A COMPARISON OF 3-DIMENSIONAL MULTIMODE HYDRODYNAMIC INSTABILITY GROWTH ON VARIOUS NATIONAL-IGNITION-FACILITY CAPSULE DESIGNS WITH HYDRA SIMULATIONS

Three similar cryogenic ignition capsule designs for the National Igni tion Facility [J. Lindl, Phys. Plasmas 2, 3933 (1995)] are analyzed to determine surface roughness specifications required to mitigate the g rowth of hydrodynamic instabilities. These capsule utilize brominated plastic, polyimid and copper-doped beryllium ablator materials respect ively. Direct three-dimensional numerical simulations with the HYDRA r adiation hydrodynamic code [M. M. Marinak et al., Phys. Plasmas 3, 207 0 (1996)] examine the growth of multimode perturbations seeded by roug hness on the outer ablator and inner ice surfaces. The simulations, wh ich showed weakly nonlinear behavior for optimized surfaces, were carr ied through ignition and burn. A three-dimensional multimode perturbat ion achieves somewhat larger amplitudes in the nonlinear regime than a corresponding two-dimensional simulation of the same rms-amplitude. T he beryllium and polyimid capsules exhibit enhanced tolerance of rough ness on both the ice and ablator surfaces. (C) 1998 American Institute of Physics.