Some of the characteristics of X-ray generation by proton bombardment are described. With work still in progress, it has been proven that this method is particularly suitable for soft X-rays >10 Å. Excitation efficiencies equal or excel electron excitation efficiencies, while the resulting spectrum consists of a single characteristic radiation line, but with complete absence of bremsstrahlung. Experimental results, the design of an instrument, and some applications are discussed.

The photons resulting from the interaction of beta particles and matter have a certain complexity of origin; but the spectrum is made up, in large part, of two primary components, one of these being the white radiation continuum produced by the external bremsstrahlung mechanism of beta acceleration at the target atom. The second fraction consists of the characteristic K and L X-rays of the target atom. Published beta-excited X-ray spectra are centered about a small fraction of the available pure beta emitters and a restricted group of target materials. Furthermore, intercomparisons between references are difficult, due to an infinite variety of source and detector parameters influencing the data.

This laboratory has begun a comprehensive reference compilation of these spectra, done on a comparative basis and simplified and standardized for sensible cataloging and easy reproduction of the experimental design. The prime purpose is to make available coherent data for many beta-excited X-ray sources in which beta activities, target geometries, and other critical parameters are known, controlled, and constant. Spectral sets for given source-target combinations may, therefore, be intercompared, and application of the beta-excited X-ray may be made with the best possible source-target atom combination.

The spectra are studied by three proportional counters (operating down to the 1 kV energy range) and two standard scintillation crystals, accumulated in a 256-channel analyzer, and are presented in sets (representing one beta source-target combination) consisting of a minimum of eight spectra, six of which represent the most critical transmission target geometry.

Examples of the cataloging of the spectral sets, for the mixture, apposition, and compound isotopic X-ray sources, are presented.

This paper describes the detailed assembly of an X-ray automatic analyzer for the continuous estimation of elemental contents in flowing pulp streams as applied in a concentrator of the Northern Rhodesian Copperbelt. Arguments are given for the selection of electronic components, the programming of operations, mechanical movements, and other aspects concerned with the consecutive analysis of a number of pulp streams of widely different composition and elemental concentration. Details are given of a method of automatic compensation for pulp density and matrix variations using X-ray absorption.

An instrument for soft X-ray selected-area microd infraction has been constructed fulfilling the principles of optimum intensity for given specimen size and resolution, and permitting direct visual beam focusing and alignment for specimen sizes in the 1-10 μ region. The X-ray source is a modified, two-lens, microfocus tube manufactured by Canal Industrial Corporation supplemented by a camera, specimen stage, and incident-light microscope. Target-to-film distance may be adjusted from 50 μ to several millimeters which allows the use of wavelengths as long as Al K radiation in air. The use of soft radiation for microsamples simplifies the collimation requirements and permits shorter specimen-to-film distance for a given resolution. Collimating apertures are punched in foil with etched tungsten points or with the microfocus electron beam. Results confirm the prediction that microsamples do not require excessive exposure times using optimum geometry for source size and camera dimensions.

A new X-ray probe attachment for the standard Norelco Vacuum Spectrograph has been developed. The X-ray optical design is essentially the same as that of the Norelco/AMR Microprobe goniometer, being an Ogilvie-type varying curvature Johann focusing device. A light optical system which allows the examination of the specimen during analysis is incorporated in a prealigned module along with the X-ray beam defining aperture. This arrangement assures a constant relationship between beam and optical field centers. Apertures ranging in diameter from 50–500 μ are provided. Data are presented giving the effective size of the specimen area analyzed using each of these apertures. A detailed description of the component parts of the instrument is given.

X-ray probe accessories for commercial flat-crystal X-ray secondary emission (fluorescence) spectrometers have consisted of pinhole apertures in the primary or secondary X-ray beam. The smaller the aperture the lower the intensity, and apertures having diameters less than approx. 0.1 mm are of real value only for relatively high concentrations of elements having intense spectral lines.

There are two practical methods for increasing the intensity obtained with small apertures. One method is use of curved crystals ; it is applicable to any type of sample. The other method m use of a slit instead of a pinhole. It is limited to samples such as long linear inclusions ; sections of coated surfaces, diffusion couples, and metal-to-metal and metal-to-ceramic interfaces; and other layered structures where composition varies in a direction normal to the layers, but not along any one layer. The slit also has several other disadvantages that do not apply to the pinhole. However, when used with samples of the proper type, the slit has two outstanding advantages : Increased sensitivity and statistical precision are realized by replacing a pinhole of a given diameter with a slit of the same width ; alternatively, improved resolution is realized without loss of intensity by replacing the pinhole with a slit of smaller width. Moreover, the slit can be installed on a commercial X-ray spectrometer quickly and conveniently, and often allows useful X-ray probe work to be done on samples for which pinhole apertures would be inadequate.

A slit probe of the type already described by the writer has been improved and evaluated on a General Electric X-ray spectrometer equipped with a curved crystal. The improved accessory has been applied to studies of several metal-tometal and metal-to-ceramic systems. Some of these studies are discussed in detail.

Standard X-ray fluorescence spectrogmphs are capable of measuring elements in areas as small as ⅛-in. diameter, while an electron mitroprobe specialises in areas less than 10 μ. Frequently, a sample of an intermediate size (0.1 mm to 2 mm) requires analysis, so an attachment was designed for Philips Electronics Company equipment. Reasons for its design, sensitivity of the system, and several metallurgical examples showing its versatility are discussed in the report.

Chemical analysis by the X-ray fluorescence microprobe technique offers potential means for the determination of compositional differences arising from the segregation of elements during the solidification of metals. The dimensional scale of the probe is expected to be suitable for the study of macro segregation and, in coarse-grained cast materials, of interdendritic micro segregation.

This paper describes preliminary work carried out to establish analytical sensitivity in respect of some minor constituents present in homogeneous steel samples of known composition. The significance of the results is discussed in relation to the problems of segregation in steel, and it is concluded that the Siemens Kristalloflex IV equipment needs to be adapted for fully focusing operation to achieve the sensitivity required for this work. Details are given of the work so far undertaken in this direction.

Methods and instrumentation have heen developed for the extension of X-ray fluorescence analysis into the light element region, magnesium through beryllium. Examples of current values for the minimum detectable limits for these elements and associated instrumental parameters are presented. Some specific techniques are described for the use of an ultrasoft X-ray vacuum spectrograph, for the development of large d-spacing multilayer analyzers, and for the construction of thin window systems.

Analyses performed have been to determine the feasibility of using pyrolytic graphite (PG) as an X-ray analyzing crystal. Pyrolytic graphite is formed by the pyrolysis of a hydrocarbon, which yields a hexagonal structure graphite with a high degree of anisotropy. After annealing, the anisotropic properties are enhanced even more. For most applications, the intensity and resolution are not as good as with, the best analyzing crystals; however, the extreme durability of pyrolytic graphite makes it a feasible X-ray analyzing crystal.

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.

Large single crystals of ammonium dihydrogen phosphate (ADP) have been grown from solutions of reagent grade materials by means of precisely controlled temperature programs. We have studied the perfection of these crystals by means of double-crystal rocking curves and diffraction topographs. In the course of this study, effects associated with various techniques of sectioning and polishing specimens from these crystals were examined. A combination of string sawing and chemical polishing procedures produced specimens exhibiting the best diffraction characteristics. Results obtained from surfaces so prepared are tentatively taken as being characteristic of the bulk crystal and may be interpreted in terms of longrange strain fields and imaging of both emergent and nonemergent dislocations. In some specimens, regions of 1 cm2 or more have been found to be free of defect images and to have uniform reflectance.

The perfection of some specimen pairs and the intrinsic properties of certain reflections suggest their possible application to spectroscopic problems. Some crystal pairs cut parallel to (101) planes have exhibited physical resolving powers of 104 at 8.3 Å; others cut for the 600 reflection have given 4 x 105 at 1,5 Å, These crystals deteriorate on exposure to moist laboratory air and preservation techniques had to be employed.

The diffraction of X-rays by multilayer stearate soap films has been studied as a function of (a) the number of diffracting layers and (b) the bivalent metal present. Both “Y” and “X” type structures have been built and analyzed with Al and C Kα radiation. The measured diffraction efficiency is compared with that predicted theoretically and with that obtained from a single crystal such as potassium acid phthalate.

An ultrasoft X-ray spectrograph employing a demountable, water-cooled, cleanable X-ray target will be described. The effects of the spectra emanating from various target materials, operated under several conditions, on the efficiency of excitation of C K radiation will be discussed.

In the microprobe, lead stearate decanoate multilayer analyzers have proven to be practical components for X-ray spectrochemical analysis of the light elements. Better controlled techniques in the deposition of the layers have already produced analyzers yielding improved peak to background ratios as well as higher counting rates. Operational techniques, optimizing instrumental performance, will be discussed. Analytical data on the elements fluorine through boron, obtained with a modified commercial microprobe, will be presented.

Several binary systems of uranium with lighter elements (atomic numbers of 6 to 26) have been analyzed in an ARL microprobe analyzer using conventional X-ray techniques and also by sample-current measurements. The techniques of the analysis, the parameters employed, and the results obtained are discussed.

The field of electron probe microanalysis has rapidly spread from metallurgy, geology, and biology to many allied fields. It is the purpose of this discussion to cover an application that has not received much attention—namely, the study of relay contact surfaces with this technique.

In this case, many of the problems encountered are somewhat different, but the ultimate results are quite gratifying. Sample preparation is greatly simplified inasmuch as the surface condition is of prime interest and absolutely no preparation is a prerequisite. Unfortunately, this does lead to some problems of sample mounting and makes the interpretation of results more difficult. Examples are given of the types of information that can be obtained on the substrate materials as well as the finished plated contacts.

Wavelengths and intensities are reported for the K series of magnesium, aluminum, and silicon, using primary excitation. Included in the tabulation for magnesium and aluminum are the diagram lines α1α2 and β and the nondiagram lines α', α3, α4, α5, and α6. Data are given for the Si K spectral lines α1α2, β, α3, and α4, Spectra are shown and line positions and intensities are detailed using both metal and oxide as the X-ray source. Significant differences are seen between metal and oxide spectra especially in wavelength and shape of Kβ, and large changes are noted in the intensities of some satellite lines. Spectra from a number of aluminum intermetallic compounds are discussed, including line positions, satellite line ratios, and line shape. It is shown that the spectra fall into three predictable groups; good conductors; poorer conductors; and semiconductors and insulators. Structurally similar compounds give similar spectra. For instance, line positions, shapes, and intensities are nearly identical for NbAl3 and TaAl3. It is not possible to correlate spectra with aluminum coordination number, and previous work using Kα, where secondary excitation was used, could not be reproduced using primary excitation. Possible reasons for this disagreement are discussed.

Data are presented from several systems for which the emitted X-ray intensity goes through a maximum as accelerating voltage is increased. An attempt is made to systematize the data in terms of absorption, wavelength, and atomic number. A very simple model, analyzed graphically, is capable of displaying many of the features of the experimental data.

An X-ray diffraction system is under development for remote analysis of lunar rocks from an unmanned, soft-landed spacecraft. The objective of this experiment is the identification of rock-forming phases and estimation of their abundances, compositions, and other data which are indicative of the nature of genetic processes on the moon. A 2:1 scanning parafocusing geometry was successfully miniaturized for this purpose by W. Pavrish, and a complete diffraction system, based on the design is in preparation. The diffract ometer including high-voltage power supply weighs 18 lb, occupies 0.9 ft3, and requires 56 W of continuous power. A sample acquisition and preparation system will be an integral part of the diffractometer. Diffraction analyses of a rhyolite, basalt, and chondritic meteorite are given as examples of the capabilities and limitations of rock analysis by this method.