PROPAGATION OF A RIPPLED SHOCK-WAVE DRIVEN BY NONUNIFORM LASER-ABLATION

A simple analytical model is presented to study hydrodynamic perturbat ion growth in the start-up phase in laser fusion, namely propagation o f a rippled shock driven by nonuniform laser ablation induced by initi al target roughness or nonuniform laser irradiation. Analytical result s agree quite well with experimental data for the rippled shock propag ation in the case of uniform irradiation on a rough surface. Approxima te formulas expressing both the time evolution of the shock front and the asymptotic behavior of the ablation front are obtained in the weak shock limit.