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approvedabstract_sherwood2016_florian_effenberg_v03-1.pdf2016-04-01 14:42:40Florian Effenberg


Author: Florian Effenberg
Requested Type: Poster
Submitted: 2016-03-20 10:11:25

Co-authors: Y. Feng, O. Schmitz, H. Frerichs, S. Bozhenkov, J. Geiger, H. Niemann, M. Jakubowski, R. Koenig, M. Krychowiak, H. Niemann, T. S. Pedersen, L. Stephey, G. Wurden

Contact Info:
University of Wisconsin - Madison
1500 Engineering Drive
Madison, WI   53706

Abstract Text:
The quasi-isodynamic stellarator Wendelstein 7-X finished recently its first plasma operation. The initial standard field configuration consisted of closed magnetic flux surfaces avoiding magnetic islands in the plasma boundary [1],[2]. The scrape-off layer (SOL) was defined by five distinct limiters enabling unique studies of aspects of 3-D plasma edge transport and plasma surface interaction (PSI). This contribution focuses on the numerical investigation with the 3-D fluid plasma edge and kinetic neutral transport code EMC3-Eirene and a first comparison with some experimental results. It is shown that the 3-D SOL consists of three separate helical magnetic flux bundles of different field line connection lengths LC. It is found that the plasma edge transport is strongly correlated with LC. Parameter scans are performed revealing e.g. a drop of limiter peak heat fluxes from 12 MWm-2 down to 7.5 MWm-2 and an increase of the heat flux channel widths λq by a factor of two with raising the density from 1×10^18 m−3 to 1.9×10^19 m−3. Initial analysis of IR camera observation data confirms the correlation between deposited heat flux and topology.
Finally, a iota scan was performed which causes a change of the edge topology with significant impact on the PSI according to EMC3-Eirene predictions. The change of the limiter heat load patterns observed with IR camera shows good agreement with the expectations from 3-D modeling.

* Work supported in part by start up funds of the Department of Engineering Physics at the University of Wisconsin - Madison, USA and by the U.S. Department of Energy under grant DE-SC0013911.

[1] S. Bozhenkov, F. Effenberg, et al., “Limiter for the early operation phase of W7-X,” 41st EPS Conference on Plasma Physics (2014).
[2] T. Sunn Pedersen et al., “Plans for first plasma operation of Wendelstein 7-X,” Nuclear Fusion, 55, 12, 126001–126013 (2015)

Physics of Plasma Edge and Divertor Region