The statistical fluctuations of photon counts arediscussedas a factor limiting the precision of the analytical result. Assuming a Poisson distribution, the theoretical standard deviation of the result can be calculated. While this prediction does not consider causes of variation other than the count statistics, it is useful in developing methods and checking instrument reliability. Practical examples using experimental results are given.

The discovery of a very simple and useful relationship between the absorption coefficient of a particular element and the ratio of incoherent to coherent scattering by the sample containing the element is discussed. By measuring the absorption coefficients for a few elements in a few samples, absorption coefficients for many elements in an entire set of similar samples can be obtained.

Zn-Ni-alloy electroplated steels are used for the parts of automob iles because of their high corrosion resistance. in the x-ray stress measurement of this material, some unique experimental results were observed: (i) The sin2Φ diagrams were severely curved, and (ii) the influence of the wave length of x-ray radiations upon the shape of the d-sin2Φ diagram was very slight. As no strong texture or the gradients of composition were observed in this material, the above experimental results suggested the existence of steep stress gradients in the direction of depth, and a theoretical problem on the difference in the effective penetration depth of x-rays and the weighted mean of the lattice strain between thin films and ordinary thick materials.

The work describes a method for determining the orientation of crystallographic planes in thin samples using both asymmetric Bragg reflection and asymmetric Laue transmission method.

The method is based on the extension of a system of nonlinear equations for the reflection case. The solutions of the system of nonlinear equations in question can be positive, negative or mixed with physical significance. The positive solutions correspond to reflection case, while the negative solutions are for transmission case. The mixed solutions were generated for the planes {111} in a cubic structure.

A theoretical test is given for a silicon sample. The results are in good agreement with the experimental results given in literature.

Residual strains and stresses were measured in hot-pressed α-Al2O3 composites containing 25 wt% β (cubic) SiC whiskers with and without a 50-100Å thick carbon coating. X-ray diffraction methods were used including the separation of macrostresses from the microstresses in the -Al2O3 and SiC phases by the method of Noyan and Cohen. The presence of the carbon coating on the whiskers reduced the magnitude of the residual microstresses in the whiskers by ˜13% and in the matrix by ˜10%. The measured residual stresses in the whiskers and the reduction due to the carbon film were in good agreement with calculations from recent models proposed by Hsueh, Becher and Angelini, and by Li and Bradt.

A high-temperature crystal growth experiment produced discrete singlecrystal products of Allr and IrSi. The preparation, and examination of these phases is described within. This project is part of a materials compatibility study relating to radioisotopic heat sources. These heat sources are comprised of a PuO2 fuel pellet encapsulated in an Ir alloy containment shell. Thorium is introduced as an additive within the Ir to maintain ductility. Si and P are picked up inadvertently in the fuel processing. The compatibility of the heat sources with Al is of interest because of potential interactions with the Al alloy hardware associated with the heat source environment.

The instrumentation and software for performing X-ray intensity measurements with a paper tape controlled diffractometer are described. The hardware includes two addressable axis positioners which control Slo-Syn stepping motors on the 2θ and ω) axes of the diffractometer, an addressable scaler-timer, a multiaxis programmer and a Teletype, in addition to the normal counting electronics. This system may be manually controlled with front panel switches or with instructions entered on the Teletype. In the automatic off-line mode instructions for motor speed, motor direction, starting angle, final angle, angular increment and scaler preset (time or counts) punched on paper tape are read and executed in sequence. A Teletype output of 2θ and ω angles, time and counts is obtained at each step. This off-line system was used for the measurement of austenite in H12 hot work die steel austenitized at various conditions and which contained a maximum of 13% austenite. A helium chamber was used to extend the limit of detection to 0.4% austenite. The X-ray analysis involved measuring the areas of the (200) austenite diffraction line and the (200) martensite line. For each of these lines, the system was programmed to integrate the counts over angular intervals corresponding to a low-angle background, the peak and a high-angle background using the ability of the axis positioner to stop the scaler-timer at the end of each angular interval. The additional capability of slewing rapidly between the various diffraction lines reduced the time required for automatic data collection. The present off-line system can be used to simplify other types of X-ray diffraction analysis such as residual stress and microstrain/particle size determinations, since the manual data handling can be eliminated with the computer compatible punched paper tape output. Future development of this instrumentation includes direct computer control of the diffractometer and computerized data reduction, with the advantage of a paper tape back-up system.

Trace elements in oil may be determined by adsorption of the oil sample onto maguesium oxide followed by thermal degradation of the organic material. The resulting powder is easily pressed into a pellet suitable for X-ray spectrometric analysis. The lower limit of detection depends upon the trace impurities in the MgO and is a few parts per million for most elements determined.

For more than a decade the Institute of Geological Sciences has carried out large-scale geochemical analysis in pursuit of mineral exploration and regional geochemical reconnaissance programmes for the Department of Industry. Over this period an XRF analytical system has been developed to meet part of this requirement for multielement data. The elements of interest range from the fourth period to uranium, and have become more numerous as exploration and analytical techniques have expanded. In particular, additions have been made of those elements such as arsenic, molybdenum and tungsten which are more difficult of determination by conventional methods.

Spectrographic analysis for carbon and boron using fluorescent x-rays has been studied over the past few years; principles and applications for using those ultra-soft x-rays were described, based on the combination of total reflection and filtering rather than on the wavelength dispersive method of Bragg reflection (1, 2). However, oxygen and nitrogen, with x-ray wavelengths of 23.7lÅ and 31.60Å, respectively, cannot be detected as easily because of their high absorption by the detector window materials such as polypropylene, polyester or formvar films.

X-ray fractography is a new method utilizing the X-ray diffraction technique to observe the fracture surface for the analysis of the micromechanisms and mechanics of fracture. The X-ray residual stress has been confirmed to be a particularly useful parameter when studying the fracture surfaces of high strength steels. The method has been applied to the fracture surface of fracture toughness and fatigue specimens.

The fundamental parameter method for x-ray spectrometry has been used most commonly for bulk samples, because it permits an analysis utilizing a minimum number of standards, even for samples with complicated matrices. The need for the analysis of thin film materials, which includes multi-layer films, has been increasing in recent years along with the rapid progress of high technologies. However, there have been few reports that deal with the application of fundamental parameter methods to multi-layer thin films. There may be two situations in the analysis of thin films. In routine analysis of quality control applications, they usually require precise analysis. Fortunately, it is possible to prepare well characterized standards similar to the unknowns.

Thin film samples represent ideal samples for analysis using X-ray fluorescence in that they tend to be flat, smooth and homogeneous. However, before a sample can be characterized using XRF, several questions must be answered.

Traditionally users of x-ray spectrometers have been forced to optimize their instrument for light element analysis and heavy element analysis through the choice of either a light or heavy element anode. The advent of the rhodium tube brought some relief to this situation, but some compromise was still required. The recent addition of the scandium side-window tube to the range has provided twice the excitation efficiency of the chromium tube, whilst providing an equivalent heavy element performance.

In the past there have been attempts to produce x-ray tubes combining the properties of both light and heavy element tubes. An example of this is the dual-target tube which has two preferentially excited targets (anodes) of different materials constructed side-by-side.

The techniques of X-ray topography are reviewed, with special reference to their application to the study of surface layers and thin films. The methods of section topography, white radiation topography and double and triple crystal topography are shown to be the most appropriate, with grazing or glancing incidence methods assuming special importance. Applications to the questions of epilayer mismatch and dislocation content, process-induced defects and surface damage are discussed.

Although no revolutionary advance has been achieved in the last two decades, X-ray diffraction is not to be considered as a quiescent field of physics. Actually many improvements, in theory as well as in experiment, slight by themselves but very numerous, have considerably increased the efficiency of techniques such as the determination of crystal structures, the analysis of crystalline phases, and the applications of X-rays to various problems of the physics of solids. Only the two last points will be dealt with here:

1. 1. Crystalline phase analysis. The development of a satisfactory atlas of powder patterns has been too slow, and the data are not yet complete and precise enough to permit a rational utilization of the modern diffractometers. A very interesting new approach is the systematic indexing of the powder patterns which would be possible with computers. In the near future, anyone should be able to analyze a powder at any temperature as an easy routine experiment.

2. 2. The study of lattice defects. X-ray techniques are now in competition with electron microscopy, the development of which has been very successful in recent years. Now we have a better understanding of the possibilities of both techniques. X-rays give better results to determine the statistics of an extended disorder even if it is slight (e.g., degrees of order in a solid solution), and the microscope is more powerful for the detection of large but rare defects (e.g., dislocations).

The use of CaF2 (Dy) thermoluminescent dosimeters to diagnose the X-radiation from 1.06 μ laser-produced plasmas is described. The TLD's have been used in various cassettes to measure total X-ray yield and the X-ray continuum out to ∼100 kev. Described are experiments pertaining to maintenance and recovery of TLD soft X-ray response, their linearity, insensitivity to 1.06 μ laser light, and energy calibration. Also, described are the TLD attenuation experiments in the “soft” and “hard” components of the laser plasma X-ray spectrum.

Two kinds of improved techniques are described for precise measurement of lattice parameters with an accuracy of 1 ∼7x10-5, in both of which a differenoe of Bragg angles between two X-ray beams such as K α1 and K β1 is measured.

In the first technique, which was applied to relatively imperfect crystals such as gallium arsenide, gallium arsenide phosphide, and gallium phosphide, two different diffraction planes were utilized for two radiations such as CuK α1 and CuK β1 in order to reduce the difference of the Bragg angles to the order of several minutes of arc.

In the second technique, which was applied to a nearly perfect crystal such as silicon, a double crystal arrangement of parallel setting was used, where lattice parameter of the specimen was relatively measured in comparison with the one of the first crystal which was known beforehand.

The operation of a new polycrystalline phase identification method using the IBM Series/1 minicomputer is described. Data of the unknown can be entered by automatic transfer of previous runs, stored data sets and manually. Full screen menu selections are provided to facilitate operations and correct entries. Typical S/M time for a multi-phase inorganic mixture containing 43 reflections using a 0.3° window averaged 11 sec per 100 standards and with simple chemical prescreening less than 4 sec including program initialization and calculations of comprehensive figures of merit. Interactive options provide graphics terminal comparison of the unknown pattern with selected standards which appear as diffractometer patterns, subtraction of identified standards from the unknown and others. Utility programs permit storing data sets for later analysis, user created files and a program to display any file standard as a diffractometer pattern.

The efficiency of the recessed source geometry for the analysis of the content of wear metals in engine lubricant oils by Energy Dispersive X-Ray Fluorescence (EDXRF) methods is calculated by a Monte Carlo simulation considering X-ray detectors of the Gas Proportional Scintillation Counter type and excitation by Cd-109, Cm-244 and Fe-55 radioactive sources. Calculated spectra for the case of a typical aircraft oil with Cu, Fe, Cr, Ti, Sn and Ag impurities in the p.p.m. range were obtained and results are presented that allow the prediction of the counting rate per mCi and p.p.m. of the impurity content. The performance of the system is discussed concerning its potential applications to in-line monitoring of the wear metals.