Exposure of tungsten nano-structure to TEXTOR edge plasma

Ueda, Y.; Miyata, Kouji; Ohtsuka, Y.; Lee, H.T.; Fukumoto, M.; Brezinsek, S.; Coenen, J. W.; Kreter, A.; Litnovsky, A.; Philipps, V.; Schweer, B.; Sergienko, G.; Hirai, T.; Taguchi, Akira; Torikai, Y.; Sugiyama, K.; Tanabe, T.; Kajita, Shin; Ohno, Noriyasu; Team, Textor

doi:10.1016/j.jnucmat.2010.08.019

Cited by 41 publications

(24 citation statements)

References 14 publications

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“…W-fuzz is a very fragile structure that can be detached from W surface during sudden stress or high-heat loads [13,14]. The fuzz formation is unfavorable scenario where W fuzz may develop during the early stages of normal operations of future fusion devices [8,13] and could severely affect the PFC performance.…”

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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“…Identifying the onset of fuzz formation in tokamaks and temporal evolution of the modified surface layer during H-mode plasma operations are now a subject of joint experiments in different devices. Pioneering work has been carried out in TEXTOR [7] and Alcator C-Mod [8] -though so far only during L-mode or ELM-free H-mode operations.…”

Section: Introductionmentioning

confidence: 99%

Plasma-wall interaction studies in the full-W ASDEX upgrade during helium plasma discharges

et al. 2017

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Plasma-wall interaction was studied in the full-W ASDEX Upgrade during its dedicated helium campaign. Relatively clean plasmas with a He content of >80% could be obtained by applying ICWC discharges upon changeover from D to He. Surface analyses of W samples, however, indicated co-deposited layers with significant amounts of He and D being locally formed albeit globally D was released from the plasma-facing components. When exposing W samples to ELMy H-mode helium plasmas in the outer strike-point region of the divertor, no net erosion was observed but the surfaces had been covered with co-deposited layers. The layers were the thickest in the private flux region and extended throughout the OSP region in the case of rough and modified surfaces. Also, no clear signs of nanostructure growth or destruction could be seen The growth of such layers may impact the operation of future fusion reactors. Retention of He, for its part, remained small and uniform throughout the strike-point region.

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“…These simulation predict a thickness of a few hundred nanometers for an erosion yield of 10 −4 . It has to be noted, however, that recent experiments in TEXTOR with pre-produced W nano-structures showed a complete removal of the layer even under conditions which should lead to a further growth [72].…”

Section: Hydrogen Retentionmentioning

confidence: 99%

Preparing the scientific basis for an all metal ITER

Neu

Taskforce²,

Contributors³

2011

Plasma Phys. Control. Fusion

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Abstract. The use of beryllium, carbon and tungsten as plasma-facing materials (PFMs) in ITER calls for dedicated investigations on their behaviour under the expected particle and power loads and neutron irradiation. Their simultaneous use implies the formation of mixed materials during plasma operation, which can have significantly different properties compared to the initial materials concerning thermo-mechanical behaviour and T retention. This contribution presents the latest results on these issues mainly achieved under the umbrella of the European taskforce on Plasma Wall Interaction. While laboratory results provide the basis for the understanding of the basic properties and the behaviour of PFMs, experiments in fusion devices are indispensable in order to test their integral performance, incorporating also the internal feedback on the plasma properties. For this reason ASDEX Upgrade has been converted to a full W device, while JET is beginning operation with its ITER-like wall consisting of a Be main chamber plasma-facing components and a W divertor. In parallel, dedicated W experiments are performed in several devices in order to investigate specific uncertainties such as the characteristics of melt layer movement in the presence of a strong magnetic field. Based on the results on ASDEX Upgrade, which reveal a narrower operational space as compared to the operation with graphite plasma facing components but also provide tools for a successful operation with tungsten, the experiments at JET will provide a unique opportunity to address specific issues related to the parallel use of Be and W as PFMs with plasma parameters closest to those of ITER. Amongst these are the anticipated but still to be demonstrated reduction in hydrogen retention compared to a carbon device, the test of conditioning procedures, mixed materials effects, erosion and transport, the effect of ELMs and ELM mitigation methods as well as the behaviour of melt layers and their influence on plasma operation under steady state and transient heat loads.

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Exposure of tungsten nano-structure to TEXTOR edge plasma

Cited by 41 publications

References 14 publications

Low energy helium ion irradiation induced nanostructure formation on tungsten surface

Low energy helium ion irradiation induced nanostructure formation on tungsten surface

Plasma-wall interaction studies in the full-W ASDEX upgrade during helium plasma discharges

Preparing the scientific basis for an all metal ITER

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