Author: Posen, S.
Paper Title Page
TUBA04 Nb3Sn Cavities: Material Characterization and Coating Process Optimization 501
 
  • D.L. Hall, T. Gruber, J.J. Kaufman, M. Liepe, J.T. Maniscalco, S. Posen, B. Yu
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • Th. Proslier
    ANL, Argonne, Illinois, USA
 
  Funding: Work supported by DOE grant DE-SC0008431 and NSF grant PHY-141638. Use of CCMR via NSF MRSEC program (DMR-1120296)
Recent progress on vapour diffusion coated Nb3Sn SRF cavities makes this material a very promising alternative for CW medium field SRF applications. In this paper we report on several systematic studies to determine the sources currently limiting the performance of Nb3Sn cavities to determine improved coating parameters to overcome these limitations. These include a detailed study of the sensitivity of Nb3Sn to trapped ambient magnetic flux, a first measurement of the field dependence of the energy gap in Nb3Sn and detailed measurements of the stoichiometry of the obtained Nb3Sn coatings with synchrotron x-ray diffraction and STEM. Initial results from a study on the impact of the coating process parameters on energy gap, Q-slope, and residual resistance, show clear dependencies, and thus directions for process optimization.
 
slides icon Slides TUBA04 [3.872 MB]  
Export • reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)  
 
TUPB041 Testing Nb3Sn Coating Using muSR 651
 
  • R.E. Laxdal, T.J. Buck
    TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada
  • S. Gheidi
    UBC, Vancouver, B.C., Canada
  • R. Kiefl
    UBC & TRIUMF, Vancouver, British Columbia, Canada
  • M. Liepe, S. Posen
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  The SRF group at TRIUMF has tested samples relevant for SRF application since 2010 using the TRIUMF μSR facility. In this study collaborators at Cornell coat a Nb coin and a Nb ellipsoid sample with Nb3Sn for characterization using μSR at TRIUMF. Field of first flux entry measurements are performed at M20 on both samples. Measurements include the vortex nucleation field Hnucleate and Tc of both Nb3Sn and Nb. Interestingly the Nb3Sn increases the vortex nucleation field at 2K over standard Nb samples.  
Export • reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)  
 
FRAA04 Performance of the Cornell ERL Main Linac Prototype Cryomodule 1437
 
  • F. Furuta, B. Clasby, R.G. Eichhorn, B. Elmore, G.M. Ge, D. Gonnella, D.L. Hall, G.H. Hoffstaetter, R.P.K. Kaplan, J.J. Kaufman, M. Liepe, T.I. O'Connell, S. Posen, 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 has designed, fabricated, and tested (by the time of the conference) a high current (100 mA) CW SRF prototype cryomodule for the Cornell ERL. This talk will report on the design and performance of this very high Q0 CW cryomodule including design issues and mitigation strategies.  
slides icon Slides FRAA04 [4.614 MB]  
Export • reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)  
 
MOPB015 Trapped Flux Surface Resistance Analysis for Different Surface Treatments 115
 
  • M. Martinello, M. Checchin, A. Grassellino, O.S. Melnychuk, S. Posen, A. Romanenko, D.A. Sergatskov
    Fermilab, Batavia, Illinois, USA
  • M. Checchin
    Illinois Institute of Technology, Chicago, Illlinois, USA
  • J. Zasadzinski
    IIT, Chicago, Illinois, USA
 
  Funding: Work supported by the US Department of Energy, Office of High Energy Physics
The trapped flux surface resistance is one of the main contributions on cavity losses which appears when cavities are cooled in presence of external magnetic field. The study is focused on the understanding of the different parameters which determine the trapped flux surface resistance, and how this change as a function of different surface treatments. The study is performed on 1.3 GHz niobium cavities processed with different surface treatments after the 800 C bake: electro-polishing (EP), 120 C baking, and N-doping varying the time of the Nitrogen exposure. The trapped flux surface resistance normalized for the trapped magnetic flux is then analyzed as a function of the mean free path in order to find the surface treatment which minimized the trapped flux sensitivity.
 
Export • reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)  
 
MOPB028 Preservation of Very High Quality Factors of 1.3 GHz Nine Cell Cavities From Bare Vertical Test to Dressed Horizontal Test 149
 
  • A. Grassellino, S. Aderhold, M. Checchin, A.C. Crawford, C.J. Grimm, A. Hocker, M. Martinello, O.S. Melnychuk, J.P. Ozelis, S. Posen, A.M. Rowe, D.A. Sergatskov, N. Solyak, R.P. Stanek, G. Wu
    Fermilab, Batavia, Illinois, USA
  • D. Gonnella
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • J.M. Köszegi
    HZB, Berlin, Germany
  • M. Liepe
    Cornell University, Ithaca, New York, USA
 
  In this contribution we will report quality factor evolution of several different nine cell N doped cavities with very high Q. The evolution of the quality factor will be reported from bare to dressed in vertical test to dressed in horizontal test with unity coupling to dressed in horizontal test and CM-like environment/configuration (with RF ancillaries). Cooling studies and optimal cooling regimes will be discussed for both vertical and horizontal tests and comparisons will be drawn also for different styles titanium vessels. Studies of sensitivities to magnetic field in final horizontal configuration have been performed by applying a field around the dressed cavity and varying the cooling; parameters required for a very good flux expulsion will be presented.  
Export • reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)  
 
MOPB104 Flux Expulsion Variation in SRF Cavities 404
 
  • S. Posen, M. Checchin, A.C. Crawford, A. Grassellino, M. Martinello, O.S. Melnychuk, A. Romanenko, D.A. Sergatskov
    Fermilab, Batavia, Illinois, USA
 
  Treating a cavity with nitrogen doping significantly increases Q0 at medium fields, reducing cryogenic costs for high duty factor linear accelerators such as LCLS II. N-doping also makes cavities more sensitive to increased residual resistance due to trapped magnetic flux, making it critical to either have extremely effective magnetic shielding, or to prevent flux from being trapped in the cavity during cooldown. In this paper, we report on results of a study of flux expulsion. We discuss possible ways in which flux can be pinned in the inner surface, outer surface, or bulk of a cavity, and we present experimental results studying these mechanisms. We show that grain structure appears to play a key role and that a cavity that expelled flux poorly changed to expelling flux well after a high temperature furnace treatment. We further show that after furnace treatment, this cavity exhibited a significant improvement in quality factor when cooled in an external magnetic field. We conclude with implications for SRF accelerators with high Q0 requirements.  
Export • reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)  
 
TUPB048 Fermilab Nb3Sn R&D Program 678
 
  • S. Posen, M. Merio, A. Romanenko, Y. Trenikhina
    Fermilab, Batavia, Illinois, USA
 
  A substantial program has been initiated at FNAL for R&D on Nb3Sn coated cavities. Since early 2015, design, fabrication, and commissioning has been ongoing on a coating chamber, designed for deposition via vapor diffusion. The volume of the chamber will be large enough to accommodate not just R&D cavities, but full production-style cavities such as TeSLA 9-cells. In this contribution, we overview the development of the chamber and we introduce the R&D program planned for the coming years. We discuss research paths that may yield increased maximum fields and reduced residual resistances as well as new applications that could be explored with larger coated cavities.  
Export • reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)  
 
TUPB049 Cutout Study of a Nb3Sn Cavity 681
 
  • S. Posen, O.S. Melnychuk, A. Romanenko, D.A. Sergatskov, Y. Trenikhina
    Fermilab, Batavia, Illinois, USA
  • D.L. Hall, M. Liepe
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
 
  The first 1.3 GHz single cell Nb3Sn cavity coated at Cornell was shown in RF measurements at Cornell and FNAL to have poor RF performance. Though subsequent cavities showed much higher quality factors, this cavity exhibited Q0 on the order of 109 caused by strong heating concentrated in one of the half cells. This paper presents an investigation into the source of this excess heating, for the purpose of process improvement, so that similar degradation can be avoided in future coatings. Through the use of temperature mapping both at Cornell and at FNAL, locations with high and low surface resistance were located, cut out from the cavity, and studied with microscopic tools. We present the RF measurements and temperature maps as well as the microscopic analyses, then conclude with plans for continued studies.  
Export • reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)  
 
TUPB056 Characterization of Nb3Sn Coated Nb Samples 708
 
  • Y. Trenikhina, S. Posen, A. Romanenko
    Fermilab, Batavia, Illinois, USA
  • D.L. Hall
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • M. Liepe
    Cornell University, Ithaca, New York, USA
 
  Nb3Sn has a great potential to replace traditional Nb for the fabrication of SRF cavities. The higher critical temperature of Nb3Sn potentially allows for an increased operational temperature for SRF cavities, which promises cryogenic cost savings. We present preliminary characterization of Nb3Sn layer grown on flat Nb sample prepared by the same chemical vapor deposition method that is used for the cavity coating. SEM, TEM/EDS, TEM imaging and diffraction characterization was used in order to evaluate any chemical and structural defects that could be responsible for the limited quench field and high residual resistance. Variation of local stoichiometry was found in the Nb3Sn layer, which is in line with previous studies. Regions of decreased Sn content can have a lower Tc in comparison to the stoichiometric composition, which may be responsible for the limited performance. AES investigations of the Nb3Sn surface before and after HF-rinse were done in order to explore the mechanism that is responsible for the performance degradation of HF-rinsed Nb3Sn coated cavities.  
Export • reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)  
 
FRBA03 SRF, Compact Accelerators for Industry & Society 1467
 
  • R.D. Kephart, B.E. Chase, I.V. Gonin, A. Grassellino, S. Kazakov, T.N. Khabiboulline, S. Nagaitsev, R.J. Pasquinelli, S. Posen, O.V. Pronitchev, A. Romanenko, V.P. Yakovlev
    Fermilab, Batavia, Illinois, USA
  • S. Biedron, S.V. Milton, N. Sipahi
    CSU, Fort Collins, Colorado, USA
  • S. Chattopadhyay
    Northern Illinois Univerity, Dekalb, Illinois, USA
  • P. Piot
    Northern Illinois University, DeKalb, Illinois, USA
 
  Accelerators developed for Science now are used broadly for industrial, medical, and security applications. Over 30,000 accelerators touch over $500B/yr in products producing a major impact on our economy, health, and well being. Industrial accelerators must be cost effective, simple, versatile, efficient, and robust. Many industrial applications require high average beam power. Exploiting recent advances in Superconducting Radio Frequency (SRF) cavities and RF power sources as well as innovative solutions for the SRF gun and cathode system, a collaboration of Fermilab-CSU-NIU has developed a design for a compact SRF high-average power electron linac. Capable of 5-50 kW average power and continuous wave operation this accelerator will produce electron beam energies up to 10 MeV and small and light enough to mount on mobile platforms, such accelerators will enable new in-situ environmental remediation methods and new applications involving in-situ crosslinking of materials. More importantly, we believe this accelerator will be the first of a new class of simple, turn-key SRF accelerators that will find broad application in industry, medicine, security, and science.  
slides icon Slides FRBA03 [2.342 MB]  
Export • reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)