THE EFFECT OF SHAPE IN THE 3-DIMENSIONAL ABLATIVE RAYLEIGH-TAYLOR INSTABILITY .1. SINGLE-MODE PERTURBATIONS

The nonlinear saturation amplitudes attained by Rayleigh-Taylor perturbations growing on ablatively stabilized laser fusion targets are crucial in determining the survival time of those targets. For a given set of baseline simulation parameters, the peak amplitude is found to be a progressive function of cross-sectional perturbation shape as well as of wave number, with three-dimensional (3-D) square modes and two-dimensional (2-D) axisymmetric bubbles saturating later, and at higher amplitudes than two-dimensional planar modes. In late nonlinear times hydrodynamic evolution diverges; the 3-D square mode bubble continues to widen, while the 2-D axisymmetric bubble fills in.