SRF for Future Circular Colliders

The future circular colliders (FCC) will require superconducting RF systems for the proton-proton, electron-positron and lepton-hadron modes of the collider operation. The SCRF systems will accelerate the protons beams to 50 TeV and the lepton beams from 45.5 to 175 GeV in a staged approach with a possible 60 GeV energy recovery linac for the lepton-hadron to option as an intermediate step. The expected stored beam currents in some modes exceed 1 A with very short bunch lengths. A first conceptual design of the FCC RF system is proposed along with highlights of specfic R&D topics to reach the design performance. Challenges related to RF structure design, intensity limitations due to beam loading, RF powering and higher order modes are addressed. Synergies between the different collider modes and the present LHC are identified.