bluuebunny/crossref_metadata_2025 huggingface dataset:
Ionization and radiation dynamics of dense MHD plasmas
Authors: Duston Dwight , Duderstadt James J.
Published: February 2003

The ionization and radiation dynamics of dense magnetohydrodynamic plasmas has been modeled in a fashion suitable for implementation in MHD computer simulation codes. It has been shown that more restrictive LTE models such as those based on the Saha equation are inadequate to describe the rapidly varying temperature and density regimes characterizing many such plasmas. Detailed collisional-radiative models are developed which directly solve the time-dependent rate equations characterizing atomic processes along with those equations characterizing the hydrodynamic motion of the plasma. These models are applied to analyze high-density-helium Z-pinch and lithium exploding-wire plasmas, and they are found to yield results which compare quite favorably with experimental data.
A Fourier-Bessel solution of an Einzel-type electrostatic field with rotational symmetry
Authors: van der Merwe J. P.
Published: February 2003

A solution φ (r,z) is given of a rotationally symmetric boundary-value problem: φ (A,z) =0 for z⩽0 and z⩾L, and φ (A,z) =F (z) for 0⩾z⩾L. A and L are given constants and F (z) is a given function which is symmetrical with respect to the plane z=L/2. The solution is in the form of an infinite Fourier-Bessel series, the coefficients of which can be found without inverting matrices. It is shown that the given field can be approximated physically by means of two long equipotential cylinders and one or more central electrodes of curved cross sections. Since the electric intensity is also known at all points, the solution allows a precise determination of the electron-optical properties of a wide variety of electrostatic Einzel lenses with curved electrodes.
Radiant-energy exchange by small objects using continuum fields
Authors: Grimes Dale M.
Published: February 2003

In the emission or absorption of electromagnetic radiation by small objects, generally speaking, the smaller the size-wavelength ratio and the higher the modal number, the larger will be the ratio of reactive to real power flow. However, if the source is internally lossless and free of constraints, charge-current relationships may exist which produce combinatory sets of multipolar electric and magnetic moments for any modal number which yields zero net reactive power flow—a resonant condition. The needed reactive energy for resonance to occur decreases with increasing modal number. The radiative Q is very large and will give rise to reactive forces that are quite capable of driving an atomic source to radiate energy h/ω during electronic transition times. When resonance occurs, the resulting radiation has an energy–to–angular-momentum ratio mω, where m is an integer, and a combinatory set of modal coefficients exists for which the radiation is largely directed in that the ratio of exchanged momentum to exchanged energy is greater than 0.8/c. Other mechanisms may supply the momentum increment needed to make the exchanged ratio be exactly 1/c. This continuum-field description appears to be adequate to describe the radiative portion of atomic electronic transitions, treated as a boundary-value problem.
High-power discharge in Na-Xe vapor
Authors: Rothwell H. L. , Leep D. , Gallagher A.
Published: February 2003

High-power (10–100 MW/liter) pulsed discharges in Na-doped Xe vapor have been studied at Na densities of 1015–1016 cm−3 and Xe densities of 1019–1020 cm−3, as appropriate for excimer-laser use. Stable steady-state discharges are obtained for a number of microseconds in a small-volume cell, without use of preionization or sustainers. This stability is attributed to the observed positive V-I characteristic. Measured spectra are interpreted to yield Na excited-state densities, and the implications for a potential excimer laser are discussed.
Elastic constants of niobium-zirconium, hafnium, and tungsten alloys
Authors: Frey M. L. , Lonnee J. E. , Shannette G. W.
Published: February 2003

The adiabatic single-crystalline elastic constants of pure niobium, Nb-Zr, Nb-Hf, and Nb-W alloys were determined in the temperature range 77–298 °K. An unusual temperature dependence was noted in the Nb-rich alloys which may be related to the shape of the Fermi surface. Zr and Hf alloying additions decrease the value of C′, which indicates decreasing bcc lattice stability. The values of the elastic anisotropy ratio C44/C′ follow the behavior predicted by Fisher, which indicates that the elastic shear moduli are closely related to the filling of the d band. The Debye temperatures ϑD were calculated, and W additions tend to increase ϑD, while Zr and Hf lower ϑD.
High-pressure single-crystal structure determinations for ruby up to 90 kbar using an automatic diffractometer
Authors: d’Amour H. , Schiferl D. , Denner W. , Schulz Heinz , Holzapfel W. B.
Published: February 2003

Complete high-pressure single-crystal structure determinations have been performed up to 90 kbar on ruby (Al2O3 with less than 0.05 wt% Cr2O3) using an automatic diffractometer. The rhombohedral lattice constant aR is found to decrease linearly within the given error limits from aR=5.136±0.004 to aR=5.075±0.005 Å at 90 kbar. The rhombohedral angle αR=55.30°±0.06° as well as the atom-position parameters u (Al, Cr) =0.3520±0.0004 for Al (or Cr) and u (0) =0.556±0.003 for oxygen remain constant up to at least 86 kbar. These results are in very good agreement with earlier measurements up to 25 kbar by Schiferl and Jamieson as well as with the Birch and Murnaghan equations of state with the literature values of the isothermal compresssibility K0 and its pressure derivative K′.
Energy storage and liberation of vibro-milled γ-Fe2O3
Authors: Imai Hideo , Senna Mamoru
Published: February 2003

Energy is stored in γ-Fe2O3 during preliminary vibro-milling. The stored energy, detected from differential scanning calorimetry, amounted to up to twice as much as the reported heat of transformation to α-Fe2O3 and is associated with the formation of the amorphous phase. The amount of transformation at the first step of annealing was parallel to the stored energy. Energy liberation on annealing occurs competitively through recovery or recrystallization and transformation into the α-phase. At temperatures lower than 400 °C, recovery favorably occurs, whereas above 400 °C, transformation predominantly takes place. The lattice disturbance in vibro-milled γ-Fe2O3 does not recover completely before the completion of the transformation to the α-phase.
Weak-field magnetoresistance symmetry in epitaxial films and bulk crystals of p-type SnTe
Authors: Allgaier R. S. , Houston Bland , Restorff J. B.
Published: February 2003

Nishiyama’s weak-field magnetoresistance measurements on p-type SnTe films deviate substantially from the requirements of cubic symmetry. A simple extension of the cubic theory to the case of substrate-induced tetragonal distortion can account for the measurements. To establish internal consistency of the data with tetragonal symmetry requires an additional measurement which was not, but can easily be, made.
Elastic fields of a dislocation loop near a stress-free surface
Authors: Ohr S. M.
Published: February 2003

The displacement field around a finite circular edge dislocation loop lying parallel to a stress-free surface has been calculated. The results indicate that when the loop is located close to the free surface the displacement field is extremely asymmetric across the loop plane. This influences the elastic interaction between the loop and point defects. The free-surface effect is significant for loops located within about five times the loop radius from the free surface.
Effect of temperature on the pressure dependence of helium solubility in vitreous silica
Authors: Shelby J. E.
Published: February 2003

Helium solubility in vitreous silica was measured from 100 to 1350 atm at 5, 25, 50, and 80 °C. The results can be described by the Langmuir adsorption isotherm at each temperature. The temperature dependence of the high-pressure helium solubility in this gas-glass system can be described either by the van’t Hoff equation or by a statistical thermodynamical model.
Absolute signs of photoelastic constants of ZnO
Authors: Kushibiki J. , Chubachi N. , Mikoshiba N.
Published: February 2003

The absolute signs of the photoelastic constants of a ZnO crystal were measured by the Biegelsen method. All of them were determined to be negative.
A perturbation analysis of the attenuation and dispersion of surface waves
Authors: Tiersten H. F. , Sinha B. K.
Published: February 2003

JAPIA,49,87,1978
Electrical resistance of Manganin under high static pressures
Authors: Fujioka N. , Mishima O. , Endo S. , Kawai N.
Published: February 2003

The electrical resistance of manganin was measured under pressures up to 220 kbar at room temperature. The pressure was produced by means of a multianvil apparatus using semisintered magnesia for the pressure medium and was calibrated against well-known fixed points. Obtained results show a linear relationship between the resistance and pressure up to 180 kbar with good reproducibility. The pressure coefficient of resistance turns out to be (2.322±0.008) ×10−3 kbar−1, which is in close agreement with the value obtained under hydrostatic conditions. Manganin can be satisfactorily used as a pressure gauge for a high-pressure experiment using a solid pressure medium. The deviation from the linearity observed above 180 kbar is ascribed to either an intrinsic property of Manganin or the uncertainty of the fixed point adopted. If the linearity is assumed above 180 kbar, the transition pressure of GaP is estimated to be 206±2 kbar.
Electronic characterization of indium tin oxide/silicon photodiodes
Authors: Chang N. S. , Sites J. R.
Published: February 2003

Photodiodes of indium tin oxide deposited on single-crystal p-silicon are analyzed with respect to their electronic properties. Dark measurements include the current and capacitance dependences on voltage and temperature. Photocurrent measurements reveal the relationship to the illumination intensity, temperature, and wavelength of light. Analysis reveals a relatively large, but temperature-dependent, built-in voltage and a small interface recombination probability.
A method for the determination of optimum p-n junction depth of luminescence devices
Authors: Reichl H. , Müller J. , Huber D.
Published: February 2003

Theoretical calculations show that for maximum output power of LED’s an optimal ratio between the p-n junction depths and the diffusion lengths of minority carriers of 2–3 is required. A method based on the photoluminescence technique is described which allows the determination of the a/L ratio. Measurements on various types of luminescence diodes were carried out. In double-heterostructure lasers diffusion lengths in the range 1.2–4.6 μm were estimated.
Injection into insulators in the presence of space charge
Authors: Shatzkes Morris
Published: February 2003

Equations are derived that describe the effect of space charge on current injection into insulators under the approximations that, in the absence of space charge, lead to either the Fowler-Nordheim equation or the Schottky equation. The effect of the space charge is that the field in the insulator at the electrode interface is different from the field with no space charge, and that the triangular shape of the potential barrier is distorted. If only the alteration of the cathode field is taken into account, as is often the case, the effect of the space charge is overestimated. Explicit solutions are found for the case of constant space charge, where the effect of the shape distortion can be described in terms of a single parameter, which is different for the two injection mechanisms considered—zero temperature tunneling and thermionic emission over the potential barrier. For either mechanism, however, the parameter is a measure of the ratio of the charge on the electrode to the charge contained within a characteristic distance—the charge-free tunneling distance for tunneling injection or the position of the charge-free potential maximum for thermionic injection.
Magnetostatic surface-wave propagation in finite samples
Authors: O’Keeffe T. W. , Patterson R. W.
Published: February 2003

The dispersion relation of magnetostatic surface waves propagating in a ferromagnetic film of finite dimensions is derived. Specifically, a consideration of the finite width of the sample is introduced to the previous treatments of magnetostatic surface-wave propagation. The inclusion of a finite width produces a multiplicity of propagating modes, which can be excited individually or collectively, depending on experimental conditions. In addition, the finite width allows the excitation of magnetostatic volume waves, which exist over a narrow frequency range just below the range of magnetostatic surface waves. All aspects of the theoretical analysis are supported by measurements made on magnetostatic surface-wave propagation at frequencies around 1 and 9 GHz in yttrium iron garnet samples of different widths.
Mean field analysis of the magnetic properties of amorphous transition-metal–rare-earth alloys
Authors: Gangulee A. , Kobliska R. J.
Published: February 2003

A generalized form of mean field theory and procedures for applying it to analyze experimental data on the temperature dependence of the saturation magnetization or the effective gyromagnetic factor of n-component amorphous transition-metal–rare-earth alloys are outlined. This analysis yields the spin values of each component and the effective exchange interaction energies between them, from which other magnetic properties such as the subnetwork magnetizations and the macroscopic exchange stiffness can be calculated. Examples of application of this mean field procedure are given.
Initial permeability and intrinsic magnetic properties of polycrystalline MnZn-ferrites
Authors: Hoekstra B. , Gyorgy E. M. , Gallagher P. K. , Johnson D. W. , Zydzik G. , Van Uitert L. G.
Published: February 2003

Permeability-temperature curves of polycrystalline Mn0.41Zn0.42Fe2.16O4+x are interpreted in terms of theoretical models using the intrinsic magnetic properties as measured on a single crystal having virtually the same composition. The temperature dependence of μ can be fitted by the relation μ∼M/K1/2, as expected for cylindrical wall bulging, but the absolute value of μ is an order of magnitude below the theoretical value. Spherical bulging of a totally pinned wall is shown to yield a μ which is an order of magnitude smaller than the observed value due to the stiffness of the wall due to demagnetizing and anisotropy energy. It is suggested that a finite pinning of the walls at the grain boundary might explain our data. After annealing at pressures near the phase boundary, the theory does not fit the μ-T curves. It is suggested that the bulk composition of the grains of the polycrystalline material is different from that of the single crystal due to preferential segregation at the grain boundary even before a second phase is formed.
On the origin of pyroelectricity in polyvinylidene fluoride
Authors: Kepler R. G. , Anderson R. A.
Published: February 2003

In order to determine the relative contribution of primary pyroelectricity and secondary pyroelectricity to the total pyroelectric coefficient of polyvinylidene fluoride, samples have been heated suddenly using a 200-ps laser pulse and the time dependence of the appearance of the pyroelectric charge measured. Charge resulting from primary pyroelectricity would appear as fast as the sample is heated, but charge resulting from secondary pyroelectricity would appear only as rapidly as the sample can relax to the new higher-temperature dimensions. The results indicate that no significant fraction of the pyroelectricity of polyvinylidene fluoride is primary pyroelectricity. It is suggested that a reversible temperature dependence of the crystallinity might provide an important contribution to pyroelectricity.
Rutherford backscattering spectra distorted by peak pulse pileup
Authors: Wielopolski Lucian
Published: February 2003

A model is outlined to account for double peak pulse pileup distortions in Rutherford backscattering.
Laser in-cavity Michelson interferometer
Authors: Robertson C. M.
Published: February 2003

A new laser interferometer is proposed which can be regarded as an in-cavity Michelson interferometer. It utilizes a polarizing beam splitter in conjunction with two quarter-wave plates to produce oscillations between three mirrors. It would measure a change in length of 10−3 Å that, if used for plasma diagnostics, is equivalent to measuring an electron density of 109 cm−3 over a plasma length of 1 cm.
Correlation of collective ion acceleration diagnostics
Authors: Ecker Bruce , Straw David C. , Miller Robert B.
Published: February 2003

Collectively accelerated protons obtained in experiments injecting an intense relativistic electron beam into a drift cavity containing low-pressure neutral hydrogen were observed with both the nuclear activation technique and the time-of-flight technique. Simultaneous measurements of the accelerated proton parameters with these techniques provided correlations for peak energy and yield using high ν/γ electron beams (ν is the Budker parameter and γ is the usual relativistic factor) from the Physics International Pulserad 738. A compact proton bunch as observed by the time-of-flight detectors had the peak kinetic energies as measured by activation foil penetration. This bunch did not contain all of the accelerated protons, however, since substantial fluxes of lower-energy protons were also produced.
The influence of additives and contaminants in TEA CO2 laser discharges evaluated by electrical measurements
Authors: Lietti A.
Published: February 2003

Observation of the electrical characteristic of the glow discharge allows easy study of the influence of additives and contaminants. Moreover, when arcing occurs, interesting information is obtained by observing the damping of the arc current. The efficacy of the low-ionization organic additive to prevent arcing is confirmed, and the deleterious influence of oxygen contamination is demonstrated. This result accounts for the technical rule of preventing air from entering the discharge vessel. Increased output peak power is observed, resulting from the use of a suitable additive.
The principle of the thermal-diffusion couple and its application to gas compression and decompression with highly porous materials
Authors: Kayashima Mitsutoshi
Published: February 2003

A new method is proposed for the multiplication of the mass transport effect of thermal diffusion and is applied to gas compression using thermal energy without any machinery. Experiments were carried out for compression of air using a highly porous material as a diffusion medium in order to confirm the principle of the method.
Recombination effects in an expanding laser-produced plasma
Authors: Payne G. L. , Perez J. D. , Sharp T. E. , Watson B. A.
Published: February 2003

The expansion of a laser-produced Be plasma is studied by comparing hydrodynamical model calculations with experimentally measured distributions of each charge state as a function of energy. The plasma is generated with 1–10-J 200-ps pulses from the LPARL Nd-glass laser facility, and the distributions are obtained using a Thomson parabolic spectrograph. The hydrodynamic equations include flux-limited thermal conductivity and collisional-radiative recombination and ionization. For the proper choice of the initial parameters, we obtain qualitative agreement between the model prediction and the experimentally measured distributions.
Propagation of a laser beam in a time-varying waveguide
Authors: Chapman J. M. , Kevorkian J.
Published: February 2003

The propagation of an axisymmetric laser beam in a plasma column having a radially parabolic electron density distribution is examined. First, an extended paraxial procedure is developed for the case of an axially uniform waveguide. It is shown that the essential feature of an alternate focusing and defocusing beam is retained, but that the intensity distribution is cumulatively modified at the foci and at the outer portions of the beam as compared to that of the paraxial case. Second, some general features of paraxial beam propagation are examined for the case of axially varying waveguides. Finally, laser plasma coupling is examined for the case when laser heating generates a density distribution that is radially parabolic near the axis and when the energy absorbed over a focal length of a plasma lens is small. It is shown that stable or unstable beam propagation depends upon the relative magnitude of the density fluctuations which exist in the axial variation of the waveguides as a result of laser heating. When the fluctuations are small, the propagation is stable, and a simple algebraic expression is obtained which relates the beam diameter to the axially slow averaged variation in the waveguide. When the fluctuations are large, the propagation stability can be determined only by consistently combining plasma dynamics and beam propagation to interrelate the axial variation of the beam to that of the waveguide. In this case of beam propagation in a time-varying waveguide, it is shown that the global stability of the propagation depends upon the initial fluctuation growth rate compared to the initial time rate of change in the radial curvature of the waveguide.
Measurement of internal conversion cascading in 235U fission fragments
Authors: Withee C. J. , Wehring B. W. , Wyman M. E.
Published: February 2003

Internal conversion cascading in fragments from thermal-neutron-induced fission of 235U was studied through the measurement of the x rays emitted by the fragments. Two high-resolution Si(Li) semiconductor detectors were used to measure the x rays which are emitted when internal conversion occurs during the deexcitation of a fragment nucleus. The energies of the two coincident x rays and the kinetic energy of a fission fragment, if present, were recorded event by event as three-parameter data. The yield of x rays was obtained for the events when two or more x rays were emitted from the same element for the cases of fission and nonfission coincidences and for the events when both fission fragments emitted one or more x rays in coincidence with fission. The yield of x rays from the different elements produced in fission was also measured for single x-ray fission detections. From the results of the experiment, it was found that the odd-Z elements of the heavy-fragment region had a higher proportion of their x rays emitted in multiple-emission events than did the even-Z elements. An increase in the single-x-ray yield per fragment above Z=57 was observed for the even-Z elements 58 and 60. This rise was not present in the multiple-x-ray yields and hence was attributed to the possible enhancement of single low-energy transitions in the even-even nuclei of these two elements. It was also observed that, on the average, for a given element split x-ray emission is anticorrelated; there is a preference for x-ray emission from one or the other of the two complementary fission fragments.
Time-dependent impedance behavior of low-impedance REB diodes during self-pinching
Authors: Johnson D. J. , Goldstein Shyke A. , Lee Roswell , Oliphant W. F.
Published: February 2003

The time-dependent impedance behavior of large-aspect-ratio pinched electron-beam diodes with no external magnetic field is investigated using two pulsers having 0.4–1.0 MV voltage, and the experimental results are compared to predictions from a time-dependent computer code which incorporates several important mechanisms that affect diode impedance. A discussion of these mechanisms includes experimental evidence of their existence and their effects on the observed diode impedance. A simple model for the current is used in a time-dependent analysis of the data in order to demonstrate qualitative effects. The rise time of the electric field, the cathode-plasma velocity, the time-dependent generation of ion sources from the anode, and the special diode geometries (tapered cathodes) are shown to affect the diode impedance in good agreement with theory.
Longitudinal-mode behaviors of mode-stabilized AlxGa1−xAs injection lasers
Authors: Nakamura M. , Aiki K. , Chinone N. , Ito R. , Umeda J.
Published: February 2003

Lasing spectra of a transverse-mode-stabilized AlGaAs laser of a channeled-substrate planar structure have been investigated. These lasers, which oscillate in the fundamental transverse mode, reproducibly operate in a single longitudinal mode. In addition, their linewidth is as narrow as or smaller than 30 MHz when the injection current is ∼1.2 times above threshold. The intensity distribution and excitation dependence of a nonlasing longitudinal mode have been found to be more complicated than expected from a simple theory: sizable dips have been observed in the envelope function, and nonlasing modes have been found to decrease as the injection current is increased above threshold. Furthermore, hysteresis has invariably been observed in the lasing-wavelength–vs–device-temperature (or dc current) characteristics. These behaviors are believed to reflect a slightly inhomogeneous nature of the gain spectrum because of a finite thermalization time of injected carriers, as discussed recently by Yamada and Suematsu.
Propagation of nonlinear optical pulses in inhomogeneous media
Authors: Jain Manoj , Tzoar Narkis
Published: February 2003

We discuss the propagation of nonlinear optical pulses in dispersive media in the presence of inhomogeneities. Two kinds of inhomogeneities are considered, one arising due to radial variation of the refractive index of the medium and the other due to boundary conditions at the medium boundary, i.e., at the radius of an optical fiber. The wave equation is solved in the presence of these effects, taking an average of the radial dependence. It is shown that inhomogeneities have a remarkable influence on the dispersive properties of the medium, and even at normal dispersion, ’’light’’ pulses can be used for soliton transmission. Numerical results are obtained for a Nd : glass laser (λ=1.06 μm) propagating in SiO2 glass.
Evaporated films of arsenic trisulfide: Physical model of effects of light exposure and heat cycling
Authors: Keneman Scott A. , Bordogna Joseph , Zemel Jay N.
Published: February 2003

The optical-storage effect in evaporated films of arsenic trisulfide (As2S3) has been investigated. The physical and chemical aspects of the films were studied using a combination of etching, x-ray diffraction, ir spectroscopy, and annealing experiments. This study of the As2S3 optical-storage medium has culminated in the development of a physical model involving three well-defined states for the medium.
Annealing of radiation damage in graphite
Authors: Primak William
Published: February 2003

It is shown from step annealing data for the 002 x-ray diffraction peak that the processes annealing below 200 °C possess a frequency factor ∼1014 sec−1, while those processes annealing at higher temperatures possess much lower frequency factors. This is attributed to the lower-temperature processes being associated with the movement of single carbon interstitial atoms and the higher-temperature processes being associated with more complex configurations, including clusters of carbon atoms.
Direct measurement of pyroelectric figures of merit of proper and improper ferroelectrics
Authors: Shaulov A. , Bell M. I. , Smith W. A.
Published: February 2003

A direct method is described for measuring the figures of merit which characterize the performance of pyroelectric materials as infrared vidicon targets or point detectors. The results of experiments carried out as a function of temperature on a proper ferroelectric, triglycine sulfate, and an improper ferroelectric, terbium molybdate, are compared with the predictions of the appropriate thermodynamic theories. It is shown that within the family of rare-earth molybdates isomorphic to terbium molybdate there exists an optimum value for the figure of merit relevant to pyroelectric vidicon performance.
Determination of the binding energies of shallow acceptors from photoluminescence excitation spectra for donor-acceptor pairs in ZnTe
Authors: Nakashima S. , Yamaguchi Y.
Published: February 2003

We have measured the photoluminescence excitation spectra for the donor-acceptor pairs with long d-a distance in ZnTe. The binding energies of As, P, and Li acceptors have been estimated from the low-energy limit of threshold energies for the excitation bands. The determined values are 73.5, 60.5, and 58.3 meV for As, P, and Li acceptors, respectively. The present method of determining binding energies is compared with other methods.
Determination of In-Ga-As phase diagram at 650 °C and LPE growth of lattice-matched In0.53Ga0.47As on InP
Authors: Nakajima Kazuo , Tanahashi Toshiyuki , Akita Kenzo , Yamaoka Toyoshi
Published: February 2003

The liquidus isotherm in the In-rich corner of the In-Ga-As system at 650 °C was experimentally determined by an improved seed dissolution technique using InP seeds. The solidus isotherms at this temperature were also determined in the composition range close to lattice-matched In0.53Ga0.47As on InP. The solidus data are strongly affected by the crystallographic orientation of the substrate, but are not significantly affected by the degree of lattice matching. The calculated phase diagrams have been compared with the experimental results. The conditions for equilibrium LPE growth of exactly lattice-matched ternary layers on InP (100) and (111) B substrates were obtained from the results of the phase diagram and lattice-constant measurements. It was found that the distribution coefficient, growth rate, and surface morphology are strongly dependent on the substrate orientation. The distribution coefficient for Ga and the growth rate at 650 °C are both larger on the (100) face than on the (111) B face. Hillocks often appear on the (111) B face irrespective of degree of lattice matching, but rarely appear on the (100) face.
Investigations of the radial-electron-beam diode for gas-laser excitation
Authors: Ramirez J. J. , Prestwich K. R.
Published: February 2003

A study has been made of high-power radially converging electron-beam diodes and their application to gas-laser excitation. The REBLE accelerator, built for this study, provided reliable single-shot operation at the 1-MV 180-kA 20-ns level. It is shown that annular-blade cathodes can produce uniform anode current densities at 100–200 A/cm2. Apertured-Faraday-cup measurements indicate that the beam is transported readily through the gas. No evidence of microinstabilities in the anode current density were observed. Comparisons of energy-deposition measurements and calculations demonstrate that existing Monte Carlo electron/photon transport codes give an accurate description of the energy deposition when collective effects are not important. Measurements of zenon-excimer radiation excited by the radial electron beam show that 20% of the electron-beam energy deposited in the gas appeared as excimer light. At ∼1600 Torr the radial profile of the emitted radiation was uniform within the ±10% uncertainty in the measurement.
Estimation of the dyadic Green’s function of the electromagnetic field in an unstable medium with the use of a random current source
Authors: Agu Masahiro
Published: February 2003

A method is proposed to estimate the dyadic Green’s function of the electromagnetic field in an unstable dispersive medium with the use of an externally applied random current source.
Radial characteristics of nonequilibrium discharges
Authors: Novak Jaroslav P.
Published: February 2003

A two-temperature model of a free-burning discharge at atmospheric pressure is derived from Grad’s 13-moment approximation of the Boltzmann equation and applied to a low-current discharge in argon. The collision terms are calculated on the basis of available cross sections using expressions given by Alievskii and Zhdanov. The paper also presents a discussion of the problem of boundary conditions. Finally, radial profiles of the discharge parameters are calculated in the current range 0.5–14 A and the results, when compared to available experimental data, show satisfactory agreement.
Torque measurement of magnetic thin films
Authors: Wielinga T.
Published: February 2003

The saturation magnetization Ms and the uniaxial anisotropy Ku of a thin magnetic film can be determined by means of torque measurement. Turning a magnetic film in a magnetic field H yields a plot of the torque L versus α, the angle between the normal of the film and the field direction. This plot contains a maximum L+m at an angle α+m and a minimum L−m at an angle α−m. Carrying out the above for an appropriate set of values of H, we can plot [(L+m−L−m)/2H]2 against 2 sin(α+m−α−m)/(L+m−L−m) . Ms and Ku are determined from the intercepts with the vertical and the horizontal axis, respectively, of the line obtained.
Amorphous GdNdFe bubble films with good temperature characteristics
Authors: Heiman Neil , Kazama N. , Lee Kenneth
Published: February 2003

Nd was found to couple ferromagnetically to the transition-metal moment in the amorphous rare-earth–transition-metal alloys. A mean-field theoretical analysis of these alloys shows that temperature-independent magnetic behavior can be expected in (Gd1−yNdy)1−xFex alloys for a wide range of x and y values. Experiments on a number of film compositions confirm this. A number of other problems associated with deposition and annealing processes occur. It is suggested that other alloys containing Nd may prove more suitable as amorphous alloys for bubble-domain applications.
Thermally activated domain-wall motion in ferromagnetic single crystals
Authors: Siemers D. , Nembach E.
Published: February 2003

For picture-frame-type single-crystal specimens of the ferromagnetic nickel-base alloy PE 16, the dependence of the domain wall velocity v on the applied magnetic field H and on temperature T has been experimentally investigated for 1.7<T<5 K. The results are interpreted by assuming that the domain wall can overcome the interaction with obstacles present in the specimen by thermal activation. Interaction potentials, which have been in common use for such problems, e.g., triangular ones, failed to give agreement between theory and experiment. Therefore a formalism has been developed, by which information on the interaction force, F (x), between the obstacle and the domain wall can directly be obtained from the experimental data. By using F (x), a relation H (v,T) can be reconstructed which is in perfect agreement with the experimental results. The obstalces, which interact with the domain wall, are probably single atoms or small clusters.
On the structure of the ferroelectric-paraelectric transformation interface in barium titanate. I. Basic structure and characteristics
Authors: Malis T. , Gleiter H.
Published: February 2003

Heating tests in the transmission electron microscope (TEM) have been conducted into the nature of the ferroelectric-paraelectric transformation interface in BaTiO3. Observations on the manner in which 90° domain boundaries disappeared during passage of this interface, together with variations in the electron diffraction pattern across it, indicate that it is of the order of microns wide. This suggests a coherent interface structure by which tetragonal lattice cells of the ferroelectric phase continuously transform to cubic cells of the paraelectric phase. The relatively high mobility implied by such an interface agrees with the primarily martensitic nature of the transformation.
Dielectric function of Si-SiO2 and Si-Si3N4 mixtures
Authors: Aspnes D. E. , Theeten J. B.
Published: February 2003

Expressions for the dielectric function of Si-SiO2 and Si-Si3N4 composites are obtained by combining the Si-centered tetrahedral model of Philipp with composite-media theory. The similarity between dielectric-function spectra of a-Si and Si3N4, with scaling parameters related by the plasma sum rule and the dielectric theory of Phillips and Van Vechten is used to obtain the polarization response function for the bond part of a given tetrahedron. By treating the N and O contributions on an equal basis with Si, reasonable agreement to existing spectra is obtained for these materials over an energy range of 0–8 eV.
Bulk and surface absorptions in the 9.2–10.8-μm region in NaCl and KCl
Authors: Vora H. , Ohmer M. C. , Stoebe T. G.
Published: February 2003

The technique of tunable CO2 laser calorimetry has been used to study the wavelength dependence of optical absorption in the range 9.2–10.8 μm in NaCl and KCl. Samples grown using reactive atmosphere processing (RAP) as well as those cut from large-diameter ingots prepared commercially for fabrication of high-power CO2 laser windows have been studied. A differentiation between bulk and surface absorption has been made in several cases by employing long bar samples; these measurements have been performed at several wavelengths between 9.2 and 10.8 μm. Total absorption coefficient data at 9.27 and 10.61 μm on monocrystalline and polycrystalline commercially available NaCl are also presented. Measured bulk absorption values in RAP-grown NaCl are lower than commonly used values for the intrinsic absorption limit in the 10.1–10.8-μm wavelength region; these measured values are used to define a new operational multiphonon absorption limit for NaCl. Bulk absorption in RAP-grown KCl is nearly intrinsic at 10.61 μm, but increases to an order of magnitude above intrinsic near 9.2 μm. The residual bulk absorption observed in several KCl crystals may be related to impurities of the ClO3 type.
On the theory of bleaching of WO3 electrochromic films by an electric field
Authors: Gupta H. M. , Ferreira G. F. Leal
Published: February 2003

The theory of Faughnan, Crandall, and Lampert for the bleaching of WO3 electrochromic films by an electric field is modified considering nonzero values of XI(0). Complete agreement between the theoretical and experimental current-density–vs–time curves is obtained from the beginning, i.e., from 10−3 sec. The effect of various values of XI(0) on such characteristics is also discussed.
Second pressure derivatives of the elastic moduli of copper
Authors: Gerlich D. , Kennedy George C.
Published: February 2003

The second pressure derivatives of the elastic moduli for polycrystalline copper have been determined. While the value of the second pressure derivative of the longitudinal modulus is zero or very small, that for the shear modulus is ∼6.3×10−10 Pa−1, hence the second pressure derivative of the bulk modulus turns out to be positive, with a value of 8.4×10−10 Pa−1.
Rectification phenomena and photovoltaic effects in an amorphous Se1−x1Tex1-Se1−x2Tex2 heterostructure
Authors: Kikuchi T. , Ema Y. , Hayashi T.
Published: February 2003

A heterostructure of amorphous Se1−x1Tex1-Se1−x2Tex2 was investigated. A photovoltage characteristic and rectification characteristics were detected in the structure. To investigate the mechanism, the spectral dependence of the photoconductivity, the photovoltaic effect, and the thermoelectric power were measured. It was found that the characteristics of the heterostructure could be explained by the model of a p+p junction.
Photovoltaic properties of p-n junctions in CuInS2
Authors: Tell B. , Thiel F. A.
Published: February 2003

p-n junctions have been formed in CuInS2 by diffusing an n layer into p-type bulk material. When tested as photovoltaic detectors, typical diodes exhibit a maximum quantum efficiency of ∼15% near 0.8 μm.
A modified forward I-V plot for Schottky diodes with high series resistance
Authors: Norde H.
Published: February 2003

It is shown that by plotting the function F (V) =V/2−(kT/q)  ln(I/AA**T2) a reliable value of the barrier height can be obtained even if there is a series resistance which would hamper the evaluation of the standard lnI-vs-V plot. A theoretical examination of F (V) is followed by experimental plots for some common Schottky-barrier diodes.
Rayleigh-wave reflection from a groove in Y-Z LiNbO3: A perturbation approach
Authors: Wu S. D. , Tuan H. S.
Published: February 2003

A field theory for the reflectivity of a generalized Rayleigh wave from a single shallow groove etched on a LiNbO3 substrate is presented. The scattering properties are studied by using a perturbation approach. Induced equivalent acoustic and electric sources which produce the reflected and scattered waves are determined. Calculated reflection coefficient agrees well with known experiments.
Comparison of the grating and meander-line transducers for magnetoelastic surface-wave excitation
Authors: Robbins William P. , Bowers John
Published: February 2003

The grating transducer, the dual of the meander line, is studied and its performance compared with a meander line for the excitation of magnetoelastic surface waves. A LiNbO3-YIG-LiNbO3 epoxy-bonded composite is used to experimentally study both transducer geometries at 50 MHz. It is found that the grating transducer offers no significant improvement in performance over the meander line. Both types of transducers have large conversion losses because of large Ohmic resistance to radiation resistance ratios. Practical considerations of an allowable metalization thickness for the transducers and spatially nonuniform demagnetizing fields in the substrate permit only modest reductions in the conversion losses of either type of transducer situated on materials such as YIG.
Phase diagrams and metal-rich silicide formation
Authors: Canali C. , Majni G. , Ottaviani G. , Celotti G.
Published: February 2003

Phase formation at temperatures well below the melting point of the phases was studied in thin silicon–near-noble-metal films by means of 4He+ ion-backscattering spectrometry and x-ray diffractometry in SiO2/Si/M film systems, where the metal-film thickness was larger than that of the Si film. In the initial stage of compound formation where both unreacted Si and M layers are present, the M2Si phase has been found. At increasing annealing times and temperatures, more and more metal-rich phases have been detected. The Si-Ni thin-film system evolution follows exactly the phase diagram reported in the literature; moreover, for Ni, Pt, and Pd-Si thin-film interactions the end phases are dictated by the phase equilibrium and can be predicted by the phase diagrams.
Magnetic characteristics of rare-earth indium R2In (R=Y, Nd, Sm, Gd, Tb, Dy, Ho, Er, and Tm) intermetallic compounds
Authors: Gamari-Seale Helen , Anagnostopoulos T. , Yakinthos J. K.
Published: February 2003

Measurements of the magnetic susceptibility of the R2In compounds from 4.2 to 270 K have been made. All compounds except Y2In and Sm2In exhibit Curie-Weiss behavior at high temperatures with effective magnetic moments agreeing reasonably well with the free-ion 3+ picture modified by RKKY exchange except for Gd2In, which gives an unusually high value for the effective moment. With the exception of Y2In all other members exhibit susceptibility maxima. Gd2In, Tb2In, and Dy2In order antiferromagnetically. Gd2In is a metamagnetic compound. For the three compounds Ho2In, Er2In, and Tm2In there is no indication of their type of ordering at low temperatures. The isotherm at 4.2 K of Nd2In shows a ferromagnetic or ferrimagnetic behavior.
Pressure-induced changes in the reflectivity of SmSe and some comments on Nd-substituted SmSe
Authors: Welber Benjamin , Jayaraman A.
Published: February 2003

Pressure induced changes in the reflectivity of SmSe have been investigated up to 70 kbar hydrostatic pressure, using the gasketted diamond anvil high-pressure x-ray apparatus in conjunction with an optical microspectroscopic system. The effect of Nd substitution on the lattice parameter, resistivity, and color of SmSe has also been studied. Reflectivity data for GdSe at ambient pressure have been obtained for comparison with the metallic phase of SmSe. With increasing pressure the color of the sample (as observed in reflected light) goes through a sequence of changes, from black, steel-blue, deep purple, reddish purple, copperlike metallic color to bronze yellow at the highest pressure. From the reflectivity data, the static conductivity has been evaluated and is compared with the dc conductivity, previously measured on SmSe single crystals under hydrostatic pressure. Deviations from Drude theory indicate that the interband contribution to the dielectric constant plays an important role in determining the sequence of metallic colors observed in metallic rare-earth monochalcogenides.
A dispersive phase shifter for use in nonlinear optical interference experiments
Authors: Crane G. R. , Bergman J. G.
Published: February 2003

It is shown that a pair of counterrotating fused-quartz plates may be used to vary the phase between the second harmonic and the square of the fundamental in two-crystal optical interference techniques. The advantages are simplicity of design and ease of use.
Photo-induced optical effects in obliquely deposited amorphous Se-Ge films
Authors: Rajagopalan S. , Singh Bhanwar , Bhat P. K. , Pandya D. K. , Chopra K. L.
Published: February 2003

The photo-induced shift in the optical transmission edge has been studied in obliquely deposited amorphous Se75Ge25 films. The effect of preannealing, exposure, postannealing, and film thickness on the photo-induced optical changes have been investigated. Our studies reveal that the photoeffects consist of two distinct contributions: photothermal and photo-optical. Whereas the photothermal effect decreases with angle of deposition as well as annealing, the optical effect increases rapidly with obliqueness. The nature and the respective contributions of these two processes have been established.
Kirlian-type images and the transport of thin-film materials in high-voltage corona discharges
Authors: Opalinski John
Published: February 2003

High-voltage-radiation photographs, otherwise known as Kirlian photographs, are normally obtained as contact prints on photographic film or paper. However, the same kind of images can be formed by high-voltage corona discharges on bulk dielectrics and on thin films of various materials deposited on glass substrates. The transport of thin-film materials has been observed, accompanied by the formation of droplets in the case of oily films. Moisture released by objects of living and unanimated matter is directly recorded on some thin films.
Free-electron lasers using the Smith-Purcell effect
Authors: Wachtel J. M.
Published: February 2003

The theory of linear and stimulated free-electron lasers using the Smith-Purcell effect is presented. These lasers depend upon the resonant interaction of an electron beam with the longitudinal field of a surface-harmonic wave on a diffraction grating. Detailed design criteria for the linear Smith-Purcell-effect laser are determined. Numerical estimates show that infrared lasers are feasible at beam currents smaller than 1 A and that single-mode operation may be achieved. Saturation estimates determine the power output in the range 102 W. An expression for the gain of the stimulated Smith-Purcell laser is derived. The frequency up-conversion factor for the stimulated interaction may be very large. Its possible use as a soft x-ray laser is limited by the available intensity of the pump wave.
Effect of noise on the performance of rf SQUID magnetometers
Authors: Brunet-Brunol D. , Pascal D. , Duret D.
Published: February 2003

The various noise contributions of an rf SQUID have been studied. The importance of the noise figure of the rf amplifier has been pointed out by calculation and experiments, particularly by using a cooled GaAs FET preamplifier (noise temperature 25 K at 300 MHz) we have designed. The effects of noise upon the flux-locked loop characteristic have been investigated by introducing the notions of unlocking probability and of unlocking average time; the improvement of performances, especially of the slew rate of the flux-locked system by an increase of the modulation frequency, is limited by the noise.