We have demonstrated that structures down to 150 nm can be visualized in X-ray projection images using nanofocus X-ray sources. Due to their unlimited depth of focus, they do not possess a limit on the specimen size. This is essential for three-dimensional tomographic imaging of samples with a diameter larger than a few microns. Further simulation studies have shown that optimization of the detector response curve and switching from a reflective X-ray target to a transmission target should allow us to reach sub-100-nm resolutions.

Due to the extraordinary beam characteristics of the new PETRA III synchrotron, i.e., the high brilliance, the extremely low emittance of 1 nm rad, and the high fraction of coherent photons even in the hard X-ray range, the imaging beamline (IBL) at PETRA III will provide state of the art imaging and tomography capabilities with resolution well into the nanometer range. Novel applications of tomographic techniques allow for high speed in situ measurements as well as highest spatial and density resolutions. Additionally, the highly coherent beam enables the application of phase contrast methods in an exceptional way. Since the focus is on the energy range between 5 and 50 keV, the IBL will among others be ideally suited for microtomography and nanotomography on small engineering materials science samples as well as for studying soft matter, bones, medical implants, and biomatter.

This paper presents Monte Carlo simulations considering all stages of the creation process of two-dimensional projections in a computed tomography (CT) device: excitation of angle dependent X-ray spectra within the X-ray tube using results from a previous study [Chyba et al. (2008). Powder Diffr. 23, 150–153]; interaction of these X-rays and secondary photoelectrons with a simple inhomogeneous sample; and interaction of X-rays and photoelectrons with the components (thin layers) of a matrix scintillation detector. The simulations were carried out by using custom software running on up to 50 nodes of a computer cluster. Comparative calculations were also made by using the software package MCNP [Booth et al. (2003). MCNP—A general Monte Carlo N-particle transport code, Report LAUR 03-1987, Los Alamos National Laboratory, Los Alamos, NM]. Tube spectra were calculated with algorithms proposed by Ebel [(2006). Adv. X-Ray Anal. 49, 267–273]. Measurements for the chosen setup made with an available CT device were in relatively good agreement with calculated results. It was shown that good knowledge of the tube spectra is of importance, but most differences between resulting projections and measurements are caused by uncertainties concerning detector response due to light yield of the scintillator and to internal scattering effects within the thin detector layers which lead to spreading of a detected point signal within the detector matrix into neighboring matrix elements.

Micro-X-ray fluorescence (μ-XRF) is a rapidly evolving analytical technique which allows visualising the trace level metal distributions within a specimen in an essentially nondestructive manner. At second generation synchrotron radiation sources, detection limits at the sub-parts per million level can be obtained with micrometer resolution, while at third generation sources the spatial resolution can be better than 100 nm. Consequently, the analysis of metals within biological systems using micro- and nano-X-ray fluorescence imaging is a quickly developing field of research. Since X-ray fluorescence is a scanning technique, the elemental distribution within the sample should not change during analysis. Biological samples pose challenges in this context due to their high water content. A dehydration procedure is commonly used for sample preparation enabling an analysis of the sample under ambient temperature conditions. Unfortunately, a potential change in elemental redistribution during the sample preparation is difficult to verify experimentally and therefore cannot be excluded completely. Creating a cryogenic sample environment allowing an analysis of the sample under cryogenic condition is an attractive alternative but not available on a routine basis. In this article, we make a comparison between the elemental distributions obtained by micro-SR-XRF within a chemically fixed and a cryogenically frozen Daphnia magna, a model organism to study the environmental impact of metals. In what follows, we explore the potential of a dual detector setup for investigating a full ecotoxicological experiment. Next to conventional 2D analysis, dual detector X-ray fluorescence cryotomography is illustrated and the potential of its coupling with laboratory absorption micro-CT for investigating the tissue-specific elemental distributions within this model organism is highlighted.

Lead poisoning is a preventable condition caused by exposure to environmental sources such as lead-containing dust or lead-painted consumer products. The history of lead poisoning prevention has been defined to some extent by the quality of the analytical methods available for lead measurements whether in environmental samples or biological tissues and fluids. The quality of blood lead methods has improved so greatly over the last three decades that we now know far more about the adverse health effects from low-level exposures. Recent evidence suggests that effects such as deficit in IQ occur below the current (periodically revised) U.S. CDC threshold of 10 μg/dL, such that no safe threshold appears to exist for children. Improvements in analytical techniques have also had an impact on the environmental measurement quality, yet many environmental thresholds have remained unchanged for decades. In light of our current understanding of the adverse health effects at low levels of exposure, new thresholds for lead in children’s products have been introduced by the U.S. CPSC. The adequacy of current analytical techniques to detect lead accurately at the new, lower thresholds is questionable. XRF offers the advantage of being rapid and nondestructive compared to techniques such as AAS that require extensive sample preparation. However, the accuracy of handheld XRF determinations of lead in painted toys is generally limited. A brief comparative study on the performance of several analytical techniques for the determination of lead in toys is presented at the end of this paper.

Accurate minor and trace element analysis via micro-XRF can be more difficult to accomplish in single crystal and polycrystalline materials due to diffraction phenomena which obscure elemental peaks and distort the spectral background. A primary-beam filter is commonly used to eliminate diffractive artifacts as well as tube characteristic lines, but this dramatically reduces the sensitivity to lighter elements. One way around this is to collect a spectrum with unfiltered excitation to obtain the low-energy region, i.e., Na, Mg, Al, and Si, and then collect other portions of the spectrum under more optimized conditions. The fundamental parameter method is capable of using multiple spectra to quantify the complete element suite of the sample. By unifying the quantification for several spectra taken under different excitation conditions, the overall results can be improved. We have applied this method to selected cases for geological and metallurgical samples. The combined method gives better results for all elements than the single spectrum quantification as judged by agreement with the values from the supplier.

The National Institute of Standards and Technology (NIST) certifies a variety of standard reference materials (SRM) to address specific aspects of instrument performance for divergent beam diffractometers. This paper describes SRM 640d, the fifth generation of this powder diffraction SRM, which is certified with respect to the lattice parameter. It consists of approximately 7.5 g silicon powder specially prepared to produce strain-free particles in a size range between 1 and 10 μm to eliminate size-broadening effects. It is typically used for calibrating powder diffractometers for the line position and line shape. A NIST built diffractometer, incorporating many advanced design features, was used to certify the lattice parameter of the silicon powder measured at 22.5 °C. Both type A, statistical, and type B, systematic, errors have been assigned to yield a certified value for the lattice parameter of a=0.543 159±0.000 020 nm.