Experimental measurements of rippled shock evolution in laser-driven targets at extreme pressures using 1D VISAR*

We present the first results on time-resolved measurements of rippled-shock evolution at high energy density (HED) pressures using 1D VISAR and SOP diagnostics on the OMEGA EP laser. The experiment involves irradiating a target consisting of CH ablator and fused-silica sample with a modulated interface using two beams (~2.5 kJ, 20 ns), resulting in a ~300 GPa shock. The planar shock, driven by ablation, acquires the modulation at the interface, transitioning into a rippled shock. Initial shock amplitude is determined through shock-breakout times and impedance matching at the interface. Spatially and temporally resolved velocity of the rippled shock, extracted from VISAR data, enabled continuous tracking of its spatial amplitude. Our results are compared with synthetic diagnostics from 2D FLASH simulations, which not only qualitatively reproduce the observed data but also provide insights into the experiment's hydrodynamics. Expanding upon Sakharov et al.'s (1965) novel approach of estimating shear viscosity via perturbation decay on a rippled shock front, our technique shows promise in quantifying viscosity under extreme pressures in laser-driven experiments.