Effects of drifts and ballooning instability on the divertor in-out asymmetry in EAST tokamak

The divertor in-out asymmetry (DIOA) of the disconnected double null (DDN) configuration with the active X-point at the bottom in EAST has been investigated using the SOLPS code package to explore its forming mechanism. Effects of classical drifts and ballooning-like transport (BLT) instability are evaluated individually and compared to the DIOA during H-mode. The results show that the BLT plays a much larger role in forming the DIOA. It is further found that the combined effects of the classical drifts and BLT can account for the formation of the DIOA observed experimentally in EAST. In addition, the results also imply that reversing the toroidal magnetic field may be used to mitigate the EAST DIOA under certain circumstances.