Helium, hydrogen, and fuzz in plasma-facing materials

Hammond, Karl D.

doi:10.1088/2053-1591/aa8c22

Cited by 122 publications

(78 citation statements)

References 405 publications

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“…An evolution of porous structure to coral-like structure is observed. Coral-like structure (a mixture of fuzzy structure and deep holes [20]) on polycrystalline W after with similar high heat flux He neutral beams injection is widely reported, even at a higher surface temperature up to 2700 °C [11,18,19]. Coral-like structures on W-enriched region are uniformly distributed.…”

Section: Surface Modification After He Loading At a High Peak Surfacementioning

confidence: 87%

“…Blistering and lids exfoliation are shown on the surface of W-5V after exposed to repeated He pulses at a low peak surface temperature of 900 °C, while porous structure and coral-structure are dominant at a high peak surface temperature of 1800 °C. He bubble growth and rupture are the main factors of He-induced surface modification [20,21]. The effect of surface temperature and He fluence on He bubble evolution and surface modification is discussed.…”

Section: Discussionmentioning

confidence: 99%

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Surface modification of W–V alloy exposed to high heat flux helium neutral beams

Wang

Yuan

et al. 2018

Nucl. Fusion

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Surface modification of tungsten vanadium (W-V) alloy under high heat flux helium particle bombardment has been studied. W-5 wt.% V samples were irradiated by the repeated helium pulses at a peak surface temperature of 900 °C and 1800 °C, respectively, in the neutral beam facility GLADIS. The effect of helium fluence on the surface morphology changes was investigated by increasing helium fluence from 1 × 10 22 m-2 to 2 × 10 22 m-2. Blister is the typical structure after the repeated helium pulses loading at 900 °C, and it gets more severe with the increased fluence. Porous structure turns to be dominant at 1800 °C. An evolution of porous structure to coral-like structure is observed as fluence increases. In addition, the three typical regions in W-5V, W-enriched region, W-V solid solute region and V-enriched region, exhibit different damage features. W-V solid solute region shows better surface damage resistance compared to the other two regions.

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Section: Surface Modification After He Loading At a High Peak Surfacementioning

confidence: 87%

Section: Discussionmentioning

confidence: 99%

Surface modification of W–V alloy exposed to high heat flux helium neutral beams

Wang

Yuan

et al. 2018

Nucl. Fusion

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“…Helium bubble growth in plasma-facing materials (PFMs) is an important aspect of nuclear fusion materials research [1][2][3] . Not only do helium bubbles cause material embrittlement and fatigue, but helium also causes significant damage to plasma-facing surfaces in the form of fuzz or coral-like features [4][5][6][7] , and modelling these phenomena continues to be a challenge [8][9][10][11] .…”

mentioning

confidence: 99%

Theoretical Model of Helium Bubble Growth and Density in Plasma-Facing Metals

Hammond

Maroudas

Wirth

2020

Sci Rep

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We present a theoretically-motivated model of helium bubble density as a function of volume for high-pressure helium bubbles in plasma-facing tungsten. the model is a good match to the empirical correlation we published previously [Hammond et al., Acta Mater. 144, 561-578 (2018)] for small bubbles, but the current model uses no adjustable parameters. The model is likely applicable to significantly larger bubbles than the ones examined here, and its assumptions can be extended trivially to other metals and gases. We expect the model to be broadly applicable and useful in coarse-grained models of gas transport in metals.

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“…Besides bubbles, blistering can be formed, when the highly pressurized fine bubbles, formed close to the projected range of the incident ions, mediate inter bubble cracking [118]. At higher temperatures (1073-1273 K), when vacancies and helium bubbles can migrate thermally, large helium bubbles form [118,120]. With increase in helium fluence and temperature, bubbles can evolve into 'nanofuzz' structures (generally forming between 1000 and 2000 K) as shown in Fig.…”

Section: The Effect Of Helium On the Plasma-facing Componentmentioning

confidence: 99%

Recent advances in characterising irradiation damage in tungsten for fusion power

Das

2019

SN Appl. Sci.

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Tungsten is the front-runner candidate for building the plasma-facing armour components for future fusion reactors. However, in-service irradiation by fusion-neutrons and helium will create lattice-defects in the material, compromising its properties and lifetime. Improving the component's resilience to radiation damage and accurately predicting the lifetime of irradiated components is key for commercial feasibility of the reactor. For this purpose, understanding the creation and evolution of radiation damage is essential. This paper reviews recent advances in characterising radiation damage through experimental and modelling techniques. Tungsten-ion-and helium-ion-implantation are commonly used to mimic the damage created by neutron-and helium-irradiation respectively. Defects (> 1.5 nm) can be directly imaged using transmission electron microscopy while all defects (size-independent), may be indirectly probed by measuring lattice strains induced by them (using diffraction techniques; synchrotron X-rays or high-resolution electron-backscatter). Neutron-irradiation produces mainly ½〈111〉 prismatic loops. Loop-interaction and structural organisation evolves with changing implantation dose and temperature. Helium-irradiation, < 573 K, induces formation of small helium-vacancy clusters, which evolve into bubbles, blisters and "fuzz" structure with changing temperature and dose. Nano-indentation or micro-cantilever bending tests can be used to examine mechanical properties of ion-implanted layers. Both heliumand neutron-implantation defects induce increased hardening often followed by subsequent strain-softening and localised deformation. Such irradiation-induced alterations are detrimental to material ductility and long-term structural integrity of tungsten-based components. Development of physically-based material models that capture the physics of underlying irradiation-induced changes, inspire confidence of reliably using simulations to predict mechanical behaviour and in-service performance of irradiated engineering components in future.

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Helium, hydrogen, and fuzz in plasma-facing materials

Cited by 122 publications

References 405 publications

Surface modification of W–V alloy exposed to high heat flux helium neutral beams

Surface modification of W–V alloy exposed to high heat flux helium neutral beams

Theoretical Model of Helium Bubble Growth and Density in Plasma-Facing Metals

Recent advances in characterising irradiation damage in tungsten for fusion power

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