He cluster dynamics in fusion related plasma facing materials

The theoretical model describing spatiotemporal dynamics of He clusters in tungsten, which takes into account He trap generation associated with the growth of He clusters, is presented. This model is characterized by only one fitting dimensionless parameter γ, which describes the number of new He tr...

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Bibliographic Details
Published in:Nuclear fusion 2015-07, Vol.55 (7), p.73005-5
Main Authors: Krasheninnikov, S.I., Smirnov, R.D.
Format: Article
Language:English
Subjects:
Atomic properties
Clusters
Dynamics
Fittings
helium
Mathematical models
nano-bubbles
Nanostructure
Nuclear fusion
plasma facing components
Tungsten
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Summary:The theoretical model describing spatiotemporal dynamics of He clusters in tungsten, which takes into account He trap generation associated with the growth of He clusters, is presented. This model is characterized by only one fitting dimensionless parameter γ, which describes the number of new He traps generated per one He atom absorbed in existing traps. Application of this model to the formation of the layer of nano-bubbles underneath of the surface of thick He irradiated sample before surface morphology starts to change gives a very good agreement with all available experimental data: (i) surface modification starts to be visible when He ion fluence exceeds the critical value ∼2 − 3 × 1020cm−2, which does not depend on the magnitude of He ion flux to the surface; (ii) the thickness of the layer ∼30 nm; (iii) the characteristic size of nano-bubbles in the layer is ∼2 nm and remains the same within the whole layer. All these parameters were fitted simultaneously with a reasonable value γ ∼ 10−3.
ISSN:0029-5515
1741-4326
DOI:10.1088/0029-5515/55/7/073005