Diagnostics of the Carbon Plasma Plume Produced by Laser Ablation of Graphite in Vacuum

Abstract

A carbon plasma plume was produced in a vacuum by ablating a graphite target using KrF excimer laser, Nd:YAG laser second harmonic and fundamental light. Emission spectroscopy, two-dimensional laser induced fluorescence (2D-LIF), spectral absorption and ion probe diagnostics measurements were used to measure C atoms, C⁺ ions, C₂ and C₃ molecules in the carbon plasma plume versus laser wavelength and laser fluence. The 2D-LIF images examined the temporal and spatial profiles of C₂ and C₃ near the target surface. It was found that the KrF laser of 248 nm ablated species of carbon atoms and ions with highly excited electronic states from the target, and C₂ and C₃ were also found near the target. Nd:YAG laser light of 532 nm more effectively produced C, C⁺ than the fundamental Nd:YAG laser light of 1064 nm. The carbon species produced by the Nd:YAG laser of 1064 nm were thought to result from the thermal evaporation of the target by laser heating.