Modelling Study of Divertor Pumping Effect on Detachment and Impurity Retention with Argon Seeding in East

The effects of divertor pumping on divertor detachment and core performance were investigated by SOLPS-ITER simulations for the H-mode discharges with argon (Ar) seeding on EAST. Simulation results show that a low pumping speed (S) is advantageous for achieving divertor detachment due to increased Ar density and enhanced radiative dissipation. On the other hand, a low S has a high Ar density in the core region, which is detriment to the core performance. Increasing S improves particle removal capacity, which is conducive to reducing the core Ar accumulation and improving divertor Ar retention. In order to avoid unacceptable confinement degradation and achieve better core-divertor compatibility, a relatively high S is required. The simulation results also revealed the Ar retention is determined by the competition of neutral Ar diffusion, the net force on Ar ions and the relative distance between the velocity stagnation point and the ionization source front of Ar.