Pumping and Recycling of Hydrogen Isotopes by Superpermeable Membranes in Fusion Devices

Livshits, A. I.; Notkin, M. E.; Samartsev, A.; Busnyuk, A.O.; Pistunovich, V.I.

doi:10.1016/b978-0-444-89995-8.50230-7

Cited by 3 publications

(13 citation statements)

References 7 publications

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“…3͒, and therefore one can estimate the ␣ H magnitude to be in the order of at least 0.1. Atomic beam experiments with a number of metals covered by nonmetallic monolayers yielded ␣ H value in the range of 0.1-0.4 at T S ജ 298 K, 1,4,5,22,26,27 while the data on the superpermeation of H atoms through Nb covered by oxygen monolayer [1][2][3]17,18 are most self-consistent at ␣ H Ϸ 0.2-0.3. Taking that into account, we set ␣ H Ϸ 0.25 in Fig.…”

Section: Resultsmentioning

confidence: 75%

“…1͒ up to ϳ1770 K ͑at H 2 pressure 10 −6 -10 −4 Pa͒ results in the generation of atomic hydrogen and consequently in the radical increase in perme- ation flux. 1,21,22 One can evaluate the sticking coefficient for atoms, ␣ H , in the same way as ␣ H 2 ͓see Eq. ͑2͔͒,…”

Section: Permeation Methods To Study the Sticking Of H Atomsmentioning

confidence: 99%

“…1 The group V metals are particularly suitable for measuring ␣ H 2 by this method due to several reasons including high diffusivity and solubility of hydrogen. 1,2,19 For instance, in the case of a Nb membrane of 0.1 mm thickness, Eq. ͑2͒ is true even for a clean surface below ϳ1300 K ͑and even at higher T S , if the surface is covered by impurities͒.…”

Section: Permeation Methods To Study the Sticking Of H 2 Moleculesmentioning

confidence: 99%

“…Here, below, we introduce T S,g to designate the temperature playing the dominant role: T S,g = T S if the dissociative sticking to an active site is governed by surface vibration, while T S,g = T g if the translational or internal energy of gas molecules controls the sticking. The integral sticking coefficient of H 2 molecules can be represented, in accordance with the general surface reaction kinetics rules, 1 as…”

Section: The Concept Of Coverage Holes As Active Centers Of H 2 Stickmentioning

confidence: 99%

“…[1][2][3] Besides, the measurement of C O can be a method to predict the surface reactivity in addition to the conventional methods of surface analysis such as x-ray photoelectron spectroscopy and Auger electron spectroscopy ͑AES͒ incapable to measure a small concentration of holes in a near-monolayer coverage.…”

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confidence: 99%

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Effects of bulk impurity concentration on the reactivity of metal surface: Sticking of hydrogen molecules and atoms to polycrystalline Nb containing oxygen

Hatano

Watanabe

Livshits

et al. 2007

The Journal of Chemical Physics

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Nonmetallic impurities segregated onto metal surfaces are able to drastically decrease the chemical reactivity of metals. In the present paper, effects of bulk impurities on the reactivity of metallic surfaces were investigated in a wide temperature range on an example of the sticking of hydrogen molecules and atoms to Nb ͓polycrystalline, with mainly ͑100͔͒ containing solute oxygen. At all the investigated surface temperatures, T S ͑300-1400 K͒, we found the bulk oxygen concentration C O to have a strong effect on the integral probability, ␣ H 2 , of dissociative sticking of H 2 molecules followed by hydrogen solution in the metal lattice: ␣ H 2 monotonically decreased by orders of magnitude with increasing C O from 0.03 to 1.5 at. %. The sticking coefficient ␣ H 2 was found to depend on T S but not on the gas temperature. The effect of C O on ␣ H 2 is explained by the presence of oxygen-free sites ͑holes in coverage͒ serving as active centers of the surface reaction in the oxygen monolayer upon Nb. In contrast to H 2 molecules, H atoms were found to stick to, and be dissolved in, oxygen-covered Nb with a probability comparable to 1, depending neither on C O nor on T S . This proves that, unlike H 2 molecules, H atoms do stick to be dissolved mainly through regular surface sites covered by oxygen and not through the holes in coverage.

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Section: Resultsmentioning

confidence: 75%

Section: Permeation Methods To Study the Sticking Of H Atomsmentioning

confidence: 99%

Section: Permeation Methods To Study the Sticking Of H 2 Moleculesmentioning

confidence: 99%

Section: The Concept Of Coverage Holes As Active Centers Of H 2 Stickmentioning

confidence: 99%

mentioning

confidence: 99%

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Effects of bulk impurity concentration on the reactivity of metal surface: Sticking of hydrogen molecules and atoms to polycrystalline Nb containing oxygen

Hatano

Watanabe

Livshits

et al. 2007

The Journal of Chemical Physics

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Dissociation of hydrogen molecules on metal filaments in H^-ion sources

Livshits¹,

Balghiti²,

Bacal³

1994

Plasma Sources Sci. Technol.

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Atomic hydrogen causes significant deterioration of Hion source characteristics through vibration-translation relaxation of vibrationally excited H, molecules. We propose a method for atomic hydrogen density determination based on its selective absorption by a metal (Ta in our case) covered with a monoatomic non-metal film. The temperature-dependence of the dissociation rate by the Ta filament and the contribution of dissociation on Ta filaments to the atomic density in the Hion source are measured and reported. This contribution is noticeable but not dominant when the energy injected into the discharge is iarge enough. ii is shown that the filament surface of W, Ta, Nb or W-Th behaves as a clean one with respect to H, dissociation under the actual conditions of Hion sources. According to a phenomenological theory, filaments of W, Ta and Nb dissociate H, independently of their temperature and of the gas pressure with probability about 0.2-0.3 per single impact, while a W-Th filament dissociates H, with much lower probability, which depends on pressure and temperature.

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Fusion Reactor Fuel Cycle Design Parameters and R & D Priorities

Murdoch

1995

Fusion Technology

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Pumping and Recycling of Hydrogen Isotopes by Superpermeable Membranes in Fusion Devices

Cited by 3 publications

References 7 publications

Effects of bulk impurity concentration on the reactivity of metal surface: Sticking of hydrogen molecules and atoms to polycrystalline Nb containing oxygen

Effects of bulk impurity concentration on the reactivity of metal surface: Sticking of hydrogen molecules and atoms to polycrystalline Nb containing oxygen

Dissociation of hydrogen molecules on metal filaments in H^-ion sources

Fusion Reactor Fuel Cycle Design Parameters and R & D Priorities

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Pumping and Recycling of Hydrogen Isotopes by Superpermeable Membranes in Fusion Devices

Cited by 3 publications

References 7 publications

Effects of bulk impurity concentration on the reactivity of metal surface: Sticking of hydrogen molecules and atoms to polycrystalline Nb containing oxygen

Effects of bulk impurity concentration on the reactivity of metal surface: Sticking of hydrogen molecules and atoms to polycrystalline Nb containing oxygen

Dissociation of hydrogen molecules on metal filaments in H-ion sources

Fusion Reactor Fuel Cycle Design Parameters and R & D Priorities

Contact Info

Product

Resources

About

Dissociation of hydrogen molecules on metal filaments in H^-ion sources