MECHANISMS OF LASER-SURFACE INTERACTIONS

Abstract

Abstract : This report describes experimental and theoretical investigations of the particle emission produced in a laser-surface interaction. Measurements have been made on the angular distribution of ions emitted from a tungsten target irradiated by a ruby laser at flux densities around 10 to 20 megawatts/sq cm. In the plane perpendicular to the plane containing the incident laser radiation and normal to the target surface the number of ions emitted follows a sq cos theta distribution where theta is the angle from the normal to the target. In the plane containing the laser radiation and the target normal, most ions appear to be emitted within approximately 15 degrees of the normal to the target. The energies of ions are also maximum in the direction normal to the target and fall off as the angle from the normal increases. Calculations on a model for heating an alkali ion plasma by absorption of laser radiation indicate that runaway heating can occur at flux densities around 10 to the 9th power watts/sq cm with particle densities around 10 to the 18th power/cu cm. The magnitudes and time histories of shock waves produced in nickel and carbon targets by absorption of laser radiation have also been calculated.