Speaker
Alexander Knieps
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P2.1034.pdf
Investigating the outer magnetic field of Wendelstein 7-X using the
magnetic probe
A. Knieps1, P. Drews1, S. Liu1, C. Killer2, Y. Liang1, J. Geiger2, K. Rahbarnia2, D. Nicolai1,
G. Satheeswaran1 and the W7-X team2
1
Forschungszentrum Jülich GmbH, Institut für Energie- und Klimaforschung Plasmaphysik,
Partner of the Trilateral Euregio Cluster (TEC), 52425 Jülich, Germany
2
Max-Planck-Institut für Plasmaphysik, 17491 Greifswald, Germany
During the first phase of the second experimental campaign OP1.2a of Wendelstein 7-X
(W7-X) – featuring for the first time an island divertor – measurements of the edge magnetic
field profiles were conducted using the combined probe [1] mounted on the
Multi-Purpose-Manipulator (MPM) with its 3D coil array. The measurements with the
combined probe have been performed in different magnetic configurations as well as with
varying heating scenarios.
While the measured vacuum profiles matched the predictions quite well, it was observed that
the measurements with plasma deviated noticeably. This is in contrast to the first operational
campaign where the considerably lower pressures did not cause such a difference between
the vacuum fields and those with plasma.
The measurements have been performed in different magnetic configurations and for
different plasma heating scenarios which allows a dedicated comparison. Although W7-X
has been optimized for small bootstrap currents, finite toroidal plasma currents were present
in the scenarios and have been measured with Rogowski coils. It is currently not yet clear
whether the differences in the measurements have to be attributed to the toroidal plasma
current connected with the bootstrap current, to pressure-related effects or to a combination.
To address this uncertainty in future works the measured data will be compared with MHD
equilibrium models.
[1]: P. Drews et al. (2017). Measurement of the plasma edge profiles using the combined probe on W7-X.
Nuclear Fusion. 57. . 10.1088/1741-4326/aa8385.
