Availability and critical systems of the Future Circular Electron–Positron Collider

The Future Circular Electron–Positron Collider (FCC-ee) is planned to be the world’s largest particle collider and a precision instrument to study the heaviest known particles. Achieving substantial physics results requires producing high amounts of integrated luminosity, which calls for sufficient machine availability. Although the operational availability of lepton colliders has been high, the increased complexity of the new infrastructure creates a challenge to maintain this. At the early stage of research, the main activity of an availability study should be to identify the causes that potentially have the most significant effect on downtime. This paper identifies critical systems of the FCC-ee based on available failure data. The paper further presents an operation model for the FCC-ee that can be used for assessing the effect of unavailability on overall performance. Special attention is given to systems with built-in redundancies as this design concept has been proven to increase accelerator availability.