Simulations of high-gain direct-drive inertial confinement fusion targets*

Using the FAST radiation hydrocode, we report in this presentation on continuing numerical studies of the hydrodynamic stability of inertial-confinement-fusion targets. Our discussion focuses on a particular class of ``high-gain'' direct-drive targets that are irradiated with approximately 2.5 MJ of KrF laser light, and have fusion energy yields exceeding 100 times that value according to one-dimensional simulations. We model several different temporally-varying laser pulses --- including so-called ``relaxation'' and ``decaying-shock'' profiles with preceding ``spikes'' --- and examine the two-dimensional stability and gain characteristics for each. Both single-mode and broad-band outer-surface perturbations are considered, and where possible, their evolution is compared to quasi-analytical expressions for ablative Rayleigh-Taylor growth.