54th Annual Meeting of the APS Division of Plasma Physics
Volume 57, Number 12
Monday–Friday, October 29–November 2 2012;
Providence, Rhode Island
Session JI2: Fast Ion Physics, RF Theory
2:00 PM–5:00 PM,
Tuesday, October 30, 2012
Room: Ballroom DE
Chair: Tobin Munsat, University of Colorado
Abstract ID: BAPS.2012.DPP.JI2.3
Abstract: JI2.00003 : M3D-K Simulations of Beam-Driven Alfven Modes in DIIID
3:00 PM–3:30 PM
Preview Abstract
Abstract
Author:
Guoyong Fu
(Princeton Plasma Physics Laboratory)
Multiple beam-driven Reversed Shear Alfven eigenmodes (RSAEs) and Toroidal
Alfven Eigenmodes (TAE) were observed in the DIII-D discharge ({\#}142111)
[1]. Extensive hybrid simulations with the global kinetic/MHD hybrid code
M3D-K [2] have been carried out to investigate these beam-driven Alfven
eigenmodes using experimental parameters and profiles from this discharge.
The purpose of this work is for code verification and validation as well as
for physics understanding needed for predicting energetic particle-driven
instabilities and energetic particle transport in burning plasmas. We first
benchmark M3D-K code with the linear ideal MHD stability code NOVA. The
M3D-K results agree well with those of NOVA with respect to mode structure
and mode frequency in the MHD limit. With energetic beam ions, the
simulations results show that the destabilized n=3 mode transit from RSAEs
to TAEs as the minimum of the safety factor drops in agreement with the
measured frequency sweeping. The calculated 2D mode structure in poloidal
cross-section exhibits a twisting feature or radial phase shearing
consistent with the Electron Cyclotron Emission Imaging (ECEI) data [1]. An
analytic theory has been developed to explain the radial phase shearing
observed in the simulations and experiments. It is found that both the fast
ion drive and background damping can cause radial phase shearing. The
direction of phase shearing changes when the toroidal magnetic field is
reversed whereas the shearing direction is independent of plasma current
direction. This symmetry agrees with the experimental observation from ECEI.
Finally, nonlinear simulations of the beam-driven modes with particle
collision and particle source and sink have been carried out and results
show that other Alfven modes becomes destabilized after the initial
saturation of the n=3 RSAE mode. The details of the linear and nonlinear
simulation results will be presented.
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[1] B. J. Tobias \textit{et al.}, Phys. Rev. Lett. \textbf{106}, 075003 (2011).\\[0pt]
[2] G.-Y. Fu et al., Phys. Plasmas \textbf{13}, 052517 (2006).
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2012.DPP.JI2.3