Understanding performance-limiting MHD in spherical tokamaks

Magnetically-confined fusion is a strong candidate to fulfil the need for future clean and reliable electrical power generation, and the development of this energy source is a massive international research challenge. The Spherical Tokamak presents exciting prospects both for fundamental research into the physics of fusion plasmas and as a future power plant. The MAST (Mega Amp Spherical Tokamak) at CCFE has recently undergone a major upgrade, and MAST-U will make significant input into the international fusion research programme. Furthermore, the STEP programme opens up the possibility of a spherical tokamak as a future fusion reactor.
It will be essential to understand, avoid, mitigate or control magnetohydrodynamic (MHD) instabilities in MAST-U so that the experiment can reach high performance, long pulse operation and fulfil its mission. This knowledge can then be applied to improved MAST-U scenarios and to design future spherical tokamaks. The first part of the project will involve analysing data from MAST-U (for example, magnetics and Thomson scattering data) in order to identify which instabilities are important, such as the long lived mode or neoclassical tearing modes. Based on this, models will be developed using linear or nonlinear MHD codes, and benchmarked against the data. The modelling will be used to explore parameter regimes and determine how to mitigate or avoid the instabilities. The modelling may exploit, where relevant, synergies with solar MHD studies, for example, 3D simulations of nonlinear kink instabilities in solar flares undertaken by the supervisor.
The project is partly supported by CCFE and will be carried out in close collaboration with the CCFE supervisor and other staff at CCFE working on MAST-U.