Ion orbit modelling of ELM-induced heat load and particle flux on the ITER first wall panels

ELM filaments can carry intense particle fluxes and energies to plasma-facing components (PFC), leading to temperature excursions and potential material erosion. These effects are amplified at the edges of gaps between the castellations required on the actively cooled PFCs which ITER will use. This study focuses on ion orbit modelling of ELM impact on tile edges of the ITER first wall panels (FWP), comparing both Be and W material options. To investigate the time-dependent spatial deposition of the ELM filaments and the subsequent penetration of ions with finite ion orbits into the castellation gaps, an idealized model of a filament structure propagating across the scrape-off layer is first simulated using the SMITER field line tracing environment, in combination with a fluid parallel transport model describing the filament energy loss from a separatrix release point. The model provides scans of the particle energies and fluxes at the FWP impact points, assuming the pre-ELM magnetic equilibrium is preserved during the filament propagation and for varying release parameters (e.g. initial T_i, radial filament propagation velocity, total energy of ELM). Deploying the same 3D ion orbit modelling used for simulations of the ELM-induced ITER divertor monoblock edge loading, estimates are made of the ion impact energies and angles on the FWP gap edges for varying gap width and misalignment. These may then be used to assess the enhancement in power loading and material sputtering due to the presence of castellations.