Time-resolved analysis and optical diagnostics of Trichel corona in atmospheric air

Trichel pulses of negative corona discharge in atmospheric air are investigated in a needle-to-plate configuration. Time-resolved images of the pulsed discharge are recorded by using an ICCD camera. Light emission spectra of N₂ molecules and ions during the discharge are measured by optical diagnostics. The distributions of the positive ions and the reduced electric field along the discharge channel are analyzed accordingly. The results show that the positive ions that can accumulate in space and distort the electric field play an important role on the formation of the Trichel pulse. The Trichel pulse is a mode transition between low-current Townsend discharge and high-current glow discharge. The rising time of the pulse corresponds to the breakdown and formation of glow discharge, and the decay time is related to destroy the process of positive ion clouds and the quenching of glow discharge. The time interval between the pulses is determined by the re-accumulation of positive ions near the cathode in the low-current Townsend discharge to form the positive ion clouds as well as a strongly-distorted electric field.