Evolution of Be Migration after Be Evaporation in the JET tokamak
Beryllium will be used as main chamber armour material for ITER. Migration and re-deposition of eroded Beryllium is considered a potential hazard because Be might contribute to formation of tritium inventories by co-deposition and because of possible deterioration of tungsten armour by alloy formation with Be. In previous studies at JET, campaign integrated Be and C sources at the main chamber wall were compared to post campaign deposition measurements at retrieved divertor tiles. It turned out that both materials are predominantly deposited in the inner divertor. This observation can be interpreted as a consequence of erosion dominating at outer divertor and main chamber wall and migration of eroded material to the inner divertor following the experimentally observed plasma boundary flow pattern. To study the time scales of the corresponding erosion and migration processes in more detail and to obtain data suitable for benchmarking of impurity transport modelling, dedicated experiments with focus on a particular discharge scenario are required. L-mode discharges are particularly useful for this purpose because they allow avoiding the additional complication of ELMs.