Speaker
Description
One goal of the recently proposed SwissFEL facility upgrade
(SwissFELplus) is to enable the generation of longitudinally coherent
FEL pulses across a large photon energy range at the the hard X-ray
beamline Aramis. We consider to implement the Forward Bragg Diffraction self-seeding approach, where a diamond crystal in transmission geometry filters the SASE signal generated in the first undulator section, and where the second undulator section further amplifies the coherent seed. We performed calculations and ideal beam simulations to determine which crystal cuts and Bragg reflections provide the best longitudinal coherence for all photon energies between 3 and 14 keV. According to simulations, a high degree of longitudinal coherence is possible for photon energies above 6 keV, whereas the coherence for lower photon energies suffers from an increased FBD bandwidth. Furthermore, we discuss the implementation of advanced modes, among them the fresh bunch self-seeding to control the self-seeded FEL pulse duration and a scheme to achieve phase-locked ultra-short FEL pulse sequences.
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