A method and system for quantitatively analyzing self-insulation resistance shunt effect of a self-powered detector

Abstract

The application discloses a method and system for quantitatively analyzing self-insulation resistance shunt effect of a self-powered detector, and the design steps are as follows: a circuit model of the self-powered detector is established according to a working principle of the detector; specific parameters of each element in the circuit are calculated according to geometric structure and physical parameters of the detector; a state space equation in a matrix form is established according to a current generation mechanism of the self-powered detector in a radiation field and the circuit model, and a system state transition matrix of the self-powered detector system is established by solving a matrix index; and influences of geometric dimensions and physical parameters of the detector on the insulation resistance and the shunt effect thereof are analyzed according to the system state transition matrix. The method can quantitatively calculate the shunt effect of the insulation layer resistance of the self-powered detector with different structures and parameters, and can accurately calculate a change of a capacitive current with time, thereby providing guidance for design and application of the detector.

Description

Technical Field

[0001] This invention belongs to the field of neutron detection technology, specifically relating to a method and system for quantitatively analyzing the shunt effect of the insulation resistance of a self-powered detector. Background Technology

[0002] Self-powered detectors (SPDs) have become the primary facility for monitoring reactor operation and measuring in-reactor irradiation due to their characteristics of requiring no external bias voltage, simple structure, small size, solidified design, and simple electronics. However, in practical applications, the output signal of SPDs is affected by various factors. While the delay effect caused by the decay of unstable nuclides and the space charge effect caused by electron deposition in the insulating layer have been well studied, research on the shunt effect of the detector's own insulation resistance is relatively limited. Actual in-reactor application results show that the insulation resistance of the SPD has a significant impact on the output current; the shunt effect of the detector's own insulation resistance leads to a smaller output signal amplitude. When the insulation resistance of the SPD becomes too low due to breakdown, water immersion, or other reasons, the shunt effect can cause the detector to fail due to an excessively small output signal. Therefore, it is essential to quantitatively study the impact of the shunt effect of the SPD's own insulation resistance on the output current.

[0003] Therefore, the following technical issues need to be considered regarding the insulation resistance of the detector: 1) When designing the detector, the insulation resistance of the detector needs to be quantitatively calculated based on the detector's structural parameters to confirm that the designed structure can meet the insulation requirements; 2) When designing the measurement circuit and evaluating the actual output current of the self-powered detector, the shunting effect of the detector's own insulation resistance needs to be quantitatively calculated, and the proportion of the current shunted by the self-insulation resistance to the detector's original current needs to be given; 3) The capacitance effect of the insulation layer of the self-powered detector needs to be quantitatively studied to improve the instantaneous measurement accuracy of the detector.

[0004] Existing methods for calculating shunt effects only consider the influence of the detector's own insulation resistance, neglecting the influence of the detector's insulation capacitance on the signal waveform; furthermore, the influence of the detector structure on sensitivity was not considered when the method was developed. 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 quantitatively analyzing the shunt effect of the insulation resistance of a self-powered detector, so as to solve the technical problems of the prior art ignoring the influence of the detector's insulation capacitance on the signal waveform and not considering the influence of the detector structure on the sensitivity.

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

[0007] This invention discloses a method for quantitatively analyzing the shunt effect of the insulation resistance of a self-powered detector, comprising the following steps:

[0008] Step 1: Establish the circuit model of the self-powered detector based on its working principle;

[0009] Step 2: Calculate the specific parameters of each component in the circuit model established in Step 1 based on the geometry and physical parameters of the self-powered detector;

[0010] Step 3: Based on the current generation mechanism and circuit model of the self-powered detector in the radiation field, establish the state-space equation in matrix form, and establish the state transition matrix of the self-powered detector system by solving the matrix exponent. The sensitivity of the detector to the radiation field is obtained by simulation calculation through the SPNDSignal program.

[0011] Step 4: Based on the state transition matrix of the self-powered detector system, analyze the influence of the geometric dimensions and physical parameters of the self-powered detector on the insulation resistance and its shunting effect.

[0012] Preferably, in step 1, a circuit model is established and a circuit diagram is drawn based on the working principle of the self-powered detector. Based on the circuit diagram, a differential equation (1) is established between the capacitor voltage U(t) and the detector's native current I(t), and an output current I is established to the measurement circuit. in (t), the detector's own insulation resistance shunt I R (t), capacitor current I C Expressions (2), (3), and (4) of U(t) and voltage U(t);

[0013] The circuit model components include a current source, the insulation resistance of the self-powered detector itself, the capacitance of the insulating layer of the self-powered detector, and the input resistance of the signal readout circuit.

[0014]

[0015]

[0016]

[0017] I C (t)=I(t)-I in (t)-I R (t) (16)

[0018] Where R represents the insulation resistance of the self-powered detector; R inThe input resistance of the signal readout circuit is represented by C; the insulation capacitance of the self-powered detector is represented by t; time is represented by U(t); the voltage generated by the self-powered detector across its own insulation resistance and capacitance is represented by U(t); and the detector output current at time t is represented by I(t), i.e., the detector's native current. in (t) represents the output current to the measurement circuit; I C (t) represents the capacitor current.

[0019] More preferably, the physical parameters of insulation resistance and capacitance in step 1 are calculated, wherein the insulation resistance of the self-powered detector is determined by expression (5), and the insulation layer capacitance is determined by expression (6);

[0020]

[0021]

[0022] Where, ρ ins The volume resistivity of the insulating layer of the self-powered detector is represented by ; L represents the axial length of the self-powered detector; r emi Indicates the outer diameter of the emitter of a self-powered detector; r ins ε represents the outer diameter of the insulating layer of the self-powered detector; ε represents the dielectric constant of the insulating layer of the self-powered detector.

[0023] More preferably, in step 3, the principle diagram of the reaction mechanism of the self-powered detector material is drawn according to the physical process of the reaction in the neutron field, and the differential equation system (7) of the number of intermediate nuclides N(t) of the self-powered neutron detector with respect to the neutron flux density φ(t) is established, and the expression (8) of the detection current I(t) with the number of intermediate nuclides and the neutron flux density φ(t) is written.

[0024]

[0025]

[0026] Where V represents the detector volume, i represents the i-th intermediate nuclide, with a value from 1 to m; j represents the j-th intermediate nuclide, with a value from 1 to m; m represents the total number of m intermediate nuclides; β ji Let β represent the decay relation coefficient between the i-th and j-th intermediate nuclides. If j is the parent nucleus of i, then β ji The value is 1; if j and i are the same, then β is 1. ji The value is -1; if j is different from i and nuclide j is not the parent nucleus of nuclide i, then β ji =0; ∑ i For the macroscopic cross section of the reaction within SPND to generate the i-th intermediate nuclide; f i The efficiency of generating instantaneous current when the i-th intermediate nuclide is generated within SPND; j iλ represents the current generation efficiency during the de-excitation or decay of the i-th intermediate nuclide within the self-powered neutron detector SPND. i λ is the decay constant of the i-th intermediate nuclide; j N is the decay constant of the h-th intermediate nuclide; i (t) represents the number of nucleons of the i-th intermediate nuclide; N j (t) represents the number of nucleons of the j-th intermediate nuclide; φ(t) represents the neutron flux density at time t; S represents... This represents the transient sensitivity of the self-powered detector, where the detector's sensitivity to the radiation field is calculated using the SPNDSignal program, taking into account the impact of structural changes on the detector's sensitivity.

[0027] The voltage U(t) generated by the self-powered detector across its own insulation resistance and capacitance, and the number of intermediate nuclides N(t) in the self-powered neutron detector are selected as state variables. The neutron flux density φ(t) is selected as the control variable. The matrix form of the detector state space equation is established according to expressions (1), (7) and (8):

[0028]

[0029] Where X(t) is the system's state variable; A is the system's coefficient matrix; and B is the control matrix. The derivatives of the state variables are shown below; the matrices and variables are as follows:

[0030]

[0031]

[0032] More preferably, the intermediate nuclide of the self-powered neutron detector is an unstable nuclide generated by the capture of a neutron by the nuclide of the self-powered neutron detector emitter, and an unstable nuclide generated by the continued decay or de-excitation of the generated unstable nuclide.

[0033] More preferably, the system is discretized using matrix exponentiation to obtain the state transition matrix in the discrete space:

[0034] X(n+1)=FX(n)+Dφ(n) (22)

[0035] F = e AT (twenty three)

[0036] D = A -1 (FB-B) (24)

[0037] Where n is the nth time point; T is the time interval; F is the state transition matrix of the system; and D represents the influence of the control variable at the current time on the state variable at the next time point.

[0038] More preferably, according to expression (10), the detector output current I(n) and detector capacitor voltage U(n) under any flux density are calculated, and the detector's own insulation resistance shunt I is calculated according to expressions (2) and (3). in (n) and the input current I of the actual readout circuit in (n) Quantitative analysis of the shunting effect of the self-powered detector's insulation resistance and capacitance on the output current and its influence on the form of the output current.

[0039] This invention also discloses a system for quantitatively analyzing the shunt effect of the insulation resistance of a self-powered detector, comprising:

[0040] The self-powered detector circuit model building module is used to build the circuit model of the self-powered detector based on the working principle of the self-powered detector.

[0041] The component parameter calculation module is used to calculate the specific parameters of each component in the circuit model based on the geometry and physical parameters of the self-powered detector.

[0042] The self-powered detector system state transition matrix construction module is used to establish the state space equation in matrix form based on the current generation mechanism and circuit model of the self-powered detector in the radiation field, and to establish the state transition matrix of the self-powered detector system by solving the matrix exponent.

[0043] The self-powered detector insulation resistance shunt effect analysis module is used to analyze the influence of the self-powered detector's geometric dimensions and physical parameters on the insulation resistance and its shunt effect based on the state transition matrix of the self-powered detector system.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] This invention discloses a method for quantitatively analyzing the shunting effect of the insulation resistance of a self-powered detector. It combines the SPNDSignal simulation program to calculate detector sensitivity, comprehensively considering the influence of detector structure on sensitivity, the shunting effect of the detector's own insulation resistance, and the influence of insulation capacitance on signal waveform. This allows for more accurate calculation of the detector's output current. The design steps are as follows: First, establish a circuit model of the self-powered detector based on its working principle. Second, calculate the specific parameters of each component in the circuit based on the detector's geometry and physical parameters. Third, establish a matrix-form state-space equation based on the current generation mechanism of the self-powered detector in the radiation field and the circuit model, and establish the system state transition matrix of the self-powered detector system by solving the matrix exponent. Fourth, analyze the influence of detector geometry and physical parameters on insulation resistance and its shunting effect based on the system's state transition matrix. This method can quantitatively calculate the shunting effect of the insulation layer resistance of self-powered detectors with different structures and parameters, and can accurately calculate the change of capacitor current over time, thus providing guidance for detector design and application. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the invention process;

[0047] Figure 2 This is a circuit model diagram of a self-powered detector;

[0048] Figure 3 This is an equivalent model diagram of a self-powered detector circuit.

[0049] Figure 4 This is a schematic diagram of the cross-section of a self-powered detector;

[0050] Figure 5 A diagram illustrating typical neutron-related reaction processes detected by the detector (using a silver self-powered detector as an example);

[0051] Figure 6 The result is the shunt current calculation for the step neutron flux signal;

[0052] Figure 7 The shunt current calculation results for the step neutron flux signal of self-powered detectors with different insulating layer resistivities;

[0053] Figure 8 The shunt current calculation results for the step neutron flux signal of self-powered detectors with different insulation layer thicknesses;

[0054] Figure 9 The results show the shunt current calculations for the step neutron flux signals of self-powered detectors of different lengths. Detailed Implementation

[0055] 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.

[0056] 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.

[0057] The present invention will now be described in further detail with reference to the accompanying drawings:

[0058] The embodiments of the present invention take a silver self-powered detector as an example, whose emitter materials are Ag-107 and Ag-109. It is a self-powered neutron detector that captures neutrons and generates two intermediate nuclides, Ag-108 and Ag-110.

[0059] I. For the method of quantitatively analyzing the shunt effect of the self-powered detector's own insulation resistance according to the present invention, see [link to relevant documentation]. Figure 1 This includes the following steps:

[0060] Step 1: Establish a system based on the working principle of the self-powered detector, such as... Figure 2 The circuit model shown is simplified to the following: Figure 3 The equivalent circuit model is shown. Based on the equivalent circuit model, the differential equation (1) between the capacitor voltage U(t) and the detector's native current I(t) is established, and the output current I to the measurement circuit is established. in (t), the detector's own insulation resistance shunt I R (t), capacitor current I C The expressions (2), (3) and (4) for voltage U(t) are given; the circuit model components include a current source, the self-powered detector's own insulation resistance, the self-powered detector's insulation layer capacitance, and the input resistance of the signal readout circuit.

[0061]

[0062]

[0063]

[0064] I C (t)=I(t)-I in (t)-I R (t) (4)

[0065] Where R represents the insulation resistance of the self-powered detector; R in The input resistance of the signal readout circuit is represented by C; the insulation capacitance of the self-powered detector is represented by t; time is represented by U(t); the voltage generated by the self-powered detector across its own insulation resistance and capacitance is represented by U(t); and the detector output current at time t is represented by I(t), i.e., the detector's native current. in (t) represents the output current to the measurement circuit; I C (t) represents the capacitor current;

[0066] Step 2: Calculate the physical parameters of insulation resistance and capacitance from Step 1. A cross-sectional diagram of the self-powered detector is shown below. Figure 4 As shown, the insulation resistance of the self-powered detector is determined by expression (4), and the insulation capacitance of the self-powered detector is determined by expression (5).

[0067]

[0068]

[0069] Where, ρ ins The volume resistivity of the insulating layer of the silver self-powered detector is represented by ; L represents the axial length of the silver self-powered detector; r emi Indicates the outer diameter of the emitter of a silver-powered detector; r ins ε represents the outer diameter of the insulating layer of the silver self-powered detector; ε represents the dielectric constant of the insulating layer of the silver self-powered detector.

[0070] Step 3: Draw a schematic diagram of the reaction mechanism based on the reaction physics of the self-powered detector material in a neutron field, such as... Figure 5 As shown, a set of differential equations (6) is established for the number of intermediate nuclides N(t) of a self-powered neutron detector with respect to the neutron flux density φ(t). The expression (7) for the detection current I(t) with respect to the number of intermediate nuclides and the neutron flux density φ(t) is written. The intermediate nuclides of the self-powered neutron detector refer to the unstable nuclides generated after the nuclides of the self-powered neutron detector emitter capture neutrons, as well as the unstable nuclides generated after the generated unstable nuclides continue to decay or de-excite.

[0071] Formula (6) is then written to specify the internal structure of the silver self-sufficient detector. 108 Ag、 110 The differential equations (6-1) and (6-2) for the nucleon numbers N1(t) and N2(t) of Ag with respect to the neutron flux density φ(t) are used. Based on the working mechanism of the silver detector, equation (7) is further specified to express the detector output current I(t) and 108 Ag、 110 The expressions for the nucleon number N1(t), N2(t) and neutron flux density φ(t) of Ag are given in (7-1).

[0072]

[0073]

[0074]

[0075]

[0076] I(t) = S Ag φ(t)+j1λ1N1(t)+j2λ2N2(t) (7-1)

[0077] Where V represents the detector volume, i represents the i-th intermediate nuclide, with a value from 1 to m; j represents the j-th intermediate nuclide, with a value from 1 to m; m represents the total number of m intermediate nuclides; β ji Let β represent the decay relation coefficient between the i-th and j-th intermediate nuclides. If j is the parent nucleus of i, then β ji The value is 1; if j and i are the same, then β is 1. ji The value is -1; if j is different from i and nuclide j is not the parent nucleus of nuclide i, then β ji =0; ∑ i For the macroscopic cross section of the reaction within SPND to generate the i-th intermediate nuclide; f i The efficiency of generating instantaneous current when the i-th intermediate nuclide is generated within SPND; j i λ represents the current generation efficiency during the de-excitation or decay of the i-th intermediate nuclide within the self-powered neutron detector SPND. i λ is the decay constant of the i-th intermediate nuclide; j N is the decay constant of the j-th intermediate nuclide; i (t) represents the number of nucleons of the i-th intermediate nuclide; N j (t) represents the number of nucleons of the j-th intermediate nuclide; φ(t) represents the neutron flux density at time t; S represents... N1(t) is 108 The number of nucleons in Ag; N2(t) is 110 The number of nucleons in Ag; ∑1 is 107 Ag reacts with neutrons to produce108 The macroscopic reaction cross section of Ag; ∑2 is 109 Ag reacts with neutrons to produce 110 The macroscopic reaction cross section of Ag; λ1 is 108 The decay constant of Ag; λ² is 110 The decay constant of Ag; j1 is the detector's internal decay constant. 108 The efficiency of Ag decay electrons in generating detector current; j2 is the detector's internal... 110 The efficiency of Ag decay electrons in generating detector current; S Ag This indicates the transient sensitivity of the silver self-powered detector; 108 Ag and 110 Since the positrons produced by Ag decay constitute a small proportion and undergo annihilation to generate gamma rays, their contribution to the current is neglected. The detector's sensitivity to the radiation field is calculated using the SPNDSignal program, thus including the impact of structural changes on detector sensitivity in the calculation.

[0078] The voltage U(t) generated by the self-powered detector across its own insulation resistance and capacitance, and the number of intermediate nuclides N(t) in the self-powered neutron detector are selected as state variables, and the neutron flux density φ(t) is selected as the control variable. The state-space equation of the detector in matrix form is established according to expressions (1), (6) and (7).

[0079]

[0080] Where X(t) is the system's state variable; A is the system's coefficient matrix; and B is the control matrix. The derivatives of the state variables; for a silver self-powered detector, the matrices and variables are as follows.

[0081]

[0082]

[0083] Step 4: Discretize the system using matrix exponentiation to obtain the state transition matrix in the discrete space.

[0084] X(n+1)=FX(n)+Dφ(n) (9)

[0085] F = e AT (10)

[0086] D = A -1 (FB-B) (11)

[0087] Where n is the nth time point; T is the time interval; F is the state transition matrix of the system; and D represents the influence of the control variable at the current time on the state variable at the next time point.

[0088] Step 5: Based on expression (9), the detector output current I(n) and detector capacitor voltage U(n) under any flux density can be calculated, and the detector's own insulation resistance shunt I can be calculated based on expressions (2) and (3). in (n) and the input current I of the actual readout circuit in (n), thus enabling quantitative analysis of the shunting effect of the self-powered detector's insulation resistance and capacitance on the output current and its influence on the form of the output current.

[0089] II. Application examples based on the above methods:

[0090] To verify the effectiveness of the shunting effect calculation method, the shunting effect of the detector output signal was examined when the neutron flux was a step signal, such as during reactor start-up and shutdown. At t = 20 seconds, the neutron flux changed from φ = 0 (cm² / 2000). 2 ·s -1 Suddenly it changes to φ = 10 10 (cm 2 ·s -1 The process was performed and maintained for 20 seconds. During this simulation, all current sensitivities were obtained using the SPNDSignal program, and other relevant parameters were valued according to the specific implementation method and the value description section. To clearly obtain the change in the detector's own capacitance current, the current sampling time step T was... s = 0.01 seconds. The values ​​for each parameter are:

[0091] Table 1

[0092] parameter value parameter value <![CDATA[ρ ins ]]> <![CDATA[10 12 Ohm cm]]> <![CDATA[∑1]]> <![CDATA[1.0813cm -1 ]]> <![CDATA[r emi ]]> 0.025cm <![CDATA[∑2]]> <![CDATA[0.9861cm -1 ]]> <![CDATA[r ins ]]> 0.05cm <![CDATA[λ1]]> <![CDATA[0.0049s -1 ]]> ε <![CDATA[8.6×10 -13 F·cm -1 ]]> <![CDATA[λ2]]> <![CDATA[0.0282s -1 ]]> L 10cm <![CDATA[j1]]> <![CDATA[2.839×10 -20 A·s <!-- 7 -->]]> <![CDATA[R in ]]> 1MΩ <![CDATA[j2]]> <![CDATA[7.918×10 -20 A·s]]> <![CDATA[S Ag ]]> <![CDATA[1.702×10 -22 A·s·cm -2 ]]>

[0093] The calculation results of the diversion effect are as follows: Figure 6 As shown, the shunting effect of the self-powered detector's own insulation resistance causes the output current to the measurement circuit to be less than the detector's native current. The specific shunting situation depends on the detector's physical parameters and the input resistance of the subsequent measurement circuit. Furthermore, by amplifying the signal at 20 s, it can be seen that when the flux density changes drastically, due to the capacitor's volt-ampere characteristic, the capacitor current undergoes a sudden change while its voltage remains continuously changing, causing the output current to lag behind the detector's native current. Simultaneously, because the detector's insulation layer capacitance is relatively small, the capacitor's influence is mainly reflected within 0.5 s of the flux density step change. Therefore, evaluating the impact of the self-powered detector's own insulation resistance and capacitance on the output current using this method can provide guidance for practical detector use and reactor power reconfiguration.

[0094] The shunting effect of the detector output signal was investigated for self-powered detectors with different insulating resistivities when the neutron flux was a step signal. The insulating resistivity ranged from 10... 5 Ω·cm gradually increases to 10 14 Ω·cm, at t=20 seconds, the neutron flux changes from φ=0 (cm) 2 ·s -1 Suddenly it changes to φ = 10 10 (cm 2 ·s -1 The process is as follows: the shunt current ratio is the ratio of the actual input current to the total current when the shunt current ratio is in steady state (at which point the effect of the capacitor can be ignored). In this simulation, all current sensitivities are obtained using the SPNDSignal program. Other relevant parameters are valued according to the specific implementation method and the value description section. The current sampling time step T is... s = 0.1 seconds. The values ​​for each parameter are:

[0095] Table 2

[0096] parameter value parameter value <![CDATA[ρ ins ]]> <![CDATA[10 5 -10 14 Ohm cm]]> <![CDATA[∑1]]> <![CDATA[1.0813cm -1 ]]> <![CDATA[r emi ]]> 0.025cm <![CDATA[∑2]]> <![CDATA[0.9861cm -1 ]]> <![CDATA[r ins ]]> 0.05cm <![CDATA[λ1]]> <![CDATA[0.0049s -1 ]]> ε <![CDATA[8.6×10 -13 F·cm -1 ]]> <![CDATA[λ2]]> <![CDATA[0.0282s -1 ]]> L 10cm <![CDATA[j1]]> <![CDATA[2.839×10 -20 A·s]]> <![CDATA[R in ]]> 1MΩ <![CDATA[j2]]> <![CDATA[7.918×10 -20 A·s]]> <![CDATA[S Ag ]]> <![CDATA[1.702×10 -22 A·s·cm -2 ]]>

[0097] The results of the shunt effect of self-powered detectors with different insulating layer resistivities are as follows: Figure 7 As shown, with the increase of the insulating layer resistivity, the shunt current due to the self-powered detector's own insulation resistance decreases, and the current output to the measurement circuit is closer to the detector's native current. Furthermore, the increased insulating layer resistivity leads to an enhanced electrostatic field in the detector's insulating layer; however, in this example, the radiation field intensity is relatively small, thus having little impact on the detector's sensitivity, and the detector's native current remains essentially unchanged. Experiments show that when the detector's outer packaging is damaged and water seeps into the detector's insulating layer, the detector will fail. Calculation results based on the model proposed in this invention indicate that when the insulating layer resistivity of the self-powered detector decreases sharply due to water immersion (the resistivity of tap water is approximately 10⁻⁶), the detector will fail. 5 The resistivity of the detector is much lower than the volume resistivity (Ω·cm). Due to the shunting effect of the self-powered detector's own insulation resistance, the detector's output current will be too small, consistent with experimental conclusions. For the detector described by the above parameters, when the volume resistivity of the detector decreases to 10 Ω·cm due to immersion in water, insulation breakdown, or other reasons, the detector's output current will be too small, consistent with experimental conclusions. 9 When the current is below Ω·cm, the current output to the measurement circuit will be less than 1% of the detector's native current.

[0098] The shunting effect of the detector output signal was investigated for self-powered detectors with different insulating layer thicknesses when the neutron flux was a step signal. The outer radius of the insulating layer gradually increased from 0.03 cm to 0.07 cm. At t = 20 seconds, the neutron flux changed from φ = 0 (cm²) 2 ·s -1Suddenly it changes to φ = 10 10 (cm 2 ·s -1 The process is as follows: the shunt current ratio is the ratio of the actual input current to the total current when the shunt current ratio is in steady state (at which point the effect of the capacitor can be ignored). In this simulation, all current sensitivities are obtained using the SPNDSignal program. Other relevant parameters are valued according to the specific implementation method and the value description section. The current sampling time step T is... s = 0.1 seconds. The values ​​for each parameter are:

[0099] Table 3

[0100] parameter value parameter value <![CDATA[ρ ins ]]> <![CDATA[10 12 Ohm cm]]> <![CDATA[R in ]]> 1MΩ <![CDATA[r emi ]]> 0.025cm <![CDATA[∑1]]> <![CDATA[1.0813cm -1 ]]> <![CDATA[r ins ]]> 0.03-0.07cm <![CDATA[∑2]]> <![CDATA[0.9861cm -1 ]]> ε <![CDATA[8.6×10 -13 F·cm -1 ]]> <![CDATA[λ1]]> <![CDATA[0.0049s -1 ]]> L 10cm <![CDATA[λ2]]> <![CDATA[0.0282s -1 ]]>

[0101] When the outer radius of the insulating layer changes, the overall sensitivity of the detector also changes. Therefore, it is necessary to simulate and calculate the change in sensitivity. All simulated sensitivities are shown in the table below:

[0102] Table 4

[0103] <![CDATA[r ins -r emi (cm)]]> <![CDATA[S Ag (A·s·cm -2 )]]> <![CDATA[j1(A·s)]]> <![CDATA[j2(A·s)]]> 0.005 <![CDATA[1.836×10 -22 ]]> <![CDATA[3.457×10 -20 ]]> <![CDATA[8.443×10 -20 ]]> 0.015 <![CDATA[1.773×10 -22 ]]> <![CDATA[3.157×10 -20 ]]> <![CDATA[8.194×10 -20 ]]> 0.025 <![CDATA[1.705×10 -22 ]]> <![CDATA[2.858×10 -20 ]]> <![CDATA[7.913×10 -20 ]]> 0.035 <![CDATA[1.674×10 -22 ]]> <![CDATA[2.571×10 -20 ]]> <![CDATA[7.658×10 -20 ]]> 0.045 <![CDATA[1.598×10 -22 ]]> <![CDATA[2.296×10 -20 ]]> <![CDATA[7.335×10 -20 ]]>

[0104] The results of the shunt effect of self-powered detectors with different insulation layer thicknesses are as follows: Figure 8 As shown. On the one hand, as Figure 8 As shown by the solid line (including the hollow circle marker), as the thickness of the insulating layer increases, the detector's ability to block signal electrons increases, thus reducing the detector's sensitivity and its native output current; on the other hand, as... Figure 8 As shown by the dashed line (including the asterisk), the increased insulation layer thickness also increases the detector's own insulation resistance, thus increasing the proportion of the output current to the measurement circuit relative to the detector's native current. Combining these two effects, the following is obtained: Figure 8 The double dashes (including the upper triangle marker) show the relationship between the output current to the measurement circuit and the insulation layer thickness. Therefore, when designing the insulation layer thickness of the detector, the influence of the above factors needs to be comprehensively considered.

[0105] This study examines the shunting effect of self-powered detectors of different lengths when the neutron flux is a step signal. The detector length is gradually increased from 10 cm to 50 cm, and at t = 20 seconds, the neutron flux changes from φ = 0 (cm²). 2 ·s -1 Suddenly it changes to φ = 10 10 (cm 2 ·s -1The process is as follows: the shunt current ratio is the ratio of the actual input current to the total current when the shunt current ratio is in steady state (at which point the effect of the capacitor can be ignored). In this simulation, all current sensitivities are obtained using the SPNDSignal program. Other relevant parameters are valued according to the specific implementation method and the value description section. The current sampling time step T is... s = 0.1 seconds. The values ​​for each parameter are:

[0106] Table 5

[0107] parameter value parameter value <![CDATA[ρ ins ]]> <![CDATA[10 12 Ohm cm]]> <![CDATA[R in ]]> 1MΩ <![CDATA[r emi ]]> 0.025cm <![CDATA[∑1]]> <![CDATA[1.0813cm -1 ]]> <![CDATA[r ins ]]> 0.05cm <![CDATA[∑2]]> <![CDATA[0.9861cm -1 ]]> ε <![CDATA[8.6×10 -13 F·cm -1 ]]> <![CDATA[λ1]]> <![CDATA[0.0049s -1 <!-- 9 -->]]> L 10-50cm <![CDATA[λ2]]> <![CDATA[0.0282s -1 ]]>

[0108] When the detector length changes, the overall detector sensitivity also changes, therefore it is necessary to simulate and calculate the sensitivity change. All simulated sensitivities are shown in the table below. The sensitivity changes of the Ag-108 and Ag-110 decay signals are mainly caused by statistical fluctuations.

[0109] Table 6

[0110] <![CDATA[r ins (cm)]]> <![CDATA[S Ag (A·s·cm -2 )]]> <![CDATA[j1(A·s)]]> <![CDATA[j2(A·s)]]> 0.03 <![CDATA[1.697×10 -22 ]]> <![CDATA[2.847×10 -20 ]]> <![CDATA[7.915×10 -20 ]]> 0.04 <![CDATA[3.437×10 -22 ]]> <![CDATA[2.865×10 -20 ]]> <![CDATA[7.956×10 -20 ]]> 0.05 <![CDATA[5.101×10 -22 ]]> <![CDATA[2.850×10 -20 ]]> <![CDATA[7.932×10 -20 ]]> 0.06 <![CDATA[6.763×10 -22 ]]> <![CDATA[2.862×10 -20 ]]> <![CDATA[7.942×10 -20 ]]> 0.07 <![CDATA[8.539×10 -22 ]]> <![CDATA[2.861×10 -20 ]]> <![CDATA[7.936×10 -20 ]]>

[0111] The results of the shunt effect of self-powered detectors of different lengths are as follows: Figure 9 As shown. On the one hand, as Figure 9 As shown by the solid line (including the hollow circle marker), the native current of the self-powered detector increases with the increase of the detector length; on the other hand, the increase in detector length reduces the detector's own insulation resistance, thus increasing the current shunted by the detector's own insulation resistance, as shown in the image. Figure 9 As shown by the dashed line (including the asterisk), the proportion of the output current to the measurement circuit relative to the original current is decreasing. The final output current to the measurement circuit is as follows: Figure 9 As shown by the double dash (including the upper triangle marker). Therefore, the above factors should be fully considered when designing the detector length.

[0112] The greater the current shunting effect of the self-powered detector's insulation resistance, the smaller the proportion of the detector's native current to the output current to the measurement circuit. However, increasing the detector's length also increases its sensitive volume, thereby increasing the detector's native current. Therefore, the design of the detector's length should comprehensively consider both the current shunting effect and the detector's sensitive volume.

[0113] 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 quantitatively analyzing the shunt effect of the insulation resistance of a self-powered detector, characterized in that, Includes the following steps: Step 1: Establish the circuit model of the self-powered detector based on its working principle; Based on the working principle of the self-powered detector, a circuit model is established and a circuit diagram is drawn. The capacitor voltage is then established based on the circuit diagram. With the detector's native current The differential equation (1) is derived, and the output current to the measurement circuit is established. The detector's own insulation resistance shunts the current. Capacitor current With voltage Expressions (2), (3) and (4); The circuit model components include a current source, the insulation resistance of the self-powered detector itself, the capacitance of the insulating layer of the self-powered detector, and the input resistance of the signal readout circuit. in, Indicates the insulation resistance of the self-powered detector; This indicates the input resistance of the signal readout circuit; This indicates the capacitance of the insulating layer of a self-powered detector; Indicates time; This indicates the voltage generated by the self-powered detector across its own insulation resistance and capacitance. for The detection current output by the detector at any given time, i.e., the detector's native current; This is the output current to the measurement circuit; This is the capacitor current; Step 2: Calculate the specific parameters of each component in the circuit model established in Step 1 based on the geometry and physical parameters of the self-powered detector; Step 3: Based on the current generation mechanism and circuit model of the self-powered detector in the radiation field, establish the state-space equation in matrix form, and establish the state transition matrix of the self-powered detector system by solving the matrix exponent. The sensitivity of the detector to the radiation field is obtained by simulation calculation through the SPNDSignal program. Based on the physical process of the reaction of self-powered detector materials in a neutron field, draw a schematic diagram of its reaction mechanism and establish the number of intermediate nuclides in the self-powered neutron detector. Regarding neutron flux density Write the differential equation system (7) to determine the probe current. The number of intermediate nuclides and neutron flux density The expression (8); in, Indicates the detector volume. Indicates the first An intermediate nuclide, with values ​​ranging from 1 to... m ; Indicates the first An intermediate nuclide, with a value ranging from 1 to... m ; Indicates shared ownership One intermediate nuclide; Indicates the first The intermediate nuclide and the first The decay relation coefficients of the intermediate nuclides, if for The parent nucleus, then If it is 1; and If they are the same, then =-1; if and Different and nuclides Not a nuclide The parent nucleus, then =0; To generate the first reaction within SPND A macroscopic cross-section of an intermediate nuclide; For the generation of the first in SPND The efficiency of generating instantaneous current when using an intermediate nuclide; The first self-powered neutron detector in SPND The current generation efficiency during the de-excitation or decay of an intermediate nuclide; For the first The decay constants of the intermediate nuclides; For the first The decay constants of the intermediate nuclides; For the first The number of nucleons in each intermediate nuclide; For the first The number of nucleons in each intermediate nuclide; for Neutron flux density at time; for , representing the transient sensitivity of the self-powered detector, where the detector's sensitivity to the radiation field is obtained through simulation calculation using the SPNDSignal program, incorporating the impact of structural changes on the detector's sensitivity into the calculation; Select the voltage generated by the self-powered detector across its own insulation resistance and capacitance. and the number of intermediate nuclides in self-powered neutron detectors As a state variable, neutron flux density Selected as the control variable, the detector state-space equation in matrix form is established based on expressions (1), (7), and (8): in, These are the state variables of the system; Here is the coefficient matrix of the system; For control matrix; The derivatives of the state variables are shown below; the matrices and variables are as follows: Step 4: Based on the state transition matrix of the self-powered detector system, analyze the influence of the geometric dimensions and physical parameters of the self-powered detector on the insulation resistance and its shunting effect.

2. The method for quantitatively analyzing the shunt effect of the self-powered detector's insulation resistance according to claim 1, characterized in that, Calculate the physical parameters of insulation resistance and capacitance in step 1, wherein the insulation resistance of the self-powered detector is determined by expression (5), and the insulation layer capacitance is determined by expression (6); in, This represents the volume resistivity of the insulating layer of a self-powered detector; Indicates the axial length of the self-powered detector; This indicates the outer diameter of the emitter of a self-powered detector; This indicates the outer diameter of the insulating layer of the self-powered detector; This represents the dielectric constant of the insulating layer of a self-powered detector.

3. The method for quantitatively analyzing the shunt effect of the self-powered detector's insulation resistance according to claim 1, characterized in that, The intermediate nuclide of the self-powered neutron detector is an unstable nuclide generated after a neutron is captured by a nuclide emitted by the self-powered neutron detector, and an unstable nuclide generated after the generated unstable nuclide continues to decay or de-excite.

4. The method for quantitatively analyzing the shunt effect of the self-powered detector's insulation resistance according to claim 1, characterized in that, By using matrix exponentiation, the system is discretized to obtain the state transition matrix in the discrete space: in, For the first A point in time; For time intervals; Here is the system's state transition matrix; This indicates the influence of the control variable at the current moment on the state variable at the next moment.

5. The method for quantitatively analyzing the shunt effect of the self-powered detector's insulation resistance according to claim 4, characterized in that, Calculate the detector output current under any flux density according to expression (10). With detector capacitor voltage And calculate the shunt current of the detector's own insulation resistance according to expressions (2) and (3). The input current of the actual readout circuit The study quantitatively analyzed the shunting effect of the self-powered detector's insulation resistance and capacitance on the output current and its influence on the form of the output current.

6. A system based on the method for quantitatively analyzing the shunt effect of the insulation resistance of a self-powered detector according to any one of claims 1-5, characterized in that, include: The self-powered detector circuit model building module is used to build the circuit model of the self-powered detector based on the working principle of the self-powered detector. The component parameter calculation module is used to calculate the specific parameters of each component in the circuit model based on the geometry and physical parameters of the self-powered detector. The self-powered detector system state transition matrix construction module is used to establish the state space equation in matrix form based on the current generation mechanism and circuit model of the self-powered detector in the radiation field, and to establish the state transition matrix of the self-powered detector system by solving the matrix exponent. The self-powered detector insulation resistance shunt effect analysis module is used to analyze the influence of the self-powered detector's geometric dimensions and physical parameters on the insulation resistance and its shunt effect based on the state transition matrix of the self-powered detector system.

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