Sputtering effects on mirrors made of different tungsten grades

Because tungsten (W) is used in present fusion devices and it is a reference material for ITER divertor and possible plasma-facing material for DEMO, we strive to understand the response of different W grades to ion bombardment. In this study, we investigated the behavior of mirrors made of four pol...

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Bibliographic Details
Published in:Journal of nuclear materials 2018-03, Vol.500, p.56-63
Main Authors: Voitsenya, V.S., Ogorodnikova, O.V., Bardamid, A.F., Bondarenko, V.N., Konovalov, V.G., Lytvyn, P.M., Marot, L., Ryzhkov, I.V., Shtan', A.F., Skoryk, O.O., Solodovchenko, S.I.
Format: Article
Language:English
Subjects:
Degradation
Deuterium
Ion bombardment
Ions
Irradiation
ITER
Neutron irradiation
Neutrons
Nuclear power plants
Plasma
Polycrystals
Recrystallization
Reflectance
Simulation of neutron irradiation
Sputtering
Surface modification
Tungsten
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Summary:Because tungsten (W) is used in present fusion devices and it is a reference material for ITER divertor and possible plasma-facing material for DEMO, we strive to understand the response of different W grades to ion bombardment. In this study, we investigated the behavior of mirrors made of four polycrystalline W grades under long-term ion sputtering. Argon (Ar) and deuterium (D) ions extracted from a plasma were used to investigate the effect of projectile mass on surface modification. Depending on the ion fluence, the reflectance measured at normal incidence was very different for different W grades. The lowest degradation rate of the reflectance was measured for the mirror made of recrystallized W. The highest degradation rate was found for one of the ITER-grade W samples. Pre-irradiation of a mirror with 20-MeV W6+ ions, as simulation of neutron irradiation in ITER, had no noticeable influence on reflectance degradation under sputtering with either Ar or D ions. •The reflectance of W mirror specimens pre-damaged with W ions to a dose of 0.45 and 1.45 dpa behave just as the undamaged specimens when being subjected to sputtering with ions of Ar or D plasmas.•Behavior of the reflectance depends significantly on the W grade, namely, on the microstructure of W, such as distributions of grains on their size and orientation relative to the surface of the sample.•The dominant factor that defines the reflectance and surface roughness is the difference between the heights of grains with different sputtering rates of faces differently orientated relatively to the sample surface.
ISSN:0022-3115
1873-4820
DOI:10.1016/j.jnucmat.2017.10.020