Comparison of ICRF and NBI Heated Plasmas Performances in the JET ITER-Like Wall.

During the initial operation of the JET ITER-like wall, particular attention was given to the characterization of the Ion Cyclotron Resonance Frequency (ICRF) heating in this new metallic environment. In this contribution we compare L-modes plasmas heated by ICRF or by Neutral Beam Injection (NBI). ICRF heating as expected led to a much higher centrally peaked power deposition on the electrons and due to the central fast ion population to stronger sawtooth activity. Surprisingly, although a higher bulk radiation was observed during the ICRF phase, the thermal plasma energy was found similar for both cases, showing that a higher radiation inside the separatrix was not incompatible with an efficient central heating scheme. The higher radiation was attributed to the presence Tungsten (W). Tomographic inversion of SXR emissions allowed a precise observation of the sawtooth effect on the radiation pattern. W concentration profiles deconvolved from SXR emission showed the flattening of the profiles due to sawtooth for both heating and the peaking of the profiles in the NBI case only hinting for extra transport effect in the ICRF case. [ABSTRACT FROM AUTHOR]