Scientific Highlights

The growing request for sophisticated electron beam manipulation techniques for the optimization of Free Electron Lasers (FELs) or novel acceleration techniques requires enhanced beam control capabilities  and characterization. One of the most important challenge is the development of new diagnostic techniques able to characterize the longitudinal phase space of the beam, including spatial correlation terms, with a resolution in the range of a few tens of fs to sub-fs.

We have produced hard x-ray free-electron laser (FEL) radiation with unprecedented large bandwidth tunable up to 2%. The experiments have been carried out at SwissFEL, the x-ray FEL facility at the Paul Scherrer Institute in Switzerland. The bandwidth is enhanced by maximizing the energy chirp of the electron beam, which is accomplished by optimizing the compression setup. We demonstrate continuous tunability of the bandwidth with a simple method only requiring a quadrupole magnet. The generation of such broadband FEL pulses will improve the efficiency of many techniques such as x-ray crystallography and spectroscopy, opening the door to significant progress in photon science. It has already been demonstrated that the broadband pulses of SwissFEL are beneficial to enhance the performance of crystallography, and further SwissFEL users plan to exploit this large bandwidth radiation to improve the efficiency of their measurement techniques.