Numerical simulation on the characteristics of a micro-hollow cathode discharge with external surface of the cathode covered by a dielectric layer

Being able to generate a plasma denser than that in the usual micro-hollow cathode discharge (MHCD) device, a MHCD with the cathode outer surface covered by a dielectric layer has been numerically simulated in atmospheric pressure helium with a two-dimensional fluid model in this paper. Results indicate that before reaching a steady state, the covered MHCD sequentially undergoes three phases. In the initial phase, a strong discharge and a weak discharge appear in the vicinities of the cathode and the anode, respectively. Then, a positive streamer propagates along the axis from the anode to the cathode. After that, the entire gap between the two electrodes is filled with discharges. In addition, the evolution of averaged densities is given for various species. Moreover, voltage and current curves are compared for the covered and uncovered MHCDs in the steady state. As expected, the covered MHCD has an averaged electron density higher than that of the uncovered MHCD in the steady state. These results are helpful in generating an atmospheric pressure plasma with high electron density, which is important for the extensive applications of MHCD.