Physical mechanisms for the transition from type-III to large ELMs induced by impurity injection on EAST

Journal Article · 03 February 2022 · Physics Letters. A

DOI: https://doi.org/10.1016/j.physleta.2022.127988 · OSTI ID:1977553

Lin, X.  ^[1]; Xu, G. S.; Yang, Q. Q.; Yan, N.; Wang, Y. F.; Ye, Y. ; Zhu, P.; Cao, B.; Li, K. D.; Chen, R.; Zhang, L.; Zang, Q.; Zhang, T. ; Wang, Y. M. ; Hu, G. H.; Li, Y. Y. ; Zhou, C.; Chen, Y. J.; Meng, L. Y.; Yang, X. D. ; Duan, Y. M.; Liu, H. Q.; Ding, F.; Chen, X. H.; Xu, J. C.; Wu, M. F.; Wang, L.

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1. OSTI

Transition from type-III to large-amplitude ELMs induced by neon injection has been observed in the EAST tokamak at overlapping q₉₅ space between large and small ELMs. With neon injection, pedestal density gradient shows a remarkable increase accompanied by some decrease of pedestal electron temperature, and consequently the pressure gradient increases moderately and edge bootstrap current has minimal change. Further experiment demonstrates that the occurrence of large ELMs after neon injection is highly correlated with the change in edge density. Linear peeling-ballooning stability analysis indicates that the large ELM case is more unstable than the type-III ELM case during the ELM transition. A scan of pedestal density gradient in linear stability analysis shows that the direct destabilizing effect of steep pedestal density gradient on peeling-ballooning instabilities via two-fluid effects could also facilitate the transition to large ELMs. In conclusion, these results could provide more insight into the role of pedestal density gradient on pedestal stability and ELM behavior.

• Research Organization: Univ. of Wisconsin, Madison, WI (United States)
• Sponsoring Organization: USDOE Office of Science (SC); National MCF Energy; National Natural Science Foundation of China (NSFC); Chinese Academy of Sciences (CAS); China Postdoctoral Science Foundation (CPSF); Hefei Institutes of Physical Science of the Chinese Academy of Sciences (CASHIPS); Huazhong University of Science and Technology; National Magnetic Confinement Fusion Program of China
• Contributing Organization: EAST team
• Grant/Contract Number: FG02-86ER53218; SC0018001
• OSTI ID: 1977553
• Journal Information: Physics Letters. A, Journal Name: Physics Letters. A Journal Issue: C Vol. 431; ISSN 0375-9601
• Publisher: ElsevierCopyright Statement
• Country of Publication: United States
• Language: English