Numerical Studies on the Nonlinear Coupling in Atmospheric Dual Radio-Frequency Dielectric Barrier Discharge

Abstract

Dielectric barrier discharges (DBD) as a common method to generate plasmas with high density, low gas temperature, and abundant active particle under atmospheric pressure have been widely investigated in the past decades. Among these researches, the investigation on plasma parameters modulation represents a novel and budding focus. According to our previous works of DBD driven by dual-frequency, it has been demonstrated to provide a possible approach of controlling both averaged electron density and gas temperature independently based on the nonlinear frequency coupling effect. In this work, we used one-dimensional fluid model with semi-kinetic method, systemically studied the nonlinear behavior of the dual radio-frequency driven DBD. In term of the results of effective electron energy distribution function (EEDF) and electron impact ionization rate, it is found that the variations of power density and phase relationship provide separate control over the electron density, mean electron energy and gas temperature. Moreover, mode transitions are discussed in this paper. It is shown that there exist three kinds of discharge modes, which are governed by the nonlinear dynamics in the plasma sheath. Among which, the ionization in α mode is determined by the nonlinear coupling electron heating and local momentary charge density. While in γ mode, the ionization is caused mainly by the electron avalanches. In summary, the dual radio-frequency applied in DBD system is found to generate a nonlinear synergistic effect between two frequencies, which can provide a possible approach to enhance control over the plasma parameters.