Widely tunable two-colour seeded free-electron laser source for resonant-pump resonant-probe magnetic scattering

  • Ferrari Eugenio
  • Spezzani Carlo
  • Fortuna Franck
  • Delaunay Renaud
  • Vidal Franck
  • Nikolov Ivaylo
  • Cinquegrana Paolo
  • Diviacco Bruno
  • Penco Giuseppe
  • Ribič Primož Rebernik
  • Roussel Eléonore
  • Trovò Marco
  • Moussy Jean-Baptiste
  • Pincelli Tommaso
  • Lounis Lounès
  • Manfredda Michele
  • Pedersoli Emanuele
  • Capotondi Flavio
  • Svetina Cristian
  • Mahne Nicola
  • Zangrando Marco
  • Raimondi Lorenzo
  • Demidovich Alexander
  • Giannessi Luca
  • de Ninno Giovanni
  • Danailov Miltcho Boyanov
  • Allaria Enrico
  • Sacchi Maurizio

ART

The advent of free-electron laser (FEL) sources delivering two synchronized pulses of different wavelengths (or colours) has made available a whole range of novel pump–probe experiments. This communication describes a major step forward using a new configuration of the FERMI FEL-seeded source to deliver two pulses with different wavelengths, each tunable independently over a broad spectral range with adjustable time delay. The FEL scheme makes use of two seed laser beams of different wavelengths and of a split radiator section to generate two extreme ultraviolet pulses from distinct portions of the same electron bunch. The tunability range of this new two-colour source meets the requirements of double-resonant FEL pump/FEL probe time-resolved studies. We demonstrate its performance in a proof-of-principle magnetic scattering experiment in Fe–Ni compounds, by tuning the FEL wavelengths to the Fe and Ni 3p resonances.