A compact single sphere neutron spectrometer moderator

Abstract

The present application relates to a kind of compact single sphere neutron spectrometer's moderator, wherein inner layer is cylindrical structure, and multiple thermal neutron detectors are installed inside;Thermal neutron absorption layer is sleeved on the outside of inner layer, and the material is boron-containing polyethylene;Scattered neutron moderator layer is sleeved on the outside of thermal neutron absorption layer;Inner layer includes detector placement block and thermal neutron absorption block, and storage groove is provided on thermal neutron absorption block;Multiple thermal neutron detectors are placed in the axial direction in detector placement block, and the first thermal neutron detector is placed in storage groove, and the material of thermal neutron absorption block is boron-containing polyethylene;The diameter of inner layer is 8cm, the outer diameter of thermal neutron absorption layer is 14cm, and the outer diameter of scattered neutron moderator layer is 20cm.The present application achieves the purpose of controlling the diameter of cylindrical structure to control the size of volume, and the three-layer moderator structure is sleeved to enhance the scattering shielding effect, so that the volume of the moderator is smaller, it is convenient to transport, and the technical effect that shielding effect is stronger is achieved.

Description

Technical Field

[0001] This invention relates to the field of neutron energy spectrum measurement technology, and more particularly to a moderator for a compact single-sphere neutron spectrometer. Background Technology

[0002] Neutron spectroscopy is a crucial experimental technique with significant implications across multiple fields. It provides vital support and guidance for advancing nuclear science, improving nuclear technology, ensuring nuclear safety, promoting scientific research, and fostering social development. Through in-depth research into neutron spectroscopy, we can better understand key issues such as nuclear reactions, material properties, and radiation effects, contributing to the construction of safer and more efficient nuclear energy systems and the advancement of scientific and technological innovation.

[0003] First, neutrons are neutral particles with strong penetrating power, capable of inducing nuclear reactions and scattering processes within materials. The development of neutron spectrometers has enabled us to accurately measure the energy spectrum distribution of neutrons in materials, allowing for in-depth research into nuclear reaction mechanisms, material properties, and nuclear reactor design. While cylindrical moderators are ideal for directional neutron beams, they are susceptible to interference from lateral or backscattered neutrons. Therefore, researchers both domestically and internationally typically use large-volume moderators and incorporate collimating apertures to shield scattered neutrons. However, this design results in excessively large volumes and masses for single-sphere neutron spectrometers, posing significant challenges for measurement and transportation. Furthermore, reducing the volume leads to higher scattering ratios measured by the deepest thermal neutron detector, resulting in poorer scattering shielding.

[0004] In related technologies, there is a lack of moderators that are easy to transport and have good scattering shielding effects.

[0005] The above problems urgently need to be addressed. Summary of the Invention

[0006] This invention discloses a moderator for a compact single-sphere neutron spectrometer, aiming to solve the technical problems existing in the prior art.

[0007] This invention employs the following technical solution, comprising: an inner layer, having a cylindrical structure, in which multiple thermal neutron detectors are installed; a thermal neutron absorbing layer, having a hollow cylindrical structure, sleeved on the outside of the inner layer, and made of boron-containing polyethylene; and a scattering neutron moderation layer, having a hollow cylindrical structure, sleeved on the outside of the thermal neutron absorbing layer; the inner layer includes a detector placement block and a thermal neutron absorbing block, the detector placement block and the cylindrical plane of the thermal neutron absorbing block being in contact with each other and their central axes coinciding, the thermal neutron absorbing block being close to the detector placement block. A storage slot is provided at one end of the detector placement block; multiple thermal neutron detectors are placed along the axial direction inside the detector placement block, with the first thermal neutron detector placed in the storage slot; the thermal neutron absorption block is made of boron-containing polyethylene, wherein the first thermal neutron detector is used to indicate the thermal neutron detector at the very end among the multiple thermal neutron detectors; the inner layer has a diameter of 8 cm, the inner diameter of the thermal neutron absorption layer is 8 cm and the outer diameter is 14 cm, and the inner diameter of the scattering neutron moderation layer is 14 cm and the outer diameter is 20 cm.

[0008] Optionally, the distance between the position of the second thermal neutron detector and the plane on the side of the detector placement block away from the thermal neutron absorption block is 0.2 cm to 2.4 cm, and the second thermal neutron detector is used to indicate the thermal neutron detector at the foremost position among the plurality of thermal neutron detectors.

[0009] Optionally, the detector placement block includes: a first upper slicing structure, which is an eccentric semi-cylindrical structure, and the arc of the circular plane is a minor arc; a first lower slicing structure, which is an eccentric semi-cylindrical structure, and the arc of the circular plane is a major arc; a first groove is provided at the rectangular plane of the first lower slicing structure for placing a PCB board, and the PCB board is connected to the plurality of thermal neutron detectors.

[0010] Optionally, the thermal neutron absorber includes: a second upper slicing structure, which is an eccentric semi-cylindrical structure, and the arc of the circular plane is a minor arc; a second lower slicing structure, which is an eccentric semi-cylindrical structure, and the arc of the circular plane is a major arc; a second groove is provided at the rectangular plane of the second lower slicing structure for the PCB board connection lines to extend to the external environment.

[0011] Optionally, a third groove is provided on the circular plane of the first undercut structure, on the side facing the second undercut structure, and a protrusion is provided on the circular plane of the second undercut structure, on the side facing the first undercut structure; the third groove and the protrusion are matched with each other.

[0012] Optionally, it also includes: a sealing shell, disposed on the outside of the scattering neutron moderator layer, including an annular sealing plate and two circular sealing plates, the annular sealing plate wrapping around the curved structure of the scattering neutron moderator layer, and the two circular sealing plates respectively disposed at the circular cross-section ends of the scattering neutron moderator layer; a circuit through hole is provided on the circular sealing plate near the thermal neutron absorber block of the two circular sealing plates, and the circuit through hole allows PCB board connection wires to pass through.

[0013] Optionally, it may also include: a plurality of legs located on the sealing housing, the plane formed by the ends of the plurality of legs facing the ground being parallel to the ground; and a handle located on the sealing housing and on the opposite side of the plurality of legs.

[0014] Optionally, it also includes: a positioning pin; a first pin hole is provided on the second lower cut surface structure, a second pin hole is provided on the thermal neutron absorbing layer, and a third pin hole is provided on the scattering neutron moderation layer; the first pin hole, the second pin hole, and the third pin hole are on the same horizontal line and coaxially connected; the positioning pin passes through the first pin hole, the second pin hole, and the third pin hole.

[0015] Optionally, it further includes: an annular protrusion disposed at the inner diameter of the thermal neutron absorbing layer and located at the end of the thermal neutron absorbing layer, the thermal neutron absorbing block overlapping the annular protrusion; the inner diameter of the annular protrusion is smaller than the diameter of the thermal neutron absorbing block.

[0016] Optionally, the inner layer is made of polyethylene; the scattering neutron moderator layer is made of polyethylene.

[0017] The technical solution adopted in this invention can achieve at least one of the following beneficial effects:

[0018] In this embodiment of the invention, an inner layer has a cylindrical structure and multiple thermal neutron detectors are installed inside; a thermal neutron absorption layer has a hollow cylindrical structure and is sleeved on the outside of the inner layer, and is made of boron-containing polyethylene; a scattering neutron moderation layer has a hollow cylindrical structure and is sleeved on the outside of the thermal neutron absorption layer; the inner layer includes a detector placement block and a thermal neutron absorption block, the cylindrical planes of the detector placement block and the thermal neutron absorption block are in contact with each other and their central axes coincide, and a storage slot is provided at one end of the thermal neutron absorption block near the detector placement block; multiple thermal neutron detectors are placed along the axial direction inside the detector placement block, and a first thermal neutron detector is placed in the storage slot, the thermal neutron absorption block is made of boron-containing polyethylene, wherein the first thermal neutron detector is used to indicate the thermal neutron detector at the very end of the multiple thermal neutron detectors. The method achieves the goal of controlling the volume by controlling the diameter of the cylindrical structure and enhancing the scattering shielding effect by incorporating a three-layer modulator structure. This results in a modulator that is small in size, easy to transport, and has a strong scattering shielding effect, thus solving the technical problem of the lack of a modulator that is easy to transport and has a good scattering shielding effect in related technologies. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below, forming part of the present invention. The illustrative embodiments of the present invention and their descriptions explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0020] Figure 1 This is an isometric view of the three-layer structure of the moderator in a compact single-sphere neutron spectrometer according to the present invention.

[0021] Figure 2 This is a cross-sectional structural diagram of the moderator of a compact single-sphere neutron spectrometer according to the present invention;

[0022] Figure 3 This is an isometric sectional view of the inner layer structure of the moderator in a compact single-sphere neutron spectrometer according to the present invention.

[0023] Figure 4 This is a structural diagram of the sealing shell of the moderator in a compact single-sphere neutron spectrometer according to the present invention.

[0024] Explanation of reference numerals in the attached figures:

[0025] 1. Inner layer; 11. Detector placement block; 111. First upper slicing structure; 112. First lower slicing structure; 113. Third groove; 114. First groove; 12. Thermal neutron absorber block; 121. Storage slot; 122. Second upper slicing structure; 123. Second lower slicing structure; 124. Second groove; 125. Protrusion; 13. First pin hole;

[0026] 2. Thermal neutron absorbing layer; 21. Second pin hole; 22. Annular protrusion;

[0027] 3. Scattered neutron moderation layer; 31. Third pin hole; 32. Positioning pin;

[0028] 4. Sealing the outer casing; 41. Wiring exit hole; 42. Support feet; 43. Handle. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. In the description of this invention, it should be noted that the term "or" is generally used to include the meaning of "and / or," unless otherwise expressly indicated.

[0030] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or a magnetic connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. Furthermore, in the description of this application, the terms "first," "second," etc., are used only for distinguishing descriptions and should not be construed as indicating or implying relative importance. In the description of this invention, "a plurality of" means at least two, such as two, three, or more, unless otherwise explicitly specified.

[0031] Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0032] First, to facilitate understanding of the embodiments of the present invention, some terms or nouns involved in the present invention will be explained below:

[0033] A single-sphere neutron spectrometer is a device that uses a single spherical moderator to measure neutron energy spectra in multiple energy regions. It features a multi-layer detector layout, which improves portability and operational efficiency.

[0034] A moderator is a device used to slow down fast neutrons to the thermal or ultrathermal neutron energy range. It is commonly used in neutron detection, neutron spectrometers, reactors, and other applications.

[0035] To address the problems existing in related technologies, embodiments of this application provide a moderator for a compact single-sphere neutron spectrometer.

[0036] This embodiment provides a moderator for a compact single-sphere neutron spectrometer, such as Figure 1 and Figure 2 As shown, Figure 1 This is an isometric view of the three-layer structure of the moderator in a compact single-sphere neutron spectrometer according to the present invention. Figure 2 This is a cross-sectional structural diagram of the moderator of a compact single-sphere neutron spectrometer according to the present invention. The moderator includes:

[0037] The inner layer 1 has a cylindrical structure and houses multiple thermal neutron detectors. The thermal neutron absorption layer 2 has a hollow cylindrical structure and is fitted over the inner layer 1; it is made of boron-containing polyethylene. The scattering neutron moderator layer 3 has a hollow cylindrical structure and is fitted over the thermal neutron absorption layer 2. The inner layer 1, thermal neutron absorption layer 2, and scattering neutron moderator layer 3 are tightly fitted together. The inner layer 1 includes a detector placement block 11 and a thermal neutron absorption block 12. The cylindrical planes of the detector placement block 11 and the thermal neutron absorption block 12 are in contact with each other, and their central axes coincide. The thermal neutron absorption block 12 is close to the detector placement block 1. A storage slot 121 is provided at one end of the detector placement block 11; multiple thermal neutron detectors are placed in the detector placement block 11 along the axial direction, and the first thermal neutron detector is placed in the storage slot 121. The thermal neutron absorption block 12 is made of boron-containing polyethylene. The first thermal neutron detector is used to indicate the thermal neutron detector at the very end of the multiple thermal neutron detectors, that is, the thermal neutron detector closest to the thermal neutron absorption block 12. The inner layer 1 has a diameter of 8 cm, the thermal neutron absorption layer 2 has an inner diameter of 8 cm and an outer diameter of 14 cm, and the scattering neutron moderation layer 3 has an inner diameter of 14 cm and an outer diameter of 20 cm.

[0038] Optionally, the moderator is cylindrical in shape, consisting of three coaxial cylindrical layers and a cylindrical ring from the inside out. The inner layer 1 is a cylinder with a radius of 4 cm and a length of 20-30 cm, and is further divided into front and rear parts: a detector placement block 11 and a thermal neutron absorption block 12. A thermal neutron detector is installed within the moderator to detect the neutron dose rate, thereby obtaining the ratio of the scattered neutron flux to the direct neutron flux. The thermal neutron detectors are installed in the detector placement block 11, arranged sequentially along its axis towards the thermal neutron absorption block 12. The front surface of the last thermal neutron detector is located at the interface between the two parts, meaning the last thermal neutron detector is placed in the storage slot 121. The thermal neutron absorption block 12 is made of boron-containing polyethylene and is used to absorb backscattered neutrons. Among them, the thermal neutron detectors are arranged along the axis to realize the deep distribution measurement of neutron flux. The thermal neutron detector at the front end records the highest energy neutrons, and the subsequent detectors record the neutron energy spectrum that is slowed down step by step.

[0039] Optionally, a thermal neutron absorbing layer 2 is fitted outside the inner layer 1. The thermal neutron absorbing layer 2 has an inner and outer diameter of 8 cm and 14 cm, respectively, and a length of 25 cm to 35 cm. It is made of boron-containing polyethylene and is used to absorb side-incident scattered neutrons. The outermost scattered neutron moderator layer 3 has an inner and outer diameter of 14 cm and 20 cm, respectively, and a length of 25 cm to 35 cm. It is made of polyethylene and is used to moderate side-incident scattered neutrons to facilitate shielding by the scattered neutron absorbing layer.

[0040] Optionally, the total outer diameter of the moderating body is 20cm, and the total mass can be controlled within 20kg. Compared with multi-sphere moderating bodies with a diameter greater than 30cm, or even greater than 60cm, and a mass of several hundred kilograms, the volume is reduced by 40%, which effectively achieves the effect of facilitating transportation.

[0041] In some preferred embodiments, the position of the second thermal neutron detector is 0.2 cm to 2.4 cm away from the plane of the detector placement block 11 on the side away from the thermal neutron absorption block 12. The second thermal neutron detector is used to indicate the thermal neutron detector at the foremost position among the multiple thermal neutron detectors, that is, the thermal neutron detector farthest from the thermal neutron absorption block 12.

[0042] Optionally, fast neutrons are emitted and reach a moderator, where they are converted into thermal neutrons during the moderation process, thus achieving the effect of being recognized by a thermal neutron detector. A second thermal neutron detector is placed inside the detector placement block 11, at least 0.2 cm away from the surface of the detector placement block 11, to ensure that fast neutrons can be converted into thermal neutrons within the 0.2 cm moderator. These thermal neutrons have higher energy, and the second thermal neutron detector acquires the thermal neutrons with higher energy. The thermal neutrons are gradually slowed down in the moderator, and their energy gradually decreases. A thermal neutron detector behind the second thermal neutron detector identifies the scattered neutrons after their energy has decreased. The last thermal neutron detector, i.e., the first thermal neutron detector, can identify the scattered neutrons after their energy has decreased to a certain level.

[0043] Optionally, the thermal neutron detector at the foremost position records the highest-energy neutrons, while subsequent detectors record the neutron energy spectrum that is slowed down step by step. After determining the positions of the first and last thermal neutron detectors, the multiple thermal neutron detectors in the middle are placed along the central axis according to the neutron energy decay range.

[0044] In some preferred embodiments, the detector placement block 11 includes: a first upper sectional structure 111, which is an eccentric semi-cylindrical structure and the arc of the cross section is a minor arc; a first lower sectional structure 112, which is an eccentric semi-cylindrical structure and the arc of the cross section is a major arc; a first groove 114 is provided at the rectangular section of the first lower sectional structure 112 for placing a PCB board, and the PCB board is connected to multiple thermal neutron detectors.

[0045] like Figure 3 As shown, Figure 3 This is an isometric sectional view of the inner layer structure of the moderator in a compact single-sphere neutron spectrometer according to the present invention. Optionally, the thermal neutron detector and the preamplifier are both soldered onto a single circuit board. The entire circuit board needs to be embedded in the moderator. Therefore, the polyethylene cylindrical detector placement block 11 of the inner layer 1 needs to be further divided into upper and lower parts, and eight square holes large enough to accommodate the circuit board are cut out at corresponding positions in the lower half. The detectors are then inserted into their corresponding holes to complete the probe assembly.

[0046] Optionally, to facilitate the placement of a thermal neutron detector within the detector placement block 11, the detector placement block 11 needs to be cut into upper and lower parts. The upper part is the first upper slicing structure 111, which is an eccentric semi-cylinder with a minor arc. This first upper slicing structure 111 acts as a cover, so that after the thermal neutron detector is placed within the first lower slicing structure 112, the first upper slicing structure 111 covers the first lower slicing structure 112, forming a cylinder.

[0047] Optionally, multiple slot structures are provided within the first lower cut surface structure 112 to house thermal neutron detectors. These slot structures are perpendicular to the ground, and the thermal neutron detectors are vertically inserted into the detector placement block 11. Data received by the multiple thermal neutron detectors needs to be transmitted to the PCB board, which then transmits it to the integrated module for processing. Therefore, the PCB board is placed at the first lower cut surface structure 112 and directly connected to the multiple thermal neutron detectors.

[0048] Optionally, the first undercut structure 112 is provided with a first groove 114 parallel to the ground. The first groove 114 is perpendicular to the slot structure for placing the thermal neutron detector. The area of ​​the first groove 114 almost covers the entire rectangular surface of the first undercut structure 112.

[0049] Optionally, several thermal neutron detectors will be housed within the inner cylindrical moderator, fixed at a certain distance along the cylinder's axis. To facilitate wiring, the thermal neutron detectors are arranged in an array on a PCB board. All power supply and signal transmission lines for each thermal neutron detector are integrated onto a small PCB board, significantly reducing the difficulty of routing within the moderator.

[0050] In some preferred embodiments, the thermal neutron absorber 12 includes: a second upper sectional structure 122, which is an eccentric semi-cylindrical structure and the arc of the cross section is a minor arc; a second lower sectional structure 123, which is an eccentric semi-cylindrical structure and the arc of the cross section is a major arc; a second groove 124 is provided at the rectangular cross section of the second lower sectional structure 123 for the PCB board connection lines to extend to the external environment.

[0051] like Figure 3 As shown, optionally, since the area of ​​the PCB board may be larger than the rectangular surface of the first lower cut structure 112, that is, the length of the PCB board is longer and exceeds the length of the long side of the rectangular surface of the first lower cut structure 112, the PCB board needs to be extended and placed inside the thermal neutron absorber block 12. In addition, the PCB board has an interface for connecting with the external integrated module, and the interface needs to be moved out of the moderator. Therefore, the PCB board is passed through the thermal neutron absorber block 12 and extends to the external environment from the position where the thermal neutron absorber block 12 is connected to the outside.

[0052] Optionally, for the reasons mentioned above, the thermal neutron absorber block 12 needs to be cut into a second upper cut surface structure 122 and a second lower cut surface structure 123. A second groove 124 is provided at the second lower cut surface structure 123. The second groove 124 is parallel to the first groove 114 and is on the same horizontal plane, which facilitates the PCB board to extend into the second groove 124. At the same time, the connecting lines and interfaces of the PCB board can extend from the second groove 124 to the external environment.

[0053] In some preferred embodiments, a third groove 113 is provided on the circular plane of the first undercut structure 112 and on the side facing the second undercut structure 123, and a protrusion 125 is provided on the circular plane of the second undercut structure 123 and on the side facing the first undercut structure 112; the third groove 113 and the protrusion 125 match each other.

[0054] like Figure 3 As shown, optionally, since the inner layer 1 is divided into a detector placement block 11 and a thermal neutron absorption block 12, in order to prevent the two parts from rotating relative to each other in the moderator, causing the second groove 124 and the first groove 114 to rotate to a state where they are not on the same horizontal plane, it is necessary to fix the first undercut structure 112 and the second undercut structure 123 to ensure that the two cannot rotate relative to each other.

[0055] Optionally, a third groove 113 is provided on the first undercut structure 112, and a protrusion 125 is provided on the second undercut structure 123. The third groove 113 and the protrusion 125 can be inserted into each other. After insertion, the first undercut structure 112 and the second undercut structure 123 will not rotate relative to each other, effectively avoiding the intersection of the second groove 124 and the first groove 114.

[0056] In some preferred embodiments, the system further includes: a positioning pin 32; a first pin hole 13 is provided on the second lower cut surface structure 123, a second pin hole 21 is provided on the thermal neutron absorbing layer 2, and a third pin hole 31 is provided on the scattering neutron moderation layer 3; the first pin hole 13, the second pin hole 21, and the third pin hole 31 are on the same horizontal line and coaxially connected; the positioning pin 32 passes through the first pin hole 13, the second pin hole 21, and the third pin hole 31.

[0057] like Figure 1 As shown, optionally, the moderating body includes a three-layer structure. To prevent the three layers from rotating relative to each other, a hole that can be completely penetrated is required, namely the first pin hole 13, the second pin hole 21, and the third pin hole 31. At the same time, a positioning pin 32 is provided, which can pass through the first pin hole 13, the second pin hole 21, and the third pin hole 31 to effectively fix the three-layer structure and prevent the three layers from rotating relative to each other.

[0058] Optionally, the first pin hole 13 needs to be set on the second undercut structure 123, and the central axis of the first pin hole 13 is parallel to the surface of the second groove 124. That is, the first pin hole 13 cannot intersect with the second groove 124 to avoid the positioning pin 32 damaging the circuit at the second groove 124 when it passes through the first pin hole 13.

[0059] In some preferred embodiments, the system further includes: a sealing shell 4, disposed on the outside of the scattering neutron moderator layer 3, comprising a barrel-shaped sealing plate and two circular sealing plates, the barrel-shaped sealing plate wrapping around the curved structure of the scattering neutron moderator layer 3, and the two circular sealing plates respectively disposed at the circular cross-section ends of the scattering neutron moderator layer 3; a circuit through hole 41 is provided on the circular sealing plate near the end of the thermal neutron absorber block 12, the circuit through hole 41 allowing PCB board connection wires to pass through.

[0060] like Figure 4 As shown, Figure 4 This is a structural diagram of the sealing shell of the moderator in a compact single-sphere neutron spectrometer according to the present invention. Optionally, to protect the moderator from wear, a sealing shell 4 needs to be installed outside the scattering neutron moderation layer 3. The sealing shell 4 is detachable, that is, the circular sealing plate and the annular sealing plate are fixed together by bolts.

[0061] Optionally, a wire through hole 41 can be made on the circular sealing plate so that the connection wires of the PCB board can be transmitted out and connected to the external integrated module.

[0062] In some preferred embodiments, it further includes: a plurality of legs 42 located on the sealing housing 4, the plane formed by the ends of the plurality of legs 42 facing the ground (i.e. the ends away from the sealing housing 4) being parallel to the ground; and a handle 43 located on the sealing housing 4 and on the opposite side of the plurality of legs 42.

[0063] like Figure 4 As shown, optionally, for ease of transportation, a handle 43 is provided on the sealing shell 4. The handle 43 allows the entire moderating body to be easily lifted and moved to other locations. At the same time, since the moderating body is a cylindrical structure, multiple legs 42 are provided on the sealing shell 4. The multiple legs 42 are located on the opposite side of the handle 43, and the multiple legs 42 can ensure that the moderating body is stably standing on the ground.

[0064] In some preferred embodiments, it further includes: an annular protrusion 22 disposed at the inner diameter of the thermal neutron absorbing layer 2 and located at the end of the thermal neutron absorbing layer 2, the thermal neutron absorbing block 12 overlapping the annular protrusion 22; the inner diameter of the annular protrusion 22 is smaller than the diameter of the thermal neutron absorbing block 12.

[0065] like Figure 1 and Figure 2 As shown, optionally, the annular protrusion 22 is disposed at the inner diameter of the thermal neutron absorption layer 2. Since both the thermal neutron absorption block 12 and the detector placement block 11 of the inner layer 1 are cut into two parts, the second lower cut surface structure 123 is fixed by the positioning pin 32 and will not rotate relative to the thermal neutron absorption layer 2, nor will it move up, down, left, or right. The first lower cut surface structure 112 will also not move due to the action of the third groove 113 and the protrusion 125. However, the first upper cut surface structure 111 and the second upper cut surface structure 122 are not restricted in any way, and may move relative to the lower cut surface structure. Therefore, the annular protrusion 22 is provided in the thermal neutron absorption layer 2 to resist the second upper cut surface structure 122, ensuring that the second upper cut surface structure 122 will not move to the outside of the thermal neutron absorption layer 2. After the second upper cut surface structure 122 is fixed, the first upper cut surface structure 111 has no room for movement and will not move.

[0066] Optionally, the annular protrusion 22 can effectively fix the second upper slicing structure 122 and prevent the second upper slicing structure 122 from moving to the right to the outside of the thermal neutron absorption layer 2. The annular protrusion 22 cannot be set on the left side of the first upper slicing structure 111. Since the inner layer 1 needs to be disassembled and removed, there needs to be an opening for the inner layer 1 to be removed at this location.

[0067] In some preferred embodiments, the inner layer 1 is made of polyethylene; the scattering neutron moderation layer 3 is made of polyethylene.

[0068] Optionally, the front half of the inner layer 1, namely the detector placement block 11, is made of polyethylene with a density of 0.95 g / cm3, the rear half of the inner layer 1, namely the thermal neutron absorption block 12, is made of boron-containing polyethylene with a density of 1.102 g / cm3, the thermal neutron absorption layer 2 is made of boron-containing polyethylene with a density of 1.102 g / cm3, and the scattering neutron moderation layer 3 is made of polyethylene with a density of 0.95 g / cm3.

[0069] Specifically, the design of multiple thermal neutron detectors within a single moderator makes the overall device more compact and safer, eliminates the need to replace the moderator sphere, and simplifies operation. Combined with appropriate electronics for signal filtering and a communication system, the electronic signals can be transmitted to a host computer, where online energy spectrum measurements can be achieved using the spectral analysis software. Based on the three-layer moderator structure, the optimal moderator size was determined through Monte Carlo simulation calculations, the specific calculation process of which is as follows.

[0070] First, a corresponding geometric model was established. The responses of each detector were statistically analyzed under various conditions when the neutron source emitted 1×10⁹ neutrons. To obtain the scattering ratio, two calculations were performed for each condition. The detector response under the normal model condition was taken as the result including the scattering effect, while the calculation result when all wall materials in the beam measurement space model were set to air was taken as the detector response under the no-scattering condition. The scattering ratio evaluation method is as follows:

[0071]

[0072] in, This represents the scattering ratio of the i-th thermal neutron detector. This represents the response of the i-th thermal neutron detector under normal conditions. This represents the response of the i-th thermal neutron detector when the wall is set to air conditions.

[0073] First, the calculation was performed using a two-layer structure of the moderator. By changing the thickness of the moderator structure, the effect of the thickness on the scattering ratio was determined. The final calculation results of the scattering ratio are shown in Table 1.

[0074] Table 1. Scattering ratio of boron-containing polyethylene of different thicknesses when the moderating body is divided into two layers.

[0075]

[0076] The vertical axis of the table represents the scattering ratio corresponding to the i-th thermal neutron detector.

[0077] Secondly, by designing a three-layer moderator structure and simultaneously varying the thickness of the moderator structure, the scattering ratio of each layer with different thicknesses was considered from the inside out under the conditions of polyethylene-boron-polyethylene-polyethylene. Since the side length of the preamplifier itself reaches 2.6 cm, to ensure sufficient moderation performance, the radius of the innermost polyethylene layer 1 should preferably be no less than 4 cm. Considering the actual processing difficulty, the thickness of the two outer layers should also be no less than 2 cm. Based on the above considerations, this work calculated the scattering ratios of structures with 4 cm-6 cm-10 cm, 4 cm-7 cm-10 cm, 4 cm-8 cm-10 cm, 5 cm-7 cm-10 cm, and 5 cm-8 cm-10 cm, respectively. Among them, 4 cm-6 cm-10 cm refers to an inner layer 1 with a radius of 4 cm, a middle layer with a radius of 6 cm, and an outermost layer with a radius of 10 cm. The specific calculation results are shown in Table 2.

[0078] Table 2. Scattering ratio of boron-containing polyethylene of different thicknesses when the moderating body is divided into 3 layers.

[0079]

[0080] Finally, the scattering of the moderator under more layered structure conditions was calculated. Based on previous considerations, the radius of the inner cylinder 1 was not less than 4 cm, and the material was changed every 1 cm outward. The scattering of structures with dimensions of 4cm-5cm-6cm-7cm-8cm-9cm-10cm, 5cm-6cm-7cm-8cm-9cm-10cm, and 6cm-7cm-8cm-9cm-10cm was calculated. The layers marked in bold used boron-containing polyethylene material. Specific results are shown in Table 3.

[0081] Table 3 Scattering ratios under different structures when the modulator is divided into multiple layers

[0082]

[0083] Simulation calculations show that, with a three-layer structure, the scattering ratio of the thermal neutron detector at the deepest point can be reduced to less than 7%, demonstrating excellent scattering shielding. Therefore, a three-layer structure is chosen for the moderator, with the optimal combination of 4 cm-7 cm-10 cm.

[0084] Compared to multi-sphere neutron spectrometers, this moderator structure requires only one moderator, offering significant advantages in storage, transportation, and use. The absence of moderator replacement during measurements effectively reduces radiation dose to personnel. Furthermore, while typical single-sphere neutron spectrometers incorporate collimating apertures to shield scattered neutrons, resulting in a volume exceeding 60 cm in diameter and 100 cm in length, with a corresponding mass of several hundred kilograms, this moderator structure, while maintaining good shielding performance, reduces its size to Ф20 cm × 30 cm, and its mass can be controlled to within 20 kg.

[0085] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A moderator for a compact single-sphere neutron spectrometer, characterized in that, include: The inner layer (1) has a cylindrical structure and multiple thermal neutron detectors are installed inside. The thermal neutron absorbing layer (2) has a hollow cylindrical structure and is sleeved on the outside of the inner layer (1). The material is boron-containing polyethylene. The scattering neutron moderator layer (3) has a hollow cylindrical structure and is fitted on the outside of the thermal neutron absorbing layer (2); the inner layer (1), the thermal neutron absorbing layer (2), and the scattering neutron moderator layer (3) are tightly bonded together; The inner layer (1) includes a detector placement block (11) and a thermal neutron absorption block (12). The cylindrical planes of the detector placement block (11) and the thermal neutron absorption block (12) are in contact with each other and their central axes coincide. A storage slot (121) is provided at one end of the thermal neutron absorption block (12) near the detector placement block (11). Multiple thermal neutron detectors are placed along the axial direction inside the detector placement block (11). The first thermal neutron detector is placed in the storage slot (121). The thermal neutron absorption block (12) is made of boron-containing polyethylene. The first thermal neutron detector is used to indicate the thermal neutron detector closest to the thermal neutron absorption block (12) among the multiple thermal neutron detectors.

2. The moderator of a compact single-sphere neutron spectrometer according to claim 1, characterized in that, The second thermal neutron detector is placed on the side of the detector placement block (11) away from the thermal neutron absorption block (12). The second thermal neutron detector is used to indicate the thermal neutron detector that is farthest from the thermal neutron absorption block (12) among the plurality of thermal neutron detectors.

3. The moderator of a compact single-sphere neutron spectrometer according to claim 1, characterized in that, The detector placement block (11) includes: The first upper tangential structure (111) is an eccentric semi-cylindrical structure, and the arc of the cross section is a minor arc; The first lower cut surface structure (112) is an eccentric semi-cylindrical structure, and the arc of the cross section is a superior arc; A first groove (114) is provided at the rectangular section of the first lower cut surface structure (112) for placing a PCB board, which is connected to the plurality of thermal neutron detectors.

4. The moderator of a compact single-sphere neutron spectrometer according to claim 3, characterized in that, The thermal neutron absorber (12) includes: The second upper tangential structure (122) is an eccentric semi-cylindrical structure, and the arc of the cross section is a minor arc; The second lower cut surface structure (123) is an eccentric semi-cylindrical structure, and the arc of the cross section is a superior arc; A second groove (124) is provided at the rectangular section of the second lower cut surface structure (123) for the connection lines of the PCB board to extend to the external environment.

5. The moderator of a compact single-sphere neutron spectrometer according to claim 4, characterized in that, A third groove (113) is provided on the cross section of the first undercut structure (112) facing the second undercut structure (123), and a protrusion (125) is provided on the cross section of the second undercut structure (123) facing the first undercut structure (112). The third groove (113) matches the protrusion (125).

6. The moderator of a compact single-sphere neutron spectrometer according to claim 4, characterized in that, Also includes: Positioning pin (32); A first pin hole (13) is provided on the second lower cut surface structure (123), a second pin hole (21) is provided on the thermal neutron absorbing layer (2), and a third pin hole (31) is provided on the scattering neutron moderation layer (3). The first pin hole (13), the second pin hole (21) and the third pin hole (31) are on the same horizontal line and coaxially connected; The positioning pin (32) passes through the first pin hole (13), the second pin hole (21) and the third pin hole (31).

7. The moderator of a compact single-sphere neutron spectrometer according to claim 4, characterized in that, Also includes: The sealing shell (4) is disposed on the outside of the scattering neutron moderator layer (3), including a barrel-shaped sealing plate and two circular sealing plates. The barrel-shaped sealing plate is wrapped around the outside of the scattering neutron moderator layer (3), and the two circular sealing plates are respectively disposed at the circular cross-section ends of the scattering neutron moderator layer (3). One of the two circular sealing plates is provided with a line exit hole (41) on the circular sealing plate near the thermal neutron absorber (12), and the line exit hole (41) is provided for the PCB board connection wire to pass through.

8. The moderator of a compact single-sphere neutron spectrometer according to claim 7, characterized in that, Also includes: Multiple legs (42) are located on the sealing shell (4), and the ends of the multiple legs (42) away from the sealing shell (4) are located on the same plane; The handle (43) is located on the sealing housing (4) and on the opposite side of the plurality of legs (42).

9. The moderator of a compact single-sphere neutron spectrometer according to claim 1, characterized in that, Also includes: An annular protrusion (22) is disposed at the inner diameter of the thermal neutron absorbing layer (2) and located at the end of the thermal neutron absorbing layer (2), and the thermal neutron absorbing block (12) overlaps the annular protrusion (22); The inner diameter of the annular protrusion (22) is smaller than the diameter of the thermal neutron absorber (12).

10. The moderator of a compact single-sphere neutron spectrometer according to claim 1, characterized in that, The inner layer (1) is made of polyethylene; The scattering neutron moderation layer (3) is made of polyethylene.

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