It is generally accepted that longitudinal stochastic cooling of bunched beams is not possible without a synchrotron frequency spread. Experiments in the Fermilab Recycler storage ring demonstrate the opposite: with an antiproton bunch in a parabolic potential well (no synchrotron frequency spread), the cooling was almost as efficient as in a trapezoidal potential well (with a relative synchrotron frequency spread of ). A possible explanation is that, at Recycler parameters, diffusion processes are sufficient to provide particle mixing.
