中子导管末端中子束角发散分布规律研究

Research on Angular Divergence Distribution of Neutron Beam at the End of Neutron Guide

摘要: 本文针对常被忽略的中子导管末端束流角发散现象，基于全反射光学几何原理推导了准确描述中子束角发散分布规律的理论公式,揭示了角发散分布不连续特性的本质是源于导管系统中空间间隔的影响。利用蒙特卡罗模拟软件建立计算模型，验证了公式的正确性。模拟结果发现，角发散分布的不连续性将引起使用光阑的光路系统样品处中子强度空间分布不均匀，甚至出现栅格暗纹效应。依据理论解析公式，提出了优化角发散分布从而减小或消除暗纹效应的方法。

Abstract: The theoretical formulae were deduced based on the principle of total reflection optical geometry, and they can accurately depict the angular divergence distribution of any point at the end of the neutron guide. The theoretical formulae were verified by Monte Carlo simulation. The simulation results show that the angular divergence distribution discontinuous nature will cause the inhomogeneous spatial distribution of the neutron intensity at the sample position, even result in grid dark lines effect. Finally, according to the theory of analytic formula, several effective methods were given, which can reduce or eliminate the grid dark lines effect.