Erosion and impurity migration modelling in neon-seeded plasma discharges in ITER with a full-tungsten wall

Abstract The present work investigates global tungsten erosion and transport in two neon-seeded ITER discharges under burning plasma conditions using three-dimensional Monte-Carlo simulations with the ERO2.0 code. The modelling considers toroidally-symmetric plasma backgrounds obtained with the SOLPS-ITER code package, which cover the entire plasma edge from the pedestal up to the first wall. The calculations of the erosion source include contributions from all ionic charge states of deuterium, helium, and neon introduced as main radiating species in ITER, as well as from deuterium charge-exchange neutrals. In order to estimate the latter, bivariate energy- and angular-resolved impact distributions at 30 different poloidal locations across the device are used. Though this increases the accuracy of the corresponding erosion source estimate, the simulations demonstrate that contributions of charge-exchange neutrals and fuel isotopes in general remain only minor and that the erosion is clearly dominated by neon for both the main chamber and the divertor. In fact, the low-field side of the machine reveals higher erosion with most pronounced locations at the lower part of the main chamber wall and especially along the outer divertor target. It is also shown that a comparable amount of tungsten is released from divertor and main chamber surfaces. In more detail, ratios of divertor to main-chamber source between 0.6 and about 7 are obtained depending on the neon seeding level. Anomalous tungsten transport is chosen in agreement with the profiles imposed in SOLPS-ITER in order to maintain consistency throughout the scrape-off-layer plasma. For the low neon-seeded case, four times higher tungsten densities are observed at the outer midplane, which is explained by a more stagnant scrape-off-layer (SOL) allowing increased upstream transport. In contrast, transport of tungsten is predominantly downstream for less stagnant SOL conditions observed in the high-seeding case. The results contribute to a more comprehensive understanding of plasma–wall interactions in ITER, in particular in view of the transition to a full-tungsten machine.