A small-angle scattering neutron spectrometer for material research is under construction at the China Spallation Neutron Source. An intervening neutron beam monitor behind the sample is needed to measure the beam int...A small-angle scattering neutron spectrometer for material research is under construction at the China Spallation Neutron Source. An intervening neutron beam monitor behind the sample is needed to measure the beam intensity in order to reduce the measurement uncertainty caused by beam fluctuation. Considering the mobility requirement and limited space, we proposed a compact monitor using a type of lithium-glass scintillator provided by China Building Materials Academy. Its performance was studied experimentally using ^(252)Cf and ^(60)Co sources.The neutron light yield of the selected scintillator was measured to be 5:3 × 10~3 photons/neutron. The feasibility of n-gamma discrimination using the charge comparison method was verified. By using the Geant4 toolkit, themonitor was modeled with precise physical processes including neutron tracking, scintillation, and optical photon transmission. The gamma sensitivity and detection efficiency were investigated in the simulation. It was concluded that a 0.5-mm-thick lithium-glass scintillator with natural lithium is an appropriate choice to satisfy both the neutron detection efficiency and gamma elimination requirements.展开更多
A new thermal neutron beam monitor with a Gas Electron Multiplier （GEM） is developed to meet the needs of the next generation of neutron facilities. A prototype chamber has been constructed with two 100 mm×100 ...A new thermal neutron beam monitor with a Gas Electron Multiplier （GEM） is developed to meet the needs of the next generation of neutron facilities. A prototype chamber has been constructed with two 100 mm×100 mm GEM foils. Enriched boron-10 is coated on one surface of the aluminum cathode plate as the neutron convertor. 96 channel pads with an area of 8 mm×8 mm each are used for fast signal readout. In order to study the basic characteristics of a boron-coated GEM, several irradiation tests were carried out with of source ^239pu and neutron source ^241Am（Be）. The signal induced by the neutron source has a high signal-to-noise ratio. A clear image obtained from of source ^239pu is presented, which shows that the neutron beam monitor based on a boron-coated GEM has a good two-dimensional imaging ability.展开更多
A Monte Carlo method of the 3D GEM simulation is introduced.The physical process of the neutron detection is described with the Geant4 code and the Garfield code.The results of the optimized electric-fields,the emitte...A Monte Carlo method of the 3D GEM simulation is introduced.The physical process of the neutron detection is described with the Geant4 code and the Garfield code.The results of the optimized electric-fields,the emitted ions spectrum,the electrons transverse diffusion and the signal width are presented.Moreover,the preliminary result with a CF-252 neutron source is reported.These are useful in designing detector structures and to provide an optimized option for the development of the boron-coated GEM neutron beam monitor.展开更多
针对钍基熔盐堆白光中子源(Thorium Molten Salt Reactor with a Particle and Neutron Source,TMSRPNS)在运行过程中出现中子束流掉束或打火导致的束流不稳定的问题,有必要设计研发一种具有高计数率、低中子束流影响、高中子/伽马甄别...针对钍基熔盐堆白光中子源(Thorium Molten Salt Reactor with a Particle and Neutron Source,TMSRPNS)在运行过程中出现中子束流掉束或打火导致的束流不稳定的问题,有必要设计研发一种具有高计数率、低中子束流影响、高中子/伽马甄别性能的中子束流监测器。基于蒙特卡罗模拟软件Geant4,系统研究了薄膜塑料闪烁中子束流监测器的中子转换层厚度、闪烁体厚度,以及入射窗材料等关键参数对薄膜闪烁体的影响规律,分析结果表明:闪烁体中子转换层厚度约为2μm时具有相对合适的本征探测效率;闪烁体厚度为0.5 mm、甄别阈值为0.8 MeV时监测器具备γ射线不灵敏性能。同时,通过对比不同入射窗材料对于γ射线产生电子以及对中子散射的影响,选取电子产生较少且中子散射较小的铝作为入射窗材料。研究结果可为后续的中子束流监测器实物制备提供理论依据。展开更多
简要介绍了一种基于GEM(Gas Electron Multiplier气体电子倍增器)的、用于对中子束进行实时监测的中子束线监测器GEM Monitor,重点介绍了其中电子学部分的设计,包括电路工作原理、系统结构、子板设计及Monitor母板FPGA逻辑及其算法的实...简要介绍了一种基于GEM(Gas Electron Multiplier气体电子倍增器)的、用于对中子束进行实时监测的中子束线监测器GEM Monitor,重点介绍了其中电子学部分的设计,包括电路工作原理、系统结构、子板设计及Monitor母板FPGA逻辑及其算法的实现。最后给出了相关测试结果。展开更多
Design and construction of the first prototype ionization chamber for CSNS and Proton Accelerator （PA） beam loss monitor （BLM） system is reported. The low leakage current （〈0.1 pA）, good plateau （≈800 V） and...Design and construction of the first prototype ionization chamber for CSNS and Proton Accelerator （PA） beam loss monitor （BLM） system is reported. The low leakage current （〈0.1 pA）, good plateau （≈800 V） and linearity range up to 200 Roentgen/h are obtained in the first prototype. All of these give us good experience for further improving the ionization chamber construction.展开更多
基于硼转换的GEM(Gas Electron Multiplier)探测器性能突出,计数率高达10 MHz以上,耐辐射,信号读出方式简单、灵活,位置与时间分辨率高,是下一代中子束流监测器极具优势的候选者。这种新型中子束流监测器主要由硼中子转换层、气体电离...基于硼转换的GEM(Gas Electron Multiplier)探测器性能突出,计数率高达10 MHz以上,耐辐射,信号读出方式简单、灵活,位置与时间分辨率高,是下一代中子束流监测器极具优势的候选者。这种新型中子束流监测器主要由硼中子转换层、气体电离粒子放大的GEM以及二维读出电极组成。通过Geant4程序包对探测器物理过程进行蒙特卡罗(Monte Carlo)模拟,主要研究了硼中子转换层转换效率与厚度及中子波长的关系、出射粒子的能谱、不同气体比分不同气体厚度中的能量沉积、以及γ的能量沉积,计算比较了不同厚度GEM膜对快中子产生的影响。模拟结果表明,出射粒子在漂移区的能量沉积几乎与气体比分无关,硼层厚度取0.1μm以下,漂移区厚度6 mm时,可以确保出射粒子在漂移区能量完全沉积,同时具有最佳n/γ区分能力。展开更多
基金supported by the National Key R&D Program of China(No.2017YFA0403702)the Instrument Developing Project of the Chinese Academy of Sciences(No.YZ201512)the National Natural Science Foundation of China(Nos.11635012,11405191,and11205036)
文摘A small-angle scattering neutron spectrometer for material research is under construction at the China Spallation Neutron Source. An intervening neutron beam monitor behind the sample is needed to measure the beam intensity in order to reduce the measurement uncertainty caused by beam fluctuation. Considering the mobility requirement and limited space, we proposed a compact monitor using a type of lithium-glass scintillator provided by China Building Materials Academy. Its performance was studied experimentally using ^(252)Cf and ^(60)Co sources.The neutron light yield of the selected scintillator was measured to be 5:3 × 10~3 photons/neutron. The feasibility of n-gamma discrimination using the charge comparison method was verified. By using the Geant4 toolkit, themonitor was modeled with precise physical processes including neutron tracking, scintillation, and optical photon transmission. The gamma sensitivity and detection efficiency were investigated in the simulation. It was concluded that a 0.5-mm-thick lithium-glass scintillator with natural lithium is an appropriate choice to satisfy both the neutron detection efficiency and gamma elimination requirements.
文摘A new thermal neutron beam monitor with a Gas Electron Multiplier （GEM） is developed to meet the needs of the next generation of neutron facilities. A prototype chamber has been constructed with two 100 mm×100 mm GEM foils. Enriched boron-10 is coated on one surface of the aluminum cathode plate as the neutron convertor. 96 channel pads with an area of 8 mm×8 mm each are used for fast signal readout. In order to study the basic characteristics of a boron-coated GEM, several irradiation tests were carried out with of source ^239pu and neutron source ^241Am（Be）. The signal induced by the neutron source has a high signal-to-noise ratio. A clear image obtained from of source ^239pu is presented, which shows that the neutron beam monitor based on a boron-coated GEM has a good two-dimensional imaging ability.
基金supported by the National Natural Science Foundation of China(Grant Nos.11127508 and 11175199)China Spallation Neutron Source and the State Key Laboratory of Particle Detection and Electronics
文摘A Monte Carlo method of the 3D GEM simulation is introduced.The physical process of the neutron detection is described with the Geant4 code and the Garfield code.The results of the optimized electric-fields,the emitted ions spectrum,the electrons transverse diffusion and the signal width are presented.Moreover,the preliminary result with a CF-252 neutron source is reported.These are useful in designing detector structures and to provide an optimized option for the development of the boron-coated GEM neutron beam monitor.
文摘针对钍基熔盐堆白光中子源(Thorium Molten Salt Reactor with a Particle and Neutron Source,TMSRPNS)在运行过程中出现中子束流掉束或打火导致的束流不稳定的问题,有必要设计研发一种具有高计数率、低中子束流影响、高中子/伽马甄别性能的中子束流监测器。基于蒙特卡罗模拟软件Geant4,系统研究了薄膜塑料闪烁中子束流监测器的中子转换层厚度、闪烁体厚度,以及入射窗材料等关键参数对薄膜闪烁体的影响规律,分析结果表明:闪烁体中子转换层厚度约为2μm时具有相对合适的本征探测效率;闪烁体厚度为0.5 mm、甄别阈值为0.8 MeV时监测器具备γ射线不灵敏性能。同时,通过对比不同入射窗材料对于γ射线产生电子以及对中子散射的影响,选取电子产生较少且中子散射较小的铝作为入射窗材料。研究结果可为后续的中子束流监测器实物制备提供理论依据。
文摘Design and construction of the first prototype ionization chamber for CSNS and Proton Accelerator （PA） beam loss monitor （BLM） system is reported. The low leakage current （〈0.1 pA）, good plateau （≈800 V） and linearity range up to 200 Roentgen/h are obtained in the first prototype. All of these give us good experience for further improving the ionization chamber construction.
