Efficiency enhancement of ion acceleration from thin target irradiated by multi-PW few-cycle laser pulses

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.