Estimation of ELM effects on Be and W erosion at JET-ILW

Abstract

An important W erosion mechanism in JET divertor is the physical sputtering by both, impurity (e.g. Be) and hydrogenic ions hitting the W divertor with energies determined by the pedestal temperature during edge-localized modes (ELMs)—the so-called intra-ELM sputtering of W. The earlier developed analytical approach for the W divertor gross erosion estimation using the Langmuir probe measurements has been improved in this work taking into account the time-resolved pedestal temperature and density drop during the pedestal crash under intra-ELM conditions. The improved model allows reproducing the measured at the divertor tile particle and heat fluxes evolution at the effective magnetic connection length matched with the previous JET- ITER like wall (ILW) studies. The estimates for the tungsten sputtered flux in intra- and inter-ELM conditions for quasi-steady state plasmas executed at the end of the first year of JET-ILW operation (C30C experiment) show that Type I ELMs contribute significantly (∼85%) to the gross tungsten erosion which is in a good agreement with the divertor optical emission spectroscopy (W I 400.9 nm line). ELM filament radial propagation is considered based on the advective-diffusive model and JET-C experiment results. The estimation for the ELM-induced local Be main chamber erosion at JET-ILW reveals the increase of the Be sputtered flux by 30% under intra-ELM conditions.