Neutron Generation Device and Substance Composition Analysis System

Abstract

A neutron generating device and a substance composition analysis system. The neutron generating device includes: an electron accelerator (10) configured to emit an electron beam (eb); a photon generating target (20) configured to interact with the electron beam (eb) to generate bremsstrahlung photons (bp); a neutron generating target (30) configured to interact with the bremsstrahlung photons (bp) to generate neutrons (n); and a neutron beam outlet (60) adjacently arranged with the neutron generating target (30) and configured to output a neutron beam along a second direction (dr2). Wherein, the neutron generating target (30) is spaced apart from the photon generating target (20) along a first direction (dr1), the first direction (dr1) is the emission direction of the electron beam (eb), the second direction (dr2) is parallel to the extending direction of the neutron beam outlet (60), and the first included angle (α1) between the second direction (dr2) and the first direction (dr1) is a right angle or an obtuse angle. The present disclosure can reduce the interference of accompanying photons during neutron output.

Description

Technical Field

[0001] The present invention relates to the field of radiation technology, and particularly to a neutron generating device and a substance composition analysis system. Background Art

[0002] When neutrons react with different elements, they can emit characteristic energy photons. Based on the different reaction mechanisms and cross-sections between the atomic nuclei of specific elements and neutrons, it is possible to detect whether specific substances such as explosives and drugs are present by detecting the characteristic γ-rays of the object to be detected, analyze the elemental composition and content of the object to be detected by analyzing the γ-energy spectrum generated by the object in the detector, or determine the elemental composition of the substance by analyzing the attenuation of neutrons before and after penetrating the substance. Neutron technology is widely used in fields such as explosives and drug inspections in the security inspection industry, and on-line industrial material elemental composition detection.

[0003] In related technologies of photon neutron sources based on electron accelerators, a photon conversion target is usually arranged inside a neutron generating target. High-energy electrons bombard the photon conversion target to generate bremsstrahlung photons, and the bremsstrahlung photons bombard the neutron generating target to generate neutrons. Summary of the Invention

[0004] It has been found through research that since such photon neutron generating devices need to utilize the interaction between electrons and the target nuclei of photon conversion targets to generate bremsstrahlung photons, and then utilize the interaction between the bremsstrahlung photons and the target nuclei of neutron generating targets to generate neutrons. The reaction cross-section for the generation of neutrons by the interaction of bremsstrahlung photons with target nuclei is small, and it faces competition from photoatomic reactions whose cross-section is much larger than this process. Since the photon conversion target is arranged inside the neutron generating target, neutron generation and photon generation basically occur in the same or adjacent spaces, and it is not easy to shield and separate the photons accompanying the neutrons. Therefore, the neutrons emitted by the photon neutron generating device are often accompanied by strong bremsstrahlung photons and secondary photons generated by photoatomic reactions. The intensities of these bremsstrahlung photons and secondary photons are more than 3 orders of magnitude higher than the neutron emission intensity, resulting in the characteristic γ-rays generated after neutron activation of the material to be measured being submerged or giving a saturation signal to the neutron imaging detector and generating dead time, thus limiting the application of such photon neutron generating devices.

[0005] In view of this, embodiments of the present disclosure provide a neutron generating device and a substance composition analysis system, which can reduce the interference of accompanying photons during neutron output.

[0006] In one aspect of the present disclosure, a neutron generating device is provided, including:

[0007] An electron accelerator configured to emit an electron beam;

[0008] A photon generating target configured to interact with the electron beam to generate bremsstrahlung photons;

[0009] A neutron generation target configured to interact with bremsstrahlung photons to generate neutrons; and

[0010] A neutron beam outlet, adjacently arranged to the neutron generation target, configured to output the neutron beam generated by the neutron generation target in a second direction;

[0011] Wherein, the neutron generation target is arranged at an interval from the photon generation target in a first direction, the first direction is the emission direction of the electron beam, the second direction is parallel to the extending direction of the neutron beam outlet, and the first included angle between the second direction and the first direction is a right angle or an obtuse angle.

[0012] In some embodiments, the surface of the neutron generation target adjacent to the photon generation target includes a first photon receiving area, and the first photon receiving area is configured to receive the bremsstrahlung photons within a preset angle θ expanded relative to the first direction generated by the photon generation target. The ratio of the bremsstrahlung photons received by the first photon receiving area to the total number of bremsstrahlung photons generated by the photon generation target is a preset percentage.

[0013] In some embodiments, the preset angle θ corresponding to the preset percentage is less than or equal to the preset angle θ corresponding to 80% 80 and greater than or equal to the preset angle θ corresponding to 60%. 60 .

[0014] In some embodiments, the preset angle θ corresponding to the preset percentage 80% 80 satisfies the following formula:

[0015] ;

[0016] Wherein, θ 80 is the preset angle θ required to collect 80% of the total number of bremsstrahlung photons (bp) generated by the photon generation target (20), in degrees; E e is the energy of the electron beam (eb) emitted by the electron accelerator (10) for bombarding the photon generation target (20), in MeV.

[0017] In some embodiments, E e takes a value of 7 to 30 MeV.

[0018] In some embodiments, the preset angle θ corresponding to the preset percentage 60% 60 satisfies the following formula:

[0019] ;

[0020] Wherein, θ 60The preset angle θ, in degrees, required to collect 60% of the total number of bremsstrahlung photons (bp) generated by the photon generation target (20); E e The energy of the electron beam (eb) emitted by the electron accelerator (10) for bombarding the photon generation target (20), in MeV.

[0021] In some embodiments, E e takes a value of 7 to 30 MeV.

[0022] In some embodiments, the neutron generation device further includes:

[0023] A photon shielding structure, disposed on the side of the photon generation target, configured to shield at least a portion of the bremsstrahlung photons generated by the photon generation target that expand beyond a preset angle θ range relative to the first direction.

[0024] In some embodiments, the preset angle θ corresponding to the preset percentage satisfies:

[0025] D ≥ 2d · tgθ;

[0026] wherein, D is the maximum width of the cross-section of the neutron generation target in the first direction, and d is the distance from the center of the photon generation target to the neutron generation target along the first direction.

[0027] In some embodiments, d takes a value of 2 to 10 cm.

[0028] In some embodiments, the neutron generation device further includes:

[0029] A neutron moderation structure having a receiving cavity for receiving the neutron generation target;

[0030] wherein, the photon generation target is located outside the neutron moderation structure.

[0031] In some embodiments, the neutron generation device further includes:

[0032] A photon shielding structure having a first inner cavity penetrating along the first direction, and the photon generation target is located inside the first inner cavity;

[0033] wherein, the neutron moderation structure is adjacently disposed to the photon shielding structure, and has a receiving cavity for receiving the neutron generation target and a second inner cavity, the second inner cavity is separated from the receiving cavity and communicates with the first inner cavity, and a neutron beam outlet is provided on the side wall of the neutron moderation structure.

[0034] In some embodiments, the neutron generation device further includes:

[0035] A filter element, disposed at the neutron beam outlet, configured to filter photons accompanying the neutron beam.

[0036] In some embodiments, the second included angle between the surface of the neutron generation target adjacent to the photon generation target and the plane perpendicular to the first direction is an acute angle, and the distance from the photon generation target along the first direction to the surface of the neutron generation target adjacent to the photon generation target increases gradually from the side far from the neutron beam outlet to the side adjacent to the neutron beam outlet.

[0037] In some embodiments, the photon generation target includes at least one of tantalum, tungsten, and bismuth, and the neutron generation target includes at least one of deuterium-containing materials, beryllium, uranium, and tungsten.

[0038] In one aspect of the present disclosure, a substance composition analysis system is provided, including the aforementioned neutron generation device.

[0039] According to an embodiment of the present disclosure, the electron beam emitted by the electron accelerator bombards the photon generation target to generate bremsstrahlung photons. The bremsstrahlung photons need to travel a certain distance before hitting the neutron generation target and generate neutrons through a photonuclear reaction. Compared with setting the photon generation target inside the neutron generation target, in this embodiment, the neutron generation target is spaced apart from the photon generation target along the emission direction of the electron beam, so that the generation of bremsstrahlung photons and the generation of neutrons do not occur in the same and adjacent spaces. This is beneficial for shielding and separating the unconsumed bremsstrahlung photons generated by the photon generation target and the secondary photons generated by the photoatomic reaction with respect to the neutrons generated by the photon generation target, thereby reducing the photon background accompanying the neutrons and further reducing the interference of the photons accompanying the neutron output process. And by designing the extension direction of the neutron beam outlet to be at a large angle of a right angle or an obtuse angle with the emission direction of the electron beam, the photon background intensity led out from the neutron beam outlet can be made smaller and mainly low-energy photons that are easy to filter out, which is beneficial for reducing the interference of the photons accompanying the neutron output process. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The drawings constituting a part of the specification depict embodiments of the present disclosure and, together with the specification, are used to explain the principles of the present disclosure.

[0041] Referring to the drawings, the present disclosure can be more clearly understood from the following detailed description, wherein:

[0042] Figure 1 is a schematic diagram of the cross section of the photoatomic reaction of photons with deuterium 2 H and the (γ,n) cross section;

[0043] Figure 2 is a schematic structural diagram of some embodiments of the neutron generation device according to the present disclosure;

[0044] Figure 3 is an angular distribution diagram of the scattered photons generated after the bremsstrahlung photons undergo Compton scattering with the neutron generation target;

[0045] Figure 4 It is a schematic diagram of the dimensional relationship according to some embodiments of the neutron generating device of the present disclosure;

[0046] Figure 5 It is an angular distribution diagram of high-energy bremsstrahlung photons greater than 1.67 MeV generated by electron beam currents of multiple different energies;

[0047] Figure 6 It is a schematic diagram of the preset angles respectively required for the neutron generating target to collect 60% and 80% of the total number of bremsstrahlung photons generated by the photon generating target;

[0048] Figure 7 It is a schematic diagram of the neutron generating region according to some embodiments of the neutron generating device of the present disclosure;

[0049] Figure 8 It is a photon energy spectrum diagram obtained by Monte Carlo simulation for the neutron generating device example and the comparative example of the present disclosure;

[0050] Figure 9 It is a schematic structural diagram of some embodiments of the substance composition analysis system of the present disclosure.

[0051] It should be understood that the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship. In addition, the same or similar reference numerals represent the same or similar components.

[0052] Description of reference numerals:

[0053] 10. Electron accelerator; 20. Photon generating target; 30. Neutron generating target; 40. Photon shielding structure; 50. Neutron moderation structure; 60. Neutron beam outlet; 70. Filter element; 81. Photon shielding layer; 82. Detector assembly; 83. Specimen.

[0054] eb. Electron beam current; bp. Bremsstrahlung photon; n. Neutron; dr1. First direction; dr2. Second direction; pr. First photon receiving region; α1. First included angle; α2. Second included angle. Detailed embodiments

[0055] Now, various exemplary embodiments of the present disclosure will be described in detail with reference to the drawings. The description of the exemplary embodiments is merely illustrative and in no way limits the present disclosure and its application or use. The present disclosure can be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are provided to make the present disclosure thorough and complete and to fully convey the scope of the present disclosure to those skilled in the art. It should be noted that: Unless otherwise specifically stated, the relative arrangements of components and steps, the components of materials, numerical expressions, and numerical values set forth in these embodiments should be construed as merely exemplary and not as limitations.

[0056] As used in this disclosure, terms such as "first", "second" and the like do not denote any order, quantity or importance, but are merely used to distinguish different components. Words such as "comprising" or "including" mean that the elements before such word cover the elements listed after such word, and do not exclude the possibility of also covering other elements. Terms such as "upper", "lower", "left" and "right" are only used to indicate relative positional relationships, and when the absolute position of the object being described changes, such relative positional relationships may also change accordingly.

[0057] In this disclosure, when it is described that a specific device is located between a first device and a second device, there may or may not be an intermediate device between the specific device and the first device or the second device. When it is described that a specific device is connected to other devices, the specific device may be directly connected to the other devices without an intermediate device, or may not be directly connected to the other devices but have an intermediate device.

[0058] All terms used in this disclosure (including technical terms or scientific terms) have the same meaning as understood by those of ordinary skill in the art to which this disclosure pertains, unless otherwise specifically defined. It should also be understood that terms defined in a general dictionary, such as those, should be interpreted as having a meaning consistent with their meaning in the context of the relevant art, and should not be interpreted in an idealized or overly formal sense, unless specifically defined as such herein.

[0059] Technologies, methods and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, such technologies, methods and devices should be regarded as part of the specification.

[0060] In the related art of an electron-accelerator-based photo-neutron source, a photon conversion target is usually disposed within a neutron production target, and an electron accelerator bombards the photon conversion target to generate bremsstrahlung photons, and the bremsstrahlung photons bombard the neutron production target to generate neutrons.

[0061] Through research, it is found that since such a photo-neutron generation device needs to utilize the interaction between electrons and the target nucleus of the photon conversion target to generate bremsstrahlung photons, and then utilize the interaction between the bremsstrahlung photons and the target nucleus of the neutron production target to generate neutrons. Refer to Figure 1 the schematic diagrams of the cross section of the photon and deuterium 2 H photoatomic reaction and the (γ,n) cross section shown, the reaction cross section of the bremsstrahlung photons interacting with the target nucleus to generate neutrons is small, and it faces the competition of photoatomic reactions whose cross section is much larger than this process.

[0062] Since the photon conversion target is disposed within the neutron generation target, neutron generation and photon generation basically occur within the same or adjacent spaces, and it is not easy to shield and separate the photons accompanying the neutrons. Therefore, the neutrons emitted by the photo-neutron generation device are often accompanied by strong bremsstrahlung photons and secondary photons generated by photo-atomic reactions. The intensities of these bremsstrahlung photons and secondary photons are more than three orders of magnitude higher than the neutron emission intensity, resulting in the characteristic γ-rays generated after neutron activation of the material to be measured being submerged or giving a saturation signal to the neutron imaging detector to generate dead time, thereby limiting the application of such photo-neutron generation devices.

[0063] In view of this, embodiments of the present disclosure provide a neutron generation device and a substance composition analysis system, which can reduce the interference of photons accompanying the neutron output process.

[0064] Figure 2 is a schematic structural diagram according to some embodiments of the neutron generation device of the present disclosure. Refer to Figure 2 Embodiments of the present disclosure provide a neutron generation device, including: an electron accelerator 10, a photon generation target 20, a neutron generation target 30, and a neutron beam outlet 60.

[0065] The electron accelerator 10 is configured to emit an electron beam eb. The electron accelerator 10 can accelerate the electrons emitted by a particle source such as an electron gun through an acceleration mechanism such as an acceleration tube to form an output electron beam eb. The electron accelerator 10 can adopt a medium-low energy electron accelerator, and the energy of the output electron beam can be selected from 7 to 30 MeV, such as 7 MeV, 9 MeV, 12 MeV, 15 MeV, 18 MeV, 20 MeV, 24 MeV, or 30 MeV, etc.

[0066] The photon generation target 20 is configured to interact with the electron beam eb to generate bremsstrahlung photons bp. The photon generation target 20 can generate high-energy bremsstrahlung photons such as X-rays or γ-rays under the bombardment of the electron beam eb. The photon generation target 20 can include at least one of high atomic number materials such as tantalum Ta, tungsten W, and bismuth Bi.

[0067] The neutron generation target 30 is configured to interact with the bremsstrahlung photons bp to generate neutrons n. The neutron generation target 30 can generate neutrons n under the bombardment of the bremsstrahlung photons bp. The neutron generation target 30 can include at least one of materials containing deuterium 2 H substances (such as heavy water), beryllium Be, tungsten W, and uranium U, etc.

[0068] The neutron generation target 30 is spaced apart from the photon generation target 20 along a first direction dr1, and the first direction dr1 is the emission direction of the electron beam eb. That is to say, in the first direction dr1, the neutron generation target 30 and the photon generation target 20 are not in contact and have a preset distance.

[0069] The neutron beam outlet 60 is adjacently arranged to the neutron production target 30 and is configured to output the neutron beam produced by the neutron production target 30 along the second direction dr2. The second direction dr2 is parallel to the extending direction of the neutron beam outlet 60 and forms a right angle or an obtuse angle with the first included angle α1 between the first direction dr1.

[0070] Figure 3 It is the angular distribution diagram of the scattered photons produced after the bremsstrahlung photons undergo Compton scattering with the neutron production target. As Figure 3 shown, the high-energy part of the scattered photons produced after the bremsstrahlung photons undergo Compton scattering with the neutron production target (i.e., the main part of the photoatomic reaction of high-energy photons with matter) also has forwardness. In Figure 3 , the scattered photons with relatively high energies above 1.67 MeV are mainly distributed in the acute angle region within 90° with respect to the first direction dr1, while the scattered photons with reduced energies of 1 keV, 100 keV, and 500 keV are mainly distributed in the right angle and obtuse angle ranges from 90° to 180° with respect to the first direction dr1.

[0071] In this embodiment, the electron beam eb emitted by the electron accelerator 10 bombards the photon production target 20 to generate bremsstrahlung photons bp. The bremsstrahlung photons bp need to travel a certain distance and then hit the neutron production target 30, and neutrons n are generated through the photonuclear reaction.

[0072] Compared with some related technologies in which the photon production target is arranged inside the neutron production target, in this embodiment, the neutron production target 30 is spaced apart from the photon production target 20 along the emission direction of the electron beam eb (i.e., the first direction dr1), so that the generation of bremsstrahlung photons and the generation of neutrons do not occur in the same and adjacent spaces. This is conducive to shielding and separating the unconsumed bremsstrahlung photons bp produced by the photon production target 20 and the secondary photons produced by the photoatomic reaction from the neutrons n produced by the neutron production target 30, thereby reducing the photon background accompanying the neutrons n and further reducing the interference of the accompanying photons during the output of the neutrons n. Moreover, in this embodiment, the extending direction of the neutron beam outlet 60 is designed to be led out at a large angle of 90° or more with respect to the movement direction of the bremsstrahlung photons bp (close to the emission direction of the electron beam eb), which can make the intensity of the photon background led out by the neutron beam outlet 60 smaller and mainly low-energy photons that are easy to filter, facilitating the reduction of the interference of the accompanying photons during the output of the neutrons n.

[0073] In this way, the possibility of bremsstrahlung photons bp accompanying neutrons and secondary photons drowning out the characteristic γ-rays generated after neutron activation of the material to be measured can be reduced or eliminated, or the risk that the bremsstrahlung photons bp accompanying neutrons and secondary photons give a saturation signal to the neutron imaging detector and generate dead time can be reduced, which is beneficial to expanding the application of the neutron generation device in the fields of neutron activation analysis, neutron imaging, neutron lifetime measurement, etc.

[0074] Figure 4 is a schematic diagram of the dimensional relationship according to some embodiments of the neutron generation device of the present disclosure. Refer to Figure 2 and Figure 4 , in some embodiments, the surface of the neutron generation target 30 adjacent to the photon generation target 20 includes a first photon receiving region pr, and the first photon receiving region pr is used to receive the bremsstrahlung photons bp within a preset angle range expanded relative to the first direction dr1 generated by the photon generation target 20. The ratio of the bremsstrahlung photons bp received by the first photon receiving region pr to the total number of bremsstrahlung photons bp generated by the photon generation target 20 is a preset percentage.

[0075] The surface of the neutron generation target 30 adjacent to the photon generation target 20 may only include the first photon receiving region pr, or may include both the first photon receiving region pr and other photon receiving regions, such as a second photon receiving region located outside the first photon receiving region pr.

[0076] For the definition of the first photon receiving region pr, it can be determined by its receiving the bremsstrahlung photons bp within a preset angle range expanded relative to the first direction dr1 generated by the photon generation target 20. In Figure 4 , the emission range of the bremsstrahlung photons formed by expanding a preset angle θ to the left and right sides relative to the first direction dr1 can be seen, and the region formed by the intersection of this emission range and the surface of the neutron generation target 30 adjacent to the photon generation target 20 is the first photon receiving region pr.

[0077] Figure 5 is the angular distribution diagram of high-energy bremsstrahlung photons greater than 1.67 MeV generated by multiple electron beam currents with different energies. Refer to Figure 5 , the bremsstrahlung photons bp generated after bombarding the photon generation target 20 with high-energy electrons have strong forward impact and are mainly distributed within a small angle range around the emission direction of the electron beam current eb.

[0078] Figure 5 shows five curves, corresponding to electron beam currents eb with energies of 7 MeV, 9 MeV, 15 MeV, 20 MeV, and 30 MeV respectively, and different-shaped points on the curves are used to distinguish each curve. These electron beam currents eb are in Figure 5The relative number (per 5°) of bremsstrahlung photons bp with energies greater than 1.67 MeV (i.e., the photonuclear reaction threshold when the material of the neutron production target 30 is beryllium Be) produced is shown at various expansion angles (hereinafter sometimes simply referred to as the divergence angle) with respect to the emission direction of the electron beam eb. It can be seen that a relatively large number of high-energy bremsstrahlung photons bp are concentrated within the range of 80° to the left.

[0079] In this way, the fluence rate loss of the high-energy bremsstrahlung photons bp that can undergo photonuclear reactions with the neutron production target 30 received by the first photon reception region pr is small at the neutron production target 30, and a higher neutron yield can be obtained.

[0080] In some embodiments, the preset angle θ corresponding to a preset percentage is less than or equal to the preset angle θ corresponding to 80% 80 , and greater than or equal to the preset angle θ corresponding to 60% 60 .

[0081] Through the structural design of the neutron generation device, the preset angle θ is made to satisfy θ 60 ≤θ≤θ 80 , so that the percentage of the total number of bremsstrahlung photons generated by the photon production target 20 collected can meet the divergence angle requirements of less than or equal to 80% and greater than or equal to 60%. In this way, both a higher neutron yield and a relatively compact structure can be achieved.

[0082] Figure 6 is a schematic diagram of the preset angles respectively required for 60% and 80% of the total number of bremsstrahlung photons generated by the photon production target collected by the neutron production target. Figure 6 Four curves are shown, corresponding to the divergence angles (i.e., the preset angle θ) required for the neutron production target 30 to collect bremsstrahlung photons with energies above two values (1.67 MeV, 2.23 MeV) and two percentages (60%, 80%) of the total number of photons at different electron beam energies.

[0083] As Figure 6 shown, for a neutron generation device with an electron beam eb energy of 9 MeV, when the divergence angle between the neutron production target 30 and the photon production target 20 is 75°, 80% of the bremsstrahlung photons with energies above 2.23 MeV (i.e., the photonuclear reaction threshold when the material of the neutron production target 30 is deuterium 2 H) can be collected.

[0084] Referring to these curves, for the energy E of the electron beam eb in multiple sets of historical data of the test eIt is fitted with a preset angle θ to represent the numerical relationship between the two by the fitted polynomial. For different materials of the neutron production target 30, the corresponding photonuclear reaction thresholds may be different. For example, the photonuclear reaction thresholds of beryllium and deuterium are 1.67 MeV and 2.23 MeV respectively. Accordingly, the fitting formula for the neutron production target 30 to collect photons above 1.67 MeV accounting for 60% of the total number of photons is different from the fitting formula for the neutron production target 30 to collect photons above 2.23 MeV accounting for 60% of the total number of photons, and the fitting formula for the neutron production target 30 to collect photons above 1.67 MeV accounting for 80% of the total number of photons is different from the fitting formula for the neutron production target 30 to collect photons above 2.23 MeV accounting for 80% of the total number of photons.

[0085] Taking the material of tungsten W for the photon production target 20 as an example, for the preset angle θ corresponding to the preset percentage of 80% 80 the following formula can be satisfied:

[0086] ;

[0087] where θ 80 is the preset angle θ required to collect 80% of the total number of bremsstrahlung photons bp generated by the photon production target 20, and E e is the energy of the electron beam eb emitted by the electron accelerator 10 for bombarding the photon production target 20. Here, E e can take values from 7 to 30 MeV.

[0088] For the preset angle θ corresponding to the preset percentage of 60% 60 the following formula can be satisfied:

[0089] ;

[0090] where θ 60 is the preset angle θ required to collect 60% of the total number of bremsstrahlung photons bp generated by the photon production target 20, and E e is the energy of the electron beam eb emitted by the electron accelerator 10 for bombarding the photon production target 20. Here, E e can take values from 7 to 30 MeV.

[0091] Referring to Figure 6 , as the energy of the electron beam increases, the forwardness of the bremsstrahlung photons generated by it will become more significant, and the opening angle required to collect the bremsstrahlung photons will further decrease. Based on this, corresponding structural designs can be carried out according to the opening angle.

[0092] Referring to Figure 4, in some embodiments, the preset angle θ corresponding to the preset percentage satisfies: D≥2d·tgθ. D is the maximum width of the cross-section of the neutron generation target 30 in the first direction dr1, and d is the distance from the center of the photon generation target 20 to the neutron generation target 30 along the first direction dr1.

[0093] Figure 7 is a schematic diagram of the neutron generation region in some embodiments of the neutron generation device according to the present disclosure. The neutron generation target 30 can be in the shape of a column with a cross-section such as Figure 4 shown as a polygon, circle or ellipse, or can also be in other shapes, for example, according to Figure 7 the simulation results of the neutron generation region shown, the neutron generation target 30 is designed into a spindle-shaped structure. In Figure 7 , the neutron generation target 30 represents the concentration of the neutron generation region through color blocks of different grayscales. The lower the grayscale value, the more neutrons are generated.

[0094] In Figure 4 , D is taken from the maximum width of the cross-section of the neutron generation target 30 in the first direction dr1, such as the diameter of a cylinder, the diameter of the circumscribed circle of the maximum cross-section of a spindle-shaped structure, etc. The value of D can be calculated and determined according to d and the preset angle θ. The preset angle θ can be selected from a certain angle value between θ 60 and θ 80 .

[0095] In the process of designing the size of the neutron generation target 30, if the value of D is controlled to remain unchanged, the distance d between the neutron generation target 30 and the photon generation target 20 can be correspondingly increased as the energy of the electron beam eb increases, so as to avoid a decrease in the neutron yield. Optionally, the value of d is 2 to 10 cm, such as 2 cm, 3 cm, 5 cm, 8 cm or 10 cm, etc.

[0096] Refer to Figure 2 and Figure 4 , in some embodiments, the neutron generation device further includes a photon shielding structure 40. The photon shielding structure 40 is arranged on the side of the photon generation target 20 and is configured to shield at least part of the bremsstrahlung photons bp generated by the photon generation target 20 that expand beyond the preset angle θ range relative to the first direction dr1. It can be understood that the size of the preset angle θ can be adjusted by the relative position of the photon generation target 20 and the photon shielding structure 40.

[0097] The material of the photon shielding structure 40 can be lead, tungsten, etc., which can effectively shield bremsstrahlung photons. The bremsstrahlung photons bp emitted within the preset angle θ range can be received by the first photon receiving region pr and meet the requirement of a preset percentage of the total number of photons. Correspondingly, the bremsstrahlung photons bp outside the preset angle θ range can be shielded by the photon shielding structure 40 to reduce the output of these bremsstrahlung photons bp accompanied by neutrons, thereby reducing the photon background intensity of the neutrons.

[0098] Moreover, since the neutron production target 30 and the photon production target 20 are spaced apart by a distance d, the photon shielding structure 40 can be conveniently arranged and adjusted near the photon production target 20 while minimizing the impact on the extraction of the neutron beam, which is beneficial to simplifying the structural design.

[0099] Reference Figure 2 , in some embodiments, the neutron production device further includes a light filter 70. The light filter 70 is arranged at the neutron beam outlet 60 and is configured to filter the photons accompanying the neutron beam. The light filter 70 can be made of a relatively thin material such as bismuth, which has a large interaction cross-section with photons and a small cross-section with neutrons, so as to filter the scattered photons without significantly weakening the neutron beam.

[0100] Reference Figure 2 , in some embodiments, the second angle α2 between the surface of the neutron production target 30 adjacent to the photon production target 20 and the plane perpendicular to the first direction dr1 is an acute angle, and the distance from the photon production target 20 along the first direction dr1 to the surface of the neutron production target 30 adjacent to the photon production target 20 gradually increases from the side far from the neutron beam outlet 60 to the side adjacent to the neutron beam outlet 60.

[0101] By designing the second angle α2 as an acute angle and making the distance between the photon production target 20 and the neutron production target 20 along the first direction dr1 gradually increase towards the side adjacent to the neutron beam outlet 60, more neutrons generated can be directed towards the neutron beam outlet 60, so as to increase the number of neutrons entering the neutron beam outlet 60, which is beneficial to improving the neutron yield.

[0102] Reference Figure 2 and Figure 4 , in some embodiments, the neutron production device further includes a neutron moderation structure 50, and the neutron moderation structure 50 has a receiving cavity for receiving the neutron production target 30. The photon production target 20 is located outside the neutron moderation structure 50.

[0103] The neutron moderation structure 50 can moderate and reflect the neutrons generated by the neutron production target 30 to output the neutrons that meet the output requirements to the outside. The moderation materials used in the neutron moderation structure 50 may include hydrogen-containing materials (such as H2O), deuterium-containing materials (such as heavy water), carbon-containing materials (such as polyethylene), beryllium Be, etc.

[0104] Reference Figure 2 and Figure 4 , in some embodiments, the photon shielding structure 40 included in the neutron production device has a first inner cavity c1 penetrating along the first direction dr1, and the photon production target 20 is located in the first inner cavity c1. The first inner cavity c1 can accommodate the photon production target 20, and acceleration structures such as the acceleration tube of the electron accelerator 10 can enter the first inner cavity c1 to approach or abut against the photon production target 20. The photon shielding structure 40 can then control the emission range of the bremsstrahlung photons generated by the photon production target 20 through the position of the photon production target 20 in the first inner cavity c1.

[0105] The neutron moderation structure 50 is adjacently arranged with the photon shielding structure 40 and has an accommodation cavity for accommodating the neutron production target 30. The neutron moderation structure 50 may further include a second inner cavity c2, and the second inner cavity c2 can be separated from the accommodation cavity by the wall of the moderation material. The second inner cavity c2 is located on the side of the neutron moderation structure 50 adjacent to the photon shielding structure 40 and can communicate with the first inner cavity c1.

[0106] In Figure 2 , the neutron moderation structure 50 can adopt the structure of a bottomed cylinder, and two chambers can be separated inside it by the moderation material. One (i.e., the accommodation cavity) is located inside and is used to accommodate the neutron production target 30, and the other (i.e., the second inner cavity c2) is located outside and is used to communicate with the first inner cavity c1. Some of the bremsstrahlung photons bp generated by the photon production target 20 can reach the neutron production target 30 through part of the first inner cavity c1 and the second inner cavity c2.

[0107] The neutron beam outlet 60 is opened on the side wall of the neutron moderation structure 50 and can output the neutron beam generated by the neutron production target 30 along the second direction dr2. The second direction dr2 is parallel to the extension direction of the neutron beam outlet 60 and points from the second inner cavity c2 to the outside of the neutron moderation structure 50.

[0108] Based on the large angle between the opening direction of the neutron beam outlet 60 and the emission direction of the electron beam eb, and the shielding effect of the photon shielding structure 40 on the bremsstrahlung photons bp, the photon background of the bremsstrahlung photons bp and scattered photons accompanying the neutrons can be greatly reduced.

[0109] Such as Figure 2 、 Figure 4 and Figure 7As shown, a photon shielding layer 81 can be provided outside the neutron moderation structure 50. In the figure, the coverage of this layer over the neutron moderation structure 50 is indicated by thickened lines. The photon shielding layer 81 can cover not only the neutron moderation structure 50 but also the photon shielding structure 40. The material of the photon shielding layer 81 can be lead, tungsten, etc., which can effectively shield bremsstrahlung photons.

[0110] Figure 8 is the photon energy spectrum diagram obtained by Monte Carlo simulation for the neutron generation device examples and comparative examples of the present disclosure. Refer to Figure 8 , the photon energy spectra obtained from the structures and detector assemblies of an example and a comparative example of the neutron generation device of the present disclosure will be compared below.

[0111] In an example of the neutron generation device of the present disclosure (hereinafter simply referred to as this example), the energy of the electron accelerator 10 is 7 MeV. The material of the photon generation target 20 is tungsten with a thickness of 1.2 mm. The material of the neutron generation target 30 is heavy water. The maximum diameter of the neutron generation target 30 is 10 cm, and its maximum length along the emission direction of the electron beam eb is 20 cm. The surface of the neutron generation target 30 is 2.0 cm away from the center of the photon generation target 20, and the angle between this surface and the emission direction of the electron beam eb is 90°. The neutron beam outlet 60 is at a 90° angle to the emission direction of the electron beam eb. The detector assembly is located outside the neutron beam outlet 60 along the extension direction of the neutron beam outlet 60. In the comparative example, except that the photon generation target 20 is arranged inside the neutron generation target 30, other structures and parameters are the same as those in this example.

[0112] In Figure 8 , the photon energy spectrum of this example is schematically shown by curve a, and the photon energy spectrum of the comparative example is schematically shown by curve b.

[0113] After Monte Carlo simulation, the neutron yield of this example is 1.13×10 -4 n / e, and the neutron yield of the comparative example is 1.47×10 -4 n / e. The neutron yield of this example is about 77% of that of the comparative example. Although the neutron yield has decreased, as Figure 8 shown, compared with curve b of the comparative example, curve a of this example has a significant reduction in both energy spectrum and flux. The total number of photons above 1 MeV is only 2.3% of that of the conventional scheme. It can be seen that this example can effectively reduce the photon background intensity accompanying neutrons and reduce the interference of photons accompanying neutron output.

[0114] Figure 9 is a schematic structural diagram of some embodiments of the substance composition analysis system of the present disclosure. Refer to Figure 9, embodiments of the present disclosure further provide a substance composition analysis system, including the neutron generation device 80 of any of the foregoing embodiments. The substance composition analysis system may further include a detector assembly 82. The detector assembly 82 may be located outside the neutron beam outlet 60 along the extension direction of the neutron beam outlet 60 for detecting the radiation signal output from the neutron beam outlet 60.

[0115] In Figure 9 , the radiation signal containing neutrons n output from the neutron beam outlet 60 may act on the specimen 83 to obtain the characteristic γ-rays of the specimen 83, so as to analyze the elemental composition and content contained in the specimen 83.

[0116] Since the neutron generation device can reduce the interference of accompanying photons during neutron output, it is beneficial for the substance composition analysis system to obtain more accurate analysis results.

[0117] So far, the embodiments of the present disclosure have been described in detail. To avoid obscuring the concept of the present disclosure, some details well known in the art have not been described. Those skilled in the art can fully understand how to implement the technical solutions disclosed herein based on the above description.

[0118] Although some specific embodiments of the present disclosure have been described in detail by way of examples, those skilled in the art should understand that the above examples are only for illustration and not for limiting the scope of the present disclosure. Those skilled in the art should understand that the above embodiments can be modified or some technical features can be equivalently replaced without departing from the scope and spirit of the present disclosure. The scope of the present disclosure is defined by the appended claims.

Claims

1. A neutron generating device, comprising: An electron accelerator (10) configured to emit an electron beam (eb); A photon generating target (20) configured to interact with the electron beam (eb) to generate bremsstrahlung photons (bp); A neutron generating target (30) configured to interact with the bremsstrahlung photons (bp) to generate neutrons (n); and A neutron beam outlet (60) adjacently arranged to the neutron generating target (30) and configured to output the neutron beam generated by the neutron generating target (30) along a second direction (dr2); Wherein, the neutron generating target (30) is spaced apart from the photon generating target (20) along a first direction (dr1), the first direction (dr1) is the emission direction of the electron beam (eb), the second direction (dr2) is parallel to the extending direction of the neutron beam outlet (60), and the first angle (α1) between the second direction (dr2) and the first direction (dr1) is a right angle or an obtuse angle.

2. The neutron generating device according to claim 1, wherein, The surface of the neutron generating target (30) adjacent to the photon generating target (20) includes a first photon receiving area (pr), the first photon receiving area (pr) is used to receive the bremsstrahlung photons (bp) generated by the photon generating target (20) within a preset angle θ range of expansion relative to the first direction (dr1), and the ratio of the bremsstrahlung photons (bp) received by the first photon receiving area (pr) to the total number of bremsstrahlung photons (bp) generated by the photon generating target (20) is a preset percentage.

3. The neutron generating device according to claim 2, wherein, The preset angle θ corresponding to the preset percentage is less than or equal to the preset angle θ corresponding to 80% 80 and greater than or equal to the preset angle θ corresponding to 60% 60 .

4. The neutron generating device according to claim 2 or 3, wherein, The preset angle θ corresponding to the preset percentage of 80% 80 Satisfies the following formula: ； where θ 80 is a preset angle θ required to collect 80% of the total number of bremsstrahlung photons (bp) generated by the photon generation target (20), in degrees; E e is the energy of the electron beam (eb) emitted by the electron accelerator (10) for bombarding the photon generation target (20), in MeV.

5. The neutron generating device according to claim 4, wherein, E e The value ranges from 7 to 30 MeV.

6. The neutron generating device according to claim 2 or 3, wherein, The preset angle θ corresponding to the preset percentage of 60% 60 Satisfies the following formula: ； where θ 60 is a preset angle θ required to collect 60% of the total number of bremsstrahlung photons (bp) generated by the photon generation target (20), in degrees; E e is the energy of the electron beam (eb) emitted by the electron accelerator (10) for bombarding the photon generation target (20), in MeV.

7. The neutron generating device according to claim 6, wherein, E e The value ranges from 7 to 30 MeV.

8. The neutron generating device according to claim 2, further comprising: A photon shielding structure (40) arranged on the side of the photon generating target (20) and configured to shield at least part of the bremsstrahlung photons (bp) generated by the photon generating target (20) outside the preset angle θ range of expansion relative to the first direction (dr1).

9. The neutron generating device according to claim 2, wherein, The preset angle θ corresponding to the preset percentage satisfies: D≥2d·tgθ; Wherein, D is the maximum width of the cross-section of the neutron generating target (30) in the first direction (dr1), and d is the distance from the center of the photon generating target (20) to the neutron generating target (30) along the first direction (dr1) of the neutron generating target (30).

10. The neutron generating device according to claim 9, wherein, The value of d is 2 - 10 cm.

11. The neutron generating device according to claim 1, further comprising: A neutron moderation structure (50) having a receiving cavity for receiving the neutron generating target (30); Wherein, the photon generating target (20) is located outside the neutron moderation structure (50).

12. The neutron generating device according to claim 11, further comprising: A photon shielding structure (40) having a first inner cavity (c1) penetrating along the first direction (dr1), and the photon generating target (20) is located within the first inner cavity (c1); Wherein, the neutron moderation structure (50) is adjacently arranged to the photon shielding structure (40), and has a receiving cavity for receiving the neutron generation target (30) and a second inner cavity (c2). The second inner cavity (c2) is separated from the receiving cavity and communicates with the first inner cavity (c1). The neutron beam outlet (60) is opened on the side wall of the neutron moderation structure (50).

13. The neutron generation device according to claim 1, further comprising: A light filter (70), arranged at the neutron beam outlet (60), configured to filter photons accompanying the neutron beam.

14. The neutron generating device according to claim 1, wherein, A second included angle (α2) between a surface of the neutron generation target (30) adjacent to the photon generation target (20) and a plane perpendicular to the first direction (dr1) is an acute angle, and a distance from the photon generation target (20) along the first direction (dr1) to the surface of the neutron generation target (30) adjacent to the photon generation target (20) gradually increases from a side away from the neutron beam outlet (60) to a side adjacent to the neutron beam outlet (60).

15. The neutron generating device according to claim 1, wherein, The photon generation target (20) comprises at least one of tantalum, tungsten, and bismuth, and the neutron generation target (30) comprises at least one of deuterium-containing materials, beryllium, uranium, and tungsten.

16. A substance composition analysis system, comprising: The neutron generation device according to any one of claims 1-15.

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