Scanning coherent X-ray microscopy (ptychography) has gained considerable interest during the last decade since the performance of this indirect imaging technique does not necessarily rely on the quality of the X-ray optics and, in principle, can achieve highest spatial resolution in X-ray imaging. The method can be easily extended to 3D by adding standard tomographic reconstruction schemes. However, the tomographic reconstruction is often applied in a subsequent step using a sequence of aligned ptychographic 2D projections. In this contribution, we outline current developments of a GPU-accelerated framework for direct 3D ptychography, coupling 2D ptychography and tomography. The program utilizes a custom GPU-accelerated framework for ptychography that offers three distinct ptychographic reconstruction algorithms. The tomographic reconstruction runs simultaneously and uses numerical routines of the ASTRA Toolbox. This parallel-computing approach results in a high performance increase considerably reducing the reconstruction time of 3D ptychographic datasets.
The X-ray scanning microscope PtyNAMi at beamline P06 of PETRA III at DESY in Hamburg, Germany, is designed for high-spatial-resolution 3D imaging with high sensitivity. Besides optimizing the coherent ux density on the sample and the precision mechanics of the scanner, special care has been taken to reduce background signals on the detector. The optical path behind the sample is evacuated up until the sensor of a four-megapixel detector that is placed into the vacuum. In this way, parasitic scattering from air and windows close to the detector is avoided. The instrument has been commissioned and is in user operation. The main commissioning results of the low-background detector system are presented. A signal-to-noise model for small object details is derived that includes incoherent background scattering.
To date, compound refractive X-ray lenses made out of Beryllium (Be CRLs) have been seldom applied for full-field microscopy with high spatial resolution, which was probably due to residual aberrations of these optics. However, in combination with the recent development of made-to-measure phase plates, the typical spherical aberration of beryllium compound refractive lenses (Be CRLs) can now be completely removed. In this way, distortion-free images of a sample are obtained, which is especially important for tomographic applications. First full-field imaging experiments with aberration-corrected Be CRLs were carried out at beamline P06 at the synchrotron radiation X-ray source PETRA III (DESY Hamburg, Germany). In order to maximize the magnification of the X-ray microscope for full-field microscopy, the full length of the beamline combining the micro- and nanohutch was utilized, enabling a large sample-to-detector distance. In this contribution, we present first imaging results, demonstrating the potential of Be CRLs for direct high-resolution X-ray tomography.
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