Nonlinear simulations of turbulence suppression with external flows and impurity injection in toroidal plasmas

Ion temperature gradient-driven (ITG) turbulence plays an important role in explaining measured ion thermal transport in tokamaks, particularly under L-mode conditions. Nonlinear global toroidal gyrokinetic simulation results are presented with radiative impurity seeding in TEXTOR-like L-mode plasma. Reduced levels of ITG turbulence and ion heat transport are observed, possibly explaining the origin of the improved confinement regime radiative improved(RI)-mode. In a separate investigation, ITG turbulence in several DIII-D-like discharges has been analyzed using our nonlinear model under different experimental conditions, with high and low density and central ion temperature, and comparisons with experiment have been favorable. Turbulence radial correlation lengths have been compared and are found to be similar when the effect of zonal flows is included. (author)