Method and system for obtaining SPND insulating layer space electric field evolution and calculating detector sensitivity

Abstract

The invention discloses a method and system for obtaining SPND insulating layer space electric field evolution and calculating detector sensitivity, and belongs to the technical field of neutron detection. Comprising the following steps: establishing a charge density evolution dynamic equation; decomposing the total irradiation current density into a stable part and a time-varying part, and simulating stable current density distribution and time-varying current density distribution contributed by single source particles under a decay balance condition through a Monte Carlo method; obtaining an expression of SPND time-varying part current density, and solving the charge density evolution dynamic equation to obtain an analytical expression of charge density evolution; based on the charge density distribution, electric field intensity distribution is obtained through integration, and the sensitivity of the detector is obtained through simulation. The method directly reveals the influence of the detector parameters and the neutron flux on the space electric field and the evolution thereof, solves the problems of large calculation amount and long time consumption in the prior art, and remarkably improves the calculation efficiency, thereby achieving the efficient simulation of the sensitivity of the self-powered neutron detector.

Description

Technical Field

[0001] The present invention belongs to the technical field of neutron detection, and relates to a method for obtaining the spatial electric field evolution of a SPND insulating layer and calculating the detector sensitivity, and specifically relates to a method, system, terminal device and storage medium for calculating the sensitivity of a SPND detector based on the spatial electric field evolution of an insulating layer. Background Art

[0002] Self-Powered Neutron Detector (SPND) has been widely used in the measurement of reactor neutrons due to its simple structure, high temperature and high pressure resistance, and strong radiation resistance. The detector is mainly composed of an emitter, an insulating layer, and a collector. The emitter is usually made of a metal material with a large neutron capture cross section, an insulating material is used in the middle, and the collector is made of an alloy with good conductivity. When the detector is placed in the reactor, the emitter material will capture neutrons, directly generate electrons through decay or generate secondary electrons by emitting gamma rays. These electrons pass through the insulating layer to the collector, and the magnitude of the current generated is related to the neutron current, thereby realizing the measurement of neutrons in the reactor.

[0003] During the operation of SPND, electrons may be retained in the insulating layer due to insufficient kinetic energy, forming a spatial electric field, which will affect the subsequent electron transport behavior in the insulating layer, and thus affect the sensitivity of the detector. Therefore, in order to improve the calculation accuracy of the detector sensitivity, it is necessary to quantitatively analyze the spatial charge effect (also known as the electrostatic effect) of the insulating layer. In addition, when designing the detector, the maximum electric field strength of the insulating layer must be calculated in combination with the working environment to ensure that 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] At present, there have been many studies on the electrostatic effect of SPND, but there are still some shortcomings, mainly reflected in: 1) In most studies, the charge distribution form of the insulating layer is hypothetical, which is quite different from the actual situation; 2) Some studies simulate charge deposition by Monte Carlo method, adding real electric field in the simulation process, and iteratively simulate the accumulation process of electric field. Although it can reflect the distribution and dynamic changes of electric field, the calculation efficiency of simulated charge deposition is low, especially in the case of electric field. The simulation of the interaction between radiation and matter is very complicated, the calculation time is lengthy, and it is difficult to optimize the design; 3) Under the actual commercial reactor operating conditions, the electric field has little effect on the sensitivity of the detector, but when designing the detector size and selecting the detector material, it is necessary to calculate the spatial electric field size of the insulating layer to evaluate whether breakdown occurs. At this time, it takes too long to simulate the accumulation of electric field by iterative method, which is difficult to meet the design requirements. Summary of the invention

[0005] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is 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 in the prior art.

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

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

[0008] Establish the dynamic equations for charge density evolution;

[0009] The total irradiation current density is decomposed into a stable part and a time-varying part, and the stable current density distribution and the time-varying current density distribution contributed by a single source particle under the decay equilibrium condition are simulated by Monte Carlo method.

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

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

[0013] Based on the law of conservation of charge, it is as follows:

[0014]

[0015] In the formula, represents the total current density, ρ(r,t) represents the charge density, is the Laplace operator, i.e. the gradient operator; the total current density can be written as the irradiation current density and 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 change of charge density in time and space is established as follows:

[0022]

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

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

[0025] For instantaneous SPND, when the electric field is small, the effect of the electric field on the signal electrons is ignored. It has nothing to do with t, so (let is recorded as the time constant)

[0026]

[0027] For delayed-type SPND, the current density can be divided into two parts, including the time-varying part With the time-invariant part (When the electric field is small, the influence of the electric field on the signal electrons is ignored), that is:

[0028]

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

[0030]

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

[0032] Then, when When the half-life is not equal to that of any nuclide, we get

[0033]

[0034] when When the half-life of a nuclide is equal to

[0035]

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

[0037] Furthermore, the step of simulating the stable current density distribution and the time-varying current density distribution under the decay equilibrium condition by the Monte Carlo method includes:

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

[0039] Furthermore, the steps of obtaining the electric field intensity distribution by integration based on the charge density distribution and simulating the sensitivity of the detector include:

[0040] According to the relationship between electric field and charge density, the obtained analytical expression of charge density is spatially integrated to calculate the electric field intensity distribution. The calculated electric field intensity distribution is used to simulate and evaluate the sensitivity of the detector under different working conditions.

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

[0042]

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

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

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

[0046] Establish a module for establishing the dynamic equation of charge density evolution based on the law of charge conservation;

[0047] A simulation module is used to decompose the irradiation current density into a stable part and a time-varying part, and use the Monte Carlo method to simulate the stable current density and the time-varying current density under the decay equilibrium condition;

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

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

[0050] A terminal device comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the steps of the method are implemented when the processor executes the computer program.

[0051] A computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the method are implemented.

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

[0053] The method disclosed in the present invention for obtaining the spatial electric field evolution of the SPND insulating layer and calculating the detector sensitivity can theoretically calculate the evolution process of the electric field through the analytical expression of the electric field evolution, estimate its evolution time, and establish a quantitative relationship between the detector parameters, the neutron radiation field intensity and the electric field of the insulating layer. This method directly reveals the influence of the detector parameters and the neutron flux on the spatial electric field and its evolution, provides a new theoretical basis for the design and optimization of the self-powered neutron detector, solves the problems of large amount of calculation and long time consumption in the prior art, significantly improves the calculation efficiency, and thus realizes the efficient simulation of the sensitivity of the self-powered neutron detector.

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

[0055] Furthermore, the present invention can directly obtain a steady-state electric field through a single simulation when the electric field is small, thereby effectively improving calculation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 The figure is a flow chart of the method for calculating the sensitivity of the SPND detector based on the spatial electric field evolution of the insulating layer.

[0057] Figure 2 The flowchart of the theoretical method for obtaining the spatial electric field evolution of the SPND insulating layer of the present invention.

[0058] Figure 3 This is a diagram showing the evolution of charge deposition on 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 of the present invention.

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

[0062] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme 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 only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work 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 and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0064] It should be noted that the terminals involved in the embodiments of the present 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 (for example, smart glasses, smart watches, smart bracelets, etc.), smart home devices and other smart devices.

[0065] In addition, the term "and / or" in this article is only a description of the association relationship between the associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0066] The present invention is further described in detail below in conjunction with the accompanying drawings:

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

[0068] Establish the dynamic equations for charge density evolution;

[0069] The total irradiation current density is decomposed into a stable part and a time-varying part, and the stable current density distribution and the time-varying current density distribution contributed by a single source particle under the decay equilibrium condition are simulated by Monte Carlo method.

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

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

[0072] The expression of charge density distribution includes the stable current density and the time-varying current density, i.e., the "analytical expression of charge density evolution". However, the time-varying current density cannot be directly obtained, so it is necessary to use the "time-varying current density distribution contributed by a single source particle under decay equilibrium" to express it.

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

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

[0075] Among them, the charge conservation law is as follows:

[0076]

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

[0078]

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

[0080]

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

[0082]

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

[0084]

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

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

[0087] SPND is divided into instantaneous type and delayed type. Different types of detectors have different expressions for the time-varying current part.

[0088] For instantaneous SPND, when the electric field is small, the effect of the electric field on the signal electrons is ignored. It is independent of t, that is, the current only contains the stable part, then:

[0089]

[0090] Solving, we get:

[0091]

[0092] Where C is the unknown coefficient. For the unused detector, when t = 0, the insulator free charge density is 0, so (let Recorded as time constant):

[0093]

[0094] For the delayed SPND, the current can be divided into two parts, including the time-varying part With the time-invariant part (When the electric field is small, the influence of the electric field on the signal electrons is ignored), that is:

[0095]

[0096] For an emitter with a total of m unstable nuclides, the nucleon number density N of the ith nuclide is i (t) can be expressed as:

[0097]

[0098] Among them, N i,s is the nucleon number density of the ith nucleus when decay is balanced, φ is the neutron flux density, α ij is a constant coefficient.

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

[0100]

[0101] Among them, λ i is the half-life of the ith nuclide, a i (r) is the surface current density distribution generated in the insulating layer by each decay of the i-th nuclide when it is in steady state.

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

[0103]

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

[0105]

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

[0107]

[0108] It can be seen that the electric field equilibrium time of the instantaneous SPND is determined by τ, while the delayed SPND is determined by 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 the time-varying current distribution under decay equilibrium by using the Monte Carlo method;

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

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

[0112] For instantaneous SPND, there are:

[0113]

[0114] in, represents the integral of the charge density, i.e. the total charge Q of the k-th hollow cylinder k (t); represents the integral of the irradiation current density on the outer surface, i.e., the charge deposition rate Q of the kth 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 (t) The relationship is

[0117]

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

[0119]

[0120]

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

[0122] Step 4: Based on the charge density distribution, the electric field intensity distribution is obtained by integration, and the sensitivity of the detector is obtained by simulation.

[0123] According to the relationship between electric field and charge density, the obtained analytical expression of charge density is spatially integrated to calculate the distribution of electric field intensity. The integral can be numerically integrated or analytically integrated. The integral expression is as follows:

[0124]

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

[0126] The radiation field information, detector geometry and material are input into the Monte Carlo simulation program, the corresponding electric field intensity distribution is set, the interaction between the rays and the detector is simulated, and the sensitivity of the detector is obtained.

[0127] It should be pointed out that although the derivation of this method ignores the influence of the electric field on signal electrons, in the case of large electric fields, this method can be used to calculate the evolution of the electric field until the electric field is sufficiently large, and then continue the numerical iterative calculation based on the calculation results, which can improve the calculation efficiency; in addition, this method also gives the equilibrium time information of the electric field for the first time, which can guide the step size setting of the numerical iterative method.

[0128] Example 1

[0129] This embodiment uses a typical cobalt self-powered neutron detector with a length of 18 cm. The detector dimensions and materials are shown in the following table.

[0130] Table 1 Detector size and material

[0131] Geometry 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 Collector 0.145 Stainless steel 8.0

[0132] The radiation source is a cylindrical isotropic radiation source located on the outer surface of the collector. It uses a thermal neutron source at a temperature of 600K with a flux density of 1E13n·cm -2 s -1 The bulk resistivity of the insulating layer is set to 5E12Ω·m.

[0133] Figure 3 is the distribution change of total charge deposition in the insulating layer, Figure 4 This is the distribution of the electric field of the insulator in the steady state. It can be seen that the theoretical method is in good agreement with the high-precision numerical iteration method, which proves that this method can effectively predict the evolution of the electric field in the insulating layer.

[0134] On this basis, different insulating layer resistivities are set to obtain Figure 5 The relationship between the maximum electric field strength of the insulating layer and the volume resistivity of the insulating layer is shown in Figure 1. The results show that the calculation results of the maximum electric field strength under different volume resistivities by the theoretical method are consistent with the calculation results of the high-precision numerical iteration method. Based on the simulated electric field strength, the detector sensitivity is simulated by the Monte Carlo method, as shown in Figure 1. Figure 6 As shown, from Figure 6 It can be seen that under the current detector parameters and given radiation environment, the volume resistivity has little effect on the sensitivity. It should be pointed out that different detector parameters and different radiation field environments have an impact on the electric field distribution, so calculations need to be carried out according to specific circumstances.

[0135] Since the theoretical method only requires one calculation, the calculation time is much lower than numerical iteration, thus greatly improving the calculation efficiency.

[0136] It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, systems or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented 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] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0138] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0139] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0140] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for obtaining the spatial electric field evolution of the SPND insulating layer and calculating the detector sensitivity, characterized in that: include: Establish the dynamic equations for charge density evolution; The total irradiation current density is decomposed into a stable part and a time-varying part, and the stable current density distribution and the time-varying current density distribution contributed by a single source particle under the decay equilibrium condition are simulated by Monte Carlo method. Obtain the expression of the time-varying partial current density of SPND, solve the dynamic equation of charge density evolution, and obtain the analytical expression of 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 simulated.

2. The method for obtaining the spatial electric field evolution of the SPND insulating layer and calculating the detector sensitivity according to claim 1 is characterized in that: The dynamic equation of charge density evolution is based on the law of charge conservation and is a partial differential equation that describes the change of charge density over time and space. The equation is as follows: Where σ is the conductivity of the detector insulator, and ε is the dielectric constant of the insulator; represents density, and ρ(r,t) represents 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 operations of simulating the steady current density distribution and time-varying current density distribution contributed by a single source particle under decay equilibrium by Monte Carlo method include: 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 the condition of decay equilibrium, 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 partial current density of SPND includes: For instantaneous SPND, when the electric field is small, the effect of the electric field on the signal electrons is ignored. It has nothing to do with t, so let Recorded as the time constant, the current density is: For delayed-type SPND, the current density is divided into two parts, including the time-varying part With the time-invariant part When the electric field is small, the effect of the electric field on the signal electrons is ignored, that is, Solve the dynamic equation of charge density evolution and obtain the analytical expression of charge density evolution, including: For an emitter with a total of m unstable nuclides, the irradiation current density of the time-varying part of the i-th nuclide is Written as: In the formula, λ i is the half-life of the ith nuclide, a i When (r) is steady state, the surface current density distribution generated by each decay of the i-th nuclide in the insulating layer, N i,s is the nucleon number density of the ith nucleus when decay is balanced, φ is the neutron flux density, α ij is a constant coefficient; Then, when When the half-life is not equal to that of any nuclide, we obtain: when When it is equal to the half-life of a 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: Based on the charge density distribution, the electric field intensity distribution is obtained by integration, and the steps of simulating the sensitivity of the detector include: According to the relationship between electric field and charge density, the obtained analytical expression of 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 working 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 of spatially integrating the obtained analytical expression of charge density is numerical integration or analytical integration.

7. The method for calculating the sensitivity of a SPND detector based on the spatial electric field evolution of an insulating layer 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 is 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 insulating layer of a SPND and calculating the detector sensitivity as described in any one of claims 1 to 7, characterized in that: include: Building modules for establishing dynamic equations for charge density evolution; A simulation module is used to decompose the total irradiation current density into a stable part and a time-varying part, and use the Monte Carlo method to simulate the stable current density distribution and the time-varying current density distribution contributed by a single source particle under decay equilibrium; The calculation module is used to obtain the expression of the time-varying partial current density of the SPND, solve the dynamic equation of charge density evolution, and obtain the analytical expression of charge density evolution; The integration module is used to obtain the electric field intensity distribution through integration based on the charge density distribution, and 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, the steps of the method according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

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