Suppressing electron turbulence and triggering internal transport barriers with reversed magnetic shear in the National Spherical Torus Experiment

Journal Article · Tue May 15 00:00:00 EDT 2012 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.4718456· OSTI ID:22072398

Peterson, J L ^[1]; Bell, R; Guttenfelder, W; Hammett, G W; Kaye, S M; LeBlanc, B; Mikkelsen, D R ^[2]; Candy, J ^[3]; Smith, D R ^[4]; Yuh, H Y ^[5]

---

1. Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)
2. Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (United States)
3. General Atomics, San Diego, California 92186 (United States)
4. Department of Engineering Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States)
5. Nova Photonics Inc., Princeton, New Jersey 08540 (United States)

The National Spherical Torus Experiment (NSTX) [M. Ono et al., 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.

• OSTI ID: 22072398
• Journal Information: Physics of Plasmas, Vol. 19, Issue 5; Other Information: (c) 2012 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
CHARGED-PARTICLE TRANSPORT
ELECTRON TEMPERATURE
ELECTRONS
MAGNETIC FIELD CONFIGURATIONS
NONLINEAR PROBLEMS
NSTX DEVICE
PLASMA
PLASMA CONFINEMENT
REVERSED SHEAR
SHEAR
TEMPERATURE GRADIENTS
THERMAL BARRIERS
TURBULENCE