Batch compression to 50 ns spacing at PS flat-top

The bunch spacing in the injector chain has a direct impact on the total number of bunches in the LHC and hence on its integrated luminosity. The baseline scheme for lead ion beams within the LHC Injector Upgrade (LIU) project fore- sees the transfer of multiple batches of four bunches spaced by 100 ns from the PS to the SPS. The bunch spacing will then be reduced by momentum slip-stacking from 100 ns to 50 ns. Studies have been performed in view of alternatively producing 50 ns spacing directly at extraction from the PS, with the aim of demonstrating a batch compression-like RF manipulation to approach two bunches. Additionally, the proof-of principle tests allow to define the requirements for an additional RF system in the PS for the batch compression of four bunches to 50 ns spacing. Together with slip stacking in the SPS, this scheme would yield 25 ns bunch spacing with ions in the LHC.