ICRH modelling of the Baseline D-T scenario in JET

In the 2021 and 2023 D-T campaigns in JET various scenarios with potential for application in fusion reactors have been studied. The mandate of the “Baseline” experiments was to explore the possibility to operate at high density, magnetic field and current. Although extremely promising results were obtained in D plasmas in the running-up to the actual D-T campaign and up to 8MW of fusion power was produced when adopting this scenario in D-T [1],[2], it was - in contrast to the record T-rich scenario [3] - not possible to sustain D-T shots for the envisaged 5 seconds while also steadily producing more than 10MW of fusion power. In view of the Baseline being considered as a prime candidate for maintaining a high-density plasma in future machines, the underlying reasons are still being explored to enable offering perspectives for possible cures for next-generation experiments. The present paper contributes to that: It concentrates on the detailed modelling of auxiliary (RF & NBI) heating aspects and on the synergy between them, allowing a better understanding of the key role of the auxiliary heating in these high-performance shots. It complements papers that concentrated on key - interrelated - aspects such as transport (see e.g. [4]), MHD (see e.g. [5]), impurities [6, 7], pedestal dynamics [8] and control [9]. One aspect setting the scenarios tested in D-T apart and which has several repercussions is that the Baseline plasma current and hence the density is higher and flatter. This allows to profit optimally from the fact that the neutron rate is proportional to the densities of the fusion fuel ions. However, the higher density affects the beam penetration and modifies the collisionality as well as the beam power deposition profiles. This has nonnegligible implications, some of which will be discussed here.