Numerical analyses of impurity behaviors for CFETR advanced scenarios by core-edge integrated simulations

Abstract The impurity behaviors for the advanced scenarios of CFETR with full tungsten divertor have been analyzed. Core plasma profiles for steady state and hybrid scenarios are simulated by consistently iterative transport calculations within the OMFIT framework. The core-SOL integrated COREDIV code is then used to evaluate the effects of different seeding impurities (Ne, Ar, Kr) with the OMFIT modelled core plasma parameters as input. The impurity behaviors for the two modelled scenarios are similar. Seeding by all the considered impurities can effectively reduce the power to the divertor below the acceptable level. For Ne and Ar seeding, it is possible to achieve H-mode plasma operation with power from the core plasma to the SOL higher than L-H transition power threshold. However, higher Ne seeding rate would strongly reduce the fusion power due to the dilution effect. Kr seeding seems to be infeasible because the power crossing the separatrix would be lower than the L-H transition threshold, when the seeding rate is high enough to meet the divertor requirements. Higher separatrix electron density or SOL diffusion can slightly reduce the core radiation. Although normal COREDIV simulations are performed with a fixed H98 factor, simulations with fixed transport indicate that higher impurity seeding rate leads to a decrease of confinement and fusion gain, due to the increase of impurity radiation loss in the core plasma.