The location of x-ray diffractometer line profiles is of fundamental importance in x-ray stress analysis. Objective estimates of the line profile position may be derived from diffractometer measurements at a number of equally-spaced points in the region of maximum intensity. These estimates are generally based upon the corresponding turning-point of a polynomial fitted to step-scanning data. Techniques are described which simplify the computation involved. A least-squares fitting of a quadratic is satisfactory for most routine applications provided that a reasonable number of points is involved. The three-point parabola method is less satisfactory. Expressions are presented, derived using the maximum-likelihood approach, for peak location and counting variance using both quadratic and cubic equations.

There are three factors which may influence the method by which a piece of evidence is analyzed in a forensic laboratory. The first stems from the definition of the word forensic. It means ”… pertaining to, connected with, or used in the courts of law…” The major areas of forensic analysis are criminal, regulatory, and civil. The purpose of an analysis may be to aid in the prosecution or defense of criminal charges, to determine if a product meets its statutory requirements, to satisfy a consumer complaint, or to determine liability. For these reasons the legal aspects of an analysis may often put constraints upon the analyst. These may require special handling or documentation procedures.

The back reflection x-ray divergent beam technique is examined as a tool for studying elastic strains. In particular, a method of calculating interplanar spacings using a least squares fit of experimental "conic" coordinates to Newman's general equation for back reflection (J. Appl. Cryst. 3 (1970) 191) is described. Using this technique, interplanar spacings can be obtained from partial conies. To determine the precision of this method an unstrained silicon single crystal is studied, and the errors associated with determining its interplanar spacings are discussed. The technique is then applied to elastically strained silicon and the results compared to theoretical predictions. It is shown that strains down to 2 × 10−5 are readily measured on high angle planes in silicon.

A prototype of a new high temperature chamber has been developed at our institute. Like most of such chambers it has an evacuated housing which is watercooled, and in its center a tungsten heating strip is mounted on watercooled clamps (fig.1). A special way of clamping compensates for thermal expansion automatically and thus keeps the specimen in an aligned position. The specimen is mounted directly onto the heating strip's surface. Specimens are prepared using fine powders mixed with distilled water and acetone to give a thin slurry. This mixture is put onto the heating strip and carefully dried with a heatgun. This way of preparing a specimen makes it cling to the heating strip quite well even at temperatures above 3000K and therefore provides good thermal contact.

An IBM 7090 computer program has been written to determine precise lattice parameters for cubic, tetragonal, orthorhombic, and hexagonal systems. Leastsquares analysis is made with data fitted to the equation

where E is the eccentricity and A. is the absorption-divergence error. The computer program will make the least-squares analysis with neither, either, or both of the error(s) included. Data can then be reprocessed for other combinations of errors. After having determined the lattice parameter(s), on request, the computer program will predict the interplanar spacings, including the errors, so that observed data in the high-angle region may be indexed by comparison. Use of the program indicates that the most consistently reproducible parameters are obtained using only A, the absorption—divergence error.

Recently variable sample exit-angle x-ray fluorescence spectrometry (VEA-XRF) has been shorn to be a useful analytical tool for monitoring the oxidation of the surfaces of bulk Cu, Ni as well as that of Fe. In these studies advantage was taken of the well known phenomenon that for each transition metal oxide (MO) Lβ/Lα intensity ratio value is higher than for the transition metal (M), itself. Within the limits of the photon-escape depth de, which for these photons are generally below 5000 Å, varying the sample exit-angle θ offers an opportunity for seeing whether or not the oxidation of the surfaces of bulk M belongs to one of the following two classes: (I) uniform oxidation throughout the entire observable sample-depth, (II) preferential oxidation of the top surface layer, i.e. depth dependent oxidation.

Computed tomography (CT), commonly known as CAT scanning (computerized axial tomography), is a technology that produces an image of the internaI structure of a cross sectional slice through an object via the reconstruction of a matrix of X-ray attenuation coefficients. This non-destructive method is fast (50 ms to 7 min per image depending on the technological generation of the instrument) and requires minimal sample preparation. Images are generated from digital computations, and instruments essentially have a linear response. This allows quantitative estimations of density variations, dimensions and areas directly from console displays.

Spectrum analysis in the ultrasoft X-ray region is complicated by the fact that this radiation is almost totally absorbed in any medium. This has necessitated spectrometer components which minimize this effect. Nondispersive and total reflection techniques, though high in speed, lack good resolution and in the case of the latter, are usually restricted to analysis of elements differing by at least three atomic numbers.

Diffracting media which have proven successful are the long-chain organic crystals and gratings at grazing incidence. The grating is superior to the organic crystal concerning resolution and dispersion and has proven to be comparable arid in some cases better for peak intensity and line-to-background ratios.

Lightly-ruled gratings have been used for many years, but little attention has been given the blazed grating until recently. Since the critical angle of total reflection for a given material is wavelength-dependent, it may be utilized to discriminate against shorter wavelengths and thus improve line-to-background ratios. The optimum conditions for sensitivity, then, would be to relate the input angle to the blaze angle and vary the input angle as a function of wavelength, thereby maximizing the line intensity or the line-to-backgrourid ratio as required.

Several gratings with varying blaze angles and surface finishes are evaluated with O Kα (23.7Å) and C Kα (44Å) radiation.

The importance of groove profile is emphasized by comparing the profile as determined by the electron microscope with the experimental evidence. The variation of diffraction efficiency with wavelength and input angle is then considered theoretically and compared with experimental results.

The variations in the threshold registration of a number of plastic dielectric nuclear track detectors, DNTD's, have been investigated in terms of range energy relationships and the changes in structure affecting electron density distributions studied, using small angle X-ray diffraction. A similar mechanism has been employed to investigate the presence and formation of microcrystallite nucleation sites in lunar and terrestrial minerals, following proton and charged particle bombardments of 10-18 particles/cm2.

X-ray stress analyses were performed on seven (7) nickel-plated camshafts from helicopter transmissions. The purpose of this investigation was to determine if this residual stress technique was useful in determining the state of stress in load-bearing plated surfaces of critical reworked aircraft components. Specifically, it was desired to characterize six different stages of nickel plating processing. These were: as-plated, plated and baked, machined, machined and baked, ground, and ground and baked. Three different radiation wavelengths with different penetrations were used In this investigation. CrKα , CoKα , and CuKα, radiations were each used on all of the camshafts. These wavelengths were selected to determine if there were stress gradients in the plated layers. This paper presents and discusses the results of these studies.

Clay minerals are one of the most difficult classes of materials to analyze by x-ray powder diffraction, yet powder diffraction is the only technique which can yield the important crystallographic information necessary to identify and classify the minerals. The importance of clay minerals in industry and in the studies of rocks, due to their chemical properties and sensitivity to geological changes, often requires the analyses of large numbers of samples in short periods of time. Such sample throughput requires computerized analysis* Because definitive, meaningful d-I data are difficult to obtain from the broad diffraction peaks obtained from most clay samples, this problem has been approached by using the whole diffraction, trace as the basis of a computerized analytical scheme.

Different geometries are considered for source excited energy-dispersive X-ray fluorescence (EDXRF) analysis Systems, including the recessed source geometry introduced in the present work. The calculated physical excitation-detection efficiencies, for the side (or annular), central, receded and recessed source geometries are presented as a function of the target to source distance, for Ca, K, S and Si targets excited with a Fe-55 XBF-3 X-ray source and xenon filled gas proportional scintillation counters. The last two geometries present in gênerai the highest efficiencies. The recessed source geometry présent the best performance with peak efficiencies a factor of 3.3 better than those for the standard side or annular source geometries.

The P-L2,3 emission spectra of the phosphorus compounds were obtained using a secondary excitation. We found that the spectra depended upon the chemical state, the main peak of L2,3 emission spectra shifts to a higher energy, and the peak of intensity of higher energy increases with an increase of oxidation number. It should be noted that the phosphorous spectra of the phosphate anions scarcely reveal influences of the phosphate compounds, except that of H3PO4. We concluded that the spectral feature for the phosphorus compounds is influenced by the condition of surrounding atoms but is not influenced by the bond condition.

Intrinsic stresses as a function of σ, the 1/e penetration depth were measured for a smooth, 1μm thick, fine grained, cylindrical post magnetron sputtered molybdenum film deposited on a vycor glass substrate in the dynamic deposition mode. Using grazing incidence diffraction and the Mo (321) reflection, lattice spacing profiles were determined for τ values from 200-4400 Å. The in-plane intrinsic stresses parallel and perpendicular to the post axis were determined employing the ϕ-integral method and assuming elastic isotropy. The results were related to the surface structure and composition profiles via atomic force microscopy (AFM) and auger electron spectroscopy (AES) respectively.

The growing need for multielement analytical capability is currently being emphasized by the ever broadening governmental regulations on metallic pollutants in water sources. These new regulations cover more elements and are more restrictive in the type and amounts allowable in waste water and natural sources. For example, the California Public Health Law of 1970 states that 0.01 ppm arsenic, 1.0 ppm barium, 0.01 cadmium, 0.05 ppm manganese and 5.0 ppm zinc are the limiting concentrations of these elements in drinking water. Monitoring programs, both for compliance-enforcement and general survey work, have become a greater burden on both governmental agencies and private inductries. While trace analysis in solutions presents certain difficulties to the analytical chemist, regardless of the technique used, the results of this study indicate that x-ray analysis provides a more useful analytical tool for routine work and offers multielement capability with minimal sample preparation.

Increasing attention is currently focused on the generation of characteristic x-ray by proton irradiation. This has the advantage of yielding “clean” x-ray- i. e. free from background brerasstrahlung radiation, from even the lightest elements. The disadvantage is that the yields are naturally much lower than those produced by electrons of the same energy. A recent study has extended characteristic x-ray production to a variety of heavy ions and has shown that the cross- sections for the production of clean x-rays are often higher , by as much as several orders of magnitude, than those produced by protons of the same energy. In addition, there has emerged a further advantage, viz. the ability of specially chosen heavy ions to excite characteristic x-ray from a particular element in a selective manner. Since heavy ions penetrate only a few hundred Angstroms in to most solids, the phenomenon can be used as the basis of a technique for the examination of surface deposits, or to measure depth distributions of impurities. For example, Kr ions can be used t o determine the range distribution of antimony which had been implanted in to silicon at 100 keV. The antimony concentration was determined as a function of ∼ 150 Å steps, and was found to exhibit a maximum concentration of ∼ 1 part in 103 of silicon at 450 Å below the surface, falling to zero concentration at ∼2000 Å a depth. In the past, in order to obtain the required degree of sensitivity, such range determinations have relied on radio active tracer techniques.

An entirely new type of proportional counter has been developed during the course of these studies. This instrument, because of its special construction, can be positioned very close to targets in non-dispersive studies, so as to collect the highest possible fraction of emitted x-ray. It incorporates a replaceable anode unit, together with a built- in miniature head amplifier, and exhibits extremely good performance, particularly for ultra-soft x-ray. In addition, rotation of a dial on the end of the counter body allows alteration of the active gas volume during operation, and so permits tuning into x-rays of a particular energy.

Considering all fields of analysis by X-ray fluorescence spectrometry geochemical analysis is probably the most complex. The geochemical analyst is often requested to analyse samples of unknown composition and origin. While these samples need to be analysed for a number of elements of economic or geochemical significance it is often impossible or uneconomic to analyse for all elements that could possibly be present in the sample.

The x-ray fluorescence (XRF) method is well known for its capability to perform fast and accurate quantitative analysis for all elements with atomic numbers greater than ten. Energy dispersive x-ray fluorescence (EDXRF) adds to this capability the benefit of quick qualitative analysis, due to its simultaneous sensitivity to all the elements. The method has the potential for rapid and complete chemical analysis of any sample which arrives on the analytical chemist's doorstep. Although the method has been a productive tool for fast and accurate repetitive analysis of similar samples, its applicability to unique unknowns has been rather limited. The limitation arises from the usual need to calibrate the instrument's response with a set of 6 to 12 standards, whose compositions must be similar to the unknown sample. Anyone who has struggled to develop and maintain such a suite of accurately certified standards knows that a great deal of effort and expense is involved. This effort is well justified when the analyst expects to analyze the same type of material frequently over an extended tine period. However, for a unique sample analysis, the task of developing a suite of similar standards simply makes the analysis impractical. What is needed is a method that requires minimal standards, or uses no standards at all.

Photoelectron spectrometry is shown to be an excellent technique for the analysis of x rays in the ultrasoft and soft x-ray regions. X rays are converted into photoelectrons which are ejected from a suitable atomic level, and the photoelectrons are analyzed with an electron spectrometer. The method is energy dispersive, provides a resolution ranging from 0.1 eV at 20 eV to 1.1 eV at 3 keV, and gives well-defined intensity characteristics throughout the range. The energy range can be extended into the 10 keV decade. Properties of the new technique are discussed, compared with conventional techniques, and exemplified by a series of measurements which include determination of the emission spectra of M x rays of yttrium to rhodium, L x rays of zirconium, and the band structures of molybdenum and holmium.