Recent Sawtooth Studies on the Tokamak a Configuration Variable*

We report recent studies performed on the Tokamak a Configuration Variable on the sawtooth instability and its relation with Tearing Modes (TMs). The primary long-term aim of this work is to provide understanding of the relation between sawteeth and TMs so that reliable real-time schemes can be devised for combined sawtooth and TM control in burning plasma experiments such as ITER. Hence, our work has focused on studying: dynamical relation between sawtooth crash and subsequent onset of TMs, sometimes leading to disruptions, as a function of the plasma shape and current profile; coupling of the low m/n modes generated at the sawtooth crash; dynamical evolution of the toroidal rotation during sawteeth; real-time control techniques for the sawtooth period using localized electron cyclotron heating and current drive; distribution function of high energy electrons generated at the sawtooth crash.