MEASUREMENT OF RADIATION-DRIVEN SHOCK-INDUCED MIXING FROM NONLINEAR INITIAL PERTURBATIONS

We present the first experimental measurement of the growth of a mixin g region at a density interface from a high-amplitude, initially nonli near perturbation. Thermal radiation from a gold Hohlraum irradiated b y the Nova laser was used to drive a shock across a perturbed plastic- foam interface in a cylindrical shock tube attached to the Hohlraum. W hen the effects of target decompression are removed, the width of the mix region was found to grow logarithmically with time- in agreement w ith recent theories for the nonlinear phase of the Richtmyer-Meshkov i nstability.