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

S.S. Henderson, M. Bernert, S. Brezinsek, M. Carr, M. Cavedon, R. Dux, D.S. Gahle, J. Harrison, A. Kallenbach, B. Lipschultz, B. Lomanowski, A. Meigs, M. O'Mullane, F. Reimold, M.L. Reinke, S. Wiesen, The EUROfusion MST1 team, ASDEX Upgrade team, JET Contributors

Research output: Contribution to journalArticle

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.

LanguageEnglish
Pages147-152
Number of pages6
JournalNuclear Materials and Energy
Volume18
Early online date20 Dec 2018
DOIs
Publication statusPublished - 31 Jan 2019

Fingerprint

Nitrogen
Plasmas
detachment
nitrogen
Scaling laws
gas valves
Gases
Spectroscopy
Impurities
Fluxes
scaling laws
vessels
scaling
impurities
predictions
spectroscopy
Uncertainty

Keywords

  • concentration
  • divertor
  • impurity
  • nitrogen
  • spectroscopy
  • tokamak

Cite this

Henderson, S. S., Bernert, M., Brezinsek, S., Carr, M., Cavedon, M., Dux, R., ... JET Contributors (2019). An assessment of nitrogen concentrations from spectroscopic measurements in the JET and ASDEX upgrade divertor. 18, 147-152. https://doi.org/10.1016/j.nme.2018.12.012
Henderson, S.S. ; Bernert, M. ; Brezinsek, S. ; Carr, M. ; Cavedon, M. ; Dux, R. ; Gahle, D.S. ; Harrison, J. ; Kallenbach, A. ; Lipschultz, B. ; Lomanowski, B. ; Meigs, A. ; O'Mullane, M. ; Reimold, F. ; Reinke, M.L. ; Wiesen, S. ; The EUROfusion MST1 team ; ASDEX Upgrade team ; JET Contributors. / An assessment of nitrogen concentrations from spectroscopic measurements in the JET and ASDEX upgrade divertor. 2019 ; Vol. 18. pp. 147-152.
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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.",
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Henderson, SS, Bernert, M, Brezinsek, S, Carr, M, Cavedon, M, Dux, R, Gahle, DS, Harrison, J, Kallenbach, A, Lipschultz, B, Lomanowski, B, Meigs, A, O'Mullane, M, Reimold, F, Reinke, ML, Wiesen, S, The EUROfusion MST1 team, ASDEX Upgrade team & JET Contributors 2019, 'An assessment of nitrogen concentrations from spectroscopic measurements in the JET and ASDEX upgrade divertor' vol. 18, pp. 147-152. https://doi.org/10.1016/j.nme.2018.12.012

An assessment of nitrogen concentrations from spectroscopic measurements in the JET and ASDEX upgrade divertor. / Henderson, S.S.; Bernert, M.; Brezinsek, S.; Carr, M.; Cavedon, M.; Dux, R.; Gahle, D.S.; Harrison, J.; Kallenbach, A.; Lipschultz, B.; Lomanowski, B.; Meigs, A.; O'Mullane, M.; Reimold, F.; Reinke, M.L.; Wiesen, S.; The EUROfusion MST1 team; ASDEX Upgrade team; JET Contributors.

Vol. 18, 31.01.2019, p. 147-152.

Research output: Contribution to journalArticle

TY - JOUR

T1 - An assessment of nitrogen concentrations from spectroscopic measurements in the JET and ASDEX upgrade divertor

AU - Henderson, S.S.

AU - Bernert, M.

AU - Brezinsek, S.

AU - Carr, M.

AU - Cavedon, M.

AU - Dux, R.

AU - Gahle, D.S.

AU - Harrison, J.

AU - Kallenbach, A.

AU - Lipschultz, B.

AU - Lomanowski, B.

AU - Meigs, A.

AU - O'Mullane, M.

AU - Reimold, F.

AU - Reinke, M.L.

AU - Wiesen, S.

AU - The EUROfusion MST1 team

AU - ASDEX Upgrade team

AU - JET Contributors

PY - 2019/1/31

Y1 - 2019/1/31

N2 - 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.

AB - 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.

KW - concentration

KW - divertor

KW - impurity

KW - nitrogen

KW - spectroscopy

KW - tokamak

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