RECENT XPS STUDIES OF THE EFFECT OF PROCESSING ON NB SRF SURFACES
XPS studies have consistently shown that Nb surfaces for SRF chiefly comprise of a few nm of Nb2O5 on top of Nb metal, with minor amounts of Nb sub-oxides. Nb samples after BCP/EP treatment with post-baking at the various conditions have been examined by using synchrotron based XPS. Despite the confounding influence of surface roughness, certain outcomes are clear. Lower-valence Nb species are always and only associated with the metal/oxide interface, but evidence for an explicit layer structure or discrete phases is lacking. Post-baking without air exposure shows decreased oxide layer thickness and increased contribution from lower valence species, but spectra obtained after subsequent air exposure cannot be distinguished from those obtained prior to baking, though the SRF performance improvement remains.
- Research Organization:
- Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- AC05-06OR23177
- OSTI ID:
- 923388
- Report Number(s):
- JLAB-ACC-07-792; DOE/OR/23177-0313; TRN: US0801823
- Resource Relation:
- Conference: 13th Workshop on RF Superconductivity, Beijing, China, Oct. 14 - 19, 2007
- Country of Publication:
- United States
- Language:
- English
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