Optimizing gated detection in high-jitter kilohertz powerchip laser-induced breakdown spectroscopy
Powerchip lasers provide short, reproducible ablation pulses at rates in excess of a kilohertz, but the pulse to pulse jitter resulting from their passive Q-switches has prevented previous intra-pulse gated measurements. We have performed time-resolved measurements of the analytical figures of merit for the powerchip LIBS determination of copper in aluminum under air, argon and helium atmospheres. Minimum limits of detection were measured 25–125 ns after ablation and were as much as 15× better than the ungated values. These optimal delays would not require an optical delay line in most cases as a result of the short insertion delay of modern ICCDs. Argon cover gas was found to improve LODs slightly. Using gated detection, 1064 nm laser ablation and argon cover gas, we calculate a LOD as low as 0.65 ppm of copper.