Deep deuterium retention and Be/W mixing at tungsten coated surfaces in the JET divertor

H. Bergsker, I. Bykov, Y. Zhou, P. Petersson, G. Possnert, J. Likonen, J. Pettersson, S. Koivuranta, A.M. Widdowson

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    Abstract

    Surface samples from a full poloidal set of divertor tiles exposed in JET through operations 2010-2012 with ITER-like wall have been investigated using SEM, SIMS, ICP-AES analysis and micro beam nuclear reaction analysis (µ-NRA). Deposition of Be and retention of D is microscopically inhomogeneous. With careful overlaying of µ-NRA elemental maps with SEM images, it is possible to separate surface roughness effects from depth profiles at microscopically flat surface regions, without pits. With (3He, p) µ-NRA at 3-5 MeV beam energy the accessible depth for D analysis in W is about 9 µm, sufficient to access the W/Mo and Mo/W interfaces in the coatings and beyond, while for Be in W it is about 6 µm. In these conditions, at all plasma wetted surfaces, D was found throughout the whole accessible depth at concentrations in the range 0.2-0.7 at% in W. Deuterium was found to be preferentially trapped at the W/Mo and Mo/W interfaces. Comparison is made with SIMS profiling, which also shows significant D trapping at the W/Mo interface. Mixing of Be and W occurs mainly in deposited layers.
    Original languageEnglish
    Article number014061
    Number of pages8
    JournalPhysica Scripta
    Volume2016
    Issue numberT167
    DOIs
    Publication statusPublished - 2016
    MoE publication typeA1 Journal article-refereed

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    Keywords

    • beryllium
    • deuterium
    • ion beam analysis
    • materials migration

    Cite this

    Bergsker, H., Bykov, I., Zhou, Y., Petersson, P., Possnert, G., Likonen, J., Pettersson, J., Koivuranta, S., & Widdowson, A. M. (2016). Deep deuterium retention and Be/W mixing at tungsten coated surfaces in the JET divertor. Physica Scripta, 2016(T167), [014061]. https://doi.org/10.1088/0031-8949/T167/1/014061