München 2019 – wissenschaftliches Programm
P 18.65: Poster
Donnerstag, 21. März 2019, 16:30–18:30, Foyer Audimax
Formation of turbulent transport in 3D stellarator geometry — •Mirko Ramisch, Stephen Garland, Bernhard Schmid, and Til Ullmann — Institute for Interfacial Process Engineering and Plasmatechnology - University of Stuttgart, Germany
At the stellarator TJ-K, investigations have been carried out into the spatial dependencies of different types of turbulent transport: particle and momentum cross-field transport in the confined edge region as well as intermittent blob transport in the scrape-off layer (SOL). Multi-probe measurements were conducted for correlation of fluctuation data with local characteristics of the magnetic field, in particular field-line curvature. As a result, the transport phenomena share striking features in spatial locality: particle and momentum transport as well as density intermittency levels show peak values, where regions of negative normal curvature fall together with regions of positive geodesic curvature. This allows to understand particle transport in terms of linear instability of drift waves, and to view observed spatial Reynolds stress concentration in correlation with instability regions. Moreover, intermittency in density fluctuations turns out to result from density-potential decoupling taking place in the same region. Extended Hasegawa-Wakatani simulations point to the specific structure of curvature being responsible for the decoupling process under conditions of low magnetic shear. Geodesic curvature is also demonstrated to determine the poloidal propagation of blobs in the SOL. This contribution illustrates magnetic field curvature as an element bridging between dynamics of the drift-wave/zonal-flow system and blob filaments across the separatrix.