Estimation of 2D distributions of electron density and temperature in the JET divertor from tomographic reconstructions of deuterium Balmer line emission

, J. Karhunen*, V. Solokha, M. Groth, H. Kumpulainen

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

Abstract

Estimates for 2D distributions of electron density, ne, and temperature, Te, have been obtained using reflection-corrected tomographic reconstructions of deuterium Balmer line emission in the JET divertor. The solutions are obtained by a two-dimensional Monte Carlo optimization model, based on intensity ratios of the Balmer Dα, Dγ and Dε emission and the ADAS photon emission coefficients with additional constraints provided by line-integrated spectroscopic measurements of ne and Te. Synthetic benchmarks utilizing EDGE2D-EIRENE simulation outputs yield reproduction of reference ne and Te distributions within 25% with statistical error estimates of 5–15%. Experimental analysis of an L-mode ne ramp shows extension and movement of the outer divertor high-ne region with ne,div up to 1.5 × 1020 m−3 from the outer strike point to above the X-point and decrease of the divertor Te to the range of 0.5–1.0 eV within 25% agreement with the line-integrated measurements. Comparison between the local estimates and their corresponding line integrals suggests underestimation of ne and Te by up to 75% and 50%, respectively, due to the geometric effects of line integration.

Original languageEnglish
Article number100831
Number of pages7
JournalNuclear Materials and Energy
Volume25
DOIs
Publication statusPublished - Dec 2020
MoE publication typeA1 Journal article-refereed

Keywords

  • Camera tomography
  • Detachment
  • Divertor physics
  • Divertor spectroscopy
  • Fusion

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