In collisions of high energy charged particles the bremsstrahlung process takes place over macroscopic lateral distances, or at extremely large impact parameters. As a result, bremsstrahlung becomes suppressed in high energy collisions of beams with small lateral sizes, as was observed at VEPP-4, HERA, LEP and KEKB. A good understanding of bremsstrahlung at colliders is important as it might become the limiting factor for the electron and positron beam lifetimes.

In this talk, the origin of beam-size effects will be described first, and be followed by a comprehensive discussion of their impact at future colliders – in particular, at the electron-positron Future Circular Collider (FCC-ee).