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Inferring divertor plasma properties from hydrogen Balmer and Paschen series spectroscopy in JET-ILW
KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
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Number of Authors: 11102015 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 55, no 12, article id 123028Article in journal (Refereed) Published
Abstract [en]

A parametrised spectral line profile model is formulated to investigate the diagnostic scope for recovering plasma parameters from hydrogenic Balmer and Paschen series spectroscopy in the context of JET-ILW divertor plasmas. The separate treatment of Zeeman and Stark contributions in the line model is tested against the PPP-B code which accounts for their combined influence on the spectral line shape. The proposed simplified model does not fully reproduce the Stark-Zeeman features for the alpha and beta transitions, but good agreement is observed in the line width and wing profiles, especially for n > 5. The line model has been applied to infer radial density profiles in the JET-ILW divertor with generally good agreement between the D 5 -> 2, 5 -> 3, 6 -> 2, 7 -> 2 and 9 -> 2 lines for high recycling and detached conditions. In an L-mode detached plasma pulse the Langmuir probe measurements typically underestimated the density by a factor 2-3 and overestimated the electron temperature by a factor of 5-10 compared to spectroscopically derived values. The line model is further used to generate synthetic high-resolution spectra for low-n transitions to assess the potential for parameter recovery using a multi-parametric fitting technique. In cases with 4 parameter fits with a single Maxwellian neutral temperature component the D 4 -> 3 line yields the best results with parameter estimates within 10% of the input values. For cases with 9 parameter fits inclusive of a multi-component neutral velocity distribution function the quality of the fits is degraded. Simultaneous fitting of the D 3 -> 2 and 4 -> 3 profiles improves the fit quality significantly, highlighting the importance of complementary spectroscopic measurements for divertor plasma emission studies.

Place, publisher, year, edition, pages
IOP PUBLISHING LTD , 2015. Vol. 55, no 12, article id 123028
Keywords [en]
plasma spectroscopy, tokamak divertor diagnostics, spectral line profiles
National Category
Fusion, Plasma and Space Physics
Identifiers
URN: urn:nbn:se:kth:diva-270477DOI: 10.1088/0029-5515/55/12/123028ISI: 000366534500030Scopus ID: 2-s2.0-84948662447OAI: oai:DiVA.org:kth-270477DiVA, id: diva2:1424469
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QC 20200417

Available from: 2020-04-17 Created: 2020-04-17 Last updated: 2020-04-17Bibliographically approved

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Bergsåker, HenricBykov, IgorElevant, ThomasFrassinetti, LorenzoGarcia-Carrasco, AlvaroHellsten, TorbjörnIvanova, DaryaJohnson, ThomasMenmuir, SheenaPetersson, PerRachlew, ElisabethRubel, MarekStröm, PetterTholerus, EmmiWeckmann, Armin
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