3-DIMENSIONAL SIMULATIONS OF NOVA HIGH GROWTH-FACTOR CAPSULE IMPLOSION EXPERIMENTS

Capsule implosion experiments carried out on the Nova laser [IE. M. Ca mpbell et al., Rev. Sci. Instrum. 57, 2101 (1986)] are simulated with the three-dimensional HYDRA radiation hydrodynamics code [NTIS Documen t No. DE-96004569 (M. M. Marinak et al. in UCRL-LR-105821-95-3)]. Simu lations of ordered, near single mode perturbations indicate that struc tures which evolve into round spikes can penetrate farthest into the h ot spot. Bubble-shaped perturbations can burn through the capsule shel l fastest, in which case they cause even more damage. A simulation of a capsule with a multimode perturbation of moderate amplitude shows sp ike amplitudes evolving in good agreement with a saturation model duri ng the deceleration phase. The presence of sizable low mode asymmetry, caused either by drive asymmetry or perturbations in the capsule shel l, can dramatically affect the manner in which spikes approach the cen ter of the hot spot. Three-dimensional coupling between the low mode s hell perturbations intrinsic to Nova capsules and the drive asymmetry is found to be important, bringing the simulated neutron yields into c loser agreement with the experimental values. (C) 1996 American Instit ute of Physics.