Author: Chetri, S.
Paper Title Page
MOPMB041 Microstructure Development in a Cold Worked SRF Niobium Sheet After Heat Treatments 191
 
  • S. Balachandran, P. Dhakal, A-M. Valente-Feliciano
    JLab, Newport News, Virginia, USA
  • T.R. Bieler
    Michigan State University, East Lansing, Michigan, USA
  • S. Chetri, P.J. Lee
    NHMFL, Tallahassee, Florida, USA
  • Z.L. Thune
    MSU, East Lansing, USA
 
  Funding: Jefferson Science Associates, LLC under U.S. DOE Grant DEAC05-06OR23177, U.S. DOE, Office of HEP under Grant DE-SC0009960, and NHMFL through NSF Grant DMR-1644779 and the State of Florida.
Bulk Nb for TESLA shaped SRF cavities is a mature technology. Significant advances are in order to push Q0’s to 1010-11(T= 2K), and involve modifications to the sub-surface Nb layers by impurity doping. In order to achieve the lowest surface resistance any trapped flux needs to be expelled for cavities to reach high Q0’s. There is clear evidence that cavities fabricated from polycrystalline sheets meeting current specifications require higher temperatures beyond 800 °C leads to better flux expulsion, and hence improves Q0. Recently, cavities fabricated with a non-traditional Nb sheet with initial cold work due to cold rolling expelled flux better after 800 °C/3h heat treatment than cavities fabricated using fine-grain poly-crystalline Nb sheets. Here, we analyze the microstructure development in Nb from the vendor supplied cold work non- annealed sheet that was fabricated into an SRF cavity as a function of heat treatment building upon the methodology development to analyze microstructure being developed by the FSU-MSU-UT, Austin-JLAB collaboration. The results indicate correlation between full recrystallization and better flux expulsion.
 
DOI • reference for this paper ※ doi:10.18429/JACoW-SRF2023-MOPMB041  
About • Received ※ 19 June 2023 — Revised ※ 23 June 2023 — Accepted ※ 26 June 2023 — Issue date ※ 09 July 2023
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