In recent years, electron cyclotron wave (ECW) heating and current drive (ECCD) have been widely used in tokamak discharge experiments. The inevitable presence of impurity particles in the tokamak plasma affects the ECCD through radiation energy, inhibition of turbulent transport, and change the collision rate. Changes in plasma density, temperature and other transport quantities caused by the change of impurity concentration, induce the changes of Shafranov displacement at the center of magnetic surface of the plasma.

This study aims to investigate the influence of impurity concentration changes on the ECW deposition position and current drive efficiency theoretically with consideration of all above related variations.

The One Modeling Framework for Integrated Tasks (OMFIT) platform was used to conduct integrated simulation study of the effect of impurity effect on ECW heating and current drive. The HL-2M Tokamak device parameters were combined with self-consistent coupled plasma equilibrium, external auxiliary heating and current drive, transport and other physical processes for simulation computation with the carbon ions as the unique impurity ions.

The simulation results show that when the influence of impurities on the plasma is considered, with the increase of the impurity concentration, the radial position of the ECW deposition first moves to the plasma core and then moves to the edge, and the current drive efficiency first increases and then decreases. Due to the competition between the radiation effect and the dilution effect of the impurity-plasma interaction, the radiation loss power basically increases linearly with the increase of Z_eff, while the dilution effect suppresses the turbulence and improve the confinement, but the stabilization effect slows down with the increase of Z_eff.

When the influence of impurities on the plasma is not considered, the deposition position of ECW is basically unchanged, and the current drive efficiency decreases. Results of this study have guiding significance for electron cyclotron current drive (ECCD) to control the plasma current profile and control the instability of magnetic fluid.