Observation of tearing mode triggering by sawtooth crash with high-Z impurity accumulation in EAST

The high-Z impurity accumulation in the plasma core could degrade the plasma performance and may affect sawtooth crash and trigger tearing modes (TMs) in experimental advanced superconducting tokamak (EAST). Triggering of m/n = 3/2 TM (m and n are the poloidal and toroidal mode numbers, respectively) and m/n = 2/1 TM by a large sawtooth crash is observed and studied under the condition of high-Z impurity accumulation in core plasma in EAST tokamak. This work mainly focuses on the relationship among impurity, sawtooth crashes, and TMs. When there is a certain amount of impurity in the plasma core, sawtooth crash leads to impurity transport, resulting the changes in impurity concentration, and by inducing the density perturbation near the rational surface, TMs become destabilized. The experimental analyses indicate that the outward impurity transport after a sawtooth crash plays an important role in the destabilization of TMs. (c) 2023 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license(http://creativecommons.org/licenses/by/4.0/).

Automated summary

Accumulation of high-Z impurities in the plasma core can adversely affect plasma performance and trigger sawtooth crashes and tearing modes (TMs) in EAST. Experimental observations in the EAST tokamak show that a large sawtooth crash can trigger m/n = 3/2 and m/n = 2/1 TMs under the condition of high-Z impurity accumulation. This study focuses on the relationship between impurities, sawtooth crashes, and TMs, revealing that impurity transport after a sawtooth crash plays a crucial role in the destabilization of TMs.