Destabilization of a stationary neoclassical tearing mode due impurity influx can lead to a potentially destructive disruption and is of significant concern for current and future tokamaks. A representative scenario was developed on TCV to experiment with applicable disruption avoidance techniques and produce a real time control system capable of handling such an event. Soft x-ray (SXR) radiation intensity and magnetic diagnostics analyses available in real time were used to provide plasma state information to the control system. Electron cyclotron current drive (ECCD) was employed to prevent NTM destabilization. Deposition of ECCD near the calculated q = 2 surface was able to prevent destabilization of the NTM if a large increase in SXR radiation intensity was used as the trigger. A delay in avoidance resulted in the plasma entering a disruptive state which required over 100 ms of continuous ECCD around the q = 2 surface to stabilize. Ramp down scenarios were studied to complete the design of a closed loop system. This system was then successfully tested using increasingly disruptive scenarios, through increased gas quantities, and the system was able to extend the discharge for a prescribed amount of time and safely ramp down the plasma current to the minimum controllable level. The system demonstrated in this work is presently limited to this specific type of disruption but this approach could be applied to other disruptive situations on the path to building a global disruption handling system.

New experiments at JET with the ITER-like wall show for the first time that ITER-relevant low field side resonance first harmonic ion cyclotron resonance heating (ICRH) can be used to control sawteeth that have been initially lengthened by fast particles. In contrast to previous (Graves et al 2012 Nat. Commun. 3 624) high field side resonance sawtooth control experiments undertaken at JET, it is found that the sawteeth of L-mode plasmas can be controlled with less accurate alignment between the resonance layer and the sawtooth inversion radius. This advantage, as well as the discovery that sawteeth can be shortened with various antenna phasings, including dipole, indicates that ICRH is a particularly effective and versatile tool that can be used in future fusion machines for controlling sawteeth. Without sawtooth control, neoclassical tearing modes (NTMs) and locked modes were triggered at very low normalised beta. High power H-mode experiments show the extent to which ICRH can be tuned to control sawteeth and NTMs while simultaneously providing effective electron heating with improved flushing of high Z core impurities. Dedicated ICRH simulations using SELFO, SCENIC and EVE, including wide drift orbit effects, explain why sawtooth control is effective with various antenna phasings and show that the sawtooth control mechanism cannot be explained by enhancement of the magnetic shear. Hybrid kinetic-magnetohydrodynamic