The FCC-ee vacuum system, from conceptual to prototyping

Abstract The FCC-ee is a very challenging accelerator project from the point of view vacuum. Apart sheer size machine, twin-ring 100 km circumference, vacuum system design must be capable dealing with low-energy 45.6 GeV, high-current version machine (the Z -pole) as well higher energy, lower current versions. main difficulty related to much different synchrotron radiation (SR) spectra -pole vs other energies, in particular ttbar at 182.5 GeV. critical energy SR spectrum 19.5 keV, while exceeds 1.2 MeV. It particularly terms shielding beryllium chamber detectors, for Machine Detector Interface (MDI) area. We discuss evolution arc sections, and some new ideas on NEG-coating, absorbers, pumping system, aim build prototypes soon, framework FCC Innovation Study program. hardware depends choices made magnets, required high-energy generated by circulating beam interacting residual gas interaction intense fans photon. There also an important collaboration engineering integration tunnel, considering full-energy booster injector, which not detailed here. briefly describe raytracing montecarlo modelling efforts carried out MDI area, its configuration.