Momentum slip-stacking in CERN SPS for the ion beams

The LHC Injectors Upgrade (LIU) project at CERN aims at doubling the total intensity of the lead ion beam for the High-Luminosity (HL) LHC. Achieving this goal requires using momentum slip-stacking in the SPS, the LHC injector. Slip-stacking will be applied on an intermediate energy plateau to interleave two batches, reducing the bunch spacing from 100 ns to 50 ns and thus increasing the total number of bunches injected into the LHC. Realistic macro-particle simulations, with the present SPS impedance model are used to study and design this complicated beam manipulation. Slip-stacking can be tested experimentally only after the upgrade of the SPS 200 MHz RF system, in 2021. Preliminary, slip-stacking related beam measurements were performed at the end of 2018. In this paper both macro-particle simulations and beam measurements are reported with emphasis given on optimisation of the process, crucial to achieve the required HL-LHC parameters (bunch lengths, beam losses).