This work assesses the effect of the isotope mass on the linear pedestal magnetohydrodynamic (MHD) stability in JET, starting from a reference deuterium shot that is part of an isotope mass scan at fixed gas rate and βN. The stability is studied using the JOREK code with an extended visco-resistive MHD model, by building the pedestal profiles until an unstable mode is triggered, and studying the changes in critical pedestal pressure when the isotope mass is varied. The work shows that changing the isotope mass from deuterium to tritium can allow for an increase in the achievable pedestal pressure. This is shown to be due to the impact of the isotope mass on the diamagnetic stabilization, and the change in pedestal pressure predicted in this way is in qualitative agreement with the experimental results. The work also shows that increasing the pedestal density at fixed pedestal temperature can result in a significantly different critical pressure than increasing the pedestal temperature at fixed pedestal density. This is again attributed to the influence of the diamagnetic flows on the pedestal stability, which changes differently when the temperature is increased compared to when the density is increased. These results validate previous results which have been obtained with the lower fidelity linear resistive MHD code CASTOR, which does not self-consistently treat the diamagnetic flows.
Nyström et al. (Sun,) studied this question.