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Analysis of the topographic transformation of Nb surface under controlled EP conditions

Conference ·
OSTI ID:1999154
As the field requirements of niobium SRF cavities approach fundamental material limits, there is increased interest in understanding the details of topographical influences on realized performance limitations. In this study, a set of samples representing 24 different starting conditions used in cavity processing has been assembled. This set includes fine grain, large grain, and single crystal Nb samples under electron beam welding (EBW), hand grinding, and centrifugal barrel polishing (CBP) with a variety of stones, the latter provided by KEK colleagues. Sample topography has been carefully characterized in both the initial condition and after removal of 30 microns via well-controlled EP. A power spectral density (PSD) approach based on Fourier analysis of surface topography, stylus profilometry (SP) and atomic force microscopy (AFM) is used to distinguish the scale-dependent smoothing effects. The detailed topographic transformation of Nb surface with the varied starting state Nb surface is reported. This study will help to identify optimum EP parameter sets for controlled and reproducible surface levelling of Nb for cavity production. References: [1] ?Surface Roughness Characterization of Niobium Subjected to Incremental BCP and EP Processing Steps? , Hui Tian, G. Ribeill, Charles E. Reece, and Michael J. Kelley. Proceedings of 13th Workshop on RF Superconductivity, Beijing, China (Oct. 2007). This work was authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177
Research Organization:
Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Nuclear Physics (NP)
DOE Contract Number:
AC05-06OR23177
OSTI ID:
1999154
Report Number(s):
JLAB-ACC-09-1082; DOE/OR/23177-1013
Country of Publication:
United States
Language:
English

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