Sawteeth dynamics in JET Baseline Discharges with Mixtures of Isotopes

Sawteeth (ST) dynamics in JET Baseline discharges with Deuterium (D), Tritium (T) and D-T mixtures has been considered in order to investigate the confinement at high beta operations at 3.5 MW, 3.3 T and q95=3. . In this framework, ST can play a key role in the energy loss triggering magnetoidrodynamic (MHD) instabilities, as the Neoclassical Tearing Modes (NTMs) responsible for a decrease of performances at high beta. As the long ST periods increasing with isotope mass, the destabilization of these modes should be more favoured in D-T plasmas than in D. However, in these plasma scenario at high current the NTM onset is not frequent because the betaN is often below a critical threshold needed to trigger these modes. So, the observed NTM, triggered at intermediate poloidal (m=4,5,6) and toroidal (n=3,4,5) numbers, should guarantee poor confinement loss except in some cases for modes 4/3. On the other hand, it is important to study under which conditions similar ST crashes in isotopes mixtures at high current and power can /cannot trigger NTMs with effect on confinemet for predictive analysis. To meet this goal, the simulation of experimental ST and NTM dynamics with theoretical models allows to provide indications in order to understand and possibly avoid the onset of these resistive modes.