Stabilization of ion-temperature-gradient-driven tokamak modes by magnetic-field gradient reversal

Global gyrokinetic particle simulations have been used to search tokamak configurations which are stable again st the ion-temperature-gradient - driven (ITG) modes commonly held responsible for the core anomalous 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 (poloidal beta) tokamak experiments, we conjecture, as a result of our simulations, that this may be due to the stabilization of ITG modes by the reduction of the del B drifts.