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

Research output: Contribution to journalArticle

Details

Original languageEnglish
Pages (from-to)935-941
JournalNuclear Materials and Energy
Volume12
StatePublished - 2017
MoE publication typeA1 Journal article-refereed

Researchers

  • Juuso Karhunen

  • Mathias Groth

  • Petteri Heliste
  • Thomas Pütterich
  • Eleonora Viezzer
  • Daniel Carralero
  • David Coster
  • Luis Guimarais
  • Valentina Nikolaeva
  • Antti Hakola
  • Steffen Potzel
  • team ASDEX Upgrade

Research units

  • Max-Planck-Institut für Plasmaphysik
  • Inst Super Tecn, Instituto Superior Tecnico, Universidade de Lisboa, Assoc Euratom IST, Inst Plasmas & Fusao Nucl
  • Technische Universität München
  • VTT Technical Research Centre of Finland

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+.

    Research areas

  • Impurity migration, Doppler spectroscopy, SOL flow, Divertor detachment

ID: 9796323