Experimental Signatures of Critically Balanced Turbulence in MAST
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.; MAST Team; ... Show more Show less
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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 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].
DepartmentMassachusetts Institute of Technology. Plasma Science and Fusion Center
Physical Review Letters
American Physical Society
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).
Final published version