Stacking of 3 GeV Antiprotons with a Moving Barrier Bucket Method at the RESR

At FAIR 3 GeV antiprotons are to be accumulated in the RESR up to an intensity of 10. If the CR is equipped for full performance, every 5 s a batch of 10 antiprotons will be transferred to the RESR. The antiprotons are precooled to a momentum spread of 0.1% and an emittance of 5 mm mrad. As an option, azimuthal separation of injected and stacked beams with barrier buckets was studied. The process was simulated for 1000 injections. The movement of the barrier pulses proceeds as follows (Fig. 1). After injection one of the barrier pulses (P2) is adiabatically moved to P1 within 200 ms. The energy spread of the particles confined between the two pulses grows as the distance of the pulses shrinks. Eventually ∆E becomes so large that the particles overflow the barriers and move into the accumulation area. When P2 reaches P1, all injected particles have overflown into the accumulation area and the barrier pulses are turned off. Now the beam is coasting with two streams separated by ± 4 MeV which corresponds to a barrier bucket height of 3 kV. Then stochastic cooling is applied. After 5 s stochastic cooling is stopped and P1 and P2 are adiabatically turned on at the same azimuth. P2 moves to the original position. The barrier pulses compress the cooled/stacked beam into the accumulation area and the injection area is empty. A new batch is injected. This process will be repeated according to the cooling time in CR.