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Title: 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 » degradation of the cavity quality factor, which starts at peak surface magnetic field as low as 20 mT.« less

Authors:
 [1];  [1];  [2]
  1. Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
  2. 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}
}

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Works referenced in this record:

Improved surface treatment of the superconducting TESLA cavities
journal, January 2004

  • Lilje, L.; Antoine, C.; Benvenuti, C.
  • Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Vol. 516, Issue 2-3
  • DOI: 10.1016/j.nima.2003.08.116

Review of the frontier workshop and Q-slope results
journal, July 2006


Study of the surface resistance of superconducting niobium films at 1.5 GHz
journal, May 1999


Grain boundary engineering: an overview after 25 years
journal, March 2010


Role of the densest lattice planes in the stability of crystalline interfaces: A computer simulation study
journal, January 1989


The structure of high-angle grain boundaries
journal, November 1966


Grain boundary engineering for superplasticity in steels
journal, February 2005


Etch pits on single crystals and bicrystals of niobium
journal, March 1983


Dislocation etch pit studies in annealed and deformed polycrystalline niobium
journal, April 1964


Physical and mechanical metallurgy of high purity Nb for accelerator cavities
journal, March 2010

  • Bieler, T. R.; Wright, N. T.; Pourboghrat, F.
  • Physical Review Special Topics - Accelerators and Beams, Vol. 13, Issue 3
  • DOI: 10.1103/PhysRevSTAB.13.031002

The role of near-surface dislocations in the high magnetic field performance of superconducting niobium cavities
journal, March 2010


High field Q slope and the baking effect: Review of recent experimental results and new data on Nb heat treatments
journal, February 2010

  • Ciovati, G.; Myneni, G.; Stevie, F.
  • Physical Review Special Topics - Accelerators and Beams, Vol. 13, Issue 2
  • DOI: 10.1103/PhysRevSTAB.13.022002

Works referencing / citing this record:

Superconducting radio-frequency cavities made from medium and low-purity niobium ingots
journal, April 2016

  • Ciovati, Gianluigi; Dhakal, Pashupati; Myneni, Ganapati R.
  • Superconductor Science and Technology, Vol. 29, Issue 6
  • DOI: 10.1088/0953-2048/29/6/064002