Ablative Richtmyer--Meshkov instability: Theory and experimental results

Abstract
Rayleigh-Taylor instability, the main source of symmetry degradation in ICF experiments, is seeded at the early stage of an implosion, during the shock transit through the shell. The ablation-front nonuniformities at such a time can be amplified by an instability, which is similar to the Richtmyer-Meshkov instability. In the presence of ablation, however, the dynamic overpressure (rocket effect) significantly reduces the perturbation growth. The modes localized inside the conduction zone between the laser-absorption region and the ablation front are totally stabilized. An analytical model is presented to describe the perturbation evolution at the ablation front during the shock propagation time. The model is compared against the results of both the multidimensional simulations and a series of experiments performed on the OMEGA Laser System.