Influence of sample temperature on nanosecond laser-induced Cu plasma spectra

Abstract

There are many experimental methods to increase the emission intensity of laser-induced breakdown spectroscopy (LIBS). Among these methods, pre-heating the target is a simple and effective method to improve LIBS signal intensity. This study used Nd: YAG nanosecond laser pulse to ablate Cu target and produce Cu plasma, and time-resolved spectra of the Cu plasma were measured at different Cu temperatures. The measurement suggested that the higher the target temperature, the stronger the time-resolved spectra of the Cu plasma, and the higher the time-resolved electron temperature and density. Next, the morphology of ablation craters was observed by microscope at different target temperatures. As the Cu target was heated, the melting area in the center of ablation crater became larger, which indicated that more mass targets were ablated to produce plasma, thus producing stronger spectral signal. Finally, the thermal behavior of Cu at different target temperatures was simulated by one-dimensional heat conduction equation. The simulated results show that the temperature of the Cu under laser irradiation increased with the increase of initial temperature of the Cu, and the melting depth also increased, which was consistent with the observed results of Cu target morphology.