Influence of dielectric shape on the propagation speed and selectivity of cathode or anode directed surface ionization waves in dielectric barriers discharges

For plasma catalysis applications, the propagation of surface ionization waves (SIW) over dielectric (catalyst support) pellets in dielectric barrier discharges (DBD) is very important for plasma and catalyst interactions. Most past works have investigated the SIW propagation over spherical-like shaped dielectric pellets. The shape of the dielectric pellets is known to influence the performance of the packed bed DBDs [1]. In this work, we have compared the streamer propagation speed for semisphere, cone, and inverted semisphere shaped pellets through both experiments and computations in helium and oxygen mixtures for different voltage amplitudes and polarities. The computations have been performed using plasma hydrodynamics model nonPDPSIM [2]. The results show that the contrasting shapes have a strong influence on the surface streamer’s speed as well as electron impact excitation dynamics. A stronger cathode directed (CD) SIW and a much weaker anode directed (AD) SIW are generated at low voltage independent of the polarity for all shapes. At high voltage, the SIW propagating over the dielectric pellet is always stronger and the polarity can be used for selectivity control towards a dominant CD SIW or AD SIW. The selectivity aspect is also linked with the pellet shape.

[1] Takaki, K., K. Urashima, and J.S. Chang, Ieee Transactions on Plasma Science, 32(6), p. 2175-2183 (2004)

[2] Juliusz Kruszelnicki et al. J. Phys. D: Appl. Phys. 50 025203 (2017)