Self-similar spherical expansion of a laser plasma or of detonation products into a low-density ambient gas

Self-similar solutions are given which represent an analytic theory of a spherical explosion at the stage when the action of the mass source (a detonation wave in the explosive or an ablation front in an irradiated target) driving a shock wave in the ambient gas is relevant. It is shown that during this stage, which precedes that described by the conventional blast-wave theory, the velocity of the shock wave in the ambient gas is constant