Numerical Verification of Bounce Harmonic Resonances in Neoclassical Toroidal Viscosity for Tokamaks
Authors: Kimin Kim, Jong-Kyu Park and Allen H. Boozer
Abstract:
This Letter presents the rst numerical veri cation for the bounce-harmonic (BH) resonance phenomena
of the neoclassical transport in a tokamak perturbed by non-axisymmetric magnetic elds.
The BH resonances were predicted by analytic theories of neoclassical toroidal viscosity (NTV), as
the parallel and perpendicular drift motions can be resonant and result in a great enhancement of
the radial momentum transport. A new drift-kinetic f guiding-center particle code, POCA, clearly
veri ed that the perpendicular drift motions can reduce the transport by phase-mixing, but in the
BH resonances the motions can form closed orbits and particles radially drift out fast. The POCA
calculations on resulting NTV torque are largely consistent with analytic calculations, and show that
the BH resonances can easily dominate the NTV torque when a plasma rotates in the perturbed
tokamak and therefore is a critical physics for predicting the rotation and stability in ITER.
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Submitted to: Physical Review Letters (November 2012)
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