Expansion dynamics of the plasma plume created by laser ablation in a background gas

The dynamics of the expansion of the plasma plume induced by laser ablation of a copper target at a fluence of 17 J/cm(2) was investigated theoretical ly by means of a Monte Carlo simulation. When the expansion occurs under a relatively high pressure, the ambient gas particles may be involved in the collective motion of the plume. The simulation allows the study of the simu ltaneous collective motion of different species, such as the laser-ablated and the ambient gas particles. The influence of the background gas, nature and pressure on the laser-induced plasma plume expansion behavior was studi ed. The expansion dynamics were found to be different in the case of the expans ion in ambient gases of different molecular weight. The dynamics of the plu me expansion under an argon pressure of 200 Pa seem to be strongly related to the equilibration of the pressure gradients in the gas phase, and eviden ce of the oscillatory behavior of the plume expansion was shown from the ev olution over time of the pressure profiles in the plume. This behavior has also been observed in similar conditions for a krypton atmosphere, but fora lower pressure than for argon. The vortical flow formation at the plume pe riphery, involving both the laser-ablated and the argon particles at modera te pressure, was also predicted from the Monte Carlo simulation.