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1 Apr 1958

Volume 29, Issue 4, pp. 601-744

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Cleavage Cracks and Dislocations in LiF Crystals

J. J. Gilman, C. Knudsen, and W. P. Walsh

J. Appl. Phys. 29, 601 (1958); http://dx.doi.org/10.1063/1.1723237 (7 pages) | Cited 61 times

Online Publication Date: 15 June 2004

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It is shown that dislocations are nucleated ahead of the tips of cracks that move slower than ∼6×103 cm∕sec in LiF crystals. The motion of cracks that move slower than ∼3×103 cm∕sec is unstable; that is, the velocity oscillates.
About 2×105 cm∕sec is the terminal velocity for (100) cleavage cracks in LiF.
For constant driving force, cracks move more slowly in crystals with high dislocation densities than in relatively perfect crystals.

Method for Making Successive Replicas of the Same Spot

J. T. Fourie

J. Appl. Phys. 29, 608 (1958); http://dx.doi.org/10.1063/1.1723238 (3 pages) | Cited 8 times

Online Publication Date: 15 June 2004

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A technique is described in which use is made of the slit type electron microscope specimen carrier for replicating successively the same spot on a metal sample. The main advantage is that no specialized apparatus is required. By using the slit type specimen carrier a relatively large undisturbed field of view is obtained. A series of electron micrographs showing the formation and growth of slip lines on an α‐brass single crystal is used to demonstrate the capabilities of the method.

Production of Dislocations During Growth from the Melt

W. A. Tiller

J. Appl. Phys. 29, 611 (1958); http://dx.doi.org/10.1063/1.1723239 (8 pages) | Cited 48 times

Online Publication Date: 15 June 2004

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The segregation of solute on a microscopic scale during crystal growth leads to the introduction of dislocation lines into the crystal at the bounding surfaces of the segregate. A layer type of segregate resulting from platelet growth leads to dislocation densities of 103−106 lines∕cm2. A cellular type of segregation resulting from cellular or dendritic growth leads to dislocation densities of 106−108 lines∕cm2 in the crystal.

Small Signal Power Conservation Theorem for Irrotational Electron Beams

J. Wilhelm Klüver

J. Appl. Phys. 29, 618 (1958); http://dx.doi.org/10.1063/1.1723240 (5 pages) | Cited 7 times

Online Publication Date: 15 June 2004

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The first‐order linearized set of Maxwell‐Lorentz equations are used as basis for the derivation of a power conservation theorem describing the balance between the rf kinetic power and the rf electromagnetic power in the electron beam. The theorem applies to laminar electron beams in which the electron flow is irrotational and the thermal velocity distribution at the cathode surface is neglected. The kinetic power flow is given in terms of the longitudinal rf kinetic potential or the Chu potential, the longitudinal part of the rf beam current and the equivalent longitudinal surface current on the beam boundary. This surface current embodies the effect of the transverse rf motion in the beam. A short discussion of the application of the theorem to thin beams is given.

Heavy Moderator Approximations in Neutron Transport Theory

Harvey Amster

J. Appl. Phys. 29, 623 (1958); http://dx.doi.org/10.1063/1.1723241 (5 pages) | Cited 3 times

Online Publication Date: 15 June 2004

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The flow of neutrons slowing down into a given angular and lethargy (or energy) interval equals an integral over the contributions from neutrons at other angles and lethargies within the medium. The two angular dependences of the integrand are commonly expanded in Legendre polynomials, and for heavy moderators, the lethargy dependence being integrated over is expanded in a power series about the lethargy of the exit neutrons. For each of these three expansions there is an index whose effect on the rate at which the resulting coefficients TLL'n vanish with increasing moderator mass is found. These estimates indicate where to terminate the lethargy expansions of the components of the current so as to maintain a consistent order of accuracy for each, and the sensitivity of the approximations to individual Legendre coefficients of the scattering cross sections follows. Exact recursion formulas derived for the TLL'n contain infinite sums, which can be terminated such that the uncertainty in the terms retained in the transport theory approximations are no larger than the estimated values of terms neglected. The familiar ``consistent P1 approximation'' is generalized as a particular example, and it is shown to be sensitive to only the first three Legendre coefficients of the cross section. The Greuling‐Goertzel approximation is also generalized and its merits noted. The associated difficulties in treating recoil due to inelastic scattering are discussed.

Use of an Electro‐Optical Method to Determine Detonation Temperatures in High Explosives

F. C. Gibson, M. L. Bowser, C. R. Summers, F. H. Scott, and C. M. Mason

J. Appl. Phys. 29, 628 (1958); http://dx.doi.org/10.1063/1.1723242 (5 pages) | Cited 19 times

Online Publication Date: 15 June 2004

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A method has been devised for sampling the optical radiation from the interior of a detonating solid‐explosive charge by introducing a transparent plastic rod axially into the charge at the time of fabrication. The radiation was analyzed by a grating spectrograph, using four bands 100 A wide and 600 A apart. The radiation intensities were used to calculate the color temperatures within the detonating explosive. The apparatus was calibrated by a radio‐frequency‐excited lamp known to have gray‐body radiation. The explosive charges were vacuum‐impregnated with propane to replace the air in the intergranular voids to eliminate light emission from the air shock.

Analysis of a Multipole State Separator and Focuser for Polarizable Molecules

Friedrich O. Vonbun

J. Appl. Phys. 29, 632 (1958); http://dx.doi.org/10.1063/1.1723243 (5 pages) | Cited 5 times

Online Publication Date: 15 June 2004

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The electrostatic field of a multipole focuser, consisting of parallel rods arranged in a circle, is treated. The field equation is derived from the known field of a two‐wire line, and results are given in the form of equations that express the field in terms of practical parameters. The field and the radial gradient of a (p+q)‐pole focuser is compared to that of a p‐pole focuser in order to indicate the value of increasing the number of poles.
Both a complete and a simplified set of differential equations (in cylindrical coordinates) of the path of polarizable molecules in this inhomogeneous field are also given. Based on the simplified differential equations, the path of a NH3 molecule in the J=K=3 (MJ=3) inversion state is graphically presented.

Orientation Study of Ultra‐Thin Molybdenum Permalloy Tape

P. K. Koh

J. Appl. Phys. 29, 636 (1958); http://dx.doi.org/10.1063/1.1723244 (22 pages) | Cited 4 times

Online Publication Date: 15 June 2004

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Quantitative pole density stereograms of {111}, {220}, {200}, and {113} poles of ⅛ mil molybdenum Permalloy tape were developed in order to establish its cold‐rolled deformation texture and annealed textures.
Cold rolling the tape induced multiple slip common to all face‐centered‐cubic metals and developed (110) [335] and (110) [335] end orientations which deviate 5° about [110] from the recognized {100} <112> brass deformation texture.
On annealing at 771°C the cold‐rolled tape was found to develop (120) [001] + (210) [001] and (113) [785] + (113) [785] orientations as components of the annealed texture which bear in general at 35°–45° rotation orientation relationship about <111> with the cold rolled end orientations.
Annealing at 1160°C developed the same texture as that obtained after 771°C annealing.
From the pole figures made on 927°C annealed tape, the same annealed texture prevailed whether the pole figure was made on its full ⅛ mil thickness or on its central 0.00005‐in. section.
Hysteresis loop tracings made on the cold rolled tape revealed an apparent direction of easy magnetization along the rolling direction. No easy magnetization direction was revealed in the rolling plane on the annealed tapes. These findings support the deductions from the corresponding pole figures.

Electron Mirror Microscopy of Patterns Recorded on Magnetic Tape

Ludwig Mayer

J. Appl. Phys. 29, 658 (1958); http://dx.doi.org/10.1063/1.1723245 (3 pages) | Cited 8 times

Online Publication Date: 15 June 2004

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This paper deals with the utilization of electron mirror microscopy for the observation of magnetic patterns recorded on magnetic tapes. Experimental evidence is presented demonstrating that, contrary to a statement in the literature, electron mirror microscopy can provide micrographs of magnetic patterns written on magnetic tapes. Successful utilization of the principle of electron mirror microscopy for depiction of magnetic patterns on magnetic tapes may have general significance with respect to magnetic memory systems in the event that evaporated magnetic films do become available. The high resolving power of the electron mirror microscope and the fact that it is an electronic device suggests further experimentation aimed at an all‐electronic, fast‐reading magnetic memory system with large storage capacity.

Surface Motions of a Thick Plate

L. Knopoff

J. Appl. Phys. 29, 661 (1958); http://dx.doi.org/10.1063/1.1723246 (10 pages) | Cited 16 times

Online Publication Date: 15 June 2004

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The motion of a thick elastic plate, infinite in two dimensions and bounded by air on the two parallel faces, has been studied. The plate is excited at a point on one face, as in Lamb's problem, by a force impulsive in time, and directed normal to the surface. The early motions of this surface have been described by Lamb. An exact solution, in closed form, for the motion of the opposite face is available only at the epicenter. The motions at all other points are evaluated by a seismic model. At the epicenter, the measurements and the calculations are in agreement; at this point a strong P pulse and a weaker S pulse are observed. This S phase has a wave form, for short pulses, which is the time integral of the wave form of the P phase. Off the axis of symmetry, the form of the S pulse is the same as that of the P pulse. The S pulse becomes quite strong away from the epicenter, attaining an amplitude of nearly four times that of the P pulse at about 45° in the Solenhofen limestone plate. A bodily S‐surface P phase, whose existence is in agreement with predictions based upon geometrical arguments is discerned at angles exceeding the critical angle.
A simplified description of the early motion of the reverse face may be constructed. This simplified response is a useful tool which may be used to reduce the complexity of the calculations encountered in other boundary value problems.

Model for Solute Diffusion in Crystals with the Diamond Structure

R. A. Swalin

J. Appl. Phys. 29, 670 (1958); http://dx.doi.org/10.1063/1.1723247 (5 pages) | Cited 22 times

Online Publication Date: 15 June 2004

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A theory for solute diffusion in crystals with the diamond structure such as germanium and silicon is derived by considering the effect of impurity ion size difference and also the coulombic interaction between impurity ions and charged vacancies. The theory is compared with experimental results reported for germanium and silicon and the agreement is considered quite good. The experimental observations that n‐type impurities diffuse considerably faster than p‐type impurities in germanium, whereas the opposite effect is observed in silicon, are explained by the theory. Because of the relation between the Fermi energy and vacancy acceptor level, the coulombic interaction is shown to be the predominating factor in germanium, whereas in silicon the size difference between impurity ions is shown to predominate.

Fast Neutron Attenuation in Graphite

V. P. Duggal and S. M. Puri

J. Appl. Phys. 29, 675 (1958); http://dx.doi.org/10.1063/1.1723248 (5 pages) | Cited 3 times

Online Publication Date: 15 June 2004

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Spatial distribution of a fast neutron flux has been measured experimentally in graphite (density 1.62 g∕cc) using threshold radioactivants. For these measurements neutrons were obtained from D‐T and D‐Be reactions. Assuming the neutron flux to vary as 1∕R2e−R∕L, the values of relaxation length L (between 50 cm and 70 cm) obtained with a phosphorous detector from D‐T and D‐Be neutrons are 23.5±1.5 cm and 19.7±1.0 cm, respectively. It is also seen that fast flux falls off less rapidly than resonance neutron (1.46 ev) flux after about 50 cm in graphite.
The spatial distribution of neutrons between the energies 1 Mev to 3 Mev from a plane monoenergetic source of 3‐Mev neutrons has also been obtained using a Monte‐Carlo calculation.

X‐Ray Investigation of Perfection in Tin Whiskers

H. G. Smith and R. E. Rundle

J. Appl. Phys. 29, 679 (1958); http://dx.doi.org/10.1063/1.1723249 (5 pages) | Cited 8 times

Online Publication Date: 15 June 2004

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Tin whiskers with elasticities far above that of bulk tin were examined for perfection by x‐ray diffraction. Intensities were measured for several whiskers varying in diameter from 2 μ to 11 μ. Some of the data were obtained by means of a Geiger counter with CuKα radiation and some by photographic methods with MoKα radiation. The observed structure factors were corrected for extinction according to the dynamical theory of x‐ray diffraction with the crystallite size as a parameter and then compared to the calculated structure factors. The agreement with dynamical theory for imperfect crystals is very good, yielding a crystallite size of 1.5 μ for a 5.5 μ whisker and 2.7 μ for whiskers of about 10 μ in diameter. The whiskers were observed growing in several crystallographic directions.

Elastic Constants by the Ultrasonic Pulse Echo Method

S. Eros and J. R. Reitz

J. Appl. Phys. 29, 683 (1958); http://dx.doi.org/10.1063/1.1723250 (4 pages) | Cited 30 times

Online Publication Date: 15 June 2004

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The elastic constants of single‐crystal KCl and NaI have been measured by means of the ultrasonic pulse echo method using a wide‐band amplifier to display the unrectified echo pattern directly. The experimental results agree with previous measurements made using other techniques. From detailed observations of successive echoes, made possible by the wide‐band receiving unit, it was determined that the pulse was attenuated at the front, and at the same time elongated, due to reflection from the specimen‐transducer interface. This effect turns out to be just what one would expect theoretically, and is responsible for the so‐called ``transit‐time error.'' The transit‐time error may be as large as one vibration period of the fundamental frequency in the pulse, and is most pronounced for crystal samples in which the acoustic impedance is the same as that of the quartz transducer.

Volumes and Surface Areas of Pendular Rings

Walter Rose

J. Appl. Phys. 29, 687 (1958); http://dx.doi.org/10.1063/1.1723251 (5 pages) | Cited 29 times

Online Publication Date: 15 June 2004

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A packing of spheres is taken as a suitable model of porous media. The packing may be regular and the sphere size may be uniform, but in general, both should be random. Approximations are developed to give the volumes and surface areas of pendular rings that exist at points of sphere contact. From these, the total free volume and interfacial specific surface area are derived as expressive of the textural character of the packing.
It was found that the log‐log plot of volumes and surface areas of pendular rings vary linearly with the angle made by the line joining the sphere centers and the line from the center of the largest sphere to the closest edge of the pendular ring. The relationship, moreover, was found not to be very sensitive to variation in the size ratio of the spheres in contact.
It also was found that the addition of pendular ring material to various sphere packings results in an unexpected decrease in the surface area of the boundaries that confine the resulting pore space.

Adsorption of Activated Gases

D. G. Bills and N. P. Carleton

J. Appl. Phys. 29, 692 (1958); http://dx.doi.org/10.1063/1.1723253 (6 pages) | Cited 10 times

Online Publication Date: 15 June 2004

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The adsorption of gases activated by electron bombardment has been investigated theoretically and experimentally. From postulates concerning probabilities of adsorption and deactivation for activated molecules in collision with surfaces an expression is derived giving the rate of adsorption in terms of these probabilities and of the amount of activated gas already adsorbed on the surfaces. This relation is also determined experimentally by a new method in which constant pressure is maintained in the adsorption vessel by admitting gas to it from a reservoir through a controlled leak, while the adsorption is taking place. The theoretical expression fits the experimental data, suggesting that the assumptions of the theory are essentially correct. From numerical values obtained under various experimental conditions some information is derived about the processes involved in adsorption of activated gases.

Neutron Production at High Energies

Walter E. Crandall and George P. Millburn

J. Appl. Phys. 29, 698 (1958); http://dx.doi.org/10.1063/1.1723254 (7 pages) | Cited 6 times

Online Publication Date: 15 June 2004

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Neutron yields from several targets bombarded by deuterons, protons, neutrons, and He3 ions with energies of hundreds of Mev were measured by detecting the neutrons with MnSO4 solution. The effect of secondary targets of U and Th in multiplying the primary yield was investigated, and the energy dependence for Be and U targets bombarded by deuterons was measured for energies between 90 and 320 Mev. The data were analyzed in terms of the average number of neutrons produced in an inelastic collision; the largest number observed was 17 for 340‐Mev protons bombarding U. The data are in reasonable agreement with evaporational theory and Monte Carlo calculations.

Evidence of Dislocation Jogs in Deformed Silicon

William C. Dash

J. Appl. Phys. 29, 705 (1958); http://dx.doi.org/10.1063/1.1723255 (5 pages) | Cited 63 times

Online Publication Date: 15 June 2004

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Trails extending from dislocations in plastically deformed silicon have been observed by decoration and also by an etching technique which develops channels on a {111} plane. The trails extending from screws tend to follow parallel <110> directions; those from mixed edge and screw dislocations are generally not crystallographic. Cusps occur where the trails are joined to the dislocations. A type of work hardening is found wherein trails from one turn of a Frank‐Read spiral obstruct the motion of subsequent turns. Trails are sometimes segmented or zig‐zag and appear to be composed of small discrete sections. Reversal of the direction of motion of a dislocation when the applied stress is removed is indicated by inversion of cusps. The main features of these trails can be accounted for on the basis of nonconservative motion of jogs which inject vacancies or interstitial atoms into their paths.

Excitation of Short Infrared Pulses with High Repetition Rate by Electron Bombardment of Cuprous Oxide

Rudolf Frerichs and Frank Weichman

J. Appl. Phys. 29, 710 (1958); http://dx.doi.org/10.1063/1.1723256 (4 pages) | Cited 5 times

Online Publication Date: 15 June 2004

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The infrared emission of Cu2O under electron‐bombardment was investigated. Lamps containing an electron‐bombarded Cu2O target emit a single band between 0.8 and 1.4 μ. They can be very accurately pulsed with the help of a built‐in grid. The efficiency at 6500 v is about 4 to 5% of the electrical input. With improved cooling of the target such lamps should form a powerful source for repetitive μsec pulses of the near infrared spectral region which can be observed with photoemissive tubes and image converters.

Maser Oscillator with One Beam through Two Cavities

Willard H. Wells

J. Appl. Phys. 29, 714 (1958); http://dx.doi.org/10.1063/1.1723257 (4 pages) | Cited 5 times

Online Publication Date: 15 June 2004

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A two‐cavity beam type of maser is studied by a geometrical representation of the Schrödinger equation developed by Feynman, Vernon, and Hellwarth. By this method complicated effects may be readily visualized. As an example, the qualitative explanation will be developed for the experimental observation that a cavity in a maser will oscillate simultaneously at two frequencies (differing by 1000–5000 cps) under certain conditions when the beam is first passed through another cavity. A possible amplifier application is noted.

Ultrasonic Interferometer for the Measurement of the Temperature Dependence of Elastic Constants

R. P. Espinola and P. C. Waterman

J. Appl. Phys. 29, 718 (1958); http://dx.doi.org/10.1063/1.1723258 (4 pages) | Cited 10 times

Online Publication Date: 15 June 2004

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An ultrasonic interferometer method for relatively precise measurement of changes in velocities in solids is described; fractional velocity changes as small as 5×10−6 can be detected by this method. Application of the interferometer to specimens in which the temperature is varied yields the temperature dependence of the appropriate adiabatic elastic stiffness constants. Some results are reported for steel, fused silica, and single crystals of KBr, KCl, and LiF.

Zeros of Gaussian Noise

Gerald M. White

J. Appl. Phys. 29, 722 (1958); http://dx.doi.org/10.1063/1.1723259 (8 pages) | Cited 2 times

Online Publication Date: 15 June 2004

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For many years statisticians and research workers in communication theory have been interested in the problem of the ``zeros'' i.e., the statistics of the times a random function crosses through its average value. At present very few of the desired results are amenable to analytic or numerical solution; therefore, an experiment was designed for generating and measuring the zeros of Gaussian noise having various spectral shapes. This article contains several experimentally determined distributions and statistics. Those that could be checked with numerical calculations {e.g., P[+z(t)|+z(0)], the probability of finding a zero in an increment of time Δt, t seconds after a zero has occurred} agreed closely with their calculated values. The others, e.g., W(N,T), the number of zeros in an increment of time T, verified what would be intuitively expected. The article also briefly outlines the equipment used in this investigation.

Field Modulation of Liquid Induced Excess Surface Currents on Germanium p‐n Junctions

W. T. Eriksen

J. Appl. Phys. 29, 730 (1958); http://dx.doi.org/10.1063/1.1723260 (4 pages) | Cited 1 time

Online Publication Date: 15 June 2004

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The field modulation of liquid induced surface currents on germanium surfaces has been investigated. The field induced current is shown to conform to the behavior seen by liquid induced currents on germanium surfaces. The modulation increases with decreasing temperature down to the melting point of the liquid and then decreases radically to nearly zero. The modulation effect is seen only when polar liquid ambients are used. A qualitative explanation of the effect is discussed in terms of a model for current conduction in which the charge carriers move in the liquid outside of the semiconductor. The increased current with external field is thought to arise from the orientation of the dipoles in the liquid giving increased mobility to the charge carriers.
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Mechanism of Electron Emission from the Arc Cathode

A. Von Engel and A. E. Robson

J. Appl. Phys. 29, 734 (1958); http://dx.doi.org/10.1063/1.1723261 (1 page) | Cited 8 times

Online Publication Date: 15 June 2004

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On the Discussion of the T‐F Theory by Robson and von Engel

T. H. Lee

J. Appl. Phys. 29, 734 (1958); http://dx.doi.org/10.1063/1.1723262 (2 pages) | Cited 6 times

Online Publication Date: 15 June 2004

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