Effects of Oxygen Concentration on Pulsed Dielectric Barrier Discharge in Helium-Oxygen Mixture at Atmospheric Pressure

In this work the effects of O₂ concentration on the pulsed dielectric barrier discharge in helium-oxygen mixture at atmospheric pressure have been numerically researched by using a one-dimensional fluid model in conjunction with the chosen key species and chemical reactions. The reliability of the used model has been examined by comparing the calculated discharge current with the reported experiments. The present work presents the following significant results. The dominative positive and negative particles are He₂⁺ and O₂⁻, respectively, the densities of the reactive oxygen species (ROS) get their maxima nearly at the central position of the gap, and the density of the ground state O is highest in the ROS. The increase of O₂ concentration results in increasingly weak discharge and the time lag of the ignition. For O₂ concentrations below 1.1%, the density of O is much higher than other species, the averaged dissipated power density presents an evident increase for small O₂ concentration and then the increase becomes weak. In particular, the total density of the reactive oxygen species reaches its maximums at the O₂ concentration of about 0.5%. This characteristic further convinces the experimental observation that the O₂ concentration of 0.5% is an optimal O₂/He ratio in the inactivation of bacteria and biomolecules when radiated by using the plasmas produced in a helium oxygen mixture. (paper)