Dispersive Detector Research Articles

Calibration of X-ray imaging devices for accurate intensity measurement

National Security Technologies (NSTec) has developed calibration procedures for X-ray imaging systems. The X-ray sources that are used for calibration are both diode type and diode/fluorescer combinations. Calibrating the X-ray detectors is a key to accurate calibration of the X-ray sources. Both energy dispersive detectors and photodiodes measuring total flux were used. We have developed calibration techniques for the detectors using radioactive sources that are traceable to the National Institute of Standards and Technology (NIST). The German synchrotron at Physikalische Technische Bundestalt (PTB) was used to calibrate the silicon photodiodes over the energy range from 50 to 60 keV. The measurements on X-ray cameras made using the NSTec X-ray sources included quantum efficiency averaged over all pixels, camera counts per photon per pixel, and response variation across the sensor. The instrumentation required to accomplish the calibrations is described. The X-ray energies ranged from 720 to 22.7 keV. The X-ray sources produce narrow energy bands, allowing us to determine the properties as a function of X-ray energy. The calibrations were done for several types of imaging devices. There were back and front illuminated CCD (charge-coupled device) sensors, and a CID (charge injection device) type camera. The CCD and CID camera types differ significantly in some of their properties that affect the accuracy of the X-ray intensity measurements. All the cameras discussed here are silicon based. The measurements of the quantum efficiency variation with the X-ray energy are compared to the models for the sensor structure. The cameras that are not back-thinned are compared to those that are.

Study of electron densities of normal and neoplastic human breast tissues by Compton scattering using synchrotron radiation

Electron densities of 33 samples of normal (adipose and fibroglangular) and neoplastic (benign and malignant) human breast tissues were determined through Compton scattering data using a monochromatic synchrotron radiation source and an energy dispersive detector. The area of Compton peaks was used to determine the electron densities of the samples. Adipose tissue exhibits the lowest values of electron density whereas malignant tissue the highest. The relationship with their histology was discussed. Comparison with previous results showed differences smaller than 4%.

EDXRD Setup for Real Time Observation of a Gas Tungsten Arc (GTA) Welding Process

Residual stresses in welds are of major concern for the structure integrity assessment in industrial components. The stresses in the final weld can be determined relatively simple using well established destructive or non-destructive techniques. However, such measurements reflect only the final condition and it remains unclear how stresses built up during the welding process. In order to optimise the final residual stresses in the weld, it is important to monitor the formation of residual strain and stress during the welding process and as such to gain insight into the mechanisms of stress development. In this work non-destructive high energy dispersive synchrotron X-ray diffraction at a high count rate is applied in order to dissolve the welding process in-situ in time and temperature. However, the achievable time resolution at commonly used instruments is restricted by either a limited photon flux or the read out electronics of the detector system resulting in counting times usually much longer than 1sec. We present an energy dispersive detector and read-out-electronics setup realized at the high flux and energy beam line ID15A at the ESRF. The setup allowed for monitoring the strain evolution in two perpendicular directions simultaneously at a sampling rate of 5Hz, resulting in sufficient time and temperature resolution. The change in detector dead time is accounted for by a correction function, which was specifically determined for the detector setup as used for this in-situ experiment.

PRECONCENTRATION AND DETERMINATION OF SHORT CHAIN MERCAPTANS IN THE PRODUCED WATER BY DISPERSIVE LIQUID-LIQUID MICROEXTRACTION AND GAS CHROMATOGRAPHY

ABSTRACT This paper describes the preconcentration of short chain n-alkyl C 1 -C 6 mercaptans in the produced water using the dispersive liquid-liquid microextraction. In the present experiments, 0.8 mL dispersive solvent (acetonitrile) containing 10.0 μL extraction solvent (carbon tetrachloride) was rapidly injected into the samples and followed by centrifuging and direct injection into the gas chromatograph equipped with flame ionization detector. According to the results, dispersive liquid-liquid microextraction gas chromatography flame-ionization detector was successfully used for determination of short chain n-alkyl C 1 -C 6 mercaptans. The parameters affecting the extraction efficiency were evaluated and optimized. Under the optimum conditions, the figures of merits for six short chain n-alkyl C 1 -C 6 mercaptans were determined to be 4.0-100.0 ng/L (n = 6, RSD = 6.8%), 6.0-80.0 ng/L (n = 6, RSD = 11.0%), 2.0-90.0 ng/L (n = 6, RSD = 2.6%), 5.0-120.0 ng/L (n = 6, RSD = 4.4%), 3.0-80.0 ng/L (n = 6, RSD = 9.2%) and 2.0-110.0 ng/L (n = 6, RSD = 6.5%), respectively.

Chemical Modification of Dust Particles during Different Dust Storm Episodes

Two dust episodes (D1: February 13 and D2: March 28–29, 2004) of long-range transport from desert and loess sources, and one dust episode (D3: March 30) mainly from local area, were investigated in spring 2004 in Beijing, China. Dust samples were collected in different dust episodes and scanning electron microscopy with X-ray energy dispersive detector (SEM/EDS) was applied to study the morphology, elemental composition, and chemical modification on the surfaces of dust particles with radius from 0.1 to 6.4 μm. The morphological features of the particles reveal that the three dust plumes carried both dust particles (90–98% by number) and anthropogenic pollutants (e.g., fly ash and soot, 2–10%). Particle compositions show that the amount of S-containing dust particles was higher in D1 and D2 than in D3. Sulfates were introduced into the dust particles through heterogeneous uptake of SO2 during their transport. In all three dust episodes, fine dust particles (radius < 1 μm) showed a higher degree of chemical modification by SO2 compared to the coarse particles (radius ≥ 1 μm). Furthermore, long-range transport dust particles were more deeply modified by SO2 than particles from local areas. The composition of the dust particles indicates that alkaline mineral components determined the level of chemical modification of individual particles. Heterogeneous uptake of SO2 on a large number of dust particles would increase mass of the internally mixed sulfates on their surfaces. The results suggest that the optical properties of dust particles during dust storm episodes are gradually altered based on how far they are transported.

3D elemental distribution images in biological samples by XRFµCT

An X-ray transmission microtomography (CT) system combined with an X-ray fluorescence microtomography (XRFµCT) system was implemented in the Brazilian Synchrotron Light Laboratory (LNLS), Campinas, Brazil. The aim of this work was to determine the elemental distribution in biological samples (breast, prostate and lung samples) in order to verify the concentration of some elements correlated with characteristics and pathology of each tissue observed by the transmission CT. The experiments were performed at the X-ray fluorescence beamline (D09B-XRF) of the Brazilian Synchrotron Light Laboratory, Campinas, Brazil. A quasi-monochromatic beam produced by a multilayer monochromator was used as an incident beam. The sample was placed on a high-precision goniometer and translation stages that allow rotating as well as translating it perpendicularly to the beam. The fluorescence photons were collected with an energy dispersive HPGe detector placed at 90° to the incident beam, while transmitted photons were detected with a fast Na(Tl) scintillation counter placed behind the sample on the beam path. The CT images were reconstructed using a filtered-back projection algorithm and the XRFµCT images were reconstructed using a filtered-back projection algorithm with absorption corrections. The 3D images were reconstructed using the 3D-DOCTOR software. Results from the 3D visualization showed that the distribution of iron, copper and zinc is different and heterogeneous from the analyzed samples. Copyright © 2011 John Wiley & Sons, Ltd.

Compact pnCCD-Based X-ray Camera with High Spatial and Energy Resolution: A Color X-ray Camera

For many applications there is a requirement for nondestructive analytical investigation of the elemental distribution in a sample. With the improvement of X-ray optics and spectroscopic X-ray imagers, full field X-ray fluorescence (FF-XRF) methods are feasible. A new device for high-resolution X-ray imaging, an energy and spatial resolving X-ray camera, is presented. The basic idea behind this so-called "color X-ray camera" (CXC) is to combine an energy dispersive array detector for X-rays, in this case a pnCCD, with polycapillary optics. Imaging is achieved using multiframe recording of the energy and the point of impact of single photons. The camera was tested using a laboratory 30 μm microfocus X-ray tube and synchrotron radiation from BESSY II at the BAMline facility. These experiments demonstrate the suitability of the camera for X-ray fluorescence analytics. The camera simultaneously records 69,696 spectra with an energy resolution of 152 eV for manganese K(α) with a spatial resolution of 50 μm over an imaging area of 12.7 × 12.7 mm(2). It is sensitive to photons in the energy region between 3 and 40 keV, limited by a 50 μm beryllium window, and the sensitive thickness of 450 μm of the chip. Online preview of the sample is possible as the software updates the sums of the counts for certain energy channel ranges during the measurement and displays 2-D false-color maps as well as spectra of selected regions. The complete data cube of 264 × 264 spectra is saved for further qualitative and quantitative processing.

Portable energy dispersive X-ray fluorescence and X-ray diffraction and radiography system for archaeometry

Starting on a laboratory developed portable X-ray fluorescence (PXRF) spectrometer; three different analytical results can be performed: analysis of chemical elements, analysis of major chemical crystalline phase and structural analysis, which represents a contribution to a new, low cost development of portable X-ray analyzer; since these results are respectively obtained with independent equipments for X-ray fluorescence, X-ray diffraction and radiography. Detection limits of PXRF were characterized using standard reference materials for ceramics, glass, bronze and bones, which are the main materials requiring quantitative analysis in art and archeological objects. A setup for simultaneous energy dispersive X-ray fluorescence and diffraction (ED (XRF–XRD)) in the reflection mode has been tested for in situ and non-destructive analysis according to the requirements of art objects inspection. The system uses a single low power X-ray tube and an X-ray energy dispersive detector to measure X-ray diffraction spectrum at a fixed angle. Application to the identification of jadeite-jade mineral in archeological objects by XRD is presented. A local high resolution radiography image obtained with the same low power X-ray tube allows for studies in painting and archeological bones.

Improved radiographic methods for the investigation of paintings using laboratory and synchrotron X-ray sources

It is generally known that radiographic inspection of 15–17th century paintings can easily be done with a polychromatic X-ray source using a voltage between 20 kV and 40 kV in combination with classic X-ray films. Unfortunately, the spatial structure of numerous 19th and early 20th century paintings cannot be visualized with conventional radiography due to several reasons such as the use of lead white grounds or low absorbing pigments. Radiographic images are blurred or worse, they do not contain the picture of the painting. During the last decades, many technological innovations have been introduced in the field of radiography but their possibilities in cultural heritage have not been explored in full detail. In our investigation we used phosphor imaging plates, energy dispersive detectors and CCD-cameras in combination with synchrotron radiation and conventional X-ray tubes in order to improve the quality of radiographic images. Several promising techniques that could improve the quality of radiographs of paintings were identified.

Transport Properties of Over-doped Epitaxial NdCeCuO Films

The transport properties of slightly overdoped Nd2−x Ce x CuO4−δ (NCCO) c-axis oriented thin films with x=0.17 have been investigated in the temperature range from 2.5 K to 300 K and in magnetic fields up to 6 T applied perpendicular to the CuO2 planes. The films have been grown by a dc sputtering technique in on-axis configuration. They have been optimized on (001)-oriented SrTiO3 substrates and successively annealed in pure Argon at 900 °C. Structural and compositional analyses were carried out by means of X-ray diffraction and scanning electron microscopy equipped with a wavelength dispersive spectroscopy detector. Current-voltage characteristics of the NCCO films have been measured and the temperature and the magnetic field dependence of the critical current density J c(T,H) has been obtained. Finally, an increase of the low-temperature normal state resistance with the field has also been observed.

3D elemental distribution images by XRFμCT at LNLS—Brazil

An X-ray Transmission Microtomography (CT) system combined with an X-ray Fluorescence Microtomography (XRFμCT) system was implemented in the Brazilian Synchrotron Light Laboratory (LNLS), Campinas, Brazil. The main objective of this work is to determine the elemental distribution in biological samples (breast, prostate and lung samples) in order to verify the concentration of some elements correlated with characteristics and pathology of each tissue observed by the transmission CT. The experiments were performed at the X-Ray Fluorescence beamline (D09B-XRF) of the Brazilian Synchrotron Light Laboratory, Campinas, Brazil. A quasi-monochromatic beam produced by a multilayer monochromator was used as an incident beam. The sample was placed on a high precision goniometer and translation stages that allow its rotation as well as translation perpendicular to the beam. The fluorescence photons were collected with an energy dispersive HPGe detector placed at 90° to the incident beam, while transmitted photons were detected with a fast Na(Tl) scintillation counter placed behind the sample on the beam direction. The CT images were reconstructed using a filtered back-projection algorithm and the XRFμCT were reconstructed using a filtered back-projection algorithm with absorption corrections. The 3D images were reconstructed using the 3D-DOCTOR software.

Advanced experimental facilities for SHS Studies and physico-chemical characterization of inorganic materials: An autoreview

Overviewed are new experimental methods for investigating the processes of phase formation during SHS. The first experiments using penetrating synchrotron radiation and energy dispersive detectors for different classes of complex inorganic materials were carried out in ESRF (Grenoble, France), LURE (Orsay, France) and Daresbury (UK). A new and very sensitive thermal imaging method (Thermal Imaging Technique, TIT) is based on continuous registration of the whole combustion process by using a highly sensitive IR camera and software developed by MIKRON Instruments Co. (USA) was also used for precise registration of combustion parameters. SHS was performed on different types of pure on doped complex inorganic materials in pellet and powder form in a range of dc magnetic field induction up to 20 T and electrical field strength up to ±220 kV/m. The dc magnetic field was applied during the reaction, supplied either by permanent magnet (transverse, 1.1 T) or by an electromagnet (longitudinal, up to 20 T). The dc electrical field was applied along direction of the combustion wave propagation. The combined processes of SHS and SLS (Selective Laser Sintering) of 3D articles for different powdered compositions was realized with optimal parameters of laser irradiation, under what SHS reactions proceeded in controlled regime.

Examination of Multiphase (Zr,Ti)(V,Cr,Mn,Ni)2 Ni-MH Electrode Alloys: Part I. Dendritic Solidification Structure

The solidification microstructures of three nine-element Zr-Ni–based AB2 type C14/C15 Laves hydrogen storage alloys are determined. The selected compositions represent a class of alloys being examined for usage as an MH electrode in nickel metal-hydride batteries that often have their best properties in the cast state. Solidification is accomplished by dendritic growth of hexagonal C14 Laves phase, peritectic solidification of cubic C15 Laves phase, and formation of cubic B2 phase in the interdendritic regions. The B2 phase decomposes in the solid state into a complex multivariate platelike structure containing Zr-Ni–rich intermetallics. The observed sequence C14/C15 upon solidification agrees with predictions using effective compositions and thermodynamic assessments of the ternary systems, Ni-Cr-Zr and Cr-Ti-Zr. Experimentally, the closeness of the compositions of the C14 and C15 phases required the use of compositional mapping with an energy dispersive detector capable of processing a very high X-ray flux to locate regions in the microstructure for quantitative composition measurement and transmission electron microscope examination.

Low-crosstalk bifurcation detectors for coupled flux qubits

We present experimental results on the crosstalk between two ac-operated dispersive bifurcation detectors, implemented in a circuit for high-fidelity readout of two strongly coupled flux qubits. Both phase-dependent and phase-independent contributions to the crosstalk are analyzed. For proper tuning of the phase the measured crosstalk is 0.1% and the correlation between the measurement outcomes is less than 0.05%. These results show that bifurcative readout provides a reliable and generic approach for multipartite correlation experiments.

Effects of In-Office and Home Bleaching Gels on the Surface Mercury Levels of Dental Amalgam

The aim of this study was to evaluate the effect of different in-office and home bleaching gels on the surface mercury levels of dental amalgam. Sixty disk-shaped amalgam specimens (GS-80, SDI- Australia) were prepared and randomly divided into the following treatment groups: 1. Distilled water (control); 2. 15% home-bleach carbamide peroxide (Opalescence PF, Ultra dent, USA) applied for 6 h/day for 3 weeks; and 3. 35% in-office bleach carbamide peroxide (Opalescence Quick, Ultradent) applied for 30 min/week for 3 weeks. Levels of mercury were measured as weight percentages using an energy dispersive x-ray micro-analyzer detector connected to an electron microscope. Data was analyzed using one-way ANOVA and a post hoc Tukey tests (P<.05). There were no significant differences between the surface mercury levels measured following treatment with the tested home-bleach and in-office bleach products (P=0.71). However, both materials yielded significantly more mercury levels than that of the control group (P<.001). The tested bleaching products significantly elevated the surface mercury levels of amalgam in vitro.

Spatially resolved 3D micro-XANES by a confocal detection scheme

A confocal setup based on polycapillary half-lenses was used to demonstrate three-dimensional (3D) spatially resolved mu-XANES in fluorescence detection mode at the DUBBLE XAS station of the ESRF (BM26A). The incoming beam was focused using a polycapillary half-lens and a second glass polycapillary was placed in front of the energy dispersive detector to establish the confocal detection. The full-width-half-maxima along the main axes of the resulting ellipsoidal detection volume were 18.5 x 12.0 x 10.0 microm(3) at the Cu K-edge. The confocal mu-XANES mode is applied in the 3D resolved study of mineral inclusions in rare natural diamonds at the Fe K edge.

Polycapillary based μ-XAS and confocal μ-XANES at a bending magnet source of the ESRF

Glass polycapillary optics are shown to be easy to use focusing optics for bending magnet XAS stations. These achromatic optics have acceptances of several mm horizontally and vertically, while their angular acceptances can be matched to the source divergence by the design of the polycapillary. A polycapillary half-lens based focusing system was successfully tested for transmission and fluorescence μ-XAS at the DUBBLE beamline (BM26A, ESRF) and the feasibility of confocal μ-XANES in fluorescence mode is presented.Transmission efficiencies of 25–45% with flux density gain factors of about 2000 and beam sizes of 10–20 μm were obtained in the 7–14 keV energy range. Although the polycapillary optic has a smoothly changing energy dependent transmission efficiency, the amplitude and shape of the EXAFS oscillations are not influenced by this. The focusing properties of the polycapillary lens cancel slight vertical motions of the incoming X-ray beam, resulting in a fixed μ-beam spot in the focal plane, making polycapillaries also suitable optic in combination with a non-fixed exit monochromator.In addition, by mounting a second polycapillary half-lens in front of an energy dispersive detector, a confocal set-up is obtained, which restricts the part of the sample seen by the detector to a microscopic volume of about 20×20×15 μm3 at the Fe K absorption edge for example.

Si Wafer Analysis of Light Elements by TXRF

The determination of light elements (Z<14) requires a set of precautions and experimental modifications in comparison to the analysis of higher Z elements. All measurements have to be performed in vacuum around 1mbar pressure as achieved from a membrane pump. A high resolution energy dispersive detector with ultra thin window and efficiency high enough from 200eV upward is required. The analysis is performed under x-ray total reflection conditions (TXRF) and mechanical components for translation and rotation have to be foreseen for the adjustment. The measurement set-up consisted of a modified vacuum chamber suitable to accommodate 6"- 8" wafers on a rotatable sample carrier and will be described. Droplets containing Mg and two types of elemental matrices consisting of a) medium Z elements (Ti-Zn) and b) light elements (Na, Mg, Al) were prepared on 6" Si wafers in the laboratory of Siltronic AG in Freiberg. For the low Z elements concentrations of 10ng, 100ng, and 1000ng were taken and for the medium Z elements a variable concentration range from 1ng to 100ng was chosen. It was assumed that the presence of medium Z elements causes a stronger absorption of the light elements' fluorescence, whereas light elements affect each other non-serious. The results with respect to the made assumptions and detection limits for the new set-up will be shown.

Preparation of hydroxyapatite nanoparticles: Comparison between hydrothermal and Solvo-Treatment processes and colloidal stability of produced nanoparticles in a dilute experimental dental adhesive

The main purpose of this study is to investigate the colloidal stability of hydroxyapatite (HAp) nanoparticles prepared by different methods. Nano-sized hydroxyapatite particles are synthesized by two different methods including hydrothermal and solvo-treatment processes. In hydrothermal process nanoparticles are synthesized at high temperature, while in solvo-treatment method nanoparticles are synthesized at room temperature by the use of surfactants and organic solvent. The samples are characterized by powder X-ray diffraction (XRD), fourier-transformed infrared spectroscopy (FT-IR), scanning electron microscopy coupled with energy dispersive X-ray analysis detector (SEM + EDXA), and phase separation analyzer. The produced nanoparticles are different in size, stoichiometric ratio, morphology, crystallinity and colloidal stability in a dilute dental adhesive. The results show that the nanoparticles synthesized by these two methods are quite dissimilar and particles prepared by hydrothermal method have a smaller size and higher colloidal stability.

Imaging System for XRF Microtomography at LNLS-Brazil

An X-ray transmission microtomography (CT) system combined with an X-ray fluorescence microtomography (XRFCT) system was implemented in the Brazilian Synchrotron Light Laboratory (LNLS), Campinas, Brazil. The main of this work is to determine the elemental distribution map in reference samples and breast tissue samples in order to verify the concentration of some elements correlated with characteristics and pathology of each tissue observed by the transmission CT. The experiments were performed at the X-Ray Fluorescence beamline (D09B-XRF) of the Brazilian Synchrotron Light Laboratory, Campinas, Brazil. A quasi-monochromatic beam produced by a multilayer monochromator was used as an incident beam. The sample was placed on a high precision goniometer and translation stages that allow rotating as well as translating it perpendicularly to the beam. The fluorescence photons were collected with an energy dispersive HPGe detector placed at 90deg to the incident beam, while transmitted photons were detected with a fast Na(Tl) scintillation counter placed behind the sample on the beam direction. The CT images were reconstructed using a filtered-back projection algorithm and the XRFCT were reconstructed using a filtered-back projection algorithm with absorption corrections.