bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of the Motion of a Strongly Magnetized Plasma on the Emission of Radiation by a Finite Dipole
Authors: McKenzie J. F.
Published: January 2005

The effect of the motion of a strongly magnetized and cold plasma on the propagation and radiation of electromagnetic waves is considered. The radiation loss suffered by a finite dipole situated in a moving plasma is calculated. It is shown that when the dipole frequency exceeds the plasma frequency, the total radiation emitted by the dipole can be ehnanced by several orders of magnitude by a slowly moving plasma. The radiation output can also be enhanced when the dipole frequency is less than the plasma frequency, particularly at relativistic speeds, provided the scale length of the dipole is sufficiently large.
Evidence for Indirect Annihilation of Free Excitons in II-VI Semiconductor Lasers
Authors: Packard J. R. , Campbell D. A. , Tait W. C.
Published: January 2005

Experimental results obtained on CdS, ZnO, and CdSe are presented which show electron-beam-pumped laser emission resulting from the decay of free excitons to photons and longitudinal optical (LO) phonons. Calculations based on available absorption data for ZnO and CdS show that at 77°K the required exciton density for stimulated emission is about 1017 and 1018 cm−3, respectively.
Optical Quenching of Photoconductivity in CdS and ZnS Crystals
Authors: Hemila Simo O. , Bube Richard H.
Published: January 2005

The optical quenching spectrum in CdS and ZnS single crystals has been investigated as a function of temperature, using a high-resolution monochromator and polarized light. The well-known spectrum in both materials consists of a narrow band with maximum at about 0.9 eV and a broader band with onset at about 1.1 eV. Poorly resolved fine structure was detected in the 0.9 eV band in CdS between 0.83 and 0.92 eV; no fine structure was detected in the higher-energy band. No fine structure could be detected in the less accurate measurements on ZnS. No polarization effects of any kind were detected in either material. Studies of the temperature dependence of optical quenching confirm the early indications described by Bube, and indicate anew the intrinsically complex nature of the sensitizing center. The problems related to distinguishing between intrinsic-defect and copper-impurity effects are discussed.
Trapping Effects in Drift Mobility Experiments
Authors: Tefft Wayne E.
Published: January 2005

Theoretical expressions have been derived for the charge-distribution function and resultant voltage-decay curve applicable to drift mobility experiments in the presence of traps. The charge-distribution function was obtained under the assumption of constant electric field and the neglect of recombination and diffusion. The results are, therefore, limited to the case of low carrier densities.

The general expression for the voltage-decay curve is quite complicated, but useful approximations are made for various time regions. In addition, it is shown how the theory may be applied to the xerographic discharge mode under certain limited conditions.
Ion Microprobe Mass Analyzer
Authors: Liebl Helmut
Published: January 2005

This paper describes the development of an instrument which is analogous to an electron microprobe x-ray analyzer, whereby the electron microprobe is replaced by an ion microprobe, and the x-ray spectrometer by a mass spectrometer. A duoplasmatron is the primary ion source. The primary ion beam is mass separated to eliminate impurity ions. A probe diameter of less than 2 μ at 2×10−10 A is realized for 12-kV Ar+ ions. A new mass spectrometer was developed with the emphasis on high transmission, yet simple construction. It is stigmatic imaging, double focusing, has a mass-resolving power of 300 with a solid acceptance angle of 1.5×10−2 sr (4° half-angle) and a transmitted-energy bandwidth of 10%. It consists of an axially symmetrical electrostatic Einzel lens, a 45° spherical condenser sector, and a magnetic field with plane but inclined pole faces, which deflects the beam by 90°. No entrance slit is used. Experimental results are presented.
Propagation of Partially Polarized Waves in a Slightly Anisotropic Medium
Authors: Lenoir William B.
Published: January 2005

The behavior of partially polarized waves in a homogeneous, dispersive medium with small anisotropy is considered. The field solutions for a medium specified by a tensor permeability are derived from Maxwell's equations. A power coherency matrix and a brightness temperature matrix are defined and discussed. The tensor equivalent to the equation of radiative transfer for an emitting and absorbing medium is derived from a form of Poynting's theorem, and the general solution to this equation for the brightness temperature matrix is given. The assumptions and restrictions employed in the development are reviewed and the effect of relaxing them is discussed. Finally, the method is applied to a simplified version of absorption by Zeeman-split resonance lines.
Propulsion and Angular Stabilization of Dust Particles in a Laser Cavity. II
Authors: May A. D. , Rawson E. G. , Hara E. H.
Published: January 2005

Certain dust particles exhibit steady rectilinear motion when situated in the standing light wave inside a laser cavity. Some observations and a simple theory are presented which show that these particles are oriented by the laser beam. In addition, semiquantitative calculations are given which indicate that the driving force and stabilizing torque are radiometric in origin.
Uniformly Moving Transonic and Supersonic Dislocations
Authors: Weertman J.
Published: January 2005

General solutions have been obtained for screw, gliding edge, climbing edge, and mixed dislocations traveling with a uniform motion at velocities in the transonic and supersonic velocity range. The motion is considered to occur on planes that give up finite amounts of energy per unit distance of dislocation movement. The only previous work on this problem is Eshelby's general solution of the supersonic screw dislocation and Stroh's and Ang and Williams' work on discrete dislocations that move on planes that give up an infinite amount of energy per unit distance of dislocation movement. The most interesting new result is that the limiting dislocation velocity of an ordinary dislocation pushed by an applied stress lies in the transonic velocity region, not at the shear-wave velocity as is usually assumed in the literature. Only the screw dislocation is limited by this latter velocity. We have reached the following conclusions: Any dislocation that runs on a plane that gives up energy must move at a supersonic velocity if the force law across the plane never changes sign. A supersonic dislocation, like a subsonic dislocation, can move at an arbitrary velocity. A dislocation that moves on a plane that gives up energy will move in the transonic velocity region if the force law does have a sign reversal. A dislocation that moves in the transonic velocity region cannot move at an arbitrary velocity; it moves at a unique velocity whose value depends on the exact force law.
Turbulent Effects in Detonation Flow: Diluted Nitromethane
Authors: Mallory H. Dean
Published: January 2005

Pressure irregularities are shown to be present within the wave front in reacting nitromethane-acetone solutions. Throughout the test series described, the reaction wave was overdriven, thereby producing reaction in solutions too dilute to detonate in a normal manner. This device served to produce large pressure irregularities which could easily be seen with our optical system. The irregularities in the more dilute nitromethane solutions are several millimeters in lateral extent although quite shallow normal to the wave front. High-speed photographs are presented which show the irregularities to vary with the nitromethane dilution and with the strength of the initiating shock.
Stability of a Rotating Ring of Discrete Charges in Crossed Electric and Magnetic Fields
Authors: Heath Gregory E.
Published: January 2005

Experimental results indicate that certain configurations of discrete charges may be more stable than continuous distributions possessing the same charge and corresponding symmetries. A model of N identical infinitely long negatively charged rods rotating under the influence of a uniform applied magnetic field is here investigated for stability of perturbations about an equilibrium configuration and compared to a continuous charged sheet. For the continuous sheet, a countably infinite number of modes of oscillation are possible of which only a finite number may be stable. The finite number of stable modes are those corresponding to the longer wavelengths and the growth rates of the infinite number of unstable modes increase as the wavelength decreases. In contrast, the discrete distribution may support only 2N-3 modes of oscillation. The first modes to become unstable when critical parameters are adjusted are those corresponding to the shortest wavelengths. These also have the highest growth rates. The most significant result of this investigation is that the discrete distribution may have all vibrational modes stable while this is impossible for the continuous distribution. Application of the discrete-charge theory to explain the stability of experimentally observed vortex patterns in unneutralized electron beams is also discussed.
Laser-Generated Stress Waves in a Dispersive Elastic Rod
Authors: Percival C. Mark
Published: January 2005

Elastic stress waves generated in a pressure bar by in-depth absorption of laser energy were measured using a thin piezoelectric quartz crystal. The experimental results showed very good quantitative agreement with theoretical predictions based on Love's modified wave equation. Higher modes of wave propagation not predicted by the one-dimensional theory were evident in the experimental results.
Ferromagnetic Resonance in a Uniaxial Anisotropic Ferrite: BaFe12O19
Authors: Silber L. M. , Tsantes E. , Angelo P.
Published: January 2005

Ferromagnetic resonance has been observed in a single-crystal sample of barium ferrite, BaFe12O19, under both single-domain and multidomain conditions, for orientations of the static field from 0°–90° with the easy axis of magnetization. The results verify in detail the predictions of the theory of Smit and Beljers for single-domain conditions, and show qualitative agreement with the multidomain theory.
Gunn Effect in ZnSe
Authors: Ludwig G. W. , Aven M.
Published: January 2005

We have observed the Gunn effect in n-type ZnSe crystals subjected to pulsed electric fields. At room temperature the threshold field is about 38 kV/cm, in rough agreement with the dielectric breakdown field as calculated from Stratton's formulas. In samples showing a spiking mode of current instability, the field outside the domain E1≈22 kV/cm, the domain field E2≥100 kV/cm, the domain drift velocity vdd≈1.0×107 cm/sec, and the peak-to-valley current ratio is about 3:2. Thus, the high-field behavior of ZnSe is similar to that of GaAs, except for the higher characteristic fields. However, current runaway limits operation of ZnSe units to very short pulses and fields near threshold.
Avalanche Breakdown Effects in Near-Intrinsic Silicon and Germanium
Authors: Park J. N. , Rose K. , Mortenson K. E.
Published: January 2005

Impact ionization effects have been observed in near-intrinsic silicon and germanium structures which exhibit an abrupt transition from a high-resistance state to a low-resistance state through a negative resistance region. Measurements on high-resistivity n- and p-type silicon samples with symmetric Ohmic or blocking contacts show that the threshold voltage for this transition is proportional to sample thickness which is indicative of bulk breakdown. On the other hand, the sustaining voltage in the low-resistance state is thickness independent, indicating the formation of an avalanche breakdown layer. The results agree generally with Gunn's theory of avalanche injection.
A Consideration of the Appearance of Long-Tail Trichel Pulses
Authors: Sawa Goro , Shinohara Ukichi , Ieda Masayuki
Published: January 2005

Effects of solid dielectrics on the negative-point Trichel pulse have been studied with a series of C-R networks giving equivalent circuits for the dielectrics. As we pointed out in previous papers, the wave tail of the Trichel pulse is markedly elongated up to the order of 10 μsec, when a solid dielectric is inserted within some distance from the point electrode. It is concluded from the experimental results and the discussion that the primary cause of the appearance of the long-tail Trichel pulse in this case is based on the reduction of a counter electric field stemming from the accumulated negative space charge through the increased capacitance outside them due to the insertion of the solid dielectric, while the modification of the negative space charge itself, due to those such as charge decay, may give a change to the termination time of the pulse in which the long tail is pre-established.
Space-Charge Effects in Insulators Resulting from Electron Irradiation
Authors: Monteith L. K. , Hauser J. R.
Published: January 2005

A detailed model of space-charge effects resulting from trapping of thermalized irradiation electrons in insulating materials is presented. Analytical solutions for a particular insulating material (polyethylene terephthalate) have been obtained. When the trapping sites are uniformly distributed in energy below the energy level where charge transport occurs, the rate of charge buildup and release depends primarily on a ratio of the material relaxation time constant ρε to a release rate of electrons from traps. Agreement between theory and experiment is reasonably good in the case of polyethylene terephthalate when this ratio of time constants is approximately unity.
Determination of Elastic Constants from Sound-Velocity Measurements in Crystals of General Symmetry
Authors: Neighbours J. R. , Schacher G. E.
Published: January 2005

The ``elastic constants'' of a crystal are referred to a Cartesian coordinate system which has a definite relation to the crystal axes. In determining these constants from sound-velocity measurements at least as many measurements must be made as there are constants to be determined and in general more than one propagation direction will be used. Thus, in order to relate the measured velocities to the elastic properties of the crystal one needs to solve the equation of motion for the direction under consideration, and to know the transformation equations that relate the elastic properties along the propagation direction to the desired elastic constants. In this paper a perturbation solution to the equation of motion is presented as well as the transformation equations for triclinic and all higher symmetry crystal classes. Also presented are simplifications that will be of use in designing experiments and reducing the data. Several mistakes in previously published work are corrected.
Two-Stream Instability in Anisotropic Semimetals
Authors: Kakihana S. , Buchmiller L.
Published: January 2005

Dispersion relations for two-stream instabilities in electron—hole plasmas in bismuth and pyrolytic graphite have been obtained. The band structure of these anisotropic semimetals has been incorporated into the dispersion relations. These dispersion relations were numerically evaluated for the growth rate and frequency of oscillation for waves propagating in the three principal crystal axes of bismuth and for the wave propagating in the a-plane of pyrolytic graphite. For the wave propagating along the trigonal axis of bismuth there is one optical branch and one acoustical branch. For the acoustic branch the growth rate exceeds the collision damping at an applied electric field of 7 V/cm. The frequency of oscillation where the growth rate is maximum is 510 GHz, which is in the submillimeter-wave range (λ≈0.6 mm). For the wave propagating along the binary axis there is an optical branch, a high-frequency acoustical branch, and a low-frequency acoustical branch. The high-frequency branch is damped even for electrons drifting with velocity near the Fermi velocity. The low-frequency branch exhibits growth but the threshold electric field of 15 V/cm is higher than the field required for the trigonal case. The frequency which corresponds to the peak growth rate for this electric field is 2.3×1012 cps, or λ = 130 μ, which falls in the far-infrared region. Waves propagating along the bisectrix axis of bismuth exhibit anomalous behavior which results in two coupled acoustic modes. The threshold conditions for pyrolytic graphite are less favorable than those for bismuth. The threshold electric field is 160 V/cm which is very much higher than the threshold for bismuth. The frequency of oscillation corresponding to peak growth rate is 3×1013 Hz, or λ = 10 μ, which is in the near-infrared range.
Narrow-Band Self-Filtering Junction Detectors
Authors: Burns J. W. , Kaye S. , Medved D. B. , Prince M. B. , Rolik G. P.
Published: January 2005

The general principles and design theory of p-n junction detectors with narrow spectral responses are described. These detectors do not require the use of external filters and are capable of maintaining their narrow spectral response over large fields of view. Use of zinc diffusion in n-type gallium arsenide has produced detectors peaking in the neighborhood of 8850 Å with characteristic bandwidths on the order of 200 Å and quantum efficiencies from 0.2–0.3 electrons per photon. The principle has been experimentally extended to a second material, indium-arsenide—phosphide, whose composition is tuned to provide a narrow spectral response peaking at 1.06 μ. The experimental results are compared with theoretical predictions.
Attenuation of Shock Waves in Aluminum
Authors: Erkman J. O. , Christensen A. B.
Published: January 2005

Targets of 2024-T351 aluminum were shocked to approximately 110 kbar and 340 kbar by flyer plates having velocities of 0.12 and 0.32 cm/μsec, respectively. Free-surface velocities were determined as a function of target thickness by recording the time of flight across known distances of thin shims which were originally in intimate contact with the surfaces of the samples. The experimental data are believed to be more accurate than any obtained previously. In earlier work it appeared that the free-surface velocity decreased in a stepwise manner as the target thickness was increased. The new data do not show a stepwise decrease, so the simple elastoplastic relations cannot be used to predict attenuation. Some improvement in the predictions was obtained by using a variable shear modulus. The relation between the shear modulus and the strain was obtained from the results of the attenuation experiments. Further improvement may be obtained by the inclusion of the Bauschinger effect in the calculations. Some data were obtained for annealed 1060 aluminum at 110 kbar. The response of 1060 aluminum appears to differ significantly from that of the hard aluminum.
Low-Temperature Thermal Conductivity of Fast-Neutron-Irradiated Silicon and Germanium
Authors: Albany H. J. , Vandevyver M.
Published: January 2005

The thermal conductivity K of initially n-type silicon and germanium irradiated at about 30°C at four fast-neutron doses (1.1×1017, 2.5×1017, 1.7×1018, and 3.4×1018 n/cm2) was measured between 5°K and 300°K. The thermal-conductivity behaviors of the two irradiated materials differ by significant features: Pronounced shifts of the maximum of K to higher temperatures are observed in germanium after irradiations, leading to a depression of K which is more pronounced below than above the maximum. No noticeable shift, however, appears in silicon after bombardment, the depressions of K on both sides of the peak remaining comparable. The additive thermal resistivity (K−1−K0−1) at 20°K is found to increase with the integrated flux φ, approximately as 7.9×10−13 φ0.65 cm·deg/W, and 3.8×10−12 φ0.65 cm·deg/W, for irradiated silicon and germanium, respectively. Similar flux dependences were observed by Vook for 2-MeV electron-irradiated silicon and germanium. Using the Callaway model, it is shown that the experimental data for irradiated silicon can be accounted for by considering only an increase in the τ−1=A′ω4 scattering, the factor A′ increasing linearly with the flux. The additional scattering mechanism is most likely to be associated with strain fields arising from bombardment-induced defects instead of an electron-phonon interaction, unless one assumes for the latter a Rayleigh-type scattering law. In agreement with Vook's results on electron-irradiated germanium, the dominant additional scattering in the present irradiated germanium, at least for the lower doses, appears to be due to electron-phonon interaction. On the basis of the Keyes model, the difference between bombardment-induced scatterings in silicon and germanium is attributed to the predominant effects of irradiation in these materials, silicon approaching an intrinsic behavior and germanium becoming highly p type.
Effect of ``a'' Domains on the Movement of ``c'' Domain Walls in BaTiO3
Authors: Callaby D. R.
Published: January 2005

It has been found that the activation field for 180° domain wall motion in a BaTiO3 crystal is increased when the wall intersects an ``a'' domain for the case where the wall is parallel to the edge of the ``a'' domain. It is shown that this increase is only an apparent increase due to a reduction of the mean field E2 acting on the wall in the ``a'' domain region compared with the field E1 acting on the walls which do not intersect ``a'' domains. If d1=crystal thickness and d2=``a'' domain thickness, then E1/E2 = (d1+d2)/d1. As a result, it is calculated that the contribution of any ``a'' domain spikes in the surface to the increased surface-layer activation field is negligible. It is also shown that the motion of 180° walls is determined by the fields acting throughout the whole of the crystal and not just by the fields at the surface of the crystal.
Temperature Dependence of the Elastic Constants of the Alkali Halides. II. The Solid Solution KCl–KBr
Authors: Slagle O. D. , McKinstry H. A.
Published: January 2005

The elastic constants for the solid solution KCl–KBr have been measured from room temperature to 400°C. The general trend of the elastic constants versus composition is in agreement with theory but indicates that the dependence on interionic distance is greater than predicted theoretically. The temperature coefficients of the elastic constants are found to agree fairly well with the theory of Mitskevich for c11 and ½(c11–c12), but those for c44 were best fit by an expression taken from Leibfried and Hahn. The dependence on composition of ½(c11–c12) at high temperature strongly supports the theory of Thompson that melting is due to the instability of the acoustic mode associated with this shear elastic constant.
Determination of Instantaneous Heat Sources with Inert Thermometers
Authors: Erdmann Joachim C. , Jahoda James A.
Published: January 2005

The temperature transients arising from instantaneous plane heat sources in a linear heat conductor are analyzed. The thermal conductivity and the specific heat of the conductor are assumed to be temperature independent. Two thermometers are fastened to the conductor. The thermometers possess heat capacity causing inert response. It is found that the position and strength of a heat source can be calculated from the first and second time integral of the observed transient temperature difference between the two thermometers. If the inertia parameter is large, the thermometer heat capacity can be derived from the response to a uniform short heat pulse. The method can be applied to problems of low-temperature plastic deformation and superconductivity. An experimental example is discussed, in which instantaneous plane heat sources are generated by localized discontinuous tensile deformation at 4.2°K. The positions of the slipped zones and the amount of heat released during each slip are determined.
Correction for Finite-Pulse-Time Effects in Very Thin Samples using the Flash Method of Measuring Thermal Diffusivity
Authors: Larson K. B. , Koyama Karl
Published: January 2005

A method is described for eliminating errors due to the finite-pulse-time effect in the flash technique for measuring thermal diffusivity. The method depends on the employment of a mathematical model which incorporates an empirical function closely describing the actual waveform of the heat pulse produced by a flash lamp. The analytical solution obtained forms the basis of a digital computer data-reduction procedure devised for calculating the thermal diffusivity from the experimental measurements. The method of data reduction employed leads to an improvement in the precision of measurement heretofore unattainable by the flash technique. This is accomplished, in effect, by replication of the experiment through utilization of the information contained over a wide range of the temperature transient, in addition to that provided by the usual measurement of the time at which the transient reaches half-maximum.

The analysis described makes it possible to use the flash technique with samples having very small thickness-to-diameter ratios. This has the advantage of widening the range of temperatures within which heat losses may be neglected without the introduction of serious error. Experimentally, the method has been successfully tested for some very thin disk-shaped samples having axial dimensions of the order of (ατ)1/2, where α is the thermal diffusivity and τ is the duration of the pulse.
Compact Rheometer for Dynamic Measurements on Polymer Solutions or Gels
Authors: Chompff A. J. , Lamb G. E. R. , Prins W.
Published: January 2005

A Pochettino-type rheometer is described which is suitable for polymer solutions or diluted networks, i.e., gels. It directly measures sinusoidally varying stress and strain together with the phase angle between them. The design makes use of the piezoelectric properties of titanate ceramics for both the ``driver'' and the ``pickup.'' Thanks to these, the rheometer is rather compact and temperature control is greatly simplified. The sample is located in a narrow gap (0.3 mm) between two coaxial cylinders. The very small displacements (0.1 μ) are measured with a high-resolution inductive displacement transducer. An important feature of the design is a ``compensator'' ceramic, between the driver and the pickup, which eliminates secondary modes of motion generated by the driver. The rheometer is calibrated by an absolute method which avoids the use of standard viscosity samples. The instrument can measure moduli from 500 to 6×107 N/m2. The frequency range—not yet fully exploited—is from 10 to 3500 cps. Measurements have been made between −80° and +30°C. The temperature range possible with the present design is −85° to +100°C. With the above rheometer, the relaxation spectrum of a 25.5% solution of polymethyl acrylate (PMA) in toluene was obtained. Below −25°C this solution exhibits a phase separation on a microscopic scale, leading to a very broad distribution of relaxation times and analogous to that observed for some heterogeneous polymer systems.
Dislocation Studies in Bi2Te3 by Etch-Pit Technique
Authors: Sagar A. , Faust J. W.
Published: January 2005

Dislocation studies in Bi2Te3 were made by etch-pit technique. All work was done on c planes. The etch marks the dislocations in the c plane by producing etch grooves, and marks the sites of emergence of dislocations from the surface with pyramidal etch pits. Evidence was found for the presence of networks of dislocations lying predominantly in the c plane. Experimental evidence was also found for bending of the dislocations within the crystal being responsible for different size pyramidal etch pits, and flat bottom pits observed on the etched surfaces. The same mechanism was found to be responsible for bringing out new etch pits on longer etching. The slip traces on the c plane were found by controlled surface-damage studies to be parallel to the binary axes.
A Model for the Interaction of Magnetic Domain Walls with Crystalline Imperfections
Authors: Baldwin John A.
Published: January 2005

The interaction of a domain wall with a crystalline defect is frequently represented by means of a potential-energy function which gives the energy of the wall as a function of position. However, it was shown ten years ago by Rodbell and Bean that the experimental dependence of wall velocity on applied magnetic field is inconsistent with the predictions of a theory in which the interaction of a wall with a defect is taken to be conservative. In the present paper a model is proposed in which this interaction is mainly nonconservative. It is shown that this model is in agreement with wall-velocity measurements. It also predicts the reversible spikes found on the leading and trailing edges of the switching voltage when a pulse of magnetic field is applied to a square-loop sample. Finally, it is shown that the model predicts a Rayleigh hysteresis loop. A one-parameter expression is given for the Rayleigh loop of a single-crystal window frame.
The Detonation Electric Effect
Authors: Hayes Bernard
Published: January 2005

Electromagnetic signals have been found to originate from the wave fronts in detonating high explosives. The effect is that of small positive electric charge on the detonation front. For the liquid explosive, nitromethane, the amplitude of the detected signal increases smoothly as the wave approaches the detector. For particulate explosives there is superimposed on the signal a complex oscillatory pattern, the amplitude and frequency distribution of which are dependent on the kind of explosive, the particle size, and the presence of macroscopic disturbances of the detonation wave. Signal detection is achieved with an external passive probe, which has no effect on the explosive system under investigation and requires only a high-speed oscilloscope to record detonation events. These signals form the basis of a powerful new method for studying propagation times, initiation phenomena, and the structure of the detonation front.
Generation and Detection of Dynamic Gravitational-Gradient Fields
Authors: Forward Robert L. , Miller Larry R.
Published: January 2005

We have constructed a generator of dynamic Newtonian gravitational-force-gradient fields and used it as a signal generator to calibrate the response of the gravitational-gradient detectors being developed in our research work on gravitational-mass sensors. The gravitational-gradient-field generator is a flat aluminum cylinder 14 cm in diameter, with four holes than can be filled with slugs of different density to create a rotating mass-quadrupole moment. The generator is mounted on an air-bearing-supported motor and rotated at a nominal speed of 44 rps (2640 rpm). Because of the bisymmetric mass distribution, the dynamic gravitational-gradient fields generated have a frequency of 88 Hz, or twice the rotation frequency. The detector is a 12-cm-diam cruciform-shaped structure which responds to 88 Hz gravitational-gradient forces. The small (10−11 cm) motions induced in the detector arms are sensed by piezoelectric strain transducers attached to the arms near the point of maximum strain. A simple vacuum system, an iron shield plate, and spring mounts suffice for acoustic and magnetic isolation, since most of the nongravitational noises were generated at 44 Hz, the rotation frequency, rather than at 88 Hz, the gravitational-gradient frequency. Data taken with four different mass distributions varying from 0 to 1000 g and separation distances varying from 4.8 to 12 cm agree well with the theory, indicating that only gravitational energy was being transmitted from the generator to the detector. The minimum dynamic gravitational-gradient field observed during this test was 6×10−9 sec−2 or 0.002 of the earth's gradient. The equivalent differential acceleration exerted on the sensor arms by this field was 3×10−11 g's.
The Conduction-Diffusion Theory of Semiconductor Junctions
Authors: Chang Y. F.
Published: January 2005

This is a mathematical analysis of the conduction-diffusion equation, which governs the carrier motions in semiconductor materials. The model used for the junction devices is based on the Fletcher—Harrick injection relations at junctions and on the vanRoosbroeck conduction—diffusion equation in bulk regions. The exact solution of this analysis is obtained by numerical computation using the Automatic Taylor Series (ATS) method. Besides the numerical solution, there is a closed-form exact solution for zero recombination; this is the Gunn solution.

The limitations of this analysis are those imposed on the Fletcher—Harrick and vanRoosbroeck developments. They are the abrupt-junction condition, and the quasineutrality condition. Satisfaction of the first condition depends on device fabrication. This analysis does not include the effects found in diffused junctions. Satisfaction of the quasineutrality condition depends on the internal electric fields in the devices. This analysis examines these electric fields and keeps watch over its own validity.

The characteristics of semiconductor junction devices are analyzed by the conduction—diffusion theory with mathematical uniformity and exactitude. Application of this theory to the p—n and n—n+ junctions yields these results. The characteristics of p—n junctions analyzed here basically agree with the results of previous researchers. The n—n+ junction exhibits a current-saturation effect in the forward bias direction. This is due to a limitation on the injected carrier concentration in this device. The p—n—n+ and n+—n—n+ junctions are analyzed to eliminate metal contacts to the base region, because the quasineutrality condition is violated near these contacts. The three-layer devices have basically the same characteristics as the two-layer diodes. In p—i—n junction devices with long base regions, the quasineutrality condition is violated in the middle of the base region. In such cases, the solutions of Lampert and Rose and of Baron are more appropriate.
Domain Structure of Ordered Equiatomic Pt–Co Observed in the Field-Ion Microscope
Authors: Tsong Tien Tzou , Müller Erwin W.
Published: January 2005

By comparing field-ion micrographs of ordered equiatomic Pt–Co alloy with the surface structure expected from a hemisphere of the established L10 lattice, it is found that the Co atoms are not imaged. This greatly facilitates the domain structure analysis. Using the FIM, 90-deg oriented domains and antiphase domains are observed at the atomic scale. It is found that, in general, randomly distributed 90-deg oriented domains and antiphase domains of size about 20–300 Å constitute the ordered Pt–Co crystal. Additionally, platelets of thickness 20–80 Å, oriented at 90-deg with respect to the main matrix have been observed. By comparing the ion micrographs of in situ annealed specimens at increasing ordering times, it is concluded that both nucleation and homogeneous rearrangement are responsible for the ordering mechanism at low temperature.
Atomic Structure of Platinum Crystals Electrolytically Overgrown on Field-Ion Microscope Tips
Authors: Rendulic Klaus D. , Müller Erwin W.
Published: January 2005

The platinum deposits overgrown on iridium and tungsten are polycrystalline with a crystal size of 50–500 Å. The orientation is mainly [111]. Some deposits on iridium grow epitaxially. A variety of defects, such as twinning, vacancy clusters, and high dislocation density (1011/cm2), are observed. Additionally, some experiments with copper deposits on iridium and tungsten are described. The corrosion of field-evaporated iridium tips both in air and in the plating solution is studied prior to the application of the electroplating.
Photoresponse Studies of Vapor-Deposited Mo–Si Systems
Authors: Skadron P.
Published: January 2005

Photoresponse measurements on vapor-deposited Mo–Si systems in the range from 1.2 μ to 1.6 μ have been used to study the barrier height at the metal—semiconductor interface, and to obtain estimates of the hot carrier attenuation length in the metal and of the influence of semiconductor backscattering on the hot carrier collection efficiency. The metal films were formed by the chemical vapor deposition of molybdenum on silicon at 700°C, and some of the units were subsequently heat-treated at 850°C in an H2 atmosphere. Electron diffraction evidence indicates that the films are composed of polycrystalline molybdenum in the units not heated above 700°C. In units heated at 850°C, the metal layer consists of molybdenum and one or more molybdenum—silicon compounds in proportions which depend on the duration of heat treatment. The results indicate a barrier height of approximately 0.67 eV, and an attenuation length probably below 350 Å. The variation of the magnitude of the photoresponse with reverse bias voltage under conditions of fixed wavelength and optical intensity was also investigated. A comparison with similar measurements made on Au–Si diodes suggests that electron backscattering due to optical phonon generation may be of relatively small importance in the Mo–Si system.
Intensity of Particle Motion in Solid—Gas Suspension Flow
Authors: Min Kun
Published: January 2005

Based on the multiflash photographs of particle motion, Soo has found that the turbulent intensity of particle motion in solid—gas suspension flow is greater than the corresponding fluid intensity by a factor of as much as three. This has been a source of puzzlement, since it is contrary to what is expected from the nature of particle—fluid interaction. The present paper shows that the ``particle intensity'' as reported by Soo is associated with the velocity distribution of the particles, each of which travels almost uniformly in a straight line at different inclination to the direction of mean flow. This particle behavior is due to collisions between the particles and the wall of the flow channel. Soo's evaluation of the ``particle intensity'' from the same photographic records but using a different optical autocorrelation technique is also examined and found to be in error.
Relations between Electrical Noise and Dislocations in Silicon
Authors: Yu K. K. , Jordan A. G. , Longini R. L.
Published: January 2005

The effect of edge dislocations on electrical noise in n-type silicon has been investigated. Parallel arrays of edge dislocations have been introduced by plastic deformation in vacuum at near 950°C, and the amount of dislocations introduced has been examined by etch pits. Electrical conductivity and noise measurements confirm the Shockley—Read model, according to which edge dislocations behave as lines of acceptors in semiconductors with the diamond structure. From the conductivity measurements, values of the fractional disturbed volume, ε, of the conductive sample are deduced in accordance with Read's theory. Noise results in dislocated samples show 1/f and g—r components differing from those of control samples obtained from the same ingot and also differing from samples subjected to the same heat treatment but without introduced dislocations. The g—r noise can be explained in terms of fluctuations in ε, which in turn are caused by fluctuations in the number of captured electrons at the dislocation sites. It is found that, in the temperature range 25°–170°C, for 200-Ω·cm samples, the observed time constants and noise amplitudes are consistent with fluctuation phenomena associated with the dislocation sites acting as recombination centers. However, at near and below room temperature, trapping at the dislocation sites seems to be the primary cause of the observed noise behavior.
Electron-Beam-Probing Studies of Beam—Plasma Interactions
Authors: Cannara A. B. , Crawford F. W.
Published: January 2005

This paper describes experimental observations of electron-beam—plasma amplification in a low-pressure, beam-produced, mercury-vapor discharge. A nonperturbing probing technique, employing a fine auxiliary electron beam, was used to measure rf growth, phase velocity, and axial and radial electric-field profiles in the interaction region. The comprehensive data obtained have been compared with predictions based on cold- and warm-plasma theories of beam—plasma amplification. It is concluded that the experimental growth rates and electric-field profiles are approached more closely by warm-plasma theory, but that the measured phase velocities are somewhat slower than either theory suggests. The electric-field profiles are smoother than expected, probably owing to the beam boundary being less sharp in practice than is assumed in the theories.
Structure of Martensite
Authors: Ron M. , Kidron A. , Schechter H. , Niedzwiedz S.
Published: January 2005

X-ray measurements cannot give a complete microscopic interpretation of the structure of carbon—iron martensite because of the broad diffuse diffraction lines. They show that the iron martensite has a body-centered tetragonal lattice on the average, but cannot give an exact picture of the distortion centers around the carbon atoms.

Several samples of martensite were studied by means of the Mössbauer effect to separate the octahedra occupied by carbon atoms from the rest of the lattice. The iron atoms around each octahedron gave two extra different hyperfine fields, with an isomer shift relative to Armco iron. The strength of the new fields coupled with the intensity ratio of the absorption lines leads to the interpretation that the distortion around a carbon atom is local, and that most of the crystal has an almost bcc structure, probably with a small strain field centered at the carbon atom.
The Martensitic Transformation in Cobalt
Authors: Johnson R. T. , Dragsdorf R. D.
Published: January 2005

The properties of the fcc to hcp transformation in cobalt single-crystal whiskers have been determined. Studies of the crystallographic properties and dislocation structure using optical, standard x-ray diffraction, and high-resolution x-ray diffraction topographic techniques are herein reported. It is shown that the atomic movements associated with the transformation in cobalt initiate at the most highly strained regions in the crystal. The strain configuration and the crystal boundaries act as a combined mechanism restricting the transformation to a particular set of {111} planes. When the strain distribution is nonuniform throughout the crystal, localized regions within the crystal utilize different sets of {111} transformation planes. The transformation from the fcc to hcp phase is accomplished by the glide of Shockley partial dislocations through the lattice. Frank partial dislocations remain pinned in the lattice. These partials are formed from the extension of total dislocations. Martensitic platelets result from either the glide of Shockley partial dislocations which have different slip vectors in parallel and adjacent sections of the crystal or the pinning of Frank partial dislocations which form the boundary of faulted regions. The platelets intersecting the crystal surfaces produce observable slip bands.
Electrical Breakdown between Metal Electrodes in High Vacuum. I. Theory
Authors: Charbonnier Francis M. , Bennette Carol J. , Swanson Lynwood W.
Published: January 2005

A theoretical description of electrical breakdown across narrow gaps in high vacuum is presented under conditions for which surface cleanliness, work functions, gap geometry, and cathode surface roughness are well defined. Two basic initiating mechanisms are considered: (1) thermal processes initiated at both the anode and the cathode by the prebreakdown field-emitted electron current, and (2) mechanical processes resulting from yield of one of the electrode surfaces under the action of electrostatic stress produced by the electric field in the gap. In the case of thermal breakdown initiation, there exists a boundary between an anode and a cathode-initiated arc which can be expressed in terms of the factor γ by which the gross field in the gap is enhanced at the tip of microscopic cathode protrusions. Solution of the heat conduction equation is given for the general case of dc or pulsed gap voltages. This leads to a distinction between three ranges of pulse duration, and for each region, a simple analytical expression is given for the boundary value γ0 which separates cathode- and anode-initiated breakdown. Based on the considerations presented here, some practical limitations of several electrode materials are given.
Electrical Breakdown between Metal Electrodes in High Vacuum. II. Experimental
Authors: Bennette Carol J. , Swanson Lynwood W. , Charbonnier Francis M.
Published: January 2005

Experiments were performed in order to test the validity of the theory outlined in I. Significant theoretical parameters varied experimentally included electrode material, electrode geometry, and applied voltage pulse length. Electrode materials chosen included W, Mo, Cu, and Al. Gap spacings varied from a few tenths to a few thousandths of a centimeter at gap voltages up to 30 kV applied either continuously or in single pulses of 1 to 100 μsec duration. For all electrode materials except Al, thermal processes are the primary initiation mechanism, and experimental observations agree with the theoretical predictions of I. With electrode materials of low tensile strength such as Al, the primary cause of electrical breakdown is due to the electrostatic stress produced by the high electric field.
Recovery of Ultrasonic Attenuation in Copper Single Crystals Following Small Plastic Deformation
Authors: Frankel Julius , Meisel L. V.
Published: January 2005

Migration of deformation-produced defects to dislocations was studied by means of an ultrasonic technique. Copper single crystals of 3N and 4N nominal purity were deformed about 0.3% in tension at temperatures between 40° and 90°C. After deformation the stress was released and the change in ultrasonic attenuation was measured continuously at the deformation temperature. The recovery of the ultrasonic attenuation fits the predictions of the Granato, Hikata, and Lücke theory. This indicates the validity of the Cottrell—Bilby ``t2/3'' strain-aging law for stress-assisted diffusion of point defects to dislocations in copper. A single mobile defect was detected, and its migration energy was measured as 0.67±0.06 eV. The defect was identified as the divacancy. The divacancy concentration after about 0.3% deformation was estimated as 5×10−8.
Thermal Expansion and Elastic Constants of β′-AgMg. I. The Coefficient of Thermal Expansion from 77° to 800°K
Authors: Neumann J. P. , Chang Y. A.
Published: January 2005

The linear coefficient of thermal expansion of β′-AgMg has been determined from 77° to 800°K by means of lattice-parameter measurements below room temperature and dilatometric measurements at higher temperatures. At room temperature, the linear coefficient of thermal expansion was found to be 21×10−6 per °C. The Grüneisen parameter derived from the coefficient of thermal expansion obtained here and from other thermal data available in the literature is essentially constant (γ≃1.8) above the Debye temperature, but increases at lower temperatures. Using Slater's formula, a value of 2.2 was obtained for the Grüneisen parameter at 0°K.
Reflection and Refraction of Electromagnetic Waves by a Moving Dielectric Medium
Authors: Pyati V. P.
Published: January 2005

The problem of reflection and refraction of a plane electromagnetic wave by a semi-infinite dielectric medium moving uniformly parallel to its surface is analyzed. The scope of this paper is wider than earlier ones in that the orientation of the plane of incidence is arbitrary.

Certain interesting features are revealed. First, Snell's law is modified. Secondly, the resultant reflected and transmitted E and H vectors are not parallel (or antiparallel) to the incident E and H. Furthermore, when the incident wave is polarized with its electric field parallel to the plane of incidence, there is no angle of incidence (Brewster's angle) for which the reflected wave vanishes. An exception to these results occurs when the plane of incidence is parallel to the velocity. In this case, there is a strong resemblance to the nonmoving case.