Efficiency enhancement of ion acceleration from thin target irradiated by multi-PW few-cycle laser pulses
Xuezhi Wu, Zheng Gong, Yinren Shou, Yuhui Tang, Jinqing Yu, G. Mourou, Xueqing Yan
Abstract
We investigate the energy conversion efficiency from the laser to the accelerated ion beams in the interaction of different duration laser pulses with a simple plane foil, while the laser energy is kept constant. By employing multi-dimensional particle-in-cell simulations, we demonstrate that an intense few-cycle pulse is more beneficial for the energy transferring from the laser to the generated ions. Owing to the short acceleration time window of few-cycle pulses, the overwhelming majority of laser energy could be transferred to ions through a high-efficiency radiation pressure acceleration mechanism before the rupture of the target caused by transverse instabilities and finite spot effects. More importantly, it is found that a laser pulse with a too short duration also fails to reach the highest energy conversion efficiency for a given laser energy. The optimal pulse duration is related to laser energy and ion species. Our three-dimensional particle-in-cell simulations show that the highest energy conversion efficiency is obtained with a laser pulse with a duration of two cycles, which, unlike a single-cycle pulse, is the optimal duration for the given laser energy (49 J). Furthermore, when the laser energy is reduced to 12 J, four-cycle becomes the optimal duration.