Effect of pulse duration and coupling efficiency on laser generated shocks in multi-material targets*

The use of lasers as an alternative x-ray source to ablate and drive shocks in a target is an attractive possibility due to their wider availability. A practical application is the ablation of multi-material satellite components such as solar panels. It is therefore crucial to compare x-ray-driven and laser-driven shocks results. The first step for such a goal has been to validate the scaling of ablation pressure in a range of laser-pulse durations at constant laser intensity. However, the comparison between experiments and simulations exhibits discrepancies in the shock characteristics in the short (~100 ps) and long (~10 ns) pulse durations of the scaling.

In this work, we present a comparison between experimental and simulation shock conditions through the adjustment of laser conversion efficiencies. Quantities such as shock breakout time and shock velocity are matched and compared for the pulse durations of our scaling, investigating the modified plasma characteristics. Moreover, we address discrepancies between experimental and simulation density profiles encountered in late plasma expansion. Finally, we provide a physical explanation for the modified laser conversion efficiency, addressing skin effect and collisionless absorption for short pulses, and the development of laser plasma instabilities for long ones.