Description
Fast Ions (FIs), generated from auxiliary heating or fusion reactions, can resonantly interact with MHD modes, leading to their redistribution or loss thus reducing the overall fusion power. One method to modelling such interactions is the self-consistent hybrid kinetic-MHD approach in which the bulk thermal plasma is treated within the MHD framework and the FIs are treated with a full-F particle-in-cell approach. The wave-particle coupling is achieved via particle orbits determined fully by the electromagnetic MHD fields, while the MHD equations are solved accounting for the anisotropic pressure arising from the FI population.
In this contribution, we present recent developments of the unified hybrid kinetic-MHD model in the non-linear code JOREK. Existing modules of JOREK used to model the FIs have been integrated into a unified framework that enables consistent coupling between reduced- or full-MHD models and kinetic particle populations. This restructuring improves maintainability, flexibility, and facilitates future extensions to enable other kinetic species, or more detailed kinetic physics. Benchmark comparisons between the legacy and unified implementations have been performed using the ITPA-TAE test case, demonstrating consistent behaviour between the two approaches.
The hybrid framework developed here establishes the computational capability to explore such FI-MHD interactions in detail and represents an important step towards realistic simulations of FI effects. In particular, this will be applied to MAST-U experiments, which provide a rich variety of FI-driven phenomena, including fishbone and TAE activity. Understanding these effects is central to predicting and optimizing plasma performance. As a first case, MAST-U shot #48821, which exhibits significant fishbone activity, has been selected for initial modelling; input profiles prepared, and preliminary MHD-only simulations performed, with hybrid kinetic-MHD simulations including FIs currently underway.