Greifswald 2009 – wissenschaftliches Programm
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P: Fachverband Plasmaphysik
P 16: Poster: Magnetischer Einschluss
P 16.7: Poster
Mittwoch, 1. April 2009, 17:30–19:30, Foyer des IfP
Edge Turbulence Studies in the Helically Symmetric Experiment — •Mirko Ramisch1, Robert Wilcox2, F. Simon B. Anderson2, Ulrich Stroth1, Joseph N. Talmadge2, David T. Anderson2, and HSX Team2 — 1Institut für Plasmaforschung, Universität Stuttgart — 2The HSX Plasma Laboratory, University of Wisconsin-Madison
The helically symmetric experiment (HSX) is a modular stellarator featuring quasi-helical symmetry (QHS), which minimizes neoclassical transport and reduces viscous flow damping. Reduced viscous damping benefits turbulence generated zonal flows, which are considered as a trigger mechanism for transport barriers. Therefore, magnetic field optimization with respect to neoclassical transport could affect turbulent transport levels as well. In order to study the turbulence properties in QHS compared to a non-optimized configuration, the symmetry in HSX can selectively be degraded by means of auxiliary coils. A key issue is the effect of symmetry breaking on zonal flow damping. In a first step, a movable poloidal 16-pin Langmuir-probe array is used to detect turbulent structures in the density and the potential in the edge region of QHS plasmas. Special attention is paid to long-range correlations in the potential fluctuations, which are indicative for zonal flows. First results are presented. Coherent, low-frequency potential structures with long poloidal correlation lengths are found in a narrow radial range. In the same range, a reversal in the poloidal propagation of density structures is observed.