Control of disruption-generated runaway plasmas in TFTR

Many disruptions in the Tokamak Fusion Test Reactor (TFTR) (Meade and the TFTR Group 1991 Proc. Int. Conf. on Plasma Physics and Controlled Nuclear Fusion (Washington, DC, 1990) vol 1 (Vienna: IAEA) pp 9–24) produced populations of runaway electrons which carried a significant fraction of the original plasma current. In this paper, we describe experiments where, following a disruption of a low-beta, reversed-shear plasma, currents of up to 1 MA carried mainly by runaway electrons were controlled and then ramped down to near zero using the ohmic transformer. In the longer lasting runaway plasmas, events resembling Parail–Pogutse instabilities were observed. (paper)