Experimental Signatures of Critically Balanced Turbulence in MAST
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Ghim-2013-Experimental Signatures of Critically Balanced Turbulence in MAST.pdf
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Author(s)
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.
Date Issued
April 2013
Journal
Physical Review Letters
Publisher
American Physical Society
Citation
Ghim, Y.-c., A. A. Schekochihin, A. R. Field, I. G. Abel, M. Barnes, G. Colyer, S. C. Cowley, F. I. Parra, D. Dunai, and S. Zoletnik. Experimental Signatures of Critically Balanced Turbulence in MAST. Physical Review Letters 110, no. 14 (April 2013).
Version
Final published version
Abstract
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].
MIT Department
Massachusetts Institute of Technology. Plasma Science and Fusion Center
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DOI of Published Version
https://doi.org/10.1103/PhysRevLett.110.145002
