LHCD coupling during H-mode and ITB in JET plasmas

Good coupling of the LH power during the whole internal transport barrier (ITB) phase has been achieved in JET by fitting the plasma shape to the LH antenna shape and by injecting CD4 gas from a pipe near to the LH grill. No adverse effect on the edge pedestal or on the ITB quality, or significant impurity influx is observed. The key is the low ionization potential of all the CD4 dissociation chain, which is completed inside the SOL. Promising perspectives are open for injecting safely LHCD with more power during an ITB.