Surface charge accumulation and discharge development in diffuse and filamentary barrier discharges operating in He, N2 and mixtures

A new discharge cell configuration was developed which allows the joint investigation of important volume and surface processes of the barrier discharge (BD) operation. In particular, the spatio-temporal and spectrally resolved discharge emission in the volume was studied together with the temporally resolved formation of surface charges on a dielectric BSO crystal. This was possible by the application of the cross-correlation spectroscopy and the electro-optic Pockels effect for surface charge measurement, respectively. Surface charges play an important role for the re-ignition of BDs. In pure nitrogen and helium, the diffuse Townsend-like discharge mode was studied, characterized by an emission maximum near the anode. Small admixtures of nitrogen to helium resulted in the filamentary discharge operation. Under these conditions, the importance of the so-called memory effect has been verified.The lateral extent of the discharge spots in the filamentary mode differs significantly for the positive and negative charges. Both can be approximated by Gaussian profiles. The deposited surface charges are in good agreement with the transferred charge of subsequent discharge breakdowns.