Berlin 2001 – scientific programme

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P: Plasmaphysik

P 8: Magnetic Confinement and Plasma Technology (Poster Session)

P 8.1: Poster

Monday, April 2, 2001, 12:30–15:00, AT2

Experiments on influencing the turbulence in the plasma boundary of Wendelstein 7-AS stellarator with active Langmuir probes — •Henning Thomsen, Martin Schubert, and Michael Endler — Max-Planck-Institut für Plasmaphysik, Teilinstitut Greifswald, Wendelsteinstrase 1, 17491 Greifswald

The fluctuations in the edge plasmas of magnetic fusion experiments are thought to play an important role in terms of anomalous energy and particle transport [1]. The possibility of changing turbulence properties by externally applying electrical signals to probes was already shown in smaller devices [2,3,4] One approach is to lock the turbulence on a mode by the application of external electric field and current patterns. Another method is to feed signals from passive Langmuir probes back into the plasma boundary with appropriate phase shifts. Therefore, experiments were carried out at the Wendelstein 7-AS stellarator to investigate the influence of these methods on the turbulence in the plasma boundary of a larger toroidal magnetic confinement device. Two movable poloidal probe arrays, one located on the inboard side of the vessel and the other on the outboard side, were used for the experiments. Those probe tips, that were not used for feeding-in signals, collected data from the fluctuations in the plasma boundary. Therefore, the influence of the active probes on the plasma turbulence could be studied in poloidal direction as well as toroidally. [1] B. Richards, Phys. Plasmas 1(5), 1994 ; T. Uckan, Nuc. Fus. 35(4), 1995 [2] Chr. Schröder, Th. Klinger, to be published