Analysis of single-spike FEL visible radiation from three-dimensional and realistic beams

An analysis of the single-spike FEL radiation in the visible range starting from noise is presented, taking into account realistic characteristics of the electron beam such as emittance and energy spread. A parametric study of the power emitted respect to emittance and energy spread is carried out and the influence of these quantity on the production of a single-spike radiation pulse is shown. Furthermore, we propose some examples of start-to-end simulations in the specific case of the SPARC apparatus from the photocathode to the end of the undulator, describing a possible experiment aimed at generating sub-picosecond light pulses and exploring the single-spike regime.