Author: Karapetrova, E.A.
Paper Title Page
MOPFDV010 MICROSTRUCTURE CHANGES OBSERVED IN THE NEAR-SURFACE REGION OF SRF Nb CAVITIES CUTOUTS UPON COOLING/HEATING CYCLES USING GI-SYNCHROTRON XRD 339
 
  • A. Cano, D. Bafia, A. Grassellino, J. Lee, M. Martinello, A.S. Romanenko, T. Spina, Z-H. Sung
    Fermilab, Batavia, Illinois, USA
  • E.A. Karapetrova
    ANL, Lemont, Illinois, USA
 
  We have mapped microstructural changes in the near-surface region of Nb from SRF cavity-cutouts upon thermal cycles in the range from 300 to 30K using grazing incidence synchrotron X-ray diffraction (GIXRD). Segregation of secondary phases was observed after the thermal cycle, and their nature has been clarified and discussed in view of previous studies on hydrides formation in SRF bulk Nb cavities. The temperature dependence of the relative population of these formed phases was obtained from GIXRD patterns profile fitting. Both, Nb bulk matrix and the new phases formed after cool-down show specific structural features as thermal contraction/expansion, structural transitions, and Nb lattice variation due to the induced strain by precipitates formation. The information derived from this structural study can explain some phenomena as the dissipation at high accelerating field (i.e. High Field Q Slope, HFQS) in the Nb SRF performance as well as new mechanisms never addressed in previous studies.
A Romanenko, F Barkov, LD Cooley, A Grassellino, Proximity breakdown of hydrides in superconducting niobium cavities, Superconductor Science and Technology, 2013
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-MOPFDV010  
About • Received ※ 28 June 2021 — Revised ※ 12 August 2021 — Accepted ※ 21 August 2021 — Issue date ※ 23 September 2021
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