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 t^-3/2 and thus is dominant at sufficiently large values of t. 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