The plasma focus device, a form of linear pinch discharge, produces an intense x-ray and neutron (D2) burst from a magnetically heated dense plasma. Rapidly changing magnetic fields at pinch time generate large axial electric fields which accelerate electrons and ions. In the experiments reported here the x-ray production during the plasma pinch of a 96 kilojoule (at 20 kV) plasma focus device was measured.

The purpose of these experiments was to evaluate the energy in accelerated electrons in the plasma focus device and to learn how to enhance these electron hursts. Well focused, megampere electron beams at a few hundred kilovolts, lasting less than 10 nanoseconds have applications in fusionable pellet heating experiments. (1) X-rays were monitored to evaluate these electron bursts using a defocusing bent crystal spectrometer, doubly diffused silicon (PIN) detectors, with Ross filters, thermoluminescent dosimeters (TLDs) with filters, and x-ray pinhole photography.

Thermoluminescent dosimeters indicated maximum x-ray yields of 140 joules above 3 keV at 57.3 kilojoules stored energy (16 kV) for a conversion efficiency to x-rays of 0.2%. 40 joules are above 60 keV and 15 joules above 80 keV. The hard x-ray pulse typically rises in 3 ns and frequently has a pulse width less than 10 ns. The low energy x-ray spectrum consists almost entirely of lines from the high Z anode insert, and the high energy spectrum is characteristic of a nonthermal power law distribution with an exponent of 2.2 ± 0.8. Peak hard x-ray production is obtained at 1 torr deuterium in contrast to peak neutron production (3 x 1010) at 5 torr. The addition of argon reduces total x-ray yield and increases the relative fraction of soft x-rays.

These measurements suggest that the plasma focus produces 1200 joules of electrons with an average energy of 150 keV, in 10 nanoseconds with a stored energy of 57.3 kilojoules. This is a power of 1.2 × 1011 watts and power density of 1.5 × 1013 watts cm−2.

Existing theories of X-ray absorption-edge fine structure do not adequately explain details of spectra observed for solids. However, the possibility that X-ray absorption spectra might eventually be used as tools for the characterizatiori of new insulator materials has prompted the study of an extensive selection of simple oxides of known chemistry and structure. The complete K absorption fine structure has been measured for some forty simple oxides of six elements of the fourth period. The L absorption-edge spectra have been measured for metallic lead and several lead oxides. The several isostructurat and polymorphic sets included among these oxides, as well as the Magnéli phases for three of the elements, have made it possible to study the effects of valence, coordination number, electron configuration, and crystal structure. The applicability of current theories of the fine structures are discussed in the light of these findings. An automated single-crystal spectrometer is described.

Strontium appears in the earth's crust at a concentration of about 400 ppm and in sea water about 8,1 ppm. Consequently, all living forms have evolved in the presence of this alkaline earth and have incorporated it in their tissues. The exact role of Sr in the human body remains ambiguous (1), even though Sr has been extensively studied with reference to the radiation hazard from 90Sr (2).

Metabolic behavior of Sr, in some aspects, is similar to that of Ca (3), but substantial dissimilarities between these two are also well recognized (1,4). It has been suggested that Sr stimulates the formation of bone matrix. At higher concentrations, however, it interferes with calcification mechanism of the bone matrix (5).

An effective technique using grazing-incidence X-rays and asymmetric-Bragg diffraction (GIABD) for the characterization of crystalline phases on surfaces and structural depth-profiles in thin films is described. The application of the GIABD using both X-ray and synchrotron radiation sources for the analysis of an iron-oxide magnetic thin film previously reported to have an unexpected magnetically-dead layer is discussed. The X-ray diffraction analysis using the GIABD and the conventional θ-2θ scanning techniques detected an anti-ferromagnetic hexagonal α-Fe2O3 on the surface and a ferromagnetic tetragonal γ-Fe2O3 in the bulk of the film, respectively. The synchrotron diffraction analysis using incident angles below and above the critical angle of total reflection quantitatively determined the structural depth-profiles of α-Fe2O3 and γ-Fe2O3 in the film.

Use of a reference crystal to condition the beam in the double-axis diffractometer permits the Bragg peak width to be reduced to the correlation of the two crystal reflecting ranges. Some recent applications of double axis diffractometry to the study of heteroepitaxial layers are discussed. The advantages of multiple reflections for beam conditioning and the four reflection DuMond monochromator are examined. Glancing incidence and exit diffractometry permits the study of very thin layers, down to a few tens of nanometres in thickness and both synchrotron radiation and skew reflections can be used to tune the glancing angle close to the critical angle. Recent applications of triple-axis diffraction, where an analyzer crystal is used after the specimen, to the study of very thin single epitaxial layers and multiquantum well structures are reviewed.

The use of target current measurements in the electron microprobe for quantitative analysis of binary samples has been proposed by several authors. However, the equations proposed for calculations as well as instrumental conditions differ considerably. The present paper relates the target current measurements made with the Applied Research Laboratories microprobe to the backscatter coefficients determined independently. Equations for analyzing binary samples as well as applications to line scans and concentration mapping are given.

The back-reflect ion double-scanning diffractometer method, by which lattice parameters can be measured with a reproducibility of one part in 150,000 has been applied at liquid helium temperatures. A cryostat attachment is described which enables diffraction profiles to be scanned on both sides of the primary X-ray beam up to 163°, 2θ. Alignment errors may, thus, be eliminated by measuring the included angle 4θ between respective Bragg reflections. The method is illustrated by measuring the lattice parameters of the I.U.Cr. standard specimens of silicon and tungsten at various cryogenic temperatures.

The application of x-ray topographic techniques to the measurement of stress in thin, films is discussed. Quantitative measurements of stresses in thin films deposited on semiconductor substrates, such as silicon, are also discussed. Double crystal and single crystal techniques are used for such measurements. Both techniques are applied to the measurements of stress in silicon oxide, silicon nitride and polycrystalline silicon films on silicon. The doubly crystal technique is useful for measurements of stresses as low as 109 dynes/cm2 in films only 1000A thick. The single crystal technique is less sensitive by one order of magnitude. The advantage of the single crystal technique is its simplicity and speed. It is useful for large scale measurements as encountered in the manufacture of silicon integrated circuit.

Residual strains and stresses were determined in both phases of a hot pressed α-Al2O3 composite containing 25 wt % β (cubic) SiC whiskers using conventional x-ray diffraction and profile analysis. Both phases in this composite were randomly oriented as confirmed by back reflection pinhole photographs. The reflections found most useful with Cu Kα radiation were: 511 + 333 for β-SiC at -134° 2θ and 146 for α-Al2O3 at -136° 2θ. The peak shift and broadening observed in these reflections, relative to the starting powders, were largely due to the two phases mutually constraining each other elastically. This was confirmed by the reversal of the peak shift and most of the broadening in the SiC reflections when the Al2O3 matrix was etched away. Using the method of Cohen and Noyan, it was found possible to separate the macrostresses from the microstress components in each phase. The microstresses were largely hydrostatic; of the order of 895 MPa (130 ksi) compressive in the whiskers and 370 MPa (54 ksi) tensile in the matrix. The macrostresses were ~79 MPa (11.5 ksi) tensile.

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.

Many advanced semiconductor device designs require the growth of heteroepitaxial layers with lattice parameters differing by up to a few percent with respect to the substrate. X-ray diffraction offers a nondestructive method of determining the extent of relaxation. This paper discusses the sensitivity of x-ray techniques to small amounts of relaxation, describes how relaxation is measured in cubic materials for layer on (001) substrates and suggests nomenclature for the case of asymmetric relaxation.

An x-ray fluorescence analysis method applicable to the case of fluorescent spectra excited with monoenergetic x-rays has been developed. The technique employs a minimum number of calibration steps using single element thin film standards and depends upon theoretical cross sections and fluorescent yield data to interpolate from element to element. The samples are treated as thin films and corrections for absorption effects are easily determined- Enhancement effects, if not negligible, are minimized by sample dilution techniques or by selective excitation.

A precise and practical method for the determination of d-values and lattice parameters from digital diffraction data is described. Systematic errors are corrected mathematically during a d-spacing / lattice-parameter least-Squares refincment process making it unnecessary to use internal standards. X-ray and synchrotron diffraction data of an ICDD alumina plate obtained with a wide variety of experimental conditions and analysis parameters were used to study the precision in the derivation of d-values and the accuracy in the determination of lattice parameters. Results showed that the precision in determining d-values was high with |Δd/d|avg ranging from 2x105 to 4x10-5. Using the results obtained from the high precision XRD analysis as a reference standard, the accuracy in the lattice parameter determinations from the synchrotron diffraction data reached the l-2x10-6] range. Lattice parameters, with an accuracy in the high 10-5 range, were also obtained using parameters commonly used in a routine XRD analysis such as a wide RS (0.11°) for high intensity, peaks only in the front reflection region, no Kα2 stripping, and a Single 2θo parameter for systematic error corrections.

Magnitude and distribution of residual stresses around cold-worked holes in 1045 steel were measured with the Fastress automatic stress X-ray analyzer. Permanent interferences between 0.8% and 6.2% at a hole with 0.5 in. diameter produced compressive hoop and radial stresses up to -60 ksi and -40 ksi respectively. The size of the zone with compressive stress is significantly wider than existing analysis predicts.

At grazing incidence all X-ray techniques become surface sensitive. Far below the angle of total reflection the X-rays penetrate only 20 to 70 Å into condensed matter. X-ray reflectivity measurements give the density and the thickness of layers on substrates and the roughness of external and internal interfaces. The diffuse scattering in the vicinity of the specular reflection gives, besides the interface roughness, also the height-height correlation of the surface. From the angular dependence of the fluorescence intensity, emitted as a consequence of X-ray absorption, the depth profile of the absorbing species can be deduced. Artificial periodic multilayers give rise to Bragg reflexes and to standing X-ray wave fields, the angular dependence of which give the distribution of atomic species in the periodic stack. A number of examples illustrate the possibilities of the technique.

X-ray spectrometry is an old technique dating back some sixty-odd years and although most of the early interest revolved around the qualitative aspects of the method it wasn't long before attempts were made to obtain quantitative data. One of the first recorded attempts was that by Coster and von Hevesey who in 1923 accurately determined the amount of hafnium in zirconium using tantalum as an internal standard. Glocker and Schreiber were the first to attempt calculation of X-ray characteristic line intensity from first principles although no attempt was made at that time to correct for secondary fluorescence. In von Hevesey's book, “Chemical Analysis by X-Rays,” published in 1932 , a whole chapter is devoted to what is called “Disturbing effects and their avoidance.” Among the effects discussed were primary and secondary absorbtion and third element effects. Matrix correction equations were developed although most of the quantitative work at that time was done using internal standards.

Theories explaining the dependence of characteristic X-ray intensity on particle size in heterogeneous materials are reviewed. Several discrepancies between the theories and between theory and experiment have been discovered. A new theory is proposed based on a more rigorous physical model. It is shown to explain well-established phenomena at least as precisely as do previous formulae. Excellent agreement is also obtained with new observations of the variation of characteristic X-ray intensity with packing degree and, in samples consisting of only one type of particle, with both packing degree and particle size. The same basic theory also predicts the observed variation of X-ray Intensity backscattered from or transmitted through a sample. It is also shown that similar results are obtained with particles suspended In a homogeneous matrix, such as an aqueous slurry.

The design of an x-ray detector suitable for use in tomography must be optimized for the intended application. Recently, we have developed microtomography applications that require resolution of -1 micron in three spatial dimensions and -1% statistical accuracy in the reconstruction of attenuation coefficients for each cubic micron volume element in a .1 cubic mm specimen. X-ray detector design for these applications must take into account much more than just the demanding micron spatial resolution requirement. The detector must be optimized to take into account the physical properties of the specimen to be measured, the characteristics of the x-ray beam available to probe the specimen, signal to noise ratios needed in the reconstructed image and requirements of the data processing algorithm. In addition, the detector design should be sufficiently flexible to allow significant variation in the kinds of specimens that can be examined.

The Pennsylvania State University has developed and tested a miniature x-ray instrument for the measurement of residual stress (strains). The stress head including x-ray source and detection surface is approximately four and one-half inches long and can be inserted into an orifice less than two and one-half inches in diameter. This head is on the end of a several-foot long cable and is extremely manipulatable.

The instrumentation design is based upon a unique position sensitive scintillation detector which ie capable of applying the single-exposure x-ray stress measurement technique. Total lapse time data collection periods for aluminum alloys are less than ten seconds with x-ray tube powers of 120 watts. Results from a four-point bend test on an aluminum alloy specimen showed excellent precision. The configuration of the instrument and the procedures for its application are described.

XRF has become over the years a method of choice when dealing with elemental analysis of large quantities of samples. Geochemical analysis pushes the technique to its limits because of the large number of samples to be analysed as well as the lower limits of detection required for many trace elements of geochemical and economic importance. The Analytical Geochemistry Group at the British Geological Survey (BGS) has access to a wide variety of methods for instrumental analysis. Instrumental methods for inorganic analysis include x-ray fluorescence as well as DC arc emission spectrometry, atomic absorption spectrometry, inductively coupled plasma optical emission spectrometry (ICP-OES) and inductively coupled plasma mass spectrometry (ICP-MS). X-ray fluorescence, however, is the technique of choice when it comes to the routine analysis of large numbers of solid samples. The XRF section at BGS currently runs three sequential spectrometers (one PW1480 and two PW2400s made by Philips Analytical X-Ray). In this paper, some aspects of the method of sample preparation and the calibration of the spectrometers for the analysis of the trace elements are discussed.