Simulation And Experimental Study On NTHGEM Applied To Thermal Neutron Detection

Based on the characteristics of the neutron itself,neutron scattering technology has become a very important method to study the structure and dynamic properties of materials at present,and it has been widely used in many fields,such as chemistry,magnetism and superconductivity,crystalline materials,structural biology,complex fluids,etc.At the same time,in order to adapt to the development of neutron application technology,various large-scale high-throughput neutron sources have been built around the world,which poses even greater challenges for high-performance neutron detectors.At present,most of the detectors used in neutron detection are based on ³He gas detectors.In recent years,due to the shortage of ³He gas and high price,it has begun to restrict the development of neutron application technology.The Institute of High Energy Physics,Chinese Academy of Sciences has developed a ceramic substrate n THGEM?neutron THick GEM?for the detection of neutrons.The n THGEM-based neutron detector has the advantages of high counting rate,high position and time resolution,large gain,simple manufacturing process,and convenience for large-area production.It is one of the important directions for the development of alternative ³He detection technology in the world.In this paper,the performance of the detector based on the novel ceramic substrate n THGEM was studied through simulation and experiments.The performance of n THGEM was simulated using ANSYS,Geant4,and Garfield++ Monte Carlo programs.Through Monte Carlo simulation,the working principle of the gas detector is more deeply understood.The change rules of the gain and electron drift velocity of the detector with different field strength and different Ar/CO₂ gas component have been obtained,and also the 55 Fe energy spectrum in Ar based gas.The neutron conversion ability of the boron-coated layer was simulated and it shows that the thermal neutron conversion efficiency is about 0.082% when the thickness of B4 C is 0.1 um.By using the 55 Fe radioactive source,the relationship between the key parameters such as gain,count rate stability,energy resolution of the n THGEM film and the n THGEM film voltage,collected field strength,drift field strength was.The working parameters of n THGEM in different working gases are optimized and it lays a foundation for further optimizing the design and process of n THGEM.The experimental results show that the single-layer n THGEM film has a gain of 103 in a 90% Ar + 10% CO₂ mixture,and the count rate is stable.At the same time,a two dimensional position sensitive detector based on n THGEM was specially designed,the design,assembly and debugging of the detector were completed,and the preliminary test of the n THGEM-based detector on the Xray machine showed that the detector has good detection performance.In addition,a neutron beam experiment was carried out on the China Advanced Research Reactor,the position resolution of the detector was?3.01±0.03?mm?FWHM?through slit measurement,which was close to the high pressure ³He MWPC neutron detector.