Depth profiling of WTa based fusion-relevant samples using picosecond laser ablation

Abstract

This study presents a detailed picosecond LIBS analysis of WTa coatings on Molybdenum substrate with varying layer thicknesses for fusion relevant applications. Ps-LIBS is performed on three WTa layers; two without deuterium ($\sim$7 μm thickness) and one with deuterium ($\sim$1 μm thickness). The LIBS measurements are conducted under argon gas flow at $5\pm 0.2$ mbar pressure with different laser pulse energies (1 mJ, 3 mJ) and 100 spectra are recorded consecutively at one spot on the sample for different set of gate delay/gate width (200/200 ns, 300/300 ns, 450/450 ns). The obtained LIBS and Glow-Discharge Optical Emission Spectroscopy (GDOES) depth profiles are compared with the confocal microscopic measurements showing good agreement. Additionally, the ablation rate and layer thickness are calculated for different experimental conditions. The Calibration-Free LIBS approach is used for elemental analysis and the results are compared with GDOES results. The capability of ps-LIBS to quantify Ta in WTa alloy is explored for 2 at.% of Ta. However, due to higher ablation rate of laser and thin coating in WTaD sample, the layer is irradiated in few laser pulse and therefore, CF-LIBS analysis is not performed for it.