High Energy LHC Machine Options in the LHC Tunnel

The LHC infrastructure, i.e. the tunnel itself as well as the services associated with power, cooling, ventilation, network and access (among others), represent a considerable asset, and may be considered for hosting and supporting future versions of a “LHC” beyond its present configuration and the HL-LHC upgrade. In this chapter, we provide an overview of possible machine parameters and energy reach of a future higher-energy hadron collider in the LHC tunnel. We sketch four options with arc dipole magnetic fields in the range of 12 T to 24 T, each of which represents a well-defined discrete step in future accelerator magnet technology. We discuss the corresponding main machine and magnet parameters, and describe readiness, challenges and opportunities.