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TY - CONF AU - Martinello, M. AU - Aderhold, S. AU - Chandrasekaran, S.K. AU - Checchin, M. AU - Grassellino, A. AU - Melnychuk, O.S. AU - Posen, S. AU - Romanenko, A. AU - Sergatskov, D.A. ED - Schaa, Volker RW ED - He, Yuan ED - Li, Lu ED - Zhao, Ning TI - Advancement in the Understanding of the Field and Frequency Dependent Microwave Surface Resistance of Niobium J2 - Proc. of SRF2017, Lanzhou, China, July 17-21, 2017 C1 - Lanzhou, China T2 - International Conference on RF Superconductivity T3 - 18 LA - english AB - The radio-frequency surface resistance of niobium resonators is incredibly reduced when nitrogen impurities are dissolved as interstitial in the material, conferring ultra-high Q-factors at medium values of accelerating field. This effect has been observed in both high and low temperature nitrogen treatments. As a matter of fact, the peculiar anti Q-slope observed in nitrogen doped cavities, i.e. the decreasing of the Q-factor with the increasing of the radio-frequency field, come from the decreasing of the BCS surface resistance component as a function of the field. Such peculiar behavior has been considered consequence of the interstitial nitrogen present in the niobium lattice after the doping treatment. The study here presented show the field dependence of the BCS surface resistance surface of cavities with different resonant frequencies, such as: 650 MHz, 1.3 GHz, 2.6 GHz and 3.9 GHz, and processed with different state-of-the-art surface treatments. These findings show for the first time that the anti Q-slope might be seen at high frequency even for clean Niobium cavities, revealing useful suggestion on the physics underneath the anti Q-slope effect. PB - JACoW CP - Geneva, Switzerland SP - 364 EP - 367 KW - ion KW - cavity KW - ECR KW - niobium KW - resonance DA - 2018/01 PY - 2018 SN - 978-3-95450-191-5 DO - 10.18429/JACoW-SRF2017-TUYAA02 UR - http://jacow.org/srf2017/papers/tuyaa02.pdf ER -