High Mach number mix instability experiments of an unstable density interface using a single-mode, nonlinear initial perturbation

The growth of an unstable density interface from a nonlinear, single-mode, two-dimensional initial perturbation (10 μm amplitude; 23 μm wavelength) has been studied experimentally using a miniature shock tube attached to a gold hohlraum irradiated by the Nova laser [J. T. Hunt and D. R. Speck, Opt. Eng. 28, 461 (1989)]. The initial perturbation was machined into a brominated plastic ablator (1.22 g/cm3) adjacent to a low density carbon foam (0.10 g/cm3). Upon laser illumination of the hohlraum and x-ray ablation of the plastic, a strong shock wave (Mach∼30) propagated across the perturbed density interface causing the onset of the Richtmyer–Meshkov (RM) instability. The interface subsequently experienced a relatively weak Rayleigh–Taylor (RT) unstable deceleration. The nonlinear growth of the mixing layer was obtained from time-resolved radiography of the x-ray transmission through the shock tube, and the decompression-corrected results were compared to published incompressible models, including a Lagrangian energy formulation. The experimental data were also compared with the results of two-dimensional numerical simulation.