Fast Ion Interactions with RF Waves in IC Range of Frequencies in JET D-T Experiments

This work analyses synergistic interactions between radio frequency (RF) waves in the Ion Cyclotron Resonance Heating (ICRH) range and fast ion populations—both Neutral Beam Injection (NBI)-driven and fusion-born alpha particles—based on recent Deuterium-Tritium (D-T) experiments at JET [1]. These effects raise important considerations for future fusion reactors using ICRH, such as ITER and SPARC. Key issues include (i) parasitic RF power absorption by alphas and NBI ions, (ii) enhanced fast ion losses, and (iii) impacts on alpha heating efficiency. However, such interactions may also boost fusion performance by increasing reactivity between fast D or T ions and the bulk plasma.

Systematic studies during JET's D-T campaign [2, 3] using TRANSP [3] and JETTO [4], supported by neutron diagnostics, predict a 10–29% rise in fusion reactivity due to ICRH-accelerated fast ions, depending on scenario and plasma conditions. Effects on alpha orbit losses and heating were evaluated using data from the Neutral Particle Analyzer, scintillator detectors, Faraday cups, and TRANSP simulations. Results show RF-induced changes in alpha distribution without increased losses. Simulations also indicate a modest rise in electron and ion heating from alpha particles due to these synergistic effects.