Neutron detector

Abstract

The embodiment of the specification provides a neutron detector, comprising: a housing, the interior of which is vacuum; the at least one detection electrode group is arranged in the shell, each detection electrode group comprises a coating electrode, and the surface of the coating electrode is covered with a fission material layer; and the collecting electrode is used for collecting electrons escaping from the fission material layer after the neutrons are injected into the fission material layer.

Description

Technical Field

[0001] This specification relates to the field of radiation measurement technology, and in particular to a neutron detector. Background Art

[0002] Large nuclear devices usually generate extremely high-intensity radiation fields during operation. Obtaining information such as the yield, spatial distribution, and intensity changes over time of various components in such radiation fields is the basis for studying the physical laws of the evolution of radiators. Neutrons are one of the main radiation particles contained in such radiation fields. Obtaining neutron information through diagnosis and measurement is of great significance for physical research on related devices and status monitoring of the devices themselves. Neutron measurement systems have become essential diagnostic tools for such devices. The fission method is one of the commonly used methods for measuring neutrons. Its characteristics are that the fission reaction releases high energy, which is conducive to generating stronger signal outputs. In addition, the fission reaction cross sections of some nuclides are flat in specific energy regions (mainly the fast neutron energy region), such as 235 U (uranium 235) and 239 Pu (Plutonium-239), so fission-based neutron detection easily achieves a flat energy response. Current fission-based neutron detection technology primarily detects fission fragments produced by the reaction of neutrons with fissionable materials. Related detectors include fission ionization chambers, track fission neutron detectors, and fission diamond detectors.

[0003] This manual provides a neutron detector that is easy to use and has a wide range of applications. Utility Model Content

[0004] Some embodiments of the present specification provide a neutron detector, comprising: a shell, the interior of the shell being a vacuum; at least one detection electrode group arranged inside the shell, each of the detection electrode groups comprising: a coating electrode, the surface of the coating electrode being covered with a fission material layer; and a collecting electrode, the collecting electrode being used to collect electrons escaping from the fission material layer after being irradiated by neutrons.

[0005] In some embodiments, the neutron detector includes a plurality of detection electrode groups, and the plurality of detection electrode groups are sequentially arranged inside the shell along the incident direction of the neutrons.

[0006] In some embodiments, a support frame is provided in the shell, and a plurality of slots are provided along the length direction of the support frame; the neutron detector also includes a plurality of support rings detachably connected to the slots, and each support ring is used to place one of the detection electrode groups.

[0007] In some embodiments, the distance between two adjacent card slots is in the range of 5 cm to 25 cm.

[0008] In some embodiments, the distance between the coating electrode and the collecting electrode in each detection electrode group is in the range of 10 mm to 50 mm.

[0009] In some embodiments, the coating electrode and the collecting electrode include a stainless steel substrate, and the fissile material layer is disposed on a surface of the stainless steel substrate of the coating electrode.

[0010] In some embodiments, the fissile material layer includes a uranium-233 coating, a uranium-235 coating, a uranium-238 coating, and a plutonium-239 coating.

[0011] In some embodiments, the radial dimension of the fissile material layer is in the range of 60 mm to 150 mm.

[0012] In some embodiments, the thickness of the fissile material layer is less than or equal to the maximum movement distance of fission fragments generated after the fissile material layer is irradiated by neutrons in the fissile material layer.

[0013] In some embodiments, a vacuum pumping interface, a vacuum monitoring interface, a voltage loading interface and a signal output interface are provided on the side wall of the shell. The vacuum pumping interface is used to connect a vacuum pumping device, the vacuum monitoring interface is used to connect a vacuum degree monitoring device, the voltage loading interface is used to connect an external power supply, and the signal output interface is used to connect a current measuring device; vacuum sealing windows are provided at both ends of the shell. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] This specification will be further described in the form of exemplary embodiments, which will be described in detail with reference to the accompanying drawings. These embodiments are not limiting, and in these embodiments, like numbers represent like structures, wherein:

[0015] Figure 1 is a simplified module schematic diagram of a neutron detector according to some embodiments of this specification;

[0016] Figure 2 is a schematic diagram of a structure in which a detection electrode group is disposed in a housing according to some embodiments of this specification;

[0017] Figure 3 This is a schematic structural diagram of a detection electrode group in which the coated electrode is coated on one side according to some embodiments of this specification;

[0018] Figure 4 is a schematic structural diagram of a support device according to some embodiments of this specification;

[0019] Figure 5 It is a schematic structural diagram of a shell according to some embodiments of this specification.

[0020] Figure 1: Neutron detector 100; shell 10; signal output interface 11; vacuum pumping interface 12; vacuum monitoring interface 13; voltage loading interface 14; vacuum sealing window 15; detection electrode group 20; coating electrode 21; fission material layer 22; collecting electrode 23; support device 30; support frame 31; card slot 311; support card ring 32. DETAILED DESCRIPTION

[0021] To more clearly illustrate the technical solutions of this application, the following briefly describes the drawings used in the description of the embodiments. Obviously, the drawings described below are merely examples or embodiments of this specification. Those skilled in the art can apply this specification to other similar scenarios based on these drawings without inventive effort. Unless otherwise apparent from the context or otherwise noted, the same reference numerals in the figures represent the same structure or operation.

[0022] As shown in this specification and claims, unless the context clearly indicates an exception, the words "a", "an", "an" and / or "the" do not specifically refer to the singular and may also include the plural. Generally speaking, the terms "include" and "comprise" only indicate the inclusion of the steps and elements that have been clearly identified, and these steps and elements do not constitute an exclusive list. The method or device may also include other steps or elements. The term "based on" means "at least partially based on". The term "some embodiments" means "at least one embodiment"; the term "other embodiments" means "at least one other embodiment". The relevant definitions of other terms will be given in the following description.

[0023] Since the placement or use position of the products in this manual can be changed at will, the directional words such as "up", "down", "left", "right", "front", and "back" mentioned in this manual only indicate relative position relationships and are not used to limit absolute position relationships.

[0024] Figure 1 is a simplified module schematic diagram of a neutron detector according to some embodiments of this specification;

[0025] Figure 2 is a schematic diagram of a structure in which a detection electrode group is disposed in a housing according to some embodiments of this specification; Figure 3 This is a structural schematic diagram of a detection electrode group in which the coated electrode is coated on one side according to some embodiments of this specification.

[0026] In some embodiments, combined Figure 1-Figure 3As shown, the neutron detector 100 may include a housing 10 and a detection electrode group 20. The interior of the housing 10 is a vacuum environment, and the housing 10 may be used to accommodate the detection electrode group 20. Each detection electrode group 20 may include a coating electrode 21 and a collecting electrode 23, and the surface of the coating electrode 21 is covered with a fissile material layer 22.

[0027] When a neutron strikes the coated electrode 21 and the fissile material layer 22, the neutron undergoes a nuclear fission reaction with the fissile material layer 22 on the surface of the coated electrode 21, producing fission fragments. The fission fragments then move within the fissile material layer 22, generating electrons. After the electrons escape from the fissile material layer 22, they move toward the collecting electrode 23. Since the detection electrode assembly 20 is located in a vacuum environment, the electrons are not ionized. During the electron movement, a positive signal is generated when the electrons leave the fissile material layer 22 on the coated electrode 21, and a negative signal is generated when the electrons enter the collecting electrode 23, thereby generating a current between the coated electrode 21 and the collecting electrode 23. This allows for neutron measurement based on the current signal output by the collecting electrode 23, giving the neutron detector 100 improved statistical performance. In the process of detecting neutrons, the neutron detector 100 provided in this specification can react with fission materials to generate electrons, without the need to use additional working gas and external power supply to apply voltage to ionize the fission fragments to generate electrons. This not only simplifies the structure of the neutron detector 100, but also enables the neutron detector 100 to be used in a passive (i.e., without external power supply) and working gas-free environment, and is suitable for the operating environment of large nuclear devices.

[0028] Furthermore, when the neutron detector 100 measures neutrons in the mixed radiation field, the primary background component of the mixed radiation field also includes gamma rays. However, when gamma rays collide with the fissile material layer 22, no electrons are generated, and therefore the collecting electrode 23 does not generate any unnecessary electrical signals. In other words, the neutron detector 100 provided herein has a low sensitivity to gamma rays, and gamma rays have a minimal impact on the measurement results of the neutron detector 100, thereby reducing the impact of gamma rays, the primary background component of the mixed radiation field. The sensitivity of the neutron detector 100 refers to the ratio of the amount of charge output by the detector for incident particles of a specific energy over a period of time to the number of particles of the same energy incident on a unit area of the sensitive body of the neutron detector 100 over the same period of time.

[0029] In some embodiments, the collecting electrode 23 may be provided on the side of the coating electrode 21 covered with the fissile material layer 22. For example, Figure 2 and Figure 3In the illustrated embodiment, one side of the coating electrode 21 is covered with the fissile material layer 22, and the collecting electrode 23 is disposed on the side of the coating electrode 21 covered with the fissile material layer 22 and spaced a certain distance from the coating electrode 21. For another example, when both sides of the coating electrode 21 are covered with the fissile material layer 22, there are two collecting electrodes 23, each located on one side of the coating electrode 21 and spaced a certain distance from the coating electrode 21.

[0030] In some embodiments, the coating electrode 21 in each detection electrode group 20 is parallel to the collecting electrode 23. Figure 2-Figure 3 In the illustrated embodiment, the coating electrode 21 and the collecting electrode 23 are both disc-shaped, and the surface of the coating electrode 21 is parallel to the surface of the collecting electrode 23. In other embodiments, the coating electrode 21 and the collecting electrode 23 in each detection electrode group 20 form an angle greater than 0 degrees and less than 90 degrees.

[0031] In some embodiments, the coating electrode 21 and the collecting electrode 23 may include a stainless steel substrate, and the fissile material layer 22 may cover the stainless steel substrate surface of the coating electrode 21. When fission fragments knock out electrons in the fissile material layer 22, since the substrate of the coating electrode 21 is stainless steel, the electrons cannot penetrate the coating electrode 21 and can only move toward the collecting electrode 23. Since the collecting electrode 23 also has a stainless steel substrate, the electrons cannot penetrate the collecting electrode 23 either, which can effectively improve the electron collection efficiency of the collecting electrode 23.

[0032] In some embodiments, the output signal (i.e., output current) of the neutron detector 100 is affected by the spacing and voltage between the coating electrode 21 and the collecting electrode 23. The spacing between the coating electrode 21 and the collecting electrode 23 refers to the distance between the two surfaces of the coating electrode 21 and the collecting electrode 23 that are close to each other. For example, Figure 2 and Figure 3 In the embodiment, the surface of the coating electrode 21 near the collecting electrode 23 is covered with a fissile material layer 22, so the distance L between the surface of the coating electrode 21 covered with the fissile material layer 22 and the surface of the collecting electrode 23 near the fissile material layer 22 can represent the distance between the coating electrode 21 and the collecting electrode 23. The voltage applied between the coating electrode 21 and the collecting electrode 23 can also be referred to as the operating voltage of the neutron detector 100. For example, when the neutron detector 100 includes one detection electrode group 20, the voltage applied between the coating electrode 21 and the collecting electrode 23 of the detection electrode group 20 is the operating voltage of the neutron detector 100. For another example, when the neutron detector 100 includes multiple detection electrode groups 20, the voltage applied between the coating electrode 21 and the collecting electrode 23 of each detection electrode group 20 is the same.

[0033] To verify the effects of the spacing between the coating electrode 21 and the collecting electrode 23 and the voltage loading conditions on the output signal of the neutron detector 100, this manual sets two spacing conditions, 15 mm and 30 mm, as well as multiple voltage loading conditions ranging from 0 V to 4000 V. It should be noted that because the output current of the neutron detector 100 fluctuates to a certain extent, for each experimental condition, this manual records the maximum and minimum output current of the neutron detector 100 within 10 seconds, and uses the average of the two as the final output current of the neutron detector 100. When no irradiation was performed, the circuit noise current of the neutron detector 100 under the same experimental conditions was recorded and was less than 0.4 pA. Table 1 shows the sensitivity data of the neutron detector 100 obtained when the spacing between the coating electrode 21 and the collecting electrode 23 was 30 mm and the voltage was applied from 0 to 4000 V. Table 2 shows the sensitivity data of the neutron detector 100 obtained when the spacing between the coating electrode 21 and the collecting electrode 23 was 15 mm and the voltage was applied from 0 to 4000 V.

[0034] Table 1 is as follows:

[0035]

[0036] Table 2 is as follows:

[0037]

[0038]

[0039] According to the data in Table 1 and Table 2, when no voltage is applied (i.e., when the voltage value in Table 1 and Table 2 is 0), the sensitivity of the neutron detector 100 is 1.33×10 -18 C cm 2 (the distance between the coating electrode 21 and the collecting electrode 23 is 15 mm) and 2.84×10 -18 C cm 2 (The distance between the coating electrode 21 and the collecting electrode 23 is 30 mm.) Compared to the case where no voltage is applied, voltage application significantly improves the sensitivity of the neutron detector 100 under both spacing conditions. The change in applied voltage has little effect on the sensitivity of the neutron detector 100. As can be seen in Tables 1 and 2, the differences in maximum and minimum sensitivity values from 400 V to 4000 V are approximately 8% (when the distance between the coating electrode 21 and the collecting electrode 23 is 30 mm, as shown in Table 1) and 13% (when the distance between the coating electrode 21 and the collecting electrode 23 is 15 mm, as shown in Table 2).

[0040] In summary, compared to no voltage applied, applying a relatively low positive voltage (e.g., a voltage on the order of hundreds of volts, including 100V, 200V, 400V, 600V, and 800V) can significantly improve the sensitivity of the neutron detector 100. This indicates that applying a voltage on the order of hundreds of volts can significantly improve electron collection efficiency, but further increasing the voltage on top of a voltage on the order of hundreds of volts will not significantly improve electron collection efficiency. Therefore, the neutron detector 100 provided in this specification can also have a high sensitivity even at a relatively low operating voltage, reducing the neutron detector's 100 need for a high-voltage environment, ensuring that operators work in a low-voltage environment on the order of hundreds of volts, and improving the safety performance of the neutron detector 100.

[0041] In some embodiments, this specification also considers the effect of the change in the distance between the coating electrode 21 and the collecting electrode 23 on the sensitivity of the neutron detector 100 under the condition of no voltage loading, and compares the experimental results of sensitivity with the theoretical results (see Table 3). It can be seen that the sensitivity of the neutron detector 100 decreases as the distance between the coating electrode 21 and the collecting electrode 23 decreases, and the experimental results have the same changing trend as the theoretical results.

[0042] Table 3 is as follows:

[0043]

[0044] Analysis of the physical process of the fission-based neutron detector 100 reveals that, without applying an additional voltage, a portion of the electrons escaping from the fissile material layer 22 will be backscattered by the collecting electrode 23 and enter the coated electrode 21, thereby reducing the output of the neutron detector 100. Furthermore, the magnitude of the reduction in the output signal of the neutron detector 100 is negatively correlated with the distance between the coated electrode 21 and the collecting electrode 23. That is, the closer the distance between the coated electrode 21 and the collecting electrode 23, the greater the magnitude of the reduction in the output signal of the neutron detector 100 due to electrons backscattered from the collecting electrode 23 and entering the coated electrode 21. The greater the distance between the coated electrode 21 and the collecting electrode 23, the smaller the magnitude of the reduction in the output signal of the neutron detector 100 due to electrons backscattered from the collecting electrode 23 and entering the coated electrode 21.

[0045] In some embodiments, when no additional voltage is applied, escaping fission fragments will also knock out electrons when they collide with the nuclei of the collecting electrode 23. Some of these electrons will also enter the coated electrode 21 and reduce the output of the neutron detector 100. The magnitude of the reduction in the output of the neutron detector 100 is negatively correlated with the distance between the coated electrode 21 and the collecting electrode 23. That is, the closer the distance between the coated electrode 21 and the collecting electrode 23, the greater the magnitude of the reduction in the output of the neutron detector 100 caused by the electrons knocked out when the escaping fission fragments collide with the nuclei of the collecting electrode 23. The greater the distance between the coated electrode 21 and the collecting electrode 23, the smaller the magnitude of the reduction in the output of the neutron detector 100 caused by the electrons knocked out when the escaping fission fragments collide with the nuclei of the collecting electrode 23.

[0046] Based on the above, it can be seen that when the distance between the collector electrode 23 and the coating electrode 21 is relatively large, the amplitude of the neutron detector 100 output signal, which is reduced by the backscattered electrons from the collector electrode 23 and enter the coating electrode 21, can be reduced. Furthermore, the amplitude of the neutron detector 100 output signal, which is reduced by the portion of electrons knocked out by escaping fission fragments when they strike the nuclei of the collector electrode 23 and enter the coating electrode 21, can be reduced. However, when the distance between the collector electrode 23 and the coating electrode 21 is relatively large, the time response efficiency of the neutron detector 100 can also be reduced. Therefore, in some embodiments, to further balance the performance of the neutron detector 100, it is necessary to control the distance between the collector electrode 23 and the coating electrode 21.

[0047] In some embodiments, the distance between the coated electrode 21 and the collecting electrode 23 in each detection electrode group 20 may be in the range of 10 mm to 50 mm. In some embodiments, the distance between the coated electrode 21 and the collecting electrode 23 in each detection electrode group 20 may be in the range of 15 mm to 40 mm. In some embodiments, the distance between the coated electrode 21 and the collecting electrode 23 in each detection electrode group 20 may be in the range of 20 mm to 30 mm.

[0048] In some application scenarios, such as high-intensity pulsed neutron measurements, a large number of escape electrons will be generated in a short period of time. If the electric field generated by these electrons affects the electron collection process, resulting in not all electrons being collected, the output signal of the neutron detector 100 will not be able to linearly reflect the input of the measured neutrons, that is, the linear current range output by the neutron detector 100 will be limited.

[0049] In some embodiments, to increase the linear current of the neutron detector 100, a voltage can be applied between the coating electrode 21 and the collecting electrode 23. The applied voltage is positively correlated with the linear current of the neutron detector 100. However, the higher the applied voltage, the higher the vacuum requirement for the environment in which the neutron detector 100 resides. Therefore, the magnitude of the applied voltage between the coating electrode 21 and the collecting electrode 23 requires a balance between the linear current and the vacuum level. In some embodiments, the operating voltage of the neutron detector 100 can be in the range of 0 to +4000V. Applying a positive high voltage between the coating electrode 21 and the collecting electrode 23 can boost positive signals while suppressing negative signals. Based on the descriptions in Tables 1 and 2 above, applying a positive high voltage can also effectively improve detector sensitivity. In some embodiments, the operating voltage of the neutron detector 100 can be in the range of +1000V to +3000V. In some embodiments, the operating voltage of the neutron detector 100 can be +2000V, which can reduce the vacuum requirement while ensuring that the linear current meets measurement requirements.

[0050] To improve the detection accuracy of the neutron detector 100, it is necessary to obtain the largest possible output signal (i.e., output current) of the neutron detector 100. In some embodiments, the magnitude of the output signal of the neutron detector 100 is related to factors such as the radial size of the fissile material layer 22, the thickness of the fissile material layer 22, and the type of the fissile material layer 22.

[0051] In some embodiments, the fissile material layer 22 may include a uranium-233 coating, a uranium-235 coating, a uranium-238 coating, and a plutonium-239 coating. The fissile materials uranium-233, uranium-235, uranium-238, and plutonium-239 release high energy in fission reactions, which facilitates the generation of stronger signal outputs. Furthermore, their fission reaction cross sections are relatively flat in specific energy regions (primarily the fast neutron energy region), thereby facilitating the neutron detector 100 to achieve a flat energy response. In some specific embodiments, the fissile material layer 22 may be a uranium-235 coating. By utilizing the larger fission cross section of uranium-235 in the thermal neutron energy region, the fissile material layer 22 made of uranium-235 can enable the neutron detector 100 to have higher detection efficiency and a larger output signal.

[0052] Figure 4 is a schematic structural diagram of a support device according to some embodiments of this specification; Figure 5 It is a schematic structural diagram of a shell according to some embodiments of this specification.

[0053] In some embodiments, the signal output of the neutron detector 100 can be as large as possible by increasing the radial dimension of the fission material layer 22. The radial dimension of the fission material layer 22 refers to the minimum dimension of the fission material layer 22 on a plane perpendicular to its own thickness direction. For example, when the fission material layer 22 is circular, the radial dimension of the fission material layer 22 refers to the diameter of the circle. For another example, when the fission material layer 22 is rectangular, the radial dimension of the fission material layer 22 refers to the length of the short side of the rectangle. In some embodiments, when the detection electrode group 20 is placed in the shell 10, the thickness direction of the coating electrode 21, the fission material layer 22 and the collecting electrode 23 can be parallel to the length direction of the shell 10, such as Figure 4 As shown by the arrow X in the figure.

[0054] In some embodiments, the radial dimension of the fissile material layer 22 may be less than or equal to the radial dimension of the coated electrode 21. For example, the coated electrode 21 is a square plate, the fissile material layer 22 is square in shape, and the side length of the fissile material layer 22 is the same as the side length of the coated electrode 21. For another example, the coated electrode 21 is a circular plate, the fissile material layer 22 is circular in shape, and the ratio of the diameter of the fissile material layer 22 to the diameter of the coated electrode 21 is less than or equal to 0.95.

[0055] In some embodiments, the fissile material layer 22 can be coated on the surface of the coating electrode 21 by electroplating. In some embodiments, the bonding force between the fissile material layer 22 and the coating electrode 21 is negatively correlated with the area (or radial dimension) of the fissile material layer 22 and the mass thickness of the fissile material layer 22. Specifically, the larger the area or mass thickness of the fissile material layer 22, the smaller the bonding force between the fissile material layer 22 and the coating electrode 21. When the area and mass thickness of the fissile material layer 22 increase to a certain extent, severe shedding may occur. In fact, shedding may occur before the thickness of the fissile material layer 22 corresponding to the saturation sensitivity of the neutron detector 100 is reached. Therefore, in order to balance the sensitivity of the neutron detector 100 and the bonding force between the fissile material layer 22 and the coating electrode 21, the mass thickness and radial dimension of the fissile material layer 22 need to be controlled. The mass thickness of the fissile material layer 22 refers to the mass of the fissile material layer 22 per unit area in the thickness direction of the fissile material layer 22.

[0056] In some embodiments, the mass thickness of the fissile material layer 22 may be 0.3 mg / cm 2 ~1.5mg / cm 2 In some embodiments, the mass thickness of the fissile material layer 22 may be 0.5 mg / cm 2 ~1.2mg / cm 2In some embodiments, the mass thickness of the fissile material layer 22 may be 0.7 mg / cm 2 ~1mg / cm 2 within the range.

[0057] In some embodiments, the radial dimension of the fissile material layer 22 may be in the range of 60 mm to 150 mm. In some embodiments, the radial dimension of the fissile material layer 22 may be in the range of 70 mm to 120 mm. In some embodiments, the radial dimension of the fissile material layer 22 may be in the range of 80 mm to 100 mm.

[0058] In some embodiments, the fissile material layer 22 may cover one side of the coating electrode 21, such as Figure 3 As shown. For example only, 235 Taking U (uranium 235) as an example, when the diameter of the fissile material layer 22 reaches 93 mm, the single-sided coating (i.e., the fissile material layer 22 is electroplated on one side of the coating electrode 21) can obtain a mass thickness of 1 mg / cm 2 The fission material layer 22 can improve the sensitivity of the neutron detector 100 as much as possible while taking into account the coating bonding strength.

[0059] In some embodiments, the fissile material layer 22 may cover both sides of the coating electrode 21. 235 Taking U (uranium 235) as an example, when the diameter of the fissile material layer 22 reaches 93 mm, double-sided coating (i.e., electroplating the fissile material layer 22 on both sides of the coating electrode 21) can obtain a mass thickness of 0.5 mg / cm 2 Two layers of fissile material 22.

[0060] In some embodiments, in order to further improve the bonding strength between the fission material layer 22 and the coating electrode 21 , the coating electrode 21 and the fission material layer 22 may be subjected to a high-temperature burning treatment after the electroplating is completed.

[0061] In some embodiments, the output signal and sensitivity of the neutron detector 100 can be improved by increasing the thickness of the fissile material layer 22. It is understood that the neutron detection sensitivity of the neutron detector 100 based on the fission principle increases with the thickness of the fissile material layer 22, reaches a maximum value when the fissile material layer 22 reaches a certain thickness, and then remains substantially unchanged. Specifically, when neutrons are incident on the fissile material layer 22, a fission reaction occurs in the fissile material and fission fragments are generated. The high-speed fission fragments interact with the fissile material to generate electrons. The energy of the fission fragments continues to decrease while the speed continues to decrease. The movement distance of the fission fragments in the fissile material layer 22 is limited. When the thickness of the fissile material layer 22 is less than the maximum movement distance of the fission fragments in the fissile material layer 22, the fission fragments can pass through the surface of the fissile material layer 22, and electrons can escape from the fissile material layer 22, thereby being collected by the collecting electrode 23 and outputting a current signal. Therefore, the movement of fission fragments in the fission material layer 22 includes the following situations: (1) When the thickness of the fission material layer 22 is greater than the maximum movement distance of the fission fragments in the fission material layer 22, the fission fragments cannot pass through the surface of the fission material layer 22, the electrons cannot escape from the fission material layer 22 and are collected by the collecting electrode 23, the neutron detector 100 does not output a current signal or the output current signal is small, and the neutron detector 100 cannot measure neutrons at this time. (2) When the thickness of the fission material layer 22 is less than the maximum movement distance of the fission fragments in the fission material layer 22, the fission fragments can pass through the surface of the fission material layer 22. When the thickness of the fission material layer 22 increases, the probability of neutrons and fission materials in the fission material layer 22 undergoing nuclear fission reactions increases, the number of fission fragments generated by the nuclear fission reaction increases, the number of electrons generated and escaped by the movement of the fission fragments in the fission material layer 22 increases, and the number of electrons collected by the collecting electrode 23 increases, so that the current signal output by the neutron detector 100 increases accordingly. (3) When the thickness of the fission material layer 22 is equal to the maximum movement distance of the fission fragments in the fission material layer 22, the fission fragments can just pass through the fission material layer 22. At this time, the sensitivity of the neutron detector 100 reaches the maximum value.

[0062] To maximize the sensitivity and output signal of the neutron detector 100, the thickness of the fissile material layer 22 can be less than or equal to the maximum travel distance of the fission fragments in the fissile material layer 22. In some specific embodiments, the thickness of the fissile material layer 22 can be equal to the maximum travel distance of the fissile fragments in the fissile material layer 22. In some embodiments, the thickness of the fissile material layer 22 can be in the range of 0.4 mm to 1.5 mm. In some embodiments, neutrons reacting with different fissile material layers 22 produce different fission fragments, and different fission fragments have different maximum travel distances in corresponding fissile material layers 22. Therefore, the thickness of the fissile material layer 22 can be selected based on the type of fissile material layer 22. For example, when the fissile material layer 22 is a uranium-235 coating, the thickness of the fissile material layer 22 can be 0.525 mm. For another example, when the fissile material layer 22 is a uranium-238 coating, the thickness of the fissile material layer 22 can be 1.14 mm. For another example, when the fissile material layer 22 is a plutonium 239 coating, the thickness of the fissile material layer 22 may be 0.87 mm. For another example, when the fissile material layer 22 is a thorium coating, the thickness of the fissile material layer 22 may be 1.36 mm.

[0063] In some embodiments, the number of detection electrode groups 20 can be multiple, and the multiple detection electrode groups 20 can be arranged in sequence inside the shell 10 along the incident direction of the neutron. By placing multiple detection electrode groups 20, the detection efficiency range of the neutron detector 100 (i.e., the sensitivity range of the neutron detector 100) can be increased, making the neutron detector 100 suitable for neutron measurement in more sensitive ranges. For example, when the operating voltage is 100V, the number of detection electrode groups 20 is 15, and the spacing between the coating electrode 21 and the collecting electrode 23 of each detection electrode group 20 is 30mm, the detection efficiency of the neutron detector 100 varies in the range of 9.94E - 18C·cm 2 ~1.49E-16C·cm 2 .

[0064] In some embodiments, when there are multiple detection electrode groups 20, the multiple detection electrode groups 20 can be arranged at a certain distance. For example, the multiple detection electrode groups 20 can be arranged along the length direction of the housing 10, and the central axis of the coating electrode 21 and the collecting electrode 23 of each detection electrode group 20 (for example, the coating electrode 21 and the collecting electrode 23 are disc structures) is parallel to the length direction of the housing 10.

[0065] In some embodiments, when there are multiple detection electrode groups 20, adjacent detection electrode groups 20 may be in direct contact. Figure 2In the illustrated embodiment, there are two detection electrode groups 20. For each detection electrode group 20, the coating electrode 21 is a single-layer coating (i.e., one side of the coating electrode is coated with a fissile material layer by electroplating). The collecting electrode 23 is located on the side of the coating electrode 21 coated with the fissile material layer 22 and is spaced a certain distance from the fissile material layer 22. The two coating electrodes 21 are in contact with each other on their sides facing away from the fissile material layer 22.

[0066] In some embodiments, the neutron detector 100 may further include a support device 30, which is disposed inside the housing 10, and the detection electrode group 20 is detachably disposed on the support device 30. By providing the support device 30, the number of detection electrode groups 20 can be increased or decreased according to measurement requirements, thereby adapting to different measurement needs.

[0067] In some embodiments, as Figure 4 As shown, the support device 30 may include a support frame 31 and a support snap ring 32. The support frame 31 is arranged in the housing 10. A plurality of snap rings 311 are provided along the length direction of the support frame 31. The length direction of the support frame 31 may be aligned with the length direction of the housing 10 (e.g., Figure 4 311). The support clamping ring 32 is detachably arranged in the card slot 311, and each support clamping ring 32 is used to place a detection electrode group 20. When installing the detection electrode group 20, the detection electrode group 20 can be first set on the support clamping ring 32, and then the support clamping ring and the detection electrode group 20 are placed together in the card slot 311 of the support frame 31. When disassembling the detection electrode group 20, the support clamping ring 32 can be directly taken out from the card slot 311. By providing the card slot 311 and the support clamping ring 32, the detection electrode group 20 can be installed and disassembled more conveniently, thereby improving the assembly and disassembly efficiency of the detection electrode group 20.

[0068] In some embodiments, the support frame 31 can be fixedly connected to the housing 10. Exemplary fixed connection methods may include riveting, welding, etc. In some embodiments, the support frame 31 can be detachably connected to the housing 10. Exemplary detachable connection methods may include threaded connection, snap-on connection, etc.

[0069] In other embodiments, the detection electrode group 20 can be directly and detachably disposed in the slot 311 without being connected to the slot 311 through the supporting clamp ring 32 .

[0070] In some embodiments, the spacing between two adjacent card slots 311 can be in the range of 5cm to 25cm. In some embodiments, the spacing between two adjacent card slots 311 can be in the range of 5cm to 20cm. In some embodiments, the spacing between two adjacent card slots 311 can be in the range of 5cm to 15cm. The spacing between two adjacent card slots 311 refers to the spacing in the length direction of the support frame 31 (such as Figure 4 The distance between two opposing surfaces of two adjacent slots 311 (as indicated by arrow X in the figure) is referred to as the distance between two opposing surfaces of two adjacent slots 311. By way of example only, each slot 311 may include a first blocking surface (not labeled in the figure), a second blocking surface (not labeled in the figure), and a third blocking surface (not labeled in the figure). The first blocking surface and the second blocking surface are respectively configured to abut against both ends of the support snap ring 32 to limit movement of the support snap ring 32 in the length direction of the support frame 31. The third blocking surface connects the first blocking surface and the second blocking surface and is configured to abut against the sidewall of the support snap ring 32 to limit movement of the support snap ring 32 in the radial direction of the support frame 31. The first blocking surfaces of two adjacent slots 311, or the second blocking surfaces of two adjacent slots 311, are two opposing surfaces of the two adjacent slots 311. Therefore, the distance between the first blocking surfaces of two adjacent slots 311, or the distance between the second blocking surfaces of two adjacent slots 311, may be the distance between the two slots 311.

[0071] In some embodiments, two adjacent slots 311 may be parallel to each other. That is, the two opposite surfaces of the two adjacent slots 311 are parallel. Figure 4 In the illustrated embodiment, the first blocking surfaces of two adjacent slots 311 are parallel to each other, the second blocking surfaces of two adjacent slots 311 are parallel to each other, and the first blocking surface and the second blocking surface of each slot 311 are also parallel to each other.

[0072] In some embodiments, when the two opposing surfaces of two adjacent slots 311 are parallel, the distance between the two opposing surfaces of the two adjacent slots 311 can be the distance between any two opposing points on the two opposing surfaces. For example, the center points of the first blocking surfaces of two adjacent slots 311 can be considered as two opposing points, and thus the distance between the center points of the first blocking surfaces of two adjacent slots 311 is the distance between the two adjacent slots 311.

[0073] In some embodiments, adjacent slots 311 may form an angle greater than 0° and less than 90°. The angle between adjacent slots 311 refers to the angle between two opposing surfaces of two adjacent slots 311, such as the angle between the planes where the first blocking surfaces of two adjacent slots 311 are located.

[0074] In some embodiments, when the two opposing surfaces of two adjacent slots 311 form an angle greater than 0° and less than 90°, the distance between the two opposing surfaces of the two adjacent slots 311 may be the average distance between all opposing points on the two opposing surfaces.

[0075] In some embodiments, the spacing between the plurality of slots 311 may be different. For example, some of the plurality of slots 311 may be more densely distributed, i.e., the spacing between two adjacent slots 311 is shorter, while other slots 311 may be more sparsely distributed, i.e., the spacing between two adjacent slots 311 is longer.

[0076] In some embodiments, combined Figure 1 、 Figure 4 and Figure 5 As shown, the housing 10 is provided with a signal output interface 11 for connecting to a current measuring device (not shown in the figure) for measuring the number of electrons collected by the collecting electrode 23. An exemplary current measuring device may include an electrometer.

[0077] In some embodiments, a vacuum pumping port 12 is provided on the housing 10. The vacuum pumping port 12 can be used to connect a vacuum pumping device, which can be used to extract air from the housing 10 and maintain a vacuum level inside the housing 10. An exemplary vacuum pumping device can include a vacuum pump.

[0078] In some embodiments, a vacuum monitoring interface 13 is provided on the housing 10 . The vacuum monitoring interface 13 is used to connect a vacuum monitoring device, which can be used to detect the vacuum level inside the housing 10 .

[0079] In some embodiments, the housing 10 is provided with a voltage loading interface 14. The voltage loading interface 14 is used to connect to an external power source, which can be used to load a voltage between the coating electrode 21 and the collecting electrode 23. For more details on loading a voltage between the coating electrode 21 and the collecting electrode 23, please refer to the description of other embodiments in this specification.

[0080] In some embodiments, the housing 10 may be provided with one or more of the aforementioned interfaces. For example, the housing 10 may be provided with a signal output interface 11, a vacuum monitoring interface 13, and a vacuum pumping interface 12. The vacuum monitoring device may be in communication with the vacuum pumping device, and the vacuum pumping device may perform corresponding operations based on the detection results of the vacuum monitoring device. By way of example only, when the vacuum monitoring device detects that the vacuum level inside the housing 10 is below a vacuum threshold, the vacuum monitoring device may generate a first vacuum detection signal and transmit the first vacuum detection signal to the vacuum pumping device. The processor of the vacuum pumping device may then begin operating at a specific power level based on the first vacuum detection signal, evacuating the housing 10 to maintain the vacuum environment within the housing 10. When the vacuum monitoring device detects that the vacuum level inside the housing 10 is above the vacuum threshold, the vacuum monitoring device may generate a second vacuum detection signal and transmit the second vacuum detection signal to the vacuum pumping device. The processor of the vacuum pumping device may then cease operation based on the second vacuum detection signal. The vacuum threshold refers to the ambient vacuum level that allows electrons escaping from the fissile material layer 22 to travel to the collecting electrode 23. For example, the vacuum threshold may be 99%, 97%, 95%, etc.

[0081] In some embodiments, when the shell 10 is a cylindrical structure (such as a cylinder or a prism), the vacuum pumping interface 12, the vacuum monitoring interface 13, the voltage loading interface 14 and the signal output interface 11 can be arranged at both ends of the shell 10 in the length direction to ensure that the outer diameter of the neutron detector 100 is reduced to facilitate adaptation to various experimental environments.

[0082] In some embodiments, the housing 10 may be a stainless steel cylinder, with vacuum sealing windows 15 provided at both ends of the housing 10. The planes of the vacuum sealing windows 15 may be perpendicular to the length direction of the housing 10. The vacuum sealing windows 15 may be used to allow an external radiation source to enter the neutron detector 100, thereby causing neutrons to collide with the fissile material layer 22.

[0083] The beneficial effects that may be brought about by the neutron detector in the embodiments of this specification include but are not limited to: (1) Since fission fragments can move in the fission material layer and generate electrons, there is no need to use additional working gas and voltage to ionize the fission fragments. Therefore, during the measurement process of the neutron detector, there is no need to add additional working gas and additional external power supply to ionize the fission fragments to generate electrons. This not only simplifies the structure of the neutron detector, but also can be used in a passive working environment, and is suitable for the operating environment of large nuclear devices; (2) The neutron detector provided in this specification has a low measurement sensitivity to gamma rays, and gamma rays have a small impact on the measurement results of the neutron detector, thereby reducing the influence of gamma rays, the main background component in the mixed radiation field; (3) When the fission fragments are in the After the electrons are knocked out from the fission material layer, since the base of the coating electrode is stainless steel, the electrons cannot penetrate the coating electrode and can only move toward the collecting electrode. Since the base of the collecting electrode is also stainless steel, the electrons cannot penetrate the collecting electrode either, which can effectively improve the collection efficiency of the collecting electrode for electrons. (4) The neutron detector provided in this specification can reduce the demand for a high voltage environment, ensure that the operator works in a low voltage environment, and improve safety performance. (5) The linear current of the neutron detector is increased by applying a voltage between the coating electrode and the collecting electrode. (6) By utilizing the characteristic that the fission cross section of uranium 235 is larger in the thermal neutron energy region, the fission material layer made of uranium 235 can enable the neutron detector to have a higher detection efficiency and a larger output signal. It should be noted that different embodiments may produce different beneficial effects. In different embodiments, the beneficial effects that may be produced may be any one or a combination of the above, or any other possible beneficial effects.

[0084] While the basic concepts have been described above, it will be apparent to those skilled in the art that the detailed disclosure is merely illustrative and does not limit this specification. Although not explicitly stated herein, various modifications, improvements, and revisions to this specification may be made by those skilled in the art. Such modifications, improvements, and revisions are suggested in this specification and remain within the spirit and scope of the exemplary embodiments of this specification.

Claims

1. A neutron detector, characterized in that: include: a housing, wherein the interior of the housing is vacuum; At least one detection electrode group is disposed inside the housing, each detection electrode group comprising: a coated electrode, wherein the surface of the coated electrode is covered with a layer of fissile material; The collecting electrode is used to collect electrons that escape from the fission material layer after being injected by neutrons.

2. The neutron detector according to claim 1, characterized in that The neutron detector includes a plurality of detection electrode groups, which are sequentially arranged inside the shell along the incident direction of the neutrons.

3. The neutron detector according to claim 2, characterized in that A support frame is provided in the shell, and a plurality of slots are provided along the length direction of the support frame; the neutron detector further comprises a plurality of support rings detachably connected to the slots, and each support ring is used to place one detection electrode group.

4. The neutron detector according to claim 3, characterized in that The distance between two adjacent card slots is within the range of 5 cm to 25 cm.

5. The neutron detector according to claim 1, characterized in that The distance between the coating electrode and the collecting electrode in each detection electrode group is in the range of 10 mm to 50 mm.

6. The neutron detector according to claim 1, characterized in that The coating electrode and the collecting electrode include a stainless steel substrate, and the fissile material layer is arranged on the surface of the stainless steel substrate of the coating electrode.

7. The neutron detector according to claim 1, characterized in that The fissile material layer includes a uranium 233 coating, a uranium 235 coating, a uranium 238 coating and a plutonium 239 coating.

8. The neutron detector according to claim 1, characterized in that The radial dimension of the fissile material layer is within the range of 60 mm to 150 mm, and / or the mass thickness of the fissile material layer is within the range of 0.3 mg / cm 2 ~1.5mg / cm 2 within the range.

9. The neutron detector according to claim 1, characterized in that The thickness of the fissile material layer is less than or equal to the maximum movement distance of fission fragments generated after the fissile material layer is irradiated by neutrons in the fissile material layer.

10. The neutron detector according to claim 1, characterized in that A vacuum pumping interface, a vacuum monitoring interface, a voltage loading interface and a signal output interface are provided on the side wall of the shell. The vacuum pumping interface is used to connect a vacuum pumping device, the vacuum monitoring interface is used to connect a vacuum degree monitoring device, the voltage loading interface is used to connect an external power supply, and the signal output interface is used to connect a current measuring device; vacuum sealing windows are provided at both ends of the shell.

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