bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Dynamical Theory Approach to the Berg-Barrett Technique
Authors: Roessler B. , Armstrong R.W. 
Published: March 2019

AbstractCrystals with a dislocation density low enough so that individual dislocations can be resolved by X-ray diffraction contrast techniques should be regarded as highly perfect crystals. A complete description of the diffraction process, therefore, requires the approach of the dynamical theory of X-ray diffraction. In the Berg-Barrett arrangement each point on the crystal surface integrates the incident X-ray intensity over the angular range received from the X-ray source. For most experimental arrangements this range is about 1/2 degree and corresponds, therefore, to integrating over the entire range of reflection of the crystal, which is of the order of a minute or so of arc. The Berg-Barrett image is a recording of a localized integrated intensity, integrated over the complete range of incident angles. We consider as essential, however, primarily the range of total reflection, since it makes the major contribution to the integrated intensity.The dynamical theory shows that the details of the diffraction process depend very strikingly on the boundary ocnditions at the crystal surface through two angles of incidence - one between the incident beam and the crystal surface, the other between the incident beam and the diffracting plane of atoms. Calculations of the parameters of the dynamical theory which describe the diffraction process in the Berg-Barrett arrangement show that the description depends very strongly on the details of the specific boundary conditions employed. In particular, two parameters seem especially important in dislocation image formation: 1) ΔθR, the angular range of the exit beam diffracted from the crystal, which we call the range of total rejection to distinguish It from ΔθA, the angular range over which the entrance beam is totally accepted, and 2) σe, the extinction coefficient, the parameter which describes the X-ray penetration depth. Both parameters are extremely sensitive to the specific boundary conditions employed.This dynamical theory approach suggests that, by suitable choice of the experimental conditions, the boundary conditions can be advantageously adjusted so that satisfactory Berg-Barrett images can be obtained.
X-Ray Analysis of Fatigue Softening in Cold Worked Copper
Authors: Baggerly Roy G. , Pelloux Regis M. N. 
Published: March 2019

AbstractThe recovery and recrystallization of cold rolled copper during reverse bending fatigue at room temperature has been studied with x-ray diffraction, optical microscopy and transmission electron microscopy techniques. Recovery of x-ray line breadth was recorded as a function of number of cycles at all strain amplitudes investigated. Recrystallization was observed to take place only at small strain amplitudes (life of 106 to 107 cycles). The rate of nucleation of the recrystallized grains increases with increasing strain amplitude and is a linear function of the number of cycles. The formation and growth of the grains was confined to regions near the surface of the specimen. Since comparable thermal recovery occurs at approximately 435°F it is concluded that the dynamic generation and migration of numerous point defects during fatigue is responsible for the room temperature recrystallization.
A Total reflection X-Ray Spectrograph for Fluorescent Analysis of Light Elements
Authors: Davies R. D. , Herglotz H. K. 
Published: March 2019

AbstractA novel x-ray spectrograph for the analysis of light elements has been developed based on previous computations and confirming experiments by one of as (H. K. Herglotz). The major components of the instrument are an efficient fluorescent source, a totally reflecting mirror, and an open window photomultiplier. Identification of wavelengths in the range 15 < λ < 80 Å is achieved by the wavelength dependence of the critical angle of reflection of an x-ray beam incident on a suitably chosen low absorption reflector. As the incident angle is increased through the critical angle for a particular wavelength, the reflected beam intensity is sharply reduced; hence, a periodic vibration of the incident beam through a small angular range about the critical angle furnishes a strong a.c. reflected signal characteristic of one narrow wavelength band only.Initial results promise a simple, easy-to-operate instrument for the routine analysis of elements boron to fluorine.
A Correction Method for Elemental Interactions and Physical Effects in the X-Ray Fluorescent Analysis of Silicate Powders
Authors: Poole A. B. , Holloway S. M. 
Published: March 2019

AbstractBrieketted rock powder discs provide a convenient type of specimen for use in x-ray fluorescent analysis for both major and trace elements. The method is limited because variation of matrix makes calibration difficult over more than a limited range of specimen compositions.Standard grinding and preparation procedures together with a ratio technique of measurement eliminate variation except that arising from chemical, mineralogical and particle size differences. Several series of standard rock samples have been prepared and the variation of measured intensity per unit concentration have been investigated for the analytical Lines of silicon, aluminium, iron, selenium and cadmium. Computer methods of multivatiate regression analysis have been used to calculate empirical correction factors based on this data and the mineralogical and chemical composition of the specimens. These correction factors have been used to correct the measured intensities of other specimens measured in separate experiments.
Particle Size Effects in Radioisotope X-Ray Spectrometry
Authors: Berry P. F. , Furuta T. , Rhodes J. R. 
Published: March 2019

AbstractTheories explaining the dependence of characteristic X-ray intensity on particle size in heterogeneous materials are reviewed. Several discrepancies between the theories and between theory and experiment have been discovered. A new theory is proposed based on a more rigorous physical model. It is shown to explain well-established phenomena at least as precisely as do previous formulae. Excellent agreement is also obtained with new observations of the variation of characteristic X-ray intensity with packing degree and, in samples consisting of only one type of particle, with both packing degree and particle size. The same basic theory also predicts the observed variation of X-ray Intensity backscattered from or transmitted through a sample. It is also shown that similar results are obtained with particles suspended In a homogeneous matrix, such as an aqueous slurry.
Applications of a New Multielement Portable X-Ray Spectrometer to Materials Analysis
Authors: von Alfthan C. , Rautala P. , Rhodes J. R. 
Published: March 2019

AbstractA new hand-portable, microprocessor-based, multielement X-ray fluorescence analyzer is described. The instrument is light in weight (19 1b), completely self-contained and powered by internal rechargeable batteries. The detector is a special proportional counter whose room temperature energy resolution is sufficient to enable adjacent element X-rays to be deconvoluted with the help of the microprocessor. The instrument yields concentration readout of elements, corrected for matrix effects, in groups of four at a time. A number of field and laboratory applications to ore, solution and alloy analysis are described.
A Minicomputer and Methodology for X-Ray Analysis
Authors: Parrish W. , Ayers G. L. , Huang T. C. 
Published: March 2019

AbstractThis paper outlines the use of an IBM Series/1 small computer for instrument automation and data reduction for X-ray polycrystalline diffractometry and wavelength dispersive X-ray fluorescence spectrometry. The profile fitting method is used to determine 2θ, d and relative peak and integrated intensities in diffraction, and the fundamental parameters method (LAMA program) is used for quantitative analysis of bulk and thin film samples. The methods are precise and rapid.
Techniques of Low Energy X-Ray Spectroscopy (0.1 to 2 keV Region)
Authors: Henke Burton L. , Tester Murray A. 
Published: March 2019

AbstractPresented here is a report on the development of practical techniques for laboratory spectroscopy in the 5 to 150 A wavelength region as may be applied, for example, to light element and surface state analysis, high temperature plasma diagnostics and to the design and calibration of x-ray astronomy measurements.
Soft X-Ray Vacuum Ultraviolet Diagnostics of High Density, High Temperature Plasmas at the Air Force Weapons Laboratory
Authors: Burns Erskine J. T. 
Published: March 2019

AbstractSoft X-ray, vacuum ultraviolet diagnostics of high temperature, high density plasmas are used to determine the temporal, spatial, spectral and total fluence of radiation emitted from plasmas. Some of the radiation diagnostics used to characterize these plasmas are: metallic photocathodes with thin anodes; Ross filter - PIN detector combination; time-resolved pinhole cameras; metallic calorimeter; bent crystal and grazing incidence spectrographs; and differentially pumped, windowless, Samson-type ionization chambers.
Sub-Kilovolt X-Ray Calibration of Photographic Film
Authors: Koppel Louis N. 
Published: March 2019

AbstractThe x-ray spectroscopy of laser-generated plasmas can be applied to photon energies of less than 1 keV, provided calibrations of the response of energy discriminators and detectors are performed in the sub-kilovolt region. In our application we use photographic film to monitor the intensity of radiation dispersed by a curved lead stearate crystal. We have determined the response to sub-kilovolt x-rays of two types of film, Kodak No-Screen and the special vacuum ultra-violet Kodak type 101-01. This calibration was obtained by exposing samples of film to continuous beams of nearly monochromatic characteristic radiation from an array of targets. The fluorescent radiations were the K series of carbon and magnesium and the L series of titanium, nickel, cobalt and copper. The response data are presented as a series of characteristic curves, plotting for each film type and photon energy the net diffuse photographic density as a function of the photon flux incident on the film. The processing of all film was in accordance with the manufacturer's suggestions. We attempt to characterize the accuracy and reproducibility of these data. The data demonstrate the greater sensitivity of the type 101-01 to sub-kilovolt x-rays.The intensity and spectral purity of the incident fluorescent beams were monitored by a thin-window gas proportional counter that used flowing propane gas at sub-atmospheric pressures. We describe the procedures and results of a determination of the quantum efficiency of this counter as a function of photon energy.
X-Ray Analysis for Electron Beam Enhancement in the Plasma Focus Device*
Authors: Gullickson R. L. , Barlett R. H. 
Published: March 2019

AbstractThe plasma focus device, a form of linear pinch discharge, produces an intense x-ray and neutron (D2) burst from a magnetically heated dense plasma. Rapidly changing magnetic fields at pinch time generate large axial electric fields which accelerate electrons and ions. In the experiments reported here the x-ray production during the plasma pinch of a 96 kilojoule (at 20 kV) plasma focus device was measured.The purpose of these experiments was to evaluate the energy in accelerated electrons in the plasma focus device and to learn how to enhance these electron hursts. Well focused, megampere electron beams at a few hundred kilovolts, lasting less than 10 nanoseconds have applications in fusionable pellet heating experiments. (1) X-rays were monitored to evaluate these electron bursts using a defocusing bent crystal spectrometer, doubly diffused silicon (PIN) detectors, with Ross filters, thermoluminescent dosimeters (TLDs) with filters, and x-ray pinhole photography.Thermoluminescent dosimeters indicated maximum x-ray yields of 140 joules above 3 keV at 57.3 kilojoules stored energy (16 kV) for a conversion efficiency to x-rays of 0.2%. 40 joules are above 60 keV and 15 joules above 80 keV. The hard x-ray pulse typically rises in 3 ns and frequently has a pulse width less than 10 ns. The low energy x-ray spectrum consists almost entirely of lines from the high Z anode insert, and the high energy spectrum is characteristic of a nonthermal power law distribution with an exponent of 2.2 ± 0.8. Peak hard x-ray production is obtained at 1 torr deuterium in contrast to peak neutron production (3 x 1010) at 5 torr. The addition of argon reduces total x-ray yield and increases the relative fraction of soft x-rays.These measurements suggest that the plasma focus produces 1200 joules of electrons with an average energy of 150 keV, in 10 nanoseconds with a stored energy of 57.3 kilojoules. This is a power of 1.2 × 1011 watts and power density of 1.5 × 1013 watts cm−2.
Silicon Detector System for X-Ray Pulse Calorimetry of Laser-Produced Plasmas*
Authors: McQuaid J. H. , Violet C. E. , Petruzzi J. 
Published: March 2019

AbstractThe instrumentation for measuring x-ray yields from laser produced plasma is described. This new type of calorimeter is composed of a silicon detector, a charge-sensitive preamplifier and an analog-to-digital readout scheme for multiplexing up to ten detector outputs.X-rays interacting with the detector produce hole-electron pairs in proportion to the total energy lost in the detector (∼1012 eV). In this application the detector can be characterized as a solid-state ionization chamber. The detector signal is coupled to a charge-sensitive preamplifier which generates a voltage pulse proportional to the x-ray energy absorbed. In this way the x-ray energy is measured by “direct conversion” rather than measuring the temperature rise due to an energy flux.
Chemical State Analyses of Sulfur, Chromium and Tin by High Resolution X-Ray Spectrometry
Authors: Gohshi Y. , Hirao O. , Suzuki I. 
Published: March 2019

AbstractChemical shifts of SKα, CrKβ1,3 and SnLβ2 were precisely measured with a two-crystal X-ray spectrometer (Toshiba AFV 701). Sulfur in the coke for iron smelting takes two oxidation states, i.e., S2− and S6+. Quantitative analyses of S2− and S6+ were performed by precisely measuring the profile of SKα and fitting the standard S2− of S6+ curve to the observed SKα profile with the non-linear least square method. Chemical shifts of CrKβ1,3 and SnLβ2 were utilized for the determinations of Cr6+, Cr3+, Sn4+ and Sn2+ in electro-plating solutions. Intensity ratio of IA to Ig was measured, where B means the point which showed an intensity independent of oxidation states. A means the point which showed the most dependent. Linear relations were found between intensity ratio IA/IB and Cr3+/Cr or Sn2+/Sn.
Excitation-Energy-Dependent Resonances in Soft X-Ray Appearance Potential Spectra of the Cerium 4d- and 3d-Electron Levels
Authors: Chamberlain M. B. , Baun W. L. 
Published: March 2019

AbstractWhen the excitation energy lies near the ionization potential of many core electrons, core-hole relaxation effects strongly affect x-ray emissions. Under near-threshold electron excitation of the cerium 4d subshell both the incident electron and a 4d-core electron are promoted into 4f-orbital excitation states which exist only during the life of and are bound to the 4d vacancy. The exchange interaction between the 4d hole and the excited electrons in the unfilled 4f subshe11 spreads the energies of the discrete excitation states over a 20eV range sending some levels well below the 4d threshold and others into the continuum. Exchange interactions and potential barrier effects have a dominant influence upon the cerium 4d and 3d soft x-ray appearance potential spectra reported in this paper. We observe sub-threshold x rays extending to 8.6eV below the binding energy of the 4d level as well as a maximum in the yield at 12eV above the 4d onset. As the electron excitation energy is swept through the thresholds of the two 3d levels we observe resonant x-ray emissions, while at 28eV above these levels we see plasmon loss structures.
Anomalies in Measurement of Residual Stress by X-Ray Diffraction
Authors: Marion R. H. , Cohen J. B. 
Published: March 2019

AbstractResidual stresses are expected to lead to a linear dependence of the interplanar spacing, d, on sin2ψ (where ψ is the sample tilt) and the stress can be obtained from the slope of this line, As a result of the linear dependence a two-tilt method is often employed to obtain the stress. However, when a specimen is subjected to extensive plastic deformation large deviations from a straight line can occur and a two-point method can lead to an erroneous stress determination. The results reported here show that: (1) this is more likely to occur in homogeneous materials than in multiphase materials (2) the oscillations follow closely the variation in peak intensity due to texture (3) the oscillations are caused by microstresses which are due to an "orientation" effect as suggested by Weidemann,A simple, easy-to-use procedure has been developed and tested to correct the data and obtain the correct macrostress.
X-Ray Analysis of Ti3Al Precipitation in Ti-Al Alloys
Authors: Baggerly R. G. 
Published: March 2019

AbstractThe effect of temperature on nucleation and growth of Ti3Al precipitates in two Ti-Al alloys was determined using sensitive X-ray diffraction techniques. The X-ray peaks arising from the ordered Ti3Al phase were compared with the fundamental peaks of the matrix. Peak broadening due to particle size resulted from the small Ti3Al precipitates and this was analysed using Fourier methods to determine a mean particle size and particle size distribution. The two alloys used for this investigation were Ti-8.5 wt.% Al and Ti-8%Al-1%Mo-1%V (8-1-1) alloy. The precipitate size in Ti-8.5 wt% Al was considerably more dependent on temperature than the precipitate size in 8-1-1 alloy, achieving a size of 190Å after 20 hrs at 650°C. The solvus temperature for precipitation was the same for both alloys, vis, 675°C to 700°C. These results compare favorably with transmission electron microscopy of thin foils prepared from the same samples.
X-Ray Stress Measurements in Ground Surface of Steel by Position Sensitive Detector
Authors: Kawata M. , Morinaga M. , Yoshioka Y. 
Published: March 2019

AbstractThe residual stress produced by surface and cylindrical grinding was measured by a position sensitive proportional counter. In medium carbon steels the residual stress depends largely on the grinding conditions. For a gentle cylindrical grinding compressive stress was observed, but for a rough grinding tensile stress was present in the workpiece.
Measurement of Cumulative Fatigue Damage by X-Ray Double-Crystal and Scanning Diffraction Methods
Authors: Pangborn R. N. , Weissmann S. , Kramer L. R. 
Published: March 2019

The ability to predict fatigue failure has long eluded scientists and engineers. Because they can be applied nondestructively, X-ray diffraction methods have been employed to measure fatigue induced lattice misorientation, lattice strain, residual stress and subgrain formation. The changes in the X-ray patterns, however, were found to be restricted principally to the very early and late fractions of the fatigue life. Their invariance during the intermediate portion of the life has hampered the evaluation of cumulative fatigue damage and prediction of ultimate failure.The primary difference between previous investigations and our recent X-ray diffraction studies is the emphasis we placed on characterizing both the surface and subsurface response to fatigue. By evaluating the prefracture damage with depth from the specimen surface a more reliable procedure for failure estimation emerged.
The Present State of X-Ray Spectrometry
Authors: de Vries J. L. , Philips N. V. 
Published: March 2019

If we want to evaluate the present state of X.R.S., we should do this in perspective with other methods, e.g. Optical Emission and Atomic Absorption Spectrometry.One way to compare would be to estimate the number of papers published or given at conferences on these three methods. Table 1 gives a survey af some meetings. It is evident that X.R.S. is less talked about than the other methods. The rejuvenation of OES, thanks to the Plasma sources, can also clearly be seen.
The Application of a Multichannel Fixed and Sequential Spectrometer System to the Analysis of Air Pollution Particulate Samples from Source Emissions and Ambient Air
Authors: Bennett Roy L. , Wagman Jack , Knapp Kenneth T. 
Published: March 2019

The design and application of a newly-developed Siemens multichannel wavelength x-ray fluorescence spectrometer that has been specially adapted to the needs of the Environmental Protection Agency for rapid analysis of particulate samples is described. The system consists of sixteen fixed-wavelength spectrometers which are optimized for sixteen pre-selected elements and a computer-operated scanning channel which is used to determine additional elements that might be desired on a given sample. A minicomputer operates the instrument and custom-designed sample changer and processes the data.Requirements for standards suitable for air pollution samples and the approaches used for the preparation of thin layer standards are discussed. Sensitivities, detection limits for elements of interest in air pollution, and the relative merits of aerosol filter types for x-ray fluorescence analysis have been determined. The system has been used to measure the elemental composition of a large number of samples from stationary source emissions, mobile sources, and ambient air.
Advance in NPL X-Ray Gratings and Spectrometers
Authors: Stedman M. , Franks A. 
Published: March 2019

NPL x-ray gratings for use at grazing incidence in the wavelength range of 0.05 to 20 nm have diffraction efficiencies in the first order ranging from approximately 3% at 0.1 nm to 20% at wavelengths greater than 2 nm. X-ray gratings may have either a rectangular profile produced by processing a ruled or holographic grating or may have a shallow blazed waveform. In both types of grating, the grooves are formed in a vitreous silica blank and are usually overcoated with gold.A precision short wavelength (0.05 to 0.5 nm) Rowland circle focusing spectrometer has bee n constructed, which can cater for concave gratings of radii between 5 and 15 m.
X-Ray Diffraction Analysis of the Calcium Carbonate Polymorphs
Authors: Silk S. T. , Lewin S. Z. 
Published: March 2019

AbstractIt is shown that the integrated intensities of diffraction lines from calcite and aragonite powders prepared by precipitation vary markedly, due to variations in sample packing efficiency arising from different degrees of polydispersity in the particle size distributions. Since prolonged grinding to equalize initially divergent distributions changes the polymorph composition, the packing effect imposes the principal limitation on the precision of the x-ray method for certain types of calcium carbonate preparations.