Repository logo

Infoscience

  • English
  • French
Log In
Logo EPFL, École polytechnique fédérale de Lausanne

Infoscience

  • English
  • French
Log In
  1. Home
  2. Academic and Research Output
  3. Journal articles
  4. Poloidal asymmetry in the narrow heat flux feature in the TCV scrape-off layer
 
research article

Poloidal asymmetry in the narrow heat flux feature in the TCV scrape-off layer

Tsui, C. K.
•
Boedo, J. A.
•
Halpern, F. D.
Show more
2017
Physics of Plasmas

Heat flux profiles inferred from a reciprocating probe at the outer midplane of the TCV tokamak during inner wall limited discharges feature radial fall-off lengths that shorten near the last closed flux surface (LCFS) consistent with the so-called narrow feature. The narrow feature is significantly wider on the outboard side compared with that measured on the inner wall by infrared thermography, so it is difficult to discern from the main scrape-off layer feature. After small shifts were applied for alignment, the fraction of the power contained in the narrow feature matches between inboard and outboard measurements, and they scale together with plasma current I-p, suggesting that we are observing the same phenomenon. The outboard side fall-off length within the narrow feature is found to scale closely with the radial correlation length of the edge turbulence as expected if the narrow feature arises due to radially sheared E x B flows. This is found to hold true even for cases where the narrow feature is weak and the fall-off lengths are approaching that of the far scrape-off layer. After the small shifts for alignment, non-zero floating potential profiles were found to match between inboard and outboard sides. A simple model of polarization and diamagnetic cross-field currents is described, which is consistent with the shape of these floating potential profiles. The model predicts that the floating potential at the LCFS must be negative, which supports the argument to shift the upstream measurements. The predicted currents are also consistent with the E x B flows believed to cause the narrow feature. The model is used to predict the magnitude of the floating potential of the LCFS, and the results are found to match measurements for all values of Ip. This paper therefore demonstrates consistency between the measurements of the narrow feature on the inboard and outboard sides of the plasma, as well as consistency between the measurements, non-linear turbulence simulations, and analytical models of the narrow feature arising from sheared E x B flows.

  • Details
  • Metrics
Type
research article
DOI
10.1063/1.4985075
Web of Science ID

WOS:000404639000038

Author(s)
Tsui, C. K.
Boedo, J. A.
Halpern, F. D.
Loizu, J.
Nespoli, F.
Horacek, J.
Labit, B.
Morales, J.
Reimerdes, H.
Ricci, P.
Show more
Corporate authors
TCV Team; EUROfusion MST1 Team
Date Issued

2017

Publisher

American Institute of Physics (AIP)

Published in
Physics of Plasmas
Volume

24

Issue

6

Article Number

062508

Subjects

CRPP_EDGE

Editorial or Peer reviewed

REVIEWED

Written at

EPFL

EPFL units
SPC  
Available on Infoscience
July 12, 2017
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/139255
Logo EPFL, École polytechnique fédérale de Lausanne
  • Contact
  • infoscience@epfl.ch

  • Follow us on Facebook
  • Follow us on Instagram
  • Follow us on LinkedIn
  • Follow us on X
  • Follow us on Youtube
AccessibilityLegal noticePrivacy policyCookie settingsEnd User AgreementGet helpFeedback

Infoscience is a service managed and provided by the Library and IT Services of EPFL. © EPFL, tous droits réservés