bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal expansion of AlN, sapphire, and silicon
Authors: Yim W. M. , Paff R. J.
Published: February 2004

Thermal expansion coefficients of high-purity AlN, sapphire, and silicon were calculated from the data obtained with precision high-temperature x-ray lattice parameter measurements. The mean thermal expansion coefficients obtained in the range 20–800°C are α⊥ = 5.3 × 10−6/°C and α∥ = 4.2 × 10−6/°C for AlN, α⊥ = 7.3 × 10−6/°C and α∥ = 8.1 × 10−6/°C for α-Al2O3, and α = 3.6 × 10−6/°C for Si.
Additional studies of rf plasmoids
Authors: Goforth James H. , Miller August
Published: February 2004

Data have been obtained that support the belief that the particular form of the static-electric-potential profile that arises when negative ions are present in an rf plasmoidal discharge is necessary for the formation of dark-sheath plasmoids. In addition, ethanol and acetone vapors have been found to yield visible emission spectra containing the prominent lines of the CO+ comet tail system which readily reveal dark-sheath plasmoid characteristics. Pure water-vapor discharges do not exhibit dark-sheath plasmoids, but in the presence of air impurities the conditions necessary for the formation of a dark sheath apparently arise when the relative intensity of the O2+ spectrum is large enough.
Photopolarization characteristics of mercuric iodide binder layers
Authors: Pillai P. K. C. , Arya S. K. , Ahuja R. C.
Published: February 2004

Photopolarization characteristics of mercuric iodide-polystyrene layers have been investigated for use in photoelectret electrophotography. The highest charge density, which is a measure of photopolarization, is found to be of the order of 10−8 C/cm2 for 10% polystyrene in a mercuric iodide photoconductor. Considerations from electrophotographic applications show that a good image-recording photoconductive layer is also obtained for 10% polystyrene in mercuric iodide.
Grain-boundary diffusion and boundary widths in metals and ceramics
Authors: Mistler R. E. , Coble R. L.
Published: February 2004

A technique is presented to calculate grain-boundary widths and grain-boundary diffusion coefficients in metals and nonmetals using grain growth, sintering, diffusion and/or creep data. High-purity metals yield boundary widths of the order of a few atomic diameters, whereas ionic materials yield ``effective boundary widths'' orders-of-magnitude wider.
Role of sequential annealing, oxidation, and diffusion upon defect generation in ion-implanted silicon surfaces
Authors: Prussin S.
Published: February 2004

Ion implantation of boron was substituted for the chemical deposition of boron in the manufacture of a bipolar integrated circuit. The n+p+ test diodes were found to exhibit excessive reverse leakage while the p+n test diodes behaved normally. This was attributed to the defect structures developed by the interaction of sequential diffusion with defect nuclei introduced by ion implantation. We have found that the low-temperature annealing treatments which are used to return full electrical activity to the implanted atoms leave a high density of defect nuclei in the implanted area. When the silicon surface is subjected to wet oxidation, these defect nuclei expand to form stacking faults or dislocations loops of such size that they can be detected by chemical etching and optical microscopy. This technique has permitted us to determine the annealing temperatures necessary to eliminate these implantation-induced defect nuclei. A model is presented to describe the manner in which defect nuclei are generated by ion implantation and the means by which these defects are expanded by subsequent oxidation.
On the question of charged-particle motion in a focused laser field
Authors: McIver J. K. , Lubin M. J.
Published: February 2004

The motion of an electron traversing the intense coherent electromagnetic field in the focal region of an f/0.5 aplanatic lens is calculated for the purpose of studying charged-particle acceleration. The results are compared with two simplified plane-wave models for this interaction. This comparison emphasizes the need to consider longitudinal field components and three-dimensional spatial modulation that are absent in simple models. Plane-wave results overestimate the electron energy gain by an order of magnitude.
Atomic beam velocity distributions with a cooled discharge source
Authors: Miller Thomas M.
Published: February 2004

Time-of-flight measurements have been made for hydrogen, nitrogen, and metastable helium, argon, and nitrogen beams emerging from a cooled discharge source, in order to determine the velocity distributions in these beams. We observe typically 85% H and 15% H2 relative beam number densities from a hydrogen discharge, and 10% N and 90% N2 relative beam number densities from a nitrogen discharge. The results show the effects of variation of the source gas pressure, microwave power, cooling rate, and in the case of a hydrogen discharge, the effect of adding water vapor to enhance dissociation. Argon seeding of the hydrogen discharge has been investigated as a means of determining the beam temperature without resorting to direct velocity or time-of-flight measurements. Some results are also given for room-temperature and low-temperature beams, obtained without a discharge.
Radial electric field influence on wire explosions in vacuum
Authors: Nyberg S.-O. , Händel S. K. , Stenerhag B.
Published: February 2004

Wires made of materials having high boiling points were exploded in an evacuated vessel of coaxial design. It was found that the influence of the radial electric field on the x-ray emission as well as on the initiation of the shunting discharge was small. In addition, the shunting discharge and the vaporization of the wires were studied by a Kerr-cell camera. Tungsten and molybdenum wires were found to vaporize in a nonuniform way. A model to explain this behavior is suggested.
Light deflection in multimode waveguides using the acousto-optic interaction
Authors: Giallorenzi T.G. , Milton A.F.
Published: February 2004

The deflection of light by acoustic surface waves in multimode waveguides is studied in the present work. Conditions on deflection of single-mode and multimode optical power are derived, and expressions are presented for the number of resolvable spots and the efficiency that may be obtained with these scattering processes. A description of the waveguide analog to anisotropic Bragg scattering is given, and the advantages and disadvantages of this approach are discussed in detail.
Temperature dependence of the band gap of silicon
Authors: Bludau W. , Onton A. , Heinke W.
Published: February 2004

The band-gap energy Eg of silicon has been reevaluated with high precision between 2 and 300 K by the following method: the derivative of the absorption coefficient, resulting from free-exciton absorption, has a well-defined singularity, which can be detected unambiguously by wavelength-modulation spectroscopy. The energy of this singularity yields the band gap. Our data deviated by more than 5 meV from the earlier results of MacFarlane et al. and Haynes et al. and fell between their Eg(T) curves. The approximation of Eg(T) = A + BT + CT2 gives A = 1.170 eV, B = 1.059×10−5 eV/K, and C = −6.05×10−7 eV/K2, for 0<T≤190 K, and A = 1.1785 eV, B = −9.025×10−5 eV/K, and C = −3.05×10−7 eV/K2, for 150≤T≤300 K, which fits our data within 0.2 meV. The major uncertainty of about 1 meV lies in the energies of exciton and TO phonon.
Validity of Schopper's formulas for anisotropic films
Authors: Tomar M. S. , Srivastava V. K.
Published: February 2004

The present work reports a detailed experimental investigation of Schopper's formula for investigating the case of a uniaxial nonabsorbing film of barium stearate on a transparent substrate. The required theoretical conditions for the experimental study of Schopper's formulas are well fulfilled for the film studied. The experimentally measured values of the reflectances and transmittances for Ba stearate films are found to be in agreement with the corresponding values calculated from the corrected Schopper's formulas. The experimental values, in general, are found to be in considerable disagreement with the corresponding values calculated by assuming the films to be isotropic. The studies have thus tested the validity of Schopper's formulas and have, indeed, confirmed the films to be anisotropic. Thus, assuming the validity of Schopper's formulas, the refractive indices of several other Blodgett-Langmuir films have been determined.
Conductance switching of thermally grown SiO2
Authors: Wilmsen C. W. , Allender M. C.
Published: February 2004

Experimental measurements of the electrical conductivity of thermally grown SiO2 switched into a high-conductance state are presented. A p-n junction formed under a non-self-healed breakdown filament is found to control the current of the high-conductance state.
Acoustic wave second-harmonic generation in materials with strain-dependent dielectric constants
Authors: Agarwal A. K. , Sharma S. K.
Published: February 2004

Acoustic wave second-harmonic generation in materials with strain-dependent dielectric constants is investigated in the presence of static electric and magnetic fields. It is shown that for such materials with large dielectric constants, the second-harmonic yield is much larger in magnitude than in materials exhibiting piezoelectricity.
Nonlinear surface-wave interactions: Parametric mixing and harmonic generation
Authors: Vella P. J. , Padmore T. C. , Stegeman G. I. , Ristic V. M.
Published: February 2004

The nonlinear interaction of surface acoustic waves propagating in the same direction has been treated from the rigorous theory of thermoelasticity. Exact expressions were derived for the nonlinear volume forces and surface stresses, and the nonlinear cross sections were calculated under two separate assumptions. First, the work done by the nonlinear forces and surface stresses on a normal-mode surface wave was evaluated and assumed to be totally converted into surface-wave energy. In the second approach, a linear analytic solution was formulated which simultaneously satisfies the nonlinear wave equation and maintains a stress-free boundary condition. Numerical values for the strength of second-harmonic generation were calculated for 24 materials. The characteristics of nonlinear surface-wave generation were compared with those of nonlinear bulk-wave generation and significant differences were found. Coupled amplitude equations were derived to treat the case of multiharmonic generation. Finally, a characteristic power parameter which describes energy conversion from the fundamental into the second harmonic was derived for surface waves and evaluated for 24 materials.
Forces on a line current moving above a discontinuous ground plane
Authors: Marin Lennart , Lee K. S. H.
Published: February 2004

The forces acting on a current-carrying wire moving above a ground plane with discontinuities are investigated. Two types of discontinuities are considered: (i) a gap, and (ii) a step. In both cases, the forces on the wire are calculated and graphed for different wire locations. The relevance of these calculations to guideway discontinuities in magnetically levitated systems is pointed out.
Plasma expansion as a cause of metal displacement in vacuum-arc cathode spots
Authors: McClure G. W.
Published: February 2004

The pressure on the molten surface of a vacuum-arc cathode due to the recoil from outward-directed ion jets is calculated for copper arcs. The calculation uses current density data and electrode force per unit current data from experiment. In addition, the force per unit current measured by Tanberg is shown to be consistent with a calculation of the same quantity based on the energy of outgoing ions measured by Davis and Miller and the so-called saturated positive-ion current measured by Kimblin. The ion recoil pressure is shown to be sufficient to remove molten metal from a cathode-spot crater in time of the order of 25–250 nsec with a velocity of 2×103−2×104 cm sec−1. It is shown that motion of molten metal in the cathode-spot crater must be considered as a first-order effect in rigorous calculations of surface temperature and heat flow in the metal in contact with the cathode-spot plasma. It is suggested that the rapid removal of metal by the plasma pressure causes molten droplets to be ejected, as has been observed experimentally, and causes a preference for the cathode to operate, after the liquid is ejected, on the rim of the crater or nearby on the surface where hotter metal may exist due to liquid-metal overflow and spatter.
Auger-limited carrier lifetimes in HgCdTe at high excess carrier concentrations
Authors: Bartoli F. , Allen R. , Esterowitz L. , Kruer M.
Published: February 2004

The performance of n-type Hg0.8Cd0.2Te (PC) detectors under high optical flux densities was investigated. Detector photoconductivity and response time were measured, in the presence of 10.6-μm laser radiation. Flux densities, φ, were varied over four orders of magnitude up to a maximum level of φ=1021 photons/cm2 sec. For high flux levels the photoconductivity varies as the cube root of the incident flux and the detector response time varies as φ−2/3. It is concluded that the observed saturation in photoconductivity is due to the decrease in carrier lifetime with carrier concentration. The dominant recombination mechanism at high flux levels was determined to be Auger recombination.
Near-ultraviolet emission spectrum from an intense relativistic electron-beam discharge
Authors: Wei P. S. P. , Leavens W. M. , Adamski J. L.
Published: February 2004

Time-integrated emission spectra from the pulsed discharge of a 3.5-MeV electron beam, with 90-kA peak current of about 30-nsec duration, and guided by a glass rod protruding from the cathode in a field-emitting diode, have been studied with a quartz-prism spectrograph. With anodes of graphite or polyethylene, the spectrum in the near-uv to visible range is found to consist mainly of emission lines from C, C+, C++, and C+3, and similar ones from silicon. The spatial dependence of emission intensity indicates that a hot spot is present during the discharge near the anode surface. The temperature and the electron density in the plasma are estimated through a theoretical analysis of the composition of carbon in the gas phase.
Origin of hysteresis in the I-V curves of point-contact junctions
Authors: Fulton T. A. , Dunkleberger L. N.
Published: February 2004

Point-contact weak-link junctions often possess hysteresis in their current-voltage characteristics. We describe experimental evidence which suggests that this hysteresis is not due to the effects described by Stewart and McCumber but rather that this hysteresis is a self-heating phenomenon.
Field modulation technique with synchronous detection for measuring magnetic properties in time-dependent fields
Authors: Feu Alfonso , Trueba Antonio
Published: February 2004

A method to measure magnetic quantities of ferrimagnetic and ferromagnetic samples under the effect of time-dependent fields [Ha(t)] is presented. The method is based on the alternating field method together with the powerful technique of synchronous detection. Interesting quantities such as the total Bloch wall area present during the magnetization reversal, the reversible permeability, and its first derivative with respect to the magnetic field at any point of the hysteresis loop are plotted rapidly, even in the case of very small samples (for instance, iron whiskers). Reversible permeability is obtained without need of extapolation. The switching time and the dynamic coercive field are easily measured as well. The sensitivity of the method is very high, and the noise is widely rejected. The technique is applied to iron whiskers and polycrystalline YIG.
Diamagnetic effects in a tape-wound superconducting solenoid
Authors: Walstrom P. L.
Published: February 2004

The effect of diamagnetic shielding currents on the magnetic field in a tape-wound superconducting solenoid is calculated on the basis of the isothermal critical-state model and compared with measured values. The calculation is found to be in reasonable agreement with the data. Additional calculations showing the effect of the tape width on the diamagnetic correction to the central field are presented.
Three-anode accelerating lens system for the field emission scanning electron microscope
Authors: Kuroda Katsuhiro , Ebisui Hirotaka , Suzuki Tatsuro
Published: February 2004

The characteristics of an accelerating lens system composed of three anodes in the scanning electron microscope are described. The main advantages of this accelerating lens system are that the working distance can be changed freely or the accelerating voltage can be changed over a wide range (about 0.3–100 kV) without changing the working distance, by adjusting only the control voltage of the second anode. Some problems in the manufacturing and operating conditions are also discussed.
Microwave properties of liquids and solids using a resonant microwave cavity as a probe
Authors: Hong K. H. , Roberts J. A.
Published: February 2004

The frequency shifts and Q changes of a resonant microwave cavity were utilized as a basis for determining microwave susceptibilities and loss tangents for solids and liquids. The method employed consisted of varying the depth of penetration of a continuous cylindrical sample of the material into a cavity operating in the TM010 mode with the resonant frequency and quality factor determined at each incremental setting of the perturbing sample. The perturbation of the cavity was achieved by advancing the sample into the cavity along the symmetry axis by employing a micrometer drive appropriately calibrated for depth of penetration of the sample. A differentiation method was used to obtain the half-power points of the cavity resonance profile at each depth of penetration. The perturbation techniques for resonant cavities were used to reduce the experimental data obtained to physical parameters for the samples. The probing frequency employed was near 10 GHz.
Ion and electron parameters measured with cooled plane electrostatic probes in a cesium plasma
Authors: Michel C. , Kornmann M. , Braun J. C.
Published: February 2004

To control the collector temperature of an electrostatic probe, we have studied and built a cooling circuit to cool by convection; we have considered two possibilities for the cooling liquid—with and without phase conversion. We give the corresponding thermic study and the cooling effects on the experimental results, obtained from a simple Langmuir probe and a grid probe. The cooling is indispensable at all temperatures for a probe with a positively biased grid. We find that the reemission current varies when the collector is still negative.
Radiation into anisotropic plasma from flanged parallel-plate waveguide
Authors: Ogawa Yoshihisa , Hongo Kohei
Published: February 2004

The radiation characteristics of a flanged parallel-plate waveguide in an anisotropic plasma medium are treated as a boundary value problem. Numerical results are presented on the effect of the anisotropic medium on the radiation pattern, the reflection coefficient, and the input impedance for the TEM- and TM01-wave incidence.
Oblique incidence of an electromagnetic wave at a moving ferrite medium
Authors: Mukherjee P. K. , Talwar S. P.
Published: February 2004

The interaction of an electromagnetic wave at a planar interface between a dielectric and a moving magnetized ferrite medium has been considered for arbitrary angles of incidence. The ambient magnetic field has been assumed normal to both the plane of incidence and the direction of motion of the ferrite medium. The modified form of Snell's law of refraction is derived and the possibility for total reflection of the incident wave is discussed. The expressions for the phase and the group velocities, the equivalent refractive indices of the moving medium, and the reflection and the transmission coefficients for both an incident E wave and an incident H wave have been obtained. It is found that two modified Brewster angles can exist for the case of an incident H wave and that, unlike the case of an incident E wave, the various reflection and transmission properties for an incident H wave are independent of the ferrite anisotropy. Numerical results on the angles of refraction, critical angles for total reflection, and power transfer coefficients for incident E and H waves are presented for several values of the translational velocity of the ferrite medium, the ambient magnetic field strength, and the saturation magnetization. It is revealed that substantial changes in the reflection and propagation characteristics appear only for velocities within a factor of 5 of the velocity of light.
Interferometric measurement of shock-induced internal particle velocity and spatial variations of particle velocity
Authors: Asay J. R. , Barker L. M.
Published: February 2004

Methods of applying laser interferometry to measure particle velocity history at the interface between a shocked specimen and a transparent window material are discussed. Particular emphasis is given to diffusely reflecting interface surfaces, to shock-induced light polarization shifts which can occur in the window material, and to a transient loss of fringe contrast which occurs whenever the reflecting surface velocity is spattially nonuniform. It is shown that the loss of finge contrast can be used to provide time-resolved measurements of the spatial variations in particle velocity.
Semiconductor conductivity measurements using a high-sensitivity microwave technique
Authors: Dixon S. , Giordano R. F. , Jacobs H.
Published: February 2004

An experimental study of a microwave reflection arrangement used to measure changes in the conductivity of semiconductor samples is presented. A germanium sample with associated microwave circuitry acts as a highly sensitive system whereby in the null condition almost complete absorption occurs. Changes in conductivity from the null point will cause a sharp increase in reflected microwave power. This technique will allow electrodeless measurements of both bulk and thick-film semiconductor properties and may have application as a large-area detector of infrared radiation.
Study of magnetic structures induced by bending in (100) Fe–Si single crystals
Authors: Labrune M. , Kléman M.
Published: February 2004

Magnetic domain structures induced by bending (axis of bending along [010]) in (100) Fe–Si single crystals have been investigated by means of the Kerr technique and the Lang method. In the zone of the sample under tension (A), the magnetization is parallel to the surface and the classical 180° wall domain pattern is observed. In part of the zone under compression (B), the easy axis is normal to the surface and two kinds of stray-field-free structures (P and N) similar to the Landau and Lifschitz structure are observed. The magnetic configurations in zones A and B are linked by an inner magnetic structure located near the neutral plane which is a (100) 90° wall and a (100) 180° wall for structures P and N, respectively. An hexagonal pattern is observed on x-ray topographs in the case of both structures P and N. We propose tentatively to relate this pattern to the classical zigzag instability of the 90° walls in the Landau closure domains (structure N), as well as (structure P) to a new kind of instability of the (100) 90° wall, due to the magnetostrictive relaxation of long-range stresses created by such a wall. The energy of each structure is calculated. Theoretical periodicities compare well with the experimental ones. The volume occupied by the structures in zone B increases when the radius of curvature decreases, up to one-half of the sample volume. A critical value of the radius of curvature is computed, above which structure P or N disappears.
Temperature dependence of minority-carrier lifetime in low-resistivity GaAs
Authors: Kladis D. I. , Euthymiou P. C.
Published: February 2004

The temperature behavior of minority-carrier lifetimes was measured in undoped n-type and Cd-doped p-type GaAs single crystals. The results were explained on the basis of a model for the recombination mechanism using one type of minority-carrier trapping centers and one type of recombination centers, the latter having a very small density. Furthermore, the model assumed a gradual transformation of trapping centers to recombination ones with decreasing temperature. The same model also explained the difference between our results on the majority-carrier lifetime behavior and the results of other investigators on the same subject.
Change of surface composition of SiO2 layers during sputtering
Authors: Turos A. , van der Weg W. F. , Sigurd D. , Mayer J. W.
Published: February 2004

The composition of thin SiO2 films was measured in situ by MeV He+ backscattering spectrometry after sequential sputtering with 2-keV Ar ions. Results indicate that the relative concentration of the constituents in the film changes during sputtering. However, differential analysis showed that after an initial period the ratio of the removed constituents agrees with the original composition. We interpret the change in composition with an existing model according to which only the composition of a thin surface layer changes due to the dissimilar sputtering ratios of the two constituents, while the composition in the remainder of the specimen is unchanged.
Transverse-junction-stripe-geometry double-heterostructure lasers with very low threshold current
Authors: Namizaki H. , Kan H. , Ishii M. , Ito A.
Published: February 2004

A new geometry DH laser is developed in which a very thin GaAs homojunction laser is sandwiched by (GaAl)As layers. The minimum threshold current is 63 and 80 mA for pulsed and cw operation at room temperature, respectively. The possibility of further reduction of threshold current is briefly mentioned.
Doppler interpretation of the frequency shifts of light diffracted by sound waves
Authors: Mahajan Virendra N. , Gaskill Jack D.
Published: February 2004

When light is diffracted by a sound wave, the frequencies of the diffracted waves are shifted from the incident frequency by an integral multiple of the acoustic frequency. These frequency shifts are interpreted as a relativistic Doppler effect due to the motion of the acoustic wavefronts, which act as the source of the diffracted waves.
Low-frequency dielectric constants of α-quartz, sapphire, MgF2, and MgO
Authors: Fontanella John , Andeen Carl , Schuele Donald
Published: February 2004

The 1000-Hz 300°K dielectric constants were measured for crystalline α-quartz, sapphire, MgF2, and MgO, and polycrystalline sapphire (Lucalox), magnesium fluoride (IRTRAN 1), and magnesium oxide (IRTRAN 5). The measurements were performed using the method of substitution (two-fluid method). The results are as follows: single-crystal α-quartz, εs∥=4.6368±0.001 and εs⊥=4.5208±0.001; single-crystal sapphire, εs∥ = 11.589±0.005 and εs⊥=9.395±0.005; polycrystalline sapphire (Lucalox), εs=10.154±0.007; single-crystal MgF2, εs∥ =4.826±0.01 and εs⊥=5.501±0.01; polycrystalline MgF2 (IRTRAN 1), εs=5.289±0.001; single-crystal MgO, εs=9.830 ±0.001; and polycrystalline MgO (IRTRAN 5), εs=9.833±0.001, where εs∥ and εs⊥ are the dielectric constants parallel and perpendicular, respectively, to the c axis.
Electrical and optical properties of thin films of Pb2+- and Si4+-doped YIG produced by liquid phase epitaxy
Authors: Larsen P. K. , Robertson J. M.
Published: February 2004

Thin films of Si4+-doped YIG have been grown on Gd3Ga5O12 substrates by liquid phase epitaxy. The electrical resistivity, the sign of the Seebeck coefficient, and the optical transmission have been measured for a number of films prepared from the same melt at different growth temperatures in the range 780–960°C. The measurements show a high optical absorption for films prepared at low growth temperatures, while at intermediate temperatures there is a change from p-type to n-type conduction. A resistivity maximum and minimum in the optical absorption are also found. The results are discussed in terms of the charge-compensation mechanism that occurs as Pb2+ ions are incorporated from the flux into the films at the lower growth temperatures. It is found that intrinsic donors, probably oxygen vacancies, are present in concentrations up to 0.03 per formula unit. The increase in the optical absorption coefficient, Δα, relative to pure YIG, is proportional to the concentration of nonionized holes, [p], i.e., Δα=α′[p]. The extinction coefficient α′ increases with decreasing wavelength in the wavelength range 0.55–1.0 μm and has the value (1.2±0.3)×104 cm−1 per formula unit at 0.6 μm. With these results it was possible to propose an ionic model for the doped YIG films as {Pbx2+Y3−x3+}[Fe2−yYy3+](Fe3−zSiz4+)O12−w2−[VOw], where the ionic valence state of the iron ions depends upon the lead and the silicon content and the concentration and valence state of the oxygen vacancies.
Study of cataphoresis in the positive column of an argon-neon discharge
Authors: Hackam Reuben
Published: February 2004

The cataphoresis separation has been studied in the positive column of a steady-state electric discharge using the binary mixture 0.1% argon-neon. The discharge is scanned spectroscopically from cathode to anode and the emitted spectra of argon (4181 Å) and neon (5852 Å) are monitored. The effectiveness of the separation of the constituents of the gas mixture is studied with variation of both the gas pressure and the electric current flowing between the electrodes. The cataphoresis is found to improve with increasing both the gas pressure and the discharge current until a saturation is reached at a high current.
Heat and mass transport in cylindrical gas-filled incandescent lamps
Authors: Fischer E. , Fitzgerald J.
Published: February 2004

The heat and mass transport in a gas-filled incandescent lamp is governed by convection and heat conduction or mass diffusion, respectively. Proceeding from the basic equations of continuum mechanics a numerical method has been developed to calculate the temperature distribution, the flow field of the filling gas, and the flow of the wire material in a horizontal cylindrical lamp. The results are compared to interferometric temperature measurements and to flow patterns obtained by a tracer technique.
Two-wavelength holographic interferometry of exploding wires
Authors: Seftor J. Laurence
Published: February 2004

A pulsed ruby laser, equipped with a frequency-doubling crystal, has been used to make two-wavelength holographic interferograms of exploding-wire events. For selected times after initiation, estimates of electron density have been made by noting the dependence of the phase index of refraction on wavelength. Once the electron contribution to refractivity is known, the heavy-particle contribution to refractivity can be isolated. With an estimate of specific refractivity from oscillator strengths, the concentration of heavier particles has been calculated.
Superheterodyne detection of spontaneous emission
Authors: Sze R. C.
Published: February 2004

The signal-to-noise ratio of a spontaneous emission source beat with a strong coherent local oscillator is considered in terms of electric fields. The superheterodyne detection scheme allows for a resolution limited only by the frequency stability of the local oscillator. Results indicate that the emission source can be considered as a sum of independent radiation elements beating with the local oscillator and that the antenna theorem calculation usually overestimates the signal-to-noise ratio by an order of magnitude.
Effect of dissolved atmospheric gases upon the decomposition of cryptocyanine in methanolic Q-switch solutions
Authors: Hollier Roberta A. , Macomber James D.
Published: February 2004

We have investigated the effect of dissolved atmospheric gases upon the decomposition of cryptocyanine dye molecules in dilute (≃10−6M) methanolic solution. The removal of oxygen stabilizes the dye if the solutions are exposed to visible light or to a combination of visible and ultraviolet radiation. If the solutions are exposed to pure ultraviolet light, however, the removal of oxygen accelerates the photolysis. Previously irradiated solutions continue to decompose in the dark if they initially contained oxygen; samples which have been degassed and then irradiated are stable in the dark. All decomposition reactions are evidently first order with respect to cryptocyanine. The greatest stability for cryptocyanine Q switches is achieved by degassing the solutions and sealing them in vacuum-tight glass spectrophotometer cells, opaque to ultraviolet radiation.
Characteristics of a laser-pumped 1.5-μm infrared quantum counter
Authors: Stokowski S. E.
Published: February 2004

The characteristics of room-temperature laser-pumped Er3+ infrared quantum counters (IRQC's) have been investigated. One such detector, employing BaY2F8 : Er3+ and a GaAs laser pump, exhibited an NEP of 3 × 10−9 W/Hz1/2 at 1.493 μm, the smallest NEP reported thus far for an IRQC. The limiting source of noise was found to be a generation of visible emission by the laser light alone, which provides an output equivalent to the dark current of a conventional detector. It is proposed that this output, which has a quadratic dependence on the laser power, arises largely from absorption of the 854-nm pump light by the anti-Stokes sideband of the 4I9/2 state of Er3+. The absorption coefficient for this process was determined to be approximately 3 × 10−6 cm−1. Minor modifications of the present system appear capable of improving the NEP to 2 × 10−10 W/Hz1/2, and further improvements may be possible by selecting an IRQC host crystal that has a smaller absorption of the pump radiation than does BaY2F8 : Er3+.
Detection of transverse single and sequential voltage pulses axially induced by a laser in a thin molybdenum film
Authors: Vezzoli G. C. , Walsh P. J. , Kisatsky P.
Published: February 2004

A short pulse (50–100 nsec) of laser light incident in the z direction causes sequential voltage pulses of opposite polarity in the xy plane of a thin molybdenum film deposited on a polycrystalline aluminum oxide substrate. A laser pulse incident in the z direction to a molybdenum thin film deposited on a transparent glass substrate generates a single voltage pulse in the xy plane whose polarity reverses when the laser beam is introduced from the —z direction. The pulses are interpreted as consequences of a forward and reverse thermal gradient in an anisotropic film, and the data can be quantitatively described using the heat-diffusion equation.
Defect magnetic lattice: An application of the molecular field theory
Authors: Kugimiya K. , Steinfink H.
Published: February 2004

The application of the molecular field theory to defect magnetic lattices leads to the introduction of an additional parameter δ that takes into account nonlinear relationships between transition temperatures and magnetic lattice defects.
Lattice image of Nb12O29 observed by a 1000-kV electron microscope
Authors: Horiuchi Shigeo , Muramatsu Kunitaka , Uchida Yuji
Published: February 2004

A two-dimensional lattice image, representing the array of niobium atoms in a Nb12O29 crystal, was observed by means of a high-resolution 1000-kV electron microscope. A large number of diffracted waves, being characteristic of the fast electron beam, were used in imaging.
Photovoltaic polarity of CdTe films obliquely deposited in vacuum
Authors: Onishi Hideomi , Kurokawa Susumu , Ieyasu Kenzo
Published: February 2004

Photovoltaic polarity is studied on obliquely deposited CdTe films. The sign of the photopotential that appears on the electrode on the far side of an evaporator is always negative in the case of front illumination. The polarity reverses from positive to negative with an increase of the wavelength of light in the case of illumination through a glass substrate. The critical wavelength of inversion shifts towards longer wavelengths with a decrease of the substrate temperature and an increase of the film thickness.
Temperature and field dependence of magnetization of Si-doped YIG crystals
Authors: Pandey R. K.
Published: February 2004

Temperature dependence of saturation magnetization and of magnetization at low fields of Si-doped yttrium iron garnet single cystals are reported. For samples of the composition Y3Fe4.63+(Fe2+Si4+)0.2O12, the lattice parameter, saturation magnetization at room temperature, and Curie point are 12.364 Å, 22.6 G cm3 g−1, and 264±2°C, respectively. Values of these parameters are compared with those for unsubstituted YIG. It is discussed why at low fields dσ/dT is positive, whereas it is negative for the saturated samples.
Study of thermally activated polarization effects in purified and magnesium-doped lithium fluoride
Authors: Moran P.R. , Fields D.E.
Published: February 2004

Thermally activated polarization (TAP) and thermally activated depolarization (TAD) effects resulting from impurity-vacancy dipole reorientation occur in Mg-doped and undoped lithium fluoride in the temperature region 200–250°K. These polarizations appear related radiation-induced thermally activated depolarization (RITAD) effect in the same samples. We measure reorientation rate activation parameters of activation energy Ea=0.44±0.03 eV and preexponential factor W0=108.5±1.5 sec−1 for simple divalent impurity-vacancy dipole reorientation. Conversion to a second polarization phenomenon, stabilizing at Ea=0.86±0.03 eV and W0=1019±1.5 sec−1 is observed during annealing for several days at room temperature. This seems to be caused by aggregation into dipolar complexes for which the activation energy becomes significantly temperature dependent.
Structural dependence of electrical conductivity of thin tellurium films
Authors: Dinno Mumtaz A. , Schwartz Manuel , Giammara Beverly
Published: February 2004

Tellurium films were deposited on glass substrates and maintained in vacuum during the course of the measurement of electrical conductivity. The films were found by electron microscopy to have polycrystalline structure with a grain size dependent on deposition parameters. The electrical conductivity increased with increasing thickness, with increasing rate of deposition, and with the transition from the nonannealed to the annealed state. The increase in deposition rate from 100 to 1000 Å/min led to an increase in both grain size and number of surface defects. Annealing resulted in a further increase in grain size but in a decrease in the number of defects. The conductivity could further be explained in terms of mobility and carrier concentration, the former increasing with increasing grain size and decreasing defects, and the latter increasing with increasing defects. A comparison of quenched and annealed films confirms the dependence of mobility on the number of defects.
Spreading functions in secondary-electron analysis
Authors: Slocomb C. A. , Ellis W. P.
Published: February 2004

At low primary-electron beam energies, Auger and loss transitions frequently interfere. The distinction between the two types can be accomplished easily by modulating the crystal. Auger peaks, which shift with crystal bias, are spread in energy and thus are effectively removed from the spectra whereas the loss peaks are relatively unaffected. The spreading functions are treated mathematically, and computer-generated results agree with experimental data.
Electronic density of states in TiNi II and TiNi III
Authors: Mitchell M. A. , Wang F. E. , Cullen J. R.
Published: February 2004

The electronic charge transfer during the TiNi martensitic transition is pictured as a shift of the s band relative to the d band. Such a description not only is consistent with the earlier postulate that a portion of the valence electrons behaves covalentlike in TiNi II and metallike in TiNi III, but also gives a good account of the low-temperature specific heat, magnetic susceptibility, enthalpy, and Hall coefficient changes observed during the transition. The strength of electron correlation is calculated to be 1.1 eV; the work-function change during the transition is also about 1.1 eV.
Helical instability in injected semiconductor plasmas
Authors: Tacano Munecazu , Chen Wen S.
Published: February 2004

An experimental and theoretical investigation is made into the helical instability in injected semiconductor plasmas. Dispersion relations and spatial growths of the instability are studied theoretically as a function of magnetic field, injection level, and electric field. Experiments are made by launching the waves (2–30 MHz) on injected plasmas of p-InSb with sample currents and magnetic fields in the ranges 30–150 mA and 200–1000 G, respectively. The phase shift and amplitude of the waves along the potential probes of a sample make it possible to determine the wave number, the wavelength, the phase velocity, and the spatial growth rate, and are compared in reasonable agreement with the theory. Feedback control of the launched waves as well as the spontaneous oscillations are studied, while the waves and the oscillations are compared with respect to the threshold conditions and the oscillation frequency.
Electrostatic recording on insulators by nonwetting conducting liquids
Authors: Engelbrecht R. S.
Published: February 2004

Highly efficient charge transfer to and from insulator surfaces (e.g., Mylar) has been obtained using moving nonwetting liquid probes (e.g., water). Within a range of measurements (applied fields ≥ 103 V/cm and current densities ≤ 10−4 A/cm2) good agreement exists with calculated charging rates for applied voltages ≥ 20 V of either polarity. Recording charge patterns exhibit resolutions < 10 μm and storages > 500 h.
Expansion of superheated metals
Authors: Bennett F. D. , Burden H. S. , Shear D. D.
Published: February 2004

The short interval of an exploding-wire expansion characterized by rapid rise of resistance, voltage, and electrically deposited energy is studied using time-correlated image-converter photographs, x-ray shadowgraphs, and electrical measurements from identical explosions. Striations in density of the molten expanding core appear concurrently with the electrical signature of the vaporization expansion wave and shortly before billows appear on the boundary surface of the expanding vapor cloud. Even though resolution and penetration do not allow correlation between individual striations and billows, this concurrence suggests that striations are a product of the vaporization process. Arguments are given to show that skin effect and pinch effect do not initiate striation. The same cannot yet be said of Joule heating dependent on the inverse fourth power of radius. Thus striation spacing may reflect underlying departures from uniformity in radius or in microcrystalline structure of the wire.
PbxSn1−xTe layers by rf multicathode sputtering
Authors: Corsi Carlo
Published: February 2004

High-quality epitaxial PbxSn1−xTe films have been obtained for the first time on Ge substrates. The films have been deposited employing a rf multicathode sputtering system capable of simultaneous and sequential sputtering at different rates from three different targets. Heteroepitaxial films of PbxSn1−xTe at substrate temperatures lower than the ones needed in conventional evaporation techniques have been obtained using NaCl and BaF2 substrates. Using the cosputtering technique, it has been possible to obtain n -type and p -type PbxSn1−xTe layers by controlling the quantity of excess metal, or tellurium, respectively. Electrical properties close to the best reported single-crystal values have been measured. Middle-infrared detector arrays have been made using PbxSn1−xTe films deposited on silicon and germanium substrates since such substrates can easily incorporate the electronic readout elements for a completely integrated thermal imaging system. Peak detectivity values up to 2.4×108 cm Hz1/2/W have been measured in photoconductive epitaxial thin films. Polycrystalline films deposited on SiO2-covered Ge and Si substrates have shown exceptionally high responsivity values (480 V/W). Peak detectivities, D*λ (8.5 μ, 800,1), higher than 109 cm Hz1/2/W have been obtained with a 2π-sr field of view at an operating temperatue of 77°K. Measurements of noise, responsivity, and detectivity of linear detector arrays are reported.
Chemiluminescence from the supersonic jet of a cw HF chemical laser
Authors: Kwok M. A. , Spencer D. J. , Gross R. W. F.
Published: February 2004

The spontaneous emission from HF infrared bands in the free jet of a continuous HF chemical laser with a slit nozzle bank has been measured at a number of downstream positions. Three flows are reported: He–SF6–H2-(1) with O2, (2) without O2, and (3) with reduced SF6 without O2. Spatially averaged number densities of the HF vibrational levels (ν = 1, 2, 3, 4) have been determined during zero-power conditions. Vibrational nonequilibrium is evident. The largest HF densities are ∼1015 No./cm3. Observed rotational temperatures, equilibrated to jet static temperature, range from 560 down to 390°K. The largest zero-power gain coefficient deduced is 0.12 cm−1 on the P branch of the 2 → 1 band.
Theory of magnetic domain dynamics in uniaxial materials
Authors: Cape J. A. , Hall W. F. , Lehman G. W.
Published: February 2004

We have calculated the total Lagrangian and Rayleigh dissipation functions for an isolated domain of arbitrary cross section in an infinite plate with perpendicular anisotropy. Variation of these functions yields a set of coupled equations describing the motion of the center of mass and the boundary R (φ) (in general noncircular) of the domain. We neglect z dependence and assume δ/R≪1 where δ is the wall ``thickness''. The theory is applicable for applied field variations of arbitrary speed and magnitude. For uniform field pulses, the equations reduce to the Callen-Josephs theory in the weak-pulse limit. For pulses >2πMs/α, where α is the Gilbert parameter, the behavior again tends to be linear with, generally, a greatly reduced apparent mobility, while in the transition region 2πMs α<Hp <2πMs/α, the predicted behavior is highly nonlinear with an oscillatory substructure which causes an alternating sequence of collapse-noncollapse regions in the conventional plot of inverse pulse length vs pulse height. Translatory motion of the domain in a field gradient is also highly nonlinear reducing to ``effective mass'' behavior only when R H′≪4πMα. An approximate prediction of the theory is that regardless of the magnitude of the pulse gradient (i) the net displacement is given by x0≈μWR (dH/dx)t0, where μW is the wall mobility and (ii) the minimum elapsed time for a displacement is ≈ τA =(M s/2K)(R2/δ2)(γα)−1, where K is the anisotropy constant and γ the gyromagnetic ratio. Finally, the theory predicts a finite displacement in a direction transverse to the sense of the field gradient.
Bubble dynamics and growth-induced anisotropy in (Y,Eu,Tm)3(Ga,Fe)5O12
Authors: Tabor W. J. , Vella-Coleiro G. P. , Hagedorn F. B. , Van Uitert L. G.
Published: February 2004

The wall dynamics in two samples of a garnet with the composition Y1.7Eu0.65Tm0.65Ga0.7Fe4.3O12 are compared. Both samples have an easy axis normal to the plane of the material, but in one case the sample is an epitaxial film and is magnetically isotropic in the plane, and in the other case it is a thin platelet cut from a bulk sample and has in-plane anisotropy. The dynamic behavior as measured by the bubble-collapse technique is significantly different in the two samples. The sample with the in-plane anisotropy has an approximately linear velocity reponse to ∼6000 cm/sec corresponding to a drive field of 60 Oe, whereas the isotropic sample saturates at a velocity of ∼650 cm/sec for a drive field of about 20 Oe. However, both samples have nearly the same dynamic behavior as measured by the bubble-transport technique. The results are compared with the existing theories. In addition, the A and B parameters describing growth-induced anisotropy for this composition are determined