Reversed-field-pinch research

Abstract

Theoretical and experimental research in the reversed-field pinch (RFP) is reviewed. In this system, Bθ ∼ Bϕ, q < 1 and Bϕ reverses in the outer regions of the plasma; stability at relatively high values of β is possible because there is high shear and, experimentally, confinement with β > 10% has been observed. Following a historical review of pinch research, the basic theoretical properties of the RFP are established including the equilibrium, toroidal displacement, diffusion and confinement; studies of ideal and dissipative MHD stability theory are then described. Experimental and theoretical work on relaxation and self-reversal, the process whereby an RFP distribution can be set up spontaneously and subsequently sustained, is presented and discussed. There follows a general account of RFP experiments. These are divided into ‘fast experiments’, which utilize small-bore insulating tori in which the distribution is usually set up by fast programming on microsecond timescales, and ‘slow experiments’, carried out in large metal-walled tori in which the field configuration is set up slowly by self-reversal on millisecond timescales. A brief account of RFP reactor studies and of new and future experiments is then given, followed finally by a general discussion in which the main conclusions are presented.

Fundamental statistical descriptions of plasma turbulence in magnetic fields

“…An application of considerable practical importance is turbulence in reversed-field pinches (Bodin and Newton, 1980), which is adequately described by MHD equations (including Ohm's law E + c −1 u × B = η cl j, where η cl is the classical resistivity). In a typical experimental situation, the axial current is specified.…”

Physics of magnetic confinement fusion

“…But the next element, 8 Be is not stable. The triple-alphaprocess 3 4 He → 12 C, 12 C being stable itself, involves three particles and has, therefore, a low probability.…”

“…In tokamaks, the ratio of B tor /B pol > 1. Another concept with plasma currents is the reversed field pinch (RFP) with B tor /B pol ∼ 1 [8]. Tokamaks and RFPs belong to the category of internal confinement systems because part of the confining magnetic field is produced by currents flowing inside the plasma.…”

Extreme ultra-violet burst, particle heating, and whistler wave emission in fast magnetic reconnection induced by kink-driven Rayleigh-Taylor instability

“…4 Furthermore, magnetic reconnection enables Taylor relaxation, 5 the mechanism by which plasmas selforganize into spheromak 6 or reversed field pinch (RFP) configurations. 7,8 Magnetic reconnection involves extreme magnetic nonuniformity and was long considered to be governed by a resistive magnetohydrodynamics (MHD) differential equation 9,10 for the out-of-plane vector potential component A z . Because this equation predicts reconnection far slower than observed, 4,11 much effort has gone into developing models predicting faster reconnection and this effort has culminated in the general agreement that fast reconnection results from Hall and finite m e terms missing from MHD.…”