ICRF heating of JET plasmas with the third harmonic deuterium resonance

Ion cyclotron range of frequencies (ICRF) heating experiments with the third harmonic deuterium resonance in the plasma centre have been carried out at JET. These experiments were the first to demonstrate third harmonic damping on initially Maxwellian plasmas. A record deuterium-deuterium (DD) fusion reaction rate for ICRF-only heating on JET was achieved. The discharges have been simulated with the PION code (a self-consistent calculation of the evolution of the distribution function and the ICRF power deposition). To obtain reasonable agreement between the measurements and the simulations, three additions to the PION code were necessary: (a) parasitic absorption at the plasma edge, (b) a particle loss term that removes particles above 4 MeV, i.e. the particles that were not confined in the discharges, and (c) a sawtooth model that accounts in a simplified way for the redistribution of fast ions at the sawtooth crashes. According to the simulations high energy tail formation on the distribution function of the resonating ions plays a crucial role in the power absorption.