Sawtooth pacing with on-axis ICRH modulation in JET-ILW

Abstract

A novel technique for sawteeth control in tokamak plasmas using ion-cyclotron resonance heating (ICRH) has been developed in the JET-ILW tokamak [2]. Unlike previous ICRH methods, which explored the destabilization of the internal kink mode when the radiofrequency (RF) wave absorption was placed near the q=1 surface, the technique presented here consists of stabilizing the sawteeth as fast as possible by applying the ICRH power centrally and inducing a sawtooth crash by switching it off at the appropriate instant. Since it employs on-axis ICRH, this technique is aligned with other ICRH applications that require central plasma heating such as high-Z impurity control and fusion power enhancement. The validation of this method in JET-ILW L-mode discharges is presented.