Persistent Wakefields Associated with Waveguide Damping of Higher Order Modes*

By means of an analytic model and numerical simulations we demonstrate that the wake of a waveguide damped cavity contains a persistent component which decays as tm3f2 and thus is dominant at sufficiently large values oft. Because there are scenarios for which the effect gives rise to unacceptable beam instability, it cannot be ignored, but it seems likely that such an outcome can be avoided with proper design.