一、前言从反应堆水平孔道出来的热中子束,伴随着强的γ射线和快中子,这些γ射线和快中子是各种谱仪的本底计数和工作场所的辐射剂量的主要来源,为此,常采用晶体过滤器等加以控制和消除。而决定晶体材料过滤特性的主要参数是晶体的全截面。对于单晶硅,最早由Brugger测定了25,50和70 meV三个能量点的全截面,并拟合成一条能量从几 I. INTRODUCTION Thermal neutron beams emerging from the horizontal bore of the reactor, along with strong gamma and fast neutrons, are the primary source of background counts and workplace radiation doses for various spectrometers , To this end, often using crystal filters to control and eliminate. The main parameter that determines the filtration characteristics of the crystalline material is the full cross-section of the crystal. For monocrystalline silicon, the full cross-section of the three energy points of 25, 50 and 70 meV was first measured by Brugger,