Comparison of calculated, measured, and beam sampled impedances of a higher-order-mode-damped rf cavity

Abstract

Accelerating structures with damped higher-order modes (HOMs) have been the focus of many studies over the past decade. This report compares the results of numerical simulations of damping of HOMs using a new calculation technique applied to the case of the PEP-II rf cavity. We compare these results using this technique, which was not yet developed at the time of the original design, with bench and beam-based measurements of the HOM damping. These results show agreement with bench measurements of the shunt impedances of the strongest HOMs as well as measurements of the beam-induced signals on cavities installed in PEP-II.