München 2019 – wissenschaftliches Programm

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P: Fachverband Plasmaphysik

P 18: Postersitzung

P 18.107: Poster

Donnerstag, 21. März 2019, 16:30–18:30, Foyer Audimax

Experimental Study of the Influence of the Scrape-off Layer Radial Electric Field on the Transition to the High Confinement Mode — •Ulrike Plank^1,2, Thomas Pütterich^1,2, Marco Cavedon¹, Elisabeth Wolfrum¹, Ulrich Stroth¹, and The ASDEX Upgrade Team¹ — ¹MPI für Plasmaphysik, Garching, Germany — ²Ludwig-Maximilian-Universität, München, Germany

The high confinement mode (H-mode) is a state of improved plasma confinement in diverted tokamaks. It is achieved when the input power exceeds a threshold and it exhibits a transport barrier in the edge of the confined plasma region. This transport barrier is considered to be caused by local gradients in the radial electric field (E_r) at the edge of the confined plasma region, which lead to sheared E × B flows (v_{E × B}). These flows suppress turbulent transport in the edge, resulting in an improved plasma confinement. On ASDEX Upgrade (AUG) it was found that a critical value for the v_{E × B} minimum, a proxy for the v_{E × B} shear, is needed to sustain H-mode. However, the power threshold to enter H-mode changes when the conditions at the plasma boundary, i.e. in the scrape-off layer (SOL), are altered. Modeling results indicate that these effects impact the magnitude of E_r in the SOL. Therefore, E_r in the SOL could influence the gradients of E_r in the confined region and the access to H-mode. In order to experimentally access E_r in the SOL a charge exchange recombination spectroscopy diagnostics was installed in AUG. First experimental results will be presented.