Research highlights

Extreme ultraviolet multilayer for the FERMI@Elettra free electron laser beam transport system

A new kind of multilayer interferential coating has been developed for the beam transport system of FERMI@Elettra Free Electron Laser. The system is based on an aperiodic capping layer on the top of a Pd/B4C multilayer structure optimized for high reflectance at 6.67 nm. This system allows to combine the high reflectance of the buried ML with the filter properties of the capping layer, useful in rejecting the fundamental harmonic when the goal is to select only the third FEL harmonic.

The structure has been deposited and also characterized along one year in order to investigate its temporal stability.  Reflectance measurements have been done and repeated after one year at the BEAR beamline, and revealed no measurable performance changes, suggesting good temporal stability. Presented in: Extreme ultraviolet multilayer for the FERMI@Elettra free electron laser beam transport system, A.J. Corso et al., Optics Express, 20, 7 (2012)