Electromagnetic Landau-fluid simulation of turbulent transport in reversed magnetic shear tokamak plasmas with impurity ions

The linear eigenmodes of kinetic ballooning modes (KBMs) and their associated turbulent transports in reversed magnetic shear (RMS) configurations with impurity ions are numerically studied using a global electromagnetic Landau-fluid model. Linear eigenmode analysis reveals that the eigenstructure of KBM is predominantly localized near the minimum safety factor q_min region for the low toroidal number n mode. While, the ballooning structure becomes more pronounced in the positive shear region for high n mode. Due to the large mass number of the impurity ions, both of the linear growth rate and mode frequency of dominated KBM in the presence of impurity ions with relatively weak density gradient are a bit smaller than those without impurity ions. A distinct phase difference between bulk ion and impurity ion density perturbations are observed on the low-field side. The discontinuous mode structure of KBM density perturbations in RMS configurations leads to corresponding discontinuities in radial density flux profiles. Despite impurity ions have stabilizing effect on linear growth rates of KBM in the case of weak impurity density gradients, nonlinear transport level remain higher than that in the impurity-free case. The intermittent transports of impurity particle and heat can be clearly obtained, when the impurity density gradient is near the impurity peaking factor threshold. When the initial impurity density gradient deviates from the peaking factor threshold, turbulent transport will still transitions into an intermittent regime following a relaxation phase, accompanying with small-scale corrugations of impurity density profile.