Large area high resolution neutron detector and method for small angle neutron scattering experiments

Abstract

The application discloses a large-area high-resolution neutron detector for small-angle neutron scattering experiments and a manufacturing method thereof; the detector comprises a grazing incidence multilayer boron-coated wire chamber detection unit, an anode wire plane, an aluminum-based PCB boron-coated readout substrate, a readout electronic system and a data acquisition system. The 5° grazing incidence, 128-layer stacked structure, 8mm layer spacing, 2um boron carbide film as the neutron conversion layer, precise positioning through the anode-cathode two-dimensional digital compatible readout and barycenter method position reconstruction are adopted; the effective detection area of the application is 1 square meter, the neutron detection efficiency is greater than or equal to 70% at 4 angstroms, the position resolution is less than or equal to 1mm*1mm, the misjudgment rate of gamma signals is less than or equal to 1 / 10 6 , the mean time between failures is greater than or equal to 5000 hours, the core device is localized, can be mass-produced, and is suitable for small-angle neutron scattering experiments, nuclear safety imaging instruments and nuclear device waste monitoring instruments.

Description

Technical Field

[0001] This invention belongs to the field of neutron detection technology, specifically relating to a large-area high-resolution neutron detector and method for small-angle neutron scattering experiments. Background Technology

[0002] Neutron scattering is a key research technique in materials science, condensed matter physics, and nuclear technology applications, and is widely used in experimental systems such as small-angle neutron scattering, neutron reflection, and neutron imaging. The neutron detector, as the core component of a neutron scattering device, directly determines the detection efficiency, spatial resolution, count rate, and system reliability.

[0003] Traditional neutron detection relies heavily on ³He tube detectors. However, ³He is a scarce strategic resource, with global supply shortages and continuously rising prices, severely restricting the large-scale application of neutron science facilities and nuclear monitoring instruments. Furthermore, existing ³He detectors struggle to simultaneously meet the comprehensive performance requirements of large detection area, high detection efficiency, high position resolution, high count rate, and low gamma false positives, exhibiting significant bottlenecks in effective detection area, engineering mass production, and long-term reliability.

[0004] Currently, both domestic and international developments are underway. 6 Li,¹ 0 Among boron-based and other He-based neutron detection technologies, boron-10-based boron carbide (B4C) thin-film detectors have become one of the most promising industrialization routes due to their moderate neutron absorption cross-section, controllable fabrication process, and reasonable cost. However, existing single-layer boron-plated detectors have the following technical drawbacks: low detection efficiency, making it difficult to achieve efficiency above 70% at a wavelength of 4 Å; small effective detection area, making it difficult to meet the needs of large-area detection of 1 m² and above; few readout electron channels and low readout rate, making it impossible to achieve high count rate and high-precision position reconstruction; lack of standardized, mass-producible large-area B4C thin-film fabrication and detector integration processes; and high gamma sensitivity but poor anti-interference ability, making it difficult to meet the stringent requirements of nuclear safety monitoring.

[0005] In addition, existing small-angle neutron scattering detectors generally suffer from problems such as simple structural design, difficulty in balancing position resolution and detection efficiency, low degree of engineering, and insufficient reliability, which cannot meet the urgent needs of major national scientific facilities and nuclear safety instruments for high-efficiency, large-area, high-resolution, low-power, long-life, and domestically produced neutron detectors. Summary of the Invention

[0006] To address the aforementioned issues, developing a large-area, high-resolution neutron detector that can completely replace ³He and is suitable for small-angle neutron scattering experiments, along with its standardized manufacturing method, is a key technical problem that urgently needs to be solved in this field. This is especially applicable to nuclear safety imaging, nuclear device waste monitoring, and small-angle neutron scattering scientific experimental devices.

[0007] The technical solution adopted in this invention is: a large-area high-resolution neutron detector for small-angle neutron scattering experiments, comprising a multilayer boron-plated wire chamber detection unit, an anode wire plane, an aluminum-based PCB boron-plated readout substrate, a high-performance readout electronics system, and a data acquisition system; the multilayer boron-plated wire chamber detection unit adopts a grazing incidence multilayer structure with a layer spacing of 8mm, and the boron plating layer is a B4C thin film with a thickness of 2μm; the anode wire plane is composed of multiple anode wires welded to a wire frame; the aluminum-based PCB boron-plated readout substrate has boron plating on one side and readout strips on the other side, and neutron position is located through anode-cathode digital coincidence readout; the detector has an effective detection area ≥1m², a neutron detection efficiency ≥70%@4Å, a position resolution ≤1mm×1mm, a signal response time ≤1μs, and a gamma signal false alarm rate ≤1 / 10. 6 .

[0008] The grazing incidence angle of the multi-layer boron-plated wire chamber detection unit is 5°, and the total number of boron-plated surfaces and wire surfaces is 128, with a total area of ​​24m².

[0009] The anode wires have a spacing of 6 mm and a diameter of 20 μm, with 3840 readout channels. The cathode readout bars have a spacing of 0.5 mm and a width of 0.4 mm, with 2000 readout channels, for a total of 5840 signal channels.

[0010] The minimum thickness of the aluminum-based PCB boron-plated readout substrate is 0.3mm. Readout strips at the same horizontal position are connected in series for integrated readout. The boron-plated electrode size is 184mm×1000mm.

[0011] The readout electronics system includes a self-developed high-speed ASIC chip and a digital circuit based on a high-speed FPGA; the ASIC chip has a single-channel count rate >1MHz, an input charge range of ±10fC to ±400fC, and an output threshold adjustable 2.5VTTL digital signal.

[0012] The digital circuit employs a two-dimensional coincidence, TOT pulse amplitude measurement, and centroid method position reconstruction algorithm, which improves the detector's position resolution by more than 100%.

[0013] The data acquisition system is developed based on the distributed data stream processing platform Kafka, enabling highly reliable data processing and sharing.

[0014] The detector has a mean time between failures (MTBF) of ≥5000 hours and a technology readiness level of 9, and can be applied to nuclear safety imagers and nuclear device waste monitors.

[0015] A method for manufacturing a large-area high-resolution neutron detector for small-angle neutron scattering experiments includes the following steps: 1) Monte Carlo simulation was used to optimize detection efficiency, position resolution, gas gain and electron drift parameters, and to determine 5° grazing incidence, 128-layer structure and 6mm anode wire spacing; 2) Establish a dedicated large-area coating machine with a coating area of ​​1500mm×500mm, prepare a 2μm thick B4C thin film and complete the fabrication of a boron-plated cathode; 3) Weld 20μm diameter anode wires to the wire frame at 6mm intervals to form an anode wire plane; 4) A 0.3mm thick aluminum-based PCB board is used, with one side coated with B4C film and the other side fabricated with a 0.5mm periodic readout strip to form a readout substrate; 5) Integrate multi-layer boron-plated wire chamber units, ASIC chips, and FPGA digital circuits to complete the detector system assembly; 6) Equip the system with Kafka data acquisition to conduct reliability and third-party off-site testing, and achieve mass production.

[0016] The ASIC chip has undergone multiple iterations and optimizations to achieve multi-channel, low power consumption, high speed and radiation resistance. It adopts COB packaging and has a size of 2cm×1cm.

[0017] Compared with existing ³He neutron detectors and traditional single-layer boron-plated neutron detectors, this invention has the following outstanding advantages: Significantly improved detection efficiency and area: This invention adopts a 5° grazing incidence multilayer boron-plated structure, and the 128-layer combination design enables a neutron detection efficiency of ≥70%@4Å and an effective detection area of ​​1m², breaking through the bottleneck of low efficiency and small area of ​​traditional detectors, and fully meeting the requirements of small-angle neutron scattering and large-area imaging.

[0018] Excellent position resolution and count rate performance: This invention achieves high resolution and high count rate compatibility through anode-cathode digital coincidence readout, centroid method position reconstruction and high-speed ASIC chip collaboration, with position resolution ≤1mm×1mm, single-channel count rate >1MHz, and signal response time ≤1μs.

[0019] Strong resistance to gamma interference: The gamma signal misjudgment rate in this invention is ≤1 / 10 6 With low gamma sensitivity, it can work stably in strong radiation environments and is suitable for high-interference scenarios such as nuclear safety imaging and nuclear device waste monitoring.

[0020] The core technologies are all domestically produced and independently controllable: The B4C thin film preparation, aluminum-based PCB readout substrate, dedicated ASIC chip, FPGA electronics and data acquisition system in this invention are all independently developed, freeing us from dependence on He resources and foreign chips, and possessing complete independent intellectual property rights.

[0021] Engineering and reliability standards met: The mean time between failures of this invention is ≥5000 hours, the technology readiness level is 9, it supports mass production, and it can be applied on a large scale to at least two types of instruments and equipment, with a clear prospect for industrialization.

[0022] Strong adaptability to structure and process: This invention uses an 8mm interlayer spacing, a 2μm thick B4C film, and a 0.3mm ultrathin aluminum-based PCB substrate, which has a compact structure, high assembly precision, and low power consumption, and can be adapted to major scientific facilities at home and abroad, such as the European spallation source. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the overall structure of the grazing incidence multilayer boron-plated wire chamber detector of the present invention; Figure 2 This is a schematic diagram of the aluminum-based PCB boron-plated readout substrate structure of the present invention; Figure 3 This is a schematic diagram of the assembly of the anode wire plane and the wire frame according to the present invention; Figure 4 This is a schematic diagram of the readout electronics system architecture of the present invention; Figure 5 This is a block diagram of the front-end ASIC chip of the present invention; Figure 6 This is a schematic diagram of the detector position reconstruction and data acquisition process of the present invention; Figure 7 This is a flowchart of the large-area B4C thin film preparation process of the present invention.

[0024] Figure labeling: 1-Multilayer boron-plated wire chamber detection unit; 2-Anode wire plane; 21-Anode wire; 3-Aluminum-based PCB boron-plated readout substrate; 4-Readout strip; 5-B4C thin film layer; 6-Wire frame. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Those skilled in the art should understand that the following embodiments are only for explaining the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0026] The overall structure of a large-area high-resolution neutron detector for small-angle neutron scattering experiments is described as follows: Figure 1 As shown, the overall structure is a multi-layered stacked grazing incidence boron-plated wire chamber structure, including: The multi-layer boron-plated wire chamber detection unit 1 employs a 128-layer grazing incidence structure with a uniform interlayer spacing of 8mm, resulting in an overall effective detection area of ​​1000mm × 1000mm (1m²). The anode wire plane 2 is formed by stretching multiple anode wires 21 along the X-direction and welding them onto the wire frame 6. The aluminum-based PCB boron-plated readout substrate 3 is arranged along the Y-direction, perpendicularly intersecting with the anode wire plane 2. The readout electronics system includes an ASIC chip and FPGA digital circuitry. The data acquisition system is based on the Kafka distributed data stream platform. Neutrons are incident at a 5° grazing incidence angle onto the B4C thin film layer 5, undergoing a nuclear reaction to generate a signal, which is read out by a two-dimensional digital coincidence between the anode and cathode, achieving high-resolution positioning.

[0027] The aluminum-based PCB boron-plated readout substrate of this invention is as follows: Figure 2 As shown, the substrate is an aluminum-based PCB board with a minimum thickness of 0.3mm. One side is a B4C thin film boron-plated surface, and the other side is the readout strip 4. The boron plating layer is 2μm thick, and the boron-plated electrode size is 184mm×1000mm. The readout strips 4 are arranged along the Y direction with a strip spacing of 0.5mm and a strip width of 0.4mm. The readout strips 4 at the same horizontal position are connected in series and then connected to the electronics. The total number of readout strip channels is 2000, forming a flat readout strip structure. The substrate as a whole supports the multi-layer boron-plated wire chamber detection unit 1, ensuring structural flatness and reliable electrical contact.

[0028] The anode wire plane and wire frame are assembled as follows in this invention: Figure 3 As shown, the anode wires are made of metal wires with a diameter of 20μm and are evenly arranged along the X direction; the spacing between the anode wires is 6mm, and the total number is 3840, corresponding to 3840 readout channels; the two ends of the anode wires are welded and fixed on the insulating wire frame 6 to form a taut and flat anode wire plane 2; the anode wire plane 2 is perpendicularly intersected with the aluminum-based PCB boron-plated readout substrate 3 to form a two-dimensional detection surface.

[0029] The readout electronics system architecture in this invention is as follows: Figure 4 As shown, the front end consists of 92 ASIC chips with 64 channels each, forming an analog readout channel. The total number of channels covers 3840 channels for the anode and 2000 channels for the readout strip, totaling 5840 channels. The ASIC chips convert the neutron signal into an overthreshold digital signal (2.5 VTTL). The digital part uses a high-speed FPGA circuit to complete: two-dimensional anode-cathode coincidence judgment; TOT pulse amplitude measurement; and centroid method position reconstruction. After algorithm optimization, the position resolution is improved by more than 1 times, achieving high count rate and high resolution readout.

[0030] In this invention, the front-end ASIC chip is as follows: Figure 5As shown, the chip uses TSMC 0.25μm technology and has a COB package size of 2cm×1cm; input charge range: ±10fC~±400fC; single-channel count rate >1MHz, each chip integrates 32×2 channels; the threshold is adjustable by an external DAC, and the output is a digital level signal; the chip meets the requirements of multi-channel, low power consumption, high speed, and radiation resistance, and is stable and usable after the third iteration optimization.

[0031] The location reconstruction and data acquisition process in this invention is as follows: Figure 6 As shown, neutrons react with the B4C thin film to generate charge carriers, which are collected by the anode wire and readout bar; the front-end ASIC chip acquires the signal and digitizes it; the FPGA digital circuit performs two-dimensional coincidence determination to determine the impact coordinates. Submillimeter-level position reconstruction was achieved using the centroid method; the data was fed into a Kafka-based data acquisition system to achieve distributed processing, high-speed storage and sharing; the system outputs position, time and amplitude information for use in small-angle neutron scattering experiments and nuclear monitoring.

[0032] The large-area B4C thin film preparation process in this invention is as follows: Figure 7 As shown, S1 designed and built a dedicated large-area coating machine with an effective coating area of ​​1500mm×500mm; S2 aluminum-based PCB substrate cleaning, activation, and clamping; S3 uses physical vapor deposition to deposit a 2μm thick B4C film on the substrate surface; S4 characterizes the uniformity, adhesion, and thickness of the film; S5 fabricates the readout electrode, leads, and interface to complete the overall fabrication of the boron-plated cathode. During mass production of S6, process parameters are solidified to achieve consistent coating and large-scale preparation.

[0033] The structural assembly of the present invention involves alternately stacking 128 layers of boron-plated cathodes and anode wire plane 2 with a layer spacing of 8mm; the whole assembly is fixed to form a 1000mm×1000mm detection surface; the anode and the readout strip are respectively connected to the ASIC chip and the FPGA digital circuit.

[0034] The electronics and software integration in this invention involves using a self-developed high-speed ASIC chip and FPGA processing unit; deploying a Kafka data acquisition system to complete the loading of driver and location reconstruction algorithms.

[0035] This invention achieves the following performance indicators: detection efficiency: ≥70%@4Å; position resolution: ≤1mm×1mm; effective area: 1m²; signal response time: ≤1μs; gamma false positive rate: ≤1 / 10 6 Mean time between failures: ≥5000 hours; Technology readiness level: 9.

[0036] This invention can be directly used with small-angle neutron scattering spectrometers; it can be integrated into two types of instruments: nuclear safety imagers and nuclear device waste monitors; and it meets the requirements for mass production and third-party off-site testing. The structure, process, electronics, and algorithms disclosed in this embodiment fully support repeated implementation and mass production by those skilled in the art, and can stably solve the technical problems of traditional ³He detectors, such as limited resources, low efficiency, small area, poor resolution, and large gamma interference.

[0037] This invention relates to a large-area, high-resolution neutron detector for small-angle neutron scattering experiments. The overall structure employs a grazing-incidence multilayer boron-plated wire chamber design. The core components include a multilayer boron-plated wire chamber detection unit, an anode wire plane, an aluminum-based PCB boron-plated readout substrate, a readout electronics system, and a data acquisition system. The detector uses a boron carbide thin film as the neutron conversion layer and employs an anode-cathode two-dimensional digital coincidence method for neutron position readout. Signal processing and position reconstruction are performed using a high-speed dedicated integrated circuit chip and a field-programmable gate array (FPGA) digital circuit. Data acquisition and sharing are achieved through a distributed data stream platform.

[0038] This invention relates to a large-area, high-resolution neutron detector for small-angle neutron scattering experiments. The overall structure employs a grazing-incidence multilayer boron-plated wire chamber design. The core components include a multilayer boron-plated wire chamber detection unit, an anode wire plane, an aluminum-based PCB boron-plated readout substrate, a readout electronics system, and a data acquisition system. The detector uses a boron carbide thin film as the neutron conversion layer and employs an anode-cathode two-dimensional digital coincidence method for neutron position readout. Signal processing and position reconstruction are performed using a high-speed dedicated integrated circuit chip and a field-programmable gate array (FPGA) digital circuit. Data acquisition and sharing are achieved through a distributed data stream platform.

[0039] Example 1: Standard 1-square-meter large-area high-resolution neutron detector like Figure 1-7 As shown, the multi-layer boron-plated wire chamber detection unit adopts a grazing incidence multi-layer structure with a grazing incidence angle set to 5 degrees. The detection unit consists of 128 boron-plated surfaces and 128 wire surfaces, with a layer spacing of 8 mm. The total area after multi-layer assembly reaches 24 square meters, and the effective detection area of ​​the detector is 1000 mm × 1000 mm, or 1 square meter. (See attached image) Figure 1 The overall assembly relationship of the multilayer boron-plated wire chamber detection unit 1, the anode wire plane 2, the aluminum-based PCB boron-plated readout substrate 3, and the wire frame 6 is shown.

[0040] In this embodiment, the aluminum-based PCB boron-plated readout substrate 3 is made of aluminum-based material with a minimum thickness of 0.3 mm. A boron carbide thin film with a thickness of 2 micrometers is deposited on one side of the substrate; cathode readout strips are formed on the other side of the substrate. The spacing between the readout strips is 0.5 mm, and the width of each readout strip is 0.4 mm. Readout strips at the same horizontal position are interconnected and led out uniformly, with a total of 2000 readout strip channels. The overall dimensions of the boron-plated electrode are 184 mm × 1000 mm.

[0041] In this embodiment, the layered structure of the aluminum-based PCB boron-plated readout substrate 3, readout strip 4, and boron carbide thin film layer 5 can be understood as the readout strip board 41 and the B4C board. In this embodiment, the anode wire plane and wire frame are assembled as follows... Figure 3 As shown, the anode wire plane is formed by welding multiple anode wires to a wire frame. The diameter of the anode wire is 20 micrometers, and the spacing between the anode wires is 6 millimeters. There are a total of 3840 anode wires, corresponding to 3840 anode wire readout channels. The anode wire plane and the boron-plated aluminum PCB readout substrate are arranged perpendicularly and alternately to each other, together forming a two-dimensional position detection structure. (See attached image) Figure 3 The diagram shows the anode wire plane 2, the wire frame 6, and the arrangement and fixing method of the anode wire.

[0042] In this embodiment, the readout electronics system is as follows: Figure 4-5 As shown, the readout electronics system includes front-end application-specific integrated circuit (ASIC) chips and field-programmable gate array (FPGA) digital circuitry. The ASIC chips are manufactured using TSMC's 0.25-micron process and are packaged on-board with a size of 2 cm × 1 cm. The chip input charge range is ±10 femtocoulombs to ±400 femtocoulombs, with a single-channel count rate greater than 1 MHz. Each chip contains 64 signal channels. The system uses a total of 92 ASIC chips, fully covering 5840 signal channels. The chips convert analog signals into 2.5-volt transistor-to-transistor logic level digital signals, and the signal threshold is adjusted via an external digital-to-analog converter. The FPGA digital circuitry performs two-dimensional signal coincidence determination, pulse amplitude and time measurement, and centroid-based position reconstruction, more than doubling the detector's position resolution. (Appendix) Figure 4 This diagram illustrates the readout electronics system architecture, the connection relationships of the application-specific integrated circuit (ASIC) chip 7, and the field-programmable gate array (FPGA) digital circuit 8; Appendix Figure 5 The internal principle block diagram and signal flow of the front-end application-specific integrated circuit chip 7 are shown.

[0043] In this embodiment, the data acquisition system is as follows: Figure 6As shown, the data acquisition system is developed based on an open-source distributed data stream processing platform, enabling high-speed data processing, reliable data storage, and experimental data sharing. The system receives position, time, and amplitude signals from a field-programmable gate array (FPGA) digital circuit and outputs standard data that can be directly used for small-angle neutron scattering experiments and nuclear radiation monitoring.

[0044] In this embodiment, the large-area boron carbide thin film preparation process is as follows: Figure 7 As shown, a dedicated large-area coating equipment was used to prepare the boron carbide thin film. The effective coating area of ​​the equipment was 1500 mm × 500 mm. The process involved sequentially cleaning the aluminum-based PCB substrate, activating the substrate surface, clamping and fixing the substrate, depositing the boron carbide thin film, characterizing the film properties, fabricating the readout electrode, soldering the leads and assembling the interface, and finally completing the overall fabrication of the boron-plated cathode.

[0045] In this embodiment, the overall assembly and performance indicators of the detector are as follows: the multi-layer boron-plated wire chamber detection unit, the anode wire plane, the aluminum-based PCB boron-plated readout substrate, the readout electronics system, and the data acquisition system are assembled and integrated sequentially. The detector achieves the following performance: neutron detection efficiency of not less than 70%@4Å, position resolution of not more than 1 mm × 1 mm, signal response time of not more than 1 microsecond, gamma signal false alarm rate of not more than one in a million, mean time between failures of not less than 5000 hours, and technology readiness level 9.

[0046] Example 2: High Count Rate Neutron Detector for Nuclear Safety Imagers This embodiment is based on the structure of Embodiment 1, combined with... Figure 1 , Figure 2 , Figure 4 The optimizations are as follows: In this embodiment, the structure of the detection unit is adjusted as follows: Figure 1 As shown, the multilayer boron-plated wire chamber detection unit maintains a 128-layer grazing incidence structure, with the grazing incidence angle remaining at 5 degrees and the interlayer spacing at 8 mm. The effective detection area has been adjusted to 500 mm × 500 mm to meet the installation space requirements of the nuclear safety imager. The boron carbide film thickness remains at 2 micrometers, and the boron-plated electrode size has been adjusted to 184 mm × 500 mm.

[0047] In this embodiment, the parameters of the anode wire and readout bar are optimized as follows: Figure 2-3 As shown, where Figure 2 The arrangement of readout strip 4 is shown; Appendix 3 shows the denser arrangement structure of anode wire plane 2; the anode wire diameter is maintained at 20 micrometers, and the anode wire spacing is adjusted to 4 millimeters to improve spatial sampling density and position resolution uniformity. The number of anode wire channels is increased accordingly. The cathode readout strip spacing is maintained at 0.5 millimeters, the readout strip width is maintained at 0.4 millimeters, and the number of readout strip channels is adjusted accordingly based on the effective area.

[0048] In this embodiment, the readout electronics system is enhanced as follows: Figure 4-5 As shown, Figure 4 The enhanced readout electronics system connections are shown. Figure 5 The signal processing flow of the dedicated integrated circuit chip 7 is shown. In this embodiment, the front-end dedicated integrated circuit chip maintains its original electrical performance, with a single-channel count rate greater than 1 MHz, and enhanced radiation resistance and low power consumption design. The field-programmable gate array digital circuit uses a processing unit with a higher clock frequency and optimizes the two-dimensional compound logic and position reconstruction algorithm, enabling the detector to achieve a maximum instantaneous count rate of 500 kHz per square millimeter, meeting the high count rate operating scenario of the nuclear safety imager.

[0049] In this embodiment, the thickness of the boron-plated aluminum-based PCB readout substrate is maintained at 0.3 mm to enhance the substrate's mechanical strength and heat dissipation capacity. The detector adopts a sealed structure design to reduce the impact of environmental humidity and dust, ensuring that the gamma signal false alarm rate is no higher than one in a million and the mean time between failures is no less than 6000 hours.

[0050] The detector in this embodiment has a neutron detection efficiency of no less than 70%@4Å and a position resolution of no more than 0.8 mm × 1 mm. It can be stably applied to nuclear safety imagers to achieve rapid, clear and accurate imaging of nuclear devices and nuclear materials.

[0051] Example 3: Long-life neutron detector for nuclear facility waste monitoring instruments This embodiment is based on the structure of Embodiment 1, combined with... Figure 1 , Figure 2 , Figure 4 , Figure 6 The optimizations are as follows: In this embodiment, the detector unit structure is configured as follows: Figure 1 As shown, the multi-layer boron-plated wire chamber detection unit adopts a 64-layer grazing incidence structure with a grazing incidence angle of 5 degrees and a layer spacing of 8 mm. The effective detection area is set at 300 mm × 300 mm, which is suitable for the fixed installation and long-term online monitoring requirements of nuclear waste monitoring instruments.

[0052] In this embodiment, the boron carbide thin film and electrode are optimized as follows: Figure 2 As shown, the boron carbide thin film thickness has been increased to 3 micrometers to improve long-term operational stability and neutron absorption reliability. The boron-plated electrodes utilize a thickened metal plating layer to reduce contact resistance and long-term wear. The aluminum-based PCB boron-plated readout substrate maintains a thickness of 0.3 millimeters, with an added insulating protective layer on the surface to enhance radiation resistance and aging resistance.

[0053] In this embodiment, the anode wire and readout system are optimized as follows: Figure 3-4As shown, the anode wire diameter is maintained at 20 micrometers, and the anode wire spacing is set to 6 millimeters to reduce wire vibration and signal crosstalk. The readout electronics system adopts a lower power consumption design to reduce operating heat and improve long-term continuous operation capability. The application-specific integrated circuit (ASIC) chip and field-programmable gate array (FPGA) digital circuitry are equipped with self-test and fault diagnosis functions, enabling real-time monitoring of channel status and signal quality.

[0054] In this embodiment, data acquisition and remote monitoring are as follows: Figure 6 As shown, the data acquisition system adds local data storage and remote data transmission capabilities, supporting unattended long-term operation. The system can automatically record detector operating time, channel status, fault information, and detection data, meeting the requirements for long-term online monitoring of nuclear waste.

[0055] The detector in this embodiment has a neutron detection efficiency of no less than 65%@4Å, a position resolution of no more than 1 mm × 1 mm, a gamma signal false alarm rate of no more than one in a million, and a mean time between failures of no less than 6000 hours. It can be stably applied to nuclear waste monitoring instruments to achieve continuous, reliable, and accurate monitoring of radioactive waste.

Claims

1. A large-area, high-resolution neutron detector for small-angle neutron scattering experiments, characterized in that, The system includes a multilayer boron-plated wire chamber detection unit, an anode wire plane, an aluminum-based PCB boron-plated readout substrate, a high-performance readout electronics system, and a data acquisition system. The multilayer boron-plated wire chamber detection unit adopts a grazing incidence multilayer structure with an 8mm interlayer spacing. The boron plating layer is a B4C thin film with a thickness of 2μm. The anode wire plane is composed of multiple anode wires welded to a wire frame. The aluminum-based PCB boron-plated readout substrate has boron plating on one side and readout strips on the other, achieving neutron position localization through anode-cathode digital coincidence readout. The detector has an effective detection area ≥1m², a neutron detection efficiency ≥70%@4Å, a position resolution ≤1mm×1mm, a signal response time ≤1μs, and a gamma signal false alarm rate ≤1 / 10. 6 .

2. The large-area high-resolution neutron detector for small-angle neutron scattering experiments according to claim 1, characterized in that, The grazing incidence angle of the multi-layer boron-plated wire chamber detection unit is 5°, and the total number of boron-plated surfaces and wire surfaces is 128, with a total area of ​​24m².

3. The large-area high-resolution neutron detector for small-angle neutron scattering experiments according to claim 1, characterized in that, The anode wires have a spacing of 6 mm and a diameter of 20 μm, with 3840 readout channels. The cathode readout bars have a spacing of 0.5 mm and a width of 0.4 mm, with 2000 readout channels, for a total of 5840 signal channels.

4. The large-area high-resolution neutron detector for small-angle neutron scattering experiments according to claim 1, characterized in that, The minimum thickness of the aluminum-based PCB boron-plated readout substrate is 0.3mm. Readout strips at the same horizontal position are connected in series for integrated readout. The boron-plated electrode size is 184mm×1000mm.

5. The large-area high-resolution neutron detector for small-angle neutron scattering experiments according to claim 1, characterized in that, The readout electronics system includes a self-developed high-speed ASIC chip and a digital circuit based on a high-speed FPGA; the ASIC chip has a single-channel count rate >1MHz, an input charge range of ±10fC to ±400fC, and an output threshold adjustable 2.5VTTL digital signal.

6. The large-area high-resolution neutron detector for small-angle neutron scattering experiments according to claim 5, characterized in that, The digital circuit employs a two-dimensional coincidence, TOT pulse amplitude measurement, and centroid method position reconstruction algorithm, which improves the detector's position resolution by more than 100%.

7. The large-area high-resolution neutron detector for small-angle neutron scattering experiments according to claim 1, characterized in that, The data acquisition system is developed based on the distributed data stream processing platform Kafka, enabling highly reliable data processing and sharing.

8. The large-area high-resolution neutron detector for small-angle neutron scattering experiments according to claim 1, characterized in that, The detector has a mean time between failures (MTBF) of ≥5000 hours and a technology readiness level of 9, and can be applied to nuclear safety imagers and nuclear device waste monitors.

9. A method for manufacturing a large-area, high-resolution neutron detector for small-angle neutron scattering experiments, characterized in that, Includes the following steps: 1) Monte Carlo simulation was used to optimize detection efficiency, position resolution, gas gain and electron drift parameters, and to determine 5° grazing incidence, 128-layer structure and 6mm anode wire spacing; 2) Establish a dedicated large-area coating machine with a coating area of ​​1500mm×500mm, prepare a 2μm thick B4C thin film and complete the fabrication of a boron-plated cathode; 3) Weld 20μm diameter anode wires to the wire frame at 6mm intervals to form an anode wire plane; 4) A 0.3mm thick aluminum-based PCB board is used, with one side coated with B4C film and the other side fabricated with a 0.5mm periodic readout strip to form a readout substrate; 5) Integrate multi-layer boron-plated wire chamber units, ASIC chips, and FPGA digital circuits to complete the detector system assembly; 6) Equip the system with Kafka data acquisition to conduct reliability and third-party off-site testing, and achieve mass production.

10. The method for manufacturing a large-area high-resolution neutron detector for small-angle neutron scattering experiments according to claim 9, characterized in that, The ASIC chip has undergone multiple iterations and optimizations to achieve multi-channel, low power consumption, high speed and radiation resistance. It adopts COB packaging and has a size of 2cm×1cm.

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