The purpose of the beamline is first and foremost to deliver the highest flux possible within a small focused beam over the 100 to 1000 eV spectral range, with good performance over an extended range going from 50 to 1700 eV. The flux at the sample position should exceed 1013 photons.s-1 over the optimized energy range.
This will involve two tunable undulators in a medium-length straight section and a monochromator designed to provide a resolving power in excess of 10000 at full throughput in a ~ 20 µm x 80 µm spot at the exit slit. Further, a set of refocusing mirrors (some of them bendable) will be available to focus the beam to three distinct working areas at two branch lines. Switching mirrors will enable the alternate use of the two branch lines. Refocusing optics will be adapted to each experimental technique. A very small vertical spot (~2 µm) will be necessary for high resolution inelastic scattering. A more symmetric spot (80 µm x 50 µm H x V) will provide optimum performance for coherent scattering. Finally, elastic scattering and diffraction experiments can require different conditions. Bendable mirrors will make it possible to adjust the focal distance, spotsize or beam divergence to the specific needs. Many experiments will be dealing with magnetic samples or involving orbital symmetry selection, thus helical undulators providing variable polarization have been specified.
The beamline will serve three types of experiment involving four instruments, three of them already financed through CNRS, ANR and cooperation with outside laboratories.
- Resonant inelastic x-ray scattering (RIXS)
- X-ray resonant magnetic scattering (XRMS), 2 instruments
- Coherent x-ray scattering and Fourier transform holography
These are photon-in-photon-out resonant techniques, highly appropriate to the assessment of element specific magnetic properties under applied magnetic fields, with tunable bulk versus surface sensitivity.
