Enhanced ion acceleration in the relativistic transparent regime due to the laser rising edge

Abstract

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 µm, 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.