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An assessment of nitrogen concentrations from spectroscopic measurements in the JET and ASDEX upgrade divertor
CCFE, Culham Sci Ctr, Abingdon OX14 3DB, Oxon, England.;Univ Strathclyde, Dept Phys & Appl Phys, Glasgow G4 ONG, Lanark, Scotland..
KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
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Number of Authors: 12382019 (English)In: Nuclear Materials and Energy, E-ISSN 2352-1791, Vol. 18, p. 147-152Article in journal (Refereed) Published
Abstract [en]

The impurity concentration in the tokamak divertor plasma is a necessary input for predictive scaling of divertor detachment, however direct measurements from existing tokamaks in different divertor plasma conditions are limited. To address this, we have applied a recently developed spectroscopic N II line ratio technique for measuring the N concentration in the divertor to a range of H-mode and L-mode plasma from the ASDEX Upgrade and JET tokamaks, respectively. The results from both devices show that as the power crossing the separatrix, P-sep, is increased under otherwise similar core conditions (e.g. density), a higher N concentration is required to achieve the same detachment state. For example, the N concentrations at the start of detachment increase from approximate to 2% to approximate to 9% as P-sep, is increased from approximate to 2.5 MW to approximate to 7 MW. These results tentatively agree with scaling law predictions (e.g. Goldston et al.) motivating a further study examining the parameters which affect the N concentration required to reach detachment. Finally, the N concentrations from spectroscopy and the ratio of D and N gas valve fluxes agree within experimental uncertainty only when the vessel surfaces are fully-loaded with N.

Place, publisher, year, edition, pages
Elsevier, 2019. Vol. 18, p. 147-152
Keywords [en]
Impurity, Nitrogen, Divertor, Concentration, Spectroscopy, Tokamak
National Category
Physical Sciences
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URN: urn:nbn:se:kth:diva-270861DOI: 10.1016/j.nme.2018.12.012ISI: 000460107500026Scopus ID: 2-s2.0-85058630263OAI: oai:DiVA.org:kth-270861DiVA, id: diva2:1414975
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QC 20200316

Available from: 2020-03-16 Created: 2020-03-16 Last updated: 2020-05-11Bibliographically approved

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