Observation and analysis of lower-hybrid-current-drive density limit in EAST

Nuclear Fushion

article

M.H. Li¹  S.G. Baek²  G.M. Wallace²  B.J. Ding¹  C.B. Wu¹  G.H. Yan¹  P.T. Bonoli²  M. Wang¹  L. Liu¹  L.M. Zhao¹  Z.G. Wu¹  H. Yang¹  S.Y. Lin¹  Q. Zang¹  N. Yan¹  H.L. Zhao¹  J. Huang¹  X.M. Zhai¹  X.X. Li³  X.J. Zhang¹  X.Z. Gong¹ 

[1] Institute of Plasma Physics, Chinese Academy of Sciences;MIT Plasma Science and Fusion Center;Department of Nuclear Physics, University of South China

关键词: lower hybrid current drive;    current drive efficiency;    density limit;    parametricdecay instability;    wave accessibility;   

DOI  :  10.1088/1741-4326/ac99ed

来源: Institute of Physics Publishing Ltd.

【 摘 要 】

Lower hybrid current drive (LHCD) experiments with line-averaged density up to ∼5.1×10¹⁹ m⁻³ were performed in EAST L-mode plasmas. When the line-averaged density rises above a critical value, the hard x-ray (HXR) emission falls to the noise level, indicating that the LHCD density limit is encountered. The experimental results show that the LHCD density limit can be increased with higher wave source frequency ( f ₀) and higher magnetic field ( B _t). Although a higher LHCD density limit is obtained by a higher magnetic field for both 2.45 GHz and 4.6 GHz waves, the results show a stronger dependence on the magnetic field for the 4.6 GHz case. Analysis suggests that, for normal operation with a relatively low magnetic field (1.6 T ⩽B _t ⩽ 2.5 T) on EAST, the dominant mechanisms responsible for the LHCD density limit are different between the 2.45 GHz and 4.6 GHz waves. The wave accessibility plays a more significant role during 4.6 GHz LHCD experiments, while parasitic losses due to parametric decay instability (PDIs) dominate the accessibility issue in the 2.45 GHz case. Collisional loss in the scrape-off layer (SOL) may explain the 4.6 GHz result when combined with the accessibility limit at high density and low temperature.

【 授权许可】

Unknown