Sample element composition detection system based on neutron activation analysis

Abstract

The utility model relates to the technical field of sample detection, particularly provides a sample element component detection system based on neutron activation analysis, and aims to solve the problem that the detection precision is influenced by low signal-to-interference ratio in a signal acquisition process in an existing element component detection mode. In order to achieve the purpose, the detection system comprises a neutron source used for generating a neutron beam; the gamma detector is provided with a detection probe, and the gamma detector is located in front of the emission port of the neutron source, so that characteristic gamma rays generated after the neutron beam bombards the sample to be detected can be incident to the detection probe, and therefore a gamma energy spectrum is formed; the shielding device comprises a first shielding layer surrounding the outer side of the detection probe, the first shielding layer is used for absorbing secondary gamma rays and environmental background gamma rays around the detection probe, and a collimation channel allowing characteristic gamma rays to enter is reserved in the shielding device. According to the invention, the signal-to-interference ratio in the sampling process can be improved, and the accuracy and reliability of the detection result are improved.

Description

Technical Field

[0001] The present application relates to the technical field of sample detection, and specifically provides a sample element composition detection system based on neutron activation analysis. Background Art

[0002] Prompt gamma neutron activation analysis technology refers to the use of neutron beams emitted by neutrons to bombard the atomic nuclei of the sample to be tested, causing nuclear reactions and producing characteristic gamma rays. The above characteristic gamma rays are then collected and analyzed by a gamma detector to generate a gamma energy spectrum. The type and content of elements in the sample to be tested are determined based on the gamma energy spectrum.

[0003] Neutron activation analysis devices currently used in industrial applications are generally suitable for online detection of large-volume samples. However, due to interference with the sampling signal from stray fast neutrons and secondary gamma rays in the environment surrounding the gamma detector, the accuracy and reliability required for precise detection of elements in small-volume samples are often difficult to meet.

[0004] Accordingly, this field requires a new technical solution to solve the above problems. Utility Model Content

[0005] The present application aims to solve the above technical problem, that is, to solve the problem that the existing element composition detection method affects the detection accuracy due to the low signal-to-noise ratio during the signal acquisition process.

[0006] In a first aspect, the present application provides a sample element composition detection system based on neutron activation analysis, comprising:

[0007] a neutron source for generating a neutron beam;

[0008] A gamma detector having a detection probe, wherein the gamma detector is located in front of the emission port of the neutron source so that characteristic gamma rays generated after the neutron beam bombards the sample to be detected can be incident on the detection probe and thus form a gamma energy spectrum;

[0009] The shielding device includes a first shielding layer surrounding the outside of the detection probe, the first shielding layer is used to absorb secondary gamma rays and environmental background gamma rays around the detection probe, and a collimation channel is reserved on the shielding device for the characteristic gamma rays to enter.

[0010] In one technical solution of the above detection system, the shielding device further includes:

[0011] The first moderator layer is surrounded by the first shielding layer and is used to moderate the fast neutrons around the detection probe.

[0012] In one technical solution of the above detection system, the shielding device further includes:

[0013] The second shielding layer is located between the first shielding layer and the moderator layer, and is used for absorbing moderated neutrons.

[0014] In a technical solution of the above detection system, the material of the first shielding layer is metal lead; and / or

[0015] The thickness of the first shielding layer is 20-40 mm.

[0016] In a technical solution of the above detection system, the material of the first moderation layer is high-density polyethylene; and / or

[0017] The thickness of the first moderation layer is 20-30 mm.

[0018] In a technical solution of the above detection system, the material of the second shielding layer is metal cadmium; and / or

[0019] The thickness of the second shielding layer is 1-2 mm.

[0020] In a technical solution of the above detection system, the cross section of the collimating channel is circular.

[0021] In a technical solution of the above detection system, the normal direction of the emission port of the neutron source is perpendicular to the normal direction of the collimation channel.

[0022] In one technical solution of the above detection system, the detection system further includes:

[0023] The storage platform is located between the emission port of the neutron source and the entrance of the collimation channel, and the storage platform is a liftable structure so that the table top of the storage platform can be raised and lowered according to the size of the sample to be detected, thereby adjusting the relative position of the sample to be detected and the collimation channel.

[0024] In one technical solution of the above detection system, the detection system further includes:

[0025] A shielded room, wherein the neutron source is located in the shielded room, and the shielded room includes a second moderation layer and a third shielding layer arranged in sequence from the inside to the outside, the second moderation layer is used to slow down the fast neutrons generated by the neutron source, and the third shielding layer is used to shield neutrons in the external environment.

[0026] As mentioned above, when adopting the above-mentioned technical solution, the present application sets a first shielding layer on the outside of the detection probe of the gamma detector to absorb the secondary gamma rays and environmental background gamma rays around the detector, which is beneficial to improving the signal-to-interference ratio during the sampling process, thereby improving the accuracy and reliability of the detection results, and can meet the elemental composition detection needs of small-volume samples, such as but not limited to nickel-based matrix alloys, pyrotechnic products and other samples.

[0027] Furthermore, the present application sets the above-mentioned first moderation layer and second shielding layer. During the detection process, the first moderation layer first slows down the fast neutrons in the environment around the detector, and then absorbs the slowed-down neutrons through the second shielding layer. In this way, the damage caused to the detection probe by fast neutrons in the environment and fast neutrons leaked from the neutron source can be reduced, thereby reducing the problem of the energy resolution of the detector affected by the damage to the lattice of the detection probe, and further improving the accuracy and reliability of the detection results. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The preferred embodiments of the present application are described below with reference to the accompanying drawings, in which:

[0029] Figure 1 is a schematic diagram of a sample element composition detection system based on neutron activation analysis according to one embodiment of the present application;

[0030] Figure 2 This is a schematic diagram of the positional relationship between a gamma detector and a shielding device according to an embodiment of the present application.

[0031] In the figures, the reference numerals refer to the following:

[0032] 1. Neutron source; 2. Gamma detector; 21. Detection probe; 3. Shielding device; 31. First shielding layer; 32. Second shielding layer; 33. First moderator; 4. Shielding room; 41. Second moderator; 42. Third shielding layer;

[0033] 100, sample to be tested; 200, collimation channel. DETAILED DESCRIPTION

[0034] The preferred embodiments of the present application are described below with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely intended to illustrate the technical principles of the present application and are not intended to limit the scope of protection of the present application. Those skilled in the art may adjust these embodiments as needed to suit specific applications.

[0035] It should be noted that, in the description of this application, terms such as "upper," "lower," "left," "right," "inner," and "outer" indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings. This is merely for ease of description and does not indicate or imply that the relevant devices or components must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, ordinal numbers such as "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0036] Furthermore, it should be noted that, in the description of this application, unless otherwise specified or limited, the terms "installed" and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections, electrical connections; and direct connections or indirect connections through an intermediary. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

[0037] Reference Figure 1 , is a schematic diagram of a sample element composition detection system based on neutron activation analysis according to an embodiment of the present application, which includes a neutron source 1, a gamma detector 2, and a shielding device 3 arranged around the detection probe 21 of the gamma detector 2.

[0038] Reference Figure 1 The neutron source 1 is used to generate a neutron beam. In one embodiment of the present application, the sample elemental composition detection system further includes a shielded chamber 4, in which the neutron source 1 is disposed. The shielded chamber 4 includes a second moderator layer 41 and a third shielding layer 42, arranged from the inside out. The second moderator layer 41 can be made of high-density polyethylene and wraps around the outside of the neutron source 1. The portion of the second moderator layer 41 corresponding to the emission port of the neutron source 1 can also be provided with collimating holes and other structures. The second moderator layer 41 slows down the fast neutrons generated by the neutron source 1 into slow neutrons, and the moderated neutron beam is collimated to increase the flux density of the neutron beam. The third shielding layer 42 can be made of boron-containing polyethylene and surrounds the second moderator layer 41 and the neutron source 1, thereby shielding the second moderator layer 41 and the neutron source 1 from neutrons and reducing interference with the detection process caused by stray neutrons in the external environment.

[0039] The gamma detector 2 is located in front of the emission port of the neutron source 1. Specifically, the gamma detector 2 is located outside the second moderator 41, and the sample 100 to be detected is located between the gamma detector 2 and the neutron source 1, so that the characteristic gamma rays generated after the neutron beam bombards the sample to be detected can be incident on the detection probe 21 and thus form a gamma energy spectrum.

[0040] In one embodiment of the present application, the gamma detector 2 may be a high-purity germanium detector, in which case the detection probe 21 is a high-purity germanium crystal. When characteristic gamma rays strike the high-purity germanium crystal, they interact with the atoms within the crystal, releasing energy and generating electron-hole pairs. Driven by the electric field within the detector, these electron-hole pairs are separated and migrate along specific paths, ultimately converting them into measurable electrical signal outputs, forming a gamma spectrum. The above detection principles are well known in the art and are not further elaborated herein.

[0041] Reference Figure 2 The shielding device 3 includes a first shielding layer 31 surrounding the outside of the detection probe 21. The first shielding layer 31 is used to absorb the secondary gamma rays and environmental background gamma rays around the detection probe 21. In one embodiment of the present application, the material of the first shielding layer 31 is metal lead. Of course, the first shielding layer 31 can also be made of metal bismuth and other materials, and the present application does not limit this. The thickness of the first shielding layer 31 can be selected to be 20-40 mm. It should be noted that the enclosure described in the present application is not completely closed, that is, the first shielding layer 31 is provided with an opening corresponding to the area in front of the detection probe 21, and the opening area forms a collimating channel 200 for the characteristic gamma rays to enter. The effective characteristic gamma rays generated in the process of the neutron beam bombarding the sample to be detected are introduced into the high-purity germanium crystal, that is, the detection probe 21 through the collimating channel 200.

[0042] It should be noted that the above-mentioned secondary gamma rays refer to gamma rays produced by nuclear reactions between neutrons leaked from the neutron source and external substances other than the sample to be detected, and environmental background gamma rays refer to non-target signals generated by the gamma detector 2 under the influence of internal or external factors. They may come from cosmic rays, natural radioactivity in the environment, the physical properties of the detector itself (such as ionization, stray radiation), noise in the circuit, etc. These are not characteristic gamma rays generated by the sample to be detected, but interference signals, which will affect the accuracy of the detection results. Therefore, the present application provides a first shielding layer 31 on the outside of the detection probe 21 of the gamma detector 2 to absorb the secondary gamma rays and environmental background gamma rays around the detector, which is beneficial to improving the signal-to-interference ratio during the sampling process, thereby improving the accuracy and reliability of the detection results.

[0043] Reference Figure 2 In a possible implementation of the present application, the shielding device 3 further includes a second shielding layer 32 and a first moderator layer 33 sequentially stacked on the outside of the first shielding layer 31. Specifically, the second shielding layer 32 and the first moderator layer 33 are both surrounded by the outside of the detection probe 21, and the second shielding layer 32 is located between the first moderator layer 33 and the first shielding layer 31. The second shielding layer 32 and the first moderator layer 33 are both provided with openings at positions corresponding to the front area of ​​the detection probe 21 to form the above-mentioned collimation channel 200.

[0044] The first moderator layer 33 is used to moderate fast neutrons surrounding the detection probe 21. The material of the first moderator layer 33 can be high-density polyethylene (HDPE, as used herein, refers to a thermoplastic resin material with a density between 0.941 and 0.965 g / cm³) and has a thickness of 20-30 mm. The second shielding layer 32 is used to absorb moderated neutrons. The material of the second shielding layer 32 can be metallic cadmium. Of course, the second shielding layer 32 can also be made of boron, lithium fluoride, or other materials, as long as they can absorb neutrons. This application does not limit the specific material of the second shielding layer 32.

[0045] It should be noted that in the actual detection process, when the fast neutrons generated by the neutron source 1 are moderated and emitted, some fast neutrons will inevitably leak into the environment. When these fast neutrons collide with the germanium atoms in the high-purity germanium crystal, the germanium atoms will move out of the original lattice position, thereby causing lattice defects. The lattice defects generated by the high-purity germanium crystal will capture electrons (for N-type detectors) or holes (for P-type detectors) generated by the characteristic gamma-ray absorption. During the charge collection process, a part of the charge carriers generated by the characteristic gamma-ray absorption will be lost at these capture points, resulting in a smaller detected pulse height, a lower characteristic peak value recorded in the gamma energy spectrum, and a decrease in the energy resolution of the detector, thereby affecting the accuracy and reliability of the detection results.

[0046] Therefore, the present application sets the above-mentioned first moderation layer 33 and second shielding layer 32. During the detection process, the first moderation layer 33 first slows down the fast neutrons in the environment around the detector, and then absorbs the slowed down neutrons through the second shielding layer 32. In this way, the damage caused to the detection probe 21 by fast neutrons in the environment and fast neutrons leaked from the neutron source can be reduced, thereby reducing the problem of the energy resolution of the detector affected by the lattice damage of the detection probe 21, and improving the accuracy and reliability of the detection results.

[0047] In one embodiment of the present application, the cross section of the collimating channel 200 is circular, so that it can play a role in collimating and guiding the characteristic gamma rays entering the detector.

[0048] Optionally, the normal direction of the emission port of the neutron source 1 is perpendicular to the normal direction of the collimation channel 200. In the above description, the "normal direction" of the emission port of the neutron source 1 refers to the normal direction of the cross section of the port through which the neutron source 1 emits the neutron beam, or can also be understood as the axial direction of the channel through which the neutron source 1 emits the neutron beam. Similarly, the "normal direction" of the collimation channel 200 refers to the axial direction of the collimation channel 200.

[0049] During the process of neutron beam bombarding the sample to be detected, although the characteristic gamma rays generated diverge along the 4π direction, the intensity of the rays in each direction is different. Theoretically, the intensity of the characteristic gamma rays is highest in the plane perpendicular to the neutron beam path. Therefore, the present application sets the relative position of the neutron source 1 and the gamma detector 2 to the above-mentioned form, which is conducive to improving the characteristic gamma ray flux density in the collimation channel 200, thereby improving the accuracy and reliability of the sample element composition detection results.

[0050] In an optional embodiment of the present application, the detection system also includes a storage table (not shown in the figure) for holding the sample 100 to be detected. The storage table is located between the emission port of the neutron source 1 and the entrance of the collimation channel 200. Optionally, the storage table is located at the intersection of the normal of the emission port of the neutron source 1 and the axis of the collimation channel 200, thereby maximizing the characteristic gamma ray flux density in the collimation channel 200.

[0051] Furthermore, the storage table is configured as a liftable structure (for example, height adjustment is achieved by a telescopic structure, etc., which is a common mechanical structure known to those skilled in the art and will not be described in detail in this application). Since in actual applications, the sizes of the samples to be detected are different, in order to make the geometric centers of the samples to be detected of different sizes coincide with the intersection of the normal of the emission port of the neutron source 1 and the axis of the collimation channel 200 as much as possible, so as to ensure the characteristic gamma ray flux density in the collimation channel 200 during the bombardment of the neutron beam on the sample to be detected, before detection, the storage table can be controlled to be raised and lowered according to the size of the sample to be detected, and the relative position between the sample to be detected and the collimation channel 200 can be adjusted by adjusting the height of the storage table surface to achieve the above purpose.

[0052] As mentioned above, the present application can improve the detection accuracy and reliability of the elemental composition of the sample by setting a shielding device 3 on the outside of the gamma detector 2 to meet the elemental composition detection requirements of small volume samples, such as but not limited to nickel-based matrix alloys, pyrotechnic products and other samples.

[0053] Thus far, the technical solutions of the present application have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is readily understood by those skilled in the art that the scope of protection of the present application is obviously not limited to these specific embodiments. Without departing from the principles of the present application, those skilled in the art may make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will fall within the scope of protection of the present application.

Claims

1. A sample element composition detection system based on neutron activation analysis, characterized in that: include: a neutron source for generating a neutron beam; A gamma detector having a detection probe, wherein the gamma detector is located in front of the emission port of the neutron source so that characteristic gamma rays generated after the neutron beam bombards the sample to be detected can be incident on the detection probe and thus form a gamma energy spectrum; The shielding device includes a first shielding layer surrounding the outside of the detection probe, the first shielding layer is used to absorb secondary gamma rays and environmental background gamma rays around the detection probe, and a collimation channel is reserved on the shielding device for the characteristic gamma rays to enter.

2. The detection system according to claim 1, characterized in that The shielding device further comprises: The first moderator layer is surrounded by the first shielding layer and is used to moderate the fast neutrons around the detection probe.

3. The detection system according to claim 2, characterized in that The shielding device further comprises: The second shielding layer is located between the first shielding layer and the moderator layer, and is used for absorbing moderated neutrons.

4. The detection system according to claim 1, characterized in that The material of the first shielding layer is metal lead; and / or The thickness of the first shielding layer is 20-40 mm.

5. The detection system according to claim 2, characterized in that: The material of the first moderation layer is high-density polyethylene; and / or The thickness of the first moderation layer is 20-30 mm.

6. The detection system according to claim 3, characterized in that The material of the second shielding layer is metal cadmium; and / or The thickness of the second shielding layer is 1-2 mm.

7. The detection system according to claim 1, characterized in that The cross section of the collimating channel is circular.

8. The detection system according to claim 7, characterized in that: The normal direction of the emission port of the neutron source is perpendicular to the normal direction of the collimation channel.

9. The detection system according to claim 7, characterized in that: The detection system also includes: The storage platform is located between the emission port of the neutron source and the entrance of the collimation channel, and the storage platform is a liftable structure so that the table top of the storage platform can be raised and lowered according to the size of the sample to be detected, thereby adjusting the relative position of the sample to be detected and the collimation channel.

10. The detection system according to any one of claims 1 to 9, characterized in that: The detection system also includes: A shielded room, wherein the neutron source is located in the shielded room, and the shielded room includes a second moderation layer and a third shielding layer arranged in sequence from the inside to the outside, the second moderation layer is used to slow down the fast neutrons generated by the neutron source, and the third shielding layer is used to shield neutrons in the external environment.

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