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  4. Understanding and suppressing the near Scrape-Off Layer heat flux feature in inboard-limited plasmas in TCV
 
research article

Understanding and suppressing the near Scrape-Off Layer heat flux feature in inboard-limited plasmas in TCV

Nespoli, Federico  
•
Labit, Benoît  
•
Furno, Ivo  
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2017
Nuclear Fusion

In inboard-limited plasmas, the Scrape-Off Layer (SOL) shows two regions: the near SOL, extending a few mm from the Last Closed Flux Surface (LCFS), characterized by a steep gradient of the parallel heat flux radial profile, and a far SOL, typically some cm wide, with flatter heat flux profiles. The physics of the near SOL is investigated in TCV with two series of experiments featuring deuterium and helium plasmas, in which the plasma current, density and elongation have been varied. The parallel heat flux profiles are measured on the limiter by means of infrared thermography. For the first time, the near SOL is reported to disappear for low plasma current or at high density, for values of the SOL collisionality νlowast corresponding to a conduction-limited regime. The power in the near SOL ∆PSOL is shown to decrease with the normalized Spitzer resistivity ν as ∆PSOL ~ ν−1. The floating potential profiles, measured at the limiter using flush-mounted Langmuir probes (LP), show the presence of non-ambipolar currents, and their relation to the presence of a velocity shear layer is discussed. The shearing rate is shown to strictly correlate with the power in the near SOL ∆PSOL, consistently with a recent theoretical model. Measurements of the near SOL on the Low Field Side (LFS) are performed using a reciprocating Langmuir probe (RP). The near SOL is reported to vanish simultaneously at the LFS and at the limiter. The near and far SOL widths are compared with the predictions from existing theoretical models, to which empirical corrections with resistivity and elongation are proposed.

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Type
research article
DOI
10.1088/1741-4326/aa84e0
Web of Science ID

WOS:000411702700003

Author(s)
Nespoli, Federico  
Labit, Benoît  
Furno, Ivo  
Horacek, Jan
Tsui, Cedric Kar-Wai  
Boedo, Jose
Maurizio, Roberto  
Reimerdes, Holger
Theiler, Christian Gabriel  
Ricci, Paolo  
Corporate authors
EUROfusion MST1 Team; TCV Team
Date Issued

2017

Publisher

International Atomic Energy Agency

Published in
Nuclear Fusion
Volume

57

Article Number

126029

Subjects

plasma

•

TCV

•

tokamak

•

near scrape off layer

•

sol

•

nuclear fusion

•

CRPP_EDGE

Editorial or Peer reviewed

REVIEWED

Written at

EPFL

EPFL units
SPC  
Available on Infoscience
August 14, 2017
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/139641
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