Simulation studies of 6 nm free electron laser at the TESLA test facility starting from noise

The paper presents simulation results of Self-Amplified Spontaneous Emission (SASE) FEL at the TESLA Test Facility (TTF) at DESY. One-dimensional, time-dependent program package FEL1D was used for simulations. When simulating linear mode of operation, we have used actual number of electrons in the beam, N ⋍ 6 × 109, to calculate initial shot noise conditions at the undulator entrance. It was found that there is good agreement between simulation and analytical results. We also performed calculations of autocorrelation functions of the first and the second order, temporal and spectral characteristics of the output radiation of TTF FEL operating in linear and nonlinear SASE modes.