Neutron beam detection device, neutron beam detection method, and neutron beam detection program

Abstract

To provide a small-sized neutron beam detection device, a neutron beam detection method and a neutron beam detection program.SOLUTION: A neutron beam detection device comprises: a solar cell type detector having a surface with a conversion membrane for converting a neutron to a charged particle beam or a photon, and generating a current by the incident of a radiation; a radiation detector for setting a current having no sensitivity to the neutron as an output signal by the incident of the radiation; an ammeter for detecting a current generated by the solar cell type detector, and a current generated by the radiation detector as signals; and a flux calculation unit for comparing current signals from the detectors which are detected by the ammeter. The flux calculation unit makes the current signals from the solar cell type detector and the radiation detector correspond to a relationship between a flux of the incident radiation related to a pre-acquired prescribed beam type and detection currents from the solar cell type detector and the radiation detector, and calculates a flux of the neutron.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a neutron beam detection device, a neutron beam detection method, and a neutron beam detection program. [Background technology]

[0002] One known technique for detecting neutron beams involves ionizing enclosed gas molecules with neutrons or alpha particles generated from a gas or solid containing boron, which generates alpha particles when neutrons are used. The resulting charge is then collected and detected by electrodes to which a high voltage is applied. Another known method involves detecting neutrons by amplifying the optical signal from a material called a scintillator, which emits light due to the energy of the aforementioned alpha particles, as an electrical signal using a photomultiplier tube or the like. Currently, these two detection methods are widely known as representative and common methods for detecting neutrons.

[0003] Furthermore, regarding neutron detectors using semiconductors, the technologies described in Patent Documents 1 and 2 below are known. In the detector described in Patent Document 1, an intrinsic semiconductor layer containing boron, which converts neutrons into alpha particles, is inserted in the middle of the p / n junction of the diode structure. The detector described in Patent Document 2 uses an organic conversion layer made of organic material as the semiconductor material, and does not use an element that converts neutrons into alpha particles, and the detector requires the application of voltage to operate. The heterogeneous radiation measuring sensor described in Patent Document 3 has electrodes made of a diode pin junction or Schottky junction, and a film for detecting X-rays, gamma rays, alpha rays, beta rays, neutron rays, etc. is made on the surface. This sensor measures the amount of flash generated by X-rays and gamma rays, the transmittance of alpha rays and beta rays, and the amount of chemical reaction that occurs with neutron reactants. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2018-141749 [Patent Document 2] Japanese Patent Publication No. 2019-145751 [Patent Document 3] Special Publication No. 2016-539324 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] The aforementioned neutron detectors that use gas ionization require a certain volume of gas to achieve sufficient detection sensitivity, which inevitably leads to a problem of large detection unit size. Furthermore, the enclosed gas contains boron trifluoride and 3 The need to use expensive gases such as helium, and the requirement for a power supply to apply voltage, result in a problem where the detector becomes expensive.

[0006] The detection devices described in Patent Documents 1 and 2 both require the design and manufacture of a dedicated detection device with a special structure, and when the costs associated with establishing the stability and reliability of the product performance are included, the price of the detector becomes high. In the heterogeneous radiation measurement sensor described in Patent Document 3, the radiation passing through each membrane is a minute analog signal, making signal conversion difficult. Considering the inclusion of noise and other factors, it is considered a sensor with low practicality. Furthermore, since it is necessary to measure a pulse signal amplified by a preamplifier using an external power supply, there is a problem in that signal detection is not easy.

[0007] The present invention has been made in view of the problems of the prior art described above, and aims to provide a neutron detection device that can easily detect neutrons with a small detector. Furthermore, the present invention aims to provide a neutron beam detection method using the neutron beam detection device and a neutron beam detection program. [Means for solving the problem]

[0008] As a means for solving the above problems, the present invention has the following configuration. (1) The neutron detection device according to this embodiment is a neutron ray detection device that detects neutron rays, and is provided with a conversion film on the surface that converts neutrons into predetermined radiation, and a solar cell type detector that generates an electric current by the incidence of radiation through the conversion film, a radiation detector that outputs a current insensitive to neutrons as an output signal by the incidence of the radiation, a current measuring device that detects, as signals, the current generated by the solar cell type detector and the current generated by the radiation detector by the incidence of the radiation, and a flux calculation unit that compares the current signal generated by the solar cell type detector detected by the current measuring device with the current signal generated by the radiation detector. The flux calculation unit has a function of calculating the flux of neutron rays based on the relationship between the flux of incident radiation related to a predetermined line type acquired in advance and the detected current from the solar cell type detector and the radiation detector, and corresponding the current signals from the solar cell type detector and the radiation detector detected by the current measuring device to this relationship.

[0009] The solar cell type detector referred to here is preferably a PN junction element that is designed in advance so as to enable the output of a detection signal driven by an internal potential by increasing the current output by light irradiation and to have high radiation resistance. In the case of this element, it is clearly distinguished from a photodiode type detector that is designed to require an external voltage application or signal amplification by a preamplifier in terms of the necessity of an external power source related to the manifestation of functions and the presence or absence of radiation resistance.

[0010] According to this embodiment, the neutron detection device may use an existing solar cell, and there is no need to design and manufacture a dedicated detection device having a special structure. Also, no voltage application is required to extract the charge generated by the absorption of any charged particle beam or photon of alpha particles, protons, lithium nuclei, gamma rays, or beta rays using the internal electric field of the p / n junction diode structure. Therefore, no voltage source, circuit, or wiring for voltage application is required, and the neutron detection system can have a simple configuration and the feature of being able to reduce costs.

[0011] In addition, as the solar cell type detector, if one with a size of about 1 cm square is used, it is sufficient to realize the structure of this embodiment, so the neutron detection part can be made small. As a result, it becomes possible to measure neutron rays at locations such as in the immediate vicinity of the neutron generation part of the accelerator type neutron generation device where installation has been difficult and measurement has not been possible until now.

[0012] (2) In the neutron detection device according to the present invention, the solar cell type detector is a first solar cell type detector, the radiation detector is a second solar cell type detector without an attached conversion film for converting neutrons into predetermined radiation, and the flux calculation unit calculates the difference between the current signal from the first solar cell type detector and the current signal from the second solar cell type detector. It is preferable to have a function of calculating the flux of neutron rays based on the relationship between the difference between the incident neutron flux related to a predetermined line type acquired in advance and the detected current from the first solar cell type detector.

[0013] (3) In the neutron detection device according to the present invention, it is preferable to have a function of calculating the neutron flux based on a calibration curve based on a linear function, a power function, or a quadratic function stored in advance in the flux calculation unit.

[0014] (4) In the neutron detection device according to the present invention, the conversion film is composed of any one of lithium, boron, or gadolinium single elements containing an isotope having a function of converting neutrons into any charged particle beam or photon such as alpha particles, protons, lithium nuclei, gamma rays, or beta rays, or a nitride, fluoride, oxide, or other compound of lithium, boron, or gadolinium containing an isotope having a function of converting neutrons into any charged particle beam or photon such as alpha particles, protons, lithium nuclei, gamma rays, or beta rays, or a mixture of the single element and the compound.

[0015] (5) In the neutron detection device according to the present invention, the solar cell type detector is preferably made of a binary compound semiconductor such as gallium arsenide, indium phosphide, or cadmium telluride, having a band gap of 0.8 eV to 2.2 eV, or a compound semiconductor which is a ternary or quaternary or more multi-component mixture such as indium gallium phosphide, aluminum gallium arsenide, or copper indium sulfide selenide, or a perovskite semiconductor.

[0016] (6) The neutron detection method according to the present invention is a neutron beam detection method for detecting neutron beams, characterized in that a solar cell type detector has a conversion film attached to its surface that converts neutrons into predetermined radiation, and generates an electric current by incidence of radiation through the conversion film, and a radiation detector outputs a current that is insensitive to neutrons by incidence of the radiation, and detects the current generated in the solar cell type detector and the current generated in the radiation detector as signals with a current measuring instrument, compares the current signal generated in the solar cell type detector and the current signal generated in the radiation detector detected by the current measuring instrument in a flux calculation unit, and in the flux calculation unit, correlates the current signals from the solar cell type detector and the radiation detector detected by the current measuring instrument with the relationship between the flux of the incident radiation related to a predetermined radiation type obtained in advance and the detected current from the solar cell type detector and the radiation detector, and calculates the flux of the neutron beam based on the result of the correlation.

[0017] The neutron beam detection program according to the present invention is a program used in a neutron beam detection method for detecting neutron beams, and is characterized in that it uses a solar cell type detector that has a conversion film attached to it that converts neutrons into predetermined radiation and generates an electric current when radiation is incident on it through the conversion film, and a radiation detector that outputs a current signal that is insensitive to neutrons when radiation is incident on it, and detects the current generated in the solar cell type detector and the current generated in the radiation detector with a current measuring instrument when radiation is incident on it, and uses a flux calculation unit that compares the current signal generated in the solar cell type detector detected by the current measuring instrument with the current signal generated in the radiation detector, and in the flux calculation unit, it correlates the current signals from the solar cell type detector and the radiation detector detected by the current measuring instrument with the relationship between the flux of incident radiation related to a predetermined type of radiation obtained in advance and the detected current from the solar cell type detector and the radiation detector, and calculates the flux of the neutron beam based on the result of the correlation. [Effects of the Invention]

[0018] According to the present invention, a neutron beam detection device can be provided that can measure and calculate the flux of neutron beams over a wider detection range, at a lower cost, over a wider operating temperature range, and in a smaller detection device installation volume. Furthermore, according to the present invention, it is possible to provide a neutron beam detection method and a neutron beam detection program that can measure and calculate the flux of neutron beams over a wider detection range, at a lower cost, over a wider operating temperature range, and in a smaller detection device installation volume. [Brief explanation of the drawing]

[0019] [Figure 1] Figure 1 is a system block diagram showing a neutron beam detection device according to the first embodiment of the present invention. [Figure 2] Figure 2 shows the cross-sectional structure of an InGaP solar cell type detector applied to the neutron beam detection device of the first embodiment. [Figure 3]Figure 3 is a graph showing the relationship between the amount of neutrons with an energy of 50 meV and the total amount of alpha particles generated on the solar cell-side surface of the boron plate, as determined by calculation. [Figure 4] Figure 4 is a graph showing the relationship between the flux (He ion irradiation flux) and the output current (induced current) of an InGaP solar cell when alpha particles with an energy of 200 keV are incident on it. [Figure 5] Figure 5 is a graph showing the generated current (induced current) from solar cells with and without a conversion film when neutrons are irradiated onto them using a neutron generator equipped with an accelerator. [Figure 6] Figure 6 is a graph showing the ratio of the magnitude of the current generated by the InGaP solar cell to the energy of the alpha particle (normalized to the value of a 200 keV alpha particle as 1). [Figure 7] Figure 7 is a graph showing the spectrum representing the relationship between the energy of alpha particles generated and emitted by a single neutron incidence in a conversion film consisting of a 0.05 mm thick boron film, calculated using Monte Carlo simulation, and the number of alpha particles generated on the solar cell surface of the boron film. This graph is intended to explain that the spectrum is the same regardless of the energy of the incident neutron. [Figure 8] Figure 8 shows the spectrum representing the relationship between the energy and the number of neutrons generated by the neutron generator used in the example (normalized to a peak energy value of 1). [Figure 9] Figure 9 is a graph showing the spectrum representing the relationship between the neutron energy and a physical quantity called the reaction cross-section, which has an equivalent meaning to the probability that 10B absorbs the incident neutron and generates an alpha particle. [Figure 10] This graph shows the results of measuring the current density generated when a 650nm monochromatic light source was irradiated onto a solar cell-type detector while changing the light intensity. [Figure 11]This graph shows the difference in neutron sensitivity between a conversion film containing boron carbide (B4C) and a conversion film containing lithium fluoride (LiF). [Figure 12] This graph shows the film thickness dependence of the amount of alpha particles emitted from the incident and transmitted sides of a boron-containing conversion film when a 25 meV neutron is incident on it. [Figure 13] Figure 1 is a configuration diagram showing one configuration of a neutron beam measurement system S equipped with a neutron beam detection device A. [Figure 14] This is a configuration diagram showing an example of a computer (arithmetic unit) that stores a program used in a neutron detection device according to the first embodiment. [Figure 15] Figure 10 shows an example of a calibration curve illustrating the relationship between current density and neutron flux obtained when fitting each region with a linear, power, or quadratic function in the data shown. [Modes for carrying out the invention]

[0020] "First Embodiment" The present invention will be described in detail below with reference to a first embodiment, but the present invention is not limited to the embodiments described below. Figure 1 is a system block diagram showing a neutron beam detection device according to the first embodiment of the present invention. The neutron beam detection device A of this embodiment includes a first solar cell type detector 1 equipped with a conversion film 6 (described later), a radiation detector (second solar cell type detector) 2 without a conversion film 6, current measuring instruments 3 and 4, and a neutron beam detector. Flux calculation Device It has 5. The first solar cell type detector 1 is a detector that generates an electric current when irradiated with radiation such as sunlight. The radiation input section (light-receiving surface) of this first solar cell type detector 1 is laminated with a conversion film 6 that has the function of generating charged particle beams or photons of alpha particles, protons, lithium nuclei, gamma rays, or beta rays when irradiated with neutrons. This conversion film 6 can be described as a conversion film that converts neutron beams into the predetermined radiation described above.

[0021] Figure 2 shows the main structure of the first solar cell type detector 1 with the conversion film 6 attached. The first solar cell detector 1 has a p / n junction type solar cell diode structure formed by joining p-type and n-type semiconductor layers. For example, it has a structure in which an electrode layer 10 is stacked on the back side of a laminate 9 made of a p-type layer 7 made of an InGaP layer and an n-type layer 8 made of an InGaP layer, and an electrode layer 11 is stacked on the front side. In the first solar cell type detector 1, the electrode layer 11 side becomes the surface, and the electrode layer 10 and the electrode layer 11 are connected by wiring to form a circuit, and when radiation such as sunlight is irradiated to the surface side, electricity is generated and current can flow through the circuit.

[0022] In the first solar cell type detector 1 of this embodiment, a conversion film 6 is laminated on the surface side of the electrode layer 11, and the conversion film 6 is attached to the first solar cell type detector 1. The radiation detector (second solar cell type detector) 2 of this embodiment has the same structure as the first solar cell type detector 1, except for the conversion film 6. That is, the radiation detector 2 has a p / n junction type solar cell type diode structure in which p-type and n-type semiconductor layers are joined together. For example, it has a structure in which an electrode layer 10 is stacked on the back side of a laminate 9 made of a p layer 7 made of an InGaP layer and an n layer 8 made of an InGaP layer, and an electrode layer 11 is stacked on the front side.

[0023] In the first solar cell type detector 1 and the radiation detector (second solar cell type detector) 2, more specifically, binary compound semiconductors such as gallium arsenide (GaAs), indium phosphide (InP), and cadmium telluride (CdTe), or compound semiconductors that are ternary or quaternary or more multi-component mixtures such as indium gallium phosphide (InGaP), aluminum gallium arsenide (AlGaAs), and copper indium selenide sulfide, or perovskite semiconductors can be used as constituent compounds for the semiconductors constituting the p-type layer 7 or n-type layer 8.

[0024] The conversion film 6 can be exemplified by a film made of any of the simple substances of lithium (Li), boron (B), or gadolinium (Gd) containing an isotope having a function of converting neutrons into charged particle beams or photons when irradiated with neutrons. Further, the conversion film 6 may be a nitride film, a fluoride film, an oxide film, or other compound thin films of lithium, boron, and gadolinium. Alternatively, the conversion film 6 may include a mixture of any of the simple substances of lithium, boron, and gadolinium and the lithium compound, boron compound, or gadolinium compound. When neutrons enter the conversion film 6, they react with any of the elements of lithium, boron, and gadolinium contained in the conversion film 6, and charged particle beams or photons such as protons, alpha particles (α particles), lithium nuclei, gamma rays, and beta rays are generated in various directions starting from the reaction position.

[0025] For example, ordinary lithium obtained industrially 6 has two isotopes of Li (lithium 6) and 7 Li (lithium 7), 7 the abundance ratio of Li is about 93%, 6 and the abundance ratio of Li is about 7%. Also, ordinary boron obtained industrially 10 has two isotopes of B (boron 10) and 11 B (boron 11), 10 the abundance ratio of B is about 20%, 11 and the abundance ratio of B is about 80%. Also, ordinary gadolinium obtained industrially 154 consists of six natural isotopes of Gd (2.18%), 155 Gd (14%), 156 Gd (20.5%), 157 [[ID=3�]]Gd (15.6%), 158 Gd (24.8%), 160 Gd (21.8%) and 152 a radioactive isotope of Gd (0.2%). In these elements, the presence of isotopes (the presence of radioactive isotopes) leads to the emission of prompt charged particles, such as alpha particles (the nucleus of He), from the isotopic elements when irradiated with neutrons. Thus, the neutrons are converted into alpha particles.

[0026] When the conversion film 6 is irradiated with neutrons, it converts the neutrons into alpha particles, lithium nuclei, and gamma rays. However, if the thickness of the conversion film 6 is made too large, some of the alpha particles, lithium nuclei, and gamma rays will be attenuated inside the conversion film 6. Therefore, even if the conversion film 6 is made thicker than necessary, some of the alpha particles, lithium nuclei, and gamma rays will be attenuated inside the conversion film 6. For this reason, it is preferable to make the thickness of the conversion film 6 very thin, such as a few micrometers, or about 1 to 10 μm. Conversely, by making the conversion film 6 even thinner than 1 μm, the detection sensitivity and output current can be reduced. This makes it possible to apply the conversion film 6 even in high-flux neutron environments. For example, the neutron detector 1 equipped with the conversion film 6 of this embodiment can be applied in high-flux neutron environments such as nuclear reactors and their surrounding facilities. In the case of high-flux neutron environments, the film can be formed to a thickness of, for example, 0.001 to 1 μm. Furthermore, by thinning the conversion film 6 as described above, it becomes possible to reduce gamma-ray noise.

[0027] A current measuring instrument 3 is electrically connected to the first solar cell type detector 1, and a current measuring instrument 4 is electrically connected to the radiation detector (second solar cell type detector) 2. A flux calculation device 5 is also electrically connected to the current measuring instrument 3 and the current measuring instrument 4. The current measuring instrument 3 can measure the induced current generated by the first solar cell type detector 1 as a current signal, and the current measuring instrument 4 can measure the induced current generated by the radiation detector 2 as a current signal. The flux calculation device 5 includes a difference calculation unit 15 that compares the current signals measured by the current measuring instrument 3 and the current measuring instrument 4 and calculates the difference between these current signals, and a flux calculation unit 16 that calculates the neutron flux from the difference current value based on the calculation results of the difference calculation unit 15, as described later.

[0028] In order to calculate the neutron flux in the flux calculation unit 16, the following relationships must be understood in advance and stored in a memory or other storage unit provided in the flux calculation unit 16. Of the information stored in the flux calculation unit 16, the first piece of information is relationship data regarding how many alpha particles the conversion film 6 applied to the first solar cell type detector 1 generates in relation to the incident neutron flux. This relationship data is obtained by using an accelerator-type neutron generator or the like, controlling the amount of neutrons generated by adjusting the accelerator-type neutron generator, and acquiring the relationship between the flux of the neutron beam incident on the conversion film 6 and the generation rate of alpha particles generated on the conversion film 6, as shown in Figure 3, which is obtained in the embodiment described later. Figure 3 shows the neutron incidence flux number [particles / cm²] for a specific energy (e.g., 50 meV). 2 [particles per second] (number of particles per unit area per unit time) and alpha particle generation rate [particles / cm²] 2 This shows a correlation with [ / second]. By understanding the relationship in Figure 3, it is possible to understand the alpha particle generation rate, which is how many alpha particles the conversion film 6 generates in response to the neutron flux incident on the conversion film 6. Therefore, the relationship shown in Figure 3 is stored in the flux calculation unit 16.

[0029] Of the information stored in the flux calculation device 5, the second piece of information is the relationship between the irradiation flux of alpha particles and the current output of the first solar cell type detector 1 when alpha particles are irradiated onto the first solar cell type detector 1 which does not have a conversion film 6. This relationship data is obtained, for example, in the example described later, as shown in the graph of Figure 4, with the horizontal axis being the irradiation flux of alpha particles (He ion irradiation flux: × 10⁻¹⁰ 9 He+ / cm 2 Let the vertical axis be the induced current (×10) ( / s), and the vertical axis be the induced current (×10) -5 A) The relationships between these factors are determined in advance, and the relationships shown in Figure 4 are stored in the flux calculation device 5.

[0030] Next, since the neutron flux that can be generated from the accelerator-type neutron generator can be controlled by changing the incident proton beam current using the accelerator-type neutron generator, a first solar cell-type detector 1 equipped with a conversion film 6 and a radiation detector 2 without a conversion film 6 are placed adjacent to each other, and neutrons generated from the aforementioned neutron generator are irradiated onto them. When this irradiation test is performed, a current output from the first solar cell type detector 1 (with conversion film) and a current output from the radiation detector 2 (without conversion film) can be obtained, as illustrated in the graph of Figure 5, which is obtained in the embodiment described later. The current value obtained by subtracting the current output of the radiation detector 2 (without the conversion film) from the current output of the first solar cell type detector 1 shown in the graph of Figure 5 can be determined to be the current generated by the corresponding dose of neutrons. In other words, the difference calculation unit 15 can calculate the current generated by the corresponding neutrons by calculating the difference between the current signals of both current measuring instruments 3 and 4.

[0031] In this embodiment, the calculation of the neutron quantity from the detected differential current can be performed by the flux calculation unit 16 located in the final stage block shown in Figure 1. One calculation method involves first obtaining data (see Figure 3) relating how much current a solar cell-type detector 1 with a conversion film 6 induces in relation to the number of alpha particles and lithium nuclei, and then calculating the amount of neutrons based on data (see Figure 4) relating how many alpha particles are generated in relation to the neutrons absorbed by the conversion film 6. Alternatively, a method can be employed in which the induced current of the fabricated solar cell detector 1 is measured in a calibration field where the neutron quantity has been quantified in advance, and the neutron quantity is determined by proportional calculation based on that value. The results shown in Figure 4 clearly show that the current quantity is proportional to the neutron flux by a linear or power function.

[0032] The proportional relationship described earlier is based on observations in the range of several tens of nA. To obtain the range in which the above linearity is guaranteed, it is possible to utilize the characteristics of solar cells and conduct linearity calibration tests using light. For example, as shown in Figure 10, by measuring the current density generated when a 650 nm monochromatic light source is irradiated onto the solar cell-type detector 2 while changing the light intensity, it is possible to understand the behavior of minute generated carriers in the semiconductor when they are extracted as current into an external circuit. The graph in Figure 10 shows the results obtained by inputting a 635 nm wavelength laser light (visible light) through a variable attenuator (0 to -60 dB) and a two-way branch to a photodiode and a solar cell type detector 2 as shown in Figure 2, respectively, into the solar cell type detector used in the embodiment described later.

[0033] The data shown in Figure 10 indicates a current density of 100 pA / cm². 2 (approximately 1 x 10) -10 A / cm 2 In the above region, a high degree of linearity, comparable to that of a linear or power function, is observed, with a diametrical amplitude of several μA / cm². 2 It can be seen that this continues to the end. Therefore, it is thought that radiation-induced currents also exhibit linearity similar to that of visible light as described above. Also, several hundred pA / cm² 2 Below (approximately 1×10 -10 A / cm 2 In the region shown below, linearity is broken, and the curve resembles a quadratic function. Therefore, by using the induced current behavior by visible light described above as the calibration curve for the solar cell detector 1, it becomes possible to analyze the neutron flux in the nonlinear region as well.

[0034] For example, Figure 15 shows the data used for the calibration curve. By multiplying the light intensity values ​​shown in Figure 10 by 4000, the induced current behavior due to neutron irradiation estimated from Figure 5 is obtained. The neutron flux conversion can be calculated by substituting the measured current amount into the function equation obtained from the calibration curve. The region for linear or power functions is 100 pA / cm². 2 The above region is a linear function, y=dx+e, and when fitted, it can be expressed as the relationship y=7E-14x+2E-09, and the power function y=x d When fitting with +e, y = 6 × 10 16 x 1.002 It can be expressed using the relationship +0. Furthermore, the region of the quadratic function is 1 pA / cm 2 From 100 pA / cm² 2 This is the region up to the quadratic function y=ax 2 When fitted with +bx+c, we get y = -1E+27x 2 It can be expressed by the relationship +1E+17x-170469. In other words, the calibration curve can be displayed using the relationship of the fitted function described above. From these calibration curves for each region, the relationship between light intensity and radiation-induced current can be determined and understood as neutron flux.

[0035] The solar cell detectors 1 and 2 of this embodiment can use solar cell devices manufactured using existing solar cell manufacturing technology, and do not require any special design or manufacturing method for neutron measurement. This is because current can be obtained directly from the solar cell detectors 1 and 2. To make the device sensitive to neutrons, a conversion film 6 that generates charged particle beams or photons when irradiated with neutrons should be directly formed on the surface of the solar cell device using a coating method, vacuum deposition method, or sputtering method. Alternatively, a separately fabricated plate-shaped conversion film can be attached to the surface of the solar cell device by adhering it to the surface, making it possible to manufacture the detector easily and at low cost.

[0036] For example, by replacing the surface of a solar cell device with a plate-shaped conversion film containing boron carbide (B4C) or lithium fluoride (LiF), the sensitivity to neutrons can be changed, as shown in Figure 11. In this case, the conversion film is not limited to boron carbide or lithium fluoride; as mentioned earlier, plate or film materials containing elements capable of converting neutrons into charged particles or photons are also effective. Because the neutron absorption cross-section is energy-dependent depending on the element, a structure can be created in which the conversion film can be easily replaced depending on the neutron environment being measured. For example, following the example shown in Figure 11, a conversion film containing lithium fluoride can be used in environments with a large neutron flux to be measured, while a conversion film containing boron carbide can be used in environments with a small neutron flux to be measured.

[0037] The sensitivity / output current ratio of solar cell detectors 1 and 2 is proportional to the area of ​​the solar cell device; therefore, the sensitivity can be adjusted by changing the size of the solar cell device. Using this relationship, it is easy to adjust the detection range to suit the application. For example, the sensor described in Patent Document 3 lacks sensitivity to light, making sensitivity correction impossible. Furthermore, it measures pulse signals amplified from minute analog signals using a preamplifier powered by an external power supply, which differs from measurement based on current signals driven by the internal potential of the solar cell detectors 1 and 2.

[0038] Conventional solar cell devices made from inorganic crystalline materials operate in a temperature range of approximately -150°C to +300°C, giving them a wider operating temperature range than existing neutron detectors. This high-temperature resistance makes it possible to measure neutron flux in high-temperature environments, such as inside or near a nuclear reactor in a nuclear power plant. Furthermore, solar cell devices are susceptible to crystal damage due to radiation exposure, which can lead to degradation and a decrease in output current. Therefore, neutron detection device A in this configuration requires correction for degradation during continuous use. By pre-acquiring data on the decrease in output current in response to radiation exposure of the solar cell device (alpha particles, beta particles, gamma rays, etc.) and storing this data as a database in the flux calculation unit, self-correction becomes possible. With this correction, accurate neutron measurement becomes possible even when used continuously for long periods in environments exposed to radiation.

[0039] According to this embodiment, the neutron detection unit can use a solar cell based on existing technology, eliminating the need to design and manufacture a dedicated detection device with a special structure. Furthermore, since the charge generated by alpha particle absorption is extracted using the internal electric field of the p / n junction diode structure, voltage application is not required. Therefore, there is no need for a voltage source, voltage application circuits, or wiring, resulting in a simple configuration for the neutron detection system and enabling low-cost implementation.

[0040] Furthermore, since solar cell detectors 1 and 2 can be approximately 1 cm square in size, which is sufficient to realize the structure of this configuration, the neutron detection unit can be made smaller. This has the effect of enabling the measurement of neutron radiation in locations where installation was previously difficult and measurement was not possible, such as immediately adjacent to the neutron generator of an accelerator-type neutron generator.

[0041] Since the solar cell detectors 1 and 2 generate current even when absorbing radiation other than neutrons, the output of the solar cell detector 1, which has a neutron / charged particle beam or photon conversion film 6, includes current due to radiation other than neutrons. Therefore, it is necessary to detect the radiation other than neutrons using a radiation detector that is not sensitive to neutrons and determine the difference. This is the same for existing neutron detectors. However, in the structure of this embodiment, a solar cell type detector 2 without a neutron / charged particle beam or photon conversion film 6 is used as a radiation detector that is not sensitive to neutrons. Therefore, by installing it alongside a solar cell type detector 1 with a conversion film 6, simultaneous and same-position measurements become possible, and the accuracy of the calculated neutron dose can be improved.

[0042] According to this embodiment of the neutron beam detection device A, it is possible to provide a neutron beam detection device that can measure and calculate the flux of neutron beams with a wider detection range, at a lower cost, with a wider operating temperature range, and with a smaller detector installation volume. [Examples]

[0043] A solar cell device (hereinafter referred to as an InGaP solar cell) was prepared using a laminate of p-type and n-type layers made of InGaP. Thin (less than 0.1 μm) metal films made of an alloy of gold and tin or zinc for low contact resistance were formed on both sides of the laminate, and relatively thick (more than 0.1 μm) metal films made of molybdenum, ruthenium, iron, lead, zirconium, etc., which are activated by neutrons to reduce electrode resistance and do not cause noise, were formed to create electrodes. A 0.5 mm thick boron plate, formed by sintering boron powder, was attached to the surface of this InGaP solar cell to fabricate a solar cell-type neutron detector with the laminated structure shown in Figure 2. Simultaneously, an InGaP solar cell of the same structure and size, without the boron plate, was used as a radiation detector for non-neutron radiation.

[0044] InGaP solar cells were irradiated with visible light or a reference radiation source, such as alpha particles, beta particles, and gamma rays, and data on the relationship between brightness or the respective flux rates and output current were acquired in advance. Simultaneously, data on the relationship between irradiation flux and the decrease in current output were also acquired in advance. Figure 3 shows the relationship between the alpha particle flux (total alpha particle generation rate) and the neutron particle flux intensity (50 meV neutron incident flux), and Figure 4 shows the relationship between the alpha particle flux (He ion irradiation flux) and the excitation current (output current).

[0045] In this accelerator-type neutron generator, which uses an InGaP solar cell detector with a boron plate attached and an InGaP solar cell detector without a boron plate placed side by side, and generates neutrons by accelerating protons to 7 MeV and colliding them with a beryllium plate, both solar cells were installed in the neutron generation section, specifically 14 cm away from the beryllium plate, in close proximity to a 40 mm polyethylene plate that was set up as a moderator.

[0046] In an accelerator-type neutron generator, the neutron flux was changed by varying the current of the incident proton beam, and the output currents from InGaP solar cell detectors with and without boron plates were measured. Figure 5 shows the relationship between the neutron flux calculated from the proton beam current and the current output of the two types of InGaP solar cells. In this neutron generator, it was found that the current output of the InGaP solar cell without a boron plate was generated by absorbing gamma rays generated simultaneously with neutrons and radiation from the activation of the InGaP solar cell itself.

[0047] The current value obtained by subtracting the excitation current value of the InGaP solar cell detector without the conversion film (shown in Figure 5) from the excitation current value of the InGaP solar cell detector with the conversion film (shown in Figure 5) can be said to be the current value generated by neutrons. Therefore, in a simplified manner, by knowing the current value generated by neutrons as described above, the neutron flux irradiated onto the InGaP solar cell can be determined by considering the relationship shown in Figure 4 and the relationship shown in Figure 3. Furthermore, since the energy of the alpha particles generated by neutron absorption within the boron plate differs from the energy of the alpha particles (He ions) used in the experiment shown in Figure 4, the following relationship is required to more precisely understand the neutron flux.

[0048] The flux calculation unit 16 stores the relationship between the generation rates of neutrons and alpha particles shown in Figure 3, the values ​​of the excitation current and He ion irradiation flux shown in Figure 4, and a coefficient representing the ratio of current generation calculated or measured in a Monte Carlo simulation of an InGaP solar cell type detector, such as shown in Figure 6 (in this case, the value of 200 keV alpha line is normalized to 1). In addition, for example, as shown in Figure 7, we will obtain a spectrum representing the relationship between the energy of alpha particles at the interface between the bottom surface of the boron film and the top surface of the InGaP solar cell detector, calculated or measured by Monte Carlo simulation, and the generation rate (number of particles generated per unit time) of alpha particles emitted from the conversion film (a boron film with a thickness of 0.05 mm). Based on the relationship between the coefficients from Figures 3, 4, and 6 and the generation rate from Figure 7, and the current value calculated by the difference calculation, it can be understood that the neutron flux can be calculated.

[0049] The method for determining the number of neutrons from the detected current is described below. First, the current generated in an InGaP solar cell detector with a conversion film is subtracted from the current generated in an element without a conversion film to determine the detection current value due to neutrons alone. This current is induced by neutrons having the energy spectrum shown in Figure 8. The probability of a boron film generating alpha particles varies depending on the neutron energy, as shown in Figure 9. Therefore, by multiplying the values ​​on the vertical axis of Figure 8 by the values ​​on the vertical axis of Figure 9, the relative number of alpha particles generated for each neutron energy in this neutron generator can be determined.

[0050] By normalizing this relative value to the value at a neutron energy of 50 meV as 1, and integrating it over the entire energy range, we can obtain the ratio of alpha particle generation when the total number of alpha particles generated by neutrons of all energies is converted to the number generated by neutrons of 50 meV. Multiplying this value by the value on the vertical axis of Figure 3 yields the relationship between the amount of neutrons incident in this neutron detection device and the total amount of alpha particles generated on the solar cell-side surface of the boron film. Let this relationship be denoted as F. On the other hand, the relationship between the number of alpha particles generated by neutron incidence and their energy is shown in Figure 7. By multiplying the values ​​on the vertical axis of Figure 7 by the values ​​on the vertical axis of Figure 6, the relative value of the current generated in the InGaP solar cell with respect to the energy of the alpha particles from the boron film can be determined.

[0051] Figure 7 is a graph showing the spectrum representing the relationship between the energy of alpha particles generated and emitted by a single neutron incidence in a conversion film consisting of a 0.05 mm thick boron film, and the number of alpha particles generated on the solar cell surface of the boron film, as calculated by Monte Carlo simulation. The spectrum shown in Figure 7 is the same regardless of the energy of the incident neutron.

[0052] If we normalize the aforementioned relative values ​​by setting the value at 200 keV for alpha particles to 1, and integrate over the entire energy range, we obtain a value that represents the ratio of current values ​​when the currents generated by alpha particles at all energies are converted to the currents generated at 200 keV. Next, by multiplying the detection current value obtained earlier, which is due to neutrons only, by this current ratio, the current value obtained is plotted on the vertical axis of Figure 4, and the corresponding alpha particle flux value on the horizontal axis can be obtained from the graph. By applying this flux value to the aforementioned relationship F, the amount of neutrons generated (flux) can be obtained. In the application of this patent, the energy spectrum of the generated neutrons shown in Figure 8 is required. However, in applications such as nuclear reactors, the energy spectrum of the generated neutrons may be known in advance, and even if it is unknown, it is possible to determine the energy spectrum of the generated neutrons through measurement or nuclear reaction simulation. In these cases, the energy spectrum of the generated neutrons that is known in advance can be used as a substitute for that shown in Figure 8.

[0053] As mentioned above, the sensitivity of the conversion film can be changed by varying its film thickness. Figure 12 is a graph showing the film thickness dependence of the amount of alpha particles emitted from the incident and transmitted sides of a boron-containing conversion film when a 25 meV neutron is incident on it. Figure 12 shows that when the film thickness of the conversion film is a few micrometers or less (e.g., 4 μm or less), the amount of neutrons emitted on the incident side and the transmitted side are almost the same. On the other hand, when the film thickness is a few micrometers or more (e.g., greater than 4 μm), the amount of alpha particles emitted from the incident side saturates, while the amount of alpha particles emitted on the transmitted side decreases with increasing film thickness.

[0054] The reason why the amount of alpha particles emitted on the incident side saturates is that, because the range of alpha particles in the conversion film is several micrometers, alpha particles generated at a thickness greater than several micrometers in the boron-containing conversion film are shielded by the boron-containing conversion film and are not emitted. The reason why the amount of alpha particles emitted on the transmission side decreases is that neutrons are absorbed inside the boron-containing conversion film, reducing the amount of neutrons that reach the transmission side. Therefore, by controlling the film thickness of the conversion film, it is possible to control the sensitivity characteristics and directional dependence of the detector.

[0055] Furthermore, the film thickness dependence of the amount of charged particles and photons emitted from the surface is not limited to boron and alpha particles, but is applicable to plates that can convert neutrons into charged particles and photons, such as boron and lithium, boron and gamma rays, lithium and proton beams, lithium and alpha particles, and gadolinium and gamma rays.

[0056] In this embodiment, the output of the two InGaP solar cell devices used as solar cells, i.e., the current output when irradiated with light, was measured before and after the measurement. No degradation due to radiation exposure was observed, confirming that degradation correction was unnecessary. Thus, the degradation of detectors made of solar cells such as InGaP can be investigated using a simple method: measuring the output of the solar cell.

[0057] Figure 13 is a configuration diagram showing one form of a neutron beam measurement system S equipped with the neutron beam detection device A shown in Figure 1. A first solar cell detector 1 and a second solar cell detector 2 are housed in a sensor housing 20. The output lines of the first solar cell detector 1 and the second solar cell detector 2 are connected to a noise filter 25 via an SMA (Sub Miniature Type A) connector 21, a connecting cable 22, and an SMA connector 23, respectively. The connecting cable 23 is preferably a shielded cable.

[0058] A portion of the internal wiring of the wiring box 25 of the noise filter 25 is grounded by an earth wire 26. By connecting the output lines of the first solar cell detector 1 and the output lines of the second solar cell detector 2 to the noise filter 25, noise components of the current generated in the first solar cell detector 1 and the second solar cell detector 2 in a radiation environment can be removed. Possible noise components include noise from minute ripple voltages generated by the measurement system, or noise generated by the system becoming charged due to radiation. Ripple voltage-induced noise can be removed mainly using capacitors or low-pass filters. Radiation-induced noise can be removed by grounding the measurement system.

[0059] The output side of the noise filter 25 is connected to a minute ammeter 29 via a BNC connector 27 and a coaxial cable 28, and the minute ammeter 29 is connected to a computing device 31 such as a personal computer via a digital signal cable 30. The computing device 31 incorporates the difference calculation unit 15 and flux calculation unit 16 shown in Figure 1. The minute ammeter 29 performs A / D conversion of the current sent from the output line of the first solar cell detector 1 and the output line of the second solar cell detector 2. The difference calculation unit 15 and flux calculation unit 16 incorporated in the arithmetic unit 31 convert the current signal into a flux rate, as described above, and during this conversion, they can calculate the neutron flux using the calibration curve created using the visible light or reference radiation source described above.

[0060] The neutron beam measurement system S described above can be described as a system that performs the following steps: 1. Reading the current value; 2. Reading the calibration curve; 3. Calculating the neutron flux from the calibration curve and current; and 4. Outputting the neutron beam flux.

[0061] As an example, the computing device 31, such as a personal computer shown in Figure 13, includes an input means 32, a control unit 33, a storage means 34, and an output means 35, as shown in Figure 14. The input means 32 is, for example, a keyboard for entering characters and numbers, and various types of information can be input to the control unit 33 or the storage means 34 via the input means 32. The control unit 33 is composed of a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), and other components, and can perform various numerical calculations, information processing, and equipment control using various programs.

[0062] The storage means 34 is, for example, an information recording medium such as an SSD (Solid State Drive) or an HDD (Hard Disk Drive), and can store various programs, various information necessary for the execution of the calculation means 36, such as the information stored in the storage unit of the flux calculation unit 16 as described above, and the results obtained therefrom, as needed, or read out the contents of the stored information. The output means 35 is, for example, a monitor or a printer, and can display or print on a screen or on paper, as necessary, various information obtained from various programs stored in the storage means 34, as well as various relationships described later.

[0063] Furthermore, the storage means 34 can store necessary programs and various information necessary for executing the calculation means 36 (described later) in advance before the program is executed, allowing these to be read and manipulated at will. It is also possible to store and read calculation results obtained by executing the program as needed. Of course, the storage means 34 may also be equipped with communication functions for the Internet or a network, and configured to perform calculations and calculate results in the same way as the arithmetic unit 31 by utilizing storage means, calculation means, and prediction means provided in other personal computers connected to the Internet or a network.

[0064] The information stored in the memory means 34 is, for example, the same information stored in the neutron flux calculation unit 16 described earlier, such as the first information and the second information. Also, as described earlier, the relationship shown in Figure 3 can be acquired and stored based on the first information, and the relationship shown in Figure 4 can be acquired and stored based on the second information. Furthermore, based on this information, the calculation means 36 performs calculations similar to those of the difference calculation unit 15 described earlier, and calculates the difference between the current signals of the current measuring instruments 3 and 4 as described earlier, and can calculate the neutron flux from the relationship data shown in Figure 3 and the relationship data shown in Figure 4. In addition, the calculation means 36 may also have a function to calculate the neutron flux using a fitting function, taking advantage of the fact that the amount of current follows a power function proportional relationship with respect to the neutron flux based on the graph shown in Figure 15, as described earlier.

[0065] Furthermore, based on the graph shown in Figure 15, the memory means 34 and calculation means 36 may be equipped with a function that allows for the analysis of the neutron flux in the nonlinear region based on a quadratic relationship, utilizing the calibration curve of the solar cell type detector 1 described earlier.

[0066] The program described above uses a first solar cell type detector 1 that has a conversion film attached to its surface that converts neutrons into charged particle beams or photons of alpha particles, protons, lithium nuclei, gamma rays, or beta rays, and generates an electric current when radiation is incident on it, and a radiation detector 2 that outputs a current that is insensitive to neutrons when radiation is incident on it, and when radiation is incident on it the current generated by the first solar cell type detector 1 and the current generated by the radiation detector 2 are detected as signals by a current measuring instrument 3. Furthermore, this program can be described as a program that causes the computing device (computer) 31 to function as a comparison means (flux calculation unit) 36 that compares the current signal generated by the first solar cell type detector 1 detected by the current measuring instruments 3 and 4 with the current signal generated by the radiation detector 2, and as a means in which the calculation means (flux calculation unit) 36 corresponds the current signals from the solar cell type detector 1 and the radiation detector 2 detected by the current measuring instruments 3 and 4 with the relationship between the flux of incident radiation related to a predetermined type of radiation obtained in advance and the detected current from the solar cell type detector and the radiation detector, and calculates the flux of neutron radiation based on the result of this correspondence.

[0067] Furthermore, when measuring in environments with high and low neutron flux, based on Figure 11, the difference calculation unit 15 and flux calculation unit 16 described earlier can also perform the same actions as the difference calculation unit 15 and flux calculation unit 16 by using a program incorporated into the arithmetic unit 31. Furthermore, the functions of the difference calculation unit 15 and the flux calculation unit 16, which have the function of calculating the neutron flux based on the relationship shown in Figures 3 to 12 described in the embodiment, are provided as programs in the storage means 34 and calculation means 36, respectively. By executing these programs stored in the storage means 34, a configuration can be adopted in which the neutron flux can be calculated as described above, in the same way as described in the embodiment. [Industrial applicability]

[0068] The neutron detection device according to the present invention can be applied to monitoring neutron flux in high-temperature, high-flux environments, such as immediately adjacent to a nuclear reactor. Furthermore, the neutron beam detection device according to the present invention can be applied to monitoring neutron flux in confined environments, such as immediately adjacent to the neutron generating material of an accelerating neutron generator. [Explanation of Symbols]

[0069] A...Neutron beam detection device, S...Neutron beam detection system, 1...First solar cell type detector, 2...Radiation detector (second solar cell type detector), 3, 4...Current measuring instrument, 5...Flux calculation device, 6...Conversion film, 7...P layer, 8...N layer, 9...Laminate, 10, 11...Electrode layer, 12...Conversion film, 15...Difference calculation unit, 16...Flux calculation unit, 25...Noise filter, 26...Ground wire, 29...Micro ammeter, 31...Calculation unit (personal computer), 32...Input means, 33...Control unit, 34...Storage means, 35...Output means, 36...Calculation means.

Claims

1. A neutron beam detection device for detecting neutron beams, comprising: a solar cell type detector having a conversion film attached to its surface that converts neutrons into predetermined radiation, and which generates an electric current upon incidence of radiation through the conversion film; and a radiation detector that outputs a current insensitive to neutrons as an output signal upon incidence of the radiation; The current generated in the solar cell type detector due to the incidence of the aforementioned radiation, and the current measuring device that detects the current generated in the radiation detector as a signal, The system includes a flux calculation unit that compares the current signal generated by the solar cell type detector detected by the current measuring instrument with the current signal generated by the radiation detector. The flux calculation unit is a neutron beam detection device that has the function of calculating the flux of neutron beams based on the results obtained by matching the current signals from the solar cell type detector and the radiation detector detected by the current measuring instrument with the relationship between the flux of incident radiation for a predetermined type of radiation obtained in advance and the detected current from the solar cell type detector and the radiation detector.

2. The aforementioned solar cell type detector is the first solar cell type detector, The neutron beam detection device according to claim 1, wherein the radiation detector is a second solar cell type detector that does not have a conversion film attached to convert neutrons into predetermined radiation, the flux calculation unit calculates the difference between the current signal from the first solar cell type detector and the current signal from the second solar cell type detector, and has a function to calculate the neutron beam flux based on the result of corresponding the relationship between the incident neutron flux for a predetermined radiation type obtained in advance and the difference in detection current from the first solar cell type detector.

3. The neutron beam detection device according to claim 2, characterized in that it has a function to calculate the neutron flux based on a calibration curve based on a linear function, a power function, or a quadratic function that has been stored in advance in the flux calculation unit.

4. The neutron beam detection device according to any one of claims 1 to 3, wherein the conversion film comprises a single element of lithium, boron, or gadolinium containing an isotope having the function of converting neutrons into charged particle beams or photons of any of alpha particles, protons, lithium nuclei, gamma rays, or beta rays, or a nitride, fluoride, oxide, or other compound of lithium, boron, or gadolinium containing an isotope having the function of converting neutrons into charged particle beams or photons of any of alpha particles, protons, lithium nuclei, gamma rays, or beta rays, or a mixture of the single element and the compound.

5. The neutron beam detection device according to any one of claims 1 to 4, wherein the solar cell type detector is made of a binary compound semiconductor such as gallium arsenide, indium phosphide, or cadmium telluride, or a compound semiconductor which is a ternary or quaternary or more multi-component mixture such as indium gallium phosphide, aluminum gallium arsenide, or copper indium sulfide selenide, with a band gap of 0.8 eV to 2.2 eV, or a perovskite semiconductor.

6. A neutron beam detection method for detecting neutron beams, A solar cell type detector is used, which has a conversion film attached to its surface that converts neutrons into a predetermined type of radiation, and generates an electric current when radiation is incident on it through the conversion film, and a radiation detector is used that outputs a current that is insensitive to neutrons when the radiation is incident on it. Upon the incidence of the aforementioned radiation, the current generated in the solar cell type detector and the current generated in the radiation detector are detected as signals by a current measuring instrument. The flux calculation unit compares the current signal generated by the solar cell type detector detected by the current measuring instrument with the current signal generated by the radiation detector. A neutron beam detection method characterized in that, in the flux calculation unit, the current signals from the solar cell type detector and the radiation detector detected by the current measuring instrument are correlated with the relationship between the flux of incident radiation related to a predetermined type of radiation acquired in advance and the detected current from the solar cell type detector and the radiation detector, and the flux of neutron beams is calculated based on the result of this correlation.

7. The aforementioned solar cell type detector is the first solar cell type detector, The neutron beam detection method according to claim 6, wherein the radiation detector is a second solar cell type detector that does not have a conversion film attached to convert neutrons into predetermined radiation, the flux calculation unit calculates the difference between the current signal from the first solar cell type detector and the current signal from the second solar cell type detector, and correlates the relationship between the incident neutron flux for a predetermined radiation type obtained in advance and the difference in the detected current from the first solar cell type detector, and calculates the dose of neutron beams based on the result of the correlation.

8. The neutron beam detection method according to claim 7, characterized in that the flux of neutrons is calculated based on a calibration curve based on a linear function, a power function, or a quadratic function that has been stored in advance in the flux calculation unit.

9. The neutron beam detection method according to any one of claims 6 to 8, wherein the conversion film comprises a single element of lithium, boron, or gadolinium containing an isotope having the function of converting neutrons into charged particle beams or photons of any of alpha particles, protons, lithium nuclei, gamma rays, or beta rays, or a nitride, fluoride, oxide, or other compound of lithium, boron, or gadolinium containing an isotope having the function of converting neutrons into charged particle beams or photons of any of alpha particles, protons, lithium nuclei, gamma rays, or beta rays, or a mixture of the single element and the compound.

10. The neutron beam detection method according to any one of claims 6 to 9, wherein the solar cell type detector is a binary compound semiconductor such as gallium arsenide, indium phosphide, or cadmium telluride, or a compound semiconductor which is a ternary or quaternary or more multi-component mixture such as indium gallium phosphide, aluminum gallium arsenide, or copper indium sulfide selenide, with a band gap of 0.8 eV to 2.2 eV.

11. A program used in a neutron detection method for detecting neutron beams, A solar cell type detector that includes a conversion film that converts neutrons into predetermined radiation, and generates an electric current by the incidence of radiation through the conversion film, A radiation detector is used, which outputs a current that is insensitive to neutrons as an output signal upon the incidence of the aforementioned radiation. The current generated in the solar cell type detector and the current generated in the radiation detector are detected by a current measuring instrument upon the incidence of the aforementioned radiation. A flux calculation unit is used to compare the current signal generated by the solar cell type detector detected by the current measuring instrument with the current signal generated by the radiation detector. The flux calculation unit is characterized in that it correlates the current signals from the solar cell detector and the radiation detector detected by the current measuring instrument with the relationship between the flux of incident radiation of a predetermined type of radiation acquired in advance and the detected current from the solar cell detector and the radiation detector, and calculates the flux of neutron radiation based on the result of this correlation. A program for detecting neutron beams.

12. The aforementioned solar cell type detector is the first solar cell type detector, The neutron beam detection program according to claim 11, wherein the radiation detector is a second solar cell type detector that does not have a conversion film attached to convert neutrons into predetermined radiation, the flux calculation unit calculates the difference between the current signal from the first solar cell type detector and the current signal from the second solar cell type detector, and correlates the relationship between the incident neutron flux for a predetermined radiation type obtained in advance and the difference in detection current from the first solar cell type detector, and calculates the neutron beam flux based on the result of the correlation.

13. The neutron beam detection program according to claim 12, characterized in that it has a function to calculate the neutron dose based on a calibration curve based on a linear function, a power function, or a quadratic function that has been stored in advance in the flux calculation unit.

14. The neutron detection program according to any one of claims 11 to 13, wherein the conversion film comprises a single element of lithium, boron, or gadolinium containing an isotope having the function of converting neutrons into charged particle beams or photons of any of alpha particles, protons, lithium nuclei, gamma rays, or beta rays, or a nitride, fluoride, oxide, or other compound of lithium, boron, or gadolinium containing an isotope having the function of converting neutrons into charged particle beams or photons of any of alpha particles, protons, lithium nuclei, gamma rays, or beta rays, or a mixture of the single element and the compound.

15. The neutron beam detection program according to any one of claims 11 to 14, wherein the solar cell type detector is a binary compound semiconductor such as gallium arsenide, indium phosphide, or cadmium telluride, or a compound semiconductor which is a ternary or quaternary or more multi-component mixture such as indium gallium phosphide, aluminum gallium arsenide, or copper indium sulfide selenide, with a band gap of 0.8 eV to 2.2 eV.

Images