Effective post-acceleration of ion bunches in foils irradiated by ultra-intense laser pulses

Abstract

Two-step laser acceleration of protons with two foils and two laser pulses is modelled and optimized. It is shown that a nearly mono-energetic distribution of proton bunches can be realized by a suitable parameter choice. Two-step acceleration schemes make it possible to obtain both higher efficiency and energy as compared to the acceleration with only one laser pulse of an energy equal to the sum of the energy of the two pulses. With the aid of our analytical model, the optimal distance between the two targets, the delay between the two laser pulses, and the parameters of the laser pulses are determined. Estimates and results of the modelling are proven with 2D PIC simulations of the acceleration of proton bunches moving through the second target.

Accelerated protons with energies up to 70 MeV based on the optimized SG-II Peta-watt laser facility

“…Thus, the original electric field was inevitably attenuated; this resulted in a weakened total electric field. This was completely different from conventional cascade LDPA [ 60 ] , where the second electric field was generated with a second laser-driven film target, so the total effect of the two electric fields is increased. This was also confirmed by Chen et al [ 61 ] , who used a double-film target for LDPA experiments, which affected the quality of the proton beam but with lower cutoff energy.…”