Characteristic X-ray Research Articles

Monte Carlo simulations for dose enhancement in cancer treatment using bismuth oxide nanoparticles implanted in brain soft tissue.

The objective of this work is to study the dosimetric performances of bismuth oxide nanoparticles implanted in tumors in cancer radiotherapy. GEANT4 based Monte Carlo numerical simulations were performed to assess dose enhancement distributions in and around a 1 × 1 × 1 cm3 tumor implanted with different concentrations of bismuth oxide and irradiated with low energies 125I, 131Cs, and 103Pd radioactive sources. Dose contributions were considered from photoelectrons, Auger electrons, and characteristic X-rays. Our results show the dose enhancement increased with increasing both bismuth oxide concentration in the target and photon energy. A dose enhancement factor up to 18.55 was obtained for a concentration of 70mg/g of bismuth oxide in the tumor when irradiated with 131Cs source. This study showed that bismuth oxide nanoparticles are innovative agents that could be potentially applicable to in vivo cancer radiotherapy due to the fact that they induce a highly localized energy deposition within the tumor.

Energy Dispersive X-ray (EDX) microanalysis: A powerful tool in biomedical research and diagnosis.

The Energy Dispersive X-ray (EDX) microanalysis is a technique of elemental analysis associated to electron microscopy based on the generation of characteristic Xrays that reveals the presence of elements present in the specimens. The EDX microanalysis is used in different biomedical fields by many researchers and clinicians. Nevertheless, most of the scientific community is not fully aware of its possible applications. The spectrum of EDX microanalysis contains both semi-qualitative and semi-quantitative information. EDX technique is made useful in the study of drugs, such as in the study of drugs delivery in which the EDX is an important tool to detect nanoparticles (generally, used to improve the therapeutic performance of some chemotherapeutic agents). EDX is also used in the study of environmental pollution and in the characterization of mineral bioaccumulated in the tissues. In conclusion, the EDX can be considered as a useful tool in all works that require element determination, endogenous or exogenous, in the tissue, cell or any other sample.

Specific Features of Energy Dispersive X-Ray Electron Probe Microanalysis in the Low Vacuum Mode

Experimental data on the generation and detection of characteristic X-radiation of elements in electron probe microanalysis of dielectric samples in the low vacuum mode without the deposition of conducting coatings are discussed. The main advantage of the considered method of analysis is the stability of the intensity ratio between diagnostic analyte lines in the wide range of currents of the electron probe and gas phase pressure in the chamber in the range 60–130 Pa, sufficient for obtaining undistorted images of the surface of dielectrics. The stability of the intensity ratio ensures obtaining correct data of the quantitative analysis of nonconducting samples without the deposition of conducting coatings. The main features of low-vacuum microanalysis for the range of gas phase pressures used are discussed, which can create additional difficulties in the study. Among such features is a possibility of the manifestation of reflexes of gas-phase elements, significant underestimation of the relative emission intensity from lighter elements in the composition of the studied samples, loss of scanning locality in the analysis of small sites on the sample surface. An example of the correct quantitative elemental analysis of a dielectric surface without the deposition of an electroconductive coating for a number of aluminosilicates is presented.

Evaluation of the Use of New Matrix Corrections in Quantitative X-Ray Spectral Analysis

New possibilities for the quantitative description of matrix corrections for the absorption of characteristic X-ray radiation and backscattering of primary beam electrons are considered when solving the direct problem of quantitative X-ray spectral microanalysis. It is shown that the proposed procedure for calculating the given matrix corrections, together with the correctly chosen correction for the stopping power, makes it possible to calculate the quantitative content of elements for a large array of binary compositions from B to U.

Using Cu Kα1/Kα2 Splitting and a Powder XRD System To Discuss X-ray Generation

When single crystals are probed by powder X-ray diffraction (PXRD) systems, the peak widths are smaller and signal intensities are greater than those from powdered samples. Instead of the expected single peak, a doublet can be observed, and undergraduate students face a big challenge explaining its origin. This activity is suitable as an inquiry-based, upper-level undergraduate laboratory activity. Students typically engage in an extensive literature search and reading in order to understand observed diffraction data. With a little bit of guidance from the instructor, students can learn how X-rays are generated, and which X-rays are used in PXRD experiments. They can also learn about the electronic transitions in the target electrode leading to characteristic X-rays and learn about the role of spin–orbit coupling.

Simulation Model of Transmitted X-Rays in Polycapillary Optics for TES Microcalorimeter EDS System on Scanning Transmission Electron Microscope

We created a simple simulation model of transmitted X-rays in polycapillary optics for improved understanding of the transmission characteristics and to aid in the design of the geometrical parameters of the polycapillary optics. New polycapillary optics for a 64-pixel array transition-edge sensor (TES) microcalorimeter energy-dispersive spectrometer system that was installed in a scanning transmission electron microscope (STEM) were developed using the simulation model. The characteristic X-rays that are emitted from the STEM specimen were transmitted and focused on the pixel array TES microcalorimeter by the polycapillary optics. The experimental X-ray transmission characteristics of the manufactured polycapillary optics agreed with the simulated results.

Comparison of the sorption properties of natural and synthetic zeolites for the purification of aqueous solutions from cobalt: sorption of the cobalt from aqueous solutions in dynamic conditions and the quantitative determination of cobalt by the PIXE method

A methodology of quantitative determination of cobalt using the PIXE method has been developed. The method is based on the use of instant nuclear-physical analysis with the inducement of a target by a 1.6 MeV proton beam and the recording of the characteristic X-ray emission of the K-series of the cobalt. The linear relationship between the quantitative content of cobalt strontium and its X-ray emission K-shell was obtained. The sorption of cobalt by natural and synthetic zeolites from aqueous solutions in dynamic conditions has been studied. Sorption of cobalt with clinoptilolite after 80 cycles of sorption was about 60%. Sorption of cobalt after 80 cycles of sorption by zeolites NaX and NaA was 86 and 70%. Consideration was given to the influence of competing ions (sodium) on the sorption of cobalt by zeolites. The introduction of competing ions leads to a decrease in sorption of the cobalt by 25–60%, depending on the content of competing ions.

Development of SEM/STEM-WDX for highly sensitive detection of light elements

In this study, to detect the light element lithium (Li) and to detect low dosed Boron (B) in the local area at nm order, we developed an analytical electron microscope equipped with an improved serial (S)-type WDX (wavelength dispersive X-ray spectroscopy) system. In detail, to detect Li, we developed a high-conductivity multi-capillary X-ray (MCX) lens, and a diffractor with a lattice spacing (d) of 15 nm, and with a spacing variation (δ d) of 0.8 nm. Moreover, to detect low dosed light element B, we designed a high-conductivity MCX lens based on the soft X-ray reflectivity in the capillary and calculation. We developed a large-solid-angle MCX lens whose conductivity of the characteristic X-rays of B became 20 times higher than that of an MCX lens with a 30-mm focal length. Our developed analytical electron microscope was applied to a LiAl specimen and a low B-doped Si substrate specimen, and the performance of this analytical electron microscope was evaluated. As a results, this analytical electron microscope could detect the characteristic X-rays of Li with a minimum mass fraction (MMF) of 8.4 atomic % (at. %). The energy resolution was 1 eV at 55 eV. From the results of measuring the line profile of B for the unpatterned B-implantation area on a B-doped Si substrate specimen, the measured line profile data were in good agreement with secondary ion mass spectrometry data up to a depth of 100 nm with a B concentration of 0.05 at. %.

X-ray spectrometer with a low-cost SiC photodiode

A low-cost Commercial-Off-The-Shelf (COTS) 4H-SiC 0.06 mm2 UV p-n photodiode was coupled to a low-noise charge-sensitive preamplifier and used as photon counting X-ray spectrometer. The photodiode/spectrometer was investigated at X-ray energies from 4.95 keV to 21.17 keV: a Mo cathode X-ray tube was used to fluoresce eight high-purity metal foils to produce characteristic X-ray emission lines which were used to characterise the instrument. The energy resolution (full width at half maximum, FWHM) of the spectrometer was found to be 1.6 keV to 1.8 keV, across the energy range. The energy linearity of the detector/spectrometer (i.e. the detector’s charge output per photon as a function of incident photon energy across the 4.95 keV to 21.17 keV energy range), as well as the count rate linearity of the detector/spectrometer (i.e. number of detected photons as a function of photon fluence at a specific energy) were investigated. The energy linearity of the detector/spectrometer was linear with an error <± 0.7 %; the count rate linearity of the detector/spectrometer was linear with an error <± 2 %. The use of COTS SiC photodiodes as detectors for X-ray spectrometers is attractive for nanosatellite/CubeSat applications (including solar flare monitoring), and for cost sensitive industrial uses.

The effect of well-characterized, very low-dose x-ray radiation on fibroblasts.

The purpose of this study is to determine the effects of low-dose radiation on fibroblast cells irradiated by spectrally and dosimetrically well-characterized soft x-rays. To achieve this, a new cell culture x-ray irradiation system was designed. This system generates characteristic fluorescent x-rays to irradiate the cell culture with x-rays of well-defined energies and doses. 3T3 fibroblast cells were cultured in cups with Mylar® surfaces and were irradiated for one hour with characteristic iron (Fe) K x-ray radiation at a dose rate of approximately 550 μGy/hr. Cell proliferation, total protein analysis, flow cytometry, and cell staining were performed on fibroblast cells to determine the various effects caused by the radiation. Irradiated cells demonstrated increased proliferation and protein production compared to control samples. Flow cytometry revealed that a higher percentage of irradiated cells were in the G0/G1 phase of the cell cycle compared to control counterparts, which is consistent with other low-dose studies. Cell staining results suggest that irradiated cells maintained normal cell functions after radiation exposure, as there were no qualitative differences between the images of the control and irradiated samples. The result of this study suggest that low-dose soft x-ray radiation might cause an initial pause, followed by a significant increase, in proliferation. An initial “pause” in cell proliferation could be a protective mechanism of the cells to minimize DNA damage caused by radiation exposure. The new cell irradiation system developed here allows for unprecedented control over the properties of the x-rays given to the cell cultures. This will allow for further studies on various cell types with known spectral distribution and carefully measured doses of radiation, which may help to elucidate the mechanisms behind varied cell responses to low-dose x-rays reported in the literature.

Experimental study on Ti K shell ionization cross sections induced by 8-9.5 keV positrons

Due to lack of experimental data of the inner shell ionization cross sections induced by low-energy positron, advanced theoretical models developed in recent years cannot be correctly evaluated, and the application of slow positron beam technique is greatly limited. Here we present the method of obtaining reliable experiment data of atomic inner-shell ionization cross section by positron impact. In this work, the slow positron beam device is used to generate 8-9.5 keV positron beams impacting on a pure thick Ti target, and the silicon drift detector (SDD) is adopted to collect the X-ray spectra produced by positrons impacting on thick Ti target, and the incident positron numbers are obtained by applying an HPGe detector to on-line collect annihilation photons. Then the experimental characteristic X-ray yields of Ti K shell impacted by 8-9.5 keV positron could be acquired. Meantime, the simulated characteristic X-ray yields are acquired by the PENELOPE program simulating the experiments. In the comparison between the experimental yields and the simulated yields based on two sets of different inner shell ionization cross section database in the PENELOPE code, i.e. the optical data model (ODM) and the distorted-wave Born approximation model (DWBA), there is a large difference between the simulated data from the ODM theoretical model and the experimental values, while the simulated yields from the DWBA theoretical model are in good agreement with the experimental results. Accordingly, a correction factor is introduced to modify the DWBA theoretical model database which is used in the PENELOPE, and then the experimental process is re-simulated. When the simulated yields and the experimental yields are in the highest consistence, the reliable Ti K shell ionization cross sections impacted by 8-9.5 keV positron could be obtained. The biggest advantage of using this method to obtain atomic inner-shell ionization cross section impacted by positron is that the effects of the multiple scattering of incident positrons in the thick target, from the bremsstrahlung and annihilation photons, and other secondary particles on the experimental characteristic X-rays do not need calculating (the calculation method that has been developed previously cannot give the more correct result about the contribution of the multiple scattering of incident positrons, from the bremsstrahlung and annihilation photons, and other secondary particles to characteristic X-rays).

Particle size and concentration effects on low energy X-ray attenuation in nanostructure and microstructure materials

The effects of microsize and nanosize particles in composite structures as well as the incident radiation energy on X-ray attenuation is the focus of this study. To examine these effects, composite samples with different particle sizes of Al2O3 and with different thicknesses were prepared. Characteristic X-rays are applied as monochromatic X-rays and measurements were performed using an X-ray tube with a secondary excitation source instead of radioisotopes. In order to improve the efficiency and minimize the background effects a special detection system was designed and prepared. The linear attenuation coefficients of these samples are measured for X-ray photo energies of 6.40-28.49 keV. The results show that these low energy X-ray beams are more attenuated by nano-structured material compared to the micro-structured one.

Multiple ionization effect of Au induced by different ions

We report the experimental data of characteristic X-ray spectra produced by the impact of H&lt;sup&gt;+&lt;/sup&gt;, Ar&lt;sup&gt;8+&lt;/sup&gt;, Ar&lt;sup&gt;12+&lt;/sup&gt;, Kr&lt;sup&gt;13+&lt;/sup&gt; and Eu&lt;sup&gt;20+&lt;/sup&gt; ions with different kinetic energies on Au surface in the National Laboratory of Heavy Ion Research Facility in Lanzhou, China. The energy shifts of X-ray spectra are analyzed and the ratio of X-ray yield is calculated. The results show that H&lt;sup&gt;+&lt;/sup&gt; can excite the characteristic X-ray spectra of M&lt;sub&gt;ζ&lt;/sub&gt; and M&lt;sub&gt;α&lt;/sub&gt; of Au, while Ar&lt;sup&gt;8+&lt;/sup&gt;, Ar&lt;sup&gt;12+&lt;/sup&gt;, Kr&lt;sup&gt;13+&lt;/sup&gt; and Eu&lt;sup&gt;20+&lt;/sup&gt; can excite the characteristic X-ray spectra of M&lt;sub&gt;ζ&lt;/sub&gt;, M&lt;sub&gt;α&lt;/sub&gt;, M&lt;sub&gt;γ&lt;/sub&gt; and M&lt;sub&gt;δ&lt;/sub&gt; of Au, because the inner shells of target atom are multiply ionized by heavy ions impact, so that the relative intensity ratio of the X-rays changes when the heavy ions are incident. There are different energy shifts of Au M X-ray due to multiple ionization effect in collision. When the ion incident energy is lower, the degree of multiple ionization of the inner shells of the target atom is almost independent of the incident energy, when the ion energy is higher, the degree of multiple ionization increases with incident ion energy increasing. At the same time, the degree of multiple ionization also depends on the number of holes in the outer shell of the ion and its atomic number. That the ratio of X-ray yield increases with the increase of the atomic number of the incident ion further indicates that the degree of multiple ionization increases with atomic number of the incident ion increasing. The multiple ionization and electron configuration of the inner shells of the atom can be determined by the energy shift and spectra broadening. These measurements provide basic data for further studying the multiple ionization mechanism of the inner shells of the atom. But due to the limitation of the resolution of the detector, the spectral broadening data cannot be measured. It is necessary to use a higher-resolution detector to further study the multi-ionization effect of the inner shells of the atom.

Gamma-ray line diagnostics of supernova explosions - SN2014J and Cas A

Gamma-rays from nuclear de-excitation of newly procuced isotopes during supernovae (SNe) provide a unique window to the explosion mechanisms. SNe interiors are accessible only by γ-rays as they are energetic enough to penetrate the SN cloud. Both thermonuclear explosions (type Ia) and core-collapse SNe (CCSN, type II) are key producers of heavy elements in the Universe. In SNe Ia, a white dwarf (WD) is disrupted by ignition from inside or by triggering the explosive event from outside, producing major amounts of 56Ni. Type II SNe are powered by the gravitational collapse of a massive star, having burnt all its nuclear fuel.In this work, we present a diagnostic study of γ-ray lines from SN2014J and Cassiopeia A (Cas A). INTEGRAL observed SN2014J for several months and for the first time, it was possible to measure the characteristic lines from the 56Ni-decay chain in a SN Ia event. Surprisingly, 56Ni was seen only 20 days after the explosion which indicates that some 56Ni must be located outside the WD and not deeply embedded. We provide a 56Co γ-ray line light curve and estimate a visible 56Ni mass of 0.5 M⨀ from a comparison to 1D model light curves. Cas A observations have been revisited and we detect both, the characteristic hard X-ray line from the decay of 44Ti at 78 keV, and the subsequent γ-ray line from the decay of 44Sc at 1157 keV in one coherent data set. Expansion velocities in the range of 2000 − 5000 km s−1 and an initially synthesised 44Ti mass of 1.37 × 10−4 M⨀ are found.

Determination Of The Content Of Hf In Zirconium Alloys With Using A Wide Band X-Ray Emission Filter

The possibilities of a non-destructive method of determination of the content of hafnium in zirconium alloys are studied. The method is based on excitation of the characteristic X-ray emission of the atoms of the object of interest, including the L-series of atom of Hf, by external beam of protons accelerated up to 2 MeV. The excited emission is modified by a wide band X-ray emission filter, which is made from pyrolytic graphite plates and measured by a Si-PIN detector. Optimal conditions for measurement of analytical signal were determined after experimental studying. It was shown that under the selected experimental conditions and the measurement time of 10 minutes, the detection limit of Hf in the zirconium matrix is equal 20 ppm. The ways for improving of the metrological characteristics of the technique in the presence of interfering elements are proposed. The content of hafnium and uniformity of its distribution in the cladding of nuclear fuel rod made from the alloy Zr1% Nb was determined.

Hyperfine structure effect on circular polarization of X-ray radiation

During the last decades, the electron impact excitation (EIE) process has aroused much interest in various research areas. This process is crucial to the diagnoses of astrophysical and laboratory plasmas. Moreover, the EIE studies play an important role in understanding the quantum electrodynamic, many-electron, and hyperfine interaction effects in heavy atomic systems. As is well known, when ions are excited by collisions with a unidirectional beam of electrons, the magnetic sublevels of the excited state may be populated with nonstatistical probability. In the decay of the excited state, the emitted radiation is found to be anisotropic and polarized. From the analysis of the polarization, valuable information can be obtained. These properties have become indispensable tools for the diagnosis of plasma state and the analysis of complex spectrum formation mechanism. Up to now, however, most of studies have dealt with the linear polarization of X-ray radiation. Fewer publications have reported the circular polarization. Moreover, theoretical studies of the characteristic X-ray emission have just dealt with ions having zero nuclear spin, or have simply omitted all contributions that arise from such a spin. It is known that some kinds of ions each have a nuclear spin I 0. Owing to the hyperfine coupling, new decay channel will be open, namely, hyperfine-induced transition. It is thus important to analyze how the hyperfine interaction affects the polarization properties of X-ray radiation. In this study, we present a systematically theoretical analysis of the polarization and angular distribution of X-ray radiation during the hyperfine-induced transition. The calculations are performed by using a fully relativistic distorted-wave method. Special attention is paid to the studies of angular correlations and polarization properties of the 1s2p 3P2 Fi=3/2 1s2 1S Ff=1/2 decay for highly charged He-like Sc19+ and 205Tl79+ ions with nuclear spin I=1/2 following impact excitation by a completely longitudinally-polarized electron beam. Two effects, i.e.the BI and the mutipole mixing between the leading M2 decay and hyperfine-induced E1 decay, on the polarization of the emitted radiation are discussed. Our results show that both the BI and the E1-M2 interference effects may significantly affect the polarization and angular emission pattern of the transition line. For example, the BI and the E1-M2 mixing lead the circular polarization to increase by about 50% and 40% for 205Tl79+ ions, respectively. With the development of the X-ray detectors, the measurement on the polarization during the hyperfine-induced transition becomes feasible. We hope that the present results would be useful in resolving some disagreement between the theories and experiments relating to the polarization properties of the X-ray radiation.

Microprobe Mapping of Rare Earth Element Distribution in Round Top Yttrofluorite Deposit

The electron microprobe maps the spatial distribution of elements in a rock at a sub-mineral-grain scale to provide a basis for understanding mineralization processes and to determine optimal strategies for extraction of valuable target elements. Round Top Mountain (near the town of Sierra Blanca, Hudspeth County, west Texas, USA) is a peraluminous rhyolite laccolith that is homogeneously mineralized at over 500 ppm rare earths, more than 70% of which are yttrium and heavy rare earths (YHREEs). The massive deposit is exposed at the surface as a mountain some 2 km in diameter and 375 m in height. Round Top Mountain also contains Li, Be, U, Th, Nb, Ta, Ga, Rb, Cs, Sn, and F. The valuable YHREEs are hosted in yttrofluorite, which is soluble in dilute sulfuric acid. Texas Mineral Resources Corporation proposes to surface mine, crush, and heap leach the deposit. The distribution of YHREEs, and that of other trace elements, is remarkably homogeneous at outcrop drill hole scale. Here we document that YHREE mineralization appears pervasive through the rhyolite at a millimeter scale. Back scattered electron (BSE) and characteristic X-ray maps reveal the fine grain size and apparently random and dispersed spatial distribution of the yttrofluorite that hosts Round Top’s valuable YHREEs. The yttrofluorite grains do not appear to cluster at special mineralized locations, e.g., in pores or along cracks in the rhyolite. The same is apparently true of such other potentially valuable minerals as cassiterite and uranium species. These findings confirm that the distribution of YHREEs in Round Top Mountain rhyolite is homogeneous through different orders of magnitude of scale, i.e., from outcrop (as seen in the companion work in this volume) to sub-thin section. The material thus is ideal for a heap leach operation where homogeneous feedstock is crucial to consistent and economic operation. The findings also confirm and explain why mechanical separation would prove very difficult and expensive due to the astronomical number of yttrofluorite grains in even a golf-ball-size piece of Round Top rhyolite.

Fabrication of carbon nanospheres using natural resources and their voltametric studies of dopamine

In this study, mesoporous carbon nanospheres with particle size of ∼ 50 nm and primary mesopores of ∼ 2.0 nm in diameter were prepared and used in the detection of dopamine. The Paper Mulberry bark was employed as the carbon precursor under pyrolysis technique at annealing temperature of 500 °C without adding any catalyst. The formation of carbon nanospheres with high graphitic content is evident from their characteristic X-ray diffraction (XRD). The surface morphology of mesoporous carbon nanospheres were observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) and the expected elemental composition by energy dispersive X-ray (EDX) analysis. The electrochemical response of the carbon nanospheres modified carbon paste electrode was found to be 5.0 ×10−5 M for dopamine at pH 7.2 PBS solution with a scan rate of 50 mVs-1. Moreover, the modified carbon paste electrode using carbon nanospheres shows an excellent voltammetric response and exhibit excellent electrochemical sensor for dopamine having high sensitivity when compared to the bare carbon paste electrode.

Сравнение методик на основе радиометрического анализа и характеристического рентгеновского излучения для определения стронция с помощью цеолитов

Сравнение методик на основе радиометрического анализа и характеристического рентгеновского излучения для определения стронция с помощью цеолитов

Element composition of additive products from electroerozive cobalt-chromum powders

The wide use of the EED method for processing metal waste into powders for the purpose of their reuse and application in additive technologies is hampered by the lack in the scientific and technical literature of full-fledged information on the effect of the initial composition, regimes and media on the properties of powders and technologies of practical application. Therefore, in order to develop technologies for the reuse of electroerosive powders and to evaluate the effectiveness of their use, complex theoretical and experimental studies are required. The aim of the work was to conduct X-ray spectral microanalysis of additive products from electroerosive cobalt-chrome powders. For the implementation of the planned studies, wastes of the cobaltochrome alloy of the brand KHMS “CELLIT” were chosen. As a working fluid, butyl alcohol (butanol-1) was used. For the production of cobalt-chrome powders, a unit for EED of conductive materials was used. Dispersion parameters: voltage 100 V, capacity 48 μF, repetition rate 120 Hz. The microstructure of the samples (on the surface) was studied by scanning electron microscopy. The surface of the samples was ground and polished. With the help of an energy-dispersive X-ray analyzer from EDAX, built into the scanning electron microscope QUANTA 200 3D, spectra of characteristic X-ray radiation were obtained at various points on the surface of the sample and along the cross-section. Based on the results of X-ray spectral analysis of additive products from electroerosive cobalt-chrome powders, it has been established experimentally that the main elements in them are Co, Mo, and Cr.