Plain carbon steels are primarily composed of iron (~97%), but generally have small quantities of carbon, manganese, sulfur, phosphorous and silicon also present. Lead or copper may also be present. The steel industry is in need of an on-line technique of analysis for manganese in these steels. The manganese concentration of these steels varies from 0.3 to 1.5%. A technique is presented for the rapid analysis of manganese in carbon steels using energy dispersive x-ray fluorescence spectroscopy. It is capable of determining the manganese content of a carbon steel in. less than 30 sec with an uncertainty of less than 0.05% manganese. Because this method can analyze a steel from a distance of two feet, it should be possible to adequately protect the x-ray fluorescence spectrometer from the environment even when analyses are made of hot steel ingots at temperatures ranging up to 2400°F.

Recently developed, miniature, steady state, field emission tubes are finding application in several areas of x-ray analysis. These tubes require only a high voltage, low current power supply to produce relatively intense beams of x-rays. Since anodes can be fabricated from almost any element, and since the tubes can be operated at potentials up to about 70 kV, many different output x-ray spectra are available. Miniaturized battery operated x-ray sources of this type, occupying a volume of about one liter, have several advantages over radioisotope sources. These include cost, safety, and controllable output spectra and intensity. X-ray sources for energy dispersive fluorescence analyzers are designed so that no scattered characteristic radiations will interfer with the analysis of the sample fluorescence. Sources which are essentially monoenergetic can be fabricated for use in non-dispersive x-ray fluorescence analyzers. Because of the intensity and safety of the field emission tubes, such analyzers can be made which are sensitive while compact, portable, and inexpensive. In x-ray absorption analysis the measurement of absorption edge jump ratios provides a quantitative measure of sample impurities. Field emission tubes whose output spectra consist primarily of bremsstrahlung are particularly well suited to such measurements. The techniques involved in using these tubes in x-ray analysis are described.

In recent years there has been an increasing awareness of the errors involved in X-Ray line profile analysis which is used to calculate coherently diffracting particle size, local strains and stacking fault probabilities in materials. Here a modified version of a Least Squares Analysis (L.S.A.) of the Fourier coefficients is presented. This method gives a possibility of making new corrections in a more natural and accurate way to the errors in the line profile analysis.

The first error involves the fact that experimentally one accumulates data as a function of θ - the Bragg angle, whereas the Fourier analysis is made in terms of equidistant steps in sin θ, In the L.S.A. the data does not have to be given in equidistant steps of sin θ in order to be analyzed, so that this type of error does not exist at all.

In the L.S.A. there is also no need for the explicit separation of the Kαl component from the total doublet line profile. This type of analysis is taken here one step further and it is shown that one can calculate the Fourier coefficients of each one of two merging lines. Each of these lines may be doublets in themselves and the two series of Fourier coefficients are calculated around the centers of gravity of their Kαl components respectively.

The existence of an extra background which usually affects the Fourier coefficients when calculated by the Fourier transform method does not affect the L.S.A. except for a normalization factor. Here it is shown that this gives the possibility of calculating the strains without errors associated with the extra background.

As a function of self-irradiation, the crystalline lattice of 238(80%) PuO2 is gradually altered. The technique of x-ray line broadening was used to search for changes in the crystallite size and strain in the lattice following an initial annealing treatment. She integral breadth, Fourier coefficient, and variance methods were used to analyze the broadening of the x-ray powder pattern lines. The mechanism of alteration appears to be one of retained strain as no evidence was forthcoming from these techniques to indicate that the material undergoes significant crystallite size change. The strain in the lattice increased from zero at time zero to approximately 0.2% during a 2-year period.

The progressive ordering of a single crystal of Ni4Mo by isothermal ageing at 650°C (transformation temperature = 868°C) has been studied by x-ray line broadening techniques using the Warren- Averbach method employing computer techniques. The long-range-order parameter, antiphase domain size, and internal strains were measured as a function of ordering time and compared with those previously obtained at 700°C. The activation energies for domain growth and ordering were found to be 91 kcal/mole and 44.5 kcal/mole respectively. The rms strain developed during ordering was found to be dependent on the degree of tetragonality of the structure.

All published accounts of the use of Bond's method for lattice parameter measurements have used step-scanning (at equal angle increments) of the diffraction peaks, followed by graphical or computer analysis of the data to locate the peak positions. It has been found that the peaks angles can be determined with little loss in accuracy or precision by manually setting the crystal angle to give a counting rate (observed on a rate-meter) equal to l/2 the peak rate and defining- the peak angle as the average of the angles on the two sides of the peak. Because of the asymmetry of the spectral line, defining the peak in this manner results in a shift of the peak angle from that determined by the mid-chord peak method. This shift can be compensated by determining an effective value of the wavelength based on a silicon standard. Using the method described, a lattice parameter measurement, including mounting and orienting the sample, taking the data and computing the result using a time-sharing computer terminal, can be made in less than 20 mins.

Bremsstrahlung emission from four x-ray tubes operating at 12 to 300 kV was measured. Spectral distributions are given in terms of absolute-photon and energy fluxes. Silicon and germanium semiconductors, sodium iodide scintillators, and a xenon proportional counter were used to measure the spectra. Detector distortions were corrected by assuming an undistorted spectrum, distorting the spectrum with a Monte Carlo computer program, and comparing the results with measurement. The assumed undistorted spectrum was revised until the Monte Carlo calculation gave satisfactory agreement with spectral measurements from all four types of detectors. The effects on the spectra of varying the tube potential, tube current, target aperture, and detector aperture were investigated. Corrections for the intervening material and the solid angle subtended by the detector were applied to obtain the absolute-photon and energy flux from the target. Total fluxes in the L lines, K lines, and continuum are given. X-ray-production efficiencies varied from 0.026% at 12 kV to 1% at 300 kV. The constant of proportionality varied in the range (0.23 to 0.73) x 10-6 kV-1.

Revised tables of x-ray mass attenuation and absorption cross sections have been prepared for the elements with atomic numbers one to 94 at selected wavelengths of interest to spectroscopists, microprobe users, diffraction workers, etc. The tables are derived from an x-ray cross section compilation to be published during the summer of 1971. The new compilation is a revision of a previous work and provides photoelectric, coherent scattering, incoherent scattering, absorption component of incoherent scattering and total attenuation cross sections for 94 elements for the photon energy range 0.1 keV to 1 MeV (0.0124 Å to 124 Å). The cross sections for energies greater than 1 keV (12.4 Å) were determined from experimental attenuation data and theoretical scattering cross sections calculated using form factors and incoherent scattering functions based on a relativistic self consistent field method. For hydrogen, the photoelectric absorption cross sections were calculated exactly. Least squares procedures were used to interpolate and extrapolate for elements and photon energies where no experimental data were found. Cross sections for the energy range 0.1 keV to 1 keV (12.4 Å to 124 Å) were calculated using nonrelativistic, single electron, self-consistent field theory with Herman-Skillman bound state wavefunctions, A brief description is given of the assumptions and methods used in preparing the revised compilation, and estimated uncertainties in the cross section are reported. Examples illustrating agreement between tabulated values and experimental data are given and a comparison is made with values taken from earlier x-ray cross section compilations.

The technique of plotting a complete pole figure composed of data points in both longitude and latitude from 0 to 180 degrees by a computer program is described. X-ray data were obtained by a reflection method from a specimen cut into three sections mutually perpendicular to one another. The computer program calculates each position in the pole figure based on the time rate of change of the tilt angle ϕ and the spin angle α which are transformed into rectangular coordinates.

The advantage of the present technique is to minimize the x-ray intensity loss due to geometric defocusing, since each section of a given specimen is required to tilt not more than 55 degrees. Due to the fact that a complete pole figure is plotted, one is allowed to examine the symmetry or lack of symmetry in a given specimen with respect to a set of references axes.

Using protons in the MeV range as excitation source and a high resolution Si(Li) detector, X-ray emission spectroscopy is shown to be capable of analysing many elements with Z > 15 simultaneously at the 10-12 g level, This work discusses a theoretical lower limit of detection at moderate proton energies and gives examples of possible applications: analysis of the elemental composition of air-borne particles as a function of particle size, oil slick identification, and analysis of water and blood serum.

The analysis of alpha-excited X-rays has been studied as a possible addition to the alpha-scattering technique used on the Surveyor spacecraft for the first in situ chemical analyses of the lunar surface.

Targets of pure elements, simple compounds, and silicate rocks have been exposed to alpha particles and other radiation from a curium-214 source and the resulting X-ray spectra measured by means of a cooled lithium-drifted silicon detector and pulse-height analysis.

Alpha-particle bombardment is a simple and efficient means of X-ray excitation for light elements. Useful spectra of silicate rocks may be obtained in a few minutes with a source activity of 50 millicuries, a detector area of 0.1 cm2 and a sample distance of 3 cm. An advantage over electron excitation is the higher characteristic response relative to the bremsstrahlung continuum. Peak-to- background ratios of greater than 100 to 1 have been obtained for elemental targets. Relative efficiencies of X-ray excitation by alpha particles and by X-rays from the curium source have been determined.

Resolution of the detector system used is approximately 150 eV for the lighter elements. This is sufficient to resolve the Kα X-rays of the geochemically important elements, Na, Mg, Al, and Si in silicate rocks. Although these and lighter elements are analyzed as well or better by the alpha-scattering and alpha-proton technique, the X-ray mode enables results to be obtained more quickly.

The study shows that the addition of an X-ray mode to the alpha-scattering analysis technique would result in a significant improvement in analytical capability for the heavier elements. In particular, important indicators of geochemical differentiation such as K and Ca (which are only marginally separated in an alpha-scattering and alpha-proton analysis) may be determined quantitatively by measuring the alpha-excited X-rays. An X-ray detector is under consideration as an addition to an alpha-scattering instrument now under development for possible use on a Mars-lander mission.

Characteristic x rays have been produced for a variety of samples by bombardment with protons in the energy range from 75 keV to 5 MeV. The experiments were performed with two accelerators. For the low-energy studies (less than 150 keV), a Cockcroft-Walton accelerator was used. The higher-energy studies were done with a 5 MV Van de Graaff. The x rays were measured with high-resolution Si(Li) and Ge(Li) detectors. Yields for the cross section of characteristic K- and L-shell ionizations were measured for titanium, vanadium, chromium, manganeses iron, cobalt, nickel, copper, silver, gold, bismuth, and uranium. The experimental cross-sections have been compared to the theoretical predictions of the Born approximation for an interaction of this type.

Trace element analysis by 4-MeV proton bombardment of samples in the 10-12 gm range has also been performed. Some comments with regard to analysis with these sensitivities will be made.

Proposed experiments in X-ray astronomy require a detector capable of forming a high resolution image of a weak source. An X-ray image intensifier incorporating a microchannel plate (MCP) has been studied as a candidate for this application. Experiments have shown that the device is sensitive to single X-ray photons and has adequate quantum efficiency. Consideration has been given to the possibility of improving the quantum efficiency by deposition on the input surface of the MCP of a material with high photoelectric yield in the wavelength region of interest. Photographs of the output light from the image intensifier show than an X-ray photon detected at the MCP results in a spot on the film of about 60μ M diameter. Since the position of the centroid of the spot could be determined to better accuracy, the device h as sufficient resolution for the contemplated experiment. Detector noise is found to be so low that it would no limitation on the experiment's sensitivity. The image can be retrieved and transmitted to the ground by focussing a television camera on the face of the fiber optic output of the X-ray image intensifier; the data show that a Secondary Electron Conduction vidicon is sensitive enough to se e the output resulting from a single X-ray photon. An alternative technique would sense charge pulses from the MCP on a fine wire grid, avoiding the need for a phosphor and providing superior time resolution and simpler data compression. Since the detector is to be used in a satellite-borne experiment, its space qualification must be established. Two launches on sounding rockets have failed to impair the usefulness of one unit that has been studied over a period of more than a year. A long term test of continuous performance in high vacuum has so far shown encouraging results. A count life test has shown that an MCP can last through detection of orders of magnitude more counts than could be expected in the course of a mission. X-ray image intensifiers appear entirely suitable for high resolution X-ray astronomy.

Considerable work has been undertaken in order to gain an understanding of the mechanisms responsible for the generation of recrystallization textures developed upon annealing of cold-worked metals. Most direct measurements have consisted of measuring the increase in average diameter of the largest grain growing into a polycrystalline aggregate. Experimental measurements of individual boundaries migrating into deformed single crystals, though of a more fundamental nature, have been made by far fewer investigators. This is probably due to the increased experimental difficulties associated with careful control of such experiments. Most previous investigators have made grain boundary migration measurements by the heat-cool-etch method, despite the fact that it has several marked disadvantages. Other investigators have constructed an X-ray goniometer furnace and used it to measure grain boundary migration rates while the test specimen was maintained at temperature. Since there have been no published reports of the use of such a system in the past thirteen years, it must be concluded that the technique was unsuccessful in general.

The system described in the present work is relatively simple in design and extremely simple to use. Not only does it permit absolute measurement of grain boundary position at temperature but it also permits boundary migration measurements to be made of extremely fast moving boundaries. The basic components of the system are as follows. A continuous spectrum X-ray beam is converted by a slit collimating system into a beam which is incident along the entire length of the test specimen. This beam is interrupted by a wire grid just prior to impingement on the test specimen. The test specimen is supported vertically in a furnace maintained at the temperature required for grain boundary migration. The various diffracted X-ray beams pass out of the furnace through a highly reflecting insulating baffle made from very thin aluminum foil and impinge on a fluorescent screen. This screen converts the X-ray image into a visible one which is amplified and recorded using the electro-optical system.

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.

The total soft x-ray emission of an electron-bombarded surface exhibits abrupt changes at the threshold potentials for the excitation of core levels of surface atoms. These features represent the excitation probabilities of the core states superimposed on a smoothly increasing background and can be sensitively detected by differentiating the x-ray emission with respect to sample potential. The application of this technique to the study of surface composition, chemical shifts, and band structure is discussed.

Degraded detector pulses are shown to contribute most of the background in spectra produced by semiconductor-detector X-ray spectrometers. A new guard-ring detector is used with appropriate circuits to reduce background by a large factor. We discuss the sensitivity of the new arrangement with various excitation sources.

Many glass materials can be made more resistant to failure if the surface layers are in a state of permanent compressive stress. For purposes of monitoring production quality at the factory, as well as to verify compliance with specifications before incorporation into special devices, it is desirable to measure nondestructively this stress magnitude. For those glass compositions in which the stress generating process creates a residual, finely divided, and uniformly dispersed crystalline phase (e.g. “Pyroceram“), a stress measuring technique based upon X-ray diffraction has been adapted and successfully used. Lattice spacings for near-surface crystallites are determined under the stressed conditions present in the final glass product. These lattice spacings are compared with values obtained from a powdered sample of the identical glass composition. In the powdered state the induced stress effects are minimal. Hence, the shift in lattice spacings is a measure of the compressive surface stress level attained in the manufacturing process.

It is known that a change in texture may take place in various metals and alloys following cold working, fabrication and recrystallization processes. Such change may be determined by an analysis of the pole figures obtained from the x-ray diffraction data. In numerous occasions, it is analogous to a lattice rotation.

In the present paper, a method is derived to identify the axis of rotation with respect to the starting and final texture of a given specimen. Once this axis is identified, the amount and the direction of the lattice rotation can be accurately determined. The techniques in obtaining a solution by mathematical calculation, and by stereographic presentation will be described. Discussion will be made also of the various parameters which may affect the validity and accuracy of the determination.

The X-ray reflection method according to Schulz is used for investigations of textures in rolled materials. The pole figures are measured either along spirals or along circles. Points of equal intensity are transposed from the record of X-ray intensity to a spiral diagram. Finally contour lines are delineated, pointing out regions of equal pole density. Three ways are known for simplification of the evaluation.

• a) The results of the measurement are stored, evaluated by a computer and the pole figure is plotted. Points of equal pole density are represented by equal symbols (2 ,3 ).

• b) The pole figure is recorded synchronously with the X-ray measurement along circles or spirals. Ranges of different pole density are characterized by different colors (4 ,5 ).

• c) The pole figure is recorded on a photographic film along a spiral. The blackening depends on the measured countrate (6 ,7 ).

An outline on different instruments using photographic registration is given.