Description
Self-regulation magnetic flux pumping has been experimentally investigated in different devices, such as DIII-D, ASDEX Upgrade (AUG), JET, MAST-U, and some other tokamaks. Such experiments address sawtooth control and improve plasma confinement in hybrid scenarios, especially for future long-pulse discharges. Magnetohydrodynamic (MHD) modelling has revealed that the negative MHD dynamo effect, produced by m/n = 1/1 quasi-interchange mode, plays a critical role in redistributing plasma current and poloidal magnetic flux, which clamps the central safety factor (q0) close to unity and prevents sawtooth onset. On this basis, the modelling at realistic parameters for the AUG flux pumping discharge challenges the capability of JOREK code to quantitatively reproduce the experimentally observed dynamo loop voltage during flux pumping. The parameter regions of flux pumping are systematically investigated to support the development of a fast predictive surrogate model, which also shows that flux pumping is mainly accessible at the high-Hartmann numbers and above the plasma beta threshold. This work constitutes a further study of the nonlinear dynamics of flux pumping and sawtooth in AUG and JET. At low Hartmann numbers and below the plasma beta threshold of flux pumping, sawteeth are observed in the AUG modelling. The extended MHD model incorporating the two-fluid effect is being adopted to study the linear properties of quasi-interchange and internal kink modes, as well as the nonlinear dynamics of flux pumping and sawtooth. In parallel, nonlinear MHD modelling of flux pumping for the relevant JET discharge is being carried out, with the objective of extrapolating the knowledge of flux pumping from moderate devices (e.g., AUG) to larger ones (JET).