2010/01/20 by Gianluca Geloni, Geloni, Gianluca, Vitali Kocharyan +3
Physics and Astronomy · #Accelerator Physics (physics.acc-ph) #FOS: Physical sciences #physics.acc-ph
paper · pdf · doi:10.48550/arxiv.1001.3544
arxiv created 2010/01/20 · arxiv updated 2010/02/26
In this paper we describe a measurement technique capable of resolving femtosecond X-ray pulses from XFEL facilities. Since these ultrashort pulses are themselves the shortest event available, our measurement strategy is to let the X-ray pulse sample itself. Our method relies on the application of a "fresh" bunch technique, which allows for the production of a seeded X-ray pulse with a variable delay between seed and electron bunch. The shot-to-shot averaged energy per pulse is recorded. It turns out that one actually measures the autocorrelation function of the X-ray pulse, which is related in a simple way to the actual pulse width. For implementation of the proposed technique, it is sufficient to substitute a single undulator segment with a short magnetic chicane. The focusing system of the undulator remains untouched, and the installation does not perturb the baseline mode of operation. We present a feasibility study and we make exemplifications with typical parameters of an X-ray FEL.