Experimental Signatures of Critically Balanced Turbulence in MAST

Experimental Signatures of Critically Balanced Turbulence in MAST

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Beam emission spectroscopy (BES) measurements of ion-scale density fluctuations in the MAST tokamak are used to show that the turbulence correlation time, the drift time associated with ion temperature or density gradients, the particle (ion) streaming time along the magnetic field, and the magnetic...

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Bibliographic Details
Main Authors: Ghim, Y.-c., Schekochihin, A. A., Field, A. R., Abel, I. G., Barnes, Michael, Colyer, G., Cowley, S. C., Parra Diaz, Felix Ignacio, Dunai, D., Zoletnik, S., MAST Team
Other Authors: Massachusetts Institute of Technology. Plasma Science and Fusion Center
Format: Article
Language:en_US
Published: American Physical Society 2013
Online Access:http://hdl.handle.net/1721.1/81999
https://orcid.org/0000-0001-9621-7404
Description
Summary:Beam emission spectroscopy (BES) measurements of ion-scale density fluctuations in the MAST tokamak are used to show that the turbulence correlation time, the drift time associated with ion temperature or density gradients, the particle (ion) streaming time along the magnetic field, and the magnetic drift time are consistently comparable, suggesting a “critically balanced” turbulence determined by the local equilibrium. The resulting scalings of the poloidal and radial correlation lengths are derived and tested. The nonlinear time inferred from the density fluctuations is longer than the other times; its ratio to the correlation time scales as ν*i[superscript -0.8±0.1], where ν*i=ion   collision   rate/streaming   rate. This is consistent with turbulent decorrelation being controlled by a zonal component, invisible to the BES, with an amplitude exceeding those of the drift waves by ∼ν*i[superscript -0.8].

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