Time and Momentum Exchange for Production and Collection of Intense Antiproton Beams at Fermilab

Antiprotons for the Fermilab pp colliding beam project are accumulated by rf stacking of successive 8 GeV antiproton batches in a storage ring using stochastic cooling to reduce both transverse and longitudinal emittance. The rate of accumulation is increased 15-fold by interchange of bunch length and momentum spread of the antiproton bunches in a special purpose debuncher ring. Tightly bunched antiprotons are produced at the target by 120 GeV protons from the Main Ring. From 2.5×10¹² protons every 2 seconds the debuncher receives 7×10⁷ antiprotons within a momentum bite Δp/p=3%. These antiprotons are injected into mismatched stationary rf buckets in the debuncher so that synchrotron oscillation produces bunch rotation. After 90° of rotation followed by adiabatic debunching, the narrow time spread has been converted into a momentum spread Δp/p=.2%. We describe the rf technique used to shorten the bunches of the primary proton beam in the Main Ring and report test results. We describe the complementary procedures to be used in the Debuncher and demonstrate the expected reduction of the momentum spread by particle tracking simulation.