Scalings of Ion-Temperature-Gradient-Driven Anomalous Transport in Tokamaks

Results are presented from the first systematic nonlinear gyrokinetic simulation study of the scalings and parameter dependences of toroidal ion-temperature-gradient-driven (ITG) turbulence and transport in large magnetic-fusion-relevant tokamaks. Such simulations are made possible by significant advances in computational physics algorithms which are summarized. The simulated ion-thermal transport rates have clear ``gyroreduced Bohm'' scaling and are too low to account for the anomalous transport seen in the outer half of some TFTR $L$-mode discharges, indicating that additional mechanisms, such as nonadiabatic-electron effects, are operative.