Recent results from ICRF experiments on ASDEX upgrade

ICRF has been applied at power levels up to of 4 MW for plasma heating with good results in the L‐ and H‐modes, alone and in combination with NI. Mainly minority heating has been applied so far, in some cases combined with second harmonic. Modulation experiments allowed to determine the power absorption efficiency, deposition profiles and the local heat conduction. The ICRF was also shown to have further interesting and beneficial effects on the plasma: the central impurity concentration of tungsten injected by Laser Blow Off was reduced, and a transiently improved energy confinement at the beginning of the NBI pulse was stabilized. The influence of plasma variations on the RF system and methods allowing stable operation, e.g. during the ELMy H‐mode, were studied. Coupling measurements were also used to examine SOL characteristics. Experiments comparing antennas with and without Faraday screen show only minor differences of their electrical properties and heating characteristics.