Numerical simulation of He/CF₄ plasma for surface treatment of insulating materials

The surface modification of insulating materials by carbon-fluorine plasma can effectively enhance their surface flashover voltage. This study established a numerical simulation model for atmospheric-pressure He/CF 4 dielectric barrier discharge (DBD) driven by nanosecond pulse voltage. We investigated the electron density distribution and discharge evolution process in the He/CF 4 DBD, analyzing the densities, spatiotemporal distributions, and generation mechanisms of dominant positive ions, neutral species, and negative ions. Simulation results show that, three primary and secondary discharges are found within one discharge pulse cycle by observing the spatial distribution of particles of He * in a double-ring DBD. The primary discharge initiated during the rising edge of the pulse voltage and persisted until the initial voltage fall phase, while secondary discharges occurred during the later voltage fall stage. Regarding fluorocarbon species, the highest densities of CF 3 + and CF 3 − ions were observed at the discharge center region, whereas neutral CF 3 radicals predominantly accumulated near the dielectric tube wall. These findings provide valuable guidance for surface treatment of insulating materials.