Fast-ion transport optimization using the integrated TGLF-EP+Alpha Alfvén eigenmode transport model

Control of Alvfén eigenmodes (AEs) driven by energetic neutral beam injection (NBI) ions in DIII-D is explored with the TGLF-EP+Alpha model. TGFL-EP+Alpha is a reduced model assuming stiff-transport informed by DIII-D experiments and nonlinear gyrokinetic simulations. Neutron deficit below classical predictions (a proxy for AE transport of fast ions) is experimentally reduced by up to 35% by moving NBI off axis and/or moving electron cyclotron current drive to on-axis. TGLF-EP+Alpha captures these trends, predicting the evolving neutron signal to within 12% and qualitative features of the radius-time AE spectrogram across the entire current ramp. The general utility of TGLF-EP+Alpha is further demonstrated with other DIII-D whole-shot AE validations over a range of AE activity, with neutron predictions within 20% (or much better) across time in multiple AE-dominant and quiet cases. The physics-based TGLF-EP+Alpha model improves over ad hoc energetic particle diffusivity currently used in integrated modeling workflows. It’s inexpensive enough for scenario optimization and validated over a wide parametric range.