Bochum 2015 – scientific programme

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P: Fachverband Plasmaphysik

P 29: Magnetic Confinement II

P 29.2: Fachvortrag

Thursday, March 5, 2015, 17:00–17:25, HZO 30

Interplay between sheared flows and turbulent eddies at the TEXTOR tokamak — •Ilya Shesterikov¹, Yuhong Xu², and Carlos Hidalgo³ — ¹Max Planck Institute for Plasma Physics, 17491 Greifswald, Germany — ²Southwestern Institute of Physics, China — ³Laboratorio Nacional de Fusion (CIEMAT) , 28040 Madrid

Turbulent structures are considered to be highly elongated along magnetic field lines. Consequently, characterizing and understanding the underlying physical mechanisms require essentially two-dimensional (radial vs poloidal) turbulence measurements. For these purposes, the gas-puff imaging diagnostic (GPI), assigned to measure 2D effects of the plasma turbulence, has been developed for the TEXTOR tokamak.

The systematic study of the eddy decorrelation by sheared flows observed by the GPI diagnostic in the edge of the TEXTOR tokamak is presented in this work. In particular, we present the direct experimental evidence of breaking and tilting of turbulent eddies. Here, one has to emphasize that the breaking of eddies in fusion plasma by sheared E_r× B flows has been observed for the first time.

Meanwhile, externally induced poloidal flows are applied in order to study intermediate mechanisms involved in the turbulence-flow interaction across the transition to an improved confinement. These results present the first evidence of the eddy stretching and splitting process in a confinement device and the intimate interaction among sheared flows, eddy structures, Reynolds stress, zonal flows and ambient fluctuations during the transition to an improved confinement.