A neutron / gamma discrimination system and method for gadolinium-based materials

Abstract

The present invention provides a gadolinium-based neutron / gamma discrimination system, comprising a gadolinium-based neutron detector, a gamma-ray detector, a preamplifier circuit connected to the detector, and a dual-channel digital multichannel spectrometer. The dual-channel digital multichannel spectrometer receives two pulses amplified by the preamplifier circuit. When the time difference between the arrival times of the two pulses is within a set threshold, the system counts neutron signal events and further extracts amplitude values, recording them in the neutron response energy spectrum and gamma energy spectrum, respectively. The present neutron / gamma discrimination system combines physical processes with electronic technology. A thin sheet of gadolinium-based material absorbs only internal conversion electrons and low-energy background gamma rays. The system then uses the temporal relationship between internal conversion electrons and secondary prompt gamma rays to further distinguish whether the signal detected by the gadolinium-based material sheet is internal conversion electrons or low-energy background gamma rays, thereby achieving neutron / gamma discrimination.

Description

Technical Field

[0001] The present invention belongs to the field of radiation detection, and in particular relates to a neutron / gamma discrimination system and method. Background Art

[0002] In recent years, with the increasing application of neutron detection in nuclear energy utilization, nuclear physics and astrophysics research, and nuclear radiation environmental monitoring, neutron detector technology has garnered increasing attention from industry and researchers. Neutron flux and energy spectrum measurements, in particular, are of crucial importance in the nuclear energy sector, directly impacting the safe and reliable operation of various nuclear power plants. Neutrons themselves are uncharged and cannot directly ionize matter. They must interact with intermediate converters to produce secondary particles that can ionize matter before they can be detected. Therefore, a key technical challenge in neutron detection is how the detection system accurately distinguishes whether charged particle signals are generated by neutrons and converters, or from other charged particles or gamma rays in the neutron field. Depending on the energy of the charged particles or the energy deposition method, different neutron detectors employ different neutron / gamma discrimination techniques, the most commonly used being pulse amplitude discrimination (PHD) and pulse shape discrimination (PSD).

[0003] Pulse amplitude discrimination is the simplest neutron / gamma discrimination technology. This technology is applicable to the case where the gamma ray pulse amplitude differs from the neutron signal pulse amplitude by one or several orders of magnitude. This method is usually used in gas ionization chambers, such as fission ionization chambers and BF3 proportional counters. On the one hand, the gas ionization chamber has low detection efficiency for gamma rays, and the corresponding pulse amplitude is naturally very small; on the other hand, the secondary particles produced by the reaction of neutrons with converters have relatively large energy. For example, a single fission of uranium 235 releases about 200 MeV of energy, while 10 The energy of the secondary particles produced by B and neutrons is 2.79 MeV. By setting an appropriate threshold, pulse amplitudes below the threshold can be identified as gamma rays, while those above the threshold are neutron signals.

[0004] Compared with pulse amplitude discrimination, pulse waveform discrimination is more complicated. 6 Scintillator neutron detectors with Li as neutron converter all use PSD. Gamma rays deposit energy by generating electrons through photoelectric effect, Compton scattering and electron pair effect. 6 Li reacts with neutrons to produce tritium nuclei and alpha particles. Due to their greater mass and charge, alpha particles deposit energy more quickly than electrons, resulting in a narrower pulse width. Thus, the wider pulses are gamma rays, in contrast to the neutron pulse signal.

[0005] Natural gadolinium has the largest thermal neutron cross section, which is 3 He, 10 B. 7Gadolinium-based scintillators have a thermal neutron cross section that is over 20 times greater than that of lithium. They not only have high neutron detection efficiency, but also possess a strong luminescence yield and fast fluorescence decay time. Theoretically, gadolinium-based scintillators are excellent materials for neutron detection. However, the neutron environment typically contains a large amount of background gamma rays. Therefore, the primary challenge facing gadolinium-based materials for neutron detection is how to distinguish neutrons from gamma rays.

[0006] It is well known that gadolinium (Gd) has a very high thermal neutron cross section, but the composition of its reaction products, namely secondary particles, is quite complex. 157 Gd, 155 The neutron reaction equation of Gd is as follows:

[0007]

[0008]

[0009] isotope 157 Gd and 155 Gd generates an unstable excited state nuclide with a very short lifetime after absorbing a neutron. 158 Gd * and 156 Gd * The excitation energies are 7.94 MeV and 8.53 MeV, respectively. Upon deexcitation, both emit a series of gamma rays and internal conversion electrons with varying energies. Each absorbed thermal neutron releases an average of 3.288 gamma rays with an average energy of 2.394 MeV, along with 0.67 internal conversion electrons with an average energy of 71 keV. Gadolinium-based materials have a high density, resulting in excellent gamma ray detection efficiency. Gamma rays deposit energy within the crystal through the photoelectric effect, Compton scattering, and the electron pair effect, generating secondary electrons. This mechanism is similar to the fluorescence generated by internal conversion electrons within the crystal. Because the secondary particles produced by the reaction of gadolinium with neutrons are complex and produce a range of gamma rays with varying energies, and because the neutron environment typically contains a large amount of background gamma rays, neutron / gamma discrimination cannot be achieved using conventional pulse amplitude discrimination and pulse waveform analysis. Conventional neutron / gamma discrimination techniques, such as pulse amplitude discrimination and PSD waveform analysis, are generally ineffective for neutron / gamma discrimination in gadolinium-based materials.

[0010] Pulse amplitude discrimination (PHD) is relatively simple to implement, but its scope of application is quite limited. It only works if there is a significant difference between the gamma ray pulse amplitude and the neutron signal amplitude. Otherwise, external electromagnetic interference or temperature-induced threshold changes can easily lead to false discrimination. Secondly, the gamma ray energy in the neutron field is also continuous, ranging from tens of keV to several MeV, and even tens or hundreds of MeV. Pulse amplitude discrimination can easily mistake high-energy gamma rays for neutrons. Considering that the secondary gamma rays produced by the reaction between gadolinium and neutrons contain a large number of low-energy gamma rays and X-rays at tens of keV, and that gadolinium-based materials have a high density and high gamma detection efficiency, the use of PHD for neutron / gamma discrimination in gadolinium-based materials inevitably introduces a high error rate.

[0011] The premise of pulse shape discrimination (PSD) is that the secondary particles generated by neutron response cannot be electrons, but must be particles with a charge or mass significantly different from electrons, such as protons, alpha particles, etc. PSD discrimination is generally applicable to 10 B. 6 Scintillator neutron detectors use Li as a neutron converter. Furthermore, the fluorescence decay time of the scintillation crystal cannot be too long, otherwise statistical fluctuations in fluorescence will annihilate the differences in pulse shape caused by the energy deposition speed of different particles. However, for gadolinium-based scintillators, gadolinium initially reacts with neutrons to produce a series of gamma rays and internal conversion electrons of varying energies. Gamma rays then generate secondary electrons through the photoelectric effect, Compton scattering, and the electron pair effect, ultimately resulting in energy deposition in these secondary electrons. Therefore, pulse shape discrimination is completely unsuitable for neutron / gamma discrimination with gadolinium-based scintillators.

[0012] Considering the strong background gamma rays often present in neutron measurements, neutron n / gamma γ discrimination is a scientific challenge that must be addressed when using gadolinium-based scintillators for neutron detection and neutron imaging. To address this challenge, a new neutron / gamma discrimination technique is urgently needed to achieve efficient neutron detection using gadolinium-based scintillators. Summary of the Invention

[0013] The object of the present invention is to provide a neutron / gamma discrimination system and method for gadolinium-based materials, so as to achieve efficient neutron detection of gadolinium-based materials.

[0014] To achieve the above objectives, the present invention provides a neutron / gamma discrimination system for gadolinium-based materials, comprising a gadolinium-based neutron detector, a gamma-ray detector, a preamplifier circuit connected to the gadolinium-based neutron detector and the gamma-ray detector via two channels, and a dual-channel digital multi-channel spectrometer connected to the preamplifier circuit via two channels. The dual-channel digital multi-channel spectrometer is configured to receive two pulse signals amplified by the preamplifier circuit, and when the time difference between the arrival times of the two pulse signals is within a set threshold time, neutron signal event counting is performed, and amplitude values ​​of the two pulse signals are further extracted and recorded in a neutron response energy spectrum and a gamma energy spectrum, respectively.

[0015] The gadolinium-based neutron detector is composed of a gadolinium-based material sheet and a photomultiplier tube bonded to the rear end of the gadolinium-based material sheet. The gadolinium-based neutron detector is connected to the preamplifier circuit via the photomultiplier tube.

[0016] The gadolinium-based material sheet is directly bonded to the photomultiplier tube or coupled to the photomultiplier tube via an optical path.

[0017] The gamma ray detector is placed behind the gadolinium-based material sheet.

[0018] The gamma ray detectors are placed on the four sides of the gadolinium-based material slice.

[0019] The dual-channel digital multi-channel spectrometer is configured to sequentially perform AD conversion, digital filtering, and pulse arrival time extraction on two pulse signals to obtain the time difference between the arrival times of the two pulse signals.

[0020] The thickness of the gadolinium-based material sheet is less than 1 mm.

[0021] The gamma ray detector adopts a scintillator detector, a semiconductor detector, an ionization chamber, a proportional counter tube or a GM counter tube.

[0022] In another aspect, the present invention provides a method for neutron / gamma discrimination of gadolinium-based materials, comprising:

[0023] S1: a step of determining a time threshold, which includes:

[0024] S11: placing the neutron / gamma discrimination system based on the gadolinium-based material described above at a relatively determined position of the neutron flux;

[0025] S12: setting an estimated value of the threshold time, and measuring a neutron count rate using the estimated value of the threshold time and the neutron / gamma discrimination system of the gadolinium-based material;

[0026] S13: Determine whether the measured neutron count rate is consistent with the actual neutron flux. If so, determine the estimated value of the threshold time at that time as the threshold time and end the process. Otherwise, adjust the estimated value of the threshold time and return to step S12.

[0027] S2: Neutron / gamma online identification and detection steps, which include:

[0028] A threshold time is set and used to simultaneously process two pulse signals within a dual-channel digital multi-channel spectrometer of the neutron / gamma discrimination system for gadolinium-based materials. When the time difference between the arrival times of the two pulse signals is less than the threshold time, the dual-channel digital multi-channel spectrometer counts neutron signal events and further extracts amplitude values ​​of the two pulse signals, which are recorded in the neutron response energy spectrum and the gamma energy spectrum, respectively.

[0029] The gadolinium-based material neutron / gamma discrimination system of the present invention combines physical processes with electronic technology. First, the gadolinium-based material sheet only absorbs internal conversion electrons and low-energy background gamma rays, spatially separating the secondary particles generated by gadolinium absorbing neutrons from the high-energy background gamma rays. Then, the temporal relationship between the internal conversion electrons and the secondary prompt gamma rays is used to further distinguish whether the signal detected by the gadolinium-based material sheet is the internal conversion electron or the low-energy background gamma, ultimately achieving neutron / gamma discrimination. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic diagram of the timing coincidence technology for the gadolinium-based material sheet and the gamma detector.

[0031] Figure 2 FIG. 4 is a block diagram of a neutron / gamma discrimination system for gadolinium-based materials according to an embodiment of the present invention.

[0032] Figure 3 The flowchart is a step of determining a coincidence time threshold value of a neutron / gamma discrimination method for gadolinium-based materials according to an embodiment of the present invention.

[0033] Figure 4 The figure is a flow chart of the neutron / gamma online discrimination and detection steps of the neutron / gamma discrimination method for gadolinium-based materials according to one embodiment of the present invention. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0035] This invention provides a neutron / gamma discrimination system and method for gadolinium-based materials. These systems are used to achieve efficient neutron detection of gadolinium-based materials, particularly gadolinium-based scintillators, while also enabling high-resolution, high-signal-to-noise ratio neutron imaging. Based on this, gadolinium-based materials are expected to have broad application prospects in neutron microscopy, nondestructive testing, and in-situ neutron field measurement.

[0036] The neutron / gamma discrimination system of the gadolinium-based material of the present invention is based on the timing coincidence technology of the gadolinium-based material slice and the gamma detector. The physical process and principle structure of the timing coincidence technology are as follows: Figure 1 shown.

[0037] The prior art generally uses scintillators based on lithium 6 and boron 10, or bulk gadolinium-based scintillators (thickness greater than 1 mm). Figure 1 As shown, the gadolinium-based material sheet is obtained by processing or preparing a gadolinium-based material (such as a gadolinium-based scintillator material) into a sheet or a film. The thickness of the gadolinium-based material sheet is less than 1 mm.

[0038] Therefore, when a neutron beam containing background gamma rays passes through a thin film of gadolinium-based material, the neutrons are absorbed by the thin film, resulting in prompt internal conversion electrons and gamma rays of varying energies. Both the internal conversion electrons and the low-energy background gamma rays are deposited within the thin film; the prompt gamma rays escape from the thin film crystal, while the higher-energy background gamma rays directly penetrate the thin film, and both can be absorbed by the gamma detector. Theoretically, the internal conversion electrons and prompt gamma rays generated after neutron absorption are generated almost simultaneously, exhibiting a temporal correlation. The probability of background gamma rays simultaneously generating signals in both is extremely low. Therefore, the principle of the present invention is to achieve neutron / gamma discrimination by exploiting the spatiotemporal differences in the signals generated by the internal conversion electrons and gamma rays generated after neutron absorption in the thin film crystal and gamma detector.

[0039] Figure 2 FIG. 1 is a system block diagram of a neutron / gamma discrimination system of gadolinium-based materials according to an embodiment of the present invention. Figure 2 As shown, the gadolinium-based neutron / gamma discrimination system comprises a gadolinium-based neutron detector 10, a gamma-ray detector 20, a preamplifier circuit 30 connected to the gadolinium-based neutron detector 10 and the gamma-ray detector 20 via two channels, and a dual-channel digital multi-channel spectrometer 40 connected to the preamplifier circuit 30 via two channels.

[0040] The gadolinium-based neutron detector 10 comprises a gadolinium-based material sheet 11 and a photomultiplier tube 12 bonded to the rear end of the gadolinium-based material sheet 11. The gadolinium-based neutron detector 10 is connected to the preamplifier circuit 30 via the photomultiplier tube 12. In this embodiment, the gadolinium-based material sheet 11 is directly bonded to the photomultiplier tube 12. The gamma-ray detector 20 is positioned behind the gadolinium-based material sheet 11, preferably on all four sides of the sheet 11, as close to the sheet as possible. However, in other embodiments, the gamma-ray detector 20 may also be positioned at the rear end of the gadolinium-based material sheet 11, or to the left or right of the sheet 11. Regardless of whether the gamma-ray detector 20 is positioned front-to-back, left-to-right, or in a center-to-periphery relationship with the gadolinium-based material sheet 11, it is protected by the present invention.

[0041] It should be noted that the front and back here are relative to the propagation direction of the neutron beam, and the back refers to the downstream of the propagation direction of the neutron beam.

[0042] Among them, the dual-channel digital multi-channel spectrometer 40 is configured to receive two pulse signals amplified by the preamplifier circuit 30, and perform AD conversion, digital filtering, and pulse arrival time extraction on the two pulse signals in sequence to obtain the time difference between the arrival times of the two pulse signals; when the time difference between the arrival times of the two pulse signals is within the set threshold time, the event counting of the neutron signal is performed, and the amplitude values ​​of the two pulse signals are further extracted and recorded in the neutron response energy spectrum and the gamma energy spectrum respectively for energy spectrum processing.

[0043] The gadolinium-based neutron detector 10 uses a gadolinium-based material sheet 11 as a neutron converter, and the thickness of the gadolinium-based material sheet 11 is less than 1 mm, and can even be as thin as ten microns.

[0044] The gamma-ray detector 20 can also be a scintillator detector, a semiconductor detector, or any other type of detector, such as an ionization chamber, a proportional counter, or a GM counter. The gamma-ray detector 20 must be capable of detecting gamma rays in the range of tens of keV to 1 MeV, and must have high detection efficiency and fast time resolution for gamma rays in the range of tens of keV to 1 MeV. Specifically, the output pulse signal must have steep leading and trailing edges.

[0045] The gadolinium-based material neutron / gamma discrimination system of the present invention consists of two relatively independent detectors. When neutrons enter the gadolinium-based material slice 11, the internal conversion electrons generated by the absorbed neutrons return to the ground state, generating fluorescence. This fluorescence is converted into a voltage pulse by a photomultiplier tube 12, amplified by a preamplifier circuit 30, and input into one channel of a dual-channel digital multichannel spectrometer 40. The pulse signal from the gamma-ray detector 20 is also amplified by the preamplifier circuit 30 and input into the other channel of the dual-channel digital multichannel spectrometer 40. The dual-channel digital multichannel spectrometer 40 determines whether the pulse signal output by the gadolinium-based material slice 11 is a neutron signal based on the arrival times of the two pulse signals. The fundamental reason why the gadolinium-based material neutron / gamma discrimination system of the present invention can achieve neutron and gamma discrimination in gadolinium-based materials is that it combines physical processes with electronic technology, rather than relying solely on electronic signal processing methods. First, the gadolinium-based material sheet 11 only absorbs internal conversion electrons and low-energy background gamma rays, spatially separating the secondary particles produced by gadolinium absorbing neutrons and high-energy background gamma rays. Then, the timing relationship between the internal conversion electrons and the secondary prompt gamma rays is used to further distinguish whether the signal detected by the gadolinium-based material sheet 11 is an internal conversion electron or a low-energy background gamma ray, ultimately achieving neutron / gamma discrimination.

[0046] In the prior art, pulse amplitude discrimination processes the size of a single pulse amplitude and focuses on the energy information of a single detection event. Pulse waveform discrimination processes the rising or falling edge of a single pulse signal and focuses on the time information of a single detection event. When gadolinium-based materials, especially gadolinium-based scintillators, are used for neutron detection, whether pulse waveform discrimination or pulse amplitude discrimination is used, effective neutron gamma discrimination cannot be achieved. Pulse waveform discrimination and pulse amplitude discrimination are both single electronic processing methods, and both are one-dimensional information. The mechanism of energy deposition of internal conversion electrons, prompt gamma rays and background gamma rays produced by the reaction of gadolinium with neutrons is the same, which determines the consistency of fluorescence decay time, so that the pulse waveforms are completely similar, and it is impossible to distinguish neutron pulses and gamma pulses from the pulse shape. The internal conversion electrons generated by gadolinium absorbing neutrons are not monoenergetic, and mainly include 29Kev, 39Kev, 71Kev, 78Kev, 81Kev, 131Kev, etc. These internal conversion electrons can all be detected using gadolinium-based materials, but the detected pulse amplitudes are different. The density of gadolinium-based material crystals is relatively high. Even a 50-micron-thick crystal still has a detection efficiency of about 10% for 60Kev gamma rays. Therefore, pulse amplitude discrimination of gadolinium-based material slices cannot achieve effective neutron gamma discrimination.

[0047] The gadolinium-based neutron / gamma discrimination system of the present invention also focuses on the timing information of detection events, but with a different emphasis, specifically on processing the timing relationship between two detection events. Whether this timing relationship is processed directly by processing the two pulse signals, or by first storing the two pulse signals and then processing them offline, or whether it is processed by analog circuits or digital signals, any neutron / gamma discrimination based on a timing comparison between the gadolinium-based neutron pulse signal and the gamma detector pulse signal is protected by the present invention.

[0048] Based on the neutron / gamma discrimination system of gadolinium-based materials described above, the neutron / gamma discrimination method of gadolinium-based materials implemented includes two main steps: Figure 3 The step of determining the time threshold as shown (i.e., step S1), and Figure 4 The neutron / gamma online identification and detection step (ie, step S2) is shown.

[0049] The compliance time threshold determination step is used to determine the value of the threshold time.

[0050] The step of determining the time threshold (i.e., step S1) specifically includes the following steps:

[0051] Step S11: placing the gadolinium-based neutron / gamma discrimination system described above at a relatively determined position of the neutron flux;

[0052] There are no specific requirements for the location of the gadolinium-based neutron / gamma discrimination system; however, the actual neutron flux at that location must be known. This can be measured using other detectors or the Institute of Metrology's standard neutron source flux.

[0053] Step S12: setting an estimated value of the threshold time (i.e., coincidence time), and using the estimated value of the threshold time and the neutron / gamma discrimination system of the gadolinium-based material to measure the neutron count rate;

[0054] Step S13: Determine whether the measured neutron count rate is consistent with the actual neutron flux. If so, determine the estimated value of the threshold time at this time as the threshold time and end the process; otherwise, adjust the estimated value of the threshold time and return to step S12.

[0055] Therefore, the present invention can continuously adjust the estimated value of the threshold time until the measured neutron count rate matches the actual neutron flux, and then determine the corresponding estimated value of the threshold time as the threshold time.

[0056] The neutron / gamma online identification and detection step (i.e., step S2) specifically includes:

[0057] A threshold time is set and used to simultaneously process the pulse signals of the gadolinium-based neutron detector 10 and the gamma-ray detector 20 within the dual-channel digital multi-channel spectrometer 40 of the gadolinium-based material neutron / gamma discrimination system. When the time difference between the arrival times of the two pulse signals is less than the threshold time, the dual-channel digital multi-channel spectrometer 40 counts neutron signal events and further extracts amplitude values ​​of the two pulse signals, recording them in the neutron response energy spectrum and the gamma energy spectrum, respectively, for energy spectrum processing.

[0058] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the present invention. Various modifications are possible. Any simple, equivalent changes and modifications made in accordance with the claims and description of the present invention are within the scope of protection of the patent claims. Anything not fully described in this invention is conventional technology.

Claims

1. A neutron / gamma discrimination method for gadolinium-based materials, characterized in that: include: Step S1: a time threshold determination step, which includes: Step S11: placing a neutron / gamma discrimination system made of gadolinium-based materials at a relatively determined position of the neutron flux; The gadolinium-based neutron / gamma discrimination system comprises a gadolinium-based neutron detector, a gamma-ray detector, a preamplifier circuit connected to the gadolinium-based neutron detector and the gamma-ray detector via two channels, and a dual-channel digital multi-channel spectrometer connected to the preamplifier circuit via two channels. The dual-channel digital multi-channel spectrometer is configured to receive two pulse signals amplified by a preamplifier circuit, and when the time difference between the arrival times of the two pulse signals is within a set threshold time, the neutron signal event count is performed, and the amplitude values ​​of the two pulse signals are further extracted and recorded in the neutron response energy spectrum and the gamma energy spectrum respectively; Step S12: setting an estimated value of the threshold time, and using the estimated value of the threshold time and the neutron / gamma discrimination system of the gadolinium-based material to measure the neutron count rate; Step S13: Determine whether the measured neutron count rate is consistent with the actual neutron flux. If so, determine the estimated value of the threshold time at that time as the threshold time and terminate the process. Otherwise, adjust the estimated value of the threshold time and return to step S12. Step S2: Neutron / gamma online identification and detection step, which includes: A threshold time is set and used to simultaneously process two pulse signals within a dual-channel digital multi-channel spectrometer of the neutron / gamma discrimination system for gadolinium-based materials. When the time difference between the arrival times of the two pulse signals is less than the threshold time, the dual-channel digital multi-channel spectrometer counts neutron signal events and further extracts amplitude values ​​of the two pulse signals, which are recorded in the neutron response energy spectrum and the gamma energy spectrum, respectively.

2. The neutron / gamma discrimination method of gadolinium-based materials according to claim 1, characterized in that: The gadolinium-based neutron detector is composed of a gadolinium-based material sheet and a photomultiplier tube bonded to the rear end of the gadolinium-based material sheet. The gadolinium-based neutron detector is connected to the preamplifier circuit via the photomultiplier tube.

3. The neutron / gamma discrimination method of gadolinium-based materials according to claim 2, characterized in that: The gadolinium-based material sheet is directly bonded to the photomultiplier tube or coupled to the photomultiplier tube via an optical path.

4. The neutron / gamma discrimination method of gadolinium-based materials according to claim 2, characterized in that: The gamma ray detector is placed behind the gadolinium-based material sheet.

5. The neutron / gamma discrimination method of gadolinium-based materials according to claim 4, characterized in that: The gamma ray detectors are placed on the four sides of the gadolinium-based material slice.

6. The neutron / gamma discrimination method of gadolinium-based materials according to claim 1, characterized in that: The dual-channel digital multi-channel spectrometer is configured to sequentially perform AD conversion, digital filtering, and pulse arrival time extraction on two pulse signals to obtain the time difference between the arrival times of the two pulse signals.

7. The neutron / gamma discrimination method of gadolinium-based materials according to claim 2, characterized in that: The thickness of the gadolinium-based material sheet is less than 1 mm.

8. The neutron / gamma discrimination method of gadolinium-based materials according to claim 1, characterized in that: The gamma ray detector adopts a scintillator detector, a semiconductor detector, an ionization chamber, a proportional counter tube or a GM counter tube.

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