Study of ICRH scenarios for thermal ion heating in JET D-T plasmas

Various ion cyclotron resonance heating (ICRH) scenarios relevant for the D-T phase of the JET tokamak are studied. Recent ICRH experiments in JET ( ³He)-D and ( ³He)-H plasmas confirmed the possibility of electron heating enhancement in the mode conversion (MC) regime due to the constructive interference of the reflected fast waves. Such a heating enhancement in D-T plasma is investigated first for JET-like conditions for both dipole and +π/2 ICRH antenna phasing, and for T concentration varied from 0% to 100%. It is shown that most of the MC scenarios at comparable concentrations of D and T species suffer from a parasitic absorption by fusion-born alpha-particles and NBI-produced fast ions whereas the impact of such fast ions in the minority heating (MH) ICRH schemes is substantially smaller. A possibility of ion heating enhancement due to the interference effect is shown for the MH scenarios. It is found that thermal ion heating becomes dominant in tritium-rich plasmas with T concentration ∼80%. The efficiency of ion heating in such a scenario is compared with the alternative ³He minority ICRH scenario in D:T=50:50 plasmas.