Low-power X-ray Tube Research Articles

Characterization of Pictorial Materials of Two 18th Century Sculptures: King David and Bathsheba

In this {work}, the X-ray fluorescence technique was employed to characterize the pictorial materials used in two sculptures from the 18th. In addition, Raman spectroscopy was used to characterize the preparation layers used in the sculptures. {The analyzed sculptures} are carved in wood, with gilding and polychrome, and represent the biblical characters, Bathsheba, and King David. The sculptures are property of the Church of \textit{Nossa Senhora do Pilar}, in Duque de Caxias, RJ. XRF {analyzes} were performed using a portable ED-XRF system, which has a low-power X-ray tube (Amptek) with a silver target (Ag) and an SDD detector (Amptek). Raman spectroscopy {analyzes} were performed using the DXR2 Raman microscopy equipment (Thermo Fisher Scientific) with a 785 nm laser source. The results obtained from the XRF and Raman spectroscopy techniques suggest the presence of Gypsum, Calcite, Calcium Sulfate. In addition, the results obtained suggest the presence of the following pigments in the sculptures: Lead white, Titanium White, Lithopone, Ochre, Vermilion, Red Lead and gilding with gold leaf. The studies also showed that the Bathsheba sculpture was probably subjected to some processes of chromatic reintegration over the years due to the heterogeneity of pigments found in the same region

X-ray phase-contrast microtomography of soft tissues using a compact laboratory system with two-directional sensitivity.

X-ray microtomography is a nondestructive, three-dimensional inspection technique applied across a vast range of fields and disciplines, ranging from research to industrial, encompassing engineering, biology, and medical research. Phase-contrast imaging extends the domain of application of x-ray microtomography to classes of samples that exhibit weak attenuation, thus appearing with poor contrast in standard x-ray imaging. Notable examples are low-atomic-number materials, like carbon-fiber composites, soft matter, and biological soft tissues. We report on a compact and cost-effective system for x-ray phase-contrast microtomography. The system features high sensitivity to phase gradients and high resolution, requires a low-power sealed x-ray tube, a single optical element, and fits in a small footprint. It is compatible with standard x-ray detector technologies: in our experiments, we have observed that single-photon counting offered higher angular sensitivity, whereas flat panels provided a larger field of view. The system is benchmarked against known-material phantoms, and its potential for soft-tissue three-dimensional imaging is demonstrated on small-animal organs: a piglet esophagus and a rat heart. We believe that the simplicity of the setup we are proposing, combined with its robustness and sensitivity, will facilitate accessing quantitative x-ray phase-contrast microtomography as a research tool across disciplines, including tissue engineering, materials science, and nondestructive testing in general.

Research on a laboratory monochromatic micro X-ray fluorescence spectrometer based on polycapillary X-ray lenses and flat crystal

Monochromatic micro X-ray fluorescence (Mμ-XRF) analysis has the advantages of high resolution and low detection limit and is a powerful tool to obtain information on element distribution and concentration in materials. An Mμ-XRF spectrometer for laboratory X-ray tubes is developed in this paper, which mainly composed of an X-ray tube, two polycapillary X-ray lenses and a flat crystal. The polycapillary parallel X-ray lens converts the divergent broadband X-rays emitted by the X-ray tube into quasi-parallel X-rays and projects them onto a flat crystal, where monochromatic X-rays are obtained by crystal diffraction. The monochromatic X-rays are then focused by a polycapillary half-focusing X-ray lens to provide spatial resolution for fluorescence analysis. The combination of the two makes it possible to perform Mμ-XRF under laboratory low-power X-ray tube conditions (5.3 W molybdenum tube). By selecting polycapillary half-focusing X-ray lenses with different parameters, the spectrometer can provide a spatial resolution of tens to hundreds of microns to suit various application requirements. The detection limits of the Mμ-XRF spectrometer are also measured using standard solutions. Experimental results show that the detection limit of Se is 52 μg/L and that the detection limit for light elements such as Mn is 970 μg/L.

Position dispersive X-ray fluorescence

A novel scanning-free wavelength dispersive X-ray fluorescence spectrometer has been developed by combining low power X-ray tubes with X-ray optics. The X-rays are focused to a single point on the sample and then dispersed onto a flat diffracting crystal where they are spread depending on their energy through Bragg's law of diffraction onto a silicon strip detector. Throughout this study, the proposed method is referred to as Position Dispersive X-ray Fluorescence (PDXRF). The X-ray emission spectra of vanadium and copper as well as, CuO, CuS2 and V2O5 were measured. In the spectrometer energy resolutions of 3.14 eV and 8.94 eV FWHM were measured for V and Cu when measuring over a range of 4.8–5.8 keV and 6.2–9.1 keV respectively. The Kβ line shapes were fitted with a series of Voigt profiles and the energies and intensities of the Kβ valence transition peak, Kβ2,5, were determined. There was also sufficient variation in the intensity ratio of Kβ2,5/Kβ1,3 that the oxygen and sulphur compounds of V and Cu could be successfully observed and measured. The result demonstrates that this experimental setup is capable of measuring the Kβ line shape at resolutions of a few eV, allowing for chemical state analysis to be performed on 3d transition metals and their compounds such as the measurement of redox reactions to aid in battery development.

Cold Cathodes Based on an Assembly of Microchannel Plates for Low-Power X-Ray Tubes

t—A simple and economical method for manufacturing a cold cathode (electron generator) for a miniature and low-power X-ray emitter is described. The autoelectronic generator contains an assembly of two microchannel plates (MCPs) of the chevron type with an emissive carbon layer of Graphite 33 conductive glue, which contains carbon nanostructures (CNSs). The operating voltage does not exceed 2000 V. The dependence of the electron-generator output current on the distance between the MCPs in the assembly is determined. Thus, when the gap is increased from 0.2 to 0.63 mm the maximum DC current value increases from 0.65 to 4 μA; when the gap is further increased to 1.4 mm, the current increases to 4.5 μA. It is established that the maximum current of the electron generator in the pulsed mode of 53 μA is achieved if the first MCP in the assembly with a CNS layer at the input end is supplied with a pulse voltage of 800 V, a frequency of 2.3 kHz, and an off-duty ratio of 28, while a constant voltage of 1200 V is fed to the second MCP. In this case, the gap between the MCPs in the assembly is 1.4 mm.

Using Geant4 Monte Carlo toolkit to evaluate a low power X-ray tube generator configuration

Monte Carlo technique has been widely used as an important tool to develop new irradiation equipment, prototype medical equipment parts, and test methodologies for dosimetry. In this manuscript, we present a methodology to design a low power X-ray tube generator using the Geant4 Monte Carlo toolkit. The simulations were performed considering a large number of variables, namely, the material composition of the target track, the window thickness, and the air pressure of the X-ray tube. The X-ray production was simulated considering monoenergetic electron beams impinging on targets of tungsten and copper with incident kinetic energies ranging from 20 keV to 60 keV and initial divergences from 5° to 30°. For the polyenergetic emission, a conservative approach with Gaussian energy distribution was adopted. The analysis indicates that among the evaluated parameters, the incident kinetic energy, and the target material produced the most notable changes in the spectra shape and conversion efficiency (CE), significantly impacting the X-ray tube design. The studies provide a reliable methodology to explore general configurations for X-ray tube generators, defining the best geometry, material compositions, and thicknesses to be used on spectroscopy applications.

Combination of Instrumental Neutron Activation Analysis with X-Ray Fluorescence Spectrometry for the Determination of Rare-Earth Elements in Geological Samples

A combined use of comparator instrumental neutron activation analysis (INAA) including the internal standard method and energy-dispersive X-ray fluorescence spectrometry (EDXRF) for the determination of 14 rare-earth elements (REE) in geological samples at the level of their clarke concentrations is studied. A rapid analysis with the determination of light REE from La to Sm with Fe as an internal standard is performed using a portable RLP-21T energy-dispersive X-ray fluorescence spectrometer (Republic of Kazakhstan) with the excitation of K-series lines of characteristic radiation of a sample with a low-power (10 W) X-ray tube with a tungsten anode and the maximum voltage 70 kV. The neutron activation analysis of other REE was performed using a WWR-K nuclear research reactor. Based on the analysis of ten certified reference materials of geological samples, a possibility of using a complex of INAA and EDXRF methods for routine qualitative analyses of REE in the III accuracy class in accordance with the branch standard OST41-08-212-04 is shown. Examples of using a complex of INAA and EDXRF methods for solving geochemical problems and determining REE in out-of-balance ores of the Kundybay deposit are presented.

A feasibility investigation of speciation by Fe K-edge XANES using a laboratory X-ray absorption spectrometer

We demonstrate effective speciation of Fe in model compounds from analysis of the weak pre-edge features in Fe K-edge XANES spectra, with a commercially available laboratory X-ray spectrometer, using a spherically bent crystal analyser and a low power X-ray tube, in Rowland circle geometry. Direct comparison with XANES data acquired from a third generation synchrotron bending magnet beamline, using the same specimens, validated quantitative agreement in determination of the total integrated intensity and centroid position of the pre-edge feature, which are a probe of the electronic configuration and symmetry of the absorber atom, and hence oxidation state and co-ordination number. This work opens the door to rapid and routine speciation studies of Fe by laboratory XANES, even for materials with relatively dilute absorber concentration of only a few mol. %.

Determination of X-ray tubes radiation beam characteristics with semiconductor pixel detectors

X-ray tubes belong among the most important sources of ionizing radiation and are used in various applications and methods, i.e. investigation of materials, diagnostics in medicine, irradiation, etc. For such applications, the exact properties of X-ray sources or their X-ray beams need to be known, as well as when Monte Carlo simulations of experimental setups are considered with the aim of optimization or calibration of X-ray systems. These properties include X-ray spectra, beam profiles, divergence and homogeneity of beams. Properties of low power X-ray tubes with the maximum voltage up to 50 kV were investigated in this study. These devices included a small laboratory X-ray tube with collimated X-ray beam and a microfocus X-ray tube with polycapillary focusing optics. Beam shape features were reconstructed using a silicon pixel detector. The pixel detector was inserted into X-ray beams at different distances from X-ray sources. Beam 2D profiles were obtained and since the pixel detector worked in a single event detection mode, approximate energy of individual photons could be measured as well as their position. In this way, detailed information about the beam properties was obtained. • X-ray beam parameters are mapped by a pixel detector. • The beam shape and energy distribution of the emitted photons are assessed. • The size of the irradiated point and the quality of the collimators are determined.

Application of a Portable XRF Spectrometer for <i>In-Situ</i> and Nondestructive Investigation of Pigments in Two 15th Century Icons

A simple portable X-Ray Fluorescence (XRF) spectrometer was successfully used for in-situ and nondestructive identification of the painting materials in two 15th century icons from the Onufri Museum in Beart, Albania. The spectrometer is based on a low power X-ray tube, a thermoelectrically cooled Si PIN detector and the spectrum acquisition system. It was assembled and adjusted at our laboratory for the investigation of the icons. A small number of pigments were clearly identified by X-Ray Fluorescence (XRF) measurements in both icons. This includes Lead white for the white color, gold and yellow ochre for the yellow color, red lead, cinnabar and red ochre for the red color, as well as cooper based pigments for the green color. At the same time, the investigation raised some new questions that need further investigations by the use of additional analytical techniques. The results show that in both icons are used similar pigments, which are in accordance with the Byzantine icon painting tradition.

The clinical contribution of SPECT/CT with 99mTc-HMPAO-labeled leukocyte scintigraphy in hip and knee prosthetic infections.

White blood cell scanning with 99mTc-hexamethylpropylene amine oxime (HMPAO) has proven a sensitive and specific imaging method in the diagnosis of suspected prosthesis infection. The aim of this retrospective study was to evaluate the usefulness of SPECT/CT performed simultaneously using a hybrid imaging device of prosthesis infections. 99mTc-HMPAO scintigraphy was performed on 37 patients (11 men and 26 women; age range 38-84 years; mean age±SD, 65.7±5.6 years). Planar scans were acquired 2.4 and 24hour after injection. SPECT/CT was obtained 4 h after injection, using a dual-head hybrid gama camera coupled with a low-power x-ray tube. In all patients, scintigraphic results were matched with the results of surgery, cultures and clinical follow-up. Seventeen (45,9%) out of 37 patients had prosthesis infection and 20 (54,1%) out of 37 patients had non-infectious prosthesis pathologies with 99mTc-HMPAO scintigraphy and SPECT/CT. The 99mTc-HMPAO scintigraphy was true-positive for infection in 16 of 37 patients and true-negative in 20 of 37 patients. SPECT/CT provided an accurate anatomic localization of all positive foci. With regard to the final diagnosis, SPECT/CT added a significant clinical contribution in 22 of 37 patients (59,4%). Sensitivity, specificity, negative predictive value and positive predictive values were 100%,59.1%,100%,62.5% in planar images with 99mTc-HMPAO scintigraphy and 100%,90.1%,100%,88.2% in the planar+SPECT/CT imaging, respectively. Our results indicate that SPECT/CT performed using a hybrid device can improve imaging with 99mTc-HMPAO scintigraphy in patients with suspected osteomyelitis by providing accurate anatomic localization and precise definition of the extent of infection.

Development of a portable grazing exit X-ray fluorescence system using a gold anode X-ray tube

A portable grazing exit X-ray fluorescence system (GE-XRF) composed of a low power X-ray tube (gold anode), a SiPIN detector, quartz reflector and an XY table plus rotary stage for positioning the reflector in grazing exit condition was developed in this work. The accuracy of the system was checked using a certified bovine liver sample (SRM 1577b, NIST). The relative errors between measured and certified values ranged from 2 to 22%, except P (39%) and S (26%). The absolute detection limits obtained with the portable system were in the range of 4–300 ng (15 ≤ Z ≤ 30). The portable GE-XRF system developed does not favor the detection of light elements since absorption effects were more critical (sample-to-detector distance ∼ 35 mm). Besides that, it was operated under room temperature and atmospheric pressure, 20 °C and 1.0 atm, respectively. The quantitative results of a multielement reference sample were compared with the results of a GI-XRF system. Both techniques were compatible and presented good accuracy with reference values. The portable GE-XRF system developed in this work was efficient, showing that it is possible to produce a grazing exit X-ray fluorescence system using a low power X-ray tube, a Si-PIN detector and quartz reflector.

The clinical contribution of SPECT/CT with 99mTc-HMPAO-labeled leukocyte scintigraphy in hip and knee prosthetic infections

ObjectivesWhite blood cell scanning with 99mTc-hexamethylpropylene amine oxime(HMPAO) has proven a sensitive and specific imaging method in the diagnosis of suspected prosthesis infection. The aim of this retrospective study was to evaluate the usefulness of SPECT/CT performed simultaneously using a hybrid imaging device of prosthesis infections. Materials and methods99mTc-HMPAO scintigraphy was performed on 37 patients (11 men and 26 women; age range 38-84 years; mean age±SD, 65.7±5.6 years). Planar scans were acquired 2.,4. and 24. hour after injection. SPECT/CT was obtained 4 h after injection, using a dual-head hybrid gama camera coupled with a low-power x-ray tube. In all patients, scintigraphic results were matched with the results of surgery, cultures and clinical follow-up. ResultsSeventeen (45,9%) out of 37 patients had prosthesis infection and 20 (54,1%) out of 37 patients had non-infectious prosthesis pathologies with 99mTc-HMPAO scintigraphy and SPECT/CT. The 99mTc-HMPAO scintigraphy was true-positive for infection in 16 of 37 patients and true-negative in 20 of 37 patients. SPECT/CT provided an accurate anatomic localization of all positive foci. With regard to the final diagnosis, SPECT/CT added a significant clinical contribution in 22 of 37 patients(59,4%). Sensitivity, specificity, negative predictive value(NPD) and positive predictive values(PPD) were 100%,59.1%,100%,62.5% in planar images with 99mTc-HMPAO scintigraphy and 100%,90.1%,100%,88.2% in the planar+SPECT/CT imaging, respectively. ConclusionOur results indicate that SPECT/CT performed using a hybrid device can improve imaging with 99mTc-HMPAO scintigraphy in patients with suspected osteomyelitis by providing accurate anatomic localization and precise definition of the extent of infection.

Portable grazing exit X-ray fluorescence system using a low-power X-ray tube

In this work was developed a portable system of grazing exit X-ray fluorescence (geometric 90° - 0°) that can be applied in several areas science and technology. GE-XRF portable system is formed by a mini X-ray tube of low power (anode of Au) and a SiPIN detector. The reflectors used as sample support (sampler carrier) were quartz discs. The grazing exit angle was experimentally determined by measuring a cooper solution (10 μg.g-1). The accuracy of the system was checked using multielement reference solution as standard reference material. The relative errors between measured and certified values are in the range of 4 to 19%. The first results showed a background was drastically reduced at grazing exit angles, enabling trace elemental analysis. The system of GE-XRF proved to be quite stable and reproducible. This paper shows that it is possible to produce a portable system of grazing exit X-ray fluorescence compact, efficient, low-cost and easy-to-handle instrumentation using a low power X-ray tube and a SiPIN compact detector.

Analysis of milk trace elements with a home-made portable automated total reflection x-ray fluorescence system

This paper presents a portable, high-tech, low-cost, total reflection X-ray fluorescence system. This system features a compact arrangement consisting of a 50 W X-ray mini-tube with a Mo anode and a Si-PIN detector, quartz reflectors, lucite monochromator and micrometric tables driven by step motors controlled through the Arduino programming software. A certified sample of bovine liver SRM 1577b by NIST was used for the validation of the portable automated TXRF system. The TXRF system was used in the analysis of bovine milk samples collected in the industrialized region of the city of Bauru, São Paulo. In the analysis of the bovine milk samples the following elements were detected: P, S, K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, Zn, Se, Rb and Sr. The TXRF portable automated system proved to be efficient, showing that it is possible to produce X-ray fluorescence with a low-cost system using a low-power X-ray tube and a compact Si-PIN detector.

Temporary implementation and testing of a confocal SR-[formula omitted]XRF system for bone analysis at the X-ray Fluorescence beamline at Elettra

The confocal μXRF spectrometer of Atominstitut (ATI) was transported and set up at the X-ray Fluorescence beamline at Elettra - Sincrotrone Trieste. It was successfully adjusted to the incoming beam (9.2 keV). Test measurements on a free-standing Cu wire were performed to determine the size of the focused micro-beam (non-confocal mode, 56 × 35 μm2) and the size of the confocal volume (confocal mode, 41×24×34μm2) for the Cu–Kα emission. In order to test the setup’s capabilities, two areas on different human bone samples were measured in confocal scanning mode. For one of the samples the comparison with a previous μ XRF measurement, obtained with a low power X-ray tube in the lab, is presented.

Polarized XRF Spectrometer with a 40-mW X-Ray Tube

A three-dimensional polarized X-ray fluorescence (XRF) spectrometer was assembled with a low-power X-ray tube of 40 milliwatts, and a sample of stainless steel was measured with an acrylic polarizer. Based on the Schrodinger’s wave picture of Compton scattering, the dependence of the de Broglie wavelength and the scattering angle of a recoil electron on the incident X-ray energy were calculated. When the incident X-rays were scattered at an angle of 90°, the de Broglie of the recoil electron always went away at an angle of 45° with the incident X-rays and the de Broglie wavelength varied for any wavelength of the incident X-rays, i.e. we could select the scattering angle of the recoil electron to be 45°according to the incident X-ray energy and it could then be regarded as 45° Bragg diffraction that could produce highly polarized X-rays. The polarization measurement of scattered X-rays from an acrylic and lead plates substantiated that Compton scattered X-rays from the acrylic plate had higher degree of polarization than the elastically scattered X-rays from the lead plate. Highly polarized Compton scattered X-rays from the light-element polarizer led to the background reduction and the changes of the characteristic X-ray intensity in XRF spectra measured by our laboratory-made spectrometer. Key words: polarized X-ray fluorescence spectrometer, stainless steel, acrylic polarizer, Compton scattering, background. DOI: http://dx.doi.org/10.15826/analitika.2018.22.2.010

3D-printed compact XRF spectrometer

In order to address the applicability of 3D printers to assembling a spectrometer, we made a compact energy dispersive X-ray fluorescence (XRF) spectrometer with the use of a 3D printer and applied it to the measurements of trace elements in multicomponent alloys. The spectrometer was made of polycarbonate. The X-ray path was in the air, and the distance between equipment was designed so as to obtain enough input count rate even though a low-power X-ray source was employed. As an X-ray source and a detector, we used a low-power X-ray tube (4 watts) and a silicon drift detector. Although the effect of scattered X-rays from resin materials on measured spectra should be taken into account, the 3D-printed spectrometer was comparable with the conventional spectrometer in terms of the qualitative analysis. By using the simple 3D-printed spectrometer, trace elements included in stainless steels and an Ni-based alloy could be detected. 3D printers should therefore provide a simple and quick way of making an improvement on analytical instruments combined with the conventional way.

Nutrients' K X-ray peak energy shift measurements in fenugreek plants and different soils treated with fertilisers

Energy dispersive X-ray Fluorescence measurements on plants and soils from a pot experiment on fenugreek with different soils; garden/sewage/factory and a specific peak analysis have been used to study cumulative effect of soil conditions/nutrient fertilisers on potassium/calcium/iron nutrients. Experimental set up comprises low power X-ray tube as photon source and Si (PIN) detector with energy resolution 145eV at 5.959 keV Mn K X-rays as X-ray detector. K peak energies of potassium/calcium/iron in plants and soils were precisely evaluated with SOLVER program of precision up to 10−4 of channel width. Potassium/calcium fertilisations produced large variations in peak energies in garden and sewage soils as compared to that in factory soil. Iron contents beyond its permissible limits in sewage and factory soils were found to suppress the nutrients uptake of plants with potassium/calcium fertilisers as compare to that in garden soil plants.

Comparison of different excitation modes for the analysis of light elements with a TXRF vacuum chamber

The aim of this work was to compare different excitation modes for the analysis of light elements from carbon (Z = 6) upwards using a total reflection X-ray fluorescence analysis (TXRF) vacuum chamber which allows the attachment of different X-ray tubes and detectors. In the first set of experiments, two water-cooled high-power X-ray tubes with Cr (Z = 25) and Cu (Z = 29) anodes, respectively, were compared with an air-cooled low-power tube with Mo anode (Z = 42) and a thin Be window for the transmission of Mo-L lines. In the first two cases, monochromatic Kα radiation was used for excitation, while in the case of the Mo tube the multilayer acted as a cut-off reflector and part of the Mo bremsstrahlung continuum together with the Mo-L series were used for excitation. Multi-element standards containing elements ranging from Na (Z = 11) to Ti (Z = 22) were analyzed by a silicon drift detector (SDD) with a 300 nm ultrathin polymer window (UTW). Detection limits were calculated and compared for the three excitation modes. The second set of experiments was performed using an air-cooled low-power X-ray tube with Rh anode (Z = 45) in order to show that a conventional SDD with a 25 μm beryllium window can be used for the detection of elements from Na upwards. The use of compact air-cooled low-power X-ray tubes together with Peltier-cooled SDDs with UTW should lead to the development of highly sensitive tabletop vacuum TXRF spectrometers with a design optimized for the analysis of light elements. Detection limits as achieved by vacuum chambers using conventional water-cooled high-power tubes (e.g. Streli et al., 2004) are realistically achievable with the new approach.