Energy confinement in ohmic discharges in H, D and T on JET-ILW*

The energy confinement of ohmic discharges is investigated in JET-ILW using discharges with steady density plateaus and neutral beam blips to obtain accurate profiles of the intrinsic rotation and ion temperature using main ion charge exchange spectroscopy. A comparison between matched hydrogen and deuterium pulses has experimentally demonstrated a shift from electron to ion dominated transport at the LOC-SOC transition and a reduction in energy confinement with reduced isotope mass. The latter is largely due to an increase in electron-ion equipartition power at lower isotope mass, but when accounting for the difference in heat flux at matched density we still find a higher effective ion heat diffusivity at lower isotope mass.

This contribution is expanding on earlier preliminary results [1] with more deuterium data and further interpretation using a gyro-fluid model (TGLF). We aim to present our dataset including matched tritium pulses by the time of the conference.

[1] E. Delabie et al., proceeding of the 44^th EPS conference, Belfast, UK (2017)