Observation of nonlinear resonances in the advanced light source

Observations of nonlinear resonances in the Advanced Light Source have been made by scanning betatron tunes and observing count rates in a beam-loss radiation monitor placed down stream of a beam scraper. The authors have found that it is possible to see structural resonances which are unallowed as well as those which are allowed by the ring's natural 12-fold symmetry. By systematically breaking the amount of symmetry they see that the widths of the unallowed resonances grow while the widths of the allowed resonances do not. In this paper the authors briefly discuss the importance of symmetry and its effect on resonances in the design of the ALS. Next they describe their experimental setup and discuss the performance of the beam loss monitor which they used to view the resonances. They then present scans of the tune space where one can see the presence of the structural resonances and their evolution when the lattice symmetry is systematically broken