SAMBA

Schéma de la cabane Optique

• Miroirs
• Monochromateur double cristaux sagital focalisant

Miroirs

Deux miroirs en silicium cylindriques et courbables (WinlightX), recouverts d'une couche de 50 nm de Pd, sont utilisés pour:

1. La collimation verticale du faisceau
2. La focalisation verticale du faisceau à la position de l'échantillon
3. Le réjet harmonique

Les miroirs sont utilisés sur toute la gamme en E (4-40 keV) couverte par la ligne, en les inclinant de 10 à 1 mrad (c.a.d. de 0.57° à 0.057°) en fonction de l’énergie nécessaire pour satisfaire le rejet harmonique.

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).

Then the typical flux at the sample position at 8.5 keV is 5x10¹¹ ph/s with the Si(220) DCM  (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

No picture. 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.