Speaker
Description
Modern free electron laser facilities can now produce x-ray pulses as short as hundreds of attoseconds. Optimal utilization of these short pulses for ultra-fast science requires the accurate characterization of the pulse durations which there are promising methods to achieve. However, these are still developing experimental techniques, far from being routine procedure. In the meantime, the most reliable information about the x-rays is available in the spectra and pulse energies. We show that while this information is insufficient to draw any conclusions about a single shot, the statistics from a large dataset are enough to determine the average length of the electron bunches. FEL theory then determines the statistics of the x-ray pulse durations, which can be compared to the statistics obtained from direct time-resolving measurement. On the way, we extend the analytical frameworks put in place by (Bonifacio, Saldin?), generalizing to finite length, non-uniform current profiles. Using a Green function for the linearized 1D FEL model and treating shot noise as a random signal we derive integral expressions for some key statistical observables. The analytical is approach compared to 1D nonlinear simulations, showing good agreement until saturation sets in.
Funding Agency
VG acknowledges funding from Swedish Research Council (VR), 2022-03983
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