During the past year the NORELCO Autrometer has been modified with respect to several details. Operation with the helium path and flow counter is now possible for work with the soft elements. Rotation in and out of the loading position is automatic so that all that an operator is required to do is to load the specimen holder. The sample or standard in the reading position can be rotated in its own plane for elimination of diffraction effects and other sample preparation problems. Other modifications in the electronics have increased the reliability and ease of maintenance in the production models, A description will be given of this latest unit and data will be presented on the results obtained both with respect to precision and analytical determinations.

An X-ray fluorescence analysis unit has been designed and built especially for the measurement of certain mineral elements in individual biological tissue sections. Such a section may contain in the neighborhood of 10-10 grams of an element of interest, in a concentration in the range of 1-100 p.p.m.

The unit consists of a special high-power X-ray tube with a builtin interchangeable secondary radiator, which irradiates the speciman with the characteristic lines of the radiator element) and a proportional counter and pulse-height analyzer system, which provides analysis of the X-ray spectrum emitted by the specimen. Because the emitted spectrum is greatly simplified by the use of an appropriate radiator element, a diffracting crystal can be omitted, permitting a great increase in absolute sensitivity.

The system is feasible only because of two peculiarities of our biological specimens: they are so thin that matrix effects are negligible, and they consist essentially of a few mineral elements in a light matrix.

Design considerations, calibration procedures, procedures for the analysis of the observed proportional counter pulse-height spectra and results to date will be discussed.

Our laboratory has been interested in the use of the X-ray spectragraph for routine rock analysis within limited rock types. This paper is meant as a progress report and to indicate the direction of our work on amphibolites to others interested ill the problem of rock analysis.

Even with the use of flow counters and pulse discriminators the intensities of the magnesium, aluminum and silicon peaks are quite low and most dilution techniques may not be used. The direct determination of major elements (except sodium) yields results directly comparable to the chemical results for potassium; manganese and titanium in the range from 0: 1 to 3% as the oxides. For iron (10-20%), calcium (8-12%) and silicon (45-52%) the accuracy is 2-3% but for each element occasional samples will be 5% from the chemical values. Aluminum and magnesium yield erratic results.

The use of ratios between elements occurring in. the samples yields slightly improved accuracies. The use of a strong absorber such as tungstic acid (40% by weight) greatly improves the ratios for aluminum and magnesium., without appreciably affecting their intensities. By a combination of the direct and tungstic acid techniques it is possible to attain accuracies of 2-3% with analysis time of two hours. At present we are attempting a combination with an internal standard method to yield greater accuracy.

Fine focus X-ray tubes developed for projection X-ray microscopy can also be used for X-ray micro-analysis. Areas about 10 microns in diameter of thin sections have been analyzed by measuring differences in X-ray transmission, with particular reference to the determination of calcium in biological materials and in minerals. The high intensity of this X-ray point source has permitted micro-fluorescence analysis of similar small areas with high sensitivity and reasonable time. The same electron optical system has been used for micro-emission analysis of rock slices and mineral grains. By scanning the electron beam over the specimen surface and recording either the scattered electrons or the emitted X-rays, a two-dimensional picture can be displayed of the physical features or of the distribution of a particular element respectively. The analysis of a selected, volume of 1 cubic micron in the surface has been obtained by plotting the characteristic line emission spectrum with a crystal spectrometer and proportional counter. The sensitivity is 0. 1% or 10−1 gram. Micro-beam X-ray diffraction has also been used with a stationary X-ray source both for transmission and back reflection with a 10 minute exposure from a 10 micron diameter area.

Applications to nonmetallic specimens such as minerals will be shown and the special techniques required for such specimens described. These include coating the surface with a thin conducting layer and prepho to graphing to map out the areas of interest. Specific examples of copper-iron minerals will be given. Other applications to metallic systems such as mass transfer studies in liquid metal cooling systems will also be shown.

Techniques are presented whereby X-ray spectrographic analyses are carried out on alloys and metallurgical products which enter the Laboratory in the form of drillings, millings, or filings. The techniques described include direct analysis, with and without internal standards. Analysis of high temperature alloys without a aeries of chemically analysed standards by these techniques have greatly extended the usefulness of the X-ray spectrograph.

An X-ray emission spectrographic method of analysis is presented for the determination, of rare earth elements in fractions obtained from bastnaesite ore. The method includes the determination of yttrium, thorium, lanthanum., and the rare earth elements in various complex mixtures. The analysis technique is based upon comparing the samples to synthetic standards approximating the composition of the samples. Working curves are plotted on an absolute intensity basis, with, no correction for background. Examples of working curves and the analyses of typical rare earth concentrates are included. The selection of spectral lines for the various sample matrices is discussed. A special technique is used for samples in which rapid hydration and carbonation occurred.

By analyzing synthetic samples of known composition, the accuracy of the method was determined. The error of analysis was about 3 per cent of the amount present in the range from 5 to 100 per cent and about 7 per cent in the 0.2 to 5 per cent range. A maximum of about 40 samples per day may be analyzed for 7 elements each. The advantages and disadvantages of the method are discussed.

It has been found possible to determine quickly the concentrations of molybdenum and ruthenium in non-radioactive alloys representative of high burn-up reactor fuels by the method of X-ray emission spectrometry. Preliminary steps of chemical dissolution and separation are not required. The alloys, essentially ternaries of molybdenum and ruthenium with uranium, are being studied because they are considered to typify the alloys which will result from cycling uranium fuel elements through the sequence of fabrication, use and pyro.metallurgical processing.

The analytical procedure involves sampling of the ingot by slicing with a silicon carbide wheel at the plane of interest and reducing the surface to the flatness and finish obtained by a five-minute grinding and polishing operation. In the X-ray spectrograph the flat surface is examined for the intensities of its molybdenum and ruthenium K emission lines, with counting times of one to eight minutes. Calibration plots of intensity versus chemically determined weight per cent are established and used for subsequent sets of analyses.

Studies have been made of the application of X-ray spectrography to continuous analysis for process control. To date the most widespread application of fluorescent X-ray spectrography to process control has been in measurement of plating thickness. Realizing that many other processes could use a method of continuous analysis of moving materials, these studies were undertaken.

A modified tube housing and sample holder was constructed so that material could be passed through the X-ray beam, of a conventional X-ray spectrograph at various linear speeds. Detectability versus material speeds were studied for a number of elements in various mediums.

Application of fluorescent X-ray spectrography as a continuous analytical tool looks very promising. Further studies on specific plant problems should provide useful and advantageous industrial applications of the basic information developed here.

The potential of the beta-ray excited X-ray source was evaluated in the search for a small, low energy, planar source for gross apposition studies. Such a. source utilizes the familiar phenomena wherein target impingement by particulate radiation from certain pure beta emitters is utilized for the production o£ useful bremsstrahlung and characteristic X-radiation. Some of the favorable attributes of such a source are; simplicity of design and fabrication, diminutive size, stability, low cost, zero power consutnption and the gamut of synthetic radioisotopes with which they may be powered. This paper deals with the preliminary development of such a beta-excited source for application to apposition radiography as well as with the small, compound source-target.

The design of such a source type is concerned with certain stimulating problems, some of which are; development of adequate photon intensity, reduction of excessive white radiation production, shielding for scattered and spurious radiation, target and source s elf-absorption, Simple illustrations of source-target geometries are reviewed both for compound and separate source-target design. Some resolution studies for the gross apposition source are shown, plus some exposures made with compound sources. The available synthetic isotopes are described and preliminary applications with P32 , Sr90, Y90 and Pm147 sources are outlined. The paper is divided into two portions; one, a brief review of theory and design; two, construction and results for the apposition and compound source.

When two metals are allowed to diffuse into one another, a diffusion aone is formed, the shape of which is determined by the relative diffusivities of the two elements, the time and temperature of the diffusion, and the number of phases existing in equilibrium at the diffusion temperature.

An X-ray absorption technique has been developed to analyze such concentration gradients. This involves the preparation of a thin section from a typical diffusion couple parallel to its axis. This is then scanned with a monochromatic X-ray beam and the transmitted X-rays are measured with a Gejger counter. The intensity of the transmitted beam is determined by the composition of the area in question and the absorption coefficients of the two elements.

The two general uses of proportional counters in X-ray analysis are discussed in the light of advantages and limitations inherent in the type of counter construction. Some effects on spectrographic results and industrial gaging are cited.

The use of the Polychromator (multichannel spectrometer) for X-ray analysis allows choice of the optimum combination of slit width, crystal type, focussing circle radius and detector for each of the elements to be determined by the instrument.

Comparisons will be made of various curved and ground crystals such as quartz, lithium fluoride, sodium chloride and ADP used in a focussing spectrometer. The effect of the width of the entrance and exit slits upon resolution, line intensity and line-to-background ratios will be discussed. Gas filled detectors such as Multitrons, flow proportional counters and Geiger counters will be discussed as to the effect of the filling upon efficiency and upon their use with counting or integrating techniques. Limits of detectability for various elements with optimum combinations of the above components will be reported.

The X-ray microscope is an electrostatic optical instrument employing X-rays for shadow projection to magnify and reveal detailed internal structure of specimens opaque to light or electrons. Its many advantages — high resolving power, greater penetration, large depth of field, and stereographic presentation — make the X-ray Microscope a versatile instrument for industrial research and development. Because the instrument was recently introduced, little information is available on specimen preparation techniques, or types of specimens suitable for study. A few of the many possible applications will be discussed, as well as a brief review of the technical details of the instrument.