An assessment of nitrogen concentrations from spectroscopic measurements in the JET and ASDEX upgrade divertor

the EUROfusion MST1 Team, ASDEX Upgrade Team, JET Contributors

Research output: Contribution to journalArticlepeer-review

8 Scopus citations

Abstract

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, Psep, 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 ≈ 2% to ≈ 9% as Psep is increased from ≈ 2.5 MW 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.

Original languageEnglish
Pages (from-to)147-152
Number of pages6
JournalNuclear Materials and Energy
Volume18
DOIs
StatePublished - Jan 2019
Externally publishedYes

Funding

This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014–2018 under grant agreement No 633053 and from the RCUK Energy Programme [grant number EP/P012450/1 ]. To obtain further information on the data and models underlying this paper please contact [email protected]. The views and opinions expressed herein do not necessarily reflect those of the European Commission. This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014–2018 under grant agreement No 633053 and from the RCUK Energy Programme [grant number EP/P012450/1]. To obtain further information on the data and models underlying this paper please contact [email protected]. The views and opinions expressed herein do not necessarily reflect those of the European Commission.

FundersFunder number
Euratom research and training programme 2014–2018
Horizon 2020 Framework Programme633053
H2020 Euratom
Research Councils UKEP/P012450/1

    Keywords

    • Concentration
    • Divertor
    • Impurity
    • Nitrogen
    • Spectroscopy
    • Tokamak

    Fingerprint

    Dive into the research topics of 'An assessment of nitrogen concentrations from spectroscopic measurements in the JET and ASDEX upgrade divertor'. Together they form a unique fingerprint.

    Cite this