Numerical Study on Mode Transition Characteristics in Atmospheric-Pressure Helium Pulsed Discharges With Pin–Plane Electrode

A 2-D fluid model is developed to study the pulsed discharges with pin-plane electrode in atmospheric pressure. A positive streamer forms at the pin electrode connecting to the applied voltage and then propagates toward to the ground plane electrode (cathode). Simulation results show if the streamer head is close enough to the cathode, in front of the original streamer a new streamer forms, and simultaneously a second positive current peak is observed, suggesting that the discharge mode transforms into glow mode. Otherwise, the discharge operates at corona mode. The characteristics of the two typical discharge modes are analyzed through the spatiotemporal evolution behaviors of conduction current, electron density, electric field, and electron flux. The transition between corona and glow modes depending on the discharge parameters such as applied voltage, curvature radii, and secondary electron emission coefficients are studied in this paper. It should be noted that no matter what discharge mode is, discharge with reversed direction appears at the falling edge of voltage pulse, which is caused by space charges.