Detailed modelling of alpha transport due to ELM control fields in ITER: implications for PFCs and diagnostic design

This paper presents simulations of alpha-particle transport in ITER driven by static 3D magnetic field perturbations in the high-performance 15 MA Q = 10 baseline scenario, specifically resonant magnetic perturbations arising from edge-localized mode (ELM) control coils, combined with toroidal field ripple and effects from ferromagnetic materials. We employ the Lorentz-Orbit Code for Use in Stellarators and Tokamaks (LOCUST), which tracks fast-ion orbits under the Lorentz force and Monte Carlo collisions with the bulk plasma, taking into account the detailed geometry of ITER plasma-facing components. LOCUST uses GPU cards to enable the high-resolution modelling required to accurately resolve power fluxes across surfaces with complex morphologies, including unprotected cooling pipes beneath the dome divertor, and the generation of reliable synthetic diagnostics for the ITER Fast Ion Loss Detector (FILD) to support its design. The simulations include a range of ELM control coil current profiles with toroidal mode number n = 3. The results indicate that the total alpha-particle energy lost has a negligible impact on plasma performance, remaining below 1% of the alpha energy produced in D–T reactions. Furthermore, the power flux density on the divertor structures and the first wall remains well below design limits and is comparable to thermal and radiative loads. The simulated alpha flux on the FILD scintillator plate is well above the noise threshold and can be significantly higher than conservative estimates.