Open AccessBayesian inference of particle source and sink in a closed-divertor using Balmer line spectroscopy
Author(s) -
T. Nishizawa,
M. Cavedon,
F. Reimold,
R. Dux,
D. Brida,
Haosheng Wu
Publication year - 2020
Publication title -
plasma physics and controlled fusion
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.328
H-Index - 111
eISSN - 1361-6587
pISSN - 0741-3335
DOI - 10.1088/1361-6587/ab9732
Subject(s) - divertor , balmer series , plasma , asdex upgrade , spectroscopy , computational physics , physics , atomic physics , spectral line , tokamak , emission spectrum , nuclear physics , astronomy , quantum mechanics
A new analysis technique for Balmer line spectroscopy that enables recombination rate (particle sink) and ionization rate (particle source) inference in a closed divertor configuration is reported. Bayesian inference is employed to systematically utilize all available information from multiple Balmer lines and constrain parameter ranges by using prior knowledge about plasmas. While a closed-divertor facilitates detachment, neutral plugging typically leads to large spatial variations in plasma parameters. A forward model is developed to take into account non-uniformity in the plasma parameters and applied to test data generated by divertor plasma simulations. It is shown that the forward model robustly provides particle source and sink inference over a wide parameter range. In addition, the precision improves as more Balmer lines are resolved simultaneously. The new analysis technique is also applied to an L-mode ASDEX Upgrade plasma in the high-recycling regime. The inferred quantities and their profiles are consistent with the expectations of a high-recycling divertor plasma. The further insight into the detachment physics will be provided by using this new analysis technique.