Calculation of coherent synchrotron radiation in the TTF-FEL bunch compressor magnet chicanes

The bunch compression system in the TTF-FEL decreases the bunch length in order to achieve the high peak currents needed for the SASE FEL process. Along the curved trajectories in the bunch compressor magnet chicanes, these short bunches will start to radiate coherently. In this paper, a numerical calculation of the characteristics of this radiation is presented. One-dimensional bunch models are not sufficient for near-field effects, in particular, cannot completely explain the power flow to the EM field, but they can be used to estimate the radiation in the far region. For the calculation of the power flow, in presence of shielding by horizontal conducting planes, and of the far field, a two-dimensional bunch with time-dependent shape was simulated.