STABILIZATION OF ION-TEMPERATURE-GRADIENT-DRIVEN TOKAMAK MODES BY MAGNETIC-FIELD GRADIENT REVERSAL

Global gyrokinetic particle simulations have been used to search tokam ak configurations which are stable again st the ion-temperature-gradie nt - driven (ITG) modes commonly held responsible for the core anomalo us ion heat transport. The stable configurations are-characterized by strongly reduced or reversed del B drifts on the low-field side. Since excellent transport properties have been observed in high beta p (pol oidal beta) tokamak experiments, we conjecture, as a result of our sim ulations, that this may be due to the stabilization of ITG modes by th e reduction of the del B drifts.