采用Monte Carlo程序Geant4对激光固体靶相互作用正电子产生进行了研究。研究了超热电子能量分布函数对正电子产生的影响，结果表明采用不同的分布函数，最多可致正电子产额约3倍的差异，分布函数的最大截止能量在30 MeV以上时正电子产额趋于饱和。研究了正电子产生与超热电子发散角的关联，结果表明发散角模型对正电子产额影响不大，而正电子角分布对超热电子发散角较为敏感，且靶背鞘场对正电子发散角的减小贡献巨大。模拟结果显示靶厚度的增加可导致正电子发散角的增大，而当靶厚度超过2 mm时，发散角基本保持不变。此外，模拟了超热电子发散角、靶厚度及靶背鞘场对正电子电子份额比及正电子γ份额比角分布的影响。

Positron production from ultra-intense laser-solid interactions is investigated using the Monte Carlo code Geant4. The dependence of the positron production on hot electron energy distribution, angular emission and target thickness is examined. The results show that there is at most a 3 times discrepancy in yield comparison if different distribution functions of the hot electrons are used. It is also found that there is no obvious changes in positron yield when different hot electron emission models are used, but the positron beam divergence increases obviously with the hot electron divergence when a Gaussian angular distribution is assumed. In addition, the results indicate that the positron divergence increases with target thickness below 2 mm, above which a saturated trend shows up. The influences of the hot electron divergence, the target thickness and the sheath field on the angular distribution of e+/e- (ratio of positron to electron) and e+/γ (ratio of positron to gamma) are studied.