Effect of Matrix Thermal Properties on Laser Induced Plasma

Abstract

The matrix thermal properties have an important impact on laser induced plasma, as the thermal effect dominates the interaction between ns-pulsed laser and matter, especially in metals. We used a series of pure metals and aluminum alloys to measure plasma temperature and electron density through laser-induced breakdown spectroscopy, in order to investigate the effect of matrix thermal properties on laser induced plasma. In pure metals, a significant negative linear correlation was observed between the matrix thermal storage coefficient and plasma temperature, while a weak correlation was observed with electron density. The results indicate that metals with low thermal conductivity or specific heat capacity require less laser energy for thermal diffusion or melting and evaporation, resulting in higher ablation rates and higher plasma temperatures. However, considering ionization energy, thermal effects may be a secondary factor affecting electron density. The experiment of aluminum alloy further confirms the influence of thermal conductivity on plasma temperature and its mechanism explanation.