Impact of alpha effect on ICRH scenarios on CFETR

Abstract The efficiency of ion cyclotron resonance heating (ICRH) is highly sensitive to plasma composition, indicating that fusion-born alphas, which have already been observed in deuterium-tritium experiments at JET, will have a non-negligible influence in future fusion reactors. This study aims to investigate the impact of alphas on various ICRH scenarios intended for devices similar to the Chinese Fusion Engineering Testing Reactor. An equivalent Maxwellian distribution is employed for a detailed analysis of the potential effects of alphas on ICRH. Preliminary findings indicate that the Doppler broadening mechanism allows alpha particles to absorb ICRH wave energy across a considerably broad spatial area. Furthermore, the relative positioning between the cutoff layer within the plasma and the fundamental resonance layer of alpha particles is crucial for determining absorption. Among the planned ion heating scenarios, alphas are bound to absorb wave energy in both the deuterium minority and three-ion heating scenarios, potentially becoming the dominant absorbers and thereby reducing the heating efficiency for fuel ions. Conversely, the helium-3 minority and second harmonic tritium heating scenarios appear to be less affected by alphas, making them promising candidates for playing a pivotal role in future fusion reactors.