Simulation Study of the Influence of Drifts on the Upstream and Target Heat Flux Width under Different BT Directions

The heat flux width (lambda(q)) is a key parameter determining the heat load at divertor targets. In recent years, drifts have been found to play a remarkable role in the edge plasma transport, while its influence on lambda(q) has not been well understood. Investigations of the influence of drifts on lambda(q), systematic simulations using the SOLPS-ITER code are performed in this work. The statistics of the simulation results show that the drift under favorable/unfavorable B-T tends to increase the lambda(q) in the outer/inner side and decrease the lambda(q) in the other side, which is consistent with the experiment observations. At the upstream and the target, the mechanisms of the influence of the drifts on lambda(q) are different. The upstream lambda(q) (lambda(q,u)) is directly affected by the drift-induced convective heat flux, while lambda(q) at the target (lambda(q,t)) is indirectly influenced through heat conduction (in the high-recycling regime) and the sheath (in the detached regime) due to the change of plasma parameters there. Furthermore, the synergetic effect of geometry and drift under favorable B-T leads to an anomalously large lambda(q,t) in the inner side at high density.