Reduction of nonlinear resonance excitation from insertion devices in the ALS

Theoretical studies of Lawrence Berkeley Laboratory's Advanced Light Source (ALS) storage ring predict strong field insertion devices will break the rings symmetry, increasing resonance excitation that may reduce the dynamic aperture and thus the beam lifetime. The authors have embarked on an experimental program to study the strength of nonlinear resonance excitation in the ALS when insertion devices are present. They observe an enhancement in the resonance excitation of a third-order resonance when the gap of the insertion device is narrowed. They also find that it is possible to suppress this resonance by detuning two quadruples on either side of the insertion device. The results of this study are presented in this paper