Simulation of Non-resonant Internal Kink Mode with Toroidal Rotation In NSTX
Authors: G. Fu, et. al.
Abstract:
Plasmas in spherical and conventional tokamaks, with weakly reversed shear q pro le and minimum q above
but close to unity, are susceptible to an non-resonant (m, n ) = (1, 1) internal kink mode. This mode can
saturate and persist and can induce a (2; 1) seed island for Neoclassical Tearing Mode (NTMs)1 . The mode can
also lead to large energetic particle transport and signi cant broadening of beam-driven current. Motivated
by these important e ects, we have carried out extensive nonlinear simulations of the mode with nite toroidal
rotation using parameters and pro les of an NTSX plasma with a weakly reversed shear pro le. The numerical
results show that, at the experimental level, plasma rotation has little e ect on either equilibrium or linear
stability. However, rotation can signi cantly inuence the nonlinear dynamics of the (1, 1) mode and the the
induced (2, 1) magnetic island. The simulation results show that a rotating helical equilibrium is formed and
maintained in the nonlinear phase at nite plasma rotation. In contrast, for non-rotating cases, the nonlinear
evolution exhibits dynamic oscillations between a quasi-2D state and a helical state. Furthermore, the e ects
of rotation are found to greatly suppress the (2, 1) magnetic island even at a low level.
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Submitted to: Physics of Plasmas (June 2013)
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Download PPPL-4930 (pdf KB pp)
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