LHC Accelerator R&D and Upgrade Scenarios

I report the results of a CERN task force set up to investigate a possible staged upgrade of the LHC and of its injectors, with a view to increasing the machine luminosity by an order of magnitude from the nominal 10³⁴ cm^−2 s^−1 to 10³⁵ cm^−2 s^−1. Scenarios for an LHC energy upgrade by nearly a factor two have also been considered. An interesting outcome of these discussions has been a novel approach to the optimization of the collider performance, compatible with the beam-beam limit for high intensity proton bunches or long 'super-bunches'. I also sketch a new design of the interaction regions, including an alternative beam crossing scheme. To put things in perspective, I first address LHC commissioning scenarios and challenges associated with machine protection and electron cloud e ects. Finally I discuss further studies required for an LHC performance upgrade and outline an R&D programme