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research article

Comparison of detachment in Ohmic plasmas with positive and negative triangularity

Fevrier, O.  
•
Tsui, C. K.
•
Durr-Legoupil-Nicoud, G.  
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June 1, 2024
Plasma Physics And Controlled Fusion

In recent years, negative triangularity (NT) has emerged as a potential high-confinement L-mode reactor solution. In this work, detachment is investigated using core density ramps in lower single null Ohmic L-mode plasmas across a wide range of upper, lower, and average triangularity (the mean of upper and lower triangularity: delta) in the TCV tokamak. It is universally found that detachment is more difficult to access for NT shaping. The outer divertor leg of discharges with delta approximate to - 0.3 could not be cooled to below 5 eV through core density ramps alone. The behavior of the upstream plasma and geometrical divertor effects (e.g. a reduced connection length with negative lower triangularity) do not fully explain the challenges in detaching NT plasmas. Langmuir probe measurements of the target heat flux widths (lambda q ) were constant to within 30% across an upper triangularity scan, while the spreading factor S was lower by up to 50% for NT, indicating a generally lower integral scrape-off layer width, lambda int. The line-averaged core density was typically higher for NT discharges for a given fuelling rate, possibly linked to higher particle confinement in NT. Conversely, the divertor neutral pressure and integrated particle fluxes to the targets were typically lower for the same line-averaged density, indicating that NT configurations may be closer to the sheath-limited regime than their PT counterparts, which may explain why NT is more challenging to detach.

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Type
research article
DOI
10.1088/1361-6587/ad3c1c
Web of Science ID

WOS:001206067300001

Author(s)
Fevrier, O.  
Tsui, C. K.
Durr-Legoupil-Nicoud, G.  
Theiler, C.  
Carpita, Massimo  
Coda, S  
Colandrea, Claudia  
Duval, B. P.  
Gorno, Sophie Danielle Angelica  
Huett, Emanuel Paul  
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Corporate authors
TCV Team
•
EUROfusion Tokamak Exploit
Date Issued

2024-06-01

Publisher

Iop Publishing Ltd

Published in
Plasma Physics And Controlled Fusion
Volume

66

Issue

6

Article Number

065005

Subjects

Physical Sciences

•

Negative Triangularity

•

Detachment

•

Divertor

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Power Exhaust

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Tcv

Editorial or Peer reviewed

REVIEWED

Written at

EPFL

EPFL units
SPC  
FunderGrant Number

Euratom Research and Training Programmehttp://dx.doi.org/10.13039/100018708

101052200

European Union via the Euratom Research and Training Programme

Swiss State Secretariat for Education, Research and Innovation (SERI)

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Available on Infoscience
May 1, 2024
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/207737
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