DYNAMICS AND CONTROL OF INTERNAL TRANSPORT BARRIERS IN REVERSED SHEARDISCHARGES

Transitions to an enhanced confinement regime in tokamak plasmas with negative central magnetic shear have been observed in a number of devi ces. A simple model incorporating the nonlinear coupling between the t urbulent fluctuations and the sheared radial electric field is added t o a transport model in order to investigate the dynamics of the transi tion to this enhanced confinement mode. In this model, by incorporatin g; both the instability growth rate profiles and particle and/or power deposition profiles, a rich variety of transition dynamics is uncover ed. Transition dynamics and their concomitant thresholds are examined within the context of these models. In the course of investigating the se transitions, potential methods for triggering and controlling these enhanced confinement regimes have been discovered and are discussed. (C) 1998 American Institute of Physics.