X-ray computed tomographic and focused ion beam/electron microscopic investigation of coating defects in niobium-coated copper superconducting radio-frequency cavities

Aliasghari, S. and Skeldon, P. and Zhou, X. and Gholinia, A. and Zhang, X. and Valizadeh, R. and Pira, C. and Junginger, T. and Burt, G. and Withers, P.J. (2021) X-ray computed tomographic and focused ion beam/electron microscopic investigation of coating defects in niobium-coated copper superconducting radio-frequency cavities. Materials Chemistry and Physics, 273. ISSN 0254-0584

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Abstract

A combination of X-ray computed tomography (CT) and focused ion beam - scanning electron microscopy (FIB-SEM) has been employed to investigate substrate and related surface defects in a niobium coated superconducting radio frequency (SRF) copper cavity. The cavity was manufactured by spinning, with subsequent application of a sputtering-deposited niobium coating (≈40 μm thick) on the internal surface. Before coating, the copper surface was pre-treated in several stages, ending with chemical polishing. CT and FIB-SEM identified furrow defects (≈20 μm deep) in the copper beneath the coating, which originated from the spinning process. The furrows were filled with niobium and contained voids at the Nb/Cu interface that extended a few microns into the niobium coating. The presence of the defects led to similar furrows at the niobium surface. The study revealed the importance of pre-treatment of the cavity internal surface and control of the spinning process to avoid defects that may have deleterious influence on the Q slope and durability of the niobium coating.

Item Type:
Journal Article
Journal or Publication Title:
Materials Chemistry and Physics
Additional Information:
This is the author’s version of a work that was accepted for publication in Materials Chemistry and Physics. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Materials Chemistry and Physics, 273, 2021 DOI: 10.1016/j.matchemphys.2021.125062
Uncontrolled Keywords:
/dk/atira/pure/subjectarea/asjc/3100/3104
Subjects:
ID Code:
159956
Deposited By:
Deposited On:
22 Sep 2021 15:35
Refereed?:
Yes
Published?:
Published
Last Modified:
06 Oct 2021 08:24