bluuebunny/crossref_metadata_2025 huggingface dataset:
An Optical Isolation Technique for a High-Gain Chain of Laser Amplifiers
Authors: Cabezas A. Y. , Komai L. G.
Published: February 2004

A technique which eliminates the use of optical isolators in a laser oscillator-power amplifier chain is presented for the special case wherein high energy as opposed to high peak power is desired. It is demonstrated that isolation is not required for establishing optimum energy storage (population-inversion density) in the amplifier chain provided the normal-laser oscillator signal is (1) ``saturable'', i.e., sufficiently intense to significantly extract energy from the chain, and (2) introduced before the spontaneous emission from the chain can be significantly self-amplified (superfluorescence). In this study, a chain of four, neodymium-glass laser amplifiers with 66 dB of unsaturated or small-signal gain was used.
Determination of the Predominant Ionization and Loss Mechanisms for the Low-Voltage Arc Mode in a Neon Plasma Diode
Authors: Salinger S. N. , Rowe J. E.
Published: February 2004

A reaction-rate analysis is used to determine the relative importance of the predominant ionization and loss mechanisms in a neon low-voltage arc. Experimental data are derived from various experiments to determine density, cross section, etc. It is found that the resonance and metastable state atoms are primarily generated in a region near the cathode which corresponds to the ``cathode ball-of-fire'' region of the low-voltage arc. The predominant ion-generation process is found to be a result of collisions between excited atoms which cause the formation of a molecular ion. Direct ionization of ground-state atoms is of secondary but non-negligible, importance. Consideration of quasi-equilibrium multistage ionization shows that, unlike the cesium low-voltage arc, it is unimportant in the neon low-voltage arc. The escape of resonance radiation accounts for approximately one-fifth of the total power loss while ionization accounts for approximately one-eighth. Most of the remaining power loss appears as power dissipation at the anode.
ac Breakdown Voltage for a Thin Dielectric Fluid Film
Authors: Anno J. N.
Published: February 2004

The ac breakdown voltage of a mineral oil was measured across a 440-Å gap. The results indicate that the dielectric strength increases linearly with frequency from the dc value of 0.15 MV/cm to a value of 5.0 MV/cm at 77 000 Hz. Further, the data indicate that the dc dielectric strength measured for a relatively large gap (2.5 mm) agrees with that for the very thin gap in the experiment.
X-Ray Analysis of Beta-Brass after Quenching
Authors: Martin M. C. , Kollen W.
Published: February 2004

The effect of quenching on the crystal structure of beta-brass was investigated by x-ray diffraction techniques. A special apparatus was used to obtain a very rapid quench. Samples of beta-brass powder inside a beta-brass single-crystal holder were quenched from eight different temperatures ranging from 100° to 550°C in water and brine at 25°C. Some samples were also quenched in water directly without the holder. X-ray examination provided no evidence for the formation of antiphase domains or for a large amount of disorder. The long-range order parameter of quenched beta-brass has a value of 1.0 with an experimental uncertainty of 20%. There was some evidence that stacking faults might be formed by the quenching process. Diffusion of zinc from the beta-brass to form zinc and copper phases along with the beta-brass was observed in samples quenched from above 400°C.
Anomalous Elastic Behavior of Titanium at Low Temperature
Authors: Alers G. A. , Karbon J. A.
Published: February 2004

Very accurate measurements of the temperature dependence of the elastic modulus C66 of pure titanium were made from 4.2° to 36°K in order to confirm the existence and study the shape of a maximum in C66 near 20°K, which was indicated in earlier measurements by Fisher and Renken. The origin of this anomalous behavior could not be explained on the basis of an unusually large electronic contribution to the temperature dependence of the elastic moduli. It also was shown not to be associated with an electrical resistivity minimum as originally suggested because no such minimum was observed in resistivity measurements on the same sample. The shape of the modulus-temperature curve is suggestive of a phenomenon which takes place abruptly at a critical temperature of about 22°K.
Error Analysis of the Determination of Spin Concentration with the Electron Spin Resonance Method
Authors: Casteleijn G. , TEN Bosch J. J. , Smidt J.
Published: February 2004

This paper presents a discussion of the errors involved determining the concentration of paramagnetic centers with the electron spin resonance method. The work is based on a theoretical analysis of the relation describing the amplitude of the recorded derivative spectrum. Experimental and computational work has been done on a dual cavity for comparing two samples different in size, shape, and material. Special attention is given to corrections for power saturation, and to the determination of the errors made in the evaluation of the recorded signals. Recommendations are given that will facilitate the evaluation of errors from each source in any individual case. It is concluded that errors involved in the comparison of two samples of the same size, material, and in equal tubes can be performed in a dual cavity with an error of less than 5%. If these requirements are not met, however, an over-all error of 10% will only be reached with extremely careful and extensive work.
Infrared Lattice Vibrations of Zinc Selenide and Zinc Telluride
Authors: Riccius H. D.
Published: February 2004

The infrared reflection and transmission spectra of zinc selenide and zinc telluride were investigated at room temperature in the region of the transverse and longitudinal optical phonon frequencies. From the transmission measurements at oblique incidence of vacuum-evaporated films of these materials, the fundamental longitudinal optical (LO) vibration frequency could be obtained directly. Using the Lyddane-Sachs-Teller relation, the static dielectric constant was found to be 9.2 for ZnSe and 10.3 for ZnTe.
Use of Anomalous X-Ray Transmission for the Detection of Defects Produced in Silicon and Germanium by Fast Neutron Irradiation
Authors: Baldwin T. O. , Thomas J. E.
Published: February 2004

Absolute x-ray intensities anomalously transmitted through fast-neutron-irradiated silicon and germanium crystals have been measured and compared with those transmitted through nearly perfect (unirradiated) crystals. The results indicate that the Borrmann intensities in both silicon and germanium irradiated with 4×1019 fast neutrons/cm2 (E>0.6 MeV) were reduced by nearly a factor of two for μ0t0≈30. In contrast, very small (<5%) decreases in the Bragg intensities diffracted from the surfaces were observed. The observed decreases in intensity have been attributed to the strains in the vicinity of ``disordered regions,'' previously observed in electron-microscopy studies of irradiated germanium. Isochronal annealing studies have demonstrated that the crystals could be restored to near their original state of perfection by heating to ≈700°C for 30 min. Two well-defined annealing peaks were found in both kinds of crystals, silicon annealing at about 190° and 630°C, and germanium at about 150° and 400°C. These studies suggest that fast-neutron doses at ambient temperature in the range of 1019–1020/cm2 (E>0.6 MeV) are necessary for observations of appreciable effects on the x-ray intensities diffracted from silicon and germanium.
Analysis of the CS2–O2 Chemical Laser Showing New Lines and Selective Excitation
Authors: Gregg David W. , Thomas Scott J.
Published: February 2004

We investigated the lasing oscillation resulting from the flash photolysis of carbon disulfide and oxygen and found 270 new lasing lines which all could be ascribed to P- and R-branch, vibrational-rotational transitions in CO, a reaction product. A measurement of the time of initiation of the lasing lines showed that the CO was being selectively excited at two vibrational levels by two different mechanisms (collision with electronically excited SO2 and chemical formation of excited CO).
Hardening of Ionic Crystals by Neutron and Gamma Irradiation: Study of the NaCl and KCl Single Crystals
Authors: Maeng Sun-Chae , Choi Hyung Sup , Kim In Sup
Published: February 2004

The effect of neutron or gamma irradiation on the critical shear stress of sodium chloride and potassium chloride crystals has been studied. Until the irradiation dosage reached 1016 nvt, the rate of increase in the critical shear stresses was very small. However, critical shear stress of these crystals increased markedly when the dosage of the neutron irradiation exceeded 1016 nvt. At the total neutron dosage of 5×1017 nvt, the critical shear stress of sodium chloride and potassium chloride increased about 13 times and three times, respectively. Gamma irradiation caused significant hardening of NaCl when the dosage exceeded 107 R. When the irradiation dosage reached 3×108 R, the critical shear stress of NaCl increased about 11 times. The preirradiated sodium chloride crystals were annealed in the temperature range of 200°–300°C, and the activation energy for the recovery of radiation hardening was found to be 0.35–0.48 eV.
Measurement by the Flash Method of Thermal Diffusivity, Heart Capacity, and Thermal Conductivity in Two-Layer Composite Samples
Authors: Larson K. B. , Koyama Karl
Published: February 2004

The well-known flash method of measuring thermal diffusivity, heat capacity, and thermal conductivity in single-layer samples has been extended to measurements in two-layer composite samples. The analysis presented allows these measurements to be made for the material in one of the layers if the corresponding values are known for the material in the second layer. An analytical solution is obtained as the basis of a computer data-reduction procedure devised for calculating the thermal diffusivity from flash-technique data. Replication of the diffusivity measurements is accomplished, in effect, by utilizing the information contained in an arbitrary number of points distributed over a wide range of the experimental temperature transient. Through the use of an empirical function closely representing the actual waveform of the heat pulse produced by a flash lamp, the measurements remain valid in thin samples for which heat losses are small. Experimentally, the method is demonstrated with data obtained for some commercial samples of bimetallic composites.
Magnetic Shielding by Superconducting Nb-40Zr-10Ti Hollow Cylinders
Authors: Kawabe Ushio , Doi Toshio , Kudo Mitsuhiro
Published: February 2004

The magnetic shielding by the heat-treated superconducting Nb-40 at.% Zr-10 at.% Ti hollow cylinder, 5 mm in inner diameter, 9 mm in outer diameter, and 25 mm in length, was investigated at 4.2°K in applied axial magnetic field. The dependence of the magnetic shielding capacity upon the field rate of increase was examined for the samples subjected to the solution treatment at 1100°C for 5 h in vacuum of 10−6 Torr and to the heat treatment at 700°C for 3, 10, and 100 h after solution treatment. The magnetic shielding capacity of the sample, heat treated at 700°C for 100 h, was over 17.5 kOe as the magnetic field was applied with its rate of increase of 0.45 kOe/min. A possible phenomenological model estimating the maximum or minimum magnetic shielding capacity was developed by assuming that the flux front in the Bean critical state moves isothermally or adiabatically toward the interior of the hollow cylinder. The calculated value agreed well with the measured value for each sample.
Time-Domain Analysis and Measurement Techniques for Distributed RC Structures. I. Analysis in the Reciprocal Time Domain
Authors: Happ W. W. , Gupta S. C.
Published: February 2004

The impulse response in distributed-parameter systems results in a spectrum of delta functions in the time domain for LC structures. It is shown that for RC structures the impulse response results in a spectrum of Poisson-derived functions in the reciprocal time domain. This isomorphism is exploited for the analysis of RC devices to establish a calculus of Poisson-derived functions and a transform technique which is essentially the Laplace transform. Applications of this technique to thin-film devices and minority-carrier devices are examined and lead to the determination of the transient response for one-ports and two-ports that are subject to a wide range of terminations. Illustrative examples of excitations include the impulse, the step, and the ramp, as well as signals generated by the distributed parameter devices themselves. Significant advantages accrue from a spectral description of RC devices in the reciprocal time domain: (1) conceptual, by establishing a physical interpretation based on diffusion phenomena; (2) analytical, by developing a systematic approach to transients paralleling the network function approach in the frequency domain; (3) computational, by expressing the response by a rapidly converging spectrum of functions.
Dielectric Measurements on Flux-Grown Crystals of Rutile (TiO2) without Contacting Electrodes
Authors: Cross L. E. , Groner C. F.
Published: February 2004

Dielectric measurements have been made by a torque method on needle-shaped specimens of flux-grown rutile (TiO2) without contacting electrodes. The theory and operation of the method as applied to this geometry of sample is briefly discussed. The results show good agreement with earlier data on Verneuil-grown crystals, with the permittivity along the c axis at room temperature, εc=167, and a resistivity of order 107 Ω·cm. Measurements on completely gold-plated crystals confirm that the apparent relaxation is a consequence of `blocked' conductivity. The torque method is shown to be a valuable additional dielectric measuring technique covering a very wide frequency range, and particularly applicable to rod- and whisker-shaped samples.
The Change in Resonant Frequency with Pressure to 8000 atm of Quartz-Crystal Viscometers
Authors: Rein R. G. , Sliepcevich C. M. , Babb S. E. , Tuma G.
Published: February 2004

Use of a torsionally oscillating quartz rod as a high-pressure viscometer requires knowledge of the effect of pressure on the resonant frequency of the rod. Measurements were made to determine the change in resonant frequency with pressure to 8000 atm at ambient temperatures (23°–26°C) for crystals with resonant frequencies in air at atmospheric pressure of about 20 and 60 kHz. Smoothed data of the change in resonant frequency with pressure for both crystals are correlated to within ±2 Hz to 6000 atm by Δf0*(P)/f0(1 atm)=−6.897×10−7+1.122×10−4P+2.047×10−5P2,where P is in 1000 atm, and f0*(P) and f0 are in kHz. Above 6000 atm the correlation is less precise because of lower reliability of the 60 kHz data.
Theory of Ultrasonic Three-Phonon Interactions in Single-Crystal Solids
Authors: Holt Albert C. , Ford Joseph
Published: February 2004

We derive expressions relating wave amplitudes and third-order constants for resonant ultrasonic three-phonon interactions in single-crystal solids. Ten resonant interactions are tabulated for the case of copper. We reemphasize earlier suggestions that three-phonon interactions can be used to determine third-order elastic constants.
Temperature Dependence of the Energy Gap in GaAs and GaP
Authors: Panish M. B. , Casey H. C.
Published: February 2004

Absorption measurements from 300°–973°K for GaAs and to 1273°K for GaP were made in order to determine the energy gap Eg of these materials at high temperatures. These data, together with previously published results, show that the energy-gap width may be represented by a simple expression for all temperatures. As a function of the absolute temperature T, the direct gap in GaAs is given by Eg=1.522−5.8×10−4T2 / (T+300) eV, and the indirect gap in GaP is given by Eg=2.338−6.2×10−4T2 / (T+460) eV. The general form of the expression for the energy gap is Eg=Eg(0)−aT2 / (T+β), where Eg(0) is the energy gap at 0°K, β is approximately the 0°K Debye temperature, and a is an empirical constant.
Formation Energy of Individual Cation Vacancies in LiF and NaCl
Authors: Spencer O. S. , Plint C. A.
Published: February 2004

The formation energy g+ of an individual cation vacancy in LiF and NaCl has been measured by means of the temperature dependence of the electrical signals produced by push-pull deformation of bent crystals and application of the theory of charged dislocations. For LiF: g+=0.74±0.04 eV at 680°K. For NaCl: g+=0.75±0.04 eV at 627°K and 0.72±0.04 eV at 761°K. A comparison with other published results for NaCl reveals some unexplained disagreement.
Threshold Microwave-Field Amplitude for the Unstable Growth of Spin Waves under Oblique Pumping
Authors: Green J. J. , Patton C. E. , Stern E.
Published: February 2004

The threshold microwave-field amplitude hcrit required for the unstable growth of spin waves has been investigated for oblique pumping with a linearly polarized microwave field applied at an arbitrary angle with respect to the static magnetic field. The experiment was performed on YIG (1% Dy) spheres at 9.2 GHz, using a rectangular TE102 cavity and a pulsed magnetron source. Data were obtained at static external fields of 400, 600, 1100, and 1500 Oe. In general, hcrit increases with the pump angle. Theoretical expressions for the oblique pumping hcrit have been derived for ferromagnetic insulators of ellipsoidal shape and with axial symmetry about the direction of the static magnetic field sufficient to saturate the sample. The threshold field is determined by maximizing 1/h=cosψ/h∥±sinψ/h⊥ with respect to the angle between the internal field and the spin-wave propagation direction. Here, h∥ and h⊥ are the parallel and perpendicular pump threshold fields of Schlömann and Suhl. For external fields sufficient to magnetize the spherical samples to saturation, the theoretical predictions are in good agreement with the experimental data. For small fields, the agreement is poor. However, fair agreement is obtained by assuming a transverse demagnetizing factor Nt greater than the value of ⅓, which is appropriate for saturated spherical samples. The value of Nt for the best theoretical fit depends on the way in which the sample is demagnetized. This result indicates that for samples not magnetized to saturation, the magnetic structure consists of elongated domains, and that the oblique-pumping data can be explained from the theory for saturated systems, assuming demagnetizing factors appropriate to the domain structure.
Response Characteristics of Extrinsic Photoconductors
Authors: Williams R. L.
Published: February 2004

The speed of response of extrinsic germanium photoconductors is limited by the dielectric relaxation response time τρ=εε0ρ, when the resistivity of the photoconductor rises to the MΩ·cm or higher resistivity range. Further, dielectric relaxation components appear only when the drift length of charge carriers is comparable to or greater than the interelectrode distance. The appearance of the dielectric relaxation response-time component arises when a significant fraction of the photogenerated charge carriers is swept out of the photoconductor before recombination leaving a space charge throughout the crystal. For mercury-and copper-doped germanium photoconductors which were studied, an enhanced photosensitivity is observed with increasing bias. For low backgrounds, or high-resistivity conditions, the effect is largest and appears to correlate with the onset of the dielectric relaxation effects.
An Ag–GaAs Schottky-Barrier Ultraviolet Detector
Authors: Baertsch R. D. , Richardson J. R.
Published: February 2004

Ag–GaAs Schottky-barrier photodiodes have been fabricated and evaluated as detectors of uv radiation. The quantum efficiency of these detectors is a maximum near 3225 Å, and is much less in the visible and ir regions of the spectrum. The peak quantum efficiency and selectivity of the detector is determined by the thickness of the silver layer, which possesses a narrow transmission ``window'' for radiation near 3225 Å wavelength. The transmittance of silver films evaporated on 7059 glass and quartz substrates was measured and compared with calculations based on previously published optical constants. At the transmittance peak, the extinction coefficient for these silver films was measured to be 0.38. From these transmittance measurements, the fraction of the radiation, incident on the silver, which enters the GaAs of the photodetectors was calculated as a function of wavelength and silver-film thickness. This quantity was compared with the measured quantum efficiency of the diodes. At the peak, the comparison indicated that 25–50% of the carriers created within the depletion region of the barrier do not contribute to the photocurrent. Measurements of the dependence of quantum efficiency on bias and energy of the absorbed radiation suggest that at the peak, a fraction of the carriers created within the depletion layer are energetic enough to pass over the Schottky barrier and not be collected as photocurrent.
Mass-Spectrometer Analysis of a Cesium Plasma
Authors: Witting H. L.
Published: February 2004

An experiment has been performed in order to determine the dominant ionic species in a cesium plasma in the Torr pressure range. The device consists of a planar thermionic converter with a small (25 μ diam) hole in the collector. Ions that pass through the hole are accelerated by an ion gun and analyzed in a magnetic mass spectrometer. It is found that atomic cesium ions are the dominant species in both the ignited and unignited modes of operation of the discharge. The molecular cesium ions Cs2+ and Cs3+ were also detected in the ignited mode. In addition, measurements were made of the total ion and electron currents that pass through the collector hole. Here the hole acts as a probe of the plasma adjacent to the collector.
Stable Space-Charge Layers Associated with Bulk, Negative Differential Conductivity: Further Analytic Results
Authors: Lampert Murray A.
Published: February 2004

The gross features of previous computer results on stable accumulation and depletion layers are explained analytically. Further, the drift velocity of the accumulation plane in the singular limit, D=0, is obtained by a simple geometric construction based solely on the velocity-field characteristic. This result is related to the drift velocity of the finite accumulation layer, at the same outside velocity, for the D≠0 case via a stringent inequality. For the general case, D=D(F), a new integral equation is derived from the starting differential equations.
The Measurement of Thermal Properties by the Use of Empirical Functions
Authors: Adams C. H. , Wyman M. E.
Published: February 2004

A method has been developed to measure thermal properties of a media from time-dependent temperature distributions. Data from a number of locations and times are used to construct polynomial approximations to the observed phenomenon. Derivatives appearing in the differential equation describing the temperature field are evaluated from the polynomials and are then used to determine the parameters in the equations. Two examples are included. The first is a measurement of the thermal diffusivity of copper. A simple experiment is shown to give results over a range of 100°C which agree with the literature to within 3%. The second is an investigation of the space dependence of the heat generation due to nuclear radiation in a metal cylinder placed in a reactor.
Stacking Faults in Annealed Silicon Surfaces
Authors: Lawrence J. E.
Published: February 2004

Mechanical polishing can generate a flowed lattice and minute crevices in silicon surfaces. Dislocations and stacking faults develop during high-temperature annealing treatments. A systematic investigation of the fault has led to proposed mechanisms for stacking-fault formation, growth, and annihilation. Fault nucleation appears to occur at pinning centers in the flowed lattice provided by crevices fixed by a thermally grown silicon dioxide film. Such pinning centers increase the probability of dislocations intersecting with one another. The intersection of two dislocations which satisfies the Lomar-Cottrell conditions will form a stacking fault. The stacking faults which form in the above dynamic system are extrinsic, bound by ⅓ [111] Frank partials. Such faults grow by vacancy emission. Enhanced fault growth is provided by the dynamic recovering lattice. Fault annihilation can occur if the vacancies emitted by the enhanced fault growth are not annihilated. The Si–SiO2 interface appears to be the dominant vacancy sink during the period of rapid oxide growth.
The Effect of Finite Ion Mass on the Stability of a Space-Charge-Neutralized Electron Beam
Authors: Faulkner J. E. , Ware A. A.
Published: February 2004

The dispersion relation is derived for a finite length one-dimensional electron beam neutralized by positive ions with zero electron and ion temperatures. Contrary to previously published results it is shown that finite ion mass does not produce stability. There are two modes of instability, electron space-charge waves and ion oscillations. Their relative importance at different lengths is considered.
Line Parameters of Lorentzian Curves Containing Arbitrary Mixtures of Absorption and Dispersion
Authors: Linzer Melvin
Published: February 2004

A brief description is presented of various ways in which mixed absorption-dispersion modes can arise. Exact closed-form solutions are derived for the line parameters of zeroth derivatives of Lorentz shape functions containing arbitrary linear mixtures of absorption and dispersion. The parameters are obtained as functions of ε, where ε represents the fractional admixture of one signal component relative to the other, and may be determined experimentally from the signal-amplitude asymmetry. Very simple expressions are also derived for the mixed first derivative curves if terms of the order of ε3 and higher are neglected. In the case of the 1:1 admixture, this procedure introduces an uncertainty in the position of the line center of approximately 1% of the half-width of the pure absorption curve. The implications of this analysis for practical spectroscopic measurements are discussed. In particular, a very simple relationship is shown to exist between the degree of admixture and the experimental variables.
Locking in Multimode Solid-State Lasers
Authors: Statz H. , Bass M.
Published: February 2004

The nonlinear polarizations which lead to mode-locking in solid-state lasers are examined under the realistic assumption that many modes oscillate. When all possible contributions to these polarizations are included in an estimate of their strength, it is found that self-locking is to be expected in pulsed ruby and Nd-glass lasers, and in Q-switched ruby, Nd-glass, and Nd–YAG lasers. In particular, we find that the strengths of the various locking terms increase with the total energy in all the oscillating modes and also with decreasing mode spacing. The total number of modes into which the energy is distributed influences the locking range weakly through a term logarithmic in this number. Experimental evidence in support of these conclusions is also presented.
Hillock Growth and Stress Relief in Sputtered Au Films
Authors: Pennebaker W. B.
Published: February 2004

Growth of hillocks has been observed during annealing of sputtered Au films. The height of a hillock is proportional to the area it occupies in the film. This empirical relationship has been used in a model which postulates that hillock growth is associated with stress relief in the Au. The model is able to relate the sign and magnitude of the stress with hillock size and density. The general character of the growth kinetics is also predicted by the model.
Dislocation Channeling in Neutron-Irradiated Niobium
Authors: Tucker R. P. , Wechsler M. S. , Ohr S. M.
Published: February 2004

Dislocation channels cleared of radiation-produced defect clusters were observed by transmission electron microscopy in polycrystalline niobium irradiated to 4×1018 neutrons/cm2 (E>1 MeV) and then deformed in tension to 6.6% strain. From electron diffraction patterns and diffraction contrast (g·b) analysis, the {110} plane was determined to be the plane on which the dislocation channels formed in most cases. The strain due to the motion of slip dislocations in the channels was deduced from the offset at intersections between the channels and other microstructural features. The strain corresponded to the passage of 1–3 slip dislocations per slip plane. Several mechanisms for the clearing of defect clusters by slip dislocations are discussed. These include: annealing due to the heat of plastic deformation, chopping up or sweeping up of defect clusters by slip dislocations, and annihilation by antidefects.
The P-T Phase Diagram of InSb at High Temperatures and Pressures
Authors: Banus Mario D. , Lavine Mary C.
Published: February 2004

The pressure-temperature phase diagram of InSb is refined to show the boundaries between the high-pressure tetragonal (InSb II) and orthorhombic (InSb IV) phases and extended to about 125 kbar to locate the boundary of the new phase (InSb III). The existence of these structures as stable phases in their phase fields is demonstrated by high-pressure, high-temperature x-ray studies and by x-ray studies and superconductivity measurements on these phases retained by quenching to 77°K. The structures of InSb II and InSb IV are confirmed, and a hexagonal structure for InSb III is proposed. The hexagonal cell has the dimensions (at ∼90 kbar) of a=6.10 Å and c=5.71 Å with a calculated density of 8.5 g/cc. Values are reported for the compressibility of phases InSb I, InSb III, and InSb IV and for the thermal expansion coefficients, under pressure, of phases InSb I and InSb IV.
Poisoning of LaB6 Cathodes
Authors: Gallagher H. E.
Published: February 2004

Electron-emission density for LaB6 cathodes is compared with that for other common cathode types. Equations for describing the poisoning mechanism are presented. Poisoning is related to the gas pressure, cathode temperature, and heat of adsorption. Posioning was measured with a flowing gas system which maintained a constant pressure in the vicinity of the cathode for varying adsorption rates. Poisoning rates were determined by the cathode temperature and gas pressure. An equilibrium poisoned emission level was reached within a few minutes for each cathode temperature and gas pressure. Poisoning gases used were oxygen, carbon dioxide, air, hydrogen, nitrogen, and argon. Oxygen was the most active poisoning gas and argon the least active. No poisoning results until a critical pressure is reached; the emission then decays rapidly with increasing pressure. Resistance to poisoning increases with increasing cathode temperature. At a cathode temperature of 1570°C, the critical poisoning pressure for oxygen is about 5×10−5 Torr. At 1400°C, the critical poisoning pressures are as follows: 2×10−6 Torr for oxygen, 2×10−5 Torr for carbon dioxide, 5×10−5 Torr for air, and greater than 10−2 Torr for hydrogen, nitrogen, and argon. On a comparative basis, the critical poisoning pressure for LaB6 cathodes is several orders of magnitude higher than the poisoning pressure for oxide and impregnated cathodes.
The Magnetic Susceptibilities of Some Rare Earth Silicides and Germanides with the D88 Structure
Authors: Narasimhan K. S. V. L. , Steinfink H. , Ganapathy E. V.
Published: February 2004

The magnetic susceptibilities for neodymium, gadolinium and dysprosium germanides and silicides were measured between about 60° to about 700°K. Plots of 1/χ vs T show a Curie-Weiss behavior, but deviations from it are observed below room temperature. The deviations become smaller with decreasing temperature and in most instances tend to approach the asymptote just above the transition temperature. These compounds have the D88 structure and a ferromagnetic spin ordering for rare earth atoms in the crystallographic 6(g) sites, and an antiferromagnetic ordering in the 4(d) sites is consistent with the observed behavior.
Electronic Deposition of Sprayed Suspensions of Protein for Electron Microscopy
Authors: Stasny J. T. , Rubin B. A.
Published: February 2004

The deposition of microdroplets from a nebulized aerosol is enhanced by the application of an electric field. Electronic deposition facilitates the electron microscopic sampling of the aerosol by capturing those microdroplets that are electrically charged or whose dimensions are too small and therefore elude the more conventional methods of collection. The subsequent deposition of the microdroplets in the system described is a function of the strength of the electric field and the size of the individual microdroplets, and therefore negates the use of forced-air impaction of the microdroplets onto the collecting surface. Electronic deposition as applied to the collection of nebulized suspensions of particulate protein renders the resulting microdroplets (0.25 to 2.0 μ diameter size range) and their contents accessible to sampling under conditions suitable for high-resolution electron microscopy.
Dielectric Properties of Ta2O5 Thin Films
Authors: Pulfrey D. L. , Wilcox P. S. , Young L.
Published: February 2004

Alternating current bridge, step response, and dc conduction measurements are reported on anodic oxide films on tantalum with counterelectrodes of gold and indium. The step response currents followed a t−n law, where n was from 0.9 to 1.0 depending on conditions. For a linear dielectric response, this corresponds to ε″ (ω) varying as ωn−1, i.e., as either ω−0.1 or independent of frequency, respectively. For low values of applied step voltages with specimens made in certain ways, the magnitude of the step response agreed with extrapolated bridge measurements. Deviations are discussed in terms of electronic space-charge effects. Below room temperature, ε″/T was constant as expected for a superposition of Debye losses with relaxation times determined by a thermal activation process with a flat distribution of activation energies. The slope of log J vs F1/2 plots for electronic conduction corresponded to the Schottky or Poole-Frenkel values depending on whether the Ta electrode was negative or positive.
Interaction Between an Electromagnetic Plane Wave and a Spherical Shell
Authors: Chu G. , Dudley D. G. , Bristol T. W.
Published: February 2004

An efficient, exact solution for the complete field structure inside, in, and outside a spherical shell of arbitrary linear media, excited by a monochromatic plane wave is given. The fields in each region are expressed as vector multipole expansions whose coefficients are evaluated through the boundary conditions. The numerical reduction involves the use of modified spherical Bessel functions and recursion relations. The technique is illustrated by numerical results for the fields inside an imperfectly conducting shell. This analysis virtually exhausts the class of problems of spherical shells constructed of linear media.
Exact Relativistic Solution for the One-Dimensional Diode
Authors: Jory H. R. , Trivelpiece A. W.
Published: February 2004

Exact relativistic solutions for the one-dimensional space-charge-limited diode, and for the one-dimensional diode with finite field at the cathode plane are given. The results are compared with approximate solutions which are useful in different energy ranges.
Thermionic Emission from Soda-Lime Glass Surfaces
Authors: Bode W. , Fletcher Peter C.
Published: February 2004

Soda-lime glass surfaces, heated between 600° and 900°C in vacuum, have been shown to emit sodium and potassium ions and electrons. The experimental emission rates are: INa+=4.75×1037 exp(−5.61 eV/kT) ions/cm2/sec,IK+=3.30×1032 exp(−4.37 eV/kT) ions/cm2/sec,and Ie=0.288T2 exp(−3.58 eV/kT) A/cm2.
Field Assisted Glass-Metal Sealing
Authors: Wallis George , Pomerantz Daniel I.
Published: February 2004

A new process is described which permits the sealing of metals to glass and other insulators at temperatures well below the softening point of the glass. Sealing is accomplished in about 1 min by applying a dc voltage in excess of a few hundred volts between the glass and the metal in such a way that the former is at a negative potential with respect to the latter. The process has been applied to a number of glass-metal combinations. A discussion is presented of some of the mechanisms which are believed to play a role in the bonding process.
Photocurrents Through Thin Polymer Films
Authors: Colburn R. H. , Christy R. W.
Published: February 2004

Polymer films deposited by electron-beam bombardment were sandwiched between aluminum electrode films. Photocurrents through these sandwiches, with thicknesses between 150 and 300 Å, were measured in the range of photon energies from 2 to 5 eV and with applied voltage bias up to 3 V. The photocurrent vs bias characteristics are symmetrical about the origin. The photocurrent increases with photon energy at fixed bias, with a threshold photon energy of about 2.2 eV, which is independent of the bias. The optical absorption of the polymer shows approximately the same threshold. These results are discussed in terms of the band structure of amorphous semiconductors.
Pulse Delay Effects in the He–Ne Laser Mode-Locked by a Ne Absorption Cell
Authors: Frova A. , Duguay M. A. , Garrett C. G. B. , McCall S. L.
Published: February 2004

The change in the pulse repetition frequency c/2L of a He–Ne laser, mode-locked by a neon absorption cell, has been found to vary approximately as I−1/3, where I is the average power output of the laser. As c/2L is changing, the pulse width also changes approximately as I−1/3. The corresponding round trip transit times 2L/c are compared to an estimate of the empty cavity transit time obtained by an extrapolation of the data and also a direct measurement. The He–Ne and Ne media introduce an additional positive delay of 4–6 psec to the cavity transit time of 10 nsec; this delay is comparable to that estimated from group velocity considerations.
Anisotropy Linebroadening in Polycrystalline V–In Substituted YIG
Authors: Van Hook H. J. , Euler Ferdinand
Published: February 2004

Polycrystalline linewidth and magnetization have been measured between 77° and 300°K at 9.2 GHz on V–In substituted YIG in the composition range 0[equal to or less-than]x[equal to or less-than]1.50 and 0[equal to or less-than]y[equal to or less-than]0.50 for Y3−2xCa2xFe5−x−y VxInyO12. The linewidths were compared with theoretical values inferred from measurements of K1 (K2 negligible) and Ms on single crystals for 0[equal to or less-than]x[equal to or less-than]0.90 and 0[equal to or less-than]y[equal to or less-than]0.35 between 4° and 300°K on the basis of a recent theory by Schlömann. Data on dense, single-phase polycrystals are in good quantitative agreement with Schlömann's theory for samples with weak anisotropy (Ha≪4πMs, where Ha = 2 | K1 | / M). For high anisotropy materials (Ha[equal to or greater-than]4πMs), linewidth derived from area fitting of the normalized curves follows ΔH = 0.5Ha. Moderately small (<3%) amounts of porosity yield additive linebroadening effects.
Note on the Discharge of Electrophotographic Material by Light
Authors: Kiess H.
Published: February 2004

The discharge behavior of different electrophotographic materials was studied by measuring (dV/dt) − V curves. If it can be shown in a separate experiment that the discharge current is a primary saturated photocurrent (i.e., it is independent of surface potential at high potentials) a simple interpretation of these curves is possible in the saturation region. The shape of the curves is very sensitive to the details of the discharge process. It was shown that the shape of both the (dV/dt) − V and the V(t) curves can be strongly influenced by geometric effects (a change of depletion layer capacitance during discharge without trapping) or by trapping of charge carriers. From these considerations we can conclude that the interpretation of discharge curves V(t) or (dV/dt) (t) requires some care and is only meaningful if the type of discharge current and the voltage dependence of the capacitance are known.
Thermal Stress and Plastic Deformation of Thin Silicon Slices
Authors: Morizane Kenji , Gleim Paul S.
Published: February 2004

Thermal stress and subsequent plastic deformation can be caused in a thin slice of silicon by temperature gradients which arise during the transient periods of heat cycling. They arise either because of the radiation shielding effect of neighboring slices in a parallel row of slices, or the heat sink effect of the boat on which the slices stand, or because of the effect of both. Spacing between the parallel slices, type of boat used, heating and cooling rates, and furnace temperature affect the temperature gradients and the amount of plastic deformation. Study of slip patterns showed that the tangential component of thermal stress was responsible for slip, and that multiple slip was more common than single slip under the conditions investigated.
Small Polaron as the Source of the Frequency-Dependent Conductivity in Glasses Containing Transition Metal Oxides
Authors: Schmid A. P.
Published: February 2004

Studies of the ac conductivity in glasses containing transition metal oxides show that there are two mechanisms for conduction present in the glasses. That mechanism which is dominant at low temperatures is characterized by almost complete temperature independence, and it is proportional to the frequency, while the mechanism dominant at high temperatures is characterized by an activation energy-type temperature dependence, and it is independent of the frequency. An explanation of these effects based on a random glass lattice and the identification of the charge carrier as the small polaron is presented. This model leads to a prediction of a time-dependent carrier concentration for the mechanism dominant at low temperatures. A formula for the conductivity as a function of temperature and frequency, which agrees well with the experimental observations, is derived from this model, using probability arguments. The reason for the good fit is discussed and some of the predictions of the formula are pointed out.
Electrical Signals in Dynamically Stressed Ionic Crystals: A Dislocation Model
Authors: Wong J. Y. , Linde R. K. , White R. M.
Published: February 2004

A summary of new and previously published data on shock-induced electrical signals observed in nominally pure NaCl single crystals is presented. A dislocation dynamics model is developed to account for the microscopic origin of these signals. This model, although only qualitatively applied so far, is shown to be able to explain many of the interesting features of the observed data, notably the change of signal polarity at ∼10 and ∼110 kbar and the distinct signal profiles observed when the sample is shocked along different crystallographic directions. New experimental results for NaCl single crystals doped with Ca2+, Ba2+, Mg2+, and OH− impurity ions are also presented. These results are consistent with the predictions of the proposed dislocation dynamics model.
Assessment of Focused Microwave Systems for Plasma Diagnostics Against Electrostatic Probes
Authors: Richard C. , Carswell A. I.
Published: February 2004

A simplified approach in the use of focused microwave systems for the investigation of radially varying plasmas is assessed by comparison to electrostatic probes on a dc arc argon jet. The approach consists in the mathematical inversion into a radial electron density distribution, of a fit to the phase shift profile obtained by scanning a focused interferometer across a cylindrical plasma. A close fit given by Bockasten's coefficient method, and a loose fit utilizing a modified Gaussian, are considered. The assessment covers a wide range of radial refractive index gradients (as large as 0.4/cm) with electron density up to critical on axis. The modified Gaussian fit approach shows a maximum disagreement of 25% relative to the probe results for an impact parameter smaller than 0.5 and of 350% across the plasma jet. A simple modification to the method would apparently permit the reduction of the overall discrepancy to less than 30%. The close fit is found to yield discrepancies which are worse by a factor of 2–3.
Brillouin Scattering Near the Glass Transition of Polymethyl Methacrylate
Authors: Friedman E. A. , Ritger A. J. , Andrews R. D.
Published: February 2004

Brillouin scattering of laser light has been used to measure the frequency of hypersonic sound waves in the range of 1010 Hz in PMMA as a function of temperature through the glass-transition region. A discontinuity in the temperature coefficient of sound velocity is observed at the glass-transition temperature; this is explained as a consequence of a corresponding discontinuity in the temperature coefficient of the specific volume (thermal expansion coefficient). The ratio of the light scattered by isothermal density fluctuations to that scattered by adiabatic density fluctuations was also measured. This ratio was large and did not change appreciably near the glass-transition temperature. The value of the Landau-Placzek ratio is approximately what one would expect from previously observed ultrasonic-velocity-dispersion data as a function of temperature well above the glass-transition temperature. Both the velocity and intensity ratio data indicate that no velocity-dispersion effects are present for the hypersonic sound waves up to temperatures 35° above the glass-transition temperature. These results also indicate that the glass transition is not a classical second-order phase transition.
Infrared Study of Lamellar Linking by Cilia in Polyethylene Single-Crystal Mats
Authors: Bank M. I. , Krimm S.
Published: February 2004

The infrared spectra of single-crystal mats of physical mixtures of polyethylene and perdeuteropolyethylene show splittings of CH2 and CD2 bending and rocking modes which are smaller than those for the pure species. This is believed to be a result of the penetration of cilia from the surface of one crystal into the lattice of an adjacent crystal. Calculations of the concentration of cilia are in good agreement with percentages derived from the study of a mixed-crystal paraffin system, and these concentrations change with crystal thickness as is predicted. Such cilia can account for most of the amorphous component of polyethylene single crystals.
Activation Energy Spectra for Relaxation in Amorphous Materials. I. Volume Relaxation in Polystyrene and Polyvinyl Acetate
Authors: Kimmel R. M. , Uhlmann D. R.
Published: February 2004

A modification of the Primak analysis for activation energy distributions is presented and compared with the well-known analysis for relaxation time distributions. Mathematical and physical interrelationships between the two analyses are discussed. Activation energy spectra are derived from the data of Kovacs for volume relaxation in polystyrene and polyvinyl acetate. The energy spectra are bell shaped and cover the range from 5 to 20 kcal/mole. The concept of a shift factor is introduced to account for changing structure in the glass transition region. The shapes and locations of the spectra are discussed and compared with previous interpretations of volume relaxation data.
Growth Kinetics of Plate-Like Precipitates
Authors: Trivedi R. , Pound G. M.
Published: February 2004

Different models for the growth kinetics of plate-like precipitates have been critically reviewed. It is shown that the Zener-Hillert equation does not properly take into consideration the capillarity effect at the advancing interphase boundary. A mathematical treatment of the diffusion controlled steady-state growth of plate-like precipitate is presented for the case in which the variation of concentration along the interface is determined from the theory of capillarity. This variation is assumed to be small so that the steady-state shape does not deviate appreciably from a parabola. Applicability of the present treatment to the growth of a group of plates is then discussed.