Characteristics of Discharge Channel in Spark Discharge Assisted Laser-induced Breakdown Spectroscopy

The relationship between the discharge channel and the time delay between the spark discharge and the laser pulse in spark discharge assisted laser-induced breakdown spectroscopy was investigated by using a gate-able pulsed high-voltage power source as the power supplier of the spark discharge. It was demonstrated that under suitable laser pulse energy and geometrical arrangement of the electrodes, it was possible to change the discharge channel from "V-shaped" type to parallel type by adjusting this time delay. In the "V-shaped" discharge, the spark discharge was able to increase the diameters of the craters and deteriorate the lateral resolution. However, in the parallel discharge, the spark discharge did not increase the diameters of the craters ensuring that the spatial resolution in this technique was only determined by laser-ablation. Under the condition of parallel discharge, quantitative analysis of chromium in aluminum alloy with spark discharge assisted laser-induced breakdown spectroscopy was carried out and the limit of detection of chromium reached 8.8 ppm, which was 8 times better than that obtained in LIBS without the assistance of the spark discharge. By using spark discharge under external trigger mode in the spark discharge assisted laser-induced breakdown spectroscopy, it is convenient to realize parallel discharge and surface elemental analysis of samples under high spatial resolution.