction by heat. As a result, the residual weight percentage at 200° C. was 99.5 wt % or more, and the temperature at a residual weight percentage of 90 wt % was 380° C. or more, which shows extremely good heat resistance and heat stability of the composition. Mixed were 49.20 g of a hydrogenated bisphenol A epoxy resin (YL6663 (structural formula (1))), 10.00 g of a bisphenol A epoxy resin (manufactured by Yuka Shell Epoxy K. K., Epicoat 828 (structural formula (6), wherein R9 to R12 each represents a methyl group, and n is from 0 to 2)) and 25.00 g of a polyfunctional alicyclic epoxy resin (EHPE3150 (structural formula (2))) as epoxy resins. The mixture was maintained at 110° C. and sufficiently stirred until EBPE3150 (solid) was dissolved. After dissolution of EHPE3150, the mixture was allowed to stand in an environment at room temperature. When the temperature of the mixture fell to about room temperature, 15.80 g of 1,3-BAC (structural formula (5)) as a curing agent was mixed therewith and stirred. Mixed therewith was 50 g of copper as a density-increasing agent to prepare a resin composition used for a neutron shielding material. As a result of measuring the hydrogen content in the resin composition, the hydrogen content was 9.8 wt % or more (about 9.9 wt % or more) which was above the standard value satisfactorily. On the other hand, the resin composition for a neutron shielding material was cured at 80° C. for 30 minutes and at 150° C. for 2 hours to measure the weight reduction by heat. As a result, the residual weight percentage at 200° C. was 99.5 wt % or more, and the temperature at a residual weight precentage of 90 wt % was 380° C. or more, which shows extremely good heat resistance and heat stability of the composition. Mixed were 55.44 g of a hydrogenated bisphenol A epoxy resin (YL6663 (structural formula (1))) and 25.00 g of a polyfunctional alicyclic epoxy resin (EHPE3150 (structural formula (2)) as epoxy resins. The mixture was maintained at 110° C. and sufficiently stirred until EHPE3150 (solid) was dissolved. After dissolution of EHPE3150, the mixture was allowed to stand in an environment at room temperature. When the temperature of the mixture fell to about room temperature, 19.56 g of a mixed curing agent was mixed therewith and stirred, wherein the mixed curing agent was obtained by sufficiently mixing 14.67 g of Wandamin HM (manufactured by New Japan Chemical Co., Ltd. (structural formula (4))) with 4.89 g of 1,3-BAC (structural formula (5)) in advance to make the curing agents compatible with each other. Mixed therewith was 50 g of copper as a density-increasing agent to prepare a resin composition used for a neutron shielding material. As a result of measuring the hydrogen content in the resin composition, the hydrogen content was 9.8 wt % or more (about 10 wt % or more) which was above the standard satisfactorily. The resin composition for a neutron shielding material was cured at 80° C. for 30 minutes and at 150° C. for 2 hours to measure the weight reduction by heat. As a result, the residual weight percentage at 200° C. was 99.5 wt % or more, and the temperature at a residual weight percentage of 90 wt % was about 390° C., which shows extremely good heat resistance and heat stability of the composition. Mixed were 44.62 g of a hydrogenated bisphenol A epoxy resin (YL6663 (structural formula (1))), 10.00 g of an alicyclic epoxy resin (Celloxide 2021P (structural formula (3))) and 25.00 g of a polyfunctional alicyclic epoxy resin (EHPE3150 (structural formula (2)) as epoxy resins. The mixture was maintained at 110° C. and sufficiently stirred until EHPE3150 (solid) was dissolved. After dissolution of EHPE3150, the mixture was allowed to stand in an environment at room temperature. When the temperature of the mixture fell to about room temperature, 19.38 g of a mixed curing agent was mixed therewith and stirred, wherein the mixed curing agent was obtained by sufficiently mixing 15.29 g of Wandamin HM (structural formula (4)) with 5.09 g of 1,3-BAC (structural formula (5)) in advance to make the curing agents compatible with each other. Mixed therewith was 50 g of copper as a density-increasing agent to prepare a resin composition used for a neutron shielding material. As a result of measuring the hydrogen content in the resin composition, the hydrogen content was 9.8 wt % or more (about 10 wt % or more) which was above the standard satisfactorily. The resin composition for a neutron shielding material was cured at 80° C. for 30 minutes and at 150° C. for 2 hours to measure the weight reduction by heat. As a result, the residual weight percentage at 200° C. was 99.5 wt % or more, and the temperature at a residual weight percentage of 90 wt % was about 400° C., which shows extremely good heat resistance and heat stability of the composition. Mixed were 43.42 g of a hydrogenated bisphenol A epoxy resin (YL6663 (structural formula (1))), 13.28 g of a bisphenol A epoxy resin (Epicoat 828 (structural formula (6), wherein R9 to R12 each represents a methyl group, and n is from 0 to 2)) and 24.30 g of a polyfunctional alicyclic epoxy resin (EHPE3150 (structural formula (2))) as epoxy resins. The mixture was maintained at 110° C. and sufficiently stirred until EHPE3150 (solid) was dissolved. After dissolution of EHPE3150, the mixture was allowed to stand in an environment at room temperature. When the temperature of the mixture fell to about room temperature, 19.00 g of a mixed curing agent obtained by preliminarily mixing 11.4 g of Wandamin HM (structural formula (4)) with 7.6 g of 1,3-BAC (structural formula (5)) sufficiently and making the curing agents compatible with each other was mixed therewith, and the mixture was stirred. Mixed therewith was 50 g of copper as a density-increasing agent to prepare a resin composition used for a neutron shielding material. As a result of measuring the hydrogen content in the resin composition, the hydrogen content was about 9.8 wt % which satisfied the standard. The resin composition for a neutron shielding material was cured at 80° C. for 30 minutes and at 150° C. for 2 hours to measure the weight reduction by heat. As a result, the residual weight percentage at 200° C. was 99.5 wt % or more, and the temperature at a residual weight percentage of 90 wt % was 400° C. or more, which shows extremely good heat resistance and heat stability of the composition. Mixed with 80.83 g of a hydrogenated bisphenol A epoxy resin (YL6663 (structural formula (1))) as an epoxy resin was 19.17 g of a mixed curing agent, wherein the mixed curing agent was obtained by sufficiently mixing 14.38 g of Wandamin HM (structural formula (4)) with 4.79 g of 1,3-BAC (structural formula (5)) in advance and stirring to make the above curing agents compatible with one another. Mixed therewith was 50 g of copper as a density-increasing agent to prepare a resin composition used for a neutron shielding material. As a result of measuring the hydrogen content in the resin composition, the hydrogen content was 10.6 wt % or more which was considerably above the standard, satisfactorily. The resin composition for a neutron shielding material was cured at 80° C. for 30 minutes and at 150° C. for 2 hours to measure the weight reduction by heat. As a result, the residual weight percentage at 200° C. was about 99.5 wt %, and the temperature at a residual weight percentage of 90 wt % was about 330° C., which shows extremely good heat resistance and heat stability of the composition. Mixed with 69.93 g of a hydrogenated bisphenol A epoxy resin (YL6663 (structural formula (1))) and 10.07 g of an alicyclic epoxy resin (Celloxide 2021P (structural formula (3))) as epoxy resins was 20.00 g of a mixed curing agent, wherein the mixed curing agent was obtained by sufficiently mixing 15.00 g of Wandamin HM (structural formula (4)) with 5.00 g of 1,3-BAC (structural formula (5)) and stirring in advance to make the above curing agents compatible with one another. Mixed therewith was 50 g of copper as a density-increasing agent to prepare a resin composition used for a neutron shielding material. As a result of measuring the hydrogen content in the resin composition, the hydrogen content was about 10.5 wt % which was considerably above the standard, satisfactorily. The resin composition for a neutron shielding material was cured at 80° C. for 30 minutes and at 150° C. for 2 hours to measure the weight reduction by heat. As a result, the residual weight percentage at 200° C. was 99.5 wt % or more, and the temperature at a residual weight percentage of 90 wt % was about 340° C., which shows extremely good heat resistance and heat stability of the composition. Mixed with 49.48 g of a hydrogenated bisphenol A epoxy resin (YL6663 (structural formula (1))) and 30.32 g of a bisphenol A epoxy resin (Epicoat 828 (structural formula (6), wherein R9 to R12 each represents a methyl group, and n is from 0 to 2)) as epoxy resins was 20.20 g of a mixed curing agent, wherein the mixed curing agent was obtained by sufficiently mixing 15.15 g of Wandamin HM (structural formula (4)) with 5.05 g of 1,3-BAC (structural formula (5)) in advance to make the above curing agents compatible with one another. Mixed therewith was 50 g of copper as a density-increasing agent to prepare a resin composition used for a neutron shielding material. As a result of measuring the hydrogen content in the resin composition, the hydrogen content was about 9.8 wt % which satisfied the standard. The resin composition for a neutron shielding material was cured at 80° C. for 30 minutes and at 150° C. for 2 hours to measure the weight reduction by heat. As a result, the residual weight percentage at 200° C. was 99.5 wt % or more, and the temperature at a residual weight percentage of 90 wt % was about 360° C., which shows extremely good heat resistance and heat stability of the composition. Mixed with 16.00 g of 1,3-BAC (structural formula (5)) were 55.02 g of a hydrogenated bisphenol A epoxy resin (YL6663 (structural formula (1))) and 28.98 g of a bisphenol A epoxy resin (Epicoat 828 (structural formula (6), wherein R9 to R12 each represents a methyl group, and n is from 0 to 2)), and the mixture was stirred. Mixed therewith was 50 g of copper as a density-increasing agent to prepare a resin composition used for a neutron shielding material. As a result of measuring the hydrogen content in the resin composition, the hydrogen content was about 9.8 wt % which satisfied the standard. The resin composition for a neutron shielding material was cured at 80° C. for 30 minutes and at 150° C. for 2 hours to measure the weight reduction by heat. As a result, the residual weight percentage at 200° C. was 99.5 wt % or more, and the temperature at a residual weight percentage of 90 wt % was about 340° C., which shows extremely good heat resistance and heat stability of the composition. Mixed were 55.44 g of a hydrogenated bisphenol A epoxy resin (YL6663 (structural formula (1))) and 25.00 g of a polyfunctional alicyclic epoxy resin (EHPE3150 (structural formula (2)) as epoxy resins. The mixture was maintained at 110° C. and sufficiently stirred until EHPE3150 (solid) was dissolved. After dissolution of EHPE3150, the mixture was allowed to stand in an environment at room temperature. When the temperature of the mixture fell to about room temperature, 19.55 g of a mixed curing agent was mixed therewith and stirred, wherein the mixed curing agent was obtained by sufficiently mixing 14.5 g of Wandamin HM (structural formula (4)), 4.85 g of 1,3-BAC (structural formula (5)) and 0.2 g of an imidazole compound (structural formula (8)) in advance to make the above curing agents compatible with each other. Mixed therewith was 50 g of copper as a density-increasing agent to prepare a resin composition used for a neutron shielding material. As a result of measuring the hydrogen content in the resin composition, the hydrogen content was 9.8 wt % or more (about 10 wt % or more) which was above the standard satisfactorily. The resin composition for a neutron shielding material was cured at 80° C. for 30 minutes and at 150° C. for 2 hours to measure the weight reduction by heat. As a result, the residual weight percentage at 200° C. was 99.5 wt % or more, and the temperature at a residual weight percentage of 90 wt % was 390° C. or more, which shows extremely good heat resistance and heat stability of the composition. Here, a composition was prepared by further adding a neutron absorbent and a refractory material. Mixed were 43.42 g of a hydrogenated bisphenol A epoxy resin (YL6663 (structural formula (1))), 13.28 g of a bisphenol A epoxy resin (Epicoat 828 (structural formula (6), wherein R9 to R12 each represents a methyl group, and n is from 0 to 2)), and 24.30 g of a polyfunctional alicyclic epoxy resin (EHPE3150 (structural formula (2))) as epoxy resins. The mixture was maintained at 110° C. and sufficiently stirred until solid EHPE3150 was dissolved. After dissolution of EHPE3150, the mixture was allowed to stand in an environment at room temperature. When the temperature of the mixture fell to about room temperature, 19:00 g of a mixed curing agent was mixed therewith and stirred, wherein the curing agent was obtained by sufficiently mixing 11.4 g of Wandamin HM (structural formula (4)) with 7.6 g of 1,3-BAC (structural formula (5)) in advance to make the curing agents compatible with each other. Mixed therewith were 39.0 g of copper as a density-increasing agent, 76.0 g of magnesium hydroxide and 3.0 g of boron carbide, and the mixture was stirred to prepare a composition for neutron shielding material. The reference hydrogen content required for a neutron shielding material is a hydrogen content density of 0.096 g/cm3 or more. The hydrogen content density of the prepared neutron shielding material composition was measured to be 0.096 g/cm3 or more, which satisfied the standard. The resin composition for a neutron shielding material was cured at 80° C. for 30 minutes and at 150° C. for 2 hours. The cured product was subjected to the weight reduction measurement by heating. As a result, the residual weight percentage at 200° C. was 99.5 wt % or more, and the temperature at a residual weight percentage of 90 wt % was 400° C. or more, which shows extremely good heat resistance and heat stability of the composition. The cured product was enclosed in a closed vessel, and a thermal endurance test was carried out at 190° C. for 1,000 hours. After the thermal endurance test, the compressive strength was 123 MPa and 1.1 times of that before the test; the weight reduction percentage was about 0.05%; and the glass transition temperature (tanδ peak in the viscoelasticity measurements) was increased from 130° C. as a value before the test to about 175° C. It was confirmed from the result of infrared spectroscopic analysis that the chemical structure was almost not changed before and after the test. The above results confirmed that the composition has extremely good thermal durability. A bisphenol A epoxy resin (Epicoat 828 (structural formula (6), wherein R9 to R12 each represents a methyl group, and n is from 0 to 2)) as an epoxy resin was mixed with a polyamine curing agent at a mixing ratio of 1:1 (stoichiometrically equal), and the mixture was stirred to prepare a resin composition used for a neutron shielding material. No density-increasing agent was added. As a result of measuring the hydrogen content in the resin composition, the hydrogen content was 9.8 wt % or more which satisfied the standard value. The resin composition for a neutron shielding material was cured at 80° C. for 30 minutes and at 150° C. for 2 hours. The cured product was subjected to the weight reduction measurement by heat. As a result, the residual weight percentage at 200° C. was 99 wt % or less, and the temperature at a residual weight percentage of 90 wt % was 300° C. or less, which shows heat resistance and heat stability of the composition was inferior to those of the compositions of Examples. This composition system imitated the same system as in a conventionally used resin composition for a neutron shielding material. The composition of Comparative Example 1 was suitable in terms of hydrogen content, but had low heat resistance and heat stability as compared with those of the compositions of Examples. It was indicated that the compositions of Examples had excellent heat resistance and heat stability. Sufficiently stirred were 81.4 g of a bisphenol A epoxy resin (Epicoat 828 (structural formula (6), wherein R9 to R12 each represents a methyl group, and n is from 0 to 2)) as an epoxy resin and 18.6 g of isophoronediamine as a curing agent to prepare a resin composition used for a neutron shielding material. No density-increasing agent was added. As a result of measuring the hydrogen content in the resin composition, the hydrogen content was 8.2 wt % or less which was considerably below the standard, unsatisfactorily. The resin composition for a neutron shielding material was cured at 80° C. for 30 minutes and at 150° C. for 2 hours to measure the weight reduction by heat. As a result, the residual weight percentage at 200° C. was about 99.5 wt %, and the temperature at a residual weight percentage of 90 wt % was about 350° C., which shows good heat resistance and heat stability of the composition. This composition system had good heat resistance and heat stability, but had hydrogen content lower than those of the compositions of Examples, and thus was not suitable as a resin composition for a neutron shielding material. A hydrogenated bisphenol A epoxy resin (YL6663 (structural formula (1))) as an epoxy resin was mixed with a polyamine curing agent at a mixing ratio of 1:1 (stoichiometrically equivalent), and the mixture was stirred to prepare a resin composition used for a neutron shielding material. The polyamine curing agent lacked a rigid structure with high stability, unlike the curing agent used in the composition of the present invention, and was contained in the resin composition at a high percentage. No density-increasing agent was added. As a result of measuring the hydrogen content in the resin composition, the hydrogen content was 9.8 wt % or more (about 10 wt % or more) which was above the standard satisfactorily. The resin composition for a neutron shielding material was cured at 80° C. for 30 minutes and at 150° C. for 2 hours to measure the weight reduction by heat. As a result, the residual weight percentage at 200° C. was 99.0 wt % or less, and the temperature at a residual weight percentage of 90 wt % was 280° C. or less, which shows that heat resistance and heat stability of the composition is inferior to those of the compositions of Examples. Sufficiently stirred were 81.7 g of an epoxy resin having a structure in which OH at each end of polypropylene glycol was substituted with glycidyl ether (epoxy equivalent: 190) and 18.3 g of isophoronediamine as a curing agent to prepare a resin composition used for a neutron shielding material. The epoxy resin used herein did not have a rigid structure, unlike the epoxy component of the present invention. No density-increasing agent was added. As a result of measuring the hydrogen content in the resin composition, the hydrogen content was 9.8 wt % or more which satisfied the standard. The resin composition for a neutron shielding material was cured at 80° C. for 30 minutes and at 150° C. for 2 hours to measure the weight reduction by heat. As a result, the residual weight percentage at 200° C. was 99.5 wt % or less, and the temperature at a residual weight percentage of 90 wt % was less than about 250° C., which shows heat resistance and heat stability of the composition is extremely inferior to those of the compositions of Examples. Sufficiently stirred were 78.5 g of 1,6-hexane diglycidyl ether (epoxy equivalent: 155) as an epoxy resin and 21.5 g of isophoronediamine as a curing agent to prepare a resin composition used for a neutron shielding material. No density-increasing agent was added. As a result of measuring the hydrogen content in the resin composition, the hydrogen content was 9.8 wt % or more which satisfied the standard. The resin composition for a neutron shielding material was cured at 80° C. for 30 minutes and at 150° C. for 2 hours to measure the weight reduction by heat. As a result, the residual weight percentage at 200° C. was 99.5 wt % or less, and the temperature at a residual weight percentage of 90 wt % was less than 300° C., which shows heat resistance and heat stability of the composition is inferior to those of the compositions of Examples. Here, the neutron shielding effect of a composition made of an epoxy component and a polyamine curing agent with a refractory material and a neutron absorbent further added was evaluated. 50 g of a bisphenol A epoxy resin (Epicoat 828 (structural formula (6), wherein R9 to R12 each represents a methyl group, and n is from 0 to 2)) as an epoxy resin was mixed with 50 g of a polyamine curing agent (so that the components were stoichiometrically equal), and the mixture was stirred. 146.5 g of magnesium hydroxide and 3.5 g of boron carbide were mixed therewith, and the mixture was stirred to prepare a resin composition used for a neutron shielding material. No density-increasing agent was added. The reference hydrogen content required for a neutron shielding material is a hydrogen content density of 0.096 g/cm3 or more. The hydrogen content density of the prepared neutron shielding material composition was measured to be 0.096 g/cm3 or more, which satisfied the standard. The resin composition for a neutron shielding material was cured at 80° C. for 30 minutes and at 150° C. for 2 hours to measure the weight reduction by heat. As a result, the residual weight percentage at 200° C. was 99 wt % or less, and the temperature at a residual weight percentage of 90 wt % was 300° C. or less, which shows that heat resistance and heat stability of the composition is inferior to those of the compositions of Examples. The cured product was enclosed in a closed vessel, and a thermal endurance test was carried out at 190° C. for 1,000 hours. The compressive strength was decreased by 30% or more as compared with that before the test, which shows that the composition has low durability under a high-temperature environment. This composition system imitated the same system as in a currently used neutron shielding material composition. The composition of Comparative Example 6 was suitable in terms of the hydrogen content, but had heat resistance and heat stability lower than those of the composition of Example 12, which shows that the composition of Example 12 exhibits excellent heat stability and heat resistance. Since the neutron shielding material of the present invention employs an epoxy component and a curing agent with improved heat resistance, the material has good heat resistance and can endure long-term storage of spent nuclear fuels. In addition, the material has ensured neutron shielding capability. Further, since the composition of the present invention comprises a density-increasing agent, the neutron shielding material can provide an increased neutron dosage while maintaining secondary γ-ray shielding performance, and accordingly can have improved neutron shielding performance without placing a structure for shielding γ-rays outside the main body of the neutron shielding material as in a conventional manner. |
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claims | 1. A device for preparing radioactive solutions, in particular radiopharmaceutical solutions, comprising:a movable support block comprising at least two cells capable of accommodating a vial;a shielded covering, comprising a side wall surrounding the periphery of the support block and an upper wall covering the upper face of the support block, an opening being provided in the upper wall of the covering;a means for driving the support block configured to selectively displace the support block into positions, referred to as working positions, in which a given cell is aligned with the opening to allow access to said cell from the outside of the covering;a syringe carrier associated with a syringe actuating means configured to displace a syringe substantially vertically in the axis of the opening and to actuate a plunger of said syringe; andwherein the support block is configured such that it can be further brought to a position, referred to as closing position, in which the opening is sealed by a shielded element carried by the support block. 2. The device according to claim 1, wherein the shielded element carried by the support block is integral with the support block or attached therein. 3. The device according to claim 2, wherein said shielded element is a lead element, for example a disc, placed in a housing opening into an upper face of the movable support block. 4. The device according to claim 1, wherein the movable support block is a rotatably mounted cylindrical barrel, and wherein the cells open into the upper face of the barrel. 5. The device according to claim 1, wherein the cells capable of accommodating vials are cylindrical cells inclined relative to the vertical. 6. The device according to claim 1, wherein one or more of said cell(s) comprise(s):a temperature sensor; and/ora precision balance at the bottom of the cell; and/ora disinfection device comprising UV lamps, around the inlet of the cell. 7. The device according to claim 1, comprising means for detecting the angular position of the movable support block. 8. The device according to claim 1, wherein heating and/or cooling means are associated with at least one of said cells. 9. The device according to claim 8, wherein a cell is made as an insert mounted in a hollow portion of the support block, the heating and/or cooling means comprising a heater resistor mounted on a jacket disposed in a cell, as well as a fan mounted in the support block and ventilation openings in the side wall of the support block. 10. The device according to claim 1, wherein the syringe actuating means comprises:a first mobile member to which the syringe carrier is secured, the syringe carrier ensuring holding the syringe body; anda second mobile member with means for coupling to the syringe plunger;the syringe actuating means being configured to, either simultaneously displace the first and second mobile members, or to perform a displacement of the second mobile member relative to the first mobile member. 11. The device according to claim 10, whereintranslation means are mounted on the first mobile member in order to displace the syringe carrier laterally relative to the support block; and/orthe syringe carrier is associated with a support and comprises means to displace the syringe carrier downwardly relative to the support thereof. 12. The device according to claim 1, wherein the shielded covering and the shielded element carried by the support block are made of an anti-radiation material. 13. The device according to claim 12, wherein said anti-radiation material is lead or lead-based material. 14. The device according to claim 4, wherein said cylindrical barrel is rotatable about a substantially vertical central axis. 15. The device according to claim 7, wherein said means for detecting the angular position of the movable support block are optical detection means. |
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abstract | A well logging tool includes a neutron generator having an ion source for ion production by electron impact ionization wherein ionization current trajectory is determined by an electric field and an at least partially misaligned magnetic field. The electric field can be provided by an electrode arrangement having a cathode associated with a field emitter array including a multitude of nanoemitters. The magnetic field can be provided by a permanent magnet incorporated in the neutron generator to act transversely to the electric field in at least part of an ion source chamber in which an ionization current emitted by the field emitter array travels through an ionizable gas. Charged particles traveling through the ionizable gas thus follow respective trajectories that are longer than would be the case in the absence of the magnetic field, thereby increasing ionization probability. |
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abstract | Disclosed embodiments include nuclear fission reactors, nuclear fission fuel pins, methods of operating a nuclear fission reactor, methods of fueling a nuclear fission reactor, and methods of fabricating a nuclear fission fuel pin. |
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048779695 | summary | The present invention concerns a flask for the transport of radioactive material. BACKGROUND OF THE INVENTION A flask for the transport of high level vitrified radioactive waste operates dry under all conditions. The waste is contained in sealed containers which are housed within the flask and it is necessary to provide for thermal transfer between the containers and the flask wall in order to dissipate the heat generated by radioactive decay of the waste. It is known to provide a monolithic support structure within the flask to receive the sealed containers. Heat transfer from the waste through the support structure and into the flask wall is determined by the degree of thermal contact between the components. Due to the size and complexity of a monolithic support structure, good thermal contact is often difficult to achieve and distortion of the structure during use can make subsequent withdrawal from the flask a difficult operation. FEATURES AND ASPECTS OF THE INVENTION According to the present invention, a flask for the transport of radioactive material comprises a hollow cylindrical body, a plurality of substantially identical individual elongate members releasably secured within the body to define longitudinally extending channels to receive and accommodate containers for radioactive material, each member having concave longitudinally extending side surfaces which each form only a portion of a channel, another portion of which is formed by a side surface of an adjacent one of the members, and each member having a radially outer surface curved to conform to the curvature of the interior of the hollow cylindrical body whereby to maximize thermal contact therebetween for dissipation of heat generated by decay of the radioactive material. Preferably a radially inner surface of each member defines a portion only of a central channel in the hollow body and cooperates with radially inner surfaces of the other members to define a complete central channel. A stepped longitudinally extending groove may be formed in the radially outer surface of each member, and shaped keys fixedly secured to the inner wall of the hollow body may be provided to cooperate with the stepped grooves such that the keys slidably receive the stepped grooves. A clamping bar may cooperate with the keys to releasably secure the member to the wall of the hollow body. The keys may extend the length of the hollow body. Preferably each member is individually releasably secured to the body and is individually insertable into and removable from the body. |
description | FIGS. 1 and 2 show respective end views of honeycomb-filter structures for limiting the dynamic range of an X-ray image formed by an X-ray detector by exposure of an object, such as a patient to be examined, to X-rays. The hexagonal cells are formed of capillary tubes, the one ends of which communicate with a reservoir containing an X-ray absorbing liquid. The adhesion of X-ray absorbing liquid to the inner sides of the capillary tubes can be adjusted by means of electrical voltages applied to the respective electrically conductive layers provided on the inner sides of the capillary tubes. In accord with the invention groups of adjacent tubes are in mono-cyclic fashion energized in a way such that in the region of interest or ROI the object to be examined is exposed to X-ray radiation transmitted through the successive groups of filter elements energized in a way such that the X-ray absorbing liquid is during exposure temporarily removed from the capillary tubes in question. FIG. 1 indicates with the respective numerals 1, 2, 3 and 4 the single cycle of energizing the respective capillary tubes. In this case the cycle consists of four phases, viz. the energization of the groups indicated with 1, 2, 3 and 4, successively. FIG. 2 shows an alternative, in which the successive phases of the cycle are indicated with seven different hatchings instead of the numerals used in FIG. 1, clearly showing that each full exposure cycle consists of seven phases. In analogy to the prior art technique of continuous slit scanning with a moving narrow slit the discrete spot scanning apparatus according to the invention can be used to generate one or more fan-like X-ray beams. The advantage of scatter reduction achieved in this way can be enhanced by generating a moving spot pattern on basis of the principles of the present invention. A scatter component is further reduced while the total surface of the exposing spots comprised of a plurality of filter elements can be equally large as the total surface of the slit pattern of a prior art slit scanning device. Spot transmission times can be adapted individually such that the dynamic range of the absorbed signal is reduced thus resulting in a better deployment of the X-ray detector""s dynamic range and a considerable reduction of the X-ray dose to which the object is exposed. Specifically in the case of medical application this is important in view of the desired limitation of the dose to which a patient is exposed. The adjustment of one phase of the sequence of the dynamic beam attenuator takes about 200 ms. The exposure time takes about 10-100 ms. In case of a number of phases of four in accord with the FIG. 1 embodiment the entire exposure time will be a maximum of (3xc3x97200)+4xc3x97100)=1000 ms or 1 s. This result shows that even in the worst case exposure time of 100 ms the purpose of the invention to make a picture within a time period of about 1 s is realized. |
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06078640& | abstract | An exposure method and apparatus for lithographically transferring a pattern of a mask onto a substrate to be exposed, wherein a detecting system detects a relative positional relation between the mask and the substrate with respect to at least a predetermined direction, a stage member changes the relative positional relation between the mask and the substrate, on the basis of the detection by the detecting system, a magnification correcting mechanism corrects a transfer magnification of the mask pattern to the substrate, a control system for the stage member corrects one of a drive amount of the stage member and a detection result of the detecting system in accordance with a positional deviation of the mask pattern attributable to the correction operation of the magnification correcting mechanism. |
claims | 1. A nuclear reactor scram control system, comprising:a scram solenoid pilot valve (SSPV) including a plurality of SSPV solenoids and a plurality of power terminals, the plurality of power terminals configured to be coupled to separate power supplies, the plurality of SSPV solenoids electrically coupled to separate, respective power terminals of the plurality of power terminals, each SSPV solenoid of the plurality of SSPV solenoids configured to be energized or de-energized based on whether electrical power is supplied from an electrically coupled power terminal of the plurality of power terminals to the SSPV solenoid, the SSPV configured to actuate to permit a working fluid to pass through the SSPV to cause a control rod to be inserted into a nuclear reactor core based at least in part upon whether the plurality of SSPV solenoids are commonly energized or de-energized; anda plurality of solenoid indicator lights mounted directly to a housing of the SSPV, the plurality of solenoid indicator lights electrically coupled to separate, respective SSPV solenoids of the plurality of SSPV solenoids and the separate, respective power terminals electrically coupled to the separate, respective SSPV solenoids, such that each separate solenoid indicator light of the plurality of solenoid indicator lights is configured to selectively activate based on whether electrical power is supplied from a separate, coupled power terminal of the plurality of power terminals to a separate, coupled SSPV solenoid of the plurality of SSPV solenoids. 2. The nuclear reactor scram control system of claim 1, the SSPV further includinga direct current rectifier coupled in series with the SSPV solenoid of the plurality of SSPV solenoids to one power terminal of the plurality of power terminals that is electrically coupled to one SSPV solenoid, the direct current rectifier configured to convert AC electrical power received from one power terminal to direct current (DC) electrical power and supply the DC electrical power to the SSPV solenoid. 3. The nuclear reactor scram control system of claim 2, whereinthe SSPV includes an instance of circuitry electrically coupled to the SSPV solenoid of the plurality of SSPV solenoids, andthe nuclear reactor scram control system further includes at least one circuit indicator light mounted directly to the housing of the SSPV and electrically coupled to the instance of circuitry, the at least one circuit indicator light configured to selectively activate based at least in part upon a fault state of the instance of circuitry. 4. The nuclear reactor scram control system of claim 3, wherein the instance of circuitry includes an instance of voltage reduction circuitry, the instance of voltage reduction circuitry configured to reduce a voltage of DC electrical power supplied to the SSPV solenoid. 5. The nuclear reactor scram control system of claim 1, wherein each solenoid indicator light of the plurality of solenoid indicator lights includes at least one light emitting diode (LED). 6. A method, comprising:configuring a scram solenoid pilot valve (SSPV) including a plurality of SSPV solenoids to provide a visible indication of an energization state of SSPV solenoid of the plurality of SSPV solenoids of the SSPV, the SSPV including a plurality of power terminals, the plurality of power terminals configured to be coupled to a separate power supplies, the plurality of SSPV solenoids electrically coupled to separate, respective power terminals of the plurality of power terminals, each SSPV solenoid of the plurality of SSPV solenoids configured to be energized or de-energized based on whether electrical power is supplied from an electrically coupled power terminal of the plurality of power terminals to the SSPV solenoid, the SSPV configured to actuate to permit a working fluid to pass through the SSPV to cause a control rod to be inserted into a nuclear reactor core based at least in part upon whether the plurality of SSPV solenoids are commonly energized or de-energized, the configuring including,mounting a plurality of solenoid indicator lights directly to a housing of the SSPV and electrically coupling the plurality of solenoid indicator lights to separate, respective SSPV solenoids of the plurality of SSPV solenoids and the separate, respective power terminals electrically coupled to the separate, respective SSPV solenoids, such that each separate solenoid indicator light of the plurality of solenoid indicator lights is configured to selectively activate based on whether electrical power is supplied from a separate, coupled power terminal of the plurality of power terminals to a separate, coupled SSPV solenoid of the plurality of SSPV solenoids. 7. The method of claim 6, further comprising:electrically coupling a direct current (DC) rectifier in series with the SSPV solenoid of the plurality of SSPV solenoids to one power terminal of the plurality of power terminals that is electrically coupled to the one SSPV solenoid, to configure one SSPV solenoid to be energized via DC electrical power. 8. The method of claim 7, wherein,the SSPV includes an instance of circuitry electrically coupled to the SSPV solenoid of the plurality of SSPV solenoids; andthe method includes configuring the SSPV to provide a visible indication of a fault state of the instance of circuitry, the configuring including mounting at least one circuit indicator light directly to the housing of the SSPV and electrically coupling the at least one circuit indicator light to the instance of circuitry, such that the at least one circuit indicator light is configured to selectively activate based at least in part upon the fault state of the instance of circuitry. 9. The method of claim 8, wherein the instance of circuitry includes an instance of voltage reduction circuitry, the instance of voltage reduction circuitry configured to reduce a voltage of DC electrical power supplied to the SSPV solenoid. 10. The method of claim 6, wherein each solenoid indicator light of the plurality of solenoid indicator lights includes a light emitting diode (LED). 11. A method for operating a scram solenoid pilot valve (SSPV), the method comprising:electrically coupling a plurality of SSPV solenoids included in the SSPV to a separate, respective power supplies of a plurality of power supplies via separate, respective power terminals of a plurality of power terminals, such that the each SSPV solenoid of the plurality of SSPV solenoids is configured to be energized or de-energized based on whether electrical power is supplied from an electrically coupled power supply of the plurality of power supplies to the SSPV solenoid via an electrically coupled power terminal of the plurality of power terminals, the SSPV is configured to actuate to permit a working fluid to pass through the SSPV to cause a control rod to be inserted into a nuclear reactor core based at least in part upon whether the plurality of SSPV solenoids are commonly energized or de-energized; andselectively activating a solenoid indicator light of a plurality of solenoid indicator lights mounted directly to a housing of the SSPV and electrically coupled to separate, respective SSPV solenoids and separate, respective power terminals of the plurality of power terminals that are electrically coupled to the separate, respective SSPV solenoids, the selectively activating is based on whether the electrical power is supplied from a power supply of the plurality of power supplies to a SSPV solenoid of the plurality of SSPV solenoids that is electrically coupled to the solenoid indicator light. 12. The method of claim 11, wherein,each solenoid indicator light of the plurality of solenoid indicator lights is electrically coupled in parallel with the separate SSPV solenoids of the plurality of SSPV solenoids to separate power terminals of the plurality of power terminals; andthe selectively activating the solenoid indicator light includes deactivating the solenoid indicator light in response to the SSPV solenoid becoming de-energized. 13. The method of claim 11, wherein,the SSPV includes an instance of circuitry electrically coupled to one SSPV solenoid of the plurality of SSPV solenoids; andthe method includes selectively activating a circuit indicator light electrically coupled to the instance of circuitry based on a fault state of the instance of circuitry. 14. The method of claim 13, wherein the instance of circuitry includes an instance of voltage reduction circuitry, the instance of voltage reduction circuitry configured to reduce a voltage of DC electrical power supplied to the SSPV solenoid. 15. The method of claim 11, wherein each solenoid indicator light of the plurality of solenoid indicator lights includes a light emitting diode (LED). |
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052971767 | abstract | The guide pin aligning a top nozzle of a nuclear fuel assembly to an upper core plate of a nuclear reactor, is replaced working exclusively from below the upper core plate. The replacement guide pin has a shaft portion engaged with the upper core plate and the clamping nut which held the original guide pin, by threadable connection and/or by an expansion fitting. A shoulder on the pin bears against a lower surface of the upper core plate, and a nose of the pin is received in the top nozzle of the fuel assembly. A preferred expansion fitting has a bushing with ridges on its outer surface and a conical inside surface, and is inserted into the bored out original guide pin shaft. A threaded conical plug is pulled axially with rotation of the replacement pin shaft to expand the bushing. The ridges rigidly lock the replacement pin between the shoulder and the clamping nut. By attaching the replacement pin to the stub of the original pin, the invention utilizes existing attachments of the original pin to the upper core plate. |
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abstract | A padded garment having at least one pocket with at least one pad located within the at least one pocket. The at least one pad has a plurality of interconnected, spaced apart tubes. A first end of each of the spaced apart tubes are interconnected along a first pathway and a second end of each of the spaced apart tubes are interconnected along a second pathway. The first and second pathways are recessed from a top plane and a bottom plane of the pad in areas between adjacent tubes such that the pad is flexible along the recessed areas of the first and second pathways and substantially less flexible along a length of the spaced apart tubes. The pad is shaped to correspond to an area of a wearer's body it is intended to cover. |
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abstract | A fuel element has a ratio of area of fissionable nuclear fuel in a cross-section of the tubular fuel element perpendicular to the longitudinal axis to total area of the interior volume in the cross-section of the tubular fuel element that varies with position along the longitudinal axis. The ratio can vary with position along the longitudinal axis between a minimum of 0.30 and a maximum of 1.0. Increasing the ratio above and below the peak burn-up location associated with conventional systems reduces the peak burn-up and flattens and shifts the burn-up distribution, which is preferably Gaussian. The longitudinal variation can be implemented in fuel assemblies using fuel bodies, such as pellets, rods or annuli, or fuel in the form of metal sponge and meaningfully increases efficiency of fuel utilization. |
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054897351 | description | DETAILED DESCRIPTION OF THE INVENTION The present invention will now be described more fully hereinafter. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiment set forth herein; rather, this embodiment is provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. As summarized above, the decontamination composition comprises 40 to 60 percent of a compound selected from the group consisting of oxalic acid, alkali metal and ammonium salts of oxalic acid and mixtures thereof; 5 to 20 percent of a compound selected from the group consisting of citric acid, alkali metal and ammonium salts of citric acid and mixtures thereof; 20 to 40 percent of a compound selected from the group consisting of polyaminocarboxylic acid, alkali metal and ammonium salts of polyaminocarboxylic acid and the combination of a polyaminocarboxylic acid and a neutralizing compound, and mixtures thereof; 0 to 2 percent of a nonionic surfactant; 0 to 2 percent of a dispersant; and 0 to 2 percent of a corrosion inhibitor. The alkali metal and ammonium salts of the oxalic and citric acid can include mono- and disubstituted salts. A particularly preferred salt of oxalic acid is ammonium oxalate. A particularly preferred salt of citric acid is ammonium citrate. Suitable polyaminocarboxylic acids include ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, triethylenetetraamine hexaacetic acid, N-2-hydroxyethylethylenediaminetriacetic acid, propylene1,2-diaminetetraacetic acid, propylene-1,3-diaminetetraacetic acid, nitrilotriacetic acid, the ammonium and alkali metal salts of said acids, and the combination of the polyaminocarboxylic acids with neutralizing compound, and mixtures thereof. The alkali metal and ammonium salts can include mono- and disubstituted salts. A particularly preferred salt of polyaminocarboxylic acid is diammonium ethylenediaminetetraacetic acid. A suitable neutralizing compound is hydrazine. Suitable nonionic surfactants include Triton X-100, an octylphenoxy-polyethoxyethanol with 9 to 10 moles of ethylene oxide surfactant, available from Union Carbide, Danbury, Conn., and Pluronic L-101, a polyoxyethylene-polyoxypropylene block polymer surfactant, available from BASF-Wyandotte, Wyandotte, Mich. A suitable dispersant for organic solids is Tamol SN, a sodium salt napthalenesulfonic acid, available from Rohm & Haas, Philadelphia, Pa. A suitable dispersant for inorganic solids is sodium lignosulfonate. A suitable corrosion inhibitor is Rodine 95, which includes thiourea, formaldehyde, o-toluidine and substituted triazine hydrochloric acid, available from Parker+Amchem, Madison Heights, Mich. In operation, a surface (i.e., a metal surface) contaminated with NORM is contacted with the above-described decontamination compound. The contacting can be conducted at a temperature of about 20.degree. to 150.degree. C., and preferably is conducted at about 80.degree. to 100.degree. C. Agitation in any form (e.g., mechanical or ultrasonic) will increase the rate of removal. The foregoing example is illustrative of the present invention, and is not to be construed as limiting thereof. EXAMPLE The following decontamination composition is blended together: ______________________________________ Component Percent by Weight ______________________________________ Ammonium Oxalate 54.52 Diammonium EDTA 32.72 Ammonium Citrate 11.45 Triton X-100 0.13 Pluronic L-101 0.13 Tamol SN 1.00 Rodine 95 0.05 ______________________________________ A sample S to be decontaminated is a perforated steel plate from an oil refinery distillation tower contaminated with NORMs. The sample is immersed in a bath of the decontamination composition and agitated. The bath temperature is about 95.degree. C. The sample is rinsed in a solution of ESI 635.TM. available from Environmental Scientific, Inc., Research Triangle Park, N.C., to disperse loose particulate. The activity on the sample is measured using a Ludlum Model 2 survey meter available from Ludlum Measurement, Inc., Sweetwater, Tex., with a Model 44-9 pancake probe, and is mapped at several locations designated as A through H which appear to give the highest reading (see FIG. 1). Corresponding measurement are taken at one hour intervals. Referring to FIG. 2 and Table 1, the activity decreases rapidly in the first hour and gradually approaches zero. At three hours, the activity level is only about 18 percent of the initial level. TABLE 1 ______________________________________ cpm vs. time in hours Location 0 1 hr 2 hrs 3 hrs ______________________________________ A 4000 1150 900 B 4000 1200 900 800 C 3500 750 690 D 3000 690 450 E 3000 700 500 F 2800 850 425 G 3000 600 H 2300 400 ______________________________________ In the specification and example, there have been disclosed preferred embodiments of the invention. Although specific terms are employed, they are used in a generic and descriptive sense only and not for the purpose of limitation, the scope of the invention being defined by the following claims. |
040385531 | claims | 1. A radiation shielding apparatus comprising a pair of U-shaped tracks, a first element having a U-shaped cross-section and a pair of inwardly turned flanges fixedly secured to the free longitudinal edges thereof, a second element having a U-shaped cross-section and a pair of arms extending the length of the legs of said U-shaped cross-section, said pair of arms fixedly secured to said legs adjacent one end of said second element, means to removably fasten said pair of arms to portions of said first element adjacent one end thereof, means to clampingly secure lead sheeting between said first element and said second element, means to confine said one end of said first element and said one end of said second element within one of said pair of U-shaped tracks, means to confine the other end of said first element and the other end of said second element within the other of said pair of U-shaped tracks. 2. The radiation shielding apparatus as claimed in claim 1 further comprising means to dispose an exterior surface of said second element in a plane, said plane defined by an exterior surface of each of said pair of U-shaped tracks. 3. The radiation shielding apparatus as claimed in claim 1 further comprising a wooden stud disposed along the length and confined within said U-shaped cross-section and said pair of inwardly turned flanges of said first element. 4. The radiation shielding apparatus as claimed in claim 2 further comprising a wallboard fixedly secured to said second element at a surface thereof being disposed at said plane. 5. The radiation shielding apparatus as claimed in claim 1 wherein said second element comprises a non-metallic resin impregnated fibrous material. 6. The radiation shielding apparatus as claimed in claim 1 wherein said fastening means comprises at least one hole in one of said pair of arms, a bolt, a threaded opening disposed adjacent one of said pair of inwardly turned flanges at said one end of said first element, said bolt being disposed passing through said one hole and threadingly engaging said threaded opening. |
description | This application is a continuation of U.S. application Ser. No. 15/524,044, filed May 3, 2017, now U.S. Pat. No. 10,667,777, which is a National Stage Application of International Application No. PCT/US2015/059530, filed Nov. 6, 2015. This application claims priority from U.S. application Ser. No. 15/524,044, International Application No. PCT/US2015/059530, and U.S. Provisional Patent Application Ser. No. 62/076,340, filed Nov. 6, 2014. Each of these applications is hereby incorporated by reference in its entirety. The present invention in general relates to the field of imaging and in particular to an improved system and method for providing X-ray radiographs with quantitative and standardized levels for bone and other tissue density evaluations. Bone density is an important measure of bone health, and in some cases, systemic health of a subject. Low bone density has been identified as a risk factor for fractures (especially long, spinal vertebrae and pelvic bones), degenerative joint disease (arthritis), pain, decreased activity levels, certain disease states (bone cancers, select endocrine diseases, obesity, etc.), medications that result in bone loss, dental disease (due in part to loosened teeth) and even as a measure of welfare. Bone density disorders are recognized in both humans and non-human animals. By identifying poor bone density, clinicians have the opportunity to recognize and diagnose certain diseases earlier (as opposed to waiting for more overt disease to develop) and develop risk assessment protocols and hopefully preventative measures. In addition, other tissue densities may also show promise for disease identification and serve as prognostic markers of certain diseases. This includes identifying the density of foreign materials that may have an impact on health. For example, by quantifying the density of ingested metals clinicians may be able to determine if conservative therapy results in successful dissolution of the item (by measuring decreasing density over a set period of time). Additionally, non-bone tissues that are more or less radiodense than “normal” may indicate a disease process is present. As an example, hyperadrenocorticism, certain kidney disorders and select toxins can increase mineralization in soft tissues. Furthermore, low bone density also correlates with poor diet, lack of exercise, and lack of natural light exposure (especially for diurnal species), and may be compared to “normal” to better determine welfare of animals kept in captivity. The ultimate goal would be to improve conditions for captive animals by improving nutrition, activity level and natural UV light exposure, especially for those animals that have restricted access to natural light, sufficient room to ambulate, and/or are on a poor diet. Bone density has been studied in laboratory animals and in poultry species, where low bone density has been found to be a common problem in captive production birds. Advanced cases may easily be recognized by strikingly poor bone density and sometimes folding type fractures on standard radiographs, as shown in the example in FIG. 1. However, studies in other animals are critically lacking primarily due to the cost of diagnostic equipment. As a result, large scale studies that correlate bone/tissue density with health and disease states are not possible without substantial funding. Advances in medical imaging technology have allowed noninvasive visualization and measurements of a wide variety of anatomy and functions of the body. Radiodensity or radiopacity refers to the relative inability of electromagnetic radiation, particularly X-rays, to pass through a particular material. Radiolucency indicates greater transparency or “transradiancy” to X-ray photons. Materials that inhibit the passage of electromagnetic radiation are called radiodense, while those that allow radiation to pass more freely are referred to as radiolucent. The term refers to the relatively opaque white appearance of dense materials or substances on radiographic imaging studies, compared with the relatively darker appearance of less dense materials. Because calcified tissues such as bone are radio-opaque, X-ray based imaging including projection radiography (or X-ray radiography) and computed tomography (CT) are the most commonly used modalities for assessing bone morphology. Although X-ray radiography offers the highest spatial resolution useful for detecting, for example, hairline fracture in a bone, due to the lack of calibration and the physics of image formation, X-ray radiography intensities are generally only qualitative in nature. Due to its qualitative nature, X-ray radiographs give clinicians only subjective, relative evaluation of tissue density. As a result, standard radiographs, which are common in private practice, cannot be used to provide scientifically meaningful data on bone/tissue density. In contrast, CT intensities are both quantitative and standardized across all scanners, and are the best (in terms of speed and resolution) for visualizing the skeletal system and some soft tissue structures. There are several reasons why existing X-ray radiography is not suited for quantitative intensity-based evaluations. Most X-ray radiography and CT instruments employ a “point source” for generating the X-ray. As the generated X-ray radiates away from the source, the intensity of the X-ray decreases as the inverse-square of the distance. Moreover, as the X-ray arrives at the detector, which is normally flat, unless the incident angle is perpendicular to the detector, the intensity of the X-ray is further diminished as the X-ray beam is spread across a bigger area. Combined, even when the point source is aimed directly and squarely at the detector, the “source-detector geometry” imposes an inherent variability on X-ray intensity across the detector. Whether a conventional film or digital detector is used, spontaneous processes in the detector (e.g., intrinsic electronic charges in the digital detector) contributes to baseline intensity in the X-ray image even when the source is completely turned off. Due to the properties of exposure-to-intensity conversion, the conversion might not be linear (i.e., doubling the exposure may not result in doubled brightness on the image). In addition to the baseline and nonlinear responses, all detectors have finite response “dynamic range.” Unless the exposure is optimized to the range, under-exposure can lead to patches of uniformly dense regions (regardless of variability of the underlying anatomy), whereas over-exposure can lead to apparent disappearance of low-density regions. In computed tomography (CT), all of the above issues with X-ray radiography are effectively addressed by the so-called “dark-light calibration” and “exposure optimization” procedures that are performed as part of the CT acquisition. The dark-light calibration essentially involves obtaining scans with and without the source turned on, and subtracts the obtained values from all subsequent acquisitions. Exposure optimization involves an iterative process of scans and intensity analysis to find the exposure setting that is just below the upper detector dynamic range. Separately, all CT-obtained intensities are standardized by normalizing the intensities to those for air and water, such that air and water will have exactly 1000 and 0 “Hounsfield Units,” respectively, in all scanners. Even though CT provides the best speed and resolution for visualizing the skeletal system, the cost of CT scans is prohibitive and the limited availability of CT equipment makes its wide usage impractical in most veterinary and human point-of-care practices. Thus, there exists a need for improved systems and methods that provide skeletal visualizations that are comparable to CT scans but at a lower cost and with lower dosimetry. A method for radiographic tissue density evaluation is provided that includes capturing a radiographic image of a material with an X-ray image collection cassette. The cassette includes components (either built in or attached to the cassette) that allow for performing intensity standardization of the captured radiographic image. A spatial homogenous backing alone, at least one calibration bar, or a combination thereof serve as a reference for such standardization through background subtraction and known absorption, respectively. The radiographic image is analyzed to determine spatially resolved tissue/subject density in the biological or non-biologic material. The biological material can be a biopsy, a microorganism, an organ, organelle, or a living subject such as a human or an animal, or a cadaver. The non-biologic subject can be any device, structure or other item not composed of biologic material. A system for performing the method is also provided that includes a standard or specialized X-ray image recordation cassette and software for radiographic image analysis. The present invention has utility as a method and system to make X-ray radiographs sufficiently quantitative and standardized for bone, other tissue and non-biologic subject density evaluations. Embodiments of the inventive X-ray radiograph methodology and system provide a cost effective diagnostic tool that may be used in daily practice with existing X-ray radiography equipment already present in many clinics and hospitals to ultimately produce large volumes of scientifically valid data and useful diagnostic and prognostic information. Embodiments of the inventive radiograph based bone, tissue, non-biologic subject density determination system are designed to visually and numerically identify bone and other densities using digital radiographs. The values generated are based on a universal scale, different from Hounsfield units, that can be standardized from radiograph to radiograph and across machines assuming proper radiograph positioning and technique (for the subject in question) is used and radiographic equipment is functioning properly. The inventive system may be used as a low cost alternative to more expensive density imaging methods such as computerized tomography (CT) and Dual-energy X-ray absorptiometry (or DEXA) scans. Embodiments of the invention may be used in any situation where radiographs are taken—standard limb or whole body images, dental, clinical patient, research—and on potentially any animal including humans. Embodiments of the inventive X-ray radiograph methodology and system may also potentially be used on plants, minerals, metals, manmade materials and any other naturally occurring or foreign substance, industrial equipment, and other objects and structures, serving as an inexpensive way of collecting density information, with radiation dosing that is less than that of CT scanning. Materials suitable for density interrogation according to the present invention illustratively include a whole multicellular organism, a microbe, a virus, or parts of an organism (as in a specific organ, organelle, or tissue), or non-biological materials such as castings. The applications include obvious health data, but could be used as a screening tool for density variations in just about any material or object. A living human or animal or cadaver of the same are exemplary materials in a clinical setting. To form the inventive Radiograph Density Detection Device (RDDD) (hereinafter referred to as a radiographic device, or simply the device) a component may be added to a conventional X-ray film cassette (internally as a part of the cassette or peripherally attached to the cassette) and subsequently incorporated into radiographs for interpretation. The incorporated device acts as a standard against which animal, human, non-biological, and other tissue densities can be measured. An inventive software based program is provided to interpret tissue densities (including bone) to ultimately identify low, normal, or high values compared to “normal” densities. Densities created by the software may be presented in a variety of forms illustratively including density associated colors and absolute numerical values and can give local regional and whole subject values. In some inventive embodiments, orthogonal views of the same material can be used to by the software to mathematically generate volumetric color and numerical values for the material. The inventive device provides the diagnostician real data as to the density of normal and foreign body tissues to aid in disease diagnosis and prediction of health of a subject either human or animal. Non-biologic material densities can also be rapidly studied as with biologic materials to, for example, identify internal porosity or voids in a casting. Embodiments of the inventive device and method provide a low cost and relatively accurate (within an acceptable tolerance or error) alternative to CT or other more expensive and generally unavailable diagnostic tests that evaluate bone and other tissue densities in patients, with generally lower radiation exposure. Embodiments of the device may be used on digital radiograph machines which are now commonplace in human and animal medical facilities with embodiments of the inventive software to convert the images obtained into tissue density scores. Embodiments of the invention require minimal modification or additional procedure to the effort involved in taking a conventional X-ray radiography. It is appreciated that an X-ray microscope is also used to obtain density information regarding materials smaller than a few millimeters. The following are non-limiting illustrative examples of specific types of disorders where evaluation using the above RDDD system may improve diagnosis and potentially treatment: Soft tissues: muscle contraction; myositis ossificans; vascular diseases (mineralization, atherosclerosis); tenosynovitis; tendon avulsion; inflammation (traumatic, parasitic, fungal, bacterial, neoplastic, autoimmune, toxins, thermal burns, freezing injury, idiopathic, nosocomial, exogenous drug induced, endogenous drug induced, etc.); general abnormal mineralization or mineral deposits; tissue disruption; duplicate, hypertrophied, atrophied, missing, reversed or misplaced organs/tissues; foreign bodies, granulomas, calculi formation, calcinosis cutis; panniculitis; intervertebral disk disease; periodontal disease; joint/tendon/ligament ruptures; retained cartilage cores; fibrotic myopathy; and general and organ specific neoplasia. Diagnosis of any disorder that alters the density of soft tissues may potentially benefit from the RDDD. Bone tissues: osteomalacia; osteoporosis; osteodystrophy; osteomyelitis (traumatic, parasitic, fungal, bacterial, neoplastic, autoimmune, toxins, thermal burns, freezing injury, idiopathic, nosocomial, exogenous drug induced, endogenous drug induced, etc.); panosteitis; vitamin A toxicity; periosteal inflammation (traumatic, parasitic, fungal, bacterial, neoplastic, autoimmune, toxins, thermal burns, freezing injury, idiopathic, nosocomial, exogenous drug induced, endogenous drug induced, etc.); osteoarthritis/degenerative joint disease; rheumatoid arthritis; erosive arthritis (single or poly); non-erosive arthritis (single or poly) (traumatic, parasitic, fungal, bacterial, neoplastic, autoimmune, toxins, thermal burns, freezing injury, idiopathic, nosocomial, exogenous drug induced, endogenous drug induced, etc.) osteitis (traumatic, parasitic, fungal, bacterial, neoplastic, autoimmune, toxins, thermal burns, freezing injury, idiopathic, nosocomial, exogenous drug induced, endogenous drug induced, etc.); periosteal bruising; fractures; multiple cartilaginous exostoses; diskospondylitis; Legg-Calvé-Perthes disease; osteochondrosis; septic arthritis (traumatic, parasitic, fungal, bacterial, neoplastic, autoimmune, toxins, thermal burns, freezing injury, idiopathic, nosocomial, exogenous drug induced, endogenous drug induced, etc.); craniomandibular osteopathy; bone cysts; hypertrophic osteopathy; nutritional secondary hyperparathyroidism; renal secondary hyperparathyroidism; mucopolysaccharidosis; bone mutilation from injury, infection, self-trauma, other; monitor bone biopsy and graft/implant sites, and more. Diagnosis of any disorder that alters the density of bone may potentially benefit from the RDDD. With respect to FIGS. 4A and 4B, in which like numerals have like meaning when ascribed to different drawings, a specific embodiment of the inventive device 40 or 50 in the form of a flat-bed cassette 42 is configured for placement under a human subject or other material as part of the regular X-ray radiography exam, in order to make X-ray radiography more quantitative and standardized. The cassette 42 captures information to perform intensity normalization and standardization, at locations (e.g., field hospitals) where care is rendered. The cassette may have (a) a minimally radio-opaque backing 44 which may be made of acrylic polymer or other radiolucent material or an image receptive layer that directly converts X-ray information into a digital signal, of uniform thickness whose X-ray radiographic signature can be used to estimate the source-detector geometrical inhomogeneity, and (b) a calibration bar 46 consisting of known materials and known thickness whose radiographic signatures can serve as references for standardization. In inventive embodiments the calibration bar acting as the reference device may fit on top of or within a radiograph cassette that is composed of a set of standard density items. In order to accommodate the wide range of X-ray exposures that may be encountered in the field, separate sets of the inventive cassette may be configured for use with low, medium and high exposures in part based on the size the subject. The standard X-ray cassette 42 is utilized. The cassette 42 may be square, rectangular or specially shaped and sized for the subject. A calibration bar 46, composed of multiple materials of known density and proper size to account for changes in the X-ray direct and incident angles and cassette and subject sizes, may be built into the cassette 42, simply placed on top of the cassette 42 or interchangeably inserted into the cassette 42. Specially designed cassettes would house the interchangeable port or permanent location of the calibration bar. It is appreciated that a novel cassette is developed in which the entire cassette serves as the calibration bar such that additional components are not required. The terms “low,” “medium,” and “high” are in the context of X-ray exposure for a given X-ray source. It is appreciated that the thickness and radio-density of the material being investigated are important aspects in deciding the exposure. Additionally, X-ray cassettes may have built-in calibration bars or similar devices that cover a larger range than afforded by individual and interchangeable bars. The calibration bar on embodiments of the cassette is configured to have a sufficiently wide range and graduated radio-opacity (set of standard density items) for the entire dynamic range of exposure encountered in practice. This reference range provides densities which are compared to the subject's different tissues. In embodiments, software is configured to quickly interpret the information and provide real time data as to the densities of set and user defined points (a portion of a bone for example) as well as set and user defined regions (a whole bone for example). Embodiments of the inventive software are configured to perform numerical operations to convert raw X-ray radiographic intensity into standardized metrics to be used in, for example, evaluating bone density. The software may be installed on a server or computer that is located in the same hospital or location where the scans are performed, or the software may be on a remote server or offered as a software on-demand service in the cloud that is accessed over the Internet. The images may be transmitted to a central location to be processed and analyzed by the same persons, although the software for the analysis can also be distributed to the field locations. The inventive software includes capabilities to (a) estimate the background (created by the instrument source-detector geometry and baseline responses) and subtract it from the raw image, and (b) convert the grayscale images into color-coded images (an intuitive colormap) based on the reference materials, since the human eye can more readily discern different colors over different shades of grey. In a specific embodiment, the colormap scale follows the visible spectrum with normalized radiodensity values from 0-100 corresponding to a color progression from red to violet, or vice versa. Because of the inherent variation in background intensity generated in X-ray radiography (in part due to the physics of x-rays diverging from the perfect perpendicular orientation of the central ray and the receptor plate), another embodiment of the inventive software is to adjust for this variation and create a homogeneous background on the image. FIGS. 2A-C demonstrate the gradient naturally present in X-ray images. Without correction, this gradient affects the visual brightness of images and ultimately results in variation, of what may be the exact same density, from one side of the film to the other. The inventive software corrects for this gradient across the X-ray image creating density values consistent with the true density of the subject. In another embodiment of the inventive software enhancement tools added to the image, by the native digital image processing software, are accounted for and counteracted, minimized or otherwise adjusted for to reduce their effect on further density processing. Such digital imaging tools, such as sharpening type tools, are common with digital imaging software. These tools are designed to help the viewer discern subtleties in the greyscale of the image. Sharpening and shadowing can help define lines in between various grey scales and are often used to help the image visually “pop.” However, these shadows, sharpenings and other changes can artificially affect the density of certain subject attributes and must be considered. The inventive software also works to address some or all of these enhancement tools that may be present—especially those that may affect density readings. Correction may include working with the manufacturer of the native software to turn off these features or by adjusting for the changes created from the enhancement tool(s). The ability of the inventive software to convert the grayscale images into color-coded images allows for creation of density color maps that may be adjusted through a series of density ranges. This allows the image to be intensified (amplify the density signal) for specific regions as needed. The adjustable intensity range may be applied to any image and directly compared between images of different subjects. Embodiments of the inventive software generate real values that correspond to the density range (whether amplified or not), which assigns a “number” on the density value that can also be compared with the subject and between subjects. Specific embodiments of software algorithms used for image correction create a correction methodology that will produce quantitative values of radio-opacity in X-ray radiography that are within 5-15% accuracy of the values measured by CT. In a preferred embodiment radiographic density information is within 95%, or greater, correlation of CT density values (Hounsfield units). The radiographic density score is consistent between any X-ray machine using the inventive flat-bed cassette and only requires proper patient/subject positioning and the use of the inventive operating software. The user would simply click a “button” and get a color coded density map for an overview of density, regional, and even localized views. Real “density” values may be collected regionally, locally, and even in very specific spots/pixels on a subject. These density values may be used to identify variations from “normal” or expected values. In inventive embodiments identified combinations of materials and thicknesses that have discrete, gradated radio-opacity suitable for the construction of a radio-opacity calibration bar are formed. The identification of material includes the backing board and/or its thickness in order to accommodate the X-ray exposures that will be used for different-sized animals and subjects. FIGS. 2A-2C show a radiograph of an ex vivo hamster (FIG. 2A) with an embodiment of the intensity calibration bar (top of image). In the radiograph of FIG. 2A, there is a conspicuous background that increases in intensity (dark to light) from left to right of the image. The non-uniform background is isolated (FIG. 2B), which contributes to approximately 10-15% of the intensity variation across the image in this specific example. After subtracting the background, the corrected image (FIG. 2C) shows visibly improved contrast and detail, especially in the animal head. Importantly, the intensities can now be assigned bone density values with more certainty by cross-referencing with the calibration bar. Validation of embodiments of hardware-software methodology in making X-ray radiography quantitative is obtained with radiographs of different objects as well as ex vivo animals of varying sizes, and performing post-analysis corrections, and compare the corrected radiographs directly with CTs of the identical objects and animals. The results may be used as feedback for improving the software algorithms of the correction. FIGS. 3A-3D are corrected radiographs (X-ray image) with color density maps of two cockatiels. FIGS. 3A and 3B refer to cockatiel 1, and FIGS. 3C and 3D refer to cockatiel 2. The animals are approximately the same size and radiographs were completed on the same machine with identical settings. FIGS. 3A through 3D show the calibration bar (represented by circles of varying colors and, subsequently, densities). The birds were first radiographed with a standardized calibration bar creating unprocessed images. Next the same images underwent post-processing to even the background gradient. The second step ensures that all, or at least most, points on the image have been adjusted for the gradient variation and is crucial to the next step of assigning density values to the tissues. FIGS. 3A and 3C show cockatiel 1 and cockatiel 2, respectively, with a color map and identical density scale (right side of image). Each color corresponds to a density value that can also be represented with a numerical value. The reddish-brown color indicates the greatest density while blue indicates the lowest density. Both subjects can be compared directly. The black arrows point to regions that are brighter in FIG. 3A compared to 3C. The density scale can also be narrowed which makes the density readings more sensitive for those areas with decreased density. FIGS. 3B and 3D demonstrate a narrowed density scale that increases subtleties in the images. Again, both subjects are shown at identical density scales. The arrows are placed to allow for direct comparison of color based densities between the two subjects. The arrows point to greater density readings (as shown with increased reddish-brown and yellow) in FIG. 3B compared to the same regions on FIG. 3D (more white and blue representing lower density). In this example, bird 1 (represented by FIGS. 3A-3B) has much greater bone density than the bird represented by FIGS. 3C-3D. However, this difference is not readily observable in plain radiographs. The color scheme is directly tied to numeric values and can be compared between subjects and machines. The color representation allows for quick assessment of density. Even if the scale (and corresponding colors) is changed, the numeric values are consistently reported (as long as the area being measured is not over or undersaturated). The numeric values allow for reporting that can be compared to “normals” and “abnormals” without the risk of over or under interpreting the color map. A validation study of hardware-software methodology is conducted to test how well it performs under various conditions of normal usage on different X-ray equipment. To provide a basis for comparison, “phantoms” (objects for test scans) are constructed that correspond to large, medium and small-size animals or human tissues. CT scans are performed on the phantoms to obtain absolute quantification of their radio-opacity values. Moreover, 4 duplicate sets of the backing boards, calibration bars, and phantoms are sent to 10-24 selected veterinary clinics around the country for trial scans on different equipment. The scans obtained from different sites are compared and the results may be used to improve the robustness of the post-analysis algorithm with a goal is to obtain quantitative X-ray radiograph values that are consistent within 5% across different scanners at different sites. Additional veterinary and human hospitals and other testing centers may be recruited to aid in product improvement. A study of 4 sets of birds (2 species, each under 2 sets of conditions) using the inventive Radiograph Density Detection Device (RDDD) and a micro computerized tomography (μCT). The μCT will serve as the gold standard. Data is collected on all birds at two separate times. The study is designed to accomplish two goals: correlate the RDDD to μCT and collect bone density readings between the different groups of birds. As a tertiary goal, the study serves as a model of how the RDDD can be used on a large scale basis. Data points collected are used to form a best fit model on the radiographs compared to μCT, to determine how reliable the RDDD data is at specific points on the radiographs and to provide a correlation coefficient with μCT. Clinical use of the Radiograph Density Detection Device (RDDD) to develop normal and abnormal density ranges for specific tissues/items, study individuals/single items and populations/groups. The test may be used as a typical component of X-ray testing whether for screening, diagnostic or monitoring purposes. The development of normal and abnormal density ranges may be used as a diagnostic tool and as a long term ongoing means to develop and refine what normal density is for the specific subject being studied. For example, the RDDD may be used to collect data on bone density values for a population of people living in a certain local. In an alternative example, the RDDD could be used to monitor environmental degradation of select minerals or metals after exposure to acids and other contaminants. Studies may be based on data gathered using the RDDD system. The data generated by embodiments of the RDDD system could provide a large amount of information relating to individuals (such as people), populations (such as captive animals), construction materials (as with weathering and mineral leaching of materials) and more. Examples of such studies in humans and animals include but are not limited to relating bone density to inactivity; obesity; cage or space confinement; subzero, zero or increased gravity; nutrition; whole organism or organ specific development, and much more. The foregoing description is illustrative of particular embodiments of the invention, but is not meant to be a limitation upon the practice thereof. The following claims, including all equivalents thereof, are intended to define the scope of the invention. |
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description | Preferred embodiments of this invention will now be described with reference to the accompanying drawings. In the description that follows, an electron beam lithography system for rendering fine circuit patterns on a semiconductor wafer will be shown as embodying the invention. [First Embodiment] FIG. 2 is a schematic view of an electron beam lithography system embodying the invention. A cross-sectional view in the right-hand portion of FIG. 2 comprises an electron beam enclosure 10, a specimen table 11 and a transporting unit 12. An electron gun 13 at the top of the electron beam enclosure 10 emits an electron beam 14 that is suitably shaped by lenses 16 inside. The electron beam 14 thus shaped is polarized by a polarizer 17 composed of an electromagnetic and an electrostatic polarizer. The polarized electron beam is irradiated to a target spot on a semiconductor wafer 18 placed on the specimen table 11. Several cross-sectional shapes of the irradiated electron beam 14 may be transcribed onto the wafer 18 by selecting a mask 15 appropriately. The left-hand portion of FIG. 2 shows components of a system control computing section controlling the entire system and providing an interface with the outside. A group of functional blocks enclosed in a frame 21 constitutes a group of digital processing units for control purposes. These processing units convert rendering data from a computer 22 into polarization data about the electron beam in a continuous manner (i.e., on a pipeline basis) at a high speed. The individual processing units carry out the following processes: (1) Figure Data Unit A figure data unit stores compressed pattern data transferred from the computer 22. (2) Figure Reassembling Unit A figure reassembling unit reassembles the compressed pattern data into figure data. (3) Figure Disassembling Unit A figure disassembling unit replaces each reassembled figure with a shape (i.e., shot) that may be rendered by electron beam, thereby creating position, shape and exposure data about each shot. (4) Alignment Correcting Unit An alignment correcting unit monitors the wafer 18 for misalignment and distortion using a sensor 19, and makes corrections to compensate for any misalignment or distortion detected. (5) Proximity Effect Correcting Unit A proximity effect correcting unit corrects the proximity effect by first obtaining a unit pattern area map (i.e., exposure map) of a pattern to be rendered and by correcting the level of exposure for each shot with reference to the values in the exposure map. (6) Absolute Follow-up Calibrating Unit An absolute follow-up calibrating unit permits continuous rendering. Based on position data from a specimen table position measuring unit 20, this calibrating unit calculates the position of the polarized electron beam so that the electron beam 14 is kept irradiated precisely onto the target spot on the wafer 18, and corrects distorted polarization in the electron beam enclosure. (7) Procedure Controlling Unit A procedure controlling unit provides monitoring and controlling functions such as to keep the above units performing their processing smoothly. Data coming from the above control-related units are converted from digital to analog format by a D/A converter 23. The converted data are sent to a beam controlling unit 24 that controls electromagnetic lenses as well as the electromagnetic and electrostatic polarizers. A high voltage supply 25 provides the electron gun 13 with power to generate acceleration voltages. A mask controlling unit 26 selects the shape of a mask 15. A specimen table controlling unit 27 controls movements of the specimen table 11 in the enclosure 10. The transporting unit 12, under control of a transport controlling unit 28, loads the wafer 18 into the enclosure. The units exchanging their signals through an interface may be controlled by computer. FIG. 3 is a block diagram of a typical proximity effect correcting unit of the invention. This proximity effect correcting unit differs from its counterpart in the way in which exposure maps are created. An exposure map for mock rendering is created by first having rendering data sent from the preceding stage. An input unit 31 divides the rendering data into meshes of a predetermined size each. A judging unit 32 computes positional relations between each shot and meshes based on the position and shape of the shot in question, and makes a judgment accordingly. Illustratively, if each shot is smaller than any one of the meshes involved, the judging unit 32 reaches one of the following four judgments that may be called conditions: Condition 1 The shot in question is included in a mesh. Condition 2 The shot exceeds a mesh boundary in the X direction only. Condition 3 The shot exceeds a mesh boundary in the Y direction only. Condition 4 The shot exceeds mesh boundaries in both the X and the Y directions. In each of the above conditions, the judging unit 32 computes shot areas divided by mesh boundaries and included in each mesh, and writes the computed values to memory locations. Obviously, the data coming from the preceding stage are unpredictable and may represent any one of the four conditions above. Whereas the data falling under the condition 1 alone are accommodated with no problem by a single memory, the data under the condition 4 cannot be processed on a pipeline basis using one memory because one shot has been divided into four meshes. In the latter case, there is no avoiding the slowing-down of the processing. This snag is circumvented by the inventive proximity effect correcting unit utilizing four partial memories 34a through 34d (memories 0 through 3). Each of the four partial memories 34a through 34d has its own address (m, n). As will be described later in more detail, area values S0, S1, S2 and S3 calculated by area value computing units 33a through 33d are stored simultaneously into the four partial memories 34a through 34d, whereby the processing is carried out rapidly on a pipeline basis. Addresses at which to store the area values S0 through S3 are given as (m, n+1), (m+1, n) and (m+1, n+1) adjacent to address (m, n) of the mesh containing illustratively the bottom left end point of the shot in question. For conditions such as the condition 1 under which no area value is computed, zero is written to addresses (m, n+1), (m+1, n) and (m+1, n+1) of the partial memories 1, 2 and 3 respectively (S1=0, S2=0, S3=0). It is possible to calculate levels of exposure by referring to the area values stored in the partial memories 34a through 34d. Generally, the flow of data from the preceding stage is rapid enough to necessitate the use of S-RAMs for the partial memories 34a through 34d. At present, it is difficult for such an S-RAM makeup to accommodate the whole rendering data. Preferably, the area values placed temporarily in the memories 34a through 34d should then be transferred to an exposure map memory (e.g., D-RAM) 36 capable of accommodating large quantities of data. Different data are found in the four partial memories 34a through 34d at a single address thereof. Thus when data are to be transferred form the partial memories 34a through 34d to the exposure map memory 36, the data are retrieved from the same address of the four partial memories and are added up by an adding circuit 35 in the subsequent stage totaling the data for each address. The totaled data are transferred to the exposure map memory 36. In this manner, one set of data is associated with one address. The data stored in the exposure map memory 36 are subjected to such processes as smoothing by a smoothing filter 37 in order to simulate primary and secondary scattering of electrons. The data thus processed are again placed into the exposure map memory 36 whereby a desired exposure map is created. When actual rendering is performed, the same data are again transmitted from the preceding stage. Given position and shape data about each shot, an address computing unit 38 calculates an address in the exposure map 36. The area value of the address is converted simultaneously to a level of exposure by an exposure level converting unit 39, and an adder 40 adds or subtracts the converted value to or from the level of exposure of each shot for correction. At this point, the address in the exposure map 36 is calculated by the address computing unit 38 with reference to the center of the shot in question. In the present example, the four partial memories 34a through 34d are used because the size of shots is assumed not to exceed that of meshes. The number of patterns may vary depending on the size of the largest shot. For example, if the maximum shot size is 1.5 times larger than the mesh size, nine partial memories are provided because conditions need to be considered over a 3xc3x973 mesh region. In this manner, furnishing a suitable number of partial memories in keeping with the maximum shot size makes it possible for the proximity effect correcting unit of FIG. 3 to correct the proximity effect where the relationship between the maximum shot size and the mesh size varies. With reference to FIGS. 4 and 5 and using simulations, an illustrative description is made below of judgments formed by the judging unit 32 and of area value calculations made by the area value computing units 33a through 33d (shown included in the block diagram of FIG. 3). FIG. 4 is a block diagram of a typical circuit that divides the area of the shot in question and adds up the divided area values by judging positional relations between the position and shape of rendering data (shot data in this case) on the one hand and mesh boundaries on the other hand. FIG. 5 is a schematic view depicting positional relations between a shot 50 and meshes. Judgments are formed in the setup of FIG. 5 by use of a bottom left end point 51 and a top right end point 52 of the shot 50. The parameters shown in FIGS. 4 and 5 include position data (x, y) about the bottom left end point 51 of the shot 50 (in FIG. 5), shape data xe2x80x9cwxe2x80x9d and xe2x80x9chxe2x80x9d on the shot 50, and a mesh size of xcex1. A rectangular shot is used for the purpose of simplifying position and shape data. Reference characters xe2x80x9cxxe2x80x9d and xe2x80x9cyxe2x80x9d stand for an X and a Y coordinate, respectively, of the bottom left end point 51 belonging to the shot 50. Reference characters xe2x80x9cwxe2x80x9d and xe2x80x9chxe2x80x9d denote a width and a height of the rectangular shot 50 respectively. Each mesh is assumed to be a square on condition that xcex1xe2x89xa7w and xcex1xe2x89xa7h. How the circuit of FIG. 4 works will now be described using the above parameters. Address (m, n) of the mesh containing the shot 50 is defined by expression (1) below with respect to the position where the bottom left end point 51 exists. The definition is adopted with a view to simplifying the conditions with reference to an end point. In the expression below, [I] means a maximum integer not exceeding I. m=[x/xcex1], n=[y/xcex1]xe2x80x83xe2x80x83(1) It is in one of four conditions (1 through 4 described below) that the bottom left end point 51 of a given shot 50 is included in the mesh having address (m, n) in FIG. 5. As shown in FIG. 4, the judging unit 32 makes a judgment on each of the conditions using seven parameters xcex1, m, x, w, n, y, h coming from the input unit 31, and computes as shown below area values S0 through S3 for the meshes having addresses (m, n), (m, n+1), (m+1, n) and (m+1, n+1) . That is, the values S0 through S3 denote the shot areas included in the meshes (m, n), (m, n+1), (m+1, n) and (m+1, n+1) respectively. In any of the four conditions, the area values S0 through S3 are written to addresses of partial memories as indicated below. If any address of a partial memory to which to write a newly computed area value has area value data already, the new value is added to the existing data. S0xe2x86x92written to address (m, n) of partial memory 0 S1xe2x86x92written to address (m, n+1) of partial memory 1 S2xe2x86x92written to address (m+1, n) of partial memory 2 S3xe2x86x92written to address (m+1, n+1) of partial memory 3 Condition 1 This is a case where the top right end point 52 of the shot 50 is included in the mesh (m, n), i.e., where (n+1)xc2x7xcex1xe2x88x92xxe2x89xa7w and (m+1)xc2x7xcex1xe2x88x92y xe2x89xa7h. S0=wxc2x7h S1=0 S2=0 S3=0 Condition 2 This is a case where the top right end point 52 of the shot 50 is included in the mesh (m, n+1), i.e., where (n+1)xc2x7xcex1xe2x88x92x less than w and (m +1)xc2x7xcex1yxe2x89xa7h. S0=[(n +1)xc2x7xcex1xe2x88x92x]xc2x7h S1=[x+wxe2x88x92(n+1)xc2x7xcex1]h S2 0 S3 0 Condition 3 This is a case where the top right end point 52 of the shot 50 is included in the mesh (m+b 1, n), i.e, where (n+1)xc2x7xcex1xe2x88x92xxe2x89xa7w and (m+1)xc2x7xcex1xe2x88x92y less than h. S0=wxc2x7[(m+1)xc2x7xcex1xe2x88x92y] S1=0 S2=wxc2x7[y+hxe2x88x92(m+1)xc2x7xcex1] S3=0 Condition 4 This is a case where the top right end point 52 of the shot 50 is included in the mesh (m+, n+), i.e., where (n+1)xc2x7xcex1xe2x88x92x less than w and (m+1)xc2x7xcex1xe2x88x92y less than h. S0=[(n+1)xc2x7xcex1xe2x88x92x]xc2x7[(m+1) xc2x7xcex1xe2x88x92y] S1=[x+wxc2x7(n+1)xc2x7xcex1]xc2x7[(m+1) xc2x7xcex1xe2x88x92y] S2=[(n+1)xc2x7xcex1xe2x88x92x]xc2x7[y+hxe2x88x92(m+1)xc2x7xcex1] S3=[(x+wxe2x88x92(n+1)xc2x7xcex1]xc2x7[y+hxe2x88x92(m+1)xc2x7xcex1] FIG. 6 is a graphic representation of an exposure map shown three-dimensionally and created by disassembling rendering data on a 60 xcexcmxc3x9760 xcexcm square in FIG. 20 using a 3.0 xcexcmxc3x973.0 xcexcm shot. For this exposure map, calculations are made over a range of 20xc3x9720 meshes each measuring 5.12 xcexcmxc3x975.12 xcexcm. The acquired values are each expressed as a percentage of the shot area included in each mesh, i.e., as an area ratio. A comparison of FIG. 6 with FIG. 21 indicates a uniform area ratio distribution obtained inventively over the region where the figure exists. The results remain the same when the shot size is set for 0.64 xcexcmxc3x970.64 xcexcm or when the mesh size is 5.12xcexcmxc3x975.12 xcexcm. Exposure maps may thus be created independently of the shot size as long as the mesh size is not exceeded by the shot. In other words, highly precise exposure maps are created without having to reduce the shot size as has been the case conventionally. According to the invention, the time required for the processing is shortened while precision is maintained. When the exposure process is performed with the proximity effect corrected by use of an inventive exposure map, patterns are exposed in high degrees of precision. Although it has been shown above that the judgments and area value computations are made by hardware on a pipeline basis, this is not limitative of the invention. Similar judgments and calculations may also be accomplished on a software basis. The method outlined above will now be described in more detail with reference to FIG. 7. The emphasis will be on the reasons why four partial memories are employed and why an adding circuit is incorporated to integrate four items of data held in the four partial memories (i.e., partial memories 34a through 34d explained with reference to FIGS. 3 and 4). Suppose that an exposure map has nine meshes (whose addresses are indicated by encircled numerals) as shown in FIG. 7, and that four shot data A, Axe2x80x2, Axe2x80x3 and Axe2x80x2xe2x80x3 have been input as indicated. A figure represented by the shot data A straddles the meshes having addresses 5, 6, 8 and 9. Likewise, a figure denoted by the shot data Axe2x80x2 straddles the meshes with addresses 1, 2, 4 and 5. A figure defined by the shot data Axe2x80x3 straddles the meshes with addresses 4 and 5, and a figure of the shot data Axe2x80x2xe2x80x3 straddles the meshes having addresses 1 and 4. Data to be written to the partial memories in this makeup are shown in Table 1. Illustratively, the shot A has its area value S0 written to address 5 of memory 0, its area value S1 written to address 6 of memory 1, its area value S2 written to address 8 of memory 2, and its area value S3 written to address 9 of memory 3. It should be noted that the shot area values are stored at different addresses in different memories. In the case of the shots Axe2x80x2 and Axe2x80x2xe2x80x3, their bottom left end point is included in the same mesh. For that reason, the area values S0xe2x80x2xe2x80x2and S0xe2x80x2xe2x80x3 are written to the same address of the same memory and so are the area values S2xe2x80x2 and S2xe2x80x2xe2x80x3. In the memories thus grouped, one signal address may have different values written thereto as shown in Table 1. This means that simply accessing one address in one memory does not provide a correct area value included in a mesh. The area value included in each mesh should thus be computed by reading area values from the same address in the four memories and by adding up the retrieved values. The calculations are performed on a pipeline basis by use of an adding circuit which is located downstream of the partial memories for the purpose of integrating four pieces of data. [Second Embodiment] With the first embodiment shown in FIGS. 3 and 4, simplified address assignments make it relatively easy to build circuitry. However, because each address is assigned to four memories in replicated fashion, the embodiment requires four times as much storage space as that of the single memory setup. Increased memory requirements signify a growing number of circuit elements needed, which makes mounting of component parts on the substrate more difficult and incurs higher costs than before. The second embodiment, by contrast, provides an appreciable saving in the total amount of partial memories by dividing exposure map addresses into four portions each allocated to a partial memory. With reference to FIG. 9 showing relations between meshes on the one hand and partial memories on the other hand, description will now be made in detail of the memories and their addresses for accommodating area values S0, S1, S2 and S3 of each shot divided between meshes. Four memories are used to retain different data. It is thus necessary to regard each address as representative of four meshes so that their data will not conflict. FIG. 9 shows a partial region made of Moxc3x97Na meshes in groups of four, with each mesh group assigned an address. Each encircled numeral corresponding to a group of four meshes represents a partial memory address. Of the four meshes given an identical address, the bottom left mesh is allocated to the partial memory 0, the bottom right mesh to the partial memory 1, the top left mesh to the partial memory 2, and the top right mesh to the partial memory 3. When area density data on each mesh are to be stored, a normal mesh address is halved and the halved addresses are used as the addresses of partial memories (0 through 3). If a shot straddles a boundary where addresses change from one partial memory to another, the memories need to be switched so as to accommodate the area values, and the addresses also need to be changed. If a partial memory address is assumed to be (M, N) and if the remainder involved is assumed to be (M LSB, N LSB), these values are defined by expression (2) as follows: M=Floor[m(i)/2], MLSB=Mod[m(i)/2] N=Floor[n(i)/2], NLSB=Mod[n(i)/2]xe2x80x83xe2x80x83(2) where, Floor[a/b] stands for the quotient (integer) of a/b and Mod[a/b] for the remainder (integer) of a/b. In other words, a mesh address (m, n) is defined by expression (3) given below. The address may be expressed by data with the least significant bits given as (M LSB, N LSB) as shown in FIG. 10. m(i)=2xc3x97M+MLSBn(i)=X2xc3x97N+NLSBxe2x80x83xe2x80x83(3) The numeral of each partial memory and its address are designated by use of the above parameters. A point of reference is assumed to be located in the mesh including the bottom left end point of a shot. Judgments are then formed about address (m, n) of the mesh in which the bottom left end point of the shot is found. In that case, there are provided four conditions in which to divide the area value of the shot in question and to store the divided values. The divided shot area values S0, S1, S2 and S3 are written to designated addresses in designated partial memories as will be shown below. The values S0, S1, S2 and S3 stand for the area values included in the meshes (m, n), (m, n+1), (m+1, n) and (m+1, n+1) respectively. In the description that follows, a partial memory address is given as (M, N) under conditions (i) through (iv) for purpose of simplification and illustration. In practice, the address of a given partial memory is defined by expression (4) below. (Partial memory address)=Mxc3x97(Ns/2)+Nxe2x80x83xe2x80x83(4) where M=0, 1, 2, . . . , Ms/2 and N=0, 1, 2, . . . , Na/2. Condition (i) This is a case where the entire shot is included in a partial memory with address (M, N) such as is shown in FIG. 11, i.e., where the least significant bits of (m, n) are both zero, or {M LSB=0}∩{{N LSB=0. In this case, the area values S0, S1, S2 and S3 are written to the partial memory addresses designated as shown in Table 2. Condition (ii) This is a case where the shot straddles partial memories with addresses (M, N) and (M, N+1) such as is shown in FIG. 12, i.e., where the least significant bits of xe2x80x9cmxe2x80x9d and xe2x80x9cnxe2x80x9d are 0 and 1 respectively, or {M LSB=0}∩{{N LSB=1}. In this case, the area values S0, S1, S2 and S3 are written to the partial memory addresses designated as shown in Table 3. Condition (iii) This is a case where the shot straddles partial memories with addresses (M, N) and (M+1, N) such as is shown in FIG. 13, i.e., where the least significant bits of xe2x80x9cmxe2x80x9d and xe2x80x9cnxe2x80x9d are 1 and 0 respectively, or {M LSB=1}∩{{N LSB=0}. In this case, the area values S0, S1, S2 and S3 are written to the partial memory addresses designated as shown in Table 4. Condition (iv) This is a case where the shot straddles all for partial memories such as is shown in FIG. 14, i.e., where the least significant bits of xe2x80x9cmxe2x80x9d and xe2x80x9cnxe2x80x9d are both 1, or {M LSB=1}∩{{N LSB=1}. In this case, the area values S0, S1, S2 and S3 are written to the partial memory address designated as shown in Table 5. Table 6 below summarizes the partial memory assignments relative to the area values shown illustratively above. FIG. 15 schematically depicts how area values divided by mesh boundaries are typically allocated to partial memories. In FIG. 15, a simplified map of 4xc3x974 meshes is shown containing shots 1 through 4. If the map is assumed to be divided into groups of 2xc3x972 meshes, then the partial memories are given four addresses ({circle around (1)} through {circle around (4)}. In FIG. 15, each region enclosed by thin lines is a mesh, and each region enclosed by thick lines is covered by a partial memory address. If it is assumed that a shot xe2x80x9cnxe2x80x9d is divided by mesh boundaries into areas whose values are S0(n), S1(n), S2(n) and S3(n), then these area values are written to addresses of partial memories as designated in Table 7 that follows. Illustratively, the area of the shot 4 is divided so that the divided area values are stored into the memories as shown below. S0(4)xe2x86x92written to address {circle around (1)} of partial memory 3 S1(4)xe2x86x92written to address {circle around (2)} of partial memory 2 S2(4)xe2x86x92written to address {circle around (3)} of partial memory 1 S3(4)xe2x86x92written to address {circle around (4)} of partial memory 0 FIG. 8 is a block diagram of another proximity effect correcting unit of the invention. In FIG. 8, the components with their functionally identical or equivalent. counterparts included in FIG. 3 are designated by like reference numerals. In this proximity effect correcting unit, partial memories 44a through 44d are laid out in the same manner as in the circuit of FIG. 3 while a selector 41 is located downstream of area value computing units 33a through 33d which calculate area values for each mesh. The selector 41 judges through address calculations which of the four meshes (bottom left, bottom right, top left, top right) enclosed by thick lines in FIG. 9 corresponds to the position of the mesh whose area value has been computed. In so doing, the selector 41 selects one of partial memories 0 through 3 in which to store the calculated area value. The address of the selected partial memory is sent from an address computing unit 38. The area value is then written to four partial memories 44a through 44d in accordance with the assignments shown in Tables 2 through 5. At the same time, the data at the same address in the partial memories 44a through 44d are retrieved therefrom and added to the data existing at the same address before the write operation. In practice, to retrieve the existing data requires selecting the partial memories 44a through 44d. The requirement is met by a selector 42 located downstream of the partial memories 44a through 44d. Alternatively, the selector 42 is not needed if a downstream exposure map 36 is constituted by four memories. In such a case, the partial memory numbers (i.e., partial memories 0 through 3) need only be assigned to the four exposure map memories. More specifically, the selector 42 may be omitted where the partial memory 0 is allocated to the exposure map memory 0, the partial memory 1 to the exposure map memory 1, partial memory 2 to the exposure map memory 2, and the partial memory 3 to the exposure map memory 3. This arrangement affords an appreciable memory saving. With the area of the memory layout thus reduced, the area for mounting component parts is diminished correspondingly. Although the examples above have been shown utilizing partial memories, this is not limitative of the invention. Alternatively, area values or area density data may be written directly to the exposure map, i.e., without memory intervention. As described and according to the invention, highly precise exposure maps are created regardless of the shot size. With no need to minimize the shot size, the time required to create exposure maps is shortened substantially. As many apparently different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that the invention is not limited to the specific embodiments thereof except as defined in the appended claims. |
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039881539 | claims | 1. A method of manufacturing a thin film iris diaphragm having at least one opening for passing a beam of particles of a corpuscular beam apparatus, in particular electron microscopes and vidicons, said iris diaphragm having a thin metal layer with at least one opening therethrough and an integral reinforcing portion of the same metal which is set back from the edge of each of the openings in the thin metal layer, said method comprising the steps of providing a substrate; applying at least one metal base film on a surface of the substrate; forming a first mask having a negative image of the configuration of the thin metal layer of the iris diaphragm on the metal base film by depositing on the base metal film a first coating of photo-sensitive material which is resistant to electro-depositing, by exposing selected areas of the first coating, and by developing the coating to form the first mask; electro-depositing a thin metal layer on the base film; forming a second mask having a negative image of the configuration of the reinforcing portion by applying a second coating of photo-sensitive material which is resistant to electro-depositing on the first coating and metal layer, by exposing the second coating of material with a negative image of the reinforcing portion, and by developing the second coating to form the second mask with a portion covering each opening of the thin metal layer and the thin metal layer surrounding each opening; electro-depositing a thick layer of the same metal as the thin metal layer to form the reinforcing portion; removing said masks; and then removing the substrate by selectively etching away the base metal film. 2. A method according to claim 1, wherein the step of forming both the first and second masks form a plurality of spaced first masks and an aligned second mask for each first mask so that a plurality of iris diaphragms are formed by the steps of electro-deposition. 3. A method according to claim 1, which prior to the step of applying the metal base film on the substrate, includes the step of applying a bonding layer on the substrate so that a better bond of the metal base film on the substrate is obtained. 4. A method according to claim 3, wherein the step of forming the first mask comprises forming a plurality of first masks and wherein the step of forming the second mask includes forming an aligned second mask for each first mask so that a plurality of iris diaphragms are formed on the substrate. 5. A method of manufacturing a thin film iris diaphragm having at least one opening for passing a beam of particles of a corpuscular beam apparatus such as electron microscopes and vidicons, said iris diaphragm having a thin metal layer with at least one opening therethrough and an integral reinforcing portion of the same metal which is set back from the edge of each opening in the thin metal layer, said method comprising the steps of providing a surface; forming a first mask on said surface, said mask leaving a portion of the surface exposed with the exposed surface having a configuration of the thin metal layer of the iris diaphragm, galvanically applying a thin metal layer to the exposed surface; forming a second mask on the first mask and thin metal layer, said second mask having a configuration of the reinforcing portion and covering a portion of the thin metal layer adjacent the edge of each opening therein, galvanically depositing a thick layer of the same metal as the thin metal layer to form the reinforcing portion and then removing the iris diaphragm from the surface and the masks thereon. 6. A method according to claim 5, wherein the step of providing the surface comprises providing a substrate having a metal base film provided thereon to form the surface. 7. A method according to claim 5, wherein the step of providing the surface comprises providing a substrate having a surface and depositing a metal base film on the surface. 8. A method according to claim 7, wherein prior to the step of depositing the metal base film on the surface of the substrate, a thin bonding layer is applied to facilitate the adhesion of the metal base film to the substrate. |
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052710491 | description | DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, it is seen in FIG. 1-3 that the invention is generally indicated by the numeral 10. Grid key 10 is formed in the shape of a rectangular bar to provide a main body portion 12 having first and second ends 14, 16. Main body portion 12 is bent near the middle to form an approximate 90 degree angle in main body portion 12. First end 14 is provided with two wings or tabs 18. In the preferred embodiment tabs 18 are integral with main body portion 12 for ease of fabrication and strength. The following terms will be used for the sake of clarity in referring to the various dimensions of main body portion 12 and tabs 18. The dimension of main body portion 12 between first and second ends 14, 16 shall be indicated as the length of main body portion 12. The dimension of tabs 18 from first end 14 back toward the bend in main body portion 12 shall be indicated as the length of tabs 18. The dimension across both tabs 18 shall be indicated as the width across tabs 18 with the corresponding dimension across main body portion 12 being indicated as the width of main body portion 12. The thickness of tabs 18 and main body portion 12 is that dimension perpendicular to the width. Solid lines are used in FIG. 2,3,5, and 6 to clearly distinguish between main body portion 12, tabs 18, and thickened section 20 of main body portion 12. As best seen in FIG. 2-4, tabs 18 extend outward in opposite directions from the width of first end 14 and along a portion of the length of main body portion 12. Although the length of tabs 18 will depend on the type of grid to be keyed, the length of tabs 18 in the preferred embodiment is 0.400 inch +/-0.010 inch when used for zircaloy or inconel grids. As best seen in FIG. 4, one side of tabs 18 is flush with main body portion 12 while the opposing side of tabs 18 tapers inwardly toward main body portion 12 at approximately a 45 degree angle. It is also seen in FIG. 2 and 4 that main body portion 12 is provided with thickened section 20 that is thicker than the remainder of main body portion 12 and has a length equal to that of tabs 18. During loading of fuel rods into the interior grid cells of the fuel assembly, grid key 10 is used in the following manner. Grid key 10 is positioned in interior grid cell 22 as seen in FIG. 5 so that first end 14 is adjacent soft stops 24. A separate tool is then used to press thickened section 20 against soft stops 24 as seen in FIG. 1 and 6 and wedge first end 14 in place. Tabs 18 restrict the installation depth of thickened section 20. FIG. 1 is a cutaway view of a grid assembly 26 that illustrates grid key 10 when in its operative position. Second end 16 is above grid assembly 26 and extends away from cell 22 being keyed at approximately a 45 degree angle. After a fuel rod is loaded into cell 22, grid key 10 is removed by using second end 16 as a lever to twist or pivot thickened section 20 out of its wedge position between soft stops 24. Because many varying and differing embodiments may be made within the scope of the inventive concept herein taught and because many modifications may be made in the embodiment herein detailed in accordance with the descriptive requirement of the law, it is to be understood that the details herein are to be interpreted as illustrative and not in a limiting sense. |
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claims | 1. An electron beam irradiation device, comprising:a light pattern generating section for generating a two-dimensional light pattern;an electron amplification section for (i) generating an electron beam array based on the light pattern entered, (ii) amplifying the electron beam array, and (iii) emitting the electron beam array as an amplified electron beam array, wherein said electron amplification section includes multiple cylindrical microchannels which are arranged adjacent to one another in a direction perpendicularly crossing a direction of a light axis of the light pattern so that respective axes of the microchannels are parallel to the direction of the light axis;an electron beam lens section for converging the amplified electron beam array on an electron ray resist; anda controller for controlling the light pattern generating section so as to generate, in a time-sharing manner, multiple divided light patterns which compensate one another, from the light pattern entering the microchannels. 2. The electron beam irradiation device as set forth in claim 1, wherein:said electron beam lens section is performs at least one of (i) acceleration of the amplified electron beam array, (ii) alignment of the amplified electron beam array, and (iii) projection of the amplified electron beam array. 3. The electron beam irradiation device as set forth in claim 1, wherein:said electron amplification section includes a photoelectric film for (i) converting, into an electron, a photon entering from a light pattern entering side, and (ii) for emitting the electron. 4. The electron beam irradiation device as set forth in claim 1, wherein:said light pattern generating section includes: a femto-second laser; and a micro-mirror array section for reflecting thereon a laser beam from the femto-second laser, thereby forming the two-dimensional light pattern. 5. The electron beam irradiation device as set forth in claim 1, wherein:the controller includes a compensating section for compensating the light pattern so as to reduce distortion that occurs in a pattern formed by the said amplified electron beam array. 6. The electron beam irradiation device as set forth in claim 5, wherein:said compensating section includes a section generating reversely-distorted light pattern which controls the light pattern generating section to generate a reverse-distortion light pattern so as to cancel distortion that occurs in the amplified electron beam array. 7. The electron beam irradiation device as set forth in claim 1, further comprising:a grid electrostatic lens section provided on an emitting side of the electron amplification section, for restraining divergence in emission angle of the amplified electron beam array from the electron amplification section. 8. The electron beam irradiation device as set forth in claim 1, wherein each of the microchannels has a diameter not greater than 10 μm. 9. The electron beam irradiation device as set forth in claim 1, wherein each of the microchannels has a diameter between 2 μm and 10 μm. 10. An electron beam irradiation device, comprising:a light pattern generating section for generating a two-dimensional light pattern;an electron amplification section for (i) generating an electron beam array based on the light pattern entered, (ii) amplifying the electron beam array, and (iii) emitting the electron beam array as an amplified electron beam array; andan electron beam lens section for converging the amplified electron beam array on an electron ray resist, wherein:said electron amplification section includes multiple cylindrical microchannels which are arranged adjacent to one another in a direction perpendicularly crossing a direction of a light axis of the light pattern so that respective axes of the microchannels are parallel to the direction of the light axis, andeach of said microchannels has such a shape that its inner peripheral surface of an end portion, on an emission side of the amplified electron beam array, is gradually spread outwardly towards an emission end of the microchannel, for a purpose of restraining divergence in emission angle of the amplified electron beam array from the electron amplification section. |
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summary | ||
abstract | A grating that includes a multilayer structure that has alternating layers of materials, a plurality of grooves formed between a plurality of lands, wherein at least one structural parameter of the plurality of grooves and plurality of lands is formed randomly in the multilayer structure. |
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description | 1. Field of the Invention The present invention relates generally to gamma scanning apparatus that measures radiation emitted from a fuel assembly at a nuclear power plant and thus measures burn-up and a power distribution of the fuel assembly. More particularly, the invention is directed to gamma scanning apparatus suitable for measuring burn-up and a power distribution of a fuel assembly accurately, not depend on the accuracy of an installation location and installation angle of the fuel assembly, and hence for measuring radiation emissions from a number of fuel assemblies within a short time. 2. Description of the Related Art It is traditionally known that gamma rays are used to measure the burn-up of a spent fuel assembly, as in JP-10-332873-A. A method of measuring burn-up and a power distribution by measuring the radiation from an active fuel assembly at a nuclear power plant is also coming into use in recent years. In these measurements, a housing is fixedly installed to obtain a constant relative angle between the housing and an outer surface of the fuel assembly having a square cross section, and the fuel assembly is moved vertically with the relative angle kept constant. In this case, a collimator is provided on a radiation detector present inside the housing, and a central portion of the height section of the fuel assembly that is included in a solid angle defined by the collimator is identified as a vertical central position. The measurement of the vertical burn-up and power distribution of the fuel assembly is conducted by repeating several steps. First, the fuel assembly is moved vertically and fixed to a given position. Next, a first measuring operation is performed and then the fuel assembly is moved vertically once again. After this, the fuel assembly is fixed again and a second measuring operation follows. For measurement at a relative angle between at least two positions, the burn-up and the power distribution have traditionally been measured in a vertical direction with the angle kept constant, then this angle has been changed and the fuel assembly fixed, and the angle has been kept constant once again and the fuel assembly moved vertically again for measurement. In addition, referring to measuring angles, if the angle at which one side of the square of the fuel assembly having the square cross section faces the detector is defined as 0 degrees, for example, measurements have been conducted at an angle of 45 degrees and the angle of 225 degrees established by rotating the fuel assembly through 180 degrees from the state of 45 degrees. Given a constant gamma-ray intensity distribution in the fuel assembly, if the relative angle between the fuel assembly and the housing changes, the self-shielding effect of the fuel assembly and other factors change a counting rate of the radiation detector within the housing. Before starting the measurements, therefore, it has been necessary to accurately determine an axial rotational position of the fuel assembly with respect to the housing. However, since the fuel rods in the fuel assembly usually have some minor bends or shifts in horizontal position, even if the rotational position of the fuel assembly is accurately determined prior to the measurements, errors occur with the distribution measurement during the vertical movement of the fuel assembly. One conceivable solution to this problem would be by using two gamma-ray detectors as one pair, arranging the two detectors to include a central axis of the fuel assembly and to be left-right symmetrical with respect to the central axis, and combining detection signals of these detectors prior to inspection. This solution, however, causes measurement errors associated with errors relating to the layout of the two detectors at the above positions. Additionally, that has been a problem in that the necessity of using the two detectors to perform the measurement at one vertical position involves the use of large-size apparatus including a collimator, and makes the apparatus expensive. An object of the present invention is to provide gamma scanning apparatus that can accurately measure burn-up and a power distribution of a fuel assembly not depend on the accuracy of an installation angle of the fuel assembly, and can thus measure radiation emissions from a number of fuel assemblies accurately within a short time. (1) In order to achieve the above object, the present invention is the gamma scanning apparatus according to includes a gamma-ray detector, a collimator that limits a measuring range in a fuel assembly and limits entry of gamma rays from the fuel assembly into the gamma-ray detector, an absorber that controls intensity of the gamma rays entering the gamma-ray detector, a shield that shields the gamma-ray detector, a housing that contains the gamma-ray detector, the collimator, the absorber, and the shield, and moving and fixing means that moves the housing to a definite position and fixing the housing thereto. The gamma scanning apparatus further includes rotating and moving means that moves the fuel assembly vertically in addition to rotating the assembly, a gamma-ray counting circuit that measures an output (power) of the gamma-ray detector, and data collecting/analyzing and controlling apparatus that analyzes data output from the gamma-ray counting circuit, in association with data relating to the rotation and movement of the fuel assembly by the rotating and moving means. The rotating and moving means, after fixing the vertical position of the fuel assembly with that of the housing also fixed, rotates the fuel assembly through 360 degrees with its height kept constant, at a fixed or variable angular velocity. During the 360-degree rotation of the fuel assembly, the gamma-ray counting circuit measures either a time average of any count values which the gamma-ray detector has detected during the rotation of the fuel assembly (i.e., an average counting rate), or an integral value of any counts detected within a fixed time by the detector. The data collecting/analyzing and controlling apparatus analyzes the data output from the gamma-ray counting circuit, in association with the data relating to the rotation and movement of the fuel assembly by the rotating and moving means, and thus derives a burn-up distribution and power distribution of the fuel assembly. This configuration allows the gamma scanning apparatus to accurately measure the burn-up and power distribution of the fuel assembly not depend on the accuracy of an installation angle of the fuel assembly, and hence to accurately measure radiation emissions from a number of fuel assemblies within a short time. (2) In item (1) described above, after the housing has been fixed, the rotating and moving means preferably conducts the rotation and vertical movement of the fuel assembly at the same time, and during 360-degree rotation, moves the fuel assembly vertically to an appropriate position according to desired measuring height. During this time, the gamma-ray counting circuit preferably measures either the time average of the count values which have been detected during the rotation and vertical movement of the fuel assembly (i.e., the average counting rate), or the integral value of the counts detected within a fixed time by the detector, and thus derives the burn-up and power distribution of the fuel assembly. (3) In item (1), after the housing has been fixed, the rotating and moving means preferably conducts the rotation and vertical movement of the fuel assembly at the same time, and during 180-degree rotation, moves the fuel assembly vertically to an appropriate position according to desired measuring height. During this time, the gamma-ray counting circuit preferably measures either a time average of any count values which have been detected during the rotation and vertical movement of the fuel assembly (i.e., an average counting rate), or an integral value of any counts detected within a fixed time by the detector, and thus derives a burn-up and power distribution of the fuel assembly. (4) In item (1), the gamma-ray detector is preferably disposed in plurality in a vertical direction and the detectors are installed at desired measuring height in the vertical direction or at an integral multiple of the desired measuring height. (5) In item (1), during the rotation and vertical movement of the fuel assembly, the data collecting/analyzing and controlling apparatus preferably collects, at the same time, data on rotational and vertical positions of the fuel assembly existing at the moving time of day, and data on counting rates of the gamma-ray detector existing at the particular time. (6) In item (1), the burn-up or power distribution of the fuel assembly is preferably derived by using an average counting rate with respect to a burn-up index nuclide or power index nuclide or using an integral value of any count values detected within a fixed time. (7) In item (1), a germanium semiconductor detector or an LaBr3(Ce) scintillation detector is preferably used as the gamma-ray detector. (8) In item (1), preferably, the gamma scanning apparatus further includes collimator driving means that drives a collimator, the collimator being disposed in the gamma scanning apparatus, so as to make height of the collimator variable and to render a distance between the fuel assembly and the detector variable, wherein the collimator driving means makes variable a solid angle at which the fuel assembly is viewed from the detector. (9) In item (1), the shield preferably includes a metal, such as iron or stainless steel, that is placed around the gamma-ray detector in order to shield against characteristic X-rays generated when a heavy metal is irradiated with the gamma rays. In the present invention, the burn-up and power distribution of the fuel assembly is accurately measured not depend on the accuracy of the installation angle of the fuel assembly, and hence, radiation from a number of fuel assemblies is measured within a short time. Hereunder, a configuration and operation of gamma scanning apparatus according to an embodiment of the present invention will be described with reference to FIGS. 1 to 5. An overall configuration of the gamma scanning apparatus according to the present embodiment is first described below with reference to FIG. 1. FIG. 1 is a block diagram showing the overall configuration of the gamma scanning apparatus according to the present embodiment. The gamma scanning apparatus of the present embodiment includes a housing 2, a gamma-ray detector 3, a shield 4, a collimator 5, a collimator driving unit 6, an absorber 7, a fuel assembly moving and rotating unit 8, a gamma-ray counting circuit 9, data collecting/analyzing and controlling apparatus 10, and a moving and fixing mechanism 11. The gamma-ray detector 3, the shield 4, the collimator 5, the collimator driving unit 6, and the absorber 7 are retained inside the housing 2. The collimator 5 limits a measuring range of a fuel assembly 1. The collimator also limits entry of gamma rays from the fuel assembly 1 into the gamma-ray detector 3. Longitudinal and vertical positions of the collimator 5 can be varied by using the collimator driving unit 6. The absorber 7 controls intensity of the gamma rays entering the gamma-ray detector 3. The gamma-ray detector 3 can be a germanium semiconductor detector or an LaBr3(Ce) scintillation detector. The shield 4 shields the gamma-ray detector 3. The shield 4 is a double structure including a shield 4A formed from a metal, such as iron or stainless steel, that is disposed directly on an outer surface of the gamma-ray detector 3, and a shield 4B formed from lead forming an outer surface of the shield 4A. The shield 4A is provided to shield against characteristic X-rays generated when a heavy metal is irradiated with the gamma rays. The fuel assembly 1 has a shape of a quadrangular pillar, with its overall length being about 4 m, for example. The fuel assembly 1 is placed underwater at a water depth of at least 3 m. The moving and fixing mechanism 11 moves the housing 2 and then fixes the housing to a definite position. The moving and fixing mechanism 11 fixes the housing 2 to, for example, a position that is 7 m deep underwater. The fuel assembly moving and rotating unit 8 rotates the fuel assembly 1 and moves the assembly vertically as well. The fuel assembly moving and rotating unit 8 moves an upper end of the fuel assembly 1 vertically to depths of 3-7 m underwater. The gamma-ray counting circuit 9 measures gamma-ray intensity using a detection signal received from the gamma-ray detector 3. Next, a manner in which the fuel assembly moving and rotating unit 8 in the gamma scanning apparatus of the present embodiment moves the fuel assembly 1 is described below with reference to FIG. 2. FIG. 2 is an explanatory diagram of an example in which the fuel assembly moving and rotating unit in the gamma scanning apparatus of the present embodiment moves the fuel assembly. The fuel assembly moving and rotating unit 8, after fixing the fuel assembly 1 to a vertical position, rotates the fuel assembly 1 through 360 degrees with its height kept constant, at a fixed or variable angular velocity. At this time, the fuel assembly moving and rotating unit 8 outputs information on the height, to the data collecting/analyzing and controlling apparatus 10. While rotating the fuel assembly 1, the fuel assembly moving and rotating unit 8 also outputs information on the rotational angle, to the data collecting/analyzing and controlling apparatus 10. During this time, the gamma-ray counting circuit 9 uses the detection signal from the gamma-ray detector 3 to measure a time average of any count values which have been detected during the rotation of the fuel assembly (i.e., an average counting rate), or measure an integral value of any counts detected within a fixed time. After the measurement at the rotational angle of 360 degrees, the fuel assembly moving and rotating unit 8 moves the fuel assembly 1 to an appropriate position in the vertical direction according to desired measuring height. After the movement, the fuel assembly moving and rotating unit 8 once again fixes the fuel assembly 1 to that vertical position (height) and then rotates the fuel assembly 1 through 360 degrees with the height kept constant, at a fixed or variable angular velocity. During this time, the gamma-ray counting circuit 9 uses a new detection signal received from the gamma-ray detector 3, to measure a time average of any count values which have been detected during the rotation of the fuel assembly (i.e., an average counting rate), or measure an integral value of any counts detected within a fixed time. Thus, during the rotation and vertical movement of the fuel assembly 1, data on rotational and vertical positions of the fuel assembly 1 existing at the moving time of day is output from the fuel assembly moving and rotating unit 8 to the data collecting/analyzing and controlling apparatus 10. Data on counting rates of the gamma-ray detector 3 existing at the particular time is also collected at the same time, whereby counting rate data with respect to the rotational and vertical positions of the fuel assembly 1 is then collected. The data collecting/analyzing and controlling apparatus 10 uses the counting rate data to derive burn-up or a power distribution of the fuel assembly 1. After measurement at an rotational angle of 180 degrees, the fuel assembly 1 may be moved vertically for further measurement. The vertical burn-up or power distribution of the fuel assembly is measured by the repetition of the above measuring process. An example of measuring a counting rate of the gamma-ray detector in the gamma scanning apparatus according to the present embodiment is described below with reference to FIG. 3. FIG. 3 is an explanatory diagram of the example in which the gamma scanning apparatus according to the present embodiment measures a counting rate of the gamma-ray detector. FIG. 3 shows the example of measuring a counting rate of the gamma-ray detector 3 for a rotational angle of the fuel assembly 1. Since internal fuel rods of the fuel assembly 1 also serve as a shield against the gamma rays, a gamma-ray counting rate periodically changes according to rotational angle, as shown in FIG. 3. The fuel assembly has a square cross section, so an angle at which one side of the square faces the detector is taken as 0 degrees. Under these conditions, in conventional technology, measurements have been conducted with installation angles of the gamma-ray detector and fuel assembly fixed at, for example, 45 degrees (to obtain a high counting rate) and 225 degrees (by further 180-degree rotation from the 45-degree angle position). In this case, an error dependent upon the installation angle has occurred. In the present embodiment, however, measuring accuracy improves since measurement not dependent upon the installation angle is possible by using the time average of the count values detected during rotation (i.e., an average counting rate), or using the integral value of the counts detected within a fixed time. An example of a method of moving the collimator in the gamma scanning apparatus housing according to the present embodiment is described below with reference to FIGS. 4A to 4C. 4A to 4C are the explanatory diagrams of the example in which the gamma scanning apparatus according to the present embodiment moves the collimator in the housing. FIG. 4A shows an initial position of the collimator 5 inside the housing 2. The collimator driving unit 6 can vary a vertical position of the collimator 5, as shown in FIG. 4B. The collimator driving unit 6 can also move the collimator 5 in a longitudinal direction of the collimator, as shown in FIG. 4C. Hence a solid angle at which the fuel assembly 1 is viewed from the detector 3 can be varied and the measuring range in the fuel assembly 1 and the intensity of the gamma rays therefrom can be controlled. The solid angle is described below with reference to FIG. 4C. Lines in this figure that extend from the detector 3 through the collimator 5 to the fuel assembly 1 denote the solid angle at which the fuel assembly 1 is viewed from the detector 3. As shown in FIG. 4B, the solid angle decreases as the collimator 5 moves close to the fuel assembly 1 from the state of FIG. 4C. As shown in FIG. 4A, the solid angle further decreases as a distance across the vertical section of the collimator 5 is narrowed by vertical movement of the collimator from the state of FIG. 4B. Next, an example of pulse height spectra of the gamma-ray detector in the gamma scanning apparatus of the present embodiment is described below with reference to FIG. 5. FIG. 5 is an explanatory diagram of the example of the pulse height spectra of the gamma-ray detector in the gamma scanning apparatus of the present embodiment. FIG. 5 shows the example of the pulse height spectra of the gamma-ray detector 3. Either a time average of any count values detected during rotation of a burn-up or power distribution index nuclide (i.e., an average counting rate), or an integral value of any counts detected during the rotation within a fixed time is used to derive the burn-up or power distribution. Caesium-137 or caesium-134 is available as an example of a burn-up index nuclide. Barium-140 and lanthanum-140, zirconium-95 and niobium-95, ruthenium-106 and rhodium-106, or the like are available as examples of a power distribution index nuclide. The average counting rate or the integral value of the counts within a fixed time, with respect to the index nuclide, may be derived using counts in a peak area of the index nuclide in gamma-ray spectra or using counts within a certain data range corresponding to energy of the gamma rays released from the index nuclide. As described above, according to the present embodiment, in gamma scanning apparatus that measures the radiation emitted from a fuel assembly at a nuclear power plant and thus measures burn-up and a power distribution of the fuel assembly, the burn-up and the power distribution can be accurately measured not depend on the accuracy of an installation angle of the fuel assembly. Radiation from a number of fuel assemblies can also be measured within a short time. Next, a gamma scanning apparatus configuration according to another embodiment of the present invention is described below with reference to FIG. 6. An overall configuration of the gamma scanning apparatus according to the present embodiment is substantially the same as the configuration shown in FIG. 1. FIG. 6 is an operational explanatory diagram of the gamma scanning apparatus according to the present embodiment. After the housing moving and fixing unit 11 has moved the housing 2 and fixed it to a definite position, the fuel assembly moving and fixing unit 8 simultaneously conducts the rotation of the fuel assembly 1 at a fixed or variable angular velocity and the vertical movement of the fuel assembly at a fixed or variable speed. While the fuel assembly 1 rotates through 360 degrees, the fuel assembly moving and fixing unit 8 moves the fuel assembly vertically to the appropriate position according to desired measuring height. During this time, the gamma-ray counting circuit 9 uses the detection signal from the gamma-ray detector 3 to measure either the time average of the counts detected during the rotation (i.e., the average counting rate), or the integral value of the counts detected within a fixed time. The burn-up or power distribution of the fuel assembly is thus derived. In the above example, the fuel assembly is moved vertically according to the desired measuring height while being rotated through 360 degrees, but the fuel assembly can also be moved vertically according to the desired measuring height while being rotated through 180 degrees. In the present embodiment, there is no need to fix the fuel assembly for each measuring operation at one vertical position, and the measuring time required can therefore be shortened. Next, a gamma scanning apparatus configuration according to yet another embodiment of the present invention is described below with reference to FIG. 7. FIG. 7 is a block diagram showing the gamma scanning apparatus configuration according to the present embodiment. The same reference numbers as used in FIG. 1 denote the same elements. In the present embodiment, a plurality of gamma-ray detectors 3A, 3B and 3C are arranged in the vertical direction and height of each detector is controlled to match desired measuring height or an integral multiple of the desired measuring height. The vertical layout of the gamma-ray detectors allows reduction in the number of vertical fuel-assembly moving and fixing operations after fixing, and hence, reduction in the measuring time required. When fuel assembly rotation at a fixed or variable angular velocity and vertical movement of the fuel assembly at a fixed or variable speed are conducted at the same time, although the layout of the plurality of gamma-ray detectors does not lead to shortening the measuring time, measurement results can be verified since the measurement at the same vertical position (height) can be repeated a plurality of times. |
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051611791 | description | DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment Referring to FIG. 2 and 3 of the drawings, a beryllium window 10 embodying the present invention largely comprises a beryllium plate 11 and a reinforcing frame 13 for retaining the beryllium plate 11. The beryllium plate 11 is mainly composed of beryllium, but any substance containing beryllium as an essential element may be available. In this instance, the beryllium plate 11 is of the order of 25 microns in thickness and has a disk-shaped configuration. A welding film 12 is formed around the outer periphery of the beryllium plate 11, and is of the order of 10 microns in thickness. In this instance, the welding film is formed of nickel, however, one of silver, gold and copper may be used to form the welding film 12. In another implementation, the welding film 12 may be formed of any substance containing more than one elements selected from the group consisting of silver, gold, nickel and copper. The welding film 12 ranges from about 1 micron to about 200 microns in thickness. If the welding film 12 is thinner than about 1 micron, the amount of nickel is too small to achieve a sufficient adhesion. Any welding film more than 200 microns is also undesirable in view of strong welding. The reinforcing frame 13 comprises a retaining member 13a and a pressing member 13b. In this instance, the retaining member 13a is formed of a stainless steel such as, for example, SUS 304 or SUS 430 in the JIS (Japanese Industrial Standards) rules. The retaining member 13a is generally circular in shape, and the inner aperture 13c is smaller in diameter than the beryllium plate 11. The inner peripheral portion of the retaining member 13a is thinner than the outer peripheral portion thereof, and a step configuration takes place between the inner peripheral portion and the outer peripheral portion. The beryllium window 11 is mounted on the retaining member 13a in such a manner that the welding film 12 is held in contact with the inner peripheral portion of the beryllium plate 11. The beryllium plate 11 and, accordingly, the welding film 12 are sandwiched between the retaining member 13a and the pressing member 13b, and the welding film 12 is partially diffused into the retaining member 13a as well as the beryllium plate 11 for welding the beryllium plate 11 to the retaining member 13a. As described hereinbelow in detail in connection with a process sequence, a diffusion welding technique is used for the assembly. The pressing member 13b is also shaped into a ring configuration and has a ring-shaped projection on the inner peripheral portion thereof. The pressing member 13b is larger in diameter than the beryllium plate 11 and smaller than the retaining member 13a. However, the ring-shaped projection has the outer diameter approximately equal to that of the beryllium plate 11. The ring-shaped projection of the pressing member 13b is inserted into the retaining member 13a and provides a protection to the beryllium window 10. Description is hereinbelow made on a process of fabricating a beryllium window according to the present invention with reference to FIGS. 4A to 4F of the drawings. A process sequence starts with preparation of a disk-shaped copper plate 41, and a beryllium film 42 is deposited to a thickness of about 25 microns on the entire surface of the disk-shaped copper plate 41. In this instance, the deposition of the beryllium plate 42 is carried out through a vacuum evaporation of beryllium. The resultant structure of this stage is shown in FIG. 4A. After the deposition of the beryllium film 42, the disk-shaped copper plate 41 is etched away in a solution of nitric acid. The copper-plate 41 is removed from the structure, and, then, the disk-shaped beryllium plate 42 is left as shown in FIG. 4B. An appropriate mask layer 43 is formed on a central portion of the beryllium plate 42 through, for example, lithographic techniques and exposes the outer peripheral portion of the beryllium plate 42. Silver is deposited to a thickness of about 20 microns on the entire surface of the structure by using, for example, a vacuum evaporation technique as shown in FIG. 4C. However, the silver film may be deposited through another vapor-phase deposition technique, and the vapor-phase deposition includes both physical and chemical vapor-phase deposition techniques. The mask layer 43 is stripped off so that only a ring-shaped silver film 44 is left on the outer peripheral portion of the beryllium plate 42 as shown in FIG. 4D. The ring-shaped silver film 44 serves as a welding film. The beryllium film 42 is placed on a retaining member 45 in such a manner that the ring-shaped silver film 44 is held in contact with the inner peripheral portion of the retaining member 45. The beryllium film 42 thus mounted on the retaining member 45 is placed in a vacuum ambience of about 10.sup.-5 torr at about 650 degrees in centigrade. The beryllium plate 42 and, accordingly, the ring-shaped silver film 44 are pressed at 10 kg/mm.sup.2 against the inner peripheral portion of the retaining member 45 with, for example, a suitable plunger 46 for about 30 minutes as shown in FIG. 4E. The silver atoms are diffused into the beryllium plate 42 as well as into the retaining member 45, and the welding film 44 is merged into the outer peripheral portion of the beryllium plate 42 and into the inner peripheral portion of the retaining member 45. In other words, the beryllium plate 42 is welded to the retaining member 45. In this instance, the pressure exerted on the beryllium plate 42 is adjusted to about 10 kg/mm.sup.2, however, the pressure may range from about 1 kg/mm.sup.2 to about 100 kg/mm.sup.2. If the pressure is lower than about 1 kg/mm.sup.2, the diffusion welding hardly takes place between the beryllium plate 42 and the retaining member 45. A pressure larger than 100 kg/mm.sup.2 is causative of undesirable deformation of the outer peripheral portion of the beryllium plate 42 and the inner peripheral portion of the retaining member 45. The vacuum ambience is preferably heated at about 300 degrees to 900 degrees in centrigrade. A vacuum ambience lower than 300 degrees in centigrade is not high enough to diffuse the silver, and the diffusion of silver is excessively promoted in a vacuum ambience higher than 900 degrees in centigrade. Such an excessive diffusion deteriorates the mechanical strength at the welded spot between the beryllium plate 42 and the retaining member 45. In this instance, the beryllium plate 42 is maintained for 30 minutes. However, the time period may range between 30 minutes and 120 minutes. If the time period is shorter than 30 minutes, any sufficient diffusion welding is hardly achieved. Even though the time period exceeds 120 minutes, no substantial improvement of welding is hardly achieved, and, therefore, such a long time period is too expensive in view of the production cost. The vacuum ambience may be fallen within a range between 10.sup.-2 torr and 10.sup.-6 torr. If the pressure of a vacuum ambience is greater than 10.sup.-2 torr, the surface of the beryllium plate 42 and the surface of the welding film 44 are rapidly oxidized, and the oxide films suppresses the diffusion of silver. A vacuum ambience less than 10.sup.-6 requests the manufacturer an expensive evacuation system, and the expensive evacuation system increases the production cost of the beryllium window. The beryllium plate 42 thus welded to the retaining member 45 is taken out from the vacuum chamber, and a pressing member 47 is inserted into the retaining member 45 as shown in FIG. 4F so as to provide an appropriate protection to the beryllium plate 42. In this instance, the retaining member 45 and the pressing member 47 form in combination a reinforcing unit. The melting point of silver is as high as about 960 degrees in centigrade, and, for this reason, the beryllium window according to the present invention well withstands a baking treatment at 200 degrees to 400 degrees. Since the beryllium plate 42 is welded to the retaining member 45 through the diffusion of the welding substance, the beryllium plate 42 is fixed to the retaining member 45 in a low temperature process, and the beryllium plate 42 is not subjected to a serious heat impact. For this reason, the mechanical strength of the beryllium plate 42 is not deteriorated, and the beryllium plate 42 incorporated in the beryllium window according to the present invention is less deformative. This results in an extremely thin beryllium plate with a large transmissibility without sacrifice of mechanical strength, and, therefore, the beryllium window equipped with the beryllium plate is preferable to an x-ray radiation system such as, for example, an x-ray aligner. Moreover, the welding film 44 is deposited on the beryllium plate 42 through the vacuum evaporation, and such a low-temperature vapor-phase deposition less damages the beryllium plate 42. This also improves the properties of the beryllium plate and, accordingly, the beryllium window according to the present invention. As will be understood from the foregoing description, the beryllium window according to the present invention is improved in transmissibility without sacrifice of the mechanical strength, because the beryllium plate is hardly damaged in the diffusion welding. Second Embodiment The second embodiment is featured by a fabrication process, but the final structure is similar to that of the first embodiment. No further description on the structure is incorporated hereinbelow. The second process sequence traces the steps shown in FIGS. 4A to 4B as well as FIGS. 4E and 4F, however, a step shown in FIG. 5 is inserted between the steps shown in FIGS. 4B and 4E instead of the steps shown in FIGS. 4C and 4D. Namely, a welding film 51 is formed on the inner peripheral portion of the retaining member 45, and a foil-shaped welding substance may be used for formation of the welding film 51. The welding substance also contains one or more than one elements selected from the group consisting of silver, gold, nickel and copper. After the formation of the welding film 51, the beryllium plate 42 is inserted into the retaining member 45 and pressed against the welding film 51. In a high-temperature vacuum ambience, the welding film 51 welds the beryllium plate 42 to the retaining member 45 through diffusion of the welding substance into both of the beryllium plate 42 and the retaining member 45. The beryllium window thus fabricated is also thin enough to transmit an x-ray without sacrifice of mechanical strength as similar to the first embodiment described hereinbefore. Although particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the present invention. For example, the beryllium plate 11 may be formed of a beryllium alloy in, for example, the Be--Al system, the Be--Si system, the Be--Ni system or the Be--Li system. |
063339617 | claims | 1. A reflection mask for use in microlithography, the reflection mask comprising: a multilayer mirror that reflects incident electromagnetic radiation of a prescribed wavelength; and an absorptive layer superposed on the multilayer mirror, the absorptive layer defining elements of a pattern defined by the mask, wherein the multilayer mirror has a thickness period, through a thickness dimension of the multilayer mirror, that varies through the thickness dimension. providing a reflection mask as recited in claim 1; illuminating the reflection mask with the illumination light; and passing the reflected illumination light through an imaging-optical system to as to form an image of the pattern on the substrate. an illumination-optical system situated and configured to irradiate electromagnetic radiation from a source onto a reflection mask, the reflection mask defining a pattern to be projected onto a substrate; an imaging-optical system situated and configured to direct portions of the electromagnetic radiation reflected from the reflection mask to the substrate so as to form an image of the pattern on the substrate; and the reflection mask comprising a multilayer mirror that reflects a prescribed wavelength of the electromagnetic radiation and an absorber layer, superposed on the multilayer mirror, that absorbs the electromagnetic radiation and defines elements of the pattern, the multilayer mirror having a thickness period, through a thickness dimension of the multilayer mirror, that varies through the thickness dimension. the electromagnetic radiation comprises soft X-rays; and the multilayer mirror of the reflection mask is reflective to the soft X-rays. 2. The reflection mask of claim 1, wherein the electromagnetic radiation comprises soft-X-rays. 3. The reflection mask of claim 1, wherein the multilayer mirror is formed by laminating multiple blocks of multilayer, each block having a different thickness period. 4. The reflection mask of claim 3, wherein one layer of each multilayer includes silicon, and another layer of each multilayer includes molybdenum. 5. The reflection mask of claim 1, wherein the multilayer mirror is formed by laminating multiple multilayers superposedly such that the multilayer mirror has a thickness period that varies progressively with distance through a thickness dimension of the multilayer. 6. The reflection mask of claim 5, wherein one layer of each multilayer includes silicon, and another layer of each multilayer includes molybdenum. 7. In a method for performing microlithography of a pattern, defined by a reflection mask, onto a substrate, a method for reducing adverse effects on linewidth of the pattern, as transferred to the substrate, caused by a non-uniformity of reflection of illumination light from the reflection mask, the method comprising: 8. A microlithography apparatus, comprising: 9. The apparatus of claim 8, wherein: 10. In a method for manufacturing an integrated circuit, a microlithography step in which a circuit pattern, defined on a mask, is transferred to a wafer to form the circuit pattern on the wafer, the microlithography step being performed using a reflection mask comprising a multilayer mirror that reflects a prescribed wavelength of electromagnetic radiation and an absorber layer, superposed on the multilayer mirror, that absorbs the electromagnetic radiation and defines elements of the pattern, the multilayer mirror having a thickness period, through a thickness dimension of the multilayer mirror, that varies through the thickness dimension. 11. The method of claim 10, wherein the electromagnetic radiation comprises soft X-rays. |
abstract | A method and apparatus to provide evidence that a person who is intended to make a required inspection was actually physically present at a predefined location associated with the inspection, so that the inspection could have been done, and if not, to provide an indication of the failure to perform the inspection. This invention is particularly well suited to determine if required pre/post-trip inspections of vehicles have been performed. Detecting a triggering condition, such as powering on (or off) equipment, indicates the beginning of a period of time during which the inspection is to be performed. The monitoring system waits for a predetermined event to occur, which indicates the period of time has expired and determines if data corresponding to the inspection have been received. If not, it is concluded that the inspection has not been performed. |
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abstract | Radiation shields and techniques for radiation shielding are provided. Bitumen substances, such as asphalt or tar, are mixed with radioactive waste, leaded glass, or a radioactive waste and leaded glass composite. In embodiments where the bitumen substance is mixed with leaded glass, the resulting mixture can be coated onto containers that house radioactive waste or the resulting mixture can be coated onto the outer surface of the radioactive waste. |
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abstract | A protective garment for a fire fighter or emergency worker is provided. The protective garment includes an outer shell and a drag harness located at least substantially within the outer shell. The drag harness includes a wearer portion, a gripping portion and a flap operably coupled to the gripping portion. The flap is releasably secured to the outer shell in a stored state. The flap and the gripping portion remaining operably coupled to one another and extend away from the outer shell in a deployed state to drag a wearer. |
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description | This application is a continuation of International Application No. PCT/CN2017/092442, filed on Jul. 11, 2017, which claims priority to Chinese Patent Application No. 201610966285.3, filed on Oct. 28, 2016 and Chinese Patent Application No. 201621187821.1, filed on Oct. 28, 2016, the disclosures of which are hereby incorporated by reference. The present disclosure relates to a beam shaping assembly, and, more particularly, to a beam shaping assembly for neutron capture therapy. As atomics moves ahead, such radiotherapy as Cobalt-60, linear accelerators and electron beams has been one of major means to cancer therapy. However, conventional photon or electron therapy has been undergone physical restrictions of radioactive rays; for example, many normal tissues on a beam path will be damaged as tumor cells are destroyed. On the other hand, sensitivity of tumor cells to the radioactive rays differs greatly, so in most cases, conventional radiotherapy falls short of treatment effectiveness on radioresistant malignant tumors (such as glioblastoma multiforme and melanoma). For the purpose of reducing radiation damage to the normal tissue surrounding a tumor site, target therapy in chemotherapy has been employed in the radiotherapy. While for high-radioresistant tumor cells, radiation sources with high RBE (relative biological effectiveness) including such as proton, heavy particle and neutron capture therapy have also developed. Among them, the neutron capture therapy combines the target therapy with the RBE, such as the boron neutron capture therapy (BNCT). By virtue of specific grouping of boronated pharmaceuticals in the tumor cells and precise neutron beam regulation, BNCT is provided as a better cancer therapy choice than conventional radiotherapy. BNCT takes advantage that the boron (10B)-containing pharmaceuticals have high neutron capture cross section and produces 4He and 7Li heavy charged particles through 10B(n,α)7Li neutron capture and nuclear fission reaction. As illustrated in FIGS. 1 and 2, a schematic drawing of BNCT and a nuclear reaction formula of 10B (n, α)7Li neutron capture are shown, the two charged particles, with average energy at about 2.33 MeV, are of linear energy transfer (LET) and short-range characteristics. LET and range of the alpha particle are 150 keV/micrometer and 8 micrometers respectively while those of the heavy charged particle 7Li are 175 keV/micrometer and 5 micrometers respectively, and the total range of the two particles approximately amounts to a cell size. Therefore, radiation damage to living organisms may be restricted at the cells' level. When the boronated pharmaceuticals are gathered in the tumor cells selectively, only the tumor cells will be destroyed locally with a proper neutron source on the premise of having no major normal tissue damage. In the process of neutron capture therapy, the generation of neutrons and the changes of the neutron energy spectrum in the beam shaping assembly tend to produce a large number of gamma rays. The gamma rays have a strong penetrating ability. When the human body is exposed to the gamma rays, the gamma rays can enter the interior of the body and ionize with cells of the body. Ionization-generated ions can erode complex organic molecules, such as proteins, nucleic acids and enzymes, which are the main components constituting the living cell tissues. Once they are destroyed, it can cause normal chemical processes in the human body to be disturbed, even cause the death of cells in severe cases. It has not been found in the prior art to change the beam shaping assembly to reduce the gamma ray content in the neutron beam under the premise that the neutron beam quality is not affected. The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. In order to reduce the gamma ray content in the neutron beam during neutron capture therapy, one aspect of the present disclosure provides a beam shaping assembly for neutron capture therapy, the beam shaping assembly includes a neutron generating device, a moderator, a disturbing unit and a beam outlet. The neutron generating device is housed within the beam shaping assembly for generating neutrons that form a neutron beam in a direction from the neutron generating device to the beam outlet, the neutron beam defines a beam axis. The moderator is adjacent to the neutron generating device for moderating fast neutrons in the neutron beam to epithermal neutrons. Wherein the beam shaping assembly produces gamma rays in the process of adjusting the neutron beam energy spectrum, the disturbing unit is located between the moderator and the beam outlet for passing through the neutron beam and reducing the gamma ray content in the neutron beam passing through the beam outlet. Accordingly, the disturbing unit is located between the moderator and the beam outlet for passing the neutron beam therethrough and reducing the gamma ray content in the neutron beam passing through the disturbing unit under the premise of minimal influence on the neutron energy. The present disclosure uses the ratio of gamma rays in the neutron beam to the neutron beam flux to evaluate the effects of addition of the disturbing unit and using use of different materials of the disturbing units on the gamma rays. The present disclosure uses the advantage depth, the advantage dose rate, and the 30 RBE-Gy treatable depth in the phantom beam quality to evaluate the effects of addition of the disturbing unit and use different materials of the disturbing units on the neutron beam. The effect of the disturbing unit on the absorption and reflection of the gamma rays is also related to the material constituting the disturbing unit. Preferably, in the beam shaping assembly for neutron capture therapy, the material of the disturbing unit is selected from the group consisting of rhenium, hafnium, lutetium, lead, cerium, zinc, bismuth, terbium, indium, antimony, gallium, lanthanum, tellurium, tin, selenium, yttrium, aluminum, strontium, barium, silicon, zirconium, rubidium, calcium, sulfur, iron, carbon, beryllium, magnesium, phosphorus, chromium, lithium, sodium, nickel element and combinations thereof. Furthermore, in the beam shaping assembly for neutron capture therapy, the internal structure of the disturbing unit is a dense structure or a porous structure. The porous structure is called relative to the dense structure, which means that the interior of the disturbing unit is not tight and compact, and the solid material that constitutes the disturbing unit is a complete whole with a plurality of pores inside thereof, for example, a honeycomb structure or an internal hollow structure. The density of the porous structure is less than the density of the dense structure. Further, in the beam shaping assembly for neutron capture therapy, the disturbing unit is a cylinder and the axis of the cylinder coincides or is parallel to the beam axis. The size of the cylinder is preferably such that the radius of the bottom surface of the cylinder is 5 to 6 cm, and the height of the cylinder is 3 to 5 cm. In a preferred embodiment, the disturbing unit having such size and shape is placed in a beam shaping assembly with a height of 80 to 100 cm and a radius of the bottom surface of 60 to 70 cm, and significantly reduces the gamma ray content by comparison with the beam shaping assembly to which the disturbing unit is not added. Certainly, it is well known to those skilled in the art that placing the disturbing unit in the beam shaping assembly with other shapes or sizes also significantly reduces the gamma ray content, as will be detailed below. Preferably, in the beam shaping assembly for neutron capture therapy, the moderator and the disturbing unit are externally surrounded by a reflector. The reflector is used for reflecting the neutrons deviating from the neutron beam back to the neutron beam to enhance the neutron beam intensity. The reflector is made of a material having a strong neutron reflection ability, preferably at least one of lead or nickel. When the gamma rays encounters a substance, there is a photoelectric effect, a Compton effect, and an electron pair effect, which cause a certain degree of attenuation. When gamma rays in a neutron beam encounter the disturbing unit, the disturbing unit reduces the gamma ray content in the neutron beam by absorbing gamma rays through photoelectric effect, scattering gamma rays through Compton effect, or converting gamma rays into positive and negative electron pairs through electron pair effect, respectively, and the gamma rays scattered by the disturbing unit is further attenuated by reabsorption or reflection after encountering the reflector. Preferably, in the beam shaping assembly for neutron capture therapy, when the disturbing unit is made of any single element of rhenium, hafnium, lutetium, lead, cerium, zinc, bismuth, terbium, indium or antimony, the proportion of gamma rays in the neutron beam is reduced by at least 30%, which means that the ratio of gamma rays in the neutron beam to the neutron beam flux is reduced by at least 30%. It can be seen that the above element can effectively reduce the gamma ray content in the neutron beam when it is used as a disturbing unit. Further, in the beam shaping assembly for neutron capture therapy, when the material of the disturbing unit is selected from the group consisting of rhenium, hafnium, lutetium, lead, cerium, zinc, bismuth, terbium, indium, antimony, gallium, lanthanum, tellurium, tin, selenium, yttrium, aluminum, strontium, barium, silicon, zirconium, rubidium, calcium, sulfur, iron, carbon, beryllium, magnesium, phosphorus, chromium, lithium, sodium, nickel element and combinations thereof, in the phantom beam quality of the neutron beam passing through the disturbing unit, the advantage depth is ≥10.69 cm, the advantage dose rate is ≥5.54, and the 30 RBE-Gy treatable depth is ≥6.77 cm. Neutron beam quality plays a crucial role in the treatment effect during the process of neutron capture therapy. Another aspect of the present disclosure is to reduce the gamma ray content in the neutron beam under the premise that the quality of the neutron beam is not significantly adversely affected. When the advantage depth is greater than or equal to 10 cm, the advantage dose rate is greater than or equal to 5.5, the 30 RBE-Gy treatable depth is greater than or equal to 6.5 cm, the therapeutic effect is good. Preferably, the advantage depth is ≥10.69 cm, and the advantage dose rate is ≥5.54, and the 30 RBE-Gy treatable depth is ≥6.77 cm. In another aspect of the present disclosure provides a beam shaping assembly for neutron capture therapy, including: a neutron generating device housed within the beam shaping assembly for generating neutrons, wherein neutrons form a neutron beam in a direction from the neutron generating device to the beam outlet, the neutron beam defines a beam axis; a moderator adjacent to the neutron generating device for moderating fast neutrons in the neutron beam to epithermal neutrons; a reflector surrounding the moderator and the disturbing unit for reflecting the neutrons deviating from the neutron beam back to the neutron beam to enhance the neutron beam intensity; a disturbing unit; and a beam outlet; wherein the beam shaping assembly produces gamma rays in the process of adjusting the neutron beam energy spectrum, the disturbing unit is located after the neutron generating device for passing through the neutron beam and reducing the gamma ray content in the neutron beam passing through the beam outlet. More particularly, the material of the disturbing unit is selected from the group consisting of rhenium, hafnium, lutetium, lead, cerium, zinc, bismuth, terbium, indium, antimony, gallium, lanthanum, tellurium, tin, selenium, yttrium, aluminum, strontium, barium, silicon, zirconium, rubidium, calcium, sulfur, iron, carbon, beryllium, magnesium, phosphorus, chromium, lithium, sodium, nickel element and combinations thereof. More particularly, the internal structure of the disturbing unit is a dense structure or a porous structure. More particularly, when the neutron beam containing gamma rays passes through the disturbing unit, the disturbing unit reduces the gamma ray content in the neutron beam by absorbing gamma rays through photoelectric effect, scattering gamma rays through Compton effect, or converting gamma rays into positive and negative electron pairs through electron pair effect, respectively, and the gamma rays scattered by the disturbing unit is further attenuated by reabsorption or reflection after encountering the reflector. More particularly, the disturbing unit is a cylinder defining an axis and the axis of the cylinder coincides or is parallel to the beam axis. In yet another aspect of the present disclosure provides a beam shaping assembly for neutron capture therapy, including: a neutron generating device housed within the beam shaping assembly for generating neutrons, wherein neutrons form a neutron beam in a direction from the neutron generating device to the beam outlet, the neutron beam defines a beam axis; a moderator adjacent to the neutron generating device for moderating fast neutrons in the neutron beam to epithermal neutrons; a disturbing unit; and a beam outlet; wherein the beam shaping assembly produces gamma rays in the process of adjusting the neutron beam energy spectrum, the disturbing unit defines an axis and the axis of the disturbing unit coincides or is parallel to the beam axis for passing through the neutron beam and reducing the gamma ray content in the neutron beam passing through the beam outlet, the internal structure of the disturbing unit is a porous structure. More particularly, the material of the disturbing unit is selected from the group consisting of rhenium, hafnium, lutetium, lead, cerium, zinc, bismuth, terbium, indium, antimony, gallium, lanthanum, tellurium, tin, selenium, yttrium, aluminum, strontium, barium, silicon, zirconium, rubidium, calcium, sulfur, iron, carbon, beryllium, magnesium, phosphorus, chromium, lithium, sodium, nickel element and combinations thereof. More particularly, the beam shaping assembly further includes a reflector surrounding the moderator and the disturbing unit for reflecting the neutrons deviating from the neutron beam back to the neutron beam to enhance the neutron beam intensity, and wherein the reflector is made of a material having a strong neutron reflection ability. More particularly, when the neutron beam containing gamma rays passes through the disturbing unit, the disturbing unit reduces the gamma ray content in the neutron beam by absorbing gamma rays through photoelectric effect, scattering gamma rays through Compton effect, or converting gamma rays into positive and negative electron pairs through electron pair effect, respectively, and the gamma rays scattered by the disturbing unit is further attenuated by reabsorption or reflection after encountering the reflector. More particularly, the disturbing unit is a cylinder, the radius of the bottom surface of the cylinder is 5 to 6 cm, and the height of the cylinder is 3 to 5 cm. The shape, structure, and material of the disturbing unit mentioned in the present disclosure are not limited to those defined by the above preferred technical solutions, and any disturbing unit placed in the beam shaping assembly is within the scope of the present disclosure as long as it satisfies the ability to reduce the gamma ray content in the neutron beam without significantly adversely affecting the quality of the neutron beam. Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. The present disclosure will now be described in further detail with reference to the accompanying drawings in order to enable those skilled in the art to practice with reference to the specification. The following description of the preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. Neutron capture therapy (NCT) has been increasingly practiced as an effective cancer curing means in recent years, and BNCT is the most common. Neutrons for NCT may be supplied by nuclear reactors or accelerators. Take AB-BNCT for example, its principal components comprise, in general, an accelerator for accelerating charged particles (such as protons and deuterons), a target, a heat removal system and a beam shaping assembly. The accelerated charged particles interact with the metal target to produce the neutrons, and suitable nuclear reactions are always determined according to such characteristics as desired neutron yield and energy, available accelerated charged particle energy and current and materialization of the metal target, among which the most discussed two are 7Li (p, n) 7Be and 9Be (p, n)9B and both are endothermic reaction. Their energy thresholds are 1.881 MeV and 2.055 MeV respectively. Epithermal neutrons at a keV energy level are considered ideal neutron sources for BNCT. Theoretically, bombardment with lithium target using protons with energy slightly higher than the thresholds may produce neutrons relatively low in energy, so the neutrons may be used clinically without many moderations. However, Li (lithium) and Be (beryllium) and protons of threshold energy exhibit not high action cross section. In order to produce sufficient neutron fluxes, high-energy protons are usually selected to trigger the nuclear reactions. The ideal target should have these characteristics of high neutron yield, produced neutron energy distribution close to the epithermal neutron energy zone (described in detail below), no excessively strong radiation generation, safety, inexpensive, easy to operate, and high temperature resistance. However, it is practically impossible to find a nuclear reaction that meets all the requirements. A target made of lithium metal is used in the embodiments of the present disclosure. However, it is well known to those skilled in the art that the target can also be made of other metal materials other than the metal materials discussed above. Regardless of whether the neutron source of the boron neutron capture therapy come from the nuclear reactor or the nuclear reaction of the charged particles accelerated by an accelerator and the target, a mixed radiation field is generated, i.e., the beam contains low-to-high energy neutrons and photons. The boron neutron capture therapy for deep tumors, except for epithermal neutrons, the greater the amount of rest of the radiation is, the greater the proportion of non-selective dose deposition in normal tissue is, so these radiation which will cause unnecessary doses should be minimized. The International Atomic Energy Agency (IAEA) has given recommendations for the air beam quality factors for neutron sources for clinical boron neutron capture therapy. The recommendations can be used to differentiate the neutron sources and as reference for selecting neutron production pathways and designing the beam shaping assembly. Wherein, the recommendation for photon contamination: photon contamination <2×10−13 Gy-cm2/n. Photon contamination is also called gamma-ray contamination. The gamma ray belonging to long-range penetration radiation will non-selectively cause dose deposit of all tissues in beam path, so that lowering the quantity of gamma ray is also the exclusive requirement in the neutron source design. Gamma ray dose accompanied per unit epithermal neutron flux is defined as gamma ray contamination which is suggested being less than 2×10-13 Gy-cm2/n. Note: the epithermal neutron energy range is between 0.5 eV and 40 keV, the thermal neutron energy range is lower than 0.5 eV, and the fast neutron energy range is higher than 40 keV. In addition to the air beam quality factors, in order to better understand the neutron dose distribution in the human body, the human head tissue prosthesis is used for dose calculation in the embodiments of the present disclosure, and beam quality factors of the prosthesis are used as references for the design of the neutron beam, which will be described in detail below. The dose distribution in the tissue is obtained using a prosthesis, and, the phantom beam quality factors are derived based on the dose-depth curves of the normal tissue and the tumor. The following two parameters can be used to compare the benefits of different neutron beam treatments. 1. Advantage Depth (AD) Tumor dose is equal to the maximum dose of the normal tissue. At a position behind this depth, the dose received by the tumor cells is less than the maximum dose of the normal tissue, that is, the advantage of boron neutron capture is lost. The advantage depth represents the penetrability of the neutron beam, wherein the larger the advantage depth is, the larger the treatable tumor depth is, and the unit is cm. 2. Advantage Dose Rate (AR) From the brain surface to the advantage depth, the average dose rate received by tumor and normal tissues is called the advantage dose rate. The calculation of average dose can be obtained by integrating the dose-depth curve. The greater the advantage dose rate is, the better the therapeutic effect of the neutron beam is. In order to provide a comparative basis for the design of beam shaping assembly, the following parameters are used to evaluate the performance of neutron beam dose in the embodiments of the present disclosure: 1. 30.0 RBE-Gy treatable depth ≥7 cm; 2. AD≥10 cm; 3. AR≥5.5. Note: RBE represents relative biological effectiveness. Because the biological effectiveness caused by photons and neutrons are different, the above dose should be respectively multiplied with the relative biological effectiveness of the different tissues to obtain the equivalent dose. The present disclosure will be described in further detail with reference to the accompanying drawings. The beam shaping assembly 100 for neutron capture therapy as shown in FIG. 1 includes a neutron generating device 110, a moderator 120, a disturbing unit 130, a beam outlet 140, and a reflector 150. Wherein the neutron generating device 110 is classified into a nuclear reactor type neutron generating device and an accelerator type neutron generating device. Although the two types of neutron generating devices have different mechanisms for generating neutrons, a large number of strong penetrating gamma rays are accompanied in the process of neutron production. The neutrons generated by the neutron generating device converge into a neutron beam 160, and the center line of the neutron beam 160 is defined as a neutron axis X. Since the neutron beam 160 generated from the neutron generating device includes not only the epithermal neutrons required for the treatment, but also radiation such as fast neutrons, thermal neutrons, and gamma rays that cause damage to the patient, the neutron beam 160 needs to be filtered by the moderator 120. The function of the moderator 120 is to moderate the fast neutrons in the neutron beam 160 to an epithermal neutron energy region. During the process of moderating of the moderator 120, the neutrons will deviate from the onward direction of the neutron beam 160 and spread to the periphery, and the reflector 150 is used to reflect neutrons that diffuse around back to the neutron beam 160 to enhance the intensity of the neutron beam 160. The reflector 150 is mainly made of a substance having a strong neutron reflection ability such as lead or nickel. The disturbing unit 130 is located between the moderator 120 and the beam outlet 140, and the axis of the disturbing unit 130 is parallel or coincides with the neutron axis X. The material of the disturbing unit 130 is selected from the group consisting of rhenium, hafnium, lutetium, lead, cerium, zinc, bismuth, terbium, indium, antimony, gallium, lanthanum, tellurium, tin, selenium, yttrium, aluminum, strontium, barium, silicon, zirconium, rubidium, calcium, sulfur, iron, carbon, beryllium, magnesium, phosphorus, chromium, lithium, sodium, nickel element and combinations thereof. The disturbing unit 130 may be a cuboid, a cube, a sphere, a cylinder or an irregular shape of a small volume to satisfy the ability to reduce the gamma ray content in the neutron beam without significant negative impact to the quality of the neutron beam. The disturbing unit 130 in the beam shaping assembly 100 shown in FIG. 1 is a cylinder. The drawing of the cylinder is only for demonstrating the technical solutions of the present disclosure, and does not limit the technical solutions to be protected by the present disclosure. The neutron beam 160 passes through the disturbing unit 130, wherein the gamma rays are absorbed, reflected or scattered by the disturbing unit 130 to reduce the gamma ray content in the neutron beam 160. In addition, the gamma rays reflected or scattered by the disturbing unit 130 deviates from the neutron beam and irradiates onto the reflector 150, and the gamma rays undergo the Compton effect, the photoelectric effect or the electron pair effect under the action of the reflector 150 to be further attenuated, and the neutron beam 160 exits the beam shaping assembly 100 from the beam outlet 140 after the gamma rays are filtered. FIG. 3 is a schematic view of a beam shaping assembly comprising a cylindrical moderator, which has the same principle in the process for neutron capture therapy as the beam shaping assembly comprising a diamond-shaped moderator shown in FIG. 1. The beam shaping assembly 200 comprises a neutron generating device 210, a moderator 220, a disturbing unit 230, a beam outlet 240, and a reflector 250. The center line of the neutron beam is defined as a neutron axis Y, wherein the moderator 220 is a cylinder. FIG. 3 is a schematic cross-sectional view of a cylindrical moderator. The attenuation of gamma rays is not only related to the material of the disturbing unit, but also related to the structure and shape of the disturbing unit. The disturbing units are classified into a disturbing unit with dense structure and a disturbing unit with porous structure according to the differences of the structures. Under normal circumstances, the shielding effect on the gamma ray of the disturbing unit with dense structure is better than that of the disturbing unit with porous structure. FIG. 2 is a schematic cross-sectional view of a cylindrical disturbing unit 130. The material 131 constituting the disturbing unit 130 is a complete whole with a plurality of pores 132 inside thereof. Although the disturbing unit with the porous structure is less effective at shielding gamma rays than the disturbing unit with the dense structure, it requires relatively few materials. In the economic sense, when there is not much requirement for the attenuation of gamma rays in the neutron beam, the disturbing unit with the porous structure not only satisfy the requirement of reducing the gamma ray content in the neutron beam, but also has no significant adverse influence on the quality of the neutron beam. The beneficial effects of the technical solution of the present disclosure are further described below by way of embodiments. The gamma ray attenuation and neutron beam quality in this present embodiment are calculated by MCNP software (which is a general-purpose software package for calculating neutrons, photons, charged particles or coupled neutron/photon/charged particle transport problems in three-dimensional complex geometries based on Monte Carlo method developed by the Los Alamos National Laboratory, US). Wherein, in this embodiment, the disturbing unit in the beam shaping assembly is a cylinder having a porous structure as shown in FIGS. 1 and 2 and the moderator in the beam shaping assembly is composed of 85% magnesium fluoride and 15% lithium fluoride. The moderator is a diamond shape as shown in FIG. 1. The diamond-shaped moderator is composed of a first cone portion and a second cone portion, and the first cone portion adjacent to the second cone portion, and the outer contours of the two cones are tilted in opposite directions as shown in FIG. 1. Wherein, the height of the cylindrical disturbing unit was 10 cm, the radius of the bottom circular surface was 5 cm, and the disturbing unit is located between the moderator and the beam outlet. The influence of the disturbing unit on the neutron beam quality and the shielding effect on the gamma rays under the above conditions are shown in Table 1. TABLE 1Influence of cylindrical disturbing unit with a radius of the bottom surfaceof 5 cm and a height of 10 cm on neutron beam quality and shieldingeffect on gamma raysNeutron beam qualityMaterial ofGamma ray content30 RBE-Gydisturbingin neutron beamAdvantageAdvantagetreatableunit(Gy * cm2/n)depth (cm)dose ratedepth (cm)rhenium4.15 * 10−1410.825.677.35hafnium4.33 * 10−1410.795.667.34lutetium4.59 * 10−1410.835.657.33lead4.60 * 10−1410.795.697.40cerium4.79 * 10−1410.735.677.37zinc4.81 * 10−1410.765.697.42bismuth4.86 * 10−1410.805.677.40terbium5.03 * 10−1410.865.667.37indium5.24 * 10−1410.765.677.32antimony5.26 * 10−1410.785.677.38gallium5.29 * 10−1410.755.667.41lanthanum5.30 * 10−1410.765.667.37tellurium5.31 * 10−1410.725.667.37tin5.38 * 10−1410.805.677.42selenium5.41 * 10−1410.735.667.34yttrium5.78 * 10−1410.775.677.42aluminum6.36 * 10−1410.765.677.40strontium6.54 * 10−1410.825.647.37barium6.54 * 10−1410.745.657.35silicon6.73 * 10−1410.805.657.34zirconium6.78 * 10−1410.835.667.41rubidium7.06 * 10−1410.785.657.27calcium7.33 * 10−1410.735.637.26sulfur7.40 * 10−1410.755.647.31iron7.49 * 10−1410.755.657.36carbon7.59 * 10−1410.765.677.43beryllium7.71 * 10−1410.735.677.43magnesium7.81 * 10−1410.825.667.41phosphorus7.81 * 10−1410.705.667.35chromium8.15 * 10−1410.765.657.37lithium8.61 * 10−1410.795.627.30sodium8.69 * 10−1410.805.647.36nickel8.73 * 10−1410.695.667.43 The disturbing unit is not provided in the comparative example of the present example, and the remaining parameters of the comparative example is the same as those of the beam shaping assembly in the above embodiment. In the neutron beam of the comparative example, the gamma ray content is 8.78*10-14Gy*cm2/n, the advantage depth is 10.74 cm, the advantage dose rate is 5.61, and the treatment depth of 30RBE-Gy is 7.27 cm. By comparison, it is found that the disturbing units made of 33 kinds of single elements in the present embodiment had no obvious negative influence on the neutron beam quality of the beam shaping assembly, and the advantage depth (AD) values all are 10.74±0.12, the advantage dose rate (AR) values are 5.6±0.09, and the 30 RBE-Gy treatable depth are 7.3±0.13. And the gamma ray contents in the neutron beams were reduced to varying degrees. In the present embodiment, the disturbing unit is a cylinder with a compact structure, wherein the radius of the bottom surface of the cylinder is 6 cm, and the height of the cylinder is 3 cm. The other conditions are the same as those in Embodiment 1. When lead, antimony, nickel, aluminum and carbon are used as the disturbing units respectively, the disturbing units on the neutron beam quality and shielding effect on gamma rays are calculated by MCNP software. The results are shown in Table 2: TABLE 2Influence of cylindrical disturbing unit with compact structure with aradius of the bottom surface of 6 cm and a height of 3 cm on the neutronbeam quality and shielding effect on gamma rays of magnesium fluorideand lithium fluoride as moderatorNeutron beam qualityMaterial ofGamma ray content30 RBE-Gydisturbingin neutron beamAdvantageAdvantagetreatableunit(Gy * cm2/n)depth (cm)dose ratedepthlead5.58 * 10−1410.755.647.33bismuth6.03 * 10−1410.725.647.33nickel7.33 * 10−1410.735.647.33aluminum8.09 * 10−1410.745.637.33carbon8.36 * 10−1410.725.627.34 The principles of different materials used as disturbing units to shield gamma rays are the same. Therefore, in the present embodiment, only lead, antimony, nickel, aluminum and carbon are randomly selected as the disturbing unit to illustrate the technical effect of adding the disturbing unit in the beam shaping assembly, and the material constituting the disturbing unit is not limited to these substances. The comparative example in the present embodiment is the same as the comparative example in Embodiment 1, both the comparative example are not provided with the disturbing unit, and the remaining parameters are the same as those of the present embodiment. In the neutron beam of the comparative example, the gamma ray content is 8.78*10-14Gy*cm2/n, the advantage depth is 10.74 cm, the advantage dose rate was 5.61, and the 30 RBE-Gy treatable depth is 7.27 cm. By comparison, it can be seen that the solid disturbing unit can also have a better shielding effect on the gamma rays under the premise of improving the quality of the neutron beam. In the present embodiment, the material of the moderator is aluminum fluoride, and the shape of the moderator is the diamond shape as Embodiment 1, and the disturbing unit is a cylinder with porous structure, wherein the size of the cylinder is the bottom radius is 6 cm and a height is 3 cm. The disturbing unit is located between the moderator and the beam outlet. Under the above conditions, when lead, antimony, aluminum and carbon are used as the disturbing units respectively, the disturbing unit on the neutron beam quality and shielding effect on gamma rays are calculated by MCNP software. The results are shown in Table 3: TABLE 3Influence of cylindrical disturbing unit with porous structure with aradius of the bottom surface of 6 cm and a height of 3 cm on the neutronbeam quality and shielding effect on gamma rays of aluminum fluorideas moderatorNeutron beam qualityMaterial ofGamma ray content30 RBE-Gydisturbingin neutron beamAdvantageAdvantagetreatableunit(Gy * cm2/n)depth (cm)dose ratedepthlead6.31 * 10−1410.885.607.09bismuth6.68 * 10−1410.795.597.10aluminum8.75 * 10−1410.865.597.06carbon9.22 * 10−1410.795.597.16 The principles of different materials used as disturbing units to shield gamma rays are the same. Therefore, in the present embodiment, only lead, antimony, aluminum and carbon are randomly selected as the disturbing unit to illustrate the technical effect of adding the disturbing unit in the beam shaping assembly, and the material constituting the disturbing unit is not limited to these substances. The different experimental condition between the comparative example in the present embodiment and the Embodiment 3 is only that disturbing unit the comparative example in the present embodiment is not provided with the disturbing unit, and the other conditions is the same as those in the beam shaping assembly in Example 3. In the neutron beam of the comparative example, the gamma ray content is 11.9*10-14Gy*cm2/n, the advantage depth is 10.81 cm, the advantage dose rate is 5.54, and the 30 RBE-Gy treatable depth is 6.98 cm. It can be seen from Table 3 that the moderators with different materials has an influence on the neutron beam quality. The 30 RBE-Gy treatable depth in the present embodiment is lower than that in Embodiment 1 and Embodiment 2, and the reduction of the 30 RBE-Gy treatable depth is caused by the difference in the materials of the moderator. Comparing the comparative example of Example 3 with Example 3, it can be found that under the condition that the materials of the moderators is the same, the presence of the disturbing unit has an improved effect on the neutron beam quality, and the disturbing unit can effectively shield the gamma rays in the neutron beam. In the present embodiment, Fluental is selected as the material of the moderator (Fluental is the moderating material mentioned in U.S. Pat. No. 5,703,918B), and the other parameters are the same as those in Embodiment 3. Whenlead, antimony, aluminum and carbon are used as the disturbing units respectively, the disturbing units on the neutron beam quality and shielding effect on gamma rays are calculated by MCNP software. The results are shown in Table 4: TABLE 4Influence of cylindrical disturbing unit with porous structure with aradius of the bottom surface of 6 cm and a height of 3 cm on the neutronbeam quality and shielding effect on gamma rays of Fluental as moderatorNeutron beam qualityMaterial ofGamma ray content30 RBE-Gydisturbingin neutron beamAdvantageAdvantagetreatableunit(Gy * cm2/n)depth (cm)dose ratedepthlead4.85 * 10−1410.885.556.77bismuth5.17 * 10−1410.915.546.79aluminum6.81 * 10−1410.895.546.80carbon6.83 * 10−1410.855.576.89 The principles of different materials used as disturbing units to shield gamma rays are the same. Therefore, in the present embodiment, only lead, antimony, aluminum and carbon are randomly selected as the disturbing unit to illustrate the technical effect of adding the disturbing unit in the beam shaping assembly, and the material constituting the disturbing unit is not limited to these substances. The beam shaping assembly of the present embodiment is not provided with the disturbing unit as a comparative example. In the neutron beam of the comparative example, the gamma ray content is 9.25*10-14, the advantage depth is 10.86 cm, the advantage dose rate is 5.47, and the 30 RBE-Gy treatable depth is 6.67 cm. Comparing the neutron beam quality of the present embodiment with those of embodiment 1 to 3, the 30 RBE-Gy treatable depth are reduced to varying degrees due to the use of moderators with different materials. However, by comparison of Embodiment 4 with the comparative example, it can be concluded that due to the presence of the disturbing units, the gamma ray content in the neutron beam is significantly reduced and the 30 RBE-Gy treatable depth of the neutron beam quality is increased. In the present embodiment, 85% magnesium fluoride and 15% lithium fluoride are selected as the moderator material, wherein the shape of the moderator is a cylinder. FIG. 3 is a cross-sectional view showing the beam shaping assembly in the present embodiment. The disturbing unit is a porous cylinder, and is located between the moderator and the beam outlet, wherein the height of the cylindrical disturbing unit is 10 cm, and the radius of the bottom circular surface is 5 cm. The effect of the disturbing unit on the neutron beam quality and the shielding effect on the gamma rays under the above conditions are shown in Table 5: TABLE 5Influence of the disturbing unit on the neutron beam generated by thecylindrical moderator and shielding effect on the gamma rays in thebeam shaping assemblyNeutron beam qualityMaterial ofGamma ray content30 RBE-Gydisturbingin neutron beamAdvantageAdvantagetreatableunit(Gy * cm2/n)depth (cm)dose ratedepthrhenium2.59 * 10−1413.245.649.43lead2.99 * 10−1413.155.639.35bismuth3.04 * 10−1413.105.649.30aluminum5.64 * 10−1412.915.639.12carbon6.06 * 10−1413.225.669.35 The principles of different materials used as disturbing units to shield gamma rays are the same. Therefore, in the present example, only rhenium, lead, bismuth, aluminum and carbon are randomly selected as the disturbing unit to illustrate the technical effect of adding the disturbing unit in the beam shaping assembly, and the material constituting the disturbing unit is not limited to these substances. The beam shaping assembly of the present embodiment without the disturbing unit is used as a comparative example. In the neutron beam of the comparative example, the gamma ray content is 6.47*10-14, the advantage depth is 12.82 cm, the advantage dose rate is 5.58, and the 30 RBE-Gy treatable depth y is 8.76 cm. It can be seen from the comparison between Embodiment 5 and the corresponding comparative example that the neutron beam quality of the neutron beam at the beam outlet of the beam shaping assembly where the disturbing units made of different materials is located has different degrees of improvement disturbing unit, for example, the advantage depth and the 30 RBE-Gy treatable depth are increased to different extents compared with the comparative example, which are beneficial to the treatment effect. Moreover, the gamma ray contents in the neutron beam are reduced to different extents compared with the comparative example. Since the moderator used in the present embodiment is a cylinder, it is further explained that regardless of the shape of the moderator in the beam shaping assembly, the presence of the disturbing unit can effectively reduce the gamma ray content in the neutron beam under the premise that the quality of the neutron beam is not significantly adversely affected. It can be found from Embodiment 1 and 2 that whether the internal structure of the disturbing unit is a porous structure or a compact structure, the disturbing unit has a shielding effect on the gamma rays in the neutron beam. It can be found from the comparison of Embodiments 1, 3 and 4 that under the condition that the other parameters are the same, the moderators of different materials has influence on the neutron beam quality, under the condition that the materials of the moderators are the same, the presence of the disturbing unit can significantly reduce the gamma ray content in the neutron beam, thereby further illustrating the improvement effect of the disturbing unit on the quality of the neutron beam. The beam shaping bodies in Embodiments 1 to 5 are all cylinders, and the height of the cylinders as the beam shaping assembly are 80 to 100 cm, and the radii of the bottom surfaces of the cylinders are 60 to 70 cm. It can be concluded from Embodiments 1 to 5 that the nature of the disturbing unit to reduce the gamma ray content in the neutron beam without any significant negative effect on the quality of the neutron beam is substantially unaffected by factors other than the disturbing unit. In the technical solution provided by the present disclosure, regardless of the size of the disturbing unit relative to the beam shaping assembly, the presence of the disturbing unit can reduce the content of the gamma ray in the neutron beam. However, it should be noted that in the same beam shaping assembly, the larger the size of the disturbing unit is, the greater the influence of the disturbing unit on the neutron beam quality is, accordingly, the smaller the size of the disturbing unit is, although the smaller the influence of the disturbing unit on the neutron beam quality is, the attenuation of the gamma ray in the neutron beam is also reduced accordingly. The shielding effect of the disturbing unit on the gamma rays in the neutron beam is mainly by the absorption or reflection of the gamma rays by the material constituting the disturbing unit. The gamma rays in the neutron beam will have a certain degree of attenuation as long as it passes through the disturbing unit. Whether the disturbing unit can reduce the gamma ray content in the neutron beam is not depend on the shape and size of the disturbing unit and the position of the disturbing unit in the beam shaping assembly. The beam shaping assembly for neutron capture therapy disclosed in the present disclosure is not limited to the contents described in the above embodiments and the structure represented by the drawings. Obvious modifications, substitutions or alterations of the materials, shapes and positions of the components in the present disclosure are intended to be within the scope of the present disclosure. The above illustrates and describes basic principles, main features and advantages of the present disclosure. Those skilled in the art should appreciate that the above embodiments do not limit the present disclosure in any form. Technical solutions obtained by equivalent substitution or equivalent variations all fall within the scope of the present disclosure. |
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abstract | A mask of certain type has a transparent base and a transparent film formed on the transparent base. The transparent film has at least one mask member formed in a predetermined mask pattern and having a relatively low exposure beam transparency. The mask member sometimes has a placement error from a designed placement. This is mainly because an in-plane stress distribution of the transparent film is nonuniformity. The transparent film is partially decreased in thickness to unity the in-plane stress distribution. |
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047117540 | description | DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1, there is shown a plan view of a nuclear reactor power generating system of the pressurized water type illustrating the relative position of the impact sensors, e.g., accelerometers, for monitoring the metal impacts sustained by the primary system components confining the reactor coolant. The system includes a pressure vessel 10 which forms a pressurized container when sealed by its head assembly. The vessel 10 has coolant flow inlets 16 and coolant flow outlets 14 formed integral with and through its cylindrical walls. As is known in the art, the vessel 10 contains a nuclear core (not shown) consisting mainly of a plurality of clad nuclear fuel elements which generate substantial amounts of heat depending primarily upon the position of a control means, the pressure vessel housing 18 of which is shown. The heat generated by the reactor core is conveyed from the core by coolant flow entering through inlets 16 and exiting through outlets 14. The coolant flow exiting through outlet 14 is conveyed through a hot leg conduit 20 to a heat exchange steam generator 22 which is of the type wherein the heated coolant flow is conveyed through tubes (not shown) which are in heat exchange relationship with the water which is utilized to produce steam. From the steam generator 22, the coolant flow is conveyed through conduit 24 to a pump 26 and then via a conduit 28 to the inlet 16 so as to provide a closed recycling primary or steam generating loop. The system illustrated in FIG. 1 has four such closed fluid systems or loops. Although the number of such systems or loops can vary from plant to plant, commonly two, three or four are employed. In order to detect the presence of metal debris in the reactor coolant system, a plurality of impact sensors or accelerometers 30 are strategically positioned on the surface of the cooling system. As shown, and as indicated above, the impact sensors 30 are disposed at the upper and lower plenums of the reactor vessel 10, the input plenum of each steam generator 22, and at other places throughout the system. As explained above, in order to monitor the sensitivity of the sensors 30, it is periodically necessary to externally apply an impact of an energy corresponding to the desired sensitivity to an outer surface of the coolant system or loop adjacent the sensor 30 to be monitored. For this purpose, an impacting device is appropriately positioned and one or more sequential impacts are produced until an impact of the desired energy is realized. Such a positioned impacting device 32 for monitoring the sensitivity of the impact sensor 30 attached to the bottom plenum of the vessel 10 is shown schematically in FIG. 1. Turning now to FIG. 2, there is shown the basic block circuit diagram of a preferred embodiment of an impacting device 32 according to the invention. Although theoretically any device which can supply an impact in response to an input signal and whose impact energy can be measured, for example, compressed air, springs, pneumatics, can be used for the impact device 32, for various reasons, including simplicity, reliability and safety as a result of the environment in which the present invention is primarily intended to be used, according to the present invention the impacting device selected is a solenoid 34. The coil (not shown in this Figure) of solenoid 34 is connected to the output of a power amplifier 36 which can provide a controllable and variable input signal to the solenoid coil and cause the plunger (likewise not shown in this Figure) to move with a corresponding force against an adjacent surface to cause an impact. As indicated above, according to the present invention, the kinetic energy of the impact caused by the plunger of the solenoid 34 is determined, compared with a value corresponding to the desired kinetic energy, the results of the comparison are indicated, for example, high, low or desired value, and the output voltage of the amplifier 36 is adjusted and reapplied to the solenoid 34 in order to attempt to obtain an impact energy of the desired value. The process is repeated until an impact energy of the desired value is indicated by the results of the comparison. According to the present invention, the impact energy of the solenoid plunger is derived from the known relationship that kinetic energy =0.5 mV.sup.2. Since the mass of the plunger of solenoid 34 (plus any mass connected to the solenoid plunger), for a given impacting device 32 will be known, a determination of the final velocity of the plunger of solenoid 34, i.e. the velocity just prior to impact, will provide a measure of the impact energy. To determine this final velocity according to the illustrated preferred embodiment of the invention, the position of the plunger of the solenoid 34 is continuously detected by means of a position sensor 38 which produces an output signal corresponding, preferably linearly, to the instantaneous position of the solenoid plunger. Preferably the position sensor comprises a linear variable differential transformer arrangement as shown in FIG. 3 which will be discussed in more detail below. In any case, the output signal from the position sensor 38, which according to the preferred embodiment of the invention is a d.c. voltage whose magnitude is linearly proportional to the position of the plunger of the solenoid 34, is fed to an analog to digital converter 40 whose output is sampled at discrete time intervals by a microcomputer 42. Since the output state of the analog to digital converter 40 is, according to the preferred embodiment of the invention, an approximation type analog to digital converter whose output state is constantly changing, a latch 44 is provided between the output of the analog to digital converter 40 and the input of the microcomputer 42 in order to hold the position data between conversion cycles of the converter 40 so that the microcomputer 42 can read the position data asynchronously. That is, the microcomputer 42 need not read or sample the position data precisely when the conversion cycle of the converter 40 is complete. In the microcomputer 42, the sampled position data from the analog to digital converter 40 are stored and utilized to calculate the final velocity of the solenoid plunger, and thus the kinetic energy of the impact. Since, as indicated above, sampling of the position data by the microcomputer 42 is carried out at discrete constant time intervals, for example, at 1 millisecond intervals, a first order approximation of the velocity can be derived by the difference between the values of two successively sampled position values, which is a measure of the distance travelled by the solenoid plunger during one sampling time interval. Accordingly, the microcomputer 42 compares successive sampled position values until no difference is detected, indicating that the solenoid plunger has stopped moving and thus delivered an impact, and then utilizes the immediately previous difference value to calculate the final velocity. That is, if x(t) is the sampled position value at the time of impact, i.e., no difference is detected between x(t) and x(t+1), then the difference between the successive values x(t) and x(t-1) is utilized by the microcomputer 42 to calculate the final velocity of the plunger solenoid. Moreover, if the sampling interval is selected so that it is some power to the base ten of one, e.g. 1 millisecond as indicated above, then the difference between position values x(t) and x(t-1) can be directly used as a measure of the final velocity, i.e. no further calculation in the microcomputer 42 is required. After calculation of the final velocity, the microcomputer 42 compares this calculated final velocity value with a precalculated value corresponding to the desired kinetic impact energy, which precalculated value is stored in a read only memory of the microcomputer 42, and provides an output signal indicating the results of the comparison to an input-output expander circuit 46 which causes a velocity indicator 48 to indicate the results of the velocity comparison, for example, a high, a low or an accepted indication. As a result of the velocity comparison, the microcomputer 42 also, if necessary, adjusts a stored digital value, which corresponds to the magnitude of the last voltage supplied to the solenoid 34 to initiate an impact, in a manner so as to reduce any error and thus attempt to cause the adjusted voltage subsequently applied to the solenoid 34 to produce an impact of the desired impact energy. Of course, if an accepted value of velocity (kinetic energy) is determined, then no further adjustment of the stored digital voltage value takes place. The "adjusted" digital voltage value, which is stored in the input/output expander circuit 46, is then fed via a digital to analog converter 50 and a voltage amplifier 52 to the power amplifier 36 so as to initiate a further impact by the solenoid 34. The above described process is repeated until such time as an acceptable velocity (kinetic energy) value is indicated by the indicator 48, and preferably until a repeatable acceptable value is indicated by the indicator 48. Referring now to FIG. 3, there is shown a preferred arrangement for the position sensor 38 for the plunger of the solenoid 34. As shown, position sensor 38 includes a linear viable differential transformer 53 having a primary winding 54, a pair of secondary windings 56, 58 which are spaced symmetrically from the primary winding 54 and are connected in series opposition, and a magnetic core 60 which is axially moveable between the primary and secondary windings and whose position changes the mutual inductance between each secondary winding and the primary winding and determines the output across the secondary windings. The core 60 of the linearly variable differential transformer is connected to the plunger 62 of the solenoid 34 by means of a rod 64 so that the position of the moveable core 60, and hence the output voltage across the series connected secondary windings 56, 58, will correspond to the position of the plunger 62. The rod 64 is formed of a non-metallic material so as not to effect the mutual inductance between the primary and secondary windings of the transformer. The a.c. carrier voltage excitation for the primary winding 54 is provided by a carrier generator 66 and is sufficiently high so as to permit linearity throughout the range of movement of the core 60 so that the output will be proportional to the input throughout this range. The output signal across the secondary windings 56, 58, is fed to a passive demodulator 68 and then to an a.c. amplifier 70 which provides a d.c. output voltage whose magnitude is directly proportional to the position of the core 60, and thus of the solenoid plunger 62. For example, in the preferred embodiment of the invention the amplifier 70 provides an output voltage of 10V through one inch of displacement of the core 60. That is, the output voltage will vary from 0 to 10 V d.c. upon one half inch of movement of the core from the null position of the core 60. The use of a liner variable transformer arrangement as shown in FIG. 3 for the position sensor 32 provides a number of substantial advantages. Initially, if the solenoid plunger 62 with the attached core 60 are properly aligned, there is no physical contact between the core 60 and the coil structure of the transformer, which means that the position sensor 32 is practically frictionless. This permits critical measurements that can tolerate the low mass core 60, which for example has a mass of 0.022 kg, but cannot tolerate friction loading. Moreover, the frictionless operation of the linear voltage differential transformer arrangement combined with the induction principle and operation permits the device to respond to minute motions of the core 60, and thus of the plunger 62 of the solenoid 34. This is of course an important consideration in attempting to detect impact energy of the magnitude indicated above, i.e. 0.5 ft.-lb. (0.68 joules) which necessarily implies very small masses for the solenoid plunger 62 and very small travel lengths. For example, in order to create such an impact energy with the system according to the invention, a solenoid 34 having a plunger weighing 0.15 pounds (0.33 kg) with an attached core weighing 0.01 pounds (0.022 kg), i.e., a total weight of 0.16 pounds (0.352 kg) which travelled through a distance of 0.5 inch (0.127 cm) was utilized. Referring now to FIG. 4, there is shown a block circuit diagram for a specific embodiment of the invention generally shown in FIG. 2, and accordingly the same reference numerals are utilized in FIG. 4 to identify the corresponding structure in FIG. 2. As indicated above, and as shown in FIG. 4, the basic control of the circuit according to the invention is the microcomputer or microprocessor 42 which is realized by an Intel 8741 integrated circuit microprocessor. Clock pulses for the microprocessor 42 are provided by a six MZ clock pulse generator 72 which may for example be a TTL DIP crystal clock type integrated circuit. Since the selected microcomputer 42 requires complementary clock inputs at its pins 2 and 3, the output of the clock pulse generator 72 is initially fed to a complementary driver circuit 74 whose complementary outputs are fed via respective buffer amplifiers 76 (which may form part of a common integrated circuit, for example a 7404 integrated circuit) to the clock input pins of the microprocessor 42. In order to be able to reset the internal program counter of the microprocessor 42 to 0, and thus initialize the program, a reset circuit is connected between the reset input (pin 4) and pin 7 (which is connected to ground) of the microprocessor 42. The reset circuit includes a one microfarid capacitor 78 which is connected between the pins 4 and 7 of the microprocessor 42, and which, via internal circuitry contained in the 8741 microprocessor chip, will provide an automatic initialization pulse whenever power is supplied to the microprocessor. To provide an external reset pulse at the desired time, the series connection of a resistor 80 and a normally open switch 82 is connected in series with the capacitor 78. The output signal from the solenoid plunger position sensor 38, and in particular the output signal from the AC amplifier 70, (FIG. 3) is fed to appropriate pins of the analog to digital converter 40, which is realized by an ADC82AM analog to digital converter integrated circuit chip which is a high speed 8 bit successive approximation A/D converter. To ensure adequate sampling by the circuit used for the analog to digital converter 40 within its linear range, a 3 megahertz external clock is applied to the analog to digital converter 40. This is achieved by connecting the output of the driver circuit 74 to the clock input of the converter 40 via a D-type flip flop 84, which divides the clock pulse signal from the circuit 74 in half, and a buffer amplifier 86. The ADC82AM converter chip used for the analog to digital converter 40 was configured, by selection of its scaling resistors, for a 0 to +10 volt input range, and for complementary straight binary by connecting pin 16 to pin 17 as illustrated. As indicated above, in order to hold the sample from the analog to digital converter 40 between conversion cycles, the output samples from the A/D converter 40 are fed to the microprocessor 42 via a sample and hold circuit or latch 44 which is realized by a 74LS377 octal D-type flip flop integrated circuit. In this latch circuit, there is a data set up time, i.e. the time the data is stable before a clock, of approximately 25 nanoseconds. In order to accommodate a minimum set up time and clock phase, three series connected NAND-gates 88 (which are realized by a single 74LS00 integrated circuit) are connected between the the status line pin of the A/D converter 40 and the clock input of the latch 44. The input/output expander circuit 46 is, as shown in FIG. 4, realized by a intel 8243 integrated circuit chip which is specifically designed for use with the intel 8741 single chip microprocessor. The input/output expander circuit 46 was implemented in order to expand the microprocessor 42 for additional output lines and so as to offer higher drive capability in order to drive the velocity indicator 48, which, as shown in FIG. 4 is realized by three light emitting diodes 90, 92, 94 which indicate "low", "normal", and "high" comparison results respectively, and for the eight bits of the digital time analog inverter 50. The D/A converter 50 (which in the illustrated embodiment of the invention is a Burr-Brown DAC 90BG digital to analog converter) provides an output current proportional to the input code thereto from the expander circuit 46. To provide the proper loading for the D/A converter 50 so as to ensure minimal effects on the accuracy of the converter 50, the output of the D/A converter 50 is fed to the high impedance summing junction of an operation amplifier 96 (for example, an LF351 operational amplifier) whose output is connected to an internal feedback resistor in the D/A converter 50. The illustrated disclosed configuration of the D/A converter 50 and the operational amplifier 96 operates as a current to voltage source having an output V which conforms to the relationship V=-IR, where I is the output current of the D/A converter 50, and R is the internal feedback resistor contained in the D to A converter 50. The control voltage signal provided at the output of the operational amplifier 96, which in the disclosed illustrated embodiment can vary from -5 volts to +5 volts depending on the coded input signal to the D/A converter 50, is fed to the voltage amplifier 52, which in the illustrated embodiment is a noninverting operational amplifier strated embodiment is a noninverting operational amplifier (e.g., a 741 operational amplifier circuit), having a gain of approximately 3. The output of the voltage amplifier 52 is in turn connected by a diode 98 to the control input of the power amplifier 36, which is illustrated and realized by a Darlington transistor pair which is connected in series between the +15 V supply and one end of the coil 100 of the solenoid 34, whose other end is connected to -15 V. With this arrangement, the voltage across the solenoid can be effectively varied up to 28 V, which is the voltage required in order to obtain the maximum velocity of the solenoid plunger 62 for the selected solenoid. Before turning to a description of the flow diagrams for the preferred embodiment of the invention, it should be pointed that, it has been found that some error can be introduced into the velocity measurement due to surface adhesion which may exist between the rear surface of the solenoid plunger 62 and a stop plate normally provided in the solenoid plunger to limit the rearward travel of the plunger 62 and against which the plunger rests before moving in response to an applied voltage. This surface adhesion is due to molecules on the end of the plunger and the surface of the stop plate which exert strong internal molecular forces on each other at the area of contact. In order to eliminate this error, according to a further feature of the invention, after initialization of the program but before to the application of the desired predetermined voltage to the solenoid to initiate impact, the program of the microprocessor 42 causes the voltage applied to the solenoid coil 100 to be increased in small increments or steps until movement of the solenoid plunger 62 is detected, and only then is the actual velocity measurement initiated by the application of the predetermined or adjusted voltage value to the solenoid coil 100. Movement of the solenoid plunger 62 is detected by the microprocessor 42 by sampling the output from the analog to digital converter 40 after each increment and by substracting the position value of the initial sample, i.e. the at rest position, and the position value for the present sample, until a difference other than zero is determined, indicating that the solenoid plunger 62 has moved. In the preferred illustrated embodiment of the invention wherein the A to D converter 40 is an eight bit converter with a unipolar 0 to 10 volt input range, resulting in approximately 39 millivolts per step change for the A/D converter 40, the initial incrementing of the solenoid voltage is carried out in forty millivolt steps or increments so as to provide for the greatest accuracy. Turning now to FIG. 5, operation of the preferred embodiment of the invention shown in FIG. 5 is started in that, upon application of power to the apparatus, the program is initialized (block 102), and the initial position of the solenoid plunger 62 is sampled (block 104) and stored (block 106) in a rotating buffer. Thereafter, the voltage applied to the solenoid coil is incremented (block 108) by forty millivolts and, according to a further feature of the invention, the velocity indicator status lights 90, 92 and 94 are caused to light (block 110) in a rotating manner so as to indicate to the operator that a measurement sequence is in progress. After a delay (block 112) and application of the voltage increment, the position of the solenoid plunger 62 is sampled (block 114), and the difference between the sampled position and the stored initial position is determined (block 116). If the outcome (block 118) is equal to 0 (Y), indicating that the solenoid plunger 62 has not moved, the voltage being applied to the solenoid coil is incremented (block 108) by an additional forty millivolts and the sampling and comparison with the initial position repeated until such time as a difference other than 0 is detected (N), indicating that the solenoid plunger 62 has moved. Upon detection of the movement of the solenoid plunger, as shown in FIG. 6, the impact byte "ADJUST", i.e. the coded value corresponding to the predetermined voltage value to be applied to the solenoid coil 100, is fed (block 120) to the digital to analog converter 50, and thus the corresponding voltage value is applied to the solenoid coil 100. At that time, an internal sampling timer in the microprocessor 42 is started (block 122) and the position data for the solenoid plunger 62 as provided by the A/D converter 40 is sampled (block 124) at equal time intervals, for example, 1 millisecond. The sequentially sampled position data is stored (block 126) in a rotating buffer and the last two sequentially sampled position values compared (block 128). If the two compared sampled values are not equal (block 130; N), then the comparison process is repeated until such time as the current last two sampled values are equal (Y), indicating that impact has occurred. At that time, a flag in the microprocessor is set (block 132) and the internal timer is stopped (block 134). As further shown in FIG. 6, after a delay of 0.5 seconds (block 136), i.e. a delay sufficiently long to enable impact to have occurred, the solenoid 34 is de-energized (block 138) and a check is made (block 140) to see if the flag has been set. If the flag is set (Y), indicating that an impact has occurred, the subroutine for calculating velocity is initiated (block 142). Alternatively, if the flag is not set (N), then a check is made (block 144) to see if the calculation is complete, and if not (N) the setting of the flag continues to be checked. It should be noted, that although not indicated, the setting of the flag can additionally be controlled so that it will not be set unless the sampled position data indicating that the solenoid plunger 62 has travelled a predetermined minimal distance, for example three quarters of its travel length, in order to be able to detect a possible malfunction of the solenoid, and thus a false velocity reading. As shown in FIG. 7, in the "calc" subroutine (146), the sampled position data for the sample immediately proceeding the impact position is moved (block 148) from the buffer into the working register R of the microprocessor 42 and the sampled position data at the impact position is moved (block 150) into the accumulator register A of the microprocessor 42. Thereafter, the position data or value before impact is subtracted (block 152) from the position data or value at impact in the accumulator register A to provide a difference value A' in the accumulator register. Since, as indicated above, the sampling takes place at one millisecond intervals, the difference value A' is a direct measure of the final velocity of the plunger 62 and thus of the impact energy. Thereafter, the value A' is compared with a value corresponding to the desired velocity (impact energy) stored in a memory in the microprocessor 42. Since the difference value A', is simply a measure of the step difference of the A/D converter 40 in the measuring time interval, the stored desired value may simply correspond to the desired step difference. For example, with the particular solenoid 34, linear differential transformer 53 and A/D converter 40, it was found that a step difference of twenty eight would produce the desired impact energy of 0.68 joules. In order to carry out the comparison, as shown in FIG. 7, the stored value corresponding to the desired velocity, i.e. the desired step difference, is subtracted (block 154) from the value A' and a determination is made (block 156) whether the resulting difference is greater than A'. If such is the case (Y), then a check is made (block 158) to see whether the value A' is within a given tolerance range of the desired velocity value and if so (Y), the normal velocity light 92 is lit (block 160). Alternatively, if the difference value is greater than A' but A' is not within the given tolerance value (N), indicating that the impact velocity was too low, then the "ADJUST" byte stored in the input/output expander circuit 46 is adjusted so as to produce an increased velocity upon the next test cycle, and the low velocity indicator light 90 is lit (block 162). In the preferred embodiment of the invention illustrated in FIG. 4, and as indicated in FIG. 7, the modification of the "ADJUST" byte upon detection of a low velocity measurement is achieved by subtracting (block 164) a stored predetermined value "DELTA" from the "ADJUST" byte, with "DELTA" initially having a value equal to one half of the initial "ADJUST" byte. As further shown in FIG. 7, if the difference between the value A' and the desired velocity value is not greater than the value A' (i.e., an N result from block 156), then an additional check is made (block 166) to determine whether the value A' is within the given tolerance value, and if so (Y) the normal velocity indicator light 92 is lit (block 160). Alternatively, if the value A' is not (N) within the given tolerance value, indicating that the measured velocity was too high, in this case the value "DELTA" is added (block 168) to the stored "ADJUST" byte, and the high velocity indicator light 94 is lit (block 170). After lighting the appropriate one of the indicator lights, 90, 92 and 94, the flag is cleared (block 172) after a suitable delay (block 174). Accordingly, upon the next check of the flag condition (block 140 in FIG. 6), and a determination that the calculation has now been completed (Y), the program will cause the value "DELTA" to be divided (block 176) in half after a delay (block 178). The division (block 176) may be accomplished, for example, by simply shifting the "DELTA" value one step to the right in its storage register, so as to provide a new "DELTA" value for the immediately subsequent measurement. Thereafter, the program causes the next measurement to be initiated (see FIG. 5) by applying an increment (block 108) of 40 millivolts to the solenoid 34, and the above described measurement process to be successively repeated until such time as the power is removed from the microcomputer 42 or, as indicated above, the program is reset by use of the switch 82 (FIG. 4). The measuring process is preferably repeated until such time as the normal velocity indicator light 92 has been lit (block 160 in FIG. 7) upon two successive velocity measurements. It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims. |
description | The present application is a national phase entry under 35 U.S.C. § 371 of International Application No. PCT/FRO3/001879 filed Jun. 19, 2003, published in Dec. 31, 2003, which claims priority from FRO3/00623 filed Jan. 21, 2003, which claims priority to FRO2/07546, filed Jun. 19, 2002. 1. Field of the Invention The present invention concerns an optical device for X-ray instrumentation applications with high resolutions in wavelength. More precisely, the invention concerns an optical device intended to treat an incident X-ray beam, said device comprising: a monochromator, and an optical element for treating the incident beam whose reflective surface is able to produce a two-dimensional optical effect in order to adapt a beam in destination of the monochromator, said optical element comprising a surface reflecting X-rays of the multilayer structure type. The reflective surface or surfaces used can in particular be of the multilayer type with lateral gradient. The invention thus applies in all X-ray instrumentation fields using monochromators. By way of example, the following applications can be cited non-limitingly: high-resolution X-ray diffractometry, X-ray fluorescence, X-ray micromapping (or microcartography) applications for microelectronics. The invention applies to X-ray instrumentation fields requiring excellent spectral purity and therefore the use of a monochromator. The basic constituent element of the monochromator is a crystal which makes it possible to achieve very high resolutions, angular and in terms of wavelength. The monochromator can be formed from a crystal or several aligned crystals. For monochromators of the type mentioned above, the diffraction of the incident X-rays is effected according to Bragg's law. The Bragg condition for a crystal is of the form nλ=2d sin θβ where n is the reflection order, λ the wavelength of the incident radiation for which the diffraction occurs, d the spacing period between the atomic planes of the crystal involved in the diffraction and θβ the angle of incidence on these same atomic planes which is necessary for the diffraction phenomenon to occur. If an incident beam of X-rays is considered, the rays of wavelength λ striking the crystal with an angle of incidence θβ which is very precise with respect to a certain family of atomic planes of the crystal will be diffracted by these same atomic planes if the Bragg condition indicated above is satisfied. This phenomenon of diffraction of a monochromatic beam occurs with a certain angular acceptance Δθ about the reference angle θβ. This angular acceptance can therefore be defined by: An angle θβ corresponding to the reference angle of incidence of the diffractive rays on the monochromator (θβ is known by the term Bragg angle), θβ being a function of the crystal and the wavelength and corresponding to the maximum of the reflectivity peak R=f(θ) for a given wavelength, and A tolerance of Δθ about this reference angle of incidence. The tolerance defines the width of the range of angles of incidence which corresponds to the angular acceptance. The monochromators used in the devices of the type mentioned above have a very small angular acceptance. By way of example, for a germanium crystal monochromator, used for example for applications where the X-ray source is a Kα copper source (λ=1.54 Angstroms), the angular acceptance is 0.00336° (about a reference angle of incidence of approximately 20°). It will therefore be understood that, from a given X-ray source (this source being able for example to be of the rotating anode, X-ray tube or microsource type), without an appropriate conditioning of the X-rays emitted by the source, a large number of these rays which are emitted in all directions arrive at the monochromator with an angle of incidence well outside the angular acceptance of the monochromator. These photons will not be able to be reflected by the monochromator and thus cause very large losses of flux. 2. Description of Related Art To attempt to mitigate this drawback, it is known to dispose, upstream of the monochromator, means of conditioning the incident beam. The main function of such conditioning means is to orient the largest possible part of the incident X-rays, at an angle of incidence (with respect to the surface of the monochromator) which is included within the incidence range defined by the angular acceptance of the monochromator about a reference angle of incidence θβ. It is thus known to produce these conditioning means in the form of a glass capillary for collecting by total reflection a divergent initial beam issuing from a source and to collimate it into a beam directed towards a monochromator. However, one limitation associated with such conditioning means is that this type of optical component can reflect X-rays only at very small angles of incidence (typically less than 0.1°). Consequently the flux delivered by the optics is generally small. It also known to produce the conditioning means in the form of a multilayer optical element producing a one-dimensional optical effect. These optical elements have a parabolic shape which makes it possible to collimate the divergent incident beam, and a multilayer coating which diffracts the incident X-rays according to Bragg's law. One illustration of this known configuration will be found in FIG. 1, which depicts a source S of X-rays producing an initial beam X1 having a certain divergence in destination of conditioning means 31 (the parabola in which the surface of these conditioning means fits being depicted in a broken line). Here also, the conditioning means reflect the initial beam X1 as a beam X2 directed towards a monochromator M. A one-dimensional optical element of this type is known by the term Göbel mirror. In the case of curved substrates such as Göbel mirrors, the multilayer has a layer structure (meaning thereby the period d of the multilayer) which varies along the mirror in order to maintain the Bragg conditions on a large surface of the mirror. Such a multilayer mirror with lateral gradient thus allows reflection of the X-rays whose wavelength belongs to a predetermined domain, by different regions of the mirror on which the incident rays have variable local angles of incidence. Such conditioning means make it possible to collimate the incident beam into a beam X2 in which the directions of propagation of the X-rays are made substantially parallel to an incident direction with respect to the monochromator which corresponds to the value θβ of this monochromator, and this within the angular acceptance range of the monochromator. However, such conditioning means allow the collimation of an initial beam X1 only in a single plane (the plane of FIG. 1 in the example which has just been described). The divergences in the planes perpendicular to this plane are thus not treated: as a result many X-rays are not usable. One limitation of these known conditioning means with one-dimensional effect is thus that, for a given initial beam X1, the flux of collimated X-rays in a direction compatible with the angular acceptance of the monochromator remains limited. It should also be stated in this regard that it is necessary to have at the output from the monochromator a beam of small size in the fields of application of the invention (typically less than 2 mm). The beam issuing from the monochromator in fact generates an “image spot” whose dimensions must be of this order of magnitude. The image spot is included in a plane known as the “image plane”. To increase the “useful” flux arriving at the monochromator, it is known how to produce the means of conditioning the initial beam in the form of two-dimensional optics whose reflective surface exhibits a lateral gradient. Such optics are produced in the form of a “side by side Kirkpatrick-Baez” device, as illustrated in FIG. 2. In the remainder of this text, the “Kirkpatrick-Baez” configuration will be referred to as “KB”. This figure thus illustrates an element 33 comprising two mirrors 331 and 332 associated side by side (axis parallel to the direction Z for the mirror 331, to the direction X for the mirror 332). The surfaces of these two mirrors have curvatures centred on two axes perpendicular to one another. For this type of optics, the conditioning desired is provided by a double reflection, each mirror 331, 332 producing a one-dimensional optical effect along one axis. Each of the two mirrors can thus produce a collimation or a focusing. A monochromator M receives the flux X2 reflected by the element 33. A description of this type of optical element 33 will be found in the patent U.S. Pat. No. 6,041,099. It should be stated that the conditioning means can also be produced in the form of a “KB” device where the two mirrors are not disposed side by side. Compared with conditioning means of the Göbel mirror type, such conditioning means with two-dimensional effect make it possible to recover, within a range of angles of incidence compatible with the angular acceptance of a monochromator, a greater proportion of rays issuing from a divergent initial beam X1. One aim of the invention is to improve still further the performance of such devices. In particular, the invention aims to collect a maximum amount of flux from a divergent initial beam and to produce at the output a monochromatic flux which is superior compared with what can be produced by a device comprising conditioning means as described above. Thus the invention in particular aims, in order to increase the flux at the output of such devices, to make it possible to exploit X-ray sources of increased size. The invention also aims to make it possible to improve the compactness of such devices. In order to achieve these aims, the invention proposes an optical device intended to treat an incident X-ray beam, said device comprising: a monochromator (M) and an optical element (20) for treating the incident beam whose reflective surface is able to produce a two-dimensional optical effect in order to adapt a beam in destination of the monochromator, said optical element comprising a surface reflecting X-rays of the multilayer structure type, characterised by the fact that said reflective surface consists of a single surface, said reflective surface being shaped according to two curvatures corresponding to two different directions. Preferred but non-limiting aspects of this device are as follows: said single reflective surface is of the multilayer type with lateral gradient, said single reflective surface comprises a depth gradient, said reflective surface is shaped in each of the said two different directions in order to produce two respective one-dimensional effects, said reflective surface has a geometry which is substantially circular in a first direction and substantially parabolic in a second direction, said first direction is the saggital direction of the optical element and the second direction is the meridional direction of the optical element, said reflective surface has a substantially toroidal geometry, said reflective surface has a substantially paraboloidal geometry, said reflective surface has a substantially ellipsoidal geometry, said reflective surface is able to reflect rays of the lines Cu—Kα or Mo—Kα, the monochromator is a germanium crystal and the optical conditioning element consists of a W/Si multilayer coating with lateral gradient, the optical element of said device has a length of around 2 cm, said device being able to be used with an X-ray source whose size is around a few tens of microns by a few tens of microns, in order to produce a sample spot of around 300*300 microns. As a preamble to this description, it should be stated that the figures are intended to illustrate the principle of the invention and do not necessarily depict the dimensions and scales realistically. This is true in particular for the angles of incidence (or even reflection) of the X-rays. These X-rays in reality arrive on the reflective surfaces according to the invention with an angle of incidence of less than 10°. The meridional and saggital directions are also defined with respect to the general direction of propagation of the X-ray beam: The meridional direction corresponds to the mean direction of propagation of this beam (and more precisely to the mean direction between the mean directions of propagation of the beam before and after its reflection on the optical assemblies concerned), The saggital direction corresponds to a horizontal transverse direction of this meridional direction (the vertical being defined here by the mean normal to the part of the reflective surface of the optical assemblies which will be described and which is actually used for reflecting the incident X-ray beam). With reference to FIG. 3, a device according to the invention is shown placed upstream of a sample E. This device comprises: means of conditioning an initial X-ray beam, denoted X1, having a certain divergence, a monochromator M associated with a given angular acceptance. The conditioning means are in this embodiment of the invention produced in the form of an optical element 20 intended to reflect the rays of the initial beam X1 issuing from a source S of X-rays. In the case of FIG. 3, the optical element 30 provides collimation in a first dimension and focusing in a second different dimension. The source S can in particular be of the X-ray tube, rotating anode or X-ray source with microfocus type. The optical element 20 comprises a multilayer structure formed on a substrate (for example made from glass), which defines a reflective surface for the X-rays of the beam X1. The single reflective surface of this optical element has a special geometry. More precisely, this reflective surface is shaped according to two curvatures corresponding to two different directions. This reflective surface thus has significant differences with respect to reflective surfaces of the type used in optical assemblies such as those disclosed by the document U.S. Pat. No. 6,041,099: The reflective surface is a single reflective surface, unlike what is the case with optical assemblies in which two different elementary mirrors have been assembled, This reflective surface is regular (this term meaning in the present text that the reflective surface does not exhibit any second-order discontinuity: angular points or edges—salient or hollow—etc), Moreover, a difference which is also significant is that, in the case of the invention, the incident rays undergo only a single reflection in order to produce the required two-dimensional optical effect, whilst two reflections are necessary in the case of an optical assembly using conditioning means reproducing for example the teachings of the document U.S. Pat. No. 6,041,099. Description of the Optical Conditioning Element Considered in the Invention Before describing in detail the embodiment illustrated in FIG. 3, the general characteristics of the invention will be disclosed. The reflective surface of the optical element according to the invention has a curvature Cx in the saggital direction X and a curvature Cy in the meridional direction Y. FIG. 3 represents these curvatures, two curves Cx and Cy having been depicted in broken lines. Each of the curves Cx, Cy can be a circle, but also an ellipse, a parabola or other curve (open or closed). In any event, the reflective surface of the optical conditioning element does not have a simple spherical shape. Each of the curves Cx, Cy is thus associated with a different direction in space (two perpendicular directions in the example commented on here). And each of these curves produces a one-dimensional optical effect on the X-rays which have just been reflected on the reflective surface: The curve Cx produces a one-dimensional optical effect in the direction X, The curve Cy produces a one-dimensional optical effect in the direction Y. And each of these dimensional effects depends on the curvature associated with the curve and its law of change along this curve. It will thus be possible to parameterise the curves Cx and Cy in order to selectively obtain associated one-dimensional effects such as a focusing or a one-dimensional collimation. FIG. 3 depicts one embodiment of the invention. In this embodiment, the curve Cx produces a one-dimensional focusing and the curve Cy produces a one-dimensional collimation. The reflective surface of the multilayer of the optical element 20 of FIG. 3 is for this purpose shaped in the respective directions X and Y in two curves Cx and Cy respectively circular and parabolic, each of these curves producing a one-dimensional effect in a given plane, respectively in the plane XY and in the plane YZ. Thus, from the divergent beam X1, a collimation is generated in one dimension in space and a focusing in another dimension. According to a variant of the invention the means of conditioning the incident beam on the monochromator can be an optical element providing a collimation in two dimensions. In this case, the curves Cx and Cy are both shaped as parabolae. Returning to the embodiment of the invention in FIG. 3, the monochromator M is positioned so that the mean direction of the beam X2 corresponds to the angle of incidence θβ of the monochromator, or to an angle compatible with the angular acceptance of this monochromator. In this way the X-rays flux which arrives at the monochromator within the tolerances defined by the angular acceptance of this monochromator is maximised in the vertical direction (direction Z) but also in the saggital direction. It should be stated here that it is thus possible to produce according to the invention conditioning means with optical elements composed of a multilayer mirror (with lateral gradient, and possibly also with depth gradient as will be seen later in this text), whose reflective surface can have one from amongst various aspherical complex shapes making it possible to fulfil the necessary function for redirecting the reflected beam X2 to the monochromator. It is thus possible in particular to give this reflective surface one of the following geometries: geometry with a substantially toroidal shape, geometry with a substantially paraboloidal shape, geometry with a substantially ellipsoidal shape, geometry with a substantially circular shape in a first direction (in particular the saggital direction) and a substantially parabolic shape in a second direction (in particular the meridional direction). The lateral gradient can in particular extend in the meridional direction of the incident X-rays. And the period of the multilayer can be adapted to reflect in particular rays of the lines Cu—Kαor Mo—Kα. In the case of an embodiment of the invention with a focusing in the saggital plane (that is to say in the plane XY in FIG. 3) the radius of curvature Rx (saggital radius of curvature) can have a value of less than 20 mm, necessary for focusings over short distances, less than 90 cm (the source-point focusing distance) according to one favoured application of the invention. It will be noted that the optical element used as a beam conditioning means in the device according to the invention dispenses with the drawbacks and limitations of the optical assemblies of the KB type. In particular: this optical assembly is in a single piece (not requiring any tricky assembly) the incident X-rays undergo only a single reflection on its reflective surface. It was stated that the reflective surface of the optical element 20 was defined by a multilayer. This multilayer (like all multilayers dealt with in this text) in practically all cases comprises at a minimum one “lateral gradient”. This characteristic makes it possible to effectively reflect the X-rays having different local angles of incidence with respect to the reflective surface of the element 20. It will be understood in fact that the various points on this reflective surface do not receive the incident X-rays with the same local angle of incidence (because of the divergence of the incident beam and the geometry of this reflective surface). Multilayer with lateral gradient means here a multilayer where the layer structure is adapted so that the Bragg condition is complied with at every point on the useful surface of the mirror. Thus, for a radiation of incident X-rays in a narrow wavelength band containing for example the Kα lines of copper (Cu—Kα lines with wavelengths close to 0.154 nm), the multilayer mirror with lateral gradient makes it possible to maintain the Bragg conditions over the entire useful surface of the mirror. This leads to the reflection of the band with a predetermined wavelength (in the above example containing the copper Kα lines), by different regions of the mirror on which the incident rays have variable local angles of incidence. It is thus possible to increase the surface area of the mirror which is actually used. The gradient is obtained by varying the period of the multilayer according to the position on the mirror. This type of lateral-gradient multilayer structure thus makes it possible to increase the solid angle of collection of the optical assembly, which leads to a higher reflected flux for an identical geometry compared with monolayer mirrors functioning in total reflection. It should however be noted that, in extreme cases, the multilayer may not have a lateral gradient in particular if the curvature of the optical element is small and does not require this type of gradient. The multilayer of the various embodiments of the invention can also have a depth gradient. Such a depth gradient makes it possible to fulfil the Bragg conditions for fixed angles of incidence and variable wavelengths, or vice-versa. It is thus possible for example to increase the wavelength bandwidth of the multilayer of the optical assembly, and to focus or collimate X-rays with different wavelengths, at one and the same given image plane (the case of a fixed geometry—that is to say a configuration in which the relative positions of the source of incident rays, of the optical assembly and of the image plane are fixed). In this way it is possible to use sources of X-rays with different wavelengths to reflect the X-rays issuing from the various sources with the same optical assembly, without this requiring a new positioning of the source and/or of the image plane or planes with respect to the optical assembly. In this case use is made of the tolerance in wavelength of the optical assembly (tolerance in Δλ). In the same way, it is also possible to translate this tolerance in Δλ into a tolerance in Δθ, θ being the angle of incidence on the element 20. A tolerance on the wavelength corresponding in fact—in the context of the Bragg condition—to a tolerance on the angle of incidence, it is possible, for a constant wavelength of the incident beam, to collect and reflect an incident light flux where the rays with the same wavelength have different local angles of incidence. In particular it is possible in this way to use sources of X-rays of larger size (increase in the angular acceptance of the optical component). Producing the conditioning means with a depth gradient in the multilayer thus constitutes one option for implementing the invention. Information on the Two-Dimensional Conditioning Means The use of a two-dimensional optics for conditioning the incident radiation on a monochromator may in particular make it possible to achieve a collimation in a first dimension in order to maintain a fixed angle of incidence on the reference plane of the monochromator whilst producing a second one-dimensional effect in a second dimension (defined by the saggital plane XY) in order to collect a maximum incident flux. The conditioning in the second dimension can be a focusing or a collimation. By way of illustration, such a function is depicted in FIG. 3: the divergent rays in the plane YZ are collimated in the plane YZ in order to maintain, for the beam X2 (which is reflected by the conditioning element 20), an angle of incidence of around θβ in the angular acceptance of the monochromator. The collimation function according to the first dimension, produced by the optical element 20, makes it possible to limit the angular divergence of the beams in the diffraction plane (for each reflected X-ray, the diffraction plane is defined as the plane perpendicular to the reflective surface containing the incident beams and the reflected beams). For the purpose of increasing the X-ray flux collected at the sample, it is advantageous to effect a conditioning in a second dimension, for example in the case of FIG. 3 in the XY plane (saggital plane). This makes it possible to limit the divergence in this plane and thus to maximise the X-ray flux collected from the source and projected at the sample after reflection on the monochromator. This conditioning in the second dimension (still with reference to FIG. 3) is carried out whilst ensuring the operating conditions of the monochromator (limiting the angular divergence in the diffraction plane). As indicated previously, the conditioning in the second dimension may be a focusing or a collimation. The possibility of increasing the flux in the second direction (saggital) by effecting a focusing is notably advantageous as the angular divergence a tolerated in the saggital plane at the monochromator is great in the case of the applications in question. This is because a divergence α in the second dimension (the saggital dimension) has little effect on the angle of incidence of the incident X-rays on the monochromator in the case of the field of application of the invention (for the focusing conditions encountered and the types of monochromators in question). With reference to FIG. 4, the divergence a in the saggital plane is given by the useful width of the conditioning optics XI in this same plane (determined for example at the centre of the optics), and the focusing distances dFoc (optics-image spot distance). The divergence α in the direction X can thus be approximated by the following equation:Tan(α)=((XI/2−L/2)/(dFoc)), where L is the width of the image spot in the saggital plane. It is known that the angular tolerance of a monochromator on a divergence α in the saggital plane (which will be called Δα) is a function of the Bragg angle θβ and of the angular acceptance Δθ of this monochromator. With reference to the document by M. Schuster and H. Göbel, J. Phys. D: Applied Physics 28 (1995) A270-A275 “Parallel-Beam Coupling into channel-cut monochromators using tailored multilayers”, this angular tolerance Δα can be expressed as follows:((Δθ/tan θβ)*2)1/2=Δα, in this formula Δα and Δθare expressed in radians. The tolerance on the angular divergence in the saggital plane can thus be determined by way of example for a germanium crystal for Cu—Kα applications (θβ=22.650, Δθ=0.00336°). Thus limit divergences (angular tolerance on the divergence of the beam X2) of the order of 1° are calculated, which is well above the convergences required for the field of application of the invention. Consequently the monochromator can accept more divergence of the incident beam X2 in the second direction in question (the direction X in FIG. 3). It is therefore advantageous to collect a maximum amount of flux from the source for the second direction in question (the saggital direction). This general objective concerns both the device according to the invention and the devices using in a known manner, as conditioning means, an optical assembly of the KB type. Additional Highlight on Specific Advantages Compared with Devices Comprising Conditioning Means of the KB Type In the second direction in question, that is to the say the direction for which the monochromator can tolerate more divergence (in the case of FIG. 3 the direction X) the invention makes it possible to collect more flux from the source compared with the device implementing an initial beam conditioning by a two-dimensional optical assembly of the “KB” type (side by side or not) with multilayer coatings. Two phenomena give rise to this gain in flux and they will be explained below. Firstly, in the case of the invention with an optical element such as the element 20, having a given length (in the meridional direction), a capture angle is obtained in the saggital direction which is greater than what is obtained with a conventional configuration implementing a conditioning by KB optics, Secondly, the two-dimensional optical element 20 as used in the invention can accept more divergence of the initial beam X1 in a saggital direction, and therefore picks up a larger surface of the source at any point on this element 20. This is because, and with reference to the first type of advantage mentioned above, in the case of the conditioning carried out by an optical assembly of the KB type, in order to increase the solid angle of collection in a direction transverse to the mean direction of propagation of the beam on the optical assembly, it is necessary to increase the length of this optical assembly. This is because obtaining a two-dimensional effect according to a KB configuration is linked to a double reflection. By way of illustration and considering FIG. 2, if the device is extended in the X or Z direction it is necessary to extend the mirror in the Y direction. This phenomenon is illustrated in FIGS. 5a and 5b. It is in fact known that, for optical elements of the KB type, any incident ray must strike the optics in a particular area (corresponding to the hatched areas in FIGS. 5a and 5b) in order to undergo a double reflection. The result therefore is that, for such a known type of optical conditioning element (whether or not the mirrors are contiguous), the solid angle able to be collected is limited by the length of the component both for the horizontal transverse directions and for the vertical transverse directions (direction Z or direction X). For the optical assembly of the KB type, the length of the component (in the meridional direction) therefore has an influence both on the transverse components and the longitudinal components of the solid angle of collection. In the case of the invention, it is possible to increase the solid angle of collection in a saggital direction, without increasing the length of the device. This is important in particular in the case where it is wished to limit the bulk and therefore the size of the optics. This is in particular the case by way of example for applications of X-ray micromapping for microelectronics where the sources used are X-ray microsources having sizes of a few tens of microns by a few tens of microns (for example 40 microns by 40 microns) and the sample spot analysed is of the order of a hundred microns by a hundred microns (for example 300 microns by 300 microns). It is wished in this case to limit the length of the optical conditioning element to approximately 2 cm. And in general terms, for applications where it is sought to limit the length of the device, the optical combination used in the invention proves to be particularly advantageous and makes it possible to maximise the flux reflected by the monochromator whilst minimising the size of the device. In addition, an extension of the conditioning mirror in a meridional direction (which is the mean direction of propagation of the X-rays on the optics) has the effect of increasing the multilayer surface on which a lateral gradient is applied. This type of gradient is applied in order to compensate for the curvature of the surface of the optical component. In FIGS. 5a and 5b, the gradient of the multilayers is applied along the Y axis for the two mirrors of the optical assembly. In consequence increasing the length of the component amounts to increasing the surface on which a gradient is applied—which amounts to making the manufacture of the device more complex. For conditioning optics with a single reflection such as those considered in the invention, the solid angle of collection can be increased in a saggital direction by way of example by increasing simply the size of removable slots which can be positioned at the entry and exit of the optics. Another advantage of the invention is the possibility of capturing a larger source surface at a given point on the optical conditioning assembly and thus being able to maximise the flux at the image spot. This phenomenon can be illustrated by means of FIGS. 6a and 6b and FIG. 2, if an X-ray source whose surface is parallel to the plane XZ defined in these figures is considered. FIGS. 6a and 6b illustrate an optical conditioning element 20 as used in the invention. If an alignment of the various optics according to FIGS. 6a and 6b in FIG. 2 is considered, for the optical conditioning element as considered in the invention, the angular divergence of the incident X-rays tolerated in a saggital direction at any point on the optics is relatively large in comparison with the angular divergence tolerated for the conditioning optics of the KB type in the same direction (that is to say the direction X). Along the other dimension of the source (that is to say the direction Z), the angular divergences tolerated at any point on the two types of two-dimensional-effect optics are very close and limited by the angular acceptance of the multilayer. A movement of the incident X-ray emission source point from the centre S of the source in the direction Z has an influence directly and significantly on the angle of incidence of these X-rays at a given point on the two-dimensional optical element whatever the type of optics in question (of the KB type or an optics with a single reflection as considered in the invention). In the case of the optical conditioning element as considered in the invention, and with reference to FIGS. 6a and 6b, an opening of the emission beam in the direction X (which corresponds to the saggital direction) compared with a direct beam coming from the centre of the source gives rise to only small variations on the angle of incidence at any point on the optics. With reference to these FIGS. 6a and 6b, it is possible to determine the angular divergence tolerated for the incident X-rays at the centre C of the conditioning optics. The source size in the direction Z able to be reflected effectively at the centre of the optics is given by the following equation: ZI=(cos θs*p)(tan θI−tan θI′), where p is the distance between the centre of the source and the centre of the optics, θs is the angle of incidence on the optics for a ray issuing from the centre S of the source, and θI and θI′, the limit angles of incidence given by the angular acceptance of the multilayer (Δθ=θI−θI′). Still with reference to FIGS. 6a and 6b, in the case of the direction X, the source size able to be reflected at the centre C of the optics is given by the following equation:XI=2((p sin θs/tan θI′)2−(p cos θs)2)1/2. The values XI and ZI given above are source sizes determined within the limit of the angular acceptance of the multilayer. By way of example, for W/Si coatings used for copper Ka applications, the angular acceptance of the multilayer (of the optical conditioning element 20) is 0.052° about an angle of 1.26°. It can also be considered that the optics and source are aligned so that the angle of incidence θs on the optics of a beam issuing from the centre of the source is given by the Bragg angle of the multilayer. For standard source-optics distances of 12 cm, the source size able to be collected in a saggital direction at the centre of the optics as considered in the invention could thus be of the order of 5 cm, and approximately 110 microns for the direction Z. Still by way of example, in the case of KB optical assemblies for one and the same type of multilayer and source-optics distance, the source size able to be collected effectively at a given point is limited to approximately 110 microns for the two directions concerned (X and Z with reference to FIG. 2). We will return to the reasons explaining this later in the description. The values mentioned above constitute theoretical limits (in the above cases for a W/Si multilayer) of the angular divergence of the incident beam which can be tolerated by the optical conditioning elements compared above. However, it is also necessary, in the case of a device according to the invention, to consider the divergence tolerated by the monochromator in the saggital direction as well as the specifications relating to the image which it is wished to obtain (size, distance), in order finally to maximise the flux collected at the image spot. Taking these considerations into account, the potential gain in flux captured from the source for optical conditioning elements as considered in the invention is significant. Indeed, if by way of example consideration is given to a standard X-ray source of size 300 microns by 300 microns with a distance of 12 cm between the X-ray source and the optical conditioning assembly, at a given point on this optical assembly it is possible to see a larger surface of the source in the saggital direction than in the case of known devices, with a conditioning by KB optical assembly. In the case of the invention, it is thus possible to collect the 300 microns of the source in the saggital direction at any point on the optics and this can represent a sure advantage in the case where the image spot required is relatively broad in the saggital direction, for example for image spots 1 mm wide positioned at 40 cm from the optics. It will therefore be understood that the device according to the invention tolerates a relatively large divergence of the beam X1 issuing from the source, in a particular direction. This is not the case with the known devices using conditioning elements of the KB type. With reference to FIG. 2 and the KB optics, the direction which provides a certain degree of freedom on the divergence of the incident beam which is effectively reflected at a given point on the optics for the first horizontal mirror 332 is the direction perpendicular to the centre of the second optics, which is the vertical mirror 331. However, in the case of this known configuration with two mirrors, the direction perpendicular or approximately perpendicular to the surface of the mirror corresponds to the direction in which the divergence of an incident beam gives rise to significant variations on the angle of incidence. The source size able to be collected at a given point on the assemblies of the KB type is therefore, due to the double reflection phenomenon, limited by the angular acceptance of the multilayer for the two dimensions of the source. The invention also dispenses with this limitation. |
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description | This application is based upon and claims the benefit of priority from prior European Application No. 12178382.3 filed on Jul. 27, 2012, the entire contents of which are incorporated herein by reference. 1. Technical Field The present invention generally relates to a hadron therapy facility. It relates more particularly to a beam transport system for such a hadron therapy facility with at least two patient treatment stations. 2. Background Art High investment costs of a hadron therapy facility require optimizing patient throughput as much as possible. A modern hadron therapy facility typically includes several patient treatment stations, which are successively supplied with a hadron beam generated in a common hadron accelerator. If it takes e.g. 10 minutes for correctly positioning a patient in a treatment station, the throughput of a hadron therapy facility with a single treatment station would be limited to 6 patients per hour. In a hadron therapy facility with 5 treatment stations it is however possible to treat up to 30 patients per hour. This means however that—in average—only 2 minutes are available for switching the hadron beam from one treatment station to the other and for performing the irradiation itself. A beam transport system for such a multi-station hadron therapy facility typically comprises a main beam transport line into which the hadron accelerator injects a hadron beam. Secondary beam transport lines branch off from this main beam transport line for successively delivering the hadron beam into the patient treatment stations. A switching electromagnet is associated with each of these secondary beam transport lines. When this switching electromagnet is energised, its magnetic field deviates the hadron beam from the main beam transport line into the respective secondary beam transport line. Such a switching electromagnet comprises an electromagnet coil associated with a DC power source in an electromagnet energising circuit. A switching device allows for interrupting the electromagnet energising circuit, i.e. to terminate the magnetic field deviating the hadron beam, so that the latter is now guided along the main beam transport line past the respective branch-off point. As the electromagnetic field generated by an energised switching electromagnet is quite important, opening the switching device would produce—without any further measures—an electric arc with a very high current density between the contacts of this device. In accordance with the state of the art, this discharge arc is eliminated or reduced by a fly-back diode (also called freewheeling diode) that is mounted in parallel with the coil of the switching electromagnet. This fly-back diode allows for the electromagnetic energy stored in the electromagnet to dissipate in a closed circuit, comprising as circuit resistance essentially the resistance of the electromagnet coil. As the electromagnetic energy stored in the switching electromagnet is quite high and the characteristic R/L of the closed discharge circuit is quite low, the decay of the current in the circuit is rather slow. Thus, it can take up to 10 s until the electromagnetic field of the switching electromagnet has sufficiently decreased for safely re-establishing the beam that is to be deviated into an irradiation room located downstream of the patient treatment station in which the previous irradiation has been carried out. Considering that the irradiation time of a patient is itself only a matter of tens of seconds, losing with every treatment already up to 10 s for the switching-off operation, is surely a matter of concern when trying to optimize patient throughput in a particle beam therapy system with several treatment stations. This is in particular true, the more patient treatment stations the hadron therapy facility has. A first problem underlying the present invention is to increase the patient throughput in a multi-station hadron beam therapy facility. A further problem underlying the present invention is to increase the time during which a hadron beam can be used in a multi-station hadron beam therapy facility. The invention concerns a beam transport system for a hadron therapy facility with at least two patient treatment stations, comprising: a main beam transport line into which a hadron beam is injected; a secondary beam transport line branching off from the main beam transport line for delivering the hadron beam into one of the patient treatment stations; a switching electromagnet for deviating the hadron beam from the main beam transport line into the secondary beam transport line, the switching electromagnet comprising an electromagnet coil; an energising circuit associated with the electromagnet coil for energising the latter so as to produce a hadron beam deviation from the main beam transport line into the secondary beam transport line; a switching device for interrupting the energisation of the electromagnet coil producing the hadron beam deviation; and a discharge circuit capable of dissipating the electromagnetic energy stored in the switching electromagnet, when the energisation of the electromagnet coil is interrupted. In accordance with a first aspect of the invention, the discharge circuit comprises a discharge accelerating circuit capable of generating a voltage opposing the counter electromotive force induced in the electromagnet coil when the energisation of the electromagnet coil producing the hadron beam deviation is interrupted, wherein the voltage stays substantially constant or increases as the current induced in the electromagnet coil decreases. Such a discharge accelerating circuit accelerates the decay of the current induced in the electromagnet coil and thereby the decay of the residual electromagnetic field in the switching electromagnet that is de-energised. Accelerating the decay of the electromagnetic field of a de-energised switching electromagnet substantially reduces the waiting time for safely re-injecting the hadron beam into the beam transport system. Hence, the time during which a hadron beam can be effectively used in a multi-station hadron beam therapy facility is increased, which allows for an increased patient throughput. A constant voltage provides a constant contribution to the decay rate of the induced current. However, it may also be of advantage to increase the voltage as the current induced in the electromagnet coil decreases, thereby increasing the contribution of the voltage to the decay rate at smaller decay currents. Indeed, as the decay rate also includes a resistive component that is proportional to the instantaneous value of the induced current, i.e. a component which diminishes with the current, increasing the voltage as the current induced in the electromagnet coil decreases allows compensating for the diminishing resistive component of the decay rate. In conclusion, it will be appreciated that the invention provides a simple measure for improving patient throughput in multi-station hadron therapy facilities, by efficiently reducing the waiting time for safely re-injecting the hadron beam into the beam transport system, when switching the hadron beam from one treatment station to the other. It may be of advantage if the discharge accelerating function of the discharge accelerating circuit only starts when the current induced in the electromagnet coil drops below a certain value. At the beginning, the resistive component of the decay rate, which is proportional to the instantaneous value of the induced current, still warrants a rapid decay of the magnetic field. This resistive decay rate diminishes however as the induced current decreases. Consequently, the discharge accelerating circuit gets more efficient if the current induced in the electromagnet coil has already dropped below a certain value. As the costs of the discharge accelerating circuit normally increase with the power to be absorbed, it is consequently of interest to start the discharge accelerating function of the discharge accelerating circuit only when the current induced in the electromagnet coil has already dropped below a certain value. A first embodiment of the discharge accelerating circuit comprises a power source capable of generating an electromotive force opposing the counter electromotive force induced in the electromagnet coil when the energisation of the electromagnet coil is interrupted. This solution allows most probably for achieving the best results in terms of discharge acceleration, but necessitates an auxiliary power source, which may not be the most cost efficient solution. A second embodiment of the discharge accelerating circuit comprises a Zener diode, wherein the breakdown voltage of the Zener diode opposes the counter electromotive force induced in the electromagnet coil when the energisation of the electromagnet coil is interrupted. This solution allows for achieving good results in terms of discharge acceleration if the breakdown voltage of the Zener diode is sufficiently high. However, as the power to be absorbed in the Zener diode is rather high, it is presently rather difficult to find a suitable Zener diode at reasonable costs. It may be of advantage if the discharge accelerating circuit comprises at least two Zener diodes mounted in parallel or in series. These solutions allow for reducing the power to be absorbed in a single Zener diode. The parallel solution is generally preferred. For the serial solution, it must be possible to replace a Zener diode with a breakdown voltage VDZ with n Zener diodes with a reduced breakdown voltage of VDZ/n. A third embodiment of the discharge accelerating circuit further comprises a current sensitive bypass circuit mounted in parallel with the Zener diode, respectively the Zener diodes, the current sensitive bypass circuit bypassing the decay current around the Zener diode, respectively the Zener diodes, until this current drops below a certain value. In this solution the current sensitive bypass circuit is used to “start” the Zener diode(s) only when the current induced in the electromagnet coil has already dropped below a certain value. Thereby the Zener diode has to absorb a reduced power in comparison to a Zener diode through which the initial decay current flows. A further embodiment of the discharge accelerating circuit comprises: a first circuit including a first Zener diode and a first current sensitive bypass circuit mounted in parallel with the first Zener diode, wherein the first current sensitive bypass circuit bypasses the decay current around the first Zener diode until this decay current drops below a certain value I1; and at least one second circuit mounted in series with the first circuit and including a second Zener diode and a second current sensitive bypass circuit mounted in parallel with the second Zener diode, wherein the second current sensitive bypass circuit bypasses the decay current around the second Zener diode until this decay current drops below a certain value I2<I1. It will be appreciated that this relatively simple and cost efficient embodiment allows increasing the voltage as the current induced in the electromagnet coil decreases, thereby compensating—at least partially—a decrease of the resistive component of the decay rate. A fly-back diode is advantageously mounted in series with the discharge accelerating circuit. If necessary, the fly-back diode warrants that no energising current flows through the discharge accelerating circuit, but that the induced electromagnetic field decay current may flow through the discharge accelerating circuit. A third embodiment of the discharge accelerating circuit comprises: a first branch including a Zener diode; a second branch connected in parallel with the first branch, the second branch including a high-power MOSFET; and an OP amplifier controlling the gate of the MOSFET so that the breakdown voltage VZD of the Zener diode defines the drain-source voltage VDS of the MOSFET; wherein this discharge accelerating circuit is designed so that the current flowing through the first branch is small in comparison to the current flowing through the second branch. This circuit allows for achieving a very cost efficient solution with presently available circuit components. In a preferred embodiment of the beam transport system, a single power source is associated with several electromagnet coils; a switching device is connected between the power source and the electromagnet coils for selectively disconnecting one electromagnet coil from the power source and connecting another electromagnet coil to the power source; and a discharge accelerating circuit is associated with each of the electromagnet coils. In a preferred embodiment of the beam transport system, the power source has a voltage output adjustable between a maximum value and a steady state value; the beam transport system further includes a controller setting the voltage of the power source to its maximum value when the power source is newly connected to one of the electromagnet coils and reduces it to its steady state value as soon as the current in the electromagnet coil reaches its steady state value. This solution allows for reducing—at relatively low costs—the time necessitated for building up the required electromagnetic field in a switching magnet. The energising circuit and the discharge accelerating circuit are advantageously designed so that the time interval required for reducing to zero the decay current induced in the electromagnet coil associated with a first patient treatment station when its energising circuit is interrupted is substantially equal to the time interval required for establishing a desired working current in the electromagnet coil associated with a second patient treatment station, when the hadron beam is to be switched from the first patient treatment station into the second treatment station. It will be understood that the following description (and the drawings to which it refers) describe by way of example several embodiments of the claimed subject matter for illustration purposes. They shall not limit the scope, nature or spirit of the claimed subject matter. The diagram of FIG. 1 schematically illustrates the layout of a beam transport system, globally identified with reference number 10, for a hadron therapy facility with five patient treatment stations (or treatment rooms) 121, 122, 123, 124, 125. Reference number 14 identifies a hadron accelerator (e.g. a cyclotron or a synchrotron) connected to the beam transport system 10. The hadron beam produced by the hadron accelerator 14 is injected in a main beam transport line 16. Secondary beam transport lines 181, 182, 183, 184, 185 branch off from this main beam transport line 14 for delivering the hadron beam into the patient treatment stations 121, 122, 123, 124, 125, where it is injected into an equipment used to irradiate the patient as e.g. a rotating gantry or a fixed beam treatment device (not shown). Each of these beam transport lines 16, 181, 182, 183, 184, 185 comprises—in a manner known per se—a beam transport tube and a series of powerful electromagnets (not shown) capable of focussing the hadron beam and routing it through the beam transport tube. Reference numbers 201, 202, 203, 204, 205 identify switching electromagnets, whose function is to switch the hadron beam from the main beam transport line 16 into the respective secondary beam transport line 181, 182, 183, 184, 185 with which they are associated. Each of these switching electromagnets 201, 202, 203, 204, 205 comprises an electromagnet coil (or coil system) 221, 222, 223, 224, 225. When the electromagnet coil 22i is energised, the respective switching electromagnet 20i generates a strong magnetic field deviating the hadron beam from the main beam transport line 16 into the secondary beam transport line 18i, with which the respective switching electromagnet 20i is associated. FIG. 2 shows a prior art energising circuit 24 comprising the aforementioned electromagnet coil (or coil system) 22, a DC power source 26 and a switching device 28 for interrupting the energising circuit 24 (i.e. for suppressing the electromotive force in the energising circuit 24 which generates the magnetic field deviating the hadron beam from the main beam transport line 16 into the secondary beam transport line 18i). Reference number 30 identifies a fly-back (or freewheeling) diode. The latter forms with the electromagnet coil 22 a discharge circuit, wherein—when the energisation of the electromagnet coil 22 is interrupted by opening the switching device 28—a current I is induced in the discharge circuit, which opposes the decay of the electromagnetic field stored in the switching electromagnet 20. As long as this residual electromagnetic field is capable of substantially influencing the trajectory of the hadron beam, it is not safe to re-inject this hadron beam into the main beam transport line 14. Consequently, the time required for a sufficient decay of the electromagnetic field in a switching electromagnets 20i is a time overhead during which the hadron beam is not available for the next treatment station 12i+1. If R is the resistance in the discharge circuit, L is the inductance in the discharge circuit, and VD is the voltage drop at the fly-back diode (for I>0, one may assume that VD is constant), the electromagnetic field decay current I in the prior art circuit of FIG. 2 is determined by the following differential equation: - L · ⅆ I ⅆ t = R · I + V D As R is typically small (a typical value for R would e.g. be 30 mΩ), L is large (a typical value for L would e.g. be 30 mH) and VD is small, the current decay rate (−dI/dt) in the discharge circuit is relatively small considering the high currents used in these magnets (>300 A). A typical curve for the electromagnetic field decay current I in the discharge circuit of FIG. 2 is shown in FIG. 3. It will be noted that it takes more than 6 s for the current induced in the in the discharge circuit to drop below 10 A. It will further be noted that simply increasing the resistance R in the discharge circuit is not an efficient solution for accelerating the decay of the electromagnetic field in the switching electromagnet 20. Indeed, increasing R would increase the value of the counter electromotive force (−L·dI/dt) induced in the discharge circuit, thereby increasing the electric potential difference between the contacts of the switching device 28, when the latter opened. Furthermore, the contribution of the resistance R to the current decay rate (−dI/dt) is proportional to the instantaneous value of current I, i.e. its contribution diminishes as the current I diminishes. FIG. 4 shows a first embodiment of a discharge circuit with a first embodiment of a discharge accelerating circuit 32. The latter is mounted in series with the fly-back diode 30 and comprises a high power Zener diode 34. In this discharge circuit of FIG. 4, the breakdown voltage of the high power Zener diode 34, which is generated by the current passing through the fly-back diode 30, opposes the counter electromotive force induced in the electromagnet coil 22 when the energisation of the latter is interrupted. If R is the resistance in the discharge circuit′, L is the inductance in the discharge circuit, VD is the voltage drop at the fly-back diode 30 and VZD is the breakdown voltage of the high power Zener diode 34, the electromagnetic field decay current I is determined by following differential equation: - L · ⅆ I ⅆ t = R · I + V D + V ZD The current decay rate (−dI/dt) in the discharge circuit is increased by the constant term VZD/L. Expressed in more general terms, the discharge circuit of FIG. 4 comprises a discharge accelerating circuit 32 that generates a constant voltage VZD opposing the counter electromotive force induced in the electromagnet coil 22i when its energisation is interrupted. A typical curve for the electromagnetic field decay current I in the discharge circuit of FIG. 4 is shown in FIG. 5 (the breakdown voltage VZD of the high power Zener diode is 15 V, and R, L and VD have the same values as in FIG. 2). It will be noted that it only takes about 2 s for the current in the discharge circuit′ to drop to 0 A. Consequently, in the discharge circuit of FIG. 4, the discharge accelerating circuit 32 reduces by about 70% the time required before the decaying electromagnetic field in the de-energised switching electromagnet 20 is sufficiently weak for safely injecting the hadron beam again into the beam transport system 10. It will however be noted that in the discharge circuit of FIG. 4 the high power Zener diode 34 has to dissipate a considerable energy, corresponding more precisely to the product VZD·I over the time during which this power is dissipated, i.e. about 3 kJ in a couple of seconds. A Zener diode 34 capable of dissipating more than 3 kJ is presently not easy to find and would moreover be very expensive. To reduce the power for which the Zener diode is to be designed, the discharge accelerating circuit 32 may e.g. comprise several Zener diodes mounted in parallel. FIG. 6 shows a second embodiment of a discharge circuit with a second embodiment of a discharge accelerating circuit 32′. The latter comprises a high power Zener diode 34′ mounted in parallel with a current sensitive bypass circuit 36. This current sensitive bypass circuit 36 bypasses the decay current around the Zener diode 34′ until this current drops below a certain value I1. Such a current sensitive bypass circuit 36 may e.g. comprise a resistor transforming the current into voltage, an operational amplifier detecting a voltage level and a relay opening the bypass circuit. As soon as the decay current falls below this preset value I1, the bypass circuit 36 opens. The decay current now flows through the Zener diode 34′, generating the breakdown voltage of the high power Zener diode 34′. It will be noted that the Zener diode 34′ has to be dimensioned for absorbing a power of (I1·VZD), which may be several times lower than the power for which the Zener diode 34′ in FIG. 4 has to be designed. To still further reduce the current for which the Zener diode 34′ is to be designed, one may connect several Zener diodes in parallel with the bypass circuit 36. A typical curve for the electromagnetic field decay current I in the discharge circuit of FIG. 6 is shown in FIG. 7 (the breakdown voltage VZD of the high power Zener diode is 15 V; the Zener diode is switched into the circuit when the current has dropped to 100 A; and and R, L and VD have the same values as in FIG. 2). It will be noted that it only takes about 3.5 s for the current in the in the discharge circuit to drop to 0 A. Consequently, discharge circuit of FIG. 6 allows for reducing by about 50% the time required before the decaying electromagnetic field in the de-energised switching electromagnet 20 is sufficiently low for safely injecting the hadron beam again into the beam transport system 10. It is to be noted that this embodiment dissipates much less energy in the diode than the previous embodiment as most of the energy stored in the magnet is dissipated within the magnet (e.g. 750 J). FIG. 8 shows an embodiment of a discharge circuit with a discharge accelerating circuit 32′, 32″ capable of generating a voltage that increases as the current induced in the electromagnet coil 22 decreases. This discharge circuit comprises two discharge accelerating circuit 32′, 32″ as shown in FIG. 6, which are mounted in series. Each of these circuits 32′, 32″ comprises high power Zener diode 34′, 34″ mounted in parallel with a current sensitive bypass circuit 36′, 36″. First, both bypass circuits 36′, 36″ are closed. As soon as the decay current falls below a preset value I1, the bypass 36′ of the first Zener diode 34′ opens, whereby the decay current now flows through the first Zener diode 34′ generating the breakdown voltage VZD1 of the latter. The bypass 36″ of the second Zener diode 34″ stays closed until the decay current drops below a preset value I2 (<I1) and then opens. The decay current now flows through the second Zener diode 34″, generating the breakdown voltage VZD2 of the latter. It follows that if the decay current drops below I2, the voltage opposing the counter electromotive force induced in the electromagnet coil 22 increases from VZD1 to VZD1+VZD2. It is to be noted that in this embodiment, the second Zener diode 34″ has to dissipate less energy than the first Zener diode 34′. FIG. 9 shows a fourth embodiment of a discharge circuit with a discharge accelerating circuit 32′″. The latter comprises in a first branch a low power Zener diode 40 mounted in series with a resistor R1, which limits the current flowing through the low or medium power Zener diode 40 and thereby the power dissipated in the latter. A second branch comprises an n-channel-depletion-type high-power MOSFET 42 mounted in series with a resistor R2 (<<R1). An OP amplifier 44 compares the voltage drop at the low power Zener diode 40 and the drain-source voltage VDS of the MOSFET 42 to set the MOSFET's gate voltage. It follows that the breakdown voltage VZD of the low power Zener diode 40 defines the drain-source voltage VDS of the MOSFET 42. As R2<<R1, the current in this second branch is much bigger than the current in the first branch, so that most of the electromagnetic power stored in the switching electromagnet 20 will be dissipated in the second branch. It will be appreciated that the high-power MOSFET 42 required for the discharge accelerating circuit 32″ is by far less expensive than a high-power Zener diode capable of dissipating the same power. FIG. 10 shows an energising/discharge circuitry for three switching electromagnets represented by their electromagnet coils 221, 222, 223. Each of these electromagnet coils 221, 222, 223 is equipped with a discharge branch comprising a discharge accelerating circuit 321, 322, 323. Reference 26′ identifies a common DC power source, which may be selectively connected by a 2-deck selector switch 28′ to one of the electromagnet coils 221, 222, 223. The switching operation is governed by a controller 50. As the controller 50 issues a signal to the selector switch 28′ to switch to another position—thereby interrupting the energisation of one electromagnet coil 22i and starting the energisation of another electromagnet coil 22j—it simultaneously issues a signal to the DC power source 26′ to temporarily increase its voltage to a multiple of the steady-state voltage applied to the electromagnet coil 22j for deviating the hadron beam into the respective secondary beam transport line 18j. This temporarily increased starting voltage shortens the time required for building up the required magnetic field in the switching electromagnet magnet 20j. The current in the electromagnet coil 22i will exponentially decrease to 0 A during a time interval t1, which is shortened by the discharge accelerating circuit 32i integrated into the discharge circuit of the electromagnet coil 22i. The current in the electromagnet coil 22j will exponentially increase to its steady state value Ij during a time interval t2, which is shortened by the controller 50 temporarily increasing the voltage of the DC power source 26′. In an optimized system, t1 and t2 are substantially equal. Due to the much higher costs involved with the discharge accelerating circuits 32i, t1 will generally determine the time overhead during which the hadron beam is not available for the next treatment station 12j. Reference signs list10beam transport system30fly-back diode12ipatient treatment32,dischargestations32′, accelerating circuit14hadron accelerator32′′,16main beam transport32′′′line34high power Zener18isecondary beam34′diodetransport lines34′′20iswitching36,current sensitiveelectromagnets36′, bypass circuit22ielectromagnet coil36″24energising circuit40low or medium power26DC power sourceZener diode26′common DC power42n-channel-depletion-sourcetype high-power28switching deviceMOSFET28′2-deck selector44OP amplifierswitch50controller |
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abstract | A side-slotted nozzle type double sheet spacer grid for nuclear fuel assemblies is disclosed. The spacer grid includes intersecting inner strips and four perimeter strips. Each inner strip has unit strip parts, each fabricated by integrating two unit sheet parts together into a single structure, such that the two unit sheet parts face each other and a nozzle type coolant channel is defined between the two unit sheet parts. Each perimeter strip is fabricated by integrating an inner thin sheet having the unit sheet parts with a flat outer thin sheet having a width corresponding to the width of the inner thin sheet into a single structure. The coolant channel has one or more outlets formed by cutting an upper portion of one of the two unit sheet parts of each unit strip part. Each unit sheet part has a slot longitudinally formed on each side surface of a spring that is projected from the unit sheet part to support a fuel rod within a four-walled cell. The spacer grid thus effectively deflects and mixes coolants together to improve the heat transfer effect between fuel rods and coolants, and enhances its strength to effectively resist laterally directed forces acting thereon, and remarkably improves spring performance of its fuel rod support parts, thus accomplishing desired soundness of the fuel assemblies. |
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claims | 1. An energy modulator for use with a particle source that provides a beam of particles, comprising:a first block moveable between a first position and a second position, wherein when the first block is at the first position, it is out of a path of the beam, and wherein when the first block is at the second position, it is in the path of the beam; anda second block moveable relative to the first block, wherein the second block and the first block are offset from each other in a direction of the beam;wherein the first block has a first energy absorption characteristic, and the second block has a second energy absorption characteristic that is different from the first energy absorption characteristic; andwherein the first block is moveable between the first position and the second position as a single unit, and has a size sufficient to traverse an entire cross section of the beam when the first block is at the second position. 2. The energy modulator of claim 1, wherein the first block has a first thickness, and the second block has a second thickness that is different from the first thickness. 3. The energy modulator of claim 1, wherein the first block has a thickness, and the second block has a thickness that is two times the thickness of the first block. 4. The energy modulator of claim 1, wherein the first block is made from a first material, and the second block is made from a second material that is different from the first material. 5. The energy modulator of claim 1, wherein the first block is made from a first material and has a first thickness, and the second block is made from a second material and has a second thickness, the second material being different from the first material, and the second thickness being different from the first thickness. 6. The energy modulator of claim 1, wherein the first block is made from a material that is at least partially transparent to the particle beam. 7. The energy modulator of claim 1, further comprising a third block, wherein the first, second, and third blocks are offset relative to each other in a direction of the beam. 8. The energy modulator of claim 7, wherein the third block has a thickness that is four times the thickness of the first block, and the second block has a thickness that is two times the thickness of the first block. 9. The energy modulator of claim 1, further comprising a positioner for moving the first block. 10. The energy modulator of claim 9, wherein the positioner is driven by hydraulics, a pneumatic mechanism, a rotating motor, or a linear motor. 11. The energy modulator of claim 1, wherein a surface of the first block is perpendicular to the beam. 12. The energy modulator of claim 1, further comprising a first mounting structure to which the first and the second blocks are slidably mounted. 13. The energy modulator of claim 12, wherein the first mounting structure is mounted to a particle delivery system having the particle source, a particle transport system, and a nozzle. 14. The energy modulator of claim 13, wherein the first mounting structure is mounted to the particle delivery system such that the first mounting structure is closer to the particle source than the nozzle. 15. The energy modulator of claim 14, further comprising a second mounting structure to which a plurality of blocks are slidably mounted, wherein the second mounting structure is mounted to the particle delivery system such that the second mounting structure is closer to the nozzle than the particle source. 16. The energy modulator of claim 15, wherein the first block is made from a first material, the second block is made from a second material, and the second material has a Z value that is less than a Z value of the first material. 17. The energy modulator of claim 1, further comprising a cooling system coupled to the first block, the second block, or both. 18. The energy modulator of claim 1, further comprising an energy sensor, and a control coupled to the energy sensor, wherein the control is configured to adjust a position of the first block based on a feedback signal provided by the energy sensor. 19. The energy modulator of claim 1, wherein the particle source comprises a proton source. 20. The energy modulator of claim 1, further comprising a frame having a first side and a second side, wherein the first block has a thickness that is less than 1 cm and is mounted between the first and second sides. 21. The energy modulator of claim 20, further comprising a cooling system for providing cooling to the first block via convection. 22. The energy modulator of claim 1, further comprising a shield for protecting a patient from being irradiated by neutrons generated as a result of an interaction between the beam and one of the blocks. 23. The energy modulator of claim 1, wherein the first block comprises a solid portion that is moveable relative to the path of the beam. 24. The energy modulator of claim 1, wherein the first block, when placed in the path of the beam, is aligned with a longitudinal axis of a particle accelerator. 25. An energy modulator for use with a particle source that provides a beam of particles, comprising:a first block moveable between a first position and a second position, wherein when the first block is at the first position, it is out of a path of the beam, and wherein when the first block is at the second position, it is in the path of the beam; anda second block moveable relative to the first block, wherein the second block and the first block are offset from each other in a direction of the beam;wherein the first block and the second block are at least partially transparent to the particle beam, the first block having a surface that is perpendicular to the beam; andwherein the first block is moveable between the first position and the second position as a single unit, and has a size sufficient to traverse an entire cross section of the beam when the first block is at the second position. 26. The energy modulator of claim 25, further comprising a third block, wherein the first, second, and third blocks are offset from each other in a direction of the beam. 27. The energy modulator of claim 26, wherein the third block has a thickness that is four times the thickness of the first block. 28. The energy modulator of claim 26, wherein, the third block is moveable relative to the first block and the second block. 29. The energy modulator of claim 25, further comprising a positioner for moving the first block. 30. The energy modulator of claim 29, wherein the positioner is driven by hydraulics or pneumatically. 31. The energy modulator of claim 29, wherein the positioner is driven by a rotating or linear motor. 32. The energy modulator of claim 25, wherein the first block has an opposite surface that is parallel to the surface. 33. The energy modulator of claim 25, further comprising a first mounting structure to which the first and the second blocks are slidably mounted. 34. The energy modulator of claim 33, wherein the first mounting structure is mounted to a particle delivery system having the particle source, a particle transport system, and a nozzle. 35. The energy modulator of claim 34, wherein the first mounting structure is mounted to the particle delivery system such that the first mounting structure is closer to the particle source than the nozzle. 36. The energy modulator of claim 35, further comprising a second mounting structure to which a plurality of blocks are slidably mounted, wherein the second mounting structure is mounted to the particle delivery system such that the second mounting structure is closer to the nozzle than the particle source. 37. The energy modulator of claim 25, wherein the first block is made from a first material, and the second block is made from a second material that is different from the first material. 38. The energy modulator of claim 37, wherein the second material has a Z value that is less than a Z value of the first material. 39. The energy modulator of claim 25, further comprising a cooling system coupled to the first block, the second block, or both. 40. The energy modulator of claim 25, further comprising an energy sensor, and a control coupled to the energy sensor, wherein the control is configured to adjust a position of the first block based on a feedback signal provided by the energy sensor. 41. The energy modulator of claim 25, wherein the particle source comprises a proton source. 42. The energy modulator of claim 25, further comprising a frame having a first side and a second side, wherein the first block has a thickness that is less than 1 cm and is mounted between the, first and second sides. 43. The energy modulator of claim 42, further comprising a cooling system for providing cooling to the first block via convection. 44. The energy modulator of claim 25, wherein the second block has a thickness that is two times a thickness of the first block. 45. The energy modulator of claim 44, wherein the thickness of the second block is measured in a direction of the beam. 46. The energy modulator of claim 25, wherein the first block comprises a solid portion that is moveable relative to the path of the beam. 47. The energy modulator of claim 25, wherein the first block, when placed in the path of the beam, is aligned with a longitudinal axis of a particle accelerator. 48. An energy modulator for use with a particle source that provides a beam of particles, comprising:a first block moveable between a first position and a second position, wherein when the first block is at the first position, it is out of a path of the beam, and wherein when the first block is at the second position, it is in the path of the beam; anda second block moveable relative to the first block, wherein the second block and the first block are offset from each other in a direction of the beam;wherein the first block and the second block are at least partially transparent to the particle beam, and wherein the first block is made from a first material, the second block is made from a second material that is different from the first material; andwherein the first block is moveable between the first position and the second position as a single unit, and has a size sufficient to traverse an entire cross section of the beam when the first block is at the second position. 49. The energy modulator of claim 48, further comprising a third block, wherein the first, second, and third blocks are offset relative to each other in a direction of the beam. 50. The energy modulator of claim 49, wherein the second block has a thickness that is two times a thickness of the first block, and the third block has a thickness that is four times the thickness of the first block. 51. The energy modulator of claim 49, wherein the third block is moveable relative to the first block and the second block. 52. The energy modulator of claim 48, further comprising a positioner for moving the first block. 53. The energy modulator of claim 52, wherein the positioner is driven by hydraulics or a pneumatic mechanism. 54. The energy modulator of claim 52, wherein the positioner is driven by a rotating or linear motor. 55. The energy modulator of claim 48, wherein the first block comprises a rectangular block. 56. The energy modulator of claim 48, wherein a surface of the first block is perpendicular to the beam. 57. The energy modulator of claim 48, further comprising a first mounting structure to which the first and the second blocks are slidably mounted. 58. The energy modulator of claim 57, wherein the first mounting structure is mounted to a particle delivery system having the particle source, a particle transport system, and a nozzle. 59. The energy modulator of claim 58, wherein the first mounting structure is mounted to the particle delivery system such that the first mounting structure is closer to the particle source than the nozzle. 60. The energy modulator of claim 59, further comprising a second mounting structure to which a plurality of blocks are slidably mounted, wherein the second mounting structure is mounted to the particle delivery system such that the second mounting structure is closer to the nozzle than the particle source. 61. The energy modulator of claim 48, wherein the second material has a Z value that is less than a Z value of the first material. 62. The energy modulator of claim 48, further comprising a cooling system coupled to the first block, the second block, or both. 63. The energy modulator of claim 48, further comprising an energy sensor, and a control coupled to the energy sensor, wherein the control is configured to adjust a position of the first block based on a feedback signal provided by the energy sensor. 64. The energy modulator of claim 48, wherein the particle source comprises a proton source. 65. The energy modulator of claim 48, further comprising a frame having a first side and a second side, wherein the first block has a thickness that is less than 1 cm and is mounted between the first and second sides. 66. The energy modulator of claim 65, further comprising a cooling system for providing cooling to the first block via convection. 67. The energy modulator of claim 48, wherein the first block comprises a solid portion that is moveable relative to the path of the beam. 68. The energy modulator of claim 48, wherein the first block, when placed in the path of the beam, is aligned with a longitudinal axis of a particle accelerator. 69. A method for modulating an energy of a particle beam, comprising:determining information regarding a desired particle beam energy;determining a combination of blocks to be placed in a path of a beam based on the determined information, wherein the blocks are offset from each other in a direction of the beam; andpositioning the blocks such that they are in the path of the beam;wherein at least one of the blocks includes a solid portion that is positionable from a first location that is out of the path of the beam, to a second location that is in the path of the beam; andwherein the at least one of the blocks is moveable between the first location and the second location as a single unit, and has a size sufficient to traverse an entire cross section of the beam when the at least one of the blocks is at the second position. 70. The method of claim 69, wherein the particle beam comprises a proton beam. 71. The method of claim 69, wherein the act of determining the combination of blocks comprises selecting the blocks from a set of blocks, each of the blocks in a part of the set having a thickness that is different from the remaining blocks in the part of the set. 72. The method of claim 71, wherein one of the blocks in the part of the set has a thickness that is two times a thickness of another one of the blocks in the part of the set. 73. The method of claim 69, wherein the blocks are at least partially transparent to the beam. 74. The method of claim 69, wherein each of the blocks has two surfaces that are parallel to each other. 75. The method of claim 69, wherein one of the blocks has a Z value that is different from a Z value of another one of the blocks. 76. The method of claim 69, further comprising cooling the blocks. 77. The method of claim 76, wherein one of the blocks is cooled using liquid, and another one of the blocks is cooled using convection. 78. The method of claim 69, wherein the act of determining the information regarding the desired particle beam energy comprises obtaining the information from a treatment plan. 79. The method of claim 69, wherein the act of determining the information regarding the desired particle beam energy comprises: measuring an energy of a delivered beam; and determining a difference between the measured energy and a desired energy, wherein the information comprises the determined difference. 80. The method of claim 69, wherein the blocks comprise respective solid portions that are moveable relative to each other. |
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summary | ||
062857436 | claims | 1. A soft X-ray source comprising: a mirror having a focal point, the mirror being parabolic or ellipsoidal; a nozzle delivering a target material to a plasma generation point substantially coincident with the focal point; and a laser source delivering a pulsed laser beam to the plasma generation point, wherein a plasma is generated at the plasma generation point upon irradiation by the pulsed laser beam, the plasma emitting soft X-rays that are formed into X-ray beams by the mirror, wherein the X-ray beams are parallel if reflected from the parabolic mirror and converging if reflected from the ellipsoidal mirror, and wherein one of an axis of the nozzle and an axis of the pulsed laser beam is coaxial with an axis of the mirror. a protective plate that protects the mirror from the target material; and a target material recovery device that collects the target material when the protective plate is protecting the mirror. ejecting a target material from a nozzle towards a plasma generation point; irradiating the target material with a pulsed laser beam; and forming soft X-ray beams by reflecting soft X-rays emitted by the plasma from a mirror, the mirror being parabolic or ellipsoidal, the soft X-ray beams being parallel or converging, wherein the pulsed laser beam is directed towards substantially a focal point of the mirror, the focal point being substantially coincident with the plasma generation point, and wherein one of an axis of the nozzle and an axis of the pulsed laser beam is coaxial with an axis of the mirror. a nozzle ejecting a target material towards a plasma generation point; a mirror having a focal point that substantially corresponds to the plasma generation point, the mirror being parabolic or ellipsoidal; and a laser source delivering at least two pulsed laser beams to the plasma generation point, wherein a plasma is generated at the plasma generation point in response to irradiation by the two pulsed laser beams, and wherein the plasma emits the soft X-rays, the soft X-rays being reflected into parallel or converging X-ray beams by the mirror, and wherein one of an axis of the nozzle and an axis of the pulsed laser beam is coaxial with an axis of the mirror. ejecting a target material towards a plasma generation point from a nozzle; irradiating the target material at the plasma generation point with at least two pulsed laser beams so as to form a plasma; and reflecting soft X-rays emitted by the plasma from a mirror to form beams, the mirror being parabolic or ellipsoidal, wherein the beams are parallel if reflected from the parabolic mirror and converging if reflected from the ellipsoidal mirror, wherein a focal point of the mirror is substantially coincident with the plasma generation point, and wherein one of an axis of the nozzle and an axis of the pulsed laser beam is coaxial with an axis of the mirror. wherein the soft X-ray reflective mirror has a focal point corresponding to the plasma generation point. a low pressure vessel; a nozzle in the low pressure vessel, the nozzle ejecting a target material towards a plasma generation point; a mirror having a focus corresponding to the plasma generation point, the mirror being parabolic or ellipsoidal; and a laser irradiating the target material at the plasma generation point to convert a portion of the target material into a plasma, wherein electromagnetic energy emitted by the plasma is reflected from the mirror to form beams, wherein the beams are parallel if reflected from the parabolic mirror and converging if reflected from the ellipsoidal mirror. a source of electromagnetic waves in a wavelength range between 0.1 nm to 300 nm; a source of target material, the target material being one of a liquid, liquid droplets, fine particles, gas and clusters; an irradiation source for irradiating the target material and converting the target material into a plasma that emits radiation in the wavelength range between 0.1 nm to 300 nm, wherein the source of electromagnetic waves includes an optical element for shaping the radiation into the electromagnetic waves, wherein a reflective surface of the optical element is substantially axially symmetrical, wherein the irradiation source irradiates the target material from a direction of the optical element, wherein the source of the target material does not block a path of the electromagnetic waves, and wherein the electromagnetic waves are parallel if reflected from the parabolic mirror and converging if reflected from the ellipsoidal mirror. wherein a central axis of the source of the target material and a central axis of the mirror coincide, and wherein an optical axis of the irradiation source does not pass through the source of the target material. wherein the target material is irradiated from a plurality of directions. 2. The soft X-ray source of claim 1, further including a reflective surface on a concave face of the mirror that reflects the soft X-rays emitted from the plasma. 3. The soft X-ray source of claim 2, wherein the reflective surface does not reflect the soft X-rays towards the nozzle. 4. The soft X-ray source of claim 1, wherein the target material is a liquid. 5. The soft X-ray source of claim 1, wherein the target material is a solid. 6. The soft X-ray source of claim 5, further including: 7. The soft X-ray source of claim 1, wherein the target material is one of a gas and clusters. 8. The soft X-ray source of claim 1, further including a hole in the mirror, wherein the pulsed laser beam is delivered through the hole to the plasma generation point. 9. A method of generating soft X-rays comprising the steps of: 10. The method of claim 9, wherein the mirror includes a reflective surface that reflects the soft X-rays emitted by the plasma and forms the soft X-ray beams. 11. An apparatus for generating soft X-rays comprising: 12. The apparatus of claim 11, wherein the pulsed laser source delivers at least four pulsed laser beams to the plasma generation point. 13. The apparatus of claim 11, wherein the nozzle is positioned away from the plasma generation point, such that the pulsed laser beams do not impact the nozzle. 14. The apparatus of claim 11, further including at least two apertures in the mirror, wherein the at least two pulsed laser beams are delivered through the at least two apertures to the plasma generation point. 15. The apparatus of claim 14, wherein a number of the apertures corresponds to a number of the pulsed laser beams. 16. The apparatus of claim 11, further including a soft X-ray filter in a path of the X-ray beams, the soft X-ray filter including a first portion that passes the soft X-rays, and a second portion that blocks the soft X-rays. 17. The apparatus of claim 11, further including a soft X-ray reflection mirror that reflects the soft X-rays towards the mirror, the soft X-ray reflection mirror having a focal point substantially coincident with the plasma generation point. 18. The apparatus of claim 11, wherein the mirror includes a multi-layer reflective film having a thickness distribution so that the mirror has the same reflection wavelength throughout its surface for soft X-rays emitted from the focal point of the mirror. 19. A method of generating soft X-rays comprising the steps of: 20. The method of claim 19, wherein the nozzle is positioned away from the plasma generation point such that the two pulsed laser beams do not impact the nozzle. 21. The method of claim 19, further including the step of passing a first portion of the soft X-rays through a soft X-ray filter, and blocking a second portion of the beams with the soft X-ray filter. 22. The method of claim 19, further including the step of reflecting the soft X-rays emitted by the plasma from a soft X-ray reflective mirror towards the mirror, 23. An electromagnetic wave source comprising: 24. An exposure apparatus comprising: 25. The exposure apparatus of claim 24, wherein the optical element includes a mirror, the mirror being parabolic or ellipsoidal, 26. The exposure apparatus of claim 24, wherein the target material jets out of the source of the target material in a direction along an axis of rotational symmetry of the optical element, and 27. The exposure apparatus of claim 26, wherein the plurality of directions are distributed at substantially equal angular intervals. 28. The exposure apparatus of claim 26, wherein beams from the irradiation source directed at the target material from the plurality of directions have substantially the same intensity, and irradiate the target material at substantially the same time. 29. The exposure apparatus of claim 26, wherein beams from the irradiation source directed at the target material irradiate the target material from one of the same direction and different directions at the same time. 30. The exposure apparatus of claim 24, wherein the optical element includes a multi-layer reflective film whose film having a thickness distribution so that the optical element has the same reflection wavelength throughout the reflective surface for electromagnetic waves emitted from a focal point of the optical element. 31. The exposure apparatus of claim 24, further including a filter to block a portion of the electromagnetic waves in the wavelength range between 0.1 nm to 300 nm emitted from a focal point of the optical element. 32. The exposure apparatus of claim 24, further including a reflective mirror reflecting the electromagnetic waves in the wavelength range between 0.1 nm to 300 nm generated at a focal point of the optical element, the reflective mirror having a focal point substantially coinciding with the focal point of the optical element and reflecting the electromagnetic waves in the wavelength range between 0.1 nm to 300 nm towards the optical element. 33. The exposure apparatus of claim 24, wherein the target material is one of xenon, krypton, oxygen, a compound of oxygen and a mixture gas including any one of xenon, krypton, oxygen, and the compound of oxygen. |
description | The United States Government has rights in this invention pursuant to Contract No. W-31-109-ENG-38 between the United States Government and The University of Chicago and/or pursuant to Contract No. DE-AC02-06CH11357 between the United States Government and UChicago Argonne, LLC representing Argonne National Laboratory. The present invention relates to an improved apparatus and method of making the apparatus for sharper focusing of hard x-rays; and more specifically, relates to a Multilayer Laue Lens (MLL) zone plate for focusing of hard x-rays and a method of making the MLL zone plate. Modern synchrotron-radiation facilities provide unprecedented levels of intensity and collimation in x-ray beams and offer tremendous research opportunities. The development of improved x-ray focusing optics is essential for further advances in x-ray microimaging and microanalysis applications. Focusing optics for x-rays differ from those for visible light, as the refractive index of solids is slightly smaller than unity for x-rays and significantly greater than unity for visible light. Reflective x-ray mirrors, such as elliptical Kirkpatrick-Baez (KB) mirrors and tapered hollow capillaries, can be used only at very small grazing angles below the critical angle of the reflecting material. Refractive lenses for x-rays have the opposite curvature to that for visible light. A solid focusing lens for visible light corresponds to a cavity with the same shape for x-rays. Since the refractive index is very close to one, a series of concave lenses is needed to give a reasonable focal length for x-rays. This kind of refractive lens, using materials of low absorption, has been used to focus x-rays. While submicron x-ray spots have been achieved with reflective and refractive optics, the smallest x-ray focal spots obtained were produced using Fresnel zone plates. Spatial resolution on the order of 20 nm in the soft-x-ray range has been reported. Fresnel zone-plate lenses are diffractive optics. Traditional zone plates are circular transmission gratings consisting of alternating transparent and opaque (or phase-shifting) rings. Each ring (or zone) is positioned so that the optical path from the zone plate to the primary focus differs by λ/2 between consecutive zones, where λ is the x-ray wavelength. X-rays diffracted by the zones thus add “in phase” at the primary focus. The optimum zone positions are given by the Fresnel zone-plate formula,rn2=nλf+n2λ2/4, (1)Where rn is the radius of the nth zone, and f is the focal length. The second term in Eq. (1) is a correction for spherical aberration and can be omitted when nλ<<f. The width of the nth zone is (rn−rn−1). The focusing capability of a zone plate depends on the width of the outermost zone, the optical contrast between the alternating zones, and the accuracy of the zone placement. Both transmission- and reflection-geometry zone plates have been developed. For optimized x-ray zone plates, depths of several microns are typically required for efficient focusing of hard x-rays. Traditional Fresnel zone plates have been used extensively to build x-ray microscopes for soft x-rays. For example, such a microscope is available from Xradia Inc. of Concord, Calif. A major effort in the field of x-ray nanoprobes and microscopes is to achieve efficient, high-spatial-resolution focused x-ray beams. Several approaches have been explored using traditional zone plates, refractive lenses, Kirkpatrick-Baez (KB) mirrors, and channel waveguides combined with KB mirrors, which have pushed the spatial resolution below the 100-nm level. Traditional zone plates are fabricated using lithographic techniques with metal electroplating on silicon nitride membranes. For efficient focusing of hard x-rays, a very large aspect ratio is required, which presents a formidable challenge for the manufacturing process. To achieve a high aspect ratio of zone depth to width, a mask with the zone-plate pattern is first made using e-beam lithography, and x-ray lithography is then used with a thick resist and subsequent metal electroplating on silicon nitride membranes for zone-plate fabrication. Tremendous progress has been made in this field, and very recently a spatial resolution of 60 nm was achieved for 8 keV hard x-rays using zone plates with a 50 nm outermost zone width and 1 μm zone depth with gold as the zone material. However, as the desired zone width becomes smaller and zone depth larger, the manufacturing process becomes increasingly difficult. A principal aspect of the present invention is to provide a Multilayer Laue Lens (MLL) zone plate for effectively focusing hard x-rays and a method of making the MLL. Another aspect of the present invention is to provide such Multilayer Laue Lens (MLL) zone plate enabling a fine zone width and a large aspect ratio for effectively focusing hard x-rays. Other important aspects of the present invention are to provide such Multilayer Laue Lens (MLL) zone plate and a method of making the MLL zone plate substantially without negative effect and that overcome some of the disadvantages of prior art arrangements of traditional zone plate. In brief, a zone plate multilayer structure and method of making a Multilayer Laue Lens (MLL) for focusing hard x-rays are provided. The zone plate multilayer structure includes a substrate carrying a plurality of alternating layers respectively formed of tungsten silicide (WSi2) and silicon (Si). The alternating layers are sequentially deposited precisely controlling the thickness of each layer from a minimum thickness of a first deposited layer adjacent the substrate to a maximum thickness of a last deposited layer. The first minimum thickness layer has a selected thickness of less than or equal to 5 nm with the thickness of the alternating layers monotonically increasing to provide a zone plate multilayer structure having a thickness of greater than 12 μm (microns). The multilayer structure is sliced and polished to many sections with desired dimensions. Each section can be used as a partial linear zone plate to focus hard x-rays to a line. The x-rays are diffracted in Laue transmission geometry by the specific arrangement of silicon and tungsten silicide. Two such sections crossed focus the x-rays to a point. The sections are tilted at an optimum angle for high diffraction efficiency. For example, highest efficiency is achieved with the layers in the multilayer sections are tilted towards the Bragg angle of diffraction. Ideally, four such sections can be used to form a complete MLL. A two-section pair focuses the x-rays to a line and two pairs crossed focus the x-rays to a point. Substantial mechanical design is needed to hold and align the sections. Alternatively, two multilayer structures are bonded together face to face so that the thickest layers are near the bonding layer. They are then sliced and polished to a desired dimension to form a full linear zone plate to focus the x-rays to a line. Two such linear zone plates crossed form a complete MLL to focus the x-rays to a point. In accordance with features of the invention, the thickness of each layer is precisely controlled, for example, in a range of less than three angstroms. Sputtering, such as, direct current (DC) magnetron sputter deposition forms the layers. For example, the plurality of alternating tungsten silicide (WSi2) and silicon (Si) layers is formed on a substrate that is sliced and polished to form many substantially identical multilayer sections. These sections have a selected depth to form partial linear zone plates with a large aspect ratio. In accordance with features of the invention, two multilayers are bonded together face to face to form the full linear zone plate after slicing and polishing, for example, using a sputter-coated gold-tin mixture as a bonding agent and heating in a vacuum oven at a selected temperature for a set time period. For example, the selected temperature is provided in a range between 280 and 300 degrees C. The thickness of the sputter-coated gold-tin layer is precisely controlled so that each layer in the multilayer is placed accurately as required. In accordance with features of the invention, fabrication of linear zone plates is achieved using sputtered-sliced planar multilayers made of selected materials. The fabrication of zone plates by alternative techniques of the invention surmounts some prior art limitations. A growth of a multilayer film to be used in transmission or Laue diffraction geometry is provided, in which the thickness of consecutive layers gradually increases according to the Fresnel zone formula. The film is sectioned after growth to the required depth. For a planar multilayer, this produces a linear zone plate that can focus x-rays substantially in one dimension. In accordance with features of the invention, a method of making a Multilayer Laue Lens (MLL) zone plate includes the deposition and sectioning of a multilayer consisting of high-Z and low-Z layers, where Z is the electron density. The thickness of deposited films can be controlled in the Angstrom range much more precisely than the x-y positioning in a lithographic system. With slicing and polishing, large aspect ratios can easily be obtained. In accordance with features of the invention, it has been determined that WSi2/Si is the selected good multilayer system because of its excellent mechanical and thermal properties and sharp interfaces. Thick zone-plate multilayers (>10 μm) have been grown without cracking or peeling. A partial zone-plate multilayer structure of 8 μm with p=0.27 and Δrmin=15 nm has produced a 72.7-nm line focus for 19.5-keV x rays, where p is the fraction number of the partial structure relative to the full zone plate structure. Techniques of the invention are provided to perfect the multilayer growing process and related thin-film growth issues for a structure of 12.43 μm with Δrmin=10 nm. In accordance with features of the invention, a multilayer structure of 728 alternating WSi2 and Si layers with thicknesses gradually increasing from 10 to ˜58 nm according to the Fresnel zone-plate formula has been fabricated using dc magnetron sputtering. This structure was analyzed with a scanning electron microscope (SEM) and tested with 19.5-keV synchrotron x-rays after sectioning and polishing. Line focus sizes as small as 30.6 nm have been achieved using a sectioned multilayer in transmission diffraction geometry. In accordance with features of the invention, another multilayer structure of 1588 alternating WSi2 and Si layers with thicknesses gradually increasing from 5 to ˜25 nm according to the Fresnel zone-plate formula for a total thickness of approximately 13.25 μm has been fabricated using DC magnetron sputtering. This structure was analyzed with a scanning electron microscope (SEM) and tested with 19.5-keV synchrotron x-rays after sectioning and polishing. Line focus sizes as small as 17 nm have been achieved. In accordance with features of the invention, a Multilayer Laue Lens (MLL) zone plate advantageously is used for focusing x-rays in the 5 to 100 KeV range, and can be used long term, whereas conventional devices used in the 5 to 24 KeV range typically show signs of deterioration after only several weeks of use. In accordance with features of the invention, two partial multilayer linear zone plates aligned in series perpendicularly can be used to form a partial Multilayer Laue Lens to focus the x-rays to a point. In accordance with features of the invention, with sophisticated mechanical design to hold and align the partial linear zone plates, four partial multilayer linear zone plates can be used to form a complete Multilayer Laue Lens to focus the x-rays to a point. In accordance with features of the invention, by using a metallic bonding technique detailed in this invention, two zone-plate multilayer structures can be bonded together face to face with precision to keep the zone positions that are required for a zone plate. Two sliced and polished bonded zone-plate multilayer structures aligned in series perpendicularly can be used to form a complete Multilayer Laue Lens to focus the x-rays to a point. Having reference now to the drawings, in FIG. 1 there is shown an exemplary Multilayer Laue Lens (MLL) in accordance with the preferred embodiment and generally designated by the reference numeral 100. The Multilayer Laue Lens (MLL) zone plate 100 is a multilayer device for focusing hard x-rays. The Multilayer Laue Lens (MLL) zone plate 100 is based on x-ray diffraction and obeys the zone-plate law as a traditional zone-plate while having a different shape and fabrication method. The Multilayer Laue Lens (MLL) zone plate 100 of the invention is robust, and does not crack while prior known construction methods have resulted in fragile layers that would crack and fail. The Multilayer Laue Lens (MLL) zone plate 100 includes a first section 102 and a second section 102. The first and second sections 102 are substantially identical. Each section 102 includes a substrate 104 carrying a multilayer 106 of a plurality of alternating layers respectively formed of tungsten silicide (WSi2) and silicon (Si). The alternating layers of multilayer 106 have an increasing thickness from a minimum thickness adjacent the substrate 104 and a maximum thickness near the bonded portion 110 nearest to an optical axis (OA) of the MLL zone plate 100 indicated by an arrow labeled OA. The x-rays are diffracted in Laue transmission geometry by the specific arrangement of silicon and tungsten silicide. As illustrated in FIG. 1, two substantially identical planar multilayer sections 102 fabricated using sputtered-sliced multilayers grown on flat Si substrates are assembled to form the two halves of the MLL linear zone plate 100, to produce a focus in one dimension. The separation of the two halves without a bonding layer allows the multilayer sections 102 to be tilted at the optimum angle (typically ˜0.1 degree according to our experiments) for high diffraction efficiency. With a bonding layer the two halves cannot be tilted independently. The natural bending for the thin polished bonded halves can help to enhance the diffraction efficiency. Another pair of multilayer sections 102 rotated by 90° about the optical axis advantageously can be used to produce a point focus. This new type of linear zone plate is called a Multilayer Laue Lens (MLL) zone plate 100. The MLL zone plate or structure 100 is defined by the Fresnel zone-plate formularn2=nλf+n2λ2/4 Eq. (1),where λ is the x-ray wavelength, f is the focal length, and rn is the layer position of the nth zone. The second term can be omitted when nλ<<f, leading to a d-spacing of d(rn)≡(rn−rn-2)≈fλrn. A plot of 1/d(rn) versus rn is then a straight line with a slope of 1/fλ related to the focal length. The resolution limit for an ideal full MLL equals the outermost zone width Δrmin. For a partial structure, the resolution becomes Δrmin/p, where p is the fraction number of the partial structure. To achieve a nanofocus, one needs an unprecedented multilayer with thousands of layers and precise layer thickness correlations. It has been determined by the present inventors that WSi2/Si is the multilayer system to achieve this goal. Since the multilayer sections 102 are assembled with the substrate side 104 oriented away from the optical axis OA, the thinnest zones of multilayer 106 are grown first, minimizing the impact of accumulated growth imperfections on zone-plate performance. The fabrication of the MLL linear zone plate 100 achieves three major challenges to growing the linear zone-plate multilayer structures. First, MLL linear zone plate 100 including alternating layers of tungsten silicide (WSi2) and silicon (Si) has both low stress and good adhesion to survive the subsequent cutting and polishing. Second, the growth process of the alternating layers of tungsten silicide (WSi2) and silicon (Si) enables each zone layer to be precisely placed. Third, automatically performing prolonged deposition according to the zone-plate formula and with growth-rate correction for each layer advantageously is provided in accordance with the preferred embodiment. Referring to FIGS. 2A, 2B, 2C and 2D, there are shown exemplary steps for making three kinds of Multilayer Laue Lens (MLL) zone plates in accordance with the preferred embodiment starting with a planar silicon (Si) substrate, such as a flat super polished Si substrate as indicated in a block 202. A first layer of tungsten silicide (WSi2) with a minimum thickness, such as 5 nm is deposited by magnetron sputtering as indicated in a block 204. A next layer of silicon Si also having a minimum thickness, such as 5 nm is deposited by magnetron sputtering as indicated in a block 206. Controlled depositing of alternating layers of tungsten silicide (WSi2) and silicon (Si) layers with gradually increasing thickness is provided as indicated in a block 208. The thickness of each layer is precisely controlled, for example, in a range of less than three angstroms. Sputtering, such as, direct current (DC) magnetron sputter deposition forms the layers, to provide a total thickness of 13.25 microns with a maximum layer thickness of ˜25 nm at block 208. Then as indicated in a block 210, for example, the plurality of alternating tungsten silicide (WSi2) and silicon (Si) layers being formed on a substrate is sliced to form multiple identical multilayer sections. The multilayer sections are then polished to a selected depth to form multiple partial linear zone plates with a large aspect ratio. As indicated in a block 220 in FIG. 2B, two partial multilayer linear zone plate sections are assembled in series and crossed perpendicularly to form a partial Multilayer Laue Lens to focus x-rays to a point; each partial multilayer linear zone plate section is tilted at an optimum angle for high diffraction efficiency. For example, highest efficiency is achieved with the layers in the multilayer sections are tilted towards a certain Bragg angle of diffraction in the multilayer (typically ˜0.1 degree according to our experiments). As illustrated in FIG. 1, each multilayer section 102 produces a line focus, and two identical sections advantageously are combined to give a higher numerical aperture (higher reception of x-rays) and higher spatial resolution. Since only one section is used to produce a line focus in the partial Multilayer Laue Lens configuration, the optimum spatial resolution and efficiency are not utilized. However, the mechanical design for holding and aligning the sections are greatly simplified. As indicated in a block 230 in FIG. 2C, four partial multilayer linear zone plate sections are assembled to form a full Multilayer Laue Lens to focus x-rays to a point; sophisticated mechanical design is needed to hold and align the partial linear zone plates with two of them forming a pair to focus the x-rays to a line and another pair crossed to focus the x-rays to a point. As indicated in a block 240 in FIG. 2D, two zone-plate multilayer structures are bonded together face to face with the thickest layers near the bonding layer, with for example a gold-tin mixture used for a bonding agent, and heating in a vacuum oven at a selected temperature for a set time period. For example, the selected temperature is provided in a range between 280 and 300 degrees C. Then as indicated in a block 242, the bonded multilayer structures are sliced into multiple identical sections and polished to a selected depth to produce multiple full linear zone plates to focus x-rays to a line. Due to the thinness of the polished sections (in the order of 5-25 μm), the polished piece naturally bends slightly to one side. By selecting the favorable side to face the x-rays, the diffraction efficiency can be enhanced. By controlling the length-to-width ratio of the sliced pieces, the bending degrees of the polished pieces are controlled with the right curvatures selected to enhance the diffraction efficiency of the linear zone plate. As indicated in a block 244, two bonded full linear zone plates are aligned perpendicularly to produce a full Multilayer Laue Lens to focus x-rays to a point. Experimental Results Two multilayer systems have been investigated: WSi2/Si and W/Si on Si substrates. All depositions reported here were carried out at the Advanced Photon Source deposition laboratory at Argonne National Laboratory using DC magnetron sputtering. Multiple substrates can be loaded at different locations on a 60-inch-long substrate holder, with no detectable difference because of the location and a lateral uniformity within 1% across a 100-mm width for thin films. All targets were 3 inches in diameter and 0.25 inch thick. The Si target was 99.999% boron-doped, and the WSi2 target was 99.5% powder-hot-pressed with a density of 8.04 to 8.08 g/cc. The substrates were loaded on a carrier with the optical surface facing down and were alternately translated back and forth over two 3-in.-diam planar sputter guns during deposition. The substrate-to-target distance was 107 mm with no bias applied to the substrates. Laterally uniform depositions were achieved through the design of shaped apertures above the sputter guns. The sputter guns were operated at a constant current of 0.5 A, and the film thicknesses were controlled by the translation speeds and the number of loops over the gun according to growth-rate calibrations. The guns were programmed to turn on 7 seconds before the substrate was moved over and to turn off after a desired thickness was deposited. This procedure reduces the use of the target material, lowers the target temperature, and helps ensure comparable growth conditions for each sequential layer growth. We measured the composition of our sputtered WSi2 films using energy dispersive x-ray (EDX) analyses. The typical ratio of Si to W was 1.874±0.118. The sputter guns and depositions advantageously are automated. The voltage, current, and power readings of the sputter power supplies advantageously are logged into a computer during deposition for monitoring purposes. Zone-plate multilayers are grown according to the Fresnel zone formula, precalibrated growth rates, and predetermined growth-rate-drift corrections. Growth rate tests advantageously are performed on targets at different states of usage using both constant current and constant power modes. Periodic test samples are analyzed using x-ray reflectance measurements with an optical modeling software, and zone-plate multilayers were studied by SEM image analyses. To satisfy the zone-position requirement of Eq. (1), the thickness of each layer must be precisely controlled. We need to understand the growth rate for each multilayer component and how the growth rate changes during the growth of each layer and over the course of the multilayer deposition. For these purposes, periodic multilayer test samples were grown using different procedures and measured using x-ray reflectance. The analysis of the reflectivity was done with the aid of IMD, a computer program for modeling the optical properties of multilayers. Reflectivity measurements were made in θ-2θ geometry over the range from 0<θ<6°, using Cu Kα1 x-rays with a collimating multilayer optic followed by a Ge crystal monochromator. The measured data were compared with that calculated using the IMD software for a best fit to determine layer thicknesses and interface parameters. The following procedure was designed to understand the multilayer growth and to calibrate the growth rates. Two 12.5×25×0.5 mm3 Si test substrates (cut from an ordinary wafer) were loaded on the substrate holder ˜40 cm apart. Two different [WSi2/Si]×15 multilayers were grown on these substrates with certain fixed moving speeds when they were passing the sputter guns. For substrate A, three loops over the WSi2 gun and two loops over the Si gun were used to complete a bilayer. For substrate B, two loops over the WSi2 gun and three loops over the Si gun were used to complete a bilayer. The fitted thickness for Si was 50.28 Å for sample Å and 75.42 Å for sample B, and for WSi2 was 36.12 Å for A and 24.08 Å for B. The results indicate that the thicknesses of both WSi2 and Si scale linearly with the number of loops over the target. The same procedure was later used to study W/Si multilayers, with W replacing WSi2 and with different fixed speeds. This time the Si thickness was 20.58 Å for sample A and 37.85 Å for sample B, and the W thickness was 52.92 Å for A and 35.65 Å for B. The thicknesses for W and Si do not scale linearly with the number of loops. In other words, the traditional scaling method using the deposition time for thickness control cannot be applied to the W/Si multilayer system but can be used in the WSi2/Si system. One possible explanation is that Si is very reactive with W, and a portion of the deposited Si and incoming Si atoms might have diffused into W for the W/Si multilayer system during deposition and cannot be accounted for in the simulation. For the WSi2/Si system, this effect is negligible, since WSi2 is already a silicide. The desired total thickness of the multilayer for the zone-plate application is quite large, at least a few microns for each multilayer material. The growth rate may change from the beginning to the end of deposition. How the rate changes with the target use has to be measured and incorporated in the calculation of the growth of each zone layer. To demonstrate the change of the growth rate with the target use, three Si targets with different target erosion levels were selected for three sets of WSi2/Si×15 and W/Si×15 multilayers under identical growth conditions and the same substrate translation speeds. Only the number of loops over the Si gun was changed: one for sample A, two for B, and three for C. A total of 18 samples were grown and measured with x-rays and analyzed with the IMD software. Three 12.5×25×0.5 mm3 Si substrates were loaded at one time, ˜40 cm apart, for one set of multilayer growth. FIG. 2 summarizes the results of the Si layer thickness as a function of Si deposition time. The WSi2 (and W) layer thicknesses were very close in value for each set of samples. The three Si targets are: “new”—barely used, “middle”—with an erosion depth of ˜4.8 mm, and “old”—with an erosion depth of ˜6.1 mm. The targets were all 3 inches in diameter and 0.25 inch in thickness. Referring now to FIG. 3, one can see that the growth rate decreases with target use, with the decrease most rapid when the target is new. We thus use only targets that have been moderately used for zone-plate multilayer growth. Also one can clearly see that the Si layer thickness does not extrapolate to zero at zero growth time for W/Si, in contrast to the case for WSi2/Si. The nonlinearity of layer thicknesses with deposition time has been previously reported for the W/Si multilayer system using x-ray reflectance analyses and the IMD software. Interfacial diffusion, mixing due to energetic bombardment, and resputtering were attributed as possible causes for the nonlinearity. Our studies support the case for interdiffusion, since the WSi2/Si system obeys a linear scaling. It is well known that multilayers consisting of chemically reacting materials (such as W/Si and Mo/Si) suffer more diffusive mixing and are less stable than multilayers consisting of nonreacting materials (such as WSi2/Si and MoSi2/Si). The diffusive mixing in these multilayers is a dominant factor in interfacial imperfection. In our pursuit of small-d-spacing multilayers for narrow-bandpass monochromator applications, we have found that WSi2/Si multilayers have sharper interfaces than W/Si multilayers. Because of its linear growth-rate behavior and sharp interfaces, WSi2/Si is an ideal multilayer system for linear zone-plate applications. An added advantage for the WSi2/Si system is the relatively high growth rate. Under the same growth conditions, Si grows approximately eight times faster than other traditional low-Z materials such as C or B4C. A high growth rate is critical for thick zone-plate growth. By using periodic multilayer and x-ray analyses, one can thus determine the initial growth rate and the growth-rate drift with the growth time for the WSi2/Si system. In the following, we discuss how to grow a linear zone-plate multilayer structure. The Growth of Linear Zone-Plate Multilayers A linear zone-plate structure is defined by Eq. (1), with rn defined as the distance between the outer edge of the nth zone and the optical axis. One may choose an outermost zone width and calculate the zone-plate structure according to the intended x-ray energy range and focal length. For our test sample, we have chosen an outermost zone of 15 nm, λ=0.413 Å (30 keV), and f=10.89 mm. One may use the same zone plate at different energies by adjusting the focal length. For fixed λ and f, the maximum number of zones is determined by the width of the outermost zone Δrout according tonmax≈fλ/4(Δrout)2. (2)Equation (2) is easily derived from Eq. (1) by taking a derivative of rn and using the condition of λ<<f. From Eq. (2), we have nmax of 500 for our test zone plate with r500≈15 μm. Then from Eq. (1) and (rn−rn−1), the layer thickness of each zone was obtained. Zone 500 with a width of (r500−r499)≈15 nm is the outermost zone (layer 1). The corresponding zone plate structure thus has a 30 μm diameter and a 15 nm outmost zone width. It is not necessary to fabricate the full zone structure to produce a focusing optic; the diffraction-limited resolution of a partial zone-plate structure simply varies inversely with the size of the partial structure. We chose to fabricate the zone structure from zone 31 to zone 500, for a total of 470 layers and a total deposition thickness of r500−r30=11.33 μm. Zone 31 has a width of (r31−r30)≈60 nm and is the last-coated layer (Layer 470). When the outermost zone is thin, the difference between neighboring outer zones becomes very small. In our test zone-plate structure, the thickness difference between the first and second WSi2 layer (zone 500 and zone 498) is only 0.3 Å. To produce an ideal zone plate, the layer positions in the structure must be controlled to within a small fraction of the layer width. This means that the accumulated thickness error over hundreds of layers totaling ˜10 μm thickness should be less than a few nanometers. The resolution of the substrate speed control should therefore be significantly smaller than 1×10−4 so that it does not contribute significantly to the accumulated error. A microstepping motor with built-in indexing, manufactured by Compumotor, drives the transport in our deposition system. The indexer can resolve velocities to the fifth decimal place, while the speed we use is in the first decimal place. Growth-rate tests were used to determine the initial speeds for a 1 nm deposition per loop for each material. The required thickness for each zone layer in units of nanometers determines how many loops to use, and the remainder is distributed equally into each loop with a calculated difference in speed. A computer program was developed to calculate the thickness of each layer from Eq. (1) and the time needed for its growth, taking into account the decrease in growth rate during multilayer deposition. The decrease of growth rate over the whole deposition duration was determined according to a series of studies on uniform test multilayers as a function of the target usage. The predetermined growth rate change was used for the growth correction for the WSi2/Si multilayer, apportioned according to the accumulated “target on” time. This computer program compiles a command script to be executed by the system control program. Using this control system, the zone-plate multilayer structure was grown in 2.3 mTorr Ar onto five 12.5×25×0.5 mm3 Si substrates. The coating was carried out automatically and took ˜32 h to complete for the 11.33 μm WSi2/Si multilayer. The same zone-plate multilayer structure was also grown using W/Si with a total growth time of ˜45 h. We noticed that the targets used in growing the W/Si multilayer were “older,” which might contribute to the substantially longer growth time as well. The W/Si zone-plate multilayer cracked and peeled from the substrate on the edges of the multilayer. WSi2/Si multilayers with the same thickness and multilayer structure remained intact and survived subsequent slicing and polishing. During the growth of the 11.33 μm WSi2/Si multilayer we noticed quite a few fallen flakes on the bottom of the Si deposition chamber. For WSi2, the situation was much better; WSi2 has better adhesion to the inner walls of the shield can. Since then we have used aluminum foil to cover the inside of the shield can, especially the upper part directly facing the gun. We noticed improved stability of the sputter guns and no more fallen Si flakes during subsequent zone-plate multilayer growths. Characterization of Linear Zone-Plate Multilayer The face of the WSi2/Si zone-plate multilayer was glued to another Si substrate and sectioned to ˜1×2 mm2 pieces using a diamond dicing saw. A scanning electron microscope (SEM) image of the polished cross section of the multilayer shows flat and sharp interfaces of the multilayer. A gradual increase in d spacing is clearly evident for all WSi2/Si multilayers we studied. SEM images of the multilayer cross section were analyzed to determine the positions of every layer in the multilayer. According to Eq. (1), a plot of the inverse of the layer spacing 1/Δrn versus layer position rn should be a straight line (for λ<<f) with a slope equal to −2/λf. A plot of the inverse of d spacing 1/d(rn) versus layer position rn is also a straight line with a slope equal to −1/λf. Referring to FIG. 4, there is shown measured inverse of d spacing 1/d(rn) versus layer position rn from SEM images for a zone-plate multilayer with 5 nm outermost zone width and 1558 layers, together with a linear fit of the data. The measured data fit beautifully with a straight line, indicating an almost perfect zone plate structure. This zone plate structure has produced a 17-nm line focus for 19.5-keV x-rays. Bonding of Zone-Plate Multilayer Structures As revealed in this invention, a metallic bonding technique is used to bond two multilayer structures together, face to face, with a precise AuSn layer. The AuSn layer is sputter-coated onto the surfaces of both multilayer structures with a thickness calculated from the SEM image analyses of the multilayer. The thickness of AuSn is precisely controlled so that the layers in the zone-plate multilayer still follow the zone plate law. Then the AuSn-coated multilayer structures are clamped together, face to face, and heated in a vacuum oven at a selected temperature for a set time period. For example, the selected temperature is provided in a range between 280 and 300 degrees C. Experiments have been carried out to demonstrate that the multilayer structure does not change after bonding. Periodic test multilayers were heated up to ˜350 degrees C. and x-ray reflectivity measurements were compared before and after heating. Our results demonstrated that no change was observed after heating. A bonded test zone-plate multilayer was sectioned and polished and measured with SEM. The test zone-plate multilayer has an outermost zone width of 12.4 nm and a total multilayer thickness of 13.13 μm. The plot of inverse of d spacing 1/d(rn) versus layer position rn shows that the data in the thinner region of 8.4 μm fit to a straight line and the rest of data in the thicker region deviate from the straight line. FIG. 5 shows the inverse of d spacing 1/d(rn) versus layer position rn of the bonded test zone-plate multilayer as measured from SEM images together with linear fits of the data over the ±8.88 to ±17.28 μm region. The two straight lines extrapolate to the zero position, indicating that a precise bonding layer has been achieved. The bonded test zone-plate multilayer was sliced and polished to as thin as 5 μm without cracking, indicating that the bonding is very strong. A slight natural bending of the thin polished bonded test zone-plate multilayer was observed. This natural bending can be used advantageously in bonded full linear zone plate to enhance the diffraction efficiency. By controlling the length-to-width ratio of the sliced pieces, the bending degrees of the polished pieces can be modified to suit the specific applications. In brief summary, the feasibility of using planar depth-graded multilayers in fabricating high-aspect-ratio linear zone plates for hard x-ray focusing applications has been demonstrated. WSi2/Si is the preferred candidate for growing such multilayers with the required layer-position accuracy. Detailed studies of uniform W/Si and WSi2/Si multilayers demonstrated that WSi2/Si multilayers have more predictable growth rates and sharper interfaces than W/Si ones. WSi2/Si multilayers with layer spacings following the Fresnel zone-plate formula for an outermost zone width of 5 nm have been successfully grown. The analysis of SEM images verified that an almost perfect zone-plate structure was obtained over the entire region of the deposition, which produced very promising line focusing performance of 17 nm for 19.5 KeV x-rays. The feasibility of bonding two zone-plate multilayer structures to produce full linear zone plates has also been demonstrated. Either partial Multilayer Laue Lenses or bonded full Multilayer Laue Lenses can be produced. With a sophisticated mechanical design to hold and align the partial linear zone plates, a full Multilayer Laue Lens without bonding may also be produced. While the present invention has been described with reference to the details of the embodiments of the invention shown in the drawing, these details are not intended to limit the scope of the invention as claimed in the appended claims. |
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047132132 | description | DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The FIGURE shows a steel pressure vessel 1 with a cylindrical cross section, drawn-in in its center part 1a and expanding in its upper part 1b. In the principal part, the lower part, a small high temperature reactor 2 is installed, the core 3 whereof consists of a pile of spherical fuel elements. The pile is surrounded on all sides by a graphite reflector 4. The fuel elements are removed by means of four pebble extraction tubes 5 from the core 3. The fuel elements are added in from above (not shown). The cooling gas primary helix flows through the fuel element pile from bottom to the top. Over the roof part 4a of the graphite reflector 4 there is a hot gas collector chamber 6. A cold gas collector chamber 7 is provided under the core 3. Around the drawn-in part 1a of the steel pressure vessel 1 is a plurality of absorber rods 8 arranged on the pitch circle with a diameter smaller than that of the lower portion of the steel pressure vessel 1. The absorber rods are insertable into the graphite reflector 4 for the shutdown and control of the small high temperature reactor 2. Reservoirs 9 for small absorber pebbles are mounted in close proximity to the pressure vessel, outside said vessel. The absorber pebbles, which are introduced through conduits 10 into the core 3 and removed by means of the pebble extraction tubes 5, represent a second shutdown system for the small high temperature reactor. A heat utilization system is located in the center part 1a and the upper part 1b of the steel pressure vessel 1, which in the present case is a He/He heat exchanger 11. It comprises in this exemplary embodiment two separate annular coil bundles 12 and 13, arranged concentrically and connected in series. The two coil bundles 12 and 13 have different lengths, with the inner, longer coil bundle 12 extending to the hot gas collector chamber 6 and the shorter, outer coil bundle 13 being included in the pressure vessel 1b. The hot primary helium flows from the hot gas collector chamber 6 from below into the coil bundle 12 and is conducted on the outside along the bundle tubes upward, while transferring its heat to the secondary helium flowing through the bundle tubes. At the upper end of the inner coil bundle 12 the primary helium is reversed and enters from above the outer coil bundles 13, wherein it is cooled down further. By means of an annular conduit 14 located between the steel pressure vessel 1 and the jacket of the heat exchanger, and the annular gap 15 provided between the steel pressure vessel 1 and the graphite reflector 4, the cold primary helium is conducted to the bottom of the steel pressure vessel 1, on which on the outside two circulating blowers 16 connected in parallel, are mounted. The circulating blowers 16 move the cold helium back into the cold gas collector chamber 7. In the upper part 1b of the vessel, within the outer coil bundle 13 an annular decay heat exchanger 17 is installed; it follows in line on the primary side the outer coil bundle 13 and is therefore in normal operation located in the flow of cold gas. It is arranged concentrically on the inner coil bundle 12. The decay heat exchanger 17 may be divided in two systems, equipped with separate feed water lines 18a and 18b and the discharge lines 19a and 19b, respectively. To conduct the secondary side helium to the He/He heat exchanger 11, several connection fittings 20 are mounted laterally on the upper part 1b of the vessel, between the decay heat exchanger 17 and the outer coil bundle 13, and connected with a ring header 21. From the ring header 21, conduits lead to the heating surface tubes of the outer coil bundles 13. Above the outer coil bundle 13 a further ring header 23 is provided, wherein the secondary helium heated by the hot primary helium flowing in the opposite direction on the jacket side, is collected and then conducted--through the lines 24--to the heating surface tubes of the inner coil bundle. In these tubes the gas flows downward and enters an outlet header 25. The latter is connected with a tube 26 passing through the center of the inner coil bundle 12 and exiting on top from the steel pressure vessel 1. The secondary helium is removed by the tube 26 and conducted to its place of utilization. |
description | The field of the invention relates generally to a collimators for use in X-ray imaging systems and, more particularly, to a secondary collimator for use with an X-ray diffraction imaging (XDI) system. Known security detection devices are used at travel checkpoints to inspect carry-on and/or checked bags for concealed weapons, narcotics, and/or explosives. At least some known security devices utilize X-ray imaging for screening luggage. For example, XDI systems provide an improved discrimination of materials, as compared to that provided by the X-ray baggage scanners, by measuring d-spacings between lattice planes of micro-crystals in materials. A “d-spacing” is a spacing between adjacent layer planes in a crystal. A checkpoint screening system with XDI using an inverse fan-beam geometry (a large source and a small detector) and a multi-focus x-ray source (MFXS) has been proposed. To reduce the size of the MFXS in such systems, a greater number of detector elements are required. At least one known XDI system includes a secondary collimator defined by an array of slits in a series of high Z (tungsten alloy) baffles. A “high Z” material is a material having a high atomic number, such as, for example, tungsten (Z=74), platinum (Z=78), gold (Z=79), lead (Z=82), and/or uranium (Z=92). However, such a secondary collimator does not permit the number of detector elements to be increased because the baffles cannot be fabricated to include a high number of slits without the operability of the secondary collimator being adversely affected. Moreover, such known secondary collimators are difficult and expensive to manufacture because the collimators are fabricated from tungsten alloy. Known aluminum composite panel (ACP) is used for advertising signs, external walls, curtain boards, recoating for external walls, roofs, private rooms, internal decoration of sound-insulated rooms, advertising boards, automobile skins, and/or internal and external boat decoration. FIG. 4 shows an exploded perspective view of a known aluminum composite panel (ACP). A conventional ACP sheet 300 includes an inner foam core 302 of EPS with a honeycomb geometry. An aluminum skin 304 is coupled to each length-and-height-wise surface 306 and 308 of foam core 302 with adhesive 310 to form ACP sheet 300. In one aspect, a method for assembling a secondary collimator including a first face plate having a first surface and an opposing second surface is provided. The method includes positioning a lamella assembly on the first face plate, wherein the lamella assembly includes at least one radiation-absorbing material layer and at least one radiation-transmitting material layer, such that a first surface of the lamella assembly is adjacent the second surface of the first face plate. The method also includes coupling a second face plate to the first face plate and the lamella assembly such that a first surface of the second face plate is adjacent a second surface of the lamella assembly. In another aspect, a secondary collimator is provided. The secondary collimator includes a first face plate, a second face plate, and a lamella assembly coupled between the first face plate and the second face plate. The lamella assembly includes at least one lamella, wherein each said lamella includes at least one radiation-absorbing material layer and at least one radiation-transmitting material layer. In still another aspect, an X-ray diffraction imaging (XDI) system is provided. The system includes an X-ray source, a detector array including a plurality of detector elements, and a secondary collimator coupled between the X-ray source and the detector array. The secondary collimator includes a first face plate, a second face plate, and a lamella assembly coupled between the first face plate and the second face plate. The lamella assembly includes at least one lamella, wherein each lamella includes at least one radiation-absorbing material layer and at least one radiation-transmitting material layer. While described in terms of detecting contraband including, without limitation, weapons, explosives, and/or narcotics, within baggage, the embodiments described herein can be used for any suitable XDI application. Furthermore, the term “parallel” as used herein refers to planes, lines, curves, and/or layers that are equidistantly spaced apart and never intersect each other. FIG. 1 is a schematic cross-sectional view, in an X-Z plane, of an exemplary embodiment of an X-ray diffraction imaging (XDI) system 10. In the exemplary embodiment, XDI system 10 includes an X-ray source 12, an examination area 14 shown by phantom lines in FIG. 1, a detector array 16, and a secondary collimator 18. X-ray source 12, in the exemplary embodiment, is a multi-focus X-ray source (MFXS) that is movable along a Y-axis 50 and emits an X-ray beam 20 along an X-axis 52 such that a direction 22 of X-ray beam 20 is substantially parallel to the X-axis 52. As such, X-ray source 12 moves in a direction substantially perpendicular to direction 22 of X-ray beam 20. In the exemplary embodiment, detector array 16 is a one-dimensional or two-dimensional pixellated detector array. Alternatively, detector array 16 is a strip detector. In the exemplary embodiment, detector array 16 extends either along a Z-axis 54 or along Z-axis 54 and Y-axis 50 such that X-ray beam 20 is substantially perpendicular to detector array 16. Furthermore, in the exemplary embodiment, detector array 16 has a width WD of approximately 20 mm such that each pixel (not shown) is approximately 1 mm2 and includes more than fourteen detector elements (not shown). Alternatively, detector array 16 has any width and/or number of detector elements that enables XDI system 10 to function as described herein. In the exemplary embodiment, detector array 16 is configured to detect scattered radiation 24 passing through an object 26. Furthermore, in the exemplary embodiment, detector array 16 includes a number of channels 28, for example, N number of channels C1, . . . CN, wherein N is selected based on the configuration of system 10. In the exemplary embodiment, examination area 14 is at least partially defined by a support 30 configured to support object 26 within examination area 14. More specifically, in the exemplary embodiment, object 26 is baggage, luggage, cargo, and/or any other container in which contraband, such as explosives and/or narcotics, may be concealed. Support 30 may be a conveyor device, a table, and/or any other suitable support for object 26. Although in the exemplary embodiment, support 30 is positioned between object 26 and X-ray source 12, support 30 may be positioned between object 26 and detector array 16. Secondary collimator 18, in the exemplary embodiment, is positioned between detector array 16 and object 26 and has a length (not shown) along Y-axis 50 and a width WC along Z-axis 54. In the exemplary embodiment, secondary collimator 18 includes a lamella assembly 32 that is oriented at an angle θ to X-ray beam 20. Lamella assembly 32 is configured to facilitate ensuring that scattered radiation 24 arriving at detector array 16 has a constant scatter angle α with respect to X-ray beam 20 and that a position of detector array 16 permits determination of a depth, such as D1 and/or D2, in object 26 at which the polychromatic X-ray scattered radiation 24 (hereinafter “scattered radiation 24”) originated. For example, lamella assembly 32 is arranged parallel to a direction of scattered radiation 24 to absorb scattered radiation (not shown) that is not parallel to the direction of the scattered radiation 24. More specifically, lamella assembly 32 is arranged such that angle θ is approximately equal to angle α, wherein neither angle θ nor angle α is parallel to direction 22 of X-ray beam 20. Furthermore, although, in the exemplary embodiment, secondary collimator 18 is positioned on one side of X-ray beam 20 with respect to Z-axis 54, secondary collimator 18 may be positioned on both sides of X-ray beam 20 with respect to Z-axis 54. During operation, XDI system 10 implements an inverse fan geometry to measure scattered radiation 24 from object 26 at a substantially constant in-plane angle α. More specifically, X-ray source 12 emits X-ray beam 20 substantially parallel to X-axis 52. X-ray beam 20 passes through object 26 within examination area 14. As X-ray beam 20 passes through object 26, radiation is scattered at a range of angles to X-ray beam 20. At least some of the radiation is scattered radiation 24 at angle α to X-ray beam 20. Scattered radiation 24 passes through lamella assembly 32 of secondary collimator 18 and is detected by detector array 16. Data collected by detector array 16 is transmitted through channels 28 to a control system 34 for further processing. In one embodiment, such processing identifies a material (not shown) of object 26 using d-spacings between lattice planes of micro-crystals in the material, as described above. FIG. 2 is a schematic cross-sectional view of an exemplary secondary collimator 100 suitable for use as secondary collimator 18 in system 10. FIG. 3 is an alternative exemplary secondary collimator 200 suitable for use as secondary collimator 18 in system 10. Secondary collimator 200 is substantially similar to secondary collimator 100 with the exception that secondary collimator 200 is at least partially non-planar in profile, rather than having the substantially planar profile of secondary collimator 100. Because secondary collimators 100 and 200 are substantially similar, for simplicity, only secondary collimator 100 will be described in detail, unless otherwise described. In one exemplary embodiment, secondary collimator 100 includes a lamella assembly 102, a first face plate 104, and a second face plate 106. In the exemplary embodiment, lamella assembly 102 is an assembly that attenuates a portion of radiation and is substantially transparent to another portion of radiation. More specifically, in the exemplary embodiment, lamella assembly 102 is an assembly that includes at least one radiation-absorbing material layer and at least one radiation-transmitting material layer, as described in more detail below. As used herein the term “radiation-transparent material” includes materials that allow a relatively large amount of radiation to pass therethrough, and the term “radiation absorbing material” includes materials that absorb and/or attenuate a relatively large amount of radiation that is directed to the material. Furthermore, as used herein “radiation-absorbing layer,” “radiation-attenuating layer,” “X-ray attenuating layer,” and variations thereof, may be used interchangeably with “metal layer” although a radiation-absorbing layer may be other than metal, and “radiation-transmitting layer,” “radiation-transparent layer,” “non-X-ray attenuating layer,” “X-ray transparent layer,” and variations thereof, may be used interchangeably with “porous material layer” although a radiation-transparent layer may be other than porous material. In the exemplary embodiment, lamella assembly 102 is coupled between first face plate 104 and second face plate 106 such that a first surface 108 of lamella assembly 102 is adjacent an inner surface 110 of first face plate 104, and a second surface 112 of lamella assembly 102 is adjacent an inner surface 114 of second face plate 106. First face plate 104, second face plate 106, and lamella assembly 102 are coupled together using mechanical fasteners, chemical processes, and/or any suitable fastening technique and/or mechanism that enables secondary collimator 100 to function as described herein. One example of a mechanical fastener is clamps 116. As further explained below, each clamp 116 may include a biasing member 126 that applies pressure to the lamella once the secondary collimator 100, 200 is assembled. In the exemplary embodiment, each clamp 116 includes a bar 118 having a first end 122 and a second end 124. A retaining nut 120 may be coupled to the first end 122 of the bar 118. Another retaining nut 120 may be coupled to the second end 124 of the bar 118. A portion of the bar 118 may be threaded. A biasing member 126, such as a spring, may be operatively coupled to bar 118 between first face plate 104 and/or second face plate 106 and respective retaining nut 120. The secondary collimator 100 and/or 200 may include X clamps 116, where X is a number. In the exemplary embodiment, secondary collimator 100 and/or 200 includes a clamp 116 at each corner 142 of secondary collimator 100 and/or 200. First face plate 104 has a length (not shown), a width WP1, and a height HP1. Similarly, second face plate 106 has a length (not shown), a width WP2, and a height HP2. In the exemplary embodiment, the length of first face plate 104 and the length of second face plate 106 are substantially equal, and height HP1 and height HP2 are substantially equal. In one embodiment, the lengths are between approximately 0.5 m and approximately 1.0 m, and heights HP1 and HP2 are each approximately 500 mm. Alternatively, the dimensions of first face plate 104 and/or second face plate 106 are selected based on the configuration of system 10. Furthermore, first face plate 104 and second face plate 106 each has a predetermined profile. In the exemplary embodiment, first face plate 104 and second face plate 106 are substantially planar. Alternatively, as shown in FIG. 3, at least a portion of first face plate 104 and/or a least a portion of second face plate 106 are substantially non-planar such that first face plate 104 and/or second face plate 106 is at least partially non-planar. As such, secondary collimator 200 has an at least partially non-planar profile. In one embodiment, the profile is selected based on the configuration of X-ray source 12 (shown in FIG. 1). In the exemplary embodiment, inner surface 110 of first face plate 104 and inner surface 114 of second face plate 106 have the same or similar profile within a precision of approximately 10 μm over substantially all of a surface area AP1 of inner surface 110 and a surface area AP2 of inner surface 114. In the exemplary embodiment, an outer surface 128 of first face plate 104 and/or an outer surface 130 of second face plate 106 is configured to maintain the profile of the respective first face plate 104 and/or second face plate 106. More specifically, outer surface 128 and/or outer surface 130 may include a configuration, such as ribs (not shown), that facilitates maintaining the planarity of the profile under a pressure force applied to outer surface 128 and outer surface 130. Moreover, each face plate 104 and 106 may be fabricated from steel and/or any other suitable material that enables secondary collimator 100 to function as described herein. Lamella assembly 102, in the exemplary embodiment, is oriented at angle α to X-ray beam 20 (shown in FIG. 1), as described above. Lamella assembly 102 has a length (not shown), a width WL, and a height HL, wherein the width WL is measured from first surface 108 to second surface 112 of lamella assembly 102. In the exemplary embodiment, the length of lamella assembly 102 is substantially equal to the lengths of first face plate 104 and/or the length of second face plate 106, the height HL is substantially equal to heights HP1 and/or HP2, and the width WL is approximately 20 mm. Alternatively, lamella assembly 102 has any suitable dimensions that enable secondary collimator 100 to function as described herein. In one embodiment, width WL is selected based on width WD (shown in FIG. 1) and/or the number of elements of detector array 16 (shown in FIG. 1). In the exemplary embodiment, lamella assembly 102 includes a plurality of lamellae 132. For example, lamella assembly 102 includes M number of lamellae L1, . . . LM, wherein M is based on the configuration of system 10. More specifically, in the exemplary embodiment, the number M of lamellae 132 is equal to the number N of channels 28 (shown in FIG. 1). In an alternative embodiment, the number of lamellae M is any suitable number of lamellae 132 that enables system 10 to function as described herein. Each lamella 132 has a length (not shown), a width WL1, and a height HL2, wherein the width WL1 is measured from a first surface 134 to a second surface 136 of lamella 132. In the exemplary embodiment, the length of the lamellae 132 is substantially equal to the length of first face plates 104 and/or the length of second face plates 106, and height HL1 is substantially equal to heights HP1 and/or HP2. Furthermore, in the exemplary embodiment, width WL1 is selected based on the number M of lamellae 132. In one embodiment, width WL1 is approximately 1.0 mm. Each lamella 132, in the exemplary embodiment, is oriented at angle α to X-ray beam 20 such that each lamella 132 is substantially parallel to adjacent lamellae 132. Furthermore, lamellae 132 are oriented such that scattered radiation 24 (shown in FIG. 1) between neighboring lamellae 132 is incident on at least one detector element of detector array 16. In one embodiment, lamellae 132 are oriented such that scattered radiation 24 between neighboring lamellae 132 is incident on a corresponding detector element of detector array 16. In the exemplary embodiment, each lamella 132 includes at least one layer that is substantially radiation-attenuating, such as a metal layer 138, and at least one layer that is substantially radiation-transparent or non-attenuating, such as a porous material layer 140. In an alternative embodiment, each lamella 132 includes two metal layers 138 and porous material layer 140 is coupled between metal layers 138. In the exemplary embodiment, each metal layer 138 is substantially parallel to each porous material layer 140, and vice versa. Metal layer 138 and porous material layer 140 are coupled together using adhesive bonding, chemical bonding, and/or any suitable coupling technique that enables secondary collimator 100 to function as described herein. In the exemplary embodiment, the porous material is a material that is transparent to X-ray radiation and that facilitates providing suitable strength to secondary collimator 100. For example, the porous material may include, without limitation, foam, expanded polystyrene (EPS), a material with a honeycomb geometry, and/or any suitable X-ray transparent material that enables secondary collimator 100 to function as described herein. In the exemplary embodiment, porous material layer 140 has a width WP that is approximately 0.5 mm. Metal layer 138 includes, in the exemplary embodiment, a radiation-absorbing or radiation-attenuating material, such as, for example, aluminum (Al), copper (Cu), steel, and/or any suitable material that enables secondary collimator 100 to function as described herein. Furthermore, in the exemplary embodiment, metal layer 138 has a width WM that is smaller than the width WP of porous material layer 140. For example, width WM is between approximately 50 μm and approximately 500 μm. In the exemplary embodiment, width WM is approximately 100 μm. In one embodiment, each lamella 132 is a sheet 300 of aluminum composite panel (ACP), such as shown in FIG. 4, and described above. FIG. 5 is a flowchart 500 of an exemplary method for assembling secondary collimator 100 (shown in FIG. 2) and/or secondary collimator 200 (shown in FIG. 3). Unless otherwise indicated, one or more of the functions represented by blocks 502, 504, 506, 508, and 510 may be performed sequenentially, concurrently, or in any suitable order. To assemble secondary collimator 100 and/or 200, first face plate 104 (shown in FIG. 2) is fabricated 502 using any suitable fabrication technique such that inner surface 110 (shown in FIG. 2) is within a tolerance of the predetermined profile. In the exemplary embodiment, inner surface 110 of first face plate 104 is fabricated 502 to within approximately 10 μm of being substantially planar. Furthermore, first face plate 104 is fabricated 502 such that outer surface 128 (shown in FIG. 2) is configured to facilitate strengthening and/or maintaining the predetermined profile of first face plate 104 and/or secondary collimator 100 and/or 200 during assembly and/or use. In the exemplary embodiment, outer surface 128 is fabricated 502 to include ribs (not shown). Similarly, inner surface 114 (shown in FIG. 2) of second face plate 106 (shown in FIG. 2) is fabricated 502 within a tolerance of the predetermined profile, and outer surface 130 (shown in FIG. 2) of second face plate 106 is configured to strengthen second face plate 106 and/or secondary collimator 100 and/or 200. In the exemplary embodiment, first face plate 104 is positioned 504 horizontally on a support structure (not shown), such as a table (not shown). Alternatively, first face plate 104 is positioned other than horizontally. More specifically, in the exemplary embodiment, outer surface 128 of first face plate 104 is adjacent to the support structure and inner surface 110 is exposed and facing upwards. Next, in the exemplary embodiment, to position lamella assembly 102 (shown in FIG. 2) onto first face plate 104, a first lamellae 132 (shown in FIG. 2) of lamella assembly 102 is positioned 506 on inner surface 110 of first face plate 104. As such, at least one radiation-absorbing material layer or metal layer 138 and at least one radiation-transmitting material layer or porous material layer 140 is positioned 506 on first face plate 104. More specifically, the length and the height HL1 of lamella 132 are generally aligned with the respective length and the height HP1 of first face plate 104. An M-1 number of lamellae 132 are positioned 506 on the first lamella 132 such that lamellae 132 are generally aligned with each other and first face plate 104. As such, in the exemplary embodiment, lamellae 132 are assembled such that the length and the height HL of lamella assembly 102 are generally aligned with the respective length and the height HP1 of first face plate 104. In one embodiment, when each lamella 132 includes porous material layer 140 (shown in FIG. 2) as first surface 134 (shown in FIG. 2) and metal layer 138 (shown in FIG. 2) as second surface 136 (shown in FIG. 2), or vice versa, lamellae 132 are layered onto first face plate 104 such that first surface 134 of lamella 132 is in contact with second surface 136 of an adjacent lamella 132. As such, metal layers 138 and porous material layers 140 of lamellae 132 alternate to form lamella assembly 102. Alternatively, when first and second surfaces 134 and 136 of each lamella 132 are metal layers 138, metal layer 138 is in contact with an adjacent metal layer 138 and porous material 140 is coupled between first and second surfaces 134 and 136. Referring briefly to FIG. 4, for example, when ACP is used as lamellae 132, adjacent skins 304 are in contact to form a metal layer 138, and foam core 302 is coupled between skins 304 to form porous material layer 140. Referring again to FIGS. 2 and 5, second face plate 106 is, in the exemplary embodiment, positioned 508 on lamella assembly 102, which includes M lamellae 132 positioned on first face plate 104. More specifically, the length and the height HP2 of second face plate 106 are generally aligned with the respective length and the height HL of lamella assembly 102 and/or the respective length and the height HP1 of first face plate 104. Second face plate 106 is then coupled 510 to first face plate 104 and/or lamella assembly 102 such that lamellae 132 conform to the profile of first and second face plates 104 and 106. More specifically, clamps 116 are coupled to first face plate 104 and/or second face plate 106 at each corner 142 (two corners 142 are shown in FIG. 2) of secondary collimator 100 and/or 200 and apply pressure forces to first face plate 104 and/or second face plate 106. When pressure forces are applied to first face plate 104 and/or second face plate 106, lamellae 132 of lamella assembly 102 deform to the predetermined profile of first face plate 104 and second face plate 106 while metal layers 138 remain substantially parallel to each other, porous material layers 140, and first face plate 104 and second face plate 106. An assembled secondary collimator 100 and/or 200 may be coupled into XDI system 10 such that XDI system 10 functions as described herein. The above-described embodiments facilitate collimating scattered radiation within an X-ray diffraction imaging (XDI) system. More specifically, the above-described secondary collimator facilitates using any size detector array within the XDI system because the secondary collimator may be fabricated to include any number of lamellae. For example, the above-described secondary collimator facilitates using a detector array having more than fourteen (14) detector elements with the XDI system. Furthermore, the secondary collimator facilitates the selection of scatter rays of radiation from varying depths in luggage, baggage, cargo, and/or other containers to image scatter rays onto a segmented detector array. Accordingly, the secondary collimator facilitates measuring energy-dispersive diffraction profiles at constant scatter angle in a depth-resolved (tomographic) system. Moreover, because the above-described secondary collimator may be fabricated using ACP and/or other industry-standard materials, the time and/or cost of fabricating the secondary collimator is reduced, as compared to fabrication of known tungsten alloy collimators having a plurality of slits defined therethrough. Furthermore, the above-described porous material layer coupled between metal layers provides strength to the secondary collimator and facilitates ensuring that the metal layers are substantially parallel throughout the secondary collimator. Because the metal layers and porous material layers are thin and flexible, the above-described secondary collimator may be formed to any desired profile. Additionally, the face plates facilitate securing the lamella in position within the secondary collimator through friction forces resulting from the pressure applied to the lamella assembly by the face plates. The face plates also facilitate determining the geometrical form and/or profile of the lamella assembly because the above-described lamellae can be easily and arbitrarily deformed when pressure is applied thereto. Furthermore, the above-described method of fabrication facilitates ensuring high parallelism among the metal layers, thus facilitating achieving high transmission through the above-described secondary collimator. Accordingly, the above-described methods and apparatus provide a secondary collimator that is more precise, less expensive, and has more design flexibility to allow an arbitrary number of detection elements to be employed, as compared to known secondary collimators that include a plurality of slits. Exemplary embodiments of a secondary collimator and a method for assembling the same are described above in detail. The method and secondary collimator are not limited to the specific embodiments described herein. For example, the secondary collimator may also be used in combination with other inspection/detection systems and/or inspection methods, and is not limited to practice with only the XDI system as described herein. While various embodiments of the invention have been described, those skilled in the art will recognize that modifications of these various embodiments of the invention can be practiced within the spirit and scope of the claims. |
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description | The invention relates to an optical system and method for illumination a sample as well as a detection device that includes the illumination system and a detection method including the illumination method. The optical illumination and the detection system is applicable in fluorescence detection systems and methods for analytical purposes. An example of the use of fluorescence detection is in nucleic acid testing (NAT). This is a core element in molecular diagnostics for detecting genetic predispositions for diseases, for determining RNA expression levels or identification of pathogens, like bacteria and viruses that cause infections. In many cases, particularly in the identification of pathogens, the amount of target DNA present in a reasonable sample volume is very low, and this does not allow direct detection. Amplification techniques are necessary to obtain detectable quantities of the target material. Different amplification techniques have been proposed and are used in daily practice. The most widely used are based on the so-called Polymerase Chain Reaction (PCR). The amplification involves the denaturing of double-stranded DNA at elevated temperature (typically >90 degrees Celsius), specific binding of primers to the DNA sample at a reduced temperature (approximately 65 degrees) and copying of the original sequences starting from the primer position (at approximately 70 degrees). This procedure is repeated and in every cycle the amount of DNA with the specific sequence is doubled (when proceeding at 100% efficiency). After amplification, the presence of target DNA is detected by measuring the fluorescence intensity of the labeled amplified DNA, for instance after electrophoretic separation in a capillary or after hybridization to so-called capture probes which are applied in spots on a surface over which the amplification product is flowed. This invention relates to an apparatus used to provide the illumination to the sample, and the method of use. The standard technique for fluorescence detection is the use of a scanning confocal microscope. Typically, a small (<1 μm), diffraction limited spot is used to excite the fluorescence in the focal plane. In the detection part of the system, only the light resulting from this single excitation point is detected. It has previously been proposed that the excitation of a number of spots or a complete line in parallel enables an increase in the scanning speed, without a major impact on the confocality of the detection system. A pixellated detector can be used to detect the fluorescent emission. In order to generate the excitation beam for a confocal line scan, it has been proposed to modify an optical device for making a scan with a focused spot by adding an optical element such as a cylinder lens, that adds so-called astigmatism. If the cross-section of a beam is defined as the xy-plane, then each ray in the beam is characterized by coordinates (x,y). The beam is astigmatic if the rays on the x-axis, coordinates (x,0) have a different focus from the rays on the y-axis, coordinates (0,y). The generation of astigmatism with an extra component, such as an cylinder lens, adds complexity and cost to the solution described hereinbefore. It is the aim of this invention to combine a number of functions in a single optical element to provide an improved solution. According to a first aspect of the invention, there is provided an optical system for illuminating a sample with a line beam. The invention enables the use of existing beam shaping apparatus, normally used to make a light output have a more circular cross section, in combination with the imaging system which illuminates the sample, in order to provide line beam inspection or analysis of a sample. The optical system preferably comprises means for scanning the line beam across the sample. The invention thus allows for a much smaller and more compact scanning system with line illumination based on the reuse of standard optical storage components within the optical system. This more compact optical system enables a completely miniaturized light path based on the confocal optics and light path used in a CD or DVD system with a minimal number of changes with respect to a standard DVD light path. This enables a solution that can be easily fabricated on existing DVD production lines. The ratio of the length of one of the focal lines of the final astigmatic image and the distance between the beam shaper and the position of the beam shaper for which the astigmatic distance of the intermediate image is zero is preferably given by: NA ( M x 2 - M y 2 ) 1 - NA 2 / n 2 M 2 ,where n is the refractive index of the sample medium, NA is the exit numerical aperture of the imaging system, M is the magnification of the imaging system and Mx and My are a first and second magnification of the beam shaper for the two focal lines of the intermediate image. The final astigmatic image preferably comprises a line focus, as explained above. The width of the line can be diffraction limited, so that a confocal imaging system is provided. For example, the system can comprise a confocal microscope based on absorption, reflection luminescence or a combination of these. The light source may comprise a laser diode, but any other light source such as a light emitting diode or the like may be used without departing from the invention. According to a second aspect of the invention there is provided a detection device incorporating the illumination system according to the invention and a detection system. In one embodiment the detection device is separate from the illumination system. Thus, the detection system may be located on an opposite side of the sample/substrate as the illumination system and they may make use of separate optics and components. Hence, advantageously, both sides of a substrate can be used to optically access a sample within the substrate. In another embodiment the illumination system and collection arrangement of the detection device can share an excitation/collection lens, and the detector can comprise an imaging lens which focuses onto the detection surface. This provides a compact detection device benefiting amongst others from the advantageous offered by the illumination system. It may be more robust and cheap due to lesser parts and less complicated construction. According to a third aspect of the invention there is provided an illumination method of illuminating a sample with a line beam. The method allows line illumination using simple CD and DVD optics as described hereinbefore. According to a fourth aspect of the invention there is provided a detection method using the illumination method of the invention in conjunction with a detection method according to which light emitted from the sample and generated by the line beam is collected and detected. Thus, in this detection method, the line beam is used to illuminate the sample such that the light beam interacts with the sample. After interaction the by this illumination light generated light emanating from the sample and emitted from the sample is collected and detected. The term ‘generated light’ is herein understood to include light of the light beam that remains after absorption or scattering of part of the light beam by the sample to be analyzed, i.e. in the interaction herein is absorption or scattering of light by the sample. This remaining light to be collected may be collected and detected using a transmission or reflection setup as known to those skilled in the art. Hence in this case the detection method measures for example absorption using line illumination. Furthermore, the term ‘generated light’ is understood to include luminescence which is generally known to cover fluorescence and phosphorescence. In the latter case the detection method measures light resulting from excitation of the sample by the line beam. The method may include that the substrate or sample is scanned. The invention relates to an optical system for illuminating a sample with a line beam. A beam shaper transforms the beam of light emitted by the light source into an intermediate astigmatic image, and an imaging system transforms the intermediate astigmatic image into a final astigmatic image and illuminates the sample. The beam shaper provides the different non-unity magnifications in a lateral plane and in a transversal plane, and comprises a toroidal entrance surface and a toroidal exit surface, each with finite radii of curvature. Methods and devices are known for detecting fluorophores in a device by exciting the fluorophores by light radiation through an objective lens and collecting the fluorescence, for example through the same lens in a reflective mode. The fluorescence radiation is projected onto a sensor device after having passed a filter device to select the appropriate wavelength range. The lens can be moved in a controlled way in three directions by different actuation means, to enable scanning over a sample of interest. A confocal imaging arrangement is typically used. FIG. 1 shows the basic components of a known fluorescence scanner based on a DVD optical system. The sample to be investigated is confined into a given volume within a substrate 20. The light generated by a light source 24 such as a laser is used to excite fluorescence. The light is collimated by a collimator lens L1 and subsequently focused in the sample by means of an excitation lens 26. The lens 26 can move relative to the sample, preferably in all three dimensions. This relative motion can be decoupled arbitrarily, for example the sample can move in to the x-y plane and the lens in the z direction. Alternatively, the sample can be kept fixed and the lens has all the three-degree of freedom (x-y-z) on its own. Any other arrangement is also possible. The laser light is reflected by a polarization beam splitter 21, i.e. a polarization dependent reflector, and is passed through a quarter wave plate 22 and a first band pass filter 23. A dichroic beam splitter 25, i.e. a wavelength dependent reflector, directs the laser light to the excitation lens 26. The induced fluorescence, as a result of the excitation light focused into the sample, is collected by a collection lens, which in this example is the same component as the excitation lens 26, and is directed toward a detector 28. Any reflected unabsorbed laser light is reflected again by the beam splitter 25, whereas the fluorescence is passed through the beam splitter 25. A second band pass filter 27 provides further filtering, and the light is then focused on the detector 28 by an imaging lens L2 which images the sample onto the detector 28. Many different types of detector can be used such as a photon tube multiplier, avalanche photon detector, CCD detector or photodiode detector. Preferably a detector offering spatial resolution is used such as a pixellated detector. This allows line detection and obviates scanning of the detector over the an illuminated region by the line beam. For confocal imaging, the excitation volume is kept to a minimum, ideally to the diffraction limited spot that the excitation lens 26 can create. A typical confocal volume is in the order of a cubic micron, depending on the strength (numerical aperture, NA) of the excitation lens 26. The fluorescence created in this volume is collected by the collection lens and is imaged on the detector. In a confocal method, the focal point is confocal with a point in the detection path. At this point in the detection path, a small pinhole is typically placed to filter out any light coming from a location other than the focal point. The light passing the pinhole is directed toward the detector. It is possible for the detector itself to play the role of the pinhole, with the restriction that the lateral size of the detector has to match the size of the focal point scaled by the focal length of the collection lens 26 divided by the focal length of the imaging lens L2. This confocal mode is best suited to investigate a surface immobilization assay, as the result of an endpoint bio-experiment. The surface is scanned to analyze the full sample. The lateral dimensions of the detector are designed taking into account the fields of the collection lens 26 and the imaging lens L2. A control arrangement 29 keeps the focus of the objective lens precisely at the inner surface of the analytical device; a surface of the volume within the substrate 20 which is in contact with the analyte, while scanning the same surface. The focus of the objective lens can also be offset on purpose. The invention can be implemented as a modification to the system of FIG. 1, which is adapted to provide an excitation beam in the form of a confocal line, rather than a confocal spot. Preferred examples of the invention are again based on standard DVD (or DVD/CD) optics. In a preferred example of the invention, a standard beam shaper is used at the output of the laser source, and this is normally used to make the intensity distribution within the cone of light emitted by the laser more symmetric. However, in the system of the invention, the beam shaper is positioned differently with respect to the laser to generate a required amount of astigmatism. This can then be arranged to result in a narrow diffraction limited line in the focus of the collection lens 26 instead of the normal diffraction limited circular spot. The use of a conventional beam shaper enables the optical system to be based on the optics of a standard CD/DVD player/writer. The known optical system is shown schematically in FIG. 2, and where components correspond to those in FIG. 1, the same reference numerals are used. For a DVD reader, a red laser diode 24 is used. The intensity distribution over the angles within the emitted cone of light is very asymmetric; the angular width in one direction orthogonal to the optical axis is a factor two to three larger than the width in the other direction orthogonal to the optical axis. This asymmetry is compensated with a beam shaper 30. The beam shaper 30 has an entrance surface, an exit surface located opposite thereto and an optical axis which coincides with the Z axis of a three-axis rectangular XYZ system of coordinates. The beam shaper 30 is for converting a beam having a first ratio between a first angular aperture in the YZ plane of the system of coordinates and a second, smaller angular aperture in the XZ plane into a beam having a second, smaller ratio between said angular apertures, said element realizing different angular magnifications in said two planes. Thus, the beam shaper is designed to alter the elliptical output of the laser into a more uniform circular output. The beam shaper used in the system of the invention preferably provides an angular magnification in a lateral plane and an angular reduction in a transversal plane. The difference between the angular magnifications realized by the beam shaper 30 in the transversal plane on the one hand and the lateral plane on the other hand is substantially entirely realized by the entrance surface which changes the divergence of the beam, both in the transversal plane and in the lateral plane. If the beam shaper is arranged in a medium having a refractive index n1 and if the refractive index of the material of this element is n2, the angular reduction in the transversal plane is n1/n2 and the angular magnification in the lateral plane is n2/n1 and the beam-shaping power is approximately (n1/n2)2. Since the two virtual images formed by the entrance surface are located at different positions along the Z axis, the exit surface should have a slightly toroidal shape so as to combine these images to one image. The radius of curvature in the XZ plane is larger than that in the YZ plane. Toroidal is understood to mean that the radius of curvature of the surface in the lateral plane differs from that in the transversal plane. The entrance surface is centrally provided with a substantially cylindrical portion whose cylindrical axis is parallel to the Y axis and introduces the angular reduction in the YZ plane and the angular magnification in the XZ plane. The beam-shaping power is now constituted by two components being angular magnification n2/n1 in the lateral plane and angular reduction n1/n2 in the transversal plane. Each of these components can be realized with less stringent tolerance requirements than those which apply to a beam shaper in which the beam shaping is realized in only one of these planes. A possible beam shaper is described in more detail in U.S. Pat. No. 5,467,335, which is incorporated herein by way of reference. A grating 32 is placed in the beam path in order to generate satellite spots. A polarizing beam splitter 21 reflects the light and a collimator lens L1 is used to form a collimated beam. This is reflected by a folding mirror 34, a quarter wave plate 22 converts the linearly polarized light into circularly polarized light and this light is then focused by the lens 26 onto the data layer, within a substrate 20. Of course, for the optical system to be used in a medical diagnostic apparatus, the data layer becomes the surface on which immobilization of capture probes occurs. The light is then reflected and collected by the same collection lens 26. The light then passes through the quarter wave plate 22 again, resulting in linearly polarized light that is perpendicular to the original polarization. Via the folding mirror 34, the light is focused by the collimating lens L1. The light then passes through the polarizing beam splitter 21. The light then mostly passes through a dichroic mirror 36. The servo imaging lens L2 adds some astigmatism that is used in combination with a focus and tracking detector 40 to generate the focus error signals in order for steering and/or positioning the focus and therewith provide feedback during for example scanning of a sample or substrate. The light path for CD light is nearly identical to the DVD path described above. When a CD is to be read out, the DVD laser is switched off and an infrared laser diode 43 in combination with a beam shaper 44 provides the illumination light. A grating 42 is again used to generate the satellite spots. The light is largely reflected by the dichroic mirror 36 and then passes largely through the polarizing beam splitter 21. Again, the light is focused on the data layer via lens 26. The reflected light is again collected by lens 26. This light again passes partly through the polarizing beam splitter 21 and the dichroic beam splitter 36 and is again imaged on the focus and tracking detector 40. In one example of the invention, the beam path is modified such that it becomes suitable for sensitive fluorescence detection. As mentioned above, when sufficient laser power is available, it is advantageous to spread the excitation light over a larger area to improve the throughput and increase the total detected signal without compromising confocality. To this end, the normally circular diffraction limited spot can be elongated in one direction while remaining diffraction limited in the perpendicular direction. This can be done by adding some type of astigmatism to the beam entering the lens 26. The applicant has considered different methods for introducing this astigmatism, for example via a cylinder lens or a phase plate. A phase plate can be used to provide a linear array of focus spots or a solid illumination line, and a cylinder lens can be used to provide a solid illumination line. In one example of the invention, the beam shaper 30 described above is moved along the optical axis. No special component is required to implement this. The position of the beam shaper is typically already fine-tuned during assembly and has the possibility to slide back and forth. The invention thus uses displacement of the beam shaper of an optical pickup-unit such that the exit beam is focused into a line that can be scanned across a plane. The beam shaper in the system of the invention can be considered to transform the beam of light emitted by the light source into an intermediate astigmatic image, and the imaging system; e.g. the combination of collimator lens and objective lens can then be considered to transform the intermediate astigmatic image into a final astigmatic image. An astigmatic image of a (light emitting) point is defined as consisting of two focal lines that are mutually perpendicular and perpendicular to the optical axis and that are separated along the optical axis over a certain distance, the astigmatic distance. The sample is scanned with one of the two focal lines in a direction substantially perpendicular to the line and to the optical axis. The length of the focal lines is proportional to this astigmatic distance. If the astigmatic length goes to zero, so will the length of the two focal lines, meaning that the lines will coalesce into a single point. To implement the beam shaping functions described above, the beam shaper has a first refractive surface with curvature radii along a first and second direction perpendicular to an optical axis that are substantially different, a second refractive surface with curvature radii along a first and second direction perpendicular to an optical axis that are substantially different, a thickness and a refractive index. There is generally a first position of the beam shaper with respect to the light source for which the astigmatic distance of the intermediate image is zero. The beam shaper is positioned with respect to this first position. In particular, the position of the beam shaper with respect to the light source is displaced with respect to the first position by a distance Δv given by: Δ v = L 1 - NA 2 / n 2 M 2 NA ( M x 2 - M y 2 ) where L is the length of (one of) the focal lines of the final astigmatic image, NA is the exit numerical aperture of the imaging system, n is the refractive index of the sample, and Mx and My are a first and second magnification of the beam shaper pertaining to the two focal lines of the intermediate image. The magnification is defined as sin α/sin β, where α and β are the largest ray angles in the system; α is the input ray angle, and β is the output ray angle. The numerical aperture is defined as sin α for the entrance numerical aperture, and sin β for the exit numerical aperture. If the object and/or image side is in a medium with refractive index n then the numerical aperture is n×sin α or n×sin β, respectively. In this arrangement, the length of the focal line that is used for scanning can be adapted to the requirements of the scanning process by changing the position of the beam shaper. Thus, a single optical design is suitable for multiple types of scanning devices. Moving the beam shaper 30 to control the shape of the excitation beam will however also induce some defocus. This may not cause any problem. However, it can in any case be compensated by either moving the position of the laser 24 or in a preferred embodiment this is done by changing the optical thickness of a component replacing the grating 32. FIG. 3 shows the light path which arises in a first example of system of the invention, used for fluorescence excitation and detection. Most components remain the same and are given the same reference numbers. The beam shaper is the same as the normally used but it is moved forward. The grating 32 that generates the satellite spots is replaced by a bandpass filter 50 that will spectrally purify the laser light. The thickness of this filter can be used to fine tune the defocus induced by the movement of the beam shaper. By moving the beam shaper 30, the light after the collimating lens will have a fairly large astigmatism. In one direction the light “is parallel” whereas the perpendicular direction is slightly diverging. This results after the objective lens 26 in a line focus. On the surface of the sample fluorescence will be generated. This fluorescence light is collected by the objective lens 26 and passes partly through the polarizing beam splitter 21. The dichroic mirror 36 reflects most of the fluorescent light towards a detector 52 after passing through an additional filter 54 to reject the remaining excitation light. The detector is preferably implemented as a pixellated detector. The dichroic mirror can be the same as in FIG. 2, or a different mirror can be used that is optimized to reflect the fluorescence. The reflected excitation light still passes through the dichroic mirror 36. A modified servo lens 56 is used to correct for most of the earlier induced astigmatism. The residual astigmatism can be used in combination with a (standard) quadrant detector 40 to generate the focus error signals. The direction of the line in the focus plane is arranged to be perpendicular to the fast scan direction. This can be achieved by rotating the laser and beam shaper assembly, or by rotating the complete OPU with respect to the axis of movement. In the return path of the reflected light the astigmatism in the beam is nearly completely compensated by the servo lens 56. The remainder of the astigmatism is used in combination with a standard quadrant detector 40 to generate the auto focus error signals. The residual astigmatism of light beam means that a change in the focus position will change the relative contribution of the light falling on the different quadrants of the detector. From these signals an autofocus error signal can be derived. A second embodiment of a device according to the invention is shown in FIG. 4. The same excitation method is used as in FIG. 3, but the detector is moved to a different position. By replacing the folding mirror 34 by a dichroic mirror 60, the fluorescent light can be transmitted by this element. Behind the dichroic mirror, the light is filtered with a filter 62 and is then focused by a lens 64 on the detector 66. This embodiment requires more modifications with respect to the DVD light path described with reference to FIG. 2. The sensitivity of this embodiment will however be better than that of FIG. 3 since the fluorescence light is not split into two parts at the polarizing beam splitter 21. Furthermore, in this embodiment it is possible to place the filter 62 in a parallel part of the beam. When interference filters are used this will result in a better rejection of excitation light resulting in a reduced background noise. In a standard OPU, the glue that usually fixes the beam shaper can simply be removed, such that the position can be moved back and forth towards the laser. The system of the invention has been tested and found to provide the required elongation of the confocal excitation beam simply by adjusting the relative positions of the beam shaper and laser in the standard OPU. Two examples have been described above based on the adaptation of DVD/CD optics. The invention is not limited to this approach. FIG. 5 shows a number of embodiments based on the different combinations of components which can be used to implement the current invention. If only a line illumination mode is desired, a simplest embodiment shown in FIG. 5a can be used. The numbering of the components is the same as used in FIG. 3 and FIG. 4, and the system comprises the beam shaper 30, laser 24 and lens 26. Line illumination can be used in systems other than for fluorescence detection, such as scanning microscopes for instance to measure cells or pathology slides. An autofocus system is added to form the system shown in FIG. 5b, which uses a polarizing beam splitter 21 in combination with a quarter wave plate 22 to separate the excitation and reflected light. In order to combine line illumination with fluorescence detection, the addition of a dichoric mirror 34 is required as shown in FIG. 5c, in combination with filters 50 and 62 to separate the excitation light from the fluorescence. The invention provides modification of the beam path such that it becomes suitable for sensitive fluorescence detection in combination with a line illumination mode. In the preferred implementation, the “standard” beam shaper is shifted to solve this problem. There are, however, other ways to solve this same problem. Two examples are explained below: (i) The standard collimator shown in FIG. 4 as L1 can be replaced with a new dedicated component, to implement the beam shaping function, and thereby replace the beam shaper 30. (ii) The beam shaper can be replaced by a new dedicated component that adds the required astigmatism to excitation beam. This may be provided at the output of the laser diode, which can already include an integrated beam shaper. In the example above, the lens 26 is used both for the excitation light and the fluorescence light, and it can also be used for focus and tracking signals. Separate lenses may be used for the excitation light and the fluorescence light, for example with non-normal directions of illumination, or with operation in a transmissive mode. The invention is not limited to the examples described herein. Various modifications exist. Thus, for example, the invention is described with reference to a sample that fluoresces by means of fluorophores. However, the invention may in general be used in devices that generate in a general way an optical signal. Thus samples may be measured that absorb part of the illuminating line beam so that the remaining line beam light is collected and provides a clue with respect to constitution of a sample with respect to presence, identity and/or concentration of one or more of its constituents or added substances that facilitate the constituents detection such as for example label substances. Likewise the effect of reflection of the line beam caused by the sample may be used in the detection process. Alternatively, the line beam may function as an excitation source in order to excite one/or more of the constituents of the sample or the added substances so that luminescence radiation results that can be collected and detected. Herein luminescence is meant to include fluorescence and/or phosphorescence. In generally, the invention relates to the generation of a line for illumination of a sample. The illumination line is of advantage in a detection device as described hereinbefore. The invention is of particular interest for line scanning or confocal line scanning in order to speed up the detection process. In some cases, scanning to cover an area of a surface may however not be required. The invention will also then provide its advantages. The invention is in general applicable in the field of sample analysis wherein samples need to be examined volumetric or on a surface. The application of the invention may thus be in analytical methods requiring line excitation. These also include analysis on gaseous, liquid and/or solid samples. Thus the invention may be used for chemical analysis of samples such as to determine their constitution or it may be used to inspect the evolvement or progress of a chemical or biochemical or biological process. Improved scanning speed enables the collection of more data points per time unit resulting in improved dynamic measurements. Without being limited to the field of bioanalysis, the preferred application of the invention is in the field of molecular diagnostics based on the detection of for example nucleic acids after amplification, proteins or other biochemical or biological entities. Further preferred fields of application include, clinical diagnostics, point-of-care diagnostics, advanced bio-molecular diagnostic research and optical biosensors, in particular related to DNA detection in combination with amplification methods, such as PCR, q-PCR, etc. The invention can also be used as a line scanner for imaging cells and/or tissue for example for pathology purposes. The can also be used for detection in an immunoassay to detect proteins. The above-mentioned embodiments illustrate rather than limit the invention, and at that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. 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 elements or steps other than those listed in a claim. The word “a” or “an” preceding an element does not exclude the presence of a plurality of such elements. In the device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that the combination of these measures cannot be used to advantage. |
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abstract | A technique for ion beam angle spread control for advance applications is disclosed. In one particular exemplary embodiment, the technique may be realized as a method for ion beam angle spread control for advanced applications. The method may comprise directing one or more ion beams at a substrate surface at two or more different incident angles. The method may also comprise varying an ion beam dose associated with at least one of the one or more ion beams based at least in part on the two or more incident angles, thereby exposing the substrate surface to a controlled ion beam angle-dose distribution. |
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055330754 | claims | 1. An alignment device for use with a spent fuel shipping container including a plurality of fuel pockets for spent fuel arranged in an annular array and having a rotatable cover including an access opening therein, said alignment device comprising: a plate for installation over the access opening of the cover and including a laser admittance window therein; a laser device mounted on said plate for directing a laser beam through said laser admittance window into said container; and indexing means provided on said container for providing an indication of the angular position of the rotatable cover when the laser beam produced by the laser is brought into alignment with a fuel pocket in the container. preestablishing an alignment target for each of the fuel pockets; mounting a support plate including a laser admittance window therein over the access opening of the cover of the spent fuel container; affixing a laser to said support plate in alignment with said laser admittance window in an orientation wherein, when the laser is energized, a laser beam is directed into said container through the window; energizing the laser and rotating the cover until the laser beam directed by the laser into said container is in alignment with the target of a first fuel pocket; using an index ring arrangement at the top of the container to determine the angular position of the cover, and hence the relative angular alignment position of the first fuel pocket, when the laser beam is in alignment with the target of the first fuel pocket; and repeating the process for each of the other fuel pockets. 2. A device as claimed in claim 1 wherein said plate further comprises a viewing window therein for enabling viewing of the laser beam within the container. 3. A device as claimed in claim 1 wherein said laser admittance window is sized so as to permit viewing of the laser beam within the container. 4. A device as claimed in claim 1 further comprising fixing means for fixing the orientation of the plate, and the laser mounted thereon, on the cover of the container. 5. A device as claimed in claim 4 wherein said fixing means comprises a pair of pin members on the plate and a corresponding pair of pin openings formed in the cover. 6. A device as claimed in claim 4 wherein said fixing means comprises a pair of pin members on the cover and a corresponding pair of pin openings formed in the plate. 7. A device as claimed in claim 1 wherein said plate further comprises at least one handle for facilitating installation and removal of the plate. 8. A device as claimed in claim 1 further comprising sealing means for providing a seal between said plate and the cover of the container. 9. A device as claimed in claim 8 wherein said plate is circular in shape and said sealing means comprises a sealing O-ring disposed around the periphery of the plate. 10. A device as claimed in claim 1 wherein said laser device comprises a low power laser and a laser mount comprising a cage in which the laser is supported and a bracket securing the cage to the plate. 11. A method for determining the alignment position of an access opening of a cover for a spent fuel container with respect to each of a plurality of annularly arranged fuel pockets within the spent fuel container so that spent fuel can be placed into each of said fuel pockets through said access opening, said method comprising: 12. A method as claimed in claim 11 wherein each of said targets is established by providing a target groove at the site of the respective fuel pocket which produces reflection enhancement of a laser beam in alignment with said groove. 13. A method as claimed in claim 12 wherein said groove is provided on a slanted shoulder at the top of the fuel pocket. 14. A method as claimed in claim 11 further comprising viewing the laser beam within said container so as to determine when said laser beam is in alignment with the target. 15. A method as claimed in claim 11 wherein affixing of said laser to the support plate comprises mounting the laser in a fixture on said plate. 16. A method as claimed in claim 11 wherein said support plate is mounted on said cover in a predetermined orientation determined by a mounting assembly for said plate. 17. A method as claimed in claim 16 wherein said mounting assembly comprises a pair of pin members and a corresponding pair of openings for receiving the pin members. |
description | This application claims priority from Korean Patent Application No. 10-2012-0049681, filed on May 10, 2012, in the Korean Intellectual Property Office, the contents of which are incorporated herein by reference in its entirety 1. Field of the Invention The present invention relates to a method of producing zirconium alloy with improved resistance to oxidation at very high temperature. 2. Description of the Related Art Zirconium was hardly known before 1940, but gained attention mainly for its low neutron-capture cross-section and was utilized mostly in the nuclear energy-related engineering materials and nuclear energy substances. Because zirconium particularly has low neutron absorption cross-section and good resistance to corrosion, and intrinsically does not form radioactive isotopes, the material is critically used in the nuclear reactor components such as spacer grid, guide tube, heavy water reactor pressure tube, or cladding tube for a nuclear fuel rod, or alloy with uranium.Zr+2H2O→ZrO2+2H2 Oxidation of zirconium However, zirconium alloy component generates hydrogen due to oxidation reaction between zirconium and water, which is absorbed into zirconium alloy components to form hydroxide layer(s) and, in turn, causes mechanical deformation and degradation of resistance to instability of the fuel assemblies. To overcome this shortcoming, studies have been conducted to find ways to increase resistance to oxidation and resistance to corrosiveness of the zirconium alloy. Considering the advantage of prolonged lifespan of the reactor rod structures, studies are actively conducted to develop appropriate alloys for use therein. In the meantime, the stability of the cladding tube has been in increasing demand particularly in the event of emergency such as accident. As learned from the incidence of reactors 1, 2 and 3 of Fukushima I Power Plant (Japan), when cooling of reactors is interrupted due to natural disasters such as earthquake or tsunami or man-made disaster, the cladding tube is exposed to high temperature so that hydrogen with high risk of detonation is massively generated due to considerably high velocity of corrosion. The hydrogen detonates when it is leaked into the containment buildings of the reactor. The hydrogen explosion in the power plant must be prevented, because this could lead to tragic disasters which could accompany leakage of radioactive substance. Looking at the zirconium alloys currently available, these alloys do not pose considerable problems under normal condition. However, the safety of the alloys is not guaranteed when an accident occurs such as generation and detonation of hydrogen. A sufficient time has to be ensured for the management of the emergent situation before the generation of hydrogen in order to improve the safety of the nuclear power plant, and this will be possible if the nuclear fuel cladding tube has a sufficient resistance against oxidation when exposed to the emergency conditions. The currently-available method for fabricating a zirconium alloy for use in a cladding tube basically adjusts the ratios of the alloying elements such as niobium (Nb), tin (Sn), iron (Fe), chromium (Cr), oxygen (O), or the like. However, limited oxidation resistance is expected by the method of using such alloying elements at high temperature environment. The effect of oxidation resistance that can be provided by adjusting ratios in the alloying elements is particularly insufficient to maintain resistance to oxidation under the emergency condition of the power plant which accompanies exposure to extremely high temperature for a prolonged time. The zirconium alloy has rapidly degrading oxidation resistance when temperature rises. The currently-available alloying technique, which is based on the fine adjustment of alloying composition, would not be sufficient to ensure efficiency under high temperature corrosion condition. Accordingly, it is necessary to take a step forward, for the improved accident safety of the nuclear fuel. Meanwhile, the stability of the nuclear fuel assemblies can be increased by coating anti-oxidation material onto the surface of zirconium alloy to thus improve the resistance of zirconium alloy against oxidation at high temperature. If an anti-oxidation substance, which is stable at high temperature, is coated on the surface of the zirconium alloy to prevent oxidation from occurring when the alloy is unexpectedly exposed to high temperature environments due to changes in the environment, the oxidation reaction can be effectively restricted and less hydrogen would be generated, and therefore, danger factors such as hydrogen explosion can be prevented or reduced. However, a few substances are known for inhibiting oxidation at high temperature, and it is also a great challenge to ensure good bonding between zirconium alloy layer and coating layer of the anti-oxidation substance to prevent physical damages even at high temperature. U.S. Pat. Nos. 5,171,520 and 5,268,946 teach a technology to coat ceramic and glass material with flam spraying to enhance wear resistance of the cladding tube. U.S. Pat. No. 5,227,129 discloses a method for coating zirconium nitride (ZrN) with cathodic arc plasma decomposition to enhance corrosion resistance and wear characteristics. The above patents aim to improve anti-corrosion and wear resistance of the nuclear fuel cladding tube under normal condition, and has drawbacks of limited control on the compositions of the coating layer due to use of inter-metallic compounds (ZrN, ZrC), or ceramic (zircon) or glass (CaZnB, CaMgAl, NaBSi) as the coating material. The patents also have the shortcoming of considerable differences between the coating layer and the parent material causing physical damage (e.g., crack and scrape off) due to thermal expansion and deformation. Indeed, studies reported that the layer becomes porous when oxidized at high temperature so that improvement of corrosion resistance is hardly anticipatable under emergency condition of the nuclear power plant (S. Shimada, Solid state ionics 141 (2001), 99-104; L. Krusin-Elbaum, M. Wittmer, Thin Solid Films, 107 (1983), 111-117). Conventional studies on coatings on nuclear fuel claddings aim to overcome limited corrosion resistance by utilizing alloying elements, i.e., by forming a layer with resistance to corrosion and wear using methods such as ion implantation, Zr—N layer deposition, or the like. U.S. Pat. No. 4,279,667 discloses a zirconium alloy structure and a processing method thereof, which use ion implantation to improve corrosion resistance. Korean Pat. No. 2006-0022768 discloses a technology to form Zr(C, N) layer on the surface of a cladding tube by chemical vapor deposition (CVD) or physical vapor deposition (PVD) to improve corrosion characteristic of the zirconium alloy cladding tube. However, these technologies have shortcomings in that the layer newly generated on the surface is not thick enough to effectively prevent corrosion, or due to columnar crystal structure thereof, unable to prevent oxidation due to inter-granular diffusion of oxygen. Accordingly, a process is necessary, which generates a layer that does not easily allow diffusion of oxygen on the surface of the nuclear fuel cladding tube to a sufficient thickness to prevent corrosion of the cladding tube during the normal operation condition in reactor. In consideration of the above, the present inventors have come up with a zirconium alloy with greatly improved resistance to oxidation at very high temperature by evenly coating a pure metallic substance with excellent resistance to oxidation onto zirconium alloy with plasma spraying. An embodiment of the present invention provides a zirconium alloy with excellent resistance to oxidation at very high temperature, and excellent resistance to corrosion and also excellent bonding with parent material. Another embodiment of the present invention provides a method for fabricating the zirconium alloy. In a specific embodiment of the present invention, a zirconium alloy is provided with excellent resistance to oxidation at very high temperature, and excellent resistance to corrosion and also excellent bonding with parent material, in which silicon (Si) or chromium (Cr) as a pure metallic material is evenly coated on a surface of the parent material by plasma spraying. In another specific embodiment of the present invention, a method is provided for fabricating a zirconium alloy, which may include steps of: pre-treatment the surface of a zirconium alloy parent material (step 1); coating a pure metallic material on the pre-treated parent material surface by plasma spraying (step 2); and thermally treating the parent material coated at step 2. In some embodiments according to the present invention, since the method of coating zirconium alloy by plasma-spraying with pure metallic material is not limited by the shape of the coated product and also does not require vacuum equipment, it is very useful to evenly coat surfaces of the components such as 4 m tube in length and spacer grid with rather complicated shape. Further, since the nuclear fuel assembly using zirconium alloy coated articles according to embodiments of the invention has excellent resistance to oxidation and corrosion under emergency condition as well as normal condition, economic and safety aspects of the nuclear fuel can be improved. Further, since the coating technique to provide this improved resistance to oxidation at very high temperature is applicable in other existent industrial substances, the technique provides benefits, considering cost and time that would be otherwise useful for developing new materials, when particularly implemented in the fields of general industry and logistics industry. Reference will now be made in detail to non-limiting embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. These embodiments are described below to explain the present invention by referring to the figures. An embodiment of the present invention provides a zirconium alloy in which a pure metal is evenly coated on a surface of parent material by plasma spraying. In one embodiment, the pure metallic material may preferably be silicon (Si) or chromium (Cr). To be specific, the silicon (Si) or chromium (Cr) as pure metallic material may be coated by room temperature processing. Further, these metallic materials are less limited by the surface morphology. Further, because plasma spraying is used for the coating, additional equipment such as vacuum equipment, which is required for CVD or PVD, is not required and thus cost is saved. By evenly coating the metallic materials on the surface of a parent material using highly-efficient plasma spraying, oxide layer, which remains stable under high-temperature condition due to the presence of the coating layer, is generated, thus providing increased resistance to oxidation and corrosion. Further, the thermal expansion rate of the pure metallic materials which are similar to the parent material can minimize cracks and interfacial debonding of the bonded portions. As a result, it is possible to fabricate a zirconium alloy for use in nuclear fuel assembly components, with providing improved bonding to the parent material. Further, for the Zirconium alloy according to the present invention, the parent material may include alloys of zirconium sold commonly under the trademarked names, such as Zircaloy-4, Zircaloy-2, ZIRLO, M5 or HANA, but not limited thereto. The cladding tubes used in the nuclear fuel of the nuclear power plants currently run for electricity supply are fabricated from zirconium alloy, and more specifically, Zircaloy-4 and Zircaloy-2 are mainly used as the nuclear fuel cladding tubes for commercial power plants. Further, ZIRLO, M5 and HANA have been relatively recently developed to improve resistance to corrosion and used in commercial power plant. These alloys are among the preferable parent materials according to the present invention. Although the thickness of the coating layer of pure metallic material on the parent material according to the present invention is not strictly limited as long as the coating layer improves the properties of the fabricated components such as resistance to oxidation, resistance to corrosion and bonding, the thickness of the coating layer may be adjusted to be within a range of 1 to 500 micrometer. If the thickness of the pure metallic material coating layer is below 1 micrometer, the coating layer would be too thin to form sufficient oxide layer to prevent oxidation of the zirconium alloy. On the contrary, if the thickness of the coating layer exceeds 500 micrometer, such increased thickness can compromise the mechanical wholesomeness and it is also not beneficial economically. Furthermore, the zirconium alloy according to the present invention is applicable to wide range of technical fields including not only the nuclear fuel assemblies, but also metallic or ceramic materials for use in thermal power generation, the aerospace industry, or military. Further, the nuclear fuel assemblies according to the present invention may include cladding tubes, guide tubes, instrumentation tubes, or spacer grids. The material for the nuclear fuel assemblies will desirably have enough resistance to oxidation to prevent or inhibit the growth of oxide layers and mechanical deformation due to corrosive environments under high temperature and pressure. It is also desirable that the materials used in nuclear fuel assemblies and their components which can prevent or inhibit hydrogen production and detonation of massive amounts of hydrogen under high temperature oxidative atmosphere where the temperature of the nuclear fuel is extremely high as in the case of accident. In consideration of the above, the metal plasma coated zirconium alloy according to the present invention can be effectively used in the nuclear fuel assemblies. Furthermore, the pure metallic substance coated on the surface of the zirconium alloy parent material according to the present invention is oxidized at high temperature to form oxides such as silicon dioxide (SiO2) or chromium oxide (Cr2O3), to thus confer oxidation resistance. As for the pure metallic materials for coating on the parent material, silicon (Si) has the properties that reduce hydrogen absorption on the zirconium matrix, and also retard transition phenomenon in which corrosion rapidly increases over time. Silicon (Si) also has oxidation resistance from room temperature to high temperature by forming oxide (i.e., SiO2) when it is oxidized. Chromium (Cr) is also a transition metal and causes irregular orientations of the growth of the oxide layer particles. This prevents growth of the oxide layer in one direction. Accordingly, abrupt disintegration of the oxide layer is restricted. Similar to Silicon (Si), chromium also forms oxide layer of chromium oxide (Cr2O3) which confers oxidation resistance from room temperature to high temperature as silicon dioxide does. Because the pure metallic material coated on the zirconium alloy parent material plastic deforms at high temperature, cracking or scraping away of the coating layer is restricted, and bonding with the parent material is improved. The pure metallic materials (Si, Cr) are used because the materials confer high heat conductivity, which is their characteristic property, to the ceramic which has been generally used, to thereby guarantee heat conductivity of the zirconium cladding tube of the nuclear energy generation after coating. Further, the interfacial debonding or crack of the coating layer occurs due to differences of thermal expansion rates according to temperature increase when the metallic material is coated with ceramic and intermetallic compound. However, when the metallic coating material (e.g., Si, Cr) has thermal expansion rate and/or other properties similar to those of the parent material, the relatively higher plasticity than ceramic, the crack and interfacial debonding due to thermal expansion rates can be minimized. Further, the conventional ceramic coating does not ensure even coating layers due to high melting point of the ceramic, and the intermetallic compounds do not ensure accurate control on the composition or deposition rates and crystal structure of the compounds. However, coating with the pure metallic material can solve the problems mentioned above. Furthermore, the present invention provides a method for fabricating zirconium alloy, which may include steps of: pre-treatment a surface of a zirconium alloy parent material (step 1); coating a pure metallic material on the surface of the pre-treated alloy parent material of step 1 by plasma spraying (step 2); and thermally treating the parent material coated at step 2 (step 3). Note FIG. 4, for example. The respective steps of the fabricating method will be explained in greater detail below. First, in step 1, the surface of the zirconium alloy parent material is pre-treated. The pre-treatment of the surface of the parent material is performed with a purpose to improve or enhance interfacial bonding. To be specific, step 1 may include removal of foreign substances and contaminants from the surface of the zirconium alloy. The pre-treatment of step 1 according to the present invention may preferably include grinding, by using particles of an oxide, intermetallic compounds or silicon compounds. By treating the surface with these particles, foreign substances are removed, and adjustment of surface roughness also improves bonding with the coating material. For example, the pre-treatment may be performed by sandblasting or shot blasting. In step 2, pure metallic material is coated on the surface of the pre-treated parent material of step 1 by plasma spraying. To be specific, the coating by plasma spraying of step 2 generates inactive gas plasma at temperatures ranging between several-thousand degrees and several hundred and thousand degrees (° C.), and thereby instantly converts the pure metallic material powder into liquid form for the coating. This coating technique has the advantages such as availability for room temperature processing, less limits on the surface morphology, and no need for vacuum equipment for the chemical or physical vapor deposition. Next, in step 3 according to the present invention, the parent material coated in step 2 is thermally treated. The heat treatment of step 3 according to the present invention may preferably be performed at temperatures below a melting temperature of the pure metallic material. By the heat treatment of the zirconium parent material, which is evenly coated, the energy from the surface stress facilitates diffusion reactions with the coating material, to thereby increase bonding. If the temperature of the heat treatment exceeds the melting temperature of the pure metallic material, the coated pure metallic material would melt during heat treatment, causing formation of uneven coating layers after the heat treatment, i.e., during cooling, and undesirable variations in the dimensions of the tube. The present invention will be explained below in greater detail with reference to the examples. However, the examples are given only for illustrative purpose, and the embodiments of the present invention is not limited to specific examples. Except for the variations in the condition of fabrication and coating thicknesses listed in the following table, the zirconium alloy coated with the pure metal plasma spray coating was fabricated in the same manner as in Example 1. TABLE 1SandblastingCoatingCoatingbeforethicknessHeat treatmentNon-coatedmaterialcoating(micron)after coatingsurfaceEx. 1Si✓90350° C. @ 4 hrCom. Ex 1Ex. 2SiN/A90350° C. @ 4 hrCom. Ex 2Ex. 3Si✓90N/ACom. Ex 3Ex. 4Si✓20N/ACom. Ex 4Ex. 5Si✓130350° C. @ 4 hrCom. Ex 5Ex. 6Cr✓5350° C. @ 4 hrCom. Ex 6Ex. 7Cr✓20350° C. @ 4 hrCom. Ex 7Ex. 8CrN/A5N/ACom. Ex 8Ex. 9CrN/A20N/ACom. Ex 9 In order to compare oxidation characteristics of the coating layers at high temperature condition, only one surface of each of the samples of the Example was coated, while the other surface was left un-coated and observed as Comparative Examples 1-9. The experiment result of high temperature oxidation of zirconium alloy parent material, coated with the pure metallic material, is provided below. <Experiment 1> High Temperature Oxidation In order to investigate differences of the oxidative properties between the zirconium alloy coated according to the present invention and non-coated zirconium alloy, the following experiment has been conducted with respect to the zirconium alloys of Examples 1-9 and those of Comparative Examples 1-9. The zirconium alloys of Examples 1-9 and the zirconium alloys of Comparative Examples 1-9 were cut to 10×10 mm samples sizes, and the cut surface was ground with silicon carbide (Sic) paper. The ground sample was washed by ultrasonic cleaning in 50:50 acetone and alcohol solution for 5 min, and dried. The dried samples were mounted on test equipment for high temperature oxidation and then mixed gas of steam and argon was flowed with 10 ml/min flowrate. The temperature of the samples were raised 20° C. per sec using the reverberatory furnace attached to the equipment, and the temperature was maintained at a very high temperature of about 1000° C. for 1000 sec. Power to the reverberatory furnace was then turned off and the samples were cooled down by increasing the argon gas pressure 3-fold or greater. The evaluation of oxidation characteristic was carried out in a manner in which samples were prepared to enable observation on the cross section thereof after oxidation occurred at high temperature vapor condition, so that the coated surfaces (FIG. 2: Examples) and the non-coated surfaces (FIG. 3: Comparative Examples) of the samples were observed with scanning electron microscope (SEM) and the thickness of the oxide layer was measured and the results were tabulated as below. TABLE 2Thickness (micron)of oxide layerThickness (micron) of oxide layeron coated surface (plasma spraying)on non-coated surfaceEx. 1<3Com. Ex. 136Ex. 2<3Com. Ex. 235Ex. 3<3Com. Ex. 337Ex. 4<4Com. Ex. 434Ex. 5<3Com. Ex. 535Ex. 6<2Com. Ex. 635Ex. 7<2Com. Ex. 737Ex. 8<2Com. Ex. 836Ex. 9<2Com. Ex. 935 Referring to FIG. 2, from the oxidation experiment consisting of heating up to 1000° C. and cooling down, scraping off of the coating layer, which is the usual result of thermal expansion and oxidation reaction, was not observed. However, the diffusion layer was observed on the interface between the coating layer (Si or Cr) and the parent material (Zr). Table 2 particularly lists the results of measuring, by SEM, the thickness of the oxide layer which underwent oxidation experiment under high temperature environment mixed with steam and argon for 1000 sec, and this confirms improved resistance to oxidation of the coated zirconium parent material by showing that the thickness of the oxide layer was only several or a few microns on the surface which underwent plasma spray coating, while the thickness of the oxide layer was above 30 microns on the zirconium parent material which was not coated. As a result, by confirming the excellent resistance to oxidation of the plasma coating layer of the pure metal (Si or Cr) even at high temperature, it was confirmed that metallic or ceramic parent materials coated according to embodiments of the present invention are efficiently applicable for use in environments that require resistance to oxidation at very high temperature. While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. |
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abstract | Disclosed herein is a method for preparing a scandium nano-radiopharmaceutical. The method comprises forming a plurality of scandium-encapsulated dendrimers by encapsulating scandium in polyamidoamine (PAMAM) dendrimers with amine surface groups, and forming a scandium nano-radiopharmaceutical by irradiating the plurality of scandium-encapsulated dendrimers by bombarding neutrons toward the scandium-encapsulated dendrimers. |
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abstract | Methods and systems for health operations analysis models to compare a first and second fleet of vehicles are disclosed. In one embodiment, a method for providing a system health operations analysis model including determining a first system health operations analysis of a first fleet of vehicles, determining a second system health operations analysis of a second fleet of vehicles, comparing the first and second system health operations analyses, and generating a system health operations output of the first and second system health operations analyses. |
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claims | 1. A containment device comprising a curtain that can be deployed from a wound or folded first position into an unwound or unfolded second position, comprising a storage box for storing the curtain in the first position, wherein the box is made up of a plurality of juxtaposed modules, the plurality of modules comprising active modules which are provided with means for retaining and releasing the curtain and passive modules which do not have said means for retaining and releasing the curtain. 2. The containment device as claimed in claim 1, wherein the means for retaining and releasing the curtain are actuating cylinders. 3. The containment device as claimed in claim 2, wherein each actuating cylinder of the actuating cylinders comprises a finger able to move between a deployed curtain-retaining position and a retracted curtain-release position. 4. The containment device as claimed in claim 3, wherein the finger of each actuating cylinder is inserted in the deployed position into a first eyelet of an associated curtain retaining strap, the fingers, of the actuating cylinders, in the retracted position releasing the curtain retaining strap so as to allow the curtain to fall. 5. The containment device as claimed in claim 4, comprising a curtain retaining web connected to the straps and on which the curtain rests in the wound position. 6. The containment device as claimed in claim 4, wherein the ends of the straps that accept the fingers of the actuating cylinders are provided with rigid plates in which the first eyelets are made. 7. The containment device as claimed in claim 1, wherein each module of the plurality of modules comprises a rear face for attaching the module to a wall, which rear face is provided with holes for accepting rods projecting from the wall, said holes being sized to allow the modules some clearance with respect to the diameter of the rods. 8. The containment device as claimed in claim 7, wherein the fixing of the module to the rods involves shims to compensate for the clearances for fitting the rear face to the wall. 9. The containment device as claimed in claim 8, wherein at least one of said shims is arranged in the lower part of the module in a space accommodating the curtain, which is rounded in shape and not likely to damage the curtain. 10. The containment device as claimed in claim 7, comprising bars for supporting a top end of the curtain, said bars being fixed to the rear face of each module of the plurality of modules by fixing means which are provided with a range of position adjustment in the vertical direction of deployment of the curtain. 11. The containment device as claimed in claim 1, wherein the each module of the plurality of modules comprises an upper wall, a front wall and lateral walls, the lateral walls comprising rounded cutouts provided with curtain centering plates which press on or cover the external diameter of the rolled curtain. 12. The containment device as claimed in claim 1, wherein the active modules comprise at least one means for disabling the means for retaining and releasing the curtain. 13. The containment device as claimed in claim 4, wherein the active modules comprise at least one means for disabling the means for retaining and releasing the curtain and wherein the means for disabling comprises a handle equipped with a locking bolt which, in a disabling position at least, engages in second eyelets of the straps retaining the curtain whatever the position of the fingers of the actuating cylinders. 14. The containment device as claimed in claim 13, wherein the handle is received in a tube provided with grooves defining three positions of the handle, a curtain installation position, a curtain immobilizing position and a curtain release position, the handle being able to signal these positions to the operator. |
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claims | 1. A method for analyzing a measurement, comprising:a) programming a measurement device with a predetermined trigger value corresponding to a characteristic of interest detected by said measurement device;b) recording a first set of data by said measurement device to a first location;c) recording a second set of data by said measurement device to a second location, wherein said second set of data corresponds to a time of occurrence for said trigger value and said first set of data corresponds to a time prior to said occurrence;d) playing said first and second sets of data at a time after said occurrence on a simulator of said measurement device, said simulator suitable to operate on said first and second sets of data to produce simulator output data, said output data being smaller than said first and second sets of data. 2. The method of claim 1, said first set of data including first set of data including first temporal information and said second set of data including second temporal information. 3. The method of claim 1, further comprising:e) recording a third set of data by said measurement devise to a third location, wherein said third set of data corresponds to a timer after said occurrence;f) playing said third set of data on said simulator. 4. The method of claim 3, said first set of data including first temporal information, said second set of data including second temporal information, and said third set of data including third temporal information. 5. The method of claim 1, wherein said measurement device provides measurement device output data, said simulator output data being identical to said measurement device output data. 6. The method of claim 1, said measurement device being an ultrasonic flow meter. 7. The method of claim 1, wherein said characteristic of interest is time of flight for an ultrasonic signal. 8. The method of claim 1, said playing step being conducted on a portable computer. 9. The method of claim 1, wherein said first and second locations are on a hard disk drive. 10. The method of claim 1, said simulator including a signal processing chain substantially similar to one located in said measurement device. 11. A method for analyzing a measurement device performance, comprising:a) recording an uninterrupted stream of data from said measurement device to a first location, said measurement device having a measurement portion to detect a characteristic of interest and generate said uninterrupted stream of data, said uninterrupted stream of data being of a substantially longer duration that fluctuations in said characteristic of interest;b) retrieving said stream of data from said first location; andc) playing said uninterrupted stream of said data on a replay device, said replay device suitable to process said stream of data in a substantially similar manner as electronics associated with said measurement device. 12. The method of claim 11, wherein said characteristic-of-interest does not satisfy a pre-set trigger, preset trigger condition at a second time, said uninterrupted stream of data being from said first time through some time after said second time. 13. The method of claim 11, wherein said measurement device is an ultrasonic meter. 14. The method of claim 11, wherein said first location is a hard disc drive. 15. The method of claim 11, wherein said replay device is a portable computer. 16. The method of claim 11 further comprising:d) stopping said playing of said uninterrupted stream of data in order to analyze data from a single instant in time. 17. The method of claim 11, wherein the duration of said uninterrupted stream of data is at least greater than one hour. 18. The method of claim 11, wherein the duration of said uninterrupted stream of data is several minutes. 19. The method of claim 11, wherein said reply device processes said uninterrupted stream of data in substantially identical manner as said electronics. 20. The method of claim 11, wherein said step of playing occurs at a time later than said recording and at a location other than said measurement device. 21. The method of claim 11, further comprising transmitting said uninterrupted stream of data wirelessly prior to said step of recording. 22. A method for analyzing measurement data from a measurement device, comprising:a) measuring a characteristic-of-interest in a medium by a measurement device to produce measurement data at a measurement data acquisition rate;b) producing output data at an output data rate from said measurement device, said output data being based on said measurement data, wherein said output data rate is lower than said measurement data acquisition rate;c) recording said measurement data from said measurement device to a first location;d) transmitting temporal data corresponding to said measurement data along with said measurement data from said first location to a second location, said second location being outside of said measurement device; ande) playing said measurement data from said second location on a simulator, said simulator being outside said measurement device, said simulator being programmed to provide a set of output data that substantially reproduces the characteristic-of-interest recorded at said first location. 23. The method of claim 22, wherein said step of recording begins by a manual actuation. 24. The method of claim 23, wherein said manual actuation includes a switch on said measurement device. 25. The method of claim 22, wherein said step of recording begins by an automatic response by said measurement device to a condition. 26. The method of claim 22, wherein said temporal data are timestamps. 27. The method of claim 22, said method being deterministic. 28. The method of claim 22, said measurement device being an ultrasonic flow meter. 29. The method of claim 22, said simulator being programmed to include a signal processing chain the same as one programmed in said measurement device. 30. The method of claim 22, said output data from said simulator being the same as said output data from said measurement device with respect to said characteristic of interest. 31. The method of claim 22, said output data from said simulator being identical to said output data from said measurement device. |
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abstract | An electron microscope includes an illuminating lens system that illuminates an electron beam that is emitted from an electron source onto a specimen as a planar illuminating electron beam having a two-dimensional spread, an imaging lens system that projects and magnifies the reflecting electron beam emitted from the specimen to project and form a specimen image, a beam separator that separates the illuminating electron beam from the reflecting electron beam, and a controller. The controller controls the reflecting electron beam so as to go straight through the beam separator, and the illuminating electron beam so as to keep a deflection angle of the illuminating electron beam which is made by the beam separator substantially constant. |
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abstract | The present invention provides a nuclear fuel assembly, where a boron-containing compound is used as a burnable poison and is distributed in a majority of the rods in the assembly. The assembly comprises a plurality of fuel rods, each fuel rod containing a plurality of nuclear fuel pellets, wherein at least one fuel pellet in more than 50% of the fuel rods in the fuel assembly comprises a sintered admixture of a metal oxide, metal carbide or metal nitride and a boron-containing compound. |
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abstract | A system for adjusting the energy level of a proton beam provided by a cyclotron includes the cyclotron and a target holder assembly including a removable degrader. The removable degrader can be removed and/or replaced without removal of the target holder assembly from the cyclotron. A method for adjusting an energy level of a proton beam of a cyclotron includes providing a target holder assembly with a removable degrader in the path of the proton beam of the cyclotron to reduce the energy level of the proton beam, where the removable degrader can be removed from the path of the proton beam without removal of the target holder assembly from the cyclotron. |
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042723213 | description | DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows a reactor 10 comprising the reactor vessel 12 and the reactor closure head 14. The reactor 10 is located within the reactor cavity defined by the cavity walls 16, and is supported therein by struts 18. During normal operation, the lower portion of the vessel 12 contains fuel assemblies 20 within which control rod fingers 24 reciprocate. The weight of the fuel assemblies 20 is borne by the core support barrel 26, which hangs from the lip 28 on the upper end of the vessel 12. Each rod finger 24 is part of a control rod 30, which typically includes four to twelve fingers 24 and which has a drive shaft 32 by which the rod 30 may be reciprocated from above. The control rod 30 passes through the area of strong lateral forces generated by the reactor coolant as it changes direction from the vertical along the assemblies 20 to the horizontal as it exits through the outlet nozzle 34. Protection of the fingers 24 is provided by the upper guide structure (UGS) 36 which, like the core support barrel 26, depends from the lip 28. The UGS 36 comprises an upper barrel portion 38 to which are rigidly attached upper and lower tube sheets 40, 42. Tubes 44 are rigidly connected between the upper and lower tube sheets whereby the fingers 24 may be reciprocated therein without being affected by the lateral flow forces. In the space above the upper tube sheet 40, each control rod 30 and its associated drive shaft 32 are surrounded by a shroud 48, each of which is connected to the upper tube sheet 40. It can be seen that over the full range of control rod reciprocation, the rod fingers 24 of each rod 30 are positively maintained in spaced relationship by the corresponding fuel assembly 20 and tubes 44, and the rods 30 are separated from each other by the shrouds 48. Referring now to FIG. 2, the first step in the refueling process is to fill the vessel 12 and much of the installation surrounding the vessel with water to an elevation approximately 25 feet above the level of the reactor ledge 50. When the closure head 14 is removed, only the shrouds 48 and the control rod drive shafts 32 extend above the elevation of the ledge 50. In modern nuclear reactors, there may be up to 100 drive shafts 32, but to simplify the description of the preferred embodiment only two shafts are shown. Likewise, there are up to one hundred shrouds 48, which are for simplicity shown as presenting a solid surface. Reactor installations include an overhead crane 52 which can be positioned above the vessel 12 and the UGS storage pit 46. The inventive apparatus is a lift rig 54, shown suspended from the crane 52 and positioned directly over the vessel 12, for removing and reinserting the upper guide structure 36 and control rods 30. The rig 54 comprises a frame 56 having attachment means 58 at its lower end, a rod support member 60 reciprocable within the frame including a horizontal platform 62 and a plurality of gripper means 64. The upper end of the frame 56 has cross beams 66 which provide an interference surface to limit the upward travel of the rod support member 60. In the preferred embodiment, the platform 62 is connected to the crane 52 through tie rods 98 and link blocks 68. The link blocks 68 are adapted to interfere with the cross beams 66 and transfer the upward force of the crane from the platform 62 to the frame 56 when the platform 62 is in the maximum upward position relative to frame 56. The lower end of the frame 56 includes alignment collars 69 which, as described below, aid in properly positioning the rig 54 onto the UGS. In FIG. 2 the rig 54 is shown as having only two columns 70. This is for illustrative purposes, since three equidistant columns 70 are preferred, connected by cross bars 72 and diagonal braces 74 according to the load that must be handled. As indicated in FIGS. 2 and 3, alignment posts 71 are attached to the vessel 12 and then the closure head 14 is removed. The rig 54 is then lowered towards the vessel 12 until the alignment collars 69 register with the alignment posts 71, thereby assuring that when the rig 54 is fully lowered the attachment means 58 will be properly positioned with respect to the UGS. As shown in FIG. 5b, the attachment means 58 engages a threaded opening 82 in the rim 39 of the UGS barrel 38. The attachment means 58 is conventional and does not in itself constitute the invention. In this embodiment of the invention, the attachment means 58 is a bolt which is operated from the upper end of the rig by means of a wrench 86 disposed within the column 70. Referring again to FIG. 3, once the attachment means 58 are secured, the crane 52 lowers the platform 62 within the frame 56 until the gripper means 64 are immediately above the drive shafts 32. This position of the platform 62 and gripper means 64 is shown by phantom lines. The single phantom shaft 32' shows one of nearly 100 drive shafts 32 representing the control rods 30 in their lowest position in the vessel 12, i.e., inserted to the bottom of the assemblies 20 in FIG. 1. Upon inspection that registry of grippers 64 and shafts 32 is accurate, (guide structuring may be added to independently assure accurate registry) the platform 62 is lowered to its maximum downward position against lower stop 80 whereby the gripper means 64 simultaneously engage all drive shafts 32. A slight upward movement of the platform 62 automatically locks the shafts within the gripper means 64. The details of the gripper means 64 are disclosed in co-pending U.S. application Ser. No. 842,576, filed Oct. 17, 1977, "Extension Shaft Latching Mechanism for a Nuclear Reactor Control Rod Lift Rig." The platform 62 is then lifted through the frame 56, simultaneously lifting all control rod fingers 24 out of the fuel assemblies 20 and into the tubes 44 and shrouds 48 of the UGS 36 (shown in FIG. 1). The platform 62 in its highest position relative to the frame 56 is shown in solid lines in FIG. 3. When the platform 62 is in the highest position and the crane 52 continues pulling, the upward force is transferred by the link blocks 68 from the platform 62 to the cross beams 66, which are adapted to mate with link blocks 68. The crane then lifts the entire rig 54 which in turn lifts the UGS 36 out of the vessel 12. The UGS 36 is lifted without the danger of the control rod fingers 24 being damaged because, as described above, the fingers are always within the protective surrounding of tubes 44 and shrouds 48. After the UGS 36 is clear of the vessel 12, the crane 52 is moved laterally until the rig 54 and UGS 36 are above the temporary storage pit 46 shown in FIG. 4. The crane 52 is lowered until the base of the UGS 36 rests on a stand 47 on the floor of the storage pit 46. In the preferred embodiment, the platform 62 carrying the control rods 30 is locked in the maximum upward position as soon as possible so that any slack in the crane 52 after the upper guide structure 36 is resting on the stand 47 will not cause the platform 62 to apply a compressive load on the control rod fingers 24. The lower tips of the fingers 24' are shown in phantom in their storage position in the UGS when the platform 62 is properly locked. After the platform 62 is locked in the up position with the UGS 36 on the floor stand 47, the tie rods 98 and cross beams 66 may be disengaged from the rig 54 and repositioned over the vessel 12 in order to remove other reactor internals if the need arises. For example, the core support barrel 26 can be removed during a refueling operation if inspection is required or a modification must be made to the structures in the lower portion of the vessel 12. This feature will be more fully described below. It can be appreciated that the method and apparatus generally described above provide an efficient, essentially continuous way of safely performing an otherwise very time-consuming operation. In particular, heavy components such as the UGS 36 and very delicate components such as the control rod fingers 24 are sequentially and continuously moved remotely while under water. The general description and operation of the invention having been described, a more detailed description of the various parts will be presented. FIG. 6 shows a plan view of the rig 54 showing the equilaterally spaced columns 70, the alignment collars 69, the braces 72, 74 and the cross beams 66. The platform 62 occupies most of the cross section inside the frame 56, and contains a multiplicity of holes 94 through which the gripper means 64 (see FIG. 2) may be attached to its underside. The platform 62 is reciprocated within the frame 56 by the action of crane 52 through the tie rods 98 and tie rod tongue 108. The entire rig 54 is lifted by the interaction of the link block 68 with the interference beams 66, which in the preferred embodiment are formed as a delta beam spreader. FIG. 7 is a more detailed view of the connection between the platform 62 and the tie rods 98. The link block 68 is connected to the platform 62 by a yoke 104 and is connected to the tie rod tongue 108 by means of a link pin 106 running through the opening (not shown) on the lower end of the tie rod tongue 108. The cross beam 66 (only one shown fully) consist of I-beams 100 in which an interference plate 102 is attached to the surface of each I-beam 100 facing the tongue 108. The interference plate 102 has a recessed portion 110 forming a curved surface adapted to mate with the contoured upper portion of the link block 68. It can be seen that as the crane 52 lifts the platform 62 to its maximum height within the frame 56, the upward force of the crane 52 will be transferred through the link block 68 to the cross beams 66. It is to be understood that other arrangements not requiring positive mating may be used without departing from the scope of the invention. Referring to FIG. 3, 5a, and 5b, one column 70 and its associated structure are shown in detail, but it should be understood that all columns 70 will in the preferred embodiment have similar structures. A guide bar 78 is attached to the column 70 and runs from the lower stop 80 upward to the collar 122 near the top of column 70. As shown in FIG. 8, the guide plate 120 on the platform 62 slides along the guide bar 78 as the platform 62 reciprocates within the frame 56. The guide plate 120 interacts with the guide bar 78 to prevent rotational motion of the platform 62 as it reciprocates within the frame 56. FIG. 5a shows the relationship of the platform 62, link block 68, cross beams 66, and column 70 when the platform is locked in the up position within the frame 56. In this view, the closer cross beam 66 and its interference plate 102 are not shown. Reference to FIG. 6 will facilitate understanding of the details of FIG. 5a. The end of the shown cross beam 66 is behind column 70 and rests on an annular support 109 formed around the column 70. The column cap 112 is threaded into column 70 and torqued against a rectangular washer 113 which is seen in FIG. 6 to cover both cross beams 66 at each corner of the delta beam spreader. The cross beams 66 are thus rigidly connected to the frame 56, and in particular, it can be seen that when the link block 68 is raised against the interference plate 102 and cross beams 66, the upward force is transferred to the frame 56 so that the UGS 36 may be lifted. When the UGS 36 and the control rods 30 contained therein are stationary on the floor of the UGS storage pit 46, the upper portion of the rig 54 can be disassembled and used to lift other core components such as the core support barrel 26. In the preferred embodiment, the wrench handle 87 is removed, the column cap 112 is unscrewed from the column 70 and the yoke pin 107 is removed. The crane can then lift the cross beams 66, column cap 112, washer plate 113, tie rod 98, tie rod tongue 108, and link block 68 to be used in another operation. The remaining rig structure will continue performing the intended function of suspending the control rod fingers 24 within the UGS 36 provided, of course, that the platform 62 is locked in the maximum upward position within the frame 56. In the preferred embodiment, the platform 62 can be locked in the maximum up position in two different ways, as shown in FIG. 5a. In the mannually operated method, operating personnel standing on the platform 62 move the dead bolt handle 116 so that the dead bolt 114 engages the support bar 118 formed on the upper portion of stop support 126 attached to column 70 by collar 122. Dead bolt 114 is located in dead bolt box 115 attached to the underside of the platform 62. As shown in FIG. 8, the dead bolts 114 are disposed on either side of, and below, the guide plate 120. It can be seen that when the dead bolt handles 116 are in the extreme left position the dead bolts 114 are completely within the box 115 and the platform 62 is free to slide past the stop support 126. The platform 62 can thus be positioned as desired within the frame 56. When the platform 62 is in the maximum upward position with the frame, the dead bolt handle 116 can be moved to the right-most position to engage the support bar 118, locking the platform 62 in essentially the maximum vertical position. An independent, automatic stop means is also provided in the preferred embodiment. The purpose of the automatic stop is to prevent the movement of the platform 62 unless the lift rig 54 is positioned on the UGS 36 when the UGS is on the vessel 12. This is an important safety feature because when the control rods 30 are attached to the platform 62 and the platform is not positioned directly above the vessel 12, the downward motion of the plate 62 may cause the control rod fingers 24 to hit unyielding objects and be damaged. Only when the lift rig 54 is in the position shown in FIG. 3 is it desirable that the platform 62 be movable within the frame 56. Referring again to FIG. 5, an automatic stop actuator 88 runs vertically along each column 70 and has a foot 90 which, as shown in FIG. 4, hangs below the UGS rim 39 under all circumstances except when, as shown in FIG. 3 and FIG. 5b, the rig 54 is resting on the UGS 36 when the UGS is inside the vessel 12. In this latter condition, the foot 90 is pushed upward by contact with the reactor vessel ledge 50. The actuator 88 automatically operates the gate 92 and latch 96 which prevents the platform 62 from moving downward within the frame except when the actuator 88 is in the up position. The gate 92 connects the actuator 88 to a pair of latches 96 which in the locking position extend horizontally from column 70, alongside the guide bar 78, and under the platform 62. In this position, the latch 96 rests on a stop support 126 which is rigidly connected to the collar 122. The latches 96 are shown in phantom FIG. 6 in their horizontal position beneath platform 62. When the actuator 88 is in the up, or unlocked position, the latch 96 is in a vertical orientation (not shown) and out of the vertical path of the platform 62 as it travels along the guide bar 78. FIGS. 9 and 10 show the operation of the automatic stop mechanism in more detail. In FIG. 9, it may be seen that the stop support 126 is attached to the collar 122 in a manner tht does not obstruct the guide bar 78. In FIG. 10, it may be seen that the latch 96 is pivotally connected at 134 to an upright portion of step 128 and at 136 to a gate link 132 which is connected to the gate 92. In actual operation, the actuator 88 would be in the down, or locked position, as the rig is lowered towards the uncovered reactor vessel 12 in the condition shown in FIG. 2. When the rig 54 is on the vessel 12 as shown in FIG. 3, the automatic latch 96 is in the vertical, or unlocked position so that the platform 62 can reciprocate within the frame 56. When the platform 62 with the control rods attached thereto is lifted to the maximum height within the frame 56 and the crane 52 continues pulling, the rig 54 will lift the upper guide structure 36 out of the vessel 12. As the UGS 36 rises above the vessel 12, the weight of the actuator 88 causes the foot 90 to drop relative to the bottom of column 70, thereby operating the gate 92 and latch 96 such that the latch 96 moves from a vertical to the horizontal position below the platform 62, as shown in FIG. 5a. The latches 96 are horizontally oriented during the movement of the rig 54 towards the storage pit 46, during the entire storage period as shown in FIG. 4, and during the return of the rig 54 to the reactor vessel 12 after the fuel has been shuffled. Only after the UGS 36 is fully within the vessel 12 does the latch 96 return to the unlocked (vertical) orientation so that the platform 62 can be lowered to reinsert the control rods 30 into the fuel assemblies within the vessel. Although the preferred embodiment shows both the dead bolt and self-actuated stop arrangements, they are independent and one may be used without the other. In addition, it may be appreciated that although the preferred embodiment shows the actuator 88 being responsive to contact with the vessel ledge, it could be responsive to contact with any structure having a fixed relationship to the vessel. |
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claims | 1. A sample holder for holding a sample to be observed in an electron microscope, comprising: a sample mount on which said sample is affixed; and a rotation driving mechanism for rotating said sample mount about a predetermined axis in the range of 0 to 360xc2x0, wherein said predetermined axis extends along a direction other than a direction of electron beam incidence in said electron microscope, a position of said electron beam incidence in said sample being changed as said sample mount rotates. 2. The sample holder according to claim 1 , further comprising: claim 1 a cartridge portion coupled to said sample mount; and a fixed portion coupled to a main body of said sample holder, wherein said cartridge portion can be attached to and removed from said fixed portion. 3. A sample mount jig for grasping and holding a sample mount provided in a sample holder for holding a sample to be observed in an electron microscope, said sample mount jig comprising: a protecting portion for covering said sample affixed on said sample mount when said sample mount jig is grasping said sample mount; and a grip portion fixed to said protecting portion. 4. The sample mount jig according to claim 3 , wherein said protecting portion has a fitting part in which said sample mount fits. claim 3 5. A sample mount on which a sample to be observed is affixed and which is provided in a sample holder for holding said sample in an electron microscope, said sample mount comprising: a mount plate having a gap whose width is narrower than the length of said sample, for supporting said sample affixed thereon, wherein said sample is laid over opposite portions of said gap of said mount plate, and wherein said gap extends throughout a thickness of said mount plate and extends from an end of said mount plate. 6. The sample mount according to claim 5 , wherein said sample mount is composed of said mount plate and a support plate for supporting said mount plate, said mount plate and said support plate being combined in the shape of L in section. claim 5 7. The sample mount according to claim 5 , wherein said mount plate is in the form of a flat plate. claim 5 8. A sample holder for holding a sample to be observed in an electron microscope, comprising: a sample mount composed of a mount plate on which said sample is affixed and supported and a support plate for supporting said mount plate, said mount plate and said support plate being are combined in the shape of L in section; and a holding portion for holding said support plate of said sample mount, wherein said mount plate has a gap whose width is narrower than the length of said sample and said sample is laid over opposite portions of said gap of said mount plate, wherein said gap extends throughout a thickness of said mount plate and extends from an end of said mount plate. 9. The sample holder according to claim 8 , wherein said holding portion holds said sample mount in such a manner that a part of said mount plate where said sample is affixed protrudes from said sample holder. claim 8 10. The sample holder according to claim 8 , wherein said holding portion comprises, claim 8 a first holding portion for holding said support plate in such a manner that a normal direction of said mount plate extends along a direction of electron beam incidence in said electron microscope, a second holding portion for holding said support plate in such a manner that said normal direction of said mount plate extends along a first direction which is vertical to said direction of the electron beam incidence, and a third holding portion for holding said support plate in such a manner that said normal direction of said mount plate extends along a second direction which is vertical to both of said direction of the electron beam incidence and said first direction. 11. The sample holder according to claim 8 , wherein said holding portion holds said support plate in such a manner that a normal direction of said mount plate extends along a direction of electron beam incidence in the electron microscope or along a first direction which is vertical to said direction of the electron beam incidence and said holding portion can be rotated in the range of 0 to 360xc2x0 about an axis extending along said first direction. claim 8 12. A sample holder for holding a sample to be observed in an electron microscope, comprising: a sample mount on which said sample is affixed; a rotation driving mechanism for rotating said sample mount about a predetermined axis in the range of 0 to 360xc2x0; a cartridge portion coupled to said sample mount; and a fixed portion coupled to a main body of said sample holder, wherein said cartridge portion can be attached to and removed from said fixed portion, wherein said rotation driving mechanism transmits power from said fixed portion to said cartridge portion, and wherein said rotation driving mechanism rotates said sample mount in the range of 0 to 360xc2x0 about an axis extending along a direction other than a direction of electron beam incidence in said electron microscope. |
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055703992 | description | DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to the FIGS. 1 to 9. The same reference numerals are attached to the same parts and equivalent parts in FIGS. 1 to 9. FIG. 1 is a schematic vertical sectional view showing a control rod and fuel supporting member gripping apparatus according to the first embodiment of the present invention which is hoisted in a reactor pressure vessel. FIGS. 2 to 8 show the details of respective sections thereof. The CR (control rod) 4 is detachably connected to the CRD (control rod driving mechanism) 8 by means of a bayonet coupling 14 designated by a reference numeral 15. A control rod and fuel supporting metal gripping apparatus 20 which is the first embodiment of the present invention is hoisted and carried into the reactor pressure vessel 1 at the time of the periodic inspection of a boiling water reactor (BWR). The CR 4 and the FS (fuel supporting member) 6 which are mounted in the core are removed and hoisted to be carried out of the reactor pressure vessel 1. The control rod and fuel supporting member gripping apparatus 20 is used for reinstalling the CR 4 and the FS 6 and comprises an upper plate 30 which is tied with a hoisting rope or the like of an auxiliary hoist of a fuel exchanging device, not shown, a CR gripping device 40 which is hoisted by the upper plate 30 so that the device is axially rotatable and an FS gripping device 50 which is mounted on the CR gripping device 40 so that the FS gripping device can be lifted up and down. The upper plate 30 is hoisted on a given lattice of the upper lattice plate 5 as shown in FIGS. 1 and 2 so that the entire weight of the control rod and fuel supporting member gripping apparatus 20 is loaded on the upper lattice plate 30 and the supporting member gripping apparatus 20 is prevented from rotating. An upper plate settling detection lever 30a is disposed on the bottom of the square corner of the upper plate 30 so that the detection lever can be swung freely. When the upper plate 30 is settled on the upper lattice plate 5, the swing end of the upper plate settling detection lever 30a swings and then the upper plate settling detection lever 30a turns "ON" the upper plate settling detection limit switch 30b in order to output an upper plate settling detection signal to the fuel exchanging device or the like through a cable, not shown. A square supporting cylinder 31 is fastened to the upper plate 30 so that the cylinder 31 goes vertically through the center of the upper plate 30 and a square stud 32 is provided on the top center of the supporting cylinder by means of a pin 32a so that the stud 32 can be swung. Thus, it is not possible to easily change the state of the long control rod and fuel supporting metal gripping device 20 from its storage condition in which the gripping device is laid to the state in which the gripping device 20 is vertically hoisted. The square stud 32 has a screw hole 32b formed on the top end as shown in FIGS. 2 and 5. A bolt which is provided on the front end of a wire rope such as a torqueless wire is screwed into the screw hole 32b in order to prevent the auxiliary hoist of the fuel exchanging device from rotating. Thus, it is possible to hoist entirely the control rod and fuel supporting member gripping apparatus 20 freely so that the gripping device is not rotated. The supporting cylinder 31 contains a CR gripping device 40. The CR gripping device 40 contains double internal and external cylinders 41 and 42 which are located coaxially in the supporting cylinder 31. The external cylinder 42 is fastened to the supporting cylinder 31 and the internal rotating cylinder 41 is mounted on the external cylinder by means of a thrust bearing 43a and a radial bearing 43b so that the internal cylinder 41 is axially rotatable. The rotating cylinder 41 has a hook 44 provided on the bottom end thereof which grips and releases the handle 4d as shown in FIGS. 1 and 4. As shown in FIGS. 2 and 6, the rotating cylinder 41 is axially rotatable clockwise and counterclockwise by means of a CR rotating mechanism 45. The CR rotating mechanism 45 contains a rotating gear 45a which is provided on the side in the middle of the rotating cylinder along the length thereof, the rotating gear 45a being interlocked with the rotating cylinder 41. Both ends of the wire 45b which is wound around the rotating gear 45a are wound around pulleys 45c and 45d and connected to both the top and bottom ends of piston rods 45g of a pair of right and left air cylinders 45e and 45d for rotation driving. When the piston rods 45g reciprocate, the rotating cylinder 41 is rotated axially clockwise and counterclockwise. The rotating cylinder 41 is lifted up and down by means of a CR lifting air cylinder 46. When low pressure air is supplied to the lift-up chamber, i.e. lower chamber, in the air cylinder 46, the hook 44 which grips the handle 4d of the CR 4 is lifted up slightly and then the hook 44 is lifted up so as to eliminate a play of the handle 4d thereby making the hook 44 fit to the handle 4d. This mechanism relaxes a shock which occurs when the hook 44 is lifted up all at once. When the supplied air pressure is high, the CR lifting air cylinder 46 lifts the handle 4d higher than a time when a low pressure is supplied, for example, by several tens mm. As shown in FIG. 4, the rotating cylinder 41 incorporates the CR gripping mechanism 47 which is provided on the bottom end of the rotating cylinder 41. The CR gripping mechanism 47 makes the piston rod 47b of the hook opening/closing air cylinder 47a communicate with the swing end of the hook 44 through a link mechanism 47c to change the supply of air to the hook opening/closing air cylinder 47a to the top chamber or the bottom chamber thereby opening or closing the hook 44. Consequently, the handle 4d of the CR 4 is gripped or released. The CR gripping mechanism 47 comprises a hook open detecting limit switch 47d for detecting that the hook 44 is opened, a hook detecting limit switch 47e for detecting that the hook 44 is closed, and a CR settling detection limit switch 47f for detecting that the hook 44 is settled on the handle 4d of the CR 4. The rotating cylinder 41 has a guide protrusion 47g which is provided on the bottom thereof. The guide protrusion 47g has a guide groove which fits to the cross shaped center of the cross shaped handle 4d, the guide groove being provided on the bottom thereof. If the hook 44 is lifted down to the CR 4, the handle 4d gradually fits to the cross shaped guide groove so as to guide the hook 44 to an optimum position of the handle 4d. Further, the hook opening/closing air cylinder 47a includes a holding spring 47i which urges the piston rod 47b to the gripping position as a means for corresponding to a trouble of the hook opening/closing air cylinder 47a, so as to hold the gripping action when the supply of air to the air cylinder 47a is interrupted due to a rupture of the air hose. A releasing wire 47h is connected to the piston rod 47b and when the wire 47h is pulled up to resist the force of the holding spring 47i, the hook opening/closing air cylinder 47a is forcibly released. On the other hand, in the FS gripping device 50, as shown in FIG. 3, the lower half portions of a square shaped supporting cylinder 31 and a rotating cylinder 41 are inserted into a lifting square cylinder 51 having a diameter larger than that of the supporting cylinder 31, and as shown in FIGS. 7A and 7B, the lifting square cylinder 51 is mounted so as to be lifted up and down so that the lifting square cylinder 51 is axially deviated by 45.degree. with respect to the internal supporting cylinder 31. That is, an FS lifting air cylinder 52 is fixed on the external side face in the middle along the length of the square supporting cylinder 31 and the lifting square cylinder 51 is held by a piston rod 52a which goes up and down within the FS lifting air cylinder 52 so that the lifting square cylinder can be lifted freely. As shown in FIG. 8, a plurality of guide rollers 53, 53,--which move on the external faces of the respective corners of the external side face of the square supporting cylinder 31 are provided inside the lifting square cylinder 51. On the other hand, as shown in FIG. 4, the lifting square cylinder 51 has a cross shaped insertion hole 51b which allows the cross shaped handle 4d of the CR 4 to pass therethrough, the hole being provided on the bottom of the lifting square cylinder 51. As shown in FIG. 8, the lifting square cylinder 51 has corner pins 54 which protrude vertically downward and which are in contact with the guide pins of the core supporting plate 7, the core supporting plate 7 being provided on the external faces of the respective corners of the bottom 51a. Further, as shown in FIG. 4, the bottom face 51a of the lifting square cylinder 51 has a pair of sheet-shaped guides 55, 55 which are disposed on a pair of corners which diagonally corresponds to each other. The sheet-shaped guides 55, 55 are inserted into a pair of fuel supporting engagement holes 6b and 6d which face each other with respect of the diameter of the FS 6 shown in FIG. 16 so as to guide the hook 44 to the handle 44d of the CR 4. The lifting square cylinder 51 has a pair of right and left FS gripping mechanisms 56, an FS gripping lock mechanism 57 and an FS settling detection device 58, these mechanisms and device being disposed on the bottom end thereof. FIG. 4 shows only one of a pair of right and left FS gripping mechanisms 56 and the representation of the other side is omitted. Each FS gripping mechanism 56 comprises an air cylinder 56c which advances or retracts a pair of plungers 56 through a link mechanism 56b, the plungers being protruded through a pair of orifices which face each other with respect to the diameter of the FS 6, for example, 6f, 6h, in order to grip the FS 6, an FS gripping detection limit switch 56d for detecting the gripping action of the FS 6 by means of the FS gripping air cylinder 56c and an FS releasing detection limit switch 56e for detecting the releasing action of the FS 6. The FS gripping air cylinder 56c contains a gripping holding spring 56g which urges the piston rod 56f in the direction in which the gripping action is held, as a means for treating a trouble of the FS gripping air cylinder 56c, if the supply of air to the FS gripping air cylinder 56c is interrupted due to a breakage of an air hose when the FS 6 is gripped by means of the FS gripping air cylinder 56c. A wire rope 56h for the releasing operation is connected to the FS gripping air cylinder 56c. By pulling the wire rope 56h so as to resist the force of the gripping holding spring 56g, the gripping action of the FS gripping air cylinder 56c is forcibly changed to releasing action so as to retract a pair of the plungers 56a, 56a from a pair of the orifices 6f and 6h of the FS 6 backward, that is, to the inside, thereby forcibly releasing the FS 6. The FS gripping lock mechanism 57 has a lock lever 57a which is provided so as to be able to swing freely on the bottom face 51b of the lifting square cylinder 51. The lock lever 57a is urged always to be engaged with an engagement hole 56i in a communicating rod 56f of the link mechanism 56b of the FS gripping mechanism 56 in order to hold the communicating rod 56f. When the bottom face 51a of the lifting square cylinder 51 is settled on the top face of the FS 6, the lock lever 57a is swung and disengaged from the engagement hole 56i of the communicating rod 56f of the lifting square cylinder 51. Consequently, the communicating rod 56f is released to allow the link mechanism to operate. When the bottom face 51a of the lifting square cylinder 51 is separated from the top face of the FS 6, the lock lever 57a is swung to be engaged with the engagement hole 56i of the communicating rod 56f. Consequently, the action of releasing the communicating rod 56f is held to lock the gripping action of the FS 6. The FS settling detection device 58 has a settling detection lever 58a which is provided so as to be swung freely on the bottom face 51a of the lifting square cylinder 51. When the settling detection lever 58a is settled on the top face of the FS 6, an FS settling detection limit switch 58 is turned on/off by the swing end thereof in order to output or stop an FS settling signal. As shown in FIGS. 1 and 3, a cable absorbing mechanism 59 is provided on the internal face of the top of the lifting square cylinder 51. This mechanism absorbs ropes 60 such as air hoses, cables connected to respective air cylinders 45e, 45f, 46, 47a, 52, 56c and operating wires 45h, 47h, 56h by means of pulleys 59a, 59b and a spring 59c in order to prevent a trouble due to the looseness of the ropes 60. Next, a case in which the CR 4 and the FS 6 are lifted up from a water filled reactor pressure vessel 1 by using the control rod and fuel supporting member gripping apparatus 20 having the aforementioned construction at the time of the periodic inspection of the BWR will be described below. As shown in FIG. 9A, the CR 4 is inserted fully into the core to maintain the subcriticality of four fuel assemblies 3, 3, 3, 3 which are placed in a lattice and two fuel assemblies 3, 3 which are placed diagonally are pulled out of the core by means of a fuel exchanging device or the like. As shown in FIG. 9B, a blade guide (control rod guiding device) 61 in which a pair of dummy channels 61a, 61b are connected diagonally by the handle 61c is inserted into positions from which two fuel assemblies 3, 3 are removed. After that, the remaining two fuel assemblies 3, 3 are pulled out of the core, as shown in FIG. 9C. As shown in FIG. 9D, the CR 4 is guided by means of the blade guide 61 and moved downward of the core by means of the CRD 8 so that the CR 4 is completely pulled out. Further, as shown in FIG. 9E, the blade guide 61 is pulled out of the core. After these operations, the bolt of the wire rope of the auxiliary hoist of a fuel exchanging device, not shown, is screwed into the screw hole 32b of the square stand of the control rod and fuel supporting metal gripping device 20 according to the present invention, and then the fuel assembly is lowered into the reactor pressure vessel 1. Thereafter, as shown in FIG. 1, the upper plate 30 of the control rod and fuel supporting metal gripping device 20 is settled on the upper lattice plate 5 to transfer the total weight of the control rod and fuel supporting member gripping apparatus 20 from the wire rope to the upper lattice plate 5. When the upper plate 30 is settled on the top face of the upper lattice plate 5, the upper plate settling detection lever 30a comes into contact with the top face of the upper lattice plate 5 to turn on the upper plate settling detection limit switch 30b. Then, an upper plate settling detection signal is output to the fuel exchanging device or the like through a cable, not shown. At this time, the bottom face 51a of the lifting square cylinder 51 is settled on the top face of the FS 6 and the top face of the handle 4d of the CR 4 at the same time, and both the CR settling detection limit switch 47f and the FS settling limit switch 58b output settling signals. Further, the lock lever 57a is disengaged from the engagement hole 56i of the communicating rod 56f in order to release the locking condition of the lock mechanism 57. Next, when air is supplied to the FS gripping air cylinder 56c, a pair of right and left plungers 56a, 56a are protruded into a pair of orifices 6f, 6h of the FS 6 through the link mechanism 56b which is unlocked, in order to hold the FS 6. At this time, the FS gripping detection limit switch 56d outputs a gripping signal for detecting the gripping condition of the FS 6. When air is supplied to the gripping side of the hook opening/closing air cylinder 47a, the hook 44 is closed while gripping the handle 4d with a slight vertical play, thereby gripping the CR 4. At this time, the hook close detection limit switch 47e outputs a hook close signal. Then, when low pressure air is supplied to the CR lifting air cylinder 46, the rotating cylinder 41 rises slightly so that the hook 44 comes into contact with the bottom face of the handle 4d. That is, because the pressure of air supplied to the CR lifting air cylinder 46 is low, the rotating cylinder 41 rises by only a gap, i.e. play, between the hook 44 and the handle 4a of the CR 4 so as to make the hook 44 contact the handle 4d firmly. When air is supplied to the lift-up chamber, i.e. lower chamber, of the FS lifting air cylinder 52, the lifting square cylinder 51 rises. Thus, the FS 6 which is held by means of the FS gripping mechanism 56 is pulled slightly upward to remove the FS 6 from the core supporting plate 7. The FS 6 is raised slightly higher than the top face of the handle 4d of the CR 4 and the FS 6 is maintained at that height. When the lifting square cylinder 51 is lifted up, a plurality of guide rollers 53, 53,--which are provided inside thereof rotate on the external face of the supporting cylinder 31 in order to prevent the FS 6 which is held by means of the lifting cylinder 51 and the FS gripping mechanism 56 from rotating axially. Thus, it is possible to prevent the FS 6 from colliding with the fuel assembly 3 loaded within the lattice. After this operation, high pressure air is supplied to the lift-up chamber, i.e. lower chamber, of the CR lifting air cylinder 46 in order to raise the CR gripping mechanism 47 by several tens mm and rotate the CR 4. Consequently, all the weight of the CR 4 and the members which are connected with the bayonet coupling 14 of the CR 8 are received from the control rod and fuel supporting member gripping apparatus 20 and the weight is loaded and supported by the upper lattice plate 5. When air is supplied to one of the CR rotating air cylinders 45e, 45f, for example, 45e, while hoisting the CR 4 as described above, the rotating gear 45a is turned clockwise. By turning the rotating cylinder 41 by 45.degree. for example, by means of the rotating gear 45a, it is possible to release connection between the CR 4 and the CRD 8 by the bayonet coupling 14. If air is supplied to the other CR rotating air cylinder 45f to turn the rotating cylinder 41 by 45.degree., the CR 4 is connected with the CRD 8 by the bayonet coupling 14. After the CR 4 is removed from the CRD 8, the CR 4 and the FS 6 are hoisted to the top portion of the core by winding the wire rope of the auxiliary hoist or the like of the fuel exchanging device. The CR 4 and the FS 6 are lifted through the upper lattice plate 5 from the inside of the reactor pressure vessel to a reactor well located above the reactor pressure vessel and then moved to a fuel storage pool which communicates with the reactor well while keeping the CR 4 and the FS 6 in water. Thereafter, the CR and FS gripping mechanisms 47 and 56 are actuated to release the CR 4 and the FS 6 at a predetermined position. Then, the CR 4 and the FS 6 are released and stored to terminate the operation. However, if these gripping mechanisms 47 and 56 are not capable of releasing the CR 4 and the FS 6 for some reason, the releasing operation wires 47h and 56h are pulled strongly. Consequently, it becomes possible to forcibly release the CR 4 and the FS 6. If the CR 4 and the FS 6 are gripped by means of both the CR gripping mechanism 47 and the FS gripping mechanism 56, the gripping action is maintained by the holding springs 47g and 56g and the locking mechanism 57. Thus, it is possible to prevent an unexpected accident which may occur when the CR 4 and the FS 6 are accidently released if the CR 4 and the FS 6 are being gripped and transferred. According to the described embodiment of the present invention, it is possible to grip and remove the CR 4 and the FS 6 by means of the control rod and fuel supporting member gripping apparatus 20 and further to hoist the CR 4 and the FS 6 and carry them out of the reactor pressure vessel 1 at the same time. Thus, a sequence of such operations can be performed simply, securely and rapidly, and the working efficiency of BWR's periodic inspection can be enhanced remarkably. FIG. 10 represents a second embodiment according to the present invention, and referring to FIG. 10, the gripping apparatus body 100 is hoisted down into the reactor pressure vessel by means of a wire rope 101 driven by a hoist, not shown. A hanging member 102 is secured to the upper portion of the gripping apparatus body 100 and the wire rope 101 is firmly engaged with the hanging member 102. A fuel supporting member gripping device 103 is mounted to a lower portion of the gripping apparatus body 100 to grip the fuel supporting member 6 mounted on a core supporting plate 7. Further, a control rod gripping device 106 for gripping a neck portion of a control rod 4 is supported by the gripping apparatus body 100 through a shaft member 107 and a support plate 108 supporting the shaft member 107 so that the shaft member 107 is attached to the support plate 108 to be movable up and down with respect to the support plate 108. A control rod rotating mechanism 109 for rotating the shaft member 107 with respect to the support plate 108 is mounted to a portion near the attaching portion of the shaft member 107 to the support plate 108. A stopper member 110 is provided for the upper end of the shaft member 107 for preventing the control rod gripping device 106 and the shaft member 107 from coming off from the support plate 108 at a time when the gripping apparatus body 100 is lifted upward. In FIG. 10, an upper lattice plate 5 is a plate for supporting the top end of a fuel assembly, not shown, in a horizontal plane and four fuel assemblies are charged, in a usual core running state, in one cell 113 in which the gripping apparatus body 100 is located. The gripping body 100 has a horizontal cross section of a square shape slightly smaller than that of the cell 113 so as to prevent the gripping body 100 from being rotated in the cell 113. Hereunder, a method for taking out, i.e. uncoupling, the control rod (CR) 4 and the fuel supporting member (FS) 6 will be described with reference to FIGS. 10 and 11. FIG. 11A shows a state before the uncoupling operation, in which the FS 6 is settled on a control rod guide tube 114 supported by the core supporting plate 7 and the FS 6 is prevented from rotation by a pin 115 secured to the core supporting plate 7. The CR 4 penetrates inside the FS 6 so that the top end thereof extends upward, as viewed, from the FS 6. From this state, the gripping apparatus body 100 is hoisted down from an upper portion on the FS 6 by means of the wire rope 101, and this state corresponds to the state shown in FIG. 10. Then, the fuel supporting member gripping device 103 is operated to grip the FS 6, and the control rod gripping device 106 is also operated to grip the CR 4. The wire rope 101 is thereafter lifted up to thereby lift up the gripping apparatus body 100. At this time, the FS 6 is also lifted up together with the gripping apparatus body 100, but the control rod gripping device 106 is not lifted up because of the sliding motion of the shaft member 107. FIG. 11B shows a state in which the FS 6 is lifted up. In the next step, the control rod rotating member 109 is driven to rotate the control rod gripping device 106 and the CR 4 by 45.degree. to thereby uncouple the CR 4 and the control rod driving mechanism. FIG. 11C shows a state before this rotation. Then, the CR 4 and the FS 6 are taken out of the core by hoisting up the gripping apparatus body 100. FIG. 11D shows a state before the lift-up of the CR 111. When the gripping apparatus body 100 is lifted up, the control rod gripping device 106 is not slid off because of the location of the stopper member 110 and the control rod 4 is lifted up together with the FS 6. As described hereinbefore with reference to two preferred embodiments, according to the present invention, the FS 6 is not rotated horizontally from the setting state of FIG. 12A to the state of FIG. 12B, and only the CR 4 is rotated to thereby uncouple the same. Accordingly, the CR 4 and the FS 6 can be taken out of the core simultaneously. FIG. 12C shows a state in which fuel assemblies are withdrawn for setting a television camera for monitoring the working state of the gripping apparatus body. The fuel assemblies are expected in future not to be withdrawn through the used reliance of the gripping apparatus. As described hereinbefore with reference to two preferred embodiments, according to the present invention, the fuel supporting member is not moved horizontally in the state shown in FIG. 12B from the state shown in FIG. 12A mentioned with reference to the conventional structure, and only the control rod is rotated to perform the uncoupling thereof. Accordingly, the control rod and the fuel supporting member in the given fuel assembly can be withdrawn at the same time without moving or shifting the fuel assemblies disposed neighboring the given fuel assembly. With reference to FIG. 12C, the fuel assembly 116 is now withdrawn for disposing a television camera for monitoring the operation of the control rod and fuel supporting member gripping apparatus, but it will be expected in future not to remove such fuel assembly upon repeated confirmation of the performance of this gripping apparatus. As described above, according to the present invention, it is possible to grip and remove the control rod and the fuel supporting member which are located within the reactor pressure vessel and hoist the control rod and the fuel supporting member so as to be taken out of the reactor pressure vessel. Thus, as compared with the conventional case in which the control rod and the fuel supporting member are gripped separately by means of different gripping devices successively and conveyed out of the reactor pressure vessel after they are removed from the gripping devices, the present invention is capable of improving the working efficiency of hoisting operation markedly. Consequently, it is possible to improve the working efficiency of the BWR's periodic inspection. That is, for example, in the conventional technique, it is required to remove totally twenty fuel assemblies, but, according to the present invention, only the seven fuel assemblies have to be removed, and preferably four fuel assembly, in future. Thus, the working of the operator to remove the fuel assemblies can be extremely reduced, being advantageous. This advantage results in the reduction of a space of a pool in which the withdrawn control rods and the fuel supporting members are stored. Further, in the control rod rotating mechanism, the rotating members which rotate the rotating body which has the hook for gripping the handle of the control rod are connected to the clockwise/counterclockwise rotating air cylinder through a wire in order to turn the rotating body. Thus, it is possible to reduce the load of the rotating force. If the supply of a drive medium such as air to the control rod gripping driving source such as air cylinder is interrupted when the control rod is gripped by means of the hook which is actuated by the control rod gripping driving source, the gripping action of the control rod gripping driving source is maintained by the force of the spring. Thus, even if the supply of the drive medium to the control rod gripping air cylinder is interrupted due to a breakage of the air hose or the like when the control rod is gripped and hoisted by means of the hook, the hook does not release the control rod. Thus, the safety operation can be assured. When the control rod cannot be released due to a trouble in the control rod gripping driving source, it is possible to forcibly release the control rod by pulling the rope. A pair of plungers are protruded into a pair of the existing side holes of the fuel supporting metal to support the fuel supporting metal, it is not necessary to make devices for the fuel supporting metal for assuring the gripping operation. Further, because a pair of plungers are inserted into a pair of side holes which faces each other with respect to the diameter of the fuel supporting metal to support and hoist the fuel supporting metal, the fuel supporting metal can be supported and hoisted stably with a balance with respect to the diameter thereof. Thus, it is possible to increase the operational reliability and the safety of supporting and hoisting the fuel supporting member. When the fuel supporting member is gripped by means of the fuel supporting member gripping device and hoisted, the gripping state is locked by the locking mechanism. Thus, it is possible to prevent the fuel supporting member from dropping due to an action of releasing the fuel supporting member and damaging, thereby increasing the operational reliability and safety. If the supply of a drive medium such as air to the fuel supporting member gripping driving source such as air cylinder is interrupted due to a breakage of the drive line such as air hose when the fuel supporting member is held by means of the fuel supporting member gripping driving source, the gripping action of the fuel supporting member gripping driving source is maintained by the force of a spring. Thus, if the supply of the drive medium to the fuel supporting member gripping driving source is interrupted due to a breakage of the air hose when the fuel supporting metal is gripped and hoisted, the fuel supporting member is held, thereby securing the safety operation. When an action of releasing the fuel supporting member cannot be performed due to a trouble in the fuel supporting member gripping driving source, it is possible to forcibly release the fuel supporting member by pulling a rope. |
description | This application is a continuation-in-part of U.S. application Ser. No. 15/505,941, filed Feb. 23, 2017, which is a U.S. national phase of PCT Application No. PCT/EP2015/067211, filed Jul. 28, 2015, which claims priority to Belgian Patent Application No. 2014/0653, filed Aug. 29, 2014, the contents of which are hereby incorporated by reference. The present invention is related to kit for radiolabelling. Recently, some very interesting clinical results based on gallium-68 radiolabeled molecules for imaging in vivo by PET were published and presented. These radiotracers are generally made by assembly of a chelating agent with a targeting agent, generally DOTA-functionalized targeting agents, allowing, respectively, the reaction with a metallic radioisotope or radiometal and biological/metabolic activity of the radiotracer. However, due to the short half-life of gallium-68 (68 minutes), the radiotracer, i.e. radiolabelled chelate-functionalized targeting agent, based on this radioisotope are not suitable for long-distance distribution and require on the spot production and suitable production equipment, such as automated synthesizers, for the radiolabelling process, making it difficult for widespread use in routine nuclear medicine. The labelling reaction with the gallium-68 is performed by chelating the radioactive metal with a suitable chelating agent in a suitable reaction medium, usually in a buffered medium in order to ensure an optimum pH for both the chelation reaction and the gallium solubility. Gallium-68 itself is obtained from a generator. Said generator is an alternative to the in situ production using a cyclotron or daily delivery of radioisotopes. The system was initially developed for technecium-99. The principle is based on the radiochemical separation between a parent element of long half-life (or nonradioactive elements such as germanium-68) contained in the generator and a daughter element which is a short half-life element resulting from the disintegration of the parent element. The daughter is recovered with excellent radiochemical purity and radionuclidic properties (i.e. without contamination from other radionuclides or other radiochemical impurities) and with good chemical purity (low metal ion content). This separation is made possible by the different chemical properties of the two elements (parent and daughter). The characteristics of a germanium-68/gallium-68 generator can be summarized as follows: The eluate is obtained in an acid solution (0.05M-5M HCl, or specified by the manufacturer of the generator) The eluate contains zinc-68, resulting from both the manufacturing process of germanium-68 and disintegration of gallium-68, whose concentration increases continuously in function of time elapsed since the last elution of the generator. Indeed, this zinc-68 accumulates in the generator. This can be detrimental to the performance of radiolabelling since this zinc-68 enters in direct competition with gallium-68 for chelation reactions used for radiolabelling. The eluate further contains germanium-68 (the “breakthrough”) released from the generator. The eluate also contains a variety of metal leaching from the solid phase of the generator column, tubings, but also brought by the HCl used for elution: Microg/ml level: Fe (III), Zn (II), Al (III) Picog/L level: Mn (II), Pb (II), Ti (IV), Cr (III), Ni (II) (Sn (IV)) The efficiency of the chelation reaction is dependent on a suitable pH, but also on possible competition of the metallic impurities mentioned above with the gallium-68 during the chelation reaction as well. In addition, it is generally accepted that heat facilitates the chelation reaction for the most commonly used gallium-68 based radiotracers. In the state of the art, the presence of metal ions that compete with gallium-68 is generally reduced by pre-labelling purification or fractionation of the eluate (as described in WO 2010/092114). These additional steps however represent a loss of radioactivity resulting from, either wasted time or the process itself. These losses can reach up to 30% of the total radioactivity, respectively, 10% due to decay and 20% coming from the pre-purification process itself. The possibility of partial chelation of gallium-68 requires, in general, a final post-labelling purification in order to obtain a radiotracer having a radiochemical purity that meets the pharmaceutical specifications (>90% radiochemical purity). These steps also represent an additional loss of activity that can rise to up to 10% resulting from wasted time or the process itself. According to known processes, at the end of the radiolabelling, a sequestering agent having a particular affinity for the gallium-68 may be added to chelate the non-reacted part of the isotope. This complex formed by the sequestering agent and the non-reacted gallium-68 is then discarded in order to reach a better radiochemical purity after radiolabelling. In addition, the need for these pre- and post-labelling purification steps makes these gallium-68 labeled radiotracer synthesis dependent, to some extent, on automation and on the use of a synthesis module. In addition to technical expertise, this requires extra time loss unfavorable to the overall performance. Due to the short half-life of the Gallium-68 radionuclide (68 minutes) and to the limited activity supplied by the generator (max. 100 mCi), any improvement in order to achieve rapid, direct and high efficiency chelation of target molecules is thus highly desirable. In order to maintain the pH of the labelling solution in a range where it is possible to ensure both the chelating reaction and the gallium-68 solubility, a buffering medium is generally used. The desired buffer must be nontoxic, must effectively maintain the pH within a range of 3.0 to 5.0, should not compete with gallium-68 ions and have preferably a low capacity for metal chelation with regard to the capacity of the chelating agent as assembled with the targeting agent. It must also be able to tolerate possible small changes in the volume of generator eluate (and therefore the amount of HCl), i.e. it must be strong enough to maintain the pH within the desired range with 10% changes in the volume of eluate. Management of competing metal impurities is another challenge. It has been shown in WO2013024013 that adding a co-chelating agent could allow inhibition of competing metal impurities. Indeed, any species that would inhibit metal impurities by avoiding or having limited capacity to interfere negatively on the gallium-68 chelation reaction can act as a trap for these impurities. In other words, this inhibitory effect brings the apparent concentration of competitor metal, i.e. the concentration of metallic impurities yet available for chelation to a level which allows high yields and reproducible radiolabelling. This co-chelating agent is by definition different than the chelating agent assembled with the targeting agent. In this context, it is clear that a need exists for an improved process for the preparation of 68Ga complex which overcomes one or more of the above mentioned problems. This involves identifying an appropriate medium that maintains the pH within a tolerable range, to handle the metal contamination, which avoids the need to heat for promoting the chelating reaction and allows gallium-68 chelation yields upper 90%. In addition, the sequence of the steps performed and the assembly of the kit for performing all steps without being exposed to radioation during the labelling process is very important. The present inventors have developed a user-friendly, time-saving radiolabelling kit which reduces the risk of exposure of the user to the buffering medium, the targeting agent and/or the radioactive material; which allows to radiolabel target agents at a temperature near or equal to room temperature; and/or which allows to directly elute gallium-68 in the kit and performing the radiolabelling reaction without the need for any prior or subsequent operation. More particularly, the present inventors found that the use of the kit in an assembly with a self-shielded device, especially a self-shielded device comprising an invertible container unit comprising a void space for holding a vial and a channel configured to hold a dismountable conduit for connecting the vial within the self-shielding device to an environment external of the self-shielded device, allows to radiolabel a targeting agent and to withdraw a dose of the radioactive-labelled targeting agent or to guide a dose of a radioactive-labelled targeting agent to a patient by using the force of gravity, thereby avoiding the need to pressurize a vial comprising the radioactive-labelled targeting agent (for example by use of a pump) and reducing risk of exposure of the user to radioactive material. The present invention relates to the following aspects: Aspect 1. A radiolabelling kit comprising: a first vial, wherein said vial is empty and vacuum; a second vial, wherein said second vial comprises a suitable amount of acetate buffer for balancing the pH of the eluate from a gallium-68 generator to a pH value ranging from 3 to 5 when said generator is eluted in the kit; and a third vial, wherein said third vial comprises a lyophilized chelate-functionalized targeting agent and a lyophilized metal inhibitor. Aspect 2. The radiolabelling kit according to aspect 1, wherein the chelate-functionalized targeting agent is prostate-specific membrane antigen (PSMA)-targeting peptide. Aspect 3. The radiolabelling kit according to aspect 1 or 2, wherein the metal inhibitor is selected from the group comprising: DOTA and its derivatives, DTPA and its derivatives, and sugars. Aspect 4. The radiolabelling kit according to any one of aspects 1 to 3, wherein the metal inhibitor is sugar selected from the group comprising: monosaccharides and their derivatives, disaccharides and their derivatives, and polysaccharides and their derivatives and sulfated sugars. Aspect 5. The radiolabelling kit according to any one of aspects 1 to 4, wherein the kit comprises one or more of the list consisting of: a needleless transfer device for connecting two vials; an extension line comprising a proximal end adapted for connecting the extension line to the vial adapter and a distal end adapted for connecting the extension line to the needleless syringe; a vial adapter adapted for connecting the extension line or a needleless syringe to a vial; and a needleless syringe. Aspect 6. An assembly comprising the kit according to anyone of aspects 1 to 5 and a self-shielded device configured to hold said first vial. Aspect 7. The assembly according to aspect 6, further comprising a gallium-68 generator. Aspect 8. The assembly according to aspect 6 or 7, wherein the self-shielded device is invertible. Aspect 9. The assembly according to any one of aspects 6 to 8, wherein the self-shielded device comprises a support (2) and a container unit (4), wherein said container unit comprises a lid (3) and a vessel comprising a void space dimensioned to hold said first vial; and wherein the support comprises a base (1) and extending from the base and in fixed relation to the base at least one longitudinal member (6). Aspect 10. The assembly according to aspect 9, wherein the dimensions of the void space suitable for holding the vial are at most 10% larger than the dimensions of the vial. Aspect 11. The assembly according to aspect 9 or 10, wherein the at least one longitudinal member (6) is provided in revolute attachment with respect to the vessel, where an axis of rotation is horizontal, non-parallel to a central axis of the vial and/or parallel to an underside of the base (1). Aspect 12. The assembly according to any one of aspects 9 to 11, wherein the lid (3) is in revolute attachment with respect to the vessel, where an axis of rotation is vertical, parallel to a central axis of the vial and/or non-parallel to an underside of the base (1). Aspect 13. The assembly according to any one of aspects 9 to 12, wherein the container unit (4) is provided with a channel configured to hold a dismountable conduit for connecting the vial within the self-shielding device to an environment external of the self-shielded device, preferably wherein the channel configured to hold a dismountable conduit is provided at the interface of the lid (3) and the vessel. Aspect 14. Use of the kit according to any one of aspects 1 to 5 or the assembly according to any one of aspects 6 to 13, for radiolabelling a chelate functionalized targeting agent with gallium-68 carried out at a temperature near or equal to room temperature. Aspect 15. A method for radiolabelling a chelate-functionalized targeting agent with gallium-68, comprising the elution of a gallium-68 generator with an eluent comprising HCL, in a kit according to any one of aspects 1 to 5 or an assembly according to any one of aspects 6 to 13. Aspect 16. A method for radiolabelling a chelate-functionalized targeting agent with gallium-68, comprising recovering an eluate of a gallium-68 generator into a first vial located within a self-shielded device, preferably wherein said first vial is a vacuumed vial; adding a suitable amount of acetate buffer to the lyophilized chelate-functionalized targeting agent and lyophilized metal inhibitor comprised in a second vial to balance the pH of the eluate from a gallium-68 generator to a pH value ranging from 3 to 5 when said mixture of acetate buffer, chelate-functionalized targeting agent and metal inhibitor is contacted with the eluate; recovering the mixture of acetate buffer, chelate-functionalized targeting agent and metal inhibitor from the second vial; adding the mixture of acetate buffer, chelate-functionalized targeting agent and metal inhibitor to the recovered eluate of the gallium-68 generator comprised in the first vial located within the shielding device; and allowing radiolabelling of the chelate-functionalized targeting agent with gallium-68. Aspect 17. The method according to aspect 16, wherein the step of allowing radiolabelling of the chelate-functionalized targeting agent with gallium-68 is performed for at least 1 minute, preferably for at least 5 minutes. Aspect 18. The method according to aspect 16 or 17, wherein the first vial located within the self-shielded device is connected to a vial adapter which is connected to an extension line comprising a proximal end adapted for connecting the extension line to the vial adapter and a distal end adapted for connecting the extension line to a needleless syringe; wherein said distal end is located outside the self-shielded device. Aspect 19. The method according to any one of aspects 16 to 18, wherein the suitable amount of acetate buffer is contained in a third container and the suitable amount of acetate buffer is added to the lyophilized chelate-functionalized targeting agent and lyophilized metal inhibitor by interconnecting said second and third vial via a needleless transfer device. Aspect 20. The method according to aspect 19, wherein the needleless transfer device comprises a valve and a luer-lock. Aspect 21. The method according to aspect 20, wherein the step of adding a suitable amount of acetate buffer present in a third vial to the lyophilized chelate-functionalized targeting agent and lyophilized metal inhibitor comprised in a second vial comprises: interconnecting the third vial comprising the acetate buffer and the second vial comprising lyophilized chelate-functionalized targeting agent and lyophilized metal inhibitor by a needleless transfer device; wherein the third vial is located above the second vial, wherein the luer-lock is capped, and wherein the valve can be configured to be in fluid communication with the third vial and the luer-lock, the second vial and the luer-lock, or the third and second vials and the luer-lock; allowing the acetate buffer to flow from the third vial to the second vial through the valve of the needleless transfer device which is configured to be in fluid communication with the third and second vials and the luer-lock; and mixing the acetate buffer, lyophilized chelate-functionalized targeting agent and lyophilized metal inhibitor. Aspect 22. The method according to aspect 20 or 21, wherein the step of recovering the mixture of acetate buffer, chelate-functionalized targeting agent and metal inhibitor from the second vial comprises: configuring the valve of the needleless transfer device to be in fluid communication with the second vial and the luer-lock, but not in fluid communication with the third vial, wherein the luer-lock is capped; uncapping the luer-lock; connecting a needleless syringe comprising air in a volume which is at least 50% the volume of the second vial to the uncapped luer-lock; injecting the air in a volume which is at least 50% the volume of the second vial from the needleless syringe into the second vial via the uncapped luer-lock; turning the third vial and the second vial interconnected by the needleless transfer device so that the second vial is located above the third vial; and withdrawing the mixture of acetate buffer, chelate-functionalized targeting agent and metal inhibitor from the second vial via the uncapped luer-lock, using the needleless syringe. Aspect 23. The method according to any one of aspects 16 to 22, wherein the step of adding the mixture of acetate buffer, chelate-functionalized targeting agent and metal inhibitor to the recovered eluate of the gallium-68 generator comprised in the first vial located within the self-shielded device comprises injecting the mixture of acetate buffer, chelate-functionalized targeting agent and metal inhibitor into the first vial located within the self-shielded device using a needleless syringe. Aspect 24. The method according to any one of aspects 16 to 23, wherein the self-shielded device comprises a container unit comprising a void space dimensioned to hold the first vial, wherein said container unit is rotatable around a horizontal axis. Aspect 25. The method according to aspect 24, further comprising inverting the container unit; and withdrawing the gallium-68-labelled chelate-functionalized targeting agent from the first vial. As used herein, the singular forms “a”, “an”, and “the” include both singular and plural referents unless the context clearly dictates otherwise. The terms “comprising”, “comprises” and “comprised of” as used herein are synonymous with “including”, “includes” or “containing”, “contains”, and are inclusive or open-ended and do not exclude additional, non-recited members, elements or method steps. The terms also encompass “consisting of” and “consisting essentially of”. The recitation of numerical ranges by endpoints includes all numbers and fractions subsumed within the respective ranges, as well as the recited endpoints. The term “about” as used herein when referring to a measurable value such as a parameter, an amount, a temporal duration, and the like, is meant to encompass variations of and from the specified value, in particular variations of +/−10% or less, preferably +/−5% or less, more preferably +/−1% or less, and still more preferably +1-0.1% or less of and from the specified value, insofar such variations are appropriate to perform in the disclosed invention. It is to be understood that the value to which the modifier “about” refers is itself also specifically, and preferably, disclosed. Whereas the term “one or more”, such as one or more members of a group of members, is clear per se, by means of further exemplification, the term encompasses inter alia a reference to any one of said members, or to any two or more of said members, such as, e.g., any ≥3, ≥4, ≥5, ≥6 or ≥7 etc. of said members, and up to all said members. All documents cited in the present specification are hereby incorporated by reference in their entirety. Unless otherwise specified, all terms used in disclosing the invention, including technical and scientific terms, have the meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. By means of further guidance, term definitions may be included to better appreciate the teaching of the present invention. In the following passages, different aspects or embodiments of the invention are defined in more detail. Every aspect or embodiment so defined may be combined with each of the other aspects or embodiments unless stated otherwise. In particular, any feature indicated as being preferred or advantageous in one embodiment may be combined with any other embodiment or embodiments indicated as being preferred or advantageous. The present invention overcomes one or more of the problems identified and observed in the state of the art and allows the direct radiolabelling of a chelate-functionalized targeting agent with gallium-68 at a temperature below 50° C. and preferably at room temperature, using a kit as described herein, this gallium-68 being eluted from a germanium-68/gallium-68 generator in an acidic aqueous solution. Accordingly, in one aspect, the invention provides a kit comprising: A suitable amount of acetate salt to balance at least the acidic pH eluate from a gallium-68 generator to a pH value ranging from 3 to 5 when said generator is eluted in the kit; and A chelate-functionalized targeting agent, able to chelate gallium-68 in the radiolabeling conditions A metal inhibitor, which is a co-chelating agent, capable of inactivating metals other than gallium-68 without interfering with the chelation between gallium-68 and the said chelate-functionalized targeting agent, under the conditions of the labelling reaction. In other words, said metal inhibitor is selected for its ability to chelate contaminating metals interfering and competing with the chelation of gallium-68 while being mostly unable gallium-68 in the said conditions of the labelling reaction as opposed to the chelate-functionalized targeting agent. Said kit being suitable to perform the radiolabelling reaction of said chelate-functionalized targeting agent with gallium-68 as carried out at a temperature near or equal to room temperature, preferably at a temperature below 50° C. and more preferably at room temperature. The invention also relates to a kit wherein the acetate salt, the chelate-functionalized targeting agent and the metal inhibitor are (co-) lyophilized. The invention also relates to a kit wherein the chelate-functionalized targeting agent and the metal inhibitor are (co-)lyophilized, the acetate salt being added subsequently. The invention also relates to a kit wherein the chelate-functionalized targeting agent and the metal inhibitor are (co-)lyophilized, an acetate buffer being added subsequently. The invention also relates to a kit wherein the acetate salt, the chelate-functionalized targeting agent and the metal inhibitor are solubilized and further frozen. The kit as described herein can not only provide an optimum pH for carrying out the chelation reaction or radiolabelling, but also allows to tolerate or manage the variation of the eluate volume and acidity associated with different types of gallium-68 generators, through the use of a suitable amount of acetate salt that when mixed with the acid generator eluate, form an acetic acid/acetate buffer having an acid pH comprised in the interval 3-5. In these conditions, the amount of non-chelated gallium-68 because of a too low or too high pH, which leads respectively to a high content of free gallium-68 cations or to gallium-68 hydroxides (gallium colloids), is minimized. In addition, the acetate buffer is well tolerated as a buffer or as an excipient for pharmaceuticals. Furthermore, the present inventors have found that a metal inhibitor can be used in the radiolabelling method for neutralizing, at least partially, interfering species and allows the gallium-68 to react with the chelate-functionalized targeting agent. These metal inhibitors may temporarily or permanently remove metals that compete with gallium-68 for the reaction with the chelate-functionalized targeting agent. Said metal inhibitor is thus unable to chelate gallium-68 in the said conditions of the labelling reaction, but chelate other metals interfering with the chelation of gallium-68 by the chelate-functionalized targeting agent. The presence of a metal inhibitor during the radiolabelling reaction provides an advantageous alternative to current approaches for managing the presence of metallic impurities, such as increasing the amount chelate-functionalized targeting agent, or the pre-treatment of the eluate of the generator, since these additional purification steps consume time (and radioactivity). These aspects as described herein advantageously allow obtaining an appropriate chelation yield, particularly of about 90% and more, and therefore a sufficient radiochemical purity without any preliminary or further final purification. The presence of a chelate-functionalized targeting agent, an acetate salt and a metal inhibitor in the kit advantageously allows to directly elute gallium-68 generator in the kit and performing the radiolabelling reaction without the need for any prior or subsequent operation. In addition, all kit components as described herein can be lyophilized altogether or frozen which ensures a longer shelf life. Thus, the main advantages of a kit as disclosed herein that differentiate said kit from the state of the art are: A completely dry or frozen kit that allows a better shelf life of the chelate-functionalized targeting agent; The possibility of radiolabelling without the need for an automated synthesizer; The possibility of a radiolabelling without the need for heating; The presence of a metal inhibitor which advantageously allows to use less chelate-functionalized targeting agent and allowing the implementation of more affordable radiopharmaceutical synthesis; The presence of a metal inhibitor which advantageously allows to improve the radiolabelling yields; The fact that any brand generator can be used with this kit provided as acetate or partially neutralized with HCl so that when mixed with the acid generator eluate, the optimal pH for the radiolabelling is obtained. As used herein, “acetate” refers to the anionic molecule CH3COO—. The term “acetate salt” herein is meant any metal salt acetate. Non-limiting examples of acetate salts include sodium acetate, potassium acetate, aluminium acetate, and ammonium acetate. Preferably sodium acetate is used in the kits as described herein. Said acetate salt can be present in solid form or can be comprised in a buffered solution or buffer. The amount of salt of the acetate present in the kit as described herein can be adapted according to the type and/or the kind of gallium-68 generator, in particular the quantity of acetate salt present in the kit is able to balance the pH, i.e. to manage the quantity of HCl as eluted from a gallium-68 generator such that the resulting solution has a pH between 3 and 5, preferably between 3.5 and 4.7, preferably between 3.9 and 4.5. Alternatively, the kit as described in the present invention may comprise a fixed quantity of acetate salt. The amount of HCl differences from the generator eluate (depending on the type and/or the generator brand gallium-68) can then be adjusted by adding an appropriate amount of HCl to the kit as described herein prior to elution. The amount of HCl added to the kit as described in the present invention is partially neutralizing the acetate salt such that the non-neutralized acetate salt is able to balance the pH of a quantity of HCl from a generator eluate such that the resulting solution has a pH between 3 and 5, preferably between 3.5 and 4.7, preferably between 3.9 and 4.5. Preferably, the acetate salt is present in the kit as taught herein in an amount between about 1 mg and about 1000 mg, preferably in an amount between about 10 mg and about 750 mg, more preferably in an amount between about 20 mg and about 500 mg. Metal inhibitors used in the present invention are selected for their ability to inhibit the competing metals, without (substantially) inhibiting gallium-68 ions in their chelation reaction with the chelate-functionalized targeting agent. Indeed, these metal inhibitors should (substantially) not interfere negatively on the main radiolabelling reaction or lead to the formation of secondary radiolabeled species. In other words metal inhibitors should have a limited or no capacity to complex gallium-68 in the conditions used for the radiolabelling reaction, i.e. below 50° C. in an acetate buffer between pH 3 and pH 5. Limited means at least 100 times less than the chelating agent used for the chelate-functionalized targeting agent. It is interesting to note that the function of metal inhibitors in the present invention is the opposite of the function of the sequestering agents used in the prior art. Indeed, according to known methods, at the end of the labelling reaction, a sequestering agent having a particular affinity for the gallium-68 may be added to chelate the unreacted portion of the isotope, whereas, according to the present invention an agent capable of reducing the competition of metallic impurities other than the gallium-68 is added at the beginning of the reaction. In addition, being able to perform the radiolabelling reaction at a temperature close to room temperature (<50° C.) advantageously allows the use of metal inhibitors that would not be usable at the usual temperatures of radiolabelling DOTA-functionalized targeting agents by such as used in WO2013024013, because they would be entering in direct competition with gallium-68 at such temperatures of above 50° C. The temperature is therefore also described in the invention as a parameter for adjusting the reactivity of the metal inhibitor. As used herein, a “metal inhibitor” refers to any molecule capable of interacting with, or competing metals, or the chelating moiety of the chelate-functionalized targeting agent or with gallium-68 directly, to inhibit wholly or partially the chelation the chelate-functionalized targeting agent said competing metals and/or promote the chelating of gallium-68 by said targeting agent. Such metal inhibitors should have a limited or no capacity to complex gallium-68 in the conditions used for the radiolabelling reaction, i.e. below 50° C. in an acetate buffer between pH 3 and pH 5. Limited means at least 100 times less than the chelating agent used for the chelate-functionalized targeting agent. Metal inhibitors are preferably selected from the group comprising or consisting of: DOTA and its derivatives, such as, DOTATOC, DOTANOC, DOTATA, TRITA, DO3A-Nprop, BisDO3A and TrisDO3A; DTPA and its derivatives such as tetra-tBu-DTPA, p-SCN-Bz-DTPA, MX-DTPA and CHX-DTPA; and sugars. Sugars used as metal inhibitors in the kit of the invention can be monosaccharides or derivatives of monosaccharides such as tetracetose, pentacetose, hexacétose, tetrose, pentose, hexose, D-mannose, D-fructose, and derivatives; and/or disaccharides and their derivatives such as maltose and its derivatives; and/or polysaccharides and their derivatives such as dextrins, cyclodextrins, cellulose and derivatives thereof. Preferably, the metal inhibitor is present in the kit as described herein in micromolar amounts, preferably in nanomolar quantities, preferably in an amount of less than 500 nanomolar, still more preferably in an amount less than 100 nanomoles. It is important to note that metal inhibitors as shown above can also be advantageously used in chelation reactions wherein other buffers than buffered acetic acid/acetate are used. Metal inhibitors as shown above can also be advantageously used in chelation reactions wherein said metal inhibitor is included in the eluent generator, in the HCl solution, or in water possibly added before elution of the generator. Said metal inhibitor is thus found in the radiolabelling solution. The metal inhibitor may also be chemically bound to the chelate-functionalized targeting agent. This chemical bond can or cannot be a labile bond under the conditions of radiolabelling with the chelate-functionalized targeting agent. This means that in the conditions of radiolabelling the metal inhibitor is formed and released in situ. Examples of such preferred bonds are . . . . As used herein, a “chelate-functionalized targeting agent” refers to a targeting agent capable of being labeled with a radioisotope such as for example gallium-68, by means of a chelating agent which is bound to the targeting molecule. Preferred chelating agents for functionalizing a targeting agent to be radiolabeled with gallium-68 are those which form stable chelates with Ga3+, in particular 68-Ga3+(the radioisotope generator eluted from a germanium-68/gallium-68 generator using HCl), at least for a time sufficient for diagnostic investigations using such radiolabelled targeting agents. Suitable chelating agents include aliphatic amines, linear or macrocyclic such as macrocyclic amines with tertiary amines. While these examples of suitable chelating agents are not limited, they preferably include the NOTA and its derivatives, such as TACN, TACN-TM, DTAC, H3NOKA, NODASA, NODAGA, NOTP, NOTPME, PrP9, TRAP, Trappist Pr, NOPO, TETA; Tris(hydroxypyridinone) (THP) and derivatives, chelates open chain such as HBED, DFO or desferrioxamine or desferal, EDTA, 6SS, B6SS, PLED, TAME, YM103; NTP (PRHP) 3; the H2dedpa and its derivatives such as H2dedpa-1, 2-H2dedpa, H2dp-bb-NCS, and H2dp-N-NCS; (4,6-MeO2sal) 2-BAPEN; and citrate and derivatives thereof. The chelate-functionalized targeting agent can be a peptide, for example, a peptide comprising 2 to 20 amino acids, a polypeptide, a protein, a vitamin, a saccharide, for example a monosaccharide or a polysaccharide, an antibody and its derivatives such as nanobodies, diabodies, antibodies fragments, nucleic acid, an aptamer, an antisense oligonucleotide, an organic molecule, or any other biomolecule that is able to bind to a certain diagnostic target or to express a certain metabolic activity. Chelate-functionalized targeting agents as described herein preferably have a capacity of biological targeting. Non-limiting examples of suitable targeting agents include molecules that target VEGF receptors, analogs of bombesin or gastric-releasing peptide (GRP) receptor targeting molecules, molecules targeting somatostatin receptors, RGD peptides or molecules targeting αvβ3 and αvβ5, annexin V or molecules targeting the apoptotic process, molecules targeting estrogen receptors, biomolecules targeting the plaque, prostate-specific membrane antigen (PSMA)-targeting peptides, Bombesin (BN), aminopeptidase N-targeting peptides, peptide transporter 1-targeting peptides, epidermal growth factor (EGF) receptor-targeting peptides, Mucin1-targeting peptides (e.g. GO-201), urokinase plasminogen activator receptor-targeting peptides (e.g AE105), cholecystokinin receptor-targeting peptides (e.g. CCK8), neurotensin receptor-targeting peptides (e.g. neurotensin), transferrin receptor-targeting peptides, vascular endothelial growth factor receptor-targeting peptides (e.g. peptide K237, SP 5.2, . . . ), retinoblastoma-targeting peptides, or ephrin receptor-targeting peptides. More generally, a list targeting molecules, organic or not, functionalized by a chelating agent can be found in the journal of Velikyan et al., Theranostic 2014, Vol. 4, Issue 1 “Prospective of 68Ga-Radiopharmaceutical Development”, hereby incorporated by reference. In some embodiments, the metal inhibitor is included in the eluent generator, in the HCl solution, or possibly in the added water prior to elution of the generator. Said metal inhibitor and is thus found in the radiolabelling solution. The various components of the kit as described herein are preferably present in a container or vial, preferably a siliconized glass vial. However, also a kit wherein the individual components are present in separate containers or vials is envisaged. The invention further provides a radiolabelling kit comprising: a first vial, wherein said vial is empty and contains a vacuum; a second vial, wherein said second vial comprises a suitable amount of acetate buffer for balancing an eluate from a gallium-68 generator to a pH value ranging from 3 to 5 when said generator is eluted in the kit; and a third vial, wherein said third vial comprises a lyophilized chelate-functionalized targeting agent and a lyophilized metal inhibitor. When the radiolabeling kit is used in a method for radiolabeling of a chelate-functionalized targeting agent as described herein with an eluate of a gallium-68 generator, the presence of a vacuum in the first vial will reduce the risk of exposure of the user to the radioactive material. In particular embodiments, the first, the second and the third vials are siliconized glass vials. In particular embodiments, the first, the second and the third vials are sealed by a pierceable rubber stopper. In particular embodiments, the first, the second and the third vials have a height of at least 4 cm, at least 5 cm, at least 6 cm, at least 7 cm, at least 8 cm, at least 9 cm or at least 10 cm. For example, the first, the second and the third vials may have a height of about 5 cm, 5.5 cm, 6 cm, 6.5 cm, 7 cm, 7.5 cm, or 8 cm. In particular embodiments, the first, the second and the third vials are vials with a diameter of at least 10 mm, at least 15 mm, at least 20 mm, such as a diameter of 15 mm, 16 mm, 17 mm, 18 mm, 19 mm, 20 mm, 21 mm, 22 mm, 23 mm, 24 mm or 25 mm. Preferably, the first, the second and the third vials are vials with a diameter of 20 mm. In particular embodiments, the first, the second and the third vials are vials with a volume of at least 5 ml, at least 10 ml or at least 20 ml, such as a volume of 5 ml, 6 ml, 7 ml, 8 ml, 9 ml or 10 ml. In particular embodiments, the acetate buffer is lyophilized and is present in an amount of between 100 and 200 mg, such as about 150 mg. In particular embodiments, the second vial of the kit further comprises a stabilizer which is able to protect the chelate-functionalized targeting agent from radiolysis upon radiolabelling said chelate-functionalized targeting agent with gallium-68. Non-limiting examples of suitable stabilizers are ethanol, gentisic acid and ascorbic acid. In particular embodiments, the chelate-functionalized targeting agent present in the third vial is prostate-specific membrane antigen (PSMA)-targeting peptide, more preferably PSMA-11. In particular embodiments, the metal inhibitor present in the third vial is selected from the group comprising: DOTA and its derivatives, DTPA and its derivatives, and sugars. In particular embodiments, the third vial of the kit further comprises a cryoprotectant. The cryoprotectant typically allows stabilizing the chelate-functionalized targeting agent and/or the metal inhibitor during lyophilisation. Non-limiting examples of suitable cryoprotectants are dimethyl sulphoxide (DMSO), glycerol (GI), sucrose, sugars and mannitol. In particular embodiments, the metal inhibitor is sugar selected from the group comprising: monosaccharides and their derivatives, disaccharides and their derivatives, and polysaccharides and their derivatives and sulfated sugars. In particular embodiments, the metal inhibitor is selected from the group comprising: Glucose, Fructose, Beta-cyclodextrin, D-Mannose, and Sulfated sugars. In particular embodiments, the radiolabelling kit as taught herein further comprises one or more, preferably all, of the list consisting of: a needleless transfer device for connecting two vials; an extension line comprising a proximal end adapted for connecting the extension line to the vial adapter and a distal end adapted for connecting the extension line to the needleless syringe; a vial adapter adapted for connecting the extension line or a needleless syringe to a vial; and/or a needleless syringe. The term “needleless transfer device” as used herein refers to a device which avoids the necessity to utilize a needle in conjunction with a syringe for purposes of transferring and/or injecting a liquid medium from one environment (e.g., a first vial) into another environment, (e.g., a second vial) by interconnecting both environments and allowing a fluid communication from one to the other environment. A needleless transfer device may comprise at least one (such as one or two) holder(s) for a container into which or from which a liquid is to be transferred (e.g., a vial); a hollow enclosure for holding the valve mechanism and a hollow spike member for piercing the closure of a container, wherein said hollow spike member is in fluid communication with the hollow enclosure for holding the valve mechanism. If the needless transfer device comprises two holders for a vial, these two holders may hold vials with the same or different diameters. For example, both holders may fit a vial with a diameter of 20 mm or one holder may hold a vial with a diameter of 20 mm, while the other socket may hold a vial with a diameter of 13 mm. In particular embodiments, the needleless transfer device comprises two vial connections, a valve and a luer-lock. In particular embodiments, the valve can be configured to be in fluid communication with a first vial attached to the needleless transfer device and the luer-lock, in fluid communication with a second vial attached to the needleless transfer device and the luer-lock, or in fluid communication with the first and second vials attached to the needleless transfer device and the luer-lock. In particular embodiments, the needleless transfer device is a needleless transfer device of Medimop Medical Projects LTD with reference number 7070105. The term “extension line” as used herein refers to a tubing system which is at one end connectable to a first environment and at another end connectable to a second environment, and which brings the first and second environment in fluid communication. An extension line allows transferring and/or injecting a liquid medium from one environment (e.g., a first vial) into another environment, wherein said two environments separated by a distance, wherein said distance is at most the length of the extension line. The extension line may further comprise further ends connectable to a third environment, a fourth environment, a fifth environment etc. For example, the first environment may be a vial and the second environment may be a needleless syringe. If the first or second environment is a vial, the extension line may be connected to the vial directly or via a vial adaptor. In particular embodiments, the extension line comprises a proximal end adapted for connecting the extension line to a vial adapter and a distal end adapted for connecting the extension line to a needleless syringe. In particular embodiments, the extension line is a B-safe extension line-smallbore of Bicakcilar with reference number 13100101. The term “vial adapter” as used herein refers to a device for connecting a vial to another vial, for connecting a vial to a needleless syringe or for connecting a vial to an extension line and to allow withdrawal of at least one dose of the vial content. A vial adaptor typically comprises a sharp, thin, hollow piercing spike that allows the adapter to penetrate the stopper/cover of the vial. In particular embodiments, the vial adapter is a vial adapter of Medimop Medical Projects LTD with reference number 8072026. In particular embodiments, the needleless syringe is a needleless syringe with a volume of at least 5 ml, at least 10 ml or at least 15 ml. For example, a needleless syringe with a volume of 10 ml, 12 ml or 15 ml. In particular embodiments, the needleless syringe is a 10 ml (12 ml) Norm Ject needleless syringe of Henke Sass Wolf with reference number 4100.X00V0. The radiolabelling kit as taught herein allows to easily radiolabel a chelate-functionalized targeting agent, shortens the synthesis time of the radiolabelled chelate-functionalized targeting agent and avoids the need of expensive hardware. A further aspect provides the use of the kit as taught herein for radiolabelling a chelate-functionalized targeting agent with gallium-68 carried out at a temperature near or equal to room temperature. A further aspect provides a method for radiolabelling a chelate-functionalized targeting agent with gallium-68, comprising the elution of a gallium-68 generator with HCL, in a kit or an assembly as taught herein. The invention further provides an assembly comprising a vial and a self-shielded device configured to hold a vial. In particular embodiments, the assembly further comprises an extension line comprising a proximal end adapted for connecting the extension line to a vial (directly or via a vial adapter) within the self-shielding device and a distal end adapted for connecting the extension line to an environment external of the self-shielded device (e.g., to a needleless syringe or a gallium-68 generator). In more particular embodiments, the extension line comprises a proximal end adapted for connecting the extension line to a vial adapter and a distal end adapted for connecting the extension line to a needleless syringe. In particular embodiments, the self-shielded device comprises a support (2) and a container unit (4), wherein said container unit comprises a lid (3) and a vessel comprising a void space dimensioned to hold a vial. In particular embodiments, the support (2) comprises a base (1). The base typically provides a stable surface for placing the self-shielded device on a surface, such as a bench. In particular embodiments, the dimensions of the base are equal to or at least 1%, at least 2%, at least 3%, at least 4%, at least 5%, at least 6%, at least 7%, at least 8%, at least 9%, or at least 10% larger than the dimensions of the top surface or bottom surface of the container unit. In particular embodiment, the container unit has a cylindrical shape and the base has a circular shape, wherein the diameter of the base is equal to or larger than the diameter of the container. In particular embodiments, the base does not contact the container unit. In more particular embodiments, the space between the base and the container unit is such that the latter can be freely rotated with respect to the support means. In particular embodiment, said distance can be at least 1 cm, at least 2 cm, at least 3 cm, at least 4 cm, or at least 5 cm, in inverted and non-inverted configuration. In particular embodiments, the support comprises extending from the base and in fixed relation to the base at least one longitudinal member (6), preferably one longitudinal member. In more particular embodiments, the at least one longitudinal member is positioned perpendicularly to the base and to a central axis of the vial and/or container. In particular embodiments, the self-shielded device is an invertible self-shielded device. In particular embodiments, the at least one longitudinal member is provided in revolute attachment with respect to the vessel, where an axis of rotation is horizontal, non-parallel to a central axis of the vial and/or parallel to an underside of the base. In particular embodiments, the at least one longitudinal member is provided in revolute attachment with respect to the vessel by at least one, preferably one, pivoting means (e.g., a pivote point). In particular embodiments, the at least one longitudinal member is dimensioned to allow a rotation of the container unit by more than 90 degrees, such as at least 120 degrees, at least 150 degrees, at least 160 degrees, at least 170 degrees or at least 180 degrees. In particular embodiments, rotation of the container unit around the at least one pivoting means (e.g., pivot point) can be blocked by blocking means, such as by a tightenable pin (e.g., a screw or a clip). In particular embodiments, the container unit is cylindrical shaped. In particular embodiments, the container unit a height of at least 10 cm, at least 15 cm, at least 20, or at least 25 cm, preferably at least 15 cm. For example, the container unit may have a height of 15 cm, 16 cm, 17 cm, 18 cm, 19 cm or 20 cm. In particular embodiments, the container unit has a diameter of at least 10 cm, at least 15 cm, or at least 20 cm, preferably at least 10 cm. For example, the container unit may have a diameter of 10 cm, 11 cm, 12 cm, 13 cm, 14 cm or 15 cm. In particular embodiments, the void space has at least one side wall, preferably one side wall. In more particular embodiment, the at least one side wall has a thickness of at least 2 cm, at least 3 cm, at least 4 cm or at least 5 cm. For example, the at least one side wall may have a thickness of 2 cm, 3 cm, 4 cm, 5 cm, 6 cm or 7 cm. In particular embodiments, the at least one side wall of the void space consists of a radiation shielding material, for example lead or tungsten. In particular embodiments, the void space dimensioned to hold a vial is connected to the exterior with an opening. The opening can be shielded from the exterior of the container with the lid. In particular embodiments, the dimensions of the void space suitable for holding the vial are at most 2%, at most 3%, at most 4%, at most 5%, at most 6%, at most 7%, at most 8%, at most 9%, or at most 10% larger than the dimensions of the vial. The void space specifically adapted to hold the vial allows to easily and firmly position the vial within the self-shielded device. In particular embodiments, the void space suitable for holding the vial has a height of at least 4 cm, at least 5 cm, at least 6 cm, at least 7 cm, at least 8 cm, at least 9 cm or at least 10 cm. For example, the void space may have a height of about 5 cm, 5.5 cm, 6 cm, 6.5 cm, 7 cm, 7.5 cm, or 8 cm. In particular embodiments, the void space suitable for holding the vial has a diameter of at least 1.5 cm, at least 2 cm, at least 2.5 cm, or at least 3 cm. For example, the void space may have a diameter of about 2 cm, 2.5 cm, 3 cm, 3.5 cm, or 4 cm. In particular embodiments, the lid is provided with a further pivoting means (5) and/or is in revolute attachment with respect to the vessel, where an axis of rotation is vertical, parallel to a central axis of the vial and/or non-parallel to an underside of the base. In particular embodiments, the lid is provided in revolute attachment with respect to the vessel by at least one, preferably one, pivot point. In particular embodiment, the container unit, preferably the vessel, is provided with a channel configured to hold a dismountable conduit such as the extension line referred to above, for connecting the vial (directly or via a vial adapter) within the self-shielding device to an environment external of the self-shielded device (e.g., to a needleless syringe or a gallium-68 generator). Typically one end of the conduit is adapted for connecting the conduit to the vial in the void space and the other end of the conduit is located adapted for connecting the conduit to an environment external of the self-shielded device (e.g., to a needleless syringe or a gallium-68 generator). For example, the container unit may be provided with a channel configured to hold an extension line comprising a proximal end adapted for connecting the extension line to a vial (or a vial adapter) and a distal end adapted for connecting the extension line to an environment external of the self-shielded device (e.g. to a needleless syringe, a second conduit or a gallium-68 generator). The channel is configured to hold a dismountable conduit and prevents that the dismountable conduit hinders the sealing of the vessel by the lid, while still allowing a fluid communication between the vial and the environment externally of the container unit. Furthermore, the channel configured to hold a dismountable conduit allows the injection of fluids into and the elution of fluids from the vial located within the container unit in a more convenient manner, without being exposed to a source of radioactivity contained within the vial. In particular embodiment, the channel configured to hold a dismountable conduit is provided at the interface of the lid (3) and the container vessel (4). In particular embodiment, a side wall of the void space is provided with the channel configured to hold a dismountable conduit at the interface of the lid and the container vessel. The channel configured to hold a dismountable conduit may have one end at the interface of the void space and the sidewall of the vessel and one end at the interface of the sidewall of the vessel and the exterior of the vessel. In particular embodiments, the depth of the channel is equal to or larger than the diameter of the dismountable conduit. In particular embodiments, the depth of the channel is at least 2 mm, at least 3 mm, at least 4 mm, at least 5 mm, at least 6 mm, at least 7 mm, at least 8 mm, at least 9 mm or at least 10 mm. In particular embodiments, the self-shielded device comprises a heating device. In particular embodiments, said heating device is capable of heating its contents to a temperature of from 40 to 120° C., preferably from 70 to 110° C., and more preferably from 85 to 100° C. In particular embodiments, the self-shielded device comprises a system to measure the radioactivity contained within the vial located within the self-shielded container. In particular embodiments, the self-shielded device is a self-shielded dispensing device. A further aspect provides the use of the assembly as taught herein for radiolabelling a chelate functionalized targeting agent with gallium-68 carried out at a temperature near or equal to room temperature. A further aspect provides a method for radiolabelling a chelate-functionalized targeting agent with gallium-68, comprising the elution of a gallium-68 generator with an eluent comprising HCl, in an assembly as taught herein. The invention also discloses a self-shielded device as described herein with regard to the assembly. The invention further provides a method for radiolabelling a targeting agent with gallium-68, said method comprising the elution of a gallium-68 generator with an eluent comprising an acid, in a kit as described herein, e.g. comprising the metal inhibitor, the chelate-functionalized targeting agent and acetate salt. As indicated above, when the chelate-functionalized targeting agent is included in the kit, a gallium-68 generator can be eluted directly into the kit. In other embodiments, the chelate-functionalized targeting agent can be added to a kit comprising the acetate salt and a metal-inhibiting agent as described herein, prior to elution. In some embodiments, the gallium-68 generator is eluted directly into the kit. In other embodiments, water is added to the solution prior to elution. In some embodiments of the present invention, an appropriate amount of HCl is added to the solution prior to elution. Said HCl is added to partially neutralize the acetate. The amount of HCl added, preferably partially neutralizes the quantity of acetate salt in such a manner that the remaining quantity of acetate salt, i.e. unneutralized acetate salt, is able to balance the pH of said amount of HCl from the generator eluate (and thus dedicated to one type or brand of given generator) such that the pH of the solution obtained for the radiolabelling reaction or chelating reaction, resulting from the addition of HCl and the generator eluate in the kit as described herein, is in a pH range between 3 and 5, preferably between 3.5 and 4.5, preferably between 3.9 and 4.3. Said HCl may be added directly to the solution, or after a certain amount of water is added to said kit. All gallium-68 generator may be used in the methods of the present invention. Typically, a commercial gallium-68 generator comprises a column on which the germanium-68 is fixed. A gallium-68 generator is typically eluted with an eluent comprising an acid, preferably HCl. Therefore, in preferred embodiments of the method, as taught herein, the gallium-68 generator is eluted with an eluent comprising HCl. After elution of the gallium-68 generator in the kit as described herein, the solution obtained is left to react in the radiolabelling reaction for a short period of time, in particular between about 2 minutes and about 60 minutes, preferably from about 2 minutes to about 30 minutes, for example about 10 minutes. Preferably, the radiolabelling reaction or chelation is performed at a temperature below 50° C., preferably of below 45° C., below 40° C., below 35° C., or below 30° C., most preferably at room temperature, e.g. between 20 and 25° C. Preferably, the radiolabelling reaction or chelation is performed at a pH between about 3 and about 5, more preferably between about 3.5 and about 4.5, more preferably between about 3.9 and about 4.3. The invention further provides a method for radiolabelling a chelate-functionalized targeting agent with a radionuclide, preferably gallium-68, comprising the following sequential steps: reconstituting lyophilized a chelate-functionalized targeting agent and a lyophilized metal inhibitor with a buffering medium, preferably an acetate buffer; adding the buffering medium, and the reconstituted chelate-functionalized targeting agent and metal inhibitor to an eluate of a radioactive metal generator, preferably a gallium-68 generator; and allowing radiolabelling of the chelate-functionalized targeting agent with the radioactive metal, preferably gallium-68 for about 1 minute or up to about 5 or 10 minutes. In particular embodiments, the buffering medium allows to maintain the pH in the range 3-8, more preferably in the range of 3-5. In particular embodiments, the buffering medium consists of phosphate, nitrate, HEPES, acetate, TRIS, ascorbate, or, citrate or a mixture thereof. In particular embodiments, the radioactive metal is selected from the group comprising: copper-64, gallium-68, gallium-67, gallium-66, lutecium-177, yttrium-86, yttrium-90, indium-114, indium-111, scandium-47, scandium-44, scandium-43, zirconium-89, bismuth-213, bismuth-212, actinium-225, lead-212, rhenium-188, rhenium-186, and rubidium-82. In particular embodiments, the method for radiolabelling a chelate-functionalized targeting agent with a radioactive metal, preferably gallium-68, comprises: recovering an eluate of a radioactive metal generator, preferably a gallium-68 generator, into a first vial located within a self-shielded device, preferably wherein said first vial is a vacuumed vial; adding a suitable amount of a buffering medium to the lyophilized chelate-functionalized targeting agent and lyophilized metal inhibitor comprised in a second vial to balance the pH of the eluate from a gallium-68 generator to a pH value ranging from 3 to 5 when said mixture of buffering medium, chelate-functionalized targeting agent and metal inhibitor is contacted with the eluate, preferably wherein said buffering medium is an acetate buffer; recovering the mixture of buffering medium, chelate-functionalized targeting agent and metal inhibitor from the second vial; adding the mixture of buffering medium, chelate-functionalized targeting agent and metal inhibitor to the recovered eluate of the radioactive metal generator, preferably gallium-68 generator, comprised in the first vial located within the shielding device; and allowing radiolabelling of the chelate-functionalized targeting agent with the radioactive metal, preferably gallium-68, for about 1 minute or up to about 5 or 10 minutes. In particular embodiments, the first vial (containing a vacuum) is connected to a vial adapter which is connected to an extension line comprising a proximal end adapted for connecting the extension line to the vial adapter and a distal end adapted for connecting the extension line to a needleless syringe; wherein said distal end is located outside the self-shielded device. In particular embodiments, the suitable amount of buffering medium, preferably acetate buffer, is contained in a third container and the suitable amount of buffering medium is added to the lyophilized chelate-functionalized targeting agent and lyophilized metal inhibitor by interconnecting said second and third vials via a needleless transfer device. In more particular embodiments, the needleless transfer device comprises a valve and a luer-lock, preferably wherein said valve can be configured to be in fluid communication with the third vial and the luer-lock, the second vial and the luer-lock, or the third and second vials and the luer-lock. In particular embodiments, the step of adding a suitable amount of buffering medium, preferably acetate buffer present in a third vial, to the lyophilized chelate-functionalized targeting agent and lyophilized metal inhibitor comprised in a second vial comprises: interconnecting said third vial comprising the buffering medium, preferably acetate buffer, and the second vial comprising lyophilized chelate-functionalized targeting agent and lyophilized metal inhibitor by a needleless transfer device; wherein the third vial is located above the second vial, wherein the luer-lock is capped, and wherein said valve can be configured to be in fluid communication with the third vial and the luer-lock, the second vial and the luer-lock, or the third and second vials and the luer-lock; allowing the buffering medium, preferably acetate buffer, to flow from the third vial to the second vial through the valve of the needleless transfer device which is configured to be in fluid communication with the third and second vials and the luer-lock; and mixing the buffering medium, preferably acetate buffer, lyophilized chelate-functionalized targeting agent and lyophilized metal inhibitor. In particular embodiments, the step of recovering the mixture of buffering medium, preferably acetate buffer, chelate-functionalized targeting agent and metal inhibitor from the second vial comprises: configuring the valve of the needleless transfer device to be in fluid communication with the second vial and the luer-lock, but not in fluid communication with the third vial, wherein the luer-lock is capped; uncapping the luer-lock; connecting a needleless syringe comprising air in a volume which is at least 50% the volume of the second vial to the uncapped luer-lock; injecting the air in a volume which is at least 50% the volume of the second vial from the needleless syringe into the second vial via the uncapped luer-lock; turning the third vial and the second vial interconnected by the needleless transfer device so that the second vial is located above the third vial; and withdrawing the mixture of buffering medium, preferably acetate buffer, chelate-functionalized targeting agent and metal inhibitor from the second vial via the uncapped luer-lock, using the needleless syringe. In particular embodiments, the step of adding the mixture of buffering medium, preferably acetate buffer, chelate-functionalized targeting agent and metal inhibitor to the recovered eluate of the radioactive metal generator, preferably gallium-68 generator, comprised in the first vial located within the self-shielded device comprises injecting the mixture of acetate buffer, chelate-functionalized targeting agent and metal inhibitor into the first vial located within the self-shielded device using a needleless syringe. In particular embodiments, the step of allowing radiolabelling of the chelate-functionalized targeting agent with the radioactive metal, preferably gallium-68, is performed for at least 30 seconds, at least 40 seconds, at least 50 seconds, at least 1 minute, at least 2 minutes, at least 3 minutes, at least 4 minutes, at least 5 minutes, at least 6 minutes, at least 7 minutes, at least 8 minutes, at least 9 minutes or at least 10 minutes, preferably for at least 5 minutes. In particular embodiments, all steps of the method for radiolabelling a targeting agent with gallium-68 are carried out at a temperature of below 50° C., preferably of ambient or room temperature (e.g. of between 20 and 30° C.). In particular embodiments, the self-shielded device comprises a container unit comprising a void space dimensioned to hold a vial, wherein said container unit is rotatable and/or invertible around a horizontal axis. In further particular embodiments, the method for radiolabelling a targeting agent with a radioactive metal, preferably gallium-68, further comprises after the step of allowing radiolabelling of the chelate-functionalized targeting agent with the radioactive metal, preferably gallium-68, inverting the container unit, thereby also inverting the first vial located within the self-shielded device. In particular embodiments, the method for radiolabelling a chelate-functionalized targeting agent with a radioactive metal, preferably gallium-68, further comprises withdrawing the radioactive metal-labelled, preferably gallium-68-labelled, chelate-functionalized targeting agent from the first vial, preferably via the distal end of the extension line. The inversion of the first vial comprising the radioactive metal-labelled, preferably gallium-68-labelled, chelate-functionalized targeting agent allows to withdraw a dose of the radioactive metal-labelled chelate-functionalized targeting agent or to guide a dose of the radioactive metal-labelled chelate-functionalized targeting agent to a patient by using the force of gravity, thereby avoiding the need to pressurize the first vial comprising the radioactive metal-labelled chelate-functionalized targeting agent (for example by use of a pump) and reducing risk of exposure of the user to radioactive material. The invention also encompasses the solution obtained by elution of a gallium-68 generator with an eluent comprising an acid, preferably HCl, in a kit as taught herein. Preferably, said solution has a pH between about 3 and about 5, preferably between about 3.5 and about 4.5, more preferably between about 3.9 and about 4.3. The invention also discloses a gallium-68 radiolabeled targeting agent, obtained by anyone of the methods as described herein. In one aspect, the invention also provides a preparation method of a kit as described herein, said method comprising the steps of: a) preparing a solution comprising the acetate salt, a chelate-functionalized targeting agent and an inhibitor of metal; and b) lyophilizing the solution obtained in step a). Alternatively, the invention further provides a process for preparing a kit of the invention comprising the steps of: a) preparing a solution comprising a chelate-functionalized targeting agent and an inhibitor of metal; and b) lyophilizing the solution obtained in step a). c) adding the acetate salt as a powder in the obtained lyophilized product in step b). Further alternatively, the invention further provides a process for preparing a kit of the invention comprising the steps of: a) preparing a solution comprising a chelate-functionalized targeting agent and an inhibitor of metal; and b) lyophilizing the solution obtained in step a). c) adding an acetate buffer in the obtained lyophilized product in step b). Finally, the invention further provides a process for preparing a kit of the invention comprising the steps of: a) preparing a solution comprising the acetate salt, a chelate-functionalized targeting agent and an inhibitor of metal; and b) optionally freeze the solution obtained in step a). While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as follows in the spirit and broad scope of the appended claims. The above aspects and embodiments are further supported by the following non-limiting examples. Labelling a Peptide with a 68Ga Eluate of 5 mL of 0.1 M HCl A commercial gallium-68 generator 1850 MBq (Eckert & Ziegler) is eluted with 5 mL of 0.1M HCl (Ultrapure grade) directly into a flask containing 150 mg of sodium acetate (Ultrapure grade) lyophilized, 240 μl of HCl 3M (Ultrapure grade), 760 μl of Milli-Q and 50 μg lyophilized NODAGA-NOC. The flask was left for 10 min at room temperature. The product is obtained with a radiochemical purity of 64% according to TLC analysis of the reaction medium. RadiolabellingChelatingyield for 10agentminutes, roomuse in theT ° vschelate-radiolabellingfunction-yeild withoutalizedmetal inhibitorGeneratorKittargetingusing similarcleanili-Prepara-EntryAcetateagentInhibitorGeneratorconditionsnesstion*1150NOTADOTAE&Z82% vs 51%Generator Amg25 μgcleaned2150NOTAFructoseE&Z87% vs 51%Generator Amg25 μgcleaned3150NOTABeta-E&Z83% vs 51%Generator Amg25 μgcyclo-cleaneddextrin4150NODAGABeta-E&Z95% vs 64%Generator Amg25 μgcyclo-cleaneddextrin5150HBEDBeta-E&Z91% vs 77%Generator Amg25 μgcyclo-cleaneddextrin6150HBEDFructoseE&Z94% vs 77%Generator Amg25 μgcleaned7150 NOTAFructoseE&Z85% vs 39%Generator Amg10 μgcleaned9150NODAGABeta-E&Z84% vs 55%Generator Amg10 μgcyclo-cleaneddextrin9150HBEDBeta-E&Z87% vs 51%Generator Amg10 μgcyclo-cleaneddextrin10150NODAGABeta-ITG94% vs 46%Generator Amg50 μgcyclo-cleaneddextrin11150NODAGABeta-E&Z97% vs 70%Generator Amg50 μgcyclo-cleaneddextrin12150NODAGAD-E&Z91% vs 44%Generator Amg50 μgMannosenot cleaned13150NODAGADOTAE&Z95% vs 70%Generator Amg50 μgcleaned14150NODAGABeta-iThemba91% vs 61%Generator Amg50 μgcyclo-cleaneddextrin15150NODAGAFructoseE&Z95% vs 70%Generator Amg50 μgcleaned16150HBEDDOTAITG91% vs 75%Generator Amg20 μgcleaned17150NODAGAD-ITG95% vs 60%Generator Amg25 μgMannosecleaned18150 NODAGABeta-ITG96% vs 60%Generator Amg25 μgcyclo-cleaneddextrin19150NODAGAtetra-tBu- ITG89% vs 60%Generator Amg25 μgDTPAcleaned20150NOAGABeta-ITG96% vs 61%Generator Bmg25 μgcyclo-cleaneddextrin21150NODAGADOTAE&Z94% vs 64%Generator Bmg25 μgcleaned22150 NODAGADOTAE&Z89% vs 64%Generator Cmg25 μgcleaned23150 NODAGAGlucoseITG89% vs 61%Generator Cmg25 μgcleaned24150DFO DOTAITG98% vs 85%Generator Amg10 μgcleaned*A = a preparation method comprising the steps of: a) preparing a solution comprising the acetate salt, a chelate-functionalized targeting agent and an inhibitor of metal; and b) lyophilizing the solution obtained in step a).B = a preparation method comprising the steps of: a) preparing a solution comprising a chelate-functionalized targeting agent and an inhibitor of metal; and b) lyophilizing the solution obtained in step a). c) adding the acetate salt as a solidC = a preparation method comprising the steps of: a) preparing a solution comprising a chelate-functionalized targeting agent and an inhibitor of metal; and b) lyophilizing the solution obtained in step a). c) adding the acetate salt as a buffer solution adapted to the generator used To conclude, the results above clearly show the increased gallium-68 radiolabelling yield of about 90% or more in all set-ups where a metal inhibitor as defined herein is used in addition to the chelator-functionalized targeting agent. If said agent is not added, much lower yields are obtained. The yield is virtually independent of the use of acetate in solid form or in buffer form. Also when the acetate salt is co-lyophilized with the metal inhibitor and the chelator-functionalized targeting agent, a very good yield is obtained. 1. Transfer of Gallium-68 into a Sterile Vacuumed Vial (Vial 1) Step 1. Removing the cover from the vial adapter package, while not removing the vial adapter from the blister package. Step 2. Attaching the vial adapter to the sterile vacuumed vial (vial 1), using the blister pack as a holder. Seating the vial adapter on the sterile vacuumed vial by pushing down until the spike penetrates the rubber stopper and the vial adapter snaps in place. Step 3. Removing the blister package. Step 4. Taking the extension line from its package and attaching it to the swabable vial adapter. Step 5. Placing the sterile vacuumed vial in the self-shielded dispensing device as described herein. Step 6. Transferring up to 1.85 GBq of gallium chloride dissolved in 1.1 ml of 0.1 M hydrochloric acid Ph. Eur. Inside the sterile vacuumed vial through the extension line. 2. Transfer of PSMA-11 and Acetate Buffer into the Sterile Vacuumed Vial Step 1. Removing the cover from the needleless transfer device package, while not removing the needleless transfer device from the blister package (FIG. 2, Step 1). Step 2a: Placing the device on top of the sterile acetate buffer vial (vial 2), Configuration B, using the blister pack as a holder. Seating the device on the sterile acetate buffer vial, Configuration B by pushing down until the spike penetrates the rubber stopper and the device snaps in place (FIG. 2, Step 2a). Step 2b. Removing the needleless transfer device from the blister pack (FIG. 2, Step 2b). Step 3. Inverting the sterile acetate buffer vial, Configuration B with the needleless transfer device attached; seating the open end of the device on the PSMA-11 sterile vial (vial 3) by pushing down until the spike penetrates the rubber stopper and the device snaps in place. Acetate buffer will flow into the PSMA-11 sterile vial (FIG. 2, Step 3). Step 4. Gently swirling the vials to make sure the product is thoroughly mixed (FIG. 2, Step 4). Step 5a. Turning the valve on the side of the device in medium position (FIG. 2, Step 5a). Step 5b. Removing the cap from the luer connector (FIG. 2, Step 5b). Step 6. Removing the 10 mL syringe's protective cap. Connecting the 10 mL syringe to the luer lock by turning it clockwise (FIG. 2, Step 6). Step 7. Pulling back on the plunger (FIG. 2, Step 7). Step 8. Turning the system so the PSMA-11 sterile vial is on top. Pulling back on the plunger to withdraw the solution (FIG. 2, Step 8). Step 9. Removing the syringe from the device (FIG. 2, Step 9). 3. Radiolabelling and Quality Control Step 1. Attaching the 10 mL syringe containing PSMA-11 dissolved in acetate buffer to the extension line and transferring its content inside the sterile vacuumed vial (vial 1). Step 2. Incubating for 5 minutes. Step 3. Collecting 50 μL of the sterile vacuumed vial content using the 10 ml syringe and removing the syringe from the extension line. Step 4. Performing a quality control. First, the lid of the container unit is opened and a sterile vacuumed vial (vial 1) attached to an extension line by a vial adapter is placed into the void space dimensioned to hold a vial of the self-shielded dispensing device as taught herein (FIG. 3). Next, the lid of the container unit is closed and gallium-68 is transferred to the sterile vacuumed vial (vial 1) by connecting the extension line to a gallium-68 generator and eluting the gallium-68 eluate into the sterile vacuumed vial (FIG. 3). Then, PSMA-11 and acetate buffer are mixed as described in steps 1 to 10 of Example x and the PSMA-11/acetate buffer mixture is transferred to the sterile vacuumed vial located within the self-shielded dispensing device by attaching the 10 mL syringe containing to the extension line and injecting the PSMA-11/acetate buffer mixture into the sterile vacuumed vial. The labelling of PSMA-11 with gallium-68 is allowed for 5 minutes at room temperature (FIG. 3). Subsequently, the container unit is inverted and fixed at its inverted position. A single dose or multiple doses of gallium-68 labelled PSMA-11 can be dispensed from the self-shielded dispensing device by the extension line (FIG. 3). |
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041742575 | claims | 1. In a nuclear reactor having a pressure vessel and a core within the pressure vessel, said core comprised of a plurality of fuel assemblies each comprised of a plurality of vertically oriented fuel elements, the reactor having fluid under pressure passed upwardly over said fuel elements; the improvement comprising: a pressure plate attached to the lower end of a fuel assembly, and having an upper surface and a lower surface, said upper surface exposed to the fluid at the fuel assembly inlet; a sealing plate spaced below said pressure plate, portions of said seal plate peripherally engaged the outer portion of said pressure plate in closely spaced relationship for substantially restricting fluid flow therebetween, thereby forming a pressurizable plenum defined by the lower surface of said pressure plate and the upper surface of said seal plate; and a control rod guide tube extending vertically through said fuel assembly and said pressure plate, said control rod guide tube open to said pressure plenum at the lower end and open to the fluid flowing upwardly at the upper end of said fuel assemblies. 2. An apparatus as in claim 1 having also an alignment plate located above said fuel assembly, and a spring means located intermediate said alignment plate and said fuel assembly, and urging said fuel assembly downwardly away from said alignment plate. |
062263544 | summary | BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to short-wavelength electromagnetic-radiation generators that generate electromagnetic radiation having short wavelengths by causing photons and electrons to collide. 2. Description of the Related Art In lithography applied to the production of semiconductor devices, a base is formed and patterned by performing predetermined exposure of a resist, developing the exposed resist, and etching the developed resist. Recently, with refinement of design rules, it is necessary to use photolithography using a short-wavelength electromagnetic-radiation source. A KrF excimer laser (whose wavelength is 248 nm), an ArF excimer laser (whose wavelength is 193 nm), etc., are used as the short-wavelength electromagnetic-radiation source. For obtaining short-wavelength electromagnetic radiation, electron-beam lithography, and X-ray-beam lithography to which synchrotron radiation is applied, are under consideration. The electron-beam lithography is suitable for limited production of a wide variety of goods, but is not suitable for mass production due to its low throughput. The X-ray-beam lithography to which synchrotron radiation is applied requires a large, complicated apparatus as an X-ray source, which disadvantageously increases cost in production of semiconductor devices. Accordingly, a method is being researched utilizing the inverse Compton effect as a technique which will allow a small apparatus to be used to yield short-wavelength exposure electromagnetic radiation. An electromagnetic radiation source which utilizes the inverse Compton effect uses electromagnetic-radiation scattering caused by electrons moving at a relativistic velocity, to supply photons with the energy of the electrons, whereby shortening the wavelength of the scattered electromagnetic radiation. In the inverse Compton effect, a problem occurs in that the yield of obtained photons in X-ray regions is small because a scattering cross section based on the electrons and the photons is an extremely small value of 10.sup.-27 cm.sup.2. Therefore, in lithography, sufficient X-ray energy cannot be produced, which is a likely problem in practice. SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a short-wavelength electromagnetic-radiation generator capable of generating sufficient X-ray energy for lithography. To this end, according to an aspect of the present invention, the foregoing object has been achieved through provision of a short-wavelength electromagnetic-radiation generator including: reflector means composed of at least a pair of concave reflectors; emitting means for emitting electromagnetic radiation so as to be incident on the reflector means; and electron-beam generating means for emitting an electron beam so as to be incident on the electromagnetic radiation, which is repeatedly reflected and converged. According to another aspect of the present invention, the foregoing object has been achieved through provision of a short-wavelength electromagnetic-radiation generator including: reflector means composed of at least a pair of concave reflectors; electron-beam generating means for emitting an electron beam having a diameter adjusted to the diameter of electromagnetic radiation converged by at least a pair of concave reflectors in the reflector means so that the electron beam is incident on a region where the electromagnetic radiation is converged by the pair of concave reflectors; and emitting means for emitting a pulse beam having a pulse width corresponding to the diameter of the electron beam so as to be incident on the reflector means. Preferably, the reflector means comprises concave reflector groups disposed to be opposed, each concave reflector group being composed of a plurality of aligned concave reflectors The emitting means may comprise a Q-switched laser source, a mode-locked laser source, a Q-switched laser source, or a mode locked laser source. According to the present invention, in a small short-wavelength electromagnetic-radiation generator, an electron beam is emitted to be incident on electromagnetic radiation being repeatedly reflected and converged by reflectors, whereby the electron beam and the electromagnetic radiation can collide successively. Thus, high scattering frequency can greatly increase the yield of scattered electromagnetic radiation. This makes it possible to apply the present invention to lithography in the production of semiconductor devices. |
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051494930 | description | DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a pipe 1 for circulating the liquid sodium in a secondary loop of a fast neutron nuclear reactor. A cold trap dump 2 is established on the pipe 1 which may be separated by two valves 3, 3' at its extremities. A cold trap 4 to be regenerated is installed on the dump 2. It is mainly composed of a tank lined inside with structures for retention of solid impurities and is surrounded by a jacket 5 passed through by a cooling fluid. An extremely high number of cold traps exist available to be used in the invention; a more detailed description shall not be given here, but if appropriate it is possible to refer to the French patent 2 624 032. The dump 2 forms near the cold trap 4 a first thermal exchanger device 6 by means of which the sodium arriving at the cold trap 4 is cooled by passing close to the sodium leaving this cold trap. A dump pipe 7 may be provided so as to interrupt the thermal exchange by, in collaboration with two valves 8 and 9, preventing the liquid sodium having left the cold trap passing through the first exchanger 6. When the cold trap is used to purify the sodium, this exchanger makes it possible to control the average functioning temperature of the cold trap. The installation also includes a liquid sodium tank 11 connected to the dump 2 by means of an induction pipe 12 and a driving back or repression pipe 13 which forms with these a liquid sodium circuit whose circulation may be forced through the cold trap 4 by means of a first pump 14. Similar induction and repression pipes 12', 12", 13' and 13" parallel to the preceding ones may also be connected to the tank 11 and dumps on other reactor secondary loops (not shown), even if the regeneration installation may be common to the power plant and be successively used for several cold traps. Valves 15 and 16 established on each of the induction and repression pipes 12, 13, etc., ensure correct switching. The other essential elements on the liquid sodium circuit consist of a first heater 17 situated on the section of the repression pipe 13 nearest the tank 11 and designed to bring the calories required to keep the storage to the desired temperature, a sealing indicator 49 established on the dump 2 and which is used to control the concentration of the impurities when the cold trap is used to purify the sodium of the secondary loop, and a first device 18 to measure the oxygen and hydrogen content in the tank 11. A bypass 7' equipped with a valve 9' makes it possible to short-circuit the cold trap to be regenerated 4 during the stage for heating the sodium of the storage tank 11. A dump circuit 20 is also connected to the tank 11. It includes an outlet pipe 21 on which a second pump 19 is installed, a return pipe 22 and a cold storage trap 23 at which the two pipes 21 and 22 end after having formed a second thermal exchanger 24 at its inlet. The cold storage trap 23 is not regenerated and is used to exclusively keep the oxygen in the form of an oxide. It is thus able to have a large capacity and has been selected so as to conform to the indications of the French patent 2 603 497 to be referred to subsequently. But it is clear that any type of cold trap may be used in this respect. To sum up the foregoing, the cold storage trap 23 indicated above is cooled by a plurality of cooling modules 25 disposed in series along its cylindrical casing 28 and the inside of the casing contains a series of parallel and alternate plates 26 and 27 which delimit a baffle hollow space: the plates 26 are ring-shaped and delimit a central hollow space, whereas the plates 27 are disks which delimit a ring-shaped interval along with the casing 28. Each of the plates 26 and 27 is constituted by an open-worked plate lined with metallic wool: when the storage trap 23 is new, the sodium passes roughly in a straight line through the plates 26 and 27 and then when the latter are fouled, the sodium deforms them without reducing the effectiveness of retention of the crystallized impurities by virtue of the elongation of the path. The terracing or stepping of several cooling modules 25 makes it possible to vary the locations where the deposit of impurities predominates and thus to properly distribute the fouling. The inlet pipe 21 opens at the top of the cold storage trap 23 and the outlet pipe 22 at the bottom of the latter after having traversed it axially. A sub-dump 29 is connected to the dump 20: the inlet pipe 21 bifurcates and forms an inlet branch 30, whereas the outlet pipe 22 also bifurcates and forms an outlet branch 31. The two branches 30 and 31 draw close together so as to form a third thermal exchanger 32 and are joined at the extremities of a permeation system known as a "permeator" 33. A heater 34 is disposed on the inlet branch 30 between the third thermal exchanger 32 and the permeator 33. Valves 45 to 48 are established on these various pipes so as to favor, limit or interrupt the outflows of the sodium by the cold storage trap 23 and the permeator 33. A second device 39 to measure the content of oxygen and hydrogen is then installed on the inlet pipe 21. The permeator 33, shown in detail on FIG. 2, is constituted by a casing 34 traversed by a looped pipe 35 covered with lengthening pieces 36 which extend inside the casing 34 and constitute a permeation membrane. They are made of a finger-shaped material, such as nickel, with a high permeation rate of several hundreds or thousands and these finger shaped pieces are several hundred millimeters thick. The branches 30 and 31 end at the casing 34 by means of collectors 37 and 38 separated from the lengthening pieces 36 by perforated plates 39 and 40 which distribute the flow and render it approximately perpendicular to the lengthening pieces 36. The looped pipe 35 ends at a vacuum pump 41 and storage tank 42 lined with a material to retain the hydrogen, said material being, for example, in the form of chips of a lanthanum, nickel and manganese alloy. The internal face of the lengthening pieces 36 opening onto the looped pipe 35 is kept in a partial depression with respect to the external face bathed by the sodium so as to facilitate transfer of the hydrogen contained in the sodium to the pipe under vacuum through the membrane. FIG. 1 delineates a slightly different disposition where the sub-dump 29 would be omitted and the permeator--then referenced 33'--would be in the tank 11, which would result in a simplified disposition but preventing the use of the second heater 34 which significantly reinforces the effectiveness of regeneration. So as to carry out regeneration, as soon as the valves 3 and 3' have been closed to separate the dump 2 from the loop 1, the first pump 14 is activated so as to establish a forced circulation of the liquid sodium through the tank 11 and the cold trap 4 to be regenerated. The first heater 17 is also activated, whereas the functioning of the cooling system 5 of the cold trap is interrupted so that the sodium circulated by the first pump 14 is heated to a relatively high temperature, such as 520.degree. C. It is important to mention that the decomposition reactions (1) and (2) listed earlier are not able to occur owing to the presence of the sodium. In place of these, dissolutions of hydride and oxide deposits progressively occur according to the ionic dissociation reactions (3) and (4): EQU NaH.sup.- .fwdarw.Na.sup.+ +H (3) EQU Na.sub.2 O.fwdarw.2Na.sup.+ +O (4) When it is established by means of the first measuring device 18 that the sodium is saturated with oxygen and hydrogen, one part is in fact passed through the permeator 33 after having opened the valves 47 and 48 and activated the second pump 19 and the heater 34. This heater sets up an overheating temperature, such as 600.degree. C., in the permeator 33. The filtration of the hydrogen ions including tritium through the lengthening pieces 36 is facilitated and these ions are pumped up to the storage tank 42 where they are adsorbed by the alloy. A subsequent thermal treatment of this alloy so as to extract the hydrogen and tritium may easily be effected. The largest oxygen ions do not traverse the permeation membrane and therefore remain in the liquid sodium. When the hydrogen concentration has again stabilized, the valves 45 and 46 are opened. Sodium also passes through the cold storage trap 23 and which is cooled by the modules 25 so that the oxide is deposited there according to a reaction being opposite the reaction (4). It is also possible to set up a temperature at the cold point of the cold storage trap 23, this temperature being less than the oxide crystallization temperature but greater than the hydride crystallization temperature. Thus, it is possible to provide a temperature of 495.degree. C. if the two crystallization temperatures mentioned are respectively 515.degree. C. and 480.degree. C. As a result, the hydride and in particular the tritium do not remain in the cold storage trap 23 and a segregation of the two main impurities is effected. If desired, it is a simple matter to clean the cold storage trap 23 after a regeneration process: it merely suffices to disassemble it from the installation and to wash it with soda without taking any particular precautions, as the sodium oxide is not radioactive. FIG. 3 explains the method. The abscissae represent the time and the ordinates represent the temperatures or flows (the scale of the latter is not specified). The curves 51 to 58 respectively represent the temperature in the permeator 33, the temperature in the tank 11 and in the trap 4 to be regenerated, the oxide crystallization temperature, the temperature in the cold storage trap 23, the hydride crystallization temperature, the flow passing through the permeator 33, the flow passing through the trap 4 to be regenerated and the flow passing through the cold storage trap 23. The transitory stages of the method are clearly distinguished and in particular also the drop of the concentration of the hydride as soon as the permeator 33 is used, this being expressed by a difference between the crystallization temperatures of the hydride and the oxide and thus ensures that no hydride is collected in the cold storage trap 23. The process is continued until the cold trap 4 has been completely regenerated. When the hydrogen or oxygen has been completely eliminated, it is obviously possible to close the circuit ending at the corresponding retention device by means of the valves 45, 46 or 47, 48. For certain types of reactors, especially those excluding a water/sodium reaction, pollutions occuring by hydrides is preponderant. The overall time of all the operations naturally depends mainly on the quantity of impurities to be eliminated and contained in the trap 4, the size of the permeator 33 and all the selected operational conditions. By way of example, for the Super Phenix 1 reactor, the period of the operation may last for one week for a cold trap having purified the sodium for eight years of functioning. This regeneration method may be advantageously used to recover the tritium produced in a fusion reactor tritigen blanket, especially when the tritium is extracted from a tritigen blanket constituted by the lithium/lead eutectic and then introduced into a liquid metal circuit through a permeation membrane and finally crystallized in a solid form in a cold trap: the extraction of the sodium tritide is carried out in accordance with the invention when the cold trap is full. There is no need to disassemble the cold trap 4, which would have been required for some of these traps before draining, and the installation described is constructed at the same time as the power plant and does not require any particular connection in order to have it function. |
051695936 | description | DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to FIG. 1, there is shown, generally at 10, a nuclear reactor having a containment 12 with a reactor vessel 14 therein. It will be recognized by one skilled in the art that different nuclear reactors 10 may have numbers and dimensions which may vary from the illustrative example used in the preceding. The apparatus and methods of the present invention are equally adaptable to such other systems. A control rod drive 16, which may be one of, for example, 180 such items, is affixed in reactor vessel 14 using a flange 18 affixed to a bottom 20 of reactor vessel 14 that mates with a flange 22 affixed to control rod drive 16. Flanges 18 and 22 are urged together by a ring of bolts 24. A criss-cross pattern of heavy steel plates 26 form eggcrate compartments below bottom 20 to surround external parts of control rod drive 16, to catch control rod drives 16 in case of an accident, and for protection of instrumentation (not shown) affixed below bottom 20. An inverted jungle of relatively fragile instrumentation cables 28 is suspended below bottom 20 (only one instrumentation cable 28 is represented in the figure to reduce clutter). A sub-pile room 30 in containment 12 below reactor vessel 14 is divided by a rotatable work platform 32 into an upper portion 34 and a lower portion 36. A floor 38 is located at the bottom of lower portion 36. A door 40 in containment 12 permits entry and exit of personnel and equipment. In a typical nuclear reactor 10, sub-pile room 30 measures about 18 feet from floor 38 to bottom 20. A typical control rod drive 16 is about 16 feet long. There is thus a minimum of maneuvering room for lowering control rod drive 16 and upending it for passage through door 40. Work platform 32 is positioned so that its work surface 42 is about five to seven feet below a bottom 44 of steel plates 26. This permits workers on work surface 42 to reach items mounted on bottom 20, but it also provides a relatively cramped workspace. Referring now to FIG. 2, there is shown an early step in the removal of a control rod drive 16. Elements not necessary to the following description are omitted. Bolts 24 are removed and a cable 46 of a hoist 48 is attached to control rod drive 16. Referring now to FIG. 3, control rod drive 16 is lowered until the balance point of control rod drive 16 has emerged from flange 18. It will be noted that, at this time, the bottom of control rod drive 16 is below work platform 32. A slot in work platform 32 provides for this. Referring now to FIG. 4, cable 46 is re-rigged at the balance point of control rod drive 16. Referring now to FIG. 5, lowering continues until the top of control rod drive 16 clears flange 18, as shown in solid line. Then control rod drive 16 is rotated about its balance point to the horizontal condition, as shown in dashed line. Once in the horizontal position, it may be removed from sub-pile room 30 using, for example, a trolley cart (not shown). It should be evident that the rigging, rerigging, lowering and rotating steps in the prior art technique provide less than optimum control of control rod drive 16 during the process. The poor control of control rod drive 16 presents a substantial danger of damage to instrumentation cables (not shown in FIGS. 2-5). Also, the manual method consumes substantial time. It is estimated that a crew of four workers is capable of removing or installing about two control rod drives 16 in an eight-hour shift. This low level of productivity is worsened if an instrumentation cable is damaged and has to be repaired before proceeding. Referring now to FIG. 6, there is shown, generally at 50, a handling system according to the present invention. A slot 52 in work surface 42 includes opposed support rails 54 and 56. A trunnion cart 58 includes a plurality of wheels 60 rolling on rails 54 and 56. Trunnion cart 58 supports a tower 62. A winch 64 is affixed to work platform 32 at one end of slot 52. A cable 65 is paid out from winch 64 for attachment to the bottom of tower 62, as will be explained. A lead cart 66, whose structure and function will be described later, is rollably supported on rails 54 and 56 by a plurality of wheels 68. Referring now to FIG. 7, tower 62 includes first and second facing side rails 70 and 72 (side rail 72 is hidden by side rail 70 in FIG. 7). Side rails 70 and 72 are tied together by a plurality of cross braces 74. Cable 65 is affixed near the bottom of side rail 70 by any convenient means such as, for example, a safety hook 76 on cable 65 engaging an eye 78 on side rail 70. An hoist motor 80 is affixed at the bottom end of side rail 70. An extension piece 82, used at various stages of removal and installation of a control rod drive, is shown alongside tower 62. A torque breaker 84 and a load transfer plate 86 are also shown. Referring now to the front view of tower 62 in FIG. 8, an elevator platform 88 is driveable upward and downward between side rails 70 and 72 by actuation of hoist motor 80. Any convenient means for transferring motion from hoist motor 80 to elevator platform 88 may be employed. In one embodiment of the invention, a cross shaft 90 is driven through a roller chain 92 from hoist motor 80. An endless roller chain (not shown) inside side rail 70, and a further endless roller chain (not shown) inside side rail 72, are driven by cross shaft 90. The ends of elevator platform 88 are connected to the two roller chains whereby, as cross shaft 90 rotates, elevator platform 88 is moved upward or downward. Other techniques for driving elevator platform 88 would be evident to one skilled in the art, and thus do not require further elaboration. A retractable wheel 94 is affixed near the lower end of side rail 70. Similarly, a retractable wheel 96 is affixed near the lower end of side rail 72. In the retracted position shown, the maximum transverse dimension through retractable wheels 94 and 96 is less than the spacing between rails 56, whereby retractable wheels 94 and 96 can pass therethrough. Later in the operation of the system, tower 62 is rotated until retractable wheels 94 and 96 are above rails 56. Then retractable wheels 94 and 96 are moved into their unretracted positions. The end of tower 62 may then be lowered until retractable wheels 94 and 96 contact the upper surfaces of rails 56 to support tower 62. It is to be noted that the transverse dimension of hoist motor 80 is less than the space between rails 56. This permits rotation of tower 62 to move hoist motor 80 upward between rails 56 during a stage of operation of the system. A journal shaft 100, extending from side rail 70, is rotatably engaged in a trunnion bearing 98 on one trunnion cart 58. Similarly, a journal shaft 102, extending from side rail 72, is rotatably engaged in a trunnion bearing 104 on the other trunnion cart 58. Referring now to FIG. 9, the apparatus of the invention is shown in an early stage of use. Extension piece 82 includes a shaft 106 having a support 108 at its lower end for engaging elevator platform 88. A cylindrical bearing 110 supports an upward-pointing locating pin 112. Locating pin 112 is sized to enter an axial hole 114 in the bottom of control rod drive 16. An indexing guide 116 is disposed about an intermediate point on shaft 106. A detorque yoke 118 is installed above indexing guide 116. Referring now to FIG. 10, in the next stage in removal of control rod drive 16, elevator platform 88 is raised until locating pin 112 enters axial hole 114 (neither of which are seen in FIG. 10). Cylindrical bearing 110 permits a limited rotation of locating pin 112 to facilitate its entry into, and alignment with axial hole 114. Initially, elevator platform 88 is positioned so that no upward force is applied to the bottom of control rod drive 16. This permits extension piece 82 to be rotated, as desired. Referring momentarily to FIG. 11, indexing guide 116 is formed of first and second semi-circular halves 117 and 119, permanently installed on shaft 106 using, for example, bolts 121. A plurality of radial slots 120, equal in number to bolts 24 securing control rod drive 16 are formed in an upper surface. Radial slots 120 give indexing guide 116 an appearance similar to a castellated nut. Referring now to FIG. 11A, detorque yoke 118 includes a wishbone-shaped member 122 having first and second legs 124 and 126 enclosing a gap 128. A closing bar 129 is secured in place closing gap 128 using, for example, a nut 131. A boss 133, on the underside of detorque yoke 118, engages a selected one of radial slots 120, as will be explained hereinafter. A hole 137 is sized to permit the entry thereinto of a lower end of torque breaker Returning now to FIG. 10, torque breaker 84 includes a shaft 130 having a socket-engaging portion 132 at one end thereof, and a guide rod 134 at the other. A coil spring 136 covers at least part of guide rod 134. A handle 138 is fitted in torque breaker 84 above coil spring 136. Guide rod 134 is sized to fit into hole 137. The length of shaft 130 is such that, guide rod 134 may be pressed downward into a hole 137, thereby compressing coil spring 136 to permit socket-engaging portion 132 to be moved into alignment with a bolt 24. When downward force on torque breaker 84 is removed, coil spring 136 urges socket-engaging portion 132 upward into full engagement with a bolt 24, while guide rod 134 remains within hole 137. The engaged position of torque breaker 84 is shown in FIG. 12. In an initial adjustment, while extension piece 82 is held in the unforced position shown in FIG. 10, extension piece 82 is rotated until radial slots 120 in indexing guide 118 are aligned below respective ones of bolts 24. Selection of this alignement may be aided by installing detorque tool 84 in hole 137 and in one of bolts 24. When substantial rotational alignment is attained, elevator platform 88 is urged upward by hoist motor 80 until a substantial upward force is exerted on the bottom of control rod drive 16 by extension piece 82. This force is sufficient to hold extension piece 82 in the selected rotational position and to provide reaction torque to permit adequate torque to be applied to bolt 24 by manual actuation of handle 138. In one embodiment of the invention, the full upward drive capability of hoist motor 80 is applied and maintained during the detorquing of bolts 24. The applied upward force of about 1000 pounds was adequate to permit detorquing of bolts 24 which are installed with a torque of 800 foot-pounds. Once one of bolts 24 is loosened, boss 133 is disengaged from a radial slot 120, and detorque yoke 118 is rotated until hole 137 is aligned below a next selected bolt 24. Since radial slots 120 are generally aligned with bolts 24, the new position of detorque yoke 118 is certain to align hole 137 vertically with the selected bolt 24. Numerous conventional mechanisms could be substituted for the apparatus described above for providing the indexing function. A detailed discussion of such conventional mechanisms is considered unnecessary to satisfy the disclosure requirements of the present application. It is found most productive to use torque breaker 84 only to break the initial torque. Once all of bolts 24 are loosened slightly, torque breaker 84 is removed, and all bolts 24 can be removed rapidly with a low-powered electric or pneumatic drive. Referring now to FIGS. 12 and 13, as a preferable next step in the removal of control rod drive 16 one pair of diametrically opposite bolts 24 are removed and a pair of guide rods 140 are screwed, hand tight, in their place. Each guide rod 140 includes a tapered tip 142 at its end, and a narrow diameter portion 144 in an intermediate location. A safety block 146 is installed on the narrow diameter portion 144 of each guide rod 140. Each safety block 146 includes a slot 148 having a width permitting it to fit onto narrow diameter portion 144, and to prevent it from being forced axially along guide rod 140. Thus, in the event that control rod drive 16 is released accidentally, safety blocks 146 stop downward motion of control rod drive 16 after only a small amount of motion has taken place. When a maintenance operation requires removal of a control rod drive 16 and its reinstallation or replacement, guide rods 140 are permitted to remain in place after removal, or are installed in preparation for reinstallation. The presence of guide rods 140 simplifies attaining correct linear and rotational alignment of flange 22 with flange 18. Referring now to FIG. 15, elevator platform 88 is lowered until the bottom of control rod drive 16 enters the top of tower 62. Conventional guiding elements at the top of tower 62, which may be employed to stabilize extension piece 82 during the process of reaching the condition shown, are omitted to reduce clutter in the figure. At this point, extension piece 82 must be removed so that control rod drive 16 can be further lowered into tower 62. Referring now to FIG. 16, a load transfer plate 150 is slid into place in tower 62 to bear the load of control rod drive 16 while elevator platform 88 is lowered further to disengage extension piece 82 from the bottom of control rod drive 16. Extension piece 82 is then removed, supported by an integral hanger, and swung aside in preparation for the next step in removal. With extension piece 82 removed, elevator platform 88 is moved upward to assume support of control rod drive 16. Load transfer plate 150 is removed. Referring now to FIG. 17, elevator platform 88 is lowered until a top end 152 of control rod drive 16 is clear of flange 18. Referring now to FIG. 18, winch 64 is actuated to raise the lower end of tower 62 until retractable wheels 94 and 96 are above rails 56. In this raising operation and by referring to FIGS. 7, 8, 17 and 18, it is seen that the entire tower structure is pivoted or rotated to effect this raising. As FIG. 8 shows, an upper end of the tower has support on trunnion cart 58 via the two journal shafts 100, 102 and their companion trunnion bearings 98, 104. The journal shafts 100, 102 serve as pivot points so that when cable 65 is taken up, the lower tower end is lifted and the whole tower structure pivots about these said pivot points to bring the tower lower end slightly above horizontal. The short length of tower 62 seen extending above rail 54 in FIG. 8 will of course also pivot, but downwardly slightly as part of the shifting of tower orientation from vertical to generally horizontal. Then, retractable wheels 94 and 96 are moved into their outward unretracted positions, and cable 65 is paid out slightly until retractable wheels 94 and 96 rest on rails 56 to support the end of tower 62. Safety hook 76 is disengaged from eye 78 so that tower 62 is converted to a rollable cart which can be rolled out through door 40 (FIG. 1). Tower 62 can similarly be used to move control rod drive 16 inward through door 40 in preparation for installation. In some installations, the bottom of door 40 is raised a substantial distance above work surface 42. Generally a ramp (not shown) is provided so that materials can be rolled up and down between the two levels. Such a ramp could contact top end 152 of control rod drive 16 during the transition from work surface 42 to the ramp, possibly causing damage. Referring again to FIG. 6, lead cart 66 solves the problem of maneuvering control rod drive 16 in tower 62 onto a ramp without damaging top end 152 of control rod drive 16. When tower 62 is brought to the horizontal position, the protruding end of control rod drive 16 is clamped into clamps 154 and 156 in lead cart 66. Thus, as tower 62 and control rod drive 16 are moved onto a ramp, lead cart 66 rolls up the ramp to raise top end 152. It may be desirable to block rotation of control rod drive 16 with respect to tower 62. In this event, when lead cart 66 rolls up a ramp, trunnion cart 58 may be raised off rails 56, thereby leaving control rod drive 16 and tower 62 supported by lead cart 66 and retractable wheels 94 and 96. Two additional problems are solved by the present invention. When the seal between flanges 18 and 22 is first cracked during removal, an initial burst of contaminated water pours out through the gap between them. In the most common situation, this water pours down over the workers below. Although the workers wear protective clothing and breathing gear, it is considered undesirable to permit such contaminated water to fall on them. One Japanese Utility Model Application Publication NO. 57-49834, employs a sump that can be affixed to the control rod drive to catch and channel away water as the seal between flanges 18 and 22 is cracked. Top end 152 of control rod drive 16 is located closest to the nuclear reaction in reactor vessel 14, and a filter therein tends to collect radioactive contaminants. Thus this area is much more radioactive than is the remainder of control rod drive 16. In the prior art, a cylindrical lead radiation shield pig is placed over top end 152 to shield against the radiation in this area. A lead cylinder of the required size and thickness is relatively heavy and difficult to handle quickly. Thus, more radiation exposure occurs than is desirable. The present invention addresses this problem with a radiation shield pig that permits faster and more positive installation of shielding upon top end 152. Referring to FIGS. 19-21, an effluent container 158 is shown with its elements partially installed to catch and channel effluent water that will escape between flanges 18 and 22 when the seal between them is broken. Four sway braces 160 are conventionally disposed, 90 degrees apart, in contact with each flange 18. A water container 161 consists of two halves 162 and 164 having half-cylindrical sidewall 166 and 168 with half-circular bottoms 170 and 172, respectively. Bottoms 170 and 172 include semi-circular cutouts 174 and 176, respectively which, when halves 162 and 164 are fitted together, form a close fit to the outer peripheral surface of extension piece 82. Four notches 178, 180, 182 and 184 are positioned and sized to slip over the four sway braces 160. A hole 186 in bottom 170 is connected to a drainage nipple 188 outside water container 161. A flexible hose 190 carries off water that falls into water container 161. A clamp cylinder 192 consists of a right circular cylinder having a single vertical split 194 therein. The material of clamp cylinder 192 is resilient enough to permit deformation to expand split 194 sufficiently to pass over extension piece 82. Four L-shaped slots 196, 198, 200 and 202 (L-shaped slot 202 is hidden in the figure), are disposed in the upper edge of clamp cylinder 192. The L-shaped slots fit upon sway braces 160 and, when clamp cylinder 192 is rotated slighty, hook over the top thereof to retain clamp cylinder 192 in the installed position. In this position, clamp cylinder 192 holds the two halves of water container 161 together. In use, bolts 24 are removed while a strong upward force is exerted on control rod drive 16 through extension piece 82. This prevents any substantial leakage during the initial stages. Halves 162 and 164 are assembled upon extension piece 82 with notches 178, 180, 182 and 184 engaging their respective sway braces 160. Split 194 is opened to permit slipping clamp cylinder 192 over extension piece 82. Clamp cylinder 192 is slid upward over the outside of water container 161 and L-shaped slots 196, 198, 200 and 202 are latched over their respective sway braces 160. Extension piece 82 is then lowered slightly to break the seal between flanges 18 and 22. This permits liquid effluent to drain into water container 161 and thence through 190 to a location where it can be controlled. Control rod drive 16 may be lowered still further as desired. At some point, water container 161 begins sliding downward within clamp cylinder 192, which stays in place. The fit between mating edges of halves 162 and 164 is close enough to limit leakage therepast to a very small amount. Similarly, the fit of semi-circular cutouts 174 and 176 is close enough to limit leakage. Although gasketing could be used on these mating surfaces to reduce even further the leakage, such an addition may not be needed since the principal goal of eliminating the shower of contaminated water has been substantially attained. Water container 161 and clamp cylinder 192 may be made of any convenient material. We have discovered that a plastic resin, and especially a polycarbonate plastic resin, has suitable properties of lightness, strength and resilience for these parts. Typical polycarbonate resins are transparent. This provides the important benefit of permitting a worker to see the flow of water inside, and thus to monitor proper drainage, and to determine when substantially all of the water flow is completed. Referring now to FIG. 22, there is shown, generally at 204, a radiation shield pig according to an embodiment of the invention. A hanger assembly 206 includes a top bar 208 and a bottom bar 210 rigidly tied together in parallel spaced-apart relationship by a connecting pin 212. Top bar 208 includes a hole 214 therein fittable over guide rod 140. Similarly, bottom bar 210 includes a hole 216, axially aligned with hole 214 and also fittable over guide rod 140. A spring-loaded latch 218 snaps into a latching position in narrow diameter portion 144 when hanger assembly 206 is slipped upward onto guide rod 140. First and second swing arms 220 and 222 are pivoted to connecting pin 212. A half shiedl 224, of semi-cylindrical shape, includes a connecting loop 226 on an outer surface thereof. Each of swing arms 220 and 222 includes a hole 228 (hole 228 in swing arm 222 is not visible in the figure) to receive a connecting pin 230, which also passes through connecting loop 226 to pivotably affix half shield 224 to guide rod 140. A clamp hanger 232, affixed to half shield 224 at its upper end, is pivotably attached at its lower end to a friction clamp half 234. First and second hooks 236 and 238 are disposed adjacent an edge of half shield 224. A second half shield 240 inlcudes elements thereon that correspond to those on half shield 224. First and second luggage latches 242 and 244 are positioned where they can be engaged with hooks 236 and 238, respectively on half shield 224. A further pair of luggage latch components is hidden adjacent the rear mating surfaces of radiation shield pig 204. In a further embodiment, only one latch is used at each side of radiation shield pig 204. In use, while top end 152 of control rod drive 16 is still well above flange 18, the two half shields 224 and 240 of shield pig 204 are installed on guide rods 140 in the unengaged position shown. Then, when the highly radioactive top end 152 emerges from flange 18, luggage latches 242 and 244 are latched to form a complete cylinder about top end 152, and the two friction clamp halves 234 are clamped together about control rod drive 16, whereby shield pig 204 is firmly secured to control rod drive 16. Then the two connecting pins 230 (one hidden in the figure) are pulled. This releases radiation shield pig 204 for movement with control rod drive 16. This required actions following emergence of top end 152 are accomplished rapidly and positively, whereby a minimum of radiation exposure occurs. Having described preferred embodiments of the invention with reference to the accompanying drawings, it is to be understood that the invention is not limited to those precise embodiments, and that various changes and modifications may be effected therein by one skilled in the art without departing from the scope or spirit of the invention as defined in the appended claims. |
043897304 | abstract | An X-ray collimator is disclosed having longitudinal and cross shutter assemblies disposed between an input port and an output port. Image area boundaries are defined by two pairs of inner edge portions. Mating inner edge portions of each pair move in an essentially rectilinear path. |
description | Embodiments of the subject matter disclosed herein relate to diagnostic medical imaging, and more particularly, to contrast enhanced computed tomography imaging. Noninvasive imaging modalities may transmit energy in the form of radiation into an imaging subject. Based on the transmitted energy, images may be subsequently generated indicative of the structural or functional information internal to the imaging subject. In computed tomography (CT) imaging, radiation transmits from a radiation source to a detector through the imaging subject. A bowtie filter may be positioned between the radiation source and the imaging subject for adjusting the spatial distribution of the radiation energy based on the anatomy of the imaging subject. For example, a human body in the axial plane is thicker in the middle and thinner on the periphery. The bowtie filter may be designed to distribute higher radiation energy to the middle and less radiation energy to the peripheral of the subject. As a result, the amplitude of signal received by the imaging detector is equalized, and the radiation dose on the periphery of the imaging subject is reduced. Different anatomy of the subject may require different bowtie filters. For example, bowtie filters of different shape and size may be designed to image the head, the chest, and the abdomen of the human body. To further enhance contrast of specific organ and/or tissue type, an external contrast agent may be injected into the imaging subject. The duration for acquiring the contrast enhanced images may be short due to limited contrast agent circulation time at the anatomy being imaged. Therefore, a method for acquiring high quality contrast enhanced images across different anatomies of the subject, wherein different bowtie filters are required for imaging each of the anatomies, is needed. In one embodiment, a method comprises determining a first contrast enhancement of an injected contrast agent within an imaging subject; responsive to the first contrast enhancement being higher than a first threshold, acquiring a first dataset of the imaging subject by transmitting a radiation beam to the imaging subject via a first filter; switching to a different, second filter after acquiring the first dataset; and acquiring a second dataset of the imaging subject by transmitting the radiation beam to the imaging subject via the second filter, wherein an average contrast enhancement of the injected contrast agent in the imaging subject during the acquisition of the first dataset is substantially the same as an average contrast enhancement of the injected contrast agent in the imaging subject during the acquisition of the second dataset. It should be understood that the brief description above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure. The following description relates to various embodiments of contrast enhanced imaging. In particular, systems and methods are provided for contrast enhanced CT imaging using more than one bowtie filter. FIGS. 1-2 show an example embodiment of an imaging system, wherein a filter is positioned between the radiation source and the imaging subject. Different filters may be selected based on the anatomy of the imaging subject being imaged. FIG. 3 shows an example method of contrast enhanced CT imaging with fast switching bowtie filters. In particular, after contrast agent injection, the bowtie filter is switched before imaging a different section of the subject by operating a filter driving system. FIG. 4A shows an example timeline of CT imaging and filter switching with respect to the contrast agent enhancement in the imaging subject. FIG. 4B illustrates sections of the subject that have been imaged during the timeline of FIG. 4A. FIG. 5 shows another example timeline of CT imaging and filter switching, wherein images are acquired at multiple time points to track variation of the contrast enhancement in the subject over time. The fast filter switching may also be used for fast imaging of multiple sections of the imaging subject, as shown in FIGS. 6-7. FIGS. 8A-8D show various positions of an example filter assembly with three filters. FIGS. 9A-9B show detailed configuration of the filter driving system. Though a CT system is described by way of example, it should be understood that the present techniques may also be useful when applied to images acquired using other imaging modalities, such as tomosynthesis, C-arm angiography, and so forth. The present discussion of a CT imaging modality is provided merely as an example of one suitable imaging modality. Various embodiments may be implemented in connection with different types of imaging systems. For example, various embodiments may be implemented in connection with a CT imaging system in which a radiation source projects a fan- or cone-shaped beam that is collimated to lie within an x-y plane of a Cartesian coordinate system and generally referred to as an “imaging plane.” The x-ray beam passes through an imaging subject, such as a patient. The beam, after being attenuated by the imaging subject, impinges upon an array of radiation detectors. The intensity of the attenuated radiation beam received at the detector array is dependent upon the attenuation of an x-ray beam by the imaging subject. Each detector element of the array produces a separate electrical signal that is a measurement of the beam intensity at the detector location. The intensity measurement from all the detectors is acquired separately to produce a transmission profile. In third-generation CT systems, the radiation source and the detector array are rotated with a gantry within the imaging plane and around the object to be imaged such that the angle at which the x-ray beam intersects the imaging subject constantly changes. A complete gantry rotation occurs when the gantry concludes one full 360 degree revolution. A group of x-ray attenuation measurements (e.g., projection data) from the detector array at one gantry angle is referred to as a “view.” A view is, therefore, each incremental position of the gantry. A “scan” of the object comprises a set of views made at different gantry angles, or view angles, during one revolution of the x-ray source and detector. In an axial scan, the projection data is processed to construct an image that corresponds to a two-dimensional slice taken through the imaging subject. One method for reconstructing an image from a set of projection data is referred to in the art as a filtered backprojection technique. This process converts the attenuation measurements from a scan into integers called “CT numbers” or “Hounsfield units” (HU), which are used to control the brightness of a corresponding pixel on a display. FIG. 1 illustrates an exemplary CT system 100 configured to allow fast and iterative image reconstruction. Particularly, the CT system 100 is configured to image a subject such as a patient, an inanimate object, one or more manufactured parts, and/or foreign objects such as dental implants, stents, and/or contrast agents present within the body. In one embodiment, the CT system 100 includes a gantry 102, which in turn, may further include at least one x-ray radiation source 104 configured to project a beam of x-ray radiation 106 for use in imaging the patient. Specifically, the radiation source 104 is configured to project the x-rays 106 towards a detector array 108 positioned on the opposite side of the gantry 102. Although FIG. 1 depicts only a single radiation source 104, in certain embodiments, multiple radiation sources may be employed to project a plurality of x-rays 106 for acquiring projection data corresponding to the patient at different energy levels. In certain embodiments, the CT system 100 further includes an image processing unit 110 configured to reconstruct images of a target volume of the patient using an iterative or analytic image reconstruction method. For example, the image processing unit 110 may use an analytic image reconstruction approach such as filtered backprojection (FBP) to reconstruct images of a target volume of the patient. As another example, the image processing unit 110 may use an iterative image reconstruction approach such as advanced statistical iterative reconstruction (ASIR), conjugate gradient (CG), maximum likelihood expectation maximization (MLEM), model-based iterative reconstruction (MBIR), and so on to reconstruct images of a target volume of the patient. FIG. 2 illustrates an exemplary imaging system 200 similar to the CT system 100 of FIG. 1. In accordance with aspects of the present disclosure, the system 200 is configured to perform automatic exposure control responsive to user input. In one embodiment, the system 200 includes the detector array 108 (see FIG. 1). The detector array 108 further includes a plurality of detector elements 202 that together sense the x-ray beam 106 (see FIG. 1) that pass through a subject 204 such as a patient to acquire corresponding projection data. Accordingly, in one embodiment, the detector array 108 is fabricated in a multi-slice configuration including the plurality of rows of cells or detector elements 202. In such a configuration, one or more additional rows of the detector elements 202 are arranged in a parallel configuration for acquiring the projection data. A bowtie filter housing 240 may be mounted within gantry 102 between radiator source 104 and the subject 204. The bowtie filter may change the energy distribution of the radiation beam in the axial plane of the imaging subject (such as a patient). For example, the re-distributed radiation beam may have higher energy at the center and lower energy at the periphery of the subject. One or more bowtie filters may be positioned within the filter housing 240. Each and every bowtie filter is rigid and non-deformable. Each of the bowtie filters may be designed to image a specific anatomy or section of the human body, such as head, chest, and abdomen. Three different bowtie filters 241, 242, and 243 are shown in FIG. 2 as an example. The bowtie filters are shown here in rectangular shape as an example. The bowtie filters alternatively be in different shapes and materials to provide proper x-ray special spectrum for imaging various types of anatomies. During imaging, one of the bowtie filters may be selected based on the anatomy of the subject, and be placed into the radiation beam path. Responsive to a change in the anatomy, the filter may be changed from one to another. Example arrangement of the filters in the filter housing is shown in FIGS. 8A-8D. A filter driving system (not shown here) may be coupled to the filter to move the filter into and out of the radiation beam path. Examples of the filter driving system are shown in FIGS. 9A-9B. In one embodiment, the motor may couple the filters through a shaft. The bowtie filters may be switched from one to another by translating the filters along the shaft by rotating the shaft with a motor. One of the filters may be selected and translated into the x-ray beam between the radiation source and the imaging subject to image a specific section of the human body. Computing device 216 may send command to the motor of the filter driving system to move the selected filter in to the radiation beam. The filter driving system may also send filter position information back to the computing device 216. In certain embodiments, the system 200 is configured to traverse different angular positions around the subject 204 for acquiring desired projection data. Accordingly, the gantry 102 and the components mounted thereon (such as the radiation source 104, the filter housing 240, and the detector 202) may be configured to rotate about a center of rotation 206 for acquiring the projection data, for example, at different energy levels. Alternatively, in embodiments where a projection angle relative to the subject 204 varies as a function of time, the mounted components may be configured to move along a general curve rather than along a segment of a circle. In one embodiment, the system 200 includes a control mechanism 208 to control movement of the components such as rotation of the gantry 102 and the operation of the x-ray radiation source 104. In certain embodiments, the control mechanism 208 further includes an x-ray controller 210 configured to provide power and timing signals to the radiation source 104. Additionally, the control mechanism 208 includes a gantry motor controller 212 configured to control a rotational speed and/or position of the gantry 102 based on imaging requirements. In certain embodiments, the control mechanism 208 further includes a data acquisition system (DAS) 214 configured to sample analog data received from the detector elements 202 and convert the analog data to digital signals for subsequent processing. The data sampled and digitized by the DAS 214 is transmitted to a computing device (also referred to as processor) 216. In one example, the computing device 216 stores the data in a storage device 218. The storage device 218, for example, may include a hard disk drive, a floppy disk drive, a compact disk-read/write (CD-R/W) drive, a Digital Versatile Disc (DVD) drive, a flash drive, and/or a solid-state storage device. Additionally, the computing device 216 provides commands and parameters to one or more of the DAS 214, the x-ray controller 210, and the gantry motor controller 212 for controlling system operations such as data acquisition and/or processing. In certain embodiments, the computing device 216 controls system operations based on operator input. The computing device 216 receives the operator input, for example, including commands and/or scanning parameters via an operator console 220 operatively coupled to the computing device 216. The operator console 220 may include a keyboard (not shown) or a touchscreen to allow the operator to specify the commands and/or scanning parameters. Although FIG. 2 illustrates only one operator console 220, more than one operator console may be coupled to the system 200, for example, for inputting or outputting system parameters, requesting examinations, and/or viewing images. Further, in certain embodiments, the system 200 may be coupled to multiple displays, printers, workstations, and/or similar devices located either locally or remotely, for example, within an institution or hospital, or in an entirely different location via one or more configurable wired and/or wireless networks such as the Internet and/or virtual private networks. In one embodiment, for example, the system 200 either includes, or is coupled to a picture archiving and communications system (PACS) 224. In an exemplary implementation, the PACS 224 is further coupled to a remote system such as a radiology department information system, hospital information system, and/or to an internal or external network (not shown) to allow operators at different locations to supply commands and parameters and/or gain access to the image data. The computing device 216 uses the operator-supplied and/or system-defined commands and parameters to operate a table motor controller 226, which in turn, may control a motorized table 228. Particularly, the table motor controller 226 moves the table 228 for appropriately positioning the subject 204 in the gantry 102 for acquiring projection data corresponding to the target volume of the subject 204. As previously noted, the DAS 214 samples and digitizes the projection data acquired by the detector elements 202. Subsequently, an image reconstructor 230 uses the sampled and digitized x-ray data to perform high-speed reconstruction. Although FIG. 2 illustrates the image reconstructor 230 as a separate entity, in certain embodiments, the image reconstructor 230 may form part of the computing device 216. Alternatively, the image reconstructor 230 may be absent from the system 200 and instead the computing device 216 may perform one or more functions of the image reconstructor 230. Moreover, the image reconstructor 230 may be located locally or remotely, and may be operatively connected to the system 100 using a wired or wireless network. Particularly, one exemplary embodiment may use computing resources in a “cloud” network cluster for the image reconstructor 230. In one embodiment, the image reconstructor 230 stores the images reconstructed in the storage device 218. Alternatively, the image reconstructor 230 transmits the reconstructed images to the computing device 216 for generating useful patient information for diagnosis and evaluation. In certain embodiments, the computing device 216 transmits the reconstructed images and/or the patient information to a display 232 communicatively coupled to the computing device 216 and/or the image reconstructor 230. Turning to FIG. 3, an example method 300 for performing contrast enhanced imaging with multiple filters is presented. To achieve high image quality, it is optimal to perform the contrast enhanced imaging at high radiation attenuation of the targeting anatomy. In other words, it is optimal to perform the contrast enhanced imaging at high contrast agent enhancement. The amount of the attenuation, or the degree of contrast enhancement, may be measured by the CT numbers. For example, increased attenuation or increased contrast enhancement corresponds to high CT numbers. Further, it is preferable to minimize the dose of the contrast agent and the number of contrast injections during scan. Method 300 achieves fast image acquisition of multiple anatomies of the imaging subject by fast changing the filters during the scan. Method 300 may be performed according to instructions stored in the non-transitory memory in a computing device (such as computer 216 of FIG. 2) of the imaging system. In particular, after the contrast agent is injected into the imaging subject, a first section of the subject is imaged using a first filter. After fast filter switching, a second, different, section of the subject is imaged with a second filter. The first and the second sections may have different anatomies. As such, contrast enhanced images of different anatomies of the subject may be acquired with a one-time contrast agent injection. Herein, a section of the subject is a three-dimensional volume along the length of a human body. At 302, method 300 includes setting up scan parameters. For example, a user may input or select the scan parameters according to a scanning protocol or a menu. The scan parameters may include the type and sequence of the filters that are going to be used during the scan. The type of the filters may be chosen based on the anatomy of imaging subject that is to be imaged. Method 300 may also include setting scan timing. As one example, the scan timing may include a start time and a duration for imaging each section. As another example, method 300 may include setting up one or more contrast enhancement thresholds, and the imaging of each section may start responsive to the actual contrast agent enhancement reaching the thresholds. Method 300 may also include loading anatomy information of the imaging subject to the memory of the computation device. The anatomy information may be acquired from a pre-scan. This step may also include moving the first filter to a position in the x-ray beam path between the radiation source and the subject, and moving the subject so that the first section of the subject is within the gantry for imaging. The type of the first filter is determined based on the anatomy of the first section of the subject. At 304, contrast agent is injected into the imaging subject. Method 300 starts monitoring the enhancement of the contrast agent within the subject, at the anatomy of interest. As one example, the contrast agent enhancement at the anatomy of interest may be monitored by periodically imaging the same location of the subject and analyzing the change if contrast enhancement over time. As another example, the enhancement of the contrast agent in one section of the subject may be derived from the contrast enhancement in another section of the subject. As yet another example, the contrast enhancement may be estimated based on time elapsed since injection based on empirical knowledge of the physiological circulation time of the contrast agent in the anatomy of interest. As one example, the physiological circulation time of the contrast agent may be the circulation time of blood. The estimated enhancement may further be adjusted based on the dose of the contrast and the mass of the subject. For example, the estimated enhancement may increase with the increased contrast dose and decrease with the mass of the subject. At 306, method 300 compares the estimated contrast agent enhancement with a predetermined positive non-zero first threshold. The first threshold may be determined based on a predicted minimum concentration of the contrast agent in the subject, as well as the duration and sequence of image acquisition as defined by the scan parameters described above. The first threshold may be a sensitivity of the imaging system to the contrast agent in the imaged anatomy. In one example, the first threshold may be determined so that each dataset of each section of the subject is acquired at an enhancement (CT number) higher than the threshold. For example, the first threshold may be slightly lower than a predicted maximum enhancement, such as 10% lower than the predicted maximum enhancement. In this way, a plurality of imaging datasets may be obtained when the contrast enhancement is within a threshold range of the maximum enhancement (e.g., as the enhancement approaches, reaches, and then recedes from the maximum enhancement threshold). In one embodiment, the contrast agent enhancement in a first section of the subject is compared with the first threshold. Responsive to the estimated enhancement being higher than the first threshold, method 300 proceeds to 310 to acquire an image dataset. Otherwise, method 300 moves to 308 to continue monitoring contrast agent enhancement. At 310, method 300 starts acquiring the first dataset of the first section of the subject using the first filter. For example, the radiation source (such as 104 of FIGS. 1-2) may be activated, and start emitting radiation exposure (such as 106 of FIGS. 1-2) to the imaging subject through the first filter. The dataset is acquired from the detector (such as 108 of FIG. 2) upon receiving the attenuated radiation beam from the imaging subject. Herein, a dataset corresponds to the projection data acquired during imaging a section of the subject. In one example, the first section of the subject may be imaged once. In another example, the first section of the subject may be imaged multiple times to capture the change of enhancement of the contrast agent in the subject. At 312, after acquiring the first dataset, the first filter is moved out of the radiation beam path and the second filter is moved into the radiation beam path. The first and the second filters may be moved by operating one or more motors, such as shown in FIGS. 8A-8B, which show example filter driving systems. By moving the filters with a motor, filters may be automatically switched quickly within one scan. In one example, switching one filter with another filter may be completed within two seconds. Step 312 may also include moving the subject via the motorized table (such as motorized table of 228 in FIGS. 1-2) to a proper location to start acquiring a second dataset. The filter switching and subject relocation may be performed simultaneously. The type of the second filter may be determined based on the anatomy of a second section of the subject. The first section and the second section of the subject may have different anatomies (such as different size and shape), so that different filter types are used for imaging each section. As an example, the first section may be the chest and the second section may be the abdomen. As another example, the first section may be one of the chest, the head, and the abdomen, and the second section may be one of the head, the chest, and the abdomen. At 314, method 300 estimates the enhancement of the contrast agent and compares it with a predetermined second threshold. Similar to 304, the contrast agent enhancement may be monitored by periodically imaging at the same location of the subject and analyzing the contrast enhancement over time. The contrast agent enhancement may alternatively be determined based on time elapsed since injection, the physiological circulation time of the anatomy of interest, the dose of the contrast, and the mass of the subject. The second threshold may be determined so that the average contrast enhancement while acquiring the first dataset is substantially the same as the average contrast enhancement while acquiring the second dataset. Herein, the average contrast enhancements are substantially the same means the difference between the average contrast enhancements is within a threshold range. For example, the difference between the average contrast enhancements is within 1% (or other suitable range, such as 5%) of either the average contrast enhancement of the first dataset or the second dataset. In another embodiment, the second threshold may be determined so that the average contrast enhancement while acquiring the first dataset is the same as the average contrast enhancement while acquiring the second dataset. As such, the degree of contrast enhancement of the first and the second datasets are the same. In one example, the second threshold may be higher than the first threshold. In one embodiment, the contrast agent enhancement in the second section of the subject is compared with the second threshold. If the contrast enhancement is lower than the second threshold, method 300 proceeds to 316 to acquire the second dataset. Otherwise, method 300 continues to monitor contrast agent enhancement. In one embodiment, steps 314 and 316 may be skipped, and the second dataset is acquired immediately after filter switching at 312. Further, in some examples, the second dataset may be acquired when the contrast agent enhancement is lower than the second threshold yet still higher than the first threshold. In this way, the second dataset may be acquired after the contrast agent enhancement has reached the maximum enhancement and is at the approximate same enhancement as when the first dataset was collected. At 318, the second dataset of the second section of the subject is acquired with the second filter. At least in some examples, due to the fast switching of the filters, no additional contrast agent is injected to the imaging subject between the acquisition of the first dataset and the acquisition of the second dataset. As one example, the second section of the subject may be imaged once. As another example, the second section of the subject may be imaged multiple times to capture the change of enhancement of the contrast agent in the subject. At 320, the acquired first and second datasets are displayed and stored. In one embodiment, the first dataset and the second dataset may be re-constructed to form an image. The image may include the first and the second sections displayed on the display. The image may be two-dimensional or three-dimensional. As one example, the re-constructed first and second datasets may be displayed with the same dynamic range (that is, the same range of signal amplitudes in the datasets are displayed), as the average contrast enhancement is substantially the same for the first and the second dataset. As such, images of the first and the second sections of the subject are comparable to each other, and diagnosis may be made by analyzing the images acquired with one contrast agent injection. In another embodiment, data of the first and the second datasets that have the same average contrast enhancement may be selected, and then processed to be displayed together in one image. Images of the first and second sections of the subject acquired at various contrast enhancement may be generated to provide functional information of the imaged organs. The first and the second dataset, as well as the processed images may be saved in the storage of the imaging system. Turning to FIG. 4A, an example timeline of contrast enhancement 430, status of the motor for driving the filters 440, and the status of the radiation source 450 while implementing method 300 are shown. In graph 430, the y-axis is the enhancement of contrast agent in the imaging subject. The contrast enhancement increases as indicated by the arrow of the y-axis. Curve 401 shows the contrast enhancement over time. In one example, curve 401 may be predetermined based on empirical knowledge (such as physiological circulation time) of the contrast agent, the dose, and the mass of the subject. In another example, curve 401 may be estimated or measured during the contrast enhanced imaging. For example, the contrast enhancement may be periodically estimated or measured. Curve 401 may be then generated by interpolating the estimated/measured contrast enhancement. In graph 440, the motor status may be on or off. When the motor is on, filters are switched. For example, the motor may be activated to rotate a shaft coupled to the filters. By rotating the shaft, the filter may be translated into and out of the radiation beam path. In graph 450, the radiation source status may be on or off. When the radiation source is on, dataset of the imaging subject is acquired. In FIG. 4A, the x-axes indicate time. The time increases as indicated by the arrows of the x-axes. Prior to T1, scan parameters are set up. The first filter is positioned into the radiation beam path. At T1, contrast agent is injected into the subject. Responsive to the contrast agent administration, the contrast enhancement increases with time from zero. At T2, the contrast enhancement reaches the first nonzero threshold 412. Responsive to the contrast enhancement higher than the first threshold 412, the radiation source is turned on, and acquisition of the first dataset of the first section of the subject is started. Acquisition of the first dataset proceeds from T2 to T3. FIG. 4B shows an example first section 421 of the subject 112. The first section covers the chest, and the first filter is designed to image the chest. To complete the scan of the first section, a sequence of axial scans may be performed in the direction along the length of the subject, as shown with arrow 423. At T3, the imaging of the first section of the imaging subject ends, and the radiation source is turned off. Right after the acquisition of data during the first scan at T3, the filters are switched by activation of the motor, and the first filter is moved out of the path of radiation and the second filter is moved into the path. At T4, the filter switching is completed. Due to the fast switch of the filter, the average contrast enhancement is high during imaging. The duration from T3 to T4 may be less than two seconds. In one example, the subject may be moved starting from T3 to a new location for imaging the second section of the subject. The contrast agent enhancement keeps increasing from T2 to T3 and peaks at T5. In another example, the peak T5 of the contrast enhancement may be anywhere between T3 and T6. At T6, responsive to the contrast enhancement being lower than the second threshold 410, the second dataset is acquired from T6 to T7 with the second filter. As one example, the second threshold may be determined so that the average contrast enhancement from T2 to T3 is substantially the same as the average contrast enhancement from T6 to T7. As another example, the second threshold 410 may be higher than the first threshold 412. FIG. 4B shows an example of the second section 422 of the subject 112. The second section covers the abdomen. To complete the scan of the second section, a sequence of axial scans may be performed in the direction along the length of the subject, as shown with arrow 423. In FIG. 4B, the first section and the second section are connected to each other at location 424. That is, the acquisition of first dataset ends at 424 and the acquisition of the second dataset starts at 424. In this example, the subject is not moved after acquiring the first dataset and before acquiring the second dataset. In another embodiment, the first section and the second section may not be connected with each other, or the first section and the second section are overlapped with each other. The subject is then moved upon completion of the acquisition of the first dataset at T3. For example, the first section is the head and the second section is the abdomen, and subject is moved after acquiring the first dataset and before acquiring the second dataset. At T8, the contrast enhancement decreases to zero. In another embodiment, contrast enhancement curve 401 may include the enhancement of contrast agent in different sections of the subject. For example, the contrast enhancement from T1 to T5 is the contrast enhancement in the first section of the subject, and the contrast enhancement from T5 to T8 is the contrast enhancement in the second section of the subject. The physiological circulation of the contrast agent may be different in different sections of the human body. For example, the physiological circulation of contrast agent in head may be longer than the physiological circulation in abdomen. By using contrast enhancement of the imaged section, optimal image quality may be achieved. Turning to FIG. 5, another example timeline of the contrast agent enhancement 510, the status of motor for driving the filter 520, and the status of the radiation source 530 while implementing method 300 of FIG. 3 are shown. Different from FIG. 4A, herein, a plurality of datasets of the first section of the subject are acquired with the first filter at multiple time points while the contrast enhancement increases, and a plurality of datasets of the second section of the subject are acquired at multiple time points with the second filter while the contrast enhancement decreases. As such, the phases of the contrast circulation in the subject may be obtained. In graph 510, the y-axis is the enhancement of contrast agent in the imaging subject. The contrast agent enhancement increases as indicated by the arrow of the y-axis. Curve 507 shows the contrast enhancement over time. In one example, curve 507 may be predetermined based on empirical knowledge (such as physiological circulation) of the contrast agent, the dose, and the mass of the subject. In another example, curve 507 may be estimated or measured during the contrast enhanced imaging. For example, the contrast enhancement may be periodically estimated or measured. Curve 507 may be then generated by interpolating the estimated/measured contrast enhancement. In graph 520, the motor status may be on or off. When the motor is on, filters are switched. For example, the motor may be activated to rotate a shaft coupled to the filters. By rotating the shaft, the filters may be translated into and out of the radiation beam path. In graph 530, the radiation source status may be on or off. When the radiation source is on, dataset of the imaging subject is acquired. In FIG. 5, the x-axes are time. The time increases as indicated by the arrows of the x-axes. At T1, contrast agent is injected into the subject. Responsive to the contrast agent administration, the contrast enhancement increases with time from zero. The contrast enhancement increases from T1 to T6, and decreases from T6 to zero at T10. From T1 to T6, multiple datasets of the first section of the subject are acquired using the first filter. From T6 to T10, multiple datasets of the second section of the subject are acquired using the second filter. Upon completion of imaging the first section, the first filter is moved out of the radiation path and is replaced by the second filter by actuating one or more motors in the filter driving system. The peak of the contrast enhancement curve 401 may be anywhere between T5 and T7. Each of the datasets may be acquired responsive to the contrast enhancement reaching a predetermined nonzero threshold. For example, acquisition of the first dataset starts at T2, responsive to the contrast enhancement higher than the first threshold 501; acquisition of the second dataset starts at T3, responsive to the contrast enhancement higher than the second threshold 502; and acquisition of the third dataset starts at T4, responsive to the contrast enhancement higher than the third threshold 503. Acquisition of the fourth dataset starts at T7, responsive to the contrast enhancement lower than the fourth threshold 504; acquisition of the fifth dataset starts at T8, responsive to the contrast enhancement lower than the fifth threshold 505; and acquisition of the third dataset starts at T9, responsive to the contrast enhancement lower than the third threshold 506. The thresholds may be chosen such that the average contrast enhancement while imaging the first and the second sections are substantially the same. For example, the average contrast enhancement while acquiring the first dataset is substantially the same as the average contrast enhancement while acquiring the sixth dataset; the average contrast enhancement while acquiring the second dataset is the substantially same as the average contrast enhancement while acquiring the fifth dataset; and the average contrast enhancement while acquiring the third dataset is substantially the same as the average contrast enhancement while acquiring the fourth dataset. As such, at specific contrast enhancement, contrast enhanced images of the first and the second sections of the subject may be comparable and displayed with the same dynamic range. Similar to FIG. 4A, in one embodiment, the contrast enhancement curve 507 may include contrast enhancement of different sections of the subject. For example, curve 507 from T1 and T6 is the contrast enhancement in the first section of the subject. Curve 507 form T6 to T10 is the contrast enhancement in the second section of the subject. FIG. 6 shows an example method 600 for imaging multiple different anatomies of the imaging subject with fast filter switching. Method 600 may be carried out according to instructions stored in the non-transitory memory in a computing device (such as computer 216 of FIG. 2) of the imaging system. At 602, method 600 includes setting up scan parameters. For example, a user may input or select the scan parameters according to a scanning protocol or a menu. The scan parameters may include the type and sequence of the filters that are going to be used during the scan. The type of the filters may be chosen based on the anatomy of imaging subject that is to be imaged. Method 600 may also include setting scan timing. As one example, the scan timing may include a start time and a duration for imaging each section. Method 600 may also include loading anatomy information of the imaging subject to the memory of the computation device. The anatomy information may be acquired from a pre-scan. As another example, the anatomy information may be acquired from a scout or a localized scan. This step may also include moving a filter to a position in the x-ray beam path between the radiation source and the subject, and moving the imaging subject via the motorized table (such as motorized table 228 of FIGS. 1-2) so that the proper section of the subject is within the gantry for imaging. The type of the filter is determined based on the anatomy of the currently imaged section of the subject. At 604, method 600 starts acquiring the dataset of the imaging subject using the first filter. Simultaneously, method 600 monitors the anatomy of the imaging subject. For example, the radiation source (such as 104 of FIGS. 1-2) may be activated, and start radiation exposure (such as 106 of FIGS. 1-2) of the imaging subject through the first filter. The dataset is acquired from the detector (such as 108 of FIG. 2) upon receiving the transmitted radiation signal from the imaging subject. As one example, the anatomy of the imaging subject may be monitored by analyzing the acquired dataset. As another example, the anatomy of the imaging subject may be estimated by the currently imaged location. The currently imaged location may be calculated based on the starting location of the scan and the travel distance of the motorized table. In one embodiment, the anatomies of the subject may be grouped in different types. For example, the anatomy of a human body may be grouped based on size, into types of such as the head, the chest, and the abdomen. In one embodiment, the acquisition of the dataset may be started responsive to a contrast agent enhancement higher than a threshold. At 606, method 600 determines whether the scan is ended. Method 600 may determines the end of the scan based on the protocol setup at 602. If the scan ends, method 600 proceeds to 608 to display and store the acquired dataset. If additional scan is needed, method 600 proceeds to 610. At 608, the acquired dataset is displayed and stored. In one embodiment, dataset acquired from different sections of the subject may be re-constructed to form an image. The image may be two-dimensional or three-dimensional. The acquired dataset, as well as the processed images may be saved in the storage of the imaging system. At 610, method 600 determines whether the anatomy of the imaging subject that is being imaged has changed or is about to change. In one embodiment, the anatomy may be determined to have changed when the size to type of the anatomy changes. Responsive to the change in anatomy, method 600 proceeds to 614 to switch the filter. Otherwise, method 600 moves to 640 to continue acquiring the dataset with the current filter and monitoring the anatomy. At 614, responsive the change in anatomy, the current filter is moved out of the radiation beam path and a different filter is moved into the radiation beam path. The filters may be moved by operating one or more motors, such as motors shown in FIGS. 9A-9B. By moving the filters with a motor, filters may be automatically switched quickly within one scan. In one example, switching one filter with another filter may be completed within two seconds. Step 614 may also include moving the subject via the motorized table (such as motorized table of 228 in FIGS. 1-2) to a predetermined location. The filter switching and subject relocation may be performed simultaneously. After filter switching, method 600 continues acquiring the dataset with the new filter and monitoring the anatomy. In one embodiment, the data acquisition may be continued through the filter switching process. In this way, time delays between imaging different anatomies of the subject is reduced or avoided. While method 600 is described above as including a filter switch that is performed in response to a detected or predicted change in imaged anatomy, other triggers for switching the filters are possible. For example, the scanning protocol selected by the operator of the imaging system may include a series of images (reconstructed from acquired projection data) to be acquired along the imaging subject. A prescribed first set of images may be acquired while a first filter is in the radiation path and while the imaging system table is at a first position. Once the first set of images has been acquired, the scanning protocol may command or instruct the table to be moved to a second position in order to move the imaging subject relative to the radiation source and detector. The scanning protocol may also command or instruct the filter driving system to move the first filter out of the radiation path and move a second filter into the radiation path. The filters may be moved/switched while the table is moving. A prescribed second set of images may then be acquired while the second filter is in the radiation path and the table is in the second position. In such a configuration, the switching of the filters may be triggered by a predetermined number of images (e.g., projection data sets) being acquired, by a predetermined amount of time having elapsed since commencement of the scanning procedure, and/or by a user input instructing the filters to be switched. FIG. 7 shows an example timeline of the status of the radiation source 710 the type of the anatomy 720, the speed of the motorized table (such as motorized table 228 of FIGS. 1-2), and the status of the motor for driving the filters 740 while implementing method 600 of FIG. 6. In one example, the imaging system performs helical scan of different types of anatomy. In graph 710, the radiation source status may be on or off. When the radiation source is on, a dataset of the imaging subject is acquired. In graph 720, different types of the anatomy is shown. For example, the first type of the anatomy is the head, the second type of the anatomy is chest, and the third type of the anatomy is the abdomen. In graph 730, the speed of the motorized table for moving the subject is shown. The speed increases with the y-axis. In graph 740, the motor status may be on or off. When the motor is on, filters are switched. For example, the motor may be activated to rotate a shaft coupled to the filters. By rotating the shaft, the filter may be translated into and out of the radiation beam path. At T1, the radiation source is turned on for imaging the first type of the anatomy. A filter designed for imaging the first type of anatomy is positioned between the radiation source and the imaging subject. The motorized table is moved at a nonzero speed to translate the subject through the gantry for the scan. The motor for driving the filter is off. In one embodiment, the radiation source may be started responsive to an enhancement of the contrast agent higher than a nonzero threshold. At T2, the anatomy being imaged or to be imaged changes from the first type to the second type. Responsive to the change, the motor for driving the filter is actuated to switch the current filter to a different filter designed for imaging the second type of anatomy. The duration for switching the filter lasts ΔT, which is less than two seconds. The motorized table may be operated at a different speed from prior to T2 and move the imaging subject to a section with different anatomy. As one example, the motorized table may be moved at a higher speed from T2 to T3 comparing to prior to T2. As another example, the motorized table may be stationary and the speed is zero from T2 to T3. As yet another example, the motorized table may move at the same speed as during T1-T2. While switching the filter, the radiation source is turned off and no radiation exposure is emitted to the imaging subject. As such, the overall patient radiation dose may be reduced. In one embodiment, the duration for moving the imaging subject (T2−T3) may be greater than the duration for switching the filter (ΔT), and the radiation source is turned off while moving the imaging subject. From T3 to T4, the second type anatomy is imaged and the motorized table is moved at a low speed. As one example, the speed of the motorized table from T3 to T4 is the same as the speed of the motorized table from T1 to T2. At T4, the anatomy being imaged or to be imaged changes from the second type to the third type. Responsive to the change, the motor for driving the filter is actuated to switch the current filter to a different filter designed for imaging the third type of anatomy. During T4 to T5, the motorized table may move at a different speed from during T3-T4. The radiation source is turned off while switching the filter. From T5 to T6, the third type anatomy is imaged and the motorized table is moved at a low speed. As one example, the speed of the motorized table from T5 to T6 is the same as the speed of the motorized table from T3 to T4. At T6, the scan is finished. The speed of the motorized table goes to zero and the radiation source is turned off. FIGS. 8A-8D show an example configuration of a filter assembly with three filters 805, 806, and 807 within filter housing 810. In this example, the first and second filters are positioned together in a housing 804. The housing 804 is coupled to a ballscrew 811, and can be translated along the first shaft 808 by rotating the first shaft with a first motor 802. The third filter 807 is coupled to a ballscrew 812 and can be translated along the second shaft 809 by rotating the second shaft with the second motor. A localized clearance feature (not shown) is present in the housing 804 to prevent interference of the second shaft 809 from interfering with the housing 804 as the housing 804 translates along the first shaft 808. The direction of the x-ray beam (such as x-ray radiation 106 of FIGS. 1-2) is indicated by 801. One of the three filters may be translated into the beam path of the x-ray beam by rotating one or both shafts 808 and 809 via motors 802 and 803. The first and the second shafts may be aligned in one line along the shafts, and are spaced apart from each other by a gap 813. The x-ray beam may transmit through the gap. The motor (such as motor 803), the shaft (such as shaft 809) coupled to the motor, and the filter (such as filter 807) coupled to the shaft form a filter driving system 890. The filter assembly may include one or more filter driving systems. Example configuration of the filter driving system is shown in FIGS. 9A-9B. FIG. 8A shows a first position of the filter assembly. The x-ray beam transmits through the filter housing without passing through any filter. The first and the second filters are at a location close to the first motor 802, and the third filter is at a location close to the second motor 803. FIG. 8B shows a second position of the filter assembly. The x-ray beam transmits though the first filter 805 in the filter housing 810. The filter assembly may transit from the first position to the second position by actuating the first motor 802 and translating the first filter 805 into the x-ray beam path. FIG. 8C shows a third position of the filter assembly. The x-ray beam transmits though the second filter 806 in the filter housing 810. The filter assembly may transit from the first position or the second position to the third position by actuating the first motor 802 and translating the second filter 806 into the x-ray beam path. FIG. 8C shows a fourth position of the filter assembly. The x-ray beam transmits through the third filter 807 in the filter housing 810. The filter assembly may transit from either the second or the third positions to the fourth position by actuating the first motor 802 to translate the housing 804 closer to the first motor 802, and subsequently or simultaneously actuating the second motor 803 to translate the third filter into the x-ray beam path. Based on the instructions stored in the non-transient memory, the computing device (such as computing device 216 of FIG. 2) may move the filter assembly from any one of the above positions to another position by actuating one or more of the two motors. In one embodiment, two filters are positioned in the filter housing. As one example, the two filters may be coupled to one shaft and driven by one motor. As another example, one of the two filters is coupled to one shaft and driven by one motor, and the other of the two filters is coupled to a second shaft and driven by a second motor. In another embodiment, more than three filters may arranged within the filter housing. For example, the numbers of filters coupled to each shaft are the same, if the total number of filters in the housing is even. The numbers of filters coupled to each shaft is different, if the total number of filters in the housing is odd. As such, duration of filter switching may be reduced due to low average filter distance from the x-ray beam path. In yet another embodiment, the arrangement of the filters in the filter housing may be based on the type of the filters. Herein, the filter type may be determined by the section of the subject that the filter is designed to image. For example, the first filter used for imaging the first section of the subject and the second filter used or imaging the second section of the subject may be positioned next to each other, if the first section and the second section are connected. The first filter and the second filter may be positioned apart from each other (such as separated by another filter), if the first section and the second section are not connected. As an example, the filter for imaging the abdomen may be positioned next to the filter for imaging the chest, but apart from the filter for imaging the head. In this way, when the chest is imaged after imaging the abdomen, the filters may be quickly switched from one to another. When the head is imaged after imaging the abdomen, the duration for filter switching may be longer, as the imaging subject needs to be physically moved from imaging the abdomen to imaging the head. FIGS. 9A and 9B show examples of the filter driving system. Each filter assembly (such as filter assembly shown in FIGS. 8A-8D) may have one or more of the filter driving systems. FIG. 9A shows an example configuration of the filter driving system. Filter 906 is mechanically coupled to a ballscrew nut 904. The ballscrew shaft 902 is mechanically coupled to motor 903 via shaft 908. As motor 903 rotates, the filter 906 may translate in directions indicated by arrow 907 along the ballscrew shaft 902. As such the rotational motion of the shaft is translated to linear motion of the filter along the shaft. The motor is fixed to support 901. A second filter 905 may be coupled to filter 906. The filter 905 and filter 906 are not movable relative to each other. As such, filters 905 and 906 are translated together along the ballscrew shaft 902. FIG. 9B shows another example configuration of the filter driving system. Filter 926 is mechanically coupled to ballscrew nut 924. The ball screw nut is coupled to motor 923 via shaft 910, flex coupling 929, and shaft 928. The flex coupling is positioned between shaft 910 and shaft 928. Shaft 910 is directly coupled to the ballscrew shaft 922, and shaft 928 is directly coupled to motor 923. The flex coupling may increase the tolerance of misalignment between the motor 923 and the ballscrew shaft 922. The ballscrew shaft 922 is supported by support bearings 912 and 913 at each distal end of the shaft. By rotating the motor 923, the filter 926 may translate in directions as shown by arrow 927. A second filter 925 may be coupled to filter 926. The filter 925 and filter 906 are not movable relative to each other. As such, filters 905 and 906 are translated together along the ballscrew shaft 922. In other embodiments, the filter may be translated with any one of a rack and pinion, a belt, or a cable-driven system. The filter driving system in the filter assembly switches one filter to another within two seconds. For example, the filter can be translated 3-5 inches in less than two seconds by the filter driving system. In this way, mixed-size anatomy may be imaged with high image quality during time-sensitive scans such as contrast enhanced imaging. The technical effect of switching filters after the contrast agent injection is that different anatomies of the subject may be imaged with one contrast agent injection. The technical effect of actuating the motor to switch the filters is that the duration for switching the filters may be reduced. The technical effect of acquiring dataset responsive to contrast enhancement is that the average contrast enhancement in different imaged anatomies may be the same, and the dataset may be displayed with the same dynamic range for diagnostic analysis. In one embodiment, a method comprises monitoring the contrast enhancement; responsive to a first contrast enhancement being higher than a first threshold, acquiring a first dataset of the imaging subject by transmitting a radiation beam to the imaging subject via a first filter; switching to a different, second filter after acquiring the first dataset; and acquiring a second dataset of the imaging subject by transmitting the radiation beam to the imaging subject via the second filter. In a first example of the method, wherein acquiring the second dataset comprises acquiring the second dataset without additional contrast agent being injected to the imaging subject between the acquisition of the first dataset and the acquisition of the second dataset. A second example of the method optionally includes the first example and further includes wherein both the first filter and the second filter are non-deformable. A third example of the method optionally includes one or more of the first and second examples, and further includes wherein an average contrast enhancement of the injected contrast agent in the imaging subject during the acquisition of the first dataset is substantially the same as an average contrast enhancement of the injected contrast agent in the imaging subject during the acquisition of the second dataset. A fourth example of the method optionally includes one or more of the first through third examples, and further includes, measuring a second contrast enhancement of the injected contrast agent within the imaging subject, and acquiring the second dataset of the imaging subject with the second filter responsive to the second contrast enhancement being less than a second threshold. A fifth example of the method optionally includes one or more of the first through fourth examples, and further includes, wherein both the first threshold and the second threshold are nonzero, and the second threshold is higher than the first threshold. A sixth example of the method optionally includes one or more of the first through fifth examples, and further includes, wherein the first contrast enhancement of the injected contrast agent is a contrast enhancement of the injected contrast agent within a first section of the imaging subject, and the second contrast enhancement of the injected contrast agent is a contrast enhancement of the injected contrast agent within a second section of the imaging subject. A seventh example of the method optionally includes one or more of the first through sixth examples, and further includes, wherein a first section of the imaging subject is imaged while acquiring the first dataset, and a different, second section of the imaging subject is imaged while acquiring the second dataset. An eighth example of the method optionally includes one or more of the first through seventh examples, and further includes, wherein the first section of the imaging subject and the second section of the imaging subject have different anatomies. A ninth example of the method optionally includes one or more of the first through eighth examples, and further includes, 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. A tenth example of the method optionally includes one or more of the first through ninth examples, and further includes, displaying the first dataset and the second dataset simultaneously with a same dynamic range. In a second embodiment, a method comprises measuring a contrast enhancement of an injected contrast agent within an imaging subject; responsive to the contrast enhancement being higher than a first nonzero threshold, acquiring a first number of a first dataset, wherein the first dataset is acquired by transmitting a radiation beam to the first section of the imaging subject via a first filter; switching to a different, second filter after acquiring the first number of the first datasets; acquiring second number of a second dataset by transmitting the radiation beam to a different, second section of the imaging subject via the second filter, wherein the contrast enhancement of the injected contrast agent with in the imaging subject is higher than the first threshold while acquiring the second number of the second datasets. In a first example of the method, the first number is the same as the second number. A second example of the method optionally includes the first example and further includes determining a time point to start acquiring each of the first and second datasets based on the contrast enhancement of the injected contrast agent within the imaging subject. A third example of the method optionally includes one or more of the first and second examples, and further includes wherein the first filter and the second filter are bowtie filters. In a third embodiment, an imaging system comprises a gantry for receiving an imaging subject; a radiation source positioned in the gantry for emitting radiation exposure; a detector positioned on the opposite of the gantry relative to the radiation source; a filter housing mounted to the gantry; a first filter and a second filter positioned in the filter housing; a filter driving system for switching filters by moving filters into or out of the radiation exposure; a motorized table for moving an imaging subject; and a computation device with instructions stored in a non-transient memory, the computation device may execute the instructions to: emit radiation exposure via the radiation source; move the imaging subject via the motorized table at a nonzero speed; while moving the imaging subject, acquire a dataset of the imaging subject by detecting the emitted radiation exposure transmitted through the imaging subject via the detector, wherein a first filter is positioned within the emitted radiation exposure, between the radiation source and the imaging subject; and while acquiring the dataset, estimate the anatomy of the imaging subject, responsive to a change in the anatomy, operate the filter driving system to switch the first filter with the second filter, wherein during filter switching, the radiation source does not emit radiation exposure. In a first example of the imaging system, the computation device may execute the instructions to further monitor a contrast enhancement of an injected contrast agent, and start acquiring the dataset responsive to the contrast enhancement higher than a nonzero threshold. A second example of the imaging system optionally includes the first example and further includes, wherein the filter driving system includes a motor coupled to the first filter and the second filter via a shaft, and switching the first filter with the second filter includes actuating the motor to translate the first filter out of the radiation beam, and translate the second filter into the radiation beam. A third example of the imaging system optionally includes one or more of the first and second examples, and further includes, wherein the first filter is different from the second filter, and the acquired dataset are from a plurality of different anatomies of the imaging subject. A fourth example of the imaging system optionally includes one or more of the first and third examples, and further includes wherein a duration for switching the first filter to the second filter is less than two seconds. As used herein, an element or step recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural of said elements or steps, unless such exclusion is explicitly stated. 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,” “including,” or “having” an element or a plurality of elements having a particular property may include additional such elements not having that property. The terms “including” and “in which” are used as the plain-language equivalents of the respective terms “comprising” and “wherein”. Moreover, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements or a particular positional order on their objects. This written description uses examples to disclose the invention, including the best mode, and also to enable a person of ordinary skill in the relevant art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those of ordinary skill in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. |
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description | This application is a national phase of International Application No. PCT/EP2007/063040, entitled “DEVICE FOR TRANSFERRING NUCLEAR FUEL CARTRIDGES BETWEEN A TRANSPORT CONTAINER AND A STORAGE DEVICE”, which was filed on Nov. 30, 2007, and which claims priority of French Patent Application No. 06 55295, filed Dec. 4, 2006. The present invention relates to a device for transferring nuclear fuel between a transport container and a storage device, and particularly a canister filled with spent nuclear fuel. Within the scope of the management of irradiated fuel, after its use in reactors, said fuel is stored in a pool to be cooled before its evacuation to a storage device while awaiting a definitive outlet, which may be reprocessing or long term storage. The irradiated fuel, which may be in fuel rod form, is stored in sealed canisters forming a first biological barrier. These canisters are then intended to be transported in a transport container to a place of storage comprising a storage housing enabling the cooling of the fuel. Such a transfer of a canister from the transport container to the storage device or conversely from the storage device to the transport container is known from document U.S. Pat. No. 4,780,269. Yet in this document, no biological barrier is provided between the container and the storage device in order to protect the external environment from radiation, particularly the personnel carrying out this transfer. Indeed, it is preferable to provide for a biological protection in addition to that formed by the canister in order to assure maximum safety for the personnel. A sealable connecting device between shielded enclosures is also known from documents FR1 395 783 and GB 2 336 409; however these documents do not disclose how the covers of the enclosures may be withdrawn and isolated from the external environment. Consequently, it is an aim of the present invention to present a device for transferring a nuclear fuel canister between a transport container and a storage device forming a continuous biological barrier between the nuclear fuel and the external environment. The aforementioned aim is attained by a device comprising a body in which is moveably assembled a multifunctional slide capable of assuring the functions of withdrawal of caps from the transport container on the one hand, and from the storage device on the other hand, and transfer of the canister between the transport container and the storage device. In other words, the transfer device forms a slide valve of large size, at least one stage of the slide making it possible to open the transport container and the storage device, and another stage of the slide enabling the actual transfer of the canister from the transport container to the transfer device and vice-versa. Thus, the external environment is never in contact either with the canister, or with the inside of the storage device, or with the inside of the transport container, the transfer device assuring the confinement and limiting the leakage of contaminations. The transfer device forms in itself a biological protection. This moreover comprises sealed devices making it possible to carry out its operations of loading and unloading of storage devices without breakage of confinement. The device according to the invention moreover enables the opening of a transport container and the storage device without breakage of confinement, without need for additional biological protection and without direct human intervention. The transfer device according to the present invention makes it possible in a particularly advantageous manner to carry out a loading or an unloading in the open air; it is not necessary to provide for these manipulations to be carried out within a confined space, the transfer device assuring in combination with the transport container and the storage device the necessary and sufficient confinement of the canister. Moreover, this transfer device has the advantage of being portable and thus of being used for the loading of all the housings of a storage unit. This moreover reduces the cost of the storage. The subject-matter of the present invention is then principally a device for transferring a nuclear fuel canister between a container for transporting said canister and a device for storing said canister, said container comprising a cylindrical cavity for receiving the canister and an opening sealed by a transport plug for the loading/unloading of the canister, said storage device comprising at least one housing to receive said canister and an opening sealed by a storage plug for the loading/unloading of said canister, said transfer device comprising a body and a slide of longitudinal axis, capable of sliding in said body along its longitudinal axis, said slide comprising at least one first compartment to withdraw a plug from the transport container and a plug from the storage device and a second compartment for allowing the canister to pass from the transport container to the storage device and conversely, and means for sealing the transfer between the transport container and the transfer device and between the transfer device and the storage device. In a particularly advantageous example, the transfer device according to the invention also comprises an intermediate compartment between the first and the second compartment, comprising a passage in which are assembled means of withdrawing a biological protection cap contained in the storage device behind the plug, said cap being stored in said passage. The first compartment may comprise an axial passage in which are assembled first means of withdrawing the plug from the transport container and seconds means of withdrawing the plug from the storage device, said withdrawal means being of the bayonet or clamp type, assembled in a sliding manner in said passage, said plugs being stored in said passage during the withdrawal. In one embodiment, the first withdrawal means and the second withdrawal means are assembled head to tail, and are assembled in two chambers isolated from each other, which makes it possible to form a compact slide and avoid a transfer of contamination between the plugs. The second compartment may comprise a passage of diameter greater than that of a canister for allowing a canister to be transferred between the transport container and the storage device via said passage, said diameter being substantially equal to that of the cavity of the transport container and to that of the housing of the storage device, this making it possible to limit impacts on the canister during its transfer. The body of the transfer device may comprise a jacket defining an interior sealed space in which the slide can slide, said jacket comprising lateral end-plates each provided with an opening intended to be facing the cavity of the transport container and an opening intended to be facing the housing of the storage device, and said means for sealing the transfer comprising a first and a second inflatable seal integral with the lateral end-plates surrounding in a continuous manner each of the openings, and each intended to come into contact with one end face of the transport container and with one end face of the storage device respectively. The lateral end-plates comprise advantageously removable panels enabling maintenance, said panels being assembled in a sealed manner in order to assure the sealing of the jacket. For example, the slide is displaced by means of an electric motor. The withdrawal means are for example operated by compressed air, which makes it possible to avoid pollution by oil. A further subject-matter of the present invention is a method of transferring a nuclear fuel canister between a transport container and a storage device by means of a transfer device comprising a slide provided with at least one first compartment for the withdrawal of plugs from the transport container and the storage device, a second compartment for allowing the canister and sealing means to pass between the transfer device and the transport container and the storage device, said method comprising the steps of: a) alignment of the transfer device with the transport container and the storage device, b) alignment of the first compartment of the slide with the cavity of the transport container and a housing of the storage device by moving the slide, c) removal of the transport plug and the storage plug, d) alignment of the second compartment with the cavity of the transport container and said housing of the storage device by moving the slide, e) sliding the canister between the storage device and the transport container. Advantageously, the method according to the invention comprises a step c′) of alignment of intermediate compartment with the cavity of the transport container and said housing of the storage device by moving the slide, and a step c″) of withdrawing a cap contained in said housing set back from the storage plug. The method may also comprise a step of inflating seals borne by the device and in contact with the transport container and the storage device to assure a sealed contact between the transfer device and the transport container and the storage device. During step a), an attachment of the transfer device to the storage device and to the transport container may also be provided for. In FIG. 1, may be seen an example of an embodiment of a transfer device 2 according to the present invention in a state of opening of the transport container. The transfer device according to the present invention is intended to be inserted between a transport container 4 and a storage device 6. The transport container 4 comprises a body 8 provided with a cylindrical cavity 10 to receive a canister of axis X10. The cylindrical cavity 10 emerges from either side of the cylindrical body by a first end (not represented) and a second longitudinal end 10.1. The second end 10.1 is sealed by a removable plug 12, as well as the first end (not represented). The storage device 6 comprises a body 11, in which are formed cylindrical housings 14, 16, 18 of axis X14, X16, X16 parallel to each other. Each housing 14, 16, 18 opens into a front face 20 of the storage device 6 and is sealed respectively by a plug 24, 26, 28. The storage device with three housings is given by way of example, this may comprise more or less than three housings, which may be distributed vertically and/or horizontally. The transfer device 2 comprises a body of longitudinal axis Y intended to be orthogonal to the axes X10, X14, X16, X18. The body comprises a sealed jacket 23 formed by the walls 26 at the longitudinal ends formed by panels, and front and rear lateral end-plates 27, 30 respectively. The panels of the walls 26 are, for example, welded in order to assure a sealing at the longitudinal ends. The lateral end-plates 27, 30, in the example represented, comprise removable panels to enable the maintenance of the transfer device 2. The sealable assembly of the panels is obtained for example by means of O-ring seals (not represented). The jacket 23 delimits a sealed cavity 32 in which is assembled in a sliding manner a slide 34 along the Y axis. The slide 34 is thus never in contact with the external environment. The slide 34 comprises three compartments C1, C2, C3 each comprising a cylindrical passage 25, 27, 29 of axis XC1, XC2, XC3 respectively. The axes XC1, XC2, XC3 are parallel to each other and orthogonal to the Y axis. In an advantageous manner, the transfer device comprises on each of its front lateral faces 27, 30 inflatable seals 35, 37 intended to come into contact with the longitudinal end face of the transport container 4. Any other means capable of assuring a sealing between the transfer device and the transport container and the storage device could be suitable, for example O-ring seals or flexible sleeves. Each seal 35, 37 comprises for example a circular shape intended to border the periphery of the open end 10.1 of the cavity 10 and the open end of a housing 14, 16, 18. Thus the seals 35, 37 assure a continuous confinement. The front 27 and rear 30 end-plates comprise respectively an opening 31, 33 of diameter for allowing the plugs 12, 24, 26, 28 to pass, the openings 31, 33 are aligned along an axis orthogonal to the Y axis. The compartment C1 comprises means 36 to enable the withdrawal of the sealing plug 12 from the transport container 4 and means 38 to enable the withdrawal of the transport plug 24, 26, 28 from the housing 14, 16, 18. Since the withdrawal means 36, 38 are formed similarly, only the withdrawal means 36 will be described in a detailed manner. The withdrawal means 36 comprise a jack 40 movable along the axis XC1 and provided with means 42 of attachment to the plug 12 of the transport container 4. For example these attachment means 42 are of the bayonet type or the clamp type. For example, one free end of the jack 40 comprises at least one pin capable of cooperating with a corresponding pin on an external face 12.1 of the plug 12 by rotation. The jack 40 moves in the direction indicated by the reference F1 to come up against the plug 12. When the attachment of the jack 40 on the plug 12 is made, this slides in the opposite direction along the arrow F2, withdrawing the plug 12 from the end of the cavity 10 and freeing the access to the cavity 10. The jack 40 is advantageously a pneumatic jack, the compressed air supply of which is provided from a nacelle which will be described later. A jack moved electrically could also be envisaged. The internal diameter of the passage 25 is at least equal to the external diameter of the plugs 12, 24, 26, 28 to enable the storage of the plugs 12, 24, 26, 28 in the compartment C1. The withdrawal means 38 comprise in a symmetrical manner a jack 43, assembled head to tail in relation to the jack 40 and operating in a symmetrical manner in relation to a plane P orthogonal to the axis XC1. Thus the jack 43 moves in the direction of the arrow F2 to come up against the plug 24, 26, 28 and moves in the direction F1 to withdraw it and enable access to the housing 14, 16, 18. In an advantageous manner, a wall 44 is provided to isolate the withdrawal means 36 and the withdrawal means 38 so as to delimit two chambers 46, 48 separated in a sealed manner from each other. Thus no contamination borne by the plug 12 may be transferred to the plugs 14, 16, 18 and conversely. The withdrawals of the plug 12 and one of the plugs of the storage device may be successive or simultaneous. The compartment C1 thus enables the withdrawal and the storage of plugs from the transport container and the storage device and their storage. The compartment C2 comprises means of withdrawing 50 a cap 54, 56, 58 assembled in each housing 14, 16, 18 behinds plugs 24, 26, 28 in order to form an additional biological barrier. The withdrawal means 50 also comprise a jack 52 movable axially along the axis XC2 and capable of coming up against, by one free end, an external face of the cap 54, 56, 58. The attachment may be, for example, of the bayonet type or the clamp type. The internal diameter of the passage 27 of the compartment C2 is substantially equal to the external diameter of the biological protection cap 54, 56, 58, to enable its housing in the compartment C2. The compartment C2 thus enables the withdrawal of the biological protection cap 54, 56, 58 from the housing of the storage device and its storage. Similar means to those of the compartment C1 may also be provided for in the case where the transport container comprises a cap identical or similar to that 54, 56, 58 of the storage device. The compartment C3 comprises an empty cylindrical passage to allow the canister to slide from the cavity 10 of the transport device to the housing 14, 16, 18 of the storage device. The internal diameter of the passage 29 is substantially equal to that of the cavity 10 and the housings 14, 16, 18 in order to perform a movement without collision of the canister, thus when the axes X10 of the cavity 10, the XC3 axis of the compartment C3 and the axis X14 or X16 or X18 are aligned, the cavity 10, the passage 29 and the housing 14, 16, 18 form a channel having a substantially continuous cylindrical wall. The risks of impact are thus minimised. The slide 34 is advantageously moved by an electric motor and rack system. A pneumatic motor may also be envisaged. Thanks to the present invention, a continuity of the biological barrier is thus perfectly assured by forming a sealed passage for the transfer of the canister and by assuring the confinement of the plugs and biological protection caps, any transfer with the external environment being avoided. According to the present invention, it is also provided to check the sealing of the contact between the inflatable seals 35, 37 and the transport container and the storage device respectively by means well known to those skilled in the art, of the pressure increase type. A vacuum is formed in the zone delimited by the inflatable seal supposed to be sealed and the pressure is checked. If it increases, the contact is not sealed and maintenance is required. Moreover, a checking of the sealed assembly of the end-plates of the body during their assembly is provided for. The transfer device according to the present invention is, for example, intended to be assembled on a nacelle (not represented) on which will be deposited the transport container 4 in contact with the front end-plate 27 of the transfer device, so as to align the axis X10 of the cavity 10 with the opening axis 31 provided in the front end-plate 27. Thus the transfer device 2 and the transport container 4 are immobile in relation to each other. Advantageously, removable linking means (not represented) between the container 4 and the transfer device 2 are provided to avoid any movement between them. The nacelle can, for its part, move horizontally and vertically in order to align the axis of the opening made in the rear end-plate of the transfer device 2 with an axis X14, X16, X18 with a housing 14, 16, 18 respectively of the storage device 6. Removable linking means (not represented) between the storage device and the transfer device are also provided, in an advantageous manner, to avoid any movement between them. The operation of the transfer device according to the present invention will now be explained. By way of non limiting example, it will be considered that it is wished to store the canister in the housing 14. In an advantageous manner, the transfer device 2 is fastened to the storage device 6, during the operations of transferring the canister. Moreover, it is supported by the nacelle. To do this, the nacelle is moved in direction of the storage device 6 until the rear end-plate 30 is placed parallel to the front face of the storage device 6, so that the inflatable seal 37 comes into contact with the front face of the storage device 6. Before inflating the seal 37, the axis of the rear opening 33 is aligned with that of the housing 14. The transport container loaded with a canister is placed on the platform of the nacelle so as to align the axis X10 of the cavity 10 and the axis of the front opening 31, guiding means may be provided for this purpose on the platform of the nacelle. The container may be placed on the nacelle before it comes up against the storage device. The end face of the transport container 4 is placed sufficiently near to the front end-plate 27, so that the inflatable seal 35 borne by the front end-plate 27 comes into contact with the end face of the transport container 4 and forms a sealed zone around the front opening 31. The inflating of the seal 35 is carried out after the transport container 4 is put in place. The slide 34 is then moved along the Y axis, so as to align the axis XC1 of the compartment C1 with those of the front 31 and rear 33 openings. The means of withdrawing 36, 38 the plugs are successively or simultaneously operated to withdraw the plugs 12 and 24 as may be seen in FIG. 1. Then the slide 34 is moved along the Y axis upwards until the axis XC2 is aligned with the axes X14. The withdrawal means are then operated and the biological protection cap is withdrawn and stored in the passage 27, as is represented in FIG. 2. The slide 34 is again moved upwards to align the XC3 axis with the axes X10 and X14. The canister is then moved from the cavity 10 to the housing 14 by sliding, for example by means of a jack that applies a pushing thrust on the canister. Traction means passing through the housing 14 and the passage 29 and attached to the canister could be envisaged. When the canister is placed in the housing 14, the steps of putting back in place the biological protection cap then the plugs are carried out in a reverse manner to those described above. For the loading of the other housings 16, 18, the same operating procedure is carried out. For the withdrawal of the canisters from the housings 14, 16, 18 the same procedure is used except that, when the compartment C3 is aligned with the cavity 10 and the housing concerned, the canister is transferred from the housing of the storage device to the transport container. At the end of the transfer operation, the transfer device is dissociated from the storage device, the nacelle is then freed. Control means are provided inside the transfer device, these are advantageously visual, for example of the camera type, to check the position of the jacks and the state of removal of the plugs and the biological protection caps. The control of the slide 34 is conducted by an operator, who orders the sliding of the slide 34 after having validated the end of the operation underway. Likewise, it is the operator who manages the withdrawal of the plugs, caps and the transfer of the canister. An automatic sequencing of the different steps could also be envisaged. In the case where the biological protection cap 54, 56, 58 is not provided for or is removable in a different manner, a transfer device only comprising two compartments, the compartment for the withdrawal of the plug from the transport container and the plug from the housing of the storage device, and the compartment for the transfer of the canister do not fall outside of the scope of the present invention. A transfer device wherein the withdrawal of the plug 12 and the withdrawal of the plug 24, 26, 28 takes place in two separate compartments also does not fall outside the scope of the present invention. A transfer device comprising more than three compartments and/or comprising compartments assuring other functions also does not fall outside the scope of the present invention. The method of transferring a canister between the storage device and the transport container by means of the transfer device according to the present invention comprises the steps of: alignment of the cavity 10 and the housing 14 of the storage device to be loaded or unloaded with the openings 31, 33 of the transfer device, alignment of the compartment C1 with the cavity 10 and the housing 14, removal of the plugs 12, 24, alignment of the compartment C2 with the cavity 10 and the housing 14, if the housing 14 comprises a cap 54, removal of the cap 54, if necessary, alignment of the compartment C3 with the cavity 10 and the housing 14 and transfer of the canister from the cavity 10 to the housing 14 or from the housing 14 to the cavity 10. It may be provided, after the first step, to immobilise the transfer device on the storage device and on the transport container. A device making it possible to transfer, in a safe manner, the nuclear fuel contained in a canister between a transport container and a storage device has thus been produced. |
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description | This invention relates to the field of substrate processing. More particularly, this invention relates to using integrated circuit yield information to identify and correct integrated circuit fabrication problems. Modern integrated circuits are extremely complex devices that are fabricated using equally complex processes. As the term is used herein, “integrated circuit” includes devices such as those formed on monolithic semiconducting substrates, such as those formed of group IV materials like silicon or germanium, or group III–V compounds like gallium arsenide, or mixtures of such materials. The term includes all types of devices formed, such as memory and logic, and all designs of such devices, such as MOS and bipolar. The term also comprehends applications such as flat panel displays, solar cells, and charge coupled devices. Because of the complexity of integrated circuits and the processes by which they are formed, it can be extremely difficult to determine the reasons why some devices function properly and other devices function improperly, or fail altogether. Integrated circuits are typically manufactured on thin silicon substrates, commonly referred to as wafers. The wafer is divided up onto smaller rectangular sections for each device, typically known as the die or device. The methods and other embodiments according to the present invention can be applied to processes that are performed on other substrates to make other devices or components, such as flat panel display manufacturing, which is performed on rectangular glass substrates. Thus, this disclosure generally refers to substrates, substrate profiles, and substrate contact points, even though silicon wafer processing may be the most common application for the embodiments of the invention. It is appreciated that the same or similar methods are just as applicable to the analysis of a wide variety of substrates. Wafer test yield of die, or simply yield, is predominantly used as an example herein of an important dependent variable of interest. However, it is appreciated that any other dependent variable that is spatially associated with the substrate can also be used. One method to assist in failure analysis is mapping important variables, such as yield, according to the position at which the variable is read on the substrate. Wafer mapping, for example, has traditionally been done by plotting the pass/fail data (i.e. yield) or other variable of interest versus the die position on the wafer. These wafer maps can be enhanced by combining values from many wafers in what is known as a stacked map. Recently there have been improvements in substrate mapping that can combine data from many wafers and many devices into what is known as a high-resolution wafer profile. Such substrate profiles are created from databases of information that is associated with substrates. A graphical representation is developed from the information, which representation depicts the yield or other variable read from the devices on the substrate, according to their position on the substrate. Substrate profiles such as these look somewhat like a topographical map, where the various contours of the profile delineate areas of different average (or otherwise computed) yield or other measured variable of interest for the devices bounded by those contours on the substrates. Such substrate profiles are used by manually inspecting the substrate profile, and thinking about what might be responsible for the patterns depicted in the profile. Obviously, for this method to work at all, some knowledge of the equipment, processes, and methods that are used to process the substrates is required. As the person reviewing the profile acquires greater knowledge of the fabrication process, the interpretation of the information presented in the substrate profile becomes commensurately more accurate and beneficial. Unfortunately, such a method of reviewing a substrate profile tends to be extremely inefficient. For example, the reviewer may not have the experience needed to identify the patterns caused by different process problems. Even if the reviewer does have a relatively high level of experience, the mundane and repetitive nature of the job may lead to lack-of-attention errors in interpreting the profiles. Further, the amount of information that is compiled in a substrate profile tends to both obscure some problems and confound other problems. What is needed, therefore, is a system for constructing, using, and interpreting substrate profiles that reduces some of the problems mentioned above. The above and other needs are met by a system for analyzing fabrication processes, such as analyzing device yield on a substrate. An input accesses fabrication information, such as the substrate processing history, fabrication equipment used, measurement information, and device yield. The fabrication information includes at least one dependent variable that is associated with substrate location information, and at least one independent variable that is associated with at least one of the fabrication processes. Desired portions of the fabrication information are selected, based on at least one of the independent variable and the dependent variable. A substrate profile is produced, based on the desired portions of the fabrication information. In this manner, a substrate profile is produced based on information that is selectable by either the person interacting with the system, or by the system itself, such as by acting on programmed instructions. Thus, for example, the fabrication information input to the system can include or exclude certain pieces of processing equipment, or can include or exclude certain measured characteristics of the substrate. By so doing, the person reviewing the substrate profile can quickly determine the effects of certain independent variables on the yield or other dependent variable profile of the substrate. Thus, confounding influences, which are typically present in a substrate profile, can be isolated as to their source. In various embodiments, the independent variable includes at least one of time frame during which substrates were processed from which the fabrication information was gathered, equipment on which the substrates were processed, and recipes used for processing the substrates. The dependent variable preferably include at least one of measured physical characteristics of substrates from which the fabrication information was gathered, measured electrical characteristics of the substrates, and defect inspection information of the substrates. Means are preferably provided for storing the substrate profile in association with the desired portions of the fabrication information. Preferably, there are means provided for adjusting the substrate profile, including at least one of adjusting a resolution of the substrate profile, smoothing contours of the substrate profile, adjusting a coordinate system of the substrate profile, and adjusting the substrate profile based on simulations of the fabrication processes. The system is preferably adapted to automatically and graphically compare the substrate profile to a database of historical substrate profiles, where the historical substrate profiles have known associated processing conditions. A profile analysis table is preferably presented, which has columns of combinations of the fabrication information. Each column preferably includes: (1) a substrate profile produced using the fabrication information for a given one of the columns of combinations; (2) a summary of the fabrication information for the given one of the columns of combinations, and (3) an indication of a degree of similarity between the given one of the columns of combinations and a selected substrate profile. According to the preferred embodiments of the present invention, a user's ability to identify unique patterns in substrate profiles and associate the patterns with the source of the patterns is enhanced through the use of a database, which preferably includes substrate profiles, and which can be quickly and selectively manipulated to generate for comparison many variations and subsets of the substrate profiles. A method for selecting and displaying for comparison the profiles generated by the system is also disclosed. The system enables the user to compare patterns to each other and to the overall substrate profile. It is also enables automatic comparisons and rankings of the degree to which profiles match each other. A central aspect of the preferred system according to the present invention is a fabrication information database that enables a user or computer-driven comparison algorithm to quickly compare substrate profiles one to another, to determine how well the profile patterns match. The database preferably contains the data used to generate the substrate profiles, such as substrate test data, measurement data, or defect inspection data, which information is considered to be dependent variables, as the term is used herein. The dependent data tends to be specific to individual devices on the substrate, or to other discrete locations on the substrate, and thus all such dependent variables are most preferably stored in the database in association with location information for the substrate, such as x and y coordinates. The dependent variables are generally referred to as yield or yield information herein. In addition, the database preferably contains information about the substrate fabrication processes that result in the substrate profile appearing the way that it does. For semiconductor substrate manufacturing this is commonly known as the lot or substrate history. The lot or substrate history includes data associated with the process tools, recipes, and other manufacturing conditions that were used on a given substrate or lot at the various steps of its manufacturing process. As used herein, this information is referred to as independent variables. The independent variables typically do not have location information associated with them, because the independent variables typically apply as a group to an entire substrate, such as the piece of equipment that the substrate was processed through, or the time at which the processing occurred. However, some independent variables can have location information associated with them. With this combination of fabrication information, substrate profiles can be quickly produced. The database preferably enables substrate profiles to be calculated using different subsets of the data, most preferably based on a selection of the independent variables. For example, the substrate profile can be calculated based only on the substrates that went through a certain process tool. This profile can be compared to the profile of the substrates that went through a different process tool, to see which tool has the best yield, or if one tool has an undesirable yield pattern. This approach can be very useful in identifying the source of a pattern that is causing yield loss. It is appreciated that the substrate profiles can be produced based on different dependent variables also. For example, the substrate profiles produced using the selection of independent variables as given in the example above can also be based on one or more electrical characteristic of the devices as measured at final test. In this manner, the effects of different processing tools on specific electrical parameters can also be visually determined using the substrate profiles as described herein. Thus, an overall pass/fail designation for the devices is not the only dependent variable on which the substrate profiles can be based. There are preferably three major types of variables that are used for generating substrate profiles. These variables are preferably manipulated to create useful versions of the substrate profiles. These manipulated variables are (1) data selection, (2) measurement basis, and (3) profile calculation. These are described in more detail below. Data selection is the subset of data that is included in the calculation by which the substrate profile is produced. The data can preferably be selected in many different ways, such as limiting to a certain time frame, processing tool, process recipe, and so forth. Any subset of the original data that defines how substrates were processed can preferably be used in this way. It can preferably selectively include combinations of tools or different process recipes. This method generally equates to the selection of independent variables, as the concept of such is introduced above. Measurement basis is the measurement that the substrate profile is calculated for. There are many different types of measurements that can be used, such as the substrate sort test bin, film thickness measurements, or substrate defect inspection data. This method generally equates to the selection of dependent variables, as the concept of such is introduced above. The profile calculation method is a variation in the calculation, such as the resolution at which the substrate profile is produced, smoothing algorithms used for the contours of the substrate profile, or coordinate assignment algorithms used to overlay the data used in producing the substrate profile. This type of manipulation could also include algorithmically modifying selected portions of the substrate profile, so that it simulates what a substrate profile would look like for substrates that were processed according to a theoretical process flow, or otherwise subjected to a selected combination of processing conditions. The profile manipulations can thereby be used either individually or in combination to create various profiles of interest. Profile manipulations are applied to substrate profiles that are generated using one of the two methods described above. Examples of how these manipulations are accomplished are described in greater detail below. Data Selection Method In this example, substrate profiles are preferably created from subsets of the entire dataset, which subsets preferably include substrates run only in specific tools or processes. For example, only the substrates that went through etcher A at a given process step are used to generate one of the substrate profiles. This substrate profile is then compared to a substrate profile for all etchers, or to a substrate profile generated from all of the substrates that were processed on etcher B. FIG. 1 shows how such profiles might differ. As depicted in FIG. 1A, a substrate profile 100 depicts the profile for a combination of tools. The substrate 10 is represented with various gradient lines 12 that depict regions of differing dependent variable values. For example, region 14 may represent an area on the substrate 10 that generally has a lower yield than those devices that are disposed within region 16 on the various substrates 10 that were included in the substrate profile 100 as depicted. Further, central region 18 may depict a region of very low yield for the dependent variable or variables selected for the substrate profile 100. Because the substrate profile 100 as depicted in FIG. 1A is for all tools, it is impossible to tell from the substrate profile 100 of FIG. 1A whether the region 18 of very low yield is dependent on one or more of the tools or some other independent variable. According to the prior art for substrate profiles, such a confounding and obscuring of the source of the yield problem in region 18 would go unresolved by reference only to the prior art substrate profile. However, according to the preferred methods of the present invention, the substrate profile 100 can be recomputed using different selections of the independent variables, such as the tool used to process the substrates, so as to resolve the source of the yield problem indicated by region 18. FIG. 1B depicts the substrate profile 100 for just tool A, and FIG. 1C depicts the substrate profile 100 for just tool B. By comparing the substrate profile 100 for tool A to the substrate profile 100 for tool B, it is readily seen that the region 18 of low yield is produced solely within tool A. Thus, it is readily determined that tool A has a problem, and tool B does not—at least not in regard to the region 18. Measurement Basis Method Many of the measurement tools that are used during substrate processing are capable of measuring across the substrate surface and associating a die or other substrate position, such as an x-y coordinate, to the measurement. This information is preferably translated into a common substrate profile coordinate system. An example of this type of data is gate oxide thickness measurements from an ellipsometer. In general, any measurable or tested parameter that can be associated with a location on the substrate can be converted into a substrate profile. One type of data that fits this criteria is generated by automated defect inspection equipment. Such defect inspection maps are preferably converted to the substrate profile format with contour lines, so that they can be compared against other types of substrate profiles. FIG. 2A depicts an example of a defect inspection map after a chemical mechanical polishing process, where a problem is occurring due to the water jet pressure being set too high on the right side of the substrate. The defect inspection map depicted in FIG. 2A depicts individual dice 20 and discrete defects 22. However, because the information in the defect inspection map has location information associated with it, the information from a database of defect inspection maps can be converted into a substrate profile as depicted in FIG. 2B. As depicted in FIG. 2B, the regions 24 of reduced yield are quite evident when presented in the substrate profile 100 format. After the information is converted to a substrate profile format, all of the applicable methods for analyzing profiles described herein can be applied to the measurement based data. Profile Calculation Method The profile calculation method preferably includes modifying the data that is used to create the substrate profile, so as to simulate the presence of a problem. Substrate profiles are preferably first created using normal methods or a selectable subset of the database. The resulting substrate profile as given in FIG. 3A is then preferably modified to show what the overall substrate profile would look like if a specific problem were to occur. For example, the substrate profile 100 as given in FIG. 3A can be combined with the substrate profile 100 as depicted in FIG. 3B, which depicts the water jet problems as discussed above, to produce the substrate profile 100 as depicted in FIG. 3C. This process can be useful, for example, to monitor for damage that occurs near a point where equipment touches the edge of the substrate, if the substrate handling is miss adjusted. Thus, if the effect of a problem has been seen before, the substrate profile signature for the problem can be combined into a model that modifies a clean or current reference profile. The model could be produced in many ways. For example, a simple cell by cell averaging is used in the example depicted in FIG. 3C. Profile Analysis Table A user interface called a Profile Analysis Table 400 as depicted in FIG. 4 is preferably employed to generate and use the substrate profiles 100. The Profile Analysis Table 400 preferably organizes images of the substrate profiles 100 into columns 402 and rows 408, with an indication of how they are generated (such as the data selection and profile calculation methods) given in row 412, with summaries of the variable selections given in rows 406. An indication of the degree of similarity between the substrate profile 100 of a given column 402 and a selected substrate profile is preferably provided for each column 402, such as in row 410. The graphical images are arranged in rows that represent a common measurement basis for easy comparison of profiles that are produced with a different data selection or profile calculation. In a most preferred embodiment, the various substrate profiles 100 as described herein are all saved in a graphical format in the database. Thus, when a new substrate profile 100 is generated, it can be automatically compared to the existing substrate profiles 100 under the control of the system, such as by using image comparison techniques. Thus, as depicted in FIG. 4, the system itself can provide an indication of how well different substrate profiles 100 compare to each other, and thus the system itself can provide an initial diagnosis of any problems that may be evident in the newly constructed substrate profile 100. This is preferably accomplished by matching graphical elements between new and old substrate profiles 100, where the graphical features of the old substrate profiles 100 have preferably been identified as to their source. The method as described herein can be implemented in a variety of different ways. Although the system can be implemented manually, where the substrate profiles are manually computed and stored, such a system would tend to be at the lower end of the range of utility that can be provided by the system. Alternately, the system can be implemented as a dedicated hardware and software system, capable only of producing the substrate profiles and tables as described herein. Most preferably, however, the system is implemented on a general computing platform, such as a personal computer. In various embodiments, the system is distributed across a computer network, with various functional units of the system disposed on different physical platforms that are all logically coupled through the network. FIG. 5 depicts a functional block diagram of a preferred embodiment of the system 500 according to the present invention. The system 500 preferably includes a database 502 that contains all of the fabrication information as described above. An input 504 provides for communication between the various elements of the system 500, such as communication to the database 502. A selector 506 selects various portions of the information that is resident in the database 502. Most preferably, the selections are made such as through a human interface 508, such as a mouse or a keyboard. The substrate profiles 100 and other information and controls are preferably presented such as on a display 510. A controller 512 is preferably programmed to perform the calculation of the substrate profiles 100 as described above. The various elements preferably communicate one with another such as through a buss or network 514. The controller 512 is preferably adapted to adjust the substrate profiles 100, such as under the control of a user through the interface 508, or under the control of a preprogrammed recipe. In various embodiments the resolution at which the substrate profiles 100 are calculated or displayed is adjustable. In addition, the algorithms used to smooth the contours between regions of the substrate profiles 100 are preferably also selectable and adjustable. Further, the substrate profiles 100 are preferably adjustable as to the coordinate system used for the substrate profiles 100, or in other words the location information that is used to construct the substrate profiles 100. In summary, the database preferably contains image, substrate test data, substrate measurement data, substrate inspection data, and associated substrate processing and location information, so that substrate profiles can be quickly generated, reviewed and compared. The Profile Analysis Table facilitates working with substrate profiles, for purposes such as comparing and identifying patterns caused by variables in the substrate processing. A substrate profile can be generated from a subset of the data, so that the maps resulting from processing differences can be compared to one another. Substrate profiles can be modified with a model so that they simulate the profile that would be expected from a processing difference. Model modified profiles can be based on a dynamic substrate profile that is generated automatically from recent fabrication data. Substrate profiles can be created with a common coordinate system from defect inspection data, so that they can be compared to profiles generated such as by substrate test, substrate measurement, model modified, or other means. Substrate profiles are preferably created with a common coordinate system from substrate measurement data, so that they can be compared to profiles generated by substrate test, substrate inspection, model modified, or other means. A difference profile can be created for profile comparisons, where one or more profiles are subtracted from each other. Thus, the system according to the preferred embodiments of the present invention enables users to quickly generate and compare substrate profiles, to determine what substrate processing affects which profile. Users can quickly see what substrate profiles exist, and use the system to quickly track down the source of undesirable patterns. The system preferably provides automatic comparisons and quantitative matching so that known profile-effecting mechanisms can be detected quickly, thereby enabling a faster response and reducing the number of integrated circuits effected. The foregoing description of preferred embodiments for this 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. Obvious modifications or variations are possible in light of the above teachings. The embodiments are chosen and described in an effort to provide the best illustrations of the principles of the invention and its practical application, and to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled. |
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052805069 | description | DESCRIPTION OF THE PREFERRED EMBODIMENTS For a better understanding of the present invention, general aspect and conventional art of the present invention will be first described with reference to FIGS. 18 to 20. First, referring to FIG. 18, generally, in a boiling water reactor (BWR) plant, a reactor pressure vessel 1 is directly connected to a steam turbine 3 through a plurality, four for example in the illustration, of main steam lines 2, and first and second main steam isolation valves 5 and 6 are incorporated to each of the main steam lines 2 inside and outside of the reactor container 4. The reactor pressure vessel 1 is isolated as occasion demands by closing the main steam isolation valves 5 and 6. The steam used in the steam turbine 3 is condensed into condensate in a condenser 7 and the condensate is then returned to the reactor pressure vessel 1 through a condensate return line 8. In FIG. 18, a third main steam valve 9 is also incorporated on the way of the steam line 2, and reference numeral 10 denotes a header. Referring to FIG. 19, in a conventional main steam isolation valve 5 or 6 provided with a valve body 11, inlet and outlet end portions 11a and 11b of the valve body 11 are connected to each of the main steam lines 2 and a cylindrical valve disk 12 is accommodated in a valve disk accommodation portion 11c of the valve body 11 in an axially reciprocal manner. The valve disk 12 is provided with a valve shaft 13 which extends and is inclined inwardly, in an illustrated and installed state, by about 45.degree. with respect to the flow direction, arrowed in FIG. 19, of the main steam thereby to reduce flow resistance. The valve shaft is connected at one end to a driving means 14 to move reciprocatingly the valve disk 12 thereby to open or close the fluid passage. As shown in FIG. 20, the reciprocating motion of the valve disk 12 is guided by means of a central guide rib 15 and a bilaterally pair of side guide ribs 16a and 16b inwardly projecting at rear side portions of the valve body 11 circumferentially apart from the central guide rib 15 with a separation angle of about 120.degree. with each other. In such a structure, when the valve disk 12 is rested on a valve seat 17, the valve disk 12 is fully closed and the valve disk 12 is upwardly lifted thereby to fully open a valve port. The conventional structure of the main steam isolation valve, however, involves problems or defects described hereinbefore. Accordingly, the present invention conceived for substantially eliminating the described problems or defects encountered in the prior art will be described hereunder by way of preferred embodiments in conjunction with FIGS. 1 to 17, in which like reference numerals are added to those elements or members corresponding to those of the respective embodiments. FIG. 1 shows a longitudinal sectional view of a first embodiment of the main steam isolation valve according to the present invention. Referring to FIG. 1, a main steam isolation valve 21 includes a valve body 22 having a valve disk accommodation portion 22a in which a valve disk 23 is accommodated. The valve body 22 is provided with inlet and outlet end portions 22b and 22c connected to the main steam line 2, FIG. 18, and the main steam flows as shown by arrows from the inlet end portion 22b towards the outlet end portion 22c in the valve body 22. The valve disk 23 is composed of a bottomed cylindrical member and accommodated in the portion 22a so that a valve shaft 24 connected to the central portion of the bottom of the valve disk 23 inwardly, as viewed, i.e. in a steam flow direction, inclines by about 45.degree. with respect to the axis of the inlet end portion 22b. A flange portion 25 is formed to the upper, as viewed, end of the valve disk accommodation portion 22a to air-tightly close the opening thereof. A valve disk driving mechanism 26 is mounted to the flange portion 25 and comprises an output shaft 26a connected to the valve shaft 24 thereby to reciprocate the valve disk 23 in the axial direction thereof along the inner peripheral surface of the valve body 22 to open or close a valve port, i.e. fluid passage. Namely, as shown in FIG. 1, when the driving mechanism 26 is actuated to obliquely lift the valve disk 23, the valve port is fully opened, whereas when the valve disk 23 is seated on a valve seat 27 disposed around the valve port, the valve port is fully closed. Such reciprocating motion of the valve disk 23 is guided by a central guide rib 28 and a pair of side guide ribs disposed apart, in a circumferential direction of the valve disk 23, from the central guide rib 28 with a separation angle of about 120.degree. with each other. A coupling 29 is secured to the valve body 22 and detachably fitted to the opening of the valve disk 23 so as to abut against the flange portion 25. Referring to FIGS. 2A and 2B, the valve disk 23 has a bottomed cylindrical shape and has an upper open end having an inner tapered surface 23a. As shown in FIG. 1, the coupling 29 has a cylindrical body 29a having a lower open end portion having an outer tapered surface having a shape in conformity with the shape of the tapered surface 23a of the valve disk 23. Accordingly, when the coupling 29 is fitted into the valve plug 23, both the tapered surfaces 23a and 26a are engaged with each other. According to such a structure, when the valve disk 23 is fully open, the upper open end thereof is fixedly engaged with the coupling 26 and the valve disk 23 is secured to the valve body 22 through the coupling 29 and the flange portion 25, so that, when the valve disk 23 is fully opened, the oscillation thereof is significantly reduced even if the lower portion of the valve disk 23 projects towards the main steam passage. Accordingly, the friction of the valve disk 23, the central guide rib 28 and the side guide ribs caused by the oscillation of the valve disk 23 are reduced, resulting in the reduction of the wearing thereof, thus preventing the fluid from leaking during the fully closing operation of the main steam isolation valve 21. The coupling 29 may be formed as shown in FIGS. 3, 5 and 6 by reference numeral 30. Namely, referring to FIGS. 3 and 4, a tapered surface 30b is formed to the inner peripheral portion of a cylindrical body 30a of the coupling 30 and an outer tapered surface 23b is formed to the outer peripheral portion of the upper open end portion of the valve disk 23 so as to be firmly engaged with the inner tapered surface 30b of the coupling body 30a. In this modified embodiment, substantially the same effects as those described hereinbefore can be attained. As shown in FIGS. 6A and 6B, the coupling 30 may be composed of a plurality of arcuate coupling compartments each having a tapered surface as described above. FIGS. 7 and 8 represent a second embodiment of the main steam isolation valve 31, the driving means of the structure shown in FIG. 1 being eliminated, in which FIG. 7 is a longitudinal section thereof and FIG. 8 is a sectional view taken along the line VIII--VIII of FIG. 7. In the second embodiment, as shown in FIGS. 7 and 8, the main steam isolation valve 31 has such main feature as that a tubular wall 32 is provided integrally with the valve body 22 so as to surround the outer periphery of the valve disk with a slight gap therebetween. Namely, as shown in FIG. 8, the tubular wall 32 extends rearwardly, leftwardly as viewed, along the peripheral surface of the valve disk 23 and is integrated with the valve body 22 at the rear end portion of the tubular wall 32. According to this structure, since substantially the entire structure of the valve disk 23 is accommodated in the tubular wall 32 in the fully opened state of the valve disk 23, the direct striking of the steam flow on the valve disk 23 can be prevented, thus reducing the oscillation of the valve disk 23. This results in the reduction of the friction between the valve disk 23 and the central and side guide ribs, thus also reducing the wearing. Accordingly, the fluid can be prevented from leaking during the fully closing operation of the valve disk 23, thus improving the reliance of the valve disk 23 and, hence, the main steam isolation valve 31. In a modification shown in FIG. 9, the valve disk 23 may be formed so as to have outwardly arcuate bottom 33 thereby to effectively reduce resistance against the steam flow striking the outwardly protruded bottom 33 of the valve disk 23, thus stabilizing the steam flow and hence further improving the oscillation suppressing performance. FIG. 10 is a view similar to that of FIG. 8 and represents a third embodiment of a main steam isolation valve 41 according to the present invention. Referring to FIG. 10, reference numerals 42a and 42b denote fluid passages in the valve body 22 with the guide rib 28 being disposed at the central position of the passages. In this embodiment, one side peripheral wall of the valve body 22, on the side of the fluid passage 42a in the illustration, is formed to be thick. Namely, an inwardly protruded portion 43 is integrally formed to the valve body 22 and the cross sectional flow area of the passage 42a is hence made smaller than that of the passage 42a, thus providing bilaterally asymmetric cross sectional area. In FIG. 10, reference numerals 44a and 44b denote a pair of side guide ribs for guiding the reciprocating motion of the valve disk 23 at the rear portion thereof. The side guide ribs 44a and 44b are formed integrally with the inner surface of the valve body 22 and disposed circumferentially apart from each other with a separation angle of about 120.degree. with the center being the central guide rib 28. According to this embodiment, when the main steam isolation valve 41 is fully opened, the flow velocity of the main steam passing the fluid passage 42a is made always lower than that flowing in the fluid passage 42a and, accordingly, the static pressure in the fluid passage 42b is always high. For this reason, there always causes one-sidedly unidirectional force for forcing the valve disk 23 from the passage 42b of high static pressure side towards the passage 42a of low static pressure side, so that the oscillation of the valve disk 23 reciprocating between these passages 42a and 42b can be then suppressed. In a further modification, it may be possible to form a protruded portion to the central guide rib 28a as shown in FIG. 11 instead of the location of the protruded portion 43 of FIG. 10. Referring to FIG. 11, the central guide rib 28a has a bilaterally asymmetric shape of substantially triangle so as to have a portion on the side of the fluid passage 42a having a sectional area smaller than that of a portion on the side of the other fluid passage 42b. Accordingly, this embodiment can attain substantially the same effect as that attained by the main steam isolation valve 41. The shape of the central guide rib 28a is not limited to such triangular shape and other modifications may be made as far as substantially the same effect is attained. FIGS. 12 and 13 represents further modifications of the central guide ribs of the present invention in which like reference numerals are added to elements or members corresponding to those used for the disclosure of the aforementioned embodiments or modifications. Referring to FIG. 12, the central guide rib 28b is disposed on the side of the steam flow passage 42a from the central portion of the flow passages 42a and 42b. According to this modified embodiment of the central guide rib 28b, substantially the same effect as that attained by the embodiment represented by FIG. 10 or 11 can be attained. Referring to FIG. 13, two central guide ribs 28c and 28d are arranged to the front, rightward as viewed, side of the valve disk 23 in symmetrical arrangement with respect to the valve shaft 24. According to this structure, the fluid pressure of the main steam is made stable between the two central guide ribs 28c and 28d, whereby the oscillation of the valve disk 23 can be significantly suppressed. FIG. 14 represents a fourth embodiment of the main steam isolation valve 51 according to the present invention, in which an inlet end portion 52a of a valve body 52 of the main steam isolation valve 51 stands vertically, as viewed, so as to be substantially parallel to side walls of the reactor pressure vessel 1 and the reactor container 4 (FIG. 18) and an outlet end portion 52b is mounted to a horizontally near portion with a predetermined angle. In this embodiment, the inlet side duct 53 connected to the inlet end portion 52a can be constructed to have a long length and it is also possible to make large a bent angle of an outlet side duct 54 connected to the outlet end portion 52b. According to these structures, the variation of pressure of the main steam flowing in the valve body 52 can be effectively made small, thus suppressing the oscillation of the valve disk 23. It is to be noted that the embodiment of FIG. 14 may be applied to the afore- mentioned embodiments. FIG. 15 shows an arrangement of the main steam isolation valve 51 shown in FIG. 14, in which the isolation valve 51 stands vertically so as to be substantially parallel to the side walls of the reactor pressure vessel 1 and the reactor container 4 (FIG. 18), and the valve shaft 24 is directed to the circumferential direction of the reactor pressure vessel 1. According to such arrangement, the length of the inlet side duct 53 is made sufficiently long and the bent angle of the outlet side duct 54 can be made large, whereby the variation of pressure of the main steam flowing in the valve box 54 can be significantly reduced and the oscillation of the valve disk 23 can be hence suppressed. FIG. 16 shows a portion of the valve body 22 in which the paired side guide ribs 44a and 44b are provided with cutout slits 60 for escaping pressure along the circumferential direction of the valve disk accommodation portion 22a. These slits 60 are formed to the side guide ribs 44a and 44b in their longitudinal directions with predetermined pitches. According to this structure, the main steam flows between the inner peripheral surface of the valve body 22 and the rear side of the valve disk 23 through the slits 60, thus the pressure of the main steam being made substantially even. Accordingly, the force for forcing the valve disk 23 against the side guide ribs 44a and 44b can be reduced, resulting in the reduction of the friction and wear between the side guide ribs 44a and 44b and the outer rear peripheral surface of the valve disk 23 and preventing the main steam from leaking at the time of fully closing the valve, and the reliance of the main steam isolation valve can be hence improved. As shown in FIG. 17, the valve disk 23 may be formed so that the valve disk body 23a thereof has a drum shape having a reduced diameter from the end portions towards the axially central portion thereof. According to this structure, the main steam is flows, as indicated by arrows, towards the rear side of the valve plug disk body 23a, i.e. the paired side guide rib sides, through the reduced diameter portion of the valve plug disk body 23a, whereby the pressure of the main steam can thus be made even and substantially the same effects as those described with reference to FIG. 16 can be achieved. It is to be understood that the present invention is not limited to the described embodiments and modifications and many other changes and modifications may be made without departing from the scopes of the appended claims. For example, embodiments or modifications constituted by the combinations of the described embodiments and modifications may be within the scope of the present inventions. |
039708551 | description | DETAILED DESCRIPTION OF THE INVENTION An embodiment of an unfatigued substrate positron probe is shown in FIG. 1. Positron-emitting radioactive material 10, such as sodium 22 chloride, or cobalt 58, for example, is placed on a substrate 12 and covered with a thin cover 14 which acts as a window for the emitted positrons. The window 14 is any low-density material which can act as a seal for the radioactive material 10 and yet will not significantly impede the passage of the positrons. A thin layer of vacuum-deposited metal or a thin layer of polymer film may be employed. The substrate 12 is fabricated from the same material on which fatigue studies are to be made, and the substrate material is in the "as received" (unfatigued) condition. In use, the probe is placed against the material on which the fatigue studies are to be made with the material abutting the upper surface of the window 14. When a positron is emitted from the radioactive material, a nuclear gamma ray (NGR) is emitted at approximately the same time. A pair of scintillation detectors (not shown) are used, one of which records the emission of the NGR. A second scintillation detector records the emission of the gamma ray produced by the annihilation of the positron when it collides with an electron in the substrate 12 or in the fatigued material. The latter will be called the annihilation gamma ray (AGR). The two types of gamma ray can be identified because they have different energy levels. Electronic circuits are used to determine the lifetimes of positrons which pass into the substrate of unfatigued material and the sample, or object, of fatigued material. A positron lifetime spectrum (FIG. 5) is then prepared. It will be noted that there is a separation (difference in shape) between the curves for the fatigued and unfatigued materials. Positron lifetime curves are obtained with a set of reference samples of the same material as that to be tested, each having a different but known amount of fatigue damage, thereby yielding different curves. These curves are used by the tester to determine, by comparison, the extent of fatigue damage in the material tested. The curve obtained in a test is then the sum of data derived from annihilations in the "as received" substrate material and in the material being tested. The advantage of having the same substrate and test materials is that the reference curve for the unfatigued state (using a reference sample of "as received" material) is not an admixture of data from different materials. In the electric-field positron probe (see FIG. 2), the positron-emitting material 10 is sealed between an electrically conductive window 14 and an electrically conductive thin substrate 12. These are located internally of a electrically conductive ring 16 which is grounded, so that the window and thin substrate are also at ground potential. A high-voltage electrode 18 is placed above and spaced from the substrate 12 and the grounding ring, or housing, 16. A high-voltage lead 20 is brought in through insulation (the lead insulation) 22 to the high-voltage electrode 18. A high-voltage insulator 24 supports the high-voltage electrode and lead and spaces the lead and its insulation from the grounded housing. The high-voltage insulator 24, which is ring-shaped in this embodiment, and the window 14 seal off the central cavity 26 of the housing 16, which is evacuated. The high-voltage electrode 18 and the grounded substrate 12 form an electric field between them, when the high voltage is applied, which forces positrons emitted toward the electrode 18 downward through the window 14. The effect is to increase the number of positrons in the downward direction (hence, into test samples), thereby reducing the time involved for making a fatigue measurement. A fatigued object is placed in contact with the window and its curve is compared with those for the set of reference fatigue samples of the same material as that being tested. The magnetic-field positron probe in FIG. 3 utilizes a magnetic field to collimate positrons onto the sample. A magnet 28 (permanent or electro-magnet) is spaced from the substrate 12. The upper part of the housing, or supporting ring, 16 abuts and is sealed to the magnet 28. The window 14 and substrate 12 are of nonmagnetic materials, such as polymer film and aluminum, respectively. Those emitted positrons that have momentum components perpendicular to the magnetic field lines are constrained to move along helical trajectories about the magnetic field lines. The magnetic-field probe is especially suited to non-contact applications (e.g. moving parts, where a space is maintained between the probe window and the tested item). When the area to be tested is comparable to or smaller than the size of the probe, the downward-directed but divergent positrons which would not otherwise intercept this area are redirected by the magnetic field onto the test area. The thin scintillator positron probe shown in FIG. 4 may be used for those radioactive materials 10 which emit positrons but not NGR's with the positrons. This embodiment uses a thin scintillator sheet 32 as a window and as a photon, or light, producer. A pair of photon detectors 30 and 30' are placed at the ends of the scintillator sheet 32. The photon detectors may be photomultipliers, for example, and the assemblage may be ring-shaped, if desired. That is, the scintillator sheet may be a circular disc with photomultipliers placed in a ring around its peripheral area and the substrate 12 may be circular when viewed from above. The substrate is made of a gamma-ray-attenuating material, such as lead, so that gamma rays generated by positron annihilations do not reach the photon detectors. The test sample is placed in contact with the bottom surface of the sheet 32. A positron which passes through the thin scintillator sheet produces light-photons which are detected to establish the time of emission of the positrons. This detection signifies the injection of a positron into the test item. The scintillator sheet material may, for example, be a material comprising a plastic matrix of polyvinyltoluene in which there is p-terphenyl and p, p'-diphenyl stilbene, known by the trade name of "Pilot B." A fifth embodiment of the invention (not shown in the drawing) may include both the electric field of the embodiment of FIG. 2 and the magnetic field of the embodiment of FIG. 3. Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described. |
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description | The present invention relates to a specific polymer crystal estimating apparatus, namely a specific macromolecule crystal evaluator, for evaluating specific macromolecule crystal by utilizing an X-ray diffraction phenomenon, and particularly an apparatus suitable to evaluate biological polymer crystal such as protein crystal or the like. Worldwide attention has been paid to the structural analysis of protein crystals in connection with the development in the genome plan since a double helix structure of DNA was discovered. A method using NMR (Nuclear Magnetic Resonance apparatus) a method using an electron microscope, a method using the X-ray diffraction phenomenon, etc. have been developed for the structure analysis of protein crystals, and particularly the X-ray crystal structure analysis using the X-ray diffraction phenomenon has been rapidly advanced in connection with the developments of a two-dimensional X-ray detector such as an imaging plate or the like, analyzing software for two-dimensional data, etc. The protein crystal structural analysis using the X-ray diffraction phenomenon has been hitherto carried out as follows. First, protein is crystallized in solution to achieve protein crystals, and a protein crystal thus achieved is placed in a glass tubule called as a capillary. Under this state, the structural analysis is carried out while the capillary is set in an X-ray diffraction apparatus. In order to conduct the X-ray structural analysis on protein crystal, it is required to carry out a work of accurately positioning the protein crystal as a target to an X-ray irradiation position. Therefore, it has been hitherto general that a microscope for detecting a protein crystal is affixed to an X-ray diffraction apparatus, and an operator manually positions the protein crystal through visual observation by using the microscope. The positioning operation based on the visual observation and the manual labor as described above is cumbersome and it takes much time. In addition, since the positioning operation in the X-ray diffraction apparatus has been hitherto required to be carried out every time one measuring operation is finished, and thus it has been impossible to quickly evaluate many protein crystals. For example, it is said that the number of kinds of proteins constituting the human body extends to 50,000 to 100,000 kinds, and it has been an urgent issue in the recent structural biology that the structures of many protein crystals are clarified in a short time. The present invention has been implemented in view of the foregoing situation, and has an object to automate the structural analysis of specific macromolecule crystals by using the X-ray diffraction phenomenon to thereby speed up the processing thereof. In order to attain the above object, according to the present invention, an apparatus for using a sample container through which X-ray, ultraviolet light and visible light are transmissible and evaluating specific macromolecule crystals existing in the sample container is characterized by comprising: A sample detecting stage for detecting the specific macromolecule crystal in the sample container; an X-ray measuring stage that is disposed so as to be spaced from the sample detecting stage and carries out an X-ray diffraction measurement of the specific macromolecule crystal; feeding means for feeding the sample container from the sample detecting stage to the X-ray measuring stage; and control means for recognizing the position of the specific macromolecule crystal on the basis of information achieved in the sample detecting stage and controlling the feeding means on the basis of the position information to position the specific macromolecule crystal to a sample disposing portion of the X-ray measuring stage. As described above, the specific macromolecule crystal in the sample container is detected by the sample detecting stage, and the feeding means is controlled on the basis of the information achieved there to position the specific macromolecule crystal to the sample disposing portion of the X-ray measuring stage. Therefore, the work from the detection of the specific macromolecule crystal to the positioning to the sample disposing portion can be automated, and the evaluating processing can be speeded up. Particularly when a protein crystal is evaluated, a crystallization plate on which many recess portions for generating protein crystals are formed is used as the sample container, and a protein crystal is generated in each recess portion of the crystallization plate. Each protein crystal is detected by the sample detecting stage, and then the crystallization plate is fed to the X-ray measuring stage. The protein crystals in the respective recess portions are successively subjected to the X-ray diffraction measurement while positioned to the sample disposing portion, whereby many protein crystals can be sequentially evaluated and the working time can be greatly reduced. Here, the sample detecting stage may comprise specific macromolecule crystal detecting means for irradiating ultraviolet light to the sample container and detecting a fluorescent image emitted from the sample in the sample container, and crystal detecting means for detecting the outline of the sample from a visible light image of the sample existing in the sample container. Furthermore, the control means judges as a specific macromolecule crystal the sample for which the fluorescent image is detected by the specific macromolecule detecting means and the outline showing the crystal is detected by the crystal detecting means, and recognizes the position of the specific macromolecule crystal. Many polymer crystals, particularly biological polymers generate fluorescence when ultraviolet light is irradiated to them. In this specification, a polymer crystal having a characteristic that it generates fluorescence when ultraviolet light is irradiated to the polymer crystal concerned will be referred to as “specific macromolecule crystal”. For example, protein crystals are contained in the specific macromolecule crystal. According to the present invention, taking notice of the characteristic of the specific macromolecule crystal as described above, ultraviolet light is irradiated to a sample container, and a fluorescent image emitted from a sample in the sample container concerned is detected, thereby detecting the specific macromolecule in the sample container. However, there is a case where it is not identifiable by only the fluorescent image whether the thus-detected specific macromolecule forms a crystal. For example, when aggregation of the specific macromolecule exists in the sample container, the aggregation concerned generates fluorescence, and thus the fluorescent image caused by the crystal and the fluorescent image caused by the aggregation are detected with being mixed with each other. Therefore, according to the present invention, the outline of the sample is detected on the basis of a visible light image of the sample existing in the sample container, and discriminates the crystal from the other materials on the basis of the outline thereof. Accordingly, the “crystal” of the “specific macromolecule” is identified by cooperating the above result with the detection result of the fluorescent image, and the position of the specific macromolecule crystal concerned is recognized. Furthermore, the X-ray measuring stage comprises: X-ray irradiating means for irradiating X-ray from the upper side or lower side to the specific macromolecule crystal in the sample container disposed in the sample disposing portion; X-ray detecting means that is disposed so as to confront the X-ray irradiating means through the sample container, and detects diffracted X-ray from the specific macromolecule crystal transmitted through the sample container; a rotary arm for supporting the X-ray irradiating means and the X-ray detecting means; and a rotationally driving mechanism for rotating the rotary arm with respect to the substantially horizontal shaft center by any angle. According to the above construction, the integrated intensity of the diffracted X-ray from the specific macromolecule crystal can be determined without rotating the sample container. The integrated intensity of the diffracted X-ray is determined by detecting the intensity of the diffracted X-ray when X-ray is irradiated to the crystal from various angles while varying the X-ray irradiation angle to the crystal, and integrating the intensity data thus achieved. It has been hitherto general that the integrated intensity of the diffracted X-ray is determined by rotating a capillary in which a crystal sample is encapsulated. In order to analyze the structure of the specific macromolecule crystal such as protein crystal or the like, it is required to determine the integrated intensity of X-ray diffracted from the crystal. That is, reflected X-ray from a crystal which may cause diffraction is spherically distributed in the reciprocal space (diffraction space). Accordingly, the peak intensities of the diffracted X-ray (diffraction spots) detected at positions fixed with respect to the crystal are achieved by observing only one cross section of the reflected X-ray distributed spherically as described, and the number of them is merely equal to one several hundredths to one several thousandths of the number of peak intensities required for the structural analysis of a crystal (that is, determination of a molecular structure). According to the present invention, by rotating the X-ray irradiating means and the X-ray detecting means relatively to a sample holder, the peak intensities (diffraction spots) can be detected from plural cross sections with respect to the reflected X-ray from the crystal which is spherically distributed, and the integrated intensity of the thus-detected peak intensities can be determined. As a result, the analysis/evaluation of the crystal structure having high reliability can be implemented on the basis of the integrated intensity of the diffracted X-ray thus detected. Particularly when a crystallization plate is used as a sample container, solution is filled in recess portions of the crystallization plate, and specific macromolecule crystals such as protein crystals or the like exist in this solution with being floated. Accordingly, when the crystallization plate is rotated, the solution gets out of the crystallization plate or crystals in the solution move. Therefore, it is impossible to rotate the crystallization plate. However, according to the apparatus of the present invention, the integrated intensity of the diffracted X-ray can be determined without rotating the crystallization plate. Furthermore, the feeding means comprises a sample table on which a sample container is mounted, an XYZ table for mounting the sample table thereon and moving the sample table in X and Y directions orthogonal to each other on the horizontal plane and in the height direction, and a slider for feeding the XYZ table from the sample detecting stage to the X-ray measuring stage (claim 4). By controlling the driving of the XYZ table and the slider, the specific macromolecule crystal existing in the sample container can be automatically positioned to the sample disposing portion provided to the X-ray measuring stage, and thus the workability can be remarkably enhanced. Preferred embodiments according to the present invention when a protein crystal is set as an evaluating target (a specific macromolecule crystal) will be described with reference to the drawings. (Whole Construction of Apparatus) FIG. 1 is a plan view showing the whole construction of a specific macromolecule crystal evaluating apparatus according to an embodiment, and FIG. 2 is a front view. As shown in FIG. 1, the specific macromolecule crystal evaluating apparatus is equipped with a sample container accommodating portion 100, a supply robot 200, a sample container identifying portion 300, a feeding unit 200 (feeding means), a sample detecting stage 500, an X-ray measuring stage 600 and a central processing unit 700 (control means). The sample container accommodating portion 100 is constructed by partition shelves on which plural sample containers 10 can be arranged and accommodated, and the sample containers 10 in which protein crystals are stored are arranged and mounted in the sample container accommodating portion 100. It is preferable that a crystallization plate formed of material such as polyimide or the like through which ultraviolet light, visible light and X-ray are transmitted is used as the sample container 10. Many recess portions 11 are formed in the sample container 10 using the crystallization plate as shown in FIG. 3A, and a protein crystal S can be generated in each recess portion 11. Various methods containing a vapor diffusion method are known as a method of generating a protein crystal by using a crystallization plate. FIG. 3B is a schematic diagram showing the state that the protein crystal S is generated according to the vapor diffusion method, and the protein crystal S is generated in a drop of sample solution L placed on the lower surface of a cover plate 12. Protein crystals S can be separately generated in the many recess portions 11 formed in the sample container 10 while the generating condition is changed or the kind of the protein crystals S to be generated is changed. The supply robot 200 is quipped with a robot arm that is freely expandable and contractable in the axial direction, freely movable in the height direction and swingable on the horizontal plane, and an opening/closing chuck 202 is provided to the tip of the robot arm 201. Each of the sample containers 10 accommodated in the sample container accommodating portion 100 is drawn out from the accommodating portion 100 while grasped by the opening/closing chuck 202, and it is first fed to a sample container identifying portion 300. An information reading device for reading out identification information attached to each sample container 10 in advance is mounted in the sample container identifying portion 300, and the sample container 10 is disposed at a position (information reading position) at which the information reading device can read the identification information. Here, when a bard code is used as the identification information, the information reading device is constructed by a bar code reader. In this embodiment, a container re-grasping portion 310 is provided in the neighborhood of the sample container accommodating portion 100 for the purpose of surely grasping and feeding the sample container 10 drawn out from the sample container accommodating portion 100 by the opening/closing chuck 202. A sample container 10 drawn out from the sample container accommodating portion 100 is temporarily put on the container re-grasping portion 310. Then, it is accurately grasped by the opening/closing chuck 202 again and fed to the sample container identifying portion 300. The feeding unit 400 comprises a sample table 401 on which the sample container 10 is put, an XYZ table 402 for mounting the sample table 401, and a slider 403 for feeding the XYZ table 402 integrally with the sample table 401. As shown in FIG. 4A, the sample table 401 is provided with a positioning block 404 and a pressing actuator 405 on the upper surface thereof, and a corner portion of the sample container 10 mounted on the upper surface is pressed by the actuator 405 so that another corner portion of the sample container 10 which is disposed diagonally to the corner portion concerned is brought into contact with the positioning block 404, whereby the sample container 10 is mounted at a fixed position on the sample table 401 at all times. As shown in FIG. 4B, the sample table 401 is provided with a through hole 401a is formed at the site at which the sample container 10 is put. The through hole 401a transmits therethrough ultraviolet light and visible light irradiated to the sample container 10 in a sample detecting stage 500 described later and X-ray irradiated to the protein sample S in the sample container in the X-ray measuring stage 600. The XYZ table 402 is a mechanism for moving the sample table 401 in the X direction and Y direction orthogonal to each other on the horizontal plane and move the sample table 401 in the height direction (Z direction). The XYZ table 402 is mounted on the slider 403. The slider 403 forms a feeding passage through which the sample detecting stage 500 and the X-ray measuring stage 600 are connected to each other, and has a function of linearly feeding the sample table 401 mounted on the XYZ table 402 between the sample detecting stage 500 and the X-ray measuring stage 600. The sample detecting stage 500 is a stage for detecting the protein crystal S in the sample container 10 and recognizing the position of the center of gravity thereof. The X-ray measuring stage 600 is a stage for carrying out X-ray diffraction measurement on the protein crystal S in the sample container 10 detected by the sample detecting stage 500. Each stage will be described in detail later. The central processing unit 700 is constructed by a general-purpose computer, and controls the driving of each part of the apparatus described above. The central processing unit 700 executes the identification of the protein crystal S and the recognition of the position of the center of gravity of the protein crystals in the sample detecting stage 500, and also executes the X-ray measurement processing in the X-ray measuring stage 600. Particularly, the central processing unit 700 has a function of controlling the XYZ table 402 and the slider 403 on the basis of the position information (the information of the position of the center of gravity) of the protein crystal S which is recognized on the basis of the information achieved in the sample detecting stage 500, and positioning the protein crystal S to the sample disposing portion 610 of the X-ray measuring stage 600. Here, the driving of the slider 403 is controlled so that the slider 403 is gradually accelerated from the start time for a fixed period, then driven at a fixed speed and then gradually decelerated to be stopped at the sample disposing portion 610. Accordingly, the inertial force is suppressed and the protein crystal S in the sample container 10 mounted on the sample table 401 can be prevented from moving. [Sample Detecting Stage] Next, the sample detecting stage 500 will be further described in detail. FIG. 5 is a diagram showing the outline of the sample detecting stage. The sample detecting stage 500 is provided with a visible light irradiating unit 520 and an ultraviolet light irradiating unit 521 which are disposed at the lower side of a sample detector 510 in which the sample container 10 is disposed. The visible light irradiating unit 520 and the ultraviolet light unit 521 serve as light sources for irradiating visible light or ultraviolet light to the sample container 10 disposed in the sample detector 510. The visible light irradiating unit 520 and the ultraviolet light irradiating unit 521 are laterally slid, and any one unit of them is disposed so as to confront the sample container 10. If a reflection mirror is disposed at the middle position between the sample container 10 and the visible light irradiating unit 520 and the ultraviolet light irradiating unit 521 to lead the visible light emitted from the visible light irradiating unit 520 or the ultraviolet light emitted from the ultraviolet light irradiating unit 521 to the sample container 10, it would be unnecessary that each irradiating unit 520, 521 is disposed so as to confront the sample container 10. The sample container 10 is put on the sample table 401 as described above, and the sample detector 510 is disposed by the movement of the XYZ table 402 and the slider 403. A microscope 530 and a two-dimensional image pickup unit 540 are disposed above the sample detector 510. The microscope 530 enlarges an image achieved when ultraviolet light or visible light is irradiated to the sample container 10 and transmitted therethrough, and leads the enlarged image to the two-dimensional image pickup unit 540. The microscope 530 is constructed so that the protein crystal S in the sample container 10 can be searched by varying the focal position thereof in the vertical direction. CCD may be used as the two-dimensional image pickup unit 540. The two-dimensional image pickup unit 540 converts the enlarged image incident through the microscope 530 to an electrical signal (image data), and outputs the electrical signal to the central processing unit 700. The central processing unit 700 processes the image data input from the two-dimensional image pickup unit 540 to detect the protein crystal S in the sample container 10 and recognize the position thereof. FIGS. 6 and 7 are flowcharts showing the method of detecting the protein crystal that is executed by the central processing unit. First, the light source is set to the ultraviolet light irradiating unit 521, and the ultraviolet light emitted from the ultraviolet light irradiating unit 521 is irradiated to the sample container 10. The image achieved when the ultraviolet light is transmitted through the sample container 10 is enlarged by the microscope 530, and incident to the two-dimensional image pickup unit 540. The central processing unit 700 receives the image data transmitted from the two-dimensional image pickup unit (step S1), and detects a fluorescent image from the image data (step S2). That is, since the protein crystal S generated in the sample solution L generates fluorescence when ultraviolet light is irradiated to the protein crystal S, the fluorescent image is incident to the two-dimensional image pickup unit 540. Therefore, the central processing unit 700 analyzes the image data input from the two-dimensional image pickup unit 540 to detect the fluorescent image, and grasps the position of the fluorescent image, that is, the protein. The position of the protein thus grasped is the position on the horizontal plane (xy coordinate), and the position in the height direction (z coordinate) is grasped on the basis of the focal position of the microscope 530. Subsequently, the light source is switched from the ultraviolet irradiation unit 521 to the visible light irradiating unit 520, and the visible light emitted from the visible light irradiating unit 520 is irradiated to the sample container 10. At this time, the visible image achieved when the visible image is transmitted through the sample container 10 is enlarged by the microscope 530, and incident to the two-dimensional image pickup unit 540. The central processing unit 700 receives the image data transmitted from the two-dimensional image pickup unit 540 (step S3), and processes the image data to detect the crystal in the sample solution L and also recognize the position of the center of gravity (step S4). The step S4 (crystal detecting step) is processed along the subroutine shown in FIG. 7. That is, the image data input from the two-dimensional image unit 540 is binarized by using a predetermined threshold value as a reference, and each pixel on the xy coordinate is converted to binary data of “1” or “0” (step S10). Subsequently, the pixels corresponding to the edge of the sample existing in the sample solution L are detected on the basis of the binarized image data (step S11). Here, it is judged whether a noted pixel as an identification target is black (data “1”) or not as shown in FIG. 8. If the noted pixel is black, it is likewise judged whether each of the surrounding pixels (pixels 1 to 8) around the noted pixel concerned is black (data “1”) or white “data “0”). If all the surrounding pixels (pixels 1 to 8) are white (data “0”), it is concluded that the noted pixel concerned is an isolated point. On the other hand, if all the surrounding pixels (pixels 1 to 8) are black (data “1”), it is concluded that the noted pixel concerned is an internal point of the image. As described above, all the pixels corresponding to isolated points and internal points are excluded, and a noted pixel for which some of the surrounding pixels (pixels 1 to 8) of the noted pixel concerned are white (data “0”) is recognized as an edge of the sample, and the xy coordinate thereof is stored. The above processing is executed on all the pixels of the xy coordinate system, and all the pixels corresponding to the edge of the sample are extracted. Subsequently, the pixels corresponding to the edge of the extracted sample are noted, and the neighboring pixels are linked to one another to detect the contour line of the sample (step S12). If the start and end points of the contour line are coincident with each other, the contour line is judged as a closed contour line. Furthermore, the sample having the closed contour line is judged as a crystal having a fixed area. On the other hand, the sample whose contour line is not closed is excluded as a non-crystallized material such as aggregation or the like. Subsequently, the internal area of the sample having the closed contour line (that is, crystal) is recognized, and the position of the center of gravity of the internal area is calculated by using a well-known calculation method (step S13). As a method of calculating the position of the gravity center of a planar image, the moment quantity of a linked figure S recognized as a crystal is determined, and the position of the gravity center is calculated on the basis of the moment quantity. That is, when the weight of each pixel of the linked figure S is equally set to 1, the moment M(m,n) is defined by the following equations. M ( m , n ) = ∑ ( x , y ) ∈ S ( x m × y n ) M(0, 0) represents the area of the linked figure S M(1,0) represents the moment with respect to the x-axis M(0,1) represents the moment with respect to the y-axis The gravity center coordinate (p, q) can be calculated by using the above moment quantity according to the following equations:P=M(1,0)/M(0,0)Q=M(0,1)/M(0,0) After the gravity center position of the crystal thus detected is calculated, the central processing unit 700 returns to the main routine shown in FIG. 6 again, and superposes the position of the protein detected on the basis of the fluorescent image with the position of the crystal detected on the basis of the visible light image to recognize the protein crystal S. The gravity center position achieved n step S13 of FIG. 7 for the protein crystal S is stored (step S5). As described above, the gravity center position of the protein crystal S existing in the sample container 10 can be automatically detected. FIGS. 9A and 9B are sketches showing microscope images achieved by observing sample solution containing the mixture of a protein crystal and a crystal of a material generating no self-fluorescence, wherein FIG. 9A shows a visible light image achieved by irradiating visible light to the sample solution, and FIG. 9B shows a fluorescent light image achieved by irradiating ultraviolet light to the sample solution. As shown in FIG. 9A, when visible light is irradiated to the sample solution, a visible light image A of the protein crystal and a visible light image B of the other crystal B are observed. In this image, it is unidentifiable which one of the visible images corresponds to the protein crystal. However, as shown in FIG. 9B, when ultraviolet light is irradiated to the sample solution, only a fluorescent image C of the protein crystal is observed, and the other crystal is not detected. Accordingly, by superposing the visible light image A with the fluorescent image C, the position of the protein crystal can be recognized. FIGS. 10A and 10B are sketches of microscope images achieved by observing the sample solution containing aggregation of protein, wherein FIG. 10A shows a fluorescent image achieved by irradiating ultraviolet light to the sample solution, and FIG. 10B shows a visible image achieved by irradiating visible light to the sample solution. As shown in FIG. 10A, when the ultraviolet light is irradiated to the sample solution, a fluorescent image D emitted from the aggregation of the protein is observed. It is unidentifiable on the basis of the fluorescent image D which one of the aggregation of the protein and the crystal of the protein it corresponds to. However, as shown in FIG. 10B, when the visible light is irradiated to the sample solution, a visible light image having a needle-like shape characteristic of the aggregation of protein is observed, and thus the observation target can be identified as the aggregation of the protein. As described above, the position of the protein crystal can be recognized with excluding the crystals of materials other than the protein and the aggregation of the protein by integrating the fluorescent image achieved when the ultraviolet light is irradiated to the sample solution and the visible light image achieved when the visible light is irradiated to the sample solution. [X-Ray Measuring Stage] Next, the X-ray measuring stage will be further described in detail. FIG. 11 is a side view showing the construction of the X-ray measuring stage, and FIG. 12 is a diagram showing the principle of measuring the protein crystal in the X-ray measuring stage. As shown in FIG. 11, the X-ray measuring stage 600 is provided with an X-ray irradiating unit 620 (X-ray irradiating means) and an X-ray detector 630 (X-ray detecting means) disposed at the lower and upper sides of the sample disposing portion 610, respectively. As described above, the sample container 10 put on the sample table 401 is positioned to and disposed at the sample disposing portion by moving the XYZ table 402 and the slider 403. The X-ray irradiating unit 620 contains an X-ray source 621 and an X-ray optical system 622. An X-ray generator for a laboratory which contains an electron gun and a target is used as the X-ray source 621. This type of X-ray generator is remarkably smaller in dimension and weight as compared with large-scale X-ray generating equipment for generating radiation light. Therefore, it can be mounted on a rotary arm and rotatably driven as described later. The X-ray optical system 622 has a function of selecting only X-ray having a specific wavelength (made monochromatic), and converging the X-ray to the sample disposing portion 610, and it is constructed by combining optical devices such as a confocal mirror, a collimator, etc. A two-dimensional X-ray detector is used as the X-ray detector 630. Particularly, in this embodiment, CCD is used as the X-ray detector 630. Therefore, the intensity of the diffracted X-ray detected on the plane is converted to an electrical signal, and the electrical signal is output to the central processing unit 700. The X-ray irradiating unit 620 and the X-ray detector 630 are mounted on the rotary arm 640. The rotary arm 640 is designed in any shape, and for example it may be designed in a plate-like shape or rod-like shape. The X-ray irradiating unit 620 is mounted at one end portion of the rotary arm 640, and the X-ray detector 630 is mounted at the other end portion so as to confront the X-ray irradiating unit 620. The center portion of the rotary arm 640 is mounted to the rotating shaft 641a of the rotationally driving mechanism 641, and the rotary arm 640 is rotatable around the rotating shaft 641a by any angle by the rotationally driving mechanism 641. The center line O of the rotating shaft 641a of the rotationally driving mechanism 641a is located substantially horizontally, and the optical axis of the X-ray radiated from the X-ray irradiating unit 620 is adjusted so as to cross the center line O of the rotating shaft 641a. This rotationally driving mechanism 641 comprises a driving motor such as a stepping motor or the like which can control the rotational angle with high precision, and a gear mechanism for transferring the rotation of the driving motor to the rotating shaft 641a, and the rotational angle of the driving motor is controlled by the central processing unit 700. It is preferable that the rotational angle is freely controllable in the range of about 45° in both the forward and reverse directions. In this embodiment, the X-ray irradiating unit 620 mounted on the rotary arm 640 is disposed below the sample disposing portion 610, and the X-ray detector 630 is disposed above the sample disposing portion 610. X-ray is irradiated from the lower side to the protein crystal S generated in the sample container 10 on the sample disposing portion 610, and diffracted X-ray reflected from the protein crystal S is detected by the X-ray detector 630 above the sample container 10. The arrangement of the X-ray irradiating unit 620 and the X-ray detector 630 may be inverted in the vertical direction so that the X-ray irradiating unit 620 is disposed above the sample disposing portion 610 and the X-ray detector 630 is disposed below the sample disposing portion 610. Furthermore, a detection position adjusting mechanism 650 is affixed to the X-ray detector 630. The detection position adjusting mechanism 650 is a mechanism for moving the X-ray detector 630 in the radial direction (the direction a of the figure) and in a direction (the direction of b in the figure) parallel to the sample container 10 disposed on the sample disposing portion 610. In the construction shown in FIG. 11, the detection position adjusting mechanism 650 comprises a first guide rail 651 disposed on the rotary arm 640, a first moving table 652 movable along the first guide rail 651, a second guide rail 653 extending from the moving table 652 in the direction of b, a second moving table (not shown) movable along the second guide rail 653, and a driving motor (not shown) for driving each moving table, and the X-ray detector 630 is fixed to the second moving table. Next, the method of measuring the protein crystal in the X-ray measuring stage 600 will be described. The protein crystal S in the sample container is automatically positioned to the sample disposing portion 610 by moving the XYZ table 402 and the slider 403. Here, the distance between the protein crystal S and the X-ray detector 630 is adjusted as occasion demands. That is, as the X-detector 630 approaches to the protein crystal S, the diffraction spots of the X-ray reflected radially from the protein crystal S can be detected in a broad angle range. However, when the reciprocal lattice density of the protein crystal S is high, if the X-ray detector 630 approaches to the protein crystal S, there is a risk that the diffraction spots of the X-ray reflected radially from the protein crystal S are detected with being overlapped with one another. Therefore, by adjusting the movement of the X-ray detector 630 in the direction of a of FIG. 11 through the detection position adjusting mechanism 650, the distance between the protein crystal S and the X-ray detector 630 can be properly adjusted, and suitable detection data can be achieved. Furthermore, by adjusting the movement of the X-ray detector 630 in the direction of b of FIG. 11 through the detection position adjusting mechanism 650, the detection range of the diffracted X-ray reflected radially from the protein crystal S can be varied. Subsequently, X-ray is irradiated from the X-ray irradiating unit 620 to execute the X-ray diffraction measurement. As shown in FIG. 12, the X-ray irradiated from the X-ray irradiating unit 620 is incident from the lower side to the protein crystal S in the sample container 10. The X-ray is radially diffracted from the protein crystal S, and the diffracted X-ray is detected by the X-ray detector 630. The central processing unit 700 executes the crystal evaluation and the crystal structure analysis on the basis of the intensity data of the diffracted X-ray thus detected. Furthermore, when X-ray is irradiated from various angles to the protein crystal S to detect the intensity of the diffracted X-ray, the rotary arm 640 is rotated by the rotationally driving mechanism 641 to adjust the angles of the X-ray irradiating unit 620 and the X-ray detector 630 to the lattice plane of the protein crystal S, and the X-ray diffraction measurement described above is repeated. By this operation, the integrated intensity of the diffracted X-ray from the protein crystal S can be determined without rotating the sample container 10, and the crystal structure analysis having high reliability can be implemented on the basis of the integrated intensity thus determined. The above embodiments have been described by setting the protein crystal as a detection target. However, the target of the method of the present invention is not limited to the protein crystal, and various kinds of specific macromolecule crystals each having the characteristic that they generate fluorescence when ultraviolet light is irradiated to them may be used as detection targets. As described above, according to the present invention, the specific macromolecule crystal in the sample contained is detected in the sample detecting stage, and the feeding means is controlled on the basis of the information achieved there, whereby the specific macromolecule crystal is positioned to the sample disposing portion of the X-ray measuring stage. Therefore, the work form the detection of the specific macromolecule crystal to the positioning to the sample disposing portion can be automated, and thus the evaluation processing can be speeded up. |
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