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| Home > Publications database > Hochauflösende dreidimensionale Mikrotomographie für die Werkstofforschung |
| Home > Publications database > Hochauflösende dreidimensionale Mikrotomographie für die Werkstofforschung |
| Book/Report | FZJ-2019-01586 |
1996
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
Jülich
Please use a persistent id in citations: http://hdl.handle.net/2128/21677
Report No.: Juel-3274
Abstract: The aim of the dissertation was to build a microtomography system, which is suitable for routine measurements for particular probes. The important role of the system calibration before the measurement with respect to the quality of the reconstruction and the attainable resolution was treated. The detector system and the probe-holder were build on manipulators; to avoid the time-consuming positioning and calibration of the different components a software prograrn was developed to control the system with a PC. Aresolution of less then 7 $\mu$m was obtained. With the particular system components used aresolution improvement is not possible. With the use of the conebearn geometry the resolution is limited mainly by the source dimensions. The X-ray tubes used have a source bigger than 5 $\mu$m, which leads to additional blurring after the geometrical magnification of the probe. A reduction in the source dimensions in the future should not lead to reduction of the power of theX-ray tube, because the application for a bigger or strong attenuating probes would be impossible. The influence of the different factors, which impact the quality of thereconstruction images was considered. It was determined that the signal-to-noise ratio is particularly important. Because of the small quanta-densities of the X-raytubes and their statistical character it was attempted to increase the number of photons registered at the detector system. Three different detector systems wereused and it was shown that because of the cascaded structure of the X-ray detectors the first stage - the transformation of the X-ray- into lightphotons is particularly important. In the next stages can the los ses due to these transformationscan not be compensated for. In that respect were the advantages and disadvantages of the different detector systems considered. A new cone-beam reconstruction algorithm was presented which allows an exact reconstruction. It calculates the contributions to the three dimensional Fourier transform from each projection separately in Cartesian coordinates, which avoids the errors that the interpolation step introduces. For new implementations this algorithm can be modified for any possible source trajectories.
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