Recent key contributions of ICRF heating in support of plasma scenario development and fast ion studies on JET and ASDEX Upgrade

Ion Cyclotron Resonance Frequency (ICRF) heating plays an important role in many present day experiments and it is one of the auxiliary heating methods that will be used in ITER. This paper reports on recent ICRF experiments carried out in H-mode and improved confinement regimes on the JET and ASDEX Upgrade (AUG) tokamaks to further consolidate the ICRF physics basis for ITER. The design of all the experiments has been guided by ICRF modelling, which has allowed the identification of the most suitable experimental configuration to obtain and/or observe the desired effects. First, 3He minority heating, which is one of the main ICRF scenarios at the full magnetic field of 5.3 T in ITER deuterium-tritium plasmas, has been investigated in JET high-performance hybrid target plasmas as well as AUG H-mode plasmas. The experiments were carried out in deuterium and will be expanded to deuterium-tritium and pure tritium isotope mixtures in the forthcoming JET campaigns. Second, new ICRF scenarios have been developed and tested on AUG to expand the parameter space for ITER relevant studies on AUG. This work has included second harmonic heating of hydrogen to provide central ICRF power deposition in ITER-like baseline like plasma scenario on AUG. The scheme has been compared and used in conjunction with the standard hydrogen minority heating. One of the advantages of using second harmonic heating of hydrogen is that it allows the use of ICRF heating in ITER relevant plasma scenario studies on AUG at lower magnetic fields than would be otherwise possible. Finally, third harmonic ICRF heating of D beam ions has been developed on AUG to provide a new tool to create very energetic ICRF-accelerated fast deuteron populations for fast ion studies as well as for testing fast ion and fusion product related diagnostics. Selected discharges have been modelled with ICRF modelling tools which has provided invaluable test cases for their experimental validation as well as supported the analysis of the experimental results.