Multipinch – a reversed-field pinch with a magnetic well

The Multipinch is an axisymmetric, vertically elongated toroidal pinch with a reversed toroidal field and an internal figure-eight separatrix. Unlike the circular cross-section pinch, the Multipinch configuration has a magnetic well. A magnetohydrodynamic equilibrium code for a non-circular reversed-field pinch is described and equilibrium calculations for the experimental device are presented. Experimental results concerning plasma configuration and stability are given. It was found that the up-down symmetric configuration became asymmetric when the toroidal current was increased to a level at which the toroidal field at the conducting shell wall became zero. This was found to be consistent with the minimum-energy Taylor configuration for the vertically elongated Multipinch.