Influence of ExB shear flows on plasma edge turbulence
- Institut fuer Plasmaforschung, Universitaet Stuttgart, Pfaffenwaldring 31, 70569 Stuttgart (Germany)
- Institut fuer Experimentelle und Angewandte Physik, Universitaet Kiel, Olshausenstr. 40, 24098 Kiel (Germany)
Poloidal ExB shear flows are widely accepted as a trigger mechanism of transport barriers in the edge of fusion plasmas. Strong ExB flows can act on turbulence and turbulent transport through the shear decorrelation mechanism, which can reduce the radial size of turbulent structures or change the phase relation between density and potential fluctuations. In this contribution the influence of ExB shear flows on the microscopic structure of turbulence is investigated. The experiments have been carried out on the toroidally confined low-temperature plasma of the torsatron TJ-K. The plasma is dimensionally similar to fusion edge plasmas and accessible throughout for Langmuir probes. Multi-probe arrays are used to resolve the turbulent dynamics perpendicular to the confining magnetic field in high detail.Strong ExB flows are externally generated by core plasma biasing. It is shown that the fluctuations are dominated by large-scale coherent structures even though strong flow shear is present. These structures reveal increased correlation lengths. It is found that these structures can contribute to improved confinement through inwards transport due to cross-phase modifications. Furthermore, the response of the turbulent Reynolds stress, which is supposed to drive zonal flows as internally ExB shear flows, is investigated. The externally generated flow shear leads to a redistribution of the Reynolds stress with increased poloidal symmetry.
- OSTI ID:
- 21136885
- Journal Information:
- AIP Conference Proceedings, Vol. 993, Issue 1; Conference: PLASMA 2007: International conference on research and applications of plasmas; 4. German-Polish conference on plasma diagnostics for fusion and applications; 6. French-Polish seminar on thermal plasma in space and laboratory, Greifswald (Germany), 16-19 Oct 2007; Other Information: DOI: 10.1063/1.2909086; (c) 2008 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0094-243X
- Country of Publication:
- United States
- Language:
- English
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