Advanced Photon Source booster synchrotron low-emittance lattice commissioning results

Recent efforts at the APS have focused on reducing beam loss during storage ring (SR) injection to minimize radiation damage to the APS undulators. Reducing beam loss at injection is particularly important during top-up operation where injection occurs once every two minutes. One way to potentially improve injection efficiency is to simply reduce the emittance of the beam from the APS booster, thereby allowing the beam to be brought closer to the injection septum. Recently several low-emittance operating modes for the APS booster have been studied. The emittance is lowered from the standard value by increasing the horizontal tune in stages. The vertical tune is simultaneously decreased to minimize the required defocusing sextupole strength for chromaticity correction. Calculations indicate that up to 29% reduction in emittance is possible-a result that has been achieved in studies. A lattice with emittance 17% lower than the standard lattice has been thoroughly commissioned and has been used for routine APS top-up operation since July 2002. Results of beam measurements and comparison to calculations for various low-emittance lattices are reported in this paper.