The unique beam characteristics of PETRA III at DESY promote novel applications for many scientific fields,
including imaging applications. For tomography these are techniques like high-speed and in-situ measurements
marked by highest density resolutions and spatial resolutions down to the nanometer range. Furthermore, the
high coherence enables phase contrast applications in an exceptional way. Therefore, the Imaging Beamline IBL
is equipped with two dedicated endstations, one for micro and one for nano tomography. In addition, a very
flexible X-ray and light optics concept is implemented. The micro tomography endstation is designed for samples
requiring (sub-) micrometer resolution. The technical specifications of the nano tomography endstation aim for
a spatial resolution of below 100 nm. The nanometer resolution will be achieved by using different combinations
of compound refractive lenses as X-ray optics. The overall setup is designed to be very flexible, which allows
also the implementation of other optical elements as well as the application of different magnifying techniques.
X-ray phase-contrast radiography and tomography enables to increase contrast for weakly absorbing materials.
Recently, x-ray grating interferometers were developed which extend the possibility of phase-contrast imaging
from highly brilliant radiation sources like third-generation synchrotron even to non-coherent sources. Here,
we present a setup of an x-ray grating interferometer designed and installed at low-coherence wiggler source
at the GKSS beamline W2 (HARWI II) operated at the second-generation synchrotron storage ring DORIS at
the Deutsches Elektronen-Synchrotron (DESY, Hamburg, Germany). The beamline is dedicated to imaging in
materials science. Equipped with the grating interferometer, it is the first synchrotron radiation beamline with
a three-grating setup combining the advantages of phase-contrast imaging with monochromatic radiation with
very high flux and a sufficiently large field of view for centimeter sized objects. Examples of radiography on
laser-welded aluminum and magnesium joints are presented to demonstrate the high potential of the new gratingbased
setup in the field of materials science. In addition, the results of an off-axis phase-contrast tomography of
a human urethra with 15 mm in diameter are presented showing internal structures, which cannot be resolved
by the conventional tomography in absorption mode.
Using laser welding in fabrication of metallic airframes reduces the weight and hence fuel consumption. Currently only limited parts of the airframes are welded. To increase laser beam welded parts, there is the need for a better understanding of crack propagation and crack-pore interaction within the welds. Laser beam welded Al-alloys may contain isolated small process pores and their role and interaction with growing crack need to be investigated. The present paper presents the first results of a crack propagation study in laser beam welded (LBW) Al-alloy T-joints using synchrotron radiation based micro computed tomography (SRμCT). A region-of-interest technique was used, since the specimens exceeded the field of view of the X-ray detector. As imaging with high density resolution at high photon energies is very challenging, a feasibility measurement on a small laser weld, cut cylindrically from the welded region of a T-joint, was done before starting the crack-propagation study. This measurement was performed at the beamline HARWI-II at DESY to demonstrate the potential of the SRμCT as non-destructive testing method. The result has shown a high density resolution, hence, the different Al alloys used in the T-joint and the weld itself were clearly separated. The quantitative image analysis of the 3D data sets allows visualizing non-destructively and calculating the pore size distribution.
During the last few years microtomography using synchrotron radiation (SR) has become a standard technique to characterize samples 3-dimensionally in the fields of biology, medicine and materials science. The GKSS Research Center Geesthacht, Germany, is responsible for developing and running the microtomography experiments at the
SR-facility DESY, Hamburg, Germany. The application of SRμCT using attenuation-contrast at the beamlines W2/HARWI-II and BW2 of the storage ring DORIS III results in high throughput investigations. For achieving tomograms showing not only high spatial resolution but also high density resolution special emphasis was given to the stability of the used monochromators and the calibration of the total system. The influence of the photon statistic from the measurement to the tomograms is simulated and the achieved high density resolution
is demonstrated showing selected results.
Due to the high brilliance of the new storage ring PETRA III at DESY in Hamburg, the low emittance of 1 nmrad and the high fraction of coherent photons also in the hard X-ray range extremely intense and sharply focused X-ray light will be provided. These advantages of the beam fulfill excellently the qualifications for the planned Imaging BeamLine IBL and the High Energy Materials Science Beamline (HEMS) at PETRA III, i.e. for absorption tomography, phase enhanced and phase contrast experiments, for diffraction, for nano focusing, for nano tomography, and for high speed or in-situ experiments with highest spatial resolution. The existing HARWI II beamline at the DORIS III storage ring at DESY completes the GKSS beamline concept with setups
for high energy tomography (16-150 keV) and diffraction (16-250 keV), characterized by a large field of view and an excellent absorption contrast with spatial resolutions down to 2 μm.