Roadmap towards High Accelerator Availability for the CERN HL-LHC Era

High Luminosity-LHC is the future upgrade of the LHC that aims at delivering an integrated luminosity of 3000 fb-1 over about 10 years of operation, starting from 2025. Significant modifications will be implemented to accelerator systems, including new superconducting magnets, crab cavities, superconducting links, new collimators and absorbers based on advanced materials and design and additional cryo-plants. Due to the limit imposed by the number of simultaneous events at the experiments (pile-up) on peak luminosity, the latter will be levelled to 5*10³⁴ cm⁻²s⁻¹. The target integrated luminosity can only be achieved with a significant increase of the total available time for beam collisions compared to the 2012 LHC run, despite a beam current that is planned to double the nominal 0.58 A. Therefore one of the key figures of merit to take into account for system upgrades and new designs is their impact on the accelerator availability. In this paper the main factors affecting LHC availability will be discussed and predictions on the impact of future system upgrades on integrated luminosity presented. Requirements in terms of the maximum allowed number of dumps for the main contributing systems to LHC unavailability will be derived.