JP6613464B2 - Neutron beam detector - Google Patents

Description

  The present invention relates to a neutron beam detection apparatus.

  2. Description of the Related Art Conventionally, there is known a neutron beam detection apparatus that arranges a scintillator that emits light upon incidence of a neutron beam at the tip of an optical fiber, and transmits the light emitted by the scintillator to the optical fiber. For example, Patent Document 1 describes that light generated when ionizing radiation enters a scintillator is transmitted to an optical fiber, and signals based on the light are counted.

International Publication No. 2008/038662

  By the way, in the neutron beam detector, if the neutron field disturbance is increased by the neutron beam detector itself, the detection accuracy of the neutron beam is deteriorated, which is not preferable. Therefore, in order to improve the detection accuracy of the neutron beam detector, it has been required to suppress the disturbance of the neutron field.

  This invention is made in view of the said situation, and makes it a subject to provide the neutron beam detection apparatus which can suppress the disturbance of a neutron field.

  A neutron beam detection apparatus according to the present invention includes a scintillator that emits light upon incidence of a neutron beam, a scintillator disposed at the tip of one end, an optical fiber that transmits light emitted by the scintillator, and an end of the optical fiber. A ferrule provided on the outer periphery and containing aluminum.

  In this neutron beam detector, a scintillator is disposed at the tip of one end of an optical fiber, and a ferrule containing aluminum is provided on the outer periphery of the one end. Since aluminum has a property that it is less likely to react with neutrons than other metals used as materials for conventional ferrules, it is possible to suppress disturbance of the neutron field.

  Here, the radial thickness of the ferrule may be 0.75 mm or less. In this case, the effect of suppressing the disturbance of the neutron field can be particularly preferably achieved.

The scintillator and at least a part of one end of the optical fiber are covered, and a cap that shields light other than the light emitted by the scintillator, and at least a part of the scintillator and one end of the optical fiber are covered. , ⁶ Li, and a shield that shields neutron beams having energy lower than a predetermined energy. In this case, it is possible to suppress the entry of light from the outside into the optical fiber by the cap, and it is possible to suppress the neutron beam having low energy scattered outside rather than the neutron beam to be detected from entering the scintillator by the shield. . Thereby, the deterioration of the detection accuracy of a neutron beam can be suppressed.

  Moreover, you may further provide the reflection part which reflects light while covering at least one part of a scintillator inside a cap and a shield. In this case, since the reflecting portion covers at least a part of the scintillator, the reflecting portion reflects light emitted from the scintillator in a direction other than the direction in which the optical fiber is transmitted in the direction in which the optical fiber is transmitted. be able to. Thereby, a condensing rate can be improved.

  Moreover, the reflection part may comprise the curved surface which becomes convex in the opposite direction with respect to the transmission direction of the light in an optical fiber. In this case, the light emitted from the scintillator in the direction opposite to the light transmission direction in the optical fiber can be efficiently reflected in the light transmission direction in the optical fiber by the curved surface that is convex of the reflecting portion. . Thereby, a condensing rate can be improved.

  According to the present invention, neutron field disturbance can be suppressed.

It is a schematic sectional drawing which shows the neutron capture therapy apparatus with which a neutron beam detection apparatus is applied. It is a schematic sectional drawing which shows the neutron beam detection apparatus provided in the collimator. It is a schematic sectional drawing which shows the neutron beam detection apparatus which concerns on 1st Embodiment. It is a schematic diagram which shows the disturbance of the neutron field by a ferrule. It is a figure which shows the simulation result of disturbance of the neutron field by a ferrule. It is a schematic sectional drawing which shows the neutron beam detection apparatus which concerns on 2nd Embodiment.

  Preferred embodiments of the present invention will be described below with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

[First Embodiment]
First, the neutron capture therapy apparatus 1 to which the neutron beam detection apparatus 12 according to the first embodiment is applied will be described. However, the neutron beam detection device 12 is not applicable only to the neutron capture therapy device 1 and its use is not particularly limited. For example, the neutron beam detection device 12 may be applied to a monitor for monitoring the operation state of a nuclear reactor, may be applied to an acceleration neutron measuring instrument used in a physical experiment, and is used for nondestructive inspection. You may apply to a neutron irradiation apparatus.

FIG. 1 is a schematic cross-sectional view showing a neutron capture therapy apparatus to which a neutron beam detection apparatus is applied. A neutron capture therapy device 1 shown in FIG. 1 is a device that performs cancer treatment using boron neutron capture therapy (BNCT). In neutron capture therapy apparatus 1, for example, boron ^{(10 B)} is subjected to neutron beam irradiation N1 tumor of patient 50 administration.

  The neutron capture therapy apparatus 1 includes a cyclotron 2. The cyclotron 2 is an accelerator that generates charged particle beams R by accelerating charged particles such as negative ions. In the present embodiment, the charged particle beam R is a proton beam generated by stripping charges from negative ions. The proton beam is generated by stripping electrons in the cyclotron 2 using a foil stripper or the like in the cyclotron 2 and is emitted from the cyclotron 2. The cyclotron 2 has a capability of generating a charged particle beam R having a beam radius of 40 mm and 60 kW (= 30 MeV × 2 mA), for example. The accelerator is not limited to a cyclotron, and may be a synchrotron, a synchrocyclotron, a linac, or the like.

  The charged particle beam R emitted from the cyclotron 2 is sent to the neutron beam generation unit M. The neutron beam generator M includes a target 7 that generates a neutron beam N1 when a charged particle beam is incident thereon. The charged particle beam R emitted from the cyclotron 2 passes through the beam duct 3 and travels toward the target 7 disposed at the end of the beam duct 3. A plurality of quadrupole electromagnets 4, a current detector 5, and a scanning electromagnet 6 are provided along the beam duct 3. The plurality of quadrupole electromagnets 4 adjust the beam axis and beam diameter of the charged particle beam R using, for example, an electromagnet.

  The current detection unit 5 detects the current value of the charged particle beam R irradiated to the target 7 in real time during irradiation of the charged particle beam R. The current detector 5 uses a non-destructive DCCT (DC Current Transformer) that can measure current without affecting the charged particle beam R. That is, the current detector 5 can measure the current value of the charged particle beam R without touching the charged particle beam R (without contact). The current detection unit 5 outputs the detection result to the control unit 30 described later.

  The scanning electromagnet 6 scans the charged particle beam R and controls irradiation of the charged particle beam R to the target 7. The scanning electromagnet 6 controls the irradiation position of the charged particle beam R with respect to the target 7.

  Moreover, the neutron capture therapy apparatus 1 is provided with the control part 30 (refer FIG. 2). The control unit 30 is composed of a CPU [Central Processing Unit], a ROM [Read Only Memory], a RAM [Random Access Memory], and the like, and is an electronic control unit that comprehensively controls the neutron capture therapy apparatus 1.

  Then, the state of the neutron beam in the neutron beam generation part M and the neutron beam generation part M is demonstrated in detail.

  The neutron beam generation unit M generates a neutron beam N1 by being irradiated with the charged particle beam R, decelerates the neutron beam N1 to a predetermined energy, and emits it toward the patient 50. In this embodiment, the neutron beam N1 emitted toward the patient 50 is decelerated to the energy of epithermal neutrons. Note that gamma rays are generated with the generation of the neutron beam N1. The neutron beam generation unit M includes a target 7, a shield 8, a moderator 9, a collimator 10, and a gamma ray detection unit 11.

  The target 7 receives a charged particle beam R and generates a neutron beam N1. The target 7 here is formed including, for example, beryllium (Be), lithium (Li), tantalum (Ta), or tungsten (W), and has a disk shape with a diameter of 160 mm, for example. In addition, the target 7 is not limited to plate shape, For example, a liquid may be sufficient.

  The moderator 9 reduces the energy of the neutron beam N1 by decelerating the neutron beam N1 generated by the target 7. The moderator 9 includes a first moderator 9A that mainly decelerates fast neutrons contained in the neutron beam N1, and a second moderator 9B that mainly decelerates epithermal neutrons contained in the neutron beam N1. It has a laminated structure. As described above, the neutron beam N1 generated by the target 7 is decelerated when passing through the moderator 9 and becomes epithermal neutrons having a predetermined energy.

  The shield 8 is generated when the moderator 9 decelerates the generated neutron beam N1, secondary radiation such as gamma rays generated in the target 7 with the generation of the neutron beam N1, and the neutron beam N1. In addition, secondary radiation such as gamma rays generated in the moderator 9 is shielded to prevent the radiation from being emitted to the irradiation room side where the patient 50 is located. The shield 8 is provided so as to surround the moderator 9. The upper part and the lower part of the shield 8 extend to the upstream side of the charged particle beam R from the moderator 9, and a gamma ray detection unit 11 is provided in these extended parts. The gamma ray detection unit 11 detects gamma rays generated from the neutron beam generation unit M by irradiation of the charged particle beam R in real time during generation of the neutron beam N1 (that is, during irradiation of the patient 50 with the neutron beam N1).

  The collimator 10 shapes the irradiation field of the neutron beam N1 of epithermal neutrons irradiated to the patient 50, and has an opening 10a through which the neutron beam N1 passes. The collimator 10 is a block-shaped member having an opening 10a at the center, for example. The collimator 10 includes a neutron beam detection device 12 for detecting the neutron beam N1 passing through the opening 10a of the collimator 10 in real time during generation of the neutron beam N1 (that is, during irradiation of the neutron beam N1 to the patient 50). Provided (details will be described later).

  When the patient 50 is irradiated with the epithermal neutron beam N1 generated in such a neutron beam generation unit M, a part of the epithermal neutron is decelerated in the body of the patient, and heat with lower energy than the epithermal neutron. It reaches the affected area as neutrons. However, another part of the epithermal neutron is scattered in the body of the patient 50 to become a neutron beam N2 of the thermal neutron, and is emitted from the body of the patient 50 toward the collimator 10 side.

  Accordingly, during generation of the neutron beam N1 (that is, during irradiation of the neutron beam N1 to the patient 50), a neutron beam that reaches the neutron beam detector 12 provided in the collimator 10 is generated in the neutron beam generation unit M. Thus, both the neutron beam N1 of epithermal neutrons irradiated to the patient and the neutron beam N2 of thermal neutrons whose energy has been reduced due to the neutron beam N1 being scattered in the patient's body are included.

  Next, the neutron beam detection device 12 will be described in detail.

  FIG. 2 is a schematic sectional view showing a neutron beam detection apparatus provided in the collimator, and FIG. 3 is a schematic sectional view showing the neutron beam detection apparatus according to the first embodiment. The neutron beam detection device 12 is a detector that detects a neutron beam dose. In particular, in this embodiment, the neutron beam dose that passes through the opening 10a of the collimator 10 is generated during generation of the neutron beam N1 (that is, the patient 50). During neutron beam N1 irradiation).

  As shown in FIG. 2, the neutron beam detection apparatus 12 includes a scintillator 13, an optical fiber 14, and a photodetector 15. The neutron beam detection device 12 includes a scintillator 13 provided in the vicinity of the opening 10 a in the through hole 10 b of the collimator 10. The optical fiber 14 extends inside a through hole 10 b formed in the collimator 10. The tip 14b of one end 14a of the optical fiber 14 is connected to the scintillator 13, and the other end extends to the outside of the through hole 10b and is connected to the photodetector 15. The light detector 15 is electrically connected to the control unit 30 and outputs the detection result of the light generated by the scintillator 13 and transmitted through the optical fiber 14 to the control unit 30.

  In FIG. 2, only the epithermal neutron beam N1 generated in the neutron beam generation unit M and irradiated to the patient 50 is shown, and the traveling direction of the neutron beam N1 is shown by a straight line. However, actually, there is also a neutron beam N2 of thermal neutrons from the patient 50 side toward the collimator 10, and the neutron beams N1 and N2 travel so as to diffuse. For this reason, the neutron beams N1 and N2 are incident on the scintillator 13 provided in the vicinity of the opening 10a in the through hole 10b, and the dose obtained by adding the doses of both the neutron beams N1 and N2 by the neutron beam detector 12 is Detected.

The scintillator 13 is a phosphor that emits light upon incidence of radiation such as a neutron beam. The scintillator 13 emits light (scintillation light) when the internal crystal is excited according to the dose of incident radiation. The scintillator 13 has a substantially rectangular shape and is formed smaller than the outer diameter of the optical fiber 14. The shape and size of the scintillator 13 are not particularly limited. The scintillator ^13, 6 Li glass scintillator ^may employ a ^{scintillator,} a plastic scintillator coated with 6 ^LiF, a 6 LiF / ZnS scintillator or the like including a 6 Li.

  The optical fiber 14 functions as a light guide that transmits the light emitted by the scintillator 13 to the photodetector 15. The optical fiber 14 extends from the scintillator 13 disposed at the tip 14b of the one end portion 14a extending to the vicinity of the opening 10a in the through hole 10b of the collimator 10 to the photodetector 15 disposed outside the collimator 10. . The photodetector 15 detects the light transmitted through the optical fiber 14. As the photodetector 15, various types of photodetectors such as a photomultiplier tube and a photoelectric tube can be employed. The photodetector 15 outputs an electrical signal (detection signal) to the control unit 30 when detecting light.

  More specifically, as shown in FIG. 3, the neutron beam detection apparatus 12 includes a reflection coating 16 provided on the outer periphery of one end portion 14a of the optical fiber 14, a ferrule 17 provided on the outer periphery thereof, and one end portion. And coating 18 provided on the outer periphery excluding the vicinity of 14a. Further, the neutron beam detection device 12 includes a reflection seal (reflection part) 19 provided so as to cover the scintillator 13, a shield 20 provided so as to cover the reflection seal 19, and further covering this shield 20. And a cap 21 provided.

  The reflection coating 16 diffusely reflects light leaking from the optical fiber 14 out of the light emitted from the scintillator 13 and transmitted through the optical fiber 14. That is, the reflective coating 16 transmits light that travels at an angle exceeding the angle at which the inside of the optical fiber 14 is totally reflected with respect to the direction along the extending direction of the optical fiber 14. Diffuse reflection. A part of the light irregularly reflected by the reflection coating 16 travels in a direction in which the light is totally reflected with respect to the extending direction of the optical fiber 14, and thus the light collection efficiency of the neutron beam detector 12 is improved by providing the reflection coating 16. . The reflective coating 16 is provided over a predetermined length from the tip 14b of the one end 14a of the optical fiber 14 toward the other end of the optical fiber. In addition, it is preferable that the reflective coating 16 also reflects ultraviolet light. For example, a paint containing titanium oxide may be used.

  The ferrule 17 is provided on the outer periphery of the optical fiber 14 to protect the optical fiber 14. For example, in the manufacturing process of the neutron beam detection device 12, when the tip 14 b of the one end portion 14 a of the optical fiber 14 is polished, the ferrule 17 is provided on the outer periphery of the one end portion 14 a of the optical fiber 14 to suppress the damage of the optical fiber 14. Is done.

  The ferrule 17 surrounds the outer periphery of the optical fiber 14 provided with the reflective coating 16, and is formed to have a cylindrical shape with a radial thickness of 0.75 mm or less. However, the dimension of the thickness in the radial direction of the ferrule 17 is not particularly limited, and may be larger than 0.75 mm. Further, one end of the ferrule 17 is disposed so as to be flush with the tip 14b of the one end portion 14a of the optical fiber 14, and the other end is within a range where the reflection coating 16 is provided on the outer periphery of the optical fiber 14. It extends. The other end of the ferrule 17 may extend beyond the range where the outer periphery of the optical fiber 14 is provided with the reflective coating 16.

  The ferrule 17 is made of aluminum. That is, the ferrule 17 is formed containing aluminum. Aluminum has a property that it is difficult to react with neutrons compared to other metals such as SUS used as a material for conventional ferrules. For this reason, by using the ferrule 17 made of aluminum, the disturbance of the neutron field is low as compared with the case where a ferrule made of SUS or the like is used (details will be described later). In addition, “containing aluminum” includes a state in which a film made of an aluminum compound is formed on the surface, and also includes a state in which the whole including not only the surface but also the inside is an aluminum compound. .

  The covering 18 is provided so as to overlap even part of the ferrule 17. The coating 18 is for preventing light from the outside from entering the optical fiber 14 and protecting the optical fiber 14.

  The cap 21 is provided at a position covering at least a part of the scintillator 13 and one end portion 14a of the optical fiber 14 in which the scintillator 13 is disposed. The shield 20 is provided between the cap 21 and the ferrule 17 at a position that covers at least a part of the scintillator 13 and the one end portion 14 a of the optical fiber 14. The reflective seal 19 is a position that covers at least a part of the scintillator 13 inside the cap 21 and the shield 20 (in this embodiment, a position that covers at least a part of the scintillator 13 and the one end portion 14a of the optical fiber 14). ). In addition, the relationship of the relative length from the front-end | tip 14b of the one end part 14a of the optical fiber 14 is not specifically limited for the reflective seal 19, the shield 20, and the cap 21, Any member may be the longest, Any member may be the shortest.

  The reflective seal 19 is for reflecting light emitted from the scintillator 13 in a direction other than the direction in which the optical fiber 14 is transmitted in the direction in which the optical fiber 14 is transmitted. In particular, when the reflective coating 16 is provided on the outer periphery of the one end portion 14a of the optical fiber 14 as in the present embodiment, it may be formed so as to cover at least the scintillator 13 only. The reflective seal 19 is in the form of a flexible sheet.

  The shield 20 is for suppressing the neutron beam with low energy from the outside other than the neutron beam N1 to be detected from reaching the neutron beam detector 12. As described above, the neutron capture therapy apparatus 1 attempts to detect the dose of the epithermal neutron beam N1 generated in the neutron beam generation unit M and irradiated to the patient. However, the neutron beam detection apparatus 12 also reaches the neutron beam N2 of thermal neutrons whose energy has been reduced due to the neutron beam N1 of epithermal neutrons being scattered inside the patient 50. When such a neutron beam N2 has been detected by the neutron beam detector 12, it becomes a background of the detection result, so it is preferable to remove the neutron beam N2. The shield 20 shields such a neutron beam N2 and causes only the neutron beam N1 to reach the neutron beam detection apparatus 12.

  The side surface of the shield 20 has a substantially cylindrical shape, one end of which is sealed and the other end is opened. The inner side surface of the shield 20 is in contact with the side surface of the reflective seal 19 with the one end portion 14 a of the optical fiber 14 entering the shield 20 from the other end side.

The shield 20 is formed using a material containing ⁶ Li. The material used for the shield 20 is preferably a substance that easily reacts with neutrons, and a substance that does not generate gamma rays by reacting with neutrons, and a material containing ⁶ Li has these properties. An example of the material forming the shield 20 is LiF containing ⁶ Li and ⁷ Li in a ratio of 95: 5.

  The cap 21 shields light other than the light emitted by the scintillator 13 and suppresses such other light from being transmitted through the optical fiber 14. The cap 21 has a function of protecting the optical fiber 14, the scintillator 13, the shield 20, the reflective seal 19, and the like. The side surface of the cap 21 has a substantially cylindrical shape, and one end thereof is sealed and the other end is opened. Further, the outer surface of the shield 20 is in contact with the inner surface of the cap 21. Note that the cap 21 and the shield 20 may be integrated, or may be removable from each other. The open end on the other end side of the cap 21 has a slightly reduced diameter and is in contact with the side surface of the ferrule 17 over the entire circumference. The shape of the cap 21 is not particularly limited and can be any shape. For example, when the cap 21 has a shape that extends long from the one end portion 14a of the optical fiber 14 to the other end portion side, the function of shielding light and protecting the optical fiber 14 and the like can be more effectively exhibited. Therefore, for example, the cap 21 may extend long to a position overlapping the optical fiber coating 18 or may extend long to a position covering the entire ferrule 17.

  Next, the state of the neutron field disturbance due to the application of the ferrule 17 in the neutron beam detection device 12 will be specifically described with an example of the ferrule 17. However, the ferrule 17 according to the present invention is not limited to the following example.

  FIG. 4 is a schematic diagram showing the neutron field disturbance caused by the ferrule, and FIG. 5 is a diagram showing the simulation result of the neutron field disturbance caused by the ferrule. FIG. 4 shows a state in which the neutron beam N travels in a plane perpendicular to the axial direction of the cylindrical ferrule 17 and is scattered by the ferrule. In FIG. 5, the X axis in FIG. 4 is taken along the horizontal axis, and the dose of the neutron beam N on the X axis is taken along the vertical axis. When the solid line is an aluminum ferrule, the broken line is a SUS ferrule. Show. SUS is a metal used as a material for conventional ferrules. Further, in FIG. 5, the simulation is performed with the ferrule cross-sectional shape having an outer diameter of 2 mm and an inner diameter of 1 mm (that is, the thickness dimension in the radial direction is 0.5 mm), and the central axis of the ferrule is in FIG. This corresponds to a position of 0 cm on the horizontal axis. As shown in FIG. 5, in the case of the ferrule made of SUS, the dose of the neutron beam is reduced by about 15% (the disturbance of the neutron field is about 15%), whereas in the case of the ferrule 17 made of aluminum It was confirmed that the decrease in neutron beam dose was 5% or less (the neutron field disturbance was 5% or less).

  As described above, according to the neutron beam detection apparatus 12 according to the present embodiment, the scintillator 13 is disposed at the tip 14b of the one end portion 14a of the optical fiber 14, and the ferrule 17 containing aluminum on the outer periphery of the one end portion 14a. Is provided. Since aluminum has a property that it is less likely to react with neutrons than other metals such as SUS used as a material for conventional ferrules, it is possible to suppress disturbance of the neutron field.

  Here, since the thickness of the ferrule 17 in the radial direction is 0.75 mm or less, the disturbance of the neutron field can be suppressed to 5% or less, and the effect of suppressing the disturbance of the neutron field can be particularly suitably achieved. it can.

Further, the cap 21 that covers at least a part of the scintillator 13 and the one end portion 14 a of the optical fiber 14 and shields light other than the light emitted by the scintillator 13, the scintillator 13, and one end portion of the optical fiber 14 A shield 20 that covers at least a part of 14a and shields neutron beam N2 containing ⁶ Li and having an energy lower than a predetermined energy. For this reason, it is possible to prevent the light from the outside from entering the optical fiber 14 by the cap 21 and to cause the neutron beam N2 having low energy scattered outside to enter the scintillator 13 instead of the neutron beam N1 to be detected. Can be suppressed by the shield 20. Thereby, the deterioration of the detection accuracy of the neutron beam N1 can be suppressed.

  Further, since the scintillator 13 is further provided inside the cap 21 and the shield 20 so as to cover the scintillator 13 and reflect light, the reflective seal 19 faces in a direction other than the direction in which the optical fiber 14 is transmitted from the scintillator 13. The light emitted in this way can be reflected in the direction of transmission through the optical fiber 14. Thereby, a condensing rate can be improved.

[Second Embodiment]
Next, the neutron beam detection apparatus 22 according to the second embodiment will be described. In the description of the present embodiment, differences from the first embodiment will be mainly described, and a duplicate description will be omitted.

  FIG. 6 is a schematic cross-sectional view showing a neutron beam detection apparatus according to the second embodiment. As shown in FIG. 6, the difference between the neutron beam detection apparatus 22 according to the second embodiment and the neutron beam detection apparatus 12 (see FIG. 3) according to the first embodiment is that a reflection seal (reflection part) 19 is used. Instead, it has a reflecting dome (reflecting part) 29.

  Specifically, like the reflective seal 19, the reflective dome 29 reflects light emitted from the scintillator 13 in a direction other than the direction in which the optical fiber 14 is transmitted in the direction in which the optical fiber 14 is transmitted. belongs to. The reflection dome 29 has a curved surface that is convex in the opposite direction to the light transmission direction in the optical fiber 14. In addition, the curved surface portion of the reflective dome 29 has a thin plate shape that is curved, and the inside is hollow. The shape of the curved surface is not particularly limited. For example, the cross-sectional shape may be a parabola or hemisphere. Moreover, if it is a part of curved surface, a protrusion, a notch, a discontinuous surface, etc. may exist.

  According to the neutron beam detection apparatus 22 according to the present embodiment, the light emitted from the scintillator 13 toward the opposite direction to the light transmission direction in the optical fiber 14 is mainly formed on the curved surface that is the convex of the reflection dome 29. Since the light can be efficiently reflected in the light transmission direction in the optical fiber 14 on the inner surface or the like, the light collection rate can be improved.

  The neutron beam detection apparatus according to the present invention is not limited to the above embodiment. For example, in the first embodiment and the second embodiment, the shield 20 is provided between the cap 21 and the ferrule 17, and the reflective seal 19 or the reflective dome 29 is provided between the shield 20 and the ferrule 17. However, the cap 21 may be provided between the shield 20 and the ferrule 17, and the reflective seal 19 or the reflective dome 29 may be provided between the cap 21 and the ferrule 17. Even in this case, the same effects as those of the above embodiment can be obtained.

  In the second embodiment, the curved surface portion of the reflective dome 29 is a thin plate shape that is curved, and the inside is a cavity, but the curved surface portion may be a lump without a cavity inside, and in this case The scintillator 13 and the optical fiber 14 may be in direct contact with the reflection dome 29.

  DESCRIPTION OF SYMBOLS 1 ... Neutron capture therapy apparatus, 12, 22 ... Neutron beam detection apparatus, 13 ... Scintillator, 14 ... Optical fiber, 14a ... One end part, 14b ... Tip, 17 ... Ferrule, N1, N2 ... Neutron beam.

Claims (5)

A scintillator that emits light upon incidence of a neutron beam;
The scintillator is disposed at the tip of one end, and an optical fiber that transmits the light emitted by the scintillator;
A reflective coating applied to contact the outer periphery of the one end of the optical fiber;
A neutron beam detection apparatus comprising: a ferrule provided in contact with an outer periphery of the reflective coating, containing aluminum, and having one end flush with the tip of the one end of the optical fiber . Having a coating provided on the outer periphery excluding the vicinity of the one end of the optical fiber;
The neutron beam detection apparatus according to claim 1, wherein the coating overlaps a part of the ferrule. A cap that covers at least a part of the scintillator and the one end of the optical fiber and shields light other than the light emitted by the scintillator;
The shield further comprising: the scintillator; and a shield that covers at least a part of the one end of the optical fiber and shields a neutron beam containing ⁶ Li and having an energy lower than a predetermined energy. The neutron beam detector described in 1.   4. The neutron beam detection apparatus according to claim 3, further comprising a reflection part that covers at least a part of the scintillator and reflects the light inside the cap and the shield. 5.   The said ferrule is a neutron beam detection apparatus as described in any one of Claims 1-4 which does not oppose the front end surface of the said one end part of the said optical fiber.

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