Nonlinear evolution of localized perturbations in the deceleration-phase Rayleigh-Taylor instability of an inertial confinement fusion capsule

The evolution of axially symmetric localized perturbations in the deceleration-phase Rayleigh-Taylor instability of an inertial confinement fusion shell capsule is studied by two-dimensional simulations. Large amplitude divot-like mass perturbations were tracked into the deeply nonlinear regime. Dense fluid spikes penetrating the hot spot as well as light material bubbles rising into the dense shell have been studied, using both a full physics model and a simplified classical model neglecting thermal conductivity and fusion reactions. The stabilizing effect of ablation due to electron thermal conductivity and fusion alpha-particle transport is found to be more pronounced for spikes than for bubbles. For small width perturbations, bubbles grow faster than spikes, contrary to classical model results.