Aachen PK 2003 – scientific programme

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P: Plasmaphysik

P 10: Poster II

P 10.13: Poster

Tuesday, March 18, 2003, 17:30–19:15, Foyer

Investigations on drift waves in a helicon discharge — •Christiane Schröder, Olaf Grulke, and Thomas Klinger — Max-Planck-Institut für Plasmaphysik, Teilinstitut Greifswald, EURATOM Association, Wendelsteinstr. 1, 17491 Greifswald, Germany

Experiments on drift wave dynamics are conducted in the linear, magnetized (B = 20… 100 mT) plasma device VINETA. A helicon plasma source (pulsed RF power up to 5kW) is used to create a 4 m long Argon plasma column with peaked density profiles (n_max≈ 10¹⁹ m⁻³). Drift waves are destabilized in the region of strong density gradients. In the VINETA device single saturated modes as well as weakly turbulent states are observed. Electrostatic probes are used to measure time averaged plasma parameters as well as density fluctuations. Different probe positioning systems and an azimuthal 64 probe array allow for spatio-temporal characterization of the drift wave dynamics. In this paper we will present recent results on the characterization of the drift waves observed in VINETA for different operation parameters. Particularly, the influence of the magnetic field and neutral gas pressure is studied. Attention is also paid to the influence of velocity shear on the poloidal and axial wave structure. The observed frequencies, mode structures and growth rates are compared to a numerical solution of the drift wave dispersion relation in a cylindrical plasma.