Determination of isotope ratio in the divertor of JET-ILW by high-resolution H alpha spectroscopy: H-D experiment and implications for D-T experiment

V. S. Neverov, JET Contributors, Tommy Ahlgren

Research output: Contribution to journalArticleScientificpeer-review

Abstract

The data of the H alpha high-resolution spectroscopy, collected on the multiple lines of sight, which cover the entire divertor space in poloidal cross-section, during the recent hydrogen-deuterium experiments in JET-ILW (ITER-like wall), are processed. A strong spatial inhomogeneity of the hydrogen concentration, H/(H + D), in divertor is found in many pulses. Namely, the H/(H + D) ratio may be lower in the inner divertor than that in the outer divertor by the values of 0.15-0.35, depending on the conditions of gas puffing and plasma heating. This effect suggests the necessity of spatially-resolved measurements of isotope ratio in the divertor in the upcoming deuterium-tritium experiments. Also, separation of the overlapped T alpha and D alpha spectral lines is shown to be a challenging task especially when the local Doppler-broadened (Gaussian) line shapes are noticeably distorted by the net inward flux of fast non-Maxwellian neutral atoms. We use the respective, formerly developed model of an asymmetric spectral line shape, while analysing the data of the first deuterium-tritium experiment in JET-C (carbon wall), and test the model via comparing the isotope ratio results with another diagnostic's measurements. This model is shown to increase the accuracy of tritium concentration measurements in the divertor.

Original languageEnglish
Article number046011
JournalNuclear Fusion
Volume59
Issue number4
Number of pages18
ISSN0029-5515
DOIs
Publication statusPublished - Apr 2019
MoE publication typeA1 Journal article-refereed

Fields of Science

  • LINE-SHAPE
  • PERFORMANCE
  • PLASMAS
  • RETENTION
  • TILES
  • inverse problems
  • isotope ratio
  • spectral line shapes
  • tokamak diagnostics
  • 114 Physical sciences

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