Multi-channel transport experiments at Alcator C-Mod and comparison with gyrokinetic simulations

White, Anne; Howard, Nathan; Greenwald, M.; Reinke, M.L.; Sung, C.; Baek, Seung Gyou; Barnes, Michael; Candy, J.; Dominguez, A.; Ernst, D. R.; Gao, C.; Hubbard, A.; Hughes, J. W.; Lin, Y.; Mikkelsen, D. R.; Parra, Félix I.; Porkoláb, M.; Rice, J.E.; Walk, J.; Wukitch, S.J.; Team, Alcator C‐Mod

doi:10.1063/1.4803089

Cited by 50 publications

(57 citation statements)

References 48 publications

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“…When the uncertainty in the experimental and simulated heat fluxes are considered, the multi-scale electron and ion heat fluxes are now found to be in quantitative agreement with the experiment. This result suggest that electronscale turbulence may explain the robust Q e under-prediction observed in this discharge [18][19][20][21] and demonstrates for the first time that, in realistic plasma conditions with significant ion-scale turbulence, electron-scale turbulence can drive experimentally relevant levels of electron heat flux.…”

Section: Simulation Resultsmentioning

confidence: 94%

“…We emphasize that this plasma possesses no unique and experiment was identified in the ion heat and impurity particle channels while an underprediction (∼ 3×) was reported in the electron heat flux [19][20][21] . In these previous works, scans of the turbulence drive terms a/L T i , a/L Te , a/L n , n i /n e , and E × B shear were performed using ion-scale simulations (k θ ρ s < 1.3) to demonstrate that the under prediction of the electron heat flux is robust within experimental uncertainties.…”

Section: Experimental and Simulation Setupmentioning

confidence: 99%

“…All work in this paper focuses on a low-power Alcator C-Mod L-Mode plasma discharge that has been described previously [18][19][20][21] . We emphasize that this plasma possesses no unique and experiment was identified in the ion heat and impurity particle channels while an underprediction (∼ 3×) was reported in the electron heat flux [19][20][21] .…”

Section: Experimental and Simulation Setupmentioning

confidence: 99%

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Synergistic cross-scale coupling of turbulence in a tokamak plasma

et al. 2014

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For the first time, realistic, nonlinear gyrokinetic simulations spanning both the ion and electron spatio-temporal scales have demonstrated the coexistence of ion (k θ ρ s ∼ O(1.0)) and electron-scale (k θ ρ e ∼ O(1.0)) turbulence in the core of a tokamak plasma and the possible explanation of a documented discrepancy between simulation and experiment. These cutting-edge, multi-scale simulations utilized the GYRO code [J.Candy and R.E. Waltz, J Comput. Phys. 186, 545 (2003)] to study the coupling of ion and electron-scale turbulence in the core (r/a = 0.6) of an Alcator C-Mod L-mode discharge shown previously to exhibit an under-prediction of the electron heat flux when using simulations only including ion-scale turbulence. Electron-scale turbulence is found to play a dominant role in setting the electron heat flux level and radially-elongated "streamers" are found to coexist with larger ion-scale eddies in experimental plasma conditions. Inclusion of electron-scale turbulence in these simulations is found to increase both ion and electron heat flux levels by enhancing the transport at the ion-scale while also driving electron heat flux at sub-ρ i scales. These results suggest that previously observed discrepancies in the electron heat flux may be explained by inclusion of electron-scale contributions in gyrokinetic simulation.

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Section: Simulation Resultsmentioning

confidence: 94%

Section: Experimental and Simulation Setupmentioning

confidence: 99%

Section: Experimental and Simulation Setupmentioning

confidence: 99%

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Synergistic cross-scale coupling of turbulence in a tokamak plasma

et al. 2014

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“…231,285 In this experiment, designed for validating gyrokinetic models of the energy and particle transport, a base-case steady, sawtoothing L-mode plasma with 1.2 MW of on-axis RF heating was established. When the density was raised by 20%, it was found that the measured rotation profiles changed from peaked to hollow in shape while the electron density and impurity profiles remain peaked.…”

Section: Momentum Transportmentioning

confidence: 99%

20 years of research on the Alcator C-Mod tokamak

et al. 2014

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The object of this review is to summarize the achievements of research on the Alcator C-Mod tokamak [Hutchinson et al., Phys. Plasmas 1, 1511 and Marmar, Fusion Sci. Technol. 51, 261 (2007)] and to place that research in the context of the quest for practical fusion energy. C-Mod is a compact, high-field tokamak, whose unique design and operating parameters have produced a wealth of new and important results since it began operation in 1993, contributing data that extends tests of critical physical models into new parameter ranges and into new regimes. Using only highpower radio frequency (RF) waves for heating and current drive with innovative launching structures, C-Mod operates routinely at reactor level power densities and achieves plasma pressures higher than any other toroidal confinement device. C-Mod spearheaded the development of the vertical-target divertor and has always operated with high-Z metal plasma facing componentsapproaches subsequently adopted for ITER. C-Mod has made ground-breaking discoveries in divertor physics and plasma-material interactions at reactor-like power and particle fluxes and elucidated a) Paper AR1 1, Bull. Am. Phys. Soc. 58, 21 (2013). b) Invited speaker.

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“…q i < 1. 5 While modifications of fluctuation spectra due to a change of turbulence regime have been reported from different diagnostics in various machines, [6][7][8][9] it was recently established that the ITG-and TEM-dominated regimes could be differentiated from the reflectometry spectra. 10 In the latter work, the experimental observations were supported by the non-linear gyrokinetic simulations, which qualitatively reproduced the shape of the reflectometry spectra in the ITG and TEM regimes.…”

Section: Introductionmentioning

confidence: 99%

Simulation of core turbulence measurement in Tore Supra ohmic regimes

Hacquin¹,

Citrin²,

Arnichand³

et al. 2016

Physics of Plasmas

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This paper reports on a simulation of reflectometry measurement in Tore Supra ohmic discharges, for which the experimental observations as well as gyrokinetic non-linear computations predict a modification of turbulence spectrum between the linear (LOC) and the saturated ohmic confinement (SOC) regimes. Synthetic reflectometry simulations coupling full-wave computations with gyrokinetic data are carried out. This allows a direct comparison between the gyrokinetic non-linear predictions and experimental observations. The synthetic diagnostic results are found in a good agreement with the experimental findings; in particular, they reproduce well the quasi-coherent peak in the fluctuation spectrum of LOC regimes dominated by a trapped electron mode turbulence. It is also shown that such synthetic tools are valuable for (i) an enhanced interpretation of the reflectometry measurement (for instance, through the investigation of the 2D effects) and (ii) a better understanding of the turbulence properties (for instance, via the analysis of its poloidal asymmetry).

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Multi-channel transport experiments at Alcator C-Mod and comparison with gyrokinetic simulations

Cited by 50 publications

References 48 publications

Synergistic cross-scale coupling of turbulence in a tokamak plasma

Synergistic cross-scale coupling of turbulence in a tokamak plasma

20 years of research on the Alcator C-Mod tokamak

Simulation of core turbulence measurement in Tore Supra ohmic regimes

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