AVS 50th International Symposium
    Plasma Science and Technology Wednesday Sessions
       Session PS2-WeA

Paper PS2-WeA3
Generation Mechanism of the Atmospheric Glow in a DBD Configuration

Wednesday, November 5, 2003, 2:40 pm, Room 315

Session: Atmospheric Plasmas & Micro Discharges
Presenter: E. Aldea, Eindhoven University of Technology, The Netherlands
Authors: E. Aldea, Eindhoven University of Technology, The Netherlands
C.P.G. Schrauwen, TNO-TPD , The Netherlands
M.C.M. van de Sanden, Eindhoven University of Technology, The Netherlands
Correspondent: Click to Email
Conventional wisdom attributes the generation of atmospheric glow plasmas to gas pre-ionization, which is related to ions or to electron generation by metastable-metastable and metastable-surface collisions . However there is not yet unambiguous experimental evidence, which can prove the validity of either of the proposed mechanisms. Beside that this pre-ionization mechanisms can not explain either how the glow to arc transition a notorious instability of atmospheric plasmas is avoided. Therefore to our opinion the physical basis of the atmospheric glow remains an open and challenging issue. In this contribution we analyze the basic conditions needed for uniform glow plasma generation. A simple analysis of the glow generation indicates that it is extremely improbable that the metastables or ions can have a significant contribution to glow generation via a pre-ionization mechanism. The low diffusion rate of ions and metastables excludes any mechanism of streamers or electron avalanches superposition. The preionization mechanism based on ions or metastables cannot also explain why the standard breakdown mechanism of atmospheric plasma streamer breakdown does not occur. Besides these theoretical arguments no evidence was found in the experimental current-voltage characteristics, plasma emission or breakdown voltage suggesting a significant pre-ionization or even the presence of a large amount of metastables. We conclude that the major problem in generation of atmospheric glow plasma is glow to arc transition. In this respect metastables are rather the problem for a stable plasma generation because their presence enhance the probability of stepwise ionization and glow to arc transition. The experimental data suggests that the surface of the dielectrics plays a major role in uniform and stable atmospheric glow plasma generation. The surface effect is probably due to a high secondary emission at the surface.