Keyword: survey
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MOPFDV009 On the Nature of Surface Defects Found in 2/0 N-Doped 9-Cell Cavities cavity, SRF, electron, superconductivity 336
 
  • A. Cano, D. Bafia, A. Grassellino, J. Lee, M. Martinello, A.S. Romanenko, T. Spina, Z-H. Sung
    Fermilab, Batavia, Illinois, USA
 
  In this contribution, we present a systematic study on the microstructure of 1.3 GHz 9-cell TESLA type SRF cavity, processed with 2/0 Nitrogen-doping surface treatment, to explain the premature quench phenomena commonly observed in N-doping treated cavities. The microstructure characterization was carried out using Secondary electron images, advanced metallurgical techniques such as EBSD in parallel with chemical information obtained from spectroscopic techniques. The most remarkable difference is observed in the ends-cavities (1 and 9), which showed roughening of the surface, revealing a series of morphologies associated with Nb cubic phase. The cell-to-cell analysis also showed standard features such as pits with different geometry and distribution, located in grains and grain boundaries. The defects found in this system suggest that the standard electropolishing chemical etching was insufficient to eliminate history defects produced during the manufacture of the cavity, without discarding the role of the impurities, N and O, that could have induced the growth of these morphologies.
H. Padamsee, RF superconductivity (Wiley-VCH Verlag GmbH and Co., KGaA, Weinheim, 2009)
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-MOPFDV009  
About • Received ※ 29 June 2021 — Revised ※ 11 March 2022 — Accepted ※ 10 May 2022 — Issue date ※ 11 May 2022
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TUPFDV004 A SIMS Approach for the Analysis of Furnace Contamination cavity, niobium, SRF, electron 406
 
  • J.W. Angle, M.J. Kelley
    Virginia Polytechnic Institute and State University, Blacksburg, USA
  • M.J. Kelley, E.M. Lechner, A.D. Palczewski, C.E. Reece
    JLab, Newport News, Virginia, USA
  • F.A. Stevie
    NCSU AIF, Raleigh, North Carolina, USA
 
  Detection of surface contamination for SRF material is difficult due to the miniscule quantities and near atomic resolution needed. Visual inspection of samples known to have experienced surface contamination were found to have inconsistent nitride coverage after nitrogen doping. EBSD analysis suggest that nitride suppression tends to be most prevalent when deviating from the [111] and [001] zone axes. XPS suggested that tin was present as a contaminant on the surface with SIMS mass spectra also confirming its presence. SIMS depth profiles show a depletion of nitrogen content as well as an increase in car-bon content for contaminated samples.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-TUPFDV004  
About • Received ※ 22 June 2021 — Revised ※ 11 July 2021 — Accepted ※ 21 August 2021 — Issue date ※ 19 February 2022
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