Аннотация:The CIP method is used to calculate macroscopic plume expansion combined with the Zeldovich-Raiser theory for cluster formation process such as nucleation and growth. The effect of background gas and latent heat is examined in one-dimensional case. The latent heats keep the plume temperature at 2500K for a long period and this explains the delayed photoluminescence. Two contradicting experiments on the size dependence on ambient pressure are clearly explained and are attributed to the difference of laser energy. In two dimensional simulation, mushroom-like plume shape is replicated consistent with experimental results.