Experimental Signatures of Critically Balanced Turbulence in MAST

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 ${\nu }_{\ast i}^{-0.8\pm 0.1}$, where ${\nu }_{\ast i}=$ 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 the drift waves' by $\sim {\nu }_{\ast i}^{-0.8}$.

6 pages, 4 figures, submitted to PRL

References in corpus (5)

• Anisotropic scaling of magnetohydrodynamic turbulence
• Evidence of Critical Balance in Kinetic Alfven Wave Turbulence Simulations
• Nonlinear entropy transfer via zonal flows in gyrokinetic plasma turbulence
• Zero-Turbulence Manifold in a Toroidal Plasma
• Measurement and physical interpretation of the mean motion of turbulent density patterns detected by the BES system on MAST

Cited by in corpus (14)

• Phase mixing vs. nonlinear advection in drift-kinetic plasma turbulence
• Collisionality scaling of the electron heat flux in ETG turbulence
• Ion-scale turbulence in MAST: anomalous transport, subcritical transitions, and comparison to BES measurements
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• Weak Alfvénic turbulence in relativistic plasmas. Part 1. Dynamical equations and basic dynamics of interacting resonant triads
• Energy-flux vector in anisotropic turbulence: application to rotating turbulence
• Interpreting Radial Correlation Doppler Reflectometry using Gyrokinetic Simulations
• Symmetry breaking in MAST plasma turbulence due to toroidal flow shear
• Experimental determination of the correlation properties of plasma turbulence using 2D BES systems
• Conditions for generating synthetic data to investigate characteristics of fluctuating quantities
• Energy-based analysis and anisotropic spectral distribution of internal gravity waves in strongly stratified turbulence
• Suppression of temperature-gradient-driven turbulence by sheared flows in fusion plasmas
• Reliability of the two-point measurement of the spatial correlation length from Gaussian-shaped fluctuating signals in fusion-grade plasmas
• Saturation of magnetised plasma turbulence by propagating zonal flows