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1 Dec 1961

Volume 32, Issue 12, pp. 2499-2651

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Electron Microscope Investigation on the Nature of Tracks of Fission Products in Mica

Guido Bonfiglioli, Andrea Ferro, and Adriana Mojoni

J. Appl. Phys. 32, 2499 (1961); http://dx.doi.org/10.1063/1.1728339 (5 pages) | Cited 36 times

Online Publication Date: 11 June 2004

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Specimens of biotite, muscovite, artificial fluorophlogopite, and muscovite annealed at 900°C were examined using an electron microscope after having been covered with a uranium layer and irradiated in a reactor. Tracks due to fission products appeared on every specimen except biotite, and the respective diameters were put into correspondence with the resistance of the various micas to thermal decomposition. The tracks were larger in muscovite (240 A), thinner in fluorophlogopite (150 A), and still more in dehydrated muscovite (115 A). The writers believe that the mechanism of damage has its origin in the heat released by the heavy ionizing particles. Peculiar recovery effects were often observed.

Growth of Stannic Oxide Crystals from the Vapor Phase

J. A. Marley and T. C. MacAvoy

J. Appl. Phys. 32, 2504 (1961); http://dx.doi.org/10.1063/1.1728340 (2 pages) | Cited 23 times

Online Publication Date: 11 June 2004

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Single crystals of stannic oxide up to 30×4×2 mm have been prepared by a high temperature vapor deposition technique. Using high purity SnO2 powder, crystallization and growth were studied under both neutral and oxidizing conditions. Neutral carrier gases, with the exception of helium, encouraged the formation of voids and inclusions. However, the use of a helium‐oxygen system was found to eliminate these defects. An explanation is offered for this behavior. Three distinct variations in the crystalline habit of SnO2 have been observed, apparently dependent upon the temperature at which growth occurred.

Magnetic Investigation of Pure Manganese and of Several of its Alloys

H. W. Cooper, A. S. Arrott, and H. W. Paxton

J. Appl. Phys. 32, 2506 (1961); http://dx.doi.org/10.1063/1.1728341 (7 pages) | Cited 2 times

Online Publication Date: 11 June 2004

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Arrott, Coles, and Goldman have shown that a parasitic ferromagnetism can be induced at low temperatures in antiferromagnetic α manganese by pickling in nitric acid, and that this effect can be subsequently removed by a vacuum anneal. We have confirmed this result. Furthermore, we have eliminated as possible sources for this effect the presence of hydrogen or nitrogen in solid solution and the formation of nitrides or hydrides. However, strains arising upon transforming from the β phase to the α phase can induce this parasitic ferromagnetism. These results fit well with Li's hypothesis of antiferromagnetic domain boundaries giving rise to parasitic ferromagnetism. According to Li, strains should serve well to stabilize the domain boundaries.

Theory of Electron Collection of Spherical Probes

G. Medicus

J. Appl. Phys. 32, 2512 (1961); http://dx.doi.org/10.1063/1.1728342 (9 pages) | Cited 27 times

Online Publication Date: 11 June 2004

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The theory of spherical probes based on the impact parameter of the carriers is given. Fields outside the sheath are neglected, which is justified for electron collection. The results are obtained more directly than by Mott‐Smith and Langmuir. General results such as the transition from impact parameter limitation to sheath limitation for the spherical case, not previously treated in the literature, are derived. The case of a uniformly accelerated half‐Maxwellian (as opposed to a Maxwellian with drift) is treated in detail; the case of a pure Maxwellian superimposed on the accelerated half‐Maxwellian and the superposition of two different accelerated half‐Maxwellians is discussed briefly.

Characteristic Electron Energy Loss Measurements at Low Temperatures

E. M. Hörl and J. A. Suddeth

J. Appl. Phys. 32, 2521 (1961); http://dx.doi.org/10.1063/1.1728343 (5 pages) | Cited 8 times

Online Publication Date: 11 June 2004

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A method is described for the investigation of characteristic energy losses of electrons in solids at temperatures in the liquid helium and liquid hydrogen temperature range. This method had been primarily developed for the investigation of thin films of solidified permanent gases, but it is also very suitable for the study at low temperatures of any substance, which is obtainable as a thin film. For the measurement of the energy losses itself, a very versatile electrostatic analyzer lens has been constructed which allows the observation of electron diffraction patterns of the samples before and after energy loss measurements. First results are reported on thin films of solid oxygen and solid xenon.

Defect Mechanisms in a Noncrystalline Solid

W. C. Levengood

J. Appl. Phys. 32, 2525 (1961); http://dx.doi.org/10.1063/1.1728344 (9 pages) | Cited 11 times

Online Publication Date: 11 June 2004

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It is proposed that spiral defects originate at torque stress fields in glass and represent variations in localized bond energy. By postulating shear stress couples across flaw lines, extension and annihilation of flaws from neighboring spiral sources were tentatively explained. Distortion or movement within a spiral was indicated on samples subjected to localized stress before etching. Experimentally it was shown that substitution of lead and bismuth for silica in a nonspiral glass produced a rigid, brittle network which ultimately disclosed spirals originating at minute nuclei. Details of structure were quantitatively studied by using the dynamic spherical indenter. Flaw loops were also discovered which originated at random etch pit sources and increased in diameter with applied stress. Rows of etch pits were observed on samples stressed in torque. The conjecture was introduced that the torsion stress caused collapse of flaws into point defect rows. The etch pit rows appeared to be more stable than linear flaws. The minimum length of stability of a void derived from dislocation theory was in agreement with experimental measurements from the point defect rows.

Growth of Refractory Crystals Using the Induction Plasma Torch

Thomas B. Reed

J. Appl. Phys. 32, 2534 (1961); http://dx.doi.org/10.1063/1.1728345 (2 pages) | Cited 37 times

Online Publication Date: 11 June 2004

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Apparatus is described for growing refractory crystals using the induction plasma torch in a Verneuil‐type geometry. The plasma torch makes possible crystal growth at higher temperatures than can be achieved with flames and in inert or reactive atmospheres. Conditions are given for growth of sapphire, stabilized zirconia, and niobium crystals.

Properties of Single‐Domain Particles of Cobalt‐Nickel

R. B. Falk and G. D. Hooper

J. Appl. Phys. 32, 2536 (1961); http://dx.doi.org/10.1063/1.1728346 (3 pages) | Cited 7 times

Online Publication Date: 11 June 2004

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Single‐domain particles of cobalt‐nickel have been prepared by electrodeposition into mercury, and the intrinsic coercive force observed as a function of particle composition. A marked increase in coercive force occurred in particles having a composition of 87.5% cobalt–12.5% nickel. On the basis of the spherical structure of the particles observed in electron micrographs and from the constancy of the coercive force with packing, crystal anisotropy was assumed to be the principal factor contributing to the coercivity of the cobalt‐nickel particles. An intrinsic coercive force of 1750 oe was achieved, and a minimum crystal anisotropy of −2.4×106 ergs∕cc calculated at −196°C for the above composition. Magnets were prepared with a maximum magnetic energy of 1.3×106 gauss‐oe.

Improved Representation of Calculated Surface Mobilities in Semiconductors. I. Minority Carriers

N. B. Grover, Y. Goldstein, and A. Many

J. Appl. Phys. 32, 2538 (1961); http://dx.doi.org/10.1063/1.1728347 (2 pages) | Cited 7 times

Online Publication Date: 11 June 2004

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A simple and convenient representation is given of calculated values of minority carrier surface mobility over the range of practical interest of surface potential from depletion to strong inversion layers for an extended range of material resistivity and temperature.

Improved Representation of Calculated Surface Mobilities in Semiconductors. II. Majority Carriers

Y. Goldstein, N. B. Grover, A. Many, and R. F. Greene

J. Appl. Phys. 32, 2540 (1961); http://dx.doi.org/10.1063/1.1728348 (2 pages) | Cited 14 times

Online Publication Date: 11 June 2004

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Improved representation is given of calculated values of majority carrier surface mobility. For extrinsic material the semiconductor effectively constitutes a single‐carrier system. The surface mobility is then independent of the bulk potential and can be expressed as a function of the potential barrier Vs by a single family of curves over the entire range of interest of surface potential, material resistivity, and temperature.

A cw Solid State, Push‐Pull Maser in the 5 to 6 Millimeter Wavelength Region

David L. Carter

J. Appl. Phys. 32, 2541 (1961); http://dx.doi.org/10.1063/1.1728349 (2 pages) | Cited 2 times

Online Publication Date: 11 June 2004

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Cw maser oscillation from 49 to 57 kMc was achieved with 0.12% Fe3+‐doped rutile, using push‐pull pumping at 78.2 kMc. A short experiment on cross‐relaxation effects was also performed.

Low‐Temperature Thermoelectric Power of the Rare‐Earth Metals

H. J. Born, Sam Legvold, and F. H. Spedding

J. Appl. Phys. 32, 2543 (1961); http://dx.doi.org/10.1063/1.1728350 (7 pages) | Cited 25 times

Online Publication Date: 11 June 2004

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The Seebeck coefficients (thermoelectric powers) of yttrium, lanthanum, and 11 of the rare earths have been measured for the temperature range 7° to 300°K. The transitions reported by other investigators on specific heat, magnetic moment, and resistivity at the magnetic ordering temperatures are, in many instances, visible also in the curves of thermoelectric power (TEP) vs temperature. The Néel temperature is evidenced by a change in slope in the TEP vs T curve. The ferro‐antiferro transition temperature is obvious only in the case of dysprosium and appears as a sharp drop in the curve. With the exception of samarium and ytterbium, the TEP's of the metals are negative throughout most of the temperature range covered, and, with the same exceptions, the TEP curves have about the same slope near room temperature.

A Method for the Measurement of Short Minority Carrier Diffusion Lengths in Semiconductors

Alvin M. Goodman

J. Appl. Phys. 32, 2550 (1961); http://dx.doi.org/10.1063/1.1728351 (3 pages) | Cited 165 times

Online Publication Date: 11 June 2004

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A method is presented whereby short minority carrier diffusion lengths in semiconductors may be determined by measuring the variation of surface photovoltage as a function of optical absorption coefficient. The method does not depend upon the specific form of the relationship between the surface photovoltage and the density of the excess minority carriers injected at the bulk edge of the surface space charge region. Only capacitive contacts to the sample are needed for the measurement. The method has been used to determine the minority carrier diffusion length in both n and p type gallium arsenide.

Theory of the Potential Well Produced by Multipacting Electrons. I. Very Low‐Pressure Regime

R. L. Ingraham

J. Appl. Phys. 32, 2553 (1961); http://dx.doi.org/10.1063/1.1728352 (6 pages) | Cited 1 time

Online Publication Date: 11 June 2004

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Electrons multipacting in an evacuated discharge tube produce an effective static potential well in which the positive ions can be contained. The theory of the positive ion behavior in this ``electron well'' in the very low pressure regime (P [less than double similar] 10−5 mm Hg) is developed here. The electron potential well is expressed finally as a double numerical integral of complete elliptic integrals for the general field point; for on‐axis points it reduces to a single numerical integral of irrational expressions. With the ``short tube'' and ``constant sheet velocity'' approximations, the well is parabolic; the corresponding ion harmonic vibration frequencies are calculated. For the rigorous well these parabolas are flattened in the central parts and steepened near the electrodes. A self‐consistent calculation of the ion density is made using an individual particle description of the ion gas (appropriate to very low densities) which results in an inhomogeneous integral equation. The solutions describe ion distributions peaked in the middle of the tube. For comparison with experiment the deflection of an ion beam fired across the tube is worked out.

A Comparison of Theory and Experiment for a Thermoelectric Cooler

M. H. Norwood

J. Appl. Phys. 32, 2559 (1961); http://dx.doi.org/10.1063/1.1728353 (5 pages) | Cited 2 times

Online Publication Date: 11 June 2004

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The performance of single‐stage Peltier thermocouples was calculated using the experimentally measured values of thermoelectric power, electrical resistivity, and thermal conductivity as functions of temperature. These calculations were made by solving numerically the differential equation for the temperature distributions in the thermoelements. The boundary conditions were the hot junction temperature and the heat flow at the cold junction. The calculated behavior of the thermocouples agreed well with the measured performance in the three cases studied. The measured thermocouple figure of merit agreed with that calculated from the material properties.
The effect of temperature variations of the material properties on thermocouple performance was studied by comparing exact calculations with calculations involving one temperature‐averaged constant material property. This type of calculation showed that the Thomson effect caused about 4°K of the maximum ΔT of 66°K for one couple studied. The temperature variation of resistivity was found to be the major cause of disagreement between exact calculations and the simpler theory (Ioffe equations).

Hardening of Lithium Fluoride Crystals by Irradiation

J. S. Nadeau and W. G. Johnston

J. Appl. Phys. 32, 2563 (1961); http://dx.doi.org/10.1063/1.1728354 (3 pages) | Cited 21 times

Online Publication Date: 11 June 2004

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The very soft, pure crystals of LiF that are now commercially available are unsuitable for some experimental work because they suffer accidental plastic deformation during cleavage and tend to split on (110) planes. Irradiation with gamma rays produces harder crystals that can be cleaved and handled without much damage. The radiation‐induced hardening and the color centers produced by moderate irradiation can be completely removed by annealing for several hours at 450°C. This method for handling very soft crystals may be useful for other types of crystals, and various types of irradiation can be employed.

Motion of c Domain Centers in BaTiO3

G. L. Link

J. Appl. Phys. 32, 2566 (1961); http://dx.doi.org/10.1063/1.1728355 (8 pages) | Cited 4 times

Online Publication Date: 11 June 2004

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A novel effect has been observed in BaTiO3. By applying a biased alternating field to a BaTiO3 crystal which contains an a domain, one can observe a large number of small dots which move in straight lines. The dots are shown to be small c domains, and their motion can be accounted for by the electric field perturbation caused by the a domain.

High‐Temperature Kilocycle Internal Friction in Al2O3 Single Crystals

R. J. Huber, G. S. Baker, and P. Gibbs

J. Appl. Phys. 32, 2573 (1961); http://dx.doi.org/10.1063/1.1728356 (7 pages) | Cited 10 times

Online Publication Date: 11 June 2004

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Dislocation damping in Al2O3 single crystals has been measured to 1850°C. Undeformed specimens show no damping greater than δ = 10−5. Deformed specimens have an exponentially rising damping above 1450°C with an activation energy of 100–120 kcal∕mole. The damping is amplitude independent at least to 10−5 strain amplitude. Dislocation densities and distributions for the specimens were determined by surface etching.

Momentum and Energy of Waves

J. R. Pierce

J. Appl. Phys. 32, 2580 (1961); http://dx.doi.org/10.1063/1.1728357 (5 pages) | Cited 4 times

Online Publication Date: 11 June 2004

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Elementary arguments of conservation of energy and momentum are used to derive expressions for what Sturrock terms the ``formal'' momentum, angular momentum, and energy of a plane wave in a moving medium. If E is the energy per unit length, p the momentum per unit length, q the angular momentum per unit length, vf the phase velocity, and if the angular variation of a circulatory polarized wave is as exp(—jnθ),
math
If E0 is the energy per unit length observed moving with the medium, and then if the medium moves past the observer with a velocity u and the observer measures a phase velocity vf, he observes an energy per unit length E,
math
.When p, q, and E are not the physical momenta and energy, they lead to the correct power and force for sinusoidal sources moving with respect to the medium.

Magnetic Domain Patterns in Cr‐Modified Mn2Sb

J. D. Wolf and J. E. Hanlon

J. Appl. Phys. 32, 2584 (1961); http://dx.doi.org/10.1063/1.1728358 (3 pages) | Cited 7 times

Online Publication Date: 11 June 2004

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The relationship between microstructure and the magnetic properties of Cr‐modified Mn2Sb has been studied using the Bitter pattern technique. The solid solution formed when Cr is substituted for Mn in Mn2Sb exhibits a ferrimagnetic to antiferromagnetic first order phase transformation which occurs at about room temperature for 5 at.% Cr. In the transformation temperature range, we have followed the initiation and growth of the ferrimagnetic phase by observing the associated domain patterns. In addition, the Bitter pattern technique has been used to examine precipitates with magnetic properties differing from the matrix.

Growth from the Melt. III. Dendritic Growth

G. F. Bolling and W. A. Tiller

J. Appl. Phys. 32, 2587 (1961); http://dx.doi.org/10.1063/1.1728359 (19 pages) | Cited 67 times

Online Publication Date: 11 June 2004

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See Also: Erratum

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A mathematical treatment of steady‐state dendritic growth from pure and alloy liquids has been developed for isothermal and nonisothermal dendrites. The velocity of dendritic growth, dendrite size, dendrite direction, and the alloy content of the dendrite have been calculated as a function of the bath supercooling, the alloy content of the bulk liquid, and the atomic kinetics of the material. To specify the problem completely it was necessary to choose some ``optimization'' condition. We have chosen the condition of ``maximum velocity.'' Comparison of the theoretical predictions with experimental data for pure nickel, tin, and ice, and for KCl and acetic acid solutions have been made. Satisfactory agreement with experiment was found using the atomic mechanism of ``uniform interface advance.''

High‐Field Conductivity in Germanium and Silicon at Microwave Frequencies

J. Zucker, V. J. Fowler, and E. M. Conwell

J. Appl. Phys. 32, 2606 (1961); http://dx.doi.org/10.1063/1.1728360 (6 pages) | Cited 30 times

Online Publication Date: 11 June 2004

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The effect on the conductivity of germanium and silicon samples of 2.85‐kMc electric fields up to peak values of 10 000 v∕cm was measured. These measurements differ from earlier ones in that: (1) the microwave field was in the form of progressive rather than standing waves, which made possible more accurate determination of the field strength in the sample, and (2) to determine whether any frequency effects occur at 2.85‐kMc conductivity was measured at high dc fields on the same samples. From the average conductivity under microwave excitation the instantaneous conductivity was calculated and found to agree, within experimental error, with the dc conductivity, indicating that the conductivity can still follow the 2.85‐kMc field at least up to peak fields of 10 000 v∕cm.

Space‐Charge Instabilities in Electron Diodes and Plasma Converters

Charles K. Birdsall and William B. Bridges

J. Appl. Phys. 32, 2611 (1961); http://dx.doi.org/10.1063/1.1728361 (8 pages) | Cited 46 times

Online Publication Date: 11 June 2004

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Space‐charge instabilities in diodes have been found to produce variations in potential and current that are larger than predicted from classical static analyses and, moreover, which produce sustained electrokinetic oscillations. This report reviews the classical static solution and presents the new transient solution briefly. As applications, tentative explanations are offered for recent observations of extra shot‐noise smoothing and of oscillations in thermionic converters.

Magnetically Confined Cold‐Cathode Gas Discharges at Low Pressures

R. L. Jepsen

J. Appl. Phys. 32, 2619 (1961); http://dx.doi.org/10.1063/1.1728362 (8 pages) | Cited 21 times

Online Publication Date: 11 June 2004

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Most previous treatments have been restricted to calculations of striking characteristics of planar and cylindrical magnetrons. In the present paper, a theory is developed which considers some effects of space charge in inverted and normal magnetrons and in Penning structures. Estimates are made of current flow and its dependence on voltage, magnetic field, electrode geometry, and pressure. It is shown that discharges of much greater intensity may be expected in normal magnetrons with filamentary cathodes than in inverted magnetrons with filamentary anodes. It is also shown that comparable maximum discharge intensities should be obtainable in Penning structures and in normal magnetrons. A scaling relation involving magnetic field and radial dimensions of the electrodes is obtained.

Harmonic Generation and Frequency Mixing in Ferromagnetic Insulators

R. L. Jepsen

J. Appl. Phys. 32, 2627 (1961); http://dx.doi.org/10.1063/1.1728363 (4 pages) | Cited 2 times

Online Publication Date: 11 June 2004

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When a transverse rf magnetic field is applied to a ferromagnetic insulator, a second harmonic frequency term arises in mz (the axial or longitudinal component of the rf magnetization). If in addition an axial component of the rf field is applied, then a second harmonic frequency term appears in mt (the transverse component of the rf magnetization) as well. It happens further that mt exhibits two dc magnetic field resonances. One resonance occurs when the material is biased to the fundamental, and the other arises when the material is biased to the second harmonic.
In a similar way, application of two frequencies having both axial and transverse components results in sum and difference frequency terms appearing in mt, in addition to the usual mz. The mixed frequency terms in mz are resonant for the two values of dc magnetic field corresponding to the two applied frequencies. The mixed frequency terms in mt exhibit additional resonances for dc magnetic fields corresponding to the sum and difference frequencies.
The present paper describes calculations of second harmonic generation and second‐order frequency mixing under the assumption of uniform precession of the magnetization, for small and ellipsoidally shaped samples of material and with loss included in the Landau‐Lifshitz form. A simple case of third harmonic generation is also discussed. Results of the calculations are applied to a simple example of second harmonic generation. The detailed calculations and results are contained elsewhere in a rather lengthy report.
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