JP6875265B2 - Neutron beam detector - Google Patents

Description

The present invention relates to a neutron beam detector.

Conventionally, a neutron beam detection device that detects a neutron beam by using a scintillator that emits light when radiation is incident has been studied. Patent Document 1 discloses a method of calculating the number of arrivals of neutrons based on the output from a scintillator that emits light for thermal neutrons and gamma rays and the output from a scintillator that emits light for gamma rays.

International Publication No. 2005/008287

However, in the method described in Patent Document 1, it is necessary to measure the output from each scintillator individually. Therefore, the number of channels of the detector may increase and the device may become complicated.

The present invention has been made in view of the above, and an object of the present invention is to provide a neutron beam detection device capable of detecting a neutron beam with a simpler configuration.

In order to achieve the above object, the neutron beam detector according to one embodiment of the present invention has a first detector that emits light when a gamma ray is incident and does not emit light even if a neutron beam is incident, and a neutron beam. It has a second detector that emits light when the radiation is incident on it, and a photodetector that detects the light emitted from the second detector, and the first detector is from the second detector. Also adjacent to the second detector on the radiation source side, and the center position of the first detector and the center position of the second detector are different from each other when viewed from the radiation source side. The light emitted from the first detector can be in a mode that can be detected by the photodetector via the second detector.

According to the above-mentioned neutron ray detection device, a first detector that emits light when a gamma ray is incident and does not emit light even if a neutron beam is incident, and a first detector that emits light when a neutron beam is incident. By combining the two detectors, it is possible to distinguish and detect neutron rays in an environment irradiated with radiation including neutron rays and gamma rays. Further, in the neutron beam detector, the light emitted by the first detector and the light emitted by the second detector can be detected by the photodetector. Further, since the center position of the first detector and the center position of the second detector are arranged so as to be different from each other, the light emitted by either the first detector or the second detector based on the detection result of the photodetector. It is possible to distinguish whether it is. Therefore, the light emitted by the first detector and the light emitted by the second detector can be detected without attaching a photodetector to the first detector, so that the light is emitted from the first detector. The number of photodetectors can be reduced as compared with the case where a detector is attached. Therefore, according to the above-mentioned neutron beam detection device, the neutron beam can be detected with a simpler configuration.

Here, the plurality of the first detectors are arranged two-dimensionally adjacent to each other on a plane, and the plurality of the second detectors have their respective center positions with the plurality of first detectors. Are arranged adjacent to each other on a plane parallel to the plane on which the plurality of first detectors are arranged in different states, and the plurality of the first detectors and the plurality of the second detectors are adjacent to each other. The light detector may be provided for each of the second detectors.

As described above, it is possible to detect the distribution of neutron rays by configuring the plurality of first detectors and the plurality of second detectors to be arranged adjacent to each other on a plane parallel to each other. Become. Further, since the plurality of first detectors and the plurality of second detectors are arranged adjacent to each other, the light emitted from the first detector is also suitably detected by the photodetector provided in the second detector. Therefore, it is possible to detect the distribution of neutron rays with a simple configuration.

In addition, it has an analysis unit that analyzes the detection results of the plurality of photodetectors, and the analysis unit determines the position of the center of gravity of the light based on the detection results of the light detected by each photodetector at a specific time. It can be an aspect to be calculated.

As described above, the analysis unit calculates the position of the center of gravity of the light based on the detection result of the light detected by each photodetector at a specific time. The position can be estimated.

In addition, the analysis unit may be in a mode of specifying whether the light is emitted from the first detector or the second detector based on the position of the center of gravity of the light.

As described above, the neutron beam detector detects whether the light is emitted from the first detector or the second detector based on the position of the center of gravity of the light calculated by the analysis unit. It is possible to more accurately identify the type of radiation.

Based on the wave height information of the light detected by the plurality of photodetectors, the analysis unit identifies whether the light is emitted from the first detector or the second detector. can do.

As described above, it was detected by the neutron beam detector by identifying whether the light was emitted from the first detector or the second detector based on the wave height information of the light detected by the photodetector. The type of radiation can be identified more accurately.

According to the present invention, there is provided a neutron beam detection device capable of detecting a neutron beam with a simpler configuration.

It is a schematic diagram which shows the neutron capture therapy apparatus which uses the neutron ray detection apparatus. It is a schematic diagram of the neutron beam detection apparatus, and the figure explaining the attachment state to the neutron capture therapy apparatus. It is a figure explaining the operation of the neutron beam detection apparatus. It is a figure which shows the example of the analysis result by the analysis part of the neutron beam detection apparatus. It is a figure which shows the example of the analysis result by the analysis part of the neutron beam detection apparatus.

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 designated by the same reference numerals, and duplicate description will be omitted.

FIG. 1 is a schematic view of a neutron capture therapy device using a neutron beam detection device. The neutron capture therapy device 1 shown in FIG. 1 is a device that performs cancer treatment using boron neutron capture therapy (BNCT). In the neutron capture therapy device 1, for example, the tumor of the patient (irradiated body) 50 to which ^{boron (10 B) is administered is irradiated with neutron rays N.}

The neutron capture therapy device 1 includes a cyclotron 2. The cyclotron 2 is an accelerator that accelerates charged particles such as anions to produce a charged particle beam R. In the present embodiment, the charged particle beam R is a proton beam generated by stripping an electric charge from an anion. The proton beam is generated by stripping electrons in the cyclotron 2 using a foil stripper or the like, and is emitted from the cyclotron 2. The cyclotron 2 has the ability to generate a charged particle beam R having a beam radius of 40 mm and a beam radius of 60 kW (= 30 MeV × 2 mA), for example. The accelerator is not limited to the 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 generator M. The neutron beam generator M includes a target 7, a moderator 9, and a collimator 10. The charged particle beam R emitted from the cyclotron 2 passes through the beam duct 3 and travels toward the target 7 arranged at the end of the beam duct 3. A plurality of quadrupole electromagnets 4, a current detection unit 5, and a scanning electromagnet 6 are provided along the beam duct 3. The plurality of quadrupole electromagnets 4 use, for example, an electromagnet to adjust the beam axis and the beam diameter of the charged particle beam R.

The current detection unit 5 detects the current value (that is, charge, irradiation dose rate) of the charged particle beam R irradiated to the target 7 in real time during irradiation of the charged particle beam R. As the current detection unit 5, for example, a non-destructive DCCT (DC Current Transformer) capable of measuring the current without affecting the charged particle beam R is used.

The scanning electromagnet 6 scans the charged particle beam R and controls the 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.

The neutron capture therapy device 1 generates a neutron beam N by irradiating the target 7 with a charged particle beam R, and emits the neutron beam N toward the patient 50. The neutron capture therapy device 1 includes a target 7, a shield 8, a moderator 9, a collimator 10, and a gamma ray detection unit 11.

The target 7 is irradiated with a charged particle beam R to generate a neutron beam N. The target 7 here is formed of, for example, beryllium (Be), lithium (Li), tantalum (Ta), and tungsten (W), and has a disk shape having a diameter of 160 mm, for example. The target 7 is not limited to a plate shape, and may be, for example, a liquid.

The moderator 9 decelerates the energy of the neutron beam N generated by the target 7. The moderator 9 is composed of a first moderator 9A that mainly decelerates fast neutrons contained in the neutron beam N and a second moderator 9B that mainly decelerates extrathermal neutrons contained in the neutron beam N. It has a laminated structure.

The shield 8 shields the generated neutron beam N and the gamma ray generated by the generation of the neutron beam N so as not to be emitted to the outside. 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 the gamma ray detection unit 11 is provided in these extending portions.

The collimator 10 shapes the irradiation field of the neutron beam N, and has an opening 10a through which the neutron beam N passes. The collimator 10 is, for example, a block-shaped member having an opening 10a in the center.

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 the generation of the neutron beam (that is, during the irradiation of the patient 50 with the neutron beam N). is there. As the gamma ray detection unit 11, a scintillator, an ionization chamber, and various other gamma ray detection devices can be adopted. In the present embodiment, the gamma ray detection unit 11 is arranged inside the upper part and the lower part of the shield 8 extending around the target 7 on the upstream side of the charged particle beam R from the moderator 9, respectively. The configuration may not include the gamma ray detection unit 11.

Further, the neutron capture therapy device 1 includes a control unit (not shown). The control unit is an electronic control unit composed of a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like, and comprehensively controls the neutron capture therapy device 1.

The neutron beam detection device according to the present embodiment is used to detect the distribution and intensity of the neutron beam in the above neutron capture therapy device 1. Therefore, as shown in FIG. 2, the neutron beam detection device 20 includes a plurality of first detectors 21, a plurality of second detectors 22, and a plurality of light guides 23 attached to each of the plurality of second detectors 22. It also has a photodetector 24 and an analysis unit 25 that calculates the distribution of neutron rays based on the amount of light detected by the photodetector 24 and the like.

The neutron beam detection device 20 is used for measuring the distribution of the neutron beam N emitted through the collimator 10. Further, the neutron beam detection device 20 is used not during irradiation of the patient 50 with the neutron beam N, but before irradiation or during maintenance of the neutron capture therapy device 1. Therefore, as shown in FIG. 2, the neutron beam detection device 20 is attached so as to close the opening 10a of the collimator 10 on the downstream side (the side on which the patient 50 is placed) of the collimator 10.

A scintillator can be used as both the first detector 21 and the second detector 22. A scintillator is a phosphor that converts incident radiation (neutron rays N, gamma rays) into light. In the scintillator, the internal crystal is excited according to the dose of the incident radiation, and scintillation light is generated. However, the types of radiation emitted by the first detector 21 and the second detector 22 are different from each other. Specifically, the first detector 21 has a feature that it emits light when a gamma ray is incident, but does not emit light even when a neutron beam N is incident. On the other hand, the second detector 22 has a feature of emitting light at least when a neutron beam N is incident. However, the second detector 22 may be configured to emit light even when a gamma ray is incident in addition to the neutron beam N.

In addition, "emitting light" in this embodiment means emitting light to the extent that it can be detected by the photodetector 24. Further, "does not emit light" means a state in which light is not detected by the photodetector 24. Therefore, it can be said that "no light is emitted" even when light that cannot be detected by the photodetector is emitted.

As the second detector 22, a ⁶ Li glass scintillator, a LiCAF scintillator, a ⁶ LiF-coated plastic scintillator, a ⁶ LiF / ZnS scintillator, or the like can be adopted. The scintillators used as the second detectors are all scintillators that emit (sensitive) light to neutron rays N and gamma rays. On the other hand, as the first detector 21, a known scintillator different from the above scintillator, which does not emit light to neutron rays (has no sensitivity), can be adopted.

The plurality of first detectors 21 are arranged two-dimensionally on a predetermined plane. In the present embodiment, the first detector 21 is in a direction orthogonal to the radiation emission direction (in the case of the present embodiment, it corresponds to the emission direction of the neutron beam N (the beam axis of the charged particle beam R)). It is arranged two-dimensionally on an extending plane. Further, by making the gap between the adjacent first detectors 21 smaller, the distribution of the neutron beam N can be detected more preferably.

Further, the plurality of second detectors 22 are arranged two-dimensionally on a predetermined plane. In the present embodiment, the second detector 22 is also on a plane extending in a direction orthogonal to the emission direction of the neutron beam N (the beam axis of the charged particle beam R), like the plurality of first detectors. It is arranged in a two-dimensional manner. Further, by making the gap between the adjacent second detectors 22 smaller, the distribution of the neutron beam N can be detected more preferably.

The second detector 22 is arranged at a position downstream of the first detector 21, that is, farther than the radiation source (target 7 in the case of the present embodiment). Further, in the present embodiment, the first detector 21 and the second detector 22 are arranged on a plane parallel to each other. Further, the first detector 21 and the second detector 22 are arranged adjacent to each other (without a gap) when viewed along the radiation emission direction. By arranging the first detector 21 and the second detector 22 adjacent to each other, the light emitted from the first detector 21 can be suitably detected.

Further, the first detector 21 and the second detector 22 are arranged at positions where the center positions are different from each other when viewed from the radiation source. When the first detector 21 and the second detector 22 are scintillators and their sizes are the same, the first detector 21 and the second detector 21 and the second detector so that the center positions are different from each other when viewed from the radiation source. When 22 is arranged, as shown in FIG. 2, the boundary between the adjacent first detectors 21 and the boundary between the adjacent second detectors 22 are at different positions when viewed from the radiation source. It becomes. In this way, by setting the center positions of the first detector 21 and the second detector 22 to be different from each other when viewed from the radiation source, the analysis unit 25 described later emits light in which detector. It will be easier to identify this, but the details will be described later.

The light guide 23 is a member that transmits the light generated by the second detector 22. The light guide 23 is composed of an optical fiber. The light guide 32 may be composed of, for example, a bundle of flexible optical fibers. The light guide 23 is connected to each of the plurality of second detectors 22. The light emitted by each of the plurality of second detectors 22 is individually transmitted by the plurality of light guides 23.

The photodetector 24 detects the light transmitted through the light guide 23. The photodetector 24 is connected to each of the plurality of light guides 23. Therefore, the light guide 23 and the photodetector 24 are provided for each of the plurality of second detectors 22. As the photodetector 24, various photodetectors such as a photomultiplier tube and a phototube can be adopted. The photodetector 24 outputs an electric signal (detection signal) to the analysis unit 25 at the time of light detection.

The analysis unit 25 has a function of calculating the intensity and distribution of the light detected by the second detector 22 based on the electric signals transmitted from the plurality of photodetectors 24.

In the neutron beam detection device 20 according to the present embodiment, the light guide 23 and the photodetector 24 are not connected to the plurality of first detectors 21 arranged on the emission source side of the emission beam. However, the emission of light by the first detector 21 is also detected by using the photodetector 24 provided for the second detector 22 via the plurality of second detectors 22 and the light guide 23. .. With such a configuration, the analysis unit 25 can distinguish and detect the neutron beam N and the gamma ray by using the light guide 23 and the photodetector 24 connected to the plurality of second detectors 22. .. This point will be described with reference to FIGS. 3 and 4.

First, FIG. 3A shows a state in which the first detector 21 emits light with the incident of gamma rays. In FIG. 3A, for the sake of simplicity, only one first detector 21A out of the plurality of first detectors 21 is shown, and the other adjacent first detectors 21 are omitted. .. Further, in FIG. 3A, of the plurality of second detectors 22, four fourths arranged behind (downstream side) with respect to the first detector 21A when viewed from the emission source side of the emission line. 2 Only detectors 22A to 22D are shown. Further, the light guides 23A to 23D are connected to the second detectors 22A to 22D.

FIG. 3A shows a state in which the gamma ray G is incident on the first detector 21A. In this case, the first detector 21A emits light as the gamma ray G is incident. A part of this light is incident on the light guides 23A to 23D connected to the second detectors 22A to 22D via the second detectors 22A to 22D in the subsequent stage. Then, these lights are converted into electric signals by the photodetectors 24 in the subsequent stages of the light guides 23A to 23D and detected by the analysis unit 25. Since the center position of the first detector 21A is provided at a position different from the center position of the second detectors 22A to 22D, the light emitted from the first detector 21A is the second detectors 22A to 22D. After that, the light guides 23A to 23D are dispersed and incident on the light guides 23A to 23D. The energy of the light emitted from the first detector 21A with the incident of the gamma ray G is smaller than the energy of the light emitted from the second detectors 22A to 22D with the incident of the neutron beam N. Further, a part of the light emitted by the first detector 21A is incident on each of the light guides 23A to 23D. Therefore, the amount of light incident on each of the light guides 23A to 23D is smaller than that in the case where the second detectors 22A to 22D emit light.

When a plurality of first detectors 21 are arranged two-dimensionally on a plane in a state of being adjacent to each other, gamma rays G from a radiation source are incident on one of the two-dimensionally arranged first detectors 21.

FIG. 3B shows a state in which the neutron beam N is incident on the second detector 22B. In this case, the second detector 22B emits light as the neutron beam N is incident. This light mainly enters the light guide 23B connected to the second detector 22B, is converted into an electric signal by the photodetector 24 in the subsequent stage of the light guide 23B, and is detected by the analysis unit 25. When the second detector 22B emits light, a part of the light guides 23A, 23C, 23D connected to the second detectors 22A, 22C, 22D may also be incident on the light guides 23A, 23C, 23D. Becomes very small.

When a plurality of second detectors 22 are arranged two-dimensionally on a plane in a state of being adjacent to each other, the neutron beam N from the radiation source passes through the first detector 21 arranged two-dimensionally and the plurality of second detectors 22 are arranged. It is incident on any of the detectors 22.

As described above, in the neutron beam detection device 20, regardless of which of the first detector 21 and the second detector 22 emits light, the neutron beam detector 20 is incident on the plurality of light guides 23 connected to the plurality of second detectors 22. Light can be detected. Further, the amount of light incident on the plurality of light guides 23 and the degree of dispersion thereof differ depending on which of the first detector 21 and the second detector 22 emits light. The analysis unit 25 identifies which light guide 23 is incident with light and which detector emits the light based on the dispersion thereof.

The analysis unit 25 identifies the position of the light emission source based on the position information of the light guide 23 connected to the photodetector 24 that has detected the light and the amount of the light. The position of the emission source can be identified by analyzing the light detected by the photodetectors 24 connected to the plurality of second detectors 22. It is assumed that the light emitted from the first detector 21 or the second detector 22 is incident on the plurality of light guides 23 at substantially the same time. Therefore, in the analysis unit 25, is the electric signal detecting the same light emitted from a specific light emission source from the transmission timing of the electric signal transmitted from each photodetector 24? Can be identified. The analysis unit 25 obtains the position of the center of gravity of the electric signal related to the same light emitted from the specific light emission source detected at a specific time, and uses the calculated center of gravity position as the position of the light emission source. It is the information indicating. When calculating the position of the center of gravity, it is not necessary to consider the amount of light detected by the photodetectors 24 connected to the plurality of second detectors 22, but the amount of light is taken into consideration when determining the position of the center of gravity. When the calculation is performed, the calculation accuracy of the position of the center of gravity is improved.

For example, as shown in FIG. 3A, when the first detector 21A emits light due to the incident of gamma rays G, the light guides 23A to 23D connected to the second detectors 22A to 22D are incident on each other. , Each of which is converted into an electric signal by the photodetector 24 and output to the analysis unit 25. Therefore, the analysis unit 25 can identify from this electrical signal that the same light emitted from a specific emission source is incident on the light guides 23A to 23D. Therefore, the position of the center of gravity of the light guides 23A to 23D is determined by using the information indicating the intensity of the electric signal related to the light incident on the light guides 23A to 23D and the position information of the light guides 23A to 23D (the end face on the side where the light is incident). Is calculated. The position of the center of gravity is on a plane extending in a direction orthogonal to the emission direction of the neutron beam N (the beam axis of the charged particle beam R), that is, on the extending plane of the first detector 21 and the second detector 22. Calculated as the position of the center of gravity. Here, the direction in which the second detectors 22A and 22B are lined up is the X-axis, the direction in which the second detectors 22C and 22A are lined up is the Y-axis, and the positions of the light guides 23A to 23D (end faces on the side where the light is incident) are located. Is also specified by XY coordinates. Then, the position of the center of gravity of the light in the above XY plane can be calculated from the information indicating the intensity of the electric signal related to the light incident on the light guides 23A to 23D and the position information of the light guides 23A to 23D. .. When the intensities of the light incident on the light guides 23A to 23D are substantially the same, the position of the center of gravity thereof is considered to be near the center position of the light guides 23A to 23D, that is, the position corresponding to the first detector 21.

On the other hand, as shown in FIG. 3B, the second detector 22B emitted light and the other second detectors 22A, 22C, 22D did not emit light as the neutron beam N was incident (light guide). When the light did not enter the 23A, 23C, and 23D), the analysis unit 25 calculated that the center of gravity of the light was near the position of the light guide 23B, that is, the position corresponding to the second detector 22B. Become.

FIG. 4 shows an example in which the analysis result in the analysis unit 25 is plotted on the XY plane. Each point included in the plurality of points P1 and the plurality of points P2 shown in FIG. 4 is the position of the center of gravity of the light emitted from the first detector 21 or the second detector 22 of the neutron beam detection device 20, that is, It is information indicating the source of light emission. As shown in FIG. 4, the plurality of points P1 and the plurality of points P2 can be distinguished from each other as different groups. Further, the position (XY coordinates) where the group of the plurality of points P1 shown in FIG. 4 is formed corresponds to the first detector 21, and the position where the group of the plurality of points P2 is formed corresponds to the second detector 22B. It is assumed that it corresponds to. In this case, it is determined that the light corresponding to the plurality of points P1 is the light emitted from the first detector 21, and the light corresponding to the plurality of points P2 is the light emitted from the second detector 22B. can do. Further, although omitted in FIG. 4, there are a plurality of regions C1 corresponding to the second detector 22A, a region C2 corresponding to the second detector 22C, and a plurality of regions C3 corresponding to the second detector 22D. It is considered that a group is formed by the points.

As described above, in the analysis unit 25, the plurality of light guides 23 connected to the plurality of second detectors 22 for each of the lights emitted by the plurality of first detectors 21 and the plurality of second detectors 22. From the electric signal related to the light incident on the light, the position of the center of gravity of the light corresponding to the information indicating the position of the light emitting source is calculated. The analysis unit 25 can identify which detector is detecting the light emitted from the information indicating the position of the light emission source. When the analysis unit 25 can distinguish which detector emits the detected light, the information of the light detected by the first detector 21 and the second detector 22 is combined and analyzed. Therefore, the neutron beam can be detected accurately, and the dose distribution of the neutron beam can be obtained more accurately.

As described above, the first detector 21 and the second detector 22 emit different types of radiation. When the neutron beam N is incident, the second detector 22 emits light, but the first detector 21 does not emit light. On the other hand, when gamma rays are incident, light may be emitted by both the first detector 21 and the second detector 22. Therefore, it may be difficult to discriminate between the neutron beam N and the gamma ray only by detecting the light from the second detector 22. Therefore, it is possible to arrange a detector that emits light to gamma rays like the first detector 21 and a detector that emits light to neutron rays N like the second detector 22 side by side. It has been studied conventionally. However, when measuring the dose distribution of neutron rays in the neutron capture therapy device 1, especially in the case of surface measurement, the neutron rays are measured with a plurality of detectors arranged in two dimensions, for example. Although it is necessary, each detector needs to be provided with an output circuit for detecting the emitted light, such as a light guide and a photodetector, which makes it difficult to handle the output circuit and complicates the device. there's a possibility that. Further, since it is difficult to arrange the detectors adjacent to each other due to the routing of the output circuit, the measurement accuracy of the entire device may be lowered.

Therefore, in the neutron beam detection device 20 according to the present embodiment, first, by combining the first detector 21 and the second detector 22, the neutron beam is irradiated in an environment in which radiation including neutron beam and gamma ray is irradiated. Can be detected separately. Further, in the neutron beam detection device 20, the light emitted by the first detector 21 and the light emitted by the second detector 22 can be detected by the photodetector 24. The center position of the first detector 21 and the center position of the second detector 22 are arranged so as to be different from each other. Therefore, it is possible to distinguish which of the first detector 21 and the second detector 22 is the emitted light from the detection result of the photodetector 24. Therefore, even if the photodetector is not attached to the first detector 21, the light emitted by the first detector 21 and the light emitted by the second detector 22 can be detected by the photodetector 24. Since the number of photodetectors 24 can be reduced, neutron beams can be detected with a simpler configuration.

Further, in the neutron beam detection device 20, a plurality of first detectors 21 and a plurality of second detectors 22 are arranged adjacent to each other on a plane parallel to each other. With such a configuration, it is possible to detect the distribution of neutron rays by using the neutron beam detection device 20. Further, since the plurality of first detectors 21 and the plurality of second detectors 22 are arranged adjacent to each other, the light emitted from the first detector 21 is also an optical detector provided in the second detector 22. Since it can be preferably detected at 24, it is possible to detect the distribution of neutron rays with a simple configuration.

Further, in the neutron beam detection device 20, the analysis unit 25 calculates the position of the center of gravity of the light based on the detection result of the light detected by each photodetector at a specific time. With such a configuration, it is possible to estimate the position of the light emitting source from the calculated position of the center of gravity.

Then, the neutron beam detection device 20 is configured to specify whether the light is emitted from the first detector 21 or the second detector 22 based on the position of the center of gravity of the light calculated by the analysis unit 25. The type of detected radiation can be identified more accurately.

The photodetector 24 also acquires information on the wave height (intensity) of the light emitted by the first detector 21 or the second detector 22. Therefore, the analysis unit 25 uses the wave height information of the light in addition to the position of the center of gravity of the light described above to identify whether the light is emitted from the first detector 21 or the second detector 22. It can be configured.

FIG. 5 shows an example in which the analysis result XY plane of the analysis unit 25 is plotted in the same manner as in FIG. 4, and the wave height information detected by each photodetector 24 is applied to the Z axis for each point. In FIG. 5, similarly to FIG. 4, the plurality of points P1 and the plurality of points P2 can be distinguished from each other as different groups. Further, in FIG. 5, even based on the wave height information, it is possible to clearly distinguish between the position where the group of the plurality of points P1 is formed and the position where the group of the plurality of points P2 is formed. The light emitted from the first detector 21 is basically light derived from gamma rays, but the wave height of the light derived from the gamma rays is smaller than the wave height of the light derived from the neutron rays. Further, the light emitted from the first detector 21 enters the photodetector 23 via the second detector 22 and reaches the photodetector 24, so that the wave height (intensity) is also reduced from that point. Further, the region C1 corresponding to the second detector 22A, the region C2 corresponding to the second detector 22C, and the region C3 corresponding to the second detector 22D also have the same wave height as the group of the plurality of points P2. Is expected to be. In this way, if the configuration is such that it is possible to specify whether the light is emitted from the first detector 21 or the second detector 22 by using the wave height information of the light, the type of radiation detected by the neutron beam detection device 20 Can be identified more accurately.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments.

For example, in the above embodiment, the case where a plurality of the first detector 21 and the second detector 22 are provided has been described, but the number of the first detector 21 and the second detector 22 may be one or more. It can be changed as appropriate. Further, the arrangement of the light guide 23 and the photodetector 24 can be changed as appropriate.

Further, the photodetector 24 may be provided directly after the second detector 22 without providing the light guide 23. In that case, a plurality of photodetectors 24 are connected to the second detectors 22A to 22D, respectively. In the case of such a configuration, the position of the center of gravity of the light corresponding to the information indicating the position of the light emitting source is determined from the electric signal related to the light incident on the plurality of photodetectors 24 connected to the plurality of second detectors 22. It will be calculated. In this way, the light guide 23 may be omitted.

Further, in the above embodiment, the neutron beam detection device is applied to the neutron capture therapy device 1, but the use of the neutron beam detection device is not limited. For example, the neutron beam detector of the present invention may be applied as a monitor for monitoring the operating state of a nuclear reactor. Further, the neutron beam detection device of the present invention may be used when measuring the accelerated neutron used in the physical experiment. Further, the neutron beam detection device of the present invention may be used in the neutron irradiation device for non-destructive inspection.

1 ... Neutron capture therapy device, 10 ... Collimator, 20 ... Neutron beam detector, 21 ... 1st detector, 22 ... 2nd detector, 23 ... Light guide, 24 ... Light detector, 25 ... Analytical unit.

Claims (5)

The first detector that emits light when gamma rays are incident and does not emit light when neutron rays are incident,
A second detector that emits light when a neutron beam is incident,
A photodetector that detects the light emitted from the second detector, and
Have,
The first detector is adjacent to the second detector on the radiation source side of the second detector, and is located at the center position of the first detector when viewed from the radiation source side. The center positions of the second detector are arranged so as to be different from each other.
A neutron beam detector capable of detecting the light emitted from the first detector by the photodetector via the second detector. A plurality of the first detectors are arranged two-dimensionally adjacent to each other on a plane.
The plurality of second detectors are adjacent to each other on a plane parallel to the plane on which the plurality of first detectors are arranged, in a state where the center positions thereof are different from the center positions of the plurality of first detectors. Arranged,
The plurality of the first detectors and the plurality of the second detectors are adjacent to each other.
The neutron beam detection device according to claim 1, wherein the photodetector is provided for each of the plurality of second detectors. It has an analysis unit that analyzes the detection results of a plurality of the photodetectors.
The neutron beam detection device according to claim 2, wherein the analysis unit calculates the position of the center of gravity of the light based on the detection result of the light detected by each photodetector at a specific time. The neutron beam detection device according to claim 3, wherein the analysis unit identifies whether the light is emitted from the first detector or the second detector based on the position of the center of gravity of the light. The analyzer identifies whether the light is emitted from the first detector or the second detector, based on the wave height information of the light detected by the plurality of photodetectors. Item 4. The neutron beam detection device according to item 4.

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