Bruker SkyScan 1294
Phase-Contrast Desktop X-Ray Micro-CT
The Bruker SkyScan 1294 is the world’s first commercially available phase-contrast desktop microtomography scanner. It reveals local X-ray refraction and scattering in object features, far beyond reconstructed pixel sizes – as well as traditionally observed local object absorption.
- Absorption, differential phase and dark-field (scattering) images are acquired simultaneously
- Three-grating X-ray interferometer with 30 keV design energy
- Micro-focus 100 W X-ray source; 20-60 keV peak energy
- 5-position filter changer for energy window selection
- 11 megapixel cooled CCD X-ray detector
- Compact and fully shielded
- World’s fastest hierarchical 3D reconstruction: InstaRecon
- Intuitive touchscreen for main functions
- Export surface and volume renders to your phone or tablet
Based on unique phase-contrast imaging technology with polychromatic X-rays, patented by the Paul Scherrer Institute at the Swiss Light Source (Zurich, Switzerland) and licensed to Bruker micro-CT for commercialisation.
These are just a couple of example applications – micro-CT is extremely versatile so please get in touch to discuss your area of work.
Carbon-fibre reinforced plastic contains carbon-fibre fabric, with bundles in two orthogonal orientations. The 3D volume rendering shows the morphology in absorption contrast, together with orientation-selective data in dark-field (scattering) contrast. The combined image shows both fibre orientations and plastic filler.
The example above is the electronic chip from a credit card, which is attached to the back of the metal contacts.
- Left: Virtual slice in absorption contrast showing the metal contacts, die attachment and thin wires that connection to the contacts.
- Right: Phase-contrast virtual slice showing the layer of glue that sticks the chip to the card – you can even see the air bubbles in the glue.
3D volume render of a 5 carat rough diamond:
- Absorption contrast image – Shows the external surface and metal-oxide inclusions.
- Scattering image – Highlights internal defects and a significant carbon (graphite) cluster at the bottom left. This cluster is not visible in the absorption image because graphite and diamond have an identical chemical composition.
How Phase-Contrast Scanning Works
When it passes through the object, the X-ray beam changes:
- Loss in intensity because of absorption
- Change in wave phase because of differences in propagation speed
- The wavefront behind the object is modulated by absorption and changes the direction of propagation due to phase shift.
Conventional X-ray cameras are not sensitive to the direction of incoming X-rays and can only detect absorption in the object. The directional part can provide data about object details without significant absorption, at sizes much smaller than can usually be distinguished.
To access phase-shift data, the information has to be converted into an intensity signal that can be picked up by an X-ray camera. This is performed by a Talbot-Lau X-ray interferometer, which contains several absorption and phase-shift gratings at micron-size pitch.
The G1 phase grating creates an interference pattern with local maxima and minima of intensity. If the sample changes the direction of the primary beam, the pattern shifts. The G2 absorption grating strips this pattern and transforms it into intensity modulation. This can be detected by relatively large pixels in the detector.
To reproduce the conditions necessary for interference, an additional G0 absorption grating in front of the X-ray source divides the primary beam into many spatially correlated thin beams. The gratings must all be in precise alignment for the process to work.
The X-ray interferometer converts local phase shifts into intensity modulation. This is detected by the camera, along with absorption data.
To distinguish between phase-shift and absorption information, one of the three gratings is moved through various positions within a single grating pitch. This creates sinusoidal modulation for each pixel of the camera. By comparing sine curves from pixels from the sample and from around it, phase shift and scattering information can be separated from the absorption information.
All types of information are acquired using one single calculation process. They can be displayed on screen simultaneously for a complete picture of your sample.
Here, the camera image is shown on the top left, absorption image on the top right, differential phase-contrast image on the bottom left and the dark-field (scattering) on the bottom right.