München 2019 – wissenschaftliches Programm
P 17.2: Hauptvortrag
Donnerstag, 21. März 2019, 14:30–15:00, HS 17
The role of the radial electric field in the edge of fusion plasmas — •Marco Cavedon1, Gregor Birkenmeier1, Ralph Dux1, Tim Happel1, Ulrike Plank1, Thomas Pütterich1, Francois Ryter1, Ulrich Stroth1, Eleonora Viezzer2, Matthias Willensdorfer1, Elisabeth Wolfrum1, and The Asdex Upgrade Team1 — 1Max Planck Institute for Plasma Physics, Garching (Germany) — 2Dept. of Atomic, Molecular and Nuclear Physics, Uni. Seville, Seville (Spain)
It is widely accepted that the edge radial electric field (Er) gradient and the accompanying E × B velocity shear is responsible for the suppression of the edge turbulence, thus leading to the transition from the low (L-) to the high (H-) confinement mode in diverted tokamaks. The latter shows a factor of two higher energy confinement time making this regime the baseline for any future fusion device based on the tokamak concept. However, the origin of Er is still debated. The E × B flow may be generated by turbulence stresses, collisional (neoclassical) processes via the main ion pressure gradient or by any non-ambipolar transport process. Several experiments were performed at the ASDEX Upgrade tokamak to clarify the dominant drive of Er. A comparison of neoclassical Er, neo and of measured Er profiles close to the L-H transition and during a complete edge localized mode cycle shows the main role of the neoclassical contribution to the E × B velocity. In line with the above, across a large database of L-H transitions the same E × B shear is observed at the H-mode onset, which indicates that the key role of Er, neo is a general property.