Three-dimensional single mode Rayleigh-Taylor experiments on nova.

The effect of perturbation shape on the growth and saturation of the Rayleigh-Taylor (RT) instability has been measured on brominated polystyrene 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 number and initial amplitude on foils of similar thicknesses accelerated with similar drives. The 3D mode is found to saturate later at a larger amplitude. During the nonlinear phase it evolves into narrow spikes joined by spike sheets surrounding wide bubbles, which continue to broaden. Differences in the evolution of the perturbations due to 3D shape effects are in quantitative agreement with our simulation results.