Characterization of etch pits found on a large-grain bulk niobium superconducting radio-frequency resonant cavity
Abstract
The performance of superconducting radio-frequency (SRF) resonant cavities made of bulk niobium is limited by nonlinear localized effects. Surface analysis of regions of higher power dissipation is thus of intense interest. Such areas (referred to as “hotspots”) were identified in a large-grain single-cell cavity that had been buffered-chemical polished and dissected for examination by high resolution electron microscopy, electron backscattered diffraction microscopy (EBSD), and optical microscopy. Pits with clearly discernible crystal facets were observed in both “hotspot” and “coldspot” specimens. The pits were found in-grain, at bicrystal boundaries, and on tricrystal junctions. They are interpreted as etch pits induced by crystal defects (e.g. dislocations). All coldspots examined had a qualitatively lower density of etch pits or relatively smooth tricrystal boundary junctions. EBSD mapping revealed the crystal orientation surrounding the pits. Locations with high pit density are correlated with higher mean values of the local average misorientation angle distributions, indicating a higher geometrically necessary dislocation content. In addition, a survey of the samples by energy dispersive x-ray analysis did not show any significant contamination of the samples’ surface. In conclusion, the local magnetic field enhancement produced by the sharp-edge features observed on the samples is not sufficient to explain the observedmore »
- Authors:
-
- Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
- Michigan State Univ., East Lansing, MI (United States)
- Publication Date:
- Research Org.:
- Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
- Sponsoring Org.:
- USDOE Office of Science (SC)
- OSTI Identifier:
- 1001033
- Report Number(s):
- JLAB-ACC-09-1123; DOE/OR/23177-1066
Journal ID: ISSN 1098-4402; PRABFM; TRN: US201101%%799
- Grant/Contract Number:
- AC05-06OR23177
- Resource Type:
- Accepted Manuscript
- Journal Name:
- Physical Review Special Topics. Accelerators and Beams
- Additional Journal Information:
- Journal Volume: 13; Journal Issue: 12; Journal ID: ISSN 1098-4402
- Publisher:
- American Physical Society (APS)
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; BICRYSTALS; CAVITIES; CONTAMINATION; CRYSTAL DEFECTS; DIFFRACTION; DISLOCATIONS; ELECTRON MICROSCOPY; ELECTRONS; MAGNETIC FIELDS; MICROSCOPY; NIOBIUM; OPTICAL MICROSCOPY; ORIENTATION; PERFORMANCE; QUALITY FACTOR; RESOLUTION
Citation Formats
Zhao, Xin, Ciovati, G., and Bieler, T. R. Characterization of etch pits found on a large-grain bulk niobium superconducting radio-frequency resonant cavity. United States: N. p., 2010.
Web. doi:10.1103/PhysRevSTAB.13.124701.
Zhao, Xin, Ciovati, G., & Bieler, T. R. Characterization of etch pits found on a large-grain bulk niobium superconducting radio-frequency resonant cavity. United States. https://doi.org/10.1103/PhysRevSTAB.13.124701
Zhao, Xin, Ciovati, G., and Bieler, T. R. Wed .
"Characterization of etch pits found on a large-grain bulk niobium superconducting radio-frequency resonant cavity". United States. https://doi.org/10.1103/PhysRevSTAB.13.124701. https://www.osti.gov/servlets/purl/1001033.
@article{osti_1001033,
title = {Characterization of etch pits found on a large-grain bulk niobium superconducting radio-frequency resonant cavity},
author = {Zhao, Xin and Ciovati, G. and Bieler, T. R.},
abstractNote = {The performance of superconducting radio-frequency (SRF) resonant cavities made of bulk niobium is limited by nonlinear localized effects. Surface analysis of regions of higher power dissipation is thus of intense interest. Such areas (referred to as “hotspots”) were identified in a large-grain single-cell cavity that had been buffered-chemical polished and dissected for examination by high resolution electron microscopy, electron backscattered diffraction microscopy (EBSD), and optical microscopy. Pits with clearly discernible crystal facets were observed in both “hotspot” and “coldspot” specimens. The pits were found in-grain, at bicrystal boundaries, and on tricrystal junctions. They are interpreted as etch pits induced by crystal defects (e.g. dislocations). All coldspots examined had a qualitatively lower density of etch pits or relatively smooth tricrystal boundary junctions. EBSD mapping revealed the crystal orientation surrounding the pits. Locations with high pit density are correlated with higher mean values of the local average misorientation angle distributions, indicating a higher geometrically necessary dislocation content. In addition, a survey of the samples by energy dispersive x-ray analysis did not show any significant contamination of the samples’ surface. In conclusion, the local magnetic field enhancement produced by the sharp-edge features observed on the samples is not sufficient to explain the observed degradation of the cavity quality factor, which starts at peak surface magnetic field as low as 20 mT.},
doi = {10.1103/PhysRevSTAB.13.124701},
journal = {Physical Review Special Topics. Accelerators and Beams},
number = 12,
volume = 13,
place = {United States},
year = {Wed Dec 15 00:00:00 EST 2010},
month = {Wed Dec 15 00:00:00 EST 2010}
}
Web of Science
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Works referencing / citing this record:
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journal, April 2016
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