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.