【摘要】 激光尾波场电子束作用于固体金属靶产生正电子，是一种新兴的获取正电子的实验方法。文章对其实验方案进行详细地模拟分析。利用FLUKA蒙特卡罗程序开展数值模拟，研究激光尾波场正电子实验中靶材料的选择标准，提出引入平均角分布熵产额(mean angular entropy yield, MAEY)函数指标进行正电子的实验可用性评价；计算结果表明，原子序数高的固体金靶正电子产额和平均角分布熵产额均较高，正电子的可用性相对较好。对选用固体金靶的实验方案，构建蒙特卡罗物理模型开展模拟计算，研究正电子在输运过程中的空间分布特征；计算数据显示，金靶产生正电子的角分布范围在0°～70°之间，通过准直器后正电子数目减少到原来的1.05%,存在电子、光子和中子等干扰粒子，其中光子干扰最大，在通过偏转磁场后的正电子分布空间，光子密度仍比正电子密度高2个数量级。该文的研究对于激光驱动正电子实验固体靶材料的合理选用以及相关正电子测量与应用实验方案的优化设计具有一定的参考价值。更多还原

【Abstract】 Laser wakefield electron beam acting on solid metal target is a new experimental method to produce positrons. The experimental program was numerically simulated in detail in this study. The selection criteria of target material for positron production were studied by using Monte Carlo program FLUKA. The definition of mean angular entropy yield(MAEY) was proposed, by which the availability of positrons was evaluated. The results showed that the higher Z target had higher positrons yield and higher MAEY, which had higher availability of positrons. Then, angular distribution characteristics of positrons transport were studied by simulating the Monte Carlo physical model of experimental program, in which gold solid target was used. The calculation data indicated that angular distribution range of positrons generated by the gold solid target was between 0° and 70°. The number of positrons was reduced to 1.05% after passing through the collimator. There were interference particles in the region of positrons transport, such as electrons, photons and neutrons, among which photons had the strongest interference on the positrons. After passing deflecting magnetic field region, the photon density was still two orders of magnitude higher than that of the positron. The study can provide a reference for selecting solid target material in the experiment of positrons generated by laser drive and optimizing the experimental program of positrons measurement and application.更多还原