Two-Step Spheroidal Shock Wave Driven by TEA CO2 Laser

Abstract

A conical target made of brass was irradiated by a transversely excited atmospheric CO2 laser having a pulse duration of ∼ µs in atmospheric air and He. A two-step structure composed of two spheroidal shock waves was observed to be driven by the irradiation. The shock front evolved at more than 7 km/s corresponding to a shock Mach number of 20. Before the two-step evolution of the shock wave, we observed a streamer-like structure in the laser-irradiated region, which indicates a phenomenon driven by energetic electrons.