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P: Fachverband Plasmaphysik

P 11: Helmholtz Graduate School - Poster

P 11.23: Poster

Dienstag, 6. März 2018, 16:15–18:15, Redoutensaal

Dependence of small Edge Localized Modes on Plasma Parameters — •G. F. Harrer^1,2, E. Wolfrum², T. Eich², M. G. Dunne², P. Manz², P. T. Lang², H. Meyer³, M. Bernert², B. Labit⁴, G. Birkenmeier², J. Stober², F. Aumayr¹, the EUROFUSION MST1 Team⁵, and the ASDEX Upgrade Team² — ¹TU Wien, Austria — ²IPP Garching, Germany — ³CCFE Culham, United Kingdom — ⁴SPC Lausanne, Switzerland — ⁵see H. Meyer et al. 2017 Nucl. Fusion 57 102014

The development of small Edge Localized Mode (ELM) scenarios is important in order to understand how to reduce the strain on plasma facing components. One such scenario can be found at high densities, in highly shaped, close to double-null plasmas as small ELMs or type-II ELMs in ASDEX Upgrade, which are characterized by a frequency f_ELM>300Hz and a low power loss. Comparing deuterium gas and pellet fuelling showed that this small ELM regime is dependent on the separatrix density, by decoupling it from the pedestal top density. This strong local dependence of small ELMs on the scrape-off layer parameters is in agreement with a ballooning model for the separatrix region. It has also been shown, that changing the vertical plasma position and with that, the plasma shape, the small ELMs shrink in size and get replaced by large type I ELMs. One hypothesis to explain this behavior is a strong dependence of these ballooning modes on the magnetic shear (global and local).