Spectroscopic camera analysis of the roles of molecularly assisted reaction chains during detachment in JET L-mode plasmas

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Abstract

The roles of the molecularly assisted ionization (MAI), recombination (MAR) and dissociation (MAD) reaction chains with respect to the purely atomic ionization and recombination processes were studied experimentally during detachment in low-confinement mode (L-mode) plasmas in JET with the help of experimentally inferred divertor plasma and neutral conditions, extracted previously from filtered camera observations of deuterium Balmer emission, and the reaction coefficients provided by the ADAS, AMJUEL and H2VIBR atomic and molecular databases. The direct contribution of MAI and MAR in the outer divertor particle balance was found to be inferior to the electron–atom ionization (EAI) and electron–ion recombination (EIR). Near the outer strike point, a strong atom source due to the D2+-driven MAD was, however, observed to correlate with the onset of detachment at outer strike point temperatures of Te,osp=0.9–2.0 eV via increased plasma-neutral interactions before the increasing dominance of EIR at Te,osp< 0.9 eV, followed by increasing degree of detachment. The analysis was supported by predictions from EDGE2D-EIRENE simulations which were in qualitative agreement with the experimental observations.

Original languageEnglish
Article number101314
JournalNuclear Materials and Energy
Volume34
DOIs
StatePublished - Mar 2023

Funding

This work has been carried out within the framework of the EUROfusion Consortium, funded by the European Union via the Euratom Research and Training Programme (Grant Agreement No 101052200 — EUROfusion). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Commission. Neither the European Union nor the European Commission can be held responsible for them.

Keywords

  • Balmer emission
  • Divertor detachment
  • Fusion
  • Molecules

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