Measurement of N+ flows in the high-field side scrape-off layer of ASDEX upgrade with different degrees of inner divertor detachment

J. Karhunen (Corresponding Author), M. Groth, P. Heliste, T. Pütterich, E. Viezzer, D. Carralero, D. Coster, L. Guimarais, A. Hakola, V. Nikolaeva, S. Potzel, ASDEX Update Group

Research output: Contribution to journalArticleScientificpeer-review

Abstract

Toroidal and poloidal flows of injected N+ ions were measured in the high-field side (HFS) scrape-off layer (SOL) of ASDEX Upgrade by Doppler spectroscopy with different degrees of HFS divertor detachment. In high-recycling conditions, the results suggest reversed parallel N+ flow away from the inner divertor in the near SOL close to the separatrix, while the flow is towards the inner divertor throughout the SOL in detached conditions. The measured poloidal N+ flows were directed away from the HFS divertor in the near SOL for all density cases. Divertor plasma oscillations, characterized by momentary peaking of the HFS target ion flux and decrease of the HFS SOL density, were observed slightly before the roll-over of the ion saturation current to the HFS target and lead to an increase in the N+ flow towards the HFS divertor. SOLPS and ERO simulations of the experiment predict entrainment below 50% between the velocities of N+ and D+ ions, suggesting that N+ ions are quantitatively a limited proxy for measuring D+ flows. ERO simulations show significantly higher entrainment for higher ionization states, e.g., N2+ and N3+.
Original languageEnglish
Pages (from-to)935-941
Number of pages7
JournalNuclear Materials and Energy
Volume12
Early online date2017
DOIs
Publication statusPublished - 1 Aug 2017
MoE publication typeA1 Journal article-refereed

Fingerprint

detachment
Ions
entrainment
ions
Plasma oscillations
Ionization
Recycling
plasma oscillations
recycling
Spectroscopy
Fluxes
simulation
saturation
ionization
Experiments
spectroscopy

Keywords

  • impurity migration
  • Doppler spectroscopy
  • SOL flow
  • divertor detachment

Cite this

Karhunen, J. ; Groth, M. ; Heliste, P. ; Pütterich, T. ; Viezzer, E. ; Carralero, D. ; Coster, D. ; Guimarais, L. ; Hakola, A. ; Nikolaeva, V. ; Potzel, S. ; ASDEX Update Group. / Measurement of N+ flows in the high-field side scrape-off layer of ASDEX upgrade with different degrees of inner divertor detachment. In: Nuclear Materials and Energy. 2017 ; Vol. 12. pp. 935-941.
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abstract = "Toroidal and poloidal flows of injected N+ ions were measured in the high-field side (HFS) scrape-off layer (SOL) of ASDEX Upgrade by Doppler spectroscopy with different degrees of HFS divertor detachment. In high-recycling conditions, the results suggest reversed parallel N+ flow away from the inner divertor in the near SOL close to the separatrix, while the flow is towards the inner divertor throughout the SOL in detached conditions. The measured poloidal N+ flows were directed away from the HFS divertor in the near SOL for all density cases. Divertor plasma oscillations, characterized by momentary peaking of the HFS target ion flux and decrease of the HFS SOL density, were observed slightly before the roll-over of the ion saturation current to the HFS target and lead to an increase in the N+ flow towards the HFS divertor. SOLPS and ERO simulations of the experiment predict entrainment below 50{\%} between the velocities of N+ and D+ ions, suggesting that N+ ions are quantitatively a limited proxy for measuring D+ flows. ERO simulations show significantly higher entrainment for higher ionization states, e.g., N2+ and N3+.",
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Karhunen, J, Groth, M, Heliste, P, Pütterich, T, Viezzer, E, Carralero, D, Coster, D, Guimarais, L, Hakola, A, Nikolaeva, V, Potzel, S & ASDEX Update Group 2017, 'Measurement of N+ flows in the high-field side scrape-off layer of ASDEX upgrade with different degrees of inner divertor detachment', Nuclear Materials and Energy, vol. 12, pp. 935-941. https://doi.org/10.1016/j.nme.2017.02.020

Measurement of N+ flows in the high-field side scrape-off layer of ASDEX upgrade with different degrees of inner divertor detachment. / Karhunen, J. (Corresponding Author); Groth, M.; Heliste, P.; Pütterich, T.; Viezzer, E.; Carralero, D.; Coster, D.; Guimarais, L.; Hakola, A.; Nikolaeva, V.; Potzel, S.; ASDEX Update Group.

In: Nuclear Materials and Energy, Vol. 12, 01.08.2017, p. 935-941.

Research output: Contribution to journalArticleScientificpeer-review

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T1 - Measurement of N+ flows in the high-field side scrape-off layer of ASDEX upgrade with different degrees of inner divertor detachment

AU - Karhunen, J.

AU - Groth, M.

AU - Heliste, P.

AU - Pütterich, T.

AU - Viezzer, E.

AU - Carralero, D.

AU - Coster, D.

AU - Guimarais, L.

AU - Hakola, A.

AU - Nikolaeva, V.

AU - Potzel, S.

AU - ASDEX Update Group

PY - 2017/8/1

Y1 - 2017/8/1

N2 - Toroidal and poloidal flows of injected N+ ions were measured in the high-field side (HFS) scrape-off layer (SOL) of ASDEX Upgrade by Doppler spectroscopy with different degrees of HFS divertor detachment. In high-recycling conditions, the results suggest reversed parallel N+ flow away from the inner divertor in the near SOL close to the separatrix, while the flow is towards the inner divertor throughout the SOL in detached conditions. The measured poloidal N+ flows were directed away from the HFS divertor in the near SOL for all density cases. Divertor plasma oscillations, characterized by momentary peaking of the HFS target ion flux and decrease of the HFS SOL density, were observed slightly before the roll-over of the ion saturation current to the HFS target and lead to an increase in the N+ flow towards the HFS divertor. SOLPS and ERO simulations of the experiment predict entrainment below 50% between the velocities of N+ and D+ ions, suggesting that N+ ions are quantitatively a limited proxy for measuring D+ flows. ERO simulations show significantly higher entrainment for higher ionization states, e.g., N2+ and N3+.

AB - Toroidal and poloidal flows of injected N+ ions were measured in the high-field side (HFS) scrape-off layer (SOL) of ASDEX Upgrade by Doppler spectroscopy with different degrees of HFS divertor detachment. In high-recycling conditions, the results suggest reversed parallel N+ flow away from the inner divertor in the near SOL close to the separatrix, while the flow is towards the inner divertor throughout the SOL in detached conditions. The measured poloidal N+ flows were directed away from the HFS divertor in the near SOL for all density cases. Divertor plasma oscillations, characterized by momentary peaking of the HFS target ion flux and decrease of the HFS SOL density, were observed slightly before the roll-over of the ion saturation current to the HFS target and lead to an increase in the N+ flow towards the HFS divertor. SOLPS and ERO simulations of the experiment predict entrainment below 50% between the velocities of N+ and D+ ions, suggesting that N+ ions are quantitatively a limited proxy for measuring D+ flows. ERO simulations show significantly higher entrainment for higher ionization states, e.g., N2+ and N3+.

KW - impurity migration

KW - Doppler spectroscopy

KW - SOL flow

KW - divertor detachment

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