Wide-range neutron measurement method

Abstract

The invention discloses a wide-range neutron measurement method, and belongs to the technical field of neutron detection and measurement, and the method comprises the steps: selecting a wide bandgap semiconductor material, an electrode metal material, a neutron conversion material and a neutron conversion material coating method, obtaining a wide bandgap semiconductor radiation detector coated with the neutron conversion material, and taking the wide bandgap semiconductor radiation detector as a neutron detector; a neutron detector is connected with a pre-amplifier, the pre-amplifier is connected with a rear-end digital sampling circuit, the rear-end digital sampling circuit processes pulse waveforms output by the pre-amplifier, and digital pulse signals are output; processing the digital pulse signal by using a pulse counting method and a Campbell method in upper computer software to obtain a pulse counting rate value and a Campbell value, and calculating neutron fluence rates obtained by the two methods; and obtaining the neutron fluence rate as an output result by adopting different methods according to the size of the neutron fluence rate. According to the invention, a neutron fluence rate measurement system with a small size, high temperature resistance, radiation resistance and a wide range can be obtained, and real-time accurate measurement under the condition of large-range change of the neutron fluence rate is realized.

Description

Technical Field

[0001] This invention belongs to the field of neutron detection and measurement technology, and specifically relates to a wide-range neutron measurement method. Background Technology

[0002] Neutrons are key particles that initiate nuclear reactions. In nuclear energy applications such as fission reactors and fusion reactors, real-time neutron monitoring is essential for monitoring the state of nuclear reactions and measuring parameters such as power levels. It is crucial for monitoring equipment status and ensuring safe operation. To effectively monitor the reactor's entire operating range from startup to full power, the neutron monitoring system needs an extremely wide flux rate monitoring range, exceeding 10 orders of magnitude for fission reactors, ranging from less than 0.1 n·cm⁻¹. -2 ·s -1 Up to 10 n·cm -2 ·s -1 Existing single-type neutron detectors cannot achieve such a wide measurement range. Therefore, different types of detectors are typically used across different flux rate ranges, such as combinations of boron-coated proportional counters, gamma-compensated ionization chambers, and uncompensated current ionization chambers. The combined use of multiple detectors increases the number of probes required, and different types of electronic circuitry need to be matched at the back end, increasing the workload and system complexity.

[0003] Multi-mode fission ionization chambers represent a novel wide-range neutron detection technology. By combining pulse counting, Campbell, and current modes, they extend the measurement range of traditional counting methods, covering the ranges of both compensated and uncompensated ionization chambers. However, the operating principle of fission ionization chambers relies on highly enriched fissionable materials rich in elements such as uranium and plutonium. The scarcity of these materials leads to high material and manufacturing costs, complex processes, and the reactivation of nuclear materials after long-term use, resulting in high reprocessing costs. Therefore, developing novel, low-cost, wide-range neutron detection technologies holds promise for replacing fission ionization chambers and contributing to the development of neutron monitoring systems.

[0004] Neutron detectors based on gas detection technologies such as boron-coated proportional counters and fission ionization chambers have low volumetric sensitivity. To obtain sufficient counts, large-volume probes are required, which adversely affects the design of the external shielding of micro-reactors and the compact arrangement of equipment. Especially when core power distribution measurements are required, multiple wide-range neutron detectors need to be deployed. Using traditional wide-range neutron detection technologies will significantly increase the size and weight of the microreactor system. Summary of the Invention

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] A wide-range neutron measurement method includes:

[0007] Step 1: Select a wide bandgap semiconductor material, electrode metal material, neutron conversion material, and neutron conversion material coating method to obtain a wide bandgap semiconductor radiation detector coated with neutron conversion material and use it as a neutron detector. The number of pulse signals output by the neutron detector under neutron irradiation is proportional to the number of incident neutrons.

[0008] Step 2: Connect the neutron detector to the preamplifier using AC coupling, and connect the preamplifier to the back-end digital sampling circuit using AC coupling. The back-end digital sampling circuit samples and processes the pulse waveform output by the preamplifier and outputs a digital pulse signal.

[0009] Step 3: In the host computer software, the digital pulse signal is processed using the pulse counting method and the Campbell method respectively, and the pulse count rate value and Campbell value are obtained simultaneously. Based on the linear relationship between the pulse count rate value and the Campbell value and the actual neutron fluence rate, the neutron fluence rate obtained by the pulse counting method and the Campbell method is calculated respectively.

[0010] Step 4: When the neutron fluence rate is less than the lower limit of the Campbell method, the neutron fluence rate obtained by the pulse counting method is used as the output result in the low range. When the neutron fluence rate is higher than the upper limit of the pulse counting method, the neutron fluence rate obtained by the Campbell method is used as the output result in the high range. In the medium range where the upper limit of the pulse counting method and the lower limit of the Campbell method overlap, the final neutron fluence rate is calculated based on the combined neutron fluence rates obtained by the pulse counting method and the Campbell method as the output result.

[0011] The present invention has the following beneficial effects:

[0012] (1) This invention uses a combination of wide bandgap semiconductor radiation detector and Campbell mode to measure high count rate neutron signals. It not only meets the requirements of reactor monitoring such as high temperature resistance, radiation resistance, long life and high stability, but also has the advantages of low cost and mass production. It breaks through the traditional scheme of using fission ionization chamber for wide range neutron detectors, avoids the restrictions on nuclear material control, use and decommissioning, and helps to accelerate the research and development and manufacturing cycle and reduce the overall cost of neutron monitoring system.

[0013] (2) The present invention uses a combination of pulse counting mode and Campbell mode to process pulse accumulation signal. Combined with AC coupling circuit connection and digital signal acquisition and processing method, it can achieve wide range coverage on a single type of detector and measurement channel. It can be used for continuous measurement under large range of reactor neutron flux, which greatly simplifies the design of traditional wide range measurement system. In addition, the wide bandgap semiconductor neutron detector is small in size, which can significantly reduce volume occupation and facilitate multi-probe layout.

[0014] (3) The present invention utilizes a wide bandgap semiconductor radiation detector and a method of using two working modes simultaneously to achieve continuous and accurate measurement of neutron flux under a wide range of changes, which helps to reduce the complexity of reactor neutron monitoring system equipment, reduce manufacturing and usage costs, and also helps to reduce equipment volume occupation, realize multi-probe distributed arrangement and reactor system capacity and weight reduction. Attached Figure Description

[0015] Figure 1 This is a flowchart of the wide-range neutron measurement method of the present invention;

[0016] Figure 2 This is a schematic diagram of the structure of a wide bandgap semiconductor neutron detector in an embodiment of the present invention, wherein 201-neutron conversion material, 202-upper electrode, 203-semiconductor sensitive region, and 204-lower electrode;

[0017] Figure 3 This is a schematic diagram illustrating the use of two working modes to achieve wide-range measurement and range connection in an embodiment of the present invention;

[0018] Figure 4 The images show the energy deposition spectra of neutron-induced secondary charged particles and gamma rays in the detector in this embodiment of the invention, where (a) is the energy deposition spectrum of neutron-induced secondary charged particles and (b) is the energy deposition spectrum of gamma rays.

[0019] Figure 5 This is a schematic diagram of the output pulse waveform of the preamplifier in an embodiment of the present invention;

[0020] Figure 6 The above is a waveform diagram of the stacked signal obtained in an embodiment of the present invention, wherein (a) is 10 6 The stacked waveform at the CPS count rate, (b) is the count rate 10 7 Stacked waveform at cps count rate, (c) is at count rate 10 9 Stacked waveform at CPS count rate;

[0021] Figure 7 The graphs show the measurement results of the pulse counting method and the Campbell method, and the response curves of the neutron fluence rate in the embodiments of the present invention.

[0022] Figure 8 This is a fitted curve of the measured count rate and neutron fluence rate obtained using the pulse counting method and Campbell's method in an embodiment of the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0024] It should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings. Unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0025] It should be noted that the concepts of "first" and "second" mentioned in this invention are only used to distinguish different devices, modules or units, and are not used to limit the order of functions performed by these devices, modules or units or their interdependencies.

[0026] It should be noted that the terms "a" and "a plurality of" used in this invention are illustrative rather than restrictive. Those skilled in the art should understand that, unless otherwise expressly indicated in the context, they should be understood as "one or more".

[0027] The names of the messages or information exchanged between the multiple devices in the embodiments of the present invention are for illustrative purposes only and are not intended to limit the scope of these messages or information.

[0028] This invention provides a wide-range neutron measurement method, comprising the following steps:

[0029] Step 1: Select a wide bandgap semiconductor material, an electrode metal material, a neutron conversion material, and a neutron conversion material coating method to obtain a wide bandgap semiconductor radiation detector coated with neutron conversion material, and use it as a neutron detector. The number of pulse signals output by the neutron detector under neutron irradiation is proportional to the number of incident neutrons.

[0030] Step 2: Connect the neutron detector to the preamplifier using AC coupling, and connect the preamplifier to the back-end digital sampling circuit using AC coupling. The back-end digital sampling circuit samples and processes the pulse waveform output by the preamplifier and outputs a digital pulse signal.

[0031] Step 3: In the host computer software, the digital pulse signal is processed using the pulse counting method and the Campbell method respectively, and the pulse count rate value and Campbell value are obtained simultaneously. Based on the linear relationship between the pulse count rate value and the Campbell value and the actual neutron fluence rate, the neutron fluence rate obtained by the pulse counting method and the Campbell method is calculated respectively.

[0032] Step 4: At a low neutron fluence rate, i.e., when the neutron fluence rate is less than the lower range limit of the Campbell method, the neutron fluence rate obtained by the pulse counting method is used as the output result in the low range interval. At a high neutron fluence rate, i.e., when the neutron fluence rate is higher than the upper range limit of the pulse counting method, the neutron fluence rate obtained by the Campbell method is used as the output result in the high range interval. At a medium neutron fluence rate, i.e., in the medium range interval where the upper range limit of the pulse counting method and the lower range limit of the Campbell method overlap, the final neutron fluence rate is calculated based on the combined neutron fluence rates obtained by the pulse counting method and the Campbell method as the output result.

[0033] Further, step 1 includes: selecting a suitable wide-bandgap semiconductor material; determining the thickness of the semiconductor sensitive region 203 of the wide-bandgap semiconductor radiation detector based on the range of secondary particles generated by the nuclear reaction between incident neutrons and neutron conversion material 201 within the semiconductor; ensuring that the energy of secondary particles can be fully deposited while maintaining a minimum thickness to reduce the energy deposition of other interfering rays; selecting a suitable metal material for the upper electrode 202 based on the type of wide-bandgap semiconductor material. The metal material and thickness of the upper electrode 202 should ensure a stable connection between the semiconductor and the upper electrode while minimizing energy loss of secondary particles emitted from the neutron conversion material as they pass through the upper electrode. Selecting a suitable neutron conversion material coating method based on the surface structure of the wide-bandgap semiconductor radiation detector ensures precise control over the thickness and uniformity of the neutron conversion material.

[0034] Further, step 2 includes: the neutron detector and the preamplifier are connected by AC coupling to filter out the DC component of the output pulse signal of the neutron detector; the preamplifier and the back-end digital sampling circuit are connected by AC coupling to filter out the DC level generated by pulse accumulation in the signal after amplification and broadening by the preamplifier, thereby reducing the signal amplitude input to the back-end digital sampling circuit; the preamplifier can be a charge-sensitive preamplifier or a voltage-sensitive preamplifier, and its amplification factor is determined according to the output pulse charge of the wide bandgap semiconductor radiation detector and the input voltage range of the back-end digital sampling circuit, ensuring that the amplified signal does not exceed the maximum input range of the back-end digital sampling voltage.

[0035] Further, step 3 includes: inputting a digital signal into firmware or software; implementing the pulse counting method and Campbell method signal processing through an algorithm; the two signal processing processes run simultaneously without interference, obtaining the pulse count rate value and Campbell value respectively; the algorithm parameters of the pulse counting method and Campbell method, such as statistical signal duration and threshold, can be set remotely and independently; calibrating the output results of the measurement system consisting of the neutron detector, preamplifier, back-end digital sampling circuit, and host computer software under various known fluence rates in neutron radiation fields; linearly fitting the relationship between the pulse count rate value, Campbell value, and neutron fluence rate; defining the upper and lower limits of the pulse counting method and Campbell method based on the range of good linear response; and converting the pulse count rate value and Campbell value into the measured neutron fluence rate based on the linear fitting relationship through an algorithm.

[0036] Furthermore, the pulse counting method and the Campbell method are implemented through digital algorithms. The pulse count value and the Campbell value can be obtained by performing mathematical operations on the signal waveform acquired by the back-end digital sampling circuit. The Campbell method includes second-order, third-order, or fourth-order Campbell methods.

[0037] Furthermore, in step 4, when calibrating the output results of the measurement system under various known neutron fluence rates in neutron radiation fields, based on the relationship between the pulse count rate value and the Campbell value and the true neutron fluence rate, linear fitting of the results within different measurement ranges can identify the interval where the output results have a good linear relationship with the neutron fluence rate. The lower limit of this interval is the lower limit of the range of the pulse counting method or the Campbell method, and the upper limit of this interval is the upper limit of the range of the pulse counting method or the Campbell method.

[0038] Further, the method for comprehensively calculating the final neutron fluence rate based on the neutron fluence rates obtained by the two methods in step 4 includes: obtaining the upper and lower limits of the overlapping interval of the two methods according to the range coverage of the pulse counting and Campbell methods, wherein the upper limit of the overlapping interval is the upper range limit of the pulse counting method, and the lower limit of the overlapping interval is the lower range limit of the Campbell method; when the neutron fluence rate output result is located in the overlapping interval, calculating the first proportional coefficient of the range between the neutron fluence rate output result of the pulse counting method and the lower limit of the overlapping interval in the total range of the overlapping interval, and simultaneously calculating the second proportional coefficient of the range between the neutron fluence rate output result of the Campbell method and the upper limit of the overlapping interval in the total range of the overlapping interval, calculating the product of the first proportional coefficient and the result of the pulse counting method and the product of the second proportional coefficient and the result of the Campbell method, and dividing it by the sum of the first proportional coefficient and the second proportional coefficient, the comprehensive calculation result (final neutron fluence rate) can be obtained as the output result of the overlapping region.

[0039] Furthermore, the wide bandgap semiconductor material includes, but is not limited to, silicon carbide, gallium nitride, boron nitride, gallium oxide, or diamond; the sensitive region of the wide bandgap semiconductor radiation detector is a space charge region formed by a PN junction, PIN junction, MOS junction, or Schottky junction, or a space charge region generated by a high-purity crystal made of the above-mentioned wide bandgap semiconductor material under a bias voltage applied to the electrodes on both sides; the surface structure of the wide bandgap semiconductor radiation detector includes, but is not limited to, planes, micro trenches, micro channels, micropillar arrays, etc.; the neutron conversion material coating method includes, but is not limited to, filling method, coating method, evaporation method, and sputtering method (the surface structure of the wide bandgap semiconductor radiation detector and the neutron conversion material coating method can be arbitrarily combined); the types of neutron conversion materials include, but are not limited to, lithium fluoride, lithium hydride, boron nitride, and boron carbide rich in boron-10 and lithium-6 elements, as well as lithium metal and elemental boron.

[0040] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0041] See Figure 1 A wide-range neutron measurement method includes the following steps:

[0042] Step 1: A wide-bandgap semiconductor radiation detector coated with neutron conversion material is used as a neutron detector. The number of pulse signals output by the neutron detector under neutron irradiation is proportional to the number of incident neutrons.

[0043] Specifically, such as Figure 2As shown, a suitable semiconductor material is selected to fabricate the particle detector, and electrodes are fabricated on both the upper and lower sides and coated with neutron conversion material. Incident neutrons undergo nuclear reactions with the neutron-sensitive elements abundant in the neutron conversion material 201 covering the wide-bandgap semiconductor radiation detector (neutron detector), generating secondary charged particles. A voltage is applied between the lower electrode 204 and the upper electrode 202, causing the semiconductor sensitive region 203 to be completely depleted, forming a space charge region. The secondary charged particles pass through the upper electrode 202 and enter the semiconductor sensitive region 203, where complete energy deposition occurs, generating a pulsed current signal in the external circuit connected to the upper electrode 202 and the lower electrode 204. The thickness of the semiconductor sensitive region 203 is set according to the type and energy of the secondary charged particles, as well as the type and density of the selected semiconductor material elements, so that the secondary charged particles just achieve complete energy deposition. At this point, due to the small thickness of the semiconductor sensitive region 203, the interfering gamma rays present in the neutron field only lose extremely low energy. Therefore, in the output signal of a wide-bandgap semiconductor radiation detector, the amplitude of the neutron-induced pulse signal is much larger than that of the gamma-ray-induced pulse signal. In pulse counting mode, amplitude discrimination can eliminate the influence of interference signals generated by gamma rays, making the number of output pulse signals proportional to the number of incident neutrons. In Campbell mode, since the contribution of the gamma signal amplitude is small, the mean square voltage value of the signal is mainly determined by the neutron-induced signal, and the influence of gamma-ray noise can be ignored.

[0044] Step 2: Connect the wide bandgap semiconductor radiation detector (neutron detector) to the preamplifier using AC coupling. Connect the preamplifier to the back-end digital sampling circuit using AC coupling. The back-end digital sampling circuit samples and processes the pulse waveform output by the preamplifier and outputs a digital pulse signal.

[0045] Specifically, the neutron detector and the preamplifier are AC-coupled. The AC coupling uses a coupling capacitor to filter out the DC component of the detector's output pulse signal, ensuring the amplifier only amplifies the changing signal, reducing the DC level of the output signal and suppressing baseline drift. The preamplifier is also AC-coupled to the back-end digital sampling circuit to filter out the DC level caused by pulse accumulation in the amplified and broadened signal after preamplification. This ensures that the positive and negative areas of the signal input to the back-end digital sampling circuit are equal, i.e., the average value is zero. This reduces the signal amplitude input to the back-end digital sampling circuit and simplifies the calculation of the Campbell's value from signal variance to mean square voltage. The preamplifier can be a charge-sensitive or voltage-sensitive preamplifier, and its amplification factor is determined based on the output pulse charge of the wide-bandgap semiconductor detector and the input voltage range of the back-end digital sampling circuit. This ensures a suitable signal-to-noise ratio while preventing the amplified signal from exceeding the dynamic range of the back-end digital sampling circuit.

[0046] Step 3: Process the digitized signal using the pulse counting method and the Campbell method respectively, and obtain the pulse count rate value and the Campbell value. Based on the linear relationship between the pulse count rate value and the Campbell value and the actual neutron fluence rate, calculate the neutron fluence rate obtained by the two methods respectively.

[0047] Specifically, the digital signal is input into the firmware or software, and the pulse counting method and Campbell's method signal processing are implemented through algorithms. The two signal processing processes run simultaneously and do not interfere with each other, respectively obtaining the pulse count rate value and Campbell's value.

[0048] The main steps of the pulse counting method include: setting an amplitude threshold to detect only pulses higher than this value; setting a minimum pulse width to avoid interference from short-term noise; and setting a minimum pulse interval to prevent adjacent pulses from being misidentified as the same pulse due to their close proximity. Through these steps, the pulse counting method can count the number of pulse signals over a given period of time and calculate the pulse count rate.

[0049] The main steps of the Campbell method include: calculating the square mean or variance of the voltage amplitude of the signal waveform over a certain period of time as the Campbell value, which is proportional to the number of pulses that generate the stacked signal.

[0050] The algorithm parameters of the pulse counting method and the Campbell method, such as the statistical signal duration and threshold, can be set remotely and independently. This allows for testing the time response and error of the wide-range neutron measurement system under different operating conditions, adapting to various usage environments. The output results of the wide-range neutron measurement system, consisting of a wide-bandgap semiconductor neutron detector, preamplifier, back-end digital sampling circuit, and host computer software, are calibrated under various neutron radiation fields with known fluence rates. Linear fitting is performed on the relationship between the pulse count rate and Campbell value and the neutron fluence rate. Based on the range of good linear response, the upper and lower limits of the pulse counting method and the Campbell method are defined. Figure 3 As shown, the direct outputs of the pulse counting method and the Campbell method exhibit a linear relationship with the true neutron fluence rate within a certain range, while a nonlinear relationship exists in other intervals. Within the linear interval, a linear relationship between the direct outputs of the pulse counting method and the Campbell method and the true neutron fluence rate can be fitted by calibration at a certain number of test points. Thus, the true neutron fluence rate can be calculated from the outputs throughout the entire linear interval.

[0051] Step 4: At a low neutron fluence rate, i.e., below the lower range limit of the Campbell method, the neutron fluence rate obtained by the pulse counting method is used as the output result in the low range range. At a high neutron fluence rate, i.e., above the upper range limit of the pulse counting method, the neutron fluence rate obtained by the Campbell method is used as the output result in the high range range. At a medium neutron fluence rate, i.e., in the medium range range where the upper range limit of the pulse counting method and the lower range limit of the Campbell method overlap, the final neutron fluence rate is calculated based on the combined neutron fluence rates obtained by the two methods and used as the output result.

[0052] Specifically, such as Figure 3 As shown, the upper and lower limits of the overlapping interval of the pulse counting and Campbell methods are obtained based on the range coverage of the pulse counting and Campbell methods. The upper limit of the overlapping interval is the upper range limit TH of the pulse counting method, and the lower limit of the overlapping interval is the lower range limit TL of the Campbell method. In actual operation, it is necessary to find a suitable measurement boundary point to switch between the results of the two methods to ensure a smooth transition of the neutron fluence output of the two methods under transient changes in neutron fluence rate. When the output results are within the overlapping region, calculate the proportionality coefficient K1 = (YM-TL) / (TH-TL) of the range between the neutron fluence rate result YM output by the pulse counting method and the lower limit TL of the overlapping region, and simultaneously calculate the proportionality coefficient K2 = (TH-YC) / (TH-TL) of the range between the neutron fluence rate result YC output by the Campbell method and the upper limit TH of the overlapping region. Calculate the sum of the product of the first proportionality coefficient K1 and the pulse counting method result YM and the product of the second proportionality coefficient K2 and the Campbell method result YC, and divide this sum by the sum of the two proportionality coefficients to obtain the comprehensive calculation result as the output result of the overlapping region. This integrated calculation method utilizes the outputs of two methods simultaneously: when the pulse counting method result YM is less than the lower limit of the overlap region TL, K1=0, and only the pulse counting result is used; when the Campbell method result YC is greater than the upper limit of the overlap region TH, K2=0, and only the Campbell method result is used; when within the overlap region, the final result is calculated based on the proportions of the two methods' distances from the upper and lower limits of the overlap region. This method ultimately achieves smooth output under a wide range of neutron fluence rate variations.

[0053] The present invention will be further illustrated below through specific embodiments:

[0054] In this embodiment, according to step 1, a wide bandgap semiconductor radiation detector coated with neutron conversion material is used as a neutron detector. The number of pulse signals output by the detector under neutron irradiation is proportional to the number of incident neutrons.

[0055] Specifically, in this embodiment, a wide-bandgap semiconductor radiation detector is fabricated using silicon carbide (SiC) semiconductor material. The wide-bandgap semiconductor radiation detector has a Schottky (SBD) structure, and is fabricated by epitaxially growing low-doped N-type SiC on a highly doped N-type substrate. The front electrode is made of metallic nickel, and the back electrode is made of nickel and gold. A lithium fluoride powder is coated above the front electrode as a neutron conversion layer, with a lithium hexavalent (Li-6) content higher than 90% and a thickness of 10 μm. The sensitive region thickness of the silicon carbide detector is set to 30 μm, which can completely block the 2.73 MeV tritium emitted by the reaction of neutrons and Li-6. The thickness of the metal electrodes on both sides is 100 nm. By stacking multiple detectors or fabricating a large-area detector, the sensitivity can reach 0.1 cps / (n·cm). -2 ·s -1 Therefore, the neutron fluence rate at the location of the wide-bandgap semiconductor radiation detector can be calculated by statistically measuring the pulse count rate of the system. Figure 4 (a) shows the energy deposition spectrum produced by secondary particles emitted from the neutron conversion material within the sensitive region under this detector structure. Figure 4 (b) shows the energy deposition spectrum produced by gamma rays. It can be seen that the energy range of secondary particles is wide and the energy is high, while the energy deposition caused by gamma rays is small, resulting in less interference with neutron signal measurements.

[0056] Step 2: The neutron detector is connected to the preamplifier via AC coupling, and the preamplifier is connected to the back-end digital sampling circuit via AC coupling to output a digital signal.

[0057] Specifically, in this embodiment, a charge-sensitive preamplifier is used to connect to the silicon carbide neutron detector. The amplitude of the preamplifier's output signal is related to the energy of the incident charged particle and the amplifier parameters. Using a fast-response charge-sensitive preamplifier with an amplification gain of approximately 1.4 mV / fC, the response sensitivity to the SiC detector can be calculated to be approximately 28 mV / MeV. The pulse waveform output after 1 MeV of energy deposition through the detector and preamplifier is as follows: Figure 5 As shown, combined with Figure 4 The particle deposition energy spectrum shown can be used to calculate the waveforms of different pulse amplitudes generated after a large number of particles with a certain energy distribution are incident on the detector.

[0058] Specifically, in this embodiment, computer code was used to simulate the signal superposition and digital sampling calculation process, simulating the operation of the back-end digital sampling circuit and software algorithm. Based on the random characteristics of radioactive particles, the time it takes for a particle to enter the detector follows a Poisson distribution, and the time interval between two consecutive incident particles follows an exponential distribution. Therefore, the accumulated waveform generated by a large number of signals over a period of time under different count rates can be simulated. For example... Figure 6 As shown, Figure 6 of (a) Figure 6 (b) Figure 6 (c) shows count rates of 10 6 cps, 10 7 cps, 10 9 The accumulated waveform at CPS, based on the detector sensitivity described in this embodiment, indicates that the corresponding neutron fluence rate is ten times the count rate. The accumulated waveform shows that as the count rate increases, the waveform gradually accumulates, generating a DC component. Therefore, the threshold-based method used in pulse counting is insufficient for accurate count rate estimation. Figure 6 The signal waveform shown is numerically calculated using the pulse counting method and the Campbell method, and the direct output results of the two methods can be obtained—the pulse count rate value and the Campbell value.

[0059] Step 3: Process the digitized signal using the pulse counting method and the Campbell method respectively, and obtain the pulse count rate value and the Campbell value. Based on the linear relationship between the pulse count rate value and the Campbell value and the actual neutron fluence rate, calculate the neutron fluence rate obtained by the two methods respectively.

[0060] Specifically, in this embodiment, an algorithm is used to perform mathematical operations on the voltage values ​​of the stacked signal waveform to obtain pulse count values ​​and Campbell values. The pulse count calculation is set with an amplitude threshold of 8 mV, a minimum pulse width of 100 ns, and a minimum pulse interval of 2 ns. Through these steps, the pulse count value within each 10 ms signal segment of the stacked waveform can be statistically determined. The Campbell value is calculated by AC coupling the pulse stacked waveform and then statistically analyzing the mean square voltage value within each 10 ms signal segment. Figure 7 The relationship between pulse count rate and Campbell's value and neutron fluence rate is shown, exhibiting a linear relationship within a certain range. The pulse counting method is effective when the count rate is less than 10-1. 6 Linear fitting R under cps case 2 =0.9957, Campbell's method at a count rate of 10 4 ~10 11 Linear fitting R under cps case 2 =0.9995. A linear conversion of the Campbell value using the range established by the two methods yields the measured count rate. It can be seen that the pulse counting method and the Campbell method have a range coverage interval of 2-3 orders of magnitude. At any point on the curve exhibiting a linear relationship, the neutron fluence result can be obtained by outputting the measured count rate from the measurement system.

[0061] Step 4: At a low neutron fluence rate, i.e., below the lower range limit of the Campbell method, the pulse counting method is used as the output result within the low range range; at a high neutron fluence rate, i.e., above the upper range limit of the pulse counting method, the Campbell method is used as the output result within the high range range; at a medium neutron fluence rate, i.e., within the medium range range where the upper range limit of the pulse counting method and the lower range limit of the Campbell method overlap, the final neutron fluence rate is calculated based on the combined neutron fluence rates obtained from the two methods as the output result.

[0062] Specifically, in this embodiment, based on the range coverage of pulse counting and the Campbell method, the upper and lower limits of the overlapping range of the two methods are respectively 10. 6 and 10 4 cps, i.e. 10 7 and 10 5 n·cm -2 ·s -1 When the outputs YM and YC of the pulse counting method and Campbell's method are in the overlapping region, the combined calculation result is used as the output result for the overlapping region. When the result YM of the pulse counting method is less than the lower limit TL of the overlap region, K1=0, and only the pulse counting result is used; when the result YC of the Campbell method is greater than the upper limit TH of the overlap region, K2=0, and only the result of the Campbell method is used. Figure 8 The linear response relationship R between the output count rate and the neutron fluence rate obtained based on the above method is shown. 2 =0.9999, indicating that the method of the present invention can obtain accurate and stable output results over a wide range.

[0063] The above description is merely an embodiment of the present invention and does not limit the scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related system fields, are similarly included within the protection scope of the present invention.

[0064] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

Claims

1. A wide-range neutron measurement method, characterized in that, include: Step 1: Select a wide bandgap semiconductor material, electrode metal material, neutron conversion material, and neutron conversion material coating method to obtain a wide bandgap semiconductor radiation detector coated with neutron conversion material and use it as a neutron detector. The number of pulse signals output by the neutron detector under neutron irradiation is proportional to the number of incident neutrons. Step 2: Connect the neutron detector to the preamplifier using AC coupling, and connect the preamplifier to the back-end digital sampling circuit using AC coupling. The back-end digital sampling circuit samples and processes the pulse waveform output by the preamplifier and outputs a digital pulse signal. Step 3: In the host computer software, the digital pulse signal is processed using the pulse counting method and the Campbell method respectively, and the pulse count rate value and Campbell value are obtained simultaneously. Based on the linear relationship between the pulse count rate value and the Campbell value and the actual neutron fluence rate, the neutron fluence rate obtained by the pulse counting method and the Campbell method is calculated respectively. Step 4: When the neutron fluence rate is less than the lower limit of the Campbell method, the neutron fluence rate obtained by the pulse counting method is used as the output result in the low range. When the neutron fluence rate is higher than the upper limit of the pulse counting method, the neutron fluence rate obtained by the Campbell method is used as the output result in the high range. In the medium range where the upper limit of the pulse counting method and the lower limit of the Campbell method overlap, the final neutron fluence rate is calculated based on the combined neutron fluence rates obtained by the pulse counting method and the Campbell method as the output result.

2. The wide-range neutron measurement method according to claim 1, characterized in that, Step 1 includes: selecting a suitable wide-bandgap semiconductor material; determining the thickness of the semiconductor sensitive region of the wide-bandgap semiconductor radiation detector based on the range of secondary particles generated by the nuclear reaction between incident neutrons and the neutron conversion material within the semiconductor; ensuring that the energy of secondary particles can be fully deposited while having a minimum thickness to reduce the energy deposition of other interfering rays; selecting a suitable metal material for the upper electrode based on the type of wide-bandgap semiconductor material; ensuring a stable connection between the semiconductor and the upper electrode while minimizing energy loss of secondary particles emitted from the neutron conversion material when passing through the upper electrode; and selecting a suitable neutron conversion material coating method based on the surface structure of the wide-bandgap semiconductor radiation detector to ensure precise control over the thickness and uniformity of the neutron conversion material.

3. The wide-range neutron measurement method according to claim 1, characterized in that, Step 2 includes: the neutron detector and the preamplifier are connected by AC coupling to filter out the DC component of the output pulse signal of the neutron detector; the preamplifier and the back-end digital sampling circuit are connected by AC coupling to filter out the DC level generated by pulse accumulation in the signal after amplification and broadening by the preamplifier, thereby reducing the signal amplitude input to the back-end digital sampling circuit; the preamplifier is a charge-sensitive preamplifier or a voltage-sensitive preamplifier, and its amplification factor is determined according to the output pulse charge of the wide bandgap semiconductor radiation detector and the input voltage range of the back-end digital sampling circuit.

4. The wide-range neutron measurement method according to claim 1, characterized in that, Step 3 includes: inputting digital signals into firmware or software; implementing signal processing for the pulse counting method and Campbell's method through algorithms; the two signal processing processes run simultaneously and independently to obtain pulse count rate and Campbell's value, respectively; calibrating the output of the measurement system consisting of a neutron detector, preamplifier, back-end digital sampling circuit, and host computer software under various known fluence rates in neutron radiation fields; linearly fitting the relationship between pulse count rate and Campbell's value and neutron fluence rate; defining the upper and lower limits of the pulse counting method and Campbell's method based on the range of good linear response; and converting the pulse count rate and Campbell's value into the measured neutron fluence rate based on the linear fitting relationship using algorithms.

5. The wide-range neutron measurement method according to claim 4, characterized in that, The algorithm parameters for the pulse counting method and Campbell's method include the duration of the statistical signal and the threshold, which are set remotely and independently.

6. The wide-range neutron measurement method according to claim 4, characterized in that, The pulse counting method and Campbell method are implemented through digital algorithms. The pulse count value and Campbell value are obtained by performing mathematical operations on the signal waveform acquired by the back-end digital sampling circuit. The Campbell method includes second-order, third-order or fourth-order Campbell methods.

7. The wide-range neutron measurement method according to claim 1, characterized in that, Step 4 includes: when calibrating the output results of the measurement system under various known neutron fluence rates in neutron radiation fields, based on the relationship between the pulse count rate value and the Campbell value and the true neutron fluence rate, linear fitting is performed on the results in different measurement ranges to identify the interval where the output results have a good linear relationship with the neutron fluence rate. The lower limit of this interval is the lower limit of the range of the pulse counting method or the Campbell method, and the upper limit of this interval is the upper limit of the range of the pulse counting method or the Campbell method.

8. The wide-range neutron measurement method according to claim 7, characterized in that, In step 4, the final neutron fluence rate is calculated as the output result based on the combined neutron fluence rates obtained from the pulse counting method and the Campbell method. This includes: obtaining the upper and lower limits of the overlapping interval of the two methods according to the range coverage of the pulse counting and Campbell methods, where the upper limit of the overlapping interval is the upper range limit of the pulse counting method and the lower limit of the overlapping interval is the lower range limit of the Campbell method; when the neutron fluence rate output result is within the overlapping interval, a first proportionality coefficient is calculated for the range between the neutron fluence rate output result of the pulse counting method and the lower limit of the overlapping interval, and a second proportionality coefficient is calculated for the range between the neutron fluence rate output result of the Campbell method and the upper limit of the overlapping interval, and the sum of the product of the first proportionality coefficient and the pulse counting method result and the product of the second proportionality coefficient and the Campbell method result is calculated. This sum is then divided by the sum of the first and second proportionality coefficients to obtain the final neutron fluence rate as the output result of the overlapping region.

9. The wide-range neutron measurement method according to claim 1, characterized in that, The wide bandgap semiconductor material includes silicon carbide, gallium nitride, boron nitride, gallium oxide, or diamond; the sensitive region of the wide bandgap semiconductor radiation detector is the space charge region formed by a PN junction, PIN junction, MOS junction, or Schottky junction, or the space charge region generated by a high-purity crystal made of the wide bandgap semiconductor material under the bias voltage applied to the electrodes on both sides.

10. The wide-range neutron measurement method according to claim 1, characterized in that, The surface structure of the wide bandgap semiconductor radiation detector includes a plane, micro trenches, micro channels, and micropillar arrays. The neutron conversion material coating method includes filling, coating, evaporation, and sputtering. The types of neutron conversion materials include lithium fluoride, lithium hydride, boron nitride, and boron carbide rich in boron-10 and lithium-6 elements, as well as lithium metal and elemental boron.

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