Some remarks on the location of higher order modes in tapered accelerating structures with the use of a coupled oscillator model

This work is an attempt to overcome the difficulties which electrodynamical codes meet when calculating of RF characteristics of long accelerating structures consisting of cells of different geometry. The model of coupled oscillators (a kind of network model) seems to be an useful instrument in this case and may at least improve our understanding of higher order mode behavior in long tapered structures. The parameters of the model of multiple coupled oscillators (MCO) were determined on the basis of MAFIA calculations of the high order mode characteristics. The frequency spectra, field distribution along the structure and normalized loss factor for the first band of HOMs in an S-band accelerating section have been calculated. A comparison of the results of MCO calculations with the experimental data and the results of certain MAFIA calculations are presented