Laser-triggered ion acceleration with low-density targets

Still unreachable sub-GeV scale laser-accelerated ion energies per nucleon, necessary for a number of practical applications, can be obtained using a new generation ultrashort-pulse laser XCELS. To accelerate ions to such energies, it is proposed to use low-density targets obtained, for example, as a result of pre-irradiation of a solid-state foil with an additional, longer laser pulse. Targets with controlled preplasma on the front side make it possible to significantly increase the efficiency of electron heating and subsequent acceleration of ions by the charge separation field from the rear side of the target. This, in general, classical acceleration mechanism is compared with the recently proposed mechanism of synchronised acceleration of ions by 'slow light'. The PIC simulation of laser acceleration of protons is supplemented by hydrodynamic calculations to find the optimal preplasma profile, which allows high-energy particles to be most efficiently generated. The possibility of generation of a large number of protons with a 1 GeV energy-scale is demonstrated.