Effect of isotope mass on transport simulations of Joint European Torus high-mode plasmas with Edge Localized Modes

The effect of isotopic mass on heat and particle transport in Joint Europea n Torus (JET) [P.-H. Rebut , Nucl. Fusion 25, 1011 (1985)] plasma discharge s is studied using the Multi-Mode model in the BALDUR predictive transport code [Bateman , Phys. Plasmas 5, 1793 (1998)]. Temperature and density prof iles from these simulations generally agree with the experimentally measure d profiles for high-mode JET discharges with Edge Localized Modes in hydrog en, deuterium, and tritium discharges. It is surprising that a purely gyro- Bohm transport model, used in these simulations, correctly predicts the exp erimentally observed improvement in confinement as the isotope mass is incr eased-given the fact that gyro-Bohm diffusion coefficients increase with is otope mass when the shapes of all the plasma profiles are held fixed. Howev er, in the JET experiment, it was found that the electron and ion temperatu re at the top of the edge pedestal increases systematically as the isotope mass in increased (J. G. Cordey , Report No. JET-P (98)53, 1998). The numer ical simulations reported here show that this increase in the edge temperat ures and subsequent broadening of the temperature profiles account for the improvement in confinement as the isotope mass is increased. (C) 1999 Ameri can Institute of Physics. [S1070-664X(99)00112-3].