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The Influence Of Sample And Detector Angles Upon Auger Electron Signal, Robert L. Gerlach

Scanning Electron Microscopy

The effects of the sample to incident electron beam angle and of the detector. angle on the Auger electron signal are important for quantitative Auger analysis, particularly for Auger mapping and line scans. A first approximation, single scattering, mean free path model is employed to simulate the Auger signal resulting from a range of sample and detector angles. The model is single scattering in the sense that the excitation path is taken to be a straight line into the solid. A second model approximates multiple scattering by a normal distribution of ionizing flux angles about the incident beam direction.

Since …

Various Attempts To Reduce The Dimensions Of Magnetic Electron Lenses Used For High Voltage Microscopes, J. L. Balladore, R. Murillo, J. Trinquier

Scanning Electron Microscopy

Magnetic fields are used in electron microscopy for a variety of purposes: image formation, energy analysis and correction of astigmatism, for example.

We are interested in the problems of designing short focal length lenses to be used for focusing high energy electrons in the energy range 1-3 MeV.

These lenses are generally very large and we have tried to reduce their dimensions to simplify their construction and use. From this point of view, it is necessary to diminish the magnetic coil and the magnetic circuit iron.

Several solutions have been proposed in the case of the coil. We have obtained …

A Comparison Of Lanthanum Hexaboride, Cold Field Emission And Thermal Field Emission Electron Guns For Low Voltage Scanning Electron Microscopy, J. Orloff

Scanning Electron Microscopy

A comparison of lanthanum hexaboride, cold W(310) field emission and Zr/W thermal field emission cathodes was made by calculating the current-spot size relationship for each, using comparable lenses, to determine which would be suitable for high current operation at 1 keV beam energy, with a focused beam diameter < 0.05 μm. On the criteria of highest current, reasonable operating conditions for the gun for low noise operation and long term cathode stability it was found that the lanthanum hexaboride and cold field emission cathodes are inadequate or marginal and that the best performance is obtainable from the thermal field emission cathode.

Electron Detectors Used For Imaging In The Scanning Electron Microscope, V. N. E. Robinson

Scanning Electron Microscopy

Electron detectors used for imaging in the scanning electron microscope include those which detect secondary electrons, various portions of the backscattered electron signal, and the residual specimen current. The use of a different detector will often produce a different image of the same specimen. The information contained in these images depends upon the signal detected and the properties of the detector used. The choice of detector to be used depends upon the information desired.

Low Voltage Scanning Electron Microscopy, James B. Pawley

Scanning Electron Microscopy

The scanning electron microscope (SEM) usually operates with a beam voltage, V₀, in the range of 10-30 kV, even though many early workers suggested the use of lower voltages to increase topographic contrast and to reduce specimen charging and beam damage. The chief reason for this contradiction is low instrumental performance when V₀ = 1-3 kV. The problems include low source brightness, greater defocussing due to chromatic aberration, greater sensitivity to internal and external stray fields and difficulty in collecting the secondary electron signal without defocussing the probe. Recently considerable efforts have been made to overcome these …

Recent Developments In Numerical Electron Optics, Erwin K. Kasper

Scanning Electron Microscopy

The familiar methods for the numerical calculation of fields in electron optical devices are outlined briefly. for the solution of self- adjoint elliptic differential equations in orthogonal curvilinear coordinate systems a favourable ninepoint discretization is worked out which can be applied favourably e.g. to spherical mesh grids. The field calculation in magnetic deflection systems by means of an integral equation method is also highly advantageous. The methods for the field calculation can be still more improved by means of suitable hybrid procedures.

A second and shorter contribution is concerned with ray tracing and aberrations. Some favourable numerically stable new forms …

Energy Selecting Electron Microscopy, F. P. Ottensmeyer

Scanning Electron Microscopy

One of the major improvements in transmission electron microscopy over the last years is the addition of the capability of producing images with electrons that have specific narrow energy bands out of the total spectrum of energies they possess after having passed through the specimen. Though the idea is not new, the power of this application is only beginning to be recognized. Most simply, selection of elastically scattered electrons permits increased contrast in high resolution i mages in bright field, dark field, and diffraction. The use of combined elastic and inelastic signals adds entirely new contrast mechanisms, partially independent of …

Mineral Migration In The Wheat Kernel During Mill Conditioning, A. Al Saleh, B. Bouchet, D. J. Gallant

Food Structure

The structure and histology of the kernel govern migration of water during conditioning or drying. Studies by the energy dispersive x-ray system under the SEM have shown that during an increase of water content from 11.5 to 16.5 per cent, soluble elements migrated from the peripheral bran, accumulated in the aleurone cells and passed through its walls to the endosperm of the kernel if the water content was above 14.5 per cent. Results of study were compared with analyses of milling fractions obtained under the same conditions.

Proceedings From The 21st Annual Marschall Invitational Cheese Seminar 1984, Various Authors

Cheese Industry Conference

No abstract provided.

Computer Programs For Analyzing Certain Classes Of 3-D Electrostatic Fields With Two Planes Of Symmetry, Norm Franzen

Scanning Electron Microscopy

At Tektronix, two classes of non-rotationally symmetric electrostatic lenses which lead to significant three-dimensional-field problems are currently under investigation. Extensive interactive computer programs have been developed to study these lens structures.

The first class is referred to as Klemperer lipped lenses; the accelerating quadrupole being the most important. Klemperer lenses are formed from shaped concentric cylindrical electrodes and employ two or three independent voltages. These lenses are predominantly of quadrupole type, but possess higher multipoles to correct for geometry distortion.

The second class of lenses, referred to as wafer-lenses, consists of lenses formed from spaced sequences of metal wafer electrodes …

Magnetic Electron Lenses, Wolfgang Dieter Riecke

Scanning Electron Microscopy

The electron optical properties of magnetic lenses are determined by the ratio S/D of gap width S to bore diameter D, by the actual size of the gap and by the lens strength NJ√U*. Objective lenses of particularly small aberrations are obtained if the specimen is positioned close to the center of the gap and if the width of the gap is made as small as possible. For projector lenses the best performance results if the lens is employed at its minimum focal length. Another aspect important for high resolution lenses is that a stigmator is available for the correction …

Progress In The Theory Of Electron-Beam Deflection, E. F. Ritz Jr.

Scanning Electron Microscopy

Analysis, simulation, and design of electron-beam-deflection systems are reviewed in light of the current state of theoretical understanding. A brief review of the physical principles is followed by a detailed discussion of electrostatic, magnetostatic, mixed-field, traveling-wave, and scan-expansion systems. Each methodology is examined from a triple perspective: calculation of electromagnetic fields, calculation of electron trajectories, and calculation of the ensemble of trajectories forming the beam. Applications discussed include deflectors for television displays, lithography, scanning microscopes, and CRT oscillography. Developments of the last ten years are stressed, thereby supplementing and updating the author's previous review on this subject.

In field calculation, …

Magnetic Electron Lenses Ii, T. Mulvey

Scanning Electron Microscopy

Conventional magnetic electron lenses have evolved to their present highly developed state under the pressure of meeting the exacting requirements of high resolution electron microscopy. More recently, however, the desire to extract quantitative analytical information from the specimen has led to significant changes in the design of electron optical systems. The introduction of efficient lanthanum hexaboride cathodes and high beam current field-emission sources has strengthened this tendency. In addition, more complex lens systems than previously envisaged are now possible since microprocessors can be employed to assist in the rapid and reliable readjustment of the lens system, including the extensive alignment …

Optimization Of Stroboscopic Electron Deflection Systems, H. Rose, J. Zach

Scanning Electron Microscopy

Highly corrected electron-beam blanking systems (EBBS) are required for analyzing fast periodic processes at submicron spatial resolutions by stroboscopic methods. The deleterious degradation of the probe during the blanking operation can be avoided by a new straight-vision deflection system. Chopping of the beam is performed within this system by deflecting it across a knife edge. Calculations demonstrate that this system should be able to generate almost rectangular beam pulses with rise times of a few picoseconds and spot sizes smaller than 0.5 µm. The proposed EBBS consists of two wedge-shaped plate capacitors located symmetrically about the midplane of a rotationally …

Electron Image Simulation: A Complementary Processing Technique, Michael A. O'Keefe

Scanning Electron Microscopy

At present it is difficult to use direct image processing techniques to determine the specimen structure from electron micrographs obtained under non-linear imaging conditions, and impossible when the effects of dynamical scattering are strong (as in the case of thicker specimens). However, computing techniques are available to simulate high-resolution transmission electron microscope (HRTEM) images of postulated model structures. With these techniques it is possible to confirm the validity of interpretation of recorded micrographs, to help analyze crystal defects, to characterize microscope parameters, and to determine the ranges of validity of commonly used interpretive approximations. Because processed micrographs can lead to …

A Computer Controlled Scanning Transmission Electron Microscope Equipped With An Energy Analyzer For Special Investigations On Electron Diffraction- And Channeling Patterns, W. Hylla, H.-J. Kohl, H. Niedrig, D. Wendtland

Scanning Electron Microscopy

A scanning electron microscope was equipped with a double tilting stage, driven by stepping motors, to investigate electron channeling patterns (ECPs) and large angle convergent beam patterns (LACBPs) of single crystals. Transmitted electrons may be energy-selected by a magnetic sector-field energy analyzer. The recording of experimental data and the experimental arrangement are controlled by a microprocessor system, including a picture storage unit of 512 x 512 pixels of 16 bit. Recorded patterns can be stored on 1 Megabyte floppies.

A set of useful programs allows one to perform calculations with stored patter ns, e.g., contrast enhancement or -inversion, noise reduction, …

Synthesis Of Electron Lenses, M. Szilagyi

Scanning Electron Microscopy

This paper is a review of different approaches to one of the most ambitious goals of Electron and Ion Optics: to produce elements and systems with prescribed first-order properties and minimal aberrations. Synthesis of such elements is usually done in two steps: the first is a search for a field distribution with the given properties and the second is the reconstruction of electrodes (pole pieces) that would produce this field distribution. The first problem can be solved by the use of different techniques: Calculus of Variations, Dynamic Programming or Function Minimization. The second one is more complicated and requires a …

The Meridional Thermospheric Neutral Wind Measured By Radar And Optical Techniques In The Auroral Region, Vincent B. Wickwar, J W. Meriwether Jr., P B. Hays, A F. Nagy

All Physics Faculty Publications

Radar observations of ion velocities in the magnetic zenith over Chatanika, Alaska, were used to determine the geomagnetic meridional component of the thermospheric neutral wind. Corrections for molecular diffusion and molecular ion contamination of the pure O⁺ composition assumed for the ionosphere were included in the analysis. Comparison of the averaged diurnal variation of the meridional wind showed good agreement between the two measurement techniques. Good agreement was also found for several cases of simultaneous observations. The evidence suggested that differences were caused by gravity waves. The 7 years of radar meridional wind results were examined with respect to …

Pitch Angle Properties Of Magnetospheric Thermal Protons And Satellite Sheath Interference In Their Observation, Jan Josef Sojka, G. L. Wrenn, J.F. E. Johnson

All Physics Faculty Publications

Cold proton observations from the geosynchronous GEOS 2 satellite are presented to show the pitch angle distribution of the refilling cold ion population found beyond the plasmapause. This refilling cold ion population flows into the depleted equatorial regions of the flux tubes from the topside ionosphere. This refilling is observed both day and night. The ions have energies between 0.5 and 3 eV. These energy characteristics are consistent with other recent observations. Although the observed angular distribution of these ions is highly complex, when allowance is made for the satellite sheath several conclusions can be made concerning the ion pitch …

Plasma Characteristics Of Polar Cap F-Layer Arcs, H C. Carlson Jr., Vincent B. Wickwar, E J. Weber, J Buchau, J G. Moore, W Whiting

All Physics Faculty Publications

First results are reported of a comprehensive campaign to measure ionospheric structure and dynamics of nighttime polar cap F‐layer or F‐region arcs. Airborne optical and digital ionosonde data were collected simultaneously with ground based incoherent scatter radar data, continuously over many hours in time and 500 to 1000 km in space. Polar cap F‐region sub‐visual auroral arcs, which are commonly observed during quiet magnetic conditions, are found to represent boundaries (or shears) in the polar cap plasma circulation pattern. F‐region electron concentration enhancements are found in these features and can be of significance to polar thermospheric circulation, composition, and thermal …

Thermospheric Neutral Wind At –39° Azimuth During The Daytime Sector At Sondrestrom, Vincent B. Wickwar

All Physics Faculty Publications

Measurements with the Sondrestrom radar have been used to examine the daytime thermospheric neutral wind and to relate that wind to other geophysical parameters. Ion drag is found to be particularly important for determining the wind pattern. However, evidence is presented that the wind pattern is significantly influenced by soft particle precipitation and, possibly, by Joule heating.

Dayside Red Auroras At Very High Latitudes: The Importance Of Thermal Excitation, Vincent B. Wickwar, W Kofman

All Physics Faculty Publications

Extensive radar observations have been made from Sondrestrom of the F region in the daytime sector between 70 and 79° Λ. Regions of enhanced electron temperature and electron density are found in close association with the velocity reversal in the morning and afternoon convection cells. From the radar measurements, calculations are made of the contributions to the atomic oxygen emission at 6300A from dissociative recombination and thermal excitation. The latter mechanism, in particular, in the enhancement regions gives rise to intensities that are comparable to those observed at very high latitudes during the past decade.

Sondrestrom Overview, Vincent B. Wickwar, J D. Kelly, O De La Beaujardiere, C A. Leger, F Steenstrup, C H. Dawson

All Physics Faculty Publications

This overview of the Sondrestrom radar provides background material to help understand the early scientific results discussed in the following series of papers. It describes the geophysical region probed by the radar, the data acquisition procedure, and the extensive set of physical parameters derived.

Studies On The Microdistribution Of Aerobic Enzymes And Myoglobin In Pork, H. J. Swatland

Food Structure

Techniques were developed to study the microdistribution of aerobic enzymes and myoglobin directly on the surfaces of slices of meat. Despite its solubility, the in vivo distribution of myoglobin was preserved post mortem and, in pork, the distribution of myoglobin followed the distribution of aerobic muscle fibers. Aerobic fibers were grouped centrally in their fasciculi. Differences in oxidative enzyme activity between central and peripheral fibers within fasciculi were detected by staining with methylene blue in an atmosphere with controlled levels of oxygen and nitrogen. Within individual aerobic fibers, there was a radial gradient of SOH (succinate dehydrogenase) activity with more …

The Effect Of Salt And Pyrophosphate On The Structure Of Meat, C. A. Voyle, P. D. Jolley, G. W. Offer

Food Structure

Our obective was to determine whether or not salt and pyrophosphate have the same effect on the structure of pieces of meat as they have on isolated myofibrils. Blocks of pig M. longissimus dorsi were incubated in solutions of sodium chloride at pH 5.5 or sodium chloride plus sodium pyrophosphate at pH 5.5 or 8.0. The blocks were obtained from fresh (24h post- mortem) or aged (72h post-mor tem) muscle and incubated for 5 or 24h with minimal agitation. There was considerable uptake of water by the tissue especially at the higher pH and longer times.

Electron microscopy of the …

Use Of The Hewlett-Packard 9810 Calculator System In Water Quality Analysis, Jerald S. Fifield

Reports

Introduction: It is the purpose of this manual to illustrate the utilization of the Hewlett-Packard, Model 9810A calculator for analyzing water quality data. Familiarization of each program's capabilities is essential for successful application, thus the user should read over the section used before beginning. Each section is complete with instructions and illustrative examples.

Erosion And Sedimentation In Utah: A Guide For Control, C. Earl Israelsen, Eugene K. Israelsen

Reports

No abstract provided.

Sediment-Phosphorus Relationships In Deer Creek Reservoir, Jay J. Messer, Thomas B. Hardy, Jean M. Ihnat

Reports

Summary and Conclusions: Laboratory analyses of sediment samples recovered from Deer Creek Reservoir showed the sediments to have amoderate potential for serving as a source of phosphorus (P) for the overlying water solumn under anaerobic conditions. This source could account for the occurrence or exacerbation of blue-green algal blooms in the upper end of the reservoir when the sediment surface becomes anaerobic late in the summer. It could also delay the response of the reservoir to programs that decrease external P loading, if the upper end of the reservoir still has large enough algal blooms to render the sediment-water interface …

Abstracts Of Specialty Conference Papers; Delineation Of Landslide, Flash Flood And Debris Flow Hazards In Utah, B. Kaliser, M. K. Mccarter, R. Pack, J. Newman

Reports

No abstract provided.

Management Of Groundwater Recharge Areas In The Mouth Of Weber Canyon, Calvin G. Clyde, Christopher J. Duffy, Edward P. Fisk, Daniel H. Hoggan, David E. Hansen

Reports

Proper management of surface and groundwater resources is important for their prolonged and a beneficial use. Within the Weber Delta area there has existed a continual decline in the piezometric surface of the deep confined aquifer over the last 40 years. This decline ranges from approximately 20 feet along the eastern shore of the Great Salt Lake to 50 feet along in the vicinity of Hill Air Force Base. Declines in the piezometric surface are undesirable because of the increased well installation costs, increased pumping costs, decreased aquifer storage, increased risk of salt water intrusion, and the possibility of land …