Dresden 2011 – wissenschaftliches Programm
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A: Fachverband Atomphysik
A 1: Interaction with VUV and X-ray light (FEL) I
A 1.7: Vortrag
Montag, 14. März 2011, 12:45–13:00, BAR 205
Statistical modeling of FEL pulse shapes using a partial-coherence colored-noise approach — •Thomas Pfeifer1, Yuhai Jiang1, Stefan Düsterer2, Robert Moshammer1 und Joachim Ullrich1 — 1Max-Planck Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany — 2Deutsches Elektronen-Synchrotron (DESY), Notkestrasse 85, 22605 Hamburg, Germany
Most free-electron lasers (FELs) producing intense pulses in the extreme ultraviolet (XUV) and x-ray spectral regions are currently operated in the self-amplified spontaneous emission (SASE) mode. Under these conditions, light emission starts from (quantum) noise and amplification of a light pulse occurs by a relativistic electron bunch oscillating in an undulator. This noisy origin of SASE FEL pulses results in dramatic fluctuations of pulse energy and pulse shape from shot to shot. Here, we present a simple numerical approach to model the pulse-shape statistics of such FEL pulses, even without specific knowledge of technical machine parameters such as electron bunch energy characteristics or undulator geometry. Only the measured average spectral shape and average pulse duration are required to produce sets of FEL pulse shapes for the exponential-growth (``linear'') regime that fulfill statistical properties required by FEL theory. The modeled single-shot spectral shapes agree well with measured single-shot spectra. This method allows to include statistical variations of FEL pulse shapes into simulations of nonlinear FEL--matter interaction in pump--probe experiments. It will be shown that agreement of simulation results and experimental data is only achieved when pulse-shape statistics are accounted for.