Wakefield excitation in multimode structures by a train of electron bunches

We discuss wakefield excitation and propagation in dielectric structures, particularly concentrating on the case of multiple drive beam excitation in multimoded structures. We emphasize calculations of the energy loss of the drive beam train, the amplitude of the wakefield, and the relationship between power flow and stored energy in the dielectric wakefield device. We show that for a collinear multimode structure the amplitude of the wakefield generated by a bunch train is less than or equal to the wakefield generated by a single bunch of the same total charge. Furthermore, the transformer ratio R is shown to be always less than 2, even in the multiple drive beam case.