Temporal Variation of Two-Dimensional Temperature in a Laser-Ablation Plume Produced from a Graphite Target

Laser-induced fluorescence imaging spectroscopy was employed for measuring temporal variation of two-dimensional temperature in plumes produced by laser ablation of a graphite target in ambient He gas. The plume temperature at 10 µs after laser ablation was 700–800 K. It decreased rapidly with time and reached ∼350 K at 0.3 ms. It was found that the decay curve of the plume temperature was roughly independent of the ambient He pressure. This is because the dominant cooling mechanism of the plume is adiabatic expansion. The relationship between the temporal decrease in the plume temperature and the growth of carbon clusters is discussed based on the experimental results.