The self-organizing regime has been studied in an Experimental Advanced Superconducting Tokamak (EAST) long-pulse discharge. Multiple magnetohydrodynamic (MHD) instabilities and associated change in the core toroidal rotation were observed. A m/n= 3/2 tearing mode (TM) persisted for ∼42 s, until being damped as a result of current profile evolution. The deposition of a lower-hybrid wave (LHW) was coupled with the current profile via the magnetic field, and gradually changed the current profile with a stable heating power in the progress. A m/n = 1/1 long-lived mode (LLM) co-existed with the TM, but appeared alternatively with a m/n = 1/1 high frequency mode (HFM). The HFM appeared when the normalized electron temperature gradient (ETG) R/LTe near the q = 1 surface exceeded ∼8.5, and its frequency chirped as varied. Disappearance of the TM was followed by an increase in the core electron temperature and an acceleration of toroidal rotation in the counter-current direction. The neoclassical toroidal viscosity (NTV) torque driven by these modes was modeled by NTVTOK, and the results indicated that the TM drove a toroidal torque in the co-current direction which damped the intrinsic rotation. These results enhance the understanding of the self-organizing regime in long-pulse discharges and provide a prospective study on the physics under long-pulse conditions for future fusion reactors.
This paper explores the self-organizing regime in a long-pulse discharge on the EAST tokamak. It investigates various magnetohydrodynamic (MHD) instabilities and their impact on the core toroidal rotation. The findings enhance the understanding of long-pulse fusion reactor operation.