激光等离子体加速电子与固体靶相互作用产生相对论正电子的模拟计算  

Positron Beam Generation by Simulation from Laser Plasma Accelerated Electron-Target Interaction

作　　者：唐甜[1] 罗文[1] 周剑良[1] 宋英明[1] 朱志超[1] 马燕云[2] 

机构地区：[1]南华大学核科学技术学院,湖南衡阳421001 [2]国防科学技术大学理学院,湖南长沙410073

出　　处：《南华大学学报（自然科学版）》2015年第2期14-19,共6页Journal of University of South China：Science and Technology

基　　金：国家自然科学基金资助项目(11347028;11405083);湖南省自然科学基金资助项目(13JJ4074);湖南省教育厅重点基金资助项目(13A080);南华大学博士启动基金资助项目(2012XQD57);南华大学研究生创新课题基金资助项目(2014XCX17)

摘　　要：通过理论分析,建立了激光等离子体加速电子与固体靶相互作用产生相对论正电子的物理模型,以及Geant4模拟程序.以100 Me V量级的激光等离子体加速电子束参数为输入,模拟研究了不同靶材和靶厚条件下正电子束的产额、能量、角分布等主要物理参数.结果表明:金靶和钽靶是较优秀的电子—正电子转换靶材;对于相同的金属靶材面密度,正电子产额与原子序数Z的四次方成正比,与原子质量数A的平方成反比,即Ne+∝(Z2/A)2;对于不同的靶材,正电子产额有Ne+∝d2,其中d为靶材厚度,但仍存在一个最佳靶厚度.与利用拍瓦、皮秒激光束与固体靶相互作用产生正电子束的方案相比,利用本方案有望获得更高能量以及更小角发散的相对论正电子束,其流强可达107/shot.Using theoretical analysis, a physical model and the resulting C, eant4 simulation code were set up for producing relativistic positron beam from the interactions between laserplasma-accelerated electrons and solid target. Using the 100 MeV-class electrons accelerated by laser interacting plasma as an input, the main characteristics of positron beam such as the positron yield, spectral and angular distributions were investigated by Monte Carlo simulation for different target materials and thicknesses. Simulation results show that gold and tantalum targets could be regarded as a good electron-positron converter. For metal targets with con- stant areal density ,the positron yield was proportional to the fourth power of the atomic number Z and varies inversely with the square of atomic mass A, i. e. Ne＋∝（Z^2/A）^2. For different target materials ,the positron yield has Ne＋∝d^2, and d is the target thickness, but exists an optimized target thickness. Compared to the scheme using hot electron interacting with solid target ,the proposed scheme is beneficial for producing relativistic positrons with higher energy and smaller angular distribution,whose intensity approaches 10^7/shot.

关 键 词：激光等离子体加速电子 相对论正电子 金属靶材 Geant4模拟程序 

分 类 号：O536[理学—等离子体物理] O571.1[理学—物理]