Effect of isotope mass on transport simulations of JET ELMy H-mode plasmas

The effect of isotopic mass on heat and particle transport in Joint European Torus (JET) plasma discharges is studied using the Multi-Mode model in the BALDUR predictive transport code [Bateman et al., Physics of Plasmas, 5, 1793 (1998)]. Temperature and density profiles from these simulations generally agree with the experimentally measured profiles for ELMy H-mode JET discharges in hydrogen, deuterium, and tritium discharges. It is surprising that a purely gyro-Bohm transport model, used in these simulations, correctly predicts the experimentally observed improvement in confinement as the isotope mass is increased - given the fact that gyro-Bohm diffusion coefficients increase with isotope mass when the shapes of all the plasma profiles are held fixed. However, in the JET experiment, it was found that the electron and ion temperature at the top of the edge pedestal increases systematically as the isotope mass is increased [J. G. Cordey et. al., report JET-P(98)53 to be published in Nuclear Fusion, 1999]. The numerical simulations reported here show that this increase in the edge temperatures and subsequent broadening of the temperature profiles account for the improvement in confinement as the isotope mass is increased. (author)