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TY - CPAPER AU - Trenikhina, Y. AU - Grassellino, A. AU - Melnychuk, O.S. AU - Romanenko, A. TI - Characterization of Nitrogen Doping Recipes for the Nb SRF Cavities J2 - Proc. of International Conference on RF Superconductivity (SRF2015), Whistler, BC, Canada, Sept. 13-18, 2015 AB - For the future development of the nitrogen doping technology, it’s vital to understand the mechanisms behind the performance benefits of N-doped cavities as well as the performance limitations, such as quench field. Following various doping recipes, cavity cutouts and flat niobium samples have been evaluated with XRD, SEM, SIMS and TEM in order to relate structural and compositional changes in the niobium near-surface to SRF performance. Annealing of Nb cavities with nitrogen for various durations and at various temperatures lead to a layer containing inclusions of non-superconducting Nb nitride phases, followed by unreacted Nb with an elevated N-interstitials concentration. We found that EP of the N-treated cavities removes the unwanted niobium nitride phases, confirming that performance benefits are originating from the elevated concentration of N interstitials. The role of low temperature Nb hydride precipitants in the performance limitation of N-doped cavities was evaluated by TEM temperature dependent studies. Finally, extended characterization of the original cavity cutouts from the N-doped RF tested cavity sheds some light on quenching mechanisms. PB - JACoW CY - Geneva, Switzerland SP - 223 EP - 227 KW - niobium KW - cavity KW - SRF KW - cryogenics KW - electron DA - 2015/12 PY - 2015 SN - 978-3-95450-178-6 DO - 10.18429/JACoW-SRF2015-MOPB055 UR - http://srf2015.vrws.de/papers/mopb055.pdf ER -