Comparative study of streamer inception in pulsed dielectric barrier discharges in Ar and N₂-O₂ mixture

Pulsed-driven single-filament dielectric barrier discharges (DBDs) in a symmetric configuration with hemispherical electrodes are investigated by time-dependent, spatially two-dimensional fluid modelling. The fluid model comprises balance equations for the particle number densities, the electron energy density, and the surface charges as well as Poisson's equation. The numerical analysis is carried out at atmospheric pressure for Ar and for N₂ with an admixture of 0.1 vol. % of O₂ to analyse different features during discharge inception and streamer propagation. The comparison of modelling results with measured currents and streamer velocities shows good agreement. The temporal evolution of the spatial profiles of the particle number densities and the electric field are used to study the Townsend prephase and the streamer breakdown of the DBDs. The discharges show a qualitatively similar behaviour during the streamer propagation, while the streamer inception differs significantly for the DBD in Ar and in the N₂-O₂ mixture. The current rise and streamer propagation are considerably slower in Ar, which is connected to the lower breakdown voltage in Ar compared to N₂-O₂.