Microstability in a “MAST-like” high confinement mode spherical tokamak equilibrium

Microstability in a “MAST-like” high confinement mode spherical tokamak equilibrium

Microstability in a “MAST-like” high confinement mode spherical tokamak equilibrium 150 150 UKAEA Opendata

Microstability in a “MAST-like” high confinement mode spherical tokamak equilibrium

Gyrokinetic microstability analyses, with and without electromagnetic effects, are presented for a spherical tokamak plasma equilibrium closely resembling that from a high confinement mode ( H mode ) discharge in the mega-ampere spherical tokamak ( MAST ) [ A. Sykes et al. , Nucl. Fusion 41 , 1423 ( 2001 )] . Electrostatic ion temperature gradient driven modes ( ITG modes ) were found to be unstable on all surfaces, though they are likely to be substantially stabilized by equilibrium E x B flow shear. Electron temperature gradient driven modes ( ETG modes ) have stronger growth rates that substantially exceed the equilibrium flow shearing rates. Mixing length arguments suggest that ITG modes would give rise to significant transport if they are not stabilized by sheared flows, and predict weak transport from ETG turbulence. Significant plasma flows have been neglected in this first analysis, and are probably important in the delicate balance between ITG growth rates and flow shear, and in the formation of internal transport barriers on MAST.

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01/11/2004