Quasi-isentropic material property studies at extreme pressures: from Omega to NIF

Abstract

We are developing an experimental platform that can compress materials quasi-isentropically to very high pressures at ultrahigh strain rates. This laser driven, ramped (shockless) drive is used to study material properties such as strength, equation of state, phase, and phase transition kinetics under extreme conditions. We have achieved a ramped, shockless drive up to 2 Mbar on the Omega laser using both direct laser illumination and indirect x-ray illumination. In order to probe high-Z materials under extreme pressures, we are also developing high energy x-ray backlighters, 17 to 100 keV, created by high intensity (>1018 W/cm2) short pulse lasers (1 to 50 ps) such as the Titan laser at LLNL. Using a micro-wire embedded in a low-Z substrate, we have obtained radiographs with better than 10 ?m spatial resolution. This paper will show designs of isentropic platforms that can reach >10 Mbar on the NIF laser, using both direct and indirect drive configurations.