High-k turbulence characteristics in density modulation experiments of EAST

• Published in: AIP advances 2024-06, Vol.14 (6), p.065213-065213-9
• Main Authors: Chen, F., Li, P., Li, Y. D., Wang, X. J., Wu, G. J., Geng, J. S., Wang, Y. H., Sun, N., Sun, P. J., Wang, M., Ding, B. J., Wu, C. B., Li, E. Z., Zhou, T. F., Zhao, H. L., Zang, Q., Wang, S. X., Liu, H. Q., Jin, Y. F., Lyu, B., Li, J. G.
• Format: Article
• Language: English
• Subjects: Active control; Beam injection; Broadband; Coherence analysis; Density; Diagnostic systems; Frequency ranges; Modulation; Neutral beams; Spectrograms; Thomson scattering; Tokamak devices; Turbulence
• ISSN: 2158-3226
• DOI: 10.1063/5.0197005

High-k turbulence (1 < kθρs < 5) spectrograms have been directly measured in density modulation experiments of the EAST tokamak using the collective Thomson scattering diagnostic system. Density-peaking modulation is achieved in Lower Hybrid Wave (LHW) modulation experiments, revealing that the broadband turbulence is sensitive to the power modulation of LHW and the concomitant variation of density-peaking. Additionally, the contributions of 2.45/4.6 GHz LHW to density peaking differ when Neutral Beam Injection (NBI) is on/off, displaying distinct responses of broadband turbulence in low/high frequency ranges. It is found by cross-coherence analysis that the phase angle is negative in cases without NBI, while in NBI cases it can be modulated from negative to positive, indicating a significant transition of radial turbulence propagation. These findings highlight the active control of density-peaking via auxiliary heating in tokamak plasmas and suggest the potential role of high-k turbulence in density-peaking modulation.