Energy Dispersive Detector Research Articles

Three-Dimensional Trace Element Analysis by Confocal X-ray Microfluorescence Imaging

A three-dimensional (3D) variant of scanning micro X-ray fluorescence (XRF) is described and evaluated at the ID18F instrument of the European Synchrotron Radiation Facility (ESRF). The method is based on confocal excitation/detection using a polycapillary half-lens in front of the energy-dispersive detector. The experimental arrangement represents a significant generalization of regular two-dimensional (2D) scanning micro-XRF and employs a detector half-lens whose focus coincides with that of the focused incoming beam. The detection volume defined by the intersection of the exciting beam and the energy-dependent acceptance of the polycapillary optics is 100-350 mum(3). Minimum detection limits are sub-ppm, and sensitivities are comparable with regular scanning XRF. Next to the reduction of in-sample single/multiple scattering, the setup provides the possibility of sample depth scans with an energy-dependent resolution of 10-35 mum in the energy range of 3-23 keV and the possibility of performing 3D-XRF analysis by simple XYZ linear scanning. This provides a suitable alternative to X-ray fluorescence tomography. The method is illustrated with results of the analysis of solid inclusions in diamond and fluid inclusions in quartz.

Analysis of non-organic elements in plant foliage using polarised X-ray fluorescence spectrometry

An X-ray fluorescence (XRF) method for the rapid and non-destructive analysis of 30 non-organic elements in plant leaves over five orders of magnitude concentration from several percentage of dry weight to sub-milligram per kilogram, is described. There is a growing need for a simple method of monitoring non-organic trace elements in plant material, especially those which accumulate in soils with application of fertilisers, both inorganic and biosolids. Earlier attempts to use XRF for the analysis of plant material suffered from sensitivity loss due to the high background of organic matrices caused by scattering of the X-ray source. We overcome this by using polarised X-ray sources in a Cartesian geometrical arrangement with sample and energy dispersive detector (EDPXRF), a configuration which can achieve an order of magnitude reduction in background compared with unpolarised sources. Further sensitivity gains are made using a high power tube as a source of primary X-rays and for some analytes employing secondary targets for near-monochromatic excitation. Sample preparation is simple involving only pulverising and briquetting of dried samples. Accuracy is evaluated by comparing data obtained for the suite of NIST plant leaf samples (NIST 1515 apple leaves, NIST 1547 peach leaves, NIST 1570a spinach leaves, NIST 1573a tomato leaves and NIST 1575a pine needles) and tobacco leaf standards CTA-OTL-1 and CTA-VTL-2. The data compare well over the whole concentration range and the method provides a rapid analytical tool for monitoring potentially toxic trace elements in all types of foliage with adequate sensitivity for many purposes.

Design, fabrication and testing of elliptical crystal bender for the EXAFS beam-line at INDUS-II synchrotron source

An extended X-ray absorption fine structure (EXAFS) beam-line for X-ray absorption studies using energy dispersive geometry and position sensitive detector is being developed for the INDUS-II synchrotron source. The optical design of the beam-line has been completed based on the working principle that a single crystal bent in the shape of an ellipse by a crystal bender would act as a dispersing as well as focusing element. The heart of the beam-line is the crystal bender which has been designed on the basis of the principle of four-point bending and has been fabricated indigenously. The crystal bender is capable of producing pre-defined elliptical curvature on a crystal surface by applying different couples at the two-ends of the crystal which has variable width along its length. The focusing property of the crystal bender has been tested using a laser source and has been compared with the theoretically simulated results.

Confocal microscopic X-ray fluorescence at the HASYLAB microfocus beamline: characteristics and possibilities

The possibilities of performing non-destructive elemental analysis in three dimensions on a variety of heterogeneous materials by means of an innovative variation of the microscopic X-ray fluorescence analysis (μ-XRF) method are described. Next to employing focusing optics for concentration of the primary beam of X-rays, a second optical element between the sample and the energy-dispersive detector is used in confocal μ-XRF. Thus, only X-ray fluorescence signals from a cube-like volume (within certain limits imposed by the absorption of the radiation in the sample) can be arbitrarily positioned within the sample. The distribution of major, minor and trace elements (down to the sub-ppm concentration level in some matrices) along lines and planes within the sample can be visualized with a spatial resolution of the order of 15–40 μm. The lowest detectable amounts in confocal mode using pink-beam excitation are situated at the sub-femtogram level.

Measurements of the X-ray linear attenuation coefficient for low atomic number materials at energies 32–66 and [formula omitted

The X-ray linear attenuation coefficient was measured for materials containing elements hydrogen to calcium. Characteristic X-rays with energies 32– 66 keV were produced by X-ray fluorescence using a secondary target system, and 140 keV gamma rays were obtained from an unsealed 99 m Tc source. The photon beams were highly collimated and recorded using energy dispersive detection. A high-purity germanium detector was utilised to distinguish between measurements with K α and K β characteristic X-rays, and the gamma ray measurements used a sodium iodide detector. Samples were selected on the basis of having known composition and mass densities were measured using a pycnometer. The samples comprised six plastics, seven crystalline materials, three tissue substitute materials, three liquids and six salt solutions. Our results have an uncertainty of less than 2% and are a few percent lower than values predicted by the tabulations.

A modular system for XRF and XRD applications consisting of a microfocus X‐ray source and different capillary optics

AbstractIn recent years, new components for x‐ray analysis have been developed: capillary optics, microfocus x‐ray tubes and compact detectors, e.g. energy‐dispersive detectors without liquid nitrogen cooling. Microfocus tubes have a relatively low power but their brightness is up to 100 times higher than for normal x‐ray tubes which are used in diffractometry. A combination of these tubes with highly efficient capillary optical elements allows one to obtain parallel or focused beams of high intensity. Combining such a special source with detectors of different kinds, a compact system can be realized which may be successfully used in micro‐XRF, in diffraction and microdiffraction, etc. The system presented is designed in a modular way so that the components may be replaced by each other. Some examples of applications of such systems are reported. Copyright © 2004 John Wiley & Sons, Ltd.

Energy-dispersive wide angle x-ray scattering (WAXS) measurements applied to polymer characterization

A prototype x-ray equipment, initially designed and constructed in our laboratory for thickness measurement of thin silicon carbide coatings (<200 µm), is used for the characterization of epoxy polymers. The spectra delivered by wide angle x-ray scattering (WAXS) experiments allow, for instance, several kinds of characterization: (i) distinction between polymers of different chemical formulae, (ii) distinction between tightly and loosely packed networks and (iii) real-time follow-up of a curing process. Our equipment, flexible and robust, uses an energy-dispersive HpGe detector. Spectra are obtained for a constant scattering angle, i.e. without any rotation of the detector, which allows great mechanical simplicity and gain in terms of measurement time. The device can easily be set on an assembly line for the purpose of automatic non-destructive evaluation of some factory output. Alternatively, it can be set on a robot for the purpose of local inspection of a big structure.

A Morphological Study of Biomimetic Approach for Pathological Calcification In Vitro

Pathological calcification is included in disorders such as arteriosclerosis, circulatory failure of the heart valves, and renal failure and many studies have been performed to elucidate the development mechanism of pathological calcification. In this study, it has been carried out the observation of pathological calcification using simulated body fluid (SBF) under biomimetic approach. The aim of this study was to understand the mechanism of calcification in biological tissues. The porcine heart, aortic valve and small intestine were used in this study. The solutions for this study were prepared to suspend those specimens such as SBF pH 7.4, pH 5.0, supplemented with Mg, supplemented with CO3, porcine serum (PS) and saline solution. The specimens were suspended and were kept at 37 °C in an incubator. After 7 and 14 days, they were analyzed using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscope detector (EDS). The deposits that had crystal-like structure were observed in SEM from those specimens after 7 days, and some of them showed high peak of calcium and phosphate by EDS. They were roughly classified into five types based on the shape. This study suggested that calcified deposits on biological tissue in vitro in this biomimetic approach were affected with physicochemical factors such as Mg, CO3 and pH. This biomimetic approach would contribute to understand the mechanism of pathological calcification. Moreover, it showed that calcified deposit could be formed in vitro without cell involvement in the solution.

The design and performance of beamline BL16XU at SPring-8

A new X-ray undulator beamline has been designed and constructed by an industrial consortium of 13 companies at SPring-8. The beamline, named BL16XU, is intended for the characterization of various materials developed for industrial purposes and, together with its sister bending-magnet beamline (BL16B2), has been open to user experiments since the autumn of 1999. The new beamline provides high-brilliance synchrotron radiation in the energy range from 4.5 to 40 keV from an X-ray undulator of the in-vacuo type. The beamline has an experimental hutch for the performance of several experiments: e.g. microscopic observation of materials and micro-fabricated devices by using X-ray beams that have spot sizes of 1 μm or less; X-ray diffraction experiments on thin films with nanometer-scale thickness by using an ω−2 θ diffractometer; fluorescence X-ray analysis of trace elements on Si wafer surfaces by using a total reflection fluorescence X-ray analysis system equipped with wavelength- and energy-dispersive detectors.

Residual Stresses in an Induction Hardened Gear Tooth Mapped by Synchrotron X-ray Diffraction

Surface hardening in components subjected to severe contact loading, such as gears, is accompanied by the generation of a layer of residual stress. Compressive residual stresses in surface engineered components are often induced deliberately to provide improved toughness and wear resistance. However, a near-surface layer of compressive stress often generates a balancing region of tensile stress deeper within the component, which may accelerate damage in this region and promote failure. To quantify the effect of treatment on the stress distribution, residual strains in an induction hardened gear tooth were mapped using high energy synchrotron diffraction on Station 16.3 at SRS, Daresbury. White beam mode and an energy dispersive detector were used, and two components of strain and stress in the plane transverse to the gear axis were evaluated.

Time-resolving and energy-dispersive photoelectron detector for combined laser and synchrotron radiation experiments

A time-resolving and energy-dispersive photoelectron detector for time-resolved experiments has been set up for pump–multiple-probe experiments with combined laser and synchrotron radiation. The time resolution of the detector of about 1 ns allows an assignment of the photoelectron signal to a specific synchrotron radiation pulse for any filling pattern of third-generation synchrotron storage rings. This leads to an overall temporal resolution given by the synchrotron radiation pulse width, which is 30 ps at the synchrotron radiation facility BESSY, Berlin. Application of the pump–multiple-probe technique is demonstrated for time-resolved photoemission experiments with combined laser and synchrotron radiation.

Rapid structural and chemical characterization of ternary phase diagrams using synchrotron radiation

A technique based on synchrotron radiation was developed that allows for rapid structural and chemical characterization of ternary alloys over a wide range of composition. The technique was applied to isothermal sections of the Cr–Fe–Ni system grown on Al2O3(0001) sapphire substrates by sequential deposition of layers of graded.thickness followed by annealing to interdiffuse the elements. A film spanning the Cr–Fe–Ni ternary system was measured in 4 h at a resolution of 2 at.% by rastering the sample under a focused beam of synchrotron radiation while simultaneously measuring the diffraction pattern with a charge-coupled device detector to determine crystallographic phases, texture, and lattice parameters and also measuring the x-ray fluorescence with an energy-dispersive detector to determine elemental composition. Maps of phase composition and lattice parameter as a function of composition for several annealing treatments were found to be consistent with equilibrium values. The technique will be useful in combinatorial materials design.

F49 Characterization Techniques for Miniature Low-Power X-ray Tubes

An X-ray shielded test chamber has been designed and built that includes a CCD-pinhole camera and energy-dispersive silicon PIN-diode detector for spectrum collection. The use of this chamber is an innovative approach that allows rapid imaging of the electron beam spot on the anode, as well as the spectral characterization of the tube. The beamspot dimensions and location can be measured at several high-voltage settings to ensure stability. This setup allows monitoring spectral contamination lines, total output flux, and net target-peak intensity at the anode line. To ensure tube X-ray output stability a spotstability test is performed. Relative standard deviations of less than 1% are typical. Leakage current must be very low since operating conditions are typically less than 10 µA of emission current. In the case of arcing tubes the measurement of leakage current is problematic, as arcing will damage the measuring equipment. By using a resistor string and measuring the voltage drop across this string, it is possible to achieve a very sensitive current measurement while protecting the meter from high-voltage transients. Finally, the filament impedance is monitored as an indicator of the tube vacuum integrity and/or the tube high internal pressure.

Double pinhole diffraction of white synchrotron radiation

The spatial coherence of hard X-rays provided by a bending magnet of the storage ring BESSY II was investigated by performing Young's interference experiment. The interference pattern was created by the diffraction of two 2 μm pinholes drilled into a thin tantalum foil by focused ion sputtering. Using an energy-dispersive detector with an energy resolution of 200 eV the interference patterns were detected simultaneously between 5 keV< E<16 keV scanning a 5 μm pinhole through the detector window. The set-up is suitable to characterize the coherence properties of the beamline in a simple manner, i.e. to deduce parameters as the effective source size, the coherence length and the visibility. For the present case the visibility was close to 100% at 5 keV and decreased to 20% at 16 keV.

Coherence experiments at the energy-dispersive reflectometry beamline at BESSY II

Fraunhofer patterns of a 5 μm entrance pinhole were detected at the white-beam bending-magnet beamline at BESSY II. Using an energy-dispersive detector the Fraunhofer fringes could be recorded simultaneously between 5<E<15 keV. At the present apparative conditions the intensity is sufficient to resolve Fraunhofer fringes of more than five orders. After the successful investigation of the Fraunhofer diffraction over a large energy band pass static speckle pattern were measured from the optical components of the set-up. The proposed technique seems to be suitable for a fast characterization of coherent properties over a wide energy range.

The effects of artificial aging on wear properties of AA 6063 alloy

Wear behaviour of age-hardened 6063 aluminium alloy was evaluated under dry sliding conditions. A certain part of the aluminium samples was solution treated at 510 °C for 2, 4, 6 and 8 h, water-quenched then aged at 180 °C for 4 h, and the other part was solution treated at 510 °C for 6 h, water-quenched then aged at 180 °C for 1, 2, 3, 4 and 5 h in a muffle furnace. The as-cast and the aged samples were fully characterised before and after the wear testing using hardness, profilometer, scanning electron microscopy (SEM), optical microscopy, X-ray diffraction, and energy dispersive detector (EDS). The wear tests using on a pin-on-disc machine showed that the aging treatments improved the wear behaviour of AA 6063 alloy compared to as-cast samples.

Real-time surface composition and roughness analysis in MBE using RHEED-induced X-ray fluorescence

Using a compact, retrofittable energy-dispersive detector, we measure the RHEED-induced fluorescence signal at grazing exit during molecular beam epitaxy. First results show sub-monolayer sensitivity to all relevant elements down to Al with a time resolution of 1 s. The method is sensitive enough to detect surface reconstruction changes through relative changes in the As signal. In addition, the background signal shows a variation similar to the surface roughness and independent of the chemical composition.

G.S. Henderson and D.R. Baker (Eds) Synchrotron Radiation: Earth, Environmental and Materials Sciences Applications. Mineralogical Association of Canada: Short Course Series, Volume 30, 2002, iv + 178 pp. Price $(Can) 40.00. ISBN 0-902-585-1816.

G.S. Henderson and D.R. Baker (Eds) Synchrotron Radiation: Earth, Environmental and Materials Sciences Applications. Mineralogical Association of Canada: Short Course Series, Volume 30, 2002, iv + 178 pp. Price $(Can) 40.00. ISBN 0-902-585-1816. - Volume 66 Issue 6

Investigation of a Roman age “bulk pigment” found in Vicenza

This work is devoted to the study of a violet-pink material, which was found in a fairly good quantity during an excavation in Vicenza (Contrà Pedemuro S. Biagio), both on the bottom of a black varnished goblet and in a red purified small amphora with black traces of a titulus pictus (inscription) on its neck. The techniques used were optical microscopy, scanning electron microscopy (SEM), equipped with an energy dispersive microanalysis detector, X-ray powder diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and cyclic voltammetry (CV). The results demonstrated that the sample was not a mixture of natural pigments, but a synthetic product deriving from alunite (KAl(SO 4) 2·12H 2O) dissolved or suspended in water, from which white aluminium hydroxide was precipitated. An alkaline madder root extract solution was probably added to aluminium hydroxide to obtain the “Garance Lacquer”. The colour of this lacquer varied depending on the pH of the extract. The bulk pigment could have been used in the decoration of objects or, most probably, attributed to pharmacopoeia products for the treatment of blood diseases or as skin astringent.

Development of a total reflection X-ray fluorescence spectrometer for ultra-trace element analysis

A simple and fairly inexpensive total reflection X-ray fluorescence (TXRF) spectrometer has been designed, constructed and realized. The spectrometer is capable of ultra-trace multielement analysis as well as performs surface characterization of thin films. The TXRF setup comprises of an X-ray generator, a slit-collimator arrangement, a monochromator/cutoff-stage, a sample reflector stage and an X-ray detection system. The glancing angle of incidence on the two reflectors is implemented using a sine-bar mechanism that enables precise angle adjustments. An energy dispersive detector and a GM counter are employed for measuring respectively the fluorescence intensities and the direct X-ray beam intensity. A Cu-target X-ray generator with its line focus window is used as an excitation source. The spectrometer is quite portable with its compact design and use of a peltier cooled solid state detector for energy dispersive detection. Alignment and characterization of the TXRF system has been performed and the minimum detection limits for various elements have been determined to be in the range of 100 pg to 5 ng even at low X-ray generator powers of 30 kV, 5 mA. The capability of the TXRF system developed for thin film characterization is also demonstrated.