Drift wave based modelling of poloidal spin-up precursor and stepwise expansion of transport barriers

The rich phenomenology of internal transport barriers (ITBs) observed in to kamaks includes a poloidal spin-up precursor for balanced injection neutral beam heating and stepwise expansion of the barrier for unbalanced injectio n. Examples of numerical simulations of these phenomena are presented. Two drift wave based predictive transport models (GLF23 and multimode) are used . Both models include the suppression of ion temperature gradient modes as the E x B shear approaches the computed maximum linear growth rate. Modelli ng of discharges with ITBs from the DIII-D, JET and TFTR tokamaks are compa red.