Fast imaging of filaments in the X-point region of Alcator C-Mod
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Author(s)
Ballinger, S.
Zweben, S.J.
Terry, James L
Brunner, Daniel Frederic
Labombard, Brian
White, Anne E.
Date Issued
January 2017
Journal
Nuclear Materials and Energy
Publisher
Elsevier BV
Citation
Terry, J.L. et al. “Fast Imaging of Filaments in the X-Point Region of Alcator C-Mod.” Nuclear Materials and Energy 12 (August 2017): 989–993 © 2016 Elsevier Ltd
Version
Final published version
Abstract
A rich variety of field-aligned fluctuations has been revealed using fast imaging of Dαemission from Alcator C-Mod's lower X-point region. Field-aligned filamentary fluctuations are observed along the inner divertor leg, within the Private-Flux-Zone (PFZ), in the Scrape-Off Layer (SOL) outside the outer divertor leg, and, under some conditions, at or above the X-point. The locations and dynamics of the filaments in these regions are strikingly complex in C-Mod. Changes in the filaments’ generation appear to be ordered by plasma density and magnetic configuration. Filaments are not observed for plasmas with n/nGreenwald≲ 0.12 nor are they observed in Upper Single Null configurations. In a Lower Single Null with 0.12 ≲ n/nGreenwald ≲ 0.45 and Bx∇B directed down, filaments typically move up the inner divertor leg toward the X-point. Reversing the field direction results in the appearance of filaments outside of the outer divertor leg. With the divertor targets “detached”, filaments inside the LCFS are seen. These studies were motivated by observations of filaments in the X-point and PFZ regions in MAST, and comparisons with those observations are made. Keywords: Alcator C-Mod; Turbulence; Divertor; X-point; Filaments
MIT Department
Massachusetts Institute of Technology. Department of Nuclear Science and Engineering
Massachusetts Institute of Technology. Plasma Science and Fusion Center
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Creative Commons Attribution-NonCommercial-NoDerivs License
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DOI of Published Version
https://doi.org/10.1016/J.NME.2016.11.020
