Synchrotron frequency spread independence of bunched-beam stochastic cooling at the Fermilab Recycler

D Broemmelsiek,A Burov,D Neuffer,S Nagaitsev

doi:10.1103/physrevstab.8.124404

Abstract

It is generally accepted that longitudinal stochastic cooling of bunched beams is not possible without a synchrotron frequency spread. Experiments in the Recycler storage ring (Fermilab) 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 {approx} 100%). A possible explanation is that, at Recycler parameters, diffusion processes are sufficient to provide particle mixing.

Highlights

Bunched-beam stochastic cooling has been experimentally demonstrated in ICE (CERN) and in the Antiproton Accumulator (Fermilab) [1,2]
In this paper we suggest that there is a mechanism, effective for the Recycler ring, that makes stochastic cooling insensitive to the synchrotron frequency spread
The synchrotron frequency spread can be insignificant for bunched-beam longitudinal stochastic cooling

Summary

INTRODUCTION

Bunched-beam stochastic cooling has been experimentally demonstrated in ICE (CERN) and in the Antiproton Accumulator (Fermilab) [1,2]. This method was not used in operations. In ICE, only 15 000 antiprotons were successfully cooled in the bunched mode. The synchrotron frequency spread is considered to be an essential parameter for bunched-beam stochastic cooling [4]. For an ideal parabolic potential well, there is no synchrotron frequency spread and cooling should not be possible. This conclusion sharply disagrees with recent observations at the Fermilab Recycler antiproton storage ring

OBSERVATIONS

DIFFUSIVE RANDOMIZATION

CONCLUSIONS