Two-dimensional simulations of repetitive pulsed laser interactions with solid targets in air

Abstract

Summary form only given. When a repetitively pulsed laser beam of sufficient intensity strikes a solid target that is immersed in a gas at sufficient pressure, numerous interesting plasma phenomena take place. Of particular interest to us is the production of a sequence of laser-supported detonation waves that originate in the gas, as well as plume of target material that propagates into the gas from the focal spot of the laser beam. Both of these phenomena are observed in laboratory experiments: e.g. the case of a mode-locked CO/sub 2/ laser interacting with a solid copper target in neon at 1 atmosphere pressure. To aid in the understanding of these observations, we perform time-dependent numerical simulations of the propagation and partial absorption via inverse bremsstrahlung of a CO/sub 2/ laser beam through various gases at 1 atmosphere, and the subsequent interaction with solid copper and aluminum targets aligned at various angles with respect to the incident laser beam. For this numerical study, we use the general-purpose two-dimensional finite-difference MHD code MACH2. Our simulations are motivated by an earlier study by Buff et al. (1996). We include in our simulations the possible spontaneous generation of a magnetic field via the grad(P) term of a generalized Ohm's law.