Observation of ion cyclotron range of frequencies mode conversion plasma flow drive on Alcator C-Mod
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Author(s)
Lin, Yijun
Rice, John E.
Wukitch, Stephen James
Greenwald, Martin J.
Hubbard, Amanda E.
Alex, Ince-Cushman
Lin, Liang
Marmar, Earl S.
Porkolab, Miklos
Reinke, Matthew Logan
Date Issued
March 2009
Journal
Physics of Plasmas
Publisher
American Institute of Physics
Citation
Lin, Y. et al. “Observation of ion cyclotron range of frequencies mode conversion plasma flow drive on Alcator C-Mod.” Physics of Plasmas 16.5 (2009): 056102-9. ©2009 American Institute of Physics.
Version
Final published version
Abstract
At modest [superscript 3]He levels (n[subscript 3He]/n[subscript e]~8%–12%), in relatively low density D([superscript 3]He) plasmas, [overline n]e<=1.3×10[superscript 20] m[superscript −3], heated with 50 MHz rf power at B[subscript t0]~5.1 T, strong (up to 90 km/s) toroidal rotation (Vphi) in the cocurrent direction has been observed by high-resolution x-ray spectroscopy on Alcator C-Mod. The change in central Vphi scales with the applied rf power (<=30 km s[superscript −1] MW[superscript −1]), and is generally at least a factor of 2 higher than the empirically determined intrinsic plasma rotation scaling. The rotation in the inner plasma (r/a<=0.3) responds to the rf power more quickly than that of the outer region (r/a>=0.7), and the rotation profile is broadly peaked for r/a<=0.5. Localized poloidal rotation (0.3<=r/a<=0.6) in the ion diamagnetic drift direction (~2 km/s at 3 MW) is also observed, and similarly increases with rf power. Changing the toroidal phase of the antenna does not affect the rotation direction, and it only weakly affects the rotation magnitude. The mode converted ion cyclotron wave (MC ICW) has been detected by a phase contrast imaging system and the MC process is confirmed by two-dimensional full wave TORIC simulations. The simulations also show that the MC ICW is strongly damped on 3He ions in the vicinity of the MC layer, approximately on the same flux surfaces where the rf driven flow is observed. The flow shear in our experiment is marginally sufficient for plasma confinement enhancement based on the comparison of the E×B shearing rate and gyrokinetic linear stability analysis.
MIT Department
Massachusetts Institute of Technology. Department of Physics
Massachusetts Institute of Technology. Plasma Science and Fusion Center
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DOI of Published Version
http://dx.doi.org/10.1063/1.3082936
