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A new x-ray tomographic method to image a particular element is proposed and described. This method uses an x-ray tube spectrum and a pair of balanced filters with absorption edges just above and just below the edge of the desired element. The proposed system consists of a microfocus x-ray tube as an x-ray source and a 2-D detector array to collect projection data. The main advantage of this system over traditional differential tomography using two monoenergetic sources is its easy application to fan-beam or cone-beam geometry without reducing too much its intensity. ART is used to reconstruct the 3-D images from the simulated projection data generated by a Monte Carlo program. Computer experiments demonstrate the feasibility of selective imaging in cone-beam geometry.

A method of imaging the composition and density of industrial samples by combining information obtained from a transmission tomographic scanner and a projective Compton scatter imaging system is described. A reconstruction algorithm with attenuation and multiple scatter correction capabilities is developed around a detailed model of the Compton scatter imaging system. Monte Carlo simulation is used to generate realistic data for the determination of model parameters, the analysis and design of device components, and for testing the reconstruction algorithm.

We report the first observation of the Cabibo disfavored semileptonic decay mode D+ → ρ(770)0 μ+v and measure its decay rate relative to the Cabibbo favored mode D + → K ∗ (892) 0 μ + v to be Λ(D + → ρ(770) 0 μ + v Λ(D + → K ∗ (892) 0 μ + v) = 0.044 0.031 −0.025 ( stat. ) ± 0.014 ( syst. ) . The results are compared to theoretical predictions and to previous experimental upper limits.

Composition imaging of industrial samples has been reported using dual energy and multiple energy transmission computed tomography [1,2]. The simplest approach utilizes monoenergetic sources to obtain tomographs of a sample at two different energies. Each tomograph represents the linear attenuation coefficient distribution of the sample at the given source energy.

The great advantage of the atomic force microscope and related technologies (tunneling current, near field optical, tips that oscillate vertically or laterally, etc.) has been simplicity of design. Vertical deflection of a reference tip on a cantilevered probe is detected by light scattering and used to shift the sample in the z direction to restore tip position. The output is generally in the form of surface images rather than measurements with high dimensional accuracy. Atomic scale resolution is achievable but lower magnification imaging is more difficult.Piezo devices used for x-y and z axis control have a limited range of motion and are noisy, nonlinear and subject to creep. Piezo displacement is not simply a function of voltage, or of the time integral of current, but depends upon many factors including rate and distance of motion, and internal resistance and capacitance in the device. It is possible in principle to calibrate such a system using a reference grid standard, but even this is highly dependent on scanning speed (different in the x, y, z directions) and will not provide quantitative z information.

An X-ray fluorescence program, similar to NRLXRF2 has been written by John Criss to fit into the DEC LSI-11 32K computer with floppy disk system. EDAX has combined the new version with our own software to create a set of FORTRAN programs, called “XRAY 95” to use with the new EDAX EXAM 9500 energy dispersive X-ray fluorescence system. The XRAY 95 program employs both fundamental-parameter equations and influence coefficient equations to optimize the matrix corrections for multicomponent samples. It is an extremely versatile program, using whatever reference standards the user provides and supplementing them with physical theory. The result is a practical approach to fast, accurate analysis.

It might seem at first glance that quantitative models relating intensity to concentration should be identical for energy - or wavelength - dispersive fluorescence analysis. In both cases the interelement effects that complicate the use of simple linear calibration curves occur in the specimen, at which time the X-rays are not yet aware of which kind of detector will be used to count them. This can be true in some cases, but not in general.

Instrument specifications as published by manufacturers generally include values for stability of various parameters or components. For an X-ray fluorescence system, a typical example might be the generator high voltage stability (perhaps 0.01%). Parameters of this sort are of course of some use in comparing systems, and they may be (and often are) of great importance to the manufacturer as a criterion of manufacturing quality. It is difficult for the user to know how any single one, or combination of these factors really affect the total system performance as it may relate to his application.

Interest in the analysis of inks on paper has come primarily, although not exclusively, from forensic scientists. Two classes of problems are encountered: comparison of inks in different regions of a single document, to detect additions (such as adding a “ty” to your handwritten check for “nine” dollars) made with a visually similar but hopefully compositionally distinct ink; and verification of authenticity in documents (including stamps, stock certificates, currency, etc.) by the presence of specific tag elements in certain of the inks present.

The use of energy dispersive analysis of x-rays (EDAX method) is now well entrenched in the electron column field(l), where more scanning electron microscopes have been fitted with EDAX instrumentation than all of the conventional (wavelength-dispersive spectrometer) microprobes ever made. The principle advantage of the EDAX approach for the SEM user is the efficiency of detection, which permits its use at the low power levels of the SEM. In addition, the simultaneous analysis of the entire spectrum and the lack of focusing restrictions that permits analysis of rough samples are important advantages.

When making a pattern for a solid-state device from a silicon wafer coated with photoresist by the scanning electron beam exposure technique, the positioning accuracy of the pattern is as important as its resolution and dimensional accuracy. A pattern positioning system automated by an electronic computer which is included in the electron beam exposure apparatus type JEBX-2B, is introduced and described. Information conveyed by backscattered electrons from the wafer surface is utilized as a signal which detects the wafer locus and automatically corrects any x-, y-directional and rotational errors. It is shown that the positioning accuracy is within 0.5 µm. It can be improved under some limited conditions.

This research investigation relates to sintered simulation ceramic waste forms of the generic SYNROC compositional type. Though they have been formulated with simulated wastes only, they serve as prototypes for potential hot, processed, crystalline waste forms whose combined thermodynamic stability and physical integrity are considered to render them capable of long-term imobilization of high-level radwastes under deep geologic disposal conditions. The problems involved are nontrivial, largely because of the very complex nature of the radwastes: a typical waste stream would contain more than 31 cation species. When the stabilizing matrix constituents are included, the final batch composition must successfully account (and find substitutional homes for some 35 different cation species. One of the important objectives of this study thus has been to develop a computer-based method for simulating these complex ion substitutions, and for calculating the resultant phase demands and batch formulations. Primary goals of the study have been (1) use of that computer simulation capability to incorporate rationally the radwaste ions from a specific waste stream (PW-7a) into the available SYNROC lattice sites and (2) utilization of existing ceramic processing and sintering methodologies to assure (and to understand) the attainment of high density, fine microstructure, full phase development andmore » other features of the sintered product which are known to relate directly to its integrity and leach resistance. Though improved resistance to leaching has been a continuing goal, time and budget constraints have precluded initiation of any leachability studies of these new compositions during this contract period. 27 references, 15 figures, 6 tables.« less

Solid state lithium-diffused silicon detectors are commonly used as energy-dispersive X- ray detectors. These devices will, however, produce electrical pulses with a height proportional to the energy of electrons (and other particles) as well. We have used a Si(Li) detector with conventional electronics (amplifier, multi-channel pulse-height analyzer) to measure the energy spectrum of electrons backscattering from pure elements with atomic numbers from 12 (Mg) to 92(U).Since the electron beam striking the target also generates X-rays (characteristic and continuum) that are measured by the detector along with the backscattered electrons, and since it is not possible to stop the X-rays from reaching the detector while allowing the electrons to pass, we measured the electron spectrum by difference. Figure 1 shows superimposed, the spectra (for a copper target) of X-rays plus electrons (upper curve) and X-rays only (lower curve), the latter obtained with the use of a magnetic electron trap in front of the detector.

For the high percentage of scanning electron microscopes equipped with x-ray analytical capability, a common mode of operation is the x-ray “dot image” to describe the distribution on the specimen surface of an element of interest. As with the conventional microprobe, this is done by displaying a pulse or dot on the display tube whenever an x-ray with an energy (or wavelength) corresponding to the element of interest is detected. By photographically integrating many of these dots, an image that correlates with other specimen images (e.g. backscattered or secondary electrons) is produced. When very many dots are recorded, the image may take on a continuous-tone appearance but, in general, it is possible to make only very rough qualitative estimates of relative intensity in different areas because the human eye does a very poor job of estimating dot density. Edges or other sudden changes are more easily recognized than gradual variations.