Characteristic X-ray flux from sealed Cr, Cu, Mo, Ag and W tubes

A multipurpose laboratory diffractometer for operando powder X-ray diffraction investigations of energy materials

This paper describes the design and implementation of an in-house laboratory powder X-ray diffractometer tailored for structural investigations of energy materials. The performance characteristics of the diffractometer together with some example research applications are presented.

Laboratory X-ray diffractometers are among the most widespread instruments in research laboratories around the world and are commercially available in different configurations and setups from various manufacturers. Advances in detector technology and X-ray sources push the data quality of in-house diffractometers and enable the collection of time-resolved scattering data during operando experiments. Here, the design and installation of a custom-built multipurpose laboratory diffractometer for the crystallographic characterization of battery materials are reported. The instrument is based on a Huber six-circle diffractometer equipped with a molybdenum microfocus rotating anode with 2D collimated parallel-beam X-ray optics and an optional two-bounce crystal monochromator. Scattered X-rays are detected with a hybrid single-photon-counting area detector (PILATUS 300K-W). An overview of the different diffraction setups together with the main features of the beam characteristics is given. Example case studies illustrate the flexibility of the research instrument for time-resolved operando powder X-ray diffraction experiments as well as the possibility to collect higher-resolution data suitable for diffraction line-profile analysis.

Pushing data quality for laboratory pair distribution function experiments

Over the last decade, some studies with laboratory pair distribution function (PDF) data emerged. Yet, limited Q_max or instrumental resolution impeded in-depth structural refinements. With more advanced detector technologies, the question arose how to design novel PDF equipment for laboratories that will allow decent PDF refinements over r = 1-70 Å. It is crucial to reflect the essential requirements, namely, monochromatic X-rays, suppression of air scattering, instrumental resolution, and overall measurement times. The result is a novel PDF setup based on a STOE STADI P powder diffractometer in transmission-/Debye-Scherrer geometry with monochromatic Ag Kα₁ radiation, featuring a MYTHEN2 4K detector covering a Q range of 0.3-20.5 Å^-1. PDF data are collected in a moving PDF mode within 6 h. Structural signatures of liquids can be satisfactorily resolved in the PDF as shown for the ionic liquid hmimPF₆. The high instrumental resolution is mirrored in low q_damp values determined from LaB₆ measurements. PDF data from a powder sample of ca. 7 nm TiO₂ nanoparticles were successfully refined over up to 70 Å with goodness-of-fit values R_w < 0.22 (respectively R_w = 0.18 over 30 Å), thanks to the low background and high instrumental resolution, hereby enlarging the accessible r range by several tens of Angstroms compared to previous laboratory PDF studies.

Estimating the absolute flux distribution for a synchrotron X-ray beam using ionization-chamber measurements with various filters

It is shown that an extensive set of accurate ionization-chamber measurements with a primary polychromatic synchrotron X-ray beam transmitted through various filter combinations/thicknesses can be used to quite effectively estimate the absolute flux distribution. The basic technique is simple but the `inversion' of the raw data to extract the flux distribution is a fundamentally ill-posed problem. It is demonstrated, using data collected at the Imaging and Medical Beamline (IMBL) of the Australian Synchrotron, that the absolute flux can be quickly and reliably estimated if a suitable choice of filters is made. Results are presented as a function of the magnetic field (from 1.40 to 4.00 T) of the superconducting multi-pole wiggler insertion device installed at IMBL. A non-linear least-squares refinement of the data is used to estimate the incident flux distribution and then comparison is made with calculations from the programs SPECTRA, XOP and spec.exe. The technique described is important not only in estimating flux itself but also for a variety of other, derived, X-ray properties such as beam quality, power density and absorbed-dose rate. The applicability of the technique with a monochromatic X-ray beam for which there is significant harmonic contamination is also demonstrated. Whilst absolute results can also be derived in this monochromatic beam case, relative (integrated) flux values are sufficient for our primary aim of establishing reliable determinations of the percentages of the various harmonic components.

McXtrace: a Monte Carlo software package for simulating X-ray optics, beamlines and experiments

This article presents the Monte Carlo simulation packageMcXtrace, intended for optimizing X-ray beam instrumentation and performing virtual X-ray experiments for data analysis. The system shares a structure and code base with the popular neutron simulation codeMcStasand is a good complement to the standard X-ray simulation softwareSHADOW.McXtraceis open source, licensed under the General Public License, and does not require the user to have access to any proprietary software for its operation. The structure of the software is described in detail, and various examples are given to showcase the versatility of theMcXtraceprocedure and outline a possible route to using Monte Carlo simulations in data analysis to gain new scientific insights. The studies performed span a range of X-ray experimental techniques: absorption tomography, powder diffraction, single-crystal diffraction and pump-and-probe experiments. Simulation studies are compared with experimental data and theoretical calculations. Furthermore, the simulation capabilities for computing coherent X-ray beam properties and a comparison with basic diffraction theory are presented.

X-ray colour imaging

A prototype X-ray colour imaging system has been assembled using the principle of tomographic energy-dispersive diffraction imaging (TEDDI). The new system has been tested using samples of nylon-6, aluminium powder and deer antler bone. Non-destructive three-dimensional images of the test objects have been reconstructed on a 300 microm scale with an associated diffraction pattern at each voxel. In addition, the lattice parameters of the polycrystalline material present in the sampled voxels have been determined using full pattern refinement methods. The use of multiple diffracted parallel colour X-ray beams has allowed simultaneous spatially resolved data collection across a plane of the sample. This has simplified the sample scan motion and has improved data collection times by a factor scaling with the number of detector pixels. The TEDDI method is currently limited to thin samples (approx. 1-2mm) with light atoms owing to the very low detection efficiency of the silicon detector at X-ray energies above 25 keV. We describe how these difficulties can be removed by using semiconductor detectors made from heavier atomic material.