Studies of a poloidal divertor reversed field pinch

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

OSTI ID:6822267

Sarff, J S

Several attempts have been made to form a reversed field pinch (RFP) in a four-node, poloidal divertor configuration which positions the plasma far from a conducting wall. In this configuration, the plasma is localized within a magnetic separatrix formed by the combination of toroidal currents in the plasma and four, internal, conducting rings. These experiments were conducted on three devices: Tokapole II, the Wisconsin Levitated Octupole, and the modified Octupole with smaller conducting rings. Transient, RFP-like equilibria were obtained on Tokapole II and the Wisconsin Levitated Octupole. RFP-like equilibria with field reversal duration /approximately/1 msec were obtained in the small ring Octupole. None of these plasmas was sustained against resistive magnetic diffusion. Local, internal measurements of the magnetic field in Tokapole II plasmas indicated the plasma current and density were mostly confined to the region inside the magnetic separatrix. The sharp drop in plasma pressure near the separatrix generated a large diamagnetic current in that region. Large magnetic perturbations observed in the startup phase of these plasmas. On the small ring Octupole, the perturbation was measured to have a dominant poloidal mode number of m = 1 and toroidal mode numbers n /approximately/ /minus/5, i.e., internally resonant or nonresonant modes. This perturbation was stationary and was phase-locked to a magnetic field error. If the tenuous plasma region outside the separatrix is ''vacuum-like,'' then this behavior might represent current-driven instability owing to the lack of nearly, stabilizing boundary. Such instability is consistent with linear magnetohydrodynamic stability calculations and nonlinear simulations of a cylindrical REP plasma bounded by a large vacuum region and a distant conducting wall. 53 refs., 48 figs.

• Research Organization: Wisconsin Univ., Madison (USA). Plasma Physics Research
• DOE Contract Number: FG02-85ER53198
• OSTI ID: 6822267
• Report Number(s): DOE/ER/53198-130; ON: DE89005498
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700202* -- Fusion Power Plant Technology-- Magnet Coils & Fields
CONFINEMENT
DIVERTORS
EQUILIBRIUM
INSTABILITY
MAGNETIC FIELD CONFIGURATIONS
MHD EQUILIBRIUM
OPERATION
PINCH EFFECT
PLASMA CONFINEMENT
PLASMA DIAGNOSTICS
PLASMA INSTABILITY
POLOIDAL FIELD DIVERTORS
REVERSE-FIELD PINCH