Showing papers in "X-Ray Spectrometry in 2005"

Quantitative determination of essential and trace element content of medicinal plants and their infusions by XRF and ICP techniques

Abstract: Macro- and microelement contents of five medicinal plants (Taraxacum officinale Weber, Eucalyptus globulus Labill, Plantago lanceolata L., Matricaria chamomilla L. and Mentha piperita L.) and their infusions were evaluated by the combined use of x-ray fluorescence (WDXRF and EDXRF, bulk raw plants) and inductively coupled plasma (ICP-MS and ICP-AES, infusions) techniques. The analytical methods allow the determination of 17 elements (Na, Mg, Al, Si, P, S, K, Ca, Ti, Mn, Fe, Cu, Zn, As, Rb, Sr, and Pb) both in plants and in the infusions. The use of XRF techniques offer a good multielemental approach for the rapid quality control of bulk raw plant materials whereas ICP techniques are well suited for the analytical control of infusions in order to ascertain the nutritional role of medicinal plants and the daily dietary intake. Copyright © 2005 John Wiley & Sons, Ltd.

Influence of and correction for moisture in rocks, soils and sediments on in situ XRF analysis

Abstract: This paper discusses the influence of water contained in rocks, soils and sediments on in situ XRF analysis with a portable XRF analyzer. Water in natural rocks, soil and sediments absorbs the characteristic x-rays from the elements and also causes the primary radiation from the excitation sources to scatter, which results in a decrease in the intensity of characteristic x-rays and an increase in the intensity of scattered x-rays in a fluorescence spectrum. A method for correcting for the influence of the water on the analysis of wet samples is proposed, based on the fact that the intensity of scattered radiation is directly proportional to the water content of wet samples. Tests on a set of wet soil samples showed that the method can effectively correct for the influence of the water in wet samples up to a 20% water content. The method was also applied to the analysis of soil with an IED-2000P XRF analyzer in a copper prospecting area in Yunnan, China. The results show satisfactory agreement of the results for Cu, Zn and Sr analyses before and after rain. Copyright © 2004 John Wiley & Sons, Ltd.

Layout and first XRF applications of the BAMline at BESSY II

Abstract: The first hard x-ray beamline at BESSY II has been installed by BAM and PTB at a superconducting 7 T wavelength shifter. The main optical elements of the beamline are a double-multilayer monochromator and a double-crystal monochromator. Depending on the application, the two devices are used separately or in-line. The main applications of the monochromatic radiation with photon energies up to 60 keV are x-ray fluorescence analysis, micro computed tomography, x-ray topography, detector calibration and reflectometry. Calculable undispersed radiation up to 200 keV is available for radiometric applications. Copyright © 2004 John Wiley & Sons, Ltd.

Characterization of airborne particulate matter in an industrial district near Florence by PIXE and PESA

Abstract: The composition of airborne particulate matter in Montelupo Fiorentino (a small town about 20 km west of Florence characterized by the presence of a large number of ceramic and glass factories) was studied by means of continuous and sequential sampling, ion beam analysis (IBA) techniques and statistical methods. The aerosol PM 10 fraction was collected on a daily basis for about 9 months (September 2002-June 2003). To investigate the elemental size distribution, for a shorter period (about 3 weeks) we collected PM 10 , PM 25 and PM 1 simultaneously. A continuous streaker sampler was also used, which allows the study of the aerosol composition with 2 h time resolution. Mass concentrations were obtained using an analytical balance. The elemental analysis was performed at the INFN accelerator laboratory at the Physics Department of Florence University by particle-induced x-ray emission and particle elastic scattering analysis (the latter implemented for this campaign). The use of the two techniques allowed a complete reconstruction of the gravimetric mass. An absolute principal component analysis showed industrial sources to be, on average, the main contributors to PM 10 mass; however, the weight of the 'soil' source (connected to local soil re-suspension and to long-range Saharan transport episodes) becomes dominant during some of the days when the 50 μg m -3 limit is exceeded.

The status of theoretical K‐shell ionization cross sections by protons

Abstract: The accuracy of PIXE analysis depends on inner-shell ionization cross sections that are often calculated in the ECPSSR theory which accounts with analytical functions for the energy (E) loss and Coulomb (C) deflection of the projectile plus for the perturbed-stationary state (PSS) and relativistic (R) nature of the target's inner shell. Although the ECPSSR is within 10% overall agreement with the K-shell data - as the proton energy falls below 0.1 to 1 MeV, respectively, in ionization of light- to heavy-target atoms - the ECPSSR increasingly overestimates the empirical database of Paul and Sacher (1989). Except for an enhancement of this overestimate at low energies, a modified ECPSSR based on the Chen-Crasemann (1985, 1989) plane wave Bom approximation - evaluated with the exact limits for the momentum transfers and the Dirac-Hartree-Slater wavef unctions-yields cross sections that remain within 10% of the data and the ECPSSR theory. Codes that use only the exact limits instead of the energy-loss function are confirmed to be improper for evaluation of the ECPSSR. Further enhancement of the cross sections at the low energies is limited to light target atoms after the function derived in the separated atom approach to account for the PSS effect is joined with an expression obtained in the united atom limit. An empirical database, updated with cross sections from post-1989 publications, is normalized to the modified ECPSSR theory and various forms of the Coulomb deflection factor are revisited.

Chemical composition and mass closure for fine and coarse aerosols at a kerbside in Budapest, Hungary, in spring 2002

Abstract: A comprehensive chemical aerosol characterization was carried out at a kerbside in downtown Budapest in spring 2002. Several filter samplers were deployed in parallel for day and night collections, and a total of 23 parallel collections were made. All samples were analysed for the particulate mass (PM) by weighing. Depending on the sampler type and/or collection substrate, further analyses were performed for up to 46 elements by a combination of particle-induced x-ray emission (PIXE) spectrometry and instrumental neutron activation analysis (INAA), for major anions and cations by ion chromatography and for organic carbon and elemental carbon by a thermal-optical transmission technique. Some of the elements measured could clearly be associated with traffic-related sources, e.g. Cu and Sb were attributed to emissions from brake linings. Aerosol chemical mass closure calculations were made for the separate fine (<2 μm) and coarse (2-10 pm) size fractions and also for the PM 10 aerosol. For reconstituting the gravimetric PM, eight aerosol types were considered, and three aerosol types were deduced from the PIXE/INAA elemental data set. Organic matter and elemental carbon were the dominant aerosol types in the fine fraction; they explained on average 43 and 21%, respectively, of the fine PM. The coarse PM consisted mainly of crustal matter (49%) and organic matter (30%). The large contribution from crustal matter (road dust) to the coarse fraction is consistent with other data from kerbside sites in Europe.

Distribution of Pb and Zn in slices of human bone by synchrotron µ-XRF

Abstract: Synchrotron radiation-induced micro x-ray fluorescence analysis (µ-XRF) at HASYLAB beamline L was used to determine the distribution of Pb and other trace elements in slices of human bone. Using a focused synchrotron x-ray beam of about 15 µm in diameter it was found that Pb was mostly located at the outer border of the cortical bone in various samples. Ratios of Pb intensities of cortical and trabecular bone varied from 0.027 for hip head to 0.408 for proximal tibia. Additionally Ca, Zn and Sr distributions were simultaneously recorded. A remarkable association between Pb and Zn content could be observed. Copyright © 2004 John Wiley & Sons, Ltd.

Detection efficiency of energy-dispersive detectors with low-energy windows

Abstract: Energy dispersive X-ray spectrometry offers the opportunity for fast composition determination of specimens by X-ray fluorescence or electron probe microanalysis. For fundamental parameter based quantification, the knowledge of the detection efficiency of the spectrometer is essential. At low energies the efficiency is strongly influenced by X-ray absorption in the radiation entrance window. State-of-the-art windows consist of polymer foil containing C, N, and O, coated with Al and in some cases with a special B compound. The foil is supported by a Si grid to withstand the atmosphere pressure. The absorption of all these components must be known to describe the detection efficiency. The transmittance of three types of widely used commercial windows has been measured. Transmittance curves have been fitted by analytical expressions using tabulated mass absorption coefficients. Because tabulated mass absorption coefficients do not consider near edge effects, there are strong deviations between measured and calculated transmittance below 0.6 keV. It is proposed to model the spectrometer efficiency by the measured window transmittance and calculated absorptions from front contact and possible contaminations. This reduces the number of unknown parameters drastically.

EXAFS and XANES study of arsenic in contaminated soil

Abstract: Historical mining, processing and refinement of arsenic in purpose built calciners in Cornwall, UK, have resulted in extremely high contamination of soils with arsenic in some localized areas. The x-ray absorption spectroscopic methods XANES (x-ray absorption near-edge structure) and EXAFS (extended x-ray absorption fine structure) were used to retrieve arsenic molecular information, i.e. oxidation state and local structure around As atoms, in the soil from a calciner's residue dump near Camborne (which contained 8.82 wt% arsenic) and identify the most abundant modes of As bonding. The results show that arsenic is predominantly in pentavalent form, tetrahedrally bound to oxygen atoms in the first coordination sphere. Fe and Al atoms are found in the next neighbour coordination shells around As. The As-Fe and As-Al distances and coordination numbers strongly suggest that arsenate in the soil is present in two forms, viz. as amorphous or poorly crystalline hydrous oxides of Fe (most likely FeAsO 4 ) and adsorbed on aluminium (hydr)oxides or aluminosilicates such as clay.

A new approach to the determination of the Fano factor for semiconductor detectors

Abstract: Values of the Fano factor are widely scattered in the literature, indicating the difficulties in its determination. We chose to analyze both the escape peaks and parent peaks of Ge detector spectra where the parent peak penetration depth and the escape peak escape depth are much larger than the size of the incomplete charge collection region. Hence, the escape peaks are expected to be free of low-energy tailing as, although the actually deposited energy is low, it is deposited beyond the incomplete charge collection region. It was found that the product of electron–hole pair creation energy (e) and the Fano factor (F) has an energy dependence at low energies, as is expected from electron transport theories. Although e is expected to have its own energy dependence, if a reference value of 2.96 eV is assumed for e, then the Fano factor values varied between 0.059 and 0.083. The escape peak is less advantageous for Si, hence a different method was used for Si(Li) detectors. Assuming the reference value of 3.8 eV for e, the Fano factor was found to be 0.063 at 5.9 keV x-ray energy. We consider the Fano factors reported here as upper limits, rather than the mean values. Copyright © 2004 John Wiley & Sons, Ltd.

La/B4C small period multilayer interferential mirror for the analysis of boron

Abstract: An La/B4C multilayer interferential mirror with small period d (4.8 nm) was produced by diode sputtering for the detection of the boron K emission by wavelength-dispersive x-ray spectrometry at a large Bragg angle (close to 45°). The structure of the mirror was characterized by grazing incidence x-ray reflectometry and its performance at the energy of the boron K emission (183 eV) was evaluated by means of polarized synchrotron radiation. Spectrometric measurements showed that the La/B4C mirror improved the detection limit of boron using by a factor of 2 with respect to similar Mo/B4C mirrors and by a factor of 4 with respect to a lead stearate crystal. Copyright © 2005 John Wiley & Sons, Ltd.

Energy‐dispersive XRF spectrometer for Ti determination (TITAN)

Abstract: An energy-dispersive XRF analyser was designed and constructed for determining Ti in plant and peat materials at low (ppm) concentrations. The XRF analyzer for Ti analysis (TITAN) uses monochromatic excitation obtained from a crystal diffraction monochromator and Co target x-ray diffraction tube. In addition to precise and sensitive analyses of Ti, other minor elements (Ca, K, Cl, S, P, Ba) in powdered plant and peat samples can be measured with only a minimum of sample preparation (drying, milling). The limits of detection obtained are K 2.5, Ca 1.5, Ti 0.9, Cr 0.7 and Mn 0.5 ppm using a 600 s acquisition time. The instrument was used to determine Ti concentrations in pre-anthropogenic peat samples up to 9000 years old. Copyright © 2004 John Wiley & Sons, Ltd.

Chemical state analysis employing sub‐natural linewidth resolution PIXE measurements of Kα diagram lines

Abstract: A high-energy resolution crystal spectrometer in Johansson geometry, which allows energy resolution below the natural linewidth of the Ka diagram lines, was employed in the measurements of proton-induced Ka x-ray emission spectra of titanium and sulfur pure and compound targets. The results demonstrate a clear dependence of the Ka energy shifts on the chemical state of the element in the sample. This dependence permits the chemical state speciation of low-Z elements in an unknown sample by employing high-resolution PIXE measurements of the Ka line. The potential of the technique in speciation studies is demonstrated in the case of an aerosol sample. The analysis of the Ka line obtained from the high-energy resolution proton-induced S Ka x-ray spectrum allowed the identification of sulfur in the aerosol sample as sulfate ([SO 4 ] 2- ).

A new microfocus x-ray source, iMOXS, for highly sensitive XRF analysis in scanning electron microscopes

Abstract: Scanning electron microscopes are usually equipped with energy-dispersive X-ray detectors for electron probe microanalysis. This widespread analytical method allows investigators to determine the elemental composition of specimens with a spatial resolution of about 1 μm. However, owing to the electron-specimen interaction, the emitted spectra reveal, in addition to characteristic lines, also a high level of continuous bremsstrahlung background. As a result, elements with low concentrations cannot be identified. The minimum detection limit can be diminished by two orders of magnitude if the characteristic lines are excited as fluorescence by an additional x-ray source. In this case, the emergence of bremsstrahlung is considerably reduced. Combining a high-brilliance microfocus x-ray tube with efficient polycapillary optics enables one to realize an experimental arrangement for performing local fluorescence analysis at the same point where the electron beam hits the sample. The polycapillary optics under consideration focuses the emitted x-radiation onto focal spots between 30 and 100 μm in diameter. Count rates of several thousands cps have been achieved. Elemental maps have been obtained by means of the motorized specimen stage of the microscope.

Three decades of in vivo x‐ray fluorescence of lead in bone

Abstract: In vivo measurements of lead in bone were first made in the early 1970s. Of the three systems that have been used ( 57 Co excited K, 125 I or polarized excited L, 109 Cd excited K), 109 Cd excited K x-ray fluorescence has been most widely adopted. Bone lead measured in vivo has been shown to reflect cumulative exposure, but the rate of input to bone varies with level of exposure. Chelated lead does not relate directly to bone lead. Endogenous exposure has been highlighted by bone lead measurements and this release of lead from bone and hence the half-life of lead in bone have been shown to depend on age and on intensity of lead exposure. Thus x-ray spectrometry has made a significant contribution to the understanding of long-term human lead metabolism.

Micro-PIXE in Ecophysiology

Abstract: Two selected examples of PIXE microanalysis in ecophysiology have been shown. Studies of heavy metal distribution in mycorrhizal and nonmycorrhizal roots of Plantago lanceolata showed different mechanisms in filtering of Zn/Pb and Fe/Mn, both enabling plants to cope with metals present in the environment. Studies of the mechanism used by the beetle Chrysolina pardalina to eliminate excessive amounts of Ni revealed that Malpighian tubules are responsible for the elimination of this metal from the hemolymph. In both examples GeoPIXE software was used for true elemental mapping using Dynamic Analysis method and analysis of spectra from selected micro-areas. Specimen thickness and matrix composition were obtained from proton backscattering spectra.

Semiempirical approach for standardless calibration in µ‐XRF spectrometry using capillary lenses

Abstract: Quantitative µ-XRF analysis based on standardless calibration is limited by the lack of information on the shape of the excitation spectrum resulting from using capillary lenses The measurement of radiation scattered from a sample was used in combination with Monte Carlo simulation of radiation transport to estimate the energy spectral distribution of the excitation radiation Further, a standardless calibration based on the fundamental parameter method implemented in the IAEA-QXAS software package was carried out and verified for glass and fused ore certified reference materials The accuracy and repeatability achieved are reported Copyright © 2004 John Wiley & Sons, Ltd

Concentrations and sources of trace elements in particulate air pollution, Dar es Salaam, Tanzania, studied by EDXRF

Abstract: Trace elements in near-ground atmospheric aerosols were investigated in Dar es Salaam, Tanzania. Particles were collected at two sites, one urban and one rural, during, two months with different meteorological conditions. The samplers, dichotomous impactors, segregate the particles into two size fractions, fine (PM2.5, d(a) < 2.5 mum) and coarse (2.5 < d(a) < 10 mum). A sharp cyclone was used to sample finer particles (PM1, d(a) < 1 mum). Meteorological parameters were also examined at both sites. An EDXRF spectrometer, based on three-axial geometry, was used for quantitative elemental analysis. Concentrations of elements heavier than phosphorus were determined. Also, the content of black carbon on the filters was measured with a reflectometer. The elemental concentrations were compared with respect to season and geographical location in the city. The levels of different species in Dar es Salaam were also compared with similar data from other African and European countries. This showed low values of Pb with respect to the size of the city and no legislation on the use of leaded petrol, that often is the main source of lead. High values of Cl were also found, as would be expected in a coastal city. The coarse particles in the air, originating from soil, had a different composition in Dar es Salaam than in Gaborone, Botswana, and the concentration of black carbon was higher than in other cities. On the basis of the data collected, source assignments were made and the following sources found; sea-spray, soil, city road dust, biomass burning industries and traffic. Comparing the concentrations of different elements in PM2.5 and PM1 revealed that black carbon, Zn, Pb, K and Br are present only in the smallest particles. Copyright (C) 2005 John Wiley Sons, Ltd.

Differential PIXE measurements for the stratigraphic analysis of the painting Madonna dei fusi by Leonardo da Vinci

Abstract: Traditional PIXE does not provide information about the layered structure that is characteristic of wood and canvas paintings. In such cases, a solution to discriminate the depth sequence of elements within the analysed sample is to use differential PIXE, i.e. by measuring on the same spot with different beam energies. At the Florence accelerator, laboratory differential PIXE measurements were performed on the wood painting Madonna deifusi (ex-Redford version, 1501) by Leonardo da Vinci, in the framework of an extensive project aimed at discovering the 'secrets' of the painting and drawing techniques of the artist. The analysis allowed us to characterize the pigments and the substrate composition.

Intraneuronal investigations of organic components and trace elements with the use of synchrotron radiation

Abstract: Three techniques based on synchrotron radiation microbeam analysis were applied to biochemical investigations of human central nervous system (CNS) tissue. Thin tissue slices representing Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS) and control cases were studied. Synchrotron radiation microbeam x-ray fluorescence (micro-SRXRF) was applied to the analysis of the elemental distribution inside single nerve cells. Investigation of copper oxidation state was performed with the use of micro x-ray absorption near-edge structure spectroscopy (micro-XANES). Moreover, the organic components of the tissues were analyzed by means of synchrotron radiation Fourier transform infrared microspectroscopy (SR-FTIRM). Topographic differences in elemental composition were observed for the nerve cell body. Higher levels of Fe, Zn and Ca were found for the neurons of PD cases in comparison with the control group. The IR spectra measured in neurons of PD, ALS and control cases showed differences in absorption bands associated with characteristic groups of selected biological molecules. Additionally, results of SR-FTIRM measurements indicated inhomogeneous accumulation of the main organic components in PD nerve cells, in contrast to the control cases.

Multi-element analysis of sea water from Sepetiba Bay, Brazil, by total reflection x-ray fluorescence spectrometry using synchrotron radiation

Abstract: Trace elements in the surface waters of Sepetiba Bay were studied by total reflection x-ray fluorescence spectrometry using synchrotron radiation (SRTXRF). The bay is located in the south of Rio de Janeiro State, Brazil. The water samples were collected at 21 sampling stations, prepared in order to preconcentrate the metallic elements with ammonium pyrrolidinedithiocarbamate and to remove the salt matrix. Samples were spiked with an internal standard (Se) and the precipitated dithiocarbamates of trace elements were separated by filtration through a Millipore filter, then transferred to a Perspex reflector and digested with HNO3 for SRTXRF measurement. Elemental concentrations of Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo and Pb were determined and a comparison was made between the results obtained and the values given in the literature for sea water. Copyright © 2005 John Wiley & Sons, Ltd.

Analysis and localization of metal- and metalloid-containing proteins by synchrotron radiation x-ray fluorescence spectrometry

Abstract: Synchrotron radiation x-ray fluorescence (SRXRF) spectrometry has been applied for the determination of metals and metalloids in electrophoretically separated proteins and histological samples. The method was tested by the analysis of trace element-containing proteins in rat testis homogenate and the determination of the spatial distribution of some metals in brain sections of scrapie-infected hamsters. After sodium dodecyl sulfate—polyacrylamide gel electrophoresis (SDS-PAGE) and transfer on to a blotting membrane, the distribution of selenium among the proteins of testis homogenate was determined. The comparison with the autoradiogram of 75Se-labeled testicular proteins separated in the same way showed that of nine selenium-containing proteins found by autoradiography, four could be detected by SRXRF. The distribution of several metals and metalloids in cryo-sections of 10 µm thin brain sections of three Syrian hamsters intracerebrally infected with the scrapie strain ME7-H and of three control animals was investigated at the HASYLAB beamline L by scanning with a synchrotron radiation beam focused by a polycapillary lens. The copper-binding prion protein (PrP) in its pathological form PrPSc, determined by immunohistochemistry on cryo-sections, was found to be diffusely dispersed in the scrapie-infected brains, and the copper distribution differed from that in the control animals. The question whether, and to what extent, PrPSc and copper hot-spots are related, remains to be investigated. The method was shown to be suitable for the determination of trace element distribution patterns in electrophoretically separated proteins and histological tissue preparations. Copyright © 2004 John Wiley & Sons, Ltd.

Scattering signatures for some human tissues using synchrotron radiation

Abstract: At photon energies below 100 keV, coherent scatter becomes important and because of its sharply forward peaked nature, it is the dominant interaction at small angles. Further, in the momentum transfer region above 0.5 A -1 , free atom form factors are sufficient to describe coherent scattering. The angular distribution of the coherent scattering carries detailed information about the object and can be used as a signature of the tissue type of the object. The aim of this work was to analyze the scattering properties of different human tissues according to histological classifications. The coherent scattering signatures of healthy and neoplastic breast, uterus and kidney tissues were measured using x-ray synchrotron radiation at the XRD2 beamline at the Brazilian Synchrotron Light Laboratory (LNLS).

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

Abstract: 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.

Development of a portable x-ray fluorescence spectrometer equipped with two monochromatic x-ray sources and silicon drift detector and field analysis of Islamic glasses at an excavation site in Egypt

Abstract: A portable x-ray fluorescence spectrometer equipped with a silicon drift detector (SDD) and a digital signal processor (DSP) was developed for in-field analysis of archeological samples at an excavation site. This spectrometer allows us to carry out highly sensitive analyses of various elements with atomic numbers down to Na in air by using two monochromatic x-ray sources obtained by doubly bent toroidal monochromators of graphite (0002) (Pd Kα for medium–heavy elements) and PET (200) (Pd Lα for light elements) and white x-rays with a Zr filter excited at 40 kV for heavy elements. The detection limit was 0.31% for Al and 4 ppm for Sr in a standard cement sample. The spectrometer was set in a room of the excavation laboratory at al-Tūr Sinai in the Sinai Peninsula in Egypt in the summer of 2001. The Middle Eastern Culture Center has been conducting an excavation of the sites in al-Tūr al-Kilani and Rāya, which were important port cities of Red Sea trade from early Islamic periods: al-Tūr (A.D.14–20) and Rāya (A.D.8–12). The instrument was operated without any problems and 222 glass objects, 26 pottery sherds, seven pigments and 88 metallic objects were analyzed non-destructively during a 1 month stay. Since this was the first chemical analysis done at the sites, many important archaeological findings were obtained in the present study. Glass objects were successfully classified based on their chemical compositions. Characterization of stained (luster) glasses was conducted. Copyright © 2004 John Wiley & Sons, Ltd.

Detection angle resolved PIXE and the equivalent depth concept for thin film characterization

Abstract: The characterization of thin films using PIXE, although basically a simple matter, in practice suffers from significant problems Here two case studies are presented in which the use of grazing detection geometry is shown to be a good solution The first case study, the analysis of GaSb-InAs films deposited on a GaSb substrate, relates to the measurement of elements of atomic number close to and below that of the substrate Problems may be due to the tail of the peaks that correspond to x-rays emitted from the substrate, and also to the presence in the substrate of an element having large x-ray emission cross-sections The use of the simulation capability implemented on the DATTPIXE package is shown to be of good help in the proper planning of the analysis procedure In the second case study, the distinction between film contamination and substrate material contamination is discussed In this case the characterization of a ZnO film deposited on sapphire is presented The concept of equivalent depth is discussed and it is shown to be an important tool for a straightforward distinction between film and bulk contamination

High‐energy PIXE using very energetic protons: quantitative analysis and cross‐sections

Abstract: Latterly, PIXE using high-energy protons has been applied effectively for the qualitative analysis of archaeological and art objects, providing information from deep inside the object. This is due to the high cross-sections for the excitation of K-lines of heavy elements together with the large penetration depth of high-energy protons, resulting in analysable depth of up to several millimetres. After the extension of the GUPIX software package to proton energies of up to 100 MeV, quantitative analysis came within reach. Measurements on thin and thick metal targets, and also on alloy standards with known composition and various thickness, were performed. The concentrations obtained were compared with the certified values. The agreement was good for samples with a thickness of around 2 mm. However, for several centimetre thick samples, the heavy elements were overestimated when using the K-lines of these elements for the data evaluation. To clarify this, K-shell cross-section measurements were carried out for various Z. The measurements and the results are presented and discussed.

A novel high-resolution XRF spectrometer for elemental mapping based on a monolithic array of silicon drift detectors and on a polycapillary x-ray lens

Abstract: This paper describes a novel x-ray fluorescence spectrometer designed for elemental mapping applications. The spectrometer is based on a ring-shaped monolithic array of silicon drift detectors (SDDs) with a hole in the center. The coaxial x-ray excitation beam, focused by a polycapillary x-ray lens, reaches the sample after passing through the central hole. This geometry optimizes the useful solid angle for collecting the fluorescence from the sample, while the optics maximizes the photon density in the excitation spot. These features, together with the very high detection rate of SDDs, allow a high scanning rate in elemental mapping to be achieved. Moreover, the spectroscopic resolution of SDDs (cooled by thermoelectric Peltier elements) is comparable to that of the classical Si(Li) liquid nitrogen-cooled detectors. Several examples of applications of the novel spectrometer in various fields, from archeometry to biology, are presented. This paper introduces also a new multi-element detector based on SDDs whose structure has been specifically optimized for very high resolution and very fast elemental mapping.

Application of polarized EDXRF in geochemical sample analysis and comparison with WDXRF

Abstract: An EDXRF technique with polarized (P) excitation has been introduced into geochemical analysis research in China. Preliminary work on a Spectro X-Lab 2000 spectrometer showed that, in a total analysis time of 600 s per sample, over 30 elements can be quantified with detection limits of 0.5–30 µg g−1, comparable to internationally published values. To test the capability of the method for practical sample analysis, about 100 unknown samples were measured. Also, a comparison of P-EDXRF and WDXRF with respect to results and performance was made. Both methods gave satisfactory results for over 30 elements. As P-EDXRF has the advantages of higher throughput, lower purchase price, lower running costs and full spectra collection, it is more competitive for geochemical mapping analysis whereas WDXRF is advantageous for more precise analysis. However, the relatively smaller detection area with a polarized target may present some problems when analyzing light elements in pressed pellet samples or when the samples are not homogeneous enough. Copyright © 2005 John Wiley & Sons, Ltd.

An annular Si drift detector µPIXE system using AXSIA analysis

Abstract: Sandia and Rontec have developed an annular, 12-element, 60 mm 2 , Peltier-cooled, translatable, silicon drift detector called the SDD-12. The body of the SDD-12 is only 22.8 mm in total thickness and easily fits between the sample and the upstream wall of the Sandia microbeam chamber. At a working distance of 1 mm, the solid angle is 1.09 sr. The energy resolution is 170 eV at count rates <40 kcps and 200 eV for rates of 1 Mcps. X-ray count rates must be maintained below 50 kcps when protons are allowed to strike the full area of the SDD. Another innovation with this new μPIXE system is that the data are analyzed using Sandia's Automated eXpert Spectral Image Analysis (AXSIA).