Formation of small-scale modes via ECCD injection into KSTAR plasma core

Abstract In KSTAR experiments exhibiting sawtooth instability, the formation of multiple flux tubes (MFTs) has been frequently observed when electron cyclotron resonance heating or a current drive is applied near the inversion radius of the sawtooth. On the global scale, these MFTs evolve into a sin...

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Published inNuclear fusion Vol. 64; no. 4; pp. 46004 - 46016
Main Authors Kim, Dong-Kwon, Lee, Jaehyun, Choi, Minjun J., Dae Yoon, Young, Woo, Minho, Kim, Minho, Yun, Gunsu S.
Format Journal Article
LanguageEnglish
Published IOP Publishing 01.04.2024
Subjects
electron cyclotron emission imaging(ECEI)
heating and current drive
KSTAR
sawtooth instability
signal correlation technique
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Summary:Abstract In KSTAR experiments exhibiting sawtooth instability, the formation of multiple flux tubes (MFTs) has been frequently observed when electron cyclotron resonance heating or a current drive is applied near the inversion radius of the sawtooth. On the global scale, these MFTs evolve into a single flux tube mode or dual modes. The modes are observed as multiple Fourier harmonics in the spectrogram. A comprehensive correlation analysis of 2D imaging diagnostic data reveals a notable energy transfer within structures of varying sizes during the global mode transition. Broadband fluctuations are enhanced, and energy transfer between Fourier harmonics occurs in the presence of MFTs. Cross-power spectrum in the presence of multiple Fourier harmonics aligns with power law of inverse cascade. This suggests that energy inverse cascade process can contribute to formation of MFTs.
Bibliography:NF-106474.R3
ISSN:0029-5515
1741-4326
DOI:10.1088/1741-4326/ad279c