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P: Fachverband Plasmaphysik
P 5: Sonstiges
P 5.2: Talk
Monday, March 30, 2009, 17:45–18:00, INP-Staffelgeschoß
Modulated ECRH scans in ASDEX Upgrade for electron heat transport studies — •Philip Schneider, Francois Ryter, Hans-Ulrich Fahrbach, Anja Gude, Fritz Leuterer, Marc Maraschek, Grigori Pereverzev, Dietmar Wagner, and the ASDEX Upgrade Team — Max Plank Institut für Plasmaphysik, EURATOM Association, D-85748 Garching, Germany
The new electron cyclotron heating system of ASDEX Upgrade is equipped with steerable mirrors, which allow us to vary the localized energy deposition position during a single plasma discharge. Combining modulation of the ECH power with the deposition scan, we investigated the profile of the electron heat conductivity (χe) and the possible existence of radially localized variations of this quantity. Usually, in power modulation experiments, the radial propagation of the heat pulses are analysed. In the present work we used a new approach better suited to search for local changes of χe: amplitude and phase of the induced Te modulation at the position of the ECH deposition are analysed. These two quantities react sensitively to the local value of χe and the results yield the profile of the heat diffusivity, which indeed exhibits local radial variations.
Besides local radial variations, which are clearly not due to MHD activity, we also investigated locked MHD modes, which show reduced transport inside an island and increased transport around it. Furthermore, the mode could be excited to rotate again due to ECH deposition at the island’s location.