Radiative preheat in decelerating interface experiments on Omega

Results of recent experiments to assess the radiative and hot-electron preheat in decelerating interface experiments will be discussed. These experiments were performed on the Omega Laser at intensities of ∼ 10^15 W/cm^2. In decelerating interface experiments, preheat of an interior surface due to heating prior to shock arrival can alter the initial conditions for further evolution and can change the nature of the experiment. Simulations using the HYADES code suggest that radiative preheat alone causes the interface to move approximately 2μm before the shockwave reaches it. Hot-electron preheat could cause much larger motions. Models using increased radiation as a surrogate suggests that motions up to 50μm are possible. This experiment used VISAR to examine the motion of an Al sample layer at the interface during the period before the shock reaches it. The target forms a blast wave in an initial layer of polyimide, as is often done in hydrodynamic experiments. This work is supported by the Department of Energy under grants DE-FG03-99DP00284, DE-FG03-00SF22021.