Author: Melnychuk, O.S.
Paper Title Page
TUYAA02 Advancement in the Understanding of the Field and Frequency Dependent Microwave Surface Resistance of Niobium 364
 
  • M. Martinello, S. Aderhold, S.K. Chandrasekaran, M. Checchin, A. Grassellino, O.S. Melnychuk, S. Posen, A. Romanenko, D.A. Sergatskov
    Fermilab, Batavia, Illinois, USA
  
  The radio-frequency surface resistance of niobium resonators is incredibly reduced when nitrogen impurities are dissolved as interstitial in the material, conferring ultra-high Q-factors at medium values of accelerating field. This effect has been observed in both high and low temperature nitrogen treatments. As a matter of fact, the peculiar anti Q-slope observed in nitrogen doped cavities, i.e. the decreasing of the Q-factor with the increasing of the radio-frequency field, come from the decreasing of the BCS surface resistance component as a function of the field. Such peculiar behavior has been considered consequence of the interstitial nitrogen present in the niobium lattice after the doping treatment. The study here presented show the field dependence of the BCS surface resistance surface of cavities with different resonant frequencies, such as: 650 MHz, 1.3 GHz, 2.6 GHz and 3.9 GHz, and processed with different state-of-the-art surface treatments. These findings show for the first time that the anti Q-slope might be seen at high frequency even for clean Niobium cavities, revealing useful suggestion on the physics underneath the anti Q-slope effect.
*M. Martinello, A. Grassellino, M. Checchin, A. Romanenko, O. Melnychuk, D.A. Sergatskov, S. Posen, J. Zasadzinski App. Phys. Lett. 109, 6 (2016) 		 
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DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUYAA02  
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TUPB071 Test Result of 650 MHz, Beta 0.61 Single-cell Niobium Cavity 553
 
  • S. Seth, P. Bhattacharyya, A. Dutta Gupta, S. Ghosh, S. Ghosh, A. Mandal, S. Som
    VECC, Kolkata, India
  • A. Grassellino, T.N. Khabiboulline, O.S. Melnychuk, C.S. Mishra, T.H. Nicol, A.M. Rowe, D.A. Sergatskov
    Fermilab, Batavia, Illinois, USA
  • M.P. Kelly, T. Reid
    ANL, Argonne, Illinois, USA
  • K.K. Mistri, P.N. Prakash
    IUAC, New Delhi, India
  
  VECC has been involved in the design, analysis and development of 650 MHz, beta 0.61 (LB650), elliptical Superconducting RF linac cavity, as part of research and development activities on SRF cavities and associated technologies under Indian Institutions Fermilab Collaboration (IIFC). A single-cell niobium cavity has been indigenously designed and developed at VECC, with the help of Electron Beam Welding (EBW) facility at IUAC, New Delhi. Various measurements, processing and testing at 2K in Vertical Test Stand (VTS) of the single-cell cavity was carried out at ANL and Fermilab, USA, with active participation of VECC engineers. It achieved a maximum accelerating gradient(Eacc) of 34.5 MV/m with Quality Factor of 2·109 and 30 MV/m with Quality Factor of 1.5·1010. This is probably the highest accelerating gradient achieved so far in the world for LB650 cavities. This paper describes the design, fabrication and measurement of the single cell niobium cavity. Cavity processing and test results of Vertical Test of the single-cell niobium cavity are also presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB071  
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