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

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

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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 5...

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Bibliographic Details
Main Authors: Mikkelsen, D. R., Edlund, E. M., Kung, C., Holland, C., Candy, J., Petty, C. C., Reinke, M. L., Theiler, C., White, Anne E., Howard, Nathaniel Thomas, Creely, Alexander James, Chilenski, Mark Alan, Greenwald, Martin J, Hubbard, Amanda E, Hughes Jr, Jerry, Marmar, Earl S, Rice, John E, Sierchio, Jennifer M., Sung, Choongki, Walk Jr, John R, Whyte, Dennis G
Other Authors: Massachusetts Institute of Technology. Plasma Science and Fusion Center
Format: Article
Language:en_US
Published: American Institute of Physics (AIP) 2017
Online Access:http://hdl.handle.net/1721.1/108750
https://orcid.org/0000-0003-2951-9749
https://orcid.org/0000-0002-0026-6939
https://orcid.org/0000-0002-4464-150X
https://orcid.org/0000-0002-3616-8484
https://orcid.org/0000-0002-4438-729X
https://orcid.org/0000-0002-5283-0546
https://orcid.org/0000-0001-8319-5971
https://orcid.org/0000-0001-7700-848X
https://orcid.org/0000-0001-8324-4227
https://orcid.org/0000-0002-9001-5606
Description
Summary: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.

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