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Persistent URL http://purl.org/net/epubs/work/12196851
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Record Id 12196851
Title The secondary electron yield from transition metals
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Abstract Non-evaporable getter (NEG) thin films, which are currently being used in the ultra-high vacuum system of the Large Hadron Collider (LHC), normally consist of Ti, Zr and V, deposited by physical vapour deposition (PVD). In this study, the secondary electron yield (SEY) of bulk Ti, Zr, V and Hf have been investigated as a function of electron conditioning. The maximum SEYs of as-received Ti, Zr, V and Hf, are respectively 1.96, 2.34, 1.72 and 2.32, these reduce to 1.14, 1.13, 1.44 and 1.18 after electron conditioning. Surface chemical composition was studied by X-ray photoelectron spectroscopy (XPS) which revealed that surface conditioning by electron bombardment promotes the growth of a thin carbon layer on the surface and consequently reduces the SEY of the surface as a function of electron dose. Heating a vanadium sample to 250 °C resulted in diffusion of oxygen into the bulk and induced formation of metal carbide at the surface. However, the SEY stays the same even after heat-induced surface chemistry modification. Prolonged electron conditioning increases the surface oxygen but the surface is still predominantly covered with a thin graphitic layer and hence the SEY stays approximately constant.
Organisation ASTeC , ASTeC-VS , STFC
Keywords ASTeC 2014-2015 , transition metals , secondary electron yield , e-cloud
Funding Information
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Language English (EN)
Type Details URI(s) Local file(s) Year
Paper In Conference Proceedings In 5th International Particle Accelerator Conference (IPAC14), Dresden, Germany, (2014): 2403-2406. http://accelconf.…/papers/wepme057.pdf 2014
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