Shadow cone optimization design method for neutron scattering correction

Abstract

The invention discloses a shadow cone optimization design method for neutron scattering correction. The method comprises the following steps: establishing an air room model and a real room model, and calculating a corresponding detector count value; parameters such as the distance between the center of a neutron source and the center of a detector, the front end diameter and the rear end diameter of a shadow cone, and the distance between the center of the neutron source and the shadow cone are respectively fixed. The optimal distance between the center of the neutron source and the shadow cone, the diameter of the front end of the shadow cone and the diameter of the front end of the shadow cone are determined through calculation and comparison with the detector count values of the real room model and the air room model, and then the shadow cone is designed for the target room. The Monte Carlo method is adopted to simulate and calculate the shadow cone parameters, the optimal shadow cone parameter combination can be efficiently found out, the optimal shadow cone parameter combination can be accurately determined by gradually adjusting the parameters of the shadow cone and comparing the corrected detector count with the count under the scattering-free condition, and the accuracy of the shadow cone parameter combination is improved. Therefore, the calibration accuracy and reliability of the neutron measuring instrument are improved.

Description

Technical Field

[0001] The invention relates to the technical field of neutron detection, and in particular to a shadow cone optimization design method for neutron scattering correction. Background Art

[0002] The calibration of neutron measuring instruments needs to be carried out in a calibration laboratory. The contribution of neutrons scattered from the walls in the calibration laboratory to the neutron measuring instruments cannot be ignored. In order to ensure the accurate calibration of the instrument, it is necessary to use an appropriate method to correct the contribution of scattered neutrons. Commonly used methods include the shadow cone method, the universal fitting method, the semi-empirical method, and the simplified fitting method. The shadow cone method is easy to use and can directly measure the contribution of scattered neutrons. Therefore, it is widely used in neutron scattering correction in calibration laboratories.

[0003] The general process of the shadow cone method includes: first, measuring the reading of the detector at a given position when there is no shadow cone, then placing the shadow cone at a specific position between the neutron source and the detector, ensuring that the geometric shape, size and placement of the shadow cone meet the experimental requirements, and then placing the detector at the same position when there is no shadow cone, and measuring the reading after being blocked by the shadow cone; processing the detector readings with and without shadow cones to obtain scattering-corrected neutron measurement instrument readings.

[0004] The accuracy of the shadow cone method is closely related to the shape and size design of the shadow cone and the geometric position of the shadow cone relative to the neutron source-detector. In the process of correcting the scattered neutron measurement by the shadow cone method, several key parameters of the shadow cone, such as the distance between the front end and the center of the neutron source, the front diameter, and the back diameter, have a significant impact on the measurement results, and the accurate determination of these parameters faces many challenges. On the one hand, the distance between the front end of the shadow cone and the center of the neutron source is crucial. This distance not only determines the path length of the neutron beam when it passes through the shadow cone, but also affects the distribution and intensity of scattered neutrons. However, since the size, shape, and emission characteristics of the neutron source may change with time and experimental conditions, it is particularly difficult to accurately determine this distance. On the other hand, the diameters of the front and back ends of the shadow cone are also important factors affecting the measurement results. The front diameter determines the range of the neutron beam being blocked, while the back diameter affects the angle and number of scattered neutrons entering the detector. However, due to the complexity and uncertainty of neutron scattering, the accurate values ​​of these diameters are often difficult to obtain directly through experiments. Therefore, how to design a shadow cone optimization design method is a technical problem that needs to be solved urgently. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the technical problem to be solved by the present invention is: how to provide a shadow cone optimization design method for neutron scattering correction, which uses the Monte Carlo method to simulate and calculate the shadow cone parameters, and can efficiently find the optimal shadow cone parameter combination. By gradually adjusting the various parameters of the shadow cone and comparing the corrected detector counts with the counts in the no-scattering case, the optimal shadow cone parameter combination can be accurately determined, thereby improving the accuracy and reliability of the calibration of neutron measuring instruments.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A shadow cone optimization design method for neutron scattering correction, comprising:

[0008] S1: Determine the maximum distance l that the detector can use max ;

[0009] S2: Establish an air room model for the target room with no walls, no ceiling, and no floor and an air environment; set a neutron source in the air room model and adjust the distance between the center of the neutron source and the center of the detector to l max , calculate the detector count value M A (l max ); where A represents an air room model;

[0010] S3: Establish a real room model for the target room; set up a neutron source in the real room model, and adjust the distance between the center of the neutron source and the center of the detector to l max , calculate the detector count value M T (l max ), where T represents the real room model;

[0011] S4: Set the distance between the neutron source center and the detector center to l max , set the front diameter of the shadow cone to d and the rear diameter to D; adjust the distance a between the neutron source center and the shadow cone, and calculate the detector count value M after adding the shadow cone S (l max ,a,d,D) with the distribution of a; through M T (l max ) minus M S (l max ,a,d,D) to obtain the count value M1 after room scattering correction; by dividing M1 with M A (l max ) to determine the optimal distance a between the neutron source center and the shadow cone op ;

[0012] S5: Fixed distance l between the center of neutron source and the center of detector max、The distance a between the neutron source center and the shadow cone op , the rear end diameter D of the shadow cone; adjust the front end diameter d of the shadow cone, and calculate the detector count value M after adding the shadow cone s (l max ,a op ,d,D) with the distribution of d; through M T (l max ) minus M s (l max ,a op ,d,D) to obtain the count value M2 after room scattering correction; by dividing M2 and M A (l max ) to determine the optimal shadow cone front diameter d op ;

[0013] S6: Fixed distance l between the center of neutron source and the center of detector max 、The distance a between the neutron source center and the shadow cone op , the front diameter of the shadow cone d op ; Adjust the rear end diameter D of the shadow cone and calculate the detector count value M after adding the shadow cone s (l max ,a op ,d op ,D) with the distribution of D; through M T (l max ) minus M s (l max ,a op ,d op , D), and obtain the count value M3 after room scattering correction; by dividing M3 and M A (l max ) to determine the optimal shadow cone front diameter D op ;

[0014] S7: Through the optimal distance a between the neutron source center and the shadow cone op , the front diameter of the shadow cone d op The front diameter of the shadow cone is D op Design shadow cones for target rooms.

[0015] Preferably, in step S1, the maximum distance l available to the detector is determined by the following steps: max :

[0016] S101: Establish an ideal room model without walls, ceilings, or floors and in a vacuum environment for the target room; set a neutron source in the ideal room model, and adjust the distance l between the center of the neutron source and the center of the detector, and calculate the detector count value M at different distances l. I (l), where I represents the ideal room model;

[0017] S102: Set a neutron source in the air room model and adjust the distance l between the neutron source center and the detector center. Calculate the detector count value M at different distances l. A (l), where A represents the air room model;

[0018] S103: Set a neutron source in the real room model, and adjust the distance l between the center of the neutron source and the center of the detector. Calculate the detector count value M at different distances l. T (l), where T represents the real room model;

[0019] S104: According to the detector count value M I (l), detector count value M A (l) and the detector count value M T (l) Determine the maximum distance at which the detector can be used.

[0020] Preferably, in step S104, according to M I (l), M A (l) and M T (l) Calculation room scattering contribution S n (l); The room scattering contribution S n (l) is equal to the preset value (40%), and the corresponding distance l between the center of the neutron source and the center of the detector is taken as the maximum distance l available for the detector. max ;

[0021] Room scattering contribution S n The calculation formula of (l) is:

[0022]

[0023] Preferably, in step S4, the optimal distance a between the center of the neutron source and the shadow cone is op Need to meet:

[0024]

[0025] Where: S bound Indicates the allowable error boundary.

[0026] Preferably, in step S5, the optimal shadow cone front diameter d op Need to meet:

[0027]

[0028] Where: S bound Indicates the allowable error boundary.

[0029] Preferably, in step S6, the optimal shadow cone front diameter D op Need to meet:

[0030]

[0031] Where: S bound Indicates the allowable error boundary.

[0032] Compared with the prior art, the shadow cone optimization design method for neutron scattering correction in the present invention has the following beneficial effects:

[0033] First, by simulating the scattering of neutron sources in air room models and real room models, the present invention can effectively calculate the influence of scattered neutrons on detector counts caused by room structure; by introducing shadow cones and adjusting their parameters (including front diameter, rear diameter and the distance between the neutron source and the shadow cone), the correction effect of neutron scattering is further optimized, so that the detector count is closer to the ideal situation without scattering. Secondly, the present invention uses the Monte Carlo method to simulate and calculate the shadow cone parameters, and can efficiently find the optimal shadow cone parameter combination. By gradually adjusting the various parameters of the shadow cone and comparing the corrected detector count with the count without scattering, the optimal shadow cone parameter combination can be accurately determined. Finally, the present invention can flexibly adjust the parameters of the shadow cone according to the needs and room structure, adapt to different experimental conditions and requirements, have a wide range of application prospects, and can be applied to various neutron measurement instrument calibration experiments and research; at the same time, the optimized shadow cone design can significantly reduce the influence of neutron scattering on the experimental results, improve the accuracy and reliability of the calibration of neutron measurement instruments, and has important significance for neutron measurement, material science, nuclear physics and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to make the purpose, technical solution and advantages of the invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings, in which:

[0035] Figure 1 Schematic diagram of the neutron source, shadow cone and detector.

[0036] Logic block diagram of the shadow cone optimization design method for neutron scattering correction.

[0037] Figure 2 This is a graph showing the relationship between the detector count values ​​in the ideal room model, air room model, and real room model as the distance between the neutron source center and the detector center changes.

[0038] Figure 3 This is a graph showing the relationship between the detector count value and the distance between the neutron source center and the shadow cone (front end).

[0039] Figure 4 This is a graph showing how the detector count value changes with the distance from the front diameter of the shadow cone.

[0040] Figure 5This is a graph showing how the detector count value changes with the distance from the rear end diameter of the shadow cone. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. The components of the embodiments of the present invention generally described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but only represents selected embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the scope of protection of the present invention.

[0042] It should be noted that similar numbers and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings. In the description of the present invention, it should be noted that the orientation or position relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc. is based on the orientation or position relationship shown in the drawings, or the orientation or position relationship in which the invention product is usually placed when used, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance. In addition, the terms "horizontal", "vertical", etc. do not mean that the components are required to be absolutely horizontal or suspended, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted. In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0043] The following is a further detailed description through specific implementation methods:

[0044] Example:

[0045] This embodiment discloses a shadow cone optimization design method for neutron scattering correction.

[0046] The positions of the neutron source 100, the shadow cone 200 and the detector 300 are shown in FIG. Figure 1 shown.

[0047] like Figure 1 As shown, the shadow cone optimization design method for neutron scattering correction includes:

[0048] S1: Determine the maximum distance l that the detector can use max ;

[0049] S2: Establish an air room model for the target room with no walls, no ceiling, and no floor and an air environment; set a neutron source in the air room model and adjust the distance between the center of the neutron source and the center of the detector to l max , calculate the detector count value M A (l max ); where A represents an air room model;

[0050] In this embodiment, the target room is 8 m long, 8 m wide, and 5 m high, and the walls, ceiling, and floor are set as 50 cm thick concrete.

[0051] The air room model room is 8m long, 8m wide and 5m high. The room has no walls, ceiling or floor. The interior of the room is set to an air environment. The neutron source is located in the center of the room. The neutron source is a 241Am-Be neutron source with a neutron emission rate of 1×107nps. The detector is a long neutron counter.

[0052] S3: Establish a real room model for the target room; set up a neutron source in the real room model, and adjust the distance between the center of the neutron source and the center of the detector to l max , calculate the detector count value M T (l max ), where T represents the real room model;

[0053] In this embodiment, based on the air room model, the walls, ceiling and floor are set to 50 cm thick concrete to form the air room model.

[0054] S4: Set the distance between the neutron source center and the detector center to l max (150cm), set the front diameter of the shadow cone to d (5cm) and the rear diameter to D (15cm); adjust the distance a between the neutron source center and the shadow cone, and calculate the detector count value M after adding the shadow cone S (l max ,a,d,D) with the distribution of a; through M T (l max ) minus MS (l max ,a,d,D) to obtain the count value M1 after room scattering correction; by dividing M1 with M A (l max ) to determine the optimal distance a between the neutron source center and the shadow cone op (10cm);

[0055] S5: Fixed distance between neutron source center and detector center (150cm) max 、The distance a between the neutron source center and the shadow cone op (10cm), the rear end diameter D of the shadow cone (15cm); adjust the front end diameter d of the shadow cone, and calculate the detector count value M after adding the shadow cone s (l max ,a op ,d,D) with the distribution of d; through M T (l max ) minus M s (l max ,a op ,d,D) to obtain the count value M2 after room scattering correction; by dividing M2 and M A (l max ) to determine the optimal shadow cone front diameter d op (8cm);

[0056] S6: Fixed distance l between the center of neutron source and the center of detector max (150cm), the distance a between the neutron source center and the shadow cone op , (10cm) the front diameter of the shadow cone d op (8cm); adjust the rear end diameter D of the shadow cone and calculate the detector count value M after adding the shadow cone s (l max ,a op ,d op ,D) with the distribution of D; through M T (l max ) minus M s (l max ,a op ,d op , D), and obtain the count value M3 after room scattering correction; by dividing M3 and M A (l max ) to determine the optimal shadow cone front diameter D op (20cm);

[0057] S7: Through the optimal distance a between the neutron source center and the shadow cone op , the front diameter of the shadow cone d op The front diameter of the shadow cone is D opDesign shadow cones for target rooms.

[0058] In this embodiment, the target room is 8m long, 8m wide, and 5m high, with 50cm thick concrete walls, ceilings, and floors. The neutron source is a 241Am-Be neutron source with a neutron emission rate of 1×107nps, and the detector is a long neutron counter. The front diameter of the shadow cone is 8cm, the rear diameter is 20cm, and the distance between the neutron source center and the front end of the shadow cone is 10cm, which can most effectively deduct the room scattering background and make full use of the laboratory space.

[0059] First, by simulating the scattering of neutron sources in air room models and real room models, the present invention can effectively calculate the influence of scattered neutrons on detector counts caused by room structure; by introducing shadow cones and adjusting their parameters (including front diameter, rear diameter and the distance between the neutron source and the shadow cone), the correction effect of neutron scattering is further optimized, so that the detector count is closer to the ideal situation without scattering. Secondly, the present invention uses the Monte Carlo method to simulate and calculate the shadow cone parameters, and can efficiently find the optimal shadow cone parameter combination. By gradually adjusting the various parameters of the shadow cone and comparing the corrected detector count with the count without scattering, the optimal shadow cone parameter combination can be accurately determined. Finally, the present invention can flexibly adjust the parameters of the shadow cone according to the needs and room structure, adapt to different experimental conditions and requirements, have a wide range of application prospects, and can be applied to various neutron measurement instrument calibration experiments and research; at the same time, the optimized shadow cone design can significantly reduce the influence of neutron scattering on the experimental results, improve the accuracy and reliability of the calibration of neutron measurement instruments, and has important significance for neutron measurement, material science, nuclear physics and other fields.

[0060] In the specific implementation process, the maximum distance l available for the detector is determined by the following steps: max :

[0061] S101: Calculate the detector count value by Monte Carlo method: establish an ideal room model without walls, ceilings and floors and in a vacuum environment for the target room; set a neutron source in the ideal room model, and adjust the distance l between the center of the neutron source and the center of the detector, and calculate the detector count value M at different distances l. I (l), where I represents the ideal room model; the results are shown in Figure 2 Ideal room in the

[0062] In this embodiment, the ideal room model room is 8m long, 8m wide and 5m high. The room has no walls, ceilings or floors. The interior of the room is set to a vacuum environment. The neutron source is located at the center of the room. The neutron source is a 241Am-Be neutron source with a neutron emission rate of 1×107nps. The detector is a long neutron counter. The distance between the center of the neutron source and the center of the instrument is adjusted to calculate the count value M of the ideal room model instrument at different positions l. I (l).

[0063] S102: Calculate the detector count value by Monte Carlo method: Set a neutron source in the air room model, and adjust the distance l between the neutron source center and the detector center. Calculate the detector count value M at different distances l. A (l), where A represents the air room model; M A (l) represents the theoretical reference value of the contribution of room-free scattered neutrons (scattered neutrons passing through the laboratory floor, walls, and ceiling). Figure 2 Air room in the room.

[0064] In this embodiment, the vacuum environment is set as an air environment based on the ideal room model, that is, the air room model.

[0065] S103: Calculate the detector count value by Monte Carlo method: Set the neutron source in the real room model, and adjust the distance l between the neutron source center and the detector center. Calculate the detector count value M at different distances l. T (l), where T represents the real room model; the results are shown in Figure 2 A real room in the.

[0066] In this embodiment, based on the air room model, the walls, ceiling and floor are set to 50 cm thick concrete to form the air room model.

[0067] S104: According to the detector count value M I (l), detector count value M A (l) and the detector count value M T (l) Determine the maximum distance at which the detector can be used.

[0068] Specifically, according to M I (l), M A (l) and M T (l) Calculation room scattering contribution S n (l); The room scattering contribution S n (l) is equal to the preset value (40%), and the corresponding distance l between the center of the neutron source and the center of the detector is taken as the maximum distance l available for the detector. max In this embodiment, the maximum distance l max is 150cm.

[0069] Room scattering contribution S n The calculation formula of (l) is:

[0070]

[0071] Specific:

[0072] like Figure 3 As shown, the optimal distance a between the neutron source center and the shadow cone is op Need to meet:

[0073]

[0074] Where: S bound Indicates the allowable error boundary.

[0075] like Figure 4 As shown, the optimal shadow cone front diameter d op Need to meet:

[0076]

[0077] Where: S bound Indicates the allowable error boundary.

[0078] like Figure 5 As shown, the optimal shadow cone front diameter D op Need to meet:

[0079]

[0080] Where: S bound Indicates the allowable error boundary.

[0081] Through the above definition, the present invention can accurately determine the optimal shadow cone parameter combination, thereby improving the accuracy and reliability of the calibration of the neutron measurement instrument.

[0082] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the technical solution. Those skilled in the art should understand that those modifications or equivalent substitutions of the technical solution of the present invention that do not depart from the purpose and scope of the technical solution should be included in the scope of the claims of the present invention.

Claims

1. A shadow cone optimization design method for neutron scattering correction, characterized in that: include: S1: Determine the maximum distance l that the detector can use max ; S2: Establish an air room model for the target room with no walls, no ceiling, and no floor and an air environment; set a neutron source in the air room model and adjust the distance between the center of the neutron source and the center of the detector to l max , calculate the detector count value M A (l max ); where A represents an air room model; S3: Establish a real room model for the target room; set up a neutron source in the real room model, and adjust the distance between the center of the neutron source and the center of the detector to l max , calculate the detector count value M T (l max ), where T represents the real room model; S4: Set the distance between the neutron source center and the detector center to l max , set the front diameter of the shadow cone to d and the rear diameter to D; adjust the distance a between the neutron source center and the shadow cone, and calculate the detector count value M after adding the shadow cone S (l max ,a,d,D) with the distribution of a; through M T (l max ) minus M S (l max ,a,d,D) to obtain the count value M1 after room scattering correction; by dividing M1 with M A (l max ) to determine the optimal distance a between the neutron source center and the shadow cone op ; S5: Fixed distance l between the center of neutron source and the center of detector max 、The distance a between the neutron source center and the shadow cone op , the rear end diameter D of the shadow cone; adjust the front end diameter d of the shadow cone, and calculate the detector count value M after adding the shadow cone s (l max ,a op ,d,D) with the distribution of d; through M T (l max ) minus M s (l max ,a op ,d,D) to obtain the count value M2 after room scattering correction; by dividing M2 and M A (l max ) to determine the optimal shadow cone front diameter d op ; S6: Fixed distance l between the center of neutron source and the center of detector max 、The distance a between the neutron source center and the shadow cone op , the front diameter of the shadow cone d op ; Adjust the rear end diameter D of the shadow cone and calculate the detector count value M after adding the shadow cone s (l max ,a op ,d op ,D) with the distribution of D; through M T (l max ) minus M s (l max ,a op ,d op , D), and obtain the count value M3 after room scattering correction; by dividing M3 and M A (l max ) to determine the optimal shadow cone front diameter D op ; S7: Through the optimal distance a between the neutron source center and the shadow cone op , the front diameter of the shadow cone d op The front diameter of the shadow cone is D op Design shadow cones for target rooms.

2. The shadow cone optimization design method for neutron scattering correction according to claim 1, characterized in that: In step S1, the maximum distance l available to the detector is determined by the following steps: max : S101: Establish an ideal room model without walls, ceilings, or floors and in a vacuum environment for the target room; set a neutron source in the ideal room model, and adjust the distance l between the center of the neutron source and the center of the detector, and calculate the detector count value M at different distances l. I (l), where I represents the ideal room model; S102: Set a neutron source in the air room model and adjust the distance l between the neutron source center and the detector center. Calculate the detector count value M at different distances l. A (l), where A represents the air room model; S103: Set a neutron source in the real room model, and adjust the distance l between the center of the neutron source and the center of the detector. Calculate the detector count value M at different distances l. T (l), where T represents the air room model; S104: According to the detector count value M I (l), detector count value M A (l) and the detector count value M T (l) Determine the maximum distance at which the detector can be used.

3. The shadow cone optimization design method for neutron scattering correction according to claim 2, characterized in that: In step S104, according to M I (l), M A (l) and M T (l) Calculation of room scattering contribution S n (l); The room scattering contribution S n (l) is equal to the preset value (40%), and the corresponding distance l between the center of the neutron source and the center of the detector is taken as the maximum distance l available for the detector. max ; Room scattering contribution S n The calculation formula of (l) is:

4. The shadow cone optimization design method for neutron scattering correction according to claim 1, characterized in that: In step S4, the optimal distance a between the neutron source center and the shadow cone is op Need to meet: Where: S bound Indicates the allowable error boundary.

5. The shadow cone optimization design method for neutron scattering correction according to claim 1, characterized in that: In step S5, the optimal shadow cone front diameter d op Need to meet: Where: S bound Indicates the allowable error boundary.

6. The shadow cone optimization design method for neutron scattering correction according to claim 1, characterized in that: In step S6, the optimal shadow cone front diameter D op Need to meet: Where: S bound Indicates the allowable error boundary.

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