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(OV/2-4) Major Results from Wendelstein 7-AS Stellarator

F. Wagner1), R. Burhenn1), F. Gadelmeier1), J. Geiger1), M. Hirsch1), H.P. Laqua1), A. Weller1), A. Werner1), S. Baeumel1), J. Baldzuhn1), R. Brakel1), A. Dinklage1), P. Grigull1), M. Endler1), V. Erckmann1), H. Ehmler1), Y. Feng1), R. Fischer1), L. Giannone1), H.-J. Hartfuss1), D. Hildebrandt1), E. Holzhauer1), Y. Igitkhanov1), R. Jaenicke1), M. Kick1), A. Kislyakov2), A. Kreter3), J. Kisslinger1), T. Klinger1), S. Klose1), J.P. Knauer1), R. Koenig1), G. Kuehner1), H. Maassberg1), K. McCormick1), D. Naujoks1), H. Niedermeyer1), C. Nuehrenberg1), E. Pasch1), N. Ramasubramanian1), N. Rust1), E. Sallander1), F. Sardei1), U. Wenzel1), H. Wobig1), E. Wuersching1), M. Zarnstorff4), S. Zoletnik5), W7-AS Team1)
1) Max-Planck-Institut für Plasmaphysik, EURATOM Assoc., Garching/Greifswald, Germany
2) IOFFE-Institute, St. Petersburg, Russia
3) Forschungszentrum Jülich, EURATOM Association, Jülich, Germany
4) Princeton Plasma Physics Laboratory, Princeton, USA
5) KFKI-RMKI, EURATOM Association, Budapest, Hungaria

Abstract.  W7-AS operates with an island divertor, which utilises the natural edge islands of the low-shear stellarator configuration to divert the plasma. High densities (up to 4×1020m- 3) and partly detached divertor conditions have been attained. The details of the divertor operation will be described along with the 3D-efforts to model the divertor observations. At a density beyond 1.5×1020m- 3 another confinement bifurcation appears, which allows steady state operation at good energy and low impurity confinement. The transition is possible from a state of normal confinement or from ELMy or quiescent H-modes. Starting with normal confinement, bifurcation is initiated by a broadening of the density profile. This regime can easily be heated above cut-off by ECRH using electron-bernstein-wave mode conversion. The highest beta-values (>3%) are achieved at high density. The relevance of the W7-AS data for Wendelstein 7-X and the Helias-reactor will be discussed.

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IAEA 2003