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Title: Validation of nonlinear gyrokinetic simulations of L- and I-mode plasmas on Alcator C-Mod

New validation of global, nonlinear, ion-scale gyrokinetic simulations (GYRO) is carried out for L- and I-mode plasmas on Alcator C-Mod, utilizing heat fluxes, profile stiffness, and temperature fluctuations. Previous work at C-Mod found that ITG/TEM-scale GYRO simulations can match both electron and ion heat fluxes within error bars in I-mode [White PoP 2015], suggesting that multi-scale (cross-scale coupling) effects [Howard PoP 2016] may be less important in I-mode than in L-mode. New results presented here, however, show that global, nonlinear, ion-scale GYRO simulations are able to match the experimental ion heat flux, but underpredict electron heat flux (at most radii), electron temperature fluctuations, and perturbative thermal diffusivity in both L- and I-mode. Linear addition of electron heat flux from electron scale runs does not resolve this discrepancy. These results indicate that single-scale simulations do not sufficiently describe the I-mode core transport, and that multi-scale (coupled electron- and ion-scale) transport models are needed. In conclusion a preliminary investigation with multi-scale TGLF, however, was unable to resolve the discrepancy between ion-scale GYRO and experimental electron heat fluxes and perturbative diffusivity, motivating further work with multi-scale GYRO simulations and a more comprehensive study with multi-scale TGLF.
Authors:
ORCiD logo [1] ;  [1] ;  [1] ;  [1] ;  [1] ; ORCiD logo [1] ;  [1] ;  [1] ; ORCiD logo [2] ;  [2] ;  [3] ;  [3] ;  [4]
  1. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Plasma Science and Fusion Center
  2. General Atomics, San Diego, CA (United States)
  3. Max Planck Inst. for Plasma Physics, Garching (Germany)
  4. Univ. of California, Los Angeles, CA (United States)
Publication Date:
Grant/Contract Number:
SC0006419; FC02-99ER54512; AC02-05CH11231
Type:
Published Article
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 24; Journal Issue: 5; Journal ID: ISSN 1070-664X
Publisher:
American Institute of Physics (AIP)
Research Org:
Massachusetts Inst. of Tech., Cambridge, MA (United States)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
OSTI Identifier:
1348024
Alternate Identifier(s):
OSTI ID: 1349367; OSTI ID: 1430264

Creely, A. J., Howard, N. T., Rodriguez-Fernandez, P., Cao, N., Hubbard, A. E., Hughes, J. W., Rice, J. E., White, A. E., Candy, J., Staebler, G. M., Conway, G. D., Freethy, S. J., and Sung, C.. Validation of nonlinear gyrokinetic simulations of L- and I-mode plasmas on Alcator C-Mod. United States: N. p., Web. doi:10.1063/1.4977466.
Creely, A. J., Howard, N. T., Rodriguez-Fernandez, P., Cao, N., Hubbard, A. E., Hughes, J. W., Rice, J. E., White, A. E., Candy, J., Staebler, G. M., Conway, G. D., Freethy, S. J., & Sung, C.. Validation of nonlinear gyrokinetic simulations of L- and I-mode plasmas on Alcator C-Mod. United States. doi:10.1063/1.4977466.
Creely, A. J., Howard, N. T., Rodriguez-Fernandez, P., Cao, N., Hubbard, A. E., Hughes, J. W., Rice, J. E., White, A. E., Candy, J., Staebler, G. M., Conway, G. D., Freethy, S. J., and Sung, C.. 2017. "Validation of nonlinear gyrokinetic simulations of L- and I-mode plasmas on Alcator C-Mod". United States. doi:10.1063/1.4977466.
@article{osti_1348024,
title = {Validation of nonlinear gyrokinetic simulations of L- and I-mode plasmas on Alcator C-Mod},
author = {Creely, A. J. and Howard, N. T. and Rodriguez-Fernandez, P. and Cao, N. and Hubbard, A. E. and Hughes, J. W. and Rice, J. E. and White, A. E. and Candy, J. and Staebler, G. M. and Conway, G. D. and Freethy, S. J. and Sung, C.},
abstractNote = {New validation of global, nonlinear, ion-scale gyrokinetic simulations (GYRO) is carried out for L- and I-mode plasmas on Alcator C-Mod, utilizing heat fluxes, profile stiffness, and temperature fluctuations. Previous work at C-Mod found that ITG/TEM-scale GYRO simulations can match both electron and ion heat fluxes within error bars in I-mode [White PoP 2015], suggesting that multi-scale (cross-scale coupling) effects [Howard PoP 2016] may be less important in I-mode than in L-mode. New results presented here, however, show that global, nonlinear, ion-scale GYRO simulations are able to match the experimental ion heat flux, but underpredict electron heat flux (at most radii), electron temperature fluctuations, and perturbative thermal diffusivity in both L- and I-mode. Linear addition of electron heat flux from electron scale runs does not resolve this discrepancy. These results indicate that single-scale simulations do not sufficiently describe the I-mode core transport, and that multi-scale (coupled electron- and ion-scale) transport models are needed. In conclusion a preliminary investigation with multi-scale TGLF, however, was unable to resolve the discrepancy between ion-scale GYRO and experimental electron heat fluxes and perturbative diffusivity, motivating further work with multi-scale GYRO simulations and a more comprehensive study with multi-scale TGLF.},
doi = {10.1063/1.4977466},
journal = {Physics of Plasmas},
number = 5,
volume = 24,
place = {United States},
year = {2017},
month = {3}
}