Berlin 2014 – scientific programme

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P: Fachverband Plasmaphysik

P 5: Low Temperature Plasmas I

P 5.2: Topical Talk

Monday, March 17, 2014, 17:00–17:25, SPA HS201

The influence of small oxygen admixture to helium on the barrier discharge operation — •Marc Bogaczyk¹, Lenka Dosoudilova², Robert Tschiersch¹, and Hans-Erich Wagner¹ — ¹Institut für Physik, Ernst-Moritz-Arndt Universität, 17489 Greifswald — ²Department of Physical Electronics, Masaryk University, 60200 Brno

An innovative discharge cell configuration allows the investigation of important volume and surface processes during He/O₂ barrier discharge (BD) operation. The influence of small oxygen admixtures on the discharge mode was studied by electrical measurements combined with the electrically triggered cross-correlation spectroscopy disclosing the discharge development, and the measurement of surface charges on a BSO crystal by means of the electro-optic Pockels effect. A crucial influence of oxygen on the microdischarge (MD) formation is the effective quenching of helium metastables which induce secondary electron emission as well as Penning ionization of nitrogen impurities substantial for diffuse BDs. In the case of sine-driven BDs, adding more than 250 ppm of oxygen to helium causes a transition from the diffuse Townsend-like mode to filamentary MDs. In particular, the transition region is characterized by a rising number of successive Townsend-like breakdowns per half-period connected with an increasing oxygen admixture. Finally, the transition to the square-driven discharge operation results in higher power input which in turn aids filamentation, too. Supported by “Deutsche Forschungsgemeinschaft, Sonderforschungsbereich SFB TR24”.