Future Circular Collider Feasibility Study Report. Volume 2: Accelerators, Technical Infrastructure and Safety

In response to the 2020 Update of the European Strategy for Particle Physics, the Future Circular Collider (FCC) Feasibility Study was launched as an international collaboration hosted by CERN. The FCC ‘integrated programme’, described in this report, in a first stage consists of a highest-luminosity electron-positron collider, FCC-ee, serving as Higgs, top and electroweak factory, with a subsequent energy-frontier proton-proton collider, FCC-hh, as the second stage. The FCC-ee is designed to operate at four baseline centre-of-mass energies, corresponding to the Z pole, the WW pair production threshold, the ZH production peak, and the top/anti-top production threshold, always delivering the highest possible luminosities to four experiments. Over a span of 15 years, FCC-ee will produce more than 6 trillion Z bosons, 200 million WW pairs, almost 3 million Higgs bosons, and 2 million top anti-top pairs. On the Z pole and at the WW pair threshold, the collision energy can be precisely calibrated by frequent resonant depolarisation of pilot bunches. The sequence of operation modes and beam energies is flexible, between the Z, WW and ZH substages. The hadron collider, FCC-hh, will operate at a centre-of-mass energy of about 85 TeV, extending the energy frontier by almost an order of magnitude compared with the LHC, and providing integrated luminosity 5-10 times higher than that of the upcoming High-Luminosity LHC. The mass reach for direct discovery at the FCC-hh amounts to several tens of TeV. The FCC-hh can also accommodate ion-ion, ion-hadron, and lepton-hadron collision options. This second volume of the Feasibility Study Report covers the complete design of the FCC-ee collider, the operation and staging concepts, the design of the full-energy booster and of the FCC-ee injector complex, the accelerator technologies required, safety concepts, and technical infrastructures, along with the design of the FCC-hh hadron collider, the associated high-field magnet developments, hadron injector options, and FCC-hh key technical systems.