Standard configuration for absorption-based and edge-enhanced radiography and tomographyThe TOMCAT endstation for tomographic microscopy allows translation along the three spatial directions with a resolution better than 1μm. The axis perpendicular to the beam direction has a reproducibility of 0.1μm; this is imperative for an artifact-free acquisition of reference images. The sample can also be centered within 0.1μm reproducibility.
The rotation axis is a custom-modified, aerotech air-bearing-based system (link) and has a run-time error of less then 1μm at 100 mm from the rotation surface. It rotates with speeds up to 10Hz (1800deg/s). The whole sample manipulator can be rotated by 90°, allowing thick and short samples (vertical rotation axis) or long and thin samples (horizontal rotation axis) to be scanned. Please contact the beamline staff if you require a non-standard configuration for your experiments.
Additional details on sample mounting and sample environment can be found here.
Standard configuration for Elevated Temperature In Situ Tomographic MicroscopyThe TOMCAT beamline offers a laser-based heating system for time-resolved in situ imaging. The system incorporates two 150W lasers at 980nm wavelength that are positioned approximately 180° apart. Two sets of laser heads, with different spot sizes (1(h) x 0.2(v) mm2 or 4 x 6 mm2) are available. The lasers are manipulated by x, y, and z linear stages such that a user-specified position can be heated. The lasers are also capable of moving as the sample moves. Temperatures are measured either with a pyrometer (non-contact infra-red (IR) temperature measuring device), accessing a temperature range of 350-1800°C or a thermocouple for temperatures from room temperature to 1200°C. Power to the lasers is dynamically controlled based on the temperature read-out from the pyrometer/thermocouple, and temperature profiles are determined based on user specifications. The current setup is capable of both near-isothermal and directional heating within these temperature ranges. The laser system is compatible with various beamline configurations and can be used in multiple imaging modalities. If an atmosphere different from air is required, a gas cover solution is available. The user is responsible for providing sample holders and setups that are compatible with the layout of the laser system (beamline staff will assist with this process). J.L. Fife, M. Rappaz, M. Pistone, T. Celcer, G. Mikuljan, and M. Stampanoni. Development of a laser-based heating system for in-situ synchrotron-based x-ray tomograpic microscopy, J. Synch. Rad. 19, 352-358, (2012).
Ultra-fast acquisitionsInformation will be available soon.
Differential Phase Contrast (DPC) ImagingThe TOMCAT endstation offers phase contrast imaging based on grating interferometry (see T. Weitkamp, A. Diaz, C. David, F. Pfeiffer, M. Stampanoni, P. Cloetens, E. Ziegler X-ray phase imaging with a grating interferometer, Opt. Express 13, 6296-6304 (2005), pdf).
The plug-in for DPC imaging can be easily mounted on the standard setup at TOMCAT. The figure below shows the interferometer mounted on the beamline.
Experimental setup for Differential Phase Contrast at TOMCAT. The nanometer-precise periodic phase stepping is obtained by using a PSI in-house developed nanoconverter. For more details see S. Henein, M. Stampanoni, U. Frommherz, M. Riina, 'The Nanoconverter: a novel flexure-based mechanism to convert microns into nanometers', Proceedings of the 7th euspen International Conference – Bremen - May 2007, PDF-file.
The beam splitter grating (G1 – pitch 4 mm) splits the incident beam into essentially two first diffraction orders, which form a periodic pattern in the plane of the analyzer grating (G2 – pitch 2 mm). A phase object in the incident beam will cause slight refraction and therefore modifications of the original wave-front profile. These variations result in changes of the locally transmitted intensity through the analyser. This detected signal contains quantitative information on the phase gradient of the object. To separate this phase information from other contributions, a phase-stepping approach is used (T. Weitkamp, A. Diaz, C. David, F. Pfeiffer, M. Stampanoni, P. Cloetens, E. Ziegler, X-ray phase imaging with a grating interferometer, Opt. Express 13, 6296-6304 (2005), PDF-file).
NanoscopeLinking micrometer and nanometer scales, the TOMCAT nanoscope was commissioned in 2009. Based on Zernike phase contrast, this full-field microscope is composed of:
- a condenser: a custom designed beamshaper producing a top-flat illumination in the focal plane
- a series of Fresnel Zone Plates (FZP) objectives, with different diameters on the same frame (to be selected according to the working energy)
- phase dots (optional) placed at the back-focal distance of the FZP to generate Zernike phase contrast.
Thanks to the latest improvements in optical design, specifically with regards to the beamshaper and the Fresnel Zone Plate, as well as on the hardware of the setup itself to produce higher stability, we are now able to use the nanoscope from 8 keV to 20 keV in multilayer or Silicon Monochromatique mode, leading to a pixel size down to 60nm (approximately 150/200 nm spatial resolution). The setup can be used in absorption or phase contrast mode for a wide range of applications, including biology, geology, materials science, and paleontology.
For further information, please see: