A new look at JET operation with Be as plasma facing material

Experiments at JET with Be as plasma-facing material demonstrate that although Be PFCs are easily damaged, the consequences for plasma operation are mild. L-mode plasmas up to a current of 7MA and heating power ∼30MW were obtained on heavily damaged Be limiter with ∼12MJ plasma energy, albeit with a very high Be content. The behaviour of H-mode plasmas in contact with a molten Be divertor target was studied. Despite the heavy damage to the target (∼3mm molten grooves) no plasma performance deterioration was observed for medium density ELMy H-modes. Type I ELMs, in these conditions, lead to ∼40μm melt layer formation but to an average melt layer loss of only ∼4%. Based on these results, conclusions for ITER limiter and divertor operation are extracted.