Diameter X-ray Beam Research Articles

X-ray micro-beam characterization of an elastically bent thin diamond plate for x-ray optics applications

Insufficient information on the diffraction and energy-dispersion properties of elastically bent diamond limits its range of application in X-ray optics. Laue micro-beam diffraction has excellent potential for studying these properties. With this method, we explained the origin of the Laue spots asterism, calculated the strain–stress fields generated due to the bending of the diamond plate, and determined the bending radius in situ with high accuracy. The method can be used to control the dispersion characteristics of bent plates by changing the x-ray beam diameter or bending radius. Important conclusions are drawn for practical application of bent diamonds.

Multi-contrast CT imaging using a high energy resolution CdTe detector and a CZT photon-counting detector

Computed tomography (CT) imaging with high energy resolution detectors shows great promise in material decomposition and multi-contrast imaging. Multi-contrast imaging was studied by imaging a phantom with iodine (I), gadolinium (Gd), and gold (Au) solutions, and mixtures of the three using a cadmium telluride (CdTe) spectrometer with an energy resolution of 1% as well as with a cadmium zinc telluride (CZT) detector with an energy resolution of 13%. The phantom was imaged at 120 kVp and 1.1 mA with 7 mm of aluminum filtration. For the CdTe data collection, the phantom was imaged using a 0.2 mm diameter x-ray beam with 96 ten-second data acquisitions across the phantom at 45 rotation angles. For the CZT detector, we had 720 projections using a cone beam, and the six detector energy thresholds were set to 23, 33, 50, 64, 81, and 120 keV so that three thresholds corresponded to the K-edges of the contrast agents. Contrast agent isolation methods were then examined. K-edge subtraction and novel spectrometric algebraic image reconstruction (SAIR) were used for the CdTe data. K-edge subtraction alone was used for the CZT data. Linearity plots produced similar R 2 values and slopes for all three reconstruction methods. Comparing CdTe methods, SAIR offered less noise than CdTe K-edge subtraction and better geometric accuracy at low contrast concentrations. CdTe contrast agent images of I, Gd, and Au offered less noise and greater contrast than the CZT images, highlighting the benefits of high energy resolution CdTe detectors for possible use in pre-clinical or clinical CT imaging.

Reproducibility analysis of diamond pixel detectors for large ionizing radiation fields

This work reports on reproducibility tests performed on 20 high-quality single-crystal chemical vapour deposition (scCVD) diamond samples. By the analysis of the average mobility-lifetime product of the photogenerated carriers, 12 samples were selected and arranged as pixels in a 2.5 × 2.5 cm2 mosaic detector. Measurements carried out under a large (4 cm diameter) X-ray beam show a very high pixel response uniformity (<1% standard deviation relative to the mean photocurrent value) for a wide range of applied bias voltages (20 ÷ 80 V). Results suggest a very high level of reproducibility, mostly due to the excellent quality of the bulk material, meeting the requirements for monitoring large ionizing radiation fields with no need for individual pixel calibration. Moreover, mobility-lifetime product demonstrated to be the most effective figure of merit for the selection of CVD diamond samples with reproducible detection performance.

Assessing zinc from a nail clipping using mono-energetic portable X-ray fluorescence

A mono-energetic X-ray beam from a portable X-ray fluorescence device was used to excite characteristic X-rays from zinc in a series of nail clipping phantoms. Twenty nail clipping phantoms having equal zinc concentrations of ~40 µg/g, but with different physical characteristics, were measured individually for 300 s using a small diameter (~1 mm) X-ray beam. Energy spectra obtained from the measurements were analyzed using PyMca software. Zinc signal size varied widely between the different clippings, with a relative standard deviation of 41% observed in the combined signal from zinc Kα and Kβ characteristic X-rays. Three different normalization approaches were introduced to account for variation in the amounts of sample interrogated by the X-ray beam. All three approaches produced similar results, and successfully reduced the relative standard deviation to between 12% and 13%. A clear trend was still observed, however, between the normalized zinc signal and the thickness of clipping measured. To account for this effect, normalized signals were adjusted to calculate “thickness-corrected” values. The relative standard deviation of these thickness-corrected values was 6.2%. Reproducibility of measurement from individual clippings was excellent, with relative standard deviations on the order of 1%, with or without normalization. Overall, this new method of measuring zinc in nail shows promise for the assessment of zinc status in humans using a portable device. The method is sensitive, rapid, and requires only a single nail clipping.

30 nm X-ray focusing correlates oscillatory stress, texture and structural defect gradients across multilayered TiN-SiOx thin film

Resolving depth gradients of microstructure and residual stresses within individual sublayers of multilayered thin films and understanding their origin as well as their influence on functional properties are challenging tasks. In this work, a newly developed synchrotron focusing setup based on Multilayer Laue Lenses, providing an X-ray beam diameter of ∼30 nm, is used to characterize the cross-sectional properties of a 2.9 μm thick sculptured multilayered TiN-SiOx film, which consists of twelve ∼230 nm thick nano-crystalline TiN sublayers of zigzag columnar grain morphology separated by eleven amorphous SiOx sublayers, both prepared by oblique magnetron sputtering on a Si(100) substrate. The X-ray nano-diffraction analysis of the TiN sublayers reveals (i) an oscillatory variation of compressive residual stresses across the film ranging between −1.8 and −0.25 GPa, (ii) the presence of <100> fiber textures with three different fiber axis orientations, which abruptly change between the individual sublayers, and (iii) gradually decreasing densities of structural defects within every TiN sublayer, exhibiting a sawtooth-like depth-profile across the film. The near-substrate TiN sublayer shows the highest compressive stress reaching ∼ −1.8 GPa, a unique texture and the largest density of defects among all sublayers, which indicates diverse nucleation mechanisms of TiN on the native Si oxide and on the SiOx sublayers. The results demonstrate that the average stress state and the microstructure within the individual TiN sublayers can be influenced effectively by the applied deposition conditions, although self-organization processes during the sublayers' evolution give rise to the occurrence of qualitatively similar gradual trends, which differ in intensity and which were characterized also by complementary laboratory X-ray diffraction, as well as scanning and transmission electron microscopies. Finally, the presented results document that the novel X-ray nano-probe approach allows for the characterization of nano-scale gradients within individual microstructural features of polycrystalline thin films and pioneers the way for knowledge-based synthesis of thin films with predefined cross-sectional microstructure and property gradients.

Collimated superfine x-ray beam based x-ray luminescence computed tomography.

X-ray luminescence computed tomography (XLCT) is a hybrid imaging modality with the potential to achieve a spatial resolution up to several hundred micrometers for targets embedded in turbid media with a depth larger than several millimeters. In this paper, we report a high spatial resolution XLCT imaging system with a collimated superfine x-ray beam in imaging the deeply embedded targets. A collimator with a 100 micrometer pinhole was mounted in the front of a powerful x-ray tube to generate a superfine x-ray pencil beam with a beam diameter of 0.175 mm. For the phantom experiment of four capillary targets with an edge-to-edge distance of 400 micrometers, we were able to reconstruct the targets in a depth of 5 mm successfully, which were validated with microCT images. We have further investigated the effect of different x-ray beam diameters on the reconstructed XLCT images with numerical simulations. Our results indicate that XLCT has the ability to image successfully multiple deeply embedded targets when the collimated x-ray beam diameter is less than or equal to the target edge-to-edge distance. Our numerical simulations also demonstrate that XLCT can achieve a spatial resolution of 200 micrometers for targets embedded at a depth of 5 mm if the scanning beam has a diameter of 100 micrometers.

Synchrotron beam test of a photon counting pixel prototype based on Double-SOI technology

The overall noise performances and first synchrotron beam measurement results of CPIXETEG3b, the first counting type Silicon-On-Insulator (SOI) pixel sensor prototype without crosstalk issue, are reported. The prototype includes a 64 × 64 pixel matrix with 50 μm pitch size. Each pixel consists of an N-in-P charge collection diode, a charge sensitive preamplifier, a shaper, a discriminator with thresholds adjustable by an in-pixel 4-bit DAC, and a 6-bit counter. The study was performed using the beam line 14A at KEK Photon Factory (KEK-PF) . The homogeneous response of the prototype, including charging-sharing effects between pixels were studied. 16 keV and 8 keV monochromatic small size (∼ 10 μm diameter) X-ray beams were used for the charge sharing study, and a flat-field was added for homogenous response investigation. The overall detector homogeneity and the influence of basic detector parameters on charge sharing between pixels has been investigated.

Round robin: Quantitative lateral resolution of PHI XPS microprobes Quantum 2000/Quantera SXM

The quantitative lateral resolution is a reliable measure for the quality of an XPS microprobe equipped with a focused X-ray beam. It describes the long tail contributions of the X-ray beam intensity distribution. The knowledge of these long tail contributions is essential when judging on the origin of signals of XPS spectra recorded on small-sized features.In this round robin test the quantitative lateral resolution of 7 PHI XPS microprobes has been estimated. As expected, the quantitative lateral resolution has significantly larger values than the nominal X-ray beam diameter. The estimated values of the quantitative lateral resolution follow a trend in time: the newer the monochromator of an XPS microprobe so much the better the quantitative lateral resolution.

Immediate screening of lead exposure in the workplace using portable X-ray fluorescence

ABSTRACTThe use of a portable X-ray fluorescence spectrometer (PXRF) equipped with a miniaturised X-ray tube producing a small 8 mm diameter X-ray beam required the validation of two new sampling protocols for the immediate screening of occupational lead exposure.First, lead in dust and fumes, collected by Institute of Occupational Medicine (IOM) inhalable samplers on 25 mm diameter membrane filters, is quantified using PXRF. To account for irregular dust deposition, the filters are rotated manually by quarter turns. Multiple PXRF readings are collected from the central region and from two locations in the outer region. The inner region is distinguishable from the outer region, but the two outer region locations are indistinguishable.High correlations (R2 > 0.99) are found between the PXRF results and historical results obtained using a reference method based on a laboratory wavelength-dispersive sequential XRF instrument (WDXRF) for lead loadings between 1–161 μg. The PXRF results from the outer regions of the filters show a bias of −13% with respect to the WDXRF. Once this bias is allowed for, 95% of all PXRF results lie within −28% and +38% of the WDXRF results. Neither instrument accounts for potential dust accumulation on the walls of the IOM sampler. Therefore, methods based on their use can only be considered semi-quantitative.Second, a protocol combining direct PXRF measurements on workplace surfaces with surface wipes is designed for immediate on-site quantification of removable surface lead residues. The quantification of such residues by this method is compared with subsequent off-site wet chemistry analysis of the surface wipes. The two methods show a good correlation (R2 ∼ 0.88). The ratio of the amount of removable residues determined by PXRF and wipe sampling is close to one with range 0.26–3.94.It is demonstrated that PXRF can be used as an effective tool for the immediate screening of occupational lead exposure. Although this article focused on lead, PXRF can identify simultaneously a number of other metals.

Coherent convergent-beam time-resolved X-ray diffraction.

The use of coherent X-ray lasers for structural biology allows the use of nanometre diameter X-ray beams with large beam divergence. Their application to the structure analysis of protein nanocrystals and single particles raises new challenges and opportunities. We discuss the form of these coherent convergent-beam (CCB) hard X-ray diffraction patterns and their potential use for time-resolved crystallography, normally achieved by Laue (polychromatic) diffraction, for which the monochromatic laser radiation of a free-electron X-ray laser is unsuitable. We discuss the possibility of obtaining single-shot, angle-integrated rocking curves from CCB patterns, and the dependence of the resulting patterns on the focused beam coordinate when the beam diameter is larger or smaller than a nanocrystal, or smaller than one unit cell. We show how structure factor phase information is provided at overlapping interfering orders and how a common phase origin between different shots may be obtained. Their use in refinement of the phase-sensitive intensity between overlapping orders is suggested.

Characterization of the primary X-ray source of an XPS microprobe Quantum 2000

The outstanding design feature of an XPS microprobe Quantum 2000 is the double focussing ellipsoidally shaped quartz monochromator of the X-ray source. This device monochromatizes the Alkα radiation and refocuses the X-rays from the Al anode to the sample surface. This way, on one hand a variation of the diameter of the X-ray generating electron beam allows to vary the X-ray beam diameter on the sample surface. On the other hand a scanning of the electron beam across the Al anode scans the X-ray beam across the sample surface.The X-ray source was characterized in detail. The lateral dependency of the primary X-ray intensity and the peaks FWHM were measured as function of the position within the electrostatically rasterable scan area. Additionally, the focussing quality of the monochromator was determined. Therefore the lateral intensity distribution within the primary X-ray beam was estimated far below the 1% intensity level.

Pots, plates and provenance: sourcing Indian coarse wares from Mleiha using X-ray fluorescence (XRF) spectrometry analysis

The identification of more than 25% of the pottery sherds from the late PIR.D period (ca. 2nd - mid. 3rd c. AD) assemblage from the recently excavated building H at Mleiha as Indian is based on form and fabric, but using only visual assessment. Petrographic analysis of the fabrics can provide more precise indicators of the geographical origin of the wares. In this study, a total of 21 sherds from various key sites in Western India were compared with 7 different 'Indian' coarse-ware vessels sampled at Mleiha using X-ray fluorescence (XRF) spectrometry. The analyses were conducted on powdered samples collected from the core of each sherd. Each sample was irradiated for 1000 seconds using a 1.2 mm diameter X-ray beam. The resulting spectra were used for quantification of the X-ray intensity and elemental concentration. Levels of correlation in the elemental ratios of the sherds were statistically tested using an F-test as well as a Chi-test. Initial review of the XRF results indicates that the Maharashtra and Gujarat regions of India are probable source areas for at least two of the types of wares. Collection of additional samples from these areas and other regions of India, and further statistical analysis through methods such as Principal Component Analysis will help to isolate groups of wares from India and correlate them with types of vessels imported into the Oman peninsula in antiquity.

Beam damage of HS(CH2)15 COOH Terminated Self Assembled Monolayer (SAM) as Observed by X-ray Photoelectron Spectroscopy

XPS spectra of a HS(CH2)15 COOH terminated self assembled monolayer (SAM) sample were collected over a period of 231 min to determine specimen damage during long exposures to monochromatic Al Kα x-rays. For this COOH terminated SAM the loss of oxygen was measured as a function of time while rastering a focused 100 W, 100 μm diameter x-ray beam over a 1.4 mm × 0.2 mm area of the sample.

Use of a synchrotron X-ray microbeam to map composition and structure of multimetallic metal oxide films deposited by combinatorial chemical vapor deposition

Using anhydrous metal nitrates as single source precursors, combinatorial chemical vapor deposition was used to create compositional gradients in the bimetallic ZrO 2/HfO 2 system and the trimetallic ZrO 2/HfO 2/SnO 2 system. Composition and structural information were probed simultaneously by measuring the fluorescence and diffraction resulting from exposure of the film to a 30 μm diameter X-ray beam at the Advanced Photon Source. The higher resolution made possible by the small beam size provided an accurate map of composition and structure. In the homologous zirconia–hafnia series a decrease in lattice constants and a change in film texture was observed as a function of increased Hf concentration. As reported elsewhere, at intermediate compositions, gradients involving ZrO 2 and SnO 2 or HfO 2 and SnO 2 give rise to a crystalline phase(α-PbO 2 structure type) that differs from that found for either of the end members. The simultaneous measurement of fluorescence and diffraction coupled with the small spot X-ray source provides a more accurate correlation between composition and structure.

Acidic demineralization of apatites studied by scanning X-ray microradiography and microtomography

AbstractThe mineral in bones and teeth is an impure form of hydroxylapatite (HAP), the principal impurity being 2—5 wt.% carbonate. This mineral dissolves during remodelling of bone and also in dental caries as a result of the action of acids produced by osteoclasts and by bacteria, respectively. In enamel, demineralization proceeds with preferential loss of carbonate relative to phosphate. Surprisingly, in the early stages, the demineralization is subsurface. In order to facilitate the understanding of physical chemical aspects of these processes, we have undertaken studies of demineralization in model systems. We give three examples here. The first two used scanning microradiography in which the specimen is stepped across a 10—30 μm diameter X-ray beam. Intensity measurements allow calculation of the mineral mass per unit area in the X-ray path through the specimen. In the first experiment, porous HAP sections were separated from a reservoir of acidic buffer by a column initially filled with water (the diffusion length) and scanned with the X-ray beam perpendicular to the axis of the diffusion length. The rate of total loss of mineral along each profile was calculated from the scans. The rate of demineralization fell as the diffusion length increased. We believe the explanation is that the rate-controlling step is the diffusion of dissolved HAP away from the solid to the buffer reservoir. In the second experiment, demineralizing solution and water were pumped alternately, for equal lengths of time, past blocks of porous HAP or enamel. The X-ray beam was perpendicular to the exposed surface. As the rate of switching between solutions decreased, the mean rate of demineralization also fell. We propose that this effect is due to retention of acid in the pores of the HAP during the time when water flows, allowing further demineralization to take place during this time. The third study used X-ray microtomography, a form of 3D microscopy, to study the loss of mineral in compacted carbonate apatite powders. The powders were packed in six 10 mm internal diameter acrylic cylinders to a depth of 4 mm (after pressing). One end was covered with a porous polyethylene disc and each tube placed in acidic buffer for 70 days. Periodic examination by microtomography showed the development of subsurface demineralization. Infrared spectroscopy of the dissected-out surface layers showed preferential loss of carbonate over phosphate by comparison with deeper layers. Rietveld analysis of X-ray powder diffraction data showed changes in the crystallographic structures of the apatites between the initial and dissected-out apatite.

IDENTIFICATION OF SCORODITE IN FINE-GRAINED, HIGH-SULFIDE, ARSENOPYRITE MINE-WASTE USING MICRO X-RAY DIFFRACTION ( XRD)

Secondary phases precipitated during oxidation of sulfides in mine wastes can be very fine-grained and poorly crystalline, making accurate identification difficult. As part of a study to examine arsenic mobility within the arsenopyrite residue stockpile, Snow Lake, Manitoba, arsenic-rich secondary phases were examined by a combination of micro X-ray diffraction (μXRD) and electron-probe micro-analysis (EPMA). With EPMA, we found one of the secondary As-containing phases to have an Fe:As ratio of 1:1. Examination of μXRD data allowed positive identification of this phase as scorodite (FeAsO4· 2H2O). Two texturally distinct occurrences of scorodite were identified in specific areas of the polished thin sections. Type-1 scorodite occurs around grains of primary arsenopyrite, and Type-2 scorodite is disseminated throughout an amorphous iron sulfo-arsenate (AISA) matrix in highly altered material. Our observations suggest that μXRD can be used to routinely identify phases comprising <1% of the bulk sample, provided that these phases are positioned under the X-ray beam. All of the scorodite examined is very fine-grained polycrystalline material, displaying homogeneous Debye powder rings in the two-dimensional (2D) General Area Diffraction Detector System (GADDS) image, using either a 500 or 50 μm X-ray beam diameter. The homogeneous texture of fine-grained secondary scorodite makes it easily discernable from relatively coarse-grained primary minerals, which give large discrete diffraction-spots or discontinuous “grainy” Debye rings in the GADDS image.

Analysis of Stress Transfer in Two-Phase Polymer Systems Using Synchrotron Microfocus X-ray Diffraction

Microfocus X-ray diffraction has been used to analyze interfacial stress transfer in two-phase polymer systems consisting of a highly oriented polymer fiber in an isotropic resin matrix. Synchrotron radiation has been used to obtain high-quality X-ray diffraction patterns from single poly(p-phenylene benzobisoxazole) (PBO) and poly(p-phenylene terephthalamide) (PPTA) fibers in these model two-phase systems. Two different specimen geometries were studied: a fully embedded fiber composite and a microdroplet specimen. A procedure is demonstrated whereby well-defined diffraction patterns can be obtained, using a 5 mum diameter X-ray beam, from individual 12 mum diameter polymer fibers in over 1 mm thickness of resin by subtracting the scattering of the resin matrix from that of the fiber and matrix to obtain a diffraction pattern of the fiber only. Shifts of meridional diffraction peaks of the fibers were determined as a function of stress and were converted into crystal strain. The fiber stress was then determined from calibrations obtained from previous X-ray diffraction studies of fiber deformation. The point-to-point variation of fiber stress was mapped along the fibers in the specimens, and a force-balance approach was used to determine the shear stress at the fiber-matrix interface. This present study was concerned only with an optically transparent polymer matrix, but the possible extension of the technique to opaque matrices and other multiphase polymer systems is discussed.

An image guided conformal radiation platform for small animals

An image guided conformal radiation platform for small animals

Beam Damage of Poly(vinyl chloride) [PVC] Film as Observed by X-ray Photoelectron Spectroscopy

XPS spectra of a spin-coated film poly(vinyl chloride)(PVC) were collected over a period of 243 min at 303 K to determine specimen damage during long exposures to monochromatic Al Kα x-rays. For this PVC film we measured the loss of chlorine as a function of time by rastering a focused 104.6 W, 100 μm diameter x-ray beam over a 1.4 mm × 0.2 mm area on the sample.

Commentary reply

The outstanding design feature of an XPS microprobe Quantum 2000 is the double focussing ellipsoidally shaped quartz monochromator of the X-ray source. This device monochromatizes the Alkα radiation and refocuses the X-rays from the Al anode to the sample surface. This way, on one hand a variation of the diameter of the X-ray generating electron beam allows to vary the X-ray beam diameter on the sample surface. On the other hand a scanning of the electron beam across the Al anode scans the X-ray beam across the sample surface.The X-ray source was characterized in detail. The lateral dependency of the primary X-ray intensity and the peaks FWHM were measured as function of the position within the electrostatically rasterable scan area. Additionally, the focussing quality of the monochromator was determined. Therefore the lateral intensity distribution within the primary X-ray beam was estimated far below the 1% intensity level.