The performance of a recently developed full-field X-ray micro-imaging system based on an in-line Bragg magnifier is reported. The system is composed of quasi-channel-cut crystals in combination with a Medipix single-photon-counting detector. A theoretical and experimental study of the imaging performance of the crystals-detector combination and a comparison with a standard indirect detector typically used in high-resolution X-ray imaging schemes are reported. The spatial resolution attained by our system is about 0.75 µm, limited only by the current magnification. Compared with an indirect detector system, this system features a better efficiency, signal-to-noise ratio and spatial resolution. The optimal working resolution range of this system is between ∼0.4 µm and 1 µm, filling the gap between transmission X-ray microscopes and indirect detectors. Applications for coherent full-field imaging of weakly absorbing samples are shown and discussed.

We present the theoretical description of the image formation with the in-line germanium Bragg Magnifier Microscope (BMM) and the first successful phase retrieval of X-ray holograms recorded with this imaging system. The conditions under which the BMM acts as a linear shift invariant system are theoretically explained and supported by the experiment. Such an approach simplifies the mathematical treatment of the image formation and reconstruction as complicated propagation of the wavefront onto inclined planes can be avoided. Quantitative phase retrieval is demonstrated using a test sample and a proof of concept phase imaging of a spider leg is also presented.

We present an improved, single-distance phase retrieval algorithm applicable for holographic X-ray imaging of biological objects for an in-line germanium Bragg Magnifier Microscope (BMM). The proposed algorithm takes advantage of a modified shrink-wrap algorithm for phase objects, robust unwrapping algorithm as well as other reasonable constraints applied to the wavefield at the object and the detector plane. The performance of the algorithm is analyzed on phantom objects and the results are shown and discussed. We demonstrated the suitability of the algorithm for the phase retrieval on a more complex biological specimen Tardigrade, where we achieved successful phase retrieval from only a single hologram. The spatial resolution obtained by Fourier spectral power method for biological objects is ∼ 300 nm, the same value as obtained from the reconstructed test pattern. Our results achieved using the new algorithm confirmed the potential of BMM for in-vivo, dose-efficient single-shot imaging of biological objects.

This work focused on a Timepix chip [1] coupled with a bulk semi-insulating GaAs sensor. The sensor consisted of a matrix of 256 × 256 pixels with a pitch of 55 μm bump-bonded to a Timepix ASIC. The sensor was processed on a 350 μm-thick SI GaAs wafer. We carried out detector adjustment to optimize its performance. This included threshold equalization with setting up parameters of the Timepix chip, such as Ikrum, Pream, Vfbk, and so on. The energy calibration of the GaAs Timepix detector was realized using a 241Am radioisotope in two Timepix detector modes: time-over-threshold and threshold scan. An energy resolution of 4.4 keV in FWHM (Full Width at Half Maximum) was observed for 59.5 keV γ-photons using threshold scan mode. The X-ray imaging quality of the GaAs Timepix detector was tested using various samples irradiated by an X-ray source with a focal spot size smaller than 8 μm and accelerating voltage up to 80 kV. A 700 μm × 700 μm gold testing object (X-500-200-16Au with Siemens star) fabricated with high precision was used for the spatial resolution testing at different values of X-ray image magnification (up to 45). The measured spatial resolution of our X-ray imaging system was about 4 μm.

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A: Nowadays, pixelated detectors based on Timepix readout chip play important role in various fields of science and research like particle physics, advanced spectrometry and especially X-ray imaging for medical and material purposes. Present work is focused on the evaluation of the 350 µm thick prototype (semi-insulating) SI GaAs sensor performance and its comparison to 300 µm thick Si sensor that was chosen as a reference. Both sensors consist of 256 × 256 pixels matrix with pixel pitch of 55 µm. We performed flat field illumination to test the pixel homogeneity and found out that the response of GaAs sensor is less homogeneous in terms of number of counts across the sensor compared to Si sensor. The imaging performance was tested using two samples of different absorption strength, specifically one less-absorbing sample and one more-absorbing sample. We found out that our fabricated SI GaAs sensor shows better imaging performance than Si sensor in case of imaging more-absorbing sample and vice versa. This is due to different prevalent detection efficiency regions. The spatial resolution was determined to be 8.73 lp/mm and 8.25 lp/mm for GaAs and Si sensor, respectively. Also, spectrometric measurements were carried out and results show that Si sensor has about 2 times higher energy resolution in comparison with SI GaAs sensor. K: X-ray detectors; Inspection with x-rays; X-ray radiography and digital radiography (DR)

A tomographic method for three-dimensional reconstruction of low density objects is presented and discussed. The experiment was performed in the extreme ultraviolet (EUV) spectral region using a desktop system for enhanced optical contrast and employing a compact laser-plasma EUV source, based on a double stream gas puff target. The system allows for volume reconstruction of transient gaseous objects, in this case gas jets, providing additional information for further characterization and optimization. Experimental details and reconstruction results are shown.

A volume, tomographic reconstruction of a novel, multi-jet gas puff target, developed for possible applications in high-order harmonic generation (HHG), is presented. The target, produced by pulsed injection of argon gas through nozzle in a form of linearly oriented small orifices, has been characterized in the extreme ultraviolet at 13.5 nm wavelength. Target density estimations were performed, and 3-D representation of pulsed gaseous target has been obtained by combining 2-D shadowgram images, recorded at various rotation angles. More detailed information about higher-order jets, formed as a result of collisions of primary jets, was obtained. Tomographic studies of such type of targets dedicated for HHG have been obtained to our knowledge for the first time.