Quantitative comparison of electron temperature fluctuations to nonlinear gyrokinetic simulations in C-Mod Ohmic L-mode discharges
Long wavelength turbulent electron temperature fluctuations (k[subscript lower case y]ρ[subscript lower case s] < 0.3) are measured in the outer core region (r/a > 0.8) of Ohmic L-mode plasmas at Alcator C-Mod [E. S. Marmar et al., Nucl. Fusion 49, 104014 (2009)] with a correlation electron cy...
| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | en_US |
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American Institute of Physics (AIP)
2017
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| Online Access: | http://hdl.handle.net/1721.1/108782 https://orcid.org/0000-0003-2951-9749 https://orcid.org/0000-0002-4438-729X |
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| author | Holland, C. Howard, N. T. Sung, Choongki White, Anne E. Mikkelsen, David Theiler, Christian Greenwald, Martin J. Churchill, Randy |
| author2 | Massachusetts Institute of Technology. Department of Nuclear Science and Engineering |
| author_facet | Massachusetts Institute of Technology. Department of Nuclear Science and Engineering Holland, C. Howard, N. T. Sung, Choongki White, Anne E. Mikkelsen, David Theiler, Christian Greenwald, Martin J. Churchill, Randy |
| author_sort | Holland, C. |
| collection | MIT |
| description | Long wavelength turbulent electron temperature fluctuations (k[subscript lower case y]ρ[subscript lower case s] < 0.3) are measured in the outer core region (r/a > 0.8) of Ohmic L-mode plasmas at Alcator C-Mod [E. S. Marmar et al., Nucl. Fusion 49, 104014 (2009)] with a correlation electron cyclotron emission diagnostic. The relative amplitude and frequency spectrum of the fluctuations are compared quantitatively with nonlinear gyrokinetic simulations using the GYRO code [J. Candy and R. E. Waltz, J. Comput. Phys. 186, 545 (2003)] in two different confinement regimes: linear Ohmic confinement (LOC) regime and saturated Ohmic confinement (SOC) regime. When comparing experiment with nonlinear simulations, it is found that local, electrostatic ion-scale simulations (k[subscript lower case y]ρ[subscript lower case s] ≲ 1.7) performed at r/a ∼ 0.85 reproduce the experimental ion heat flux levels, electron temperature fluctuation levels, and frequency spectra within experimental error bars. In contrast, the electron heat flux is robustly under-predicted and cannot be recovered by using scans of the simulation inputs within error bars or by using global simulations. If both the ion heat flux and the measured temperature fluctuations are attributed predominantly to long-wavelength turbulence, then under-prediction of electron heat flux strongly suggests that electron scale turbulence is important for transport in C-Mod Ohmic L-mode discharges. In addition, no evidence is found from linear or nonlinear simulations for a clear transition from trapped electron mode to ion temperature gradient turbulence across the LOC/SOC transition, and also there is no evidence in these Ohmic L-mode plasmas of the “Transport Shortfall” [C. Holland et al., Phys. Plasmas 16, 052301 (2009)]. |
| first_indexed | 2024-09-23T12:38:51Z |
| format | Article |
| id | mit-1721.1/108782 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T12:38:51Z |
| publishDate | 2017 |
| publisher | American Institute of Physics (AIP) |
| record_format | dspace |
| spelling | mit-1721.1/1087822023-02-26T02:08:28Z Quantitative comparison of electron temperature fluctuations to nonlinear gyrokinetic simulations in C-Mod Ohmic L-mode discharges Holland, C. Howard, N. T. Sung, Choongki White, Anne E. Mikkelsen, David Theiler, Christian Greenwald, Martin J. Churchill, Randy Massachusetts Institute of Technology. Department of Nuclear Science and Engineering Massachusetts Institute of Technology. Plasma Science and Fusion Center White, Anne Sung, Choongki White, Anne E. Mikkelsen, David Greenwald, Martin J Churchill, Randy Michael Theiler, Christian Long wavelength turbulent electron temperature fluctuations (k[subscript lower case y]ρ[subscript lower case s] < 0.3) are measured in the outer core region (r/a > 0.8) of Ohmic L-mode plasmas at Alcator C-Mod [E. S. Marmar et al., Nucl. Fusion 49, 104014 (2009)] with a correlation electron cyclotron emission diagnostic. The relative amplitude and frequency spectrum of the fluctuations are compared quantitatively with nonlinear gyrokinetic simulations using the GYRO code [J. Candy and R. E. Waltz, J. Comput. Phys. 186, 545 (2003)] in two different confinement regimes: linear Ohmic confinement (LOC) regime and saturated Ohmic confinement (SOC) regime. When comparing experiment with nonlinear simulations, it is found that local, electrostatic ion-scale simulations (k[subscript lower case y]ρ[subscript lower case s] ≲ 1.7) performed at r/a ∼ 0.85 reproduce the experimental ion heat flux levels, electron temperature fluctuation levels, and frequency spectra within experimental error bars. In contrast, the electron heat flux is robustly under-predicted and cannot be recovered by using scans of the simulation inputs within error bars or by using global simulations. If both the ion heat flux and the measured temperature fluctuations are attributed predominantly to long-wavelength turbulence, then under-prediction of electron heat flux strongly suggests that electron scale turbulence is important for transport in C-Mod Ohmic L-mode discharges. In addition, no evidence is found from linear or nonlinear simulations for a clear transition from trapped electron mode to ion temperature gradient turbulence across the LOC/SOC transition, and also there is no evidence in these Ohmic L-mode plasmas of the “Transport Shortfall” [C. Holland et al., Phys. Plasmas 16, 052301 (2009)]. United States. Department of Energy (Grant No. DE-SC0006419) United States. Department of Energy (Grant No. E-FC02-99ER54512) United States. Department of Energy. Office of Science (Contract No. DE-AC02-05CH11231) 2017-05-09T17:31:02Z 2017-05-09T17:31:02Z 2016-04 2016-01 Article http://purl.org/eprint/type/JournalArticle 1070-664X 1089-7674 http://hdl.handle.net/1721.1/108782 Sung, C., A. E. White, D. R. Mikkelsen, M. Greenwald, C. Holland, N. T. Howard, R. Churchill, and C. Theiler. “Quantitative Comparison of Electron Temperature Fluctuations to Nonlinear Gyrokinetic Simulations in C-Mod Ohmic L-Mode Discharges.” Physics of Plasmas 23, no. 4 (April 2016): 042303. https://orcid.org/0000-0003-2951-9749 https://orcid.org/0000-0002-4438-729X en_US http://dx.doi.org/10.1063/1.4945620 Physics of Plasmas Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. application/pdf American Institute of Physics (AIP) Prof. White via Chris Sherratt |
| spellingShingle | Holland, C. Howard, N. T. Sung, Choongki White, Anne E. Mikkelsen, David Theiler, Christian Greenwald, Martin J. Churchill, Randy Quantitative comparison of electron temperature fluctuations to nonlinear gyrokinetic simulations in C-Mod Ohmic L-mode discharges |
| title | Quantitative comparison of electron temperature fluctuations to nonlinear gyrokinetic simulations in C-Mod Ohmic L-mode discharges |
| title_full | Quantitative comparison of electron temperature fluctuations to nonlinear gyrokinetic simulations in C-Mod Ohmic L-mode discharges |
| title_fullStr | Quantitative comparison of electron temperature fluctuations to nonlinear gyrokinetic simulations in C-Mod Ohmic L-mode discharges |
| title_full_unstemmed | Quantitative comparison of electron temperature fluctuations to nonlinear gyrokinetic simulations in C-Mod Ohmic L-mode discharges |
| title_short | Quantitative comparison of electron temperature fluctuations to nonlinear gyrokinetic simulations in C-Mod Ohmic L-mode discharges |
| title_sort | quantitative comparison of electron temperature fluctuations to nonlinear gyrokinetic simulations in c mod ohmic l mode discharges |
| url | http://hdl.handle.net/1721.1/108782 https://orcid.org/0000-0003-2951-9749 https://orcid.org/0000-0002-4438-729X |
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