New RF Exercises Envisaged in the CERN-PS for the Antiprotons Production Beam of the ACOL Machine

The new antiproton collector machine (ACOL)[1] presently under development at CERN, requires the highest possible proton intensity (more than 1013 protons per pulse) in one quarter of the PS circumference, and a guaranteed bunching factor, for its p production beam: possibly less than 25ns bunches, 105 ns apart. The present 26 GeV longitudinal merging technique [2], cannot meet these specifications, so that new quasi-adiabatic processes had to be imagined [3]. First, before transition energy, a "bunch pair merging" operation reduces from 10 to 5 the number of bunches, with a moderate blow-up, by slowly bunching the beam on half the initial harmonic number. Then, on the high energy flat top, the length of circumference occupied by the bunches is halved, by a technique tentatively named "bunch batch compression". This is basically a slow increase of the RF harmonic number seen by the beam, implemented by operating part of the existing cavities stepwise at increasing harmonic numbers (10, 12, 14, 16, 18 and finally 20). Computer outputs are presented, together with machine experiment results.