Analysis of bulk ion heating with ICRH in JET high-performance plasmas

Ion cyclotron resonance heating (ICRH) of JET high-performance (optimized shear and hot-ion H-mode) deuterium discharges, characterized by strong neutral beam injection (NBI), high ion and electron temperatures and high deuterium-deuterium fusion reactivity, is analysed using numerical simulations. The main aim is to investigate under which conditions good bulk ion heating can be obtained with ICRH tuned to the fundamental hydrogen resonance, coinciding with the second-harmonic deuterium resonance, near the plasma centre. The analysis has been facilitated by adding NBI source terms in the ion cyclotron range of frequencies (ICRF) code PION, which calculates the time evolution of the ICRF power deposition and the resonating ions distribution functions in a self-consistent way. The results show that damping ICRF power on deuterons results in a more central bulk ion heating profile than minority hydrogen ions, which is an advantage. The highest bulk ion heating fractions of up to 50% of the total ICRF power were obtained by using multiple frequencies, the effects of which have been simulated in detail for the first time. Furthermore, operating with high plasma densities has been found to be beneficial for maximizing the bulk ion heating.