Systematic investigation of density incrustation at low-Z/high-Z interfaces in HED systems

A systematic investigation of the phenomenon of density incrustation was done by performing radiation hydrodynamics simulations at the interface of low-Z and high-Z materials. In this work, a high-Z material was maintained at a very high temperature compared to an adjacent low-Z material. This led to propagation of heat wave and shock wave into the low-Z medium. Rarefaction of the high-Z interface was arrested by a shock compressed low-Z medium. A sharp increase in density (density incrustation) was observed in rarefying high-Z plasmas at the interface. Density incrustation was not observed when rarefaction in the high-Z material occurred in the absence of the adjacent low-Z medium or when the radiation drive was incident on the low-Z material transmitting heat wave and shock wave into the high-Z material. The effect of the radiation drive, opacity, and equation of state on density incrustation at the interfaces of different high-Z (Au, U, and Pb) and low-Z (CH, Be, and Al) materials was studied. We observed that the height of incrustation depends on the temperature of the radiation drive, density, and opacity of the low-Z arrester material. This work has significance in the design of inertial confinement fusion systems wherein peaking of density in rarefying high-Z plasmas increases the Atwood number, contributing toward the growth of Rayleigh–Taylor instability at the interface.