Dynamics of Laser-Induced Shock Waves in Supercritical CO2

We studied the dynamics of laser-induced shock waves in supercritical CO2 (scCO2) for different pressures and temperatures under nanosecond optical breakdown. We estimated the shock wave pressure and energy, including their evolution during shock wave propagation. The maximal shock wave pressure ~0.5 GPa was obtained in liquid-like scCO2 (155 bar 55 °C), where the fluid density is greater. However, the maximal shock wave energy ~25 μJ was achieved in sub-critical conditions (67 bar, 55 °C) due to a more homogeneous microstructure of fluid in comparison with supercritical fluid. The minimal pressure and energy of the shock wave are observed in the Widom delta (a delta-like region in the vicinity of the critical point) due to the clusterization of scCO2, which strongly affects the energy transfer from the nanosecond laser pulse to the shock wave.