Comparative study on atmospheric pressure helium barrier discharges with the planar dielectric surfaces and the wavy ones simulated by a fluid model

Abstract As a popular plasma source at atmospheric pressure, dielectric barrier discharge (DBD) has been extensively used in various application fields, which normally operates in a uniform mode or a filamentary mode depending on the experimental conditions. Previous studies revealed that the uniform mode transitions to the filamentary mode when one planar dielectric is replaced by a wavy dielectric [ Plasma Process. Polym. 17 1900182 (2019)]. In their paper gap width varies for different positions along the radial directions. Hence, it is hard to know whether the surface morphology or the gap width determines the discharge mode. Aiming to this status, with a 2-dimensional fluid model, DBD with two wavy dielectrics forming a uniform gap is compared to DBD with the planar dielectrics under the same gap width. Simulations indicate that there is one discharge pulse per voltage half cycle with the wavy dielectrics or the planar ones. However, current waveforms of the positive discharge and the negative discharge are symmetric with the planar dielectrics, while asymmetric with the wavy dielectrics. In addition, DBD with the planar dielectrics is in the uniform mode, while that with the wavy dielectrics operates in the filamentary mode. Moreover, the filaments in the positive discharge are complementary to those in the negative discharge. With the planar dielectrics or the wavy ones, the discharge commences from the Townsend discharge regime, which transitions to the glow discharge regime at the peak current moment. Finally, spatiotemporal evolutions of electron density and electric field are investigated to reveal the formation of the distinct modes with the different dielectrics.