Frequency Effects on Helium–Oxygen Dielectric Barrier Discharges from Multibreakdowns to Single Breakdown per Half-Cycle

In this work, a one-dimensional fluid model is established to study the effects of frequency on (He + O 2 ) dielectric barrier discharge. As the frequency increases from 20 to 30 kHz, the first pulse becomes more intensive, while the second pulse gradually decreases and finally disappears. The plasma transforms from multibreakdowns to single breakdown per half-cycle. In order to study the production of reactive oxygen species (ROS) during this transformation, the spatiotemporal distributions of ROS densities are presented and the average ROS densities, as well as their wall fluences, are statistically analyzed. It is suggested that the production of each species increases along with the frequency, but when the second pulse disappears, the productions of some species, such as O^ - and O_2^ * , decline slightly. Moreover, the wall fluence and average density of a specific species vary with similar trends.