The Gandolfi camera, which produces simulated powder diffraction patterns from single crystals, has been found to be a very useful tool in applied mineralogical research. For many micro-diffraction problems, the advantages of the method far outweigh its weaknesses, and Gandolfi films are usually quite adequate for identification purposes. A simple modification to the small Gandolfi camera permits the recording of low-angle reflections corresponding to d-spacings of nearly 14 angstroms for CuKα radiation. Applications of the method include identification of radioactive minerals, other heavy minerals, contaminants, and glass stones.

The chemical analyses of pigments and fillers are important to both the manufacturer and the papermaker. Most standard analytical methods, including those of Technical Association of the Paper and Pulp Industry, are based on the so-called classical gravimetric and volumetric techniques. The major components analyzed are TiO2, SiO2 and Al2O3 . X-ray diffraction methods are available for the identification of crystalline fillers and pigments in finished paper.

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.

The microbeam X-ray diffraction technique was used for the evaluation of fracture analysis on the fatigued low carbon steel specimens.

It is possible to evaluate both monotonic and cyclic plastic zone sizes beneath fatigue fracture surface. Thus the stress intensity factor can be estimated.

Electron fractography has been widely applied to analyze fracture processes and service failures. However, the results obtained by the fractographic method are restricted to information in a topograph of the fracture surface. Therefore, other methods are needed to analyze the fracture. One of the hopeful advanced techniques is thought to be X-ray diffraction, because another type of structure sensitive information would be obtained.

A position-sensitive proportional counter suitable for the X-ray stress measurement has been developed and residual stresses were measured with an apparatus that uses this PSD system. The counter was designed to have a good angular resolution over the counter length for the diffracted X-ray beam and high counting rates. The mean angular resolution measured was about 0.2° in 2θ (FWHM) at 200 mm, and the maximum allowable counting rate reached about 40,000 cps.

The time required for the data accumulation was shown to be 1/10 to 1/30 of the time required with a standard diffractometer.

Measurements on the heat affected zone of a weldment are presented using a gas filled position sensitive detector and a normal diffractometer equipped with a scintillation detector and a solid state detector. The sample, a surface ground titanium alloy, provided a difficult application for the X-ray technique from which a test of the real usefulness of the position sensitive detector could be made. The diffraction profile from the Ti alloy is very broad and the fluorescence produces a high background. The fluorescence is easily rejected using a solid state detector; however, the time of analysis is very long. With the position sensitive detector, the combination of increased energy discrimination over the scintillation detector and the simultaneous measurement of many data points over the broad peak enabled the measurements to be made for the same accuracy in much shorter times than for either the solid state detector or the scintillation detector.

Residual stresses on the inner surface of stainless steel pipe used in nuclear reactors are of exceptional importance. Apparatus for measuring these in situ, in welded lengths of 10-inch diameter austenitic (304) stainless pipe has been developed at the University of Denver Research Institute under the sponsorship of the Electric Power Research Institute.

Instrumentation has been developed which employs standard x-ray diffraction equipment and an energy dispersive analyzer for elemental and phase analysis. A General Electric XRD-6 diffractometer, a sample chamber, a Nuclear Semiconductor energy dispersive analyzer (EDA) with 155 eV resolution, and a Tracor Northern multichannel analyzer are its main components.

The scanning speed of powder diffractometers can be increased by about two orders of magnitude by replacing the normal detection system (receiving slit/scintillation counter) by a linear position sensitive detector (PSD) which collects diffracted x-rays of a larger part of the diffractometer measuring arc simultaneously. The velocity increase is proportional to the section of the arc 29 in which the diffracted x-rays are detected. With respect to the Bragg-Brentano focussing geometry, a range of several degrees (typically 5°) can be tolerated without affecting the resolution remarkably. Diffractograms over extended angular regions of 2θ are received by slewing the PSD continuously along the arc while the diffracted x-rays are accumulated with their accurate 2θ angle address on a digital base.

The method has been named the continuous position sensitive detection technique (CPSD). With this technique, diffraction patterns with similar quality (resolution, linearity, peak/background ratio) as conventional, scintillation counter recorded diagrams can be received at slewing rates of several hundred degrees per minute. Additionally, the CPSD technique augments the number of crystallites contributing to the diffraction intensity by the same amount, thus producing much better crystallite statistics for quantitative measurements.

The radiation from plasmas produced by the interaction of a pulsed laser and a solid target can be made to fall in the soft x-ray regime. The x-rays can serve as an alternative to the increasingly important synchrotron radiation facilities for a variety of techniques such as Extended X-ray Absorption Fine-Structure Spectroscopy and X-ray Lithography. In addition, the x-rays are of special interest for general microradiography of thin samples.

In the X-ray fluorescence analysis of homogeneous specimens, the correlation between the characteristic line intensity of an analyte element and the concentration of that element, is typically non-linear over wide concentration ranges, due to interelement effects between the analyte element and other elements making up the specimen matrix. Although in many cases limiting the analyte concentration range may allow the use of linear calibration curves based on type-standardisation, it is usually more desirable to work with general purpose calibration schemes which are applicable to a variety of matrix types over wide concentration ranges.

A critical discussion of the equivalent wavelength representation of polychromatic primary radiation as applied to the fundamental parameters method is given. This representation raises problems with appropriate selection of equivalent wavelengths and with accurate calculation of secondary fluorescence. Methods for reducing these difficulties are discussed and have been incorporated into a mini-computer program which achieves reasonable accuracy for alloy test cases.

This paper reviews x-ray fluorescence (XRF) matrix correction methods which use scattered radiation and discusses their typical analytical applications. It also discusses some of the underlying assumptions of these methods and thus provides a basis for estimating their merits and limitations in quantitative analytical applications.

A procedure to obtain analytical models for the elemental X-ray pulse-height distribution libraries necessary in the library least-squares analysis of energy-dispersive x-ray fluorescence spectra is outlined. This is accomplished by first obtaining the response function of Si(Li) detectors for incident photons in the energy range of interest. Subsequently this response function is used to generate the desired elemental library standards for use in the least-squares analysis of spectra, or it can be used directly within a least-squares computer program, thus eliminating the large amount of computer storage required for the standards.

Exact is a mini-computer based fundamental parameters program which is utilized for matrix corrections in energy-dispersive X-ray analyses. We have previously shown this technique to work well with radioactive sources. However, due to the limited selection of isotopic sources available and their inherent low X-ray flux, we have investigated the use of Fe, Sn, and Dy secondary-targets as sources of monochromatic X-rays. Results to date indicate that the secondary-targets provide X-ray radiation which has sufficient monochromaticity for our technique to remain valid.

Least squares computer programs have been used for the resolution of complex gamma-ray spectra obtained from NaI(Tl) detectors for many years. With the addition of computer codes, which account for the differences “between gamma-ray and x-ray fluorescence spectra, these same programs can be used to quantify energy dispersive x-ray fluorescence data.

A review of the application of the Monte Carlo, fundamental parameters method to XRF fluorescence analysis for the reduction of matrix effects is made. The analytical solutions arising from theoretical equations are given along with the restrictive assumptions that are necessary to this approach. The extensions of the fundamental parameters method by the Monte Carlo simulation to practical situations that require much less restrictive assumptions are outlined. The average angle approach to the use of the analytical solutions is investigated by comparison with the Monte Carlo method. Future extensions of the fundamental parameters method by the Monte Carlo approach are discussed.

Multielement data as they are obtained from energy-dispersive x-ray spectrometry can only be interpreted efficiently if multivariate statistical techniques are employed. It is shown that these and pattern recognition techniques can easily be implemented on the dedicated mini-computer system that is usually supplied with the spectrometer. These algorithms are helpful in interpreting multielement data and in gaining insight in and understanding of those aspects of the data structure that are inherent to the data. Such a program was tested using ground water data. Further extensions of the concept of integrated data interpretation are discussed.

Identification of asbestos fibers and other small particulate matter observed in TEM and STEM is often based in whole or part on the ratios of elemental intensities. The underlying principle in this method is the linear relationship between concentration ratio and intensity ratio, which has been proposed by many authors, some of whom measure the proportionality factors and others calculate them from quasi-theoretical relationships.