The role of plasma–atom and molecule interactions on power & particle balance during detachment on the MAST Upgrade Super-X divertor

The role of plasma–atom and molecule interactions on power & particle balance during detachment on the MAST Upgrade Super-X divertor

Abstract This paper shows first quantitative analysis of the detachment processes in the MAST Upgrade Super-X divertor (SXD). We identify an unprecedented impact of plasma-molecular interactions involving molecular ions (likely D 2 + ), resulting in strong ion sinks (Molecular Activated Recombinatio...

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Bibliographic Details
Published in:Nuclear fusion Vol. 63; no. 12; pp. 126023 - 126041
Main Authors: Verhaegh, K., Lipschultz, B., Harrison, J.R., Federici, F., Moulton, D., Lonigro, N., Kobussen, S.P., O’Mullane, M., Osborne, N., Ryan, P., Wijkamp, T., Kool, B., Rose, E., Theiler, C., Thornton, A.J.
Format: Journal Article
Language:English
Published: United States IOP Publishing 01-12-2023
IOP Science
Subjects:
MAST Upgrade
plasma detachment
plasma spectroscopy
plasma-molecular interactions
Super-X divertor
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Summary:Abstract This paper shows first quantitative analysis of the detachment processes in the MAST Upgrade Super-X divertor (SXD). We identify an unprecedented impact of plasma-molecular interactions involving molecular ions (likely D 2 + ), resulting in strong ion sinks (Molecular Activated Recombination—MAR), leading to a reduction of ion target flux. The MAR ion sinks exceed the divertor ion sources before electron-ion recombination (EIR) starts to occur, suggesting that significant ionisation occurs outside of the divertor chamber. In the EIR region, T e ≪ 0.2 eV is observed and MAR remains significant in these deep detached phases. The total ion sink strength demonstrates the capability for particle (ion) exhaust in the Super-X Configuration. Molecular Activated Dissociation is the dominant volumetric neutral atom creation process can lead to an electron cooling of 20% of P S O L . The measured total radiative power losses in the divertor chamber are consistent with inferred hydrogenic radiative power losses. This suggests that intrinsic divertor impurity radiation, despite the carbon walls, is minor in the divertor chamber. This contrasts previous TCV results, which may be associated with enhanced plasma-neutral interactions and reduced chemical erosion in the detached, tightly baffled SXD. The above observations have also been observed in higher heat flux (narrower SOL width) type I ELMy H-mode discharges. This provides evidence that the characterisation in this paper may be general.
Bibliography:NF-106279.R1
USDOE
AC05-00OR22725
ISSN:0029-5515
1741-4326
DOI:10.1088/1741-4326/acf946