Measurement and tuning of beam parameters in the heavy ion storage ring ESR

The ESR is a cooler ring with large momentum acceptance Δp/p0 of about 2.5 %. The authors bound the Q variation in both transverse planes to less than 0.02, thereby allowing for rf stacking over the large momentum range without crossing resonances up to the fifth order. Tunes are measured very accurately in cooled beams via the BTF technique. The field quality in the large dipole magnets was improved by the excitation of pole face windings, leading to an improved linearization of natural chromaticity. Linear coupling due to large solenoid fields in the electron cooler could be detected and was then corrected by auxiliary solenoids installed in the vicinity of the cooler. Momentum compaction was determined by comparison of the cooler voltage and the measured revolution frequency. The transverse beam dimensions are measured by means of position sensitive detection of ions that captured an electron in the cooler