JP2022135616A - Neutron measurement chip and neutron measurement system - Google Patents

Abstract

To provide a neutron measurement chip and a neutron measurement system that can improve handleability in performing measurement of a neutron beam and guarantee measurement accuracy.SOLUTION: An absorption member 62 is covered by a cover member 63. Thus, even when the absorption member 62 is formed of material for which direct touch should be avoided such as cadmium, an operator can handle a neutron measurement chip 60 while touching the cover member 63 without directly touching the absorption member 62. Passing a neutron beam N with which an irradiation target member 61 is irradiated through an organic material close to a human body can bring a condition during measurement closer to a condition during medical treatment, and thereby a reduction in measurement accuracy can be prevented.SELECTED DRAWING: Figure 3

Description

The present invention relates to a neutron measuring chip and a neutron measuring system.

In recent years, it may be required to measure the amount of neutrons. For example, boron neutron capture therapy (BNCT) using a boron compound is known as a neutron capture therapy that kills cancer cells by irradiating neutron beams. In boron neutron capture therapy, cancer cells are selectively destroyed by scattering heavy charged particles generated by irradiating neutron beams to boron pre-loaded into cancer cells.

In order to measure the amount of neutron beams used for the purposes described above, for example, a neutron measurement system disclosed in Patent Document 1 is used. The neutron measurement system disclosed in Patent Literature 1 detects neutron beams in a detection unit and calculates the amount of neutron beams based on the detection result.

JP 2016-166777 A

Here, in order to measure the amount of neutron beams, a member to be irradiated may be irradiated with neutron beams and gamma rays emitted by activation may be measured. At this time, the member to be irradiated may be irradiated with neutron beams while being covered with an absorbing member that absorbs thermal neutrons. However, there are cases where the absorbing member is made of a material that should be avoided from direct contact. In this case, handling becomes difficult when setting the member to be irradiated at the neutron beam irradiation position or when measuring gamma rays. A problem arises. On the other hand, when the absorbing member is covered with a predetermined cover or the like, it reacts with the neutron beam, resulting in a problem of lowering the measurement accuracy.

Accordingly, it is an object of the present invention to provide a neutron measurement chip and a neutron measurement system that can ensure measurement accuracy while improving handling properties when measuring neutron beams.

A neutron measuring chip according to the present invention is a neutron measuring chip for measuring the amount of neutron beams, and includes an irradiated member formed of a material that emits gamma rays when irradiated with neutron beams, and a material that absorbs thermal neutrons. and a cover member formed of an organic material and covering the absorbing member.

A neutron measuring chip according to the present invention includes an irradiated member made of a material that emits gamma rays when irradiated with neutron beams, and an absorbing member made of a material that absorbs thermal neutrons and covering the irradiated member. Therefore, the member to be irradiated can be irradiated with a neutron beam in a state in which thermal neutrons are shielded by the absorbing member. The amount of neutron beams can be obtained by using the measurement result of the irradiated member that has been irradiated. Such an absorbent member is covered by a cover member. Therefore, even if the absorbing member is made of a material that should be avoided from direct contact, the operator can handle the neutron measuring chip while touching the cover member without directly touching the absorbing member. can. Therefore, the handling of the neutron measuring chip is improved. Also, the cover member is made of an organic material. Organic materials interact with neutrons (absorption, nuclear reaction, etc.) similar to those of the human body. As described above, it is possible to secure the measurement accuracy while improving the handleability of the neutron measurement chip when measuring neutron beams.

The irradiated member may be foil-shaped with respect to the absorbing member. In the case of a foil shape, the mass can be increased, so the amount of activation can be increased accordingly, and the measurement accuracy can be increased.

The irradiated member may be linearly formed with respect to the absorbing member. In the linear case, the neutron flux can be measured by gamma ray measurement at any point from the gold wire measured once in the depth direction.

The member to be irradiated may be made of gold or aluminum. These materials are easy to measure gamma rays emitted by irradiation with neutron beams.

The neutron measurement chip may include a main body that supports the irradiated member, and a lid that covers the irradiated member supported by the main body. In this case, when gamma rays are measured after neutron beam irradiation, the member to be irradiated can be exposed simply by removing the cover from the main body. Therefore, workability for workers is improved.

The portion of the cover member corresponding to the lid portion may support the peripheral surface of the portion of the absorbing member corresponding to the lid portion. In this case, the member to be irradiated can be easily exposed when the cover is removed from the main body before measurement.

The portion of the cover member corresponding to the lid portion may have a peripheral wall portion extending so as to cover the peripheral surface of the portion of the cover member corresponding to the body portion. In this case, since the cover member has a structure in which the peripheral wall portion of the lid portion is hooked to the main body portion, the gap between the two can be reduced.

A portion of the absorbent member corresponding to at least one of the lid portion and the main body portion may have a recess that fits with a portion corresponding to the other. In this case, since the absorbing member has a structure in which the lid portion and the main body portion are fitted to each other, the gap between them can be reduced.

A neutron measurement system according to the present invention is a neutron measurement system for measuring the amount of neutron beams generated by irradiating a target with a charged particle beam. An irradiation unit that irradiates a member to be irradiated with a neutron beam in space, and a measurement unit that measures gamma rays emitted from the member to be irradiated that has been irradiated with the neutron beam. an irradiated member formed of a material that emits gamma rays, an absorbing member formed of a material that absorbs thermal neutrons and covering the irradiated member, and a cover member formed of an organic material covering the absorbing member; The irradiation section supports the neutron measurement chip with a support member made of an organic material in the internal space.

According to the neutron measurement system, it is possible to obtain the same functions and effects as the neutron measurement chip described above. Further, the irradiation section supports the neutron measurement chip with a support member made of an organic material in the internal space. Therefore, in the irradiating section, the neutron measuring chip can be easily moved and positioned through the support member.

ADVANTAGE OF THE INVENTION According to this invention, the neutron measurement chip|tip and neutron measurement system which can ensure a measurement precision can be provided, improving the handleability at the time of measuring a neutron beam.

1 is a schematic diagram showing a neutron measurement chip according to an embodiment of the present invention and a neutron capture therapy device that generates neutron beams to be measured by a neutron measurement system; FIG. 1 is a block diagram of a neutron measurement system; FIG. 1 is a cross-sectional view of a neutron measuring chip; FIG. 1 is a cross-sectional view of a neutron measuring chip; FIG. It is a schematic sectional drawing of an irradiation part. 1 is a graph showing the neutron energy dependence of the neutron capture area of ¹⁹⁷ Au.

Preferred embodiments of the present invention will now be described in detail with reference to the drawings.

First, an overview of a neutron measurement chip according to an embodiment of the present invention and a neutron capture therapy device that generates neutron beams to be measured by a neutron measurement system will be described with reference to FIG. A neutron capture therapy device 1 shown in FIG. 1 is a device that performs cancer treatment using boron neutron capture therapy (BNCT). The neutron capture therapy apparatus 1 irradiates, for example, a tumor of a patient 50 to which boron ( ¹⁰ B) has been administered with a neutron beam N.

A neutron capture therapy device 1 comprises an accelerator 2 . The accelerator 2 accelerates charged particles such as negative ions and emits a charged particle beam R. The accelerator 2 is configured by, for example, a cyclotron. In this embodiment, the charged particle beam R is a proton beam generated by stripping charges from negative ions. This accelerator 2 generates a charged particle beam R with 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, an electrostatic accelerator, or the like.

A charged particle beam R emitted from the accelerator 2 is sent to a neutron beam generator M. The neutron beam generator M consists of a beam duct 9 and a target 10 . A charged particle beam R emitted from the accelerator 2 travels through the beam duct 9 toward the target 10 arranged at the end of the beam duct 9 . A plurality of quadrupole electromagnets 4 and scanning electromagnets 6 are provided along the beam duct 9 . The plurality of quadrupole electromagnets 4 adjust the beam axis of the charged particle beam R using electromagnets, for example.

The scanning electromagnet 6 scans the charged particle beam R and controls irradiation of the charged particle beam R to the target 10 . This scanning electromagnet 6 controls the irradiation position of the charged particle beam R with respect to the target 10 .

The neutron capture therapy apparatus 1 generates neutron beams N by irradiating a target 10 with a charged particle beam R, and emits the neutron beams N toward a patient 50 . The neutron capture therapy device 1 has a target 10 , a shield 8 , a moderator 39 and a collimator 20 .

The target 10 is irradiated with a charged particle beam R to generate a neutron beam N. As shown in FIG. The target 10 is a solid member made of a material that generates neutron beams when irradiated with charged particle beams. Specifically, the target 10 is made of, for example, beryllium (Be), lithium (Li), tantalum (Ta), or tungsten (W), and has a disk-like solid shape with a diameter of 160 mm, for example. Note that the target 10 is not limited to a disc shape, and may have another shape.

The moderator 39 moderates the neutron beams N generated by the target 10 (reduces the energy of the neutron beams N). The moderator 39 may have a laminated structure including a layer 39A that mainly moderates fast neutrons contained in the neutron beam N and a layer 39B that mainly moderates epithermal neutrons contained in the neutron beam N. .

The shield 8 shields the generated neutron beams N and the gamma rays and the like generated along with the generation of the neutron beams N from being emitted to the outside. The shield 8 is provided so as to surround the moderator 39 . The upper and lower portions of the shield 8 extend upstream of the charged particle beam R from the moderator 39 .

The collimator 20 shapes the irradiation field of the neutron beams N, and has an opening 20a through which the neutron beams N pass. The collimator 20 is, for example, a block-shaped member having an opening 20a in the center.

Next, a detailed configuration of the neutron measurement system 100 according to this embodiment will be described with reference to FIG. The neutron measurement system 100 is a system that measures the amount of neutron beams N generated by irradiation of the target 10 with the charged particle beam R. FIG. The neutron measurement system 100 measures the amount of neutron beams N using a neutron measurement chip 60 having an irradiated member 61 . The neutron measurement system 100 includes an irradiation section 101 and a measurement section 102 .

The irradiation unit 101 is a part that accommodates the neutron measurement chip 60 having the irradiated member 61 and irradiates the irradiated member 61 with the neutron beam N in the internal space. The irradiation unit 101 guides the neutron beam N irradiated from the neutron capture therapy device 1 to the internal space, and irradiates the irradiated member 61 arranged in the internal space with the neutron beam N. It is preferable that the irradiation unit 101 be made of a substance that has a close interaction (absorption, nuclear reaction, etc.) between the human body and neutrons. As the irradiation unit 101, for example, an acrylic phantom or a water phantom is preferably used.

Specifically, as shown in FIG. 5, the water phantom is configured by containing water W in the inner space of an acrylic water tank 103 . In this case, the neutron beam N from the neutron capture therapy device 1 is irradiated toward the side surface of the water tank 103 of the water phantom, and passes through the water W from the side surface. Accordingly, the irradiated member 61 is arranged at a predetermined position within the water tank 103 . The position in the water tank 103 is appropriately changed according to the progress of the measurement.

As shown in FIG. 2, the measurement unit 102 is a device that measures gamma rays emitted from the irradiated member 61 irradiated with the neutron beam N. As shown in FIG. The measurement unit 102 includes a gamma ray detector 104 , a signal processing unit 106 and a display unit 107 . The gamma ray detector 104 is a device for detecting gamma rays. The signal processing unit 106 calculates the amount of neutron rays N by processing the signal from the gamma ray detector 104 . The processing of the signal processing unit 106 will be described later together with the measurement procedure. The display unit 107 is a device that displays various information. The display unit 107 may display the amount of neutron beam N calculated by the signal processing unit 106 .

For example, when gold is used as the irradiated member 61, when neutron beam N is irradiated to 197Au, it emits gamma rays (412 keV) and decays to 198Au in the ground state due to a neutron capture reaction. The measurement unit 102 measures the neutron flux by measuring the gamma rays. The gamma ray detector 104 counts gamma rays with an energy of 412 keV as gamma rays from Au. The signal processing unit 106 calculates the neutron flux based on the count number. Here, neutrons are divided into thermal neutrons, epithermal neutrons, and fast neutrons according to their energy range (see FIG. 6). Since thermal neutrons are required for neutron capture therapy, measurement of thermal neutron flux is necessary. However, as shown in FIG. 5, epithermal neutrons also have a large reaction cross-section with respect to gold. Neutron flux is measured. Therefore, using the neutron measuring chip 60, the neutron beam N is irradiated in a state in which the irradiated member 61 is covered with the absorbing member 62 (see FIG. 3) to block thermal neutrons. In this case, the measurement unit 102 can measure the epithermal neutron flux. As described above, the irradiating unit 101 irradiates the irradiated member 61 made of only gold with the neutron beam N, and the measurement unit 102 measures the irradiated member 61 made of only gold. Further, the irradiation unit 101 irradiates the irradiated member 61 in the state of the neutron measurement chip 60 with the neutron beam N, and the measurement unit 102 measures the irradiated member 61 in the state of the neutron measurement chip 60 . The signal processing unit 106 calculates the thermal neutron flux from the relationship of "thermal neutron flux=measurement result of gold only-measurement result of gold with the neutron measuring chip".

Here, as the gamma ray detector 104, various known gamma ray detection devices such as a germanium semiconductor detector and a CdZnTe semiconductor detector can be adopted. However, in this embodiment, as the gamma ray detector 104, it is preferable to employ a detector such as a CdZnTe semiconductor detector that does not require cooling of the element. For example, when a germanium semiconductor detector using Peltier cooling is employed, it is necessary to evacuate the area around the germanium element. In this case, vacuum leak due to aged deterioration and deterioration due to repetition of cooling and normal temperature of the element itself may occur. In addition, when cooling is required, the measurement system, including the shielding around the detector, becomes large, cannot be easily moved, and may require a dedicated space. In contrast, when a detector such as a CdZnTe semiconductor detector that does not require cooling is employed as the gamma ray detector 104, the occurrence of the above problems can be suppressed. In addition, it becomes possible to bring the detection element and the irradiated member 61 close to each other, reduce the area of the detection element, and achieve integration including the signal processing system.

In addition, since the energy of the gamma rays to be measured in this embodiment is only the gamma rays (411.8 kev in the case of gold) from the member to be irradiated 61 such as gold, the number of radiations with a plurality of energies normally used is measured simultaneously. A multi-channel analyzer (MCA) is not required, and the measurement unit 102 may employ a single-channel analyzer (SCA) that only detects specific energies. In this case, measurement time can be shortened.

Next, a detailed configuration of the neutron measuring chip 60 according to the present embodiment will be described with reference to FIGS. 3 and 4. FIG. The neutron measurement chip 60 is a chip for measuring the amount of neutron beams N generated by irradiation of the target 10 with charged particle beams. The neutron measuring chip 60 includes an irradiated member 61 , an absorbing member 62 and a cover member 63 .

The irradiated member 61 is a member made of a material that emits gamma rays when irradiated with neutron beams N. As shown in FIG. For example, gold, aluminum, or the like is used as the material of the irradiated member 61 . Here, the material that emits gamma rays when irradiated with neutron beams N is a material that emits gamma rays to such an extent that it is possible to measure the amount of neutron beams N using the measurement unit 102 by being irradiated with neutron beams N. is a material that can emit In other words, a material that emits only gamma rays so small that the amount of neutrons N cannot be measured by the measuring unit 102 does not correspond to the "material that emits gamma rays upon exposure to neutrons" in this specification. The shape of the irradiated member 61 in the neutron measuring chip 60 is not particularly limited, but it may be formed in a circular or polygonal thin film shape, for example. The irradiated member 61 may be formed in a foil shape with respect to the absorbing member 62 . That is, the irradiated member 61 may be formed by attaching gold foil or aluminum foil to the surface of the absorbing member 62 . Alternatively, the irradiated member 61 may be linearly formed with respect to the absorbing member 62 . For example, a mesh of a sample holder for an electron microscope or the like may be used as the irradiated member 61 . In this case, it is possible to use a member set to a specified amount as an existing sample.

The absorbing member 62 is a member that is made of a material that absorbs thermal neutrons and covers the irradiated member 61 . In this manner, the absorbing member 62 absorbs thermal neutrons while covering the member to be irradiated 61, thereby shielding the member to be irradiated 61 from reacting with the thermal neutrons. As shown in FIG. 3(b), in the state of being irradiated with the neutron beam N, the absorbing member 62 covers both main surfaces 61a and 61b of the member 61 to be irradiated, and also covers the entire peripheral surface 61c. Materials that absorb thermal neutrons include, for example, cadmium, boron, hafnium, gadolinium, europium, and tantalum. Since the absorbing member 62 has a low absorption rate of epithermal neutrons, it allows the irradiated member 61 to react with the epithermal neutrons. A material that absorbs thermal neutrons is specifically a material that has a thermal neutron absorption cross section of 100 barns or more.

The cover member 63 is a member that is made of an organic material and covers the absorbent member 62 . As shown in FIG. 3B, in the state of irradiation with the neutron beam N, the cover member 63 covers the main surfaces 62a and 62b on both sides of the absorbing member 62 and also covers the peripheral surface 62c over the entire circumference. The organic material is a substance that has a close interaction (absorption, nuclear reaction, etc.) between the human body and neutrons, and when the neutron beam N is irradiated, the neutron beam N is guided to the irradiated member 61 under conditions similar to those of the human body. It is a material that can An organic material is a material composed of oxygen, hydrogen, nitrogen atoms, etc., with carbon as the main element. A light element plastic is adopted as the organic material. Materials such as acrylic and polyethylene are adopted as light element plastics.

As shown in FIG. 3A, the absorbing member 62 and the cover member 63 include a body portion 66 that supports the irradiated member 61 and a lid portion 67 that covers the irradiated member 61 supported by the body portion 66. , provided. The main body 66 is composed of a portion of the absorbing member 62 (referred to as a main body side portion 62A), a portion of the cover member 63 (referred to as a main body side portion 63A), and the member 61 to be irradiated. The lid portion 67 does not include the irradiated member 61, and is configured by a portion of the absorbing member 62 (referred to as a lid-side portion 62B) and a portion of the cover member 63 (referred to as a lid-side portion 63B). be.

In the main body 66, the main body side portion 62A of the absorbing member 62 supports the irradiated member 61 with the main surface 61a of the irradiated member 61 exposed from the dividing surface 66a. In the body portion 66, the body portion side portion 62A of the absorbing member 62 supports the main surface 61b on the opposite side of the irradiated member 61 and the peripheral surface 61c so as to cover the peripheral surface 61c. In the body portion 66, the body portion side portion 63A of the cover member 63 exposes the main surface 61a of the irradiated member 61 and the dividing surface 66a of the body portion side portion 62A of the absorbing member 62 from the dividing surface 66a. It supports the irradiated member 61 and the body portion side portion 62A of the absorbing member 62 . In the body portion 66, the body portion side portion 63A of the cover member 63 supports the main surface 62b opposite to the body portion side portion 62A of the absorbing member 62 and the peripheral surface 62c.

In the lid portion 67, the lid portion side portion 62B of the absorbing member 62 is in contact with the exposed main surface 61a of the irradiated member 61 at the dividing surface 67a, and covers the main surface 61a. In the lid portion 67, the lid portion side portion 63B of the cover member 63 is attached to the lid portion side portion 62B of the absorbing member 62 in a state where the dividing surface 67a of the lid portion side portion 62B of the absorbing member 62 is exposed from the dividing surface 67a. support. In the lid portion 67, the lid portion side portion 62B of the absorbing member 62 is joined to the dividing surface 66a of the body portion side portion 62A of the body portion 66 at the dividing surface 67a. By thus combining the body portion side portion 62A and the lid portion side portion 62B, the absorption member 62 that covers the irradiated member 61 from all directions is configured (see FIG. 3). In the lid portion 67, the lid portion side portion 63B of the cover member 63 supports the lid portion side portion 62B of the absorbing member 62 so as to cover the main surface 62a and the peripheral surface 62c. In the lid portion 67, the lid portion side portion 63B of the cover member 63 is joined to the dividing surface 66a of the body portion side portion 63A of the body portion 66 at the dividing surface 67a. By combining the main body side portion 63A and the lid portion side portion 63B in this way, the cover member 63 that covers the absorbing member 62 from all directions is configured (see FIG. 3B).

When irradiating the member 61 to be irradiated with the neutron beam N, as shown in FIG. It is covered with a lid portion 67 . When measuring with the measuring unit 102, the lid 67 is removed from the main body 66 as shown in FIG. 3(c). As a result, the irradiated member 61 irradiated with the neutron beam N emits gamma rays G from the exposed main surface 61a. The bonding force between the lid portion 67 and the main body portion 66 is set to a strength that prevents thermal neutrons from entering the member 61 to be irradiated during irradiation, while allowing the operator to remove the lid portion 67 during measurement. preferably.

The structures of the body portion 66 and the lid portion 67 are not particularly limited, and structures such as those shown in FIG. 4 may be employed. As shown in FIG. 4 , the lid portion side portion 63B of the cover member 63 has a peripheral wall portion 68 extending so as to cover the peripheral surface 63c of the body portion side portion 63A of the cover member 63 . The peripheral wall portion 68 extends so as to protrude toward the main body portion 66 from the outer peripheral end portion of the lid portion side portion 63</b>B of the cover member 63 . The peripheral wall portion 68 is formed over the entire circumference of the cover member 63 . A side surface 68a on the inner peripheral side of the peripheral wall portion 68 is in contact with the peripheral surface 63c of the body portion side portion 63A of the cover member 63 over the entire circumference without gaps, thereby suppressing the infiltration of water.

In addition, a main body side portion 62A corresponding to the main body portion 66 of the absorbing member 62 has a concave portion 69 that fits with a lid portion side portion 62B corresponding to the lid portion 67. As shown in FIG. The recessed portion 69 is configured by providing a peripheral wall portion 70 projecting toward the lid portion 67 side at the outer peripheral end portion of the body portion side portion 62A of the absorbing member 62 . In this case, the main surface 62Aa of the body portion side portion 62A of the absorbing member 62 and the side surface 70a on the inner peripheral side of the peripheral wall portion 70 form the concave portion 69. As shown in FIG. On the other hand, the lid-side portion 62B of the absorbing member 62 protrudes from the main surface 63Ba of the lid-side portion 63B of the cover member 63 . Therefore, as shown in FIG. 4B, when the body portion 66 is covered with the lid portion 67, the lid portion side portion 62B of the absorbing member 62 is accommodated and fitted in the recessed portion 69 of the body portion side portion 62A. state. At this time, the main surface 62Aa and the main surface 62Ba are in contact with each other without a gap, and the side surface 70a of the peripheral wall portion 70 and the peripheral surface 62Bb of the lid portion side portion 62B are in contact with each other without a gap.

Although there is no particular limitation on how the neutron measurement chip 60 as described above is supported in the internal space of the irradiation unit 101, for example, a support structure as shown in FIG. 5 may be employed. As shown in FIG. 5, the irradiation unit 101 may support the neutron measurement chip 60 in the internal space with a support member 80 made of an organic material such as acrylic. The support member 80 is a block of organic material and has a groove 81 for inserting the neutron measurement chip 60 . With the neutron measuring chip 60 inserted into the groove 81 , the support member 80 is arranged in the water tank 103 so that the irradiated member 61 is arranged at a predetermined irradiation position. At this time, the support member 80 is preferably arranged at a position where it does not come into contact with the neutron beam N. The positioning method of the support member 80 is not particularly limited, and it may be supported by legs (see FIG. 5) or suspended from above. The structure of the support member 80 is not particularly limited, and the number of neutron measuring chips 60 to be supported is also not particularly limited. For example, the neutron measurement chip 60 may be supported by the support member 80 from both upper and lower sides.

Next, the actions and effects of the neutron measurement chip 60 and the neutron measurement system 100 according to this embodiment will be described.

A neutron measuring chip 60 according to the present embodiment includes an irradiated member 61 made of a material that emits gamma rays G when irradiated with a neutron beam N, and an absorption material that covers the irradiated member 61 and is made of a material that absorbs thermal neutrons. a member 62; Therefore, the member to be irradiated 61 can be irradiated with the neutron beam N in a state in which thermal neutrons are shielded by the absorbing member 62 . The amount of epithermal neutrons can be measured by using the measurement results of the irradiated member 61 that has been irradiated. As a result, by subtracting the amount of epithermal neutrons from the measurement result (including the amounts of thermal neutrons and epithermal neutrons) when only the irradiated member 61 is irradiated with the neutron beam N, the amount of thermal neutrons necessary for treatment can be obtained. It is possible to calculate the amount of Such an absorbing member 62 is covered with a cover member 63 . Therefore, even if the absorbing member 62 is made of a material such as cadmium that should be avoided from direct contact, the operator can touch the cover member 63 without directly touching the absorbing member 62 . while the neutron measuring chip 60 can be handled. Moreover, when the neutron measuring chip 60 is submerged in water, by protecting it with the cover member 63, diffusion of the material of the absorbing member 62 into water is suppressed. As described above, the handling of the neutron measuring chip 60 is improved. Also, the cover member 63 is made of an organic material. Since the organic material interacts with neutrons (absorption, nuclear reaction, etc.) similar to the human body, the decrease in measurement accuracy is suppressed by suppressing the influence on the neutron beam N irradiated to the member 61 to be irradiated. can. During treatment, the neutron beam N passes through the inside of the human body. The state of the neutron beam N after treatment may differ from that during treatment. On the other hand, in the present embodiment, the neutron beam N irradiated to the irradiated member 61 is passed through an organic material close to the human body, so that the conditions at the time of measurement can be brought closer to the conditions at the time of treatment. can suppress the decrease in As described above, it is possible to secure the measurement accuracy while improving the handleability of the neutron measurement chip when measuring neutron beams.

The irradiated member 61 may be formed in a foil shape with respect to the absorbing member 62 . In the case of a foil shape, the mass can be increased, so the amount of activation can be increased accordingly, and the measurement accuracy can be increased. In the case of a wire, the wire must be cut before measurement, and cannot be reused. Setting the gold wire takes time and effort, and mass measurement after cutting is also required. On the other hand, in the case of a foil shape, these steps can be omitted.

The irradiated member 61 may be linearly formed with respect to the absorbing member 62 . In the linear case, the neutron flux can be measured by gamma ray measurement at any point from the gold wire measured once in the depth direction.

When a foil-shaped or linear member is removed from the case for measurement, it is not easy to handle when setting it in the measuring device. It is preferable in that the measurement can be performed without removing the member from the case.

The irradiated member 61 may be made of gold or aluminum. These materials are easy to measure the gamma rays emitted by the neutron beam N irradiation.

The neutron measuring chip 60 may include a body portion 66 that supports the member to be irradiated 61 and a lid portion 67 that covers the member to be irradiated 61 supported by the body portion 66 . In this case, when gamma rays are measured after irradiation with the neutron beams N, the member to be irradiated 61 can be exposed simply by removing the lid portion 67 from the main body portion 66 . Therefore, workability for workers is improved.

A lid-side portion 63</b>B of the cover member 63 corresponding to the lid portion 67 may support the peripheral surface of a lid-side portion 62</b>B of the absorbing member 62 corresponding to the lid portion 67 . In this case, when the cover portion 67 is removed from the main body portion 66 before measurement, the irradiated member 61 can be easily exposed.

A lid-side portion 63B of the cover member 63 corresponding to the lid portion 67 may have a peripheral wall portion 68 extending to cover the peripheral surface 63c of the body-side portion 63A of the cover member 63 corresponding to the body portion 66 . In this case, since the cover member 63 has a structure in which the peripheral wall portion 68 of the lid portion 67 is hooked on the main body portion 66, the gap between them can be reduced.

A main body side portion 62A corresponding to the main body portion 66 of the absorbing member 62 may have a concave portion 69 that fits with the lid side portion 62B. In this case, since the absorbing member 62 has a structure in which the lid portion 67 and the main body portion 66 are fitted to each other, the gap between them can be reduced.

According to the neutron measurement system 100, it is possible to obtain the same functions and effects as the neutron measurement chip 60 described above. In addition, the irradiation unit 101 supports the neutron measurement chip 60 with a support member 80 made of an organic material in the internal space. Therefore, in the irradiation unit 101 , the neutron measurement chip 60 can be easily moved and positioned through the support member 80 .

The invention is not limited to the embodiments described above.

For example, the system configuration of the neutron measurement system 100 described above is merely an example, and can be changed as appropriate.

Also, the structure of the neutron measuring chip 60 is not limited to the above embodiment. For example, the hooking structure and fitting structure between the lid portion 67 and the main body portion 66 are not limited to those shown in FIG. For example, the lid-side portion 62B may have a recess, and the body-side portion 62A may be fitted into the recess.

REFERENCE SIGNS LIST 1 Neutron capture therapy device 60 Neutron measurement chip 61 Irradiated member 62 Absorption member 63 Cover member 66 Main body 67 Lid 80 Support member 100 Neutron measurement system.

Claims (9)

A neutron measuring chip for measuring the amount of neutrons,
an irradiated member made of a material that emits gamma rays when irradiated with the neutron beam;
an absorbing member made of a material that absorbs thermal neutrons and covering the member to be irradiated;
and a cover member made of an organic material and covering the absorbing member. 2. The neutron measuring chip according to claim 1, wherein said irradiated member is formed in a foil shape with respect to said absorbing member. 2. The neutron measuring chip according to claim 1, wherein said irradiated member is linearly formed with respect to said absorbing member. The neutron measuring chip according to any one of claims 1 to 3, wherein said member to be irradiated is made of gold or aluminum. The neutron measuring chip according to any one of claims 1 to 4, comprising a body portion that supports the member to be irradiated, and a lid portion that covers the member to be irradiated while being supported by the body portion. 6. The neutron measuring chip according to claim 5, wherein the portion of the cover member corresponding to the lid portion supports the peripheral surface of the portion of the absorbing member corresponding to the lid portion. 7. The neutron measuring chip according to claim 5, wherein the portion of the cover member corresponding to the lid portion has a peripheral wall portion extending so as to cover the peripheral surface of the portion of the cover member corresponding to the main body portion. The neutron measuring chip according to any one of claims 5 to 7, wherein a portion of said absorbing member corresponding to at least one of said lid portion and said main body portion has a concave portion that fits with a portion corresponding to the other. A neutron measurement system for measuring the amount of neutron beams generated by irradiation of a target with a charged particle beam,
an irradiation unit that houses a neutron measurement chip having an irradiated member and irradiates the irradiated member with the neutron beam in an internal space;
a measurement unit that measures gamma rays emitted from the irradiated member irradiated with the neutron beam,
The neutron measurement chip is
the irradiated member made of a material that emits gamma rays when irradiated with the neutron beam;
an absorbing member made of a material that absorbs thermal neutrons and covering the member to be irradiated;
a cover member made of an organic material and covering the absorbent member;
The neutron measurement system, wherein the irradiation unit supports the neutron measurement chip with a support member made of an organic material in the internal space.

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