Gyrokinetic simulations of reverse shear Alfven eigenmodes in DIII-D plasmas
- University of Colorado at Boulder, Boulder, Colorado 80309 (United States)
- University of California, Irvine, California 92697 (United States)
- General Atomics, San Diego, California 92186 (United States)
- Princeton Plasma Physics Lab, Princeton, New Jersey 08540 (United States)
- University of California, Davis, California 95616 (United States)
A gyrokinetic ion/mass-less fluid electron hybrid model as implemented in the GEM code [Y. Chen and S. E. Parker, J. Comput. Phys. 220, 837 (2007)] is used to study the reverse shear Alfven eigenmodes (RSAE) observed in DIII-D, discharge no. 142111. This is a well diagnosed case with measurement of the core-localized RSAE mode structures and the mode frequency, which can be used to compare with simulations. Simulations reproduce many features of the observation, including the mode frequency up-sweeping in time and the sweeping range. A new algorithmic feature is added to the GEM code for this study. Instead of the gyrokinetic Poisson equation itself, its time derivative, or the vorticity equation, is solved to obtain the electric potential. This permits a numerical scheme that ensures the E Multiplication-Sign B convection of the equilibrium density profiles of each species cancel each other in the absence of any finite-Larmor-radius effects. These nonlinear simulations generally result in an electron temperature fluctuation level that is comparable to measurements, and a mode frequency spectrum broader than the experimental spectrum. The spectral width from simulations can be reduced if less steep beam density profiles are used, but then the experimental fluctuation level can be reproduced only if a collision rate above the classical level is assumed.
- OSTI ID:
- 22113321
- Journal Information:
- Physics of Plasmas, Vol. 20, Issue 1; Other Information: (c) 2013 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
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