Fully electromagnetic gyrokinetic eigenmode analysis of high-beta shaped plasmas
- General Atomics, P.O. Box 85608, San Diego, California 92186-5608 (United States)
A new, more efficient method to compute unstable linear gyrokinetic eigenvalues and eigenvectors has been developed for drift-wave analysis of plasmas with arbitrary flux-surface shape, including both transverse and compressional magnetic perturbations. In high-beta, strongly shaped plasmas like in the National Spherical Torus Experiment (NSTX) [M. Ono et al., Nucl. Fusion 40, 557 (2000)], numerous branches of closely spaced unstable eigenmodes exist. These modes are difficult and time-consuming to adequately resolve with the existing linear initial-value solvers, which are further limited to the most unstable eigenmode. The new method is based on an eigenvalue approach and is an extension of the GYRO code [J. Candy and R. E. Waltz, J. Comput. Phys. 186, 545 (2003)], reusing the existing discretization schemes in both real and velocity-space. Unlike recent methods, which use an iterative solver to compute eigenvalues of the relatively large gyrokinetic response matrix, the present scheme computes the zeros of the much smaller Maxwell dispersion matrix using a direct method. In the present work, the new eigensolver is applied to gyrokinetic stability analysis of a high-beta, NSTX-like plasma. We illustrate the smooth transformation from ion-temperature-gradient (ITG)-like to kinetic-ballooning (KBM)-like modes, and the formation of hybrid ITG/KBM modes, and further demonstrate the existence of high-k Alfvenic drift-wave 'cascades' for which the most unstable mode is a higher excited state along the field line. A new compressional electron drift wave, which is driven by a combination of strong beta and pressure gradient, is also identified for the first time. Overall, we find that accurate calculation of stability boundaries and growth rates cannot, in general, ignore the compressional component {delta}B{sub ||} of the perturbation.
- OSTI ID:
- 21531969
- Journal Information:
- Physics of Plasmas, Vol. 17, Issue 11; Other Information: DOI: 10.1063/1.3495976; (c) 2010 American Institute of Physics; ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ALFVEN WAVES
BALLOONING INSTABILITY
DRIFT INSTABILITY
EIGENFUNCTIONS
EIGENVALUES
ELECTRON DRIFT
EXCITED STATES
HIGH-BETA PLASMA
ION TEMPERATURE
NSTX DEVICE
PRESSURE GRADIENTS
TEMPERATURE GRADIENTS
CLOSED PLASMA DEVICES
ENERGY LEVELS
FUNCTIONS
HYDROMAGNETIC WAVES
INSTABILITY
PLASMA
PLASMA INSTABILITY
PLASMA MACROINSTABILITIES
PLASMA MICROINSTABILITIES
SPHEROMAK DEVICES
THERMONUCLEAR DEVICES
TOKAMAK DEVICES