Time-resolved neutron detector

Abstract

To provide a neutron conversion laminate which enables one neutron detection device to detect neutrons in an energy band across the neuron range, thermal neutron range, and fast neutron range, and which can be used to obtain a two-dimensional image in this wide energy band.SOLUTION: A neutron conversion laminate 1000 of the present invention comprises a hydrogen-containing resin film 1001, and a membrane 1002 made of 10B alone or a compound of 10B formed on the resin film 1001.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a neutron conversion laminate, a neutron detection device, and a time-resolved neutron detection device. [Background technology]

[0002] Neutrons have characteristics not found in conventional X-rays, such as a good response to hydrogen and strong penetrating power, making them a focus of attention in the fields of non-destructive testing and materials analysis. In the medical field, their strong penetrating power also makes them a target for neutron therapy, where they are combined with boron, which reacts strongly with neutrons, to develop cancer treatment. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Special Publication No. 2018-524560 [Patent Document 2] Japanese Patent Publication No. 2004-233283 [Patent Document 3] Japanese Patent Publication No. 2000-206261 [Overview of the project] [Problems that the invention aims to solve]

[0004] On the other hand, since neutrons have no electric charge, their detection utilizes ionization. Furthermore, neutron sources have a wide energy range, and different detection mechanisms are required for each energy range. For example, thermal neutrons (2.5 × 10⁻¹⁰ -2 For neutrons below eV, absorption by atomic nuclei that readily absorb neutrons is utilized. For example, thermal neutrons 10 The nuclear reaction with B (boron isotope) produces an alpha particle. 7 Since Li nuclei are emitted, their alpha particles are detected. Also, fast neutrons (5 × 10⁻¹⁰) are detected. 5 For electrons above eV, the scattering of hydrogen nuclei is utilized. For example, recoil protons knocked out by high-speed neutrons from a resin containing a high density of hydrogen are detected. Since the detection mechanisms required in each energy band are different in this way, users usually had to prepare substances and detectors for converting neutrons into charged particles according to the energy band, respectively.

[0005] In addition, a micropattern gas detector is known as a radiation detector that can obtain two-dimensional detection position information. If two-dimensional images can be obtained in a wide energy band from cold neutrons to thermal neutrons to fast neutrons, new uses of neutrons can be expected.

[0006] Patent Document 3 discloses an invention in which a boron plate converter containing 10B (containing 95% of 10B) and a high-density polyethylene radiator are stacked, and a single silicon neutron detector detects thermal neutrons and fast neutrons (see

[0014] ). Further, Patent Document 3 describes that, in the case of the same area, based on the fact that the sensitivity of the radiator to fast neutrons is two to three orders of magnitude smaller than the sensitivity of the converter to thermal neutrons, the area of the converter can be made about 1 / 100 of that of the radiator (see

[0010] ,

[0011] ). It is difficult to conceive of obtaining two-dimensional images in a wide energy band from cold neutrons to thermal neutrons to fast neutrons based on this invention.

[0007] The present invention has been made in view of the above circumstances, and an object thereof is to enable detection of a wide energy band from cold neutrons to thermal neutrons to fast neutrons with one neutron detection device, and to provide a neutron conversion laminate and a neutron detection device that can be used to obtain two-dimensional images in this wide energy band.

Means for Solving the Problems

[0008] In order to solve the above problems, the present invention provides the following means.

[0009] The neutron conversion laminate according to the first aspect of the present invention includes a resin film containing hydrogen, and a film formed on the resin film and made of 10 elemental B or 10 a compound of B.

[0010] In the neutron conversion laminate according to the above aspect, the resin may be a resin material selected from the group consisting of PET, PI, PEN, PE, PC, and PEEK.

[0011] In the neutron conversion laminate according to the above aspect, the film 10 may be made of a nitride of B.

[0012] In the neutron conversion laminate according to the above aspect, the thickness of the resin film may be 50 μm or more and 2 mm or less.

[0013] In the neutron conversion laminate according to the above aspect, the thickness of the film may be 0.05 μm or more and 3 μm or less.

[0014] The neutron detector according to the second aspect of the present invention includes the neutron conversion laminate according to the above aspect, and a micro-pattern gas detector that detects α particles and protons generated from the neutron conversion laminate.

[0015] In the neutron conversion laminate according to the above aspect, the micro-pattern gas detector may be a gas electron multiplier.

[0016] The time-resolved neutron detector according to the third aspect of the present invention includes the neutron conversion laminate according to the above aspect, a time-of-flight micro-pattern gas detector that detects α particles and protons generated from the neutron conversion laminate, and a pulsed neutron source.

Effect of the Invention

[0017] According to the neutron conversion laminate of the present invention, it is possible to detect an energy band from cold neutrons to thermal neutrons to fast neutrons with one neutron detector, and to provide a neutron conversion laminate that can be used to obtain a two-dimensional image in this wide energy band.

Brief Description of the Drawings

[0018] [Figure 1] This is a schematic cross-sectional view of the neutron conversion laminate according to the present invention. [Figure 2] This is a perspective view showing an overview of the neutron detection device according to the present invention. [Figure 3] Figure 2 is a schematic cross-sectional view of the neutron conversion stack shown. [Figure 4] This is a schematic cross-sectional diagram illustrating the configuration of the neutron detection device according to the present invention. [Figure 5] This is a schematic perspective view showing the configuration inside the chamber of the neutron detection device according to the present invention. [Figure 6] This is a schematic perspective view of an electrode for a gas electron amplifier. [Figure 7] This is a conceptual diagram of a time-resolved neutron detector according to the present invention. [Figure 8] This is a diagram illustrating the principle of the time-resolved neutron detector according to the present invention. [Figure 9A] (a) is a schematic diagram of the neutron detection device used, and (b) is a schematic cross-sectional diagram of the neutron conversion stack used. [Figure 9B] This is a photograph of the neutron conversion laminate used. [Figure 10] (a) is a thermal neutron image, and (b) is a fast neutron image. [Modes for carrying out the invention]

[0019] The present invention will be described in detail below, with reference to the figures as appropriate. The drawings used in the following description may be enlarged for convenience to clearly illustrate the features, and the dimensional ratios of each component may differ from those of the actual components. The materials, dimensions, etc., exemplified in the following description are examples only and can be modified as appropriate within the scope of achieving the desired effect.

[0020] [Neutron Conversion Layer] Figure 1 shows a schematic cross-sectional view of the neutron conversion laminate according to the present invention. The neutron conversion laminate 1000 shown in FIG. 1 includes a resin film 1001 containing hydrogen and a film 1002 formed on the resin film 1001 and composed of elemental B or a compound of B. 10 elemental B or 10 a film 1002 composed of a compound of B. The shape of the neutron conversion laminate 1000 shown in FIG. 1 is in the form of a film, which can be referred to as a neutron conversion laminate film, but is not limited to the film form.

[0021] The neutron conversion laminate 1000 may have other films as long as it has the effect of being able to detect fast neutrons and thermal neutrons. For example, when applied to the micro-pattern gas detector described later, an electrode film may be sandwiched between the hydrogen-containing resin film 1001 and the B-containing film 1002. 10 the B-containing film 1002.

[0022] (Resin film) The resin film 1001 is made of a resin material containing hydrogen. Since the resin film 1001 contains hydrogen, fast neutrons (5×10 5 eV or more) knock out protons from hydrogen nuclei. By utilizing this phenomenon, fast neutrons can be detected by detecting the recoil protons. Such a resin material preferably contains hydrogen at a high density. Examples of resin materials containing hydrogen at a high density include PE (polyethylene), PET (polyethylene terephthalate), PI (polyimide), PEN (polyethylene naphthalate), PC (polycarbonate), PEEK (polyether ether ketone), and the like. Among these, in order to form a film composed of elemental B or a compound of B on the resin film 10 elemental B or 10 ;a compound of B on the resin film 1001 by a dry film-forming method, it is preferable to have high heat resistance. Examples of resin materials with high heat resistance include PET (polyethylene terephthalate), PI (polyimide), PEN (polyethylene naphthalate), PC (polycarbonate), PEEK (polyether ether ketone), and the like.

[0023] The thickness of the resin film 1001 is preferably 50 μm or more and 2 mm or less. This is because the detection efficiency of fast neutrons is sufficient within this thickness range. The thickness of the resin film 1001 is more preferably 100 μm or more and 1 mm or less.

[0024] ( 10 B-containing film) 10 The B-containing film 1002 is 10 B alone or 10 It is a membrane made of compound B. 10 B (a boron atom with mass number 10; borontene) has a large neutron capture cross-section, so low-energy neutrons (2.5 × 10) -2 It is an element that readily undergoes nuclear reactions with electrons below eV, and is hardly activated by neutrons. 10 Compound B is, 10 Examples of various compounds of B include oxides, nitrides, carbides, silicides, borides, salts, and so on. 10 B is a stable boron atom that exists at an isotopic ratio of approximately 20%. 10 The content of B is not particularly limited; generally, any product containing 20% ​​or more is acceptable. 10 It is preferable that the product contains 99% or more of B. 10 Of the compounds in B, this one is easy to handle because it is insulating and stable. 10 Nitride of B ( 10 BN) is particularly preferred.

[0025] 10 The thickness of the B-containing film 1002 is preferably 0.05 μm or more and 3 μm or less. This is because the detection efficiency of thermal neutrons is sufficient within this thickness range. 10 The thickness of the B-containing film 1002 is more preferably 0.05 μm or more and 2.0 μm or less, and even more preferably 0.1 μm or more and 1.5 μm or less.

[0026] 10The B-containing film can be formed on the resin film 1 by known film formation methods, but high adhesion between the film and the resin film 1 can be obtained by forming it by sputtering. 10 Before forming the B-containing film, the resin film surface may be cleaned and activated by plasma irradiation. Generally, boron film deposition is often performed by electron beam evaporation, but resin films and 10 In some cases, sufficient adhesion may not be obtained between the B-containing film and the resin film. In such cases, adhesion can be improved by performing plasma treatment on the surface of the resin film and depositing the film using the magnetron sputtering method. Furthermore, the magnetron sputtering method also allows for easy deposition of boron compounds. PET films and PE films are examples of such films. 10 Because it has a film-forming surface that can stably hold the B-containing film, sufficient adhesion can be obtained.

[0027] [Neutron detection device] Figure 2 shows a perspective view illustrating the neutron detection device according to the present invention. Figure 3 shows a schematic cross-sectional view of the neutron conversion stack shown in Figure 2. The neutron detection device 2000 shown in Figure 2 comprises a neutron conversion stack 1000A and a micropattern gas detector 200 that detects alpha rays and protons generated from the neutron conversion stack 1000A.

[0028] (Micro-pattern gas detector) The Micro Pattern Gas Detector (MPGD) 200 comprises a cathode electrode 211 contained in the neutron conversion stack 1000A, a readout electrode 212, and electrodes 210-1 and 210-2 disposed between the cathode electrode 211 and the readout electrode 212, within a chamber 220. There are two electrodes disposed between the cathode electrode 211 and the readout electrode 212, but there may be one or three or more. The readout electrode 212 consists of an X-strip and a Y-strip arranged so that the X and Y directions can be read simultaneously. This allows for the acquisition of two-dimensional position information, i.e., a two-dimensional image.

[0029] The neutron conversion laminate 1000A is composed of a hydrogen-containing resin film 1001 and 10 A cathode electrode 211 is provided between the B-containing film 1002 and the other element.

[0030] Chamber 220 contains an ionizing gas. For example, a mixed gas of Ar and CO2 in a ratio of 7:3 can be used as the ionizing gas.

[0031] The neutron conversion stack according to the present invention can be easily incorporated into conventional micropattern gas detectors (MPGDs). This makes it possible to obtain two-dimensional images across a wide energy range from cold neutrons to thermal neutrons to fast neutrons.

[0032] Figures 4 to 6 illustrate an example of applying a neutron conversion laminate to a type of micropattern gas detector, specifically a gas electron amplifier (GEM) that amplifies generated electrons.

[0033] Figure 4 is a schematic diagram of the neutron detection device according to the present invention. In the neutron detection device shown in Figures 4 to 6, when a fast neutron is incident on the neutron conversion stack, a proton is generated as a charged particle, and when a thermal neutron is incident on the neutron conversion stack, an alpha particle is generated as a charged particle. These charged particles ionize the ionizing gas and generate electrons, which are then amplified using electron avalanche amplification and detected.

[0034] "Electron avalanche amplification" refers to a phenomenon in which, when free electrons collide with gas molecules in a strong electric field, electrons are knocked out of the gas molecules. These knocked-out electrons are then accelerated by the electric field and collide with other gas molecules, resulting in an exponential increase in the number of electrons.

[0035] The neutron detection device 2001 shown in Figure 4 is equipped with a neutron conversion laminate including a cathode electrode, instead of the cathode electrode found in conventional gas electron amplifiers. Therefore, in a conventional gas electron amplifier, the neutron detection device according to the present invention can be easily obtained simply by replacing the cathode electrode with the neutron conversion laminate according to the present invention. In the neutron conversion laminate 1000A shown in Figure 4, the cathode electrode 211 is a solid film formed on the entire surface of the resin film 1001, but its shape may be adjusted as appropriate to optimize the neutron detection efficiency, such as by having an opening or a comb-shaped configuration. Also, in the neutron conversion laminate 1000A shown in Figure 4, the cathode electrode 211 is a solid film formed on the entire surface of the resin film 10001 and 10 The structure is sandwiched between the B-containing film 1002 and the resin film 10001. 10 It may also be configured to be placed on one side of the laminate with the B-containing film 1002.

[0036] The neutron detection device 2001 shown in Figure 4 has a neutron conversion laminate 1000A including a cathode electrode 211, a readout electrode 12, a predetermined gas electron amplifier electrode 10, a chamber 20, and a connection terminal 30, all integrated together. Figure 5 is a schematic perspective view showing the configuration inside the chamber 20, corresponding to the neutron detection device in Figure 4. In Figures 4 and 5, the gas electron amplifier electrode 10 is shown as a three-layer configuration between the cathode electrode 211 and the readout electrode 12, but it is not limited to a three-layer configuration. The gas electron amplifier electrode 10 may be a single-layer configuration or a configuration of two or more layers.

[0037] Chamber 20 is sealed. An ionizing gas is sealed inside Chamber 20 as the reaction gas. As the ionizing gas, a noble gas such as argon or neon, or a mixture of gases containing these, can be used.

[0038] A first voltage application terminal 31 is connected to the cathode electrode 211. A predetermined voltage can be applied to the cathode electrode 211 via the first voltage application terminal 31. In addition, second voltage application terminals 32 are connected to both sides of the gas electron amplifier electrode 10. A predetermined voltage can be applied to both sides of the gas electron amplifier electrode 10 via the second voltage application terminals 32.

[0039] By applying a potential difference between the gas electron amplifier electrode 10, the cathode electrode 211, and the readout electrode 12, an electric field is generated in the region between the cathode electrode 211 (neutron conversion laminate 1000A) and the gas electron amplifier electrode 10 (hereinafter referred to as the "drift region") 13, and in the region between the gas electron amplifier electrode 10 and the readout electrode 12 (hereinafter referred to as the "induction region") 14. An electric field is also generated inside the through-hole 3 of the gas electron amplifier electrode 10.

[0040] If the neutrons incident from the entrance port 21 of chamber 20 are fast neutrons, when those fast neutrons are incident on the neutron conversion laminate 1000A, protons are generated from the resin film 10001. Also, if the neutrons incident from the entrance port 21 of chamber 20 are thermal neutrons, when those thermal neutrons are incident on the neutron conversion laminate 1000A, 10 Alpha particles are generated from the B-containing film 1002, and these charged particles, the alpha particles and protons, ionize the ionized gas in the drift region 13, generating electrons. The generated electrons are attracted toward the gas electron amplifier electrode 10 by the electric field generated in the drift region 13.

[0041] Then, as the electrons pass through the through-holes 3 in the gas electron amplifier electrode 10, electron avalanche amplification occurs, and the number of electrons is doubled. The amplified electrons are attracted to the readout electrode 12 side by the electric field generated in the induction region 14.

[0042] Electrons that reach the readout electrode 12 are read out to the outside by the readout terminal 33. As shown in Figures 4 and 5, the readout electrode 12 is divided into areas, making it possible to determine how many electrons were measured in each area. In a gas electron amplifier, neutrons, which are the target of detection, can be measured as described above.

[0043] The following describes each component of the neutron detection device.

[0044] (Neutron transmutation stack) The neutron conversion laminate 1000A consists of a resin film 10001 and 10 The configuration consists of a B-containing film 1002 and a cathode electrode 211 sandwiched between them. Resin film 10001 and 10 The structure is sandwiched between the B-containing film 1002 and the resin film 10001. 10 It may also be configured to be placed on one side of the laminate with the B-containing film 1002.

[0045] (Cathode electrode) The cathode electrode 211 is an electrode that generates a potential difference with respect to the readout electrode 12. The cathode electrode 211 can be a known electrode that is conductive and can transmit the radiation to be detected.

[0046] (Readout electrode) The readout electrode 12 is positioned opposite the cathode electrode 211. The readout electrode 12 has a wiring 12a and a base material 12b.

[0047] The wiring 12a can be made of any conductive metal. For example, silver, copper, gold, chromium, ITO, etc., can be used for the wiring 12a. The wiring 12a can be arranged in a matrix configuration, for example. By arranging the wiring in a matrix configuration, the position where electrons are incident can be read out as planar coordinates.

[0048] The base material 12b is a support for arranging the wiring 12a. The base material 12b can be made of inorganic material. If the base material 12b is made of inorganic material, the entire readout electrode 12 will be made of inorganic material, thus avoiding it becoming a source of emitted gas in the chamber 20.

[0049] (Electrodes for gas electron amplifiers) The electrode 10 for the gas electron amplifier is positioned between the cathode electrode 211 and the readout electrode 12.

[0050] Figure 6 is a schematic perspective view of an electrode for a gas electron amplifier. The electrode 10 for the gas electron amplifier comprises an insulating layer 1 and conductive layers 2 formed on both sides of the insulating layer 1. As shown in Figure 6, the electrode 10 for the gas electron amplifier has multiple through holes 3 that penetrate the insulating layer 1 and the conductive layer 2.

[0051] As described above, second voltage application terminals 32 (see Figure 4) are connected to both sides of the electrode 10 for the gas electron amplifier, allowing voltage to be applied. Since the conductive layer 2 is continuous in plan view as shown in Figure 6, only one contact point is needed for each of the second voltage application terminals 32. By applying different voltages to the two conductive layers 2, a strong electric field is generated within the through-hole 3.

[0052] The insulating layer 1 can be made of an inorganic material or resin. Examples of inorganic materials include functional glass such as photosensitive glass and ceramics. It is desirable that the insulating layer 1 be made of an inorganic material because it can be avoided becoming a source of released gas in the chamber 20.

[0053] A potential difference of approximately 300V to 700V is applied between the conductive layers 2 that sandwich both sides of the insulating layer 1. Therefore, if organic material is used for the insulating layer 1, it is likely to generate heat and release gas when voltage is applied. In contrast, if the insulating layer 1 is made of inorganic material, even if heat is generated when voltage is applied, almost no gas is released. Therefore, even if the chamber 20 is sealed, electron avalanche amplification is hardly hindered by released gas. In other words, it can be configured as a module with an integrated gas electron amplifier. Furthermore, the stability and reliability of the operation of the gas electron amplifier electrode 10 are also improved.

[0054] Furthermore, if the insulating layer 1 is made of an inorganic material, short circuits between the two conductive layers 2 due to carbonized conductive paths can be avoided. When organic material is used as the insulating layer, carbonized conductive paths are formed as the organic material carbonizes, which can cause short circuits between the two conductive layers 2. If a short circuit occurs, it becomes impossible to generate an electric field within the through-hole 3.

[0055] The insulating layer 1 is preferably made of ceramics among inorganic materials, and more preferably of fine ceramics. In this specification, ceramics means a sintered body obtained by firing inorganic materials. Fine ceramics refer to ceramics whose chemical composition, microstructure, shape, and manufacturing process are controlled in order to exhibit a desired function. Specifically, it is preferable to use low-temperature sintered ceramics (LTCC), high-temperature sintered ceramics (HTCC), etc.

[0056] Furthermore, among inorganic materials, ceramics are less expensive than functional glasses such as photosensitive glass. They are also softer and easier to process than glass. Therefore, through-holes 3 can be easily processed into the desired shape.

[0057] Furthermore, when using photosensitive glass for the insulating layer, it has been reported that it is difficult to use inexpensive argon as the ionizing gas, and it is preferable to use expensive neon. In contrast, in the electrode 10 for a gas electron amplifier in which the insulating layer 1 is made of ceramics, inexpensive argon can be suitably used as the ionizing gas.

[0058] The conductive layer 2 can be any conductive inorganic material. For example, silver, copper, gold, chromium, ITO, etc., can be used. The conductive layer 2 may be formed by deposition, sputtering, etc., or by coating, etc.

[0059] The through-holes 3 are arranged regularly in a plan view in the electrode 10 for the gas electron amplifier. The diameter and spacing (pitch) of the through-holes 3 can be set as appropriate. To increase the amplification factor of the neutron detector 2001, it is preferable to increase the diameter of the holes, narrow the pitch, and increase the aperture ratio. When the insulating layer is made of organic material, it is not possible to maintain strength, so it was common to have a ratio of diameter to pitch of 1:2. In contrast, the insulating layer 1 made of inorganic material is harder and has higher strength than when organic material is used, so the aperture ratio can be increased further.

[0060] The diameter of the through-hole 3 is preferably approximately constant in the thickness direction. Here, "approximately constant" means that the diameter of the through-hole 3 at the center of the insulating layer 1 in the thickness direction is 0.9 to 1.0 times the diameter of the through-hole 3 on one surface of the insulating layer 1. Here, "one surface of the insulating layer 1" is determined by the processing method. In the case of punching, it means the surface opposite to the surface to which the punch is pressed; in the case of laser processing, it means the surface to which the laser is irradiated; and in the case of photolithography, it means the surface on which the mask is formed.

[0061] When the diameter of the through-hole 3 is approximately constant in the thickness direction, the electric field generated within the through-hole 3 becomes uniform. Furthermore, a uniform electric field suppresses the significant localized decrease in electric field strength. In other words, by making the diameter of the through-hole 3 approximately constant in the thickness direction, it is possible to generate an electric field strength sufficient for electron avalanche amplification within the through-hole 3, even at low voltage levels when applying voltage to the conductive layer 2.

[0062] Furthermore, if the diameter of the through-hole 3 is approximately constant in the thickness direction, the aspect ratio of the through-hole 3 can be increased. An aspect ratio of 0.5 or higher is preferable. The aspect ratio refers to the ratio of the depth of the through-hole 3 (the sum of the thicknesses of the insulating layer 1 and the conductive layer 2) to the diameter of the through-hole 3 on one surface of the insulating layer 1.

[0063] When the shape of the through-hole 3 changes in the thickness direction, the diameter of the through-hole 3 becomes smallest in the center in the thickness direction. In other words, even if the diameter of the through-hole 3 on one surface of the insulating layer 1 is wide, the effective aperture ratio when the through-hole 3 is viewed from above becomes narrower. In other words, when the shape of the through-hole 3 changes in the thickness direction, if the aspect ratio is high, the amplification characteristics of the neutron detector 2001 cannot be maximized.

[0064] In contrast, if the diameter of the through-hole is approximately constant in the thickness direction, increasing the aspect ratio will not result in any difference in the effective aperture ratio. In other words, increasing the aspect ratio will not degrade the amplification characteristics of the neutron detector 2001. Furthermore, increasing the aspect ratio will make short circuits between the conductive layers 2 less likely to occur.

[0065] (chamber) The chamber 20 can be configured to surround the cathode electrode 211, the readout electrode 12, and the gas electron amplifier electrode 10, and can be sealed or have a reaction gas flowing through it. In other words, the cathode electrode 211, the readout electrode 12, and the gas electron amplifier electrode 10 are arranged within the space formed by the chamber 20.

[0066] As described above, if the electrodes 10 for the gas electron amplifier, which generate heat when voltage is applied, are made of inorganic material, the generation of emitted gas is suppressed. Therefore, even if the chamber 20 is sealed, it is hardly affected by the emitted gas.

[0067] Chamber 20 has an inlet 21 into which neutrons are injected. The material constituting the inlet 21 can be selected depending on the type of neutron being injected. For example, aluminum foil (Al-foil) can be used.

[0068] It is preferable that the parts of the chamber 20 other than the inlet 21 be made of inorganic material in order to further suppress the generation of exhaust gas. It is also preferable that the chamber 20 and all the components disposed within the chamber 20 be made of the same inorganic material. If each component is made of the same inorganic material, integral molding becomes easier and mass production becomes more efficient.

[0069] (Connection terminals) The connection terminal 30 consists of a first voltage application terminal 31, a second voltage application terminal 32, and a read terminal 33. The connection terminal 30 can be made of a known conductive material.

[0070] The first voltage application terminal 31 is connected to the cathode electrode 211, creating a potential difference between the cathode electrode 211 and the readout electrode 12. The second voltage application terminal 32 is connected to the conductive layers 2 on both sides of one gas electron amplifier electrode 10, forming an electric field within the through-hole 3. The readout terminal 33 is connected to the readout electrode 12, reading out electrons incident on the readout electrode 12 as a signal.

[0071] The neutron conversion stack according to the present invention can be easily incorporated into conventional gas electron amplifiers (GEMs). This makes it possible to obtain two-dimensional images across a wide energy band, from cold neutrons to thermal neutrons to fast neutrons.

[0072] [Time-resolved neutron detector] Figure 7 shows a conceptual diagram of the time-resolved neutron detector according to the present invention. Figure 8 shows a diagram illustrating the principle of the time-resolved neutron detector according to the present invention.

[0073] The time-resolved neutron detector 3000 shown in Figure 7 comprises a neutron conversion stack according to the present invention, a time-of-flight micropattern gas detector 3001 for detecting alpha particles and protons generated from the neutron conversion stack, and a pulsed neutron source 3002.

[0074] The pulsed neutron source 3002 is preferably capable of generating neutrons across a wide energy range, from cold neutrons to fast neutrons. An accelerator or the like can be used as the pulsed neutron source 3002.

[0075] In the time-of-flight micropattern gas detector 3001, the neutron detection device 2001 according to the present invention can be used as the neutron detector.

[0076] The kinetic energy En of a neutron is given by the following equation, where Mn is the mass of the neutron and T is the time it takes for it to travel a distance L.

number

[0077] As illustrated in Figure 8, by performing neutron energy resolution using the time-of-flight (ToF) method based on the above equation, it becomes possible to simultaneously acquire images of the same sample in various energy bands, from fast neutrons to cold neutrons. For example, consider a sample or sample surface that has regions that readily react with neutrons of each energy band, such as regions that readily react with fast neutrons, regions that readily react with thermal neutrons, and regions that readily react with cold neutrons. In the time-resolved neutron detector 3000 shown in Figure 7, after neutrons of each energy band react in the sample, protons and alpha particles are generated and detected during time T1, which is the time relative to the trigger signal output simultaneously with the emission of neutrons from the pulsed neutron source 3002. These are then detected during time T2, and further detected during time T3. By imaging the two-dimensional position distribution at each time point, an image for each energy band can be obtained. [Examples]

[0078] The effects of the present invention will be made clearer by the following examples. However, the present invention is not limited to the following examples and can be modified as appropriate within the scope of achieving its effects.

[0079] We conducted an experiment to confirm the effect of the neutron conversion laminate according to the present invention. Figure 9A(a) shows a schematic diagram of the neutron detection device used, Figure 9A(b) shows a schematic cross-sectional diagram of the neutron conversion stack used, and Figure 9B shows a photograph of the neutron conversion stack used. Figure 10(a) shows the thermal neutron image, and (b) shows the fast neutron image.

[0080] The neutron conversion laminate consists of a 500 μm thick PET film, a 100 nm thick aluminum (Al) film as the cathode electrode, and an 800 nm thick layer on top of that. 10 This was obtained by sequentially forming a BN film.

[0081] As a neutron source, natural radiation source californium ( 252Cf) was used. The fast neutron image shown in Figure 10(b) was obtained by directly injecting fast neutrons emitted from the neutron source into the neutron detector, while the thermal neutron image shown in Figure 10(a) was obtained by placing a polyethylene block (moderator) at the entrance of the neutron detector.

[0082] Measurements were performed by applying an electric field of the magnitude shown in Figure 9A(a).

[0083] 10 During the deposition of the BN film, the film was supported at four points using a clamp. Figure 9B shows a photograph of the neutron conversion laminate. 10 Four notches are visible where the BN film has not been deposited. In the thermal neutron image in Figure 10(a), areas where thermal neutrons are not detected are visible, corresponding to four notches. In contrast, the fast neutron image in Figure 10(b) does not show any locations corresponding to the four notches. Regarding fast neutrons, since the PET film is distributed throughout, there are no areas where fast neutrons do not react, indicating that the entire surface is reacting. The images in Figures 10(a) and (b) show that two types of neutrons have been detected. [Industrial applicability]

[0084] The neutron conversion laminate and neutrality detector of the present invention can be used as a detector for radiation with unknown energy, such as from a nuclear reactor, as an in-line beamline monitor during radiation medical treatment, and for compositional analysis of material properties. [Explanation of symbols]

[0085] 1000, 1000A Neutron Conversion Layer 1001 Hydrogen-containing resin film 1002 10 B-containing membrane 2000, 2001 Neutron detection device 3000-hour resolved neutron detector

Claims

1. A resin film containing hydrogen, and formed on the resin film １０ B alone or １０ A neutron conversion laminate having a film made of compound B, A time-of-flight micropattern gas detector for detecting alpha particles and protons generated from the neutron conversion stack, A pulsed neutron source, The time-of-flight type micropattern gas detector includes an image generation means that, based on a time reference to a trigger signal output simultaneously with the emission of neutrons from the pulsed neutron source, images the two-dimensional detection position distribution of neutrons for each time-of-flight range corresponding to each of the multiple energy bands. The image generation means is a time-resolved neutron detection device capable of simultaneously imaging the two-dimensional detection position distribution of neutrons in multiple energy bands, from cold neutrons to fast neutrons.

2. The time-resolved neutron detector according to claim 1, wherein the resin is a resin material selected from the group consisting of PET, PI, PEN, PE, PC, and PEEK.

3. The aforementioned film １０ A time-resolved neutron detector according to claim 1 or 2, comprising a nitride of B.

4. The time-resolved neutron detection device according to any one of claims 1 to 3, wherein the thickness of the resin film is 50 μm or more and 2 mm or less.

5. The time-resolved neutron detection apparatus according to any one of claims 1 to 4, wherein the thickness of the aforementioned film is 0.05 μm or more and 3 μm or less.

6. The time-resolved neutron detection apparatus according to any one of claims 1 to 5, wherein the micropattern gas detector is a gas electron amplifier.

Images