Abstract
A simple analytical model is presented to study hydrodynamic perturbation growths induced by nonuniform laser ablation in the start-up phase in laser fusion. Namely, propagation of a rippled shock and deformation of an ablation surface caused by nonuniform laser ablation are studied for cases of initial target roughness and nonuniform laser irradiation. The perturbation growth is very important because it seeds the Rayleigh-Taylor instability in the subsequent acceleration and stagnation phases. In result, it can be shown that high intensity of laser irradiation promotes the ablation surface to distort and short wavelength of laser inhibits its deformation. Those behaviors are also investigated in the case that nonuniformity of laser irradiation oscillates with time.
