利用1维粒子模拟程序, 研究了超短超强激光脉冲与超薄双层靶(基底层和加速层厚度均为nm量级)相互作用产生准单能质子束的过程。研究表明, 基底层厚度及加速层厚度对质子能谱的影响至关重要。减小基底层厚度, 靶后静电场增强, 质子的最大能量显著增大；减小加速层厚度, 靶后静电场分布变得更加均匀, 质子能谱中心能量变化不大, 单能性变好。通过优化参数, 获得了能散度为7%的准单能质子束。

The quasi-monoenergetic proton beam generated from ultra-short ultra-intense laser pulse interacting with ultrathin double-layer target (both the thickness of the substrate layer and that of the acceleration layer are in nanometer scale) is examined by one-dimensional particle-in-cell simulation. The thickness of the substrate and the acceleration layer is crucial to the proton spectrum. The quasi-static electric field becomes stronger as the substrate layer thickness decreases, which results in the enhancement of the maximum proton energy. Reducing the acceleration layer thickness induces a more uniform quasi-static electric field. As a result, the proton spectrum becomes more monoenergetic with nearly unchanged mean energy. The quasi-monoenergetic proton with an energy spread of about 7% has been produced by optimizing parameters.