Beamline Description

Monochromator and optics

The BaDElPh beamline is based on a 4-m-long normal incidence monochromator (NIM) with a constant included angle of 5°.
The radiation from the Fgure-8 undulator is deflected toward the BaDElPh branch by a silicon plane-switching mirror. The spherical prefocusing mirror upstream of the monochromator focuses the beam into the entrance slit. The bare silicon portion of the surface of the mirror is used for photon energies up to about 13 eV while the reflectivity of the Pt-coated part is suitable for higher photon energies.
The monochromator is equipped with three (Al/MgF₂, SiC, Pt) interchangeable spherical gratings to cover the photon energy range 4.6-40 eV at 2.0 GeV of electron ring energy. When Elettra operates at 2.4 GeV the lowest photon energy available is 6.7 eV. The Al/MgF₂ grating has 1500 l/mm, a laminar profile, and is used for the photon energy range of 4.6-13 eV. The SiC grating has 3000 l/mm with a laminar profile and, since March 2009 when the Pt grating was installed, can be used for the photon energy range 13-19 eV. The Pt grating has 3000 l/mm, a blaze profile, and is optimized for the photon energy range of about 19-40 eV.
The monochromatic beam is focalized into the moveable exit slit. Both the entrance and exit slit apertures can be set in the 10-400 µm range. The last optical element of the beamline, namely the gold-coated toroidal refocusing mirror, focuses the light onto the sample inside the experimental chamber.
The measured size of the synchrotron radiation beam spot at the sample position is in the order of the exit slit aperture in the vertical direction and less than 300 µm in the horizontal direction.
 

Layout of the BaDElPh beamline