Predictive transport simulations of internal transport barriers using the multi-Mode model

The formation of internal transport barriers observed in both Joint Europea n Torus (JET) [P. H. Rebut, R. J. Bickerton, and B. E. Keen, Nucl. Fusion 2 5, 1011 (1985)] and Doublet III-D Tokamak (DIII-D) [J. L. Luxon and L. G. D avis, Fusion Technol. 8, 441 (1985)] are reproduced in predictive transport simulations. These simulations are carried out for two JET-optimized shear discharges and two DIII-D negative central shear discharges using the Mult i-Mode model in the time-dependent 1-1/2-D BALDUR transport code [C. E. Sin ger , Comput. Phys. Commun. 49, 275 (1988)]. The Weiland model is used for drift modes in the Multi-Mode model in combination with either Hahm-Burrell or Hamaguchi-Horton flow shear stabilization mechanisms, where the radial electric field is inferred from the measured toroidal velocity profile and the poloidal velocity profile computed using neoclassical theory. The trans port barriers are apparent in both the ion temperature and thermal diffusiv ity profiles of the simulations. The timing and location of the internal tr ansport barriers in the simulations and experimental data for the DIII-D ca ses are in good agreement, though some differences remain for the JET disch arges. The formations of internal transport barriers are interpreted as res ulting from a combination of ExB flow shear and weak magnetic shear mechani sms. (C) 2000 American Institute of Physics. [S1070-664X(00)04107-0].