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

Abstract

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.