FEEDBACK STABILIZATION OF DISRUPTION PRECURSORS IN A TOKAMAK

Magnetic feedback control has been used in the DITE tokamak to substantially reduce saturated m=2, n=1 instabilities in both Ohmic discharges and discharges with lower hybrid current drive (LHCD). Feedback has been used for the first time to significantly increase the disruptive density limit in a tokamak. LHCD on DITE stabilizes the sawtooth instability but generates a large m=1,2, n=1 instability. Both components of this mode have been controlled for the first time with feedback. Open loop experiments with LHCD show that mode locking occurs and allow detailed study of this phenomenon. © 1990 The American Physical Society.