Klick-CT: modular and compact micro-CT measurement technology for down to 0.3 µm

Scientists in the Fraunhofer project group NanoCT Systems in Würzburg and at the Fraunhofer Application Center for CT in Metrology in Deggendorf are working together to develop a compact, modular micro-CT system to meet the highest requirements. It scans specimens up to a volume of 5 mm at down to 0.3 µm/voxel. The system can be converted to phase contrast and dark-field CT, so it is eminently suited for material research for analyzing three-dimensional structures, e.g., fibrous materials, metal structures, granular substances, and foams.

3D-CT-Aufnahme einer Holzprobe
© Fraunhofer IIS

Example for a micro-CT measurement: wood

The Klick-CT system

The name “Click-CT” stands for the simplicity of equipping the micro-CT with flexible source and detector components and for the easy, intuitive operation of the measurement technology. In the high-resolution version, Click-CT is equipped with a closed micro-focus source (150 kVp, ~5 μm focal spot size) and a high-resolution X-ray camera. The latter allows fully automatic switching among three fields of view from which the smallest scans your specimens at 0.3 µm/voxel and the largest scans measurement volumes up to 5 mm (scan at 1.4 µm/voxel).

Applications

Typical applications for microstructures that are measured with the help of Click-CT include carbon-fiber and fiberglass composites (fiber density and spatial orientation), metal alloys (phase fractions and microstructures), metallic and organic foams (pore size and distribution), and natural materials such as wood, bone, and stone.

3D-CT-Aufnahme einer CFK-Platte

Example for a micro-CT measurement: CFRP RC-plate

Unique selling points

Thanks to advanced algorithms from the Development Center for X-ray Technology (EZRT), with Click-CT it is possible to measure small areas, even within larger specimens, at a high resolution. Using this region-of-interest (ROI) CT eliminates the laborious preparation of very small specimens, which is extremely advantageous, particularly with brittle materials such as CFRP. The accurate ex-factory calibration of Click-CT and the easy, semiautomatic recalibration guarantee long-term dimensional accuracy of measurements at the smallest scale and make the manual adjustment of reconstruction parameters unnecessary. In contrast to conventional micro-CT systems, which use a high degree of projective magnification, Click-CT has an innovative X-ray camera, which enables its high degree of spatial resolution. This not only makes the system less expensive, but it also dispenses with well-known problems such as source-spot drift and fluctuations in performance, which are inherent to conventional micro-CT systems.

Outlook

Like the source, the X-ray camera can be easily mounted and removed. In the near future, Fraunhofer EZRT will be offering a conversion kit for Click-CT with which the high-resolution camera can be exchanged for a Talbot-Lau grating interferometer for measuring CT images in differential phase and dark-field contrast. This will make Click-CT the first compact laboratory system that supports a conversion like this one, which, in turn, offers price-related and technical advantages in comparison to a second system.

Table: Characteristic values of Click-CT for the three different fields of view of the X-ray camera (sCMOS chip: 2048² pixels with 6.5 μm/pixel) and a distance between the source and the detector of 50 mm. *When pixel binning is used, the values shown change, so the measuring time is considerably shorter than that at full resolution. The expansion of the measuring field requires two angle scans, which doubles the measuring time. The actual local resolution of the 3-D measurement depends on the scintillation screen and, in general, is somewhat below the optical light threshold value.

 

Optical unit Voxel sampling/μm
Measuring field (FOV)/mm
Expanded measuring field/mm
20 X 0.30 0.62 1.1
10 X 0.56 1.2 2.1
4 X 1.4 2.8 5.0