Burn control resulting from toroidal field ripple

Abstract

The enhanced transport due to toroidal magnetic field ripple is proposed as a means of averting thermal runaway in a tokamak reactor in the post-ignition stage. A theoretical analysis applied to a typical reactor design reveals that peak-to-average edge ripple of the order of 2% is sufficient to terminate the thermal excursion at reasonable values of β without significantly increasing the difficulty of reaching ignition. These analytic predictions, which are shown to agree well with radial transport code results, suggest that a properly specified ripple is one way of achieving a controlled burn in tokamak reactors.