Higher stable beta by use of pre-emptive electron cyclotron current drive on DIII-D

Electron cyclotron current drive (ECCD) is used in conjunction with accurate real-time equilibrium reconstructions to operate a tokamak plasma at high beta without the destabilization of a performance-degrading neoclassical tearing mode that otherwise is metastable and therefore appears consistently. This is the first experiment in which the alignment of the ECCD on the rational surface being stabilized is maintained in the absence of the mode. Driving current at the rational surface eliminates the metastable condition, thereby making the mode stable. (letter)