Neutron source azimuth measurement device and method

Abstract

The application relates to a neutron source azimuth measurement device and method. The method comprises a neutron source to be measured, a polyhedral neutron detector, a neutron moderator structure and an electronic and data acquisition system; the neutron moderator structure is wrapped outside the polyhedral neutron detector; the polyhedral neutron detector is connected by a plurality of planar neutron detectors, each planar neutron detector is connected with the electronic and data acquisition system; the electronic and data acquisition system comprises a ratio calculation module and an azimuth acquisition module; the ratio calculation module obtains a neutron count rate according to the number of electric pulse signals output by the planar neutron detector per unit time, and obtains a relative ratio of the neutron count rate between each planar neutron detector, and the azimuth acquisition module is used for inputting the relative ratio into a pre-trained azimuth acquisition model to obtain the azimuth of the neutron source to be measured. The method can shorten the neutron source azimuth measurement time and improve the neutron source azimuth measurement precision.

Description

Technical Field

[0001] This application relates to the field of nuclear radiation detection technology, and in particular to a neutron source orientation measurement device and method. Background Technology

[0002] The flow of special nuclear materials can be monitored by measuring the neutrons released during the spontaneous fission of these materials (especially plutonium). Furthermore, neutron sources have wide applications in materials detection, neutron activation, and oil well logging. To achieve effective monitoring of neutron sources and rapid search after their loss, a detection device capable of measuring the location of neutron sources is needed.

[0003] Traditional neutron source orientation measurement methods primarily rely on measuring the elastic scattering events of a single fast neutron emitted from the radioactive source with protons within a detector. The detector records the position, time, and recoil proton energy of the first scattering of a single fast neutron within the detector, as well as the position, time, and recoil proton energy of the second scattering. By recording detailed information from both scattering events, information such as the incident neutron energy, the energy and direction of the first scattering neutron, and the recoil proton energy can be obtained. Based on the laws of conservation of momentum and energy, the cone containing the neutron's incident direction can then be determined. The orientation of the neutron source can be measured by measuring the intersection points of numerous cones representing neutron incident directions. This method requires the fast neutron to undergo at least two elastic scattering events within the detector and places high demands on the detector's energy resolution, time resolution, and position resolution. This results in drawbacks such as low neutron detection efficiency, complex readout electronics systems, and high maintenance costs. Summary of the Invention

[0004] Therefore, it is necessary to provide a neutron source orientation measurement device and method to address the aforementioned technical problems.

[0005] A neutron source orientation measurement device, the device comprising:

[0006] The neutron source to be tested, the polyhedral neutron detector, the neutron moderator structure, and the electronics and data acquisition system;

[0007] The neutron moderator structure is wrapped around the outside of the polyhedral neutron detector to receive fast neutrons released by the neutron source under test and to dissipate the energy of the fast neutrons so that low-energy neutrons can pass through.

[0008] The polyhedral neutron detector is composed of multiple planar neutron detectors connected together, and each planar neutron detector is connected to the electronics and data acquisition system; the planar neutron detector is used to convert the low-energy neutrons into electrical pulse signals with a corresponding detection efficiency;

[0009] The electronics and data acquisition system includes a ratio calculation module and an orientation acquisition module. The ratio calculation module obtains the neutron count rate based on the number of electrical pulse signals output per unit time, and obtains the relative ratio of the neutron count rates between each planar neutron detector based on the neutron count rate. The orientation acquisition module is used to input the relative ratio into a pre-trained orientation acquisition model to obtain the orientation of the neutron source to be measured.

[0010] In one embodiment, the neutron moderator structure is made of a low atomic number element material.

[0011] In one embodiment, the device further includes: the planar neutron detector comprising a first neutron conversion screen, a wave-shifting fiber array, a photoelectric converter, and a second neutron conversion screen; the wave-shifting fiber array comprising an fiber arrangement portion and a fiber bundle portion, the first end of the fiber arrangement portion being coated with a light-reflecting layer, and the second end of the fiber arrangement portion being connected to the photoelectric converter; the first neutron conversion screen and the second neutron conversion screen being respectively bonded to both sides of the fiber arrangement portion; the edges of the first neutron conversion screen and the fiber arrangement portion being aligned with the edge of the second neutron conversion screen.

[0012] In one embodiment, it further includes: the side of the first neutron conversion screen and the second neutron conversion screen connected to the wave-shifting fiber array is coated with... 6 LiF / ZnS(Ag) scintillator.

[0013] In one embodiment, the photoelectric converter of each of the planar neutron detectors is connected to the electronics and data acquisition system.

[0014] In one embodiment, the neutron moderator structure further includes: a plurality of plate-shaped neutron moderators and a filled neutron moderator; each of the plate-shaped neutron moderators is fixed on a first neutron conversion screen of each of the planar neutron detectors; the filled neutron moderators and the neutron moderators enclose the polyhedral neutron detector into a polyhedral structure.

[0015] In one embodiment, it further includes a dark box made of opaque material, which is installed on the outside of the moderating body structure.

[0016] A method for measuring the orientation of a neutron source, the method comprising:

[0017] The neutron source under test releases fast neutrons;

[0018] The neutron moderator structure receives fast neutrons released by the neutron source under test and dissipates the energy of the fast neutrons to pass through low-energy neutrons.

[0019] The low-energy neutrons are converted into electrical pulse signals with a corresponding detection efficiency by the polyhedral neutron detector.

[0020] The neutron count rate is obtained by the electronics and data acquisition system based on the number of electrical pulse signals output per unit time. The relative ratio of the neutron count rates between each planar neutron detector is obtained based on the neutron count rate. The relative ratio is input into a pre-trained orientation acquisition model to obtain the orientation of the neutron source to be measured.

[0021] The aforementioned neutron source orientation measurement device and method, by combining multiple planar neutron detectors into a polyhedral neutron detector, improves the accuracy of neutron source orientation measurement. Based on the measured neutron count rates of the multiple planar neutron detectors, the relative ratio of the neutron count rates between different planar detectors is calculated, and the ratio is processed using an electronics and data acquisition system to obtain the orientation of the neutron source under test. This embodiment of the invention can shorten the neutron source orientation measurement time and improve the accuracy of neutron source orientation measurement. Attached Figure Description

[0022] Figure 1 This is an application scenario diagram of a neutron source orientation measurement device in one embodiment;

[0023] Figure 2 This is a schematic diagram of the planar neutron detector in one embodiment;

[0024] Figure 3 This is a schematic diagram of the structure of a hexahedral neutron detector in one embodiment;

[0025] Figure 4 This is a schematic diagram of the structure of a plate-shaped neutron moderator in one embodiment;

[0026] Figure 5 This is a schematic diagram of the structure of the first columnar neutron moderator in one embodiment;

[0027] Figure 6 This is a schematic diagram of the structure of the second columnar neutron moderator in one embodiment;

[0028] Figure 7 This is a schematic diagram of the structure of a cube-shaped neutron moderator in one embodiment;

[0029] Figure 8 This is a flowchart illustrating a neutron source orientation measurement method in one embodiment;

[0030] Figure 9 This is a schematic diagram showing the relationship between the count rate ratio of different planar detectors and the angle when the distance is 100cm in one embodiment.

[0031] Figure 10This is a schematic diagram showing the relationship between the count rate ratio of different planar detectors and distance when the angle is 30° in one embodiment. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0033] In one embodiment, such as Figure 1 As shown, a neutron source orientation measurement device is provided, comprising:

[0034] The neutron source to be tested, the polyhedral neutron detector, the neutron moderator structure, and the electronics and data acquisition system;

[0035] The neutron moderator structure is wrapped around the outside of the polyhedral neutron detector to receive fast neutrons emitted by the neutron source under test and to dissipate the energy of the fast neutrons so that low-energy neutrons can pass through.

[0036] A polyhedral neutron detector is composed of multiple planar neutron detectors connected together. Each planar neutron detector is connected to the electronics and data acquisition system. The planar neutron detectors are used to convert low-energy neutrons into electrical pulse signals with a corresponding detection efficiency.

[0037] The electronics and data acquisition system includes a ratio calculation module and an orientation acquisition module. The ratio calculation module obtains the neutron count rate based on the number of electrical pulse signals output per unit time, and obtains the relative ratio of the neutron count rates between each planar neutron detector based on the neutron count rate. The orientation acquisition module is used to input the relative ratio into a pre-trained orientation acquisition model to obtain the orientation of the neutron source to be measured.

[0038] Each module in the aforementioned neutron source orientation measurement device can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in the processor of a computer device in hardware form or independent of it, or stored in the memory of a computer device in software form, so that the processor can call and execute the operations corresponding to each module.

[0039] In the aforementioned neutron source orientation measurement device, multiple planar neutron detectors are combined into a polyhedral neutron detector, which helps improve the accuracy of neutron source orientation measurement. Based on the measured neutron count rates of the multiple planar neutron detectors, the relative ratio of the neutron count rates between different planar detectors is calculated, and the ratio is processed using an electronics and data acquisition system to obtain the orientation of the neutron source under test. This embodiment of the invention can shorten the neutron source orientation measurement time and improve the accuracy of neutron source orientation measurement.

[0040] In one embodiment, the neutron moderator structure is made of a low atomic number element material. In this embodiment, the neutron moderator structure is generally made of a material rich in low atomic number elements, typically polyethylene, but graphite can also be used. In this embodiment, fast neutrons released from the neutron source are incident on the moderator, undergoing multiple elastic collisions inside the moderator and losing energy. After their energy decreases, the neutrons exit the moderator and enter a planar neutron detector, where they are converted into electrical pulse signals at a certain efficiency.

[0041] In one embodiment, such as Figure 2 As shown, a schematic diagram of a planar neutron detector is provided. The planar neutron detector includes a first neutron conversion screen, a wave-shifting fiber array, a photoelectric converter, and a second neutron conversion screen. The wave-shifting fiber array includes a fiber arrangement section and a fiber bundle section. The first end of the fiber arrangement section is coated with a light-reflecting layer, and the second end of the fiber arrangement section is connected to the photoelectric converter. The first and second neutron conversion screens are respectively bonded to both sides of the fiber arrangement section. The edges of the first neutron conversion screen and the fiber arrangement section are aligned with the edge of the second neutron conversion screen. In this embodiment, the side length A (10cm≤A≤30cm) of the sensitive area of ​​the planar neutron detector can be determined by the user according to actual needs. The planar neutron detector is used for low-energy neutron detection. When low-energy neutrons are incident on the detector, they are converted into electrical pulse signals with a certain probability. The number of output electrical pulse signals is proportional to the number of incident neutrons. The ratio of the number of output electrical pulses to the number of incident neutrons is called the detection efficiency. In order to shorten the neutron orientation measurement time, the thermal neutron detection efficiency of the planar neutron detector is generally required to be greater than 50%. The planar neutron detector has a sandwich structure, consisting of neutron conversion screens placed symmetrically on both sides, a wave-shifting fiber array placed in the middle, and photoelectric conversion devices.

[0042] In one embodiment, the side of the first neutron conversion screen and the second neutron conversion screen connected to the wave-shifting fiber array is coated with... 6 LiF / ZnS(Ag) scintillator. In this embodiment, the first and second neutron conversion screens have the same structure, consisting of a coating on a thin aluminum plate. 6 The structure is composed of LiF / ZnS(Ag) scintillators with geometric dimensions of A×A×h (where h is the thickness of the neutron conversion screen, typically less than 1 mm). The neutron conversion screens are symmetrically placed on both sides and coated with... 6 One side of the LiF / ZnS(Ag) scintillator faces the center. After low-energy neutrons enter the neutron conversion screen, there is a certain probability that they will interact with the internal neutrons. 6 Li nuclei undergo nuclear reactions, releasing alpha particles and tritium nuclei. These alpha particles and tritium nuclei deposit energy within ZnS(Ag) through ionization and excitation interactions, producing blue fluorescence.

[0043] The waveshifting fiber array consists of waveshifting fibers with a diameter of d (typically 1-2 mm), a length of S (S>A), and a quantity of N = A / d. N waveshifting fibers are arranged parallel to each other against a neutron conversion screen, forming a plane. A portion of these N fibers, of length A, forms a plane with an area of ​​A×A; this portion, the fiber arrangement section, is placed between the two neutron conversion screens, with its edges aligned with the screen edges. The SA portion of the fibers is bundled together (i.e., the fiber bundle section) and connected to the photoelectric conversion device. The waveshifting fibers absorb the blue fluorescence emitted by the neutron conversion screen and release green fluorescence, which propagates along the fibers to both ends. To improve light collection efficiency, a light-reflecting layer is coated on the fiber end face not connected to the photoelectric conversion device.

[0044] In one embodiment, the connection between each planar neutron detector and the electronics and data acquisition system includes: the photoelectric converter of each planar neutron detector being connected to the electronics and data acquisition system. In this embodiment, the photoelectric conversion device is a photomultiplier tube, and the end face of the scintillation fiber, which is converged into a bundle, is connected to the photomultiplier tube. The photomultiplier tube converts optical pulses into electrical pulse signals, which are then used as input signals to the electronics and data acquisition system. The electronics and data acquisition system is connected to the photoelectric conversion device of the planar neutron detector, amplifies and shapes the electrical pulse signals output by the detector, and records the number of electrical pulse signals output per unit time to obtain the neutron count rate, which refers to the number of electrical pulses output by the planar detector per unit time.

[0045] In one embodiment, the neutron moderator structure surrounding the polyhedral neutron detector comprises: a plurality of plate-shaped neutron moderators and a filling neutron moderator; each plate-shaped neutron moderator is fixed to the first neutron conversion screen of each planar neutron detector; the filling neutron moderator and the neutron moderators enclose the polyhedral neutron detector into a polyhedral structure. In this embodiment, using a neutron moderator structure to enclose the polyhedral neutron detector can improve the detection accuracy and efficiency of the neutron source orientation.

[0046] In one embodiment, the dark box is made of opaque material and is installed on the outside of the moderator structure. In this embodiment, the dark box is made of opaque aluminum and is fixed to the outside of the moderator to prevent external natural light from entering the detector and to provide physical protection for the detector and the moderator.

[0047] In one specific embodiment, the neutron source orientation measurement device includes six planar neutron detectors, a neutron moderator structure, electronics and data acquisition systems, and a dark box. For example... Figure 3The schematic diagram of the hexahedral neutron detector shown depicts six planar neutron detectors connected together, forming a hexahedral cavity. Each planar neutron detector includes a first neutron conversion screen, a wave-shifting fiber array, a photoelectric converter, and a second neutron conversion screen. The wave-shifting fiber array includes a fiber arrangement section and a fiber bundle section. The first and second neutron conversion screens are respectively bonded to both sides of the fiber arrangement section, and the fiber bundle section is connected to the photoelectric converter. The edges of the first neutron conversion screen and the fiber arrangement section are aligned with the edge of the second neutron conversion screen. The neutron moderator structure includes six plate-shaped neutron moderators, six first columnar neutron moderators, six second columnar neutron moderators, and eight cubic neutron moderators. Each plate-shaped neutron moderator includes a neutron incident surface and a neutron exit surface. The plate-shaped neutron moderators are connected to the first neutron conversion screen, with their edges aligned. The planes containing the neutron incident surfaces of each plate-shaped neutron moderator intersect to form a hexahedral structure. One vertex of each of the eight cube-shaped neutron moderators is a vertex of the hexahedral structure. The edge length of each of the eight cube-shaped neutron moderators is the sum of the thicknesses of the plate-shaped neutron moderators, the first neutron conversion screen, the fiber optic arrangement, and the second neutron conversion screen. The bottom surface of each of the first columnar neutron moderators is connected to the face of the cube-shaped neutron moderators, and the side surface of each columnar neutron moderator is connected to the fiber optic bundle. The bottom surface of each of the second columnar neutron moderators is connected to the face of the cube-shaped neutron moderators, and the side surface of each columnar neutron moderator is connected to the plane containing the plate-shaped neutron moderators and the side surface of the planar neutron detector. In this embodiment, the hexahedral neutron detector can determine the direction of the neutron source within a 4π solid angle, and the dodecahedral neutron detector can also measure the neutron source orientation. The specific measuring devices and methods will not be described in detail here.

[0048] In this embodiment, as Figure 4 The schematic diagram shown illustrates the structure of a plate-shaped neutron moderator. The side length of the sensitive region of the planar neutron detector is A, the geometric dimensions of the neutron conversion screen are A×A×h, and the geometric dimensions of the plate-shaped neutron moderator are A×A×H, where H is the thickness of the moderator, typically taken as 1cm≤H≤6cm. The plate-shaped neutron moderator is placed on the outside of each planar neutron detector, with its edges aligned with the edges of the planar neutron detectors. Figure 5 The schematic diagram of the first columnar neutron moderator shown is illustrated. The first columnar neutron moderator is made of the same material as the plate-shaped neutron moderator, with geometric dimensions of A×H×(H+d+2×h). It is placed on the six edges of a hexahedron composed of six planar neutron detectors, where the A×H×(h+d) hollow portion is the fiber optic array lead-out slot of the planar neutron detector. Figure 6The diagram shows the structure of the second columnar neutron moderator. The second columnar neutron moderator is made of the same material as the plate-shaped neutron moderator, with geometric dimensions of A×(H+d+2×h)×(H+d+2×h), and is placed on the other six edges of a hexahedron composed of six planar neutron detectors. Figure 7 The schematic diagram of the cubic neutron moderator shown is as follows. The cubic neutron moderator is made of the same material as the plate-shaped neutron moderator and has geometric dimensions of (H+d+2×h)×(H+d+2×h)×(H+d+2×h). It is placed on the eight corners of a hexahedron composed of six planar neutron detectors.

[0049] The aforementioned neutron source orientation measurement device can be used to measure the orientation of a neutron source. The usage method is explained using a hexahedral neutron detector as an example:

[0050] S1, select or customize a neutron conversion screen of appropriate specifications according to experimental needs.

[0051] S2. Determine the number of optical fibers based on the size of the neutron conversion screen and the diameter of the wave-shifting fiber.

[0052] S3 consists of a layer of wave-shifting optical fibers tightly arranged between two neutron conversion screens and fixed with optical adhesive. Three edges of the fiber array are aligned with the edges of the neutron conversion screens, while the other end is left with a certain length and converges into a single fiber bundle.

[0053] S4. Based on the size of the end face of the converged fiber bundle, determine the matching photomultiplier tube model and couple the end face of the fiber bundle to the photomultiplier tube.

[0054] S5. Repeat S1-S4 to complete the fabrication of six planar neutron detectors.

[0055] S6 connects the photoelectric conversion device to the electronics and data acquisition system, enabling the measurement of the count rate of six planar neutron detectors via computer.

[0056] S7 consists of a plate-shaped neutron moderator, a first columnar neutron moderator, a second columnar neutron moderator, and a cube-shaped neutron moderator, all customized to the dimensions of a planar neutron detector, and assembled with the planar neutron detector using glue or screws.

[0057] S8, according to the maximum size of the assembled detection device, a custom aluminum box is installed on the outermost side to achieve light protection and physical protection for the detector.

[0058] S9. Compile Monte Carlo method simulation program and establish 1:1 model of neutron orientation measurement device.

[0059] S10, simulates and calculates the neutron count rate and its relative ratio of the six planar neutron detectors when the neutron source is at different distances from the device and in different orientations.

[0060] S11. Establish a machine learning model, using typical algorithms such as the nearest neighbor algorithm or neural network algorithm, and use the simulation results from step 10 as input parameters for pattern training and testing to determine the model parameters.

[0061] S12, place the device in the neutron radiation field, turn it on and operate it for a period of time to obtain the counts of each planar neutron detector.

[0062] S13, calculate the relative ratio of the counts on each plane, and use it as the input variable for the machine learning program to obtain the location of the neutron source.

[0063] In one embodiment, such as Figure 8 As shown, a method for measuring the orientation of a neutron source is provided, including:

[0064] Step 802: The neutron source to be tested releases fast neutrons.

[0065] Step 804: The fast neutrons released by the neutron source under test are received through the neutron moderator structure, and the energy of the fast neutrons is dissipated to allow the low-energy neutrons to pass through.

[0066] Step 806: The low-energy neutrons are converted into electrical pulse signals with the corresponding detection efficiency by a polyhedral neutron detector.

[0067] Step 808: The neutron count rate is obtained by the electronics and data acquisition system based on the number of electrical pulse signals output per unit time. The relative ratio of the neutron count rates between each planar neutron detector is obtained based on the neutron count rate. The relative ratio is input into the pre-trained orientation acquisition model to obtain the orientation of the neutron source to be tested.

[0068] In one embodiment, the step of training the orientation acquisition model includes: simulating a neutron source orientation measurement device, using the neutron source orientation measurement device as a reference center, simulating and calculating the relative ratio of neutron count rates among multiple planar neutron detectors at different distances and angles to obtain training samples; and using the training samples to train a pre-constructed orientation acquisition model so that when the orientation acquisition model is input with the relative ratio of neutron count rates among multiple planar neutron detectors, it outputs the distance and angle of the neutron source under test relative to the neutron source orientation measurement device.

[0069] In one embodiment, the polyhedral neutron detector converts low-energy neutrons into electrical pulse signals with a corresponding detection efficiency, including: low-energy neutrons interacting with signals on a first neutron conversion screen and a second neutron conversion screen. 6Li nuclei undergo nuclear reactions and release alpha particles and tritium nuclei; the alpha particles and tritium nuclei deposit energy and produce blue fluorescence in ZnS(Ag) on ​​the first and second neutron conversion screens through ionization and excitation interactions; the wave-shifting fiber array absorbs the blue fluorescence and releases green fluorescence, which propagates to the photoelectric converter, which converts the light pulses of green fluorescence into electrical pulse signals.

[0070] In one specific embodiment, the effective area of ​​the planar neutron detector in this invention has a side length of 10 cm and a moderating volume thickness of 6 cm. It is placed on the central horizontal plane (z=0 plane) at different distances (100cm-200cm) and different angles (0°-90°) from the center point of the measuring device. 252 Cf neutron sources, such as Figure 1 As shown, the five special symbols on the ring formed by the dashed lines represent the positions of the neutron sources, and x1, y1, z1, x2, y2, and z2 represent the six planar neutron detectors. Through simulation calculations, the count rates of each plane of the detectors were obtained, and it was found that the ratio of the output count rates of each planar detector changes significantly with the angle, such as... Figure 9 As shown. When the angle remains fixed at 30°, changing the distance between the radiation source and the center of the detection device results in a relatively stable output count rate ratio among the planar detectors, such as... Figure 10 As shown, data simulated under different distances and angles were used as the training and testing sets in a 7:3 ratio to establish a neural network model. The test set showed that the device's angular resolution for neutron source orientation measurement was better than 2°.

[0071] It should be understood that, although Figure 8 The steps in the flowchart are shown sequentially as indicated by the arrows, but these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order in which these steps are executed, and they can be performed in other orders. Figure 8 At least some of the steps in the process may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be executed in turn or alternately with other steps or at least some of the sub-steps or stages of other steps.

[0072] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0073] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this invention should be determined by the appended claims.

Claims

1. A neutron source azimuth measurement device, characterized by, The device comprises: a neutron source to be tested, a polyhedral neutron detector, a neutron moderator structure, and an electronic and data acquisition system; the neutron moderator structure is wrapped outside the polyhedral neutron detector, for receiving fast neutrons released by the neutron source to be tested, and losing energy of the fast neutrons to pass out low-energy neutrons; the polyhedral neutron detector is connected by a plurality of planar neutron detectors, each of the planar neutron detectors is connected with the electronic and data acquisition system; the planar neutron detector is used to convert the low-energy neutrons into electrical pulse signals with corresponding detection efficiency; the electronic and data acquisition system comprises a ratio calculation module and an orientation acquisition module; the ratio calculation module obtains a neutron count rate according to the number of electrical pulse signals output per unit time, and obtains a relative ratio of neutron count rates between each planar neutron detector according to the neutron count rate; the orientation acquisition module is used to input the relative ratio into a pre-trained orientation acquisition model to obtain the orientation of the neutron source to be tested.

2. The apparatus of claim 1, wherein, The neutron moderator structure adopts a low-atomic-number element material.

3. The apparatus of claim 1, wherein, The planar neutron detector comprises a first neutron conversion screen, a wave-shift optical fiber array, a photoelectric converter, and a second neutron conversion screen; The wave-shift optical fiber array comprises an optical fiber arrangement part and an optical fiber bundle part, a first end of the optical fiber arrangement part is coated with a light reflection layer, and a second end of the optical fiber arrangement part is connected with the photoelectric converter; The first neutron conversion screen and the second neutron conversion screen are respectively adhered on both sides of the optical fiber arrangement part; The edge of the first neutron conversion screen and the edge of the optical fiber arrangement part are aligned with the edge of the second neutron conversion screen.

4. The apparatus of claim 3, wherein, The first and second neutron conversion screens are coated on the side connected to the wave shifting fiber array with 6 LiF / ZnS(Ag) scintillator.

5. The apparatus of claim 3, wherein, Each of the planar neutron detectors is connected with the electronic and data acquisition system, comprising: The photoelectric converter of each of the planar neutron detectors is connected with the electronic and data acquisition system.

6. The apparatus of claim 3, wherein, The neutron moderator structure wrapped outside the polyhedral neutron detector comprises: The neutron moderator structure comprises a plurality of plate-shaped neutron moderators and a filling neutron moderator; each of the plate-shaped neutron moderators is fixed on the first neutron conversion screen of each of the planar neutron detectors; the filling neutron moderator and the neutron moderators wrap the polyhedral neutron detector into a polyhedral structure.

7. The apparatus of claim 1, wherein, The device further comprises a dark box made of light-proof material and installed outside the moderator structure.

8. A method of azimuthal measurement of a neutron source using the device according to any one of claims 1 to 7, characterized in that, The method comprises: releasing fast neutrons by the neutron source to be tested; receiving the fast neutrons released by the neutron source to be tested through the neutron moderator structure, and losing energy of the fast neutrons to pass out low-energy neutrons; converting the low-energy neutrons into electrical pulse signals with corresponding detection efficiency through the polyhedral neutron detector; obtaining a neutron count rate according to the number of electrical pulse signals output per unit time through the electronic and data acquisition system, obtaining a relative ratio of neutron count rates between each planar neutron detector according to the neutron count rate, and inputting the relative ratio into a pre-trained orientation acquisition model to obtain the orientation of the neutron source to be tested.

9. The method of claim 8, wherein, The step of training the orientation acquisition model comprises: The neutron source azimuth measurement device is simulated, and the relative ratio of neutron count rates between multiple planar neutron detectors is simulated and calculated when the neutron source is at different distances and different angles, taking the neutron source azimuth measurement device as a reference center, to obtain training samples; The azimuth acquisition model is trained by using the training samples, so that the azimuth acquisition model outputs the angle of the to-be-measured neutron source relative to the neutron source azimuth measurement device when the relative ratio of neutron count rates between multiple planar neutron detectors is input.

10. The method of claim 8, wherein, The polyhedral neutron detector converts the low-energy neutrons into electric pulse signals at a corresponding detection efficiency, including: The low-energy neutrons are converted on the first and second neutron conversion screens 6 The Li nuclei undergo a nuclear reaction and release an alpha particle and a tritium nucleus; Alpha particles and tritium nuclei deposit energy and generate blue fluorescence in ZnS(Ag) on the first neutron conversion screen and the second neutron conversion screen through ionization and excitation interaction modes; The blue fluorescence is absorbed by the wave shift fiber array and green fluorescence is released and propagated to the photoelectric converter, and the photoelectric converter converts the green fluorescence light pulse into an electric pulse signal.

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