Plasma parameters characterization of laser induced breakdown spectroscopy on solid materials at different wavelengths

Abstract

The purpose of this research is to investigate the influence of laser wavelength on the plasma parameters in Laser Induced Breakdown of three different types of samples. The samples used were carbon rod, iron rod and stainless steel which represent non-metal, metal and alloy sample respectively. The source used is Nd:YAG laser operating at 1064 nm and 532 nm with laser energy of 150 mJ and 110 mJ respectively. The experiment was conducted in air at atmospheric pressure. The samples were placed at 5 cm, approximately 45º from a detector and 12 cm from the laser source. The plasma emission spectra were recorded and analyzed. Plasma parameters that have been taken into consideration were plasma emission spectrum, area of ablated surface, plasma spark shape, plasma electron temperature and plasma electron density. The results show that each sample produced different emission spectra. In addition the carbon sample shows the largest circular ablated area with radius 1.313 mm when generated using 1064 nm laser. Each sample produces different shapes of plasma sparks when generated using both laser sources. The plasma electron temperatures of carbon and iron samples produced by 1064 nm laser were estimated at 36671 K and 28200 K respectively while those generated with 532 nm laser were at 27271 K and 21585 K respectively. The stainless steel is consisted of Fe, Ni, Cr and Mn elements. The plasma electron temperatures of these elements were 21005 K, 2901 K, 10676 K and 12649 K respectively when generated using 1064 nm laser and 15202 K, 2785 K, 9748 K and 11697 K respectively using 532 nm laser. The other result shows that carbon rod as a non-metal sample has the highest plasma electron density when generated using 532 nm laser while the stainless steel sample has the highest plasma electron density when used with 1064 nm laser. In conclusions, the plasma emission spectra in all samples have been captured. The study shows that both types of laser are suitable for elemental detection. The plasma electron temperature and the plasma electron density have been determined for both laser sources.