DocumentCode :
917325
Title :
Effect of Different Cutting Techniques on the Surface Morphology and Composition of Niobium
Author :
Cooper, Charlie A. ; Wu, Andy ; Bauer, Pierre ; Antoine, Claire
Author_Institution :
Fermi Nat. Accel. Lab., Batavia, IL, USA
Volume :
19
Issue :
3
fYear :
2009
fDate :
6/1/2009 12:00:00 AM
Firstpage :
1399
Lastpage :
1403
Abstract :
The surface morphology and chemical purity of superconducting radio frequency (SRF) niobium cavities are very important for proper accelerator operation. Typically on the order of 120 micrometers of niobium (Nb) is removed from cavities to remove damage done during the forming of Nb sheets and cavities. A study was done to find the effect of cutting or finishing Nb with a band saw, diamond saw, electrical discharge machining (EDM) wire, garnet water jet, sheer, and mill. Surface contamination of the samples was measured before and after buffered chemical polish (BCP) by secondary ion mass spectroscopy (SIMS), energy dispersive spectroscopy (EDS), and by measuring relative resistivity ratios (RRRs). Surface morphology was examined with a digital microscope, a surface profilometer and scanning electron microscope (SEM). It was found that all techniques altered the top 3-5 micrometers of the Nb. It was also found by SIMS that the water jet technique introduced the most hydrogen and oxygen to the Nb in the first 2.5 micrometers of the sample. The EDM wire cutting technique introduced the least amount of hydrogen to the Nb. After 5 micrometers were etched away by BCP on the various samples, no contaminants were found except on the water jet cut samples. Even after 20 micrometers of Nb removal silica could be seen on the surface with EDS. The water jet produced the roughest surface with 50-100 micrometer deep pits made from embedded garnet particles. It was found that the garnet water jet damages the surface to the point where even the typical 120 micrometers of BCP etching may not remove all the defects created.
Keywords :
X-ray chemical analysis; electrical discharge machining; electrical resistivity; etching; milling; niobium; polishing; sawing; scanning electron microscopy; secondary ion mass spectra; surface composition; surface finishing; surface morphology; surface roughness; type II superconductors; water jet cutting; BCP etching; EDM wire; EDS; Nb; SEM; SIMS; SRF niobium cavity; band saw; buffered chemical polish; chemical purity; cutting; diamond saw; digital microscope; electrical discharge machining wire; embedded garnet particles; energy dispersive spectroscopy; finishing; garnet water jet; mill; niobium composition; relative resistivity ratio; scanning electron microscope; secondary ion mass spectroscopy; sheer; superconducting radio frequency niobium cavities; surface contamination; surface damage; surface morphology; surface profilometer; surface roughness; Cutting; materials processing; niobium; surface contamination;
fLanguage :
English
Journal_Title :
Applied Superconductivity, IEEE Transactions on
Publisher :
ieee
ISSN :
1051-8223
Type :
jour
DOI :
10.1109/TASC.2009.2018315
Filename :
4982570
Link To Document :
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