Design studies of copper strength via Rayleigh-Taylor instability from directly laser-driven experiments at the OMEGA-EP laser facility

We present the design of experiments conducted at the OMEGA-EP laser facility using face-on radiography to measure ripple growth in solid copper and other metals to understand their dynamic strength under high pressure and high temperature. Historically these ramp-compression experiments have been accomplished by releasing a reservoir of material from a laser driven hohlraum onto a target configuration of materials. Here the target containing the copper sample is directly irradiated by the laser. The ramp-compression is achieved by the laser pulse shaping. Strength is inferred from experimentally obtained measurements using face-on radiographic measurements of ripple growth which are then compared to simulated growth factors using different strength models. The copper was designed to follow two different loading paths to megabar pressures: first using a smooth ramp yielding a low-temperature adiabatic path; the other by first shocking to a given pressure and then accelerating it to create a high-temperature adiabat path. The design simulations were set up using a combination of 1D and 2D simulations and the growth factor calculated through an areal density integration method.