A method for neutron deconvolution based on perturbation theory

Abstract

The present application belongs to the technical field of neutron spectrum measurement, and provides a neutron spectrum resolving method based on perturbation theory, which does not require the user to provide preset spectrum or neutron field information, divides the number of neutron energy groups into the same number of equivalent detectors of the detection system, thereby converting the "inverse problem" into a process of solving a well-posed equation, and based on the perturbation theory, uses Monte-Carlo random sampling to solve the neutron spectrum. The solving result of the method can be directly applied, or further used as a preset spectrum for correction iteration of other "multi-group" neutron spectrum resolving methods, effectively improving the accuracy, stability and universality of neutron spectrum resolving.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of neutron spectrum measurement, and particularly relates to a neutron spectrum inversion method based on perturbation theory. BACKGROUND

[0002] Neutron spectrum measurement is one of the important components of neutron detection physics, and is mainly used for obtaining neutron fluence (rate) distribution information of different neutron energies. Neutron spectrum measurement plays an important role in basic and applied research of neutron nuclear physics and research of neutron radiation dose and shielding design, and is widely used in fields such as design and operation of nuclear reactor devices, radiation measurement of space, laboratory neutron ray measurement and environmental impact assessment, boron neutron capture therapy, nuclear arms security and identification, and the like.

[0003] At present, main neutron spectrum measurement methods include time-of-flight method, recoil proton method, nuclear reaction method, multi-foil activation sheet method, Bonner multi-sphere neutron spectrometer method, quasi-multi-sphere neutron spectrometer method, and single-sphere multi-detector neutron spectrometer method. Except the time-of-flight method, the remaining measurement methods cannot directly measure and obtain neutron spectrum, and need to inversely deduce the real neutron spectrum of a measurement point by combining measurement data with a neutron spectrum inversion method.

[0004] In a classical neutron spectrum inversion model, a neutron spectrum is associated with a detector count M j of the jth detector through an energy response function R j (E), and satisfies a Fredholm homogeneous integral equation:

[0005]

[0006] In actual application, a neutron energy E is usually approximated into n discrete energy groups E i , and a neutron spectrum function that continuously varies with the neutron energy E is approximated into a discrete distribution about the discrete energy groups A detector count M j can be obtained through experimental measurement, and a response function R ij can be obtained by using a software simulation calculation method combined with experimental calibration. Thus, the neutron spectrum inversion process becomes a solving process of a discrete Fredholm homogeneous equation group as follows

[0007]

[0008] Aiming at the inverse problem of neutron spectrum unfolding, a large number of spectrum unfolding methods have been developed, mainly including the least square method based on preset neutron spectrum correction iteration, maximum entropy algorithm, Bayesian algorithm, regularization algorithm, undetermined parameter method based on prior neutron field information and Monte Carlo algorithm, genetic intelligent algorithm and artificial neural network algorithm for global optimization solution.

[0009] The existing neutron spectrum unfolding method is mainly based on a single spectrum unfolding algorithm, depends on preset spectrum or neutron field information, and still has a large space for improvement in terms of accuracy, universality, solving speed and the like. SUMMARY

[0010] The present application aims to overcome the deficiencies in the prior art, and provides a neutron spectrum unfolding method based on perturbation theory, which does not require the user to provide preset spectrum or neutron field information, divides the number of neutron energy groups into the same number of equivalent detectors of the detection system, thereby converting the inverse problem into a process of solving a well-posed equation, and solving the neutron spectrum based on perturbation theory and Monte-Carlo random sampling.

[0011] The purpose of the present application is achieved by the following technical measures.

[0012] The present application provides a neutron spectrum unfolding method based on perturbation theory, comprising the following steps:

[0013] (1) Determine the number of neutron energy groups

[0014] The number of neutron energy groups should be the same as the number of equivalent detectors of the neutron spectrum detection system: in a Bonner multi-sphere neutron spectrum detection system, the number of neutron energy groups is the same as the number of Bonner spheres; in a single-sphere neutron spectrum measurement system, the number of neutron energy groups is the same as the number of layers; in an activation sheet neutron spectrum detection system, the number of neutron energy groups is the same as the number of activation sheets;

[0015] (2) Divide the neutron energy group

[0016] The neutron energy group is divided logarithmically in a wide energy range of 0.025eV-20MeV, and the logarithmic division includes equal-lerz and non-equal-lerz division. In the application related to unknown neutron field or non-neutron radiation dose measurement, equal-lerz neutron energy group division is adopted. In the application related to known neutron field or neutron radiation dose measurement, non-equal-lerz neutron energy group division is adopted.

[0017] In the application of neutron spectrum measurement of known neutron field, the neutron energy group is divided according to the following principles: the energy group division is dense in the energy range of interest, and the number of energy groups is large; the energy group division is sparse in the non-energy range of interest, and the number of energy groups is small;

[0018] In the application of neutron radiation dose measurement, the neutron energy group is divided according to the following principles:

[0019] In the thermal neutron ~10 -2 MeV range at least one energy group is distributed; in the 10 -2 MeV ~ 1 MeV range at least two energy groups are distributed; in the 1 MeV ~ 10 MeV range at least one energy group is distributed; in the 10 MeV ~ 20 MeV energy range at least one energy group is distributed; and in the 10 MeV, 1 MeV, 10 MeV energy points or nearby points, energy boundaries are set; -2

[0020] (3) Import the same group neutron energy response matrix R'

[0021] Import the initial divided energy group and the initial energy response matrix R, if the initial energy group number is n, the equivalent detector number of the system is m, then the dimension of R is n x m, the energy group number of the same group neutron energy response matrix R' is the same as the equivalent detector number, and the dimension is m x m, n initial energy groups of m equivalent detectors are combined into m new energy groups;

[0022] Energy group combination principle: for each equivalent detector, the total neutron response of each energy interval of the new energy response curve is equal to the total neutron response of the original energy response curve in the energy interval;

[0023] The upper limit of the new energy interval i is determined by the step (2) neutron energy group division The lower limit is In a wide energy range, the upper limit of the new energy interval i-1 And the lower limit of the new energy interval i Coincide, that is, satisfy

[0024] Assuming that the upper limit of the original energy group covered by the new energy interval i is The lower limit is Then find the upper limit And the lower limit Corresponding to the energy group sequence ind of the initial energy group, that is, the hth initial energy boundary is ind(h), which satisfies At the same time The upper limit of the original energy interval i-1 And the lower limit of the original energy interval i Coincide, that is, satisfy

[0025] The neutron energy response R i ′ of the new energy interval i can be divided into three parts: the front part R' i，before The energy range of The equivalent response function is R ind(h-1) , and the equivalent neutron energy is​ the intermediate part R′ i，middle The energy range of the intermediate part R′ The equivalent response function is the equivalent energy response function of the energy groups between ind(h) and ind(h-1), that is, the sum of the response and energy products corresponding to each energy group in the initial energy group interval covered; the latter part R′ i，after The energy range of the latter part R′ The equivalent response function is R ind(h) The equivalent neutron energy is

[0026]

[0027] R′ i = R′ i，before + R′ i，middle + R′ i，after , i = 1, 2, 3, …, m

[0028]

[0029] (4) Inverse neutron energy spectrum

[0030] A set of readings M of the equivalent detector of the measuring device, that is, an m-dimensional vector, is taken as input, and the direct method is used to directly obtain the m-group neutron energy spectrum through response matrix deformation, as shown in the following formula

[0031]

[0032] The m-group neutron energy spectrum solved is divided into two cases: Case 1: Each element of the energy spectrum

[0033] vector is non-negative, which meets the physical meaning, and is accepted as the neutron energy spectrum result;

[0034] Case 2: At least one element of the energy spectrum vector is negative, which does not meet the physical meaning, and the result cannot be accepted;

[0035] When case 2 occurs, the result needs to be divided and processed again, and a perturbation threshold is set. The threshold is a negative number, and the threshold is a critical value for determining whether to use the perturbation theory;

[0036] Case 2-a, the elements in the energy spectrum vector have negative numbers, but the values are close to 0, that is, greater than the perturbation threshold;

[0037] Case 2-b, the elements in the energy spectrum vector have negative numbers, and at least one element is not close to 0, that is, less than the perturbation threshold;​

[0038] Case 2-a, using perturbation theory to solve, that is, assuming where is a non-negative vector, taking the corresponding non-negative element in the vector, and taking 0 for the negative element close to 0, M0 is the corresponding equivalent detector reading, ε M is an added random perturbation term, and satisfies the following formula:

[0039]

[0040] ε M is set to a Gaussian random distribution with an average of 0 and a standard deviation of σ, Monte-Carlo random sampling is performed on the random perturbation term ε M , if case 1 does not occur within the set sampling number range, the σ value of the random perturbation term ε M is increased according to the set step size until is found, so that each element in it is non-negative;

[0041] Case 2-b, random perturbation needs to be used on the response function, then can be expressed as:

[0042]

[0043] Monte-Carlo random sampling is performed on the random perturbation term ε R , if is the result of case 1, it is directly accepted, if is the result of case 2, case 2-a is used to continue to find If neither of them is satisfied, resampling is needed until is found to be case 1, if case 1 does not occur within the set sampling number range, the σ value of the random perturbation term ε R is increased according to the set step size until each element in it is non-negative. If a suitable solution cannot be found within the set maximum variance range of the perturbation, the neutron energy group can be fine-tuned by setting the step size until a suitable solution is found.

[0044] The present application is based on the perturbation theory neutron spectrum method, without user providing preset spectrum or neutron field information, the solving result can be directly applied, or further used as the preset spectrum of other "multi-group" neutron spectrum solving method (such as least square method, maximum entropy algorithm, Bayesian algorithm, regularization algorithm and genetic algorithm based on initial neutron spectrum group) for correction iteration, which improves the accuracy, stability and universality of neutron spectrum solving. Meanwhile, it provides a new development direction for neutron spectrum solving technology research, and has positive and important contribution to neutron spectrum measurement research. BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 The whole flow chart of the neutron spectrum solving method of the present application.

[0046] Figure 2 The curve diagram of the peripheral dose equivalent value of ICRP-74 unit neutron fluence relative to neutron energy.

[0047] Figures 3-9 The effect diagram before and after the grouping of 7 neutron energy response function groups in the 7-ball Bonner multi-ball neutron spectrum detection system.

[0048] Figure 10 The effect diagram of the neutron spectrum solving result of Am-Be obtained by using the method of the present application and the theoretical neutron spectrum. 241 Am-Be neutron spectrum solving result and theoretical neutron spectrum comparison effect diagram. DETAILED DESCRIPTION

[0049] The technical solutions of the present application will be described in detail below with reference to the drawings and specific algorithm formulae. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application.

[0050] As shown in the formula (1), the present application embodiment provides a neutron spectrum solving method based on perturbation theory, which comprises the following steps: Figure 1

[0051] (1) Determine the number of neutron energy groups.

[0052] The number of neutron energy groups should be the same as the number of equivalent detectors of the neutron spectrum detection system. For example, in the Bonner multi-ball neutron spectrum detection system, the number of neutron energy groups is the same as the number of Bonner balls; in the single-ball neutron spectrum measurement system, the number of neutron energy groups is the same as the number of layers; in the activated sheet neutron spectrum detection system, the number of neutron energy groups is the same as the number of activated sheets. Different from the traditional "few-channel spectrum solving" method, "same channel" or "same group" is the basis for solving the present application method by using "well-posed equation".

[0053] ​(2) Division of neutron energy group

[0054] In the field of neutron radiation protection and detection, the neutron energy range is usually 0.025eV-20MeV, spanning 9 orders of magnitude. If m energy groups (m is usually 5-10) are needed to cover the entire range, the division of energy groups is usually not linear. Otherwise, the energy resolution of slow neutrons and medium-energy neutrons in the neutron energy spectrum will be poor relative to fast neutrons. Unless the neutron field to be measured is a fast neutron spectrum, and the distribution of slow neutrons and medium-energy neutrons in the entire energy range is not concerned, but this is not the usual case. The division of energy groups can be logarithmic. The difference between the logarithm of the upper energy limit E upper of a certain energy region and the logarithm of the lower energy limit E lower of the energy region is called the logarithmic width ΔlnE of the energy region. The equal-logarithmic-width division method makes the energy resolution of the neutron energy spectrum uniform in the entire energy range, and the weight distribution of neutrons of different energies is relatively uniform. If there is a certain understanding of the neutron field to be measured, the energy range of interest can be divided more densely, and the energy range not of interest can be divided more sparsely.

[0055] ΔlnE = lnE upper - lnE lower

[0056] If applied to the calculation of neutron ambient dose equivalent rate based on neutron energy spectrum, since the conversion factors of ambient dose equivalent for neutrons of different energies are different (see the conversion factors of dose equivalent for neutrons of different energies calculated by the International Commission on Radiological Protection (ICRP) through the organization of equivalent materials in its report ICRP-74 in 1996, see Figure 2 ), especially when the neutron energy is between 10 -2 MeV and 1MeV, the difference in conversion factors is as much as tens of times. The same energy resolution will lead to inaccurate calculation of neutron ambient dose equivalent rate in the entire energy range. If the dose equivalent rates of neutrons of different energies are normalized, taking the dose equivalent contribution of neutrons with an energy of 1MeV as 1, the contribution of thermal neutrons-10 -2 MeV neutrons is nearly 0.03, the contribution of 0.1MeV neutrons is nearly 0.26, the contribution of 1MeV-10MeV neutrons is about 1.07, and the contribution of 20MeV neutrons is about 1.28. Therefore, at least one energy group should be distributed in the range of thermal neutrons-10 -2 MeV, and the energy limit should be set at or near the 10 -2 MeV point; at least two energy groups should be distributed in the range of 10 -2 MeV-1MeV, and the energy limit should be set at or near the 1MeV point; at least one energy group should be distributed in the range of 1MeV-10MeV, and the energy limit should be set at or near the 10MeV point; and at least one energy group should be distributed in the range of 10MeV-20MeV.

[0057] (3) Import the same group neutron energy response matrix R'

[0058] Import the initial energy group and the initial energy response matrix R, if the initial energy group number is n, the equivalent detector number of the system is m, then the dimension of R is n x m, the energy group number of the same group neutron energy response matrix R' is the same as the equivalent detector number, and the dimension is m x m, n initial energy groups of m equivalent detectors are combined into m new energy groups;

[0059] Energy group merging principle: for each equivalent detector, the total neutron response of each energy interval of the new energy response curve is equal to the total neutron response of the original energy response curve in the energy interval;

[0060] The upper limit of the new energy interval i is determined by the step (2) neutron energy group division The lower limit is In a wide energy range, the upper limit of the new energy interval i-1 And the lower limit of the new energy interval i Coincide, that is, satisfy

[0061] Assume that the upper limit of the original energy group covered by the new energy interval i is The lower limit is Then find the upper limit And the lower limit Corresponding to the energy group sequence ind of the initial energy group, that is, the hth initial energy boundary is ind(h), which satisfies At the same time The upper limit of the original energy interval i-1 And the lower limit of the original energy interval i Coincide, that is, satisfy

[0062] The neutron energy response R of the new energy interval i i ′ can be divided into three parts: the energy range of the front part R' i，before is The equivalent response function is R ind(h-1) , and the equivalent neutron energy is The energy range of the middle part R' i，middle is The equivalent response function is the equivalent energy response function of the energy group between ind(h) and ind(h-1), that is, the sum of the response and energy products corresponding to each energy group in the initial energy group interval covered; The energy range of the rear part R' i，after is The equivalent response function is R ind(h) , and the equivalent neutron energy is

[0063]

[0064] R′ i =R′ i，before +R′ i，middle +R′ i，after , i = 1, 2, 3, …, m

[0065]

[0066] (4) Inverse solution of neutron spectrum

[0067] The set of readings M (m-dimensional vector) of the equivalent detector of the measuring device is taken as the input, and the direct method is used to directly obtain the m-group neutron spectrum through response matrix deformation, as shown in the following formula

[0068]

[0069] The solved m-group neutron spectrum is divided into two cases:

[0070] Case 1: If each element of the spectrum vector is non-negative, which meets the physical meaning, it is accepted as the result of the neutron spectrum.

[0071] Case 2: If at least one element of the spectrum vector is negative, which does not meet the physical meaning, because the neutron fluence in each energy group cannot be negative, the result cannot be accepted.

[0072] When the second case occurs, the result needs to be divided and processed again. A perturbation threshold is set, which is a negative value, and is the critical value for determining whether to use the perturbation theory.

[0073] Case 2-a, although the elements in the spectrum vector have negative numbers, the values are close to 0, i.e., greater than the perturbation threshold; Case 2-b, the elements in the spectrum vector have negative numbers, and at least one element is not close to 0, i.e., less than the perturbation threshold.

[0074] Case 2-a, the perturbation theory can be used for solving, that is, to consider where is a non-negative vector, and the corresponding non-negative element in the vector is taken, and the negative element close to 0 is taken as 0. M0 is the corresponding equivalent detector reading, and ε M is an added random perturbation term, and satisfies the following formula:

[0075]

[0076] ε M Set a Gaussian random distribution with mean 0 and standard deviation σ, where the value of σ can be changed in steps, to the random disturbance term ε M Perform Monte-Carlo random sampling. If case 1 does not occur within the set number of sampling times, increase the value of the standard deviation σ of the random disturbance term ε M until case 1 is found. So that each element is non-negative.

[0077] Case 2-b, random perturbation needs to be applied to the response function, then can be expressed as:

[0078]

[0079] Perform Monte-Carlo random sampling on the random disturbance term ε R If it is case 1, directly accept it. If it is case 2-a in case 2, continue to find using the method in case 2-a. If neither is satisfied, re-sample until case 1 is found. If case 1 does not occur within the set number of sampling times, increase the value of the standard deviation σ of the random disturbance term ε R until each element in is non-negative.

[0080] (5) Judgment and selection of the solution spectrum.

[0081] Case 1: Without using perturbation theory, directly give the neutron energy spectrum with physical meaning. This result is the unique solution and does not need to be distinguished, directly accepted.

[0082] Case 2: Need to use perturbation theory, use Monte-Carlo random sampling method, the solution is usually not unique, and the neutron energy spectrum solution needs to be selected. The principle of selection is based on the continuity of the neutron energy spectrum distribution. Unless the number of energy groups is particularly small and the division is particularly sparse, otherwise for the case of more than 3 energy groups, the energy spectrum distribution should not appear obvious wave peak-valley-wave peak shape in any continuous three-energy region.

[0083] (6) Change and cycle of perturbation with step size

[0084] Without perturbation, directly solve case 1, which is less likely, usually need to add perturbation, the quantitative measurement of perturbation is mainly the perturbation term ε M of the detector reading and the perturbation term ε R ​, two perturbation terms are Gaussian random distribution with average of 0; if the expected neutron spectrum result is not found within the set total number of sampling, the perturbation term needs to be gradually increased, and the random sampling is continued, by determining the step size and gradually increasing the perturbation term, the expected neutron spectrum result can be finally obtained.

[0085] The implementation effect is explained, Figures 3-9 The initial response function of 53 energy groups in the neutron spectrum detection system of 7 equivalent detectors and the "same group" neutron energy response function after group processing are compared.

[0086] Figure 10 The neutron spectrum obtained by using the neutron spectrum solving method based on the perturbation theory 241 Am-Be neutron spectrum and the reference neutron spectrum obtained by using the difference between the measured data with and without the shadow cone in the report of IAEA table 4.IX (PTB). The detector reading is obtained by using the Fredholm equation group to calculate the reference neutron spectrum and the initial neutron response function of 53 groups, and the detector reading is input into the 7-group neutron spectrum obtained by using the solving method of the neutron spectrum, and it is found that the degree of coincidence is very good.

[0087] The contents not described in detail in the specification belong to the prior art known to the person skilled in the art.

[0088] The above method is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited to this. Any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A method for neutron deconvolution based on perturbation theory, characterized in that The method comprises the following steps: (1) determining the number of neutron energy groups The number of neutron energy groups should be the same as the number of equivalent detectors of the neutron energy spectrum detection system: in the Bonner multi-sphere neutron energy spectrum detection system, the number of neutron energy groups is the same as the number of Bonner spheres; in the single-sphere neutron energy spectrum measurement system, the number of neutron energy groups is the same as the number of layers; in the neutron energy spectrum detection system of the activated sheet, the number of neutron energy groups is the same as the number of activated sheets; (2) dividing the neutron energy groups The neutron energy groups are divided in a logarithmic manner in a wide energy range of 0.025 eV to 20 MeV, and the logarithmic division includes equal- and non-equal-let division. The equal-let division of neutron energy groups is used in unknown neutron field or non-neutron radiation dose measurement related applications, and the non-equal-let division of neutron energy groups is used in known neutron field or neutron radiation dose measurement related applications. In the application of neutron energy spectrum measurement in a known neutron field, the neutron energy groups are divided according to the following principles: the energy group division is dense in the energy range of interest, and the number of energy groups is large; the energy group division is sparse in the energy range of non-interest, and the number of energy groups is small. In the application of neutron radiation dose measurement, the neutron energy groups are divided according to the following principles: In the range of thermal neutron ~ 10 -2 MeV at least one energy group is distributed; in the range of 10 -2 MeV ~ 1 MeV at least two energy groups are distributed; in the range of 1 MeV ~ 10 MeV at least one energy group is distributed; in the range of 10 -2 MeV, 1 MeV, 10 MeV energy points or near points, energy limits are set; (3) importing the same-group neutron energy response matrix R' The initial divided energy groups and the initial energy response matrix R are imported. If the number of initial energy groups is n and the number of equivalent detectors of the system is m, the dimension of R is n x m, the number of energy groups of the same-group neutron energy response matrix R' is the same as the number of equivalent detectors, and the dimension is m x m. The n initial energy groups of the m equivalent detectors are combined into m new energy groups. Energy group combination principle: for each equivalent detector, the total neutron response in each energy range of the new energy response curve is equal to the total neutron response in the same energy range of the original energy response curve. The upper bound of the new energy interval i is determined by the sub-group division in step (2) as The lower bound is In a wide energy range, the upper bound of the new energy interval i-1 And the lower bound of the new energy interval i Coincide, that is, satisfy Assume that the upper bound of the original energy group covered by the new energy interval i is The lower bound is Then the upper bounds And the lower bounds of each original energy group are found, and the energy group sequence ind corresponding to the initial energy group, i.e. the hth initial energy group, satisfies At the same time The upper bound of the original energy interval i-1 And the lower bound of the original energy interval i Coincide, i.e. satisfy The neutron energy response R of the new energy bin i i is divided into three parts: a front part R' i，before The energy range of R The equivalent response function is R ind(h-1) The equivalent neutron energy is The middle part R' i , middle The energy range of R The equivalent response function is the equivalent energy response function of the energy groups between ind(h) and ind(h-1), i.e. the sum of the response and energy products corresponding to each energy group in the initial energy group interval covered; the back part R' i，after The energy group range of R The equivalent response function is R ind(h) The equivalent neutron energy is R' i = R' i，before + R' i，middle + R' i，after , i = 1, 2, 3,..., m (4) inverse solution of neutron energy spectrum A set of readings M, i.e. an m-dimensional vector, of the equivalent detector of the measuring device is taken as input, and the m-group neutron spectrum is directly obtained by response matrix transformation using the direct method, as shown in the following equation The calculated m-group neutron energy spectrum is divided into two cases: Case 1: the result of the spectrum Each element of the vector is non-negative, in line with the physical meaning, and it is accepted as the result of the neutron spectrum; Case 2: the energy spectrum in the solution result There is at least one negative element in the elements of the vector, which does not conform to the physical meaning and the result cannot be accepted. When case 2 occurs, the results need to be divided and processed again. A perturbation threshold is set, which is a negative number. The threshold is a critical value for determining whether to use the perturbation theory. Case 2-a, energy spectrum The elements in the vector have negative numbers, but the values are close to 0, i.e. greater than the perturbation threshold; Case 2-b, Energy Spectrum There are negative numbers in the vector and at least one element is not close to zero, i.e., less than the perturbation threshold. Case 2-a, solved using perturbation theory, i.e. considering where is a non-negative vector, taken as the corresponding non-negative element of the vector, and 0 for negative elements close to 0, M0is the corresponding equivalent detector reading, ε M is an added random perturbation term, satisfying the following equation: ε M A Gaussian random distribution with mean 0 and standard deviation σ is set for the random disturbance term ε M Monte-Carlo random sampling is performed, and if case 1 does not occur within a set sampling number range, the σ value of the random disturbance term ε M is increased according to a set step size until case 1 is found so that each element is non-negative Case 2-b, where a random perturbation is needed to the response function, then may be represented as: For the random disturbance term ε R Perform Monte Carlo random sampling if If the result is case 1, then accept it directly. For case 2-a in the result of case 2, continue searching using the method corresponding to case 2-a. If none of these conditions are met, resampling is required until the desired result is found. For case 1, if case 1 does not occur within the set number of samplings, the random disturbance term ε can be increased according to the set step size. R The standard deviation σ value, until it is made The process continues until every element in the set is non-negative.

2. The perturbation theory based neutron deconvolution method according to claim 1, wherein This method needs to judge and screen the spectrum results: Case 1: directly give the neutron energy spectrum with physical meaning. This result is a unique solution and does not need to be distinguished. It is directly accepted. Case 2: the Monte-Carlo random sampling method needs to be used. The solution is not unique and needs to be screened. The principle of screening is based on the continuity of the neutron energy spectrum distribution. For the case where the number of energy groups is greater than 3, the energy spectrum distribution should not appear any obvious wave-peak-valley-wave-peak shape in any continuous three-energy region.

3. The perturbation theory based neutron deconvolution method of claim 1, wherein This method includes the change and cycle of the perturbation step size: The quantitative measure of the perturbation is the perturbation term ε of the probe reading M and the response matrix perturbation term ε R Both perturbation terms are Gaussian random distribution with mean 0; if the expected neutron spectrum result is not found within the set total number of samples, the perturbation term needs to be gradually increased and continue random sampling, by determining the step size and gradually increasing the perturbation term, the expected neutron spectrum result can be finally obtained.

4. The perturbation theory based neutron deconvolution method of claim 1, wherein This method includes the forward combination of neutron energy groups, which changes the inverse solution process of the few-channel spectrum into the solution process of a well-posed equation.

5. The perturbation theory based neutron deconvolution method according to claim 1, wherein The results of this method can be used as the preset neutron energy spectrum of other multi-group neutron energy spectrum solution methods after being disassembled.

6. The perturbation theory based neutron deconvolution method according to claim 1, wherein: If a suitable solution cannot be found within the maximum variance range of the user-set perturbation, the neutron energy group division is fine-tuned by setting the step size until a suitable solution is found.

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