Speaker
Alex LeViness
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P4.1022.pdf
Neutral particle fluxes on the divertor during overload mimic scenarios in
Wendelstein 7-X
A. LeViness1, P. Drewelow2, J.D. Lore3, G. Schlisio2, G. Wurden4, B. Cannas6,
K. Hammond2, M. Jakubowski2,5, F. Pisano6 and W7-X team
1
Universität Greifswald, Greifswald, Germany
2
Max-Planck-Institut für Plasmaphysik, Greifswald, Germany
3
Oak Ridge National Laboratory, Oak Ridge, United States
4
Los Alamos National Laboratory, Los Alamos, United States
5
Faculty of Mathematics and Physics, University of Szczecin, Szczecin, Poland
6
Università degli Studi di Cagliari, Cagliari, Italy
Wendelstein 7-X will perform high-power long-pulse discharges with the actively cooled
divertor from the early 2020’s. It is predicted [1] that in some configurations, during the first
100 s of the discharge, the toroidal current in the plasma will evolve and change the magnetic
topology such that the edges of the divertor may be overloaded. The planned solution to this is
the installation of ‘scraper element’ components. Two of these components are expected to be
installed for OP 1.2b [2] to test their effectiveness and influence on plasma performance. One of
the key questions is whether neutral divertor compression will be reduced too much due to
strong interaction of the plasma with the surface of the scraper element.
Because of the limits on pulse length and energy input, the overload scenario cannot occur
during OP 1.2. Instead, five magnetic configurations were designed to mimic the topology
created by the toroidal current as it evolves from 0 to 43 kA, including the peak overload case of
22 kA. In order to compare actual heat and particle loads to those predicted by EMC3-EIRENE
simulations, and to establish baseline measurements for comparing performance with and
without the test divertor scraper elements, experiments were performed during the previous
campaign using these mimic configurations.
In this work, we analyze the H-alpha camera diagnostic data in order to quantify divertor
particle fluxes and relate them to neutral divertor pressure measured by pressure gauges.
Results showed heat and particle flux patterns closely matching those predicted by simulations.
References
[1] H. Hoelbe, et al., Nucl. Fusion 56, 025015 (2016)
[2] J.D. Lore, et al., IEEE TPS 42, 539 (2014)
