An Enhanced Nonlinear Critical Gradient for Electron Turbulent Transport due to Reversed Magnetic Shear
Authors: J. L. Peterson, G.W. Hammett, D.R. Mikkelsen, H.Y. Yuh, J. Candy, W. Guttenfelder, S.M. Kaye, and B. LeBlanc
Abstract:
The first nonlinear gyrokinetic simulations of electron internal transport barriers (e-ITBs) in
the National Spherical Torus Experiment show that reversed magnetic shear can suppress thermal transport by increasing the nonlinear critical gradient for electron-temperature-gradient-driven
turbulence to three times its linear critical value. An interesting feature of this turbulence is non-
linearly driven off-midplane radial streamers. This work reinforces the experimental observation
that magnetic shear is likely an effective way of triggering and sustaining e-ITBs in magnetic fusion
devices.
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Submitted to: Physical Review Letters (April 2011)
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