Speaker
Marcin Sleczka
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P2.1020.pdf
Modulation of the strike line position using control coils
in Wendelstein 7-X
M. Śl˛eczka1 , A. Ali2 , P. Drewelow2 , Y. Gao3 , M. Jakubowski1,2 , H. Niemann2 ,
A. Puig Sitjes2 , G. Wurden4 and W7-X team
1 Faculty of Mathematics and Physics, University of Szczecin, Szczecin, Poland
2 Max-Planck-Institut für Plasmaphysik, Greifswald, Germany
3 Forschungszentrum Jülich GmbH, IEK-4, Jülich, Germany
4 Los Alamos National Laboratory, Los Alamos, USA
The stellarator Wendelstein 7-X (W7-X) restarted operation in 2017 with ten divertor modules
made of inertially cooled graphite plasma-facing components (PFCs)[1]. They serve a purpose
of testing the heat and power exhaust concept of so-called island divertor before installation
of water-cooled divertor planned for 2020. The island divertor, developed at Wendelstein 7-AS,
uses large magnetic islands to remove heat and particles from the plasma boundary. As W7-X in
near future will operate as a quasi steady state device, it is crucial to control the power loads to
the divertor to avoid overheating. Therefore W7-X is equipped with ten 3D-shaped control coils
which, by creating additional magnetic fields, can be used to modulate position and geometry
of strike line and island divertor [2, 3]. This extra field can also correct symmetry of the field,
sweep the strike line on the target in order to avoid local overheating or change the X-point
position to control detachment.
We will present changes in the geometry of the island divertor as measured by the thermographic
diagnostics. Ten infrared cameras, one per each divertor, collected the temperature distribution
at the divertor surface. The THEODOR code was used for data analysis in order to extract
geometry and movement of the strike line on the horizontal and vertical elements of the diver-
tor during the discharge. Apart of small deviations due to error fields, the measured strike line
shows good agreement with predicted by field line tracing codes.
To observe the effect of the correction field on the strike line position and island divertor geom-
etry several discharges with different amplitude of the control coils DC currents (from -2000 A
to 2000 A) have been performed. Moreover, AC current of 600 A and frequency of 5 Hz was
used to sweep the strike line and caused its movement by a few centimeters.
References
[1] Wolf, R. C. et al. Nucl. Fusion 57, 102020 (2017)
[2] McCormick, K. et al. J. Nucl. Mater. 313, 1131-1140 (2003)
[3] Jauregi, E. et al. Fusion Eng. Des. 66-68, 1125-1132 (2003)
