Speakers
Description
X-ray free electron lasers (XFELs) are modern photon sources which generate widely tuneable, high-brilliance, ultrafast laser pulses. External seeding schemes transfer the coherence properties of optical laser sources to the FEL pulses, while performing a photon energy upconversion. In this contribution, we show the latest external seeding results from the soft X-ray beamline at SwissFEL, Athos. With a 200 pC, 3 GeV electron beam and two ultraviolet (266 nm or 4.66 eV) seed lasers, we obtained an echo-enabled harmonic generation (EEHG) signal at photon energies between 320 and 450 eV, with pulse energies between 20 and 10 uJ. Furthermore, we employed “fresh-bunch” schemes. In one case, we further amplified the EEHG signal to reach up to 75 uJ at 320 eV. In another case, we employed additional chicanes for a second harmonic upconversion, achieving coherent emission at photon energies up to 1.6 keV. This corresponds to a total harmonic conversion factor close to 350. Our results constitute an essential step towards fully coherent and controllable FEL outputs across the entire soft X-ray range. In future work we intend to exploit longitudinally coherent XFEL pulses to facilitate various spectroscopy and pump-probe schemes, as well as to achieve coherent control of quantum states in the soft X-ray regime.
Funding Agency
European Research Council under the European Union’s Horizon 2020 research and innovation program, within the Hidden, Entangled and Resonating Orders (HERO) project with Grant Agreement 810451
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