Isotope Dependence of Confinement in JET-ILW Deuterium and Hydrogen Plasmas

Heat, particle and momentum confinement in L- and H-mode in deuterium, hydrogen and in D/H mixtures have been investigated in JET with the ITER-like wall (JET-ILW). The paper expands on previous work [1,2] by presenting new results on heat, momentum and particle transport using measured ion temperatures and toroidal rotation frequencies, as well as new gyrokinetic analyses and pedestal studies. In L-mode a weak positive scaling of thermal stored energy with ion mass, EthA0.15, is found [1], consistently with multi-machine scaling EthA0.2 [3]. Differences between species in global particle confinement are similarly weak. Core temperature profiles are resilient to changes in input power with R/LTe8 at mid-radius [1]. Flux-driven core transport modelling with JETTO-TGLF show ITG’s to be dominant and predict no isotope scaling as a result of the Ti profile resilience (stiffness), showing that global confinement can depart from simple local GyroBohm scaling. In type I ELMy H-mode it was not possible, except in a couple of cases, to establish the same pedestal and core densities in H as in D, despite gas fuelling rates several times higher in H, showing a strong reduction of global particle confinement in hydrogen. These discharges, too, have stiff temperature profiles with no apparent difference in core R/LTe between species, i.e. differences between species in core and global confinement arise as a result of differences in the pedestal, the most striking of which are differences in pedestal density and pedestal density width. Regressions for the thermal stored energy from kinetic measurements and independently from EFIT equilibrium reconstructions provide mass exponents near 0.4, i.e. twice that of IPB98(y,2). Momentum and particle confinement have a similar strong scaling with isotope mass. Nonlinear GENE gyrokinetic flux-tube calculations at mid-radius, including the effects of collisions, EB and impurities, show a reversal of GyroBohm scaling in the core of H-modes. Dimensionless identity experiments (identical *,*,q) for H and D pairs provided good matches for the kinetic profiles in L-mode and near-identical normalised confinement times, in agreement with JETTO-TGLF modelling [4].