Trace elemental determination by portable total reflection X‐ray fluorescence spectrometer with low wattage X‐ray tube

A specimen containing nanograms of Sb, rare earth elements, Pb, and Bi and a specimen containing a few nanograms each of As and Pb were measured using a portable total reflection X‐ray fluorescence spectrometer. Nanograms of Sb, rare earth elements, Pb, and Bi were detected. Although the As Kα line (10.54 keV) overlapped with the Pb Lα line (10.55 keV) in a spectrum of the specimen containing nanograms of As and Pb, the Pb Lβ line was detected. Therefore, the net intensity of the As Kα line was calculated using the Pb Lα/Lβ intensity ratio in a spectrum of a Pb standard solution and the net intensity of the Pb Lβ line in the spectrum of the specimen containing As and Pb. This result indicates that these two elements can be quantified by using the portable spectrometer. Commercially available bottled drinking water was also measured. The portable spectrometer detected several tens of ppb of V in the drinking water sample. Copyright © 2013 John Wiley & Sons, Ltd.     

Intensity correction of WD‐XRF spectra from 2θ to energy

Generally, the energy‐dispersive X‐ray fluorescence spectra are plotted as an equi‐energy interval with the constant energy resolution. On the other hand, the wavelength‐dispersive X‐ray fluorescence spectra are usually measured with an equi‐angle interval supposed the constant angular resolution. When the wavelength axis of wavelength‐dispersive X‐ray fluorescence spectra is converted into energy, the intensity should be also corrected. This intensity correction is important even for a narrow scan range such as Pb Lα and Lβ peaks. The intensity ordering is Lβ > Lα for 2θ plot, but it becomes Lα > Lβ for energy plot. The detailed conversion equations for abscissa and ordinate axes are presented. Copyright © 2012 John Wiley & Sons, Ltd.     

Confocal full‐field X‐ray microscope for novel three‐dimensional X‐ray imaging

A confocal full‐field X‐ray microscope has been developed for use as a novel three‐dimensional X‐ray imaging method. The system consists of an X‐ray illuminating `sheet‐beam' whose beam shape is micrified only in one dimension, and an X‐ray full‐field microscope whose optical axis is normal to the illuminating sheet beam. An arbitral cross‐sectional region of the object is irradiated by the sheet‐beam, and secondary X‐ray emission such as fluorescent X‐rays from this region is imaged simultaneously using the full‐field microscope. This system enables a virtual sliced image of a specimen to be obtained as a two‐dimensional magnified image, and three‐dimensional observation is available only by a linear translation of the object along the optical axis of the full‐field microscope. A feasibility test has been carried out at beamline 37XU of SPring‐8. Observation of the three‐dimensional distribution of metallic inclusions in an artificial diamond was performed.     

A multiplexed high‐resolution imaging spectrometer for resonant inelastic soft X‐ray scattering spectroscopy

The optical design of a two‐dimensional imaging soft X‐ray spectrometer is described. A monochromator will produce a dispersed spectrum in a narrow vertical illuminated stripe (～2 µm wide by ～2 mm tall) on a sample. The spectrometer will use inelastically scattered X‐rays to image the extended field on the sample in the incident photon energy direction (vertical), resolving the incident photon energy. At the same time it will image and disperse the scattered photons in the orthogonal (horizontal) direction, resolving the scattered photon energy. The principal challenge is to design a system that images from the flat‐field illumination of the sample to the flat field of the detector and to achieve sufficiently high spectral resolution. This spectrometer provides a completely parallel resonant inelastic X‐ray scattering measurement at high spectral resolution (～30000) over the energy bandwidth (～5 eV) of a soft X‐ray absorption resonance.     

A comparative study on determination of uranium and thorium in their mixed oxides by EDXRF using tube and radioisotope X‐ray sources

Studies on the matrix effects of uranium and thorium on the determinations of each other in their mixed oxides using energy dispersive X‐ray fluorescence (EDXRF) spectrometry with tube and radioisotope excitations of U Lα and Th Lα are reported. An internal standard method for the determination of uranium and thorium in these mixed oxides is found suitable. Comparison of the analytical results of EDXRF determinations of uranium and thorium using tube and radioisotope excitation sources has been made. The analytical methodology involves preparation of mixed oxide calibration/sample mixtures of uranium and thorium oxides, mixing of internal standard yttrium in these mixtures, pelletizing the mixtures after thorough mixing and grinding using boric acid binder and measuring EDXRF spectra of the specimens thus prepared using Rh X‐ray tube as well as ¹⁰⁹Cd radioisotope source. The samples were analyzed for uranium and thorium on the basis of the calibration plots obtained by plotting the intensity ratios of the analyte and internal standard characteristic X‐ray lines and their corresponding amount ratios. An average precision of 1.2% (1 s RSD) was observed for the determination of U and Th and the results deviated from the corresponding expected values by 3% on average. Due to the refractory nature of thorium oxide, comparatively more grinding time was required for thorium determinations. Copyright © 2011 John Wiley & Sons, Ltd.     

Can the HVL help the mechanical X‐ray tube characterization?

High‐intensity X‐ray beams are usually characterized by their kVp (kilovoltage peak) value and half‐value layer (HVL). While the first parameter is reasonably well known (apart from accelerating potential fluctuations), on the second, there is a greater deal of uncertainty. The HVL depends on the used filtration, the effective kVp value and on some of the X‐ray tube mechanical features, such as the anode angle. This last parameter is not always provided by the tube manufacturer, so we may question if the HVL dependence on the anode angle can be used to extract information on this angle. We tried to give an answer to this question using two different numerical models and a full Monte Carlo (MC) program to simulate the photon field produced by the X‐ray tube for several anode angles. One of the numerical models was developed by the Institute of Physics and Engineering in Medicine and gives X‐ray spectra and HVL values for a wide range of kVp values and anode angles. The other model, named SpekCalc, is based on a theoretical work developed by Gavin Poludniowski and Phil Evans. The MC simulation was done using the PENELOPE code for coupled electron‐photon transport. Using the computed photon spectra, HVLs were obtained and compared with experimental HVL values obtained with a Philips PW 2184/00 X‐ray tube with a 26° tungsten anode and accelerating potentials in the range of 40–90 kVp. We are now able to show the PENELOPE simulation can deliver the correct anode angle value. Copyright © 2011 John Wiley & Sons, Ltd.     

A miniature X‐ray tube approach to measuring lead in bone using L‐XRF

Using a miniature X‐ray tube and silicon PiN diode detector, an approach to measuring lead (Pb) in bone phantoms was tested. The X‐ray tube was used to excite L‐line X‐ray fluorescence (L‐XRF) of lead in bone phantoms. The bone phantoms were made from plaster of Paris and dosed with varying quantities of lead. Phantoms were made in two sets with different shapes to model different bone surfaces. One set of bone phantoms was circular in cross‐section (2.5‐cm diameter), the other square in cross‐section (2.2 cm × 2.2 cm). Using an irradiation time of 180 s (real time), five trials were run for each bone phantom. Analysis was performed for both Lα and Lβ lead X‐rays. Based on these calibration trials, (3σ₀/slope) minimum detection limits of 7.4 ± 0.3 µg Pb g^?1 (circular cross‐section) and 8.6 ± 0.6 µg Pb g^?1 (square cross‐section) were determined for the bare bone phantoms. To simulate a more realistic in vivo scenario with soft tissue overlying bone, further trials were performed with a resin material placed between the experimental system and the bone phantom. For the square cross‐section bone phantoms, a layer of resin with a thickness of 1.2 mm was used, and a minimum detection limit of 17 ± 3 µg Pb g^?1 determined. For the circular cross‐section phantoms, a layer of resin with an average thickness of 2.7 mm was used. From these, a more realistic minimum detection limit for in vivo applications (43 ± 7 µg Pb g^?1) was determined. Copyright © 2011 John Wiley & Sons, Ltd.     

Recording X‐ray spectra with an audio digitizer

X‐ray spectra were recorded with a notebook computer and analyzed by software on the computer, without a pulse height analyzer (PHA) or a digital signal processor (DSP). An audio (microphone or line) input on a personal computer has a built‐in analogue‐to‐digital converter (ADC) for digital audio recording. The output signal of the X‐ray detector is recorded through the audio input of the computer and then analyzed by software on the computer. On the basis of this method, X‐rays from a radium source were measured with a cadmium telluride detector. K X‐rays of bismuth were detected. Full width at half maximum (FWHM) was 5.6 keV at Kα of bismuth (77.1 keV), enough to separate Kβ (87.3 keV) from Kα of bismuth. The present method achieved almost equal energy resolution as that of the regular method (5.3 keV FWHM at 77.1 keV). Copyright © 2010 John Wiley & Sons, Ltd.     

Background estimation based on Fourier Transform in the energy‐dispersive X‐ray fluorescence analysis

This paper discusses a new method of background estimation in the energy‐dispersive X‐ray fluorescence (EDXRF) analysis, which is based on Fourier Transform (in this paper, we call it Fourier Transform background estimation method). Compared with the Sensitive Nonlinear Iterative Peak method, the new method has the feature of FWHM independence. It has been proved that a background can be estimated automatically and accurately by the new method in the synthesized spectrum and the spectra from measurement. Fourier Transform background estimation method can estimate the background accurately in the EDXRF spectrum using an X‐ray tube source. Copyright © 2011 John Wiley & Sons, Ltd.     

Time‐resolved X‐ray PIV technique for diagnosing opaque biofluid flow with insufficient X‐ray fluxes

X‐ray imaging is used to visualize the biofluid flow phenomena in a nondestructive manner. A technique currently used for quantitative visualization is X‐ray particle image velocimetry (PIV). Although this technique provides a high spatial resolution (less than 10 µm), significant hemodynamic parameters are difficult to obtain under actual physiological conditions because of the limited temporal resolution of the technique, which in turn is due to the relatively long exposure time (～10 ms) involved in X‐ray imaging. This study combines an image intensifier with a high‐speed camera to reduce exposure time, thereby improving temporal resolution. The image intensifier amplifies light flux by emitting secondary electrons in the micro‐channel plate. The increased incident light flux greatly reduces the exposure time (below 200 µs). The proposed X‐ray PIV system was applied to high‐speed blood flows in a tube, and the velocity field information was successfully obtained. The time‐resolved X‐ray PIV system can be employed to investigate blood flows at beamlines with insufficient X‐ray fluxes under specific physiological conditions. This method facilitates understanding of the basic hemodynamic characteristics and pathological mechanism of cardiovascular diseases.     

The energy dispersive scheme of X‐ray fluorescence analysis with a crystal polarizer and polycapillary optics

The efficiency of the polarization scheme based on polycapillary optics and a diamond crystal polarizer was demonstrated. The scheme provides suppression of the background of scattered radiation in measuring X‐ray fluorescence spectra. A quasi‐parallel X‐ray beam with an angular divergence of 4.2 mrad was formed by a microfocus source with a copper anode and polycapillary half‐lens. Simultaneous polarization and monochromatization of radiation was obtained with a crystal of natural diamond, which was set at the diffraction reflection (113). The degree of polarization of CuK_α1 spectral line and the maximum radiation flux were respectively equal to 99.86% and 5 · 10⁶ photon/s. In the direction orthogonal to the plane of diffraction, the maximum attenuation of the background was up to 19 dB.     

X‐ray spectrum unfolding using a regularized truncated SVD method

New procedures to characterize the x‐ray primary beam, obtaining an accurate assessment of the actual photon spectrum, are needed for quality control of x‐ray tubes for medical purposes. The Compton scattering technique is very useful for determining x‐ray spectra (in the 10–150 kV_p range), avoiding the pile‐up effect in the detector, since usually there is insufficient space available to apply other techniques. The Compton scattering procedure was simulated using the Monte Carlo method by means of the MCNP code. In order to validate the simulation model, experimental measurements were made at the Centro Nacional de Dosimetría (CND), Valencia, Spain, using a calibrated x‐ray tube. Different spectra were measured varying the operational parameters (kV, mA, Al). Furthermore, CND provided the theoretical spectra corresponding to the x‐ray measurement conditions. Using the developed model, a response matrix was obtained by simulating the interactions of different monoenergetic beams. During the construction of the primary photon spectrum it is necessary to calculate the inverse of the response matrix. Because this matrix is ill‐conditioned, its inversion is not a simple process. This problem was solved using a truncated singular value decomposition (TSVD), method together with variational regularization. The performance of the methodology was tested with experimental and simulated x‐ray spectra. Copyright © 2005 John Wiley & Sons, Ltd.     

X‐ray spectra by means of Monte Carlo simulations for imaging applications

X‐ray tubes have a broad range of applications worldwide, including several techniques for atomic physics, like X‐ray fluorescence, as well as for medical imaging, like computed tomography. The performances of X‐ray imaging detectors have shown to be significantly sensitive to the incident beam spectrum. Therefore, an accurate knowledge of the X‐ray beam becomes necessary for the emission source characterization and the whole imaging process comprehension. Direct measurements and suitable Monte Carlo simulations may be used to establish the X‐ray spectra. Dedicated Monte Carlo simulation routines, based on the PENELOPE code, have been developed to determine the Bremsstrahlung X‐ray spectra generated by conventional X‐ray tubes. The simulated spectra have been validated by comparison with the corresponding experimental data showing an overall good agreement. The incorporation of a suitably designed virtual grid allowed to assess the angular distribution of Bremsstrahlung yield, showing a remarkable anisotropy. In addition, a dedicated program has been developed for virtual imaging, which enables to perform suitable X‐ray absorption contrast images. Also, the developed program includes a user‐friendly graphic interface to allow the upload of required input parameters, which include setup arrangement, beam characteristics, sample properties and image simulation parameters (spatial resolution, tracks per run, etc.). The software includes dedicated subroutines which handle the physical process from X‐ray generation up to detector signal acquisition. The aim of the developed program is to perform virtual imaging by means of absorption contrast and using conventional X‐ray sources, which may be a useful tool for the study the X‐ray imaging techniques in several research fields as well as for educational purposes. The performed comparisons with experimental data have shown good agreement. The obtained results for X‐ray imaging may constitute useful information for the comprehension and improvement of X‐ray image quality, like absorption contrast optimization, detail visualization, definition and detectability. Copyright © 2010 John Wiley & Sons, Ltd.     

基于X射线衍射仪的X光晶体本征参量的标定

X光晶体本征参量的实验标定是准确鉴定X光晶体种类和品质,研制各种类型晶体谱仪,X光线谱定量测量和高分辨X光单能成像的基础.基于X射线衍射仪,通过制作平面晶体样品架,采取控制X射线管电源、滤波片选取和厚度控制等措施,极大地抑制了Cu-KJ3及韧致辐射,使X射线管光源Cu-Kα单能化,提出了用滤片作为光源单能化的判据.对X光线谱测量中常用的X光分光晶体季戊四醇[PET(002)]的晶格常量2d和Cu-Ka能点的积分衍射效率R.进行了标定方法研究,其标定值分别为(0.87425±0.00042)nm和(1.759±0.024)×10-4 Rad.基于X射线衍射仪的X光晶体本征参量的精密实验标定方法既快速高效,且十分方便和灵活.通过更换衍射仪的X射线管靶材,采取类似方法,可以标定其它能点的晶体积分衍射效率,可为X光晶体的本征参量库提供更多的标定数据.     

Determination of kernel emission spectrum of a mini X‐ray tube for EDXRF applications

Knowing the spectrum near the output of the relatively new mini X‐ray tube (MXRT) commercial models is fundamentally important in energy‐dispersive X‐ray fluorescence scan images, especially in the in vivo applications. This information is relevant for determining the absorbed dose during a measurement and for absolute quantification by a fundamental parameter method. However, it is not possible to measure it directly using a silicon drift detector (SDD) given the high saturation in the counts. In this work, an experimental methodology is developed for determining the kernel spectrum emitted by the MXRT, enabling the quantification of its energy flux density over short distances. Different distances were used: source–detector, solid emission angle (collimation), attenuation characteristics of the medium (air), and in a vacuum, within an energy range of 1–40 keV, to determine the X‐ray tube spectrum. The spectrum is measured by an SDD, taking its efficiency and dead time into account. In order to verify the method, a spectrum that is rebuilt starting with the kernel is compared, under the same conditions, with a reference spectrum that is directly measured in air and with a theoretical spectrum obtained by the Ebel model. The results are consistent and validate the methodology employed in this work. Additionally, low‐energy peaks were detected, corresponding to the tube material's L lines, which are not present in the original spectrum reported by the manufacturer. Copyright © 2015 John Wiley & Sons, Ltd.     

L‐series X‐ray emission spectra of 3d‐metal compounds with various excitation conditions

L‐series emissions of manganese, iron, and zinc oxides were studied using electron beam excitation and highly brilliant synchrotron radiation excitation. We showed that manganese and iron oxides show different Lβ/Lα intensity ratio because of their oxidation states and excitation electron voltages. On the other hand, we could not get any L‐series emissions from those bulk samples when excited by normal incident high‐energy monochromatic X‐rays, while samples of thin films and samples excited by grazing incident monochromatic X‐rays showed clear emissions. It is suggested that the difference of Lβ/Lα intensity ratio due to the oxidized states mainly concerns with the Coster–Kronig transition ratio of the samples, while self‐absorption effects should also deeply contribute the ratio, considering the experimental results. Copyright © 2016 John Wiley & Sons, Ltd.     

Measurement of relative line intensities for L‐shell X‐rays from selected elements between Z = 68 (Er) and Z = 79 (Au)

Relative line intensities of L1, L2 and L3 sub‐shell X‐rays were measured for Er, Tm, Yb, Hf, Ta, W, Pt and Au. The L‐shell X‐ray spectra were recorded by exciting pure element samples (eight cases) and oxide samples (two cases) with approximately 17‐keV exciting radiation from a filtered X‐ray tube source, and measuring the fluorescence spectra with a silicon drift detector. The spectra were carefully fitted to determine line energies and intensities, accounting for Lorentzian line broadening, incomplete charge collection and escape effects. A Monte Carlo approach was used to calculate attenuation and detector efficiency corrections. We report up to 15 line intensity ratios for each element and compare these to Scofield's theoretical predictions and Elam's extrapolated experimental database. Our measured relative line intensities agree best with Elam's data, but overall we find significant discrepancies with previously reported results. For the element Ta, we also find significant errors in the accepted L‐shell line energies in the widely used National Institute of Standard and Technology (NIST) database. Our results highlight the need for an experimental and theoretical re‐evaluation of L‐shell intensity databases to support high‐accuracy X‐ray analysis methods such as X‐ray fluorescence and particle‐induced X‐ray emission. Copyright © 2016 John Wiley & Sons, Ltd.     

Momentum‐resolved resonant inelastic X‐ray scattering on a single crystal under high pressure

A single‐crystal momentum‐resolved resonant inelastic X‐ray scattering (RIXS) experiment under high pressure using an originally designed diamond anvil cell (DAC) is reported. The diamond‐in/diamond‐out geometry was adopted with both the incident and scattered beams passing through a 1 mm‐thick diamond. This enabled us to cover wide momentum space keeping the scattering angle condition near 90°. Elastic and inelastic scattering from the diamond was drastically reduced using a pinhole placed after the DAC. Measurement of the momentum‐resolved RIXS spectra of Sr_2.5Ca_11.5Cu₂₄O₄₁ at the Cu K‐edge was thus successful. Though the inelastic intensity becomes weaker by two orders than the ambient pressure, RIXS spectra both at the center and the edge of the Brillouin zone were obtained at 3 GPa and low‐energy electronic excitations of the cuprate were found to change with pressure.     

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 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.