Atmospheric-Pressure Air Glow Discharge in a Three-Electrode Configuration

Nonthermal non-self-sustained dc glow discharge in atmospheric-pressure air was developed in a three-electrode configuration. A self-sustained normal dc atmospheric-pressure glow discharge in helium served as a ldquoplasma cathoderdquo for the main discharge in ambient air. Conditions of discharge transfer from helium volume to atmospheric air are under investigation. It is shown that a smooth transfer between the discharges in both volumes takes place only at small gaps between the ldquoplasma cathoderdquo and the third electrode (less than 5 mm) as the voltage applied to the air gap is increased. For larger gaps, this transfer is accompanied by discontinuous changes in both the voltage and current. After the jump, the discharge is contracted. But if the interelectrode gap is increased (more than 10 mm), then two forms of the discharge exist in one discharge space: diffuse and contracted.