Author: Checchin, M.
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WEPTY021 Origin of Trapped Flux Caused by Quench in Superconducting Niobium Cavities 3309
 
  • M. Checchin, A. Grassellino, M. Martinello, O.S. Melnychuk, A. Romanenko, D.A. Sergatskov
    Fermilab, Batavia, Illinois, USA
  • M. Checchin, M. Martinello
    Illinois Institute of Technology, Chicago, Illlinois, USA
  
  Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
In this study we prove that the mechanism at the basis of quality factor degradation due to quench involves the entrapment of ambient magnetic field. The cavity quench in the absence of magnetic field does not introduce any extra losses, and a clear trend between the external field and the extra losses introduced by the quench was observed. It is demonstrated that the quality factor can be totally recovered by quenching in zero applied magnetic field. A dependence of the amount of quality factor degradation on the orientation of the magnetic field with respect to the cavity was also found. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY021  
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WEPTY022 Modifications of Superconducting Properties of Niobium Caused by Nitrogen Doping Recipes for High Q Cavities 3312
 
  • A. Vostrikov, M. Checchin, A. Grassellino, A. Romanenko
    Fermilab, Batavia, Illinois, USA
  • Y.K. Kim, A. Vostrikov
    University of Chicago, Chicago, Illinois, USA
  
  Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
Discovery at Fermilab of a drastic effect of nitrogen doping leading to unprecedented high Q values in niobium cavities * motivated a strong interest in revealing the physics underlying the effect. In this contribution we present new results obtained by DC magnetometry, AC susceptibility, resistivity and thermal properties measurements on nitrogen doped samples prepared by different recipes/doping levels, which shed light on the possible origin of the effect.
* A. Grassellino et al, 2013 Supercond. Sci. Technol. 26 102001 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY022  
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WEPTY034 T-map Studies on Gradient-limiting Mechanism in Nitrogen Doped Cavities 3348
 
  • M. Martinello, M. Checchin, A. Grassellino, A. Romanenko
    Fermilab, Batavia, Illinois, USA
  
  Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
Nitrogen doping * results in ultra-high quality factors in SRF niobium cavities but currently achievable gradients in doped cavities are, on average, somewhat lower than in EP/120C baked cavities. The origin of this difference is explored in the reported work by detailed temperature mapping studies on several single cell nitrogen doped cavities.
* A. Grassellino et al, 2013 Supercond. Sci. Technol. 26 102001 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY034  
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