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Surface analysis of Nb materials for SRF cavities
Author(s) -
Maheshwari P.,
Tian H.,
Reece C. E.,
Kelley M. J.,
Myneni G. R.,
Stevie F. A.,
Rigsbee J. M.,
Batchelor A. D.,
Griffis D. P.
Publication year - 2011
Publication title -
surface and interface analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.52
H-Index - 90
eISSN - 1096-9918
pISSN - 0142-2421
DOI - 10.1002/sia.3513
Subject(s) - niobium , materials science , analytical chemistry (journal) , niobium oxide , single crystal , transmission electron microscopy , crystallite , ion , ion beam analysis , surface layer , crystal (programming language) , ion beam , chemistry , layer (electronics) , nanotechnology , crystallography , metallurgy , organic chemistry , chromatography , computer science , programming language
Superconducting Radio Frequency (SRF) cavities provide enhanced efficiency and reduced energy consumption in present‐day particle accelerators. Niobium is the material of choice for SRF cavities due to its high critical temperature and critical magnetic field. In order to understand why certain treatments, especially a low temperature bake, improve performance, it is important to study Nb surface characteristics and identify elemental contaminants which may affect the performance of the cavity.1 Initial studies using SIMS and Focused Ion Beam (FIB) prepared specimens for Transmission Electron Microscopy (TEM) have helped to characterize the Nb surface and measure the surface oxide layer thickness.2 C, N and O are of particular interest as interstitial contaminants and earlier studies suggested very high H concentration. In the present study, ion implants of C, N, O and deuterium ( D ) in Nb and Si were analyzed using SIMS. D was implanted to characterize H while avoiding interference from the high H background. The D implant was easily detectable in Si, but showed a constant value and no implant shape in Nb. This result implies either that D (and by implication, hydrogen) has a high mobility in Nb, or that there is movement of D due to the primary ion beam. Nevertheless, C, N, and O could be quantified using the ion implants. Depth profiles of polycrystalline and single crystal Nb samples were also obtained. While both types of Nb samples contained low C concentration, the single crystal Nb samples showed higher N and O content. Copyright © 2010 John Wiley & Sons, Ltd.