Higher order mode damping for the storage ring of the Advanced Photon Source (APS)

As to higher order mode (HOM) damping for the APS, shift HOM frequency, coaxial dampers and waveguide dampers are explained. The coupled bunch instability has been studied for the storage ring of the Argonne APS. The maximum growth rate of the coupled bunch instability for each monopole and each dipole higher order mode is shown. The incremental elongation of cavities is to be done by making the cavity length different as discussed. The result of measuring the HOM damping with coaxial dampers is shown. The electric field probe damper is used in the equatorial plane of the cavity in order to eliminate the coupling of the fundamental mode frequency. The optimization has been made, and the damping property is shown. An H-loop damper with a fundamental mode frequency rejection filter was constructed and tested. Also an H-loop damper without the fundamental mode frequency rejection filter was tested. An E-probe damper and an H-loop damper were used together in the equatorial plane of the cavity. The results of measurement for a single hollow waveguide damper are shown. (K.I.)