bluuebunny/crossref_metadata_2025 huggingface dataset:
Stress Relief and Hillock Formation in Thin Lead Films
Authors: Lahiri S. K.
Published: February 2004

The growth of hillocks on Pb films on glass substrates was observed by heating the films inside a scanning electron microscope. Hillocks were found to grow with increasing temperature. The kinetics were such that, at 50°C, the growth was essentially complete in a few minutes. During subsequent cooling, the size of many of the hillocks decreased with decreasing temperature, and cavities formed and grew at the film surface. Analysis of the observations suggests that the stress-relaxation phenomenon which causes hillock growth may be due to grain-boundary sliding and diffusion creep.
Diffusion of Copper in Nickel Single Crystals
Authors: Helfmeier H. , Feller-Kniepmeier M.
Published: February 2004

The lattice diffusion coefficient of copper in high-purity nickel single crystals is measured between 775° and 1050°C. The diffusion coefficient satisfies the equation D=0.27 exp(−61.02/RT) cm2 sec−1, with an error in D0 of ±22% and in Q of ±1%. A comparison with the results of other authors is given, showing that the dc measured is considerably lower than in previous investigations. This effect is referred to grain-boundary diffusion and chemical impurities in the specimens used earlier.
Diffusion in Wide Grain Boundaries
Authors: Mimkes J. , Wuttig M.
Published: February 2004

The rigorous solution of the grain-boundary diffusion problem has been approximated by a series expansion method. The calculations show that higher-order terms may be neglected in the bulk adjacent to the grain boundary. Thus, in this region Whipple's and Suzuoka's solutions represent a close approximation to the problem. Inside the grain boundary, however, higher-order approximations have to be taken into account. These approximations gain importance in the case of wide grain boundaries. The solutions obtained for an instantaneous source have been fitted to available grain-boundary diffusion data of Ni2+ in MgO at 1200°C. Numerical calculations give for the bulk diffusion coefficient D=2.9×10−12 cm2 sec−1, the ratio of diffusion coefficient Δ=1.5 and for the grain-boundary width a=75 μ.
Ferrite-Filled Elliptical Waveguides. II. Faraday Effects
Authors: Salmond W. E. , Yeh C.
Published: February 2004

Detailed analyses were carried out for the Faraday effect of electromagnetic waves propagating in longitudinally magnetized ferrite-filled elliptical waveguides. Few resemblances were found between the Faraday rotation effect in a circular waveguide and that in an elliptical waveguide. The circular waveguide features strong coupling between the dominant vertically and horizontally polarized modes, whereas in the elliptical ferrite-filled guide very little mode coupling occurs for large eccentricities.
Voltage-Current Characteristics for Electrical Conduction Through Thin MgO Films
Authors: Soukup R. J. , Speliotis D. E.
Published: February 2004

The voltage-current characteristics of Au–MgO–Au thin-film emission diodes formed by electron beam evaporation of Au and MgO are consistent with an expression derived for Schottky field emission into the conduction band of the oxide. These results however indicate a potential barrier height of about 0.72 eV when determined from the zero-field intercept of the straight line logI vs V1/2 plot and about 0.33 eV when obtained from an Arrhenius plot. These apparent barrier heights were different for devices fabricated by depositing the MgO film in an oxygen atmosphere. The apparent barrier height determined from the zero-field intercept went up for increasing oxygen pressure and the barrier height determined from the Arrhenius plot went down. Emission of electrons into vacuum was observed from each device at very low sample biases indicating that preferential emission through pinholes in the Au overlayer was occurring.
Cavity Mode of a High-Pressure Mercury Arc
Authors: White John E.
Published: February 2004

The conditions necessary to establish a stable hollow-cathode or cavity mode in a high-pressure mercury vapor discharge have been studied by analysis of the physical processes at the electrodes. The electron emission is primarily Schottky-enhanced thermionic, so the cavity mode is favored by a thermally shielded cavity design, at low currents. Techniques have been developed for measurement of the temperature of the arc terminus of the probe contact potential relative to the electrode, of the cathode fall of potential, and of the power input to the electrode. Positive ion current densities, work functions of the dispenser-type electrode at the arc terminus and other interesting quantities have been obtained by computation. The analysis giving these results has been partially verified by experiment.
Measurement of the Effective Dissociation Potential of Seed Compounds in MHD Experiments
Authors: Fu T. , George D. W. , Messerle H. K. , Sakuntala M.
Published: February 2004

A method is developed for the determination of the effective dissociation potential (Vd) of an alkali compound used as a seed in the low-temperature and high-pressure working fluid of a magnetohydrodynamic (MHD) generator. For a simple compound like potassium chloride (KCl) Vd can be derived directly by measuring the ion density in the plasma from the current-voltage characteristics observed in MHD generator. For complex seed compounds like potassium sulphate (K2SO4), the method leads to an effective Vd as referred to an assumed dissociation reaction. Additional experimental information as to the specific radical involved would be required to establish the true dissociation energy. In the experiments presented here, the working gas is argon at atmospheric pressure and the temperature ranges from 2000° to 3000°K. In the temperature range used and for KCl undergoing the reaction KCl⇄K+Cl, the actual dissociation potential Vd is found to be 3.6±0.4 eV. For K2SO4 the assumed dissociation reaction, K2SO4⇄2K+S+4O leads to the effective Vd=10.7±3.1 eV.
Collapse of a Hollow Inviscid Cylinder
Authors: Dumbleton J. H.
Published: February 2004

In the production of a hollow inviscid cylinder, it is necessary to maintain an internal pressure to prevent collapse. If this pressure is too low, collapse ensues. The process of collapse is herein examined and equations are given which enable the shape of the initially cylindrical surfaces to be calculated. This collapse mechanism is compared with that arising from capillary instability.
Optical Index Damage in LiNbO3 and Other Pyroelectric Insulators
Authors: Johnston W. D.
Published: February 2004

Laser-induced optical index damage in LiNbO3 and other pyroelectrics of ABO3 structure is discussed in the light of recent results of stoichiometry investigations. The damage is attributed to the presence of B-excess stacking-fault defects. The dc photovoltaic effect in LiNbO3 as well as the detailed spatial distribution of refractive-index variation is explained in terms of photoinduced variation of the macroscopic spontaneous polarization density. This variation results in a polarization charge-density distribution, and an approximately compensatory space-charge distribution. The index damage results from the polarization-based electrooptic effect.
Study of the Quenching Propagation of Bare and Insulated Semistabilized Superconducting Wires
Authors: Shimamoto S. , Desportes H.
Published: February 2004

The minimum propagating current, the velocity of propagation, and the temperature rise in semistabilized superconducting wires with and without insulation have been measured by heat pulse tests in magnetic fields up to 70 kG. These experiments have shown that insulated wire can be more stable under external heat perturbation than bare wire and that its temperature rise after quenching is slower. The tests also show that the velocity of propagation is strongly affected, at any current level, by the cooling conditions and by even a very thin surface coating on the wire.
Factors Controlling Infrared-Pumped Visible Emission of Yb3+–Er3+ in the Scheelites
Authors: van der Ziel J. P. , Van Uitert L. G. , Grodkiewicz W. H.
Published: February 2004

The rate equations for green fluorescence of the Yb3+–Er3+ doubly doped quantum counter are solved for the case of an infrared pump at the Yb3+ 2F7/2−2F5/2 transition. The successive transfer of excitation from two Yb3+ ions to the Er3+ produces green emission from the Er3+ 4S3/2 level. The increase of the 4S3/2 lifetime with increasing Yb3+ concentration in Na0.5(Y, Yb, Er)0.5WO4 confirms the consecutive transfer model of Auzel. Emission from Er3+ in a solid solution of divalent cation tungstates or molybdates (having the scheelite structure) under long-wave ultraviolet excitation is proportional to the inverse of the cation-anion separation, and hence the binding energy. The emission under infrared excitation is relatively independent of this separation.
Application of Internal-Stress-Distribution Theory to ΔE Effect, Initial Permeability, and Temperature-Dependent Magnetomechanical Damping
Authors: Smith George W. , Birchak J. Robert
Published: February 2004

The internal-stress-distribution model of magnetomechanical hysteresis is extended to a calculation of the ΔE effect, the irreversible low-field permeability, and temperature-dependent magnetomechanical damping. The calculation of the strain dependence of the ΔE effect agrees well with experimental results for Fe-7.65% Ge. The model for permeability yields results for the product λσi(λ=magnetostriction, σi=average internal stress) in reasonable agreement with values from the Becker-Kersten model for reversible initial permeability μ0 and coercive force Hc. The temperature-dependent damping observed in Ni by Roberts and Barrand is ascribed to an increase in domain-wall thickness as anistropy decreases. The model gives reasonable agreement with the measured temperature dependence.
Measurement on Misalignment of the Axis of a Magnetic Field for Electron-Beam Focusing
Authors: Nishihara H. , Terada M.
Published: February 2004

The method, which was previously proposed by the authors, of locating the magnetic-field axis has been applied to measure the misalignment of the axes of a uniform magnetic field produced by a solenoidal coil and of a periodic one produced by a permanent-magnet stack. In the former the tilt of field axis has been detected with a resolution of the order of 10−3 rad. In the latter the displacement of the field axis has been detected with a resolution of the order of 10−2 mm, which is equal to about one part in 103 of the inner diameter of magnets. It has been found experimentally that even a slight local misalignment considerably influences electron-beam transmission.
Magnetic Anisotropy of Vanadium-Indium-Substituted YIG
Authors: Euler Ferdinand , Van Hook H. Jerrold
Published: February 2004

Crystals of the general composition {Y3−2xCa2x} [Fe2−yIny] (Fe3−xVx)O12 were grown by the PbO flux method. Electron microprobe studies revealed zoning patterns of varying x within these crystals, while the indium content was found uniform among all crystals from the same crucible. Average x and y was determined by measuring the saturation magnetization Ms and the Curie temperature. Three series of crystals were produced with y=0, 0.11 and 0.35, and x ranging from 0.19 to 0.82. Ferrimagnetic resonance between 4 and 300 K yielded the anisotropy constants K1 and K2. These single-crystal data were supplemented by the results of line-shape analysis of polycrystalline samples with low Ms. At T=0, | K1 (x) | is nonlinear with a maximum at x≈0.2. The reduced temperature dependence of the reduced anisotropy field was found independent of composition.
Reversible Susceptibility of an Assembly of Single-Domain Particles and Their Magnetic Anisotropy
Authors: Köster E.
Published: February 2004

The anisotropy properties of fine magnetic particles can be determined by measurements of the initial reversible susceptibility. The effects of magnetostatic interactions on the reversible magnetization in low magnetic fields near zero and saturation remanence are treated in detail with regard to packing fraction p and particle axes orientations. It is shown among other results that for any symmetrical orientation distribution, the reciprocal initial reversible susceptibility decreases linearly with p. Thus, by extrapolation to p=0 (the susceptibility without interaction effects) the effective anisotropy constant of the particles can be obtained. From the temperature dependence of the susceptibility it is conjectured that γ-Fe2O3 has 〈110〉 easy directions of crystalline anisotropy. The corresponding anisotropy field as a function of temperature between 77° and 400°K was thus determined from susceptibility measurements. For CrO2 particles the anisotropy data are already known and are shown to be in good agreement with the present results.
Concerning the Origin of Uniaxial Magnetic Anisotropy in Electrodeposited Permalloy Films
Authors: Kench J. R. , Schuldt S. B.
Published: February 2004

Experimental evidence is adduced to suggest that electrodeposited iron-nickel alloys may contain α-phase regions in a γ-phase matrix. This observation is taken as evidence of large variations in composition on a scale of 1000 Å or less, and calculations are presented which show that it may be feasible to explain the observed uniaxial anisotropy in electrodeposited iron-nickel alloys in terms of a magnetostrictive mechanism even though the average plating composition be that of a zerostrictive material.
Delayed Elasticity in Ionic Conductors
Authors: Doremus R. H.
Published: February 2004

A mechanism for relating the redistribution of ions in a periodic stress gradient to internal friction peaks is proposed. The calculated internal friction peak is broad and asymmetric, and the frequency of maximum loss is proportional to the conductivity of the material, as is found experimentally, for silicate glasses. There is good agreement between the calculated and measured peak temperatures for some glasses, although further work is needed to test the theory completely. It is possible that this mechanism makes an important contribution to delayed elasticity in other ionic conductors.
Sonic Resonances of a Bar and Compound Torsion Oscillator
Authors: Spence G. B. , Seldin E. J.
Published: February 2004

Methods of solution are given for the sonic resonances corresponding to the free flexural and torsional vibrations of an anisotropic bar of rectangular cross section. The resonance equations for the torsional vibrations of a symmetric, three-piece, cylindrical compound oscillator are derived. The particular application of the methods and equations for the determination of some of the elastic constants of compression-annealed pyrolytic graphite, a highly anisotropic material, is discussed.
Photocurrents Due to Pulse Illumination in the Presence of Trapping
Authors: Batra I. P. , Seki H.
Published: February 2004

The expression for transient photocurrent due to light pulse of arbitrary intensity has been derived in the presence of trapping and detrapping. The pulse duration is assumed to be short compared to the transit time and the analytic solutions are obtained for ``weak'' trapping case alone. Transcendental equations involving transit time and injected charge density have been solved numerically and the solutions are displayed graphically. In various limiting cases our expressions reduce to previously reported results. Analysis presented in this article may be useful in obtaining trapping parameters from experimental data.
Discharge Characteristics of Photoconducting Insulators
Authors: Batra I. P. , Kanazawa K. Keiji , Seki H.
Published: February 2004

The conventional technique for the measurement of mobility sandwiches the sample between two electrodes, at least one of which is transparent. The sample is illuminated through this surface and the resultant current is measured under constant voltage conditions. In the present work we describe a modified method for the determination of mobility where one surface of the sample is grounded and the other is left floating. The floating surface is charged to an initial voltage, V0 and its subsequent decay upon exposure to intense light is observed experimentally. The relation between the instantaneous surface voltage V(t) and the exposure time t is referred to as the ``photoinduced discharge characteristic'' (PIDC) of the photoconductor plate. Knowing the PIDC and the theoretical expressions derived in this paper one can obtain an accurate value for the mobility of the charge carriers. As verification of our analysis we have measured the PIDC of amorphous Se films deposited onto Al substrates. Both the surface potential and its time rate of decay were measured simultaneously through a NESA surface potential probe. The agreement between theory and experiment is excellent and the value of the hole mobility obtained using our analysis is in good agreement with those already reported in the literature.
Effects of Contamination on Langmuir Probe Measurements in Glow Discharge Plasmas
Authors: Thomas T. L. , Battle E. L.
Published: February 2004

The effects of surface contamination of the surface of Langmuir probes have been studied experimentally. These experiments were carried out in three different argon glow discharge tubes. One tube was designed to simulate conditions found in large plasma facilities used in engineering studies, while the other two were designed and prepared in accordance with high-purity laboratory standards. In addition, the effect of a small amount of air on an argon plasma was investigated. The data are presented in the form of original probe traces taken on a two-axis recorder. These data were used to construct curves of contamination versus time and of the logarithm of electron current versus probe voltage. It was found that sufficient contamination is present, even in relatively well-prepared systems, to cause gross errors in probe measurements. The errors are found to be especially insidious in that the self-consistency checks commonly used in Langmuir probe applications do not reveal the presence of contamination. It is concluded that probe measurements will be compromised unless particular attention is given to the problem of maintaining a clean probe.
Spectroscopic Measurements on Laser-Produced LiH Plasmas
Authors: Seka W. , Schwob J. L. , Breton C.
Published: February 2004

Spectroscopic measurements in the extreme uv and visible have been carried out on a plasma produced by giant-laser impact on small LiH pellets suspended in vacuum. The experimental results indicate a fast-expanding periphery containing Li, H, and some oxygen impurities, and a plasma core with a smaller mean expansion velocity. The latter gives rise to a sequence of emission lines due to ions of successively decreasing charge. This plasma core is completely recombined after about 100 to 150 nsec.
Drift Velocities of Electrons in the Positive Column of a Neon Discharge
Authors: Sugawara M. , Chen C. J.
Published: February 2004

Drift velocities of electrons in a gaseous neon plasma have been obtained by measuring the discharge current, radial density profile of electrons, and axial electric field in the positive column of a neon discharge for E/na(V cm2) values ranging between 2.8×10−17 and 2.4×10−16 at a temperature of 300°K. The data agree very well with that of the previous workers. The validity of the Langmuir probe measurement for the electron densities in this experiment is discussed in detail.
High-Temperature Properties of Lithium-Diffused Silicon
Authors: Moore M. H. , Fang P. H.
Published: February 2004

Isothermal changes in the electrical resistivity of lithium-diffused silicon have been measured in the range of 370°–650°C. Silicon with high and low oxygen content was used to study the effect of lithium-oxygen interaction. The change of the isothermal curve due to the radiation was also studied. Some important observations can be made: (1) There is evidence of the formation of a new defect at high temperature which would explain the observed redegradation in the post radiation recovery in silicon with low oxygen concentration. (2) There is a very slow formation of a donor state in silicon with high oxygen concentration. (3) The final resistivity after a long period of heat treatment is dependent on the initial donor concentration before the diffusion of lithium in the silicon with low oxygen concentration, while in the case of high oxygen concentration the final resistivity is substantially independent of the initial donor concentration.
Auger Recombination in Hg1−xCdxTe
Authors: Petersen P. E.
Published: February 2004

We have computed the excess carrier lifetime for conduction band-heavy-hole band Auger recombination for n-type Hg1−xCdxTe. The general theory assuming parabolic bands and a constant value for the overlap integrals has been developed by Beattie and Landsberg. We have included the effects of nonparabolic bands and have used the f-sum rule to obtain the k dependence of the overlap integrals. Using numerical techniques we have evaluated the temperature dependence of the lifetime for several x values.
Temperature Dependence of Double Injection in a Long Silicon p+-π-n+ Structure
Authors: Lee D. H.
Published: February 2004

Current-voltage characteristics from 140° to 350°K are measured on a long p+-π-n+ silicon structure biased into the double-injection regime. The I-V characteristics obey a J ∝ V2/L3 relation throughout the considered temperature range, and the magnitude of the double-injection current is predicted within 10% by the Lampert expression J = (9/8) qμpμnτ (p0-n0) V2/L3. The transient response of double injection as analyzed by Baron provides a direct measure of the common high-level lifetime τ, which is given by the formula τ=30.7×10−6 (T/298)1.93±0.23 sec. Conductivity, Hall effect, and the large-signal-step-response method of Dean establish the electron and hole mobility as μn=1280 (298/T)1.75±0.31 cm2/V-sec and μp=410 (298/T)2.18±0.04 cm2/V-sec, respectively, for 140°≤T≤350°K. The consistency between the measured values of the lifetime and mobilities with values reported by the literature establishes that the temperature dependence of a long double-injection p+-π-n+ silicon device is in agreement with the Lampert expression and the temperature variation of τ (T), μp(T), and μn(T). A 14-MeV neutron irradiation of 1.25×1011 n/cm2 does not alter the quadratic law J ∝ V2/L3 of the device but results in lower current levels when compared to the preirradiation condition. Pulse and dc measurements analogous to the preirradiated case give τ̂=8.9×10−6(T/298)0.68±0.07 sec, μ̂p=385(298/T)1.30±0.10 cm2/V−sec, and μ̂n=1160(298/T)1.28±0.21 cm2/V−sec for the carrier lifetime and mobilities, respectively. After irradiation reasonable agreement is found between the measured double-injection current and that predicted from Baron's first-order correction of the Lampert expression for diffusion and thermal generation effects.
Grain-Boundary Conductivity of Cu2O Polycrystals and Rectifiers
Authors: Weichman F. L. , Kužel R.
Published: February 2004

The contribution to the electrical conductivity of grain boundaries in polycrystalline Cu2O was measured in vacuum and in air between 200° and −145°C. It was found to follow a simple exponential temperature dependence with a single activation energy of about 0.31 eV. Heat treatment at 200°C can be used to vary the contribution of the grain boundaries from 5×10−9 Ω−1 in air to 8×10−10 Ω−1 in vacuum at room temperature. The effects are explained by impurities conglomerating at the grain boundaries and the diffusion of oxygen along these boundaries. The deterioration of the volt-ampere characteristics of cuprous oxide rectifiers after preparation or as a result of extensive heating above 150°C is explained by the same mechanism. The studies of the rectifiers were based on measurements on capacity and resistance of the barrier layers at room temperature.
Note Concerning the Velocity of Gunn Domains
Authors: Jones E. L. , Stratton R. , Barlow C. A. , Powell D. R.
Published: February 2004

Using computer solutions of the relevant differential equations, many authors have determined the velocity for which traveling domains exist in a semiconductor with a region of negative differential mobility. Recently, Gunn presented a topological argument leading to a closed form equation for the velocity of a finite amplitude domain. For the case of a domain shape controlled by diffusion we show that Gunn's argument is based on a necessary, but not sufficient, condition that a certain singular point be a center. This leads to an incorrect expression for the domain velocity for all but infinitesimal amplitude domains. The topological character of each solution as the velocity parameter is varied is also described.
Effects of Uniaxial Compressive Stress on Minority-Carrier Lifetime in Silicon and Germanium
Authors: Sloan B. J. , Hauser J. R.
Published: February 2004

Experimental measurements are reported of the effect of mechanical stress on minority-carrier lifetime in germanium and silicon. Lifetime has been measured as a function of temperature and for stress in the 〈111〉, 〈100〉, and 〈011〉 directions at stress levels up to 1010 dyn/cm2. The lifetime changes were found to be reversible, and changes in lifetime of as much as a factor of 3 were observed at stress levels of 1010 dyn/cm2. For all samples investigated, lifetime was observed to increase in n-type material and to decrease in p-type material. A theoretical model has been developed for explaining the effects of mechanical stress on minority-carrier lifetime in germanium and silicon. The model is an extension of the Shockley-Read model to account for stress-induced splitting of the conduction and valence bands plus a possible shift in energy of recombination levels with stress.
Variation of the Shock Piezoresistance Coefficient of Manganin as a Function of Deformation
Authors: Keough D. D. , Wong J. Y.
Published: February 2004

This paper reports recent measurements of the shock piezoresistance coefficient of manganin (in wire and thin-foil geometries) in high-density polycrystalline alumina (Lucalox). For manganin in a wire geometry and for shock stresses below the Hugoniot elastic limit (HEL) of Lucalox, this coefficient was found to be much higher in Lucalox than in C-7 epoxy, Hi-D glass, and soda-lime glass. The cause of the higher coefficient is postulated as the production of lattice defects in the manganin wire arising from large plastic deformation of the wire at compressive stresses below the HEL of Lucalox. For stresses above the HEL of Lucalox, the shock piezoresistance coefficient of manganin wire in Lucalox agrees quite well with that of manganin wire in other insulators. In a thin-foil geometry in Lucalox, the coefficient was found to remain constant above and below the HEL of Lucalox.
Optical Reflection at Grazing Incidence from a Shock Front
Authors: Pert G. J. , Seeds G. M. , Simpson D. , Smy P. R.
Published: February 2004

The reflection of light at grazing incidence from a shock wave at Mach No. 1.94 in air at atmospheric pressure is measured. It is found that the reflection coefficient is equal to that calculated when second-order effects are included. From the variation of the reflectivity across the front it is found that the shock has a curvature of 5.4±0.4 m, a tilt of less than ±⅕, and distortion amplitude of less than 3×10−3 cm.
Nature of the Planar Faults in Cold-Worked β AlNi Intermetallic
Authors: Mohanty G. P. , Schmidt R. A.
Published: February 2004

The defect substructure in cold-worked β AlNi intermetallic has been examined by means of x-ray diffraction. The broadenings exhibited by the fundamental and superstructure powder peaks were analyzed in terms of contributions from inhomogeneous strain and planar faults on the 211 and 110 planes. No account was taken of possible contributions from microtwinning. The analysis shows that the pattern of particle size anisotropy exhibited by β AlNi can be satisfactorily accounted for in terms of certain concentrations of a/8[110](11̄0)- and a/6[111] (1̄1̄2)-type stacking faults, with the former predominating. Possible contribution from a/3[1̄1̄1̄] (1̄1̄2)-type stacking faults, however, was found to be negligible. Similarly antiphase boundaries were also not found to be important in the cold-worked structure of stoichiometric AlNi.
Impurity and Time Effects in the Electrical Breakdown of Alkali Halides
Authors: Hanscomb J. R.
Published: February 2004

Electrical breakdown in single crystals of NaCl, NaCl+MnCl2, KCl, and KCl+SrCl2 is studied in the temperature range 100°–320°C. Two types of breakdown are distinguished and detailed study is given to that type in which no strong dependence of the breakdown strength on the time of application of voltage is found. ``Intrinsic''-type mechanisms would appear to be involved, but the nature of breakdown and of the prebreakdown current is such as to suggest that space-charge effects, if present, are not primarily of ionic origin as has been previously suggested.
Formulation of Admittance for Parallel Field Excitation of Piezoelectric Plates
Authors: Yamada Tomoaki , Niizeki Nobukazu
Published: February 2004

Parallel field excitation of piezoelectric plates has been analyzed with a matrix method, and the admittance of the plate is derived. This formulation affords the definition of coupling factor to each of three vibrational modes, which is shown to be modified by the antifield effect due to the induced charges on major surfaces of the plate in case of anisotropic crystals. In contrast to the perpendicular field excitation case, the resonant frequencies in this case are odd multiples of the fundamentals and the antiresonant frequencies are determined as solutions of a transcendental equation. The validity of the derived equations is confirmed by comparing measured and calculated frequency constants of lithium tantalate single crystal.
Kinetic Theory of the Energy Spread in Electron Beams
Authors: Fischer M.
Published: February 2004

A kinetic theory of the anomalous energy spread in electron beams is given which is based on a new method of solving the nonlinear Vlasov equation. Basically we assume that the thermal velocity of the electrons is small compared to their drift velocity. The energy spread is caused by noise fed into the beam from the electron gun. The theoretical relationships are in agreement with the experiments.
Numerical Study of the Inductive Electrodeless Discharge
Authors: Pridmore-Brown D. C.
Published: February 2004

A numerical study is reported of the equations describing the steady state of a column of thermal plasma that is heated inductively by a radio-frequency axial magnetic field. The electric and thermal conductivities and the specific radiation of the plasma are taken to be given functions of the temperature. A numerical technique is described which yields self-consistent solutions for given values of the input parameters, these being the frequency and the number of ampere turns per unit length of the driving solenoid, and the radius of the tube. Typical results are shown for an argon plasma at atmospheric pressure.
Direct Measurement of the Maintenance Voltage of a Thermal Induction Plasma
Authors: Eckert Hans U.
Published: February 2004

The axial distribution of voltage induced near the inner wall of a 3.8-cm-diam tube confining an rf argon induction plasma at atmospheric pressure was measured at a flow rate of 115 cm3/sec with a water-cooled ring probe. Also measured as functions of probe position were the excitation frequency, voltage, and current on the inductor coil. The plasma reduced the probe voltage to about 60% of its value in the absence of the plasma. After correction for the effects of cooling and displacement of the plasma by the probe, the total induced voltage around the circumference of the plasma at the midsection was found to be 64 V. The corresponding value for electric-field intensity was 6 V/cm. This value falls between published values obtained by indirect methods and is in fair agreement with prediction on the basis of a one-dimensional theory.
Passive Cone Angle Amplifier for Sounding Rockets
Authors: McNutt Douglas P.
Published: February 2004

A passive mechanical device for slowly expanding the yaw cone of a spinning sounding rocket is described in mathematical detail. The equations of motion for the system are solved and approximations useful for design are developed. The device has been used for sky scanning in the infrared and results of a test flight are presented.
Shear-Dependent Relaxation Spectrum: Conversion from Steady-Flow Viscosities to Relaxation Spectrum for Polymer Melts
Authors: Shroff Ramesh N.
Published: February 2004

The steady-flow viscosity η(γ̇), the loss modulus G″(ω), and the storage modulus G′(ω) for five linear polyethylene melts (190°C) were measured using the Weissenberg rheogoniometer and the Instron rheometer. An excellent agreement was observed between the experimental G′(ω) and G″(ω) values and those calculated from the relaxation spectrum obtained from η(γ̇) using the relation η(γ̇)=∫H(lnτ)h(θ)g(θ)3/2τd lnτ,  θ=γ̇τ/2. Here, γ̇ is the shear rate, ω is the radian frequency, and τ is the relaxation time. The functions g(θ) and h(θ) are expressed as g(θ)=(2/π)[cot−1θ+θ/(1+θ2)]  and  h(θ)=(2/π)[cot−1θ+θ(1−θ2)/(1+θ2)2]. No coordinate shift was required. An interative procedure was used in such an interconversion. The first approximation to the spectrum H1(lnτ) was (2/π)[η(γ̇)×γ̇] and the corresponding viscosity was η1(γ̇). The successive approximations were expressed by the equation HK(lnτ)=HK−1(lnτ)+pγ̇[η(γ̇)−ηK−1(γ̇)],where p=2/π and K≥2. In all cases, only six iterations were required to achieve satisfactory convergence. The relaxation spectra so obtained from viscosity measurements at large shearing deformation were in excellent agreement with those calculated from G″(ω) measured in oscillatory experiments carried at small deformation.
Thermal Effects in a Nd:YAG Laser
Authors: Foster J. D. , Osterink L. M.
Published: February 2004

A theoretical model for the thermal lens and birefringent effects induced in a continuously pumped Nd:YAG rod is developed. Experimental measurements of these effects using a 6328-Å probe are described and compared to theory. Excellent agreement between the two types of measurements and theory is obtained. The thermally birefringent and bifocusing phenomena are suggested as causes of reductions in the polarized and fundamental TEM00 powers from a high-power multimode Nd:YAG laser. Typical results are described using a laser which operates in the 200−300-W range of average powers.
Theoretical Behavior of Twisted Multicore Superconducting Wire in a Time-Varying Uniform Magnetic Field
Authors: Morgan G. H.
Published: February 2004

A simplified model is used to study the response to a slowly changing uniform magnetic field of a wire consisting of fine filaments of superconductor embedded in a normal metal matrix, the entire wire being twisted about its axis. Expressions for the critical twist pitch, the power loss in the normal metal, and the time constant are obtained.
Critical Current Studies of Flux Trapping in Superconducting Lead
Authors: Leupold H. A. , Winter J. J. , Breslin J. T.
Published: February 2004

A convenient critical current method for observing the salient features of flux trapping in superconductors is used to study a variety of lead and lead-alloy samples. The critical fields Ht, Ha, Hc for type I and Hc2 for type II superconductors are obtained and found to be in accord with the results of other investigators employing different techniques. Because of self-fields due to current asymmetries, the full critical currents of some samples are observed in nonzero applied fields HpI. The critical current versus applied-magnetic-field characteristics of lead pressure contacts and their application to a simple magnetic null detector are discussed. It is found that trapping flux in certain solid specimens can cause a fourfold enhancement of the peak critical current.
Luminescence, Trapping, and F Centers in Lithium Fluoride Crystals
Authors: Miller Lewis D. , Bube Richard H.
Published: February 2004

Single crystals of lithium fluoride from various sources were investigated by optical absorption in the visible and in the vacuum ultraviolet, irradiation with x rays or with ultraviolet from a microwave discharge source, measurement of total luminescence output and of luminescence emission spectra as a function of temperature, optical and thermal bleaching of absorption centers, and thermally stimulated luminescence. In addition to obtaining specific quantitative data on the parameters of the F center, hole traps and luminescence centers in lithium fluoride, it is concluded that the dominant luminescence and trapping centers are associated with specific impurities in the lithium fluoride, and that the F centers are not involved in the production of visible x-ray-induced or thermally stimulated luminescence.
Image Effects in Vibrating Sample Magnetometer Systems
Authors: Stoner R. E. , Herbert R. H. , Sill L. R.
Published: February 2004

The effect of the varying permeability of the pole faces of an electromagnet with applied field on the signal detected by the pickup coils of a vibrating sample magnetometer has been analyzed by using the technique of magnetic images. It is shown that such an effect can significantly alter the signal detected by the pickup coils and, as a result, the calibration of the instrument.
Stresses in Epitaxially Grown Single-Crystal Films: YIG on YAG
Authors: Zeyfang R.
Published: February 2004

Strains in thin epitaxially grown films resulting mainly from the difference in the coefficients of thermal expansion between film and substrate have been measured using an x-ray double-crystal diffractometer. The measured strains are in agreement with those predicted from known thermal expansion data. Tensile stresses of about 6.5×109 dyn/cm2 parallel to the surface have been found at room temperature in a film deposited at 1225°C.
Representation of Elastic Behavior in Cubic Materials for Arbitrary Axes
Authors: Turley John , Sines George
Published: February 2004

Several methods are advanced to represent the directional dependence of elastic coefficients for cubic materials which are then illustrated using silicon, copper, and molybdenum. The extensively displayed coefficient is the shear stiffness. Also presented are some rarely shown coefficients such as C1123′ and C1312′ whose on-axes values are zero. Polar plots are made of the shear stiffness coefficient C1313′ for silicon, for some planes that have a common zone axis. A method particularly suitable for illustrating anisotropy in transverse coefficients is presented in which a family of polar plots is superimposed on the standard triangle.
Effect of Impurities on the Mechanical Behavior of MgO Single Crystals
Authors: Srinivasan M. , Stoebe T. G.
Published: February 2004

The effect of impurities on the critical resolved shear stress (CRSS) of magnesium oxide single crystals has been determined using compression testing in crystals containing up to 40 mole ppm Fe3+ and up to 500 mole ppm of Ni+2 impurities. In pure crystals containing small amounts of Fe2+, the value of 0.73±0.07 kg/mm2 is determined as the CRSS, and two distinguishable strain hardening regions are identified. The effect on CRSS on Fe3+ content and of isochronal and isothermal aging is also studied; precipitation hardening is observed on aging even for very low concentrations of Fe3+. Heat treatments have very little effect on Ni+2-doped crystals, and yielding studies show that Fe3+ is much more significant than Ni2+ in hardening MgO.
Photovoltaic Properties of Cu2S–CdS Heterojunctions
Authors: Gill W. D. , Bube R. H.
Published: February 2004

The photovoltaic properties of Cu2S–CdS heterojunctions have been compared before and after short heat treatment, using measured I-V characteristics, junction capacitance, and spectral response. After heat treatment slow transients in the photoresponse and effects of secondary illumination were investigated. Optical quenching of the photocurrent was observed in two ir bands corresponding to transitions at 0.8 and 1.1 eV, and enhancement of the photocurrent was seen for hv>1.5 eV. Long persistence of the enhancement effect was observed, which thermally quenched with an activation energy of 0.95 eV. A model for the heterojunction is proposed in which hole trapping in deep imperfection centers in the CdS near the junction is the key mechanism. A conduction band spike is assumed to exist at the Cu2S–CdS interface. The transparency of this spike to photoexcited electrons diffusing from the Cu2S is modulated by variations in the CdS depletion width caused by the deep trapping.
Ion Current from a Collision-Dominated Flowing Plasma to a Cylindrical Electrode Surrounded by a Thin Sheath
Authors: Clements R. M. , Smy P. R.
Published: February 2004

Experimental results for the ion current to a cylindrical electrode in a flowing continuum plasma are compared with the currents calculated from a convection-dependent thin-sheath theory obtained by extending the theory of Lam to cover convection rather than diffusion-generated currents. The relation derived with this theoryIi≈5.3ε01/4e3/4μi1/4rp1/4vf3/4ne3/4V1/2l,  (mks)where ε0 is the permittivity of free space, e is the electronic charge, μi is the ion mobility, rp is the probe radius, vf is the plasma/probe velocity, ne is the ionization density, V is the probe bias, and l is the probe length, is found, on the average, to predict the experimental currents to within ±30% over ranges of 0.1–5 mm in probe radius, 5×102−4×103 cm/sec in probe/plasma velocity, 5×1016−2×1018/m3 ionization density, and 10–100 V in probe bias. Further support for a convection-dependent thin-sheath model is provided by two experimental observations: (1) The current is observed to vary as V1/2 as predicted by the convection-dependent theory rather than to saturate as would be expected of a diffusion-generated current. (2) Separate measurements reveal a marked asymmetry in the current distribution around the probe surface as expected in a thin-sheath situation.
Analysis of Ions Extracted from a Plasma Puff in Magnetic Guide Fields
Authors: Leffel Claude S.
Published: February 2004

An iron skimmer and extractor tube have been used to extract ions from a high-β plasma puff as it traveled down Bz and octopole magnetic guide fields. The plasma puff was generated by a theta-pinch plasma gun operating with H2. The extracted ions were analyzed by a crossed-field velocity analyzer in series with an electrostatic energy analyzer. For the case of the octopole guide field, analysis of the energy spectrum yielded values for the plasma parameters in good agreement with other determinations. For the Bz guide field, the magnetic field trapped in the extractor apparatus produced a magnetic barrier that reflected the plasma so as to distort the energy spectrum and produced temperature estimates that were too high and density estimates that were too low. However, for the Bz guide field, an upper limit could be placed on the concentration of impurity ions.
Spatial Distribution of the Fluorescent Radiation Emission Caused by an Electron Beam
Authors: Cohn A. , Caledonia G.
Published: February 2004

We have measured the side-view intensity profiles of the N2+(1−) (0, 0) radiation emission caused by an electron beam fired into N2 gas. By Abel inversion the three-dimensional radiation emission distribution has been computed from these profiles. Measurements were made for beam energies of 2.0–5.0 keV and gas density of 0.69–2.8 Torr. With proper normalization, the spatial intensity distribution shows no significant variation with voltage. The close relationship between the radiation, energy loss, and ionization deposition distributions is discussed. Integrals of our data reasonably agree with the theory of Spencer and Fano and the data of Grün.
Depth Profiles of the Lattice Disorder Resulting from Ion Bombardment of Silicon Single Crystals
Authors: Feldman L. C. , Rodgers J. W.
Published: February 2004

The depth profile of the lattice disorder resulting from the ion bombardment of single crystals is of interest in many applications. It has been shown that the channeling effect is sensitive to such lattice damage and has been used in extracting the total damage caused by short-range ion bombardment. This paper describes an extension of the channeling technique which yields not only the amount of damage but certain parameters of the depth distribution of the damage. This method is applied to the case of 200–500 keV light ion bombardment in silicon. The results of the measurements and analysis indicate

(1) Annealing at room temperature is an important process in determining the extent and characteristics of the damage.

(2) The peak of the damage distribution is 10%–20% shallower than the expected range of the ion.

(3) The widths of the damage distribution are significantly broader than the expected width of the ion distribution.
Defect Centers in GaAs1−xPx Electroluminescent Diodes Due to High-Energy Electron Irradiation
Authors: Schade H. , Nuese C. J. , Herrick D.
Published: February 2004

Defect centers have been generated in GaAs1−xPx electroluminescent diodes by 1-MeV electron irradiation. Junction capacitance and thermally stimulated current measurements on the irradiated diodes indicate two distinct types of centers. The first, an acceptor center in concentrations of 1−5×1017 cm−3, is found to be independent of GaAs1−xPx alloy composition, and is thought to be primarily responsible for an efficiency degradation previously described for irradiated GaAs1−xPx diodes. The second is a trapping center which is located 0.20–0.35 eV from either band edge, and whose concentration is shown to increase with alloy composition from 1×1015 cm−3 at x=0 to 4×1016 cm−3 at x=0.5. The two types of defects are each found to anneal from GaAs1−xPx at temperatures less than about 550°C. Furthermore, the annealing characteristics of the irradiated diodes establish a definite correlation between the generation and removal of the defect centers and the degradation and recovery of junction electroluminescent efficiencies.
Some Optical Properties of Cadmium Sulfide Containing Phosphorus and Arsenic
Authors: Tell B.
Published: February 2004

Ion implantation and sputtering have generated renewed interest in the possibility of obtaining p-type CdS. However, little is known concerning the properties of acceptors. In an attempt to learn something about acceptors in CdS, phosphorus- and arsenic-doped samples have been prepared by diffusion in a saturated Cd atmosphere at 800°C for 24 h. The electrical and optical properties of the doped samples are compared with undoped test samples (fired in saturated Cd atmosphere but without added dopant). The electrical properties indicate only a slight compensation due to the presence of P and As. The optical studies (photoluminescence, photoconductivity, and optical absorption) yield a level about 1-eV above the valence band, which is presumably the binding energy of an electron to a compensated P or As acceptor.
Wave Instabilities in Bulk Semiconductors with Field-Dependent Drift Velocity and Carrier Temperature
Authors: Sasaki Akio
Published: February 2004

Wave instabilities are studied considering the field dependencies of the drift velocity and the carrier temperature. Wave instabilities caused by negative dependency of the carrier temperature on an external field are derived. These instabilities are associated with the energy (transport) equation. The diffusion instability is derived for an extrinsic semiconductor, and it is shown that a negative value of the effective diffusion coefficient does not always lead to wave instability. The analysis in this paper is equally valid for a collision-dominated, weakly ionized gas plasma although it is presented with reference to semiconductors.