Measurements of rarefaction wave dynamics driven by shock-release in conditions relevant to inertial confinement fusion

The kinetic energy of material released by the initial shock-breakout plays a critical role in determining the hot-spot pressure at the onset of deceleration and therefore the final stagnation conditions of inertial confinement fusion (ICF) implosions. Accurate characterization of the shock release is essential for improving predictive models and optimizing implosion performance. We report on a series of experiments designed to infer the properties of the release material via measurements of shock velocity driven by a collision of the shock release with a witness. These experiments employed a variety of radiative preheat shielding configurations to enhance signal fidelity for the Velocity Interferometer System for Any Reflector (VISAR) diagnostic at early times during the collision. Minimizing preheating of the witness enables probing a wide range of densities in the tail of the shock release rarefaction wave. Experimental results in both planar and spherical geometries are presented and compared with radiation-hydrodynamics simulations. These findings provide valuable constraints for ICF simulation codes and contribute to ongoing efforts to improve ICF implosion convergence.