A method for quick estimation of129I by low energy photon spectrometry

Methods have been developed for the routine analysis of¹²⁹I in effluents of fuel reprocessing plants using 29.4 keV xenon X-rays. Direct counting methods have been standardized in liquid medium as well as in ion-exchange resin medium. A low energy photon spectrometry Ge detector system and a well-type NaI/Tl/ detector are used for direct counting. Attenuation of xenon X-rays in liquid medium as well as in ion-exchange resin medium have been studied. Sample size is optimized by studying the self attenuation of xenon X-rays in the sample. Activity as low as 1 Bq could be detected with an accuracy of 11% and 30% using LEPS and NaI/Tl/counting systems, respectively.     

Effects of tritiated water on the DNA of plasmid pBR 322

In an attempt to shed light on the influence of tritiated water for DNA we have investigated the damage with a simple plasmid DNA, pBR 322. The survival of covalently closed circular (CCC DNA) form was directly followed by agarose of gel electrophoresis. It was found that the survival percentage of DNA in tritiated water was observed almost the same as the irradiation of X-rays at the same absorbed doses. For the irradiation of gamma-rays, on the other hand, the decay rate was larger than those of both tritiated water and X-rays. The yields percentage of the broken pieces of DNA in tritiated water, X-rays and gamma-rays were found to be 43, 38 and 33% at 10(4) rad of the absorbed dose. It may be considered that the degree of danger in tritiated water is quite larger than of gamma-rays. It was also found that the dose rate effect was not observed in the case of tritiated water, X-rays and gamma-rays irradiation.     

Method for improving the accuracy of continuous X-ray fluorescence analysis of iron ore mixtures

The dependence of the intensity of X-ray fluorescence on the distance between the spectrometer and the test sample is studied. Changes in the intensity of primary X-radiation, absorption of X-rays by the air, and surface area of the analyzed material are calculated. An efficient method is proposed for improving the accuracy of continuous X-ray fluorescence analysis of iron ore mixtures on the conveyor belt through the exclusion of incorrect results by the dead time of the detection unit. The proposed method is universal and can be used for various loose materials.     

An X-ray fluorescence spectrometer with a pyroelectric X-ray generator and a secondary target for the determination of Cr in steel

An X-ray fluorescence (XRF) setup with a pyroelectric X-ray generator and a secondary target for the determination of Cr in steel is presented. The pyroelectric X-ray generator, which can be driven by a dry battery, is a low power X-ray source and emits X-rays over a large solid angle. X-rays emitted by this generator can be effectively put to use by a disk-shaped secondary target. An appropriate arrangement of (i) X-ray generator, (ii) sample support, (iii) secondary target, and (iv) detector enables secondary X-rays to irradiate the sample from a short distance. The secondary X-rays are emitted from a wide-area secondary target. The present arrangement also enables the sample to be placed near the detector. The short distance from the sample to both the secondary target and the detector enhances signal intensity. An absolute amount of 1.3 μg Cr can be detected by the present setup. A minimum detection limit of 0.09 wt.% Cr in steel by 1000-s measurement has been achieved.     

Structure of Redispersible SnO2 Nanoparticles

Suspensions of undoped SnO₂ nanoparticles and containing Eu³⁺ ions were prepared by a sol-gel procedure. Using the classical synthesis method (precipitation), the particles tend to grow by a coarsening process in order to minimize the surface free energy. This effect can strongly be reduced by the addition of an amide and surfactant during the synthesis, which decreases the surface free energy of the colloidal particles. These additives promote the formation of powders composed of very small primary particles formed by a crystallite of 10 Å, and exhibit good redispersion properties. The local and long order structures of the redispersible powder were studied by X-rays absorption spectroscopy at Sn L_I edge and X-rays diffraction, respectively. The structure of the colloidal aggregates in suspension was investigated by small angle X-rays scattering (SAXS). SAXS results indicate the sol are composed by a polidisperse system of hard spheres resulting of agglomeration of the primary particles and their size increasing by agglomeration for progressively higher Eu³⁺ content.     

Localized thin-film analysis by grazing-exit electron probe microanalysis

We have studied the application of grazing-exit electron probe microanalysis (GE-EPMA) for surface and thin-film analysis. In this method, characteristic X-rays are measured at small take-off angles of less than 1°. Under grazing-exit conditions, the X-rays emitted from deep inside the sample are not detected because they are stopped by a slit mounted in front of the energy-dispersive X-ray detector. Hereby, it becomes possible to perform localized surface analysis with GE-EPMA. We applied this method to thin-film analysis of a small surface area. The exit-angle dependence of the characteristic X-ray intensities was measured for thin films of Cr and Ti. Thickness and density of thin films were determined by fitting the experimental plots with theoretically calculated curves. Differences were found in the densities of two Cr thin films deposited by magnetron sputtering and vacuum evaporation. The advantage of GE-EPMA is that non-destructive thin-film analysis of small surface areas can be incorporated in simple scanning electron microscope (SEM) analysis.     

Determination of uranium isotopic composition in aqueous solutions by combined gamma-spectrometry and X-ray fluorescence

The possibility of use of combined gamma spectrometry and X-ray fluorescence for uranium isotopic analysis in dilute aqueous solutions has been studied. Uranium K X-rays were excited by gamma-rays of⁵⁷Co radionuclide source and were measured together with 185.7 keV gamma-rays of²³⁵U using a planar pure Ge detector. Uranium K_α1 fluorescent X-rays were used for the evaluation. The method was proved to be independent of total uranium concentration in the region of 8–20 mg U/ml. The procedure making use of measurement of 7 ml samples and allowing to achieve an accuracy better then 1% in the region of 0.4–4.5 at. % of²³⁵U is proposed.     

Über die berücksichtigung von streuanteilen bei der messung von röntgenfluoreszenzintensitäten

A theoretical treatment of the contributions of scattered X-rays to the intensity of fluorescent radiation is given. These contributions are caused as well by scattering of white X-rays as by scattering of characteristic X-rays. The amount is calculated for different elements and thin films. From these considerations follows an increase of the X-ray fluorescence intensity of approximately 1 per cent for bulk materials and up to 30 per cent for thin films.

Since for a quantitative analysis reference samples are needed, values of the concentration or mass per unit area are found, which are higher or lower as compared with the true value, depending on the amount of fluorescent X-rays caused by scattering.     

Enhancement of electron-induced X-ray intensity for single particles under grazing-exit conditions

Grazing-exit electron probe microanalysis (GE-EPMA) was performed for single Al₂O₃ and atmospheric particles, deposited on a flat Si substrate coated by gold, by using an aperture (1 mm in diameter) in front of an energy-dispersive X-ray detector. Silicon Kα X-rays from the Si substrate were strongly observed at an exit angle of ∼45°. However, they disappeared at grazing-exit angles about 0° and only the X-rays from particles were detected. Furthermore, Al Kα and O Kα intensities from single Al₂O₃ particle were enhanced approximately three- and sixfold at the grazing-exit angles (∼1°), respectively, in comparison with those at large angle (∼7°). The background intensities at the energy of Al Kα and O Kα almost monotonously decreased with decreasing exit angle. As a result, the intensity ratios of Al Kα and O Kα X-rays to the background intensities were enhanced five- and sixfold, respectively. This enhancement is considered to be caused by the interference effect of both directly detected X-rays and reflected X-rays on the flat substrate. The similar results are also obtained for Al Kα, Si Kα, K Kα and Ca Kα emitted from single atmospheric particle. The significance of the matrix effect in the particle is also pointed out.     

On the photoexcitation of the 2s→2p transition in light muonic atoms

It is known that the energy of the 2s→2p transition of light μ-atoms can be precisely measured by laser spectroscopy. Such measurements provide a good test of quantum electrodynamics predictions. Here we consider how the hyperfine muon-nucleus interaction effects on the photoexcitation of this transition and on the subsequent X-rays emission. Besides the obvious change of the transition energy the hyperfine interaction mixes the 2p 1/2 and 2p 3/2 orbits. This mixing is rather effective in μ-atoms of¹H,⁷Li,⁹Be,¹⁰B and¹¹B. Its taking into account changes the photoexcitation cross-section of electric dipole transitions between the hyperfine components of the 2s and 2p orbits and an angular X-rays distribution as well. These changes prove to be considerable for some transitions. For example, in μ²H and μ⁷Li the cross-section is decreased by factors of two and four respectively. In μ⁹Be it is increased by a factor of two. Moreover, in μ¹H the angular X-rays distribution becomes more anisotropic. Besides the above subject one more question is discussed here. The fact is that the laser experiments can give an information on the residual muon spin polarization at the 2s orbit and on the degree of alignment of the angular μ-atom momentum in this state. The polarization can be determined by measuring an angular correlation between the X-rays emission direction and the momentum of a hard μ-decay electron. The alignment degree can be found by measuring an anisotropy of the angular X-rays distribution.     

Characteristic x-rays from (n, γ) products and their utilization in activation analysis

The possibility of using characteristic X-rays from radioactive elements in activation analysis was investigated during this work with particular emphasis on (n, γ) products. At least 27 of 56 elements investigated during this work were found to yield themselves to activation analysis employing characteristic X-rays from electron capture or internal conversion processes during isomeric transition. In presenting the results, a survey made of several elements and the limits of detection of 21 elements have been reported. Specific applications of this method were studied for the analysis of copper in a variety of samples (ores, minerals, steels, spent lubricants and human blood). The results of this investigation show that the use of characteristic X-rays in activation analysis has several advantages because the energies of these radiations are closely related to the periodicity of the elements themselves. Presented at the First IMR International Symposium, Trace Characterization—Chemical and Physical, National Bureau of Standards, USA (October, 1966).     

Development of a new approach to trace element analysis using neutron activation followed by high resolution X-ray spectrometry

The interference of beta particles with the measurement of X-rays with Si(Li) detectors, is eliminated by the use of magnetic fields. The latter defect the beta particles preventing them to reach the detector, but have no effect on the X-rays to be measured. Thus the high background which obscures the X-ray peaks of low and medium Z elements is reduced to a minimum and the resolution of the detector restored to ist normal value. As a result the X-ray peaks may be accurately integrated. Several experiments which show the usefulness of the method are discussed. This work was supported by the U.S.-Israel Binational Science Foundation.     

X-ray imaging during plasma-source ion implantation

Plasma source ion implantation (PSII) is a technique for modifying stafaces that places the object to he modified directly into a plasma and then negatively pulse biases the object so as to implant positive ions. If the voltage is high enough, X-rays can he generated by electrons that are also accelerated by the pulse. This work describes techniques for imaging and characterizing the X-rays A pinhole camera was used to image the X-rays being emitted as electrons collided with surfaces in the chamber. The images show that X-rays are generated at the chamber walls and near the target. The time dependence of these X-rays during each pulse was examined using a PIN diode X-ray detector. Then, using another X-ray sensor and pulseheight analyzer, the spectra of the emitted X-rays was determined. The object is to relate the X-ray intensity and spectrum to the temporal and spatial values of the implantation dose so that it may he used as a process monitor and a control sensor.     

Poly-capillary X-ray and neutron optics (Kumakhov optics)

Poly-capillary X-ray optics (Kumakhov optics) are based on multiple total external reflections of radiation in small-diameter hollow capillary tubes. Such tubes can be made to form different kinds of lens and make it possible to focus and control X-rays and neutrons over broad angular and energy ranges. Thus, as instances, X-rays can be focused for medical therapy and material sciences, and intense quasi-parallel X-ray and neutron beams can be produced from divergent sources for medical diagnosis and X-ray lithography. This new form of optical control offers improved efficiency and effectiveness in almost all uses of X-rays or slow neutrons, and makes possible many new applications.     

Effect of pre-irradiation with X-rays on the direct liquefaction of coal

Coal is pre-irradiated with X-rays before being submitted to liquefaction with the aim to depolymerize (upgrade) the complex network to simple chemical species. It was found taht the pre-irradiation enhances the liquefaction yield from 48% (liquefaction without pre-irradiation) to 65% (after 10 h of pre-irradiation with X-rays). Our data suggests that since pyrolytic bond breaking is considered to be the first step in the coal liquefaction process, pre-irradiation with X-rays will create free radicals which then enhance the liquefaction.     

The influence of chondroitin sulfate on composite multilamellar liposomes containing chitosan

A composite multilamellar liposome containing chitosan attached to the inside and outside of the membrane as well as an opposite charged polyelectrolyte, chondroitin, adsorbed at the surface was developed. Not only the chitosan/chondroitin ratio but also the concentration of them were varied. The structure and superficial properties of the liposomes were studied through a combination of light scattering, zeta potential, and small-angle X-rays scattering techniques. While the chitosan/chondroitin ratio affected the superficial charge distributions, the concentration of polyelectrolytes affected the structural properties of the liposomes, as the rigidity of the phospholipid layers. The superficial charge of the resultant composite liposome was influenced by the type and concentration of the polyelectrolyte. Information about the charge density could be obtained by the treatment of zeta potential data, and it was used to estimate the amount of chondroitin adsorbed to the liposome surface. Applying the modified Caillé theory to the X-rays scattering curves, information about the internal structure of the liposomes was accessed. The ability to control the properties of composite multilamellar liposomes is an important issue when they have to be applied as a biomaterial device component.     

Quantitative analysis by (p,X) and (p, γ) reactions at low energies

Production of atomic X-rays and nuclear γ-rays by bombardment with 0–3 MeV protons of thick targets is described. In the case of low-Z atomic X-rays, the absorption in the target is very large, while in the case ofK X-rays from high-Z atoms or for γ-rays, this phenomenon is negligible. Both of these reactions can be used for analysis of elements from F to U, and the sensitivities and the accuracies of the determinations are discussed. A table is given showing the γ-ray energies observed in 11 substances and the limits of sensitivity.     

Strong X-ray emission from electrified insulators.

Terasawa reported strong X-ray emission from charged-up insulators, and proposed an X-ray production device only using the electrification. We constructed a similar device and studied the conditions of X-ray emission. It was shown that X-rays could be produced without supplying electrons from a filament.     

Application of off-specular scattering of X-rays and neutrons to the study of soft matter

Recent applications of the use of off-specular reflection of neutrons and X-rays in the study of soft matter are reviewed after a brief introduction to the status of the current theoretical treatment of such data. The review is intended to highlight the range of systems that may now be studied with off-specular reflection and recent progress in understanding the results that are observed. A few specific experimental cases are discussed as well as recent technical developments that may enable further more sophisticated treatments of off-specular scattering to be investigated.     

Toward on-chip X-ray analysis

The possibility of performing chemical analysis and structure determinations with the use of X-rays in a microfluidic chip environment is explored. Externally generated radiation, radioisotope irradiation and on-chip generated X-rays were considered as excitation means for the performance of sample analysis with the techniques of X-ray fluorescence and diffraction. The absorption properties of chip-building materials by different radiation sources are reviewed and data on absorption coefficients calculated, upon which recommendations for optimisations with the use of various X-ray sources may be made. The capabilities and limitations of on-chip X-ray analysis are placed in perspective by preliminary experimental results of diffraction, fluorescence and on-chip X-ray generation experiments.