Structure of flows due to interaction of CO2 laser pulse pairs with a target in air

An analysis is made of two pulses from an electric-discharge CO₂ laser, of 6–12 μs duration and separated in time, incident on a target surrounded by air of normal density. The main attention is concentrated on breakdown of air by the second pulse at a boundary separating the "cold gas" and the plasma generated by the first pulse ("hot gas"). A gasdynamic system of waves is then generated. It consists of an absorption wave traveling along the cold gas opposite to the laser radiation and a wave propagating along the hot gas toward the target. The best agreement between the theory and experiment is obtained employing a model in which an absorption wave travels along the hot gas in an overcompressed detonation regime. The density of the radiation flux needed to maintain such a wave is 20–30% of the average density of the laser radiation flux carried by the second pulse.