相对论正电子束在实验物理中非常重要，它可以直接应用于核物理、粒子物理、材料科学和医学成像等众多前沿领域。小尺度电子-正电子喷注产生的可行性分析对研究神秘莫测的核天体物理现象（譬如黑洞沦陷、活动星系核，长脉冲伽玛爆等）同样至关重要。本项目针对近年来提出的基于超短超强激光与靶相互作用的正电子产生及加速问题，分析正电子产生与加速的相关细致物理过程，研究该过程中超热电子-正电子转换效率；开发考虑高能电子与靶相互作用、正电子产生与加速等过程的蒙特卡罗模拟程序包，定量分析靶背鞘层静电势、激光场强和有质动力对正电子加速作用的影响；探索产生飞秒超短、超相对论（γ_{e+}≥500）的正电子束的物理方案，以及诊断正电子产生及加速后的物理特征如能谱分布、脉冲时间结构、角分布和数密度等。上述研究将有望阐述目前实验观测到但理论难以解释的正电子峰位移动现象，可为高能量、高密度的正电子源产生及其前沿应用提供理论参考。

Relativistic positron beams are of paramount importance in experimental physics due to their direct applications to a wide range of physical fields, including nuclear physics, particle physics, material science, and medical imaging application. The possibility of generating small-scale electron-positron jets is also a key problem to understand enigmatic astrophysical phenomena, such as out-spills of Black Holes, Active Galactic Nuclei, long Gamma-ray Bursts, etc. Relativistic positron production and acceleration using intense laser-solid interaction have attracted a lot of attention in these years. In this project, we analyze the detailed positron generation and acceleration processes, and study the transfer efficiency from hot electron to positron; considering high-energy electron-target interaction, positron production and acceleration processes, we will develop a special Monte Carlo package to simulate the processes of relativistic positron generation and acceleration from high-Z solid target, quantitatively analyze the effects of target normal sheath potential, laser electric field and laser ponderomotive force on positron acceleration; then we will discuss the possibility of generating femtosecond, ultrarelativistic (γ_{e+}≥500) positron beame, and valuate the beam properties of the positrons, such as energy and angular distribution, pulse duration and number density. These studies may give possible interpretations on the peak energy shift in the positron spectrum observed in many experiments, and may benefit the researches on generation of positron beams with high energy and high density.