Expansion property of plasma plume for laser ablation of materials

We analysed the plasma expansion characteristics during a laser ablation process and derived dynamics equations to describe the plasma expansion. The equations include the plasma concentration spatial distribution equation, plasma expansion pressure equation and plasma dynamics equation for both the isothermal expansion stage and adiabatic expansion stage. The equations are reasonable, and the required parameters are related only to the laser parameters and materials properties, imparting the model with high versatility and practicability. The models were applied to a numerical simulation of plasma expansion characteristics in the laser ablation of a bronze-bonded diamond grinding wheel. The dimension of plasma isothermal expansion and plasma adiabatic expansion, the expansion velocity of the isothermal plasma, and the contour evolution of plasma expansion were determined. Experiments were then conducted with a high-speed camera to observe the same plasma expansion process for ablating the grinding wheel. A grating spectrometer was used to measure the emission spectrum during the laser ablation process, and the electron temperature and electron density were characterized. The results of the experiments and numerical simulation were found to be essentially consistent, verifying the accuracy and feasibility of the as-developed plasma dynamics equations, with positive implications for optimizing the laser ablation process. (C)2018 Elsevier B.V. All rights reserved.