Steady radiation fronts behind windows

Abstract

If radiation of constant intensity W ionizes a gas of density ρ1 behind a window, a steady radiation front may be established and the gas will be heated, accelerated, and compressed. The properties of such radiation-induced waves are discussed as a function of the external parameters W and ρ1. With high absorber density ρ1 the radiation front acts like a "leaky piston" accelerating and compressing the neutral gas ahead, and leaving plasma of reduced density behind. This leads to the formation of a precursing shock wave travelling at vshock α (W/ρ1)1/3. The shock develops as a sharp spike near the Jouguet point which requires a sonic speeds a4 α (W/ρ1)J1/3in the ionized gas. With lower absorber density, the radiation front propagates as vr α W/ρ1 and accelerates and compresses the ionized gas at its rear. This plasma is then brought to rest and expanded in a subsequent rarefaction wave.