Three — fluid hydrodynamic simulation of proton beam generation by a subpicosecond laser pulse

Abstract

The skin-layer ponderomotive acceleration (S-LPA) induced by a short laser pulse is considered to be a promising method of producing dense high-current ion beams having the potential to be applied in high energy density physics or for fast ignition of inertial fusion. In this contribution properties of proton beam generation by S-LPA are studied using a three-fluid relativistic hydrodynamic model of laser-plasma interaction. The numerical calculations were performed for the subpicosecond neodymium-glass laser pulses of intensities up to 1018 W/cm2 interacting with inhomogeneous plasma consisting of three fluids: electron, proton and Au ion fluid. The impact of the initial plasma density gradient and of the different ratio of fluids constituting the plasma slab on proton velocities and proton current densities is presented. In particular, it is shown that the proton velocity increases and the proton current density decreases when the heavy ion fluid content increases. It results in the proton beam intensity having the maximum for the specific ratio of proton and Au ion fluids. The numerical computations were compared to the results of experiment, in which a 1 ps laser pulse of subrelativistic intensity (1017 W/cm2) interacted with a single-layer (plastic) or a double-layer (plastic + Au) thin foil target.