Monte-Carlo simulation of the laser-ablated particle transport under vacuum and background gas.

The expansion of the plasma plume created during the interaction between an excimer laser and a copper target is studied by a Monte-Carlo simulation. The global shape of the plume is followed in time using a three dimensional algorithm, allowing the simulation of the expansion both under vacuum and background gas. The laser energy absorption by the plume of evaporated part icles is found to have dominant effects on the plume shape. An approximatio n of these effects is made by taking into account a kinetic energy transfer in the plume through the recombination of ionized and excited particles by collisional recombinative processes. Results of the simulation of the expa nsion under vacuum are compared with experimental results obtained by fast photography of the plume and time of flight measurements. First results of the simulation by a Monte-Carlo method of the plasma plume expansion under residual pressure show clearly the snowplow of the leading edge of the plum e and the background particles deficiency:in the dense region of the plume. (C) Elsevier, Paris.