A multi-sphere neutron spectrometer for monitoring pulsed neutron radiation fields

Abstract

The present invention discloses a multi-sphere neutron spectrometer for monitoring pulsed neutron radiation fields, comprising: 3 He gas detector, 4H-SiC semiconductor detector, neutron moderator, preamplifier, spectrometer main amplifier, high voltage power supply, multi-channel analyzer. 3 He gas detector and 4H-SiC semiconductor detector are designed in the neutron moderator of a multi-sphere neutron spectrometer. The dual-detector multi-sphere neutron spectrometer is used in the pulsed neutron radiation field. The neutron flux is 10 1 ~10 4 n·cm ‑2 s ‑1 and a neutron flux of 10 3 ~10 6 n·cm ‑2 s ‑1 The present invention uses the pulsed neutron radiation field to measure the neutron energy spectrum and dose. 3 The dual-detector multi-sphere neutron spectrometer data acquisition system, which consists of a He gas detector and a 4H‑SiC semiconductor detector, enables the measurement of neutron energy spectrum distribution information and neutron dose in a wide energy range.

Description

Technical Field

[0001] The present invention belongs to the technical field of radiation monitoring, and in particular relates to a multi-sphere neutron spectrometer used for monitoring pulsed neutron radiation fields. Background Art

[0002] Neutron detection technology has a wide range of applications in fields such as nuclear energy, radiation monitoring, geological exploration, and medical diagnosis. Neutron detectors, due to their high sensitivity and precise measurement capabilities, hold significant value in these areas. However, due to the wide neutron energy spectrum generated by pulsed neutron radiation, ranging from thermal neutrons to 20 MeV, the neutron dose measurements from conventional neutron monitors can deviate significantly from the actual ambient dose equivalent. Summary of the Invention

[0003] In order to solve the above problems in the prior art, the present invention provides a multi-sphere neutron spectrometer for monitoring pulsed neutron radiation field. 3 A set of neutron detectors suitable for neutron flux of 10 is proposed, which is composed of He gas detector as central counting, 4H-SiC semiconductor detector as thermal neutron counter, neutron moderator, preamplifier, fast charge sensitive preamplifier, spectrometer main amplifier, high voltage power supply, and multi-channel analyzer. 1 ~10 4 n·cm -2 s -1 and a neutron flux of 10 3 ~10 6 n·cm -2 s -1 The dual-detector multi-sphere neutron spectrometer is used to measure neutron energy spectrum and dose in an environment with high sensitivity. The Monte Carlo method is used to calculate the eight neutron moderators with different detectors. -9 MeV to 20MeV wide energy range response matrix. The present invention is used for the energy spectrum and dose measurement of pulsed neutron radiation field, and can achieve the measurement of neutron energy spectrum distribution information and neutron dose in a wide energy range without multiple sets of multi-sphere neutron spectrometers.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is:

[0005] A multi-sphere neutron spectrometer for monitoring pulsed neutron radiation fields, comprising 3 He gas detector, 4H-SiC semiconductor detector, neutron moderator ball, preamplifier, fast charge sensitive preamplifier, spectrometer main amplifier, high voltage power supply, digital multi-channel analyzer, designed dual detector neutron moderator ball, in 10 -9The energy range from MeV to 20MeV is evenly divided into 60 energy points according to logarithmic coordinates. The Monte Carlo method is used to calculate the response function of eight neutron moderator spheres at each energy point under different detectors. The response matrix of the entire multi-sphere neutron spectrometer is obtained. The maximum entropy principle and SAND-II algorithm are then used to inversely solve the neutron energy spectrum. 3 The He gas detector and the 4H-SiC semiconductor detector are both set in the neutron moderator ball. A part of the neutrons entering the neutron moderator ball enters the 4H-SiC semiconductor detector and 28 Si and 12 The ionization signal generated by the nuclear reaction of C nuclide is amplified by the fast charge sensitive preamplifier; the other part of neutrons entering the neutron moderation sphere enters 3 In He gas detectors, 3 He gas generation 3 He (n, p) T reaction, the generated proton p and tritium nucleus T release energy, causing 3 He gas detector counting, the preamplifier is used to 3 The counting signal generated by the He gas detector is preliminarily amplified, and the main amplifier of the spectrometer filters the electrical signal amplified by the preamplifier. The high-voltage power supply provides bias voltage for the preamplifier and the fast charge sensitive preamplifier. The multi-channel analyzer records and analyzes the amplitude of the pulse signal amplified by the fast charge sensitive preamplifier and the preamplifier, selectively counts the pulse signal amplitude, and then performs binary encoding. The counted pulse signals are then sorted in order from low to high to form a pulse amplitude spectrum, and then the neutron energy spectrum can be inversely solved using the maximum entropy principle and the SAND-II algorithm.

[0006] The present invention has the following beneficial effects:

[0007] The present invention adopts 3 The data acquisition system of the dual-detector multi-sphere neutron spectrometer with He gas detector and 4H-SiC semiconductor detector enables a single dual-detector multi-sphere spectrometer to measure different radiation environments, making it more portable. 3 He gas detector and 4H-SiC semiconductor are set in the same neutron moderator sphere, taking advantage of the different sensitivity ranges of different detectors. 3 He gas detector count rate is usually 10 5 cps, it is easy to accumulate signals at high counting rates. The detection efficiency of 4H-SiC semiconductor detector is low and it is applicable at high counting rates. The dual-detector multi-sphere neutron spectrometer with different sensitivity characteristics improves the accuracy and range of the energy spectrum and dose monitoring of the pulsed neutron radiation field. 1 ~10 4 n·cm-2 s -1 Under conditions (low neutron yield), use based on 3 He detectors are used to measure neutron energy spectrum and dose; 3 ~10 6 n·cm -2 s -1 Under the condition of high neutron yield, the neutron spectrum and dose are measured by using a 4H-SiC semiconductor detector. 3 The data acquisition system of the dual-detector multi-sphere neutron spectrometer with He gas detector and 4H-SiC semiconductor detector realizes the measurement of wide neutron energy spectrum distribution information and neutron dose in the pulsed neutron radiation field. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 Schematic diagram of the structure of a multi-sphere neutron spectrometer for monitoring pulsed neutron radiation fields according to the present invention;

[0009] Figure 2 Schematic diagram of a circuit of a multi-sphere neutron spectrometer for monitoring pulsed neutron radiation fields according to the present invention;

[0010] Figure 3 It is a neutron moderator sphere with an outer diameter of 30.48 cm in the pulsed neutron radiation field. 3 Pulse amplitude distribution spectrum of He detector;

[0011] Figure 4 The pulse amplitude distribution spectrum of the 10.16 cm neutron moderator sphere 4H-SiC detector in the pulse neutron radiation field;

[0012] Figure 5 for 3 Comparison of simulated and experimental energy spectra of pulsed neutron radiation field in He gas detector;

[0013] Figure 6 Comparison of simulated and experimental energy spectra of the pulsed neutron radiation field of 4H-SiC semiconductor detector.

[0014] Among them: 1. Neutron moderator sphere, 2. 4H-SiC semiconductor detector, 3. 4H-SiC semiconductor detector signal cable duct, 4. Tray, 5. Tray bracket, 6. Metal aluminum cylindrical head, 7. 3 He gas detector stainless steel housing, 8. 3 He gas detector, 9. 3 He gas detector signal wire duct. DETAILED DESCRIPTION

[0015] In order to make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other. To achieve the above-mentioned objectives, the present invention adopts the following technical solutions.

[0016] The present invention provides a multi-sphere neutron spectrometer for monitoring pulsed neutron radiation fields, such as Figure 2 As shown, it is a 3 The data acquisition system of the dual-detector multi-sphere neutron spectrometer of He gas detector 8 and 4H-SiC semiconductor detector 2 improves the accuracy and range of the energy spectrum and dose monitoring of the pulsed neutron radiation field; the multi-sphere neutron spectrometer of the present invention includes 3 He gas detector 8, 4H-SiC semiconductor detector 2, neutron moderator 1, preamplifier, fast charge sensitive preamplifier, spectrometer main amplifier, high voltage power supply, multi-channel analyzer; 3 The He gas detector 8 and the 4H-SiC semiconductor detector 2 are both arranged in the neutron moderation sphere 1. Since the neutrons generated in the pulsed neutron radiation field will undergo various scattering reactions with various building structures in the pulsed neutron radiation field, they will be gradually moderated, forming a wide neutron energy spectrum distribution from the thermal neutron region to 14MeV energy. A part of the scattered neutrons will enter the neutron moderation sphere, a part of which will be slowed down by the neutron moderation sphere and disappear, and a part of the neutrons will enter the center of the sphere after being slowed down by the neutron moderation sphere. 3 He gas detector 8, enter 3 Neutrons from He gas detector 8 will react with 3 He gas generation 3 He (n, p) T reaction, the proton p and tritium nucleus T released by the reaction distribute the generated 765keV energy, the proton p obtains 574keV energy, the tritium nucleus T obtains 191keV energy, the generated proton p and tritium nucleus T will cause 3 He gas detector counting; the 4H-SiC semiconductor detector 2 can directly pass neutrons and the detector 28 Si and 12 C nuclide generation 28 Si(n, p) 28 A1, 28 Si(n, α) 25 Mg, 28 Si(n, n) 28 Si, 12 C(n, α) 9 Be, 12 C(n, n′) 12C and 12 C(n, n')3α and other nuclear reactions are used to detect fast neutrons. The surface of 4H-SiC crystal is coated with 6 The Li thermal neutron conversion material is used to detect thermal neutrons, and the charged particle products produced by the reaction generate ionization signals in the silicon carbide detector; the preamplifier is used to convert 3 The counting signal generated by the He gas detector 8 is preliminarily amplified, and the main amplifier of the spectrometer filters the electrical signal amplified by the preamplifier to reduce background noise and interference; the fast charge sensitive preamplifier is used to amplify the ionization nuclear signal generated in the 4H-SiC semiconductor detector 2; the multi-channel analyzer records and analyzes the amplitude of the pulse signal amplified by the fast charge sensitive preamplifier and the preamplifier, selectively counts the pulse signal amplitude, and then performs binary encoding, and then sorts the counted pulse signals from low to high to form a pulse amplitude spectrum.

[0017] Furthermore, the neutrons are slowed down by the neutron moderator and enter the 4H-SiC semiconductor detector 2. 6 LiF converter undergoes nuclear reaction: ; The 4.78MeV energy released by the reaction is in the product helium nucleus and tritium nuclei T, among which the helium nuclei The energy of the helium nucleus is 2.05 MeV, and the energy of the tritium nucleus T is 2.73 MeV. They are emitted in opposite directions. The emitted helium nucleus or tritium nucleus enters the sensitive volume of silicon carbide, causing electrons to rise from the valence band to the conduction band. Due to the lack of electrons in the valence band, holes are generated. The formed electron-hole pairs are collected by the electric field at electrodes of opposite polarity, forming an experimental signal.

[0018] Furthermore, the fast charge sensitive preamplifier (CAEN A1426) is used to amplify the detector signal, and the bias voltage BV (Bias Voltage) used by the 4H-SiC semiconductor detector 2 is +45V.

[0019] Furthermore, the multi-channel analyzer uses an analog-to-digital converter to convert each pulse signal to a corresponding channel. Each channel corresponds to a very narrow voltage amplitude. As time accumulates, the multi-channel analyzer allocates many addresses in its memory to store the amplitudes of these signals. These signals are arranged in order of pulse amplitude, thus forming a pulse amplitude spectrum, such as Figure 3 and Figure 4 As shown; then the neutron energy spectrum in the pulse radiation field is obtained by inverse solution based on the maximum entropy principle and the SAND-II algorithm and compared with the neutron energy spectrum calculated using the Monte Carlo method, as shown Figure 5 and Figure 6 shown.

[0020] Furthermore, the model of the preamplifier is Ortec142pc, and the recommended high voltage is set to +700V to ensure the best signal-to-noise ratio and extend the life of the amplifier.

[0021] Furthermore, the neutron moderator balls are all made of high-density polyethylene material to moderate scattered neutrons. There are 8 neutron moderator balls, and the outer diameters of each neutron moderator ball are: 7.62, 8.89, 10.16, 12.70, 15.24, 20.32, 25.40 and 30.48 cm, respectively, and the density is 0.94 g / cm 3 , including the design of a suitable bracket to ensure that the center of the neutron moderator spheres of all sizes are at the same vertical height. -9 The energy range from MeV to 20MeV is evenly divided into 60 energy points according to logarithmic coordinates. The Monte Carlo method is used to calculate the response function of eight neutron moderator spheres at each energy point under different detectors, and the response matrix of the entire multi-sphere neutron spectrometer is obtained. The neutron energy spectrum can then be inversely solved using the maximum entropy principle and the SAND-II algorithm.

[0022] Furthermore, the interior of the 4H-SiC semiconductor detector 2 is a Schottky barrier structure, and the silicon carbide surface coating area is , thickness is 30 of 6 LiF thermal neutron converter.

[0023] like Figure 1 FIG. 1 is a schematic diagram of the structure of a multi-sphere neutron spectrometer for monitoring pulsed neutron radiation fields according to the present invention, wherein the neutron moderator sphere 1 has a hemispherical cross-section and is made of high-density polyethylene. 3 The He gas detector 8 is located at the center of the neutron moderation sphere 1. 3 A 4H-SiC semiconductor detector 2 is set 1 mm away from the He gas detector 8. Neutrons enter the 4H-SiC semiconductor detector 2 or 3 The He gas detector 8 generates a corresponding nuclear reaction to produce a pulse signal that can be counted and analyzed.

[0024] 4H-SiC semiconductor detector signal line slot 3 and 3 The He gas detector signal wire slot 9 is a wire slot that fits the detector signal wire, and its purpose is to prevent excessive gaps from affecting the detector's response.

[0025] The tray 4 and the tray bracket 5 are both made of metal aluminum. Their function is to ensure that the centers of the other seven neutron moderator balls are located on the same horizontal plane, avoiding neutron flux measurement errors caused by position reasons, ensuring that the neutrons have the same attenuation path, ensuring the reliability of the experimental results, and simplifying the data analysis process.

[0026] Metal aluminum cylindrical head 6 and 3 He gas detector stainless steel housing 7 can effectively seal 3 He gas detector 8 3 He gas and other components to prevent the external environment from affecting the interior of the detector, such as air, moisture or other substances that may cause gas leakage or corrosion, while also having a better protection of its structure and function, providing structural support and protection for the interior and reactions.

Claims

1. A multi-sphere neutron spectrometer for monitoring pulsed neutron radiation fields, characterized by: The multi-sphere neutron spectrometer includes 3 He gas detector, 4H-SiC semiconductor detector, neutron moderator, preamplifier, fast charge sensitive preamplifier, spectrometer main amplifier, high voltage power supply, digital multi-channel analyzer; in, 3 The He gas detector and the 4H-SiC semiconductor detector are both set in the same neutron moderator sphere. A part of the neutrons entering the neutron moderator sphere enters the 4H-SiC semiconductor detector and 28 Si and 12 The ionization signal generated by the nuclear reaction of C nuclide is amplified by the fast charge sensitive preamplifier; the other part of neutrons entering the neutron moderation ball enters 3 He gas detector 3 He gas generation 3 He (n, p) T reaction, the generated proton p and tritium nucleus T release energy, causing 3 He gas detector counting, the preamplifier is used to 3 The counting signal generated by the He gas detector is preliminarily amplified, and the main amplifier of the spectrometer filters the electrical signal amplified by the preamplifier. The high-voltage power supply provides bias voltage for the preamplifier and the fast charge sensitive preamplifier. The multi-channel analyzer records and analyzes the amplitude of the pulse signal amplified by the fast charge sensitive preamplifier and the preamplifier, selectively counts the pulse signal amplitude, and then performs binary encoding, and then sorts the counted pulse signals from low to high to form a pulse amplitude spectrum.

2. The multi-sphere neutron spectrometer for pulsed neutron radiation field monitoring according to claim 1, characterized in that: There are 8 neutron moderator balls, and the outer diameters of each neutron moderator ball are: 7.62, 8.89, 10.16, 12.70, 15.24, 20.32, 25.40 and 30.48 cm, respectively. The material selected is a density of 0.94g / cm 3 A bracket is set for each neutron moderator sphere so that the centers of neutron moderator spheres of all sizes are at the same horizontal height.

3. The multi-sphere neutron spectrometer for pulsed neutron radiation field monitoring according to claim 1, characterized in that: 3 The He gas detector consists of a spherical stainless steel cavity, a hexagonal prism support, and a cylindrical joint, located in the center of the moderator; the cavity inner diameter is 32mm, of which 3 The He gas pressure is 203 kPa, and the anode wire in the cavity is fixed inside the cylindrical joint.

4. The multi-sphere neutron spectrometer for pulsed neutron radiation field monitoring according to claim 1, characterized in that: The 4H-SiC semiconductor detector is located at 3 The He gas detector is located at 1mm, and the internal structure is a Schottky barrier structure, including: a silicon carbide surface coating area of ​​10mm×10mm, a thickness of 30μm 6 LiF thermal neutron converter.

5. The multi-sphere neutron spectrometer for pulsed neutron radiation field monitoring according to claim 1, characterized in that: Also included is a power supply for providing 12V to the preamplifier and fast charge sensitive preamplifier.

6. The multi-sphere neutron spectrometer for pulsed neutron radiation field monitoring according to claim 1, characterized in that: The high voltage power supply is used to provide a 700V bias voltage to the preamplifier and a 45V bias voltage to the fast charge sensitive preamplifier.

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