Characterization of a laser-generated LiAg plasma plume

摘要

Abstract: Time- and spatially-resolved spectroscopy in conjunction with detailed modeling constitutes a powerful technique for the understanding of plasma plume dynamics. To this end, in a series of experiments performed at Sandia National Laboratories, laser-generated LiAg plasma plumes were produced by irradiation of solid targets using a Nd laser. Time- and spatially-resolved (along a direction normal to the target's surface) optical spectra were recorded with a framing spectrograph. In order to limit gradients along a direction perpendicular to the target normal, targets with strips of LiAg coated on top of Pt were used. The PT plume collisionally confines the LiAg, thus reducing the LiAg lateral expansion. This technique allows a better characterization of the LiAg plasma. The spectra displays line transitions in Li and Ag atoms, and evidence of ions in the plume is suggested by the presence of forbidden lines and Stark-broadened line shapes. A spectroscopic model based on collisional-radiative atomic kinetics, detailed line shapes, and radiation transport calculations is used to interpret the data. From this analysis temperature, density and ionization in the plume as a function of time and position along the normal to the target surface can be extracted. !7