Two-dimensional simulation of a low-current dielectric barrier discharge in atmospheric helium

A two-dimensional computational study is presented to unravel radial structure of a dielectric barrier discharge in atmospheric helium when the gas voltage exceeds slightly the breakdown voltage and the discharge current is low to retain a repetitive dynamic pattern of one discharge event every half cycle of the applied voltage. Simulation results reveal that during each half cycle of the applied voltage gas breakdown occurs first in a central region around the electrode axis. After it is extinguished, a second breakdown is triggered in the boundary region near the radial edge of the two electrodes as confirmed by the dynamic evolution of the radial profile of the electric field, the current density and the charged particles. These predictions are consistent with relevant experimental observations in literature. It is also shown that an increase in the applied voltage or in the excitation frequency reduces the time delay between the two breakdown events and the difference between their corresponding current densities. This offers a route to improve the uniformity of atmospheric dielectric barrier discharges for their intended applications.