Alfven eigenmodes in reversed shear plasmas in JT-60U negative-ion-based neutral beam injection discharges

Journal Article · Mon Aug 15 04:00:00 EDT 2005 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.1938973· OSTI ID:20764469

Takechi, M; Shinohara, K; Ozeki, T; Kusama, Y; Takeji, S; Fujita, T; Oikawa, T; Suzuki, T; Oyama, N; Morioka, A ^[1]; Fukuyama, A ^[2]; Ishikawa, M ^[3]; Cheng, C Z; Gorelenkov, N N; Kramer, G J; Nazikian, R ^[4]

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1. Japan Atomic Energy Research Institute, Naka Fusion Research Establishment, Naka-machi, Ibaraki-ken (Japan)
2. Department of Nuclear Engineering, Kyoto University, Kyoto 606-8501 (Japan)
3. Plasma Research Center, University of Tsukuba, Tsukuba-shi 305-8877 (Japan)
4. Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (United States)

Rapid frequency sweeping modes observed in reversed magnetic shear (RS) plasmas on the Japan Atomic Energy Research Institute Tokamak 60 Upgrade (JT-60U) [H. Ninomiya and the JT-60 Team, Phys. Fluids B 4, 2070 (1992)] have been identified as reversed-shear-induced Alfven eigenmodes (RSAEs), which are ideal magnetohydrodynamic Alfven eigenmodes (AEs) localized to the region of minimum safety factor, q{sub min}, and are excited by negative-ion-based neutral beam injection. The chirping and subsequent saturation of the mode frequency are consistent with theoretical predictions for the transition from RSAEs to toroidal Alfven eigenmodes (TAEs). The previously observed rapid frequency sweeping modes in ion cyclotron wave heated plasmas in JT-60U can also be similarly explained. The observed AE amplitude is largest during the transition from RSAEs to TAEs, and fast ion loss is observed when the AE amplitude is largest at this transition. It is preferable to operate outside the transition range of q{sub min}, e.g., 2.4<q{sub min}<2.7 for the n=1 AE to avoid substantial fast ion loss in RS plasmas.

• OSTI ID: 20764469
• Journal Information: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 8 Vol. 12; ISSN PHPAEN; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ALFVEN WAVES
AMPLITUDES
ANIONS
AUGER ELECTRON SPECTROSCOPY
BEAM INJECTION HEATING
ELECTRIC DISCHARGES
JT-60 TOKAMAK
JT-60U TOKAMAK
MAGNETIC CONFINEMENT
MAGNETIC FIELD CONFIGURATIONS
MAGNETOHYDRODYNAMICS
PLASMA
PLASMA BEAM INJECTION
PLASMA INSTABILITY
REVERSED SHEAR