High-speed imaging at ANKA
Nowadays, there is an increasing demand for fast X-ray detectors and short exposure times in order to investigate fast processes in real time or to minimise the radiation dose to the sample when it is a critical problem. This issue is of outstanding relevance especially for 3D (tomography) imaging applications, where a large set of 2D frames has
to be acquired at different sample orientations.
ANKA’s TOPO-TOMO beamline is located at a bending magnet port, and therefore is characterised by a moderate flux density, which requires the use of a highly sensitive detector system. A dedicated high-speed detector, which can withstand the intense white beam, has been designed and manufactured with magnifications in the range of 1x to 3x. The use of white beam ensures that enough photons are available to realize shortest integration times without compromising X-ray signal-to-noise ratio. Frame rates of several ten thousand frames per second have been achieved using this detector optical system in combination with TOPO-TOMO’s high-speed CMOS camera in radiography mode (effective pixel size of 6.6 μm).
By coupling this high-speed image acquisition with a fast, continuous rotation of the specimen, it was possible to decrease the total scan time for a complete tomogram from 2-3 hours down to 400 ms. Application examples include the study of eggs of Peruphasma schultei, a stick insect species from Peru (Figure 1). Here, the extremely short total acquisition times guarantee that the dose is as small as possible.
Figure 1: The image shows a surface rendering of the reconstructed tomogram, acquired
using a white beam filtered with 0.7 mm Al, continuous rotation with 2000 frames per second,
800 projections for the full tomogram. Total acquisition time was 0.4s.