Hannover 2020 – wissenschaftliches Programm
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P: Fachverband Plasmaphysik
P 15: Helmholtz Graduate School 3 and Magnetic confinement 3
P 15.6: Vortrag
Mittwoch, 11. März 2020, 15:50–16:05, b305
Reynolds stress formation of ZF drive under imposed shear flows at the stellarator TJ-K — •Til Ullmann1, Bernhard Schmid1, Peter Manz2, and Mirko Ramisch1 — 1IGVP Universtität Stuttgart, Germany — 2IPP, Max-Planck Institut, Garching
Shear flows in magnetized fusion plasmas are considered to have a major impact on the non-linear dynamics. In drift-wave (DW) turbulence, shear flows tilt and stretch turbulent eddies, resulting in the generation of large structures such as zonal flows (ZF). ZFs tap energy from the DW turbulence and, hence, are supposed to be involved in the formation of transport barriers at the transition into the high confinement regime. ZFs are themselves shear flows and react upon the turbulence. The stellarator TJ-K confines low-temperature plasmas, which allow for measurements of potential fluctuations with Langmuir probes inside the confinement region. In order to identify ZFs and to calculate the Reynolds stress (RS), which indicates the tilt of stretched eddies, 128 probes are poloidally positioned on four neighbouring flux surfaces. The background E× B flow as imposed by external plasma biasing is calculated from radial profiles of the plasma potential, measured by an emissive probe. The influence of stationary E× B flow shears on the tilt of turbulent eddies, the RS drive of ZFs and the energy transfer process into the ZFs are investigated experimentally.