High-frequency core localized modes in neutral beam heated plasmas on TFTR

R. Nazikian, Z. Chang, E. D. Fredrickson, E. Mazzucato, S. H. Batha, R. Bell, R. Budny, C. E. Bush, C. Z. Cheng, A. Janos, F. Levinton, J. Manickam, D. K. Mansfield, H. K. Park, G. Rewoldt, S. Sabbagh, E. J. Synakowski, W. Tang, G. Taylor, L. E. Zakharov

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29 Citations (Scopus)


A band of high-frequency modes in the range 50-150 kHz with intermediate toroidal mode numbers 4<n<10 are commonly observed in the core of supershot plasmas on TFTR [R- Hawryluk, Plasma Phys. Controlled Fusion 33, 1509 (1991)] Two distinct varieties of magnetohydrodynamic (MHD) modes are identified, corresponding to a flute-like mode predominantly appearing around the q = 1 surface and an outward ballooning mode for q>1. The flute-like modes have nearly equal amplitude on the high-field and low-held side of the magnetic axis, and are mostly observed in moderate performance supershot plasmas with τE<2τL, while the ballooning-like modes have enhanced amplitude on the low-field side of the magnetic axis and lend to appear in higher performance superhot plasmas with τE>2τL, where τL is the equivalent L-mode confinement time. Both modes appear to propagate in the ion diamanagnetic drift direction and are highly localized with radial widths Δr∼5-10 cm, fluctuation levels n̈/n, T̃e/Te<0.01. and radial displacements ξr.∼0.1 cm. Unlike the toroidally localized high-n activity observed just prior to major and minor disruptions on TFTR [E. D. Fredrickson et al., Proceedings of the 15th International Conference on Plasma Physics and Controlled Nuclear Fusion Research, Seville, Spain (International Atomic Energy Agency, Vienna, 1995), No. IAEA-CN-60/A-2-II-5], these modes are typically more benign and may be indicative of MHD activity excited by resonant circulating beam ions.

Original languageEnglish
Pages (from-to)593-605
Number of pages13
JournalPhysics of Plasmas
Issue number2
Publication statusPublished - 1996 Feb

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics


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