Nonlinear gyrokinetic simulations of the I-mode high confinement regime and comparisons with experiment

Journal Article · Fri May 15 00:00:00 EDT 2015 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.4921150· OSTI ID:22410389

Howard, N. T.; Creely, A. J.; Chilenski, M. A.; Greenwald, M.; Hubbard, A. E.; Hughes, J. W.; Marmar, E.; Rice, J. E.; Sierchio, J. M.; Sung, C.; Walk, J. R.; Whyte, D. G. ^[1]; Mikkelsen, D. R.; Edlund, E. M.; Kung, C. ^[2]; Holland, C. ^[3]; Candy, J.; Petty, C. C. ^[4]; Reinke, M. L. ^[5]; others, and

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1. MIT Plasma Science and Fusion Center, Cambridge, Massachusetts 02139 (United States)
2. Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540 (United States)
3. University of California, San Diego (UCSD) San Diego, California 92093 (United States)
4. General Atomics, P.O. Box 85608, San Diego, California 92186 (United States)
5. York University, Heslington, York YO10 5DD (United Kingdom)

For the first time, nonlinear gyrokinetic simulations of I-mode plasmas are performed and compared with experiment. I-mode is a high confinement regime, featuring energy confinement similar to H-mode, but without enhanced particle and impurity particle confinement [D. G. Whyte et al., Nucl. Fusion 50, 105005 (2010)]. As a consequence of the separation between heat and particle transport, I-mode exhibits several favorable characteristics compared to H-mode. The nonlinear gyrokinetic code GYRO [J. Candy and R. E. Waltz, J Comput. Phys. 186, 545 (2003)] is used to explore the effects of E × B shear and profile stiffness in I-mode and compare with L-mode. The nonlinear GYRO simulations show that I-mode core ion temperature and electron temperature profiles are more stiff than L-mode core plasmas. Scans of the input E × B shear in GYRO simulations show that E × B shearing of turbulence is a stronger effect in the core of I-mode than L-mode. The nonlinear simulations match the observed reductions in long wavelength density fluctuation levels across the L-I transition but underestimate the reduction of long wavelength electron temperature fluctuation levels. The comparisons between experiment and gyrokinetic simulations for I-mode suggest that increased E × B shearing of turbulence combined with increased profile stiffness are responsible for the reductions in core turbulence observed in the experiment, and that I-mode resembles H-mode plasmas more than L-mode plasmas with regards to marginal stability and temperature profile stiffness.

• OSTI ID: 22410389
• Journal Information: Physics of Plasmas, Vol. 22, Issue 5; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
COMPARATIVE EVALUATIONS
ELECTRIC FIELDS
ELECTRON TEMPERATURE
FLEXIBILITY
FLUCTUATIONS
H-MODE PLASMA CONFINEMENT
ION TEMPERATURE
L-MODE PLASMA CONFINEMENT
MAGNETIC FIELDS
NONLINEAR PROBLEMS
PLASMA IMPURITIES
PLASMA SIMULATION
SHEAR
TURBULENCE
WAVELENGTHS