一种基于成像板的能量卡阈式快中子图像测量方法

摘要

A method of fast-neutron imaging with energy threshold is presented in this paper, which is based on an imaging plate covered with a metal foil and a hydrogen-rich foil in order to reduce the contribution from the neutrons with a lower energy such as the scattering neutrons from samples. The method is capable of effectively reducing the relative sensitivity of the imaging detector to neutrons with energies in a certain energy range. The 14 MeV neutron imaging structure with an energy threshold is designed, and it includes a TR imaging plate covered with an about 150 µm Pb foil and a 500 µm polyethylene foil. The calculated results show that for the present structure its sensitivity to the neutrons with smaller than 8 MeV is reduced by 30% less than that to the neutrons with 14 MeV. The fast-neutron radiography is validated experimentally on a DT neutron generator (K400). The results indicate that the neutron imaging structure with an energy threshold is available to remove the edge enhancement effect introduced by scattering neutrons from samples.%为减小散射中子等较低能量的中子对快中子图像的贡献，提出了在成像板前依次紧贴金属卡阈片和富氢元素薄片的能量卡阈式快中子成像方法。该方法通过改变卡阈片材料、厚度等参数，可有效降低成像结构对某一能段中子的相对灵敏度。以14 MeV中子照相为例设计的能量卡阈式成像结构为TR成像板依次覆盖约150µm Pb膜和500µm聚乙烯膜，计算表明该结构对8 MeV以下快中子灵敏度小于其对14 MeV中子灵敏度的30%。利用K400加速器DT中子源开展了验证实验，结果表明能量卡阈式快中子成像结构能够有效消除样品散射中子引起的边界增强效应。