Publications [#335095] of David R. Smith

Papers Published
  1. Peterson, JL; Bell, R; Candy, J; Guttenfelder, W; Hammett, GW; Kaye, SM; Leblanc, B; Mikkelsen, DR; Smith, DR; Yuh, HY, Suppressing electron turbulence and triggering internal transport barriers with reversed magnetic shear in the National Spherical Torus Experiment, Physics of Plasmas, vol. 19 no. 5 (May, 2012), pp. 056120-056120, AIP Publishing [doi] .

    Abstract:
    The National Spherical Torus Experiment (NSTX) [M. Ono, Nucl. Fusion 40, 557 (2000)] can achieve high electron plasma confinement regimes that are super-critically unstable to the electron temperature gradient driven (ETG) instability. These plasmas, dubbed electron internal transport barriers (e-ITBs), occur when the magnetic shear becomes strongly negative. Using the gyrokinetic code GYRO [J. Candy and R. E. Waltz, J. Comput. Phys. 186, 545 (2003)], the first nonlinear ETG simulations of NSTX e-ITB plasmas reinforce this observation. Local simulations identify a strongly upshifted nonlinear critical gradient for thermal transport that depends on magnetic shear. Global simulations show e-ITB formation can occur when the magnetic shear becomes strongly negative. While the ETG-driven thermal flux at the outer edge of the barrier is large enough to be experimentally relevant, the turbulence cannot propagate past the barrier into the plasma interior. © 2012 American Institute of Physics.

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