Modern projects of accelerators for High Energy Physics and FEL demand operation of the SRF cavities in CW regime. In this situation, low cryogenic losses are essential. The N-doping technique, that allows to achieve high Q0 at medium field, is described. The current implementation of this technique for the LCLS-II cavity production, allow us to present how ultra-high Q-factors can be maintained from the vertical to the horizontal test to the cryomodule test. In particular, efficient cooling and optimization of shielding design will be discussed to address potential Q degradation from the remnant magnetic fields in the cryomodule. The talk will also present recent development on how it is possible to obtain high-Q at high gradient, with the recently discovered N-infusion treatment.
Fermi National Accelerator Laboratory