Effects of Ohmic heating on the time scale of current quench during a disruption on EAST

The physical mechanism governing the process of thermal and current quench (TQ & CQ) during disruption has not been well understood. Performing resistive MHD simulation using NIMROD code, after choosing initial profiles from a recent EAST disruption discharge induced by massive helium gas injection, we compare experimental and simulation results, and find good agreement in the time history of total radiation power and MHD activity preceding thermal quench (TQ) and current quench (CQ) phases. It is demonstrated that the post-TQ re-increase of plasma temperature is due to the Ohmic heating (OH) power, which despite its imbalance with the radiation power loss, continuously feeds a lower temperature plasma during CQ phase. This produces a CQ time up to 8 times longer than the case without OH effect at all. Further simulations indicate that the effect of OH on CQ time scale is prominent in both natural and MGI induced disruption.