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arXiv · 1902.04750

I-mode investigation on the Experimental Advanced Superconducting Tokamak

X. Feng·A. D. Liu·C. Zhou·Z. X. Liu·M. Y. Wang·G. Zhuang·X. L. Zou·T. B. Wang·Y. Z. Zhang·J. L. Xie·H. Q. Liu·T. Zhang·Y. Liu·Y. M. Duan·L. Q. Hu·G. H. Hu·D. F. Kong·S. X. Wang·H. L. Zhao·Y. Y. Li·L. M. Shao·T. Y. Xia·W. X. Ding·T. Lan·H. Li·W. Z. Mao·W. D. Liu·X. Gao·J. G. Li·S. B. Zhang·X. H. Zhang·Z. Y. Liu·C. M. Qu·S. Zhang·J. Zhang·J. X. Ji·H. R. Fan·X. M. Zhong
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Abstract

By analyzing large quantities of discharges in the unfavorable ion $ \vec B\times \nabla B $ drift direction, the I-mode operation has been confirmed in EAST tokamak. During the L-mode to I-mode transition, the energy confinement has a prominent improvement by the formation of a high-temperature edge pedestal, while the particle confinement remains almost identical to that in the L-mode. Similar with the I-mode observation on other devices, the $ E_r $ profiles obtained by the eight-channel Doppler backscattering system (DBS8)\cite{J.Q.Hu} show a deeper edge $ E_r $ well in the I-mode than that in the L-mode. And a weak coherent mode (WCM) with the frequency range of 40-150 kHz is observed at the edge plasma with the radial extend of about 2-3 cm. WCM could be observed in both density fluctuation and radial electric field fluctuation, and the bicoherence analyses showed significant couplings between WCM and high frequency turbulence, implying that the $ E_r $ fluctuation and the caused flow shear from WCM should play an important role during I-mode. In addition, a low-frequency oscillation with a frequency range of 5-10 kHz is always accompanied with WCM, where GAM intensity is decreased or disappeared. Many evidences show that the a low-frequency oscillation may be a novel kind of limited cycle oscillation but further investigations are needed to explain the new properties such as the harmonics and obvious magnetical perturbations.

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X. Feng, A. D. Liu, C. Zhou, Z. X. Liu, M. Y. Wang, G. Zhuang, X. L. Zou, T. B. Wang, Y. Z. Zhang, J. L. Xie, H. Q. Liu, T. Zhang, Y. Liu, Y. M. Duan, L. Q. Hu, G. H. Hu, D. F. Kong, S. X. Wang, H. L. Zhao, Y. Y. Li, L. M. Shao, T. Y. Xia, W. X. Ding, T. Lan, H. Li, W. Z. Mao, W. D. Liu, X. Gao, J. G. Li, S. B. Zhang, X. H. Zhang, Z. Y. Liu, C. M. Qu, S. Zhang, J. Zhang, J. X. Ji, H. R. Fan, X. M. Zhong. 2019-05-31. I-mode investigation on the Experimental Advanced Superconducting Tokamak. https://doi.org/10.1088/1741-4326%2Fab28a7

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