Using theoretical analysis,a physical model and the resulting Geant4 simulation code were set up for producing relativistic positron beam from the interactions between laser-plasma-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 num-ber Z and varies inversely with the square of atomic mass A,i. e. Ne+∝(Z2/A)2. For differ-ent target materials,the positron yield has Ne+∝d2 ,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 107/shot.%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 MeV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.
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