Effects of impurities on electron temperature gradient modes

The persistence of large anomalous electron heat transport in regions of improved ion confinement sometimes observed in tokamak plasmas suggests that the electron-temperature-gradient-driven drift waves may be the antecedents of the small-scale turbulence and associated energy flow. Whereas most previous investigations of these modes were carried out for a two-species plasma, in this study we retain impurities and examine their effects using gyrokinetic simulations supported by interpretations based on a simple analytic model. The inclusion of impurities is found to have a strong stabilizing effect on the electron temperature gradient modes.