Session KP01 - Poster Session III.
POSTER session, Tuesday afternoon, March 23
Exhibit Hall, GWCC
There is a wide consensus that sawtooth instabilities in tokamaks are a direct consequence of the destabilization of the m=n=1 internal kink mode followed by a relaxation process enabling the plasma core to stabilise. The stability properties of this mode have been calculated using a state-of-the-art expression for the kinetic-MHD energy principle in the presence of an energetic ICRH minority ion population. Comparison with measurements of giant sawtooth duration in recent ICRH pulses from the JET DTE1 campaign suggests that energetic ions contribute significantly to countering the destabilizing effect that results from higher plasma pressures. It is found that the stabilising influence of the hot ions increases in parallel with sawtooth period, whilst the destabilising toroidal effects, notably the gradient of the Shafranov shift, also increase. This further suggests that analytical expressions for the perturbed generalised MHD energy can play a useful role in assessing the sawtooth stability of JET and predicting the performance for Next Step devices.