Specifications

 


Beamline Flux 

The experimental flux curves for the 2 storage ring operation energies at Elettra (i.e. 2.0 and 2.4 GeV) normalized to the beam current (300 and 160 mA respectively, typical top-up conditions) are shown below. The output flux was characterized immediately downstream of the refocusing mirror, at 14.3 m from the source, by using 2 ionization chambers behind a 0.3mm thick Beryllium window. The output curves are following closely the expected spectral dependence.

Light Source

Type: Bending Magnet Ring energy: 2.0 GeV Ring Energy: 2.4 GeV
Critical Energy 3210 eV 5590 eV
Source Size (nominally)  sx = 0.33 mm
sy = 0.066 mm
sx = 0.46 mm
sy = 0.07 mm

For more information, please refer to Elettra parameters.

Further details on the optical concept for the X-Ray Fluorescence beam transport system are reported in:

  • Optimisation of a compact optical system for the beamtransport at the x-ray fluorescence beamline at Elettra for experiments with small spots;
    W. Jark, D. Eichert. L. Luehl, A. Gambitta;
    Proceedings of SPIE, Vol. 9207 Advances in X-Ray/EUV Optics and Components IX, pp: 92070G (2014);
    doi: 10.1117/12.2063009;

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. 






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]
 Multilayers
 
 ~ 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.
 


Sample holders

Different supports are available to host the samples.
Users willing to bring their sample holders are asked to contact the staff to ensure the compatibility with the sample manipulation system.

1. Teflon holders

These holders are ideal for transmission measurements and are designed to work at 45° with respect to the X-ray beam direction.
Their dimensions are 12 x 2.5 cmand they have a longitudinal hole (at 45°, as shown by the drawings below) for the X-ray beam to pass through it.
Two different versions are available: one has a hole of 7.1 mm, the other one of 10 mm.
 

                                                                



Several samples can be mounted at once. They can be kept in place using teflon stripes screwed to the main structure, or kapton/carbon tapes.

                         




 

2. Stainless steel holders 

These supports are best suited for Grazing Incidence and Reflectivity measurements, but they can also be used for collecting XRF maps.
They offer a large surface (12 x 5.5 cm2) to accomodate samples which can be mounted using teflon stripes screwed in the main structure. 
Sample nature may vary from thin films to artefacts of different shapes.


     
 

3. Glass slide holders 

These supports are designed to host sample supports having a circular shape of diameter 26mm.
This choice has proven very efficient for XRF maps collection in the case of thin sections (few μm) of biological samples.
The picture below shows 4 samples of rat organs freeze dried and deposited on an ultralene foil. The ultralene is kept tight and wrinkle-free by two plastic rings.


 

4. Total reflection holders 

These holders can host up to 3 glass reflectors and are dedicated to total reflection measurements.

 
Ultima modifica il Venerdì, 24 Luglio 2020 12:08