Part of the mission of NBS is to disseminate knowledge in the scientific and technical community.To aid in reaching this objective, the Analytical Chemistry Division has sponsored a series of workshops on various topics in analytical chemistry. The workshop topics are chosen to fulfill current needs for detailed discussions on sharply defined subjects in a wide variety of specialist areas.The objective is to bring together specialists from throughout the world to concentrate intensively on a particular subject in order to advance the state-of-the-art.It is often very difficult to achieve this goal at large international meetings where the size and diversity of topics presented often limits detailed discussion of special subjects.Past topics of these workshops and the published proceedings include:Quantitative The workshop format consisted of a keynote talk on each topic followed by extensive discussions. The papers in this volume are based on the keynote talks augmented with some points raised in the discussion.The extensive development of electron beam instrumentation for the microscopy and analysis of samples of diverse scientific interest has resulted in a need for detailed studies of the origin and characteristics of the signals involved. This publication provides a detailed view of one approach to the study of such signals, namely the Monte Carlo technique for electron trajectory calculation.The publication should be of value to the numerous workers who utilize the scanning electron microscope and electron probe microanalyzer. The utility of electron probe microanalysis and scanning electron microscopy is demonstrated by the fact that more than 2500 such instruments costing from $25,000 to $200,000 are now in use worldwide, and more instruments are constantly being added. Moreover, the instruments are at work in fields as diverse as biology, metallurgy, electronics, chemistry, and forensic science.Simultaneously with the development and distribution of the instrumentation, much work has been devoted to the study of electron interactions with solids with the purpose of characterizing the signals which are utilized in microscopy and analysis.One approach which has proven especially useful in both qualitative and quantitative studies of electron interactions is that of Monte Carlo electron trajectory simulation.Monte Carlo calculations have enabled scientists to visualize the electron interaction volume in solids as to size and shape, to predict the parameters characterizing the secondary and back-scattered electrons, the x-rays, and the Auger electrons, and to analyze factors which determine resolution in micrographs.The purpose of the present workshop was to bring together a number of workers in Monte Carlo trajectory techniques to assess the current state of development and to look for areas of future development.The list of participants in the meeting does not include all active workers in the field, but we hope that this document contains a reasonably complete description of the subject.By examining the a...
Nickel and nickel alloy consumption other than electroplate and stainless steels (year ended June 1972) Copper and copper alloys 21,600,000 kg of copper and alloy pipe and tube (year ended
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LITERATURE CITEDMore detailed discussion of the -ray interferences is given in earlier work (78).3) As already mentioned above, the possibilities of nuclear interferences are few at 10 MeV. It may be seen in column 3, Table I, that the only interference is between Li and B, 7Be is produced by 7Li(p,n)7Be and by 10B(p,o:)7Be.No other interference was detected by direct -ray spectrometry of elements irradiated at 10 MeV. With chemical separations, it would probably be possible to observe some ( , ) reactions on the lighter elements. Anyhow, if one considers all the Q-values for the nuclear reactions and the relative positions of the stable and of the radioactive isotopes for the studied elements, one sees that for all of them it is possible to find a suitable and interference free (p,n) reaction (except for Li and B). CONCLUSIONS 10-MeV proton activation may be used for the determination of trace concentrations of the 22 elements studied in this work; 47 radioisotopes and over 100 associated -rays are obtained via (p,n) reactions, thus offering a great choice to perform the analysis and a great selectivity (except for Li and B).This study was complemented by an application to the analysis of trace elements in 19 different matrices. In the case of these 19 matrices, 10-MeV proton activation is a powerfull technique because it is sensitive, selective, and also nondestructive.
A complete theory of the lens-shaped intersection of Kossel lines in the transmission pseudo-Kossel method is developed. The general expression gives the lattice parameter with respect to the characteristics of the interaction of two arbitrary conics, i.e., conics corresponding to arbitrary diffracting planes and arbitrary wavelengths. Geometrical considerations involving the conics are developed and from these, the errors involved in lattice parameter measurement are evaluated. Lattice parameter variations of 10−5 can be easily measured with suitably chosen conic intersections. The precision to be expected as a function of measurement errors is expressed as a sensitivity ratio and tabulated for an Fe-3wt.%Si alloy. Several methods of reducing measured lengths to lattice parameter data are evaluated. The IBM 7090 computer has been used to find suitable intersections for precise lattice parameter measurement. The computer supplies the wavelengths and conics to be used in the transmission pseudo-Kossel method. Consequently, a long and tedious experimental investigation is avoided. Examples using Fe-3wt.% Si are given; the lattice parameter for this alloy is found to be 2.86268±0.00003 Å. Proper radiations for investigation of Ge and diamond are indicated.
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