JACoW is a publisher in Geneva, Switzerland that publishes the proceedings of accelerator conferences held around the world by an international collaboration of editors.
TY - CONF AU - Cano, A. AU - Bafia, D. AU - Grassellino, A. AU - Karapetrova, E.A. AU - Lee, J. AU - Martinello, M. AU - Romanenko, A.S. AU - Spina, T. AU - Sung, Z-H. ED - Saito, Kenji ED - Xu, Ting ED - Sakamoto, Naruhiko ED - Lesage, Ana ED - Schaa, Volker R.W. TI - Microstructure Changes Observed in the Near-Surface Region of SRF Nb Cavities Cutouts upon Cooling/Heating Cycles Using GI-Synchrotron XRD J2 - Proc. of SRF2021, East Lansing, MI, USA, 28 June-02 July 2021 CY - East Lansing, MI, USA T2 - International Conference on RF Superconductivity T3 - 20 LA - english AB - 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 30 K 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. PB - JACoW Publishing CP - Geneva, Switzerland SP - 339 EP - 341 KW - site KW - cavity KW - lattice KW - SRF KW - niobium DA - 2022/10 PY - 2022 SN - 2673-5504 SN - 978-3-95450-233-2 DO - doi:10.18429/JACoW-SRF2021-MOPFDV010 UR - https://jacow.org/srf2021/papers/mopfdv010.pdf ER -