Integrated modeling of the TESLA X-ray FEL

The TESLA linear collider incorporates an X-ray SASE FEL which demands challenging electron beam parameters (typically transverse emittance of 1.6 mm-mrd and peak current of 5 kA). For a realistic electron beam distribution at the entrance of the undulator, tracking has to be done from the cathode through the whole accelerator. Non-Gaussian beam profiles have to be taken into account as well as nonlinear effects such as space-charge, coherent synchrotron radiation field and wake fields. We have done this with several codes: Astra, for the low energy part (<100 MeV), TraFiC⁴ for the bunch compressor chicanes where CSR influences the particle trajectories and the code Elegant for the 6D tracking with wake fields in the linacs and transport lines. The so-generated electron phase space density at the undulator entrance can then passed to SASE FEL simulation codes. Results of this integrated modeling is discussed