Effect of divertor plasma-facing materials and drift on the power decay width in the scrape-off layer and divertor on EAST

Abstract

The narrow power decay width λ q may lead to high heat flux density to the divertor target, which is one of the most severe challenges for future fusion devices. EAST has upgraded its lower graphite (C) divertor to a tungsten (W) one, and it is important to reveal the dependence of λ q on the divertor condition. In the present work, SOLPS-ITER is applied to estimate the effect of various conditions [C/W plasma facing material (PFM), with/without drift] on λ q of EAST in attached divertor regime. The simulation results confirm that the power decay width of the upstream λ q,SOL, divertor λ q,OT, and private-flux region (PFR) S OT all depend on the PFMs and drifts. However, the effect of PFM on λ q,SOL is slight, while it has a significant influence on λ q,OT and S OT. In the upstream, positive correlation between λ q,SOL and is obtained, and the simulation is in qualitative agreement with the two-point model. Both λ q,SOL and λ q,OT in without drift case are larger than that of with drift case. The regression of simulation results is obtained, showing a strong positive correlation between SOL collisionality , power radiation friction in divertor region f rad,OD and λ q,OT. Thus, the C PFM with intrinsic impurity has the largest λ q,OT. In the PFR, S OT with drift is smaller than that of without drift. Moreover, the combination of more D atoms accumulation and stronger E p × B drift lead to larger S OT in W PFM case than that of C PFM case.