Title: Gyrokinetic Simulations of Isotope Effect on Turbulent Transport
Speaker: Shengming Li
Abstract: Self-generated zonal flow plays an important role in regulating turbulent transport in tokamaks. Isotope effects on zonal flow generation and turbulent transport are important issues in burning plasmas. In this work, simulations using Gyrokinetic Toroidal Code (GTC) are carried out to study isotopic dependence of hydrogen (H), deuterium (D), and tritium (T) on residual zonal flow level and on typical electrostatic turbulence such as ion temperature gradient (ITG) mode and trapped electron mode (TEM). It is found that the residual zonal flow has significant isotope effect where 0.1 < k_perp*rho_H < 2 and becomes stronger when increasing isotope mass from H to T. That agrees with previous Hahm’s analytic theory. Linear simulations show that the growth rate, real frequency, unstable k_theta range of ITG and TEM also have significant isotope effect. The linear dispersion is shrunk toward lower m mode due to the increase of gyroradius from H to T. Nonlinear simulation shows that the saturation level of energy transport in TEM turbulence has a strong isotope dependence between H, D and T. With the gyroradius increasing from H to T, the turbulent transport of TEM is significantly reduced which favors burning plasmas.