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1 Dec 1952

Volume 23, Issue 12, pp. 1289-1413

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Radiofrequency Field Quenching of Ultraviolet Excited Phosphors

Theodore Miller

J. Appl. Phys. 23, 1289 (1952); http://dx.doi.org/10.1063/1.1702061 (5 pages) | Cited 5 times

Online Publication Date: 15 June 2004

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The quenching action of radiofrequency field on ultraviolet excited phosphors has been investigated for a number of sulfide phosphors. The phosphor layer is sandwiched between two parallel plane electrodes. The radiofrequency potential is applied to the electrodes. Data are presented showing the dependence of the quenching action on field strength, field frequency, and ultraviolet excitation. The quenching response to an amplitude modulated rf potential, and the fatigue effects resulting from prolonged exposure to the rf field have also been investigated.

The Electromagnetic Field of a Rotating Uniformly Magnetized Sphere

Alfredo Baños and Robert K. Golden

J. Appl. Phys. 23, 1294 (1952); http://dx.doi.org/10.1063/1.1702062 (6 pages) | Cited 6 times

Online Publication Date: 15 June 2004

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The problem discussed here is a first step towards a more complete understanding of the modern theories of geomagnetism which are based on the differential rotation of the earth's crust with respect to its inner core and on magneto‐hydrodynamical effects in the core. This paper considers first the computation of the electric and magnetic fields that a stationary observer attributes to a uniformly magnetized sphere which, in his frame of reference, rotates at constant angular velocity about an axis parallel to the direction of magnetization. It is found that, neglecting the terms of order v2∕c2, the observed magnetic fields are identical to the fields of the stationary sphere, but in addition there is an external electric field identical to that produced by an axial quadrupole located at the origin. The interior electric field is directed towards the axis of rotation and its magnitude is proportional to the distance from the axis. Next, when the rotating magnet is surrounded by a stationary concentric shield, it is found that the electric fields vanish in the interior of the shield and in outer space in contrast to the results that one would find on the assumption that the shield was being ``cut'' by the lines of magnetic induction of the rotating magnet. Finally, the limiting case is considered in which the inner radius of the shield approaches the radius of the sphere, an insulating layer still being maintained between them. Here, again, no electric fields are found outside the rotating magnet.

Fast Jets from Collapsing Cylinders

W. S. Koski, F. A. Lucy, R. G. Shreffler, and F. J. Willig

J. Appl. Phys. 23, 1300 (1952); http://dx.doi.org/10.1063/1.1702063 (6 pages) | Cited 12 times

Online Publication Date: 15 June 2004

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A method is described for producing fast jets from the collapse of metal‐lined cavities in high explosives. The behavior of these jets suggests that they cannot be accounted for by the simple hydrodynamical considerations that have in the past been successful when applied to slower type jets. Various experiments, including time‐resolved spectrographic observations, show the jets to be, at least in part, of a gaseous nature. Velocities as high as 90 km∕sec have been observed for beryllium jets, with heavier elements exhibiting lower velocities in inverse order of their atomic weights.

Solubility and Diffusion Coefficient of Carbon in Nickel: Reaction Rates of Nickel‐Carbon Alloys with Barium Oxide

J. J. Lander, H. E. Kern, and A. L. Beach

J. Appl. Phys. 23, 1305 (1952); http://dx.doi.org/10.1063/1.1702064 (5 pages) | Cited 53 times

Online Publication Date: 15 June 2004

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Experimental values for the solubility of carbon in nickel in the range 700°C to 1300°C yield the equation lnS=2.480−4,880∕T, where S is the solubility in grams of carbon per 100 grams of nickel. Values obtained for the diffusion coefficient in the same range fit the equation lnD=0.909−20,200∕T, where D is in cm2 per second. These results are of some interest in the problem of the activation of thermionic oxide coated cathodes, and the experimental method used to measure the diffusion coefficients is related to phenomena occurring in vacuum tubes. To extend the usefulness of the results in this direction, rates of reaction between diffused carbon and barium oxide coatings on nickel have been measured. It was found that the rates are diffusion limited over a wide range of conditions of interest.

A Method for the Measurement of Spherical Aberration of an Electrostatic Electron Lens

Daryl W. Shipley

J. Appl. Phys. 23, 1310 (1952); http://dx.doi.org/10.1063/1.1702065 (7 pages)

Online Publication Date: 15 June 2004

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A relatively simple method for the experimental determination of spherical aberration of electrostatic electron lenses is described. This method uses an effective point source of electrons at the center of deflection of a magnetic deflection yoke; the yoke deflects the beam through any desired aperture angle. From the measurement of the displacement of the electron beam in the Gaussian image plane as a function of the aperture angle, the coefficient of spherical aberration can be calculated. The value for this coefficient obtained from the measurement of a unipotential lens and that calculated for this lens by numerical integration are compared; the agreement is within twelve percent. An effective method for the detection of axial astigmatism (which is due to an ellipticity of the lens field) of a lens is described. Diagrams and photographs are given which qualitatively substantiate the method.

The Mechanism of the Ring Discharge in Negative Point‐to‐Plane Corona

Allan Greenwood

J. Appl. Phys. 23, 1316 (1952); http://dx.doi.org/10.1063/1.1702066 (4 pages)

Online Publication Date: 15 June 2004

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Conditions favoring the formation of the ring discharge, and changes in the electrical characteristics which it brings about, are discussed. A theory is developed which seeks to explain the formation of the ring in terms of field distortion caused by negative space charges in the gap. This requires a change of view on the subject of space charge transit times, but this is justified by theoretical and experimental considerations. The paper concludes with a description of two experiments designed to test the theory, and analyzes the results of these tests.

Some Experiments on Centimeter‐Wavelength Scattering by Small Obstacles

N. R. Labrum

J. Appl. Phys. 23, 1320 (1952); http://dx.doi.org/10.1063/1.1702067 (4 pages) | Cited 6 times

Online Publication Date: 15 June 2004

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The scattering of electromagnetic waves by small obstacles has been measured in several cases which are of interest in connection with the interpretation of radar echoes from rain and cloud formations. The measurements were made at a frequency of 3000 Mc∕sec by an impedance‐bridge technique, the specimens being contained in a wave guide. The results verify the theoretical relationship between the size of the scatterer and the intensity of the backscattered wave. Observations have also been made of the variation in scattering during the melting of an obstacle initially composed of ice. In this case, it was not possible to simulate exactly the conditions of large‐scale meteorological phenomena; however, the experiments demonstrate qualitatively that, as had been predicted, the power backscattered from an initially nonspherical ice particle passes through a maximum value during the transition to a water drop.

The Scattering of Radio Waves by Meteorological Particles

N. R. Labrum

J. Appl. Phys. 23, 1324 (1952); http://dx.doi.org/10.1063/1.1702068 (7 pages) | Cited 6 times

Online Publication Date: 15 June 2004

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The scattering of electromagnetic waves by clouds of small spheroidal obstacles is considered from a theoretical standpoint. Numerical data are obtained for the case of clouds composed of partly melted ice particles. These results are applied to the interpretation of ``bright band'' radar echoes from meteorological formations.
It is also shown that these echoes may contain a component with polarization at right angles to that of the transmitted beam. It is suggested that this property could be utilized in certain cases to provide additional information as to the nature of the scattering particles.

Excess Thermal Noise Due to Current Flow Through (Ba Sr) Oxide Coating

K. Amakasu

J. Appl. Phys. 23, 1330 (1952); http://dx.doi.org/10.1063/1.1702069 (3 pages) | Cited 2 times

Online Publication Date: 15 June 2004

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A study has been made to clarify the nature of the thermal noise generated within the layer of the (Ba Sr) oxide coating of the cathode when a current flows through it, and to determine how much this noise affects the flicker noise. The results of this investigation show that (1) the excess noise generated by the flow of current is proportional to the square of the current flowing through the coating layers, (2) the frequency spectrum of the noise is inversely proportional to the frequency, (3) the noise is greatly affected by the activation of cathode, a slight decrease in activation causing a sudden increase of noise (4) the portion of the cathode flicker noise due to this excess noise may be neglected when the activation of the cathode is good, but when the activation is poor, it becomes considerably larger. The characteristic of (3) may be considered to give a clue to a clarification of the electron conductivity mechanism in the oxide cathode.

Potential Distribution for Space‐Charge Limited Current between a Plane Accelerating Grid and Parallel Anode

E. G. Ramberg and L. Malter

J. Appl. Phys. 23, 1333 (1952); http://dx.doi.org/10.1063/1.1702070 (3 pages)

Online Publication Date: 15 June 2004

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Expressions are derived for the potential distribution between a plane accelerating grid and parallel anode under conditions of space‐charge limitation, taking account of the Maxwellian velocity distribution of the electrons. The distribution is determined by Langmuir's diode functions in combination with a function depending on the current transmission of the grid‐anode space, which is represented graphically.

Contribution to the Theory of Impulse Breakdown

Frank R. Dickey

J. Appl. Phys. 23, 1336 (1952); http://dx.doi.org/10.1063/1.1702071 (4 pages) | Cited 13 times

Online Publication Date: 15 June 2004

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The experiments of R. C. Fletcher on impulse breakdown are discussed and a simple theory for these experiments is developed by assuming that the breakdown consists of ionization and charge separation in a uniform field. The theory accounts reasonably well for the time lags and also explains the shapes of the breakdown voltage transients. It indicates also that measurement of the mean ionizing time for electrons in the gap should be possible.

Complicated Domain Patterns on Iron‐Silicon Single Crystals

C. F. Ying, S. L. Levy, and R. Truell

J. Appl. Phys. 23, 1339 (1952); http://dx.doi.org/10.1063/1.1702072 (7 pages) | Cited 2 times

Online Publication Date: 15 June 2004

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Domain patterns on (100) surfaces of iron‐silicon single crystals were observed between successive electrolytic or mechanical polishings. By repeatedly interrupting the electropolishings to examine the surfaces, complicated patterns were observed before simple ones were seen at the time when the surfaces were deeply polished. With fine mechanical polishing alone, results similar to those observed with interrupted electropolishing were obtained, including the final appearance of simple patterns. These complicated patterns are interpreted as characteristic of strained surfaces. Complicated patterns appearing on heavily polished surfaces are, therefore, believed to be induced by local strains which are not completely removed, like those along deep scratches formed during the rough mechanical polishing.

Elastic Wave Propagation in Solid Media

Robert A. Mapleton

J. Appl. Phys. 23, 1346 (1952); http://dx.doi.org/10.1063/1.1702073 (9 pages) | Cited 1 time

Online Publication Date: 15 June 2004

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The reflection of elastic waves at plane solid‐vacuum interfaces and the two‐dimensional solutions of the vector equation of equilibrium for elastic waves propagating through elastic plates of uniform thickness are investigated. Both the isotropic solid and the cubic system of nonpiezoelectric single crystals are treated. The objective is to compare multiple reflection solid delay lines, isotropic versus single crystal, in terms of the thickness of the plate required for satisfactory propagation and reflection characteristics. The sections on wave propagation are not exhaustive, but consider the particular wave mode that most closely resembles the plane shear wave with diplacement component normal to the faces of the plate. In the sections on single crystals, it is shown that plane shear waves propagate with a speed independent of the direction provided that the displacement is parallel to a crystallographic axis. The reflection laws for these plane shear waves are the same for isotropic solids and single crystals provided that the displacement is contained in a plane that is parallel to the stress‐free interface. A calculation compares the wave propagating characteristics of plates of fused quartz and calcium fluoride for operation at 15 mcs. The plate of calcium fluoride should be roughly three times thicker to give the same performance as the plate of fused quartz.

Film Boiling Termination Mechanism

J. W. Marx and B. I. Davis

J. Appl. Phys. 23, 1354 (1952); http://dx.doi.org/10.1063/1.1702074 (4 pages) | Cited 2 times

Online Publication Date: 15 June 2004

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It is suggested that free molecule heat conduction provides the critical energy transfer that just precedes the collapse of the vapor blanket in the film boiling process. An expression for the extreme possible values of the heat transfer coefficient, as a function of pressure, is derived for solid‐boiling liquid systems and numerically evaluated for water. The wetting temperature is given in terms of measurable parameters of the system, and experiments are suggested.

A Mathematical Analysis of an Inductively Loaded Parallel‐Connected Magnetic Amplifier

Louis A. Pipes

J. Appl. Phys. 23, 1358 (1952); http://dx.doi.org/10.1063/1.1702075 (4 pages)

Online Publication Date: 15 June 2004

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A mathematical analysis of a parallel‐connected magnetic amplifier with an inductive load is presented. The analysis is based on the representation of the normal magnetization curve of the core material by a polynomial of the fifth degree. The load current is expressed in terms of the magnetic intensity of one of the cores. The magnetic intensity is shown to satisfy a nonlinear differential equation and an approximate solution of this equation is obtained by an iterative procedure. An estimate of the response time of the amplifier is determined and the steady‐state response of the amplifier is obtained.

Vertical Entry of Missiles into Water

Albert May

J. Appl. Phys. 23, 1362 (1952); http://dx.doi.org/10.1063/1.1702076 (11 pages) | Cited 27 times

Online Publication Date: 15 June 2004

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Investigations, carried out principally on the vertical water entry of steel spheres, are described. Graphs show the effect of several experimental parameters on the time and place of occurrence of various events in the life of the cavity which accompanies the entry. These parameters include the density and pressure of the atmosphere above the water, and the velocity, size, and nose shape of the missile. Froude‐scaling is found to be a good first approximation in describing cavity behavior, and some improvement is effected by the pressure‐density scaling of the atmosphere above the water. The energy lost by a missile during the open‐cavity phase of its water entry is found to be used up principally in the formation of the cavity, and the cavity shape is not dependent on the nose shape of the missile for a given drag force.

The Interaction of Plane Shock Waves and Rough Surfaces

Russell E. Duff

J. Appl. Phys. 23, 1373 (1952); http://dx.doi.org/10.1063/1.1702077 (7 pages) | Cited 1 time

Online Publication Date: 15 June 2004

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Shock tube experiments have been conducted to determine the effect of surface roughness on shock waves in nitrogen passing over the surface. Shock retardation was measured for a series of two‐ and three‐dimensionally rough surfaces at shock strengths from ξ=0.1 to ξ=0.9. The first‐order approximation was made that the volume between the positions of the shock wave, with and without the rough surface present, multiplied by the specific energy behind the undisturbed shock wave represented energy dissipated by the roughness. The space rate of energy dissipation is presented as a function of the average particle size of the rough surface. It is also shown that the curvature of the shock wave in the vicinity of the surface depends on the roughness of the surface, the length of roughness covered, and the strength of the shock wave. In addition, the hundreds of measurements of shock wave contours made in this investigation showed that there is a random fluctuation in the angle of incidence of the primary shock wave of 1∕15°. This fluctuation is presumably caused by the details of the diaphragm rupture even though measurements were made 14 ft from the diaphragm in a shock tube with a 2×7 in. cross section.

Neutron Diffraction Studies of Cold‐Worked Brass

R. J. Weiss, J. R. Clark, L. Corliss, and J. Hastings

J. Appl. Phys. 23, 1379 (1952); http://dx.doi.org/10.1063/1.1702078 (4 pages) | Cited 13 times

Online Publication Date: 15 June 2004

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Powder diffraction data with neutrons have shown the integrated intensities to be identical in cold‐worked (filed) and annealed brass with no trace of extinction effects. Long wavelength transmission studies have also shown that the diffuse scattering is increased by less than 0.4 percent upon severely cold rolling brass. A new technique of examining the Bragg discontinuities supports the hypothesis that the major part of the broadening is due to lattice distortion. Some remarks are presented concerning the analogy between long wavelength neutrons and conduction electrons with respect to scattering by dislocations. The effects of dislocations on coherent scattering are also considered.

On the Magnetic Resonance Absorption in Conductors

N. Bloembergen

J. Appl. Phys. 23, 1383 (1952); http://dx.doi.org/10.1063/1.1702079 (7 pages) | Cited 63 times

Online Publication Date: 15 June 2004

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The electromagnetic losses in conductors are analyzed in terms of magnetic absorption and conduction losses. The quantities observed in a magnetic resonance experiment have a different meaning depending on whether the dimensions of the sample are large or small compared to the skin depth. Explicit formulas for electric and magnetic losses are given for the case of a plane sheet and a sphere. The influence of the conductivity on the line shape and saturation effects is discussed both for nuclear and ferromagnetic resonance.

The Production of High Temperature Gases in Shock Tubes

E. L. Resler, Shao‐Chi Lin, and Arthur Kantrowitz

J. Appl. Phys. 23, 1390 (1952); http://dx.doi.org/10.1063/1.1702080 (10 pages) | Cited 114 times

Online Publication Date: 15 June 2004

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This paper is intended to set forth aerodynamic and thermodynamic calculations which are useful in the production of strong shock waves. The experimental production of strong shock waves is discussed. Comparison of the experimental shock strengths with the theoretical calculations is made, and finally, some preliminary results of shock tube studies in high temperature gases (up to 18,000°K) are briefly surveyed.

On Solutions to the Wave Equation in Hyperbolic Space

John W. Miles

J. Appl. Phys. 23, 1400 (1952); http://dx.doi.org/10.1063/1.1702145 (1 page) | Cited 2 times

Online Publication Date: 15 June 2004

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Cold Work Studies on Copper at Low Temperatures

R. R. Eggleston

J. Appl. Phys. 23, 1400 (1952); http://dx.doi.org/10.1063/1.1702146 (2 pages) | Cited 15 times

Online Publication Date: 15 June 2004

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Abstract Unavailable

Mechanism of Growth of Whiskers on Cadmium

Milton O. Peach

J. Appl. Phys. 23, 1401 (1952); http://dx.doi.org/10.1063/1.1702147 (3 pages) | Cited 13 times

Online Publication Date: 15 June 2004

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Abstract Unavailable

Diffraction of Electromagnetic Waves by an Aperture in an Infinite Screen

G. Bekefi

J. Appl. Phys. 23, 1403 (1952); http://dx.doi.org/10.1063/1.1702148 (1 page) | Cited 5 times

Online Publication Date: 15 June 2004

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Abstract Unavailable

Reflection of Electromagnetic Waves Obliquely from An Inhomogeneous Medium

James R. Wait

J. Appl. Phys. 23, 1403 (1952); http://dx.doi.org/10.1063/1.1702149 (2 pages) | Cited 1 time

Online Publication Date: 15 June 2004

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Abstract Unavailable
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