Speaker
Description
Fast ion (FI) transport by Toroidal Alfven Eigenmodes (TAEs) is predicted to be of great importance in future tokamaks with high rates of deuterium-tritium fusion, since plasma self-heating capability relies on good confinement of fast alpha particles. Resonance between fast ions and TAEs occurs within distinct ‘resonance regions’ of phase space, which grow wider when the TAE mode amplitude increases. If these resonance regions are separate then fast ion transport is limited; if multiple resonance regions overlap then large-scale stochastic transport of fast ions can occur, jeopardizing confinement. This paper introduces a reduced model to predict the ‘resonance overlap threshold’ – the transition between these two transport scenarios – under various plasma conditions. The reduced model is formulated using only simple analytical expressions, in order to produce a computationally inexpensive alternative to existing fast ion transport codes, for ease of implementation in integrated modelling. Model validation is carried out using HALO code simulations, as well as comparison with experimental data from ITER-relevant scenarios in the spherical tokamak MAST-Upgrade. This model provides a useful step in increasing efficiency of predictive modelling for next-generation fusion reactors.
