Gyrokinetic Studies of the Effect of Beta on Drift-wave Stability in NCSX
Authors: J.A. Baumgaertel, G.W. Hammett, D.R. Mikkelsen, M. Nunami, and P. Xanthopoulos
Abstract:
The gyrokinetic turbulence code GS2 was used to investigate the effects of plasma β on linear, collisionless
ion temperature gradient (ITG) modes and trapped electron modes (TEM) in National Compact Stellarator
Experiment (NCSX) geometry. Plasma β affects stability in two ways: through the equilibrium and through
magnetic fluctuations. The first was studied here by comparing ITG and TEM stability in two NCSX
equilibria of differing β values, revealing that the high β equilibrium was marginally more stable than the low
β equilibrium in the adiabatic-electron ITG mode case. However, the high β case had a lower kinetic-electron
ITG mode critical gradient. Electrostatic and electromagnetic ITG and TEM mode growth rate dependencies
on temperature gradient and density gradient were qualitatively similar. The second β effect is demonstrated
via electromagnetic ITG growth rates' dependency on GS2's β input parameter. A linear benchmark with
gyrokinetic codes GENE and GKV-X is also presented.
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Submitted to: Physics of Plasmas (September 2012)
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Download PPPL-4815 (pdf 848 KB 11 pp)
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