München 2019 – scientific programme
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P: Fachverband Plasmaphysik
P 7: Helmholtz Graduate School II - Magnetic Confinement I
P 7.2: Talk
Monday, March 18, 2019, 17:00–17:25, HS 21
A ballooning mode description of small ELMs — •G.F. Harrer1, E. Wolfrum2, M.G. Dunne2, T. Eich2, M. Griener2, P. Hennequin3, B. Labit4, P. Manz2, L. Radovanovic1, F. Aumayr1, the ASDEX Upgrade Team2, and the EUROfusion MST1 Team5 — 1Institute of Applied Physics, TU Wien, Fusion@ÖAW, Vienna, Austria — 2Max Planck Institute for Plasma Physics, Garching, Germany — 3Laboratoire de Physique des Plasmas, CNRS, Ecole Polytechnique, Palaiseau, France — 4Swiss Plasma Center, EPFL, Lausanne, Switzerland — 5see author list in H. Meyer et al. Nuclear Fusion 57 102014 (2017)
The foreseen operational scenario for future fusion devices is the high confinement mode, which is characterized by a strong increase in confinement due to the formation of a transport barrier at the plasma edge. The periodic crash of this so-called pedestal is caused by large edge localized modes (type-I ELMs) which can lead to possibly intolerable heat and particle loads if not controlled. In ASDEX Upgrade, discharges with high separatrix collisionality νe* ∝ ne/Te2 , comparable to ITER, exhibit small ELMs at good confinement, if the plasmas are strongly shaped. In the experiment, type-I ELMs and small ELMs can coexist. In this contribution a model is proposed that explains how the small ELMs modify the shape of the pedestal close to the separatrix in such a way that it is stable against large type-I ELMs. The manifestation of small ELMs at reactor-like separatrix conditions as filamentary transport rather than large bursts offers a possible route to tolerable heat loads at high pedestal top pressure in future devices.