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P: Plasmaphysik
P 8: Magnetic Confinement and Plasma Technology (Poster Session)
P 8.2: Poster
Monday, April 2, 2001, 12:30–15:00, AT2
Conditional averaging of fluctuations in the SOL of the Stellarator W7-AS — •O. Grulke1,2, T. Klinger3, M. Endler2 und A. Piel1 — 1IEAP,Christian-Albrechts-Universität, 24098 Kiel — 2Max-Planck-Institut für Plasmaphysik, EURATOM Association, 85748 Garching — 3Institut für Physik, Ernst-Moritz-Arndt-Universität, 17489 Greifswald
The results of an experimental study of the dynamics of large-scale density and potential fluctuations in the SOL of the stellarator Wendelstein-7AS are presented. The fluctuations are measured by electrostatic probes. To extract large-scale coherent fluctuation structures from the noisy uncorrelated background, data is analyzed with conditional averaging [1]. It turns out that monopole-like potential structures with typical lifetimes of 20µ s and spatial extension of 5mm-10mm propagate poloidally in ion diamagnetic drift direction. The cross-parameter study between potential and density fluctuations shows that the fluctuations are poloidally phase–shifted by −π/2. A toroidal phase shift is not observed. The results strongly support that the formation of the large-scale fluctuation structures is based on the interchange instability [2].
[1] Johnsen et al., Phys. Fluids 30(7),1987
[2] Endler et al., Nucl. Fusion 35(11),1995