Surface morphology of tungsten exposed to helium plasma at temperatures below fuzz formation threshold 1073 K

Sakamoto, R.; Bernard, E.; Kreter, A.; Yoshida, N.

doi:10.1088/1741-4326/57/1/016040

Cited by 39 publications

(29 citation statements)

References 29 publications

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“…The surface morphology of the helium exposed tungsten changes significantly as compared to the non-exposed samples that has been shown earlier by Sakamoto et al [5]. Helium irradiation in PSI-2 caused the appearance of holes of about 10 to 30 nm in diameters on the surfaces of both samples.…”

Section: Sample Surface Sem Observation and Cross-sectional Tem Analysis After The Helium Irradiationsupporting

confidence: 64%

“…Highly porous structures, so-called W "fuzz" nanostructures, are formed when W is submitted to low energy He irradiation at temperature above 1100 K [3,4]. At lower temperatures, undulating surface structures that depend on the grain orientation as well as numerous holes may appear on W surfaces [5,6]. Furthermore, helium irradiation affect the near-surface region of W PFC causing the formation of helium bubbles and dislocation loops [7].…”

Section: Introductionmentioning

confidence: 99%

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Hydrogen trapping in tungsten: impact of helium irradiation and thermal cycling

et al. 2020

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The impact of helium (He) plasma exposure with He fluxes relevant for ITER and WEST on the near-surface microstructure of polycrystalline tungsten (W) is investigated by coupling transmission electron microscopy (TEM) analysis and thermal desorption spectrometry (TDS) measurements. The samples were exposed in the PSI-2 linear plasma device to 75 eV He ions up to the fluence of 3 × 10 23 He m −2 with the surface temperature in the range 1053-1073 K. The obtained He bubbles-enriched W samples are subsequently probed with sequences of low flux and low fluence 250 eV deuterium (D) ion implantations and TDS measurements in an ultra-high-vacuum setup to study the effects of the near-surface morphology changes due to the helium irradiation on fundamental mechanisms of deuterium retention. The results obtained for two different nearsurface layer He bubbles morphologies revealed that the effects of He irradiation on D retention in W strongly depend on its subsequent thermal cycling. For annealing below 900 K, deuterium retention is similar to the one measured in pristine W. In contrast, for annealing above 1150 K, deuterium retention in the He bubbles enriched W is increased 3 to 8-fold as compared to non-damaged W. Additionally, the deuterium desorption peak shifts from 540 to 450 K. This increase of D trapping in the He bubbles enriched W annealed above 1150 K is presumably associated with a modification of the near-surface microstructure concurrent with an outgassing of He.

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Section: Sample Surface Sem Observation and Cross-sectional Tem Analysis After The Helium Irradiationsupporting

confidence: 64%

Section: Introductionmentioning

confidence: 99%

Hydrogen trapping in tungsten: impact of helium irradiation and thermal cycling

et al. 2020

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“…[34] Although the efficiency was improved by nano-cone formation, the enhancement was sufficiently less than the enhancement in the surface area. As was previously identified on W, [62] He implantation could perturbed atomic arrangement in the top surface layer (< 10 nm). [32] It was discussed that presences of defects and impurities lead to those degradation.…”

Section: Discussionsupporting

confidence: 60%

“…Because the XRD analysis is not sensitive to the surface thin layer, the variation in the top surface layer less than 100 nm is likely to be greater. As was previously identified on W, [62] He implantation could perturbed atomic arrangement in the top surface layer (< 10 nm). Similarly, the existence of He bubbles and clusters might have deteriorated the crystallinity of Nb 2 O 5 and balanced out the increase in the effective surface area.…”

Section: Discussionmentioning

confidence: 99%

One‐Step Plasma Synthesis of Nb₂O₅ Nanofibers and their Enhanced Photocatalytic activity

et al. 2018

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Fiberform nanostructured niobium (Nb) was fabricated by one step helium (He) plasma irradiation. He ion implantation formed He nano-bubbles on a Nb plate and led to formation of protrusions while migrating in Nb matrix; fiberform nanostructures (FN) were grown when the fluence became high (> 10 26 m À2 ). The necessary conditions for the formation of Nb FN were revealed to be the surface temperature range of 900-1100 K and the incident ion energy higher than 70 eV. The sample was oxidized at 573-773 K in an air atmosphere, and Pt nanoparticles were photo-deposited on the Nb 2 O 5 samples. The surface was analyzed by scanning electron microscope, transmission electron microscope, x-ray photoelectron spectroscopy, and ultraviolet-visible spectrophotometry. Photocatalytic activity of the fabricated materials was studied using methylene blue (MB) decolorization process. An enhanced photocatalytic performance was identified on FN Nb 2 O 5 substrate with Pt deposition.[a] Dr.

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“…A nanoscale undulating surface structure, which has a periodic arrangement, is formed at temperature below fuzz formation threshold ∼ 1073 K. The direction and the interval of the undulating surface structure depend on the crystal orientation of the grain. The previous study shows that the crests of undulation, which have ∼ 8 nm height, align with the <100> direction [15]. Figure 1 shows the relationship between the crystal orientation and the interval of the undulating structure.…”

Section: Tungstenmentioning

confidence: 76%

Surface morphology in tungsten and RAFM steel exposed to helium plasma in PSI-2

et al. 2017

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Impact of the helium plasma exposure on the surface modification in tungsten and RAFM (Reduced Activation Ferritic/Martensitic) steel have been investigated on the linear plasma device PSI-2 assuming the condition of DEMO first wall. In tungsten, a nanoscale undulating surface structure, which has a periodic arrangement, is formed under low temperature conditions below fuzz nanostructure formation threshold ∼ 1000 K. Interval and direction of the undulation shows dependence on the crystal orientation. A large variation in surface level up to 200 nm has been observed among grains at a fluence of 3 × 10 26 He/m 2 showing dependence of the surface erosion rate on the crystal orientation. The {100} plane in which the undulating surface structure is not formed shows the highest erosion rate. This significant erosion is due to the multistage sputtering through impurity. In RAFM steel, sponge-like nanostructure is developed and it grows with increasing helium fluence beyond 1 µm. In the sponge-like nanostructure, a composition change from the base material is observed in which the tungsten ratio increases while the iron ratio decreases showing differences in sputtering ratio depending on the atomic mass.

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Surface morphology of tungsten exposed to helium plasma at temperatures below fuzz formation threshold 1073 K

Cited by 39 publications

References 29 publications

Hydrogen trapping in tungsten: impact of helium irradiation and thermal cycling

Hydrogen trapping in tungsten: impact of helium irradiation and thermal cycling

One‐Step Plasma Synthesis of Nb₂O₅ Nanofibers and their Enhanced Photocatalytic activity

Surface morphology in tungsten and RAFM steel exposed to helium plasma in PSI-2

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Surface morphology of tungsten exposed to helium plasma at temperatures below fuzz formation threshold 1073 K

Cited by 39 publications

References 29 publications

Hydrogen trapping in tungsten: impact of helium irradiation and thermal cycling

Hydrogen trapping in tungsten: impact of helium irradiation and thermal cycling

One‐Step Plasma Synthesis of Nb2O5 Nanofibers and their Enhanced Photocatalytic activity

Surface morphology in tungsten and RAFM steel exposed to helium plasma in PSI-2

Contact Info

Product

Resources

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One‐Step Plasma Synthesis of Nb₂O₅ Nanofibers and their Enhanced Photocatalytic activity