期刊
APPLIED PHYSICS LETTERS
卷 106, 期 8, 页码 -出版社
AMER INST PHYSICS
DOI: 10.1063/1.4913617
关键词
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资金
- U.S. Department of Energy, Office of Sciences, Office of High Energy Physics [FWP 50335]
- DOE [ER41628]
- U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences and Office of Science User Facility [DE-AC02-06CH11357]
We present an analysis of Nb3Sn surface layers grown on a bulk Niobium (Nb) coupon prepared at the same time and by the same vapor diffusion process used to make Nb3Sn coatings on 1.3 GHz Nb cavities. Tunneling spectroscopy reveals a well-developed, homogeneous superconducting density of states at the surface with a gap value distribution centered around 2.7 +/- 0.4 meV and superconducting critical temperatures (T-c) up to 16.3 K. Scanning transmission electron microscopy performed on cross sections of the sample's surface region shows an similar to 2 mu m thick Nb3Sn surface layer. The elemental composition map exhibits a Nb:Sn ratio of 3:1 and reveals the presence of buried sub-stoichiometric regions that have a ratio of 5:1. Synchrotron x-ray diffraction experiments indicate a polycrystalline Nb3Sn film and confirm the presence of Nb rich regions that occupy about a third of the coating volume. These low Tc regions could play an important role in the dissipation mechanisms occurring during RF tests of Nb3Sn-coated Nb cavities and open the way for further improving a very promising alternative to pure Nb cavities for particle accelerators. (C) 2015 AIP Publishing LLC.
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