Portable x‐ray fluorescence spectrometer with a pyroelectric x‐ray generator

A portable x‐ray fluorescence spectrometer was assembled with an x‐ray generator that was driven by a 9 V dry electric battery. Several possible optimum geometries of the x‐ray generator and detector were evaluated, and the results showed that the intensity of fluorescent x‐rays was strong enough when the angle between the x‐ray generator and detector was as small as 30°. The geometrically optimized x‐ray spectrometer was applied to the analysis of paints, plastics and aluminum foils. Pigments in paint and toxic elements in plastic could be easily detected with on‐site analysis. Fe in aluminum foil was quantitatively determined down to the sub‐% level. The detection limit of Fe was 180 ppm for 100 s of measurement. Copyright © 2005 John Wiley & Sons, Ltd.     

Laboratory vacuum spectrometer for the soft x‐ray region

A laboratory surface x‐ray absorption near edge structure ((S)XANES) spectrometer used for measurements in the soft x‐ray region is described. The x‐ray beam path of the spectrometer is enclosed in a vacuum chamber directly connected to the x‐ray generator output port. With this setup, the absorption of the x‐rays in the air is avoided. The developed spectrometer uses a monochromator equipped with cylindrically bent PET(002), KAP(001), and Ge(111) crystals of different Rowland radii working in the Johann focusing geometry. Nine stepping motors are used to control the positions of the monochromator, receiving slit, sample, and detectors. An x‐ray photon energy available in experiment ranges from about 1 keV to 5 keV. A registration of the photoelectrons emitted from the sample with the channeltron is used to carry out surface‐sensitive measurements. The performance of the developed spectrometer is illustrated by spectra measured at the absorption K‐edges of several elements from the Na‐Ti set. Copyright © 2008 John Wiley & Sons, Ltd.     

The advantages of using digital signal processing in polarized x‐ray fluorescence analysis

Improving the specificity and productivity of XRF is of great relevance for the determination of trace elements in samples of diverse origin. The advantages of using digital signal processing in energy‐dispersive polarized x‐ray fluorescence analysis are demonstrated by comparing the instrumental sensitivities achieved with those obtained by using a conventional analogue signal processing‐based spectrometer. A compact geometry secondary target arrangement was designed to increase the effective solid angles and to reduce the distances between secondary target, sample and detector, thus achieving larger x‐ray fluxes for both the excitation and detection process, resulting in improved instrumental sensitivities. The performance of both spectrometers was evaluated for two different detectors: an Si(Li) detector and a thermoelectrically cooled passivated‐implanted planar silicon detector (X‐PIPS). The uncertainties achieved and accuracy are illustrated for the analysis of a group of sediment and organic‐origin certified reference materials using two different quantitative procedures. Copyright © 2006 John Wiley & Sons, Ltd.     

Spectrometer for hard X‐ray free‐electron laser based on diffraction focusing

X‐ray free‐electron lasers (XFELs) generate sequences of ultra‐short spatially coherent pulses of X‐ray radiation. A diffraction focusing spectrometer (DFS), which is able to measure the whole energy spectrum of the radiation of a single XFEL pulse with an energy resolution of ΔE/E? 2 × 10^?6, is proposed. This is much better than for most modern X‐ray spectrometers. Such resolution allows one to resolve the fine spectral structure of the XFEL pulse. The effect of diffraction focusing occurs in a single‐crystal plate due to dynamical scattering, and is similar to focusing in a Pendry lens made from a metamaterial with a negative refraction index. Such a spectrometer is easier to operate than those based on bent crystals. It is shown that the DFS can be used in a wide energy range from 5 keV to 20 keV.     

Total reflection x‐ray fluorescence spectrometer with parallel primary beam

A new type of x‐ray optical device with two curved mirrors was tested experimentally for total reflection x‐ray fluorescence (TXRF). When focusing optics are used to increase the primary beam intensity at the sample position of TXRF spectrometers, it is always associated with an increase in the angular divergence, which is tolerable to only a limited extent. The possibility of improving the divergence by means of an additional curved mirror was reported in the past. One may hope that this additional mirror will correct some of the adverse characteristics of conventional x‐ray sources, such as the angular divergence and the intensity at the sample position. Copyright © 2005 John Wiley & Sons, Ltd.     

Measurement of background components in wavelength dispersive X‐ray fluorescence spectrometry

Three components of the background have been investigated: first, characteristic radiation of the lamellas of the collimator excited by secondary x‐ray beam; second, secondary x‐ray beam scattered by the lamellas of the collimator; third, diffusive and incoherent scattering of the secondary x‐ray beam by the focusing crystal. The relationships between chemical content of the specimen and the intensity of the first and the second components were determined by a wavelength‐dispersive x‐ray spectrometer that has an energy‐dispersive x‐ray detector. The intensity of the third component was very low. It was not found in this experiment. Copyright © 2006 John Wiley & Sons, Ltd.     

A three‐crystal spectrometer for high‐energy resolution fluorescence‐detected X‐ray absorption spectroscopy and X‐ray emission spectroscopy at SSRF

A Johann‐type spectrometer for the study of high‐energy resolution fluorescence‐detected X‐ray absorption spectroscopy, X‐ray emission spectroscopy and resonant inelastic X‐ray scattering has been developed at BL14W1 X‐ray absorption fine structure spectroscopy beamline of Shanghai Synchrotron Radiation Facility. The spectrometer consists of three crystal analyzers mounted on a vertical motion stage. The instrument is scanned vertically and covers the Bragg angle range of 71.5–88°. The energy resolution of the spectrometer ranges from sub‐eV to a few eV. The spectrometer has a solid angle of about 1.87 × 0^?3 of 4π sr, and the overall photons acquired by the detector could be 10⁵ counts per second for the standard sample. The performances of the spectrometer are illustrated by the three experiments that are difficult to perform with the conventional absorption or emission spectroscopy. Copyright © 2016 John Wiley & Sons, Ltd.     

Planar waveguide‐resonator: a new device for x‐ray optics

Systematic investigations of the width dependence on the x‐ray beam propagation mechanism for a narrow extended slit formed by two plane dielectric plates are presented. It is shown that the mechanism of a multiple consecutive total reflection for Cu Kα radiation dominates in a slit width range s ≥ 3 µm. At the same time the manner of Cu Kα radiation propagation for super‐narrow slits s ≤ 0.1 µm is very different from the multiple total reflection mechanism. The x‐ray beam intensity proves to be constant for all this range of magnitude. This gives grounds to expect that the super‐narrow slit area is characterized by a specific type of mechanism of x‐ray beam propagation: waveguide‐resonance. A simple model for the waveguide‐resonance propagation mechanism based on the formation of a uniform x‐ray standing wave interference field in the total space of a narrow extended slit was developed. The design of a new x‐ray optical device, namely a planar x‐ray waveguide‐resonator, is proposed based on the waveguide‐resonance mechanism. Some properties of the composite planar x‐ray waveguide‐resonator are discussed. It is shown that under specific conditions the composite waveguide can demonstrate a partial tunneling effect of the x‐ray beam. The main applications of the new technique are discussed. Copyright © 2004 John Wiley & Sons, Ltd.     

Combined X‐ray diffraction and alpha particle X‐ray spectrometer analysis of geologic materials

The shallow interrogation depth of the lightest elements (Na, Mg, Al, and Si) detected by the particle‐induced X‐ray emission branch of the Curiosity Rover's alpha particle X‐ray spectrometer suggests that the X‐rays of these elements very likely emerge from a single mineral grain. This reality violates the assumption of atomic homogeneity at the micron scale made in both existing spectrum‐reduction approaches for the alpha particle X‐ray spectrometer. Consequently, analytical results for these elements in igneous geochemical reference materials exhibit deviations from certified concentrations in a manner that can be related to the total alkali‐silica diagram. A computer code is introduced here to provide quantitative prediction of these deviations using the mineral abundances determined from X‐ray diffraction. The latter are converted to area coverage fractions to represent the sample surface, and a fundamental parameters computation predicts the elemental X‐ray yields from each mineral and sums these. In this process, the chemistry of each individual mineral has to be varied by an iterative simplex approach; X‐ray yields are computed and compared with the peak areas from the fit of the bulk sample. When the difference between mineral yields and peak areas for each element are minimized, the mineral formulae are set and elemental X‐ray yields provided. The ratio between the summed mineral X‐ray yields and the corresponding yields based on the homogeneity assumption may then be compared directly with the concentration deviations measured in our earlier work. For several rock types, good agreement is found, thereby consolidating our understanding of the effects of sample mineralogy on alpha particle X‐ray spectrometer results. Copyright © 2017 John Wiley & Sons, Ltd.     

A miniature X‐ray emission spectrometer (miniXES) for high‐pressure studies in a diamond anvil cell

Core–shell X‐ray emission spectroscopy (XES) is a valuable complement to X‐ray absorption spectroscopy (XAS) techniques. However, XES in the hard X‐ray regime is much less frequently employed than XAS, often as a consequence of the relative scarcity of XES instrumentation having energy resolutions comparable with the relevant core‐hole lifetimes. To address this, a family of inexpensive and easily operated short‐working‐distance X‐ray emission spectrometers has been developed. The use of computer‐aided design and rapid prototype machining of plastics allows customization for various emission lines having energies from ～3 keV to ～10 keV. The specific instrument described here, based on a coarsely diced approximant of the Johansson optic, is intended to study volume collapse in Pr metal and compounds by observing the pressure dependence of the Pr Lα emission spectrum. The collection solid angle is ～50 msr, roughly equivalent to that of six traditional spherically bent crystal analyzers. The miniature X‐ray emission spectrometer (miniXES) methodology will help encourage the adoption and broad application of high‐resolution XES capabilities at hard X‐ray synchrotron facilities.     

Calculation of the transmission efficiency of a monolithic polycapillary x‐ray lens for an x‐ray source of any shape

A method for calculating the transmission efficiency of a monolithic polycapillary x‐ray lens is presented. Using this method, the transmission efficiency of an x‐ray source of any shape can be calculated by using the transmission efficiency measured with a microfocus x‐ray source. Copyright © 2005 John Wiley & Sons, Ltd.     

An X‐ray Raman spectrometer for EXAFS studies on minerals: bent Laue spectrometer with 20 keV X‐rays

An X‐ray Raman spectrometer for studies of local structures in minerals is discussed. Contrary to widely adopted back‐scattering spectrometers using ≤10 keV X‐rays, a spectrometer utilizing ～20 keV X‐rays and a bent Laue analyzer is proposed. The 20 keV photons penetrate mineral samples much more deeply than 10 keV photons, so that high intensity is obtained owing to an enhancement of the scattering volume. Furthermore, a bent Laue analyzer provides a wide band‐pass and a high reflectivity, leading to a much enhanced integrated intensity. A prototype spectrometer has been constructed and performance tests carried out. The oxygen K‐edge in SiO₂ glass and crystal (α‐quartz) has been measured with energy resolutions of 4 eV (EXAFS mode) and 1.3 eV (XANES mode). Unlike methods previously adopted, it is proposed to determine the pre‐edge curve based on a theoretical Compton profile and a Monte Carlo multiple‐scattering simulation before extracting EXAFS features. It is shown that the obtained EXAFS features are reproduced fairly well by a cluster model with a minimal set of fitting parameters. The spectrometer and the data processing proposed here are readily applicable to high‐pressure studies.     

Chemical speciation via X‐ray emission spectra

Since the early days of X‐ray spectrometry, X‐ray emission and fluorescence spectra have been used to investigate chemical speciation, e.g. the dependence on the formal oxidation state. Laboratory wavelength‐dispersive spectrometers have adequate resolution for these measurements. However, almost all studies have employed empirical methods to interpret the spectra. We aim to place such methods on a quantitative basis by means of efficient ab initio calculations of the X‐ray emission line shapes based on a self‐consistent, real‐space Green's function approach, as implemented in the X‐ray spectroscopy code FEFF8.2. Calculations are presented for the phosphorus K‐M_{2, 3}, and the chromium L‐series emission lines for a selection of simple compounds. These lines exhibit changes depending on the oxidation state and on the neighboring atoms in the compounds that can be observed with instruments available in many XRF laboratories. The calculated spectra, as modified by convolution with a model monochromator response function, are compared with measured spectra. Simulated and measured spectra are found to be in reasonable agreement, and show that the approach has the potential to yield quantitative information about the chemical state. Copyright © 2006 John Wiley & Sons, Ltd.     

Experimental evaluation of X‐ray optics applied for microanalysis

The performance of x‐ray capillary lenses has been evaluated. The tests were carried out using an x‐ray tube set‐up. A single glass capillary with tapered inner channel, a monolithic glass polycapillary, and an in‐house manufactured single metallic capillary with parabolic inner channel were characterized in terms of gain, spatial resolution, and element detection limits. The spatial resolution of a confocal set‐up utilizing a monolithic glass polycapillary and a polycapillary conical collimator has also been measured. The highest gain of about 2500 was observed for the glass polycapillary. The maximum gain achieved with the single glass capillary was equal to about 25, and the gain of the metallic capillary was only slightly greater than 1. For the glass capillary and polycapillary lenses, significant filtering of the higher‐energy photons (energy > 8 keV) was observed. The lowest relative detection limits were obtained with an ordinary cylindrical collimator and the polycapillary lens. Similar absolute detection limits were achieved with the use of the polycapillary and single capillary lenses. A relation between the ratios of the detection limits of elements achieved with different x‐ray lenses and the lens parameters (spatial resolution and gain) has been proposed and was verified experimentally. The monolithic polycapillary lens was found to be an optimum focusing device for an x‐ray tube‐based scanning spectrometer. This type of x‐ray lens can be coupled with a polycapillary conical collimator or a polycapillary half‐lens to make a confocal x‐ray microscope capable of depth profiling with a spatial resolution equal to about 30 micrometers. Copyright © 2008 John Wiley & Sons, Ltd.     

A high‐resolution X‐ray fluorescence spectrometer and its application at SSRF

A high‐resolution X‐ray fluorescence spectrometer based on Rowland circle geometry was developed and installed at BL14W1 XAFS beamline of Shanghai Synchrotron Radiation Facility. The spectrometer mainly consists of three parts: a sample holder, a spherically curved Si crystal, and an avalanche photodiode detector. The simplicity of the spectrometer makes it easily assembled on the general purpose X‐ray absorption beamline. X‐ray emission spectroscopy and high‐resolution X‐ray absorption near edge spectroscopy can be carried out by using this spectrometer. X‐ray emission preliminary results with high‐resolution about 3 eV of Mn compounds were obtained, which confirmed the feasibility of the spectrometer. The application about Eu (III) retention on manganese dioxide was also studied using this spectrometer. Compared with conventional X‐ray absorption fine structure spectroscopy technique, the fluorescence peak of probed element [Eu (III) Lα] and matrix constituents (Mn Kα) were discriminated using this technique, indicating its superiority in fluorescence detection. Copyright © 2013 John Wiley & Sons, Ltd.     

Calculation of attenuation and x‐ray fluorescence intensities for non‐parallel x‐ray beams

With the nowadays widespreaded use of x‐ray optics in x‐ray fluorescence analysis, large convergence or divergence angles can occur. This experimental situation violates a basic assumption of the usual fundamental parameter quantification procedure. In order to take beam divergences in micro x‐ray fluorescence analysis into account, a way of calculating fluorescence intensities numerically by Monte Carlo integration is described. For three examples of typical micro‐XRF set‐ups the fluorescence intensities and their deviation from the parallel beam geometry are calculated. Furthermore, we propose a new approach with ‘equivalent angles’ which correct for the beam divergences in fundamental parameter methods. Copyright © 2003 John Wiley & Sons, Ltd.     

A high‐energy‐resolution resonant inelastic X‐ray scattering spectrometer at ID20 of the European Synchrotron Radiation Facility

An end‐station for resonant inelastic X‐ray scattering and (resonant) X‐ray emission spectroscopy at beamline ID20 of ESRF – The European Synchrotron is presented. The spectrometer hosts five crystal analysers in Rowland geometry for large solid angle collection and is mounted on a rotatable arm for scattering in both the horizontal and vertical planes. The spectrometer is optimized for high‐energy‐resolution applications, including partial fluorescence yield or high‐energy‐resolution fluorescence detected X‐ray absorption spectroscopy and the study of elementary electronic excitations in solids. In addition, it can be used for non‐resonant inelastic X‐ray scattering measurements of valence electron excitations.     

X‐ray fluorescence spectrometry in Dar es Salaam

Energy‐dispersive x‐ray fluorescence (EDXRF) analysis has been established at the University of Dar es Salaam, Faculty of Science, Department of Physics. Calibration was conducted using thin films from Micromatter (USA) for secondary target XRF. We report on the performance of the spectrometer including the detection limits attained, which range from 0.01 to 10 ng cm^?2 using collimators of 6 and 8 mm diameter under excitation conditions of 50 kV, 35 mA. The accuracy of the measurements was checked using IAEA SOIL‐7 and NIST 3087a Certified Reference Materials. The experimental values differed by <5% from the certified values. The total reflection x‐ray fluorescence (TXRF) facility added as a module to the existing XRF system provides detection limits between 0.1 and 100 pg for most of the elements measured. Copyright © 2005 John Wiley & Sons, Ltd.     

Analysis of Limoges painted enamels from the 16th to 19th centuries by using a portable micro x‐ray fluorescence spectrometer

Material analysis of Limoges painted enamels was undertaken by using an x‐ray fluorescence spectrometer equipped with a low‐power x‐ray tube, polycapillary x‐ray optics and a silicon drift chamber detector. The spectrometer, which includes helium purging for detecting elements down to sodium, can easily be assembled and dismantled within 1 h. A quantification method for enamel and glass objects was developed and verified using standard materials. The layer arrangement and possible influence on the XRF measurements were especially considered in theoretical calculations. Over 160 painted enamels from the late Renaissance and Revival periods in the 19th century in various collections were investigated. Comparison of the quantitative results from objects which are securely dated and attributed by art historians allowed a more reliable attribution of pieces with doubted authenticity. Copyright © 2004 John Wiley & Sons, Ltd.