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research article

Access to an ELM-suppressed X-point radiator regime in TCV snowflake minus configurations

Reimerdes, Holger  
•
Theiler, Christian Gabriel  
•
Bernert, M.
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October 20, 2024
Nuclear Materials and Energy

TCV’s operating regime with an X-point radiator (XPR) has been broadened by changing the magnetic geometry. XPRs have properties that could make them an attractive power exhaust solution for fusion reactors. These include the conversion of a high fraction of exhaust power into radiation. TCV had previously accessed the XPR regime only with difficulties, as predicted for plasmas where radiative losses are dominated by carbon impurities, that are ubiquitous in TCV. Guided by this theoretical model of the XPR, recent experiments employed TCV’s configurational versatility to demonstrate that XPR access can be facilitated by introducing a second X-point in the vicinity of the separatrix. This configuration, which has a snowflake-minus topology, features a particularly long magnetic connection length from the region just above the X-point to the outer midplane together with a wide geometrical interface with the private flux region that reaches high neutral pressure. Transitioning to this configuration in a high-power H-mode leads to a shift in the radiating region across the separatrix from the divertor to a volume above the X-point, i.e. within the last closed flux surface (LCFS). This displacement of the radiating region is co-incident with the disappearance of edge localised modes (ELMs), while retaining H-mode confinement, a behaviour only, to date, observed in devices with metallic walls. In contrast to observations in these other devices, on TCV, the primary strike points in these configurations remain attached. Detailed measurements of the plasma kinetic parameters inside and outside of the separatrix now challenge the models for access and stability of the XPR and ELMs alike.

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Type
research article
DOI
10.1016/j.nme.2024.101784
Author(s)
Reimerdes, Holger  

EPFL

Theiler, Christian Gabriel  

EPFL

Bernert, M.

Max Planck Institute for Plasma Physics

Duval, Basil  

EPFL

Février, Olivier  

EPFL

Gorno, Sophie Danielle Angelica  

EPFL

Hamm, Daniele  

EPFL

Lee, Kenneth  

EPFL

Pan, O.

Max Planck Institute for Plasma Physics

Perek, Artur  

EPFL

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Corporate authors
TCV team
•
EUROfusion tokamak exploitation team
Date Issued

2024-10-20

Publisher

Elsevier

Published in
Nuclear Materials and Energy
Volume

41

Article Number

101784

Editorial or Peer reviewed

REVIEWED

Written at

EPFL

EPFL units
SPC  
SPC-TCV  
SPC-PB  
FunderGrant Number

Euratom Research and Training Programme

Available on Infoscience
November 7, 2024
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/241875
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