Neutral beam injection for DEMO alternative scenarios

Within the current EU pre-conceptual design activities, reference demonstrative fusion power plant concept relies on ITER-like, pulsed H-mode plasmas (“DEMO1”). Simultaneously, alternative options are being considered. An example is “Flexi-DEMO”, which designed for steady-state plasma discharges, but can also be run at same with auxiliary heating systems if confinement time turns out to not sufficient non-inductive operations. Preliminary investigations have started ELM-free regimes, such as I-mode or QH-mode, due issues encountered in ELMs active control reactor scales. Neutral beam injection (NBI) one of candidates a DEMO and current-drive system. Depending system design, NBI optimized e.g. central (as DEMO1), Flexi-DEMO) even provide torque (which may favour access QH-mode regime). In present contribution we describe main features terms parameters (NBI energy, geometry) that would optimize these scenarios, particular regarding Flexi-DEMO regime. Wide-range parametric scans through METIS numerical simulations indicate optimal windows each configuration. These results need however further validations against technical constraints, available technology limits detailed transport simulations.