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TY - CONF AU - Gonnella, D. AU - Gruber, T. AU - Kaufman, J.J. AU - Koufalis, P.N. AU - Liepe, M. AU - Maniscalco, J.T. ED - Yamazaki, Yoshishige ED - Facco, Alberto ED - McCausey, Amy ED - Schaa, Volker RW TI - Optimal Nitrogen Doping Level to Reach High Q0 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 - New continuous wave (CW) accelerators such as LCLS-II at SLAC require many SRF cavities operating in the medium field region at unprecedented high Q. In order to achieve this demanding goal, nitrogen-doping of the SRF cavities will be used. Nitrogen-doping has been shown to affect the BCS resistance both by a lowering of Rbcs at low fields and by the introduction of an anti-Q slope which enables the Q to continue increasing as the RF field is increased. The exact strength of this anti-Q slope is heavily dependent on the doping recipe and specifically the mean free path of the RF penetration layer of the doped cavities. In addition to its effect on Rbcs, the mean free path affects the amount of residual resistance obtained due to trapped magnetic flux. We have analyzed nine cavities prepared with different levels of nitrogen-doping to understand how BCS and residual resistance are affected by changes in the mean free path. Here we present a model based on these experimental results to predict the optimal doping level to reach the maximum Q at 16 MV/m based on the ambient magnetic field conditions. We find that if the cavities can be cooled with small amounts of trapped flux, moderate nitrogen-doping is better, while if they will have large amounts of trapped flux, lighter dopings should be used. PB - JACoW CP - Geneva, Switzerland SP - 523 EP - 526 KW - cavity KW - cryomodule KW - SRF KW - niobium KW - electron DA - 2017/05 PY - 2017 SN - 978-3-95450-169-4 DO - 10.18429/JACoW-LINAC2016-TUPLR025 UR - http://jacow.org/linac2016/papers/tuplr025.pdf ER -