Short wavelength turbulence generated by shear in the QH-mode edge on DIII–D
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Porkolab_Short wavelength.pdf
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Author(s)
Burrell, K. H.
Rost, Jon C.
Porkolab, Miklos
Dorris, James
Alternative Title
Short wavelength turbulence generated by shear in the quiescent H-mode edge on DIII–D
Date Issued
June 2014
Journal
Physics of Plasmas
Publisher
American Institute of Physics (AIP)
Citation
Rost, J. C., M. Porkolab, J. Dorris, and K. H. Burrell. “Short Wavelength Turbulence Generated by Shear in the Quiescent H-Mode Edge on DIII–D.” Phys. Plasmas 21, no. 6 (June 2014): 062306.
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Author's final manuscript
Abstract
A region of turbulence with large radial wavenumber (k[subscript r]ρ[subscript s] > 1) is found in the high-shear portion of the plasma edge in Quiescent H-mode (QH-mode) on DIII–D using the Phase Contrast Imaging (PCI) diagnostic. At its peak outside the minimum of the Er well, the turbulence exhibits large amplitude [~ over n]/n ~ 40%, with large radial wavenumber ∣[¯over k][subscript r]/[¯ over k][subscript θ]∣ ~ 11 and short radial correlation length L[subscript r]/ρ[subscript i] ~ 0.2. The turbulence inside the E[subscript r] well minimum is characterized by the opposite sign in radial wavenumber from that of turbulence outside the minimum, consistent with the expected effects of velocity shear. The PCI diagnostic provides a line-integrated measurement of density fluctuations, so data are taken during a scan of plasma position at constant parameters to allow the PCI to sample a range in k[subscript r]/k[subscript θ]. Analysis of the Doppler shift and plasma geometry allows the turbulence to be localized to a narrow region 3 mm inside the last closed flux surface, outside the minimum of the E[subscript r] well. The turbulence amplitude and radial wavenumber and correlation length are determined by fitting the PCI results with a simple non-isotropic turbulence model with two regions of turbulence. These PCI observations, made in QH-mode, are qualitatively similar to those made in standard edge localized modes (ELM)-free H-mode and between ELMs, suggesting a similar role for large k[subscript r] turbulence there.
MIT Department
Massachusetts Institute of Technology. Department of Physics
Massachusetts Institute of Technology. Plasma Science and Fusion Center
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DOI of Published Version
https://doi.org/10.1063/1.4883135
