Interpreting radial correlation doppler reflectometry using gyrokinetic simulations
Name
Ruiz_Ruiz_2022_Plasma_Phys._Control._Fusion_64_055019.pdf
Description
Published version
Size
4.02 MB
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Checksum (MD5)
346777a9f87c20ab6061141e51c1e101
Author(s)
Ruiz Ruiz, J
Parra, FI
Hall-Chen, VH
Christen, N
Barnes, M
Candy, J
Garcia, J
Giroud, C
Guttenfelder, W
Hillesheim, JC
Date Issued
2022
Journal
Plasma Physics and Controlled Fusion
Publisher
IOP Publishing
Citation
Ruiz Ruiz, J, Parra, FI, Hall-Chen, VH, Christen, N, Barnes, M et al. 2022. "Interpreting radial correlation doppler reflectometry using gyrokinetic simulations." Plasma Physics and Controlled Fusion, 64 (5).
Version
Final published version
Abstract
A linear response, local model for the DBS amplitude applied to gyrokinetic simulations shows
that radial correlation Doppler reflectometry measurements (RCDR, Schirmer et al 2007
Plasma Phys. Control. Fusion 49 1019) are not sensitive to the average turbulence radial
correlation length, but to a correlation length that depends on the binormal wavenumber k⊥
selected by the Doppler backscattering (DBS) signal. Nonlinear gyrokinetic simulations show
that the turbulence naturally exhibits a nonseparable power law spectrum in wavenumber space,
leading to a power law dependence of the radial correlation length with binormal wavenumber
lr ∼ Ck−α
⊥ (α ≈ 1) which agrees with the inverse proportionality relationship between the
measured lr and k⊥ observed in experiments (Fern´andez-Marina et al 2014 Nucl. Fusion 54
072001). This new insight indicates that RCDR characterizes the eddy aspect ratio in the
perpendicular plane to the magnetic field. It also motivates future use of a nonseparable
turbulent spectrum to quantitatively interpret RCDR and potentially other turbulence
diagnostics. The radial correlation length is only measurable when the radial resolution at the
cutoff location Wn satisfies Wn ≪ lr
, while the measurement becomes dominated by Wn for
Wn ≫ lr
. This suggests that lr
is likely to be inaccessible for electron-scale DBS measurements
(k⊥ρs > 1). The effect of Wn on ion-scale radial correlation lengths could be nonnegligible.
MIT Department
Massachusetts Institute of Technology. Department of Nuclear Science and Engineering
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Creative Commons Attribution 4.0 International license
Persistent DSpace Link
DOI of Published Version
https://doi.org/10.1088/1361-6587/AC5916
