Behavior of the reversed field pinch with nonideal boundary conditions

Technical Report · Tue Nov 01 04:00:00 EST 1988

OSTI ID:6548016

Ho, Yung-Lung

The linear and nonlinear magnetohydrodynamic stability of current-driven modes are studied for a reversed field pinch with nonideal boundary conditions. The plasma is bounded by a thin resistive shell surrounded by a vacuum region out to a radius at which a perfectly conducting wall is situated. The distant wall and the thin shell problems are studied by removing either the resistive shell or the conducting wall. Linearly, growth rates of tearing modes and kink modes are calculated by analytical solutions based on the modified Bessel function model for the equilibrium. The effects of variation of the shell resistivity and wall proximity on the growth rates are investigated. The modes that may be important in different parameter regimes and with different boundary conditions are identified. The nonlinear behaviors are studied with a three-dimensional magnetohydrodynamics code. The fluctuations generally rise with increasing distance between the conducting wall and the plasma. The enhanced fluctuation induced v x b electric field primarily oppose toroidal current; hence, loop voltage must increase to sustain the constant. Quasilinear interaction between modes typically associated with the dynamo action is identified as the most probable nonlinear destabilization mechanism. The helicity and energy balance properties of the simulation results are discussed. The interruption of current density along field lines intersecting the resistive shell is shown to lead to surface helicity leakage. This effect is intimately tied to stability, as fluctuation induced v x b electric field is necessary to transport the helicity to the surface. In this manner, all aspects of helicity balance, i.e., injection, transport, and dissipation, are considered self-consistently. The importance of the helicity and energy dissipation by the mean components of the magnetic field and current density is discussed. 88 refs., 41 figs., 3 tabs.

• Research Organization: Wisconsin Univ., Madison (USA). Dept. of Physics
• DOE Contract Number: FG02-85ER53212
• OSTI ID: 6548016
• Report Number(s): DOE/ER/53212-131; ON: DE89005497
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700101 -- Fusion Energy-- Plasma Research-- Confinement
Heating
& Production
700107* -- Fusion Energy-- Plasma Research-- Instabilities
ALGORITHMS
BOUNDARY CONDITIONS
EQUILIBRIUM
INSTABILITY
INSTABILITY GROWTH RATES
MAGNETIC FIELDS
MATHEMATICAL LOGIC
MHD EQUILIBRIUM
NONLINEAR PROBLEMS
PINCH EFFECT
PLASMA INSTABILITY
PLASMA SIMULATION
REVERSE-FIELD PINCH
SIMULATION