Cleaning efficiency of carbon films by oxygen plasmas in the presence of metallic getters

Tabarés, F.L.; Ferreira, J. A.; Tafalla, D.; Tanarro, Isabel; Herrero, Vı́ctor J.; Méndez, Isabel; Gómez‐Aleixandre, C.; Albella, J. M.

doi:10.1088/1742-6596/100/6/062025

Cited by 2 publications

(3 citation statements)

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“…There are two aspects of the ITER facing components of particular concern: the extensive coverage of the first wall by Be and the presence of narrow gaps [38]. Experiments specifically oriented to these issues were performed at CIEMAT, and described in previous works [19,21,39,40]. In summary, He/O 2 mixtures (at several ratios) and H 2 /N 2 mixtures (20 : 80) were used in a dc GD plasma in order to remove pure and doped [Mg, Li, B] a-C : H films [39].…”

Section: Removal By O 2 N 2 Nh 3 and No 2 Plasmasmentioning

confidence: 99%

“…Experiments specifically oriented to these issues were performed at CIEMAT, and described in previous works [19,21,39,40]. In summary, He/O 2 mixtures (at several ratios) and H 2 /N 2 mixtures (20 : 80) were used in a dc GD plasma in order to remove pure and doped [Mg, Li, B] a-C : H films [39]. The films were either fully exposed to the plasmas or lying on the sides of a gap (0.2-1 mm wide ×25 mm deep).…”

Section: Removal By O 2 N 2 Nh 3 and No 2 Plasmasmentioning

confidence: 99%

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Tritium inventory control during ITER operation under carbon plasma-facing components by nitrogen-based plasma chemistry: a review

Tabarés¹

2013

Plasma Sources Sci. Technol.

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In spite of being highly suited for advanced plasma performance operation of tokamaks, as demonstrated over at least two decades of fusion plasma research, carbon is not currently considered as an integrating element of the plasma-facing components (PFCs) for the active phase of ITER. The main reason preventing its use under the very challenging scenarios foreseen in this phase, with edge-localized modes delivering several tens of MW m −2 to the divertor target every second or less, is the existing concern about reaching the tritium inventory value of 1000 g used in safety assessments in a time shorter than the projected lifetime of the divertor materials eroded by the plasma, set at 3000 shots. Although several mechanisms of tritium trapping in carbon components have been identified, co-deposition of the carbon radicals arising from chemically eroded chlorofluorocarbons in remote areas appears to play a dominant role. Several possible ways to keep control of the tritium build-up during the full operation of ITER have been put forward, mostly based on the periodic removal of the co-deposits by chemical (thermo-oxidation, plasma chemistry) or physical (laser, flash lamps) methods. In this work, we review the techniques for the inhibition and removal of tritium-rich co-deposits based on the strong chemical reactivity of some N-bearing molecules with carbon. The integration of these techniques into a possible scheme for tritium inventory control in the active phase of ITER under carbon-based PFCs with minimum down-time is discussed and the existing caveats are addressed.

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Section: Removal By O 2 N 2 Nh 3 and No 2 Plasmasmentioning

confidence: 99%

Section: Removal By O 2 N 2 Nh 3 and No 2 Plasmasmentioning

confidence: 99%

Tritium inventory control during ITER operation under carbon plasma-facing components by nitrogen-based plasma chemistry: a review

Tabarés¹

2013

Plasma Sources Sci. Technol.

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“…It has been repeatedly considered as a possible tracer for molecular oxygen [9][10][11] in a similar way as N 2 H + is for N 2 , but the available thermodynamic and kinetic data suggest that the concentration of this ion in the ISM should be too small to be detectable [10]. In fusion research, discharge cleaning is used to eliminate the residual molecules in a vacuum vessel, of which oxygen and water are major components [12,13], and oxygen-containing cold plasmas have been proposed for the removal of co-deposits at the reactor walls [14,15]. Hydrogen and oxygen plasmas are also widely used in surface treatments, like chemical modification [16][17][18], decontamination [19] or functionalization of carbon nanotubes [20].…”

Section: Introductionmentioning

confidence: 99%

Chemistry in glow discharges of H₂/O₂mixtures: diagnostics and modelling

Jiménez-Redondo¹,

Carrasco²,

Herrero³

et al. 2015

Plasma Sources Sci. Technol.

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The chemistry of low pressure H 2 + O 2 discharges with different mixture ratios has been studied in a hollow cathode DC reactor. Neutral and positive ion distributions have been measured by mass spectrometry, and Langmuir probes have been used to provide charge densities and electron temperatures. A simple zero order kinetic model including neutral species and positive and negative ions, which takes into account gas-phase and heterogeneous chemistry, has been used to reproduce the global composition of the plasmas over the whole range of mixtures experimentally studied, and allows for the identification of the main physicochemical mechanisms that may explain the experimental results. To our knowledge, no combined experimental and modelling studies of the heavy species kinetics of low pressure H 2 + O 2 plasmas including ions has been reported before.As expected, apart from the precursors, H 2 O is detected in considerable amounts. The model also predicts appreciable concentrations of H and O atoms and the OH radical. The relevance of the metastable species O( 1 D) and O 2 (a 1 Δ g ) is analysed. Concerning the charged species, positive ion distributions are dominated by H 3 O + for a wide range of intermediate mixtures, while H 3 + and O 2 + are the major ions for the higher and lower H 2 /O 2 ratios, respectively. The mixed ions OH + , H 2 O + and HO 2 + are also observed in small amounts. Negative ions are shown to have a limited relevance in the global chemistry; their main contribution is the reduction of the electron density available for electron impact processes.

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Cleaning efficiency of carbon films by oxygen plasmas in the presence of metallic getters

Cited by 2 publications

References 7 publications

Tritium inventory control during ITER operation under carbon plasma-facing components by nitrogen-based plasma chemistry: a review

Tritium inventory control during ITER operation under carbon plasma-facing components by nitrogen-based plasma chemistry: a review

Chemistry in glow discharges of H₂/O₂mixtures: diagnostics and modelling

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Cleaning efficiency of carbon films by oxygen plasmas in the presence of metallic getters

Cited by 2 publications

References 7 publications

Tritium inventory control during ITER operation under carbon plasma-facing components by nitrogen-based plasma chemistry: a review

Tritium inventory control during ITER operation under carbon plasma-facing components by nitrogen-based plasma chemistry: a review

Chemistry in glow discharges of H2/O2mixtures: diagnostics and modelling

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Chemistry in glow discharges of H₂/O₂mixtures: diagnostics and modelling