Effects of Steady-State Plasma Exposure on Tungsten Surface Cracking due to Elm-Like Pulsed Plasma Bombardment

Nishijima, D.; Kikuchi, Yusuke; Nakatsuka, Masaya; Baldwin, M.J.; Doerner, R.; Nagata, Masayoshi; Ueda, Y.

doi:10.13182/fst11-a12703

Cited by 45 publications

(19 citation statements)

References 13 publications

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“…A reduction of these compressive and tensile stresses can inhibit crack formation. While the exact mechanism how the helium induced modifications would lower the stresses is unclear, it could be similar to the improved resistance to surface cracking for fuzzy surfaces [15], where an increased effective surface is suggested. The sub-surface bubbles, which cause a porous surface layer, could act as some kind of stress relaxation by facilitating thermal expansion and contraction without stress accumulation.…”

Section: Resultsmentioning

confidence: 96%

Synergistic effects of ELMs and steady state H and H/He irradiation on tungsten

Lemahieu

Greuner

Linke

et al. 2015

Fusion Engineering and Design

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Section: Resultsmentioning

confidence: 96%

Synergistic effects of ELMs and steady state H and H/He irradiation on tungsten

Lemahieu

Greuner

Linke

et al. 2015

Fusion Engineering and Design

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“…For nuclear fusion devices, the nanostructure growth could change the plasma material interaction completely, especially with regard to the influence of transients accompanied by plasma instabilities called edge localized modes (ELMs) 14 . Because the material property would be altered significantly 15 – 18 , transients could easily lead to melting 19 , 20 and initiation of unipolar arcing 21 , 22 ; the fuzz layer could also be a protective layer for producing cracks 22 . Industrial applications of the developed nanostructures have been explored as well for solar light absorber 23 and photocatalysis to split water 24 and decompose organic material using visible light 12 , 25 .…”

Section: Introductionmentioning

confidence: 99%

Enhanced growth of large-scale nanostructures with metallic ion precipitation in helium plasmas

Kajita

Kawaguchi

Ohno

et al. 2018

Sci Rep

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Helium plasma irradiation on metal surfaces leads to the formation of metallic fuzzy nanostructures accompanied by the growth of helium bubbles in metals. The mechanism of the growth process, its impact for fusion devices, and potential application have been explored. Here we show enhanced growth of large-scale fuzz by precipitating additional metallic particles during helium plasma irradiation. The growth rate of the fuzzy structures became orders of magnitude greater than conventional fuzz growth; in an hour of irradiation, 1 mm-thick visible tungsten and molybdenum fuzzy fur structures covered a tungsten metal substrate. Additional precipitation of metallic ions breaks the bottleneck diffusion process; moreover, further acceleration in the growth rate could have occurred if the electric sheath shape was influenced by the grown structure and the electric field that formed around the structure started collecting ions.

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“…The existence of the unipolar arc has been confirmed phenomenologically by erosion craters found in numerous fusion devices [4][5] [6] [7]. Arcing on fuzzy tungsten has recently been investigated in special model experiments using amongst others a plasma gun [8] and a laser pulse [9].…”

Section: Introductionmentioning

confidence: 99%

The occurrence and damage of unipolar arcing on fuzzy tungsten

Aussems

Nishijima

Brandt

et al. 2015

Journal of Nuclear Materials

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This research investigated whether unipolar arcing in the divertor of fusion reactors is a potential cause for enhanced wear of the divertor. It was found that of nano-fuzz growth is sufficient to initiate arcing, mainly depending on the sheath potential drop and electron density. The average mass loss rate induced by the arc was determined from mass loss measurements and found to be consistent with the value estimated from the arc current. The average arc track erosion depth was estimated by using the measured mass loss and damaged surface area and was found to be one tenth of the fuzzy layer thickness. Due to melting of the fuzzy structures the actual depth is larger and some arc tracks occasionally appeared to even reach the bulk beyond the fuzzy layer. The conclusion of this study is therefore that arcing in the divertor of future tokamaks (e.g. ITER) potentially is an important cause for surface damage and plasma pollution.

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Effects of Steady-State Plasma Exposure on Tungsten Surface Cracking due to Elm-Like Pulsed Plasma Bombardment

Cited by 45 publications

References 13 publications

Synergistic effects of ELMs and steady state H and H/He irradiation on tungsten

Synergistic effects of ELMs and steady state H and H/He irradiation on tungsten

Enhanced growth of large-scale nanostructures with metallic ion precipitation in helium plasmas

The occurrence and damage of unipolar arcing on fuzzy tungsten

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