Response of beryllium to deuterium plasma bombardment

Doerner, R.; Grossman, A.; Luckhardt, S.; Seraydarian, R.; Sze, F. C.; Whyte, D.G.; Conn, R.W.

doi:10.1016/s0022-3115(98)00435-8

Cited by 44 publications

(26 citation statements)

References 25 publications

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“…The increased roughness of fine-scale grass-like surface structures can lead to a higher fraction of promptly re-deposited Be atoms, reducing the net erosion by a factor of 2-3. This effect is similar to the enhanced prompt re-deposition found on rough surfaces in 13 CH 4 tracer injection experiments in the TEXTOR tokamak (figure 5 in [6]). The second effect reducing the Be sputtering is the dilution of beryllium by hydrogen in the interaction layer and the less efficient change of the momentum direction of the incident particles necessary for sputtering.…”

Section: Introductionsupporting

confidence: 79%

“…by the TRIM code [3], are often used as the reference when comparing with experimental findings. While measurements of the Be sputtering yield by the hydrogen isotopes in low-flux ion beam facilities are in good agreement with TRIM [2], values measured in the high-flux linear plasma device PISCES-B are persistently by about one order of magnitude lower than the TRIM predictions [4]. This discrepancy was explained by the evolving surface morphology and the protective role of hydrogen incorporated in the Be surface [5].…”

Section: Introductionmentioning

confidence: 57%

“…The deuterium retention in other molecules was at most of a few additional percent and was therefore neglected. Postmortem nuclear reaction analysis (NRA) was applied to determine the amount of material deposited on the witness sample using the following reactions: 3 He(D,p) 4 He for deuterium and 3 He(Be,p) 11 B for beryllium, both using a 2 MeV 3 He beam, and 27 Al(D,p) 28 Al for aluminium with a 1.4 MeV D beam. The NRA technique was applicable to determine the amounts of Be and D deposited on the witness sample in the case of mixed D/Ar plasmas, while in the case of pure D plasma the amount of deposition was below the detection limit of 6 NRA.…”

Section: Experimental Procedures and Post-mortem Analysesmentioning

confidence: 99%

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Erosion, formation of deposited layers and fuel retention for beryllium under the influence of plasma impurities

et al. 2014

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The impact of argon as a seeded plasma impurity on the plasma-material interaction properties of beryllium was studied in the PISCES-B linear plasma device. When exposed to pure deuterium plasma, the surface of beryllium forms a fine-scale grass-like structure and contains a significant fraction of deuterium, leading to the reduction of the sputtering yield.An argon fraction in plasma of 10% prevents the formation of rough surface and reduces the deuterium retention in the beryllium target by >50%. Consequently, the beryllium sputtering yield in the presence of argon remains at a level close to the prediction by the binary collision code TRIM. The total retention of deuterium in co-deposited layers remains at a similar level when argon is added, since a higher amount of deposited Be is compensated by a lower D/Be value. Aluminium also forms a fine-scale surface structure and displays a reduction of the effective sputtering yield when exposed to pure deuterium plasma and can therefore be considered as a non-toxic proxy for studying selected plasma-material interaction properties of beryllium.

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Section: Introductionsupporting

confidence: 79%

Section: Introductionmentioning

confidence: 57%

Section: Experimental Procedures and Post-mortem Analysesmentioning

confidence: 99%

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Erosion, formation of deposited layers and fuel retention for beryllium under the influence of plasma impurities

et al. 2014

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“…11,[27][28][29] The available experimental data on hydrogen mobility mostly evidence that hydrogen isotopes are fast diffusers in Be, with the experimental estimates for the migration energy of 0.12-0.36 eV, 23,24,[29][30][31][32] though a relatively high estimate of 0.77 eV can also be met in the literature. 33 In order to get a better understanding of hydrogen properties at the atomistic level, it is a common practice to use numerical techniques, though the simulations of defects in beryllium are still rare. In particular, Krimmel and Fähnle 10 studied energetic preference of different individual hydrogen atom locations in bulk beryllium and inside a monovacancy and predicted that interstitial hydrogen resides preferentially in basal tetrahedral and octahedral positions, while hydrogen in a vacancy lies in an off-center position in the same basal plane, where the missing atom site is located.…”

Section: Introductionmentioning

confidence: 99%

Hydrogen in beryllium: Solubility, transport, and trapping

2009

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The paper presents the results of ab initio simulation of hydrogen properties in beryllium. Both interstitial hydrogen positions in the lattice and various hydrogen positions in a vacancy have been studied. The most energetically favorable interstitial hydrogen configuration among the four considered high-symmetry configurations is the basal tetrahedral one, in agreement with the earlier predictions. The most probable diffusion pathway for hydrogen atoms in the bulk involves the exchange of octahedral and basal tetrahedral positions with the effective migration energy of ϳ0.4 eV. For hydrogen atom in a vacancy, an off-center ͑nearly basal tetrahedral͒ configuration is definitely preferred. Addition of more hydrogen atoms to a vacancy remains energetically favorable up to at least five hydrogen atoms, though the binding energies fall down with the increase in the number of hydrogen atoms in the vacancy.

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“…Although in general TRIM.SP [23] calculations satisfactorily reproduce experimental results on sputter yields, there are large deviations in the case of Be. Ion beam experiments point to maximum sputter yields of 8% [24], whereas measurement in PISCES-B [25], which were confirmed only recently under controlled surface conditions [26], reveal maximum yields below 1%. The situation is even more complicated under typical conditions existent in a fusion device.…”

Section: Erosionmentioning

confidence: 92%

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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Response of beryllium to deuterium plasma bombardment

Cited by 44 publications

References 25 publications

Erosion, formation of deposited layers and fuel retention for beryllium under the influence of plasma impurities

Erosion, formation of deposited layers and fuel retention for beryllium under the influence of plasma impurities

Hydrogen in beryllium: Solubility, transport, and trapping

Preparing the scientific basis for an all metal ITER

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