Ricerc@Sapienza

SAXSLab Sapienza is a laboratory for structural characterization which operates the X-ray diffractometer Xeuss 2.0 HR P300K Q-Xoom (XENOCS), purchased thanks to the grant “Grandi Attrezzature d’Ateneo 2015”.

The instrument is capable of Small Angle X-Ray Scattering (SAXS), Wide Angle X-ray Scattering (WAXS) and Grazing Incidence Small Angle Scattering (GISAXS) experiments. These techniques are widely applicable for the characterization of matter at the nano- and meso-scale.

Instrumental characteristics

The instrumental platform of SAXSlab Sapienza is a Xeuss 2.0 HR P300K Q-Xoom (XENOCS) system with the following set-up:

• Genix3D micro-focus Cu Ka source (X-ray wavelength 1.54189 Å) with power 30W and collimation optics FOX3D single reflection;

• Beam collimation system with two modules of scatterless slits, having four independent blades with motorized opening;

• Sample chamber for measurements in vacuum (P<0.2 mbar) or in ambient pressure with mounting of additional windows;

• Stage for several sample holders with motorized X, Y and Z translations and rotation for GISAXS;

• 2D detector Dectris Pilatus3 R 300K in vacuum for measurements SAXS/WAXS with motorized movement along Y to vary the sample-detector distance (from around 25 to 250 cm) and along an horizontal axis perpendicular to the incident beam for measurements with azimuth 180° or 90°;

• A second detector Pilatus3 R 100K for simultaneous WAXS, with accessible scattering angles 18°< 2theta < 46° (or, for a different sample position 24°< 2theta < 60°).

The system is programmable for simultaneous SAXS/WAXS acquisitions on a set of samples. Thanks to the detector motorized support, data can be collected in several SAXS configurations. The presence of the two detectors enables an overall accessible q range 0.03 < q < 33 nm-1.

The instrument is controlled by a SPEC software with SPECFE user graphical interface, in Unix environment.

Data treatment and reduction of 2D images in 1D scattering profiles are performed with the software FOXTROT (from the collaboration between the XENOCS company and the French synchrothron Soleil).

SAMPLE ENVIRONMENTS

Vacuum-tight refillable capillary cells for thermalized holders.

The quartz capillaries have an inner diameter around 1.5 mm and a volume of sample around 100 µl is needed for filling. These cells can be used for samples (liquids, solutions) that can be easily washed away after use. The chemical compatibility of the O-rings should be checked.

Empty metal holders are available to also thermalize vacuum-tight disposable capillaries (e.g. sealed with hot glue).

The temperature is controlled via a Julabo thermal bath equipped with a temperature probe at the capillary position. The range of operable temperatures is approximately from -10 to 70 °C.

Disposable capillaries holder

The holes can accommodate capillaries with diameter up to 2.0 mm. It is necessary to "seal" the capillaries in a vacuum-proof way (e.g. with hot glue), or use the ambient pressure setup with additional windows.

Powder holder

Washers are used as spacers, placing the powder sample in the central hole, and sticky Kapton windows are placed on the two sides to keep the sample. Washers or other compatible spacers with holes can be also used to fix thin solids, fibers.

Gel/powder holder

The holder accommodates capsules with 0.5 or 1.0 mm spacers and Kapton windows (not sticky) with thickness 50 µm or 12.5 µm. Around 20 µl (advised to have at least 50 µl) of sample are needed for filling. The capsules (with 50 µm-thick windows) allow for keeping viscous samples vacuum tight. A certain evaporation rate (around 0.09 µl/h for water) due to the permeability of the windows, should be taken into account in planning the measurements.

Standard GISAXS stage

The sample (at least 1 cm long) is manually placed on the stage, determining both the position in the y direction, and the orientation in the x-y plane. The sample alignment in the z, x directions and omega rotation angle is controlled by motors.

Generic holder for thin solids