An SLC-type $e^{+}e^{-}/\gamma\gamma$ facility at a Future Circular Collider

It is proposed to place the arcs of an SLC-type facility inside the tunnel of a Future Circular Collider (FCC). Accelerated by a linear accelerator (linac), electron and positron beams would traverse the bending arcs in opposite directions and collide at centre-of-mass energies considerably exceeding those attainable at circular $e^{+}e^{-}$ colliders. The proposed SLC-type facility would have the same luminosity as a conventional two-linac $e^{+}e^{-}$ collider. Using an optical free-electron laser, the facility could be converted into a $\gamma\gamma$ collider. A superconducting L-band linac at the proposed facility may form a part of the injector chain for a 100-TeV proton collider in the FCC tunnel. The whole accelerator complex would serve as a source of $e^{+}e^{-}$, $\gamma\gamma$, $pp$ and $ep$ interactions. The L-band linac could also be used to produce high-intensity neutrino, kaon and muon beams for fixed-target experiments, as well as X-ray free-electron laser (XFEL) photons for applications in material science and medicine.