Author: Furuta, F.
Paper Title Page
WEPRI060 Investigation of Thermocurrents Limiting the Performance of Superconducting Cavities 2621
 
  • R.G. Eichhorn, C.G. Daly, F. Furuta, A. Ganshin
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  As the surface resistance of superconducting cavities approach the theoretical limits parasitic effects limiting the performance came into focus of current research. One of these effects is that the quality factor of a cavity is impacted by the cooldown rate. We will present results from recent investigations on thermocurrents, driven by the temperature difference between the two material interfaces between the superconducting Niobium cavity and its Titanium helium-vessel, leading to the presence of a magnetic field while the cavity transits to the superconducting state.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPRI060  
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WEPRI061 Cornell's Main Linac Cryomodule for the Energy Recovery Linac Project 2624
 
  • R.G. Eichhorn, B. Bullock, J.V. Conway, B. Elmore, F. Furuta, Y. He, G.H. Hoffstaetter, J.J. Kaufman, M. Liepe, T.I. O'Connel, P. Quigley, D.M. Sabol, J. Sears, E.N. Smith, V. Veshcherevich
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  Cornell University has been designing and building superconducting accelerators for various applications for more than 50 years. Currently, an energy-recovery linac (ERL) based synchrotron-light facility is proposed making use of the existing CESR facility. As part of the phase 1 R&D program funded by the NSF, critical challenges in the design were addressed, one of them being a full linac cryo-module. It houses 6 superconducting cavities- operated at 1.8 K in continuous wave (CW) mode - with individual HOM absorbers and one magnet/ BPM section. Pushing the limits, a high quality factor of the cavities (2•1010) and high beam currents (100 mA accelerated plus 100 mA decelerated) are targeted. We will present the status of the main linac cryomodule (MLC) fabrication and the findings on the cavity performance and component testing.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPRI061  
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WEPRI062 The Joint High Q0 R&D Program for LCLS-II 2627
 
  • M. Liepe, R.G. Eichhorn, F. Furuta, G.M. Ge, D. Gonnella, G.H. Hoffstaetter
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • A.C. Crawford, A. Grassellino, A. Hocker, O.S. Melnychuk, A. Romanenko, A.M. Rowe, D.A. Sergatskov
    Fermilab, Batavia, Illinois, USA
  • R.L. Geng, A.D. Palczewski, C.E. Reece
    JLab, Newport News, Virginia, USA
  • M.C. Ross
    SLAC, Menlo Park, California, USA
 
  The superconducting RF linac for LCLS-II calls for 1.3 GHz 9-cell cavities with an average intrinsic quality factor Q0 of 2.7·1010 at 2K and 16 MV/m accelerating gradient. A collaborative effort between Cornell University, FNAL, and JLab has been set up with the goal of developing and demonstrating a cavity treatment protocol for the LCLS-II cavities meeting these specifications. The high Q0 treatment protocol is based on nitrogen doping of the RF surface layer during a high temperature heat treatment. This novel SRF cavity preparation was recently developed at FNAL and shown to result in SRF cavities of very high Q0 at 2K with an increase in Q0 from low to medium fields. N-doped single cell cavities at Cornell, FNAL, and JLab routinely exceed LCLS-II specification. 9-cell N-doped cavities at FNAL achieve an average Q0(T=2K, 16 MV/m) of ≈ 3.4·1010 with an average quench field of ≈ 19 MV/m, meeting therefore overall with good margin the LCLS-II specification.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPRI062  
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