Comparison of long term fuel retention in JET between carbon and the ITER-Like Wall

Abstract Long term fuel retention experiments have been performed in JET with the ITER- Like Wall (JET-ILW) and compared with reference discharges in the preceding phase with carbon wall (JET-C) in ohmic, L and H-mode plasma scenarios. The long term fuel retention is evaluated through global gas balance with an accuracy of 1.2% for series of repetitive pulses (10–25) carried out over a full day of experiments. Compared to carbon wall, with the JET-ILW, for L mode, the retention exhibits also a drop from 1.26 × 10 21  Ds −1 to 4–8 × 10 19  Ds −1 . Finally for Type III and type I ELMy H-mode, the retention decreases from 1.37 × 10 21  Ds −1 to 7.2 × 10 19  Ds −1 and from 1.7 × 10 21  Ds −1 to 2.7 × 10 20  Ds −1 respectively. The retention rates with the JET-ILW exhibit a decrease by a factor of about 10 compared to JET-C attributed to a reduction of carbon impurities and less fuel content in Be codeposition.