2-D Initial Plasma Formation Modeling of High-intensity Laser Illumination of Polystyrene and Aluminum-Sapphire Targets*

A 2-D initial plasma formation model has been developed and integrated with the radiation-hydrodynamics code DRACO, for inertial confinement fusion (ICF) applications. The improved model was used in this study to simulate two planar-target experiments. The first experiment used a high-intensity 355-nm laser pulse to illuminate a polystyrene (CH) target, a typical ablator material for ICF. The effects of multi-photoionization, impact ionization, and recombination on the initial plasma formation in CH at different ICF-relevant laser intensity levels are described. The second experiment used an 800-nm laser pulse to illuminate an aluminum target. In this experiment, a long penetration length (~200 nm) is shown to be related to the ultrafast electron heat transport in the initial femtoseconds as well as to a long electron thermal diffusion length scale. By considering negative material pressures in solid aluminum, the simulated shock propagation dynamics demonstrate a reasonable agreement with experimental observations.