Blister formation of tungsten due to ion bombardment

Wang, Wenmin; Roth, J.; Lindig, S.; Wu, C.H.

doi:10.1016/s0022-3115(01)00679-1

Cited by 190 publications

(116 citation statements)

References 12 publications

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“…When an applied strain is introduced, an additional amount of work will be done by this average force against the applied strain. Since the applied strain is linear with the stress, the migration energies, E * H (ε 11 , ε 22 ) and E * Ex (ε 11 , ε 22 ), for adatoms on tungsten surfaces were fitted to a model that allows extraction of a migration volume tensor, as the strain-conjugate of energy (Eq. 1)…”

Section: Model and Methodologymentioning

confidence: 99%

“…For example, at a He ion fluence of 3 × 10 21 /m 2 blistering starts to take place, and exfoliation occurs at a fluence around 10 22 /m 2 19,20 . Tokitani et al reported the formation of fine helium bubbles and the essential decrease of density of W matrix due to void swelling after high fluence of helium irradiation 21,22 . The local surface stress state in the vicinity of sub-surface bubbles and other defect clusters may be compressive or tensile, depending on the elastic properties of the defect inclusion, which, in turn, is expected to influence local material flow through diffusion mechanisms.…”

Section: Introductionmentioning

confidence: 99%

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Biaxial strain effects on adatom surface diffusion on tungsten from first principles

Chen

Ghoniem

2013

Phys. Rev. B

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Using first-principles electronic structure calculations, the energy barriers for diffusion mechanisms of adatoms on the tungsten (W) (001) and (110) surfaces under externally-applied biaxial strain fields are determined. Adatoms move either by hopping on the surface or by an exchange process with a surface atom, which is found to be completed in one step (direct exchange), or via the formation of a surface crowdion (crowdion-mediated exchange). As a result of the compact atomic stacking, hopping is found to be the major diffusion mechanism on the W(110) surface, irrespective of the surface strain state. On the other hand, the main diffusion mechanism on the less compact W(001) surface is found to be a competition between direct exchange and crowdion-mediated exchange, depending on the magnitude of the surface biaxial strain. Results of the model reveal that, if surface crowdions form, they will be highly mobile and migrate anisotropically. A microscopic explanation is presented by analyzing the charge density associated with surface crowdions. A "mechanism diagram"for atomic surface diffusion on the W(001) indicates that the diffusion direction and its rate can both be modulated by an applied biaxial strain. Migration volumes for the three mechanisms are calculated, and the significance of the results to the understanding of surface evolution under plasma or other energetic ion bombardment is highlighted.

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Section: Model and Methodologymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Biaxial strain effects on adatom surface diffusion on tungsten from first principles

Chen

Ghoniem

2013

Phys. Rev. B

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“…In addition, there is evidence of blistering occurred on tungsten surface exposed to hydrogen plasmas with ion energies well below the displacement threshold [4][5][6][7][8]. Not much is known about the hydrogen retention in different W materials irradiated with low-energy hydrogen ions and exposed to low-energy, high-flux hydrogen plasma.…”

Section: Introductionmentioning

confidence: 99%

Temperature dependence of surface topography and deuterium retention in tungsten exposed to low-energy, high-flux D plasma

Alimov

Shu

Roth

et al. 2011

Journal of Nuclear Materials

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“…In order to close this gap, experiments are performed in (linear) plasma devices, allowing much larger irradiation times. Under high hydrogen fluence, low surface temperature conditions (< 600 K) blistering of W can be observed (see for example [34,35]), which could increase the hydrogen inventory and lead to increased erosion if the blister cap is removed in course of power loading [36]. Many investigations have been performed to uncover the detailed conditions for the formation of blisters.…”

Section: Blisters Bubbles and Mixed Materials Effectsmentioning

confidence: 99%

Benefits and Challenges of the Use of High-Z Plasma Facing Materials in Fusion Devices

Neu

2010

AIP Conference Proceedings

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Abstract.The use of high-Z plasma facing components requires intensive research in all areas, i.e. in plasma wall-interaction, in the physics of the confined plasma, diagnostic, and in material development. Only a few present day divertor tokamaks -mainly Alcator C-Mod and ASDEX Upgrade -gained experience with the refractory metals molybdenum and tungsten, respectively. ASDEX Upgrade was stepwise converted from graphite to tungsten PFCs and in parallel a reduction of the deuterium retention by almost a factor of ten has been observed due to the strong suppression of D co-deposition with carbon. The deuterium retained in W is in line with laboratory results. In order to diagnose W sources and the W content in the main plasma adequate spectroscopic methods had to be developed. As expected from the sputtering threshold of Mo and W, negligible erosion by the thermal divertor background plasma is found in ASDEX Upgrade and Alcator C-Mod under low temperature divertor conditions. However, erosion by fast particles and intrinsic impurities, which additionally might be accelerated in rectified electrical fields observed during ion cyclotron frequency heating, plays an important role. The Mo and W concentrations in the plasma centre are strongly affected by plasma transport and variations up to a factor of 50 are observed for similar influxes. However, it could be demonstrated that sawteeth and turbulent transport driven by central heating can suppress central accumulation. The inward transport of high-Z ions at the edge can be efficiently reduced by 'flushing' the pedestal region caused by frequent edge instabilities. Since with metal walls the edge radiation by low-Z impurities is reduced, it has to be substituted in a pure high-Z device by artificially injected low-Z impurities in order to keep the power load at an acceptable level. Experiments at ASDEX Upgrade suggest that a regime with benign erosion and favourable confinement can be achieved. Extrapolations to ITER and DEMO are difficult since the physics of plasma transport is not yet completely understood, the particle and energy fluxes are orders of magnitude higher and the technical boundary conditions in DEMO strongly differ from those of present day devices.

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Blister formation of tungsten due to ion bombardment

Cited by 190 publications

References 12 publications

Biaxial strain effects on adatom surface diffusion on tungsten from first principles

Biaxial strain effects on adatom surface diffusion on tungsten from first principles

Temperature dependence of surface topography and deuterium retention in tungsten exposed to low-energy, high-flux D plasma

Benefits and Challenges of the Use of High-Z Plasma Facing Materials in Fusion Devices

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