In-situ observation of sputtered particles for carbon implanted tungsten during energetic isotope ion implantation

Tungsten is a candidate for plasma facing materials in future fusion reactors. During DT plasma operations, carbon as an impurity will bombard tungsten, leading to the formation of tungsten-carbon (WC) layer and affecting tritium recycling behavior. The effect of carbon implantation for the dynamic...

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Bibliographic Details
Published inFusion science and technology Vol. 67; no. 3
Main Authors Oya, Y., Sato, M., Uchimura, H., Okuno, K., Ashikawa, N., Sagara, A., Yoshida, N., Hatano, Y.
Format Journal Article
LanguageEnglish
Published United States 15.03.2015
Subjects
CARBON IONS
D-T OPERATION
DESORPTION
DEUTERIUM
FIRST WALL
GRAPHITE
HYDROGEN
HYDROGEN IONS 2 PLUS
ION IMPLANTATION
IRRADIATION
MATERIALS SCIENCE
METHANE
RECYCLING
SPUTTERING
THERMONUCLEAR FUELS
THERMONUCLEAR REACTORS
TRITIUM
TUNGSTEN
TUNGSTEN CARBIDES
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Summary:Tungsten is a candidate for plasma facing materials in future fusion reactors. During DT plasma operations, carbon as an impurity will bombard tungsten, leading to the formation of tungsten-carbon (WC) layer and affecting tritium recycling behavior. The effect of carbon implantation for the dynamic recycling of deuterium, which demonstrates tritium recycling, including retention and sputtering, has been investigated using in-situ sputtered particle measurements. The C{sup +} implanted W, WC and HOPG were prepared and dynamic sputtered particles were measured during H{sub 2}{sup +} irradiation. It has been found that the major hydrocarbon species for C{sup +} implanted tungsten is CH{sub 3}, while for WC and HOPG (Highly Oriented Pyrolytic Graphite) it is CH{sub 4}. The chemical state of hydrocarbon is controlled by the H concentration in a W-C mixed layer. The amount of C-H bond and the retention of H trapped by carbon atom should control the chemical form of hydrocarbon sputtered by H{sub 2}{sup +} irradiation and the desorption of CH{sub 3} and CH{sub 2} are due to chemical sputtering, although that for CH is physical sputtering. The activation energy for CH{sub 3} desorption has been estimated to be 0.4 eV, corresponding to the trapping process of hydrogen by carbon through the diffusion in W. It is concluded that the chemical states of hydrocarbon sputtered by H{sub 2}{sup +} irradiation for W is determined by the amount of C-H bond on the W surface. (authors)
ISSN:1536-1055
1943-7641
DOI:10.13182/FST14-T68