Neoclassical toroidal plasma viscosity in the vicinity of the magnetic axis in tokamaks with broken symmetry

Ker-Chung Shaing, H. Lee, J. Seol, A. Y. Aydemir

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

Theory for neoclassical toroidal plasma viscosity in the low collisionality regime is extended to the vicinity of the magnetic axis in tokamaks with broken symmetry. The toroidal viscosity is induced by particles drifting off the perturbed magnetic surface under the influence of the symmetry breaking magnetic field. In the region away from the magnetic axis, the drift orbit dynamics is governed by the bounce averaged drift kinetic equation in the low collisionality regimes. In the vicinity of the magnetic axis, it is the drift kinetic equation, averaged over the trapped particle orbits, i.e., potato orbits, that governs the drift dynamics. The orbit averaged drift kinetic equation is derived when collision frequency is low enough for trapped particles to complete their potato trajectories. The resultant equation is solved in the 1/ν regime to obtain transport fluxes and, thus, toroidal plasma viscosity through flux-force relation. Here, ν is the collision frequency. The viscosity does not vanish on the magnetic axis, and has the same scalings as that in the region away from magnetic axis, except that the fraction of bananas is replaced by the fraction of potatoes. It also has a weak radial dependence. Modeling of plasma flow velocity V for the case where the magnetic surfaces are broken is also discussed.

Original languageEnglish
Article number082504
JournalPhysics of Plasmas
Volume22
Issue number8
DOIs
Publication statusPublished - 2015 Aug 1

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toroidal plasmas
broken symmetry
potatoes
viscosity
kinetic equations
orbits
trapped particles
collisions
magnetohydrodynamic flow
flow velocity
trajectories
low frequencies
scaling
magnetic fields

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics

Cite this

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abstract = "Theory for neoclassical toroidal plasma viscosity in the low collisionality regime is extended to the vicinity of the magnetic axis in tokamaks with broken symmetry. The toroidal viscosity is induced by particles drifting off the perturbed magnetic surface under the influence of the symmetry breaking magnetic field. In the region away from the magnetic axis, the drift orbit dynamics is governed by the bounce averaged drift kinetic equation in the low collisionality regimes. In the vicinity of the magnetic axis, it is the drift kinetic equation, averaged over the trapped particle orbits, i.e., potato orbits, that governs the drift dynamics. The orbit averaged drift kinetic equation is derived when collision frequency is low enough for trapped particles to complete their potato trajectories. The resultant equation is solved in the 1/ν regime to obtain transport fluxes and, thus, toroidal plasma viscosity through flux-force relation. Here, ν is the collision frequency. The viscosity does not vanish on the magnetic axis, and has the same scalings as that in the region away from magnetic axis, except that the fraction of bananas is replaced by the fraction of potatoes. It also has a weak radial dependence. Modeling of plasma flow velocity V for the case where the magnetic surfaces are broken is also discussed.",
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Neoclassical toroidal plasma viscosity in the vicinity of the magnetic axis in tokamaks with broken symmetry. / Shaing, Ker-Chung; Lee, H.; Seol, J.; Aydemir, A. Y.

In: Physics of Plasmas, Vol. 22, No. 8, 082504, 01.08.2015.

Research output: Contribution to journalArticle

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