Microstructure and inhomogeneous fuel trapping at divertor surfaces in the JET tokamak

H Bergsåker (Corresponding Author), I Bykov, P Petersson, G Possnert, Jari Likonen, Seppo Koivuranta, J P Coad, A M Widdowson

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    Abstract

    The plasma deposited layers at divertor surfaces in the JET tokamak with carbon wall have been studied post mortem, using micro ion beam analysis (µ-IBA) methods, optical microscopy and scanning electron microscopy (SEM). The layers were formed during plasma operations over different periods through 1998-2009. They frequently have a columnar structure. For µ-IBA a 3 MeV 3He beam was used, focused to about 5-15 µm size. Nuclear reaction analysis was used to measure D, Be and C. Elemental mapping was carried out both at the original surface and on polished layer cross sections. Trapped deuterium is predominantly found in remote areas on the horizontal bottom divertor tiles and in regions with locally enhanced deuterium concentration on the vertical tiles. Pockets with enhanced deuterium concentration are found in the carbon fibre composite (CFC) substrate. Areas with dimensions of about 100 µm with enhanced deuterium concentration are also found inside the deposited layers. The inhomogeneous fuel trapping is tentatively explained with co-deposition in partly protected pits in the substrate and by incorporation of dust particles in the growing layers
    Original languageEnglish
    Pages (from-to)266-270
    JournalNuclear Instruments and Methods in Physics Research. Section B: Beam Interactions with Materials and Atoms
    Volume332
    Issue numberAugust
    DOIs
    Publication statusPublished - 2014
    MoE publication typeA1 Journal article-refereed

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    Keywords

    • Deposited layers
    • deuterium retention
    • fusion
    • microbeam
    • microstructure

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