Perturbative thermal diffusivity from partial sawtooth crashes in Alcator C-Mod
Abstract
Perturbative thermal diffusivity has been measured on Alcator C-Mod via the use of the extended-time-to-peak method on heat pulses generated by partial sawtooth crashes. Perturbative thermal diffusivity governs the propagation of heat pulses through a plasma. It differs from power balance thermal diffusivity, which governs steady state thermal transport. Heat pulses generated by sawtooth crashes have been used extensively in the past to study heat pulse thermal diffusivity, but the details of the sawtooth event typically lead to non-diffusive 'ballistic' transport, making them an unreliable measure of perturbative diffusivity on many tokamaks. Partial sawteeth are common on numerous tokamaks, and generate a heat pulse without the 'ballistic' transport that often accompanies full sawteeth. This is the first application of the extended-time-to-peak method of diffusivity calculation to partial sawtooth crashes. Furthermore, this analysis was applied to over 50 C-Mod shots containing both L- and I-Mode. Results indicate correlations between perturbative diffusivity and confinement regime (L- versus I-mode), as well as correlations with local temperature, density, the associated gradients, and gradient scale lengths (a/LTe and a/Ln). In addition, diffusivities calculated from partial sawteeth are compared to perturbative diffusivities calculated with the nonlinear gyrokinetic code GYRO. We find that standard ion-scale simulations (ITG/TEMmore »
- Authors:
-
- MIT Plasma Science and Fusion Center, Cambridge, MA (United States)
- Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
- Oak Ridge Inst. for Science and Education (ORISE), Oak Ridge, TN (United States)
- Publication Date:
- Research Org.:
- Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Plasma Science and Fusion Center
- Sponsoring Org.:
- USDOE Office of Science (SC), Fusion Energy Sciences (FES)
- OSTI Identifier:
- 1897509
- Alternate Identifier(s):
- OSTI ID: 1236974
- Grant/Contract Number:
- SC0006419; FC02-99ER54512; DEFC02-99ER54512-CMOD
- Resource Type:
- Accepted Manuscript
- Journal Name:
- Nuclear Fusion
- Additional Journal Information:
- Journal Volume: 56; Journal Issue: 3; Journal ID: ISSN 0029-5515
- Publisher:
- IOP Science
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; Perturbative Transport; Thermal Diffusivity; Sawtooth
Citation Formats
Creely, A. J., White, A. E., Edlund, E. M., Howard, N. T., and Hubbard, A. E. Perturbative thermal diffusivity from partial sawtooth crashes in Alcator C-Mod. United States: N. p., 2016.
Web. doi:10.1088/0029-5515/56/3/036003.
Creely, A. J., White, A. E., Edlund, E. M., Howard, N. T., & Hubbard, A. E. Perturbative thermal diffusivity from partial sawtooth crashes in Alcator C-Mod. United States. https://doi.org/10.1088/0029-5515/56/3/036003
Creely, A. J., White, A. E., Edlund, E. M., Howard, N. T., and Hubbard, A. E. Fri .
"Perturbative thermal diffusivity from partial sawtooth crashes in Alcator C-Mod". United States. https://doi.org/10.1088/0029-5515/56/3/036003. https://www.osti.gov/servlets/purl/1897509.
@article{osti_1897509,
title = {Perturbative thermal diffusivity from partial sawtooth crashes in Alcator C-Mod},
author = {Creely, A. J. and White, A. E. and Edlund, E. M. and Howard, N. T. and Hubbard, A. E.},
abstractNote = {Perturbative thermal diffusivity has been measured on Alcator C-Mod via the use of the extended-time-to-peak method on heat pulses generated by partial sawtooth crashes. Perturbative thermal diffusivity governs the propagation of heat pulses through a plasma. It differs from power balance thermal diffusivity, which governs steady state thermal transport. Heat pulses generated by sawtooth crashes have been used extensively in the past to study heat pulse thermal diffusivity, but the details of the sawtooth event typically lead to non-diffusive 'ballistic' transport, making them an unreliable measure of perturbative diffusivity on many tokamaks. Partial sawteeth are common on numerous tokamaks, and generate a heat pulse without the 'ballistic' transport that often accompanies full sawteeth. This is the first application of the extended-time-to-peak method of diffusivity calculation to partial sawtooth crashes. Furthermore, this analysis was applied to over 50 C-Mod shots containing both L- and I-Mode. Results indicate correlations between perturbative diffusivity and confinement regime (L- versus I-mode), as well as correlations with local temperature, density, the associated gradients, and gradient scale lengths (a/LTe and a/Ln). In addition, diffusivities calculated from partial sawteeth are compared to perturbative diffusivities calculated with the nonlinear gyrokinetic code GYRO. We find that standard ion-scale simulations (ITG/TEM turbulence) under-predict the perturbative thermal diffusivity, but new multi-scale (ITG/TEM coupled with ETG) simulations can match the experimental perturbative diffusivity within error bars for an Alcator C-Mod L-mode plasma. Perturbative diffusivities extracted from heat pulses due to partial sawteeth provide a new constraint that can be used to validate gyrokinetic simulations.},
doi = {10.1088/0029-5515/56/3/036003},
journal = {Nuclear Fusion},
number = 3,
volume = 56,
place = {United States},
year = {Fri Feb 05 00:00:00 EST 2016},
month = {Fri Feb 05 00:00:00 EST 2016}
}
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Works referencing / citing this record:
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