Laser produced plasma interaction with a matter

Abstract

The model of plasma generation by laser radiation and plasma interaction with a copper target was proposed. The target heating, ablation and electron emission from the hot surface and atom ionization were considered. The target is presented as a semi-infinite body solving the heat conduction equation. The kinetics of the target evaporation was analyzed taking into account the direct atom flux and plasma back flux. The plasma interaction with the target was due to ion and back electron fluxes bombardment. A space charge sheath at the target surface was considered where the charge particles acquired their energy. The electron and target temperatures, sheath potential drop, plasma and neutral densities were calculated as dependencies on laser pulse time and low power density (∼ 1 MW/cm2) and spot laser radius 100 µm. The solution shows that the plasma not only shields the laser radiation from the target, but also converts absorbed laser energy transported by the plasma particles through the electrostatic sheath to the matter. Critical power density of laser irradiance was found, consequently no plasma was formed.