Heating D ions to optimal D–T fusion energies in JET-ILW

Abstract In JET-ILW, beam-target reactions contribute to a large fraction of the fusion power generated in deuterium–tritium (D–T) plasmas, with core ion temperatures of 10–12 keV and large neutral-beam injection (NBI) power. Previous modelling done in preparation for the recent D–T campaigns in JET have shown that injecting D beam ions with energies of ∼120 keV in T–rich plasmas produces larger 14 MeV fusion yield than in 50:50 D:T plasmas, but such scenario had never been tested in past D–T experiments. In addition, the simulations showed that fundamental ion cyclotron resonance heating (ICRH) of the D ions can significantly boost the net fusion reactivity, since both the D-bulk ions and the fast D-beam ions are accelerated to energy ranges that are optimal for the D–T reactions to take place. In the last JET D–T campaigns (DTE2 and DTE3), dedicated experiments confirmed—for the first time—the improved fusion performance of T-rich plasmas with high D-NBI power and highlighted the key impact of fundamental D ICRH on the fusion performance. This new scenario led to the world-wide D–T fusion energy record ever achieved in a fusion device and allowed to sustain more than 12 MW of fusion power averaged over 5 s. The main results of these unprecedented experiments will be presented and the NBI + ICRF physics responsible for the high fusion performance achieved will be highlighted through numerical modelling.