Spatio-temporally resolved investigation of surface charges, N <inf>2</inf>A³Σ<inf>u</inf>⁺) metastables and discharge development in barrier discharges

Abstract

To study the interaction of an insulated surface with the volume of a barrier discharge, a discharge cell was developed to combine for the first time three diagnostic techniques in ONE discharge cell configuration. The discharge development was investigated by the cross-correlation-spectroscopy (CCS), the surface charge measurement on the dielectrics by the application of the optoelectronic Pockels effect in combination with a CCD camera, and the determination of the metastable N2(A3Σ u+) molecule by laser induced fluorescence spectroscopy. Under the conditions studied, in pure N2 and He the discharge usually operates in the diffuse Townsend-like mode. At over voltages in nitrogen as well as at small admixtures of N2 (in percent range) to He the filamentary mode appears. The time dependent surface charge density in the helium diffuse mode of about |σ |∼0.5nC/cm2 is in good agreement with the time integrated current pulses. The measurements in the filamentary mode show remaining charges from the previous half-cycle as well as a memory effect for the microdischarge ignition. The detection of the nitrogen metastables was performed in the filamentary mode, resulting in a density of about 1013 cm-3. The maximal density is reached clearly after the microdischarge and a difference between the anode and cathode phase is obvious. © 2012 Science & Technology Network, Inc.