JP2019219264A - Radiation measurement device - Google Patents

Abstract

To provide a radiation measurement device which is less sensitive to a low-energy γ-ray and is more sensitive to a high-energy γ ray.SOLUTION: A radiation measurement device 100 includes: a converter 10 for discharging charged particles by a photonuclear reaction with a γ-ray; and a light emitting element 20 in contact with the converter 10, the light emitting element having a thickness equal to or less than the range of the charge particles. The converter 10 has a thickness equal to or less than the range of the charge particles. The radiation measurement device further includes a photoelectron multiplier 40 for performing a photoelectric conversion of light emitted by the light emitting element 20. The photoelectron multiplier 40 is provided in the position of the light emitting element 20 which is away from the radiation emission region.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to a radiation measurement device.

  Conventionally, a method has been known in which a substance is disposed on the surface of a detection layer, secondary electrons emitted from the substance are discharged to the detection layer, and the detection layer measures the secondary electrons. For example, Patent Literature 1 discloses a laminated portion in which a plastic scintillator that emits light by detecting radiation and a plate made of a substance having an atomic number greater than 13 are alternately laminated, and an optical transmission path that transmits light emitted by the plastic scintillator. A radiation detector including a photoelectric conversion element that converts light that has passed through an optical transmission path into an electric signal, and a signal processing circuit that processes an electric signal from the photoelectric conversion element is disclosed.

JP-A-9-197050

Meanwhile, high energy γ-rays (for example, γ-rays having an energy of 3 [MeV] or more) have a high penetrating power to crystals, and thus require a large crystal for energy analysis in a radiation measurement device.
However, in a radiation measurement device, when the size of the crystal increases, the sensitivity to low-energy γ-rays also increases, so that the analysis of γ-rays becomes difficult due to pile-up of detection signals and saturation of the signal processing system. There was a problem.

  An object according to an embodiment of the present disclosure is to provide a radiation measurement device that has low sensitivity to low-energy γ-rays and high sensitivity to high-energy γ-rays.

  A radiation measuring apparatus according to an embodiment of the present disclosure includes a converter that emits charged particles by a photonuclear reaction with γ-rays, and a light emitting device that has a thickness equal to or less than the range of the charged particles and is provided in contact with the converter. And an element.

  According to the radiation measurement device according to the embodiment of the present disclosure, it is possible to provide a radiation measurement device having low sensitivity to low energy γ-rays and high sensitivity to high energy γ-rays.

It is a figure showing an example of composition of a radiation measuring device concerning a 1st embodiment. It is a figure showing an example of composition of a radiation measuring device concerning a 2nd embodiment. It is a figure showing an example of composition of a radiation measuring device concerning a 3rd embodiment. It is a figure showing an example of composition of a radiation measuring device concerning a 4th embodiment. It is a figure showing an example of composition of a radiation measuring device concerning a 5th embodiment. It is a figure showing an example of composition of a radiation measuring device concerning a 6th embodiment. It is a figure showing an example of composition of a data analysis device in a radiation measuring device concerning a 6th embodiment.

  Hereinafter, the radiation measurement device according to the embodiment will be described. The drawings referred to in the following description schematically show the embodiments, and the scale, interval, positional relationship, and the like of each member are exaggerated, or some of the members are not illustrated. There are cases. Further, for example, the scale and the interval of each member may not match in the plan view and the cross-sectional view thereof. In the following description, the same names and reference numerals indicate the same or similar members in principle, and a detailed description thereof will be omitted as appropriate. Also, in this specification, "up", "down", and the like indicate relative positions between components, and are not intended to indicate absolute positions.

[First Embodiment]
≫Configuration of radiation measurement device≫
First, the configuration of the radiation measuring apparatus 100 according to the first embodiment will be described with reference to FIG.

  As shown in FIG. 1, the radiation measuring apparatus 100 includes a converter 10, a light emitting element 20, an optical fiber 30, a photomultiplier tube 40, a wave height analyzer 50, and the like.

The converter 10 emits charged particles 101 (for example, α particles and protons) by a photonuclear reaction with high energy γ rays A (for example, γ rays having energy of 3 [MeV] or more). The photonuclear reaction occurs for high energy γ-rays A and not for low energy γ-rays B.
The threshold energy of the photonuclear reaction depends on the material of the converter 10. For example, when the converter 10 is beryllium, the threshold energy of the photonuclear reaction is about 3 [MeV].

  Due to the photonuclear reaction with the high energy γ-ray A, charged particles 101 are generated in the converter 10. The charged particles 101 apply energy to the converter 10 while moving in the converter 10. The energy loss of the charged particles 101 increases as the distance that the charged particles 101 move in the converter 10 increases, and decreases as the distance that the charged particles 101 move in the converter 10 decreases.

The thickness of converter 10 is preferably equal to or less than the range of charged particles 101. When the thickness of the converter 10 is equal to or less than the range of the charged particles 101, the charged particles 101 easily enter the light emitting element 20.
The range of the charged particles 101 depends on the type of the charged particles 101, the energy of the charged particles 101, and the substance of the converter 10. Note that the range of the charged particle 101 means an average moving distance in a substance in which the charged particle 101 loses all energy.

  The converter 10 emits the electrons 102 by an interaction with the low-energy γ-ray B such as Compton scattering and electron pair generation. The electrons 102 generated in the converter 10 enter the light emitting element 20 and apply energy to the light emitting element 20 while moving in the light emitting element 20. Thereby, the light emitting element 20 emits light.

The range of the electrons 102 depends on the energy of the electrons 102. The range of the electrons 102 is longer as the energy of the electrons 102 is larger, and is shorter as the energy of the electrons 102 is smaller.
In general, the range of the electrons 102 is longer than the range of the charged particles 101. For example, the range of alpha particles (energy of 4 [MeV]) in beryllium is about 0.02 [mm]. On the other hand, the range of electrons (energy 4 [MeV]) in beryllium is about 11 [mm]. Note that the range of the electron 102 means an average moving distance in a substance in which the electron 102 loses all energy.

  FIG. 1 illustrates an example in which the converter 10 is provided in contact with at least one surface of the light emitting element 20, but the converter 10 may be provided in contact with the entire surface of the light emitting element 20.

  Light emitting element 20 is provided in contact with at least one surface of converter 10. The light emitting element 20 is connected to the photomultiplier tube 40 via the optical fiber 30, and light emitted by the light emitting element 20 enters the photomultiplier tube 40 via the optical fiber 30.

The light-emitting element 20 is configured such that, when high-energy γ-rays A having a threshold energy of a photonuclear reaction or more enter the converter 10, at least a part of energy is imparted from the charged particles 101 generated in the converter 10. Emits light.
The emission intensity of the light emitting element 20 increases as the applied energy increases, and decreases as the applied energy decreases.

In addition, the light emitting element 20 emits the electron 102 by an interaction with the low energy γ-ray B such as Compton scattering and generation of an electron pair. The light-emitting element 20 emits light by applying at least a part of energy from the electrons 102 generated in the light-emitting element 20.
It is preferable that the thickness of the light emitting element 20 be equal to or less than the range of the charged particles 101. If the thickness of the light emitting element 20 is within the range of the charged particles 101, the charged particles 101 can apply all energy to the light emitting element 20. On the other hand, the range of the electrons 102 is longer than the range of the charged particles 101. Therefore, if the thickness of the light emitting element 20 is about the same as the range of the charged particles 101, only a part of the energy of the electrons 102 is reduced. Cannot be assigned to That is, when the thickness of the light emitting element 20 is equal to or less than the range of the charged particles 101, the high energy γ-ray A and the low energy γ-ray B can be separated. Thereby, the radiation measurement apparatus 100 having low sensitivity to low energy γ-rays and high sensitivity to high energy γ-rays can be realized.

  The optical fiber 30 is provided between the light emitting element 20 and the photomultiplier tube 40, connects the light emitting element 20 and the photomultiplier tube 40, and sends light emitted by the light emitting element 20 to the photomultiplier tube 40. Lead. The optical fiber 30 is not an essential component, and the light emitting element 20 and the photomultiplier tube 40 can be directly connected.

  The photomultiplier tube 40 is connected to the light emitting element 20 via the optical fiber 30, photoelectrically converts light emitted by the light emitting element 20, and outputs an electric signal to the wave height analyzer 50. The photomultiplier tube 40 is preferably provided at a position away from the radiation irradiation area of the light emitting element 20. The photomultiplier tube 40 may be connected to the light emitting element 20 via the optical fiber 30, or may be connected to the light emitting element 20 without the optical fiber 30.

  The wave height analyzer 50 performs wave height analysis of the electric signal output from the photomultiplier tube 40. That is, the pulse height analyzer 50 calculates the peak value of the electric signal that appears when the charged particles 101 apply energy to the light emitting element 20 from the peak value of the electric signal that appears when the electrons 102 apply energy to the light emitting element 20. Separate and measure only the high peak value component. The peak value of the electric signal increases as the emission intensity increases, and decreases as the emission intensity decreases.

The light emission intensity of the light emitting element 20 that emits light based on the energy imparted from the charged particles 101 is higher than the light emission intensity of the light emitting element 20 that emits light based on the energy imparted from the electrons 102.
For this reason, the wave height analyzer 50 is configured such that the light emission intensity of the light emitting element 20 that emits light based on the energy given from the charged particles 101, the light emission intensity of the light emitting element 20 that emits light based on the energy given from the electrons 102, By comparing the high energy γ-rays A and the low energy γ-rays B, only the high energy γ-rays A can be measured.

  According to the radiation measuring apparatus 100 according to the first embodiment, the surface of the light emitting element that emits light based on the energy imparted from the charged particles is covered with the substance that emits the charged particles by a photonuclear reaction with high-energy γ-rays. Further, the light emitting device has a configuration in which the thickness of the light emitting element is equal to or less than the range of the charged particles. Thereby, the radiation measurement apparatus 100 having low sensitivity to low energy γ-rays and high sensitivity to high energy γ-rays can be realized.

[Second embodiment]
≫Configuration of radiation measurement device≫
Next, a configuration of a radiation measuring apparatus 200 according to the second embodiment will be described with reference to FIG.

  The radiation measurement device 200 according to the second embodiment is different from the radiation measurement device 100 according to the first embodiment in that the radiation measurement device 100 according to the first embodiment includes the light emitting element 20. The radiation measuring apparatus 200 according to the second embodiment is provided with the long-wavelength light emitting element 21.

  The light emitted by the long-wavelength light-emitting element 21 preferably has a wavelength of 700 nm or more. The transmission distance of light by the optical fiber 30 is longer for light of longer wavelength and shorter for light of shorter wavelength. Further, the transmission efficiency of the long wavelength light by the optical fiber 30 is higher than the transmission efficiency of the short wavelength light by the optical fiber 30.

  The photomultiplier tube 40 is installed at a position away from the radiation irradiation range. The photomultiplier tube 40 acquires an electric signal having a higher peak value as the luminous intensity is higher, and acquires an electric signal having a lower peak value as the luminous intensity is lower. Therefore, the photomultiplier 40 converts the peak value of the electric signal caused by the high-energy γ-ray A as a value higher than the peak value of the electric signal caused by the low-energy γ-ray B.

  That is, the long-wavelength light-emitting element 21 can perform long-distance transmission and has higher transmission efficiency by radiation irradiation than the light-emitting element 20. Thereby, the photomultiplier tube 40 can be retracted from the environment with a high dose rate, and the failure of the device due to radiation can be reduced. In addition, the photomultiplier tube 40 can be replaced in an environment with a low dose rate without stopping irradiation of radiation to the place where the long-wavelength light-emitting element 21 is installed.

For example, when the long-wavelength light-emitting element 21 is YAG; Nd, the light emitted by the long-wavelength light-emitting element 21 has a wavelength of about 1064 [nm].
At this time, assuming that the converter 10 is lithium and the energy of the high-energy γ-ray A is 6 [MeV], the charged particles 101 generated by the photonuclear reaction in the converter 10 have an alpha energy of about 1.6 [MeV]. It becomes particles and tritium ions having an energy of about 2.1 [MeV].

  For alpha particles having an energy of about 1.6 [MeV], the range in lithium is about 0.017 [mm] to about 0.018 [mm], and the range in YAG is about 0.003 [mm]. mm] to about 0.004 [mm]. Therefore, assuming that the thickness of the converter 10 is about 0.018 [mm] and the thickness of the long wavelength light emitting element 21 is about 0.004 [mm], the long wavelength light emitting element 21 has a maximum thickness of about 1. Energy of 6 [MeV] will be provided by the alpha particles.

  On the other hand, since the threshold energy of the photonuclear reaction of lithium is about 3 [MeV], if the maximum energy of the low energy γ-rays B is about 3 [MeV], the low energy γ-rays B and the converter 10 or the long wavelength The maximum energy of the electrons 102 generated by the interaction with the light emitting element 21 is also about 3 [MeV]. Since the range of electrons of about 3 [MeV] in YAG is about 3 [mm], about 3 [mm] is necessary for the electrons to apply the total energy. When the thickness of the YAG is set to about 0.004 [mm], which is the range of the alpha particles, the thickness is about three orders of magnitude less than the thickness required to apply the total energy of electrons to the YAG. Only a part of energy is given from electrons.

  According to the radiation measuring apparatus 200 according to the second embodiment, by including the long-wavelength light-emitting element 21, even in a high dose rate environment, the light transmission efficiency of the optical fiber 30 can be reduced over a long distance without reducing the transmission efficiency for a long time. Can be transmitted. Thereby, it is possible to realize the radiation measuring apparatus 200 having low sensitivity to low energy γ-rays and high sensitivity to high energy γ-rays while suppressing a decrease in transmission efficiency due to the optical fiber.

[Third embodiment]
≫Configuration of radiation measurement device≫
Next, a configuration of a radiation measuring apparatus 300 according to the third embodiment will be described with reference to FIG.

The radiation measurement apparatus 300 according to the third embodiment is different from the radiation measurement apparatus 100 according to the first embodiment only in that the radiation measurement apparatus 100 according to the first embodiment includes only a detection system including a converter 10. On the other hand, the radiation measurement apparatus 200 according to the second embodiment includes both a detection system including the converter 10 and a detection system not including the converter 10.
The radiation measurement apparatus 300 according to the third embodiment is different from the radiation measurement apparatus 100 according to the first embodiment in that the radiation measurement apparatus 100 according to the first embodiment does not include the difference processing apparatus 60. On the other hand, the radiation measurement apparatus 300 according to the third embodiment is provided with a difference processing apparatus 60.

As shown in FIG. 3, system 300a (first system) is a detection system including converter 10, and system 300b (second system) is a detection system not including converter 10.
The system 300a is a detection system including the long wavelength light emitting element 23a (first long wavelength light emitting element), and the system 300b is a detection system including the long wavelength light emitting element 23b (second long wavelength light emitting element).
In the system 300a, light emitted by the long-wavelength light emitting element 23a is transmitted to the photomultiplier tube 40a via the optical fiber 30a. Similarly, in the system 300b, light emitted by the long wavelength light emitting element 23b is transmitted to the photomultiplier tube 40b via the optical fiber 30b.

  In the system 300a, the long wavelength light emitting element 23a is formed in contact with the converter 10. A photonuclear reaction occurs in the converter 10, and the charged particles 101 enter the long-wavelength light emitting element 23a and impart energy to the long-wavelength light emitting element 23a. Each time the charged particle 101 enters the long wavelength light emitting element 23a, one photon enters the photomultiplier tube 40a. In addition, since an interaction also occurs between the converter 10 and the γ-ray, the electrons 102 generated in the converter 10 enter the long-wavelength light-emitting element 23a and impart energy to the long-wavelength light-emitting element 23a.

  In the system 300b, no charged particle 101 is generated because no photonuclear reaction occurs. Accordingly, the long wavelength light emitting element 23b emits light when the high energy γ-ray A and the long wavelength light emitting element 23b interact. In this case, the thickness of the long-wavelength light-emitting element 23b is set such that the light emission of the long-wavelength light-emitting element 23a and that of the long-wavelength light-emitting element 23b become equal when the photonuclear reaction is excluded in the environment where the radiation dose is the same. Adjusted. With such a configuration, the difference between the number of photoelectric conversions in the system 300a and the number of photoelectric conversions in the system 300b is limited to the number resulting from the photonuclear reaction between the high-energy γ-ray A and the converter 10. Becomes possible.

The photomultiplier tube 40a is connected to the long-wavelength light emitting element 23a via the optical fiber 30a, photoelectrically converts light emitted by the long-wavelength light emitting element 23a, and outputs an electric signal to the wave height analyzer 50a. Similarly, the photomultiplier tube 40b is connected to the long-wavelength light-emitting element 23b via the optical fiber 30b, photoelectrically converts the light emitted by the long-wavelength light-emitting element 23b, and converts the electric signal to the wave height analyzer 50b. Output.
For example, one of the measurement methods using YAG; Nd is a measurement method in which one photon per radiation is photoelectrically converted by a photomultiplier tube. In this case, a single photon is photoelectrically converted by the photomultiplier tube 40 per number of times energy is applied to YAG; Nd in proportion to the amount of radiation applied to YAG; Nd.
In addition, regardless of the type of radiation, the distance between the optical fiber 30a and the photomultiplier tube 40a is adjusted as needed to adjust the number of photons generated per radiation detection by the long wavelength light emitting element 23 to one. An attenuating filter or the like may be inserted between the optical fiber 30b and the photomultiplier tube 40b.

The wave height analyzer 50a separates and measures a signal component caused by light emission of the long wavelength light emitting element 23a from a background low wave height component such as electric noise or dark current in the photomultiplier tube 40a. Similarly, the wave height analyzer 50b separates and measures a signal component caused by light emission of the long wavelength light emitting element 23b from a background low wave height component such as electric noise or dark current in the photomultiplier tube 40b. .
Then, the pulse height analyzer 50 calculates the count of the electric signal analyzed to be equal to or more than the predetermined peak value.

  The difference processing device 60 subtracts the count calculated by the pulse height analyzer 50b from the count calculated by the pulse height analyzer 50a, thereby counting only components caused by the photonuclear reaction between the high energy γ-ray A and the converter 10. I do.

  The radiation measurement apparatus 300 according to the third embodiment has both a detection system including a converter and a detection system not including a converter. Thus, even for a measurement system such as single photon measurement using a long-wavelength light emitting element, it is possible to realize a radiation measurement apparatus 300 that has reduced sensitivity to low energy γ-rays and increased sensitivity to high energy γ-rays. .

[Fourth embodiment]
≫Configuration of radiation measurement device≫
Next, a configuration of a radiation measuring apparatus 400 according to the fourth embodiment will be described with reference to FIG.

  The radiation measurement apparatus 400 according to the fourth embodiment is different from the radiation measurement apparatus 100 according to the first embodiment in that the radiation measurement apparatus 100 according to the first embodiment uses the converter 10 only on one surface of the light emitting element 20. In contrast to this, the radiation measurement apparatus 400 according to the fourth embodiment is provided with the converter 10 on all surfaces of the light emitting element 21.

The converter 10, the light emitting element 21, and the converter 10 are arranged in the traveling direction of the high energy γ-ray A_2. The high-energy γ-rays A_2 do not cause photonuclear reaction or interaction with the upper converter 10 (the converter 10 provided in contact with the upper surface of the light emitting element 21). When no interaction occurs, the high-energy γ-ray A_2 enters the lower converter 10 (the converter 10 provided in contact with the lower surface of the light emitting element 21).
There is no difference between the reaction probability of the lower converter 10 and the reaction probability of the upper converter 10 in the high-energy γ-ray A_2 after passing through the light emitting element 21. Therefore, when a photonuclear reaction occurs between the lower converter 10 and the high-energy γ-ray A_2, charged particles 101 are generated.

  When the converter 10 is Li and the energy of the high-energy γ-ray A_2 is about 6 [MeV], the charged particle 101_2 is an alpha particle having an energy of about 1.6 [MeV] and about 2.1 [MeV]. Is a tritium ion having the energy of

  These are generated in the lower converter 10 by a photonuclear reaction, and some of them proceed in a direction whose direction cosine is 90 degrees or more. At this time, the alpha particles or tritium ions enter the light emitting element 20 and impart energy to the light emitting element 21. That is, by covering the entire circumference of the light emitting element 21 with the converter 10, it is possible to realize the radiation measuring apparatus 400 in which the sensitivity to high-energy γ-rays is improved at least twice or more.

  According to the radiation measuring apparatus 400 according to the fourth embodiment, by covering the entire circumference of the light emitting element 21 with the converter 10, the sensitivity to the measurement of high energy γ-rays is increased, and the probability of generating charged particles is increased. It is possible. Thus, the radiation measurement device 400 having low sensitivity to low energy γ-rays and high sensitivity to high energy γ-rays can be realized.

[Fifth Embodiment]
≫Configuration of radiation measurement device≫
Next, a configuration of a radiation measuring apparatus 500 according to the fifth embodiment will be described with reference to FIG.

The radiation measurement apparatus 500 according to the fifth embodiment is different from the radiation measurement apparatus 100 according to the first embodiment in that the radiation measurement apparatus 100 according to the first embodiment uses the converter 10 only on one surface of the light emitting element 20. In contrast to this, the radiation measuring apparatus 500 according to the fifth embodiment is provided with the converter 10 on all surfaces of the light emitting element 25.
The radiation measurement apparatus 500 according to the fifth embodiment is different from the radiation measurement apparatus 100 according to the first embodiment in that the radiation measurement apparatus 100 according to the first embodiment includes one optical fiber 30. On the other hand, the radiation measuring apparatus 500 according to the fifth embodiment is provided with four optical fibers 30 and a coupler 310.

A converter 10_f is provided on an upper surface of the light-emitting element 25_k, and a converter 10_g is provided on a lower surface of the light-emitting element 25_k. A converter 10_g is provided on an upper surface of the light-emitting element 25_1, and a converter 10_h is provided on a lower surface of the light-emitting element 25_1. A converter 10_h is provided on an upper surface of the light-emitting element 25_m, and a converter 10_i is provided on a lower surface of the light-emitting element 25_m. A converter 10_i is provided on an upper surface of the light-emitting element 25_n, and a converter 10_j is provided on a lower surface of the light-emitting element 25_n.
Each converter and each light emitting element are of the same type. Therefore, the threshold energy of the photonuclear reaction in the converter is the same in each layer, and the measured high-energy γ-rays (high-energy γ-ray A_k, high-energy γ-ray A_l, high-energy γ-ray A_m, high-energy γ-ray The energy of A_n) does not differ from layer to layer.

  Since the thickness of all the light emitting elements is about the same as the range of the charged particles 101, it is shorter than the range of the electrons generated by the interaction of the γ rays, and the entire energy of the electrons is not applied. For this reason, high-energy γ-rays can be measured by counting components having a peak value equal to or greater than a certain value in the pulse height analyzer 50. Further, even if the number of layers is increased, there is no change in the peak value level to be discriminated. Therefore, it is also possible to increase only the layer for which a necessary count is obtained.

  The coupler 310 aggregates light transmitted by the optical fiber 30_k, light transmitted by the optical fiber 30_1, light transmitted by the optical fiber 30_m, and light transmitted by the optical fiber 30_n. Note that the coupler 310 is not always necessary, and all optical fibers (optical fiber 30 — k, optical fiber 30 — 1, optical fiber 30 — m, and optical fiber 30 — n) may be directly connected to the photomultiplier tube 40. .

  The photomultiplier 40 photoelectrically converts the light emitted by the light emitting element 25 — k and outputs an electric signal to the wave height analyzer 50. Further, the photomultiplier tube 40 photoelectrically converts the light emitted by the light emitting element 25 </ b> _ <b> 1 and outputs an electric signal to the wave height analyzer 50. Further, the photomultiplier tube 40 photoelectrically converts the light emitted by the light emitting element 25 — m and outputs an electric signal to the wave height analyzer 50. Further, the photomultiplier tube 40 photoelectrically converts the light emitted by the light emitting element 25 — n and outputs an electric signal to the wave height analyzer 50. Note that since the light emitting elements have the same configuration, light emitted from all the light emitting elements can be photoelectrically converted by the same photomultiplier tube 40.

  As shown in FIG. 5, the high energy γ-rays A are incident on the radiation measuring device 500 from above to below.

  The charged particles 101_fk generated by the photonuclear reaction between the high-energy γ-ray A_k and the converter 10_f impart energy to the light-emitting element 25_k, and the light-emitting element 20_k emits light.

  The high-energy γ-ray A_l having approximately the same energy as the high-energy γ-ray A_k transmits through the converter 10_f and the light-emitting element 25_k, and causes a photonuclear reaction in the converter 10_g. The light emitting element 25_1 emits light by the generated charged particles 101_gl imparting energy to the light emitting element 25_1.

  The high-energy γ-ray A_m having the same energy as the high-energy γ-ray A_k and the high-energy γ-ray A_l transmits through the converter 10_f, the converter 10_g, the light-emitting element 25_k, and the light-emitting element 25_1, and undergoes photonuclear reaction in the converter 10_h. Wake up. The light-emitting element 25_m emits light by the generated charged particles 101_hm imparting energy to the light-emitting element 25_m.

  The high-energy γ-ray A_k, the high-energy γ-ray A_l, and the high-energy γ-ray A_n having approximately the same energy as the high-energy γ-ray A_m are transmitted to the converter 10 — i and cause a photonuclear reaction in the converter 10 — i. The light-emitting element 25_n emits light by the generated charged particles 101_in imparting energy to the light-emitting element 25_n.

  Note that the light-emitting element to which energy is applied from the charged particles 101 in these series of processes does not necessarily need to have a direction cosine in the high-energy γ-ray incident direction in a range of 90 degrees or less. For example, charged particles 101_im generated when a photonuclear reaction occurs between the high-energy γ-ray A_n and the converter 10_i may impart energy to the light emitting element 25_m.

  According to the radiation measuring apparatus 500 according to the fifth embodiment, an opportunity for a high-energy γ-ray (high-energy γ-ray A_k, high-energy γ-ray A_1, high-energy γ-ray A_m, high-energy γ-ray A_n) to cause a photonuclear reaction. Can be increased. That is, since the generated charged particles easily enter the light emitting element before losing the total energy, the number of counts can be increased. Accordingly, the radiation measurement apparatus 500 having low sensitivity to low energy γ-rays and high sensitivity to high energy γ-rays can be realized.

[Sixth embodiment]
≫Configuration of radiation measurement device≫
Next, a configuration of a radiation measuring apparatus 600 according to the sixth embodiment will be described with reference to FIGS.

The radiation measurement apparatus 600 according to the sixth embodiment is different from the radiation measurement apparatus 100 according to the first embodiment in that the radiation measurement apparatus 100 according to the first embodiment includes one light emitting element 20. The radiation measurement apparatus 600 according to the sixth embodiment is provided with four light emitting elements 26.
The radiation measurement apparatus 600 according to the sixth embodiment is different from the radiation measurement apparatus 100 according to the first embodiment in that the radiation measurement apparatus 100 according to the first embodiment has a converter on only one surface of the light emitting element 20. The radiation measuring apparatus 600 according to the sixth embodiment has different converters 10 on all the surfaces of the light emitting element 26, whereas the radiation measuring apparatus 600 according to the sixth embodiment has different converters 10.
The radiation measurement apparatus 600 according to the sixth embodiment is different from the radiation measurement apparatus 100 according to the first embodiment in that the radiation measurement apparatus 100 according to the first embodiment does not include the data analyzer 70. On the other hand, the radiation measurement apparatus 600 according to the sixth embodiment is provided with a data analyzer 70.

The first layer 601 includes a light emitting element 26_11 and a converter 10_11, and is connected to the photomultiplier tube 40_11 via the optical fiber 30_11. The photomultiplier tube 40_11 is connected to a wave height analyzer 50_11 via a signal cable.
The second layer 602 includes a light emitting element 26_12 and a converter 10_12, and is connected to the photomultiplier tube 40_12 via the optical fiber 30_12. The photomultiplier tube 40_12 is connected to a wave height analyzer 50_12 via a signal cable.
The third layer 603 includes a light emitting element 26_13 and a converter 10_13, and is connected to the photomultiplier tube 40_13 via the optical fiber 30_13. The photomultiplier tube 40_13 is connected to a wave height analyzer 50_13 via a signal cable.
The fourth layer 604 includes a light emitting element 26_14 and a converter 10_14, and is connected to the photomultiplier tube 40_14 via the optical fiber 30_14. The photomultiplier tube 40_14 is connected to a wave height analyzer 50_14 via a signal cable.
Note that the number of layers in the radiation measurement device 600 according to the sixth embodiment is not particularly limited, and may be less than four or more than four.

  Each of the converters (converter 10_11, converter 10_12, converter 10_13, converter 10_14) has a different threshold energy of the photonuclear reaction, and the threshold energy of the photonuclear reaction is higher as the energy is closer to the side where high energy γ-rays are incident.

The high energy γ-ray A_11 has an energy higher than the threshold energy of the photonuclear reaction of the converter 10_11.
The high energy γ-ray A_12 has energy equal to or higher than the threshold energy of the photonuclear reaction of the converter 10_12 and equal to or lower than the threshold energy of the photonuclear reaction of the converter 10_11.
The high energy γ-ray A_13 has energy equal to or higher than the threshold energy of the photonuclear reaction of the converter 10_13 and equal to or lower than the threshold energy of the photonuclear reaction of the converter 10_12.
The high energy γ-ray A_14 has energy equal to or higher than the threshold energy of the photonuclear reaction of the converter 10_14 and equal to or lower than the threshold energy of the photonuclear reaction of the converter 10_13.
That is, the converter installed at a position near the high energy γ-ray incidence side has a higher threshold energy of the photonuclear reaction than the converter installed at a position far from the high energy γ-ray incidence side. Further, adjacent converters have threshold energies sandwiching the energy of the high-energy γ-rays to be measured.

The high-energy γ-ray A_14 does not cause a photonuclear reaction in the converters 10_11, 10_12, and 10_13, and has energy that causes a photonuclear reaction in the converter 10_14.
The charged particles 101_14 generated by the photonuclear reaction between the high energy γ-ray A_14 and the converter 10_14 give energy to the light emitting element 26_14, so that the light emitting element 26_14 emits light.
Light generated by the light emitting element 26_14 is transmitted through the optical fiber 30_14, and is converted into an electric signal by being photoelectrically converted by the photomultiplier tube 40_14. The wave height analyzer 50_14 discriminates the wave height value and measures the light generated by the light emitting element 26_14.

The high-energy γ-ray A_13 does not cause a photonuclear reaction in the converters 10_11 and 10_12, and has energy which causes a photonuclear reaction in the converter 10_13.
The light emitting element 26_13 emits light when the charged particles 101_13 generated by the photonuclear reaction between the high energy γ-ray A_13 and the converter 10_13 impart energy to the light emitting element 26_13.
Light generated in the light emitting element 26_13 is transmitted through the optical fiber 30_13, and is converted into an electric signal by being photoelectrically converted by the photomultiplier tube 40_13. The wave height analyzer 50_13 discriminates the wave height value and measures the light generated by the light emitting element 26_13.

The high-energy γ-ray A_12 does not cause a photonuclear reaction in the converter 10_11, and has energy that causes a photonuclear reaction in the converter 10_12.
The light emitting element 26_12 emits light when the charged particles 101_12 generated by the photonuclear reaction between the high energy γ-ray A_12 and the converter 10_12 impart energy to the light emitting element 26_12.
Light generated by the light emitting element 26_12 is transmitted through the optical fiber 30_12, and is converted into an electric signal by being photoelectrically converted by the photomultiplier tube 40_12. The wave height analyzer 50_12 discriminates the wave height value and measures the light generated by the light emitting element 26_12.

The high energy γ-ray A_11 has energy that causes a photonuclear reaction in the converter 10_11.
The light emitting element 26_11 emits light when the charged particles 101_11 generated by the photonuclear reaction between the high energy γ-ray A_11 and the converter 10_11 impart energy to the light emitting element 26_11.
The light generated by the light emitting element 26_11 is transmitted through the optical fiber 30_11, and is converted into an electric signal by being photoelectrically converted by the photomultiplier tube 40_11. The wave height analyzer 50_11 discriminates the wave height value and measures the light generated by the light emitting element 26_11.

At this time, a photonuclear reaction between the high energy γ-ray and the converter can occur if the energy of the high energy γ-ray is higher than the threshold energy. Therefore, a photonuclear reaction may occur even in a converter in which high-energy γ-rays are incident after passing through the first converter in which a photonuclear reaction can occur.
That is, the high energy γ-ray A_13 may cause a photonuclear reaction not only in the converter 10_13 but also in the converter 10_14. The high energy γ-ray A_12 may cause a photonuclear reaction not only in the converter 10_12 but also in the converters 10_13 and 10_14. Also, the high energy γ-ray A_11 may cause a photonuclear reaction in the converters 10_12, 10_13, and 10_14.

  As shown in FIG. 7, the data analysis device 70 includes a γ-ray intensity calculation function 701, a γ-ray intensity calculation function 702, a γ-ray intensity calculation function 703, a γ-ray intensity calculation function 704, a conversion device 711, a conversion device 712, and a conversion device. The apparatus includes a device 713, a conversion device 714, a conversion device 715, a conversion device 716, a difference processing device 721, a difference processing device 722, a difference processing device 723, and the like.

The data analyzer 70 is based on data obtained from each of the pulse height analyzers (the pulse height analyzer 50_11, the pulse height analyzer 50_12, the pulse height analyzer 50_13, and the pulse height analyzer 50_14). The intensity of γ-ray A_12, the intensity of high energy γ-ray A_13, and the intensity of high energy γ-ray A_14 are output.
Note that the data analyzer 70 does not necessarily need to be directly connected to the wave height analyzer, and may be connected via a scaler or the like. Further, the data analysis device 70 may be an independent device that performs data analysis by directly inputting a count.

  The data analyzer 70 aggregates data for each layer (first layer 601, second layer 602, third layer 603, and fourth layer 604) classified by the type of converter, and analyzes the intensity of high-energy γ-rays. I do. For example, the data analyzer 70 analyzes the intensity of the high-energy γ-ray in order from the layer on the side where the high-energy γ-ray to be analyzed is incident. Specifically, the data analysis device 70 calculates the number of times that the high-energy γ-rays whose intensities have been calculated based on the number of times of light emission of the upper layer light emitting element contributed to the light emission of the lower layer light emitting element. Then, the data analyzer 70 subtracts the number of high-energy γ-rays whose intensity has been calculated based on the total number of times of emission of the lower-layer light-emitting element, and thereby the lower-layer light-emitting element first contributes to light emission in the high-energy energy band. Γ-ray intensity is calculated.

The method of calculating the intensity of the high-energy γ-ray is not particularly limited.For example, the intensity may be calculated based on a database from the light emission amount or the count of the light-emitting element by the target high-energy γ-ray, For example, it may be calculated using the photonuclear reaction cross-section, the probability of charged particles being incident on the light-emitting element, or the like.
The output of the data analyzer 70 may be not only the intensity of the high-energy γ-ray but also a count, radioactivity, dose rate, or the like other than the intensity of the high-energy γ-ray. In this case, a dose rate conversion device, a radioactivity calculation device, or the like can be used instead of a γ-ray intensity calculation device described later.

  The γ-ray intensity calculation function 701 calculates the intensity of the high-energy γ-ray A_11 based on the count of the electric signal having a certain peak value or more input from the peak analyzer 50_11. Here, high energy γ-rays enter the converter 10_11.

  Based on the intensity of the high energy γ-ray A_11 calculated by the γ-ray intensity calculation function 701, the conversion device 711 causes a photonuclear reaction in the converter 10_12 by the high energy γ-ray A_11, causing the light emitting element 26_12 to emit light, The analyzer 50_12 calculates a count of signals analyzed as having a certain peak value or more.

  The conversion device 712 causes a photonuclear reaction in the converter 10_13 by the high-energy γ-ray A_11 based on the intensity of the high-energy γ-ray A_11 calculated by the γ-ray intensity calculation function 701, causing the light emitting element 26_13 to emit light, The analyzer 50_13 calculates the count of signals analyzed as having a certain peak value or more.

  The conversion device 713 causes a photonuclear reaction in the converter 10_14 by the high energy γ-ray A_11 based on the intensity of the high energy γ-ray A_11 calculated by the γ-ray intensity calculation function 701, causing the light emitting element 26_14 to emit light, The analysis device 50_14 calculates the number of signals analyzed as having a certain peak value or more.

  The difference processing device 721 outputs a count obtained by subtracting the count converted by the conversion device 711 from the count input from the pulse height analysis device 50_12 to the γ-ray intensity calculation function 702.

  The γ-ray intensity calculation function 702 calculates the intensity of the high energy γ-ray A_12 based on the count input from the difference processing device 721.

  The conversion device 714 causes a photonuclear reaction in the converter 10_13 by the high-energy γ-ray A_12 based on the intensity of the high-energy γ-ray A_12 calculated by the γ-ray intensity calculation function 702, and causes the light emitting element 26_13 to emit light. The analyzer 50_13 calculates the count of signals analyzed as having a certain peak value or more.

  The conversion device 715 causes a photonuclear reaction in the converter 10_14 by the high-energy γ-ray A_12 based on the intensity of the high-energy γ-ray A_12 calculated by the γ-ray intensity calculation function 702, causes the light emitting element 26_14 to emit light, and performs wave height analysis. The device 50_14 calculates a count of signals analyzed as having a certain peak value or more.

  The difference processing device 722 outputs a count obtained by subtracting the count converted by the conversion device 712 and the count converted by the conversion device 714 from the count input from the pulse height analysis device 50_13 to the γ-ray intensity calculation function 703. .

  The γ-ray intensity calculation function 703 calculates the intensity of the high-energy γ-ray A_13 based on the count input from the difference processing device 722.

  The conversion device 716 causes a photonuclear reaction in the converter 10_14 by the high-energy γ-ray A_13 based on the intensity of the high-energy γ-ray A_13 calculated by the γ-ray intensity calculation function 703, causing the light emitting element 26_14 to emit light, The analysis device 50_14 calculates the count of signals analyzed as having a certain peak value or more.

  The difference processing device 723 subtracts the count converted by the conversion device 713, the count converted by the conversion device 715, and the count converted by the conversion device 716 from the count input from the pulse height analysis device 50_14, Output to the γ-ray intensity calculation function 704.

  The γ-ray intensity calculation function 704 calculates the intensity of the high-energy γ-ray A_14 based on the count input from the difference processing device 723.

As described above, the data analyzer 70 separately calculates the intensity of the high energy γ-ray A_11, the intensity of the high energy γ-ray A_12, the intensity of the high energy γ-ray A_13, and the intensity of the high energy γ-ray A_14 having different energies. can do.
The conversion method of the count in the conversion device is not particularly limited, and may be calculated based on a database, or may be based on the photonuclear reaction cross-section of the converter or the probability of incidence of charged particles on the light emitting element. May be calculated.

  According to the radiation measuring apparatus 600 according to the sixth embodiment, the layer composed of the light emitting element and the converter has a multilayer structure having different types of converters. Gamma rays can be measured separately for each energy band. This makes it possible to realize the radiation measuring apparatus 600 having low sensitivity to low energy γ-rays and high sensitivity to high energy γ-rays.

  Although the present invention has been described in detail with reference to the embodiments, the gist of the present invention is not limited to these descriptions, and should be widely interpreted based on the description of the claims. It goes without saying that various changes and modifications based on these descriptions are also included in the gist of the present invention.

10 converter 20, 25 light emitting element 21, 23a long wavelength light emitting element (first long wavelength light emitting element)
23b Long wavelength light emitting device (second long wavelength light emitting device)
Reference Signs List 30 optical fiber 40 photomultiplier tube 50 wave height analyzer 60 difference processing device 70 data analyzer 100 radiation measuring device 200 radiation measuring device 300 radiation measuring device 300a system (first system)
300b system (second system)
400 radiation measuring device 500 radiation measuring device 600 radiation measuring device

Claims (12)

a converter that emits charged particles by photonuclear reaction with γ-rays,
A light-emitting element provided in contact with the converter,
The converter has a thickness equal to or less than the range of the charged particles,
A radiation measuring device, characterized in that: a converter that emits charged particles by photonuclear reaction with γ-rays,
A light-emitting element having a thickness equal to or less than the range of the charged particles, and provided in contact with the converter,
A radiation measurement device comprising: Further comprising a photomultiplier tube for photoelectrically converting the light emitted by the light emitting element,
The photomultiplier tube,
Provided at a position away from the radiation irradiation area of the light emitting element,
The radiation measuring apparatus according to claim 1 or 2, wherein Further comprising an optical fiber connecting the light emitting element and the photomultiplier tube,
The radiation measuring apparatus according to claim 3, wherein: The light emitting element,
Emits light having a wavelength of 700 nm or more,
The radiation measuring apparatus according to claim 1, wherein The apparatus further includes a wave height analyzer for analyzing a wave height of an electric signal output from the photomultiplier tube,
The radiation measuring apparatus according to claim 3 or 4, wherein: The converter and the light emitting element are plural,
The radiation measuring apparatus according to claim 1, wherein: The converter is formed of different materials;
The radiation measuring apparatus according to claim 7, wherein: The converter installed at a position closer to the γ-ray incidence side has a higher threshold energy of photonuclear reaction than the converter installed at a position farther from the γ-ray incidence side,
The radiation measuring apparatus according to claim 8, wherein: Adjacent converters each have a threshold energy sandwiching the energy of the gamma ray to be measured,
The radiation measuring apparatus according to claim 7, wherein Further comprising a data analyzer for analyzing the intensity of the γ-ray,
The radiation measuring apparatus according to any one of claims 7 to 10, wherein a first device including a converter that emits charged particles by a photonuclear reaction with γ-rays, and a first long-wavelength light-emitting element having a thickness equal to or less than the range of the charged particles and provided in contact with the converter. Strain and
A second system including a second long-wavelength light emitting element;
A difference processing device that calculates a difference between the count obtained in the first system and the count obtained in the second system,
A radiation measurement device comprising:

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