Three-dimensional numerical simulations of the relaxation process in spheromak plasmas

Journal Article · Sun Jun 01 00:00:00 EDT 1986 · Phys. Fluids; (United States)

DOI:https://doi.org/10.1063/1.865621· OSTI ID:5705965

Katayama, K; Katsurai, M

Nonlinear evolution of three-dimensional magnetohydrodynamic (MHD) instabilities of a toroidal spheromak in a cylindrical flux conserver has been studied by numerical simulations for various initial equilibrium states with different q profiles. In spheromaks with q/sub a/>1, where q/sub a/ is the safety factor on the magnetic axis, nonlinear evolution of the resonant internal kink mode dominates with a poloidal mode number m = 1 and a toroidal mode number n = 1 that causes the poloidal flux amplification. This process corresponds to that of the internal disruption model for tokamaks by Kadomtsev (Sov. J. Plasma Phys. 1, 389 (1975)). In spheromaks with a very high q/sub a/, namely q/sub a/> or approx. =3, the gross n = 1 kink mode grows extensively in the region including the major axis of the torus, which causes the flux conversion from the toroidal to poloidal directions. For spheromaks with a low q/sub a/, namely q/sub a/< or approx. =0.5, the internal kink mode with a toroidal mode number napprox.1/q/sub a/ is first destabilized, and the excitation of the modes with lower n numbers down to n = 1 proceeds, while the n = 2 mode saturates. Nonlinear coupling of various modes leads to the flux conversion from the poloidal to toroidal directions. When a center conductor is present in this case, a reversed-field pinch (RFP) configuration once formed is sustained. Relaxations through pressure-driven modes are also discussed. All final states obtained in our simulations are quite near the Taylor state with an excess magnetic energy less than 10% of that of the Taylor state.

• Research Organization: Department of Electronic Engineering, University of Tokyo, Tokyo 113, Japan
• OSTI ID: 5705965
• Journal Information: Phys. Fluids; (United States), Vol. 29:6
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
PLASMA
MAGNETOHYDRODYNAMICS
NONLINEAR PROBLEMS
PLASMA INSTABILITY
RELAXATION
SPHEROMAK DEVICES
PLASMA CONFINEMENT
CYLINDRICAL CONFIGURATION
MAGNETIC FLUX
NUMERICAL ANALYSIS
SIMULATION
THREE-DIMENSIONAL CALCULATIONS
TOROIDAL CONFIGURATION
ANNULAR SPACE
CLOSED PLASMA DEVICES
CONFIGURATION
CONFINEMENT
FLUID MECHANICS
HYDRODYNAMICS
INSTABILITY
MATHEMATICS
MECHANICS
SPACE
THERMONUCLEAR DEVICES
TOKAMAK DEVICES
700107* - Fusion Energy- Plasma Research- Instabilities
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