Impact of the ITER-Like Wall on Divertor Detachment and on the Density Limit in the JET Tokamak

L-mode and H-mode density limit experiments with the ITER-Like Wall (ILW) have been investigated in the recent experimental campaign and compared with experiments in the JET carbon material configuration. The density limit is up to 40% higher in the Be/W- than in the C-machine. This is linked to the higher radiation fraction and correspondingly to earlier divertor detachment in the C- configuration. In the ILW configuration, the discharge demonstrates a stable operation with a completely detached outer divertor or even with stable X-point MARFE giving an opportunity for the realization of a feedback control for stabilization of the operation domain under fully detached divertor conditions. The H-L transition constitutes an effective undisruptive density limit for an H-mode plasma. Detachment itself does not trigger the H-L back transition, hence does not present a limit on plasma density. The H mode studies show that before an H mode quenches into an L mode the maximum achievable density is practically independent of the heating power.
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