Experimental signatures of critically balanced turbulence in MAST

Y. C. Ghim, A. Schekochihin, A. R. Field, I. G. Abel, M. Barnes, G. Colyer, S. C. Cowley, F. I. Parra, D. Dunai, S. Zoletnik

Research output: Contribution to journalArticle

23 Scopus citations

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-0. 8±0.1, where ν*i=ion  ⠀Šcollision   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-0.8. Published by the American Physical Society.

Original languageEnglish (US)
Article number145002
JournalPhysical review letters
Volume110
Issue number14
DOIs
StatePublished - Apr 1 2013
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)

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