bluuebunny/crossref_metadata_2025 huggingface dataset:
Fine Structure of Viscose Rayon
Authors: Ingersoll H. G.
Published: January 2005

Quantitative x-ray diffraction methods have been used to study the orientation of the cellulose chains and lateral ordering around the long chain axes in various commercial and experimental rayons. Lateral order can vary independently of orientation in cellulose, as is the case with other linear polymers such as the polyamides. The degree of lateral order obtainable by aqueous annealing of regenerated cellulose appears to be restricted by the structure originally set up. As noted by Sisson, the well-known relations between yarn tenacity and orientation and elongation to break and orientation are not unique. At a given orientation, a range of tenacities and elongations are possible, depending upon the influence of other variables. Study of a series of yarns prepared under constant mechanical conditions showed that elongation to break increased with lateral disordering of the cellulose chains at constant orientation. The data support Baker's proposal that local chain disordering in any linear polymer favors higher extensibility. Some yarns of essentially the same orientation and lateral order have shown different properties indicating that other as yet undefined structural variables also have an important effect on physical properties.
A Theoretical Comparison of the Visual, Aural, and Meter Reception of Pulsed Signals in the Presence of Noise
Authors: Van Vleck J. H. , Middleton David
Published: January 2005

The present paper examines theoretically the relative sensitivity of the detection of signal pulses in the presence of noise, (a) by observation of an oscilloscope, (b) by aural perception, in which one listens to the fundamental or a low harmonic of the pulse repetition frequency (PRF), (c) and by a meter. The metering scheme may be either aperiodic, where the rectified current is fed directly to a meter with a long time-constant, or periodic, where the rectified current is sent through an audio-filter tuned to the PRF, given a supplementary rectification, and then passed through the meter. The dependence of the sensitivities of the different methods on various relevant parameters is studied in some detail. These parameters include the width and the shape of the IF response, the pulse length, the PRF, and in aural or meter reception, the duration of the gate, the width of the audio-filter, and/or the time constant of the meter. The descriptive survey of the results is given in Part I and the mathematical analysis in Part II. Among the more important results are (I): The optimum IF filter is the conjugate of the Fourier transform of the pulse, not merely for visual reception, as was previously known, but also for aural or meter reception as well. (II): For very weak signals the linear detector requires only about 5 percent more input signal power than does the quadratic to achieve the same minimum detectable signal (same final signal-to-noise ratio). (III): The aperiodic meter has the advantage of not requiring knowledge of the PRF, and has potentially great sensitivity if spurious fluctuations in gain can be balanced out. (IV): Meter methods can be made more sensitive than the oscilloscope if long time-constants are available. Gating is also necessary. (V): Although the best IF filter is the Fourier transform of the pulse, the best pulse is not the Fourier transform of the filter in aural reception (though it is in visual), for the best results in meter or audio-detection are obtained by using long pulses. In visual work, the pulse length is immaterial, to a first approximation. Curves are given showing the power required to achieve a given signal-to-noise ratio as a function of pulse length, IF filter width, the PRF, gating time, and audio-filter width, in some cases when the pulse and filter are not matched (i.e., are not related as Fourier transforms). Some numerical estimates of aural and meter performance relative to visual are also essayed.
The Study of a Certain Type of Resonant Cavity and Its Application to a Charged Particle Accelerator
Authors: Akeley E. S.
Published: January 2005

A linear accelerator for charged particles, consisting of a number of cavity resonators placed end to end with the inside end plates removed, and thus forming a wave guide with two closed ends, is discussed. The shape of each section must be so chosen that the velocity of the particle will correspond to the phase velocity of the radiation of the cavity. In order to determine possible shapes for the cavity, the stationary TM01 modes between two parallel conducting planes are determined. In Part 1, excitation of a single mode is discussed, including the shape of the conducting surface that can be used to connect the planes and thus form a cavity. Three cases are considered—when the phase velocity in the cavity is greater than, equal to, and less than that of light. If only one mode is excited, and the phase velocity is not greater than that of light, then the radius of the cavity becomes infinite at the two plates. In Part 2, the simultaneous excitation of two modes is considered. The phase velocity of one mode is that of light; the other has a phase velocity 1/n that of light, where n is an odd integer. The cavity can be made finite by a suitable choice of the relative amplitude of the two modes, and the radius of one end of the cavity. This requires a rather elaborate discussion. This case is of particular interest for the acceleration of electrons. It is shown, furthermore, that only the first mode contributes to the acceleration of the electron. In Section 4, the application of the methods used in Part 3 to the case of an accelerator for heavy particles is touched upon.
A Method of Determining the Size of Droplets Dispersed in a Gas
Authors: Stoker R. L.
Published: January 2005

A method applicable to determining droplet sizes in the interior of an already existing atmosphere of fog or mist is developed and described. The method makes use of the fact that if droplets strike a suitably coated surface without wetting the surface, a track of the contact area is formed. A criterion is derived and experimentally evaluated for relating the droplet diameter and the track diameter. An apparatus for utilizing this method is briefly described.
Determination of the Temperature Rise and the Maximum Safe Current through Multiconductor Electric Cables
Authors: Iskenderian Haig P. , Horvath William J.
Published: January 2005

A general method of calculating the temperature rise in multiconductor rubber insulated electric cables based upon the thermal constants of the cable has been derived. The predictions of the theory have been verified experimentally for a number of cables and values of the thermal resistivity constants have been obtained as a function of size and composition of the cable. The results are used to predict the maximum safe current for different size cables to limit the temperature rise at the center to 25°C above an ambient temperature of 50°C.
Correction of Diffraction Amplitudes for Lorentz and Polarization Factors
Authors: Buerger M. J. , Klein Gilbert E.
Published: January 2005

The corrections for Lorentz and polarization factors for trial and error crystal structure computations are discussed, following the general method recently presented for correcting x-ray diffraction data used in Fourier syntheses. The Lorentz correction has the form (1/S) csc y̢, where S is a scale constant characteristic of the reciprocal lattice level and whose form varies with the method of recording the data. The scale constant is eliminated by appropriate timing of the exposure. When many trial and error computations have to be made, there are advantages in using a scheme involving a correction factor (csc y̢)½ instead of csc y̢. Tables are provided for these functions, for the polarization correction and for the combined Lorentz-polarization correction which is used in the special case of zero-level photographs. Tables are also provided for the functions (h2+k2)½ and (h2+k2+hk)½, which are useful for computing the argument for the zero-level corrections of tetragonal and hexagonal crystals.
The Theory of Permanent Set at Elevated Temperatures in Natural and Synthetic Rubber Vulcanizates
Authors: Andrews R. D. , Tobolsky A. V. , Hanson E. E.
Published: January 2005

A molecular theory is developed to describe quantitatively the permanent set taking place in thin samples of vulcanized natural and synthetic rubbers held at constant extension at elevated temperatures. Permanent set is considered to be the result of the formation, through the action of molecular scission and cross-linking reactions, of a dual molecular network in the rubber sample, in which the network chains are of two types: chains which are at equilibrium when the sample is at its unstretched length, and chains which are at equilibrium when the sample is at its stretched length. According to the theory the amount of permanent set in a rubber sample is a function of only two quantities: the relative ratio of the number of chains of the two types, and the elongation at which the sample was held. Experimental data on permanent set for various rubber types and under different conditions are presented and are shown to be in good agreement with the theory.
A Study of Distortion in Electron Microscope Projection Lenses
Authors: Hillier James
Published: January 2005

The origin of distortion in electron microscope projection lenses is discussed and the serious nature of its effect on the measurement of particle size distributions is pointed out. Methods of measuring distortion are described. By means of first-order theory it is shown to be possible to correct distortion by the use of a two element projection lens. The degree of correction obtainable is shown to be satisfactory for most practical purposes. A double gap projection lens polepiece and the correction of distortion obtained with it are described.
The General Relations for Flow in Solids and Their Application to the Plastic Behavior of Tire Cords
Authors: Lyons W. James
Published: January 2005

Numerous researches on metals, rocks, glass, rubber, and textiles are cited to show that what may be regarded as normal creep in amorphous and polycrystalline solids conforms to the general relation ε=ε1+at+blogt,where ε is the total strain at time t, ε1 is a parameter interpretable as the approximate initial strain, and a, b are other parameters. A special form of this equation, having a = 0, has been frequently applied. Reference is made to several other studies on the same class of solids, which have established for normal relaxation the relation σ=σ1−βlogt,where σ is the stress at time t, σ1 is the stress at unit time, and β is a parameter. A theoretical foundation for both equations is provided by the reaction-rate theory of plastic flow. Observations in the present study indicate that creep extension in cotton and rayon tire cords over prolonged periods of time follows the above creep equation, and, in general, is not adequately represented by an equation omitting the term at. From the presence of this term in the equation, the existence of a component of the viscous type in tire cord growth is deduced. The pattern of creep recovery in cotton tire cord appears to be set by the behavior of the cord in creep extension.
Dynamic Characteristics of Rubber Supports from Vibration Table Data
Authors: Chilton Ernest G.
Published: January 2005

Measurements of the vibration of a free mass which is isolated by a rubber support from a surface vibrating at constant amplitude permit calculations of the dynamic characteristics of the support. This method permits high loadings and the application of considerable force.
A Spark Shadowgraphic Study of Body Waves in Water
Authors: McMillen J. Howard , Harvey E. Newton
Published: January 2005

Shadows of shock waves in water were photographed by means of a point-spark of less than one-tenth micro-second duration; the waves were formed when high velocity spheres struck the water surface. The shock wave front had the form of an elliptical arc of small eccentricity; the ellipticity was caused by the greater strength and velocity of the wave at its center. The absence-of-light band had a varying width which depended on the strength of the wave. A large number of secondary waves behind the impact wave were observed; these were produced by the vibrating spherical missile as it traveled through the water. The period of vibration was determined from the spacing of the waves for 4/32″, 6/32″, and 8/32″ spheres; these agreed to within 19 percent of the periods calculated on the basis of Lamb's theory. Interference of the vibration waves was also observed when two spheres were shot into the water simultaneously. The cavity behind the missile was nearly conical in shape with the forward tip being distorted by pressure changed immediately ahead of the missile. A sphere produced a cusp at the forward tip of the cavity; cylinders and cones each produced their own characteristic shadow pattern. When a grid was placed in front of the tank, distortions in its shadowgram were observed. These were caused by the high pressures surrounding the missile and, from the shift in the grid pattern, the direction and magnitude of the pressure gradient could be inferred. When the shock waves were reflected with the wave front nearly normal to the surface there was an indication that the stem, which is characteristic of Mach reflections, was present. All other reflections were regular. Focusing of the wave by a brass mirror was demonstrated in the spark shadowgram. Waves reflected near normal incidence from substances having a lower acoustic impedance than water were reflected with a presence-of-light band ahead of the usual absence-of-light band. At glancing incidence this reversal occurred even when the reflecting substance had a higher acoustic impedance. Striations frequently appeared in the shadowgrams when waves were reflected. These striae were from 0.02 to 0.08 cm apart and represented a quasi-stationary state. They were believed to be formed when the reflected vibration waves passed through the incident waves.
Lightning Recorded by Aeroplane Propeller
Authors: Bryant J. M. , Newman M.
Published: January 2005

A lightning stroke to the propeller blades of an aeroplane in flight left a remarkably complete record of its own characteristics. Sputtering of the discharge on the rotating blades left a clear time scale of duration of the stroke. The lightning current direction was also recorded by magnetization of steel rings inherent in the propeller mechanism.
Stresses in Cylindrical Glass-Metal Seals with Glass Inside
Authors: Hull Albert W.
Published: January 2005

It was shown previously that, when a cylinder of glass is sealed to the outside of a metal rod, the principal stresses in the glass are of opposite sign, so that tensile stresses cannot be avoided except by a perfect match. In this article the stresses are calculated for a solid glass cylinder sealed to the inside of a metal cylinder. It is shown that the stresses are all of the same sign, so that a moderate mismatch in thermal expansion, with the metal expansion the greater, is allowable and perhaps desirable. Large differences in expansion should be avoided, because of the shearing stresses at the ends.
The Effect of Hydrostatic Pressure on Plastic Flow under Shearing Stress
Authors: Bridgman P. W.
Published: January 2005

This paper presents measurements of the forces required to drive a punch into plates of several grades of steel as a function of the distance of penetration, the entire punching operation being conducted in a fluid medium subjected to hydrostatic pressures up to 30,000 kg/cm2. Qualitatively, the effects are similar to those already found for the tensile properties of steel subjected to hydrostatic pressure, namely, ductility is greatly increased, and greatly increased distortion is tolerated without fracture. The effects are similar in general character for all the steels experimented on here, but are quantitatively accentuated for the softer steels. At a pressure of 20,000 kg/cm2 or more a punch may be driven completely through a plate of mild steel, with no loss of coherence at any stage of the process, and with strain hardening, when expressed in terms of true shearing stress, which may increase by a factor of as much as 3. If the punching operation is suspended at any intermediate stage before complete penetration and afterward completed at atmospheric pressure, very material strengthening will be found as compared to virgin material of the same geometrical configuration. There are certain qualitative differences in the details of the ductility exhibited during the processes of punching and pulling. At intermediate pressures and penetrations the true shearing stress in punching may, under proper circumstances, exhibit maxima, for which there is no analog in the pulling operation. This is to be understood in terms of a difference of geometry, there being greater opportunity for self-healing during the punching operation, and, furthermore, partial deterioration of the coherence of the metal not necessarily leading to complete catastrophe.
Internal Friction and Plastic Extension of Zinc Single Crystals
Authors: Read Thomas A. , Tyndall E. P. T.
Published: January 2005

This paper presents data on the internal friction of four single crystals of zinc while oscillating longitudinally, and a description of various slow speed tension tests on a fifth crystal within and beyond the elastic limit. In the first named measurements the behavior of the crystals bears little resemblance to that of crystals of zinc of greater purity prepared by another method, which has previously been reported (see reference 1). The most outstanding feature is that the decrement, although higher at the lowest stress amplitude than for the previous ones, shows very little rise with increasing stress amplitude, even up to stresses far beyond the statically-determined elastic limit. The difference in behavior seems to be caused by the difference in purity of the zincs. An optically mosaic structure, such as that described by Schilling (see reference 4), does not appear to be responsible. In the slow speed tension tests the zinc crystal, after a period of self-annealing at room temperature, has a Hooke's law region up to about 70 g/mm2 (R.S.S.=28 g/mm2) and at greater stress shows transient and steady creep. Under some circumstances the transient creep is in two parts, a slow starting creep followed by much more rapid creep. The crystal, when measured following a permanent strain, shows creep at loads well below the previous elastic limit and has a large amount of hysteresis. Self-annealing occurs during rest periods and the initial elastic limit is gradually regained while the hysteresis disappears.
The Thermoluminescence and Conductivity of Phosphors
Authors: Herman Robert C. , Meyer Charles F.
Published: January 2005

A simple theoretical treatment is given for the emission of light and associated variations of dark current that occur on warming zinc sulphide and zinc silicate type phosphors previously irradiated with ultraviolet light at low temperatures. Reasonably good agreement is found between the calculated and observed glow curve for Willemite. The same type of treatment is applied to the case of infra-red illumination of phosphors at low temperatures.
The Order-Disorder Transformation in Cu3Au at High Pressure
Authors: Franzblau M. C. , Gordon R. B.
Published: January 2005

The order-disorder transformation in the alloy Cu3Au has been studied at pressures ranging up to 21 kbar by means of electrical-resistance measurements made while the sample is at high temperature and under pressure. The rate of change of the critical temperature with pressure is 2.1°K/kbar from 7 to 21 kbar. The kinetics of the order transformation below Tc are adequately described by the homogeneous reaction rate equation and an activation volume of 6.8 cm3/mole of atoms. The magnitude of this activation volume indicates that the formation of vacancies on the gold sublattice is the rate-limiting step in the homogeneous ordering process.
Emission Studies of Mercury in the Negative Glow of a Hg–H2 Discharge
Authors: Silver M. , Neusel R. H.
Published: January 2005

The relative intensities of the 4358, 3651, and 3131 Å radiation and the ratios of intensities of the 5461, 4358, 3651, 3131, 3125, and 2967 Å radiation were studied experimentally as a function of position in the negative glow of a Hg–H2 dc abnormal glow discharge. These results are displayed in graphical form under conditions of varying H2 pressure. Extrapolations of the relative density ratios of the 63D3,2,1 and 73S1 states were obtained from these intensity measurements. Quenching of the Hg 63P2,1,0 states by H2 in the negative glow region is discussed.
Diffusion Coefficient of Nitrogen in Chromium
Authors: Klein Mark J.
Published: January 2005

By combining internal friction and elastic-aftereffect measurements the temperature dependence of the relaxation time for the stress-induced migration of nitrogen in chromium was determined. The experimental results can be expressed by the diffusion equation D=D0 exp (−ΔH/RT) where D0 and ΔH are 1.6×10−2 cm2/sec and 27 500 cal/mole, respectively. These experimentally determined constants yield an entropy of activation in general agreement with that predicted by Wert and Zener.
Growth of Thin Gold Films on Rocksalt from 80°K to 475°K
Authors: Wassermann E. F. , Hines R. L.
Published: January 2005

The thin gold films are evaporated in an ultrahigh vacuum system onto clean and air-contaminated rocksalt crystals at liquid-nitrogen temperature. The structure and orientation of the deposits are investigated with an electron microscope. The changes in film topology during the warmup to room temperature, caused by surface diffusion, can effectively be prevented by covering the films with a carbon layer immediately after their deposition at 80°K. Comparison of stripped carbon-covered films with those examined by transmission through thinned-down areas of the rocksalt shows that the stripping causes only minor changes in film topology. Changes in structure and orientation of the gold films with varying substrate temperature are investigated over a wide range of temperature. The results are discussed with respect to the work in the epitaxial temperature region.
Finite-Strain Elastic—Plastic Theory with Application to Plane-Wave Analysis
Authors: Lee E. H. , Liu D. T.
Published: January 2005

In the generation of plane waves in metal plates by detonation of contact explosives, the pressures reached can be sufficiently high to produce finite elastic and plastic strain components, and appreciable changes in temperature due to thermomechanical coupling effects. A theory of elastic—plastic deformation is developed to include these conditions. Finite elastic and plastic deformations are represented in terms of the initial and final configurations of the body, and an unstressed configuration subject only to plastic flow. In general, this configuration cannot be represented by a continuous displacement function. The analysis of the kinematics of these three states is carried out for general deformation history. The discussion of the application of finite deformation thermoelastic theory is limited to the conditions in a plane wave with fixed principal directions. Plasticity theory with the consideration of variable temperature is also restricted to the plane-wave situation. The influence of the thermodynamic irreversibility of plastic flow is included in an entropy production term which modifies the temperature variation. Application to the plane-wave propagation problem is discussed.
Estimate of Extrinsic Stacking-Fault Energies from Dislocation Configurations
Authors: Hartl W. F. , DeWit R. , Howard R. E.
Published: January 2005

In this paper we use straight-line models of observed extrinsic nodes to estimate extrinsic stacking-fault energies. Using isotropic elasticity theory and neglecting interactions, we find simple expressions for the energy in terms of the inscribed radii of the nodes. We apply the results to observed extended nodes in a silver—8 at.% tin alloy and find a ratio of extrinsic to intrinsic stacking-fault energy of about 3.
Measurements of Plasma Energy Density and Conductivity from 3 to 120 kbar
Authors: Robinson James W.
Published: January 2005

Plasma energy density, conductivity, and temperature were measured at various pressures ranging from 3 to 120 kbar. The experimental work was conducted in two parts; plasmas with pressures to 15 kbar were formed by capacitor discharges in water, and plasmas with higher pressures were formed by detonating 10 g of PETN in the water adjacent to the electrical discharge path. At 9.4 kbar and 35 000°K, the energy density was 15 J/mm3. An equation of state based upon the Debye shielding theory, without accounting for the distortion of electron quantum states, predicts an energy density of only 3.3 J/mm3. An approximate calculation is presented which accounts for these distortions, and furnishes an estimate of particle densities from measured energy densities. A peak energy density of 75 J/mm3 was obtained at 117 kbar and 1029 atoms/m3. At 10 kbar and 35 000°K, the conductivity was 3×105 (Ω m)−1 and increased with pressure. At 110 kbar and 10 000°K, the conductivity was 2.5×105 (Ω m)−1 and also was an increasing function of pressure.
Shock-Wave Compression of 30% Ni-70% Fe Alloys: The Pressure-Induced Magnetic Transition
Authors: Graham R. A. , Anderson David H. , Holland J. R.
Published: January 2005

The compressibility of 30% Ni-70% Fe (wt %) in the fcc phase is investigated from atmospheric pressure to 40 kbar with shock-wave loading techniques. The experiments are accomplished utilizing projectile impact techniques with stress profile measurements by the quartz gauge. A sharp change in compressibility indicates a second-order ferromagnetic Curie point transition at a stress of 25 kbar and a volume of 0.9807 V0. The coefficient of Curie temperature change with pressure is found to be −5.8±0.3°C kbar−1. The agreement of this value with previous magnetic measurements, along with the anomalously large compressibility below the transition and the large decrease in compressibility at an elevated temperature, clearly indicates that this transition is a ferromagnetic to paramagnetic transition. Values for the change of thermal expansion and specific heat at the transition are computed from the Ehrenfest relations. These values are consistent with the magnetic character of the transition and give a complete description of the thermodynamic properties of the transition. To provide more compressibility data on various types of ferromagnetic materials, a few additional measurements are reported for Invar and 30% Ni-70% Fe in the bcc phase.
Effects of Lasering upon the Electron Gas and Excited-State Populations in Xenon Discharges
Authors: Freiberg R. J. , Weaver L. A.
Published: January 2005

Spatially resolved electron density measurements are reported for dc-excited xenon laser discharges over a pressure range of 12.5 to 25.5 mTorr. Due to electrophoretic effects within the closed capillary tube, anode-directed gradients in electron density are established which affect local population inversions. The influence of lasering upon these discharges is investigated experimentally by using a 3.51-μ (5d33−6p22) laser whose optical cavity Q is periodically spoiled by a mechanical chopping wheel. It is observed that lasering noticeably alters the state of the electron gas and the populations of excited xenon atoms. The discharge current is decreased due to lasering by up to 0.02%, and spatially resolved microwave cavity measurements reveal that lasering may either increase or decrease the electron density by approximately 109 cm−3 depending upon local discharge conditions. Laser-induced changes in the microwave cavity Q and the electron drift velocity indicate that lasering also affects the mean electron energy. Ionization via electron impact from the upper laser level and the xenon metastables is suggested as the dominant physical process responsible. Confirming spectroscopic observation of laser-induced changes in the spontaneous radiation are presented. It is demonstrated that excitation from the xenon metastables populated the 6p and 6p′ levels, degrading the laser population inversion and significantly decreasing the 3.51-μ laser output power. Radiative and collisional mechanisms responsible for the propagation of the laser-induced perturbation from the 5d33 and 6p22 levels to other excited levels are also discussed. It is suggested that laser media in general can be analyzed and improved upon by studying the laser-induced changes in excitation and relaxation processes.
Effect of a Randomly Oriented Cubic Crystalline Anisotropy on Stoner-Wohlfarth Magnetic Hysteresis Loops
Authors: Hagedorn F. B.
Published: January 2005

Experimental hysteresis loops are presented for thin anisotropic films (81% nickel-19% iron) in which cusplike bumps exist for angles larger than 20° between the applied field and the hard magnetic direction. The Stoner—Wohlfarth model for a uniaxially anisotropic magnetic material indicates these cusps should vanish for angles larger than 13°, and a new model is developed which accounts for the larger angles which are observed. This new model takes into account, in an approximate way, the effects of the crystalline anisotropy in randomly oriented, polycrystalline magnetic materials. In addition to providing an understanding of the observed hysteresis loop behavior, this model leads to the suggestion of a possible mechanism for creep in magnetic thin-film memory devices. According to this suggestion, creep may be reduced by reducing the magnitude of the crystalline anisotropy of the magnetic material, and a discussion of some possible alloys for accomplishing this goal is given.
Numerical Self-Consistent Field Approximation to the Interaction of an Ion Beam with a Plasma Boundary
Authors: Seitz W. S. , Eilenberg S. L.
Published: January 2005

Experimental results indicate that, under certain conditions, ion beams undergo severe deflection preceding the region where neutralization of the beam occurs. It is believed that this effect is related to the existence of a conducting plasma which forms in the neutral region of the beam. This effect is analyzed in terms of an axially symmetric model. The plasma is simulated by assigning appropriate boundary conditions at the plasma surface. The method consists of specifying the electric field on a trial boundary, then examining the resulting potential distribution for a unipotential surface on this boundary. A sequence of numerical solutions is found in which the trial boundary is perturbed for each iterate until the Cauchy conditions are satisfied. After the location and shape of this boundary are determined, the effect of variations in electrode potentials is examined and compared with observation. It is shown that under some conditions the plasma can significantly influence the structure of the ion beam.
Shock-Wave-Generated Plasmas as Light Sources for Optical Pumping
Authors: Buser R. G. , Papayoanou A. , Ramm D.
Published: January 2005

Electrodeless discharges in coaxial tubes, capable of holding a laser crystal in the center, have been studied to obtain a measure of the energy coupled into the tube, to understand the dynamical processes, and to quantitatively determine the radiation emitted by the tube. The energy coupling and emitted radiation have been found to depend on the voltage stored on the capacitor, the primary coil dimensions, the fill gas and fill-gas pressure, and the tube dimensions. The dominant dynamical processes are those due to strong cylindrically imploding shock waves. Radiation emitted is found to be due to particles liberated from tube walls as well as that of the fill gas. Curves of radiation intensity vs wavelength, as well as spectral pictures and calculations of spectral matching coefficients, indicate the possibility of pumping very high powers into ruby crystals.
X-Ray Images of Ultrasonic Waves in a Crystal
Authors: Saccocio Edward J. , Lopez Michael A. , Lazara Kenneth J.
Published: January 2005

Topographic x-ray diffraction images of ultrasonic waves in a thick silicon crystal are presented. The stationary nodal pattern of an acoustic field in the crystal is displayed, including that due to a set of plane standing waves. The images were achieved by making use of the anomalous transmission of x rays, and are of preliminary nature.
High-Order Anisotropies in Uniaxial Magnetic Films
Authors: Yelon A.
Published: January 2005

The coupling of uniaxial ferromagnets whose easy directions are not parallel is studied. It is shown that field-dependent effective high-order anisotropies may be produced, and that as the coupling is weakened increasingly high-order anisotropies will become detectable. These results are applied to uniaxial thin films with anisotropy dispersion. It is shown that treating such films as having complex uniaxial and biaxial anisotropy is somewhat oversimplified.
Scattering of Low-Energy Noble Gas Ions from Metal Surfaces
Authors: Smith David P.
Published: January 2005

The energy distributions of positive ions ejected from polycrystalline Mo and Ni by He+, Ne+, and Ar+ primary ions in the energy range of 0.5 to 3.0 keV have been found to consist of a low-energy distribution characteristic of sputtered ions and a sharp peak at higher energy. These high-energy ions are shown to be primary ions which have experienced single two-body collisions with the surface atoms. Multiply-charged ions were not detected. It was found that, approximately, a monolayer of adsorbed gas was sufficient to prevent the detection of incident ions which have scattered from the metal target atoms. He+ primary ions have been used to identify CO as an adsorbed gas on the Ni surface. Furthermore, the data suggest that the CO molecule forms a linear bond with the Ni surface through the C atom, as has been previously observed by other techniques. In contrast, when more reactive gas ions were used as primaries, nonsharp or continuous scattered ion energy distributions were observed, suggesting that lower neutralization probabilities associated with these ions allow the detection of ions which have penetrated deeply into the surface and emerged with varying energy losses.
Linear Compression of α-Quartz to 150 kbar
Authors: McWhan D. B.
Published: January 2005

The linear compression of α-quartz relative to NaCl has been determined by x-ray diffraction methods. The data agree within experimental error with an extrapolation formula derived by Thurston in which the parameters are the elastic constants and their first-pressure derivatives. This is an extrapolation of two orders of magnitude. A high-pressure Guinier-type focusing x-ray camera is described and the problem of pressure calibration is discussed.
Analysis of the Negative Resistance Associated with the Semiconductor—Insulator—Semiconductor (SIS) Structure
Authors: Shewchun J.
Published: January 2005

A new negative-resistance device, the semiconductor—insulator—semiconductor or SIS structure, is analyzed. The effect is due to quantum-mechanical current transmission through a thin insulator barrier and leads to an N-shaped current—voltage characteristic similar to that of the tunnel or Esaki diode. A highly qualitative analysis using general current equations is used to predict the major characteristics. Among these is the fact that the height and shape of the potential barrier, as created by the insulator, influence the current—voltage characteristics significantly—the former controls the amount of diffusion current and the latter the shape of the tunnel-current characteristic. Diffusion currents should be negligibly small as compared to those in the conventional tunnel diode because the barrier height is very high (∼5 eV) for most typical insulators. These and other features, such as wider adjustment of the negative-resistance cutoff voltage through variation in impurity concentration, give the SIS structure enormous versatility in terms of current—voltage shape adjustment through material control. A crude calculation, using the Wannier formalism, is used to derive an expression for the current in a simple, closed analytic form. This analysis shows that, at low temperatures, the slope of current characteristic (dJ/dVA) is a function of the insulator energy gap, ΔI, and will usually be less than that for the equivalent tunnel diode. The general conclusion reached is that realization of the SIS diode is perhaps just beyond the scope of current semiconductor technology. Nevertheless, if developed properly, this structure could conceivably find wide application in current MOS integrated circuits.
Microwave Loss in a Reflex Plasma Discharge
Authors: Lichtenberg A. J. , Govindan P. , Woodyard J. R.
Published: January 2005

The Q of a partially ionized plasma with fluctuating density, created by a reflex discharge, is determined by measuring the decay of microwave energy in a cavity coaxial to the plasma column. For the temperature and neutral gas pressure range of the experiment (Te≃5 eV, p≃5×10−4 Torr for a hot-cathode discharge) the experimental results agree with the theory that electron-neutral collisions dominate below a few percent ionization, and electron-ion collisions become important at higher ionizations. For cold-cathode discharges, with higher temperature, the electron-ion collisions are not significant. Virtual collisions with the ends of the interaction region also contribute to the loss for both hot and cold cathode discharges. Anomalous diffusion does not play a significant role in the microwave losses. The absolute magnitude of the experimentally determined collision time is lower than that calculated from the theory by a factor of three to four, which is in agreement with other measurements reported in the literature. For cold-cathode operation there remain some unexplained inconsistencies within the experimental results.
Ferroelectric Properties of PbZrO3–BiFeO3 Solid Solutions
Authors: Gerson Robert , Chou Pen-chu , James W. J.
Published: January 2005

Solid solutions of BiFeO3 and PbZrO3 were investigated for crystallographic and dielectric properties. A new pseudocubic perovskite phase was found, which has been tentatively indexed as orthorhombic with the same unit cell as PbZrO3 but with dielectric properties characteristic of a ferroelectric substance. The Curie point in this series of solid solutions has a minimum of about 155°C at a composition of about (PbZrO3)0.80 (BiFeO3)0.20, which at room temperature lies on the boundary between the orthorhombic antiferroelectric and the pseudocubic ferroelectric phases. This composition has a relative dielectric constant of 800 at room temperature and shows appreciable dielectric nonlinearity. The Curie point rises to about 400°C for (PbZrO3)0.50 (BiFeO3)0.50 and is extrapolated to about 900°C for pure BiFeO3, in agreement with previous data from similar solid solutions. It is felt that this is additional evidence that the distortion from cubic symmetry in BiFeO3 may be of ferroelectric origin.
Electroviscous Fluids. II. Electrical Properties
Authors: Klass Donald L. , Martinek Thomas W.
Published: January 2005

The induced interfacial polarization mechanism invoked to explain electroviscosity requires a direct relationship between the rheological and electrical properties of an electroviscous system. Static and dynamic measurements of the electric and dielectric properties of electroviscous silica dispersions were made to study these relationships. An electrokinetic potential and conductivity and a small dc power output that depend upon shear rate were observed. Electroviscous fluids under shear exhibit the characteristics of small electric cells. Shear-induced desorption of weakly held charge carriers out of the double layer is suggested to explain these effects.

On application of an external electric field, electroviscosity appears at the onset of current flow. Dielectric measurements under zero-shear conditions show that the medium in contact with the disperse phase is essentially a low-dielectric-constant vehicle while the particles are composites having higher dielectric constants, thereby facilitating interfacial polarization. Anomalous dispersion occurs under zero-shear conditions at low frequencies as expected on the basis of the proposed interfacial polarization mechanism. Simultaneous dielectric-constant, loss, and electroviscosity measurements under shear conditions correlate with the effects of changing shear rate, field strength, temperature, and frequency. Increasing temperatures promote polarization while shear stresses transverse to the direction of the applied field perturb the field-induced polarization. When an electroviscous dispersion is subjected to both mechanical shearing and an external electric field, a dynamic equilibrium is established between the rheological and electrical properties of the system.
Diffusion-Induced Defects in Silicon. II
Authors: Levine E. , Washburn J. , Thomas G.
Published: January 2005

The defect substructure produced by a double diffusion of boron and phosphorus into a silicon wafer has been studied by transmission electron microscopy. Specimens were examined at all stages in the diffusion and at all important levels in the final n-p-n transistor wafer for both {111}- and {110}-oriented wafers. Similar specimens in the {112} orientation were examined at the emitter surface only.

Diffusion-induced dislocations and precipitates were observed at the emitter surface in all orientations. No defects were found at other levels in the doubly diffused wafers except for {110} foils in which long dislocations capable of glide on the inclined {111} planes were observed at the emitter base junction.

The precipitates were in the form of thin platelets which produced displacement fringes parallel to their intersection with the surface (g·R contrast) and parallel moiré fringe contrast. In addition they were strongly attacked by both HF and HNO3 solutions. Diffraction patterns from the precipitates were indexed as from a base-centered orthorhombic structure with a=6.3, b=3.8, and c=6.75 Å. The orientation relationship with the silicon matrix was [111] Si ‖ [011]p. The thin platelets appeared to be a partially coherent precipitate with an associated misfit vector of ∼⅓[111] such that the platelets compressively stressed the matrix. This compressive stress acts to partially relieve the diffusion-induced tensile stress normal to the habit plane, and so the operating planes are those which are most perpendicular to the diffusion front so as to have the greatest possible resolved compressive stress in the diffusion front.
Flux Jumping in Synthetic High-Field Superconductors
Authors: Watson J. H. P.
Published: January 2005

The magnetic field, Hfj, of the first flux jump during the initial magnetization of synthetic high-field superconductors, composed of indium in porous glass, has been measured as a function of the temperature and the field-sweep rate dH/dt. The behavior is reasonably well described by Hfj∝log(dH/dt). At low values of dH/dt, log Hfj is approximately proportional to 1/(dH/dt). It is shown that under rather special conditions the flux-jumping behavior depends upon the condition of the sample surface.
Correlations of Field-Emitter Ring-Rate Transients and Temperature Variations of Surface-Tension Anisotropies
Authors: Bettler P. C. , Love G. G.
Published: January 2005

Transients in the ring-rate changes, which take place when the temperature of a field-electron emitter is varied, have been observed for several crystal directions on bcc, fcc, and hcp crystals. It is proposed that these transients are the result of changes in the size of small surface facets which are in turn related to anisotropies in the surface tension.
Thermogravimetric and Seebeck-Effect Measurements on Li-Doped CoO at High Temperatures
Authors: Fisher B. , Wagner J. B.
Published: January 2005

Gravimetric and Seebeck-effect measurements have been made on CoO single crystals doped with Li in the temperature range of 900°–1200°C and partial pressures of oxygen up to 1 atm.

For low-doped crystals and high oxygen pressures, the gravimetric and Seebeck-effect results confirm a simple model by which the positive-charge carriers are given at equilibrium by the singly ionized vacancies and the Li ions. By this model the concentration of holes is increased, and the concentration of vacancies is decreased by the addition of Li.

The results at low pressures of oxygen for the low-doped samples as well as the results in all the range of oxygen pressures for the heavier-doped samples show that the model has to be enlarged, taking into account the contribution of Co interstitials to the defect structure of CoO(Li) and that of electrons to the conductivity in CoO(Li).
Thermoluminescence and Color Centers in LiF:Mg
Authors: Klick Clifford C. , Claffy Esther W. , Gorbics Steven G. , Attix Frank H. , Schulman James H. , Allard James G.
Published: January 2005

A variety of optical absorption, emission and luminescence excitation spectra have been measured in an attempt to identify the centers involved in the thermoluminescence of commercial LiF:Mg. It is concluded that the principal trapping centers consist of a hole trapped near various groupings of Mg2+ ions and vacancies. The optical absorption bands of these centers occur in the 3100–3800 Å region which contains several absorption bands corresponding to different geometries of the centers. It is suggested that the 2200-Å band arises from Mg2+ ion-vacancy complexes which have captured two holes. During thermoluminescence, holes are transported from traps to emitting centers. The luminescent center appears to be the F center both in an isolated position and when adjacent to a complex involving Mg2+ ions.
Behavior of the p-n Depletion Layer following Injection of Intense Density of Carriers
Authors: Beckner Everet H.
Published: January 2005

An investigation has been made of p-n junction devices performing under conditions when the depletion layer was subjected to sudden generation of extreme carrier densities. Significant local distortion to the layer was identified, arising from the fact that the instantaneous high carrier density grossly changed the effective conductivity of the depletion layer. These findings are shown to be of particular significance when such junction devices are employed to analyze intense radiation phenomena.
Time and Temperature Dependence of Irradiation Effects in Solid Dielectrics
Authors: Brown R. G.
Published: January 2005

Decay of the electron distribution injected into a polymeric solid at 2MeV was investigated by measuring the charge released during a triggered discharge. From the decay time constant τ=ρε, resistivity ρ was calculated. For polymethylmethacrylate, the variation of ρ with temperature yielded an activation energy or trap depth W≈0.6 eV. Discharges resulting in Lichtenberg figures were also produced in polystyrene and polypropylene. Trap depths were estimated to be W≈0.6 eV for polystyrene and W≳0.4 eV for polypropylene.
Rise-Rate Dependence of the Critical Current of Superconducting Solenoids
Authors: Meyerhoff R. W.
Published: January 2005

The influence of charging current rise rate on the maximum operating current was determined for a 42-layer Nb–Zr solenoid 15.24 cm long with an i.d. of 3.05 cm and an o.d. of 5.74 cm which generated a magnetic field of 1.4 kG/A. A rise rate of 10.7 A/sec (15 kG/sec) was found to lower the maximum operating current of this solenoid by ∼30%. In addition, the rise-rate dependence of the transition current was determined with various configurations of built-in electrical shorts. In all cases, the presence of a short greatly increased the rise rate dependence, and in several cases led to depression of the transition current by more than 50% for rise rates as small as 0.2 A/sec (0.28 kG/sec). These results indicate that the strong rise-rate dependence of the transition current observed in some superconducting solenoids arises from the presence of shorts, and is influenced more strongly by the rate of change of field than by the current rise rate. Several relations have been derived which accurately predict the rise-rate dependence of the critical current of a shorted superconducting solenoid.