Isotopic dependence of impurity transport driven by ion temperature gradient turbulence

Abstract

Hydrogenic ion mass effects, namely, the isotopic effects on impurity transport driven by ion temperature gradient (ITG) turbulence are investigated using gyrokinetic theory. For non-trace impurities, changing from hydrogen (H) to deuterium (D), and to tritium (T) plasmas, the outward flux for lower (higher) ionized impurities or for lighter (heavier) impurities is found to decrease (increase), although isotopic dependence of the ITG linear growth rate is weak. This is mainly due to the decrease of outward (inward) convection, while the isotopic dependence of diffusion is relatively weak. In addition, the isotopic effects reduce (enhance) the impurity flux of fully ionized carbon (C6+) for weaker (stronger) magnetic shear. In the trace impurity limit, the isotopic effects are found to reduce the accumulation of high-Z tungsten (W). Moreover, the isotopic effects on the peaking factor of trace high-Z W get stronger with stronger magnetic shear.