The phase-stepping (PS) mode of X-ray Grating Talbot interferometer (XGTI) data processing technique can yield
high-spatial resolution images, albeit with lower throughput since each projection of a tomogram requires at least five
phase-stepping images. To overcome this problem, we can use a setup with only a single phase grating in combination
with a high-resolution detector system and a Spatial Harmonic Imaging (SHI) technique. The latter technique makes use
of the fact that a Talbot interferogram consists of carrier frequency spectrum of the grating overlapping with the sample
spectrum and by Fourier transforming the interferogram we can separate the two. The disadvantage of this is that the
spatial resolution is inferior. In this manuscript we will compare these two single grating data processing techniques
using a single data set measured with mouse embryo heart and discuss advantages and disadvantages of each technique.
These two techniques can be used as complementary; one for high resolution, and the other for high-speed imaging.
The Diamond Beamline I13L is dedicated to imaging on the micro- and nano-lengthsale, operating in the energy range
between 6 and 30keV. For this purpose two independently operating branchlines and endstations have been built. The
imaging branch is fully operational for micro-tomography and in-line phase contrast imaging with micrometre
resolution. Grating interferometry is currently implemented, adding the capability of measuring phase and small-angle
information. For tomography with increased resolution a full-field microscope providing 50nm spatial resolution with a
field of view of 100μm is being tested. The instrument provides a large working distance between optics and sample to
adapt a wide range of customised sample environments. On the coherence branch coherent diffraction imaging
techniques such as ptychography, coherent X-ray diffraction (CXRD) are currently developed for three dimensional
imaging with the highest resolution.
The imaging branch is operated in collaboration with Manchester University, called therefore the Diamond-Manchester
Branchline. The scientific applications cover a large area including bio-medicine, materials science, chemistry geology
and more. The present paper provides an overview about the current status of the beamline and the science addressed.
We developed a corrective phase plate that enables the correction of residual aberration in reflective, diffractive, and refractive X-ray optics. The principle is demonstrated on a stack of beryllium compound refractive lenses with a numerical aperture of 0.49 10-3 at three synchrotron radiation and x-ray free-electron laser facilities, where we corrected spherical aberration of the optical system. The phase plate improved the Strehl ratio of the optics from 0.29(7) to 0.87(5), creating a diffraction-limited, large aperture, nanofocusing optics that is radiation resistant and very compact.
A noninvasive technique to image soft tissue could expedite diagnosis and disease management in the auditory system.
We propose inline phase contrast imaging with hard X-rays as a novel method that overcomes the limitations of
conventional absorption radiography for imaging soft tissue. In this study, phase contrast imaging of mouse cochleae
was performed at the Argonne National Laboratory Advanced Photon Source. The phase contrast
tomographic reconstructions show soft tissue structures of the cochlea, including the inner pillar cells, the inner spiral
sulcus, the tectorial membrane, the basilar membrane, and the Reissner's membrane. The results suggest that phase
contrast X-ray imaging and tomographic techniques hold promise to noninvasively image cochlear structures at an
unprecedented cellular level.
An instrument for high-resolution imaging and tomography has been built at the APS beamline 34 ID-C, Argonne
National Laboratory. In-line phase contrast tomography can be performed with micrometer resolution. For imaging
and tomography with resolution better than 100nm a hard X-ray microscope has been integrated to the instrument. It
works with a Kirkpatrick-Baez (KB) mirror as condenser and a Fresnel-Zone plate (FZP) as an objective lens. 50
nm-features have been resolved in a Nickel structure operating the microscope at a photon energy of 9keV. Phase
objects with negligible absorption contrast have been imaged. Tomography scans were performed on photonic
During grain growth, larger grains tend to grow at the expense of their smaller neighbors, resulting in a steady increase in the average crystallite size. Because the growth rate of any given grain is affected by that of its neighbors, the manner in which growth occurs is determined to a large extent by correlations in the sizes of neighboring grains. Quantitative information concerning these correlations can be extracted only from a truly three-dimensional characterization of the sample microstructure. We have used x-ray microtomography to measure the nearest-neighbor size correlations in a polycrystalline specimen of Al alloyed with 2 at.% Sn. The tin atoms segregate to the grain boundaries, where they impart a strong contrast in x-ray attenuation that can be reconstructed tomographically. From such reconstructions, we measured the size, topology and local connectivity of nearly 5000 contiguous Al grains and subsequently computed the size correlations in this material. The resulting information was incorporated into a non-mean-field theory for grain growth, the accuracy of which could be evaluated by comparing its predictions to the observed microstructure of the Al-Sn samples.
For several years efforts have been made to improve the resolution for imaging and tomography with hard X-rays. Recently we demonstrated sub-100 nm resolution at 13 keV with a microscope including a Kirkpatrick-Baez multilayer-mirror (KB) as a condenser followed by a micro-Fresnel Zone Plate (FZP) as an objective lens. We built since a new tomography station at UNICAT at the Advanced Photon Source integrating the KB-FZP microscope for 100 nm tomography.
In recent years, hard x-ray full field microscopy and tomography has been developed for synchrotron radiation sources based on parabolic refractive x-ray lenses. These optics are used as objective lens in a hard x-ray microscope that can image objects in transmission free of distortion. Using beryllium as lens material, an optical resolution of about 100nm has been reached in a field of view that is larger than 500 micrometers. In the future, the spatial resolution may be improved to below 50nm. Recording a large number of micrographs from different perspectives allows one to reconstruct non-destructively the 3-dimensional inner structure of an object with resolutions well below one micrometer. Different contrast mechanisms can be exploited, such as absorption and near field phase contrast. The method is demonstrated using a microchip as a test sample.
In various scientific fields -- such as materials sciences, biology or even astrophysics -- the relation between morphology and the chemical composition is a key for the understanding of structures and their function. Hard x-ray tomography is a suitable tool for structural analyzes on the micrometer scale and can give additional chemical information by combining this imaging technique with spectroscopic methods. In chemistry, X-ray absorption near-edge spectroscopy (XANES) is a well-known and established technique. By scanning the X-ray energy in the vicinity (50-100 eV) of the absorption edge of an element, information can be obtained about the oxidation state of the probed atoms. We used a fast read-out and low noise detector for XANES imaging and were able to distinguish different oxidation states in three dimension performing tomographic scans at different characteristic energies of the probed atom.
Recently, we have been able to fabricate high quality parabolic refractive x-ray lenses made of beryllium. We report first experimental results in both full field microscopy and microbeam production using these new lenses. In full field microscopy, undistorted images of test patterns were recorded in a field of view of 450 μm full width half maximum at 12keV with 10 fold magnification. A significant improvement of the lateral resolution as compared to imaging with aluminium refractive lenses was achieved. Microbeam characteristics were determined at 12keV demagnifying a high β undulator source 82 times. The lateral beam size was measured by fluorescence knife-edge. Microbeam characteristics, such as flux, lateral beam size, and low intensity background are discussed.
In chemistry, x-ray absorption near-edge spectroscopy (XANES) is a well-known and established technique. By scanning the x-ray energy in the vicinity (50-100 eV) of the absorption edge of an element, information can be obtained about the oxidation state of the probed atoms. The (conventional) technique mainly employed until now applies for homogeneous, specifically prepared flat samples where the measured signal can be considered as the average over the whole irradiated volume. This restriction for samples is partially released when the XANES method is combined with imaging techniques. Two-D resolved data is acquired using area detectors or by scanning with a focused beam. X-ray absorption tomography is a method of choice for investigating the 3D structure of objects and its dual energy version is used for getting information about the 3D distribution of a given element within the sample. Although the combination of XANES and tomography seems to be a natural extension of dual-energy tomography, in practice several experimental problems have to be overcome in order to obtain useable data. In the following we describe the results of XANES imaging and tomography obtained measuring a phantom sample of pure molybdenum compounds using a FreLoN 2000 camera system at the ESRF undulator beamline ID22. This system allowed making volume resolved distinctions between different oxidation states with spatial resolution in the micrometer range.
Parabolic compound refractive lenses (PCRLs) are high quality imaging optics for hard x-rays that can be used as an objective lens in a new type of hard x-ray full field microscope. Using an aluminium PCRL, this new type of microscope has been shown to have a resolution of 350 nm. Further improvement of the resolution down to 50 nm can be expected using beryllium as a lens material. The large depth of field (several mm) of the microscope results in sharp projection images for samples that fit into the field of view of about 300 micrometers. This allows to combine magnified imaging with tomographic techniques. First results of magnified microtomography are shown. Contrast formation in the microscope and the consequences for tomographic reconstruction are discussed. An outlook on further developments is given.
One major goal in x-ray tomography is to increase the resolution in space and time. For the methods with high temporal resolution we will present pink beam imaging and tomography. Experiments were realised at the ESRF undulator beamline ID22 with hard x-rays in the range from 11 keV to 20 keV. For the tomographic scans the exposure time per image was reduced by one to two orders of magnitude to less than 50 ms per image. The obtained image quality was comparable to that done with monochromatic beam. Further time reducing for a tomographic scan is possible with an improved acquiring and control system. The goal in the future is to realise tomographic scans within a minute with micrometer resolution. In order to achieve in the hard x-ray range sub-micrometer resolution we will show first results of x-ray magnified tomography. Different lens systems are available for this purpose. We obtained with aluminium parabolic compound refractive lenses a resolution of 1 micrometers and expect to overcome this limit hand in hand with the improvement of lens technology.
The inadequacies of current analytical models for grain growth are thought to arise in part from their mean-field nature: they ignore the presence of correlations in the sizes of neighboring grains induced by the process of grain growth itself. Although grain-size correlations have been identified in microstructures generated by computer simulations of grain growth, no comparable evidence has been obtained from real samples - primarily because of the experimental difficulties associated with evaluating this inherently three-dimensional property. Using absorption- contrast x-ray microtomography, we have attempted to characterize the network of grain boundaries in polycrystalline samples of Al doped with up to 3 at.% Sn. In principle, since the tin atoms segregate to the grain boundaries, it should be possible to determine the size and relative position of each grain from a three-dimensional reconstruction of the Sn distribution, from which the desired correlation function could be calculated directly. However, the grain boundaries in Al-Sn are not uniformly decorated with tin, which presents a formidable challenge to quantifying the microstructural properties of such samples. Significant progress toward overcoming this problem has been achieved by applying a constrained phase-field grain-growth algorithm to an approximate microstructure gleaned from the tomographic contrast data.
Microtomography based on synchrotron radiation sources is a unique technique for the 3D characterization of different materials with a spatial resolution down to about 1 micrometers . The interface between implant materials (metals, ceramics and polymers) and biological matter is nondestructively accessible, i.e. without preparation artifacts. Since the materials exhibit different x-ray absorption, it can become impossible to visualize implant material and tissue, simultaneously. Here, we show that coating of polymer implants, which are invisible in bone tissue, does not only improve the interfacial properties but also allows the imaging of the interface in detail. Titanium implants, on the other hand, absorb the x-rays stronger than bone tissue. The difference, however, is small enough to quantify the bone formation near interface. Another advantage of microtomography with respect to classical histology is the capability to examine samples in a hydrated state. We demonstrate that ceramic hollow spheres can be imaged before sintering and fibroblasts marked by OsO4 are visible on polymer textiles. Consequently, scaffolds of different materials designed for tissue engineering and implant coatings can be optimized on the basis of the tomograms.
When used in microimaging, hard x rays from third-generation synchrotron radiation (SR) sources inevitably generate noninterferometric or in-line phase contrast. It is formed by the propagation of a distorted x-ray wavefront after the sample. In this paper, we discuss phase contrast and its properties in two altogether different experimental modes. First, in edge-enhanced microtomography, we show by phase- propagation simulations that local tomography is possible without special effort. The second part of the paper discusses phase contrast and phase artifacts in magnified x- ray imaging and tomography using refractive lenses. Here, the phase effects degrade resolution to a considerable extent. This part of the paper contains experimental results from the ESRF beamline ID 22 in the photon energy range around 20 keV that are compared to simulated images and to experimental results from conventional high-resolution microtomography. The experimental results show that coherence-degrading devices can reduce but not completely eliminate phase effects, and recent microtomography data gathered with an x-ray microscope still cannot beat conventional state-of-the-art high-resolution microtomography with micrometer resolution.
The planar microelectronics technology, involving lithography and highly anisotropic plasma etching techniques, allows manufacturing high quality refractive and diffractive lenses, which may be used in hard X-ray microprobe and microscopy applications. These silicon lenses are mechanically robust and can withstand high beat load of the white X-ray beam at third generation synchrotron radiation sources. For the first time we designed and manufactured a new type of lenses: kinoform lenses and parabolic lenses with scaled reduction of curvature radii. The theoretical background for such type of lens features is presented. Focusing properties in the terms of focus spot and efficiency of all these lenses were tested at the ESRF beamlines. Magnified imaging with planar lense was realized. Some future developments are discussed.
We describe parabolic compound refractive lenses for hard x- rays that are genuine imaging devices similar to glass lenses for visible light. They open considerable possibilities in both full field and scanning x-ray microscopy, microanalysis, and coherent scattering. They can operate in a range from about 2 keV to 100 keV, are robust, and withstand the white beam of a third generation undulator source. Using aluminum lenses in full field microscopy a field of view of about 300 micrometer can be imaged with magnifications between 10 and 50 and a resolution of about 300 nm. With beryllium lenses an improvement of the resolution to below 100 nm is expected. For microbeam applications, the synchrotron source is imaged onto the sample in a strongly demagnifying setup. With focal distances between 0.3 m and 2 m, the source can be demagnified by a factor 20 to 200 producing a beam with lateral extensions in the micron and sub-micron range. For aluminum lenses, monochromatic microbeams with fluxes above 1010 ph/s and a gain above 1000 are routinely produced at third generation undulator sources. Compound refractive lenses will allow to produce microbeams at energies up to at least 100 keV, making for example, microfluorescence experiments at the K-edges of heavy elements possible. The modular setup of compound refractive lenses allows to adjust the focal length to ideally match the experimental requirements. Assembling and aligning the lens take about 15 minutes. No order sorting apertures are required and the straight optical path allows to remove the lens to align other components.
Silicon planar parabolic refractive lenses with relief depth of 100 micrometer are realized by microfabrication technique. A set of 5 planar lenses with simple parabolic profiles and equal apertures and equal focal distances is realized. This set consists of different number (from 1 to 8) of individual lenses. Lenses with minimized absorption as a set of parabolic segments are fabricated too. Focusing and spectral properties of silicon planar parabolic lenses were studied with synchrotron radiation in the x-ray energy range 8 - 25 keV at the ESRF. Linear focus spots of 1.5 micrometer width were recorded for the parabolic lenses and 1.8 micrometer for the lenses with minimized absorption. The intensity transmission of the lens with minimized absorption is two times greater than this value of simple parabolic lenses at 8 keV and in the x-ray energy range over 15 keV overcomes 90%. Spectral properties of the lenses with minimized absorption are discussed in details. Heatload properties of the silicon planar lenses are analyzed and compared with the lenses made of diamond.