Spatio-temporal evolution of laser ablation W plasma under low-pressure Ar gas and Ar plasma ambients

Understanding the spatio-temporal evolution of laser ablation plasma under low-pressure ambients is a crucial area of study in the field of laser-induced breakdown spectroscopy (LIBS). In this work, LIBS combined with plasma imaging is employed to diagnose the spatio-temporal evolution of laser ablation W plasma under Ar gas ambient and continuous Ar plasma ambient in low-pressure conditions. The results reveal that laser ablation W plasma under the Ar plasma ambient exhibits higher radiative recombination loss and radiative thermal bremsstrahlung loss in the early stages of spatio-temporal evolution. This leads to increased continuous radiation background and W II signal intensity. It is found that the electron temperature initially exhibits a brief decline, followed by an increase, and then slowly decreases. This corresponds to a temporary temperature drop caused by the inertia of plasma expansion, which is quickly compensated by the recompression of the shockwave layer. Plasma imaging results reveal phenomena of plume splitting, plume sharpening, and plume turbulence in laser ablation W plasma under the Ar gas ambient. The front position and area of the plasma plume under the Ar gas ambient and Ar plasma ambient are compared. In the later stages of temporal evolution, the plume area of the plasma can be described by a drag model. This study provides new insights into the physical mechanisms of laser ablation W plasma under different background ambients, which is important for real-time diagnostics of wall materials by LIBS during tokamak discharges.