Effects of impurities on zonal flows in tokamak plasmas

Effects of impurities on zonal flows (ZFs) driven by the ion density and temperature perturbations in tokamak plasmas are investigated using gyrokinetic theory and simulations. The Rosenbluth–Hinton collisionless gyrokinetic model for ZFs is used, with model source terms designed to represent the drive from different plasma species in the plasma. For ZFs driven by the main ion density perturbations, the presence of impurities could decrease the amplitude of ZFs by increasing the total ion mass density of plasmas. For ZFs driven by the main ion temperature perturbations, the presence of impurities could decrease the amplitude of ZFs by decreasing the main ion mass density fraction. In addition, the driving effects of the impurity ion temperature perturbations on ZFs can be ignored, due to the low concentration of impurities.