Establishment and evolution of atmospheric pressure glow discharge channel by 2D simulation

This study combines experimental diagnostics and two-dimensional (2D) numerical simulations to elucidate the establishment mechanisms of atmospheric pressure glow discharge (APGD) channels under high-frequency AC voltage. Experimental investigations employing a needle-plate electrode configuration and a resonant power supply revealed two distinct discharge modes: unipolar, characterized by plasma formation exclusively during negative half-cycles, and bipolar, involving dualchannel development in both half-cycles. Numerical simulations based on fluid equations coupled with Poisson and photoionization models demonstrated that under the action of multiple cycles of voltage, accumulated charges will be generated within the channel. The accumulated charges will distort the local electric field, thereby lowering the breakdown voltage and facilitating stable plasma establishment. Photoionization was found to exhibit a diffuse spatial distribution with negligible channel acceleration, distinguishing APGD from streamer discharges. Crucially, increasing frequency or reducing gap distance elevated residual charge density by 1-2 orders of magnitude, triggering a transition to bipolar discharge with higher plasma density (electron density up to 10²⁰ m⁻³). These results establish residual-charge-induced field distortion as the fundamental APGD mechanism and provide quantitative guidelines (frequency/gap thresholds) for industrial plasma stabilization.