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

Abstract

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.

Authors:
; ; ; ; ; ; ; ; ;  [1];  [2];  [3]; ; ; ;  [4]
  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)
Publication Date:
OSTI Identifier:
20764469
Resource Type:
Journal Article
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 12; Journal Issue: 8; Other Information: DOI: 10.1063/1.1938973; (c) 2005 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 1070-664X
Country of Publication:
United States
Language:
English
Subject:
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

Citation Formats

Takechi, M, Shinohara, K, Ozeki, T, Kusama, Y, Takeji, S, Fujita, T, Oikawa, T, Suzuki, T, Oyama, N, Morioka, A, Fukuyama, A, Ishikawa, M, Cheng, C Z, Gorelenkov, N N, Kramer, G J, and Nazikian, R. Alfven eigenmodes in reversed shear plasmas in JT-60U negative-ion-based neutral beam injection discharges. United States: N. p., 2005. Web. doi:10.1063/1.1938973.
Takechi, M, Shinohara, K, Ozeki, T, Kusama, Y, Takeji, S, Fujita, T, Oikawa, T, Suzuki, T, Oyama, N, Morioka, A, Fukuyama, A, Ishikawa, M, Cheng, C Z, Gorelenkov, N N, Kramer, G J, & Nazikian, R. Alfven eigenmodes in reversed shear plasmas in JT-60U negative-ion-based neutral beam injection discharges. United States. https://doi.org/10.1063/1.1938973
Takechi, M, Shinohara, K, Ozeki, T, Kusama, Y, Takeji, S, Fujita, T, Oikawa, T, Suzuki, T, Oyama, N, Morioka, A, Fukuyama, A, Ishikawa, M, Cheng, C Z, Gorelenkov, N N, Kramer, G J, and Nazikian, R. 2005. "Alfven eigenmodes in reversed shear plasmas in JT-60U negative-ion-based neutral beam injection discharges". United States. https://doi.org/10.1063/1.1938973.
@article{osti_20764469,
title = {Alfven eigenmodes in reversed shear plasmas in JT-60U negative-ion-based neutral beam injection discharges},
author = {Takechi, M and Shinohara, K and Ozeki, T and Kusama, Y and Takeji, S and Fujita, T and Oikawa, T and Suzuki, T and Oyama, N and Morioka, A and Fukuyama, A and Ishikawa, M and Cheng, C Z and Gorelenkov, N N and Kramer, G J and Nazikian, R},
abstractNote = {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.},
doi = {10.1063/1.1938973},
url = {https://www.osti.gov/biblio/20764469}, journal = {Physics of Plasmas},
issn = {1070-664X},
number = 8,
volume = 12,
place = {United States},
year = {Mon Aug 15 00:00:00 EDT 2005},
month = {Mon Aug 15 00:00:00 EDT 2005}
}