Laser-induced deformation modes in thin metal targets

Abstract

Thin metal targets were irradiated with a Q-switched neodymium laser. The absorption of the laser energy produced a high-temperature and -pressure plasma which drove stress waves into the targets. In some cases the plasma was confined using the technique developed by Anderholm and it was found that the magnitude of the stress increased with confinement. The histories of the deformations were measured using quartz and single-slit diffraction gauges and two distinct deformation modes were discovered. The first occurred on a time consistent with the acoustic transit time through the target and the second occurred in terms of transit times, up to an order of magnitude later. This latter late-time deformation mode resulted in the permanent deformation of the targets.