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TY - CONF AU - Martinello, M. AU - Checchin, M. AU - Grassellino, A. AU - Melnychuk, O.S. AU - Posen, S. AU - Romanenko, A. AU - Sergatskov, D.A. AU - Zasadzinski, J. ED - Yamazaki, Yoshishige ED - Facco, Alberto ED - McCausey, Amy ED - Schaa, Volker RW TI - Impurity Content Optimization to Maximize Q-Factors of Superconducting Resonators J2 - Proc. of LINAC2016, East Lansing, MI, USA, 25-30 September 2016 C1 - East Lansing, MI, USA T2 - Linear Accelerator Conference T3 - 28 LA - english AB - Quality factor of superconducting radio-frequency (SRF) cavities is degraded whenever magnetic flux is trapped in the cavity walls during the cooldown. In this contribution we study how the trapped flux sensitivity, defined as the trapped flux surface resistance normalized for the amount of trapped flux, depends on the mean free path. A systematic study of a variety of 1.3 GHz cavities with different surface treatments (EP, 120 C bake and different N-doping) is carried out. A bell shaped trend appears for the range of mean free path studied. Over-doped cavities fall at the maximum of this curve defining the largest values of sensitivity. In addition, we have studied the trend of the BCS surface resistance contribution as a function of mean free path, showing that N-doped cavities follow close to the theoretical minimum. Adding these results together we show that the 2/6 N-doping treatment gives the highest Q-factor values at 2 K and 16 MV/m, as long as the magnetic field fully trapped during the cavity cooldown is lower than 10 mG. PB - JACoW CP - Geneva, Switzerland SP - 515 EP - 518 KW - cavity KW - SRF KW - factory KW - niobium KW - superconductivity DA - 2017/05 PY - 2017 SN - 978-3-95450-169-4 DO - 10.18429/JACoW-LINAC2016-TUPLR023 UR - http://jacow.org/linac2016/papers/tuplr023.pdf ER -