We investigate the impacts of the laser contrast on ion acceleration when an ultra-intense laser pulse irradiates on a sub-micron foil target. In high-intensity laser driven ion acceleration experiments, the rising edge of the pulse could significantly preheat the target, which is likely to cause premature relativistic induced transparency of the target before the pulse peak. In this case, our particle-in-cell simulations show that the breakout afterburner (BOA) mechanism has obvious advantages over the radiation pressure acceleration (RPA). With the ATLAS laser contrast of 10^−8.8 in 2 ps and peak intensity, the optimized target thickness is increased to 0.27 m, where BOA works well and the maximum proton energy can reach 250 MeV. The proton energy is higher than that generated via RPA in a nanometer thin target either with and without the rising edge. Besides, the BOA appears robust against the laser contrast.

当超强激光脉冲照射到亚微米箔靶上时，我们研究了激光对比对离子加速的影响。在高强度激光驱动的离子加速实验中，脉冲的上升沿会显着预热目标，这很可能在脉冲峰值之前引起目标的相对论性过早诱发。在这种情况下，我们的单元内粒子模拟显示，突破加力燃烧器（BOA）机制比辐射压力加速（RPA）具有明显优势。在2 ps的ATLAS激光对比度为10 ^8.8且峰值强度最大的情况下，最佳目标厚度增加到0.27m，BOA工作良好，最大质子能量可达到250 MeV。在有或没有上升沿的情况下，质子能量都高于纳米薄靶中RPA产生的能量。此外，BOA看起来对激光对比度很强。