Hybrid neutron gamma detector array and signal processing method

Abstract

The invention discloses a hybrid neutron gamma detector array and a signal processing method, and relates to the technical field of nuclear physical detection.During detection, eight EJ200 scintillators arranged in an array are used for energy deposition of gamma rays and fast neutrons and generating photons, and meanwhile three EJ426 thermal neutron scintillation screens are used for capturing thermal neutrons and generating photons; the response of gamma rays, fast neutrons and thermal neutrons is realized at the same time, and the detection precision is greatly improved. Meanwhile, if the three EJ426 thermal neutron scintillation screens are alternately stacked front and back, the total reflection of the EJ200 scintillators and the semi-light-proof performance of the EJ426 thermal neutron scintillation screens are utilized to block photon propagation in the X direction and only enable photons to be propagated in the Y direction and the Z direction, and each EJ200 scintillator corresponds to a four-channel photon collection structure to perform high-efficiency collection of the photons, so that the high-efficiency collection of the photons is realized. Therefore, high-precision detection and high-efficiency photon collection are realized, and support is provided for subsequent intense radiation field monitoring or high-precision positioning.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nuclear physics detection, in particular to a hybrid neutron gamma detector array and a signal processing method. BACKGROUND

[0002] Nuclear geophysical exploration, referred to as nuclear physics detection, is a geophysical method based on the interaction between particles such as neutrons and photons and medium atomic nuclei, which is used for mineral resource detection and geological problem analysis; it is different from natural radioactivity measurement, and short-range detection is realized through artificial sources, and is mainly applied to the fields of drilling, tunneling and sample analysis; the effective differentiation and accurate detection of neutrons and gamma rays have always been a research difficulty.

[0003] The mainstream detector at the present stage is mainly in the form of a single scintillator or multiple scintillators stacked, but because the detector at the present stage is only in the form of simple setting or simple stacking, the detection accuracy is low when detecting neutrons and gamma rays, and at the same time, because the detector at the present stage does not limit the propagation of photons, the photon collection efficiency is low.

[0004] Therefore, the detector at the present stage has the problems of low detection accuracy and low photon collection efficiency, which makes it difficult to meet the needs of strong radiation field monitoring or high-precision positioning scenes. SUMMARY

[0005] The embodiment of the present application provides a hybrid neutron gamma detector array and a signal processing method, which can solve the problems in the prior art.

[0006] The embodiment of the present application provides a hybrid neutron gamma detector array, which comprises eight EJ200 scintillators arranged in a three-dimensional array, three EJ426 thermal neutron scintillation screens alternately stacked between the three-dimensional array formed by the eight EJ200 scintillators, and two photomultiplier tubes arranged on each end face of each EJ200 scintillator without being blocked by the EJ426 thermal neutron scintillation screen. The EJ200 scintillator is used for depositing the energy of the gamma rays and fast neutrons emitted by the neutron source, and generating photons according to the deposited energy; after the fast neutrons emitted by the neutron source are moderated into thermal neutrons, the three EJ426 thermal neutron scintillation screens are used for capturing thermal neutrons and generating photons. The total reflectivity of the eight EJ200 scintillators and the semi-opaque property of the three EJ426 thermal neutron scintillation screens are used for limiting the propagation path direction of the photons, so that the photons propagate in the direction without being blocked by the EJ426 thermal neutron scintillation screen. Each EJ200 scintillator corresponds to four photomultiplier tubes in the four directions without being blocked by the EJ426 thermal neutron scintillation screen, and is used for forming a four-channel acquisition structure to acquire photons.

[0007] Preferably, further comprising a mechanical support structure, which is a stainless steel support, arranged at the bottom of the detector array, for fixing the detector array.

[0008] Preferably, further comprising a dark box, which is a paper dark box, the detector array is placed inside the paper dark box, and the inner wall of the paper dark box is painted with matt black paint, for reducing environmental light interference.

[0009] Preferably, further comprising a moderator, which is a high-density polyethylene (HDPE) plate, arranged between the neutron source and the detector array, for slowing down the fast neutrons emitted by the neutron source into thermal neutrons.

[0010] Preferably, the light guide material is connected between each EJ200 scintillator and the photomultiplier tube arranged at both ends of the EJ200 scintillator.

[0011] The embodiment of the present application also provides a signal processing method of a hybrid neutron gamma detector array, comprising the following steps: Collecting the charge data output by the photomultiplier tube, setting a long integration window to collect the full waveform charge of the charge data by using a pulse shape discrimination (PSD) method, and extracting the front edge feature in the charge data by using a short integration window; According to the charge amount of the full waveform charge and the charge amount of the front edge feature, obtaining a PSD value; dividing the value range of the PSD value into a gamma signal area and a neutron signal area, so as to distinguish the gamma signal and the neutron signal; For the four-channel electric signal corresponding to each EJ200 scintillator, calculating the time difference between the collection of the electric signals of two channels, and distinguishing the gamma event, the neutron event and the gamma neutron mixed event according to the time difference value, so as to position the neutron source.

[0012] Preferably, the distinguishing of the gamma signal and the neutron signal comprises: The PSD value is obtained in the following manner: PSD = 1 - Q short / Q long ; Wherein: Q short represents the charge amount of the short integration window 50ns; Q long represents the charge amount of the long integration window 1000ns; If PSD∈[-0.5, 0], it is determined as a gamma signal, if PSD∈[0.5, 1.0], it is determined as a neutron signal, and if PSD∈[0, 0.5], it is determined as a mixed signal or noise.

[0013] Preferably, the positioning of the neutron source comprises: For the four-channel electric signal corresponding to each EJ200 scintillator, calculating the time difference between the collection of the electric signals of two channels; Interval division and Gaussian fitting are performed on the time difference: The main peak of the time difference is located in [-1 ns, 1 ns], and the half-height width is 2 ns, accompanied by [-20 ns, 20 ns] incoherent fluctuations, and it is determined to be a neutron event; The time difference is concentrated in [-10 ns, 10 ns], and the peak is 0 ns, and the half-height width is 5 ns, and it is determined to be a gamma event; The time difference is concentrated in [-100 ns, 100 ns], and the time difference is 35 ns, and it is determined to be a neutron and gamma mixed event, and the event type is verified by Gaussian fitting half-height width to determine the neutron event and the gamma event; The propagation path of the photon is deduced through the time difference corresponding to the neutron event, and the position of the neutron source is obtained by combining the moderation time of the neutron through the moderator.

[0014] Compared with the prior art, the embodiment of the present application has the following beneficial effects: The eight EJ200 scintillators are arranged in a three-dimensional array, three EJ426 thermal neutron scintillation screens are alternately stacked between the three-dimensional array, and photomultiplier tubes are arranged on the two end surfaces of each EJ200 scintillator; during detection, the eight EJ200 scintillators arranged in an array are used for energy deposition of gamma rays and fast neutrons and generate photons, and at the same time, the three stacked EJ426 thermal neutron scintillation screens are used to capture thermal neutrons and generate photons, so as to simultaneously realize the response of gamma rays, fast neutrons and thermal neutrons, thereby greatly improving the detection accuracy; and at the same time, when the three EJ426 thermal neutron scintillation screens are alternately stacked in front and back, the full reflectivity of the EJ200 scintillator and the semi-opaque property of the EJ426 thermal neutron scintillation screen are utilized to block the propagation of X-direction photons, so that the photons only propagate in the Y and Z directions, and the four-channel photon acquisition structure corresponding to each EJ200 scintillator is utilized to collect photons with high efficiency, thereby realizing high-precision detection and high-efficiency photon collection, and providing support for subsequent strong radiation field monitoring or high-precision positioning.

[0015] Furthermore, the present application adopts a pulse shape discrimination (PSD) method to set a long integration window of 1000 ns to collect full-waveform charges of the electric charge data, and a short integration window of 50 ns to extract front characteristics of the electric charge data, according to the charge amount of the full-waveform charges and the charge amount of the front characteristics, to obtain a PSD value, and divide the value range of the PSD value into a gamma signal area and a neutron signal area to distinguish the gamma signal and the neutron signal, thereby solving the signal drift problem of the traditional ratio method in the mixed array and improving the classification accuracy of the neutron signal and the gamma signal.

[0016] Moreover, the application calculates the time difference between the electric signals collected by the four photomultiplier tubes corresponding to a single scintillator, focuses on the two groups of electric signals corresponding to the neutron event, that is, focuses on the two groups of electric signals with the largest time difference, to deduce the photon propagation path, and combines the neutron slowing time to obtain the position of the neutron source, so that the positioning accuracy of the neutron source can be improved. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 A schematic diagram of the overall layout structure of a hybrid neutron gamma detector array provided by the embodiment of the application is shown in the figure. Figure 2 A physical display schematic diagram of a hybrid neutron gamma detector array provided by the embodiment of the application is shown in the figure. Figure 3 A PSD value classification result schematic diagram of the four PMT responses around the scintillator 6 when the neutron source is at position 14 in a hybrid neutron gamma detector array provided by the embodiment of the application is shown in the figure. Figure 4 A two-dimensional PSD histogram of the four PMT responses around the scintillator 6 when the neutron source is at position 14 in a hybrid neutron gamma detector array provided by the embodiment of the application is shown in the figure. Figure 5 A time difference distribution schematic diagram of the two PMTs corresponding to the scintillator 6 in a hybrid neutron gamma detector array provided by the embodiment of the application is shown in the figure. Figure 6 A time difference distribution schematic diagram of the two PMTs corresponding to the scintillator 6 in a hybrid neutron gamma detector array provided by the embodiment of the application is shown in the figure. DETAILED DESCRIPTION

[0018] In order to make the above-mentioned purposes, features and advantages of the application more obvious and easy to understand, the specific embodiments of the application will be described in detail below with reference to the drawings. In the following description, a large number of specific details are set forth in order to facilitate a full understanding of the application. However, the application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the spirit of the application, so the application is not limited by the specific embodiments disclosed below.

[0019] At present, the conventional detector in the field of neutron gamma detector is a single scintillator (such as EJ200 or EJ426), but it is difficult to simultaneously respond to gamma rays and neutrons; among them, EJ200 is sensitive to gamma but has low neutron detection efficiency, EJ426 is dedicated to thermal neutrons but cannot detect gamma rays, resulting in high signal misjudgment rate in mixed radiation field; at the same time, the structure design of the detector lacks optimization of the photon propagation path, resulting in low photon collection efficiency and complex time difference distribution; and the signal processing algorithm does not fully consider the interaction of the mixed scintillator, resulting in an unsatisfactory PSD (pulse shape discrimination) index and FOM (figure of merit) value, affecting subsequent analysis.

[0020] And in the processing of the photon signal of the detector, the existing pulse shape discrimination (PSD) technology adopts a fixed integral window ratio method, and in the mixed array, the PSD value drifts due to signal attenuation, the quality factor FOM is generally lower than 2.5, and it is difficult to meet the 3 sigma classification accuracy requirement; at the same time, the time difference analysis does not distinguish the event type, and the neutron source positioning error often exceeds 10 cm; therefore, the present application provides a new type of mixed neutron gamma detector array and a signal processing method thereof.

[0021] As shown in Figure 1 , the embodiment of the present application provides a mixed neutron gamma detector array, which comprises 16 photomultiplier tubes PMT, which are respectively labeled 1, 2, 3, 4, 5, 6 (blocked), 7, 8, 9 (blocked), 10, 11, 12, 13, 14, 15 and 16; 3 EJ426 thermal neutron scintillation screens, which are respectively labeled 17, 18 and 19; 8 EJ200 scintillators, which are respectively labeled 20 (blocked), 21, 22, 23, and the EJ200 scintillators arranged below the labels 20 (blocked), 21, 22, 23; a mechanical support system comprising a support structure and a dark box shield; a neutron moderation and positioning system comprising a neutron moderator and a positioning coordinate system; wherein Figure 1 , because the labels 6, 9 and 20 are blocked, the form of adding (blocked) after the label is used to indicate the device represented by the label.

[0022] Among them, the eight EJ200 scintillators are arranged in a 2x2x2 three-dimensional array, which are used for energy deposition and photon generation of gamma rays and fast neutrons, and the size is adapted to the array layout; three EJ426 thermal neutron scintillation screens, which are specifically 12 cm x 12 cm x 1 mm thin plates, are stacked in the gap of the three-dimensional array formed by the eight EJ200 scintillators, and are stacked between the front and rear gaps, which are used for slow neutron capture reaction and photon generation; at the same time, the total reflection characteristic of the EJ200 scintillator and the semi-opaque property of the EJ426 thermal neutron scintillation screen are used to block the propagation of X-direction photons, and only the Y, Z direction straight line propagation path is reserved.

[0023] Among them, 16 photomultiplier tubes PMT correspond to both ends of each EJ200 scintillator, forming four-channel signal acquisition (such as scintillator 6 corresponding to PMT2, PMT14, PMT7, PMT8), and the photon coupling efficiency is enhanced through light guide material; The support structure uses a stainless steel bracket to fix the position of the assembly, ensuring that the three-dimensional coordinate accuracy error is ≤0.5 mm; The dark box shielding uses a paper dark box (inner wall matte black paint) to simulate the final design, and the average distance from the neutron source to the detector center is controlled to be 40 cm, reducing the environmental light interference.

[0024] Among them, the neutron moderator: a 10 cm thick HDPE material is placed between the neutron source and the detector to slow down the fast neutrons to thermal neutrons, improving the EJ426 reaction efficiency; The positioning coordinate system: taking the center of the detector as the origin, the positioning is realized by combining the time difference and the multi-position neutron source placement (such as position 14: 30 cm, 2.5 cm, -15 cm).

[0025] In signal processing, the designed PSD value classification algorithm: (1) Double-integral window parameters: long-integral window 1000 ns collects full-waveform charge, and short-integral window 50 ns extracts front feature, and the improved calculation formula is: PSD = 1 - Q short / Q long ; (2) Signal classification interval: gamma signals are concentrated in PSD ∈ [-0.5, 0] (left region L), and neutron signals are concentrated in PSD ∈ [0.5, 1.0] (right region R), and the classification accuracy is ensured by 3σ standard.

[0026] The designed time difference distribution analysis method: (1) Six groups of time difference calculation: for the four PMTs corresponding to a single scintillator, the time difference between each other is calculated, and the two groups farthest apart (such as PMT2 and PMT14) are analyzed; (2) Three-level interval screening strategy: A. Gamma event: time difference is concentrated in [-10 ns, 10 ns], showing single-peak Gaussian distribution (peak position ≈0 ns, half-height width ≈5 ns); B. Neutron event: main peak is located in [-1 ns, 1 ns] (half-height width ≈2 ns), accompanied by [-20 ns, 20 ns] incoherent fluctuation; C. Mixed event: neutron and gamma signals combined to produce time difference ≈35 ns, distributed in [-100 ns, 100 ns].

[0027] FOM value optimization strategy: (1) Two-dimensional PSD histogram analysis: threshold setting optimization (such as left upper / right lower arc line truncation control), adjusting integral parameters to maintain FOM value at about 3.00, ensuring that the histogram structure is not distorted; (2) Collector parameter adaptation: using 16 MHz clock and 4096 channel resolution, amplifying and processing short-integral signals, compatible with negative PSD calculation and not affecting FOM evaluation.

[0028] The technical advantages of the structure design of the application are: (1) multi-radiation field compatible detection: the EJ200 and EJ426 hybrid array simultaneously realizes the response of gamma rays, fast neutrons and thermal neutrons, and expands the detection range; (2) mechanical precision and shielding optimization: the combination of stainless steel supports and paper dark boxes controls the assembly error within millimeters, and balances the shielding effect and positioning feasibility through a 40 cm source distance design; (3) photon propagation path simplification: the material optical properties are used to limit the photon propagation in the Y and Z directions, reducing crosstalk and signal analysis complexity.

[0029] The performance improvement of the application in signal processing is: (1) PSD classification accuracy breakthrough: more than 3 sigma signal differentiation is realized, and the two-dimensional PSD histogram structure is stable, which is suitable for real-time analysis in complex radiation fields; (2) neutron source positioning efficiency improvement: through three-level interval fitting of time difference, the positioning error is controlled within 5 cm at a distance of 40 cm, meeting the needs of nuclear safety monitoring; (3) efficient use of hardware resources: the improved PSD algorithm is compatible with the parameter amplification design of the collector, fully utilizing the 4096 channel resolution, and improving the signal processing efficiency.

[0030] The application can be directly applied to real-time monitoring and source positioning of neutron gamma mixed fields in nuclear material transportation, radiation type identification and dose accurate evaluation in industrial nondestructive testing, and neutron background suppression and gamma dose calibration in medical radiotherapy equipment, and has significant engineering practicality and market application prospect.

[0031] In the specific experiment, as shown in Figure 2 The detector assembly is assembled as follows: A, eight EJ200 scintillators are arranged in a three-dimensional array, and EJ426 thermal neutron scintillation screens are inserted between the layers to ensure that the EJ200 and EJ426 are closely attached and reduce photon leakage.

[0032] B, 16 PMTs are respectively installed on the end face of the EJ200 scintillator, and light guide material is used to enhance the photon coupling efficiency, and each scintillator is symmetrically detected by two PMTs (such as scintillator 6 corresponding to PMT2, PMT14, PMT7 and PMT8).

[0033] C, the stainless steel support is welded in a 2x2x2 structure to ensure that the position accuracy error of each component is not more than 0.5 mm, and to avoid affecting the photon propagation path due to mechanical deviation.

[0034] Dark box and neutron source arrangement: A, the paper dark box is 30 cm x 30 cm x 30 cm in size, and the inner wall is sprayed with matte black paint to reduce light reflection interference.

[0035] B. With the center of the detector as the origin (0,0,0), place the neutron source at position 14 (30 cm, 2.5 cm, -15 cm). Place a 10 cm thick HDPE moderator between the source and the detector to ensure that the average distance from the neutron source to the center of the detector is approximately 40 cm.

[0036] Data acquisition parameters: (1) The collector uses a 16 MHz clock, a 30-bit timestamp, and a time resolution of 1 / 16 MHz = 62.5ns, and can record time differences with an accuracy of nanoseconds.

[0037] (2) In order to make full use of the 4096-channel collector, the short integration window (50ns) signal is amplified and the PSD value is allowed to be negative (which does not affect the FOM calculation).

[0038] PSD value calculation and classification: (1) PSD calculation formula: PSD=1–Q short / Q long , where Q short is the charge in the short integration window (50ns), Q long is the charge in the long integration window (1000ns).

[0039] (2) Classification by PSD value: When PSD∈[-0.5,0], it is determined to be a gamma signal, when PSD∈[0.5,1.0], it is determined to be a neutron signal, and the middle range ([0,0.5]) is considered as a mixed signal or noise. Figure 3 and Figure 4 The response diagram of the four PMTs surrounding the scintillator when the neutron source is at position 14 is shown in the figure. Figure 3 is the PSD value classification result, the distribution range of gamma signal (L area) and neutron signal (R area), where Figure 4 It is a two-dimensional PSD histogram. The upper left and lower right arc cutoffs are related to the collector threshold setting.

[0040] exist Figure 3 middle, Figure 3 The graph in the upper left corner represents the PSD value classification result of PMT6 (blocking). Figure 3 The figure in the upper right corner represents the PSD value classification result of PMT14. Figure 3 The figure in the lower left corner represents the PSD value classification result of PMT2. Figure 3 The figure in the lower right corner represents the PSD value classification result of PMT12.

[0041] Time difference distribution analysis: (1) Taking scintillator 6 as an example, calculate the time difference between the four PMTs, focusing on the two groups with the largest time difference (such as PMT2 and PMT14, PMT7 and PMT8), as shown in the following example:Figure 5 and Figure 6 as shown.

[0042] wherein, Figure 5 The time difference distribution of PMT7 and PMT8 is shown, Figure 6 The time difference distribution of PMT2 and PMT14 is shown.

[0043] (2) Interval division and Gaussian fitting are performed on the time difference data: A. In the interval [-10ns, 10ns], the gamma event corresponds to a single-peak Gaussian distribution (peak position about 0ns, half-height width about 5ns), as shown in Figure 5 .

[0044] B. Neutron events have a smaller Gaussian peak (half-height width about 2ns) in the interval [-1ns, 1ns], and appear in [-20ns, 20ns] with discontinuous fluctuations, as shown in Figure 6 .

[0045] PSD index and FOM value: (1) The PSD classification accuracy of the mixed detector array reaches more than 3σ, and the FOM value is 3.00, which is 55% lower than that of the single EJ200 + EJ426 combination (FOM = 6.61), but the two-dimensional PSD histogram does not appear distorted.

[0046] (2) The reason for the decrease is that the total reflection of photons between EJ200 and the semi-opaque characteristics of EJ426 reduce the photon collection efficiency; the mixed effect of multiple scintillators increases the signal decay path.

[0047] Time difference and signal type association: (1) In the gamma event, the time difference is concentrated in [-10ns, 10ns], which is consistent with the time expectation of linear photon propagation, and the case number accounts for 78%.

[0048] (2) In the neutron event, in addition to the main peak, the signal combination detected by PMT8 and PMT2 will produce a time difference of about 35ns, which is speculated to be due to: PMT8 / PMT2 triggers neutron signal collection first, but due to the performance of PMT or the limitation of photon propagation, no effective photons are generated, and then PMT7 / PMT14 is triggered by the gamma event.

[0049] The present application can control the positioning error of the neutron source within 5 cm (at an average distance of 40 cm) by time difference back-propagation of photon propagation path combined with neutron slowing time calculation, which meets the positioning requirements of conventional radiation monitoring scenes and proves the feasibility of neutron source positioning.

[0050] The application realizes high-precision detection and distinction of neutrons and gamma rays through mixed detector structure design and signal processing algorithm optimization, and experiment verification shows that the PSD classification precision is greater than 3 sigma, time difference analysis can assist neutron source positioning, and the application has significant technical innovation and practical value.

[0051] The application adopts a three-dimensional mixed array structure composed of EJ200 scintillators and EJ426 thermal neutron scintillation screens, configures 16 photomultiplier tubes (PMTs) to realize efficient collection of photon signals, and optimizes mechanical stability and light shielding effect through stainless steel support and paper dark box design; the signal processing method is based on pulse shape discrimination (PSD) technology and time difference analysis algorithm, accurately divides gamma signals (PSD belongs to [-0.5, 0]) and neutron signals (PSD belongs to [0.5, 1.0]), and the figure of merit (FOM) can reach about 3.00; the application effectively solves the problems of insufficient signal recognition precision and difficult neutron source positioning of traditional detectors in complex radiation fields, can be widely applied in fields such as nuclear radiation safety monitoring, medical image diagnosis and industrial nondestructive testing, and has significant technical innovation and engineering application value.

[0052] The above-mentioned embodiments only express several embodiments of the application, and the description is more specific and detailed, but it cannot be understood as a limitation on the scope of the patent. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the application, a number of modifications and improvements can be made, which belong to the protection scope of the application. Therefore, the protection scope of the patent of the application should be subject to the appended claims.

Claims

1. A hybrid neutron gamma detector array, characterized in that: include: Eight EJ200 scintillators arranged in a three-dimensional array, three EJ426 thermal neutron scintillator screens alternately stacked between the three-dimensional array formed by the eight EJ200 scintillators, and photomultiplier tubes installed on the two end faces of each EJ200 scintillator that are not blocked by the EJ426 thermal neutron scintillator screens; The EJ200 scintillator is used to deposit the energy of gamma rays and fast neutrons emitted by the neutron source and generate photons based on the deposited energy; after the fast neutrons emitted by the neutron source are slowed down into thermal neutrons, the three EJ426 thermal neutron scintillator screens are used to capture the thermal neutrons and generate photons; The total reflectivity of the eight EJ200 scintillators and the semi-opaqueness of the three EJ426 thermal neutron scintillator screens are used to limit the direction of photon propagation paths, so that photons propagate in directions not blocked by the EJ426 thermal neutron scintillator screens. Each EJ200 scintillator corresponds to four photomultiplier tubes in four directions not blocked by the EJ426 thermal neutron scintillator screen, so as to form a four-channel collection structure to collect photons.

2. A hybrid neutron gamma detector array according to claim 1, characterized in that: It also includes a mechanical support structure, which is a stainless steel bracket. The stainless steel bracket is arranged at the bottom of the detector array and is used to fix the detector array.

3. The hybrid neutron gamma detector array according to claim 1, characterized in that: It also includes a dark box, which is a paper dark box. The detector array is placed inside the paper dark box, and the inner wall of the paper dark box is painted with matte black paint to reduce interference from ambient light.

4. The hybrid neutron gamma detector array according to claim 1, characterized in that: The device also includes a moderator, which is a high-density polyethylene (HDPE) plate. The moderator is arranged between the neutron source and the detector array and is used to slow down the fast neutrons emitted by the neutron source into thermal neutrons.

5. The hybrid neutron gamma detector array according to claim 1, characterized in that: Each EJ200 scintillator is connected to the photomultiplier tubes arranged at its two end surfaces via a light-conducting material.

6. The signal processing method of a hybrid neutron gamma detector array according to any one of claims 1 to 5, characterized in that: The following steps are involved: Collect the charge data output by the photomultiplier tube, use the pulse shape discrimination (PSD) method to set a long integration window to collect the full waveform charge of the charge data, and a short integration window to extract the leading edge features in the charge data; Obtain the PSD value based on the charge amount of the full waveform charge and the charge amount of the leading edge feature; divide the value range of the PSD value into a gamma signal region and a neutron signal region to distinguish the gamma signal from the neutron signal; For the four-channel electrical signals corresponding to each EJ200 scintillator, the time difference between the electrical signals collected by each channel is calculated. Gamma events, neutron events and gamma-neutron mixed events are distinguished according to the time difference value to locate the neutron source.

7. A signal processing method according to claim 6, characterized in that: The distinguishing between the gamma signal and the neutron signal comprises: The PSD value is obtained as follows: PSD=1– Q short / Q long ; Where: Q short Indicates the charge in the short integration window of 50ns; Q long Indicates the charge in the long integration window of 1000ns; If PSD∈[-0.5,0], it is determined to be a gamma signal; if PSD∈[0.5,1.0], it is determined to be a neutron signal; if PSD∈[0,0.5], it is determined to be a mixed signal or noise.

8. A signal processing method according to claim 6, characterized in that: The positioning of the neutron source includes: For the four-channel electrical signals corresponding to each EJ200 scintillator, calculate the time difference between the two channels when collecting electrical signals; Interval division and Gaussian fitting of time difference: The main peak of the time difference is located at [-1ns, 1ns], with a half-height width of 2ns, accompanied by incoherent fluctuations at [-20ns, 20ns], which is determined to be a neutron event; When the time difference is concentrated in [-10ns, 10ns] and presents a single-peak Gaussian distribution with a peak position of 0ns and a half-width of 5ns, it is determined to be a gamma event; The time difference is concentrated in [-100 ns, 100 ns], and when the time difference = 35 ns, it is determined to be a mixed neutron and gamma event. The event type is verified by Gaussian fitting of the half-maximum width to determine whether it is a neutron event or a gamma event. The photon propagation path is inferred through the time difference corresponding to the neutron event, and the position of the neutron source is obtained by combining the slowing-down time of the neutron passing through the moderator.

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