HASYLAB Beamline Research Articles

Improved Micro-X-ray Fluorescence Confocal Imaging of Two-Dimensional Distribution of Arsenic Concentration in Cucumber Hypocotyls Using Synchrotron Radiation.

An optimized micro-X-ray fluorescence confocal imaging (μXRF-CI) analytical method has been developed to determine the 2D distribution of elemental composition in small (1–3 mm) biological objects at a 10–20 μm spatial resolution. Plants take up chemical elements from soil, and the vascular system transports them toward shoots. In order to obtain biochemical information related to this biological process, 2D distributions of chemical elements in roots and in hypocotyls of cucumber plants were analyzed by synchrotron radiation based on micro-X-ray fluorescence computer tomography and μXRF-CI techniques. The experiments were carried out at HASYLAB Beamline L of the DORIS-III storage ring in Hamburg, a facility that provided optimal physical conditions for developing and performing these unique analyses: high flux monochromatic synchrotron beam, X-ray optical elements, precision moving stages, and silicon drift detectors. New methodological improvements and experimental studies were carried out for applicability of lyophilized samples and cryo-cooling. Experimental parameters were optimized to maximize the excitation yield of arsenic Kα radiation and improvement of the spatial resolution of the μXRF-CI analytical method.

3D diffraction imaging and orientation mapping in deformed ice crystals

A method to acquire three dimensional diffraction data and orientation mapping with the 2D imaging setup of Hasylab beamline G3 is presented. The method has been successfully applied to undeformed large grains extracted from ice samples and extended to the 2D determination of lattice misorientation and lattice orientation distribution within deformed grains.

A general Monte Carlo simulation of energy-dispersive X-ray fluorescence spectrometers — Part 6. Quantification through iterative simulations

A quantification tool for energy-dispersive X-ray fluorescence (ED-XRF) spectral data is presented, based on the application of Monte Carlo simulations in an iterative, inverse manner. Acting as an open-source plug-in to the widespread PyMca package, it provides users with a superior alternative to the fundamental parameter method based built-in quantification tool, taking into account higher order interactions, M-lines and cascade effects. Examples are shown demonstrating the usefulness of our implementation through data recorded at the synchrotron X-ray fluorescence microprobe installed at the HASYLAB Beamline L, Hamburg, Germany.

A general Monte Carlo simulation of energy dispersive X-ray fluorescence spectrometers — Part 5: Polarized radiation, stratified samples, cascade effects, M-lines

A general Monte Carlo code for the simulation of energy dispersive X-ray fluorescence (ED-XRF) spectrometers is presented. As a significant extension to existing Monte Carlo codes, dedicated to ED-XRF spectrometers, the new code includes several unique features such as the simulation of M-lines and cascade effects. The detector response function was extended with fluorescence and Compton escape peaks, as well as with pulse pile-up. A full description of the underlying algorithms is given. The software was validated by means of comparison with experimental spectra of standard reference materials collected at the synchrotron XRF-microprobe installed at HASYLAB Beamline L, Hamburg, Germany.

Speciation of copper and zinc in size-fractionated atmospheric particulate matter using total reflection mode X-ray absorption near-edge structure spectrometry

The health effects of aerosol depend on the size distribution and the chemical composition of the particles. Heavy metals of anthropogenic origin are bound to the fine aerosol fraction (PM 2.5). The composition and speciation of aerosol particles can be variable in time, due to the time-dependence of anthropogenic sources as well as meteorological conditions. Synchrotron-radiation total reflection X-ray fluorescence (SR-TXRF) provides very high sensitivity for characterization of atmospheric particulate matter. X-ray absorption near-edge structure (XANES) spectrometry in conjunction with TXRF detection can deliver speciation information on heavy metals in aerosol particles collected directly on the reflector surface. The suitability of TXRF-XANES for copper and zinc speciation in size-fractionated atmospheric particulate matter from a short sampling period is presented. For high size resolution analysis, atmospheric aerosol particles were collected at different urban and rural locations using a 7-stage May cascade impactor having adapted for sampling on Si wafers. The thin stripe geometry formed by the particulate matter deposited on the May-impactor plates is ideally suited to SR-TXRF. Capabilities of the combination of the May-impactor sampling and TXRF-XANES measurements at HASYLAB Beamline L to Cu and Zn speciation in size-fractionated atmospheric particulate matter are demonstrated. Information on Cu and Zn speciation could be performed for elemental concentrations as low as 140 pg/m 3. The Cu and Zn speciation in the different size fraction was found to be very distinctive for samples of different origin. Zn and Cu chemical state typical for soils was detected only in the largest particles studied (2–4 μm fraction). The fine particles, however, contained the metals of interest in the sulfate and nitrate forms.

The use of cluster and discriminant analysis in the investigations of the role of trace metals in the pathogenesis of Parkinson’s disease

X-ray fluorescence microscopy was applied for two-dimensional elemental analysis of substantia nigra (SN) tissue. The samples representing Parkinson’s disease (PD) and control cases were examined at HASYLAB beamline L and at ESRF beamline ID22. Two-dimensional mapping of P, S, Cl, K, Ca, Fe, Cu, Zn, Se and Br was done with the spatial resolution of 15 and 5 μm. The masses per unit area of elements in neuromelanin reach nerve cells of SN were determined. The elemental data were processed using two multivariate techniques, namely cluster and discriminant analysis. The statistical methods were used for data reduction, both unsupervised and supervised classification as well as for the creation of a model that would simplify case identification based on the elemental analysis of SN tissue. The results of cluster analysis confirmed the statistical significance of the differences in elemental composition of PD and control SN nerve cells. Based on the results of discriminant analysis, the elements (P, Cl, Fe, Cu and Zn) that played the greatest role in the process of differentiation between neurons from examined groups were determined.

High resolution micro-XRF maps of iron oxides inside sensory dendrites of putative avian magnetoreceptors

Iron mineral containing sensory dendrites in the inner lining of the upper beak of homing pigeons [1] and various bird species [2] are the first candidate structures for an avian magnetic field receptor. A new concept of magnetoreception [3, 4] is based on detailed ultra-structural optical and electron microscopy analyses in combination with synchrotron radiation microscopic X-ray fluorescence analysis (micro-XRF) and microscopic X-ray absorption near edge structures (micro-XANES). Several behavioral experiments [5, 6] and first mathematical simulations [6] affirm our avian magnetoreceptor model. The iron minerals inside the dendrites are housed in three different subcellular compartments (bullets, platelets, vesicles), which could be clearly resolved and identified by electron microscopy on ultrathin sections [1, 3]. Micro-XRF and micro-XANES data obtained at HASYLAB beamline L added information about the elemental distribution and Fe speciation [3], but are averaged over the complete dendrite due to limited spatial resolution. Here we present recently performed micro-XRF maps with sub-micrometer resolution (ESRF ID21), which reveal for the first time subcellular structural information from almost bulk-like dendrite sample material. Due to the thickness of 30 μm the microarchitecture of the dendrites can be considered as undisturbed and artefacts introduced by sectioning might be widely reduced.

Determination of the elemental distribution in human joint bones by SR micro XRF

AbstractIn humans the toxic trace element lead (Pb) mainly accumulates in the skeletal tissue where it resides for a long period. Although Pb is known to play a role in bone and cartilage diseases, the distribution of Pb in these tissues is mostly unknown. Therefore synchrotron‐radiation‐induced micro x‐ray fluorescence analysis (SR µ‐XRF) in various geometries was used to determine the distributions of Pb, Ca, Zn and Sr at the cartilage‐bone interface in human femoral heads and patellae. SR µ‐XRF results were matched with backscattered electron (BE) images providing information on structural features of the tissue. Conventional SR µ‐XRF at HASYLAB beamline L showed that Pb mostly accumulates in a zone of some micrometers around the transition between non‐calcified and calcified cartilage. However, the relatively large sample thickness did not allow more precise conclusions. Exploiting the 3D capabilities of confocal SR µ‐XRF and SR microfluorescence tomography at ANKA Fluo‐Topo beamline and HASYLAB beamline L, the spatial resolution could be improved and a highly specific accumulation of Pb at the tidemark, the calcification front between non‐calcified and calcified cartilage, was detected. It was found that Pb and Zn accumulation coincide at the tidemark. Since the tidemark plays an important role in osteoarthritis, the results may strengthen other authors' conclusions that Pb is associated with this joint disease. Although offering less spatial resolution when compared to micro‐tomography, confocal SR µ‐XRF is best suited for such studies. It facilitates the comparison of element maps with other imaging techniques like BE imaging. Copyright © 2007 John Wiley & Sons, Ltd.

Recrystallization Investigated by X- Ray Diffraction Imaging

X-ray diffraction imaging allows the investigation of a large area of a polycrystalline specimen in a single shot. Dynamic processes like recystallization can, therefore, be studied without prior knowledge of where they occur. Even early stages of nucleation can be traced back using the information from images taken from the fully recrystallized specimen. Experiments performed at HASYLAB beamline G3 on cold rolled Cu and Al showed nucleation and growth behaviour that cannot be explained by classical models.

Analysis of Residual Stresses in Micro Powder Injection Moulded Micro Bending Specimens Made of Zirconia

Analysis of the residual stress state, the microstructure and surface topography of ceramic microcomponents made of Y2O3-stabilized ZrO2 produced by micro powder injection moulding were performed. During the production of the microspecimens sintering conditions were varied. The measurement of residual stresses has been carried out using the MAXIM (MAterials XRay IMaging) diffractometer at HASYLAB beamline G3 at DESY in Hamburg (Germany). The microstructure and surface topography of differently moulded specimens were examined using a scanning electron microscope (SEM) and a confocal white light microscope type NANOFOCUS. The findings are used to establish correlations between process parameters and characteristics of the microcomponents. These will allow to improve the production process with respect to the mechanical properties of the microcomponents.

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

AbstractSynchrotron 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.

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

AbstractSynchrotron 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.

Comparison of nuclear and X-ray techniques for actinide analysis of environmental hot particles

Actinide-containing radioactive hot particles have been dispersed into the environment during atmospheric nuclear tests, accidents of the nuclear fuel cycle and authorized discharges from nuclear reprocessing plants. Several other activities like illicit trafficking of radioactive material or the use of depleted uranium in shielding, weapons can also be considered as possible sources of contamination by actinides. The paper compares detection limits for actinide analysis by nuclear spectroscopy as well as various X-ray micro-fluorescence and absorption techniques using laboratory and synchrotron sources. The detection limits for X-ray techniques were calculated using Monte Carlo simulations. Detection limits obtained for X-ray microanalysis using synchrotron sources were close to that of nuclear analysis. For long half-life nuclides (more than 105 years), X-ray spectrometry was more sensitive, while being non-destructive and offering additional information on oxidation states using X-ray absorption. For U, α spectrometry resulted only in 10−7 g (238U) contrasting 10−13 g obtained for monochromatic beam µ-XRF (micro X-ray fluorescence) at HASYLAB Beamline L. Using the combination of autoradiography and µ-XRF, identification and quantitative analysis of individual radioactive particles of 20 µm diameter were possible. Despite the strong spectral overlap with the Rb-Kα characteristic line, in fluorescence mode µ-XANES (micro X-ray absorption near-edge structure) it was possible to determine the oxidation state of 15 µg g−1 U in a single hot particle.

Synchrotron radiation‐induced TXRF of reactor steel samples

AbstractSynchrotron radiation‐induced total reflection x‐ray fluorescence (TXRF) analysis was used for the trace element analysis of steels exploited in the construction of core components of existing fission plants and future fusion power plants. Detection of traces of niobium in reactor pressure vessel steel allows a retrospective determination of the fast neutron flux. For the construction of future fusion reactors, low activation steels are being investigated. Traces of Nb, Pd, Ag, Eu, Gd, Tb, Dy, Ho, Er, Os and Bi cause a higher activity of the material than the steel itself. Synchrotron radiation allows the excitation of the heavier element K shells, avoiding the strong overlaps of their L lines. Moreover, the linear polarization of synchrotron radiation combined with side‐looking detection manages to reduce the scattering due to the matrix contained in the analysed samples. Experiments were carried out at Hasylab Beamline L (bending magnet). The experimental set‐up includes a double reflector collimator, a multilayer and a vacuum chamber. Chemical preparation of the sample included dissolution and separation by means of anion‐exchange chromatography. Minimum detectable concentrations of 37 ng g−1 for Nb and 400 ng g−1 for Tb in the steel were achieved. Copyright © 2001 John Wiley & Sons, Ltd.

Accurate structure-factor measurements using high-energy synchrotron radiation: a test on cuprite, Cu2O

Using high-energy synchrotron radiation, structure factors were measured on the triple-axis diffractometer at the HASYLAB beamline BW5. A data set for cuprite, Cu2O, was recorded, and the excellent data quality [internal consistencyRint(F2) = 0.0055] allowed full multipole refinements using the programVALRAY. Extinction was still significant, but small. Using data measured at 75, 100, 125 and 150 keV photon energies, it was possible to determine and separate extinction prior to the refinements. After evaluation and comparison of extinction-affected and extinction-free data, significant differences in the electron densities were found.

Processing of X-ray diffraction imaging data using remote sensing techniques

Material properties are not only determined by the chemical composition but are modified during processing and use. The microstructure and thus the material properties are in most cases not homogeneous but exhibit spatial variations. To investigate these variations numerousμ-beam techniques have been developed during the last years [1], but even with powerful sources like those of synchrotron radiation facilities these techniques still require time consuming scans if larger areas shall be investigated. A novel technique, developed at HASYLAB, DESY [2] selects the probed region not from the primary side using a μ-beam but at the secondary side of the sample. Here a large sample area is illuminated and an array of parallel tube like collimators, a so called micro-channel plate (MCP), in front of a position sensitive detector (PSD) suppresses crossfire of radiation scattered from different regions of the specimen. Only radiation parallel to the channel axes reaches the detector yielding an entire image in a single shot. The channels also define the scattering angle 22 like a Soller collimator does in conventional diffraction experiments. If the arrangement of MCP and PSD is mounted on the 22-arm of a diffractometer scans can be performed by variation of the angles of the diffractometer or other parameters. These scans yield an entire image for each value of the scanning variable, while conventional experiments only measure one intensity for each value of a variable yielding one dimensional data sets. Using the imaging method a data set consists of images with more than 1 million pixels. A series of such images yields one spectrum per pixel. Even if the amount of data is reduced by integrating over several pixels or by restricting the analysis to a smaller region of interest (ROI) the number of spectra is still too large to be processed interactively one at a time. Furthermore, there exist strong correlations between spatial and spectral adjacent data making joint processing highly desirable. The aim of such an analysis is both the determination of the spatial distribution of different microconstituents in the sample and the extraction of their spectral properties. Images of the same scene as function of one parameter are also obtained in remote sensing where pictures are taken in different optical or infrared bands. In this field manifold techniques have been developed to extract information from such (hyperspectral) data [3] and commercial software packages are available. The similarity in data structure suggests the application of these methods also to data obtained by diffraction imaging. The experiments were performed at the 4-circle diffractometer at HASYLAB beamline G3 [4] carrying the detector arrangement consisting of a MCP in front of a Peltier-cooled CCD on its 22-arm. With this instrument manifold scans may be performed by variation of either the diffractometer angles or the conditions at the sample. Applications range from reciprocal space mapping [5] to kinetic studies [6]. The use of synchrotron radiation further allows variations of the energy of the incident radiation enabling spectroscopic investigations [7]. Here we will treat data obtained in ω− 22-scans in which the diffracted intensity is measured as function of the length of the scattering vector. The techniques used are, however, also applicable to data obtained by other scans. The new technique has been applied to a piece of railway rail which is of particular interest since the increase of axle loads in freight traffic as well as the increase in velocity of passenger trains within recent years led to an increase of wear of the rails, that appeared e.g. in an increase of frequency of structure modifications and defects in their surface layer. Among the structure modifications, the riffles and the white etching-layers (named according to their resistance towards metallographic etching) are of high practical as well as theoretical interest due to their high hardness that reaches up to 1200 HV [8, 9], their brittleness and due to the fact that their composition and crystallographic structure as well as their process of formation still are under vivid discussion [10–12]. In order to contribute towards clarifying

A new diffractometer for materials science and imaging at HASYLAB beamline G3

A 4-circle diffractometer equipped with a novel imaging system has been installed at HASYLAB beamline G3. The imaging system comprising a microchannel plate (MCP) in front of a CCD detector allows position-resolved X-ray diffraction investigations of polycrystalline materials. Alternatively, a scintillation counter behind a Soller collimator can be used. Material properties like strain and/or texture can thus be determined either position resolved using the MCP/CCD system or in an averaging mode using the Soller/scintillator combination. The field of view of the MCP/CCD system is larger than 1 cm 2 with a spatial resolution down to 12 μm. Both detection systems applied are aberration free. The spatial information can be directly extracted from pictures taken by the imaging system. Together with the wide field of view this method is especially suited for the investigation of dynamical processes in polycrystalline materials.

A Triple-Crystal Diffractometer for High-Energy Synchrotron Radiation at the HASYLAB High-Field Wiggler Beamline BW5

The triple-crystal diffractometer installed at HASYLAB beamline BW5 with a high-field wiggler of critical energy 27 keV for DORIS III, operated at 4.5 GeV electron energy, is described. Samples can be mounted in large cryostats or furnaces normally used in neutron scattering experiments. The instrument has been successfully applied to measure structure factors S(Q) in liquids and amorphous materials, to collect full data sets of highly accurate structure factors for charge-density work, to measure the spin component of the ground-state magnetization in transition-metal and rare-earth compounds, to study the diffuse scattering from stacking faults and dislocation loops in Si single crystals, and for the investigation of various aspects of structural phase transitions: critical scattering in SrTiO3, oxygen order and stripe order in high-To materials. A crossed-beam technique allows for local studies of texture, internal strain and phase changes in the bulk of materials.

Total Reflection X-Ray Fluorescence Analysis Excited by Synchrotron Radiation (SR-TXRF): Variation of Excitation Conditions and Sample Geometries

The use of synchrotron radiation as the excitation source for total reflection x-ray fluorescence analysis (SR-TXRF) in combination with a multilayer structure for monochromatization led to detection limits in the femtogram range for medium-Z elements. Experiments were performed at the Hasylab Beamline L using bending magnet radiation. Different methods for the modification of the spectral distribution, viz. multilayer monochromatization, insertion of a high-energy cut-off and a simple filter technique, were compared. Also, several possible types of geometrical arrangement of the sample and detector were examined to establish whether an improvement in excitation or detection conditions is possible. Samples were of evaporated droplets of aqueous or acidic solutions of several elements at various concentrations. Spectra were evaluated and the data used to extrapolate the detection limits (DL). Monochromatization of the synchrotron radiation in combination with a sample carrier positioned in the vertical plane and a side-looking detector in the plane of polarization turned out to give the best results with a DL of 15 fg for Ni.

A high-precision spectrometer for the absolute determination of X-ray absorption edges as calibration standards

The general characteristics and spectrometric features of a high-resolution four-crystal reflection X-ray monochromator with wavelength analysis installed at the HASYLAB beamline L at DESY are presented. The monochromator is part of a spectrometer developed to calibrate X-ray absorption edge spectra in the energy range of 6-36 keV with a relative uncertainty ΔE/E from 10 −5 to 10 −6 . This requires an extremely effective suppression of harmonics and also a negligible instrumental influence in order to obtain almost intrinsic spectra. As the results show, the monochromator fulfills the requirements, including very high stability. One essential advantage of the (+ − − +)-setting is that the monochromator itself limits the divergence of the primary radiation, which is very useful for energies above 5 keV where the natural divergence of the synchrotron radiation exceeds the width of the crystal reflection curve. This setting needs no further optics such as slits to improve the resolution, which is therefore not influenced by vertical movements of the primary radiation source. Harmonic suppression is achieved by detuning the channel-cut nondispersive monolithic part slightly out of its parallel-sided position. In preliminary tests the operation of the set-up according to the principle was demonstrated. The thermal load of the first crystal caused a temperature increase of approximately 5 K. After reaching temperature equilibrium reproducible results are received. In a measured section of 18-30 degrees of arc, the deviation of the monochromator position from that measured by the goniometer is less than the resolution of the monochromator angle decoder. The FWHM of the rocking curves is in the range of the expected values. An example of the calibration procedure for the copperK-edge is given as well as a comparison of the remeasured absorption edge energies with the previously tabulated data.