ELM-wall interaction on JET and ITER

Significant interaction of ELM filaments with the vessel wall is now observed on JET by several diagnostics. To interpret the experimental data, a model of ELM-filament evolution was developed, with the radial velocity taken from experiment and the decay of filament density and temperature calculated based on parallel losses to the divertor targets. The model was found to successfully reproduce radial e-folding lengths of density, electron temperature and energy, λnELM,λTeELM and λWELM, inferred from dedicated outer gap-scan experiment for moderate Type-I ELMs (ΔW/W ∼ 5%, where W is the plasma stored energy). It also showed excellent agreement with observations of far SOL ELM ion energies on JET. For nominal ITER conditions (4 keV pedestal, 5 cm outer gap), the same model predicts that ∼8% of the ELM energy would be deposited on the main chamber wall (mostly on the upper X-point blanket modules), with the ions carrying most of this power and striking the wall tiles with an impact energy in excess of 1 keV.