Measurements of ripple decay in reflecting shocks in epoxy under high energy density conditions.

Abstract

Polymers are widely used in high energy density (HED) experiments, but rheological properties, such as viscosity and strength, are often assumed negligible in modeling despite limited experimental validation. We report initial measurements of rippled reflecting shocks in epoxy using the Sakharov shock perturbation decay technique supported by analytical formulation from Miller and Ahrens [Rev. Mod. Phys. 63(4), 919 (1991)]. Experiments at the Jupiter Laser Facility employed drive beams delivering a 10 ns, 800 J pulse across an ∼600 μm spot, launching a shock above 400 GPa into epoxy. The highly reflective shock in the epoxy sample was diagnosed using velocimetry and optical pyrometry. Velocimetry showed strong reflectivity and evidence of perturbation structure and streaked optical pyrometry clearly captured spatial evolution of the perturbed shock and showed amplitude growth, decay, and phase inversion, in agreement with hydrodynamic simulations using ARES. Our demonstration of technical viability and the observation of rippled reflecting shocks in epoxy establish a path toward future quantitative constraints on polymer rheology in HED experiments.