基于150 MeV电子束的光中子特性模拟分析

Simulation and Analysis of Photo-neutron's Characteristics Driven by 150 MeV Electron Beam

高能中子源是研究高能太空宇宙射线中子对人体和电子仪器辐射损伤的必备装置,基于高能电子加速器的光中子源是目前能够提供较高能量白光中子的方式之一。本工作以清华大学先进加速器实验室的激光电子加速器束流参数为基础,借助Geant4对产生的光中子的能量特性、产额特性、角分布特性、时间特性进行了分析。模拟结果表明,Φ2 cm×2 cm的圆柱体Ta靶时,150 MeV电子束流可产生最高能量约为110 MeV、中子产额约为1.2×10~5n/10~7e-、出射时间在0~100 ns之间呈负指数分布的几乎各向同性的光中子。根据拟合的中子能量-出射时间离散指数函数,估算得到对产生的1~100MeV中子,在飞行距离为5m时中子飞行时间的时间分辨率好于2.23%。本工作为该加速器的光中子产生和实验测量工作提供了参考依据。

To investigate the influence of high - energy cosmic ray induced neutrons in space to human body or electronics, a high - energy neutron source is required. The photo - neutron source driven by high - energy electron aeeelerator is one way to produce white neutron beam. This work aims to simulate and analyze the char- acteristics of photo - neutrons based on the 150MeV electron beam of the Tsinghua laser plasma acceleration platform and a Ф2 cm× 2cm Ta target, such as neutron energy distribution, neutron yield, angular distribution and emission time spread. The simulation results show that, a white neutron spectrum with the maximum energy of 110 MeV can be obtained; the neutron yield could be 1.2 105 n/107e - ; neutrons prefer to have a same dis- tribution in every angle; neutrons＇ emission time spread from 0 to 100 ns and negatively exponential distributed, what＇s more, the exponential function of neutron energies and emission time spread is obtained by curve fitting, and the calculate time resolution is better than 2.23% in a 5m＇s flight - path. This work provides a reference data for the photo - neutron source design based on this laser plasma acceleration platform.