1 EX/P5-32 WALLDYN simulations of global impurity migration in JET and extrapolations to ITER

The migration of first wall material due to erosion, plasma transport and re-deposition is one of the key challenges in current and future fusion devices. To predict erosion/re-deposition patterns and to understand the underlying principal processes, the global simulation code WallDYN was developed. It couples the evolution of the first wall surface composition to plasma impurity trans-port. To benchmark the WallDYN model, it was applied to the JET ITER-Like Wall experiment (JET-ILW), which mimics the ITER first wall material configuration and is thus an ideal environ-ment to validate the predictive significance of WallDYN calculations for ITER application. The WallDYN calculations show good agreement with the Be deposition patterns determined from JET-ILW post-campaign wall tile analysis. The WallDYN results on W erosion & deposition also qualitatively match the post mortem patterns but quantitatively fall short by factor of 20 which can be consolidated by including the influence of ELMs on the W erosion source. Applying the same model and process physics as for the JET calculations, the impurity migration and resulting fuel species co-deposition in ITER for different wall configurations and background plasmas was calculated. The simulations show that C containing wall configurations lead to unacceptable T retention whereas for the current ITER material choice (Be wall & W divertor) co-deposition will not limit the ITER operation. However the erosion of W by self-sputtering even without the contribution of ELMs could hamper ITER operation under certain plasma scenarios