LHCD Operation with the ITER-Like Wall at JET

In this paper important aspects of Lower Hybrid Current Drive (LHCD) operation with the ITER Like Wall (ILW) at JET are reported. Impurity release during LHCD operation was investigated and it was found that there is no significant Be increase with LHCD power. Concentration of W was analysed in more detail and it was concluded that LHCD contributes negligibly to its increase. No cases of W accumulation in LHCD-only heating experiments were observed so far. LHCD coupling was studied and optimised to achieve the level of system performance similar to before ILW installation. Measurements by Li-beam were used to study systematic dependencies of the SOL density on the gas injection rate from a dedicated gas introduction module and the LHCD power and launcher position. Experimental results are supported by modelling. Observations of arcs in front of the LHCD launcher and hotspots on magnetically connected sections of the vessel are reported. Overall, a relatively trouble-free operation of the LHCD system up to 2.5MW of coupled microwave power in L-mode plasma was achieved with no indication that the power cannot be increased further.
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EFDP12034 2.68 Mb