Detector, passive neutron source imaging system and method

Abstract

The present disclosure provides a detector, a passive neutron source imaging system and method. Wherein the detector can be applied to passive neutron source imaging, including a plurality of detection unit modules, each detection unit module including a plurality of scintillation crystal units, wherein the plurality of scintillation crystal units include N absorber units and M moderator units. By integrating the neutron deposition energy of each absorber unit in the N absorber units and integrating the neutron deposition energy of each moderator unit in the M moderator units, the total value of the deposition energy of the plurality of scintillation crystal units is obtained to determine the neutron deposition energy distribution of each detection unit module, thereby realizing the positioning imaging of the neutron source in 4π range, not only having high detection efficiency for neutron rays, but also having a wide neutron energy detection range, and realizing the accurate positioning of the radioactive source in 4π space.

Description

Technical Field

[0001] This disclosure relates to the field of nuclear technology, specifically to a detector, a passive neutron source imaging system, and a method. Background Technology

[0002] The management of neutron radioactive materials is an important requirement for national security. Neutron source localization imaging technology has important applications in combating nuclear smuggling and supervising the transportation of special composite radioactive materials. However, passive neutron source imaging is very difficult in terms of both physical processes and technical means. Among them, the main difficulties in physical processes are: (1) The detection and passive imaging process of neutrons is full of challenges. The interaction laws of thermal neutrons and fast neutrons are very different. Thermal neutrons have low energy and are easier to deposit in the detector, but it is difficult to accurately locate the radioactive source. Fast neutrons are difficult to block, have strong penetrating power, require thick shielding, and the detection device is bulky and large in size. (2) The mechanism of neutron interaction with matter is also very complex. Neutrons can undergo elastic scattering, inelastic scattering, capture reactions, various reactions that release charged particles, and multi-particle reactions with matter. In these processes, complex secondary particles are generated, producing a lot of secondary energy. This also leads to a complex spatial distribution of neutron interaction points and deposition locations, which poses a challenge to the design of detectors. Summary of the Invention

[0003] (a) Technical problems to be solved

[0004] To address at least one of the aforementioned technical problems in the prior art, this disclosure provides a detector, a passive neutron source imaging system, and a method that offer optimal overall performance, maximize the utilization of incident neutron event information, and are portable.

[0005] (II) Technical Solution

[0006] One aspect of this disclosure provides a detector for passive neutron source imaging, comprising multiple detection unit modules for receiving incident neutron events. Each detection unit module includes multiple scintillation crystal units arranged in a three-dimensional array. Each scintillation crystal unit includes N absorber units and M moderator units. The N absorber units undergo absorption reactions upon neutron incidence, depositing incident neutron energy. The M moderator units are arranged alongside the absorber units to moderate neutron incidence, also depositing incident neutron energy. The total deposited energy of the multiple scintillation crystal units is obtained by integrating the neutron deposited energy of each absorber unit in the N units and the neutron deposited energy of each moderator unit in the M units. This total energy is used to determine the neutron deposited energy distribution of each detection unit module, thereby achieving localization imaging of the neutron source within a 4π range.

[0007] According to embodiments of this disclosure, the neutron absorption cross section of each of the N absorber units is higher than that of each of the M moderator units; the neutron scattering cross section of each of the M moderator units is higher than that of each of the N absorber units. Wherein, N ≥ 3, and / or M ≥ 3, and N and M are positive integers.

[0008] According to embodiments of this disclosure, the three-dimensional array structure satisfies the following: incident thermal neutrons can be directly absorbed by an absorber close to the incident direction without signal loss; incident fast neutrons can be absorbed by the absorber after being moderated by a moderator without escaping; wherein, for neutrons of different energies, the depth of the interaction position after incident on the three-dimensional array structure is different and has different energy and count distributions, realizing 4π panoramic detection of incident neutrons in different directions, and the incident neutrons that react at different positions react with the corresponding moderator units or absorber units, ensuring that the neutron deposition energy distribution is positively correlated with the incident neutron direction information.

[0009] According to embodiments of this disclosure, the total volume of N absorber units is A; the total volume of M moderator units is B; the total volume of the three-dimensional array structure is C, and C≥A+B; wherein A and B satisfy: k=B / A, and 1 / 9≤k≤9; or A, B and C satisfy: r=A / C, s=B / C, and 0.1≤r<1, 0.1≤s<1.

[0010] According to embodiments of this disclosure, each of the plurality of scintillation crystal units is a long cylindrical structure, and the height h of the long cylindrical structure of each scintillation crystal unit satisfies the following relationship with its length l or width d: h ≥ 3l, and / or h ≥ 3d.

[0011] According to embodiments of this disclosure, multiple detection unit modules are arranged to form a three-dimensional array structure; wherein, at least two of the multiple detection unit modules have multiple scintillation crystal units arranged in different orientations in spatial position.

[0012] Another aspect of this disclosure provides a passive neutron source imaging system, comprising the aforementioned detector, multiple photoelectric converters, an energy detection module, and a distribution reconstruction module. The multiple photoelectric converters are coupled to each of the multiple scintillation crystal units in the detector to achieve single-channel readout of the deposition energy and neutron number of incident neutrons within each scintillation crystal unit. The energy detection module integrates the deposition energy of incident neutrons in each scintillation crystal unit using each photoelectric converter to obtain the total deposition energy of a single scintillation crystal unit over a period of time, and filters the number of energy channel responses after neutron incidence to determine the neutron deposition energy distribution and neutron number distribution in the detector. The distribution reconstruction module reconstructs the distribution information of the incident neutron radiation source based on the neutron deposition energy distribution and neutron number distribution to achieve passive neutron source imaging.

[0013] According to embodiments of the present disclosure, each of the plurality of scintillation crystal units is coupled to one of the plurality of photoelectric converters; and / or at least two of the plurality of scintillation crystal units are coupled to one of the plurality of photoelectric converters.

[0014] Another aspect of this disclosure provides a passive neutron source imaging method applied to the aforementioned passive neutron source imaging system, comprising: single-channel readout of the deposition energy and number of incident neutrons in each of the multiple scintillation crystal units of the detector; integrating the deposition energy of incident neutrons in each scintillation crystal unit to obtain the total deposition energy of a single scintillation crystal unit over a period of time, and filtering the number of energy channel responses after neutron incidence to determine the neutron deposition energy distribution and neutron number distribution in the detector; and reconstructing the distribution information of the incident neutron radiation source based on the neutron deposition energy distribution and neutron number distribution to achieve passive neutron source imaging.

[0015] According to embodiments of this disclosure, reconstructing the distribution information of the incident neutron radiation source based on the neutron deposition energy distribution and neutron number distribution includes: reconstructing the distribution information x of the incident neutron radiation source in the neutron source space based on the neutron deposition energy distribution E and neutron number distribution y in each of the multiple detection unit modules in the detector, and a preset overall system energy transfer matrix P and overall system counting transfer matrix Q, wherein the following conditions are met:

[0016]

[0017] According to embodiments of this disclosure, the deposition energy of incident neutrons in each scintillation crystal unit is integrated to obtain the total deposition energy of a single scintillation crystal unit over a period of time, and the number of energy channel responses after neutron incidence is screened to eliminate incident neutron events with fewer than 3 deposition energy channel responses.

[0018] (III) Beneficial Effects

[0019] This disclosure provides a detector, a passive neutron source imaging system, and a method. The detector can be applied to passive neutron source imaging. Compared to traditional neutron counting and other imaging schemes, this disclosure, through the unique imaging physical structure design and energy integration method of the detector, not only achieves high detection efficiency for neutron rays but also possesses a wide neutron energy detection range. The energy distribution information it generates can enhance the relevant directional information carried by the incident neutron rays, and neutron rays can be detected within a 4π solid angle field of view. This enables convenient and accurate positioning of the radiation source in 4π space, while also achieving miniaturization, integration, and portability of the neutron detection and imaging function. Attached Figure Description

[0020] Figure 1 The diagram schematically illustrates a three-dimensional array structure of a plurality of detection unit modules of a detector according to an embodiment of the present disclosure;

[0021] Figure 2 A schematic diagram illustrating a three-dimensional array structure of a plurality of detection unit modules of a detector according to another embodiment of the present disclosure is shown.

[0022] Figure 3 A schematic diagram illustrating a three-dimensional array structure of a plurality of detection unit modules of a detector according to yet another embodiment of the present disclosure is shown.

[0023] Figure 4 This schematically illustrates a three-dimensional array structure diagram of a detection unit module of a detector according to an embodiment of the present disclosure;

[0024] Figure 5 A schematic diagram illustrating a three-dimensional array structure of a detector unit module according to another embodiment of the present disclosure is shown.

[0025] Figure 6 The diagram schematically illustrates a three-dimensional array structure of a detection unit module of a detector according to yet another embodiment of the present disclosure;

[0026] Figure 7 This schematically illustrates a three-dimensional array structure diagram of a detection unit module of a detector according to another embodiment of the present disclosure;

[0027] Figure 8This schematically illustrates a three-dimensional array structure diagram of a detection unit module of a detector according to another embodiment of the present disclosure;

[0028] Figure 9 The diagram schematically illustrates the relationship between neutron deposition energy distribution and incident neutron direction information (as indicated by the arrows) according to embodiments of the present disclosure.

[0029] Figure 10 A schematic diagram illustrating the structure of a scintillation crystal unit according to an embodiment of the present disclosure is shown.

[0030] Figure 11 A schematic diagram illustrating the composition of a passive neutron source imaging system according to an embodiment of the present disclosure is shown; and

[0031] Figure 12 A flowchart illustrating a passive neutron source imaging method according to an embodiment of the present disclosure is shown schematically. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0033] It should be noted that implementations not illustrated or described in the accompanying drawings or the main text of the specification are all forms known to those skilled in the art and are not described in detail. Furthermore, the definitions of the various elements and methods described above are not limited to the specific structures, shapes, or methods mentioned in the embodiments, and those skilled in the art can easily modify or substitute them.

[0034] It should also be noted that the directional terms mentioned in the embodiments, such as "up," "down," "front," "back," "left," and "right," are only for reference to the directions in the accompanying drawings and are not intended to limit the scope of protection of this disclosure. Throughout the drawings, the same elements are represented by the same or similar reference numerals. Conventional structures or constructions will be omitted where they may cause confusion in understanding this disclosure.

[0035] Furthermore, the shapes and dimensions of the components in the figures do not reflect actual size and proportion, but are merely illustrative of embodiments of this disclosure. Additionally, any reference signs placed between parentheses in the claims should not be construed as limiting the scope of the claims.

[0036] Furthermore, the word "comprising" does not exclude the presence of elements or steps not listed in the claims. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.

[0037] The use of ordinal numbers such as "first," "second," "third," etc., in the specification and claims to modify the corresponding elements does not in itself imply that the element has any ordinal number, nor does it represent the order of one element with another element or the order of manufacturing methods. The use of these ordinal numbers is only to enable a named element to be clearly distinguished from another element with the same name.

[0038] Those skilled in the art will understand that modules in the device of the embodiments can be adaptively changed and placed in one or more devices different from that embodiment. Modules, units, or components in the embodiments can be combined into a single module, unit, or component, and further, they can be divided into multiple sub-modules, sub-units, or sub-components. Except where at least some of such features and / or processes or units are mutually exclusive, any combination can be used to combine all features disclosed in this specification (including the accompanying claims, abstract, and drawings) and all processes or units of any method or device so disclosed. Unless expressly stated otherwise, each feature disclosed in this specification (including the accompanying claims, abstract, and drawings) may be replaced by an alternative feature that serves the same, equivalent, or similar purpose. Furthermore, in the unit claims enumerating several means, several of these means may be embodied by the same hardware item.

[0039] Similarly, it should be understood that, in order to simplify this disclosure and aid in understanding one or more of the various aspects of the disclosure, in the foregoing description of exemplary embodiments of the disclosure, various features of the disclosure are sometimes grouped together in a single embodiment, figure, or description thereof. However, this approach to disclosure should not be construed as reflecting an intention that the claimed disclosure requires more features than are expressly recited in each claim. Rather, as reflected in the following claims, the aspects of the disclosure consist of fewer than all features of a single foregoing disclosed embodiment. Therefore, the claims following the detailed description are hereby expressly incorporated into that detailed description, wherein each claim itself is a separate embodiment of the disclosure.

[0040] Existing passive neutron detection technologies are mainly divided into two categories: (1) absorption collimation type, such as coded plate detectors and Li-6 cage traps. However, the neutron energy range of this type of detection technology is large and shielding is difficult. Imaging devices that slow down and capture Li-6 cage traps in different directions are often bulky and have low resolution. The detectors are also bulky and have low detection efficiency. On the other hand, coded plate imaging devices that use coded plate collimation projection have high resolution but often have limited field of view. (2) multi-level scattering type, similar to Compton cameras. However, this type of detection technology also needs to detect multiple secondary events at the same time, resulting in low detection efficiency and limited field of view. The types of action mechanisms that contribute to imaging are very limited, and other action processes generate interference events, etc.

[0041] Clearly, the existing passive neutron detection techniques described above employ multiple detector units to simultaneously detect the same incident particle event. Since these detector units are not independent, they require complex processing logic and electronic overhead. Furthermore, the detection process necessitates registration and identification of information from multiple detector units for the same incident event, calculating the incident neutron deposition on the detector through position weighting. This approach fails to effectively utilize events whose effects occur across multiple detector units, significantly reducing detection efficiency.

[0042] To address this issue, existing passive neutron detection technologies also offer an array-type neutron counting detector to solve the aforementioned problem of reduced detection efficiency. However, for this array-type neutron counting detector, the reaction between neutrons and the scintillator array differs significantly from the reaction between gamma photons and the scintillator array. Therefore, during neutron incidence, it is practically difficult to determine the detection unit to which the incident neutron belongs. Furthermore, whether counting only the position of the neutron's first interaction or using Anger weighting of the energy signals from all scintillator arrays to determine the counting position, the relevant discrimination in practice is extremely difficult and prone to losing much incident direction information, resulting in extremely poor positioning and imaging accuracy. This directly leads to the extreme difficulty in implementing an array-type neutron counting detector and its low physical feasibility.

[0043] To address at least one of the aforementioned technical problems in the prior art, this disclosure provides a detector, a passive neutron source imaging system, and a method that offer optimal overall performance, maximize the utilization of neutron detection events, and are portable.

[0044] like Figures 1-10As shown, one aspect of this disclosure provides a detector for passive neutron source imaging, comprising multiple detection unit modules for receiving incident neutron events, wherein each of the multiple detection unit modules comprises multiple scintillation crystal units, the multiple scintillation crystal units being arranged in a three-dimensional array structure, wherein the multiple scintillation crystal units comprise N absorber units and M moderator units.

[0045] N absorber units are used to perform absorption reactions when neutrons are incident, thereby achieving the deposition of incident neutron energy;

[0046] M moderator units and absorber units are arranged in a way that allows for a moderation reaction to occur when neutrons are incident, thereby achieving the deposition of incident neutron energy.

[0047] Specifically, by integrating the neutron deposition energy of each of the N absorber units and the neutron deposition energy of each of the M moderator units, the total deposition energy of multiple scintillation crystal units is obtained, which is used to determine the neutron deposition energy distribution of each detection unit module, thereby achieving localization imaging of the neutron source within a 4π range.

[0048] like Figure 1 As shown, the detector 100 includes detection unit modules 101, 102, 103, and 104. These four detection unit modules 101, 102, 103, and 104 are arranged in pairs on a plane to form a three-dimensional array structure. Correspondingly, as... Figure 2 As shown, the detector 200 includes detection unit modules 201, 202, 203, 204, 205 (not shown), 206, 207, and 208. Four detection unit modules 201, 202, 203, and 204 are arranged in pairs on a plane to form a three-dimensional array structure. These modules are then correspondingly arranged in the vertical direction with another three-dimensional array structure formed by the pairwise arrangement of four other detection unit modules 205 (not shown), 206, 207, and 208 on a plane, forming a three-dimensional array structure of eight detection unit modules. Wherein, as... Figure 1 and Figure 2 In the three-dimensional array structure composed of the detection unit modules shown, gaps can exist between adjacent detection unit modules. To reduce the overall size of the detector, such as... Figure 3 As shown, the detector 300 includes detection unit modules 301, 302, and 303, wherein the three detection unit modules 301, 302, and 303 are arranged closely together along a straight line on a plane to form a three-dimensional array structure, wherein there are no gaps between the detection unit modules.

[0049] Each detector module consists of two types of detector units: absorber units and moderator units. The absorber units have a high neutron absorption cross section, while the moderator units have a high neutron scattering cross section. These units are arranged in an N+M three-dimensional array structure, enabling imaging of the neutron source within a 4π range. After neutron incidence, absorption reactions may occur in the absorber units or moderation reactions in the moderator units. These reactions can deposit energy on the corresponding detector units. The total energy deposited on the detector units of a given absorber unit or moderator unit over a given period can be used as the energy response information for that detector.

[0050] Each detector unit module in this embodiment can be arranged in a specific N+M configuration using a certain absorber unit and a certain moderator unit. This specific arrangement requires that, when a neutron is incident in different directions, the distance a detector unit travels through the moderator material of the moderator unit varies significantly. For example... Figure 4 As shown, N=32 absorber units 402 and M=32 modulator units 401 are arranged alternately to form an 8×8 detector unit module 400 three-dimensional array structure. In practice, N or M can also be 6, 7, 8, 9, 10, 11, 12, etc., without specific limitations. For each detector unit, both the modulator unit 402 and the absorber unit 401 can be set with a height of 10mm-30mm and a length and / or width of 1mm-4mm, thereby enabling miniaturized imaging equipment.

[0051] Each side of each detector unit can be coupled with a photomultiplier or a photoelectric converter. The electronic system integrates and sums the waveforms of all energy deposition events within a set time period to obtain the total energy deposition value within each detector unit during that set time period. The energy deposition distribution corresponding to this total energy deposition value is then used to image the neutron source distribution in a two-dimensional plane.

[0052] When a neutron is incident on a scintillation crystal unit of a detector module, physical processes such as scattering or trapping occur within the scintillation crystal unit. Various particles deposit energy within the scintillation crystal unit, exciting it to generate scintillation photons. This scintillation crystal unit can be coupled to a photoelectric converter (such as a silicon photomultiplier tube (SiPM) array) at one end. The photoelectric converter converts the optical signal into an electrical signal, which is then further processed by the back-end electronics system. The other end of the scintillation crystal unit can be coupled to a reflective film, allowing the generated photoelectrons to be collected by the photoelectric converter as much as possible. The energy signals read from each scintillation crystal unit by the photoelectric converter are summed after a period of time to obtain the energy deposition value of a single scintillation crystal unit. Performing the same operation on each scintillation crystal unit yields the energy deposition distribution of the corresponding detector module, and thus the energy deposition distribution of the entire detector. The coupled photoelectric converter converts the scintillation photons into electrical signals, which are then read out and input to the ADC module and FPGA in the back-end readout electronics for digital processing. The output shows the energy, time, waveform, baseline, and other information of the event collected by each photoelectric converter.

[0053] Therefore, the above embodiments of this disclosure actually provide a detector based on energy deposition. When a neutron beam is incident on a scintillation crystal unit, it interacts with matter through elastic scattering, inelastic scattering, and radiative trapping. Macroscopically, the neutron beam exhibits attenuation, and the attenuated neutrons deposit energy in the scintillation crystal unit. Thus, the energy deposition distribution of the incident neutrons in the scintillation array can be obtained. If the energy deposition distribution in the scintillation array is related to the incident direction, the energy deposition response can be obtained using mutually arranged (e.g., staggered) individual detector unit modules and electronic systems. Furthermore, the incident direction can be deduced from the incident direction-related energy deposition distribution, enabling neutron localization imaging.

[0054] Therefore, compared with traditional imaging schemes such as neutron counting, the embodiments of this disclosure can utilize the unique imaging physical structure design and energy integration method of the detector to not only achieve high detection efficiency for neutron rays, but also have a wide neutron energy detection range. The energy distribution information it generates can enhance the relevant directional information carried by the incident neutron rays, and neutron rays can be detected in a 4π solid angle field of view. This enables convenient and accurate positioning of the radiation source in a 4π spatial range, and also achieves miniaturization, integration, and portability of the neutron detection imaging function.

[0055] Each absorber unit and moderator unit in each detector unit module can also have other arrangements, such as Figure 4The absorber units 402 and moderator units 401 of the detection unit module 400 shown are arranged alternately along the x-axis to form a three-dimensional array structure with the height along the z-axis; as shown Figure 6 The absorber units 602 and moderator units 601 of the detection unit module 600 shown are arranged alternately along the z-axis to form a three-dimensional array structure with the height direction along the x-axis; as shown Figure 7 The absorber units 702 and moderator units 701 of the detector unit module 700 shown are arranged alternately along the z-axis to form a three-dimensional array structure with the height direction along the y-axis. Clearly, the scintillation crystal units of the detector unit module in this embodiment of the present disclosure have a very flexible arrangement.

[0056] In addition, such as Figure 5 The detection unit module 500 shown can also be a three-dimensional array structure composed of two absorber units 502 arranged side by side in the x-axis direction and an adjacent moderator unit 501 arranged in an alternating manner. In other words, the arrangement of each absorber unit and moderator unit in the detection unit module of this embodiment is also flexible.

[0057] like Figures 1-10 As shown, according to an embodiment of the present disclosure, the neutron absorption cross section of each of the N absorber units is higher than that of each of the M moderator units; and the neutron scattering cross section of each of the M moderator units is higher than that of each of the N absorber units.

[0058] In summary, the absorber unit has a higher neutron absorption cross section, and the absorber unit can be a GAGG crystal, CLYC crystal, CLLBC crystal, or other scintillators doped with B or containing Li. Furthermore, the moderator unit has a higher neutron scattering cross section, and the moderator unit can be various organic scintillators such as ECPS crystals.

[0059] like Figures 1-10 As shown, according to embodiments of this disclosure, N≥3, and / or M≥3, where N and M are positive integers. Preferably, 3≤N≤30, and / or 3≤M≤30, where N and M are positive integers, are used as the corresponding number of absorber units and moderator units. This allows for optimal energy deposition of incident neutron events while maintaining a relatively fixed size for each scintillation crystal unit.

[0060] like Figure 8As shown, the detector unit module 800 contains 20 × 20 = 400 scintillation crystal units, of which N = 200 absorber units and M = 200 moderator units, forming a very large-scale detector unit module. Therefore, the number of scintillation crystal units in the array of each detector unit module is generally not specifically limited. However, to ensure that neutrons incident on the array from any direction can generate a response in at least three detector units, it is preferable to select the above-mentioned N+M three-dimensional array structure that satisfies that N is greater than or equal to 3 absorber units and / or M is greater than or equal to 3 moderator units.

[0061] It should be noted that the absorber unit and the moderator unit are made of different materials. Each detection unit module must ensure that both absorber and moderator units exist simultaneously to ensure that the incident neutron direction information carried by the corresponding energy response is more accurate.

[0062] like Figures 1-10 As shown, according to the embodiments of this disclosure, the three-dimensional array structure satisfies the following: incident thermal neutrons can be directly absorbed by the absorber close to the incident direction without losing the signal; incident fast neutrons can be absorbed by the absorber after being slowed down by the moderator without escaping.

[0063] Among them, for neutrons of different energies, the depth of the interaction position after incident on the three-dimensional array structure is different and the energy and count distribution are different, realizing 4π panoramic detection of incident neutrons from different directions. The incident neutrons that react at different positions react with the corresponding moderator or absorber units, ensuring that the neutron deposition energy distribution is positively correlated with the incident neutron direction information.

[0064] The design principles for the material and quantity of absorber and moderator units in each detection unit module are: thermal neutrons can be directly absorbed by absorbers close to the incident direction without losing the signal; fast neutrons can be absorbed by absorbers after being moderated by sufficient moderators without escaping.

[0065] For neutrons of different energies, the depth of their interaction position after incident on the detector varies, and they also have different distributions. In this case, a detector unit module with alternating arrangements of moderator and absorber units can be used, so that neutrons incident from different directions (4π panoramic detection) at different positions can react with the moderator and absorber units.

[0066] like Figure 9 The results of the energy deposition distribution shown indicate that the ECPS crystal of the moderator unit has a weak attenuation coefficient for gamma rays, while the GAGG crystal of the absorber unit has a strong attenuation coefficient for neutron rays. By selecting an alternating arrangement, not only does the energy deposition distribution have directional information, but the detection unit module can also be used directly to image the neutron radiation source.

[0067] Furthermore, by rotating the detector module around its center as the origin of the coordinate axis, and by rotating its orientation around the x, y, and z axes, the response at three locations can be measured. The measured response (count or energy) allows for imaging of the neutron source distribution in 4π space. The scintillation crystal units of the absorber and moderator units are arranged alternately, ensuring a suitable response to neutron rays incident from any direction. This results in a positive correlation between the deposited energy intensity distribution measured by the detector module and the incident neutron direction information.

[0068] According to an embodiment of this disclosure, the total volume of N absorber units is A; the total volume of M moderator units is B; wherein A and B satisfy: k = B / A, and 1 / 9 ≤ k ≤ 9.

[0069] According to embodiments of this disclosure, the total volume of N absorber units is A; the total volume of M moderator units is B; the total volume of the three-dimensional array structure is C, and C ≥ A + B; wherein A, B, and C satisfy: r = A / C, s = B / C, and 0.1 ≤ r < 1, 0.1 ≤ s < 1. The total volume C of the three-dimensional array structure, without considering the gaps between scintillation crystal units, satisfies: C = A + B.

[0070] In the three-dimensional array structure of the scintillation crystal unit of a certain detection unit module, to ensure imaging effect, a suitable ratio of moderator units and absorber units can be selected. Specifically, the ratio k of the total volume B of the moderator units to the total volume A of the absorber units in a single detection unit module can be set to between 1:9 and 9:1, ensuring that neutrons incident from any direction can produce a reasonable response on both the absorber and the moderator.

[0071] In addition, the volume of any scintillation crystal unit in the detection unit module accounts for no less than 10% of the total volume of the entire three-dimensional array structure. This ensures that neutrons incident from any direction can produce reasonable responses in both the absorber and the moderator, rather than only producing responses in the moderator or absorber units when the neutron source is located in certain directions, thus avoiding affecting imaging accuracy.

[0072] like Figure 10 As shown, according to an embodiment of the present disclosure, each of the plurality of scintillation crystal units is a long cylindrical structure, and the height h of the long cylindrical structure of each scintillation crystal unit satisfies the following relationship with its length l or width d: h ≥ 3l, and / or h ≥ 3d.

[0073] The elongated cylindrical structure of each scintillation crystal unit can be selected from triangular prisms, cylinders, rectangular prisms (i.e., cuboids), and cubes, among others, with a cuboid shape being preferred. The length, width, and height dimensions can be adjusted according to the specific application. In this embodiment, the higher the energy of the neutron source to be measured, the larger the crystal size tends to be. Each scintillation crystal unit is generally selected as a rectangular prism with a height h greater than or equal to three times its length l or three times its width d, to facilitate array arrangement. Of course, other geometric shapes with at least one optical coupling end face and capable of being arranged in the aforementioned three-dimensional array structure can also be selected.

[0074] like Figure 8 As shown, a specific 20×20 arrangement is formed by alternating absorber units and moderator units. The number of absorber units N satisfies N=200, and the number of moderator units M satisfies M=200. For each scintillation crystal unit, a height h of 30mm-100mm and a length 1 or width d of 4mm-20mm can be selected, thereby effectively increasing detection efficiency, making it suitable for higher-energy neutron detection, and further improving imaging performance. Specifically, as... Figure 4 As shown, a three-dimensional array structure of 8×8 scintillation crystal units is used. In each detection unit module, GAGG crystals as absorber units 402 and ECPS crystals as moderator units 401 are arranged alternately. The dimensions of each scintillation crystal unit are 3mm×3.26mm×20mm, and the overall dimensions of the detection unit module are 25mm×25mm×20mm.

[0075] like Figures 1-3 As shown, according to an embodiment of this disclosure, multiple detection unit modules are arranged to form a three-dimensional array structure.

[0076] Among them, at least two of the multiple detection unit modules have multiple scintillation crystal units arranged in different orientations in spatial location.

[0077] like Figures 1-3 As shown, multiple detection unit modules can be combined and arranged together to form a detector. The detection unit modules can be combined in different directions to form detectors with different three-dimensional spatial distributions. To ensure the corresponding energy response effect, it is necessary to ensure that at least two detection unit modules in the detector have different orientations at different spatial positions.

[0078] Specifically, such as Figure 1 As shown, in detector 100, the height direction of detection unit module 103 is oriented towards the y-axis, and the height direction of detection unit module 104 is oriented towards the z-axis, meaning that at least two detection unit modules have multiple scintillation crystal units arranged in different orientations in spatial positions; furthermore, as Figure 2 As shown, in detector 200, the height direction of detection unit module 203 is oriented towards the x-axis, the height direction of detection unit module 204 is oriented towards the y-axis, and the height direction of detection unit module 208 is oriented towards the z-axis. Furthermore, as... Figure 3 The detector 300 shown has a detection unit module 301 with its height direction facing the z-axis, a detection unit module 302 with its height direction facing the x-axis, and a detection unit module 303 with its height direction facing the y-axis. All of these satisfy the condition that at least two detection unit modules have multiple scintillation crystal units arranged in different orientations in spatial positions.

[0079] Furthermore, such as Figures 1-3 As shown, multiple detector unit modules with staggered arrays are arranged in different directions and in different forms. While ensuring feasibility, the arrangement of each detector unit module is made as symmetrical as possible, or detector unit modules in symmetrical positions in the overall design are oriented in different directions. The orientation of each detector unit module can be changed, and it is guaranteed that at least three detector unit modules have different orientations.

[0080] Therefore, each detection unit module has at least one side coupled with a photomultiplier and a photoelectric converter. The electronic system integrates and sums the waveforms of all deposited energy events within a set time period to obtain the total energy deposition value within each detection unit module over a certain time. This energy deposition distribution of each detection unit module can then be used to image the neutron source distribution in three-dimensional space. For example... Figure 2 As shown, the three-dimensional detector 200 consists of eight detection unit modules 201-208. Each detection unit module is used by at least two other detection unit modules, ensuring the detector can image radiation sources in different two-dimensional directions. By rotating the detector's three-dimensional array around the X, Y, and Z axes, it can be arranged and stacked in different directions, enhancing its ability to image neutron sources in different directions and enabling imaging of neutron source distribution in 4π space.

[0081] It should be noted that, as mentioned above Figures 1-3 In the detector formed by combining and arranging multiple detection unit modules as shown, the photoelectric converter coupled to each detection unit module can be coupled to the exposed side of each detection unit module, thereby minimizing the influence of the photoelectric converter components on the overall combination method.

[0082] Based on the above analysis, it can be seen that the embodiments of this disclosure provide a detector for use in passive neutron imaging. The special structural composition of the core detector, combined with the selection and design principles of each scintillation crystal detection unit, the readout method and judgment logic of the detection signal, and the core reconstruction method, can provide a corresponding reliable, stable, and more accurate imaging effect.

[0083] Therefore, by designing detection unit modules with different combinations of materials and quantities of absorber and moderator units, and by obtaining the deposition energy distribution information from the energy detection module, this disclosure does not actually need to determine how many neutrons the deposition energy information comes from, nor does it care whether several scatterings occurred in between. It only needs to collect and accumulate all energy signals. The circuit readout and discrimination logic is simple, the implementation cost is lower, and the deposition energy distribution in each detection unit module is related to the incident direction. The distribution information of the incident neutron radiation source can be obtained by reconstructing it using the reconstruction algorithm module.

[0084] Clearly, this disclosure aims to provide a passive neutron source imaging scheme in which neutrons are incident from a specific direction, and over a period of time, the neutrons deposit energy in each detector element during a blocking and slowing process. Integrating the deposited energy in each detector element yields the total deposited energy of a single detector element over a set time period. Performing this operation on all detector elements yields the deposited energy distribution within each detector element, which is related to the incident direction. This distribution can then be used to reconstruct the distribution of radioactive sources in space using a specific reconstruction algorithm.

[0085] Therefore, the detector described in this embodiment not only has high detection efficiency for neutron rays, but also has a wide neutron energy detection range. The special imaging physical structure design and the energy distribution generated by the unique integration method indirectly enhance the relevant directional information carried by the incident neutron rays. Furthermore, it can detect neutron rays in a 4π solid angle field of view, accurately and conveniently locate the radiation source in 4π space, and has the characteristics of small-scale integration for neutron detection and imaging.

[0086] like Figure 11 As shown, another aspect of this disclosure provides a passive neutron source imaging system 1100, which includes the aforementioned detector 1110, multiple photoelectric converters 1120, an energy detection module 1130, and a distribution reconstruction module 1140.

[0087] Multiple photoelectric converters 1120 are coupled to each of the multiple scintillation crystal units in the detector 1110 to enable single-channel readout of the deposition energy and number of incident neutrons in each scintillation crystal unit;

[0088] The energy detection module 1130 integrates the deposition energy of the incident neutron in each scintillation crystal unit using each photoelectric converter to obtain the total deposition energy of a single scintillation crystal unit over a period of time, and filters the number of energy channel responses after neutron incident, thereby determining the neutron deposition energy distribution and neutron number distribution in the detector 1110.

[0089] The distribution reconstruction module 1140 is used to reconstruct the distribution information of the incident neutron radiation source based on the neutron deposition energy distribution and neutron number distribution, so as to realize passive neutron source imaging.

[0090] The detector can be composed of at least one detector unit module. Each detector unit module can be composed of several scintillation crystal units made of absorbers and moderators, which are arranged in an alternating manner to form a three-dimensional array structure. Each scintillation crystal unit is coupled to a photoelectric converter at least at one end, which can read out the deposition energy and number of incident neutrons in each scintillation crystal unit in a single channel.

[0091] The energy detection module can integrate the energy of incident neutrons deposited in each scintillation crystal unit, and statistically obtain the total energy of deposition in a single scintillation crystal unit over a set period of time, thereby obtaining the neutron deposition energy distribution in the detection unit module.

[0092] The reconstruction algorithm module can reconstruct the distribution information of the incident neutron radiation source based on the neutron deposition energy distribution and neutron number distribution in the detection unit module.

[0093] The scintillation crystal units of the absorber and moderator materials are arranged alternately, so that the intensity of the deposited energy distribution obtained in the detection unit module is positively correlated with the incident neutron direction information, thereby confirming the spatial distribution of the neutron radiation source, displaying its image, and confirming its location.

[0094] Since neutrons may generate secondary particles such as recoil protons, electrons, and various heavy ions in a scintillator, it is difficult to distinguish the energy signals of these particles. If the energy information is read from the two opposite ends of the scintillator to determine the depth of the interaction location, the depth of the interaction may be inaccurate due to the different attenuation patterns of the energy signals of different secondary particles. Therefore, a single-end readout design of the scintillator unit is selected to further improve the accuracy of the determination of the neutron interaction depth, thereby improving the imaging accuracy.

[0095] Therefore, by designing detection unit modules with different combinations of absorber and moderator materials and quantities, and combining them with energy integration readout methods, the imaging system disclosed above not only has high detection efficiency for neutron rays, but also has a wide neutron energy detection range. The special imaging physical structure design and the energy distribution generated by the unique integration method indirectly enhance the relevant directional information carried by the incident neutron rays. While accurately locating the neutron radiation source, it also has the characteristics of small-scale integrated neutron imaging.

[0096] It should be noted that, as mentioned above Figures 1-3 In the detector formed by combining and arranging multiple detection unit modules as shown, the photoelectric converter coupled to each other can be coupled to the exposed side, so as to minimize the influence of the photoelectric converter components on the overall combination method.

[0097] According to embodiments of the present disclosure, each of the plurality of scintillation crystal units is coupled to one of the plurality of photoelectric converters; and / or at least two of the plurality of scintillation crystal units are coupled to one of the plurality of photoelectric converters.

[0098] Each of the multiple scintillation crystal units is coupled to a photoelectric converter at least at one end, allowing for single-channel readout of the deposited energy and neutron count within each scintillation crystal unit. Alternatively, multiple scintillation crystal units can be coupled to a single photoelectric converter, thereby reducing system complexity and cost.

[0099] like Figure 12 As shown, another aspect of this disclosure provides a passive neutron source imaging method applied to the aforementioned passive neutron source imaging system, which includes operations S1201-S1203.

[0100] In operation S1201, the deposition energy and number of incident neutrons in each of the multiple scintillation crystal units of the detector are read out in a single channel.

[0101] In operation S1202, the deposition energy of the incident neutron in each scintillation crystal unit is integrated to obtain the total deposition energy of a single scintillation crystal unit over a period of time, and the number of energy channel responses after neutron incidence is screened to determine the neutron deposition energy distribution and neutron number distribution in the detector.

[0102] In operation S1203, the distribution information of the incident neutron radiation source is reconstructed based on the neutron deposition energy distribution and neutron number distribution to achieve passive neutron source imaging.

[0103] like Figure 12As shown, according to an embodiment of this disclosure, in operation S1203, reconstructing the distribution information of the incident neutron radiation source based on the neutron deposition energy distribution and neutron number distribution includes:

[0104] Based on the neutron deposition energy distribution E and neutron number distribution y in each of the multiple detection unit modules in the detector, and the preset overall system energy transfer matrix P and overall system counting transfer matrix Q, the distribution information x of the incident neutron radiation source in the neutron source space is reconstructed, where:

[0105]

[0106] Based on the neutron deposition energy distribution E and neutron number distribution y in the detection unit module, and P and Q obtained during the pre-calibration process, the distribution information x of the incident neutron radiation source in space can be solved using any iterative or non-iterative reconstruction algorithm. Here, P and Q are the system transfer matrices representing the detector counting response and energy response processes of each scintillation crystal unit array in the imaging system described above, respectively.

[0107] like Figure 12 As shown, according to an embodiment of this disclosure, in operation S1202, the deposition energy of the incident neutron in each scintillation crystal unit is integrated to obtain the total deposition energy of a single scintillation crystal unit over a period of time. The number of energy channel responses after neutron incidence is then filtered, and incident neutron events with fewer than three deposition energy channel responses are removed. For events with a single neutron incidence, the detection accuracy of neutron events can be improved by removing incident neutron events with fewer than three deposition energy channel responses.

[0108] By selecting appropriate sizes and numbers of moderator and absorber units, neutrons incident on the array from any direction can generate a response (i.e., a count value or an energy deposition value) in at least three detector units, thus allowing the direction of the neutron source to be deduced from the response distribution.

[0109] First, the average energy of the neutron source to be imaged and the neutron flux level of the application scenario can be determined to estimate the detector size and number.

[0110] Next, the ratio of detector count to energy response is estimated as a design reference standard. For a neutron with an average energy of E and a fluence rate of φ incident in a certain direction, assume that the area of ​​the detector receiving neutron irradiation along that direction is S, and that there are n detector elements arranged along that direction, including n1 moderator elements and n2 absorber elements. For convenience, further assume that the length of each detector element along that direction is d.

[0111] At this point, assume that the count value and energy deposition value per unit time in each detector unit are y, respectively. i and E i And 1≤i≤n.

[0112] Therefore, the energy deposition value in each detector element can be recursively obtained using the following formula:

[0113]

[0114]

[0115] ...

[0116]

[0117] ...

[0118]

[0119] Therefore, the count value in each detector unit can be obtained recursively in the following way:

[0120]

[0121]

[0122] ...

[0123] in, A i Let be the average mass number of the material in the i-th detector unit. Let be the average macroscopic cross section of the neutron reaction at the average energy of the neutron reaching this detector unit.

[0124] At this point, if E is estimated to be... n There is a gap compared to E1, or y n The difference from y1 indicates that the energy response and counting response on the detector unit are related to the incident direction, which can then be used to infer the neutron incident direction. For example, the following two conditions can be set; if either condition is met, the size setting is considered appropriate:

[0125]

[0126]

[0127] Furthermore, by repeating the above process along various spatial directions, the appropriate detector element size (d), the number of detector arrays (n), and the total detector size (n*d) for each direction can be finally determined. For example, for common neutron radiation sources such as Am-Be and Cf-252, the outer dimension of the detector in any direction can be selected to be no less than 20 mm to obtain better imaging results.

[0128] In addition, the readout module of the detector is designed. The detector array should couple multiple optoelectronic device units so that the detector response can be output in a reasonable form. During coupling, optical guides can be used to transmit signals. It is required that the count value on each detector unit can be output independently to the data processing module to improve the response characteristics of the output data to the neutron source direction. An alternative approach is to couple multiple detector modules to a single optoelectronic device unit, reducing system complexity and cost.

[0129] The photoelectric converter coupled to the scintillation crystal unit can output the energy deposition amount, or it can output the count and energy deposition amount simultaneously, thereby further improving the response characteristics of the output data to the direction of the neutron source.

[0130] The reconstruction algorithm module can reconstruct the distribution information of the incident neutron radiation source based on the neutron deposition energy distribution in the detection unit module. The specific steps are as follows:

[0131] In the imaging system, assuming it consists of the aforementioned three-dimensional array structure composed of M detector unit modules, each detector unit module is arranged and combined in a specific way, and the detection process is represented by the system transfer matrix:

[0132] y i =P i x(1≤i≤M) (10)

[0133] in, The i-th detection unit module consists of m... i An array of scintillation crystal units, y ik This represents the energy deposited per unit time by the k-th scintillation crystal unit in the i-th detection unit module; x = [x1, x2, ..., xk]. n ]′ represents the distribution of neutron radiation sources in space, denoted as a vector representing the activity distribution of radiation sources at each angle in space, and n represents the number of angles in the field of view. P i For the system transfer matrix of the neutron detector, P i The size is m i ×n.

[0134] By combining the M expressions, we can obtain:

[0135]

[0136] y = Px (12)

[0137] Where y = [y1, y2, ..., y] M ]′ is a column vector representing the energy values ​​deposited in all detector unit modules. P=[P1,P2,...,P M ]′ represents the overall system transmission matrix.

[0138] Using the y obtained from the above formula (12) obtained by measurement and the P obtained in the prior calibration process, the spatial distribution x can be solved.

[0139] Assume that the response X = [X1, X2, ..., X] of the detector elements is acquired and arranged. N After ]′, among which, X i For a specific detector element, the count or energy value is given, where N represents the total number of output detector element energies and count values. The following iterative framework can be used for calculation:

[0140]

[0141] Where x = [x1, x2, ..., x] n ]′ represents the spatial distribution of the radioactive source, expressed as a vector representing the radioactive source activity distribution at each angle in space, where n represents the number of angles in the field of view. P is the system transmission matrix of the detector, with a size of N×n. θ ij The value in the i-th row and j-th column of matrix P represents the response of the j-th detector unit to the i-th image unit. The superscript n indicates the iteration number.

[0142] Preferably, when performing reconstruction, the energy deposition amount of each incident event and each cell can be input into the reconstruction algorithm to further improve the reconstruction and localization effect.

[0143] Similarly, assuming it consists of M detection unit modules as described above, and each detection unit module is arranged and combined in a specific way, the detection process can be represented by the system transmission matrix:

[0144] E i =Q i x(1≤i≤M) (14)

[0145] In the above formula, The i-th detector array consists of m i An array of detector units, E ik Let x represent the energy deposition value detected by the k-th detector element in the i-th detector array per unit time. x = [x1, x2, ..., xk] n]′ represents the distribution of the radioactive source in space, denoted as a vector representing the distribution of radioactive source activity at each angle in space, and n represents the number of angles in the field of view. Q i For the system transfer matrix of the detector, Q i The size is m i ×n.

[0146] By combining the M expressions, we can obtain:

[0147]

[0148] E = Qx (16)

[0149] Where E = [E1, E2, ..., E M ]′ is a column vector representing the count values ​​of all detector elements in the array. P=[Q1,Q2,...,Q M ]′ represents the overall system transmission matrix.

[0150] Combining the above equation with the system transfer matrix from weight 6, we get:

[0151]

[0152] Using the measured values ​​y and E, and the values ​​P and Q obtained during the pre-calibration process, the spatial distribution x can be solved using any iterative or non-iterative reconstruction algorithm. Using the accumulated energy deposition value as input data for the reconstruction algorithm yields better imaging results than algorithms that simply use counting, while significantly reducing the counting complexity.

[0153] At this point, the following formula can be used:

[0154] E = Qx (18)

[0155] Using E obtained from measurements and Q obtained during the prior calibration process, the spatial distribution x can be solved using any iterative or non-iterative reconstruction algorithm.

[0156] Therefore, by designing detection unit modules with different combinations of materials and quantities of absorber and moderator units, and by obtaining the deposition energy distribution information from the energy detection module, this disclosure does not actually need to determine how many neutrons the deposition energy information comes from, nor does it care whether several scatterings occurred in between. It only needs to collect and accumulate all energy signals. The circuit readout and discrimination logic is simple, the implementation cost is lower, and the deposition energy distribution in each detection unit module is related to the incident direction. The distribution information of the incident neutron radiation source can be obtained by reconstructing it using the reconstruction algorithm module.

[0157] Clearly, this disclosure aims to provide a passive neutron source imaging scheme in which neutrons are incident from a specific direction, and over a period of time, the neutrons deposit energy in each detector element during a blocking and slowing process. Integrating the deposited energy in each detector element yields the total deposited energy of a single detector element over a set time period. Performing this operation on all detector elements yields the deposited energy distribution within each detector element, which is related to the incident direction. This distribution can then be used to reconstruct the distribution of radioactive sources in space using a specific reconstruction algorithm.

[0158] Therefore, the detector described in this embodiment not only has high detection efficiency for neutron rays, but also has a wide neutron energy detection range. The special imaging physical structure design and the energy distribution generated by the unique integration method indirectly enhance the relevant directional information carried by the incident neutron rays. Furthermore, it can detect neutron rays in a 4π solid angle field of view, accurately and conveniently locate the radiation source in 4π space, and has the characteristics of small-scale integration for neutron detection and imaging.

[0159] The embodiments of this disclosure have now been described in detail with reference to the accompanying drawings.

[0160] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A detector used for imaging a passive neutron source, wherein, It includes multiple detection unit modules for receiving incident neutron events, wherein each of the multiple detection unit modules includes: Multiple scintillation crystal units are arranged in a three-dimensional array structure, wherein the multiple scintillation crystal units include: N absorber units are used to perform an absorption reaction when neutrons are incident, thereby achieving the deposition of the incident neutron energy; M moderator units are arranged and distributed with the absorber units to perform a moderation reaction when neutrons are incident, thereby achieving the deposition of the incident neutron energy; Specifically, by integrating the neutron deposition energy of each of the N absorber units and the neutron deposition energy of each of the M moderator units, the total deposition energy of the multiple scintillation crystal units is obtained, which is used to determine the neutron deposition energy distribution of each detection unit module, thereby achieving localization and imaging of the neutron source within a 4π range.

2. The detector according to claim 1, wherein, The neutron absorption cross section of each of the N absorber units is higher than that of each of the M moderator units; the neutron scattering cross section of each of the M moderator units is higher than that of each of the N absorber units; wherein, N≥3, and / or M≥3, and N and M are positive integers.

3. The detector according to claim 1, wherein, The three-dimensional array structure satisfies: Incident thermal neutrons can be directly absorbed by an absorber close to the incident direction without losing signal; The incident fast neutrons can be absorbed by the absorber after being slowed down by the moderator and will not escape. In this system, neutrons of different energies have different depths of action after being incident on the three-dimensional array structure, and have different energy and count distributions. This enables 4π panoramic detection with different incident directions. The incident neutrons that react at different locations react with the corresponding moderator or absorber units, ensuring that the neutron deposition energy distribution is positively correlated with the incident neutron direction information.

4. The detector according to claim 1, wherein, The total volume of the N absorber units is A; The total volume of the M moderating bodies is B; The total volume of the three-dimensional array structure is C, and C≥A+B; Where A and B satisfy: k = B / A, and 1 / 9 ≤ k ≤ 9; or A, B and C satisfy: r = A / C, s = B / C, and 0.1 ≤ r < 1, 0.1 ≤ s < 1.

5. The detector according to claim 1, wherein, Each of the plurality of scintillation crystal units is a long cylindrical structure, and the height h of the long cylindrical structure of each scintillation crystal unit satisfies the following relationship with its length l or width d: h ≥ 3l, and / or h ≥ 3d.

6. The detector according to claim 1, wherein, The multiple detection unit modules are arranged in a three-dimensional array structure. Among the plurality of detection unit modules, at least two detection unit modules have multiple scintillation crystal units arranged in different orientations in spatial location.

7. A passive neutron source imaging system, wherein, include: The detector according to any one of claims 1-6, Multiple photoelectric converters are coupled to each of the multiple scintillation crystal units of the detector to enable single-channel readout of the deposition energy and number of incident neutrons in each scintillation crystal unit; The energy detection module integrates the deposition energy of the incident neutrons in each scintillation crystal unit using each photoelectric converter to obtain the total deposition energy of a single scintillation crystal unit over a period of time, and filters the number of energy channel responses after neutron incidence, thereby determining the neutron deposition energy distribution and neutron number distribution in the detector. The distribution reconstruction module reconstructs the distribution information of the incident neutron radiation source based on the neutron deposition energy distribution and neutron number distribution, so as to realize the passive neutron source imaging.

8. The passive neutron source imaging system according to claim 7, wherein, Each of the plurality of scintillation crystal units is coupled to one of the plurality of photoelectric converters; and / or At least two of the plurality of scintillation crystal units are coupled to one of the plurality of photoelectric converters.

9. A passive neutron source imaging method, applied to the passive neutron source imaging system described in claim 7 or 8, wherein, include: The single-channel readout of the deposition energy and number of incident neutrons in each of the plurality of scintillation crystal units of the detector according to any one of claims 1-6; The deposition energy of the incident neutrons in each scintillation crystal unit is integrated to obtain the total deposition energy of a single scintillation crystal unit over a period of time. The number of energy channel responses after neutron incidence is then filtered to determine the neutron deposition energy distribution and neutron number distribution in the detector. Based on the neutron deposition energy distribution and neutron number distribution, the distribution information of the incident neutron radiation source is reconstructed to achieve the passive neutron source imaging.

10. The passive neutron source imaging method according to claim 9, wherein, The process of reconstructing the distribution information of the incident neutron radiation source based on the neutron deposition energy distribution and neutron number distribution includes: Based on the neutron deposition energy distribution E and neutron number distribution y in each of the multiple detection unit modules in the detector, and the preset overall system energy transfer matrix P and the overall system counting transfer matrix Q, the distribution information x of the incident neutron radiation source in the neutron source space is reconstructed, where:

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