An instrument is described which is intended to perform a dual purpose (elemental-structural) analysis consistent with the environmental conditions implied by lunar or planetary operation. The dififractometer section is based on a modified Seeman-Bohlin focusing principle in which a sharp-line focus target, a powdered sample, and a movable detector slit all lie on the focusing circle. The convolution of the projections on the focal circle, of a narrow receiving slit on the detector, the line focus target, combined with a high dispersion produce higher resolution and intensity than is common with Bragg focusing diflfractorneters with simitar instrumental parameters. The range of d-spacings covered is from 1 to 7 Å (chromium target). The chemical analysis section of the instrument utilizes the fluorescent X-rays produced in the specimen by the primary beam. A proportional counter and pulse-height anaiyzer accomplish detection and energy discrimination. Resolution is low, but the analysis can distinguish between elements in the range of atomic numbers 11 to 29. Data from a breadboard model is presented. The entire unit, although primarily intended to meet the requirements of space, performs equally well as a routine laboratory analyzer. The horizontal, stationary nature of the specimen holder suggests several specific applications.

Last year at this conference we submitted a preliminary report on an X-ray powder diffraction round robin sponsored by the JCPDS-ICDD. This round robin was designed primarily to study the intensities of diffraction lines found by users in routine work. At that time only a portion of the data had been analyzed, and we reported initial findings on the α-Al2O3, and Zn0 /CaCO3 samples. These included studies on counting statistics, resolution, and the effect of software on intensity precision. Since that time, all the data from the round robin has been entered into Lotus 1-2-3 (*) spread-sheets and numerous additional tests have been carried out. This paper discusses some of the more interesting findings. A complete paper on all of the tests performed is in preparation for submission to the "Methods and Practices Manual" published by the JCPDS-ICDD.

One of the most important applications o£ XRF in the oil industry has been in the analysis of oil additives which range from Mg to Ba. In such a low atomic number, hydrocarbon matrix, small variations in the additives cause pronounced changes in the average atomic number of the matrix and hence give rise to strong interelement effects. In recent years a number of mathematical methods have been developed to correct the measured X-ray intensity of the analyte litie for these considerable effects. This paper describes a method for the determination of Zn,Ba,Ca,CI,S,P and Mg in oil additives using a concentration based correction model in which influence coefficients (alphas) are applied.

A new fundamental-parameter program has been developed which corrects for light element absorption based on the mean atomic number of the sample. The mean atomic number, in turn, is determined from the Compton/Rayleigh scatter intensity ratio. The program is quite flexible with regard to the number and the type of standards which may be used. The accuracy and precision of the method has been evaluated with several geological and biological standards. The results are in good agreement with those obtained by some other methods (CEMAS, XRF-11).

Energy-dispersive X-ray techniques can be employed in two different ways for the accurate determination of element concentrations in specimens: (1) spectrometry of fluoresced characteristic X-rays as widely applied in the various modes of the traditional XRF analysis technique, and (2) spectrometry of the energy-differential transmittance of an X-ray continuum at the element-specific absorption-edge energies.

The wafer analyzer has been used to fulfil many applications needs in the semiconductor industry. The prominent features of the XRF method for the semiconductor industry are:analysis of many types of films, e.g., oxides, silicides and metallic alloys, and simultaneous analysis of film thickness and compositions.

In the past, the analysis results of BPSG (Boron-doped Phospho-Silicate Glass) films, with thicknesses greater than 4000 Å, were reported. With the recent increased demand for larger scale and higher quality semiconductor devices (larger than 64 Mbit), more accurate analysis with high precision has been required.

X-ray diffraction studies on radioactive materials are reviewed. Considerable emphasis is placed on the safe handling and loading of not-too-exotic samples. Special considerations such as the problems of film blackening by the gamma rays and changes induced by the self-irradiation of the sample are covered. Some modifications of common diffraction techniques are presented. Finally, diffraction studies on radioactive samples under extreme conditions are discussed, with primary emphasis on high-pressure studies involving diamond-anvil cells.

XRF can be a powerful tool for quantitative elemental analysis-it can also be a big headache. The problem is, of course, that to perform a proper quantitative analysis one needs to first develop a good matrix correction model to convert the measured line intensities to concentrations. For empirical models, aside from the inherent difficulties in optimizing a set of interelement correction coefficients, the commercially available computer controlled spectrometers have in the past either provided rather poor regression analysis programs with their software or none at all. The reason for this has been the rather limited core size of the online computer and the lack of fast efficient mass storage facilities such as floppy disks.

Various sample preparation methods for Energy Dispersive X-ray Fluorescence (EDXRF) analysis of Portland cement were compared in order to evaluate improvement in analytical accuracy and precision. Sample preparation requirements for EDXRF are slightly different than for Wavelength Dispersive X-ray Fluorescence (WDXRF), and the methods commonly used in WDXRF are not optimized for EDXRF. Primarily, the work focuses on techniques for producing a fused sample with the lowest practical concentration of lithium borate flux. Determination of minimum detection limits were made from samples with varying proportions of flux in order to evaluate analytical optimization. Ease and reproducibility of preparation of the sample was also considered.

An IBM 1800 time-sharing system is used in our X-ray laboratory to control a four-circle diffractometer for structure research, several powder diffractometers, a pole-figure goniometer and a microdensitometer along with other instruments outside the diffraction area. A survey of the computer system is given and the hardware necessary to automate the diffractometers is discussed. The computer supervision ranges from simple data-logging with a minimum of control to complete control of all actions depending on the diffractometer and the requirements of the experiment. Also described is the use of the computer to process the data and to perform background jobs.

X-ray diffraction studies have generally used low current, low voltage X-ray tubes (e.g., 50 mA, 50 kV). Consequently, exposure times ranging from seconds to hours have been required, limiting X-ray diffraction techniques to the study of essentially static situations. Using such an X-ray source with a very high speed detector, R. E. Green was able to reduce the exposure time for laue patterns of aluminum crystals to a minimum of 0.003 sec. Nanosecond exposure and pulse timing are required for certain events, e.g., X-ray diffraction study of material under shock compression. Q. Johnson achieved this by using a low voltage, very high current flash X-ray source (approximately 50kV, 50kA, 30 nsec). However, such a system is difficult to build and to synchronize, and is not commercially available.

Published X-ray yield data, particularly the recent work of J. W. Motz, indicate that both continuum and characteristic X-ray yields increase rapidly with electron energy, reaching a maximum for an electron energy ranging from 150 keV for titanium to 300 keV for copper to nearly 1 MeV for molybdenum.

To take advantage of this property, a 300 kVp, 30 nsec pulse, 5 nsec jitter flash X-ray system has been built which appears to meet the intensity and timing requirements for single pulse laue or Bragg diffraction studies. System design, calculated output and initial tests are represented.

Sampling is a necessary part of the chemical analysis of particulate matter where the objective is to characterize bulk properties since it is usually undesirable or impossible to test an entire lot. The sample must be a miniature replica of the bulk material at least in respect to those features being tested. In other words, the sample must be representative to permit extrapolation from the sample to the bulk.

There is error associated with sampling particulate material, but this sampling error is only one component of the total error associated with an analytical result. Sample preparation and determination of the property being tested are two other major sources of error, These three errors combine as the squares of their standard deviations, i.e., their variances, to produce the total analytical error. Very often, sampling error is the largest of the three and, therefore, contributes a disproportionately large share to the total error.

A two-crystal spectrometer employing a Cole polarizer made from a germanium crystal as one of the crystals is described. Experimental tests show that placing the polarizer crystal in the second position markedly improves the degree of plane polarisation, in full agreement with the predictions of the dynamical theory of X-ray diffraction. Tests indicate that the twice-diffracted beam h better than 95% plane polarized. The angular resolving power of the instrument is comparable to that of conventional two-crystal spectrometers. The almost wholly planepolarized monochromatic X-radiation, moreover, permits certain tests to be carried out far more effectively than is possible with partly polarized X-ray beams.

The fluorescent excitation of long-wavelength X-ray spectra is reviewed with respect to X-ray tube target element, inherent filtration, and optimum kilovoltage. A demountable X-ray tube vacuum spectrograph designed for the determination of the light elements is described. Operation of this instrument with both secondary and combined primary—secondary excitation is evaluated. Examples from the literature are cited to show the feasibility of direct electron excitation of longwavelength spectra.

The diffractometer employs dual fixed detectors and a moving, vertically mounted X-ray tube. Lattice strain is measured in two specimen directions simultaneously. The drive has three concentric shafts; the outer driven by a cone drive worm and gear; a middle fixed shaft supporting the detectors and an inner shaft geared in a 1:2 ratio carrying the specimen mount. Scanning angles are measured to an accuracy of ±0.001°. A large range of specimen sizes can be accommodated.

A system for the calculation of first-order influence coefficients for any element in any matrix is described in detail. Influence coefficients for either K or L spectra can be evaluated by the method described.

Current methods of measuring bone mineral content In vitro are either inaccurate or measure density in non-intuitive units. A recently developed system overcomes these difficulties by utilizing the Compton scattering of photons from bone. Two sources of monoenergetic photons with related properties are required. The range includes energetic x-rays and low energy gamma rays. This study analyzes a number of the possible nuclide source combinations, and reports experimental results accomplished with a 153Gd-170-Tm combination. In vitro measurement of the density of ox bones by this method agreed with Archimedean measurements within three percent.

Thermal analysts have exploited the sensitivity of carbonate mineral decomposition to furnace atmosphere as a diagnostic tool for identifying and quantifying these minerals in mixtures and solid solutions (1-3). However, thermal analysis techniques alone cannot reveal information about the reaction products after each thermal event. In-situ high temperature x-ray diffraction is one technique that can identify these products. Using this technique, Kissinger et al. (4) identified the reaction products of the thermal decomposition of reagent grade FeCO3 (siderite) and MgCO3 (magnesite). However, the thermal behavior of analytical reagent grade carbonates differs from natural minerals (1). Milodowski and Morgan (5) used in-situ XRD to investigate the thermal behavior of the dolomite-ankerite series.

Basic lead azides are obtained by the slow thermal decomposition of PbN6 at temperatures up to 200°C in oxygen, argon, and air containing varying amounts of moisture. The decomposition diagrams show several stages due to the formation of different phases, two of which have been separated. One phase can be identified as a tetragonal deformed cubic lattice. Further slow decompositions of the basic lead azide at 250°C lead to tetragonal lead oxide. The structure of the other isolated phase Is of lower symmetry and has not yet been classified. The results of this investigation are also compared with the work of previous investigators.

Most commercially available, automated powder diffractometers include software packages for the determination of d-values from experimentally recorded digitized patterns. While many of these patterns offer great flexibility to the user, indications from a recent Round-Robin Study [1] are that many users are confused as to the correct use of such parameters as choice of step size and counting time, the degree of data smoothing, peak-hunting parameters, setting of background level, and the consequences of background subtraction and α2 stripping. This paper will reviews these various factors and give some guidelines as to the establishment of optimum conditions.