bluuebunny/crossref_metadata_2025 huggingface dataset:
Space-Time Analysis of the Sonoluminescence Emitted by Cavitated Water
Authors: Macleay Robert Q. , Holroyd Louis V.
Published: April 2005

Measurements of the intensity vs phase angle distributions of the sonoluminesce of cavitated water have been made at 400, 600, and 1200 kc. Peak acoustic pressure ranged from 1.8–2.8 atm. In agreement with the theory of Noltingk and Neppiras, the emission was found to take place in the compression phase. Calculation of the intensity vs phase angle distribution based on the Noltingk-Neppiras theory gave results which agreed well with experiment.
Residual Thermoelastic Stresses in Bonded Silicon Wafers
Authors: Riney T. D.
Published: April 2005

The residual thermoelastic stresses produced in a silicon strip when eutectic bonded to a gold plated molybdenum block are investigated photoelastically using near infrared light and an image converter tube. This is the two-dimensional analog of a problem arising when silicon wafers are bonded to headers in semiconductor devices. It is first shown that with the proper orientation of the crystal, the specimen may be studied by the methods normally employed with isotropic birefringent materials. This simplifies the quantitative evaluation of the stresses. It is found that though the mean longitudinal stress near the center of the strip is compressive, a transverse tensile stress of greater magnitude occurs near the ends of the strip.
Infrared Properties of Flame-Fused MnO Crystals
Authors: Loh E. , Newman R.
Published: April 2005

Flame-fused MnO single crystals show continuous ``absorption'' in the near-infrared region and absorption peaks near 0.1 ev, both strongly dependent on the excess oxygen content in the crystal. Evidence indicates that a precipitated phase, probably Mn3O4, is responsible for the scattering and absorption. Hydrogen treatment converts the MnO crystal from p to n type as measured thermoelectrically. The optical and mechanical properties of the MnO are altered by hydrogen treatment.
Zone Leveling and Crystal Growth of Peritectic Compounds
Authors: Mason Donald R. , Cook J. Stanley
Published: April 2005

Homogeneous samples of peritectic semiconducting compounds have been prepared for optical and electrical characterization by combining zone leveling concepts with Bridgeman crystal growth techniques. Proper temperature distribution in the zone leveling equipment must be established on the basis of the phase diagram for the material, and by considering the rate process accompanying solidification and crystal growth. The ingots produced by this method are substantially uniform and homogeneous in composition, whereas normally frozen or Czochralski-grown crystals contain concentration gradients.
Thermal Noise in Dissipative Media
Authors: Haus H. A.
Published: April 2005

To account for the spontaneous thermal fluctuations in a general dissipative medium, a current-source term may be introduced into Maxwell's equations. The dyadic correlation function of the source term is evaluated for a uniform medium at uniform temperature in which the driving field Ē and driven-current density J̄d are related by differential equations in time and space variables. In those cases in which a simple tensor relation exists between the Fourier components of Ē and J̄d at a particular frequency, the result is generalized to nonuniform media. A similar generalization is achieved only under some restrictive assumptions for media characterized by differential equations in the space variables. The results obtained may be applied to the computation of thermal noise radiated from a medium at nonuniform temperature, and can serve as an aid toward understanding of noise mechanisms. The source term is also evaluated for a thin plasma from simple physical reasoning and is found to check with the result derived from the general theory.
Dynamic Stability of a Conducting, Cylindrical Shell in a Magnetic Field
Authors: Linhart J. G.
Published: April 2005

The dynamic stability of a thin, perfectly conducting cylindrical shell in axial and azimuthal magnetic fields is investigated by means of the method of normal modes. It is found that in cases where a growth of a surface perturbation is indicated, the e-folding time corresponds to the time required for the shell to collapse radially. Where stability is predicted, an initial surface perturbation can be shown to execute an oscillatory and damped motion.
Photoconductivity of CdS-Type Photoconductors in the Vicinity of the Absorption Edge
Authors: Winogradoff N. N.
Published: April 2005

The marked drop in photoconductivity on the high-energy side of the absorption edge in high quantum-yield photoconductors cannot be explained satisfactorily in terms of the models based on the trapping of the free holes produced in band-to-band excitations. In the model described, the photocurrent is assumed to arise mainly through the excitation of electrons from discrete levels very close to the valence band. The trapped holes formed in this process are in an excited state and drop to a ground state further away from the valence band, where they are relatively stable against thermal ionization and give rise to high quantum yields. This model for the photoconductivity mechanism appears to explain a large variety of experimentally observed characteristics.
Detailed Balance Limit of Efficiency ofp-nJunction Solar Cells
Authors: Shockley William , Queisser Hans J.
Published: April 2005

In order to find an upper theoretical limit for the efficiency of p-n junction solar energy converters, a limiting efficiency, called the detailed balance limit of efficiency, has been calculated for an ideal case in which the only recombination mechanism of hole-electron pairs is radiative as required by the principle of detailed balance. The efficiency is also calculated for the case in which radiative recombination is only a fixed fraction fc of the total recombination, the rest being nonradiative. Efficiencies at the matched loads have been calculated with band gap and fc as parameters, the sun and cell being assumed to be blackbodies with temperatures of 6000°K and 300°K, respectively. The maximum efficiency is found to be 30% for an energy gap of 1.1 ev and fc = 1. Actual junctions do not obey the predicted current-voltage relationship, and reasons for the difference and its relevance to efficiency are discussed.
Double Bragg X-Ray Scattering Studies of Polycrystalline Metals
Authors: Wild R. L. , Ogier W. T. , Richards L. M. , Nickel J. C.
Published: April 2005

Small-angle double-Bragg x-ray scattering has been used for the study of recrystallization kinetics and angular misorientation of the mosaic structure in cold-worked nickel and iron foil. The scattering measurements showed that short time recrystallization in nickel took place by growth of initial blocks with an activation energy of 2.2 ev. The use of a getter during the vacuum anneal increased the growth rate by a factor of 1000. Angular misorientation was found to be associated with work hardening in both nickel and iron.
Crack Propagation in a Strain-Crystallizing Elastomer
Authors: Andrews E. H.
Published: April 2005

The dependence of small-scale crack propagation in a strain-crystallizing elastomer (natural rubber) upon the applied strain has been studied under conditions of cyclic deformation over a range of frequencies. During each cycle the crack propagates along a well-defined path, different from the axis of symmetry, which is identified as the locus of maximum stress in a stationary stress distribution (i.e., one which does not move with small advances of the crack). The stationary stress hypothesis also accounts for the quantitative dependence of crack growth upon the external constraint. It is shown that a stationary stress distribution could arise as a result of the severe mechanical hysteresis displayed by strain-crystallizing rubbers.
Cross Slip and Cross Climb of Dislocations Induced by a Locked Dislocation
Authors: Li James C. M.
Published: April 2005

The nature of double cross slip of screw dislocations as induced by a locked parallel screw dislocation, that of edge dislocations as induced by a locked edge dislocation through climb, and that of the cross climb of edge dislocations as induced by another edge dislocation through slip are studied in the light of the interaction of the mutual stress fields of the dislocations. Some quantitative calculations of the multiplication of a single loop and of the growth of slip bands in LiF are given; it is found that agreement with the experimental results of Johnston and Gilman [W. G. Johnston and J. J. Gilman, J. Appl. Phys. 30, 129 (1959); 31, 687 (1960)] is satisfactory. A mechanism for linear hardening at low stresses is suggested.
Thermodynamics of Thermally Regenerated Fuel Cells
Authors: Friauf J. B.
Published: April 2005

It is shown that d(θΔH)/dT=0 is a necessary condition for the attainment of Carnot cycle efficiency, (T1–T2)/T1, by a thermally regenerated fuel cell system in which ideal gases are reacted in a fuel cell to convert chemical to electrical energy, and are then regenerated for recycling by thermal dissociation of the product of the reaction, also assumed to be an ideal gas. In d(θΔH)/dT, T is the temperature, ΔH is the change in enthalpy for the reaction in the fuel cell, and θ is the degree of reaction, or the fraction of the road from zero to 100% product which is covered by the reaction when chemical equilibrium is reached. Formulas are given for calculating the theoretical efficiency. Curves show calculated efficiencies for hypothetical thermodynamic data chosen to illustrate the effect of thermodynamic properties on efficiency. Temperature-entropy diagrams are used to explain why the efficiency reaches a maximum and then decreases when T2 is held constant and T1 is increased. The efficiency is pressure independent when the reaction does not involve change in the number of molecules, pressure dependent when it does.
Shock-Wave Compression of Iron and Bismuth
Authors: Hughes D. S. , Gourley L. E. , Gourley Mary F.
Published: April 2005

A helium gun was used to propel metal projectiles against targets of the same materials. Pressures produced by impact were varied by varying projectile velocities. The method produced pressures up to somewhat over 100 kbar, thus overlapping the lower part of the range of pressures which can be produced by detonation of high explosives. Of particular interest was the range of pressures intermediate between the highest which can be produced statically and the lowest which can be produced by explosives.

A condenser micrometer was used to detect motion of the free surface of the target. This method permitted examination of the motion in greater detail than could reasonably be accomplished by other methods which have been used. Elastic and plastic waves were observed in iron and in bismuth. Assuming the Rankine-Hugoniot shock conditions, pressures and compressions were computed. Pressure-compression data for iron were obtained for intermediate pressures not previously investigated. Phase transitions in bismuth were observed for pressures up to about 40 kbar.
Magnetic Viscosity Due to Solute Atom Pairs. Part II. Experimental Results
Authors: Biorci G. , Ferro A. , Montalenti G.
Published: April 2005

The theory of magnetic viscosity due to solute atom pairs has been verified on several bcc alloys. The results on Fe-Si alloys with Si content up to 6% wt show that solute atom pairs give magnetic viscosity. If the strong effect of the temperature is taken into account, the induced anisotropy energy deduced from the viscosity field can be considered in agreement with the value measured directly from the magnetization curves. The results on a series of Fe-Al alloys up to 25 at. % Al, where order occurs, further confirm the theory. The viscosity field is, with reasonable agreement, proportional to the number of solute atom pairs, as deduced from studies on ordering of the alloy and from the internal friction resulting from corresponding stress-induced ordering.
Current Flow across Grain Boundaries inn-Type Germanium. I
Authors: Mueller R. K.
Published: April 2005

A theory of the current flow across grain boundaries in n-type germanium is given. In the temperature range where carrier generation in the space charge region can be neglected and for donor concentrations in the bulk larger than 1014/cm3, the current is carried essentially by electrons crossing the barrier, the zero bias conductance is independent of the donor concentration and is given by G0=2.2·108Te−φ0/kT. The apparent activation energy φ0 is directly related to the barrier height. The current for applied voltages which are large compared to kT/q fails to saturate. The deviation for saturation is related to the density of states in the boundary band. At sufficiently low temperatures the carrier generation in the space-charge region is the rate-determining process for the current flow across the boundary.
Operation of Tunnel-Emission Devices
Authors: Mead C. A.
Published: April 2005

The operation of a new class of devices employing the principle of tunnel emission is discussed. It is shown that a controlled electron source may be obtained with the use of a metal-insulator-metal diode structure where the second metal layer is very thin. A triode geometry may be secured by the addition of an additional insulator and a metal collector layer. Limitations on the operating frequency, current density, and current transfer ratio of such devices are discussed. Experimental results on diode and triode are discussed. Experimental results on diode and triode structures which employ several materials are presented. Successful triodes and vacuum emitters have been realized with the use of Al2O3 insulating films. Experiments using Ta2O5 are described, and the results are discussed.
Frequency Factors for Annealing Fast-Neutron Induced Density Changes in Vitreous Silica
Authors: Primak William , Szymanski Herman , Keiffer David
Published: April 2005

Isothermal and step-annealing data were obtained and show that the frequency factor is ∼1014/sec for processes having activation energies beyond the peak of the distribution but some orders of magnitude lower and possibly dispersed for the portions of the distribution at activation energies less than the peak.
Ultrasonic Detection of Changes in the Elastic Properties of a 70−30 Iron-Nickel Alloy upon Heat Treatment
Authors: Papadakis Emmanuel P. , Reed Everett L.
Published: April 2005

Ultrasonic attenuation and velocity measurements were made by the pulse-echo method on 30% nickel-70% iron alloy specimens after various steps in their transformation from austenite to martensite. It was found that the attenuation from Rayleigh scattering decreased, while that from elastic hysteresis increased as the transformation proceeded. It was concluded that the presence of the small martensite platelets in the grains reduced the anisotropy of the elastic constants of the grains, thus reducing the Rayleigh scattering. The increase in the hysteresis parallels the increase in residual strain and the increase in grain boundary material attending the transformation.
Small-Angle Scattering in Gold-Nickel Alloys
Authors: Nagorsen G. , Averbach B. L.
Published: April 2005

The small-angle x-ray scattering observed in gold-nickel solid solutions is shown to arise from double Bragg reflections and to be unrelated to ``critical scattering'' associated with fluctuations in short-range order.
Quantitative Analysis of Two-Dimensional Flow by Means of Streaming Birefringence
Authors: Sutera S. P. , Wayland Harold
Published: April 2005

Streaming birefringence measurements made with tobacco mosaic virus solutions in an eccentric cylinder system are compared with an orientation theory of streaming birefringence in general two-dimensional laminar flow. It is concluded that for sufficiently dilute solutions of macromolecules with a short relaxation time, the orientation theory is valid and can be used to interpret the flow from the optical measurements, provided the complete character of the flow is known along at least one streamline.
Temperature Dependence of Rolling Textures in High-Purity Silver
Authors: Hu Hsun , Cline R. S.
Published: April 2005

A rolling texture transition from the (110) [1̄12] common silver type to the (123) [4̄1̄2] copper type was produced in high-purity silver by changing the temperature of deformation. The texture determined at 0°C for a strip rolled at 0°C was a simple (110) [1̄12]. Rolling at 200°C produced a texture of the (123) [4̄1̄2] type, plus a cube texture component due to partial recrystallization. Our results also suggest that the relatively high oxygen content in common silver is probably not responsible for the formation of the (110) [1̄12] texture. The change in texture from one type to the other in high-purity silver can be obtained by merely varying the rolling temperatures.
Sintering Crystalline Solids. I. Intermediate and Final State Diffusion Models
Authors: Coble R. L.
Published: April 2005

Photomicrographs of pore and grain boundary structures in sintered powder compacts are presented to provide the basis for qualitative description of the important phases of the course of densification. From this guide, appropriate grain shapes and pore shapes and locations are selected for the formulation of diffusion sintering models. The principle models presented are for bulk diffusion transport with the grain boundaries as vacancy sinks when the pore phase is continuous and coincident with three grain edges, and also when the pore phase is discontinuous and located at four-grain corners. These models predict that the rate of density change is constant when the diffusion coefficient and grain size are constant. The need for simultaneous isothermal densification and grain growth data is indicated. The explicit change in densification rate with discontinuous grain growth is predicted in terms of pore spacing and grain size.
Influence of Magnetoconductivity Discontinuities on Galvanomagnetic Effects in Indium Antimonide
Authors: Bate R. T. , Bell J. C. , Beer A. C.
Published: April 2005

Anomalous galvanomagnetic effects associated with spatial discontinuities in carrier concentration have been observed in n-type InSb. These discontinuities result from anisotropic segregation of impurities during crystal growth. An increase in the magnitude of the Hall coefficient at 20 000 gauss to nearly twice the weakfield value was observed in one case. The magnetoresistance is especially sensitive to inhomogeneities. For an inhomogeneous sample at a particular magnetic field, the measured Δρ/ρ0 may be as much as 100 times larger than that for a homogeneous sample. Negative magnetoresistance has also been observed at room temperature in inhomogeneous samples. All of the above observations are predicted qualitatively by considering a simple model consisting of a long, thin specimen having a discontinuity in resistivity and Hall coefficient in the current direction. The boundary value problem corresponding to this case is solved to predict the electric field and current densities.
Shift of the Shadow Boundary and Scattering Cross Section of an Opaque Object
Authors: Rubinow S. I. , Keller Joseph B.
Published: April 2005

When a wave of wavelength λ is incident upon an opaque object of typical dimension a, a shadow is formed in the geometric optics limit λ/a=0. If λ/a is small and not zero, the shadow boundary is shifted slightly from the geometrical shadow boundary as was first shown by Artmann. He found the shift to be asymptotic to α(λ2a)⅓ for a circular cylinder, where α is positive or negative according as the field or its normal derivative vanishes on the cylinder. The same result was obtained by Rice for a parabolic cylinder, but for the hard cylinder his α differed from Artmann's. We have redetermined α for the circular cylinder and found it to agree with the result for the parabolic cylinder in both cases. We have also determined the shift for a circular cylinder on which the field satisfies an impedance boundary condition. The former result is implicit in the work of Goriainov and both results are implicit in the work of Wait and Conda. We have also determined the scattering cross section of a circular cylinder with an impedance boundary condition. These results lead us to propose two formulas, one for the shift of the shadow boundary and one for the scattering cross section, of any smooth two- or three-dimensional object. The latter expresses the deviation from the geometrical optics cross section as an integral, around a normal section of the shadow, of a multiple of the shift. This formula is verified for a sphere and for oblique incidence on a circular cylinder. Both electromagnetic and scalar waves are considered.
Distribution Coefficients of Impurities in Gallium Antimonide
Authors: Hall R. N. , Racette J. H.
Published: April 2005

Distribution coefficients of several column 2, 4, and 6 elements in GaSb are reported, and some of the physical properties of this material are discussed briefly.
Effect of Magnetic Clusters on the Specific Heat of Ni-Cu and Fe-V Alloys
Authors: Schröder K.
Published: April 2005

Recent experiments with Ni-Cu and Fe-V alloys indicate that the specific heat at low temperature cannot be described by electronic and lattice terms alone. An attempt is made to explain an additional term in the specific heat of these alloys on the basis of ferromagnetic clusters.
Oscillations and Saturation Current Measurements in Thermionic Conversion Cells
Authors: Zollweg R. J. , Gottlieb Milton
Published: April 2005

Radio-frequency oscillations observed in cesium-filled thermionic diodes are interpreted on the basis of a model which assumes that the cesium ions oscillate in an excess negative charge potential well outside the cathode. A simplified theoretical treatment shows that the period at the onset of oscillations is linear with cathode-anode spacing in agreement with experiment, and relates the oscillation period to the ratio of cell current to saturation emission current. It is found that the rapid decrease of oscillation amplitude as the cell current reaches a critical value can be used to measure saturation emission currents.
Cobalt Ferrite Single Crystals
Authors: Ferretti A. , Arnott R. J. , Delaney E. , Wold A.
Published: April 2005

A crystal of cobalt ferrite was grown from the melt at 1600°C under an oxygen pressure of 790 psi. Chemical analysis of a portion of the crystal gave a ferrous ion content of 1.3%.
Variation of Permittivity with Electric Field in Perovskite-Like Ferroelectrics
Authors: Diamond Howard
Published: April 2005

A model is considered for the case of polycrystalline ferroelectrics in which each crystallite is presumed to behave according to a free-energy function of the type formulated by A. F. Devonshire [Advances in Phys. 3, 85 (1954)] for BaTiO3. The Curie temperatures for the individual grains are taken in a Gaussian distribution about some chosen temperature. The permittivity is obtained by averaging with this distribution over all of the crystallites. In accordance with the free-energy function, it is assumed that the electric field induces a ferroelectric axis in those crystallites of the distribution which are not ferroelectric at a given temperature. On the basis of experimental evidence, 90° reorientation of domains in the ferroelectric part of the distribution is presumed to be negligible for semistatic and dynamic fields. Despite the seemingly severe restriction imposed by the latter assumption, a large field sensitivity is predicted. Agreement between the theory and experimental data is excellent for both parallel and transverse fields. It is concluded that the variation of incremental permittivity is associated with an induced ferroelectric state rather than being directly a property of domain processes, and that a large variation with field must necessarily be accompanied by strong thermal sensitivity.
Theory for the Cathode Mechanism in Metal Vapor Arcs
Authors: Lee T. H. , Greenwood Allan
Published: April 2005

It is shown that in the cathode drop region of a metal vapor arc, there are four equations and two limiting conditions relating five dependent variables. The five dependent variables treated are temperature of the cathode spot, electric field at the cathode, total current density, current density carried by electrons, and the radius of the spot. When these equations are combined, a current level is found below which no solution exists. It is proposed that this current corresponds to the point at which a vacuum arc extinguishes in an alternating-current circit. Experimental measurements of the current level at which this event occurs have been made, and the results are compared with the theoretical calculations.
Third-Order Elastic Moduli of Germanium
Authors: Bateman T. , Mason W. P. , McSkimin H. J.
Published: April 2005

Measurements have been made for all six third-order elastic moduli of germanium by measuring ultrasonic velocities in selected directions when directed static stresses are applied to the crystal. Three measurements are obtained by using hydrostatic pressures, three by using a static compression along the <001> axis, and six by stressing the <110> axis with measurements being made along the <001> direction and the <11̄0> direction. Using the finite strain formulas of Murnaghan, the measured velocities are related to the three second-order elastic moduli and the six third-order elastic moduli for a cubic crystal. The 12 sets of measurements provide considerable overlap, and the probable errors are shown to be moderate.
Development and Preliminary Testing of a Device for Electrostatic Classification of Submicron Airborne Particles
Authors: Langer G. , Radnik J. L.
Published: April 2005

A practical apparatus was developed for electrostatic size classification of aerosol particles of 0.1 to a few microns in diameter. The aerosol, surrounded by a sheath of clean air, is charged by passing it closely over an intense positive discharge at high speed. It enters as a fine filament at 1 m/sec into an electrostatic field between parallel plates. Charging rates several times above those predicted by conventional theory permitted good resolution. A high natural charge on the aerosols had an adverse effect on classification. Various aerosols were examined, and results of practical significance were obtained. With salt aerosols, strong, higher-order Tyndall spectra were observed from the classified deposit.
Instability of Spin Waves and Magnetostatic Modes in a Microwave Magnetic Field Applied Parallel to the dc Field
Authors: Schlömann E. , Joseph R. I.
Published: April 2005

Two methods of calculating the instability threshold are described. The first is a plane-wave analysis which is strictly applicable only in an infinite medium. The second is a more rigorous theory in which the boundary conditions at the surface of the sample are taken into account. The refined theory admits instabilities at frequencies different from half the pump frequency, which are forbidden according to the less rigorous plane-wave analysis. The general theory is applied to the magnetostatic modes of a long, circular cylinder, which is magnetized along its axis. It is concluded that: (a) Instability at half the pump frequency can occur only for those cases in which the magnetostatic potential is invariant under rotation around the cylinder axis (m=0). The instability threshold for these modes is identical to that deduced on the basis of the plane-wave analysis, except that the frequencies now have to satisfy the characteristic equation derived from the boundary conditions. (b) Instabilities at frequencies different from half the pump frequency can occur, but generally have a higher threshold. (c) Pairs of surface modes (with frequencies higher than the highest plane-wave frequency) are not subject to instability. (d) Instabilities involving a surface mode and a volume mode are not strictly forbidden. It is very likely, however, that such instabilities will be masked by the instability of spin waves of shorter wavelength.
Observations on the Striation of Electrically Exploded Copper Foils
Authors: Cnare Eugene C.
Published: April 2005

A high-energy exploding wire facility has been used to electrically explode thin metallic foils. Striation patterns are described for which the striation spacing appears to be dependent only on foil thickness and material. Magnetic probe measurements near the foil surface make evident the presence of shear currents in the foil which are believed to be, in part, responsible for the striation phenomena. The explanation of the striation phenomena described in this paper may aid in explaining the striated appearance of exploding wires in general.
Growth of Explosion in Electrically Initiated RDX
Authors: Muller G. M. , Moore D. B. , Bernstein D.
Published: April 2005

The growth of explosion has been studied both in powdered RDX, initiated by a bursting bridgewire, and in pressed RDX, initiated by passing current through a column of RDX-graphite mixture incorporated in the charge. In the former case, a reaction wave moves out from the bridgewire at a velocity characteristic of low-order detonation, with a transition to high-order detonation occurring at a reproducible induction distance which depends only weakly on the stored electrical energy. Induction distances from 9.5 mm to 17.5 mm were observed, depending on geometry and loading density. Interactions of two pre-high-order waves were investigated, as well as the ability of such waves to cause detonation in Composition B. In contrast, growth of explosion in the pressed RDX appears to be governed, at least initially, by thermal mechanisms; delays of more than 1 msec have been observed between the discharge of the electrical energy and substantial explosion of the charge.
Electron Bunching in the Multipacting Mechanism of High-Frequency Discharge
Authors: Hatch Albert J.
Published: April 2005

Electron bunching in the multipacting mechanism of low-pressure high-frequency discharge, also known as the secondary electron resonance mechanism, is analyzed by an extension of simple multipacting theory. The bunching range is assumed to be that range in the electrical phase angle φ within which secondary electrons emitted from one electrode can successfully traverse the interelectrode gap in ½ cycle and arrive at the opposite electrode with energy equal to or greater than emission energy. At the lower voltage limit of multipacting, the ½-cycle bunching range is shown to be −90° ≤ φ ≤ +90°; at the upper voltage limit, the range is narrowed to −90° ≤ φ ≤ −40°. Typical examples of multipacting bunching, including higher-order modes, are illustrated with graphical trajectories. The effects of secondary emission characteristics on bunching are also discussed.
Dislocation Relaxation Phenomena in Oxide Crystals
Authors: Chang Roger
Published: April 2005

The dislocation relaxation of MgO and Al2O3 crystals was studied by means of anelastic measurements. The experimental data are analyzed according to the theory of Seeger, Donth, and Pfaff. It is shown that the ratio of Peierls force to shear modulus is about 2×10−5 for MgO and possibly also for Al2O3. Comparison of the dislocation relaxation phenomena of oxides and metals indicates, rather surprisingly, that the ratio of Peierls force to shear modulus in oxides is about an order of magnitude smaller than that in fcc metals.
Measurement of the Partial Pressure of Cesium over Cesium Antimonides
Authors: Miyake Kiyoshi
Published: April 2005

The partial pressure of cesium over the cesium antimonides whose compositions were Cs2.95Sb, Cs3.00Sb, and Cs3.25Sb was measured at various temperatures ranging from room temperature to about 180°C. The experimental tube consists of a spherical glass envelope and an ion gauge. The sample was prepared on the inner surface of the spherical envelope. The partial pressure of the cesium dissociated thermally from cesium antimonides was measured by Langmuir's positive ion method. The composition of the samples was determined by comparing their electrical resistivities and thermal activation energies associated with electrical conductivity with those of the cesium antimonides, which had a known composition. The preparation of the sample and the measuring method of the partial pressure of cesium are described precisely. The partial pressure of cesium over cesium antimonides was measured as a function of the absolute temperature, and the results showed that it was represented by the equation log10p (mm Hg) = A — B/T, where A and B are constants. In the case of Cs3.00Sb, the values of A and B were 9.040 and 6300 deg, respectively.
Energy Interchange between Cyclotron and Synchronous Waves in Quadrupolar Pump Fields
Authors: Gordon E. I. , Ashkin A.
Published: April 2005

Passive coupling of the electron cyclotron and synchronous waves in quadrupolar pump fields is examined. It is shown that sinusoidal energy exchange occurs when the quadrupole field is pumped so that the effective or Doppler-shifted pump frequency as observed by the drifting beam equals the electron cyclotron frequency. One fast and one slow wave are coupled when the pump frequency is greater than either of the beam wave frequencies, while two fast or two slow waves are coupled when the pump frequency is less than at least one of the beam wave frequencies. Experimental results confirming these predictions are presented and possible applications are discussed. In addition, it is shown that active coupling of two synchronous waves occurs when the effective pump frequency is zero.
Transduction of Noise. Theory of a Generalized Traveling-Wave Coupler
Authors: Pease M. C.
Published: April 2005

The response of an appropriate system to a noise input is studied. The systems studied are ``generalized lossless networks'' and may include, for example, electron beams and parametrically pumped components. The noise may be introduced through several ports in an uncorrelated or correlated way. The problem is conveniently handled by the matrix analog of an eigenvector analysis. The noise input is represented as a matrix of which the diagonal elements are the self-power density spectra, and the off-diagonal elements the cross-power density spectra. This matrix is resolved into ``eigenmatrices'' which are then recombined at the output in accordance with the ``2-index eigenvalues.'' The noise invariants found by Haus (S and π) are appropriate to a system with two degrees of freedom. For a system with n degrees of freedom, there are at least n invariants of the noise—i.e., components of the noise that are unchanged by the system. The theory is finally applied to a generalized coupler, in which a single circuit mode is coupled to a degenerate multiplicity of beam modes, such as would occur in a hollow beam. It is shown that a ``Kompfner-null'' condition exists. The physical significance of this condition is studied and its effect on beam noise determined.
Square-Loop Ferrites with Temperature-Independent Properties and Improved Disturb Ratio
Authors: Weisz R. S.
Published: April 2005

Magnetic annealing of manganese-ferrous ferrites and nickel-ferrous ferrites has produced memory cores with lower temperature coefficients and higher disturb ratios than conventional square-loop ferrites. Fifty-mil diam toroids of the composition 0.5 NiFe2O4·0.5 Fe3O4 switch in approximately 1 μsec with a constant 1-amp driving current, and have disturb ratios greater than 0.7 over the range −55° to +100°C. Physical reasons for the improved properties are discussed.
Electron Interferometer Studies of Iron Whiskers
Authors: Fowler H. A. , Marton L. , Simpson J. Arol , Suddeth J. A.
Published: April 2005

Electron interference patterns have been obtained by using an iron whisker as the electrostatic fiber of a Möllenstedt [G. Möllenstedt and H. Düker, Z. Physik 145, 377 (1956)] interferometer. The tilted fringes in the shadow pattern resemble those observed by Chambers [R. G. Chambers, Phys. Rev. Letters 5, 3 (1960)] and show the relationship between flux leakage and geometrical shape of the whisker. Chambers' general model of the flux configuration is confirmed.
On the Mechanical and Thermal Stability of Low-Angle Boundaries in Zinc Single Crystals
Authors: Weissmann Sigmund , Hirabayashi Makoto , Fujita Hiroshi
Published: April 2005

The mechanical and thermal stability of low-angle boundaries in zinc single crystals was studied by methods combining metallographic techniques with x-ray reflection microscopy and diffraction analysis. It was found that low-angle boundaries perpendicular to the basal plane do not offer any appreciable resistance to a shearing force parallel to the basal plane if they are pure tilt boundaries, but are substantial barriers if they are asymmetrical. If the external force exceeds a critical value, these asymmetrical low-angle boundaries become sites where fracture may occur. The strengthening effect of the asymmetrical low-angle boundaries is attributed to the effective stress field of the screw dislocations, which are mechanically stabilized by the edge dislocations. The stress field of the screw dislocations is also responsible for the thermal instability of the asymmetrical low-angle boundaries, which on annealing are gradually converted into pure tilt boundaries. A coarse substructure established after annealing is thermally very stable. On solidification after partial melting of the crystal, the coarse substructure is re-established, whereas the fine substructure is entirely modified.
Dielectric Properties and Side-Chain Crystallinity of Polyvinyl Stearate
Authors: Broadhurst Martin G. , Fitzgerald Edwin R. , Bur Anthony J.
Published: April 2005

Measurements of the real (ε′) and imaginary (ε″) parts of the dielectric constant have been made on polyvinyl stearate at temperatures from −50° to +80°C and over a frequency range from 100 to 50 000 cps. Although no full relaxation dispersion region has been found in this frequency range, there are indications of the beginnings of a high-frequency dispersion region just above the freezing point (49.1°C) in the liquid polymer. This dispersion cuts off or is ``frozen in'' rapidly as the sample freezes, giving evidence of a slight rotational freedom in the solid polymer near the freezing and melting points. Because of this ``freezing in'' of the dispersion mechanism it is supposed that the dipolar side chain is unable to rotate in the solid form because of the combined effects of the side-chain crystalline field and angle which the C–O bond (between the main chain and side chain of the polymer) makes with the side-chain axis. Specific volume measurements were made to supplement the above work. The measurements show that a quickly frozen sample will melt at a lower temperature (52.5°C) than a slowly frozen sample (55.0°C). Also, discontinuities in the slope of the specific volume vs temperature curve are related to changes in the imaginary part of the dielectric constant and to changes in mechanical dispersion data. The above results are compared with those for other polymers.
Theory of Quantum Oscillators in a Multimode Cavity
Authors: Wagner W. G. , Birnbaum G.
Published: April 2005

The spectrum of power radiated by a solid-state optical maser in steady-state operation is obtained by considering each atomic system to be a source of randomly fluctuating dipole moment which drives every mode of the cavity. The nonlinear behavior of the collection of atomic systems is treated in such a way that a detailed examination of the distribution of power in the various modes is possible. A number of examples are considered which show how critically dependent on the relative loss rates of the various modes are the characteristics of the output from a multimode oscillator. An interesting result of this calculation is the appearance in some cases of an abrupt transition as the pumping power is increased: above this point a large fraction of energy goes into the mode which is resonant with the atomic transition and which has the lowest loss rate. Another case is studied which does not have this feature, but which could be useful in analyzing the behavior of solid-state optical masers which have substantial scattering due to crystal imperfections.
Mass Spectrographic Detection of Impurities in Liquids
Authors: Ahearn A. J.
Published: April 2005

The mass spectrograph with the vacuum spark positive ion source distinguishes between bulk impurities in the electrodes and contaminants present on their surface. Surface contamination can be detected and identified when it is the equivalent of less than 0.01 monolayer in thickness. Impurities in liquids are studied by exposing an electrode to the liquid, thereby contaminating its surface. Two ways of contaminating an electrode surface are described: (a) electroplating of impurities onto the electrode, and (b) evaporation leaving residue on the electrode. Experiments with doped water demonstrate that impurities at a concentration of 10−9 atom fraction can be detected. Only about 10−10 g of impurity is needed for detection using the evaporation technique. Some applications are discussed.
Polygonization in Bent Zinc Crystals
Authors: Sinha P. P. , Beck Paul A.
Published: April 2005

High-purity zinc crystals were grown from the melt by the soft mold technique, and bent in such a way that [01̄10] was parallel to the bending axis and the [211̄0] slip direction enclosed approximately 45° with the bending radius. A dislocation etching technique was developed, which reveals the edge dislocations introduced on bending, without the necessity of decoration. It was found that crystals bent either at room temperature or at liquid nitrogen temperature had approximately two-thirds of the edge dislocations arranged in low-angle tilt boundary segments. The fact that no observable change occurred in the dislocation structure on annealing up to 225°C for 5000 min suggests that the observed low-angle boundaries were formed directly on bending rather than by a thermally activated polygonization process, which might have been thought to take place at room temperature in the interval between bending and etching.
Observations of Cross-Tie Domain Walls by the Faraday Effect
Authors: Houde A. L.
Published: April 2005

A microscopic Faraday effect apparatus is described by means of which the fine structure of the domain configurations in thin Permalloy films has been observed. The direction of the magnetization in cross-tie domain walls and other domain configurations has been deduced from their light, dark, or gray appearance and known polarizer angles. Faraday effect hysteresis loops are presented in support of a proposal that domain walls at 45° to the easy direction represent an intermediate demagnetized state in films having a high degree of uniaxial anisotropy.
Dissociation of Adsorbed CO by Slow Electrons
Authors: Moore George E.
Published: April 2005

We have investigated ions emitted from molybdenum and tungsten surfaces in CO when the surfaces are bombarded by electrons. The surfaces, in the form of ribbons, can be cleaned at will by heating, and bombarded by an electron stream in which current and energy are controlled separately. The product ions are observed in a mass spectrometer whose envelope contains the experimental filament. Electron bombardment liberates only the O+ ion from adsorbed CO with any abundance; it may be 50–100 times more abundant from the surface than from space. No CO+ nor C+ ions are detected nor any negative ions of CO or its fragments. Carbon atoms remain on the surface. Significant amounts of F+ and Cl+ are also liberated from new filaments; these diffuse from the interior and are more tightly bound than CO, and disappear only after prolonged heating. Their surface abundance is so slight that they do not interfere with the O+ process. The threshold electron energy for liberation of O+ ions and the dependence of O+ ion current on electron current and energy are given. The method might be useful for studying kinetics of complex adsorption phenomena, although precautions are necessary to avoid perturbing the adsorbed film by the incoming electrons. The following phenomena are readily observed and probably understood: (a) The growth of a monomolecular film of CO from the ambient following a flash of the filament. (b) Competition for available sites by chlorine, fluorine, carbon, and CO. (c) Poisoning of the surface, for adsorption of CO, by carbon atoms freed by departure of O+ ions. A simple theory reproduces the experimental kinetics of adsorption and poisoning semiquantitatively.
Electric Breakdown Strengths of Single and Laminated Films of Vinyl Chloride-Acetate
Authors: Greenler Robert G. , Kay Robert M.
Published: April 2005

The electric breakdown strengths of thin, unsupported vinyl chloride-acetate films in the thickness range of 1200 to 50 000 A have been measured. No dependence of breakdown strength on thickness is found in this region. Composite films composed of alternate layers of plastic film and thin conducting layers of silver show essentially the same breakdown strength as do single films. Five and six layer laminates which do not contain metal layers show a breakdown strength greater by a factor of 2 than that of single films of the same total thickness.
Electrical Conductivity of NaCl during High-Temperature Creep
Authors: Christy R. W. , Daniels W. E.
Published: April 2005

In view of recent interest in the effect of creep on the coefficient of self-diffusion, measurements have been made on the electrical conductivity of NaCl in the intrinsic range during and after deformation by creep. The conductivity is proportional to the diffusion coefficient for Na. At about 550°C, no change in conductivity was observed, even at steady state creep rates approaching 10%/min. This negative result is shown to be in accord with theoretical estimates.
Magnetization Process in Small Particles of CrO2
Authors: Darnell F. J.
Published: April 2005

Initial magnetization curves, remanence, coercivity, reversible susceptibility, and rotational hysteresis have been measured for CrO2 in the form of small particles. The measurements allow rough division into three types of behavior with decreasing particle size: multidomain, or bulk behavior, for ∼100-μ particles; few-domain behavior for ∼1−10-μ particles; and single-domain behavior for particles with a length/diameter ratio ∼5 and a diameter ≤0.2 μ. The smaller particles studied were acicular and showed coercivity dominated by shape anisotropy.
Magnetization of Nickel Single Crystals
Authors: Tterlikkis Lambros , Jenkins Alvin W.
Published: April 2005

A calculation of the magnetization curves of nickel single crystals is made by the method of Lawton and Steward for arbitrary orientation of the crystal in the field. The anisotropy coefficients are calculated from experimental curves with the applied field in symmetry directions, and it is found that only K1 can be determined reliably with the data used. The calculated off-axis curves agree well with experimental results. A correcting field determined from the easy-axis magnetization curve is utilized to compensate for internal strain effects. The relation between the calculated field minus the observed field and the easy-axis field suggests a possible method for measuring internal strain energy in ferromagnetic crystals.
Two-Phase Permalloy for High-Speed Switching
Authors: Nesbitt E. A. , Gyorgy E. M.
Published: April 2005

The addition of gold to Permalloy has made it possible to precipitate a second phase in the alloy. As a result it is possible to control the coercive force and, to some degree, the threshold for rotational flux reversal, by appropriate heat treatments. On this basis a series of alloys have been developed by adding 2–14% gold to Permalloy. Some of these alloys have switching times approximately four times faster than that of the standard Permalloy composition. The switching time is defined as the reversal time at twice the coercive force. The alloy is prepared by annealing at the solution temperature of 900°C and then cooling rapidly. This is followed by cold rolling tape from approximately 0.014– to 0.00013-in. thickness, which is the thickness for switching applications. The material is then annealed at 600–650°C. Under these conditions, alloys containing 7% gold and 14% gold yield square hysteresis loops having coercive forces of at least 1.7 and 4.3 oe, respectively. For the 7% gold alloy, the threshold for rotational flux reversal is 2.5 oe.