Isotope mix effect on edge turbulent transport in pre-L-H transition conditions in JET-ILW

Abstract The heat flux at the edge of L-mode JET-ILW (Be wall and W divertor) pulses is studied using the gyrokinetic code GENE in its flux-tube configuration as well as the quasi-linear turbulent transport model TGLF using the SAT2 and SAT3 saturation rules. We use reference JET-ILW plasmas with different hydrogen isotopes and isotope mixes in which a power ramp to identify the LH power threshold P LH has been performed. The study focuses on two pulses with an effective mass of A eff = 2, either with pure deuterium or a 50% hydrogen - 50% tritium mix. Additional power is required to trigger an H-mode in the mix (2.98 MW) compared to the pure deuterium case (1.68 MW) despite their similar effective mass. Without E × B shear, we retrieved similar flux levels between quasi-linear (TGLF) and non-linear (GENE) simulations, within the magnitude of experimental values. The inclusion of finite E × B shear levels, which are varied as input within an assumed experimentally plausible range, showed a} global reduction of transport, for both energy and particles, with a stronger effect observed for the pure deuterium case than for the isotope mix case in GENE flux-tube non-linear simulations. The use of E × B shearing resulted in a 50-80% stronger flux for the isotope mix case than for the pure deuterium case. TGLF SAT2 and SAT3 are both unable to reproduce this behaviour.