High power ICRF experiments on TFTR

ICRF heating experiments have been conducted in a variety of conditions on the TFTR tokamak. Power levels up to 11.4 MW have been applied. During NBI driven supershot discharges the central electron temperature has been increased from 9 kev to 13 kev via 3He minority heating with 6 MW of RF power. This temperature increase leads to a 70% increase in the projected alpha energy slowing down time. In gas fueled L‐mode discharges the energetic hydrogen minority tail is observed to strongly influence the MHD stability of the discharges. Besides the stabilization of the sawtooth instability previously reported, the destabilization of both the m=1 fishbone and the TAE (toroidal Alfven eigenmode) instabilities have been observed. The TAE instability is accompanied with significant (∼10%) loss of high energy ions and degradation in global confinement time.