JP2018128384A - Proportional counter tube and neutron imaging system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a proportional counter tube capable of suppressing degradation of resolution.SOLUTION: A proportional counter tube 1 includes: a conversion film 23 which receives a neutron N and generates an alpha particle A; a capillary plate 21 that generates an electron C caused by the alpha particle A and generates scintillation light SC by the electron C; a voltage application part 11 that generates an electric field for guiding the electron C; and a chamber 2 for housing the conversion film 23, the capillary plate 21 and the voltage application part 11. The capillary plate 21 is formed with plural through holes 27 arranged in two dimensions. The conversion film 23 covers the openings 27a of the through holes 27.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a proportional counter and a neutron imaging system.

  As an apparatus for detecting radiation, the detectors disclosed in Patent Documents 1 and 2 are known. For example, the apparatus disclosed in Patent Document 1 detects X-rays. This apparatus includes a chamber, a capillary plate disposed in the chamber, and a MOS sensor array disposed below the capillary plate. A gas for detecting radiation is enclosed in the chamber. An electric field is formed between the chamber and the capillary plate.

  Radiation incident on the chamber interacts with the molecules of the sealed gas and emits primary electrons by the photoelectric effect. When the primary electrons have high energy and fly while applying energy to the molecules constituting the encapsulated gas, electron-ion pairs are generated during the flight. The electrons enter a through hole provided in the capillary plate by an electric field. When the electrons that have entered the through hole of the capillary plate move along the electric field formed inside the through hole, they collide one after another with molecules of the sealed gas existing inside the through hole. Electron multiplication and photo multiplication are performed by this collision. This propagated light is detected by the MOS sensor array.

JP 2004-241298 A JP 2009-245688 A

  In the detector of Patent Document 1, it is considered that the position of the through hole where light emission is confirmed corresponds to the position where the radiation is incident. However, the correspondence between the position of the through hole where light emission is confirmed and the position where the radiation is incident may be weak.

  Specifically, primary electrons fly a certain distance in a drift region formed between the entrance window of the chamber and the capillary plate. If it does so, when a radiation enters right above a certain through-hole, it may arise that the charged particle and ionization electron which were produced | generated by the said radiation approach into another through-hole.

  Further, the charged particles may include alpha particles. Like alpha particles, especially high energy charged particles travel longer. If it does so, the shift | offset | difference of the position of the through-hole by which light emission was confirmed and the position which the radiation injected will become large. In addition, it may be difficult to control the flight of charged particles due to the characteristics of charged particles such as charge and energy. Due to such factors, if the correspondence between the position of the through hole where light emission is confirmed and the position where the radiation is incident is weakened, the resolution of the two-dimensional image indicating the intensity of the radiation and the incident position may be reduced.

  Accordingly, an object of the present invention is to provide a proportional counter and a neutron imaging system that can suppress a decrease in resolution.

  According to one aspect of the present invention, a neutron is received from a first incident surface, a charged particle corresponding to the neutron is generated and a charged particle is emitted from the first emission surface, and the charged particle is supplied to the first emission surface. A second converter that receives from a second incident surface facing and generates scintillation light based on ionization electrons while generating ionized electrons by ionizing a gas by charged particles, and emits the scintillation light from the second emission surface; An electric field generator that generates an electric field that guides ionized electrons in a direction from the second incident surface toward the second emission surface, and a first conversion unit, a second conversion unit, an electric field generation unit, and a gas, and a first neutron conversion And a container having an exit window portion that guides the light source and an exit window portion that emits scintillation light, and the second conversion portion is arranged in a two-dimensional manner penetrating from the second entrance surface to the second exit surface. Multiple Through holes are provided, the first conversion unit, to close the opening of the second incident surface side of the through hole.

  Neutrons enter the first incident surface of the first converter from the incident window of the chamber. Due to the incidence of this neutron, the first converter generates charged particles and emits the charged particles from the first emission surface. The emitted charged particles enter the second conversion unit facing the first emission surface. Since this 2nd conversion part is provided with the several through-hole arrange | positioned two-dimensionally, a charged particle injects into the said through-hole. Then, ionization electrons are generated due to the interaction between the gas filled in the through holes and the charged particles. The ionized electrons collide with gas molecules while being accelerated in the direction toward the second emission surface by the electric field generated by the electric field generating portion, and further generate ionized electrons to generate scintillation light. Here, the 1st conversion part has block | closed the opening by the side of the 2nd entrance plane of the through-hole in a 2nd conversion part. Then, when a neutron is incident directly above a certain through hole, there is a high possibility that charged particles generated by the neutron are incident on a through hole existing immediately below. That is, the correspondence between the position where the neutron is incident and the position of the through hole where light emission is confirmed is strengthened. Therefore, according to this neutron detector, it is possible to suppress a decrease in resolution.

  The second conversion portion further includes a tapered hole that is provided at a corner between the second emission surface and the inner wall surface of the through hole, and has a smaller inner diameter along the direction from the second incidence surface to the second emission surface. It may be provided. According to this structure, the area of the 1st output surface of the 1st conversion part exposed to the opening by the side of the 2nd entrance plane of a through-hole spreads. That is, the aperture ratio increases. Accordingly, charged particles can be easily received in the through-holes, so that neutron detection efficiency can be increased.

  The proportional counter may further include a third converter that is provided on a tapered surface that forms a tapered hole and that receives charged neutrons to generate charged particles. According to this structure, the area | region which can convert a neutron into a charged particle increases. Therefore, since it becomes easier to catch neutrons, the detection efficiency of neutrons can be further increased.

  The electric field generation unit includes a first electrode unit and a second electrode unit provided so as to sandwich the second conversion unit, and the first electrode unit is an electrode provided on the second incident surface of the second conversion unit. In addition, the second electrode unit may be an electrode provided on the second emission surface of the second conversion unit. According to this configuration, a potential for acceleration and multiplication of ionized electrons can be reliably generated inside the through hole.

  The conversion film may have conductivity or may have insulating properties. According to this configuration, a potential for acceleration and multiplication of ionized electrons can be reliably generated inside the through hole.

  A neutron imaging system according to another aspect of the present invention includes a proportional counter and a light detection unit that receives scintillation light emitted from the proportional counter, and the proportional counter receives neutrons from a first incident surface. The charged particles corresponding to the neutrons are generated and the charged particles are emitted from the first exit surface, and the charged particles are received from the second entrance surface facing the first exit surface. A scintillation light based on ionization electrons is generated while generating ionization electrons by ionizing, and a second conversion unit that emits the scintillation light from the second emission surface, and an ionization electron in a direction from the second incidence surface toward the second emission surface An electric field generating unit for generating an electric field for guiding the first conversion unit, a second conversion unit, an electric field generating unit, and an incident window unit for containing a gas and guiding neutrons to the first conversion unit, and scintillation And a container having an exit window for emitting light, and the second converter is provided with a plurality of two-dimensionally arranged through holes penetrating from the second entrance surface to the second exit surface. The first converter closes the opening on the second incident surface side of the through hole. According to this system, a high-resolution neutron image can be obtained.

  According to the present invention, a proportional counter and a neutron imaging system capable of suppressing a decrease in resolution are provided.

FIG. 1 is a perspective view of a proportional counter according to the first embodiment. FIG. 2 is a schematic diagram for explaining the configuration of the proportional counter shown in FIG. FIG. 3 is an enlarged perspective view showing a part of the conversion unit shown in FIG. FIG. 4 is a diagram showing a typical process for manufacturing a proportional counter. FIG. 5 is a diagram showing a typical process for manufacturing a proportional counter. FIG. 6 is an enlarged perspective view showing a part of the conversion unit in the proportional counter according to the second embodiment. Part (a) of FIG. 7 is a diagram for explaining the function and effect of the conversion unit according to the second embodiment, and part (b) of FIG. 7 explains the function and effect of the conversion unit according to the first embodiment. FIG. FIG. 8 is an enlarged perspective view showing a part of the conversion unit in the proportional counter according to the third embodiment. FIG. 9 is a diagram for explaining the function and effect of the conversion unit according to the third embodiment. 10A is a diagram showing the configuration of the conversion unit in the proportional counter according to the first modification, and FIG. 10B shows the configuration of the conversion unit in the proportional counter according to the second modification. FIG. Part (a) of FIG. 11 is a diagram for explaining the operation of the proportional counter according to Comparative Example 1, and part (b) of FIG. 11 is for explaining the operation of the proportional counter according to Comparative Example 2. FIG.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

  The proportional counter according to this embodiment is a neutron-sensitive gas scintillation imager (n-GSI) used in a neutron detector. Analysis techniques using neutrons and their usefulness are being confirmed by basic research using nuclear reactors and large accelerators. Research on small accelerator-type neutron sources is also underway. Industrial applications of neutrons that are used complementarily to X-ray analysis include, for example, the analysis of the operation of next-generation energy devices such as lithium-ion battery members that are about sub-millimeters in size, and new products that are used for highly functional pharmaceuticals and chemical products. The importance of the development of organic materials is expected to increase in the future.

As shown in FIG. 1, the neutron imaging system 50 includes a proportional counter 1 and a light detection unit 51. When detecting particles having no charge such as neutron N, neutron N is converted into alpha particles and ⁷ Li particles (hereinafter referred to as “alpha particles”) as charged particles by a nuclear reaction. A method of indirectly detecting the alpha particles and the like by introducing them to the electron multiplication part is used. Therefore, the proportional counter 1 receives neutrons N and generates alpha particles and the like. Next, alpha particles and the like are guided to the electron multiplying portion, and ionized electrons are generated from the alpha particles and the like. The ionized electrons collide with gas molecules while being accelerated by the electric field, and generate scintillation light SC while generating ionized electrons. The scintillation light SC is detected by the light detection unit 51. According to such a configuration, a two-dimensional neutron detection image having high sensitivity and high resolution can be obtained.

The proportional counter 1 includes a chamber 2 (container) and a conversion unit 3. The chamber 2 is filled with a predetermined gas used for detecting the neutron N, and accommodates the conversion unit 3 in the atmosphere of the gas. The gas includes a rare gas and an organic gas. This organic gas generates scintillation light SC. The organic gas also plays a role of quenching. For example, the gas includes Ne / CF ₄ , Ar / CF ₄ , Ar / H ₄ / TMA, and the like. Amine-based gases such as TMA and TEA have a wavelength conversion function utilizing the so-called Penning effect.

  The chamber 2 includes a housing part 4, an incident face plate 6 (incident window part), and an exit window part 7. The casing 4 has a cylindrical outer shape as a whole by connecting a plurality of side tubes 4a in the axial direction. The incident face plate 6 is disposed at one end of the housing part 4 and closes the end. The incident face plate 6 has a main surface 6 a that receives neutrons N and a back surface 6 b that emits neutrons N. The main surface 6a is exposed to the outside of the chamber 2. The back surface 6 b is exposed inside the chamber 2. The other end of the casing 4 is closed by the exit window 7. The converter 3 receives the neutron N and emits scintillation light SC corresponding to the neutron N. The conversion unit 3 is attached to the housing unit 4 so as to be disposed between the incident face plate 6 and the exit window unit 7.

  The emission window 7 emits the scintillation light SC generated in the conversion unit 3 to the outside of the chamber 2. The exit window 7 faces the conversion unit 3. Accordingly, a gap is formed between the conversion unit 3 and the exit window 7. The exit window 7 is transparent to the scintillation light SC. The exit window 7 has a window body 8 and a transparent electrode 9 (see FIG. 2). The window main body 8 has a cylindrical shape and is composed of Kovar glass or a fiber optic plate (FOP). The window body 8 has a main surface 8a that faces the conversion unit 3 and receives the scintillation light SC, and a back surface 8b that emits the received scintillation light SC. The transparent electrode 9 is provided on the main surface 8 a of the window body 8. The transparent electrode 9 is electrically connected to the housing part 4. Since the casing 4 is grounded, it can be said that the transparent electrode 9 is electrically grounded.

  The light detection unit 51 receives the scintillation light SC emitted from the proportional counter 1 and generates information for the scintillation light SC. As the light detection unit 51, for example, an integrating camera such as a CCD camera or a CMOS camera in which image pickup elements are two-dimensionally arranged can be used.

  As shown in FIG. 2, the proportional counter 1 further includes a voltage applying unit 11 that applies a predetermined voltage to each part constituting the proportional counter 1. The voltage applying unit 11 includes a power source 12, resistance elements 13 </ b> A and 13 </ b> B, and an electric circuit 14. The voltage applying unit 11 generates a predetermined potential difference between the incident face plate 6 and the transparent electrode 9. In addition, the voltage application unit 11 generates a predetermined potential difference between the upper surface side and the lower surface side of the conversion unit 3. The power source 12 is directly connected to the upper electrode 16 provided on the upper surface side of the conversion unit 3 without using a resistance element. The power source 12 is connected to a lower electrode 17 provided on the lower surface side of the conversion unit 3 via a resistance element 13B. According to this connection configuration, it is possible to generate an electric field E for guiding downward ionized electrons generated by the interaction between the alpha particles and the like and the gas. Further, the power source 12 is connected to the incident face plate 6 via resistance elements 13A and 13B. The housing unit 4 is connected to a signal ground 18. The resistance element 13 </ b> B is provided to generate a potential difference between the lower electrode 17 and the transparent electrode 9 and attract ionized electrons to the transparent electrode 9. According to such a configuration, it is possible to output a current from the transparent electrode 9, and an inspection using the current output from the transparent electrode 9 in the manufacturing process of the proportional counter 1 can be performed. The resistance element 13B may be arranged as necessary, and the proportional counter 1 may be configured without the resistance element 13B.

  The conversion unit 3 is disposed on the back surface 6 b side of the incident surface plate 6. The converter 3 is separated from the incident face plate 6. Accordingly, a gap is formed between the conversion unit 3 and the incident face plate 6. As illustrated in FIG. 3, the conversion unit 3 includes a converter substrate 19 and a capillary plate 21 (second conversion unit). Converter substrate 19 receives neutron N and generates alpha particles A and the like. The capillary plate 21 receives the alpha particles A and the like to generate electrons C, and the electrons C are accelerated by the electric field E to generate electron multiplication, thereby generating scintillation light SC.

  The converter substrate 19 includes a substrate portion 22 and a conversion film 23 (first conversion portion). The substrate part 22 has a disk shape with a thickness of about 0.5 mm. Since the substrate portion 22 has a predetermined mechanical strength, the conversion film 23 can be easily handled by forming the thin conversion film 23 on the substrate portion 22. The substrate unit 22 has a main surface 22a that receives neutrons N and a back surface 22b from which neutrons N are emitted. The substrate unit 22 is made of a metal material such as aluminum or stainless steel (SUS).

The conversion film 23 is a film having a thickness of about 3 μm and receives neutrons N to generate alpha particles A and the like. The conversion film 23 is formed on the back surface 22 b of the substrate unit 22. The conversion film 23 is in contact with the back surface 22b of the substrate unit 22, and receives a main surface 23a (first incident surface) that receives neutrons N transmitted through the substrate unit 22, and a back surface 23b that emits transmitted neutrons N, alpha particles A, and the like. First emission surface). The conversion film 23 is made of a material such as ¹⁰ B or ¹⁰ B ₄ C. For example, the conversion film 23 composed of ¹⁰ B generates a reaction of ¹⁰ B + n → ⁷ Li (0.8 MeV) + α (1.5 MeV) when it receives neutron N. Here, “n” represents a neutron, and “α” represents an alpha particle A. Further, the conversion film 23 made of ¹⁰ B ₄ C has conductivity. It can be said that the conversion film 23 made of ¹⁰ B also has conductivity although the resistance value is high. The material constituting the conversion film 23 may be a conductive material or an insulating material regardless of whether or not it is conductive.

  The capillary plate 21 has a thickness of about 50 μm to 400 μm, for example, 300 μm. The capillary plate 21 is formed of a glass substrate such as lead-containing glass or soda glass. The capillary plate 21 has a main surface 21a (second incident surface) facing the converter substrate 19 and a back surface 21b (second emission surface) facing the exit window 7 (see FIG. 2). Specifically, the main surface 21 a of the capillary plate 21 faces the back surface 23 b of the conversion film 23.

  The capillary plate 21 has a plurality of through holes 27 penetrating in the thickness direction. The inner diameter of the through hole 27 is about 6 μm to 100 μm, preferably 25 μm or more and 50 μm, for example, 50 μm. The bias angle is zero degrees. The interval (pitch) between the through holes 27 is set so as to ensure a sufficient strength in terms of structure and satisfy desired performance (resolution, resolution, etc.). For example, the interval is about several μm to several tens of μm. The through hole 27 is filled with gas sealed in the chamber 2 (see FIG. 2). The through holes 27 constitute independent optical / electron multipliers. Therefore, the gas filled in the through hole 27 is ionized by the alpha particles A and the like, and electrons C are generated. The electrons C are accelerated by the electric field E to cause electron multiplication and generate scintillation light SC.

  The main surface 21 a of the capillary plate 21 is provided with a film-like upper electrode film 24 (first electrode part). A part of the upper electrode film 24 is also provided so as to slightly enter the through hole 27 from the main surface 21a. Specifically, the upper electrode film 24 is provided from the main surface 21a to the through hole 27 up to a position about half the inner diameter (d) of the through hole 27 (0.5 × d). The capillary plate 21 is physically connected to the back surface 23 b of the conversion film 23 via the upper electrode film 24. The upper electrode film 24 is made of, for example, Inconel. Here, when the conversion film 23 has conductivity, the substrate portion 22, the conversion film 23, and the upper electrode film 24 cooperate to form the upper electrode 16. In this case, the potential of the substrate unit 22 is the same as the potential of the conversion film 23.

  A film-like lower electrode film 26 (second electrode portion) is provided on the back surface 21 b of the capillary plate 21. As with the upper electrode film 24, a part of the lower electrode film 26 enters the through hole 27. The lower electrode film 26 is electrically insulated from the upper electrode film 24. Accordingly, since one end of the voltage applying unit 11 (see FIG. 2) is connected to the upper electrode 16 and the other end is connected to the lower electrode 17 via the resistance element 13, the upper electrode 16 and the lower electrode 17 A predetermined potential difference can be generated between the two. Due to this potential difference, an electric field E in the thickness direction of the capillary plate 21 is generated. That is, the upper electrode film 24 and the lower electrode film 26 constitute the electric field generating unit 15. Here, as described above, the electric field generation unit 15 may include the substrate unit 22 and the conversion film 23.

  Here, as already described, the capillary plate 21 is physically connected to the converter substrate 19 via the upper electrode film 24. The back surface 23b of the conversion film 23 facing the upper electrode film 24 in the converter substrate 19 is a flat surface. As a result, the converter substrate 19 exists immediately above the through hole 27 of the capillary plate 21. Specifically, the through hole 27 is blocked by the conversion film 23. For example, in this configuration, the gas in the through hole 27 can enter and exit from the opening 27b of the through hole 27 formed in the back surface 21b, but enters and exits from the opening 27a of the through hole 27 formed in the main surface 21a. There is no.

  The process of creating the proportional counter 1 will be briefly described. As shown in FIG. 4A, first, a converter substrate 19 is prepared. Next, as shown in FIG. 4B, a capillary plate 21 is prepared. Next, the upper electrode film 24 and the lower electrode film 26 are formed on the capillary plate 21 that is a glass substrate provided with the through holes 27.

  Next, as shown in part (c) of FIG. 4, the converter substrate 19 and the capillary plate 21 are assembled to the housing part 4. First, the capillary plate 21 is placed on the support portion 28. At this time, the lower electrode film 26 of the capillary plate 21 is electrically connected to the support portion 28. Next, the converter substrate 19 is placed on the main surface 21 a of the capillary plate 21. At this time, the converter substrate 19 is assembled so that the conversion film 23 of the converter substrate 19 covers a region where the through hole 27 of the capillary plate 21 is provided. Then, the connecting portion 29 is electrically connected to the substrate portion 22 of the converter substrate 19.

  Next, the entrance face plate 6 and the subassembly S are placed in the vacuum chamber F as shown in FIG. And these are heated in the vacuum chamber F, and a water | moisture content is removed. Next, the gas G is supplied into the vacuum chamber F. In this state, the incident face plate 6 is attached to the subassembly S as shown in FIG. By sealing the incident face plate 6 to the subassembly S, the chamber 2 is formed. The proportional counter 1 is completed through the above steps.

  Next, the operation of the proportional counter 1 according to this embodiment will be described while comparing with the operation of the proportional counter according to the first comparative example and the operation of the proportional counter according to the second comparative example.

  As shown in part (a) of FIG. 11, in the proportional counter 100 according to the comparative example 1, the conversion unit 103 is disposed inside the chamber 102. In the converter substrate 119 of the conversion unit 103, the conversion film 123 is provided on the back surface 122 b of the substrate unit 122. Electrode films 124 and 126 are provided on the main surface 121a and the back surface 121b of the capillary plate 121 in the conversion unit 103, respectively. Here, in the proportional counter 100 according to the comparative example 1, the conversion film 123 is not physically in contact with the capillary plate 121. In other words, in the proportional counter 100, a space is formed between the conversion film 123 and the capillary plate 121. This space is called a drift region P.

  When the neutron N enters the conversion film 123, the conversion film 123 emits charged particles B1. For example, the charged particle B1 such as the alpha particle A has high energy. Accordingly, the charged particles B1 emitted from the back surface 123b of the conversion film 123 fly in the drift region P over a long distance. The drift region P is filled with gas. Then, while the charged particle B1 flies through the drift region P, ionized electrons B2 are further generated due to the interaction between the charged particle B1 and the gas. Here, the flight distance of the charged particle B1 can be longer than the arrangement interval of the through holes 127A, 127B, and 127C. For this reason, when the neutron N is incident directly on the through hole 127A, the ionized electrons B2 may be incident on the through holes 127B and 127C different from the through hole 127A. In other words, ionized electrons B2, which are ionized electrons that become the seed signal at the time of multiplication than the spread of neutrons N, are widely generated. Here, it is conceivable to control the behavior of the charged particle B1 using an electric field or a gas pressure. However, when charged particle B1 is alpha particle A etc., since energy is high, the control is difficult. Due to the drift region P and the charged particle B1 having high energy, the position where the charged particle B1 is generated when the neutron N is incident is different from the position of the through hole 27 where the scintillation light SC is generated. Is weak.

  As shown in part (b) of FIG. 11, the proportional counter 200 according to the comparative example 2 includes a chamber 202, a conversion film 223, and a capillary plate 221. Here, in the proportional counter 200 according to the comparative example 2, the conversion film 223 is provided on the main surface 221 a of the capillary plate 221. On the other hand, the conversion film 223 has a plurality of through holes 223a communicating with the through holes 227A, 227B, and 227C, respectively. That is, in the proportional counter 200 according to the comparative example 2, the conversion film 223 does not exist directly above the through holes 227A, 227B, and 227C of the capillary plate 221. Further, the conversion film 223 is not provided on the substrate portion 222.

  For example, it is assumed that neutron N1 is incident so as to pass through through hole 227A. In this case, since the conversion film 223 does not exist on the through hole 227A, the charged particle B1 is not generated by the neutron N1. Therefore, the neutron N1 cannot be detected. On the other hand, for example, a case where neutron N2 enters the conversion film 223 is assumed. In this case, charged particles B1 are emitted from the conversion film 223. The charged particle B1 interacts with the gas during the flight, and further generates ionized electrons B2. The ionized electrons B2 enter the through holes 227B and 227C, respectively, and are accelerated by the electric field E to cause electron multiplication, thereby generating scintillation light SC1 and SC2. Even in such a case, since the position where the neutron N2 is incident and the positions of the through holes 227B and 227C where the scintillation lights SC1 and SC2 are generated are different, the correspondence is weak. In this case, when a two-dimensional image is obtained using a CCD camera or the like, the boundary of the imaging object tends to become unclear. That is, the resolution decreases.

  On the other hand, as shown in FIG. 3, in the proportional counter 1 according to the present embodiment, the conversion film 23 blocks the opening 27 a of the through hole 27. In other words, the proportional counter 1 according to the present embodiment does not have the drift region P. In other words, in the proportional counter 100 of Comparative Example 1, as described above, the charged particle B1 ionizes the gas to generate ionized electrons B2 (drift region P), and the proliferation by the ionized electrons B2 occurs. It can be said that the generated region (through hole 127) is a different region. The proportional counter 1 according to the present embodiment includes a region where charged particles B1 (alpha particles A or the like) ionize gas to generate ionized electrons B2 (electrons), and a region where proliferation due to ionized electrons B2 (electrons C) occurs. Can be said to be the same region (through hole 27).

  Then, for example, on the back surface 23b of the conversion film 23, the alpha particles A and the like emitted from the region 23b1 exposed to the through hole 27A immediately enter the through hole 27A immediately below the region 23b1. That is, alpha particles A or the like do not enter the other adjacent through holes 27B and 27C. The alpha particles A and the like incident on the through hole 27A interact with the gas filling the through hole 27A and generate electrons C. Since the electric field E is generated in the axial direction of the through hole 27 (the thickness direction of the capillary plate 21), each of the through holes 27 functions as an avalanche region. Scintillation light SC is generated during this electron multiplication. Therefore, since the position where the alpha particles A and the like are emitted is associated with the position of the through hole 27A, the correspondence can be strengthened. In other words, the spread of electrons C due to the flight of alpha particles A or the like can be kept inside the through hole 27. Therefore, it is possible to suppress a decrease in resolution. In short, the proportional counter 1 improves the resolution by bringing the conversion film 23 and the capillary plate 21 close to each other while ensuring a gas retention space.

  The proportional counter 1 according to the present embodiment limits the spread of alpha particles A and the like generated at the position where the neutron N is incident by the capillary plate 21. The electrons C generated by the interaction of the alpha particles A and the like with the gas and contributing to the electron multiplication are limited to the inside of the channel (through hole 27) corresponding to the incident position of the neutron N, and thus acquired by the light detection unit 51. The boundary of the two-dimensional light image to be made becomes clear. Furthermore, the proportional counter 1 of the present embodiment integrates the upper electrode 16 and the conversion film 23 for generating the electric field E required for the multiplication operation. Therefore, as compared with the configuration in which the drift region P is provided between the capillary plate 21 and the conversion film 23 as in the comparative example 1, the assembly is facilitated.

  Furthermore, the proportional counter 1 of the present embodiment has a larger area of the conversion film 23 that contributes to the detection of neutrons N than the proportional counter 200 of Comparative Example 2. Specifically, in the proportional counter 1 of the present embodiment, the conversion film 23 on the through hole 27 mainly contributes to the detection of the neutron N. On the other hand, in the proportional counter 1 of Comparative Example 2, the conversion film 23 on the main surface 21a of the capillary plate 21 contributes to the detection of neutrons N. In the main surface 21a of the capillary plate 21, the opening area of the through hole 27 is larger than the remaining area. Therefore, the proportional counter 1 of this embodiment has a larger area of the conversion film 23 that contributes to the detection of the neutrons N than the proportional counter 200 of the comparative example 2. Therefore, the proportional counter 1 can increase the detection efficiency.

Second Embodiment
Next, a proportional counter according to the second embodiment will be described. As shown in FIG. 6, in the proportional counter 1A according to the second embodiment, the structure of the through-hole 31 provided in the capillary plate 21A of the conversion unit 3A is the through-hole of the proportional counter 1 according to the first embodiment. 27. Hereinafter, the capillary plate 21A, the upper electrode film 24A, and the lower electrode film 26A will be described, and descriptions of common parts and structures will be omitted.

  A plurality of through holes 31 are provided in the capillary plate 21A. Furthermore, a plurality of tapered holes 32 are provided in the capillary plate 21A. Such a configuration having the tapered hole 32 can also be called a funnel type. The tapered hole 32 is provided in the main surface 21a of the capillary plate 21A. The central axis of the tapered hole 32 overlaps with the central axis of the through hole 31. One opening of the tapered hole 32 is provided in the main surface 21a. The other opening of the tapered hole 32 is connected to the through hole 31. And the internal diameter (D2) of one opening is larger than the internal diameter (D1) of the other opening (refer the (a) part of FIG. 7).

  The main surface 21a includes a flat surface portion 21a1 and a ridge portion 21a2 formed between the tapered holes 32. The upper electrode film 24A is provided so as to cover the flat portion 21a1 and the ridge portion 21a2. The tapered hole 32 is a region surrounded by the tapered surface 33. The tapered surface 33 is provided at a corner between the main surface 21 a and the inner wall surface 27 c of the through hole 27. The upper electrode film 24A is also provided on the tapered surface 33.

  As shown in FIG. 7A, according to the tapered hole 32 and the through hole 31, the inner diameter D2 of the tapered hole 32 from the inner diameter D1 of the through hole 31 along the thickness direction of the capillary plate 21A. Gradually expand until. That is, as compared with the configuration in which one opening of the through hole 27 is provided in the main surface 21a as in the first embodiment, the area of the conversion film 23 exposed to the space communicating with the through hole 31 is increased.

  More specifically, in the proportional counter 1 of the first embodiment (see the part (b) in FIG. 7), when alpha particles A1a or the like are generated immediately above the main surface 21a between the through holes 27, any penetration is made. There may be a case where alpha particles A1a and the like do not enter the hole 27 as well. On the other hand, in the proportional counter 1A of the second embodiment, since the flat portion 21a1 between the through holes 31 is small, the chance that the alpha particles A1 and the like are incident on the through holes 27 can be increased. For example, if the inner diameter D3 of the through hole 27A is the same as the inner diameter D1 of the through hole 31, the proportional counter 1A according to the second embodiment is the difference between the opening area of the tapered hole 32 and the opening area of the through hole 31. The area for receiving the alpha particles A1 and the like is enlarged. That is, since the contact area between the alpha particle A1 and the like and the gas increases, the detection efficiency of the neutron N can be increased.

  The difference from the proportional counter 1 of the first embodiment can also be indicated by the aperture ratio. The aperture ratio is the opening area of the through hole 27 occupying per unit area of the capillary plate 21. For example, the opening ratio of the proportional counter 1 of the first embodiment is 50 or more and 70 or less, whereas the opening ratio of the proportional counter 1A of the second embodiment is 70 or more and 98 or less.

  Therefore, according to the proportional counter 1A according to the second embodiment, it is possible to increase the opportunity to convert the neutron N into alpha particles A or the like. Thereby, the detection efficiency of neutron N can be improved.

  The tapered hole 32 is provided in a part of the capillary plate 21A near the main surface 21a. Accordingly, the influence of the presence of the tapered hole 32 on the strength of the capillary plate 21A is negligible. Therefore, the proportional counter 1A can increase the detection efficiency of the neutron N without impairing the strength of the capillary plate 21A.

  Furthermore, according to the taper hole 32, the enlargement of the inner diameter is a part near the main surface 21a. Then, the thickness of the partition wall that separates the through holes 31 is kept equal to that of the capillary plate 21 according to the first embodiment. Accordingly, the alpha particles A and the like are prevented from passing through the partition walls that separate the through holes 31, so that a reduction in resolution can be suppressed.

<Third Embodiment>
Next, a proportional counter 1B according to the third embodiment will be described. As shown in FIGS. 8 and 9, in addition to the configuration of the proportional counter 1A according to the second embodiment, the proportional counter 1B according to the third embodiment further includes an additional conversion film 34 (first It differs from the proportional counter 1A according to the second embodiment in that it has (3 conversion units). Accordingly, the configurations of the capillary plate 21A, the upper electrode film 24A, and the lower electrode film 26A are the same as those of the proportional counter 1A according to the second embodiment.

  Specifically, the additional conversion film 34 is provided so as to cover the upper electrode film 24A. According to this configuration, the conversion film 23 contacts the capillary plate 21A via the additional conversion film 34 and the upper electrode film 24A. Since the upper electrode film 24 </ b> A is provided on the tapered surface 33, the tapered surface 33 faces the conversion film 23. Therefore, the additional conversion film 34 also faces the back surface 23 b of the conversion film 23.

  According to the proportional counter 1B according to the third embodiment, the same effects as those of the proportional counter 1A according to the second embodiment can be obtained. That is, alpha particles A and the like generated in the conversion film 23 can be more easily received by the tapered holes 32.

  As shown in FIG. 9, the proportional counter 1B according to the third embodiment has an additional effect in addition to the above effects. The neutron N may pass through the conversion film 23 without generating alpha particles A or the like. The proportional counter 1B can make the neutron N transmitted through the conversion film 23 further enter the additional conversion film 34 (specifically, the region of the additional conversion film 34 on the tapered surface 33). Therefore, according to this additional conversion film 34, the area of the conversion film for converting neutrons N to alpha particles A or the like is increased. Therefore, the opportunity to convert the neutron N into alpha particles A or the like can be further increased, so that the detection efficiency of the neutron N can be further increased.

  The present invention has been described in detail based on the embodiments. However, the present invention is not limited to the above embodiment. The present invention can be variously modified without departing from the gist thereof.

  The conversion film 23 according to the first embodiment has conductivity. In this case, the relationship among the potential (HV1) of the substrate portion 22, the potential (HV2) of the upper electrode film 24, and the potential (HV3) of the lower electrode film 26 is HV1 = HV2 <HV3. However, as illustrated in part (a) of FIG. 10, the conversion film 23 </ b> A in the conversion unit 3 </ b> C according to Modification 1 may have insulating properties. In this case, the relationship among the potential (HV1) of the substrate portion 22, the potential (HV2) of the upper electrode film 24, and the potential (HV3) of the lower electrode film 26 is HV1 <HV2 <HV3.

  The upper electrode 16 according to the first embodiment is configured by the substrate portion 22, the conversion film 23, and the upper electrode film 24. For example, as illustrated in part (b) of FIG. 10, the upper electrode 16A of the conversion unit 3D according to Modification 2 does not include the upper electrode film 24, and is configured by the substrate unit 22 and the conversion film 23. Also good. The substrate part 22 and the conversion film 23 are both conductive. Specifically, the upper electrode film 24 is not provided on the main surface 21 a of the capillary plate 21. Therefore, the conversion film 23 is in direct contact with the main surface 21a. In this case, the relationship between the potential (HV1) of the substrate portion 22 and the potential (HV3) of the lower electrode film 26 is HV1 <HV3. In the configuration shown in part (b) of FIG. 10, since the conversion film 23 has conductivity, it is possible to prevent positive charges from staying on the back surface 23 b of the conversion film 23.

1, 1A, 1B, 100, 200 ... proportional counter, 2, 102, 202 ... chamber (container), 3, 3A, 3C, 3D, 103 ... conversion part, 4 ... housing part, 4a ... side pipe, 6 DESCRIPTION OF SYMBOLS ... Incident face plate, 7 ... Output window part, 8 ... Window main body, 9 ... Transparent electrode, 11 ... Voltage application part, 12 ... Power supply, 13, 13A, 13B ... Resistance element, 14 ... Electric circuit, 16, 16A ... Upper electrode 17 ... lower electrode, 18 ... signal ground, 19, 119 ... converter substrate, 21, 21A, 121, 221 ... capillary plate (second conversion part), 21a1 ... flat part, 21a2 ... ridge part, 22, 122 ... Substrate part, 23a ... main surface (first incident surface), 23b ... back surface (first exit surface), 21a ... main surface (second entrance surface), 21b ... back surface (second exit surface), 23, 23A, 123 , 223 ... Conversion membrane (first conversion part), 24, 24A Upper electrode film, 26, 26A ... lower electrode film, 27, 27A, 27B, 31, 127A, 127B, 127B, 227A, 227B, 227C ... through hole, 27a ... opening, 27c ... inner wall surface, 28 ... support part, DESCRIPTION OF SYMBOLS 29 ... Connection part, 32 ... Tapered hole, 33 ... Tapered surface, 34 ... Additional conversion film, 50 ... Neutron imaging system, 51 ... Photodetection part, 8a, 22a, 121a, 221a ... Main surface, 6b, 8b, 22b, 121b, 123b ... back surface, 124, 126 ... electrode film, A ... alpha particle, C ... electron, F ... vacuum chamber, D1, D2 ... inner diameter, E ... electric field, G ... gas, N, N1, N2 ... neutron, SC , SC1, SC2 ... scintillation light, S ... subassembly, P ... drift region.

Claims (7)

A first converter that receives neutrons from a first incident surface, generates charged particles corresponding to the neutrons, and emits the charged particles from a first emission surface;
The charged particles are received from a second incident surface facing the first emission surface, and ionized electrons are generated by ionizing a gas by the charged particles to generate scintillation light based on the ionized electrons. A second converter that exits from the second exit surface;
An electric field generator for generating an electric field for guiding the ionized electrons in a direction from the second incident surface toward the second emission surface;
A container that includes the first conversion unit, the second conversion unit, the electric field generation unit, and the gas, and an incident window unit that guides the neutrons to the first conversion unit and an emission window unit that emits the scintillation light. And comprising
The second conversion unit is provided with a plurality of two-dimensionally arranged through holes penetrating from the second incident surface to the second emission surface,
The first conversion unit is a proportional counter that closes the opening on the second incident surface side of the through hole.   The second conversion portion is provided at a corner between the second exit surface and the inner wall surface of the through hole, and has a small inner diameter along a direction from the second entrance surface to the second exit surface. The proportional counter of claim 1, further comprising a tapered hole.   The proportional counter according to claim 2, further comprising a third conversion unit that is provided on a tapered surface that forms the tapered hole and generates the charged particles upon receiving the neutrons. The electric field generation unit includes a first electrode unit and a second electrode unit provided so as to sandwich the second conversion unit,
The first electrode part is an electrode provided on the second incident surface of the second conversion part,
And
The proportional counter according to claim 1, wherein the second electrode unit is an electrode provided on the second emission surface of the second conversion unit.   The proportional counter according to claim 4, wherein the first conversion unit has conductivity.   The proportional counter according to claim 4, wherein the first converter has an insulating property. A proportional counter;
A light detection unit that receives the scintillation light emitted from the proportional counter,
The proportional counter is
A first converter that receives neutrons from a first incident surface, generates charged particles corresponding to the neutrons, and emits the charged particles from a first emission surface;
The charged particles are received from a second incident surface facing the first emission surface, and ionized electrons are generated by ionizing a gas by the charged particles to generate scintillation light based on the ionized electrons. A second converter that exits from the second exit surface;
An electric field generator for generating an electric field for guiding the ionized electrons in a direction from the second incident surface toward the second emission surface;
A container that includes the first conversion unit, the second conversion unit, the electric field generation unit, and the gas, and an incident window unit that guides the neutrons to the first conversion unit and an emission window unit that emits the scintillation light. And comprising
The second conversion unit is provided with a plurality of two-dimensionally arranged through holes penetrating from the second incident surface to the second emission surface,
The first conversion unit is a neutron imaging system that blocks an opening on the second incident surface side of the through hole.

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