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Characterisation of detachment in the MAST-U Super-X divertor using multi-wavelength imaging of 2D atomic and molecular emission processes

Wijkamp, T.A.; Allcock, J.S.; Feng, X.; Kool, B.; Lipschultz, B.; Verhaegh, K.; Duval, B.P.; Harrison, J.R.; Kogan, L.; Lonigro, N.; Perek, A.; Ryan, P.; Sharples, R.M.; Classen, I.G.J.; Jaspers, R.J.E.

Characterisation of detachment in the MAST-U Super-X divertor using multi-wavelength imaging of 2D atomic and molecular emission processes Thumbnail


Authors

T.A. Wijkamp

J.S. Allcock

X. Feng

B. Kool

B. Lipschultz

K. Verhaegh

B.P. Duval

J.R. Harrison

L. Kogan

N. Lonigro

A. Perek

P. Ryan

I.G.J. Classen

R.J.E. Jaspers



Abstract

In this work, we provide the first 2D spatially resolved description of radiative detachment in MAST-U Super-X L-mode divertor plasmas. The Super-X magnetic configuration was designed to achieve reduced heat- and particle loads at the divertor target compared to conventional exhaust solutions. We use filtered camera imaging to reconstruct 2D emissivity profiles in the poloidal plane for multiple atomic and molecular emission lines and bands. A set of deuterium fuelling scans is discussed that, together, span attached to deeply detached divertor states observed in MAST-U. Emissivity profiles facilitate separate analysis of locked-mode induced split branches of the scrape-off layer. Molecular deuterium Fulcher band emission front tracking reveals that the deuterium electron-impact ionisation front, for which it serves a proxy, detaches at different upstream electron densities in the split branches. Upon detachment of this ionisation front, Balmer emission attributed to molecular activated recombination appears near-target. We report a simultaneous radial broadening of the emission leg, consistent with previous SOLPS-ITER modelling. With increased fuelling this emission region detaches, implying electron temperatures below ${\sim}{\,}1{\,}$eV. In this phase, 2D Balmer line ratio reconstruction indicates an onset of volumetric direct electron-ion recombination near-target. At the highest fuelling rates this emission region moves off-target, suggesting a drop in near-wall electron density accompanying the low temperatures.

Citation

Wijkamp, T., Allcock, J., Feng, X., Kool, B., Lipschultz, B., Verhaegh, K., …Jaspers, R. (2023). Characterisation of detachment in the MAST-U Super-X divertor using multi-wavelength imaging of 2D atomic and molecular emission processes. Nuclear Fusion, 63(5), Article 056003. https://doi.org/10.1088/1741-4326/acc191

Journal Article Type Article
Acceptance Date Mar 6, 2023
Online Publication Date Mar 16, 2023
Publication Date 2023
Deposit Date Jul 12, 2023
Publicly Available Date Jul 12, 2023
Journal Nuclear Fusion
Print ISSN 0029-5515
Electronic ISSN 1741-4326
Publisher IOP Publishing
Peer Reviewed Peer Reviewed
Volume 63
Issue 5
Article Number 056003
DOI https://doi.org/10.1088/1741-4326/acc191
Public URL https://durham-repository.worktribe.com/output/1169631

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Publisher Licence URL
http://creativecommons.org/licenses/by/4.0/

Copyright Statement
Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 license. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.






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