Bochum 2015 – wissenschaftliches Programm
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P: Fachverband Plasmaphysik
P 22: Helmholtz Graduate School for Plasma Physics II
P 22.2: Fachvortrag
Mittwoch, 4. März 2015, 16:55–17:20, HZO 50
Study of the edge radial electric field during the L-H transition — •Marco Cavedon1,2, Thomas Puetterich1, Eleonora Viezzer1, Gregor Birkenmeier1,2, Tim Happel1, Francois Ryter1, Ulrich Stroth1,2, and the ASDEX Upgrade Team1 — 1Max-Planck-Institut für Plasmaphysik, Boltzmannstr. 2, D-85748 Garching — 2Physik-Department E28, TUM, D-85748 Garching
The access to the high confinement mode in fusion plasmas occurs through a transport barrier whereby plasma turbulence is reduced by the shear of the edge radial electric field (Er). The neoclassical theory predicts Er to be driven by the main plasma ions, as also suggested by experimental observations. A recent upgrade of the charge exchange recombination spectroscopy diagnostic (CXRS) in the ASDEX Upgrade tokamak (AUG) provides a full reconstruction of the impurity density, temperature and Er profiles and allows us to address the fast dynamics of these quantities during the L-H transition. The characteristic time scale of the L-H transition can be associated to the typical frequency (1-10 kHz) of the fluctuating phases (often called limit cycle oscillations) observed before the L-H transitions. The new CXRS system has a time resolution of 50µs which allows to investigate these phenomena and analyze the causality of the transition mechanism. Correlations between turbulent fluctuations and changes in the edge profile gradients will be presented.