Calculation of the transverse wake function of a highly damped periodic structure

Higher order wakefields in the CLIC multibunch accelerating structure (called the TDS, Tapered Damped Structure) are suppressed through a combination of heavy damping and moderate detuning. A new approach to computing the transverse wake function of such a highly damped periodic structure is presented. The driving bunch produces fields that travel with the propagation characteristics (given by the frequency dependent complex wave number) of the damped periodic waveguide. The fields in the structure are calculated by integrating the propagated waves excited by the Fourier decomposed driving bunch. Strong damping produces a propagated wave integral that converges within a few cells. Computational and experimental techniques to obtain wave numbers are described