Influence of Target Cavity Formation on the Emission Spectra of Nanosecond Laser Ablation Plasmas

Optical emission spectroscopy as well as time-of-flight (TOF) measurements were performed in the diagnostics of nanosecond laser produced plasmas. The target is rotated during pulsed laser ablation at 5 GW/cm(2), where the optical emission spectroscopy is performed along, as well as perpendicular to the target axis. Parallel to the target axis, the continuum radiation intensity increases up to 6000 pulses, and emission line intensities from C I and C II increase for with number of pulses. Perpendicular to the target axis, decrease in emission line and continuum intensities were observed. TOF measurements resulted to carbon cluster ions detection from C-n(+) , n >= 2, where peak shift of 4 mu s towards later times were observed after 10000 pulses ablation. Charge collection experiments showed approximately 80 percent energy loss after 10000 shots. Collision-induced recombination mechanisms were suggested as causes of energy loss and line intensity decrease. (C) 2022 The Japan Society of Plasma Science and Nuclear Fusion Research