Fuel Retention Experiments in Carbon Configuration in JET

In order to achieve high accuracy gas balance and to minimise the contribution from previous experiments (history), fuel retention has been studied in JET in series of repetitive and identical discharges (6 to 8). The particle retention has been assessed for L and H-modes type I and type III (ELM energy up to 400kJ) ELMing H modes. The main parameter ranges of these discharges were Ip = 1.8-2.5MA, BT = 1.8-2.7T, gas rate ~0.5 to 1.7 ¥ 1022 Ds-1, high triangularity and auxiliary heating from 2 to 18MW (ICRH and NBI) respectively for the L and type I ELMing H-mode. When averaged over the heating phase, the retained flux varies in the range of ~2.0~¥1022 Ds-1 for the L-mode to ~2.8 ¥ 1022 Ds-1 for the Type I ELMs. Extrapolation to higher plasma performances (Ip = 3.5MA, 24MW of NBI+ICRH, gas injection 5 ¥ 1022 Ds-1 and 9.5MJ of diamagnetic energy) using the same plasma shape exhibit retention as high as 3-4 ¥ 1022 Ds-1. The particle recovery between discharges (in the absence of disruptions) is also shown to remain in the same range from pulse to pulse at around ~2-3 ¥ 1022 D and not correlation of the retention with the plasma performance has been identified.
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