Anomalous flattening of the fast-ion profile during Alfvén-Eigenmode activity

Neutral-beam injection into plasmas with negative central shear produces a rich spectrum of toroidicity-induced and reversed-shear Alfvén eigenmodes in the DIII-D tokamak. The first application of fast-ion D_{alpha} (FIDA) spectroscopy to Alfvén-eigenmode physics shows that the central fast-ion prof...

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Published inPhysical review letters Vol. 99; no. 24; p. 245002
Main Authors Heidbrink, W W, Gorelenkov, N N, Luo, Y, Van Zeeland, M A, White, R B, Austin, M E, Burrell, K H, Kramer, G J, Makowski, M A, McKee, G R, Nazikian, R
Format Journal Article
LanguageEnglish
Published United States 14.12.2007
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Summary:Neutral-beam injection into plasmas with negative central shear produces a rich spectrum of toroidicity-induced and reversed-shear Alfvén eigenmodes in the DIII-D tokamak. The first application of fast-ion D_{alpha} (FIDA) spectroscopy to Alfvén-eigenmode physics shows that the central fast-ion profile is anomalously flat in the inner half of the discharge. Neutron and equilibrium measurements corroborate the FIDA data. The current density driven by fast ions is also strongly modified. Calculations based on the measured mode amplitudes do not explain the observed fast-ion transport.
ISSN:0031-9007
DOI:10.1103/physrevlett.99.245002