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TY - CONF AU - Rothweiler, P. AU - Bornmann, B. AU - Klaes, J. AU - Lützenkirchen-Hecht, D. AU - Wagner, R. AU - von Polheim, S. ED - Michel, Peter ED - Arnold, André ED - Schaa, Volker RW TI - In-Situ EXAFS Investigations of Nb-Treatments in N₂ at Elevated Temperatures J2 - Proc. of SRF2019, Dresden, Germany, 30 June-05 July 2019 CY - Dresden, Germany T2 - International Conference on RF Superconductivity T3 - 19 LA - english AB - Smooth polycrystalline Nb metal foils were exposed to dilute N₂ and Kr atmospheres at elevated temperatures of up to 900°C. Transmission mode X-ray absorption spectroscopy (EXAFS) experiments were used to study the resulting changes of the atomic short range order structure in-situ. EXAFS data were collected prior to any heat treatment as well as during the different process steps at elevated temperatures with a time resolution of about 1 s, and the samples were also studied after cooling to room temperature. In general, only very small changes of the Nb-EXAFS data could be detected after the processing in N₂-atmospheres, and no evidence for bulk formation of Nb-nitrides was found. In contrast, the quantitative EXAFS data evaluation revealed slightly distorted Nb-Nb coordinations, suggesting that N-atoms are increasingly incorporated on octahedral interstitial sites in the host lattice with increasing N₂-exposure. For the treatments in Kr-atmospheres, simultaneous measurements are feasible at both the K-edge of the Nb host and the Kr dopant. Those studies gave clear evidence for a Kr uptake during the heat treatment, and will be discussed in more detail at the conference. PB - JACoW Publishing CP - Geneva, Switzerland SP - 842 EP - 845 KW - experiment KW - niobium KW - cavity KW - vacuum KW - lattice DA - 2019/08 PY - 2019 SN - "" SN - 978-3-95450-211-0 DO - doi:10.18429/JACoW-SRF2019-THP007 UR - http://jacow.org/srf2019/papers/thp007.pdf ER -