Proton-induced X-ray Analysis Research Articles

Бага энергийн хурдасгагчийг ашиглах зарим боломж

The possibilities of applications of the 200 keV Cockroft - Walton accelerator for D-D neutron measurements, ion implantation. Rutherford backscattering analysis, ion channeling and proton induced X-ray analysis are discussed.

Proton-Induced X-Ray Analysis of Soil and Water Samples From Chromite Mine Environment for Determination of Toxic Metal Ion Contamination

Soil and water samples collected from chromite mine environment were analyzed by proton-induced X-ray emission (PIXE) for determination of toxic metal ion concentrations. The soil samples were collected from an active mine quarry, overburden dumps, fallow, and cultivated lands adjacent to the mines. The water samples were collected from the mine quarry, natural stream, and ground water in the mining area. Different elements such as Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Pb, and Zr were detected in both soil and water samples. The concentrations of Fe, Cr, and Mn in the samples were relatively high as compared to other elements. The concentrations of Cr in the soil and water samples collected from the chromite mine environment were found in the ranges of 792 to 33,705 mg/kg and 4 to 308 μg/L, respectively. The concentration of all elements in the soil samples collected from the active mining sites, as well as from fallow and cultivated lands, exceeded their permissible limits. However, the concentration of Cr in the water samples of the mine quarry treated with ferrous alums, the Damsala Nala river upstream, and ground water outside the mining area was found within the permissible range.

The 17th Dynasty gold necklace from Qurneh, Egypt

In 1908, the archaeologist Flinders Petrie discovered a rich intact burial of an adult and child at Qurneh, near Luxor. Stylistically, the burial has been dated to the late 17th Dynasty, in the 16th century BC. The complete burial group came to Edinburgh in 1909. A recent examination of the rings of the necklace found with the adult burial is presented as part of a wider study of the mummy collections of the National Museums Scotland (NMS). The necklace shows sophisticated workmanship, with 1,699 rings threaded onto four strands, the rings having uniform diameter and thickness, and very few of them showing any visible joints. The necklace rings have been examined by Optical Microscopy, X-radiography, Scanning Electron Microscopy with Energy Dispersive X-ray analysis (SEM-EDS), air-path X-ray Fluorescence (XRF), and proton induced X-ray analysis (micro-PIXE). We summarise these findings and propose the method of manufacture. We also describe an experimental attempt to make joint-less rings in order to compare them with the originals.

Étude technologique de pièces d’orfèvrerie datées du Moyen Empire au Nouvel Empire en Égypte

This paper presents a technological study of items of Egyptian jewellery from the collections of the National Museums Scotland: a pendant from the 19th century BC; objects from the 16th century BC royal burial unearthed at Qurneh; two gold finger-rings dated to the 14th century BC; and a group of pendants from the 13th century BC. The objects were examined using optical microscopy, X-radiography and Scanning Electron Microscopy (SEM). In addition, the elementary compositions of alloys and solder joints were investigated using air-path X-ray fluorescence (XRF), proton-induced X-ray analysis (micro-PIXE), and energy-dispersive X-ray analysis (SEM-EDS). This preliminary study provides information about the evolution of alloy composition and the use of alluvial gold, and illustrates the Ancient Egyptian goldsmiths’ skills in working with wires, granulation and joining techniques.

Dopant activation in homoepitaxial MgZnO:P thin films

Homoepitaxial MgxZn1−xO:P thin films with variable magnesium content (x<0.05) have been grown by pulsed-laser deposition. The film compositions have been determined by proton induced x-ray analysis. The phosphorous and magnesium content of the films decreases with increasing oxygen partial pressure during growth. High-resolution x-ray diffraction shows a pseudomorphic growth of the thin films with a nominal MgO content of 2 wt %. Hall-effect measurements show electron mobilities of the as-grown films as high as 820 cm2/V s at 55 K, which compares to the value observed for ZnO:P homoepitaxial thin films. Upon annealing, the free carrier concentration was reduced by several orders of magnitude, depending on the oxygen partial pressure used during growth of the MgZnO:P films, while it remained nearly unchanged in ZnO:P samples. The role of the MgO concentration in the films in acceptor defect formation is discussed.

Elemental analysis of neurofibrillary tangles in Alzheimer's disease using proton-induced X-ray analysis.

We have investigated the elemental content of hippocampal slices from normal human brain and from brains of Alzheimer's disease patients by X-ray fluorescence using both electron and proton beam microprobes. The sections have been stained with a dye--toluidine blue--which contains sulphur so that the X-ray fluorescence map can be correlated with known intracellular sites as seen under the light microscope. The results show that associated with neurofibrillary tangles and Hirano bodies (the distinctive internal visual features of cells from Alzheimer's disease patients) there is increased calcium. We cannot confirm that there are peculiarities in the distribution of aluminium in cells.

Proton induced X-ray analysis of Nd:YAG

Proton induced X-ray emission (PIXE) is famously effective for revealing trace elements in biological tissue in which the majority elements (H, C, N and O) have low Z. When the majority elements in a compound have high atomic numbers, the yield of K and L X-rays following proton bombardment often mask those of lighter trace elements, or dominate the counting rate to such an extent that the time required to detect a small signal with statistical significance becomes prohibitively long. We have confronted these difficulties with a PIXE analysis of YAG crystals and ceramics with neodymium doping up to nine atomic percent. The K X-rays of aluminum (1.74keV) and yttrium (15keV) dominate the PIXE spectrum. The L X-rays from neodymium group near 5keV provide determination of the neodymium content of Nd:YAG to 1:1000. Clear signals of traces of zinc, nickel and copper were recovered from the spectra of some of the samples by persistent experiments at low counting rates that avoided pile up of the signals from the majority elements. An appropriate polyethylene filter was used to prevent scattered protons from striking the detector and its supporting structure. Double proton beam collimation prevented spurious PIXE from the chamber walls, beam stop and the primary collimator. No material was near the sample except a polyethylene film strip that supported the sample.

The application of photon, electron and proton induced X-ray analysis for the identification and characterisation of medieval silver coins

Photons, electrons and protons beams applied to the scientific investigation of archaeological materials provide complementary information for characterising the state of preservation and the provenance of the objects. Investigations were carried out on medieval silver coins of the “Friesacher Pfennig” and the “Tiroler Kreuzer” from the Kunsthistorisches Museum Vienna and the Oesterreichische Nationalbank. Techniques employed were EDXRF, SEM/EDX and PIXE. By determining the trace elements of the alloys it was possible to assign coins to their mint. The results outline advantages and disadvantages of EDXRF, SEM/EDX and PIXE when applied to corroded objects.

Incorporation of chlorine in polymer films due to MeV proton bombardment

Adsorption of Cl on polymer films and enhanced uptake due to bombardment with 1.1 MeV protons has been studied after an occasional contamination of an analysis chamber for external proton-induced X-ray analysis (PIXE). The contamination occurred as a result of cleaning the Be window of the Si(Li) detector with CCl4. Changes in areal density of Cl on and in polymer films were measured by PIXE, at Cl partial pressures between about 10−4 and 10−5 mbar in the He backfilling gas. The partial pressure of gases with atomic numbers Z⩾10 (Ne) was measured by gas phase PIXE. After a few hours of exposure to CCl4 at 5×10−4 mbar, areal densities of 1 μg/cm2 of Cl were observed on cellulose acetate, cellulose nitrate and polycarbonate films. Detailed studies at about 2×10−5 mbar showed that uptake of Cl in proton bombarded cellulose acetate is enhanced by several orders of magnitude compared to the non-bombarded film. After exposure to low bombardment fluences, ∼1014 p/cm2, approximately two Cl atoms per incident proton were incorporated in 2 min. This rate increased by a factor of 3.3 after bombardment to 2×1015 p/cm2. Long-term exposure (45 min) in He after low-fluence bombardment showed that the rate of uptake decreases with increasing time. The results suggest that proton-induced damage produces active sites in the polymer film that can bond Cl atoms or Cl containing molecules.

Optimisation of peak-to-background ratios in proton-induced X-ray analysis of material deposited on thin and thick backings

Background generation in proton-induced X-ray emission spectrometry (PIXE) has been studied systematically using polymer films (4–34 μm thick) and thick graphite as targets. The measurements were carried out at proton energies between 1.1 and 2.6 MeV, in vacuum and with helium backfilling. The background due to bremsstrahlung generated by knock-on electrons dominates the spectra at X-ray energies up to 6–9 keV. This background was found to exhibit a power-law dependence on beam energy, with a power as high as 6.8±0.2. By contrast, characteristic X-ray signals increase much less rapidly with proton energy, i.e., with equivalent powers ranging from 1 to 3. Hence the peak-to-background ratios increase strongly with decreasing proton energy. Routine analysis at energies around 1 MeV is recommended, at least if the beam currents are adequate to achieve sufficient counting statistics within a reasonable time. Using solid state detectors, the background signals observed at X-ray energies above about 8 keV are sensitive to the choice of the X-ray filter. Pierced filters can give rise to enhanced background levels generated by backscattered protons. With coherent filters, on the other hand, detection of light elements becomes impossible. Low proton energies in combination with pierced filters are advocated.

Identification and characterization of a Streptococcus pyogenes ABC transporter with multiple specificity for metal cations.

Metal ions are crucial trace elements for bacteria infecting the human host. The LraI (lipoprotein receptor-associated antigen I) transporter in Streptococcus spp. belongs to the superfamily of ABC transporters. The transporter consists of a lipoprotein, an ATP-binding protein and a hydrophobic integral membrane protein. Here, we describe a new member of the LraI family in the important human pathogen Streptococcus pyogenes. The system was identified in silico by analysis of the S. pyogenes Genome Sequencing Project. The S. pyogenes operon exhibits an atypical organization compared with equivalents in other Streptococcus spp. The presence and atypical organization of the operon was verified in a number of S. pyogenes strains of different serotypes. Transcriptional analysis of the LraI operon demonstrates a polycistronic transcription attenuated by a stable stem-loop structure, which allows the lipoprotein to be expressed in larger quantities than the other two components. The localization of the native lipoprotein at the bacterial surface was shown by proteolytic digestion of S. pyogenes bacteria and NH2-terminal sequencing of a released lipoprotein fragment. Recombinant lipoprotein was expressed as a GST fusion protein, and studies of molecular interactions with metal radioisotopes demonstrated that the protein has affinity for Zn(II), Fe(III) and Cu(II). Zn(II) and Cu(II) were found to compete for the same binding site, whereas Fe(III) uses a second site. Also, proton-induced X-ray analysis of lipoprotein samples identified iron, copper and zinc. Finally, a mutant strain lacking a functional mtsABC operon was generated and showed reduced uptake of 55Fe and 65Zn compared with the wild-type strain. The operon encoding this novel ABC transporter with multiple specificity for metal cations is designated mtsABC, for metal transporter of Streptococcus.

Identification of an unusual source of background signals in energy dispersive PIXE analysis — A detective story

A previously unexplained source of background signals observed in energy dispersive proton induced X-ray analysis (PIXE) has been explored by systematically measuring spectra of thin polypropylene backing foils at proton energies between 0.8 and 2.9 MeV. Using X-ray filters of various thicknesses and different geometry it was found that protons with energies as low as 0.6 MeV can enter into the active zone of the employed Si(Li) detector, even though the beryllium entrance window of the detector had a nominal thickness of 25 μm, thick enough to stop 1.3 MeV protons. Measuring energy spectra with reduced gain it could be shown that the beryllium window is rather non-uniform in thickness (or highly porous), the smallest values at certain points amounting to only about one third of the nominal thickness. These findings appear to hold true for other commercial Si(Li) detectors as well.

Nondestructive Elemental Analysis in Three Dimensions

A new nuclear microprobe instrument for three-dimensional elemental analysis of solids has been developed. The instrument combines two techniques for three-dimensional analysis: Rutherford backscattering and elastic recoil detection. In the first case light ions impinge on heavy sample atoms and are scattered back to the detector. In the latter case heavy ions knock out light atoms that are then detected. The instrument is also equipped to perform proton induced x-ray analysis for trace element determinations.

Intrinsic and effective sensitivities of analysis by X-ray fluorescence induced by protons, electrons, and photons

The intrinsic analytic sensitivity to trace elements of X-ray fluorescence induced by protons, electrons and photons, defined in terms of an irreducible background and a “perfect” detector, is much lower than that observed with present source strengths. As ion flux densities increase and spatial resolutions improved, the sensitivity is likely to be limited by sample heating and by the Frenkel pair radiation damage. At a proton fluence density of ∼10 20/cm 2, the displacement damage is complete; the sample is amorphous. If the fluence density is limited to this value, then, at 1 μm resolution, the ultimate sensitivity of proton induced X-ray analysis will be about one atom of the trace element per million atoms of the host.

The comparison of pixe and other methods in the analysis of biliary and urinary calculi

Proton induced X-ray analysis (PIXE) and scanning electron microscopy together with X-ray microanalysis have been used to examine biliary and urinary calculi. Particular attention has been given to the centre or nuclear region of the stones and several interesting and unexpected trace elements have been found in these regions. Detailed analyses have indicated distinct mechanisms of formation and growth.

A comparison between proton and photon excitation for X-ray analysis of plasma

2–3 MeV protons from a Van de Graaff generator were used to irradiate thick dry plasma samples in air. Detection limits substantially below the part per million mass concentration level were obtained for Fe, Zn and Sr. A method of analysing similar plasma samples using Ag X-ray from a 6 mC 109Cd radioiosotope source was developed. Criteria for comparing the two modes of excitation were established and a comprehensive comparison performed. The results obtained showed that proton induced X-ray analysis generally yielded superior sensitivities and detection limits for the elements investigated. The X-ray excitation method described here could be significantly improved and has the potential of achieving analytical results comparable with the proton excitation method.

Proton-induced x-ray analysis of monazite inclusions possessing pleochroic halos

X-ray spectra were observed from proton-induced excitation of monazite inclusions possessing both normal and giant pleochroic halos at ${E}_{p}=4.7 \mathrm{and} 5.7$ MeV. A complete elemental analysis of these spectra is reported for elements with $Z\ensuremath{\ge}26$. Weak photopeaks are observed from monazite inclusions possessing giant halos which are absent from inclusions with normal halos, although limitations in spatial resolution of the proton beam prevented accumulation of statistically definitive data. Because of energy, width, and intensity anomalies, some of these weak photopeaks are not readily interpretable as x rays or $\ensuremath{\gamma}$ rays of known elements. Proposed evidence for superheavy elements is carefully examined.NUCLEAR STRUCTURE, Elemental analysis, measured proton-induced x-ray spectra from monazite inclusions with pleochroic halos, ${E}_{p}=4.7 \mathrm{and} 5.7$ MeV.

The morphology of thick evaporated aluminium films and their purity as determined by proton-induced x-ray analysis

Aluminium films of thickness 7–65 μm were vacuum deposited using a 99.999% purity aluminium wire, a composite ceramic boat and a continuous wire feed source. The morphology and the purity of the films were studied at various deposition and wire feed rates. X-ray diffraction and scanning electron microscopy investigations showed that the films grew mostly in a one-dimensional {311} texture orientation and that the surface grain size first increased with deposition rates up to about 100 kÅ min -1 and then decreased. The purity of the aluminium films was studied mainly by proton-induced X-ray analysis with a 4 MeV Van de Graaff accelerator. A total impurity content of about 10 atomic ppm, composed mainly of iron, copper and zinc and in some cases lead, was observed at low and medium wire feed rates. In addition, of the light elements, magnesium was qualitatively detected.

A study on proton induced X-ray analysis and its application to environmental samples

Proton induced X-ray analysis has been studied by the 5 MV Van de Graaff of Tohoku University emphasizing on backing materials and angular dependence of background. The method has further been applied to analyses of some environmental samples. From experimental results, it was found that 4 μm Mylar foil among Formvar, Mylar and carbon gives sufficiently low background spectrum, high sensitivity and good mechanical strength. The detection limit is much improved at the backward direction with respect to the incident beam comparing with that at 90° which has usually been adopted. The analytical results on soil and aerosol samples were compared with those by the Atomic Absorption Spectrophotometrical method (AAS). Vanadium can easily be analysed by this method, but not by the AAS method. Milk and human milk were also analysed.

Proton induced X-ray analysis of drinking water samples

Abstract The procedure for using proton induced X-ray emission for qualitative and quantitative multi-elemental analysis of drinking water in cities of Iran is discussed in this article.