3-DIMENSIONAL SINGLE-MODE RAYLEIGH-TAYLOR EXPERIMENTS ON NOVA

The effect of perturbation shape on the growth and saturation of the R ayleigh-Taylor (RT) instability has been measured on brominated polyst yrene foils driven by x rays. We compare RT growth of 3D square (k(x) = k(y)) and 2D (k = k(x)) perturbations having the same total wave num ber and initial amplitude on foils of similar thicknesses accelerated with similar drives. The 3D mode is found to saturate later at a large r amplitude. During the nonlinear phase it evolves into narrow spikes joined by spike sheets surrounding wide bubbles, which continue to bro aden. Differences in the evolution of the perturbations due to 3D shap e effects are in quantitative agreement with our simulation results.