Monte Carlo simulation of the laser-induced plasma plume expansion under vacuum: Comparison with experiments

Abstract

The laser induced plasma plume expansion in vacuum is studied by a Monte Carlo simulation. An original method, which allows the simulation with no size restrictions on laser spot width or ablated depth, is presented. The global shape of the plume created above a copper target is followed in time by using a three-dimensional algorithm. Particles evaporation from the sample surface during the laser pulse duration is done by taking into account a radial distribution of laser energy and the influence of vapor pressure on surface temperature. The simulation indicates that, when much more than few monolayers are ablated, the laser energy absorption by the evaporated particles has dominant effects on the plume shape during the expansion process. An approximation of these effects has been done by considering that a fraction of the recombination of ionic and excited species leads to a delayed kinetic energy transfer in the plume. It was found that this contribution has a significant effect on the angular and kinetic energy distributions of the evaporated particles. Results of Monte Carlo simulations are compared with experimental results obtained by spectroscopic time of flight measurements and fast photography of the luminous component of the plume, a particular good agreement is obtained for kinetic energy distributions of particles.