A method and system for obtaining evolution of space electric field of SPND insulating layer and calculating sensitivity of detector

Abstract

This invention discloses a method and system for obtaining the evolution of the space electric field in a self-sustaining neutron detector (SPND) insulating layer and calculating detector sensitivity, belonging to the field of neutron detection technology. The method includes: establishing a dynamic equation for charge density evolution; decomposing the total irradiation current density into a stable and time-varying component, and simulating the stable and time-varying current density distributions contributed by a single source particle under decay equilibrium conditions using the Monte Carlo method; obtaining an expression for the time-varying current density of the SPND, solving the dynamic equation for charge density evolution, and obtaining an analytical expression for charge density evolution; and based on the charge density distribution, obtaining the electric field intensity distribution through integration, and simulating the detector sensitivity. This method directly reveals the influence of detector parameters and neutron flux on the space electric field and its evolution, solving the problems of large computational load and long processing time in existing technologies, significantly improving computational efficiency, and thus achieving efficient simulation of the sensitivity of a self-sustaining neutron detector.

Description

Technical Field

[0001] This invention belongs to the field of neutron detection technology and relates to a method for obtaining the spatial electric field evolution of the SPND insulating layer and calculating the detector sensitivity. Specifically, it relates to a method, system, terminal equipment and storage medium for calculating the SPND detector sensitivity based on the spatial electric field evolution of the insulating layer. Background Technology

[0002] Self-Powered Neutron Detectors (SPNDs) are widely used in reactor neutron measurement due to their simple structure, resistance to high temperatures and pressures, and resistance to strong radiation. The detector mainly consists of an emitter, an insulating layer, and a collector. The emitter is typically made of a metal with a large neutron trapping cross-section, with an insulating material in between. The collector is made of a highly conductive alloy. When the detector is placed inside the reactor, the emitter material traps neutrons, which either decay directly to produce electrons or emit gamma rays to produce secondary electrons. These electrons pass through the insulating layer to reach the collector, and the magnitude of the resulting current is related to the neutron current intensity, thus enabling the measurement of neutrons within the reactor.

[0003] During the operation of an SPND (Special Spatial Density Detector), electrons may become trapped in the insulating layer due to insufficient kinetic energy, creating a spatial electric field. This field affects the transport behavior of subsequent electrons within the insulating layer, thus impacting the detector's sensitivity. Therefore, to improve the accuracy of detector sensitivity calculations, a quantitative analysis of the space charge effect (also known as the electrostatic effect) of the insulating layer is necessary. Furthermore, when designing the detector, the maximum electric field strength of the insulating layer must be calculated in conjunction with the operating environment to ensure it does not exceed the breakdown strength of the insulating material. Otherwise, the insulating layer may fail due to breakdown, ultimately leading to detector failure.

[0004] Currently, there are many studies on the electrostatic effects of SPND, but there are still some shortcomings, mainly in the following aspects: 1) In most studies, the charge distribution of the insulating layer is assumed and differs significantly from the actual situation; 2) Some studies simulate charge deposition using the Monte Carlo method, incorporating a real electric field into the simulation process and iteratively simulating the accumulation process of the electric field. Although this can reflect the distribution and dynamic changes of the electric field, the computational efficiency of simulating charge deposition is low, especially in the case of an electric field, where the simulation of the interaction between rays and matter is very complex, the calculation time is lengthy, and it is difficult to optimize the design; 3) Under actual commercial reactor conditions, the electric field has little impact on the detector sensitivity, but when designing the detector size and selecting detector materials, it is necessary to calculate the magnitude of the spatial electric field of the insulating layer to assess whether breakdown has occurred. At this time, the iterative method for simulating the accumulation of the electric field is too time-consuming and cannot meet the design requirements. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide a method and system for obtaining the spatial electric field evolution of the SPND insulating layer and calculating the detector sensitivity, so as to solve the technical problems of low calculation efficiency, long time consumption and difficulty in meeting design requirements of the prior art.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] A method for obtaining the spatial electric field evolution of the SPND insulating layer and calculating the detector sensitivity includes:

[0008] Establish the dynamic equation for the evolution of charge density;

[0009] The total irradiation current density is decomposed into a stable component and a time-varying component. The Monte Carlo method is used to simulate the stable current density distribution and the time-varying current density distribution contributed by a single source particle under decay equilibrium conditions.

[0010] Obtain the expression for the time-varying current density of SPND, solve the dynamic equation for charge density evolution, and obtain the analytical expression for charge density evolution;

[0011] Based on the analytical expression of charge density evolution, the evolution process of electric field intensity distribution is obtained by integration, and the sensitivity of the detector is obtained by simulation.

[0012] Furthermore, the step of establishing the dynamic equation for charge density evolution includes:

[0013] Based on the law of conservation of charge, as shown below:

[0014]

[0015] In the formula, Let ρ(r,t) represent the total current density and ρ(r,t) represent the charge density. This is the Laplace operator, i.e., the gradient operator; the total current density can be written as the irradiation current density. With conduction current density The sum is:

[0016]

[0017] Combining Ohm's law, we get:

[0018]

[0019] The relationship between electric field and electric potential is as follows:

[0020]

[0021] The partial differential equation describing the variation of charge density with time and space is established as follows:

[0022]

[0023] Where σ is the conductivity of the detector insulator (the reciprocal of the volume resistivity), and ε is the dielectric constant of the insulator.

[0024] Furthermore, the steps of obtaining the expression for the time-varying partial current density of the SPND, solving the dynamic equation for charge density evolution, and obtaining the analytical expression for charge density evolution include:

[0025] For transient SPND, when the electric field is small, the effect of the electric field on the signal electrons can be ignored. Since t is irrelevant, then we have (let t) (denoted as time constant)

[0026]

[0027] For a delayed SPND, its current density can be divided into two parts, including a time-varying component. and non-time-varying part (When the electric field is small, the effect of the electric field on the signal electrons is ignored), that is:

[0028]

[0029] For an emitter with m unstable nuclides, the irradiation current density of the time-varying component of the i-th nuclide is... It can be written as:

[0030]

[0031] In the formula, λ i Let a be the half-life of the i-th nuclide. i (r) represents the surface current density distribution in the insulating layer generated by each decay of the i-th nuclide in steady state, N. i,s At decay equilibrium, the nucleon number density of the i-th nucleus, φ is the neutron flux density, and α... ij is a constant coefficient, and e is the natural constant.

[0032] So, when When the half-life of the substance is not equal to that of any of the nuclides, we obtain

[0033]

[0034] when When the half-life is equal to that of a certain nuclide, there is

[0035]

[0036] As can be seen, the electric field equilibrium time of transient SPND is determined by τ, while that of delayed SPND is determined by both τ and the half-life of the nuclide.

[0037] Furthermore, the step of simulating the steady-state current density distribution and the time-varying current density distribution under decay equilibrium conditions using the Monte Carlo method includes:

[0038] The radiation field information, detector geometry, and materials are input into the Monte Carlo simulation program to simulate the interaction between the radiation and the detector. The stable current density distribution (derived from the contribution of secondary electrons produced by gamma generated during neutron capture) and the time-varying current density distribution (derived from the decay process) are statistically analyzed.

[0039] Furthermore, the step of obtaining the electric field intensity distribution based on the charge density distribution through integration and simulating the detector sensitivity includes:

[0040] Based on the relationship between electric field and charge density, the obtained analytical expression for charge density is spatially integrated to calculate the electric field intensity distribution. Using the calculated electric field intensity distribution, the sensitivity of the detector under different operating conditions is simulated and evaluated.

[0041] Furthermore, the method for integrating the charge density is numerical integration or analytical integration, and the integration expression is as follows:

[0042]

[0043] Among them, R i R is the outer radius of the launch vehicle. o ξ is the outer radius of the insulator; ξ is the integration variable, used to specify the variable that needs to be integrated in the equation.

[0044] Furthermore, the method is used to analyze the influence of detector parameters and neutron flux on the evolution of the space electric field, providing a theoretical basis for the design and optimization of SPND.

[0045] A system for calculating the space charge effect in an insulator of a self-powered neutron detector, comprising:

[0046] A module is established to develop a dynamic equation for the evolution of charge density based on the law of charge conservation.

[0047] The simulation module is used to decompose the irradiation current density into a stable part and a time-varying part, and to simulate the stable current density and time-varying current density under decay equilibrium conditions using the Monte Carlo method.

[0048] The calculation module is used to obtain the expression for the time-varying current density of SPND, solve the dynamic equation of charge density evolution, and obtain the analytical expression for charge density evolution.

[0049] The integration module is used to obtain the electric field intensity distribution based on the charge density distribution through integration, and to simulate the sensitivity of the detector.

[0050] A terminal device includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the method.

[0051] A computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the method.

[0052] Compared with the prior art, the present invention has the following beneficial effects:

[0053] This invention discloses a method for obtaining the spatial electric field evolution of the SPND insulating layer and calculating detector sensitivity. Through the analytical expression of electric field evolution, the evolution process of the electric field can be theoretically calculated, its evolution time estimated, and a quantitative relationship established between detector parameters, neutron radiation field intensity, and the insulating layer electric field. This method directly reveals the influence of detector parameters and neutron flux on the spatial electric field and its evolution, providing a new theoretical basis for the design and optimization of self-powered neutron detectors. It solves the problems of large computational load and long processing time in existing technologies, significantly improving computational efficiency, thereby achieving efficient simulation of the sensitivity of self-powered neutron detectors.

[0054] Furthermore, this invention explicitly provides an analytical expression for the evolution of the electric field, and defines a time constant for electric field equilibrium based on this analytical expression. This time constant can guide the simulation step size setting of the iterative calculation method.

[0055] Furthermore, this invention can directly obtain the steady-state electric field through a single simulation when the electric field is small, effectively improving computational efficiency. Attached Figure Description

[0056] Figure 1 This is a flowchart of a method for calculating the sensitivity of an SPND detector based on the evolution of the spatial electric field in the insulating layer.

[0057] Figure 2 This is a flowchart illustrating the theoretical method for obtaining the spatial electric field evolution of the SPND insulating layer according to the present invention.

[0058] Figure 3 This is a diagram showing the evolution of charge deposition in the insulating layer of the cobalt self-powered neutron detector of the present invention.

[0059] Figure 4 This is a diagram showing the electric field intensity distribution of the insulating layer of the cobalt self-powered detector under steady-state conditions according to the present invention.

[0060] Figure 5This is a graph showing the relationship between the maximum electric field strength of the insulating layer and the bulk resistivity of the cobalt self-powered detector under steady-state conditions according to the present invention.

[0061] Figure 6 This is a graph showing the relationship between the neutron sensitivity of the cobalt self-powered detector and the resistivity of the insulating layer under steady-state conditions according to the present invention. Detailed Implementation

[0062] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0063] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0064] It should be noted that the terminals involved in the embodiments of this application may include, but are not limited to, mobile phones, personal digital assistants (PDAs), wireless handheld devices, tablet computers, personal computers (PCs), MP3 players, MP4 players, wearable devices (e.g., smart glasses, smartwatches, smart bracelets), smart home devices, and other smart devices.

[0065] Furthermore, the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0066] The present invention will now be described in further detail with reference to the accompanying drawings:

[0067] See Figure 1 The method disclosed in this invention for obtaining the spatial electric field evolution of the SPND insulating layer and calculating the detector sensitivity includes:

[0068] Establish the dynamic equation for the evolution of charge density;

[0069] The total irradiation current density is decomposed into a stable component and a time-varying component. The Monte Carlo method is used to simulate the stable current density distribution and the time-varying current density distribution contributed by a single source particle under decay equilibrium conditions.

[0070] Obtain the expression for the time-varying current density of SPND, solve the dynamic equation for charge density evolution, and obtain the analytical expression for charge density evolution;

[0071] Based on the charge density distribution, the electric field intensity distribution is obtained through integration, and the sensitivity of the detector is obtained through simulation.

[0072] The expression for charge density distribution includes both steady-state current density and time-varying current density, i.e., the "analytical expression for charge density evolution". However, the time-varying current density cannot be obtained directly, so it needs to be represented by the "time-varying current density distribution contributed by a single source particle under decay equilibrium".

[0073] See Figure 2 The specific process for obtaining the spatial electric field evolution of the SPND insulating layer includes the following steps:

[0074] Step 1: Based on the law of conservation of charge, establish the dynamic equation for the evolution of charge density;

[0075] The law of conservation of charge is as follows:

[0076]

[0077] In the formula, Let ρ(r,t) represent the total current density, and ρ(r,t) represent the charge density. The total current density can be written as the irradiation current density. With conduction current density The sum is:

[0078]

[0079] Combining Ohm's law, we have:

[0080]

[0081] And from the relationship between electric field and electric potential, we obtain:

[0082]

[0083] The partial differential equation describing the variation of charge density with time and space is established as follows:

[0084]

[0085] Where σ is the conductivity of the detector insulator (the reciprocal of the volume resistivity), and ε is the dielectric constant of the insulator.

[0086] Step 2: Obtain the expression for the time-varying current of SPND, solve the dynamic equation for charge density evolution, and obtain the analytical expression for charge density evolution.

[0087] SPNDs are divided into transient and delayed types. The expressions for the time-varying current part differ for different types of detectors.

[0088] For transient SPND, when the electric field is small, the effect of the electric field on the signal electrons can be ignored. Since it is independent of t, meaning the current only contains a steady-state component, then:

[0089]

[0090] Solving for the problem, we get:

[0091]

[0092] Where C is an undetermined coefficient. For an unused detector, at t=0, the free charge density of the insulator is 0, then we have (let...) (denoted as time constant):

[0093]

[0094] For a delayed SPND, its current can be divided into two parts, including a time-varying part. and non-time-varying part (When the electric field is small, the effect of the electric field on the signal electrons is ignored), that is:

[0095]

[0096] For an emitter with m unstable nuclides, the nucleon number density N of the i-th nuclide is... i (t) can be represented as:

[0097]

[0098] Where, N i,s At decay equilibrium, the nucleon number density of the i-th nucleus, φ is the neutron flux density, and α... ij It is a constant coefficient.

[0099] Therefore, the time-varying current density generated by unstable nuclides can be expressed as:

[0100]

[0101] Where, λ i Let a be the half-life of the i-th nuclide. i (r) represents the surface current density distribution generated in the insulating layer by each decay of the i-th nuclide in steady state.

[0102] Substituting this into the charge density evolution equation, we get:

[0103]

[0104] Solve this equation when When the half-life of any of the nuclides is not equal, we obtain:

[0105]

[0106] when When the half-life is equal to that of a certain nuclide, we have:

[0107]

[0108] As can be seen, the electric field equilibrium time of transient SPND is determined by τ, while that of delayed SPND is determined by both τ and the half-life of the nuclide.

[0109] Step 3: Decompose the irradiation current into a stable part and a time-varying part, and simulate the stable current distribution and time-varying current distribution under decay equilibrium conditions using the Monte Carlo method;

[0110] The radiation field information, detector geometry, and materials are input into the Monte Carlo simulation program to simulate the interaction between the radiation and the detector. The stable current density distribution (derived from the contribution of secondary electrons produced by gamma generated during neutron capture) and the time-varying current density distribution (derived from the decay process) are statistically analyzed.

[0111] It should be noted that in actual simulations, discrete charge deposition can be simulated instead of current density. The insulator is divided into N layers of hollow cylinders. For the k-th hollow cylinder, its volume is V. k The outer surface is S k .

[0112] For instantaneous SPND, we have:

[0113]

[0114] in, The integral representing the charge density, i.e., the total charge Q of the k-th hollow cylinder. k (t); The integral of the irradiation current density on the outer surface, i.e., the charge deposition rate Q of the k-th hollow cylinder. k ',Right now:

[0115]

[0116] The total charge of the k-th hollow cylinder and the charge density ρ of the k-th hollow cylinder k The (t) relation is

[0117]

[0118] Similarly, for delayed SPND, we have:

[0119]

[0120]

[0121] In the formula, Q k,s ′ represents the charge deposition generated by the stable current in the k-th layer of the hollow cylinder; Q k,t,i ′ represents the charge deposition produced by the decay of the i-th unstable nuclide in the k-th layer of the hollow cylinder.

[0122] Step 4: Based on the charge density distribution, obtain the electric field intensity distribution through integration, and simulate to obtain the detector sensitivity.

[0123] Based on the relationship between electric field and charge density, the electric field intensity distribution is calculated by spatial integration of the obtained analytical expression for charge density. Integration can be performed numerically or analytically, as shown in the following expression:

[0124]

[0125] Among them, R i R is the outer radius of the launch vehicle. o The outer radius of the insulator.

[0126] The radiation field information, detector geometry, and materials are input into the Monte Carlo simulation program, and the corresponding electric field intensity distribution is set to simulate the interaction between the radiation and the detector, thereby obtaining the detector's sensitivity.

[0127] It should be noted that although the derivation of this method ignores the influence of the electric field on the signal electrons, it can be used to calculate the electric field evolution in the case of a large electric field until the electric field is sufficiently large, and then continue to perform numerical iteration calculations based on the calculation results, which can improve the computational efficiency. In addition, this method also provides the equilibrium time information of the electric field for the first time, which can guide the step size setting of the numerical iteration method.

[0128] Example 1

[0129] This embodiment uses a typical cobalt self-powered neutron detector, which is 18cm long. Its detector dimensions and materials are shown in the table below.

[0130] Table 1 Detector Dimensions and Materials

[0131] Geometric shape Outer radius (cm) Material <![CDATA[Density (g / cm 3 )]]> emitter 0.07 <![CDATA[ 59 Co]]> 8.9 Insulation layer 0.12 <![CDATA[Al2O3]]> 3.7 Collection pole 0.145 Stainless steel 8.0

[0132] The radioactive source is a cylindrical isotropic radioactive source located at the outer surface of the collecting electrode, using a thermal neutron source at 600K with a flux density of 1E¹³n·cm⁻¹. -2 s -1 The resistivity of the insulating layer was set to 5E12Ω·m.

[0133] Figure 3 The total charge deposition distribution in the insulating layer varies. Figure 4 The distribution of the electric field in the insulator in steady state shows that the theoretical method and the high-precision numerical iterative method agree very well, proving that the method can effectively predict the evolution of the electric field in the insulating layer.

[0134] Based on this, different resistivity of the insulating layer was set to obtain Figure 5 The relationship between the maximum electric field strength and the bulk resistivity of the insulating layer is shown. The results indicate that the theoretical calculations of the maximum electric field strength under different bulk resistivities are in agreement with those obtained by the high-precision numerical iterative method. Based on the simulated electric field strength, the detector sensitivity is simulated using the Monte Carlo method, such as... Figure 6 As shown, from Figure 6 As can be seen, under the current detector parameters and given radiation environment, the volume resistivity has a relatively small impact on sensitivity. It should be noted that different detector parameters and different radiation field environments affect the electric field distribution; therefore, calculations need to be performed based on specific circumstances.

[0135] Since the theoretical method only requires one calculation, the computation time is much shorter than that of numerical iteration, thus greatly improving computational efficiency.

[0136] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0137] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0138] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0139] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0140] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for obtaining the spatial electric field evolution of an SPND insulating layer and calculating detector sensitivity, characterized in that, include: Establish the dynamic equation for the evolution of charge density; The total irradiation current density is decomposed into a stable component and a time-varying component. The Monte Carlo method is used to simulate the stable current density distribution and the time-varying current density distribution contributed by a single source particle under decay equilibrium conditions. Obtain the expression for the time-varying current density of SPND, solve the dynamic equation for charge density evolution, and obtain the analytical expression for charge density evolution; Based on the analytical expression of charge density evolution, the evolution process of electric field intensity distribution is obtained by integration, and the sensitivity of the detector is obtained by simulation.

2. The method for obtaining the spatial electric field evolution of the SPND insulating layer and calculating the detector sensitivity according to claim 1, characterized in that, The dynamic equation for charge density evolution is derived based on the law of charge conservation. It is a partial differential equation describing the change of charge density with time and space, and the equation is as follows: In the formula, σ is the conductivity of the detector insulator, and ε is the dielectric constant of the insulator; Let ρ(r,t) represent density, and let ρ(r,t) represent charge density.

3. The method for obtaining the spatial electric field evolution of the SPND insulating layer and calculating the detector sensitivity according to claim 1, characterized in that, The simulation of the steady-state and time-varying current density distributions contributed by a single source particle under decay equilibrium conditions using the Monte Carlo method includes: The radiation field information, SPND detector geometry and materials are input into the Monte Carlo simulation program to simulate the interaction between the radiation and the SPND detector. Under decay equilibrium conditions, the stable current density distribution and time-varying current density distribution contributed by a single source particle are statistically obtained.

4. The method for obtaining the spatial electric field evolution of the SPND insulating layer and calculating the detector sensitivity according to claim 1, characterized in that, The expression for obtaining the time-varying part of the current density of SPND includes: For transient SPND, when the electric field is small, the effect of the electric field on the signal electrons can be ignored. If it is unrelated to t, then let Let denoted as the time constant, then the current density is: For delayed SPNDs, the current density is divided into two parts, including a time-varying part. and non-time-varying part When the electric field is small, the effect of the electric field on the signal electrons is ignored, i.e. Solving the dynamic equation for charge density evolution yields an analytical expression for charge density evolution, including: For an emitter with m unstable nuclides, the irradiation current density of the time-varying component of the i-th nuclide is... Written as: In the formula, λ i Let a be the half-life of the i-th nuclide. i (r) represents the surface current density distribution in the insulating layer generated by each decay of the i-th nuclide in steady state, N. i,s At decay equilibrium, the nucleon number density of the i-th nucleus, φ is the neutron flux density, and α... ij The coefficient is constant. So, when When the half-life of any of the nuclides is not equal, we obtain: when When the half-life is equal to that of a certain nuclide, we get:

5. The method for obtaining the spatial electric field evolution of the SPND insulating layer and calculating the detector sensitivity according to claim 1, characterized in that, The steps for obtaining the electric field intensity distribution based on the charge density distribution through integration and simulating the detector's sensitivity include: Based on the relationship between electric field and charge density, the obtained analytical expression for charge density is spatially integrated to calculate the electric field intensity distribution. Then, the calculated electric field intensity distribution is used to simulate and evaluate the sensitivity of the detector under different operating conditions.

6. The method for obtaining the spatial electric field evolution of the SPND insulating layer and calculating the detector sensitivity according to claim 5, characterized in that, The method for spatial integration of the obtained analytical expression for charge density is numerical integration or analytical integration.

7. The method for obtaining the spatial electric field evolution of the SPND insulating layer and calculating the detector sensitivity according to claim 6, characterized in that, The integral expression is as follows: In the formula, R i R is the outer radius of the launch vehicle. o The outer radius of the insulator.

8. A system for rapidly acquiring the spatial electric field evolution of the insulating layer of a self-powered neutron detector, based on the method for acquiring the spatial electric field evolution of the SPND insulating layer and calculating the detector sensitivity as described in any one of claims 1 to 7, characterized in that, include: A module is established to establish the dynamic equations for the evolution of charge density; The simulation module is used to decompose the total irradiation current density into a stable part and a time-varying part, and to simulate the stable current density distribution and time-varying current density distribution contributed by a single source particle under decay equilibrium conditions using the Monte Carlo method. The calculation module is used to obtain the expression for the time-varying current density of SPND, solve the dynamic equation of charge density evolution, and obtain the analytical expression for charge density evolution. The integration module is used to obtain the electric field intensity distribution based on the charge density distribution through integration, and to simulate the sensitivity of the detector.

9. A terminal device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 7.

10. A computer-readable storage medium storing a computer program thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 7.

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