中子散射成像探测角分辨研究

Angular resolution of a neutron scatter imaging system

中子散射成像技术是近年来国外正在发展的一项新型辐射成像技术，在深空宇宙探测、核材料监控等方面具有广阔的应用前景．角分辨是衡量该技术成像能力的一项重要参数．研究了位置不确定度和能量分辨对角分辨的影响．理论分析表明：以不同角度散射，成像的角分辨不同；位置不确定不仅直接影响角分辨，还通过影响能量不确定度对角分辨间接贡献；位置分辨主要来源于探测器的结构尺寸，当探测器尺寸小于5cm，影响角分辨的主要来源是能量不确定度．利用所获得的理论结果指导设计了原理探测系统，并对设计的原理系统开展了初步实验研究．结果表明，分析结果与实验得到的角分辨参数基本一致．

Using a combination of imaging and spectroscopic capabilities, neutron scatter imaging is a novel method of detecting neutrons in an energy range from 1 to 20 MeV. The technique can be applied to measurements in a variety of areas~ including solar and atmospheric physics, radiation therapy, and nuclear materials monitoring. Angular resolution is an important parameter for a neutron scatter imaging system. There are some factors causing the uncertainty in the reconstructed image due to the imperfection of the detector system and natures of neutron scattering. These factors mainly are the uncertainties of the position and the energy. In this paper, the contributions of these factors to the angular resolution are discussed. The results show that the angular resolution varies with scatter angle; the position uncertainty not only directly affects the angular resolution, but also indirectly contributes to the angular uncertainty by influencing energy uncertainty; when the detector dimension is less than 5 cm, the energy uncertainty becomes a dominating factor for angular resolution. The prototype is designed based on the above analysis results. The angular resolution of the designed prototype is tested on Cf252 source. The experimental results are basically consistent with the simulation results.