CERC -- Circular $e^+e^-$ Collider using Energy-Recovery Linac

We present a Circular Energy Recovery Collider (CERC) as an alternative approach for a high-energy high-luminosity electron-positron collider to current designs for high-energy electron-positron colliders either based on two storage rings with 100 km circumference or two large linear accelerators. Using Energy Recovery Linacs (ERL) located in the same-size 100 km tunnel would allow a large reduction of the beam energy losses, and therefore a reduction of the power consumption, while providing higher luminosity. It also opens a path for extending the center-of-mass (CM) energy to 500 GeV, which would enable double-Higgs production, and even to 600 GeV for production and measurements of the top Yukawa coupling. Furthermore, this approach would allow recycling of not only the energy but also of the particles. This feature opens the possibility for colliding fully polarized electron and positron beams.