Laser-driven shock-wave propagation in pure and layered targets

Abstract

The propagation properties of laser-driven shock waves in pure and layered polyethylene and aluminum slab targets are studied for a set of laser intensities and pulse widths. The laser-plasma simulations were carried out by means of our one-dimensional Lagrangian hydrodynamic code. It is shown that the various parts of a laser-driven compression wave undergo different thermodynamic trajectories: The shock front portion is on the Hugoniot curve whereas the rear part is closer to an adiabat. It is found that the shock front is accelerated into the cold material till $t\approx 0.8\tau$ (where $\tau$ is the laser pulse width) and only later is a constant velocity propagation attained. The scaling laws obtained for the pressure and temperature of the compression wave in pure targets are in good agreement with those published in other works. In layered targets, high compression and pressure were found to occur at the interface of C${\mathrm{H}}_2$ on Al targets due to impedance mismatch but were not found when the layers were reversed. The persistence time of the high pressure on the interface in the C${\mathrm{H}}_2$ on Al case is long enough relative to the characteristic times of the plasma to have an appreciable influence on the shock-wave propagation into the aluminum layer. This high pressure and compression on the interface can be optimized by adjusting the C${\mathrm{H}}_2$ layer thickness.