External characteristics of long gap AC and DC streamer discharges under low pressure

For the development of space power application, the research on discharge characteristics in vacuum is required. This paper carries out laboratory investigations of AC and DC discharge characteristics for 200–600 mm rod-plane gap within 2–60 kPa. The relationship between discharge voltage U and pressure P and the profile of discharge could clearly describe the characteristics of AC and DC discharges. The U-P curves under AC voltage have obvious saturation region which is caused by partially-developed streamer discharges. The external characteristics such as luminance, tortuosity and branching of discharge channels under different voltage modes are significantly different. Under negative DC voltage at 2 kPa, the self-organized ionization layer plays a decisive role in the development process of streamer which develops from the plane to the rod and has obvious dark space.