Density sensitivity of intrinsic rotation profiles in ion cyclotron range of frequency-heated L-mode plasmas
Author(s)Reinke, Matthew Logan; Rice, John E.; White, Anne E.; Greenwald, Martin J.; Howard, Nathaniel Thomas; Ennever, Paul Chappell; Gao, Chi; Hubbard, Amanda E; Hughes Jr, Jerry; ... Show more Show less
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The physical mechanisms that cause tokamak plasmas to rotate toroidally without external momentum input are of considerable interest to the plasma physics community. This paper documents a substantial change in both the magnitude of the core-rotation frequency, −1 < ω(r/a = 0) < +10 kHz, and the sign of rotation shear at mid-radius, u' = −R[superscript 2] dω/dr/v[subscript th,i], which varies in the range −0.6 < u' < +0.8 in response to very small changes in the electron density. In 0.8 MA, 5.4 T Alcator C-Mod L-mode plasmas using 1.2 MW of on-axis ion-cyclotron resonance heating, plasmas with line-averaged densities in the range 1.0 < [bar over n][subscript e] < 1.2 X 10[superscript 20] m[superscript -3] exhibit a transition from a peaked intrinsic rotation profile to one that is hollow. Gradient scale lengths of the temperature and density profiles, the drive for plasma turbulence thought to play a role in intrinsic rotation, are indistinguishable within experimental uncertainties between the plasmas, and linear stability analysis using GYRO shows the plasmas to be in the ion temperature gradient-dominated turbulence regime. The impact of changes in the rotation profile in response to minor changes under target plasma conditions is discussed in relation to established analysis techniques and cross-machine rotation scaling studies, with comparisons made with existing ASDEX-Upgrade work on intrinsic rotation shear.
DepartmentMassachusetts Institute of Technology. Department of Nuclear Science and Engineering; Massachusetts Institute of Technology. Department of Physics; Massachusetts Institute of Technology. Plasma Science and Fusion Center
Plasma Physics and Controlled Fusion
Reinke, M L, J E Rice, A E White, M Greenwald, N T Howard, P Ennever, C Gao, A E Hubbard, and J W Hughes. “Density sensitivity of intrinsic rotation profiles in ion cyclotron range of frequency-heated L-mode plasmas.” Plasma Physics and Controlled Fusion 55, no. 1 (January 1, 2013): 012001.
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