Nonlinear aspects of hydrodynamic instabilities in laser ablation

Abstract

We report on our investigation of the Rayleigh–Taylor and Kelvin–Helmholtz (KH) instabilities in laser ablatively accelerated targets for a series of single mode perturbations. We find linear growth rates well below classical values and a cutoff in the growth rates for wavelengths less than the foil thickness. However, the striking result is the dominance of nonlinear effects, i.e., the KH rollup, for the short wavelength perturbations. Although the linear growth rate increases as k1/2 up to the cutoff, the KH rollup dominates at large k, drastically reducing the penetration rate of the dense spike below its free fall value in the nonlinear phase and effectively doubling the aspect ratio before foil breakup.