Abstract
For efficient antiproton production, a maximum number of protons must be concentrated within one quarter of the CERN Proton Synchrotron (PS) ring before sending the beam to the production target. With the Antiproton Collector (AC) added to the Antiproton Accumulator (AA), the bunch length has to be shorter (by about 20 ns) than before to allow bunch rotation in the AC. While a more ambitious scheme providing such a beam is being implemented, a funneling method, in which beams of two rings of the four-ring Proton Synchrotron Booster (PSB) are recombined in pairs by an RF dipole that permits longitudinal interleaving of successive bunches, has been in operation since the start-up of the AC. Preliminary experiments had shown that the PS space-charge limit had to be overcome in order to make the scheme feasible. After raising the PSB output energy from 815 MeV to 1 GeV, beams of >10/sup 13/ protons compressed into one quarter of the PS ring were achieved. Related to this development, a record proton beam for fixed-target physics was accelerated in the Super Proton Synchrotron, while beam losses in the Proton Synchrotron Booster-Proton Synchrotron Ring (PSB-PS) line were reduced. >
Highlights
Contrary to the requirement of the ‘pre-Antiproton Collector (AC)’ production beam, the proton bunches have to be short (- 15 ns) so as to profit fully from the AC debuncher cavities, which turn the short, fat p bunches emerging from the target, into Long, thin bunches
As each Proton Synchrotron Booster (PSB) bunch is slightly less than 180” long, two of them fit into a stationary Proton Synchrotron (PS) bucket
Such instabilities account for 1% out of the approximately 10% beam losses observed throughout acceleration (Fig. 7)
Summary
Antiprotons are produced by an intense beam of protons focused onto a copper target at 26 GeV/c. Contrary to the requirement of the ‘pre-AC’ production beam, the proton bunches have to be short (- 15 ns) so as to profit fully from the AC debuncher cavities, which turn the short, fat (large momentum spread) p bunches emerging from the target, into Long, thin bunches. Three ways of achieving such production beams have been used: i) five bunches, from one PSB ring, fill five PS buckets; ii) ten bunches, from two PSB rings, are accommodated, in pairs, in five PS buckets after funnelling them by means of a vertical RF dipole [2]; iii) ten bunches, from two PSB rings, are accelerated in the PS and squeezed into five buckets by quasi-adiabatic RF manipulations at 3.5 GeV/c (merging) and 26 GeV/c (compression) [3]. Raising the PSB output energy [4, 51 proves beneficial for all schemes, in particular for the funnelling method (ii) on which this paper focuses
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