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P: Plasmaphysik

P 11: Dusty Plasmas and Low Temperature Discharges (Poster Session)

P 11.21: Poster

Donnerstag, 5. April 2001, 12:30–15:00, AT2

Discharge Modes of a Free-Burning Argon Arc — •Gerrit Kühn, Fred Könemann, Jens Reiche, Wolfgang Mende, Erhard Schulz-Gulde, and Manfred Kock — Institut für Atom- und Molekülphysik, Abteilung Plasmaphysik, Universität Hannover

We present four different discharge modes observed in a free-burning argon arc, mainly by varying arc current and argon pressure. Starting with low currents less than 1A a new blue-column mode is observed along with strong erosion of the cathode. The second regime shows a constricted plasma with a spot that can randomly move over the surface of the cathode (spot mode). Increasing the current the discharge changes into the so-called diffuse mode with a plasma ball covering the tip of the cathode. Higher currents lead to another specific new mode characterized by a small hot plasma kernel in front of the cathode’s surface (blue kernel mode). We use different diagnostic techniques including emission spectroscopy, Rayleigh- and Thomson-scattering and laser-induced fluorescence to describe the different discharge modes and to measure plasma parameters like temperatures and densities.