Scenarios for upgrading the LHC injectors

The presence of a powerful accelerator complex that could serve as injector has been instrumental in the decision to build the LHC at CERN. This existing complex has now confirmed its capability, having demonstrated that it is able to deliver beam with the nominal characteristics as well as numerous other types of beams which will be essential for tuning-in, commissioning and operating the future collider for physics in its first years. However it is also clear that the existing LHC injectors will not be able to deliver beam with the ultimate characteristics and that they suffer from reliability problems due to their age. An analysis has therefore been done by the working group in charge of "Proton Accelerators of the Future" (PAF) to determine a logical evolution of the accelerator complex, considering the needs of LHC and of the other potential future physics experiments at CERN. As a result, scenarios for a staged upgrade have been proposed, involving the progressive replacement of all the low energy accelerators