DT simulation of ICRF heated supershots in TFTR using TRANSP

Experiments using a mix of deuterium and tritium (DT) are planned for TFTR to study plasma conditions near break-even and to study the effects of fusion α particles. The principal goal of ICRF heating on TFTR is to enhance performance of plasmas during the DT physics phase of operations. Strongly centralized ICRF heating may play a critical role in obtaining high QD-T and high βα operation in TFTR as well as in future fusion reactors. ICRF heating of a dilute minority species leads to the formation of an energetic ion population which, according to existing theories, can act as a stabilizing agent against m = 1 internal kink instabilities which are thought to cause sawtooth oscillations in tokamak plasmas. Indeed, complete suppression of sawtooth oscillations has been observed for several energy confinement times during ICRF heating experiments on JET and TFTR. Furthermore, strong central electron heating has also been observed in these experiments. The corresponding rise in the central electron temperature translates into an increase in the slowing down time of either neutral beam or alpha particles in the discharge. Preliminary DT simulations of the experimental results in DD plasmas were performed with the TRANSP code. The results indicate that the βα would be increased for plasmas both with and without sawteeth. Comparison is made between H and 3He minority heating cases. In the H minority case, the application of ICRF experimentally results in enhanced neutron emission, despite the fact that shots exist for which the electron temperature is the same whether or not the ICRF is applied. TRANSP simulations indicate that this is due to second harmonic heating of the D beam ions