Spectroscopic investigation of N and Ne seeded induced detachment in JET ITER-like wall L-modes combining experiment and EDGE2D modeling

B. Lomanowski, M. Carr, A. Field, M. Groth, A. E. Jaervinen, C. Lowry, A. G. Meigs, S. Menmuir, M. O'Mullane, M. L. Reinke, C. K. Stavrou, S. Wiesen

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28 Scopus citations

Abstract

Modeling and experimental investigation of the distribution of seeded impurities and their influence on divertor detachment in all-metal tokamaks is critical for developing reactor-scale exhaust scenarios. In this work, the degree and operating space for Ne and N impurity seeded induced detachment in JET with ITER-like wall (JET-ILW) L-mode discharges is shown to be regulated by the combination of i) the local radiative dissipation in the low-field side divertor; and ii) the incursion of the ionization front towards the X-point with increased impurity seeding. Using a quantitative spectroscopic approach, it is shown that the net particle balance at the low-field side target is dominated by a marked decrease in the ionization source between the X-point and the target with increased N and Ne seeding, and only a marginal increase in the volume recombination rate. With increased seeding, the local radiated power dissipation (N only) and reduction in the power crossing the separatrix (both nitrogen and neon) leads to a reduction in the low-field side target Te. Consequently, the incursion of the ionization front away from a region of enhanced ionization rate caused by high Lyman series opacity at the outer target leads to a steep decrease of the outer target ion flux. In contrast to experiment, EDGE2D-EIRENE simulations using optically thin divertor plasma assumptions show a larger impact of volume recombination and a factor of two shortfall in the low-field side divertor ne. A detailed assessment of opacity effects using the EIRENE photon transport module is recommended.

Original languageEnglish
Article number100676
JournalNuclear Materials and Energy
Volume20
DOIs
StatePublished - Aug 2019

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 . The views and opinions expressed herein do not necessarily reflect those of the European Commission. This work is also supported, in part, by the US DOE under Contract no. DE-AC05-00OR22725 with UT-Battelle, LLC. 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. The views and opinions expressed herein do not necessarily reflect those of the European Commission. This work is also supported, in part, by the US DOE under Contract no. DE-AC05-00OR22725 with UT-Battelle, LLC.

Keywords

  • Detachment evolution
  • Divertor spectroscopy
  • EDGE2D-EIRENE
  • Impurity seeded detachment
  • JET-ILW

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