Observation of Equilibrium and Disruptive Instability in a Divertor-Tokamak Configuration in the dc Octopole

Abstract

An Ohmic current has been inductively driven in the dc octopole. Resulting flux surfaces are similar to those of a tokamak with poloidal divertors. Quiet and reproducible magnetic-probe traces indicate that the plasma has obtained a stable equilibrium. For the safety factor on the axis less than unity, a current-disruptive instability is observed to redistribute current density from the peak to the wings of the spatial distribution.