Dynamic fuel retention and release under ITER like wall conditions in JET

The dynamic retention of fuel and their subsequent release in between discharges has been analyzed under the new ITER-like wall conditions in JET. Limiter discharges are determined by plasma interaction with the Be walls and show a very reproducible dynamic wall retention and release with no significant memory effect of the loading conditions from previous discharges. The dynamic retention at the end of discharges reaches values up to ≈3 × 1022 D-atoms. The retention rate at the beginning of the density flat top is typically ≈5–10 × 1021 D/s, with only a moderate decrease of few %/s. Within the accuracy of the present pressure measurements at JET, the retained fuel during plasma operation is released in between discharges, in agreement with gas balance studies based on cryopump regenerations [1]. The temporal behavior of the deuterium releases observed for about 1 day follows a t−0.7±0.1 dependence, very similar to observations under C wall conditions