The Short-range Transverse Wake Function for Tesla Accelerating Structure

The operation of a Free Electron Laser in TESLA project requires very short bunches. It results in a very long interaction length between the bunch and the wakefields. From this fact severe problems for computer simulations arise. The longitudinal case was recently studied intensively by Novokhatski et al. [1]. In this paper we study mainly the transverse forces. Using a recently developed time domain numerical approach, we calculate the short-range transverse wakefields of the TESLA linac accelerating structure. Wake fields in a TESLA accelerating cryomodule and corresponding integral parameters are given for bunches of different length. We also consider behaviour of transverse wake potential in a periodic array of cavities and compare it with wake potential of the TESLA quasi-periodic structure. The numerical results are compared with analytical estimations.