Energetic passing particle-driven instabilities and their impact on discharge evolution in KSTAR

• Published in: Plasma physics and controlled fusion Vol. 65; no. 9; pp. 95018 - 95033
• Main Authors: Jhang, Hogun, Kim, Junghee, Kang, Jisung, Kim, Minho, Zhang, L L, Fu, G Y, Zonca, Fulvio, Chen, L, Chavdarovski, I, Choi, Minjun J, Falessi, M V, Lee, S, Qiu, Z Y
• Format: Journal Article
• Language: English
• Published: IOP Publishing 01.09.2023
• Subjects: energetic particle modes; energetic particles; fishbone instability; instability; stability analysis; tokamak plasma
• ISSN: 0741-3335; 1361-6587
• DOI: 10.1088/1361-6587/ace3f2

Abstract An experimental study is conducted on the onset and evolution characteristics of energetic particle-driven instabilities in Korea Superconducting Tokamak Advanced Research (KSTAR) with dominant tangential neutral beam injection (NBI). A scan of NBI beam energy shows the evanescence of the sawtooth crash and the concomitant onset of the strong passing particle-driven low-frequency fishbone instability. A quantitative analysis shows that the safety factor ( q )-profile in the core region is clamped by a balance between the depletion of energetic passing particles by the fishbone instability and their external replenishment. Two synchronized chirping modes with distinct toroidal mode numbers ( n  = 1 and n  = 5) supersede the fishbone instability after a self-organized q -profile is attained. An analysis shows that the n  = 1 mode is likely to be a high-frequency beta-induced Alfvén eigenmode fishbone branch, while the n  = 5 mode is an energetic particle mode (EPM). A dynamic system analysis of the synchronized EPM (S-EPM) shows that a stable S-EPM cycle can exist when the coupling between the two modes involved is insignificant. The potential impact of such EPMs on the establishment of a burning plasma scenario with a flat core q -profile is briefly discussed.