skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: A new fast two-color interferometer at Alcator C-Mod for turbulence measurements and comparison with phase contrast imaging

Abstract

Accurately predicting the turbulent transport properties of magnetically confined plasmas is a major challenge of fusion energy research. Validation of transport models is typically done by applying so-called “synthetic diagnostics” to the output of nonlinear gyrokinetic simulations, and the results are compared to experimental data. As part of the validation process, comparing two independent turbulence measurements to each other provides the opportunity to test the synthetic diagnostics themselves; a step which is rarely possible due to limited availability of redundant fluctuation measurements on magnetic confinement experiments. At Alcator C-Mod, phase-contrast imaging (PCI) is a commonly used turbulence diagnostic. PCI measures line-integrated electron density fluctuations with high sensitivity and wavenumber resolution (1.6 cm{sup −1}≲|k{sub R}|≲11 cm{sup −1}). A new fast two-color interferometry (FTCI) diagnostic on the Alcator C-Mod tokamak measures long-wavelength (|k{sub R}|≲3.0 cm{sup −1}) line-integrated electron density fluctuations. Measurements of coherent and broadband fluctuations made by PCI and FTCI are compared here for the first time. Good quantitative agreement is found between the two measurements. This provides experimental validation of the low-wavenumber region of the PCI calibration, and also helps validate the low-wavenumber portions of the synthetic PCI diagnostic that has been used in gyrokinetic model validation work in the past. We discussmore » possibilities to upgrade FTCI, so that a similar comparison could be done at higher wavenumbers in the future.« less

Authors:
;  [1]
  1. Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)
Publication Date:
OSTI Identifier:
22253184
Resource Type:
Journal Article
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 21; Journal Issue: 4; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 1070-664X
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ALCATOR DEVICE; COMPARATIVE EVALUATIONS; ELECTRON DENSITY; INTERFEROMETERS; MAGNETIC CONFINEMENT; NONLINEAR PROBLEMS; THERMONUCLEAR REACTORS; TRANSPORT THEORY; TURBULENCE

Citation Formats

Kasten, C. P., E-mail: ckasten@alum.mit.edu, White, A. E., and Irby, J. H. A new fast two-color interferometer at Alcator C-Mod for turbulence measurements and comparison with phase contrast imaging. United States: N. p., 2014. Web. doi:10.1063/1.4871392.
Kasten, C. P., E-mail: ckasten@alum.mit.edu, White, A. E., & Irby, J. H. A new fast two-color interferometer at Alcator C-Mod for turbulence measurements and comparison with phase contrast imaging. United States. https://doi.org/10.1063/1.4871392
Kasten, C. P., E-mail: ckasten@alum.mit.edu, White, A. E., and Irby, J. H. 2014. "A new fast two-color interferometer at Alcator C-Mod for turbulence measurements and comparison with phase contrast imaging". United States. https://doi.org/10.1063/1.4871392.
@article{osti_22253184,
title = {A new fast two-color interferometer at Alcator C-Mod for turbulence measurements and comparison with phase contrast imaging},
author = {Kasten, C. P., E-mail: ckasten@alum.mit.edu and White, A. E. and Irby, J. H.},
abstractNote = {Accurately predicting the turbulent transport properties of magnetically confined plasmas is a major challenge of fusion energy research. Validation of transport models is typically done by applying so-called “synthetic diagnostics” to the output of nonlinear gyrokinetic simulations, and the results are compared to experimental data. As part of the validation process, comparing two independent turbulence measurements to each other provides the opportunity to test the synthetic diagnostics themselves; a step which is rarely possible due to limited availability of redundant fluctuation measurements on magnetic confinement experiments. At Alcator C-Mod, phase-contrast imaging (PCI) is a commonly used turbulence diagnostic. PCI measures line-integrated electron density fluctuations with high sensitivity and wavenumber resolution (1.6 cm{sup −1}≲|k{sub R}|≲11 cm{sup −1}). A new fast two-color interferometry (FTCI) diagnostic on the Alcator C-Mod tokamak measures long-wavelength (|k{sub R}|≲3.0 cm{sup −1}) line-integrated electron density fluctuations. Measurements of coherent and broadband fluctuations made by PCI and FTCI are compared here for the first time. Good quantitative agreement is found between the two measurements. This provides experimental validation of the low-wavenumber region of the PCI calibration, and also helps validate the low-wavenumber portions of the synthetic PCI diagnostic that has been used in gyrokinetic model validation work in the past. We discuss possibilities to upgrade FTCI, so that a similar comparison could be done at higher wavenumbers in the future.},
doi = {10.1063/1.4871392},
url = {https://www.osti.gov/biblio/22253184}, journal = {Physics of Plasmas},
issn = {1070-664X},
number = 4,
volume = 21,
place = {United States},
year = {2014},
month = {4}
}