bluuebunny/crossref_metadata_2025 huggingface dataset:
Sputtering Ion Source for Solids
Authors: Liebl Helmut J. , Herzog Richard F. K.
Published: April 2005

A new ion source for the analysis of solids has been constructed. The ions are sputtered from the surface of the sample target by bombarding it with a concentrated beam of argon ions. The bombarding beam has an energy of 10 to 12 kV and an intensity of about 1 mA. This large intensity produces a secondary beam of target ions of about 10−8 A which is quite adequate for a routine analysis. In contrast to a spark source, the sputtering source gives very stable operation and allows electrometric recording of the mass spectrum. The mass spectra obtained are very simple and consist of peaks representing singly charged species. The source is not limited to metals or semiconductors, since good mass spectra have been obtained from insulators.
Effects of a Guardring upon Low-Energy Sputtering Yields of Flat, Single-Crystal Gold Targets
Authors: Kreye W. C.
Published: April 2005

Spectrometric sputtering yield measurements were performed upon flat, single-crystal gold targets in a supported argon plasma, and the results are compared with those obtained when a large copper guardring was placed about the target. After the results are adjusted to similar discharge conditions, the relative yields without the guardring are greater for all three orientations, (100), (110), and (111). The increase is attributed to the formation of a curvature to the Langmuir layer immediately about the gold target when the guardring is not used. This introduces ions which strike the gold surface at oblique incidence angles.

The square root of the relative yield is plotted against the target voltage, and the curves are found to be linear in the range of 40–70 V. The intercepts EE of the extrapolated linear portions of the two curves, with and without a guardring, are found to be equal for each orientation. These values, at 9 μ of argon, are 33, 28.5, and 35 eV for the (100), (110), and (111) faces, respectively. These values do not include the subtractive correction for the plasma potential whose measured value is approximately 15 eV.

For the (100) and (111) faces, the calculated differences [EE−EE(110)] are proportional to the corresponding differences in the binding energies of a surface atom which is in an upper, complete lattice plane.
Self-Diffusion in Silver during Plastic Deformation in Extension and Compression
Authors: Darby J. B. , Tomizuka C. T. , Balluffi R. W.
Published: April 2005

Self-diffusion of Ag110 in silver single crystals subjected to simultaneous deformation at 800 and 900°C was studied using the sectioning technique. The crystals were orientated for duplex slip and were deformed in extension and compression at constant strain rates in the range 1 to 28×10−5 sec.−1. Total strains as large as 0.33 were attained. Recrystallization occurred in the initially single crystal specimens during diffusion-deformation under all conditions except tension at 800°C.

The effect of straining on the rate of diffusion was found to be small in all cases. The straining changed the diffusivities by less than 50%, and it is concluded that the observed changes were probably within the experimental error. The results indicate that any increases in diffusion rate due to the generation of point defects or short-circuiting paths during deformation were small. These conclusions are shown to be consistent with other experiments involving these phenomena.
Magnetic Losses at Low Temperatures
Authors: Brown Edmund H. , Brennand John R.
Published: April 2005

The total magnetic losses in a silicon steel transformer core have been measured at temperatures from 20° to 273°K using a variable-frequency simple-harmonic flux wave with magnetic field intensity amplitudes Bm from 2 to 10 kilogauss. The hysteresis, or frequency independent, part of the losses was obtained by graphical extrapolation. For all field intensities this hysteresis loss increases with decreasing temperature but the relative increase at any temperature is independent of field intensity. At all temperatures the hysteresis loss can be represented, within the accuracy of the data, by the empirical equation of Steinmetz Wh=w(T)Bmn. In addition, the exponent n in this equation was found to be independent of temperature. A figure showing the eddy-current, or frequency dependent, part of the losses for 0.014-inch laminations is also included.
Problems of Generating High Circulating Currents of Relativistic Electrons
Authors: Neddermeyer Seth H.
Published: April 2005

The basic problems can be summarized in terms of (a) the internal kinematics, including the factors tending to dissipate the system or degrade its energy; (b) the stability of the system as a whole; (c) the initial formation, which in the view adopted here, is to be done by injection in an external magnetic field, or by some repetitive cycle of injection, acceleration and storage. Item (a) involves Coulomb scattering, especially multiple, and radiation arising from motion in the total field. The losses are described in terms of equivalent injection currents necessary to maintain a fictitious system with arbitrarily prescribed characteristics. Item (b) is discussed, mainly with reference to the ``kink'' instability in terms of a dynamical analogue, the breakdown of which leads to a formulation of the usually accepted necessary condition for stability. A stronger condition is also suggested, which, however, is probably much more than sufficient. The experimental difficulties of item (c) are discussed in only a general way, with no definite conclusions being drawn.
Inelastic Ion-Atom Collisions
Authors: Hasted J. B.
Published: April 2005

Ion-atom charge exchange cross sections of incident ion velocity v in the adiabatic region are shown to be proportional to exp (−K′a|ΔE|/v) energy defect ΔE.

Maximum cross sections of the negative ion-atom detachment collision and certain other inelastic ion-atom collisions are shown to be proportional to the maximum kinetic energy available for internal excitation, ½μv2, where μ is the reduced mass of the system. The semiempirical prediction of cross-section energy dependence is discussed.
Electron Emission at High Fields Due to Positive Ions
Authors: Kisliuk P.
Published: April 2005

Two mechanisms have been proposed to account for the observed large yield of secondary electrons in gaseous breakdown at high electric fields. In one of these a single ion in approaching the cathode surface creates a ``pass'' by decreasing the width of the potential barrier. In the other the increased over-all field due to a large number of ions in the gap is supposed to account for the increased emission. The first effect is re-examined and appears to be effective in the observed breakdowns of extremely small gaps in air. It may also be effective in breakdown at high pressure and in liquid and solid dielectrics.
Unpaired Electrons in Carbon Blacks
Authors: Collins R. L. , Bell M. D. , Kraus Gerard
Published: April 2005

An appreciable concentration of unpaired electrons has been found in colloidal carbon blacks through the application of electron spin resonance spectroscopy. The unpaired electrons in a typical channel process carbon black, Spheron 6, have been studied by noting the changes in the electron spin resonance spectrum produced by heat treatment (HT) to 3000°C and by various degrees of evacuation of the sample. The results indicate that the unpaired electrons in the original material are mobile π electrons, which are stabilized by condensed aromatic ring structures. Their concentration decreases slowly to 750°C HT and then declines more rapidly and vanishes above 1400°C HT. A different species of unpaired electrons arises at 1400°C HT. These are believed to be immobile σ electrons resulting from broken carbon-carbon bonds at lattice defects. The unpaired electrons present in several commercial carbon blacks have been examined and are believed to be π electrons also. A tentative theory of the origin of the unpaired electrons is given.
Experimental Study of Effect of Crystallite Size Statistics on X-Ray Diffractometer Intensities
Authors: De Wolff P. M. , Taylor Jeanne M. , Parrish W.
Published: April 2005

The relative rms deviation σ of the intensity of a rapidly rotating polycrystallite specimen is σ=[6.5R sinθ]/[h(mNeff)½], where R=goniometer radius, θ=Bragg angle, h=(hf+hs)/2, hf=length of focal spot, hs=length of receiving slit, m=multiplicity factor, and Neff the effective number of irradiated crystallites. Experimental data on silicon powder specimens are presented to show the dependence of σ on crystallite sizes, choice of x-ray wavelengths and various other experimental parameters. Comparisons of data for rapidly rotating and stationary specimens having crystallite sizes in the 30–50 μ range show that rotation improves σ by a factor of 7 or 8 for peak intensities and 4 or 5 for integrated intensities, using a standard diffractometer.
Low Noise in Solid State Parametric Amplifiers at Microwave Frequencies
Authors: Danielson W. E.
Published: April 2005

The principles of parametric amplification are described through the use of simple low-frequency electrical circuits and their mechanical analogs. Extension of these principles to low-noise amplification at microwave frequencies is made in a qualitative way which emphasizes the physical processes involved. Amplification is only achieved when energy is transferred from a microwave oscillator or pump to the signal frequency, and it is shown why such a transfer may take place in circuits exhibiting variable capacitance or inductance but not in circuits where only a resistance is varied. Major noise sources are discussed and the special role of the image or idler frequency is noted. Finally, experimental data on four different types of parametric amplifier (3 using semiconductor diodes and 1 using ferrite) are given.
New Mechanism of Noise Reduction in Electron Beams
Authors: Currie M. R. , Forster D. C.
Published: April 2005

Experiments have demonstrated that the basic noise quantities of an electron beam can be transformed and optimized by varying the field configuration and flow characteristics in the multivelocity region near the cathode. Tube noise figures as low as 2.9 db and numerical values of beam noisiness 2π/kTc(S−Π) <0.27 have been attained at microwave frequencies (S band). A detailed investigation of the conditions for minimum beam noisiness is presented. The beam is injected from the edge of the cathode into a highly divergent electric field and results in a distorted potential profile which greatly extends the low-velocity region below ½ v. It is shown that these features satisfy the physical conditions necessary for realizing a quasi-one-dimensional model in which the transforming properties of a ``multivelocity noise transducer'' can be adjusted by varying the rate of acceleration through this region. The experiments also suggest other models and possible approaches for further theoretical and experimental investigation.
Spherulitic Crystallization in Polypropylene
Authors: Padden F. J. , Keith H. D.
Published: April 2005

A survey has been made of spherulites formed by the isothermal crystallization of polypropylene from the melt in the temperature range 110°–148°C. Four types of spherulite have been distinguished and their structural morphology, optical properties, melting behavior, and growth rates have been examined.
Theory of Mechanical Breakdown and Molecular Orientation of a Model Linear High-Polymer Solid
Authors: Hsiao C. C.
Published: April 2005

A phenomenological theory of the molecular orientation dependence of mechanical breakdown phenomena is presented for a model linear high-polymer solid. Taking into account the variation of the volume a general microscopic molecular model is first introduced. After simplification an approximation is considered. For one-directional orientation the result indicates a rapid increase in the fracture strength as the degree of molecular orientation increases. The maximum fracture strength is found to increase to nearly six times the unoriented strength.
Neutron Irradiation Effects in a Copper-Aluminum Alloy
Authors: Houska C. R. , Averbach B. L.
Published: April 2005

Diffuse x-ray scattering and peak intensities were measured for a polycrystalline alloy of copper-14.5 atomic percent aluminum before and after irradiation. It was shown that the average short-range order configuration in the first five neighboring shells was somewhat enhanced as a result of the irradiation. In addition, a temperature independent rise was observed in the diffuse scattering. This was interpreted in terms of static atomic displacements arising from the localized volume changes associated with neutron damage. The absence of line broadening or significant line shifts after irradiation is further confirmation of the localized nature of the damage. Defect models of radiation damage involving short range effects which average out over larger distances in the lattice are discussed.
Diffuse X-Ray Scattering in Powder Patterns Arising from Static Displacements in Cubic Solid Solutions
Authors: Houska C. R. , Averbach B. L.
Published: April 2005

The diffuse scattering arising from static atomic displacements from the average lattice sites has been evaluated for cubic powder patterns. This excess scattering results from elastic interactions between atoms of different size in binary solid solutions, and is compatible with the conservative intensity loss of the main reflections. The resultant scattering was found to take the form Is = f̄2H(x) {1−exp[−2M′(x)]}, where H(x) is a weak modulation which varies by approximately 10% about unity.
Two-Carrier Space-Charge-Limited Current in a Trap-Free Insulator
Authors: Parmenter R. H. , Ruppel W.
Published: April 2005

The space-charge-limited electrical behavior of a trap-free insulator containing both mobile electrons and holes is investigated under the approximation of neglecting diffusion current. When both contacts are ohmic, the dependence of two-carrier space-charge-limited current on voltage and interelectrode spacing remains the same as in the one-carrier case; i.e., the current varies as the square of the voltage and as the inverse cube of the spacing. For given voltage and spacing, however, the two-carrier current is usually orders of magnitude larger than the one-carrier current. This is in striking contrast to the case of space-charge-limited flow of electrons and positive ions in a vacuum. The two-carrier current in an insulator can be reduced to the size of the one-carrier current either by making one contact highly blocking or by reducing the mobility of one of the carriers to zero. While the first approach yields in detail the well-known one-carrier case, the second approach differs from the one-carrier case in that no net excess space charge can be injected into the insulator. The intermediate case of a slightly blocking contact shows that, while the current may be carried mainly by one sign of carrier, the net space charge of the insulator can have the opposite sign. When both contacts are blocking, the current saturates for sufficiently high voltages. The current is smaller than the saturation value by an amount proportional to the cube of the interelectrode spacing and the inverse square of the voltage. Near such saturation, the space charge is negligible and the electric field is uniform across the insulator. It is plausible that many of the above results will also be true for an insulator with traps.
On Model Studies of Metallic Surface Asperities
Authors: Ling F. F. , Lucek R. C.
Published: April 2005

An apparatus for measuring forces generated at the tips of two cones throughout the sliding-contact life cycle is described. The cones are used to simulate surface asperities. Test results under atmospheric conditions show the following: (1) For cones with 90° internal angles, the ratio of the integrated value of the horizontal force component over the length of the life cycle to that of the vertical force component, a measure of coefficient of friction after Green, is not sensitive to the presence of lubricants in cases where the cone tips are in line or nearly in line with the direction of relative motion; but the ratio is substantially lowered in the presence of lubricants when the cone tips are far from being in line with the direction of relative motion. The former cases are always accompanied by the formation of macroscopic wear debris. (2) By increasing the internal angle of cones, the ratio defined above is decreased, but its value does not seem to approach zero for the angle approaching 180°, a flat surface. (3) Size effect as discussed by Morrison and Shaw is evidenced in this experiment.

The mutual inclusiveness of the classical interlock theory and the popular adhesion theory of friction is discussed. Moreover, the coefficient of friction for a pair of idealized surfaces with asperities in the form of 90° cones and randomly distributed is calculated from considerable amount of test data. While actual surfaces have asperities roughly in the form of cones with internal angles much larger than 90°, right circular cones were used, nevertheless, for simplicity and for amplifying the effects noted.
Cleaning of Silicon Surfaces by Heating in High Vacuum
Authors: Allen F. G. , Eisinger J. , Hagstrum H. D. , Law J. T.
Published: April 2005

Results from experiments with four independent surface-sensitive phenomena agree in demonstrating that an atomically clean surface can be produced on silicon single crystals by heating to 1550°K or above for several minutes in high vacuum. The four phenomena studied are: 1. oxidation and gas adsorption, 2. Auger neutralization of He+ ions, 3. external photoelectric emission, and 4. field electron emission in a Müller microscope. Evidence is given as to the nature of the silicon surface before cleaning, properties of the clean surface, and behavior upon contamination with gases and during subsequent recleaning. The surfaces were found to form a permanent p-type layer several microns deep as a result of the vacuum heating.
Instrumented Card-Gap or SPHF-Plate Test
Authors: Cook Melvin A. , Pack Douglas H. , Cosner Lawrence N. , Gey William A.
Published: April 2005

The deflagration to detonation transition, or DDT, was studied by means of the shock-pass-heat-filter (SPHF) method using Composition B donors in all cases and Composition B, HBX, and Baratol receptors. The SPHF plates were glass, steel, brass, and aluminum. The influence of donor charge diameter and length, and the receptor diameter on the sensitiveness limit, the curves of S1 vs τ′, and S2 vs τ′ were established for these conditions. A striking result is that S2/τ′ proved to be constant equal to the (effectively sonic) velocity of the initial (relatively) unreactive shock wave in the receptor prior to the DDT; it was independent of donor and receptor charge size, the SPHF plate thickness and type. Based on observation with nitromethane, Dithekite, and liquid TNT by the University of Utah and U. S. Naval Ordnance Test Station groups the phenomenon that eventually initiates the DDT forms on the receptor surface of the SPHF plate as a luminous spot that then flashes effecting the DDT at the instant it collides with the (relatively) nonreactive shock front. The present results are entirely consistent with this mechanism, even though one does not observe the flash-across in the opaque solid explosives.
Development and Comparison of Two X-Ray Methods for Determining the Crystallinity of Cotton Cellulose
Authors: Wakelin James H. , Virgin Hester S. , Crystal Eugene
Published: April 2005

Two x-ray methods have been developed for determining the crystallinity of cellulose using a Geiger counter spectrometer. The two methods were applied to six native cotton varieties, to a cross-bred variety, and to two cottons chemically modified with ethylamine. The x-ray scattering curves for each of the nine samples were compared with those from a highly crystalline sample, a cotton hydrolyzed in HCl, and an amorphous cotton sample to provide a relative measure of crystallinity, or crystalline index.

With fully corrected data the average crystalline index of the six cotton varieties was found to be 68.3 and 78.7% by the correlation and by integral methods, respectively. The crystalline indices of the remaining samples determined by the correlation and by the integral methods are, respectively, cross-bred cotton (S×P), 54.3 and 77.2%; cotton treated with anhydrous ethylamine, 29.7 and 50.9%; and cotton treated with 75% aqueous ethylamine, 28.3 and 50.3%.
Nonlinear Heat Transfer Problem
Authors: Chambré Paul L.
Published: April 2005

A study has been made of the time-dependent heat conduction in a semi-infinite medium subject to a boundary condition which can involve the temperature in a nonlinear manner. A formulation for the determination of the surface temperature, which is often of greatest physical interest, leads to a nonlinear Volterra integral equation. A simple iterative solution method, with an accuracy suitable for many practical purposes is presented. As an example, the problem of the time-dependent surface temperature of a body receiving heat according to the Stefan-Boltzmann law is treated. The analysis is also applicable to physical adsorption or chemisorption processes which occur at the boundary.
Surface-Dependent Losses in Variable Reactance Diodes
Authors: Sawyer D. E.
Published: April 2005

Surface effects may seriously degrade the high frequency performance of a semiconductor junction diode used as a variable reactance element without significantly degrading the diode's dc characteristics. Measurements on both p+n and n+p germanium alloy junction diodes have yielded a diode series equivalent resistance component in excess of the calculated integrated bulk resistance. This excess resistance decreased with frequency approximately as 1/f and for freshly etched devices could be varied by changing the atmosphere surrounding the diode. Those ambients which yielded a maximum surface-determined junction breakdown voltage also yielded a maximum frequency-dependent excess resistance. A model which can explain these observations assumes a surface inversion layer contiguous with the alloy junction.
Thermal Conductivity of Clear Fused Silica at High Temperatures
Authors: Wray Kurt L. , Connolly Thomas J.
Published: April 2005

The thermal conductivity of clear fused silica was measured over the temperature range 300–2100°K in an experiment which minimized radiative energy transport. This was a steady-state experiment involving the measurement of the electric current and voltage drop through a fine tungsten wire which was embedded along the axis of a cylindrical silica rod. The wire served both as a heating element and as a resistance thermometer. Thermal conductivities were calculated by graphical evaluation of the rate of change of electric power with temperature at different temperatures. The experiment yielded thermal conductivities between 2.6×10−3 and 2.9×10−3 cal/cm sec°K at room temperature, and between 4.5×10−3 and 5.5×10−3 cal/cm sec°K over the temperature range 1000–2100°K.
Normal Stress Effect in Polymer Solutions
Authors: Kotaka Tadao , Kurata Michio , Tamura Mikio
Published: April 2005

Normal stress phenomena are studied in solutions of some typical high polymers, polystyrene, methylcellulose, and sodium-carboxymethylcellulose, with a parallel plate instrument. The principle of procedures for separate determination of normal stress components with the parallel plate instrument is briefly described. The normal stress measurements are performed in shearing rates ranging from about 1.0 to 100. The results obtained, together with the flow curves, are discussed in terms of the cross-elasticity theory and of some molecular bases. It is concluded that polystyrene solutions roughly obey ``Hooke's law in shear,'' while solutions of cellulose derivatives are remarkably ``non-Hookean in shear.''
Magnetic Viscosity in Iron Due to Carbon Atoms Anchored in Dislocations
Authors: Biorci G. , Ferro A. , Montalenti G.
Published: April 2005

A specimen of iron containing 0.01% of C in solid solution has been cold worked by 7% and aged at room temperature. After this treatment it shows a new peak of magnetic viscosity at 180°C. The diffusion process giving rise to the peak is controlled by an activation energy of about 32 000 cal/g atom and a time constant at infinite temperature of about 10−14 sec. These figures agree with those of a peak of internal friction observed in similar specimens by Kê and by Köster, and interpreted as due to diffusion of C atoms in the surroundings of the dislocations. Hence the peak of magnetic viscosity can be related to the same mechanism.
Influence of the Angle of Incidence on Sputtering Yields
Authors: Wehner Gottfried
Published: April 2005

Small metal spheres are bombarded by uniform Hg+ ion beams of low energy (125 to 800 ev). Comparison of shadow micrographs of the spheres before and after sputtering makes it possible to determine the influence of the angle of incidence on sputtering yields. Fe, Ta, and Mo showed a pronounced increase in yield at more oblique incidence of the ions while Au, Ag, and Pt showed this effect only slightly.
Thermomagnetic Generator
Authors: Elliott J. F.
Published: April 2005

Calculations are made for the power output and the efficiency of energy conversion of a thermomagnetic generator. Particular attention is paid to the use of the ferromagnetic element gadolinium as a suggested material for a practical device for the generation of electrical power from a low grade heat source (i.e., in the neighborhood of 20°C).
Space Charge Waves in Cylindrical Plasma Columns
Authors: Trivelpiece A. W. , Gould R. W.
Published: April 2005

When a plasma is of finite transverse cross section, space-charge waves may propagate even in the absence of a drift motion or thermal velocities of the plasma. Some of the properties of these space charge waves have been investigated by regarding the plasma as a dielectric and solving the resulting field equations. The effect of a steady axial magnetic field is considered, but motion of heavy ions and electron temperature effects are neglected. Waves are found to exist at frequencies low compared with the plasma frequency as well as waves with oppositely directed phase and group velocities (backward waves).

Many of the features of these waves have been verified experimentally by measuring phase velocity and attenuation of waves along the positive column of a low pressure mercury arc in an axial magnetic field. Measurements of electron density have been made using these waves and the results are compared with those obtained by other methods. An interesting feature of these measurements, of value in plasma diagnostics, is that they can be made with frequencies which are small compared with the plasma frequency.
Behavior of Polytetrafluoroethylene (Teflon) under High Pressures
Authors: Beecroft R. I. , Swenson C. A.
Published: April 2005

The presence of polymorphic phase transitions, apparently unique among high polymers, enhances interest in polytetrafluoroethylene, while its potentialities for cryogenic applications make low temperature data particularly valuable. Compression measurements have been made on samples of Teflon at various temperatures between 75°K and 380°K and at pressures up to 21 000 atmos. The phase diagram found for the region above the ice point is in qualitative agreement with previously published results, with a possible additional transition appearing above room temperature at pressures of over 11 000 atmos. Time effects and a large pressure hysteresis make the transition parameters quite ambiguous, and the hysteresis becomes so broad at low temperatures that the phase diagram cannot be extended below the ice point. An apparent negative thermal expansion indicated by the isothermal compression measurements is shown to result from an incomplete high pressure transition. From an engineering standpoint, the measurements indicate that a Teflon gasket loaded to 3000 atmos at room temperature should maintain a seal at any lower temperature.
Light Emission and Noise Studies of Individual Microplasmas in Silicon p-n Junctions
Authors: Chynoweth A. G. , McKay K. G.
Published: April 2005

At low currents in the prebreakdown region of broad area diffused silicon p-n junctions in which the breakdown is by an avalanche mechanism, only a few light-emitting microplasmas are present. These appear in succession as the current is increased and the appearance of each spot is accompanied by its own set of characteristic microplasma current pulses. It is found also that effectively all the emitted light arises at these microplasmas and that they carry, essentially, all of the breakdown current. The light intensity of an individual microplasma is roughly proportional to the current flowing through it.
Motion of High Speed Arc Spots in Magnetic Fields
Authors: Zei Dino , Winans J. G.
Published: April 2005

Retrograde motion of mercury arc spots when in a groove in the cathode above the level of mercury was compared with motion of spots at the junction of mercury and the molybdenum cathode. A rapid rise in retrograde velocity occurs at about 10 000 oe for junction motion but at less than 5000 oe for groove motion. Spectra show more multiply charged ions for groove than for junction motion for the same magnetic field strength. The velocity for groove motion always exceeds the velocity for junction motion, and it increases markedly with a reduction in mercury vapor pressure. For groove motion increasing current causes the retrograde velocity to pass through a maximum. Observations are described by the mechanism proposed by St. John and Winans.
Helical Fields
Authors: Poritsky H.
Published: April 2005

This paper is devoted to a study of helical fields, that is fields which are invariant under screw motions of space which move a certain helix into itself.

Simple, analytic, helically invariant solutions of the Laplace equation are given and combined to describe the electrostatic field of a charged helix, and of the magnetic field of a helical electric current. A flux function ψ is introduced for solenoidal helical vector fields, and differential equations resembling Cauchy-Riemann equations are derived for the potential function φ and the flux function ψ. Certain graphical flux plotting methods are outlined and illustrated, and network analogies are suggested for solving these fields.
Performance of Germanium and Silicon Surface Barrier Diodes as Alpha-Particle Spectrometers
Authors: Mayer James W.
Published: April 2005

The characteristics of a germanium surface barrier diode operated at room temperature make it particularly useful as an alpha-particle spectrometer. The small size, stability, energy resolution, and relative insensitivity to β and γ radiation of the units suggest applications in medical and nuclear research. Studies were made on Au–Ge and Au–Si surface barriers with a barrier width (≅1 μ) less than the range of the incident alpha particles. In the germanium units, the pulse-height response to alpha particles increased linearly with energy up to 7.5 Mev and then increased monotonically but more slowly as the energy rose to 12 Mev. In silicon the deviation from linearity occurred around 6 Mev. The observed linearity between pulse height and energy depends simply on the fact that the number of carriers excited is proportional to the particle energy and that the time for the carriers to be collected at the barrier is less than the circuit time constant. The general theory of the transient response of the diode was developed and the calculated response compared with the observed behavior. The observed values of the energy required to create a hole-electron pair, measured over the energy range of linear response of the junction, were ε(Ge)=2.96±0.1 ev and ε(Si)=3.9±0.3 ev.
Absorption Correction in Precision Determination of Lattice Parameters
Authors: Straumanis M. E.
Published: April 2005

X-ray powder and rotation patterns of six cubic substances (W, Si, Cr, TiO, Al, and V) using specimens of different thickness were made; the patterns were measured, the lattice constants calculated and plotted against the θ angle or against the Nelson and Riley function. Such curves for thin mounts, semitransparent to x-rays (below 0.2 mm in diam), consist of two parts: a region of high slope (due to absorption) and one approaching a zero slope at high Bragg angles. The latter, varying in extent with the size and nature of the mount, indicates that due to the rapid decrease in absorption, the lines in this region are shifted, little if any, from their correct positions. Hence, lattice constants calculated from the reflections of the high θ angles lying on the horizontal portion of the curve need not be corrected for absorption. The constant, with negligible error, can be calculated from a single last strong α1 or β reflection. If an extrapolation is applied, the curve must be traced through points in the high back reflection region. Otherwise any extrapolation, disregarding the horizontal part, would lead to lattice constants too high in value. The amount of line displacement due to absorption in thin samples (below 0.2 mm in diam) agrees with the geometrical concept of Hadding and Buerger.
Measurement Broadening in Magnetic Resonance
Authors: Myers Orlo E. , Putzer Eugene J.
Published: April 2005

Phase-detection techniques used in recording magnetic resonances are the source of a measurement broadening. Results of a general mathematical treatment for arbitrary line shape and of machine computation for a Lorentz line shape lead to a series of curves which may be used to correct observed widths under circumstances where the Lorentz shape may be verified and effects of finite modulation frequency may be ignored.
Temperature Diffuse Scattering of X-Rays in Cubic Powders. I. Comparison of Theory with Experiment
Authors: Chipman David R. , Paskin Arthur
Published: April 2005

Temperature diffuse scattering of x-rays (TDS) has been examined in cubic powders to test the reliability of current TDS theory. Measurements are reported of the diffuse scattering of copper and lead along with the Bragg reflections of these metals at room and liquid nitrogen temperatures. These measurements were made using a scintillation counter diffractometer and crystal monochromated CuKα radiation. The TDS so otained is compared with TDS calculations based on the one- and two-phonon calculation as well as on the Warren (modified one-phonon) calculation. Both formulas are found to fit the magnitude of TDS by choosing appropriate Debye characteristic temperatures. The Debye Θ's which fit the copper and lead TDS data at room temperature are: 324° and 96° (one- and two-phonon) and 269° and 64° (Warren formula) as compared to values of 307° and 79° taken from the temperature dependence of the Bragg reflections and 315° and 88° from specific heat values for copper and lead, respectively. Evidence is also found for extra diffuse scattering in the low-angle region. This extra scattering is tentatively ascribed to a multiple scattering process.
Photoconductivity as a Function of Optical Absorption
Authors: Goodman Alvin M.
Published: April 2005

A theoretical analysis of the dependence of photoconductivity upon optical absorption is presented, based upon the concept of a ``schubweg'' or mean range for the optically liberated charge carriers of each sign. The analysis is based upon a model in which the light is normally incident upon a flat slab semiconductor. The electric field within the semiconductor is assumed to be either parallel or antiparallel to the direction of propagation of the incident light. The photocurrents are different for the two field directions. The ratio of the photocurrent for the parallel field direction to the photocurrent for the antiparallel field direction is found to be independent of incident light intensity, optical reflection coefficient at the front face of the slab, and photon quantum efficiency for hole-electron pair creation. The limitations of the assumed model are discussed.
Space Charge Neutralization by Positive Ions in Diodes
Authors: Auer P. L. , Hurwitz H.
Published: April 2005

The neutralization of electron space charge in diodes is analyzed on the basis of the assumption that the ion density is proportional to e−eV/kT, where V is the local potential and T is the cathode temperature. The neglect of electron-ion collisions enables solutions for the potential variation between electrodes to be obtained by a single numerical quadrature. Curves are presented for the potential as a function of position for a series of values of the ratio α of ion to electron density at the potential minimum. It is shown that for a large range of tube parameters, the electron current reaches two-thirds of its saturated value when the ion density at the cathode is about one-third the quantity Is/ev0, where Is is the saturation current and v0 = (2kT/πm)½. The electron current saturates completely when the ion density at the cathode is slightly above 0.81 Is/ev0 for large electrode spacing and slightly below Is/ev0 for small spacing. The anomalous behavior of the potential as a function of position when α lies between 0.81 and unity leads to the possibility of more than one mode of operation for a given ion density at the cathode and also causes the tube current to increase rather than decrease with increasing electrode spacing under certain conditions. Since these phenomena occur only over a narrow range of tube parameters, the effect of electron ion collisions may prevent them from being observed experimentally.
Effects of Carrier Injection on the Recombination Velocity in Semiconductor Surfaces
Authors: Dousmanis George C.
Published: April 2005

The effects of carrier injection on the surface recombination velocity are discussed on the basis of the Shockley-Read model. The relevant parameters are the surface potential φs, bulk resistivity, the injection density δn, and the properties of the surface states. At low injection the behavior of the surface recombination velocity s can be described by excursions over the usual s vs φs curves and, depending on the values of the various parameters, s can either increase or decrease with injection. At high injection s approaches a constant value that depends only on the cross sections and densities of the recombination states, and can be larger (as is predicted for the case of Ge) or smaller than the plateau value of the near-equilibrium curve. The predictions of the theory are illustrated with curves of s vs the fractional excess carrier density δn/n0 where, in the case of Ge, use is made of experimentally determined surface parameters. The curves can be used in applied work as a guide in controlling and possibly utilizing the effects of injection on s. The effects of appreciable injection on s could be used for studying the surface recombination centers.
Low-Energy X-Ray Attenuation Measurements for Elements of Low Atomic Number
Authors: Hopkins John I.
Published: April 2005

Mass attenuation coefficients have been measured for aluminum and copper in the energy range of 6 kev to 40 kev and for chromium, cobalt, nickel, and zinc in the energy range of 6 kev to 14 kev. The average most probable error is less than 3% and the agreement with theory is good.
Hydromagnetic Capacitor
Authors: Anderson Oscar , Baker William R. , Bratenahl Alexander , Furth Harold P. , Kunkel Wulf B.
Published: April 2005

Very high dielectric constants can easily be achieved by means of an ionized gas in a strong magnetic field. When an orthogonal electric field is applied, the resultant particle drift stores electrical energy. In a coaxial capacitor, which makes use of a rotating plasma disk, dielectric constants in the range 106 to 108 have been measured. The potential usefulness of hydromagnetic capacitors in fast-discharge work is considered.
Propagation of Plastic Waves in Solids
Authors: Bell James F.
Published: April 2005

A detailed experimental study of large amplitude plastic waves in annealed aluminum is presented. Using the author's diffraction grating technique, accurate strain-time and surface angle-time histories are obtained at different locations in the vicinity of impact. Verification of the strain-rate independent theory with strain amplitude modifications is provided in this region for impact velocities up to 63 ft/sec. Poisson's ratio is dynamically determined for strains up to 1.5%. Marked changes are observed in the propagation behavior above 1.06% strain, related to the abrupt increase of Poisson's ratio from ⅓. The maximum amplitude of waves above this value decreases exponentially with distance from impact.
Domain Wall Motion and Ferrimagnetic Resonance in a Manganese Ferrite
Authors: Dillon J. F. , Earl H. E.
Published: April 2005

From a single crystal of manganese ferrite, specimen cores have been cut which are capable of supporting single domain walls. These cores have been proportioned in two ways, one favoring a movable (110) wall, the other favoring a wall system perpendicular to the (110) plane. The basic experiment consists in applying rectangular current pulses to a winding, and observing the rate of change of flux as presented by the voltage in another winding. At low driving fields, the wall, once torn free of the surface, moves through the crystal at a velocity proportional to the applied field less an internal coercive force. At high fields the pulse shapes indicate complex domain structure.

Ferrimagnetic resonance experiments have also been performed on samples cut from the same crystal, and the results of these are given. It is particularly interesting to compare the loss parameter for the equation of motion which we derive from the resonance experiments with that obtained from the wall motion experiment.
Compression and the α-β Phase Transition of Plutonium
Authors: Bridgman P. W.
Published: April 2005

Recent lifting of the security restrictions now permits publication of measurements of various effects of pressure on plutonium made during the war. Compressions on the alpha phase were measured at room temperature to 40 000 kg/cm2 in one apparatus and to 100 000 in another. The total volume compression under 100 000 is very close to 10%. Compressibility decreases with increasing pressure as is normal. Exploration for other transitions was made to 20 000 kg/cm2 at 100° and 200°—none were found. The pressure and the volume change of the alpha-beta transition was measured at 162.6° and 205°. The transition curve is ``normal,'' the pressure rising with increasing temperature with downward curvature, and volume increment decreasing. The volume increment averages nearly 9%. The pressure of transition at 205° is very approximately 7000 kg/cm2. The calculated latent heat of transition at the mean pressure is roughly 4.5 cal/g.
Recombination Centers on Ion-Bombarded and Vacuum Heat-Treated Germanium Surfaces
Authors: Wang Shyh , Wallis George
Published: April 2005

Germanium surfaces were bombarded with argon ions and then heat-treated under high vacuum. Room-temperature values of surface recombination velocity, surface conductivity, dark field effect, and field effect under illumination were measured after successive heat treatments. In addition, the temperature dependence of these quantities was determined. It was confirmed that after annealing of the bombardment damage, a large number of acceptor type surface states approximately clamped the surface potential. Two types of recombination centers were identified: type 1, located near the middle of the gap and type 2, located near the valence band. The various heat treatments produced changes in the density of the type 1 centers but did not appear to effect the density of the type 2 centers.
Space-Charge Simulation in an Electrolytic Tank
Authors: Van Duzer T. , Brewer G. R.
Published: April 2005

This paper describes a method for the simulation of space charge in an electrolytic tank by the introduction of currents into the electrolyte by means of sources projecting through the tank floor. The theory and design criteria for this space-charge simulation system are presented. This method of simulation is used as a means for introducing detailed space-charge effects into the determination of electron trajectories in axially symmetric, high-perveance electron guns. The trajectories determined by use of this system are compared with beam characteristics measured experimentally.
Densification during Sintering in the Presence of a Liquid Phase. I. Theory
Authors: Kingery W. D.
Published: April 2005

The driving force leading to densification during sintering in the presence of a liquid phase and the material transport phenomena have been analyzed and relationships for the densification rate during the rearrangement process, the solution-precipitation process, and the final coalescence process have been determined. These relationships allow an experimental determination of the mechanism of sintering in the presence of a liquid phase on the basis of the time, particle size and temperature dependence of the densification rate. In addition, they allow direct calculations of densification rates to be made for certain simple systems for which property data are available.
Densification during Sintering in the Presence of a Liquid Phase. II. Experimental
Authors: Kingery W. D. , Narasimhan M. D.
Published: April 2005

Experimental measurements of the densification rate and microstructure changes taking place during sintering of the iron-copper system, which is typical of those systems showing spheroidal grain development, indicate that in this system the rate of densification during liquid phase sintering is controlled by diffusion through a liquid film between particles. Dependence of the sintering rate on time, particle size and temperature are in agreement with theoretical predictions. A theoretical estimation of the sintering rate is in good agreement with experimental measurements.
High-Speed Switching Diodes from Plastically Deformed Germanium
Authors: Pearson G. L. , Riesz R. P.
Published: April 2005

Diffused diodes, fabricated from plastically deformed germanium, were examined for high-speed switching response. The degradation of minority carrier lifetime caused by dislocations generated during plastic deformation greatly reduced the minority carrier storage effect and permitted fabrication of diodes with turnoff times of the order of 10−9 sec.
On the Effect of Nonequilibrium Vacancies on the Kinetics of Kirkendall Diffusion
Authors: Fara H. , Balluffi R. W.
Published: April 2005

Vacancy diffusion models which predict parabolic diffusion-penetration kinetics implicitly assume that vacancy equilibrium is maintained everywhere. However, a nonequilibrium vacancy distribution is generally established by the pumping action of the chemical gradient in the Kirkendall effect. A more general diffusion model is, therefore, developed in which vacancies are not necessarily maintained in equilibrium. The behavior of the model is then investigated and nonparabolic kinetics are found. However, the kinetics approach those of the equilibrium model as either the vacancy lifetime approaches zero or as the diffusion time becomes very long. The applicability of the equilibrium model, therefore, depends upon the particular system and diffusion time. The results are compared with experiment, and it is concluded that nonparabolic effects are probably of little importance in usual face-centered-cubic metallic systems by the time diffusion measurements are made by conventional sectioning methods, i.e., when Dt>∼10−5 cm2.