Suppression of Electron Temperature Gradient Turbulence via Negative Magnetic Shear in NSTX

H. Y. Yuh, S. M. Kaye, F. M. Levinton, E. Mazzucato, D. R. Mikkelsen, D. R. Smith, R. E. Bell, J. C. Hosea, B. P. LeBlanc, J. L. Peterson, H. K. Park, and W. Lee

Phys. Rev. Lett. 106, 055003 – Published 3 February 2011

Abstract

Negative magnetic shear is found to suppress electron turbulence and improve electron thermal transport for plasmas in the National Spherical Torus Experiment (NSTX). Sufficiently negative magnetic shear results in a transition out of a stiff profile regime. Density fluctuation measurements from high- $k$ microwave scattering are verified to be the electron temperature gradient (ETG) mode by matching measured rest frequency and linear growth rate to gyrokinetic calculations. Fluctuation suppression under negligible $E \times B$ shear conditions confirm that negative magnetic shear alone is sufficient for ETG suppression. Measured electron temperature gradients can significantly exceed ETG critical gradients with ETG mode activity reduced to intermittent bursts, while electron thermal diffusivity improves to below 0.1 electron gyro-Bohms.

Received 2 July 2010

DOI:https://doi.org/10.1103/PhysRevLett.106.055003

Authors & Affiliations

H. Y. Yuh^1,*, S. M. Kaye², F. M. Levinton¹, E. Mazzucato², D. R. Mikkelsen², D. R. Smith³, R. E. Bell², J. C. Hosea², B. P. LeBlanc², J. L. Peterson², H. K. Park⁴, and W. Lee⁴

¹Nova Photonics Inc., Princeton, New Jersey 08540, USA
²Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543, USA
³Department of Engineering Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
⁴POSTECH, Pohang 790-784, Korea

^*hyuh@pppl.gov

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Vol. 106, Iss. 5 — 4 February 2011

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