Study of Dielectric Barrier Townsend Discharge in 3-mm Air Gap at Atmospheric Pressure

Diffuse dielectric barrier discharge was first produced in 3-mm-thick air gap at atmospheric pressure using two plane parallel electrodes each covered by one specific alumina plate with a thickness of 2.3 mm. Based on the discharge photographs of 10 ns exposure time taken with an intensified CCD camera, the diffuse discharge was identified with Townsend discharge. The Townsend breakdown voltage for this 3-mm air gap is about 5.7 kV, significantly lower than 11.2 kV, the streamer breakdown voltage of the air gap. If the alumina plate is too thin, the discharge transits to filamentary discharge. If it is too thick, the discharge is too weak to observe. Thermally stimulated current experiments revealed that there exist more shallow traps in the ceramic than in quartz plate after discharge pretreatment. The uniqueness of the shallow traps in the surface of the specific alumina plate, as well as the effect of the current limitation by dielectric leads to a Townsend discharge.