Generation of picosecond high-density ion fluxes by skin-layer laser-plasma interaction

The possibilities of producing ultrahigh-current-density ps ion fluxes by the skin-layer interaction of a short (<= 1ps) laser pulse with plasma were studied using two-fluid hydrodynamic simulations, and the time-of-flight measurements. Backward-emitted ion fluxes from a massive (Au) target as well as forward-emitted fluxes from various thin foil targets irradiated by a 1-ps laser pulse of intensity up to 2 X 10(17) W/cm(2) were recorded. Both the simulations and the measurements confirmed that using the short-pulse skin-layer interaction of a laser pulse with a thin pre-plasma layer in front of a solid target, a high-density collimated ion flux of extremely high ion current density (similar to 10(10) A/cm(2) close to the target), can be generated at laser intensity only similar to 10(17) W/cm(2). The ion current densities produced by this way were found to be comparable to (or even higher than) those estimated from recent short-pulse experiments using a target normal sheath acceleration mechanism at relativistic laser intensities. The effect of the target structure on the current densities and energies of forward-emitted ions is demonstrated.