Nanostructure formation on tungsten exposed to low-pressure rf helium plasmas: A study of ion energy threshold and early stage growth

Baldwin, M.J.; Lynch, T.; Doerner, R.; Yu, J. H.

doi:10.1016/j.jnucmat.2010.10.050

Cited by 96 publications

(59 citation statements)

References 12 publications

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“…To the date, researchers have concluded that the major factors significantly influence the W fuzz growth are surface temperature, incident He ion-energy, -flux, and -fluence [18]. The lower energy threshold for fuzz growth is 12 to 30 eV [2,19,20] depending up on sample grade, plasma conditions, and surface temperature used during the experiments. The fuzz growth also has the lower (~900K) and upper (~2000K) temperature thresholds, referred as -temperature window‖.…”

Section: Introductionmentioning

confidence: 99%

Low energy helium ion irradiation induced nanostructure formation on tungsten surface

Al-Ajlony

Tripathi

Hassanein

2017

Journal of Nuclear Materials

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We report on the low energy helium ion irradiation induced surface morphology changes on tungsten (W) surfaces under extreme conditions. Surface morphology changes on W surfaces were monitored as a function of helium ion energy (140-300 eV), fluence (2.3 × 10 24-1.6 × 10 25 ions m-2), and flux (2.0 × 10 20-5.5 × 10 20 ion m-2 s-1). All the experiments were performed at 900 o C. Our study shows significant effect of all the three ion irradiation parameters (ion flux, fluence, and energy) on the surface morphology. However, the effect of ion flux is more pronounced. Variation of helium ion fluence allows to capture the very early stages of fuzz growth. The observed fuzz growth and morphology changes were understood in the realm of various possible phenomena. The study has relevance and important impact in the current and future nuclear fusion applications.

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Section: Introductionmentioning

confidence: 99%

Low energy helium ion irradiation induced nanostructure formation on tungsten surface

Al-Ajlony

Tripathi

Hassanein

2017

Journal of Nuclear Materials

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“…During the deuterium-tritium (D-T) fusion operation of ITER, significant helium (He) ash will be formed and will interact with the W divertor. Under plasma divertor conditions and even for impact energies below the physical sputtering threshold, which is estimated around 300 eV [5], He ions have been found to cause erosion and redeposition or codeposition as well as significant morphology changes in W [6][7][8][9][10]. It should be noted that He ion bombardment has been found to have high affinity to create bubbles, holes and nanostructures.…”

Section: Introductionmentioning

confidence: 99%

Tungsten oxide thin film exposed to low energy He plasma: Evidence for a thermal enhancement of the erosion yield

Hijazi

Addab

Maan

et al. 2017

Journal of Nuclear Materials

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Nanocrystalline tungsten oxide thin films (about 75 nm in thickness) produced by thermal oxidation of tungsten substrates were exposed to low energy He plasma (≈ 20 eV/He) with a flux of 2.5×10 18 m-2 s-1 at two temperatures: room temperature and 673 K. The structure and morphology modifications which occur after this He bombardment and annealing treatments was studied using Raman spectroscopy and transmission electron microscopy. Due to the low fluence (4×10 21 m-2) and low ion energy, we have observed only few morphology modifications after He plasma exposure at room temperature. On the contrary, at 673 K, a change in the layer color is observed associated to an important erosion. Detailed analyses before/after exposure and before/after annealing allow us to describe the He interaction with the oxide layer, its erosion and structural modification at the atomic and micrometer scale.

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“…1) whereas "nanostructured," low-density "fuzz," or "coral" structures are observed between approximately 1000 and 2000 K, [2][3][4][5] and micron-sized holes form above about 2000 K. 6 The nanostructured "fuzz" has recently been observed in the divertor regions of a tokamak device as well. 7 Such surface features could change the heat transfer, fuel (deuterium/tritium) retention, 8 erosion rates through both sputtering and dust formation, 9 as well as embrittlement of the divertor; all of which can be detrimental to the plasma. Transmission electron microscopy suggests that gas bubbles and/or cavities are present below the solid surfaces at temperatures below 1000 K, and that the nanoscale fuzz tendrils contain gas such bubbles as well, 10 which implies that bubble evolution is an important process in fuzz formation in tungsten.…”

Section: Introductionmentioning

confidence: 99%

Helium bubble bursting in tungsten

Sefta¹,

Juslin²,

Wirth³

2013

Journal of Applied Physics

115

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The same etchant produces both near-atomically flat and microfaceted Si(100) surfaces: The effects of gas evolution on etch morphology Molecular dynamics simulations have been used to systematically study the pressure evolution and bursting behavior of sub-surface helium bubbles and the resulting tungsten surface morphology. This study specifically investigates how bubble shape and size, temperature, tungsten surface orientation, and ligament thickness above the bubble influence bubble stability and surface evolution. The tungsten surface is roughened by a combination of adatom "islands," craters, and pinholes. The present study provides insight into the mechanisms and conditions leading to various tungsten topology changes, which we believe are the initial stages of surface evolution leading to the formation of nanoscale fuzz. V C 2013 AIP Publishing LLC.

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Nanostructure formation on tungsten exposed to low-pressure rf helium plasmas: A study of ion energy threshold and early stage growth

Cited by 96 publications

References 12 publications

Low energy helium ion irradiation induced nanostructure formation on tungsten surface

Low energy helium ion irradiation induced nanostructure formation on tungsten surface

Tungsten oxide thin film exposed to low energy He plasma: Evidence for a thermal enhancement of the erosion yield

Helium bubble bursting in tungsten

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