采用超薄双层靶提高质子束的单能性
Generation of quasi-monoenergetic proton beam by using ultrathin double- layer target
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摘要: 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。Abstract: 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 a
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