Beamline optical scheme

Collimation mirror

The x-ray beam produced in the bending magnet passes through a set of double slits defining an aperture of about 1.2 x 1.2 mm2.

The divergent beam passing through the slits is then collimated by a Rh-coated, spherical profile mirror. The vertically collimated beam reflected off the collimator proceeds towards the monochromator. 


The monochromator was designed internally at Elettra Sincrotrone Trieste by the X-Ray Fluorescence team. It provides a spectral coverage between 2 and 14 keV with small spectral bandwidth (Si(111), InSb crystals) or with high flux (multilayers).  The energy range from 3.7 to 14 keV is ensured by the use of a Si(111) crystal pair, while lower energies, i.e. 2 to 3.8 keV, are made available by an InSb(111) crystal pair.
Both tuning schemes are based on a single lever arm system.

Double Crystals monochromator
Crystals  Si (111)
 InSb (under commissioning)
    3700 - 14 000 eV
    2000 - 3700 eV
Multilayers High Energy: RuB4C Coating
Medium Energy: NiC Coating
Low Energy: RuB4C Coating
4000 - 14 000 eV
1500 - 8000 eV
700 - 1800 eV
Resolving Power, see resolving power of the monochromator  Si (111)
 InSb, [expected performance]
 ~ 1 eV @ 7 000 eV 
 ~ 1 eV @ 2 200 eV 
 ~ 55 eV @ 1 000 eV
 ~ 180 eV @ 14 000 eV

The crystals and multilayers are mounted on a support (shown in the picture and scheme above) which is moved according to the energy range needed for each experiment. 
Moving the support from left to right, one accesses the Si (111), InSb(111), double multilayer for high and medium energies, and low energies multilayer.

The InSb is currently under commissioning and not yet available for users experiments.

Refocusing mirror

The refocusing mirror, placed in close vicinity of the monochromator, is a Rh-coated, toroidal mirror with af bicycle tyre profile. It focuses the beam both vertically and horizontally at the exit slits.

Higher Order Suppressor

While energies above 15 keV are absorbed upon reflection on the Rh-coated mirrors, a higher order harmonics contamination exists in the monochromatised beam up to about 7 keV. 

The suppression of such higher order radiation is ensured by an independent optical device named the Higher Order Suppressor (HOS). The HOS is made up of a pair of parallel plane mirrors intercepting the beam in grazing incidence.

The mirror has two sides having different coatings: 

A Rhodium coating, for energies between 8 and 14 keV, operated at fixed angle, provides 85% of transmission.

A Carbon coating for photon energies < 8 keV,  operated with a variable angle, provides a transmission of about 95% between 3.5 and 8 keV, and of about 50% at 0.7 keV.

Ultima modifica il Venerdì, 24 Luglio 2020 12:08