Application of the GSM method and TD computation of the long range wake in linear accelerator structures

For a proper design of linear colliders it is important to know the transverse long range wake which can either be computed directly in TD or alternatively from the corresponding higher order resonant modes. In this contribution, the resonant modes of the first, third and sixth dipole passband of the 180-cell accelerating structure used for the S-band linear collider at DESY have been analyzed using an accurate and numerically efficient generalized scattering matrix (GSM) method. Furthermore, the MAFIA program package has been applied to calculate the wake function in time domain (TD). The agreement of both methods turns out to be excellent. From the results one can predict that the sixth dipole passband significantly contributes to the transverse wakefield