Edge localized linear ideal magnetohydrodynamic instability studies in an extended-magnetohydrodynamic code

Journal Article · Mon Mar 15 00:00:00 EDT 2010 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.3309732· OSTI ID:21347153

Burke, B J ^[1]; Kruger, S E ^[2]; Hegna, C C; Zhu, P; Snyder, P B; Sovinec, C R; Howell, E C ^[3]

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1. University of Wisconsin-Madison, 1500 Engineering Drive, Madison, Wisconsin 53706 (United States)
2. Tech-X Corporation, Boulder, Colorado 80303 (United States)
3. General Atomics, San Diego, California 92186 (United States)

A linear benchmark between the linear ideal MHD stability codes ELITE [H. R. Wilson et al., Phys. Plasmas 9, 1277 (2002)], GATO [L. Bernard et al., Comput. Phys. Commun. 24, 377 (1981)], and the extended nonlinear magnetohydrodynamic (MHD) code, NIMROD [C. R. Sovinec et al.., J. Comput. Phys. 195, 355 (2004)] is undertaken for edge-localized (MHD) instabilities. Two ballooning-unstable, shifted-circle tokamak equilibria are compared where the stability characteristics are varied by changing the equilibrium plasma profiles. The equilibria model an H-mode plasma with a pedestal pressure profile and parallel edge currents. For both equilibria, NIMROD accurately reproduces the transition to instability (the marginally unstable mode), as well as the ideal growth spectrum for a large range of toroidal modes (n=1-20). The results use the compressible MHD model and depend on a precise representation of 'ideal-like' and 'vacuumlike' or 'halo' regions within the code. The halo region is modeled by the introduction of a Lundquist-value profile that transitions from a large to a small value at a flux surface location outside of the pedestal region. To model an ideal-like MHD response in the core and a vacuumlike response outside the transition, separate criteria on the plasma and halo Lundquist values are required. For the benchmarked equilibria the critical Lundquist values are 10{sup 8} and 10{sup 3} for the ideal-like and halo regions, respectively. Notably, this gives a ratio on the order of 10{sup 5}, which is much larger than experimentally measured values using T{sub e} values associated with the top of the pedestal and separatrix. Excellent agreement with ELITE and GATO calculations are made when sharp boundary transitions in the resistivity are used and a small amount of physical dissipation is added for conditions very near and below marginal ideal stability.

• OSTI ID: 21347153
• Journal Information: Physics of Plasmas, Vol. 17, Issue 3; Other Information: DOI: 10.1063/1.3309732; (c) 2010 American Institute of Physics; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
BALLOONING INSTABILITY
BOUNDARY LAYERS
EQUILIBRIUM
EQUILIBRIUM PLASMA
H-MODE PLASMA CONFINEMENT
MAGNETOHYDRODYNAMICS
STABILITY
TOKAMAK DEVICES
CLOSED PLASMA DEVICES
CONFINEMENT
FLUID MECHANICS
HYDRODYNAMICS
INSTABILITY
LAYERS
MAGNETIC CONFINEMENT
MECHANICS
PLASMA
PLASMA CONFINEMENT
PLASMA INSTABILITY
PLASMA MACROINSTABILITIES
THERMONUCLEAR DEVICES