München 2019 – wissenschaftliches Programm
P 18.112: Poster
Donnerstag, 21. März 2019, 16:30–18:30, Foyer Audimax
ECCD-driven temperature collapses at W7-X — •Marco Zanini1, Heinrich Laqua1, Torsten Stange1, Christian Brandt1, Hannes Damm1, Matthias Hirsch1, Udo Höfel1, Kian Rahbarnia1, Erika Strumberger2, Henning Thomsen1, and Robert Wolf1 for the The Wendelstein 7-X Team collaboration — 1Max-Planck-Institut für Plasmaphysik, Greifswald, Germany — 2Max-Planck-Institut für Plasmaphysik, Garching, Germany
The superconducting optimized stellarator Wendelstein 7-X is equipped with an electron cyclotron resonance heating (ECRH) system, allowing up to 7.5 MW of power injected into the plasma. The ECRH itself can also be used to drive a net toroidal current in the plasma. The small amounts of toroidal currents makes W7-X a perfect testbed for such ECCD experiments. During ECCD operations, repetitive and periodic collapses of the electron temperature have been detected and they display a similar behavior to sawtooth oscillations in tokamaks. Modelling the temporal current evolution shows local changes of the rotational transform, induced by ECCD, lead to the formation of low order rational value, thus making the plasma unstable. The application of ECCD over several seconds also can result in a global loss of confinement. In order to characterize and understand the observed effects the collapses have on the plasma, different current drive profiles have been used and an initial characterization is presented here. Effects of different configurations on the inversion radius and crash frequency are analyzed and an initial attempt of a mode analysis is presented.