SAMBA

Optical layout

• Mirrors
• Sagittal focusing double crystal monochromator

Mirrors

Two cylindrically bendable silicon mirrors (WinlightX) coated by a layer of 50 nm of Pd are used for providing:

1. vertical collimation of the beam
2. vertical focusing of the beam at the sample position
3. harmonic rejection.

The mirrors are used over the whole 4-40 keV energy range available on the beamline by tilting the mirrors from 10 mrad to 1 mrad (i.e. 0.57° to 0.057°) depending on the desired cut-off energy for removing the harmonic X-rays.

The reflective Pd surfaces are 1200 mm long per 88 mm wide allowing a horizontal acceptance of about 6.2 mrad on the first collimating mirror located at 14.1 m from the source. The surface of the mirrors was polished to a rms roughness less than 3 Ǻ rms and to a  longitudinal slope error less than 2µrad rms. The first mirror is water cooled using blades immersed in In-Ga eutectic in grooves in the mirror surface.

The focusing in the vertical direction is ensured by the M2 mirror, the resulting vertical spot size at the sample position is 110 µm (FWHM) with a foot size of about 300 µm.

Sagittal focusing double crystal monochromator

Sagittal focusing double crystal monochromator

The sagittally focusing Double Crystal Monochromator (DCM) provided by Oxford Danfysik is used in the so-called high flux mode. The DCM is installed at 16.1 m from the source. It deals of a first flat water-cooled Si(220) crystal and a sagittally bent 2nd crystal. The main Bragg axis of rotation passes through the centre of the diffracting face on the 1st crystal and perpendicular to the beam axis. In this way, the incident white beam is always centred on the axis of rotation. A fixed offset to the exit beam is achieved by moving the 2nd crystal perpendicularly to the first one according to the Bragg angle. In this case the beam moves along the axis of the sagittally-bent 2nd crystal. The first crystal is indirectly water-cooled by using a multi-channel water cooling support (SOLEIL original design) in contact with the crystal through a thin film of In-Ga eutectic. The 2nd crystal is uncooled.

The horizontal acceptance of the monochromator is limited by the efficiency of the sagittal bender. For a horizontal acceptance of 1.5 mrad, the typical beam size at the sample position is around 300 µm (H) x 200 µm (V) (FWHM).

In order to avoid possible radiation damage on the sample due to the high density of photons in a so small spot, the beamline is often slightly defocused in both directions to achieve a spot size of 2 mm (H) x 1mm (V).

The typical flux at the sample position at 8.5 keV is 5×10¹¹ ph/s (6 mrad of vertical acceptance and 1.5 mrad of horizontal acceptance, I = 400 mA).

Related publications: 

SAMBA: The 4-40 keV X-ray Absorption Spectroscopy Beamline at SOLEIL. 
V. Briois, E. Fonda, S. Belin, L. Barthe, C. La Fontaine, F. Langlois, M. Ribbens, F. Villain 
UVX 2010 - 10e Colloque sur les Sources Cohérentes et Incohérentes UV, VUV et X ; Applications et Développements Récents: 41-47. EDP Sciences 2011

Detection

Transmission :

Oxford ionization chambers

Fluorescence :

Canberra 35-elements  monolithic planar Ge pixel array detector

Detector Silicon Drift : Vortex

Total electron yield

The sample must be electrical conductor otherwise a thin layer of graphite may be evaporated. 

Catalysis

Gas blower

quartz capillary oven for operando measurements up to 850°C and 10-15 bars

Gas distribution system

• Complex mixtures
• Humidifier
• Heated lines 
• Remote control

Low temperature

He cryostat suitable for transmission and fluorescence detection (20 K to 500K). Liquid nitrogen (80 K) can also be used

Grazing incidence

• Sample T° :  900°C
• T° Ramp : 10 à 30°C/min
• Pressure:  5.10-7mbar
• possible to work under partial gas pressure 
• Modes Transmission (Reflexafs) and Fluorescence possible

Liquid Cells

We have cells with different optical path available for basic or acidic solution. Kapton, Mylar, PP or PTFE can be used as windows depending of the nature of the solution.

Other

The experimental hutch can host different setups and sample environments provided by the beamline, such as potentiostats, mass spectrometer, micro GC, Raman, UV-visible, differential scanning calorimeter, and other equipment provided by users. Please contact the beamline staff to discuss any other setups.

The application for the use of specialty gases must be stipulated in your proposal in order that the security service can assess the associated risks. Specialty gases must be commanded 8 weeks before your experiment, also you have to prevent your local contact well in advance, for common gases (helium, argon, nitrogen, hydrogen, air and oxygen) only 4 weeks are sufficient.  

The application for the use of liquid helium must be stipulated in your proposal and recalled to your local contact in such a way to order sufficiently in advance the suitable volume. Please, given the high cost of liquid helium, carefully consider its use.

Beamtime Applications 
Projects are examinated twice a year by an independant peer review commitee. The projects must be filled via the SunSet Application 

Two important deadlines (standard & BAG project) : 
15 February - 15 September

Project must be written in english and submissions must comply with the following framework : 

Online submission of the web form to give general information 

1. Description of the scientific background and experimental part 
2. Figures or images in annex (format .jpeg .png) 
3. Description of experimental conditions with special safety measure 
4. Submission of the proposal

(If the application constitutes the project continuation, filing in a report of the previous experiment in the SunSet and mention of related publications are necessary) 

Also, 

- It is strongly advised to contact one of the beamline scientist, they will assist in the definition of the setups necessary for the desired experiment and in the assessment of the best conditions. 
- The justification of the required beamtime is required. 

Do not forget to mention your related publications in the sunset. 

For more informations : The general User's guide  The general User's guide