CN116679338A - Portable conical multi-sphere neutron spectrum measurement system and measurement method thereof - Google Patents
Portable conical multi-sphere neutron spectrum measurement system and measurement method thereof Download PDFInfo
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- 238000001228 spectrum Methods 0.000 title claims abstract description 54
- 238000005259 measurement Methods 0.000 title claims abstract description 33
- 238000000691 measurement method Methods 0.000 title description 4
- 239000000463 material Substances 0.000 claims abstract description 46
- 230000004044 response Effects 0.000 claims abstract description 16
- 238000000034 method Methods 0.000 claims abstract description 12
- 238000012545 processing Methods 0.000 claims abstract description 10
- 238000007405 data analysis Methods 0.000 claims abstract description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 21
- 238000005316 response function Methods 0.000 claims description 18
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 8
- 239000001257 hydrogen Substances 0.000 claims description 8
- 229910052739 hydrogen Inorganic materials 0.000 claims description 8
- 239000004698 Polyethylene Substances 0.000 claims description 7
- 239000011133 lead Substances 0.000 claims description 7
- -1 polyethylene Polymers 0.000 claims description 7
- 229920000573 polyethylene Polymers 0.000 claims description 7
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 6
- 239000011159 matrix material Substances 0.000 claims description 6
- 229910052742 iron Inorganic materials 0.000 claims description 3
- 239000012188 paraffin wax Substances 0.000 claims description 3
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 claims description 3
- 229910052721 tungsten Inorganic materials 0.000 claims description 3
- 239000010937 tungsten Substances 0.000 claims description 3
- 230000000694 effects Effects 0.000 abstract description 13
- 230000005855 radiation Effects 0.000 abstract description 6
- 230000008569 process Effects 0.000 abstract description 5
- 239000000523 sample Substances 0.000 description 11
- 238000013461 design Methods 0.000 description 3
- 238000001514 detection method Methods 0.000 description 3
- 239000007789 gas Substances 0.000 description 3
- 238000005086 pumping Methods 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- 238000004364 calculation method Methods 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 230000003993 interaction Effects 0.000 description 2
- 238000010606 normalization Methods 0.000 description 2
- 230000009257 reactivity Effects 0.000 description 2
- 238000000342 Monte Carlo simulation Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 239000011344 liquid material Substances 0.000 description 1
- 230000005658 nuclear physics Effects 0.000 description 1
- 238000005025 nuclear technology Methods 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
- G01T3/00—Measuring neutron radiation
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E30/00—Energy generation of nuclear origin
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Abstract
The invention relates to the technical field of nuclear science, in particular to a portable conical multi-sphere neutron spectrum measuring system and a measuring method thereof, wherein the system comprises a conical slowing body, cylindrical through holes, neutron detectors and a data analysis processing system, the cylindrical through holes are arranged in the conical slowing body, the cylindrical through holes are internally provided with the neutron detectors, at least 1 neutron detector is arranged, and the neutron energy of a system without auxiliary materials is 10 ‑9 The MeV-20 MeV neutrons have a good response effect; the system for adding auxiliary materials has neutron energy of 10 ‑9 The MeV-1000 MeV neutrons have a good response effect; the ball interference problem of the conventional multi-ball neutron spectrometer is avoided; the purpose of repeatedly entering the radiation place to replace the slowing ball in the measurement process is avoided, and the excrement system is simple to operate; meanwhile, the function of a plurality of slowing balls of the conventional multi-ball neutron spectrometer can be replaced by one slowing ball, so that the volume and the weight of the spectrometer are greatly reduced.
Description
Technical Field
The invention relates to the technical field of nuclear science, in particular to a portable conical multi-sphere neutron spectrum measuring system and a measuring method thereof.
Background
Neutron energy spectrum measurement is of great significance to many tasks in the fields of nuclear engineering and nuclear physics. The neutron energy spectrum can be accurately measured and rapidly analyzed in reactor design and application or under special environmental conditions, namely, the neutron source item can be determined as accurately and conveniently as possible, and the method is very important for reactor parameter design, radiation damage evaluation of special materials for nuclear and neutron shielding material design under special environments.
The multi-sphere neutron spectrometer system is firstly proposed by Bramblett in 1960 and consists of a series of polyethylene slowing balls with different diameters, a spherical proportional counter is adopted by a central detector, and the multi-sphere neutron spectrometer has the advantages of wide response range, isotropy, simplicity in operation and the like. However, with the development of nuclear technology, especially with the development of aerospace technology, a multi-sphere neutron spectrum measurement system is required to be portable and light in weight for space neutron spectrum measurement, so that the cost of aerospace transportation is reduced. In order to achieve the purpose of portable multi-sphere neutron spectrum measurement, a set of neutron spectrometer which is provided with four spheres and is arranged on a rotatable platform is designed abroad so as to achieve the purpose of multi-sphere measurement; the domestic multi-sphere neutron spectrometer is continuously researched and improved to form a plurality of types of multi-sphere neutron spectrometers, and domestic Li Taosheng develops a single-sphere multi-counter spectrometer which is essentially a multi-sphere neutron spectrometer, but a plurality of thermal neutron proportional counters are embedded in polyethylene slowing-down bodies in a pairwise orthogonal manner; a water pumping and injecting multilayer concentric sphere neutron spectrometer developed by the university of Chengdu university Yang Jianbo; the nested multi-sphere neutron spectrum measuring system designed by the university of Qinghua can achieve the aim of multi-sphere.
Although the improved multi-sphere neutron spectrometer increases the portability of the spectrometer to a certain extent and reduces the quality of the spectrometer, the nested multi-sphere neutron spectrometer increases the risk of personnel being radiated because of manual operation; at the same time, adding a moderating layer per layer increases the complexity of the operating time. The water pumping and injecting multilayer concentric sphere neutron spectrometer adopts water as a slowing material, and changes the thickness of the slowing material by changing a water layer, so that the operation complexity of the spectrometer is increased under the condition of space neutron measurement, and the spectrometer is not applicable to the measurement of space neutrons; domestic Li Taosheng developed a single-sphere multi-counter spectrometer which adopts a thermal neutron proportional counter with three probes, the number of the probes is too small, and the risk of measuring neutron spectrum accuracy is increased.
In order to simplify a neutron spectrometer measurement system and enable the neutron spectrometer measurement system to be more portable and convenient, the invention provides a single-sphere multi-neutron energy spectrum counting system and a measurement method thereof. There are two measurement modes for this system: (1) a plurality of thermal neutron detectors are needed, and are embedded in a central through hole for placing thermal neutron detection at the central shaft of the cone, so that the purpose of realizing multi-sphere measurement is achieved through different slowing thicknesses of different heights at the cone; (2) the requirements of energy spectrum measurement can be met by only one detector and one set of electronic equipment, the thermal neutron probe is pulled by a motor to move up and down at the central through hole at the central axis of the cone, the purpose of multi-ball measurement is achieved by different slowing thicknesses at different heights at the cone, and the purpose of N slowing structures can be achieved by the scheme. The single-sphere multi-neutron energy spectrum counting system solves the problems that a conventional multi-sphere neutron spectrometer is large in size and inconvenient to carry. Meanwhile, the purpose of multiple slowing bodies of multiple balls is achieved through one slowing structure, and the weight of the spectrometer is greatly reduced.
The improved multi-sphere neutron spectrometer at home and abroad increases portability of the spectrometer to a certain extent, reduces quality of the spectrometer, but increases risk of personnel being radiated because of manual operation of the nested multi-sphere neutron spectrometer; at the same time, adding a moderating layer per layer increases the complexity of the operating time. The water pumping and injecting multilayer concentric sphere neutron spectrometer adopts water as a slowing material, and changes the thickness of the slowing material by changing a water layer, so that the operation complexity of the spectrometer is increased under the condition of space neutron measurement, and the spectrometer is not applicable to the measurement of space neutrons; domestic Li Taosheng developed a single-sphere multi-counter spectrometer which adopts a thermal neutron proportional counter with three probes, the number of the probes is too small, and the risk of measuring neutron spectrum accuracy is increased.
The invention aims to solve the problems of complex operation, large quantity and large volume of the conventional multi-sphere neutron spectrometer, and provides a portable conical multi-sphere neutron energy spectrum measuring system which well solves the problems of complex operation, poor spectrum resolving effect due to small quantity of response functions, large quantity and large volume of the conventional portable multi-sphere neutron spectrometer.
Reference to the literature
1.BRAMBLETT R L,EWING R I,BONNER T W.1960.A new type of neutron spectrometer.Nuclear Instruments andMethods[J],9:1-12.
2. Li Taosheng, le Zhixi, gong Cunkui, etc. binary moderated high energy neutron dosimeters, CN101419290A [ P ].2009.
3. Hong Bing, li Taosheng, zhang Zhiyong, et al. Electronics systems for single sphere multiple counter neutron dosimeters developed [ J ]. Nuclear technology, 2014 (011): 037.
4.Dubeau J,Witharana S,YonkeuA,et al.ANEWTYPE OF NEUTRON SPECTROMETERUSING NESTED MODERATOR.
5.WIEGEL B,ALEVRAA V.2002.NEMUS-the PTB Neutron Multisphere Spectrometer:Bonner spheres and more.Nuclear Instruments&Methods in Physics Research Section a-Accelerators Spectrometers Detectors and AssociatedEquipment[J],476:36-41.
6.WIEGEL B,ALEVRAAV,SIEBERT B R L.1994.Calculations ofthe response functions ofBonner Spheres with a spheriacl He-3proportional counter using a realistic detector model[M].Physikalisch Technische Bundesanstalt.
7.ING H,CLIFFORD T,MCLEAN T,et al.1997.ROSPEC-A simple reliable high resolution neutron spectrometer.Radiation Protection Dosimetry[J],70:273-278.
Disclosure of Invention
The invention provides a portable conical multi-sphere neutron spectrum measurement system, which comprises a conical slowing body 1, cylindrical through holes 4, neutron detectors 2 and a data analysis processing system, wherein the cylindrical through holes 4 are formed in the conical slowing body 1, the cylindrical through holes 4 are internally provided with the neutron detectors 2, at least 1 neutron detector 2 is arranged in each cylindrical through hole 4, and the data analysis processing system is used for receiving and processing signals in the neutron detectors;
preferably, an auxiliary material 3 is arranged in the conical slowing body 1 near the cylindrical through hole 4, so as to improve the detection response to high-energy neutrons.
Preferably, the auxiliary material 3 is arranged in the conical slowing body 1 near the cylindrical through hole 4.
Preferably, the cone-shaped slowing body 1 is prepared from a hydrogen-rich material.
Preferably, the hydrogen-rich material is polyethylene, paraffin or water.
Preferably, the hydrogen-rich material is water, the water can be injected when the spectrometer is used, and the water is discharged when the spectrometer is not used, so that the quality of the spectrometer is reduced to the greatest extent.
Preferably, the cylindrical through hole 4 is located at the central axis of the conical slowing body 1.
Preferably, the neutron detector 2 is a spherical neutron detector.
Preferably, the auxiliary material 3 is lead, iron or tungsten.
Preferably, the neutron detector 2 is filled with cylindrical through holes 4, and 2-30 neutron detectors are arranged.
The second object of the present invention is to provide a measuring method of the portable conical multi-sphere neutron spectrum measuring system, comprising the following steps: forms m different moderated thickness structures, at 10 -9 Selecting n discrete energy values in each energy level of the neutron energy range from MeV to 20MeV, obtaining response function values under m different slowing thicknesses by using Monte Carlo simulation software, and finally forming a response function matrix in the following formula;
wherein 1-m represent m different moderation thicknesses, i represents a selected energy discrete number;
if the energy of the incident neutron is at most E max The minimum energy of the incident neutron is E min Then the fluence can be defined as follows:
wherein N is d Is the count of the detector, R φ (E) The response function of the detector, namely the response number of unit neutron fluence caused in the detector, and the neutron energy spectrum calculated by phi (E);
discretizing the formula to obtain the following formula:
the matrix of m rows and one column measured by the neutron detector is as follows:
bringing equations (1) and (4) into equation (3) yields:
obtained by deconvolutionThe neutron spectrum is obtained.
The beneficial effects of the invention are as follows: (1) The portable single-cone multi-sphere neutron spectrum measuring system solves the problem of sphere interference of a conventional multi-sphere neutron spectrometer; the purpose of repeatedly entering the radiation place to replace the slowing ball in the measuring process is avoided; (2) The portable single-cone multi-sphere neutron spectrum measuring system of the invention has the advantages that the cone without auxiliary materials is slowThe neutron energy of the chemical body is 10 -9 The MeV-20 MeV neutrons have a good response effect; the tapered moderator added with auxiliary material has neutron energy of 10 -9 The MeV-1000 MeV neutrons have a good response effect; (3) The portable single-cone multi-sphere neutron spectrum measuring system is simple to operate, and the number of the slowing spheres replaces the whole conventional multi-sphere neutron spectrum measuring system, so that the weight of the spectrometer is greatly reduced, and the portability of the spectrometer is improved.
Drawings
FIG. 1 shows a portable single cone multi-sphere neutron spectrum measurement system
1. A cone-shaped slowing body; 2. a neutron detector; 3. auxiliary materials; 4. a cylindrical through hole;
FIG. 2 is a portable single cone multi-sphere neutron spectrum measurement system
FIG. 3 is a schematic diagram of a detector without auxiliary material
FIG. 4 Monte Carlo model schematic diagram
Left: a cross-sectional view; right: plan view of a computer
FIG. 5 response function of 8 probes without auxiliary material
Neutron spectrum resolved by the detector of FIG. 6
FIG. 7 is a schematic view of the structure of the detector with auxiliary material
FIG. 8 Monte Carlo model schematic
Left: a cross-sectional view; right: plan view of a computer
FIG. 9 response function of 8 probes with auxiliary material
Note that: lead thickness 1cm
FIG. 10 response function of 8 probes with auxiliary material
Note that: lead thickness 2cm
FIG. 11 response function of 8 probes with auxiliary material
Note that: lead thickness 3cm
Detailed Description
The following describes the scope of the present invention in detail with reference to the accompanying drawings, and it should be noted that the scope of the present invention is not limited by the following examples.
Embodiment one, a portable conical multi-sphere neutron spectrum measurement system
As shown in fig. 1 and 2, the invention provides a portable conical multi-sphere neutron spectrum measurement system, which comprises a conical slowing body 1, cylindrical through holes 4, neutron detectors 2 and a data analysis processing system, wherein the cylindrical through holes 4 are arranged in the conical slowing body 1, the cylindrical through holes 4 are internally provided with the neutron detectors 2, at least 1 neutron detector 2 is arranged, and the data analysis processing system is used for receiving and processing signals in the neutron detectors; an auxiliary material 3 is arranged in the conical slowing body 1 near the cylindrical through hole 4 and is used for improving the detection response to high-energy neutrons. The conical moderator 1 is prepared from a hydrogen-rich material, wherein the hydrogen-rich material is polyethylene, paraffin or water, if the moderator material is water or other liquid materials, the water can be injected when the conical moderator is not used, the water is discharged when the conical moderator is not used, the mass of a spectrometer is reduced to the greatest extent, the cylindrical through hole 4 is positioned at the central axis of the conical moderator 1, the neutron detector 2 is a spherical neutron detector, the auxiliary material 3 is composed of lead, iron or tungsten, and the neutron detector 2 is filled with the cylindrical through hole 4.
Embodiment two, neutron spectrum measuring method
Forms m different moderated thickness structures, at 10 -9 Selecting n discrete energy values in each energy level of the neutron energy range from MeV to 20MeV, obtaining response function values under m different slowing thicknesses by using Monte Carlo simulation software, and finally forming a response function matrix in the following formula;
wherein 1-m represent m different moderation thicknesses, and i represents a selected energy discrete number.
If the energy of the incident neutron is at most E max The minimum energy of the incident neutron is E min Then the fluence can be defined as follows:
wherein N is d Is the count of the detector, R φ (E) The response function of the detector, namely the response number of the unit neutron fluence caused in the detector, and the neutron energy spectrum calculated by phi (E).
Discretizing the formula to obtain the following formula:
the matrix of m rows and one column measured by the neutron detector is as follows:
bringing equations (1) and (4) into equation (3) yields:
obtained by deconvolutionThe neutron spectrum is obtained.
Embodiment III, measuring neutron spectrum by neutron spectrum measurement method without adding auxiliary materials
The detector is mounted in the manner shown in fig. 3. When no auxiliary material is added, the conical moderator has the following dimensions: the diameter of the lower bottom is 40cm, the diameter of the upper bottom is 7cm, the height is 40cm, and the density of the conical moderator material is 0.95g/cm 3 . The diameter of the cylindrical through hole is 5cm. Neutron detector using 3 He proportional counter, gas pressure is 10 atmospheres, 3 the density of He gas was 1.89427 ×10 -3 g/cm 3 The probe diameter was 5cm.
Simulation software using Monte Carlo simulation programA Monte Carlo model as shown in the figure is built, and 8 spheres are designed in the conical moderator as shown in the figure 4 3 He is proportional to the counter. A single-energy planar source is perpendicularly incident to the conical moderator, and the source is defined as a rectangular planar source, and the side length of the planar source is the same as the diameter and the height of the lower bottom surface of the conical moderator. Calculation of response functions at different water layer combinations using MCNPX Monte Carlo radiation transport codes with ENDF/B-VI-0 neutron cross section library
Recording neutrons and using F4 card and FM4 card in MCNPX 3 He-generated (n, p) reactivity in the corresponding format FM 4C MR, where M represents the material of the cell to be recorded [ ] 3 He); r is a channel number, and the channel number of the (n, p) reaction is 103; c represents a normalization factor.
C＝-V He ·S
After the FM4 card is used, the result obtained by the FM4 card is neutron fluence response. In addition, in the interaction process of neutrons and substances, the elastic scattering effect is accompanied with inelastic scattering effect with a certain probability. Thus, neutron thermalization in the MCNPX code takes into account the use of S (α, β) cross-section libraries (water: MTn lwtr.01, polyethylene: MTnpoly.01).
The response functions of the simulated 8 neutron detectors are shown in fig. 5. The neutron energy spectrum solved by the detector is shown in fig. 6. The tapered moderator without auxiliary material has neutron energy of 10 -9 The MeV-20 MeV neutrons have a better response effect.
Fourth embodiment, adding auxiliary materials and measuring neutron spectrum by neutron spectrum measuring method
The detector is mounted in the manner shown in fig. 7. The thickness of the added auxiliary material is 1cm, 2cm and 3cm of lead respectively, the height of the auxiliary material is 15cm, the distance from the bottom of the conical slowing body is 10cm, and the size of the conical slowing body is as follows: the diameter of the lower bottom is 40cm, the diameter of the upper bottom is 7cm, the height is 40cm, and the density of the conical moderator material is 0.95g/cm 3 . The diameter of the cylindrical through hole is 5cm. Neutron detector using 3 He proportional counterThe air pressure is 10 atmospheres, 3 the density of He gas was 1.89427 ×10 -3 g/cm 3 The probe diameter was 5cm.
The Monte Carlo model as shown in the figure is established by using Monte Carlo simulation program simulation software, and 8 spheres are designed in the conical moderator as shown in figure 8 3 He is proportional to the counter. A single-energy planar source is perpendicularly incident to the conical moderator, and the source is defined as a rectangular planar source, and the side length of the planar source is the same as the diameter and the height of the lower bottom surface of the conical moderator. Calculation of response functions at different water layer combinations using MCNPX Monte Carlo radiation transport codes with ENDF/B-VI-0 neutron cross section library
Recording neutrons and using F4 card and FM4 card in MCNPX 3 He-generated (n, p) reactivity in the corresponding format FM 4C MR, where M represents the material of the cell to be recorded [ ] 3 He); r is a channel number, and the channel number of the (n, p) reaction is 103; c represents a normalization factor.
C＝-V He ·S
After the FM4 card is used, the result obtained by the FM4 card is neutron fluence response. In addition, in the interaction process of neutrons and substances, the elastic scattering effect is accompanied with inelastic scattering effect with a certain probability. Thus, neutron thermalization in the MCNPX code takes into account the use of S (α, β) cross-section libraries (water: MTn lwtr.01, polyethylene: MTnpoly.01).
The response functions of 8 neutron detectors simulated by Monte Carlo simulation software are shown in FIGS. 9-11, and the tapered moderator with the added auxiliary material has a neutron energy of 10 -9 The MeV-1000 MeV neutrons have a better response effect.
In summary, the invention provides a portable conical multi-sphere neutron spectrum measurement system, which avoids the problem of sphere interference of a conventional multi-sphere neutron spectrometer; the purpose of repeatedly entering the radiation place to replace the slowing ball in the measuring process is avoided; the portable single cone of the inventionShape multi-sphere neutron spectrum measuring system, conical slowing body without auxiliary material has neutron energy of 10 -9 The MeV-20 MeV neutrons have a good response effect; the tapered moderator added with auxiliary material has neutron energy of 10 -9 The MeV-1000 MeV neutrons have a good response effect; the portable single-cone multi-sphere neutron spectrum measuring system is simple to operate, and the number of the slowing spheres replaces the whole conventional multi-sphere neutron spectrum measuring system, so that the weight of the spectrometer is greatly reduced, and the portability of the spectrometer is improved.
Claims (10)
1. The portable conical multi-sphere neutron spectrum measurement system is characterized by comprising a conical slowing body 1, cylindrical through holes 4, neutron detectors 2 and a data analysis processing system, wherein the cylindrical through holes 4 are formed in the conical slowing body 1, the neutron detectors 2 are arranged in the cylindrical through holes 4, at least 1 neutron detector 2 is arranged, and the data analysis processing system is used for receiving and processing signals in the neutron detectors.
2. The portable cone-shaped multi-ball neutron spectrum measuring system according to claim 1, wherein the cone-shaped slowing body 1 is internally provided with an auxiliary material 3 near the cylindrical through hole 4.
3. The portable cone-shaped multi-sphere neutron spectrum measurement system according to claim 1, wherein the cone-shaped slowing body 1 is made of a hydrogen-rich material.
4. The portable cone-shaped multisphere neutron spectrum measurement system of claim 2, wherein the hydrogen-rich material is polyethylene, paraffin or water.
5. The portable cone-shaped multisphere neutron spectrum measurement system of claim 2, wherein the hydrogen-rich material is water.
6. The portable cone-shaped multi-ball neutron spectrum measurement system according to claim 1, wherein the cylindrical through hole 4 is located at the central axis of the cone-shaped slowing body 1.
7. The portable cone-shaped multi-sphere neutron spectrum measurement system of claim 1, wherein the neutron detector 2 is a spherical neutron detector.
8. The portable cone-shaped multisphere neutron spectrum measurement system of claim 1, wherein the auxiliary material 3 is composed of lead, iron or tungsten.
9. The portable cone-shaped multi-sphere neutron spectrum measurement system according to claim 1, wherein the neutron detector 2 is filled with a cylindrical through hole 4.
10. The method of measuring a portable cone-shaped multisphere neutron spectrum measurement system of claim 1, comprising the steps of: forms m different moderated thickness structures, at 10 -9 Selecting n discrete energy values in each energy level of the neutron energy range from MeV to 20MeV, obtaining response function values under m different slowing thicknesses by using Monte Carlo simulation software, and finally forming a response function matrix in the following formula;
wherein 1-m represent m different moderation thicknesses, i represents a selected energy discrete number;
if the energy of the incident neutron is at most E max The minimum energy of the incident neutron is E min Then the fluence can be defined as follows:
wherein N is d Is the count of the detector, R φ (E) The response function of the detector, namely the response number of unit neutron fluence caused in the detector, and the neutron energy spectrum calculated by phi (E);
discretizing the formula to obtain the following formula:
the matrix of m rows and one column measured by the neutron detector is as follows:
bringing equations (1) and (4) into equation (3) yields:
obtained by deconvolutionThe neutron spectrum is obtained.
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