Experimental Investigation on the Decay Characteristics of C₄F₇N/N₂ Mixed Gas Plasma by Laser Thomson Scattering

The exploration of C₄F₇N/N₂ gas mixture, as a potential substitute for SF₆, is crucial for evaluating its dielectric recovery performance in circuit breakers. To obtain the decay characteristics of electron density (n_e) and electron temperature (T_e) in plasma within C₄F₇N/N₂ gas mixture, this paper establishes an experimental platform using Laser Thomson Scattering (LTS) and Laser-induced Plasma (LIP). A series of temporal and spatial evolution of electron density and temperature are yielded by coherent Thomson scattering of LIP with varying gas mixture ratios, and the decay exponent is obtained by power law fitting to evaluate the decay rate. The results indicate that the decay of the plasma accelerates with an increasing proportion of C₄F₇N. Notably, the decay index of electron density exhibits a decrement from -1.16 to -1.62 as the C₄F₇N mixing ratio increases from 10% to 100%. Moreover, the electron density decay rate in SF₆ plasma is found to be between the rates observed for the groups containing 50% and 60% C₄F₇N.