Dependence on Laser Pulse Duration of the Maximum Energy of Protons Accelerated by Intense “Slow Light”

Three-dimensional numerical simulations were used to study the dependence of maximum energy of ions (protons) accelerated from low-density targets on the duration of the accelerating femtosecond laser pulse at its given total energy which, in particular, is important due to the latest achievements in the so-called postcompression of laser pulses to very short durations. It was shown that an optimum pulse length exists, which leads to maximum proton energy acquired in the regime of their maximum efficient synchronized acceleration by the “slow light” (A. V. Brantov et al., Phys. Rev. Lett. 116 , 085004 (2016) [1]) and that the ultra shortening of the laser pulse does not lead to the increase in the maximum ion energy despite the increased intensity of laser light.