Control of edge plasma by plate biasing in SOLPS-ITER modeling

The effect of differential biasing of the divertor plates in a tokamak is analyzed using SOLPS-ITER modeling with account of drifts and currents in the SOL. The ASDEX-Upgrade like geometry and transport parameters adjusted for modeling of the semi-detached nitrogen-seeded plasma of shot #28903 are used in analysis. The additional voltage is applied to the outer divertor plate with respect to the grounded vacuum chamber and the inner divertor plate. When high negative voltage is applied, the high field side high density region almost disappears and the divertor plates become more symmetrical than without biasing, while in the case with positive voltage, the formation of the X-point radiator begins, and both divertor plates become more detached. The results are qualitatively consistent with the experiments conducted on the JFT-2 M and DIII-D tokamaks. In addition, both signs of the applied voltage lead to a significant redistribution of the nitrogen within the SOL. Therefore, the possibility of edge plasma control by biasing is demonstrated.