Maag, C.P. Roßbach, J. Zemella, J. TUP032 electron simulation undulator radiation FEL 2015 2015-12 The superconducting linac of the European XFEL Laboratory in Hamburg will produce electron bunch trains with a time structure that allow in principle the operation of an XFELO (X-ray FEL-Oscillator). The electron bunches of the European XFEL have an expected length between 2 and 180 fs (FWHM) with an expected arrival time jitter of about 30 fs (RMS). A jitter of the electron bunch arrival time leads to a detuning between the electron and photon pulse. Since an XFEL-Oscillator relies on a spatial overlap of electron and photon pulse, the influence of a lack of longitudinal overlap is studied. The simulations are performed for different bunch lengths and levels of arrival time jitter. The results of a simulation are presented where angular, transversal and arrival time jitter are taken into account simultaneously, assuming parameters expected for the European XFEL Linac.