First Experiments on Massive Gas Injection at JET – Consequences for Disruption Mitigation in JET and ITER
The mitigation of thermal and mechanical loads during disruptions is an urgent task to be solved for ITER to ensure the integrity of Plasma-Facing Components (PFC). However, extreme loads are already an issue for present day machines like JET and in particular for the new ITER-like wall implemented in JET which will have the material used in ITER for DT operation. Reduction of such loads to tolerable values is needed, thereby, the generation of high-energy electrons (RE) is of special concern. RE in JET can carry currents of up to 50% of plasma current before the disruption, leading to a fast and localised deposition of several MJ on plasma-facing components. Disruption mitigation has to fulfil three aims: mitigation of forces by halo and eddy currents, mitigation of convective heat loads during the thermal quench, mitigation of heat loads by runaway electrons. ITER needs a reduction of the forces by a factor 3-5 and a reduction of the thermal loads on Be and W components by a factor 10 to ensure integrity and lifetime of PFC.