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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.
IAEA 2003