The rapid growth of neutron flux has driven the development of 3He-free neutron detectors to satisfy the require-ments of the neutron scattering instruments under construction or planned at the China Spallation Neutron Source(CSNS).Position-sensitive neutron detectors with a high counting rate and large area play an important role in the instruments performing neutron measurements in or close to the direct beam.The ceramic gas-electron-multiplier(GEM)detector serves as a promising solution,and considerable work has been done using the small-area GEM neutron detectors.In this article,we designed and constructed a detector prototype utilizing ceramic GEM foils with an effective area of about 307 mm × 307 mm.To evaluate and investigate their basic characteristics,the Monte Carlo(MC)tool FLUKA was em-ployed and several neutron beam tests were conducted at CSNS.The simulated spatial resolution was basically in agreement with the measured value of 2.50±0.01 mm(FWHM).The wavelength spectra measurement was verified through compar-isons with a commercial beam monitor.In addition,a detection efficiency of 4.7±0.1％was achieved for monoenergetic neutrons of 1.59 Å wavelength.This is consistent with the simulated result.The results indicate that the large-area ceramic GEM detector is a good candidate to implement neutron beam measurements.Its efficiency can be improved in a cascading manner to approach that reached by traditional 3He detectors.

This article details the calibration process for the upgraded HEPS-BPIX40, a hybrid array pixel detector designed for the High-Energy Photon Source (HEPS) in China. The detector comprises 40 modules spliced together to form a 6M detector system, enabling a significant enhancement from a single threshold to dual thresholds. Following new design requirements, a dual-threshold calibration was conducted, encompassing the relationships between energy and thresholds, the local DAC (LDAC) S-curve scan, and the fine global DAC (GDAC) and LDAC thresholds for each pixel. An accurate algorithm based on LDAC characteristics was introduced for threshold fine-tuning. The study investigates pixel gain, chip-to-chip bias differences, and the mutual influence of dual thresholds. With the refined algorithm and adjusted gain and dual thresholds, the incidence of dead pixels was reduced to 0.5 parts per thousand, and the minimum threshold energy reached approximately 3.0 keV. This work marks significant progress in large-scale pixel calibration. A 6M engineering prototype detector is planned for future construction at the HEPS, China.

Energy-resolved neutron imaging is an effective method to investigate the crystal structure and stress distribution of materials. The energy-resolved neutron imaging instrument (ERNI) has been established at China Spallation Neutron Source (CSNS). An energy-resolved neutron imaging detector based on the high-speed camera TPX3Cam is used at ERNI to achieve neutron energy resolution by recording time-of-flight (ToF) of neutrons. TPX3Cam records the photon events emitted by the neutron absorption in the scintillator. An image reconstruction algorithm is needed to reconstruct the neutron events to improve the spatial and energy resolution of the detector. The data output from the TPX3Cam contains photon events that dispersion in space and time. We want to develop an image reconstruction algorithm to identify photon events produced by a single neutron and remove the gamma ray as well as the noise. Finally, better spatial resolution and energy resolution can be obtained by neutron events reconstruction. Image reconstruction algorithms involves photon events clustering and neutron events reconstruction. Based on the traditional two-dimensional density-based spatial clustering of applications with noise (DBSCAN) algorithm, the three-dimensional DBSCAN algorithm is developed including ToF as the third dimension of information. The precision of Bragg edge of a sample is related to the energy resolution of the detector; thus, the quality of the parameters can be evaluated by the improvement in Bragg edge precision after reconstruction. The three-dimensional DBSCAN algorithm can proceed the image data effectively and identify the neutron events and noise. The precision of reconstructed Bragg edges is improved from 3.601‰ to 3.337‰, and the spatial resolution is improved from 150 m/line width to 100 m/line width.

The purpose of this study is to develop a high transmittance, sealed neutron beam monitor, which can be used in vacuum environment such as the Small-Angle Neutron Scattering spectrometer at China Spallation Neutron Source (CSNS). Boron-lined multi-wire proportion chamber was adopted to measure the neutron counting rate. A small anode spacing of 4 mm was chosen to realize high counting rate ability of the monitor. GEANT4 simulation was first carried out to optimize the cell structure of the detector. The relationship between the neutron detection and the boron layer thickness, the scattering rate of the detector body to the neutron beam, etc. were obtained. Then the monitor was manufactured and tested with Am-241 source. Finally, neutron beam tests were conducted at the 20th beamline (BL20) of the CSNS, and the response of the monitor to the neutron beam was obtained. A monitor with detection efficiency of 0.15

Thin films of 10B4C are effective candidate neutron convertors in the next generation of detectors when facing the limited availability of 3He. In this work, the purity-improved natural B4C films were fabricated using high vacuum magnetron sputtering methods. The base pressure of the sputtering chamber was reduced from 2 x 10-4 Pa to 2 x 10-5 Pa. The structural characteristics of B4C films, including density, surface morphology, and purity, were analyzed using X-ray reflectivity, X-ray photon spectra analysis, and scanning electron microscopy. B4C films with 1 mu m thickness, density of 2.23 g/cm3, and good adhesion to substrates were obtained. The element concentrations of the B4C films were measured and implemented in a Monte Carlo simulation developed with the tool Geant4. The determining neutron detection efficiency factors were the density and purities of B4C. The films were developed on a 50 x 50 mm GEM-based neutron detector at China Spallation Neutron Source (CSNS). The measured 21 % increase in neutron efficiency of GEM detectors agrees with that of simulations.

The China Spallation Neutron Source (CSNS) is designed and constructed by the Institute of High Energy Physics, Chinese Academy of Sciences. The construction of CSNS includes an 80-MeV Linac, a 1.6-GeV Rapid Cycling Synchrotron (RCS), two beam transport lines, a solid target station of 100 kW, three initial neutron instruments and other utility facilities. Based on limited funding and lack of experience in the high-power proton accelerator and the spallation target, the CSNS design was optimized to an advanced user faculty to fulfill the urgent user demand, with a high performance/cost ratio, and to have the capability for the CSNS phase two project (CSNS-II) to increase the beam power to 500 kW with less investment. The CSNS construction started in October 2011, and finished in March 2018 on schedule, and reached the acceptance parameters. Since then, CSNS has been operating efficiently and stably. In March 2024, the proton beam power on the target was increased to 160 kW. More than 1700 user experiments have been carried out so far, indicating a strong user demand. The design, construction and commissioning of CSNS are presented in this paper.

As a non-destructive testing technology,neutron imaging plays an important role in various fields,including material science,nuclear engineering,and fundamental science.An imaging detector with a neutron-sensitive image intensifier has been developed and demonstrated to achieve good spatial resolution and timing resolution.However,the influence of the working voltage on the performance of the neutron-sensitive imaging intensifier has not been studied.To optimize the performance of the neutron-sensitive image intensifier at different voltages,experiments have been performed at the China Spallation Neutron Source(CSNS)neutron beamline.The change in the light yield and imaging quality with different voltages has been acquired.It is shown that the image quality benefits from the high gain of the microchannel plate(MCP)and the high accelerating electric field between the MCP and the screen.Increasing the accelerating electric field is more effective than increasing the gain of MCPs for the improvement of the imaging quality.Increasing the total gain of the MCP stack can be realized more effectively by improving the gain of the standard MCP than that of the nMCP.These results offer a development direction for image intensifiers in the future.

Energy resolved neutron imaging has developed rapidly due to its advantage on testing the inner structure of crystal samples. Neutron detector is one of the key components to determine the imaging results quality. The neutron sensitive microchannel plate (nMCP) has been widely used in energy resolved neutron imaging experiments because of the high spatial and timing resolution. However, the ability to adjust field -of -view (FOV) and spatial resolution has not been realized in the nMCP detector, which is an attractive capability in energy resolved neutron imaging experiments. In this paper, an energy resolved neutron imaging detector was developed by coupling nMCP with a time stamping camera. The neutrons were absorbed by nMCP and converted into light through a phosphor screen. Then the light was focused on the camera by optical lens. A data algorithm was designed to improve the data quality. By changing the magnification of the optical lens, large FOV (46mm diameter) and high spatial resolution (26 mu m) were realized in the experiments at CSNS beamline 20. The energy resolved ability was demonstrated by a Bragg -edge transmission imaging experiment for aluminum and stainless -steel samples. The performance of this detector makes it a promising candidate used in energy resolved neutron imaging.

The High Energy Photon Source (HEPS) represents a fourth-generation light source. This facility has made unprecedented advancements in accelerator technology, necessitating the development of new detectors to satisfy physical requirements such as single-photon resolution, large dynamic range, and high frame rates. Since 2016, the Institute of High Energy Physics has introduced the first user-experimental hybrid pixel detector, progressing to the fourth-generation million-pixel detector designed for challenging conditions, with the dual-threshold single-photon detector HEPS-Beijing PIXel (HEPS-BPIX) set as the next-generation target. HEPS-BPIX will employ the entirely new Application-Specific Integrated Circuit (ASIC) BP40 for pixel information readout. Data flow will be managed and controlled through readout electronics based on a two-tier Field-Programmable Gate Array (FPGA) system: the Front-End Electronics (FEE) and the Input-Output Board (IOB) handle the fan-out for 12 ASICs, and the u4FCP is tasked with processing serial data on high-speed links, transferring pixel-level data to the back-end RTM and uTCA chassis, or independently outputting through a network port, enabling remote control of the entire detector. The new HEPS-BPIX firmware has undergone a comprehensive redesign and update to meet the electronic characteristics of the new chip and to improve the overall performance of the detector. We provide an overview of the core subunits of HEPS-BPIX, emphasizing the readout system, evaluating the new hardware and firmware, and highlighting some of its innovative features and characteristics.

Energy-resolved neutron imaging is an effective way to investigate the internal structure and residual stress of materials. Different sample sizes have varying requirements for the detector's imaging field of view (FOV) and spatial resolution. Therefore, a dual-mode energy-resolved neutron imaging detector was developed, which mainly consisted of a neutron scintillator screen, a mirror, imaging lenses, and a time-stamping optical fast camera. This detector could operate in a large FOV mode or a high spatial resolution mode. To evaluate the performance of the detector, the neutron wavelength spectra and the multiple spatial resolution tests were conducted at CSNS. The results demonstrated that the detector accurately measured the neutron wavelength spectra selected by a bandwidth chopper. The best spatial resolution was about 20μm in high spatial resolution mode after event reconstruction, and a FOV of 45.0 mm × 45.0 mm was obtained in large FOV mode. The feasibility was validated to change the spatial resolution and FOV by replacing the scintillator screen and adjusting the lens magnification.

Boron carbide (B4C) films used as neutron conversion layers were investigated in this paper to replace the traditional 3He detectors due to their shortage. A magnetron sputtering system was developed for depositing large-size B4C films with the 1500 × 400 mm2 uniform-area. B4C films at the micron scale were deposited on aluminum (Al), float glass (SiO2), and silicon (Si) substrates with an inserting adhesion layer. The key characteristics, including surface morphology, thickness nonuniformity, purity, and neutron efficiency of B4C films, were characterized using atomic force microscopy, scanning electron microscopy, grazing incidence x-ray reflectivity, x-ray photoelectron spectroscopy, and neutron radiation metrology. The experimental results indicate that the deposition thickness nonuniformity across a 1500 × 400 mm2 area was better than ±3%. The stoichiometric ratio of boron atoms and carbon atoms (B/C) is 5.18, with 6 at. % O and 0.79 at. % N concentrations. The measured neutron detection efficiency of a 3 µm 10B4C film for 25 meV neutrons was 3.3 ± 0.3(sys)%, which is close to the simulated results (3.4%). The results show that the B4C neutron conversion layer is a promising substitute for 3He for neutron detection in the future.

Neutron scattering instruments play an important role in studying the inner structure of materials. A neutron beam monitor is a detector commonly used in a neutron scattering instrument. The detection efficiency for most neutron beam monitors is quite low (10-4-10-6). However, in some experiments with a low neutron flux, such as small angle neutron scattering (SANS) and inelastic neutron scattering experiments, a neutron beam monitor with a higher detection efficiency (∼1% for thermal neutrons) is required to reduce the duration of the experiment. To meet this requirement, a ceramic gas electron multiplier-based neutron beam monitor equipped with a 1 µm 10B4C neutron converter was developed in this study. Its performance was determined both experimentally and in simulations. The detection efficiency in the wavelength range of 1.8-5.5 Å was measured experimentally and was confirmed by the simulation results. An algorithm based on event selection and position reconstruction was developed to improve the spatial resolution to about 1 mm full-width-half-maximum. The wavelength spectrum was measured in beamline 20 (BL20) and agreed well with the results obtained using a commercial monitor. The maximum counting rate was 1.3 MHz. The non-uniformity over the whole 100 × 100 mm2 active area was determined to be 1.4%. Due to the excellent performance of this monitor, it has been used in several neutron instruments, such as the SANS and the High-Energy Direct-Geometry Inelastic Spectrometer instruments in the China spallation neutron source.

Internet of Things (IoT) and AI are correlating with each other closer and closer. By combining these two techniques, most of the tasks can be done efficiently. In this circumstance, however, most of the recognition tasks of handwritten Tibetan is still fulfilled manually or using methods like convolutional neural network (CNN), which lowers the efficiency because of their long training time. In order to solve those problems, in this paper, we use portable IoT devices and seek for a traditional method with not only high accuracy but also short training time on the tasks. We use methods that are commonly used in handwriting recognition to recognize handwritten Tibetan numerals and compare not only accuracy but also training time of those methods. Furthermore, we adjust the best method and find the most appropriate setting for handwriting recognition task. We combine AI and IoT and provide an efficient way of recognizing handwritten Tibetan numerals.

Helium-3-filled linear position-sensitive detectors (LPSDs) have been widely applied to neutron scattering instruments in recent decades owing to the high detection efficiency, the excellent neutron/gamma discrimination, and the ability to construct the detector with large area coverage. More than 65

The multi-physics instrument(MPI)is the first user cooperative instrument at the China Spallation Neutron Source(CSNS).It was designed to explore the structures of complex materials at multiple scales based on the neutron total scattering tech-nique.This imposes the requirements for the detector,including a high detection efficiency to reduce the measurement time and a large solid angle coverage to cover a wide range of momentum transfers.To satisfy these demands,a large-area array of 3He-filled linear position-sensitive detectors(LPSDs)was constructed,each with a diameter of 1 inch and pressure of 20 atm.It uses an orbicular layout of the detector and an eight-pack module design for the arrangement of 3He LPSDs,covering a range of scattering angles from 3° to 170° with a total detector area of approximately 7 m2.The detector works in air,which is separated from the vacuum environment to facilitate installation and maintenance.The characteristics of the MPI detector were investigated through Monte Carlo(MC)simulations using Geant4 and experimental measurements.The results suggest that the detectors are highly efficient in the wavelength range of the MPI,and an efficiency over 25％is achievable for above 0.1 ? neutrons.A minimal position resolution of 6.4 mm full width at half maximum(FWHM)along the tube length was achieved at a working voltage of 2200 V,and a deviation below 2 mm between the real and measured positions was attained in the beam experiment.The detector module exhibited good consistency and an excellent counting rate capacity of up to 80 kHz,which satisfied the requirements of experiments with a high event rate.Observations of its operation over the past year have shown that the detector works steadily in sample experiments,which allows the MPI to serve the user program successfully.

The increase of neutron flux in pulsed spallation neutron facilities imposes demands on the neutron detector for beam monitoring, including excellent neutron/gamma discrimination, wide dynamic neutron-flux measurement range, wavelength resolution, and long-term stability. In this paper, we developed a ceramic GEM-based (gas electron multiplier) neutron detector with an active area of 100 mm × 100 mm. It adopted a thinner conversion material and the stopping layer to lower the detection efficiency so as to extend the dynamic measurement range of the detector. The detection efficiency of this detector was investigated by the Monte Carlo (MC) tool FLUKA, showing that the low efficiency around 0.01% for 1 Åneutrons was reached by using a 0.1 μm nat B 4 C converter appended with an aluminum film of 2 μm thickness. Its validation of the wavelength spectra measurement was verified by comparisons with that made with an LND monitor, and it could work at the condition of 7.1 × 10 9 n/s for 2.5 Åneutrons. In addition, it was demonstrated that this detector was able to measure the beam profile with a position resolution of better than 2.1 ± 0.1 mm. The results of simulations and experiments show that this ceramic-GEM neutron detector can meet the requirements of the direct measurement of high-flux beam, and it will be a new neutron detector for the beam monitoring at the China spallation neutron source (CSNS).

Energy-resolved neutron imaging has been a popular imaging method due to the progress of neutron sources and detection systems. Neutron-sensitive microchannel plate (nMCP) has been successfully used in various energy-resolved neutron imaging applications, thanks to their high spatial and temporal resolutions. However, neutron–gamma discrimination has been a critical challenge for nMCP detectors because of the high intrinsic gamma sensitivity. In the present time the methods to reduce the gamma influence for nMCP detector are mainly based on shielding or a coincidence scheme. In this paper, a novel method based on changing the gain and the content of nMCP materials is proposed to improve the neutron–gamma discrimination capability for boron-doped nMCPs. The influence of boron and lead concentration on the n/γ ratio is calculated by a simulation model. Results shows that the effect on the neutron–gamma​ discrimination of boron concentration is more significant than the lead concentration. In addition, it has been demonstrated by simulation and experiment that the neutron–gamma discrimination of nMCP could be improved by decreasing the gain. We found that as the nMCP voltage decreased, the relative n/γ ratio could be improved and the neutron loss could be reduced. These results confirm that the method is effective for improving nMCP neutron–gamma discrimination. In the future, the neutron–gamma discrimination will be further improved by optimizing the concentration of boron and lead as well as the working conditions for nMCPs and standard MCPs.

The small-angle neutron scattering (SANS) instrument, one of the first three instruments of the China Spallation Neutron Source (CSNS), is designed to probe the microscopic and mesoscopic structures of materials in the scale range 1–100 nm. A large-area 3He tube array detector has been constructed and operates at the CSNS SANS instrument since August 2018. It consists of 120 linear position-sensitive detector tubes, each 1 m in length and 8 mm in diameter, and filled with 3He gas at 20 bar to obtain a high detection efficiency. The 3He tubes were divided into ten modules, providing an overall area of 1000 mm × 1020 mm with a high count rate capability. Because each tube is installed independently, the detector can be quickly repaired in situ by replacing damaged tubes. To reduce air scattering, the SANS detector must operate in a vacuum environment (0.1 mbar). An all-metal sealing technique was adopted to avoid high-voltage breakdown by ensuring a high-voltage connection and an electronic system working in an atmospheric environment. A position resolution of 7.8 ± 0.1 mm (full width at maximum) is measured along the length of the tubes, with a high detection efficiency of 81 ± 2% at 2 Å. Operating over the past four years, the detector appears to perform well and with a high stability, which supports the SANS instrument to finish approximately 200 user scientific programs.

A front end is shared within port BL33 two beamlines, which have chicane angle +0.5 mrad and a 10 Hz rapid-switching angle -0.35 mrad. The front end will handle the total power 11.04 kW of a dual EPU66 with newly designed components to accept a high heat load. In particular, we describe the thermal stress, body temperature, and cooling-water-wall temperature of these components based on a finite-element analysis simulation under extreme conditions. The maximum temperature and stress are 96.1 degrees C and 126.29 MPa, which appear on fixed mask1. The design is safe, even under extreme conditions, as evident from the high-heat-load components.

We report the performance of a THick Gas Electron Multiplier (THGEM) fabricated by drilling holes in a gold-clad ceramic substrate using the standard PCB (Printed Circuit Board) technology and etching rims. The THGEM has a total thickness of 200μm with a hole diameter and rim size of 200μm and 80μm, respectively. In order to carry out a performance study, a detector was assembled by putting the THGEM inside a versatile chamber and irradiating it with a 55Fe X-ray source (5.9 keV). An Ar/CO2 gas mixture was flushed inside the chamber at a pressure of about 1 atm, with volume ratios varying between 70/30 and 90/10. Pulse height spectra of the detector were recorded by a multichannel analyzer to investigate the gain and energy resolution at different drift and induction electric fields. The variations in the gain and energy resolution were also interpreted using simulations. The gain and resolution data of the THGEM were compared with those of a standard GEM which was measured using the same experimental setup.