Division of accelerators, cryogenics and magnetism

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.