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

JET Contributors, EUROfusion MST1 Team, ASDEX Upgrade Team, Jan Mlynar, T. Ahlgren, L. Aho-Mantila, M. Airila, C. Björkas, A. Lahtinen, K. Nordlund, E. Safi, S. K. Sipila , O. Asunta, M. Groth, A. Hakola, J. Karhunen, S. Koivuranta, T. Kurki-Suonio, B. Lomanowski, J. LonnrothA. Salmi, M. I. K. Santala, J. Varje, P. Siren, J. Likonen, A. Jarvinen, S. S. Henderson

Tutkimustuotos: ArtikkelijulkaisuArtikkeliTieteellinenvertaisarvioitu


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.
LehtiNuclear Materials and Energy
DOI - pysyväislinkit
TilaJulkaistu - tammikuuta 2019
OKM-julkaisutyyppiA1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä, vertaisarvioitu


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