The influence of RF noise on the lifetime of bunched proton beams

In a proton-antiproton storage ring like the SPS (panti p project) RF noise limits the lifetime of the bunches. The equations describing the r.m.s. increase of individual particle oscillation amplitude are derived for phase and amplitude excitation. The non-linearity of the phase oscillation, although small, in the long run transforms the coherent noise excitation into a random excitation of each particle. Computer simulations have confirmed this picture which leads to a macroscopic description of the phenomenon by a diffusion equation. The various RF noise sources in the SPS machine are analyzed and their relative effects compared. Careful choice of the loop parameters minimizes the RF noise influence. Finally, some experimental results obtained on the SPS machine are reported and compared with theory. (Auth.)