Modelling of laser produced plasma and time-of-flight experiments in UV laser ablation of aluminium targets

Experimental and theoretical analysis have been performed to investigate UV laser ablation of Aluminium targets irradiated in vacuum. From time-of-flight (TOF) investigation a direct characterisation of the ions kinetic energy distribution and yield as a function of the laser fluence has been obtained. Moreover, the total yield of charged particles (ions and electrons) has been investigated. All the investigated plasma parameters strongly depends on the laser fluence until a roll off is reached at higher irradiance. This behaviour has been analysed by discussing a laser–solid-plasma interaction model taking into account photon absorption and ionisation mechanisms active in the Al plasma as well as laser produced plasma kinetics. Calculations suggest that the observed behaviour is due to plasma kinetics and shielding occurring around 1 GW cm−2 in nanosecond pulsed laser ablation of Al targets.