JP6377502B2 - Neutron measuring apparatus and neutron measuring method - Google Patents

Description

  Embodiments described herein relate generally to a neutron measurement apparatus and a neutron measurement method.

In materials inspection using neutron beam and boron neutron capture therapy (BNCT), it is necessary to accurately grasp the state of the neutron beam incident on the irradiation target. A detector to measure is required. Detectors that measure neutron beams include gas detectors containing ³ He and ¹⁰ B with large capture cross sections for neutrons, scintillator detectors, and liquid scintillators containing a large amount of hydrogen with large elastic scattering cross sections for neutrons. There is a detector used. Since the sensitivity changes according to the energy of neutrons, a detector suitable for the neutron energy to be measured can be selected and used.

  In particular, liquid scintillators and plastic scintillators with high sensitivity to epithermal neutrons and the like can discriminate neutrons and gamma rays. For example, the energy of neutrons can be measured by using an unfolding method.

  However, unlike those types that capture and detect neutrons, many of these neutrons scatter within the detector. For this reason, it has been a problem that the neutron beam swept to the irradiation target has a different intensity from that of the neutron beam incident on the detector when a part of the neutron beam changes direction after passing through the detector.

  In order to solve the above problems, a technique is known in which an opening is provided in a neutron beam passage leading to a measurement object, neutrons around the opening are measured, and the amount of neutrons at the beam center is measured from the data. In addition, a technique is known that can suppress the influence on the neutron beam by evaluating the activation amount of a gold thin film or the like.

JP 2014-190754 A JP 2004-233168 A

  Although it is possible to eliminate the influence on the neutron beam, it was difficult to evaluate the amount of neutron beam actually irradiated. In addition, it is difficult to measure energy. In the technique referred to in Patent Document 2, the influence on the neutron beam is small, and the energy characteristics can be evaluated by changing the type of the thin film, but the problem is that online measurement is difficult.

  Embodiments of the present invention are for solving the above-described problems, and an object of the present invention is to make it possible to measure neutrons online while suppressing the influence on the neutron beam.

In order to achieve the above object, the neutron measurement apparatus according to the present embodiment includes a neutron capture gas that captures neutrons to generate radiation and a scintillator gas that generates light by interaction with the radiation. an opening is formed Rutotomoni, and at least one container is used on the inner surface of the material to generate light by interaction with the radiation, it is attached to the opening to form a sealed space together with the container, the scintillator gas A light collecting member that guides the generated light, and a light detection unit that is provided outside the light collecting member and detects light from the light collecting member.

In addition, the neutron measurement method according to the present embodiment includes a scintillator gas that generates light by the interaction between the neutron capture gas that captures neutrons and generates radiation and the radiation, and the interaction with the radiation. A radiation generation step of irradiating a container using a light generating substance on the inner surface with neutrons, a light conversion step in which the scintillator gas generates light by interaction with the radiation, and the generated light is detected by light. And a detection step of detecting by the unit.

  According to the embodiment of the present invention, neutrons can be measured online while suppressing the influence on the neutron beam.

It is a conceptual block diagram which shows the structure including the neutron measuring apparatus which concerns on 1st Embodiment. It is a block diagram including the longitudinal cross-sectional view of the cell for a detection of the neutron measuring apparatus which concerns on 1st Embodiment. It is a table | surface which shows the characteristic regarding the neutron capture of the element used for the neutron capture gas of the neutron measuring apparatus which concerns on 1st Embodiment. It is a table | surface which shows the characteristic of the element used for the scintillator gas of the neutron measuring apparatus which concerns on 1st Embodiment. It is a flowchart which shows the procedure of the neutron measuring method which concerns on 1st Embodiment. It is a block diagram including the longitudinal cross-sectional view of the cell for a detection of the neutron measuring apparatus which concerns on 2nd Embodiment. It is a block diagram including the longitudinal cross-sectional view of the cell for a detection of the neutron measuring apparatus which concerns on 3rd Embodiment. It is a notional graph which shows the example of the energy dependence of a gamma ray neutron ratio. It is a block diagram including the longitudinal cross-sectional view of the cell for a detection of the neutron measuring apparatus which concerns on 4th Embodiment. It is a conceptual diagram which shows the effect | action of the neutron measuring apparatus which concerns on 4th Embodiment, and shows the case of the reaction which produces | generates a charged particle. It is a conceptual diagram which shows the effect | action of the neutron measuring apparatus which concerns on 4th Embodiment, and shows the case of the reaction which produces | generates only a neutron capture gamma ray. It is a block diagram including the perspective view of the cell for a detection of the neutron measuring apparatus which concerns on 5th Embodiment. It is a notional graph which shows the example of the energy dependence of multiple nuclides to the gamma ray neutron ratio. (A) shows the characteristics when all are mixed, and (b) shows the characteristics in the respective detection cells.

  Hereinafter, a neutron measurement apparatus according to an embodiment of the present invention will be described with reference to the drawings. Here, the same or similar parts are denoted by common reference numerals, and redundant description is omitted.

[First Embodiment]
FIG. 1 is a conceptual block diagram showing a configuration including a neutron measurement apparatus according to the first embodiment. The neutron measurement apparatus 100 measures a neutron beam generated by the neutron generation source 1 and irradiated on the irradiation object 2. Here, the neutron generation source 1 is, for example, an accelerator shown in FIG. 1 or a nuclear reactor. The irradiation object 2 may be, for example, a patient who receives treatment by BNCT as shown in FIG. Or in the case of a material irradiation test etc., it may be the material which receives neutron irradiation.

  The neutron measurement apparatus 100 includes a detection cell 10, a radiation type discrimination unit 30, and an energy estimation unit 40. The detection cell 10 is provided in the middle of the neutron beam BI emitted from the neutron generation source 1 to the irradiation object 2. That is, the neutron beam BI enters the detection cell 10, passes through the detection cell 10, and flows into the irradiation object 2 as a neutron beam BO.

  FIG. 2 is a configuration diagram including a longitudinal sectional view of the detection cell. The detection cell 10 includes a container 11, a light collecting member 12 that is attached to an opening formed in the container 11 and forms a sealed space 18 together with the container 11, and a side surface type that is provided along the outer surface of the light collecting member 12. It has the light detection part 20, and these are assembled integrally.

  The container 11 has a cylindrical shape with one end closed and the other end opened. The material of the container 11 is preferably a material having a small neutron absorption cross section, a scattering cross section, or a material having a small deceleration effect. For example, a plastic material containing a large amount of hydrogen is not preferable because of its large deceleration effect. Alternatively, heavy metals such as lead are not preferable. Further, the thinnest one is preferable as long as it can withstand the internal pressure or the external pressure.

  A condensing member 12 is provided at an open portion of the container 11. The condensing member 12 is preferably made of a material that transmits light and has a small neutron absorption cross section and scattering cross section, or a material that has a small deceleration effect. For example, transparent glass. The container 11 contains a neutron capture gas 13 and a scintillator gas 14. The shape of the container 11 is not limited to a cylindrical shape. For example, a shape in which one surface of the polyhedron is open or a spherical shell shape having an opening in a part thereof may be used.

  The neutron capture gas 13 uses a gas containing an element (neutron capture element) that has a large capture cross section for neutrons and generates radiation by reaction. There are roughly two types of elements for neutron capture gas. The first is an element that emits charged particles and captured gamma rays by a neutron capture reaction. The second is an element that does not produce charged particles and produces only trapped gamma rays. The neutron capture gas 13 has at least one element among them.

  The scintillator gas 14 is a gas containing an element that emits light by radiation such as charged particles or trapped gamma rays. Examples of such elements include helium (He), nitrogen (N), argon (Ar), krypton (Kr), and xenon (Xe). The scintillator gas 14 includes at least one of these elements. Have. Hereinafter, the generated light in the visible light region, far ultraviolet light, ultraviolet light, infrared light, and far infrared light is collectively referred to as “light”.

  The neutron capture gas 13 and the scintillator gas 14 are mixed and stored in the container 11. Either the pressure of the sealed gas or the gas sealing method (sealing or continuous replacement) can be supported.

  The side surface type light detection unit 20 is a detector for measuring the light emission time and the light emission amount of the scintillator gas 14. The side surface type light detection unit 20 converts incident light into an electrical pulse signal. Photomultiplier tubes (PMTs: Photomultiplier Tubes), silicon PMT (Si-PMT), photodiodes (PD: Photodiode), avalanche photodiodes (APD: Avalanche Photodiode), etc. can be used as the side surface type photodetecting unit 20. is there. Alternatively, any kind of imaging device such as a charge coupled device (CCD) / complementary metal-oxide-semiconductor (CMOS) may be used as long as it can measure light as an electrical signal, such as an imaging device such as a charge-coupled device (CCD) / complementary metal oxide semiconductor (CMOS). Any one having sensitivity to the emission wavelength of the scintillator gas 14 can be selected.

  When the scintillator gas 14 emits light inside the container 11, the light travels isotropically in the direction of the arrow in the figure in the surrounding space. In this case, since the light that travels directly in the direction of the light collecting member 12 is a part of the light, it is desirable to collect other light in the direction of the light collecting member 12. For this purpose, a reflection member 16 is provided on the inner surface of the container 11 as shown in FIG. The reflecting member 16 may be a film-like plate attached to the inner surface of the container 11 or may be formed by vapor deposition or the like on the inner surface of the container 11 using a reflecting material. The reflective member 16 is made of a material corresponding to the type of scintillator gas 14.

  The radiation type discriminating unit 30 shown in FIG. 2 is connected to the side surface type photodetecting unit 20 by a signal cable 25. The signal cable 25 can accurately transmit the electrical pulse signal of the side surface type photodetecting section 20, and is, for example, a coaxial cable.

  The radiation type discriminating unit 30 discriminates a neutron signal to be measured and a gamma ray signal from the crest value and time width of the pulse signal obtained by the side surface type photodetecting unit 20. The neutron signal to be measured and the gamma ray signal have different signal peak values because the energy released by the neutron reaction differs from the external background gamma energy other than the neutron reaction. Also, since the waveforms are different, they can be distinguished.

  Any radiation type discriminating unit 30 may be used as long as it has a function capable of analyzing the peak value and time width of a pulse signal. For example, the peak value and the time transition can be simultaneously measured by using a flash type analog-to-digital converter circuit (Flash Analog-to-digital Converter). Alternatively, a multi-channel analyzer (MCA: Multi-channel Analyzer) or a TDC (Time to Digital Converter) may be combined.

  The energy estimation unit 40 shown in FIG. 2 is a device that calculates the energy of neutrons from the peak value of the pulse signal. By referring to the measurement result and the response of the detector corresponding to the neutron energy stored in a memory or the like. Measure the energy distribution. Therefore, it is possible to cope with a computer or the like having a function capable of performing a comparison operation with a memory. The data stored in the memory can be obtained, for example, by measuring and storing response data at the time of neutron capture reaction of various nuclides described later during the calibration test. Alternatively, it can be accumulated from a nuclide data handbook or the like.

  Next, the operation of this embodiment will be described. A detection cell 10 having a container 11 containing a mixed gas of a neutron capture gas 13 and a scintillator gas 14 and a side surface type light detection unit 20 provided outside the light collecting member 12 is irradiated from the neutron source 1 to the irradiation target 2. Is provided in the middle of the neutron beam BI emitted from the beam. Since neutrons do not have an electric charge, when they enter a material, reactions such as elastic scattering, inelastic scattering, and capture occur with the nuclei in the material. These reaction cross sections are determined by the energy of neutrons and the type of nuclear material. In the case of a neutron measurement device, there are two main methods: a method of measuring protons, for example, protons that are blown off by scattering, and a method of measuring charged particles generated by reaction with neutrons. In either case, charged particles generated by the reaction can be measured with a scintillator detector or a semiconductor detector. In the present embodiment, the latter method, which is a reaction by neutron capture, is used.

  A part of the neutrons flowing into the detection cell 10 is captured by the neutron capture element in the neutron capture gas 13 in the container 11. FIG. 3 is a table showing characteristics related to neutron capture of elements used in the neutron capture gas. Each shows the case of a neutron with an energy of 1 keV.

As an element in which charged particles and capture gamma rays are generated by a neutron capture reaction, there is boron 10 (B ¹⁰ ) indicated as B-10 in FIG. The reaction cross section of the (n, α) reaction of B ¹⁰ decreases as the neutron energy increases, and for a neutron with an energy of 1 keV, the reaction cross section is about 20 barn. The (n, α) reaction of B ¹⁰ generates helium nuclei or alpha rays, lithium 7 and capture gamma rays. The energy of the emitted alpha rays is 2.5 × 10 ³ keV, ie 2.5 MeV. The energy of the generated capture gamma rays is 478 keV.

In addition, as elements that generate only trapped gamma rays without generating charged particles, there are xenon 129 (Xe ¹²⁹ ) and xenon 131 (Xe ¹³¹ ). Xe ¹²⁹ has a resonance absorption cross section as large as about 2000 barn in the case of neutrons having an energy of 1 keV. The energy of the generated capture gamma rays is 536 keV. Xe ¹³¹ has a resonance absorption cross section of about 1000 barn for neutrons with an energy of 1 keV. The energy of the generated capture gamma rays is 668 keV.

Although not shown in FIG. 3, helium 3 (He ³ ) is another element that generates charged particles and capture gamma rays by a neutron capture reaction. Generate capture gamma rays. The energy released by this reaction is 0.764 MeV. Lithium 6 (Li ⁶ ) generates helium nuclei (alpha rays), tritium, and capture gamma rays by a neutron capture reaction. The energy released by this reaction is 4.78 MeV.

Another element that generates only captured gamma rays without generating charged particles is, for example, krypton 83 (Kr ⁸³ ).

Now, neutron capture gas 13 Compounds including B ^10, for example, in the case of BF _3, between the neutrons incident (n, alpha) reaction occurs, alpha rays and capture gamma rays are generated as generated radiation. ^{Specifically,} the ^{B 10} (n, alpha) and alpha of 2.5MeV ^reaction, the capture gamma ray ^{B 10 (477.595keV),} the capture gamma ray ^{Xe 129 (536keV)} of the or ^{Xe 131} capture gamma ray (667 .79 keV) occurs. The reaction cross section of the (n, α) reaction of B ¹⁰ decreases as the neutron energy increases, whereas for example, Xe ¹²⁹ has a resonance peak in the vicinity of 0.1 keV to 2 keV. It is larger than the capture cross section and is highly sensitive only to neutrons in this region.

  A part of these generated radiations reacts with the scintillator gas 14 in the container 11 to give energy to atoms in the scintillator gas 14 and light corresponding to the given energy is generated.

  FIG. 4 is a table showing characteristics of elements that can be used in the scintillator gas. Each shows the case of a response to an alpha ray of energy of 4.7 MeV. The energy of 4.7 MeV is the energy of alpha rays of americium 241 that is generally used as an alpha ray source.

  In the case of xenon, the average emission wavelength is 325 nm, and the light emission amount defined by the number of photons having a wavelength of 200 nm or more is 3700 [1 / α]. Similarly, in the case of krypton, the average emission wavelength is 318 nm, the emission amount is 2100 [1 / α], in the case of argon, the average emission wavelength is 250 nm, the emission amount is 1100 [1 / α], and in the case of helium, the average emission wavelength is In the case of nitrogen, the average emission wavelength is 390 nm and the emission amount is 800 [1 / α]. As described above, the light emission amount and the light emission wavelength vary depending on the type of gas. In the case of the above elements, the light is all ultraviolet light.

  The generated light isotropically spreads from the light emitting place, and part of it directly reaches the light collecting member 12. Further, the other ultraviolet light is reflected by the reflecting member 16 provided on the inner surface of the container 11 and reaches the light collecting member 12 after reflection or after repeated multiple reflection. The ultraviolet light that has reached the condensing member 12 passes through the condensing member 12 and flows into the side surface type light detection unit 20.

  The ultraviolet light that has flowed into the side surface type light detection unit 20 is converted into an electrical pulse signal corresponding to its intensity. The pulse signal obtained by the side surface type light detection unit 20 is transmitted to the radiation type discrimination unit 30 through the signal cable 25. The radiation type discriminating unit 30 discriminates a signal of a neutron to be measured from a peak value of a pulse signal, a time width, and the like, and a gamma ray signal that becomes noise in measurement.

Next, the electrical pulse signal is transmitted to the energy estimation unit 40 via the signal cable 35. In the energy estimation unit 40, these types of energy including gamma rays are identified by the radiation type discrimination unit 30, and the intensity distribution is measured for each energy of radiation. From these intensity distributions, the energy estimation unit 40 can estimate the amount of thermal neutrons with a B ¹⁰ reaction cross-section of 0.1 keV or less and the amount of epithermal neutrons near 1 keV where the Xe resonance peak exists. .

  Note that the electric pulse signal level can be adjusted to an appropriate value for ensuring detection sensitivity or the like by adjusting the pressure of the mixed gas.

  FIG. 5 is a flowchart showing the procedure of the neutron measurement method according to the first embodiment. The neutron measurement method will be described with reference to FIG. First, a detection cell 10 having a container 11 enclosing a neutron capture gas 13 that generates radiation by reaction with neutrons and a scintillator gas 14 that emits light by radiation is placed in a neutron beam (step S01). The energy of charged particles generated by the reaction with neutrons is converted into light by the scintillator gas 14 (step S02).

  The generated light is received by the side-surface light detection unit 20 that is a light detection unit through the light collecting member 12, and converted into an electrical pulse signal (step S03). The electrical pulse signal is received, the radiation discrimination unit 30 discriminates the line type, and the energy estimation unit 40 measures the intensity for each energy (step S04).

  In the present embodiment, the detection cell 10 installed in the neutron beam is mainly composed of the container 11 containing the mixed gas and the side surface type light detection unit 20, and most of the volume is a gas space. As a result, disturbance to the neutron beam can be minimized. In addition, since only the detection of light emission is basically performed, no voltage application or the like is required for the detection cell 10 and there is no complexity in the apparatus configuration.

  As described above, according to this embodiment, neutrons can be measured online while suppressing the influence on the neutron beam.

[Second Embodiment]
FIG. 6 is a configuration diagram including a vertical cross-sectional view of a detection cell of the neutron measurement apparatus according to the second embodiment. This embodiment is a modification of the first embodiment. In the first embodiment, the side surface type light detection unit 20 is provided outside the light collecting member 12, whereas in the second embodiment, the separation type light detection unit 21 is for detection. It is provided separately from the cell 10. That is, in the second embodiment, the detection cell 10 does not include a light detection unit.

  An optical transmission member 24 is provided between the separation type photodetector 21 and the condensing member 12a, which are separately provided from the detection cell 10. The light transmission member 24 is a member capable of transmitting light via the light collecting member 12a, and for example, an optical fiber or the like is applicable. The optical fiber may have any structure as long as it can transmit the emission wavelength of the scintillator gas 14 with little attenuation.

  The light collecting member 12 a in this embodiment receives light generated from the scintillator gas 14 in the container 11 and transmits the light to the light transmission member 24. Although not shown, the condensing member 12a is formed so that the light incident on the condensing member 12 is totally reflected on its inner surface and reaches the light transmission member 24 directly or after multiple reflection.

  The light that has passed through the condensing member 12 a and the light transmission member 24 reaches the separation-type light detection unit 21. The light that has flowed into the separation type light detection unit 21 is converted into an electrical pulse signal corresponding to the intensity thereof. The pulse signal obtained by the separation type light detection unit 21 is transmitted to the radiation type discrimination unit 30 through the signal cable 25.

  According to this embodiment, since the detection cell installed on the neutron beam does not include the light detection unit, the influence on the neutron beam can be further reduced.

[Third Embodiment]
FIG. 7 is a configuration diagram including a longitudinal sectional view of a detection cell of a neutron measurement apparatus according to the third embodiment. This embodiment is a modification of the first embodiment. In the third embodiment, the side surface type light detection unit 20 a and the side surface type light detection unit 20 b are provided in parallel to each other outside the light collecting member 12. A signal cable 26 a is provided between the side surface type light detection unit 20 a and the radiation type discrimination unit 30. In addition, a signal cable 26 b is provided between the side surface type light detection unit 20 b and the radiation type discrimination unit 30.

The container 11 contains a scintillator gas 14 and two types of neutron capture gases. The neutron capture gas includes a first neutron capture gas 13a and a second neutron capture gas 13b. The first neutron capture gas 13a and the second neutron capture gas 13b are gases having different characteristics. For example, when He is used, He ³ causes a (n, p) reaction with a high cross-sectional area. In addition to Xe described in the first embodiment, Kr ⁸³ generates a capture gamma ray of 881 keV having a relatively high capture cross section of about 10 barn at 1 keV to 10 keV. Therefore, for example, when a mixed gas of He ³ , Xe ¹²⁹ , and Kr ⁸³ is used, the (n, p) reaction of He ³ at 100 eV or less, neutron capture of Xe ¹²⁹ from 100 eV to 2 keV, and more than that of Kr ⁸³ The cross-sectional area of each reaction of neutron capture is large, and neutron detection sensitivity can be ensured over a wide energy range.

  FIG. 8 is a conceptual graph showing an example of the energy dependence of the γ-ray neutron ratio. That is, the radiation type discriminating unit 30 discriminates between neutron-induced light and gamma-ray-derived light, but is defined as follows: neutron ratio to gamma-ray neutron = (neutron-induced light intensity) / (gamma-ray-induced light intensity) In that case, the neutron to gamma neutron ratio is energy dependent.

That is, for example, in a reaction that is large at low energy and does not have a resonance peak such as the cross-sectional area of the (n, p) reaction of He ³ , for example, a flat characteristic such as energy near E0 in FIG. Become. On the other hand, for example, in the case of a nuclide having a resonance peak in the neutron capture reaction in the vicinity of E1, like Xe ¹²⁹ , the neutron-to-gamma ray neutron ratio is greatly reduced in the vicinity of E1.

These characteristics can be grasped in advance if the neutron capture nuclide and the combination are determined. For example, consider the case where the first neutron capture gas 13a is helium containing He ³ and the second neutron capture gas 13b is Xe ¹²⁹ . When the neutron-to-gamma neutron ratio is r0 in FIG. 8, the presence of neutrons with energy in the resonance region of Xe ¹²⁹ can be almost ignored. For example, when the ratio of neutron to gamma ray is r1 in FIG. 8, the ratio of neutrons in the energy of the resonance region of Xe ¹²⁹ is large. Thus, the energy region of neutrons can also be estimated from the neutron ratio to gamma rays.

As described above, the signal obtained by the separation-type light detection unit 21 is discriminated by the radiation type discrimination unit 30 and the amount of protons derived from He ³ , 668 keV gamma rays derived from Xe ¹³¹ and 881 keV gamma rays derived from Kr ⁸³ is measured. By measuring the ratio or the ratio, it is possible to estimate the neutron energy in which energy region the neutron is large.

[Fourth Embodiment]
FIG. 9 is a configuration diagram including a longitudinal sectional view of a detection cell of the neutron measurement apparatus according to the fourth embodiment. This embodiment is a modification of the first embodiment. In the fourth embodiment, the container 11 is a container that stores the neutron capture gas 13 and the scintillator gas 14 and is also a container-type scintillator unit 15 that itself functions as a scintillator that emits light by radiation.

The container-type scintillator unit 15 has the same shape as the container in the first embodiment, but the material is different. The container-type scintillator unit 15 in the fourth embodiment uses a second scintillator 14b having a light emitting property by radiation. Examples of a material having a light emitting property for the second scintillator 14b include synthetic quartz, borosilicate glass, thallium activated sodium iodide, bismuth germanate (BGO: Bi ₄ Ge ₃ O ₁₂ ), and the like. If the structural strength of these materials is not sufficient, the material can be stored in a double container-shaped container surrounding the container-type scintillator 15 while suppressing disturbance to the neutron beam as much as possible. Good.

  As in the first embodiment, a sealed space 18 is formed by the container-type scintillator unit 15 and the light collecting member 12. In the sealed space 18, a first neutron capture gas 13a, a second neutron capture gas 13b, and a first scintillator gas 14a are enclosed.

  FIG. 10 is a conceptual diagram showing the operation of the neutron measurement apparatus, and shows the case of a reaction that generates charged particles. FIG. 11 shows the case of a reaction that generates only neutron capture gamma rays.

  In the case of FIG. 10, neutrons are captured by neutron capture atoms A1 in the first neutron capture gas 13a, and charged particles A2 and capture gamma rays A4 are generated. The charged particle A2 immediately gives energy to the scintillator atom A3 in the first scintillator gas 14a, and the scintillator atom A3 emits light. On the other hand, the probability of interaction of the capture gamma ray A4 with the first scintillator gas 14a is small, but when reaching the container-type scintillator section 15, the probability of interaction with the second scintillator 14b, which is solid, is high, and the interaction is large. The scintillator atom A5 in the container-type scintillator unit 15 emits light.

  As described above, when the neutron is captured by the neutron capture atom A1 in the first neutron capture gas 13a, the scintillator atom A5 emits light after the scintillator atom A3 emits light. Will occur with a slight time difference.

  On the other hand, in the case of FIG. 11, when neutrons are captured by the neutron capture atoms B1 in the second neutron capture gas 13b, when the capture gamma rays B2 are generated and reach the container-type scintillator unit 15, the second Interaction with the scintillator 14b occurs, and the scintillator atom B3 in the second scintillator 14b emits light.

  As described above, the two cases have different light emission modes, and therefore, it is possible to distinguish which case is based on the presence or absence of light emission with a slight time difference. The neutron energy that maximizes the neutron capture cross section of the neutron capture atom A1 in the first neutron capture gas 13a and the neutron energy that maximizes the neutron capture cross section of the neutron capture atom B1 in the second neutron capture gas 13b are Since it is known, it is possible to estimate which region the energy region of neutron is.

[Fifth Embodiment]
FIG. 12 is a configuration diagram including a perspective view of a detection cell of the neutron measurement apparatus according to the fifth embodiment. This embodiment is a modification of the first embodiment. The neutron measurement apparatus 100 in the fifth embodiment has a plurality of detection cells. The detection cells 10a, 10b, 10c, and 10d are arranged in parallel with each other in a direction perpendicular to the traveling direction of the neutron beam.

  A first neutron capture gas 13a, a second neutron capture gas 13b, and a scintillator gas 14 are accommodated in the first detection cell 10a. A first neutron capture gas 13a, a third neutron capture gas 13c, and a scintillator gas 14 are accommodated in the second detection cell 10b. A first neutron capture gas 13a, a fourth neutron capture gas 13d, and a scintillator gas 14 are accommodated in the third detection cell 10c. A first neutron capture gas 13a, a fifth neutron capture gas 13e, and a scintillator gas 14 are accommodated in the fourth detection cell 10d. The first neutron capture gas 13a, the second neutron capture gas 13b, the third neutron capture gas 13c, the fourth neutron capture gas 13d, and the fifth neutron capture gas 13e each have a maximum neutron capture cross section. It is a gas having nuclides with different energy regions.

  A signal cable 27 a is provided between the first detection cell 10 a and the radiation type discriminating unit 30. Similarly, signal cables 27b, 27c, and 27d are provided between the second detection cell 10b, the third detection cell 10c, the fourth detection cell 10d, and the radiation type discriminating unit 30, respectively. Yes.

  In the present neutron measurement apparatus 100 configured as described above, each detection cell has the first neutron capture gas 13a and the scintillator gas 14 in common, and is different from each other and the first neutron capture gas. Other than neutron capture gas.

  For this reason, each of the detection cells 10a, 10b, 10c and 10d has a neutron capture gas having sensitivity to neutrons having different energies.

FIG. 13 is a conceptual graph showing an example of the energy dependence of the multiple nuclides to gamma-ray neutron ratio. For example, the first neutron capture gas 13 a is He ³ , the second neutron capture gas 13 b is Kr ⁸³ , the third neutron capture gas 13 c is Xe ¹²⁹ , the fourth neutron capture gas 13 d is Xe ¹³¹ , the fifth neutron capture gas 13e consider the case of _{N 2.}

  When all of these gases are mixed, a characteristic that produces a plurality of peaks as shown in FIG. In this case, even if it is derived that the gamma-ray neutron ratio is, for example, r1 in FIG. 13, it cannot be distinguished from which resonance peak it originates.

  When different neutron capture gases having resonance peaks are dispersed and sealed in the respective detection cells as in this embodiment, each has the characteristics as shown in (b). As a result, it is possible to estimate the energy of neutrons.

  In the present embodiment, the case where two types of neutron capture gases are used in each of the detection cells 10a, 10b, 10c, and 10d is shown, but the present invention is not limited to this. For example, a detection cell in which only one type of neutron capture gas is used may be included. Alternatively, if separation is possible, a detection cell in which three or more kinds of neutron capture gases are used may be included.

[Other Embodiments]
As mentioned above, although some embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of invention.

  For example, in the embodiment, for the mixed gas of the neutron capture gas 13 and the scintillator gas 14 stored in the container 11, the mixing ratio and the sealing pressure are determined based on the energy, intensity, etc. of the irradiated neutron beam. And will be manufactured based on the specifications. However, it is not limited to this. For example, in the sealing method, a replenishing part and a discharging part may be provided so as to be replaced continuously or intermittently instead of such sealing.

  Further, for example, a replenishment tank and a control valve may be provided so that one gas can be replenished so that the mixing ratio of the neutron capture gas 13 and the scintillator gas 14 can be adjusted. Further, a pressure regulator may be provided so that the absolute amount of both can be adjusted by changing the pressure.

  Moreover, you may combine the characteristic of each embodiment. For example, each of the second to fifth embodiments is a modification of the first embodiment. Therefore, you may combine each characteristic of 2nd thru | or 5th embodiment.

  Furthermore, these embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 1 ... Neutron generation source, 2 ... Irradiation object, 10 ... Detection cell, 10a ... 1st detection cell, 10b ... 2nd detection cell, 10c ... 3rd detection cell, 10d ... 4th detection Cell 11, Container 12, 12 a Condensing member 13 neutron capture gas 13 a First neutron capture gas 13 b Second neutron capture gas 13 c Third neutron capture gas 13 d 4th neutron capture gas, 13e ... 5th neutron capture gas, 14 ... scintillator gas, 14a ... 1st scintillator gas, 14b ... 2nd scintillator, 15 ... container type scintillator part, 16, 16b, 16c ... reflection Members, 18 ... sealed space, 20, 20a, 20b ... side-surface type photodetection section (photodetection section), 21 ... separation type photodetection section (photodetection section), 24 ... light transmission member, 25, 26a, 26b, 27a , 27b, 27 , 27d ... signal cable, 30 ... radiation types discriminator, 35 ... signal cable, 40 ... energy estimator, 100 ... neutron measuring apparatus

Claims (13)

And neutron capture gas generated radiation by capturing neutrons, the radiation opening encloses the scintillator gas generated light is formed by interaction with Rutotomoni generates light by interaction with the radiation At least one container using a substance on its inner surface ;
A condensing member that is attached to the opening to form a sealed space with the container and guides the light generated by the scintillator gas;
A light detection unit that is provided outside the light collecting member and detects light from the light collecting member;
A neutron measurement apparatus comprising:   The neutron capture gas includes at least two or more neutron capture gases, and energy regions in which the neutron capture cross sections of the two or more neutron capture gases are maximized are different from each other. The neutron measuring device described. The neutron capture gas is neutron measuring apparatus according to claim 1 or claim 2, characterized in that, including those to generate a capture gamma ray without generating charged particles by interaction with neutrons. 4. The neutron measurement apparatus according to claim 3, wherein the neutron capture gas includes any one of krypton 83, xenon 129, and xenon 131.   The neutron measurement apparatus according to claim 3 or 4, wherein the scintillator gas also serves as the neutron capture gas. The neutron capture gas is neutron measuring apparatus according to any one of claims 1 to 4, characterized in that it comprises those generating charged particles and capture gamma ray by interaction with neutrons. The neutron measurement apparatus according to claim 6, wherein the neutron capture gas includes any one of boron 10 and helium 3. The neutron measurement apparatus according to claim 1, wherein the substance includes any one of synthetic quartz, borosilicate glass, thallium activated sodium iodide, and bismuth germanate . The light detection unit detects the container part generated light generated in the container together with the internal space generated light generated in the internal space of the container,
The energy estimation unit estimates the energy region of the neutron based on information including at least whether the generation of the internal space generated light and the generation of the container generated light are simultaneous,
The neutron measurement apparatus according to claim 1 or 8, wherein The neutron measurement device according to claim 1 , wherein the light detection unit is provided outside the light collecting member along the light collecting member . The optical transmission member for connecting between the condensing member and the light detection unit is further included, and the light reaches the light detection unit via the light transmission member. Item 11. The neutron measurement device according to any one of Items 10 to 10. The plurality of containers arranged in parallel with each other to the beam of neutron to be measured, and the neutron capture gas stored in each of the containers has different energy regions giving the maximum neutron capture cross section The neutron measurement apparatus according to any one of claims 1 to 11 , further comprising a nuclide . A container that contains a scintillator gas that generates light by interaction with a neutron capture gas that captures neutrons and generates radiation, and uses a substance that generates light by interaction with the radiation on the inner surface Radiation generating step of irradiating neutron with
  A light conversion step in which the scintillator gas generates light by interaction with the radiation;
  A detection step of detecting the generated light by a light detection unit;
  A neutron measurement method comprising:

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