A system for testing the comprehensive performance of microstructure neutron detectors

Abstract

The present invention provides a system for testing the comprehensive performance of microstructured neutron detectors. The system comprises a neutron moderator, the front side of which is equipped with a mixed radioactive source and a switchable gamma shield. A standard neutron detector, a silicon-based microstructured neutron detector, and a standard gamma detector are housed within the neutron moderator, wherein the silicon-based microstructured neutron detector is placed in a constant temperature chamber. Each of the standard neutron detector, silicon-based microstructured neutron detector, and standard gamma detector is connected to a front-end electronic device, each of which is connected to a multi-channel counter. The present invention conducts radiation performance testing on a developed silicon-based microstructured neutron detector chip prototype system, including thermal neutron detection efficiency, n / gamma discrimination ratio, applicable temperature range, and count rate, thereby filling a gap in the testing of three-dimensional silicon-based neutron detectors.

Description

Technical Field

[0001] The invention provides a system for testing the comprehensive performance of a microstructure neutron detector, belonging to the technical field of radiation detection. Background Art

[0002] Semiconductor neutron detectors are radiation detectors that use semiconductor materials as their detection medium. Unlike gas detectors, they use semiconductor materials instead of gas. Because silicon's average ionization energy is 3.6 eV, nearly an order of magnitude lower than the average ionization energy of 30 eV for gases, it produces more electron-hole pairs for the same energy deposition, resulting in higher energy resolution. Furthermore, silicon's mature manufacturing process and low cost make it one of the most widely used semiconductor materials for neutron detectors.

[0003] As for silicon-based neutron detectors, foreign countries started earlier, while domestic research is relatively weak and has not yet been commercialized. The huge demand still relies on foreign imports. At the same time, with the 3 The shortage of He resources can be alleviated by the research of silicon-based neutron detectors. 3 Therefore, the research and testing of three-dimensional silicon-based neutron detectors has great scientific research and application value, and is of great significance for the commercialization of silicon-based neutron detectors. Summary of the Invention

[0004] The present invention provides a system for testing the comprehensive performance of microstructured neutron detectors. The system performs radiation performance tests on a developed silicon-based microstructured neutron detector (MSND) chip prototype system, including thermal neutron detection efficiency, n / γ discrimination ratio, applicable temperature range, and count rate, to fill the gap in testing three-dimensional silicon-based neutron detectors.

[0005] The specific technical solutions are:

[0006] A system for testing the comprehensive performance of a microstructured neutron detector, comprising a neutron moderator, wherein a mixed radioactive source and a switchable gamma shield are provided on the front side of the neutron moderator;

[0007] The neutron moderator is provided with a standard neutron detector, a silicon-based microstructure neutron detector and a standard γ detector, wherein the silicon-based microstructure neutron detector is placed in a constant temperature box; the standard neutron detector, the silicon-based microstructure neutron detector and the standard γ detector are respectively connected to a front-end electronic device, and each front-end electronic device is connected to a multi-channel counter.

[0008] The mixed radioactive source is used for radiating neutrons and gamma rays.

[0009] The neutron moderator is made of high-density polyethylene with a density of 0.962 g / cm 3 The overall structure is a hollow cylindrical structure with an inner diameter of 160mm; the neutron moderator includes a front half and a rear half, and the front half and the rear half are connected by a mortise and tenon structure; the front end face of the front half is a closed structure with a thickness of 130mm; the rear end face of the rear half is open and is provided with a cover plate, which is provided with a central through hole and multiple small through holes for the wires to pass through.

[0010] A circular hole is provided on the switchable gamma shielding body.

[0011] The present invention determines the optimal thickness of the polyethylene neutron moderator through mcnp5 simulation, and redesigns the neutron moderator physically and mechanically to maximize the proportion of thermal neutrons incident on the detector. A switchable gamma shield is added in front of the neutron moderator to enable detector performance testing in different radiation fields to determine an important indicator for measuring detector performance (n / gamma discrimination ratio). The constant temperature chamber in this test system can simulate the detector operating in different temperature environments, thereby determining another important indicator for measuring detector performance (usable temperature range). The use of a multi-channel counter can record the counts of different detectors under the same experimental conditions.

[0012] The silicon-based microstructure neutron detector MSND of the present invention is to etch some grooves on the silicon-based material by wet etching, and then fill the neutron conversion material by centrifugal method, thereby increasing the 6 LiF filling amount and 6 The contact surface area between LiF and the semiconductor material Si.

[0013] The performance parameters of domestic silicon-based microstructured neutron detectors are derived only from simulations, without actual test data. This paper designs a comprehensive performance test system for microstructured neutron detectors that can measure several key detector performance parameters (thermal neutron detection efficiency, n / γ discrimination ratio, applicable temperature range, and count rate). This fills the gap in the testing system for three-dimensional silicon-based neutron detectors and verifies the superior performance of MSND.

[0014] When measuring the intrinsic detection efficiency of thermal neutrons, the equipment included should include a neutron source, a polyethylene moderator, a silicon-based microstructured neutron detector, and a calibrated standard neutron detector. 3 Proportional counter tube, preamplifier, main amplifier, multi-channel counter, DT5730 signal acquisition card, RDT counting module and 640-bit oscilloscope.

[0015] The polyethylene moderator is used to slow down high-energy neutrons to the thermal energy zone. The silicon-based microstructure neutron detector is a thermal neutron detector. During the test, the thermal neutron counts measured within a certain time range are recorded. 3 The He proportional counter records the total number of thermal neutrons emitted by the neutron source and incident on the detector's sensitive surface within the same time interval. The comparison of the two is the thermal neutron intrinsic detection efficiency. The preamplifier performs preliminary amplification and processing of the detector signal. However, the pulse amplitude of the preamplifier's output is relatively small, so a main amplifier is required to further amplify the signal. After processing and shaping, the signal is input to the multichannel analyzer. The multichannel analyzer can perform signal preprocessing, such as noise removal and filtering, to improve signal quality. Because the signal is divided into multiple channels for analysis, the multichannel analyzer enables parallel processing, improving processing efficiency. The DT5730 data acquisition card features multiple high-speed analog input channels, enabling simultaneous acquisition of multiple analog signals. It also features high-speed analog signal conversion, performing analog-to-digital conversion at a high sampling rate, ensuring high-precision signal acquisition and accurate recording. The 640Zi oscilloscope boasts high sensitivity, wide bandwidth, high sampling rate, and versatility, converting invisible electrical signals into visible images. Its large display clearly displays waveforms and measurement results. It also features advanced triggering and analysis capabilities, supporting a variety of waveform analysis and measurement functions, such as spectrum analysis, time domain analysis, and eye diagram analysis. The oscilloscope's trigger function helps users quickly find signals of interest, improving measurement efficiency. Trigger functions can be time, voltage, or waveform. Once the trigger conditions are set, the oscilloscope automatically begins sampling when they are met. The RDT module features high-speed data acquisition, quickly and accurately recording event occurrence times and count information. It is suitable for real-time monitoring and control scenarios requiring high-frequency, high-precision counting.

[0016] The test steps for thermal neutron intrinsic detection efficiency are as follows: Place the polyethylene moderator on the platform, adjust the platform height so that the laser, radiation hole and detector are on the same horizontal line, and then 3Place the He proportional counter tube inside the moderator, close the holes in the switchable gamma shield, and connect the detector to the front-end electronics (preamplifier and main amplifier). Cables are routed through the rear cover of the moderator and connected to the multi-channel counter. The multi-channel counter's memory port should be set to read-write mode, while the data output port should be set to read-only mode. The multi-channel counter's memory port address uses the signal amplitude value, and the input data is the address stored value plus 1. Connect the digitizer, oscilloscope, and data acquisition card. Start the RDT MSND on a laptop computer and power on. Observe the preamplifier signal. If it meets expectations, connect the main amplifier signal. After applying high-voltage power to the amplifier, exit the radiation room, close the shielded door, and then power up the pan / tilt control. Connect the preamplifier and main amplifier signals to the oscilloscope's channel 1 (ch1) and channel 2 (ch2) input channels, respectively, via oscilloscope probes. The oscilloscope's measurement functions allow accurate measurement of signal parameters such as amplitude, frequency, period, duty cycle, rise time, and fall time. Slowly adjust the oscilloscope until you see a perfect waveform on the oscilloscope, recording the counts of both detectors in the same time.

[0017] When measuring the n / γ discrimination ratio, the equipment involved includes a neutron-γ hybrid source, a switchable γ shield, a polyethylene moderator, a silicon-based microstructure neutron detector, a preamplifier, a main amplifier, a DT5730 signal acquisition card, an RDT counting module, and a 640Zi oscilloscope.

[0018] The hybrid source emits both neutrons and gamma rays. During testing, the gamma shield is first opened, allowing both neutrons and gamma rays to enter the detector's sensitive volume. When particles (neutrons or gamma rays) interact with the detector, they produce different signals or responses. Neutrons typically interact with the detector material through nuclear reactions such as elastic scattering, inelastic scattering, or nuclear fission, while gamma rays interact with the detector material through processes such as the photoelectric effect, Compton scattering, or electron pair production. A silicon-based microstructured neutron detector processes and records the electrical signals generated by these secondary charged particles. A preamplifier provides initial amplification and processing, outputting pulse amplitude and waveform. The main amplifier further amplifies and shapes the signal (using filtering and shaping to improve the signal-to-noise ratio). The waveforms are observed on a 640Zi oscilloscope, and the signals are analyzed and counted using a multi-channel counter and a DT5730 signal acquisition card. Then, the holes in the gamma shield are closed to block out the gamma rays. Under the same conditions, the pulse signal count is obtained, and the n / gamma discrimination ratio is calculated by dividing the number of neutrons correctly identified as neutrons by the number of gamma rays incorrectly identified as neutrons.

[0019] The n / γ discrimination ratio test procedure is as follows: Place the polyethylene moderator on a platform and adjust the platform height so that the laser, radiation aperture, and detector are aligned. Then, place the MSND and a standard gamma detector inside the moderator. First, open the holes in the gamma shield and connect the detector to the front-end electronics (preamplifier and main amplifier). Cables are routed through the back cover of the moderator and connected to a DT5730 signal acquisition card and a 640Zi oscilloscope. Start the RDTMSND on a laptop and power it on. First, observe the preamplifier signal. If the signal meets expectations, connect the main amplifier signal. After applying high-voltage power to the amplifier, the researcher leaves the radiation room, closes the shielded door, and then raises the power using the pan / tilt control. Then, slowly adjust the oscilloscope until a perfect waveform is visible on the oscilloscope. Record the detector counts over a specified period of time. Next, close the holes in the gamma shield to block the gamma rays. Repeat the above steps, recording the detector counts over a specified period of time.

[0020] To test the applicable temperature range, treat the MSND with a temperature-controlled device and then wrap it in thermal insulation film. Repeat the measurement process at the same source intensity, observe the oscilloscope waveform for normality, and record the pulse count. Next, change the temperature and repeat the above process, recording a graph of pulse count changes with temperature until the oscilloscope waveform becomes abnormal and the pulse count drops sharply. This determines the detector's applicable temperature range.

[0021] Count rate measurement requires equipment including a neutron source, polyethylene moderator, silicon-based microstructured neutron detector, preamplifier, main amplifier, multi-channel counter, stopwatch, DT5730 signal acquisition card, RDT counting module, and 640Zi oscilloscope. The count rate can be calculated using the following formula: Count rate = Number of events recorded by the counter / Statistical time. The number of events recorded by the counter refers to the number of particles received by the detector during the statistical time, and the statistical time refers to the length of time that particles are measured by the detector. Therefore, the count rate can be calculated by calculating the pulse signal collected per unit time.

[0022] Compared to traditional systems, this system uses a mixed radiation source, rather than a single source. A shield is placed in front of the polyethylene moderator, allowing for optional gamma ray shielding. The polyethylene moderator houses a standard neutron detector, a proprietary MSND detector, and a standard gamma detector. Test results are output via multiple holes in the conductors and recorded by a multi-channel counter, making the system even more powerful.

[0023] The moderator design used in the present invention was determined after extensive simulations. High-energy neutrons passing through this moderator produce a higher proportion of thermal neutrons, leading to higher thermal neutron detection efficiency for the neutron detector. The moderator is of appropriate size and easy to operate.

[0024] The present invention can realize that different detectors work and record at the same time under the same radiation field, which is more comparative and the radiation field is also variable.

[0025] The silicon-based microstructure neutron detector (MSND) of the present invention is provided with a constant temperature box, which allows the detector to operate at different temperatures.

[0026] The data acquisition equipment of the present invention includes a DT5730 signal acquisition card and an RDT counting module, which can simultaneously collect multiple analog signals. These channels can be connected to various types of sensors or detectors for real-time acquisition of analog signals generated in particle physics or nuclear physics experiments. Furthermore, it features high-speed analog signal conversion capabilities, enabling digital processing of analog signals at extremely high sampling rates, ensuring high-precision acquisition and accurate recording of signals. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is the overall framework diagram of the system of the present invention;

[0028] Figure 2 Schematic diagram of the structure of the neutron moderator of the present invention;

[0029] Figure 3 It is a cross-sectional view of the neutron moderator of the present invention. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0031] like Figure 1 As shown, a system for testing the comprehensive performance of a microstructure neutron detector includes a neutron moderator 6, a mixed radioactive source 1 and a switchable gamma shield 2 are provided on the front side of the neutron moderator 6;

[0032] The neutron moderator 6 is equipped with a standard neutron detector 3, a silicon-based microstructure neutron detector 7, and a standard gamma detector 5. The silicon-based microstructure neutron detector 7 is placed in a constant temperature chamber 4 with a temperature range of 0-45°C. Each of the standard neutron detector 3, silicon-based microstructure neutron detector 7, and standard gamma detector 5 is connected to a front-end electronic device 8, each of which is connected to a multi-channel counter 9. The counter is multi-channel, and the test results of different detectors are simultaneously output after passing through the front-end electronic device 8 and recorded by the multi-channel counter 9.

[0033] The supporting counting equipment includes DT5730 signal acquisition card, RDT counting module and 640Zi oscilloscope.

[0034] The mixed radioactive source 1 is used for radiating neutrons and gamma rays.

[0035] like Figure 2 and Figure 3 As shown, the neutron moderator 6 is made of high-density polyethylene material with a density of 0.962 g / cm 3 The overall structure is a cylindrical hollow structure with an inner diameter of 160mm, which can be equipped with detectors and electronic devices.

[0036] The neutron moderator 6 comprises a front section 63 and a rear section 64, connected by a mortise and tenon joint 65, allowing for removable and removable connections. The front end face 61 of the front section 63 is closed and has a thickness of 130 mm. This thickness maximizes the thermal neutron ratio after neutron moderation, as determined by simulation. The rear end face of the rear section 64 is open and features a cover plate 62. This cover plate 62 has a central through-hole 621 and multiple small through-holes 622 for wire passage. The central through-hole 621 has a diameter of 50 mm, while the adjacent small through-holes 622 have a diameter of 35 mm, allowing for wire feedthroughs and the insertion of a helium-3 proportional counter tube. Common diameters for these tubes are 19 mm, 25.4 mm, 32 mm, 38 mm, and 50 mm.

[0037] A circular hole is provided on the switchable gamma shield 2. Made of lead, iron, or concrete, the hole can be controlled to switch between neutron fields, gamma-ray fields, and mixed fields, allowing for measurement of the n / gamma discrimination ratio of the silicon-based microstructure neutron detector 7.

[0038] The present invention is used to test the comprehensive performance of microstructured neutron detectors. During testing, a mixed neutron and gamma radiation source is used as the mixed radiation source 1. The circular holes in the switchable gamma shield 2 are selectively closed as needed. The silicon-based microstructured neutron detectors 7 to be tested are placed in a constant temperature chamber 4, set to the desired temperature, and placed in a neutron moderator 6. Each detector is then connected to front-end electronics, with cables routed through the circular holes in the disc for recording by a multi-channel counter 9. After connecting the amplifier to a high-voltage power supply, researchers leave the radiation room, close the shielded door, and ramp up the source in the control room. Finally, a signal acquisition card, a counting module, and an oscilloscope are used to record and process the signals, and calculate relevant performance.

[0039] In actual thermal neutron detection tests, the radiation source should be directly in front of the switchable γ shield 2 and the neutron moderator 6. The distance between the radiation source and the detector and the test temperature should be selected according to actual needs. A layer of aluminum film can be added to the side surface inside the neutron moderator 6 to shield neutrons incident from the side into the moderator.

[0040] Through experiments, it is shown that this test system can test the comprehensive performance of microstructure neutron detectors.

Claims

1. A system for testing the comprehensive performance of a microstructured neutron detector, characterized in that: It comprises a neutron moderator (6), wherein a mixed radioactive source (1) and a switchable gamma shield (2) are provided on the front side of the neutron moderator (6); The neutron moderator (6) is provided with a standard neutron detector (3), a silicon-based microstructure neutron detector (7) and a standard gamma detector (5), wherein the silicon-based microstructure neutron detector (7) is placed in a constant temperature box (4); the standard neutron detector (3), the silicon-based microstructure neutron detector (7) and the standard gamma detector (5) are respectively connected to a front-end electronic device (8), and each front-end electronic device (8) is connected to a multi-channel counter (9).

2. A system for testing the comprehensive performance of a microstructure neutron detector according to claim 1, characterized in that: The mixed radioactive source (1) is used for radiating neutrons and gamma rays.

3. The system for testing the comprehensive performance of a microstructure neutron detector according to claim 1, characterized in that: The neutron moderator (6) is made of high-density polyethylene material with a density of 0.962g / cm 3 The neutron moderator (6) comprises a front half section (63) and a rear half section (64), and the front half section (63) and the rear half section (64) are connected by a mortise and tenon structure (65); the front end face (61) of the front half section (63) is a closed structure with a thickness of 130 mm; the rear end face of the rear half section (64) is open and is provided with a cover plate (62), and the cover plate (62) is provided with a central through hole (621) and a plurality of small through holes (622) for the wires to pass through.

4. The system for testing the comprehensive performance of a microstructure neutron detector according to claim 1, characterized in that: The switchable gamma shielding body (2) is provided with a circular hole.

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