Longitudinal limitations in the PS complex for the generation of the LHC proton Beam

The nominal operating scheme for feeding LHC with protons [1] makes use of the PS injectors complex. Many new manipulations are used in the longitudinal phase plane. The radio-frequency systems of the PS Booster (PSB) operate on harmonics 1 and 2, harmonic 10 being used for controlled emittance blow-up during acceleration. The PS accelerates on harmonics 8 and 16. Debunching takes place at 26 GeV followed by rebunching on harmonic 84 (40 MHz) and bunch compression before ejection to the SPS. Although certainly capable of providing the nominal type of beam, these processes are marginal in terms of performance and have not all been experimentally demonstrated. These limitations are described together with possible improvements. New directions of investigation including the SPS are encouraged.